JP6346448B2 - Positive electrode active material for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention includes a positive electrode active substance for a non-aqueous electrolyte secondary battery, and a nonaqueous electrolyte secondary battery using the positive electrode active material in the cathode material.

  In recent years, with the widespread use of portable electronic devices such as mobile phones and notebook computers, there is an increasing demand for small and lightweight secondary batteries having high energy density. In addition, development of a high-output secondary battery as a battery for a motor drive power supply, particularly a power supply for transportation equipment, is also strongly desired.

  As a secondary battery satisfying such requirements, there is a lithium ion secondary battery which is a kind of non-aqueous electrolyte secondary battery. This lithium ion secondary battery is composed of a negative electrode, a positive electrode, an electrolytic solution, and the like, and a material capable of desorbing and inserting lithium is used as an active material used as a material for the negative electrode and the positive electrode.

Research and development of such lithium ion secondary batteries is being actively conducted. Among these, a lithium ion secondary battery using a lithium metal composite oxide, particularly a lithium cobalt composite oxide (LiCoO ₂ ), which is relatively easy to synthesize, as a positive electrode material has a high energy density because a voltage of 4 V class is obtained. Practical use is progressing as a battery having. In the lithium ion secondary battery using this lithium cobalt composite oxide, many developments have been made so far to obtain excellent initial capacity characteristics and cycle characteristics, and various results have already been obtained.

  However, the lithium cobalt composite oxide has a small reserve and uses an expensive cobalt compound, which causes an increase in the cost of the battery. For this reason, development of the positive electrode active material using the alternative material which can implement | achieve a high energy density while being cheaper than cobalt is calculated | required.

Newly proposed materials as positive electrode active materials for lithium ion secondary batteries include lithium manganese composite oxide (LiMn ₂ O ₄ ) using manganese and lithium nickel composite oxide (LiNiO ₂ ) using nickel. Can be mentioned. Among them, the lithium-manganese composite oxide, on the raw material is inexpensive, due to its crystal structure is spinel Le structure, thermal stability, in particular, it is excellent in safety against such firing, lithium It is considered as a promising alternative material for cobalt composite oxide. In particular, lithium manganese nickel composite oxide (LiMn _1.5 Ni _0.5 O ₄ ) in which a part of Mn of the lithium manganese composite oxide is replaced with Ni is a high energy density material capable of realizing an operating voltage of 4.5 V or more. Has attracted attention in recent years

Here, in order for the lithium ion secondary battery to have excellent output characteristics, the positive electrode needs to have low resistance, and for this purpose, the particle size distribution is narrow and the particle size is moderately small. It is necessary to use a positive electrode active material. That is, if the particle size of the positive electrode active material is large, the specific surface area becomes small, and the reaction resistance increases due to the fact that the reaction area with the electrolytic solution cannot be secured. Cannot be obtained. On the other hand , when the particle size distribution of the positive electrode active material is wide, the voltage applied to the particles in the electrode becomes non-uniform, and the battery capacity decreases due to the selective deterioration of the fine particles during repeated charge and discharge. At the same time, the reaction resistance of the secondary battery increases, so that a high-power secondary battery cannot be obtained.

Therefore, research is also being conducted on the lithium manganese nickel composite oxide to achieve a particle property that the particle size distribution is narrow and the particle size is moderately small. For example, Japanese Patent Application Laid-Open No. 2011-116583 discloses that the pH value of an aqueous solution for nucleation containing at least a manganese-containing metal compound and an ammonium ion supplier is 12.0 to 14.0 based on a liquid temperature of 25 ° C. After nucleation by controlling (nucleation step), the pH value of the aqueous solution containing the produced nuclei is controlled to 10.5 to 12.0 on the basis of the liquid temperature of 25 ° C. to grow the nuclei. (Particle growth step) to obtain a manganese nickel composite hydroxide, and by using this manganese nickel composite hydroxide as a precursor, the particle property that the particle size distribution is narrow and the particle size is moderately small is obtained. A technique for obtaining a solid structure lithium manganese nickel composite oxide with a solid structure is described.

Further, in order to achieve higher output of the lithium ion secondary battery, the positive electrode active material constituting the positive electrode material, not only to adjust the particle properties, without excessively reduce its particle size, its Increasing the reaction area is effective. That is, it is possible to reduce the reaction resistance by increasing the surface area that contributes to the battery reaction of the positive electrode active material.

For example , JP 2012-246199 A discloses a manganese nickel composite hydroxide obtained from a low-density central portion and a high-density outer shell portion by controlling the reaction atmosphere in the nucleation step and the particle growth step. A technology for obtaining a lithium manganese nickel composite oxide having a hollow structure with a narrow particle size distribution and a moderately small particle size is described by using this manganese nickel composite hydroxide as a precursor. ing. That is, by making the positive electrode active material have a hollow structure, the reaction area with the electrolytic solution is increased without changing the particle size, thereby increasing the output of the secondary battery.

Furthermore, J. et al. H. Kima, S .; T.A. Myungb, C.I. S. Yoonc, I .; H. Ohd and Y.M. K. Suna, J .; Electrochem. Soc. 151 (11) A1911-A1918 (2004) suppresses a change in crystal structure during charge and discharge by substituting a part of manganese constituting the lithium manganese nickel composite oxide having a spinel structure with titanium. Describes a technique for increasing the output of a lithium ion secondary battery.

  However, secondary batteries using the lithium manganese nickel composite oxide described in these documents as a positive electrode active material have improved output characteristics in comparison with the prior art, but as a power source for portable electronic devices and transportation equipment. If the application is assumed, further higher output is required.

JP 2011-116583 A JP 2012-246199 A

J. et al. H. Kima, S .; T.A. Myungb, C.I. S. Yoonc, I .; H. Ohd and Y.M. K. Suna, J .; Electrochem. Soc. 151 (11) A1911-A1918 (2004)

An object of the present invention is to provide a positive electrode active material comprising lithium manganese nickel titanium composite oxide particles having a spinel structure, which can increase the output when used as a positive electrode active material of a secondary battery. To do. Another object of the present invention is to provide a non-aqueous electrolyte secondary battery using such a positive electrode active material .

The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention has a general formula (B): Li _t Mn _{2 (1-xyz)} Ni _2x Ti _2y M _2z O ₄ (0.96 ≦ t ≦ 1.20, 0 20 ≦ x ≦ 0.28, 0 <y ≦ 0.05, 0 ≦ z ≦ 0.05, M is Mg, Ca, Ba, Sr, V, Fe, Cr, Co, Cu, Zr, Nb, At least one element selected from Mo and W), and is composed of cubic lithium manganese nickel titanium composite oxide particles having a spinel structure, with an average particle size of 2 μm to 8 μm, and an expanded particle size distribution [(D90−d10) / average particle size] is 0.70 or less, and has a hollow structure composed of a hollow portion inside the particle and an outer shell portion outside the hollow portion, To do.

  The thickness of the outer shell is preferably 5% to 35% as a ratio to the particle diameter of the secondary particles.

The specific surface area of the positive electrode active material for the nonaqueous electrolyte secondary battery is preferably 0.5m ² /g~3.0m ² / g.

Non-aqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte, as a positive electrode material for the positive electrode, the positive electrode active material for a non-aqueous electrolyte secondary batteries are used It is characterized by that.

According to the present invention, it is possible to provide a positive electrode active material composed of lithium manganese nickel titanium composite oxide particles having a narrow particle size distribution and a moderately small particle size and having a hollow structure. In addition, according to the present invention, by using such a positive electrode active material as a positive electrode material, a nonaqueous electrolyte secondary battery excellent in output characteristics can be provided. For this reason, the industrial significance of the present invention is extremely large.

FIG. 1 is a schematic flowchart showing a process for producing composite hydroxide particles that are precursors of the positive electrode active material of the present invention. FIG. 2 is an SEM photograph (magnification: 1000 times) of composite hydroxide particles that are precursors of the positive electrode active material of the present invention. FIG. 3 is a schematic cross-sectional view of a 2032 type coin battery used for battery evaluation.

In view of the above-described problems, the present inventors have proposed a lithium battery described in JP 2012-246199 A in order to further increase the output of a secondary battery using lithium manganese nickel composite oxide particles as a positive electrode active material. An attempt was made to add titanium to manganese nickel composite oxide particles. Specifically, when producing manganese nickel composite hydroxide particles that are precursors of the lithium manganese nickel composite oxide particles, an aqueous solution in which a manganese compound, a nickel compound, and a titanium compound are dissolved is used as a raw material to produce a nucleus. An attempt was made to obtain manganese nickel titanium composite hydroxide particles by performing a step and a particle growth step. However, this way manganese nickel titanium composite hydroxide particles obtained by the small difference in density between the central portion and the outer shell, even by firing this, a lithium manganese nickel-titanium double Gosan compound particles obtained A hollow portion could not be formed inside, or the hollow portion could not be made sufficiently large.

As a result of repeated studies on this point, the present inventors have found that titanium is a tetravalent and stable metal, and the atmosphere (reaction atmosphere) during the crystallization reaction has changed from an oxidizing atmosphere to a non-oxidizing atmosphere. However, since the density of the precipitated solid does not change, the presence of titanium in the aqueous reaction solution at the initial stage of the crystallization reaction, particularly the nucleation step, causes nucleation in an oxidizing atmosphere, and in a non-oxidizing atmosphere. It was found that it was difficult to cause a density difference inside the grains even when the grains were grown. Then, on this point, a result of further extensive research, manganese nickel titanium composite water oxide particles, when prepared by crystallization reaction and a nucleation step and particle growth step described above, the addition of titanium in the nucleation step Without adding a titanium within a specific range with respect to the entire particle growth process time from the start of the particle growth process, it is possible to cause a density difference inside the resulting manganese nickel titanium composite hydroxide particles The lithium manganese nickel titanium composite oxide particles having this as a precursor can be provided with a hollow structure. The present invention has been completed based on this finding.

1. Manganese nickel titanium composite hydroxide particles
First, the manganese nickel titanium composite hydroxide particles that are precursors of the positive electrode active material of the present invention will be described. The manganese nickel titanium composite hydroxide particles (hereinafter referred to as “composite hydroxide particles”) have a general formula (A): Mn _1-xyz Ni _x Ti _y M _z (OH) _{2 + α} (0.20 ≦ x ≦ 0.28, 0 <y ≦ 0.05, 0 ≦ z ≦ 0.05, 0 ≦ α ≦ 0.5, M is Mg, Ca, Ba, Sr, V, Fe, Cr, Co, Cu And at least one element selected from Zr, Nb, Mo, and W), and a substantially spherical secondary particle formed by agglomerating a plurality of primary particles, and the average particle size of the secondary particles is 1 [mu] m to 7 [mu] m and [(d90-d10) / average particle diameter], which is an index indicating the spread of the particle size distribution, is 0.60 or less, on the center part composed of fine primary particles, and outside the center part, It has an outer shell composed of primary particles larger than the fine primary particles, and Ti exists only in the outer shell. And

(1) Composition Nickel (Ni) is an element that contributes to higher potential and higher capacity of the secondary battery. The value x indicating the amount of nickel added is 0.20 or more and 0.28 or less, preferably 0.20 or more and 0.26 or less, and more preferably 0.20 or more and 0.25 or less. When the value of x is less than 0.20, the battery capacity at a voltage of 5 V class is reduced in the secondary battery configured with the positive electrode active material having the composite hydroxide particles as a precursor as the positive electrode. On the other hand, when the value of x exceeds 0.28, it becomes impossible to obtain a positive electrode active material composed of a spinel structure single phase.

Titanium (Ti) is an element that suppresses changes in the crystal structure during charging and discharging of the secondary battery and contributes to improvement of input / output characteristics. The value of y indicating the content of titanium is more than 0 and 0.05 or less, preferably more than 0 and 0.025 or less, more preferably 0.015 or more and 0.025 or less. When the value of y exceeds 0.05, a positive electrode active material composed of a single phase of spinel structure cannot be obtained. In the composite hydroxide particles that are precursors of the positive electrode active material of the present invention, titanium does not exist in the central part inside the secondary particles, but exists only in the outer shell part outside the central part.

