JP2011003354A - Positive electrode active material, method of manufacturing the same, and nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material capable of suppressing generation of a gas, a method of manufacturing the same, and a nonaqueous electrolyte battery.SOLUTION: A positive electrode 12 has the positive electrode active material. The positive electrode active material has a lithium composite oxide and a coating layer provided on at least a part of the surface of the lithium composite oxide, the lithium composite oxide is one having nickel as a main component, and the coating layer contains heteropolyacid and/or a heteropolyacid compound.

Description

  The present invention relates to a positive electrode active material, a method for producing a positive electrode active material, and a nonaqueous electrolyte battery.

  In recent years, with the widespread use of portable devices such as video cameras and notebook personal computers, the demand for small, high-capacity secondary batteries has increased. Currently used secondary batteries include nickel-cadmium batteries and nickel-hydrogen batteries using an alkaline electrolyte, but the battery voltage is as low as about 1.2 V, and it is difficult to improve the energy density. For this reason, a lithium metal secondary battery using lithium metal having a specific gravity of 0.534, which is the lightest of the solid simple substance, the potential is extremely base, and the current capacity per unit weight is the largest among the metal negative electrode materials. It was done.

  However, in a secondary battery using lithium metal as a negative electrode, dendritic lithium (dendrites) is deposited on the surface of the negative electrode during charging, and this grows by a charge / discharge cycle. The growth of dendrites not only deteriorates the charge / discharge cycle characteristics of the secondary battery, but in the worst case, it breaks through the separator (separator) arranged so that the positive electrode and the negative electrode are not in contact with each other. As a result, there is a problem that an internal short circuit occurs and the battery is destroyed due to thermal runaway.

  Thus, for example, as described in Patent Document 1 below, a secondary battery that repeats charging and discharging by using a carbonaceous material such as coke as a negative electrode and doping and dedoping alkali metal ions has been proposed. As a result, it has been found that the above-described problem of deterioration of the negative electrode due to repeated charge / discharge can be avoided.

JP 62-90863 A

  On the other hand, as a positive electrode active material, a battery with a battery voltage of around 4 V has appeared due to the search and development of an active material exhibiting a high potential, and has attracted attention. As such active materials, inorganic compounds such as transition metal oxides containing alkali metals and transition metal chalcogens are known.

In particular, when the main component is nickel or cobalt such as Li _x NiO ₂ (0 <x ≦ 1.0) or Li _x CoO ₂ (0 <x ≦ 1.0), the lithium transition metal composite oxide has a high potential. The most promising in terms of stability and long life. Among these, the lithium transition metal composite oxide containing nickel as a main component is a positive electrode active material exhibiting a relatively high potential. By using this in a battery, it is expected that the charging current capacity is high and the energy density can be increased.

  However, in a secondary battery using a lithium transition metal composite oxide containing nickel as a main component as a positive electrode active material, gas is likely to be generated inside the battery. For this reason, there has been a problem that the internal pressure of the battery tends to increase. In particular, a battery using a laminate film for the exterior has a problem that the battery easily expands due to gas generation.

  Accordingly, an object of the present invention is to provide a positive electrode active material, a method for producing a positive electrode active material, and a nonaqueous electrolyte battery that can suppress gas generation.

  In order to solve the above-described problem, the first invention includes a lithium composite oxide and a coating layer provided on at least a part of the surface of the lithium composite oxide. The lithium composite oxide is a main component, and the coating layer is a positive electrode active material containing a heteropolyacid and / or a heteropolyacid compound.

  According to a second aspect of the present invention, there is provided a deposition step of depositing a heteropolyacid and / or heteropolyacid compound on a lithium composite oxide containing nickel as a main component, and nickel obtained by depositing a heteropolyacid and / or heteropolyacid compound. And a heat treatment step of heat-treating a lithium composite oxide containing as a main component.

  3rd invention has a positive electrode, a negative electrode, and an electrolyte, a positive electrode has a positive electrode active material, a positive electrode active material is at least one part of the surface of lithium composite oxide and lithium composite oxide. The lithium composite oxide is a lithium composite oxide containing nickel as a main component, and the coating layer includes a heteropolyacid and / or a heteropolyacid compound. It is a battery.

  According to this invention, the surface of the lithium composite oxide containing nickel as a main component is coated with the heteropolyacid and / or the heteropolyacid compound. With this configuration, it is possible to suppress the oxidation activity on the surface of the lithium composite oxide particles mainly composed of nickel in a charged state. Thereby, decomposition | disassembly of the nonaqueous electrolyte etc. in the surface of a positive electrode active material can be suppressed. Further, by depositing the heteropolyacid and / or the heteropolyacid compound, the carbonic acid radicals contained in the lithium composite oxide particles containing nickel as a main component can be reduced.

  According to the present invention, gas generation due to decomposition of a non-aqueous electrolyte component or the like can be suppressed. Moreover, gas generation from the positive electrode active material itself can be suppressed.

It is a perspective view which shows one structural example of the nonaqueous electrolyte battery by embodiment of this invention. It is sectional drawing along the II-II line of the winding electrode body 10 shown in FIG. It is sectional drawing which shows one structural example of the nonaqueous electrolyte battery by embodiment of this invention. FIG. 4 is an enlarged cross-sectional view illustrating a part of a wound electrode body 30 illustrated in FIG. 3.

Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below are specific examples of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. Unless stated to the effect, the present invention is not limited to the embodiment. The description will be given in the following order.
1. First embodiment (positive electrode active material)
2. Second Embodiment (Method for Producing Positive Electrode Active Material)
3. Third Embodiment (First Example of Nonaqueous Electrolyte Battery)
4). Fourth embodiment (second example of nonaqueous electrolyte battery)
5. Fifth embodiment (third example of nonaqueous electrolyte battery)
6). Other embodiment (modification)

1. First embodiment (positive electrode active material)
First, in order to facilitate understanding of the present invention, a technical background related to the positive electrode active material according to the first embodiment of the present invention will be described.

For example, lithium composite oxides mainly composed of nickel, such as lithium nickel oxide (LiNiO ₂ ) and nickel-based lithium composite oxides in which part of nickel of lithium nickelate is replaced with other metals, are used for non-aqueous electrolyte batteries. It can be used as a positive electrode active material. Further, for example, lithium composite oxides containing cobalt as a main component, such as lithium cobalt oxide (LiCoO ₂ ) and cobalt-based lithium composite oxide in which a part of cobalt of lithium cobalt oxide is substituted with other metals, are non-aqueous electrolytes. It can be used as a positive electrode active material for batteries.

  The lithium composite oxide containing nickel as the main component is less resource-intensive and less expensive than cobalt, and has high economic efficiency as compared with the lithium composite oxide containing cobalt as the main component. Further, the lithium composite oxide containing nickel as a main component has an advantage that the capacity is larger than the lithium composite oxide containing cobalt as a main component, and it is expected that the advantage is further increased.

  On the other hand, in a secondary battery using a lithium composite oxide mainly composed of nickel as a positive electrode active material, gas is easily generated inside the battery. As the gas is generated, the internal pressure of the battery rises. In particular, a battery using a laminate film for the exterior has a problem that the battery tends to swell, and it is desired to solve this problem.

  The positive electrode active material according to the first embodiment of the present invention corresponds to the above demand for solving the problem, and is used when a lithium composite oxide mainly composed of nickel is modified and used in a battery. It has the effect of reducing the generated gas.

