TW201519498A - Nickel-manganese complex oxide and method for producing the same, lithium-nickel-manganese complex oxide and lithium secondary battery - Google Patents

Abstract

The invention provides a nickel-manganese complex oxide in which a producing process is simple and a dispersibility of a metal element is high, and a method for producing the same, and a usage of the same. The invention is a nickel-manganese complex oxide which is characterized as that a chemical composition formula is represented by (Ni(0.25+[alpha])-xM1xMn(0.75-[alpha])-yM2y)3O4 (wherein, M1 and M2 respectively represents one selected from Mg, Al, Ti, V, Cr, Fe, Co, Cu, Zn and Zr, 0 ≤ x ≤ 0.1, 0 ≤ y ≤ 0.25, and -0.05 ≤ [alpha] ≤ 0.05) and a crystalline structure is a tetragonal spinel structure, a method for producing the same, and a usage of the same.

Description

Nickel-manganese composite oxide, method for producing the same, and use thereof

The present invention relates to a nickel-manganese composite oxide, a method for producing the same, and a use thereof, and more particularly to a nickel-manganese composite suitable as a precursor of a lithium-nickel-manganese composite oxide. An oxide, a lithium-nickel-manganese composite oxide obtained by using the nickel-manganese composite oxide, and a lithium secondary battery using the lithium-nickel-manganese composite oxide as a positive electrode.

A lithium-nickel-manganese composite oxide having a spinel structure is attracting attention as a positive electrode active material for a lithium battery of a 5V grade. The lithium-nickel-manganese composite oxide is a superlattice structure in which nickel and manganese are regularly arranged. The method for producing the substance includes a solid phase reaction method in which a nickel source and a manganese source are mixed and calcined, or a composite carbonate containing a nickel and manganese, a composite hydroxide, a complex oxygen (hydrogen oxide), and a composite oxide. A method of manufacturing a precursor. Since the composite compound containing nickel and manganese is more uniformly distributed, it is a preferable precursor in the case where the regular arrangement of nickel and manganese is premised.

For example, a nickel-manganese composite oxide obtained by calcining a nickel-manganese composite hydroxide obtained by a coprecipitation method is disclosed as a lithium-nickel-manganese composite oxidation. Precursor of the object (Patent Document 1).

Further, a nickel-manganese composite oxide obtained by spray-drying and calcining a nickel salt and a manganese salt is used as a precursor of a lithium-nickel-manganese composite oxide (Patent Document 2).

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2012-216547

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2004-303710

The manganese-nickel composite oxide particle powder of Patent Document 1 is a cubic spinel-type composite oxide having a space group of Fd-3m. The manganese-nickel composite oxide powder is obtained by neutralizing an aqueous solution of a manganese salt with an excess amount of an aqueous alkali solution to prepare an aqueous suspension containing manganese hydroxide, and performing an oxidation reaction to obtain four After the primary reaction of the trimanganese oxide particles is carried out, a manganese raw material and a nickel raw material are added to the reaction solution after the primary reaction, and then a secondary reaction for performing an oxidation reaction is carried out, followed by calcination in an oxidizing atmosphere. As described above, since the manufacturing steps are very complicated, it is presumed that the manufacturing cost is high.

Further, the MnNi composite oxide of Patent Document 2 is formed by adding a Mn salt and a Ni salt to a solvent so as to have a predetermined atomic ratio of Mn to Ni, and pulverizing and mixing until the average particle diameter is 0.1. Steps of spray-drying the obtained slurry to obtain a mixture of a Mn salt and a Ni salt below μm And a step of calcining the mixture at 800 ° C to 1000 ° C. As in Patent Document 1, it is estimated that the manufacturing cost is improved.

As described above, the nickel-manganese composite oxide in which nickel and manganese are dispersed at an atomic level is suitable as a precursor of a lithium-nickel-manganese composite oxide which is a positive electrode, but there is still a problem that the production process is complicated.

In the present invention, these problems can be solved, and a nickel-manganese composite oxide in which nickel and manganese are dispersed can be provided by a general and simple procedure such as coprecipitation, washing, and drying. Further, an object of the invention is to provide a lithium-nickel-manganese composite oxide obtained by using the nickel-manganese composite oxide and a lithium secondary battery using the lithium-nickel-manganese composite oxide as a positive electrode.

