Zinc is an ideal electrode material for green rechargeable batteries because of its abundant raw materials, light weights, excellent electrical conductivity and ductility, as well as high theoretical specific capacity. The zinc-based aqueous battery with the neutral or weak acidic aqueous solution as electrolyte and zinc as the anode has the characteristics of high security, low cost and non-toxic battery materials, simple preparation process, and environmentally friendly. It has abroad application prospects in the field of storage devices for energy and power-driven battery. However, the problems such as zinc dendrite, hydrogen evolution, corrosion, and passivation during the process of charging and discharging limit its practical application. In this paper, the existing problems and current solutions of zinc anode for zinc-based aqueous batteries were reviewed, and the developmental trend of the anode has prospected.

With the development of science and technology, great progress has been made in portable electronic products, especially in wearable devices. Flexible battery, as the core component of portable electronic products, has attracted attention of more and more researchers. Lithium-ion battery is used as the main power source in a variety of products because of its good cycle performance and long life span. In order to make portable electronic products flexible and miniaturized, the development of flexible lithium-ion batteries with high energy density can be an urgent issue. Flexible electrode materials are regarded as the important research direction because they are key materials for flexible lithium-ion battery. The article describes recent progress on researches about electrode materials for flexible lithium-ion battery, including integrated flexible electrode and new macro-flexibility electrode structure design. The carbon-based materials and Mxene-based materials all belong to integrated flexible electrode with electrochemical activity. The polymer-based materials, textile-based materials and metal-based materials all belong to integrated flexible electrode based on non-electrochemical activity. The new macro-flexibility electrode structure design meets the needs that wearable devices are woven and tolerable of large scale deformation. This paper analyzes and discusses existing problems of flexible electrodes in order to provide new ideas for researches about flexible lithium-ion battery with high energy density in future.

Contents

1 Introduction

2 Integrated flexible electrode design

2.1 Based material with electrochemical active

2.2 Other non-electrochemical activity based material

3 Macro-flexible electrode structure design

3.1 Kirigami structure

3.2 Fiber structure

4 Conclusion and outlook

Lithium-ion batteries(LIBs) have been widely used in portable electronic devices and electric vehicles owing to their characteristics of high energy density, safety, and long lifetime. Titanium dioxide(TiO₂) is a promising anode material for LIBs due to the advantages of non-toxicity, low cost, abundant sources, and stable chemical structure. However, intrinsic low electronic conductivity and poor lithium-ion(Li⁺) diffusion have restricted its development for practical applications. In this review, we firstly systematically summarize the lithium storage mechanisms of three common TiO₂ polymorphs, that is, a two-phase solid solution of anatase TiO₂, intrinsic pseudo-capacitance of TiO₂(B), and potential-dependent phase transition of rutile TiO₂. Furthermore, to enhance the electron conduction and Li⁺ diffusion, the research progress of nanostructure dimensional tailoring, intrinsic/extrinsic electronic structure manipulation(elemental doping, Ti³⁺ self-doping, and modification of highly conductive materials), and hetero-phase junction optimization are discussed in detail. Finally, the development trend and application prospect of TiO₂ anode materials for LIBs and beyond-LIBs are proposed.

The rapid development of electric vehicles and large-scale energy storage systems have created a huge demand for high energy density and power density lithium-ion batteries in the market. Because of the advantages such as high voltage(4.7 V vs. Li/Li⁺), high energy density and power density, abundant resources and low cost, LiNi_0.5Mn_1.5O₄ is considered as one of the most promising lithium-ion battery cathode materials. However, the severe undesirable side reactions between LiNi_0.5Mn_1.5O₄ and electrolyte at elevated temperature leads to worse cycling performance, which limits its commercial application. Therefore, improving the high-temperature performance of LiNi_0.5Mn_1.5O₄ has become one of the research hotspots in the field of lithium-ion batteries. In this paper, the main achievements of recent researches on LiNi_0.5Mn_1.5O₄ materials are reviewed. Starting with the basic characteristics and existing challenges of LiNi_0.5Mn_1.5O₄, strategies such as ion doping, surface coating and surface doping are focused on improving the high-temperature performance. In addition, suggestions and prospects are put forward for subsequent research.

