Lithium Phosphorus Oxynitride Coated Concentration Gradient Li[Ni_0.73Co_0.12Mn_0.15]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_0.73Co_0.12Mn_0.15]O₂ 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_0.73Co_0.12Mn_0.15]O₂ material. The LiPON-coated concentration gradient Li[Ni_0.73Co_0.12Mn_0.15]O₂ 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_0.73Co_0.12Mn_0.15]O₂ 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.