Nickel-containing hydroxyde powder and method for producing lithium-nickel composite oxide

Abstract

This invention provides a nickel-containing hydroxide powder having D50 in a range of from 5 µm to 20 µm, a span in a range of from 0.8 to 2, and a variation index of crystallinity no more than 0.25. When the nickel-containing hydroxide powder is graded into three grades so that D50 of a first graded powder F having the smallest average particle size is equal to D10 of the nickel-containing hydroxide powder, and so that D50 of a third graded powder G having the largest average particle size is equal to D90 of the nickel-containing hydroxide powder, then the variation index is expressed by |1-(FWHM(G) / FWHM(F))| (where FWHM(G) represents the half- width of a peak derived from the (101) plane in an X-ray diffraction pattern of G, and FWHM(F) represents the half-width of a peak derived from the (101) plane in an X-ray diffraction pattern of F).

Description

[0001] NICKEL-CONTAINING HYDROXYDE POWDER AND METHOD FOR PRODUCING LITHIUMNICKEL COMPOSITE OXIDE

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a nickel-containing hydroxide powder, and to a method for producing a lithium-nickel composite oxide.

[0004] BACKGROUND

[0005] Recent years have seen rapid advances in making electronic devices such as AV devices and personal computers portable and cordless, and there is growing demand for compact, lightweight and high-energy-density secondary batteries to serve as power sources for driving these devices. Furthermore, electric vehicles and hybrid vehicles are also being developed and put into practical use because of recent attention on the global environment, and there is growing demand for lithium ion secondary batteries having excellent storage characteristics for larger applications. In light of this situation, attention is focusing on lithium ion secondary batteries having a high charging / discharging capacity.

[0006] Positive electrode active materials which are generally known to be useful in 4-volt high-energy lithium ion secondary batteries include, among others: LiMn2O4 having a spinel structure, LiMnO2having a zigzag layered structure, LiCoO2having a layered rock salt structure, Li N iO2, and Li(NiCoMnM)O2(in the formula, M is an element other than Li, Ni, Co, Mn and O) combining a plurality of transition metals.

[0007] Attention is focusing on lithium ion secondary batteries employing a lithium-nickel composite oxide having a high nickel content, namely LiNiO2and Li(NiCoMnM)O2from among the materials mentioned above, as batteries having a high charging / discharging capacity. However, when this kind of lithium-nickel composite oxide is used as a positive electrode active material in a nonaqueous electrolyte secondary battery, there is a deterioration in thermal stability during charging and cycle characteristics of the battery, so there is a need for further improvement in the characteristics.

[0008] In order to curb a reduction in cycle characteristics of a lithium-nickel composite oxide having a high nickel content, Patent Document 1 , for example, discloses a lithium-nickel composite oxide having a layered structure, in which a proportion of nickel is 91-99 mol% with respect to the total number of moles of metal elements excluding lithium, wherein 1-2.5 mol% of transition metal, with respect to the total molar amount of transition metal, is present in a lithium layer, and a half-width n of a diffraction peak of a (208) plane in an X-ray diffraction pattern obtained by X- ray diffraction is 0.30°<n<0.50°.

[0009] SUMMARY OF THE INVENTION

[0010] In one aspect, the present invention provides a nickel-containing hydroxide powder comprising at least nickel as a constituent element, wherein in a volume-based particle size distribution, when a cumulative 10% particle size is D10, a cumulative 50% particle size is D50, and a cumulative 90% particle size is D90, D50 is 5 pm-20 pm, a span represented by (D90-D10) / D50 is 0.8-2, and a variation index of crystallinity of a (101) plane, defined below, is 0.25 or less, when the above-mentioned nickel-containing hydroxide powder is graded into three grades so that D50 of a first graded powder F having the smallest average particle size is equal to D10 of the nickel-containing hydroxide powder, and so that D50 of a third graded powder G having the largest average particle size is equal to D90 of the nickel-containing hydroxide powder, with the remainder being a second graded powder M, then the variation index is defined by the following Formula (I):

[0011] Variation index = |1-(FWHM(G) / FWHM(F))| Formula (I)

[0012] Wherein, in Formula (I), FWHM(G) represents the half-width of a peak derived from the (101) plane in an X-ray diffraction pattern of the third graded powder G, and FWHM(F) represents the half-width of a peak derived from the (101) plane in an X-ray diffraction pattern of the first graded powder F.

[0013] In another aspect, the present invention provides a method for producing a lithium-nickel composite oxide, the method comprising: a mixing step in which the invented nickel-containing hydroxide powder is mixed with a lithium compound to obtain a mixture; and a firing step in which the mixture is fired.

[0014] In a further aspect, the present invention provides a method for producing a lithium-nickel composite oxide, the method comprising: a heating step in which the invented nickel-containing hydroxide powder is heated to obtain a nickel-containing compound; a mixing step in which the nickel-containing compound is mixed with a lithium compound to obtain a mixture; and a firing step in which the mixture is fired.

[0015] DETAILED DESCRIPTION OF THE INVENTION

[0016] With the lithium-nickel composite oxide of JP 2022-163131A, a certain effect of curbing a reduction in cycle characteristics of a nonaqueous electrolyte secondary battery employing this lithium-nickel composite oxide as the positive electrode active material can be seen, but since there are also samples in which the charging / discharging capacity drops by around 10% after 20 cycles, which is relatively few cycles, the effect of curbing a reduction in cycle characteristics is insufficient for practical application, and there is still room for improvement.

[0017] The present disclosure has been devised in light of the situation outlined above, and the objective thereof lies in providing a nickel-containing hydroxide powder which is used as a precursor material for a lithium-nickel composite oxide capable of curbing a reduction in cycle characteristics when used as a positive electrode active material in a nonaqueous electrolyte secondary battery, and also in providing a method for producing a lithium-nickel composite oxide employing the nickel-containing hydroxide powder.

[0018] The present inventors engaged in extensive research to solve the problems noted above. As a result, it was found that when a lithium-nickel composite oxide is produced by using, as a precursor, a nickel-containing hydroxide powder comprising at least nickel as a constituent element, wherein, in a volume-based particle size distribution, when a cumulative 10% particle size is D10, a cumulative 50% particle size is D50, and a cumulative 90% particle size is D90, D50 is in a range of from 5 pm to 20 pm, a span represented by (D90-D10) / D50 is in a range of from 0.8 to 2, and a variation index of crystallinity of a (101) plane in accordance with a predetermined definition is 0.25 or less, the lithium-nickel composite oxide is capable of curbing a reduction in cycle characteristics when used as a positive electrode active material in a nonaqueous electrolyte secondary battery.

[0019] The present disclosure makes it possible to provide a nickel-containing hydroxide powder which is used as a precursor material for a lithium-nickel composite oxide capable of curbing a reduction in cycle characteristics when used as a positive electrode active material in a nonaqueous electrolyte secondary battery, and also to provide a method for producing a lithium- nickel composite oxide employing the nickel-containing hydroxide powder.

[0020] A nickel-containing hydroxide powder according to an embodiment of the present disclosure comprises at least nickel as a constituent element, and, in a volume-based particle size distribution, when a cumulative 10% particle size is D10, a cumulative 50% particle size is D50, and a cumulative 90% particle size is D90, D50 is in a range of from 5 pm to 20 pm, a span represented by (D90-D10) / D50 is in a range of from 0.8 to 2, and a variation index of crystallinity of a (101) plane, defined below, is 0.25 or less.

[0021] When the nickel-containing hydroxide powder is graded into three grades so that D50 of a first graded powder F having the smallest average particle size is equal to D10 of the nickel- containing hydroxide powder, and so that D50 of a third graded powder G having the largest average particle size is equal to D90 of the nickel-containing hydroxide powder, with the remainder being a second graded powder M, then the variation index is defined by the following Formula (I):

[0022] Variation index = |1-(FWHM(G) / FWHM(F))| Formula (I)

[0023] In formula (I), FWHM(G) represents the half-width of a peak derived from the (101) plane in an X-ray diffraction pattern of the third graded powder G, and FWHM(F) represents the half-width of a peak derived from the (101) plane in an X-ray diffraction pattern of the first graded powder F.

[0024] The span represented by (D90-D10) / D50 means the spread of the particle size distribution in the nickel-containing hydroxide powder. The span is a parameter which comes closer to 0 as the particle size distribution becomes sharper, and moves further away from 0 as the particle size distribution becomes broader. D50 being 5 pm-25 pm and a span represented by (D90- D10) / D50 being 0.8-2 means that the particle size distribution of the nickel-containing hydroxide powder is broad to a certain extent. By virtue of the nickel-containing hydroxide powder having a particle size distribution which is broad to a certain extent in this way, it is possible to increase electrode density, even when the nickel-containing hydroxide powder is used alone.

[0025] Furthermore, the variation index is a function of the half-width of the peak derived from the (101) plane in an X-ray diffraction pattern of the first graded powder F, and the half-width of the peak derived from the (101) plane in an X-ray diffraction pattern of the third graded powder G. The half-width of peaks in the X-ray diffraction patterns is an index of crystallinity. The variation index is a parameter which comes closer to 0 as the half-width of the peak derived from the (101) plane in an X-ray diffraction pattern of the first graded powder F, and the half-width of the peak derived from the (101) plane in an X-ray diffraction pattern of the third graded powder G approach the same value. The variation index being 0.25 or less means that there are few variations in crystallinity in either a large-particle-size particle group or a small-particle-size particle group in the nickel-containing hydroxide powder having a broad particle size distribution such as mentioned above.

[0026] The variation index is not particularly limited provided that it is 0.25 or less, but it is, for example, preferably 0.24 or less, 0.23 or less, 0.22 or less, 0.21 or less, 0.2 or less, 0.19 or less, 0.18 or less, 0.17 or less, 0.16 or less, 0.15 or less, 0.14 or less, or 0.13 or less. Meanwhile, the variation index should be 0 or more.

[0027] The volume-based D50 of the nickel-containing hydroxide powder is not particularly limited, but it is, for example, preferably 5 pm or more, 6 pm or more, 7 pm or more, 8 pm or more, 9 pm or more, 10 pm or more, 11 pm or more, or 12 pm or more. Meanwhile, D50 of the nickel- containing hydroxide powder is preferably 25 pm or less, 23 pm or less, 20 pm or less, 19 pm or less, 18 pm or less, or 17 pm or less.

