Synergistic Reduction and Oxidation Resistant Interface Modifier for High-Voltage and High-Loading Solid-State Lithium Batteries

Abstract

Solid-state batteries (SSBs) with high-voltage cathodes and Li-anodes offer promising energy density and safety for next-generation batteries. However, poor contact and electrochemical instability of solid electrolyte interfaces hinder their long-term performance. Traditional rigid solidification interlayers possess restricted capability to address these issues. Herein, a composite buffer interlayer (CBI) with localized high-concentration electrolytes (LHCEs) in a flexible polymer scaffold, tackling contact and stability problems and ensuring a perfect interface is developed. The extended electrochemical window provides it with synergistic antioxidation and antireduction capabilities, making it compatible with high-voltage cathodes and Li anodes, while an in situ formed LiF-Li₃N rich inorganic interface ensures uniform lithium deposition and prevents dendrite formation. This CBI enables lithium symmetric cells to achieve a super high critical current density of 7.2 mA cm⁻². Most impressively, coupled with a high-voltage LiNi_0.83Co_0.12Mn_0.05O₂ cathode (NCM83), the full cell achieves 94.1% capacity retention after 125 cycles (coulombic efficiency >99.8%) at a mass loading of 14.6 mg cm⁻² and a high voltage of 4.45 V. Additionally, a pouch cell with 17.2 mg cm⁻² NCM83 achieves an initial discharge capacity of 3.82 mAh cm⁻² an superior cycling stability (75 cycles, 89% capacity retention), showcasing the practical potential of LHCE-CBI enabled SSBs.