JP2009283344A - Negative electrode mix for lithium battery, negative electrode for lithium battery, lithium battery, device, and manufacturing method of negative electrode mix for lithium battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative electrode mix for a lithium battery, having sufficient discharge capacity in a high discharge current density, provide a negative electrode for a lithium battery, a lithium battery, a device, and a manufacturing method of the negative electrode mix for a lithium battery. <P>SOLUTION: The negative electrode mix for a lithium battery is made by mixing carbon material with solid electrolyte, wherein the carbon material has a graphitization degree value R (I<SB>D</SB>/I<SB>G</SB>) obtained from a ratio of a peak height (I<SB>D</SB>)indicating a vibration mode derived from a noncrystalline turbostratic structure in a range around 1360 cm<SP>-1</SP>measured by a raman spectrometric spectrum and a peak height (I<SB>G</SB>)indicating a vibration mode derived from a graphitizatic crystalline structure in a range around 1580 cm<SP>-1</SP>is 0.05-0.30, and a crystallite thickness dimension in a C-axis direction of a (002) face by an X-ray diffraction method is 150-2000 Å. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a negative electrode composite material for a lithium battery, a negative electrode for a lithium battery having this composite material, a lithium battery having this negative electrode, a device having this battery, and a method for producing a negative electrode composite material for lithium battery.

In recent years, with the spread of portable devices such as video cameras, mobile phones and portable personal computers, the demand for secondary batteries has increased. From the viewpoint of increasing the capacity of a battery, it is known to use a metal material that forms an alloy with Li, such as Al, Si, Sn, etc., as a negative electrode active material. However, when such a metal-based material is used alone as a negative electrode active material for a non-aqueous lithium secondary battery, the charge / discharge capacity may be significantly reduced with the charge / discharge cycle, and the cycle characteristics of the battery may be poor. On the other hand, a non-aqueous lithium secondary battery using a carbonaceous material as a negative electrode active material, a so-called carbon-based material, using LiMO ₂ (M = Ni, Co, etc.) as a positive electrode active material, and using an organic solvent as an electrolytic solution. Is known (see, for example, Patent Document 1).

  Patent Document 1 shows that a carbon material typified by graphite is used as a negative electrode material used in a lithium secondary battery.

JP 2003-068361 A

  However, a battery manufactured using a negative electrode as described in Patent Document 1 and a solid electrolyte formed of, for example, lithium sulfide and phosphorus pentasulfide has a sufficient discharge capacity at a high discharge current density. It may not be possible.

  An object of the present invention is to provide a negative electrode mixture for lithium batteries, a negative electrode for lithium batteries, a lithium battery, a device, and a method for producing a negative electrode mixture for lithium batteries having a sufficient discharge capacity at a high discharge current density. .

The negative electrode composite material for a lithium battery of the present invention has a peak height (I _D ) indicating a vibration mode derived from an amorphous turbostratic structure in the range of 1350 to 1370 cm ⁻¹ and 1570 The degree of graphitization R value (I _D / I _G ) determined from the ratio to the peak height (I _G ) indicating the vibration mode derived from the graphite crystalline structure in the range of 1620 cm ⁻¹ is 0.05 or more and 0 A carbon material having a crystallite thickness dimension (Lc) in the C-axis direction of the (002) plane of 150 mm or more and 2000 mm or less by X-ray diffraction method, and a solid electrolyte mixed with the carbon material And are mixed.

  Moreover, it is preferable that the said solid electrolyte contains lithium (Li), phosphorus (P), and sulfur (S).

Further, the carbon material is in a state where crystallites are not pulverized, and the solid electrolyte is in a state where particles are pulverized, and is observed with a scanning electron microscope using an energy dispersive X-ray analyzer. It is preferable to have the dispersity (X / X ₀ ) and the dispersity distribution ((Y / X) / (Y ₀ / X ₀ )) satisfying the expressions (1) to (4) in the mapping image of the obtained element.
(1): X = (α ₁ / β ₁ + α ₂ / β ₂ + α ₃ / β ₃ ... + Α _n / β _n ) / n
(2): Y = {(α ₁ / β ₁ ) ² + (α ₂ / β ₂ ) ² + (α ₃ / β ₃ ) ² ... + (α _n / β _n ) ² } ^1/2 / n
(3): 0.8 ≦ (X / X ₀ ) ≦ 1.0
(4): ((Y / X) / (Y ₀ / X ₀ )) ≦ 1.0
(N is a natural number indicating the number of mapping element particles (for example, phosphorus particles), α _n value is the area of the n th mapping element particle (for example, phosphorus particles), and β _n value is n It is the circumference length of the mapping element particle (for example, phosphorus particle) of the eye, and the X value is the area of the nth mapping element particle (for example, phosphorus particle) and the mapping element shown in Formula (1) The Y value is the average value of the ratio of the perimeter lengths of the particles (for example, phosphorus particles) and the area of the nth mapping element particle (for example, phosphorus particles) shown in Formula (2) This is the mean square value of the ratio of the perimeters of particles of the mapping element (for example, phosphorus particles), and the X ₀ value and the Y ₀ value are states in which the crystallites of the carbon material and the solid electrolyte particles are not pulverized, respectively. X and Y values when mixed with
Here, the scanning electron microscope using the energy dispersive X-ray analyzer is a general SEM-EDS (Scanning Electron Microscopy / Energy Dispersive Spectroscopy) apparatus.

