Composite particles, manufacturing method thereof, electrode material for secondary battery, and secondary battery

A process for producing composite particles, the process comprising:

• a first step of subjecting to surface treatment at least one carbon material selected from the group consisting of (i) fibrous carbon material, (ii) chain-like carbon material, and (iii) carbon material produced by linking together fibrous carbon material and chain-like carbon material;
• a second step of mixing the at least one surface-treated carbon material and source material for lithium-containing phosphate,
• wherein the second step of mixing the source material for the lithium-containing phosphate and the at least one surface-treated carbon material is a step of dispersing and mixing the at least one surface-treated carbon material into a solution having dissolved into a solvent a lithium ion (Li+), a phosphate ion (PO43−), and a metal ion other than from lithium,
• a third step of heating the solution to form composite particles comprising:
• the at least one surface-treated carbon material;
• and a lithium-containing phosphate precursor and/or the lithium-containing phosphate,
• wherein a method using a pressured and heated solvent is used for the steps comprising:
• dispersing the at least one surface-treated carbon material into the solution;
• mixing the solution;
• and then heating the solution to form composite particles comprising:
• the at least one surface-treated carbon material;
• and a lithium-containing phosphate precursor and/or the lithium-containing phosphate;
• and
• a fourth step of heating the composite particles to create at least one fine pore opening to outside the composite particle, wherein the at least one fine pore originates from the at least one surface-treated carbon material, and
• the composite particles comprise:
• at least one carbon material selected from the group consisting of (i) fibrous carbon material, (ii) chain-like carbon material, and (iii) carbon material produced by linking together fibrous carbon material and chain-like carbon material;
• and
• lithium-containing phosphate,
• wherein the composite particles comprise at least one fine pore originating from the at least one carbon material and opening to outside the composite particles, thus connecting the inside of the composite particles with the outside of the composite particles,
• a portion of the at least one carbon material is located inside the composite particle,
• the size of the at least one fine pore is from 0.5 nm to 12 nm,
• the at least one fine pore is made by subjecting to surface treatment the at least one carbon material and heating the composite particles, wherein the surface treatment of the at least one carbon material is a method using a polymer dispersant,
• and
• the polymer dispersant is one or more selected from the group consisting of polyvinylpyrrolidone and poly(allylamine hydrochloride).