As a kind of green rechargeable battery with high energy density and power density, lithium-ion batteries are the first choice of portable electronic products and are gradually applied in the field of power vehicles. In order to better meet application requirements, it is necessary to further improve the energy density of current lithium-ion batteries. Different from the rapid development of high-voltage anode materials, traditional electrolyte is easy to decompose under high working voltage, which greatly hinders the commercial application of high energy density lithium-ion batteries. As an important component of lithium-ion batteries, electrolyte has an important impact on performance of lithium-ion batteries in many aspects. Therefore, it is urgent to improve the working voltage of electrolyte to solve the problem of low energy density of lithium-ion batteries. In this paper, the research progress of high-voltage electrolyte at home and abroad in recent years is summarized from two aspects of new organic solvent and high-voltage additive, the effect of theoretical calculation on the design of high-voltage electrolyte is introduced, and the development and prospect of high-voltage electrolyte are summarized and forecast.

With the advantages of both lithium ion battery and supercapacitor, lithium ion capacitor battery has become a promising new energy storage system with its advantages of high energy density, high power density, long cycle life and fast charging and discharging. However, some key problems still exist, such as dynamic imbalance, less ideal energy density and poor cycling stability between battery electrode and capacitor electrode. The electrode material is an important part of the battery and seriously affects the overall electrochemical performance. To solve this problem effectively, a variety of new type of anode and cathode electrode materials should be developed in this field. Therefore, this paper introduces in detail the research progress and technical route of cathode(layered metal oxides, graphene composite anode and other novel cathode materials) and anode(transition metal oxides, carbon materials, lithium compounds and sulfides) materials for lithium ion capacitor batteries, and analyzes the existing problems. It is found that the properties of electrode materials can be improved by nano treatment, material coating and heteroatomic doping. At the same time, the future research direction of electrode materials is prospected, and new ideas and means are provided for the research of other chemical power sources.

Lithium-rich manganese-based layered cathode materials (xLi₂MnO₃·(1-x)LiMO₂, M=Ni, Co, Mn, etc.), owing to their high specific capacity (≥ 250 mAh·g^-1), low cost and environmental friendliness, are considered as one of the best candidate cathode materials for the new generation of lithium-ion batteries. However, these materials suffer from severe capacity/voltage fading during the cycle process and low rate capability which seriously hinder commercial development. In this paper, we analyze the structural characteristics and the reasons which lead to the deterioration of the electrochemical performance of the lithium-rich manganese-based layered cathode materials, systematically review the latest progress and achievements on improving the stability of the cathode materials, and the efforts to improve the electrochemical properties of the cathode materials through bulk doping and surface modification. In this process, the effects of bulk doping at different sites and different coating materials on the structure and electrochemical behavior of lithium-rich manganese-based layered cathode materials are further analyzed. Finally, considering the advantages and disadvantages of the two modification methods of bulk doping and surface coating, a joint modification mechanism combining bulk doping and surface coating has been suggested to improve the stability of lithium-rich cathode materials in the long cycle process, and the introduction and prospect of this mechanism are also given.

As a new type of energy storage devices with rapid development momentum, lithium ion batteries(LIBs)alleviate the dependence on fossil fuels in energy field and reduce the increasingly severe environmental pressure. A large number of spent lithium ion batteries are not only hazardous wastes, but also resources with high added value from different perspectives. Therefore, it is of great challenge and practical significance to realize high-efficient recycling and reuse of spent lithium ion batteries with progressively diverse components through innovation and combination of different technical means. Starting from the pretreatment process, the technical means and requirements of a series of processes such as deactivation and discharge, dismantling and classification, crushing and sieving, separation process, acid leaching and impurity removal are described in detail. This review discusses the typical strategies of reuse from three aspects and analyzes the advantages and disadvantages of various techniques in the process of material regeneration, structural repair and re-synthesis of cathode materials. In addition, the harmless treatment and recovery of spent electrolyte are discussed, especially the application of supercritical CO₂ extraction process. Finally, the outlook is put forward in view of the existing problems at the present stage to provide references for subsequent research and industrial applications of spent lithium ion battery recycling.