Further, the composite hydroxide particles of this, in addition to the above metal elements may be contained an additive element M in a predetermined amount. Such additive elements M include magnesium (Mg), calcium (Ca), barium (Ba), strontium (Sr), vanadium (V), iron (Fe), chromium (Cr), cobalt (Co), copper At least one element selected from (Cu), zirconium (Zr), niobium (Nb), molybdenum (Mo), and tungsten (W) can be used. These additive elements M are appropriately selected according to the use and required performance of the secondary battery configured using the positive electrode active material having the composite hydroxide particles as a precursor.

  The value of z indicating the amount of additive element M added to manganese is 0 or more and 0.05 or less, preferably 0 or more and 0.025 or less, and more preferably 0.015 or more and 0.025 or less. By controlling the value of z within such a range, it is possible to impart the necessary characteristics to the intended secondary battery while ensuring the desired battery characteristics. On the other hand, when the value of z exceeds 0.05, the metal element contributing to the Redox reaction is reduced, which not only decreases the battery capacity but also increases the positive electrode resistance.

(2) Particle structure The composite hydroxide particles, which are precursors of the positive electrode active material of the present invention, are adjusted so as to be composed of substantially spherical secondary particles formed by agglomerating a plurality of primary particles. Furthermore, it has adjusted so that it may have the center part which consists of fine primary particles inside particle | grains, and the outer shell part which consists of plate-shaped primary particles larger than this fine primary particle outside the center part. By adopting such a structure, in the firing step when synthesizing the positive electrode active material using the composite hydroxide particles as a precursor, lithium is sufficiently diffused into the particles, and the distribution of lithium is uniform. A good positive electrode active material can be obtained.

Here, center, since the fine primary particles are often of continuous interstices structure, as compared with high density of the shell portion made of a plate-like primary particles with a larger thickness, according to our Keru sintering in the firing step Shrinkage occurs from low temperatures. For this reason, fine primary particles undergo sintering from a low temperature during firing, shrink from the center of the particles to the outer shell side where the progress of sintering is slow, and a space is generated in the center. In addition, since the low density center portion has a large shrinkage rate, this space has a sufficient size. Thereby, the positive electrode active material obtained after firing has a hollow structure, the specific surface area can be sufficiently increased with respect to the particle size, and a positive electrode active material excellent in output characteristics can be obtained.

  The central part of the composite hydroxide particles was filled with secondary particles in a resin and made into a state in which a cross-section could be observed by cross-section polisher processing, and then this cross-section was observed with a scanning electron microscope (SEM). In some cases, it refers to the internal gray or black portion of the secondary particle outer shell that appears white (see FIG. 2).

In the composite hydroxide particles that are precursors of the positive electrode active material of the present invention, as described above, the secondary particles are required to be substantially spherical. Here, “substantially spherical” means that the secondary particles are not only spherical, but also include spherical or elliptical spheres having fine irregularities on the surface. If the shape of the secondary particles is approximately spherical, the positive electrode active material using the composite hydroxide particles as a precursor can also be approximately spherical, and can have high filling properties. The capacity characteristics of the secondary battery can be improved.

The secondary particles are preferably those in which the plate-like primary particles are aggregated in random directions to form secondary particles. When the plate-like primary particles aggregate in a random direction, voids are formed almost uniformly between the primary particles, and when mixed with the lithium compound and baked, the molten lithium compound spreads into the secondary particles, and the lithium Is sufficiently diffused. Furthermore, since the aggregation in the random direction causes the central portion to shrink evenly in the firing step, a sufficiently large space can be formed inside the positive electrode active material.

The fine primary particles constituting the central part of the secondary particles are not limited in shape, but are preferably plate-shaped, needle-shaped, or both. When the fine primary particles have these shapes, the central portion has a sufficiently low density, and large shrinkage can be generated by firing.

(3) Te composite hydroxide particles odor which is a precursor of the positive electrode active material thickness invention of the shell portion, the thickness of the outer shell portion is 5% to 47% in ratio to the particle diameter of the secondary particles It is preferably 7% to 35%, more preferably 23% to 35%. As described above, the positive electrode active material for a composite hydroxide particles of this precursor has a hollow structure, the ratio of the outer shell portion of the thickness to the particle diameter, the composite hydroxide particles (secondary particles The ratio of the thickness of the outer shell part to the particle diameter of Therefore, by setting the ratio of the thickness of the outer shell portion to the particle size of the secondary particles within the above range, a sufficient space can be formed inside the positive electrode active material. On the other hand, when the ratio of the thickness of the outer shell portion is less than 5%, the shrinkage of the composite hydroxide particles in the firing step is large, the sintering between the particles proceeds, and the particle size distribution of the positive electrode active material is deteriorated. On the other hand, if the thickness ratio of the outer shell portion exceeds 47%, a sufficiently large space cannot be formed inside the positive electrode active material.

In addition, the ratio of the thickness of an outer shell part can be calculated | required as follows. First, composite hydroxide particles (secondary particles) are embedded in a resin or the like, and a cross-section polisher process or the like is made possible to observe a cross section. next. This cross section is observed by SEM, and a particle whose cross section at the center of the particle is observable is selected , and the distance on the outer circumference and the inner circumference of the outer shell portion , measured at any three or more positions, The average thickness of the outer shell for each particle is determined from the distance between the two points that is the shortest. Thereafter, located on the outer periphery of the secondary particles, the distance between any two points in which the distance is maximum as the particle size of the secondary particles, dividing the average thickness of the outer shell portion with a grain size of the secondary particles Thus, the ratio of the thickness of the outer shell portion for each particle is obtained. Furthermore, the ratio of the thickness of the outer shell portion can be determined by averaging the ratio of the thickness of the outer shell portion for each particle determined for 10 or more secondary particles.

(4) Average particle size In the composite hydroxide particles that are precursors of the positive electrode active material of the present invention, the average particle size of the secondary particles is controlled to 1 μm to 7 μm, preferably 2 μm to 7 μm, more preferably 3 μm to 7 μm. Has been. In addition, the average particle diameter of secondary particles means a volume average particle diameter, and can be obtained from, for example, a volume integrated value measured with a laser light diffraction / scattering particle size analyzer.

  If the average particle size of the secondary particles is within such a range, it becomes possible to control the average particle size of the positive electrode active material having this composite hydroxide particle as a precursor within a predetermined range (2 μm to 8 μm). Thus, the capacity characteristics and output characteristics of the obtained secondary battery can be improved. On the other hand, if the average particle size of the secondary particles is less than 1 μm, the average particle size of the positive electrode active material is less than 2 μm and the filling property is lowered. Therefore, the obtained secondary battery may have a high capacity. become unable. On the other hand, if the average particle size of the composite hydroxide particles exceeds 7 μm, the specific surface area of the positive electrode active material decreases and the interface with the electrolyte decreases, so the positive electrode resistance of the resulting secondary battery increases and the output The characteristic will be deteriorated.

Moreover, the average particle diameter of the fine primary particles constituting the central part of the secondary particles is preferably 0.01 μm to 0.3 μm, more preferably 0.01 μm to 0.25 μm, still more preferably 0.02 μm to 0.00. 25 μm. If the average particle size of the fine primary particles is within such a range, shrinkage starts from a low temperature range during firing, and after firing, a positive electrode active material having a hollow structure having a sufficiently large space in the center is obtained. be able to. On the other hand, if the average particle size of the fine primary particles is less than 0.01 μm, the primary particles may be too fine, so that a sufficiently large central portion may not be formed. On the other hand, when the average particle size of the fine primary particles exceeds 0.3 μm, the shrinkage does not start from the low temperature range at the time of firing, the amount of shrinkage becomes insufficient, and after firing, a sufficiently large space is formed in the central portion. It may not be possible to form.

  Furthermore, the average particle size of the primary particles larger than the fine primary particles constituting the outer shell of the secondary particles is preferably 0.3 μm to 3.0 μm, more preferably 0.5 μm to 2.0 μm, and even more preferably Is 0.5 μm to 1.0 μm. By controlling the average particle size of the primary particles constituting the outer shell part within such a range, the temperature at which the primary particles of the outer shell part starts to contract can be sufficiently compared with the fine primary particles constituting the central part. In addition, the crystallinity of the obtained positive electrode active material can be made high while maintaining a high temperature. On the other hand, if the average particle size of the primary particles constituting the outer shell portion is less than 0.3 μm, the shrinkage starts from a low temperature during firing, and a sufficiently large space is formed in the central portion after firing. You may not be able to. On the other hand, when the average particle size of the primary particles constituting the outer shell portion exceeds 3 μm, it is necessary to increase the firing temperature in order to obtain sufficient crystallinity of the obtained positive electrode active material. As the sintering proceeds, it becomes difficult to control the average particle size of the positive electrode active material within a predetermined range.

  The average particle size of the primary particles constituting the central part and the outer shell part of the composite hydroxide particles can be observed by observing the cross section by embedding the composite hydroxide particles (secondary particles) in a resin, etc., and by cross-section polisher processing. After making it possible, this cross section is observed using a scanning electron microscope (SEM), and each of the fine primary particles constituting the central part or the primary particles constituting the outer shell part has a maximum diameter of 10 or more. Can be obtained by measuring the average value.

(5) Particle size distribution In the composite hydroxide particles which are precursors of the positive electrode active material of the present invention, [(d90-d10) / average particle size], which is an index indicating the spread of the particle size distribution of the secondary particles, is set to 0. .60 or less, preferably 0.59 or less, more preferably 0.58 or less. Here, d10 is the number of particles in each particle size accumulated from the smaller particle size side, and the accumulated volume is 10% of the total volume of all particles. D90 is the same as the number of particles. , Which means a particle size whose cumulative volume is 90% of the total volume of all particles. Moreover, an average particle diameter means a volume average particle diameter. The method for obtaining d10, d90 and the average particle diameter is not particularly limited , but can be obtained from, for example, a volume integrated value measured with a laser light diffraction / scattering particle size analyzer.

  The particle size distribution of the positive electrode active material of the present invention is strongly influenced by the composite hydroxide particles that are precursors thereof. For this reason, the particle size distribution of the positive electrode active material can be narrowed by controlling [(d90-d10) / average particle size], which is an index indicating the spread of the particle size distribution of the composite hydroxide particles, within the above range. The output characteristics and cycle characteristics of the obtained secondary battery can be improved.

  On the other hand, when [(d90-d10) / average particle size] of the composite hydroxide particles exceeds 0.60, the particle size distribution of the composite hydroxide particles becomes wide, and the positive electrode active using this as a precursor. The substance contains a lot of fine secondary particles having a particle size of less than 2 μm and coarse secondary particles having a particle size of more than 8 μm. When a secondary battery is configured using a positive electrode active material containing a large amount of fine secondary particles, the calorific value increases due to a local reaction of the fine secondary particles, and the fine secondary particles are selectively used. Due to the deterioration, the cycle characteristics deteriorate. In addition, when a secondary battery is configured using a positive electrode active material containing a large amount of coarse secondary particles, a sufficient reaction area between the electrolytic solution and the positive electrode active material cannot be ensured. Output characteristics deteriorate.

2. Method for producing manganese nickel titanium composite hydroxide particles
Then, the manufacturing method of the composite hydroxide particle | grains which are the precursors of the positive electrode active material of this invention is demonstrated. Aqueous solution method of producing composite hydroxide particles This is containing containing at least manganese and nickel, and an aqueous solution containing no titanium (hereinafter, referred to as "mixed solution 1") and an alkaline aqueous solution, an ammonium ion donor And a nucleation step in which nucleation is performed in an oxidizing atmosphere by controlling the pH value at a liquid temperature of 25 ° C. to be 12.0 to 14.0, and is generated in the nucleation step. And a particle growth step of growing the nuclei by controlling the aqueous solution containing the nuclei so that the pH value on the basis of the liquid temperature of 25 ° C. is 10.5 to 12.0. In particular, the production method of the composite hydroxide particles This is from the start of the particle growth step, preferably in the range of more than 30% of the whole grain growth process time from the start of the particle growth step, oxidizing The atmosphere is switched to a weak oxidizing atmosphere or non-oxidizing atmosphere having an oxygen concentration of 1% by volume or less, and the mixed aqueous solution 1 is changed to an aqueous solution containing at least manganese, nickel and titanium (hereinafter referred to as “mixed aqueous solution 2”). By switching, the composite hydroxide particles described above are obtained.

