JP5040282B2 - Positive electrode active material, method for producing the same, and nonaqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a positive electrode active material, a method for producing the same, and a nonaqueous electrolyte secondary battery. For example, a positive electrode active material containing a composite oxide containing lithium (Li) and cobalt (Co), a method for producing the same, and The present invention relates to a non-aqueous electrolyte secondary battery using the same.

  In recent years, with the widespread use of portable devices such as video cameras and notebook computers, there is an increasing demand for small and high-capacity secondary batteries. Currently used secondary batteries include nickel-cadmium 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. The growth of the dendrite has problems such as deterioration of the cycle characteristics of the secondary battery, and further breaking through a diaphragm (separator) disposed so that the positive electrode and the negative electrode are not in contact with each other, thereby causing an internal short circuit.

  Therefore, for example, as described in Patent Document 1, 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 is provided. was suggested. 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 positive electrode active materials, inorganic compounds such as transition metal oxides and transition metal chalcogens containing alkali metals are known as those capable of obtaining a battery voltage of around 4V. Among these, lithium composite oxides such as lithium cobaltate or lithium nickelate are most promising in terms of high potential, stability, and long life.

In particular, a positive electrode active material mainly composed of lithium cobaltate is a positive electrode active material exhibiting a high potential, and is expected to increase the energy density by increasing the charging voltage. However, there is a problem that the cycle characteristics deteriorate when the charging voltage is increased. Therefore, conventionally, a method of modifying the positive electrode active material by using a small amount of LiMn _1/3 Co _1/3 Ni _1/3 O ₂ or the like, or coating the surface with another material has been performed. .

By the way, the technique for modifying the positive electrode active material by the surface coating of the positive electrode active material described above has a problem of achieving a coating with high coverage. In order to solve this problem, various methods have been proposed. For example, it has been confirmed that the method of depositing with a metal hydroxide is excellent in covering properties. As such a method, for example, Patent Document 2 discloses the surface of lithium nickelate (LiNiO ₂ ) particles. Discloses the deposition of cobalt (Co) and manganese (Mn) through its hydroxide deposition process. For example, Patent Document 3 discloses that a non-manganese metal is deposited on the surface of a lithium manganese composite oxide through a hydroxide deposition process.

JP-A-9-265985 JP-A-11-71114

Furthermore, for example, Patent Document 4 describes molybdenum as a metal that is deposited on nickel hydroxide particles as a positive electrode precursor and is deposited for improving the tap density of the final positive electrode. Further, for example, Patent Document 5 discloses a positive electrode active material having a surface layer containing molybdenum and / or tungsten and lithium.
JP 2001-106534 A JP 2002-75367 A

  However, when heat treatment is performed after depositing a metal hydroxide on the composite oxide particles, there is a problem that sintering is likely to proceed between the particles and the particles are likely to be bound to each other. As a result, when a conductive agent or the like is mixed during the production of the positive electrode, the bonded portion and particles are broken or cracked, the coating layer is peeled off, and the damaged surface of the particles is exposed. End up. Such a damaged surface is very active compared to the surface formed at the time of firing, and the deterioration reaction of the electrolytic solution and the positive electrode active material is likely to occur.

  Accordingly, an object of the present invention is to provide a positive electrode active material capable of further improving chemical stability by suppressing binding between particles, a method for producing the same, and a high capacity and high charge / discharge cycle characteristic using the same. The object is to provide a water electrolyte secondary battery.

In order to solve the above-described problem, the first invention
A coating layer comprising an oxide provided on at least a part of the composite oxide particles and including lithium (Li) and nickel (Ni) or a coating element of nickel (Ni) and manganese (Mn);
Provided on at least a part of the covering layer, and a surface layer containing molybdenum (Mo),
The composite oxide particle is a positive electrode active material having an average composition represented by Chemical Formula 1.
(Chemical formula 1)
_{Li (1 + x) Co (} 1-y) M y O (2-z)
(In the chemical formula 1, M is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni ), Copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), and tungsten (W), at least one element selected from the group consisting of x, y, and z is −0. 10 ≦ x ≦ 0.10, 0 ≦ y <0.50, −0.10 ≦ z ≦ 0.20.

  In 1st invention, it is preferable that the structural ratio of nickel (Ni) and manganese (Mn) in a coating layer exists in the range of 99: 1 to 30:70.

  In the first invention, the oxide of the coating layer is 40 mol% or less of the total amount of nickel (Ni) and manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti). , Vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), tungsten (W) It is preferable that the element is replaced with at least one metal element.

  In 1st invention, it is preferable that the quantity of a coating layer exists in the range of 0.5 weight%-50 weight% of complex oxide particle.

  In 1st invention, it is preferable that an average particle diameter is 2.0 micrometers-50 micrometers.

  In the first invention, cobalt (Co) diffused from the composite oxide particles exists in the coating layer and the surface layer, and the average atomic ratio of molybdenum (Mo) to cobalt (Co) in the whole positive electrode active material is 0. It is preferable that the atomic ratio of molybdenum (Mo) and cobalt (Co) in the coating layer and the surface layer of the positive electrode active material is 0.01 or more and 0.5 or less.

  In 1st invention, it is preferable that 3d5 / 2 binding energy by XPS (X-ray Photoelectron Spectroscopy) of molybdenum (Mo) of the positive electrode active material surface is 232.4 eV or less.

The second invention is
After forming a layer made of hydroxide containing nickel (Ni) or nickel (Ni) and manganese (Mn) on at least a part of the composite oxide particles whose average composition is expressed in Chemical Formula 1, Depositing molybdic acid at least in part;
After depositing molybdic acid, heat treatment is performed to include lithium (Li) and nickel (Ni) or nickel (Ni) and manganese (Mn) covering elements in at least a part of the composite oxide particles. And a step of forming a surface layer containing molybdenum (Mo) and a coating layer made of an oxide.
(Chemical formula 1)
_{Li (1 + x) Co (} 1-y) M y O (2-z)
(In the chemical formula 1, M is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni ), Copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), and tungsten (W), at least one element selected from the group consisting of x, y, and z is −0. 10 ≦ x ≦ 0.10, 0 ≦ y <0.50, −0.10 ≦ z ≦ 0.20.

  In the second invention, nickel (Ni) or a hydroxide containing nickel (Ni) and manganese (Mn) is formed by dispersing the composite oxide particles in a water-based solvent having a pH of 12 or more, It is preferable to carry out by adding a compound of Ni) or a compound of nickel (Ni) and a compound of manganese (Mn).

  In the second invention, the solvent mainly composed of water preferably contains lithium hydroxide.

  In 2nd invention, it is preferable that the structural ratio of nickel (Ni) and manganese (Mn) in a coating layer exists in the range of 99: 1 to 30:70.

  In the second invention, the oxide of the coating layer contains 40 mol% or less of the total amount of nickel (Ni) and manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti). , Vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), tungsten (W) It is preferable that the element is replaced with at least one metal element.

  In 2nd invention, it is preferable that the quantity of a coating layer exists in the range of 0.5 weight%-50 weight% of complex oxide particle.

  In the second invention, the positive electrode active material preferably has an average particle size of 2.0 μm to 50 μm.

  In the second invention, cobalt (Co) diffused from the composite oxide particles is present in the coating layer, and the average atomic ratio of molybdenum (Mo) to cobalt (Co) in the whole positive electrode active material is 0.001 or less. The atomic ratio of molybdenum (Mo) and cobalt (Co) in the coating layer and surface layer of the positive electrode active material is preferably 0.01 or more and 0.5 or less.

The third invention is
A positive electrode having a positive electrode active material, a negative electrode, a separator and an electrolyte;
The positive electrode active material is
A coating layer comprising an oxide provided on at least a part of the composite oxide particles and including lithium (Li) and nickel (Ni) or a coating element of nickel (Ni) and manganese (Mn);
Provided on at least a part of the covering layer, and a surface layer containing molybdenum (Mo),
The composite oxide particle is a non-aqueous electrolyte secondary battery having an average composition represented by chemical formula 1.
(Chemical formula 1)
_{Li (1 + x) Co (} 1-y) M y O (2-z)
(In the chemical formula 1, M is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni ), Copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), and tungsten (W), at least one element selected from the group consisting of x, y, and z is −0. 10 ≦ x ≦ 0.10, 0 ≦ y <0.50, −0.10 ≦ z ≦ 0.20.

