JP2014212134A - Cathode active material for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cathode active material for a nonaqueous electrolyte secondary battery and a nonaqueous electrolyte secondary battery, providing both high capacity and excellent thermal stability in such case as used for a cathode of a battery.SOLUTION: A cathode active material consisting of particles of lithium nickel composite oxide is manufactured by baking a metallic compound having such atom ratio of a metal as corresponds to the atom ratio of the metal of the cathode active material. The metallic compound contains lithium hydroxide. The content of lithium in the lithium hydroxide is calculated based on a mass reduction rate at the time when a specimen collected from the lithium hydroxide blended with the metallic compound is heated and dried. Based on the content of the lithium, the amount of lithium hydroxide blended with the metallic compound is adjusted. Even in the case where the metallic compound is prepared in large amount, because adjustment of atomic ratio between the lithium contained in the metallic compound and other metal is easy, the deviation of the atomic ratio between the lithium in the cathode active material and the other metal which is obtained by baking the metallic compound from a target atomic ratio can be reduced.

Description

  The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery, a manufacturing method thereof, and a non-aqueous electrolyte secondary battery.

  In recent years, with the widespread use of small electronic devices such as mobile phones and notebook computers, demand for non-aqueous electrolyte secondary batteries as chargeable / dischargeable power sources has increased rapidly. As such a non-aqueous electrolyte secondary battery, a lithium ion secondary battery has attracted attention because of its small size and light weight and high energy density.

A lithium ion secondary battery includes a negative electrode, a positive electrode, an electrolytic solution, and the like, and a material capable of desorbing and inserting lithium is used as an active material of the negative electrode and the positive electrode.
For example, as the positive electrode active material of a lithium ion secondary battery, lithium cobalt composite oxide (LiCoO ₂ ) that is relatively easy to synthesize, lithium nickel composite oxide (LiNiO ₂ ) in which nickel cheaper than cobalt is used, Lithium manganese composite oxide particles (LiMn ₂ O ₄ ) using manganese can be used.

By the way, the lithium cobalt composite oxide is relatively easy to synthesize. On the other hand, cobalt, which is the main component, has a problem that it is expensive because its reserves are small, is unstable in supply, and has a large price fluctuation.
In addition, lithium manganese composite oxide is characterized in that it is superior in thermal stability to lithium cobalt composite oxide. However, a lithium ion secondary battery manufactured using lithium manganese composite oxide as a positive electrode active material has a very small charge / discharge capacity compared to other materials and a very short charge / discharge cycle characteristic indicating battery life. There is a problem.

  On the other hand, a lithium ion secondary battery manufactured using a lithium nickel composite oxide as a positive electrode active material exhibits a larger charge / discharge capacity than a secondary battery using a lithium cobalt composite oxide as a positive electrode active material. Moreover, nickel is cheaper than cobalt. For this reason, the lithium nickel composite oxide is expected as a positive electrode active material capable of producing an inexpensive battery with high energy density.

  The lithium-nickel composite oxide is synthesized from a mixture of a lithium compound such as lithium hydroxide serving as a lithium source and a metal compound containing nickel such as a hydroxide, carbonate, or oxide. In preparing this mixture, the atomic ratio of lithium to other metals such as nickel and other transition metal elements, group 2 elements, and group 13 elements in the mixture is different from that of lithium in the lithium nickel composite oxide. It is adjusted so as to coincide with the atomic number ratio (Li / Me ratio) of the metal. In a secondary battery using lithium nickel composite oxide as a positive electrode active material, in order to satisfy predetermined battery characteristics, the atomic ratio (Li / Me ratio) of both in the lithium nickel composite oxide is set to a predetermined value. It is necessary to accurately control within the range.

For example, when the Li / Me ratio decreases, the site occupancy of metal elements other than lithium at the lithium site in the layered structure increases, so that the battery capacity cannot be sufficiently obtained and the output characteristics also deteriorate.
In addition, when the Li / Me ratio becomes too high, excess lithium present on the surface of the lithium nickel composite oxide particles increases, so that battery characteristics are deteriorated and sufficient thermal stability cannot be obtained.
Therefore, in order to obtain a lithium nickel composite oxide having good characteristics, it is necessary to control to an optimal Li / Me ratio.

  Here, when forming the mixture, the adjustment of the atomic ratio of the other metal and lithium in the mixture is adjusted based on the mass of each compound to be mixed. Thus, in order to adjust the atomic ratio in the mixture by the mass of each compound to be mixed, the number of moles of metal and lithium in each compound must be able to be grasped based on the mass of each compound. .

  However, in general, monohydrate lithium hydroxide is used as the lithium hydroxide serving as the lithium source. However, due to handling problems, lithium hydroxide is often overdried and often in a mixed state of a monohydrate and an anhydride. Then, the lithium content in the monohydrate lithium hydroxide does not match the theoretical lithium content (16.54% by mass). Then, the atomic ratio of lithium and the other metal in the mixture deviates from the target atomic ratio, and the atomic ratio (Li / Me ratio) of both in the lithium nickel composite oxide is within a predetermined range. There is a possibility that it will come off.

  In particular, when lithium nickel composite oxide is industrially synthesized, it is necessary to use a large amount of lithium hydroxide packed in a flexible container or the like in units of several hundred kg when forming the mixture. Then, since there is a large variation in the mixed state of monohydrate and anhydride in each flexible container, the average mixing ratio of monohydrate and anhydride in each flexible container, that is, for each flexible container If the lithium content that represents the whole lithium hydroxide (hereinafter referred to as the lithium representative value) is not grasped, the atomic ratio of lithium and other metals in the mixture will be greatly deviated from the intended atomic ratio. End up.

For each flexible container, if a lithium hydroxide sample is collected and the lithium content is grasped, it is possible to grasp the lithium representative value of each flexible container.
For example, as a method for analyzing the amount of lithium contained in a compound such as lithium hydroxide, an atomic absorption method, a flame method, a neutralization titration method, and an ICP emission analysis method are generally known. Since ion chromatography has also been reported as a high analytical method (see Patent Documents 1 and 2), if these methods are used to grasp the lithium content in the collected sample, the representative lithium value can be grasped. Could be possible.

  However, in the analysis method as described above, since the amount of the sample that can be used for one analysis is as small as 0.1 to 1.0 g, the lithium content in the sample can be accurately measured. Is likely to be significantly different. Then, when the atomic ratio in the mixture is adjusted based on the lithium content obtained using the analytical method as described above, the actual atomic ratio in the mixture is determined from the target atomic ratio. There is a high possibility of misalignment.

  Because of the circumstances as described above, it is difficult to produce a lithium nickel composite oxide in which the atomic ratio of other metal to lithium is adjusted to a predetermined value. Therefore, the atomic ratio of lithium to other metal (Li / Me A lithium nickel composite oxide whose ratio is adjusted to a predetermined value is desired. And the non-aqueous electrolyte secondary battery which can make high capacity | capacitance and outstanding thermal stability compatible by employ | adopting this lithium nickel composite oxide as a positive electrode active material is desired.

