AQUEOUS SOLUTION AND METHOD FOR PRODUCING CATHODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERIES
An aqueous solution contains Li, a peroxo complex of an element α, an ammonium ion, and a nitrate ion, in which the element α is one or more elements selected from the group consisting of Nb, Ti, Ta, Zr, W, Mo, and V, and in the aqueous solution, a ratio (NH 4 + /α) of a mass molar concentration of the ammonium ion to a mass molar concentration of the element α is less than 4.5, and a mass molar concentration of the nitrate ion (NO 3 − ) is less than 4.0×10 −3 mol/kg.
1 . An aqueous solution comprising:
Li;
a peroxo complex of an element α;
an ammonium ion; and
a nitrate ion,
wherein the element α is one or more elements selected from the group consisting of Nb, Ti, Ta, Zr, W, Mo, and V, and
in the aqueous solution, a ratio (NH 4 + /α) of a mass molar concentration of the ammonium ion to a mass molar concentration of the element α is less than 4.5, and a mass molar concentration of the nitrate ion (NO 3 − ) is less than 4.0×10 −3 mol/kg.
2 . The aqueous solution according to claim 1 ,
wherein a ratio (NO 3 − /α) of the mass molar concentration of the nitrate ion to the mass molar concentration of the element α in the aqueous solution is less than 0.017.
3 . The aqueous solution according to claim 1 ,
wherein a ratio (Li/α) of a mass molar concentration of Li to the mass molar concentration of the element α in the aqueous solution is more than 1.0.
4 . The aqueous solution according to claim 1 ,
wherein the mass molar concentration of the element α is 0.10 mol/kg or more.
5 . The aqueous solution according to claim 1 ,
wherein a pH of the aqueous solution is 11.0 or more, and
the element α is Nb.
6 . A method for producing a cathode active material for lithium secondary batteries, that contains metal composite particles and a coating material with which at least part of the metal composite particles is coated, the method comprising:
a step X of bringing the aqueous solution according to claim 1 into contact with the metal composite particles to coat at least part of the metal composite particles with the coating material.
7 . The method for producing a cathode active material for lithium secondary batteries according to claim 6 ,
wherein the metal composite particles are a lithium metal composite oxide.
8 . The method for producing a cathode active material for lithium secondary batteries according to claim 6 ,
wherein the step X includes bringing the aqueous solution into contact with the metal composite particles by spraying the aqueous solution onto the metal composite particles, drying the aqueous solution adhered to a surface of the metal composite particles, and subjecting the metal composite particles to a heat treatment.
9 . A method for producing a cathode active material for lithium secondary batteries, that uses metal composite particles and a coating material with which at least part of the metal composite particles is coated, the method comprising:
a step A of preparing a coating liquid,
wherein the step A includes a step A1 of mixing a compound containing an element α, a solution containing hydrogen peroxide, a solution containing ammonia, and a lithium compound to prepare a solution L having a liquid temperature of higher than 40° C., and a step A2 of cooling the solution L to 40° C. or lower to obtain the coating liquid,
the element α is one or more elements selected from the group consisting of Nb, Ti, Ta, Zr, W, Mo, and V,
the coating liquid contains a peroxo complex of the element α, and Li,
a ratio (Li/α) of a mass molar concentration of Li to a mass molar concentration of the element α in the coating liquid is more than 1.0, and
an average cooling rate of the solution L from the liquid temperature to 40° C. in the step A2 is less than 0.9° C./min.
10 . The method for producing a cathode active material for lithium secondary batteries according to claim 9 ,
wherein the mass molar concentration of the element α in the coating liquid is 0.10 mol/kg or more.
11 . The method for producing a cathode active material for lithium secondary batteries according to claim 9 ,
wherein the step A1 includes an operation of adding the lithium compound to a slurry containing the compound containing the element α, the solution containing hydrogen peroxide, and the solution containing ammonia, the slurry having a temperature of 35° C. or higher.
12 . The method for producing a cathode active material for lithium secondary batteries according to claim 9 ,
wherein the step A1 includes an operation of heating a slurry containing the compound containing the element α, the solution containing hydrogen peroxide, and the solution containing ammonia at an average heating rate of 0.9° C./min or more and 10° C./min or less, and adding the lithium compound to the slurry having a temperature of 35° C. or higher.
13 . The method for producing a cathode active material for lithium secondary batteries according to claim 9 ,
wherein the element α is Nb.
14 . The method for producing a cathode active material for lithium secondary batteries according to claim 9 ,
wherein the compound containing the element α is a compound containing niobium oxide, and
the lithium compound is a compound including lithium hydroxide or lithium hydroxide hydrate.
15 . The method for producing a cathode active material for lithium secondary batteries according to claim 9 , further comprising, after the step A:
a step B of coating at least part of the metal composite particles with the coating liquid,
wherein the step B includes spraying the coating liquid onto the metal composite particles, drying the coating liquid adhered to a surface of the metal composite particles, and subjecting the metal composite particles to a heat treatment.