Lithium Phosphorus Oxynitride Coated Concentration Gradient Li[Ni0.73Co0.12Mn0.15]O2 Cathode Material with Enhanced Electrochemical Properties

A facile high-temperature solid phase approach is employed to coat lithium phosphorus oxynitride (LiPON) layer on the concentration gradient Li[Ni 0.73 Co 0.12 Mn 0.15 ]O 2 material with Ni-rich core and Ni-poor surface. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy demonstrate that LiPON forms an even coating with ∼4   nm of thickness on the surface without destroying the bulk structure of Li[Ni 0.73 Co 0.12 Mn 0.15 ]O 2 material. The LiPON-coated concentration gradient Li[Ni 0.73 Co 0.12 Mn 0.15 ]O 2 material exhibits a capacity retention of 87.3% at 25   °C after 1000 cycles and 89.9% at 55   °C after 250 cycles, which is 36.1% and 17.2% higher than that of pristine Li[Ni 0.73 Co 0.12 Mn 0.15 ]O 2 material, respectively, under the same operating conditions. This significantly improved cycling performance is ascribed to the noncrystalline LiPON layer on the surface, which provides a reliable interface protection. The LiPON coating is an effective approach to enhancing the electrochemical performance of electrode materials for lithium ion batteries.