JP-A-11-287793 JP 2010-25791 A

In view of the above circumstances, the present invention provides a positive electrode active material for a non-aqueous electrolyte secondary battery that can achieve both high capacity and excellent thermal stability when used for a positive electrode of a battery, and a method for producing the same. Objective.
Another object of the present invention is to provide a non-aqueous electrolyte secondary battery that has a high energy density and is inexpensive.

(Method for producing positive electrode active material for non-aqueous electrolyte secondary battery)
The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the first invention is represented by the general formula (I):
LiNi _1-a M _a O ₂ (I)
(Wherein, 0.01 ≦ a ≦ 0.5, M represents at least one element selected from the group consisting of transition metal elements other than Ni, group 2 elements and group 13 elements) A method of producing a positive electrode active material comprising nickel composite oxide particles by firing a metal compound having a metal atomic ratio corresponding to the atomic ratio of the metal in the positive electrode active material, wherein the metal compound is hydroxylated The lithium content of the lithium hydroxide is calculated based on the mass reduction ratio when the sample containing lithium and collected from the lithium hydroxide before blending with the metal compound is dried by heating. The amount of lithium hydroxide blended in the metal compound is adjusted based on the lithium content.
The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the second invention is characterized in that, in the first invention, the mass of the sample collected from the lithium hydroxide before blending with the metal compound is 20 g or more. And
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to a third aspect of the invention is characterized in that, in the first or second aspect of the invention, a sample collected from the lithium hydroxide is heated and dried at 150 ° C. to 300 ° C. The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries of Claim 1 or 2.
According to a fourth aspect of the present invention, there is provided a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery. In the first, second or third aspect, the metal compound is fired in an oxygen atmosphere at a temperature range of 650 to 850 ° C. It is characterized by that.
According to a fifth aspect of the present invention, there is provided a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the first, second, third or fourth aspect, wherein lithium contained in the metal compound and all metals other than lithium. The atomic ratio (the atomic ratio of lithium / the sum of the atomic ratios of all metals other than lithium) is adjusted to 1.00 / 1 to 1.10 / 1.
According to a sixth aspect of the present invention, there is provided a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the metal compound is nickel hydroxide and / or nickel water in the first, second, third, fourth or fifth invention. Nickel oxide obtained by roasting oxide is included, and the nickel hydroxide is composed of nickel, a transition metal element other than nickel, a group 2 element, and a group 13 element in a heated reaction vessel. An aqueous solution of a metal compound containing at least one selected element and an aqueous solution containing an ammonium ion supplier are prepared, and when preparing the nickel hydroxide, alkali metal hydroxide is prepared. An aqueous solution of the product is added so that the aqueous solution in the reaction vessel is maintained alkaline.
According to a seventh aspect of the present invention, there is provided a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the metal compound is nickel oxyhydroxide and / or nickel in the first, second, third, fourth or fifth invention. The nickel oxyhydroxide contains nickel oxide obtained by roasting oxyhydroxide, and the nickel oxyhydroxide contains nickel, a transition metal element other than nickel, a group 2 element and 13 in a heated reaction vessel. The nickel oxyhydroxide is prepared by adding an aqueous solution of a metal compound containing at least one element selected from group elements and an aqueous solution containing an ammonium ion supplier and then adding an oxidizing agent. In preparing the product, an aqueous solution of an alkali metal hydroxide is added so that the aqueous solution in the reaction vessel is maintained alkaline.
(Positive electrode active material for non-aqueous electrolyte secondary battery)
The positive electrode active material for a non-aqueous electrolyte secondary battery of the eighth invention has the general formula (I):
LiNi _1-a M _a O ₂ (I)
(Wherein, 0.01 ≦ a ≦ 0.5, M represents at least one element selected from the group consisting of transition metal elements other than Ni, group 2 elements and group 13 elements) A positive electrode active material comprising nickel composite oxide particles, which is obtained by the production method of any one of the first to seventh inventions.
The positive electrode active material for a non-aqueous electrolyte secondary battery of the ninth invention has a standard deviation of the lithium composition ratio obtained by repeating the analysis of the lithium composition ratio represented by mass% 5 times or more in the eighth invention is 0. .6 or less.
(Non-aqueous electrolyte secondary battery)
A nonaqueous electrolyte secondary battery according to a tenth aspect of the invention includes a positive electrode formed by a positive electrode active material for a nonaqueous electrolyte secondary battery according to the invention of either the seventh or eighth aspect.

(Method for producing positive electrode active material for non-aqueous electrolyte secondary battery)
According to the first invention, since the amount of lithium in lithium hydroxide can be accurately grasped, the atomic number ratio between lithium and the other metal in the metal compound can be accurately adjusted. Then, even when preparing a large amount of the metal compound, it becomes easy to adjust the atomic ratio of lithium contained in the metal compound and other metals, so the metal compound is fired for the target atomic ratio. Thus, the deviation in the atomic ratio between lithium and other metals in the positive electrode active material obtained in this manner can be reduced. Then, since the dispersion | variation in the quality of the positive electrode active material (lithium nickel composite oxide) for nonaqueous electrolyte secondary batteries manufactured can be made small, this positive electrode active material for nonaqueous electrolyte secondary batteries was used for the battery. Sometimes, it is possible to realize a battery with small variations in initial discharge capacity and internal resistance.
According to the second invention, since the amount of the sample used for one measurement is large, the variation in the crystal moisture amount between the samples can be reduced even when performing the measurement a plurality of times. For this reason, an error between the lithium content of lithium hydroxide calculated based on the mass reduction ratio when the sample is dried by heating and the lithium content that represents the entire lithium hydroxide (hereinafter referred to as lithium representative value) Can be reduced. Therefore, even when a large amount of the metal compound is prepared, it is possible to accurately adjust the atomic ratio between lithium and the other metal contained in the metal compound.
According to the third aspect of the invention, since crystal water can be removed without decomposing lithium hydroxide, the lithium content of lithium hydroxide can be accurately determined.
According to the fourth invention, since baking is performed in an oxygen atmosphere at a temperature of 650 to 850 ° C., lithium can be sufficiently diffused in the particles, and the particle form can be maintained in a spherical shape and can be chemically treated uniformly. Achieve stoichiometric composition. Therefore, when a battery having a positive electrode formed by the manufactured positive electrode active material is manufactured, a high-capacity battery can be realized.
According to the fifth invention, when the positive electrode is formed using the obtained positive electrode active material, the internal resistance can be reduced and the initial discharge capacity can be prevented from being lowered.
According to the sixth invention, nickel hydroxide and / or nickel oxide obtained by roasting nickel hydroxide can be formed as high bulk density spherical particles suitable as a positive electrode active material.
According to the seventh invention, nickel oxyhydroxide and / or nickel oxide obtained by roasting nickel oxyhydroxide can be formed as high bulk density spherical particles suitable as a positive electrode active material. .
(Positive electrode active material for non-aqueous electrolyte secondary battery)
According to the eighth invention, when a positive electrode active material for a non-aqueous electrolyte secondary battery is used for a battery, it is possible to realize a battery having a high capacity, high safety, and a small variation in initial discharge capacity and internal resistance. it can.
According to the ninth aspect of the present invention, when a positive electrode active material for a non-aqueous electrolyte secondary battery is used for a battery, a battery having a high capacity, high safety, and small variations in initial discharge capacity and internal resistance is realized. Can do.
(Non-aqueous electrolyte secondary battery)
According to the tenth invention, since the positive electrode active material for a nonaqueous electrolyte secondary battery according to the eighth or ninth invention is used as a positive electrode material, the capacity is high and the safety is excellent.

