JP2014063732A - Positive electrode for all-solid-state lithium ion battery, mixture for obtaining the positive electrode, method for manufacturing them, and all-solid-state lithium ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a positive electrode for an all-solid-state lithium ion battery, precise and low in heterophase generation degree.SOLUTION: A method for manufacturing a positive electrode for an all-solid-state lithium ion battery includes: a precursor adjustment step of pulverizing and mixing a raw material containing a lithium source and Mwhile the raw material is contained in a solvent, and drying an obtained slurry to obtain a precursor; a calcination step of calcinating the precursor at a temperature of 900°C or below to obtain a calcinated body; a mixing step of mixing a sintering assistant containing Mand the calcinated body to obtain a mixture; a molding step of performing a molding process to obtain a molded article including the mixture; and a firing step of firing the molded article to obtain a sintered body mainly consisting of a lithium composite oxide.

Description

  The present invention relates to a positive electrode for an all solid-state lithium ion battery, a mixture used for obtaining the positive electrode, a production method thereof, and an all solid-state lithium ion battery.

  Lithium batteries have a high energy density compared to other batteries, are light and can be used for a long time, and are power sources for portable devices such as mobile phones, PHS and small computers, power storage power sources, electric vehicles Development is underway for use as a power source for automobiles.

Above all, an all-solid-state lithium-ion battery that has a solid electrolyte and all other elements are made of solid is superior to lithium-ion batteries that use electrolytes such as organic solvents, and battery performance due to corrosion. In recent years, research has been actively conducted because problems such as deterioration of the resin hardly occur.
Examples of such all solid-state lithium ion batteries include those described in Patent Documents 1 to 3.

JP 2009-140910 A JP 2010-205739 A JP 2009-206084 A

However, conventional all solid-state lithium ion batteries have a high porosity in the positive electrode, and thus battery performance such as charge / discharge capacity is insufficient.
In addition, in the positive electrode manufacturing process, if the raw material is fired at a high temperature, the porosity of the positive electrode tends to decrease, but on the other hand, the heterogeneous phase generation degree increases, so the battery performance such as charge / discharge capacity is not improved. The present inventor found out.

The present invention solves the problem of the positive electrode in the conventional all solid-state lithium ion battery as described above.
That is, an object of the present invention is to provide a dense positive electrode for an all solid-state lithium ion battery having a low porosity and a low heterogeneous phase generation, a mixture used for obtaining the positive electrode, and a method for producing them. It is another object of the present invention to provide an all solid-state lithium ion battery having excellent battery performance with the positive electrode.

  The present inventor diligently studied to solve the above-mentioned problems, and when manufactured by a specific method using a specific sintering aid, the solid-state lithium-ion battery is dense, has a low porosity, and has a low heterogeneous formation rate. As a result, it was found that an all solid-state lithium ion battery using the positive electrode for use as a positive electrode had excellent performance, and the present invention was completed.

The present invention includes the following (1) to (7).
(1) A precursor adjustment step of pulverizing and mixing a raw material containing a lithium source and M ¹ in a solvent, and drying the resulting slurry to obtain a precursor;
A calcining step of calcining the precursor at 900 ° C. or less to obtain a calcined body;
A mixing step of mixing a sintering aid containing M ² and the calcined body to obtain a mixture;
With
Further, by molding and firing, it is possible to obtain a sintered body that has a lithium composite oxide represented by the following formula (I) as a main component and can be used as at least a part of a positive electrode for an all-solid-state lithium ion battery. A method for producing a mixture.
Formula (I): Li _{(x + y)} M ¹ _(2-yp) M ² _p O _(4-a)
Here, M ¹ is at least one element selected from the group consisting of Mn, Ni, Co, Mg, Fe, Al and Cr, and M ² is a group consisting of B, P, Cl, Pb, Sb, Si and V At least one element selected from the group consisting of 1.0 ≦ x ≦ 2.0, 0 ≦ y ≦ 0.2, 0 <p ≦ 1.0, and 0 ≦ a ≦ 1.0.
(2) In the manufacturing method of the mixture as described in (1) above,
A molding step of performing a molding process to obtain a molded body containing the mixture,
A firing step of firing the molded body to obtain a sintered body mainly composed of the lithium composite oxide represented by the formula (I);
A method for producing a positive electrode for an all-solid-state lithium ion battery.
(3) The manufacturing method of the positive electrode for all-solid-state lithium ion batteries as described in said (2) with which the sintered compact whose porosity is 4.5% or less is obtained in the said baking process.
(4) 2θ = 36 relative to the peak intensity [α] of the spinel-type lithium composite oxide appearing at 2θ = 18.0 to 19.0 ° of the XRD chart obtained by performing powder X-ray diffraction measurement in the firing step. The sintered body having a ratio (peak intensity [β] / peak intensity [α]) of the peak intensity [β] of the heterogeneous component appearing at .6 to 37.2 ° is 0.3 or less (2) Or the manufacturing method of the positive electrode for all-solid-state lithium ion batteries as described in (3).
(5) A mixture obtained by the production method according to (1) above.
(6) A positive electrode for an all-solid-state lithium ion battery obtained by the production method according to any one of (2) to (4) above.
(7) An all-solid-state lithium ion battery comprising the positive electrode according to (6) above, a negative electrode, and a solid electrolyte.

  According to the present invention, it is possible to provide a positive electrode for an all-solid-state lithium ion battery that is dense, has a low porosity, and has a low heterogeneous phase generation, a mixture used to obtain the positive electrode, and a method for producing them. . Moreover, the all-solid-state lithium ion battery excellent in the battery performance which has this positive electrode can be provided.

2 is an XRD chart obtained in Example 1.

The present invention will be described.
The present invention includes a precursor adjustment step of pulverizing and mixing a raw material containing a lithium source and M ¹ in a solvent, and drying the resulting slurry to obtain a precursor, and the precursor at 900 ° C. or less. A calcining step of firing to obtain a calcined body, a mixing step of mixing the sintering aid containing M ² and the calcined body to obtain a mixture, and further molding and firing. In the method for producing a mixture, a sintered body that can be used as a main component of a lithium composite oxide represented by the following formula (I) and can be used as at least a part of a positive electrode for an all-solid-state lithium ion battery is obtained. is there.
Formula (I): Li _{(x + y)} M ¹ _(2-yp) M ² _p O _(4-a)
Here, M ¹ is at least one element selected from the group consisting of Mn, Ni, Co, Mg, Fe, Al and Cr, and M ² is a group consisting of B, P, Cl, Pb, Sb, Si and V At least one element selected from the group consisting of 1.0 ≦ x ≦ 2.0, 0 ≦ y ≦ 0.2, 0 <p ≦ 1.0, and 0 ≦ a ≦ 1.0.
Hereinafter, such a method for producing a mixture is also referred to as “a method for producing the mixture of the present invention”.

Further, the present invention is represented by the formula (I) in the method for producing the mixture of the present invention, a molding step of further performing a molding process to obtain a molded body containing the mixture, and firing the molded body. And a firing step for obtaining a sintered body containing a lithium composite oxide as a main component.
Hereinafter, such a method for producing a positive electrode for an all-solid-state lithium ion battery is also referred to as “a method for producing a positive electrode of the present invention”.