[Composition of cathode active material]
The structure of the positive electrode active material according to the first embodiment of the present invention will be described. In the positive electrode active material according to the first embodiment of the present invention, a coating layer containing a heteropolyacid and / or a heteropolyacid compound is formed on at least a part of the surface of the lithium composite oxide particles mainly composed of nickel. Is.

[Lium complex oxide particles]
The lithium composite oxide particles are lithium composite oxide particles containing lithium (Li) and nickel (Ni) as constituent elements. This lithium composite oxide contains nickel as a main component. Note that the phrase “containing nickel as a main component” means that the nickel component is contained most in the metal elements (excluding lithium) constituting the lithium composite oxide.

  The lithium composite oxide particles may be primary particles or secondary particles in which a plurality of primary particles are aggregated. This lithium composite oxide contains more nickel component than cobalt component. For example, the average composition is represented by the following (formula 1).

(Formula 1)
Li _a Ni _x Co _y Al _z O ₂
(However, nickel (Ni) is manganese (Mn), chromium (Cr), iron (Fe), vanadium (V) within the range of 0.1 or less of Ni when the total amount of Ni is 1. , Magnesium (Mg), titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In) , Tin (Sn), lanthanum (La), cerium (Ce) can be substituted with one or more metal elements selected from the group consisting of a, x, y, and z, 0.20 ≦ a ≦ 1.40, 0.60 <x <0.90, 0.10 <y <0.40, 0.01 <z <0.20, and x, y There is a relationship of x + y + z = 1 between z and z.)

  Here, in (Formula 1), the range of a is, for example, 0.20 ≦ a ≦ 1.40. When this value is decreased, the layered rock salt structure of the basic crystal structure of the lithium composite oxide is destroyed, so that recharging becomes difficult and the capacity is significantly reduced. When this value increases, lithium diffuses out of the composite oxide particles described above, which hinders control of the basicity of the next processing step, and ultimately promotes gelation during kneading of the positive electrode paste. Causes harmful effects.

  In addition, the lithium composite oxide of (Formula 1) may be made to contain excessive lithium conventionally. That is, a indicating the lithium composition of the lithium composite oxide of (Formula 1) may be greater than 1.2. Here, the value of 1.2 is disclosed as the lithium composition of this type of conventional lithium composite oxide, and the same action and effect in the present application can be obtained by the same crystal structure as in the case of a = 1. (For example, refer to Japanese Patent Application Laid-Open No. 2008-251434, which is a prior application of the present applicant).

  Even if a indicating the lithium composition of the lithium composite oxide of Formula 1 is greater than 1.2, the crystal structure of the lithium composite oxide is the same as when a is 1.2 or less. Moreover, even if a which shows the lithium composition in Formula 1 is larger than 1.2, if it is 1.40 or less, the chemical state of the transition metal constituting the lithium composite oxide in the oxidation-reduction reaction accompanying charge / discharge is: Compared with the case where a is 1.2 or less, there is no significant change.

  The range of x is, for example, 0.60 <x <0.90, more preferably 0.65 <x <0.85, and still more preferably 0.70 <x <0.80. When the value decreases outside this range, the discharge capacity of the positive electrode active material decreases. If the value is increased outside this range, the stability of the crystal structure of the composite oxide particles decreases, which causes a decrease in the capacity of repeated charge / discharge of the positive electrode active material and a decrease in safety.

  The range of y is, for example, 0.10 <y <0.40, preferably 0.15 <y <0.35, and more preferably 0.20 <y <0.30. When the value is smaller than this range, the stability of the crystal structure of the composite oxide particles is lowered, which causes a reduction in the capacity of repeated charge / discharge of the positive electrode active material and a reduction in safety. When the value increases outside this range, the discharge capacity of the positive electrode active material decreases.

  The range of z is, for example, 0.01 <z <0.20, more preferably 0.02 <z <0.15, and further preferably 0.03 <z <0.10. If the value is smaller than the above range, the stability of the crystal structure of the composite oxide particles is lowered, which causes a reduction in the capacity of repeated charge / discharge of the positive electrode active material and a reduction in safety. When the value increases outside this range, the discharge capacity of the positive electrode active material decreases.

  This lithium composite oxide containing nickel as a main component is a lithium composite oxide for a lithium ion secondary battery that can realize a high voltage and high energy density substantially equal to those of a composite oxide containing cobalt as a main component. Since this lithium composite oxide is unstable in resources and has a low content of cobalt, which is an expensive material, it has the advantage of high economic efficiency. Further, this lithium composite oxide has an advantage of a large current capacity as compared with lithium cobalt oxide.

[Coating layer]
The coating layer is formed on at least a part of the surface of the composite acid particle, and includes a heteropolyacid and / or a heteropolyacid compound. A heteropolyacid is a condensate of oxo acids containing two or more central ions. The heteropolyacid or heteropolyacid compound is one in which the heteropolyacid ion has an Anderson structure, a Keggin structure, or a Dawson structure.

  Examples of the polyatom of the heteropolyacid or heteropolyacid compound include Mo, W, Nb, and V. Further, in the heteropolyacid and heteropolyacid compound, a part of the above-mentioned poly atoms is Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Zr, Tc, Rh, Cd, In, Sn, Ta , Re, Tl, and Pb may be substituted.

  Examples of the heteroatoms of the heteropolyacid and heteropolyacid compound include B, Al, Si, P, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, and As. In addition, some of the above heteroatoms are H, Be, B, C, Na, Al, Si, P, S, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge. , As, Se, Zr, Rh, Sn, Sb, Te, I, Re, Pt, Bi, Ce, Th, U, and Np may be substituted.

  Examples of the heteropolyacid include heteropolytungstic acid such as phosphotungstic acid and silicotungstic acid, and heteropolymolybdic acid such as phosphomolybdic acid. Examples of the heteropolyacid compound include heteropolytungstic acid compounds such as sodium silicotungstate, sodium phosphotungstate, and ammonium phosphotungstate. Examples of the heteropolyacid compound include heteropolymolybdate compounds such as sodium phosphomolybdate and ammonium phosphomolybdate.

  Heteropolyacids and heteropolyacid compounds preferably have high acidity. In addition, the heteropolyacid and the heteropolyacid compound are preferably a heteropolytungstic acid, a heteropolytungstic acid compound, a heteropolymolybdic acid compound, and a heteropolymolybdic acid compound from the viewpoint of practical availability and the effect obtained. Further, from the same viewpoint as described above, the hetero atom of the heteropolyacid and the heteropolyacid compound is preferably Si or P.

  When charging the battery, the oxidation effect of the heteropolyacid ion and the oxidation potential and current that synergize with it oxidize the oxidizable component in the electrolyte, forming a coating layer containing heteropolyacid ion as a component. Is done. This coating layer functions to prevent high-level oxidation of organic substances such as an electrolytic solution and to prevent generation of carbon dioxide gas and the like.

That is, this coating layer suppresses gas generation mainly by contributing to the elimination of (Factor 2) out of the following (Factor 1) and (Factor 2), which is generally regarded as a cause of gas generation. It is considered possible.
(Factor 1): Carbonic acid radicals contained in the composite oxide particles generate carbon dioxide gas by the acid component derived from the non-aqueous electrolyte.
(Factor 2): Due to the strong oxidizing power of the positive electrode active material in a charged state, organic components such as a non-aqueous electrolyte are oxidized to generate carbon dioxide gas or carbon monoxide.

