JP2018120831A - Lithium tungstate, method for manufacturing lithium tungstate, device for manufacturing lithium tungstate, positive electrode material for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a lithium tungstate suitable for a positive electrode material of a lithium ion secondary battery; a method for manufacturing the lithium tungstate; and a device for manufacturing the lithium tungstate.SOLUTION: A lithium tungstate is to be used for a positive electrode material for a nonaqueous electrolyte secondary battery. The lithium tungstate is represented by the composition formula, LiWO(HO)(where 0.4≤a≤6, 3≤b≤6 and 0≤n≤4), and has an average particle diameter of 5-100 μm, and a repose angle of 30-60°. The lithium tungstate is composed of a mixture of an anhydride and a hydrate or an anhydride; the ratio [Anhydride/(Anhydride+Hydrate)] of the anhydride to a total mass of the anhydride and the hydrate is 0.75-1.0.SELECTED DRAWING: Figure 1

Description

  The present invention relates to lithium tungstate, a method for producing lithium tungstate, an apparatus for producing lithium tungstate, a positive electrode material for a non-aqueous electrolyte secondary battery, and a non-aqueous electrolyte secondary battery.

  In recent years, with the widespread use of portable electronic devices such as mobile phones and notebook computers, development of small and lightweight lithium ion secondary batteries having high energy density is strongly desired. In addition, development of high-power secondary batteries suitable for electric vehicle applications including hybrid vehicles is also strongly desired. As a secondary battery satisfying such a demand, there is a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery.

As the positive electrode active material of the lithium ion secondary battery, a material capable of inserting and extracting lithium ions is used. Examples of positive electrode active materials that have been proposed so far include lithium cobalt composite oxide (LiCoO ₂ ) that is relatively easy to synthesize, lithium nickel composite oxide (LiNiO ₂ ) using nickel that is cheaper than cobalt, Lithium nickel cobalt manganese composite oxide (for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ etc.) and spinel lithium manganese composite oxide (LiMn ₂ O ₄ ) excellent in safety using inexpensive manganese Etc. Among these, lithium nickel composite oxide and lithium nickel cobalt manganese composite oxide are attracting attention as materials having excellent cycle characteristics and excellent battery characteristics with low resistance and high output. Further, in recent years, a technique for reducing the resistance of the secondary battery necessary for further increasing the output of the secondary battery is regarded as important.

  By the way, as a method for improving battery characteristics, addition of other types of elements other than the above-described elements to the positive electrode active material has been studied, and in particular, expensive numbers such as W, Mo, Nb, Ta, and Re can be taken. It is reported that transition metal elements that can be used are effective.

For example, Patent Document 1 describes a positive electrode active material for a non-aqueous electrolyte secondary battery having a layered or island-shaped lithium tungstate compound or a hydrate thereof on the surface of primary particles of a lithium metal composite oxide. Yes. Further, as the lithium tungstate compound, Li ₂ WO ₄ , Li ₄ WO ₅ , Li ₆ WO ₆ , Li ₂ W ₄ O ₁₃ , Li ₂ W ₂ O ₇ , Li ₆ W ₂ O ₉ , Li ₂ W ₂ O ₇ , Li ₂ W ₅ O ₁₆ , Li ₉ W ₁₉ O ₅₅ , Li ₃ W ₁₀ O ₃₀ , Li ₁₈ W ₅ O ₁₅ , or at least one lithium tungstate selected from these hydrates Is described. According to Patent Document 1, a positive electrode active material for a non-aqueous electrolyte secondary battery capable of realizing a high output with a high capacity is obtained.

  Patent Document 2 describes that lithium tungstate is mixed with lithium metal composite oxide powder such as lithium nickel composite oxide and lithium nickel cobalt manganese composite oxide to improve output characteristics while maintaining charge / discharge capacity. It is described that a positive electrode material for a lithium ion secondary battery can be obtained. Moreover, it is necessary to disperse lithium tungstate uniformly in the positive electrode material, and the average particle diameter of lithium tungstate is preferably 0.1 to 10 μm, more preferably 0.1 to 5 μm. Have been described. According to Patent Document 2, if the average particle size is less than 0.1 μm, fine lithium tungstate particles that do not have sufficient lithium ion conductivity are included, and the above output is present in a portion where such fine particles are present. As a result, when the average particle diameter exceeds 10 μm, the characteristic improvement effect may not be obtained, resulting in deterioration of cycle characteristics and an increase in reaction resistance as in the case of non-uniform dispersion. In addition, it is difficult to uniformly disperse lithium tungstate, and the effect of reducing the reaction resistance may not be sufficiently obtained.

Patent Document 3 discloses a method for producing lithium tungstate represented by _a general formula Li _a WO _b (0.3 ≦ a ≦ 6.0, 3.0 ≦ b ≦ 6.0), which includes oxidation. A tungsten source consisting of at least one of tungsten and tungstic acid and a lithium source consisting of at least one of lithium hydroxide and its hydrate are added in a mass ratio of 0.01 or more water to the tungsten source. And then performing a wet mixing to obtain a tungsten mixture, a drying step for heating and drying the obtained tungsten mixture to obtain a dried product, and a crushing step for crushing the dried product. A method for producing lithium tungstate is described. According to Patent Document 3, a positive electrode active material for a non-aqueous electrolyte secondary battery that can achieve high capacity and high output when used as a positive electrode material of a battery is easily obtained on an industrial scale.

JP2013-152866A JP 2013-171785 A JP, 2006-183090, A

  Patent Documents 1 to 3 describe that battery characteristics are improved by adding lithium tungstate as a positive electrode material.

  An object of the present invention is to optimize the properties of lithium tungstate added to the positive electrode material of a non-aqueous electrolyte secondary battery and to provide an efficient and low-cost manufacturing method.

  As a result of intensive research and trial and error in order to solve the above problems, the present inventors have found characteristics of lithium tungstate suitable for addition to the positive electrode material of a lithium ion secondary battery and a method for producing the same. It was. The present invention has been completed based on such technical findings and includes the following aspects of the invention.

According to the first aspect of the present invention, it is represented by the general formula: Li _a WO _b · (H ₂ O) _n (0.4 ≦ a ≦ 6, 3 ≦ b ≦ 6, 0 ≦ n ≦ 4), Lithium tungstate used for a positive electrode material for a non-aqueous electrolyte secondary battery having an average particle diameter of 5 μm or more and 100 μm or less and an angle of repose of 30 ° or more and 60 ° or less is provided.

Further, it is a mixture of anhydride and hydrate or an anhydride, and the ratio of the mass of the anhydride to the sum of the mass of the anhydride and the mass of the hydrate (anhydride / (anhydride + hydrate)) It is preferable that it is 0.75 or more and 1.0 or less. Moreover, when X-ray diffraction measurement is performed using a CuKα ray with a powder X-ray diffractometer, the maximum diffraction peak intensity of the anhydride is preferably three times or more of the maximum diffraction peak intensity of the hydrate. The anhydride is preferably represented by the chemical formula: Li ₂ WO ₄ .

  According to a second aspect of the present invention, there is provided a method for producing the above lithium tungstate, comprising mixing at least one tungsten compound, at least one lithium hydroxide and lithium hydroxide hydrate, and a solvent, There is provided a method for producing lithium tungstate, comprising: obtaining a solution containing a tungsten-lithium compound; and drying the obtained solution containing the tungsten-lithium compound.

  Moreover, it is preferable that the ratio of the mass of a solvent is 0.7 or more with respect to the sum total of the mass of a tungsten compound and the mass of at least 1 sort (s) of lithium oxide and lithium hydroxide hydrate. Moreover, when obtaining the solution containing a tungsten-lithium compound, it is preferable that the temperature of the solution containing the solvent and the tungsten-lithium compound is controlled to 25 ° C. or more and 60 ° C. or less from mixing to drying. Moreover, when drying the solution containing a tungsten-lithium compound, it is preferable to include a drying temperature of 80 ° C. or higher and a moisture content of 1.5% or less within a drying time of 10 minutes. In addition, when the solution containing the tungsten-lithium compound is dried, the solution containing the tungsten-lithium compound is preferably dried by contacting with a heated medium. Moreover, when drying the solution containing a tungsten-lithium compound, it is preferable to include drying the solution containing a tungsten-lithium compound by spray drying. The tungsten compound is preferably at least one of tungsten oxide, tungstic acid, and tungstate. The solvent is preferably water.

