JP2009146740A - Manufacturing method of positive active material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a positive active material for a nonaqueous electrolyte secondary battery having high capacity and high charge discharge efficiency. <P>SOLUTION: A positive electrode 2 has a positive active material. The positive active material is obtained by covering composite oxide particles containing lithium (Li) and at least one of nickel (Ni) and cobalt (Co) with ammonium sulfate and ammonium borate, and then heating the composite oxide particles covered with the ammonium sulfate and the ammonium borate in oxidizing atmosphere. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a positive electrode active material, and more particularly, to a method for producing a positive electrode active material containing a composite oxide containing lithium (Li) and at least one of nickel (Ni) and cobalt (Co). .

  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 grows by charge / discharge cycles. This dendrite growth not only deteriorates the charge / discharge cycle characteristics of the secondary battery, but in the worst case, it breaks through a separator (separator) arranged so that the positive electrode and the negative electrode do not contact each other, thereby causing an internal short circuit. As a result, there is a problem that the battery ignites and destroys the battery.

  Therefore, 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.

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. Among _{them, Li X NiO 2 (0 <} x ≦ 1.0), Li X CoO 2 (0 <x ≦ 1.0) lithium transition metal composite oxides mainly comprising nickel or cobalt such as is, a high potential, Most promising in terms of stability and long life. Among these, a positive electrode active material mainly composed of lithium nickelate (LiNiO ₂ ) is a positive electrode active material exhibiting a relatively high potential, and is expected to have a high charge current capacity and an increased energy density.

  Many studies have been made on such positive electrode active materials for the purpose of improving battery characteristics. For example, in the following Patent Document 2, a lithium transition metal composite oxide used as a positive electrode active material contains 100 to 1500 ppm of a first group and / or second group element and 150 to 10,000 ppm of sulfate ions. Thus, it is disclosed that a secondary battery excellent in cycle characteristics when performing high-temperature capacity retention and high-voltage charging is obtained.

  Further, in Patent Document 3 below, by using a lithium transition metal composite oxide mainly composed of nickel and cobalt having a sulfate ion of 0.4 mass% to 2.5 mass% as a positive electrode active material, an initial discharge capacity is obtained. And a secondary battery having high output characteristics at high and low temperatures can be obtained. In Patent Document 2 and Patent Document 3, a sulfate ion component is added in the lithium transition metal composite oxide in the coexistence process of the lithium transition metal composite oxide or after the adjustment.

JP 62-90863 A JP 2002-15739 A JP 2004-273451 A

  At present, a lithium transition metal composite oxide mainly composed of nickel or cobalt, which has a high charge current capacity and is expected to increase the energy density, has been improved, and this lithium transition metal composite oxide is used as a positive electrode active material. There is a demand for further increasing the capacity of the secondary battery.

  Moreover, it is desired to improve the charge / discharge efficiency of the secondary battery by improving the lithium transition metal composite oxide.

  Accordingly, an object of the present invention is to provide a method for producing a positive electrode active material capable of realizing an increase in capacity of a secondary battery and an improvement in charge / discharge efficiency.

In order to solve the above-described problems, the present invention
Depositing ammonium sulfate and ammonium nitrate on composite oxide particles comprising lithium (Li) and at least one of nickel (Ni) and cobalt (Co);
A step of heat-treating the composite oxide particles coated with ammonium sulfate and ammonium nitrate in an oxidizing atmosphere;
It is a manufacturing method of the positive electrode active material characterized by having.

In the present invention, it is preferable that the composite oxide particles have an average composition represented by Chemical Formula 1.
(Chemical formula 1)
Li _a Ni _x Co _y Al _z O ₂
(However, Ni, when the total amount of Ni is 1, within the range of 0.1 or less of Ni, manganese (Mn), chromium (Cr), iron (Fe), vanadium (V), magnesium ( Mg), titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In), tin ( Sn, lanthanum (La), and cerium (Ce) can be substituted with one or more metal elements selected from the group consisting of a), lanthanum (La), and cerium (Ce), where a, x, y, and z are 0.3 ≦ a ≦ 1.05, 0.60 <x <0.90, 0.10 <y <0.40, 0.01 <z <0.20, values of x, y and z (There is a relationship of x + y + z = 1 between them.)

  In this invention, it is preferable that the temperature of heat processing is 500 degreeC or more and 1200 degrees C or less.

  In this invention, in the step of depositing ammonium sulfate and ammonium nitrate, the amount of ammonium sulfate added is preferably in the range of 0.01 wt% to 20 wt% with respect to the composite oxide particles.

  In the present invention, in the step of depositing ammonium sulfate and ammonium nitrate, the amount of ammonium nitrate added is preferably in the range of 0.01 wt% to 100 wt% with respect to the composite oxide particles.

  In this invention, it is preferable that the average particle diameter of a positive electrode active material exists in the range of 2.0 micrometers-50 micrometers.