  In this invention, at least a part of the composite oxide particles is coated with an oxide containing lithium (Li) and nickel (Ni) or at least one coating element of nickel (Ni) and manganese (Mn). Since the layer is provided, a high charge voltage and a high energy density property associated therewith can be realized, and good charge / discharge cycle characteristics can be obtained under high charge voltage conditions.

  In the present invention, nickel (Ni) or composite oxide particles provided with a hydroxide containing nickel (Ni) and manganese (Mn) are coated with molybdic acid, thereby suppressing the binding between the particles. . And since crushing of the bound particles can be avoided, an increase in the active surface of the particles due to crushing and breakage of the particles can be suppressed, and the advantages of the coating layer can be fully utilized.

  In this invention, the positive electrode active material is configured so that the binding energy of 3d5 / 2 by XPS of molybdenum (Mo) is 232.4 eV or less, thereby increasing the acidity of the surface of the positive electrode active material particles, Durability can be improved.

  According to this invention, the stability of the positive electrode active material can be further improved. Moreover, the battery using this positive electrode active material can obtain a high capacity | capacitance, and can improve charging / discharging efficiency.

  Embodiments of the present invention will be described below with reference to the drawings. A positive electrode active material according to an embodiment of the present invention includes an oxide containing lithium (Li) and a coating element of nickel (Ni) or nickel (Ni) and manganese (Mn) in at least a part of the composite oxide particles. And a surface layer containing molybdenum (Mo) is provided on at least a part of the coating layer.

First, the reason why the positive electrode active material is configured as described above will be described. A positive electrode active material mainly composed of lithium cobalt oxide (LiCoO ₂ ) has a high charge voltage property and a high energy density property associated therewith. However, when a charge / discharge cycle at a high capacity is repeated at a high charge voltage, the capacity decreases. Not a few. Since this cause is caused by the surface of the positive electrode active material particles, the necessity of surface treatment of the positive electrode active material has been pointed out.

  Therefore, various surface treatments have been proposed, but the surface is made of a material that can suppress or contribute to the capacity reduction from the viewpoint of eliminating the capacity reduction per volume or weight or minimizing the capacity reduction. By performing the treatment, it is possible to obtain a positive electrode active material excellent in high charge voltage property, high energy density property associated therewith, and charge / discharge cycle characteristics at a high charge voltage.

Accordingly, the inventors of the present application have made a intensive study, and although slightly inferior in the high charge voltage property and the high energy density property associated therewith, the positive electrode active material mainly composed of lithium cobaltate (LiCoO ₂ ) is used as lithium (Li). And providing a coating layer made of an oxide containing at least one of the covering elements of nickel (Ni) and manganese (Mn), has high charging voltage and high energy density associated therewith, and It has been found that a positive electrode active material having a high capacity and excellent charge / discharge cycle characteristics can be obtained under high charge voltage conditions.

  As a method of providing a coating layer on the composite oxide particles, lithium (Li) compound, nickel (Ni) compound and / or manganese (Mn) compound are dry-mixed as composite oxide particles and finely pulverized particles. And coating and firing to form a coating layer made of an oxide containing lithium (Li) and at least one coating element of nickel (Ni) and manganese (Mn) on the surface of the composite oxide particle Lithium (Li) compound, nickel (Ni) compound and / or manganese (Mn) compound dissolved or mixed in a solvent, wet-coated and fired, lithium (Li) and nickel ( A method can be proposed in which a coating layer made of an oxide containing at least one coating element of Ni) and manganese (Mn) is provided on the surface of the composite oxide particle. However, these methods yielded results in which a highly uniform coating could not be achieved.

  Therefore, the inventors of the present application have further studied diligently. As a result, nickel (Ni) and / or manganese (Mn) was deposited as a hydroxide and heated and dehydrated to form a coating layer. It was found that highly uniform coating can be realized. In this deposition treatment, a nickel (Ni) compound and / or a manganese (Mn) compound is dissolved in a water-based solvent system, and then the composite oxide particles are dispersed in the solvent system. The basicity of the dispersion is increased by adding a base to the system, and a hydroxide containing nickel (Ni) and / or manganese (Mn) is precipitated on the surface of the composite oxide particles.

  Then, by the deposition treatment, the composite oxide particles deposited with hydroxide containing nickel (Ni) and / or manganese (Mn) are heated and dehydrated to form a coating layer on the surface of the composite oxide particles. . Thereby, the uniformity of the coating on the surface of the composite oxide particles can be improved.

  However, the inventors of the present application have made further studies and applied a hydroxide containing nickel (Ni) and / or manganese (Mn) to the surface of the composite oxide particles, and washed to fire this. In the process of dehydration and drying, the particles are bound to each other via a hydroxide containing nickel (Ni) and / or manganese (Mn) on the surface, and when the particles are crushed, the particles are relatively bonded. Interfacial delamination between hydroxide and composite oxide particles containing weak nickel (Ni) and / or manganese (Mn), or hydroxide containing nickel (Ni) and / or manganese (Mn) having weak cohesive strength Cohesive failure occurs. In connection with this, it discovered that the characteristic improvement of the positive electrode active material by providing a coating layer was impaired.

  Furthermore, the inventors of the present application leave lithium particles (Li) in a state in which particles having a hydroxide containing nickel (Ni) and / or manganese (Mn) are in contact with each other while leaving the particles bonded together. It was found that the sintering between the particles tends to proceed as the baking is performed.

  When sintering between particles proceeds, there is a problem described below. In the formation of the positive electrode, it is necessary to increase the input amount of mechanical energy in the pulverization of the particles in order to uniformly mix the particles with the carbon particles as the binder and the conductive agent. Along with this, the positive electrode active material made of composite oxide particles provided with a coating layer is damaged or broken, and the total amount of defects as powder increases.

Note that the breakage or breakage occurs in the form of breakage of the connecting portion between the sintered particles, formation of cracks in the particles themselves, crushing of the particles themselves, peeling of the coating layer, and the like. In particular, in composite oxide particles provided with a coating layer, the surface shape of the particles is not smooth and tends to have irregularities on the surface as compared with a positive electrode active material mainly composed of lithium cobaltate (LiCoO ₂ ). is there. For this reason, when an external force is applied, it is considered that the slip between particles is poor, the external force is easily concentrated locally, and is easily damaged or destroyed.

  As a result, the surface where the coating layer is not provided is exposed. That is, a surface not provided with a coating layer that does not function to improve charge / discharge cycle characteristics and an active new surface are exposed. Therefore, the high-capacity charge / discharge cycle characteristics deteriorate under high charge voltage conditions. The exposed surface is active and has a high surface energy as is well known. For this reason, the decomposition reaction of the electrolytic solution and the elution activity of the surface are extremely high as compared with the surface formed by normal firing.

  Therefore, the inventors of the present application have made extensive studies for the purpose of improving the deterioration of the positive electrode function based on the sintering between particles and improving the manufacturing process, and have developed nickel (Ni) or nickel (Ni) and manganese (Mn). It has been found that the progress of sintering can be improved by further depositing molybdic acid on the surface of the composite oxide particles to which the hydroxide containing is deposited. Along with this, it was found that particle breakage or destruction can be reduced. Next, the composite oxide, the coating layer, and the surface layer will be described.

[Composite oxide]
The composite oxide particles have, for example, an average composition represented by Chemical Formula 1. Since the composite oxide particles have an average composition expressed by Chemical Formula 1, a high capacity and a high discharge potential can be obtained.

(Chemical formula 1)
_{Li (1 + x) Co (} 1-y) M y O (2-z)
(In the chemical formula 1, M is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni ), Copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), and tungsten (W), at least one element selected from the group consisting of x, y, and z is −0. 10 ≦ x ≦ 0.10, 0 ≦ y <0.50, −0.10 ≦ z ≦ 0.20.

  Here, in the chemical formula 1, the range of x is −0.10 ≦ x ≦ 0.10, more preferably −0.08 ≦ x ≦ 0.08, and further preferably −0.06 ≦ x ≦ 0.0. 0.06. If the value decreases outside this range, the discharge capacity will decrease. If the value increases outside this range, it diffuses out of the particles and becomes an obstacle to the control of the basicity of the next processing step, and finally causes the harmful effects of gelation promotion during the kneading of the positive electrode paste. It becomes.

