Self-induced corrosion of Ni-rich cathode materials by fluor-lithium salts

Abstract

Fluor-lithium salts have been found for the serious aluminum collector corrosion in lithium-ion batteries. Herein, we unexpectedly observe that adding 10 wt% fluor-lithium salts into Ni-rich cathode can lead to irreversible decay of the initial discharge capacity. The capacity loss is related to the surface phase corrosion of Ni-rich cathode materials, where the local nickel ions work as catalytic sites to induce the breakage of the C-F bond in fluor-lithium salts, promoting the decomposition of fluor-lithium salts under the driving force of external voltage exceeding 1.93 V. The formation of F⁻ anion will attack Ni-rich cathode surface to produce nickel fluoride, resulting in the layered to rock-salt phase transformation. No corrosion behavior was found for iron, cobalt, and manganese of cathode materials. The synergistic activation by both nickel ions and voltage causes fluor-lithium salts to corrode the Ni-rich cathode materials.