  In this invention, heat treatment is performed by depositing ammonium sulfate and ammonium nitrate on composite oxide particles containing lithium (Li) and at least one of nickel (Ni) and cobalt (Co). In the process, sulfate ions can be diffused densely and uniformly on the surface of the composite oxide particles, which can increase the capacity of a secondary battery using the composite oxide particles as a positive electrode active material and improve the charge / discharge efficiency. it can.

  According to the present invention, it is possible to manufacture a positive electrode active material capable of realizing an increase in capacity of a secondary battery and an improvement in charge / discharge efficiency.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[Positive electrode active material]
The positive electrode active material according to one embodiment of the present invention is one in which sulfuric acid is deposited on at least a part of the surface of the composite oxide particles. For example, the sulfuric acid is deposited in a state of being chemically bonded to a material on the surface of the composite oxide particle or in the form of sulfate ions.

  The composite oxide particles include lithium (Li) and at least one of nickel (Ni) and cobalt (Co). For example, it is preferable that the average composition is represented by Chemical Formula 1. . By using such composite oxide particles, a discharge capacity can be realized.

(Chemical formula 1)
Li _a Ni _x Co _y Al _z O ₂
(However, Ni, when the total amount of Ni is 1, within the range of 0.1 or less of Ni, manganese (Mn), chromium (Cr), iron (Fe), vanadium (V), magnesium ( Mg), titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In), tin ( Sn, lanthanum (La), and cerium (Ce) can be substituted with one or more metal elements selected from the group consisting of a), lanthanum (La), and cerium (Ce), where a, x, y, and z are 0.3 ≦ a ≦ 1.05, 0.60 <x <0.90, 0.10 <y <0.40, 0.01 <z <0.20, and x + y + z = 1 between x, y and z There is a relationship.)

  Here, in Chemical Formula 1, the range of a is, for example, 0.3 ≦ a ≦ 1.05. When the value is smaller than this range, the layered rock salt structure of the crystal structure that is the source of the function of the positive electrode active material is destroyed, recharging becomes difficult, and the capacity is greatly reduced. If the value is increased outside this range, it diffuses out of the particles, hinders the control of the basicity of the next processing step, and finally causes the harmful effects of promoting gelation during the kneading of the positive electrode paste. It becomes.

  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. If the value decreases outside this range, the discharge capacity will decrease. When the value is increased outside this range, the stability of the crystal structure of the particles is lowered, which causes a reduction in capacity during repeated charge / discharge and a reduction 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 particles is lowered, which causes a reduction in charge / discharge capacity and a reduction in safety. If the value increases outside this range, the discharge capacity 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. When the value is smaller than the above range, the stability of the crystal structure of the particles is lowered, which causes a reduction in capacity during repeated charge and discharge and a reduction in safety. When the value increases outside this range, the discharge capacity decreases.

  The average particle diameter of the positive electrode active material is preferably 2.0 μm to 50 μm. If the average particle size is less than 2.0 μm, it peels off when pressed at the time of forming the positive electrode, and the surface area of the active material increases, so the amount of conductive agent and binder added must be increased, This is because the energy density tends to decrease. On the other hand, if the average particle size exceeds 50 μm, the particles tend to penetrate the separator and cause a short circuit.

[Method for producing positive electrode active material]
Next, a method for producing a positive electrode active material according to an embodiment of the present invention will be described. As the composite oxide particles, those usually available as a positive electrode active material can be used as a starting material. However, in some cases, secondary oxide particles can be used after pulverization using a ball mill or a grinder. .

  Lithium nickelate having a chemical composition as shown in Chemical Formula 1 can be produced by a general known method. Specifically, for example, a nickel compound, a cobalt compound, an aluminum compound, a lithium compound, and the like are dissolved in water, and a sodium hydroxide solution is added while sufficiently stirring to prepare a nickel-cobalt-aluminum composite coprecipitated hydroxide. Thereafter, lithium nickelate can be produced by a method of firing the precursor obtained by washing and drying the nickel-cobalt-aluminum composite coprecipitated hydroxide. If necessary, the fired lithium nickelate may be pulverized.

  Examples of the raw material for the nickel compound 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 cobalt compound raw materials include cobalt hydroxide, cobalt carbonate, cobalt nitrate, cobalt fluoride, cobalt chloride, cobalt bromide, cobalt iodide, cobalt chlorate, cobalt perchlorate, cobalt bromate, and cobalt iodate. , 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 the aluminum compound raw material 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 nickelate produced as described above is a lithium composite oxide for a lithium ion secondary battery that can realize a high voltage and high energy density substantially the same as lithium cobaltate. This composite oxide has the advantage of high economic efficiency because it is unstable in resources and has a low content of cobalt, which is an expensive material.

