JP2015110509A - Nickel-manganese composite oxide, method of producing the same, and application thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nickel-manganese composite oxide which is produced by a simple production process and has high metal element dispersibility, a method of producing the same, and an application thereof.SOLUTION: There are provided: the nickel-manganese composite oxide which is represented by chemical composition formula (NiM1MnM2)O(where M1 and M2 each represent one selected from Mg, Al, Ti, V, Cr, Fe, Co, Cu, Zn, and Zr, and 0≤x≤0.1, 0≤y≤0.25, and -0.05≤α≤0.05 are satisfied) and whose crystal structure is a tetragonal spinel structure; the method of producing the same; and the application thereof.

Description

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

  A spinel-type lithium-nickel-manganese composite oxide has attracted attention as a positive electrode active material for 5V class lithium secondary batteries. The lithium-nickel-manganese composite oxide has a superlattice structure in which nickel and manganese are regularly arranged. The production method of this substance includes a solid phase reaction method in which a nickel source and a manganese source are mixed and calcined, and a composite carbonate, composite hydroxide, composite oxyhydroxide, composite oxide containing nickel and manganese as a precursor. There is a manufacturing method. The composite compound containing nickel and manganese is a preferable precursor when the ordered arrangement of nickel and manganese is premised because the metal is more uniformly distributed.

  For example, it is disclosed that a nickel-manganese composite oxide obtained by firing a nickel-manganese composite hydroxide obtained by a coprecipitation method is used as a precursor of a lithium-nickel-manganese composite oxide (Patent Literature). 1).

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

JP 2012-216547 A JP 2004-303710 A

  The manganese nickel composite oxide particle powder of Patent Document 1 is a cubic spinel composite oxide having a space group of Fd-3m. The manganese nickel composite oxide powder is neutralized with an aqueous manganese salt solution using an excess amount of an alkaline aqueous solution to form an aqueous suspension containing manganese hydroxide, and an oxidation reaction is performed to obtain trimanganese tetraoxide core particles. The obtained primary reaction is performed, and after adding the manganese raw material and the nickel raw material to the reaction solution after the primary reaction, a secondary reaction is performed in which an oxidation reaction is performed, followed by firing in an oxidizing atmosphere. As described above, since the manufacturing process is very complicated, it is estimated that the manufacturing cost is expensive.

  In addition, the MnNi composite oxide of Patent Document 2 is charged with a Mn salt and a Ni salt so as to have a predetermined atomic ratio of Mn and Ni, and pulverized and mixed until the average particle size becomes 0.1 μm or less. The obtained slurry is spray-dried to obtain a mixture of Mn salt and Ni salt, and the mixture is fired at 800 to 1000 ° C. It is estimated that the manufacturing cost increases as in the case of Patent Document 1.

  Thus, although the nickel-manganese composite oxide in which nickel and manganese are dispersed at the atomic level is suitable as a precursor of the lithium-nickel-manganese composite oxide as the positive electrode, the production process is not limited. It has the problem of being complicated.

  The present invention solves these problems and can provide a nickel-manganese composite oxide in which nickel and manganese are dispersed by a general and simple process such as coprecipitation, washing and drying. Also provided are a lithium-nickel-manganese composite oxide obtained using the nickel-manganese composite oxide, and a lithium secondary battery using the lithium-nickel-manganese composite oxide as a positive electrode. For the purpose.

The present inventors have intensively studied a nickel-manganese composite oxide which is a precursor of a lithium-nickel-manganese composite oxide. As a result, it has been found that a tetragonal spinel nickel-manganese composite oxide can be obtained by controlling the pH and oxidation-reduction potential through a series of operations such as general coprecipitation, washing, and drying. A lithium secondary battery using a lithium-nickel-manganese composite oxide having a highly dispersible nickel-manganese composite oxide as a precursor as a positive electrode is found to have high performance, and the present invention is completed. It came to. That is, in 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 (where M1 and M2 are Mg, Al, Ti, respectively) Represents one selected from V, Cr, Fe, Co, Cu, Zn and Zr, 0 ≦ x ≦ 0.1, 0 ≦ y ≦ 0.25, −0.05 ≦ α ≦ 0.05 And a nickel-manganese based composite oxide characterized in that the crystal structure is a tetragonal spinel structure, its production method, and its use.