  That is, when it is intended to obtain manganese-nickel composite hydroxide particles containing titanium by the technique described in JP 2012-246199 A, in the reaction aqueous solution at the initial stage of the crystallization reaction, particularly at the stage of the nucleation step. If titanium is present, a density difference cannot be formed between the central portion and the outer shell portion of the resulting composite hydroxide particles, and the positive electrode active material using this as a precursor cannot have a hollow structure.

In contrast, in the manufacturing method of the double focus hydroxide particles as a precursor of the positive electrode active material of the present invention, the nucleation step, preferably, in the early stages of nucleation step and the particle growth step, not containing titanium The mixed aqueous solution 1 is used to form a low-density central portion, and at the start of the grain growth process, preferably within a specific range with respect to the entire grain growth process time from the start of the grain growth process. By switching the neutral atmosphere to a weak oxidizing atmosphere or non-oxidizing atmosphere having an oxygen concentration of 1% by volume or less, and switching the mixed aqueous solution 1 to the mixed aqueous solution 2 containing titanium to continue grain growth, It is possible to form a high-density outer shell containing titanium on the outside of the central part.

According to the manufacturing method of the double case hydroxide particles, narrow particle size distribution, moderately particle size is small and, while maintaining the particle characteristics of having a hollow structure, it is possible to obtain the effect of titanium addition Therefore, the output characteristics can be greatly improved without impairing the capacity characteristics and safety of the secondary battery finally obtained using the composite hydroxide particles.

Hereinafter, although the manufacturing method of the composite hydroxide particle which is a precursor of the positive electrode active material of this invention is demonstrated in detail, as above-mentioned , this manufacturing method of composite hydroxide particle is Unexamined-Japanese-Patent No. 2012-246199. Since it is based on the technique described in the gazette, the following description will focus on features of the method for producing the composite hydroxide particles or differences from the technique described in JP 2012-246199 A.

(1) Crystallization reaction (1-a) Nucleation step In the nucleation step, first, a mixed aqueous solution 1 containing at least manganese and nickel and not containing titanium is prepared. In the method for producing composite hydroxide particles that are precursors of the positive electrode active material of the present invention, the composition ratio of each metal element contained in the obtained composite hydroxide particles is the metal contained in the mixed aqueous solution 1 and the mixed aqueous solution 2. The ratio is substantially the same as the ratio of the number of atoms of each metal element to the total number of atoms of the element. Therefore, it is necessary to prepare the composition ratio of each metal element in the mixed aqueous solution 1 to be the same as the composition ratio of the target composite hydroxide particles except for titanium.

  Next, an aqueous alkali solution, an aqueous solution containing an ammonium ion supplier, and water are supplied into the reaction vessel, and these are mixed to form a pre-reaction aqueous solution. At this time, the supply amount of each aqueous solution is adjusted to adjust the pH value of the aqueous solution before the reaction to 12.0 to 14.0 based on the liquid temperature of 25 ° C., and the ammonium ion concentration is adjusted to 3 g / L to 25 g / L. Adjust to. Moreover, while adjusting the temperature of aqueous solution before reaction to 20 to 60 degreeC, let the atmosphere in a reaction tank be oxidizing atmosphere. The pH value, ammonium ion concentration and temperature of the pre-reaction aqueous solution can be measured with a general pH value, ion meter and thermometer, respectively.

After confirming that the pH value, ammonium ion concentration, temperature and atmosphere of the aqueous solution before reaction are adjusted to the above ranges, the mixed aqueous solution 1 is supplied while stirring the aqueous solution before reaction. Thus, the reaction solution before the reaction solution and the mixed aqueous solution 1 were mixed in the reaction vessel is formed during the reaction aqueous solution, constituting the central portion of the double coupling hydroxide particles, manganese-nickel composite hydroxide particles Fine nuclei (fine primary particles) consisting of Since the pH value and ammonium ion concentration of the reaction aqueous solution change with nucleation, the aqueous solution containing the alkaline aqueous solution and the ammonium ion supplier together with the mixed aqueous solution 1 is supplied to the reaction aqueous solution. It is necessary to control so that the ammonium ion concentration is maintained in the above range.

The amount of nuclei to be precipitated in the nucleation step is not particularly limited, but in order to obtain composite hydroxide particles having a good particle size distribution, all the metal compounds supplied in the nucleation step and the particle growth step can be obtained. It is preferable to set it as 0.1 mass%-2 mass% with respect to mass, and it is more preferable to set it as 0.1 mass%-1.5 mass%.

  Note that the nucleation step ends when a predetermined amount of nuclei is generated in the aqueous reaction solution. At this time, the amount of nuclei generated can be determined by the amount of the metal compound supplied to the reaction aqueous solution.

(1-b) Particle Growth Step In the particle growth step, first, an acidic aqueous solution such as sulfuric acid is supplied to the reaction aqueous solution after completion of the nucleation step, and the pH value of the reaction aqueous solution is adjusted to 10.5 to Adjust to 12.0. By adjusting and maintaining the pH value of the reaction aqueous solution within such a range, new nucleation in the reaction aqueous solution can be suppressed and grain growth can be preferentially caused.

At the same time, a mixed aqueous solution 2 containing at least manganese, nickel and titanium is prepared. As described above, in the method for producing composite hydroxide particles that are precursors of the positive electrode active material of the present invention, the composition ratio of each metal element contained in the obtained composite hydroxide particles is mixed with titanium. The ratio is substantially the same as the ratio of the number of atoms of each metal element to the total number of atoms of the metal elements contained in the aqueous solution 1 and the mixed aqueous solution 2. Therefore, the amount of titanium in the mixed aqueous solution 2 is determined in consideration of the amount of titanium in the target composite hydroxide particles and the ratio of the amount of the mixed aqueous solution 2 to the total amount of the mixed aqueous solution 1 and the mixed aqueous solution 2, Similar to the mixed aqueous solution 1, the composition ratio of each metal element in the mixed aqueous solution 2 needs to be the same as the composition ratio of the target composite hydroxide particles except titanium.

  When switching the reaction atmosphere and mixed aqueous solution from the beginning of the particle growth process, it is necessary to replace the reaction tank atmosphere with a weakly acidic or non-oxidizing atmosphere after switching the pH value of the reaction aqueous solution. It becomes. Specifically, an inert gas such as nitrogen is introduced into the reaction tank, and the oxygen concentration in the reaction tank is adjusted to 1% by volume or less.

  Subsequently, the supply of the mixed aqueous solution 2 is started to the reaction aqueous solution, and the supply of the mixed aqueous solution 2 is continued until the target particle size (average particle size of 1 μm to 7 μm) is reached, whereby the composite hydroxide particles are granulated. Grow. At this time, an aqueous solution containing an alkaline aqueous solution and an ammonium ion supplier is supplied to the reaction aqueous solution together with the mixed aqueous solution 2 so that the pH value of the reaction aqueous solution is in the range of 10.5 to 12.0 based on the liquid temperature of 25 ° C. In addition, it is necessary to control the ammonium ion concentration to be maintained in the range of 3 g / L to 25 g / L.

Incidentally, Oite to the method of manufacturing the composite hydroxide particles, the initial stage of grain growth process, specifically, in a range of not less than 30% total grain growth process time from the start of the grain growth step It is preferable to switch the reaction atmosphere and the mixed aqueous solution. At the end of the nucleation step, the produced nuclei have agglomerated to some extent, and by switching the pH value of the reaction aqueous solution, the nuclei start grain growth, and when the reaction atmosphere and the mixed aqueous solution are switched, The size of the composite hydroxide particles is moderately appropriate to some extent, but at the initial stage of the particle growth process, before switching the reaction atmosphere and the mixed aqueous solution, only the pH value of the reaction aqueous solution is switched, By growing the nuclei for a predetermined time, it is possible to form a center portion having an optimum size in the obtained composite hydroxide particles.

  In this case, when the manganese nickel composite hydroxide particles grow to a sufficient size as the center of the target composite hydroxide particles, the aqueous solution containing the mixed aqueous solution 1, the alkaline aqueous solution and the ammonium ion supplier is supplied. Stop temporarily. After the supply of each aqueous solution is stopped, the mixed aqueous solution 2 is started to be supplied to the reaction aqueous solution in a state where the atmosphere in the reaction tank is replaced with a weakly acidic atmosphere or a non-oxidizing atmosphere.

  Note that the switching of the reaction atmosphere and the mixed aqueous solution is 30% or less, preferably 20% or less, and more preferably 10% or less with respect to the entire particle growth process time from the start of the particle growth process. Must be done in range. When the reaction atmosphere and the mixed aqueous solution are switched within the range exceeding 30% of the entire particle growth process time from the start of the particle growth process, the outer shell of the resulting composite hydroxide particles has a sufficient thickness. It can not be.

The particle growth step is terminated by stopping the supply of each aqueous solution when the particle size of the composite hydroxide particles reaches the target particle size. The particle size of the manganese-nickel composite hydroxide particles or manganese-nickel-titanium composite hydroxide particles at each stage of grain terminal growth step, previously, the addition amount and give a metal compound to the reaction solution in the nucleation step and particle growth step By determining the relationship with the size of the particles to be obtained, it can be easily determined from the amount of the metal compound added.

  The composite hydroxide particles thus obtained are subjected to solid-liquid separation, washed away residual impurities such as alkali cations, and then dried at a temperature of 100 ° C. or higher to obtain powdered composite hydroxide particles. Can be obtained.

In the manufacturing method of this composite hydroxide particles, at the start of the particle growth step, preferably in the middle of the particle growth step, by switching the reaction atmosphere and the mixed aqueous solution, the composite hydroxide particles obtained by the crystallization reaction That is, the titanium-manganese composite hydroxide particles containing titanium have a structure having a low-density central portion made of fine primary particles and an outer shell portion made of primary particles larger than the fine primary particles. Can do.

(2) supplying an aqueous solution Then, a mixed aqueous solution as a raw material for double engagement hydroxide particles, the aqueous solution containing ammonium ion donor to control the alkali aqueous solution and ammonium ion concentration for pH control will be described.

(2-a) Mixed aqueous solution The manganese compound and nickel compound for producing the mixed aqueous solution 1 and the manganese compound, nickel compound and titanium compound for producing the mixed aqueous solution 2 are not particularly limited , In view of easy handling, water-soluble nitrates, sulfates, hydrochlorides, and the like can be used. In particular, it is preferable to use a sulfate, specifically, manganese sulfate, nickel sulfate and titanium sulfate from the viewpoint of preventing cost and halogen contamination.

  Further, the additive element M in the composite hydroxide particles (M is at least one element selected from Mg, Ca, Ba, Sr, V, Fe, Cr, Co, Cu, Zr, Nb, Mo, and W) As a compound for supplying the additive element M, a water-soluble compound is also preferable. For example, magnesium sulfate, calcium sulfate, barium sulfate, strontium sulfate, titanium sulfate, ammonium peroxotitanate, oxalic acid Suitable for potassium titanium, vanadium sulfate, ammonium vanadate, iron sulfate, chromium sulfate, potassium chromate, cobalt sulfate, copper sulfate, zirconium sulfate, zirconium nitrate, niobium oxalate, ammonium molybdate, sodium tungstate, ammonium tungstate, etc. Can be used.

  The concentration of the mixed aqueous solution is preferably 1 mol / L to 2.6 mol / L, more preferably 1 mol / L to the total amount of the metal compounds contained in the mixed aqueous solution in both cases of the mixed aqueous solution 1 and the mixed aqueous solution 2. 2.3 mol / L. When the concentration of the mixed aqueous solution is less than 1 mol / L, the amount of crystallized material per reaction tank is reduced, and thus the productivity is lowered. On the other hand, when the concentration of the mixed aqueous solution exceeds 2.6 mol / L, when the reaction temperature is lowered, the saturation concentration is exceeded, and crystals of each metal compound may be reprecipitated to clog piping and the like.

