Hypercrosslinked porous and coordination polymer materials for electrolyte membranes in lithium-metal batteries

Rechargeable lithium-metal batteries (LMBs) hold great promise for providing high-energy density. However, their widespread commercial adoption has been inhibited by critical challenges, for example, the capacity fading from irreversible processes at electrolyte/electrode interfaces and safety concerns originating from the inhomogeneous lithium deposition. Polymer electrolytes benefiting from enhanced electrolyte/electrode contact and low interfacial impedance provide a variable solution to address these challenges and enable a high-energy and flexible battery system. Although promising, inefficient bulky ionic conductivity and poor mechanical stability confront the stable operation of polymer electrolytes in tangible batteries, which highly requires the development of innovative polymer electrolyte chemistries. Among various polymer materials, microporous polymers stand out due to their abundant porosity and customizable micropore structure, positioning them as promising candidates for next-generation electrolyte membranes. This review, therefore, summarizes recent advances in electrolyte membranes based on two new chemistries, hypercrosslinked polymers (HCPs) and porous coordination polymers (PCPs). Other microporous polymers, such as covalent organic polymers, porous organic cages, and polymers of intrinsic microporosity, are also discussed with an emphasis on their applications in LMBs. Most importantly, by reviewing the design strategies, synthesis protocols, and performance in LMBs, we gain insights into the design principles of high-performance electrolyte membranes based on HCPs and PCPs and highlight potential future research directions.