JP2016146301A - Positive electrode material for lithium secondary battery and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode material for a lithium secondary battery excellent in lithium ion conductivity while suppressing cost increase and a manufacturing method of the same.SOLUTION: A positive electrode material 10 for a lithium secondary battery includes a positive electrode active material 1 and a lithium ion conduction body 2. The positive electrode active material 1 is at least one of lithium manganese iron phosphate and lithium iron phosphate. The lithium ion conduction body 2 is lithium aluminum titanium phosphate. The positive electrode active material 1 and the lithium ion conduction body 2 both exhibit particulate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a positive electrode material for a lithium secondary battery and a method for producing the same.

  Among the positive electrode materials used in lithium secondary batteries, lithium iron phosphate, lithium manganese iron phosphate, and phosphoric acid are excellent in stability and can be reduced in cost by being composed of resource-rich elements. Materials such as manganese lithium (hereinafter, collectively referred to as “LFP etc.” as appropriate) are attracting attention as potential candidates for future positive electrode materials.

However, since LFP and the like have a one-dimensional diffusion direction of lithium ions, lithium ion diffusion compared to a layered positive electrode material that diffuses lithium ions two-dimensionally or a spinel-type positive electrode material that diffuses lithium ions three-dimensionally. Poor sex.
In addition, since LFP or the like has low electron conductivity, it is necessary to coat carbon on the surface of LFP or the like that exhibits a particulate shape. However, when the surface of LFP or the like is covered with carbon, the diffusibility of lithium ions is further reduced.
That is, when LFP or the like is employed as the positive electrode material of the lithium secondary battery, it is necessary to solve the problem of low lithium ion diffusibility, in other words, the problem of poor lithium ion conductivity.

In consideration of the above circumstances, the following technologies have been proposed.
For example, Patent Document 1 discloses that the surface of a particle made of LiMnPO ₄ or the like is Li _y E _z PO ₄ (where E is one or two selected from the group of Fe and Ni, 0 <y ≦ 2, An electrode active material characterized by being coated with a coating layer containing 0 <z ≦ 1.5) and a LiTi composite oxide is disclosed.

JP 2013-69567 A

  However, according to the technique disclosed in Patent Document 1, it is necessary to uniformly coat a predetermined substance on the surface of fine particles such as lithium manganese phosphate. Special equipment / equipment for applying As a result, according to the technique disclosed in Patent Document 1, an increase in the number of manufacturing steps and an increase in the cost of the positive electrode material due to investment in equipment and facilities are inevitable.

  Then, this invention makes it a subject to provide the positive electrode material for lithium secondary batteries excellent in lithium ion conductivity, and its manufacturing method, suppressing the raise in cost.

  In order to solve the above problems, the inventors of the present invention are in a state in which a lithium ion conductor in a particulate form is mixed with lithium iron phosphate in a particulate form and lithium iron manganese phosphate, that is, The present inventors have found that lithium ion conductivity can be enhanced by combining both without adopting the means of coating.

  That is, the positive electrode material for a lithium secondary battery according to the present invention contains a positive electrode active material and a lithium ion conductor, and the positive electrode active material is at least one of lithium iron manganese phosphate and lithium iron phosphate. The lithium ion conductor is lithium aluminum titanium phosphate, and the positive electrode active material and the lithium ion conductor are each in the form of particles.

  In the positive electrode material for a lithium secondary battery according to the present invention, the positive electrode active material is preferably lithium manganese iron phosphate.

  Further, in the positive electrode material for a lithium secondary battery according to the present invention, the positive electrode active material is lithium iron phosphate, and the ratio of the lithium ion conductor to the total of the positive electrode active material and the lithium ion conductor is: It is preferable that it is 2 mol% or more.

  The method for producing a positive electrode material for a lithium secondary battery according to the present invention includes a mixing and pulverizing step of mixing and pulverizing a precursor of a positive electrode active material and a precursor of a lithium ion conductor; A positive electrode active material is at least one of lithium manganese iron phosphate and lithium iron phosphate, and the lithium ion conductor is lithium aluminum titanium phosphate. It is characterized by that.

  The method for producing a positive electrode material for a lithium secondary battery according to the present invention includes: a primary firing step in which the firing step performs firing at a predetermined temperature; and a secondary firing step in which firing is performed at a temperature higher than the predetermined temperature. It is preferable that a carbon mixing step of mixing a carbon raw material is included between the primary baking step and the secondary baking step.

