Solid-state batteries (SSBs) with high energy density and enhanced safety are promising alternatives to conventional lithium-ion batteries with liquid electrolytes. Significant efforts in recent years have focused on improving the ionic conductivity of solid electrolytes, The highest ionic conductivity of inorganic electrolytes is already comparable to liquid electrolytes. However, the practical application of these electrolytes is hindered by sluggish lithium-ion transport at the solid electrode/electrolyte interface, resulting in inferior battery performance compared to liquid electrolytes.
Hybrid electrolytes have emerged as strong contenders for high-performance solid-state lithium-ion batteries, owing to their combination of high ionic conductivity, excellent mechanical strength, and cost-effective manufacturing processes. Previous studies indicate that the incorporation of inorganic oxide electrolyte fillers, such as LLZO and LATP, can significantly enhance ion transport in hybrid electrolytes. Notably, PVDF-HFP-based hybrids with LLZO or LATP have demonstrated superior ionic conductivity, mechanical strength, and electrochemical stability. However, the formation of Li2CO3 on the surface of LLZO significantly sluggish interfacial ion transport, and LLZO can induce the degradation of polymer electrolytes, ultimately leading to battery failure.
This research presents a surface modification method designed to improve the interfacial ion transport and mitigate side reactions between oxide electrolytes (e.g., LLZO, LATP) and PVDF-HFP. Specifically, PEG is grafted onto the surface of LLZO to optimize the space charge layers at the interface with PVDF-HFP. Characterization techniques, including XRD, Raman spectroscopy, TEM, TGA and IR were employed to analyze the PEG-grafted LLZO. Electrochemical testing of lithium symmetric and LFP full cells utilizing PVDF-HFP/PEG-modified LLZO hybrid films demonstrated good stability and excellent electrochemical performance. This research offers new insights into enhancing interfacial ion transport and reducing degradation in polymer-oxide hybrid electrolytes, facilitating the advancement of high-performance solid-state batteries.