The negative electrode for a lithium battery according to the present invention includes the negative electrode mixture for a lithium battery.
The all-solid-state lithium battery of this invention is equipped with the said negative electrode, It is characterized by the above-mentioned.
All solid lithium batteries have a large discharge capacity at high discharge current densities.

The apparatus of the present invention includes the all solid lithium battery.
The all solid lithium battery using the negative electrode mixture of the present invention may be a secondary battery or a primary battery.
The apparatus equipped with the lithium battery of the present invention may be any device equipped with the lithium battery of the present invention, and is used in various portable electronic devices, particularly notebook computers, notebook word processors, palmtop (pocket) computers. , Mobile phone, PHS, portable fax, portable printer, headphone stereo, video camera, portable TV, portable CD, portable MD, electric shaver, electronic handrail, transceiver, electric tool, radio, tape recorder, digital camera, mobile phone It can be used for a copy machine, a portable game machine, and the like.
In addition, batteries for electric vehicles, hybrid vehicles, vending machines, electric carts, load leveling power storage systems, household power storage devices, distributed power storage systems (built in stationary electrical products), emergency power supply systems, etc. Can be used.
Lithium batteries include, for example, battery packs and battery units that are mounted on electric vehicles.
When the apparatus equipped with the lithium battery of the present invention is an electric vehicle, the lithium battery has a sufficient discharge capacity at a high discharge density. Therefore, the electric vehicle can run at a high output for a long time.

The method for producing a negative electrode composite material for a lithium battery according to the present invention has a peak height (I _D ) indicating a vibration mode derived from an amorphous turbostratic structure in the range of 1350 to 1370 cm ⁻¹ as measured by Raman spectroscopy. And a graphitization degree R value (I _D / I _G ) determined from a ratio of a peak height (I _G ) indicating a vibration mode derived from a graphite crystalline structure in the range of 1570 to 1620 cm ⁻¹ of 0. A carbon material having a crystallite thickness dimension (Lc) in the C-axis direction of the (002) plane of 150 to 2000 mm by a X-ray diffraction method and a solid electrolyte is mechano It is characterized by mixing by a chemical treatment method.

  In a high discharge current density, a lithium battery negative electrode mixture, a lithium battery negative electrode, a lithium battery, a device, and a method for producing a lithium battery negative electrode mixture having a sufficient discharge capacity can be obtained.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a lithium battery according to the present embodiment.

(Battery cell configuration)
As shown in FIG. 1, a battery cell 201 that is a lithium battery includes a positive electrode current collector sheet 240, a positive electrode sheet 205, a solid electrolyte sheet 220, a negative electrode sheet 206, and a negative electrode current collector sheet 250 that are bonded in order. , Pressed and integrated. In this integrated body, an aluminum film or the like as an exterior of the battery cell 201 is laminated.
The solid electrolyte sheet 220 is manufactured, the negative electrode mixture is laminated on the solid electrolyte sheet 220 to form a negative electrode layer, and the positive electrode composite is formed on the opposite side of the surface of the solid electrolyte sheet 220 on which the negative electrode mixture is laminated. The battery cells 201 may be manufactured by stacking materials to form a positive electrode layer and then applying pressure.
Also, a negative electrode mixture is laminated on the negative electrode current collector sheet 250 to form a negative electrode layer, the above-mentioned solid electrolyte is laminated on the negative electrode layer to form an electrolyte layer, and a positive electrode mixture is laminated on the electrolyte layer. Then, a positive electrode layer may be formed, and a positive electrode current collector sheet 240 may be laminated on the positive electrode layer, and the whole may be pressurized to manufacture the battery cell 201. Moreover, the reverse may be sufficient and a manufacturing method will not be ask | required if the battery cell 201 laminated | stacked in order of the negative electrode layer, the electrolyte layer, and the positive electrode layer can be manufactured.

(Solid electrolyte sheet)
The lithium / phosphorous sulfide solid electrolyte (hereinafter abbreviated as “solid electrolyte”) constituting the solid electrolyte sheet 220 may be lithium and phosphorus sulfide glass or lithium / phosphorous sulfide glass ceramic, and a mixture thereof. But you can. Lithium / phosphorous sulfide glass can be produced by melting and reacting raw materials and then rapidly cooling. The raw material can be obtained by a mechanical milling (hereinafter abbreviated as “MM”) method.
The lithium / phosphorous sulfide glass ceramic can be obtained by further heat-treating the lithium / phosphorous sulfide glass obtained by the above method.
A preferred lithium / phosphorous sulfide solid electrolyte is produced using lithium sulfide (hereinafter abbreviated as “Li ₂ S”) and diphosphorus pentasulfide (hereinafter abbreviated as “P ₂ S ₅ ”). However, it can also be produced using Li ₂ S, simple phosphorus and simple sulfur. It is more preferable to produce by the method described in WO2007-066539.

(Positive electrode current collector sheet and negative electrode current collector sheet)
Examples of the positive electrode current collector sheet 240 and the negative electrode current collector sheet 250 include metals such as stainless steel, gold, platinum, zinc, nickel, tin, aluminum, molybdenum, niobium, tantalum, tungsten, and titanium, and alloys thereof. In addition, a sheet, foil, net, punched metal, expanded metal or the like is used. In particular, an aluminum foil is preferable for the positive electrode current collector sheet 240, and an aluminum foil or a tin foil is preferable for the negative electrode current collector sheet 250 in terms of current collection, workability, and cost.