With the popularity of electronic equipment and the rapid rise of electric vehicle industry, lithium-ion battery, as a source of energy, plays an important role. The production and sales of lithium-ion batteries represented by lithium cobalt oxide, lithium iron phosphate and ternary cathode materials are increasing. At the same time, in order to provide longer life and stability, the research of novel lithium-ion battery cathode materials is also advancing. In this context, the failure mechanism, and recycling of lithium-ion battery cathode materials becomes more and more important. How to solve the problem of waste lithium-ion battery treatment in the downstream is gradually put on the agenda. Based on this, this paper introduces the recycling and regeneration process of spent lithium-ion battery cathode materials from the perspectives of hydrometallurgy and pyrometallurgy, including the optimization of recycling conditions, novel recycling methods and the performance of recycled materials, and summarizes the influence of impurity elements in the recycling process, including aluminum, copper and other elements on the structure and performance of recycled materials Finally, the methods of lithium-ion battery recycling are summarized and prospected.

Electrochemical impedance spectroscopy (EIS) is one of the most powerful experimental methods to study electrochemical systems, and has been extensively used in the analysis of lithium battery systems, especially to determine kinetic and transport parameters, understand reaction mechanisms, and to study degradation effects in past two decades. In this paper, the electrode polarization process in lithium ion batteries which includes three basic physical and chemical processes, namely, electronic transport process, ionic transport process and electrochemical reaction process, is briefly described, and the EIS characteristics of each transport and reaction stage of the three basic physical and chemical processes are discussed, especially the mechanism of inductance formation and contact impedance is expounded in detail. Moreover, porous electrode theory and its application in lithium ion batteries are reviewed, and emphasis is put upon the principle and method of numerical simulation of impedance with physics-based lithium-ion batteries models. Furthermore, the typical EIS characteristics and the attribution of each time constant of the electrode materials for lithium ion batteries such as graphite, silicon, simple binary transition metal oxides, LiCoO₂, spinel LiMn₂O₄, LiFePO₄, spinel Li₄Ti₅O₁₂ and transition metal oxides are also discussed. Finally, the challenges currently faced by EIS are identified and possible directions and approaches in addressing these challenges are suggested.

Contents

The development of electrolyte with high-safety and high-voltage is of significant importance for high performance lithium-ion batteries. Recently, organosilicon electrolytes with unique physicochemical properties have become one of the choices. In this review, the advances of organosilicon compounds both as electrolyte solvents and additives are reviewed from the viewpoint of molecular engineering. The design and performance of organosilicon compounds with carbonate group, carbamate group, nitrile group, ionic liquids group and fluoro substitute as high-voltage and high-safety solvent are described in detail. The versatile organosilicon compounds evaluated as high voltage additive, high safety additive, high/low temperature additive, suppression self discharge additive and acid/water scavenger additive are introduced based on their functional group and reaction mechanism. Research trend and prospects of organosilicon electrolyte are presented finally.

With the commercial application of low specific capacity silicon-carbon composites(<500 mAh/g) in lithium-ion batteries, silicon-based anode materials have also evolved from laboratory research to industrialization. In recent years, various investigations have been proposed to solve the problems caused by the volume change (>300%) of silicon during lithiation/delithiation. From the perspective of material structural design, the research focus has gradually shifted from the initial silicon nano-structuration and elaboration of silicon-based composite materials to the structural design of the silicon-carbon composite secondary particles and the surface coating design. In terms of application performance research, in addition to specific capacity and cycle performance of materials reported in the early literature, the specific surface area, tap density, initial and cyclic coulombic efficiency and other parameters of materials which are more in line with the practical application requirements of the batteries have been widely studied, thus greatly promoting the commercial application process of the silicon-based anode materials. In this review, the development of the composition and structural design of silicon-carbon composites in recent years are presented and summarized. The structural characteristics and electrochemical properties of silicon-carbon composites synthesized by graphite, soft carbon, hard carbon, carbon fiber and graphene as carbon sources are further proposed and compared. Moreover, the effects of carbon in the structure and properties of silicon-carbon composites are briefly summarized. Finally, the selection of carbon material and structural design in the preparation of silicon-carbon composites are discussed and prospected.

