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材料专题（ScienceDirect数据库） 第5期 （总30期） 2018年9月15日

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《Energy Storage Materials》 Volumes18

An overview and future perspectives of aqueous rechargeable polyvalent ion batteries

Tingting Liu, Xing Cheng, Haoxiang Yu, Haojie Zhu, ... Jie Shu

Pages 68-91

Abstract

In recent years, the rechargeable aqueous batteries have attracted great attentions among quite a few researchers because of the abundant raw materials, low cost, simple operation, safety and environmental benignity. Compared with the battery system of monovalent ions, rechargeable aqueous polyvalent ion batteries have a greater significance of research in many aspects. Although some difficulties have been encountered in the development process, plenty of efforts have been made to improve the electrochemical performance by a variety of distinct methods, such as seeking for new electrode materials, modifying surface area of materials and exploring new type of electrolytes. This review is a summary of recently reported anode materials, cathode materials and electrolytes for rechargeable aqueous polyvalent ion batteries.

Applying chemometrics to study battery materials: Towards the comprehensive analysis of complex operando datasets

Marcus Fehse, Antonella Iadecola, Moulay Tahar Sougrati, Paolo Conti, ... Lorenzo Stievano

Pages 328-337

Abstract

In the last decade, a rapidly growing number of operando spectroscopy analyses have helped unravelling the electrochemical mechanism of lithium and post-lithium battery materials. The corresponding experiments usually produce large datasets containing many tens or hundreds of spectra. This considerable amount of data is calling for a suitable strategy for their treatment in a reliable way and within reasonable time frame. To this end, an alternative and innovating approach allowing one to extract all meaningful information from such data is the use of chemometric tools such as Principal Component Analysis (PCA) and multivariate curve resolution (MCR).

PCA is generally used to discover the minimal particular structures in multivariate spectral data sets. In the case of operando spectroscopy data, it can be used to determine the number of independent components contributing to a complete series of collected spectra during electrochemical cycling. The number of principal components determined by PCA can then be used as the basis for MCR analysis, which allows the stepwise reconstruction of the “real” spectral components without needing any pre-existing model or any presumptive information about the system.

In this paper, we will show how such approach can be effectively applied to different techniques, such as Mössbauer spectroscopy, X-ray absorption spectroscopy or transmission soft X-ray microscopy, for the comprehension of the electrochemical mechanisms in battery studies.

Direct solar steam generation system for clean water production

Panpan Zhang, Qihua Liao, Houze Yao, Yaxin Huang, ... Liangti Qu

Pages 429-446

Abstract

The social development, economic growth and booming population have caused aggravated water pollution, making clean water shortage an urgent issue to be solved. In recent decades, researchers have aroused upsurge studies of direct solar steam generation (DSSG) system for the production of clean water, in which solar thermal conversion materials (STCM) can strongly transform absorbed solar light into thermal energy, tremendously speeding the evaporation of water under sunlight irradiation. DSSG system has been considered an efficient, sustainable, low-cost and environment-friendly way to solve water shortage crisis of practical importance. In this review, we will provide a comprehensive summary of the recent development of DSSG system for clean water production. The introduction about categories of DSSG, principle of solar thermal conversion on STCM and efficiency calculation in DSSG system will first demonstrate the fast water evaporation mechanism. Then strategies for high performance water evaporation in DSSG are detailed including sunlight absorption regulation on STCM for efficient light utilization, system optimization of DSSC for minimizing the heat loss, water transport adjustment for adequate water supply and so on. Benefiting from the basic understanding and effective strategies of DSSG system, the quality of produced clean water, pollutants disposal in remaining water body and various designs of solar stills for high clean water productivity are further presented. Finally, we outline the current challenges and crucial issues of recent DSSG system, aiming to provide guidances and pointers to speed the development of DSSG in clean water production for practical applications.

Asymmetric ammonium-based ionic liquids as electrolyte components for safer, high-energy, electrochemical storage devices

Sangsik Jeong, Siqi Li, Giovanni Battista Appetecchi, Stefano Passerini

Pages 1-9

Abstract

The synthesis of ionic liquids (ILs), based on the trimethyl-isobuty-ammonium cation, (N111i4)+, and, respectively, the bis(trifluoromethylsulfonyl)imide (TFSI), (fluorosulfonyl) (trifluoromethylsulfonyl)imide (FTFSI), and bis(fluorosulfonyl)imide (FSI) anions is herein reported. The NMR validation of the N111i4Br precursor as well as the ionic liquids is shown. The thermal properties were investigated via variable-temperature, coupled with mass spectroscopy, and isothermal thermo-gravimetrical analyses, and long-thermal tests. The TFSI-based IL exhibits a melting point of 29.93 °C, which is found to be shifted down to −0.12 and −14.32 °C for the FSI- and FTFSI-based samples, respectively. Additionally, the TFSI- and FTFSI-based samples are able to keep in super cooled state for more than one year. The investigated N111i4-based ionic liquids display an electrochemical stability window exceeding 5.5 V.

Self-luminous wood composite for both thermal and light energy storage

Haiyue Yang, Weixiang Chao, Siyuan Wang, Qianqian Yu, ... Guoliang Li

Pages 15-22

Abstract

High efficient energy storage devices for both thermal energy and light energy are scarce in the development of modern society to reduce energy consumption. In this work, a novel self-luminous wood composite based on phase change materials (PCMs) with superior thermal energy storage and long afterglow luminescence (LAL) materials with excellent light energy storage is reported. The obtained self-luminous wood composites shows high latent heat of fusion (146.7 J g-1), suitable phase change temperature at about 37 ℃, favorable thermal reliability and thermal stability below 105 ℃ with excellent shape-stability. More importantly, the self-luminous wood composites can absorb ultraviolet and visible light from lighting source and natural light, and emit green light in the dark for 11 h. More interesting, the addition of LAL particles can improve the thermal conductivity of self-luminous wood composites. All results demonstrate self-luminous wood composites can store both thermal energy and light energy, and have great potential in applications including furniture, emergency light, storage and building energy conservation.

Modeling of contact stress among compound particles in high energy lithium-ion battery

Xiang Gao, Peng He, Jianguo Ren, Jun Xu

Pages 23-33

Abstract

Compared to other high capacity anodes, Silicon (Si) has the highest gravimetric capacity, volumetric capacity, a relatively low discharge voltage and abundant storage on the earth, Si and Si based materials has become more and more popular in battery industries among which Silicon-Carbon (Si-C) core-shell particle has been one of the most promising and commercially feasible candidates to achieve ultrahigh capacity of the anode for lithium-ion batteries. Silicon-Carbon (Si-C) core-shell particle has been one of the most promising and commercially feasible candidates to achieve ultrahigh capacity of the anode for lithium-ion batteries. However, most silicon-based anode materials suffer from severe performance deterioration especially during fast charging process. Modeling the mechanical stress and deformation of anode particles is thus of great fundamental and practical interest to understand the mechanism of silicon-carbon anodes. We establish both computational and theoretical methods to describe the stress distribution and contact behaviors within and among Si-C particles, as well as the Li+ diffusion within Si particle. We further analyze the charging rate dependent behavior of the core-shell structure. Our analysis reveals a complete link between stress, charging rate, Li+ diffusion and the structural variables. Our study thus opens a novel pathway to design the structured high-capacity silicon-carbon at nano-scale for expanding Si-based anode application within limited amount beyond cylindrical configuration and increasing the glass ceiling of battery energy density based on graphite anode.

Defect-engineered MnO2 enhancing oxygen reduction reaction for high performance Al-air batteries

Min Jiang, Chaopeng Fu, Jian Yang, Qi Liu, ... Baode Sun

Pages 34-42

Abstract

More recently, defect-engineering has been demonstrated as a facile but effective route to boost electrocatalytic performance. In this work, an activity-enhanced MnO2 catalyst with abundant oxygen vacancies and edges is developed by Ar-plasma strategy to enhance the electrochemical performance of Al-air batteries. Based on the detailed morphology and structure analysis, rich defects are successfully induced on the surface of MnO2 nanowires, and the defect-engineered MnO2 catalyst displays higher activities (more positive reduction potential and larger reduction current density) towards oxygen reduction reaction (ORR) compared with pristine MnO2. However, excessively high defects can work against the ORR catalytic enhancement due to the structure distortion. The resultant Al-air battery displays higher voltage, larger power density and better durability. The remarkable ORR activity is due to the formation of defective active sites, which is beneficial for the oxygen species adsorption and activation of O-O bond, confirmed by density function theory (DFT) calculation. This strategy represents a new route for the development of non-noble electrocatalyst for Al-air batteries.

