The invention relates to a preparation method of a high-efficiency negative active material for a
lithium ion secondary battery.
Lithium-
silicon alloys Li4.4Si, Li3.25Si and Li1.71Si are prepared by high-energy ball milling. The preparation method is simple,
pollution-free and high in safety. At the same time, a suitable
solvent is added in the high-energy ball milling to serve as a
lubricant, thereby greatly improving the efficiency of an alloying reaction. A
composite material is prepared from a
lithium-
silicon alloy together with pre-ball-milling
silicon powder,
graphite and carbon has a unique structure, which inhibits the
volume expansion of materials during charging and discharging. Moreover, LixSi has high capacity and higher
conductivity than pure silicon, and contains
lithium, which can inhibit the formation of an SEI film in the first week and improve the first week coulombic efficiency of materials. Secondly, the experimental results of the invention show that the synthesized LixSi can be transformed into
amorphous silicon after lithium removal, thereby effectively alleviating the
volume change during charging and discharging, and exhibiting cycle performance far exceeding that of
crystalline silicon. The high-efficiency negative active material is
environmentally friendly, simple and feasible in preparation method and instrument and equipment, high in safety, and suitable for industrial production.