The range of y is 0 ≦ y <0.50, preferably 0 ≦ y <0.40, and more preferably 0 ≦ y <0.30. When it becomes larger than this range, the high charge voltage property of LiCoO ₂ and the high energy density property associated therewith are impaired.

  The range of z is −0.10 ≦ z ≦ 0.20, more preferably −0.08 ≦ z ≦ 0.18, and still more preferably −0.06 ≦ z ≦ 0.16. When the value decreases outside this range, and when the value increases outside this range, the discharge capacity tends to decrease.

  The composite oxide particles can be used as starting materials that are usually available as positive electrode active materials, but in some cases, the composite oxide particles may be used after pulverizing the secondary particles using a ball mill or a grinder. it can.

[Coating layer]
The coating layer is provided on at least a part of the composite oxide particles, and is made of an oxide containing lithium (Li) and a coating element of nickel (Ni) or nickel (Ni) and manganese (Mn). By providing this coating layer, there are high charge voltage characteristics and high energy density characteristics associated therewith, and it is possible to improve charge / discharge cycle characteristics with high capacity under high charge voltage conditions.

  As a structure of nickel (Ni) and manganese (Mn) in the coating layer, it is preferable that both nickel (Ni) and manganese (Mn) are included from the viewpoint of obtaining good charge / discharge cycle characteristics. More specifically, the constituent ratio of nickel (Ni) and manganese (Mn) is preferably in the range of 99: 1 to 30:70, and in the range of 99: 1 to 40:60. Is more preferable. The composition of nickel (Ni) and manganese (Mn) in the oxide of the coating layer preferably includes both nickel (Ni) and manganese (Mn), but the amount of manganese (Mn) increases beyond this range. Then, the occlusion property of lithium (Li) is lowered, which ultimately causes a decrease in capacity of the positive electrode active material and an increase in electric resistance when used in a battery. In addition, the range of the composition ratio of nickel (Ni) and manganese (Mn) is a range showing more effectiveness in suppressing the progress of sintering between particles in the firing of the precursor added with lithium (Li). is there.

  In addition, nickel (Ni) and manganese (Mn) in the oxide of the coating layer are replaced with magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron. Replacing at least one metal element selected from the group consisting of (Fe), cobalt (Co), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), and tungsten (W). it can.

  Thereby, the stability of the positive electrode active material and the diffusibility of lithium ions can be improved. The substitution amount of the selected metal element is 40 mol% or less of the total amount of nickel (Ni) and manganese (Mn) of the oxide of the coating layer, preferably 30 mol% or less, more preferably It is 20 mol% or less. This is because if the substitution amount of the selected metal element is increased beyond this range, the occlusion of lithium (Li) is lowered and the capacity of the positive electrode active material is lowered.

  The amount of the coating layer is 0.5% to 50% by weight of the composite oxide particles, preferably 1.0% to 40% by weight, more preferably 2.0% to 35% by weight. This is because when the amount of the coating layer exceeds this range, the capacity of the positive electrode active material decreases. This is because when the amount of the coating layer is lower than this range, the stability of the positive electrode active material is lowered.

[Surface layer]
The surface layer is provided on at least a part of the coating layer and contains molybdenum (Mo). By providing the surface layer, the binding between the particles can be suppressed. Moreover, it is thought that the surface layer containing molybdenum (Mo) also contributes to the action / effect of the coating layer. The presence of the surface layer further suppresses the surface elution activity in addition to the case of only the coating layer.

In the positive electrode active material obtained after firing, molybdenum (Mo) exists without having a crystal phase on the very surface of the coating layer. The partial charge of molybdenum (Mo) is estimated from the chemical shift of Mo3d5 / 2 in XPS. Binding energy in Mo3d5 / 2 of XPS valence 6 ⁺ molybdenum (Mo) is in the range of usually 231.9～232.7EV. Molybdenum (Mo) exists in the metal oxide as described above, and is adjacently bonded to oxygen. At this time, when the bond energy is low, the ionicity of the bond with the adjacent oxygen bond is lowered, and accordingly, the electron density of the oxygen atom bonded to the adjacent bond is lowered, and the acidity of the oxygen atom is increased. It is considered that this specific acid basicity of the surface effectively works the interaction between the electrolyte solution of the present invention and the electrode interface of the positive electrode, and improves its durability. The preferable binding energy in the present invention is 232.4 eV or less, and more preferably 232.3 eV or less. In this region, the durability of the battery can be improved.

  In order to reduce the binding energy of molybdenum (Mo) ions, the electron density of molybdenum (Mo) should not be reduced, that is, not reduced. For this purpose, it is preferable to reduce the concentration of the surface of molybdenum (Mo) so that the molybdenum does not aggregate and is dispersed at the atomic level to have uniformity.

  The average particle diameter of the positive electrode active material is 2.0 μm to 50 μm. If the average particle size is less than 2.0 μm, it peels off when pressed during positive electrode fabrication, and the surface area of the active material increases, so it is necessary to increase the amount of conductive agent and binder added, and the unit weight This is because the per-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, the manufacturing method of the positive electrode active material by one Embodiment of this invention is demonstrated. The method for producing a positive electrode active material according to one embodiment of the present invention includes forming a layer made of hydroxide containing nickel (Ni) or nickel (Ni) and manganese (Mn) on at least a part of the composite oxide particles. The first step of depositing molybdic acid on at least a part of the composite oxide particles and the heat treatment after depositing the molybdic acid, thereby forming lithium (Li And a second step of forming a coating layer made of an oxide containing nickel (Ni) or a coating element of nickel (Ni) and manganese (Mn), and a surface layer containing molybdenum (Mo). Can be separated.

(First step)
In the first step, nickel (Ni) or a hydroxide containing nickel (Ni) and manganese (Mn) and molybdic acid are applied. In the first step, for example, first, the composite oxide particles are dispersed in a solvent system mainly composed of water in which a nickel (Ni) compound or a nickel (Ni) compound and a manganese (Mn) compound are dissolved. The basicity of the dispersion is increased by adding a base to the dispersion, and nickel (Ni) or a hydroxide containing nickel (Ni) and manganese (Mn) is precipitated on the surface of the composite oxide particles. The composite oxide particles are dispersed in a solvent mainly composed of basic water, and then a nickel (Ni) compound or a nickel (Ni) compound and a manganese (Mn) compound are added to the aqueous solution. Nickel (Ni) or a hydroxide containing nickel (Ni) and manganese (Mn) may be deposited.

  Nickel (Ni) compound raw materials include nickel hydroxide, nickel carbonate, nickel nitrate, nickel fluoride, nickel chloride, nickel bromide, nickel iodide, nickel perchlorate, nickel bromate, nickel iodate, oxidation Inorganic compounds such as nickel, 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 It can be used as it is or after being treated so that it can be dissolved in a solvent system with an acid or the like, if necessary.

  Manganese (Mn) compounds include manganese hydroxide, manganese carbonate, manganese nitrate, manganese fluoride, manganese chloride, manganese bromide, manganese iodide, manganese chlorate, manganese perchlorate, and manganese bromate. , Manganese iodate, manganese oxide, manganese phosphinate, manganese sulfide, manganese hydrogen sulfide, manganese nitrate, manganese hydrogen sulfate, manganese thiocyanate, manganese nitrite, manganese phosphate, manganese dihydrogen phosphate, manganese hydrogen carbonate, etc. The organic compound or an organic compound such as manganese oxalate or manganese acetate can be used as it is or after being treated so that it can be dissolved in a solvent system with an acid or the like, if necessary.

  The pH of the above-mentioned solvent system mainly composed of water is pH 12 or higher, preferably pH 13 or higher, more preferably pH 14 or higher. The higher the pH value of the water-based solvent system described above, the better the uniformity of the deposition of nickel (Ni) or hydroxide containing nickel (Ni) and manganese (Mn), and the reaction accuracy. It has the advantage of improving productivity and quality by shortening the processing time. Further, the pH of the solvent system mainly composed of water is determined by the balance with the cost of the alkali used.

