Positive-electrode active material for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery including the same
A positive-electrode active material for a non-aqueous electrolyte secondary battery according to the present disclosure contains a layered lithium (Li)-containing transition metal composite oxide that contains Li in the transition metal layer and more than 0.4 μmol/g and less than 25 μmol/g of iodine (I) or bromine (Br).
1. A positive-electrode active material for a non-aqueous electrolyte secondary battery, comprising:
a layered crystalline lithium (Li)-containing transition metal composite oxide that has a layered structure and contains Li in a transition metal layered thereof and sodium Na,
wherein the positive-electrode active material is represented by the general formula Li x Na a [Li y M 1-y ]O 2-c+α I 2c , where M contains at least one of Ni, Co, and Mn, 0.67<x<1.1, 0<y<0.33, 0.0001≦a≦0.1, −0.1≦α≦0.1, and c is calculated by:
c =an iodine content (mol/g)/(mol/g of the positive-electrode active material)/2,
where 0.4 μmol/g<the iodine content<25 μmol/g, and
the I is contained within the layered structure of the Li-containing transition metal composite oxide.
2. The positive-electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein:
the I is also disposed on a surface of the Li-containing transition metal composite oxide.
3. The positive-electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein x in the general formula is in the range of 0.83<x<1.1.
4. The positive-electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , wherein the arrangement of the transition metal, oxygen, and Li of the positive-electrode active material has at least one of O2 structure, T2 structure, and O6 structure.
5. A non-aqueous electrolyte secondary battery, comprising:
a positive electrode containing a positive-electrode active material according to claim 1 ;
a negative electrode; and
a non-aqueous electrolyte.
6. A method for producing the positive-electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 , comprising:
allowing a positive-electrode active material precursor sodium-containing transition metal oxide to react with LiI to produce a positive-electrode active material containing I; and
washing the positive-electrode active material such that the iodine content satisfies 0.4 μmol/g<the iodine content<25 μmol/g.
7. The method for producing the positive-electrode active material for a non-aqueous electrolyte secondary battery according to claim 6 , further comprising: applying a charging activation voltage of less than 4.46 V (vs. Li/Li+) to the washed positive-electrode active material.