It is a figure showing the schematic structure of a 2032 type coin battery. It is a schematic explanatory drawing of the equivalent circuit used for internal resistance value evaluation.

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

(Positive electrode active material for non-aqueous electrolyte secondary battery)
Hereinafter, the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention will be described.

The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention has the general formula (I):
LiNi _1-a M _a O ₂ (I)
(In the formula, 0.01 ≦ a ≦ 0.5, M represents at least one element selected from the group consisting of transition metal elements other than Ni, group 2 elements and group 13 elements)
It is a positive electrode active material which consists of particle | grains of lithium nickel complex oxide represented by these.

  The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention can realize a battery having a high capacity and high safety and a small variation in initial discharge capacity and internal resistance when used in a battery.

  In addition, the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention has a standard deviation of the lithium composition ratio obtained by repeating the analysis of the lithium composition ratio expressed by mass% 5 times or more is 0.6 or less. It is preferable. When the standard deviation is within this range, the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention realizes a battery with smaller variations in initial discharge capacity and internal resistance when used for the positive electrode of the secondary battery. be able to.

(Method for producing positive electrode active material for non-aqueous electrolyte secondary battery of the present invention)
The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is a fired metal compound having a metal atomic ratio corresponding to the atomic ratio of the metal in the lithium nickel composite oxide particles represented by the composition of the general formula (I) To manufacture.

(Metal compound)
The metal compound is a mixture of a nickel compound and lithium hydroxide. The nickel compound includes nickel hydroxide and / or nickel oxyhydroxide and nickel oxide obtained by roasting the nickel hydroxide and / or nickel oxyhydroxide.

(Lithium hydroxide)
The lithium hydroxide used for the preparation of the metal compound is a monohydrate lithium hydroxide generally used industrially, and is in a mixed state of a monohydrate and an anhydride. It is.

(Nickel hydroxide and / or nickel oxyhydroxide)
The nickel hydroxide and / or nickel oxyhydroxide used for the preparation of the metal compound is not particularly limited, but at least one selected from the group consisting of transition metal elements other than nickel, group 2 elements and group 13 elements It is preferable to use those containing these elements.

(Method for producing nickel hydroxide and / or nickel oxyhydroxide)
The method for producing nickel hydroxide and / or nickel oxyhydroxide used for the preparation of the metal compound is not particularly limited. When nickel hydroxide and / or nickel oxyhydroxide produced using a crystallization method is used, the synthesized lithium nickel composite oxide particles become high-bulk-density spherical particles suitable as a positive electrode active material. . Then, when a positive electrode is formed using a positive electrode active material composed of particles of this lithium nickel composite oxide, the internal resistance of the secondary battery can be reduced and the initial discharge capacity can be prevented from decreasing. . Moreover, the filling property to the electrode of a positive electrode active material can also be improved.

  In the crystallization method, nickel hydroxide and / or nickel oxyhydroxide can be produced under various known conditions. If produced under the following conditions, particles with higher bulk density can be produced. Since it can be obtained, it is suitable.

  First, in the crystallization method, a nickel hydroxide is prepared by supplying (for example, dropping) an aqueous solution of a metal compound and an aqueous solution containing an ammonium ion supplier into a heated reaction vessel. The metal compound is a metal compound containing nickel and at least one element selected from a transition metal element other than nickel, a group 2 element, and a group 13 element.

  At this time, the temperature of the aqueous solution in the reaction vessel is maintained in a state heated to 40 to 60 ° C, preferably 45 to 55 ° C. When the temperature of the aqueous solution exceeds 60 ° C., the priority of nucleation is increased in the liquid, and crystal growth does not proceed and only a fine powder can be obtained. When the temperature is lower than 40 ° C., the generation of nuclei in the liquid is small, and the crystal growth of the particles becomes preferential, so that very large particles are generated so that irregularities are generated during electrode production, or the metal in the reaction liquid The residual amount of ions is high and the reaction efficiency is very poor.

The pH of the aqueous solution in the reaction vessel is maintained at pH 10 to 13.6, preferably pH 11 to 13.2. When the pH exceeds 13.6, the priority of nucleation is increased in the liquid, and crystal growth does not proceed and only a fine powder can be obtained. If the pH is less than 10, the generation of nuclei in the liquid is small and the crystal growth of the particles is preferential, so that very large particles are generated so that irregularities are generated during electrode preparation, or metal ions in the reaction liquid The residual amount of is high and the reaction efficiency is very poor.
In addition, the method of maintaining the pH of the aqueous solution in the reaction tank at the above pH (that is, alkaline) is not particularly limited, but only by adjusting the pH by adding an aqueous solution of an alkali metal hydroxide. preferable.

Further, the method for producing nickel oxyhydroxide is not particularly limited, but in the step of producing nickel hydroxide by the crystallization method, an aqueous solution containing an ammonium ion supplier is supplied (for example, dropped), and then oxidized. It is preferable to prepare by adding an agent. When produced by this method, nickel oxyhydroxide particles having a high bulk density can be synthesized, and therefore, it is suitable as a raw material for a lithium nickel composite oxide used for a positive electrode active material for a nonaqueous electrolyte secondary battery.
The oxidizing agent to be added to the aqueous solution is not particularly limited, and examples thereof include sodium hypochlorite and hydrogen peroxide, but the oxidizing agent that can be used in the above method is limited to such examples. It is not something.

(Ammonium ion supplier)
In the ammonium ion supplier, the ammonium ions act as a complexing agent.
Examples of the ammonium ion supplier include an aqueous ammonia solution, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, and the like, but the ammonium ion supplier that can be used in the present invention is limited to such examples. It is not a thing.

(Other)
In addition, nickel oxide or nickel oxyhydroxide obtained by roasting the above nickel hydroxide or nickel oxyhydroxide in place of or instead of nickel hydroxide or nickel oxyhydroxide May be used as a nickel compound. Since there is no unstable crystal water in nickel oxide, the ratio of the number of lithium atoms contained in the metal compound to the number of atoms of all metals other than lithium (number of lithium atoms / all metals other than lithium) The sum of the number of atoms (hereinafter referred to as Li / Me ratio) can be stabilized.

The conditions for producing nickel oxide by roasting nickel hydroxide and / or nickel oxyhydroxide are not particularly limited, but it is preferably roasted at 500 to 1100 ° C. in an air atmosphere, It is more preferable to bake at 900 to 1000 ° C.
When the roasting temperature is less than 500 ° C., particles in which nickel hydroxide and / or nickel oxyhydroxide is not sufficiently converted to nickel oxide remain. Then, the lithium nickel composite oxide obtained using the nickel oxide containing such particles is difficult to stabilize its quality, and the composition is likely to be nonuniform during synthesis. On the other hand, when the roasting temperature exceeds 1100 ° C., the primary particles constituting the nickel oxide particles rapidly grow. For this reason, in the firing of the next step, since the reaction area on the nickel oxide side is too small, it cannot react with lithium, so that the nickel oxide and the lithium compound in the molten state are separated and the lithium nickel composite oxide does not react. It becomes uniform.
Therefore, the conditions for roasting nickel hydroxide or nickel oxyhydroxide are preferably roasted at 500 to 1100 ° C., more preferably 900 to 1000 ° C. in an air atmosphere.
In addition, the conditions for roasting nickel hydroxide or nickel oxyhydroxide are not limited to the air atmosphere, and may be any conditions as long as the dehydration of nickel hydroxide or nickeloxy hydroxide proceeds. In particular, since a nickel hydroxide or nickel oxyhydroxide is reduced in a reducing atmosphere, a non-reducing atmosphere is preferable.