(Positive electrode sheet)
The positive electrode sheet 205 is formed using a positive electrode mixture. Here, the positive electrode sheet 205 includes, for example, a positive electrode layer formed by stacking a positive electrode mixture on the positive electrode current collector sheet 240. The positive electrode mixture contains the positive electrode active material 210 and the above-described solid electrolyte.
As the positive electrode active material 210, in the sulfide system, titanium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ ), iron sulfide (FeS, FeS ₂ ), copper sulfide (CuS), and nickel sulfide (Ni ₃ S ₂ ), _{LNCAO (LiNi x Co y Al 1} -x-y O 2) , or the like can be used.
In the oxide system, bismuth oxide (Bi ₂ O ₃ , Bi ₂ Pb ₂ O ₅ ), copper oxide (CuO), vanadium oxide (V ₆ O ₁₃ ), lithium cobaltate (LiCoO ₂ ), lithium nickelate ( LiNiO ₂ ), lithium manganate (LiMnO ₂ , LiMn ₂ O ₄ ) and the like can be used. Preferably, lithium cobaltate can be used. In addition to the above, niobium selenide (NbSe ₃ ) can be used.

(Negative electrode sheet)
The negative electrode sheet 206 is formed using a negative electrode mixture. Here, the negative electrode sheet 206 also includes, for example, a negative electrode layer formed by laminating a negative electrode mixture on the negative electrode current collector sheet 250. The negative electrode mixture contains the negative electrode active material 230 and the above-described solid electrolyte.
As the negative electrode active material, a powdery carbon material is preferable, and the carbon material is preferably a graphite-based material from the viewpoint of charge / discharge characteristics, capacity, and the like. Examples of the graphite-based material include graphite particles such as natural graphite and artificial graphite, and mesophase-based graphite particles obtained by heat-treating mesophase pitch using tar and pitch as raw materials, for example, mesophase microspheres. Furthermore, the composite carbon material which coat | covered these with amorphous carbon etc. is also included. The carbon material is a powdery graphite in which the crystallites are not pulverized, and the peak height indicating the vibration mode derived from the amorphous turbostratic structure in the range of 1350 to 1370 cm ⁻¹ measured by Raman spectroscopy. The degree of graphitization (hereinafter abbreviated as “R value”) determined from the ratio between (I _D ) and the peak height (I _G ) indicating the vibration mode derived from the graphite crystalline structure in the range of 1570 to 1620 cm ^−1. (I _D / I _G ) is 0.05 or more and 0.30 or less. For the R value, argon laser light having a wavelength of 532 nm was used.
When the R value is less than 0.05, the exposed edge surface of the graphite crystallite is not sufficient, and it may be difficult to smoothly remove and insert lithium ions. On the other hand, when the R value exceeds 0.30, a sufficient capacity may not be obtained. From such a viewpoint, the R value is more preferably 0.10 or more and 0.25 or less.

The carbon material has a crystallite thickness dimension (hereinafter abbreviated as “Lc”) in the C-axis direction of the Miller index (002) plane by an X-ray diffraction (XRD) method of 150 to 2000 mm. is there. If the Lc value is less than 150%, the graphite laminate may not be developed and sufficient capacity may not be obtained. On the other hand, if the Lc value is larger than 2000%, the mixed state with the solid electrolyte may be poor. From such a viewpoint, the Lc value is more preferably 470 to 1800. More preferably, the Lc value is 1500 Å or less.
The Lc value was calculated by the Scherrer equation using the diffraction peak on the (002) plane obtained from the X-ray diffraction measurement. The calculation formula is Lc = Kλ / βcosθ. K is a form factor, and in this embodiment, K = 0.9. λ is an X-ray wavelength, and in this embodiment, λ = 1.5406Å. β is the half-value width of the diffraction line after intensity correction, and θ is the diffraction angle 2θ / 2.

The solid electrolyte used for the negative electrode mixture is not particularly limited, and an organic compound, an inorganic compound, or a material composed of both organic and inorganic compounds can be used. Those known in the battery field can be used. In particular, sulfide-based inorganic solid electrolytes are known to have higher ionic conductivity than other inorganic compounds, and inorganic solid electrolytes described in JP-A-4-202024 can be used. Specifically, an inorganic solid electrolyte in which Li ₃ PO ₄ , a halogen, and a halogen compound are appropriately added to an inorganic solid electrolyte composed of a combination of Li ₂ S and SiS ₂ , GeS ₂ , P ₂ S ₅ , B ₂ S _3. Can be used.
Furthermore, since it has high lithium ion conductivity, a sulfide-based solid electrolyte powder containing lithium (Li), phosphorus (P), and sulfur (S) is preferable. The particle diameter of the solid electrolyte is preferably 0.10 μm or more and 100 μm or less. If the thickness is less than 0.10 μm, the solid electrolyte may be scattered and handling may be difficult. If the solid electrolyte exceeds 100 μm, the mixed state with a negative electrode mixture such as carbon powder may be poor. Further, the solid electrolyte used for the negative electrode mixture is in a state where the particles are pulverized, and by a scanning electron microscope (hereinafter abbreviated as “SEM-EDS”) using an energy dispersive X-ray analyzer. Expressions (1) to (4) are satisfied in the observed element mapping image. Here, n is a natural number indicating the number of mapping element particles (for example, phosphorus particles), α _n value is the area of the nth mapping element particle (for example, phosphorus particles), and β _n value is n The length of the circumference of the particle (for example, phosphorus particle) of the mapping element, and the X value is the area of the particle (for example, phosphorus particle) of the nth mapping element and the particle of the mapping element shown in Formula (1) It is an average value of the ratio of the perimeters of (for example, phosphorus particles), and the Y value is the area of the n-th mapping element particle (for example, phosphorus particles) shown in Equation (2) and the n-th mapping element. It is a mean square value of the ratio of the perimeter of particles (for example, phosphorus particles), and the X ₀ value and the Y ₀ value are X values when the crystallites of the carbon material and the particles of the solid electrolyte are mixed without being pulverized, respectively. Value and Y value.
Here, as shown in FIG. 2, the mapped element particle (for example, phosphorus particle) defines a single lump like reference numeral 300 in the mapping image as one particle.
(1): X = (α ₁ / β ₁ + α ₂ / β ₂ + α ₃ / β ₃ ... + Α _n / β _n ) / n
(2): Y = {(α ₁ / β ₁ ) ² + (α ₂ / β ₂ ) ² + (α ₃ / β ₃ ) ² ... + (α _n / β _n ) ² } ^1/2 / n
(3): 0.8 ≦ (X / X ₀ ) ≦ 1.0
(4): ((Y / X) / (Y ₀ / X ₀ )) ≦ 1.0