  The manganese compound, the nickel compound, the titanium compound, and the compound of the additive element M described above are not necessarily supplied to the reaction vessel as the mixed aqueous solution 1 or the mixed aqueous solution 2. For example, when a crystallization reaction is carried out using a metal compound that reacts when mixed to produce a compound other than the target compound, the individual concentrations of the metals are adjusted so that the total concentration of all aqueous metal compound solutions falls within the above range. A compound aqueous solution may be prepared and supplied into the reaction vessel at a predetermined rate as an aqueous solution of individual metal compounds.

  The supply amount of the mixed aqueous solution 1 and the mixed aqueous solution 2 is such that the concentration of the product in the aqueous reaction solution is preferably 30 g / L to 200 g / L, more preferably 50 g / L to 150 g / L at the end of the crystallization reaction. L. When the concentration of the product is less than 30 g / L, the primary particles may be insufficiently aggregated. On the other hand, when it exceeds 200 g / L, the mixed aqueous solution 1 or the mixed aqueous solution 2 supplied to the reaction aqueous solution may not be sufficiently diffused, and the grain growth may be biased.

(2-b) Alkaline aqueous solution The alkali aqueous solution is not particularly limited , and a general alkali metal hydroxide aqueous solution such as sodium hydroxide or potassium hydroxide can be used. The alkali metal hydroxide can be directly added to the reaction aqueous solution, but it is preferably added as an aqueous solution in view of easy pH control. In this case, the concentration of the alkali metal hydroxide aqueous solution is preferably 20% by mass to 50% by mass, and more preferably 20% by mass to 30% by mass. By regulating the concentration of the alkali metal aqueous solution to such a range, it is possible to prevent the pH value from being locally increased at the addition position while suppressing the amount of solvent (water amount) supplied to the reaction system. Thus, composite hydroxide particles having a narrow particle size distribution can be obtained efficiently.

The method for supplying the alkaline aqueous solution is not particularly limited as long as the pH value of the reaction aqueous solution is not locally increased and is maintained within a predetermined range. For example, the reaction aqueous solution is sufficiently stirred. However, it may be supplied by a pump capable of controlling the flow rate such as a metering pump.

(2-c) Aqueous solution containing ammonium ion donor Aqueous solution containing ammonium ion donor is not particularly limited, and is, for example, aqueous ammonia or an aqueous solution of ammonium sulfate, ammonium chloride, ammonium carbonate, or ammonium fluoride. Can be used.

  When ammonia water is used as the ammonium ion supplier, the concentration is preferably 20% by mass to 30% by mass, more preferably 22% by mass to 28% by mass. By restricting the ammonia water concentration to such a range, loss of ammonia due to volatilization or the like can be suppressed to a minimum, so that production efficiency can be improved.

  In addition, the supply method of the aqueous solution containing an ammonium ion supply body can also be supplied by a pump capable of controlling the flow rate, similarly to the alkaline aqueous solution.

(3) Reaction conditions (3-a) pH value In the manufacturing method of the composite hydroxide particle which is a precursor of the positive electrode active material of this invention, pH value on the basis of liquid temperature 25 degreeC is set to 12 in a nucleation process. It is necessary to control within the range of 1.0 to 14.0 and within the range of 10.5 to 12.0 in the grain growth step. In any step, the fluctuation range of the pH value during the crystallization reaction is preferably within ± 0.2. When the variation width of the pH value is large, there are cases where the proportion of nucleation amount and TsubuNaru length not constant, it is impossible to obtain a narrow composite hydroxide particles size distribution.

[Nucleation process]
In the nucleation step, the pH value of the reaction aqueous solution is within the range of 12.0 to 14.0, preferably 12.3 to 14.0, more preferably 12.3 to 13.5, based on the liquid temperature of 25 ° C. Control. When the pH value is less than 12.0, the growth of nuclei (grain growth) proceeds with the nucleation, so that the obtained composite hydroxide particles have non-uniform particle sizes and the particle size distribution deteriorates. On the other hand, if the pH value exceeds 14.0, the nuclei to be produced become too fine, causing a problem that the reaction aqueous solution gels.

[Particle growth process]
In the particle growth step, the pH value of the aqueous reaction solution is in the range of 10.5 to 12.0, preferably 10.7 to 12.0, more preferably 10.7 to 11.8, based on the liquid temperature of 25 ° C. Control. By controlling the pH value in the particle growth process in such a range, the generation of new nuclei is suppressed and the particle growth proceeds preferentially, so that the resulting composite hydroxide particles are homogeneous and have a particle size distribution. It can be narrow. On the other hand, when the pH value is less than 10.5, the ammonium ion concentration increases and the solubility of metal ions increases, so that not only the rate of crystallization reaction is slowed, but also metal ions remaining in the reaction aqueous solution. Volume increases and productivity deteriorates. On the other hand, if the pH value exceeds 12.0, the amount of nucleation in the particle growth step increases, the particle size of the resulting composite hydroxide particles becomes non-uniform, and the particle size distribution deteriorates.

  In addition, when the pH value is 12.0, it is a boundary condition between nucleation and nucleation, so it should be either nucleation process or particle growth process depending on the presence or absence of nuclei in the reaction aqueous solution. Can do. That is, when the pH value of the nucleation step is higher than 12.0 and a large amount of nuclei are produced, and the pH value of the particle growth step is 12.0, a large amount of nuclei exist in the reaction aqueous solution. Growth occurs preferentially, and composite hydroxide particles having a narrow particle size distribution can be obtained. On the other hand, if the pH value of the nucleation step is 12.0, there is no nucleus that grows in the reaction aqueous solution, so nucleation occurs preferentially, and the pH value of the particle growth step is made smaller than 12.0. The produced nuclei grow and good composite hydroxide particles can be obtained.

(3-b) Reaction atmosphere The structure of the composite hydroxide particles that are precursors of the positive electrode active material of the present invention is regulated by controlling the reaction atmosphere in the nucleation step and the particle growth step. Specifically, in the nucleation step, preferably, the reaction atmosphere is set to be an oxidizing atmosphere within a range of 30% or less of the entire particle growth step time from the start of the nucleation step and the particle growth step. Primary particles are precipitated, and a low-density central part is formed in the particle growth process. On the other hand, after switching the reaction atmosphere in the particle growth process, by controlling the reaction atmosphere to a weak oxidizing atmosphere or a non-oxidizing atmosphere, plate-like primary particles larger than the fine primary particles described above are precipitated. Thereby, a high-density outer shell portion is formed outside the center portion.

As described above, the reason why the size of the primary particles to be precipitated varies depending on the change in the reaction atmosphere is considered to be because the valence of the metal element changes according to the oxygen concentration in the reaction atmosphere. Therefore, in the manufacturing method of the composite hydroxide particles of this, it is important to properly control the reaction atmosphere in each step.

[Oxidizing atmosphere]
In the nucleation step, preferably, the reaction atmosphere is an oxidizing atmosphere, that is, the oxygen concentration exceeds 1% by volume within the range of 30% or less of the total particle growth step time from the start of the nucleation step and the particle growth step. It is necessary to have an atmosphere. In particular, it is preferable to make the air atmosphere easy to control the atmosphere. In such a reaction atmosphere, the average primary particle size of the precipitated fine primary particles is 0.01 μm to 0.3 μm, so that the central portion formed by the secondary particles formed by aggregation of the fine primary particles is sufficient. It can be of low density. On the other hand, when the oxygen concentration is 1% by volume or less, the primary particles are coarsened, and the average particle size may exceed 3 μm.

  The upper limit of the oxygen concentration is not particularly limited, but is preferably about 30% by volume. If the oxygen concentration exceeds 30% by volume, the primary particles may become too fine, or aggregation of the primary particles may be suppressed and secondary particles may not be formed.

[Weak oxidizing atmosphere to non-oxidizing atmosphere]
From the start of the particle growth process (after switching the pH value of the reaction aqueous solution), preferably within the range exceeding 30% of the total particle growth process time from the start of the particle growth process, the reaction atmosphere is weakly oxidative. Atmosphere or non-oxidizing atmosphere. Specifically, the reaction atmosphere is controlled to a mixed atmosphere of 1% by volume or less, preferably 0.5% by volume or less, and more preferably 0.2% by volume or less of oxygen and an inert gas such as nitrogen or argon. It is necessary to do. In such a reaction atmosphere, since the average particle diameter of the primary particles to be precipitated is 0.3 μm to 3 μm, a high-density outer shell portion can be formed outside the center portion described above.

  As a means for switching and maintaining the reaction atmosphere from an oxidizing atmosphere to a weakly acidic atmosphere or a non-oxidizing atmosphere, the center part composed of fine primary particles grows to a sufficient size and then is not contained in the reaction tank. A means for introducing an active gas and preferably bubbling the aqueous reaction solution with an inert gas can be mentioned.

(3-c) Ammonium ion concentration The ammonium ion concentration in the reaction aqueous solution is preferably in the range of 3 g / L to 25 g / L, more preferably 5 g / L to 25 g / L, and still more preferably 5 g / L to 15 g / L. Within a certain value.

  Since ammonium ions function as a complexing agent in the reaction aqueous solution, if the ammonium ion concentration is less than 3 g / L, the solubility of the metal ions cannot be kept constant, and the reaction aqueous solution is easily gelled. It becomes difficult to obtain composite hydroxide particles having a uniform particle size. On the other hand, when the ammonium ion concentration exceeds 25 g / L, the solubility of metal ions becomes too high, so that the amount of metal ions remaining in the reaction aqueous solution increases, resulting in a composition shift.

  If the ammonium ion concentration fluctuates during the crystallization reaction, the solubility of metal ions fluctuates, and uniform composite hydroxide particles are not formed. For this reason, it is preferable to control the fluctuation range of the ammonium ion concentration within a certain range through the nucleation step and the particle growth step, and specifically, it is preferable to control the fluctuation range of ± 5 g / L.

(3-d) Reaction temperature The temperature of the aqueous reaction solution (reaction temperature) is preferably controlled to 20 ° C or higher, more preferably in the range of 20 ° C to 60 ° C, through the nucleation step and the particle growth step. . When the reaction temperature is less than 20 ° C., nucleation is likely to occur due to the low solubility of the aqueous reaction solution, and it becomes difficult to control the average particle size and particle size distribution of the resulting composite hydroxide particles. The upper limit of the reaction temperature is not particularly limited, but when it exceeds 60 ° C., the volatilization of ammonia is promoted, and an ammonium ion supplier that is supplied to control ammonium ions in the aqueous reaction solution within a certain range. As a result, the amount of the aqueous solution containing water increases and the production cost increases.

(3-e) Particle size control of composite hydroxide particles The particle size of the composite hydroxide particles can be controlled by the time of the particle growth step, so if the particle growth step is continued until the desired particle size is reached, it is desired Composite hydroxide particles having a particle size of can be obtained.

  Further, the particle size of the composite hydroxide particles can be controlled not only by the particle growth step but also by the pH value of the nucleation step and the amount of the metal compound introduced for nucleation. That is, if the pH value at the time of nucleation is set to the high pH value side, or the nucleation time is lengthened, the amount of metal compound to be added is increased, and the number of nuclei to be generated is increased. Even when the above is performed under the same conditions, the particle size of the obtained composite hydroxide particles can be reduced. On the other hand, if the pH value and the nucleation time are controlled so that the number of nuclei to be generated is reduced, the particle size of the resulting composite hydroxide particles can be increased.

3. Positive electrode active material for non-aqueous electrolyte secondary battery The positive electrode active material of the present invention has a general formula (B): Li _t Mn _{2 (1-xyz)} Ni _2x Ti _2y M _2z O ₄ (0.96 ≦ t ≦ 1. 20, 0.20 ≦ x ≦ 0.28, 0 <y ≦ 0.05, 0 ≦ z ≦ 0.05, M is Mg, Ca, Ba, Sr, V, Fe, Cr, Co, Cu, Zr And at least one element selected from Nb, Mo, and W), and a cubic lithium manganese nickel titanium composite oxide particle (hereinafter referred to as “lithium composite oxide particle”) having a spinel structure. The average particle size is 2 μm to 8 μm, and the spread of the particle size distribution [(d90−d10) / average particle size] is 0.70 or less, and the hollow portion inside the particle and the outside of the hollow portion A hollow structure composed of a shell portion is provided.