As the secondary battery with the highest specific energy, lithium ion battery is widely used in portable electronic devices, new energy vehicles and large-scale energy storage power stations. Currently, commercial lithium-ion batteries are facing some technical bottlenecks, such as low energy density and short service life. There are many reports about the anode materials of lithium ion batteries, but most of them cannot overcome the shortcomings such as the huge volume expansion before and after lithium, the pulverization of electrode materials, and the large electrode impedance. However, metal oxides derived from metal-organic frameworks(MOFs) and composites are widely used in lithium ion batteries due to their low level charge-discharge potential platform, high capacity and stable cycle performance. Therefore, in this paper, metal oxides derived from MOFs and composites are divided into four modules: mono-metal oxides, bi-metal oxides, bi-component metal oxide composites and metal oxide/carbon composites. The relationships between their synthesis methods, morphologies and electrochemical properties are summarized, and the opportunities and challenges for their future development are forecast.

With the continuous improvement of the requirements for the power of lithium-ion batteries in electrical vehicles, high-performance lithium-ion batteries are becoming the focus of researchers. As one of the critical components in lithium-ion batteries, membranes play the role of separating the anode and cathode materials and providing the channels for lithium ions to translate. In addition, the thermal stability of membranes can affect the safety of batteries directly. Polyolefin microporous membranes are widely used in lithium batteries for their excellent chemical stability, high mechanical strengths and low cost. However, the poor thermal stability and wettability bring great hidden danger to the wide application of high-performance lithium-ion batteries. As a result, starting from the surface modification of polyolefin microporous membranes, the paper introduces the research progress of polyolefin microporous membranes which are based on polymer surface modification and inorganic nanoparticles, organic-inorganic composites. When introducing the polyolefin microporous membranes based on inorganic nanoparticles, the paper makes a brief introduction to those advanced surface modification methods such as atomic deposition, the chemical vapor deposition method and the physical vapor deposition method. Subsequently, based on the shortcomings of polyolefin, the research progress of other polymer microporous membranes are introduced with respect to the wet process, the phase inversion method, the breath figure method, electrospinning and the in-situ polymerization. At last, the paper makes an outlook for the future researches of high-performance membranes and means to provide a reference for the research and application of high-performance membranes in lithium-ion secondary battery membranes.

Increasing the voltage is one of the important ways to improve the energy density of lithium ion batteries. For example, LiNi_0.5Mn_1.5O₄ (4.7 V), LiNiPO₄(5.1 V) and lithium-rich manganese-based materials exhibit high energy density and low cost at high charge cut-off voltage, showing good application prospects. In addition, increasing the charge cut-off voltage of LiCoO₂ and NMC battery systems is a simple and effective approach to increase the energy density. However, when the charge cut-off voltage is increased, not only the electrolyte will be oxidatively decomposed at the cathode /electrolyte interface, but also the dissolution of the metal cation from the cathode materials will be accelerated. These are the main causes for the decreased cycle stability and safety. The electrolyte additives can be used for modifying positive electrode interfaces, thus passivating the cathode/electrolyte interface and inhibiting the decomposition of the electrolyte. Moreover, the modified electrolyte can effectively suppress the destruction of the cathode structure. Based on the molecular structure of the additives, the related research results of additives such as sulfonate ester, boric acid ester, phosphate ester, fluorocarbonate, nitrile, anhydride and lithium salt at the positive electrode interface are introduced in this paper. The action mechanisms of different additives are explained and generalized. Furthermore, the combination technology of additives for different batteries are introduced. At last, the development of new electrolyte additives for cathode/electrolyte interface modification are discussed.

Lithium ion batteries(LIBs) have been widely used as the energy storage system for the applications of the laptop, the communication equipment and the consumer electronics. And importantly, it will be largely used in the electrical vehicles in the near future. Silicon with a high theoretical capacity of 4200 mAh·g^-1(more than 10 time of current graphite anode) is one of the most promising alternative anode material for the next generation of LIBs. However, the electrode pulverization, continuous growth of solid electrolyte interphase(SEI) and lithium consumption in silicon anode material based batteries usually happen during charge/discharge process due to its huge volume change. Moreover, the weak interaction between conventional binder and silicon anode material results in the continuous separation of silicon active material. These problems severely hinder the practical application of silicon anode material. This review systematically summarize the recent progress of silicon and its related materials for LIBs. The content includes the fabrication of silicon materials, the structure of silicon materials, binders, electrolytes and electrolyte additives. Finally, the future development direction of silicon-based materials is presented.

