How to Uniformly Disperse Nanoparticles in Battery Cathode Coatings

34 T he materials in anodes and cathodes within a lithium-ion battery affect voltage, capacity, and battery life. When a battery is discharging, the lithium ions move from the anode into the cathode. During the charging process, that movement is reversed. Electrolytes conduct the lithium ions and serve as a carrier between the cathode and the anode when electric currents pass through an external circuit. (Fig. 1). For anodes, graphite is the primary material for lithium-ion batteries. The carbon anode is prepared and applied as a “slurry” coating layer. For cathodes, slurries of manganese, cobalt, and iron phosphate particles are frequent choices. In addition, lithium-cobalt oxide and lithium-manganese oxide are common cathode coatings. However, lithium-iron phosphate (LFP) particles provide improved safety, longer cycles, and longer operating life. Iron and phosphate are also less expensive than other materials, and their high charge capacities make them a good match for plug-in hybrid applications. LFP battery cells do contain lower voltage and energy density levels than other Liion materials, but their slower rate of capacity loss helps maintain a higher energy density level after one year of service. Fortunately, the challenges associated with limited charge and discharge rates have been alleviated by improved manufacturing techniques. These techniques involve a precise and repeatable manufacturing approach that relies on advances in nanotechnology.