  First, each process with which the manufacturing method of the mixture of this invention is provided is demonstrated.

<Precursor adjustment step>
The precursor adjustment process in the manufacturing method of the mixture of this invention is demonstrated.
In the precursor preparation step, ^first , a raw material containing a lithium source and M ¹ is contained in a solvent.

  As the lithium source, an inorganic or organic compound containing a lithium atom (that is, a lithium compound) can be used. For example, lithium hydroxide, lithium carbonate, lithium nitrate, or lithium acetate can be used. Among these, it is preferable to use lithium hydroxide and / or lithium carbonate. This is because generation of harmful gases can be suppressed.

As the raw material containing M ¹ , a compound containing at least one element selected from the group consisting of Mn, Ni, Co, Mg, Fe, Al, and Cr can be used. The element M ¹ preferably contains Mn and / or Ni.

The raw material containing M ¹ preferably contains a manganese source.
As the manganese source, an inorganic or organic compound containing a manganese atom (that is, a manganese compound) can be used. For example, manganese oxide, manganese carbonate, manganese carbonate hydrate, manganese hydroxide, manganese oxyhydroxide can be used. Among these, it is preferable to use manganese oxide, and it is more preferable to use MnO ₂ . This is because a lithium ion battery that can be obtained as an industrial raw material at a low cost and that has a higher battery performance such as charge / discharge capacity tends to be obtained.

As the raw material containing M ¹ , for example, nickel oxide, cobalt oxide, magnesia, hematite, alumina, aluminum hydroxide (Al (OH) ₃ ), chromium oxide, or the like can be used. Of these, compounds containing Ni are preferably used, and nickel oxide (NiO) can be more preferably used. A compound containing Al is preferably used, and aluminum hydroxide (Al (OH) ₃ ) can be more preferably used.
This is because it can be obtained as an industrial raw material, and is easily replaced with Mn in the crystal structure, and a lithium ion battery having higher battery performance such as charge / discharge capacity tends to be obtained.

It is preferable that at least one of the raw materials containing the lithium source and M ¹ is a solid raw material.

When contained in the solvent, the ratio of the raw material containing the lithium source and M ¹ as described above is preferably adjusted so that a lithium composite oxide having a composition represented by the formula (I) is obtained.

The solvent will be described.
The solvent containing the lithium source and the raw material containing M ¹ is not particularly limited. For example, a conventionally known solvent such as water (pure water or the like), ethanol, acetone or the like can be used, but water is preferably used.

Further, the raw material containing the lithium source and M ¹ is used as a solvent so that the solid content concentration in the solvent is preferably 5 to 40% by mass, more preferably 10 to 35% by mass, and still more preferably 15 to 30% by mass. To contain.

In the precursor adjusting step, a raw material containing a lithium source and M ¹ is contained in the solvent, and pulverized and mixed in that state.
The method of pulverization and mixing is not particularly limited, but a wet pulverization method using a wet pulverizer using a bead mill or the like is preferable.

Further, this pulverization is preferably performed until a slurry having an average particle size (D ₅₀ ) of solids of 0.50 μm or less is obtained. When the average particle size (D ₅₀ ) is pulverized and mixed so that the average particle size (D ₅₀ ) is 0.50 μm or less, the solid content is easily dispersed in the slurry. Moreover, it is because battery performances, such as charging / discharging capacity, in the obtained lithium ion battery tend to be high.
The average particle diameter is preferably 0.40 μm or less, and more preferably 0.30 μm or less.
The average particle size is preferably 0.10 μm or more, and more preferably 0.15 μm or more. This is because if the particle size is too small by pulverization, handling in the subsequent steps is worsened.

The average particle diameter (D ₅₀ ) of the solid content in the slurry was determined by adding an aqueous sodium hexametaphosphate solution to the slurry at room temperature in the atmosphere, and dispersing the slurry by ultrasonic dispersion and stirring. The integrated particle size distribution (volume basis) is measured using a laser diffraction / scattering type particle size distribution measuring apparatus, and the median diameter obtained from the particle size distribution is meant.

This pulverization is preferably performed until a slurry having a D ₉₀ particle size of 3.00 μm or less in solid content is obtained. More preferably the particle size of D ₉₀ is less than 2.00 .mu.m, even more preferably less 1.00 .mu.m. This is because battery performance such as charge / discharge capacity in the obtained lithium ion battery tends to be high.

The particle size of the solid content D ₉₀ in the slurry was determined by adding a sodium hexametaphosphate aqueous solution to the slurry at room temperature in the atmosphere, and dispersing the slurry by ultrasonic dispersion and stirring. The integrated particle size distribution (volume basis) is measured using a laser diffraction / scattering type particle size distribution measuring device, and the particle size at which the integrated particle size distribution is 90% is meant.

  Next, the slurry thus obtained is dried to obtain a precursor. The slurry can be dried by a drying method using a band dryer or a shelf dryer, but is preferably spray drying. Spray drying is to dry the slurry after spraying it into a mist or while forming a mist. By spray-drying under desired conditions, the particle size of the resulting precursor can be adjusted within a desired range.

The method of spray drying is not particularly limited. For example, by allowing slurry to flow into a two-fluid nozzle, the slurry component droplets are ejected from the nozzle tip, and the droplets are scattered by adjusting to an appropriate drying gas temperature and air flow rate. For example, a method of quickly drying the lysate. At this time, the slurry flow rate is preferably 0.5 to 700 kg / h, more preferably 1 to 600 kg / h, and still more preferably 3 to 550 kg / h.
The pulverized air pressure is preferably 0.05 to 0.5 MPa, more preferably 0.05 to 0.4 MPa, and still more preferably 0.1 to 0.4 MPa.
A treatment such as an appropriate temperature and air blowing is performed so as to quickly dry the scattered droplets, but it is preferable to introduce the dry gas in a downward flow from the upper part of the drying tower to the lower part.

  Spray drying is preferably performed using a spray dryer. Moreover, the inlet temperature of the hot air for drying of a spray dryer becomes like this. Preferably it is 60-500 degreeC, More preferably, it is 150-450 degreeC, More preferably, it is 200-400 degreeC, Outlet temperature is preferably 80-250 degreeC, More preferably, it is 100- 200 degreeC, More preferably, you may be 100-160 degreeC.

<Calcination process>
The calcination step in the method for producing the mixture of the present invention will be described.
In the calcination step, the precursor is baked at a temperature of 900 ° C. or lower.

The calcining temperature, which is the temperature at which the precursor is calcined in the calcining step, is set to a temperature of 900 ° C. or lower. The calcination temperature is preferably 850 ° C. or lower, more preferably 800 ° C. or lower, more preferably 750 ° C. or lower, and further preferably 700 ° C. or lower.
The calcining temperature is preferably 400 ° C. or higher, more preferably 450 ° C. or higher, and further preferably 500 ° C. or higher.
This is because the sinterability of the sintered body obtained by the subsequent firing step is improved when the calcination temperature is in such a range. Moreover, it is because the porosity of a sintered compact tends to become lower.

