Lithium-metal composite oxide powder, positive electrode active material for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secodary battery

Abstract

The present invention provides a lithium-metal composite oxide powder compris particles of a lithium-metal composite oxide comprising at least Li, Ni, Zr and Ti. When the particles of the lithium-metal composite oxide are analyzed in a cross section using a two-dimensional high- resolution secondary ion mass spectrometer, a ratio of the maximum intensity of Zr in the surface vicinity of the particles of the lithium-metal composite oxide to the average intensity of Zr in the center vicinity of the particles of the lithium-metal composite oxide is 1.5-3.5, and a ratio of the maximum intensity of Ti in the surface vicinity of the particles of the lithium-metal composite oxide to the average intensity of Ti in the center vicinity of the particles of the lithium- metal composite oxide is 0.60-2.6.

Description

241301W0011LITHIUM-METAL COMPOSITE OXIDE POWDER, POSITIVE ELECTRODE ACTIVE MATERIAL FOR NONAQUEOUS ELECTROLYTE SECONDARY BATTERY, AND NONAQUEOUS ELECTROLYTE SECODARY BATTERYTECHNICAL FIELDThe present disclosure relates to a lithium-metal composite oxide powder, a positive electrode active material for a nonaqueous electrolyte secondary battery, and a nonaqueous electrolyte secondary battery.BACKGROUNDRecent years have seen portable, cordless electronic devices such as cellphones and laptops rapidly becoming more widespread, and power sources for driving these devices include nonaqueous secondary batteries that are small and lightweight and have high energy density. Among these, lithium ion secondary batteries which utilize materials such as lithium nickel oxide in the positive electrode and have advantages such as high charging / discharging capacity are often used.Layered rock-salt oxide type positive electrode active materials for lithium ion secondary batteries (basic composition: Li(NiM)C>2), which are solid solutions of nickel (Ni) and other transition metals M and which are extremely versatile, have been extensively researched as positive electrode active materials in such lithium ion secondary batteries.These positive electrode active materials exhibit a similarly high battery voltage to lithium cobalt composite oxide while also having a large charging / discharging capacity, and are expected as materials capable of expanding the range of application of lithium ion secondary batteries in electric vehicles and stationary storage batteries, etc., and further research and development are being actively undertaken.It has been noted, however, that lithium ion secondary batteries generally undergo a gradual reduction in battery capacity with repeated charging / discharging cycles, and that the battery capacity decreases as a result of storage in a charged state under a high-temperature environment. This is thought to be due to the fact that positive electrode materials having a layered rock-salt structure undergo changes in the crystal structure and expansion / contraction due to repeated charging / discharging and the state of charge.In order to inhibit a drop in battery characteristics due to these repeated cycles, and to improve cycle characteristics, JP 2011-023335 A, for example, proposes a lithium-metal composite oxide having the basic composition UMO2, where M is a group of four or more elements including Ni and at least three elements selected from Co, Mn, Al, Mg and Ti. According to JP 2011-023335 A, it is indicated that a metal site in such a lithium-metal composite oxide is substituted with Al, and a metal site and Li site are furthermore substituted with Mg, whereby the rate of expansion and contraction in the crystal structure can be reduced by insertion / deinsertion of Li during charging and discharging, as a result of which the cycle characteristics can be enhanced because irreversible reactions can be alleviated.241301W0012SUMMARY OF THE INVENTIONHere, a positive electrode active material for a nonaqueous electrolyte secondary battery such as disclosed in JP 2011-023335 A exhibits excellent cycle characteristics as described above, but on the other hand, doping with foreign elements is likely to lead to an increase in electric resistance.In light of the situation described above, the objective of the present disclosure lies in providing a lithium-metal composite oxide powder which exhibits superior high-temperature storage characteristics and lower electrical resistance when used as a positive electrode active material for a nonaqueous electrolyte secondary battery, and also in providing a positive electrode active material for a nonaqueous electrolyte secondary battery employing said lithium-metal composite oxide powder, and in providing a nonaqueous electrolyte secondary battery.The inventors of the present invention engaged in extensive research to solve the problems noted above. As a result, it was found that a lithium-metal composite oxide powder, comprising particles of a lithium-metal composite oxide comprising at least Li, Ni, Zr and Ti, wherein, when the particles of the lithium-metal composite oxide are analyzed in a cross section using a two-dimensional high-resolution secondary ion mass spectrometer, a ratio of the maximum intensity of Zr in the surface vicinity of the particles of the lithium-metal composite oxide to the average intensity of Zr in the center vicinity of the particles of the lithium-metal composite oxide is 1.5-3.5, and a ratio of the maximum intensity of Ti in the surface vicinity of the particles of the lithium-metal composite oxide to the average intensity of Ti in the center vicinity of the particles of the lithium-metal composite oxide is 0.60-2.6, exhibits superior high-temperature storage characteristics and lower electrical resistance when used as a positive electrode active material for a nonaqueous electrolyte secondary battery. The present disclosure provides the following.(1) A lithium-metal composite oxide powder comprising particles of a lithium-metal composite oxide comprising at least Li, Ni, Zr and Ti, whereinwhen the particles of the lithium-metal composite oxide are analyzed in a cross section using a two-dimensional high-resolution secondary ion mass spectrometer,a ratio of the maximum intensity of Zr in the surface vicinity of the particles of the lithium-metal composite oxide to the average intensity of Zr in the center vicinity of the particles of the lithium-metal composite oxide is 1.5-3.5, anda ratio of the maximum intensity of Ti in the surface vicinity of the particles of the lithium-metal composite oxide to the average intensity of Ti in the center vicinity of the particles of the lithium-metal composite oxide is 0.60-2.6.(2) The lithium-metal composite oxide powder as disclosed in (1) above, whereinwhen the particles of the lithium-metal composite oxide are analyzed in a cross section using a two-dimensional high-resolution secondary ion mass spectrometer,a coefficient of variation of a ratio of the average intensity of Zr in the center vicinity of the cross section of the particles of the lithium-metal composite oxide to the average intensity of background Zr is 0.10-1.4.241301W0013(3) The lithium-metal composite oxide powder as disclosed in (1) or (2) above, wherein when the particles of the lithium-metal composite oxide are analyzed in a cross section using a two-dimensional high-resolution secondary ion mass spectrometer,a coefficient of variation of a ratio of the intensity of Ti in the center vicinity of the particles of the lithium-metal composite oxide to the average intensity of background Ti is 0.10-1.5.(4) The lithium-metal composite oxide powder as disclosed (1) or (2) above,which has a layered rock salt structure, andis represented by the general formula LiaNixCoyMnzZruTivMwOa (in the formula, M is one or more elements other than Li, Ni, Co, Mn, Zr, Ti and O; 0.90<a<1.4; x+y+z+u+v+w=1.00; 0<u<0.015; 0<v<0.030; and 1.60<a<2.40).(5) A positive electrode active material for a nonaqueous electrolyte secondary battery, the positive electrode active material for a nonaqueous electrolyte secondary battery comprising the lithium-metal composite oxide powder as disclosed (1) or (2) above.(6) A nonaqueous electrolyte secondary battery, comprising:the positive electrode active material for a nonaqueous electrolyte secondary battery as disclosed in (5) above.According to the present disclosure, it is possible to provide a lithium-metal composite oxide powder which exhibits superior high-temperature storage characteristics and lower electrical resistance when used as a positive electrode active material for a nonaqueous electrolyte secondary battery.BRIEF DESCRIPTION OF THE DRAWINGSFig. 1 is a schematic view of a particle to illustrate the maximum particle size of particles selected for observation.Fig. 2 is a schematic view of a particle to illustrate a method for selecting three lines used in a line profile of the particles selected for observation.Fig. 3 (a) is a schematic view of a particle selected for observation, and Fig. 3 (b) shows the correspondence of the line profile.Fig. 4 is a schematic diagram of the line profile to illustrate the maximum intensity in the surface vicinity, the center vicinity, and the surface vicinity in the line profile.Embodiments of the present disclosure (hereinafter referred to as “the present embodiment”) will be described below, but the present disclosure is in no way limited by the descriptions in these embodiments, and the present disclosure can be implemented with additional modifications, as appropriate.The lithium-metal composite oxide powder according to the present embodiment comprises particles of a lithium-metal composite oxide comprising at least Li, Ni, Zr and Ti. When the particles of the lithium-metal composite oxide are analyzed in a cross section using a two-dimensional high-resolution secondary ion mass spectrometer, a ratio of the maximum intensity of Zr in the surface vicinity of the particles of the lithium-metal composite oxide to the average241301W0014intensity of Zr in the center vicinity of the particles of the lithium-metal composite oxide is 1.5-3.5, and a ratio of the maximum intensity of Ti in the surface vicinity of the particles of the lithium-metal composite oxide to the average intensity of Ti in