Scalable synthesis of VN quantum dots encapsulated in ultralarge pillared N-doped mesoporous carbon microsheets for superior potassium storage

Haoyang Wu, Qiyao Yu, Cheng-Yen Lao, Mingli Qin, ... Xuanhui Qu

Pages 43-50

Abstract

Potassium-ion batteries (KIBs) are promising alternatives to lithium-ion batteries (LIBs) due to the advantages of low-cost and abundant natural resource. To date, the researches on KIBs are still in their early stage and only a few materials have been explored. Herein, we design VN quantum dots encapsulated in ultralarge pillared N-doped mesoporous carbon microsheets (VN-QDs/CM) via a large-scale and ultrafast (within two minutes) solution combustion synthesis method and a subsequent ammonia reduction process. The VN quantum dots with high mass loading and dispersity on conductive carbon microsheets could reduce the K-intercalation stress in particle dimensions and mitigate the volume expansion. In addition, the ultralarge pillared N-doped mesoporous carbon microsheets not only facilitate the transfer of electrons and K ions and but also prevent the active materials from breaking away from the electrode during cycling. As an advanced anode material for KIBs, a high reversible capacity and a superior cycling stability (228 mAh g−1 at 0.1 A g−1 after 100 cycles, 215 mAh g−1 at 0.5 A g−1 after 500 cycles) are obtained, among the best anodes reported. More importantly, the effective strategy can be potentially used for mass production of quantum dots encapsulated in ultralarge carbon microsheets for energy storage.

Co9S8@carbon yolk-shell nanocages as a high performance direct conversion anode material for sodium ion batteries

Yingying Zhao, Qiang Fu, Dashuai Wang, Qiang Pang, ... Gang Chen

Pages 51-58

Abstract

Cobalt sulfides based on conversion mechanisms are considered as promising anode materials for sodium-ion batteries due to their appropriate working voltage and high practical capacities. But the severe volume change and structure transformation make their cycle stability and rate capability unsatisfactory. In this study, metal-organic framework derived Co9S8@carbon yolk-shell nanocages (Co9S8@CYSNs) was prepared and its direct conversion mechanism was carefully demonstrated for the first time by various spectroscopic techniques and first-principles calculations. The unique hierarchical structure of Co9S8@CYSNs composed of Co9S8 nanoparticles dispersed in amorphous carbon matrix inside a rigid carbon shell was capable of accelerating the conversion reaction, shortening the Na+ diffusion distance and providing a fast electron transport channel. Benefiting from the accelerated electrochemical reactions and high activities of nanosized particles, the Co9S8@CYSNs exhibited a large discharge capacity of 549.4 mA h g-1 at 0.1 A g-1. In addition, a superior rate performance of 100 mA h g-1 at 10 A g-1 and excellent cycle stability with a very low capacity decay of 0.019% per cycle over 800 cycles at 10.0 A g-1 were achieved because of the confine effect of the carbon shell and improved charge transfer reactions of the electrode.

Anion-immobilized polymer electrolyte achieved by cationic metal-organic framework filler for dendrite-free solid-state batteries

Hanyu Huo, Bin Wu, Tao Zhang, Xusheng Zheng, ... Xueliang Sun

Pages 59-67

Abstract

The practical application of solid-state batteries (SSBs) is restricted by the growth of lithium dendrites, which could be attributed to uneven Li deposition mainly caused by the barrier of free anions in solid polymer electrolytes (SPEs). Herein, a novel cationic metal-organic framework (CMOF) is proposed to immobilize anions and guide Li+ uniform distribution for constructing dendrite-free SSBs. The CMOF grafted with -NH2 group protects the ether oxygen of polymer chains by hydrogen bonds, which extends the electrochemical window to 4.97 V. Such CMOF tethers anions by electrostatic interaction of charge carriers and the specific surface area as high as 1082 m2 g−1 further strengthens the effect of anion absorption on the surface of CMOF, leading to a high Li+ transference number of 0.72. With the anion-immobilized composite electrolyte, the Li symmetrical cells can continuously operate for 400 h at 0.1 mA cm−2 and 200 h at 0.5 mA cm−2 without discernable dendrites, respectively. In addition, the SSBs constructed with LiFePO4 and LiFe0.15Mn0.85PO4 cathodes demonstrate excellent rate and cycle performances at 60 °C. These results indicate that anion immobilization by CMOF is a promising strategy to realize dendrite-free SSBs with high energy density and safety.

An all-vanadium aqueous lithium ion battery with high energy density and long lifespan

Miaomiao Shao, Jintao Deng, Faping Zhong, Yuliang Cao, ... Hanxi Yang

Pages 92-99

Abstract

Aqueous Li ion batteries offer a safe and low cost alternative to their organic electrolyte counterparts; however, they usually suffer from poor cyclability due to the structural instability of electrode-active materials in the aqueous electrolytes. In the light of excellent electrochemical reversibility of vanadium-based redox couples in redox flow batteries (RFB), we propose an all-vanadium aqueous lithium ion battery (VALB) using a LiVOPO4 cathode and a VO2 anode, and a 20 m LiTFSI aqueous solution as electrolyte, respectively. This VALB battery demonstrates excellent electrochemical performances with an average operating voltage of ~1.4 V, an attractive energy density of 305 W h L−1 and 84.0 W h kg−1 based on the total active materials mass, considerably exceeding the energy density of conventional Vanadium flow battery. In addition, this battery also demonstrates an excellent cycling stability with 84% capacity retention over 1000 cycles, possibly serving for energy storage applications.

Constructing double buffer layers to boost electrochemical performances of NCA cathode for ASSLB

Xuelei Li, Ming Liang, Jian Sheng, Dawei Song, ... Lianqi Zhang

Pages 100-106

Abstract

By virtue of high specific capacity, LiNi0.8Co0.15Al0.05O2 (NCA) is considered to have a promising application in all-solid-state lithium batteries (ASSLB) using sulfide electrolyte. However, the interfacial instability between NCA cathode and sulfide electrolyte is still a serious problem, leading to poor rate and cycle performances of NCA cathode. To boost the interfacial instability and boost the rate and cycle performances of NCA cathode, a novel double buffer layer strategy is constructed in this paper. Firstly, NCA is designed as a core-shell structure to achieve self-coating, in which Ni-rich core LiNi0.85Co0.15O2 can provide high capacity, and Al-rich shell LiNi0.6Co0.15Al0.25O2 as the first buffer layer can provide the complete coating on the Ni-rich core. Secondly, a thin inactive LiNbO3 layer as the second buffer layer is coated on the core-shelled NCA (CS-NCA) particles to increase the interface stability. As expected, LiNbO3-coated CS-NCA (CS-NCA@LiNbO3) cathode displays high discharge capacity (184.1 mAh g−1 at 0.06 C), excellent initial coulombic efficiency (90.2%, 0.06 C), outstanding rate performance (130 mAh g−1 at 4.2 C) and cycle performance (capacity retention of 89.4% after 400 cycles at 0.3 C) at 60 °C. The results indicate that this novel double buffer layers strategy is effective to boost rate and cycle performances of NCA cathode for ASSLB using sulfide electrolyte.

Hetero-interface constructs ion reservoir to enhance conversion reaction kinetics for sodium/lithium storage

Libin Fang, Zhenyun Lan, Wenhao Guan, Peng Zhou, ... Yinzhu Jiang

Pages 107-113

Abstract

Developing high-capacity electrode materials is most vital to high-energy rechargeable batteries. The conversion reaction-based anode materials deliver substantially higher theoretical capacities in respect to intercalation-based materials. However, the sluggish conversion reaction kinetics is a big obstacle to deliver high practical capacity and rate capability, which is particularly severe for sodium storage. Herein, we implement an interface engineering approach by designing hetero-interfaces to enhance conversion reaction. As a proof of concept, Sb2S3-SnS2 hetero-nanostructures are synthesized and show greatly improved electrochemical performance in terms of specific capacity and rate capability. The DFT calculations reveal that the hetero-interfacial electric field prompts sodium ions pump into the interfaces, which greatly reduces the activation barrier and hence accelerates reaction kinetics. The Sb2S3-SnS2 hetero-interface serves therefore as a “reservoir” and fast diffusion channel for sodium or lithium ions. The obtained results provide important insights into engineering efficient hetero-nanostructures towards fast conversion reaction kinetics for rechargeable batteries.

