Surface double coating of a LiNi a Co b Al 1- a - b O 2 ( a > 0.85) cathode with TiO x and Li 2 CO 3 to apply a water-based hybrid polymer binder to Li-ion batteries.

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.