The inventors of the present invention have conducted active research on a nickel-manganese composite oxide which is a precursor of a lithium-nickel-manganese composite oxide. As a result, it was found that a tetragonal spinel-type nickel-manganese composite oxide was obtained by controlling a pH value and an oxidation-reduction potential by a series of operations such as general coprecipitation, washing, and drying, and found that The lithium secondary battery in which a lithium-nickel-manganese composite oxide having a nickel-manganese composite oxide having a high dispersibility of a metal element as a precursor is used as a positive electrode has high performance, and has completed the present invention. That is, the present invention is characterized in that the chemical composition formula is represented by (Ni _(0.25+α)-x M1 _x Mn _(0.75-α)-y M2 _y ) ₃ O ₄ (wherein M1 and M2 respectively represent a selected from Mg, One of Al, Ti, V, Cr, Fe, Co, Cu, Zn, and Zr, 0≦x≦0.1, 0≦y≦0.25, and -0.05≦α≦0.05), and the crystal structure is tetragonal A nickel-manganese composite oxide having a spinel structure, a method for producing the same, and a use thereof.

Hereinafter, the present invention will be described in detail.

The chemical composition formula of the nickel-manganese composite oxide of the present invention is represented by (Ni _(0.25+α)-x M1 _x Mn _(0.75-α)-y M2 _y ) ₃ O ₄ (wherein M1 and M2 are respectively selected It is represented by one of Mg, Al, Ti, V, Cr, Fe, Co, Cu, Zn, and Zr, 0≦x≦0.1, 0≦y≦0.25, and -0.05≦α≦0.05).

Ni+M1=0.25±0.05, Mn+M2=0.75±0.05. If these conditions are not met, the valence of ^ions in the form of Ni ²⁺ and Mn ^{4+ will} deviate, and the battery capacity of 5V (Li metal negative electrode reference) will decrease. .

-0.05 ≦α ≦ 0.05. When α is out of this range, the valence of the atomic form such as Ni ²⁺ or Mn ⁴⁺ deviates, and the battery capacity of the vicinity of 5 V (Li metal negative electrode reference) decreases. It is preferably α = 0 (Ni: Mn = 0.25: 0.75 (mole ratio)).

The nickel-manganese composite oxide of the present invention exhibits sufficient effects in the absence of dissimilar metals (x=0 and y=0), but battery performance can be expected by substitution of different elements (M1, M2). In particular, the stability of the charge and discharge cycle is improved or the dissolution inhibition effect of Mn is obtained. However, if the amount of dissimilar metals is too large, the regularity of the regular arrangement of Ni-Mn in the spinel-type sublattice decreases, and the battery capacity in the vicinity of 5 V (Li metal negative electrode reference) decreases, so it must be 0≦x≦0.1, 0. ≦y≦0.25. In order to maintain the regularity of the regular arrangement of Ni-Mn in the spinel-type sublattice or the battery capacity in the vicinity of 5 V (Li metal negative electrode reference), the amount of substitution of the dissimilar element with respect to Ni is preferably small.

Specific chemical compositions of the nickel-manganese composite oxide of the present invention include, for example, (Ni _0.25 Mn _0.75 ) ₃ O ₄ , (Ni _0.25 Mn _0.65 Ti _0.10 ) ₃ O ₄ , (Ni _0.20 Fe _0.05 Mn _0.75 ) ₃ O ₄ , (Ni _0.23 Mg _0.02 Mn _0.75 ) ₃ O ₄ , (Ni _0.23 Zn _0.02 Mn _0.75 ) ₃ O ₄ or the like.

The crystal structure of the nickel-manganese composite oxide of the present invention is a tetragonal spinel type. By having a tetragonal spinel type and having a uniform distribution of elements of Ni and Mn, it is easy to achieve the advantage of regular Ni-Mn arrangement. In addition, both of the lithium-nickel-manganese composite oxides which are raw materials and final products have a spinel structure, and there is a possibility that the reaction between the raw material and the lithium compound proceeds smoothly. Here, the term "tetragonal spinel type" means that the crystal lattice is classified into a tetragonal crystal and the crystal structure is a spinel type, and the space group is I41/amd. When the lattice constant a is 5.7 Å to 5.9 Å and the lattice constant c is 8.8 Å to 9.4 Å, the content of the tetragonal spinel oxide is high and the main phase is the main phase. As a subphase, one or both of a trace amount of oxygen (hydrogen oxyhydroxide) and hydrotalcite type hydroxide are generated. More preferably, the lattice constant a is 5.8 Å to 5.9 Å, and the lattice constant c is 8.8 Å to 9.1 Å. In this case, a crystal phase which is extremely close to a single crystal phase is obtained.

Since the filling property of the positive electrode active material in the electrode affects the energy density, the tap density of the nickel-manganese composite oxide of the present invention is preferably 1.0 g/cm ³ or more, and particularly preferably 1.5 g/ More preferably, it is cm ³ or more, and particularly preferably 2.0 g/cm ³ or more. When the knocking degree is 1.0 g/cm ³ or more, the filling property of the lithium-nickel-manganese composite oxide obtained by using the nickel-manganese composite oxide of the present invention as a raw material is easily improved.

