JP6338840B2 - Negative electrode material for lithium ion battery, negative electrode for lithium ion battery, and lithium ion battery - Google Patents

Description

  The present invention relates to a negative electrode material for a lithium ion battery, a negative 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 a negative electrode active material for a lithium ion battery, an active material mainly composed of metallic silicon is known. Since a silicon-based negative electrode active material can provide a high-capacity lithium ion battery, research is being conducted as an alternative to a carbon material-based negative electrode active material such as graphite (for example, Patent Document 1).

JP 2012-33440 A

  However, the silicon-based negative electrode active material has a large volume change due to charge and discharge, and the cycle characteristics are inferior to the carbon material-based negative electrode active material. Therefore, the silicon-based negative electrode active material has not yet been satisfactory as a negative electrode active material for lithium ion batteries.

  The present inventors have intensively studied to provide a silicon-based negative electrode active material that is excellent in cycle characteristics and discharge capacity. As a result, it has been found that what is obtained by grinding and mixing a sulfide solid electrolyte material containing Li, P, and S as constituent elements and an alloy material containing Li and Si as constituent elements is excellent in cycle characteristics and discharge capacity. The present invention has been reached.

According to the present invention,
A sulfide solid electrolyte material containing Li, P, and S as constituent elements;
An alloy material containing Li and Si as constituent elements;
Carbon materials,
A negative electrode material for a lithium ion battery comprising a pulverized mixture of
The pulverized mixture includes Si fine particles having a crystallite size that cannot be detected by X-ray diffraction using CuKα rays as a radiation source, and lithium sulfide.
In the X-ray diffraction measurement using CuKα ray as a radiation source, the pulverized mixture does not detect both the diffraction peak derived from the sulfide solid electrolyte material and the diffraction peak derived from the alloy material, and the diffraction of the lithium sulfide. anode material for der Ru lithium ion battery a peak is detected is provided.

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

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

  According to the present invention, a silicon-based negative electrode material for a lithium ion battery capable of obtaining a lithium ion battery excellent in cycle characteristics and discharge capacity, a negative electrode using the same, and a lithium ion battery excellent in cycle characteristics and discharge capacity are provided. Can be provided.

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 the present embodiment, unless otherwise specified, a layer formed of a positive electrode material is referred to as a positive electrode active material layer, and a layer in which a positive electrode active material layer is formed on a current collector is referred to as a positive electrode. A layer formed of the negative electrode material is referred to as a negative electrode active material layer, and a negative electrode active material layer formed on a current collector is referred to as a negative electrode.

[Anode material for lithium ion batteries]
First, the negative electrode material for a lithium ion battery of this embodiment will be described.
The negative electrode material for lithium ion batteries of the present embodiment (hereinafter also referred to as negative electrode material) is a sulfide solid electrolyte material containing Li, P, and S as constituent elements (hereinafter referred to as Li-P-S based solid electrolyte material). ) And an alloy material containing Li and Si as constituent elements (hereinafter also referred to as Li—Si alloy material) are obtained by pulverization and mixing.

An example of the Li—PS—S solid electrolyte material is a compound represented by Li _X P _Y S _Z. Here, X is preferably 4 or more and 15 or less, more preferably 5 or more and 12 or less, and still more preferably 7 or more and 11 or less. Y is preferably 1 or more and 3 or less, more preferably 2 or more and 3 or less. Z is preferably 6 or more and 14 or less, more preferably 7 or more and 13 or less, and further preferably 9 or more and 12 or less. Specific examples of the compound include Li ₁₀ P ₃ S _12, Li ₁₁ P ₃ S _12, Li ₁₂ P ₃ S _12, Li ₉ P ₃ S _12, Li ₇ P ₃ S _{11, and} Li ₄ P ₂ S _{6. , Li 4 P 2 S 7,} Li 8 P 2 S 9, Li 7 P 1 S 6 , and the like.
Here, as for the Li—PS—S solid electrolyte material, for example, Li ₂ S, P ₂ S ₅ , and Li ₃ N as necessary are mixed at a predetermined ratio, and mixed pulverization such as mechanochemical treatment is performed. Can be manufactured.

An example of the Li—Si based alloy material is a compound represented by Li _A Si _B. Here, A is preferably 7 or more and 25 or less, more preferably 13 or more and 22 or less. B is preferably 3 or more and 7 or less, more preferably 4 or more and 5 or less. Specific examples of the compound include Li ₂₂ Si _5, Li ₁₃ Si _{4, and} Li ₇ Si ₃ .
The Li—Si based alloy material can be manufactured, for example, by melting and mixing Li and Si at a predetermined ratio and then pulverizing.