[0028] The half-width of the peak derived from the (101) plane in an X-ray diffraction pattern is not particularly limited, but it may be, for example, 0.2° or more, 0.25° or more, or 0.3° or more. Meanwhile, the half-width of the peak derived from the (101) plane in an X-ray diffraction pattern is preferably 0.8° or less, 0.79° or less, or 0.78° or less.

[0029] The half-width of a peak derived from the (100) plane in an X-ray diffraction pattern is not particularly limited, but it may be, for example, 0.2° or more, or 0.21° or more. Meanwhile, the half-width of the peak derived from the (100) plane in an X-ray diffraction pattern is preferably 0.4° or less, or 0.39° or less.

[0030] The chemical composition of the nickel-containing hydroxide is not particularly limited provided that it contains nickel, but it is preferably represented by the general formula Ni i-x-y-zCOxMnyMz(OH)2+a (0<x<0.4, 0<y<0.4, 0<z<0.4, 0.5<1-x-y-z, -0.5<a<0.5, and M is at least one element other than Li, Ni, Co, Mn and O).

[0031] In the general formula, the value of x is not particularly limited, provided that it is within the range of 0<x<0.4, but it is, for example, preferably greater than 0, 0.001 or more, 0.0015 or more, 0.002 or more, 0.0025 or more, 0.003 or more, 0.0035 or more, 0.004 or more, 0.0045 or more, 0.005 or more, 0.0055 or more, 0.006 or more, 0.0065 or more, 0.007 or more, 0.0075 or more, 0.008 or more, 0.0085 or more, 0.009 or more, 0.0095 or more, 0.01 or more, 0.015 or more, 0.02 or more, 0.025 or more, 0.03 or more, 0.035 or more, 0.04 or more, 0.045 or more, 0.05 or more, 0.055 or more, 0.06 or more, 0.065 or more, 0.07 or more, 0.075 or more, 0.08 or more, 0.085 or more, 0.09 or more, 0.095 or more, 0.1 or more, 0.102 or more, 0.105 or more, 0.107 or more, 0.11 or more, 0.112 or more, 0.115 or more, 0.117 or more, 0.12 or more, 0.122 or more, 0.125 or more, 0.127 or more, 0.13 or more, 0.132 or more, 0.135 or more, 0.137 or more, 0.14 or more, 0.142 or more, 0.145 or more, 0.147 or more, 0.15 or more, 0.152 or more, 0.155 or more, 0.157 or more, 0.16 or more, 0.162 or more, 0.165 or more, 0.167 or more, 0.17 or more, 0.172 or more, 0.175 or more, 0.177 or more, 0.18 or more, 0.182 or more, 0.185 or more, 0.187 or more, 0.19 or more, 0.192 or more, 0.195 or more, 0.197 or more, 0.2 or more, 0.202 or more, 0.205 or more, 0.207 or more, 0.21 or more, 0.212 or more, 0.215 or more, 0.217 or more, 0.22 or more, 0.222 or more, 0.225 or more, 0.227 or more, 0.23 or more, 0.232 or more, 0.235 or more, 0.237 or more, 0.24 or more, 0.242 or more, 0.245 or more, 0.247 or more, 0.25 or more, 0.252 or more, 0.255 or more, 0.257 or more, 0.26 or more, 0.262 or more, 0.265 or more, 0.267 or more, 0.27 or more, 0.272 or more, 0.275 or more, 0.277 or more, 0.28 or more, 0.282 or more, 0.285 or more, 0.287 or more, 0.29 or more, 0.292 or more, 0.295 or more, 0.297 or more, 0.3 or more, 0.302 or more, 0.305 or more, 0.307 or more, 0.31 or more, 0.312 or more, 0.315 or more, 0.317 or more, 0.32 or more, 0.322 or more, 0.325 or more, 0.327 or more, 0.33 or more, 0.332 or more, 0.335 or more, 0.337 or more, 0.34 or more, 0.342 or more, 0.345 or more, 0.347 or more, 0.35 or more, 0.352 or more, 0.355 or more, 0.357 or more, 0.36 or more, 0.362 or more, 0.365 or more, 0.367 or more, 0.37 or more, 0.372 or more, 0.375 or more, 0.377 or more, 0.38 or more, 0.382 or more, 0.385 or more, 0.387 or more, 0.39 or more, 0.392 or more, 0.395 or more, or 0.397 or more. Meanwhile, the value of x is preferably 0.397 or less, 0.395 or less, 0.392 or less, 0.39 or less, 0.387 or less, 0.385 or less, 0.382 or less, 0.38 or less, 0.377 or less, 0.375 or less, 0.372 or less, 0.367 or less, 0.365 or less, 0.362 or less, 0.36 or less, 0.357 or less, 0.355 or less, 0.352 or less, 0.35 or less, 0.347 or less, 0.345 or less, 0.342 or less, 0.34 or less, 0.337 or less, 0.335 or less, 0.332 or less, 0.33 or less, 0.327 or less, 0.325 or less, 0.322 or less, 0.32 or less, 0.317 or less, 0.315 or less, 0.312 or less, 0.31 or less, 0.307 or less, 0.305 or less, 0.302 or less, 0.3 or less, 0.297 or less, 0.295 or less, 0.292 or less, 0.29 or less, 0.287 or less, 0.285 or less, 0.282 or less, 0.28 or less, 0.277 or less, 0.275 or less, 0.272 or less, 0.27 or less, 0.267 or less, 0.265 or less, 0.26 or less, 0.257 or less, 0.255 or less, 0.252 or less, 0.25 or less, 0.247 or less, 0.245 or less, 0.242 or less, 0.24 or less, 0.237 or less, 0.235 or less, 0.232 or less, 0.23 or less, 0.227 or less, 0.225 or less, 0.222 or less, 0.22 or less, 0.217 or less, 0.215 or less, 0.212 or less, 0.21 or less, 0.207 or less, 0.205 or less, 0.202 or less, 0.2 or less, 0.197 or less, 0.195 or less, 0.192 or less, 0.19 or less, 0.187 or less, 0.185 or less, 0.182 or less, 0.18 or less, 0.177 or less, 0.175 or less,

[0032] 0.172 or less, 0.17 or less, 0.167 or less, 0.165 or less, 0.162 or less, 0.16 or less, 0.155 or less,

[0033] 0.152 or less, 0.15 or less, 0.147 or less, 0.145 or less, 0.142 or less, 0.14 or less, 0.137 or less,

[0034] 0.135 or less, 0.132 or less, 0.13 or less, 0.127 or less, 0.125 or less, 0.122 or less, 0.12 or less,

[0035] 0.117 or less, 0.115 or less, 0.112 or less, 0.11 or less, 0.107 or less, 0.105 or less, 0.102 or less, 0.1 or less, 0.095 or less, 0.09 or less, 0.085 or less, 0.08 or less, 0.075 or less, 0.07 or less, 0.065 or less, 0.06 or less, 0.055 or less, 0.05 or less, 0.045 or less, 0.04 or less, 0.035 or less, 0.03 or less, 0.025 or less, 0.02 or less, 0.015 or less, 0.01 or less, 0.0095 or less, 0.009 or less, 0.0085 or less, 0.008 or less, 0.0075 or less, 0.007 or less, 0.0065 or less, 0.006 or less, 0.0055 or less, 0.005 or less, 0.0045 or less, 0.004 or less, 0.0035 or less, 0.003 or less, 0.0025 or less, 0.002 or less, 0.0015 or less, or 0.001 or less.

[0036] In the general formula, the value of y is not particularly limited, provided that it is within the range of 0<y<0.4, but it is, for example, preferably 0.001 or more, 0.0015 or more, 0.002 or more, 0.0025 or more, 0.003 or more, 0.0035 or more, 0.004 or more, 0.0045 or more, 0.005 or more, 0.0055 or more, 0.006 or more, 0.0065 or more, 0.007 or more, 0.0075 or more, 0.008 or more, 0.0085 or more, 0.009 or more, 0.0095 or more, 0.01 or more, 0.015 or more, 0.02 or more, 0.025 or more, 0.03 or more, 0.035 or more, 0.04 or more, 0.045 or more, 0.05 or more, 0.055 or more, 0.06 or more, 0.065 or more, 0.07 or more, 0.075 or more, 0.08 or more, 0.085 or more, 0.09 or more, 0.095 or more, 0.1 or more, 0.102 or more, 0.105 or more, 0.107 or more, 0.11 or more, 0.112 or more, 0.115 or more, 0.117 or more, 0.12 or more, 0.122 or more, 0.125 or more, 0.127 or more, 0.13 or more, 0.132 or more, 0.135 or more, 0.137 or more, 0.14 or more, 0.142 or more, 0.145 or more, 0.147 or more, 0.15 or more, 0.152 or more, 0.155 or more, 0.157 or more, 0.16 or more, 0.162 or more, 0.165 or more, 0.167 or more, 0.17 or more, 0.172 or more, 0.175 or more, 0.177 or more, 0.18 or more, 0.182 or more, 0.185 or more, 0.187 or more, 0.19 or more, 0.192 or more, 0.195 or more, 0.197 or more, 0.2 or more, 0.202 or more, 0.205 or more, 0.207 or more, 0.21 or more, 0.212 or more, 0.215 or more, 0.217 or more, 0.22 or more, 0.222 or more, 0.225 or more, 0.227 or more, 0.23 or more, 0.232 or more, 0.235 or more, 0.237 or more, 0.24 or more, 0.242 or more, 0.245 or more, 0.247 or more, 0.25 or more, 0.252 or more, 0.255 or more, 0.257 or more, 0.26 or more, 0.262 or more, 0.265 or more, 0.267 or more, 0.27 or more, 0.272 or more, 0.275 or more, 0.277 or more, 0.28 or more, 0.282 or more, 0.285 or more, 0.287 or more, 0.29 or more, 0.292 or more, 0.295 or more, 0.297 or more, 0.3 or more, 0.302 or more, 0.305 or more, 0.307 or more, 0.31 or more, 0.312 or more, 0.315 or more, 0.317 or more, 0.32 or more, 0.322 or more, 0.325 or more, 0.327 or more, 0.33 or more, 0.332 or more, 0.335 or more, 0.337 or more, 0.34 or more, 0.342 or more, 0.345 or more, 0.347 or more, 0.35 or more, 0.352 or more, 0.355 or more, 0.357 or more, 0.36 or more, 0.362 or more, 0.365 or more, 0.367 or more, 0.37 or more, 0.372 or more, 0.375 or more, 0.377 or more, 0.38 or more, 0.382 or more, 0.385 or more, 0.387 or more, 0.39 or more, 0.392 or more, 0.395 or more, or 0.397 or more. Meanwhile, the value of y is preferably 0.397 or less, 0.395 or less, 0.392 or less, 0.39 or less, 0.387 or less, 0.385 or less, 0.382 or less, 0.38 or less, 0.377 or less, 0.375 or less, 0.372 or less, 0.367 or less, 0.365 or less, 0.362 or less, 0.36 or less, 0.357 or less, 0.355 or less, 0.352 or less, 0.35 or less, 0.347 or less, 0.345 or less, 0.342 or less, 0.34 or less, 0.337 or less, 0.335 or less, 0.332 or less, 0.33 or less, 0.327 or less, 0.325 or less, 0.322 or less, 0.32 or less, 0.317 or less, 0.315 or less, 0.312 or less, 0.31 or less, 0.307 or less, 0.305 or less, 0.302 or less, 0.3 or less, 0.297 or less, 0.295 or less, 0.292 or less, 0.29 or less, 0.287 or less, 0.285 or less, 0.282 or less, 0.28 or less, 0.277 or less, 0.275 or less,

