Positive electrode material for lithium ion secondary batteries, positive electrode for lithium ion secondary batteries, and lithium ion secondary battery
The positive electrode material for lithium ion secondary batteries includes a mixture including a positive electrode active material in which a length of a longest side of a primary particle is 1 nm or more and 1000 nm or less and a NASICON-type compound in which a length of a longest side of a primary particle is 1 nm or more and 1000 nm or less.
1. A positive electrode material for lithium ion secondary batteries, comprising a mixture which includes:
a positive electrode active material in which a length of a longest side of a primary particle of the active material is 1 nm or more and 1000 nm or less; and
A NASICON-type compound in which a length of a longest side of a primary particle of the compound is 1 nm or more and 1000 nm or less,
wherein, the positive electrode active material is at least one selected from a group consisting of Li 3 FePO 4 , Li Fe 0.26 Mn 0.7 Mg 0.0349 Co 0.05 Ca 0.001 PO 4 , and LiCoPO 4 , and
the NASICON-type compound is represented by formula Li a Al b Ti 2-b (PO 4 ) 3 , and
a mixing ratio by mass of the positive electrode active material to the NASICON-type compound is from 99:1 to 90.5:9.5, wherein 0.8≤a≤1.5 and 0≤b≤0.5.
2. The positive electrode material for lithium ion secondary batteries according to claim 1 ,
wherein
a specific surface area of the mixture is 7 m 2 /g or more and 40 m 2 /g or less, and
wherein when 50% of a volume particle diameter of secondary particles of the mixture is represented by D50, D50 is 2 μm or more and 12 μm or less.
3. The positive electrode material for lithium ion secondary batteries according to claim 1 ,
wherein one of, or both of, a surface of the primary particle of the positive electrode active material and a surface of the primary particle of the NASICON-type compound are coated with a carbonaceous film having a thickness of 1 nm or more and 10 nm or less.
4. A positive electrode for lithium ion secondary batteries, the positive electrode comprising:
an electrode current collector; and
a positive electrode mixture layer that is formed on the electrode current collector,
wherein the positive electrode mixture layer includes the positive electrode material for lithium ion secondary batteries according to claim 1 .
5. A lithium ion secondary battery comprising:
a positive electrode;
a negative electrode; and
a non-aqueous electrolyte,
wherein the positive electrode in the positive electrode for lithium ion secondary batteries according to claim 4 .
6. The positive electrode material for lithium ion secondary batteries according to claim 1 ,
wherein the length of a longest side of a primary particle of the active material is 50 nm or more and 500 nm or less, and
the length of a longest side of a primary particle of the NASICON-type compound is 200 nm or more and 800 nm or less.
7. The positive electrode material for lithium ion secondary batteries according to claim 1 ,
wherein the length of the longest side of the primary particles of the active material is an average value of the lengths of the longest sides of 100 primary particles, and
the length of the longest side of the primary particles of the NASICON-type compound is an average value of the lengths of longest sides of 100 primary particles.
8. The positive electrode material for lithium ion secondary batteries according to claim 3 ,
wherein the carbonaceous film is a pyrolytic carbon film that is obtained by carbonizing an organic compound.
9. The positive electrode material for lithium ion secondary batteries according to claim 1 ,
wherein the mixture includes a secondary particle which includes the primary particle of the active material and the primary particles of the NASICON-type compound.
10. The positive electrode material for lithium ion secondary batteries according to claim 9 ,
wherein the secondary particle is covered by a carbonaceous film which consists of a pyrolytic carbon film.
11. The positive electrode material for lithium secondary batteries according to claim 9 ,
wherein the secondary particle is not covered by a carbonaceous film.
12. The positive electrode material for lithium ion secondary batteries according to claim 1 ,
wherein the mixing ratio by mass of the positive electrode active material to the NASICON-type compound is from 99:1 to 94:6.