The reaction molar ratio of the Li—Si based alloy material to the Li—PS—S based solid electrolyte material is the formation or crystallization of Si aggregates due to the increase in the amount of Si fine particles produced, and the Si fine particles are Li ₂ S and Li, From the viewpoint of creating a uniformly dispersed state in a glass solid electrolyte containing P and S as main components, it is preferably 1.5 or more and 7.7 or less, more preferably 1.9 or more and 3.7 or less.

When the negative electrode material of the present embodiment is used, the cycle characteristics of the lithium ion battery can be improved. Although the reason for this is not necessarily clear, the following reason is presumed.
First, when an X-ray diffraction measurement using CuKα rays as a radiation source was performed on a material obtained by pulverizing and mixing Li ₁₁ P ₃ S ₁₂ and Li ₂₂ Si _5, it was derived from Li ₁₁ P ₃ S ₁₂ . The diffraction peak and the diffraction peak derived from Li ₂₂ Si ₅ disappear, and the diffraction peak of lithium sulfide (Li ₂ S) is detected.
Since the peaks of Li ₁₁ P ₃ S ₁₂ and Li ₂₂ Si ₅ have disappeared, it can be confirmed that Li ₁₁ P ₃ S ₁₂ and Li ₂₂ Si ₅ react by pulverization and mixing and are vitrified. Further, Li ₂ since the peak of S is _detected, Li ₁₁ P _{3 S 12} is and the _Li 22 Si ₅ can be confirmed that reacts Li ₂ S is generated.
Here, since Li ₂ S is generated by the reaction of Li ₁₁ P ₃ S ₁₂ and Li ₂₂ Si ₅ , it is considered that Si is also generated at the same time, but the peak on the (111) plane of Si ( 2θ = 28.4 ± 0.3 °) is not detected.
Therefore, an arbitrary portion φ100 μm region on the φ9.5 mm × 1 mm pellet surface obtained by press-molding at 350 MPa what was obtained by pulverizing and mixing Li ₁₁ P ₃ S ₁₂ and Li ₂₂ Si ₅ is X-ray. When analyzed by photoelectron spectroscopy (XPS) (Quantera SXM manufactured by PHI), the binding energy of metal Si and Li ₂ S is detected as in the Li 1s orbital spectrum, the S 2p orbital spectrum, and the Si 2p orbital spectrum. In addition, the binding energy of SiOx (x <2), LiOH, Li ₂ O, etc. is detected because these are slightly oxidized on the pellet surface.
From this, it can be understood that the negative electrode material of the present embodiment contains Si fine particles having a crystallite size that cannot be detected by X-ray diffraction using CuKα rays as a radiation source.
From the above, in the negative electrode material of this embodiment, such Si fine particles are uniformly dispersed at an appropriate ratio in a solid electrolyte made of a compound mainly composed of Li ₂ S and Li, P, and S, and Si is extremely Since it is a small fine particle, the volume change of the Si fine particle caused by charging / discharging hardly causes poor contact with the solid electrolyte, and it is presumed that excellent cycle characteristics that have never been achieved can be realized.
Here, the crystallite size that cannot be detected by X-ray diffraction using CuKα rays as a radiation source is in the range of 0.4 nm or more and 2.0 nm or less when calculated from the following Scherrer equation.
D = 0.94λ / βcosθ
Where D is the crystallite diameter (Å), β is the half width of the X-ray diffraction peak, θ is the Bragg angle, and λ is the X-ray (CuKα) wavelength (1.54Å).

The negative electrode material of this embodiment preferably further contains a carbon material. Examples of such carbon materials include graphite materials such as natural graphite and artificial graphite; carbon blacks such as acetylene black and ketjen black; resin charcoal; carbon fibers; activated carbon; hard carbon; soft carbon; For example, CNovel, manufactured by Toyo Tanso Co., Ltd.). Among these, a graphite material is particularly preferable.
Such a carbon material functions as a negative electrode active material and also as a conductive additive. Therefore, the negative electrode material of this embodiment can further improve the charge / discharge capacity of the obtained lithium ion battery by further including the carbon material.

  The ratio of the mixing weight of the carbon material to the total weight of the Li—PS—S based solid electrolyte material and the Li—Si based alloy material is preferably 0.01 or more and 1.5 or less, more preferably 0.05 or more. It is 0.70 or less, More preferably, it is 0.12 or more and 0.40 or less.

The carbon material 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 0.02 μm or more and 30 μm or less.
The average particle size d ₅₀ of the carbon material to be in the above range, while maintaining good handling properties, can be manufactured more density of the negative electrode.

  And although the negative electrode material of this embodiment is not specifically limited, As another component, you may contain 1 or more types of materials selected from a binder, a thickener, a solid electrolyte material, etc., for example.