[0037] 0.272 or less, 0.27 or less, 0.267 or less, 0.265 or less, 0.26 or less, 0.257 or less, 0.255 or less,

[0038] 0.252 or less, 0.25 or less, 0.247 or less, 0.245 or less, 0.242 or less, 0.24 or less, 0.237 or less,

[0039] 0.235 or less, 0.232 or less, 0.23 or less, 0.227 or less, 0.225 or less, 0.222 or less, 0.22 or less,

[0040] 0.217 or less, 0.215 or less, 0.212 or less, 0.21 or less, 0.207 or less, 0.205 or less, 0.202 or less, 0.2 or less, 0.197 or less, 0.195 or less, 0.192 or less, 0.19 or less, 0.187 or less, 0.185 or less, 0.182 or less, 0.18 or less, 0.177 or less, 0.175 or less, 0.172 or less, 0.17 or less, 0.167 or less, 0.165 or less, 0.162 or less, 0.16 or less, 0.155 or less, 0.152 or less, 0.15 or less, 0.147 or less, 0.145 or less, 0.142 or less, 0.14 or less, 0.137 or less, 0.135 or less, 0.132 or less, 0.13 or less, 0.127 or less, 0.125 or less, 0.122 or less, 0.12 or less, 0.117 or less, 0.115 or less, 0.112 or less, 0.11 or less, 0.107 or less, 0.105 or less, 0.102 or less, 0.1 or less, 0.095 or less, 0.09 or less, 0.085 or less, 0.08 or less, 0.075 or less, 0.07 or less, 0.065 or less, 0.06 or less, 0.055 or less, 0.05 or less, 0.045 or less, 0.04 or less, 0.035 or less, 0.03 or less, 0.025 or less, 0.02 or less, 0.015 or less, 0.01 or less, 0.0095 or less, 0.009 or less, 0.0085 or less, 0.008 or less, 0.0075 or less, 0.007 or less, 0.0065 or less, 0.006 or less, 0.0055 or less, 0.005 or less, 0.0045 or less, 0.004 or less, 0.0035 or less, 0.003 or less, 0.0025 or less, 0.002 or less, 0.0015 or less, or 0.001 or less.

[0041] In the general formula, the value of z is not particularly limited, provided that it is within the range of 0<z<0.4, but it is, for example, preferably 0.001 or more, 0.0015 or more, 0.002 or more, 0.0025 or more, 0.003 or more, 0.0035 or more, 0.004 or more, 0.0045 or more, 0.005 or more, 0.0055 or more, 0.006 or more, 0.0065 or more, 0.007 or more, 0.0075 or more, 0.008 or more, 0.0085 or more, 0.009 or more, 0.0095 or more, 0.01 or more, 0.015 or more, 0.02 or more, 0.025 or more, 0.03 or more, 0.035 or more, 0.04 or more, 0.045 or more, 0.05 or more, 0.055 or more, 0.06 or more, 0.065 or more, 0.07 or more, 0.075 or more, 0.08 or more, 0.085 or more, 0.09 or more, 0.095 or more, 0.1 or more, 0.102 or more, 0.105 or more, 0.107 or more, 0.11 or more, 0.112 or more, 0.115 or more, 0.117 or more, 0.12 or more, 0.122 or more, 0.125 or more, 0.127 or more, 0.13 or more, 0.132 or more, 0.135 or more, 0.137 or more, 0.14 or more, 0.142 or more, 0.145 or more, 0.147 or more, 0.15 or more, 0.152 or more, 0.155 or more, 0.157 or more, 0.16 or more, 0.162 or more, 0.165 or more, 0.167 or more, 0.17 or more, 0.172 or more, 0.175 or more, 0.177 or more, 0.18 or more, 0.182 or more, 0.185 or more, 0.187 or more, 0.19 or more, 0.192 or more, 0.195 or more, 0.197 or more, 0.2 or more, 0.202 or more, 0.205 or more, 0.207 or more, 0.21 or more, 0.212 or more, 0.215 or more, 0.217 or more, 0.22 or more, 0.222 or more, 0.225 or more, 0.227 or more, 0.23 or more, 0.232 or more, 0.235 or more, 0.237 or more, 0.24 or more, 0.242 or more, 0.245 or more, 0.247 or more, 0.25 or more, 0.252 or more, 0.255 or more, 0.257 or more, 0.26 or more, 0.262 or more, 0.265 or more, 0.267 or more, 0.27 or more, 0.272 or more, 0.275 or more, 0.277 or more, 0.28 or more, 0.282 or more, 0.285 or more, 0.287 or more, 0.29 or more, 0.292 or more, 0.295 or more, 0.297 or more, 0.3 or more, 0.302 or more, 0.305 or more, 0.307 or more, 0.31 or more, 0.312 or more, 0.315 or more, 0.317 or more, 0.32 or more, 0.322 or more, 0.325 or more, 0.327 or more, 0.33 or more, 0.332 or more, 0.335 or more, 0.337 or more, 0.34 or more, 0.342 or more, 0.345 or more, 0.347 or more, 0.35 or more, 0.352 or more, 0.355 or more, 0.357 or more, 0.36 or more, 0.362 or more, 0.365 or more, 0.367 or more, 0.37 or more, 0.372 or more, 0.375 or more, 0.377 or more, 0.38 or more, 0.382 or more, 0.385 or more, 0.387 or more, 0.39 or more, 0.392 or more, 0.395 or more, or 0.397 or more. Meanwhile, the value of z is preferably 0.397 or less, 0.395 or less, 0.392 or less, 0.39 or less, 0.387 or less, 0.385 or less, 0.382 or less, 0.38 or less, 0.377 or less, 0.375 or less, 0.372 or less, 0.367 or less, 0.365 or less, 0.362 or less, 0.36 or less, 0.357 or less, 0.355 or less, 0.352 or less, 0.35 or less, 0.347 or less, 0.345 or less, 0.342 or less, 0.34 or less, 0.337 or less, 0.335 or less, 0.332 or less, 0.33 or less, 0.327 or less, 0.325 or less, 0.322 or less, 0.32 or less, 0.317 or less, 0.315 or less, 0.312 or less, 0.31 or less, 0.307 or less, 0.305 or less, 0.302 or less, 0.3 or less, 0.297 or less, 0.295 or less, 0.292 or less, 0.29 or less, 0.287 or less, 0.285 or less, 0.282 or less, 0.28 or less, 0.277 or less, 0.275 or less,

[0042] 0.272 or less, 0.27 or less, 0.267 or less, 0.265 or less, 0.26 or less, 0.257 or less, 0.255 or less,

[0043] 0.252 or less, 0.25 or less, 0.247 or less, 0.245 or less, 0.242 or less, 0.24 or less, 0.237 or less,

[0044] 0.235 or less, 0.232 or less, 0.23 or less, 0.227 or less, 0.225 or less, 0.222 or less, 0.22 or less,

[0045] 0.217 or less, 0.215 or less, 0.212 or less, 0.21 or less, 0.207 or less, 0.205 or less, 0.202 or less, 0.2 or less, 0.197 or less, 0.195 or less, 0.192 or less, 0.19 or less, 0.187 or less, 0.185 or less, 0.182 or less, 0.18 or less, 0.177 or less, 0.175 or less, 0.172 or less, 0.17 or less, 0.167 or less, 0.165 or less, 0.162 or less, 0.16 or less, 0.155 or less, 0.152 or less, 0.15 or less, 0.147 or less, 0.145 or less, 0.142 or less, 0.14 or less, 0.137 or less, 0.135 or less, 0.132 or less, 0.13 or less, 0.127 or less, 0.125 or less, 0.122 or less, 0.12 or less, 0.117 or less, 0.115 or less, 0.112 or less, 0.11 or less, 0.107 or less, 0.105 or less, 0.102 or less, 0.1 or less, 0.095 or less, 0.09 or less, 0.085 or less, 0.08 or less, 0.075 or less, 0.07 or less, 0.065 or less, 0.06 or less, 0.055 or less, 0.05 or less, 0.045 or less, 0.04 or less, 0.035 or less, 0.03 or less, 0.025 or less, 0.02 or less, 0.015 or less, 0.01 or less, 0.0095 or less, 0.009 or less, 0.0085 or less,

[0046] 0.008 or less, 0.0075 or less, 0.007 or less, 0.0065 or less, 0.006 or less, 0.0055 or less, 0.005 or less, 0.0045 or less, 0.004 or less, 0.0035 or less, 0.003 or less, 0.0025 or less, 0.002 or less, 0.0015 or less, or 0.001 or less.