  It is based on the following idea that this covering layer mainly eliminates (Factor 2), not (Factor 1). That is, in view of the volumetric size of the heteropolyacid ions, the carbonate radicals exposed and remaining on the surface of the lithium composite oxide particles mainly composed of nickel cannot be effectively replaced. Furthermore, it is difficult for the heteropolyacid ions to diffuse into the near-surface layer bulk of the composite oxide particles, and it is considered extremely difficult to effectively replace the carbonate radical contained in the near-surface layer bulk.

  In addition, this positive electrode active material has also eliminated (Factor 1). That is, this positive electrode active material is obtained by reducing carbonate radicals contained in a lithium composite oxide containing nickel as a main component. Although details of the production method will be described later, for example, this positive electrode active material is obtained by depositing a heteropolyacid and / or a heteropolyacid compound on the surface of a lithium composite oxide particle containing nickel as a main component and performing a heat treatment. It is what

  In the heat treatment, the heteropolyacid ions generated from the heteropolyacid and / or the heteropolyacid compound diffuse to the particle surface to cover the particle surface, and a part of the carbonate radical remaining on the surface of the lithium composite oxide mainly composed of nickel And a substitution reaction. And a part of carbonate radical which the lithium complex oxide which has nickel as a main component has is discharge | released out of the system as a carbon dioxide gas. Thereby, since the carbonate group content of the lithium composite oxide containing nickel as a main component is reduced, gas generation can be suppressed.

[Particle size]
The average particle diameter of the positive electrode active material is preferably 2.0 μm or more and 50 μm or less. When the average particle size is less than 2.0 μm, the positive electrode active material layer is peeled off when the positive electrode active material layer is pressed during the production of the positive electrode. Further, since the surface area of the positive electrode active material is increased, it is necessary to increase the amount of the conductive agent and the binder added, and the energy density per unit weight tends to be reduced. On the other hand, when the average particle diameter exceeds 50 μm, the particles tend to penetrate the separator and cause a short circuit.

〔effect〕
The positive electrode active material according to the first embodiment of the present invention can suppress the oxidation activity on the surface of the composite oxide particles in a charged state when used in a non-aqueous electrolyte battery. Thereby, gas generation by decomposition | disassembly of a nonaqueous electrolyte component etc. can be suppressed.

  In addition, the positive electrode active material according to the first embodiment of the present invention includes carbonic acid contained in lithium composite oxide particles containing nickel as a main component by depositing and heat treating a heteropolyacid and / or heteropolyacid compound. The roots are reduced. Thereby, gas generation from the positive electrode active material itself can be suppressed.

2. Second Embodiment Next, a method for producing a positive electrode active material according to an embodiment of the present invention will be described. In the following description, first, a method for producing lithium composite oxide particles containing nickel as a main component will be described. Next, the heteropolyacid and / or heteropolyacid compound deposition treatment on the lithium composite oxide particles and the heat treatment after the deposition treatment will be sequentially described.

[Method for producing lithium composite oxide particles]
The lithium composite oxide particles containing nickel as a main component can be produced by a known method. For example, the lithium composite oxide particles having the average composition represented by (Formula 1) described in the first embodiment can be produced by a known method.

  Specifically, for example, a nickel compound, a cobalt compound, an aluminum compound, a lithium compound, and a compound of a substitution element as necessary are dissolved in water, and a sodium hydroxide solution is added to the nickel-cobalt while stirring sufficiently. -Make aluminum composite coprecipitated hydroxide.

  Next, a precursor obtained by washing the nickel-cobalt-aluminum composite coprecipitated hydroxide with water and drying is fired. Thus, lithium composite oxide particles containing nickel as a main component can be produced. In addition, you may grind | pulverize the lithium nickelate after baking as needed.

  Examples of nickel compound raw materials include nickel hydroxide, nickel carbonate, nickel nitrate, nickel fluoride, nickel chloride, nickel bromide, nickel iodide, nickel perchlorate, nickel bromate, nickel iodate, nickel oxide, Use inorganic compounds such as nickel peroxide, nickel sulfide, nickel sulfate, nickel hydrogen sulfate, nickel nitride, nickel nitrite, nickel phosphate and nickel thiocyanate, or organic compounds such as nickel oxalate and nickel acetate. One or two or more of these may be used.

  Examples of the raw material of the cobalt compound include cobalt hydroxide, cobalt carbonate, cobalt nitrate, cobalt fluoride, cobalt chloride, cobalt bromide, cobalt iodide, cobalt chlorate, cobalt perchlorate, cobalt bromate, and cobalt iodate. Inorganic compounds such as cobalt oxide, cobalt phosphinate, cobalt sulfide, cobalt hydrogen sulfide, cobalt sulfate, cobalt hydrogen sulfate, cobalt thiocyanate, cobalt nitrite, cobalt phosphate, cobalt dihydrogen phosphate, cobalt hydrogen carbonate, etc. Organic compounds such as cobalt acid and cobalt acetate can be used, and one or more of these may be used.

  Examples of aluminum compound raw materials include inorganic substances such as aluminum hydroxide, aluminum nitrate, aluminum fluoride, aluminum chloride, aluminum bromide, aluminum iodide, aluminum perchlorate, aluminum oxide, aluminum sulfide, aluminum sulfate, and aluminum phosphate. An organic compound such as an aluminum compound or an aluminum oxalate can be used, and one or more of these may be used.

  Examples of lithium compound raw materials include lithium hydroxide, lithium carbonate, lithium nitrate, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium chlorate, lithium perchlorate, lithium bromate, and lithium iodate. Inorganic compounds such as lithium oxide, lithium peroxide, lithium sulfide, lithium hydrogen sulfide, lithium sulfate, lithium hydrogen sulfate, lithium nitride, lithium azide, lithium nitrite, lithium phosphate, lithium dihydrogen phosphate, lithium hydrogen carbonate, Alternatively, an organic compound such as methyl lithium, vinyl lithium, isopropyl lithium, butyl lithium, phenyl lithium, lithium oxalate, or lithium acetate can be used, and one or more of these may be used.

  The lithium composite oxide particles mainly composed of nickel can be used as starting materials that are usually available as positive electrode active materials. In some cases, particles obtained by crushing secondary particles using a ball mill or a crusher can also be used.

[Deposition treatment]
Next, a deposition process for depositing the heteropolyacid and / or heteropolyacid compound is performed on the lithium composite oxide particles mainly composed of nickel. For example, in the deposition treatment, a heteropolyacid and / or a heteropolyacid compound is deposited on secondary particles in which primary particles of a lithium composite oxide containing nickel as a main component are aggregated.

  The deposition process can be performed by the following wet method and dry method.

[Wet method]
Hereinafter, an example of the deposition process by the wet method will be described.
In an example of this wet method, first, a heteropolyacid and / or heteropolyacid compound, which is a deposition component, is dissolved in a solvent such as an inorganic solvent such as water to prepare a solution. Next, this solution is deposited on heated lithium composite oxide particles containing nickel as a main component, so that the solvent is removed in a short time and the deposited components are deposited on the surface of the composite oxide particles. Thus, the deposition process is performed.

  The deposition of the solution in which the deposition component is dissolved can be performed by, for example, a method of spraying the solution onto the dispersed composite oxide particles or a method of dropping and mixing the solution onto the composite oxide particles.

