Stress-adaptive conductive network and ion-segregated polymeric-inorganic interphases enable durable room-temperature silicon-based solid-state batteries

Silicon negative electrodes could increase energy density of solid-state lithium-ion batteries, however, their practical development is impeded by severe volume expansion, sluggish lithiation kinetics, and unstable solid-solid interphases. Here we develop a stress-adaptive micrometer-sized Si-Zinc-amorphous carbon composite negative electrode integrated with an elastic salt-segregated poly(vinylidene fluoride-co-hexafluoropropylene) solid electrolyte. A weakly bonded interface between silicon and nitrogen- and fluorine-doped amorphous carbon mechanically decouples silicon expansion from the conductive framework, preserving electrical connectivity during cycling. Concurrently, the preferential formation of lithium-zinc alloy enhances electronic transport and homogenizes stress distribution. The salt-segregated electrolyte further generates polymeric-inorganic bilayer solid-electrolyte interphases, consisting of a lithium fluoride/lithium oxide-rich inner layer that facilitates interfacial ion transfer and a compliant polymeric outer layer that accommodates repeated volume changes. This synergistic electrode-electrolyte design enables high capacity and stable cycling stability of solid-state batteries at 26 °C. Notably, full cells assembled with LiFePO4 and LiNi0.8Co0.1Mn0.1O2 positive electrodes exhibit long-term durability over 2000 and 800 cycles, respectively. At 2 mAh cm−2 and 0.02 A g−1, the solid-state cell delivers 337 Wh kg−1 based on positive/negative materials and solid electrolyte. Silicon electrodes promise higher-energy solid-state batteries but suffer from expansion and unstable interfaces. Here, authors combine a stress-adaptive silicon composite with a layered polymer-inorganic interface to enable fast charging and long-term cycling.