Silicon-carbon composite material for negative electrode of lithium ion battery as well as preparation method and application of silicon-carbon composite material

The preparation method comprises the following steps: uniformly dispersing nano silicon, graphite, an organic cracking carbon source and a nano conductive agent by using a dispersing agent to obtain a precursor, sintering the precursor, and then drying, carbonizing, crushing and sieving to obtain the silicon-carbon composite material. The ratio of the designed capacity (first reversible capacity) of the silicon-carbon composite material to the specific surface area of the graphite is 280-330. The material structurally comprises a graphite layer and a nano silicon/organic cracking carbon source layer from inside to outside, a conductive network is interspersed among the layers, the tap density is 0.8-1g/cm < 3 >, the first reversible capacity is 700-500mAh, the tap density of the silicon-carbon composite material is in negative correlation with the first reversible capacity, and the ratio of the first reversible capacity to the specific surface area of graphite is 280-330. The first reversible capacity of the