  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.

  The negative electrode material of this embodiment is usually unnecessary because it is relatively easy to obtain a 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.

  When the negative electrode material of this embodiment is used for a negative electrode for an all solid lithium ion battery, the negative electrode material of this embodiment preferably contains a solid electrolyte material. The solid electrolyte material 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, it can be set as the all-solid-state lithium ion battery excellent in the output characteristic.

Examples of the sulfide solid electrolyte material 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. . Among these, Li ₂ S—P ₂ S ₅ material is preferable because lithium ion conductivity is excellent and the manufacturing process is simple.

  The blending amount of the binder, thickener, and solid electrolyte material in the negative electrode material of the present embodiment is not particularly limited because it is determined as appropriate according to the intended use of the battery, and generally conforms to known information. Can be set.

[Method for producing negative electrode material for lithium ion battery]
It continues and demonstrates the manufacturing method of the negative electrode material of this embodiment.
The negative electrode material of this embodiment can be obtained by pulverizing and mixing a Li—PS—S based solid electrolyte material and a Li—Si based alloy material. Examples of the Li—PS—S solid electrolyte material and the Li—Si alloy material include those described above.

  First, the mixing molar ratio of the Li—Si based alloy material to the Li—PS—S based solid electrolyte material is preferably 1.5 or more and 7.7 or less, more preferably 1.9 or more and 3.7 or less. A Li—PS—S solid electrolyte material and a Li—Si alloy material are mixed. Here, the mixing molar ratio of the Li—Si based alloy material to the Li—PS—S based solid electrolyte material is usually the above reaction molar ratio. Here, the mixing molar ratio of the present embodiment can be determined by, for example, ICP emission spectroscopic analysis, but can usually be calculated from the weight ratio of preparation.

Subsequently, the Li—PS—S solid electrolyte material and the Li—Si alloy material are pulverized and mixed.
As a method of pulverizing and mixing the Li-PS-S solid electrolyte material and the Li-Si alloy material, a method capable of uniformly pulverizing and mixing the Li-PS solid electrolyte material and the Li-Si alloy material can be used. Although it will not specifically limit, For example, the method of performing by a mechanochemical process in non-active atmosphere is mentioned. When mechanochemical treatment is used, the Li—PS—S solid electrolyte material and the Li—Si alloy material can be mixed while being pulverized into fine particles, so that the Li—PS—S solid electrolyte material and Li— -The contact area with the Si-based alloy material can be increased. Thereby, the reaction of the Li—PS—S solid electrolyte material and the Li—Si alloy material can be promoted.

  Here, the mechanochemical treatment is a method of mixing while applying mechanical energy such as shear force, collision force or centrifugal force to the object to be mixed. Examples of the apparatus for performing pulverization and mixing by mechanochemical treatment include pulverizing / dispersing machines 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.

Conditions such as stirring speed, processing time, temperature, reaction pressure, and gravitational acceleration applied to the mixture when pulverizing and mixing the Li-PS-S solid electrolyte material and the Li-Si alloy material depend on the amount of the mixture processed. Can be determined as appropriate. In X-ray diffraction measurement using CuKα rays as a radiation source, a Li ₂ S diffraction peak (for example, 2θ = 27.0 °) is generated, and a diffraction peak derived from a Li—PS solid electrolyte material ( For example, in the case of Li ₁₁ P ₃ S ₁₂ , 2θ = 17.7 °) and a diffraction peak derived from a Li—Si based alloy material (for example, in the case of Li ₂₂ Si ₅ , 2θ = 40.8 °) are not detected. It is preferable to pulverize and mix until.

Next, a carbon material is mixed with the obtained negative electrode material as necessary. The carbon material is added when the Li—P—S solid electrolyte material and the Li—Si alloy material are pulverized and mixed, and the Li—PS—S solid electrolyte material and the Li—Si alloy material are added. It can also be pulverized and mixed together.
The ratio of the mixing weight of the carbon material to the total weight of the Li—PS—S based solid electrolyte material and the Li—Si based alloy material is preferably 0.01 or more and 1.5 or less, more preferably 0.05 or more. It is 0.70 or less, More preferably, it is 0.12 or more and 0.40 or less. When the mixing amount of the carbon material is within the above range, the charge / discharge capacity of the obtained lithium ion battery can be further improved.

  Examples of the method of mixing the carbon material with the negative electrode material obtained by mixing and pulverizing the Li—PS—S solid electrolyte material and the Li—Si alloy material include mixing by the above-described mechanochemical treatment.

  Next, if necessary, one or more materials selected from a binder, a thickener, a solid electrolyte material, and the like are mixed. As these mixers, known ones such as a ball mill and a planetary mixer can be used, and are not particularly limited. The mixing method is not particularly limited, and can be performed according to a known method.

