Synergistic Cyclodextrin-LiTFSI Coating on LLZTO toward High Ionic Conductivity PVA-Based Composite Electrolytes

Poly(vinyl alcohol) (PVA)-ionic liquid-Li_6.75La₃Zr_1.75Ta_0.25O₁₂ (LLZTO) composite electrolyte (PIL) has drawn extensive research attention for lithium-ion batteries due to its high ionic conductivity. However, LLZTO tends to aggregate in PVA solution, which significantly impairs the lithium-ion transport rate within PIL. Herein, we coated the surface of LLZTO with a cylindrical cyclodextrin-LiTFSI (abbreviated as C-T) complex and systematically investigated the effects of the C-T coating and LLZTO content on the electrochemical performance of the PIL@C-T composite electrolyte. Specifically, when the LLZTO content is 60 wt %, the ionic conductivity of PIL@C-T can reach 4 × 10^-3 S/cm. Based on lithium-ion transport mechanism analysis, we can conclude that the C-T coating can enhance the compatibility between LLZTO and the PVA matrix while constructing fast lithium-ion transport channels between LLZTO ceramic particles. Furthermore, the LiFePO₄ | PIL@C-T | Li cell delivers a discharge capacity of 162 mAh/g, and its Coulombic efficiency can be maintained at approximately 100% after 200 cycles. This work provides a new strategy to develop high-performance composite electrolytes, which hold great potential for applications in advanced lithium-ion batteries.