Phytate lithium as a multifunctional additive stabilizes LiCoO2 to 4.6 V

Abstract

The practical application of LiCoO₂ at 4.6 V suffers from the devastating H1-3 metastable phase transition, severe interfacial side reactions due to aggressive oxygen species and cobalt loss, as well as thermal run-away in commercial scenarios. Herein, the multifunctional additive phytate lithium (PL) is proposed to tackle the aforementioned issues. The strong chelating capability of PL for Co significantly enhances the structural stability, inhibiting the detrimental H1-3 phase transition and cobalt dissolution. Moreover, benefiting from the PL-enabled robust cathode-electrolyte-interphase and oxygen radical annihilation ability of PL, the parasitic interfacial side reactions are considerably suppressed. Moreover, the flame-retardant property of PL is favorable to improving the thermal stability of LIBs. As a result, the PL-reinforced LiCoO₂ demonstrates an excellent cyclic performance with a capacity retention of almost 90% after 200 cycles at 4.6 V. More importantly, a pouch cell consisting of a PL-LCO cathode and a Li anode achieves an extremely high energy density of 503 W h kg⁻¹ and an impressive cycling performance with a capacity retention of 86.5% after 100 cycles. This cathode additive strategy provides a simple and compatible strategy for current industrial manufacturing to stabilize the 4.6 V LiCoO₂.