Cathode active material for lithium-ion secondary battery and preparation method thereof, cathode pole piece for lithium-ion secondary battery, and lithium-ion secondary battery

A method of preparing a cathode active material for a lithium-ion battery, the method comprising:

• dispersing, by using a dispersant, a silicon-based active substance with a particle diameter of 1 nm-1 μm in solution to obtain a mixed solution;
• adding an oxidizer into the mixed solution and then adding an organic molecular monomer, wherein the organic molecular monomer is selected from one or more of a pyridine monomer, a pyrrole monomer, an aniline monomer, and a derivative of the pyridine monomer, the pyrrole monomer, or the aniline monomer, and the silicon-based active substance reacts with the organic molecular monomer to form a black precipitate;
• filtering the black precipitate and taking a filter residue;
• and then encasing the exterior of the silicon-based active substance in a nitrogen-doped carbon material by using a pyrolysis method, so as to obtain the cathode active material for a lithium-ion secondary battery;
• placing a silicon-based active substance with a particle diameter of 1 nm-1 μm in a tubular furnace;
• bringing in, by protective gas, a gasified organic molecular monomer, wherein the organic molecular monomer is selected from one or more of a pyridine monomer, a pyrrole monomer, an aniline monomer, and a derivative of the pyridine monomer, the pyrrole monomer, or the aniline monomer;
• and encasing the exterior of the silicon-based active substance in a nitrogen-doped carbon material by using a chemical vapor deposition method, so as to obtain the cathode active material for a lithium-ion secondary battery;
• and
• mixing one or more organic molecules of the ionic liquid 3-methyl-1-butylpyridine dicyanamide or 1-ethyl-3-methylimidazole dicyanamide and a derivative of the 3-methyl-1-butylpyridine dicyanamide or the 1-ethyl-3-methylimidazole dicyanamide, with a silicon-based active substance with a particle diameter of 1 nm-1 μm to obtain a mixed solution and then encasing the exterior of the silicon-based active substance in a nitrogen-doped carbon material by using an ionic liquid pyrolysis method, so as to obtain the cathode active material for a lithium-ion secondary battery, wherein:
• the cathode active material for a lithium-ion secondary battery comprises a silicon-based active substance and a nitrogen-doped carbon material;
• the silicon-based active substance is encased in the interior of the nitrogen-doped carbon material, and the silicon-based active substance is one or more of a nanoparticle and a nanowire,
• a particle diameter of the silicon-based active substance nanoparticle is 1 nm-1 μm, and the nanowire is 1-200 nm in diameter and 1-10 μm long;
• a micropore is arranged on at least one of the exterior and the interior of the nitrogen-doped carbon material,
• an aperture of the micropore ranges between 0.5-500 nm, and
• a material of the nitrogen-doped carbon material is a nitrogen-doped carbon network, wherein a nitrogen atom and a carbon atom in the nitrogen-doped carbon network are bonded in at least one form of pyridinic nitrogen, graphite nitrogen and pyrrolic nitrogen.

A cathode pole piece for a lithium-ion secondary battery, the cathode pole piece comprising:

• a current collector;
• a cathode active material coated on the current collector and comprising a silicon-based active substance and a nitrogen-doped carbon material, wherein the silicon-based active substance is encased in the interior of the nitrogen-doped carbon material, and the silicon-based active substance is one or more of a nanoparticle and a nanowire;
• micropores arranged on at least one of the exterior and the interior of the nitrogen-doped carbon material;
• and
• a material of the nitrogen-doped carbon material is a nitrogen-doped carbon network, wherein the nitrogen-doped carbon material comprises a plurality of interlinked branches formed by the nitrogen-doped carbon network, the silicon-based active substance is encased in an interior of the nitrogen-doped carbon material, wherein the micropores are arranged on at least one of the exterior and the interior of the plurality of interlinked branches of the nitrogen-doped carbon material, wherein a nitrogen atom and a carbon atom in the nitrogen-doped carbon network are bonded in at least one form of pyridinic nitrogen, graphite nitrogen and pyrrolic nitrogen.

A lithium-ion secondary battery comprising a cathode pole piece, an anode pole piece, a membrane, a non-aqueous electrolyte and a casing, wherein the cathode pole piece comprises:

• a current collector;
• a cathode active material coated on the current collector and comprising a silicon-based active substance and a nitrogen-doped carbon material, wherein the silicon-based active substance is encased in the interior of the nitrogen-doped carbon material, and the silicon-based active substance is one or more of a nanoparticle and a nanowire, and wherein a particle diameter of the silicon-based active substance nanoparticle is 1 nm-1 μm, and the nanowire is 1-200 nm in diameter and 1-10 μm long;
• a micropore arranged on at least one of the exterior and the interior of the nitrogen-doped carbon material, and wherein an aperture of the micropore ranges between 0.5-500 nm;
• and
• a material of the nitrogen-doped carbon material is a nitrogen-doped carbon network, wherein a nitrogen atom and a carbon atom in the nitrogen-doped carbon network are bonded in at least one form of pyridinic nitrogen, graphite nitrogen and pyrrolic nitrogen.