  In one example of this wet process deposition process, the composite oxide particles are heated during the deposition of the solution in which the deposition component is dissolved, so the solvent in which the deposition component is dissolved is removed in a short time, The deposition component can be deposited on the surface of the composite oxide particle. The heating temperature is preferably adjusted so as to be a temperature equal to or higher than the boiling point of the solution in which the deposition component is dissolved.

  In an example of the wet deposition method, the solvent in which the heteropolyacid and / or the heteropolyacid compound is dissolved can be removed in a short time. Therefore, the time when the composite oxide particles are in contact with the solvent contained in the solution can be extremely shortened.

  Normally, when the composite oxide particles are in contact with the solvent, lithium ions in the composite oxide particles are eluted in the solvent. In one example of this wet process deposition treatment, lithium ion elution is suppressed, It is possible to suppress deterioration of the surface of the composite oxide particles and the accompanying decrease in the capacity of the positive electrode active material.

  The deposition amount of the heteropolyacid and / or heteropolyacid compound is preferably 0.01 parts by weight or more and 10.0 parts by weight or less, and 0.02 parts by weight or more and 5.0 parts by weight with respect to 100 parts by weight of the composite oxide particles. The following is more preferable, and 0.03 to 3.0 parts by weight is further preferable. The weight of the heteropoly acid is a value excluding the weight of the bound water that the heteropoly acid has. Similarly, the weight of the heteropolyacid compound is a value excluding the weight of bound water of the heteropolyacid compound.

  If the deposition amount of the heteropolyacid and / or heteropolyacid compound is small outside this range, the effect of suppressing gas generation in the positive electrode active material cannot be obtained. On the other hand, if the amount of deposition increases outside this range, the discharge capacity of the positive electrode active material decreases, which is not preferable.

  In an example of a wet process deposition process, deposition of deposition components can be made uniform. Note that the wet method is not limited to this example. For example, a method in which the composite oxide is immersed in a solution in which the heteropolyacid and / or the heteropolyacid compound is dissolved in a solvent may be used. However, in this method, elution of lithium ions of the composite oxide particles into a high dielectric constant medium such as water used as a solvent is remarkable, and the capacity of the positive electrode active material is reduced. For this reason, the above-mentioned example is preferable in the case of wet deposition.

[Dry method]
Deposition processing of the heteropolyacid and / or heteropolyacid compound by the dry method will be described. For the deposition of the heteropolyacid and / or heteropolyacid compound by the dry method, a known method can be used.

  Specifically, using a dry composite oxide particle and a dry heteropolyacid and / or heteropolyacid compound particle, a method of manually applying the mixture using a mortar, a method using a crusher, or mechanical For example, a method using a high-speed machine with a high shearing force that causes strong adhesion may be used.

[Heating process]
Next, the cathode active material according to the first embodiment can be obtained by baking the composite oxide particles subjected to the deposition treatment by heat treatment. The composite oxide particles after the heat treatment may be adjusted in particle size by light pulverization or classification operation, if necessary.

  In this heat treatment, heteropolyacid ions are generated from the heteropolyacid and / or the heteropolyacid compound. And this heteropoly acid ion diffuses on the surface of the lithium composite oxide particle which has nickel as a main component, and covers the surface. This is considered to contribute to the elimination of (Factor 2).

  Further, the heteropolyacid ions generated in the heat treatment undergo a substitution reaction with a part of the carbonate radical remaining on the surface of the lithium composite oxide particles containing nickel as a main component. Thereby, a part of the carbonate radical existing on the particle surface is released out of the system as carbon dioxide gas, and it can be expected that gas generation is reduced by reducing the carbonate radical content of the positive electrode active material itself. That is, it can be expected to contribute to the elimination of (Factor 1).

[Heat treatment temperature]
In the heating step, the heat treatment temperature is preferably 150 ° C. or higher and 500 ° C. or lower. If the temperature rises outside this optimum temperature range, the thermal stability of the heteropolyacid ion is lowered, making it difficult to obtain the desired effect. On the other hand, if the temperature falls outside this optimum range, the thermal decomposition of the heteropolyacid and / or the heteropolyacid compound or the surface diffusion of the product is inhibited, making it difficult to obtain the desired effect.

[Heat treatment atmosphere]
As an atmospheric condition for the heat treatment, an oxidizing atmosphere usually used for preparing lithium nickelate is preferable.

〔effect〕
In the method for producing a positive electrode active material according to the second embodiment of the present invention, the surface of the lithium composite oxide containing nickel as a main component is deposited with a heteropolyacid and / or a heteropolyacid compound. Thereby, the coating layer containing the heteropolyacid and / or the heteropolyacid compound is formed on the surface of the lithium composite oxide containing nickel as a main component. Thereby, the oxidation activity on the surface of the lithium composite oxide particles containing nickel as a main component in a charged state can be suppressed. Therefore, gas generation due to decomposition of the non-aqueous electrolyte component or the like can be suppressed.

  In addition, in the method for producing a positive electrode active material according to the second embodiment of the present invention, a portion of the carbonate radical remaining on the surface of the positive electrode active material is removed by depositing and heating a heteropolyacid and / or heteropolyacid compound. Reduce. Thereby, gas generation from the positive electrode active material itself can be suppressed.

3. Third Embodiment (First Example of Nonaqueous Electrolyte Battery)
FIG. 1 is a perspective view showing a configuration example of a nonaqueous electrolyte battery according to a third embodiment of the present invention. This nonaqueous electrolyte battery is, for example, a nonaqueous electrolyte secondary battery. This nonaqueous electrolyte battery has a configuration in which a wound electrode body 10 to which a positive electrode lead 11 and a negative electrode lead 12 are attached is housed inside a film-like exterior member 1 and has a flat shape. .

  Each of the positive electrode lead 11 and the negative electrode lead 12 has a strip shape, for example, and is led out from the inside of the exterior member 1 to the outside, for example, in the same direction. The positive electrode lead 11 is made of a metal material such as aluminum (Al), and the negative electrode lead 12 is made of a metal material such as nickel (Ni).

  The exterior member 1 is a laminated film having a structure in which, for example, an insulating layer, a metal layer, and an outermost layer are laminated in this order and bonded together by a lamination process or the like. For example, the exterior member 1 has the insulating layer side as the inner side, and the outer edge portions are in close contact with each other by fusion bonding or an adhesive.

  The insulating layer is made of, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, modified polypropylene, or a copolymer thereof. This is because moisture permeability can be lowered and airtightness is excellent. The metal layer is made of foil-like or plate-like aluminum, stainless steel, nickel, iron, or the like. The outermost layer may be made of, for example, the same resin as the insulating layer, or may be made of nylon or the like. This is because the strength against tearing and piercing can be increased. The exterior member 1 may include a layer other than the insulating layer, the metal layer, and the outermost layer.

  Between the exterior member 1 and the positive electrode lead 11 and the negative electrode lead 12, an adhesion film 2 for improving the adhesion between the positive electrode lead 11 and the negative electrode lead 12 and the inside of the exterior member 1 and preventing intrusion of outside air. Has been inserted. The adhesion film 2 is made of a material having adhesion to the positive electrode lead 11 and the negative electrode lead 12. When the positive electrode lead 11 and the negative electrode lead 12 are made of the above-described metal material, it is preferably made of a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  FIG. 2 is a sectional view taken along line II-II of the spirally wound electrode body 10 shown in FIG. The wound electrode body 10 is obtained by stacking and winding a positive electrode 13 and a negative electrode 14 with a separator 15 and an electrolyte 16, and the outermost peripheral portion is protected by a protective tape 17.