By using the above-described negative electrode mixture for the negative electrode sheet 206 of the battery cell 201, the battery cell 201 has a large discharge capacity at a high discharge current density. Here, the high discharge current density is 1 mA / cm ² or more and 20 mA / cm ² or less.

(Method for producing solid electrolyte)
Next, a method for producing a solid electrolyte used for the negative electrode mixture of the negative electrode sheet 206 and the solid electrolyte sheet 220 will be described.
The solid electrolyte can be produced using Li ₂ S and P ₂ S ₅ , but can also be produced using Li ₂ S, simple phosphorus and simple sulfur.

As Li ₂ S, those commercially available without particular limitation can be used, but those having high purity are preferred. Preferably, Li ₂ S has a total lithium oxide lithium salt content of preferably 0.15% by mass or less, more preferably 0.1% by mass or less, and a content of lithium N-methylaminobutyrate. Is 0.15% by mass or less, more preferably 0.1% by mass or less. When the total content of the lithium salt of sulfur oxide is 0.15% by mass or less, the solid electrolyte obtained by the melt quenching method or the MM method becomes a glassy electrolyte (fully amorphous). That is, when the total content of the lithium salt of sulfur oxide exceeds 0.15% by mass, the obtained electrolyte may be a crystallized product from the beginning, and the ionic conductivity of the crystallized product is low. Furthermore, even if this crystallized product is subjected to a heat treatment, the crystallized product is not changed, and there is a possibility that a lithium / phosphorous sulfide solid electrolyte having a high ion conductivity cannot be obtained.
Further, when the content of lithium N-methylaminobutyrate is 0.15% by mass or less, a deteriorated product of lithium N-methylaminobutyrate does not deteriorate the cycle performance of the lithium battery.
By using Li ₂ S in which impurities are reduced in this way, a high ion conductive electrolyte can be obtained. The method for producing Li ₂ S used in the solid electrolyte is not particularly limited as long as it is a method that can reduce at least the impurities. For example, it can be obtained by purifying Li ₂ S produced by the following method.

Next, an example of a method for producing Li ₂ S will be described.
(A) Lithium hydroxide and hydrogen sulfide are reacted at 0 to 150 ° C. in an aprotic organic solvent to form water Li ₂ S, and then the reaction solution is dehydrosulfurized at 150 to 200 ° C. Method (refer to Japanese Patent Application Laid-Open No. 7-330312).
(B) A method of directly producing Li ₂ S by reacting lithium hydroxide and hydrogen sulfide at 150 to 200 ° C. in an aprotic organic solvent (see JP-A-7-330312).
(C) A method of reacting lithium hydroxide and a gaseous sulfur source at a temperature of 130 to 445 ° C. (Japanese Patent Laid-Open No. 9-283156).

Such purification method of the obtained Li ₂ S in the not particularly limited. Preferable purification methods include, for example, International Publication No. WO2005 / 40039. Specifically, Li ₂ S obtained as described above is washed at a temperature of 100 ° C. or higher using an organic solvent. The organic solvent used for washing is preferably an aprotic polar solvent, and the aprotic organic solvent used for the production of Li ₂ S and the aprotic polar organic solvent used for washing are preferably the same. More preferred. Examples of the aprotic polar organic solvent preferably used for washing include aprotic polar organic compounds such as amide compounds, lactam compounds, urea compounds, organic sulfur compounds, cyclic organophosphorus compounds, Or it can use suitably as a mixed solvent. In particular, N-methyl-2-pyrrolidone (NMP) is selected as a good solvent. The amount of the organic solvent used for washing is not particularly limited, and the number of times of washing is not particularly limited, but is preferably 2 or more. Cleaning is preferably performed under an inert gas such as nitrogen or argon.
The washed Li ₂ S is dried at a temperature equal to or higher than the boiling point of the organic solvent used for the cleaning, under an inert gas stream such as nitrogen, at normal pressure or reduced pressure for 5 minutes or longer, preferably for about 2 to 3 hours or longer. By doing so, Li ₂ S used in the present invention can be obtained.