According to the positive electrode material for a lithium secondary battery according to the present invention, since the positive electrode active material and the lithium ion conductor are each in the form of particles, there is no need for a coating treatment, which can suppress an increase in cost. it can.
In addition, according to the positive electrode material for a lithium secondary battery according to the present invention, the particulate lithium ion conductor adjacent to the positive electrode active material helps the diffusion of lithium ions, so that the lithium ion conductivity can be improved.

According to the method for manufacturing a positive electrode material for a lithium secondary battery according to the present invention, since the step of coating the lithium ion conductor on the positive electrode active material is not required, the number of manufacturing steps is increased, and Investment can be avoided. As a result, according to the method for manufacturing a positive electrode material for a lithium secondary battery according to the present invention, the positive electrode material for a lithium secondary battery can be manufactured while suppressing an increase in cost.
In addition, according to the method for producing a positive electrode material for a lithium secondary battery according to the present invention, not only the positive electrode active material precursor but also the lithium ion conductor precursor is mixed and pulverized in the mixing and pulverization step. The positive electrode active material and the lithium ion conductor can each be in the form of particles. As a result, according to the method for manufacturing a positive electrode material for a lithium secondary battery according to the present invention, the particulate lithium ion conductor adjacent to the positive electrode active material helps the diffusion of lithium ions, so that lithium ion conductivity is improved. A positive electrode material for a secondary battery can be manufactured.

It is a schematic diagram of the positive electrode material for lithium secondary batteries which concerns on this embodiment. It is a flowchart of the manufacturing method of the positive electrode material for lithium secondary batteries which concerns on this embodiment. It is a graph which shows the discharge curve (1C discharge) at the time of using lithium manganese iron phosphate as a positive electrode active material. It is a graph which shows the discharge curve (5C discharge) at the time of using lithium iron phosphate as a positive electrode active material. It is the graph which expanded the part immediately after the discharge start of FIG.

  Hereinafter, a positive electrode material for a lithium secondary battery according to the present invention (hereinafter, appropriately referred to as “positive electrode material”) and a mode for carrying out a manufacturing method will be described with reference to the drawings.

[Lithium secondary battery]
First, a lithium secondary battery to which the positive electrode material according to this embodiment is applied will be described.
The “lithium secondary battery” to be applied is a battery in which lithium ions (Li ⁺ ) are responsible for ion conduction during charging and discharging, and includes members such as a positive electrode, a negative electrode, and an electrolyte. And the lithium secondary battery used as application object is not specifically limited about the material, structure, etc. of members other than a positive electrode.
For example, lithium secondary batteries using various materials such as a carbon-based material, a metal oxide-based material, a silicon-based material, and a tin-based alloy material are applicable as the negative electrode. Further, lithium secondary batteries using various electrolytes such as an organic electrolyte system, an ionic liquid system, and a solid electrolyte system are also applicable.

[Positive electrode material for lithium secondary batteries]
The positive electrode material according to the present embodiment is a substance that becomes a positive electrode material of the above-described lithium secondary battery. Specifically, the positive electrode material constitutes the positive electrode by being applied to a metal foil that is a current collector.

As shown in FIG. 1, the positive electrode material 10 includes a positive electrode active material 1 and a lithium ion conductor 2. The positive electrode active material 1 and the lithium ion conductor 2 included in the positive electrode material 10 are each in the form of particles.
Here, “respectively in the form of particles” is a stipulation that excludes a state where the surface of the particulate positive electrode active material 1 is completely covered with the lithium ion conductor 2. The term “particulate” does not limit the shape to a sphere, and it may be a long sphere such as a rugby ball. It may be.
Although omitted in FIG. 1, the positive electrode active material 1 may be coated with carbon. In FIG. 1, the positive electrode active material 1 and the lithium ion conductor 2 have the same size, but may naturally have different sizes.
In addition, about the shape (particulate form) of the positive electrode active material 1 and the lithium ion conductor 2 of the positive electrode material 10, for example, a scanning electron microscope (SEM), a scanning transmission electron microscope (STEM), or a transmission electron microscope (TEM) ) Etc.

(Positive electrode active material)
The positive electrode active material 1 is a substance that directly participates in the charge / discharge reaction on the positive electrode side. Specifically, the positive electrode active material 1 is a substance in which a lithium ion insertion reaction occurs during discharge and a lithium ion desorption reaction occurs during charging.
The positive electrode active material 1 is composed of at least one of lithium iron manganese phosphate (hereinafter referred to as “LMFP” as appropriate) and lithium iron phosphate (hereinafter referred to as “LFP” as appropriate).

