Study on the regulation mechanism of a coral-like Li7La3Zr2O12 inorganic filler on the properties of poly(ethylene oxide)-based composite solid electrolytes

Abstract

Poly(ethylene oxide) (PEO)-based composite solid electrolytes have attracted extensive attention due to their potential to simultaneously achieve high lithium-ion conductivity and good interfacial compatibility, along with their potential for roll-to-roll production. Herein, a coral-like Li₇La₃Zr₂O₁₂ (LLZO) inorganic filler was obtained by electrospinning and calcination. Compared with granular LLZO, coral-like LLZO has numerous branches, which are beneficial for rapid Li⁺ migration. The lithium-ion conductivity of the PLCL (PEO + LiTFSI + coral-like LLZO) composite solid electrolyte was 1.32 × 10⁻⁴ S cm⁻¹ at 25 °C, which was about 15 times higher than that of PL (PEO + LiTFSI). The electrochemical window also increased from 4.0 to 4.8 V. Coral-like LLZO enhanced the movement of PEO segments by greatly reducing the crystallinity, increased the number of free Li⁺ by increasing the dissociation degree of LiTFSI, and improved the effective migration of Li⁺ by increasing the number of rapid Li⁺-migration channels. Results from multi-physical field simulations and Raman spectroscopy showed that Li⁺ ions were mainly transmitted in the interior of LLZO, indicating that the coral-like LLZO provides rapid channels for Li⁺ migration. In addition, due to the large contact area between coral-like LLZO and PEO, Li⁺ migration channels also appeared at the PEO/LLZO interface.