Dual-salt-additive reinforced commercial carbonate-based electrolytes for 4.7 V high-voltage practical Li-ion and Li-metal batteries

Abstract

The commercial lithium hexafluorophosphate (LiPF₆)/carbonate electrolyte system, despite dominating lithium-ion battery technologies for over three decades, remains fundamentally constrained by two critical flaws, including insufficient thermodynamic stability, resulting in aggressive lithium dendrites growth and severe cathode-electrolyte reactions at high voltages, coupled with the instability of the LiPF₆ against moisture. Herein, we introduce a dual-salt additive of 0.1 mol L⁻¹ (M) lithium difluorophosphate (LiDFP) and 0.1 M lithium nitrate (LiNO₃) into the commercial carbonate electrolyte. Both NO₃⁻ and DFP⁻ anions mainly dominate in the first solvation sheath of Li⁺ and simultaneously enrich in the inner Helmholtz plane (IHP) at the electrode surface, leading to the formation of a uniform and inorganic-rich interphase dominated by LiF, Li₃PO₄, and Li₃N, effectively stabilizing electrode interfaces. Consequently, the optimized electrolyte enables stable Li⁺ intercalation/deintercalation in graphite anodes, and cycling of over 500 cycles for 4.7 V-class Li||NCM811 batteries. Remarkably, due to the strong interaction between NO₃⁻ and H₂O molecules, this electrolyte also exhibits astonishing stability toward water. This dual-salt additive strategy bridges the gap between laboratory innovation and industrial practicality, offering a scalable, cost-effective electrolyte engineering solution for next-generation high-voltage lithium metal batteries compatible with existing manufacturing protocols.