  Hereinafter, the present invention will be described in detail.

The nickel-manganese composite oxide of the present invention has a chemical composition formula of (Ni _{(0.25 + α) -x} M1 _x Mn _{(0.75-α) -y} M2 _y ) ₃ O ₄ (where M1 and M2 are Each represents one selected from Mg, Al, Ti, V, Cr, Fe, Co, Cu, Zn and Zr, 0 ≦ x ≦ 0.1, 0 ≦ y ≦ 0.25, −0.05 ≦ α ≦ 0.05).

Ni + M1 = 0.25 ± 0.05 and Mn + M2 = 0.75 ± 0.05. When these values are deviated, they deviate from the formal valences of Ni ²⁺ and Mn ^{4+ and} are around 5V (based on Li metal negative electrode). Battery capacity decreases.

When −0.05 ≦ α ≦ 0.05 and α is out of this range, the battery capacity in the vicinity of 5 V (based on the Li metal negative electrode) decreases due to deviation from the formal valences of Ni ²⁺ and Mn ⁴⁺ . α = 0 (Ni: Mn = 0.25: 0.75 (molar ratio)) is preferable.

  The nickel-manganese based composite oxide of the present invention exhibits a sufficient effect even when there is no dissimilar metal (x = 0 and y = 0), but the battery performance, particularly by the dissimilar element substitution (M1, M2). An improvement in the stability of the charge / discharge cycle and an effect of suppressing elution of Mn can be expected. However, if there are too many different metals, the degree of ordering of the Ni—Mn ordered arrangement in the spinel sublattice decreases and the battery capacity near 5 V (based on the Li metal negative electrode) decreases. , 0 ≦ y ≦ 0.25 is essential. In order to maintain the degree of order of the Ni—Mn ordered arrangement in the spinel type sublattice and the battery capacity in the vicinity of 5 V (based on the Li metal negative electrode), it is preferable that the amount of substitution of different elements for Ni is small.

The nickel - Specific chemical composition of the manganese-based composite oxide, 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 and the} like.

  The nickel-manganese composite oxide of the present invention has a tetragonal spinel type crystal structure. By being a tetragonal spinel type, there is an advantage that the element distribution of Ni and Mn is made uniform and a Ni—Mn ordered arrangement is easily realized. In addition, since both the raw material and the final product, the lithium-nickel-manganese composite oxide, have a spinel structure, the reaction between the raw material and the lithium compound may proceed smoothly. Here, the tetragonal spinel type means that the crystal lattice is classified as tetragonal, the crystal structure is a spinel type, and the space group is I41 / amd. When the lattice constant a is 5.7 to 5.9 Å and the lattice constant c is 8.8 to 9.4。, the content of the tetragonal spinel oxide is high and is the main phase. As a secondary phase, a trace amount of either or both of oxyhydroxide and hydrotalcite hydroxide is formed. More preferably, the lattice constant a is 5.8 to 5.9 and the lattice constant c is 8.8 to 9.1. In this case, a crystal phase very close to a single crystal phase can be obtained.

The tap density of the nickel-manganese composite oxide of the present invention is preferably 1.0 g / cm ³ or more, because the filling property of the positive electrode active material in the electrode affects the energy density, and is preferably 1.5 g / cm 3. still more preferably ³ or more, and particularly preferably 2.0 g / cm ³ or more. When the tap density is 1.0 g / cm ³ or more, the filling property of the lithium-nickel-manganese composite oxide obtained using the nickel-manganese composite oxide of the present invention as a raw material tends to be high.

  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 2.5 to 2.9. It is preferably 2.6 to 2.7. Here, the average valence is determined by an iodometry method.

  The average particle size of the nickel-manganese composite oxide of the present invention is preferably 5 to 20 μm and more preferably 5 to 10 μm in order to adapt to the particle size at which an electrode can be easily formed. The average particle diameter is an average particle diameter of secondary particles in which primary particles are aggregated, that is, a so-called aggregated particle diameter.

