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.

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 BaTiO3/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.