Yang-Tse Cheng

Abstract:

Conventional, state-of-the-art, wet slurry mixing and coating processes of making battery electrodes are over 100 years old and have been recognized as slow, high-cost, low-quality steps in battery manufacturing. The mixing process is used to produce a slurry that consists of active material, polymer binder, conductive filler, and organic solvent. When an appropriate viscosity is obtained, the slurry is coated onto a conductive metal foil. Because of the large amount of organic solvent used, the coating must be dried in an oven for several hours before it is calendered to form the desired thickness and porosity. Evaporation of the organic solvent consumes energy, requires the use of a large amount of material that is not part of the final product, and has a negative environmental impact. We recently developed an electrostatic spray process for making the positive and negative electrodes in lithium-ion batteries. This process does not use organic solvents that are used in conventional wet slurry manufacturing processes, thus eliminating volatile organic compound emission and reducing the time and energy associated with thermal drying. The performance and durability of electrodes made by the dry and wet processes are comparable, suggesting that solvent-free dry coating processes, such as electrostatic spraying, may replace the conventional wet slurry method of making battery electrodes.