JP2013144625A - Nickel cobalt manganese compound hydroxide, method for producing the same, positive electrode active material for non-aqueous electrolyte secondary battery, and non-aqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nickel cobalt manganese compound hydroxide which allows a higher density of a positive electrode active material and achieves a high density non-aqueous electrolyte secondary battery, and to provide a method for producing the same.SOLUTION: The nickel cobalt manganese compound hydroxide is NiCoMn compound hydroxide, in which the atomic ratio of Ni, Co and Mn is substantially 5:2:3. The nickel cobalt manganese compound hydroxide is obtained by keeping the pH of an aqueous solution containing a nickel salt, a cobalt salt and a manganese salt within the range of 10 to 13, in an atmosphere of a mixed gas composed of an inert gas and oxygen, wherein oxygen is contained in an amount of 0.5 to 3.0 vol% of the inert gas, to deposit the compound hydroxide. The method for producing the compound hydroxide, a positive electrode active material for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery having a positive electrode using the positive electrode active material as a main part, a separator, a negative electrode, and a nonaqueous electrolyte solution are also provided.

Description

  The present invention relates to a nickel cobalt manganese composite hydroxide useful as a precursor of a positive electrode active material for a non-aqueous electrolyte secondary battery, a method for producing the same, a positive electrode active material for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery. Next battery.

  As a non-aqueous electrolyte secondary battery, a lithium ion secondary battery has been used in mobile devices such as mobile phones. In recent years, interest in the global environment has increased, and lithium ion secondary batteries are expected to be used for EV (Electric Vehicle) or PHEV (Plug-in Hybrid Electric Vehicle) applications.

  In EV and PHEV, since propulsion energy is supplied from the battery, the capacity of the battery is an important issue in order to extend the cruising distance. As a positive electrode active material of such a battery, a lithium-nickel cobalt manganese composite oxide having a relatively large capacity has become mainstream. From the viewpoint of improving the capacity of the battery, it is important to increase the density of the lithium-nickel cobalt manganese composite oxide, that is, the positive electrode active material.

  As a method for producing a lithium-nickel cobalt manganese composite oxide, there are firstly produced nickel cobalt manganese composite hydroxide fine particles as a precursor, mixed with this precursor and a lithium compound, and fired to obtain a positive electrode active material. To do. The precursor of the positive electrode active material is a precipitate produced by stirring an aqueous solution containing a nickel salt, a cobalt salt, and a manganese salt together with a complexing agent and a pH adjuster while continuously supplying the precursor to a reaction vessel under an inert gas atmosphere. Manufactured by continuously collecting products (see Patent Document 1).

Although a precursor with a high tap density can be obtained by the above production method, if the tap density is further improved, the positive electrode active material can be densified and the capacity of the battery can be further improved.
JP 2008-195608 A

  The present invention has been made in view of the above background, and provides a nickel cobalt manganese composite hydroxide capable of further increasing the density of the positive electrode active material and realizing a high-density nonaqueous electrolyte secondary battery, and a method for producing the same. The purpose is to do.

  Another object of the present invention is to provide a high-density positive electrode active material and a high-capacity nonaqueous electrolyte secondary battery using the nickel cobalt manganese composite hydroxide.

  According to the present invention, the nickel cobalt manganese composite hydroxide of (1) to (5), the method for producing the nickel cobalt manganese composite hydroxide of (6) to (8), and the nonaqueous electrolyte secondary of (9) The positive electrode active material for a battery and the nonaqueous electrolyte secondary battery of (10) are obtained.

(1) The content ratio of nickel (Ni), cobalt (Co), and manganese (Mn) is 3.5 to 5.5: 1.0 to 3.0: 2. 5 to 4.5 nickel cobalt manganese composite hydroxide,
In an atmosphere of a mixed gas of an inert gas and an oxygen gas having a volume ratio of 0.5% to 3.0% with respect to the inert gas, a nickel salt, a cobalt salt, and a manganese salt (specifically, Nickel cobalt manganese composite obtained by precipitation by maintaining an aqueous solution containing a molar ratio of 3.5 to 5.5: 1.0 to 3.0: 2.5 to 4.5 at a pH of 10 to 13 hydroxide.

In addition, the content ratio of nickel (Ni), cobalt (Co), and manganese (Mn) is 3.5 to 5.5: 1.0 to 3.0: 2.5 to the atomic ratio of Ni: Co: Mn. 4.5 means that the proportion of Ni is 3.5 or more and 5.5 or less, the proportion of Co is 1.0 or more and 3.0 or less, and the proportion of Mn is 2.5 or more and 4.5 or less. It means that. Specifically, for example, the formula: Ni _x Co _y Mn _z (OH) ₂ (where 0.35 ≦ x ≦ 0.55, 0.1 ≦ y ≦ 0.3, 0.25 ≦ z ≦ 0. 45, and x + y + z = 1) (the same applies hereinafter).

(2) The nickel-cobalt-manganese composite water according to (1), wherein the tap density is 2.0 g / ml or more, the bulk density is 1.5 g / ml or more, and the average particle size is 5 μm or more and 30 μm or less. Oxides.

(3) The nickel cobalt manganese composite hydroxide according to the above (1) or (2), wherein the inert gas is nitrogen.

(4) The nickel cobalt manganese composite hydroxide according to any one of (1) to (3), wherein the aqueous solution contains a complexing agent.

(5) The nickel cobalt manganese composite hydroxide according to any one of the above (1) to (4), which is a precursor of a positive electrode active material for a nonaqueous electrolyte secondary battery.