Well-defined cobalt sulfide nanoparticles locked in 3D hollow nitrogen-doped carbon shells for superior lithium and sodium storage

Huihui Shangguan, Wei Huang, Christian Engelbrekt, Xiaowen Zheng, ... Jingdong Zhang

Pages 114-124

Abstract

Hollow nanostructured materials present a class of promising electrode materials for energy storage and conversion. Herein, 3D hollow nitrogen-doped carbon shells decorated with well-defined cobalt sulfide nanoparticles (Co9S8/HNCS) have been constructed for superior lithium and sodium storage. Two steps are involved in the designed preparation procedure. First, hollow intermediates with preserved cobalt components are controllably fabricated by simultaneously dissociating cobalt containing zeolitic-imidazolate-frameworks-67 (ZIF-67), and polymerizing dopamine in a Tris–HCl solution (pH = 8.5). The polydopamine (PDA) wrapped intermediates inherits the polyhedral structure of the ZIF-67 crystals. In the second step, the final Co9S8/HNCS composite is obtained via a combined carbonization and sulfurization treatment of the intermediates, allowing the formation of hollow polyhedrons of nitrogen-doped carbon shells (900±100 nm) derived from PDA and the encapsulation of highly uniform cobalt sulfide nanoparticles (11±2 nm). This configuration is believed to not only shorten the lithium or sodium ion diffusion distance and accommodate volume change during lithium or sodium ion insertion/extraction, but also to enhance the overall electrical conductivity and the number of active sites. As a result, the Co9S8/HNCS composite exhibits an impressive reversible capacity of 755 mA h g-1 at 500 mA g-1 after 200 cycles for lithium ion storage, and capacities of 327 mA h g-1 at 500 mA g-1 after 200 cycles and 224 mA h g-1 at 1000 mA g-1 after 300 cycles for sodium ion storage. Essential factors especially the structural stability during cycling have been identified, and the discharge/charge mechanism is discussed.

Stable cycling of mesoporous Sn4P3/SnO2@C nanosphere anode with high initial coulombic efficiency for Li-ion batteries

Yu Xia, Shaobo Han, Yuanming Zhu, Yongye Liang, Meng Gu

Pages 125-132

Abstract

Tin dioxide is one promising anode due to its high-capacity of conversion-reaction during lithiation. However, its applications are often hindered by its low initial Coulombic efficiency caused by irreversible Li2O formation and huge volume expansion during lithiation. Here, we synthesized Sn4P3/SnO2 hollow nanospheres in carbon matrix as anode materials for lithium-ion batteries. The in-situ phosphorization of SnO2 promotes the initial Coulombic efficiency to ~77% with a high capacity of 975 mA h g−1. Moreover, it exhibits an excellent rate performance of 713 mA h g−1 at 2 A g−1. Using in-situ transmission electron microscopy, its volume increase was closely monitored to be only ~84.8% (largely improved compared with over 200% increase for SnO2) during the first lithiation and Sn4P3/SnO2@C can maintain structural integrity and form a stable SEI layer. Our approach is low-cost and simple enough for large-scale manufacture and can be widely applied to other oxide anodes to enhance its performance through phosphorization and forming composite with conductive carbon matrix.

Wettability in electrodes and its impact on the performance of lithium-ion batteries

Dong Hyup Jeon

Pages 139-147

Abstract

Wettability by the electrolyte is claimed to be one of the challenges in the development of high-performance lithium-ion batteries. Non-uniform wetting leads to inhomogeneous distribution of current density and unstable formation of solid electrolyte interface film. Incomplete wetting influences the cell performance and causes the formation of lithium plating in the anode, which leads to safety issue. Research has pointed out that insufficient wetting could be found in the electrode, and the wetting characteristics would be different in each electrode. Here we use lattice Boltzmann simulation to show the electrolyte distribution and understand the wetting characteristics in the cathode and anode. We develop a multiphase lattice Boltzmann model with the reconstruction of electrode microstructure using a stochastic generation method. We use a porous electrode model to identify the effect of wettability on the cell performance and to elucidate the dependence of capacity on the wettability. Our results would lead to more reliable lithium-ion battery designs, and establish a framework to inspect the wettability inside electrodes.

Lithium difluoro(oxalate)borate improving the zero-volt storage performance of lithium-ion batteries by offering anode SEI film tolerance to high potentials

Chun-Yu Liu, Yang Yang, Meng Yao, Hai-Tao Fang

Pages 148-154

Abstract

Keeping lithium-ion batteries (LIBs) in a state of zero charge is an effective way to prevent the risks of thermal runaway during their storage and transportation. It is of importance to achieve excellent zero-volt storage performance, meaning that the performance of LIBs changes little after long-term storage at zero volt. This paper proposes a reliable approach to improve the zero-volt storage performance, that is, the combination of electrochemical pre-lithiation to lower the zero-volt crossing potential (ZCP) and the use of appropriate electrolyte additives to enhance the stability of solid electrolyte interface (SEI) film on anodes to tolerate high potentials for a long time. We use an electrolyte additive, lithium difluoro(oxalate)borate (LiDFOB), as an SEI-film stabilizer. By comparing the chemical composition of SEI film on mesocarbon microbeads (MCMB) anode prior and subsequent to holding at 3.3 V for 10 days, we clarify how LiDFOB offers the SEI film tolerance to high potentials. The validity of the approach is confirmed by a LiCoO2 full cell using an MCMB anode pre-lithiated in the electrolyte containing 2 wt% LiDFOB. This full cell shows a recovery ratio of capacity as high as 93.3% after 7-week zero-volt storage.

Ni@Li2O co-axial nanowire based reticular anode: Tuning electric field distribution for homogeneous lithium deposition

Peichao Zou, Sum-Wai Chiang, Jing Li, Yang Wang, ... Cheng Yang

Pages 155-164

Abstract

The employment of three-dimensional (3D) conductive scaffolds can improve safety level of metallic anodes at high rates, since they can lower down the average current density per electrode area, and thus suppress/delay the formation of metal dendrites. However, metal dendrites would still preferentially grow in the anode areas which are near to cathode, due to the more concentrated electric field strength. Here, we demonstrate that in-situ forming Li2O nano-layer on the surface of 3D Ni nanowire scaffold can not only facilitate Li+ transportation, but also render more homogenous electric field strength distribution throughout the entire anode. We observed a very low voltage hysteresis (~55 mV during 200 cycles) with enhanced cycling stability of more than 150 cycles at 3 mA cm−2. When coupling with LiFePO4 cathode, the as-assembled full cell can stably run for over 300 cycles with minimal capacity degradation and an average Columbic efficiency of 99.9% at 1 C, showing significant improvement of battery cycling stability. This work may represent a key step towards scalable production of highly safe metal anodes using electric field theory.

Multi-core yolk-shell like mesoporous double carbon-coated silicon nanoparticles as anode materials for lithium-ion batteries

Niantao Liu, Jing Liu, Dianzeng Jia, Yudai Huang, ... Guangzhi Hu

Pages 165-173

Abstract

Various techniques have been developed to mitigate the volume expansion of silicon-based materials and improve their conductivity in lithium ion batteries (LIBs). Here, we have synthesized a novel cobalt and nitrogen co-doped double carbon coated silicon/carbon/metal-organic framework (MOF) multi-core yolk-shell like mesoporous materials through sol-gel and MOF self-template methods. The structure and morphology of the sample was characterized by X-ray diffraction and electron microscopy. The results show that the prepared composite is made up of multiple phenolic resin-based carbon-coated silicon embedded in MOF-derived carbon framework. The composite exhibits excellent lithium storage performance with a reversible capacity of 1107 mA h g−1 at 0.5 A g−1 after 100 cycles and cycling stability capacity of 852 mA h g−1 at a current density of 1 A g−1 over 300 cycles. The improved electrochemical performance could be attributed to double carbon coated multi-core yolk-shell mesoporous structure in conjunction with cobalt and nitrogen co-doping, which can improve electrical conductivity and the cycle performance of silicon. Moreover, as the electrolyte blocking layer, the double-layer carbon coating is beneficial to the formation of stable solid electrolyte interphase films, and empty space inside the MOF-derived carbon multi-core yolk-shell structure can effectively mitigate the volume change of silicon during the lithiation/delithiation process.

Growth and growth mechanism of oxide nanocrystals on electrochemically exfoliated graphene for lithium storage

Zexuan Xu, Ping Zhang, Jialu Chen, Wenbo Yue, Wuzong Zhou

Pages 174-181

Abstract

Difficulty of growing metal oxides on intrinsic graphene due to few defects and functional groups on its surface was overcome by deposition of polymerized precursors via multiple interacting sites, followed by crystallization of metal oxides inside the aggregated polymer. As a typical example, Mn3O4-decorated electrochemically exfoliated graphene (EEG) was successfully prepared and served as an advanced anode material for lithium-ion batteries. Because EEG possesses higher electronic conductivity and stronger mechanical strength in comparison with commonly used reduced graphene oxide (rGO), the new composite of EEG-Mn3O4 exhibits much better electrochemical performance than rGO-Mn3O4, including superior reversible capacity and better cycling stability.