Since the theoretical average valence of the nickel-manganese composite oxide of the present invention is 2.7, the average valence of Ni, Mn, M1 and M2 in the chemical composition formula is preferably from 2.5 to 2.9, particularly preferably from 2.6 to 2.7. Here, the average valence is determined by the iodine titration method.

In order to be suitable for easily forming the particle diameter of the electrode, the nickel-manganese complex of the present invention The average particle diameter of the combined oxide is preferably from 5 μm to 20 μm, particularly preferably from 5 μm to 10 μm. In addition, the average particle diameter refers to the average particle diameter of the secondary particles in which the primary particles are aggregated, that is, the so-called aggregated particle diameter.

The present invention is a nickel - manganese composite oxide of the specific surface area is not particularly limited, but in order to readily obtain a high packing property, is preferably 70m ² / g or less, and particularly preferably 50m ² / g or less, and particularly preferably 30m ² / Below g, the optimum is 10 m ² /g or less. Generally, the filling property is related to the specific surface area, and therefore, a low specific surface area is easy to obtain a highly filled powder.

The particle size distribution of the nickel-manganese composite oxide of the present invention is not particularly limited, and examples thereof include a monodisperse particle size distribution and a bimodal particle size distribution. In the case of monodisperse, that is, a particle size distribution having a distribution of a single peak, the particle diameter is also uniform when the positive electrode is formed, so that the charge and discharge reaction becomes more uniform.

Regarding the nickel-manganese composite oxide of the present invention, the chemical composition formula is (Ni _(0.25+α)-x M1 _x Mn _(0.75-α)-y M2 _y ) ₃ O ₄ (wherein M1 and M2 respectively Indicates one selected from the group consisting of Mg, Al, Ti, V, Cr, Fe, Co, Cu, Zn, and Zr, represented by 0≦x≦0.1, 0≦y≦0.25, and -0.05≦α≦0.05). However, as long as the effect is not impeded, in addition to those contained in the chemical composition formula, for example, an alkali metal such as Mg, Ca, Na, or K or an alkaline earth metal may be contained. It is preferable that the amount of Mg or the like is as small as possible, but the effect of improving the cycle performance may be obtained by including an appropriate amount. However, if it exceeds 1000 ppm, there is a problem that the capacity of the 4V potential flat portion increases and the energy density is impaired. It is 1000 ppm or less, preferably 20 ppm to 1000 ppm, particularly preferably 200 ppm to 1000 ppm, and particularly preferably 300 ppm to 600 ppm.

Next, a method for producing the nickel-manganese composite oxide of the present invention will be described.

The nickel-manganese composite oxide of the present invention can be produced by containing nickel and manganese or nickel, manganese, and selected from the group consisting of Mg, Al, Ti, V, Cr, Fe, Co, Cu, Zn, and Zr. One or more aqueous metal salt solutions, an aqueous caustic soda solution, and an aerobic gas as an oxidizing agent are mixed at a pH of 7 or more and less than 8.5 and an oxidation-reduction potential of -0.1 V to 0.2 V to obtain a mixed aqueous solution. A nickel-manganese composite oxide is precipitated in the mixed aqueous solution.

The metal salt aqueous solution contains at least nickel and manganese, and may further contain one or more metals selected from the group consisting of Mg, Al, Ti, V, Cr, Fe, Co, Cu, Zn, and Zr. The metal salt aqueous solution may be an aqueous solution obtained by dissolving a sulfate, a chloride, a nitrate, an acetate or the like containing nickel and manganese and another predetermined metal, or an organic acid such as sulfuric acid, hydrochloric acid or nitric acid, or an organic acid such as acetic acid. An aqueous solution of nickel and manganese, and other predetermined metals is dissolved in the acid. A preferred aqueous solution of a metal salt can be exemplified by an aqueous solution containing nickel sulfate and manganese sulfate.

In addition, the ratio of nickel, manganese, and other predetermined metals in the metal salt aqueous solution may be a ratio of nickel, manganese, and other predetermined metals to be the intended nickel-manganese composite oxide. The ratio of nickel, manganese, and other predetermined metals in the aqueous metal salt solution is, in terms of molar ratio, Ni+M1:Mn+M2=0.25+α:0.75-α, Ni:M1=(0.25+α)- x: x, Mn: M2 = (0.75 - α) - y: y (M1 and M2 respectively represent one selected from the group consisting of Mg, Al, Ti, V, Cr, Fe, Co, Cu, Zn, and Zr, 0 ≦x≦0.1,0≦y≦0.25, and -0.05≦α≦0.05).

The total concentration (metal concentration) of the total metal such as nickel or manganese in the metal salt aqueous solution is arbitrary, but the metal concentration affects productivity. Therefore, it is preferably 1.0 mol/L or more, and more preferably 2.0 mol/L or more.

The caustic soda aqueous solution is a sodium hydroxide aqueous solution, and for example, a solution obtained by dissolving solid sodium hydroxide in water or a solution obtained by adjusting a concentration of a sodium hydroxide aqueous solution produced by electrolysis of a salt can be used.