(6) The content ratio of nickel (Ni), cobalt (Co), and manganese (Mn) is 3.5 to 5.5: 1.0 to 3.0: 2. It is a manufacturing method of nickel cobalt manganese compound hydroxide which is 5-4.5,
Obtaining an aqueous solution containing nickel salt, cobalt salt and manganese salt (molar ratio);
Nickel having a step of maintaining an aqueous solution at a pH of 10 or more and a pH of 13 or less in an atmosphere of a mixed gas of an inert gas and an oxygen gas having a volume ratio of 0.5% to 3.0% with respect to the inert gas. Method for producing cobalt manganese composite hydroxide.

(7) The method for producing a nickel cobalt manganese composite hydroxide according to the above (6), wherein the inert gas is nitrogen.

(8) The method for producing a nickel-cobalt-manganese composite hydroxide according to any one of (6) and (7) above, wherein the mixed gas is constantly supplied into a reaction vessel containing an aqueous solution.

(9) The method for producing a nickel cobalt manganese composite hydroxide according to any one of (6) to (8), wherein the aqueous solution contains a complexing agent.

(10) A positive electrode active material for a nonaqueous electrolyte secondary battery obtained by firing a mixture of a nickel cobalt manganese composite hydroxide and a lithium compound of the positive electrode active material according to any one of (1) to (5) above .

(11) A non-aqueous electrolyte secondary battery having a positive electrode, a separator, and a negative electrode mainly composed of the positive electrode active material for a non-aqueous electrolyte secondary battery according to (10).

According to the nickel-cobalt-manganese composite hydroxide according to the present invention, the nickel-cobalt-manganese composite hydroxide particles are deposited in the slightly oxidizing inert atmosphere as described above, so the nickel-cobalt-manganese composite hydroxide tap Density and bulk density are improved, and the positive electrode active material and its precursor can be densified. As a result, the capacity of the nonaqueous electrolyte secondary battery can be further improved.
According to the method for producing a nickel cobalt manganese composite hydroxide according to the present invention, the nickel cobalt manganese composite hydroxide of the present invention can be efficiently and industrially advantageously produced.

It is a figure explaining the manufacturing apparatus of the nickel cobalt manganese compound hydroxide concerning the present invention. It is a figure explaining the manufacturing process of the nickel cobalt manganese compound hydroxide concerning the present invention. (A) and (B) are SEM enlarged images in which the nickel cobalt manganese composite hydroxide fine particles according to the example and the nickel cobalt manganese composite hydroxide fine particles according to the comparative example are compared, and (C) and (D) are It is a SEM enlarged image which contrasted the positive electrode active material fine particle by an Example, and the positive electrode active material fine particle by a comparative example.

  Hereinafter, the present invention is divided into 1) nickel cobalt manganese composite hydroxide, 2) method for producing nickel cobalt manganese composite hydroxide, 3) positive electrode active material for non-aqueous electrolyte secondary battery, and method for producing the same, and 4) The non-aqueous electrolyte secondary battery will be described in detail.

1) Nickel cobalt manganese composite hydroxide (essential component)
The nickel cobalt manganese composite hydroxide according to the present invention contains nickel (Ni), cobalt (Co) and manganese (Mn), and the content ratio of Ni, Co and Mn is the atomic ratio of Ni: Co: Mn. It is 3.5-5.5: 1.0-3.0: 2.5-4.5. Specifically, for example, the following formula Ni _x Co _y Mn _z (OH) ₂ (where 0.35 ≦ x ≦ 0.55, 0.1 ≦ y ≦ 0.3, 0.25 ≦ z ≦ 0. 45, and x + y + z = 1)
It is represented by

Among the nickel-cobalt-manganese composite hydroxide as described above, the following formula _{Ni x Co y Mn z (OH} ) 2 ( wherein, 0.43 ≦ x ≦ 0.47,0.18 ≦ y ≦ 0.22, 0.33 ≦ z ≦ 0.37, and x + y + z = 1)
Is more preferable from the viewpoint of improving the tap density or bulk density.

(Features related to manufacturing method and physical properties of powder)
The nickel-cobalt-manganese composite hydroxide according to the present invention maintains an aqueous solution containing nickel salt, cobalt salt and manganese salt at pH 10 or more and pH 13 or less in an atmosphere of a mixed gas of an inert gas and a trace amount of oxygen gas. To precipitate as high density particles. Here, the nickel salt, the cobalt salt and the manganese salt are supplied to the aqueous solution at a certain ratio, and the mixing ratio of the nickel salt, the cobalt salt and the manganese salt supplied in this way is in the nickel cobalt manganese composite hydroxide. It is substantially the same as the atom, and the molar ratio of nickel salt: cobalt salt: manganese salt is usually 3.5 to 5.5: 1.0 to 3.0: 2.5 to 4.5, preferably Is 4.3 to 4.7: 1.8 to 2.2: 3.3 to 3.7. In addition, by supplying the complexing agent aqueous solution into the reaction tank constantly, the concentration gradient relating to the dissolution of metal ions can be reduced, and high-density and sufficiently sized particles can be grown. The complexing agent may be supplied to the reaction vessel separately from the mixed aqueous solution of nickel salt, cobalt salt and manganese salt, or with the complexing agent added to the mixed aqueous solution of nickel salt, cobalt salt and manganese salt. You may supply in batch in a reaction tank.

  The mixed gas used during the reaction is 0.5% to 3.0% by volume with respect to the inert gas, preferably 1.2% to 2.5% by volume, more preferably volume. It contains 1.6% to 2.4% oxygen gas in a ratio. Examples of the inert gas that is the main component of the mixed gas include nitrogen gas, argon gas, neon gas, helium gas, and the like. Moreover, what is obtained by mixing nitrogen gas and air in a suitable ratio can also be used as a mixed gas. That is, the mixed gas can contain a small amount of various gases such as carbon dioxide gas as long as the effects of the present invention are not impaired.