  According to a third aspect of the present invention, there is provided an apparatus used for drying the solution containing the tungsten-lithium compound, the spray unit spraying the solution containing the tungsten-lithium compound, and the tungsten sprayed by the spray unit. An apparatus for producing lithium tungstate, comprising: a heating unit that dries a solution of a lithium compound.

  The heating unit includes a medium that contacts and dries a solution containing the tungsten-lithium compound sprayed by the spraying unit, and the medium is 80 degrees in a state where the solution containing the tungsten-lithium compound sprayed by the spraying unit comes into contact. It is preferable to keep the above-mentioned solution containing tungsten-lithium compound to 1.5% or less within 10 minutes after contact with the medium.

  According to the 4th aspect of this invention, the positive electrode material for non-aqueous electrolyte secondary batteries containing the said lithium tungstate is provided.

  According to the 5th aspect of this invention, the non-aqueous electrolyte secondary battery containing the said positive electrode active material for non-aqueous electrolyte secondary batteries is provided.

  When used as a positive electrode material of a non-aqueous electrolyte secondary battery, the lithium tungstate according to the present invention improves the battery capacity and output characteristics of the secondary battery. The method for producing lithium tungstate according to the present invention can produce the lithium tungstate easily and efficiently. Moreover, the lithium tungstate manufacturing apparatus according to the present invention can be suitably used in the above lithium tungstate manufacturing method.

2 is a diagram showing an X-ray diffraction pattern of lithium tungstate of Example 1. FIG. It is a flowchart of the manufacturing method of the lithium tungstate which concerns on embodiment. It is a conceptual diagram which shows the manufacturing apparatus of the lithium tungstate which concerns on embodiment. It is a schematic sectional drawing of the coin-type battery used for battery evaluation. It is a schematic explanatory drawing of the measurement example of impedance evaluation, and the equivalent circuit used for analysis. It is a figure which shows the X-ray-diffraction pattern of the lithium tungstate of the comparative example 4.

[Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Further, in the drawings, in order to make each configuration easy to understand, a part of the structure is emphasized or a part of the structure is simplified, and an actual structure, shape, scale, or the like may be different. First, the lithium tungstate according to the embodiment will be described, and then the method for producing the lithium tungstate according to the embodiment will be described.

[Lithium tungstate]
The lithium tungstate according to the embodiment is represented by a general formula: Li _a WO _b · (H ₂ O) _n (0.4 ≦ a ≦ 6, 3 ≦ b ≦ 6, 0 ≦ n ≦ 4), and average grains The diameter is 5 μm or more and 100 μm or less, and the angle of repose is 30 ° or more and 60 ° or less. This lithium tungstate has excellent powder characteristics when used in a positive electrode material for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, and is easily and uniformly dispersed in the positive electrode material. Capacitance and output characteristics can be improved.

The composition of lithium tungstate is not particularly limited as long as it is a composition satisfying the general formula (1). In the general formula (1), Li _a WO _b is, for example, Li ₂ WO ₄ , Li ₄ WO ₅ , Li ₃ WO _4.5 (Li ₆ W ₂ O ₉ ), Li ₆ WO ₆ , Li _0.5. WO _3.25 (Li ₂ W ₄ O ₁₃ ), LiWO _3.5 (Li ₂ W ₂ O ₇ ), Li ₃ WO _4.5 (Li ₆ W ₂ O ₉ ), LiWO _3.5 (Li ₂ W _{2) O 7), Li 0.4 WO 4} (Li 2 W 5 O 16), Li 4.73 WO 6.11 (Li 9 W 19 O 55), Li 0.3 WO 3 (Li 3 W 10 O 30) , Li _3.6 WO ₃ (Li ₁₈ W ₅ O ₁₅ ) and the like. In the general formula (1), _n of (H ₂ O) _n is represented by 0 ≦ n ≦ 4, and is an anhydride, a hydrate, or a mixture of an anhydride and a hydrate.

  The lithium tungstate preferably has a higher content of anhydride than hydrate. Lithium tungstate is more easily dissolved in water than hydrate, so when dispersed on the surface of the positive electrode active material, it is uniformly dispersed throughout the positive electrode active material by mixing with the positive electrode active material in a wet manner. In addition, when the content of lithium tungstate hydrate is large, when manufacturing the positive electrode, the crystal water in the lithium tungstate hydrate is detached and the positive electrode material is deteriorated, or the positive electrode mixture The gelation of the paste may be promoted.

Lithium tungstate, in view of solubility in water, even in the _anhydride, is preferably a _{Li 2 WO 4, Li 4 WO} 5, and more preferably _Li 2 WO _4. Further, Li ₂ WO ₄ is preferable because the production is simple. The lithium tungstate preferably contains Li ₂ WO ₄ and more preferably consists of Li ₂ WO ₄ .

  The lithium tungstate preferably contains an anhydride as described above, and the mass ratio of the anhydride to the total amount of the anhydride and the hydrate (anhydride / (anhydride + hydrate)) is 0.75 or more. 1.0 or less is more preferable, 0.85 or more and 1.0 or less is more preferable, 0.90 or more and 1.0 or less is more preferable, and 0.95 or more and 1.0 or less. It is particularly preferred that it is 1.0, and more preferably 1.0. When the ratio of the anhydride to the hydrate is within the above range, the above-described influence by water can be suppressed, and the reaction can be uniformly dispersed in the positive electrode active material, thereby reducing the reaction resistance of the positive electrode active material. In addition, the mass ratio of this embodiment is a mass change when it heats up to 1100 degreeC with the temperature increase rate of 20 degree-C / min in the air with a thermal mass spectrometer (example, Bruker company make, TG-DTA2020SR). It is the value calculated from

  For lithium tungstate, for example, when X-ray diffraction measurement is performed using CuKα rays with a powder X-ray diffractometer, the maximum diffraction peak intensity of anhydride is three times or more than the maximum diffraction peak intensity of hydrate. Is preferred. When the X-ray diffraction peak is in the above range, lithium tungstate has sufficient lithium tungstate anhydride and can be uniformly dispersed in the positive electrode active material.

  The lithium tungstate preferably has a low moisture content. For example, the lithium tungstate preferably has a moisture content of 2.5% or less, more preferably 2.0% or less, more preferably 1.7% or less, and 1.5%. More preferably, it is as follows. The moisture content is a value calculated from the difference in mass of lithium tungstate before and after being dried at 105 ° C. for 2 hours in an air dryer.

The crystal structure of lithium tungstate is not particularly limited. For example, when the anhydride of lithium tungstate is Li ₂ WO ₄ , the crystal structure is a rhombohedral crystal structure (eg, Example 1, FIG. 1). X-ray diffraction peak).

  The lithium tungstate has an average particle size of 5 μm to 100 μm, more preferably 10 μm to 60 μm, and still more preferably 20 μm to 50 μm. When the average particle diameter of lithium tungstate is in the above range, the reaction resistance of the positive electrode active material can be further reduced. The average particle size of lithium tungstate can be controlled by a known method (eg, spray drying conditions, dispersion concentration, pulverization, classification) or the like. In addition, the lithium tungstate of this embodiment can fully exhibit the said effect, even when an average particle diameter exceeds 30 micrometers. In addition, the average particle diameter of lithium tungstate is a value obtained by measuring the volume reference average particle diameter D50 in the laser diffraction scattering method.

  Lithium tungstate has an angle of repose of 30 degrees to 60 degrees, preferably 37 degrees to 58 degrees. When the angle of repose is in the above range, lithium tungstate has good powder characteristics and is easy to handle. For example, as shown in the examples, lithium tungstate has good fluidity and suppresses shelf hanging and adhesion to a wall surface in the hopper. The angle of repose is a value measured by an injection method using a multi-tester MT-1000 manufactured by Seishin Enterprise Co., Ltd.