The oxidant is an aerobic gas. When the oxidizing agent is not an aerobic gas (for example, sodium persulfate, sodium chlorate or the like), the target tetragonal spinel-type oxide cannot be obtained. The aerobic gas can be exemplified by air, oxygen, or the like. Economically, the best is air. A gas such as air or oxygen is added by foaming using a bubbler or the like.

A mixed aqueous solution is obtained by mixing a metal salt aqueous solution, an aqueous caustic soda solution, and an aerobic gas as an oxidizing agent at a pH of 7 or more and less than 8.5 and an oxidation-reduction potential of -0.1 V to 0.2 V, and is precipitated from the mixed aqueous solution. The nickel-manganese composite oxide of the present invention.

When the pH is 8.5 or more, the oxygen (hydrogen oxy) compound becomes the main phase, and the target oxide cannot be obtained. On the other hand, when the pH is less than 7, the hydrotalcite-type hydroxide becomes a crystal phase as a main phase. The hydrotalcite-type hydroxide is easy to take in an anion such as a sulfate ion which becomes an impurity between the layers. Therefore, in order to more easily obtain a tetragonal spinel-type oxide, the pH is preferably 7.5 or more and less than 8.5, and the pH is preferably 8 or more and less than 8.5 in order to be close to a single crystal phase.

The oxidation-reduction potential also affects the formation phase. If the oxidation-reduction potential is greater than 0.2 V, the by-product formation of oxygen (hydrogen oxide) becomes apparent. On the other hand, if the oxidation is still When the original potential is less than -0.1 V, the by-product formation of the hydrotalcite-type hydroxide becomes conspicuous. In order to be closer to a single crystal phase, it is particularly preferably in the range of -0.1 V to 0.1 V. The redox potential can be controlled by the amount of aerobic gas supplied.

The temperature at the time of mixing the metal salt aqueous solution, the caustic soda aqueous solution, and the oxidizing agent is not particularly limited, but the nickel-manganese composite oxide is more likely to precipitate in order to facilitate the oxidation reaction, and the temperature is preferably 50° C. or higher, and particularly preferably Above 60 ° C, especially preferably from 60 ° C to 70 ° C.

There is a case where the pH value fluctuates by mixing a metal salt aqueous solution, an aqueous caustic soda solution, and an oxidizing agent. In this case, the pH can be suitably controlled by mixing an aqueous alkali solution other than the aqueous solution of caustic soda in the mixed aqueous solution. The mixing of the aqueous alkali solution other than the aqueous solution of caustic soda can be carried out continuously or intermittently. An aqueous alkali solution other than the caustic soda aqueous solution can be exemplified by an aqueous solution of an alkali metal such as potassium hydroxide or lithium hydroxide. Further, the alkali concentration of the aqueous alkali solution can be 1 mol/L or more.

Further, when the nickel-manganese composite oxide of the present invention is produced, a binder may be added. When the wrong agent is allowed to coexist, the solubility of nickel ions increases, and the surface of the particles becomes smooth and the sphericity increases. The result is an advantage of improved knock tightness. The binder is preferably ammonia, an ammonium salt or an amino acid. The ammonia may, for example, be ammonia water or the like. Examples of the ammonium salt include ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium carbonate and the like. Examples of the amino acid include glycine, alanine, asparagine, and bran. Glutamine, lysine, etc. The binder is preferably fed together with an aqueous metal salt solution. In the ammonia or ammonium salt, the concentration of the complexing agent is preferably 0.1 to 2, more preferably 0.5 to 1, in terms of NH ₃ /transition metal molar ratio. In the amino acid, the concentration of the complexing agent is amino acid. The transition metal molar ratio meter is preferably from 0.001 to 0.25, particularly preferably from 0.005 to 0.1.

The production of the nickel-manganese composite oxide of the present invention does not require environmental control and can be carried out under a normal atmospheric environment.

When the nickel-manganese composite oxide is obtained, the mixing time is arbitrary. For example, it can be 3 hours to 48 hours, and further, 6 hours to 24 hours.

In the method for producing a nickel-manganese composite oxide of the present invention, the nickel-manganese composite oxide is precipitated, washed, and dried.

In the washing, impurities adhering to the nickel-manganese composite oxide are removed. The washing method may, for example, be a method in which a nickel-manganese composite oxide is added to water, and the method is washed.

In the drying, the moisture of the nickel-manganese composite oxide is removed. The drying method is, for example, drying the nickel-manganese composite oxide at 110 ° C to 150 ° C for 2 hours to 15 hours.

In the production method of the present invention, the pulverization may be carried out after washing and drying.

