Perfluorosulfonic Acid Membranes as Gel-Polymer Electrolytes for Lithium Metal Batteries

Gel-polymer electrolytes based on perfluorinated cation-exchange membranes are promising electrolytes for lithium metal batteries due to the strength and chemical stability of the fluorinated matrix and high values of ionic conductivity and cation transference numbers, which contribute to the suppression of dendrite formation. The present work compares the main characteristics of polymer electrolytes based on short-side-chain membranes Aquivion-87 and Aquivion-98 with different numbers of functional groups and content of polar aprotic solvents (mixtures of ethylene carbonate–propylene carbonate and ethylene carbonate–N,N-dimethylacetamide), i.e., ionic conductivity, transference numbers, and stability against lithium metal. Electrochemical characteristics of the electrolytes in Li|Li and LiFePO4|Li cells show good compatibility and functionality with the Li metal anode, forming a stable Li/electrolyte boundary, and LFP|Aquivion-87-EC-DMA|Li cell shows discharge capacity values of ∼142 mAh/g at 0.1 C and 136 mAh/g at 1 C and room temperature, with a 98.8% capacity retention after 70 cycles at 0.1 C. These data indicate their promising application as polymer electrolytes in lithium metal batteries.