In addition, P ₂ S ₅ can be used without particular limitation as long as it is industrially manufactured and sold. In place of P ₂ S ₅ , simple phosphorus and simple sulfur having a corresponding molar ratio can be used.
The simple phosphorus and simple sulfur can be used without particular limitation as long as they are industrially produced and sold.

A solid electrolyte can be manufactured by mixing the above-described P ₂ S ₅ and the above-described Li ₂ S. The mixing molar ratio of P ₂ S ₅ and Li ₂ S is usually 50:50 to 80:20, preferably 60:40 to 75:25. A particularly preferable mixing molar ratio is Li ₂ S: P ₂ S ₅ = 68: 32 to 74:26. A mixture of simple phosphorus and simple sulfur may be used instead of P ₂ S ₅ .

As a method for producing a solid electrolyte, there are a melt quenching method and a mechanical milling method (hereinafter abbreviated as “MM method”).
In the case of the melt quenching method, a mixture of P ₂ S ₅ and Li ₂ S in a predetermined amount in a mortar and pelletized is placed in a carbon-coated quartz tube and vacuum sealed. After reacting at a predetermined reaction temperature, glass is charged, that is, an amorphous solid electrolyte is obtained by rapid cooling. The reaction temperature at this time is preferably 400 ° C to 1000 ° C, more preferably 800 ° C to 900 ° C. Moreover, reaction time becomes like this. Preferably it is 0.1 to 12 hours, More preferably, it is 1 to 12 hours. The quenching temperature of the reaction product is usually 10 ° C. or lower, preferably 0 ° C. or lower.

In the case of the MM method, P ₂ S ₅ and Li ₂ S are mixed in a predetermined amount in a mortar and reacted for a predetermined time by the MM method, whereby an amorphous, that is, glassy solid electrolyte is obtained.
In the MM method using P ₂ S ₅ and Li ₂ S, the reaction can be performed at room temperature. According to the MM method, since a solid electrolyte can be produced at room temperature, there is an advantage that a solid electrolyte having a charged composition can be obtained without thermal decomposition of raw materials. Further, the MM method has an advantage that the solid electrolyte can be made into fine powder simultaneously with the production of the solid electrolyte. Although various types of MM methods can be used, it is particularly preferable to use a planetary ball mill. The planetary ball mill can efficiently generate very high impact energy by rotating the platform while the pot rotates. Although the rotation speed and rotation time of the MM method are not particularly limited, the faster the rotation speed, the faster the solid electrolyte production speed, and the longer the rotation time, the higher the conversion rate of the raw material to the solid electrolyte.

As conditions for the MM method, for example, when a planetary ball mill is used, the rotational speed may be set to several tens to several hundreds of revolutions / minute, and the treatment may be performed for 0.5 hours to 100 hours.
Although specific examples of the solid electrolyte by the melt quenching method and the MM method have been described above, manufacturing conditions such as temperature conditions and processing time can be appropriately adjusted according to the equipment used.
Moreover, the obtained solid electrolyte can be heat-treated at a predetermined temperature to produce a glass-ceramic solid electrolyte. The heat treatment temperature for producing the sulfide glass ceramic solid electrolyte is preferably 190 ° C. or higher and 340 ° C. or lower, more preferably 195 ° C. or higher and 335 ° C. or lower, and particularly preferably 200 ° C. or higher and 330 ° C. or lower. When the temperature is lower than 190 ° C., it may be difficult to obtain a crystal with high ion conductivity. When the temperature exceeds 340 ° C., a crystal with low ion conductivity may be generated. In the case of a temperature of 190 ° C. or higher and 220 ° C. or lower, the heat treatment time is preferably 3 hours or longer and 240 hours, and particularly preferably 4 hours or longer and 230 hours or shorter. In the case of a temperature higher than 220 ° C. and lower than 340 ° C., it is preferably 0.1 hours or longer and 240 hours or shorter, particularly preferably 0.2 hours or longer and 235 hours or shorter, and more preferably 0.3 hours or longer and 230 hours or shorter. . When the heat treatment time is less than 0.1 hour, it may be difficult to obtain a crystal with high ion conductivity. When the heat treatment time exceeds 240 hours, a crystal with low ion conductivity may be generated.

  The sulfide glass-ceramic solid electrolyte obtained as described above is 2θ = 17.8 ± 0.3 deg, 18.2 ± 0.3 deg, 19.X in X-ray diffraction (CuKα: λ = 1.5418４). Has diffraction peaks at 8 ± 0.3 deg, 21.8 ± 0.3 deg, 23.8 ± 0.3 deg, 25.9 ± 0.3 deg, 29.5 ± 0.3 deg, 30.0 ± 0.3 deg It is preferable. A solid electrolyte having such a crystal structure has extremely high lithium ion conductivity.

(Method for producing negative electrode composite for lithium battery)
Next, the manufacturing method of the negative mix for lithium batteries is demonstrated.
The above-mentioned carbon material and the above-mentioned solid electrolyte are mixed by a mechanochemical treatment at a ratio of (carbon material) :( solid electrolyte) = 30/70 to 90/10 in a weight ratio. The one molded into a shape is used as the negative electrode. The weight ratio between the carbon material and the solid electrolyte is more preferably in the range of 50/50 to 80/20 in terms of charge / discharge capacity and internal resistance.