  The negative electrode material according to this embodiment can be obtained by the above procedure.

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

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

[Method for producing negative electrode for lithium ion battery]
Below, the manufacturing method of the negative electrode for lithium ion batteries of this embodiment is demonstrated.
Although the negative 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 negative electrode material of this embodiment is formed into a sheet shape, a pellet shape, or the like by compression molding, roll molding, or the like to form the negative electrode active material layer. And the negative electrode of this embodiment can be obtained by laminating | stacking the negative electrode active material layer and collector which were obtained in this way.
Moreover, a negative electrode slurry can also be manufactured by producing a negative electrode slurry using the negative electrode material of this embodiment, apply | coating it to a collector, and drying it.

  The negative electrode active material layer may be formed on only one side of the current collector or on both sides. The thickness, length, and width of the negative electrode active material layer can be appropriately determined according to the size and use of the battery.

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

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

[Lithium ion battery]
Next, the lithium ion battery 100 of this 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 lithium ion battery 100 of the present embodiment includes, for example, a positive electrode 110, an electrolyte layer 120, and a negative electrode 130. And the negative electrode 130 is a negative electrode for lithium ion batteries of this embodiment.
The lithium ion battery 100 of this embodiment is generally manufactured according to a known method. For example, a stack of positive electrode 110, solid electrolyte layer or separator, and negative electrode 130 is formed into a cylindrical shape, a coin shape, a square shape, a film shape, or any other shape, and a non-aqueous electrolyte is enclosed as necessary. It is produced by doing.

  The electrolyte layer 120 is a layer formed between the positive electrode 110 and the negative electrode 130. Examples of the electrolyte layer 120 include those in which a separator is impregnated with a nonaqueous electrolytic solution, and solid electrolyte layers containing a solid electrolyte.

The separator of the present embodiment is not particularly limited as long as it has a function of electrically insulating the positive electrode 110 and the negative electrode 130 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.

The nonaqueous electrolytic solution of the present embodiment is a solution in which an electrolyte is dissolved in a solvent.
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 positive electrode 110 is not particularly limited, and those commonly used for lithium ion batteries can be used. The positive electrode 110 is not particularly limited, but can be generally manufactured according to a known method. For example, it can be obtained by forming a positive electrode active material layer containing a positive electrode active material on the surface of a current collector such as an aluminum foil.

  The thickness and density of the positive electrode active material layer 101 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.

It does not specifically limit as a positive electrode active material of this embodiment, Generally a well-known thing 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, Sulfides such as CuS, Li—Cu—S compound, MoS ₂ , and Li—Mo—S compound can be used.

  The positive electrode active material layer is not particularly limited, but may include, for example, one or more materials selected from binders, thickeners, conductive assistants, solid electrolyte materials, and the like as components other than the positive electrode active material of the present embodiment. Good.

  The types and blending ratios of various materials in the positive electrode active material layer are not particularly limited because they are appropriately determined according to the intended use of the battery, and can be generally set according to known information.

The lithium ion battery of this embodiment can be made into an all-solid-state lithium ion battery by using a solid electrolyte material instead of the non-aqueous electrolyte mentioned above as an electrolyte.
The all solid lithium ion battery of this embodiment has, for example, a positive electrode 110, a negative electrode 130, and a solid electrolyte layer (electrolyte layer 120) formed of a solid electrolyte between the positive electrode 110 and the negative electrode 130.
Although it does not specifically limit as a solid electrolyte material of this embodiment, Generally a well-known thing can be used. For example, the same material as the solid electrolyte material included in the negative electrode 130 described above can be used.
When the negative electrode material of this embodiment is used as the negative electrode material of the all-solid-state lithium ion battery, a lithium ion battery having good battery characteristics such as charge / discharge capacity and cycle characteristics and high safety can be obtained.

