Enabling Stable Electrode|Electrolyte Interfaces via Electrolyte Regulation for High-voltage Lithium-ion Batteries

Despite their long cycle life and safety, the energy densities of conventional lithium-ion batteries (LIBs) remain inadequate for use in long-range electric vehicles. Increasing the charging cut-off voltage enhances the energy density but is limited by the oxidative instability of conventional carbonate electrolytes at high voltages. To address this issue, we enhanced the electrochemical stability of carbonate-based electrolytes by incorporating a lithium salt, lithium difluorophosphate (LiPO₂F₂), with film-forming additives such as fluoroethylene carbonate (FEC) and vinylene carbonate (VC). The additives synergistically form robust cathode electrolyte interface and solid electrolyte interphase layers, suppressing interfacial reactions and polarization to improve high-voltage performance. Benefiting from the synergistic interfacial regulation enabled by LiPO₂F₂ and FEC/VC, Li||LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cells exhibited a 23.8% improvement in capacity retention after 300 cycles within a voltage range of 3 V-4.5 V. More importantly, under commercially relevant conditions using graphite (Gr) and NCM811 electrodes, the modified electrolyte enabled the Gr||NCM811 pouch cells to deliver a remarkable improvement of 73% in capacity retention after 200 cycles. The electrolyte additive strategy reported herein not only offers new insights into interfacial stabilization for both anode and cathode electrodes but also offers a simple, scalable, and practical approach toward enabling the commercialization of high-voltage and high-energy-density LIBs.