(mixing ratio)
In the metal compound, the mixing ratio of the nickel compound and lithium hydroxide is lithium with respect to the total amount (Me) of atoms of transition metal elements (including nickel), group 2 elements, and group 13 elements in the nickel compound. The number of lithium atoms (Li) in the compound is 1.00 / 1 to 1.10 / 1, preferably 1.00 / 1 to 1.05 / 1, in atomic ratio (Li / Me ratio). Adjust so that

When the Li / Me ratio is less than 1.00, the crystallinity of the obtained lithium nickel composite oxide powder, which is the positive electrode active material, is very poor, which causes a large decrease in battery capacity during the charge / discharge cycle.
On the other hand, if the Li / Me ratio exceeds 1.10, a large amount of excess lithium compound is present on the surface of the obtained lithium nickel composite oxide particles. The excess lithium compound present on the surface can be removed by washing with water, but if it is present in a large amount, it is difficult to remove it by washing with water. For this reason, when used as a positive electrode active material in a state where surplus lithium compound is present on the surface, not only a large amount of gas is generated during charging of the battery, but also an organic material used in electrode preparation because it is a powder exhibiting a high pH. It reacts with a material such as a solvent, causing the slurry to gel and causing a problem.

  In addition, for mixing nickel compound and lithium hydroxide, a dry blender such as a V blender or a mixing granulator can be used, but the nickel compound and Any substance that can be sufficiently mixed with a substance containing lithium can be used. For example, a general mixer such as a shaker mixer, a Laedige mixer, a Julia mixer, or the like can also be used.

(Baking)
When the metal compound is fired in an oxygen atmosphere, particles of a lithium nickel composite oxide represented by the composition of the general formula (I) are synthesized.

(Baking temperature)
The said baking temperature is 650-850 degreeC, Preferably it is 700-780 degreeC.
When the temperature is lower than 650 ° C., crystals of the lithium nickel composite oxide to be synthesized are undeveloped and structurally unstable, and the structure is easily destroyed by phase transition due to charge / discharge. If it exceeds 850 ° C., the layered structure may be destroyed, and insertion and removal of lithium ions may be difficult, and nickel oxide or the like may be generated by decomposition.

  In order to uniformly react in the temperature range in which crystal growth proceeds after removing the crystal water of lithium hydroxide and the like, the reaction is performed at a temperature of 400 to 600 ° C. for 1 hour or longer, and subsequently at a temperature of 650 to 850 ° C. for 5 hours. Baking is preferably performed in two stages over time.

  Further, the method for firing the metal compound is not particularly limited. For example, a firing furnace such as an electric furnace, a kiln, a tubular furnace, a pusher furnace adjusted to a gas atmosphere having an oxygen concentration of 20% by mass or more such as an oxygen atmosphere, a dry air atmosphere subjected to dehumidification and carbonation treatment, and the like can be given.

(Measurement method of pure lithium by heating mass reduction rate)
In the above-described method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the ratio of the nickel compound to lithium hydroxide in the metal compound is Li / Me ratio of 1.00 / 1 to 1.10. / 1, preferably, 1.00 / 1 to 1.05 / 1.

  However, as described above, since lithium hydroxide is in a mixed state of a monohydrate and an hydrate, the lithium content in the monohydrate lithium hydroxide is theoretically different from that in lithium hydroxide. Does not agree with the lithium content (16.54% by mass). Therefore, in order to obtain the above Li / Me ratio in the metal compound, it is necessary to estimate the accurate lithium content from the mass of lithium hydroxide.

Therefore, in the method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention, a sample is collected and analyzed from lithium hydroxide packed in a flexible container or the like, and a monohydrate and an hydrate are obtained. The pure lithium content in the lithium hydroxide in the mixed state is measured.
Then, it is possible to estimate the pure lithium content that is a representative value of the total lithium hydroxide packed in a flexible container or the like, and using this pure lithium content, the mass of the lithium hydroxide containing the required lithium can be calculated. Therefore, even when a large amount of a metal compound is prepared, it is easy to adjust the atomic ratio between lithium contained in the metal compound and another metal. For this reason, since the deviation of the atomic number ratio (Li / Me ratio) between lithium and other metals in the positive electrode active material obtained by firing the metal compound with respect to the target atomic number ratio can be reduced, Variation in quality of the positive electrode active material (lithium nickel composite oxide) for water electrolyte secondary batteries can be reduced. Therefore, when this positive electrode active material for a non-aqueous electrolyte secondary battery is used for a battery, a battery with small variations in initial discharge capacity and internal resistance can be realized.

  Hereinafter, a method for measuring pure lithium employed in the method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention will be described.

  In the method for measuring lithium content (hereinafter simply referred to as the method for measuring lithium content) employed in the method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention, lithium hydroxide packaged in a flexible container or the like A sample was taken from the sample, this sample was dried by heating, and the lithium content of lithium hydroxide was calculated based on the mass reduction ratio before and after the drying.

For example, in the method for measuring lithium content, the lithium content is calculated as follows.
First, the mass of a glass petri dish is measured using a balance having two digits after the decimal point in grams, and the mass is defined as W0. A sample of 20 g or more is added to this petri dish and weighed accurately. Let this mass be W1.

The petri dish containing the sample is put into a vacuum dryer and heated at 230 ° C. for 1 hour to dry, and then kept in a vacuum state and naturally cooled to obtain anhydrous lithium hydroxide. After cooling, the mass of the petri dish containing the powder to be measured is measured, and this weight is defined as W2.
After obtaining the heating mass reduction rate A (mass%) using the following formula 1, the pure lithium content L (mass%) in lithium hydroxide (a mixture of anhydrous and monohydrate) is obtained using formula 2. .
[Equation 1]
A = [(W1-W2) / (W1-W0)] × 100 Equation 1
[Equation 2]
L = L1 / (L2 + (L2 × A × 0.01) / (1-A × 0.01))) × 100 Equation 2
L1: 6.941 (Lithium atomic weight)
L2: 23.949 (anhydrous lithium hydroxide molecular weight)

  By using the pure lithium obtained by the above measurement method, by removing the required amount of lithium, even if lithium hydroxide is in a mixed state of monohydrate and hydrate, Since the amount of lithium hydroxide to be mixed can be accurately determined, the Li / Me ratio can be controlled industrially easily and with high accuracy.

