Yang Zhe, Zhong Jianjian, Zheng Chaoliang, Wei Zhicheng, Feng Jiameng, Li Jianling
State Key Laboratory of Advanced Metallurgy, School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China.
ACS Appl Mater Interfaces. 2022 Aug 10;14(31):35822-35832. doi: 10.1021/acsami.2c09779. Epub 2022 Jul 27.
Anionic charge compensation creates conditions for realizing high capacity and energy density of Li-ion batteries cathode materials. However, the issues of voltage hysteresis, capacity attenuation, and structure transformation caused by the labile anionic redox are still difficult to solve fundamentally. The superstructure formed by a Li-Mn ordered arrangement is the intrinsic reason to trigger the anionic charge compensation. In this work, manganese-based cathode materials with series of Li-Mn ordered superstructure types have been prepared by an ion exchange method, and superstructure control of the anionic redox behavior has been synthetically investigated. With the dispersion of a LiMn superstructure unit, the aggregation of Li vacancies in Mn slab is gradually inhibited, which eliminates the production of O-O dimers and improves the reversibility of oxygen redox. Therefore, the voltage hysteresis and capacity fading have been significantly improved. Meanwhile, the amount of reactive oxygen species and their capacity contribution is reduced, and the sluggish electrochemical reaction kinetics of anion requires a low current density to boost the high-capacity advantage. This paper provides effective ideas for the design of various superstructures and the rational utilization of anionic redox.
阴离子电荷补偿为实现锂离子电池正极材料的高容量和能量密度创造了条件。然而，由不稳定的阴离子氧化还原引起的电压滞后、容量衰减和结构转变等问题仍难以从根本上解决。锂-锰有序排列形成的超结构是引发阴离子电荷补偿的内在原因。在这项工作中，通过离子交换法制备了具有一系列锂-锰有序超结构类型的锰基正极材料，并综合研究了阴离子氧化还原行为的超结构调控。随着锂锰超结构单元的分散，锰板中锂空位的聚集逐渐受到抑制，消除了O-O二聚体的产生，提高了氧氧化还原的可逆性。因此，电压滞后和容量衰减得到了显著改善。同时，活性氧物种的数量及其容量贡献降低，阴离子缓慢的电化学反应动力学需要低电流密度来提升高容量优势。本文为各种超结构的设计和阴离子氧化还原的合理利用提供了有效思路。