  The method of mixing the carbon material and the solid electrolyte is preferably mechanochemical treatment. Mechanochemical treatment refers to treatment that applies compressive force and shear force at the same time, and examples of mechanochemical treatment include kneaders such as pressure kneaders and kneaders, rotating ball mills, vibration mills, planetary ball mills, bead mills, and jet mills. Among them, a planetary ball mill is preferable. The conditions of the mechanochemical treatment are not particularly limited, but the ball size and the number of rotations may be appropriately adjusted so that the crystallites of the carbon powder are not destroyed and the particles of the solid electrolyte powder are pulverized. . The compressive force and shear force applied by this treatment are larger than those in a mortar or the like, and it is considered that the mixing state of the material is greatly improved. By simultaneously performing this treatment on the carbon material and the solid electrolyte, the contact interface between the carbon material and the electrolyte becomes relatively simple and uniform, and an ion conduction path is easily formed.

  The present invention will be described in more detail with reference to examples and comparative examples. In addition, this invention is not restrict | limited to the description content of these Examples at all.

First, production examples of Li ₂ S that is a raw material of the solid electrolyte used in Examples 1 and 2 and Comparative Examples 1 to 3 will be described. The production of Li ₂ S to be described below, purification of Li ₂ S, producing a negative electrode mixture, production and manufacturing of a lithium battery of the solid electrolyte, in a dry room for all dew point -40 ℃ less, or, glove box Went in.

[Production example of Li ₂ S]
Li ₂ S was produced according to the method of the first aspect (two-step method) in JP-A-7-330312. Specifically, 3326.4 g (33.6 mol) of N-methyl-2-pyrrolidone (NMP) and 287.4 g (12 mol) of lithium hydroxide were charged into a 10 liter autoclave equipped with a stirring blade. The temperature was raised to ° C. After the temperature increase, hydrogen sulfide was blown into the liquid for 2 hours at a supply rate of 3 L / min. Subsequently, the temperature of the reaction solution was raised under a nitrogen stream (200 cc / min), and the reacted water Li ₂ S was desulfurized to obtain Li ₂ S. As the temperature increased, water produced as a by-product due to the reaction between hydrogen sulfide and lithium hydroxide started to evaporate, but this water was condensed by the condenser and extracted out of the system. While water was distilled out of the system, the temperature of the reaction solution rose, but when the temperature reached 180 ° C., the temperature increase was stopped and the temperature was kept constant. The reaction was completed after the desulfurization reaction of water Li ₂ S (about 80 minutes) to obtain Li ₂ S.

Next, an example of purification of Li ₂ S will be described.
[Example of purification of Li ₂ S]
After decanting NMP in the 500 mL slurry reaction solution (NMP-Li ₂ S slurry) obtained by the Li ₂ S production method described above, 100 mL of dehydrated NMP was added and stirred at 105 ° C. for about 1 hour. NMP was decanted at that temperature. Further, 100 mL of NMP was added, stirred at 105 ° C. for about 1 hour, NMP was decanted at that temperature, and the same operation was repeated a total of 4 times. After completion of the decantation, Li ₂ S was dried under normal pressure at 230 ° C. (temperature higher than the boiling point of NMP) under normal pressure for 3 hours. Impurity content in the obtained Li ₂ S was measured. Incidentally, lithium sulfite _(Li 2 _SO 3), the content of each sulfur oxide lithium sulfate _(Li 2 SO ₄₎ and lithium thiosulfate _(Li 2 S2O _3), and N- methylamino acid lithium (NMAB) is Quantification was performed by ion chromatography. As a result, the total content of sulfur oxides was 0.13% by mass, and NMAB was 0.07% by mass.

Next, a production example of a solid electrolyte containing purified Li ₂ S will be described.
[Production example of solid electrolyte]
Li ₂ S (manufactured by Aldrich) and P ₂ S ₅ (manufactured by Aldrich) purified in the above purification example were used as starting materials. About 1 g of a mixture obtained by adding 68 mol parts of Li ₂ S and 32 mol parts of P ₂ S ₅ and 10 alumina balls having a particle diameter of 10 mm are put into a 45 mL alumina container, and a planetary ball mill (Fritsch) is used. The solid electrolyte which is a white yellow powder was manufactured by making MM process for 20 hours with a rotational speed of 370 rpm under nitrogen atmosphere at room temperature (25 degreeC) by a product: Model No. P-7.
Powder X-ray diffraction measurement was performed on the obtained powder (CuKα: λ = 1.5418Å). Since the obtained chart showed a broad shape peculiar to the amorphous body, it was confirmed that the powder was vitrified, that is, amorphous.
This glassy solid electrolyte powder was fired in nitrogen at a temperature range from room temperature (about 25 ° C.) to 250 ° C. to produce a glass ceramic sulfide solid electrolyte. In this case, it took about 3 hours to raise or lower the temperature.

The sulfide glass ceramic solid electrolyte thus produced was subjected to powder X-ray diffraction measurement (CuKα: λ = 1.5418１．５). The obtained sulfide glass ceramic solid electrolyte has diffraction peaks at 2θ = 17.8 deg, 18.2 deg, 19.8 deg, 21.8 deg, 23.8 deg, 25.9 deg, 29.5 deg, 30.0. It was confirmed that it has a crystal phase different from the conventionally known Li ₇ PS ₆ , Li ₄ P ₂ S ₆ , and Li ₃ PS ₄ .