  Further, this composite oxide has an advantage of a large current capacity as compared with lithium cobalt oxide, and it is desired to further increase the advantage. Furthermore, this composite oxide has a charge current capacity smaller than the discharge current capacity compared to lithium cobaltate, and the so-called irreversible capacity is large. Is desired.

  Therefore, in one embodiment of the present invention, such a composite oxide particle such as lithium nickelate prepared by an ordinary known method is subjected to an additional process to perform surface modification, whereby such a composite is obtained. While increasing the discharge current capacity when using oxide particles as the positive electrode material, the charge / discharge efficiency is improved. Specifically, as the positive electrode active material, for example, lithium, nickel, cobalt, aluminum, and a part of nickel as necessary, a small amount of manganese, chromium, iron, vanadium, magnesium, titanium, zirconium, niobium, molybdenum Secondary particles in which primary particles having layered crystals formed by substitution with one or more elements selected from the group consisting of tungsten, copper, zinc, gallium, indium, tin, lanthanum, and cerium (Composite oxide particles) are subjected to heat treatment by depositing ammonium sulfate and ammonium nitrate. Thereby, the positive electrode active material for nonaqueous electrolyte secondary batteries which can improve a battery characteristic can be obtained.

  Hereinafter, the treatment applied to the composite oxide particles will be described. First, a process is performed in which the composite oxide particles are mixed with ammonium sulfate and ammonium borate to deposit the ammonium sulfate and ammonium borate on the composite oxide particles. The deposition of ammonium sulfate and ammonium borate on the composite oxide particles can be performed, for example, by wet and dry techniques. As the wet method, an ordinary known method can be used. However, in the application of the wet method, for example, when composite oxide particles such as lithium nickelate are immersed in a high dielectric constant medium such as water, lithium ion It is known that elution is remarkable and the capacity of the positive electrode active material to be produced is reduced. Therefore, it is required to perform this immersion state in a short time.

  As the dry method, an ordinary known method can be used. As a known method, specifically, the dry composite oxide particles can be mixed with dry ammonium sulfate and ammonium nitrate particles in a dry manner. As this mixing, it can be used from those using human power using a mortar and those using a crusher to those using a high-speed mechanical system with high shear force that causes mechanical adhesion.

  The addition amount of ammonium sulfate is preferably 0.01% by weight to 20% by weight, more preferably 0.02% by weight to 15% by weight, and still more preferably 0.1% by weight with respect to the weight of the composite oxide particles. 05% by weight to 10% by weight. When the addition amount is smaller than this range, it becomes difficult to obtain an effect of improving the discharge capacity and charge / discharge efficiency of the positive electrode active material mainly containing lithium (Li) and nickel (Ni). On the other hand, when the addition amount is larger than this range, the discharge capacity is reduced, and it becomes difficult to achieve the original object of the present invention.

  The amount of ammonium nitrate added is preferably 0.01% to 100% by weight, more preferably 0.02% to 50% by weight, and still more preferably 0.0% to 100% by weight with respect to the weight of the composite oxide particles. From 05% by weight to 20% by weight. When the addition amount is smaller than this range, it becomes difficult to obtain an effect of improving the discharge capacity and charge / discharge efficiency of the positive electrode active material mainly containing lithium (Li) and nickel (Ni). On the other hand, if the addition amount is larger than this range, the improvement of the effect accompanying the increase in the addition amount is not found, the processing efficiency for the composite oxide particles decreases, the waste resources increase, and the original purpose of the present invention can be achieved. It becomes difficult.

  In addition, when depositing ammonium sulfate and ammonium nitrate, the deposition treatment may be performed using a mixed salt obtained by mixing them. For example, after the deposition treatment of ammonium sulfate is performed, the deposition treatment of ammonium nitrate is performed. You may do it.

  Next, the composite oxide particles subjected to the deposition treatment of ammonium sulfate and ammonium nitrate are fired by heat treatment. In this heat treatment, ammonium sulfate and ammonium nitrate deposited on the composite oxide particles are decomposed, and ammonia and nitrogen oxides are generated and removed by gasification. Finally, sulfate ions remain.

  When this heat treatment is performed at a low temperature, the surface layer of the composite oxide particles is chemically eroded by ammonium sulfate and ammonium sulfate decomposition products, increasing the specific surface area, and using the composite oxide particles. The secondary battery has a reduced discharge capacity and a reduced charge / discharge efficiency. However, even after the development of such a state, by increasing the temperature of the heat treatment, it is found that the specific surface area is reduced and the secondary battery is restored to the discharge capacity and the charge / discharge efficiency.