[0047] In the general formula, the element M is not particularly limited, provided that it is one or more elements other than Li, Ni, Co, Mn and O, where examples that can be used include Al, Ti, Mg, Zn, Nb, W, Mo, Sb, V, Cr, Ca, Fe, Ga, Sr, Y, Ru, In, Sn, Ta, Bi, Zr, and B, etc. The type of element M should be selected depending on the purpose for which it is being added. When a plurality of elements are used as the element M, the value of w represents the total amount of the plurality of elements.

[0048] In the general formula, the value of a is not particularly limited, provided that it is within the range of -0.5<a<0.5, but it is, for example, preferably -0.49 or more, -0.48 or more, -0.47 or more, -0.46 or more, -0.45 or more, -0.44 or more, -0.43 or more, -0.42 or more, -0.41 or more, - 0.40 or more, -0.39 or more, -0.38 or more, -0.37 or more, -0.36 or more, -0.35 or more, -0.34 or more, -0.33 or more, -0.32 or more, -0.31 or more, -0.30 or more, -0.29 or more, -0.28 or more, - 0.27 or more, -0.26 or more, -0.25 or more, -0.24 or more, -0.23 or more, -0.22 or more, -0.21 or more, -0.20 or more, -0.19 or more, -0.18 or more, -0.17 or more, -0.16 or more, -0.15 or more, - 0.14 or more, -0.13 or more, -0.12 or more, -0.11 or more, -0.10 or more, -0.09 or more, -0.08 or more, -0.07 or more, -0.06 or more, -0.05 or more, -0.04 or more, -0.03 or more, -0.02 or more, - 0.01 or more, 0.00 or more, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, 0.15 or more, 0.16 or more, 0.17 or more, 0.18 or more, 0.19 or more, 0.20 or more, 0.21 or more, 0.22 or more, 0.23 or more, 0.24 or more, 0.25 or more, 0.26 or more, 0.27 or more, 0.28 or more, 0.29 or more, 0.30 or more, 0.31 or more, 0.32 or more, 0.33 or more, 0.34 or more, 0.35 or more, 0.36 or more, 0.37 or more, 0.38 or more, 0.39 or more, 0.40 or more, 0.41 or more, 0.42 or more, 0.43 or more, 0.44 or more, 0.45 or more, 0.46 or more, 0.47 or more, 0.48 or more, or 0.49 or more. Meanwhile, the value of a is preferably 0.49 or less, 0.48 or less, 0.47 or less, 0.46 or less, 0.45 or less, 0.44 or less, 0.43 or less, 0.42 or less, 0.41 or less, 0.40 or less, 0.39 or less, 0.38 or less, 0.37 or less, 0.36 or less, 0.35 or less, 0.34 or less, 0.33 or less, 0.32 or less, 0.31 or less, 0.30 or less, 0.29 or less, 0.28 or less, 0.27 or less, 0.26 or less, 0.25 or less, 0.24 or less, 0.23 or less, 0.22 or less, 0.21 or less, 0.20 or less, 0.19 or less, 0.18 or less, 0.17 or less, 0.16 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, 0.01 or less, 0.00 or less, -0.01 or less, -0.02 or less, -0.03 or less, -0.04 or less, -0.05 or less, -0.06 or less, -0.07 or less, -0.08 or less, -0.09 or less, -0.10 or less, -0.11 or less, -0.12 or less, -0.13 or less, -0.14 or less, -0.15 or less, -0.16 or less, -0.17 or less, -0.18 or less, -0.19 or less, -0.20 or less, -0.21 or less, -0.22 or less, -0.23 or less, -0.24 or less, -0.25 or less, -0.26 or less, -0.27 or less, -0.28 or less, -0.29 or less, -0.30 or less, -0.31 or less, -0.32 or less, -0.33 or less, -0.34 or less, -0.35 or less, -0.36 or less, -0.37 or less, -0.38 or less, -0.39 or less, -0.40 or less, -0.41 or less, -0.42 or less, -0.43 or less, -0.44 or less, -0.45 or less, -0.46 or less, -0.47 or less, -0.48 or less, or -0.49 or less.

[0049] The method for producing the nickel-containing hydroxide powder according to an embodiment of the present disclosure is not particularly limited, but production may be carried out by means of the following method, for example. It should be noted that the characteristics of the nickel- containing hydroxide powder according to the embodiment of the present disclosure described above may vary greatly depending on production conditions, and it may also be the case that the nickel-containing hydroxide powder according to the embodiment of the present disclosure cannot be produced, even with a production method in the scope disclosed below, depending on a combination of production conditions. However, specific production conditions enabling production of the nickel-containing hydroxide powder according to the embodiment of the present disclosure will be described in the examples, and the nickel-containing hydroxide powder according to the present disclosure can be produced with good reproducibility provided that those production conditions are followed.

[0050] As a method for synthesizing the nickel-containing hydroxide powder, it is possible to use, for example, a method in which a mixed aqueous solution of compounds of elements corresponding to the composition of the lithium-nickel composite oxide to be produced is introduced into a reaction tank in which an alkaline aqueous solution such as a sodium hydroxide aqueous solution or an ammonia solution, for example, is being stirred as a mother liquor, the pH is monitored and controlled to a suitable range while a separate alkaline aqueous solution is also introduced, and the product is coprecipitated by means of a wet reaction.

[0051] Either of a batch tank and a continuous tank may also be used as the reaction tank. When a continuous tank is used, there is likely to be non-uniformity inside the tank because there is a stream in the continuous tank, and nucleation of the nickel-containing hydroxide and crystal growth occur simultaneously in a steady state.

[0052] A specific reaction will be described below taking the example of nickel. Nickel is described as an example for convenience in the description, but the same reaction may also occur with other metals. The reaction to form a hydroxide of nickel progresses by means of the following reaction in formula (1) and the two-stage reaction in formula (2-1) and formula (2-2).

[0053] When there is a high hydroxide ion concentration in a reaction field in particular, nickel hydroxide is directly formed from nickel ions by means of the following formula (1).

[0054] Ni2++2OH- Ni(OH)2formula (1)

[0055] When there are ammonium ions in the reaction field, the nickel ions form an ammine complex (formula (2-1)), and nickel hydroxide is formed via this reaction (formula (2-2)). In this process, formula (2-2) is a partially reversible reaction, and nickel hydroxide which was formed at one time partially dissolves to become the ammine complex.

[0056] Ni2++6NH3[Ni(NH3)6]2+formula (2-1)

[0057] [Ni(NH3)6]2++2OH- Ni(OH)2+6NH3formula (2-2)

[0058] Nickel hydroxide is formed by two pathways with different rates such as above. When particles are formed by two pathways such as these, nucleation readily occurs via the reaction of formula (1), so the particles which are formed have a relatively small particle size and relatively low (101) plane crystallinity. Meanwhile, when the reaction passes through formula (2-1) and formula (2-2), nucleation occurs more slowly than in the reaction of formula (1) and crystal growth occurs more readily, so the particles which are formed have a relatively large particle size and relatively high (101) plane crystallinity.

[0059] This means that it is possible to obtain a nickel-containing hydroxide having a low variation index shown in formula (I) by controlling the reaction pathways for forming nickel hydroxide so that the main reaction pathway is the reaction pathway of formula (2-1) and formula (2-2), by which particles having relatively high (101) plane crystallinity are obtained. Measures that may be cited for producing the reaction pathway of formula (2-1) and formula (2-2) more readily include reducing the free hydroxide ion concentration, increasing the ammonium ion concentration, and raising the reaction temperature (raising the solubility of nickel hydroxide).

[0060] Furthermore, in order to produce the reaction pathway of formula (2-1) and formula (2-2) more readily, an introduction port for a starting material aqueous solution comprising nickel (and other elements, depending on the composition of the nickel-containing hydroxide to be synthesized), and an introduction port for the alkaline aqueous solution comprising ammonium ions are preferably arranged close to each other. This makes it possible to achieve a state in which the starting material aqueous solution and the alkaline aqueous solution are always flowing and mixing in the vicinity of that location. The nickel ions therefore collide with the ammonium ions in a narrow range in the vicinity of that location, so the reaction of formula (2-1) readily occurs.

[0061] The reaction tank is not particularly limited, and a stirring tank comprising a stirring device may be used, for example. A specific example of a stirring tank according to an embodiment of the present disclosure will be described below with the aid of the drawings.

[0062] Fig. 1 is a schematic diagram of an example of a stirring tank which can be used in the method for producing a nickel-containing hydroxide according to an embodiment of the present disclosure. A stirring tank 1 shown in fig. 1 comprises: a reaction tank 11 for receiving a reaction liquid L; a stirring device 12 comprising stirring blades 121 A, 121 B for stirring the reaction liquid; a starting material introduction nozzle 13 for introducing the starting material aqueous solution comprising nickel; and an alkali introduction nozzle 14 for introducing the alkaline aqueous solution comprising ammonium ions. Here, an introduction port 131 is provided at a tip end of the starting material introduction nozzle 13, an introduction port 141 is provided at a tip end of the alkali introduction nozzle 14, and both nozzles are disposed above the surface of the reaction liquid L. The nickel-containing hydroxide according to an embodiment of the present disclosure can still be produced by using the stirring tank 1 shown in fig. 1 , but a stirring tank for producing the nickel-containing hydroxide more efficiently will be described below. Fig. 2 is a schematic diagram of an example of a stirring tank which can be used in the method for producing a nickel-containing hydroxide according to an embodiment of the present disclosure. A stirring tank 2 shown in fig. 2 comprises: a reaction tank 21 for receiving a reaction liquid L; a stirring device 22 comprising stirring blades 221 A, 221 B, 221 C for stirring the reaction liquid; a starting material introduction nozzle 23 for introducing the starting material aqueous solution comprising nickel; and an alkali introduction nozzle 24 for introducing the alkaline aqueous solution comprising ammonium ions. Here, the alkali introduction nozzle 24 is formed with a larger diameter than the starting material introduction nozzle 23 and constitutes a coaxial nozzle 25 in which the starting material introduction nozzle 23 is accommodated inside the alkali introduction nozzle 24 in such a way that the two nozzles have a common center axis. By using the coaxial nozzle 25 in this way, the starting material aqueous solution comprising nickel and the alkaline aqueous solution comprising ammonium ions are mixed over a narrow range in the vicinity of two introduction ports 231, 241 , and a nickel-containing hydroxide powder in which the (101) direction crystallinity is aligned and there are few variations is readily formed via the abovementioned reactions in formula (2-1) and formula (2-2).

