Surface Coating of NCM-811 Cathode Materials with g-C 3 N 4 for Enhanced Electrochemical Performance.

Li(Ni, Co, Mn)O (NCM-811) cathode materials have been commercialized recently, aiming to increase the specific capacity and specific energy of the lithium-ion battery for practical applications in electric vehicles. The surface coating has been proved to be an effective approach for the stabilization of NCM-based cathodes, which could reduce the structural instability and prevent surface reactions between the cathode materials and electrolytes. Herein, we demonstrate the facile synthesis of graphitic carbon nitride (g-CN)-coated NCM cathodes with both the sonication-assisted liquid exfoliation method (g-CNNS@NCM-811) and chemical vapor-assisted coating method (g-CN@NCM-811). It is discovered that coating with a thin g-CN layer could reduce the impedance of the NCM-811 cathode material, as well as increase the cycle stability of the cathode material, leading to increased capacity retention from 130 mA h/g (for the pristine sample) to 140 mA h/g after 225 cycles. While the coating of thick g-CN nanosheets could hinder the lithium intercalation, resulting in significant loss of specific capacity. This study paves the way toward practical applications of the g-CN-coated NCM-811 cathode materials.