Reversible Mn/Cr dual redox in cation-disordered Li-excess cathode materials for stable lithium ion batteries
Reversible Mn/Cr dual redox in cation-disordered Li-excess cathode materials for stable lithium ion batteries
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DOI：
10.1016/j.actamat.2021.116935
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发表时间：
2021-05
期刊：
影响因子：
9.4
通讯作者：
Xuerong Zheng;Zhengrui Xu;Shaofeng Li;Yuxin Zhang;Jinfeng Zhang;C. Kuai;L. Tao;Muhammad Mominur Rahman-Muha
中科院分区：
文献类型：
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作者：
Xuerong Zheng;Zhengrui Xu;Shaofeng Li;Yuxin Zhang;Jinfeng Zhang;C. Kuai;L. Tao;Muhammad Mominur Rahman-Muha
阳离子无序的锂过量氧化物/氟氧化合物为设计替代的高能阴极打开了大门。然而，实现长循环寿命和高倍率能力是无序岩盐阴极(DRX)的主要挑战。在这里，我们通过独特的氧化还原机械力化学方法制备了Li2Mn3/4Cr1/4O2F(LMCOF)DRX材料。LMCOF含有三价Cr3+和Mn3+，允许在传统碳酸盐电解液可接受的窄电压窗口下同时访问稳定的Mn/Cr双氧化还原。与缓解和可逆的氧化学变化相结合，LMCOF在不同电流密度下的1000次循环中提供了高容量、高倍率能力和长循环寿命。多尺度同步加速器和中子散射、光谱和成像分析表明，容量来源于Mn/Cr双氧化还原，氧氧化还原的贡献很小，良好的循环寿命归因于稳定的全球晶体结构和局部氧化学环境。
Cation-disordered Li-excess oxides/oxyfluorides have opened the door for designing alternative, high energy cathodes. However, achieving long cycle life and high rate capability represents a major challenge for disordered rocksalt cathodes (DRX). Herein, we develop Li2Mn3/4Cr1/4O2F (LMCOF) DRX materials through a distinct redox mechanochemical method. The LMCOF contains trivalent Cr3+and Mn3+, which allows for simultaneously accessing stable Mn/Cr dual redox at a narrow voltage window acceptable for conventional carbonate electrolytes. Coupled with the mitigated and reversible oxygen chemical changes, the LMCOF delivers high capacity, rate capability, as well as long cycle life upon extensive 1,000 cycles at various current densities. The multiscale synchrotron and neutron scattering, spectroscopic, and imaging analyses demonstrate that the capacity originates from the Mn/Cr dual redox with minimal contribution from oxygen redox, and that the good cycle life is attributed to the stable global crystal structure and local oxygen chemical environment.