[Method for producing lithium tungstate]
Next, a method for producing lithium tungstate according to the embodiment (hereinafter also simply referred to as “manufacturing method”) will be described. FIG. 2 is a flowchart illustrating an example of a method for producing lithium tungstate according to the embodiment. By this manufacturing method, the above-described lithium tungstate of the present embodiment can be manufactured easily and efficiently.

  In the production method according to the present embodiment, at least one tungsten compound, at least one of lithium hydroxide and lithium hydroxide hydrate, and a solvent are mixed to obtain a solution containing a tungsten-lithium compound ( Step S1) and drying the solution containing the obtained tungsten-lithium compound (Step S2). Hereinafter, each step will be described.

(Synthesis of tungsten-lithium compounds)
First, at least one tungsten compound (hereinafter also referred to as “tungsten source”), at least one of lithium hydroxide and lithium hydroxide hydrate (hereinafter also referred to as “lithium source”), and a solvent are mixed. Then, a solution containing the tungsten-lithium compound is obtained (step S1). For example, in step S1, a tungsten source and a lithium source are added to a solvent and mixed to perform a tungsten-lithium compound synthesis reaction.

Tungsten compound (tungsten source) is not particularly limited, but when lithium tungstate is formed, no harmful impurities remain, high purity is obtained, high reactivity with lithium hydroxide, and easily What can obtain lithium tungstate is preferable. As the tungsten compound, for example, at least one of tungsten oxide (WO ₃ ), tungstic acid (H ₂ WO ₄ ), and tungstate can be used, and among these, at least one of tungsten oxide and tungstic acid is preferable. .

  At least one of lithium hydroxide and lithium hydroxide hydrate, which are lithium sources, does not leave harmful impurities when lithium tungstate is formed, and high purity is obtained. Water can be used as the solvent.

  The tungsten source and the lithium source are mixed so that the molar amount of lithium is 0.4 to 6 times the molar amount of tungsten (Li / W molar ratio). The Li / W molar ratio is adjusted according to the composition of the target lithium tungstate, as shown in the general formula (1). When the molar amount of lithium is 0.4 times or less with respect to the molar amount of tungsten, a tungsten source that does not react with lithium remains, and as a result, the effect of improving battery characteristics may not be efficiently exhibited. On the other hand, when the molar amount of lithium is 6 times or more than the molar amount of tungsten, an unreacted lithium source remains, and as a result, the positive electrode active material (positive electrode material) is excessively alkalized and gelled during battery production. May occur, or the thermal stability of the battery may be reduced.

  When performing the synthesis reaction of the tungsten-lithium compound, it is preferable to maintain (control) the temperature of the solution containing the tungsten-lithium compound at 60 ° C. or less. As a method for maintaining the solution containing the tungsten-lithium compound in the above range, for example, a method of mixing the reaction vessel containing the tungsten-lithium compound with a cooling jacket and mixing while cooling is preferable. In addition, when the temperature of the tungsten-lithium compound aqueous solution is less than 25 ° C., lithium tungstate precipitates, and it may be difficult to control the properties of the lithium tungstate in a subsequent drying step. It is preferable to heat (control) the above.

  The reaction between the tungsten source (tungsten compound) and the lithium source (such as lithium hydroxide) is an exothermic reaction. For example, when reacting tungsten oxide and lithium hydroxide, the mass of water to be added is 1 in a ratio to the total mass of tungsten oxide and lithium hydroxide, and the liquid temperature of the water before addition was 25 ° C. In this case, the liquid temperature temporarily rises above 60 ° C. Here, when lithium tungstate is maintained at a temperature exceeding 60 ° C., crystals of lithium tungstate hydrate are generated, and it becomes difficult to obtain an anhydrous lithium tungstate predominantly. And since lithium tungstate hydrate contains crystal water, depending on the manufacturing method, when mixed with the positive electrode material of the lithium ion secondary battery, the crystal water is detached and the positive electrode material of the lithium ion secondary battery Or when a positive electrode material for a lithium ion secondary battery is mixed with a conductive additive, a binder, and a solvent to produce a positive electrode material paste, resulting in remarkable productivity in the subsequent coating process. There are adverse effects such as worsening. Therefore, by controlling the temperature of the solution containing the tungsten-lithium compound as described above, the anhydrous lithium tungstate can be more preferentially produced.

  The amount of water (solvent) used when mixing the tungsten source and the lithium source is preferably 0.7 times or more of the total mass of the tungsten source and the lithium source. When water (solvent) is mixed at 0.7 times or more with respect to the total mass of the tungsten source and the lithium source, the liquid temperature of the solution containing the tungsten-lithium compound generated by the above exothermic reaction is stabilized at 60 ° C. or less. Thus, it is easy to hold, and generation of lithium tungstate hydrate can be suppressed. On the other hand, the greater the amount of water (solvent) added, the greater the amount of heat required for drying, so the amount of water (solvent) added is 1.2 times the total mass of the tungsten source and lithium source. It is preferable to suppress to the extent. Therefore, the amount of water (solvent) added when mixing the tungsten source and the lithium source is preferably about 0.7 to 1.2 times the total mass of the tungsten source and the lithium source.

  The apparatus used for mixing the tungsten source and the lithium source is not particularly limited as long as the tungsten source and the lithium source can be mixed and reacted uniformly. For example, as such an apparatus, various mixers such as a shaker mixer, a stirring mixer, and a rocking mixer can be selected and used according to the amount of water to be added. The mixing time of the tungsten source and the lithium source may be any time as long as the tungsten source and the lithium source react with each other. Usually, the mixing time may be 1 minute or longer. You may do it. The mixing time can be, for example, 1 minute or more and 60 minutes or less.

  The tungsten-lithium compound obtained in step S1 includes lithium tungstate produced by a reaction between a tungsten source and a lithium source. The tungsten-lithium compound is dried to obtain the lithium tungstate according to this embodiment.

(Dry)
Subsequently, in step S2 of FIG. 2, the solution containing the tungsten-lithium compound obtained in step S1 is dried. Thereby, the lithium tungstate of this embodiment is obtained. Hereinafter, an example in which the solution containing the tungsten-lithium compound synthesized in Step S1 is crystallized by drying in Step S2 to obtain lithium tungstate will be described.

  In the drying in step S2, for example, a spray dryer, an air flow dryer, a heating plate contact dryer, or the like can be used. The drying temperature is preferably 80 ° C. or higher, preferably 100 ° C. or higher, more preferably 120 ° C. or higher. As described above, when the aqueous solution of the tungsten-lithium compound is kept at 60 ° C. or higher, more lithium tungstate hydrate may be precipitated. Should be short. Moreover, it is preferable that drying time is 10 minutes or less, for example. For example, the drying is preferably performed in such a range that the drying temperature is in the above range, and the solution containing the tungsten-lithium compound has a moisture content of 1.5% or less within 10 minutes. When drying is performed under such conditions, lithium tungstate having a high content of anhydride can be produced by suppressing the formation of hydrates in a simple and short drying process.

  The drying is performed, for example, by bringing a solution containing a tungsten-lithium compound into contact with a heated medium and drying. In this case, since the solution containing the tungsten-lithium compound comes into contact with the heated medium, it can be efficiently dried. For example, this drying can be performed by spray drying. In spray drying, a solution containing a tungsten-lithium compound is divided into a predetermined size solution (liquid particles) and brought into contact with a heated medium. In the case of spray drying, since the solution to be dried is atomized to a predetermined size and dried, the lithium tungstate particles of the present embodiment described above can be easily produced in a short drying time as described above. For example, by performing spray drying as described below, the lithium tungstate particles of the present embodiment can be manufactured by a simple one-step spray drying in a short time.