The sulfide glass ceramic solid electrolyte obtained by this treatment had an ionic conductivity at room temperature (25 ° C.) of 2.0 × 10 ⁻³ S / cm. The ionic conductivity was measured while processing the glass solid electrolyte powder before the firing treatment into a pellet-shaped (diameter: about 10 mm, thickness: about 1 mm) shaped body and subjecting the shaped body to firing treatment. The measurement was performed by an alternating current two-terminal method for a molded body in which a carbon paste was applied as an electrode.

Example 1
An alumina ball having a diameter of 10 mm and 0.6 g of a carbon material having an Lc value of 1074Å and an R value of 0.16 and 0.4 g of sulfide glass ceramic solid electrolyte powder (average particle size of 30 μm) produced in the above production example. Along with 10 pieces, put them in a 45 mL alumina container and use a planetary ball mill (Fritsch: Model No. P-7) in an argon atmosphere at room temperature (25 ° C.) with a rotational speed of 150 rpm and MM treatment for 5 minutes. Thus, a negative electrode mixture was obtained.
LiNi _0.8 Co _0.15 Al _0.05 O ₂ was used as the positive electrode active material. This positive electrode active material and the above-mentioned solid electrolyte were mixed in a mortar at a weight ratio of 70%: 30% to obtain a positive electrode mixture.
50 mg of the electrolyte was put into a plastic cylinder having a diameter of 10 mm, press-molded, and 20 mg of the positive electrode mixture prepared as described above was put in and pressure-molded again. The above-mentioned 8.3 mg of the negative electrode active material mixture was introduced from the side opposite to the positive electrode mixture to form a three-layer structure and subjected to pressure molding to obtain a lithium battery of Example 1.

(Example 2)
A lithium battery of Example 2 was fabricated in the same manner as in Example 1 except that a carbon material having Lc of 716% and R value of 0.24 was used.

(Comparative Example 1)
In Example 1, a lithium battery of Comparative Example 1 was produced in the same manner as Example 1 except that the MM treatment was not performed.

(Comparative Example 2)
In Example 1, a lithium battery of Comparative Example 2 was produced in the same manner as in Example 1 except that a carbon material having Lc of 120% and R value of 0.15 was used.

(Comparative Example 3)
A lithium battery of Comparative Example 3 was produced in the same manner as in Example 1 except that a carbon material having an Lc of 567５６ and an R value of 0.04 was used.

(Evaluation of lithium batteries prepared in Examples 1 and 2 and Comparative Examples 1 to 3)
The battery was evaluated as follows. Charged to 4.2 V at 200 μA per cm ^{2 in the} first cycle, discharged to 1.5 V at 500 μA, charged to 4.2 V at 200 μA in the second cycle, discharged to 1.5 V at 1 mA, and then the third cycle The battery was charged to 4.2 V at 200 μA and discharged to 1.5 V at 3 mA. The discharge capacity at the third cycle is shown in Table 1 as the battery performance. In Table 1, the case where the MM process was performed was indicated as A, and the case where it was not performed was indicated as B.

  Moreover, Lc value and R value were calculated | required by the Raman spectroscopic measurement about the carbon material used for manufacture of negative electrode compound material. The Raman spectroscopic measurement was performed using a Raman measuring apparatus Almega (trade name) manufactured by Thermo Fisher Scientific Co., Ltd., and a laser having a wavelength of 532 nm was used. XRD measurement was performed using an XRD measurement apparatus manufactured by Rigaku. These Lc and R values are shown in Table 1.

About solid electrolyte, SEM-EDS measurement was performed on condition (a)-(c) shown below.
<SEM-EDS mapping measurement method>
(A) Model name Body: JEOL JSM-6480LA
EDS: JEOL JED-2300
(B) EDS measurement conditions Acceleration voltage: 15 kV
Current value: about 1.4nA
Count rate: 6000 to 7000 cps
Observation range: 256 × 192 μm
Duel time: 0.1 msec
Number of sweeps: 100 times (c) EDS analysis conditions P: 1.89 to 2.13 keV
S: 2.18 to 2.43 keV

  Sample adjustment conditions for performing SEM-EDS mapping measurement were as follows. Under a nitrogen atmosphere, a knife was put into the negative electrode composite pellet and it was broken. And after fixing to a sample stand with carbon tape, it put into the airtight type sample holder and introduce | transduced into the preliminary | backup exhaust chamber of SEM. After evacuating the chamber, the lid of the sample holder was opened and inserted into the SEM body. And SEM-EDS mapping measurement was performed. The obtained mapping image of phosphorus is shown in FIG.

Using the phosphorus mapping image obtained in the SEM-EDS mapping measurement, the maximum value of phosphorus element 80/255 is set as a threshold value, and phosphorus is present at a place where the value is higher (2 Value). The area where phosphorus was continuously present was defined as particles, and the area and perimeter of each particle were measured.
Further, the degree of dispersion and the degree of dispersion were calculated according to the following definitions.