(Sample collection amount)
The mass of the sample collected and analyzed at one time is not particularly limited, but is preferably 20 g or more. By setting the mass of the sample to 20 g or more, it is possible to accurately obtain a pure lithium content that represents the entire large amount of lithium hydroxide packed in a flexible container or the like.
In addition, it is not preferable that the mass of the sample is less than 20 g because a pure lithium component representing the entire lithium hydroxide may not be obtained due to fluctuations in the amount of crystal moisture between the samples, and the measurement error increases.
On the other hand, the sample is not particularly limited as long as it can measure 4 digits or more in the unit of measurement, but even if the sample exceeds 500 g, lithium hydroxide is only wasted, so the sample collection amount is 20 to 500 g. preferable.
The weighing of lithium hydroxide before and after heating is preferably performed to the last two digits of the measurement unit, that is, four or more digits in the measurement unit. By precisely weighing to the last two digits of the decimal point, the accuracy of the pure lithium is increased, and the Li / Me ratio can be accurately controlled.

(Heating conditions)
The sample needs to be heated in an atmosphere in which no carbon dioxide gas exists. This is because, in an atmosphere containing carbon dioxide gas, such as in an air atmosphere, lithium hydroxide is carbonated during heating and a mass change occurs, so that the lithium content based on the mass reduction rate cannot be accurately determined. Examples of the atmosphere in which no carbon dioxide gas exists include a vacuum atmosphere or an inert gas atmosphere such as Ar or He gas, but are not limited to these conditions.

(Heating temperature)
Moreover, it is preferable that the temperature which heats a sample shall be 150-300 degreeC. If the heating temperature is less than 150 ° C., the removal of crystal water from lithium hydroxide is not sufficient, and an accurate pure lithium content may not be obtained. Moreover, since it will decompose | disassemble when it exceeds 300 degreeC, it will become difficult to measure the mass loss by crystal water removal.

(Non-aqueous electrolyte secondary battery)
The nonaqueous electrolyte secondary battery of the present invention has a positive electrode formed of a positive electrode active material made of the above-described lithium nickel composite oxide. Since the positive electrode is used in the non-aqueous electrolyte secondary battery of the present invention, it has high capacity and excellent safety.

First, the structure of the nonaqueous electrolyte secondary battery of the present invention will be described.
The non-aqueous electrolyte secondary battery of the present invention (hereinafter simply referred to as the secondary battery of the present invention) is a positive electrode active material (hereinafter simply referred to as the positive electrode active material of the present invention) comprising the above-described lithium nickel composite oxide as the positive electrode material. The structure is substantially the same as that of a general non-aqueous electrolyte secondary battery except that the above is used.

  Specifically, the secondary battery of the present invention includes a case, a positive electrode accommodated in the case, a negative electrode, a non-aqueous electrolyte, and a separator. More specifically, a positive electrode and a negative electrode are laminated through a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte, and a positive electrode current collector of the positive electrode and a positive electrode terminal connected to the outside The secondary battery of the present invention is formed by connecting the negative electrode current collector of the negative electrode and the negative electrode terminal communicating with the outside using a current collecting lead or the like and sealing the case. In addition, the structure of the secondary battery of this invention is not limited to what was illustrated above, Various shapes, such as a cylinder shape and a laminated form, are employable as the external shape.

(Structure of each part of the secondary battery)
Next, the structure of each part of the secondary battery of the present invention will be described.

(Positive electrode)
First, the positive electrode that is a feature of the secondary battery of the present invention will be described.
The positive electrode is a sheet-like member, and is formed by applying a positive electrode mixture paste containing the positive electrode active material of the present invention to the surface of a current collector and drying it.

  The positive electrode is appropriately processed according to the battery to be used. For example, a cutting process for forming an appropriate size according to the size of the target battery, a pressure compression process using a roll press or the like to increase the electrode density, and the like are performed.

(Positive electrode paste)
The positive electrode mixture paste is obtained by adding a solvent to the positive electrode mixture and kneading. Moreover, a positive electrode compound material is obtained by mixing the positive electrode active material of this invention of a powder form, a electrically conductive material, and a binder.

(Positive electrode conductive material)
The conductive material is used to give appropriate conductivity to the electrode. The conductive material is not particularly limited as long as it is an electron conductive material that is chemically stable in the battery. For example, natural graphite (such as flake graphite), graphite such as artificial graphite and expanded graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black, carbon fibers and metal fibers Conductive fibers such as aluminum, metal powders such as aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, organic conductive materials such as polyphenylene derivatives, carbon fluoride, etc. Can be used. These may be used alone or in combination of two or more.
The amount of the conductive material added to the positive electrode mixture is not particularly limited, but is preferably 1 to 50 parts by weight, and 1 to 30 parts by weight with respect to 100 parts by weight of the positive electrode active material contained in the positive electrode mixture. Is more preferable, and 1 to 15 parts by weight is still more preferable.

(Positive electrode binder)
The binder plays a role of tethering the positive electrode active material particles. The binder used for this positive electrode mixture is not particularly limited. For example, although a thermoplastic resin and a thermosetting resin can be used, the thermoplastic resin is preferable in that it can be easily processed during electrode formation such as pressure compression treatment.
Examples of the thermoplastic resin used for the binder include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), and tetrafluoroethylene-hexafluoropropylene copolymer. Copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer Copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene Copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid Examples include acid copolymers, ethylene-methyl acrylate copolymers, ethylene-methyl methacrylate copolymers, fluorine rubber, ethylene-propylene-diene rubber, cellulose, and polyacrylic acid. These may be used alone or in combination of two or more. Moreover, these may be a crosslinked body by Na ⁺ ions or the like.

  In addition, you may add activated carbon etc. to a positive electrode compound material. The electric double layer capacity of the positive electrode can be increased by adding activated carbon or the like.

  The solvent is used for dissolving the binder and dispersing the positive electrode active material, the conductive material, activated carbon, and the like in the binder. This solvent is not particularly limited, and examples thereof include organic solvents such as N-methyl-2-pyrrolidone.

  Moreover, the mixing ratio of each component used for the positive electrode mixture paste is not particularly limited. For example, the amount of the positive electrode active material is 60 to 95 parts by mass and the amount of the conductive material is 1 to 100 parts by mass of the solid content of the positive electrode mixture excluding the solvent, as in the case of the positive electrode of a general non-aqueous electrolyte secondary battery. 20 mass parts and the quantity of a binder can be 1-20 mass parts.

(Positive electrode current collector)
The current collector to which the positive electrode mixture paste is applied is not particularly limited as long as it is an electron conductor that is chemically stable in the battery. For example, a foil or sheet made of aluminum, stainless steel, nickel, titanium, carbon, conductive resin, or the like can be used. In particular, aluminum foil and aluminum alloy foil are preferable because they can withstand an oxidizing environment, have excellent conductivity, and can be easily processed into a thin film.
Further, a carbon or titanium layer or an oxide layer may be formed on the surface of the foil or sheet.
Moreover, unevenness | corrugation can also be provided to the surface of foil or a sheet | seat. The method for providing irregularities on the surface of the foil or sheet is not particularly limited. For example, unevenness may be imparted to the surface of the foil or sheet by pressing or the like. In addition, when using a foil or sheet having a structure such as a net or punching sheet, lath body, porous body, foam, or fiber group molded body, the surface of the foil or sheet is uneven. can do.
Although the thickness of a collector is not specifically limited, For example, 1-500 micrometers is preferable and 15-20 micrometers is more preferable at the point which respond | corresponds to the winding in a post process, and raises battery capacity.