  For example, in spray drying, when using a type of dryer that mixes with a gas, such as a spray dryer or a flash dryer, a solution containing a tungsten-lithium compound is placed in a dry can body with a general one-fluid nozzle, two-fluid nozzle, By spraying using a nozzle such as a centrifugal spray nozzle, it is mixed with a gas (medium) heated to 120 ° C. to 250 ° C., and the solution containing the tungsten-lithium compound is atomized and dried. In the case of these spray drying, drying can be performed so that the solution containing the tungsten-lithium compound has a moisture content of 1.5% or less within 10 minutes. The gas used at this time is not particularly limited, but for example, it is desirable to use an inert gas or air dehumidified to 8 g / kg or less. This is because if the amount of water in the gas used is large, the production rate of lithium tungstate hydrate increases. The target physical property lithium tungstate can be obtained by adjusting spraying conditions (including conditions of a liquid containing a tungsten-lithium compound). The spray drying conditions are arbitrarily set according to the type of apparatus, the drying conditions, and the like, but are known to those skilled in the art and can be set by preliminary experiments. For example, the average particle diameter of tungsten-lithium can be controlled by changing conditions for atomizing a solution or slurry containing a tungsten-lithium compound by spraying.

  As described above, the lithium tungstate according to the embodiment is manufactured in step S2. The manufactured lithium tungstate is stored so as not to absorb moisture in the atmosphere and increase the moisture content.

  The drying in step S2 is not limited to spray drying, and may be performed by a method other than spray drying. For example, drying may be performed by bringing a solution containing a tungsten-lithium compound into contact with a heating plate (heated medium). In this case, the solution containing the tungsten-lithium compound may be dried by inserting and pulling up a heating plate (heated medium), or the solution containing the tungsten-lithium compound may be put on the heating plate (heated medium). You may spray. When spraying the solution containing the tungsten-lithium compound onto the heating plate (heated medium), as shown in Example 3, the solution containing the tungsten-lithium compound is sprayed while rotating the heating plate (heated medium). May be. Further, the drying in step S2 may be performed in two stages. For example, after performing the above-described spray drying, the drying may be further performed under different conditions.

[Production equipment for lithium tungstate]
For example, the above drying can be easily performed using the lithium tungstate manufacturing apparatus according to the embodiment. FIG. 3 is a conceptual diagram showing a lithium tungstate manufacturing apparatus according to the embodiment.

  The lithium tungstate production apparatus AP (hereinafter also referred to as “production apparatus AP”) includes a spray unit 10 that sprays a solution L (hereinafter also referred to as “solution L”) containing a tungsten-lithium compound, and a spray. The heating part 11 which dries the solution L sprayed by the part 10 and the collection | recovery part 12 are provided.

  The heating unit 11 includes a medium M on which the solution L sprayed by the spraying unit 10 comes into contact and is dried. The heating unit 11 accommodates the medium M inside. The medium M is, for example, a gas such as air or an inert gas. The spray unit 10 is, for example, a nozzle or a disk (a centrifugal disk or a rotary atomizer). The spray unit 10 is, for example, a one-fluid nozzle, a two-fluid nozzle, or a centrifugal spray nozzle. The spray unit 10 divides the solution L into a predetermined size (atomization) and sprays the solution L on the medium M in the heating unit 11. The solution L is supplied to the spray unit 10 by a pump (not shown) or the like.

  The heating unit 11 includes a heating device 13 that heats the medium M. The heating unit 11 heats the medium M by the heating device 13 and supplies the medium M to the inside of the heating unit 11. The medium M in the heating unit 11 is maintained at a temperature in the range of 120 ° C. or more and 250 ° C. or less, for example. When the temperature of the medium M is in the above range, the water content of the solution L can be easily dried to be 1.5% or less. For example, the heating unit 11 is brought into contact with the solution L sprayed by the spraying unit 10 by supplying the heated medium M into the heating unit 11 by a compressor (not shown) or the like. The heating unit 11 maintains the medium M at 80 ° C. or higher in a state where the solution M sprayed by the spray unit 10 is in contact with the medium M, and the water content is within 10 minutes after the solution L is contacted with the medium M. Dry to 1.5% or less. That is, the heating unit 11 dries the solution L sprayed by the spraying unit 10 to a moisture content of 1.5% or less within 80 minutes and within 10 minutes. Thereby, the solution L dries and lithium tungstate is manufactured.

  The manufactured lithium tungstate is recovered in the recovery unit 12 together with the exhaust of the heated medium M, for example. The gas is not particularly limited, but when the amount of water in the medium M to be used is large, the production rate of lithium tungstate hydrate is increased. Therefore, inert gas or air dehumidified to 8 g / kg or less is used. Is desirable.

  As described above, the lithium tungstate production apparatus AP according to the present embodiment brings the solution L containing the tungsten-lithium compound sprayed by being atomized into a predetermined size by the spray unit 10 into contact with the heated medium M. , In a state where it is dried to 80% or more and 1.5% or less within 10 minutes, that is, the production of hydrate is suppressed, and lithium tungstate with a high content of anhydride is produced easily and in a short time. Can do. Since the lithium tungstate manufacturing apparatus of the present embodiment has the above characteristics, it can be suitably used for the manufacturing method of the present embodiment described above.

  Note that the heating unit 11 described above may not supply the heated gas to the nozzle of the spray unit 10. For example, the heating unit 11 may supply heated gas to the inside of the heating unit 11. In the above example, the example in which the medium M heated by the heating unit 11 is a gas has been described. However, the medium M may not be a gas. For example, the medium M may be a member formed of metal or the like (for example, the disk of Example 3).

[Positive electrode material]
Hereinafter, the positive electrode material for a non-aqueous electrolyte secondary battery according to the present embodiment (hereinafter simply referred to as “positive electrode material”) will be described. The positive electrode material according to the present embodiment includes the lithium tungstate according to the above-described embodiment.

  For example, since lithium tungstate has high conductivity of thium ions and has an effect of promoting the movement of lithium ions, it is attached to the surface of a conventionally known positive electrode active material as described in Patent Document 2, Patent Document 3, and the like. Thus, in the positive electrode, a Li conduction path is formed at the interface with the electrolytic solution, and the reaction resistance of the positive electrode active material is reduced while maintaining the charge / discharge capacity. As a result, the output characteristics of the non-aqueous electrolyte secondary battery Can be improved.

  It does not specifically limit as a positive electrode active material, For example, lithium nickel complex oxide, lithium cobalt complex oxide, lithium manganese complex oxide, lithium nickel cobalt manganese complex oxide, etc. can be used. Moreover, the positive electrode active material for lithium secondary batteries generally used other than these can be used.

Hereinafter, an example of a method for producing a positive electrode active material having lithium tungstate on the particle surface will be described in the case of using lithium nickel composite oxide powder as the positive electrode active material.
(Mixing process)
First, the lithium tungstate according to the present embodiment is mixed with lithium nickel composite oxide powder and water used as a base material, and lithium tungstate is dispersed in the lithium nickel composite oxide powder (hereinafter referred to as “tungsten lithium mixture”). , Also referred to as “LWO mixture”).

  Lithium tungstate is mixed with lithium nickel composite oxide powder in the presence of water, that is, by obtaining an LWO mixture containing water, lithium tungstate is dissolved in water by heating during heat treatment in the subsequent step. Thus, tungsten can be uniformly dispersed on the surface of the primary particles of the lithium nickel composite oxide powder.

  In the above mixing step, it is sufficient that lithium tungstate is mixed in the presence of water, and mixing of lithium tungstate to the lithium nickel composite oxide powder is performed in a slurry state or after being made into a slurry and solidified. Mixing in a powder state in which the lithium nickel composite oxide powder contains water, such as mixing in a liquid-separated state or mixing with a small amount of water, is possible. Further, after washing the lithium nickel composite oxide powder with water, it may be solid-liquid separated and mixed with lithium tungstate in a state containing a small amount of moisture. Since the lithium tungstate obtained by the manufacturing method of the present embodiment described above has good powder characteristics and high dispersibility, it can be sufficiently mixed with the positive electrode active material even with a small amount of water.

Lithium tangtenate used in the mixing step is preferably an anhydride such as Li ₂ WO ₄ , Li ₆ W ₂ O ₉ , Li ₄ WO ₅ when mixed in a powder state containing moisture. It is more preferable that an anhydride such as Li ₂ WO ₄ or Li ₄ WO ₅ having solubility in water even at about 0 ° C. is included. Since the lithium tungstate obtained by the manufacturing method of this embodiment described above is easily dissolved in water and has high dispersibility, it can be efficiently and more uniformly dispersed. Further, by using the method for producing lithium tungstate according to the present embodiment, lithium tungstate containing an appropriate amount of anhydride can be easily obtained.