LMFP _{is, Li n Mn 1-x Fe} x PO 4 (n is 0 <n ≦ 1, X satisfies 0 <X ≦ 1) can be represented by the composition formula of.
On the other hand, LFP can be represented by a composition formula of Li _n FePO ₄ (n satisfies 0 <n ≦ 1).
Note that LMFP and LFP can also be represented by a compositional formula: Li _n Mn _X Fe _(1-X) PO ₄ (n satisfies 0 <n ≦ 1, X satisfies 0 ≦ X ≦ 1).

(Carbon coat)
The positive electrode active material 1 having a particulate shape may be coated with carbon (carbon coating). In particular, when LMFP having a lower electronic conductivity than LFP is used, the positive electrode active material 1 is preferably carbon-coated in order to improve the electronic conductivity.

(Lithium ion conductor)
The lithium ion conductor 2 is a substance that functions to assist the diffusion of lithium ions in the positive electrode material 10. Specifically, the lithium ion conductor 2 becomes a lithium ion conduction path, so that lithium ions from the adjacent positive electrode active material 1 are easily diffused. As a result, the lithium ion conductivity of the entire positive electrode material 10 is improved. I think that will be.
The lithium ion conductor 2 is lithium aluminum titanium phosphate (hereinafter referred to as “LTAP” as appropriate), and Li _{1 + X} Ti _2−X Al _X (PO ₄ ) ₃ (X satisfies 0 <X ≦ 1). For example, a composition formula of Li _1.3 Ti _1.7 Al _0.3 (PO ₄ ) ₃ can be given. LTAP also has a NASICON crystal structure.

(Lithium ion conductor content)
The content of the lithium ion conductor is preferably a predetermined amount or more in order to sufficiently obtain the effect of lithium ion diffusion. On the other hand, if the content of the lithium ion conductor is too large, the above effects are saturated and the charge / discharge capacity of the lithium secondary battery may be reduced.
Specifically, when LFP is used as the positive electrode active material, the ratio of the number of moles of the lithium ion conductor to the total number of moles of the positive electrode active material and the lithium ion conductor (= number of moles of lithium ion conductor / (positive electrode active material). The number of moles of lithium + number of moles of lithium ion conductor) × 100) is preferably 2 mol% or more.

(Other materials)
The positive electrode material according to this embodiment may contain a known binder, a conductive agent (conductive auxiliary agent), and the like in addition to the positive electrode active material and the lithium ion conductor.
Further, the positive electrode material according to the present embodiment may further include a positive electrode active material different from the above-described positive electrode active material.

Next, a method for producing a positive electrode material for a lithium secondary battery according to this embodiment will be described with reference to FIG.
[Method for producing positive electrode material for lithium secondary battery]
The method for producing a positive electrode material according to the present embodiment includes a mixing and grinding step S1 and firing steps S2 and S4. And the manufacturing method of the positive electrode material which concerns on this embodiment has a baking process consisting of primary baking process S2 and secondary baking process S4, and carbon mixing process S3 between primary baking process S2 and secondary baking process S4. May be included. Furthermore, the manufacturing method of the positive electrode material according to the present embodiment may include a classification step S5 after the secondary firing step S4.

In addition, in the manufacturing method of the positive electrode material according to the present embodiment, it is possible to perform the baking treatment at a time. However, the firing steps S2 and S4 are divided into two steps, a primary firing step S2 and a secondary firing step S4, and a carbon mixing step S3 is performed between the two steps to produce a positive electrode material excellent in electronic conductivity. It is preferable in that it can be performed.
Therefore, in the following, the manufacturing method of the positive electrode material when the firing treatments S2 and S4 are performed in two steps and the carbon mixing step S3 is included between the two steps will be described for each step.

(Mixing and grinding process)
The mixing and pulverizing step S1 is a step of mixing and pulverizing the positive electrode active material precursor and the lithium ion conductor precursor.
For example, in the mixing and pulverizing step S1, the precursor of the positive electrode active material and the precursor of the lithium ion conductor are mixed and pulverized for about 60 minutes using a dry or wet bead mill (ball mill) or a pulverizer. Just give it.
In the mixing and pulverization step S1, the positive electrode active material and the lithium ion conductor in the positive electrode material finally obtained by mixing and pulverizing the precursor of the positive electrode active material and the precursor of the lithium ion conductor are obtained. Each can be in the form of particles.

