Graphene-Confined Silicon and a Li6.5La3Zr1.5Ta0.5O12-Reinforced Plasticized Poly(ethylene oxide) Electrolyte Enable Contact-Stable Solid-State Lithium Batteries

Silicon is a promising anode for solid-state lithium batteries because of its high theoretical capacity, but large lithiation-induced volume changes and unstable electrode/electrolyte contact remain major challenges. Here, a contact-adaptive solid-state silicon (Si) architecture is developed by coupling an electrostatically assembled silicon/reduced graphene oxide (Si@rGO) nanosheet anode with a poly(ethylene oxide) (PEO)–lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)–ethylene carbonate (EC) electrolyte reinforced with 10 wt% Ta-doped Li6.5La3Zr1.5Ta0.5O12 (LLZTO), hereafter denoted PEC-T. Trace EC promotes Li-salt solvation and PEO plasticization, while LLZTO suppresses polymer crystallization and reinforces ion transport. PEC-T shows a reduced melting temperature from 66.7 to 51.4 °C, improved tensile strength and elongation, an ionic conductivity of 3.0 × 10−4 S cm−1 at 30 °C, a Li+ transference number of 0.57, and an oxidative stability limit of ~4.5 V. It also supports stable Li plating/stripping for 600 h at 0.1 mA cm−2. Meanwhile, the rGO framework mitigates irreversible Si thickness evolution and preserves interfacial integrity. Consequently, Si@rGO/PEC-T/Li batteries deliver strong rate capability and maintain 1.8 Ah g−1 after 250 cycles at 1 C, demonstrating a coupled chemo-mechanical strategy for stable solid-state silicon batteries.