EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

The development of commercial solid-state batteries is up to date hindered by the individual limitations of inorganic and organic solid electrolytes, motivating hybrid concepts. However, room temperature performance of hybrid solid electrolyte is limited by the sluggish interfacial Li-ion transport between the organic and inorganic electrolyte phases. This challenge is further complicated by the difficulty to assess the Li-ion transport over the interfaces directly. In order to understand the lithium ion (Li+) conductivity in hybrid solid electrolytes, the interface structure and Li+ interface transport was investigated by state-of-art solid state nuclear magnetic resonance (ssNMR) methodologies. In hybrid solid PEO polymer – inorganic electrolytes, two representative types of ionic liquids, namely piperidinium-based and imidazolium-based, having a different miscibility with PEO were used as a benchmark to tailor the local environment at the interface of the inorganic and organic solid electrolytes species. It is found that the charge transfer between phase boundaries is strongly improved by piperidinium-based ionic liquid, which driven by the poor miscibility with PEO, is located at the interfaces. The effective wetting and high polarizability of the ionic liquid lowers the barrier for diffusion between the two electrolyte species, which activates the inorganic solid electrolyte to contribute to the overall conductivity. In conclusion, by tailoring the local interface environment, the bottle neck in hybrid solid electrolytes is revealed, providing insights for the design of highly conducting hybrid solid electrolyte concepts.