JP2007242318A - Positive active material, its manufacturing method, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive active material capable of enhancing chemical stability and its manufacturing method; and to provide a nonaqueous electrolyte secondary battery having high capacity and excellent charge discharge characteristics using the positive active material. <P>SOLUTION: A positive electrode 2 has the positive active material. The positive active material has a covering layer formed in at least a part of a composite oxide particle, comprising an oxide containing lithium (Li) and at least one covering element out of nickel (Ni) and manganese (Mn), and a surface layer formed in at least a part of the covering layer and comprising an oxide containing yttrium (Y). <P>COPYRIGHT: (C)2007,JPO&INPIT

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 is 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

  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 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);
A surface layer made of an oxide containing yttrium (Y), provided on at least a part of the coating layer;
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), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), zirconium (Zr) It is composed of at least one selected element, and x, y, and z are −0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −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 100: 0 to 30:70.

  In the first 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), calcium (Ca), strontium ( It is preferable that the element is replaced with at least one metal element selected from the group consisting of Sr), tungsten (W), yttrium (Y), and zirconium (Zr).

  Furthermore, in the first invention, the oxide of the surface layer contains 20 mol% or less of the total amount of yttrium (Y), magnesium (Mg), boron (B), titanium (Ti), vanadium (V), chromium ( Cr), manganese (Mn), iron (Fe), cobalt (Co), aluminum (Al), nickel (Ni), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium ( It is preferable that the metal element be replaced with at least one metal element selected from the group consisting of Ca), strontium (Sr), tungsten (W), and zirconium (Zr).

  Furthermore, in the first invention, the amount of the coating layer is preferably 0.5 to 50 parts by weight with respect to 100 parts by weight of the composite oxide particles.

Further, in the first invention, the amount of the surface layer is 0 with respect to 100 parts by weight of the positive electrode active material as a weight obtained by converting the amount of yttrium (Y) of the oxide of the surface layer into yttrium oxide (Y ₂ O ₃ ). It is preferably 1 to 10 parts by weight.

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

The second invention is
After forming a layer made of a hydroxide containing nickel (Ni) and / manganese (Mn) on at least a part of the composite oxide particles whose average composition is expressed in Chemical Formula 1, at least a part of the composite oxide particles Forming a hydroxide containing yttrium (Y);
At least one of lithium (Li), nickel (Ni), and manganese (Mn) is formed on at least a part of the composite oxide particles by forming a hydroxide containing yttrium (Y) and then performing heat treatment. And a step of forming a surface layer containing yttrium (Y), and a method of 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), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), zirconium (Zr) It is composed of at least one selected element, and x, y, and z are −0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −0.10 ≦ z ≦ 0.20. )

  In the second invention, the deposition of the hydroxide containing nickel (Ni) and / or manganese (Mn) is performed by dispersing the composite oxide particles in a solvent mainly composed of water having a pH of 12 or more, and then nickel (Ni). It is preferable to carry out by adding a compound of the above and / or a compound of manganese.

  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 100: 0 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), calcium (Ca), strontium (Sr) , Tungsten (W), yttrium (Y), and zirconium (Zr) are preferably substituted with at least one metal element selected from the group consisting of.

  In the second invention, the oxide of the surface layer comprises 20 mol% or less of the total amount of yttrium (Y), magnesium (Mg), boron (B), titanium (Ti), vanadium (V), chromium (Cr). , Manganese (Mn), iron (Fe), cobalt (Co), aluminum (Al), nickel (Ni), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca) , Strontium (Sr), tungsten (W), and zirconium (Zr) are preferably substituted with at least one metal element selected from the group consisting of.

  In 2nd invention, it is preferable that the quantity of a coating layer is 0.5 weight part-50 weight part with respect to 100 weight part of complex oxide particles.

In the second invention, the amount of the surface layer is 0.1% with respect to 100 parts by weight of the positive electrode active material as the weight of the oxide of the surface layer converted to yttrium oxide (Y ₂ O ₃ ). It is preferable that it is 10 weight part.

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

The third invention is
A positive electrode, a negative electrode, a separator and an electrolyte;
The positive electrode has a positive electrode active material,
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);
A surface layer made of an oxide containing yttrium (Y), provided on at least a part of the coating layer;
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), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), zirconium (Zr) It is composed of at least one selected element, wherein x, y, and z are −0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −0.10 ≦ z ≦ 0.20. is there.)

  In this invention, since at least a part of the composite oxide particles includes a coating layer made of an oxide containing lithium (Li) and at least one of the coating elements of nickel (Ni) and manganese (Mn), High charge voltage and high energy density associated therewith can be realized, and good charge / discharge cycle characteristics are obtained under high charge voltage conditions.

