Synergistic Spatiotemporal Regulation of Li ⁺ ‐Flux During Formation Enables Stable Solid‐Electrolyte Interphase for Ah‐Level Si/C Anode‐Based Quasi‐Solid‐State Lithium Batteries

ABSTRACT

In practical Si/C anode‐based quasi‐solid‐state lithium batteries, the solid‐electrolyte interphase (SEI) instability arises from spatial heterogeneity and temporal accumulation of Li ⁺ ‐flux during conventional constant‐current formation. Here, we report a synergistic spatiotemporal regulation strategy for Li ⁺ ‐flux to guide uniform SEI evolution specifically during formation. Spatially, a piezoelectric BaTiO ₃ /poly(vinylidene fluoride)‐block‐poly(tetrafluoroethylene) gel polymer electrolyte film is constructed, which utilizes a local polarization electric field to promote a more uniform Li ⁺ ‐flux distribution near the electrode–electrolyte interface. Temporally, a bipolar pulse formation protocol is employed, which interrupts continuous Li ⁺ accumulation via discontinuous current input, providing necessary Li ⁺ relaxation periods. This synergy optimizes the spatial pathway and temporal rhythm of Li ⁺ at the early SEI formation stage, suppressing potential fluctuations and local Li ⁺ enrichment. Consequently, a smooth, dense, high‐modulus SEI is formed between the anode and electrolyte. Benefiting from this robust SEI, Ah‐level NCM811||Si/C full cells exhibit enhanced interfacial stability and prolonged cycling performance. This work highlights the critical role of formation‐process engineering in stabilizing the SEI and offers a practical route toward high‐performance quasi‐solid‐state lithium batteries.