A boron-nitride based dispersive composite coating on nickel-rich layered cathodes for enhanced cycle stability and safety

While Ni-rich cathodes have been widely adopted in high-energy lithium-ion batteries, there remains room for improvement regarding their cycle stability and safety. Herein, hexagonal boron nitride (h-BN) is demonstrated, for the first time, to be an effective surface modification additive for Ni-rich cathodes. The h-BN coated Ni-rich cathode, prepared via a rapid low-temperature post-calcination process, shows markedly improved cycle stability and safety with only a trace amount of h-BN being added (1 wt% relative to the cathode oxide). Systematic synchrotron post-mortem and operando X-ray analyses reveal that the improvements could be attributed to the anion-trapping ability of the B atoms in h-BN, which mitigates surface Ni-ion reduction and carbonate accumulation caused by electrolyte corrosion during both cycling and thermal runaway. Furthermore, the high thermal conductivity of h-BN contributes to efficient heat dissipation during the early stages of thermal runaway and therefore delays the onset temperature. This work identifies h-BN as well as the concept of "anion-trapping" as promising strategies for enhancing the cycle life and safety of Ni-rich cathodes and presents an industrially facile method to accomplish such applications.