  The inventors have studied in detail about the recovery effect of such discharge capacity and charge / discharge efficiency, and by selecting the conditions, improvement over the recovery effect compared to the discharge capacity and charge / discharge efficiency before treatment is achieved. It turned out that an effect can be acquired. That is, the heat treatment temperature of the composite oxide particles according to one embodiment of the present invention is preferably 500 ° C. or higher and 1200 ° C. or lower, more preferably 550 ° C. or higher and 1100 ° C. or lower, and further preferably 600 ° C. or higher and 1000 ° C. or lower. is there. If the temperature falls outside this range, as described above, the effect of improving the discharge capacity and efficiency of the positive electrode active material mainly containing lithium (Li) and nickel (Ni) cannot be obtained. On the other hand, when the temperature rises outside this range, the crystal structure of the positive electrode active material mainly containing lithium (Li) and nickel (Ni) is unstable, and the tendency to decrease the discharge capacity is conspicuous. It becomes. Note that the atmospheric condition of the heat treatment in one embodiment of the present invention is preferably an oxidizing atmosphere usually used for preparing lithium nickelate or the like, and is desirably performed in an oxygen atmosphere.

  Here, even when only the ammonium sulfate is added to the composite oxide particles and the deposition treatment is performed, the ammonium sulfate is thermally decomposed in the heat treatment and ammonia is volatilized, thereby promoting the diffusion of sulfate ions on the surface. , Non-uniformity accompanying solid phase / solid phase particle mixing is improved, and sulfate ions can be made more uniform.

  In one embodiment of the present invention, by adding ammonium sulfate and ammonium nitrate to the composite oxide particles and mixing them together, heat treatment is performed, in addition to the effects of only ammonium sulfate as described above, Additional effects associated with the combined use can be obtained.

  It is thought that the additional effect accompanying the combined addition of ammonium nitrate is caused by causing the action effect when only ammonium sulfate is added to proceed more precisely. That is, ammonium nitrate has a melting point of 170 ° C. and a decomposition temperature of 210 ° C. in one atmosphere of air. On the other hand, ammonium sulfate is considered to decompose at around 280 ° C. in air at one atmosphere without obtaining a liquid phase. Although the details of the phase diagram of the coexistence system of ammonium nitrate and ammonium sulfate on the surface of the composite oxide particles are unknown, the ammonium nitrate melts at 170 ° C. as the temperature rises in the heat treatment step of the composite oxide particles, and this liquid phase In addition, ammonium sulfate is dissolved. In connection with this, it is considered that ammonium sulfate causes a reaction in which sulfate ions are diffused more densely and uniformly on the surface of the positive electrode active material by using molten ammonium nitrate as a medium in the heat treatment. As the temperature of the heat treatment increases, ammonium nitrate on the surface of the composite oxide particles is decomposed and volatilized around 210 ° C., which is the decomposition temperature of ammonium nitrate, and is removed from the system. It can be present on the surface of the active material.

  The composite oxide particles after the heat treatment may be adjusted in particle size by light pulverization or classification operation, if necessary. Thus, the positive electrode active material according to one embodiment is obtained. The positive electrode active material according to one embodiment is preferably used as an electrode active material, and is particularly preferably used for a secondary battery electrode.

  Next, a non-aqueous electrolyte secondary battery using the positive electrode active material according to the embodiment of the present invention described above will be described.

(1-1) First Example of Nonaqueous Electrolyte Secondary Battery [Configuration of Nonaqueous Electrolyte Secondary Battery]
FIG. 1 shows a cross-sectional structure of a nonaqueous electrolyte secondary battery using a positive electrode active material manufactured by a method according to an embodiment of the present invention.

  This non-aqueous electrolyte secondary battery is a so-called coin-type battery. The disc-shaped positive electrode 2 accommodated in the outer can 6 and the disc-shaped negative electrode 4 accommodated in the outer cup 5 include: It is laminated via the separator 3. The separator 3 is impregnated with an electrolytic solution that is a liquid electrolyte, and the outer peripheral portions of the outer can 6 and the outer cup 5 are sealed by caulking through a gasket 7. The outer can 6 and the outer cup 5 are made of, for example, a metal such as stainless steel or aluminum (Al).

  The positive electrode 2 includes, for example, a positive electrode current collector 2A and a positive electrode mixture layer 2B provided on the positive electrode current collector 2A. The positive electrode current collector 2A is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil. The positive electrode mixture layer 2B contains, for example, a positive electrode active material, and may contain a conductive agent such as carbon black or graphite and a binder such as polyvinylidene fluoride as necessary. As the positive electrode active material, the positive electrode active material according to the first embodiment described above can be used. Moreover, the other positive electrode active material may further be included.

  The negative electrode 4 includes, for example, a negative electrode current collector 4A and a negative electrode mixture layer 4B provided on the negative electrode current collector 4A. The negative electrode current collector 4A is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil.

  The negative electrode mixture layer 4B includes, for example, one or more of a negative electrode material capable of occluding and releasing lithium, lithium metal, and a lithium alloy as a negative electrode active material. And a binder such as polyvinylidene fluoride.