the center vicinity of the particles of the lithium-metal composite oxide is 0.60-2.6.Since Zr and Ti are uniformly distributed within the particles of this lithium-metal composite oxide powder, the crystal structure within the particles can be strengthened by the synergistic effect of Zr and Ti. Specifically, it is thought a uniform distribution of Zr enables widening of spaces between layers of the layer structure, and it is thought that a large amount of Ti, which has a relatively large ionic radius, can be substituted in the crystal structure as a result. Li2MnOa is readily formed because of Ti being substituted in a large amount, and superior high-temperature storage characteristics are especially demonstrated when this is used as a positive electrode active material for a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery.Furthermore, the amount of Zr which is present in the surface vicinity of the particles is greater than the amount of Zr which is present in the center vicinity of the particles, so the Zr and Li react, forming a fine film of a Li-Zr compound. Additionally, it is thought that some of the Ti which was not substituted within the particles is present together with the Li-Zr compound as an Li-Ti compound, which synergistically improves the Li ion conductivity. Even lower resistance is demonstrated as a result in particular.As described above, the distribution of Zr and Ti in the present embodiment makes it possible to form a lithium-metal composite oxide powder exhibiting outstanding resistance properties at the same time as outstanding high-temperature storage characteristics.When the particles of the lithium-metal composite oxide are analyzed in a cross section using a two-dimensional high-resolution secondary ion mass spectrometer, there is no particular limitation as to the ratio of the maximum intensity of Zr in the surface vicinity of the particles of the lithium-metal composite oxide to the average intensity of Zr in the center vicinity of the particles of the lithium-metal composite oxide (this will also be referred to below as the "Zr intensity ratio"), provided that the ratio is 1.5-3.5, and it is preferably 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, 2.0 or more, 2.1 or more, 2.2 or more, 2.3 or more, or 2.4 or more, for example. Meanwhile, the Zr intensity ratio is preferably 3.4 or less, 3.3 or less, 3.2 or less, 3.1 or less, 3.0 or less, 2.9 or less, 2.8 or less, 2.7 or less, or 2.6 or less.When the particles of the lithium-metal composite oxide are analyzed in a cross section using a two-dimensional high-resolution secondary ion mass spectrometer, there is no particular limitation as to the coefficient of variation of the ratio of the average intensity of Zr in the center vicinity of the cross section of the particles of the lithium-metal composite oxide to the average intensity of background Zr (this will also be referred to below as the "coefficient of variation of the Zr intensity"), and it is preferably 0.10 or more, 0.12 or more, 0.15 or more, 0.17 or more, 0.20 or more, 0.22 or more, 0.25 or more, 0.27 or more, or 0.30 or more, for example.Meanwhile, the coefficient of variation of the Zr intensity is preferably 1.4 or less, 1.3 or less, 1.2241301W0015or less, 1.0 or less, 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, or 0.30 or less.When the particles of the lithium-metal composite oxide are analyzed in a cross section using a two-dimensional high-resolution secondary ion mass spectrometer, there is no particular limitation as to the ratio of the maximum intensity of Ti in the surface vicinity of the particles of the lithium-metal composite oxide to the average intensity of Ti in the center vicinity of the particles of the lithium-metal composite oxide (this will also be referred to below as the "Ti intensity ratio"), provided that the ratio is 0.60-2.6, and it is preferably 0.70 or more, 0.80 or more, 0.90 or more, 1.0 or more, 1.1 or more, or 1.2 or more, for example. Meanwhile, the Ti intensity ratio is preferably 2.5 or less, 2.4 or less, 2.3 or less, 2.2 or less, 2.1 or less, 2.0 or less, 1.9 or less, 1.8 or less, or 1.7 or less.When the particles of the lithium-metal composite oxide are analyzed in a cross section using a two-dimensional high-resolution secondary ion mass spectrometer, there is no particular limitation as to the coefficient of variation of the ratio of the intensity of Ti in the center vicinity of the particles of the lithium-metal composite oxide to the average intensity of background Ti (this will also be referred to below as the "coefficient of variation of the Ti intensity"), and it is preferably 0.10 or more, 0.12 or more, 0.15 or more, 0.17 or more, 0.20 or more, 0.22 or more, 0.25 or more, or 0.27 or more, for example. Meanwhile, the coefficient of variation of the Ti intensity is preferably 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, 1.0 or less, 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, or 0.35 or less.A specific method of line analysis of the cross section of the particles of the lithium-metal composite oxide using a two-dimensional high-resolution secondary ion mass spectrometer will be described below.Line analysis is performed using a two-dimensional high-resolution secondary ion mass spectrometer (NanoSIMS 50L, manufactured by CAMECA) to obtain information relating to the surface and interior of particles. Specifically, oxygen is employed as a primary ion species, and the analysis is performed on the basis of secondary ions detected with a primary ion acceleration voltage of 16 kV.A lithium-metal composite oxide powder sample being observed is fixed with a resin, crosssectioned by means of the BIB method, and charge compensated by metal-coating the processed surface. Note that all of the operations relating to sampling are carried out under an inert atmosphere, except for the metal coating operation. After this, the sample is introduced onto a sample stand, and the outermost surface is cleaned using an ion beam immediately before observation.Prior to observation with the two-dimensional high-resolution secondary ion mass spectrometer, SEM observation is performed to select particles for observation with a particle size of 0.95-1.05 times the average particle size (D50) from among the particles contained in the lithium-metal composite oxide powder sample. At this time, the coordinates of secondary particles for observation are recorded, and the observations are made with reference to the coordinates241301W0016during observation by means of the two-dimensional high-resolution secondary ion mass spectrometer. Note that the particles of the lithium-metal composite oxide may be in the form of primary particles or in the form of secondary particles formed by aggregation of multiple primary particles. When the particles are in the form of secondary particles, the line analysis described below is carried out by treating the entire secondary particle as one particle, rather than line analysis of the primary particles contained therein.Note that the D50 is measured on a volume basis by a wet laser method using a laser-type particle size distribution analyzer (Microtrac HRA, manufactured by Nikkiso Co., Ltd.).The method of selecting lines used in the line profile will be described below with the aid of Fig.1 and 2. Fig. 1 is a schematic view of a particle to illustrate the maximum particle size of particles selected for observation. Fig. 2 is a schematic view of a particle to illustrate a method for selecting three lines used in a line profile of the particles selected for observation.For the lines used in the line profile, three lines at angles of 60° in relation to each other are selected in such a way that end-to-end lengths L2-L4 are set, with respect to the size of the particle P selected for observation, at 1.5 times the length of a line segment L1 (the straight line of maximum length among straight lines joining two points on the outline of the particle; see Fig.1) representing the maximum particle size Dmax of the particle P being observed, and at least 0.6 times the length of each line passes through the interior of the particle P. All of the three lines L2-L4 are selected so that 0.6 times the length thereof (shown only as S1 with respect to L2 in the drawing) passes through the interior of the particle P (see Fig. 2). If it is not possible to select three lines in such a way that 0.6 times the length of at least any of the lines passes through the interior of the particle, then that particle is excluded from the line analysis and another particle is selected. It should be noted that, in Fig. 1 and Fig. 2, the line segment L1 representing the maximum particle size Dmax of the particle P being observed is taken to be colinear with one of the three lines selected (the line L4), but the line segment representing the maximum particle size Dmax of the particle being observed does not necessarily have to be colinear with one of the three lines selected.The interval between line profiles is 80 nm for Ti and 500 nm for Zr. The line profile is smoothed by taking a moving average of intensity at a total of five points, i.e., the center point of numerical values and the two points before and after, and the result is used for analysis.The definitions of surface vicinity and center vicinity of the particles P selected for observation will be described below with the aid of Fig. 3 and Fig. 4. And Fig. 3 (a) is a schematic view of a particle selected for observation, and Fig. 3 (b) shows the correspondence of the line profile. Fig. 4 is a schematic diagram of the line profile to illustrate the maximum intensity in the surface vicinity, the center vicinity, and the surface vicinity in the line profile.The surface vicinity in the line profile for each of the three lines constitutes the ranges between points P1, P3 where the count is more than 10 times the background, and points P2, P4 which are each a distance of 0.3 times the maximum particle size Dmax of the particle being observed further inside the particle from the points P1, P3, respectively (see Fig. 4). The maximum counts241301W0017for Zr and Ti are determined within these ranges (see Fig. 4). The surface vicinity is present at both ends of the particle, as shown in Fig. 4, and the maximum intensity is determined as the maximum count