Inhibiting homogeneous catalysis of cobalt ions towards stable battery cycling of LiCoO2 at 4.6 V

Abstract

Raising the 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-interphases (CEIs) have been constructed to stabilize the cathode interface with an additive. However, electrolyte degradation by catalytic oxidation of Co ions dissolved in the electrolyte has rarely been explored. Herein, we report a new strategy of additive engineering towards enhanced cycling stability of LiCoO₂ at 4.6 V. We found that the Co⁴⁺ ions dissolved in the electrolyte due to interfacial failure rapidly degrade the electrolyte by homogeneous catalysis, which can be deactivated by the chelation reaction of a nitrilotri(methylphosphonic acid) (ATMP) additive with Co⁴⁺. Benefiting from the deactivation of Co ions by ATMP, the catalytic oxidation of the electrolyte is suppressed, making the LiCoO₂ interface more stable than the artificially constructed CEI, and thus the LiCoO₂ cathode delivers a high capacity of 197.7 mA h 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.