Silicon is expected to replace graphite as the next-generation anode material for lithium-ion batteries because of its high theoretical specific capacity. But the huge volume expansion (~300%) of silicon during lithiation/delithiation process will cause active substance pulverization and loss contact with current collector, and continuous formation of solid electrolyte layer will further result in irreversible capacity fading. It has been demonstrated that nanocrystallization and carbon coating are effective ways to overcome these problems. In this paper, the mechanism of capacity fading of silicon is introduced, and the latest research on the synthesis of Si nanoparticles and carbon composites is reviewed, mainly including coating, core-shell and embeded silicon/carbon anode materials. The core-shell and embedded type are specifically reviewed. Finally the problems of the Si nanoparticles/carbon composites are analyzed and the prospects for research are prospected.

Lithium ion batteries, which are secondary battery with the high specific energy, play an increasingly important role in the field of sustainable energy. In order to explore the next generation of lithium ion batteries with higher specific energy density, many electrode materials with high specific capacity are being researched and developed. However, these materials usually display the large volume change during lithiation and delithiation process. Therefore, it is necessary to prepare nanostructures to achieve better electrochemical performance. However, the nanostructure leads to low Coulombic efficiency, poor cycling stability and relatively low specific energy density, which can be ascribed to its high specific surface area and low tap density. The assembly of nanomaterials into a hierarchical structure can effectively reduce the overall specific surface area, and limit the consumption of lithium during the formation of solid state interphase(SEI) film, leading to the increase of the initial Coulombic efficiency. Compared with the disordered build-up of nanoparticles, the hierarchical structure has a higher accumulation density and contact area, thus leading to the decrease of porosity and the increase of build-up density of the electrode materials. Therefore, the hierarchical structure of electrode materials can further increased the specific energy density of lithium ion batteries. In this review,we mainly focus on the preparation of hierarchical structure in lithium ion batteries and its application in lithium ion batteries. In terms of preparation, solvothermal method, emulsion method, spray drying method and template method are mainly described as well as effect of various parameters on the final hierarchical structure. In terms of application, different hierarchical structures are reviewed with the purpose of improving performances of lithium ion batteries as the mainline.
Contents
1 Introduction
2 Fabrication for hierarchical structures
2.1 Solvothermal method
2.2 Emulsion method
2.3 Spray drying method
2.4 Template method
3 The applications of hierarchical structures in lithium ion batteries
4 Conclusion

Given the environmental risk and valuable metal containing nature of spent lithium-ion batteries, it is of great significance to harmlessly dispose of spent lithium-ion batteries and recycle the valuable resources therein. At present, the spent lithium-ion batteries recycling technology is realized mainly through enhanced chemical conversion under high temperature or normal temperature conditions. High temperature boosts the chemical conversion rate of valuable elements in the spent lithium-ion battery, results in a short flow and releases material dependence. Therefore, high temperature chemical conversion is easy to implement in industry, and the related technologies have become one of the hotspots for the recycling of spent lithium-ion batteries. Based on the chemical conversion differences of various phases, this study systematically analyzes and evaluates the physicochemical mechanisms, technical characteristics, and research status of high temperature chemical reduction, roasting with molten salt, and direct regeneration. The advantages and problems of various technologies are compared. Based on this, it is advised that the future research needs in-depth study of its chemical conversion mechanism and takes into account the short flow clean regeneration of materials. It is necessary to develop a low energy-consuming and environmentally-friendly approach to enable the green treatment and recycling of spent lithium-ion batteries based on the principle of green chemistry.
Contents
1 Introduction
2 Pyrometallurgy recovery technology
2.1 High temperature reduction
2.2 Sulfation roasting
2.3 Direct regeneration
2.4 Discussion
3 Challenges and Prospects
4 Conclusion

"With the development of mobile communication equipment and electric cars, there is an increasing demand for high capacity lithium-ion batteries. It is difficult for the present commercialized lithium-ion power batteries to meet the requirement of one charge to travel above 500 km, because of low discharge capacity, like lithium iron phosphate and ternary cathode material, possessing the discharge capacity lower than 180 mAh/g. Therefore, the specific capacity of cathode materials has become a bottleneck to increase the energy density of lithium-ion batteries. Lithium-rich cathode materials with large specific capacity (≥250 mAh/g), high discharge voltage (3.8 V), and high theory energy density (900 Wh/kg) are thought as ideal cathode material of power batteries for electric cars in the future, so, it is of great realistic significance to study the lithium-rich cathode materials with high specific capacity. This paper reviews the development of cathode materials for lithium-ion batteries as well as the situation of recent commercial cathode materials with low specific capacity. Structures and electrochemical properties of lithium-rich cathode materials as a new next-generation higher capacity are summarized, and the discharge mechanism and the latest progress in modifications are presented. Moreover, some problems related with lithium-rich materials for high energy-density lithium-ion batteries are presented, followed by the corresponding ideas and approaches of solution.

