Outstanding enhancements in stability of LiNi0.8Mn0.1Co0.1O2 cathode by AlPO4/ACB double coating: Insights into surface structure and chemistry

Ni-rich layered cathode materials are highly attractive for high energy density lithiumion batteries, which however are facing serious surface issues. The effects of various coating materials on surface stability have been investigated, which mostly focus on exterior coating structure and properties. Herein, we focus on the surface variations of the cathode induced by the AlPO4/acetylene carbon black double coatings. It is the first time to discover that the AlPO4 coating greatly promotes crystallinity and lattice bonded oxygen near the surface of LiNi0.8Mn0.1Co0.1O2, which lead to decrease of Li/Ni disordering. The low ratio of Ni ions mixed in Li slab further prevents the serious Ni ions' dissolution in electrolyte at high potential. Nevertheless, the discontinuous AlPO4 coating layer is unable to suppress the formation of Li2CO3 on surface. Additional carbon coating provides better coverage to effectively isolate the moisture and CO2 in air, and the content of surface Li2CO3 remarkably decreases. Eventually, the AlPO4/acetylene carbon black double coated LiNi0.8Mn0.1Co0.1O2 exhibits greatly enhanced charge/discharge stability at both 25℃ and 55℃.