  In the present invention, particles are bound to each other by forming a hydroxide containing yttrium (Y) on a composite oxide particle provided with a hydroxide containing nickel (Ni) and / or manganese (Mn). Can be suppressed. And since crushing of the bound particles can be avoided, an increase in the active surface of the particles and destruction of the particles due to crushing can be suppressed, and the advantages of the coating layer can be fully utilized.

  According to this invention, the chemical 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. The positive electrode active material according to one embodiment of the present invention includes an oxide containing lithium (Li) and at least one covering element of nickel (Ni) and manganese (Mn) in at least a part of the composite oxide particles. And a surface layer made of an oxide containing yttrium (Y) 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, a lithium (Li) compound, a nickel (Ni) compound and / or a manganese (Mn) compound are dry-mixed as composite oxide particles and finely pulverized particles. Then, a coating layer made of an oxide containing lithium (Li) and at least one of the coating elements of nickel (Ni) and manganese (Mn) is deposited on the surface of the composite oxide particles. Lithium (Li) compound, nickel (Ni) compound and / or manganese (Mn) compound dissolved or mixed in a solvent, wet-coated and fired, lithium (Li), A method can be proposed in which a coating layer made of an oxide containing at least one coating element of nickel (Ni) and manganese (Mn) is provided on the surface of the composite oxide particles. However, with these methods, results were obtained in which highly uniform deposition 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 deposition can be realized. In this deposition treatment, a compound of nickel (Ni) and / or a compound of manganese (Mn) is dissolved in a solvent system mainly composed of water, and then complex oxide particles are dispersed in the solvent system. The basicity of the dispersion is increased, for example, by adding a base to the surface, and a hydroxide containing nickel (Ni) and / or manganese (Mn) is precipitated on the surface of the composite oxide particles.

  And the composite oxide particle which adhered the hydroxide containing nickel (Ni) and / or manganese (Mn) by the deposition process is heat-dehydrated, and a coating layer is formed on the composite oxide particle surface. Thereby, the uniformity of the deposition on the surface of the composite oxide particles can be improved. However, the inventors of the present application have made further studies and found that the sintering between the particles tends to proceed during the firing of the precursor.

  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.

  Accordingly, the inventors of the present application have made extensive studies for the purpose of improving the deterioration of the positive electrode function and improving the manufacturing process based on the sintering between particles, and water containing nickel (Ni) and / or manganese (Mn). It has been found that the progress of sintering can be improved by further depositing a hydroxide containing yttrium (Y) on the surface of the composite oxide particles to which the oxide is deposited. Accordingly, it has been found that the damage or destruction of the particles can be reduced, and that the improvement of the function can be improved by the surface modification effect of the positive electrode by the deposition.

  Next, the composite oxide, coating layer, and surface layer constituting the positive electrode active material according to one embodiment of the present invention 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), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), zirconium (Zr) It is composed of at least one selected element, and x, y, and z are −0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −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 at least one coating element of nickel (Ni) and manganese (Mn). By providing this coating layer, there are high charge voltage characteristics and high energy density characteristics associated therewith, and high capacity charge / discharge cycle characteristics under high charge voltage conditions can be improved.

  The constituent ratio of nickel (Ni) and manganese (Mn) in the coating layer is preferably in the range of 100: 0 to 30:70, and more preferably in the range of 100: 0 to 40:60. . As the amount of manganese (Mn) increases, the occlusion of lithium (Li) decreases, which ultimately causes a decrease in the capacity of the positive electrode active material and an increase in electrical resistance when used in a battery. is there. Moreover, the range of the composition ratio of nickel (Ni) and manganese (Mn) is more effective in suppressing the progress of sintering between particles in the firing of the precursor added with lithium (Li). It is a range.

  Further, nickel (Ni) and / or manganese (Mn) in the oxide of the coating layer is changed to magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), Iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), It can be replaced with at least one metal element selected from the group consisting of zirconium (Zr).

  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, when 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 is made of an oxide containing yttrium (Y). By providing the surface layer, the binding between the particles can be suppressed. Moreover, it is thought that the surface layer which consists of an oxide containing yttrium (Y) also contributes to the effect | action and effect of the said 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 oxide of the surface layer, 20 mol% or less of the total amount of yttrium (Y) is magnesium (Mg), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn). , Iron (Fe), cobalt (Co), aluminum (Al) nickel (Ni), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), It can be replaced with at least one metal element selected from the group consisting of tungsten (W) and zirconium (Zr). Thereby, the stability improvement of a positive electrode active material and the diffusibility of lithium ion can be improved.