  As described above, nickel, cobalt, or manganese ions in the aqueous solution can be obtained by using a gas mixture containing oxygen gas in a volume ratio of 0.5% to 3.0% with respect to the inert gas. Therefore, it is possible to give a slight oxidation tendency, so that the precipitation and growth of crystals become good, and the deposited fine particles can be densified.

  The nickel cobalt manganese composite hydroxide obtained as described above can have a tap density of 2.0 g / ml or more and a bulk density of 1.5 g / ml or more. Such a relatively high density nickel-cobalt-manganese composite hydroxide is useful in terms of increasing the density of the positive electrode active material as a precursor of the positive electrode active material for a non-aqueous electrolyte secondary battery. The tap density and bulk density of the nickel-cobalt-manganese composite hydroxide can be determined by measurement by a known measurement method described in the examples.

  Although there is no restriction | limiting in particular about the powder shape of nickel cobalt manganese complex hydroxide, A substantially spherical shape is preferable. The powder of nickel cobalt manganese composite hydroxide may be any of primary particles of nickel cobalt manganese composite hydroxide having a crystal structure, secondary particles formed by aggregating a plurality of such primary particles, and mixtures thereof. There may be. Such a powder shape can be easily determined by visual observation or image data processing by a generally known electron microscope measurement.

  Although there is no restriction | limiting in particular about the average particle diameter of nickel cobalt manganese composite hydroxide, The range whose average particle diameter is 5 micrometers or more and 30 micrometers or less is preferable. The particle diameter of the powder can be controlled by granulation or pulverization. By setting the particle diameter of the powder in the above range, the capacity and output of the nonaqueous electrolyte secondary battery can be sufficiently increased. When the average particle size is large, the particle size exceeds the thickness of the positive electrode current collector when a lithium-nickel cobalt manganese composite oxide obtained from nickel cobalt manganese composite hydroxide is used as an electrode, which is not practical. . The particle size can be easily determined by a generally known particle size distribution measuring method / apparatus.

(Other ingredients)
In the nickel-cobalt-manganese composite hydroxide according to the present invention, as long as the ratio of the contents of nickel, cobalt, and manganese as described above is maintained, and unless the densification that is the effect of the present invention is impaired, It is also possible to contain other elements such as metals. Examples of such elements include Fe, Sn, Al, Ti, Zr, and Mg. Moreover, there is no restriction | limiting in particular also about those content, if it is a range which does not impair the effect of this invention.

2) Manufacturing Method of Nickel Cobalt Manganese Composite Hydroxide The manufacturing method of nickel cobalt manganese composite hydroxide will be described separately for the manufacturing apparatus and the specific manufacturing process.

2a) Nickel Cobalt Manganese Composite Hydroxide Manufacturing Apparatus With reference to FIG. 1, a manufacturing apparatus used in the nickel cobalt manganese composite hydroxide manufacturing method according to the present invention will be described. The illustrated manufacturing apparatus 100 includes a reaction vessel 10, a raw material supply device 20, a pH adjustment device 30, an atmosphere control device 40, a complexing agent supply device 50, and a reaction product recovery device 60.

  The reaction tank 10 is a cylindrical container made of metal or resin, and includes a propeller type stirring device 11. The reaction tank 10 includes a heater 12 and can keep the temperature of the solution SO stored in the reaction tank 10 constant based on an output of a temperature sensor (not shown) extending into the reaction tank 10. A product outlet 13 for discharging the reaction product in the tank is provided at an appropriate height position on the side wall of the reaction tank 10, and the product outlet 13 includes the product outlet 13. A shutter that enables opening and closing at any timing is provided.

  The raw material supply device 20 supplies a reaction mixed aqueous solution obtained by mixing a nickel salt solution, a cobalt salt solution, and a manganese salt solution at an appropriate ratio to the reaction vessel 10. The supply timing and supply amount of the mixed aqueous solution are adjusted by a valve 21 provided in association with the raw material supply device 20, and the operation of the valve 21 is controlled by a control driving device (not shown).

  The pH adjusting device 30 is for adjusting the pH value of the mixed aqueous solution held in the reaction tank 10, and adjusts the pH to the reaction tank 10 supplied with the mixed aqueous solution containing nickel salt, cobalt salt, manganese salt, and the like. By supplying an alkali metal hydroxide as an agent, the solution SO in the reaction vessel 10 is controlled to be in an alkaline state, specifically, for example, in a range of pH 10 or more and pH 13 or less. The supply timing and supply amount of the alkaline solution are adjusted by a valve 31 provided along with the pH adjusting device 30, and the operation of the valve 31 is controlled by a control drive device (not shown).

  The atmosphere control device 40 includes a nitrogen supply system 41 including a nitrogen supply source 41a, an oxygen supply system 42 including an oxygen supply source 42a, a mixing unit 44 that mixes nitrogen and oxygen from both supply systems 41 and 42, and mixing And an air supply pipe 46 for supplying the mixed gas of nitrogen and oxygen that has passed through the section 44 to the space SP above the reaction tank 10. An exhaust pipe 47 is also provided at the upper part of the reaction tank 10 so that the atmosphere accumulated in the space SP above the reaction tank 10 can be discharged to the outside.

  Here, the nitrogen supply system 41 includes a valve 41b that intermittently supplies nitrogen gas from the nitrogen supply source 41a, and a flow rate control unit 41c that is arranged downstream of the valve 41b and adjusts the flow rate of nitrogen gas. The oxygen supply system 42 includes a valve 42b for intermittently supplying oxygen gas from the oxygen supply source 42a, and a flow rate control unit 42c disposed downstream of the valve 42b for adjusting the flow rate of nitrogen gas. . The former nitrogen supply source 41a can supply air containing, for example, nitrogen gas and oxygen gas in consideration of cost.

