JP2015076180A - Positive electrode active material for lithium-ion battery, positive electrode material for lithium-ion battery, positive electrode for lithium-ion battery, and lithium-ion battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sulfide-based positive electrode active material for a lithium-ion battery, capable of obtaining a lithium-ion battery excellent in cycle characteristics.SOLUTION: The positive electrode active material for a lithium-ion battery of the present invention contains Li, Mo, and S as constituent elements. The molar ratio (Li/Mo) of the content of Li to the content of Mo is preferably 2 to 20 inclusive, and the molar ratio (S/Mo) of the content of S to the content of Mo is preferably 3 to 13 inclusive.

Description

  The present invention relates to a positive electrode active material for a lithium ion battery, a positive electrode material for a lithium ion battery, a positive electrode for a lithium ion battery, and a lithium ion battery.

  Lithium ion batteries are generally used as a power source for small portable devices such as mobile phones and notebook computers. Recently, in addition to small portable devices, lithium ion batteries have begun to be used as power sources for electric vehicles and power storage.

  As positive electrode active materials for lithium ion batteries, oxide-based and sulfide-based positive electrode active materials are known. Since a high-capacity lithium ion battery is obtained, a sulfide-based positive electrode active material has been studied as a positive electrode active material that replaces an oxide system (for example, Patent Documents 1 and 2).

International Publication No. 2010/035602 Pamphlet JP 2006-032143 A

  However, although the sulfide-based positive electrode active material has a large theoretical capacity, the volume change accompanying charge / discharge is large, and the cycle characteristics are inferior to those of the oxide-based positive electrode active material. Therefore, the sulfide-based active material has not yet been satisfactory as a positive electrode active material for lithium ion batteries.

  The present inventors have intensively studied in order to provide a sulfide-based positive electrode active material for lithium ion batteries having excellent cycle characteristics. As a result, it has been found that a sulfide-based material containing Li, Mo, and S as constituent elements is excellent in cycle characteristics, and has led to the present invention.

According to the present invention,
Provided is a positive electrode active material for a lithium ion battery containing Li, Mo, and S as constituent elements.

Furthermore, according to the present invention,
There is provided a positive electrode material for a lithium ion battery comprising the positive electrode active material for a lithium ion battery of the present invention as a main component.

Furthermore, according to the present invention,
There is provided a positive electrode for a lithium ion battery, wherein the positive electrode active material layer made of the positive electrode material for a lithium ion battery of the present invention is formed on the surface of a current collector.

Furthermore, according to the present invention,
There is provided a lithium ion battery comprising the positive electrode for a lithium ion battery of the present invention, an electrolyte layer, and a negative electrode.

  According to the present invention, it is possible to provide a sulfide-based positive electrode active material for lithium ion batteries capable of obtaining a lithium ion battery having excellent cycle characteristics, a positive electrode material containing the same, and a lithium ion battery having excellent cycle characteristics. Can do.

It is sectional drawing which shows an example of the structure of the lithium ion battery of embodiment which concerns on this invention.

  Embodiments of the present invention will be described below with reference to the drawings. The figure is a schematic view and does not necessarily match the actual dimensional ratio. In this embodiment, a layer containing a positive electrode active material is referred to as a positive electrode active material layer, and a positive electrode active material layer formed on a current collector is referred to as a positive electrode unless otherwise specified. A layer containing a negative electrode active material is called a negative electrode active material layer, and a negative electrode active material layer formed on a current collector is called a negative electrode.

[Positive electrode active material for lithium ion batteries]
First, the positive electrode active material for a lithium ion battery of this embodiment will be described.
The positive electrode active material for a lithium ion battery of the present embodiment (hereinafter also referred to as a positive electrode active material) contains Li, Mo, and S as constituent elements.

The positive electrode active material of this embodiment consists of a compound containing Li, Mo, and S as essential elements. When the positive electrode active material of this embodiment is used, a lithium ion battery excellent in cycle characteristics can be obtained. Although the reason for this is not necessarily clear, the following reason is presumed.
First, although details will be described later, the positive electrode active material of the present embodiment can be obtained by mixing MoS ₂ and Li ₂ S which are usually raw materials. Here, the raw material MoS ₂ is a material with small volume shrinkage due to lithium ion intercalation. The MoS ₂ in a mixture of Li ₂ S, Increasing the amount of S, and domain refinement of crystalline structure of MoS _2, lithium ions enter and exit by Li-MoS compound as an amorphous to produce It is thought that the number of sites where lithium ions enter and exit increases as the site expands. As a result, it is presumed that the positive electrode active material of the present embodiment is a material in which volume shrinkage due to intercalation is further reduced, and excellent cycle characteristics can be realized.

