Electrode material, electrode and lithium ion battery
An electrode material which can improve the mobility of electrons and the mobility of ions at the same time, and, furthermore, does not have a problem of the impairment of the diffusion of lithium ions in a thin layer containing a carbonaceous electron-conductive substance so as to be excellent in terms of load characteristics and energy density, and an electrode and a lithium ion battery are provided. The electrode material of the invention is produced by forming a thin layer made of a carbonaceous electron-conductive substance on surfaces of primary particles made of an electrode active material, in which the carbonaceous electron-conductive substance contains nitrogen atoms.
1. An electrode material comprising:
primary particles consisting of an electrode active material and a thin layer of a carbonaceous electron-conductive substance on surfaces of the primary particles, wherein:
the thin layer has a thickness of 0.1 nm to 20.0 nm, and a coating rate of 80% or more of the surfaces of the primary particles;
the carbonaceous electron-conductive substance consists of nitrogen atoms in a range of 0.1% to 20.0% by mass based on a total mass of the carbonaceous electron-conductive substance, a graphitized portion of a carbonaceous substance, and an amorphous carbon portion;
the amount of nitrogen atoms is in a range of 0.0005% to 0.15% by mass based on a total mass of the electrode material;
the electrode active material is Li x A y PO 4 , wherein A represents one or two or more elements selected from the group consisting of Mn, Fe, Co, and Ni; 0≤x≤4; and 0<y≤1.5;
a content ratio of the carbonaceous electron-conductive substance is in a range of 0.5% by mass to 10.0% by mass with respect to the mass of the electrode active material; and
the electrode material is for a positive electrode.
2. The electrode material according to claim 1 , wherein a plurality of the primary particles made of the electrode active material is aggregated so as to form secondary particles with the thin layer made of a carbonaceous electron-conductive substance being interposed between the primary particles.
3. The electrode material according to claim 1 , wherein the electrode material is obtained by mixing an electrode active material, an organic substance which serves as a carbon source, a nitrogen source and a carbonization catalyst containing any one or both of Fe and Ni as necessary, and then thermally treating the mixture in a non-oxidizing atmosphere.
4. The electrode material according to claim 3 , wherein the organic substance which serves as the carbon source contains one or two or more elements selected from the group consisting of glucose, sucrose, polyvinyl alcohols, polyacrylic acids, and hydroxylic acids, and the nitrogen source contains one or two or more elements selected from the group consisting of pyridine, urea, thiourea, and amines.
5. The electrode material of claim 1 , wherein the carbonaceous electron-conductive substance is formed by a carbonization process comprising mixing the electrode active material with a carbon source and a nitrogen source for the nitrogen atoms prior to carbonization, thereby producing the graphitized portion of the carbonaceous substance and the amorphous carbon portion.
6. An electrode comprising:
the electrode material according to claim 1 .
7. A lithium ion battery comprising:
a positive electrode made of the electrode according to claim 6 .