  In the above atmosphere control device 40, the valve 41b and the flow rate control unit 41c in the nitrogen supply system 41, the valve 42b and the flow rate control unit 42c in the nitrogen supply system 42, and the valve 47c provided in the exhaust pipe 47 are not shown. The control drive device is operated to adjust the atmosphere of the space SP of the reaction vessel 10. Specifically, the volume ratio is 0.5% or more and 3.0% or less, preferably 1.2% or more and 2.5% or less (more preferably volume ratio 1) with respect to high purity nitrogen gas. .6% or more and 2.4% or less) can be supplied to the space SP of the reaction tank 10 through the air supply pipe 46. The space SP of the reaction tank 10 is positively charged by the supply of the mixed gas, but the positive pressure in the reaction tank 10 can be finely adjusted by adjusting the opening / closing degree of the valve 47c provided in the exhaust pipe 47. .

  The complexing agent supply device 50 supplies the complexing agent aqueous solution to the reaction vessel 10. The supply timing and supply amount of the complexing agent aqueous solution are adjusted by a valve 51 provided in association with the complexing agent supply device 50, and the operation of the valve 51 is controlled by the illustrated control driving device.

  The reaction product recovery device 60 includes an overflow pipe 61 extending from the reaction tank 10 in an inclined manner, and a recovery tank 62 in which the lower end side of the overflow pipe 61 is connected to the upper part. The overflow pipe 61 communicates with the product discharge port 13 provided on the side wall of the reaction tank 10. The recovery tank 62 is a sealed container and stores therein a reaction product RP and the like discharged from the reaction tank 10 through the overflow pipe 61. A take-out device 62 b is provided below the recovery tank 62, and the reaction product RP sealed in the recovery tank 62 is periodically discharged and stored in the container 71.

  The reaction product RP taken out from the recovery tank 62 is accommodated in the container 71, then washed by an apparatus (not shown), filtered, and dried.

2b) Specific Manufacturing Process of Nickel Cobalt Manganese Composite Hydroxide The specific process of the manufacturing method of nickel cobalt manganese composite hydroxide using the manufacturing apparatus 100 shown in FIG. 1 will be described below.

  First, a pH-adjusted solution SO is prepared in the reaction vessel 10 (step S11 in FIG. 2). Specifically, first, water is supplied into the reaction vessel 10 and the pH adjusting device 30 is operated while stirring the water for homogenization until a suitable pH value is reached. Such an alkali metal hydroxide pH adjuster is added.

  Thereafter, the solution SO in the reaction vessel 10 is heated while being stirred by the heater 12 so that the temperature of the solution SO is maintained at a predetermined temperature (step S12 in FIG. 2). The temperature set for the solution SO is a temperature suitable for the subsequent crystallization or coprecipitation reaction, and is, for example, in the range of 40 ° C. or more and 60 ° C. or less.

  As the solution SO in the reaction vessel 10 is heated, the mixed gas from the atmosphere control device 40 is introduced into the reaction vessel 10 to make the atmosphere of the space SP constant (step S13 in FIG. 2). At this time, by rotating the propeller of the stirring device 11 at a constant speed, the solution SO accumulated in the lower part of the reaction vessel 10 and the atmosphere accumulated in the space SP are brought into sufficient contact. Here, the mixed gas from the atmosphere control device 40 is mostly nitrogen and contains a slight amount of oxygen, and is an inert atmosphere that is slightly oxidized (a slightly oxidizing atmosphere). ).

  When the solution SO in the reaction vessel 10 is stabilized, the raw material supply device 20 is operated while continuing the stirring by the stirring device 11, and the mixed aqueous solution for reaction is supplied at a constant flow rate to the solution SO in the reaction vessel 10. Drop and mix (step S13 in FIG. 2). At this time, a predetermined concentration of sodium hydroxide or other alkali metal hydroxide is intermittently added to the solution SO so that the pH of the solution SO in the reaction vessel 10 is kept constant. The mixed aqueous solution for reaction mixed with the solution SO is a mixture of a nickel sulfate solution, a cobalt sulfate solution, and a manganese sulfate aqueous solution in a predetermined molar ratio. In addition, when the above mixed aqueous solution for reaction is added, the complexing agent supply device 50 is operated as appropriate to supply a complexing agent such as an ammonium sulfate solution into the reaction vessel 10 as appropriate.

  Here, in the above mixed aqueous solution for reaction, the mixing ratio (molar ratio) of the nickel salt solution, cobalt salt solution and manganese salt solution is the composition of the target nickel cobalt manganese composite hydroxide or composite metal hydroxide. For example, Ni: Co: Mn = 3.5 to 5.5: 1.0 to 3.0: 2.5 to 4.5, preferably 4. 3 to 4.7: 1.8 to 2.2: 3.3 to 3.7. Moreover, water is used as a solvent.

As the nickel salt which is the solute of the nickel salt solution, for example, nickel sulfate, nickel nitrate, nickel chloride and the like can be used. Examples of the cobalt salt that is a solute of the cobalt salt solution include cobalt sulfate, cobalt nitrate, and cobalt chloride. As the manganese salt that is the solute of the manganese salt solution, for example, manganese sulfate, manganese nitrate, manganese chloride, and the like can be used. In addition, it is desirable to arrange counter ions of nickel, cobalt, and manganese. Specifically, for example, when Ni (2+) SO ₄ is used, Co (2+) SO ₄ and Mn (2+) SO ₄ are mixed at a specified molar ratio in correspondence with Ni (2+) SO _4. become.

  Complexing agents are those that can form complexes with nickel, cobalt, and manganese ions in aqueous solution, such as ammonium ion donors (ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, etc.), hydrazine, ethylenediamine. Examples include tetraacetic acid, nitrilotriacetic acid, uracil diacetic acid, and glycine.