In the positive electrode active material for a lithium ion battery of the present embodiment, the molar ratio (Li / Mo) of the Li content to the Mo content is preferably 2 or more and 20 or less, more preferably 4 or more and 19. Or less, more preferably 5 or more and 17 or less, and particularly preferably 6 or more and 14 or less. The molar ratio (S / Mo) of the S content to the Mo content is preferably 3 or more and 13 or less, more preferably 4 or more and 12 or less, and further preferably 5 or more and 10 or less. Yes, particularly preferably 6 or more and 9 or less.
By setting Li / Mo and S / Mo within the above ranges, the charge / discharge capacity (mAh / g) can be further improved.
Here, the contents of Li, Mo, and S in the positive electrode active material of the present embodiment can be determined by, for example, ICP emission spectroscopic analysis.

Further, the positive electrode active material for a lithium ion battery of the present embodiment is not particularly limited, but the average particle size d ₅₀ in the weight-based particle size distribution by the laser diffraction / scattering particle size distribution measurement method is preferably 0.5 μm or more and 20 μm or less. More preferably, it is 1 μm or more and 10 μm or less.
The average particle size d ₅₀ of the positive electrode active material to be in the above range, while maintaining good handling properties, it can be manufactured more density of the positive electrode.

Further, the positive electrode active material for a lithium ion battery of the present embodiment is not particularly limited, but the specific surface area according to the BET three-point method in nitrogen adsorption is preferably 0.1 m ² / g or more and 4 m ² / g or less, more preferably It is 0.2 m ² / g or more and 2 m ² / g or less.
When the specific surface area by the BET three-point method in nitrogen adsorption is not more than the above upper limit value, the irreversible reaction between the positive electrode active material and the electrolyte can be further suppressed.
Moreover, the permeability of the electrolyte to the positive electrode active material can be improved by setting the specific surface area by the BET three-point method in nitrogen adsorption to be the above lower limit value or more.

[Method for producing positive electrode active material for lithium ion battery]
It continues and demonstrates the manufacturing method of the positive electrode active material for lithium ion batteries of this embodiment.
The positive electrode active material of the present embodiment can be obtained, for example, by pulverizing and mixing MoS ₂ and Li ₂ S that are raw materials and, if necessary, S (sulfur). This will be specifically described below.

First, the reaction molar ratio of MoS ₂ with respect to _{Li 2 S (MoS 2 / Li} 2 S) is preferably 0.05 to 1.2, more preferably 0.10 to 0.50, particularly preferably 0.12 MoS ₂ and Li ₂ S are mixed so as to be 0.35 or less. In order to increase the amount of S in the obtained positive electrode active material, S (sulfur) may be further added.
Here, the mixing molar ratio of MoS ₂ with respect to Li ₂ S, usually a reaction molar ratio of MoS ₂ with respect to Li ₂ S. The mixing molar ratio of the present embodiment can be determined by, for example, ICP emission spectroscopic analysis, but is usually calculated from the weight ratio of preparation.

MoS ₂ and Li 2 as a _{method S} mixing pulverization is not particularly limited as long as the mixing method capable of uniformly pulverized and mixed MoS ₂ and Li 2 _S, for example, be carried out by stirring or mechanochemical treatment under inert atmosphere Can do. It is preferable to carry out by mechanochemical treatment in an inert atmosphere. When mechanochemical treatment is used, MoS ₂ and Li ₂ S can be mixed while being pulverized into fine particles, so that the contact area between MoS ₂ and Li ₂ S can be increased. Thereby, it is possible to accelerate the reaction between MoS ₂ and Li 2 _S, can be obtained more efficiently positive electrode active material of the present embodiment.

  Here, the mixing method by mechanochemical treatment is a method of mixing while applying mechanical energy such as shearing force, collision force or centrifugal force to the object to be mixed. Examples of the apparatus that performs mixing by mechanochemical treatment include pulverizers / dispersers such as a ball mill, a bead mill, and a vibration mill.

The underactive atmosphere means a vacuum atmosphere of 1 to 10 ⁻⁵ Pa or an inert gas atmosphere. In the non-active atmosphere, the dew point is preferably −50 ° C. or lower, and more preferably −60 ° C. or lower in order to avoid contact with moisture. The term “inert gas atmosphere” means an atmosphere of an inert gas such as argon gas, helium gas, or nitrogen gas. These inert gases are preferably as high as possible in order to prevent impurities from entering the product. The method of introducing the inert gas into the mixed system is not particularly limited as long as the mixed system is filled with an inert gas atmosphere. However, the inert gas is purged, and a constant amount of inert gas is continuously introduced. The method etc. are mentioned.

