LiNi0.5Mn1.5O4 thick-film electrodes prepared by electrophoretic deposition for use in high voltage lithium-ion batteries

Highly homogeneous coatings several microns in thickness were prepared by electrophoretic deposition (EPD) from suspensions of a well-crystallized spinel of nominal composition LiNi0.5Mn1.5O4 mixed with 10% carbon black. The best dispersing conditions were found to be those provided by acetone containing citric acid and polyethyleneimine as dispersing agents; this combination resulted in increased mobility of particles and improved adherence to the substrate. These experimental conditions favored deposition of the smallest particles, thereby increasing coating uniformity. The as-prepared coatings were used as electrodes in lithium cells and found to provide virtually no electrochemical response owing to the lack of interparticle connectivity. This problem was easily overcome by compressing the coatings. Thus, coatings compressed at 517 MPa resulted in cell performance on a par with that of the cell made from the bulk spinel. Moreover, their small particle size facilitates lithium-ion diffusion and the deposits exhibit good rate capabilities and coulombic efficiencies.