POSITIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY, POSITIVE ELECTRODE FOR LITHIUM SECONDARY BATTERY, LITHIUM SECONDARY BATTERY, AND METHOD FOR PRODUCING POSITIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY
In a spectrum obtained by X-ray photoelectron spectroscopy measurement of surfaces of particles of the positive electrode active material for the lithium secondary battery, the positive electrode active material has a peak X derived from a Li element having a peak top at 54.5±3.0 eV; when, upon waveform separation of the peak X derived from the Li element into a peak (A) having a peak top at 53.5±1.0 eV and a peak (a) having a peak top at 55.5±1.0 eV, an atomic ratio calculated from the peak (A), a peak derived from the Ni element, and a peak derived from the element M is defined as Li(A)/(Ni+M), and the BET specific surface area of the positive electrode active material for the lithium secondary battery measured by a nitrogen adsorption method is defined as PS, the value of {Li(A)/(Ni+M)}/PS is 0.4 to 2.6 g/m 2 .
1 . A positive electrode active material for a lithium secondary battery, comprising a lithium metal composite oxide containing a Ni element and an element M, and a lithium compound,
wherein the lithium metal composite oxide has a layered rock-salt structure,
the element M represents one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, Si, S, and P, and
in a spectrum obtained by X-ray photoelectron spectroscopy measurement of surfaces of particles of the positive electrode active material for the lithium secondary battery, the positive electrode active material has a peak X derived from a Li element having a peak top at 54.5±3.0 eV; when, upon waveform separation of the peak X derived from the Li element into a peak (A) having a peak top at 53.5±1.0 eV and a peak (a) having a peak top at 55.5±1.0 eV, an atomic ratio calculated from the peak (A), a peak derived from the Ni element, and a peak derived from the element M is defined as Li(A)/(Ni+M), and a BET specific surface area of the positive electrode active material for the lithium secondary battery measured by a nitrogen adsorption method is defined as PS, a value of {Li(A)/(Ni+M)}/PS is 0.4 to 2.6 g/m 2 .
2 . The positive electrode active material for the lithium secondary battery according to claim 1 ,
wherein a value of PT(Li)/PS, which is a ratio of PT(Li) that is a mass proportion of the Li element derived from the lithium compound in the positive electrode active material for the lithium secondary battery, determined by neutralization titration of a filtrate obtained by filtering a slurry obtained by mixing 5 g of the positive electrode active material for the lithium secondary battery and 100 g of pure water, to the BET specific surface area PS, is 0.1 to 1.0 mass %·g/m 2 , and
the PT(Li) is determined from an amount titrated of 0.1 N hydrochloric acid when titration is carried out with 0.1 mol/L hydrochloric acid until pH of the filtrate reaches 4.5.
3 . The positive electrode active material for the lithium secondary battery according to claim 2 ,
wherein the value of the PT(Li) is 0.15 to 1 mass %.
4 . The positive electrode active material for the lithium secondary battery according to claim 1 ,
wherein the positive electrode active material for the lithium secondary battery is represented by a composition formula (I),
(in the formula (I), X represents one or more elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, Si, S, and P, and −0.1≤x≤0.2, 0≤y ≤0.2, 0<z≤0.2, and y+z≤0.3 are satisfied.)
5 . The positive electrode active material for the lithium secondary battery according to claim 1 ,
wherein the PS is 0.3 to 2 m 2 /g.
6 . The positive electrode active material for the lithium secondary battery according to claim 1 ,
wherein Li/(Ni+M), which is an atomic ratio calculated from the peak X derived from the Li element, the peak derived from the Ni element, and the peak derived from the element M, is 0.8 to 8.
7 . The positive electrode active material for the lithium secondary battery according to claim 1 ,
wherein a 50% cumulative volume particle diameter is 3 to 30 μm.
8 . A positive electrode for a lithium secondary battery, comprising:
the positive electrode active material for the lithium secondary battery according to claim 1 .
9 . A lithium secondary battery comprising:
the positive electrode for the lithium secondary battery according to claim 8 .
10 . A method for producing a positive electrode active material for a lithium secondary battery, comprising:
a calcining step of calcining a first mixture of a metal composite compound containing a Ni element and an element M and a lithium compound to obtain an intermediate product,
a mixing step of mixing the intermediate product and a liquid capable of dissolving the lithium compound to obtain a second mixture, and
a drying step of evaporating the liquid from the second mixture to obtain the positive electrode active material for the lithium secondary battery,
wherein the element M is one or more elements selected from the group consisting of Co, Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, Si, S, and P, and
when a BET specific surface area of the intermediate product is defined as IS, a mass proportion of a Li element derived from the lithium compound contained in the intermediate product is defined as IT(Li), a BET specific surface area of the positive electrode active material for the lithium secondary battery after the drying step is defined as PS, and a mass proportion of a Li element derived from the lithium compound contained in the positive electrode active material for the lithium secondary battery after the drying step is defined as PT(Li), a value of [PT(Li)/IT(Li)]/(PS/IS) is 0.1 to 0.65.
11 . The method for producing the positive electrode active material for the lithium secondary battery according to claim 10 ,
wherein the value of the PT(Li)/IT(Li) is 0.8 to 1.2.
12 . The method for producing the positive electrode active material for the lithium secondary battery according to claim 10 ,
wherein the liquid contains at least one of water and alcohol.
13 . The method for producing the positive electrode active material for the lithium secondary battery according to claim 10 ,
wherein the drying step includes heating the second mixture at 100 to 400° C.
14 . The positive electrode active material for the lithium secondary battery according to claim 2 ,
wherein the positive electrode active material for the lithium secondary battery is represented by a composition formula (I),
(in the formula (I), X represents one or more elements selected from the group consisting of Mn, Fe, Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, B, Si, S, and P, and −0.1≤x≤0.2, 0≤y ≤0.2, 0<z≤0.2, and y+z≤0.3 are satisfied.)
15 . The positive electrode active material for the lithium secondary battery according to claim 2 ,
wherein the PS is 0.3 to 2 m 2 /g.
16 . The positive electrode active material for the lithium secondary battery according to claim 2 ,
wherein Li/(Ni+M), which is an atomic ratio calculated from the peak X derived from the Li element, the peak derived from the Ni element, and the peak derived from the element M, is 0.8 to 8.
17 . The positive electrode active material for the lithium secondary battery according to claim 2 ,
wherein a 50% cumulative volume particle diameter is 3 to 30 μm.