Achievement of the High-Capacity Retention Rate for the Li[Ni0.8Co0.15Al0.05]O2 (NCA) Cathode Containing an Aqueous Binder with CO2 Gas Treatment Using the Cavitation Effect (CTCE)

The Li[Ni0.8Co0.15Al0.05]O2 (NCA) cathode containing an aqueous binder for Li ion batteries was fabricated by the CO2 gas treatment method using the cavitation effect (CTCE) with the continuous mixing device process. The CTCE is a simple process for decreasing the pH value of the cathode slurry containing an aqueous binder from the alkaline region to neutral region. With the CTCE, the retention rate of the discharge capacity at the 50th cycle with respect to that at the 2nd cycle achieved 92%. It was confirmed that almost all of the NCA particle surfaces were uniformly covered with a Li2CO3 layer after the CTCE. The Li2CO3 layer formed on the NCA particle surfaces and prevented increasing the film resistance and charge transfer resistance because the layer suppressed the electrolyte decomposition and stabilized the surfaces. These phenomena lead to improvement of the cyclability. Moreover, a part of the Li2CO3 layer on the NCA particle surfaces contains carbon black (CB) because CB is uniformly dispersed by the mixing equipment using the cavitation effect. This result improved the electrical conductivity of the NCA powder, resulting in increased capacities for all the cycles.