Tailoring Trilayer LiTa₂PO₈-Based Hybrid Solid Electrolytes to Enhance Interfacial Compatibility and Efficient...

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 Li_6.25Al_0.25La₃Zr₂O₁₂ (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.