in the entire range of the surface vicinity at both ends. The arithmetic mean value of the maximum count for each of the three lines is then taken as the maximum intensity.The center vicinity for each of the three lines is the range inside the surface vicinity at both ends of the particle (see Fig. 4). The arithmetic mean values of the Zr and Ti counts within this range are determined for each of the three lines. The arithmetic mean value is then determined for the arithmetic mean values of the counts for each of the three lines, and this is taken as the average intensity.The background for each of the three lines constitutes portions without particles in the cross-sectional SEM image, other than the portions close to the surface vicinity, such as where the line profile is rising. The Zr and Ti counts are measured for 20 background points randomly selected from each of the three lines, for a total of 60 points, and the arithmetic mean thereof is taken as the average intensity.The chemical composition of the lithium-metal composite oxide which is used is preferably, but not particularly limited to, one that has a layered rock-salt structure and that is represented by the general formula LiaNixCoyMnzZruTivMwOa (in the formula, M is one or more elements other than Li, Ni, Co, Mn, Zr, Ti and O; 0.90<a<1.4; x+y+z+u+v+w=1.00; 0<u<0.015; 0<v<0.030; and 1.60<a<2.40).There is no particular limitation as to the value of a in the general formula of the lithium-metal composite oxide, provided that it falls within the range of 0.90<a<1.4, and it may be, for example, 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, 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, 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, 1.2 or more, 1.205 or more, 1.21 or more, 1.215 or more, 1.22 or more, 1.225 or more, 1.23 or more, 1.235 or more, 1.24 or more, 1.245 or more, 1.25 or more, 1.255 or more, 1.26 or more, 1.265 or more, 1.27 or more, 1.275 or more, 1.28 or more, 1.285 or more, 1.29 or more, 1.295 or more, 1.3 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, 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, or 1.195 or more. Meanwhile, the value of a may be 1.395 or less, 1.39 or less, 1.385 or less, 1.38 or less, 1.375 or less, 1.37 or less, 1.365 or less, 1.36 or less, 1.355 or less, 1.35 or less, 1.345 or less, 1.34 or less, 1.335 or less, 1.33 or less, 1.325 or less, 1.32 or less, 1.315 or less, 1.31 or less, 1.305 or less, 1.3 or less, 1.3 or less, 1.295 or less, 1.29 or less, 1.285 or less, 1.28 or less, 1.275 or less, 1.27 or less, 1.265 or less, 1.26 or less,241301W00181.255 or less, 1.25 or less, 1.245 or less, 1.24 or less, 1.235 or less, 1.23 or less, 1.225 or less, 1.22 or less, 1.215 or less, 1.21 or less, 1.205 or less, 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, 1.16 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, 0.905 or less, or 0.90 or less.There is no particular limitation as to the value of x in the general formula of the lithium-metal composite oxide, and it may be, for example, 0 or more, 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, 0.105 or more, 0.11 or more, 0.115 or more, 0.12 or more, 0.125 or more, 0.13 or more, 0.135 or more, 0.14 or more, 0.145 or more, 0.15 or more, 0.155 or more, 0.16 or more, 0.165 or more, 0.17 or more, 0.175 or more, 0.18 or more, 0.185 or more, 0.19 or more, 0.195 or more, 0.2 or more, 0.205 or more, 0.21 or more, 0.215 or more, 0.22 or more, 0.225 or more, 0.23 or more, 0.235 or more, 0.24 or more, 0.245 or more, 0.25 or more, 0.255 or more, 0.26 or more, 0.265 or more, 0.27 or more, 0.275 or more, 0.28 or more, 0.285 or more, 0.29 or more, 0.295 or more, 0.3 or more, 0.305 or more, 0.31 or more, 0.315 or more, 0.32 or more, 0.325 or more, 0.33 or more, 0.335 or more, 0.34 or more, 0.345 or more, 0.35 or more, 0.355 or more, 0.36 or more, 0.365 or more, 0.37 or more, 0.375 or more, 0.38 or more, 0.385 or more, 0.39 or more, 0.395 or more, 0.4 or more, 0.405 or more, 0.41 or more, 0.415 or more, 0.42 or more, 0.425 or more, 0.43 or more, 0.435 or more, 0.44 or more, 0.445 or more, 0.45 or more, 0.455 or more, 0.46 or more, 0.465 or more, 0.47 or more, 0.475 or more, 0.48 or more, 0.485 or more, 0.49 or more, 0.495 or more, 0.5 or more, 0.505 or more, 0.51 or more, 0.515 or more, 0.52 or more, 0.525 or more, 0.53 or more, 0.535 or more, 0.54 or more, 0.545 or more, 0.55 or more, 0.555 or more, 0.56 or more, 0.565 or more, 0.57 or more, 0.575 or more, 0.58 or more, 0.585 or more, 0.59 or more, 0.595 or more, 0.6 or more, 0.605 or more, 0.61 or more, 0.615 or more, 0.62 or more, 0.625 or more, 0.63 or more, 0.635 or more, 0.64 or more, 0.645 or more, 0.65 or more, 0.655 or more, 0.66 or more, 0.665 or more, 0.67 or more, 0.675 or more, 0.68 or more, 0.685 or more, 0.69 or more, 0.695 or more, 0.7 or more, 0.705 or more, 0.71 or more, 0.715 or more, 0.72 or more, 0.725 or more, 0.73 or more, 0.735 or more, 0.74 or more, 0.745 or more, 0.75 or more, 0.755 or more, 0.76 or more, 0.765 or more, 0.77 or more, 0.775 or more, 0.78 or more, 0.785 or more, 0.79 or more, 0.795 or more, 0.8 or more, 0.805 or more, 0.81 or more, 0.815 or more, 0.82 or more, 0.825 or more, 0.83 or more, 0.835 or more, 0.84 or more, 0.845 or more, 0.85 or more, 0.855 or more, 0.86 or more, 0.865 or more, 0.87 or more, 0.875 or more, 0.88 or more, 0.885 or more, 0.89 or more, 0.895 or more, 0.9 or more, 0.905 or more, 0.91 or more, 0.915 or more,241301W00190.92 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, or 0.995 or more. Meanwhile, the value of x may be 1 or less, 0.997 or less, 0.995 or less, 0.992 or less, 0.99 or less, 0.987 or less, 0.985 or less, 0.982 or less, 0.98 or less, 0.977 or less, 0.975 or less, 0.972 or less, 0.97 or less, 0.967 or less, 0.965 or less, 0.962 or less, 0.96 or less, 0.957 or less, 0.955 or less, 0.952 or less, 0.95 or less, 0.947 or less, 0.945 or less, 0.942 or less, 0.94 or less, 0.937 or less, 0.935 or less, 0.932 or less, 0.93 or less, 0.927 or less, 0.925 or less, 0.922 or less, 0.92 or less, 0.917 or less, 0.915 or less, 0.912 or less, 0.91 or less, 0.907 or less, 0.905 or less, 0.902 or less, or 0.9 or less.

[0001] There is no particular limitation as to the value of y in the general formula of the lithium-metal composite oxide, and it may be, for example, 0 or more, 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 y may be 0.4 or less, 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, 0.37 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, 0.25241301W00110or 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, 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.There is no particular limitation as to the value of z in the general formula of the lithium-metal composite oxide, and it may be, for example, 0 or more, 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 z may be 0.4 or less, 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, 0.37 or less, 0.367 or241301W00111less, 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, 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.There is no particular limitation as to the value of u in the general formula of the lithium-metal composite oxide, and it may be, for example, 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, or 0.0095 or more. Meanwhile, the value of u may be 0.015 or less, 0.014 or less, 0.013 or less, 0.012 or less, 0.011 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, or 0.0015 or less.There is no particular limitation as to the value of v in the general formula of the lithium-metal composite oxide, and it may be, for example, greater than 0, 0.0005 or more, 0.0006 or more, 0.0007 or more, 0.0008 or more, 0.0009 or more, 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, 0.0105 or more, 0.011 or more, 0.0115 or more, 0.012 or more, 0.0125 or more, 0.013 or more, 0.014 or more, 0.0145 or more, 0.015 or more, 0.0155 or more, 0.016 or more, 0.0165 or more, 0.017 or more, 0.0175 or more, 0.018 or more, 0.0185 or more, 0.019 or more, 0.0195 or more, 0.02 or more, 0.0205 or more, 0.021 or more, 0.0215 or more, 0.022 or more, or 0.0225 or more. Meanwhile, the value of u may be 0.030 or less, 0.0295 or less, 0.029 or less, 0.0285 or less, 0.028 or less, 0.0275 or less, 0.027 or less, 0.0265 or less, 0.026 or less, 0.0255 or less, 0.025 or less, 0.0245 or less,241301W001120.024 or less, 0.0235 or less, 0.023 or less, 0.0225 or less, 0.022 or less, 0.0215 or less, 0.021 or less, 0.0205 or less, 0.02 or less, 0.0195 or less, 0.019 or less, 0.0185 or less, 0.018 or less, 0.0175 or less, 0.017 or less, 0.0165 or less, 0.016 or less, 0.0155 or less, 0.015 or less, 0.0145 or less, 0.014 or less, 0.0135 or less, 0.013 or less, 0.0125 or less, 0.012 or less, 0.0115 or less, 0.011 or less, 0.0105 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, or 0.0015 or less.There is no particular limitation as to the value of w in the general formula of the lithium-metal composite oxide, and it may be, for example, 0 or more, greater than 0, 0.001 or more, 0.0012 or more, 0.0015 or more, 0.0017 or more, 0.002 or more, 0.0022 or more, 0.0025 or more, 0.0027 or more, 0.003 or more, 0.0032 or more, 0.0035 or more, 0.0037 or more, 0.004 or more, 0.0042 or more, 0.0045 or more, 0.0047 or more, 0.005 or more, 0.0052 or more, 0.0055 or more, 0.0057 or more, 0.006 or more, 0.0062 or more, 0.0065 or more, 0.0067 or more, 0.007 or more, 0.0072 or more, 0.0075 or more, 0.0077 or more, 0.008 or more, 0.0082 or more, 0.0085 or more, 0.0087 or more, 0.009 or more, 0.0092 or more, 0.0095 or more, 0.0097 or more, 0.01 or more, 0.012 or more, 0.015 or more, 0.017 or more, 0.02 or more, 0.022 or more, 0.025 or more, 0.027 or more, 0.03 or more, 0.032 or more, 0.035 or more, 0.037 or more, 0.04 or more, 0.042 or more, 0.045 or more, 0.047 or more, 0.05 or more, 0.052 or more, 0.055 or more, 0.057 or more, 0.06 or more, 0.062 or more, 0.065 or more, 0.067 or more, 0.07 or more, 0.072 or more, 0.075 or more, 0.077 or more, 0.08 or more, 0.082 or more, 0.085 or more, 0.087 or more, 0.09 or more, 0.092 or more, 0.095 or more, or 0.097 or more. Meanwhile, the value of w may be 0.1 or less, 0.097 or less, 0.095 or less, 0.092 or less, 0.09 or less, 0.087 or less, 0.085 or less, 0.082 or less, 0.08 or less, 0.077 or less, 0.075 or less, 0.072 