(Mixing and grinding process: raw material)
The raw materials (LMFP raw material, LFP raw material, LTAP raw material) used in the mixing and grinding step S1 are as follows in detail.
Regarding the raw material (precursor) of LMFP, examples of the raw material for introducing lithium include hydrates such as LiOH, carbonates and hydrogen carbonates such as Li ₂ CO ₃ , halides including chlorides such as LiCl, and LiNO. It is possible to use a Li-containing decomposition volatile compound such that only Li such as nitrate such as ₃ and other organic acid salts remain in the target positive electrode material. A material containing two kinds of elements such as lithium phosphate and lithium dihydrogen phosphate may be used. In addition, as raw materials for introducing iron, for example, hydroxides, carbonates, bicarbonates, halides such as chlorides, nitrates, and other decomposition volatiles such that only Fe remains in the target cathode material. In addition to compounds (for example, organic acid salts such as oxalate and acetate, acetylacetonate complexes, and organic complexes such as metallocene complexes), phosphates and hydrogen phosphates can be used. Moreover, as a raw material for introducing manganese, for example, carbonate, phosphate, oxalate and the like can be used. Moreover, as raw materials for introducing phosphoric acid, for example, anhydrous phosphoric acid P ₂ O ₅ , phosphoric acid H ₃ PO ₄ , and decomposed volatile phosphates and phosphoric acid in which only phosphate ions remain in the positive electrode material Hydrogen salts can be used.

  Regarding the LFP raw material (precursor), the same raw material for introducing phosphoric acid, the raw material for introducing iron, and the raw material for introducing lithium can be the same as the raw material for LFP.

  Regarding the LTAP raw material (precursor), examples of the raw material for introducing aluminum include aluminum oxide and aluminum hydroxide. Moreover, as a raw material for introducing titanium, for example, titanium oxide, titanium halide or the like can be used. Titanium oxide includes a rutile type and an anatase type, and the anatase type is more reactive and preferable. As the raw material for introducing lithium and the raw material for introducing phosphoric acid, the same materials as those for the above-mentioned LMFP can be used.

Lithium and phosphoric acid overlap in both cases where LFP raw material and LTAP raw material are used, and when LFP raw material and LTAP raw material are used. A common raw material or a different raw material may be used.
In the mixing and pulverizing step S1, a carbon compound such as sucrose or ascorbic acid may be added as a reducing agent in addition to the above-described LFP raw material, LFP raw material, and LTAP raw material.

(Mixing and crushing process: mixing ratio of raw materials)
The blending ratio of the LMFP raw material (precursor) used in the mixing and grinding step S1 is not particularly limited. For example, the element ratio of “Li: Mn: Fe: P” is “1 to 1.1: 1−x: The above-mentioned raw materials may be blended so that “x: 1” (0 ≦ x <1).
Also, the mixing ratio of the LFP raw material (precursor) is not particularly limited. For example, the above raw materials are mixed so that the element ratio of “Li: Fe: P” is “1: 1: 1”. do it.

Regarding the blending ratio of the LTAP raw material (precursor), the respective raw materials are adjusted so that the ratio of the lithium ion conductor to the total of the positive electrode active material and the lithium ion conductor is a predetermined value (for example, 2 mol%) or more. What is necessary is just to mix | blend.
In addition, when a carbon compound is added as a reducing agent, the mixing ratio of the carbon compound is not particularly limited, but is 0 to 10 wt with respect to the total weight (LMFP or LFP raw material weight + LTAP raw material weight + carbon compound weight). What is necessary is just to mix | blend so that it may become%.

(Primary firing process)
The primary firing step S2 is a step of performing primary firing (temporary firing) on the pulverized product obtained in the mixing and grinding step S1.
The primary firing step S2 is a step in which the pulverized product is heated to react to an intermediate state before reaching the final positive electrode active material. Accompanied by outbreaks. Therefore, the firing temperature (final temperature) of the primary firing is a temperature at which most of the gas has been released and the reaction leading to the positive electrode active material does not proceed completely, that is, the second stage two in a higher temperature range. A temperature that leaves room for re-diffusion / homogenization of constituent elements in the positive electrode active material during the next firing may be selected.
Specifically, the firing temperature (attainment temperature) in the primary firing step S2 is preferably 300 ° C. or higher and 600 ° C. or lower, and more preferably 350 ° C. or higher and 500 ° C. or lower.

The firing time in the primary firing step S2 (the holding time after reaching the ultimate temperature) is not particularly limited, but is preferably a time during which the reaction occurs sufficiently, for example, 1 hour to 10 hours.
In addition, the firing atmosphere in the primary firing step S2 is not particularly limited, but in the absence of oxygen gas (in an inert gas atmosphere) in order to prevent the formation of oxidants as impurities and promote the reduction of remaining oxidants. Preferably there is.