[0063] Furthermore, the introduction port 231 is provided at a tip end of the starting material introduction nozzle 23, the introduction port 241 is provided at a tip end of the alkali introduction nozzle 24, and both nozzles are within the reaction liquid L. The tip end of the starting material introduction nozzle 23 is adjusted to be longer than the alkali introduction nozzle 24, and the coaxial nozzle 25 has a structure in which the tip end of the starting material introduction nozzle 23 protrudes. Furthermore, both introduction ports 231, 241 are disposed below and close to the stirring blade 221 A. By arranging the two introduction ports 231, 241 in this way, it is possible to impart a stirring force to nuclei, and, even in a state in which there are few free hydroxide ions, a nickel-containing hydroxide powder in which the (101) direction crystallinity is aligned and there are few variations is readily formed via the abovementioned reactions in formula (2-1) and formula (2-2).

[0064] Moreover, either of a batch tank and a continuous tank may also be used as the reaction tank. In a continuous tank, however, the starting material is normally supplied continuously while the reaction liquid inside the tank is also continuously released, so the residence time of particles inside the tank varies according to the timing at which the particles are released, even for particles produced at the same time, and the particles obtained in a continuous tank are likely to have a broader particle size distribution than particles obtained in a batch tank. A continuous tank is therefore preferably used for the nickel-containing hydroxide powder according to an embodiment of the present disclosure.

[0065] In synthesis-related reactions, after the alkaline aqueous solution serving as the mother liquor has been prepared, the interior of the reactor is purged with an inert gas or preferably nitrogen gas, for industrial purposes, to create a nitrogen atmosphere in order to keep the oxygen concentration within the reaction tank system or in the solution as low as possible. If the oxygen concentration is excessively high, there is a risk that the coprecipitated hydroxide will be overoxidized by any oxygen remaining over a predetermined amount, and a risk that the formation of agglomerates due to crystallization will be compromised.

[0066] The starting material serving as an element source of the elements constituting the nickel- containing hydroxide will be described below.

[0067] The starting material is not particularly limited, but it is preferably used in the form of an aqueous solution of a compound of the elements constituting the nickel-containing hydroxide, an acidic aqueous solution is more preferably used, and a sulfuric acid aqueous solution is more preferably used. Furthermore, one or two or more compounds may be used for one type of element in the aqueous solution. Furthermore, when a product comprising an element other than nickel is to be produced as the nickel-containing hydroxide, a compound of that other element may also be used. Typical elements, and compounds thereof, which may be used in the production of the nickel-containing hydroxide will be described below, but these are not limited to the examples given.

[0068] Examples of nickel compounds that can be used include, but are not particularly limited to, one or more selected from nickel sulfate, nickel oxide, nickel hydroxide, nickel nitrate, nickel carbonate, nickel chloride, nickel iodide, and metallic nickel.

[0069] Examples of cobalt compounds that can be used include, but are not particularly limited to, one or two or more selected from cobalt sulfate, cobalt oxide, cobalt hydroxide, cobalt nitrate, cobalt carbonate, cobalt chloride, cobalt iodide, and metallic cobalt.

[0070] Examples of manganese compounds that can be used include, but are not particularly limited to, one or two or more selected from manganese sulfate, manganese oxide, manganese hydroxide, manganese nitrate, manganese carbonate, manganese chloride, manganese iodide, and metallic manganese.

[0071] Examples of aluminum compounds that can be used include, but are not particularly limited to, one or two or more selected from aluminum sulfate, aluminum oxide, aluminum hydroxide, aluminum nitrate, aluminum carbonate, aluminum chloride, aluminum iodide, sodium aluminate, and metallic aluminum.

[0072] Examples of titanium compounds that can be used include, but are not particularly limited to, one or two or more selected from titanyl sulfate, titanium oxide, titanium hydroxide, titanium nitrate, titanium carbonate, titanium chloride, titanium iodide, and metallic titanium.

[0073] Examples of iron compounds that can be used include, but are not particularly limited to, one or two or more selected from iron sulfate, iron oxide, iron hydroxide, iron nitrate, iron carbonate, iron chloride, iron iodide, and metallic iron. Examples of niobium compounds that can be used include, but are not particularly limited to, one or two or more selected from niobium oxide, niobium chloride, lithium niobate, and niobium iodide.

[0074] Examples of tungsten compounds that can be used include, but are not particularly limited to, one or two or more selected from tungsten oxide, sodium tungstate, ammonium para-tungstate, ammonium meta-tungstate, tungsten hexacarbonyl, and tungsten sulfide.

[0075] Examples of magnesium compounds that can be used include, but are not particularly limited to, one or two or more selected from magnesium sulfate, magnesium oxide, magnesium hydroxide, magnesium nitrate, magnesium carbonate, magnesium chloride, magnesium iodide, and metallic magnesium.

[0076] Examples of zinc compounds that can be used include, but are not particularly limited to, one or two or more selected from zinc sulfate, zinc oxide, zinc hydroxide, zinc nitrate, zinc carbonate, zinc chloride, zinc iodide, and metallic zinc.

[0077] Examples of other elements that can be used include, but are not particularly limited to, one or two or more selected from sulfates, oxides, hydroxides, nitrates, carbonates, chlorides, iodides, and metals.

[0078] The proportions in which the various compounds are blended should be adjusted, while taking account of the composition of the nickel-containing hydroxide to be produced, to ensure the desired proportions of the amounts of the various elements.

[0079] The appropriate pH range for when the nickel-containing hydroxide is synthesized is not particularly limited and can be determined so as to achieve the desired secondary particle size and density, and the pH should generally be 10-13.

[0080] The nickel-containing hydroxide obtained by means of a wet reaction is preferably subjected to a washing treatment, and then a drying treatment after being de-watered.

[0081] Subjecting the nickel-containing hydroxide to a washing treatment makes it possible to wash out impurities such as sulfate radicals or carbonate radicals and sodium fractions that have been incorporated into agglomerated particles or that have adhered to the surface layer during the reaction. Washing treatments that can be used for small amounts of impurities include a procedure in which Nutsche washing using a Buchner funnel is performed, or a procedure in which the reacted suspension is pumped through a press filter, washed with water, and dewatered. Moreover, pure water, a sodium hydroxide aqueous solution, or a sodium carbonate aqueous solution, for example, can be used in the washing treatment, but the use of pure water is preferred for industrial purposes. For larger amounts of residual sulfate radicals, however, a sodium hydroxide aqueous solution, or the like, which is pH-controlled according to the residual amount, may be used. A method for producing a lithium-nickel composite oxide by using the nickel-containing hydroxide powder obtained in the manner above will be described below. The method for producing a lithium-nickel composite oxide according to an embodiment of the present disclosure comprises a mixing step in which the nickel-containing hydroxide powder is mixed with a lithium compound to obtain a mixture, and a firing step in which the powder mixture is fired; or comprises a heating step in which the nickel-containing hydroxide powder is heated to obtain a nickel-containing compound, a mixing step in which the nickel-containing compound powder is mixed with a lithium compound to obtain a mixture, and a firing step in which the powder mixture is fired.

[0082] A lithium-nickel composite oxide produced by this production method will be described first of all. The chemical composition of the lithium-nickel composite oxide is not particularly limited provided that it contains lithium and nickel, but it is preferably represented by the general formula LiaNii-x-y-zCOxMnyMzO2+a (0.90<a<1.15, 0<x<0.4, 0<y<0.4, 0<z<0.4, 0.5<1-x-y-z, - 0.5<a<0.5, and M is at least one element other than Li, Ni, Co, Mn and O).

[0083] It should be noted that the preferred ranges for the coefficients 1-x-y-z, x, y, z and a, and the type of element used as M are the same as in the nickel-containing hydroxide, and are therefore not given here.

[0084] In the general formula, the value of a is not particularly limited, provided that it is within the range of 0.90<a<1.2, but it is, for example, preferably 0.905 or more, 0.91 or more, 0.915 or more, 0.92 or more, 0.925 or more, 0.93 or more, 0.935 or more, 0.94 or more, 0.945 or more, 0.95 or more, 0.955 or more, 0.96 or more, 0.965 or more, 0.97 or more, 0.975 or more, 0.98 or more, 0.985 or more, 0.99 or more, 0.995 or more, 1 or more, 1.005 or more, 1.01 or more, 1.015 or more, 1.02 or more, 1.025 or more, 1.03 or more, 1.035 or more, 1.04 or more, 1.045 or more, 1.05 or more, 1.055 or more, 1.06 or more, 1.065 or more, 1.07 or more, 1.075 or more,

[0085] 1.08 or more, 1.085 or more, 1.09 or more, 1.095 or more, 1.1 or more, 1.105 or more, 1.11 or more, 1.115 or more, 1.12 or more, 1.125 or more, 1.13 or more, 1.135 or more, 1.14 or more,

[0086] 1.145 or more, 1.15 or more, 1.155 or more, 1.16 or more, 1.165 or more, 1.17 or more, 1.175 or more, 1.18 or more, 1.185 or more, 1.19 or more, 1.195 or more, or 1.2 or more. Meanwhile, the value of a is preferably 1.2 or less, 1.195 or less, 1.19 or less, 1.185 or less, 1.18 or less, 1.175 or less, 1.17 or less, 1.165 or less, 1.6 or less, 1.155 or less, 1.15 or less, 1.145 or less, 1.14 or less, 1.135 or less, 1.13 or less, 1.125 or less, 1.12 or less, 1.115 or less, 1.11 or less, 1.105 or less, 1.1 or less, 1.095 or less, 1.09 or less, 1.085 or less, 1.08 or less, 1.075 or less, 1.07 or less, 1.065 or less, 1.06 or less, 1.055 or less, 1.05 or less, 1.045 or less, 1.04 or less, 1.035 or less, 1.03 or less, 1.025 or less, 1.02 or less, 1.015 or less, 1.01 or less, 1.005 or less, 1 or less, 0.995 or less, 0.99 or less, 0.985 or less, 0.98 or less, 0.975 or less, 0.97 or less, 0.965 or less, 0.96 or less, 0.955 or less, 0.95 or less, 0.945 or less, 0.94 or less, 0.935 or less, 0.93 or less, 0.925 or less, 0.92 or less, 0.915 or less, 0.91 or less, or 0.905 or less.

