One-pot synthesis of LiAlO2-coated LiNi0.6Mn0.2Co0.2O2 cathode material

Abstract

For the first time, a one-pot synthesis of LiAlO₂-coated LiNi_0.6Mn_0.2Co_0.2O₂ particles, using a continuous stirred-tank reactor, is reported. Two methods of surface coating were compared with the pristine sample. The composition and morphology of the coated and uncoated cathode materials were characterised by MP-AES, XPS, SEM, and EDX. ²⁷Al MAS NMR coupled with structural characterisation of the materials confirms the presence of a coating layer of LiAlO₂ on the surface of the NMC particle with partial diffusion of Al³⁺ from the surface coating to the NMC structure. By comparing electrochemical performances and thermal stabilities of the coated and uncoated NMC particles at high temperature (45 °C) and at high cut-off voltage (3.0–4.4 V vs. Li⁺/Li), the coated samples indicate a significant improvement in cycling performance (specific capacity, capacity retention, and rate capability). EIS confirms that the LiAlO₂ coating layer prevents side reactions resulting in reduced cathode electrolyte interphase formation and charge-transfer resistance.