Application Of Anode Materials Based On Multi-electron Transfer Reaction In Sodium Ion Batteries

Lithium-ion batteries?LIBs?are booming and widely used in various fields currently,but limited lithium resources have aroused people's concerns about the future energy markets.Compared with lithium,sodium resources is widespread in nature,sodium-ion batteries?SIBs?is an alternative for lithium-ion batteries can effectively reduce costs,which is beneficial to large-scale electric energy storage applications in future and attracts more and more attention.It has always been a hot issue in the field of energy storage to find and optimize high-capacity anode materials,which is one of the main bottlenecks in the development and application of sodium-ion batteries.Electrode materials that participate in electrochemical reactions by applying multiple electrons are an effective way to achieve high capacity.However,these multi-electron reactive materials still face several key challenges,such as poor rate performance,inferior stability,etc.,in order to solve these problems and achieve their high performance of batteries.The use of carbon-based materials is an effective strategy.Because carbon materials have the advantages of abundant resources,low price,and good electrical conductivity,the combination with other anode materials can effectively improve the electrochemical performance of the materials.Therefore,based on the above analysis,three different materials which involve multi-electron transfer in the electrochemical reaction were selected and evaluated as anode of SIBs in my work,the electrochemical performance was optimized with various forms of carbon materials.The main research contents are as follows:Firstly,TiNb2O7 was successfully synthesized by a facile solvothermal method and evaluated its electrochemical performance as anode of SIBs.In order to improve its performace,TNO/CNTs composites was synthesized.Compared with pure TiNb2O7,a high reversible capacity reaches 261.1 mAh g^-1 at 50 mA g^-1 after 200 cycles.In addition,a prominent rate capability maintains¹10 mAh g^-1 at 500 mA g^-1 with over1000 cycles.The improvements have been explained by the corresponding kinetics analysis.Secondly,Sb6O13 was prepared via a facile method has been evaluated as anode material for sodium ion batteries.Based on the previous chapter,Sb6O13/CNTs was synthesized.Compared with Sb6O13,Sb6O13/CNTs showed an obviously enhanced electrochemical performance with a reversible capacity of 308.7 mA h g^-1 at 100 mA g^-1 after 350 cycles,which was much higher than Sb₆O₁₃.Even at 1000 mA g^-1,a capacity of 158 mA h g^-1 was obtained for Sb6O13/CNTs compared to 47 mA h g^-1 of Sb6O13.Finally,crystalline VPO4 was synthesized.In this chapter,carbon-coating was applied to improve its electrochemical performance.Benefiting from the core/shell structure,c-VPO4@C remained a reversible capacity of 209.4 mAh g^-1 after 150cycles at 100 mA g^-1,which was much higher than 19 mAh g^-11 of c-VPO4.Ex-situ XRD were introduced to explore the fundamental electrochemical mechanism of c-VPO4 anode during charge/discharge processes.