(Carbon mixing process)
The carbon mixing step S3 is a step of mixing a carbon raw material into the fired product after the primary firing step S2 in order to coat the positive electrode active material with carbon. In the carbon mixing step S3, the pulverization process may be performed while mixing the carbon raw materials.

(Carbon mixing process: raw material)
Examples of the carbon raw material to be mixed in the carbon mixing step S3 include bitumen and the like, preferably a coal pitch having a softening point of 300 ° C. or lower, particularly preferably a coal pitch having a softening point of 200 ° C. or lower. By using a coal pitch having a low softening point, the positive electrode active material is appropriately carbon-coated, the particle group of the product becomes uniform, and finally the charge / discharge capacity of the positive electrode material can be increased.

  The carbon raw material is 2 wt% or more and 8 wt% or less with respect to the total weight (weight of the fired product after the primary firing step S2 + weight of the carbon raw material) so that the positive electrode active material can be appropriately carbon coated. It is preferable to add such that 3 wt% or more and 6 wt% or less is more preferable.

(Secondary firing process)
The secondary firing step S4 is a step of performing secondary firing (main firing) on the fired product after the carbon mixing step S3.
And in secondary baking process S4, it is necessary to advance reaction which reaches the positive electrode material of a final product completely. Therefore, what is necessary is just to select the temperature which the said reaction advances completely as a calcination temperature (attainment temperature) of secondary baking.
Specifically, the firing temperature (attainment temperature) in the secondary firing step S4 is preferably 600 ° C. or higher and 800 ° C. or lower, and more preferably 650 ° C. or higher and 780 ° C. or lower.

  In the secondary firing step S4, unlike the primary firing step S2, the generation of gas hardly occurs. Therefore, the carbon mixed in the carbon mixing step S3 can be easily coated on the positive electrode active material.

The firing time in the secondary firing step S4 (holding time after reaching the reached temperature) is not particularly limited, but is preferably a time during which the above reaction occurs sufficiently, for example, 1 hour to 10 hours.
Further, the firing atmosphere in the secondary firing step S4 is not particularly limited, but in the absence of oxygen gas (in an inert gas atmosphere) in order to prevent the formation of oxidized oxidants and promote the reduction of remaining oxidants. Is preferred.

(Classification process)
The classification step S5 is a step of performing classification in order to exclude coarse particles from the fired product obtained in the secondary firing step S4.
For example, in the classification process of the classification step S5, particles having a diameter of 30 μm or more may be excluded using a sieve or the like.

  The manufacturing method of the positive electrode material for a lithium secondary battery according to the present embodiment is as described above, but includes other steps between or before and after each step within a range that does not adversely affect each step. May be. For example, when the pulverization process is performed using the wet bead mill in the mixing and pulverizing step S1, a drying step of drying the pulverized product may be included after the mixing and pulverizing step S1. Moreover, a cooling step for cooling the fired product may be included after the primary firing step S2 and the secondary firing step S4. Furthermore, after the classification step S5, a slurrying step of mixing a known binder, a conductive agent (conductive auxiliary agent) or the like may be included in order to apply the positive electrode material to the current collector.

  In addition, as for conditions that are not clearly shown in the respective steps, it is sufficient to use conventionally known conditions, and it is needless to say that the conditions can be appropriately changed as long as the effects obtained by the processing in the respective steps are exhibited.

Next, the positive electrode material for a lithium secondary battery and the manufacturing method thereof according to the present invention will be specifically described by comparing an example satisfying the requirements of the present invention with a comparative example not satisfying the requirements of the present invention.
In Example 1, the case where lithium manganese iron phosphate is used as the positive electrode active material will be described.

[Method for producing positive electrode material]
(Sample 1)
The manufacturing method of the positive electrode material of the test material 1 is shown below.
First, as a positive electrode active material precursor, 30.52 g of lithium hydroxide (LiOH · H ₂ O, manufactured by Toyo Chemical Co., Ltd.) and manganese phosphate (Mn ₃ (PO ₄ ) ₂ · 2H ₂ O, manufactured by Budenheim) and 72.95G, ferric phosphate _{(FePO 4} · 2H 2 O, manufactured by Budenheim Co.) and 26.16G, phosphoric acid _(H 3 PO _4, Kishida chemical Co., Ltd.) was prepared 28.78G. The granular lithium hydroxide was pulverized until D50 (volume-based 50% particle diameter measured based on laser diffraction / scattering method) was 100 μm or less.
In addition, 2.85 g of anatase-type titanium oxide (TiO ₂ , manufactured by Kishida Chemical Co., Ltd.) and 0.32 g of aluminum oxide (Al ₂ O ₃ , manufactured by Kishida Chemical Co., Ltd.) were prepared as precursors of the lithium ion conductor.
As a reducing agent, 6.4 g of ascorbic acid (manufactured by Kishida Chemical Co., Ltd.) was prepared.

