Agglomeration-free composite solid electrolyte and enhanced cathode-electrolyte interphase kinetics for all-solid-state lithium metal batteries

Polymer composite electrolytes are receiving ever-increasing attention due to the favorable safety and flexibility, while inferior organic/inorganic interphase compatibility inevitably leads to serious agglomeration of ceramic particles and severely blocked Li+ transport in bulky electrolytes, especially for polymer-in-ceramic (PIC) systems with ultrahigh ceramic content. Herein, a silane coupling agent 3-Isocyanatopropyltriethoxysilane (IPTS) is introduced into PIC electrolyte to build bridge model at organic/inorganic interphase. Via in-situ coupling reaction, conventional weak physical contact between organic/inorganic components has been successfully transformed into stronger chemical interaction, resulting in homogeneous ceramic dispersion, enhanced Li+ conductivity (0.6 mS cm-1 at room temperature) and transference number (0.87) with broadened electrochemical window (5.2 V vs. Li+/Li). Moreover, the in-situ built bridge model can also be applied into various cathodes. Notably, the IPTS modified LiCoO2 (SLCO) and LiNi0.8Co0.15Al0.05O2 (SNCA) deliver uniform morphology and enhanced Li+ apparent diffusion coefficient. In this case, both all-solid-state symmetric and full cells exhibit prolonged cycling life at wide operation temperature. This work provides a universal strategy to optimize the long-ignored tough issues around the interphase for both composite electrolytes and cathodes, also enlightening other composite systems to overcome their intrinsic incompatibility.

Automated summary

Polymer composite electrolytes have garnered attention for their safety and flexibility, but the compatibility issues at the organic/inorganic interface can lead to agglomeration of ceramic particles and hinder Li+ transport. In this study, a silane coupling agent was introduced to build a bridge model at the interface, resulting in improved dispersion, enhanced Li+ conductivity, and broader electrochemical window. The in-situ built bridge model was also applied to various cathodes, leading to uniform morphology and enhanced Li+ diffusion coefficient. These findings offer a universal strategy to address interphase issues and have implications for other composite systems.