  Examples of the negative electrode material capable of inserting and extracting lithium include carbonaceous materials, metal compounds, tin, tin alloys, silicon, silicon alloys, and conductive polymers, and any one or more of these are mixed. Used. When the positive electrode active material according to one embodiment of the present invention is used, a carbonaceous material is preferably used as the negative electrode material. The carbonaceous material is not particularly limited, and generally a material obtained by baking an organic material is used. Natural or artificial graphite can also be used. If the carbonaceous material has insufficient electronic conductivity for the purpose of current collection, it is also preferable to add a conductive agent.

Examples of the metal compound include an oxide such as a lithium complex oxide having a spinel structure (Li ₄ Ti ₅ O ₁₂ ), tungsten oxide (WO ₂ ), niobium oxide (Nb ₂ O ₅ ), or tin oxide (SnO). Examples of the conductive polymer include polyacetylene and polypyrrole.

  The separator 3 separates the positive electrode 2 and the negative electrode 4 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. As the material of the separator 3, those used in conventional batteries can be used, and among them, a polyolefin fine material that is excellent in short-circuit prevention effect and can improve battery safety by a shutdown effect. It is particularly preferred to use a porous film. For example, a microporous film made of polyethylene or polypropylene resin is preferable.

  Further, as the material of the separator 3, it is more preferable to use a material obtained by laminating or mixing polyethylene having a lower shutdown temperature and polypropylene having excellent oxidation resistance from the viewpoint of achieving both shutdown performance and float characteristics.

The electrolytic solution is obtained by dissolving an electrolyte salt in a non-aqueous solvent, and exhibits ion conductivity when the electrolyte salt is ionized. The electrolyte solution is not particularly limited, and a conventional nonaqueous solvent electrolyte solution or the like is used. As the electrolyte salt, alkali metal, particularly calcium halide, perchlorate, thiocyanate, borofluoride, phosphofluoride, arsenic fluoride, aluminum fluoride, trifluoromethyl sulfate, etc. are preferably used. . Specifically, for example, lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium boron tetrafluoride (LiBF ₄ ), trifluoromethane Examples thereof include lithium salts such as lithium sulfonate (LiCF ₃ SO ₃ ) and lithium bis (trifluoromethanesulfonyl) imide (LiN (CF ₃ SO ₂ ) ₂ ). Any one electrolyte salt may be used alone, or two or more electrolyte salts may be mixed and used.

  Solvents for dissolving the electrolyte salt include propylene carbonate (PC), ethylene carbonate (EC), γ-butyrolactone, N-methylpyrrolidone, acetonitrile, N, N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, 1,3- Dioxolane, methyl formate, sulfolane, oxazolidone, thionyl chloride, 1,2-dimethoxyethane, diethylene carbonate, and derivatives and mixtures thereof are preferably used. Any one of the solvents may be used alone, or two or more may be mixed and used.

  In this non-aqueous electrolyte secondary battery, when discharged, for example, lithium ions are released from the negative electrode 4 or lithium metal is eluted as lithium ions and reacts with the positive electrode mixture layer 2B through the electrolytic solution. . When charging is performed, for example, lithium ions are released from the positive electrode mixture layer 2B, and are inserted into the negative electrode 4 through the electrolytic solution or deposited as lithium metal.

  Such a non-aqueous electrolyte secondary battery is, for example, 4.25V or higher even when the open circuit voltage in a fully charged state per pair of positive electrode and negative electrode is in the range of 2.5V to 4.20V. It can also be used in high voltage specifications in the range of .55 V or less, preferably 4.25 V or more and 4.50 V or less. A battery with a high voltage specification can utilize the capacity of the positive electrode active material, which has not been used so far, which increases the amount of lithium released per unit mass of the positive electrode active material, and further increases the non-capacity of high capacity and high energy density. A water electrolyte secondary battery can be realized.

[Method for producing non-aqueous electrolyte secondary battery]
Next, the manufacturing method of the nonaqueous electrolyte secondary battery according to the first example will be described.

  The positive electrode 2 is produced as described below. First, for example, a positive electrode active material, a conductive agent, and a binder are mixed to prepare a positive electrode mixture, and this positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP). A positive electrode mixture slurry is obtained.

  Next, after applying this positive electrode mixture slurry to the positive electrode current collector 2A and drying the solvent, the positive electrode mixture layer 2B is formed by compression molding with a roll press or the like, and the positive electrode 2 is produced.

  The negative electrode 4 is produced as described below. First, for example, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and the 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 4A and drying the solvent, the negative electrode mixture layer 4B is formed by compression molding with a roll press or the like, and the negative electrode 4 is produced.

  Further, the negative electrode mixture layer 4B may be formed by, for example, a gas phase method, a liquid phase method, or a firing method, or a combination of two or more thereof. As the vapor phase method, for example, a physical deposition method or a chemical deposition method can be used. Specifically, a vacuum deposition method, a sputtering method, an ion plating method, a laser ablation method, a thermal CVD (Chemical Vapor Deposition), or the like. A chemical vapor deposition method) or a plasma CVD method can be used. As the liquid phase method, a known method such as electrolytic plating or electroless plating can be used. A known method can also be used for the firing method, and for example, an atmosphere firing method, a reaction firing method, or a hot press firing method can be used.