  The positive electrode 13 includes, for example, a positive electrode current collector 13A and a positive electrode active material layer 13B provided on both surfaces of the positive electrode current collector 13A. The positive electrode current collector 13A is made of, for example, a metal foil such as an aluminum foil.

  The positive electrode active material layer 13B includes the positive electrode active material according to the first embodiment of the present invention described above. The positive electrode active material layer 13B further includes a conductive additive such as a carbon material and a binder such as polyvinylidene fluoride or polytetrafluoroethylene.

  For example, similarly to the positive electrode 13, the negative electrode 14 includes a negative electrode current collector 14 </ b> A and a negative electrode active material layer 14 </ b> B provided on both surfaces of the negative electrode current collector 14 </ b> A. The negative electrode current collector 14A is made of, for example, a metal foil such as a copper foil.

  The negative electrode active material layer 14B includes, for example, one or more negative electrode materials capable of occluding and releasing lithium as a negative electrode active material, and a conductive additive as necessary. And may contain a binder.

  Examples of the negative electrode material capable of inserting and extracting lithium include carbon materials such as graphite, non-graphitizable carbon, and graphitizable carbon. Any one of these carbon materials may be used alone, or two or more of them may be mixed and used, or two or more of them having different average particle diameters may be mixed and used.

  Further, examples of the negative electrode material capable of inserting and extracting lithium include a material containing a metal element or a metalloid element capable of forming an alloy with lithium as a constituent element. Specifically, a simple substance, alloy, or compound of a metal element capable of forming an alloy with lithium, or a simple substance, alloy, or compound of a metalloid element capable of forming an alloy with lithium, or one or more of these. The material which has these phases in at least one part is mentioned.

  Examples of such metal elements or metalloid elements include tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc (Zn), antimony (Sb), and bismuth (Bi). , Cadmium (Cd), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y) or hafnium (Hf) Is mentioned. Among them, the group 14 metal element or metalloid element in the long-period periodic table is preferable, and silicon (Si) or tin (Sn) is particularly preferable. This is because silicon (Si) and tin (Sn) have a large ability to occlude and release lithium, and a high energy density can be obtained.

  As an alloy of silicon (Si), for example, as a second constituent element other than silicon (Si), tin (Sn), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), and chromium (Cr). The thing containing 1 type is mentioned. As an alloy of tin (Sn), for example, as a second constituent element other than tin (Sn), silicon (Si), nickel (Ni), copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag), titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), and chromium (Cr). The thing containing 1 type is mentioned.

  Examples of the compound of silicon (Si) or tin (Sn) include those containing oxygen (O) or carbon (C), and in addition to silicon (Si) or tin (Sn), Two constituent elements may be included.

  Any separator may be used as long as it is electrically stable, chemically stable with respect to the positive electrode active material, the negative electrode active material, or the solvent, and has no electrical conductivity. . For example, a polymer nonwoven fabric, a porous film, glass or ceramic fibers in a paper shape can be used, and a plurality of these may be laminated. In particular, a porous polyolefin film is preferably used, and a composite of this with a heat-resistant material made of polyimide, glass, ceramic fibers, or the like may be used.

The electrolyte 16 contains an electrolytic solution and a holding body containing a polymer compound that holds the electrolytic solution, and is in a so-called gel form. The electrolytic solution includes an electrolyte salt and a solvent that dissolves the electrolyte salt. Examples of the electrolyte salt include lithium salts such as LiPF ₆ , LiClO ₄ , LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , or LiAsF ₆ . Any one of the electrolyte salts may be used, or two or more of them may be mixed and used.

  Examples of the solvent include lactone solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone, ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. Carbonate ester solvents such as 1,2-dimethoxyethane, 1-ethoxy-2-methoxyethane, 1,2-diethoxyethane, ether solvents such as tetrahydrofuran or 2-methyltetrahydrofuran, nitrile solvents such as acetonitrile, Nonaqueous solvents such as sulfolane-based solvents, phosphoric acids, phosphate ester solvents, or pyrrolidones are mentioned. Any one type of solvent may be used alone, or two or more types may be mixed and used.

  The solvent preferably contains a compound in which part or all of hydrogen of the cyclic ester or chain ester is fluorinated. As the fluorinated compound, difluoroethylene carbonate (4,5-difluoro-1,3-dioxolan-2-one) is preferably used. Even when the negative electrode 14 containing a compound such as silicon (Si), tin (Sn), or germanium (Ge) is used as the negative electrode active material, the charge / discharge cycle characteristics can be improved. In particular, difluoroethylene carbonate is used. This is because the cycle characteristic improvement effect is excellent.

  The polymer compound may be any one that gels upon absorption of a solvent. For example, a fluorine-based polymer compound such as polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropropylene, polyethylene oxide or polyethylene oxide. And ether-based polymer compounds such as crosslinked products containing polyacrylonitrile, polypropylene oxide, or polymethyl methacrylate as repeating units. Any one of these polymer compounds may be used alone, or two or more thereof may be mixed and used.

In particular, from the viewpoint of redox stability, a fluorine-based polymer compound is desirable, and among them, a copolymer containing vinylidene fluoride and hexafluoropropylene as components is preferable. Furthermore, this copolymer contains monoesters of unsaturated dibasic acids such as monomethylmaleic acid ester, halogenated ethylenes such as ethylene trifluorochloride, cyclic carbonates of unsaturated compounds such as vinylene carbonate, or epoxy group-containing compounds. An acrylic vinyl monomer may be included as a component. This is because higher characteristics can be obtained.

[Method for producing non-aqueous electrolyte battery]
This non-aqueous electrolyte battery can be manufactured, for example, as follows. First, the positive electrode 13 is produced as follows. First, a positive electrode mixture is prepared by mixing the above-described positive electrode active material and a binder, and this positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a positive electrode mixture slurry. Next, this positive electrode mixture slurry is applied to the positive electrode current collector 13A, and the solvent is dried. Then, the positive electrode active material layer 13B is formed by compression molding using a roll press or the like, and the positive electrode 13 is obtained.

  Next, the negative electrode 14 is produced as follows. First, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and this negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a negative electrode mixture slurry. Next, after applying this negative electrode mixture slurry to the negative electrode current collector 14A and drying the solvent, the negative electrode active material layer 14B is formed by compression molding using a roll press or the like, and the negative electrode 14 is obtained.

  A precursor solution containing an electrolytic solution, a polymer compound, and a mixed solvent is applied to each of the positive electrode 13 and the negative electrode 14 obtained above, and the mixed solvent is volatilized to form the electrolyte 16. After that, the positive electrode lead 11 is attached to the end of the positive electrode current collector 13A by welding, and the negative electrode lead 12 is attached to the end of the negative electrode current collector 14A by welding.

  Next, the positive electrode 13 and the negative electrode 14 on which the electrolyte 16 is formed are laminated via a separator 15 to form a laminated body, and then the laminated body is wound in the longitudinal direction, and the protective tape 17 is adhered to the outermost peripheral portion. Thus, the wound electrode body 10 is formed. Finally, for example, the wound electrode body 10 is sandwiched between the exterior members 1 and the outer edge portions of the exterior member 1 are brought into close contact with each other by thermal fusion or the like and sealed. At that time, the adhesion film 2 is inserted between the positive electrode lead 11 and the negative electrode lead 12 and the exterior member 1. Thereby, the nonaqueous electrolyte battery shown in FIGS. 1 and 2 is completed.

