钠离子电池用高稳定性锰基层状正极材料研究

Sodium-ion batteries (SIBs) are promising in large-scale energy storage due to the low cost and abundance of sodium. Manganese-based layered oxides have been one of the most popular cathodes due to the high reversible capacity via use of earth-abundant elements. However, Mn-based layered oxides always meet the serious issues of chemical and electrochemical stability, when exposed to moisture air or electrochemically cycled in organic electrolyte. This project will mainly focus on finding solution to elevate the chemical and electrochemical stability of Mn-based layered oxides and then improve sodium storage performance. We will carry out in-depth investigation on the mechanism for chemically inserting H2O or CO2 into Mn-based layered oxides, reveal the relationship between various electrolytes and manganese dissolution in electrochemical cycling process, employ bulk doping and surface modification to further optimize the composition and microstructure of Mn-based layered oxides, additionally construct the multiphase intergrowth to enhance the structural stability of Mn-based layered oxides during charging and discharging. Consequently, this project will develop highly stable Mn-based layered oxides for superior sodium storage performance and provide new insight into the design of high-performance electrodes for SIBs.

钠离子电池资源丰富、价格低廉，是大规模储能技术的理想选择。锰基层状氧化物由低成本元素组成，并且可逆容量大、结构灵活可调，因此作为钠离子电池正极材料具有极大的应用前景。然而，层状锰基氧化物当暴露于空气或电化学循环时，常常遇到严重的化学稳定性和电化学稳定性的问题。本项目旨在为锰基层状材料的稳定性问题提供解决方案，从而改善材料的电化学储钠性能。本项目将深入研究锰基层状材料在湿态空气中的水或二氧化碳化学嵌入材料的微观机制，揭示不同电解液体系对锰溶解的影响，采用多种体相掺杂和表面修饰优化锰基层状材料的组成和微观结构，另外也通过构筑多相共生结构，增强充放电过程中的结构稳定性。本项目力争发展具有高环境稳定性的钠离子电池用锰基层状正极材料，也可为高性能电极材料的设计提供新思路。

钠离子电池具有资源丰富、价格低廉、环境友好等优点，表现出与锂离子电池相近的电化学行为，因此被认为是下一代大规模储能技术的理想选择，近年来迎来一个研究热潮。通常来说，正极材料的比容量、电压和循环寿命是影响钠离子电池的能量密度、安全性和循环表现的关键因素。层状锰基储钠正极的结构灵活性与原料丰富为发展低成本大容量的室温钠离子储能电池奠定了基础。本项目主要围绕构筑高性能钠离子电池锰基层状正极材料方面开展研究，通过多种手段对钠离子电池锰基层状正极材料的基础性质进行了系统的研究，并开发了多种高效的策略来提升此类材料的稳定性，例如双金属共掺杂、阴阳离子协同作用、设计双相结构、引入氧空位、利用钉扎效应、使用新型粘结剂等，有效抑制了不利的姜—泰勒畸变、相变、Mn溶解和颗粒裂纹等，实现了低至0.6%的晶格应变和1000圈的稳定循环，为设计先进的钠离子电池铺平了道路。此外，本项目还通过设计复合相实现了204 mA h g−1的高可逆容量，并有效提高了离子扩散动力学性能；利用金属掺杂将层状锰基正极材料的钠离子扩散系数提升至10-10~10-11 cm2 s-1；利用阴离子氧化还原实现了层状锰基正极材料理论容量的突破，并通过合适的金属掺杂抑制了晶格氧的流失。本项目的实施为设计新型高性能钠离子电池用锰基层状正极材料和实现钠离子电池产业化提供了丰富的理论和实验支撑。