In situ polymerized solid electrolytes for superior safety and stability of flexible solid-state Al-ion batteries

Abstract Research on pouch-type or flexible batteries is currently being conducted with the increasing interest in flexible devices. However, lithium-ion batteries using liquid electrolytes, which are currently the most widely used, have limitations in terms of lithium reserves and the use of flammable organic electrolytes. To solve this problem, research is being actively conducted on Al-ion batteries (AIBs) that are highly safe and capable of fast charge/discharge. In this study, gel polymer electrolytes (GPEs) were developed by in-situ polymerization of ethyl acrylates in AlCl3/[EMIm]Cl ionic liquids. AIBs with GPEs as a solid-state electrolyte medium can solve the crucial problems in current liquid AIB systems, including electrolyte leakage, anode corrosion, and moisture sensitivity. AIBs with GPEs exhibit a reasonable energy storage capacity of 90 mAh g−1 even at a high current density of 200 mA g−1 with a high coulombic efficiency of 95%. Additionally, they exhibit a high long-term stability over 500 cycles without capacity reduction. Furthermore, AIBs demonstrate exceptional operational stability and safety under harsh operating conditions, such as folding, bending, and cutting. These results suggest that new solid-state AIBs based on GPEs provide a promising strategy for the development of high-performance solid-state flexible rechargeable battery systems.