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, examples of the reference form will be added.
<Appendix>
(Appendix 1)
A sulfide solid electrolyte material containing Li, P, and S as constituent elements;
An alloy material containing Li and Si as constituent elements;
A negative electrode material for a lithium ion battery obtained by pulverizing and mixing.
(Appendix 2)
In the negative electrode material for a lithium ion battery according to attachment 1,
The sulfide solid electrolyte material is a negative electrode for a lithium ion battery, which is a compound represented by Li _X P _Y S _Z (where 4 ≦ X ≦ 15, 1 ≦ Y ≦ 3, 6 ≦ Z ≦ 14). material.
(Appendix 3)
In the negative electrode material for a lithium ion battery according to appendix 1 or 2,
The alloy material is a negative electrode material for a lithium ion battery, which is a compound represented by Li _A Si _B (where 7 ≦ A ≦ 25, 3 ≦ B ≦ 7).
(Appendix 4)
In the negative electrode material for a lithium ion battery according to any one of appendices 1 to 3,
A negative electrode material for a lithium ion battery, wherein a reaction molar ratio of the alloy material to the sulfide solid electrolyte material is 1.5 or more and 7.7 or less.
(Appendix 5)
In the negative electrode material for a lithium ion battery according to any one of appendices 1 to 4,
Further, a negative electrode material for a lithium ion battery, including a carbon material.
(Appendix 6)
In the negative electrode material for a lithium ion battery according to appendix 5,
The negative electrode material for a lithium ion battery, wherein the carbon material is a graphite material.
(Appendix 7)
In the negative electrode material for a lithium ion battery according to any one of appendices 1 to 6,
A negative electrode material for a lithium ion battery, wherein a ratio of a mixing weight of the carbon material to a total weight of the sulfide solid electrolyte material and the alloy material is 0.01 or more and 1.5 or less.
(Appendix 8)
A negative electrode material for a lithium ion battery, comprising Si fine particles having a crystallite size that cannot be detected by X-ray diffraction using CuKα rays as a radiation source.
(Appendix 9)
In the negative electrode material for a lithium ion battery according to appendix 8,
Further, a negative electrode material for a lithium ion battery, including a carbon material.
(Appendix 10)
In the negative electrode material for a lithium ion battery according to appendix 9,
The negative electrode material for a lithium ion battery, wherein the carbon material is a graphite material.
(Appendix 11)
A negative electrode for a lithium ion battery, wherein a negative electrode active material layer made of the negative electrode material for a lithium ion battery according to any one of appendices 1 to 10 is formed on a surface of a current collector.
(Appendix 12)
A lithium ion battery comprising the lithium ion battery negative electrode according to appendix 11, an electrolyte layer, and a positive electrode.
(Appendix 13)
In the lithium ion battery according to attachment 12,
A lithium ion battery, wherein the electrolyte is a solid electrolyte.

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

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

(1) X-ray diffraction analysis Diffraction spectra of the negative electrode materials obtained in Examples and Comparative Examples were obtained by X-ray diffraction analysis using an X-ray diffraction apparatus (RINT2000, manufactured by Rigaku Corporation). Note that CuKα rays were used as the radiation source.

(2) Charging / discharging test About 15 mg of the negative electrode material obtained in Examples and Comparative Examples, press molding was performed to obtain a negative electrode (diameter φ = 14 mm, thickness t = 0.15 mm).
Next, a solid electrolyte layer (Li ₁₀ P ₃ S ₁₂ , 150 mg, diameter φ = 14 mm, thickness t = 0.6 mm), positive electrode (Li ₆ MoS ₆ : acetylene black (AB): Li ₁₀ P ₃ S ₁₂ = 1: 1: 1 (% by weight), 45 mg, diameter φ = 14 mm, thickness t = 0.15 mm) were laminated in this order to produce an all-solid-state lithium ion battery.
Next, the obtained all solid lithium ion battery was charged and discharged 10 times under the conditions of a current value of 0.1 mA, a current density of 0.065 mA / cm ² , and a measurement potential of 0.9 to 3.5 V. The obtained results are shown in Table 1. Here, the discharge capacity change rate [%] was the 10th discharge capacity when the first discharge capacity was 100%.

Here, _Li 6 MoS ₆ is a positive electrode active material was prepared by the following steps.
Under an argon atmosphere, MoS ₂ (Wako Pure Chemical Industries, 970 mg, 6.1 mmol), Li ₂ S (Sigma Aldrich Japan, 835 mg, 17.8 mmol), and S (Sigma Aldrich Japan, 194 mg) , 6.1 mmol) was placed in an alumina ball mill pot (internal volume 400 ml) and treated at 97 rpm for 4 days.

