Converting Nafion into Li+-Conductive Nanoporous Materials

Sulfonated polymers have long been used as proton-conducting materials in fuel cells, and their ionic transport features are highly attractive for electrolytes in lithium-ion/metal batteries (LIBs/LMBs). However, most studies are still based on a preconceived notion of using them directly as polymeric ionic carriers, which precludes exploring them as nanoporous media to construct efficient lithium ions (Li⁺) transport network. Here, effective Li⁺-conducting channels realized by swelling nanofibrous Nafion is demonstrated, which is a classical sulfonated polymer in fuel cells. The sulfonic acid groups, interact with LIBs liquid electrolytes to form porous ionic matrix of Nafion and assist partial desolvation of Li⁺-solvates to further enhance Li⁺ transport. Li-symmetric cells and Li-metal full cells (Li₄Ti₅O₁₂ or high-voltage LiNi_0.6Co_0.2Mn_0.2O₂ as a cathode) with such membrane show excellent cycling performance and stabilized Li-metal anode. The finding provides a strategy to convert the vast sulfonated polymer family into efficient Li⁺ electrolyte, promoting the development of high-energy–density LMBs.