Inhibiting Homogeneous Catalysis of Cobalt Ions towards Stable Battery Cycling of LiCoO2 at 4.6 V

Raising cut-off voltage increases the energy density of LiCoO2 for lithium-ion batteries, but it exacerbates the decomposition of the electrolyte and the capacity decay of LiCoO2. To address such issues, many artificial cathode-electrolyte-interphase (CEI) are constructed to stabilize the cathode interface by additive. However, it is rarely explored for the electrolyte degradation by catalytic oxidation of Co ions dissolved in the electrolytes. Herein, we report a new strategy of additive engineering towards the enhanced cycling stability of LiCoO2 at 4.6 V. We found that the Co4+ ions dissolved in the electrolyte due to interfacial failure degrades the electrolyte rapidly by homogeneous catalysis, which can be deactivated by chelation reaction of nitrilotri(methylphosphonic acid) (ATMP) additive with Co4+. Benefiting from the deactivated Co ions by ATMP, the catalytic oxidation of the electrolyte is suppressed, which is more stable to the LiCoO2 interface than the artificially constructed CEI, and thus the LiCoO2 cathode delivers a high capacity of 197.7 mAh g-1 after 200 cycles at 4.6 V with a retention rate of 91.4%. This work provides new insights into additive engineering towards stable cathode/electrolyte interfaces for next-generation batteries.