Also, _Li 10 _P 3 _{S 12} is a Li-P-S-based solid electrolyte material was prepared by the following procedure.
Li ₂ S (manufactured by Alfa Aesar, purity 99.9%) and P ₂ S ₅ (reagent manufactured by Kanto Chemical) were used as raw materials. Li ₃ N was produced by the following procedure.
First, in a nitrogen atmosphere glove box, a stainless steel sword mountain was used for Li foil (purity 99.8%, thickness 0.5 mm manufactured by Honjo Metal Co., Ltd.), and a number of holes having a diameter of 1 mm or less were formed. The Li foil began to turn black-purple from the hole, and all the Li foil changed to black-purple Li ₃ N by leaving it at room temperature for 24 hours. Li ₃ N was pulverized with an agate mortar and then sieved with a stainless steel sieve, and a powder of 75 μm or less was recovered and used as a raw material for the solid electrolyte material.
Subsequently, each raw material was precisely weighed in an argon glove box so that Li ₂ S: P ₂ S ₅ : Li ₃ N = 71.1: 23.7: 5.3 (mol%). Mix in agate mortar for 20 minutes. Next, 2 g of the mixed powder was weighed, and mixed and ground for 1 hour at 100 rpm with a planetary ball mill (Fritsch P-7) together with 500 g of zirconia balls having a diameter of 10 mm. Next, the mixture was pulverized at 400 rpm for 15 hours. The mixed and pulverized powder was pressed at 270 MPa for 10 minutes using a press machine to obtain a plate-like mixture having a thickness of 0.6 mm. The obtained mixture was placed in a carbon boat and heat-treated in an argon stream at 300 ° C. for 2 hours to obtain a solid electrolyte material having a Li ₁₀ P ₃ S ₁₂ composition in which the powders were fused and sintered firmly.

[2] Production of negative electrode material <Example 1>
Under an argon atmosphere, Li foil (manufactured by Honjo Metal Co., Ltd., 1.04 g) and Si powder (manufactured by Furukawa Machine Metal Co., Ltd., 0.96 g) were melt-mixed at 300 ° C. for 1 hour in a zirconium crucible. Subsequently, the mixture was put into an alumina ball mill pot, and further ZrO ₂ balls were put therein, and the alumina ball mill pot was sealed. Subsequently, the alumina ball mill pot was treated at 97 rpm for 27 hours to obtain a Li—Si alloy 1 having a Li ₂₂ Si ₅ composition.

In addition, the _Li 11 _P 3 _{S 12} is a Li-P-S-based solid electrolyte material was prepared by the following procedure.
As the raw material, the same material as that used in the production of the solid electrolyte material having the composition Li ₁₀ P ₃ S ₁₂ was used.
First, each raw material was precisely weighed in an argon glove box so that Li ₂ S: P ₂ S ₅ : Li ₃ N = 67.5: 22.5: 10.0 (mol%). Mix in agate mortar for minutes. Next, 2 g of the mixed powder was weighed and mixed and ground for 1 hour at 100 rpm with a planetary ball mill (Fritsch, P-7) together with 500 g of φ10 mm zirconia balls. Next, the mixture was pulverized at 400 rpm for 15 hours. The powder after mixing and pulverization was placed in a carbon boat and heat-treated in an argon stream at 300 ° C. for 2 hours to obtain a Li—P—S solid electrolyte material 1 having a composition of Li ₁₁ P ₃ S ₁₂ .

Next, in the argon glove box, the raw materials were Li-Si alloy 1: Li-PS-based solid electrolyte material 1: graphite (CGC-20, manufactured by Nippon Graphite Industry Co., Ltd., average particle diameter d ₅₀ : 21.7 μm) = These were precisely weighed so as to be 4: 3: 8 (weight ratio), and these were mixed in an agate mortar for 10 minutes. Next, 1.0 g of the mixed powder was weighed and put together with 500 g of zirconia balls having a diameter of 10 mm into an alumina ball mill pot (internal volume 400 mL), and mixed and ground at 97 rpm for 24 hours to obtain a negative electrode material 1.
When the X-ray diffraction spectrum of the obtained negative electrode material 1 was measured, the diffraction peaks of Li ₁₁ P ₃ S _{12 as} the Li—P—S solid electrolyte material 1 and Li ₂₂ Si _{5 as} the Li—Si alloy 1 were as follows. It disappeared and diffraction peaks of Li ₂ S and graphite were detected. Further, no Si diffraction peak was detected. On the other hand, it was confirmed that Si was produced by X-ray photoelectron spectroscopy (XPS) (Quantera SXM manufactured by PHI).

<Example 2>
Li—Si alloy 1: Li—PS—S solid electrolyte material 1: graphite (CGC-20, manufactured by Nippon Graphite Industries Co., Ltd.) = 4: 3: 4 (weight ratio) A negative electrode material 2 was obtained.
When the X-ray diffraction spectrum of the obtained negative electrode material 2 was measured, the diffraction peaks of Li ₁₁ P ₃ S _{12 as} the Li—P—S solid electrolyte material 1 and Li ₂₂ Si _{5 as} the Li—Si alloy 1 were as follows. It disappeared and diffraction peaks of Li ₂ S and graphite were detected. Further, no Si diffraction peak was detected. On the other hand, it was confirmed by XPS that Si was generated.