  Further, this nonaqueous electrolyte battery may be manufactured as follows. First, the positive electrode 13 and the negative electrode 14 are prepared as described above, and the positive electrode lead 11 and the negative electrode lead 12 are attached to the positive electrode 13 and the negative electrode 14. Next, the positive electrode 13 and the negative electrode 14 are laminated and wound via the separator 15, and the protective tape 17 is adhered to the outermost peripheral portion to form a wound body that is a precursor of the wound electrode body 10. Next, the wound body is sandwiched between the exterior members 1, and the outer peripheral edge except for one side is heat-sealed to form a bag shape, which is stored inside the exterior member 1. Subsequently, an electrolyte composition including an electrolytic solution, a monomer that is a raw material of the polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor as necessary is prepared, and the interior of the exterior member 1 is prepared. Inject.

  After injecting the electrolyte composition, the opening of the exterior member 1 is heat-sealed in a vacuum atmosphere and sealed. Next, heat is applied to polymerize the monomer to obtain a polymer compound, thereby forming a gel electrolyte 16 and assembling the nonaqueous electrolyte battery shown in FIGS.

〔effect〕
According to the third embodiment of the present invention, the positive electrode active material according to the first embodiment described above is used as the positive electrode active material. With this configuration, gas generation of the electrolytic solution can be suppressed, and battery swelling can be suppressed.

4). Fourth embodiment (second example of nonaqueous electrolyte battery)
Next explained is the fourth embodiment of the invention. A nonaqueous electrolyte battery according to a fourth embodiment of the present invention uses an electrolyte instead of the gel electrolyte 16 in the nonaqueous electrolyte battery of the third embodiment. In this case, the electrolytic solution is impregnated in the separator 15. As the electrolytic solution, the same one as in the third embodiment described above can be used.

  The nonaqueous electrolyte battery having such a configuration can be manufactured, for example, as follows. First, the positive electrode 13 and the negative electrode 14 are produced. Next, after the positive electrode lead 11 and the negative electrode lead 12 are attached to the positive electrode 13 and the negative electrode 14, the positive electrode 13 and the negative electrode 14 are laminated and wound via the separator 15, and the protective tape 17 is adhered to the outermost peripheral portion. Thus, a wound electrode body having a configuration in which the electrolyte 16 is omitted in the configuration of the wound electrode body 10 is produced. After sandwiching the wound electrode body between the exterior members 1, the exterior member 1 is sealed by injecting an electrolytic solution.

〔effect〕
In the fourth embodiment of the present invention, the same effect as in the third embodiment described above can be obtained. That is, by using the positive electrode active material according to the first embodiment described above as the positive electrode active material, it is possible to suppress gas generation of the electrolytic solution and to suppress battery swelling.

5. Fifth embodiment (third example of nonaqueous electrolyte battery)
Next, the configuration of a nonaqueous electrolyte battery according to a fifth embodiment of the present invention will be described with reference to FIGS. FIG. 3 shows the configuration of a nonaqueous electrolyte battery according to the fifth embodiment of the present invention. This non-aqueous electrolyte battery is a so-called cylindrical type, in which a strip-shaped positive electrode 31 and a strip-shaped negative electrode 32 are wound through a separator 33 inside a substantially hollow cylindrical battery can 21. An electrode body 30 is provided. The separator 33 is impregnated with an electrolytic solution that is a liquid electrolyte. The battery can 21 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 21, a pair of insulating plates 22 and 23 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 30.

  A battery lid 24, a safety valve mechanism 25 provided inside the battery lid 24, and a heat sensitive resistance (PTC: Positive Temperature Coefficient) element 26 are caulked through a gasket 27 at the open end of the battery can 21. The inside of the battery can 21 is sealed. The battery lid 24 is made of the same material as the battery can 21, for example. The safety valve mechanism 25 is electrically connected to the battery lid 24 via the heat sensitive resistance element 26. The safety mechanism 25 is configured such that when the internal pressure of the battery exceeds a certain level due to an internal short circuit or heating from the outside, the disk plate 25A is reversed to disconnect the electrical connection between the battery lid 24 and the wound electrode body 30. It has become. When the temperature rises, the heat-sensitive resistor element 26 limits the current by increasing the resistance value, and prevents abnormal heat generation due to a large current. The gasket 27 is made of, for example, an insulating material, and asphalt is applied to the surface.

  The wound electrode body 30 is wound around a center pin 34, for example. A positive electrode lead 35 made of aluminum (Al) or the like is connected to the positive electrode 31 of the spirally wound electrode body 30, and a negative electrode lead 36 made of nickel (Ni) or the like is connected to the negative electrode 32. The positive electrode lead 35 is welded to the safety valve mechanism 25 to be electrically connected to the battery lid 24, and the negative electrode lead 36 is welded to and electrically connected to the battery can 21.

  4 is an enlarged cross-sectional view illustrating a part of the spirally wound electrode body 30 illustrated in FIG. The wound electrode body 30 is obtained by stacking and winding a positive electrode 31 and a negative electrode 32 with a separator 33 interposed therebetween.

  The positive electrode 31 includes, for example, a positive electrode current collector 31A and a positive electrode active material layer 31B provided on both surfaces of the positive electrode current collector 31A. The negative electrode 32 includes, for example, a negative electrode current collector 32A and a negative electrode active material layer 32B provided on both surfaces of the negative electrode current collector 32A. The configurations of the positive electrode current collector 31A, the positive electrode active material layer 31B, the negative electrode current collector 32A, the negative electrode active material layer 32B, the separator 33, and the electrolyte solution are respectively the positive electrode current collector 13A and the positive electrode active material in the third embodiment described above. This is the same as the material layer 13B, the negative electrode current collector 14A, the negative electrode active material layer 14B, the separator 15, and the electrolytic solution.

  Next explained is a method for manufacturing a nonaqueous electrolyte battery according to the fifth embodiment of the invention.

  The positive electrode 31 is produced as follows. The positive electrode active material layer 31B is formed on the positive electrode current collector 31A as described above to obtain the positive electrode 31. First, a positive electrode mixture is prepared by mixing the above-described positive electrode active material and a binder, and this positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a positive electrode mixture slurry. Next, this positive electrode mixture slurry is applied to the positive electrode current collector 13A, and the solvent is dried. Then, the positive electrode active material layer 13B is formed by compression molding using a roll press or the like, and the positive electrode 13 is obtained.

  The negative electrode 32 is produced as follows. First, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and this negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a negative electrode mixture slurry. Next, after applying this negative electrode mixture slurry to the negative electrode current collector 32A and drying the solvent, the negative electrode active material layer 32B is formed by compression molding using a roll press or the like, and the negative electrode 32 is obtained.

