posted on 2021-08-31, 19:38authored byLingjun Li, Jiaxin Chen, He Huang, Lei Tan, Liubin Song, Hong-Hui Wu, Chu Wang, Zixiang Zhao, Hongling Yi, Junfei Duan, Ting Dong
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 Li2O can be carried into the exhaust gas and the contents of residual
Li and oxygen vacancies in LiNi0.825Co0.115Mn0.06O2 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.