Abstract
Recently a water-based polymer binder has been getting much attention because it simplifies the production process of lithium ion batteries (LIBs) and reduce their cost. The surface of LiNi (a) Co (b) Al(1-a-b) O(2) (a > 0.85, NCA) cathode with a high voltage and high capacity was coated doubly with water-insoluble titanium oxide (TiO (x) ) and Li(2)CO(3) layers to protect the NCA surface from the damage caused by contacting with water during its production process. The TiO (x) layer was at first coated on the NCA particle surface with a tumbling fluidized-bed granulating/coating machine for producing TiO (x) -coated NCA. However, the TiO (x) layer could not coat the NCA surface completely. In the next place, the coating of the TiO (x) -uncoated NCA surface with Li(2)CO(3) layer was conducted by bubbling CO(2) gas in the TiO (x) -coated NCA aqueous slurry on the grounds that Li(2)CO(3) is formed through the reaction between CO(3) (2-) ions and residual LiOH on the TiO (x) -uncoated NCA surface, resulting in the doubly coated NCA particles (TiO (x) /Li(2)CO(3)-coated NCA particles). The Li(2)CO(3) coating is considered to take place on the TiO (x) layer as well as the TiO (x) -uncoated NCA surface. The results demonstrate that the double coating of the NCA surface with TiO (x) and Li(2)CO(3) allows for a high water-resistance of the NCA surface and consequently the TiO (x) /Li(2)CO(3)-coated NCA particle cathode prepared with a water-based binder possesses the same charge/discharge performance as that obtained with a "water-uncontacted" NCA particle cathode prepared using the conventional organic solvent-based polyvinylidene difluoride binder.