Li Lingjun, Chen Jiaxin, Huang He, Tan Lei, Song Liubin, Wu Hong-Hui, Wang Chu, Zhao Zixiang, Yi Hongling, Duan Junfei, Dong Ting
Changsha University of Science and Technology, Changsha 410004, China.
Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong 999077, China.
ACS Appl Mater Interfaces. 2021 Sep 15;13(36):42554-42563. doi: 10.1021/acsami.1c06550. Epub 2021 Aug 31.
Residual Li and oxygen vacancies in Ni-rich cathode materials have a great influence on electrochemical performance, yet their role is still poorly understood. Herein, by simply adjusting the oxygen flow during the high-temperature sintering process, some LiO can be carried into the exhaust gas and the contents of residual Li and oxygen vacancies in LiNiCoMnO cathodes can be accurately controlled. Residual Li reduces the surficial Li diffusion coefficient, thereby limiting the rate property of the cathode. Oxygen vacancies affect the oxygen release energy in the crystal, and the lowest oxygen release energy is found at an oxygen vacancy concentration of 8.35%, resulting in an unstable structure and thereby poor cycle performance. The Ni-rich cathode with low residual Li and oxygen vacancy contents exhibits superior capacity retention (89.55 and 77.66%) at 2C after 300 cycles between 2.7-4.3 and 2.7-4.5 V. These findings clarify the role of residual Li and oxygen vacancies in Ni-rich cathode materials and provide a simple way to obtain high-performance Ni-rich cathodes for high-energy-density Li-ion batteries.
富镍正极材料中的残余锂和氧空位对电化学性能有很大影响，但其作用仍知之甚少。在此，通过在高温烧结过程中简单地调节氧气流量，一些LiO可以被带入废气中，并且可以精确控制LiNiCoMnO正极中残余锂和氧空位的含量。残余锂降低了表面锂扩散系数，从而限制了正极的倍率性能。氧空位影响晶体中的氧释放能量，在氧空位浓度为8.35%时发现最低的氧释放能量，导致结构不稳定，从而循环性能较差。具有低残余锂和氧空位含量的富镍正极在2.7 - 4.3 V和2.7 - 4.5 V之间进行300次循环后，在2C下表现出优异的容量保持率（89.55%和77.66%）。这些发现阐明了残余锂和氧空位在富镍正极材料中的作用，并提供了一种简单的方法来获得用于高能量密度锂离子电池的高性能富镍正极。