<Example 3>
Li—Si alloy 1: Li—PS—S solid electrolyte material 1: Graphite (CGC-20, manufactured by Nippon Graphite Industry Co., Ltd.) = 4: 3: 2 (weight ratio) A negative electrode material 3 was obtained.
When the X-ray diffraction spectrum of the obtained negative electrode material 3 was measured, the diffraction peaks of Li ₁₁ P ₃ S _{12 as} the Li—P—S-based solid electrolyte material 1 and Li ₂₂ Si _{5 as} the Li—Si alloy 1 were as follows. It disappeared and diffraction peaks of Li ₂ S and graphite were detected. Further, no Si diffraction peak was detected. On the other hand, it was confirmed by XPS that Si was generated.

<Example 4>
Li—Si alloy 1: Li—PS—S solid electrolyte material 1: graphite (CGC-20, manufactured by Nippon Graphite Industry Co., Ltd.) = 4: 3: 0 (weight ratio) A negative electrode material 4 was obtained.
When the X-ray diffraction spectrum of the obtained negative electrode material 4 was measured, the diffraction peaks of Li ₁₁ P ₃ S _{12 as} the Li—P—S based solid electrolyte material 1 and Li ₂₂ Si _{5 as} the Li—Si alloy 1 were as follows. It disappeared and a Li ₂ S diffraction peak was detected. Further, no Si diffraction peak was detected. On the other hand, it was confirmed by XPS that Si was generated.

<Example 5>
Example 1 was used except that activated carbon (Kuraray Coal YP-17, Kuraray Chemical Co., average particle diameter d ₅₀ : 21.7 μm) was used instead of graphite (CGC-20, manufactured by Nippon Graphite Industries Co., Ltd.). A negative electrode material 5 was obtained.
When the X-ray diffraction spectrum of the obtained negative electrode material 5 was measured, the diffraction peaks of Li ₁₁ P ₃ S _{12 as} the Li—P—S-based solid electrolyte material 1 and Li ₂₂ Si _{5 as} the Li—Si alloy 1 were as follows. It disappeared and a Li ₂ S diffraction peak was detected. Further, no Si diffraction peak was detected. On the other hand, it was confirmed by XPS that Si was generated.

<Example 6>
In the same manner as in Example 3, except that acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., average particle diameter d ₅₀ : 0.04 μm) was used instead of graphite (CGC-20, manufactured by Nippon Graphite Industry Co., Ltd.), the negative electrode material 6 was prepared. Obtained.
When the X-ray diffraction spectrum of the obtained negative electrode material 6 was measured, the diffraction peaks of Li ₁₁ P ₃ S _{12 as} the Li—P—S solid electrolyte material 1 and Li ₂₂ Si _{5 as} the Li—Si alloy 1 were as follows. It disappeared and a Li ₂ S diffraction peak was detected. Further, no Si diffraction peak was detected. On the other hand, it was confirmed by XPS that Si was generated.

<Example 7>
In the same manner as in Example 3 except that porous carbon (CNovel 2200, manufactured by Toyo Tanso Co., Ltd., average particle diameter d ₅₀ : 9.5 μm) was used instead of graphite (CGC-20, manufactured by Nippon Graphite Industries Co., Ltd.), the negative electrode Material 7 was obtained.
When the X-ray diffraction spectrum of the obtained negative electrode material 7 was measured, the diffraction peaks of Li ₁₁ P ₃ S _{12 as} the Li—P—S solid electrolyte material 1 and Li ₂₂ Si _{5 as} the Li—Si alloy 1 were as follows. It disappeared and a Li ₂ S diffraction peak was detected. Further, no Si diffraction peak was detected. On the other hand, it was confirmed by XPS that Si was generated.

<Example 8>
A negative electrode material 8 was obtained in the same manner as in Example 3 except that Li ₇ Si ₃ was used instead of the Li—Si alloy 1.
When the X-ray diffraction spectrum of the obtained negative electrode material 8 was measured, the diffraction peaks of Li ₁₁ P ₃ S ₁₂ and Li ₇ Si ₃ , which are Li—P—S based solid electrolyte material 1, disappeared, and Li ₂ S A diffraction peak was detected. Further, no Si diffraction peak was detected. On the other hand, it was confirmed by XPS that Si was generated.

<Comparative Example 1>
Li-Si alloy 1: Li-PS-based solid electrolyte material 1: graphite (CGC-20, manufactured by Nippon Graphite Industry Co., Ltd.) = 0: 3: 8 (weight ratio) A negative electrode material 9 was obtained.

