Negative electrode plate, secondary battery, and apparatus thereof

A secondary battery, comprising a positive electrode plate, a negative electrode plate, a separator disposed between the positive electrode plate and the negative electrode plate, and an electrolyte, wherein the negative electrode plate further comprises a negative electrode current collector and a negative membrane disposed on the negative electrode current collector,

• wherein the negative membrane comprises:
• a first coating layer, located on an outermost layer of the negative membrane and comprising a first negative active material, a conductive agent, and a binder, the first negative active material comprising a silicon-based material and a carbon material;
• and
• a second coating layer, disposed between the first coating layer and the negative electrode current collector and comprising a second negative active material, a conductive agent, and a binder, the second negative active material comprising a silicon-based material and a carbon material;
• wherein a thickness of the first coating layer is 20 μm to 50 μm, and a thickness of the second coating layer is 60 μm to 100 μm;
• wherein, in the first coating layer, a mass percentage of the silicon-based material is 0.5% to 5%, a mass percentage of the carbon material is at least 91%, a mass percentage of the binder is 1% to 3%, a mass percentage of the conductive agent is 0.5% to 2.5%;
• wherein, in the second coating layer, a mass percentage of the silicon-based material is 20% to 40%, a mass percentage of the carbon material is 50% to 70%, a mass percentage of the binder is 6% to 10%, a mass percentage of the conductive agent is 1% to 3%;
• wherein a difference between a mass percentage of the carbon material in the first coating layer and a mass percentage of the carbon material in the second coating layer is 20% to 40%;
• wherein a difference between the mass percentage of the silicon-based material in the second coating layer and the mass percentage of the silicon-based material in the first coating layer is 10% to 40%;
• wherein the silicon-based material of the first coating layer and the second coating layer comprises one or more of amorphous silicon and crystalline silicon, silicon-oxygen compound;
• wherein the carbon material comprises one or more of artificial graphite, natural graphite, and mesocarbon microbeads;
• wherein the conductive agent comprises one or more of acetylene black, Ketjen black, conductive carbon black, and carbon nanotubes;
• wherein the binder comprises one of more of polyacrylic acid, sodium polyacrylate, sodium alginate, polyacrylonitrile, polyethylene glycol, and carboxymethyl chitosan.