  The temperature of the treatment dispersion is 40 ° C. or higher, preferably 60 ° C. or higher, more preferably 80 ° C. or higher. The higher the value of the temperature of the treatment dispersion, the better the uniformity of the deposition of the nickel (Ni) or hydroxide containing nickel (Ni) and manganese (Mn), the higher the reaction rate, and the longer the treatment time. There are advantages of improving productivity and quality by shortening. Although it is determined in consideration of the cost and productivity of the equipment, it can be performed at 100 ° C. or higher using an autoclave, and production by shortening the processing time by improving the uniformity of deposition and improving the reaction rate. From the point of view, it can be recommended.

  Furthermore, the pH of a solvent system mainly composed of water can be reached by dissolving an alkali in the solvent system mainly composed of water. Examples of the alkali include lithium hydroxide, sodium hydroxide and potassium hydroxide, and mixtures thereof. Although these alkalis can be used as appropriate, it is excellent to use lithium hydroxide from the viewpoint of the purity and performance of the positive electrode active material according to one embodiment finally obtained. The advantage of using lithium hydroxide is that nickel (Ni) or composite oxide particles in which a hydroxide containing nickel (Ni) and manganese (Mn) is formed are taken out from a solvent system mainly composed of water. In addition, the amount of lithium in the positive electrode active material according to an embodiment finally obtained can be controlled by controlling the amount of the dispersion medium made of a solvent mainly composed of water.

  Next, molybdic acid is deposited on at least part of the composite oxide particles in which a layer made of hydroxide containing nickel (Ni) or nickel (Ni) and manganese (Mn) is formed. The molybdic acid deposition treatment may be performed in a state of being suspended in a solvent system mainly composed of water in which nickel (Ni) or a hydroxide containing nickel (Ni) and manganese (Mn) is deposited. It is valid. Thus, in the stage of dehydrating and drying the composite oxide particles in which a layer made of hydroxide containing nickel (Ni) or nickel (Ni) and manganese (Mn) is dehydrated and dried, the surface nickel (Ni) or nickel It is possible to prevent the particles from binding through a hydroxide containing (Ni) and manganese (Mn).

  Preferably, it is effective to perform the molybdic acid deposition treatment in the cleaning stage after the deposition treatment of nickel (Ni) or a hydroxide containing nickel (Ni) and manganese (Mn). Thereby, the leakage of molybdic acid added to the suspension system can be prevented and the adsorptivity can be improved. Furthermore, by carrying out the molybdic acid deposition treatment, it is possible to obtain a particle aggregation promoting effect without binding between particles in the suspension system, and to perform a washing operation and a recovery operation of the particles from the dispersion medium. It can be done easily.

  Examples of the raw material of the molybdate compound that can be used for the deposition treatment include ammonium molybdate, potassium molybdate, sodium molybdate, lithium molybdate, molybdic acid, and anhydrous molybdic acid.

  The deposition weight of molybdic acid is 0.00001% by weight to 1.0% by weight with respect to the weight of the composite oxide particles. The deposition weight is preferably 0.0001% to 0.1% by weight. If the weight of molybdic acid is increased beyond this range, the capacity of the positive electrode active material decreases. When the deposition weight of molybdic acid is reduced from this range, the stability of the positive electrode active material is lowered.

  More specifically, the atomic ratio of molybdenum (Mo) and cobalt (Co) as an average of the whole positive electrode active material is 0.001 to 0.0000001, more preferably 0.0001 to 0.000001. This value should be as low as possible within the effective range. This value can be calculated by quantifying a solution in which the positive electrode active material is uniformly dissolved with an acid or the like using an inductively coupled plasma emission spectrometer (ICP-AES).

  On the other hand, the atomic ratio of molybdenum (Mo) to cobalt (Co) on the surface of the positive electrode active material is 0.01 to 0.50, more preferably 0.05 to 0.40, still more preferably 0.1 to 0. .30. As long as the effect is obtained and the harmful effect is not remarkable, the higher this value is, the better. This value can be calculated by quantifying the positive electrode active material using XPS. The effect of addition of molybdenum (Mo) is considered to be manifested only on the surface of the positive electrode active material, and it is desirable that the concentration of the surface is high, and the lower the average value of the positive electrode active material, the better.

(Second step)
In the second step, the composite oxide particles deposited in the first step are separated from the solvent system mainly composed of water, and then the hydroxide is dehydrated by heat treatment, whereby the composite oxide particles A coating layer made of an oxide containing lithium (Li) and a coating element of nickel (Ni) or nickel (Ni) and manganese (Mn) is formed on the surface. Here, the heat treatment is preferably performed at a temperature of about 300 ° C. to 1000 ° C. in an oxidizing atmosphere such as air or pure oxygen. At this time, since molybdic acid is deposited on a hydroxide containing nickel (Ni) or nickel (Ni) and manganese (Mn), sintering between particles is suppressed, and binding between particles is suppressed. Is done.

  In addition, after separating the composite oxide particles subjected to the deposition treatment in the first step from the solvent system, if necessary, in order to adjust the amount of lithium, impregnation with an aqueous solution of a lithium compound, and then heat treatment May be performed.

  Examples of lithium compounds include lithium hydroxide, lithium carbonate, lithium nitrate, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium chlorate, lithium perchlorate, lithium bromate, lithium iodate, lithium oxide, Inorganic compounds such as 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, or Organic compounds such as methyl lithium, vinyl lithium, isopropyl lithium, butyl lithium, phenyl lithium, lithium oxalate, and lithium acetate can be used.

  Further, after firing, the particle size may be adjusted by light pulverization or classification operation, if necessary.

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

(1) First Example of Nonaqueous Electrolyte Secondary Battery (1-1) Configuration of Nonaqueous Electrolyte Secondary Battery FIG. 1 shows a nonaqueous electrolyte 2 using a positive electrode active material according to the first embodiment of the present invention. The cross-sectional structure of the secondary battery is shown.

  In this secondary battery, the open circuit voltage in a fully charged state per pair of positive electrode and negative electrode is, for example, 4.25V or more and 4.65V or less.

  This secondary battery is a so-called cylindrical type, and is a wound electrode in which a strip-shaped positive electrode 2 and a strip-shaped negative electrode 3 are wound via a separator 4 inside a substantially hollow cylindrical battery can 1. It has a body 20.

  The battery can 1 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 1, a pair of insulating plates 5 and 6 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

  At the open end of the battery can 1, a battery lid 7, a safety valve mechanism 8 and a thermal resistance element (PTC element) 9 provided inside the battery lid 7 are interposed via a gasket 10. It is attached by caulking, and the inside of the battery can 1 is sealed. The battery lid 7 is made of, for example, the same material as the battery can 1. The safety valve mechanism 8 is electrically connected to the battery lid 7 via a heat sensitive resistance element 9, and the disk plate 11 is reversed when the internal pressure of the battery becomes a certain level or more due to internal short circuit or external heating. Thus, the electrical connection between the battery lid 7 and the wound electrode body 20 is cut off. The heat-sensitive resistor element 9 limits the current by increasing the resistance value when the temperature rises, and prevents abnormal heat generation due to a large current. The gasket 10 is made of, for example, an insulating material, and asphalt is applied to the surface.

  The wound electrode body 20 is wound around, for example, the center pin 12. A positive electrode lead 13 made of, for example, aluminum (Al) or the like is connected to the positive electrode 2 of the spirally wound electrode body 20, and a negative electrode lead 14 made of, for example, nickel (Ni) or the like is connected to the negative electrode 3. The positive electrode lead 13 is electrically connected to the battery cover 7 by being welded to the safety valve mechanism 8, and the negative electrode lead 14 is welded and electrically connected to the battery can 1.

[Positive electrode]
FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. As shown in FIG. 2, the positive electrode 2 includes, for example, a positive electrode current collector 2A having a pair of opposed surfaces, and a positive electrode mixture layer 2B provided on both surfaces of the positive electrode current collector 2A. In addition, you may make it have the area | region where the positive mix layer 2B was provided only in the single side | surface of 2 A of positive electrode collectors. The positive electrode current collector 2A is made of, for example, a metal foil such as an aluminum (Al) foil. The positive electrode mixture layer 2B includes, for example, a positive electrode active material, and may include a conductive agent such as graphite and a binder such as polyvinylidene fluoride as necessary. As the positive electrode active material, the positive electrode active material according to the above-described embodiment can be used.

