Kinetic characteristics up to 4.8 V of layered LiNi_1/3Co_1/3Mn_1/3O₂ cathode materials for high voltage lithium-ion batteries

Understanding the structure properties in deep delithiated states and electrochemical kinetics in the high potential window of LiNi_1/3Co_1/3Mn_1/3O₂ (NCM) cathode materials is essential to advance their performance in rechargeable lithium-ion batteries for 5 V chemistry. Here we report a layered single-phase NCM showing great structural reversibility and without H3 phase formation when charged up to 4.8 V at least for 5 cycles. However, the poor cluster scale conductivity results in inactive material in thick electrode during cycling, approximately 10% (w/w), may corresponding to the reduced capacity respective to thin electrode. The Co³⁺/Co⁴⁺ redox peaks are found clear and stable for cycles, lying between 4.5 ∼ 5.0 V. That is tightly correlated to the fast Li-ion kinetic, i.e., the electrochemical behaviour of the NCM material is not limited by Li⁺ diffusion but behaving like in a thin layer. That is very different from previously reports on charge transfer mechanisms of cathode materials for lithium-ion batteries.