The specific surface area of the nickel-manganese based composite oxide of the present invention is not particularly limited, but is preferably 70 m ² / g or less, and preferably 50 m ² / g or less because high filling properties are easily obtained. Is more preferably 30 m ² / g or less, and most preferably 10 m ² / g or less. In general, since the filling property and the specific surface area have a correlation, a powder having a high filling property is easily obtained with a low specific surface area.

  The particle size distribution of the nickel-manganese composite oxide of the present invention is not particularly limited, and examples thereof include a monodispersed particle size distribution and a bimodal particle size distribution. When the particle size distribution is monodispersed, that is, monomodal, the particle size is uniform even when the positive electrode is used, and the charge / discharge reaction is more uniform.

The nickel-manganese composite oxide of the present invention has a chemical composition formula of (Ni _{(0.25 + α) -x} M1 _x Mn _{(0.75-α) -y} M2 _y ) ₃ O ₄ (where M1 and M2 are Each represents one selected from Mg, Al, Ti, V, Cr, Fe, Co, Cu, Zn and Zr, 0 ≦ x ≦ 0.1, 0 ≦ y ≦ 0.25, −0.05 ≦ α ≦ 0.05), insofar as the effect is not inhibited, apart from those included in the chemical composition formula, for example, alkali metals such as Mg, Ca, Na, K, An alkaline earth metal may be contained. Although these Mg and the like are preferably as small as possible, the effect of improving the cycle performance may be seen by including an appropriate amount, but if it exceeds 1000 ppm, the capacity of the 4V potential flat part increases and the energy density is impaired. Therefore, it is 1000 ppm or less, preferably 20 to 1000 ppm, more preferably 200 to 1000 ppm, and particularly preferably 300 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 is nickel and manganese, or nickel, manganese, and a metal containing one or more selected from Mg, Al, Ti, V, Cr, Fe, Co, Cu, Zn, and Zr. By mixing an aqueous solution of salt, an aqueous solution of caustic soda, and an aerobic gas as an oxidant at a pH of 7 or more and less than 8.5 at an oxidation-reduction potential of -0.1 to 0.2 V to obtain a mixed aqueous solution, and depositing in the mixed aqueous solution Can be manufactured.

  The metal salt aqueous solution contains at least nickel and manganese, and can further contain one or more metals selected from Mg, Al, Ti, V, Cr, Fe, Co, Cu, Zn, and Zr. Examples of metal salt aqueous solutions include nickel, manganese, sulfates, chlorides, nitrates and acetates containing other specified metals, inorganic acids such as sulfuric acid, hydrochloric acid and nitric acid, and organic acids such as acetic acid. Examples thereof include an aqueous solution in which nickel and manganese, and other predetermined metals are dissolved in an acid. An example of a preferable aqueous metal salt solution is an aqueous solution containing nickel sulfate and manganese sulfate.

  Further, the ratio of nickel, manganese, and other predetermined metals in the metal salt aqueous solution may be the ratio of nickel, manganese, and other predetermined metals of the target nickel-manganese composite oxide. The proportions of nickel, manganese, and other predetermined metals in the aqueous metal salt solution are molar ratios of 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 each represent one selected from Mg, Al, Ti, V, Cr, Fe, Co, Cu, Zn, and Zr, and 0 ≦ x ≦ 0.1, 0 ≦ y ≦ 0.25, and −0.05 ≦ α ≦ 0.05.

  Although the total concentration (metal concentration) of all metals such as nickel and manganese in the metal salt aqueous solution is arbitrary, since the metal concentration affects the productivity, 1.0 mol / L or more is preferable, and 2.0 mol / L The above is more preferable.

  The caustic soda aqueous solution is an aqueous sodium hydroxide solution, and for example, an aqueous solution of solid sodium hydroxide or an aqueous solution of sodium hydroxide generated from salt electrolysis can be used.

  The oxidizing agent is an aerobic gas. When the oxidizing agent is not an aerobic gas (for example, sodium persulfate, sodium chlorate, etc.), the desired tetragonal spinel oxide cannot be obtained. Examples of the aerobic gas include air and oxygen. Economically, air is the most preferred. Gases such as air and oxygen are added by bubbling with a bubbler or the like.

