A novel designed trilayer composite solid electrolyte enabling high-areal-capacity all-solid-state lithium batteries with long lifespan

The interface instability between composite solid electrolytes (CSEs) and lithium anode significantly shortens the lifespan of all-solid-state lithium batteries (ASSLBs) with high areal capacity. In this work, a CSE featuring a trilayer architecture is developed by incorporating a thin polyethylene (PE) separator into a blending polymer matrix of poly(ethylene oxide) and poly(vinylidene fluoride) (PEO-PVDF) through a hot pressing technique. This structural design provides complementary functions: the flexible outer layers confine lithium deposition within a restricted area, while the robust interlayer prevents lithium dendrite penetration. Additionally, the incorporation of LiNO₃ significantly enhances the stability of the CSE/Li interface by gradually forming a Li₃N-rich interfacial film, which promotes uniform lithium deposition. Consequently, the assembled Li||Li symmetrical cell demonstrates stable cycling for over 6000 h at a current density of 0.2 mA cm^–2 with an areal capacity of 1.2 mAh cm^–2. More attractively, ASSLBs constructed with the designed CSEs, high mass loading LFP/NCM811 (LFP: LiFePO₄; NCM811: LiNi_0.8Co_0.1Mn_0.1O₂) cathodes (≥ 12 mg cm^–2), and lithium metal anodes deliver superior cycling performance without short-circuiting at current densities of 0.3/0.2 mA cm^–2, respectively. This work offers critical insights for the design of high-performance ASSLBs with improved durability at high areal capacities.