or less, 0.07 or less, 0.067 or less, 0.065 or less, 0.062 or less, 0.06 or less, 0.057 or less, 0.055 or less, 0.052 or less, 0.05 or less, 0.047 or less, 0.045 or less, 0.042 or less, 0.04 or less, 0.037 or less, 0.035 or less, 0.032 or less, 0.03 or less, 0.027 or less, 0.025 or less, 0.022 or less, 0.02 or less, 0.017 or less, 0.015 or less, 0.012 or less, 0.01 or less, 0.0097 or less, 0.0095 or less, 0.0092 or less, 0.009 or less, 0.0087 or less, 0.0085 or less, 0.0082 or less, 0.008 or less, 0.0077 or less, 0.0075 or less, 0.0072 or less, 0.007 or less, 0.0067 or less, 0.0065 or less, 0.0062 or less, 0.006 or less, 0.0057 or less, 0.0055 or less, 0.0052 or less, 0.005 or less, 0.0047 or less, 0.0045 or less, 0.0042 or less, 0.004 or less, 0.0037 or less, 0.0035 or less, 0.0032 or less, 0.003 or less, 0.0027 or less, 0.0025 or less, 0.0022 or less, 0.002 or less, 0.0017 or less, 0.0015 or less, 0.0012 or less, or 0.001 or less.In the general formula, there is no particular limitation as to the element M, provided that it is one or more elements other than Li, Ni, Co, Mn, Zr, Ti and O, and examples that can be used include Al, Mg, Zn, Nb, W, Mo, Sb, V, Cr, Ca, Fe, Ga, Sr, Y, Ru, In, Sn, Ta, Bi, and B, etc. The type of element M should be selected depending on the purpose for which it is added. When a plurality of elements are included as the element M, the value of w represents the total amount of the plurality of elements.There is no particular limitation as to the value of a in the general formula of the lithium-metal composite oxide, and it may be, for example, 1.61 or more, 1.62 or more, 1.63 or more, 1.64 or241301W00113more, 1.65 or more, 1.66 or more, 1.67 or more, 1.68 or more, 1.69 or more, 1.70 or more, 1.71 or more, 1.72 or more, 1.73 or more, 1.74 or more, 1.75 or more, 1.76 or more, 1.77 or more, 1.78 or more, 1.79 or more, 1.80 or more, 1.81 or more, 1.82 or more, 1.83 or more, 1.84 or more, 1.85 or more, 1.86 or more, 1.87 or more, 1.88 or more, 1.89 or more, 1.90 or more, 1.91 or more, 1.92 or more, 1.93 or more, 1.94 or more, 1.95 or more, 1.96 or more, 1.97 or more, 1.98 or more, 1.99 or more, or 2.00 or more. Meanwhile, the value of a may be 2.39 or less, 2.38 or less, 2.37 or less, 2.36 or less, 2.35 or less, 2.34 or less, 2.33 or less, 2.32 or less, 2.31 or less, 2.30 or less, 2.29 or less, 2.28 or less, 2.27 or less, 2.26 or less, 2.25 or less, 2.24 or less, 2.23 or less, 2.22 or less, 2.21 or less, 2.20 or less, 2.19 or less, 2.18 or less, 2.17 or less, 2.16 or less, 2.15 or less, 2.14 or less, 2.13 or less, 2.12 or less, 2.11 or less, 2.10 or less, 2.09 or less, 2.08 or less, 2.07 or less, 2.06 or less, 2.05 or less, 2.04 or less, 2.03 or less, 2.02 or less, or 2.01 or less.In one embodiment, the lithium-metal composite oxide powder may be in the form of primary particles, as described above, but may equally be in the form of secondary particles formed by aggregation of primary particles. In this case, there is no particular limitation as to the average particle size (D50) of the secondary particles, but it is preferably, for example, 1 pm or more, 2 pm or more, 3 pm or more, or 4 pm or more. Meanwhile, the average particle size (D50) of the secondary particles is preferably 30 pm or less, 25 pm or less, 20 pm or less, 17 pm or less, 15 pm or less, 12 pm or less, 10 pm or less, 9 pm or less, 8 pm or less, 7 pm or less, 6 pm or less, 5 pm or less, or 4 pm or less.A method for producing a lithium-metal composite oxide powder according to the present embodiment may comprise the following steps, for example. However, the lithium-metal composite oxide powder according to the present embodiment is not limited to production by means of the method below. There is no particular limitation as to the timing of adding the zirconium and titanium starting materials, and this may be modified according to the combination with other production conditions. For example, a precursor mixture does not need to contain zirconium, depending on other production conditions. Conversely, it may not necessarily be possible to produce the lithium-metal composite oxide powder according to the present embodiment over the scope of all methods described below.Precursor preparation step: a precursor composite compound containing at least nickel and zirconium is prepared.Precursor mixing step: a precursor mixture is prepared by mixing the precursor composite compound prepared in the precursor preparation step, at least a titanium compound and a lithium compound, and, if necessary, a zirconium compound.Firing step: the precursor mixture is fired to obtain a lithium-metal composite oxide.Water washing step: if necessary, the lithium-metal composite oxide obtained by firing in the firing step is subjected to a water washing treatment.Surface treatment step: if necessary, the lithium-metal composite oxide obtained in the firing step or the water washing step is surface-treated.A precursor composite compound containing at least nickel and zirconium is first of all synthesized. In one embodiment, the precursor composite compound can be produced as an aggregate obtained by aggregation of primary particles. There is no particular limitation as to the241301W00114method for synthesizing the precursor composite compound, and it is possible to use a method in which, for example, an aqueous solution, which includes aqueous solutions of transition metals such as nickel and zirconium as well as a variety of aqueous solutions of compounds containing other elements according to the composition of the intended lithium-metal composite oxide, is added dropwise to a reaction tank in which a mother liquor comprising an alkaline aqueous solution such as an aqueous solution of sodium hydroxide or an ammonia solution is being stirred, the pH is monitored and controlled within a suitable range as sodium hydroxide or the like is also added dropwise, and coprecipitation is brought about by means of a wet reaction to obtain a precursor composite compound in the form of, for example, a hydroxide, an oxide obtained by calcining a hydroxide, a carbonate, or the like.Note that in synthesis-related reactions, after the alkaline aqueous solution that serves as the mother liquor is prepared, the interior of the reaction tank is preferably purged with an inert gas or preferably nitrogen gas for industrial purposes, to create a nitrogen atmosphere in order to lower the oxygen concentration within the reaction tank system or in the solution. If the oxygen concentration is excessively high, there is a risk that the coprecipitated hydroxide will be overoxidized by any residual oxygen at or over a predetermined amount, and a risk that the formation of aggregates due to crystallization will be hindered.The transition metal aqueous solution is not particularly limited, but use of an acidic aqueous solution, for example, is preferred, and use of a sulfuric acid aqueous solution such as a nickel sulfate aqueous solution is even more preferred in the case of nickel compounds. One or more transition metal aqueous solutions may also be used.Examples of nickel compounds that may 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, metallic nickel, and the like.Examples of cobalt compounds that may be used include, but are not particularly limited to, one or more selected from cobalt sulfate, cobalt oxide, cobalt hydroxide, cobalt nitrate, cobalt carbonate, cobalt chloride, cobalt iodide, metallic cobalt, and the like.Examples of manganese compounds that may be used include, but are not particularly limited to, one or more selected from manganese sulfate, manganese oxide, manganese hydroxide, manganese nitrate, manganese carbonate, manganese chloride, manganese iodide, metallic manganese, and the like.Examples of zirconium compounds that can be used include, but are not particularly limited to, one or more selected from among zirconium sulfate, zirconium oxide, zirconium nitrate, ammonium zirconium carbonate, zirconium chloride, zirconium iodide, metallic zirconium, and the like.Examples of titanium compounds that may be used include, but are not particularly limited to, one or more selected from titanyl sulfate, titanium oxide, titanium hydroxide, titanium nitrate, titanium carbonate, titanium chloride, titanium iodide, metallic titanium, and the like.241301W00115Examples of aluminum compounds that may be used include, but are not particularly limited to, aluminum sulfate, aluminum oxide, aluminum hydroxide, aluminum nitrate, aluminum carbonate, aluminum chloride, aluminum iodide, sodium aluminate, metallic aluminum, and the like.Examples of iron compounds that may be used include, but are not particularly limited to, one or more selected from iron sulfate, iron oxide, iron hydroxide, iron nitrate, iron carbonate, iron chloride, iron iodide, metallic iron, and the like.Examples of niobium compounds that may be used include, but are not particularly limited to, one or more selected from niobium oxide, niobium chloride, lithium niobate, niobium iodide, and the like.Examples of tungsten compounds that may be used include, but are not particularly limited to, one or more selected from tungsten oxide, sodium tungstate, ammonium paratungstate, hexacarbonyl tungsten, tungsten sulfide, and the like.Examples of magnesium compounds that may be used include, but are not particularly limited to, one or more selected from magnesium sulfate, magnesium oxide, magnesium hydroxide, magnesium nitrate, magnesium carbonate, magnesium chloride, magnesium iodide, metallic magnesium, and the like.Other elements that may be used also include one or more selected from sulfates, oxides, hydroxides, nitrates, carbonates, chlorides, iodides, metals, and the like.The mixing ratio of the respective compounds should be adjusted to ensure that the amount of each element is at the desired ratio, taking account of the composition of the intended lithium-metal composite oxide.An appropriate pH range for when the precursor composite compound is synthesized is not particularly limited, and may be determined so as to achieve a desired secondary particle size or coarseness / fineness, but the pH is generally within the range of approximately 10-13.The precursor composite compound obtained by means of a wet reaction is preferably subjected to a washing treatment, dewatered, and then dried.Subjecting