  A mixed aqueous solution is obtained by mixing an aqueous solution of metal salt, an aqueous caustic soda solution, and an aerobic gas as an oxidant at a pH of 7 or more and less than 8.5 and an oxidation-reduction potential of -0.1 to 0.2 V. Nickel-manganese composite oxide is deposited.

  When the pH is 8.5 or more, the oxyhydroxide becomes the main phase, and the target oxide cannot be obtained. On the other hand, when the pH is less than 7, the crystal phase is mainly composed of hydrotalcite-type hydroxide. Hydrotalcite-type hydroxides easily take in anions such as sulfate ions that become impurities between layers. For this reason, in order to obtain a tetragonal spinel type oxide more easily, pH 7.5 or more and less than pH 8.5 are preferable, and in order to approach a single crystal phase, pH 8 or more and less than pH 8.5 are more preferable.

  The oxidation-reduction potential also affects the production phase, and when the oxidation-reduction potential exceeds 0.2 V, oxyhydroxide by-product becomes apparent. On the other hand, when the oxidation-reduction potential is less than −0.1 V, a by-product of hydrotalcite-type hydroxide becomes apparent. In order to make it closer to a single crystal phase, a range of −0.1 to 0.1 V is more preferable. The oxidation-reduction potential can be controlled by the supply amount of the aerobic gas.

  The temperature at which the metal salt aqueous solution, the caustic soda aqueous solution and the oxidizing agent are mixed is not particularly limited. However, since the oxidation reaction easily proceeds and the nickel-manganese composite oxide is more easily precipitated, the temperature is 50 ° C. or higher. Preferably, 60 degreeC or more is further more preferable, and 60-70 degreeC is especially preferable.

  The pH may fluctuate due to mixing of an aqueous metal salt solution, an aqueous caustic soda solution and an oxidizing agent. In this case, the pH can be controlled by appropriately mixing an alkaline aqueous solution other than the caustic soda aqueous solution with the mixed aqueous solution. Mixing of the alkaline aqueous solution other than the caustic soda aqueous solution may be performed continuously or intermittently. Examples of the alkaline aqueous solution other than the caustic soda aqueous solution include aqueous solutions of alkali metals such as potassium hydroxide and lithium hydroxide. Moreover, the alkali concentration of aqueous alkali solution can illustrate 1 mol / L or more.

In the production of the nickel-manganese complex oxide of the present invention, a complexing agent can be added. When a complexing agent is present, the solubility of nickel ions increases, the particle surface becomes smooth, and the sphericity is improved. As a result, there is an advantage that the tap density is improved. As the complexing agent, ammonia, ammonium salts or amino acids are preferred. Examples of ammonia include aqueous ammonia, and examples of ammonium salts include ammonium sulfate, ammonium chloride, ammonium nitrate, and ammonium carbonate. Examples of amino acids include glycine, alanine, asparagine, glutamine, and lysine. Is exemplified. The complexing agent is preferably fed together with an aqueous metal salt solution. The concentration of NH ₃ / transition metal in the ammonia or ammonium salt is preferably 0.1 to 2, more preferably 0.5 to 1, and in the case of amino acid, the amino acid / transition metal molar ratio is 0.001. -0.25 is preferable, More preferably, it is 0.005-0.1.

  The production of the nickel-manganese composite oxide of the present invention does not require atmospheric control and can be performed in a normal atmospheric atmosphere.

  If nickel-manganese complex oxide is obtained, mixing time is arbitrary. For example, 3 to 48 hours can be mentioned, and further 6 to 24 hours can be mentioned.

  In the method for producing a nickel-manganese composite oxide of the present invention, washing and drying are performed after the nickel-manganese composite oxide is deposited.

  In the cleaning, impurities adhering to and adsorbing to the nickel-manganese complex oxide are removed. Examples of the cleaning method include a method of adding a nickel-manganese composite oxide to water and cleaning the same.