Contents
1 Introduction
2 Structural research of lithium-rich materials
3 Investigation on electrochemical behaviors of lithium-rich materials
3.1 Interpretation on the first charge/discharge
3.2 Interpretation on capacity and voltage fade
4 Modified research on lithium-rich materials
4.1 Surface coating
4.2 Bulk doping
4.3 Nanosizing
4.4 Hierarchical structure
4.5 Concentration-gradient distribution
4.6 Layered/Spinel heterostructure
4.7 Other methods
5 Conclusion

Rechargeable lithium-ion batteries are vital for developing the electronic devices especially for the portable devices, as well as for the rapid development of plug-in hybrid-electric vehicle (PHEV)/electric vehicle (EV). And also, they are good choices for the deployment of power system (peak clipping and valley filling) and introducing the electric power into power system from the renewable energy sources. However, the disadvantages of low energy capacity are often reviled for the traditional lithium-ion batteries. In the past few decades, the researches of seeking substitutes for the traditional graphite anode material, including metal oxide, titanium-, tin- and silicon-based anode materials, have been widely investigated, and their positive effects on the high capacity and rate capability in the lithium half batteries have been demonstrated repeatedly. But to date, there is insufficient data to confirm these effects in lithium-ion full batteries, and very few kinds of anode materials were successfully utilized in commercialization. Thus, the questions of how the development of new anode-based lithium-ion full battery and whether it could be truly commercialized need to be well considered and discussed urgently, as many researchers concerned. At this stage, this review mainly discusses the development of lithium-ion full batteries starting from the irreversible capacity characteristics of anodes (graphite,Li₄Ti₅O₁₂, TiO₂, GeO_x,FeO_x,Sn- and Si-based,etc.) in initial cycles.

Contents
1 Introduction
2 Lithium-ion full batteries based on different anodes
2.1 Anode materials with initial revisable capacity
2.2 Anode materials with initial irrevisable capacity
3 Conclusion

With the rapid development of energy storage power supply and electric cars, development of high energy density for lithium ion battery becomes focus of the future study. The performance of lithium ion battery greatly depends on the cathode materials. At present, there are some defects in widely used inorganic cathode materials such as limited capacity upgrade space, large energy consumption for production process, existence of security risks, etc. Therefore, it is necessary to develop green energy materials with higher specific capacity, better safety performance and abundant reserves in nature. Compared with inorganic cathode materials, organic cathode material is a kind of energy storage material with broad application prospects due to the advantages of high theoretical capacity, abundant resources, environmental friendness, structure design easily and system security. This paper summarizes the researches which have been carried out at home and abroad recent years. Several main kinds of organic cathode materials including conductive polymer, sulfur compounds, nitrogen oxygen free radical compounds and containing oxygen conjugated compounds are introduced. The electrochemical properties, electrochemical reaction mechanism, advantages and disadvantages of these compounds are compared and analyzed. Through the analysis and prospects for the future, the problems need to be solved for cathode materials of lithium ion battery are pointed out, and the future direction for research and improvement of organic cathode materials is proposed.

Contents
1 Introduction
2 Organic conductive polymer cathode materials
3 Organic sulfide cathode materials
4 Organic containing oxygen cathode materials
5 Conclusion and prospect

Silicon has the highest theoretical capacity(4200 mAh ·g^-1) when used as the anode material for lithium-ion batteries. But the severe volume change(> 300%) during Li⁺insertion/extraction processes results in the structural destruction, which further leads to the loss of electrical contact between active materials themselves or active materials and the current collectors. Moreover, the new solid electrolyte interphase (SEI) continually forms on the surface of silicon. All of these problems cause capacity attenuation as well as the poor cycling and rate performance for silicon-based anode materials. In this review, the lithium-storage and capacity fading mechanisms of silicon-based materials for lithium-ion batteries are summarized. To overcome the severe volume change during charge/discharge, selection and structure design of silicon material are introduced. Synthetic routes, electrochemical performance and possible mechanisms of typical silicon-based composite materials, especially various silicon/carbon composite materials, are discussed. An overview of several novel fabrication techniques of the electrodes for improving the electrochemical performance of silicon-based anode materials and their possible mechanisms are given. Challenges and perspectives of silicon-based anode materials are also proposed and discussed.

