Solvent-Free Additive Manufacturing of Electrodes for Lithium-Ion Batteries

Abstract

Lithium ion battery manufacturing preparation methods have been increasingly studied to make the batteries more cost-effective for large scale platforms such as automotive vehicles. The standard method is to combine an organic solvent with a suitable binder, typically polyvinylidene fluoride (PVDF), to make a slurry. The active material and conductive additive is then mixed in to create the wet electrode material which is then cast onto a current collector. Hazards associated with the organic solvent, such as toxicity and flammability, have resulted in aqueous based slurry preparation, but this also comes with its own set of issues. The change in aqueous slurry rheology properties must be compensated for by adding thickeners and dispersing agents to aid in the wetting capability of the electrode material onto the current collector. Solvent free manufacturing methods, such as pulsed laser and sputtering deposition, have been studied but are not suitable for commercial applications due to prolonged manufacturing times. A team by Missouri S&T and WPI has been recently published a new solvent free manufacturing method by dry spraying the electrode materials onto the current collector directly. Dry sprayed electrodes were found to match, and even exceed, the electrochemical performance of slurry manufactured electrodes. Studies have also shown that the surface energy driven mixing properties of the dry particles allow for a reduction of the binder material to 1 wt% while still maintaining strong mechanical bonding.