▎ 摘　　要

NOVELTY - Preparing graphene-coated nickel-cobalt-manganese-lithium composite material comprises e. g. preparing 0.01-1 mol/l aqueous solutions of manganese sulfate and ammonium bicarbonate with deionized water, adding ethanol into the manganese sulfate aqueous solution, adding the aqueous ammonium hydrogen carbonate solution into the manganese sulfate aqueous solution, magnetically stirring for 0.1-10 hours, washing, freeze drying, obtaining manganese carbonate powder, placing the manganese carbonate powder in a tube furnace and calcining in air atmosphere to obtain spherical manganese dioxide powder. USE - The material is useful for lithium ion battery and electrochemical energy storage devices. ADVANTAGE - The method has low raw material cost and good controllability. The material has excellent electrochemical performance and is environmentally-friendly. DETAILED DESCRIPTION - Preparing graphene-coated nickel-cobalt-manganese-lithium composite material comprises (i) preparing 0.01-1 mol/l aqueous solutions of manganese sulfate and ammonium bicarbonate with deionized water, adding ethanol into the manganese sulfate aqueous solution, adding the aqueous ammonium hydrogen carbonate solution into the manganese sulfate aqueous solution, magnetically stirring for 0.1-10 hours, washing, freeze drying, obtaining manganese carbonate powder, placing the manganese carbonate powder in a tube furnace and calcining at 200-600 degrees C for 2-10 hours in air atmosphere to obtain spherical manganese dioxide powder; (ii) taking the manganese dioxide powder as template, immersing in an ethanol solution containing nickel salts, cobalt salts, and lithium hydroxide, supersonic dispersion, stirring at room temperature until ethanol evaporates to obtain a mixture, grinding the mixture to powder with an agate mortar, placing in a tube furnace, calcining at 400-1000 degrees C for 10-30 hours and adding primary particles of lithium nickel-nickel-cobalt-manganate to obtain hollow structure, spherical ternary nickel-cobalt-manganese-manganate; (iii) dissolving lithium acetate and cobalt acetate in ethanol, adding the lithium nickel cobalt manganese oxide into the ethanol solution, ultrasonically dispersing, stirring the mixture at room temperature for 1-10 hours, stirring in a water bath at 70 degrees C, evaporating the ethanol, obtaining a mixture, grinding the mixture into a powder, placing in a tube furnace and calcining in an air atmosphere at 400-1000 degrees C for 2-10 hours and obtaining surface-modified lithium nickel cobalt manganese oxide ternary material; and (iv) supersonically dispersing the surface-modified nickel-cobalt-manganese-copper ternary material in water, adding the graphene moisture dispersion under ultrasound, interacting between graphene and lithium nickel cobalt manganese oxide and coating the graphene uniformly and firmly on the surface of lithium nickel cobalt manganese oxide.