A fiber-reinforced solid polymer electrolyte by in situ polymerization for stable lithium metal batteries

Solid polymer electrolytes (SPEs) by in situ polymerization are attractive due to their good interfacial contact with electrodes. Previously reported in situ polymerized SPEs, however, suffer from the low polymerization degree that causes poor mechanical strength, Li dendrite penetration, and performance decay in Li-metal batteries. Although highly polymerized SPEs are more stable than lowly polymerized ones, they are restricted by their sluggish long-chain mobility and poor ionic conductivity. In this work, a three-dimensional fibrous membrane with ion selectivity was prepared and used as a functional filler for the in situ formed SPE. The obtained SPE has high stability due to its high polymerization degree after the long-term heating process. The fibrous membrane plays a vital role in improving the SPE’s properties. The rich anion-adsorption sites on the fibrous membrane can alleviate the polarization effect and benefit a uniform current distribution at the interface. The fibrous nanostructure can efficiently interact with the polymeric matrix, providing rich hopping sites for fast Li⁺ migration. Consequently, the obtained SPE enables a uniform Li deposition and long-term cycling performance in Li-metal batteries. This work reported an in situ formed SPE with both high polymerization degree and ionic conductivity, paving the way for designing high-performance SPEs with good comprehensive properties.