  In the above reaction, if necessary, the pH adjusting device 30 is operated and an aqueous solution of an alkali metal hydroxide is added to adjust the pH value of the solution SO in the reaction vessel 10 to an alkaline state. Specifically, the pH value of the solution SO in the reaction vessel 10 is controlled to be in the range of pH 9 or more and pH 13 or less. As the alkali metal hydroxide, for example, sodium hydroxide, potassium hydroxide or the like can be used. In place of the alkali metal hydroxide, an alkaline earth metal hydroxide such as magnesium hydroxide, calcium hydroxide, or barium hydroxide can be used.

  In the above reaction, the inside of the reaction tank 10 is made into a slightly oxidizing atmosphere, and nickel ions, cobalt ions, and manganese ions tend to be oxidized under the influence of oxygen gas dissolved from the slightly oxidizing atmosphere. For example, manganese ions in the raw material liquid exist as divalent ions, but in the reaction aqueous solution, divalent or trivalent ions are mixed, and their balance can be adjusted by a slightly oxidizing atmosphere, so that they are precipitated. It is thought that the density of the reaction product or reaction precipitate can be increased.

  At the stage where the reaction of the solution SO in the reaction vessel 10 has progressed to a steady state, the product discharge port 13 provided in the reaction vessel 10 is opened to gradually overflow the solution SO, thereby allowing the solution SO to overflow in the reaction vessel 10. Product particles that are reaction products or reaction precipitates that are supersaturated are collected in the reaction product recovery device 60 through the overflow pipe 61 (step S15 in FIG. 2). The time until the solution SO overflows depends on the apparatus and the solution, but is, for example, 8 to 32 hours.

The slurry-like product particles collected in the reaction product recovery device 60 are washed, filtered, and dried (step S16 in FIG. 2). The resulting product _{particles, LiNi x Co y Mn z (} OH) 2 ( wherein, 0.35 ≦ x ≦ 0.55,0.1 ≦ y ≦ 0.3,0.25 ≦ z ≦ 0. 45, and x + y + z = 1), which is a nickel cobalt manganese composite hydroxide (also referred to as a nickel cobalt manganese composite compound or a composite metal hydroxide in this specification).

3) Positive electrode active material for non-aqueous electrolyte secondary battery and method for producing the same
3a) Positive electrode active material for non-aqueous electrolyte secondary battery The positive electrode active material for non-aqueous electrolyte secondary battery is lithium-nickel obtained by firing a mixture of the above-described nickel cobalt manganese composite hydroxide and lithium compound. Cobalt-manganese composite oxide, formula: LiNi _x Co _y Mn _z O ₂ (where 0.35 ≦ x ≦ 0.55, 0.10 ≦ y ≦ 0.30, 0.25 ≦ z ≦ 0. 45, and x + y + z = 1)
It is represented by

  The lithium-nickel cobalt manganese composite oxide as the positive electrode active material is used as a powder. The powder shape of the lithium-nickel cobalt manganese composite oxide is not particularly limited, but is preferably approximately spherical. The powder of lithium-nickel cobalt manganese composite oxide includes primary particles of lithium-nickel cobalt manganese composite oxide having a crystal structure, secondary particles formed by aggregating a plurality of such primary particles, and mixtures thereof. Or any of them. Such a powder shape can be easily determined by visual observation or image data processing by a generally known electron microscope measurement. The particle diameter of the lithium-nickel cobalt manganese composite oxide is similar to the nickel cobalt manganese composite hydroxide described above, the tap density can be 2.3 g / ml or more, and the bulk density is 1.6 g / ml or more. And can.

3b) Method for producing positive electrode active material for nonaqueous electrolyte secondary battery The nickel cobalt manganese composite metal hydroxide compound is dried, classified, and mixed with a lithium salt. As the lithium salt, any one of lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate, lithium oxide, or a mixture of two or more can be used. The above lithium salt and nickel cobalt manganese composite metal hydroxide are LiNi _x Co _y Mn _z O ₂ (where 0.35 ≦ x ≦ 0.55, 0.1 ≦ y ≦ 0), which is the final target product. .3, 0.25 ≦ z ≦ 0.45, and x + y + z = 1). A lithium-nickel cobalt manganese composite oxide is obtained by firing a mixture of a nickel cobalt manganese composite hydroxide and a lithium salt. For the firing, dry air, an oxygen atmosphere, an inert atmosphere, or the like is used according to a desired composition, and a plurality of heating steps are performed if necessary.

  The lithium-nickel-cobalt-manganese composite oxide obtained by firing is classified after pulverization and used as a positive electrode active material applicable to a non-aqueous electrolyte secondary battery. Such a positive electrode active material has a spherical shape or a shape close to a spherical shape, preferably has an average particle diameter in the range of 1 μm to 30 μm, more preferably in the range of 3 μm to 13 μm, and the tap density is as described above. It becomes 2.3 g / ml or more.

3c) Measurement of characteristics of positive electrode active material The capacity of the positive electrode active material is 4.2 V when the practical voltage of the lithium ion secondary battery of the non-aqueous electrolyte secondary battery uses graphite as the negative electrode active material, It is practical to evaluate at this voltage. However, since the capacity of the positive electrode active material alone is measured using Li metal for the counter electrode, the potential at that time is evaluated at 4.3 V corresponding to 4.2 V in the case of graphite. Specific measurement methods will be described in Examples.

4) Nonaqueous electrolyte secondary battery The nonaqueous electrolyte secondary battery of the present invention is not particularly limited as long as it uses the positive electrode active material described above. The structure of the nonaqueous electrolyte secondary battery can be of various known types. In addition, various characteristics and performance of the obtained nonaqueous electrolyte secondary battery (lithium ion battery) can be determined based on a generally known evaluation method and measuring apparatus.
Hereinafter, an example of the structure of the nonaqueous electrolyte secondary battery will be described separately for the positive electrode, the negative electrode, the nonaqueous electrolyte, and the like.