  Then, the precursor of the positive electrode active material, the precursor of the lithium ion conductor, and the reducing agent were mixed and pulverized for 5 minutes using a dry pulverizer.

The pulverized product was heated to 450 ° C. and held for 4 hours in a N ₂ gas atmosphere (primary firing). Then, 4 wt% of coal pitch (MCP-200D: softening point: about 200 ° C., manufactured by JFE Chemical Co., Ltd.) was added to the fired product after the primary firing, and pulverized for 5 minutes with a dry pulverizer. Thereafter, the pulverized product was heated to 720 ° C. and held for 6 hours under N ₂ gas atmosphere (secondary firing). Then, the fired product after the secondary firing was cooled and then crushed and classified (excluding those having a diameter of 45 μm or more by sieving).
And the baked material after pulverization and classification, acetylene black (Denka Black (registered trademark), manufactured by Denki Kagaku Kogyo Co., Ltd., 75% press product), polyvinylidene fluoride (manufactured by Kureha Battery Materials Japan, # 9100) , 86: 7: 7 (mass ratio). Next, the obtained mixture was stirred and mixed in N-methylpyrrolidone to obtain a positive electrode mixture slurry (positive electrode material).

(Sample 2)
About the manufacturing method of the positive electrode material of the test material 2, only a different point from the manufacturing method of the positive electrode material of the test material 1 is shown below.
First, as a positive electrode active material precursor, 29.37 g of lithium hydroxide (LiOH · H ₂ O, manufactured by Toyo Chemical Co.) and manganese phosphate (Mn ₃ (PO ₄ ) ₂ · 2H ₂ O, manufactured by Budenheim) and 72.95G, ferric phosphate _{(FePO 4} · 2H 2 O, manufactured by Budenheim Co.) and 26.16G, phosphoric acid _(H 3 PO _4, Kishida chemical Co., Ltd.) was prepared 21.52G. The granular lithium hydroxide was pulverized until D50 (volume-based 50% particle diameter measured based on laser diffraction / scattering method) was 100 μm or less.
As a reducing agent, 6.4 g of ascorbic acid (manufactured by Kishida Chemical Co., Ltd.) was prepared.
In addition, the sample material 2 assumes the case where a lithium ion conductor is not used.

(Sample 3)
About the manufacturing method of the positive electrode material of the test material 3, only a different point from the manufacturing method of the positive electrode material of the test material 1 is shown below.
First, as a precursor of the positive electrode active material, lithium hydroxide (LiOH · H ₂ O, manufactured by Toyo Chemical Co., Ltd.) 32.90 g and manganese phosphate (Mn ₃ (PO ₄ ) ₂ · 2H ₂ O, manufactured by Budenheim) and 72.95G, ferric phosphate _{(FePO 4 · 2H 2 O,} Budenheim Co., Ltd.) and 26.16G, phosphoric acid _(H 3 PO _4, manufactured by Wako pure Chemical Industries, Ltd.) was prepared 21.52G. The granular lithium hydroxide was pulverized until D50 (volume-based 50% particle diameter measured based on laser diffraction / scattering method) was 100 μm or less.
In addition, 8.39 g of anatase-type titanium oxide (manufactured by Kishida Chemical Co., Ltd.) was prepared as a precursor of a lithium ion conductor.
As a reducing agent, 6.4 g of ascorbic acid (manufactured by Kishida Chemical Co., Ltd.) was prepared.
The specimen 3 is assumed to use lithium titanate (hereinafter referred to as “LTO” as appropriate) as the lithium ion conductor.

[Method for producing lithium secondary battery]
The positive electrode material obtained by the above-described manufacturing method was applied to the surface of an aluminum foil as a current collector (application amount: 8 mg / cm ² ). And after application | coating, the positive electrode was manufactured by making it dry.
Then, a metal aluminum plate, a positive and negative electrode current collector, the positive electrode and a metal lithium foil negative electrode are incorporated into a stainless steel coin battery case (model number CR2032) via a separator (manufactured by Celgard), and 1M LiPF ₆ is dissolved as an electrolytic solution. The coin-type lithium secondary battery was manufactured by filling and encapsulating the 7/3 mixed electrolyte of ethyl methyl carbonate / ethylene carbonate (Kishida Chemical Co., Ltd.).
In addition, a series of battery assemblies such as positive and negative electrodes, a diaphragm, and an electrolyte solution were performed in a glove box substituted with argon.

