表面相变原位构筑V2O5/VOx异质结及其储锌稳定性研究

层状V2O5具有锌离子快速传输通道和钒氧化物中最高的理论比容量，是水系锌离子电池最有潜力的正极材料之一。然而，溶解和脆弱的结构导致其比容量快速衰减。本项目拟通过氧缺陷诱导V2O5表面相变为低价氧化钒的方法，原位构筑V2O5/VOx（1.5＜x＜2.5）异质结来解决这一难题。利用VOx保护层低溶解度和稳定的结构分别抑制体相V2O5溶解和结构粉化，而其高电子和离子导电性则提供高速电子和离子传输通道，改善V2O5循环性的同时不损害比容量和倍率性能。探究精确调控氧缺陷浓度和扩散深度的方法，制备VOx相化学成分、晶体结构和厚度可控可调的V2O5/VOx异质结，揭示影响储锌稳定性的关键因素和电化学储锌机理。此项目开发了构筑异质结的新方法，在V2O5表面原位沉积低价氧化钒，克服了传统包覆材料电化学活性低和离子导电性差的限制，将构筑出循环稳定、比容量高和倍率性能好的水系锌离子电池正极材料。

The layered V2O5 is a very promising candidate for aqueous zinc ion battery because of rapid diffusion channels for zinc ions and the highest theoretical specific capacity among vanadium oxides. But dissolution and poor structural stability lead to quick capacity decay. This project intends to solve this problem by constructing in-situ V2O5/VOx (1.5<x<2.5) heterostructure through surface oxygen defects induced phase transformation of V2O5 nanowires into low-valent vanadium oxide. The surface layer VOx serves as a protective layer, whose low solubility and stable structure can inhibit bulk V2O5 dissolution and material pulverization respectively, while high electron and ion conductivity provide high-speed electron and ion transmission channels. It stabilizes the cycle performance of V2O5 without sacrificing its specific capacity and rate performance. The method of accurately controlling the concentration and diffusion depth of oxygen defects is investigated to prepare V2O5/VOx heterostructure with controllable and adjustable phase chemical composition, crystal structure and thickness of VOx layer. The mechanism of electrochemical zinc-ion storage and the key factors affecting electrochemical stability are to be revealed. This project provides a new method of surface phase transformation for constructing in-situ heterostructure, which overcomes the limitations of traditional coating materials with low electrochemical activity and poor ionic conductivity, and will build a series of aqueous zinc-ion cathode materials with a high specific capacity, good rate performance, and cycle stability.