The time for firing the precursor at the calcination temperature as described above is defined as the calcination time.
The calcination time is preferably 20 hours or less, more preferably 10 hours or less, more preferably 8 hours or less, and even more preferably 7 hours or less.
The calcination time is preferably 1 hour or longer, more preferably 3 hours or longer, and further preferably 5 hours or longer.
This is because the sinterability of the sintered body obtained by the subsequent firing step is improved when the calcining time is in such a range. Moreover, it is because the porosity of a sintered compact tends to become lower.

  The method of firing the precursor in the calcination step is not particularly limited as long as it is a method performed in an oxygen-containing atmosphere, and examples thereof include conventionally known methods such as a firing method using a tunnel furnace, a muffle furnace, a rotary kiln, and the like. .

<Mixing process>
The mixing process in the manufacturing method of the mixture of this invention is demonstrated.
In the mixing step, the sintering aid containing M ² which is at least one element selected from the group consisting of B, P, Cl, Pb, Sb, Si and V and the calcined body are mixed, and the mixture is obtained. obtain.

  The mixture is preferably at least partially solid, and more preferably all solid.

The sintering aid contains M ² which is at least one element selected from the group consisting of B, P, Cl, Pb, Sb, Si and V, and B, P, Cl, Pb, Sb, Si And a compound containing at least one element selected from the group consisting of V and V (compound containing M ² ) can be used. Specific examples include borides (boric acid, lithium borate, etc.), vicinals (phosphoric acid, etc.), chlorides, P ₂ O ₅ , Sb ₂ O ₃ , SiO ₂ , V ₂ O _{5 and the} like.
The element M ² preferably contains B and / or V.

When the element M ² contains B, boric acid (H ₃ BO ₃ ), diboric acid triborate (B ₂ O ₃ ), or lithium borate (Li ₂ B ₄ O ₇ ) is used as the compound containing M ^2. It is preferable to use boric acid (H ₃ BO ₃ ) or lithium borate (Li ₂ B ₄ O ₇ ). This is because it can be obtained at low cost as an industrial raw material. In addition, when the element M ² contains B, the sinterability at the time of subsequent firing is enhanced, the particle growth is promoted, and the voids in the sintered body are reduced. The inventor presumes that the battery performance is improved.

  The sintering aid may include a plurality of types of such compounds.

  The sintering aid may be a solid such as a powder, but is preferably a liquid such as a boric acid solution or a phosphoric acid solution.

A method for obtaining a mixture from such a sintering aid and the calcined body is not particularly limited. For example, when the sintering aid is a liquid, there is a method in which the calcined body is immersed in this liquid and stirred, and then spray-dried to obtain a solid mixture. The spray drying may be the same as the spray drying in the precursor adjustment step.
Further, for example, after obtaining a slurry containing the sintering aid and the calcined body, the slurry is attached to the surface of the flowing ball, and the slurry is dried on the ball surface, so that the solid state The method of obtaining the mixture of these is mentioned.

The mixing ratio of the sintering aid and the calcined body is not particularly limited, but the total molar amount of Li, M ¹ element and M ² element contained in the sintering aid and the calcined body (Li, Mn, Ni, Co , Mg, Fe, Al and Cr, and B, P, Cl, Pb, Sb, the molar amount of M ² element to a total molar amount) of Si and V (B, P, Cl, Pb, Sb, Si, and V The total molar amount) is preferably 0.0001 to 0.035, more preferably 0.00015 to 0.02, and further preferably 0.00015 to 0.01.

Thus, although the said sintering auxiliary agent and the said calcined body can be mixed and a mixture can be obtained, a mixture may contain another thing further. For example, a conductive aid or a molding aid may be included. As a conductive support agent, a conventionally well-known oxide type conductive support agent is mentioned, for example. Examples of the molding aid include conventionally known polyvinylidene fluoride, polytetrafluoroethylene, ethylene propylene diene rubber, fluororubber, styrene butadiene, cellulose resin, and polyacrylic acid.
The content of such other components in the mixture is preferably 30% by mass or less, and more preferably 15% by mass or less.

The shape of the mixture is not particularly limited, but the average particle diameter (D ₅₀ ) is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. The average particle diameter (D ₅₀ ) is preferably 1 μm or more, more preferably 3 μm or more, and further preferably 5 μm or more. This is because the porosity in the sintered body obtained by the firing process tends to be lower.

The average particle diameter (D ₅₀₎ of the mixture shall be determined by the following method.
When the mixture is a slurry, a dispersant (sodium hexametaphosphate aqueous solution) is added to the slurry-like mixture in the atmosphere at room temperature, and dispersed by ultrasonic dispersion and stirring. After adjusting to ˜90%, the integrated particle size distribution (volume basis) is measured using a laser diffraction / scattering particle size distribution measuring device, and the median diameter obtained from the particle size distribution is determined as the average particle size of the mixture. (D ₅₀ ).
When the mixture is solid, the mixture is introduced into the sample inlet of the laser diffraction / scattering type particle size distribution analyzer, and after further adding a dispersant (sodium hexametaphosphate aqueous solution), ultrasonic dispersion and stirring are performed. After dispersing and adjusting the slurry to have a transmittance of 80 to 90%, the integrated particle size distribution (volume basis) is measured using this apparatus, and the median diameter obtained from the particle size distribution is determined as the mixture. The average particle diameter (D ₅₀ ).

  When the mixture obtained by the method for producing a mixture of the present invention including such a precursor adjustment step, a calcination step, and a mixing step is further processed and fired, lithium represented by the formula (I) described later A sintered body that contains the composite oxide as a main component and can be used as at least part of the positive electrode for an all-solid-state lithium ion battery can be obtained.

Next, each process with which the manufacturing method of the positive electrode of this invention is provided is demonstrated.
The positive electrode manufacturing method of the present invention further includes a molding step and a firing step in addition to the precursor adjustment step, the calcination step, and the mixing step that are included in the manufacturing method of the mixture of the present invention.

<Molding process>
The molding process in the positive electrode manufacturing method of the present invention will be described.
In the molding step, a molded body containing the mixture is obtained.

In the molding step, the mixture can be molded to obtain a molded body, but a mixture obtained by adding a conductive additive and / or a binder to the mixture can be molded to obtain a molded body. preferable.
Here, as a conductive support agent, a conventionally well-known oxide type conductive support agent is mentioned, for example.
Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, ethylene propylene diene rubber, fluorine rubber, styrene butadiene, cellulose resin, and polyacrylic acid.
The content of the molded body other than the mixture (such as a conductive additive or a binder) is preferably 30% by mass or less, and more preferably 15% by mass or less.

  For example, a conventionally known molding process such as press molding may be performed to mold the mixture into a plate or sheet shape to obtain a molded body. When the said mixture is shape | molded in plate shape or a sheet form, it can be set as a positive electrode by baking this.