  The amount of tungsten contained in lithium tangtenate in the LWO mixture is 0.01 to 3.0 atoms with respect to the total number (Me) of nickel, cobalt and M atoms contained in the mixed lithium nickel composite oxide powder. It is preferable to adjust so that it may become%.

  In such mixing, a general mixer can be used. For example, it is sufficient that the shape of the lithium nickel composite oxide is not destroyed by using a shaker mixer, a Laedige mixer, a Julia mixer, a V blender, or the like. You can mix it.

(Drying process)
Next, the LWO mixture obtained by the above mixing step is dried to obtain a positive electrode material in which lithium tungstate adheres to the primary particle surface of the lithium nickel composite oxide powder. By drying, a positive electrode active material for a non-aqueous electrolyte secondary battery having a compound containing W and Li on the primary particle surface of the lithium nickel composite oxide is obtained.

  The drying temperature can be, for example, 50 ° C. or higher and 250 ° C. or lower, preferably 80 ° C. or higher and 200 ° C. or lower, more preferably 100 ° C. or higher and 180 ° C. or lower. The drying time can be performed, for example, within 30 minutes, preferably within 10 minutes, and more preferably within 1 minute.

[Nonaqueous electrolyte secondary battery]
The non-aqueous electrolyte secondary battery (hereinafter also referred to as “secondary battery”) of the present embodiment uses the positive electrode active material according to the above-described present embodiment for the positive electrode. Hereinafter, an example of the secondary battery of the present embodiment will be described for each component. The secondary battery of the present embodiment includes a positive electrode, a negative electrode, and a non-aqueous electrolyte, and includes the same components as a general lithium ion secondary battery. The embodiment described below is merely an example, and the nonaqueous electrolyte secondary battery may be implemented in various modifications and improvements based on the knowledge of those skilled in the art, including the following embodiment. it can. Further, the use of the secondary battery is not particularly limited.

(Positive electrode)
A positive electrode of a secondary battery is produced using the positive electrode active material according to the present embodiment. Below, an example of the manufacturing method of a positive electrode is demonstrated. First, the positive electrode active material (powder), the conductive material, and the binder (binder) are mixed, and if necessary, activated carbon or a solvent for viscosity adjustment is added, and this is kneaded to obtain a positive electrode. A composite paste is prepared.

  Since the mixing ratio of each material in the positive electrode mixture is an element that determines the performance of the lithium secondary battery, it can be adjusted according to the application. The mixing ratio of the materials can be the same as that of the positive electrode of a known lithium secondary battery. For example, when the total mass of the solid content of the positive electrode mixture excluding the solvent is 100% by mass, the positive electrode active material is 60%. -95 mass%, 1-20 mass% of electrically conductive materials, and 1-20 mass% of binders can be contained.

  The obtained positive electrode mixture paste is applied to, for example, the surface of a current collector made of aluminum foil, and dried to disperse the solvent, thereby producing a sheet-like positive electrode. If necessary, pressurization may be performed by a roll press or the like to increase the electrode density. The sheet-like positive electrode thus obtained can be cut into an appropriate size according to the target battery and used for battery production. However, the manufacturing method of the positive electrode is not limited to the above-described examples, and may depend on other methods.

  Examples of the conductive material that can be used include graphite (natural graphite, artificial graphite, expanded graphite, and the like), carbon black materials such as acetylene black and ketjen black, and the like.

  As the binder (binder), it plays the role of holding the active material particles. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluoro rubber, ethylene propylene diene rubber, styrene butadiene, cellulose series Resins and polyacrylic acid can be used.

  If necessary, a positive electrode active material, a conductive material, and activated carbon are dispersed, and a solvent that dissolves the binder is added to the positive electrode mixture. Specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used as the solvent. Activated carbon can be added to the positive electrode mixture in order to increase the electric double layer capacity.

(Negative electrode)
For the negative electrode, metallic lithium, a lithium alloy, or the like can be used. The negative electrode is prepared by mixing a negative electrode active material capable of occluding and desorbing lithium ions with a binder and adding a suitable solvent to form a paste on the surface of a metal foil current collector such as copper. You may use what was formed by compressing in order to apply | coat, dry and to raise an electrode density as needed.

  As the negative electrode active material, for example, organic compound fired bodies such as natural graphite, artificial graphite and phenol resin, and powdery bodies of carbon materials such as coke can be used. In this case, a fluorine-containing resin such as PVDF can be used as the negative electrode binder, as in the case of the positive electrode, and an organic material such as N-methyl-2-pyrrolidone can be used as a solvent for dispersing these active materials and the binder. A solvent can be used.

(Separator)
A separator is interposed between the positive electrode and the negative electrode. The separator separates the positive electrode and the negative electrode and holds the electrolyte, and a known one can be used. For example, a thin film such as polyethylene or polypropylene and a film having a large number of minute holes can be used. it can.

(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, propylene carbonate, butylene carbonate and trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate and dipropyl carbonate, tetrahydrofuran, 2- Use one kind selected from ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethyl methyl sulfone and butane sultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, or a mixture of two or more. Can do.

As the supporting salt, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , and complex salts thereof can be used. Furthermore, the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like.

(Secondary battery shape and configuration)
The non-aqueous electrolyte secondary battery of the present invention composed of the positive electrode, the negative electrode, the separator and the non-aqueous electrolyte described above can have various shapes such as a cylindrical shape and a laminated shape. In any case, the positive electrode and the negative electrode are laminated via a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte and communicated with the positive electrode current collector and the outside. Connect between the positive electrode terminal and between the negative electrode current collector and the negative electrode terminal leading to the outside using a current collecting lead, etc., and seal the battery case to complete the nonaqueous electrolyte secondary battery. .

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to the content of an Example.

(Evaluation method of lithium tungstate)
The average particle diameter of lithium tungstate was measured by using a particle size distribution measuring device MT3300EXII manufactured by Microtrac Bell Co., Ltd., and a volume-based average particle diameter D50 in the laser diffraction scattering method was measured. The angle of repose was measured by an injection method using a multi-tester MT-1000 manufactured by Seishin Enterprise Co., Ltd. The moisture content was calculated from the difference in mass before and after being dried at 105 ° C. for 2 hours in an air dryer. Moreover, the powder X-ray-diffraction measurement was performed using CuK (alpha) ray with the X-ray diffraction apparatus X'Pert PRO made from PANalytical, and the crystal structure analysis of the lithium tungstate was performed. Also, mass ratio of lithium tungstate hydrate and anhydride from mass change when heated to 1100 ° C. at a heating rate of 20 ° C./min in air using a Bruker thermal mass spectrometer TG-DTA2020SR Was determined as anhydride / (anhydride + hydrate).

(Battery characteristics evaluation method)
The battery characteristics of the positive electrode material were evaluated by preparing a 2032 type coin battery 1 (hereinafter referred to as a coin battery) shown in FIG. As shown in FIG. 4, the coin battery 1 includes 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, and the case where the positive electrode 3a is in contact with the inner surface of the positive electrode can 2a and the negative electrode 3b is in contact with the inner surface of the negative electrode can 2b. 2 is housed.

  The case 2 includes a gasket 2c, and the positive electrode can 2a and the negative electrode can 2b are fixed by the gasket 2c so as to maintain a non-contact state. 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.

  Specifically, the coin battery 1 was produced as follows. First, 52.5 mg of a positive electrode material, 15 mg of acetylene black, and 7.5 mg of polytetrafluoroethylene resin (PTFE) were mixed, and press-molded to a diameter of 11 mm and a thickness of 100 μm at a pressure of 100 MPa to obtain a positive electrode 3a. The positive electrode 3a was dried in a vacuum dryer at 120 ° C. for 12 hours.

  As the negative electrode 3b, a negative electrode sheet obtained by applying a mixture of 9 g of graphite powder having an average particle diameter of 20 μm and 1 g of polyvinylidene fluoride to a copper foil, drying it, and then punching it into a disk shape having a diameter of 14 mm was used.