[0087] The heating step is a step in which the nickel-containing hydroxide powder is heated to obtain a nickel-containing compound. This heating step makes it possible to remove moisture and carbonate fractions contained in the nickel-containing hydroxide powder by heating the nickel-containing hydroxide powder. It should be noted that the heating step is not an essential step.

[0088] The heating conditions are not particularly limited, but the heating is preferably performed at 200-700°C for 1-6 hours under an oxidizing atmosphere, for example.

[0089] The mixing step is a step in which the nickel-containing hydroxide powder and / or the nickel- containing compound obtained in the heating step are / is mixed with a lithium compound to obtain a mixture.

[0090] The nickel-containing hydroxide powder produced in the manner described above and / or the nickel-containing compound obtained in the heating step, and the lithium compound are mixed in a predetermined ratio to prepare the mixture. The mixing may be solvent-based mixing, where the nickel-containing hydroxide powder and / or the nickel-containing compound obtained in the heating step, and the lithium compound are each in the form of a solution, such as an aqueous solution, and the solutions are mixed in predetermined proportions, or the mixing may be non-solvent-based mixing, where the nickel-containing hydroxide powder and / or the nickel- containing compound obtained in the heating step, and a powder of the lithium compound are weighed out in predetermined proportions and dry-mixed.

[0091] The lithium compound is not particularly limited, and a variety of lithium salts may be used. Specific examples of lithium compounds that may be used include one or more selected from anhydrous lithium hydroxide, lithium hydroxide hydrate, lithium nitrate, lithium carbonate, lithium acetate, lithium bromide, lithium chloride, lithium citrate, lithium fluoride, lithium iodide, lithium lactate, lithium oxalate, lithium phosphate, lithium pyruvate, lithium sulfate, and lithium oxide. Among these, anhydrous lithium hydroxide and / or lithium hydroxide hydrate are / is preferably used.

[0092] The proportions in which the lithium compound and the precursor composite compound are blended are not particularly limited, but should be adjusted, as appropriate, to ensure the desired proportions of the total amounts of the lithium and various other elements in the composition of the intended composite oxide.

[0093] The firing step is a step in which the powder mixture obtained in the mixing step described above is fired. The firing step may comprise two-stage firing, consisting of a preliminary firing step and a main firing step, or single-stage firing consisting only of a main firing step.

[0094] The firing in the preliminary firing step is generally carried out by weighing out the lithium compound, the nickel-containing hydroxide powder and / or the nickel-containing compound obtained in the heating step, and a compound of other additional elements, as required, mixing the materials in a mixer, and charging the resulting mixture into a vessel such as a crucible or sagger. In the lithiation reaction at this time, it becomes more difficult for the gas that is produced to be externally discharged and for diffusion of the required oxygen concentration to be achieved closer to the lower portion of the vessel charged with the powder mixture. As a result, it becomes difficult to control the reaction homogeneity and the primary particle size.

[0095] Two-stage firing, consisting of the preliminary firing step and the main firing step, is therefore preferably performed. The preliminary firing is not an essential step, however.

[0096] In order to produce the lithium-nickel composite oxide, it is necessary to bring about a lithiation reaction of the nickel-containing hydroxide by means of firing, and to cause crystal growth of the lithium-nickel composite oxide. In this process, the preliminary firing step is mainly a step in which the lithiation reaction of the nickel-containing hydroxide is produced.

[0097] Incorporating a firing method that promotes the lithiation reaction is preferred for the preliminary firing step. A specific example that may be cited is a method that allows the mixture to be more easily heated, allows the gas that is generated from the lithium compound to be easily discharged, and allows gas having a high oxygen partial pressure to be diffused into the mixture (into the particles). As an example of such a method, the preliminary firing is performed with a smaller amount of the mixture, whereby the mixture is more easily heated, the gas is also easily discharged, and a fired product resulting from an accelerated lithiation reaction is obtained.

[0098] For the preliminary firing of the mixture, the mixture may be charged in a sagger or crucible and fired by using a static furnace, a roller hearth kiln, or a pusher furnace, but a rotary kiln in which the mixture is fired while being fluidized is preferably used.

[0099] The heating temperature in the preliminary firing is not particularly limited, and it is preferably adjusted to or above the melting point of the lithium compound serving as a lithium source. By this means, the lithiation reaction of the nickel-containing hydroxide and / or the nickel-containing compound obtained in the heating step is caused to proceed, and it is possible to obtain a lithium-nickel composite oxide having few impurities. It should be noted that the heating temperature here refers to the maximum temperature reached by heating of the material being fired.

[0100] The atmosphere for the preliminary firing is not particularly limited, and it should be an oxidizing atmosphere such that the lithiation reaction, which is an oxidation reaction, proceeds. For example, atmospheric air (oxygen concentration: 21 vol%), an oxidative decarboxylation gas atmosphere having a carbon dioxide gas concentration of 30 ppm or less, or a gas atmosphere such as an oxygen atmosphere having an oxygen concentration of 80 vol% or more, or 90 vol% or more, is preferably used.

[0101] The time of the preliminary firing is not particularly limited, and it should be a time such that the lithiation reaction progresses. For example, a time of 1-10 hours or 2-8 hours is preferred.

[0102] The main firing step is a step in which the fired product obtained by means of the preliminary firing is fired at a higher temperature to cause crystal growth. The atmosphere in the main firing is not particularly limited, and it should be an atmosphere such that crystal growth occurs, and such that elements including nickel are not reduced and unintended compounds are not formed, and specifically an oxidizing atmosphere, preferably an atmosphere with a low moisture content and carbon dioxide gas concentration. For example, an oxidative decarboxylation gas atmosphere having a carbon dioxide gas concentration of 30 ppm or less, or an oxygen atmosphere having an oxygen concentration preferably of 80 vol% or more, or 90 vol% or more, is preferably used.

[0103] The heating temperature of the main firing is not particularly limited provided that it is a higher temperature than the heating temperature of the preliminary firing, and it is preferably 650- 1100°C, 670-1000°C, or 690-980°C, for example. By setting the heating temperature within the required range, it is possible to obtain a lithium-nickel composite oxide with fewer unreacted components and a high crystal structure. Furthermore, it is also possible to prevent a reduction in battery characteristics of a nonaqueous electrolyte secondary battery employing the resulting lithium-nickel composite oxide as a positive electrode active material. Furthermore, when a composite oxide having an Ni content of 20-80 mol% among elements other than Li is obtained, for example, the mixture is preferably fired at a heating temperature that does not exceed 1100°C. It should be noted that the heating temperature here refers to the maximum temperature reached by heating of the material being fired.

[0104] The main firing time is not particularly limited, and it should be sufficient time to form a composite oxide having the desired crystal structure. For example, a time of 1-15 hours, 2-12 hours or 2-10 hours is preferred.

[0105] Unreacted lithium compounds or lithium compounds that have moved from the crystal structure to the particle surface layer over the course of the firing step are sometimes present as impurities in the lithium-nickel composite oxide obtained in the firing step. Water washing may therefore be performed by providing a water washing step, for example, in order to remove and reduce these impurities. It should be noted that the washing step is not an essential component.

[0106] In the surface treatment step, a predetermined elemental compound is admixed with the lithium- nickel composite oxide obtained in the firing step or the washing step, and a heat treatment is carried out to allow the surfaces of primary particles and / or secondary particles of the lithium- nickel composite oxide to be surface treated with a compound of lithium and the added elements, making it possible to achieve effects such as leaving fewer lithium compounds on the particle surface layer, improving lithium ion conductivity, and reducing reaction resistance. It should be noted that the surface treatment step is not an essential component.

[0107] The elemental compound added for the surface treatment noted above may be selected, for example, from aluminum compounds, boron compounds, tungsten compounds, manganese compounds, cobalt compounds, phosphorus compounds, niobium compounds, strontium compounds, antimony compounds, zirconium compounds, and titanium compounds, etc., and one or more of these compounds may be used. A nonaqueous electrolyte secondary battery according to an embodiment of the present disclosure comprises a positive electrode that contains the above composite oxide as a positive electrode active material, wherein the nonaqueous electrolyte secondary battery comprises the positive electrode, a negative electrode, and an electrolytic solution comprising an electrolyte.

[0108] When the positive electrode is produced, a conductive agent and a binder are admixed by a normal process with the composite oxide according to the embodiment of the present disclosure. Acetylene black, carbon black or graphite, etc., is preferably used as the conductive agent, for example. Polytetrafluoroethylene or polyvinylidene fluoride, etc., is preferably used as the binder, for example.

[0109] The negative electrode is not particularly limited, but it is possible to use not only a negative electrode active material such as lithium metal, graphite, or a low-crystallinity carbon material, for example, but also one or more non-metal or metal elements selected from Si, Al, Sn, Pb, Zn, Bi and Cd, or alloys comprising same, or chalcogen compounds comprising same, etc.

[0110] The solvent of the electrolytic solution is not particularly limited, but it is possible to use an organic solvent comprising one or more selected from carbonates, such as ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate, or ethers such as dimethoxyethane, for example.

[0111] In addition to, in particular, lithium hexafluorophosphate (LiPFe), one or more selected from lithium salts such as lithium perchlorate or lithium tetrafluoroborate may be used, while dissolved in a solvent, as the electrolyte, for example.

[0112] EMBODIMENT

[0113] Below embodiments further illustrate how this invention could be carried out.