In the pulverization, a powder having an average particle diameter suitable for the use is prepared. The pulverization conditions are arbitrary as long as the average particle diameter is required, and for example, pulverization by a method such as wet pulverization or dry pulverization can be exemplified.

The nickel-manganese composite oxide of the present invention has high dispersibility of a metal element and can be used for producing a lithium-nickel-manganese composite oxide.

When the lithium-nickel-manganese composite oxide is produced using the nickel-manganese composite oxide of the present invention as a raw material, the production method preferably includes mixing a nickel-manganese composite oxide with a lithium compound. A mixing step, and a calcining step.

In the mixing step, any of lithium compounds can be used. The lithium compound may be one or more selected from the group consisting of lithium hydroxide, lithium oxide, lithium carbonate, lithium iodide, lithium nitrate, lithium oxalate, and alkyl lithium. The lithium compound is preferably one or more selected from the group consisting of lithium hydroxide, lithium oxide, and lithium carbonate.

In the calcination step, the raw materials are mixed and then calcined to produce a lithium-nickel-manganese composite oxide. Calcination can be carried out in any environment such as air or oxygen at any temperature between 500 ° C and 1000 ° C.

The lithium-nickel-manganese composite oxide obtained in the above manner is used as a positive electrode active material of a lithium secondary battery.

As the negative electrode active material used in the lithium secondary battery of the present invention, metallic lithium and a substance capable of occluding and releasing lithium or lithium ions can be used. For example, metal lithium, lithium/aluminum alloy, lithium/tin alloy, lithium/lead alloy, and a carbon material capable of being electrochemically inserted and desorbed from lithium ions are particularly preferable in terms of safety and battery characteristics. It is possible to electrochemically insert a carbon material that is deprived of lithium ions.

In addition, the electrolyte used in the lithium secondary battery of the present invention is not particularly limited, and for example, an electrolyte in which a lithium salt is dissolved in an organic solvent such as a carbonate, a cyclobutanide, a lactone or an ether can be used. Or a lithium ion conductive solid electrolyte.

In addition, the separator used in the lithium secondary battery of the present invention is not particularly limited, and for example, a fine porous film made of polyethylene or polypropylene can be used.

An example of the configuration of the lithium secondary battery as described above is a configuration in which a mixture with a conductive agent is molded into a pellet shape, and then dried under reduced pressure at 100 ° C to 200 ° C to obtain a molded product. The molded product is used as a positive electrode for a battery. Further, an anode containing a metal lithium foil and an electrolytic solution in which lithium hexafluorophosphate was dissolved in a mixed solvent of ethyl carbonate and diethyl carbonate were used.

Since the nickel-manganese composite oxide of the present invention is extremely close to a single crystal phase, it can be called a precursor having high dispersibility of a metal element. In addition, it has the advantage of simple manufacturing process. A lithium secondary battery using a lithium-nickel-manganese composite oxide containing a nickel-manganese composite oxide of the present invention as a precursor is high in performance.

Fig. 1 is an X-ray diffraction (XRD) pattern of the nickel-manganese composite oxide of Example 1.

2 is an XRD pattern of the nickel-manganese composite oxide of Example 2.

3 is an XRD pattern of a nickel-manganese composite oxide of Example 3.

4 is an XRD pattern of the nickel-manganese composite oxide of Example 4.

Fig. 5 is an XRD pattern of the lithium-nickel-manganese composite oxide of Example 5 (arrows in the figure indicate superlattice peaks).

6 is an XRD pattern of a nickel-manganese composite compound of Comparative Example 1.

7 is an XRD pattern of a nickel-manganese composite compound of Comparative Example 2.

8 is an XRD pattern of a nickel-manganese composite compound of Comparative Example 3.

9 is an XRD pattern of a nickel-manganese composite compound of Comparative Example 4.

Fig. 10 is a scanning electron micrograph of the nickel-manganese composite oxide of Example 1.

Fig. 11 is a scanning electron micrograph of the nickel-manganese composite oxide of Example 2.

Fig. 12 is a scanning electron micrograph of the nickel-manganese composite oxide of Example 3.

Fig. 13 is a scanning electron micrograph of the nickel-manganese composite oxide of Example 4.

Fig. 14 is a particle size distribution curve of the nickel-manganese composite oxide of Example 1.

Fig. 15 is a particle size distribution curve of the nickel-manganese composite oxide of Example 2.

Fig. 16 is a particle size distribution curve of the nickel-manganese composite oxide of Example 3.

Fig. 17 is a particle size distribution curve of the nickel-manganese composite oxide of Example 4.

18 is a charge and discharge curve (two cycles to four cycles) of the lithium-nickel-manganese composite oxide of Example 5.

Fig. 19 is a graph showing the charge and discharge cycle performance of Example 5 (1 cycle to 10 cycles).

[Examples]

Hereinafter, the present invention will be further described in detail by way of examples, but not limited to these examples.

