Poly(ethylene oxide)-based composite solid electrolyte modified by Li7La3Zr2O12 inorganic filler with grafted imidazolium-based ionic liquids functional groups

High lithium-ion conductivity of poly(ethylene oxide)-based (PEO) composite solid electrolyte is one of the critical indicators for the development of all-solid-state lithium batteries. Herein, imidazolium-based ionic liquid (IL) functional groups are grafted on the surface of coral-like Li7La3Zr2O12 (LLZO@IL) to construct a rapid Li+ transmission channel at the PEO/LLZO interface. Results show that the IL groups are chemical bonded with LLZO and the N elemetal ratio of anion and cation is close to the theoretical equivalent in IL, suggesting that IL are successfully grafted. The lithium-ion conductivity with IL grafting is significantly improved from 6.43 × 10-6 S cm−1 to 3.41 × 10-4 S cm−1. XPS show that the grafted imidazolium cation has a fixation effect on the TFSI- anion, thus hindering the accumulation of TFSI- anions at the interface to occur decomposition. Moreover, an obvious new complex state of interface Li(TFSI)2- appears in the cycle, which indicates that the grafted IL groups form a rapid channel for Li+ transmission. The great enhancement of conductivity is ascribed to that LLZO@IL can not only promote the movement of PEO segment by reducing the crystallinity, increase the Li+ free number, but also improve the effective Li+ transmission by forming rapid channels at PEO/LLZO interface. © 2024