Single-Ion Conducting Polymer Electrolyte with Excellent Interfacial Stability toward the Lithium Metal

To improve the safety and energy density of lithium metal batteries, polymer electrolytes address the challenge by replacing flammable liquid electrolytes. We herein design an amorphous solid-state single-ion conducting polymer electrolyte (SIPE) with a strict alternating sequence of perfluorosulfonate lithium salt and poly(ethylene glycol) (PEG) with a very homogeneous dispersion of lithium salt in the electrolyte. Amorphous SIPE tailored with a moderate cross-link degree and reinforced with nanocrystals cellulose (NCC) exhibits a high Li+ conductivity exceeding 10–5 S cm–1 at 60 °C with a lithium transference number close to unity and excellent stability with Li metal. Long-term lithium stripping and plating were achieved in symmetric Li|SIPE|Li cells for over 80 days without dendrite growth. The Li|SIPE|LiFePO4 cells provide an excellent rate capability performance with a high specific capacity of 163 and 132 mA h g–1 at C/20 and C, respectively. The long-term cycling tests exhibited good performance and an average Coulombic efficiency of 99.9% for over 160 cycles. These excellent results confirmed the potential of the rationally designed single-ion conducting polymers as a safe and efficient solid-state electrolyte for next-generation high-performance energy storage.