(1) Composition The value of t indicating the lithium (Li) content is 0.96 to 1.20, preferably 0.98 to 1.20, more preferably 1.00 to 1.20. . By regulating the value of t within the above range, it is possible to improve the output characteristics and capacity characteristics of a secondary battery configured with this positive electrode active material as the positive electrode. On the other hand, if the value of t is less than 0.96, the positive electrode resistance of the secondary battery is increased, so that the output characteristics cannot be improved. On the other hand, when the value of t exceeds 1.20, the initial discharge capacity decreases.

  In the positive electrode active material of the present invention, the range of the value of x, the value of y, the value of z in the general formula (B) and the critical significance thereof are the range of each value in the general formula (A) described above. In addition, since it is the same as the critical significance thereof, description thereof is omitted here.

(2) Particle Structure The positive electrode active material of the present invention has a hollow structure composed of a hollow part inside the particle and an outer shell part outside the hollow part. By providing such a hollow structure, the reaction area with the electrolytic solution can be increased, and the electrolytic solution enters the hollow portion through the grain boundary or void between the primary particles of the outer shell portion, and the particles Lithium can be desorbed and inserted not only through the reaction interface in the outer shell but also through the reaction interface inside the particle, which facilitates the movement of lithium ions and electrons and greatly improves output characteristics. it can.

(3) Thickness of outer shell portion In the positive electrode active material of the present invention, the thickness of the outer shell portion is preferably 5% to 35%, more preferably 10% to 35%, as a ratio to the particle diameter. preferable. If the thickness of the outer shell portion is less than 5%, the hollow portion becomes too large, so that the positive electrode resistance is increased due to the reduction of the reaction interface, not only the output characteristics are lowered, but also the particle strength is lowered. When configuring the positive electrode, the particles may be destroyed and fine powder may be generated. On the other hand, when the thickness of the outer shell portion exceeds 35%, the grain boundary or void between the primary particles of the outer shell portion that allows the electrolyte to enter the hollow portion is reduced, and a sufficient reaction interface can be secured. As a result, the positive electrode resistance increases and the output characteristics deteriorate. In addition, the thickness of the outer shell part of the positive electrode active material can be obtained by the same method as the thickness of the outer shell part of the composite hydroxide particles described above.

(4) Average particle diameter The average particle diameter of the positive electrode active material of the present invention is 2 μm to 8 μm, preferably 3 μm to 8 μm, more preferably 3 μm to 6 μm. The average particle diameter of the positive electrode active material means the volume average particle diameter of the secondary particles constituting the positive electrode active material, and can be obtained from, for example, the volume integrated value measured by a laser light diffraction / scattering particle size analyzer. it can.

  If the average particle diameter of the positive electrode active material is within such a range, it becomes possible to improve the capacity characteristics and output characteristics of a secondary battery using this positive electrode active material. On the other hand, when the average particle size is less than 2 μm, the filling property of the positive electrode active material is lowered, so that the capacity characteristics of the secondary battery cannot be improved. On the other hand, when the average particle size exceeds 8 μm, the specific surface area of the positive electrode active material is reduced, so that the reaction area with the electrolytic solution is reduced and the positive electrode resistance is increased.

(5) Particle size distribution In the positive electrode active material of the present invention, [(d90-d10) / average particle size] indicating the spread of the particle size distribution is 0.70 or less, preferably 0.69 or less, more preferably 0.68. The following control is required. In addition, d10, d90 and an average particle diameter can be calculated | required by the method similar to d10, d90 and average particle diameter in composite hydroxide particle | grains.

  By controlling the value of [(d90−d10) / average particle size] indicating the spread of the particle size distribution of the positive electrode active material within the above range, the ratio of fine secondary particles and coarse secondary particles in the positive electrode active material is controlled. The output characteristics, cycle characteristics, and safety of a secondary battery using the positive electrode active material for the positive electrode can be improved. On the other hand, when the value of [(d90−d10) / average particle diameter] exceeds 0.70, the ratio of fine secondary particles and coarse secondary particles in the positive electrode active material increases. When a secondary battery is configured using a positive electrode active material containing a large amount of fine secondary particles, the calorific value increases due to a local reaction of the fine secondary particles, and the fine secondary particles are selectively used. Due to the deterioration, the cycle characteristics deteriorate. In addition, when a secondary battery is configured using a positive electrode active material containing a large amount of coarse secondary particles, a sufficient reaction area between the electrolytic solution and the positive electrode active material cannot be ensured. Output characteristics deteriorate.

(6) The specific surface area of the positive electrode active material having a specific surface area of the present invention is preferably 0.5m ² /g~3.0m ² / g, is 0.5m ² /g~2.5m ² / g It is more preferable. The specific surface area of the positive electrode active material can be measured by the BET method using nitrogen gas adsorption. When the specific surface area of the positive electrode active material is less than 0.5 m ² / g, when a secondary battery is configured, a sufficient reaction area with the electrolytic solution cannot be secured, and output characteristics cannot be improved. There is. On the other hand, when the specific surface area of the positive electrode active material exceeds 3.0 m ² / g, a film may be formed by a side reaction with the electrolytic solution, and the resistance may increase.

4). Method for Producing Positive Electrode Active Material for Nonaqueous Electrolyte Secondary Battery The method for producing a positive electrode active material of the present invention comprises mixing lithium into the above-mentioned composite hydroxide particles to form a lithium mixture (mixing step), and then predetermining this. The positive electrode active material described above is obtained by firing under conditions (firing step). In addition, in the manufacturing method of the positive electrode active material of the present invention, in addition to the mixing step and the firing step, if necessary, a step of calcining the lithium mixture before the firing step (calcination step), lithium composite oxidation after firing A step of crushing the object particles (crushing step) and / or a step of annealing the lithium composite oxide particles (annealing step) may be performed. Hereinafter, each process will be described in detail.

(1) Mixing step In the mixing step, the number of lithium atoms (Li) relative to the total number (Me) of atoms of metals other than lithium (Mn, Ni, Ti and additive element M) is added to the composite hydroxide particles described above. The lithium compound is mixed so that the ratio (Li / Me) is 0.48 to 0.60, preferably 0.49 to 0.60, more preferably 0.50 to 0.60. It is a process to obtain. That is, Li / Me does not change before and after the firing step, and Li / Me in this mixing step becomes Li / Me in the lithium composite oxide particles, so Li / Me in the lithium mixture is the lithium composite to be obtained. It is necessary to mix a lithium compound with the composite hydroxide particles so as to be the same as Li / Me of the oxide particles.

  The lithium compound to be mixed with the composite hydroxide particles is not particularly limited, and for example, lithium hydroxide, lithium nitrate, lithium carbonate, or a mixture thereof can be used. In particular, lithium carbonate is preferably used in consideration of easy handling and quality stability.

  It is preferable that the composite hydroxide particles and the lithium compound are sufficiently mixed before firing so as not to generate fine powder. If the mixing is insufficient, the Li / Me varies among individual particles, and sufficient battery characteristics cannot be obtained. In addition, a general mixer can be used for mixing. For example, a shaker mixer, a Laedige mixer, a Julia mixer, a V blender, or the like can be used.

(2) Calcination Step When lithium hydroxide or lithium carbonate is used as the lithium compound, it is lower than the firing temperature and 1 at a temperature of 350 ° C. to 750 ° C. before firing the lithium mixture at the firing temperature described later. It is preferable to calcine by holding for about 10 hours. That is, it is preferable to promote the diffusion of lithium into the composite hydroxide particles by holding for a certain time in the vicinity of the melting point or reaction temperature of lithium hydroxide or lithium carbonate, whereby the resulting lithium composite oxide The composition of the particles can be made more uniform.

  The calcining temperature is lower than the calcining temperature and more preferably 400 ° C. to 700 ° C., and the holding time at this temperature is more preferably 5 hours or less.

(3) Firing step The firing step is a step of firing the lithium mixture obtained in the mixing step at a predetermined temperature. The furnace used in the firing step is not particularly limited as long as the lithium mixture can be fired in the atmosphere described later, and either a batch type or a continuous type furnace can be used. It is preferable to use no electric furnace.

  Although the firing atmosphere is an oxidizing atmosphere, it is preferably performed in an atmosphere having an oxygen concentration of 18% by volume to 100% by volume, that is, in the atmosphere to an oxygen stream. preferable. If the oxygen concentration is less than 18% by volume, the oxidation reaction does not proceed sufficiently, and the crystallinity of the lithium composite oxide particles may not be sufficient.

  The baking temperature is higher than 850 ° C. and lower than 950 ° C., preferably 860 ° C. or higher and 940 ° C. or lower, more preferably 875 ° C. or higher and 925 ° C. or lower. When the firing temperature is 850 ° C. or lower, the specific surface area of the obtained positive electrode active material becomes too large, so that a film is formed by a side reaction occurring between the positive electrode active material and the electrolytic solution in the secondary battery, and the positive electrode resistance is reduced. To increase. On the other hand, when the firing temperature is 950 ° C. or higher, the hollow structure disappears due to the progress of sintering between the composite hydroxide particles or between the lithium composite oxide particles. Such a lithium composite oxide particle has a reduced specific surface area, and therefore, when this is used as a positive electrode active material to form a secondary battery, the positive electrode resistance increases and the output characteristics deteriorate.

  The holding time (firing time) at the firing temperature is preferably 3 hours or more, and more preferably 5 to 24 hours. If the firing time is less than 3 hours, the composite hydroxide particles and the lithium compound may not be sufficiently reacted. On the other hand, even if it exceeds 24 hours, not only the effect cannot be obtained, but also the productivity is deteriorated.

(4) Crushing step The sintered lithium composite oxide particles may be aggregated or slightly sintered. In this case, it is preferable to crush the aggregate or sintered body of lithium composite oxide particles. Thereby, since the lithium composite oxide particles can be handled as a powder having an appropriate particle size, the filling property when used as a positive electrode active material can be further improved. Note that pulverization means that mechanical energy is applied to an aggregate composed of a plurality of secondary particles generated by sintering necking between secondary particles during firing, and the secondary particles themselves are hardly destroyed. This is an operation of separating the secondary particles and loosening the aggregates.

  As a crushing method, a known means can be used, for example, a pin mill or a hammer mill can be used. At this time, it is preferable to adjust the crushing force to an appropriate range so as not to destroy the secondary particles.

(5) Annealing treatment step In the method for producing a positive electrode active material of the present invention, the lithium composite oxide particles after the firing step or the crushing step are further subjected to an oxidizing atmosphere at 500 ° C to 800 ° C for 5 hours to 40 hours. It is preferable to perform an annealing treatment for firing for a time. In this manner, after the firing step, by performing annealing treatment at a temperature lower than the firing temperature, oxygen defects in the lithium composite oxide particles generated by firing in the high temperature region can be recovered and the crystallinity can be improved.

  Although the atmosphere in the annealing process is an oxidizing atmosphere, it is preferably performed in an atmosphere having an oxygen concentration of 18% by volume to 100% by volume, that is, in the atmosphere to an oxygen stream, similarly to the atmosphere in the firing process. In consideration, it is more preferable to carry out in an air stream. When the oxygen concentration is less than 18% by volume, the oxidation reaction does not proceed sufficiently, and oxygen defects in the lithium composite oxide particles may not be sufficiently recovered.

  In addition, the firing temperature (annealing temperature) in the annealing process is lower than the above-described firing temperature, specifically 500 ° C to 800 ° C, preferably 600 ° C to 800 ° C, more preferably 650 ° C to 750 ° C. It is necessary to set it to ° C. When the annealing temperature is less than 500 ° C., oxygen defects cannot be sufficiently recovered. On the other hand, when the annealing temperature exceeds 800 ° C., oxygen defects are further generated in the lithium composite oxide particles, and the crystallinity is deteriorated.

  The holding time at the annealing temperature (annealing time) is 5 hours to 40 hours, preferably 10 hours to 40 hours, more preferably 20 hours to 40 hours. If the annealing time is less than 5 hours, oxygen defects cannot be sufficiently recovered. On the other hand, even if the annealing time exceeds 40 hours, not only a further effect cannot be obtained, but also the productivity deteriorates.

5. Non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, a non-aqueous electrolyte solution, and the like, and includes the same components as those of a general non-aqueous electrolyte secondary battery. Note that the embodiments described below are merely examples, and the nonaqueous electrolyte secondary battery of the present invention can be variously modified based on the knowledge of those skilled in the art based on the embodiments described herein. It can be implemented in an improved form. Moreover, the use of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited .

