高电压自支撑聚阴离子型正极材料的结构设计及储锌性能研究

Aqueous zinc ion batteries (ZIBs) have been regarded as one of the ideal choices for the next energy storage devices owing to their high safety, low cost and abundant resources. However, due to the higher charge and heavier mass of Zn2+(vs. Li+), serious solvation effect and large diffusion barrier, Zn2+ is difficult to embed in the cathode material of ZIBs. There are few kinds of cathode materials that can effectively store Zn2+, especially high-voltage cathode materials. Na3V2(PO4)2F3 has been considered as potential high-voltage cathode material owing to its high redox voltage and excellent structural stability. Nevertheless, the electronic conductivity is low and the zinc storage mechanism is not clear. This project intends to prepare free-standing Na3V2(PO4)2F3/C composite electrode by solvothermal method with mild reagent to construct micro-nano composite structure composed of nano-Na3V2(PO4)2F3 and in-situ coated conductive carbon layer. The composite structure can improve the conductivity and then enhance the cycle and rate performance. This project can explore the structure-activity relationship between its electrochemical properties and its structure, and also study its electrochemical zinc storage mechanism by in-situ experiments and theoretical calculation. These results will provide a certain theoretical basis for the research and development of cathode electrode materials for aqueous ZIBs with high voltage, high stability and long life.

水系锌离子电池因其安全性能高、成本低、锌资源丰富等优点被认为是下一代储能装置的理想选择之一。但是，锌离子的电荷高且其原子质量大，溶剂化效应严重，扩散能垒大，导致锌离子不易嵌入材料中，有效存储锌的正极材料种类较少，尤其是高电压的储锌电极材料。氟磷酸钒钠因具有高的氧化还原电位和优异的结构稳定性等优点成为非常有发展潜力的高电压储锌电极材料。然而，这类材料的电子电导率低，而且其电化学储锌机制尚不明确。本项目拟选用温和的试剂通过溶剂热法低温制备自支撑的氟磷酸钒钠/碳复合电极，构建由纳米氟磷酸钒钠和原位包覆的导电碳层组成的微纳复合结构，提高材料的导电性，从而改善其循环性能及倍率性能，探究其电化学性能与其结构之间的构效关系。利用原位实验手段结合理论计算，深入探讨其电化学储锌机制。本项目研究将为设计高电压、高稳定性、长寿命的水系锌离子电池正极材料的研发提供一定的理论基础。

水系锌离子电池因其安全性能高、成本低、锌资源丰富等优点被认为是下一代储能装置的理想选择之一。但是，锌离子的电荷高且其原子质量大，溶剂化效应严重，扩散能垒大，导致锌离子不易嵌入材料中，有效存储锌的正极材料种类较少，尤其是高电压的储锌电极材料。氟磷酸钒钠和磷酸钒钠因具有高的氧化还原电位和优异的结构稳定性等优点成为非常有发展潜力的高电压储锌电极材料。然而，这类材料的电子电导率低，而且其电化学储锌机制尚不明确。本项目拟通过微波水热法联合后续热处理制备氟磷酸钒钠@还原氧化石墨烯复合电极和氟磷酸钒钠@碳管复合电极，构建由纳米氟磷酸钒钠和原位包覆的导电碳层组成的微纳复合结构，提高材料的导电性，增强材料的动力学参数，从而改善其循环性能及倍率性能，探究其电化学性能与其结构之间的构效关系。氟磷酸钒钠@还原氧化石墨烯电极在0.5 C下可以提供126.9 mAh g-1的比容量，1.48/1.57 V的高氧化还原电位，在高倍率20 C下可以提供93.9 mAh g-1的比容量，在15 C下循环5000圈每圈容量损失率仅为0.0074%。氟磷酸钒钠@碳管自支撑电极在高倍率20 C可以传递66.5 mAh g-1的比容量，在5 C下循环4000圈比容量可以保持在67.5 mAh g-1。以溶液法联合后续热处理获得的磷酸钒钠-碳布自支撑复合电极在10 C下循环100圈比容量保持在41.6 mAh g-1。利用原位X射线衍射，非原位透射电镜、非原位X射线光电子能谱证明氟磷酸钒钠的可逆锌离子脱嵌机制。本项目研究将为设计高电压、高稳定性、长寿命的水系锌离子电池正极材料的研发提供一定的理论基础。