the precursor composite compound 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 aggregated particles or that have become stuck on the surface layer during the reaction. Washing treatments which may be used include a process of Nutsche washing employing a Buchner funnel for small amounts, and a process of feeding a suspension after the reaction to a press filter, washing with water and dewatering. Pure water, sodium hydroxide aqueous solution, sodium carbonate aqueous solution, or the like, for example, may also 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 hydroxide241301W00116aqueous solution, which is pH-controlled according to the residual amount, may be used.Furthermore, the precursor may be calcined by subjecting the resulting precursor composite compound to a heat treatment for 2-10 hours at 200-800°C in an oxidizing atmosphere.Moisture and impurities in the precursor composite compound can be discharged by means of the calcination.Furthermore, in one embodiment, a precursor composite compound which contains or is free from zirconium may be sprayed with a solution of zirconium or sol-gel coated therewith, in order to supply zirconium.Next, a precursor mixture is prepared by mixing the precursor composite compound synthesized in the manner above, and at least a titanium compound, a zirconium compound as required, and a lithium compound, at a predetermined ratio. The mixing may be solvent-based mixing, where the precursor composite compound 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 it may be non-solvent-based mixing, where a powder of the precursor composite compound and a powder of the lithium compound are weighed out in predetermined proportions and mixed by a dry method.There is no particular limitation as to the zirconium compound, and it is possible to use the same compound as that used in the precursor preparation step, and examples of zirconium compounds which may be used include one or more selected from zirconium sulfate, zirconium oxide, zirconium nitrate, ammonium zirconium carbonate, zirconium chloride, zirconium iodide, and metallic zirconium, and the like.There is no particular limitation as to the titanium compound, and it is possible to use the same compound as that used in the precursor preparation step, and examples of titanium compounds which may be used include one or more selected from titanyl sulfate, titanium oxide, titanium hydroxide, titanium nitrate, titanium carbonate, titanium chloride, titanium iodide, and metallic titanium, and the like.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, lithium oxide, and the like. Of these, it is preferable to use one or more selected from anhydrous lithium hydroxide and lithium hydroxide hydrate.A compound of the element M described above may further be admixed with the precursor mixture. One or more selected from transition metal and non-transition metal sulfates, oxides, hydroxides, nitrates, carbonates, chlorides, iodides, metals, and the like may be used as the compound of the element M.241301W00117The 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 consideration of the composition of the intended lithium-metal composite oxide.When a lithium-metal composite oxide containing at least a transition metal is produced, a lithiation reaction and crystal growth progress due to firing, but the lithiation reaction requires a certain oxygen partial pressure. A lithium-metal composite oxide containing lithium is obtained by means of the lithiation reaction. The temperature is then raised to a predetermined temperature to promote crystal growth.The maximum temperature of the material being fired (precursor mixture) in the firing is preferably 650-1100°C, 670-1000°C, or 700-980°C. Furthermore, the firing time at the maximum temperature is preferably 1-24 hours, 1-20 hours, 1-15 hours, 1-10 hours, 2-9 hours, or 3-8 hours. The desired lithium-metal composite compound may be obtained by setting a maximum temperature or time at which the firing temperature will be at or above the melting point of the lithium compound in the material being fired, and at which the lithium-metal composite oxide containing the lithium will undergo the desired crystal growth or particle growth.Firing is commonly carried out by loading the precursor mixture obtained in the precursor mixing step into a container such as a crucible or sagger; however, during the lithiation reaction in particular, it becomes increasingly difficult for the gas that is produced to be externally discharged and for the required oxygen concentration diffusion to be achieved closer toward the bottom of the container loaded with the powder mixture. The reaction homogeneity and the primary particle size thus become more difficult to control.A method in which pre-firing is first of all carried out under the predetermined conditions below, after which main firing is further carried out under predetermined conditions, is therefore preferably used in the firing step when producing the lithium-metal composite oxide according to the present embodiment. The pre-firing is not an essential step, however.A firing method that promotes the lithiation reaction in particular should be incorporated into this pre-firing. A specific method that may be cited allows the material being fired to be more easily heated, allows the gas generated from the lithium compound to be easily discharged, and allows gas having a high oxygen partial pressure to be diffused into the material being fired (into the particles). The desired characteristics may be achieved by, for example, pre-firing less of the material being fired.For pre-firing of the precursor mixture, the precursor may be loaded into a sagger or crucible and fired in a static furnace, roller hearth kiln, or pusher furnace, but a rotary kiln in which the material being fired is fired while flowing may also be used.The maximum temperature of the material being fired which undergoes pre-firing is not particularly limited, and is preferably adjusted depending on the type of lithium compound that is being used to prepare the material being fired. This can ensure a reliable reaction between the241301W00118precursor composite compound and lithium compound in the precursor mixture, reliable and homogeneous lithiation reaction progress, and prevention of the occurrence of foreign phases, thus allowing the intended lithium-metal composite oxide to be obtained.The atmosphere during pre-firing should be, but is not particularly limited to, an oxidizing atmosphere that ensures the reliable and homogeneous progress of the lithiation reaction. For example, the use of an oxidative decarboxylation gas atmosphere having a carbon dioxide gas concentration of 30 ppm or less, or an oxygen atmosphere having an oxygen concentration of 80% or more by volume, or 90% or more by volume is preferred.The pre-firing time should be, but is not particularly limited to, a time that ensures reliable and homogeneous progress of the lithiation reaction. For example, a time of 1-10 hours or 2-8 hours is preferred.The compound of the element M described above may further be admixed with a pre-fired material obtained by pre-firing. One or more selected from transition metal and non-transition metal sulfates, oxides, hydroxides, nitrates, carbonates, chlorides, iodides, metals, and the like may be used as the compound of the element M.The pre-fired material that has thus been obtained by pre-firing is subjected to main firing in order to produce crystal growth or particle growth at a higher temperature. Reliable and homogeneous crystal growth progress is required at this time to obtain a lithium-metal composite oxide having a desired crystal structure.The main firing atmosphere should be, but is not particularly limited to, an atmosphere that has an oxygen partial pressure, and preferably a low moisture content or carbon dioxide gas concentration, such as to ensure reliable and homogeneous crystal growth, without reducing the transition metal contained in the precursor mixture that is being fired. For example, the use of 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% or more by volume or 90% or more by volume is preferred.The main firing temperature is not particularly limited, provided that it is higher than the prefiring temperature, but can be adjusted depending on the composition etc. of the lithium-metal composite oxide that is to be obtained. The maximum temperature is preferably adjusted to 700°C-1100°C, 710°C-1000°C, or 720°C-980°C, for example. A maximum temperature within the required range makes it possible to obtain a lithium-metal composite oxide that has the desired crystal structure, with fewer unreacted components, and to prevent a drop in battery characteristics of the nonaqueous electrolyte secondary battery in which the resulting lithium-metal composite oxide is used as the positive electrode. Furthermore, when a lithium-metal composite oxide having an Ni content of 20 mol%-80 mol% among elements other than Li is obtained, for example, the material being fired is preferably fired at a maximum temperature that does not exceed 1100°C.The main firing time is not particularly limited, but should be enough time for a lithium-metal241301W00119composite oxide having the desired crystal structure to be formed. The time is preferably 1-15 hours, 2-12 hours, or 2-10 hours, for example.Unreacted lithium compounds or lithium compounds from the crystal structure that appear on the particle surface layer over the course of the primary and secondary firing steps are sometimes present as impurities in the lithium-metal composite oxide obtained in the firing step. Water washing and heat treatment can therefore be performed, for example, in order to remove or reduce such impurities. Note that the water washing step is not an essential feature.A compound of predetermined elements is admixed with the lithium-metal composite oxide obtained in the secondary firing step or the water washing step, and a heat treatment is carried out to subject the surfaces of primary particles and / or secondary particles of the lithium-metal composite oxide to a surface treatment with a compound of lithium and the added elements. As a result, it is possible to achieve effects such as lowering the amount of lithium compounds remaining in a particle surface layer, improving lithium ion conductivity, and lowering reactive resistance. Note that the surface treatment step is not an essential feature.