<Comparative example 2>
Each raw material in an argon glove box is precisely weighed so that Li—Si alloy 1: sulfur (S, manufactured by Sigma Aldrich Japan) = 1: 1.2 (weight ratio), and these are mixed in an agate mortar for 10 minutes. did. Next, 2 g of the mixed powder was precisely weighed, put into a ball mill pot made of alumina (with an internal volume of 400 mL) together with a zirconia ball having a diameter of 10 mm, mixed and pulverized at 97 rpm for 24 hours. ₂ S and Si diffraction peaks were detected and confirmed to be a mixture of Li ₂ S and Si. A negative electrode material 10 was obtained in the same manner as in Example 1 except that this mixture of Li ₂ S and Si was used instead of the Li—Si alloy 1. However, the weight of Si contained in the negative electrode material is 46% of Example 1.
When the X-ray diffraction spectrum of the obtained negative electrode material 10 was measured, the diffraction peaks of Li ₁₁ P ₃ S ₁₂ and Li ₂₂ Si ₅ , which are the Li—PS—S solid electrolyte material 1, disappeared, and Li ₂ S and A diffraction peak of graphite was detected. Further, a Si diffraction peak was detected. The crystallite size calculated from the Si diffraction peak using the Scherrer equation was 370 nm.

<Comparative Example 3>
A negative electrode material 11 was obtained in the same manner as in Example 1 except that Si powder (Furukawa Machine Metal, average particle diameter D ₅₀ : 2.0 μm) was used instead of the Li—Si alloy 1.
When the X-ray diffraction spectrum of the obtained negative electrode material 11 was measured, the diffraction peak of Li ₁₁ P ₃ S ₁₂ which is the Li—P—S solid electrolyte material 1 disappeared, and the diffraction peaks of Si and graphite were detected. It was.

(Charge / discharge test results)
The charge / discharge test results of the negative electrode materials 1 to 11 are shown in Table 1.
The negative electrode materials 1 to 8 obtained in the examples were superior in the discharge capacity change rate and the discharge capacity as compared with the negative electrode materials 9 to 11 obtained in the comparative examples.

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

Claims (10)

A sulfide solid electrolyte material containing Li, P, and S as constituent elements;
An alloy material containing Li and Si as constituent elements;
Carbon materials,
A negative electrode material for a lithium ion battery comprising a pulverized mixture of
The pulverized mixture includes Si fine particles having a crystallite size that cannot be detected by X-ray diffraction using CuKα rays as a radiation source, and lithium sulfide.
In the X-ray diffraction measurement using CuKα ray as a radiation source, the pulverized mixture does not detect both the diffraction peak derived from the sulfide solid electrolyte material and the diffraction peak derived from the alloy material, and the diffraction of the lithium sulfide. anode material for der Ru lithium ion battery a peak is detected. The negative electrode material for a lithium ion battery according to claim 1,
The sulfide solid electrolyte material is represented by Li _X P _Y S _Z (where 4 ≦ X ≦ 15, 1 ≦ Y ≦ 3, 6 ≦ Z ≦ 14, X, Y and Z are integers). A negative electrode material for a lithium ion battery. The negative electrode material for a lithium ion battery according to claim 2,
The alloy material, _Li A Si _B (however, 7 ≦ A ≦ 25,3 a ≦ B ≦ 7 .A and B are integers.) Is a compound represented by the negative electrode material for lithium ion batteries. The negative electrode material for a lithium ion battery according to claim 3,
A negative electrode material for a lithium ion battery, wherein a mixing molar ratio of the alloy material to the sulfide solid electrolyte material is 1.5 or more and 7.7 or less. The negative electrode material for a lithium ion battery according to any one of claims 1 to 4,
The negative electrode material for a lithium ion battery, wherein the carbon material is a graphite material. The negative electrode material for a lithium ion battery according to any one of claims 1 to 5,
Wherein the ratio of the combined weight of the carbonaceous material to the total weight of the sulfide solid electrolyte material and the alloy materials is 0.01 to 1.5, a negative electrode material for lithium ion batteries. The negative electrode material for a lithium ion battery according to any one of claims 1 to 6,
A negative electrode material for a lithium ion battery, wherein the crystallite size of the Si fine particles calculated from the following Scherrer equation is in the range of 0.4 nm to 2.0 nm.
D = 0.94λ / βcosθ
(Where D is the crystallite diameter (Å), β is the half width of the X-ray diffraction peak, θ is the Bragg angle, and λ is the wavelength of X-ray (CuKα) (1.54Å))   The negative electrode for lithium ion batteries formed by forming the negative electrode active material layer which consists of a negative electrode material for lithium ion batteries as described in any one of Claims 1 thru | or 7 on the surface of a collector.   The lithium ion battery provided with the negative electrode for lithium ion batteries of Claim 8, an electrolyte layer, and a positive electrode. The lithium ion battery according to claim 9,
A lithium ion battery, wherein the electrolyte is a solid electrolyte.

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