  The substitution amount of the selected metal element is 20 mol% or less of the total amount of yttrium (Y) of the oxide of the surface layer, preferably 15 mol% or less, more preferably 10 mol%. . If the amount of substitution of the selected metal element is increased beyond this range, the effect of preventing sintering due to the deposition of the surface layer and the accompanying effect of increasing the charge / discharge cycle characteristics tend to be reduced.

The amount of the surface layer is from 1.0 × 10 ⁻⁵ mol to 1.0 × 10 ⁻² mol of yttrium ions per 1 m ² of the surface area of the deposition surface as the amount of deposition as yttrium (Y). Further, the deposition amount is preferably 3.0 × 10 ⁻⁵ mol to 5.0 × 10 ⁻³ mol, and more preferably 1.0 × 10 ⁻⁴ mol to 1.0 × 10 ⁻³ mol. Is a mole. Outside this range, when the amount of the surface layer increases, the diffusion resistance of lithium ions increases and the capacity of the final positive electrode active material of the present invention decreases. On the other hand, if the amount of the surface layer decreases outside this range, the sintering preventing effect and the accompanying effect of improving the charge / discharge cycle characteristics tend to decrease.

  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 the production of 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, the manufacturing method of the positive electrode active material by one Embodiment of this invention is demonstrated. According to an embodiment of the present invention, there is provided a method for producing a positive electrode active material, wherein a layer made of a hydroxide containing nickel (Ni) and / or manganese (Mn) is formed on at least a part of composite oxide particles, and then composite oxidation is performed. The first step of forming a hydroxide containing yttrium (Y) on at least a part of the product particles, and the formation of the hydroxide containing yttrium (Y), followed by heat treatment, the composite oxide particles A coating layer made of an oxide containing at least a part of lithium (Li) and at least one of the covering elements of nickel (Ni) and manganese (Mn), and a surface made of an oxide containing yttrium (Y) It can be roughly divided into a second step of forming a layer.

(First step)
In the first step, a deposition treatment of a hydroxide containing nickel (Ni) and / manganese (Mn) and a hydroxide containing yttrium (Y) is performed. 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 and / or a manganese (Mn) compound is dissolved. The basicity of the dispersion is increased by adding a base and the like, and a hydroxide containing nickel (Ni) and / or 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 and / or a manganese (Mn) compound is added to the aqueous solution to obtain nickel (Ni). And / or a hydroxide containing 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, 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.

  Next, a hydroxide containing yttrium (Y) is deposited on the surface of the composite oxide particles coated with a hydroxide containing nickel (Ni) and / or manganese (Mn). The deposition of the hydroxide containing yttrium (Y) can be performed in the same manner as the deposition of the hydroxide containing nickel (Ni) and / or manganese (Mn). That is, composite oxide particles coated with a hydroxide containing nickel (Ni) and / or manganese (Mn) are dispersed in a solvent system mainly composed of water in which a compound of yttrium (Y) is dissolved. The basicity of the dispersion is increased by adding a base to the dispersion, and a hydroxide containing yttrium is precipitated. The composite oxide particles coated with a hydroxide containing nickel (Ni) and / or manganese (Mn) are dispersed in a solvent mainly composed of basic water, and then yttrium (Y ) May be added to precipitate the hydroxide.

  The raw materials for the yttrium (Y) compound include inorganic systems such as yttrium hydroxide, yttrium nitrate, yttrium fluoride, yttrium chloride, yttrium bromide, yttrium iodide, yttrium perchlorate, yttrium oxide, yttrium sulfate, and yttrium carbonate. A compound or an organic compound such as yttrium oxalate or yttrium acetate can be used as it is or after being treated to be soluble in a solvent system with an acid or the like as required.

  In the first step, the pH of the above-described solvent system mainly composed of water is pH 12 or more, preferably pH 13 or more, more preferably pH 14 or more. The higher the pH value of the water-based solvent system described above, the higher the uniformity of the deposition of the hydroxide containing nickel (Ni) and / or manganese (Mn) and the hydroxide containing yttrium (Y). Is good, and the reaction accuracy is high, and there is an advantage in 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.

  In the first step, the temperature of the treatment dispersion is 40 ° C. or higher, preferably 60 ° C. or higher, and more preferably 80 ° C. or higher. The higher the temperature value of the treatment dispersion, the better the uniformity of the deposition of the hydroxide containing nickel (Ni) and / or manganese (Mn) and the hydroxide containing yttrium (Y) and the reaction. The speed is high, and there is an advantage of improving productivity and quality by shortening the processing time. 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.