(Positive electrode)
The positive electrode of the non-aqueous electrolyte battery of the present invention is prepared by mixing the positive electrode active material described above, that is, the lithium-nickel cobalt manganese composite oxide, a conductive agent, a binder, and the like in a solvent, and using the resulting slurry as the positive electrode. It can manufacture by apply | coating to a collector and drying further.

  The conductive agent is added to bring out good battery performance. Examples of the conductive agent include natural graphite; artificial graphite; carbon black such as acetylene black; amorphous carbon such as needle coke;

  The binder is not particularly limited as long as it has resistance to a nonaqueous electrolyte and has adhesiveness. For example, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, ethylene-propylene-butadiene terpolymer, styrene-butadiene rubber, acrylonitrile-butadiene rubber, carboxy Methyl cellulose, fluororubber, polyvinyl acetate, polymethyl methacrylate, polyethylene, nitrocellulose, or derivatives thereof can be used alone or in combination.

  The solvent used when mixing the lithium-nickel cobalt manganese composite oxide and the binder is not particularly limited as long as the solvent dissolves or disperses the binder. For example, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, N, N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc. Water or an aqueous solution such as an aqueous solution to which a dispersant, a thickener, or the like is added can be used.

  Examples of the current collector used for the positive electrode include aluminum, titanium, stainless steel, nickel, calcined carbon, and a conductive polymer. Examples of the shape include a sheet shape, a foam shape, a sintered porous shape, and an expanded lattice shape.

(Negative electrode)
The negative electrode of the nonaqueous electrolyte battery can be produced by mixing a negative electrode material, a conductive agent, a binder, and the like in a solvent, applying the resulting slurry to a negative electrode current collector, and further drying.

  The negative electrode material may be any material as long as it can occlude and release lithium ions. For example, lithium metal, lithium alloy (lithium metal-containing alloys such as lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and wood alloy), and lithium composite oxide (titanate) Lithium, etc.), silicon, silicon oxide, tin oxide, carbon materials (eg, graphite, hard carbon, low-temperature calcined carbon, amorphous carbon, etc.). Among these, graphite has an operating potential very close to that of metallic lithium, and therefore, when a lithium salt is employed as an electrolyte salt described later, it exhibits a high discharge voltage and a small irreversible capacity, and therefore is preferable as a negative electrode material.

  As the conductive agent and binder for the negative electrode, the same conductive agent and binder as those for the positive electrode can be used. Examples of the current collector used for the negative electrode include copper, nickel, iron, stainless steel, titanium, aluminum, calcined carbon, and conductive polymer. Examples of the shape include a sheet shape, a foam shape, a sintered porous shape, and an expanded lattice shape.

(Nonaqueous electrolyte)
The nonaqueous electrolyte is an electrolyte salt containing a nonaqueous solvent.
Examples of the electrolyte salt include lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroarsenide (LiAsF ₆ ), and trifluoromethane. Examples thereof include lithium salts such as lithium sulfonate (LiCF ₃ SO ₃ ), lithium bistrifluoromethylsulfonylimide (LiN (CF ₃ SO ₂ ) ₂ ), and borate (for example, LiBOB).

  Examples of the organic solvent used in the non-aqueous electrolyte include cyclic carbonates such as ethylene carbonate, propylene carbonate, and vinylene carbonate; chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; tetrahydrofuran, 2-methyltetrahydrofuran, and the like. Cyclic ethers; chain ethers such as dimethoxyethane; lactones such as γ-butyrolactone; nitriles such as acetonitrile; sultones such as sulfolane, 1,3-propane sultone, 1,3-propene sultone; it can. These organic solvents can be used alone or in the form of a mixture of two or more. Moreover, a room temperature molten salt containing lithium ions can be used as the non-aqueous electrolyte.

(separator)
As the separator, a microporous polymer film, a synthetic resin nonwoven fabric, or the like can be used. Examples of the material include nylon, cellulose acetate, nitrocellulose, polysulfone, polyacrylonitrile, polyvinylidene fluoride, and polyolefin (for example, polypropylene, polyethylene, polybutene, etc.). A microporous film in which polyethylene and polypropylene are laminated can also be used.

  A solid electrolyte can also be used as the nonaqueous electrolyte. Examples of the solid electrolyte include Li—P—O—N composed of Li, P, O, and N in addition to Li 2 S and P 2 S 5.

  Hereinafter, specific examples of the present invention will be described. However, the present invention is not limited to these examples.

