Antioxidant Layer Enables Chemically Stable Cathode-Electrolyte Interface Towards Durable and Safe Li-Ion Batteries

Abstract

Although nickel-rich layered lithium transition metal oxides are one of the most promising candidates for high energy-density Li-ion batteries in electric vehicle applications, they yet suffer from irreversible capacity fading and poor safety properties due to the unstable cathode-electrolyte interphase (CEI), especially at high voltage and high temperature. This instability is mainly caused by the attack of free radicals generated from electrolyte decomposition and active oxygen species (especially singlet oxygen) released from the surface lattice. Here, we propose a novel modification method to construct a protective antioxidant layer on the surface of LiNi0.8Co0.1Mn0.1O2 (NCM). By scavenging free radicals and singlet oxygen, the antioxidant layer greatly reduces the interfacial side reactions and significantly suppresses irreversible rock-salt phase transitions and the associated oxygen species release, leading to the stabilization of the interface. As a result, superior electrochemical performance and enhanced thermal stabilities are achieved. Specifically, the modified NCM exhibits a capacity retention of 92.0% over 1000 cycles in full cells and a dramatic increase of onset temperature (T1) from 75.2 °C to 114.2 °C. This antioxidant layer modification by scavenging free radicals and singlet oxygen provides a new strategy for addressing challenges of CEI design, which is theoretically applicable to all layered transition metal oxide cathode materials.

Keywords: Lithium-ion batteries, Surface engineering, Nickel-rich layered cathode, Cathode-electrolyte interface, Singlet oxygen