Surface coating of a LiNi x Co y Al1-x-y O2 (x > 0.85) cathode with Li3PO4 for applying a water-based hybrid polymer binder during Li-ion battery preparation.

To produce water-stable Ni-rich lithium nickel cobalt aluminum oxides (LiNi x Co y Al1-x-y O2, x > 0.85, NCAs), the formation of trilithium phosphate (Li3PO4)-coated layers on the NCA surfaces was attempted through the use of a surface reaction in a mixture of ethanol and water and a post-heat treatment at 350 and 400 °C. Based on the results of X-ray photoelectron spectroscopy (XPS), the coated layers consisted of nickel phosphate (Ni3(PO4)2) and Li3PO4. The coated NCA surface could have sufficient water stability to maintain the cathode performance in a water slurry for 1 day. In addition, the coated layers formed on the NCA surfaces did not block Li+-ion transfer through the Ni3(PO4)2/Li3PO4-coating layers and enhanced the high-rate discharge performance.