Surface structure inhibited lithiation of crystalline silicon probed with operando neutron reflectivity

Arne Ronneburg, Marcus Trapp, Robert Cubitt, Luca Silvi, ... Sebastian Risse

Pages 182-189

Abstract

Silicon is a promising anode material for lithium ion batteries due to its ten times higher specific capacity compared to commercially used graphite anodes. However, silicon anodes suffer from strong capacity fading and low Coulombic efficiency during cycling. Here we analyzed crystalline silicon anodes by operando neutron reflectometry in combination with electrochemical impedance spectroscopy. The lithiation/delithiation processes were investigated over four cycles revealing a successive growth of the lithiated zone. Moreover, the loss of Coulombic efficiency could be directly correlated to a layer formation and its dissolution on the silicon surface that suppressed the insertion of lithium ions into the silicon anode. The comparison of the currents obtained by the scattering length density profiles and the potentiostat revealed that after an initial parasitic side reaction had occurred current losses of less than 5% could be achieved. While the lithiation was hindered by side reactions the delithiation process encountered no significant problems. The results obtained by electrochemical impedance spectroscopy suggested that a layer with high charge transfer resistance was formed after each delithiation step. Hence, these operando studies provide valuable insights into the correlation of surface formation processes and the loss in Coulombic efficiency.

Improve the electrodeposition of sulfur and lithium sulfide in lithium-sulfur batteries with a comb-like ion-conductive organo-polysulfide polymer binder

Fang-Lei Zeng, Ning Li, Yan-Qiu Shen, Xin-Yu Zhou, ... Yu-Sheng Yang

Pages 190-198

Abstract

Lithium-sulfur (Li-S) battery is a promising candidate for high-energy storage technologies due to its high energy density and low cost. However, the irreversible and unstable phase transfer between the dissolved lithium polysulfide intermediates and the insoluble charge or discharge products (S or Li2S) severely hampers the energy density and the lifespan of Li-S battery. Herein, a comb-like ion-conductive organo-polysulfide polymer (PSPEG) binder was prepared to solve the phase transfer problem. We found that the organo-polysulfide bonds in PSPEG binder could react with the agglomerated S/Li2S to improve their electrodeposition states. And the unique comb-like structure of PSPEG binder endows PSPEG with good adhesive property and compatibility with active material. Hence, the sulfur electrode with PSPEG binder could demonstrate improved cycling performance and rate capability as compared to the electrode with conventional LA132 binder. More importantly, the electrode with PSPEG can deliver a stable capacity over 500 cycles as the PSPEG content is only 1 wt%. In a word, this work provides a new strategy to address the unstable phase transfer problem utilizing the organo-polysulfide polymer, which may arouse the battery community's interest to explore the novel functional binders for the commercial application of high-energy Li-S batteries.

A corrosion-resistant current collector for lithium metal anodes

Xinyue Zhang, Aoxuan Wang, Ruijing Lv, Jiayan Luo

Pages 199-204

Abstract

Due to its high theoretical specific capacity and negative electrochemical potential, Li is considered to be the ultimate choice for the battery anode. Unfortunately, poor Coulombic efficiency and uncontrolled dendrite growth prevent it from practical application. Electrolyte additives can effectively stabilize the solid electrolyte interphase (SEI) while utilizing various nanostructured forms of current collectors can decrease the current density and alleviate the volume fluctuation. Combining these two strategies could potentially lead to high performance Li metal anodes (LMAs). However, we found that Cu, the widely used anode current collector for lithium metal batteries, suffers corrosion in polysulfides containing electrolyte, which are proved to effectively protect the surface of Li anode in the study of Li-S batteries. Such corrosion could collapse the structure of LMAs. To mitigate the incompatibility of electrolyte additives and current collectors, we propose here a lightweight 3D Ti current collector that is corrosion-resistant in electrolyte with polysulfide additive. Outstanding Coulombic efficiency over 99% was achieved under high plating/stripping capacity of 5 mAh cm-2 and no dendrite was observed. This work not only demonstrates an exceptional lightweight 3D current collector but also highlights the importance of the corrosion-resistance capability of the current collectors for LMAs.

Rational design of robust-flexible protective layer for safe lithium metal battery

Siyuan Li, Lei Fan, Yingying Lu

Pages 205-212

Abstract

Rational design of artificial protective layers with low resistance, high mechanical strength and good compliance is desirable to suppress dendritic lithium growth, thus realizing the superiority of Li metal anode for high-energy devices such as large electric grids and electrical vehicles. Here, a 2.5 μm-thick lithiated Nafion/LiCl interface (NLI) is fabricated by a simple dip-casting method, in which soft lithiated Nafion polymer can provide a fast ionic pathway as well as comfortable interfacial contact, meanwhile robust LiCl salts act as a mechanical modulus enhancer against severe interface fluctuation and dendrite growth upon cell cycling. Due to its sufficient ionic conductivity and stability, the as-prepared robust-flexible NLI layer enables lithium metal anode to operate at high current density of 8 mA cm−2 in Li/Li symmetrical cells and shows longer lifespan in Li/Cu half cells as well as full cells paired with Li4Ti5O12, LiFePO4, or sulfur cathode. This work proposes a design principle of combining robust inorganic enhancer with flexible polymer matrix to construct stable lithium metal interface and opens a new opportunity to achieve next-generation power-intensive Li metal batteries under safe operation.

Ultrahigh discharge efficiency in multilayered polymer nanocomposites of high energy density

Jianyong Jiang, Zhonghui Shen, Jianfeng Qian, Zhenkang Dan, ... Yang Shen

Pages 213-221

Abstract

Poly(vinylidene fluoride) (PVDF)-based dielectric polymers are in great demand for the future electronic and electrical industry because of their high dielectric constants and energy density. However, some issues that limit their practical applications remain unsolved. One of the most urgent issues is their high dielectric loss and hence low efficiency. In this contribution, we proposed and demonstrate that substantially enhanced discharge efficiency of PVDF-based polymers nanocomposites could be achieved by simultaneously optimizing their topological-structure and phase composition. In the poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP))/poly(vinylidene fluoride-ter-trifluoroethylene-ter-chlorofluoroethylene) (P(VDF-TrFE-CFE)) multilayered nanocomposites fabricated by non-equilibrium process, an ultrahigh discharge efficiency of ~85% is achieved up to 600 MV/m, which is the highest discharge efficiency reported so far for any polar-polymer dielectric materials at such high electric field. By adjusting the quenching temperature, the phase-composition hence dielectric permittivity in the terpolymer layers could be tuned for suppressed ferroelectric loss. Results of phase-field simulations further reveal that local electric field is substantially weakened at the interfaces between the Co/Ter polymer layers, which will act as barriers to motion of charge carriers and give rise to much suppressed conduction loss and a remarkably enhanced breakdown strength. Synergy of the optimized topological-structure and phase-composition thus leads to a nanocomposite that exhibits an unprecedented high discharge efficiency of the multilayered nanocomposites that is comparable to the bench-mark biaxially oriented polypropylene (BOPP) at high electric field as well as a high discharge energy density that is over 10 times higher than that of BOPP.

Designing Li-protective layer via SOCl2 additive for stabilizing lithium-sulfur battery

Sheng Li, Hongliu Dai, Yahui Li, Chao Lai, ... Chao Wang

Pages 222-228

Abstract

Lithium metal is among the most promising anode materials for high-energy batteries due to its high theoretical capacity and lowest electrochemical potential. However, uncontrolled lithium decomposition and dendrite formation have hindered its practical applications. Here, we propose a facile and effective strategy using thionyl chloride (SOCl2) as electrolyte additive to in-situ build a stable interfacial protective layer on lithium anode to prevent Li dendrite growth. Furthermore, the decomposition of SOCl2 could produce active sulfur to offer extra capacity for cathode in full battery. As a result, the as-assembled lithium-sulfur battery delivered an ultra-high discharge capacity (2202.3 mA h g−1 at 400 mA g−1) and excellent rate performance (1348.6 mA h g−1 at 3000 mA g−1), as well as remarkable cycling performance. This study reveals an effective avenue to suppress the Li-dendrites growth and provide a significant step towards safe and high-energy Li-S batteries.

Sn@C evolution from yolk-shell to core-shell in carbon nanofibers with suppressed degradation of lithium storage

Weixin Song, Xinhua Liu, Billy Wu, Nigel Brandon, ... D. Jason Riley

Pages 229-237

Abstract

Metallic Sn has high conductivity and high theoretical capacity for lithium storage but it suffers from severe volume change in lithiation/delithiation leading to capacity fade. Yolk-shell and core-shell Sn@C spheres interconnected by carbon nanofibers were synthesized by thermal vapor and thermal melting of electrospun nanofibers to improve the cycling stability. Sn particles in yolk-shell spheres undergo dynamic structure evolution during thermal melting to form core-shell spheres. The core-shell spheres linked along the carbon nanofibers show outstanding performance and are better than the yolk-shell system for lithium storage, with a high capacity retention of 91.8% after 1000 cycles at 1 A g-1. The superior structure of core-shell spheres interconnected by carbon nanofibers has facile electron conductivity and short lithium ion diffusion pathways through the carbon nanofibers and shells, and re-develops Sn@C structures with Sn clusters embedded into carbon matrix during electrochemical cycling, enabling the high performance.

