Trace High‐Concentration Electrolyte Enables Bilateral Interfacial Stability for Layered‐Cathode Based Solid‐State Batteries

ABSTRACT The development of high‐energy‐density garnet‐based solid‐state batteries (SSBs) is hindered by persistent interfacial issues between electrodes and electrolytes. Moreover, the divergent requirements of lithium metal anodes and layered cathodes also make it challenging for a single strategy to stabilize both interfaces. Herein, we report an effective approach to simultaneously stabilize both electrode interfaces by introducing a trace amount of high‐concentration electrolyte (HCE) as a dual‐functional modifier into the LLZO‐(PVDF‐HFP) interfaces. We demonstrate that this trace HCE not only creates an “anchoring effect” to immobilize residual DMF molecules within the PVDF‐HFP matrix, suppressing their parasitic reactivity, but also fundamentally alters the local solvation structure, thereby facilitating the spontaneous formation of robust interphases on both the anode and cathode interface. As a result, the Li||Li symmetric cell achieves exceptional stability for over 2600 h, and the assembled all‐solid‐state Li||NCM811 battery delivers a high initial discharge capacity of 182.49 mAh g −1 and remarkable capacity retention of 80% after 200 cycles. This work demonstrates a single, scalable strategy that resolves the inherent interfacial incompatibility in high‐voltage SSBs, paving the way for practical high‐energy‐density storage systems.