  Further, in the first step, for example, in a solvent system mainly composed of water, a hydroxide containing nickel (Ni) and / or manganese (Mn) is formed on the surface of the composite oxide particles, and then water is added thereto. It is possible to take out the main solvent system and deposit a hydroxide containing yttrium (Y), but the present invention is not limited to this. For example, after a hydroxide containing nickel (Ni) and / or manganese (Mn) is formed on the surface of the composite oxide particle, it is not separated from the solvent system mainly composed of water as it is. It is also possible to deposit a hydroxide containing yttrium (Y) by adding an yttrium compound.

  Furthermore, in the first step, the pH of the solvent system mainly composed of water can be reached by dissolving 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 when the composite oxide particles deposited in the first step are taken out from the solvent system mainly composed of water, the amount of the dispersion medium consisting of the solvent mainly composed of water This is because the amount of lithium in the positive electrode active material can be controlled by controlling.

(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, and the coating layer and the surface Form a layer. 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 the hydroxide containing yttrium (Y) is deposited on the hydroxide containing nickel (Ni) and / or manganese (Mn), sintering between the particles is suppressed, and the particles are The binding is suppressed.

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

  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 is a nonaqueous electrolyte secondary battery using a positive electrode active material according to an embodiment of the present invention. The cross-sectional structure of 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 the battery has a higher energy density. 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 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 the nonaqueous electrolyte secondary battery using the positive electrode active material by one 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, liquid solvent, electrolyte salt, and additive) is the same as 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.

(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 the 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, 10 parts by weight of composite oxide particles having an average composition of Li _1.03 CoO _2.02 , an average particle diameter measured by a laser scattering method of 13 μm, and a specific surface area of 0.3 m ² / g were mixed at 80 ° C. with a 2N LiOH aqueous solution of 300 weights. The mixture was stirred and dispersed for 1 hour.

Next, a nickel nitrate _{(Ni (NO 3) 2 ·} 6H 2 O) 1.54 parts by weight of commercially available reagents, manganese nitrate commercial reagents and _{(Mn (NO 3) 2 ·} 6H 2 O) 0.83 parts by weight A solution in which 10 parts by weight of pure water was dissolved was added over 2 hours.

Next, a solution obtained by dissolving 0.20 parts by weight of commercially available yttrium nitrate (Y (NO ₃ ) ₃ .6H ₂ O) in 5 parts by weight of pure water was added over 1 hour, and further at 80 ° C. The dispersion was continuously allowed to cool by stirring for 1 hour.

  The dispersion was then filtered and dried at 120 ° C. Next, in order to adjust the amount of lithium, 10 parts by weight of this 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 using an electric furnace, held at 950 ° C. for 5 hours, and then cooled to 150 ° C. at 7 ° C./min to obtain the positive electrode active material of Example 1 It was.

<Example 2>
Addition amount of nickel nitrate (Ni (NO ₃ ) ₂ · 6H ₂ O) is 3.08 parts by weight, addition amount of manganese nitrate (Mn (NO ₃ ) ₂ · 6H ₂ O) is 3.30 parts by weight, yttrium nitrate In order to adjust the amount of lithium, the amount of (Y (NO ₃ ) ₃ .6H ₂ O) added is 0.80 parts by weight, the amount of pure water dissolved when adding nickel nitrate and manganese nitrate is 5 parts by weight. The amount of 2N lithium hydroxide aqueous solution impregnated into 5 parts by weight. Other than this, the positive electrode active material of Example 2 was produced in the same manner as Example 1.

<Example 3>
Addition amount of nickel nitrate (Ni (NO ₃ ) ₂ · 6H ₂ O) is 3.08 parts by weight, addition amount of manganese nitrate (Mn (NO ₃ ) ₂ · 6H ₂ O) is 1.65 parts by weight, yttrium nitrate To adjust the amount of lithium, the amount of (Y (NO ₃ ) ₃ · 6H ₂ O) added is 0.80 part by weight, the amount of pure water dissolved when adding nickel nitrate and manganese nitrate is 20 parts by weight The amount of 2N lithium hydroxide aqueous solution impregnated into 4 parts by weight was 4 parts by weight. Other than this, a positive electrode active material of Example 3 was produced in the same manner as Example 1.

<Comparative Example 1>
In Example 1, composite oxide particles having an average composition of Li _1.03 CoO _2.02 , an average particle diameter measured by a laser scattering method of 13 μm, and a specific surface area of 0.3 m ² / g were used as the positive electrode active material of Comparative Example 1.

<Comparative example 2>
A positive electrode active material of Comparative Example 2 was produced in the same manner as in Example 1 except that yttrium nitrate (Y (NO ₃ ) ₃ .9H ₂ O) of Example 1 was not added.

