Increased Structural Integrity of Aqueous Processed Thick Electrodes for Lithium Ion Batteries

Lithium-ion batteries (LIBs) have been used extensively in portable electronic devices such as cell phones, laptops, and other personal electronics for the past two decades. However, widespread use in electrical vehicles is still limited by material cost, processing cost, and energy density capability. One approach to achieving high energy density batteries is using thick electrodes (150μm thickness instead of baseline 60μm thickness) to increase the volume ratio of active materials in a cell of given size. Traditional electrode processing requires the use of a flammable, toxic solvent, n-methyl pyrrolidone (NMP). The recovery steps required for NMP add significant processing costs to the overall LIB production cost. Aqueous processing has been explored as a method of eliminating NMP from electrode processing; however, aqueous processed thick electrodes have a tendency to crack. Surface tensions of isopropyl alcohol / water and methyl acetate / water systems of varying concentrations were evaluated to determine the effect of the additive solvents on the overall system, and electrodes processed with the mixed solvents were examined for cracking. Both types of mixed solvents successfully reduced surface tension and allowed thick electrode processing without cracking.