As the separator 3c, a polyethylene porous film having a film thickness of 25 μm was used. As the electrolytic solution, an equivalent mixed solution (manufactured by Toyama Pharmaceutical Co., Ltd.) containing ethylene carbonate (EC) and diethyl carbonate (DEC) containing LiClO ₄ having a concentration of 1 M as a supporting electrolyte was used.

  Using the positive electrode 3a, the negative electrode 3b, the separator 3c, and the electrolytic solution, the coin-type battery 1 was produced in a glove box in an Ar atmosphere in which the dew point was controlled to −80 ° C. or less.

  The initial discharge capacity and the positive electrode reaction resistance showing the performance of the manufactured coin-type battery 1 were evaluated by the following methods.

The initial discharge capacity was cut for about 24 hours after the coin-type battery was made, after the conditioning process was performed and the open circuit voltage OCV (Open Circuit Voltage) was stabilized, the current density with respect to the positive electrode was set to 0.1 mA / cm ^2. The battery was charged to an off voltage of 4.3 V, and after a pause of 1 hour, the discharge capacity when discharged to a cutoff voltage of 3.0 V was measured and used as the initial discharge capacity.

  The positive electrode reaction resistance is measured by the AC impedance method using a frequency response analyzer and a potentiogalvanostat (Solartron 1255B) after charging the coin-type battery 1 at a charging potential of 4.1 V, as shown in FIG. A plot was obtained. Fitting calculation using an equivalent circuit was performed from this Nyquist plot, and the value of the positive electrode reaction resistance was calculated.

[Example 1]
The positive electrode active material mixed with lithium tungstate is a lithium metal composite oxide powder (composition formula: Li _1.06) obtained by a known technique of mixing and firing a nickel-cobalt-aluminum composite oxide and lithium hydroxide. Ni _0.76 Co _0.14 Al _0.10 O ₂ ) was used. The lithium metal composite oxide powder had an average particle size of 11.0 μm and a specific surface area of 0.9 m ² / g. The composition was analyzed by the ICP method, the average particle size was evaluated using the volume-based average particle size D50 in the laser diffraction scattering method, and the specific surface area was evaluated using the nitrogen gas adsorption BET method.

  Lithium tungstate was synthesized as follows. 6 kg of ion-exchanged water is put into a stainless steel container with a cooling jacket, and 2.17 kg of lithium hydroxide monohydrate (FMC, purity 99.5%) and tungsten oxide (Japan Inorganic Chemical Co., Ltd., purity 99.5) %) 6.0 kg (number of moles of lithium: number of moles of tungsten = 2: 1), and the liquid temperature was monitored and the liquid temperature was kept at 25 ° C. to 60 ° C. and stirred at 100 rpm for 60 minutes. To obtain an aqueous solution of a tungsten-lithium compound.

This aqueous solution of tungsten-lithium compound was dried using a centrifugal spray type spray dryer. This spray dryer uses a pin disk type centrifugal spray nozzle with a diameter of 65 mm as the spray nozzle corresponding to the lithium tungstate production apparatus AP of the present embodiment shown in FIG. 2, and the above tungsten-lithium compound aqueous solution at a rotational speed of 16000 rpm. Was sprayed at a flow rate of 20 kg / hr. Air with an absolute humidity of 5 g / kg, air flow of 300 Nm ³ / hr, warm air so that the temperature at the dryer inlet (near the spray unit 10) is 200 ° C., and the temperature at the dryer outlet (near the recovery unit 12) is 120 ° C. The temperature was adjusted and dried to obtain a lithium tungstate powder. The drying time was within 10 minutes.

The obtained lithium tungstate was dried in air at 105 ° C. for 2 hours, and the moisture content was measured from the mass before and after that to be 0.6%. Moreover, the diffraction pattern obtained by the powder X-ray diffractometer is shown in FIG. This diffraction pattern almost coincided with the reported pattern of rhombohedral crystal Li ₂ WO ₄ , and other diffraction peaks of lithium tungstate were not confirmed. Since no hydrate peak was observed, the ratio of the maximum diffraction peak intensity of lithium tungstate anhydride to the maximum diffraction peak intensity of lithium tungstate hydrate could not be calculated. Moreover, the abundance ratio of the lithium tungstate anhydride and hydrate determined by a thermal mass spectrometer was anhydride / (anhydride + hydrate) = 1.0, that is, almost the entire amount was anhydrous.

  After 15 g of lithium metal composite oxide powder was washed with water and subjected to suction filtration and solid-liquid separation, moisture remained, 0.19 g of the prepared lithium tungstate powder was added, and after sufficient mixing, vacuum dried, A mixture of lithium metal composite oxide powder and lithium tungstate was obtained and used as a positive electrode active material. At this time, lithium tungstate was easily dissolved by moisture remaining in the lithium metal composite oxide powder. When the tungsten content in this positive electrode active material was analyzed by the ICP method, it was confirmed that it was 0.50 atomic% with respect to the total number of atoms of nickel, cobalt and aluminum.

  Battery characteristics evaluation of the obtained positive electrode active material was performed by the above-described evaluation method. Table 1 shows physical property values and battery characteristic evaluation results of lithium tungstate of Examples and Comparative Examples. In addition, the positive electrode reaction resistance of each Example and a comparative example is represented by the relative value when the positive electrode reaction resistance calculated | required in Example 1 is set to 100.

[Example 2]
An aqueous solution of a tungsten-lithium compound was obtained in the same manner as in Example 1. The aqueous solution was dried using a centrifugal spray type spray dryer. The nozzle used was a pin disk type centrifugal spray nozzle with a diameter of 65 mm, and the lithium tungstate aqueous solution was sprayed at a flow rate of 20 kg / hr with a rotation number of 16000 rpm. The diameter of the liquid feeding pipe was adjusted so that the time from the inlet of the liquid feeding pipe to the nozzle was about 3 seconds. Air with an absolute humidity of 5 g / kg is dried by adjusting the hot air temperature so that the air volume is 300 Nm ³ / hr, the dryer inlet temperature is 150 ° C., and the dryer outlet temperature is 85 ° C. Obtained. The drying time was within 10 minutes. Evaluation of physical properties and battery characteristics of lithium tungstate were performed in the same manner as in Example 1. In the manufactured lithium tungstate, the diffraction pattern obtained by the powder X-ray diffractometer almost coincides with the reported Li ₂ WO ₄ pattern of rhombohedral crystals, and diffraction peaks of other lithium tungstates were confirmed. Since it was not, it was confirmed that it is Li ₂ WO ₄ of rhombohedral crystal (not shown).

[Example 3]
An aqueous solution of a tungsten-lithium compound was obtained in the same manner as in Example 1. The aqueous solution was dried using a conical nozzle type spray dryer. As the nozzle, a two-fluid nozzle was used, and the lithium tungstate aqueous solution was sprayed at a discharge pressure of 0.6 MPa, a flow rate of 80 NL / min and a feed rate of 40 ml / min. Air with an absolute humidity of 5 g / kg is dried by adjusting the hot air temperature so that the hot air flow rate is 60 Nm ³ / hr, the dryer inlet temperature is 150 ° C., and the dryer outlet temperature is 85 ° C., and lithium tungstate powder Got. The drying time was within 10 minutes. Evaluation of physical properties and battery characteristics of lithium tungstate were performed in the same manner as in Example 1. In the manufactured lithium tungstate, the diffraction pattern obtained by the powder X-ray diffractometer almost coincides with the reported Li ₂ WO ₄ pattern of rhombohedral crystals, and diffraction peaks of other lithium tungstates were confirmed. Since it was not, it was confirmed that it is Li ₂ WO ₄ of rhombohedral crystal (not shown).

[Example 4]
An aqueous solution of a tungsten-lithium compound was obtained in the same manner as in Example 1. The aqueous solution was dried using a rotating disk type plate dryer. The nozzle was a fan-type 1-fluid nozzle, and was dried on the disk by spraying the lithium tungstate aqueous solution onto the disk surface rotating at 2 rpm heated to 130 ° C. at a liquid feed rate of 250 ml / min. A lithium tungstate powder was obtained by scraping off the lithium tungstate on the disk with a scraper. The drying time was within 10 minutes.

