Li _6.4 La ₃ Zr _1.4 Ta _0.6 O

ABSTRACT

The long‐standing “solidification penalty” and inherent strength‐conductivity trade‐off have severely restricted the development of high‐energy‐density lithium metal batteries (LMBs), as conventional solid‐state electrolytes inevitably compromise ionic transport for enhanced safety. Herein, we rationally design a Li _6.4 La ₃ Zr _1.4 Ta _0.6 O ₁₂ (LLZTO)‐reinforced hybrid eutectic polymer electrolyte (HEE@PF) that subverts this long‐held paradigm. The HEE@PF delivers a room‐temperature ionic conductivity of 0.484 mS cm ⁻¹ , exceeding that of its liquid eutectic precursor (0.336 mS cm ⁻¹ ), while simultaneously doubling puncture strength to 5.5 N, enabled by multiscale synergistic reinforcement mechanisms. LLZTO functions not merely as an inert filler but as a multifunctional active component: it promotes extensive dissociation of LiTFSI, facilitates the formation of percolating ion‐conducting pathways, and selectively modulates the decomposition of TFSI ⁻ anions to engender a robust, Li ₂ SO ₄ –enriched solid electrolyte interphase (SEI). Consequently, Li| |Li symmetric cells demonstrate long‐term cycling stability (> 600 h at 0.1 mA cm ⁻² ), and Li| |LiFePO ₄ (LFP) full cells retain 80.1% of their initial capacity after 400 cycles at 1 C. Moreover, the system exhibits outstanding rate capability and high‐temperature resilience, delivering a stable specific capacity of 99.4 mAh g ⁻¹ after 800 cycles at 1 C under 60°C. This work establishes a generalizable design strategy by transforming passive ceramic fillers into multifunctional active components, accelerating the practicalization of safe high‐performance LMBs.