High energy storage density at low electric field of ABO3 antiferroelectric films with ionic pair doping

Tiandong Zhang, Yu Zhao, Weili Li, Weidong Fei

Pages 238-245

Abstract

PbZrO3 antiferroelectric films can be used to design the energy storage capacitors for low electric field applications, and the energy storage properties are determined by electric field-induced phase transition. Here we present a simple and effective method to enhance the energy storage properties of PbZrO3 antiferroelectric through ionic pair (with small ionic radius) doping. Li+-La3+ pair induces chemical press when Li+ and La3+ are doped at the Pb2+-sites of PbZrO3. Both the analysis based on the phenomenological model and experiment results show that the critical electric fields corresponding to the field-induced phase transition of PbZrO3 can be enhanced under the compressive stress, which improves the energy storage properties. A maximum energy storage density of 16.2 J/cm3 has been obtained in Pb0.96(Li0.5La0.5)0.04ZrO3 thin films at a low electric field of 600 kV/cm, which is about 1.8 times than that of un-doped PbZrO3 films (9 J/cm3). The results provide an effective approach to design high energy storage properties in ABO3 antiferroelectrics at low electric field.

Single-atom catalyst boosts electrochemical conversion reactions in batteries

Jian Wang, Lujie Jia, Jun Zhong, Qingbo Xiao, ... Yuegang Zhang

Pages 246-252

Abstract

High energy barrier originated from the sluggish ion kinetics is considered to be a major obstacle for achieving high discharge rates in advanced battery systems, especially for electric vehicle applications. Herein, for the first time we show that the single atom catalyst can play a compelling role in boosting the electrochemical conversion kinetics and achieving previously-unreachable ultra-high-rate performance. Both experimental and theoretical results prove that atomically-dispersed single iron atoms promote the delithiation of relatively-inert Li2S cathode and accelerate the reversible electrochemical conversion reactions during its long-term cycling. The work demonstrates the effectiveness of single atom catalysis in improving the performance of Li2S/Li batteries (588 mAh g−1 at 12 C and capacity fading rate of 0.06% per cycle for 1000 cycles at 5 C) and opens a new route to breaking the rate limit for other future conversion-based high energy batteries.

Silica-grafted ionic liquid for maximizing the operational voltage of electrical double-layer capacitors

Qingyun Dou, Cheng Lian, Shulai Lei, Jiangtao Chen, ... Xingbin Yan

Pages 253-259

Abstract

A critical problem of electric double-layer capacitors (EDLCs) is that their actual operational voltages can hardly reach the theoretical values. This condition results from the unsuitable potential ranges of electrodes. Designing methods to optimize the potential ranges of electrodes is important to entirely utilize the theoretical operational voltages, thereby maximizing the energy densities of EDLCs. Here, we report a silica-grafted ionic liquid as an electrolyte additive for a model EDLC to adjust the potential ranges of electrodes. The operational voltage of the EDLC increased from 2.8 V to a theoretical value of 3.2 V, thereby resulting in an approximately 39% increase in energy density and considerably enhanced cycling stability.

Correlating structural changes of the improved cyclability upon Nd-substitution in LiNi0.5Co0.2Mn0.3O2 cathode materials

Yan Mo, Lingjun Guo, Bokai Cao, Yiguang Wang, ... Yong Chen

Pages 260-268

Abstract

Spherical LiNi0.5Co0.2Mn0.3O2 (NCM523), cycling to voltages greater than 4.3 V, often suffers from structure instability and the resultant inferior cyclability. Here, Nd is used as dopant into NCM523 to address this long-standing issue. The mechanism of Nd substitution effect on the structural evolution of NCM523 is also investigated. In-situ X-ray diffraction reveals that volume variation of the cathode could be alleviated due to the Nd doping effect. The larger-diameter Nd3+, integrating into the crystal lattice of NCM523 as a positively charged center, is beneficial to the diffusion of Li ion, stability of crystal phase and physical structure upon cycling. In-situ Raman spectroscopic measurements verify that partial Nd substitution can lead sustainable structure evolution during the first cycle. More importantly, the stable cut-off voltage could be enhanced to as high as 4.6 V.

Superior electrochemical performance of sodium-ion full-cell using poplar wood derived hard carbon anode

Yuheng Zheng, Yaxiang Lu, Xingguo Qi, Yuesheng Wang, ... Yong-Sheng Hu

Pages 269-279

Abstract

As a supplement to lithium-ion batteries, the rate capability and cycling stability of sodium-ion batteries still need to be improved for practical applications. Here we report a novel poplar wood derived hard carbon anode, exhibiting a high specific capacity of 330 mAh/g and an initial Coulombic efficiency of 88.3% in half cells, and delivering a reversible specific energy of 212.9 Wh/kg (based on two-electrode masses) at 1 C and a long cycle life of 1200 cycles at 5 C when pairing with Na[Cu1/9Ni2/9Fe1/3Mn1/3]

• cathode in full cells. In addition, with the matched areal capacity of 2 mAh/cm2 and under the industrial level cathode loading of 20.5 mg/cm2, the capacity highly maintains at 2 C, and after 1400 cycles could almost fully recover by setting the current rate to C/10. This indicates sodium-ion batteries are approaching maturity.

Nanoconfinement effects of N-doped hierarchical carbon on thermal behaviors of organic phase change materials

Xiao Chen, Hongyi Gao, Liwen Xing, Wenjun Dong, ... Ge Wang

Pages 280-288

Abstract

Nanoconfinement behaviors of organic phase change materials (PCMs) in the nanoscale porous supports greatly influence the efficiency of thermal energy transformation and utilization when they undergo phase transition. To comprehensively elucidate the effects of nanoconfinement induced by the host-guest interactions on the thermal behaviors of organic PCMs, in-situ N-doped nanoscale hierarchical host carbon is successfully prepared via pyrolysis of polyaniline hydrogel. Distinctly different phase change behaviors were found for small molecular organic guest PCMs with various organic functional terminals and carbon chain lengths in the confined nanoscale N-doped hierarchical pores. The host-guest interactions at the interfaces in the composite PCMs determine the nanoconfinement behaviors of PCMs via influencing the free mobility of PCM molecules, which mainly depend on the hydrogen bond intensity between PCMs and N-doped hierarchical carbon, and space restriction effect of the hierarchical pore on the PCMs. However, these two dominant factors are interchangeable when the carbon chain length of carboxylic acid molecules is different. Moreover, the nanoconfinements of PCMs are gradually enhanced from octadecane, octadecylamine, octadecanol to stearic acid. The atomic-level mechanism is proposed via density-functional theoretical (DFT) calculations. This study provides insights into the nanoconfinement mechanism of small molecular organic PCMs inside the confined nanoscale N-doped hierarchical carbon.

Enabling room-temperature solid-state lithium-metal batteries with fluoroethylene carbonate-modified plastic crystal interlayers

Ziheng Lu, Jing Yu, Junxiong Wu, Mohammed B. Effat, ... Francesco Ciucci

Pages 311-319

Abstract

Solid-state batteries (SSBs) with Li7La3Zr2O12 (LLZO) ceramic oxide electrolytes are attracting significant interest because of LLZO’s non-flammability, excellent ionic conductivity, electrochemical stability against Li metal anodes, and processability in air. However, the poor solid-solid contact between the electrolyte and the electrodes leads to large interfacial impedances, which are detrimental to the functioning of LLZO-based SSBs. In this work, we modified the electrode|Ta-doped-LLZO (LLZTO) interfaces by employing a plastic crystal interlayer based on succinonitrile with a fluoroethylene carbonate additive. The interlayer, which can be easily applied, drastically reduces the interfacial resistances and allows the stable operation of Li-metal based batteries. A Li|LLZTO|LiFePO4 battery with this interlayer can stably cycle at room-temperature for 50 times at 0.1 C while still retaining a capacity of 140 mAh g-1. The symmetric Li|LLZTO|Li cell with the interlayer can cycle at 0.2 mA cm-2 for over 150 hours. It also has a higher critical current density for the growth of dendrites compared with an analogous cell without the interlayer. In short, this work provides a facile and efficient methodology to enhance the effective Li transportation rates at the electrode|electrolyte interfaces of SSBs and can be readily applied to other types of electrolytes beyond LLZO.

