Insight into thermal analysis kinetics of surface protected LiNi0.8Co0.15Al0.05O2 cathode for safe lithium-ion batteries

Surface modification of Ni-rich cathode families has gained the most market interests towards energy-dense lithium-ion batteries (LIBs) due to its ability to strengthen LIBs electrochemical performance. Beyond current understandings, our study of thermal analysis kinetics has first revealed the indispensable role of surface coating against thermal decomposition, which is determinative for LIBs safety and large-scale commercialization. Al2O3 surface protection engages to induce inorganic-rich solid electrolyte interface (SEI) against its decomposition. Furthermore, it limits the formation, propagation and expansion of nanopores and dislocations inside particles, thus restraining transformation-metal ion dissolutions and oxygen releasing, which are the main reason to the stepwise thermal runaway and particle pulverization. Combined with the Arrhenius equation and non-isothermal kinetic equation, the kinetic triplet and decomposition mechanisms are well-defined for the first time, inherently elucidating the reduced decomposition rate and better safety caused by Al2O3-coating. This study has provided kinetic fundamentals and new insights of surface coating towards stable Ni-rich cathode and safe LIBs.