Due to the increasing demand and wide applications of lithium-ion batteries, higher requirements have been placed on the energy density and safety. Polymer solid-state electrolytes have gained significant popularity due to their excellent interface compatibility and safety. However, their applications have been greatly restricted by the high crystallinity at room temperature, which hinders the transport of lithium ions. Herein, we utilize inorganic tubular fillers with abundant lone-pair atoms to reduce the crystallinity of the polyethylene oxide (PEO) solid-state electrolyte membrane and improve its ionic conductivity at room temperature, enabling stable operation of the battery. The tubular lone-pair-rich inorganic fillers play a key role in providing avenues for both internal and external charge transportation. The surface lone-pair electrons facilitate the dissociation and transport of lithium ions, while the internally tubular electron-rich layer attracts ions into the cavities, further enhancing the ion transport. After 100 cycles at room temperature, the lithium battery loaded with this solid-state electrolyte membrane delivers a specific capacity of 141.6 mAh·g⁻¹, which is 51.3% higher compared to the membrane without the fillers.

Na superionic conductor (NASICON)-type Li_1.5Al_0.5Ge_0.5P₃O₁₂ (LAGP) solid state electrolytes (SSEs) have attracted significant interests thanks to the prominent ionic conductivity (> 10^–4 S·cm^–1) at room temperature and superb stability in air. Unfortunately, its application has been hindered by the lithium dendrites and the intrinsic interfacial instability of LAGP towards metallic Li, etc. Herein, by magnetron sputtering (MS), an ultrathin Al film is deposited on the surface of the LAGP pellet (Al-LAGP). By in-situ alloying reaction, the spontaneously formed LiAl buffer layer inhibits the side reaction between LAGP SSEs and Li metal, and induces the uniform distribution of interfacial electric field as well. Density functional theory (DFT) calculations demonstrate that the LiAl alloy surface promotes the diffusion of lithium atoms due to the lower energy barrier, thereby inhibiting the formation of lithium dendrites. Consequently, the Li/Al-LAGP-Al/Li symmetric cells show a low resistance of 210 Ω and a durable lifespan over 1,200 h at a high current density of 0.1 mA·cm^–2. Assembled all solid state lithium metal batteries (ASSLMBs) with LiFePO₄ (LFP) cathode significantly improve cycle stability and rate performance, proving a promising stabilization strategy towards the NASIOCN type electrolyte/anode interface in solid state Li metal batteries.