<Measurement of chemical composition>

The composition analysis of the obtained composite oxide (composite compound) was carried out by an inductively coupled plasma method (ICP method). In other words, the obtained composite oxide (composite compound) is dissolved in a mixed solution of hydrochloric acid and hydrogen peroxide to prepare a measurement solution. Use general inductively coupled plasma A luminescence analyzer (trade name: OPTIMA 3000DV, manufactured by PERKIN ELMER), and the obtained measurement solution was measured, whereby the composition of the obtained composite oxide (composite compound) was subjected to analysis.

<Measurement of average valence of metal>

The average valence of metals such as nickel and manganese is determined by iodine titration. 0.3 g of the obtained composite oxide (composite compound) and 3.0 g of potassium iodide were dissolved in 50 ml of a 7N-hydrochloric acid solution, and then 200 ml of a 1 N-NaOH solution was added thereto for neutralization. An aqueous solution of 0.1 N sodium thiosulfate was added to the neutralized sample droplets, and the average valence was calculated from the amount of dropwise addition. In addition, a starch solution is used in the indicator.

<Powder X-ray diffraction measurement>

The powder X-ray diffraction measurement of the sample was carried out using a general X-ray diffraction apparatus (trade name: MXP-3, manufactured by MAC Science). CuKα ray (λ=1.5405Å) is used in the ray source, the measurement mode is step scan, the scanning condition is 0.04° per second, the measurement time is 3 seconds, and the measurement range is set to 2θ, in the range of 5° to 100°. Determination.

<Analysis of Crystal Structure>

In the XRD pattern obtained by the XRD measurement of the above conditions, the structure of the tetragonal spinel crystal phase was refined by the Rietveld method. The lattice constant a and the lattice constant c were obtained by pattern fitting using Rietan-2000, an analytical software. Regarding the oxygen (hydrogen oxyhydroxide) and the hydrotalcite-type hydroxide as the by-product phase, the uncoordinated winding was confirmed in the tetragonal spinel structure of 2θ=19.2°±0.5° and 2θ=11.7°±1.0°, respectively. Shooting peaks, Thereby, the formation of the oxygen (hydrogen oxy) compound and the hydrotalcite type hydroxide was confirmed.

<Measurement of particle size distribution and average particle diameter>

0.5 g of the obtained composite oxide (composite compound) was placed in 50 mL of 0.1 N aqueous ammonia, and ultrasonic irradiation was performed for 10 seconds to prepare a dispersion slurry. This dispersion slurry was placed in a particle size distribution measuring apparatus (trade name: Microtrac HRA, manufactured by Honeywell), and the volume distribution was measured by a laser diffraction method. The particle size distribution and the average particle diameter (μm) were determined from the obtained volume distribution.

<Measurement of Knockness>

2 g of the obtained composite oxide (composite compound) was filled in a 10 mL glass measuring cylinder, and tapped 200 times. The knocking degree (g/cm ³ ) was calculated from the weight and the volume after the tapping.

<Measurement of specific surface area>

Using a flow type specific surface area automatic measuring device (trade name: Flowsorb 3-2305, manufactured by Micrometrics Co., Ltd.), 1.0 g of the obtained composite oxide (composite compound) was 150 in a nitrogen stream. The temperature was pretreated for 1 hour, and then the area of the gettering was measured by the Brunauer-Emmett-Teller single point method (BET 1 point method), and then the weight was divided to determine the specific surface area (m ^{2 ).} /g).

<Battery performance evaluation>

A battery characteristic test as a positive electrode of a lithium-nickel-manganese composite oxide was carried out.

Lithium - nickel - manganese composite oxide and the conductive agent, acetylene black and polytetrafluoroethylene mixture (trade name: TAB-2) weight ratio, ratio of 4: 1 were mixed to 1ton / cm ² The pressure was formed into a pellet on a mesh (manufactured by SUS316), and then dried under reduced pressure at 150 ° C to prepare a positive electrode for a battery. The obtained positive electrode for a battery, a negative electrode containing a metal lithium foil (having a thickness of 0.2 mm), and a lithium hexafluorophosphate dissolved in a mixed solvent of ethyl carbonate and diethyl carbonate at a concentration of 1 mol/dm ³ were used. The electrolyte is used to form a battery. The battery was charged and discharged at room temperature with a constant current between 4.9 V and 3.0 V at a battery voltage. The charge and discharge were performed at a current density of 0.4 mA/cm ² , and the respective specific capacities (mAh/g) were measured.

Example 1

The nickel sulfate and the manganese sulfate are dissolved in pure water to obtain an aqueous solution containing 1.5 mol/L of nickel sulfate and 0.5 mol/L of manganese sulfate, and this is used as a metal salt aqueous solution (the total concentration of the total metal in the metal salt aqueous solution is 2.0 mol/L).