Moreover, when mixing MoS ₂ and Li ₂ S, an aprotic organic solvent such as hexane, toluene, or xylene may be added, and the raw materials may be dispersed in a solvent. By carrying out like this, it can mix more efficiently.

Mixing conditions such as agitation speed, processing time, temperature, reaction pressure, and gravitational acceleration applied to the mixture when pulverizing and mixing MoS ₂ and Li ₂ S can be appropriately determined depending on the amount of the mixture processed.

(Li ₂ S)
Is not particularly restricted but includes Li 2 _S of this embodiment, use may be made of a Li 2 _S, which is commercially available, for example, be used Li 2 _S obtained by reacting lithium hydroxide and hydrogen sulfide Good. From the viewpoint of obtaining a high-purity positive electrode active material, it is preferable to use Li ₂ S with few impurities.

The average particle size d ₅₀ in the weight particle size distribution by a laser diffraction scattering particle size distribution measurement method of Li 2 _S of this embodiment is preferably not average particle size d ₅₀ 20 [mu] m or less, more preferably 10μm or less, Particularly preferably, it is 5 μm or less. The contact area between MoS ₂ and Li ₂ S can be increased by setting the average particle diameter d ₅₀ to the upper limit value or less. This makes it possible to accelerate the reaction between MoS ₂ and Li 2 _S, can be obtained more efficiently positive electrode active material of the present embodiment.
Moreover, the lower limit of the average particle diameter d ₅₀ of Li ₂ S is not particularly limited, but is, for example, 0.1 μm or more from the viewpoint of handleability.

(MoS ₂ )
Is not particularly limited as MoS ₂ of the present embodiment, it is possible to use a MoS _2, which is commercially available. From the viewpoint of obtaining a high-purity positive electrode active material, it is preferable to use MoS ₂ with less impurities.

The average particle size d ₅₀ in the weight particle size distribution by laser diffraction scattering of MoS ₂ particle size distribution measurement method of this embodiment is preferably not more than an average particle size d ₅₀ 20 m, more preferably 10μm or less. The contact area between MoS ₂ and Li ₂ S can be increased by setting the average particle diameter d ₅₀ to the upper limit value or less. Thereby, it is possible to accelerate the reaction between MoS ₂ and Li 2 _S, can be obtained more efficiently positive electrode active material of the present embodiment.
The lower limit of the average particle size d ₅₀ of MoS ₂ is not particularly limited, from the viewpoint of handling property, for example 1μm or more.

(S)
It does not specifically limit as S (sulfur) of this embodiment, Commercially available sulfur can be used. From the viewpoint of obtaining a high-purity positive electrode active material, it is preferable to use sulfur with less impurities.

  With such a manufacturing method, the positive electrode active material of the present embodiment can be obtained.

In the method for producing a positive electrode active material of the present embodiment, a step of pulverizing, classifying, or granulating the obtained positive electrode active material may be further performed as necessary. For example, a positive electrode active material having a desired particle size can be obtained by making fine particles by pulverization and then adjusting the particle size by classification operation or granulation operation. It does not specifically limit as said grinding | pulverization method, Well-known grinding | pulverization methods, such as a mortar, a rotation mill, and a coffee mill, can be used. Moreover, it does not specifically limit as said classification method, Well-known methods, such as a sieve, can be used.
These pulverization or classification are preferably performed in an inert gas atmosphere or a vacuum atmosphere from the viewpoint that contact with moisture in the air can be prevented.
Moreover, the pulverization, classification, or granulation step may be performed on the raw materials MoS ₂ , Li ₂ S, and S, or may be performed on the above mixture.

  In order to obtain the positive electrode active material of this embodiment, it is important to appropriately adjust each of the above steps. However, the manufacturing method of the positive electrode active material of this embodiment is not limited to the above methods, and the positive electrode active material of this embodiment can be obtained by appropriately adjusting various conditions.

  Since the positive electrode active material of this embodiment has a high charge / discharge capacity and excellent cycle characteristics, it is useful as a positive electrode active material for lithium ion batteries.

[Positive electrode material for lithium ion batteries]
Next, the positive electrode material for a lithium ion battery of this embodiment will be described.
The positive electrode material for lithium ion batteries of the present embodiment (hereinafter also referred to as positive electrode material) contains the positive electrode active material for lithium ion batteries of the present embodiment as a main component. And although the positive electrode material of this embodiment is not specifically limited, As a component other than the positive electrode active material of this embodiment, a binder, a conductive support agent, a thickener, a solid electrolyte, the positive electrode active material of this embodiment mentioned above, for example One or more materials selected from different types of positive electrode active materials may be included.