[0114] Embodiment 1

[0115] A nickel-containing hydroxide powder comprising at least nickel as a constituent element, wherein in a volume-based particle size distribution, when a cumulative 10% particle size is D10, a cumulative 50% particle size is D50, and a cumulative 90% particle size is D90, D50 is 5 pm- 20 pm, a span represented by (D90-D10) / D50 is 0.8-2, and a variation index of crystallinity of a (101) plane, defined below, is 0.25 or less, when the above-mentioned nickel-containing hydroxide powder is graded into three grades so that D50 of a first graded powder F having the smallest average particle size is equal to D10 of the nickel-containing hydroxide powder, and so that D50 of a third graded powder G having the largest average particle size is equal to D90 of the nickel-containing hydroxide powder, with the remainder being a second graded powder M, then the variation index is defined by the following Formula (I):

[0116] Variation index = |1-(FWHM(G) / FWHM(F))| Formula (I)

[0117] Wherein, in Formula (I), FWHM(G) represents the half-width of a peak derived from the (101) plane in an X-ray diffraction pattern of the third graded powder G, and FWHM(F) represents the half-width of a peak derived from the (101) plane in an X-ray diffraction pattern of the first graded powder F. Embodiment 2

[0118] The nickel-containing hydroxide powder as claimed in claim 1 , comprising a nickel-containing hydroxide represented by the general formula Nii-x-y-zCoxMnyMz(OH)2+a (0<x<0.4, 0<y<0.4, 0<z<0.4, 0.5<1-x-y-z, -0.5<a<0.5, and M is at least one element other than Li, Ni, Co, Mn and O).

[0119] Embodiment 3

[0120] The nickel-containing hydroxide powder as claimed in claim 1 or 2, wherein the half-width of the peak derived from the (101) plane in an X-ray diffraction pattern is in a range of from 0.2° to 0.8°.

[0121] Embodiment 4

[0122] The nickel-containing hydroxide powder as claimed in claim 1 or 2, wherein the half-width of the peak derived from the (100) plane in an X-ray diffraction pattern is in a range of from 0.2° to 0.4°.

[0123] Embodiment 5

[0124] A method for producing a lithium-nickel composite oxide, the method comprising: a mixing step in which the nickel-containing hydroxide powder as claimed in claim 1 or 2 is mixed with a lithium compound to obtain a mixture; and a firing step in which the mixture is fired.

[0125] Embodiment 6

[0126] A method for producing a lithium-nickel composite oxide, the method comprising: a heating step in which the nickel-containing hydroxide powder as claimed in claim 1 or 2 is heated to obtain a nickel-containing compound; a mixing step in which the nickel-containing compound is mixed with a lithium compound to obtain a mixture; and a firing step in which the mixture is fired.

[0127] BRIEF DESCRIPTION OF THE DRAWINGS

[0128] Figure 1 is a schematic diagram of an example of a stirring tank which can be used in a method for producing a nickel-containing hydroxide powder according to an embodiment of the present disclosure.

[0129] Figure 2 is a schematic diagram of an example of a stirring tank which can be used in a method for producing a nickel-containing hydroxide powder according to an embodiment of the present disclosure.

[0130] EXAMPLE

[0131] The present disclosure will be described in greater detail below using examples, but the present disclosure is not limited by these examples.

[0132] Samples of the examples and comparative examples were evaluated by the methods given below.

[0133] <XRD Diffraction> XRD diffraction data of the nickel-containing hydroxide powder was obtained under the following X-ray diffraction conditions using an X-ray diffraction apparatus [SmartLab, produced by Rigaku Corp.], and the XRD diffraction data was then used to obtain the full width at half maximum (FWHM), indexing with the space group P-3m1 , with reference to “R. A. Young, ed., “The Rietveld Method”, Oxford University Press (1992)”. It should be noted that Rietveld analysis was performed for the analysis.

[0134] (X-ray diffraction conditions)

[0135] X-ray source: Cu-Ka

[0136] Acceleration voltage and current: 45 kV and 200 mA

[0137] Sampling width: 0.02 deg.

[0138] Scan width: 5 deg. to 90 deg.

[0139] Scan speed: 1.0 steps / sec

[0140] Divergence slit: 2 / 3 deg.

[0141] Receiving slit width: 0.15 mm

[0142] Scattering slit: 2 / 3 deg.

[0143] <Composition of nickel-containing hydroxide and lithium-nickel composite oxide>

[0144] A 0.2 g sample of nickel-containing hydroxide and lithium-nickel composite oxide was heated and dissolved in 25 mL of 20% hydrochloric acid solution, cooled and then transferred to a 100 mL measuring flask, and pure water was introduced to prepare an adjusted liguid. The elements in the adjusted liguid were guantitatively determined using ICP-AES (Optima 8300, produced by PerkinElmer, Inc.).

[0145] <NH3concentration measurement

[0146] A slurry in the reaction tank was sampled during synthesis of the nickel-containing hydroxide, and a supernatant was collected by using a centrifuge. A predetermined guantity of the resulting liguid component was collected using a volumetric pipette, the collected liguid component was distilled using a Kjeldahl distillation apparatus, and the liguid component obtained after the distillation was titrated with hydrochloric acid to thereby obtain the NH3concentration in the reaction slurry.

[0147] <f-OH concentration measurement

[0148] A predetermined guantity of the same supernatant which was extracted for the NH3concentration measurement was collected, and, without performing a distillation operation or other treatment, this was titrated with hydrochloric acid for the concentration of the total alkali amount in the mother liguor. It should be noted that the titer based on hydrochloric acid was calculated in a state in which the NH3+and OH' fractions were combined, so the f-OH concentration was calculated by subtracting the guantity of NH3in the NH3concentration measurement. f-OH concentration = concentration of the total alkali amount in the mother liguor - NH3concentration

[0149] <Coin cell employing the lithium-nickel composite oxide> A 2032-type coin cell employing the lithium-nickel composite oxide as the positive electrode active material was produced by using a positive electrode, negative electrode and electrolytic solution produced by the following respective methods.

[0150] < Positive electrode>

[0151] Using acetylene black and graphite as the conductive agent at a weight ratio of acetylene black:graphite=1:1, and using polyvinylidene fluoride as the binder, the positive electrode active material, conductive agent and binder were blended to achieve a weight ratio of positive electrode active materiakconductive agent:binder=90:6:4, and a slurry obtained by mixing these materials with N-methylpyrrolidone was coated on an aluminum foil. The coated aluminum foil was dried at 110°C to prepare a sheet which was punched to a diameter of 15 mm and then rolled to a composite material density of 3.0g / cm3, and this was used as the positive electrode.

[0152] <Negative electrode>

[0153] A lithium foil having a thickness of 500 pm punched to a diameter of 16 mm was used as the negative electrode.

[0154] <Electrolytic solution>

[0155] A mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) was prepared at a volume ratio of EC:DMC=1 :2, and a solution obtained by mixing a 1M LiPFe electrolyte therewith was used as the electrolytic solution.

[0156] <Nonaqueous electrolyte secondary battery characteristics>

[0157] (Initial charging capacity and initial charging / discharging efficiency)

[0158] Using the coin cell produced by the method above, after constant current charging at a current density of 0.1 C (1.8 mA / g in the examples of the present invention) to 4.3 V (upper limit voltage) under a 25°C environment, constant voltage charging was performed until the current reached 0.01 C. The capacity at this time was used as the initial charging capacity (mAh / g).

[0159] After a pause of 5 minutes, constant current discharging was then performed at a current density of 0.1 C to 2.5 V under the same environment, and then there was a 5 minutes’ pause. The capacity at this time was used as the initial discharging capacity (mAh / g).

[0160] The initial charging / discharging efficiency was calculated on the basis of the following equation using the measured value of the initial charging capacity and the measured value of the initial discharging capacity.

[0161] Initial charging / discharging efficiency (%) = (initial discharging capacity / initial charging capacity) x 100%

[0162] <Cvcle retention rate>

[0163] Using the coin cell produced by the method above, 104 cycles of charging / discharging were performed under a 60°C environment and the conditions indicated below.

[0164] • 1st, 2ndand 104thcycles: Constant current charging at 0.2 C to 4.3 V, then constant voltage charging to 0.01 C

[0165] 5 minutes’ pause

[0166] Constant current discharging at 0.2 C to 3.0 V

[0167] 5 minutes’ pause

[0168] • 3rdto 103rdcycles:

[0169] Constant current charging at 0.5 C to 4.3 V, then constant voltage charging to 0.01 C

[0170] 5 minutes’ pause

[0171] Constant current discharging at 1 C to 3.0 V

[0172] 5 minutes’ pause

[0173] Using the measured value of the discharging capacity in the 2ndcycle and the measured value of the discharging capacity in the 104thcycle, the cycle retention rate at 25°C was calculated on the basis of the following equation.

[0174] Cycle retention rate (%)

[0175] = (discharging capacity in the 104th cycle I discharging capacity in the 2nd cycle) x 100%

[0176] <lnitial reaction resistance>

[0177] Using the coin cell produced by the method above, the initial reaction resistance was measured under a 25°C environment and the conditions indicated below.

[0178] • 1stcycle:

[0179] Constant current charging at 0.1 C to 4.3 V, then constant voltage charging to 0.01 C

[0180] 5 minutes’ pause

[0181] Constant current discharging at 0.1 C to 2.5 V

[0182] 5 minutes’ pause

[0183] • 2ndcycle:

[0184] Constant current charging at 0.1 C to 4.3 V, then constant voltage charging to 0.01 C

[0185] The impedance was measured under a 25°C environment and the conditions indicated below using a cell for which the 2nd cycle of charging had been completed. The result thereof was used as the impedance measurement result for the 2nd cycle (reaction resistance at the 2nd cycle (initial reaction resistance)).

[0186] Frequency range: 300 k-0.01 Hz (76 points)

[0187] Amplitude: 10 mV

[0188] Example 1

[0189] 11.6 L of pure water were introduced into a reaction tank according to the embodiment shown in fig. 2, having a capacity of 14 L and comprising an overflow pipe (not depicted), a sodium hydroxide aqueous solution and ammonia water were further weighed out to achieve an f-OH concentration of the mother liquor of 0.005 mol / L and an NH3 concentration of 0.34 mol / L, and these were each introduced into the reaction tank, into which the pure water had been introduced, and stirred.