Contents
1 Introduction
2 Lithium-storage and capacity fading mechanisms
3 Selection and structure design of silicon material
3.1 Amorphous silicon and silicon oxide
3.2 Low-dimensional silicon materials
3.3 Porous and hollow silicon materials
4 Fabrication of silicon-based composites
4.1 Silicon/metal composites
4.2 Silicon/carbon composites
4.3 Other silicon-based materials
5 Optimizing the preparation process of electrodes
5.1 Treatments of electrodes
5.2 Selection of current collectors
5.3 Choices of binders
5.4 Options of electrolyte
6 Conclusion and outlook

Graphite has been used as the negative electrode in lithium ion batteries for more than a decade. But it cant meet the needs of power battery application due to the low specific capacity. To attain higher energy density batteries, tin, which can alloy reversibly with lithium, has been considered as a replacement for graphite. However, tin anodes always suffer from high volume changes during charge/discharge cycling, leading to premature degradation of the anode. Since carbonaceous materials exhibit high electrical conductivity, good mechanical compliance, and stable lithium storage capacities with a small volume expansion, people have paid more attention to them. In order to make full use of the advantages of both tin and carbon, different matrix phases are evaluated for tin-carbon (Sn-C) nanocomposites in this paper. Several carbonaceous materials including amorphous carbon, graphite (G), graphene (GP), carbon nanotubes (CNT), and carbon nanofibers (CNF) have been exploited as an inert and conductive matrix in Sn-based anode materials, thus providing various tin-carbon composite anode materials. After reviewing that , the focus turns to alloys of tin with metal (M) and carbon,forming ternary and multiple composite anode materials. Based on the progress that has already been made on the relationship between the properties and microstructures of Sn-carbon-based anodes, it is believed that manipulating the multi-phase and multi-scale structures could offer important means for further improving the capacity and cyclability of Sn anodes. Overall, the Sn-Co-C-based composite anode materials may open the door to application.

Contents
1 Introduction
2 Sn-C binary composites
2.1 Sn-amorphous carbon
2.2 Sn-G
2.3 Sn-carbon nanomaterials
3 Sn-M-C
3.1 Sn-Co-C
3.2 Sn-Cu-C
3.3 Sn-Sb-C
4 Sn-Ms-C multiple composites
5 Conclusion

Lithium-ion batteries are currently the most widely used rechargeable batteries due to the excellent properties. Transition metal nitrides are expected to be used as efficient anode materials for lithium-ion batteries benefiting from their low and flat charging-discharging plateau, good reversibility and high capacity. This paper aims to review the research progress on transition metal nitrides and their composites synthesized by physical and chemical methods for applications of lithium-ion batteries. The key issues existed in transition metal nitrides and the viable route to improve the performance of transition metal nitrides based lithium-ion batteries are also discussed.

Contents
1 Introduction
2 Transition metal nitrides for lithium-ion batteries
2.1 Physical method synthesis of transition metal nitrides
2.2 Chemical method synthesis of transition metal nitrides
2.3 Transition metal nitrides composite materials for lithium-ion batteries
3 Conclusion and outlook

With rapidly growing application of lithium-ion batteries in electric vehicles and renewable energy storage, there is an increasing demand on high performance batteries in terms of energy density and power density. For anode materials, the traditional graphitized carbon materials cannot meet these requirements, novel high-capacity anode materials are being widely investigated, including Si-based materials. Among them, SiO_x is considered to be a promising anode material for the practical use because it can deliver a high capacity and at the same time produce relatively lower volume change upon cycling compared to pure silicon. This paper summarizes the published works on SiO_x-based anode materials. The basic electrochemical performance, structure model, electrochemical reaction mechanism and synthesis methods of SiO_x powders are systematically reviewed. Methods used to improve electrochemical performance are classified and introduced, emphasized on those of SiO and amorphous SiO₂. These works suggested that the oxygen content, disproportionation level and surface state of SiO_x have significant influence on the electrochemical performance of SiO_x. The interface clusters mixture (ICM) structural model can be used to better understand the nature of the electrochemical reaction processes of SiO_x. Introduction of second phase (carbon, metals, metal oxides, etc.), preparation of porous structure, surface modification and optimization of binder and electrolyte are proved to be effective methods to improve the coulombic efficiency and cycling performance of SiO_x electrode. Batteries with optimized SiO_x-based material showed good cycling stability with 90% capacity retention after 600 cycles. SiO_x-based composite is one of the best promising anode materials for lithium-ion batteries with high energy density.