(1) Positive electrode Using the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention, for example, a positive electrode of a non-aqueous electrolyte secondary battery is produced as follows.

First, a powdered positive electrode active material, a conductive material, and a binder are mixed, and activated carbon and a target solvent such as viscosity adjustment are added as necessary, and this is kneaded to prepare a positive electrode mixture paste. . Each mixing ratio in the positive electrode mixture paste is appropriately selected according to the use of the secondary battery and the required performance, and is not particularly limited . When the solid content is 100 parts by mass, the content of the positive electrode active material is 60 parts by mass to 95 parts by mass, and the content of the conductive material is 1 part by mass to 20 like the positive electrode of a general non-aqueous electrolyte secondary battery. Desirably, the content of the binder is 1 part by mass to 20 parts by mass.

  The obtained positive electrode mixture paste is applied to, for example, the surface of a current collector made of aluminum foil and dried to disperse the solvent. If necessary, pressurization may be performed by a roll press or the like to increase the electrode density. In this way, a sheet-like positive electrode can be produced. The sheet-like positive electrode can be cut into an appropriate size according to the target battery and used for battery production. However, the method for manufacturing the positive electrode is not limited to the above-described examples, and other methods may be used.

  In producing the positive electrode, as the conductive material, for example, graphite (natural graphite, artificial graphite, expanded graphite and the like), and carbon black materials such as acetylene black and ketjen black (registered trademark) can be used.

  The binder plays a role of anchoring the active material particles. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluorine rubber, ethylene propylene diene rubber, styrene butadiene, cellulosic resin, and polyacrylic are used. An acid can be used.

  If necessary, a positive electrode active material, a conductive material, and activated carbon are dispersed, and a solvent that dissolves the binder is added to the positive electrode mixture. Specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used as the solvent. Activated carbon can be added to the positive electrode mixture in order to increase the electric double layer capacity.

(2) Negative electrode The negative electrode composite material in which the negative electrode is made of metal lithium, lithium alloy, or the like, or a negative electrode active material capable of occluding and desorbing lithium ions, mixed with a binder, and added with an appropriate solvent to form a paste. Is applied to the surface of a metal foil current collector such as copper, dried, and compressed to increase the electrode density as necessary.

  As the negative electrode active material, for example, organic compound fired bodies such as natural graphite, artificial graphite and phenol resin, and powdery bodies of carbon materials such as coke can be used. In this case, a fluorine-containing resin such as PVDF can be used as the negative electrode binder, as in the case of the positive electrode, and an organic material such as N-methyl-2-pyrrolidone can be used as a solvent for dispersing these active materials and the binder. A solvent can be used.

(3) Separator A separator is interposed between the positive electrode and the negative electrode. The separator separates the positive electrode and the negative electrode and retains an electrolyte, and a thin film such as polyethylene or polypropylene and a film having many minute holes can be used.

(4) Non-aqueous electrolyte The non-aqueous electrolyte is obtained by dissolving a lithium salt as a supporting salt in an organic solvent.

  Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate, and tetrahydrofuran, 2- One kind selected from ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethylsulfone and butanesultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, etc. are used alone or in admixture of two or more. be able to.

As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , and complex salts thereof can be used.

  Further, the non-aqueous electrolyte may contain a radical scavenger, a surfactant, a flame retardant, and the like in order to improve battery characteristics.

(5) Shape and configuration of battery The non-aqueous electrolyte secondary battery of the present invention composed of the positive electrode, negative electrode, separator and non-aqueous electrolyte described above has various shapes such as a cylindrical shape and a laminated shape. Can be. In any case, the positive electrode and the negative electrode are laminated via a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte, and the positive electrode current collector communicates with the outside. A non-aqueous electrolyte secondary battery is completed by connecting between the terminals and between the negative electrode current collector and the negative electrode terminal communicating with the outside using a current collecting lead or the like and sealing the battery case.

(6) Characteristics A nonaqueous electrolyte secondary battery using the positive electrode active material of the present invention has a high capacity and excellent output characteristics while having a high operating potential. Specifically, the positive electrode active material of the present invention is used as a positive electrode to form a 2032 type coin battery, the current density is 0.1 mA / cm ² , the battery is charged to a cut-off voltage of 5.0 V, and rests for 1 hour. Thereafter, when discharging to a cutoff voltage of 3.0 V, an initial discharge capacity of 130 mAh / g or more, preferably 135 mAh / g or more is obtained. Moreover, the positive electrode resistance of this 2032 type coin battery can be made 22Ω or less, preferably 21Ω or less.

(7) Use of non-aqueous electrolyte secondary battery Since the non-aqueous electrolyte secondary battery of the present invention has the above characteristics, it is a small portable electronic device (such as a notebook personal computer or a mobile phone terminal) that always requires a high capacity. It is suitable for the power source. Moreover, since the nonaqueous electrolyte secondary battery of the present invention can be reduced in size and increased in output, it is also suitable as a power source for electric vehicles subject to restrictions on mounting space. The non-aqueous electrolyte secondary battery of the present invention is not only a power source for an electric vehicle driven purely by electric energy, but also a power source for a so-called hybrid vehicle used in combination with a combustion engine such as a gasoline engine or a diesel engine. Can also be used.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
[Production of composite hydroxide particles]
(1) Nucleation Step First, the temperature in the tank was set to 40 ° C. while stirring the reaction tank (5 L) with half the amount of water. At this time, the inside of the reaction vessel was set to an air atmosphere. Appropriate amounts of 25% by mass aqueous sodium hydroxide and 25% by mass ammonia water were added to the water in the reaction vessel, and the pH value in the reaction vessel was 13.0 based on the liquid temperature of 25 ° C., and the ammonium ion concentration was 5 g / A pre-reaction aqueous solution was prepared by adjusting to L. Further, a hydrate of manganese sulfate and nickel sulfate was dissolved in pure water so that the molar ratio of manganese to nickel was Mn: Ni = 2.90: 1.00, and a 1.85 mol / L mixed aqueous solution. 1 was adjusted. At the same time, hydrated manganese sulfate and nickel sulfate and titanium sulfate are purified so that the molar ratio of manganese, nickel and titanium is Mn: Ni: Ti = 2.90: 1.00: 0.105. A 1.90 mol / L mixed aqueous solution 2 was prepared.

  Next, while supplying the mixed aqueous solution 1 at a rate of 10 mL / min into the reaction tank, the pH value of the aqueous reaction solution is adjusted by supplying 25% by mass ammonia water and 25% by mass sodium hydroxide aqueous solution at a constant rate. The ammonium ion concentration was maintained at 5 g / L at 13.0 based on the liquid temperature of 25 ° C. In this state, nucleation of manganese nickel composite hydroxide particles was performed by performing crystallization for 1 minute.

  In the nucleation step, the pH value of the reaction aqueous solution was measured by a pH controller installed in the reaction tank, and was controlled within a range of ± 0.2 with respect to the set value. This also applies to the grain growth process.

(3) Particle growth step After the completion of the nucleation step, the supply of the mixed aqueous solution 1, ammonia water and sodium hydroxide aqueous solution is stopped and sulfuric acid is added to the reaction aqueous solution to adjust the pH value of the reaction aqueous solution to the liquid temperature. It adjusted so that it might become 11.6 on a 25 degreeC reference | standard.

  In this state, the supply of the mixed aqueous solution 1 is restarted, and the aqueous solution of the reaction aqueous solution is maintained at 11.6 on the basis of the liquid temperature of 25 ° C. A sodium aqueous solution was supplied, and crystallization was performed for 15 minutes.

  At this time, the supply of all the aqueous solutions was once stopped, and nitrogen gas was circulated at 5 L / min in the reaction tank so that the oxygen concentration was adjusted to 0.2% by volume or less.

  Thereafter, in place of the mixed aqueous solution 1, the supply of the mixed aqueous solution 2 containing titanium is started, the pH value of the reaction aqueous solution is maintained at 11.6 on the basis of the liquid temperature of 25 ° C., and the ammonium ion concentration is maintained at 5 g / L. Thus, 25% by mass aqueous ammonia and 25% by mass sodium hydroxide aqueous solution were supplied, and crystallization was performed for 4.75 hours. That is, in this example, the reaction atmosphere and the mixed aqueous solution were switched at the time of 5% of the total particle growth process time from the start of the particle growth process.

[Evaluation of composite hydroxide particles]
After completion of the titanium addition step, the product was washed with water, filtered and dried to obtain composite hydroxide particles.

When the composition of the composite hydroxide particles was measured with an ICP emission spectrometer (Varian, 725ES), it was confirmed that the composite hydroxide particles are represented by the general formula: Mn _0.725 Ni _0.25 Ti _0.025 (OH) ₂ .

  Next, using a laser light diffraction / scattering particle size analyzer (manufactured by Nikkiso Co., Ltd., Microtrac MT3000II), the average particle size of the composite hydroxide particles is measured, d10 and d90 are measured, and the particle size distribution is measured. [(D90−d10) / average particle diameter], which is an index indicating spread, was calculated.

  Moreover, as a result of making this composite hydroxide particle into a state in which a cross section can be observed by cross-section polisher and observing the particle structure using SEM (manufactured by JEOL, JSM-7001F), this composite hydroxide particle is a primary particle. Is composed of substantially spherical secondary particles formed by agglomerating a plurality of particles, the central portion of the secondary particles is formed of needle-like fine primary particles, and the outer shell portion is fine. It was confirmed to be formed from plate-like primary particles larger than the primary particles. In this SEM observation, the average particle size of the fine primary particles and the plate-like primary particles and the thickness of the outer shell portion with respect to the particle size of the secondary particles were measured at the same time.

[Production of positive electrode active material]
Lithium carbonate weighed so that Li / Me = 50 atomic% is added to the composite hydroxide particles obtained as described above, and mixed using a tumbler shaker mixer (manufactured by Dalton Co., Ltd., T2F). As a result, a lithium mixture was obtained.

  The lithium mixture was calcined at 500 ° C. for 2 hours in an air atmosphere using an atmosphere firing furnace (manufactured by Hiroki Co., Ltd., HAF-2020S), fired at 900 ° C. for 12 hours, cooled to room temperature, The obtained lithium composite oxide particles were crushed using a hammer mill (manufactured by IKA Japan, MF10).

  Further, the lithium composite oxide particles were fired at 700 ° C. for 36 hours in an air atmosphere using an atmosphere firing furnace (annealing treatment) to obtain a positive electrode active material.

[Evaluation of positive electrode active material]
When the composition of this positive electrode active material was measured with an ICP emission spectroscopic analyzer, it was confirmed that it was represented by the general formula: LiMn _1.45 Ni _0.50 Ti _0.05 O ₄ .

Next, the average particle diameter of this positive electrode active material is measured using a laser light diffraction / scattering particle size analyzer, and d10 and d90 are measured in the same manner, and this is an index indicating the spread of the particle size distribution [( d90-d10) / average particle diameter] was calculated. At the same time, the specific surface area of this positive electrode active material was measured using a nitrogen adsorption BET method measuring instrument (manufactured by Yuasa Ionics Co., Ltd., Kantasorb QS-10).

  In addition, as a result of making this positive electrode active material cross-sectional polisher capable of observing a cross section and observing the particle structure using an SEM, this positive electrode active material was found to have a hollow part inside the particle and an outer part outside this hollow part. It was confirmed to have a hollow structure composed of a shell. In this SEM observation, the thickness of the outer shell portion with respect to the particle size of the positive electrode active material was measured at the same time.

  Furthermore, when the obtained positive electrode active material was analyzed by powder X-ray diffraction using Cu—Kα rays, it was confirmed to be a lithium manganese nickel titanium composite oxide single phase having a spinel structure. These results are shown in Table 4.

[Production of secondary battery]
For the evaluation of the obtained positive electrode active material, a 2032 type coin battery 1 (hereinafter referred to as “coin type battery”) shown in FIG. 3 was used.

