Thick Aqueous Processed Cathodes Enabled By Phosphoric Acid Addition

Abstract

Aqueous processed cathodes for lithium-ion batteries are favorable for both cost and environmental reasons; however, these electrodes still face significant problems with increasing areal capacities (i.e. thickness). Transition metal leaching from high nickel content active materials creates a very basic slurry, pH in excess of 12. This slurry composition subsequently corrodes the aluminum current collector, which leads to hydrogen gas generation. As a consequence, bubbling at the electrode interface causes substantial damage to the dried electrode. As the loading of these electrodes is increased, this mechanism becomes more severe and results in lack of adhesion and cohesion. In this work we investigate the introduction of varying amounts of phosphoric acid to combat the rise in pH and suppress the corrosion at the current collector surface. Phosphoric acid was added in increments of 0.5, 1, and 1.5 wt% and the subsequent effects on slurry rheology, particle size, adhesion, and electrochemical cycling were investigated. In this work we report a technique for obtaining thick (6-8 mAh/cm2) cathodes that exhibit reduced surface cracking and display improved rate performance as compared to control samples.