Oxygen and nitrogen co-doped porous carbon granules enabling dendrite-free lithium metal anode

Yuanming Liu, Xianying Qin, Shaoqiong Zhang, Yulan Huang, ... Baohua Li

Pages 320-327

Abstract

Lithium (Li) metal anode is one of the most promising candidates for next-generation storage system due to its high theorectical capacity. However, the uncontrollable growth of Li dendrites still incurs serious safety issues and poor electrochemical performances, hindering the practical application of Li metal anode. Herein, oxygen and nitrogen co-doped porous carbon granules (ONPCGs) with high specific surface area (2396 m2 g−1) made from polyacrylonitrile powder were used as the host material for Li plating. The lithiophilic oxygen and nitrogen-containing functional groups could guide a uniform Li nucleation deposition, and the high specific surface area of ONPCGs could lower the regional electrical field effectively, boosting stable and homogeneous Li plating. Therefore, the ONPCG modified electrode delivered a stable Li plating/stripping with high Coulombic efficiencies>99% for over 350 cycles at a current of 2 mA cm−2 and Li capacity of 2 mAh cm−2, with a Coulombic efficiency of 96.4% after 130 cycles at a current of 20 mA cm−2. Even at exceptional high current density of 30 mA cm−2, it could stably being cycled for over 110 cycles. Furthermore, the full cells, using sulfurized carbon as cathode and ONPCGs@Li as anode, could also demonstrate excellent cycle and rate performances.

Ultra-thin Fe3C nanosheets promote the adsorption and conversion of polysulfides in lithium-sulfur batteries

Huanxin Li, Shuai Ma, Houqin Cai, Haihui Zhou, ... Yafei Kuang

Pages 338-348

Abstract

Rational design of hierarchical porous materials with comprehensive properties, e.g. good conductivity, fine dispersibility for sulfur, strong adsorption and catalytic abilities to polysulfides (LiPSs), is urgently needed for the practical application of lithium-sulfur batteries (Li-S batteries). Here, based on density functional theory (DFT) computational results and the design concept of efficient, low-cost and environmental friendliness, we report an ultra-thin (~ 1 nm) Fe3C nanosheets growing on mesoporous carbon (Fe3C-MC) with large specific surface area of 686.9 m2 g-1 and pore volume of 6.52 cm3 g-1. Meanwhile, the formation mechanism of two-dimensional Fe3C is revealed according to DFT results. In the Fe3C-MC composite, the mesoporous carbon constructs a conductive network for dispersion of sulfur species, while Fe3C nanosheets play a key role in electronic transmission, LiPSs adsorption and conversion in Li-S batteries. As a result, the Fe3C-MC composite delivers a high initial capacity of 1530 mA h g-1 at 0.1 C, and a capacity of 699 mA h g-1 after 100 cycles at 0.5 C at a super-high sulfur loading of 9.0 mg cm-2, meaning a specific area capacity of 6.291 mA h cm-2. Such sulfur host is expected to accelerate the practical applications of Li-S batteries benefiting from the low-cost and large-scale process.

Smart integration of carbon quantum dots in metal-organic frameworks for fluorescence-functionalized phase change materials

Xiao Chen, Hongyi Gao, Mu Yang, Liwen Xing, ... Ge Wang

Pages 349-355

Abstract

A novel type of metal-organic frameworks (MOFs) based photoluminescence-functionalized (PL) phase change materials (PCMs) was designed and fabricated for superior thermal energy and fluorescence harvesting using a facile synthetic strategy for the first time, which expands conventional single thermal nature of PCMs with novel fluorescence function. Stearic acid (SA) and carbon quantum dot (CQD) molecules were synchronously incorporated into the Cr-MIL-101-NH2 framework, in which MOF framework serves as an ideal compatible support host, CQD as a superior fluorescent guest, and stearic acid as an excellent thermal energy guest. Our uniquely constructed MOF-involved PCMs assisted by CQDs effectively preclude conventional aggregation-induced fluorescent quenching during the operation. This novel targeted functional strategy creates an innovative platform for developing advanced multifunctional PCMs with multiple fascinating peculiarities and desired properties, which can be universally applied to other versatile MOF hosts and other functional guests for expanding the applications of MOF-based PCMs and developing modular devices with multiple enhanced functional properties.

Sustainable supercapacitor electrodes produced by the activation of biomass with sodium thiosulfate

Marta Sevilla, Noel Diez, Guillermo A. Ferrero, Antonio B. Fuertes

Pages 356-365

Abstract

High-surface area carbons are produced from biomass-based products (wood sawdust and tannic acid) by means of an environmentally friendly process based on the use of sodium thiosulfate as activating agent and an inert salt (KCl) that serves as a confinement medium for the activation reaction. These porous carbons have high BET surface areas of up to 2650 m2 g-1, large pore volumes of up to 2.3 cm3 g-1 and a porosity that combines micro- and mesopores in different amounts depending on the quantity of activating agent employed. Such carbons have two additional remarkable properties: a) they are S-doped (2–6 wt% S) and b) they have good electrical conductivities in the 2.5–4.5 S cm-1 range. The above properties make these carbon materials highly attractive as supercapacitor electrodes. Indeed, when tested in a variety of electrolytes (H2SO4, TEABF4/AN and EMImTFSI) using commercial-level mass loadings, they show high specific capacitances (up to 200 F g-1, 140 F g-1 and 160 F g-1 in aqueous, organic and ionic liquid electrolytes, respectively) and high capacitance retention at high rates in all the electrolytes in combination with a good stability under cycling and floating modes.

Tin sulfide nanoparticles embedded in sulfur and nitrogen dual-doped mesoporous carbon fibers as high-performance anodes with battery-capacitive sodium storage

Yaping Wang, Yifang Zhang, Junrong Shi, Xiangzhong Kong, ... Anqiang Pan

Pages 366-374

Abstract

Batteries based on sodium-ion chemistry are promising alternatives to current-generation lithium-ion ones, owing to the abundant sodium sources. The larger radius of Na+ than Li+, however, has been limiting the adaptability of many electrode materials. On one hand, the insertion of Na+ harshly requires suitable layer spacing. On the other hand, the sodiation/desodiation may cause more severe volume changes. Herein, nanosized tin sulfide embedded in sulfur and nitrogen co-doped porous carbon fibers (SnS@SNCF) were designed and synthesized from a sulfur bearing electrospinning solution. This approach promises the structural stability of SnS upon cycling to ensure high capacities. Meanwhile, it introduces sulfur doping, pores and partially graphitized edges to the carbon fibers, which can contribute to fast capacitive sodium storage. An optimized SnS@SNCF electrode shows high specific capacity of 630 mA h g−1 at 0.1 A g−1, good rate capability and superior cyclic stability in half-cell. It also shows potential in SnS@SNCF//Na3V2(PO4)3 full cells.

Freestanding Mo2C-decorating N-doped carbon nanofibers as 3D current collector for ultra-stable Li-S batteries

Chaoqun Shang, Lujie Cao, Mingyang Yang, Zhenyu Wang, ... Zhouguang Lu

Pages 375-381

Abstract

The shuttle effect in Li-S batteries caused by high solubility of lithium polysulfides (LiPSs) results in rapid capacity decay and low Coulombic efficiency. To address these issues, we propose a strategy to suppress the shuttle effect by constructing freestanding N-doped carbon nanofibers with well-distributed conductive Mo2C nanoparticles (Mo2C-NCNFs) as 3D current collectors for Li-S batteries. DFT calculations demonstrate that the Mo2C possesses strong and stable adsorption affinity to LiPSs, thus effectively alleviating the shuttle effect. The 3D interconnected nanofibers possess the advantages of high electronic conductivity, structural integrity, fast electrochemical reaction kinetics, and very few dead volumes from inactive additives. As a result, a promising electrochemical performance with a good combination of high specific capacity of 1086 mAh g−1 at 0.2 C, extremely stable cycling performance of over 250 cycles without obvious capacity fading. This strategy is enlightening in designing high performance electrodes for Li-S batteries.

Designing a self-healing protective film on a lithium metal anode for long-cycle-life lithium-oxygen batteries

Yue Yu, Yan-Bin Yin, Jin-Ling Ma, Zhi-Wen Chang, ... Xin-Bo Zhang

Pages 382-388

Abstract

The development of high energy density Li-O2 batteries is hindered by many scientific and technological challenges, especially the intrinsic corrosion of the lithium metal anode induced by O2, H2O and discharge intermediates in electrolytes. In response, as a proof-of-concept experiment, we first propose and demonstrate a facile and highly efficient strategy for the in situ growth of a self-healing protective film on a lithium metal anode, wherein tetraethyl orthosilicate plays a key role as a novel film-forming electrolyte additive. This additive can spontaneously and effectively react with the main component of the detrimental surface corrosion layer (lithium hydroxide) on the lithium metal anode, forming a self-healing protective film with dynamic repair ability during the cycling process. Unexpectedly, the protected lithium metal anode endows the Li-O2 batteries with significantly improved battery cycle performance (up to 144 cycles). We consider that our facile, low-cost, and highly effective lithium protection strategy presents a new avenue to address the daunting corrosion problem of lithium metal anodes in Li-O2 batteries, which can be easily extended to other metal-O2 battery systems such as Na-O2 batteries.

