Improved Performance of Lithium Metal Batteries Based on Dry‐Processed Composite Solid‐State Electrolyte via Interfacial Engineering Method

Composite solid‐state electrolytes (CSEs) paired with high‐voltage cathode materials have emerged as a promising candidate for next‐generation lithium metal batteries (LMBs). However, interfacial incompatibility between electrodes and polymer‐ceramic components severely hinders their electrochemical performance. Herein, we synthesized a dry‐processed CSE via thermal extrusion blending of dual active fillers, Li _6.25 Al _0.25 La ₃ Zr ₂ O ₁₂ (LALZO) and LiTa ₂ PO ₈ (LTPO), into PVDF‐HFP/PEO/SN polymer matrices and LiTFSI salt. To enhance interfacial compatibility and structural integration, a poly(ethylene glycol) diacrylate (PEGDA) cross‐linked buffer layer (PDF‐CSE) was utilized. This layer synergistically interacts with lithium difluoro(oxalato)borate (LiDFOB) and lithium difluorophosphate (LiDFP), facilitating the formation of robust solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) layers. The resulting PDF‐CSE exhibited stable Li plating/stripping cycling stability over 2500 h at a current density of 0.5 mA cm ⁻² with an areal capacity of 1 mAh cm ⁻² . Our PDF‐CSE assembled with a polyacrylonitrile‐coated single‐crystal LiNi _0.86 Co _0.05 Mn _0.05 Al _0.04 O ₂ (PS‐NCMA86) cathode exhibited a high discharge capacity of 130.48 mAh g ⁻¹ after 500 cycles at 0.5C (2.8–4.3 V), with a capacity retention of 80.23% and a coulombic efficiency of 99.86%. The electrolyte demonstrated remarkable cycling stability over 100 cycles at a high voltage of 4.5 V. Our novel interfacial engineering approach paves the way for advanced high‐energy density LMBs.