Single-Ion Conducting Polyurethane-Ester Solid Polymer Electrolyte Membrane toward Lithium Metal Batteries

It is a severe challenge to exploit single-ion polymer electrolytes combining excellent mechanical properties and ionic conductivities. Here, a polyurethane-ester single-ion polymer electrolyte membrane is prepared, and the relationship between the microstructure and the properties of ionomers is investigated. The electrolytes with different micro-phase morphologies, local hydrogen bonding states, ionic association states, and electrochemical properties are synthesized by regulating the chain length of polyethylene oxide (PEG). It is found that the hard domains of polyurethane electrolytes can ensure high carrier concentration and mechanical stability. All samples exhibit a two-phase behavior and low soft-phase glass-transition temperatures close to those of pure PEG, achieving good electrochemical, thermal, and mechanical properties. The membranes show outstanding interfacial compatibility and stability with lithium metal anodes, enabling the Li/LFP cells to exhibit excellent capacity (∼175 mA h g–1) as well as cycling stability at 0.1 C. Hence, the developed polyurethane-ester single-ion polymer electrolyte meets the application requirements of the next-generation lithium batteries.