(Negative electrode)
The negative electrode is a sheet-like member formed by applying a negative electrode mixture paste on the surface of a metal foil current collector such as copper and drying it. Although this negative electrode is different from the positive electrode in the components constituting the negative electrode mixture paste and the current collector material, it can be produced by substantially the same method as the positive electrode. Various processes are performed.
Hereinafter, although each member which forms a negative electrode is demonstrated, description is abbreviate | omitted about the member (The electrically conductive material in a negative electrode compound paste, a binder, a collector) which has the material and structure which are substantially the same as a positive electrode.

(Negative electrode paste)
The negative electrode mixture paste is a paste obtained by adding an appropriate solvent to a negative electrode mixture in which a negative electrode active material and a binder are mixed.

  Any material that can electrochemically charge and discharge lithium can be used as the negative electrode active material. For example, a lithium-containing material such as metallic lithium or a lithium alloy can be used. As the lithium alloy, an alloy containing at least one element selected from the group consisting of silicon, tin, aluminum, zinc, and magnesium, in particular. Is preferable in that a high-capacity battery can be produced.

  Further, as the negative electrode active material, an occlusion material that can occlude and desorb lithium ions can be used. The occlusion material is not particularly limited, and examples thereof include a fired product of an organic compound such as natural graphite, artificial graphite and a phenol resin, and a powdery product of a carbon material such as coke.

  When the occlusion material is used as the negative electrode active material, a fluororesin such as polyfuka vinylidene (PVDF) can be used as the binder as in the positive electrode. A solvent can be used to disperse the negative electrode active material in the binder. Examples of the solvent include organic solvents such as N-methyl-2-pyrrolidone.

  The average particle diameter of the negative electrode active material is not particularly limited, and is preferably 1 to 30 μm, for example.

(Non-aqueous electrolyte)
The nonaqueous electrolytic solution is obtained by dissolving a lithium salt as a supporting salt in an organic solvent.
Examples of the organic solvent include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), and trifluoropropylene carbonate (TFPC). Chain carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dipropyl carbonate (DPC); aliphatics such as methyl formate, methyl acetate, methyl propionate, and ethyl propionate Carboxylic acid esters; Lactones such as γ-butyrolactone and γ-valerolactone; Chain ethers such as 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), and ethoxymethoxyethane (EME) Class: Tetrahydrofura Cyclic ethers such as 2-methyltetrahydrofuran; sulfur compounds such as ethyl methyl sulfone and butane sultone; phosphorus compounds such as triethyl phosphate and trioctyl phosphate; dimethyl sulfoxide, 1,3-dioxolane, formamide, acetamide, dimethylformamide, Dioxolane, acetonitrile, propylnitrile, nitromethane, ethyl monoglyme, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, 3-methyl-2-oxazolidinone, Propylene carbonate derivatives, tetrahydrofuran derivatives, ethyl ether, 1,3-propane sultone, anisole, dimethyl sulfoxide, N-methyl-2-pyrrolidone, etc. It is, but the present invention is not limited only to those exemplified. These organic substances may be used alone or in combination of two or more. Even when two or more kinds are mixed, an electrolytic solution having a high electrical conductivity can be obtained, in particular, a mixed solvent of a cyclic carbonate and a chain carbonate, or a mixed solvent of a cyclic carbonate, a chain carbonate, and an aliphatic carboxylic acid ester. This is preferable.

Examples of the lithium salt that is a supporting salt include LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCl, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li (CF ₃ SO ₂ ) ₂ , LiAsF. ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiB ₁₀ Cl ₁₀ , lower aliphatic lithium carboxylate, LiCl, LiBr, LiI, lithium chloroborane, lithium tetraphenylborate, lithium imide salt and complex salts thereof it can. These may be used alone or in combination of two or more. In particular, LiPF ₆ is preferable in terms of excellent electrical conductivity.

  The lithium salt concentration in the nonaqueous electrolytic solution is not particularly limited, but is preferably 0.2 to 2 mol / L, and more preferably 0.5 to 1.5 mol / L.

  Various additives can be added to the non-aqueous electrolyte in order to improve the charge / discharge characteristics of the battery. Examples of additives include triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, pyridine, hexaphosphoric triamide, nitrobenzene derivatives, crown ethers, quaternary ammonium salts, ethylene glycol dialkyl ethers, and the like. be able to.

(Separator)
The separator is disposed between the positive electrode and the negative electrode, and has a function of separating the positive electrode and the negative electrode and maintaining the electrolyte. Such a separator is not particularly limited as long as it has the above function, but a microporous thin film having a large ion permeability, a predetermined mechanical strength, and insulating properties is preferable.

  A microporous thin film having a function of closing the pores at a certain temperature or higher and increasing the resistance is preferable from the viewpoint of ensuring the safety of the battery. Although the material of the microporous thin film is not particularly limited, polyolefins such as polypropylene and polyethylene having excellent organic solvent resistance and hydrophobic properties are preferable, and sheets made from glass fibers, nonwoven fabrics, woven fabrics, etc. should also be used. Can do. The pore diameter and porosity of the microporous thin film are generally preferably 0.01 to 1 μm and 30 to 80% porosity, but are not particularly limited.

  The thickness of the separator is not particularly limited, but is preferably 10 to 300 μm and more preferably 15 to 50 μm in consideration of securing a sufficient amount of active material by preventing a short circuit between the positive and negative electrodes.

  Further, without providing a dedicated separator, a polymer electrolyte made of a non-aqueous electrolyte and a polymer material that maintains the non-aqueous electrolyte may be integrated with the positive electrode or the negative electrode, and this polymer electrolyte may function as a separator. Such a polymer material may be any material that can maintain a non-aqueous electrolyte, but a copolymer of vinylidene fluoride and hexafluoropropylene is particularly preferable.

(Use of the secondary battery of the present invention)
Since the secondary battery of the present invention has a high capacity and excellent safety, it can be used as a power source for small portable electronic devices (such as notebook personal computers and mobile phone terminals) that always require a high capacity.

(Example)
The nonaqueous electrolyte secondary battery (Example 1) of the present invention having a positive electrode formed of the positive electrode active material for a nonaqueous electrolyte secondary battery manufactured by the manufacturing method of the present invention, and other manufacturing methods. The initial discharge capacity and the internal resistance were compared for the nonaqueous electrolyte secondary batteries (Comparative Examples 1 and 2) having a positive electrode formed from the produced positive electrode active material for a nonaqueous electrolyte secondary battery.

In this example, a lithium nickel composite oxide was synthesized using nickel hydroxide and lithium hydroxide as raw materials, and a non-aqueous electrolyte secondary battery was produced using the synthesized lithium nickel composite oxide as a positive electrode active material.
The lithium nickel composite oxide was synthesized by preparing a mixture of nickel hydroxide and lithium hydroxide, and firing the mixture. In the mixture, the ratio of the number of atoms of all metals other than lithium including nickel in the mixture to the number of atoms of lithium is the target lithium nickel composite oxide (Li _1.02 Ni _0.82 Co _0.15 Al _0.03 O ₂ ) was adjusted to coincide with the ratio (1.02 / 1.00) of the number of atoms of all metals other than lithium including nickel and the number of atoms of lithium.