(binder)
The positive electrode material of the present embodiment may include a binder having a role of binding the positive electrode active materials to each other and the positive electrode active material and the current collector. However, since the positive electrode active material of this embodiment undergoes hydrolysis when contacted with water, water-soluble polyvinyl alcohol, polyacrylic acid, carboxymethylcellulose, polytetrafluoroethylene fine particles, styrene / butadiene rubber fine particles, etc. are dispersed in water. The binder is not suitable.
The binder of this embodiment is not particularly limited as long as it is an organic solvent-based binder among binders usually used in lithium ion batteries, and examples thereof include polytetrafluoroethylene, polyvinylidene fluoride, and polyimide. These binders may be used alone or in combination of two or more.

(Thickener)
The positive electrode material of this embodiment is usually unnecessary because it is relatively easy to obtain viscosity when using an organic solvent-based binder, but it may contain a thickener from the viewpoint of adjusting the fluidity of the slurry suitable for coating. Good. Examples of the thickening agent of the present embodiment include swellable viscous minerals such as scumite and polyvinyl carboxylic acid amide. These thickeners may be used individually by 1 type, and may be used in combination of 2 or more types.

(Conductive aid)
The positive electrode material of this embodiment may contain a conductive additive from the viewpoint of improving the conductivity of the positive electrode. The conductive auxiliary agent of the present embodiment is not particularly limited as long as it is a normal conductive auxiliary agent that can be used for a lithium ion battery. For example, carbon black such as acetylene black and ketjen black, carbon such as vapor grown carbon fiber, etc. Materials.

(Solid electrolyte)
When the positive electrode material of this embodiment is used for a positive electrode for an all-solid-state lithium ion battery, the positive electrode material of this embodiment preferably contains a solid electrolyte. The solid electrolyte of the present embodiment is not particularly limited as long as it has ion conductivity and insulating properties, but those generally used for all solid lithium ion batteries can be used. Examples thereof include a sulfide solid electrolyte material and an oxide solid electrolyte material. Among these, a sulfide solid electrolyte material is preferable. Thereby, interface resistance with the positive electrode active material of this embodiment falls, and it can be set as the all-solid-state lithium ion battery excellent in output characteristics.

Examples of the sulfide solid electrolyte material of the present embodiment include Li ₂ S—P ₂ S ₅ material, Li ₂ S—SiS ₂ material, Li ₂ S—GeS ₂ material, Li ₂ S—Al ₂ S ₃ material, and the like. Is mentioned. Among these, Li ₂ S—P ₂ S ₅ material is preferable because lithium ion conductivity is excellent and the manufacturing method is simple.

(A type of positive electrode active material different from the positive electrode active material of the present embodiment)
The positive electrode material of the present embodiment may include a different type of positive electrode active material from the positive electrode active material of the present embodiment described above as long as the object of the present invention is not impaired. The type of positive electrode active material different from the positive electrode active material of the present embodiment is not particularly limited, and generally known materials can be used. For example, composite oxides such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), and lithium manganese oxide (LiMn ₂ O ₄ ); conductive polymers such as polyaniline and polypyrrole; Li ₂ S and the like Sulfides can be used.

(Combination ratio of various materials)
The blending of various materials of the positive electrode material for a lithium ion battery of the present embodiment is not particularly limited because it is appropriately determined according to the intended use of the battery, and can be set according to generally known information. .

[Positive electrode for lithium ion batteries]
Next, a positive electrode for a lithium ion battery including the positive electrode material of the present embodiment will be described.
Although the positive electrode for lithium ion batteries of this embodiment is not specifically limited, For example, it is obtained by forming the positive electrode active material layer which consists of positive electrode materials of this embodiment on the surface of collectors, such as aluminum.

  The thickness and density of the positive electrode for a lithium ion battery according to this embodiment are not particularly limited because they are appropriately determined according to the intended use of the battery, and can be set according to generally known information.

[Method for producing positive electrode for lithium ion battery]
Below, the manufacturing method of the positive electrode for lithium ion batteries of this embodiment is demonstrated.
Although the positive electrode for lithium ion batteries of this embodiment is not particularly limited, it can be generally produced according to a known method. For example, the following steps (A) and (B) are included.
(A) The process of preparing a positive electrode slurry (B) The process of forming a positive electrode active material layer by apply | coating the obtained positive electrode slurry on a collector.