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.The heat treatment temperature is not particularly limited, but is, for example, preferably 200°C or more, 210°C or more, 220°C or more, 230°C or more, 240°C or more, or 250°C or more. Meanwhile, the heat treatment temperature is preferably 800°C or less, 775°C or less, 750°C or less, 725°C or less, 700°C or less, 675°C or less, 650°C or less, 625°C or less, 600°C or less, 575°C or less, 550°C or less, 525°C or less, 500°C or less, 490°C or less, 480°C or less, 470°C or less, 460°C or less, 450°C or less, 440°C or less, 430°C or less, 420°C or less, 410°C or less, or 400°C or less.The length of time of the heat treatment is not particularly limited, but is, for example, preferably 1-15 hours, 2-12 hours, or 2-10 hours.After this, the lithium-metal composite oxide is ground using a grinding mill or the like to obtain a lithium-metal composite oxide powder.A nonaqueous electrolyte secondary battery according to the present embodiment comprises a positive electrode that contains the above lithium-metal composite oxide powder as a positive electrode active material for a nonaqueous electrolyte secondary battery, the nonaqueous electrolyte secondary battery comprising the positive electrode, a negative electrode, and an electrolytic solution containing an electrolyte.When the positive electrode is produced, a conductive agent and a binder are admixed with the lithium-metal composite oxide according to the present embodiment. The conductive agent used241301W00120is, for example, preferably acetylene black, carbon black, graphite, or the like. The binder used is, for example, preferably polytetrafluoroethylene, polyvinylidene fluoride, or the like.The negative electrode is not particularly limited, but it is possible to use, for example, not only a negative electrode active material such as lithium metal, graphite, or a low-crystallinity carbon material, but also one or more non-metallic or metallic elements selected from Si, Al, Sn, Pb, Zn, Bi and Cd, alloys containing same or chalcogen compounds containing same, etc.The solvent of the electrolytic solution is not particularly limited, but it is possible to use, for example, an organic solvent including one or more selected from carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate, and ethers such as dimethoxyethane.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.Embodiments of the present disclosure were described above by citing specific examples, but appropriate modifications may also be added within a scope that does not compromise the effects of the present invention.EXAMPLEThe present disclosure will be described in further detail below by means of examples, but the present disclosure is not limited by those examples.<Sample Preparation>Samples of Examples 1-4 and Comparative Examples 1-3 were produced in accordance with the methods given below.Preparation of Precursor Composite Compound 1A nickel sulfate aqueous solution and a cobalt sulfate, manganese sulfate and zirconium sulfate aqueous solution were mixed so that the proportions (molar ratio) of Ni, Co and Mn were Ni:Co:Mn= 50:25:25, and Zr / (Ni+Co+Mn+Zr)=0.003, and a metal aqueous solution was obtained. 10 L of pure water to which 300 g of a sodium hydroxide aqueous solution and 510 g of aqueous ammonia had been added were prepared in advance as the mother liquor in a reaction tank, the interior of the reaction tank was flushed with nitrogen gas at a flow rate of 0.7 L / min to create a nitrogen atmosphere, and the reaction was also carried out under a nitrogen atmosphere.The metal aqueous solution, the sodium hydroxide aqueous solution, and the aqueous ammonia were then simultaneously added dropwise at a predetermined rate as a stirring blade was rotated at 950 rpm, and the Ni, Co, Mn and Zr were coprecipitated by being crystallized to form particle aggregates through a crystallization reaction in which the amount of the alkaline solution drops was adjusted to a pH of 12.0, thus giving a coprecipitate.After this, the slurry inside the reactor was subjected to solid-liquid separation and further241301W00121washed with pure water to thereby reduce residual impurities, after which the coprecipitate in a caked state was dried for 12 hours at 110°C under the atmosphere to obtain precursor composite compound 1.Production of Precursor Composite Compound 2A nickel sulfate aqueous solution and a cobalt sulfate, manganese sulfate and zirconium sulfate aqueous solution were mixed so that the proportions (molar ratio) of Ni, Co and Mn were Ni:Co:Mn= 89:6:5, and Zr / (Ni+Co+Mn+Zr)=0.003, and a metal aqueous solution was obtained.10 L of pure water to which 300 g of a sodium hydroxide aqueous solution and 500 g of aqueous ammonia had been added were prepared in advance as the mother liquor in a reaction tank, the interior of the reaction tank was flushed with nitrogen gas at a flow rate of 0.7 L / min to create a nitrogen atmosphere, and the reaction was also carried out under a nitrogen atmosphere.The metal aqueous solution, the sodium hydroxide aqueous solution, and the aqueous ammonia were then simultaneously added dropwise at a predetermined rate as a stirring blade was rotated at 1000 rpm, and the Ni, Co, Mn and Zrwere coprecipitated by being crystallized to form particle aggregates through a crystallization reaction in which the amount of the alkaline solution drops was adjusted to a pH of 11.5, thus giving a coprecipitate.After this, the slurry inside the reactor was subjected to solid-liquid separation and further washed with pure water to thereby reduce residual impurities, after which the coprecipitate in a caked state was dried for 12 hours at 110°C under the atmosphere to obtain precursor composite compound 2.Production of Precursor Composite Compound 3A nickel sulfate aqueous solution, and cobalt sulfate and manganese sulfate were mixed so that the proportions (molar ratio) of Ni, Co and Mn were Ni:Co:Mn=50:25:25, and a metal aqueous solution was obtained. 10 L of pure water to which 300 g of a sodium hydroxide aqueous solution and 505 g of aqueous ammonia had been added were prepared in advance as the mother liquor in a reaction tank, the interior of the reaction tank was flushed with nitrogen gas at a flow rate of 0.7 L / min to create a nitrogen atmosphere, and the reaction was also carried out under a nitrogen atmosphere.The metal aqueous solution, the sodium hydroxide aqueous solution, and the aqueous ammonia were then simultaneously added dropwise at a predetermined rate as a stirring blade was rotated at 950 rpm, and the Ni, Co, and Mn were coprecipitated by being crystallized to form particle aggregates through a crystallization reaction in which the amount of the alkaline solution drops was adjusted to a pH of 12.1, thus giving a coprecipitate.After this, the slurry inside the reactor was subjected to solid-liquid separation and further washed with pure water to thereby reduce residual impurities, after which the coprecipitate in a caked state was dried for 12 hours at 110°C under the atmosphere to obtain precursor composite compound 3.241301W00122Example 1Precursor composite compound 1, anhydrous lithium hydroxide, and TiC>2 were weighed out so that the ratio (molar ratio) to the total amount of Ni, Co, Mn, Zr and Ti was Ti / (Ni+Co+Mn+Zr+Ti)=0.004, and so that the ratio (molar ratio) of Li to the total amount of Ni, Co, Mn, Zr and Ti was Li / (Ni+Co+Mn+Zr+Ti)=1.055, and the materials were mixed using a mixer to prepare a precursor mixture.The precursor mixture was then fired over a 5-hour period at a maximum temperature of 850°C in an oxygen atmosphere (oxygen concentration: 97% by volume) using an electric furnace, cooled, and then milled using a grinding mill to obtain a lithium-metal composite oxide powder sample. The average particle size of secondary particles of the lithium-metal composite oxide powder sample was 4.1 pm.Example 2Precursor composite compound 1, anhydrous lithium hydroxide, ZrC>2, and TiC>2 were weighed out so that the ratio (molar ratio) to the total amount of Ni, Co, Mn, Zr and Ti was Zr / (Ni+Co+Mn+Zr+Ti)=0.005 (a fraction of Zr=0.2 mol% was added during mixing as ZrC>2) and Ti / (Ni+Co+Mn+Zr+Ti)=0.015, and so that the ratio (molar ratio) of Li to the total amount of Ni, Co, Mn, Zr and Ti was Li / (Ni+Co+Mn+Zr+Ti)=1.055, and the materials were mixed using a mixer to prepare a precursor mixture.The precursor mixture was then fired over a 5-hour period at a maximum temperature of 850°C in an oxygen atmosphere (oxygen concentration: 97% by volume) using an electric furnace, cooled, and then milled using a grinding mill to obtain a lithium-metal composite oxide powder sample. The average particle size of secondary particles of the lithium-metal composite oxide powder sample was 3.9 pm.Example 3Precursor composite compound 1, anhydrous lithium hydroxide, TiC>2 and AI(OH)3 were weighed out so that the ratio (molar ratio) to the total amount of Ni, Co, Mn, Zr, Ti and Al was Ti / (Ni+Co+Mn+Zr+Ti+AI)=0.004 and AI / (Ni+Co+Mn+Zr+Ti+AI)=0.003, and so that the ratio (molar ratio) of Li to the total amount of Ni, Co, Mn, Zr, Ti and Al was Li / (Ni+Co+Mn+Zr+Ti+AI)=1.052, and the materials were mixed using a mixer to prepare a precursor mixture.The precursor mixture was then fired over a 5-hour period at a maximum temperature of 850°C in an oxygen atmosphere (oxygen concentration: 97% by volume) using an electric furnace, cooled, and then milled using a grinding mill to obtain a lithium-metal composite oxide powder sample. The average particle size of secondary particles of the lithium-metal composite oxide powder sample was 4.2 pm.Precursor composite compound 2, anhydrous lithium hydroxide, and TiC>2 were weighed out so that the ratio (molar ratio) to the total amount of Ni, Co, Mn, Zr and Ti was Ti / (Ni+Co+Mn+Zr+Ti)=0.015, and so that the ratio (molar ratio) of Li to the total amount of Ni,241301W00123Co, Mn, Zr and Ti was Li / (Ni+Co+Mn+Zr+Ti)=1.046, and the materials were mixed using a mixer to prepare a precursor mixture.The precursor mixture was then fired over a 5-hour period at a maximum temperature of 840°C in an oxygen atmosphere (oxygen concentration: 97% by volume) using