Positive electrode active material for lithium secondary battery, positive electrode for lithium secondary battery, and lithium secondary battery
A positive electrode active material for a lithium secondary battery includes a primary particle containing a spinel phase and a layered rock-salt phase. The spinel phase is formed of a nickel-and-manganese-containing composite oxide having a spinel crystal structure that includes lithium, nickel, and manganese. The layered rock-salt phase is formed of a transition metal composite oxide having a layered rock-salt crystal structure that includes lithium and at least one transition metal element. The nickel-and-manganese-containing composite oxide contains oxygen and fluorine. The transition metal composite oxide includes oxygen and fluorine.
1. A positive electrode active material for a lithium secondary battery, the positive electrode active material comprising
a primary particle including a spinel phase and a layered rock-salt phase, wherein
the spinel phase is formed of a nickel-and-manganese-containing composite oxide having a spinel crystal structure that includes lithium, nickel, and manganese,
the layered rock-salt phase is formed of a transition metal composite oxide having a layered rock-salt crystal structure that includes lithium and at least one transition metal element,
the nickel-and-manganese-containing composite oxide contains oxygen and fluorine, and
the transition metal composite oxide includes oxygen and fluorine,
wherein the transition metal composite oxide is represented by the following Formula (II):
Li (2−a) M1 (1+a) O 3−b F b (II)
where M1 represents manganese or at least two elements including manganese, and
a and b satisfy the following relationships:
0< b≦ 1; and
0≦ a≦ 0.5.
2. The positive electrode active material for a lithium secondary battery according to claim 1 , wherein
the fluorine constituting the nickel-and-manganese-containing composite oxide is fluorine substituted with a part of the oxygen constituting the nickel-and-manganese-containing composite oxide, and
the fluorine constituting the transition metal composite oxide is fluorine substituted with a part of the oxygen constituting the transition metal composite oxide.
3. The positive electrode active material for a lithium secondary battery according to claim 1 , wherein
the nickel-and-manganese-containing composite oxide is represented by the following Formula (I):
LiMn 2−x−y Ni x M y O 4−z F z (I)
where M represents at least one element selected from the group consisting of Fe, Ti, Al, Si, Mg, Ca, Ba, Sr, Sc, V, Cr, Co, Cu, Zn, Ga, Y, Ru, Rh, Pd, In, Sn, Sb, La, Ce, Sm, Zr, Nb, Ta, Mo, W, B, C, P, and S, and
x, y, and z satisfy the following relationships:
0< z≦ 1;
0.4≦ x≦ 0.6; and
0< y≦ 0.6.
4. The positive electrode active material for a lithium secondary battery according to claim 3 , wherein
M represents two or more elements selected from the group consisting of Fe, Ti, Al, Si, Mg, Ca, Ba, Sr, Sc, V, Cr, Co, Cu, Zn, Ga, Y, Ru, Rh, Pd, In, Sn, Sb, La, Ce, Sm, Zr, Nb, Ta, Mo, W, B, C, P, and S.
5. The positive electrode active material for a lithium secondary battery according to claim 4 , wherein
the nickel-and-manganese-containing composite oxide is represented by the following Formula (IA):
LiMn 2−x−y Ni x Fe v Ti w O 4−z F z (IA)
where v and w satisfy the following relationships:
0< v< 0.6;
0< w< 0.6; and
v+w=y.
6. The positive electrode active material for a lithium secondary battery according to claim 3 , wherein
the nickel-and-manganese-containing composite oxide contains at least one of Fe and Ti as M.
7. The positive electrode active material for a lithium secondary battery according to claim 1 , wherein
the primary particle of the nickel-and-manganese-containing composite oxide has no grain boundary.
8. The positive electrode active material for a lithium secondary battery according to claim 1 , wherein
a ratio of the transition metal composite oxide is 3 mol % to 8 mol % with respect to 100 mol % of a total amount of the transition metal composite oxide and the nickel-and-manganese-containing composite oxide.
9. A positive electrode for a lithium secondary battery, the positive electrode comprising
a positive electrode active material layer that is provided on a positive electrode current collector and includes the positive electrode active material according to claim 1 .
10. A lithium secondary battery comprising:
a positive electrode that includes a positive electrode active material layer provided on a positive electrode current collector;
a negative electrode that includes a negative electrode active material layer provided on a negative electrode current collector; and
a nonaqueous electrolyte, wherein
the positive electrode active material layer includes the positive electrode active material according to claim 1 .