[Evaluation of discharge characteristics]
About the lithium secondary battery of the test materials 1-3, discharge characteristics were evaluated at room temperature (25 degreeC).
Specifically, a discharge curve (1C discharge) showing the relationship between the discharge capacity and the battery voltage was created. In addition, although the discharge curve is a thing at the time of discharging at 1C, this "1C" is the electric current value which discharges the full capacity of a battery in 1 hour.
In FIG. 3, the solid line is the discharge curve of the specimen 1, the dotted line is the discharge curve of the specimen 2, and the one-dot chain line is the discharge curve of the specimen 3.

[Examination of results]
In FIG. 3, when the discharge curves of the test material 1 and the test material 2 are compared, it can be confirmed that the battery voltage of the test material 1 is higher. In addition, it can be confirmed that the area surrounded by the discharge curve and the vertical and horizontal axes of the specimen 1 is wider than the area of the specimen 2.
From these results, the test material 1 including the lithium ion conductor has higher lithium ion conductivity than the test material 2 not including the lithium ion conductor, thereby improving the operating voltage and the discharge capacity. I understood that I was able to do it.

In FIG. 3, when the discharge curves of the test material 2 and the test material 3 are compared, it can be confirmed that the battery voltage of the test material 3 is lower.
From this result, it was found that lithium ion conductivity cannot be improved when LTO is used among lithium ion conductors.
From the results of the above test materials 1 to 3, when lithium manganese iron phosphate is used as the positive electrode active material, the lithium ion conductivity is increased by using LTAP having a particulate form as the lithium ion conductor. It was found that the operating voltage and discharge capacity can be improved.

  Next, Example 2 demonstrates the case where lithium iron phosphate is used as a positive electrode active material.

[Method for producing positive electrode material]
(Sample 4)
About the manufacturing method of the positive electrode material of the test material 4, only a different point from the manufacturing method of the positive electrode material of the test material 1 is shown below.
First, as a positive electrode active material precursor, 113.17 g of lithium carbonate (Li ₂ CO ₃ , manufactured by Toyo Chemical Co., Ltd.) and iron oxalate (FeC ₂ O ₄ .2H ₂ O, manufactured by Kohoku Komoto Co., Ltd.) 534.51 g Then, 352.33 g of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ , manufactured by Shimonoseki Mitsui Chemicals) was prepared. These were mixed and pulverized, heated to 405 degrees and held for 4 hours (primary firing). Then, 3.5 wt% of coal pitch (MCP-110C, manufactured by JFE Chemical Co., Ltd.) as a carbon raw material is mixed with the fired product after the primary firing, and the temperature is raised to 760 ° C. and held for 6 hours (secondary firing). ).
In addition, the test material 4 assumes the case where the ratio of the lithium ion conductor with respect to the sum total of a positive electrode active material and a lithium ion conductor is 0 mol%.

(Sample 5)
About the manufacturing method of the positive electrode material of the test material 5, only a different point from the manufacturing method of the positive electrode material of the test material 4 is shown below.
First, as a positive electrode active material precursor, 114.64 g of lithium carbonate (Li ₂ CO ₃ , manufactured by Toyo Chemical Co., Ltd.) and iron oxalate (FeC ₂ O ₄ .2H ₂ O, manufactured by Kohoku Komoto Co., Ltd.) 534.51 g 362.90 g of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ , manufactured by Shimonoseki Mitsui Chemicals), and 4.16 g of titanium oxide (TiO ₂ , manufactured by Kishida Chemical Co., Ltd.) as a precursor of a lithium ion conductor. Then, 0.47 g of aluminum oxide (Al ₂ O ₃ , manufactured by Kishida Chemical Co., Ltd.) was prepared.
In addition, the sample material 5 assumes the case where the ratio of the lithium ion conductor with respect to the sum total of a positive electrode active material and a lithium ion conductor is 1 mol%.

(Sample 6)
About the manufacturing method of the positive electrode material of the test material 6, only a different point from the manufacturing method of the positive electrode material of the test material 4 is shown below.
First, as a positive electrode active material precursor, 116.64 g of lithium carbonate (Li ₂ CO ₃ , manufactured by Toyo Chemical Co., Ltd.) and iron oxalate (FeC ₂ O ₄ .2H ₂ O, manufactured by Kohoku Komoto Co., Ltd.), 534.51 g Then, 373.47 g of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ , manufactured by Shimonoseki Mitsui Chemicals) was prepared.
Moreover, 8.32 g of titanium oxide (TiO ₂ , manufactured by Kishida Chemical Co., Ltd.) and 0.94 g of aluminum oxide (Al ₂ O ₃ , manufactured by Kishida Chemical Co., Ltd.) were prepared as precursors of the lithium ion conductor.
In addition, the test material 6 assumes the case where the ratio of the lithium ion conductor with respect to the sum total of a positive electrode active material and a lithium ion conductor is 2 mol%.