  The coin-type battery 1 includes a case 2 and an electrode 3 accommodated in the case 2. The case 2 has a positive electrode can 2a that is hollow and open at one end, and a negative electrode can 2b that is disposed in the opening of the positive electrode can 2a. When the negative electrode can 2b is disposed in the opening of the positive electrode can 2a, A space for accommodating the electrode 3 is formed between the negative electrode can 2b and the positive electrode can 2a. The electrode 3 includes a positive electrode 3a, a separator 3c, and a negative electrode 3b, which are stacked in this order. The positive electrode 3a contacts the inner surface of the positive electrode can 2a, and the negative electrode 3b contacts the inner surface of the negative electrode can 2b. It is accommodated in the case 2 so as to come into contact. The case 2 includes a gasket 2c, and relative movement is fixed by the gasket 2c so as to maintain a non-contact state between the positive electrode can 2a and the negative electrode can 2b. Further, the gasket 2c also has a function of sealing a gap between the positive electrode can 2a and the negative electrode can 2b to block the inside and outside of the case 2 in an airtight and liquid tight manner.

Such a coin-type battery 1 was produced as follows. First, 52.5 mg of the obtained positive electrode active material, 15 mg of acetylene black, and 7.5 mg of polytetrafluoroethylene resin (PTFE) were mixed and thinned to a weight of about 10 mg with a diameter of 10 mm to obtain the positive electrode 3a. It was prepared and dried in a vacuum dryer at 120 ° C. for 12 hours.

Next, using the positive electrode 3a, the coin-type battery 1 was produced in a glove box in an Ar atmosphere in which the dew point was controlled at −80 ° C. At this time, as the negative electrode 3b, a lithium foil punched into a disk shape having a diameter of 14 mm, or a negative electrode sheet in which graphite powder having an average particle size of about 20 μm and polyvinylidene fluoride were applied to a copper foil was used. The separator 3c is a 25 μm thick polyethylene porous membrane, and the electrolyte is a 1: 7 mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiPF ₆ as a supporting electrolyte (Toyama Chemical). Kogyo Co., Ltd.) was used.

[Evaluation of secondary battery]
The initial discharge capacity and the positive electrode resistance showing the performance of the coin-type battery 1 were evaluated as follows.

The initial discharge capacity is about 24 hours after the coin-type battery 1 using lithium foil as the negative electrode is manufactured, and after the open circuit voltage OCV (Open Circuit Voltage) is stabilized, the current density with respect to the positive electrode is 0.1 mA / Evaluation was made by measuring the capacity (initial discharge capacity) when charging to a cutoff voltage of 5.0 V as cm ² and discharging to a cutoff voltage of 3.0 V after a pause of 1 hour.

Positive electrode resistance was evaluated by measuring DC-IR resistance. Specifically, the coin-type battery 1 is charged to 60% of the initial discharge capacity, sandwiched for 1 minute, discharged for 10 seconds with a current density of 0.4 mA / cm ² , and then suspended for 1 minute again. The battery was charged for 10 seconds at a current density of 0.4 mA / cm ² . This operation, 1.3 mA / cm ^2, repeated under conditions of 4.0 mA / cm ² and 6.6 mA / cm ^2, was measured and the voltage at the discharge start in the current density, the difference in voltage until the discharge termination . Next, the current density was plotted on the vertical axis and the voltage difference was plotted on the horizontal axis, and the obtained linear relationship was found to have a slope by first-order linear approximation, and this slope was taken as the positive electrode resistance (DC-IR resistance). These results are shown in Table 4.

(Example 2)
The mixed aqueous solution 2 used had a manganese / nickel / titanium molar ratio of Mn: Ni: Ti = 2.90: 1.00: 0.111 and a concentration of 1.91 mol / L, particle growth Composite hydroxide particles were obtained in the same manner as in Example 1 except that the reaction atmosphere and the mixed aqueous solution were switched after 30 minutes from the start of the process, and then crystallization was continued for 4.50 hours. And the positive electrode active material was obtained.

The composite hydroxide particles and the positive electrode active material were evaluated in the same manner as in Example 1. As a result, the composite hydroxide particles are represented by the general formula: Mn _0.725 Ni _0.25 Ti _0.025 (OH) ₂ , and from the substantially spherical secondary particles formed by agglomerating a plurality of primary particles. The center of the secondary particles are formed from acicular fine primary particles, and the outer shell is formed from plate-like primary particles larger than the fine primary particles. Was confirmed. The positive electrode active material is represented by the general formula: LiMn _1.45 Ni _0.50 Ti _0.05 O ₄ , and is composed of a hollow portion inside the particle and an outer shell portion outside the hollow portion. It was confirmed that it had a hollow structure. Furthermore, it was confirmed that the crystal structure of the positive electrode active material is a lithium manganese nickel titanium composite oxide single phase having a spinel structure. Other particle properties are shown in Tables 2 and 4.

Finally, in the same manner as in Example 1, to configure a coin-type batteries 1 by using this positive electrode active material, and its characteristics were evaluated. The results are shown in Table 4.

(Example 3)
The mixed aqueous solution 2 used had a manganese / nickel / titanium molar ratio of Mn: Ni: Ti = 2.90: 1.00: 0.125 and a concentration of 1.91 mol / L, particle growth In the same manner as in Example 1, except that the reaction atmosphere and the mixed aqueous solution were switched after 60 minutes from the start of the process, and thereafter crystallization was continued for 4.00 hours. And the positive electrode active material was obtained.

The composite hydroxide particles and the positive electrode active material were evaluated in the same manner as in Example 1. As a result, the composite hydroxide particles are represented by the general formula: Mn _0.725 Ni _0.25 Ti _0.025 (OH) ₂ , and from the substantially spherical secondary particles formed by agglomerating a plurality of primary particles. The center of the secondary particles are formed from acicular fine primary particles, and the outer shell is formed from plate-like primary particles larger than the fine primary particles. Was confirmed. The positive electrode active material is represented by the general formula: LiMn _1.45 Ni _0.50 Ti _0.05 O ₄ , and is composed of a hollow portion inside the particle and an outer shell portion outside the hollow portion. It was confirmed that it had a hollow structure. Furthermore, it was confirmed that the crystal structure of the positive electrode active material is a lithium manganese nickel titanium composite oxide single phase having a spinel structure. Other particle properties are shown in Tables 2 and 4.

Finally, in the same manner as in Example 1, to configure a coin-type batteries 1 by using this positive electrode active material, and its characteristics were evaluated. The results are shown in Table 4.

Example 4
The mixed aqueous solution 2 used had a manganese / nickel / titanium molar ratio of Mn: Ni: Ti = 2.90: 1.00: 0.100 and a concentration of 1.90 mol / L, particle growth Composite hydroxide particles and a positive electrode active material were obtained in the same manner as in Example 1 except that the reaction atmosphere and the mixed aqueous solution were switched from the start of the process, and crystallization was continued for 5.00 hours.

The composite hydroxide particles and the positive electrode active material were evaluated in the same manner as in Example 1. As a result, the composite hydroxide particles are represented by the general formula: Mn _0.725 Ni _0.25 Ti _0.025 (OH) ₂ , and from the substantially spherical secondary particles formed by agglomerating a plurality of primary particles. The center of the secondary particles are formed from acicular fine primary particles, and the outer shell is formed from plate-like primary particles larger than the fine primary particles. Was confirmed. The positive electrode active material is represented by the general formula: LiMn _1.45 Ni _0.50 Ti _0.05 O ₄ , and is composed of a hollow portion inside the particle and an outer shell portion outside the hollow portion. It was confirmed that it had a hollow structure. Furthermore, it was confirmed that the crystal structure of the positive electrode active material is a lithium manganese nickel titanium composite oxide single phase having a spinel structure. Other particle properties are shown in Tables 2 and 4.

Finally, in the same manner as in Example 1, to configure a coin-type batteries 1 by using this positive electrode active material, and its characteristics were evaluated. The results are shown in Table 4.

(Example 5)
The mixed aqueous solution 1 used had a molar ratio of manganese to nickel of Mn: Ni = 2.80: 1.00 and a concentration of 1.90 mol / L, and the mixed aqueous solution 2 used manganese, nickel and titanium. In the same manner as in Example 1 except that a molar ratio of Mn: Ni: Ti = 2.80: 1.00: 0.211 and a concentration of 1.91 mol / L was used, composite water was used. Oxide particles and a positive electrode active material were obtained.

The composite hydroxide particles and the positive electrode active material were evaluated in the same manner as in Example 1. As a result, the composite hydroxide particles are represented by the general formula: Mn _0.700 Ni _0.25 Ti _0.050 (OH) ₂ , and from the substantially spherical secondary particles formed by agglomerating a plurality of primary particles. The center of the secondary particles are formed from acicular fine primary particles, and the outer shell is formed from plate-like primary particles larger than the fine primary particles. Was confirmed. The positive electrode active material is represented by the general formula: LiMn _1.40 Ni _0.50 Ti _0.10 O ₄ , and is composed of a hollow portion inside the particle and an outer shell portion outside the hollow portion. It was confirmed that it had a hollow structure. Furthermore, it was confirmed that the crystal structure of the positive electrode active material is a lithium manganese nickel titanium composite oxide single phase having a spinel structure. Other particle properties are shown in Tables 2 and 4.

Finally, in the same manner as in Example 1, to configure a coin-type batteries 1 by using this positive electrode active material, and its characteristics were evaluated. The results are shown in Table 4.

(Example 6)
The mixed aqueous solution 2 used had a manganese / nickel / titanium molar ratio of Mn: Ni: Ti = 2.87: 1.00: 0.144 and a concentration of 1.92 mol / L, particle growth The composite hydroxide particles were the same as in Example 1 except that the reaction atmosphere and the mixed aqueous solution were switched after 90 minutes from the start of the process, and then crystallization was continued for 3.50 hours. And the positive electrode active material was obtained.

The composite hydroxide particles and the positive electrode active material were evaluated in the same manner as in Example 1. As a result, the composite hydroxide particles are represented by the general formula: Mn _0.700 Ni _0.25 Ti _0.050 (OH) ₂ , and from the substantially spherical secondary particles formed by agglomerating a plurality of primary particles. The center of the secondary particles are formed from acicular fine primary particles, and the outer shell is formed from plate-like primary particles larger than the fine primary particles. Was confirmed. The positive electrode active material is represented by the general formula: LiMn _1.40 Ni _0.50 Ti _0.10 O ₄ , and is composed of a hollow portion inside the particle and an outer shell portion outside the hollow portion. It was confirmed that it had a hollow structure. Furthermore, it was confirmed that the crystal structure of the positive electrode active material is a lithium manganese nickel titanium composite oxide single phase having a spinel structure. Other particle properties are shown in Tables 2 and 4.

Finally, in the same manner as in Example 1, to configure a coin-type batteries 1 by using this positive electrode active material, and its characteristics were evaluated. The results are shown in Table 4.

(Example 7)
The mixed aqueous solution 1 used had a manganese / nickel molar ratio of Mn: Ni = 2.94: 1.00 and a concentration of 1.87 mol / L, and the mixed aqueous solution 2 used manganese, nickel and titanium. In the same manner as in Example 1 except that a molar ratio of Mn: Ni: Ti = 2.94: 1.00: 0.063 and a concentration of 1.90 mol / L was used, composite water was used. Oxide particles and a positive electrode active material were obtained.

The composite hydroxide particles and the positive electrode active material were evaluated in the same manner as in Example 1. As a result, the composite hydroxide particles are represented by the general formula: Mn _0.700 Ni _0.25 Ti _0.050 (OH) ₂ , and from the substantially spherical secondary particles formed by agglomerating a plurality of primary particles. The center of the secondary particles are formed from acicular fine primary particles, and the outer shell is formed from plate-like primary particles larger than the fine primary particles. Was confirmed. The positive electrode active material is represented by the general formula: LiMn _1.40 Ni _0.50 Ti _0.10 O ₄ , and is composed of substantially spherical secondary particles formed by agglomerating a plurality of primary particles. And it was confirmed that it was equipped with the hollow structure comprised from the hollow part inside particle | grains, and the outer shell part outside this hollow part. Furthermore, it was confirmed that the crystal structure of the positive electrode active material is a lithium manganese nickel titanium composite oxide single phase having a spinel structure. Other particle properties are shown in Tables 2 and 4.