<Step of preparing positive electrode slurry>
First, the process of preparing (A) positive electrode slurry will be described.
Preparation of the positive electrode slurry of this embodiment is not particularly limited because it can be generally performed according to a known method. For example, the positive electrode active material of this embodiment, and if necessary, a binder, a thickener, a conductive material. An auxiliary agent, an electrolyte, a positive electrode active material of a type different from the positive electrode active material of the present embodiment, and the like can be prepared by mixing with a mixer and dispersing or dissolving in a solvent. The mixing ratio of each material in the positive electrode slurry is appropriately determined according to the intended use of the battery.
A known mixer such as a ball mill or a planetary mixer can be used as the mixer, and is not particularly limited. The mixing method is not particularly limited, and can be performed according to a known method.

<Process for forming positive electrode active material layer>
Subsequently, (B) the step of forming the positive electrode active material layer by applying the obtained positive electrode slurry onto the current collector will be described.

  As a method for applying the positive electrode slurry onto the current collector, generally known methods can be used. Examples thereof include a reverse roll method, a direct roll method, a doctor blade method, a knife method, an extrusion method, a curtain method, a gravure method, a bar method, a dip method, and a squeeze method.

The positive electrode slurry may be applied only on one side of the current collector or on both sides. The thickness, length and width of the coating layer can be appropriately determined according to the size and use of the battery.
As a method for drying the applied positive electrode slurry, generally known methods can be used.

  It does not specifically limit as a collector used for manufacture of the positive electrode of this embodiment, The normal collector which can be used for lithium ion batteries, such as aluminum foil, can be used.

  The positive electrode for a lithium ion battery of this embodiment may be pressed as necessary to adjust the density of the positive electrode. As a pressing method, a generally known method can be used.

[Lithium ion battery]
Next, the lithium ion battery 100 according to the present embodiment will be described. FIG. 1 is a cross-sectional view showing an example of the structure of a lithium ion battery according to an embodiment of the present invention.

The all solid-state lithium ion battery 100 according to the present embodiment includes, for example, a positive electrode 110, an electrolyte layer 120, and a negative electrode 130. And the positive electrode 110 is the positive electrode 100 for lithium ion batteries which concerns on this embodiment.
The lithium ion battery 100 of this embodiment is generally manufactured according to a known method. For example, the positive electrode and the negative electrode of the present embodiment are stacked in the center of the separator and formed into a cylindrical shape, a coin shape, a square shape, a film shape, or any other shape, and the nonaqueous electrolytic solution is enclosed.

(Nonaqueous electrolyte)
The nonaqueous electrolytic solution of the present embodiment is a solution in which an electrolyte is dissolved in a solvent.

(Electrolytes)
As the electrolyte, any known lithium salt can be used, and may be selected according to the type of active material. For _{example, LiClO 4, LiBF 4, LiPF} 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiB 10 Cl 10, LiAlCl 4, LiCl, LiBr, LiB (C 2 H 5) 4, CF 3 SO ₃ Li, CH ₃
Examples thereof include SO ₃ Li, LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, and a lower fatty acid carboxylate.

  The solvent for dissolving the electrolyte is not particularly limited as long as it is usually used as a liquid for dissolving the electrolyte. Ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC) Carbonates such as diethyl carbonate (DEC), methyl ethyl carbonate (MEC), vinylene carbonate (VC); lactones such as γ-butyrolactone and γ-valerolactone; trimethoxymethane, 1,2-dimethoxyethane, diethyl ether Ethers such as 2-ethoxyethane, tetrahydrofuran and 2-methyltetrahydrofuran; sulfoxides such as dimethyl sulfoxide; oxolanes such as 1,3-dioxolane and 4-methyl-1,3-dioxolane; Nitrogenous compounds such as acetonitrile, nitromethane, formamide, dimethylformamide; organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate; phosphate triesters and diglymes; Sulfolanes such as sulfolane and methylsulfolane; oxazolidinones such as 3-methyl-2-oxazolidinone; sultones such as 1,3-propane sultone, 1,4-butane sultone and naphtha sultone; These may be used individually by 1 type and may be used in combination of 2 or more type.

  The separator of the present embodiment is not particularly limited as long as it has a function of electrically insulating the positive electrode and the negative electrode and transmitting lithium ions. For example, a porous film can be used.

  A microporous polymer film is preferably used as the porous film, and examples of the material include polyolefin, polyimide, polyvinylidene fluoride, and polyester. In particular, a porous polyolefin film is preferable, and specific examples include a porous polyethylene film and a porous polypropylene film.