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

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

  In pulverization, a powder having an average particle size suitable for the application is used. If it becomes a desired average particle diameter, grinding | pulverization conditions are arbitrary, For example, grind | pulverizing by methods, such as wet grinding and dry grinding, can be illustrated.

  The nickel-manganese composite oxide of the present invention has a high dispersibility of metal elements, 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 includes a mixing step of mixing the nickel-manganese composite oxide and the lithium compound. And a firing step.

  In the mixing step, any lithium compound can be used. Examples of the lithium compound include one or more selected from the group consisting of lithium hydroxide, lithium oxide, lithium carbonate, lithium iodide, lithium nitrate, lithium oxalate, and alkyl lithium. As a preferable lithium compound, any one or more selected from the group of lithium hydroxide, lithium oxide and lithium carbonate can be exemplified.

  In the firing step, the raw materials are mixed and then fired to produce a lithium-nickel-manganese composite oxide. Firing can be performed at any temperature of 500 to 1000 ° C. in various atmospheres such as air and oxygen.

  The lithium-nickel-manganese composite oxide thus obtained is used as a positive electrode active material for a lithium secondary battery.

  As the negative electrode active material used in the lithium secondary battery of the present invention, metallic lithium and a material capable of occluding and releasing lithium or lithium ions can be used. Examples include lithium metal, lithium / aluminum alloy, lithium / tin alloy, lithium / lead alloy, and carbon materials that can electrochemically insert and desorb lithium ions. A carbon material that can be desorbed is particularly preferable in terms of safety and battery characteristics.

  The electrolyte used in the lithium secondary battery of the present invention is not particularly limited. For example, an electrolyte obtained by dissolving a lithium salt in an organic solvent such as carbonates, sulfolanes, lactones, and ethers, or lithium ion conductivity The solid electrolyte can be used.

  Moreover, there is no restriction | limiting in particular as a separator used with the lithium secondary battery of this invention, For example, the microporous film made from polyethylene, a polypropylene, etc. can be used.

  As an example of the configuration of the lithium secondary battery as described above, for example, a molded product obtained by molding a mixture with a conductive agent into a pellet and drying under reduced pressure at 100 to 200 ° C. is used as a positive electrode for the battery. Examples include a negative electrode made of a foil, and an electrolytic solution in which lithium hexafluorophosphate is dissolved in a mixed solvent of ethylene carbonate and diethyl carbonate.

  Since the nickel-manganese composite oxide of the present invention is very close to a single crystal phase, it can be said to be a precursor having a high dispersibility of metal elements. In addition, the manufacturing process is simple. A lithium secondary battery using a lithium-nickel-manganese composite oxide having the nickel-manganese composite oxide of the present invention as a precursor as a positive electrode has high performance.

2 is an XRD pattern of a nickel-manganese composite oxide of Example 1. FIG. 3 is an XRD pattern of a nickel-manganese composite oxide of Example 2. FIG. 3 is an XRD pattern of a nickel-manganese composite oxide of Example 3. FIG. 4 is an XRD pattern of a nickel-manganese composite oxide of Example 4. FIG. It is an XRD pattern of the lithium-nickel-manganese composite oxide of Example 5 (the arrow in the figure indicates a superlattice peak). 3 is an XRD pattern of a nickel-manganese composite compound of Comparative Example 1. FIG. 4 is an XRD pattern of a nickel-manganese composite compound of Comparative Example 2. 4 is an XRD pattern of a nickel-manganese composite compound of Comparative Example 3. 4 is an XRD pattern of a nickel-manganese composite compound of Comparative Example 4. 2 is a scanning electron micrograph of the nickel-manganese composite oxide of Example 1. FIG. 3 is a scanning electron micrograph of the nickel-manganese composite oxide of Example 2. FIG. 4 is a scanning electron micrograph of the nickel-manganese composite oxide of Example 3. FIG. 4 is a scanning electron micrograph of the nickel-manganese composite oxide of Example 4. FIG. 2 is a particle size distribution curve of a nickel-manganese composite oxide of Example 1. FIG. 3 is a particle size distribution curve of a nickel-manganese composite oxide of Example 2. FIG. 4 is a particle size distribution curve of a nickel-manganese composite oxide of Example 3. FIG. 4 is a particle size distribution curve of a nickel-manganese composite oxide of Example 4. FIG. It is a charging / discharging curve of the lithium-nickel-manganese complex oxide of Example 5 (2 to 4 cycles). It is a charging / discharging cycle performance figure of Example 5 (1-10 cycles).