About the obtained product, it dried in 105 degreeC air | atmosphere for 2 hours with the dryer, and when the moisture content was computed from the mass before and behind, it was 1.3% moisture content. When X-ray diffraction measurement was performed using a CuKα ray with a powder X-ray diffractometer, the diffraction pattern was the reported rhombohedral crystal Li ₂ WO ₄ diffraction pattern and cubic (Li ₂ WO ₄ ) ₇ ( H ₂ O) ₄ diffraction pattern mixed pattern. The maximum diffraction peak intensity of rhombohedral crystal Li ₂ WO ₄ (anhydride) was 3.5 times the maximum diffraction peak intensity of (Li ₂ WO ₄ ) ₇ (H ₂ O) ₄ (hydrate). . Moreover, the abundance ratio of lithium tungstate anhydride and hydrate determined by a thermal mass spectrometer was anhydride / (anhydride + hydrate) = 0.78.

[Example 5]
Put 6 kg of ion-exchanged water in a stainless steel container with a cooling jacket, and add 2.17 kg of lithium hydroxide monohydrate and 6.0 kg of tungsten oxide (so that the molar amount of lithium: the molar amount of tungsten = 2: 1). Then, with the liquid temperature kept at 75 ° C., the mixture was stirred at 100 rpm for 60 minutes to react tungsten oxide and lithium hydroxide to obtain an aqueous solution of tungsten-lithium compound.

While the temperature of the aqueous solution was kept at 75 ° C., the solution was dried using a centrifugal spray dryer while stirring at 100 rpm. The nozzle used was a pin disk type centrifugal spray nozzle with a diameter of 65 mm, and the tungsten-lithium compound aqueous solution was sprayed at a flow rate of 20 kg / hr. The hot air temperature was adjusted to 300 Nm ³ / hr, the temperature at the dryer inlet was 200 ° C., and the temperature at the dryer outlet was 120 ° C., and drying was performed to obtain lithium tungstate powder. Evaluation of physical properties and battery evaluation characteristics of lithium tungstate were performed in the same manner as in Examples 1 to 4. The produced lithium tungstate has a diffraction pattern obtained by a powder X-ray diffractometer, the reported diffraction pattern of rhombohedral crystal Li ₂ WO ₄ and cubic (Li ₂ WO ₄ ) ₇ (H ₂ O ₄ ) It was confirmed that there was a mixture of rhombohedral crystal Li ₂ WO ₄ and cubic (Li ₂ WO ₄ ) ₇ (H ₂ O) ₄ because it was a mixed pattern of ₄ diffraction patterns (FIG. Not shown).

[Example 6]
A tungsten-lithium compound aqueous solution was obtained in the same manner as in Example 1. The aqueous solution was dried using a centrifugal spray type spray dryer. The nozzle used was a pin disk type centrifugal spray nozzle with a diameter of 65 mm, and the tungsten-lithium compound aqueous solution was sprayed at a flow rate of 20 kg / hr. The hot air temperature was adjusted to 300 Nm ³ / hr, the temperature at the dryer inlet was 120 ° C. and the temperature at the dryer outlet was 75 ° C., and drying was performed to obtain lithium tungstate powder. Evaluation of physical properties and battery characteristics of lithium tungstate were performed in the same manner as in Example 1. The produced lithium tungstate has a diffraction pattern obtained by a powder X-ray diffractometer, the reported diffraction pattern of rhombohedral crystal Li ₂ WO ₄ and cubic (Li ₂ WO ₄ ) ₇ (H ₂ O ₄ ) It was confirmed that there was a mixture of rhombohedral crystal Li ₂ WO ₄ and cubic (Li ₂ WO ₄ ) ₇ (H ₂ O) ₄ because it was a mixed pattern of ₄ diffraction patterns (FIG. Not shown).

[Example 7]
100 g of tungsten oxide and 36.2 g of lithium hydroxide monohydrate LiOH.H ₂ O so that the molar amount of lithium is twice the molar amount of tungsten are made by a shaker mixer apparatus (manufactured by Willy et Bacofen (WAB)) After adding TURBULA Type T2C), 1 g of water was added and mixed well to react tungsten oxide and lithium hydroxide to obtain a lithium tungstate paste. The lithium tungstate was dried at 80 ° C. for 12 hours using an air dryer, and then pulverized using a hammer mill to obtain lithium tungstate powder. The physical property evaluation and battery evaluation of lithium tungstate were performed in the same manner as in Example 1. The produced lithium tungstate had a diffraction pattern obtained by a powder X-ray diffractometer, which was a mixed pattern of reported cubic (Li ₂ WO ₄ ) ₇ (H ₂ O) ₄ diffraction patterns. To cubic cubic (Li ₂ WO ₄ ) ₇ (H ₂ O) ₄ (not shown).

[Comparative Example 1]
The lithium metal composite oxide powder of Example 1 (composition formula: Li _1.06 Ni _0.76 Co _0.14 Al _0.10 O ₂ ) was used as the positive electrode active material, and no lithium tungstate was mixed. A coin battery was prepared in the same manner as described above, and battery characteristics were evaluated.

[Comparative Example 2]
The lithium tungstate produced in Example 3 was sieved with a 150 Mesh stainless steel sieve to obtain a lithium tungstate powder using the sieve top. The average particle diameter of the obtained lithium tungstate was 105 μm. Evaluation of physical properties and battery characteristics of lithium tungstate were performed in the same manner as in Examples 1 to 4.

[Comparative Example 3]
The lithium tungstate produced in Example 3 was pulverized with a jet mill to obtain a lithium tungstate powder. The average particle diameter of the obtained lithium tungstate was 4 μm. Evaluation of physical properties and battery characteristics of lithium tungstate were performed in the same manner as in Examples 1 to 4.

[Comparative Example 4]
A tungsten-lithium compound aqueous solution was obtained in the same manner as in Example 1. The aqueous solution was dried using a centrifugal spray type spray dryer. The nozzle used was a pin disk type centrifugal spray nozzle with a diameter of 65 mm, and the tungsten-lithium compound aqueous solution was sprayed at a flow rate of 20 kg / hr. The hot air temperature was adjusted to 300 Nm ³ / hr, the temperature at the dryer inlet was 120 ° C. and the temperature at the dryer outlet was adjusted to 60 ° C., and drying was performed to obtain a lithium tungstate powder. Evaluation of physical properties and battery characteristics of lithium tungstate were performed in the same manner as in Example 1. The produced lithium tungstate has a diffraction pattern obtained by a powder X-ray diffractometer, the reported diffraction pattern of rhombohedral crystal Li ₂ WO ₄ and cubic (Li ₂ WO ₄ ) ₇ (H ₂ O ₄ ) It was confirmed that there was a mixture of rhombohedral crystal Li ₂ WO ₄ and cubic (Li ₂ WO ₄ ) ₇ (H ₂ O) ₄ because it was a mixed pattern of ₄ diffraction patterns (FIG. 6).

  Table 1 shows the lithium tungstate physical property values and battery characteristic evaluation results of Examples 1 to 7 and Comparative Examples 1 to 4. The ease of handling is based on the fact that the obtained lithium tungstate has good fluidity and does not cause shelf hanging or adhesion to the wall surface in the hopper, and is x when a problem occurs. Moreover, the fact that the maximum diffraction peak intensity of anhydride / the maximum diffraction peak intensity of hydrate is expressed as N / A indicates that no anhydride or hydrate peak was detected and measurement was impossible.

Almost all of the lithium tungstate prepared in Examples 1 to 3 is anhydrous, and 78% of Example 4 is also anhydrous. As shown in FIG. 1, the lithium tungstate obtained in Example 1 was Li ₂ WO ₄ . Similarly, the lithium tungstate obtained in Examples 2 to 7 was also Li ₂ WO ₄ . In addition, as a result of battery characteristic evaluation, the positive electrode active material containing these lithium tungstates had a low positive electrode reaction resistance and exhibited excellent battery characteristics.

  In particular, Example 1, which was carried out under favorable conditions such as the temperature at the time of synthesis of the added lithium tungstate, the ratio of the amount of water added, and the drying temperature conditions, showed good characteristics of lithium tungstate, and lithium ion containing it. Since the secondary battery positive electrode active material is also more suitable, both the discharge capacity and the positive electrode reaction resistance show good battery characteristic values.