[Negative electrode]
As shown in FIG. 2, the negative electrode 3 includes, for example, a negative electrode current collector 3A having a pair of opposed surfaces, and a negative electrode mixture layer 3B provided on both surfaces of the negative electrode current collector 3A. In addition, you may make it have the area | region in which the negative mix layer 3B was provided only in the single side | surface of 3 A of negative electrode collectors. The negative electrode current collector 3A is made of a metal foil such as a copper (Cu) foil. The negative electrode mixture layer 3B includes, for example, a negative electrode active material, and may include a binder such as polyvinylidene fluoride as necessary.

The negative electrode active material includes a negative electrode material capable of inserting and extracting lithium (Li) (hereinafter referred to as a negative electrode material capable of inserting and extracting lithium (Li) as appropriate). Examples of negative electrode materials capable of inserting and extracting lithium (Li) include carbon materials, metal compounds, oxides, sulfides, lithium nitrides such as LiN ₃ , lithium metals, metals that form alloys with lithium, and high Examples include molecular materials.

  Examples of the carbon material include non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbons, cokes, glassy carbons, organic polymer compound fired bodies, carbon fibers, and activated carbon. Among these, examples of coke include pitch coke, needle coke, and petroleum coke. An organic polymer compound fired body is a carbonized material obtained by firing a polymer material such as a phenol resin or a furan resin at an appropriate temperature, and part of it is non-graphitizable carbon or graphitizable carbon. Some are classified as: Examples of the polymer material include polyacetylene and polypyrrole.

  Among such negative electrode materials capable of inserting and extracting lithium (Li), those having a charge / discharge potential relatively close to lithium metal are preferable. This is because the lower the charge / discharge potential of the negative electrode 3, the easier it is to increase the energy density of the battery. Among these, a carbon material is preferable because a change in crystal structure that occurs during charge / discharge is very small, a high charge / discharge capacity can be obtained, and good cycle characteristics can be obtained. In particular, graphite is preferable because it has a high electrochemical equivalent and can provide a high energy density. Moreover, non-graphitizable carbon is preferable because excellent cycle characteristics can be obtained.

  Examples of the negative electrode material capable of inserting and extracting lithium (Li) include lithium metal alone, a metal element or metalloid element simple substance, alloy or compound capable of forming an alloy with lithium (Li). These are preferable because a high energy density can be obtained, and in particular, when used together with a carbon material, a high energy density can be obtained and excellent cycle characteristics can be obtained, and therefore, it is more preferable. Note that in this specification, alloys include those composed of one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. The structures include solid solutions, eutectics (eutectic mixtures), intermetallic compounds, or those in which two or more of them coexist.

Examples of such a metal element or metalloid element include tin (Sn), lead (Pb), aluminum (Al), 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) ). These alloys or compounds, for example, those represented by the chemical formula Ma _s Mb _t Li _u or a chemical formula Ma _p Mc _q Md _r,. In these chemical formulas, Ma represents at least one of a metal element and a metalloid element capable of forming an alloy with lithium, Mb represents at least one of a metal element and a metalloid element other than lithium and Ma, Mc represents at least one of nonmetallic elements, and Md represents at least one of metallic elements and metalloid elements other than Ma. The values of s, t, u, p, q, and r are s> 0, t ≧ 0, u ≧ 0, p> 0, q> 0, and r ≧ 0, respectively.

  Among these, a simple substance, alloy or compound of Group 4B metal element or semimetal element in the short-period type periodic table is preferable, and silicon (Si) or tin (Sn), or an alloy or compound thereof is particularly preferable. These may be crystalline or amorphous.

In addition, inorganic compounds that do not contain lithium (Li), such as MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , NiS, and MoS, can also be used for any of the positive and negative electrodes.

[Electrolyte]
As the electrolytic solution, a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent can be used. As the non-aqueous solvent, for example, it is preferable to contain at least one of ethylene carbonate and propylene carbonate. This is because the cycle characteristics can be improved. In particular, it is preferable to mix and contain ethylene carbonate and propylene carbonate because cycle characteristics can be further improved. The nonaqueous solvent preferably contains at least one of chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, or methyl propyl carbonate. This is because the cycle characteristics can be further improved.

  The non-aqueous solvent preferably further contains at least one of 2,4-difluoroanisole and vinylene carbonate. This is because 2,4-difluoroanisole can improve discharge capacity, and vinylene carbonate can further improve cycle characteristics. In particular, it is more preferable that they are mixed and contained because both the discharge capacity and the cycle characteristics can be improved.

  Non-aqueous solvents further include butylene carbonate, γ-butyrolactone, γ-valerolactone, those in which part or all of the hydrogen groups of these compounds are substituted with fluorine groups, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl Tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, methyl acetate, methyl propionate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropironitrile, N, N-dimethylformamide N-methylpyrrolidinone, N-methyloxazolidinone, N, N-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, dimethyl sulfoxide or trimethyl phosphate may be included. Yes.

  Depending on the electrode to be combined, the reversibility of the electrode reaction may be improved by using a material in which part or all of the hydrogen atoms of the substance contained in the non-aqueous solvent group are substituted with fluorine atoms. Therefore, these substances can be used as appropriate.

Examples of the lithium salt that is an electrolyte salt include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) _2. , LiC (SO ₂ CF ₃ ) ₃ , LiAlCl ₄ , LiSiF ₆ , LiCl, LiBF ₂ (ox), LiBOB, or LiBr are suitable, and any one or more of these are used in combination. be able to. Among them, LiPF ₆ is preferable because it can obtain high ion conductivity and can improve cycle characteristics.

[Separator]
Below, the separator material which can be utilized for 1st Embodiment is demonstrated. As a separator material, it is possible to use those used in conventional batteries. Among these, it is particularly preferable to use a polyolefin microporous film that is excellent in short-circuit prevention effect and that can improve battery safety by a shutdown effect. For example, a microporous film made of polyethylene or polypropylene resin is preferable.

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

(1-2) Manufacturing Method of Nonaqueous Electrolyte Secondary Battery Next, a manufacturing method of the nonaqueous electrolyte secondary battery will be described. Hereinafter, a method for manufacturing a nonaqueous electrolyte secondary battery will be described by taking a cylindrical nonaqueous electrolyte secondary battery as an example.

  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 to form a positive electrode mixture. Use slurry.

  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 3 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 3A and drying the solvent, the negative electrode mixture layer 3B is formed by compression molding using a roll press or the like, and the negative electrode 3 is produced.

  Next, the positive electrode lead 13 is attached to the positive electrode current collector 2A by welding or the like, and the negative electrode lead 14 is attached to the negative electrode current collector 3A by welding or the like. Next, the positive electrode 2 and the negative electrode 3 are wound through the separator 4, and the tip of the positive electrode lead 13 is welded to the safety valve mechanism 8, and the tip of the negative electrode lead 14 is welded to the battery can 1. The rotated positive electrode 2 and negative electrode 3 are sandwiched between a pair of insulating plates 5 and 6 and stored in the battery can 1.

  Next, an electrolytic solution is injected into the battery can 1 and the separator 4 is impregnated with the electrolytic solution. Next, the battery lid 7, the safety valve mechanism 8, and the heat sensitive resistance element 9 are fixed to the opening end of the battery can 1 by caulking through the gasket 10. Thus, a nonaqueous electrolyte secondary battery is produced.

(2) Second Example of Nonaqueous Electrolyte Secondary Battery (2-1) Configuration of Nonaqueous Electrolyte Secondary Battery FIG. 3 is a nonaqueous electrolyte secondary battery using a positive electrode active material according to an embodiment of the present invention. The structure of is shown. As shown in FIG. 3, this non-aqueous electrolyte secondary battery is sealed by housing the battery element 30 in an exterior material 37 made of a moisture-proof laminate film and welding the periphery of the battery element 30. The battery element 30 is provided with a positive electrode lead 32 and a negative electrode lead 33, and these leads are sandwiched between outer packaging materials 37 and pulled out to the outside. A resin piece 34 and a resin piece 35 are coated on both surfaces of the positive electrode lead 32 and the negative electrode lead 33 in order to improve the adhesion to the exterior material 37.

[Exterior material]
The packaging material 37 has, for example, a stacked structure in which an adhesive layer, a metal layer, and a surface protective layer are sequentially stacked. 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). 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 30 is stored.

