Tailoring Trilayer LiTa2PO8-Based Hybrid Solid Electrolytes to Enhance Interfacial Compatibility and Efficient Lithium Transport in Lithium Metal Batteries.

Herein, a spatially decoupled trilayer hybrid solid electrolyte (THSE) is designed through functional architecture engineering to simultaneously optimize ionic conduction and interfacial stability. THSE integrates a polymer matrix comprising a Li+-conductive LiTa2PO8 (LTPO) filler as the core, together with Li6.25Al0.25La3Zr2O12 (Al-LLZO)-based outer layers that provide mechanical robustness and interfacial protection. Structural analyses, including XRD, Raman, and solid-state NMR, confirm high phase purity and well-defined coordination environments within the hybrid framework. XPS analysis reveals that the Al-LLZO-protected THSE (A-THSE) preserves the Ta5+ oxidation state upon contact with Li metal, whereas the corresponding control THSE without Al-LLZO outer-layer protection (C-THSE) undergoes partial reduction to Ta3+/Ta2+ species. Benefiting from stabilized interfacial properties, the A-THSE delivers a high Li+ transference number of ca. 0.65, a wide electrochemical stability window of ~5.18 V, and a room-temperature ionic conductivity of ca. 0.83 mS cm- 1. In addition, fluoride-, borate, and phosphate-rich CEI/SEI layers effectively regulate electrode/electrolyte interfacial regions. Consequently, the Li/A-THSE/Li symmetric cell exhibits stable cycling for over 1400 h at 0.2 mA cm- 2. Furthermore, the Li/A-THSE/LFP and Li/A-THSE/PAN@SC-NCMA86 full cells retain 80% capacity after 1323 and 400 cycles, respectively.