<Dispersity and dispersity distribution>
As shown in FIG. 2, using the phosphorus mapping image observed by SEM-EDS, the dispersity (X / X ₀ ) and dispersity distribution ((Y / X) / ( Y ₀ / X ₀ )) was defined. n is a natural number indicating the number of phosphorus particles 300. The α _n value is the area of the n-th phosphorus particle 300, and the β _n value is the length around the n-th phosphorus particle 300. The X value is an average value of the ratio of the area of the n-th phosphorus particle 300 and the peripheral length of the phosphorus particle 300 shown in Formula (1). The Y value is a root mean square value of the ratio of the area of the n-th phosphorus particle 300 and the circumference length of the n-th phosphorus particle 300 shown in Expression (2). The X ₀ value and the Y ₀ value are an X value and a Y value, respectively, when the crystallites of the carbon material and the solid electrolyte particles are mixed without being pulverized. Here, X / X ₀ has a specific range shown in Formula (3), and (Y / X) / (Y ₀ / X ₀ ) also has a specific range shown in Formula (4). It is preferable. The calculated dispersity (X / X ₀ ) and dispersity distribution ((Y / X) / (Y ₀ / X ₀ )) are shown in Table 1.
(1): X = (α ₁ / β ₁ + α ₂ / β ₂ + α ₃ / β ₃ ... + Α _n / β _n ) / n
(2): Y = {(α ₁ / β ₁ ) ² + (α ₂ / β ₂ ) ² + (α ₃ / β ₃ ) ² ... + (α _n / β _n ) ² } ^1/2 / n
(3): 0.8 ≦ X / X ₀ ≦ 1.0
(4): (Y / X) / (Y ₀ / X ₀ ) ≦ 1.0

[Evaluation results]
Comparison between Example 1 and Comparative Example 1 revealed that dispersibility was improved and the discharge capacity of the lithium battery was greatly improved by performing MM treatment. As a result of comparison between Example 2 and Comparative Examples 2 and 3, by using a carbon material having an R value of 0.05 or more and less than 0.30 and an Lc value of 150 to 1500, the discharge capacity of the lithium battery Was found to improve significantly.

  The lithium battery having the negative electrode composite of the present invention can be used for, for example, an electric vehicle or an electronic device.

The schematic block diagram which shows the lithium battery of this embodiment. A mapping image obtained by mapping measurement of a scanning electron microscope using an energy dispersive X-ray analyzer.

Explanation of symbols

201 …… Battery cell as lithium battery 205 …… Positive electrode sheet 206 …… Negative electrode sheet 210 …… Positive electrode active material 220 …… Solid electrolyte sheet 230 …… Negative electrode active material 240 …… Positive electrode current collector sheet 250 …… Negative electrode current collector Sheet 300 ... Phosphorus particles

Claims (7)

The peak height ( _ID ) indicating the vibration mode derived from the amorphous turbostratic structure in the range of 1350-1370 cm ⁻¹ measured by Raman spectroscopy and the graphite crystalline structure in the range of 1570-1620 cm ^−1. the height of the peak indicating the vibration mode derived from _{(I G)} and the degree of graphitization R value calculated from the ratio of _(I D / _{I G)} is, is 0.05 to 0.30, and, X-rays diffraction A carbon material having a crystallite thickness dimension (Lc) in the C-axis direction of the (002) plane by a method of 150 to 2000 mm,
A solid electrolyte;
A negative electrode composite material for a lithium battery, characterized by being mixed. The negative electrode composite material for a lithium battery according to claim 1, wherein the solid electrolyte contains lithium (Li), phosphorus (P), and sulfur (S). The carbon material is in a state where the crystallites are not crushed,
The solid electrolyte is in a state in which particles are pulverized, and a dispersion satisfying the formulas (1) to (4) in an element mapping image observed with a scanning electron microscope using an energy dispersive X-ray analyzer The negative electrode composite material for a lithium battery, having a degree (X / X ₀ ) and a dispersity distribution ((Y / X) / (Y ₀ / X ₀ )).
(1): X = (α ₁ / β ₁ + α ₂ / β ₂ + α ₃ / β ₃ ... + Α _n / β _n ) / n
(2): Y = {(α ₁ / β ₁ ) ² + (α ₂ / β ₂ ) ² + (α ₃ / β ₃ ) ² ... + (α _n / β _n ) ² } ^1/2 / n
(3): 0.8 ≦ (X / X ₀ ) ≦ 1.0
(4): ((Y / X) / (Y ₀ / X ₀ )) ≦ 1.0
(N is a natural number indicating the number of mapping element particles, α _n value is the area of the _n-th mapping element particle, and β _n value is the n-th mapping element particle size. The X value is the average value of the ratio of the area of the nth mapping element particle and the peripheral length of the mapping element particle shown in Formula (1), and the Y value is the formula (2) is a mean square value of the ratio of the area of the n-th mapping element particle and the circumference length of the n-th mapping element particle shown in (2), and the X ₀ value and the Y ₀ value are (The X value and the Y value when the crystallites of the carbon material and the solid electrolyte particles are mixed without being pulverized.) The negative electrode mixture for lithium batteries as described in any one of Claims 1-3 is included. The negative electrode for lithium batteries characterized by the above-mentioned. An all-solid lithium battery comprising the negative electrode according to claim 4. An apparatus comprising the all-solid-state lithium battery according to claim 5. The peak height ( _ID ) indicating the vibration mode derived from the amorphous turbostratic structure in the range of 1350-1370 cm ⁻¹ measured by Raman spectroscopy and the graphite crystalline structure in the range of 1570-1620 cm ^−1. the height of the peak indicating the vibration mode derived from _{(I G)} and the degree of graphitization R value calculated from the ratio of _(I D / _{I G)} is, is 0.05 to 0.30, and, X-rays diffraction A lithium material characterized by mixing a carbon material having a crystallite thickness dimension (Lc) dimension in the C-axis direction (Lc) of 150 to 2000 mm by a mechanochemical treatment with a mechanochemical treatment. A method for producing a negative electrode composite.

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