Jia Kai, Wang Junxiong, Zhuang Zhaofeng, Piao Zhihong, Zhang Mengtian, Liang Zheng, Ji Guanjun, Ma Jun, Ji Haocheng, Yao Wenjiao, Zhou Guangmin, Cheng Hui-Ming
Tsinghua Shenzhen International Graduate School &Tsinghua-Berkeley Shenzhen Institute (TBSI), Tsinghua University, Shenzhen 518055, China.
Frontiers Science Center for Transformative Molecules, School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
J Am Chem Soc. 2023 Apr 5;145(13):7288-7300. doi: 10.1021/jacs.2c13151. Epub 2023 Mar 6.
Recycling spent lithium-ion batteries (LIBs) has become an urgent task to address the issues of resource shortage and potential environmental pollution. However, direct recycling of the spent LiNiCoMnO (NCM523) cathode is challenging because the strong electrostatic repulsion from a transition metal octahedron in the lithium layer provided by the rock salt/spinel phase that is formed on the surface of the cycled cathode severely disrupts Li transport, which restrains lithium replenishment during regeneration, resulting in the regenerated cathode with inferior capacity and cycling performance. Here, we propose the topotactic transformation of the stable rock salt/spinel phase into NiCoMn(OH) and then back to the NCM523 cathode. As a result, a topotactic relithiation reaction with low migration barriers occurs with facile Li transport in a channel (from one octahedral site to another, passing through a tetrahedral intermediate) with weakened electrostatic repulsion, which greatly improves lithium replenishment during regeneration. In addition, the proposed method can be extended to repair spent NCM523 black mass, spent LiNiCoMnO, and spent LiCoO cathodes, whose electrochemical performance after regeneration is comparable to that of the commercial pristine cathodes. This work demonstrates a fast topotactic relithiation process during regeneration by modifying Li transport channels, providing a unique perspective on the regeneration of spent LIB cathodes.
回收废旧锂离子电池（LIBs）已成为解决资源短缺和潜在环境污染问题的紧迫任务。然而，直接回收废旧LiNiCoMnO（NCM523）正极具有挑战性，因为在循环后的正极表面形成的岩盐/尖晶石相在锂层中由过渡金属八面体产生的强静电排斥严重干扰了锂的传输，这限制了再生过程中的锂补充，导致再生后的正极容量和循环性能较差。在此，我们提出将稳定的岩盐/尖晶石相进行拓扑转变为NiCoMn(OH)，然后再变回NCM523正极。结果，在具有减弱静电排斥的通道（从一个八面体位置到另一个八面体位置，经过四面体中间体）中，锂传输顺畅，发生了具有低迁移势垒的拓扑再锂化反应，这大大改善了再生过程中的锂补充。此外，所提出的方法可以扩展到修复废旧NCM523黑粉、废旧LiNiCoMnO和废旧LiCoO正极，其再生后的电化学性能与商业原始正极相当。这项工作通过修改锂传输通道展示了再生过程中快速的拓扑再锂化过程，为废旧LIB正极的再生提供了独特的视角。
