Tailoring Trilayer LiTa ₂ PO ₈ ‐Based Hybrid Solid Electrolytes to Enhance Interfacial Compatibility and Efficient Lithium Transport in Lithium Meta

ABSTRACT

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 LiTa ₂ PO ₈ (LTPO) filler as the core, together with Li _6.25 Al _0.25 La ₃ Zr ₂ O ₁₂ (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 Ta ⁵⁺ oxidation state upon contact with Li metal, whereas the corresponding control THSE without Al‐LLZO outer‐layer protection (C‐THSE) undergoes partial reduction to Ta ³⁺ /Ta ²⁺ 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.