Surface coating of a LiNi x Co y Al 1- x - y O 2 ( x > 0.85) cathode with Li 3 PO 4 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 Al 1- x - y O 2 , x > 0.85, NCAs), the formation of trilithium phosphate (Li 3 PO 4 )-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 (Ni 3 (PO 4 ) 2 ) and Li 3 PO 4 . 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 Ni 3 (PO 4 ) 2 /Li 3 PO 4 -coating layers and enhanced the high-rate discharge performance.