  Next, the positive electrode lead 35 is attached to the positive electrode current collector 31A by welding or the like, and the negative electrode lead 36 is attached to the negative electrode current collector 32A by welding or the like. Thereafter, the positive electrode 31 and the negative electrode 32 were wound through the separator 33, and the tip portion of the positive electrode lead 35 was welded to the safety valve mechanism 25, and the tip portion of the negative electrode lead 36 was welded to the battery can 21 and wound. The positive electrode 31 and the negative electrode 32 are sandwiched between a pair of insulating plates 22 and 23 and housed in the battery can 21. After the positive electrode 31 and the negative electrode 32 are accommodated in the battery can 21, the electrolyte is injected into the battery can 21 and impregnated in the separator 33. Thereafter, the battery lid 24, the safety valve mechanism 25, and the heat sensitive resistance element 26 are fixed to the opening end portion of the battery can 21 by caulking through the gasket 27. As described above, the nonaqueous electrolyte battery shown in FIG. 3 is manufactured.

〔effect〕
In the nonaqueous electrolyte battery according to the fifth embodiment of the present invention, by using the positive electrode active material according to the first embodiment, gas generation can be suppressed and damage due to an increase in internal pressure can be prevented.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples. In the following examples and comparative examples, the weight of the heteropolyacid is a value excluding the weight of the bound water of the heteropolyacid. Similarly, the weight of the heteropolyacid compound is a value excluding the weight of bound water of the heteropolyacid compound.

<Example 1>
A positive electrode active material and a nonaqueous electrolyte secondary battery were produced as follows.

[Preparation of positive electrode active material]
First, nickel sulfate, cobalt sulfate, and sodium aluminate were dissolved in water, and a sodium hydroxide solution was added with sufficient stirring. At this time, the nickel-cobalt-aluminum composite coprecipitated hydroxide is prepared so that the molar ratio of nickel (Ni), cobalt (Co), and aluminum (Al) is Ni: Co: Al = 77: 20: 3. Got. The produced coprecipitate was washed with water and dried, and then lithium hydroxide monohydrate was added, and the molar ratio was adjusted to Li: (Ni + Co + Al) = 105: 100 to prepare a precursor.

These precursors are calcined at 700 ° C. for 10 hours in an oxygen stream, cooled to room temperature, pulverized, and lithium composite oxidation mainly composed of nickel represented by the composition formula Li _1.03 Ni _0.77 Co _0.20 Al _0.03 O ₂ Product particles were obtained. In addition, when complex oxide particle | grains were measured by the laser scattering method, the average particle diameter was 13 micrometers.

To 100 parts by weight of the composite oxide particles described above, 1.0 part by weight of ammonium phosphomolybdate [(NH ₄ ) ₃ PO ₄ .12MoO ₃ ] was added and mixed well in a mortar. This mixture was calcined in an oxygen stream at 300 ° C. for 4 hours, cooled to room temperature, then taken out and pulverized to obtain a positive electrode active material.

[Production of non-aqueous electrolyte secondary battery]
A non-aqueous electrolyte secondary battery described below was produced using the produced positive electrode active material.

  First, 85 parts by mass of the obtained positive electrode active material, 5 parts by mass of graphite as a conductive agent, and 10 parts by mass of polyvinylidene fluoride as a binder were mixed to prepare a positive electrode mixture. Next, this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone as a dispersion medium to obtain a positive electrode mixture slurry. This positive electrode mixture slurry was uniformly applied to both sides of a positive electrode current collector made of an aluminum foil having a thickness of 20 μm, dried, and compression molded with a roll press to form a positive electrode active material layer, thereby producing a positive electrode. Subsequently, a positive electrode terminal was attached to the exposed portion of the positive electrode current collector of the positive electrode.

  Next, 90 parts by mass of pulverized graphite powder as a negative electrode active material and 10 parts by mass of polyvinylidene fluoride as a binder are mixed to prepare a negative electrode mixture, which is further dispersed in N-methyl-2 as a dispersion medium. -Dispersed in pyrrolidone to make a negative electrode mixture slurry. Next, the negative electrode mixture slurry is uniformly applied on both sides of a negative electrode current collector made of a copper foil having a thickness of 15 μm, dried, and compression-molded with a roll press to form a negative electrode active material layer. Produced. Subsequently, a negative electrode terminal was attached to the exposed portion of the negative electrode current collector.

  Next, the prepared positive electrode and negative electrode are closely adhered via a separator made of a microporous polyethylene film having a thickness of 25 μm, wound in the longitudinal direction, and a protective tape is attached to the outermost peripheral portion, whereby a wound body is obtained. Produced. Subsequently, this wound body was loaded between exterior materials, and three sides of the exterior material were heat-sealed, and one side was not heat-sealed but had an opening. As the exterior material, a moisture-proof aluminum laminate film in which a 25 μm thick nylon film, a 40 μm thick aluminum foil, and a 30 μm thick polypropylene film were laminated in order from the outermost layer was used.

Subsequently, 1 mol / l of lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt was added to a solvent mixed so that the mass ratio was ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 5: 5. An electrolytic solution prepared by dissolving was prepared. This electrolyte solution was injected from the opening of the exterior material, and the remaining one side of the exterior material was heat-sealed under reduced pressure and sealed to produce a nonaqueous electrolyte secondary battery.

<Example 2>
Instead of 1.0 part by weight of ammonium phosphomolybdate [(NH ₄ ) ₃ PO ₄ .12MoO ₃ ] per 100 parts by weight of the composite oxide particles, ammonium phosphotungstate [(NH ₄ ) ₃ PO ₄ .12 WO ₃ A positive electrode active material was produced in the same manner as in Example 1 except that 1.0 part by weight was mixed. Further, using this positive electrode active material, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1.

<Example 3>
Instead of 1.0 part by weight of ammonium phosphomolybdate [(NH ₄ ) ₃ PO ₄ .12MoO ₃ ] per 100 parts by weight of the composite oxide particles, phosphomolybdic acid [H ₃ (PMo ₁₂ O ₄₀₎ 1.0 A positive electrode active material was produced in the same manner as in Example 1 except that the parts by weight were mixed. Further, using this positive electrode active material, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1.

<Example 4>
Instead of 1.0 part by weight of ammonium phosphomolybdate [(NH ₄ ) ₃ PO ₄ .12MoO ₃ ] per 100 parts by weight of the composite oxide particles, 1.0 part by weight of phosphotungstic acid [H ₃ PW ₁₂ O ₄₀ ] A positive electrode active material was produced in the same manner as in Example 1 except that the parts were mixed. Further, using this positive electrode active material, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1.

<Example 5>
Silicate molybdate [H ₄ (SiMo ₁₂ O ₄₀ ) 1.0 instead of 1.0 part by weight of ammonium phosphomolybdate [(NH ₄ ) ₃ PO ₄ .12MoO ₃ ] per 100 parts by weight of the composite oxide particles. A positive electrode active material was produced in the same manner as in Example 1 except that the parts by weight were mixed. Further, using this positive electrode active material, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1.

<Example 6>
Silicate tungstic acid [H ₄ (SiW ₁₂ O ₄₀ )] instead of 1.0 part by weight of ammonium phosphomolybdate [(NH ₄ ) ₃ PO ₄ .12MoO ₃ ] with respect to 100 parts by weight of the composite oxide particles. A positive electrode active material was produced in the same manner as in Example 1 except that 0 part by weight was mixed. Further, using this positive electrode active material, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1.

<Example 7>
Instead of 1.0 part by weight of ammonium phosphomolybdate [(NH ₄ ) ₃ PO ₄ · 12MoO ₃ ] per 100 parts by weight of the composite oxide particles, ammonium phosphomolybdate [(NH ₄ ) ₃ PO ₄ · 12MoO ₃ A positive electrode active material was produced in the same manner as in Example 1 except that 0.5 part by weight was mixed. Further, using this positive electrode active material, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1.