  Subsequently, the negative electrode 4 and the separator 3 are placed in this order at the center of the outer cup 5, the electrolyte is poured from above the separator 3, and the outer can 6 containing the positive electrode 2 is covered and caulked through the gasket 7. As a result, the nonaqueous electrolyte secondary battery as shown in FIG. 1 is formed.

(1-2) Second Example of Nonaqueous Electrolyte Secondary Battery [Configuration of Nonaqueous Electrolyte Secondary Battery]
FIG. 2 shows the structure of a non-aqueous electrolyte secondary battery using a positive electrode active material according to an embodiment of the present invention. As shown in FIG. 2, this nonaqueous electrolyte secondary battery is sealed by housing the battery element 10 in an exterior material 19 made of a moisture-proof laminate film and welding the periphery of the battery element 10. The battery element 10 is provided with a positive electrode lead 15 and a negative electrode lead 16, and these leads are sandwiched between outer packaging materials 19 and pulled out to the outside. Resin pieces 17 are coated on both surfaces of the positive electrode lead 15 and the negative electrode lead 16 in order to improve the adhesion to the exterior material 19.

  The exterior material 19 has, for example, a laminated structure in which an adhesive layer, a metal layer, and a surface protective layer are sequentially laminated. The adhesive layer is made of a polymer film. Examples of the material constituting the polymer film include polypropylene (PP), polyethylene (PE), unstretched polypropylene (CPP), linear low density polyethylene (LLDPE), and low density. A polyethylene (LDPE) is mentioned. The metal layer is made of a metal foil, and an example of a material constituting the metal foil is aluminum (Al). Moreover, as a material which comprises metal foil, it is also possible to use metals other than aluminum (Al), for example. Examples of the material constituting the surface protective layer include nylon (Ny) and polyethylene terephthalate (PET). The surface on the adhesive layer side is a storage surface on the side where the battery element 10 is stored.

  For example, as shown in FIG. 3, the battery element 10 includes a strip-shaped negative electrode 12 having a gel electrolyte layer 13 provided on both sides, a separator 14, and a strip-shaped positive electrode 11 having a gel electrolyte layer 13 provided on both sides, This is a wound battery element 10 that is laminated with a separator 14 and wound in the longitudinal direction.

  The positive electrode 11 includes a strip-shaped positive electrode current collector 11A and a positive electrode mixture layer 11B formed on both surfaces of the positive electrode current collector 11A.

  One end of the positive electrode 11 in the longitudinal direction is provided with a positive electrode lead 15 connected by, for example, spot welding or ultrasonic welding. As a material of the positive electrode lead 15, for example, a metal such as aluminum can be used.

  The negative electrode 12 includes a strip-shaped negative electrode current collector 12A and a negative electrode mixture layer 12B formed on both surfaces of the negative electrode current collector 12A.

  Further, similarly to the positive electrode 11, a negative electrode lead 16 connected by, for example, spot welding or ultrasonic welding is also provided at one end of the negative electrode 12 in the longitudinal direction. As a material of the negative electrode lead 16, for example, copper (Cu), nickel (Ni) or the like can be used.

  The positive electrode current collector 11A, the positive electrode mixture layer 11B, the negative electrode current collector 12A, and the negative electrode mixture layer 12B are the same as in the first example.

  The gel electrolyte layer 13 includes an electrolytic solution and a polymer compound serving as a holding body that holds the electrolytic solution, and has a so-called gel shape. The gel electrolyte layer 13 is preferable because it can obtain high ionic conductivity and prevent battery leakage. The configuration of the electrolytic solution (that is, the liquid solvent and the electrolyte salt) is the same as that in the first example.

  Examples of the polymer compound include polyacrylonitrile, polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, and polysiloxane. , Polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene or polycarbonate. In particular, from the viewpoint of electrochemical stability, polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene, or polyethylene oxide is preferable.

[Method for producing non-aqueous electrolyte secondary battery]
Next, a method for manufacturing the nonaqueous electrolyte secondary battery according to the second example will be described. First, a precursor solution containing a solvent, an electrolyte salt, a polymer compound, and a mixed solvent is applied to each of the positive electrode 11 and the negative electrode 12, and the mixed solvent is volatilized to form the gel electrolyte layer 13. In addition, the positive electrode lead 15 is attached to the end portion of the positive electrode current collector 11A in advance by welding, and the negative electrode lead 16 is attached to the end portion of the negative electrode current collector 12A by welding.

  Next, the positive electrode 11 and the negative electrode 12 on which the gel electrolyte layer 13 is formed are laminated through a separator 14 to form a laminated body, and then the laminated body is wound in the longitudinal direction to form a wound battery element. 10 is formed.