Flower-shaped lithium nitride as a protective layer via facile plasma activation for stable lithium metal anodes

Ke Chen, Rajesh Pathak, Ashim Gurung, Ezaldeen A. Adhamash, ... Yue Zhou

Pages 389-396

Abstract

Unstable solid electrolyte interphase (SEI) layer formation and uncontrolled lithium (Li) dendrites growth are two major obstacles that hinder the application of Li metal as the anode in Li batteries. To solve these problems, a multifunctional protective layer was designed for the first time using N2 plasma activation of the Li metal. A highly [001] oriented and flower shaped Li3N layer was obtained on the surface of Li metal with a plasma activation time less than 5 min. Due to high Young's modulus (48 GPa) and high ionic conductivity (5.02×10-1 mS cm-1), this unique protective layer can physically block the direct contact between reactive Li metal and the liquid organic electrolyte, and suppress the Li dendrites formation. It gives rise to a stable voltage profile with plating/stripping for 30,000 min in a symmetric cell. For Li/LCO full cell, the plasma activated Li3N electrode shows better capacity retention of more than 96% and higher capacity at a 5 C rate compared to bare Li anode. This plasma activation strategy provides a facile, scalable and efficient approach to realize a safe Li metal battery with superior electrochemical performance.

2D mesoporous MnO2 nanosheets for high-energy asymmetric micro-supercapacitors in water-in-salt gel electrolyte

Jieqiong Qin, Sen Wang, Feng Zhou, Pratteek Das, ... Zhong-Shuai Wu

Pages 397-404

Abstract

Two-dimensional (2D) mesoporous nanosheets as electrodes present a critical materials platform for dramatically boosting the performance of planar micro-supercapacitors (MSCs) due to their unique features of interconnected porous network, enriched nanopore arrays, and high specific surface area. However, efficient strategies for constructing such complicated mesoporous architectures are very limited. Here, we developed a supramolecular bottom-up self-assembly strategy for direct synthesis of ultrathin mesoporous manganese dioxide (m-MnO2) nanosheets for high-energy all-solid-state planar asymmetric MSCs (AMSCs). The m-MnO2 nanosheets exhibited ultrathin thickness of 10 nm, uniformly interconnected network of mesopores with size of 5–15 nm, high surface area of 128 m2 g−1, and remarkably enhanced capacitance of 243 F g−1 at 1 mV s−1 in comparison with non-mesoporous MnO2 nanosheets (123 F g−1). Further, all-solid-state AMSCs were assembled based on m-MnO2 nanosheets as positive electrode, porous VN nanosheets as negative electrode, and electrochemically exfoliated graphene as conductive agent and metal-free current collector in “water-in-salt” gel electrolyte. Importantly, our all-solid-state AMSCs operated stably at 2.0 V and offered impressive energy density of 21.6 mWh cm−3, outperforming most reported MnO2 based MSCs, and two times higher than lithium thin-film batteries (≤10 mWh cm−3). Also, they presented long-term cycling stability with 90% capacity retention after 5000 cycles, outstanding flexibility without observable capacitance decay under different bending angles, and facile serial and parallel interconnection for creating high-voltage and high-capacitance integrated bipolar cells. Therefore, our proposed strategy will open many opportunites for patterning novel 2D mesoporous metal oxide nanosheets for high-performance microscale electrochemical energy storage devices.

Long-life Li–CO2 cells with ultrafine IrO2-decorated few-layered δ-MnO2 enabling amorphous Li2CO3 growth

Yangjun Mao, Cong Tang, Zhichu Tang, Jian Xie, ... Xinbing Zhao

Pages 405-413

Abstract

Li–CO2 cell recently has captured an increasing interest since it can directly convert chemical energy of greenhouse gas CO2 into electric energy. However, there is still a great challenge to realize long-term cycling of Li–CO2 cell due to the sluggish CO2 reduction/evolution kinetics. In this work, we prepared a highly efficient, ultrafine IrO2-decorated thin-layered δ-MnO2 catalyst (IrO2/MnO2) which was directly grown on carbon cloth. The superior catalytic activity of IrO2/MnO2 enables highly reversible deposition/removal of thin-layered amorphous Li2CO3 on the surface of IrO2/MnO2 nanoflakes, leading to high capacity and long cycle life of the Li–CO2 cells. At 100 mA g−1, Li–CO2 cell with the IrO2/MnO2 catalytic cathode can deliver a high capacity of 6604 mA h g−1. In a capacity-limited charge/discharge mode (1000 mA h g−1), Li–CO2 cell with the IrO2/MnO2 cathode can maintain stable cycling of over 300 cycles at 400 mA g−1. In a full charge/discharge mode over a wide electrochemical window (2–4.5 V), the cell can also maintain stable cycling at high current densities (1070 mA h g−1 remained after 200 cycles at 800 mA g−1).

Lithium phosphorus oxynitride as an efficient protective layer on lithium metal anodes for advanced lithium-sulfur batteries

Weiwen Wang, Xinyang Yue, Jingke Meng, Jianying Wang, ... Zhengwen Fu

Pages 414-422

Abstract

Developing high-energy-density Li-S batteries are highly promising for next-generation electrochemical energy storage. The unstable solid electrolyte interphase (SEI) formed on the Li metal anode and the subsequent notorious growth of Li dendrites during the cycle inevitably plague the practical application in the field. Herein, a facile and mass-produced method to modify the Li metal anode is proposed by establishing a dense and homogenous LiPON coating on the Li metal anode via nitrogen plasma-assisted deposition of electron-beam reaction evaporation. This method enables a high deposition rate up to 66 nm min-1. For Li metal, the LiPON coating serves as a highly ionic conductive, chemically stable and mechanically robust protective layer, which suppresses the corrosion reaction with organic electrolytes and promotes uniform Li plating/stripping, thus enabling a stable and dendrite-free cycling of the symmetric Li metal cells for over 900 cycles under a current density up to 3 mA cm-2. Using the LiPON-coated Li as anode, the Li-S pouch cell (sulfur loading: 7 mg cm-2) was obtained with a specific energy density of ~300 Wh kg-1, a relatively stable Coulombic efficiency of ~91% and an extended lifespan of over 120 cycles with respect to 1.0 Ah capacity retention. Our approach could lead to the practical application of high-energy-density Li-metal-based batteries.

Stable three-dimensional metal hydride anodes for solid-state lithium storage

Fangjie Mo, Xiaowei Chi, Sangpu Yang, Feilong Wu, ... Fang Fang

Pages 423-428

Abstract

Since the discovery of metal hydrides as a conversion-type anode in lithium-ion batteries in 2008, many metal hydrides have been investigated for lithium-ion battery anodes. Although much progress has been made, metal hydrides still face severe challenges such as poor first cycle reversibility, low electrical conductivity, and high reactivity with liquid electrolyte. Here we demonstrate a three-dimensional hierarchical metal hydride/graphene composite (LiNa2AlH6/3DG) that shows the best performance among reported metal hydride anodes. LiNa2AlH6 nanoparticles are uniformly anchored on graphene nanosheets which self-assemble into the 3D microflowers hierarchical structure, and exhibit outstanding cycling stability with LiBH4 as a solid electrolyte. An ultra-high capacity of 861 mA h g−1 at the current density of 5 A g−1 and a long cycle life of 500 cycles with capacity retention of 97% are demonstrated. These findings pave the way for designing nanoscale metal hydrides as electrode materials in solid-state lithium batteries.

Microwave/freeze casting assisted fabrication of carbon frameworks derived from embedded upholder in tremella for superior performance supercapacitors

Yunqiang Zhang, Song Yang, Shulan Wang, Xuan Liu, Li Li

Pages 447-455

Abstract

Three-dimensional squamous hierarchical porous self-supporting carbon frameworks (SSCF) with abundant heteroatoms are prepared through a versatile method combining both the microwave pre-treatment and freeze casting. The microwave and freeze casting treatment promote the formation of ordered pore structures by enhancing the uniform dispersion of KOH within the biomass materials and efficiently avoid the re-aggregation of tremella cell walls. The SSCF has a large accessible surface area (884.1 m2/g) induced by two-dimensional interconnected hierarchical porous carbon nanosheets (IPC1-0.25 activated by appropriate KOH dosage (mtremella:mKOH = 1:0.25)), which is beneficial for abundant ion storage and fast ion transfer. In addition to the electrostatic adsorption, the doped heteroatoms also can provide the faradic contribution. The IPC1-0.25 showed a high specific capacitance of 585.1 F/g and 401.1 F/g at a current density of 0.2 and 1 A/g in 2 M H2SO4, respectively. A record aqueous energy density for biomass carbonous materials of 34.3 W h/kg at the power density of 140 W/kg was verified in 2 M Li2SO4 (pH = 1.8) electrolyte. This work provides an environmentally benign and effective approach for the development of a high-capacitive sustainable biomass carbon-based electrode material.

