The synthesis of novel LiNiPO4 core and Co3O4/CoO shell materials by combining them with hard-template and solvothermal routes

Abstract

Pure CoO and Co₃O₄ surface-modified LiNiPO₄ nanoscale powders are successfully synthesized for the first time by newly elaborated hard-template and solvothermal methods. Using this extraordinary technique, LiNiPO₄ particles are coated with a thin CoO or Co₃O₄ layer with a perfect core-shell morphology. The technique's positive contribution to electrochemistry is investigated in detail. The HR-TEM analysis proves that it possible to achieve a continuous surface coverage of about 5nm, a result that contributes towards solving the chronic electrochemical problems of high-voltage cathode material. Our data reveal that cobalt cannot be diffused into the LiNiPO₄ crystal system during the calcination process and that the LiNiPO₄@CoO cathode demonstrates superior cycle stability and specific capacity at relatively low rates. The LiNiPO₄@CoO cathode exhibits the best electrochemical properties, achieving a discharge capacity of 149mAhg^-1 at 0.1C rate, and shows almost 82% capacity retention after 80 charge-discharge cycles. It therefore achieves partial success in terms of improving the electrochemical properties of the LiNiPO₄ cathode material. This is especially crucial for energy storage with regard to electric vehicles and plug-in hybrid electric applications.

Keywords: Cathode material; Cobalt oxide coating; Core-shell structure; Lithium nickel phosphate; Li–ion batteries.