The secondary batteries shown in FIGS. 1 and 2 were produced using the positive electrode active materials of Examples 1 to 3 and Comparative Examples 1 to 2 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 dispersed in N-methyl-2pyrrolidone as a solvent. After that, it was applied to both surfaces of a positive electrode current collector 2A made of a strip-shaped aluminum foil having a thickness of 20 μm, dried, and compression-molded with 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 3 have a high capacity and a larger discharge capacity retention rate than Comparative Examples 1 to 2.

  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 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 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 the 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 (17)

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);
A surface layer made of an oxide containing yttrium (Y), provided on at least a part of the coating layer;
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), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), zirconium (Zr) It is composed of at least one selected element, and x, y, and z are −0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −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 100: 0 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 ( V), chromium (Cr), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten ( 2. The positive electrode active material according to claim 1, wherein the positive electrode active material is replaced with at least one metal element selected from the group consisting of W), yttrium (Y), and zirconium (Zr). The oxide of the surface layer comprises 20 mol% or less of the total amount of yttrium (Y), magnesium (Mg), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn ), Iron (Fe), cobalt (Co), aluminum (Al), nickel (Ni), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) 2. The positive electrode active material according to claim 1, wherein the positive electrode active material is replaced with at least one metal element selected from the group consisting of tungsten (W) and zirconium (Zr). The positive electrode active material according to claim 1, wherein the amount of the coating layer is 0.5 to 50 parts by weight with respect to 100 parts by weight of the composite oxide particles. The amount of the surface layer is 0.1 to 10 parts by weight with respect to 100 parts by weight of the positive electrode active material as a weight obtained by converting the amount of yttrium (Y) to yttrium oxide (Y ₂ O ₃ ). The positive electrode active material according to claim 1. 2. The positive electrode active material according to claim 1, wherein the average particle size is 2.0 μm to 50 μm. After forming a layer made of a hydroxide containing nickel (Ni) and / manganese (Mn) on at least a part of the composite oxide particles whose average composition is represented by chemical formula 1, at least a part of the composite oxide particles Forming a hydroxide containing yttrium (Y) in
After forming the yttrium (Y) -containing hydroxide, heat treatment is performed, so that at least a part of the composite oxide particles includes lithium (Li), nickel (Ni), and manganese (Mn). A method for producing a positive electrode active material, comprising: forming a coating layer made of an oxide containing at least one coating element and a surface layer containing yttrium (Y).
(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), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), zirconium (Zr) It is composed of at least one selected element, and x, y, and z are −0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −0.10 ≦ z ≦ 0.20. ) The deposition of the hydroxide containing nickel (Ni) and / or manganese (Mn)
9. The positive electrode active material according to claim 8, wherein 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 and / or a manganese compound is added. Manufacturing method. The method for producing a positive electrode active material according to claim 9, wherein the water-based solvent contains lithium hydroxide. 9. The method for producing a positive electrode active material according to claim 8, wherein the composition ratio of nickel (Ni) and manganese (Mn) in the coating layer is in the range of 100: 0 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 ( V), chromium (Cr), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten ( 9. The method for producing a positive electrode active material according to claim 8, wherein the positive electrode active material is replaced with at least one metal element selected from the group consisting of W), yttrium (Y), and zirconium (Zr). The oxide of the surface layer comprises 20 mol% or less of the total amount of yttrium (Y), magnesium (Mg), boron (B), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn ), Iron (Fe), cobalt (Co), aluminum (Al), nickel (Ni), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) 9) A method for producing a positive electrode active material according to claim 8, wherein the positive electrode active material is replaced with at least one metal element selected from the group consisting of tungsten (W) and zirconium (Zr). The method for producing a positive electrode active material according to claim 8, wherein the amount of the coating layer is 0.5 to 50 parts by weight with respect to 100 parts by weight of the composite oxide particles. The amount of the surface layer is 0.1 to 10 parts by weight with respect to 100 parts by weight of the positive electrode active material as a weight obtained by converting the amount of yttrium (Y) to yttrium oxide (Y ₂ O ₃ ). The method for producing a positive electrode active material according to claim 8. 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. A positive electrode, a negative electrode, a separator and an electrolyte;
The positive electrode has a positive electrode active material,
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);
A surface layer made of an oxide containing yttrium (Y), provided on at least a part of the coating layer;
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), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), zirconium (Zr) It is composed of at least one selected element, wherein x, y, and z are −0.10 ≦ x ≦ 0.10, 0 ≦ y <0.50, and −0.10 ≦ z ≦ 0.20. is there.)

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