Fine-Tuned Synthesis for Reducing Residual Lithium in Ni-Rich Cathode Materials for Lithium-Ion Batteries

Incidentally generated residual lithium on the surface during the synthesis of Ni-rich cathode materials for lithium-ion batteries has been considered one of the most serious problems to be solved. In this work, a suitable condition for simple washing and post-heat treatment with additional lithium salt process for preparing LiNi0.8Co0.1Mn0.1O2 is optimized through a systematic evaluation. By varying amount of additional lithium salt, the most appropriate input is found to be 5 wt % in terms of electrochemical performance, such as initial capacity, capacity retention, and rate capability. In addition, it is verified by several techniques that it has the ideal composition (lithium/transition metal = 1:1) and the stable structure of R3̅m. From electrochemical impedance spectroscopy, it is found that the good performance of the cell assembled using the optimized material is originated from lowering resistance between the cathode and the electrolyte.