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, it is not limited to these.

<Measurement of chemical composition>
The composition analysis of the obtained composite oxide (composite compound) was performed by inductively coupled plasma emission spectrometry (ICP method). That is, the obtained composite oxide (composite compound) was dissolved in a mixed solution of hydrochloric acid and hydrogen peroxide to prepare a measurement solution. The composition of the obtained composite oxide (composite compound) was analyzed by measuring the obtained measurement solution using a general inductively coupled plasma optical emission analyzer (trade name: OPTIMA 3000 DV, manufactured by PERKIN ELMER).

<Measurement of average valence of metal>
The average valence of metals such as nickel and manganese was measured by iodometry. 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 neutralized by adding 200 ml of a 1N NaOH solution. A 0.1 N sodium thiosulfate aqueous solution was added dropwise to the neutralized sample solution, and the average valence was calculated from the amount added. A starch solution was used as an indicator.

<Powder X-ray diffraction measurement>
Using a general X-ray diffractometer (trade name: MXP-3, manufactured by MacScience), powder X-ray diffraction measurement of the sample was performed. A CuKα ray (λ = 1.5405 mm) is used as the radiation source, the measurement mode is step scan, the scan condition is 0.04 ° per second, the measurement time is 3 seconds, and the measurement range is 2 ° to 5 ° to 100 °. Measured in range.

<Analysis of crystal structure>
In the XRD pattern obtained by the XRD measurement under the above conditions, the structure of the tetragonal spinel crystal phase was refined by the Rietveld method. Lattice constants a and c were obtained by pattern fitting using analysis software Rietan-2000. For the oxyhydroxide and hydrotalcite type hydroxides which are by-products, the tetragonal spinel structure of 2θ = 19.2 ° ± 0.5 ° and 2θ = 11.7 ° ± 1.0 °, respectively. Their formation was confirmed by confirming diffraction peaks that could not be assigned.

<Measurement of particle size distribution and average particle size>
0.5 g of the obtained composite oxide (composite compound) was put into 50 mL of 0.1N ammonia water, and ultrasonic dispersion was performed for 10 seconds to obtain a dispersion slurry. The dispersed slurry was put into a particle size distribution measuring apparatus (trade name: Microtrac HRA, manufactured by HONEWELL), and volume distribution was measured by a laser diffraction method. The particle size distribution and average particle size (μm) were determined from the obtained volume distribution.

<Measurement of tap density>
2 g of the obtained composite oxide (composite compound) was filled in a 10 mL glass graduated cylinder and tapped 200 times. The tap density (g / cm ³ ) was calculated from the weight and the volume after tapping.

<Measurement of specific surface area>
Using a flow-type specific surface area automatic measuring device (trade name: Flowsorb 3-2305, manufactured by Micrometrics), 1.0 g of the obtained composite oxide (composite compound) was pretreated in a nitrogen stream at 150 ° C. for 1 hour, After measuring the adsorption / desorption area by the BET one-point method, the specific surface area (m ² / g) was determined by dividing by the weight.

<Battery performance evaluation>
A battery characteristic test as a positive electrode of a lithium-nickel-manganese composite oxide was performed.

A mixture of lithium-nickel-manganese based composite oxide, polytetrafluoroethylene as a conductive agent, and acetylene black (trade name: TAB-2) is mixed at a weight ratio of 4: 1 and 1 ton / cm ² . After forming into a pellet shape on a mesh (made of SUS316) with pressure, it was dried under reduced pressure at 150 ° C. to produce a positive electrode for a battery. Electrolysis in which lithium hexafluorophosphate was dissolved in a mixed solvent of ethylene carbonate and diethyl carbonate at a concentration of 1 mol / dm ^{3 in} the obtained positive electrode for a battery, a negative electrode comprising a metal lithium foil (thickness 0.2 mm), and A battery was constructed using the liquid. Using this battery, the battery voltage was charged and discharged at room temperature between 4.9 V and 3.0 V at a constant current. The battery was charged / discharged at a current density of 0.4 mA / cm ² , and each specific capacity (mAh / g) was measured.

