The invention discloses a 
tin cobalt alloy / 
graphene composite material and a preparation method of the 
tin cobalt alloy / 
graphene composite material. The preparation method of the 
tin cobalt alloy / 
graphene composite material includes the following steps that firstly, graphene 
oxide is dispersed into methyl 
alcohol or ethylalcohol or 
ethylene glycol or 
diethylene glycol, and then suspension liquid is prepared; secondly, 
cobalt salt and tin slat of which the 
mass ratio of the sum of 
mass to the 
mass of graphene 
oxide ranges from 60:1 to 30:1 dissolve in the suspension liquid prepared through the first step, wherein the 
molar ratio of a cobalt element to a 
tin element ranges from 1: 0.66 to 1:3; thirdly, a 
sodium borohydride alcoholic solution of which the concentration ranges from 1 mol / L to 2.5 mol / L is prepared, 
alcohol used in the first step is used in this step, the 
sodium borohydride alcoholic solution is mixed with the suspension liquid obtained through the second step, 
nitrogen is injected, and after 10 minutes of bubbling, 
solvent heat treatment is conducted, wherein 
solvent heat treatment refers to the process that a mixture reacts for 6 h to 12 h at the temperature of 100 DEG C to 160 DEG C in a closed reaction kettle and then is cooled to the 
room temperature, and the 
molar ratio of the cobalt element in 
sodium borohydride to the cobalt element in the 
cobalt salt is 6-13 to 1; fourthly, a sample obtained in the third step is repeatedly washed centrifugally in ethyl 
alcohol and deionized water, and a product is obtained after 
vacuum drying.