The invention relates to a composite
silicon negative
electrode material. The composite
silicon negative
electrode material comprises nanometer
silicon, a nanometer composite layer
coating the surface of nanometer silicon and a conductive
carbon layer uniformly
coating the nanometer composite layer, wherein the nanometer composite layer is
silicon oxide and
metal alloy. According to the composite silicon negative
electrode material with a three-layer structure, the nanometer composite layer composed of the
silicon oxide and the
metal alloy coating the surface of the
silicon oxide effectively reduces
volume expansion of the nanometer silicon, maintains the characteristic of
high conductivity of the silicon material, improves mobility of
lithium ions, prevents direct contact between a silicon negative electrode and an
electrolyte, and can form a hard SEI film on the surface of the composite silicon negative
electrode material, thereby allowing the cycle performance of the material to be substantially enhanced. The composite silicon negative
electrode material has the characteristics of high capacity (greater than 1500 mAh / g), long cycle life (with a capacity
retention ratio of more than 90% after 300 cycles) and
high conductivity. The preparation method for the composite silicon negative
electrode material is simple, easily controllable, and applicable to industrial production.