Novel Ternary Polymer Electrolytes Based on Poly(lactic acid) from Sustainable Sources

In search of energy storage solutions, polymer electrolytes are particularly interesting, owing to their high intrinsic safety. We show for the first time a lithium metal polymer battery working with a polymer electrolyte based on poly(lactic acid), exhibiting a remarkably low charge-transfer resistance. This polymer is produced from lactic acid, which can be obtained from waste and renewable sources. Thus, a significant fraction of fossil-based raw materials could be eliminated from the production of battery components. By incorporation of the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethane-sulfonyl) imide (Pyr(14)TFSI), fully amorphous, solvent-free, very low-volatile solid polymer electrolytes (SPEs) are obtained, which are shown to be thermally and electrochemically stable electrolytes in lithium metal polymer batteries. A lithium metal polymer battery with a composite lithium iron phosphate (LFP) cathode was successfully cycled with this electrolyte, showing its potential for applications. We conclude that alternatives to the benchmark poly(ethylene oxide), like ionic liquid plasticized polyester, are worthy of attention because of the low charge-transfer resistance with lithium metal.