(Negative electrode)
The negative electrode for lithium ion batteries of this embodiment is not particularly limited, and those generally used for lithium ion batteries can be used. The negative electrode of the present embodiment is not particularly limited, but can be generally produced according to a known method. For example, it can be obtained by forming a negative electrode active material layer containing a negative electrode active material on the surface of a current collector such as copper.

  The negative electrode active material of the present embodiment is not particularly limited as long as it is a normal negative electrode active material that can be used for the negative electrode of a lithium ion battery. For example, natural graphite, artificial graphite, resin charcoal, carbon fiber, activated carbon, hard carbon And carbon materials such as soft carbon; lithium-based metals such as lithium metal and lithium alloy; metals such as silicon and tin; and conductive polymers such as polyacene, polyacetylene, and polypyrrole.

(All-solid lithium ion battery)
The lithium ion battery of this embodiment can be made into an all-solid-state lithium ion battery by using a solid electrolyte instead of the above-mentioned non-aqueous electrolyte as an electrolyte.
The all-solid-state lithium ion battery of this embodiment has, for example, the positive electrode, the negative electrode, and the solid electrolyte layer formed of a solid electrolyte between the positive electrode and the negative electrode.
Although it does not specifically limit as a solid electrolyte of this embodiment, Generally a well-known thing can be used. For example, the same thing as the solid electrolyte contained in the positive electrode mentioned above can be used.
When the positive electrode active material of the present embodiment is used as the positive electrode active material of an all-solid-state lithium ion battery, a lithium ion battery having good battery characteristics such as charge / discharge efficiency and cycle characteristics and high safety can be obtained. it can.

As mentioned above, although embodiment of this invention was described, these are illustrations of this invention and various structures other than the above are also employable.
It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.

  Hereinafter, although an example and a comparative example explain the present invention, the present invention is not limited to these. In Examples and Comparative Examples, “mAh / g” indicates a capacity density per 1 g of the positive electrode active material.

[1] Measuring method First, measuring methods in the following examples and comparative examples will be described.

(1) Particle size distribution The particle size distribution of the positive electrode active materials obtained in Examples and Comparative Examples was measured by a laser diffraction method using a laser diffraction / scattering particle size distribution measuring apparatus (manufactured by Malvern, Mastersizer 3000). From the measurement results, the particle diameter (d ₅₀ , average particle diameter) at 50% accumulation in the weight-based cumulative distribution was determined for each positive electrode active material. Similarly, the average particle diameter of each raw material was determined.

(2) ICP emission spectroscopic analysis Each of the positive electrode active materials obtained in Examples and Comparative Examples was measured by ICP emission spectroscopic analysis using an ICP emission spectroscopic analyzer (manufactured by Seiko Instruments Inc., SPS3000). The mass% of each element was calculated | required, respectively, and the molar ratio of each element was calculated based on those values, respectively.

(3) Charge / Discharge Test Under an argon atmosphere, 333 mg of the positive electrode active material obtained in Examples and Comparative Examples, 333 mg of acetylene black as a conductive additive, and 333 mg of Li ₁₀ P ₃ S ₁₂ as a solid electrolyte Were placed in an Al ₂ O ₃ pot, ZrO ₂ balls were added, and the Al ₂ O ₃ pot was sealed. Next, the Al ₂ O ₃ pot was placed on a ball mill turntable and mixed at 97 rpm for 24 hours. The mixed powder was press-molded to obtain a positive electrode active material layer (diameter φ = 14 mm, thickness t = 0.03 mm, 3.2 mg). Subsequently, the positive electrode active material layer was press-bonded to an aluminum foil as a current collector through a conductive acrylic adhesive layer to produce a positive electrode. Ni fine particles were used for the conductive material of the conductive acrylic adhesive layer.
Further, the positive electrode obtained by the above method, the solid electrolyte layer (Li ₁₀ P ₃ S ₁₂ , 100 mg), and the indium foil (φ = 14 mm, t = 0.5 mm) as the negative electrode were laminated in this order to obtain all solid lithium An ion battery was produced. Next, the all solid state lithium ion battery obtained was charged to a charge termination voltage 3.0V at a current density of 65μA / cm ^2, at a current density of 65μA / cm ^2, until the discharge cutoff potential 0.4V discharge Charging / discharging was performed 10 times under the above conditions.
Here, the discharge capacity change rate [%] was the 10th discharge capacity when the first discharge capacity was 100%.

