Synchronous dual additives to boost multiphase interface stability of high-voltage Li-rich Mn-based batteries

Abstract

High-voltage lithium-rich manganese-based oxides (LRMOs) are expected to become next-generation mainstream cathodes due to their higher voltage, higher specific capacity and lower cost. However, currently commercialized carbonate electrolytes still face the challenge of poor decomposition of solvents and lithium salts at high voltage, leading to serious interface side reactions and electrochemical performance degradation. Herein, we propose an interfacial chemical modification strategy based on the dual additives of fluoroethylene carbonate (FEC) and tris(trimethylsilyl)phosphate (TMSPa), to promote Li⁺ migration and ensure long-term cycling stability of LRMO-based batteries. Detailed characterization reveals that the dual additives FEC-TMSPa can promote the desolvation process of Li⁺ and reduce the adverse decomposition of electrolyte components by regulating the solvation structure of the electrolyte. Simultaneously, dual additives can facilitate the formation of a robust cathode electrolyte interphase (CEI)/solid electrolyte interphase (SEI) rich-in F/P/Si species, thereby reducing the interface side reactions, inhibiting the erosion of acidic substances on electrodes, and promoting the uniform deposition/stripping of Li⁺. As a result, the high-voltage LRMO-based batteries exhibit excellent rate performance and cycling stability, with a capacity retention of 82.36% after 500 cycles at 30 °C, and 86.9% after 150 cycles at a high-temperature of 55 °C, suggesting that the proposed strategy of synergistically regulating the interface chemistry with multiple additives is anticipated to facilitate the further application of high-voltage layered cathode materials.