Positive electrode composition for lithium ion secondary battery, positive electrode for lithium ion secondary battery, and lithium ion secondary battery
A positive electrode composition for a lithium ion secondary battery includes an active material that can occlude and release lithium ions and a conductive material, wherein the active material is a lithium cobalt composite oxide; the conductive material is carbon black and carbon nanotubes; the carbon black has a BET specific surface area of 100 to 400 m 2 /g and a DBP absorption amount of 210 to 400 ml/100 g; the carbon nanotubes have an average diameter of 20 nm or less, a BET specific surface area of 170 m 2 /g or more, and an aspect ratio of 50 or more; and a carbon black content X (unit: % by mass) and a carbon nanotube content Y (unit: % by mass) in the positive electrode composition satisfy the following conditions (A) and (B): (A) 0.5≤(X+Y)≤2.0; (B) 0.80≤{X/(X+Y)}≤0.95.
1. A positive electrode composition for a lithium ion secondary battery, comprising an active material that can occlude and release lithium ions and a conductive material, wherein
the active material is a lithium cobalt composite oxide in which lithium and cobalt are the only metal components;
the conductive material is carbon black and carbon nanotubes, wherein the carbon black and the carbon nanotubes are separately dispersed in the active material;
all the carbon black comprised in the positive electrode composition has a BET specific surface area of 133 to 400 m 2 /g and a DBP absorption amount of 210 to 400 ml/100 g;
the carbon nanotubes have an average diameter of 20 nm or less, a BET specific surface area of 170 m 2 /g or more, and an aspect ratio of 50 or more, wherein the BET specific surface area of carbon black and the carbon nanotubes are measured separately; and
a carbon black content X (unit: % by mass) and a carbon nanotube content Y (unit: % by mass) in the positive electrode composition satisfy the following conditions (A) and (B):
0.5≤( X+Y )≤2.0 (A)
0.80≤{ X /( X+Y )}≤0.95. (B)
2. The positive electrode composition for a lithium ion secondary battery according to claim 1 , wherein the lithium cobalt composite oxide has an average particle diameter D 50 of 10 to 20 μm.
3. The positive electrode composition for a lithium ion secondary battery according to claim 1 , wherein the BET specific surface area of the carbon nanotubes is larger than 200 m 2 /g.
4. The positive electrode composition for a lithium ion secondary battery according to claim 1 , wherein the positive electrode composition for a lithium ion secondary battery comprises 96% by mass or more and lower than 99.5% by mass of the lithium cobalt composite oxide.
5. A positive electrode for a lithium ion secondary battery comprising the positive electrode composition for a lithium ion secondary battery according to claim 1 .
6. A lithium ion secondary battery comprising the positive electrode for a lithium ion secondary battery according to claim 5 .
7. The positive electrode composition for a lithium ion secondary battery according to claim 1 , wherein the carbon black forms conductive paths between the active material, and the carbon nanotubes form conductive paths on a surface of the active material.