Example 1
Nickel sulfate and manganese sulfate were dissolved in pure water to obtain an aqueous solution containing 1.5 mol / L nickel sulfate and 0.5 mol / L manganese sulfate. The total metal concentration was 2.0 mol / L).

  Further, 200 g of pure water was put into a reaction vessel having an internal volume of 1 L, and then this was heated to 80 ° C. and maintained.

The aqueous metal salt solution was added to the reaction vessel at a supply rate of 0.28 g / min. Further, air was bubbled into the reaction vessel as an oxidizing agent at a supply rate of 0.2 L / min. A 2 mol / L sodium hydroxide aqueous solution (caustic soda aqueous solution) is intermittently added so that the pH is 8.4 when supplying the metal salt aqueous solution and air to obtain a mixed aqueous solution. -Manganese complex oxide was precipitated to obtain a slurry. The oxidation-reduction potential at this time was 0.02V. The obtained slurry was filtered and washed, and then 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 ].

  From the XRD pattern of the obtained nickel-manganese composite oxide, a tetragonal spinel structure was the main phase and a small amount of hydrotalcite hydroxide was the subphase.

  Table 1 shows the measurement results of the nickel-manganese composite oxide.

実施例２
ｐＨが８．０となるように２ｍｏｌ／Ｌの水酸化ナトリウム水溶液を断続的に添加したこと及び１ｍｏｌ／Ｌの硫酸アンモニウム溶液を金属塩水溶液と等量添加したこと以外は実施例１と同様な方法でスラリーを得た。この際の酸化還元電位は０．１０Ｖであった。得られたスラリーをろ過、洗浄した後、乾燥することでニッケル−マンガン系複合酸化物［（Ｎｉ_０．２５Ｍｎ_０．７５）_３Ｏ_４］を得た。

Example 2
The same method as in Example 1 except that a 2 mol / L aqueous sodium hydroxide solution was intermittently added so that the pH was 8.0, and an equivalent amount of a 1 mol / L ammonium sulfate solution was added to the metal salt aqueous solution. A slurry was obtained. The redox 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 ].

  From the XRD pattern of the obtained nickel-manganese composite oxide, it could be said that it was a single crystal phase having a substantially tetragonal spinel structure although weak diffuse scattering was observed in the vicinity of 2θ = 12 °.

  Table 1 shows the measurement results of the nickel-manganese composite oxide.

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 ].

  From the XRD pattern of the obtained nickel-manganese oxide, weak diffuse scattering was observed near 2θ = 12 °, and a weak diffraction peak corresponding to oxyhydroxide was observed near 2θ = 19 °. It is clear that the crystal phase ratio of the tetragonal spinel structure is higher than other subphases.

  Table 1 shows the measurement results of the nickel-manganese composite oxide.

Example 4
Implemented except that 2 mol / L sodium hydroxide aqueous solution was added intermittently so that the pH was 8.0, and 3 mol / L ammonium sulfate solution was added in an amount equal to the metal salt aqueous solution at 0.38 g / min. A slurry was obtained in the same manner as in Example 1. At this time, the oxidation-reduction potential 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 ].

  From the XRD pattern of the obtained nickel-manganese composite oxide, it was said that it was a single crystal phase having a substantially tetragonal spinel structure, although very weak diffuse scattering was observed in the vicinity of 2θ = 12 °.

  Table 1 shows the measurement results of the nickel-manganese composite oxide.

Example 5
The nickel-manganese based composite oxide obtained in Example 4 and lithium carbonate were mixed and fired at 900 ° C. for 10 hours in an air stream, and then fired at 700 ° C. for 48 hours to obtain lithium-nickel-manganese. A composite oxide was synthesized. From the result of chemical composition analysis, it could be expressed as a composition formula Li ₂ NiMn ₃ O ₈ . Further, from the XRD pattern, a superlattice peak corresponding to the nickel-manganese ordered arrangement was clearly observed.