Electrochemical study of pseudocapacitive behavior of Ti3C2Tx MXene material in aqueous electrolytes

Hui Shao, Zifeng Lin, Kui Xu, Pierre-Louis Taberna, Patrice Simon

Pages 456-461

Abstract

In this paper, a multiple potential step chronoamperometry (MUSCA) technique is used to analyze the electrochemical behavior of pseudocapacitive Ti3C2Tx MXene material. MUSCA allows for reconstruction of cyclic voltammograms with considerably lower ohmic drop contribution. As such, the voltammogram current responses from the surface and bulk processes can be precisely deconvoluted at any given potentials, especially at high scan rates. An electrochemical kinetic analysis of the Ti3C2Tx electrode using the calculated voltammograms showed that the surface process dominates at higher scan rate while the bulk process takes over at the low scan rate in both acidic and alkaline electrolytes. By minimizing the ohmic drops, the MUSCA method is presented to be a useful tool to study the natural electrochemical behavior of pseudocapacitive electrodes and to help designing better energy storage systems.

• Hierarchical vertical graphene nanotube arrays via universal carbon plasma processing strategy: A platform for high-rate performance battery electrodes

Bo Ouyang, Dongliang Chao, Guichong Jia, Zheng Zhang, ... Rajdeep Singh Rawat

Pages 462-469

Abstract

Tailoring graphene-based nanostructures with numerous edges and large porosity is critical in developing high-capacity and fast rate-response Na-ion battery. Here, we report a rapid and generalized strategy for preparation of hierarchical vertical graphene nanotube (hVGT) array via carbon plasma processing of CuO nanowires. A plausible mechanism is provided with the successful extension of such approach to grow hVGT array on different nanostructure templates such as Ni3S2, NiO and Co3O4. Benefiting from such unique structural advantages including high electrical conductivity, strong mechanical stability and highly porous structure, the self-supported MoS2 nano-crystals anchored hVGT (MVGT) nano-frameworks deliver satisfactory Na-ion storage properties with enhanced rate capability and long-term cycling stability. Hence, it is worth emphasizing that this deterministic and plasma-based dry-synthesis method to fabricate hVGT architecture could provide new avenues in designing and fabricating high-performance carbon-based electrodes for energy storage devices.

Concentrated electrolytes unlock the full energy potential of potassium-sulfur battery chemistry

Lu Wang, Jingze Bao, Qin Liu, Chuan-Fu Sun

Pages 470-475

Abstract

Rechargeable K-S batteries provide a theoretical energy density almost double that of the current Li-ion batteries. However, in practice, this energy potential is largely compromised predominantly because of the dissolution and shuttle reactions of the redox intermediates in the commonly used electrolytes. Herein, we demonstrate for the first time that a 5 M concentrated electrolyte can effectively mitigate this parasitic effect and enables a full energy utilization of the K-S battery chemistry. The prototype K-S batteries operating at an average discharging voltage of 2.1 V deliver a discharging energy density of ~1270 Wh/kgS or ~700 Wh/kg(K2S3), which reaches the theoretical limit and is ~40%–100% higher than those of the current Li-ion batteries. X-ray powder diffraction analysis provides the first unambiguous evidence that the K-S battery chemistry involves reversible stepwise phase transformations of S8⇔K2S6⇔K2S5⇔K2S4⇔K2S3. This work shines a light on the full utilization and in-depth mechanistic understanding of high-energy-density K-S batteries.

The non-ohmic nature of intercalation materials and the consequences for charge transport limitations

A.V. Ledovskikh, T.W. Verhallen, M. Wagemaker

Pages 476-490

Abstract

Accurate modeling of the internal battery resistance is imperative in predicting the state of charge and state of health. A mathematical model has been developed that, in addition to the ionic transport, introduces an accurate description of the electronic transport in the porous semiconducting LiFePO4 electrodes. The model is based on the fundamental principles of electrochemistry, electrochemical kinetics, and semiconductor physics, combining them in an efficient model. This framework provides for the non-ohmic nature of semiconductor electrode materials and their current dependent conductivity. The model is validated by comparison with experimental data of Li-ion concentration profiles. It is demonstrated that the mass transport of the electrons, typically simplified or considered negligible in calculation models, have a significant influence on the electrode kinetics and therefore on the current dependent internal resistance of the battery. The accurate description of the internal resistance and the related heat production under various cycling conditions allows the design of safer battery electrode architectures. Additionally, the model allows optimization of the electrode components for various loading regime, increasing the effective energy density leading to decreasing demand for materials and costs. The present model, its principles, and methods are generally applicable and can be used for the description of the wide range of energy storage materials and systems where combined ion and electron transport takes place.

An ant-nest-like cathode substrate for lithium-sulfur batteries with practical cell fabrication parameters

Ran Yu, Sheng-Heng Chung, Chun-Hua Chen, Arumugam Manthiram

Pages 491-499

Abstract

Electrochemical performances of lithium-sulfur batteries have received much progress in recent years. However, their practical deployment encounters challenges with respect to optimizing the cell-fabrication parameters (e.g., amounts of the active material and electrolyte). We present here an “ant-nest-like” cathode substrate with unique architecture to synchronously attain high electrochemical performance and necessary cell-fabrication parameters. The cells with a high sulfur loading (11.5 mg cm−2), a high sulfur content (75 wt%), and a low electrolyte/sulfur ratio (9 μL mg−1) display a high areal capacity and energy density of, respectively, 7 mA h cm−2 and 14 mW h cm−2 with a capacity retention of 70% after 150 cycles. Moreover, the cells exhibit a low self-discharge behavior with a low self-discharge constant of 0.0013 per day and a long rest period of one month. These dynamic and static electrochemical stabilities are attributed to the ant-nest-like structure and low surface area of the cathode substrate that allows, respectively, the accommodation and encapsulation of a high amount of active material and reduces the consumption of electrolyte.

Electrode thickness matching for achieving high-volumetric-performance lithium-ion capacitors

Daliang Han, Zhe Weng, Pei Li, Ying Tao, ... Quan-Hong Yang

Pages 133-138

Abstract

For lithium-ion capacitors (LICs), the electrode mass balancing and the electrode potential tuning are two techniques that have been widely used to maximize the gravimetric specific capacity and voltage to achieve a maximum gravimetric energy density. However, it is also great important to consider the volumetric performances of energy storage devices for the compact and portable applications. Herein, for achieving high-volumetric-performance LICs, we propose an electrode thickness matching strategy, which is to minimize the thickness of thick cathodes as close to the one of thin anodes as possible via increasing the gravimetric specific capacity and density of cathode materials. It is demonstrated that introducing a highly dense but porous activated carbon/graphene (AC/G) composite rather than the low-density traditional activated carbon as the cathode material, the volumetric energy density of the assembled AC/G//graphite LIC can be increased by 62% to reach a maximum of 98 Wh L-1, which represents one of the highest records for the contemporary LICs. We believe that the thickness matching should be a universal strategy for achieving high volumetric performances and can be applicable to other electrochemical energy storage devices.

Observation of combination displacement/intercalation reaction in aqueous zinc-ion battery

Lutong Shan, Yongqiang Yang, Wanying Zhang, Huijie Chen, ... Shuquan Liang

Pages 10-14

Abstract

Rechargeable aqueous Zinc-ion batteries (ZIBs) are regarded as the promising battery chemistry in stationary grid energy storage applications. Exploration of new zinc storage mechanism concepts is a feasible way to achieve high energy/power density. Herein, for the first time, we demonstrate the combination displacement/intercalation (CDI) reaction mechanism in aqueous ZIBs, as an example in Zn/Ag0.4V2O5 system. Unlike the classical intercalation/deintercalation storage mechanism, the CDI reaction mechanism enables more Zn2+ ions insertion into the host structure in two different sites, i.e. most of Ag+ in Ag0.4V2O5 replaced by Zn2+, and classical intercalation of Zn2+ in Ag0.4V2O5 and Zn2(V3O8)2. Importantly, the in-situ generation of highly conductive Ag0 matrix within the electrode provides high electronic conductivity. As a result, the Ag0.4V2O5 cathode performs excellent rate capability as well as long-term cycling performance (stable capacity of 144 mA h g−1 after 4000 cycles at 20 A g−1)..

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