<Baking process>
The firing step in the method for producing a positive electrode of the present invention will be described.
In the firing step, the molded body obtained by the molding process as described above is fired to obtain a sintered body.

The firing temperature, which is the temperature at which the molded body is fired, can be a conventionally known temperature. For example, it can be fired at a firing temperature of 600 to 1400 ° C.
The firing temperature is preferably 750 ° C. or higher, more preferably 800 ° C. or higher, more preferably 850 ° C. or higher, more preferably 900 ° C. or higher, and preferably 950 ° C. or higher. Further preferred.
The firing temperature is preferably 1200 ° C. or lower, more preferably 1150 ° C. or lower, more preferably 1100 ° C. or lower, and further preferably 1050 ° C. or lower.
This is because if the firing temperature is too high, oxygen may be released from the crystal structure, and in this case, battery performance tends to decrease. On the other hand, if it is too low, sintering will be insufficient and an electrode with many voids will tend to be formed, and in this case also, battery performance tends to deteriorate.

The time for firing the molded body at the firing temperature as described above is defined as the firing time.
The firing time is preferably 20 hours or shorter, more preferably 10 hours or shorter, more preferably 8 hours or shorter, and even more preferably 7 hours or shorter.
If the firing time is too long, oxygen may be released from the crystal structure or oxygen deficiency may occur due to sintering between particles, and in this case, battery performance tends to deteriorate.

The firing time is preferably 1 hour or longer, more preferably 3 hours or longer, and further preferably 5 hours or longer.
This is because primary particle growth (increase in diameter) is promoted, voids in the electrode are reduced, and battery characteristics tend to be improved. If it is too short, sintering will be insufficient and an electrode with many voids will tend to be formed, and in this case, battery performance tends to deteriorate.

  The method for firing the molded body in the firing step is not particularly limited as long as it is a method performed in an oxygen-containing atmosphere. .

  By such a firing step, the sintered body having a porosity of preferably 4.5% or less can be obtained. Since the porosity is low and the heterogeneous phase generation rate is low, an all solid-state lithium ion battery using this sintered body as a positive electrode has excellent battery performance.

The porosity of the sintered body is preferably 4.5% or less, more preferably 4.4% or less, and even more preferably 4.3% or less. Further, it is preferably 0% or more, more preferably 0.5% or more, and further preferably 1.0% or more.
This is because, with such a porosity, the battery performance of an all-solid-state lithium ion battery using this sintered body as a positive electrode is more excellent.

The porosity of the sintered body means a value obtained by measuring as follows.
First, 1 g of the sintered body is taken in a crucible, dried at 300 ° C. for 1 hour, then placed in a desiccator and cooled to room temperature. Next, 0.7 g of the cooled sample is collected in a cell, and mercury is injected into the pores using a pore distribution measuring device PM-33GT1LP (manufactured by QUANTA CROME), and the pressure applied at that time is pushed in. The pore volume is measured from the relationship of the mercury volume that has entered (invaded). Further, the pore distribution is obtained from the relationship between the applied pressure and the pore diameter at which mercury can enter at that pressure. The measurement is performed up to a maximum pressure of 32273 psi (pore diameter 5.4 nm), the surface tension of mercury used for the analysis is σ = 473 dynes / cm, and the contact angle is θ = 130 °. And the volume density of the sintered compact which calculated the pore volume (g / cm < ³ >) to the pore diameter 5.4 nm-2000 nm from the weight (g), thickness (cm), and diameter (cm) of a sintered compact. The value divided by (g / cm ³ ) is defined as the porosity.

The sintered body contains a lithium composite oxide represented by the formula (I) as a main component.
Hereinafter, such a lithium composite oxide is also referred to as “the composite oxide of the present invention”.

  The sintered body is mainly composed of the lithium composite oxide represented by the formula (I) (that is, the composite oxide of the present invention). For example, when the composite oxide of the present invention is a spinel type lithium composite oxide, When the sintered body was subjected to powder X-ray diffraction measurement, a diffraction pattern attributed to the spinel structure (space group Fd-3m, crystal cubic) was obtained, and the sintered body was used as a positive electrode. An all-solid-state lithium ion battery that can be charged and discharged in a range of 0 <Va ≦ 5.5 volts with respect to the potential (Va) of the lithium metal is obtained. In such a case, the sintered body is mainly composed of the lithium composite oxide represented by the formula (I).

  The composite oxide of the present invention may be other than the spinel lithium composite oxide, but preferably contains a spinel lithium composite oxide.

  Further, the sintered body has 2θ = 36 relative to the peak intensity [α] of the spinel lithium composite oxide appearing at 2θ = 18.0 to 19.0 ° of the XRD chart obtained by performing powder X-ray diffraction measurement. It is preferable that the ratio (peak intensity [β] / peak intensity [α]) of the peak intensity [β] of the heterogeneous component appearing at .6 to 37.2 ° is 0.3 or less. Here, the peak intensity means the intensity from the baseline.

Such a peak intensity ratio is more preferably 0.1 or less, and further preferably 0.05 or less. Further, it is preferably 0 or more, more preferably 0.001 or more, and further preferably 0.01 or more.
This is because the battery performance of an all solid-state lithium ion battery using this sintered body as a positive electrode is more excellent when the peak intensity ratio is such.

  The peak intensity ratio was obtained after first performing powder X-ray diffraction measurement on a sintered body using a conventionally known powder X-ray diffractometer (using Cu-Kα rays) to obtain an XRD chart. The peak intensity [α] of the spinel type lithium composite oxide appearing at 2θ = 18.0 to 19.0 ° on the XRD chart, and the peak intensity [β] of the heterogeneous component appearing at 2θ = 36.6 to 37.2 ° Is read and requested.

  Further, the heterogeneous component means a component different from the space group Fd-3m and the crystal system cubic. Examples of the heterophasic component include space group R-3m, crystal trigonal nickel oxide (NiO), lithium nickelate, and analogs substituted with Mn.

<Composite oxide of the present invention>
The composite oxide of the present invention will be described.
The composite oxide of the present invention may include a spinel type lithium composite oxide, a layered rock salt type lithium composite oxide, and an inverse spinel type lithium composite oxide.
The composite oxide of the present invention may include a plurality of types of lithium composite oxides.
The composite oxide of the present invention is preferably a spinel type lithium composite oxide.

The spinel-type lithium composite oxide has a cubic structure and has a space group Fd-3m symmetry. In an ideal structure, it is considered that O (oxygen) which is an anion is close-packed in cubic, and cations are filled in the gaps.
In addition, a substituted spinel lithium composite oxide, which may be called 5V type or 5V class, which has a high operating potential of 5V level, is also included in the composite oxide of the present invention.