[2] Production of positive electrode active material <Example 1>
Under an argon atmosphere, in an Al ₂ O ₃ pot, MoS ₂ (Wako Pure Chemical Industries, 970 mg, 6.1 mmol, average particle size: 10 μm) and Li ₂ S (Sigma Aldrich Japan, 835 mg, 18 0.2 mmol, average particle diameter: 5 μm) and S (Sigma Aldrich Japan, 194 mg, 6.1 mmol) were weighed and added, and ZrO ₂ balls were further added, and the Al ₂ O ₃ pot was sealed.
Next, the Al ₂ O ₃ pot was placed on a ball mill turntable and treated at 97 rpm for 4 days to obtain a mixture.

The obtained positive electrode active material was pulverized with a mortar and classified with a sieve having an opening of 43 μm to obtain a positive electrode active material 1 having an average particle diameter d ₅₀ of 5 μm.

<Example 2>
Example 1 except that the amount of MoS ₂ charged to the Al ₂ O ₃ pot was changed to 1742 mg (10.9 mmol), the amount of Li ₂ S charged was 500 mg (10.9 mmol), and the amount of S was changed to 0 mg. in the same manner as the average particle size d ₅₀ to obtain a positive electrode active material 2 of 10 [mu] m.

<Example 3>
Example 1 except that the amount of MoS ₂ charged to the Al ₂ O ₃ pot was changed to 1424 mg (8.9 mmol), the amount of Li ₂ S charged was 818 mg (17.8 mmol), and the amount of S was changed to 0 mg. in the same manner as the average particle size d ₅₀ to obtain a positive electrode active material 3 of 7 [mu] m.

<Example 4>
Example 1 except that the amount of MoS ₂ charged to the Al ₂ O ₃ pot was changed to 1205 mg (7.5 mmol), the amount of Li ₂ S input was 1037 mg (22.6 mmol), and the amount of S input was changed to 0 mg. in the same manner as the average particle size d ₅₀ to obtain a positive electrode active material 4 of the 5 [mu] m.

<Example 5>
Example 1 except that the amount of MoS ₂ introduced into the Al ₂ O ₃ pot was changed to 1044 mg (6.5 mmol), the amount of Li ₂ S introduced was 1198 mg (26.08 mmol), and the amount of S introduced was changed to 0 mg. in the same manner as the average particle size d ₅₀ to obtain a positive electrode active material 5 of 4 [mu] m.

<Example 6>
Example 1 except that the amount of MoS ₂ charged into the Al ₂ O ₃ pot was 921 mg (5.8 mmol), the amount of Li ₂ S was 1321 mg (28.8 mmol), and the amount of S was 0 mg. In the same manner as above, a positive electrode active material 6 having an average particle diameter d ₅₀ of 4 μm was obtained.

<Example 7>
Example 1 except that the amount of MoS ₂ introduced into the Al ₂ O ₃ pot was changed to 824 mg (5.1 mmol), the amount of Li ₂ S introduced was 1418 mg (30.9 mmol), and the amount of S introduced was changed to 0 mg. In the same manner as above, a positive electrode active material 7 having an average particle diameter d ₅₀ of 3 μm was obtained.

<Example 8>
Example 1 except that the amount of MoS ₂ introduced into the Al ₂ O ₃ pot was changed to 745 mg (4.7 mmol), the amount of Li ₂ S introduced was 1497 mg (32.5 mmol), and the amount of S introduced was changed to 0 mg. in the same manner as the average particle size d ₅₀ to obtain a positive electrode active material 8 of the 2 [mu] m.

<Example 9>
Example 1 except that the amount of MoS ₂ charged into the Al ₂ O ₃ pot was changed to 680 mg (4.2 mmol), the amount of Li ₂ S was changed to 1562 mg (34.0 mmol), and the amount of S was changed to 0 mg. In the same manner as above, a positive electrode active material 9 having an average particle diameter d ₅₀ of 2 μm was obtained.

<Example 10>
Example 1 except that the amount of MoS ₂ charged to the Al ₂ O ₃ pot was changed to 626 mg (3.9 mmol), the amount of Li ₂ S input was 1616 mg (35.2 mmol), and the amount of S input was changed to 0 mg. in the same manner as the average particle size d ₅₀ to obtain a positive electrode active material 10 of 1 [mu] m.

<Example 11>
The amount of MoS ₂ charged into the Al ₂ O ₃ pot was changed to 1344 mg (8.4 mmol), the amount of Li ₂ S was changed to 386 mg (8.4 mmol), and the amount of S was changed to 269 mg (9.0 mmol). otherwise in the same manner as in example 1, the average particle size d ₅₀ to obtain a positive electrode active material 11 of the 12 [mu] m.