Further, 200 g of pure water was placed in a reaction vessel having an internal volume of 1 L, and then the temperature was raised to 80 ° C and maintained.

This aqueous metal salt solution was added to the reaction vessel at a supply rate of 0.28 g/min. Further, air as an oxidizing agent was bubbled into the reaction vessel at a supply rate of 0.2 L/min. In the case of the metal salt aqueous solution and the air supply, a 2 mol/L sodium hydroxide aqueous solution (caustic sodium aqueous solution) is intermittently added so as to have a pH of 8.4, and a mixed aqueous solution is obtained, and a nickel-manganese composite oxide is precipitated in the mixed aqueous solution. , to obtain a slurry. The oxidation-reduction potential at this time was 0.02V. After the obtained slurry was filtered and washed, the wet cake was dried at 115 ° C for 5 hours to obtain a nickel-manganese composite oxide [(Ni _0.26 Mn _0.74 ) ₃ O ₄ ].

According to the XRD pattern of the obtained nickel-manganese composite oxide, the tetragonal spinel structure is the main phase, and the trace amount of the hydrotalcite-type hydroxide is the subphase.

The measurement results of this nickel-manganese composite oxide are shown in Table 1.

Example 2

A slurry was obtained in the same manner as in Example 1 except that a 2 mol/L aqueous sodium hydroxide solution was intermittently added and a 1 mol/L ammonium sulfate solution was added in an equal amount to the metal salt aqueous solution. The oxidation-reduction potential at this time was 0.10V. The obtained slurry was filtered, washed, and dried to obtain a nickel-manganese composite oxide [(Ni _0.25 Mn _0.75 ) ₃ O ₄ ].

According to the XRD pattern of the obtained nickel-manganese composite oxide, weak diffuse scattering is observed in the vicinity of 2θ=12°, but it can be basically referred to as a single crystal phase of a tetragonal spinel structure.

The measurement results of this nickel-manganese composite oxide are shown in Table 1.

Example 3

A slurry was obtained in the same manner as in Example 2 except that a 0.5 mol/L ammonium sulfate solution was used. The oxidation-reduction potential at this time was 0.06V. The obtained slurry was filtered, washed, and dried to obtain a nickel-manganese composite oxide [(Ni _0.26 Mn _0.74 ) ₃ O ₄ ].

According to the XRD pattern of the obtained nickel-manganese-based oxide, weak diffuse scattering was observed in the vicinity of 2θ=12°, and a weak diffraction peak corresponding to oxygen (hydrogen oxide) was observed in the vicinity of 2θ=19°. It is apparent that the crystallization ratio of the tetragonal spinel structure is higher than that of the other subphases.

The measurement results of this nickel-manganese composite oxide are shown in Table 1.

Example 4

The same procedure as in Example 1 was carried out except that a 2 mol/L sodium hydroxide aqueous solution was intermittently added so as to have a pH of 8.0, and a 3 mol/L ammonium sulfate solution was added in an amount equivalent to 0.38 g/min to the metal salt aqueous solution. Method to obtain a slurry. The oxidation-reduction potential at this time was 0.03V. The obtained slurry was filtered, washed, and dried to obtain a nickel-manganese composite oxide [(Ni _0.24 Mn _0.76 ) ₃ O ₄ ].

According to the XRD pattern of the obtained nickel-manganese composite oxide, although extremely weak diffuse scattering is observed in the vicinity of 2θ=12°, it can be basically referred to as a single crystal phase of a tetragonal spinel structure.

The measurement results of this nickel-manganese composite oxide are shown in Table 1.

Example 5

The nickel-manganese composite oxide obtained in Example 4 was mixed with lithium carbonate, calcined at 900 ° C for 10 hours in an air stream, and then calcined at 700 ° C for 48 hours to synthesize lithium-nickel-manganese composite oxidation. Things. According to the results of the chemical composition analysis, it can be expressed as a composition formula of Li ₂ NiMn ₃ O ₈ . Further, according to the XRD pattern, superlattice peaks corresponding to the regular arrangement of nickel-manganese were clearly observed.

The battery performance evaluation of the lithium-nickel-manganese composite oxide was performed. According to the charge and discharge curve, it was found that the potential flat portion in the vicinity of 4 V corresponding to Mn4+/3+ redox was as small as about 3 mAh/g, and the capacity in the vicinity of 5 V corresponding to Ni4+/3+ redox was not damaged. Further, since the capacity was not observed until 10 cycles, the charge and discharge cycle performance was shown to be good.

Comparative example 1

A slurry was obtained in the same manner as in Example 1 except that the pH was set to 10. The oxidation-reduction potential at this time was 0.43V.

The obtained slurry was filtered, washed, and dried to obtain a nickel-manganese composite compound.