<Comparative Example 1>
In Example 1, lithium containing nickel represented by the composition formula Li _1.03 Ni _0.77 Co _0.20 Al _0.03 O ₂ before deposition of ammonium phosphomolybdate [(NH ₄ ) ₃ PO ₄ .12MoO ₃ ] The composite oxide particles were used as the positive electrode active material of Comparative Example 1. Further, using this positive electrode active material, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1.

<Comparative Example 2>
In Example 1, a lithium composite mainly composed of nickel represented by the composition formula Li _1.03 Ni _0.77 Co _0.20 Al _0.03 O ₂ before deposition of ammonium phosphomolybdate [(NH ₄ ) ₃ PO ₄ .12MoO ₃ ] The following treatment was performed on the oxide particles to obtain a positive electrode active material of Comparative Example 2. That is, the composite oxide particles were fired in an oxygen stream at 700 ° C. for 4 hours, cooled to room temperature, and then taken out and pulverized to obtain a positive electrode active material of Comparative Example 2. Further, using this positive electrode active material, a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1.

(Evaluation)
Using the produced positive electrode active materials and non-aqueous electrolyte secondary batteries, the following measurements and tests were performed to evaluate the characteristics.

[Measurement of carbonic acid content]
About each produced positive electrode active material, the carbonic acid component content contained in a positive electrode active material was measured by AGK method prescribed | regulated by Japanese Industrial Standard JIS-R-9101.

[High temperature storage test]
The produced nonaqueous electrolyte secondary battery was charged at a constant current of 880 mA at a constant current of 880 mA until the battery voltage reached 4.2 V in a 23 ° C. environment, and then the current value was 1 mA at a constant voltage of 4.2 V. Constant voltage charging was performed until it reached. Thereafter, the fully charged nonaqueous electrolyte secondary battery was stored in an environment of 80 ° C. for 4 days. The amount of change in the thickness of the nonaqueous electrolyte secondary battery at this time was measured as the amount of swelling during high temperature storage.

  Table 1 summarizes the measurement results.

[Evaluation]
Comparison of Examples 1 to 7 and Comparative Examples 1 and 2 revealed the following.
In Examples 1 to 7, the coating layer is formed by applying a heteropolyacid or heteropolyacid compound and performing heat treatment. Thus, it was found that the carbonic acid content of the positive electrode active material was reduced.

  Moreover, in Example 1- Example 7, it turned out that gas generation | occurrence | production is reduced and battery swelling can be suppressed by making a heteropoly acid or a heteropoly acid compound adhere, and performing heat processing.

6). Other embodiment (modification)
The present invention is not limited to the above-described embodiments of the present invention, and various modifications and applications are possible without departing from the spirit of the present invention. For example, the shape of the nonaqueous electrolyte battery is not limited to that described above. For example, a square shape or a coin shape may be used.

  Further, for example, a polymer solid electrolyte composed of an ion conductive polymer material or an inorganic solid electrolyte composed of an ion conductive inorganic material may be used as the electrolyte. Examples of the ion conductive polymer material include polyether, polyester, polyphosphazene, and polysiloxane. Examples of the inorganic solid electrolyte include ion conductive ceramics, ion conductive crystals, and ion conductive glass.

DESCRIPTION OF SYMBOLS 1 ... Exterior member 2 ... Adhesion film 10, 30, 53 ... Winding electrode body 11, 35 ... Positive electrode lead 12, 36 ... Negative electrode lead 13, 31 ... Positive electrode 13A, 31A ... Positive current collector 13B, 31B ... Positive electrode active material layer 14, 32 ... Negative electrode 14A, 32A ... Negative electrode current collector 14B, 32B ... Negative electrode active material layer 15, 33 ... Separator 16 ... Electrolyte 17 ... Protective tape 21 ... Battery can 22,23 ... Insulating plate 24 ... Battery cover 25 ... Safety valve mechanism 25A ... Disk plate 26 ... Heat feeling Resistance element 27 ... Gasket 34 ... Center pin

Claims (10)

Lithium composite oxide;
A coating layer provided on at least a part of the surface of the lithium composite oxide,
The lithium composite oxide is a lithium composite oxide containing nickel as a main component,
The coating layer is a positive electrode active material containing a heteropolyacid and / or a heteropolyacid compound. The positive electrode active material according to claim 1, wherein the lithium composite oxide containing nickel as a main component is a lithium composite oxide having an average composition represented by the formula (1).
(Formula 1)
Li _a Ni _x Co _y Al _z O ₂
(However, nickel (Ni) is manganese (Mn), chromium (Cr), iron (Fe), vanadium (V) within the range of 0.1 or less of Ni when the total amount of Ni is 1. , Magnesium (Mg), titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In) , Tin (Sn), lanthanum (La), cerium (Ce) can be substituted with one or more metal elements selected from the group consisting of a, x, y, and z, 0.20 ≦ a ≦ 1.40, 0.60 <x <0.90, 0.10 <y <0.40, 0.01 <z <0.20, and x, y There is a relationship of x + y + z = 1 between z and z.) The heteropolyacid and / or heteropolyacid compound has a polyatom selected from the following element group (a) or a polyatom selected from the following element group (a), The positive electrode active material according to claim 1, wherein the part is substituted with at least one element selected from the following element group (b).
Element group (a): Mo, W, Nb, V
2. Element group (b): Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Zr, Tc, Rh, Cd, In, Sn, Ta, Re, Tl, Pb Positive electrode active material. The heteropolyacid and / or heteropolyacid compound has a heteroatom selected from the following element group (c) or a heteroatom selected from the following element group (c), and is one of the heteroatoms. The positive electrode active material according to claim 1, wherein the part is substituted with at least one element selected from the following element group (d).
Element group (c): B, Al, Si, P, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge or As
Element group (d): H, Be, B, C, Na, Al, Si, P, S, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Zr, Rh, Sn, Sb, Te, I, Re, Pt, Bi, Ce, Th, U, Np   The positive electrode active material according to claim 1, wherein the heteropolyacid and / or heteropolyacid compound has an Anderson structure, a Keggin structure, or a Dawson structure.   The positive electrode active material according to claim 1, wherein the heteroatom of the heteropolyacid and / or heteropolyacid compound is Si or P. A deposition step of depositing a heteropolyacid and / or heteropolyacid compound on a lithium composite oxide containing nickel as a main component;
A method for producing a positive electrode active material, comprising: a heat treatment step of heat-treating a lithium composite oxide mainly composed of nickel on which the heteropolyacid and / or heteropolyacid compound is deposited. In the above deposition process,
The method for producing a positive electrode active material according to claim 7, wherein 0.01 to 5.0 parts by weight of the heteropolyacid and / or heteropolyacid compound is applied to 100 parts by weight of the lithium composite oxide. In the heat treatment step,
The method for producing a positive electrode active material according to claim 7, wherein the temperature of the heat treatment is 150 ° C. or higher and 500 ° C. or lower. A positive electrode, a negative electrode, and an electrolyte;
The positive electrode has a positive electrode active material,
The positive electrode active material has a lithium composite oxide and a coating layer provided on at least a part of the surface of the lithium composite oxide,
The lithium composite oxide is a lithium composite oxide containing nickel as a main component,
The coating layer is a nonaqueous electrolyte battery containing a heteropolyacid and / or a heteropolyacid compound.

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