an electric furnace, cooled, and then milled using a grinding mill to obtain a lithium-metal composite oxide powder sample. The average particle size of secondary particles of the lithium-metal composite oxide powder sample was 4.6 pm.Precursor composite compound 1 and anhydrous lithium hydroxide were weighed out so that the ratio (molar ratio) of Li to the total amount of Ni, Co, Mn and Zr was Li / (Ni+Co+Mn+Zr)=1.052, and the materials were mixed using a mixer to prepare a precursor mixture.The precursor mixture was then fired over a 5-hour period at a maximum temperature of 850°C in an oxygen atmosphere (oxygen concentration: 97% by volume) using an electric furnace, cooled, and then milled using a grinding mill to obtain a lithium-metal composite oxide powder sample. The average particle size of secondary particles of the lithium-metal composite oxide powder sample was 4.0 pm.Precursor composite compound 3, anhydrous lithium hydroxide, and TiC>2 were weighed out so that the ratio (molar ratio) to the total amount of Ni, Co, Mn and Ti was Ti / (Ni+Co+Mn+Ti)=0.004, and so that the ratio (molar ratio) of Li to the total amount of Ni, Co, Mn and Ti was Li / (Ni+Co+Mn+Ti)=1.053, and the materials were mixed using a mixer to prepare a precursor mixture.The precursor mixture was then fired over a 5-hour period at a maximum temperature of 850°C in an oxygen atmosphere (oxygen concentration: 97% by volume) using an electric furnace, cooled, and then milled using a grinding mill to obtain a lithium-metal composite oxide powder sample. The average particle size of secondary particles of the lithium-metal composite oxide powder sample was 4.2 pm.Precursor composite compound 3, anhydrous lithium hydroxide, ZrC>2, and TiC>2 were weighed out so that the ratio (molar ratio) to the total amount of Ni, Co, Mn, Zr and Ti was Zr / (Ni+Co+Mn+Zr+Ti)=0.003 and Ti / (Ni+Co+Mn+Zr+Ti)=0.015, and so that the ratio (molar ratio) of Li to the total amount of Ni, Co, Mn, Zr and Ti was Li / (Ni+Co+Mn+Zr+Ti)=1.055, and the materials were mixed using a mixer to prepare a precursor mixture.The precursor mixture was then fired over a 5-hour period at a maximum temperature of 850°C in an oxygen atmosphere (oxygen concentration: 97% by volume) using an electric furnace, cooled, and then milled using a grinding mill to obtain a lithium-metal composite oxide powder sample. The average particle size of secondary particles of the lithium-metal composite oxide241301W00124powder sample was 4.0 pm.<Sample EvaluationSamples of Examples 1-4 and Comparative Examples 1-3 were evaluated in accordance with the methods given below. The examples are shown along with the results.and lithium-metal composite oxides0.2 g of precursor composite compound or lithium-metal composite oxide was heated and dissolved in 25 mL of 20% hydrochloric acid solution, the solution was cooled and then transferred to a 100 mL measuring flask, and pure water was introduced to prepare an adjusted solution. The constituent elements of the adjusted solution were quantified using ICP-AES [Optima 8300, manufactured by PerkinElmer, Inc.], and it was confirmed that the precursor composite compound and the lithium metal composite oxide powder sample had the same charge ratio for each metal element.<Method for measuring particle size distribution>The average particle size (D50) of the lithium-metal composite oxide powder sample was measured on a volume basis by a wet laser method using a laser-type particle size distribution analyzer (Microtrac HRA, manufactured by Nikkiso Co., Ltd.).Line analysis by means of two-dimensional high-resolution secondary ion mass spectrometer measurementLine analysis was performed using a two-dimensional high-resolution secondary ion mass spectrometer (NanoSIMS 50L, manufactured by CAMECA) to obtain information relating to the surface and interior of particles. Specifically, oxygen was employed as a primary ion species, and the analysis was performed on the basis of secondary ions detected with a primary ion acceleration voltage of 16 kV.The lithium-metal composite oxide powder sample being observed was fixed with a resin, crosssectioned by means of the BIB method, and charge compensated by metal-coating the processed surface. Note that all of the operations relating to sampling are carried out under an inert atmosphere, except for the metal coating operation. After this, the sample was introduced onto a sample stand, and the outermost surface was cleaned using an ion beam immediately before observation.Prior to observation with the two-dimensional high-resolution secondary ion mass spectrometer, SEM observation was performed to select particles for observation with a particle size of 0.95-1.05 times the average particle size (D50) from among the particles contained in the lithium-metal composite oxide powder sample. At this time, the coordinates of secondary particles for observation were recorded, and the observations were made with reference to the coordinates during observation by means of the two-dimensional high-resolution secondary ion mass spectrometer.Note that the D50 was measured on a volume basis by a wet laser method using a laser-type particle size distribution analyzer (Microtrac HRA, manufactured by Nikkiso Co., Ltd.).241301W00125For the lines used in the line profile, three lines at angles of 60° in relation to each other were selected in such a way that end-to-end lengths were set, with respect to the size of the secondary particle selected for observation, at 1.5 times the length of a line segment representing the maximum particle size of the secondary particle being observed, and at least 0.6 times the length of each line passes through the interior of the particle.The interval between line profiles was 80 nm for Ti and 500 nm for Zr. The line profile was smoothed by taking a moving average of intensity at a total of five points, i.e. , the center point of numerical values and the two points before and after, and the result was used for analysis.Surface vicinity and maximum intensityThe surface vicinity in the line profile for each of the three lines constituted the ranges between points where the count was more than 10 times the background, and points which were each a distance of 0.3 times the maximum particle size of the particle being observed further inside the particle from the first-mentioned points, respectively. The maximum counts for Zr and Ti were determined within these ranges. The arithmetic mean value of the maximum count for each of the three lines was then taken as the maximum intensity.Center vicinity and average intensityThe center vicinity for each of the three lines was the range inside the surface vicinity at both ends of the particle. The arithmetic mean values of the Zr and Ti counts within this range were determined for each of the three lines. The arithmetic mean value was then determined for the arithmetic mean values of the counts for each of the three lines, and this was taken as the average intensity.Background and average intensityThe background for each of the three lines constituted portions without particles in the cross-sectional SEM image, other than the portions close to the surface vicinity, such as where the line profile is rising. The Zr and Ti counts were measured for 20 background points randomly selected from each of the three lines, for a total of 60 points, and the arithmetic mean thereof was taken as the average intensity.Intensity ratio and coefficient of variation of intensityThe values obtained above were used to calculate: a ratio (Zr intensity ratio) of the maximum intensity of Zr in the surface vicinity of the particles of the lithium-metal composite oxide to the average intensity of Zr in the center vicinity of the particles; a coefficient of variation (coefficient of variation of Zr intensity) of a ratio of the average intensity of Zr in the center vicinity of the cross section of the particles to the average intensity of background Zr; a ratio (Ti intensity ratio) of the maximum intensity of Ti in the surface vicinity of the particles to the average intensity of Ti in the center vicinity of the particles; and a coefficient of variation (coefficient of variation of Ti intensity) of a ratio of the intensity of Ti in the center vicinity of the particles to the average intensity of background Ti.Method for calculating lattice constant of lithium-metal composite oxide powder sample by means of XRD diffraction241301W00126XRD diffraction data of the lithium-metal composite oxide powder sample was obtained under the following X-ray diffraction conditions using an X-ray diffraction apparatus [SmartLab, manufactured by Rigaku Corp.], after which a Rietveld analysis was performed using this XRD diffraction data, with reference to “R. A. Young, ed., “The Rietveld Method”, Oxford University Press (1992)”. The a-axis length which is the lattice constant of the a-axis, and the c-axis length which is the lattice constant of the c-axis were calculated from these results.(X-ray diffraction conditions)X-ray source: Cu-KaAcceleration voltage and current: 45 kV and 200 mASampling width: 0.02 deg.Scan width: 15 deg. to 122 deg.Scan speed: 1.0 steps / secDivergence slit: 2 / 3 deg.Receiving slit width: 0.15 mmScattering slit: 2 / 3 deg.< Battery characteristics of nonaqueous electrolyte secondary battery>Production of coin cell employing lithium-metal composite oxide powder sample2032-type coin cells employing the lithium-metal composite oxide powder sample as the positive electrode active material were produced by using a positive electrode, negative electrode and electrolytic solution produced by the following methods.