[Battery element]
For example, as shown in FIG. 4, the battery element 30 includes a strip-shaped negative electrode 43 provided with a gel electrolyte layer 45 on both sides, a separator 44, and a strip-shaped positive electrode 42 provided with a gel electrolyte layer 45 on both sides. The battery element 30 is a wound type battery element 30 that is formed by laminating the separator 44 and wound in the longitudinal direction.

  The positive electrode 42 includes a strip-shaped positive electrode current collector 42A and a positive electrode mixture layer 42B formed on both surfaces of the positive electrode current collector 42A. The positive electrode current collector 42A is a metal foil made of, for example, aluminum (Al).

  One end of the positive electrode 42 in the longitudinal direction is provided with a positive electrode lead 32 connected by, for example, spot welding or ultrasonic welding. As a material of the positive electrode lead 32, for example, a metal such as aluminum can be used.

  The negative electrode 43 includes a strip-shaped negative electrode current collector 43A and a negative electrode mixture layer 43B formed on both surfaces of the negative electrode current collector 43A. The negative electrode current collector 43A is made of, for example, a metal foil such as a copper (Cu) foil, a nickel foil, or a stainless steel foil.

  Similarly to the positive electrode 42, the negative electrode lead 33 connected by, for example, spot welding or ultrasonic welding is also provided at one end portion of the negative electrode 43 in the longitudinal direction. As a material of the negative electrode lead 33, for example, copper (Cu), nickel (Ni) or the like can be used.

  Since things other than the gel electrolyte layer 45 are the same as those in the first example described above, the gel electrolyte layer 45 will be described below.

  The gel electrolyte layer 45 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 45 is preferable because it can obtain high ionic conductivity and prevent battery leakage. The configuration of the electrolytic solution (that is, the liquid solvent, the electrolyte salt, and the additive) is the same as that in the first embodiment.

  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.

(2-2) Method for Producing Nonaqueous Electrolyte Secondary Battery Next, a method for producing a nonaqueous electrolyte secondary battery using a positive electrode active material according to an embodiment of the present invention 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 42 and the negative electrode 43, and the mixed solvent is volatilized to form the gel electrolyte layer 45. In addition, the positive electrode lead 32 is attached to the end of the positive electrode current collector in advance by welding, and the negative electrode lead 33 is attached to the end of the negative electrode current collector 43A by welding.

  Next, the positive electrode 42 and the negative electrode 43 on which the gel electrolyte layer 45 is formed are laminated through a separator 44 to form a laminated body, and then the laminated body is wound in the longitudinal direction to form a wound battery element. 30 is formed.

  Next, a recess 36 is formed by deep-drawing an exterior material 37 made of a laminate film, the battery element 30 is inserted into the recess 36, and an unprocessed portion of the exterior material 37 is folded back to the upper portion of the recess 36. The outer peripheral part of is thermally welded and sealed. Thus, a nonaqueous electrolyte secondary battery is produced.

  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, 20 parts by weight of complex oxide particles having an average composition of Li _1.03 CoO _2.01 and an average particle diameter of 13 μm measured by a laser scattering method were stirred and dispersed in 300 parts by weight of pure water at 80 ° C. for 1 hour.

Next, 1.60 parts by weight of a commercially available reagent nickel nitrate (Ni (NO ₃ ) ₂ .6H ₂ O) and a commercially available reagent manganese nitrate (Mn (NO ₃ ) ₂ .6H ₂ O) 1.65 Further, 2N LiOH aqueous solution was added to pH 13 over 30 minutes, and stirring and dispersion were continued at 80 ° C. for 3 hours, and then allowed to cool.

Next, this dispersion was decanted and washed, and 0.1 parts by weight of a commercially available reagent ammonium molybdate ((NH ₄ ) ₂ MoO ₄ ) was dissolved in 1.0 part by weight of pure water and added. Further, decantation washing was performed, and finally, filtration was performed, followed by drying at 120 ° C. to form a precursor.

  Next, in order to adjust the amount of lithium, 10 parts by weight of the obtained precursor sample was impregnated with 2 parts by weight of 2N LiOH aqueous solution and uniformly mixed and dried to obtain a calcined precursor. The calcined precursor was heated at a rate of 5 ° C./min in an air flow using an electric furnace, held at 950 ° C. for 5 hours, then cooled to 150 ° C. at 7 ° C./min, and the positive electrode of Example 1 An active material was obtained.

  As a result of quantifying the solution in which the positive electrode active material was uniformly dissolved with hydrochloric acid using ICP-AES, the atomic ratio of molybdenum (Mo) and cobalt (Co) was 0.000052, and the surface of the positive electrode active material was As a result of quantification using XPS, the atomic ratio of molybdenum (Mo) to cobalt (Co) on the surface was 0.063.

  When XRD (X-ray diffraction; X-ray diffraction) of this powder was measured, no diffraction peak attributable to the molybdenum (Mo) compound was found. As a result of XPS measurement, the peak of Mo3d5 / 2 was 232.1 eV.

<Example 2>
First, 20 parts by weight of the composite oxide particles used in Example 1 were stirred and dispersed in 300 parts by weight of a 2N LiOH aqueous solution at 80 ° C. for 2 hours (this system had a pH of 14.2). Next, 1.60 parts by weight of a commercially available reagent nickel nitrate (Ni (NO ₃ ) ₂ .6H ₂ O) and a commercially available reagent manganese nitrate (Mn (NO ₃ ) ₂ .6H ₂ O) 1.65 An aqueous solution was prepared by adding pure water to 10 parts by weight, and 10 parts by weight of this aqueous solution was added over 2 hours. Further, stirring and dispersion were continued at 80 ° C. for 1 hour, and then allowed to cool.

Next, the dispersion was decanted and washed, and 0.2 parts by weight of a commercially available reagent sodium molybdate (Na ₂ MoO ₄ ) was dissolved in 2.0 parts by weight of pure water and added. The precursor was formed by subjecting it to a washing and finally filtering and drying at 120 ° C. Next, using an electric furnace, the obtained precursor was heated at a rate of 5 ° C. per minute under an air flow, held at 950 ° C. for 5 hours, then cooled to 150 ° C. at 7 ° C. per minute, and carried out. The positive electrode active material of Example 2 was obtained.

  As a result of quantifying the solution in which the positive electrode active material was uniformly dissolved with hydrochloric acid using ICP-AES, the atomic ratio of molybdenum (Mo) to cobalt (Co) was 0.000096, and the surface of the positive electrode active material was As a result of quantification using XPS, the atomic ratio of molybdenum (Mo) to cobalt (Co) on the surface was 0.18.

  When XRD of this powder was measured, a diffraction peak attributable to the molybdenum (Mo) compound was not found. As a result of XPS measurement, the peak of Mo3d5 / 2 was 232.2 eV.

<Example 3>
Pure water is added to 3.20 parts by weight of nickel nitrate (Ni (NO ₃ ) ₂ .6H ₂ O) as a commercial reagent and 3.30 parts by weight of manganese nitrate (Mn (NO ₃ ) ₂ .6H ₂ O) as a commercial reagent. Was added to prepare 20 parts by weight of an aqueous solution, and 20 parts by weight of this aqueous solution was added over 3 hours. 0.1 parts by weight of a commercially available reagent, lithium molybdate (Li ₂ MoO ₄ ), was dissolved in 1.0 part by weight of pure water and added. Other than this, the positive electrode active material of Example 3 was produced in the same manner as Example 2.

  As a result of quantifying the solution in which the positive electrode active material was uniformly dissolved with hydrochloric acid using ICP-AES, the atomic ratio of molybdenum (Mo) to cobalt (Co) was 0.000086, and the surface of the positive electrode active material was As a result of quantification using XPS, the atomic ratio of molybdenum (Mo) to cobalt (Co) on the surface was 0.072.

  When XRD of this powder was measured, a diffraction peak attributable to the molybdenum (Mo) compound was not found. As a result of XPS measurement, the peak of Mo3d5 / 2 was 232.1 eV.