The obtained nickel-manganese composite compound showed a characteristic pattern of oxygen (hydrogen oxide) in its XRD pattern, and no diffraction peak corresponding to the tetragonal spinel type oxide was observed.

The measurement results of the nickel-manganese composite compound are shown in Table 2.

Comparative example 2

A slurry was obtained in the same manner as in Example 1 except that the pH was set to 6. The oxidation-reduction potential at this time was 0.21V.

The obtained slurry was filtered, washed, and dried to obtain a nickel-manganese composite compound.

The obtained nickel-manganese composite compound was found to have a crystal phase in which a hydrotalcite-type hydroxide was used as a main phase in the XRD pattern.

The measurement results of the nickel-manganese composite compound are shown in Table 2.

Comparative example 3

A slurry was obtained in the same manner as in Example 1 except that the oxidizing agent was a 30% aqueous solution of sodium persulfate (supply rate: 0.28 g/min). The oxidation-reduction potential at this time was 0.67V.

The obtained slurry was filtered, washed, and dried to obtain a nickel-manganese composite compound.

The obtained nickel-manganese composite compound has a peak position different from that of the tetragonal spinel type oxide in its XRD pattern, and all of the peak shapes exhibit a broad pattern shape.

The measurement results of the nickel-manganese composite compound are shown in Table 2.

Comparative example 4

A slurry was obtained in the same manner as in Example 1 except that the oxidizing agent was set to 15% hydrogen peroxide water (supply rate: 0.28 g/min). The oxidation-reduction potential at this time was 0.11V.

The obtained slurry is filtered, washed, and dried to obtain nickel-manganese A compound compound.

The obtained nickel-manganese composite compound has a mixed phase of oxygen (hydrogen oxide) as a main phase and a small amount of tetragonal spinel oxide as a subphase in the XRD pattern.

The measurement results of the nickel-manganese composite compound are shown in Table 2.

As shown in Table 2, when a reaction of an aerobic gas having a pH of 6 and 10 is used, and a sodium persulfate or hydrogen peroxide different from an aerobic gas is used as the oxidizing agent, a tetragonal crystal spine having a high purity cannot be obtained. Stone oxide.

[Industrial availability]

The nickel-manganese composite oxide of the present invention can be used as a precursor of a lithium-nickel-manganese composite oxide used for a positive electrode active material of a lithium secondary battery, and can constitute the lithium-nickel-manganese composite. The oxide is used as a high-performance lithium secondary battery for a positive electrode for a battery.

Claims (10)

A nickel-manganese composite oxide characterized by (Ni _(0.25+α)-x M1 _x Mn _(0.75-α)-y M2 _y ) ₃ O ₄ (wherein M1 and M2 respectively Indicates one selected from the group consisting of Mg, Al, Ti, V, Cr, Fe, Co, Cu, Zn, and Zr, 0≦x≦0.1, 0≦y≦0.25, and -0.05≦α≦0.05), and The crystal structure is a tetragonal spinel type structure. The nickel-manganese composite oxide according to claim 1, wherein the space group is I41/amd, the lattice constant a is 5.7 Å to 5.9 Å, and the lattice constant c is 8.8 Å to 9.4 Å. The nickel-manganese composite oxide according to claim 1 or 2, wherein the tetragonal spinel structure is a main phase and comprises oxygen (hydrogen oxide) and hydrotalcite-type hydroxide. Either of the objects, or both, act as a secondary phase. The nickel-manganese composite oxide according to any one of claims 1 to 3, wherein an average valence of Ni, Mn, M1 and M2 is from 2.5 to 2.9. The nickel-manganese composite oxide according to any one of claims 1 to 4, which has an average particle diameter of 5 μm to 20 μm. A method for producing a nickel-manganese composite oxide according to any one of claims 1 to 5, which comprises nickel and manganese or Nickel, manganese, and an aqueous solution of one or more kinds of metal salts selected from the group consisting of Mg, Al, Ti, V, Cr, Fe, Co, Cu, Zn, and Zr, an aqueous solution of caustic soda, and an aerobic gas as an oxidizing agent at a pH value 7 or more and less than 8.5, and an oxidation-reduction potential of -0.1 V to 0.2 V is mixed to obtain a mixed aqueous solution, and the nickel-manganese is obtained. The composite oxide is precipitated in the mixed aqueous solution. The method for producing a nickel-manganese composite oxide according to claim 6, wherein a coupling agent is added. The method for producing a nickel-manganese composite oxide according to claim 7, wherein the crosslinking agent is ammonia, an ammonium salt or an amino acid. A lithium-nickel-manganese composite oxide, which is obtained by mixing a nickel-manganese composite oxide according to any one of claims 1 to 5 with a lithium compound, and performing heat treatment. . A lithium secondary battery characterized by using the lithium-nickel-manganese composite oxide according to claim 9 of the invention as a positive electrode active material.