  Next, a recess 18 is formed by deep-drawing the exterior material 19 made of a laminate film, the battery element 10 is inserted into the recess 18, and an unprocessed portion of the exterior material 19 is folded back to the upper portion of the recess 18. The outer peripheral part of is thermally welded and sealed. As described above, the nonaqueous electrolyte secondary battery according to the second example is manufactured.

  In one embodiment, the capacity of the nonaqueous electrolyte secondary battery can be increased and the charge / discharge efficiency can be improved by mixing the composite oxide particles with ammonium sulfate and ammonium nitrate. Therefore, the secondary battery according to the embodiment of the present invention is portable, such as a video camera, a notebook personal computer, a word processor, a radio cassette recorder, a mobile phone, etc. by utilizing the features of light weight, high capacity and high energy density. It can be widely used for small electronic devices.

  Specific embodiments of the present invention will be described below with reference to examples, but the present invention is not limited thereto.

<Example 1>
First, nickel sulfate, cobalt sulfate, and sodium aluminate are dissolved in water, a sodium hydroxide solution is added while stirring sufficiently, and nickel (Ni), cobalt (Co), and aluminum (Al) are mixed. A nickel-cobalt-aluminum composite coprecipitated hydroxide having a molar ratio of Ni: Co: Al = 77: 20: 3 was obtained. The produced coprecipitate was washed with water and dried, and then lithium hydroxide monohydrate was added, and a precursor was prepared by adjusting the molar ratio to Li: (Ni + Co + Al) = 105: 100. These precursors were calcined in an oxygen stream at 700 ° C. for 10 hours, cooled to room temperature, taken out and pulverized, and mainly composed of lithium nickelate represented by the composition formula Li _1.03 Ni _0.77 Co _0.20 Al _0.03 O ₂ Composite oxide particles were obtained. In addition, the average particle diameter which measured the obtained complex oxide particle | grains with the laser scattering method was 13 micrometers.

1.65 parts by weight of a commercially available reagent ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) and 2.00 parts by weight of ammonium nitrate (NH ₄ NO ₃ ) were sufficiently ground and mixed in a mortar. Subsequently, 100 parts by weight of composite oxide particles mainly composed of lithium nickelate were added to the pulverized and mixed ammonium sulfate and ammonium nitrate, and mixed thoroughly. This mixture was calcined in an oxygen stream at 700 ° C. for 4 hours, cooled to room temperature, and then taken out to obtain a positive electrode active material.

<Example 2>
In the same manner as in Example 1, except that 1.65 parts by weight of ammonium sulfate and 2.00 parts by weight of ammonium nitrate in Example 1 were changed to 0.83 parts by weight of ammonium sulfate and 12.00 parts by weight of ammonium nitrate. An active material was obtained.

<Comparative Example 1>
In Example 1, ammonium sulfate and ammonium nitrate were not used, and the composite oxide particles before mixing and heating were used as the positive electrode active material of Comparative Example 1.

<Comparative example 2>
A positive electrode active material was obtained in the same manner as in Example 1 except that ammonium nitrate was not used.

<Comparative Example 3>
A positive electrode active material was obtained in the same manner as in Example 2 except that ammonium nitrate was not used.

The nonaqueous electrolyte secondary battery shown in FIG. 1 was produced using the positive electrode active materials of Example 1 and Example 2 and Comparative Examples 1 to 3 that were produced by evaluation . First, 86% by weight of the prepared positive electrode active material powder, 10% by weight of graphite as a conductive agent, and 4% by weight of polyvinylidene fluoride as a binder were mixed, and N-methyl-2pyrrolidone (NMP) as a solvent was mixed. After the dispersion, the positive electrode current collector 2A made of a strip-shaped aluminum foil having a thickness of 20 μm was coated on both surfaces, dried, compressed by a roller press, and then punched into a disk having a predetermined size to obtain a pellet.

As the negative electrode 4, a lithium foil punched into a disk shape having a predetermined size was used. A non-aqueous electrolyte prepared by dissolving LiPF ₆ as an electrolyte salt to a concentration of 1 mol / dm ³ in a solvent in which ethylene carbonate and methyl ethyl carbonate are mixed at a volume ratio of 1: 1 is used as the electrolyte. Using.

  Subsequently, the prepared pellet-like positive electrode and negative electrode are laminated via a porous polyolefin film, accommodated in the exterior cup 5 and the exterior can 6 and caulked via the gasket 7 to obtain a diameter of 20 mm. A coin-type nonaqueous electrolyte secondary battery having a height of 1.6 mm was produced.

  Regarding the secondary battery produced as described above, the discharge capacity at the first cycle was determined as the initial capacity, and the charge / discharge efficiency (discharge capacity / charge capacity) at the first cycle was determined.