The layered rock salt type lithium composite oxide is considered to be an α-NaFeO ₂ type (space group R-3m), in which oxide ions have a hexagonal crystal structure and are cubic close packed. As the layered rock salt type lithium composite oxide, specifically, LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiMn _0.5 Ni _0.5 O ₂ , LiMn _1/3 Ni _1/3 Co _1/3 O ₂ , Li _4/3 M _2/3 O ₂ (wherein M is at least one selected from the group consisting of M ¹ and M ² in the composite oxide of the present invention).
Further, a solid solution compound based on LiCoO ₂ or LiNiO ₂ is also included in the composite oxide of the present invention. This solid solution compound includes LiNi _0.5 Mn _0.5 O ₂ , LiNi _1/3 Mn _1/3 Co _1/3 O _{2 and the} like. The solid solution compound of LiNi _0.5 Mn _0.5 O ₂ and LiNi _1/3 Mn _1/3 Co _1/3 O ₂ has a hexagonal structure in which oxide ions, also called space group R-3m, have cubic close packing. It is thought that there is. Further, as a solid solution compound, γLi _4/3 M _2/3 O _2. (1-γ) LiMO ₂ (0 <γ <1 where M is a group consisting of M ¹ and M ² in the composite oxide of the present invention. And at least one selected from the above).

The reverse spinel type lithium composite oxide takes a space group Fd-3m, and in the general formula of LiAMB ₄ (where M is a transition element), A is a tetrahedral site, and M (transition element) and lithium are randomly eight. It has a structure that occupies a faceted site.

Formula (I) will be described.
In the formula (I), x is in the range of 1.0 ≦ x ≦ 2.0, preferably 1.0 ≦ x ≦ 1.2, and 1.0 ≦ x ≦ 1.1. Is more preferable, and it is more preferable that x = 1.0. The closer x is to 1.0, the closer the lithium composite oxide is to the spinel type. The closer x is to 2.0, the closer the lithium composite oxide is to the layered rock salt type.

In the formula (I), y is in the range of 0 ≦ y ≦ 0.2, preferably 0 ≦ y ≦ 0.15, and more preferably 0 ≦ y ≦ 0.1.
y means the amount of Li substituted for M ¹ . In the composite oxide of the present invention, a part of M ¹ is preferably substituted with Li. That is, it is preferable that excess Li is contained from the theoretical value of the number of atoms (composition ratio) of Li in the composition formula of the lithium composite oxide used as the positive electrode active material of the lithium ion battery. In this case, the structure is such that at least a part of Li is replaced with M ¹ by reducing the amount of M ^{1 by an} amount corresponding to a part or all of the excess Li.
When the substitution amount (y) of Li increases, the charge / discharge capacity of the battery slightly decreases, but the cycle characteristics at a higher temperature than normal temperature tend to be improved. However, even if y is larger than 0.2, the cycle characteristics at a temperature higher than normal temperature tend to be hardly improved. Moreover, when Li total amount (x + y) becomes less than 1.0, the heterogeneous phase which becomes an impurity will be produced | generated and there exists a tendency for the charge / discharge performance of a battery to fall.

In the formula (I), M ¹ is at least one element selected from the group consisting of Mn, Ni, Co, Mg, Fe, Al and Cr, and preferably contains Mn and / or Ni.

2-yp which is the abundance of M ¹ is larger than 0. The lower limit of 2-yp is preferably 0.66, and the lower limit is more preferably 0.8. This is because if 2-yp is too small, it is difficult to maintain the capacity.
Moreover, although the upper limit of 2-yp is 2.0, it is preferable that an upper limit is 1.95, and it is more preferable that an upper limit is 1.90. This is because if 2-yp is too large, the cycle characteristics deteriorate.

When M ¹ contains Mn, the formula (I) can be expressed as the following formula (I-1).
Formula _{(I-1): Li (} x + y) Mn (2-ypr) M 11 r M 2 p O (4-a)
In Formula (I-1), M ¹¹ is an element other than Mn in M ¹ , that is, at least one element selected from the group consisting of Ni, Co, Mg, Fe, Al, and Cr, and r is a substitution of M ¹¹ Means quantity, 0 ≦ r ≦ 2.0.
In addition, 0 <2-ypr. The preferable upper limit and the preferable lower limit of 2-ypr are the same as those of 2-yp described above.

(If it contains a plurality of kinds of element as M ^11, their sum) r is a replacement amount of M ¹¹ is preferably 0 ≦ r ≦ 1.0, more preferably 0.01 ≦ r ≦ 0.6, further Preferably it is 0.05 <= r <= 0.5. This is because when used as a positive electrode active material, a certain discharge capacity can be secured and cycle characteristics at a temperature higher than normal temperature can be maintained. If the amount of M ¹¹ substitution is too large, the cycle characteristics at a higher temperature than the normal temperature of the battery when used as the positive electrode active material are improved, but the discharge capacity of the battery may be reduced.

In the formula (I), the element M ² is at least one element selected from the group consisting of B, P, Pb, Sb, Si and V. Among these, preferred elements are B and / or V.

(If it contains a plurality of kinds of element as M ^2, their sum) p substituted amount of M ² is 0 <p ≦ 1.0, preferably the upper limit is 0.1, 0.05 It is more preferable that This is because when used as a positive electrode active material, the cycle characteristics at a higher temperature than normal temperature tend to be improved. If the substitution amount p is too high, the discharge capacity of the lithium ion battery when used as the positive electrode active material tends to decrease.

In the formula (I), a represents the amount of O (oxygen) deficiency.
In the formula (I), a satisfies 0 ≦ a ≦ 1.0 and is preferably a = 0.
When the amount of oxygen deficiency is small (that is, when a is small), the capacity of 3.2 V or less in the charge / discharge test tends to be small. When the amount of oxygen vacancies is small, the crystal structure is stable, and the cycle characteristics at a temperature higher than normal temperature tend to be improved.

The composite oxide of the present invention is preferably a spinel type lithium composite oxide. In this case, the composite oxide of the present invention is preferably represented by the following formula (I-2).
Formula (I-2): Li _{(1 + y)} M ¹ _(2-yp) M ² _p O _(4-a)
Formula (I-2) corresponds to the case where x in Formula (I) is 1.

The composite oxide of the present invention is preferably a spinel type lithium composite oxide containing Mn. In this case, the composite oxide of the present invention is preferably represented by the following formula (I-3).
Formula (I-3): Li _{(1 + y)} Mn _(2-ypr) M ¹¹ _r M ² _p O _(4-a)
Formula (I-3) corresponds to the case where x in Formula (I-1) is 1.
M ¹¹ and r in formula (I-3) is the same as the M ¹¹ and r in formula (I-1). Further, similarly to the case of the formula (I-1), 0 <2-ypr. The preferable upper limit and the preferable lower limit of 2-ypr are the same as those of 2-yp described above.

When the composite oxide of the present invention is a layered rock salt type lithium composite oxide, the composite oxide of the present invention is preferably represented by the following formula (I-4).
Formula (I-4): Li _{(2 + y)} M ¹ _(2-yp) M ² _p O _(4-a)
Formula (I-4) corresponds to the case where x in Formula (I) is 2.

Formula (I-4) can be represented by the following formula (I-5).
Formula (I-5): Li _{(1 + z)} M ¹ _(1-zq) M ² _q O _(2-b)
Here, 0 ≦ z ≦ 0.34, 0 <q ≦ 1.0, and 0 ≦ b ≦ 1.0.