<Example 12>
The amount of MoS ₂ charged into the Al ₂ O ₃ pot was changed to 1127 mg (7.0 mmol), the amount of Li ₂ S was changed to 647 mg (14.1 mmol), and the amount of S was changed to 226 mg (7.0 mmol). otherwise in the same manner as in example 1, the average particle size d ₅₀ to obtain a positive electrode active material 12 of the 10 [mu] m.

<Example 13>
The amount of MoS ₂ charged into the Al ₂ O ₃ pot was changed to 684 mg (4.3 mmol), the amount of Li ₂ S was changed to 1178 mg (25.6 mmol), and the amount of S was changed to 137 mg (4.3 mmol). otherwise in the same manner as in example 1, the average particle size d ₅₀ to obtain a positive electrode active material 13 of 5 [mu] m.

<Comparative Example 1> Example 1 except that the amount of MoS ₂ charged into the Al ₂ O ₃ pot was changed to 1999 mg (12.4 mmol), the amount of Li ₂ S was changed to 0 mg, and the amount of S was changed to 0 mg. in the same manner as the average particle size d ₅₀ to obtain a positive electrode active material 14 of 8 [mu] m.

<Comparative Example 2> The amount of MoS ₂ charged into the Al ₂ O ₃ pot was changed to 1665 mg (8.7 mmol), the amount of Li ₂ S charged was 0 mg, and the amount of S was changed to 334 mg (10.4 mmol). otherwise in the same manner as in example 1, the average particle size d ₅₀ to obtain a positive electrode active material 15 of the 12 [mu] m.

<Comparative Example 3> Example 1 except that the input amount of Li ₂ S charged into the Al ₂ O ₃ pot was changed to 1999 mg (43.5 mmol), the input amount of MoS ₂ was changed to 0 mg, and the input amount of S was changed to 0 mg. in the same manner as the average particle size d ₅₀ to obtain a positive electrode active material 16 of 1 [mu] m.

Table 1 shows the Li / Mo molar ratio, S / Mo molar ratio, and charge / discharge test results of the positive electrode active materials 1 to 16 described above.
The positive electrode active materials 1 to 13 obtained in the examples were superior in cycle characteristics as compared with the positive electrode active materials 14 to 16 obtained in the comparative examples.

100 Lithium ion battery 110 Positive electrode 120 Electrolyte layer 130 Negative electrode

Claims (12)

  A positive electrode active material for a lithium ion battery containing Li, Mo, and S as constituent elements. The positive electrode active material for a lithium ion battery according to claim 1,
The molar ratio (Li / Mo) of the Li content to the Mo content is 2 to 20, and the molar ratio (S / Mo) of the S content to the Mo content is 3 or more. The positive electrode active material for lithium ion batteries which is 13 or less. The positive electrode active material for a lithium ion battery according to claim 1 or 2,
A positive electrode active material for a lithium ion battery, having an average particle diameter d ₅₀ in a weight-based particle size distribution measured by a laser diffraction / scattering particle size distribution measurement method of 0.5 μm to 20 μm. The positive electrode active material for a lithium ion battery according to any one of claims 1 to 3,
A positive electrode active material for a lithium ion battery obtained by pulverizing and mixing MoS ₂ and Li ₂ S as raw materials. The positive electrode active material for a lithium ion battery according to any one of claims 1 to 3,
A positive electrode active material for a lithium ion battery obtained by pulverizing and mixing raw materials MoS ₂ , Li ₂ S, and S. The positive electrode active material for a lithium ion battery according to claim 4 or 5,
The Li ₂ reaction molar ratio of the MoS ₂ for S _(MoS 2 / _Li 2 S) is 0.05 to 1.2, the positive electrode active material for lithium ion batteries.   The positive electrode material for lithium ion batteries which contains the positive electrode active material for lithium ion batteries as described in any one of Claims 1 thru | or 6 as a main component. The positive electrode material for a lithium ion battery according to claim 7,
A positive electrode material for a lithium ion battery, further comprising a conductive additive. The positive electrode material for a lithium ion battery according to claim 7 or 8,
A positive electrode material for a lithium ion battery, further comprising a solid electrolyte.   The positive electrode for lithium ion batteries formed by forming the positive electrode active material layer which consists of a positive electrode material for lithium ion batteries as described in any one of Claims 7 thru | or 9 on the surface of a collector.   The lithium ion battery provided with the positive electrode for lithium ion batteries of Claim 10, an electrolyte layer, and a negative electrode. The lithium ion battery according to claim 11,
A lithium ion battery, wherein the electrolyte layer is formed of a solid electrolyte.

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