In Example 1 and Comparative Examples 1 and 2, the metal analysis, moisture content, and specific surface area in the lithium nickel composite oxide were measured by the following methods.
(1) Metal analysis: Measured by ICP emission spectrometry.

Example 1
The positive electrode active material comprising a lithium nickel composite oxide includes (1) a step of preparing nickel oxide, (2) measurement of pure lithium in lithium hydroxide, and (3) mixing nickel oxide and lithium hydroxide. Synthesized by a firing step (firing step).
Note that the positive electrode active materials were synthesized using lithium hydroxide in 10 different packages as raw materials.

(1) Step of preparing nickel hydroxide First, nickel sulfate hexahydrate (Wako Pure Chemical), cobalt sulfate heptahydrate (Wako Pure Chemical), and aluminum sulfate (Wako Pure Chemical) are mixed. A mixed reagent was prepared, and the mixed reagent was dissolved in water to prepare an aqueous solution.
Each reagent was weighed so that the atomic ratio of each metal component in the mixed reagent was Ni: Co: Al = 0.82: 0.15: 0.03.

This aqueous solution was dropped into a stirred reaction tank with a discharge port filled with water at the same time as 25% by mass aqueous ammonia (manufactured by Wako Pure Chemical Industries) and 25% by mass aqueous caustic soda (manufactured by Wako Pure Chemical Industries). Nickel hydroxide was produced. In addition, the stirring reaction tank with a discharge port was controlled so that the temperature of the aqueous solution therein was 50 ° C., the pH was 11.5, and the residence time was 11 hours.
The obtained nickel hydroxide was confirmed to be spherical secondary particles in which primary particles were aggregated by a scanning electron microscope (SEM). The average particle size of the secondary particles was measured by a laser diffraction / scattering particle size distribution analyzer (Microtrack HRA manufactured by Nikkiso Co., Ltd.), and was 10.2 μm.

(2) Lithium Lithium Hydroxide Measurement Take a 30 g sample from the packed lithium hydroxide monohydrate, place the sample on a glass petri dish, and weigh the scale with the petri dish to the last two digits (Sartorius It was precisely weighed by ELT202) manufactured by Mechatronics Japan. In addition, the mass of the petri dish was obtained by precisely weighing in the same manner up to the last two digits before placing the sample.
The sample was placed in a vacuum dryer (model VOS-451SD, manufactured by Tokyo Rika Kikai Co., Ltd.) together with the petri dish, dried by heating at 230 ° C. for 1 hour, and then allowed to stand for 4 hours in a vacuum state for natural cooling. After cooling, the petri dish containing the sample was precisely weighed with a weigher in the same manner as before heating and drying.
From the mass before and after heating and drying obtained by precise weighing, the pure lithium content was determined using the above formulas 1 and 2.

(3) Firing step To the nickel hydroxide obtained in (1), lithium hydroxide monohydrate (manufactured by Wako Pure Chemical Industries) is added and mixed using a V blender to prepare a mixture (metal compound). did. The amount of lithium hydroxide monohydrate added is such that the atomic ratio of each metal component in the mixture is Ni: Co: Al: Li = 0.82: 0.15: 0.03: 1.02. And adjusted based on the lithium content of lithium hydroxide monohydrate measured in (2).

  The obtained mixture was calcined at 500 ° C. for 3 hours in an atmosphere having an oxygen concentration of 30% or more using an electric furnace, and then calcined at 760 ° C. for 20 hours. Then, after cooling in a furnace to room temperature, the pulverization process was performed and the positive electrode active material was obtained. Table 1 shows the standard deviation of Li quality between the obtained positive electrode active materials.

(Manufacture of secondary batteries)
Secondary batteries were manufactured using positive electrode active materials respectively obtained from 10 packages of lithium hydroxide. The manufactured secondary battery is a 2032 type coin battery (hereinafter referred to as coin type battery 1) shown in FIG.

As shown in FIG. 1, the coin-type battery 1 is composed of a case 2 and an electrode 3 accommodated in the case 2.
The case 2 has a positive electrode can 2a that is hollow and open at one end, and a negative electrode can 2b that is disposed in the opening of the positive electrode can 2a. When the negative electrode can 2b is disposed in the opening of the positive electrode can 2a, A space for accommodating the electrode 3 is formed between the negative electrode can 2b and the positive electrode can 2a.
The electrode 3 includes a positive electrode 3a, a separator 3c, and a negative electrode 3b, which are stacked in this order. The positive electrode 3a contacts the inner surface of the positive electrode can 2a, and the negative electrode 3b contacts the inner surface of the negative electrode can 2b. As shown in FIG.
The case 2 includes a gasket 2c, and relative movement is fixed by the gasket 2c so as to maintain a non-contact state between the positive electrode can 2a and the negative electrode can 2b. Further, the gasket 2c also has a function of sealing a gap between the positive electrode can 2a and the negative electrode can 2b to block the inside and outside of the case 2 in an airtight and liquid tight manner.

(Manufacture of secondary batteries)
The coin type battery 1 as described above was manufactured as follows.

First, 5 parts by weight of acetylene black and 5 parts by weight of polyvinylidene fluoride were mixed with 90 parts by weight of the positive electrode active material powder, and n-methylpyrrolidone was added to make a paste to produce a positive electrode mixture paste.
This was applied to an aluminum foil having a thickness of 20 μm, vacuum-dried at 120 ° C., and then punched out into a disk shape having a diameter of 1 cm to obtain a positive electrode. The positive electrode mixture paste was applied to the aluminum foil so that the mass of the active material after drying was 0.05 g / cm ² .

Lithium metal was used for the negative electrode, and an equivalent mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) using 1M LiClO ₄ as a supporting salt was used for the electrolyte.

  In addition, the separator made of polyethylene is impregnated with an electrolytic solution, and the above positive electrode, negative electrode, electrolytic solution, and separator are used in the glove box in an Ar gas atmosphere in which the dew point is controlled at −80 ° C. A coin battery was produced.

  The initial discharge capacity for evaluating the performance of the manufactured coin-type battery 1 was defined as follows. The internal resistance value was measured by the following method.

(Definition of initial discharge capacity)
The initial discharge capacity was defined as follows.
After the coin-type battery shown in FIG. 1 is manufactured, it is left for about 24 hours, and after the open circuit voltage OCV (open circuit voltage) is stabilized, the current density with respect to the positive electrode is 0.1 mA / cm 2 and the cutoff voltage is 4.2 V. Charged. The capacity when the battery was discharged to a cutoff voltage of 2.5 V after 1 hour of rest was defined as the initial discharge capacity.

(Measurement of internal resistance Rct)
The internal resistance Rct was measured as follows.
After the coin-type battery shown in FIG. 1 was manufactured and left for about 24 hours and the OCV was stabilized, CCCV charging was performed to a voltage of 4.0 V at an initial current density of 0.5 mA / cm ² with respect to the positive electrode. Then, the impedance measurement was performed about the charged coin battery using the impedance apparatus (The impedance analyzer 1255B by Solartron). In the measurement, the impedance was measured by scanning from a frequency of 10 kHz to 0.1 Hz under a voltage of 10 mV.