[0190] After the mother liquor had been prepared, a solution obtained by mixing nickel sulfate and manganese sulfate at a molar ratio of Ni:Mn=90:10 was prepared beforehand. A coaxial nozzle having a double-pipe structure comprising an internal pipe was installed inside the reaction tank, and the starting material introduction nozzle (internal pipe) for introducing the solution obtained by mixing nickel sulfate and manganese sulfate was lengthened so that a distance (nozzle introduction port distance) between the introduction port of the starting material introduction nozzle and the introduction port of the alkali introduction nozzle for introducing the sodium hydroxide aqueous solution and ammonia water was 2 mm, and the starting material was continuously added into the reaction mother liquor. At the same time, the sodium hydroxide aqueous solution and ammonia water were continuously added into the reaction tank so that the f-OH concentration of the mother liquor was 0.005 mol / L and the NH3concentration was 0.34 mol / L, and a crystallization reaction was performed. It should be noted that, during the crystallization reaction, the stirring speed was controlled to 1000 rpm and the slurry temperature (reaction temperature) was controlled to 60°C, while the inside of the reaction tank was purged with nitrogen gas to maintain a non-oxidizing atmosphere. Furthermore, during the crystallization reaction, the f-OH concentration, NH3concentration, particle size distribution, and pH (23°C) of the slurry discharged from the overflow pipe were measured at appropriate times, and a predetermined quantity of the slurry was recovered after a steady state had been reached. After this, the resulting slurry was washed and filtered using a Buchner funnel, and the resulting washed product was dried for 15 hours at 120°C under an air atmosphere, whereby the nickel- containing hydroxide powder sample was obtained.

[0191] After this, grading and firing were performed in the same way as in Comparative Example 1, and the lithium-nickel composite oxide sample was obtained.

[0192] Example 2

[0193] A nickel-containing hydroxide powder sample and a lithium-nickel composite oxide sample were obtained in the same way as in Example 1 , except that the crystallization reaction conditions were changed so that the pH, reaction temperature, NH3concentration, f-OH concentration, and nozzle introduction port distance were as shown in table 1.

[0194] Example 3

[0195] A nickel-containing hydroxide powder sample and a lithium-nickel composite oxide sample were obtained in the same way as in Comparative Example 1, except that the crystallization reaction conditions were changed so that the pH, reaction temperature, NH3concentration, and f-OH concentration were as shown in table 1.

[0196] Example 4

[0197] A nickel-containing hydroxide powder sample and a lithium-nickel composite oxide sample were obtained in the same way as in Example 1 , except that the crystallization reaction conditions were changed so that the pH, reaction temperature, NH3concentration, f-OH concentration, and nozzle introduction port distance were as shown in table 1.

[0198] Comparative Example 1

[0199] A nickel-containing hydroxide powder sample was synthesized in the following manner, and a lithium-nickel composite oxide sample was then synthesized. 11.6 L of pure water were introduced into a reaction tank according to the embodiment shown in fig. 1 , having a capacity of 14 L and comprising an overflow pipe (not depicted), a sodium hydroxide aqueous solution and ammonia water were further weighed out to achieve an f-OH concentration of the mother liquor of 0.04 mol / L and an NH3 concentration of 0.5 mol / L, and these were each introduced into the reaction tank and stirred.

[0200] After the mother liquor had been prepared, a solution obtained by mixing nickel sulfate and manganese sulfate at a molar ratio of Ni:Mn=90:10 was prepared beforehand and added to the mother liquor by means of the starting material introduction nozzle from above the liquid surface in the reaction tank using a metering pump. At the same time, a sodium hydroxide aqueous solution and ammonia water were continuously added by means of the alkali introduction nozzle from above the liquid surface so that the f-OH concentration of the mother liquor was 0.04 mol / L and the NH3concentration was 0.5 mol / L, and a crystallization reaction was performed. It should be noted that, during the crystallization reaction, the stirring speed was controlled to 1000 rpm and the slurry temperature (reaction temperature) was controlled to 53°C, while the inside of the reaction tank was purged with nitrogen gas to maintain a non-oxidizing atmosphere. Furthermore, during the crystallization reaction, the f-OH concentration, NH3concentration and particle size distribution of the slurry discharged from the overflow pipe were measured at appropriate times, and a predetermined quantity of the slurry was recovered after a steady state had been reached. After this, the resulting slurry was washed and filtered using a Buchner funnel, and the resulting washed product was dried for 15 hours at 120°C under an air atmosphere, whereby the nickel-containing hydroxide powder sample was obtained. The resulting nickel-containing hydroxide powder sample was subjected to particle size distribution and powder XRD measurements.

[0201] The resulting nickel-containing hydroxide powder sample was graded using an air classifier (Elbow-Jet: produced by Nittetsu Mining Co., Ltd.), so that D50 of a first graded powder (F) was D10 of the nickel-containing hydroxide powder sample, and so that D50 of a third graded powder (G) was D90 of the nickel-containing hydroxide powder sample, with the remainder being a second graded powder (M).

[0202] Each of the resulting powders were subjected to particle size distribution and powder XRD diffraction measurements. Variations in crystallinity of the first graded powder (F) and the third graded powder (G) were determined using the following Formula (I):

[0203] Variation in (100) crystallinity = |1-(FWHM(G) / FWHM(F))| Formula (I)

[0204] In Formula (I), FWHM(G) represents the half-width of a peak derived from the (101) plane in an X-ray diffraction pattern of the third graded powder G, and FWHM(F) represents the half-width of a peak derived from the (101) plane in an X-ray diffraction pattern of the first graded powder F.

[0205] The resulting nickel-containing hydroxide and anhydrous lithium hydroxide were mixed at a ratio such that Li / (N i+M n)= 1.03, and subjected to a primary firing over the course of 6 hours at 570°C under an oxygen atmosphere (oxygen concentration: 97 vol%), after which the materials were subjected to the main firing over the course of 6 hours at 750°C, whereby a lithium-nickel composite oxide was obtained. The composition of the resulting lithium-nickel composite oxide was Li1.03Ni0.9Mn0.1O2.

[0206] After this, 1 kg of the resulting lithium-nickel composite oxide was introduced into a beaker prepared with pure water in an amount of 0.67 L, and stirred for 10 minutes, then the slurry was filtered using a Buchner funnel, whereby a cake-like substance was obtained. The resulting cake-like substance was vacuum dried over the course of 10 hours at 185°C in a vacuum dryer, whereby a lithium-nickel composite oxide sample was obtained.

[0207] Comparative Example 2

[0208] A nickel-containing hydroxide powder sample and a lithium-nickel composite oxide sample were obtained in the same way as in Comparative Example 1 , except that the position of the starting material introduction nozzle 13 for introducing the mixed solution of nickel sulfate and manganese sulfate was arranged so that the introduction port 131 was in the mother liquor, close to the stirring blades.

[0209] Comparative Example 3

[0210] A nickel-containing hydroxide powder sample and a lithium-nickel composite oxide sample were obtained in the same way as in Example 1 , except that the crystallization reaction conditions were changed so that the pH, reaction temperature, NH3 concentration, f-OH concentration, and nozzle introduction port distance were as shown in table 1.

[0211] Table 1 shows the synthesis conditions (pH, reaction temperature, NH3concentration, f-OH concentration, [NH]6 / [f-OH]2, and nozzle introduction port distance) of the nickel-containing hydroxide powder samples of Examples 1-4 and Comparative Examples 1-3.

[0212] Table 2 shows the evaluation results of the nickel-containing hydroxide powder samples and lithium-nickel composite oxide samples of Examples 1-4 and Comparative Examples 1-3.

[0213] le 1:

[0214] le 2:

[0215] Key to Symbols

[0216] I , 2 Stirring tank

[0217] II,21 Reaction tank

[0218] 12, 22 Stirring device

[0219] 121 A, 121 B, 221A, 221B, 221C Stirring blade 13,23 Starting material introduction nozzle

[0220] 131, 141, 231, 241 Introduction port

[0221] 14,24 Alkali introduction nozzle

[0222] 25 Coaxial nozzle

Claims

CLAIMS1. A nickel-containing hydroxide powder comprising at least nickel as a constituent element, wherein in a volume-based particle size distribution, when a cumulative 10% particle size is D10, a cumulative 50% particle size is D50, and a cumulative 90% particle size is D90, D50 is 5 pm-20 pm, a span represented by (D90-D10) / D50 is 0.8-2, and a variation index of crystallinity of a (101) plane, defined below, is 0.25 or less, when the above-mentioned nickel-containing hydroxide powder is graded into three grades so that D50 of a first graded powder F having the smallest average particle size is equal to D10 of the nickel-containing hydroxide powder, and so that D50 of a third graded powder G having the largest average particle size is equal to D90 of the nickel-containing hydroxide powder, with the remainder being a second graded powder M, then the variation index is defined by the following Formula (I):Variation index = |1-(FWHM(G) / FWHM(F))| Formula (I) Wherein, in Formula (I), FWHM(G) represents the half-width of a peak derived from the (101) plane in an X-ray diffraction pattern of the third graded powder G, and FWHM(F) represents the half-width of a peak derived from the (101) plane in an X-ray diffraction pattern of the first graded powder F.

2. The nickel-containing hydroxide powder as claimed in claim 1 , comprising a nickel- containing hydroxide represented by the general formula Nii.x-y-zCOxMnyMz(OH)2+a (0<x<0.4, 0<y<0.4, 0<z<0.4, 0.5<1-x-y-z, -0.5<a<0.5, and M is at least one element other than Li, Ni, Co, Mn and O).

3. The nickel-containing hydroxide powder as claimed in claim 1 or 2, wherein the half-width of the peak derived from the (101) plane in an X-ray diffraction pattern is in a range of from 0.2° to 0.8°.

4. The nickel-containing hydroxide powder as claimed in claim 1 or 2, wherein the half-width of the peak derived from the (100) plane in an X-ray diffraction pattern is in a range of from 0.2° to 0.4°.

5. A method for producing a lithium-nickel composite oxide, the method comprising: a mixing step in which the nickel-containing hydroxide powder as claimed in claim 1 or 2 is mixed with a lithium compound to obtain a mixture; and a firing step in which the mixture is fired.

6. A method for producing a lithium-nickel composite oxide, the method comprising: a heating step in which the nickel-containing hydroxide powder as claimed in claim 1 or 2 is heated to obtain a nickel-containing compound; a mixing step in which the nickel-containing compound is mixed with a lithium compound to obtain a mixture; and a firing step in which the mixture is fired.

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