In the formula (I-5), z is in the range of 0 ≦ z ≦ 0.34, more preferably 0 <z ≦ (1/3), and 0.05 ≦ z ≦ 0.15. It is more preferable.
z means the amount of Li substituted for M ¹ . When the composite oxide of the present invention is represented by the formula (I-5), it is preferable that a part of M ¹ is substituted with Li. That is, it is preferable that excess Li is contained from the theoretical value of the number of atoms (composition ratio) of Li in the composition formula of the lithium composite oxide used as the positive electrode active material of the lithium ion battery. In this case, the structure is such that at least a part of Li is replaced with M ¹ by reducing the amount of M ^{1 by an} amount corresponding to a part or all of the excess Li.
When the substitution amount (z) of Li increases, the charge / discharge capacity of the battery slightly decreases, but the cycle characteristics at a higher temperature than normal temperature tend to be improved. However, even if z is larger than 0.34, the cycle characteristics at a temperature higher than normal temperature tend to be hardly improved. Further, when the total amount of Li (1 + z) is less than 1.0, a heterogeneous phase that is an impurity is generated, and the charge / discharge performance of the battery tends to be reduced.

In formula (I-5), 1-zq, which is the amount of M ¹ , is larger than 0. The lower limit of 1-zq is preferably 0.5, and more preferably 0.66. This is because the capacity cannot be maintained if 1-zq is too small.

In the formula (I-5) that, (if it contains a plurality of kinds of element as M ^2, their sum) q is a replacement amount of M ² is 0 <q ≦ 1, the upper limit is 0.1 Is more preferable, and 0.05 is more preferable. This is because when used as a positive electrode active material, the cycle characteristics at a higher temperature than normal temperature tend to be improved. If the substitution amount q is too high, the discharge capacity of the lithium ion battery when used as the positive electrode active material tends to decrease.

In the formula (I-5), b indicates the amount of O (oxygen) deficiency.
In the formula (I-5), b satisfies 0 ≦ b ≦ 1.0 and is preferably b = 0.
When the amount of oxygen deficiency is small (that is, when b is small), the capacity of 3.2 V or less in the charge / discharge test tends to be small. When the amount of oxygen vacancies is small, the crystal structure is stable, and the cycle characteristics at a temperature higher than normal temperature tend to be improved.

The sintered body produced by such a method for producing a positive electrode of the present invention can be used as a positive electrode for an all-solid-state lithium ion battery by joining with a current collector as necessary.
The current collector is not particularly limited, and for example, a conventionally known net shape, sheet shape, or film shape can be used.

  Moreover, the all-solid-state lithium ion battery which has the positive electrode using the sintered compact manufactured by the manufacturing method of the positive electrode of this invention, a negative electrode, and a solid electrolyte is also called "the battery of this invention" below.

<Battery of the present invention>
The battery of the present invention will be described.
The battery of the present invention may have the same configuration as that of a normal all solid-state lithium ion battery except that a positive electrode using a sintered body obtained by the method for producing a positive electrode of the present invention is used as the positive electrode. It may be a mold, a square, a coin, a button or the like. That is, the positive electrode, the negative electrode, and the solid electrolyte are the main battery constituent elements, and these elements are enclosed in, for example, a battery can. Each of the positive electrode and the negative electrode acts as a lithium ion carrier, and the lithium ions are occluded in the negative electrode during charging and detached from the negative electrode during discharging.

A negative electrode is not specifically limited, For example, the aspect similar to a conventionally well-known negative electrode may be sufficient. For example, as the negative electrode active material, a lithium alloy or an oxide typified by lithium or lithium-aluminum can be used.
When the negative electrode active material is lithium, a lithium alloy, or an oxide, the negative electrode can be used as it is or can be manufactured by pressure bonding to a current collector.

Solid electrolytes include, for example, oxide-based quenching glasses containing lithium ions, glass-based solid electrolytes such as sulfide-based oxysulfide-based superionic conductive glasses, and high concentrations of Li salts dissolved and dispersed in polymers such as polyethers. Examples include molecular solid electrolytes.
The polymer solid electrolyte may be in the form of a gel containing a solvent component.

  Moreover, a polymer electrolyte can be used as a solid electrolyte. That is, in the present invention, the solid electrolyte is a concept including a conventionally known polymer electrolyte.

As the polymer electrolyte, for example, a matrix polymer compound gelled with a plasticizer (non-aqueous electrolyte) can be used. Examples of the matrix polymer compound include ether resins such as polyethylene oxide and cross-linked products thereof, polymethacrylate resins, polyacrylate resins, polyvinylidene fluoride, and vinylidene fluoride-hexafluoropropylene copolymers. Etc. can be used alone or in combination.
Among these, from the viewpoint of oxidation-reduction stability, it is preferable to use a fluorine-based resin such as polyvinylidene fluoride or vinylidene fluoride-hexafluoropropylene copolymer.

The production of the polymer electrolyte is not particularly limited, and examples thereof include a method in which a polymer compound constituting a matrix, a lithium salt, and a solvent are mixed and heated to melt and dissolve. In addition, after dissolving a polymer compound, a lithium salt, and a solvent in an organic solvent for mixing, the organic solvent for mixing is evaporated, a polymerizable monomer, a lithium salt, and a solvent are mixed, and ultraviolet rays, electron beams, or molecules are mixed. Examples include a method of polymerizing a polymerizable monomer by irradiating a line and the like to obtain a polymer.
10-90 mass% is preferable and, as for the ratio of the solvent in a polymer electrolyte, 30-80 mass% is more preferable. With such a ratio, the electrical conductivity is high, the mechanical strength is strong, and the film is easily formed.

  The method for producing the battery of the present invention is not particularly limited, and for example, it can be produced by a conventionally known method. For example, a positive electrode using a plate-like or film-like sintered body produced by the method for producing a positive electrode of the present invention, a negative electrode and a solid electrolyte previously formed into a plate-like or film-like shape are laminated and covered with an exterior material. be able to. Examples of the exterior material include a metal-resin composite film having a configuration in which nickel-plated iron, stainless steel, aluminum, and metal foil are sandwiched between resin films.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

<Example 1>
LiOH · H ₂ O as a lithium source (manufactured by Kanto Chemical Co., Inc., purity: 57.8% by mass), NiO as a nickel source (manufactured by Kanto Chemical Co., Ltd., nickel purity: 77.1% by mass, average particle size: 9.4 μm) Electrolytic manganese dioxide (γ-MnO ₂ , manufactured by Kanto Chemical Co., Inc., manganese purity: 60.78% by mass, average particle size: 28.0 μm) was prepared as a manganese source. Each raw material was weighed so that the molar ratio of Li: Ni: Mn was 1.00: 0.50: 1.50.

  Next, these weighed raw materials were mixed, and after adding pure water so that the solid content concentration was 33.3% by mass, a wet pulverizer (manufactured by Ashizawa Finetech Co., Ltd .: Star Mill Lab Star LMZ-) was added. 06) to obtain a slurry. Here, it grind | pulverized until the average particle diameter (median diameter) of solid content in a slurry became 0.40 micrometer or less. In the pulverization, a 600 ml vessel was used.