Contents
1 Introduction
2 Properties of SiO_x material
2.1 Basic electrochemical performance
2.2 Structure
2.3 Mechanism of the electrochemical process
2.4 Synthesis methods
3 SiO_x-based materials
3.1 Compositing with second phase
3.2 Porous structured SiO_x
3.3 Surface modification
3.4 Other factors and issues
4 Conclusion and outlook

Li₄Ti₅O₁₂ as anode materials for lithium ion batteries has been widely studied because of its excellent rate performance and cycle performance, but the low specific capacity (175 mAh/g) limits its application in the future. Compared with Li₄Ti₅O₁₂, niobium based oxides have similar lithium ion insertion/extraction potential and higher specific capacity. In addition,they also have good rate performance and promising to be new anode materials with high power performance, that have got increasing researchers' attention in recent years. In this paper,the crystal structure, electrochemical performance and lithium ion insertion/extraction mechanism of various niobium based oxides materials (Nb₂O₅, TiNb₂O₇, LiNb₃O₈, etc.) are reviewed. The effects on lithium ion transfer and storage performance originate from component, particle morphology and preparation technology are discussed. Meanwhile, the influencing mechanism is also summarized. In addition, the generality in electrochemical lithium insertion and extraction behavior of niobium based oxides materials, the differences and similarities compared with Li₄Ti₅O₁₂ are summarized the tendency and prospect of them as anode materials for high power lithium ion batteries in the end are also discussed.

Contents
1 Introduction
2 Research status of Nb-based oxides anode materials for lithium ion battery
2.1 Niobium oxides
2.2 Titanium niobium oxides
2.3 Lithium niobium oxides
2.4 Potassium niobium oxides
2.5 Vanadium niobium oxides
2.6 Other niobium based oxides
3 Understand of intercalation and deintercalation of lithium ion for niobium based oxide
4 Summary

At present, carbonaceous materials are extensively adopted as an anode for commercial lithium-ion batteries. Zero-strain lithium titanate is generally considered as a more safe and long-life span anode compared with carbonaceous materials, and it will find specific applications in various fields such as hybrid electric vehicles, wind-light-electricity grids, and smart grids. However, the lithium-ion batteries using the lithium titanate as anode will easily swell during the charge-discharge cycle and storage, thus resulting in shell distortion, gas evolution, performance deterioration, and so on. This greatly prevents the practical application of lithium titanate.In this paper, the industrial developments of the four kinds of lithium-ion batteries using the lithium titanate anode are reviewed, and the associated cathode materials are Li (Ni_x Co_y Mn_1-x-y) O₂, LiMn₂O₄, LiFePO₄, and LiCoO₂, respectively. The latest research progress of the gas evolution mechanism is summarized from the perspectives of the interfacial characteristics, the water content, the electrolyte reductive decomposition, the negative electrode potential, and the impurities. At the same time, combined with the author's research work, the improving measures are put forward from the viewpoints of material, process, and application. Finally, the key issues and prospects of gassing are also commented.

Contents
1 Introduction
2 Industry status of lithium ion battery using lithium titanate as anode materials
3 Interface properties of lithium titanate material
4 The mechanism of gas evolution in lithium-ion batteries using an anode based on lithium titanate
4.1 Moisture
4.2 In the decomposition of electrolyte solution of lithium titanate electrode surface
4.3 Gas evolution reaction and the negative electrode potential
4.4 Impurities
5 Method to suppress gas evolution in lithium-ion batteries using an anode based on lithium titanate
5.1 Remove water or acid
5.2 Optimization of electrolyte
5.3 Surface treatment of lithium titanate material
5.4 Battery temperature and gas evolution
5.5 Optimization of lithium titanate battery manufacture process
6 Conclusion and outlook