  The battery performance of the lithium-nickel-manganese composite oxide was evaluated. From the charge / discharge curve, it was found that the potential flat portion in the vicinity of 4V corresponding to Mn4 + / 3 + redox was as small as about 3 mAh / g, and the capacity in the vicinity of 5V corresponding to Ni4 + / 3 + redox was not impaired. Moreover, since the capacity | capacitance reduction was not seen to 10 cycles, it was shown that charging / discharging cycling performance is favorable.

Comparative Example 1
A slurry was obtained in the same manner as in Example 1 except that the pH was 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 pattern characteristic of oxyhydroxide in its XRD pattern, and no diffraction peak corresponding to the tetragonal spinel oxide was observed.

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

比較例２
ｐＨを６としたこと以外は実施例１と同様な方法によりスラリーを得た。この際の酸化還元電位は０．２１Ｖであった。

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 be a crystal phase having a hydrotalcite-type hydroxide as the 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% sodium persulfate aqueous solution (feed rate: 0.28 g / min). At this time, the oxidation-reduction potential was 0.67V.

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

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

  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 15% hydrogen peroxide solution (feed rate 0.28 g / min). The oxidation-reduction potential at this time was 0.11V.

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

  In the XRD pattern, the obtained nickel-manganese composite compound became a mixed phase in which oxyhydroxide was the main phase and a small amount of tetragonal spinel oxide was the subphase.

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

  As is clear from Table 2, when a reaction with an aerobic gas at pH 6 and 10 and sodium persulfate different from an aerobic gas and hydrogen peroxide are used as an oxidant, a pure tetragonal spinel type An oxide cannot be obtained.

  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 the lithium-nickel-manganese system. It becomes possible to constitute a high-performance lithium secondary battery using the composite oxide as a battery positive electrode.

Claims (10)

The chemical composition formula is (Ni _{(0.25 + α) -x} M1 _x Mn _{(0.75-α) -y} M2 _y ) ₃ O ₄ (where M1 and M2 are Mg, Al, Ti, V, Cr, Fe, respectively) , Co, Cu, Zn, and Zr, and 0 ≦ x ≦ 0.1, 0 ≦ y ≦ 0.25, and −0.05 ≦ α ≦ 0.05. A nickel-manganese complex oxide characterized in that the crystal structure is a tetragonal spinel structure. The nickel-manganese composite according to claim 1, wherein the space group is I41 / amd, the lattice constant a is 5.7 to 5.9 〜, and the lattice constant c is 8.8 to 9.4 Å. Oxides. The nickel according to claim 1 or 2, wherein the tetragonal spinel structure is a main phase, and the secondary phase contains either or both of oxyhydroxide and hydrotalcite hydroxide. -Manganese complex oxide. The nickel-manganese composite oxide according to any one of claims 1 to 3, wherein the average valences of Ni, Mn, M1, and M2 are 2.5 to 2.9. The nickel-manganese composite oxide according to any one of claims 1 to 4, wherein an average particle diameter is 5 to 20 µm. Nickel and manganese, or nickel, manganese, and metal salt aqueous solution containing at least one selected from 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 The mixture is mixed at a pH of 7 or more and less than 8.5 at an oxidation-reduction potential of -0.1 to 0.2 V to obtain a mixed aqueous solution, which is precipitated in the mixed aqueous solution. A method for producing a nickel-manganese composite oxide according to any one of the above items. The method for producing a nickel-manganese composite oxide according to claim 6, wherein a complexing agent is added. The method for producing a nickel-manganese composite oxide according to claim 7, wherein the complexing agent is ammonia, an ammonium salt or an amino acid. A lithium-nickel-manganese composite oxide obtained by mixing the nickel-manganese composite oxide according to any one of claims 1 to 5 and a lithium compound and heat-treating the mixture. A lithium secondary battery using the lithium-nickel-manganese composite oxide according to claim 9 as a positive electrode active material.

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