Nail penetration-safe LiNi0.6Co0.2Mn0.2O2 pouch cells enabled by LiMn0.7Fe0.3PO4 cathode safety additive

Ni-rich layered oxide materials have become a major choice of cathode material for electrical vehicle batteries. However, it is an outstanding challenge to improve the safety performance of these batteries as the energy density of the batteries increases with higher Ni content in the cathode material. Here we demonstrate that Ni-rich LiNi0.6Co0.2Mn0.2O2 (NCM622) based 10 Ah pouch cells can pass nail-penetration and overcharging tests by introducing nanometer-sized LiMn0.7Fe0.3PO4 (LMFP) particles in the cathode slurry. Since LMFP exhibits appreciable Li storage capacity in the battery operation voltage window, it brings no compromise in electrochemical performance to the cell. It is shown that LMFP improves the safety feature of the cell by partially blocking the NCM622/electrolyte interface, thereby alleviates parasitic reaction between NCM622 and electrolyte, which delays the phase transformation of NCM622 during thermal runaway as well as reduces heat generation between charged cathode and liquid electrolyte.