  In addition, the average particle diameter (median diameter) of the solid content in the slurry was determined using a laser diffraction / scattering particle size distribution analyzer (Horiba, Ltd .: LA-950v2). Specifically, an aqueous sodium hexametaphosphate solution is added to the slurry at room temperature in the atmosphere, and the mixture is dispersed by ultrasonic dispersion and stirring, adjusted to have a transmittance of 87.5 to 88.5%, and then integrated particle size distribution. It was determined by measuring (volume basis).

Next, after adding pure water to the pulverized slurry and adjusting the solid content concentration to 20% by mass, spray drying is performed using a nozzle type spray dryer (Okawara Kakoki Co., Ltd .: L-8 type spray dryer). It was. Here, air was used as the drying gas. Moreover, it adjusted so that cyclone differential pressure might be set to 0.7-0.8 kPa, and the inlet temperature of the dry gas was adjusted to 220 degreeC. The slurry flow rate was 3 kg / h, and the atomization air pressure was 0.1 MPa.
By performing such spray drying, a particulate precursor [1] was obtained.

  Next, the obtained precursor [1] was calcined in the air at 700 ° C. for 6 hours to obtain a calcined body [1].

The average particle diameter of the obtained calcined body [1] was measured and found to be 9.0 μm.
Here, the average particle diameter of the calcined body [1] is the same as the case where the average particle diameter (median diameter) of the solid content in the slurry is measured after the calcined body [1] is dispersed in pure water. It measured by the method of.

  Further, powder X-ray diffraction measurement was performed on the calcined body [1]. Sample horizontal multipurpose X-ray diffractometer ("UltimaIV" manufactured by Rigaku Corporation was used, and Cu-Kα ray was used for measurement. As a result, the obtained calcined body [1] was spinel type lithium composite oxide. It was confirmed to be a thing.

Next, an aqueous boric acid solution in which H ₃ BO ₃ (manufactured by Kanto Chemical Co., Inc., purity: 99.9% by mass) was dissolved as a sintering aid was prepared. And calcined body [1] was added and mixed with this boric acid aqueous solution, and the liquid mixture was obtained. Here, the molar ratio of Li, Ni, Mn, and B contained in the boric acid aqueous solution and calcined body [1] constituting the mixed solution was set to Li + Ni + Mn + B: B = 3.00: 0.03.

Next, the mixed liquid was spray-dried using a nozzle type spray dryer (manufactured by Okawara Chemical Co., Ltd .: L-8 type spray dryer). The conditions for spray drying were the same as in the case of obtaining the particulate precursor from the pulverized slurry.
The product obtained by performing such spray drying is hereinafter referred to as a mixture [1].

It was 8.8 micrometers when the average particle diameter of the obtained mixture [1] was measured.
Here, the average particle diameter of the mixture [1] is measured by the same method as that for measuring the average particle diameter (median diameter) of the calcined body after the mixture [1] is dispersed in pure water. did.

  Moreover, powder X-ray diffraction measurement was implemented about the mixture [1]. Sample horizontal multipurpose X-ray diffractometer ("Ultima IV" manufactured by Rigaku Corporation was used, and Cu-Kα ray was used for the measurement. As a result, the obtained mixture [1] was a spinel type lithium composite oxide. It was confirmed that.

Next, 1 g of the mixture [1] was molded into a circular thin plate of φ25 mm / t1.1 mm at a pressure of 15 kN / cm ² to obtain a molded body [1].
The molded body [1] was fired in air at 1000 ° C. for 6 hours to obtain a sintered body [1].

  The obtained sintered body [1] was subjected to pore volume measurement and powder X-ray diffraction measurement.

The pore volume of the sintered body [1] was measured as follows.
First, 1 g of the sintered body was placed in a crucible, dried at 300 ° C. for 1 hour, then placed in a desiccator and cooled to room temperature. Next, 0.7 g of the cooled sample is collected in a cell, and mercury is injected into the pores using a pore distribution measuring device PM-33GT1LP (manufactured by QUANTA CROME), and the pressure applied at that time is pushed in. The pore volume was measured from the relationship of the mercury volume that had entered (invaded). The pore distribution was determined from the relationship between the applied pressure and the pore diameter at which mercury can enter at that pressure. The measurement was performed up to a maximum pressure of 32273 psi (pore diameter 5.4 nm), the surface tension of mercury used in the analysis was σ = 473 dynes / cm, and the contact angle was θ = 130 °. And the volume density of the sintered compact which calculated the pore volume (g / cm < ³ >) to the pore diameter 5.4 nm-2000 nm from the weight (g), thickness (cm), and diameter (cm) of a sintered compact. The value divided by (g / cm ³ ) was defined as the porosity.
When the pore volume of the sintered body [1] was measured by such a method, the porosity was 4.3%.

For the powder X-ray diffraction measurement of the sintered body [1], a sample horizontal multi-purpose X-ray diffractometer ("UltimaIV" manufactured by Rigaku Corporation) was used, and Cu-Kα rays were used for the measurement.
The obtained XRD chart is shown in FIG.
As a result, the peak intensity of the heterogeneous component appearing at 2θ = 36.6-37.2 ° with respect to the peak intensity [α] of the spinel lithium composite oxide appearing at 2θ = 18.0-19.0 ° on the XRD chart [ The ratio of β] (peak intensity [β] / peak intensity [α]) was 0.031.

<Example 2>
A calcined body was obtained in the same manner as in Example 1. Let the calcined body obtained here be a calcined body [2].
And when the average particle diameter of the obtained calcined body [2] was measured, it was 9.0 μm. Moreover, about calcined body [2], when the powder X-ray-diffraction measurement was implemented, it confirmed that it was a spinel type lithium complex oxide.

  Next, the mixture was made in the same manner as in Example 1 except that the sintering aid used in Example 1 was changed from boric acid to lithium borate (manufactured by Kanto Chemical Co., Inc., purity: 99.9% by mass). [2] was obtained. When the average particle diameter of the obtained mixture [2] was measured, it was 8.8 μm. Moreover, when powder X-ray-diffraction measurement was implemented about the mixture [2], it confirmed that it was a spinel type lithium complex oxide.

Thereafter, the sintered body [2] was obtained in the same manner as in Example 1.
The obtained sintered body [2] was subjected to pore volume measurement and powder X-ray diffraction measurement in the same manner as in Example 1.
As a result, the porosity of the sintered body [2] was 2.8%.
Further, the peak intensity [β] of the heterogeneous component appearing at 2θ = 36.6-37.2 ° with respect to the peak intensity [α] of the spinel-type lithium composite oxide appearing at 2θ = 18.0-19.0 ° on the XRD chart. ] (Peak intensity [β] / peak intensity [α]) was 0.105.
From this, it can be said that there are few voids in the sintered body [2] and almost no heterogeneous phase is generated.