  For charging, constant current and constant voltage charging was performed under the conditions of a charging current of 1.0 mA, a charging voltage of 4.25 V, and a total charging time of 15 hours. The discharge was performed at a constant current of 1.0 mA until the voltage reached 2.5V throughout. The measurement results are shown in Table 1.

  As shown in Table 1, in Example 1 and Example 2 in which ammonium sulfate and ammonium nitrate were deposited on the composite oxide particles and heat-treated, Comparative Example 1 in which ammonium sulfate and ammonium nitrate were not deposited and heat-treated was used. Compared with the initial capacity, the charge / discharge efficiency was improved. Further, Example 1 was able to improve the initial capacity and charge / discharge efficiency as compared with Comparative Example 2 in which ammonium nitrate was not used. Similarly, Example 2 was able to improve the initial capacity and charge / discharge efficiency as compared with Comparative Example 3 in which ammonium nitrate was not used.

  The present invention is not limited to the above-described embodiment of the present invention, and various modifications and applications are possible without departing from the gist of the present invention. For example, the shape is not particularly limited. It may be a cylindrical shape, a square shape, or the like.

In the first example, a non-aqueous electrolyte secondary battery having an electrolyte as an electrolyte has been described. In the second example, a non-aqueous electrolyte secondary battery having a gel electrolyte as an electrolyte has been described, but the present invention is not limited thereto. It is not a thing.

  For example, as the electrolyte, in addition to the above-described ones, a solid polymer electrolyte using an ion conductive polymer or an inorganic solid electrolyte using an ion conductive inorganic material can be used. It may be used in combination with the electrolyte. Examples of the polymer compound that can be used for the polymer solid electrolyte include polyether, polyester, polyphosphazene, and polysiloxane. Examples of the inorganic solid electrolyte include ion conductive ceramics, ion conductive crystals, and ion conductive glass.

It is a schematic sectional drawing of the 1st example of the nonaqueous electrolyte secondary battery using the positive electrode active material by one Embodiment of this invention. It is the schematic of the 2nd example of the nonaqueous electrolyte secondary battery using the positive electrode active material by one Embodiment of this invention. FIG. 3 is an enlarged cross section of a part of the battery element shown in FIG. 2.

Explanation of symbols

2 .... Positive electrode 2A ... Positive electrode current collector 2B ... Positive electrode mixture layer 3 .... Separator 4 ... Negative electrode 4A ... Negative electrode current collector 4B ... Negative electrode mixture layer 5 ... Exterior cup 6 ... Exterior can 7 ... Gasket 10 ... Battery element 11 ... Positive electrode 11A ... Positive current collector 11B ... Positive mix layer 12 ... Negative electrode 12A ... Negative electrode current collector 12B Negative electrode mixture layer 13 ... Gel electrolyte layer 14 ... Separator 15 ... Positive electrode lead 16 ... Negative electrode lead 17 ... Resin piece 18 ... Recess 19 ... Exterior material

Claims (6)

Depositing ammonium sulfate and ammonium nitrate on composite oxide particles comprising lithium (Li) and at least one of nickel (Ni) and cobalt (Co);
Heat-treating the composite oxide particles coated with ammonium sulfate and ammonium nitrate in an oxidizing atmosphere;
The manufacturing method of the positive electrode active material characterized by having. The method for producing a positive electrode active material according to claim 1, wherein the composite oxide particles have an average composition represented by chemical formula (1).
(Chemical formula 1)
Li _a Ni _x Co _y Al _z O ₂
(However, Ni, when the total amount of Ni is 1, within the range of 0.1 or less of Ni, manganese (Mn), chromium (Cr), iron (Fe), vanadium (V), magnesium ( Mg), titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo), tungsten (W), copper (Cu), zinc (Zn), gallium (Ga), indium (In), tin ( Sn, lanthanum (La), and cerium (Ce) can be substituted with one or more metal elements selected from the group consisting of a), lanthanum (La), and cerium (Ce), where a, x, y, and z are 0.3 ≦ a ≦ 1.05, 0.60 <x <0.90, 0.10 <y <0.40, 0.01 <z <0.20, values of x, y and z (There is a relationship of x + y + z = 1 between them.)   The method for producing a positive electrode active material according to claim 1, wherein the temperature of the heat treatment is 500 ° C. or higher and 1200 ° C. or lower.   2. In the step of depositing ammonium sulfate and ammonium nitrate, the amount of ammonium sulfate added is in the range of 0.01% by weight to 20% by weight with respect to the composite oxide particles. Of manufacturing positive electrode active material.   2. In the step of depositing ammonium sulfate and ammonium nitrate, the amount of ammonium nitrate added is in the range of 0.01% to 100% by weight with respect to the composite oxide particles. Of manufacturing positive electrode active material.   The method for producing a positive electrode active material according to claim 1, wherein an average particle diameter of the positive electrode active material is in a range of 2.0 μm to 50 μm.

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