Non-aqueous electrolyte secondary battery
A non-aqueous electrolyte secondary battery includes: a positive electrode containing a positive active material; a negative electrode; and a non-aqueous electrolyte. The positive active material contains composite oxide particles having a spinel structure including Ni and Mn. The composite oxide particles contain at least one of a crystal phase of LiNbO 3 and a crystal phase of LiMg 1-x Nb x O 3 . The “x” is higher than 0 and lower than 1. The crystal phase is segregated and located in a surface layer portion of the composite oxide particles.
1. A non-aqueous electrolyte secondary battery comprising:
a positive electrode containing a positive active material;
a negative electrode; and
a non-aqueous electrolyte, wherein
the positive active material contains composite oxide particles having a spinel structure including Ni and Mn,
the composite oxide particles contain at least one of a crystal phase of LiNbO 3 or a crystal phase of LiMg 1-x Nb x O 3 ,
x is higher than 0 and lower than 1, and
the crystal phase is segregated and located in a surface layer portion of the composite oxide particles.
2. The non-aqueous electrolyte secondary battery according to claim 1 , wherein
the spinel structure includes Ni, Mn, Nb, Mg, and Me,
Me is at least one metal element having a lower electronegativity than an electronegativity of Mn, and
the composite oxide particles primarily form the spinel structure.
3. The non-aqueous electrolyte secondary battery according to claim 2 , wherein
a combination of the spinel structure and the crystal phase is expressed by General Formula (1) as follows:
LiNi a Mn b Nb c Mg d Me e O 4 (1)
where a, b, c, d, and e in the General Formula (1) satisfy following conditions:
0.4≤ a≤ 0.6
1.2≤ b≤ 1.6
0.02≤ c≤ 0.1
0.02≤ d≤ 0.1
0≤ e≤ 0.1
1.8≤( a+b+c+d+e )≤2.2.
4. The non-aqueous electrolyte secondary battery according to claim 3 , wherein
Me is at least one metal element selected from the group consisting of Na, K, and Ca.
5. The non-aqueous electrolyte secondary battery according to claim 4 , wherein
e is 0.03 or higher and 0.05 or lower.
6. The non-aqueous electrolyte secondary battery according to claim 1 , wherein
the crystal phase contains LiMg 1-x Nb x O 3 .
7. The non-aqueous electrolyte secondary battery according to claim 6 , wherein
the crystal phase consists of LiMg 1-x Nb x O 3 .
8. The non-aqueous electrolyte secondary battery according to claim 6 , wherein
LiMg 1-x Nb x O 3 has a crystal structure of a trigonal crystal system that belongs to a space group R3C.
9. The non-aqueous electrolyte secondary battery according to claim 6 , wherein
x is higher than 0 and equal to or lower than 0.5.
10. The non-aqueous electrolyte secondary battery according to claim 9 , wherein
x is 0.001 or higher and 0.3 or lower.
11. The non-aqueous electrolyte secondary battery according to claim 10 , wherein
x is 0.005 or higher and 0.2 or lower.
12. The non-aqueous electrolyte secondary battery according to claim 11 , wherein
x is 0.01 or higher and 0.1 or lower.
13. The non-aqueous electrolyte secondary battery according to claim 1 , wherein
the crystal phase is a film that is scattered in the surface layer portion of the composite oxide particles.
14. The non-aqueous electrolyte secondary battery according to claim 6 , wherein
the crystal phase has a peak at a position shifted toward a lower angle side by 0.05° to 0.1° inclusive from a predetermined peak between 23.5° and 24.0° in an X-ray diffraction pattern measured by a powder X-ray diffraction analyzer, the predetermined peak being included among peaks attributed to the crystal phase of LiNbO 3 .