<Example 4>
Nickel nitrate _{(Ni (NO 3) 2 ·} 6H 2 O) 3.20 parts by weight of commercially available reagents, manganese nitrate commercial reagents and _{(Mn (NO 3) 2 ·} 6H 2 O) 3.30 parts by weight, commercially available reagents aluminum nitrate _{(Al (NO 3) 3 ·} 9H 2 O) was added to pure water and 0.86 parts by weight to prepare an aqueous solution with 20 parts by weight, were added over the aqueous solution 20 parts by weight the total amount 3 hours . 0.1 parts by weight of commercially available reagent sodium molybdate (Na ₂ MoO ₄ ) is dissolved in 2.0 parts by weight of pure water, and 0.05 parts by weight of commercially available reagent molybdic anhydride (MoO ₃ ) is further added to this solution. Was dissolved and added. Other than this, the positive electrode active material of Example 4 was produced in the same manner as Example 2.

  As a result of quantifying the solution in which the positive electrode active material was uniformly dissolved with hydrochloric acid using ICP-AES, the atomic ratio of molybdenum (Mo) and cobalt (Co) was 0.000075, and the surface of the positive electrode active material was As a result of quantification using XPS, the atomic ratio of molybdenum (Mo) to cobalt (Co) on the surface was 0.12.

  When XRD of this powder was measured, a diffraction peak attributable to the molybdenum (Mo) compound was not found. As a result of XPS measurement, the peak of Mo3d5 / 2 was 232.3 eV.

<Example 5>
Manganese nitrate (Mn (NO ₃ ) ₂ .6H ₂ O) is not added, and only 3.20 parts by weight of commercially available nickel nitrate (Ni (NO ₃ ) ₂ .6H ₂ O) is added to pure water to give 20 An aqueous solution with parts by weight was prepared, and a total of 20 parts by weight of this aqueous solution was added over 3 hours. 0.1 parts by weight of a commercially available reagent, lithium molybdate (Li ₂ MoO ₄ ), was dissolved in 1.0 part by weight of pure water and added. Other than this, a positive electrode active material of Example 5 was produced in the same manner as Example 2.

  As a result of quantifying the solution in which the positive electrode active material was uniformly dissolved with hydrochloric acid using ICP-AES, the atomic ratio of molybdenum (Mo) to cobalt (Co) was 0.000089, and the surface of the positive electrode active material was As a result of quantification using XPS, the atomic ratio of molybdenum (Mo) to cobalt (Co) on the surface was 0.082.

  When XRD of this powder was measured, a diffraction peak attributable to the molybdenum (Mo) compound was not found. As a result of XPS measurement, the peak of Mo3d5 / 2 was 232.1 eV.

<Comparative Example 1>
In Example 1, a composite oxide particle having an average composition of Li _1.03 CoO _2.01 and an average particle diameter of 13 μm measured by a laser scattering method was used as the positive electrode active material of Comparative Example 1 without modifying the particle surface.

<Comparative example 2>
A positive electrode active material of Comparative Example 2 was produced in the same manner as in Example 1 except that 0.1 part by weight of ammonium molybdate ((NH ₄ ) ₂ MoO ₄ ) was not added.

<Comparative Example 3>
In Example 1, instead of adding 0.1 part by weight of ammonium molybdate ((NH ₄ ) ₂ MoO ₄ ) dissolved in 1.0 part by weight of pure water, sodium molybdate (Na ₂ MoO ₄ ) 15 In the same manner as in Example 1, except that 0.0 part by weight was dissolved in 300 parts by weight of pure water and 7.5 parts by weight of a commercially available reagent, MoO ₃ anhydride, was dissolved and added to this solution. Obtained material.

  As a result of quantifying the solution in which the positive electrode active material was uniformly dissolved with hydrochloric acid using ICP-AES, the atomic ratio of molybdenum (Mo) and cobalt (Co) was 0.0032, and the surface of the positive electrode active material was As a result of quantitative determination using XPS, the atomic ratio of molybdenum (Mo) and cobalt (Co) on the surface was 0.62.

  When XRD of this powder was measured, a diffraction peak attributable to the molybdenum (Mo) compound was not found. As a result of XPS measurement, the peak of Mo3d5 / 2 was 232.7 eV.

<Comparative example 4>
100 parts by weight of the positive electrode active material prepared in Example 1 was impregnated in an aqueous solution in which 2.0 parts by weight of lithium molybdate (Li ₂ MoO ₄ ) was dissolved in 10 parts by weight of pure water and then dried. A positive electrode active material of Comparative Example 4 was obtained by heat treatment in air for 2 hours.

  A solution obtained by uniformly dissolving the positive electrode active material with hydrochloric acid was quantified using ICP-AES. As a result, the atomic ratio of molybdenum (Mo) to cobalt (Co) was 0.011, and the surface of the positive electrode active material was As a result of quantitative determination using XPS, the atomic ratio of molybdenum (Mo) and cobalt (Co) on the surface was 0.68.

  When XRD of this powder was measured, a diffraction peak attributable to the molybdenum (Mo) compound was not found. As a result of XPS measurement, the peak of Mo3d5 / 2 was 232.5 eV.

[Evaluation]
The secondary batteries shown in FIGS. 1 and 2 were produced using the produced positive electrode active materials of Examples 1 to 5 and Comparative Examples 1 to 4. 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-2-pyrrolidone (NMP) as a solvent was mixed. Then, it was applied to both sides of a positive electrode current collector 2A made of a strip-shaped aluminum foil having a thickness of 20 μm, dried, and compression-molded by a roller press to form a positive electrode mixture layer 2B, whereby a positive electrode 2 was produced. At that time, the positive electrode active material powder was sufficiently pulverized by a crusher so as to pass through a 70 μm opening sieve. Moreover, the space | gap of the positive mix layer 2B was adjusted so that it might become 26% by a volume ratio. Next, the positive electrode lead 13 made of aluminum was attached to the positive electrode current collector 2A.

  Further, 90% by weight of artificial graphite powder as a negative electrode active material and 10% by weight of polyvinylidene fluoride as a binder were mixed and dispersed in N-methyl-2-pyrrolidone as a solvent, and then a 10 μm thick strip-shaped copper The negative electrode current collector 3A made of foil was applied to both surfaces and dried, and compression molding was performed with a roller press to form the negative electrode mixture layer 3B, whereby the negative electrode 3 was produced. Next, a negative electrode lead 14 made of nickel was attached to the negative electrode current collector 3A.

The strip-shaped positive electrode 2 and the strip-shaped negative electrode 3 produced as described above were wound many times through a porous polyolefin film as a separator 4 to produce a spiral wound electrode body 20. Next, the wound electrode body 20 was housed in an iron battery can 1, and a pair of insulating plates 5 and 6 were disposed on both upper and lower surfaces of the wound electrode body 20. Next, the positive electrode lead 13 was led out from the positive electrode current collector 2A and welded to the safety valve mechanism 8, and the negative electrode lead 14 was led out from the negative electrode current collector 3A and welded to the bottom of the battery can 1. Thereafter, an electrolytic solution is injected into the battery can 1 and the battery can 1 is caulked through the gasket 10, thereby fixing the safety valve mechanism 8, the heat sensitive resistance element 9 and the battery lid 7, and having an outer diameter of 18 mm, high A cylindrical secondary battery having a thickness of 65 mm was obtained. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ as an electrolyte salt to 1.0 mol / l in a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 was used.

  About the secondary battery produced as mentioned above, it charges / discharges in a 45 degreeC temperature environment, calculates | requires the discharge capacity of the 1st cycle as an initial capacity, and calculates | requires the discharge capacity maintenance factor of the 200th cycle with respect to the 1st cycle. It was.

  Charging is performed at a constant current of 1000 mA until the battery voltage reaches 4.40 V, and then charged at a constant voltage of 4.40 V until the total charging time is 2.5 hours. The discharge was performed at a constant current of 800 mA until the battery voltage reached 2.75V. The measurement results are shown in Table 1.

  As shown in Table 1, it can be seen that Examples 1 to 5 have a high capacity and a larger discharge capacity retention rate than Comparative Examples 1 to 4. Further, from the comparison of the discharge capacity retention ratios of Example 3 and Example 5, the structure of nickel (Ni) and manganese (Mn) of the metal oxide is nickel (from the point that good charge / discharge cycle characteristics can be obtained. It can be seen that it is preferable to contain both nickel (Ni) and manganese (Mn) rather than Ni) alone.