(Sample 7)
About the manufacturing method of the positive electrode material of the test material 7, only a different point from the manufacturing method of the positive electrode material of the test material 4 is shown below.
First, as a precursor of the positive electrode active material, lithium carbonate _(Li 2 CO _3, manufactured by Toyo Chemical Co.) 117.58G and iron oxalate _{(FeC 2 O 4 · 2H 2} O, manufactured by Hubei Hiroshimotosha) 534.51G Then, 384.04 g of ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ , manufactured by Shimonoseki Mitsui Chemicals) was prepared.
Moreover, 12.48 g of titanium oxide (TiO ₂ , manufactured by Kishida Chemical Co., Ltd.) and 1.41 g of aluminum oxide (Al ₂ O ₃ , manufactured by Kishida Chemical Co., Ltd.) were prepared as precursors of the lithium ion conductor.
In addition, the sample material 7 assumes the case where the ratio of the lithium ion conductor with respect to the sum total of a positive electrode active material and a lithium ion conductor is 3 mol%.

[Method for producing lithium secondary battery]
About the manufacturing method of a lithium secondary battery, it carried out on the same conditions as Example 1. FIG.

[Evaluation of discharge characteristics]
About the lithium secondary battery of the specimens 4-7, the discharge characteristic was evaluated at room temperature (25 degreeC).
Specifically, a discharge curve (5C discharge) showing the relationship between the discharge capacity and the battery voltage was created. The discharge curve was prepared when discharged at 5C. Here, "1C" is the current value that discharges the entire capacity of the battery in one hour. This "5C" The current value is five times the current value.
4 and 5, the dotted line is the discharge curve of the specimen 4, the one-dot chain line is the discharge curve of the specimen 5, and the two-dot chain line is the discharge curve of the specimen 6, which is a solid line Is a discharge curve of the specimen 7.

[Examination of results]
In FIG. 5 showing the state at the start of discharge, the specimen 4 and specimen 5 show almost the same battery voltage, but the specimen 6 and specimen 7 are the specimen 4 and specimen. It can be confirmed that the battery voltage is higher than that of the material 5.
From this result, it was found that when the content of the lithium ion conductor is 2 mol% or more, the lithium ion conductivity is increased and the operating voltage can be improved more reliably.
From the results of the above test materials 4 to 7, when lithium iron phosphate is used as the positive electrode active material, the lithium ion conductivity is ensured by containing 2 mol% or more of LTAP that is in the form of particles as the lithium ion conductor. As a result, it was found that the operating voltage can be improved.

DESCRIPTION OF SYMBOLS 1 Positive electrode active material 2 Lithium ion conductor 10 Positive electrode material (positive electrode material) for lithium secondary batteries
S1 mixing and grinding step S2 primary firing step (firing step)
S3 Carbon mixing process S4 Secondary firing process (firing process)
S5 classification process

Claims (5)

Containing a positive electrode active material and a lithium ion conductor;
The positive electrode active material is at least one of lithium iron manganese phosphate and lithium iron phosphate, and the lithium ion conductor is lithium aluminum titanium phosphate,
The positive electrode material for a lithium secondary battery, wherein the positive electrode active material and the lithium ion conductor are each in the form of particles.   The positive electrode material for a lithium secondary battery according to claim 1, wherein the positive electrode active material is lithium manganese iron phosphate. The positive electrode active material is lithium iron phosphate,
2. The positive electrode material for a lithium secondary battery according to claim 1, wherein a ratio of the lithium ion conductor to a total of the positive electrode active material and the lithium ion conductor is 2 mol% or more. Mixing and pulverizing step of mixing and pulverizing the precursor of the positive electrode active material and the precursor of the lithium ion conductor;
A firing step of firing the pulverized product after the mixing and grinding step;
Including
The positive electrode active material is at least one of lithium manganese iron phosphate and lithium iron phosphate, and the lithium ion conductor is lithium aluminum titanium phosphate. Production method. The firing step includes a primary firing step for firing at a predetermined temperature and a secondary firing step for firing at a temperature higher than the predetermined temperature.
The method for producing a positive electrode material for a lithium secondary battery according to claim 4, further comprising a carbon mixing step of mixing a carbon raw material between the primary baking step and the secondary baking step.

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