  Examples 2 and 3 are inferior to Example 1 because the lithium water content of lithium tungstate is slightly high, but show good battery characteristic values for both discharge capacity and positive electrode reaction resistance.

  In Example 4, since the value of anhydride / (anhydride + hydrate) is slightly lower than those in Examples 1 to 3, the discharge capacity is slightly low and the positive electrode reaction resistance is slightly high. The battery characteristic value is better than

  Example 5 has a low proportion of lithium tungstate anhydride. Since the positive electrode active material containing it also has a slow dissolution rate in water, the lithium tungstate mixed after washing the base material with water is insufficiently dispersed on the surface of the positive electrode material, and the value of the positive electrode reaction resistance is slightly large. Comparative Example 1 The battery characteristic values are better than those of 2, 4 and 4.

  Since Example 6 is drying at a temperature lower than the drying temperature of lithium tungstate, the moisture content of lithium tungstate is high. Therefore, lithium tungstate may solidify due to residual moisture after drying. Therefore, when the positive electrode active material and lithium tungstate are mixed, the dispersion to the surface of the positive electrode active material becomes insufficient, and the value of the positive electrode reaction resistance is large. However, the battery characteristic values are better than those of Comparative Examples 1, 2, and 4. .

  In Example 7, since the addition amount of water in the mixing step is small, the drying time is as long as 80 ° C. and 12 hours, so that the proportion of hydrate is high. When the lithium tungstate is mixed after the positive electrode active material is washed with water because the dissolution rate in water is slow, the lithium tungstate becomes insufficiently dispersed on the surface of the positive electrode material, and anhydride / (anhydride + hydrate) Since the value of the positive electrode reaction resistance is large and the discharge capacity is low, since the value of the battery is much lower than those of Examples 1 to 3, most of them are hydrates. Show.

  In Comparative Example 1, the reaction resistance is significantly high because no lithium tungstate is added to the positive electrode active material.

  In Comparative Example 2, the particle size of lithium tungstate according to the present invention is large, and the dispersion of lithium tungstate on the surface of the positive electrode active material becomes insufficient, and a sufficient effect of reducing the positive electrode material resistance is not obtained as compared with the example.

  In Comparative Example 3, battery characteristics of high capacity and low reaction resistance were obtained. However, since the lithium tungstate powder has a small particle diameter and a large angle of repose and poor fluidity, powder handling is not possible. It is difficult and industrial use is difficult.

  Since the comparative example 4 is drying at a temperature lower than the drying temperature of the lithium tungstate in the examples, the moisture content of the lithium tungstate is significantly high. Therefore, lithium tungstate may solidify due to residual moisture after drying. Therefore, when the positive electrode active material and lithium tungstate are mixed, the dispersion on the surface of the positive electrode active material becomes insufficient, and a sufficient effect of reducing the positive electrode material resistance is not obtained as compared with the examples.

  In Examples 1-6, lithium tungstate with a large proportion of anhydride was obtained, and lithium ion secondary batteries using a positive electrode active material mixed with these had low reaction resistance and excellent battery characteristics. Was confirmed. Also in Example 7 where the ratio of anhydride is low, it was confirmed that the reaction resistance was low and excellent battery characteristics were exhibited.

  As described above, the lithium tungstate of the present invention is a lithium tungstate having a large proportion of anhydride, which is useful as a component of a positive electrode material of a lithium ion battery, and a lithium ion secondary using a positive electrode material containing the lithium tungstate. Since the output of the battery can be increased, the battery is suitable for addition to a positive electrode material for a lithium ion secondary battery for a power source for an electric vehicle or a hybrid vehicle that is restricted by a mounting space.

  The technical scope of the present invention is not limited to the aspects described in the above-described embodiments. One or more of the requirements described in the above embodiments and the like may be omitted. In addition, the requirements described in the above-described embodiments and the like can be combined as appropriate. In addition, as long as it is permitted by law, the disclosure of all documents cited in the above-described embodiments and the like is incorporated as a part of the description of the text.

DESCRIPTION OF SYMBOLS 1 ... Coin type battery 2 ... Case 2a ... Positive electrode can 2b ... Negative electrode can 2c ... Gasket 3 ... Electrode 3a ... Positive electrode 3b ... Negative electrode 3c ... Separator AP ... Lithium tungstate manufacturing apparatus L ... Solution containing tungsten-lithium compound M ... Medium (gas)
DESCRIPTION OF SYMBOLS 10 ... Spraying part 11 ... Heating part 12 ... Collection | recovery part 13 ... Heating apparatus

Claims (16)

General formula: Li _a WO _b · (H ₂ O) _n (0.4 ≦ a ≦ 6, 3 ≦ b ≦ 6, 0 ≦ n ≦ 4), the average particle size is 5 μm or more and 100 μm or less, Lithium tungstate used for a positive electrode material for a non-aqueous electrolyte secondary battery having an angle of repose of 30 ° to 60 °.   The ratio of the mass of the anhydride to the sum of the mass of the anhydride and the mass of the hydrate (anhydride / (anhydride + hydrate)) The lithium tungstate according to claim 1, wherein is 0.75 or more and 1.0 or less.   The X-ray diffraction measurement using CuKα ray by a powder X-ray diffractometer, wherein the maximum diffraction peak intensity of the anhydride is at least 3 times the maximum diffraction peak intensity of the hydrate. Item 3. The lithium tungstate according to Item 2. The lithium tungstate according to any one of claims 1 to 3, wherein the anhydride is represented by a chemical formula: Li ₂ WO ₄ . A method for producing lithium tungstate according to any one of claims 1 to 4,
Mixing at least one tungsten compound, at least one of lithium hydroxide and lithium hydroxide hydrate, and a solvent to obtain a solution containing the tungsten-lithium compound, and obtaining the obtained tungsten-lithium compound Drying the solution containing, a method for producing lithium tungstate.   The said solvent is the ratio of the mass of the said solvent with respect to the sum total of the mass of the said tungsten compound, and the mass of at least 1 sort (s) of lithium oxide and lithium hydroxide hydrate of 0.7 or more of Claim 5 A method for producing lithium tungstate.   When obtaining the solution containing the tungsten-lithium compound, the temperature of the solvent and the solution containing the tungsten-lithium compound is controlled between 25 ° C. and 60 ° C. during the mixing and before the drying. A method for producing lithium tungstate according to claim 5 or claim 6.   8. The method according to claim 5, wherein, when the solution containing the tungsten-lithium compound is dried, the drying temperature is set to 80 ° C. or more, and the moisture content is dried to 1.5% or less within 10 minutes. A method for producing lithium tungstate according to claim 1.   The tungsten according to any one of claims 5 to 8, wherein, when the solution containing the tungsten-lithium compound is dried, the solution containing the tungsten-lithium compound is dried by contacting with a heated medium. Method for producing lithium acid.   The lithium tungstate according to any one of claims 5 to 9, comprising drying the solution containing the tungsten-lithium compound by spray drying when the solution containing the tungsten-lithium compound is dried. Production method.   The method for producing lithium tungstate according to any one of claims 5 to 10, wherein the tungsten compound is at least one of tungsten oxide, tungstic acid, and tungstate.   The method for producing lithium tungstate according to any one of claims 5 to 11, wherein the solvent is water. An apparatus used for drying a solution containing the tungsten-lithium compound according to claim 5,
A spray section for spraying a solution containing the tungsten-lithium compound;
An apparatus for producing lithium tungstate, comprising: a heating unit that dries the solution of the tungsten-lithium compound sprayed by the spraying unit.   The heating unit includes a medium that contacts and dries the solution containing the tungsten-lithium compound sprayed by the spraying unit, and the heating unit is in contact with the solution containing the tungsten-lithium compound sprayed by the spraying unit. The production of lithium tungstate according to claim 13, wherein the medium is maintained at 80 degrees or more and the solution containing the tungsten-lithium compound is reduced to 1.5% or less within 10 minutes after contact with the medium. apparatus.   The positive electrode material for non-aqueous electrolyte secondary batteries containing the lithium tungstate as described in any one of Claims 1-4. A non-aqueous electrolyte secondary battery comprising the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 15.

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