Composite slurry and preparation method thereof, composite layer and battery

The invention discloses composite slurry and a preparation method thereof, a composite layer and a battery, and relates to the technical field of batteries. The preparation method comprises the steps that conductive materials are provided, the conductive materials comprise a two-dimensional material and/or a three-dimensional material, the two-dimensional material comprises a graphene-like layered compound, and the three-dimensional material comprises one or more of inorganic coating oxide and a carbon material; the method comprises the following steps: adding a conductive material into a solvent, and obtaining pre-dispersed slurry after the first viscosity eta 1 is reached; and providing a binder, adding the binder into the pre-dispersed slurry, and obtaining the composite slurry after the second viscosity eta 2 is reached. According to the preparation method provided by the invention, the composite slurry is obtained through two times of viscosity adjustment, so that uniform dispersion of a conductive mater