(1) Example 1
(Production of nickel cobalt manganese composite hydroxide)
480 L of water was placed in a 500 L cylindrical reaction tank equipped with a stirrer and an overflow pipe. Vinyl chloride resin was used as the material for the reaction vessel. Further, 8.9 kg of ammonium sulfate powder was added as a complexing agent. Next, a 32% aqueous sodium hydroxide solution was added until the pH reached 11.5, and the temperature of the aqueous solution was maintained at 50 ° C. with an electric heater. Next, the solution in the reaction vessel was stirred at a constant speed. Further, nitrogen gas is continuously supplied to the reaction tank at a flow rate of 10.0 L / min and air gas is supplied at a flow rate of 1.0 L / min, so that the oxygen concentration in the mixed gas in the reaction tank is 2.0%. It was. Next, a nickel sulfate (II) aqueous solution, a cobalt sulfate (II) aqueous solution and a manganese (II) sulfate aqueous solution are mixed so that Ni: Co: Mn = 45: 20: 35 (molar ratio), and nickel in the mixed solution is obtained. The mixture was diluted with water so that the concentration was 0.65 mol / L, the cobalt concentration was 0.29 mol / L, and the manganese concentration was 0.50 mol / L to prepare a nickel sulfate-cobalt sulfate-manganese sulfate mixed aqueous solution. This mixed aqueous solution was continuously supplied from the upper part of the reaction tank to the liquid level in the tank (the surface of the stirring solution) at a constant rate of 300 ml / min. In synchronization with this, a 2.8 mol / L ammonium sulfate aqueous solution was continuously supplied as a complexing agent from the inlet at the top of the reaction tank to the liquid level in the reaction tank at a constant rate of 24 ml / min. Furthermore, the reaction solution temperature was kept at 50 ° C., and 32% sodium hydroxide aqueous solution was intermittently added so as to keep the pH of the reaction solution at 11.5 to form composite metal hydroxide particles. The reaction tank is maintained in a state where nitrogen gas is continuously supplied at a flow rate of 10.0 L / min and air gas is supplied at a flow rate of 1.0 L / min so that the oxygen concentration becomes 2.0%. The atmosphere in the tank was maintained in a state where it was constantly replaced. The hydroxide particles discharged from the overflow pipe were collected continuously for 24 hours 72 hours after the inside of the reaction vessel reached a steady state, filtered after washing with water, and heated at 100 ° C. with a shelf-type hot air dryer. And dried for 20 hours to obtain a composite metal hydroxide as a dry powder, that is, nickel cobalt manganese composite hydroxide. The obtained nickel cobalt manganese composite hydroxide had an average particle size (APS) of 9.9 μm, a tapping density (TD) of 2.33 g / ml, and a bulk density (BD) of 1.83 g / ml.

  The obtained nickel cobalt manganese composite hydroxide (sample 1) was analyzed by X-ray diffraction. Sample 1 was used as it was as a sample at the time of analysis. The measurement apparatus for analysis is “RINT2200” manufactured by Rigaku Corporation. Cu-Kα X-rays were used as measurement conditions. As a measurement result, nickel cobalt manganese composite hydroxide was detected.

Further, the tapping density of the sample 1 was measured. The mass [A] of the 20 ml cell was measured, and the crystal was spontaneously dropped into the cell with a 48 mesh sieve and filled. The cell mass [B] and filling volume [D] were measured after tapping 200 times using a “TAPDENSER KYT3000” manufactured by Seishin Enterprise Co., Ltd. with a 40 mm spacer. The tapping density [TD] was calculated by the following formula.
[Equation 1]
Tapping density TD = (BA) / D g / ml

  The average particle diameter of the sample 1 was measured. The measuring device for measuring the particle diameter was “LA-950” manufactured by Horiba, Ltd., and the measurement conditions were in accordance with the operation procedure manual.

(Preparation of positive electrode active material)
The obtained nickel cobalt manganese composite hydroxide and lithium carbonate were mixed so that the atomic ratio of Li / Me (total of Ni, Co, Mn) was 1.05, and filled in an alumina sheath for firing, In an atmosphere in which dry air was continuously supplied into the electric furnace at a flow rate of 5 L / min using an electric furnace, the temperature was raised to 700 ° C. at a temperature rising rate of 200 ° C./hour, and held at 700 ° C. for 5 hours. Then, it heated up to 950 degreeC with the temperature increase rate of 200 degreeC / hour, and hold | maintained at 950 degreeC for 10 hours. Then, it stood to cool to room temperature. The obtained lithium-nickel cobalt manganese composite oxide particles had an average particle diameter of 10.0 μm, a tapping density of 2.61 g / ml, a bulk density of 1.87 g / ml, and a press density of 3.008 g / ml. The tapping density and average particle size were measured in the same manner as the nickel cobalt manganese composite hydroxide. Moreover, the chemical analysis was performed about lithium- nickel cobalt manganese complex oxide. Specifically, Ni, Co, Mn, Li and impurity components were analyzed by ICP, and residual Li carbonate and LiOH were analyzed by neutralization titration.

(Evaluation of positive electrode active material)
The positive electrode active material obtained by the above method, acetylene black as a conductive agent, and polyvinylidene fluoride resin (hereinafter referred to as PVDF) as a binder were mixed at a weight ratio of 90: 5: 5, and N-methyl-2 -Pyrrolidone was added and kneaded and dispersed to prepare a slurry. The slurry was applied to an aluminum foil, dried at 60 ° C. for 3 hours, and dried at 120 ° C. for 12 hours. The electrode after drying was roll-pressed and punched into a disc shape so that the area was 2 ml. As a method for producing the evaluation cell, a negative electrode plate was prepared by attaching lithium metal to a stainless steel plate. A solution obtained by adding hexafluorophosphoric acid to a solution in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 3: 7 so as to have a concentration of 1.0 mol / L was used as an electrolytic solution. A polypropylene separator was used as a separator, and a positive electrode plate, a separator, and a negative electrode plate were sandwiched between stainless plates and sealed with an exterior material to prepare a bipolar evaluation cell.

  With respect to the bipolar evaluation cell, the charge rate was 0.1 C, the discharge rate was 0.1 C, and the battery was charged at a constant current / constant voltage at 4.3 V and then discharged at a constant current to 3.0 V. The resulting initial charge capacity was 187.6 mAh / g, the initial discharge capacity was 164.0 mAh / g, and the charge / discharge efficiency was 87.5%.

Table 1 below summarizes the evaluation items of Example 1 (including Sample 1).

  SEM photographs of the precursor fine particles and positive electrode active material fine particles obtained in Example 1 are shown in FIGS. 3 (A) and 3 (C). As shown in FIG. 3A, the precursor fine particles (nickel-cobalt-manganese composite hydroxide fine particles) of Example 1 are nearly spherical and have few surface irregularities. As shown in FIG. 3C, the positive electrode active material fine particles (lithium-nickel cobalt manganese composite oxide fine particles) of Example 1 also have a spherical particle shape and few surface irregularities.

