Experimental Platform for Determining the Maximum Limiting Current in a Polymer Electrolyte

The applicability of both solid and liquid electrolytes in practical batteries is governed by limiting current. The limiting current for lithium-ion transport in a polymer electrolyte was measured from the dilute limit to the solubility limit. To our knowledge, this has not been accomplished in any other electrolyte due to practical problems such as dendrite growth. Our experiments were conducted on symmetric cells with lithium-indium alloy electrodes. The measured limiting current, ilim, in mixtures of poly(ethylene oxide) and lithium bis(trifluoromethanesulfonyl)imide, exhibits a sharp maximum as a function of salt concentration. This is in quantitative agreement with predictions of concentrated solution theory. The thickness-normalized maximum limiting current, ilimL, is 0.05 mA/cm (L is electrolyte thicknesses). It is difficult to compare different electrolytic compositions because improvements in one parameter often come at the expense of another. The measured ilimL maximum provides a single benchmark for evaluating the efficacy of next-generation polymer electrolytes.