Surface Double Coating of LiNiaCobAl1-a-bO2 (a > 0.85 ) Cathode with Tiox and Li2CO3 to Apply a Water-Based Hybrid Polymer Binder to Li-Ion Batteries’ Preparation

Recently a water-based polymer binder has been getting much attention to simplify 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 it 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 ground that Li 2 CO 3 is formed through the reaction between CO 3 2- ions and LiOH residua 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 TiOx-uncoated NCA surface. The results (Fig.1) 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 particles cathode prepared with a water-based binder possesses the same charge/discharge performance as obtained with “water-uncontacted” NCA particles cathode prepared using the conventional organic solvent-based polyvinylidene difluoride binder. Fig. 1 Charge/discharge cycle performance obtained with the cathodes prepared from (black circle) the slurry consisting of pristine NCA, PVdF and AB, (red circle) the water-based slurry consisting of TiO x /Li 2 CO 3 -coated NCA (the slurry was kept for 7 days under CO 2 atmosphere), TRD202A, CMC and AB, (blue circle) the water-based slurry consisting of TiO x -coated NCA, TRD202A, CMC and AB and (green circle) the water-based slurry consisting of Li 2 CO 3 -coated NCA (the slurry was kept for 1 h under CO 2 atmosphere), TRD202A, CMC and AB at the charging/discharging rate of 0.1 C at 25℃. Figure 1