Finally, in the same manner as in Example 1, to configure a coin-type batteries 1 by using this positive electrode active material, and its characteristics were evaluated. The results are shown in Table 4.

(Comparative Example 1)
As the mixed aqueous solution 1 and the mixed aqueous solution 2, those having a molar ratio of manganese, nickel and titanium of Mn: Ni: Ti = 2.90: 1.00: 0.100 and a concentration of 1.90 mol / L were used. In addition, the composite hydroxide particles and the positive electrode active material were the same as in Example 1 except that the reaction atmosphere was controlled to a nitrogen atmosphere having an oxygen concentration of 0.2% by volume or less through the nucleation step and the particle growth step. Got.

The composite hydroxide particles and the positive electrode active material were evaluated in the same manner as in Example 1. As a result, the composite hydroxide particles are represented by the general formula: Mn _0.725 Ni _0.25 Ti _0.025 (OH) ₂ , and from the substantially spherical secondary particles formed by agglomerating a plurality of primary particles. The center of the secondary particles are formed from acicular fine primary particles, and the outer shell is formed from plate-like primary particles larger than the fine primary particles. Was confirmed. The positive electrode active material is represented by the general formula: LiMn _1.45 Ni _0.50 Ti _0.05 O ₄ , and is composed of a hollow portion inside the particle and an outer shell portion outside the hollow portion. It was confirmed that it had a hollow structure. Furthermore, it was confirmed that the crystal structure of the positive electrode active material is a lithium manganese nickel titanium composite oxide single phase having a spinel structure. Other particle properties are shown in Tables 2 and 4.

Finally, in the same manner as in Example 1, to configure a coin-type batteries 1 by using this positive electrode active material, and its characteristics were evaluated. The results are shown in Table 4.

(Comparative Example 2)
The mixed aqueous solution 2 used had a manganese / nickel / titanium molar ratio of Mn: Ni: Ti = 2.90: 1.00: 0.150 and a concentration of 1.92 mol / L, particle growth Composite hydroxide particles were obtained in the same manner as in Example 1 except that the reaction atmosphere and the mixed aqueous solution were switched after 100 minutes from the start of the process, and then crystallization was continued for 3.33 hours. And the positive electrode active material was obtained.

The composite hydroxide particles and the positive electrode active material were evaluated in the same manner as in Example 1. As a result, the composite hydroxide particles are represented by the general formula: Mn _0.725 Ni _0.25 Ti _0.025 (OH) ₂ , and from the substantially spherical secondary particles formed by agglomerating a plurality of primary particles. The center of the secondary particles are formed from acicular fine primary particles, and the outer shell is formed from plate-like primary particles larger than the fine primary particles. Was confirmed. The positive electrode active material is represented by the general formula: LiMn _1.45 Ni _0.50 Ti _0.05 O ₄ , and is composed of a hollow portion inside the particle and an outer shell portion outside the hollow portion. It was confirmed that it had a hollow structure. Furthermore, it was confirmed that the crystal structure of the positive electrode active material is a lithium manganese nickel titanium composite oxide single phase having a spinel structure. Other particle properties are shown in Tables 2 and 4.

Finally, in the same manner as in Example 1, to configure a coin-type batteries 1 by using this positive electrode active material, and its characteristics were evaluated. The results are shown in Table 4.

(Comparative Example 3)
Composite hydroxide particles and a positive electrode active material were obtained in the same manner as in Example 1 except that the firing temperature in the firing step was 950 ° C.

The composite hydroxide particles and the positive electrode active material were evaluated in the same manner as in Example 1. As a result, the composite hydroxide particles are represented by the general formula: Mn _0.725 Ni _0.25 Ti _0.025 (OH) ₂ , and from the substantially spherical secondary particles formed by agglomerating a plurality of primary particles. The center of the secondary particles are formed from acicular fine primary particles, and the outer shell is formed from plate-like primary particles larger than the fine primary particles. Was confirmed. In addition, this positive electrode active material is represented by the general formula: LiMn _1.45 Ni _0.50 Ti _0.05 O ₄ , and has a solid structure with no hollow portion inside the particles. It was confirmed. Furthermore, it was confirmed that the crystal structure of the positive electrode active material is a lithium manganese nickel titanium composite oxide single phase having a spinel structure. Other particle properties are shown in Tables 2 and 4.

Finally, in the same manner as in Example 1, to configure a coin-type batteries 1 by using this positive electrode active material, and its characteristics were evaluated. The results are shown in Table 4.

(Comparative Example 4)
Composite hydroxide particles and a positive electrode active material were obtained in the same manner as in Example 1 except that the firing temperature in the firing step was 850 ° C.

The composite hydroxide particles and the positive electrode active material were evaluated in the same manner as in Example 1. As a result, the composite hydroxide particles are represented by the general formula: Mn _0.725 Ni _0.25 Ti _0.025 (OH) ₂ , and from the substantially spherical secondary particles formed by agglomerating a plurality of primary particles. The center of the secondary particles are formed from acicular fine primary particles, and the outer shell is formed from plate-like primary particles larger than the fine primary particles. Was confirmed. The positive electrode active material is represented by the general formula: LiMn _1.45 Ni _0.50 Ti _0.05 O ₄ , and is composed of a hollow portion inside the particle and an outer shell portion outside the hollow portion. It was confirmed that it had a hollow structure. Furthermore, it was confirmed that the crystal structure of the positive electrode active material is a lithium manganese nickel titanium composite oxide single phase having a spinel structure. Other particle properties are shown in Tables 2 and 4.

Finally, in the same manner as in Example 1, to configure a coin-type batteries 1 by using this positive electrode active material, and its characteristics were evaluated. The results are shown in Table 4.

(Comparative Example 5)
As the mixed aqueous solution 1 and the mixed aqueous solution 2, Example 1 except that the molar ratio of manganese to nickel was Mn: Ni = 3.00: 1.00 and the concentration was 1.90 mol / L. Similarly, composite hydroxide particles and a positive electrode active material were obtained.

The composite hydroxide particles and the positive electrode active material were evaluated in the same manner as in Example 1. As a result, the composite hydroxide particles are represented by the general formula: Mn _0.75 Ni _0.25 (OH) ₂ , and are composed of substantially spherical secondary particles formed by agglomerating a plurality of primary particles. It is confirmed that the central part of the secondary particles is formed from acicular fine primary particles and that the outer shell part is formed from plate-like primary particles larger than the fine primary particles. It was done. Further, this positive electrode active material is represented by the general formula: LiMn _1.50 Ni _0.50 O ₄ , and is a hollow composed of a hollow part inside the particle and an outer shell part outside the hollow part. It was confirmed to have a structure. Furthermore, it was confirmed that the crystal structure of the positive electrode active material is a lithium manganese nickel titanium composite oxide single phase having a spinel structure. Other particle properties are shown in Tables 2 and 4.

Finally, in the same manner as in Example 1, to configure a coin-type batteries 1 by using this positive electrode active material, and its characteristics were evaluated. The results are shown in Table 4.

(Comparative Example 6)
The mixed aqueous solution 1 used had a molar ratio of manganese to nickel of Mn: Ni = 2.70: 1.00 and a concentration of 1.76 mol / L, and the mixed aqueous solution 2 used manganese, nickel and titanium. In the same manner as in Example 1 except that a molar ratio of Mn: Ni: Ti = 2.70: 1.00: 0.316 and a concentration of 1.91 mol / L was used, composite water was used. Oxide particles and a positive electrode active material were obtained.

The composite hydroxide particles and the positive electrode active material were evaluated in the same manner as in Example 1. As a result, the composite hydroxide particles are represented by the general formula: Mn _0.675 Ni _0.25 Ti _0.075 (OH) ₂ , and from the substantially spherical secondary particles formed by agglomerating a plurality of primary particles. The center of the secondary particles are formed from acicular fine primary particles, and the outer shell is formed from plate-like primary particles larger than the fine primary particles. Was confirmed. The positive electrode active material is represented by the general formula: LiMn _1.35 Ni _0.50 Ti _0.15 O ₄ , and is composed of a hollow portion inside the particle and an outer shell portion outside the hollow portion. It was confirmed that it had a hollow structure. Furthermore, it was confirmed that the crystal structure of the positive electrode active material is a mixture of a lithium manganese nickel titanium composite oxide phase having a spinel structure and a Li ₂ NiTiO ₄ phase. Other particle properties are shown in Tables 2 and 4.

Finally, in the same manner as in Example 1, to configure a coin-type batteries 1 by using this positive electrode active material, and its characteristics were evaluated. The results are shown in Table 4.

(Comparative Example 7)
Other than using the mixed aqueous solution 1 and the mixed aqueous solution 2 in which the molar ratio of manganese, nickel and titanium is Mn: Ni = 2.90: 1.00: 0.100 and the concentration is 1.90 mol / L. Produced the composite hydroxide particles and the positive electrode active material in the same manner as in Example 1.

The composite hydroxide particles and the positive electrode active material were evaluated in the same manner as in Example 1. As a result, the composite hydroxide particles are represented by the general formula: Mn _0.725 Ni _0.25 Ti _0.025 (OH) ₂ , and from the substantially spherical secondary particles formed by agglomerating a plurality of primary particles. The center of the secondary particles are formed from acicular fine primary particles, and the outer shell is formed from plate-like primary particles larger than the fine primary particles. Was confirmed. The positive electrode active material is represented by the general formula: LiMn _1.45 Ni _0.50 Ti _0.05 O ₄ , and is composed of a hollow portion inside the particle and an outer shell portion outside the hollow portion. It was confirmed that it had a hollow structure. Furthermore, it was confirmed that the crystal structure of the positive electrode active material is a lithium manganese nickel titanium composite oxide single phase having a spinel structure. Other particle properties are shown in Tables 2 and 4.

Finally, in the same manner as in Example 1, to configure a coin-type batteries 1 by using this positive electrode active material, and its characteristics were evaluated. The results are shown in Table 4.

1 coin-batteries 2 cases <br/> 2a cathode can 2b the negative electrode can 2c gasket 3 electrodes 3a positive 3b negative electrode 3c separator

Claims (3)

General formula (B): Li _t Mn _{2 (1-xyz)} Ni _2x Ti _2y M _2z O ₄ (0.96 ≦ t ≦ 1.20, 0.20 ≦ x ≦ 0.28, 0.025 ≦ y ≦ 0.05, 0 ≦ z ≦ 0.05, M is at least one element selected from Mg, Ca, Ba, Sr, V, Fe, Cr, Co, Cu, Zr, Nb, Mo, and W) It consists of cubic lithium manganese nickel titanium composite oxide particles having a spinel structure,
The volume average particle size determined from the volume integrated value measured with a laser diffraction / scattering particle size analyzer is 2 μm to 8 μm,
When the number of particles in each particle size is accumulated from the smaller particle size side, the particle size at which the accumulated volume is 10% of the total volume of all particles is d10, and the particle size at 90% is also d90. [(D90-d10) / volume average particle diameter] indicating the spread of the distribution is 0.70 or less,
A hollow structure composed of a hollow portion inside the particle and an outer shell portion outside the hollow portion,
The cross section of the lithium manganese nickel titanium composite oxide particles is observed with an SEM, and the distance between the outer and inner circumferences of the outer shell portion measured at three or more arbitrary positions is the shortest. The average thickness of the outer shell part for each particle is determined from the distance between the points, and the distance between any two points on the outer periphery of the lithium manganese nickel titanium composite oxide particle that maximizes the distance is The particle diameter of the lithium manganese nickel titanium composite oxide particles, and by dividing the average thickness of the outer shell portion by the particle size of the lithium manganese nickel titanium composite oxide particles, the ratio of the thickness of the outer shell portion for each particle Further, the above-mentioned Lithium obtained by averaging the ratio of the thickness of the outer shell portion for each particle obtained for 10 or more lithium manganese nickel titanium composite oxide particles The ratio of the thickness of the outer shell portion to the particle size of the manganese-nickel-titanium composite oxide particles is 5% to 35%, the positive electrode active material for a non-aqueous electrolyte secondary battery. Specific surface area measured by the BET method by nitrogen gas adsorption is 0.5m ² /g~3.0m ² / g, the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1.   A non-aqueous electrolyte comprising a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, wherein the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 is used as a positive electrode material of the positive electrode. Secondary battery.