(2) Example 2
A nickel cobalt manganese composite hydroxide or a positive electrode active material (lithium-nickel cobalt manganese composite oxide) was used in the same manner as in Example 1 except that the oxygen concentration in the mixed gas in the reaction vessel was 1.0% by volume. Was made. Further, a bipolar evaluation cell was produced from the positive electrode active material of Example 2 by the same method as in Example 1, and the capacity was measured in the same manner as in Example 1. In Table 1 described above, the evaluation items of Example 2 are also shown.

  For the nickel cobalt manganese composite hydroxide of Example 2, the results were obtained that the average particle size (APS) was 9.6 μm, the tapping density (TD) was 2.15 g / ml, and the bulk density (BD) was 1.60 g / ml. It was. In Example 2, the initial discharge capacity was 163.8 mAh / g, and the charge / discharge efficiency was 87.8.

(3) Comparative Example 1
A nickel cobalt manganese composite hydroxide and a positive electrode active material (lithium-nickel cobalt manganese composite oxide) were produced in the same manner as in Example 1 except that the oxygen concentration in the mixed gas in the reaction vessel was 0%. . In addition, a bipolar evaluation cell was produced from the positive electrode active material of Comparative Example 1 by the same method as in Example 1, and the capacity was measured in the same manner as in Example 1. In Table 1 described above, evaluation items of Comparative Example 2 are also shown.

  For the nickel cobalt manganese composite hydroxide of Comparative Example 1, the average particle size (APS) 9.5 μm, tapping density (TD) 1.84 g / ml, bulk density (BD) 1.29 g / ml were obtained. It was. In the case of Comparative Example 1, the initial discharge capacity was 163.0 mAh / g, and the charge / discharge efficiency was 88.3.

  SEM photographs of the precursor fine particles and the positive electrode active material fine particles obtained in Comparative Example 1 are shown in FIGS. 3 (B) and 3 (D). As shown in FIG. 3B, the precursor fine particles (nickel cobalt manganese composite hydroxide fine particles) of Comparative Example 1 have a relatively non-spherical particle shape and many surface irregularities. As shown in FIG. 3D, the positive electrode active material fine particles (lithium-nickel cobalt manganese composite oxide fine particles) of Comparative Example 1 are also relatively non-spherical in shape and have many surface irregularities.

  From the above results, it can be seen that the nickel-cobalt-manganese composite hydroxide and the positive electrode active material of Examples 1 and 2 have high density and can improve the capacity of the non-aqueous electrolyte secondary battery.

  DESCRIPTION OF SYMBOLS 100 ... Manufacturing apparatus, 10 ... Reaction tank, 20 ... Raw material supply apparatus, 30 ... pH adjustment apparatus, 40 ... Atmosphere control apparatus, 50 ... Complexing agent supply apparatus, 60 ... Reaction product collection apparatus

Claims (11)

The content ratio of nickel (Ni), cobalt (Co), and manganese (Mn) is 3.5 to 5.5: 1.0 to 3.0: 2.5 to 4 in terms of atomic ratio of Ni: Co: Mn. .5 nickel cobalt manganese composite hydroxide,
In an atmosphere of a mixed gas of an inert gas and an oxygen gas having a volume ratio of 0.5% to 3.0% with respect to the inert gas, an aqueous solution containing a nickel salt, a cobalt salt, and a manganese salt has a pH of 10 Nickel-cobalt-manganese composite hydroxide obtained by precipitation by maintaining the pH at 13 or less.   2. The nickel cobalt manganese composite hydroxide according to claim 1, wherein the tap density is 2.0 g / ml or more, the bulk density is 1.5 g / ml or more, and the average particle size is 5 μm or more and 30 μm or less.   The nickel-cobalt-manganese composite hydroxide according to claim 1 or 2, wherein the inert gas is nitrogen.   The nickel cobalt manganese composite hydroxide according to any one of claims 1 to 3, wherein the aqueous solution contains a complexing agent.   The nickel cobalt manganese composite hydroxide according to any one of claims 1 to 4, which is a precursor of a positive electrode active material for a nonaqueous electrolyte secondary battery. The content ratio of nickel (Ni), cobalt (Co), and manganese (Mn) is 3.5 to 5.5: 1.0 to 3.0: 2.5 to 4 in terms of atomic ratio of Ni: Co: Mn. 5 for producing a nickel cobalt manganese composite hydroxide,
Obtaining an aqueous solution containing a nickel salt, a cobalt salt and a manganese salt;
Maintaining the aqueous solution at pH 10 or more and pH 13 or less in an atmosphere of a mixed gas of an inert gas and an oxygen gas having a volume ratio of 0.5% to 3.0% with respect to the inert gas. Method for producing nickel cobalt manganese composite hydroxide.   The method for producing a nickel cobalt manganese composite hydroxide according to claim 8, wherein the inert gas is nitrogen.   The method for producing a nickel-cobalt-manganese composite hydroxide according to any one of claims 6 and 7, wherein the mixed gas is constantly supplied into a reaction vessel containing the aqueous solution.   The method for producing a nickel cobalt manganese composite hydroxide according to any one of claims 6 to 8, wherein the aqueous solution contains a complexing agent.   The positive electrode active material for nonaqueous electrolyte secondary batteries obtained by baking the mixture of the nickel cobalt manganese composite hydroxide and lithium compound as described in any one of Claims 1-5.   The nonaqueous electrolyte secondary battery which has a positive electrode which has the positive electrode active material for nonaqueous electrolyte secondary batteries of Claim 10 as a main component, a separator, and a negative electrode.

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