  Further, the atomic ratio of molybdenum (Mo) and cobalt (Co) in the whole positive electrode active material is 0.001 or less, and the atomic ratio of molybdenum (Mo) and cobalt (Co) in the surface portion of the positive electrode active material is 0.01. It can be seen that both the initial capacity and the capacity retention ratio can be achieved when the value is 0.5 or less and the bond energy of molybdenum (Mo) is 232.4 eV or less.

  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 is not particularly limited. It may be a cylindrical shape, a square shape, a coin shape, a button shape, or the like.

  In the first embodiment, a non-aqueous electrolyte secondary battery having an electrolyte as an electrolyte has been described. In the second embodiment, a non-aqueous electrolyte secondary battery having a gel electrolyte as an electrolyte has been described. However, the present invention is not limited thereto. Is not to be done.

  For example, as the electrolyte, in addition to the above-described ones, a polymer solid 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.

  Furthermore, for example, a conventional nonaqueous solvent-based electrolytic solution is used as the electrolytic solution of the nonaqueous electrolyte secondary battery without any particular limitation. Among these, the electrolyte solution of a secondary battery comprising a non-aqueous electrolyte containing an alkali metal salt includes propylene carbonate, ethylene carbonate, γ-butyrolactone, N-methylpyrrolidone, acetonitrile, N, N-dimethylformamide, dimethylsulfate. For example, foxoxide, tetrahydrofuran, 1,3-dioxolane, methyl formate, sulfolane, oxazolidone, thionyl chloride, 1,2-dimethoxyethane, diethylene carbonate, and derivatives and mixtures thereof are preferably used. The electrolyte contained in the electrolyte includes alkali metal, especially calcium halide, perchlorate, thiocyanate, borofluoride, phosphofluoride, arsenic fluoride, yttrium fluoride, trifluoromethylsulfate, etc. Is preferably used.

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. FIG. 2 is an enlarged sectional view of a part of a wound electrode body shown in FIG. 1. 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. 4 is an enlarged cross section of a part of the battery element shown in FIG. 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Battery can 2 ... Positive electrode 2A ... Positive electrode collector 2B ... Positive electrode mixture layer 3A ... Negative electrode collector 3B ... Negative electrode mixture layer 3 ... Negative electrode 4. .. Separator 5, 6 ... Insulating plate 7 ... Battery cover 8 ... Safety valve mechanism 9 ... Heat sensitive resistance element 10 ... Gasket 11 ... Disc plate 12 ... Center pin 13 .. Positive electrode lead 14 ... Negative electrode lead 20 ... Winding electrode body 30 ... Battery element 32 ... Positive electrode lead 33 ... Negative electrode lead 34, 35 ... Resin piece 35 ... Negative electrode lead 36 ... Recess 37 ... Exterior material 42 ... Positive electrode 42A ... Positive electrode current collector 42B ... Positive electrode mixture layer 43 ... Negative electrode 43A ... Negative electrode current collector 43B ... Negative electrode Mixture layer 44 ... Separator 45 ... Gel electrolyte layer

Claims (16)

A coating layer comprising an oxide provided on at least a part of the composite oxide particles and including lithium (Li) and nickel (Ni) or a coating element of nickel (Ni) and manganese (Mn);
Provided on at least a part of the covering layer, and a surface layer containing molybdenum (Mo),
The composite oxide particle has a mean composition represented by Chemical Formula 1 and is a positive electrode active material.
(Chemical formula 1)
_{Li (1 + x) Co (} 1-y) M y O (2-z)
(In the chemical formula 1, M is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni ), Copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), and tungsten (W), at least one element selected from the group consisting of x, y, and z is −0. 10 ≦ x ≦ 0.10, 0 ≦ y <0.50, −0.10 ≦ z ≦ 0.20. 2. The positive electrode active material according to claim 1, wherein a composition ratio of the nickel (Ni) and the manganese (Mn) in the coating layer is in a range of 99: 1 to 30:70. The oxide of the coating layer contains 40 mol% or less of the total amount of nickel (Ni) and manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium ( At least selected from the group consisting of V), chromium (Cr), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), and tungsten (W) The positive electrode active material according to claim 1, wherein the positive electrode active material is replaced with one or more metal elements. 2. The positive electrode active material according to claim 1, wherein an amount of the coating layer is in a range of 0.5 wt% to 50 wt% of the composite oxide particles. 2. The positive electrode active material according to claim 1, wherein the average particle size is 2.0 μm to 50 μm. Cobalt (Co) diffused from the composite oxide particles exists in the coating layer and the surface layer,
The average atomic ratio of the molybdenum (Mo) and the cobalt (Co) of the whole positive electrode active material is 0.001 or less, and the molybdenum (Mo) and the cobalt (Co) on the surface of the positive electrode active material 2. The positive electrode active material according to claim 1, wherein the atomic ratio is 0.01 or more and 0.5 or less. 2. The positive electrode active material according to claim 1, wherein the molybdenum (Mo) of the surface layer has a 3d5 / 2 binding energy of 232.4 eV or less by XPS (X-ray Photoelectron Spectroscopy). . After forming a layer made of hydroxide containing nickel (Ni) or nickel (Ni) and manganese (Mn) on at least a part of the composite oxide particles whose average composition is represented by chemical formula 1, the composite oxide particles Depositing molybdic acid on at least a portion of
After depositing the molybdic acid, heat treatment is performed, so that at least a part of the composite oxide particles is coated with lithium (Li) and nickel (Ni) or nickel (Ni) and manganese (Mn) covering elements. And a step of forming a surface layer containing molybdenum (Mo), and a method for producing a positive electrode active material.
(Chemical formula 1)
_{Li (1 + x) Co (} 1-y) M y O (2-z)
(In the chemical formula 1, M is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni ), Copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), and tungsten (W), at least one element selected from the group consisting of x, y, and z is −0. 10 ≦ x ≦ 0.10, 0 ≦ y <0.50, −0.10 ≦ z ≦ 0.20. Formation of the nickel (Ni) or hydroxide containing nickel (Ni) and manganese (Mn),
The composite oxide particles are dispersed in a solvent mainly composed of water having a pH of 12 or more, and then a nickel (Ni) compound or a nickel (Ni) compound and a manganese (Mn) compound are added. The manufacturing method of the positive electrode active material of Claim 8. The method for producing a positive electrode active material according to claim 9, wherein the water-based solvent contains lithium hydroxide. The method for producing a positive electrode active material according to claim 8, wherein a composition ratio of the nickel (Ni) and the manganese (Mn) in the coating layer is in a range of 99: 1 to 30:70. The oxide of the coating layer contains 40 mol% or less of the total amount of nickel (Ni) and manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium ( At least selected from the group consisting of V), chromium (Cr), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), and tungsten (W) The method for producing a positive electrode active material according to claim 8, wherein the positive electrode active material is replaced with one or more metal elements. The method for producing a positive electrode active material according to claim 8, wherein the amount of the coating layer is in the range of 0.5 wt% to 50 wt% of the composite oxide particles. The method for producing a positive electrode active material according to claim 8, wherein the positive electrode active material has an average particle diameter of 2.0 μm to 50 μm. In the coating layer, there is cobalt (Co) diffused from the composite oxide particles,
The average atomic ratio of the molybdenum (Mo) and the cobalt (Co) of the whole positive electrode active material is 0.001 or less, and the molybdenum (Mo) and the cobalt (Co) on the surface of the positive electrode active material The method for producing a positive electrode active material according to claim 8, wherein the atomic ratio is 0.01 or more and 0.5 or less. A positive electrode having a positive electrode active material, a negative electrode, a separator and an electrolyte;
The positive electrode active material is
A coating layer formed of an oxide provided on at least a part of the composite oxide particles and including lithium (Li) and at least one coating element of nickel (Ni) and manganese (Mn);
Provided on at least a part of the covering layer, and a surface layer containing molybdenum (Mo),
The non-aqueous electrolyte secondary battery, wherein the composite oxide particles have an average composition represented by chemical formula 1.
(Chemical formula 1)
_{Li (1 + x) Co (} 1-y) M y O (2-z)
(In the chemical formula 1, M is magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni ), Copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), and tungsten (W), at least one element selected from the group consisting of x, y, and z is −0. 10 ≦ x ≦ 0.10, 0 ≦ y <0.50, −0.10 ≦ z ≦ 0.20.

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