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 lithium-metal composite oxide powder sample, the conductive agent, and the binder were blended to achieve a weight ratio of sample:conductive 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 mmfl) and then rolled to a composite material density of 3.0 g / cm3for use as the positive electrode.A lithium foil having a thickness of 500 pm, punched out to a diameter of 16 mm$, was used as the negative electrode.An ethylene carbonate (EC) and dimethyl carbonate (DMC) solvent mixture was prepared to an EC:DMC volume ratio of 1:2, and a solution obtained by mixing 1 M LiPFe (electrolyte) with the solvent mixture was used as the electrolytic solution.Measurement of initial discharging capacityCoin cells produced by the method above were charged (constant current) at a current density equivalent to 0.1 C to 4.30 V (upper limit voltage) at 25°C, and were then charged at a constant voltage until the current reached 0.005 C. The capacity at this time was defined as the initial charging capacity (mAh / g).241301W00127After a 5-minute pause, constant current discharging was then performed at a current density of 0.1 C to 3.00 V under the same environment, and the initial discharging capacity (mAh / g) was measured after a 5-minute pause.Measurement of low-temperature DCR at -10°CAfter the initial charging / discharging capacity had been measured as above, constant current charging was further performed at a current density of 0.1 C to 4.3 V (upper limit voltage) at 25°C, after which constant voltage charging was performed until the current reached 0.01 C. After a 5-minute pause, constant current discharging was performed at a current density of 0.1 C to 3.0 V under the same environment, and then there was a 5-minute pause. This operation was repeated twice, and charging was performed once again to 4.3 V under the same conditions.Following this, after 1 hour had elapsed under an environment of -10°C, constant current discharging was performed at a current density of 0.1 C to achieve a voltage of 20% SOC based on the discharging capacity for discharge after the second charge. Following this, after a 5-minute pause, discharging was performed at a current value corresponding to 10% SOC, and the voltage difference at that time was measured, to thereby measure direct current resistance (DCR).Measurement of capacity retention rate after high-temperature storageCells were produced as follows, and the capacity retention rate after high-temperature storage was measured.An electrode slurry was prepared by mixing the lithium-metal composite oxide powder sample and carbon black as a positive electrode active material, with polyvinylidene fluoride (PVdF) in N-methylpyrrolidinone (NMP). The resulting slurry was coated on an aluminum foil (thickness=17 pm) by using a roll coater, the coated foil was dried in a hot-air chamber which was then evacuated, and further drying was performed for 8 hours at 130°C. The load on the resulting electrode was found to be 16.4 mg / cm2. The electrode was pressed by means of a roll press producing a density of 3.4 g / cm3.An agueous slurry was prepared by mixing graphite and carbon black with CMC (carboxymethyl cellulose) and SBR (styrene butadiene rubber). The resulting slurry was coated on a copper foil (thickness=9 pm) by using a roll coater, and the coated foil was dried in a hot-air chamber (80°C-120°C). The load on the resulting electrode was found to be 10 mg / cm2. The electrode was pressed by means of a roll press producing a density of 1.4 g / cm3.An electrolyte composition was prepared by dissolving 1.0 mol / L LiPFe in a mixture of 30 mass% ethylene carbonate (EC) and 70 mass% diethyl carbonate (DMC), and adding 1 mass% vinylene carbonate (VC) and 1.5 mass% fluoroethylene carbonate (FEC).A pouch cell (170 mAh) comprising a cathode electrode and a graphite anode electrode together with a polyolefin separator stacked between the cathode and the anode was placed241301W00128inside an Ar-filled glove box. 0.7 pL of the electrolyte composition was then introduced into the laminated pouch cell which was sealed inside the Ar-filled glove box.The pouch cell was charged at a current density of 0.2 C to 4.2 V, and after constant current charging, the pouch cell was charged to 10% SOC under a condition of constant voltage charging until the current reached 0.005 C, then constant current discharging was performed at a current density of 0.2 C to 2.5 V. After this, a degassing process was applied at 25°C by creating an Ar atmosphere. The cell was further charged at a current density of 0.2 C to 4.2 V at 25°C and once again to 10% SOC, after which the cell was stored for 24 hours at 45°C.After the aging cycle and storage, the cell was charged at a current density of 0.2 C to 4.2 V at 25°C, and after a constant current charging, constant voltage charging was performed until the current reached 0.005 C, then after a 5-minute pause, constant current discharging was performed at a current density of 0.2 C to 2.5 V. The battery capacity at this time was used as the initial charging / discharging capacity.High-temperature storage characteristics testAfter the initial charging / discharging capacity evaluation, the pouch cell was charged at a current density of 0.2 C at 25°C until the SOC reached 80%, and after a 5-minute pause, the pouch cell was discharged for 10 sec at 1 C. The DOR was calculated from a value obtained by dividing the difference between OCV and CCV during this 10-second discharge by the current value of 1 C.The pouch cell was then charged for 10 sec at 1 C to 80% SOC. The pouch cell was then stored for 6 days in a thermostatic tank at 60°C. After the pouch cell had been removed from the thermostatic tank and the temperature had fallen to 25°C, the capacity after high-temperature storage was measured by charging at a current density of 0.2 C to 4.2 V at 25°C, then after constant current charging, constant voltage charging until the current reached 0.005 C, and after a 5-minute pause, constant current discharging at a current density of 0.2 C to 2.5 V.The high-temperature storage characteristics test described above was repeated four times. The fourth discharging capacity relative to the initial discharging capacity was defined as the capacity retention rate after high-temperature storage. Furthermore, the fourth DCR value relative to the initial DCR value was defined as the DCR increase rate after high-temperature storage.Taking the DCR increase rate after high-temperature storage of Comparative Example 1 as 100, relative values for the other examples and comparative examples were calculated from this.Evaluation of cell negative electrode by means of XRF, after high-temperature storage characteristics evaluationThe negative electrode disassembled after the abovementioned high-temperature storage characteristic test was subjected to XRF (X-ray fluorescence) measurement in order to determine a ratio of Mn and Ni eluted from the lithium-metal composite oxide sample into the electrolytic solution in the course of the high-temperature storage characteristic test.241301W00129Disassembly of pouch cell after high-temperature storage characteristics evaluationAfter the high-temperature storage characteristics test, the pouch cell was discharged at 0.2 C to 2.5 V at 25°C. The tested pouch cell was then introduced into a glove box having an Ar atmosphere, and bonded parts of the pouch cell were cut off with ceramic scissors. The negative electrode was recovered from inside the pouch cell, soaked in dimethyl carbonate (DMC) for approximately 5 minutes, then wiped with a Kimwipe to remove excess liquid, and dried under reduced pressure for 20 minutes in the sample exchange chamber of the glove box.Evaluation of negative electrode by means of XRFThe resulting positive electrode was punched with a <t>16 mm die, and components thereof were analyzed using an X-ray fluorescence spectrometer (ZSX Primus II, manufactured by Rigaku Corporation). The sample was stored under an Ar atmosphere until immediately before measurement, and the measurement was conducted under the atmosphere. An Rh tube was used for the X-ray tube. The measurement range (elements to be measured) was C to II. The mass percentage ratio of Mn and Ni was calculated on the basis of the mass percentage of Mn and Ni calculated by this analysis.Evaluation Results>Examples 1-4 and Comparative Examples 1-3 were evaluated in the manner described above. The results are shown in Table 1.

[0002] [Table 1]

Claims

241301W00131CLAIMS1. A lithium-metal composite oxide powder comprising particles of a lithium-metal composite oxide comprising at least Li, Ni, Zr and Ti, whereinwhen the particles of the lithium-metal composite oxide are analyzed in a cross section using a two-dimensional high-resolution secondary ion mass spectrometer,a ratio of the maximum intensity of Zr in the surface vicinity of the particles of the lithium-metal composite oxide to the average intensity of Zr in the center vicinity of the particles of the lithium-metal composite oxide is 1.5-3.5, anda ratio of the maximum intensity of Ti in the surface vicinity of the particles of the lithium-metal composite oxide to the average intensity of Ti in the center vicinity of the particles of the lithium-metal composite oxide is 0.60-2.6.

2. The lithium-metal composite oxide powder as claimed in claim 1, whereinwhen the particles of the lithium-metal composite oxide are analyzed in a cross section using a two-dimensional high-resolution secondary ion mass spectrometer,a coefficient of variation of a ratio of the average intensity of Zr in the center vicinity of the cross section of the particles of the lithium-metal composite oxide to the average intensity of background Zr is 0.10-1.4.

3. The lithium-metal composite oxide powder as claimed in claim 1 or 2, whereinwhen the particles of the lithium-metal composite oxide are analyzed in a cross section using a two-dimensional high-resolution secondary ion mass spectrometer,a coefficient of variation of a ratio of the intensity of Ti in the center vicinity of the particles of the lithium-metal composite oxide to the average intensity of background Ti is 0.10-1.5.

4. The lithium-metal composite oxide powder as claimed in claim 1 or 2,which has a layered rock salt structure, andis represented by the general formula LiaNixCoyMnzZruTivMwOa (in the formula, M is one or more elements other than Li, Ni, Co, Mn, Zr, Ti and O; 0.90<a<1.4; x+y+z+u+v+w=1.00;0<u<0.015; 0<v<0.030; and 1.60<a<2.40).

5. A positive electrode active material for a nonaqueous electrolyte secondary battery, the positive electrode active material for a nonaqueous electrolyte secondary battery comprising the lithium-metal composite oxide powder as claimed in claim 1 or 2.

6. A nonaqueous electrolyte secondary battery, comprising:the positive electrode active material for a nonaqueous electrolyte secondary battery as claimed in claim 5.

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