<Comparative Example 1>
Sintered body [11] was manufactured without performing the treatment using the boric acid aqueous solution performed in Example 1.
Specifically, 1 g of the calcined body [1] in Example 1 was molded into a circular thin plate of φ25 mm / t1.2 mm at a pressure of 15 kN / cm ² to obtain a molded body [11].
The molded body [11] was fired in air at 1000 ° C. for 6 hours to obtain a sintered body [11].

  With respect to the obtained sintered body [11], pore volume measurement and powder X-ray diffraction measurement were performed in the same manner as the method performed for the sintered body [1] in Example 1.

  When the pore volume of the sintered body [11] was measured, the porosity of the sintered body was 8.0%.

  When the powder X-ray diffraction measurement of the sintered body [11] was performed, 2θ = 36.36 with respect to the peak intensity [α] of the spinel lithium composite oxide appearing at 2θ = 18.0 to 19.0 ° on the XRD chart. The ratio (peak intensity [β] / peak intensity [α]) of the peak intensity [β] of the heterogeneous component appearing at 6-37.2 ° was zero.

  From this, it was found that the sintered body [11] has no heterogeneous phase but has many voids.

<Comparative example 2>
In Example 1, the precursor [1] was fired to obtain a calcined body [1], but in Comparative Example 1, this operation was not performed. That is, spray drying was performed using a mixed solution obtained by adding and mixing the precursor [1] with an aqueous boric acid solution to obtain a mixture [12]. Here, the molar ratio of Li, Ni, Mn and B contained in the boric acid aqueous solution and the precursor [1] constituting the mixed solution was Li + Ni + Mn + B: B = 3.00: 0.03, as in Example 1. It was made to become. The spray drying conditions were the same as in Example 1.
And the sintered body [12] was obtained from the mixture [12] by the same method as the method for obtaining the sintered body [1] from the mixture [1] in Example 1.

  When the pore volume of the obtained sintered body [12] was measured, the porosity was 7.7%.

  The peak intensity [β] of the heterophasic component appearing at 2θ = 36.6-37.2 ° with respect to the peak intensity [α] of the spinel-type lithium composite oxide appearing at 2θ = 18.0-19.0 ° of the XRD chart The ratio (peak intensity [β] / peak intensity [α]) was 0.030.

  From this, it was found that the sintered body [12] has almost no heterogeneous phase but has many voids.

<Comparative Example 3>
Similarly to Example 1, LiOH.H ₂ O as a lithium source (manufactured by Kanto Chemical Co., Inc., purity: 57.8% by mass), NiO as a nickel source (manufactured by Kanto Kagaku Co., Ltd., nickel purity: 77.1% by mass, average) Electrolytic manganese dioxide (γ-MnO ₂ , manufactured by Kanto Chemical Co., Inc., manganese purity: 60.78% by mass, average particle size: 28.0 μm) was prepared as a manganese source. Further, H ₃ BO ₃ (manufactured by Kanto Chemical Co., Inc., purity: 99.9% by mass) is prepared, and each raw material has a molar ratio of Li: Ni: Mn: B of 1.00: 0.50: 1. .50 and Li + Ni + Mn + B: B = 3.00: 0.01.

  The raw materials weighed in this way were mixed, and after adding pure water so that the solid content concentration was 33.3% by mass, the same wet pulverizer slurry as in Example 1 was obtained. Here, it grind | pulverized until the average particle diameter (median diameter) of solid content in a slurry became 0.40 micrometer or less. In the pulverization, a 600 ml vessel was used.

Next, after adding pure water to the pulverized slurry to adjust the solid content concentration to 20% by mass, spray drying was performed using the same nozzle type spray dryer as in Example 1. The drying gas and spray drying conditions used were the same as in Example 1.
By performing such spray drying, a particulate precursor [13] was obtained.

Next, the obtained precursor [13] was baked in the air at 700 ° C. for 6 hours to obtain a lithium composite oxide.
The lithium composite oxide obtained here is hereinafter referred to as a mixture [13].

Next, 1 g of the mixture [13] was molded into a circular thin plate of φ25 mm / t1.1 mm at a pressure of 15 kN / cm ² to obtain a molded body [13].
The molded body [13] was fired in air at 1000 ° C. for 6 hours to obtain a sintered body [13].

  When the pore volume of the obtained sintered body [13] was measured, the porosity was 3.1%.

  Further, the peak intensity [β] of the heterogeneous component appearing at 2θ = 36.6-37.2 ° with respect to the peak intensity [α] of the spinel-type lithium composite oxide appearing at 2θ = 18.0-19.0 ° on the XRD chart. ] Ratio (peak intensity [β] / peak intensity [α]) was 0.600.

  From this, it was found that the sintered body [13] had a large number of heterogeneous phases although the voids were small.

  The porosity and peak intensity ratio of the sintered bodies determined in Example 1, Example 2, Comparative Example 1, Comparative Example 2 and Comparative Example 3 are summarized in Table 1.

Claims (7)

A precursor adjusting step of pulverizing and mixing a raw material containing a lithium source and M ¹ in a solvent, and drying the resulting slurry to obtain a precursor;
A calcining step of calcining the precursor at 900 ° C. or less to obtain a calcined body;
A mixing step of mixing a sintering aid containing M ² and the calcined body to obtain a mixture;
With
Further, by molding and firing, it is possible to obtain a sintered body that has a lithium composite oxide represented by the following formula (I) as a main component and can be used as at least a part of a positive electrode for an all-solid-state lithium ion battery. A method for producing a mixture.
Formula (I): Li _{(x + y)} M ¹ _(2-yp) M ² _p O _(4-a)
Here, M ¹ is at least one element selected from the group consisting of Mn, Ni, Co, Mg, Fe, Al and Cr, and M ² is a group consisting of B, P, Cl, Pb, Sb, Si and V At least one element selected from the group consisting of 1.0 ≦ x ≦ 2.0, 0 ≦ y ≦ 0.2, 0 <p ≦ 1.0, and 0 ≦ a ≦ 1.0. In the manufacturing method of the mixture of Claim 1, further,
A molding step of performing a molding process to obtain a molded body containing the mixture,
A firing step of firing the molded body to obtain a sintered body mainly composed of the lithium composite oxide represented by the formula (I);
A method for producing a positive electrode for an all-solid-state lithium ion battery.   The manufacturing method of the positive electrode for all-solid-state lithium ion batteries of Claim 2 with which the sintered compact whose porosity is 4.5% or less is obtained in the said baking process.   In the firing step, 2θ = 36.6 to the peak intensity [α] of the spinel lithium composite oxide appearing at 2θ = 18.0 to 19.0 ° of the XRD chart obtained by performing powder X-ray diffraction measurement. The sintered body having a ratio (peak intensity [β] / peak intensity [α]) of peak intensity [β] of heterogeneous phase components appearing at 37.2 ° to 0.3 or less is obtained. The manufacturing method of the positive electrode for all-solid-state lithium ion batteries.   A mixture obtained by the production method according to claim 1.   The positive electrode for all-solid-state lithium ion batteries obtained by the manufacturing method in any one of Claims 2-4.   An all solid lithium ion battery comprising the positive electrode according to claim 6, a negative electrode, and a solid electrolyte.

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