Negative electrode lithium supplement additive and preparation method thereof

The invention provides a negative electrode lithium supplement additive and a preparation method of the lithium supplement additive. The preparation method comprises the steps of 1 uniformly mixing silicon oxide and an inorganic compound of a lithium element according to a molar ratio of 1: (2 to 4), sintering in a protective gas, and cooling to room temperature to obtain a lithium silicate material; 2 mixing the lithium silicate material with silicon powder, carrying out dry high-energy ball milling, and carrying out hot isostatic pressing to obtain the silicon-lithium silicate composite material, and 3 crushing the silicon-lithium silicate composite material by using a crusher, mixing the crushed silicon-lithium silicate composite material with a carbon inorganic substance, carrying outdry ball milling, calcining in a protective gas environment, and carrying out suction filtration to obtain a solid in a suspension so as to obtain the carbon-coated silicon-lithium silicate compositematerial particles. The pr