(Comparative Example 1)
The same method as in Example 1 except that the method for measuring the lithium content in lithium hydroxide in Example 1 was changed to a method for measuring the lithium hydroxide aqueous solution using the neutralization titration method (based on JIS K1200-2). Then, a positive electrode active material was obtained, and a secondary battery was manufactured using the obtained positive electrode active material.
The lithium hydroxide aqueous solution used for neutralization titration was a solution obtained by dissolving 1 g of lithium hydroxide monohydrate in 100 ml of pure water.

(Comparative Example 2)
A positive electrode active material was obtained in the same manner as in Example 1 except that the method for measuring the lithium content in lithium hydroxide in Example 1 was changed to a method for measuring an aqueous lithium hydroxide solution using ICP emission spectrometry. Then, a secondary battery was manufactured using the obtained positive electrode active material.
The lithium hydroxide aqueous solution used for ICP emission analysis was a solution obtained by dissolving 1 g of lithium hydroxide monohydrate in 100 ml of pure water.

(Experimental result)
Table 1 shows the results of measuring the initial discharge capacity and the internal resistance of the secondary batteries obtained in Example 1 and Comparative Examples 1 and 2.

In addition, the numerical value of Table 1 in each example has shown the standard deviation of the initial stage discharge capacity and internal resistance in the some secondary battery obtained in each example.
Moreover, the internal resistance value Rct of Comparative Examples 1 and 2 in Table 1 is expressed as a relative value with respect to the internal resistance value calculated from the second arc after measurement (see FIG. 2), with Example 1 as 100. It is.

Table 1 shows that in Example 1, the Li quality of the positive electrode active material, the initial discharge capacity in the battery, and the standard deviation (RSD) of the internal resistance Rct are small, and a stable positive electrode active material is obtained. That is, it can be confirmed that a uniform positive electrode active material can be provided industrially and stably.
On the other hand, in Comparative Examples 1 and 2, since the positive electrode active material was obtained by measuring the pure lithium by the conventional analysis method, the standard deviation of the Li quality, the initial discharge capacity in the battery, and the internal resistance Rct are all large. It can be confirmed that it is difficult to provide a uniform positive electrode active material industrially and stably.

  The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is suitable as a positive electrode active material for a non-aqueous electrolyte secondary battery that can achieve both high capacity and excellent thermal stability.

DESCRIPTION OF SYMBOLS 1 Coin type battery 2 Case 3 Electrode 3a Positive electrode 3b Negative electrode 3c Separator

(Positive electrode active substance for a non-aqueous electrolyte secondary battery)
The non-aqueous electrolyte secondary battery positive electrode active substance of the first invention the general formula (I):
LiNi _1-a M _a O ₂ (I)
(In the formula, 0.01 ≦ a ≦ 0.5, M represents Al and Co )
A standard deviation of the lithium composition ratio obtained by repeating the analysis of the lithium composition ratio represented by mass% five times or more, wherein the standard deviation of the lithium composition ratio is 0.6. and wherein the der Rukoto below.
( Non-aqueous electrolyte secondary battery)
The non-aqueous electrolyte secondary battery of the second invention is characterized by having a positive electrode formed by the positive electrode active material for a non-aqueous electrolyte secondary battery of the first invention.

( Positive electrode active material for non-aqueous electrolyte secondary battery)
According to the first invention, when a positive electrode active material for a non-aqueous electrolyte secondary battery is used for a battery, it is possible to realize a battery having a high capacity, high safety, and small variations in initial discharge capacity and internal resistance. it can. In addition, according to the first invention, when a positive electrode active material for a non-aqueous electrolyte secondary battery is used for a battery, a battery having high capacity, high safety, and small variation in initial discharge capacity and internal resistance is realized. can do.
(Non-aqueous electrolyte secondary battery)
According to the second invention, since the positive electrode active material for a non-aqueous electrolyte secondary battery according to the first invention is used as the positive electrode material, the capacity is high and the safety is excellent.

Claims (10)

Formula (I):
LiNi _1-a M _a O ₂ (I)
(In the formula, 0.01 ≦ a ≦ 0.5, M represents at least one element selected from the group consisting of transition metal elements other than Ni, group 2 elements and group 13 elements)
A method for producing a positive electrode active material comprising lithium nickel composite oxide particles represented by: a metal compound having a metal atomic ratio corresponding to the metal atomic ratio in the positive electrode active material;
The metal compound includes lithium hydroxide;
The lithium content of the lithium hydroxide is calculated based on the mass reduction ratio when the sample collected from the lithium hydroxide before blending with the metal compound is dried by heating, and based on the lithium content of the lithium hydroxide. And adjusting the amount of lithium hydroxide to be mixed with the metal compound. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the mass of the sample collected from the lithium hydroxide before blending with the metal compound is 20 g or more. The method for producing a positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein a sample collected from the lithium hydroxide is heated and dried at 150 ° C to 300 ° C. 4. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the metal compound is fired in an oxygen atmosphere at a temperature range of 650 to 850 ° C. 5. The atomic ratio of lithium contained in the metal compound to all metals other than lithium (sum of the atomic ratio of lithium / the atomic ratio of all metals other than lithium) is 1.00 / 1 to 1.10. 5. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein: The metal compound is
Nickel hydroxide and / or nickel oxide obtained by roasting nickel hydroxide,
The nickel hydroxide is
In a heated reaction vessel, an aqueous solution of a metal compound containing nickel and at least one element selected from a transition metal element other than nickel, a group 2 element and a group 13 element, and an aqueous solution containing an ammonium ion supplier Is prepared by supplying
In preparing the nickel hydroxide, an aqueous solution of an alkali metal hydroxide is added so as to keep the aqueous solution in the reaction vessel alkaline. 5. A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to 5. The metal compound is
Including nickel oxyhydroxide and / or nickel oxide obtained by roasting nickel oxyhydroxide,
The nickel oxyhydroxide is
In a heated reaction vessel, an aqueous solution of a metal compound containing nickel and at least one element selected from a transition metal element other than nickel, a group 2 element and a group 13 element, and an aqueous solution containing an ammonium ion supplier Is prepared by adding an oxidizing agent after supplying
The aqueous solution of an alkali metal hydroxide is added so as to keep the aqueous solution in the reaction vessel alkaline when preparing the nickel oxyhydroxide. Or the manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries of 5. Formula (I):
LiNi _1-a M _a O ₂ (I)
(In the formula, 0.01 ≦ a ≦ 0.5, M represents at least one element selected from the group consisting of transition metal elements other than Ni, group 2 elements and group 13 elements)
A positive electrode active material composed of lithium nickel composite oxide particles represented by:
A positive electrode active material for a nonaqueous electrolyte secondary battery, which is obtained by the production method according to claim 1. 9. The nonaqueous electrolyte secondary battery according to claim 8, wherein a standard deviation of the lithium composition ratio obtained by repeating the analysis of the lithium composition ratio expressed by mass% five or more times is 0.6 or less. Positive electrode active material. A non-aqueous electrolyte secondary battery comprising a positive electrode formed by the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 8 or 9.

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