JP2008176981A - Electrode for all solid lithium secondary battery and all solid lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for an all solid lithium secondary battery having high capacity per volume, or high energy density by forming a good conductive path, increasing filling density, and securing an ion conducting path, and to provide the all solid lithium secondary battery using the electrode. <P>SOLUTION: The electrode for the all solid lithium secondary battery has an active material which is a mixture of a needle or plate active material and a globular active material, and a solid electrolyte material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an all-solid lithium secondary battery, and more particularly to an electrode for an all-solid lithium secondary battery used to form a high energy density all-solid lithium secondary battery.

  With the rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones in recent years, the development of secondary batteries that are excellent as power sources, such as lithium secondary batteries, has been regarded as important. In fields other than the information-related equipment and communication-related equipment, for example, in the automobile industry, the development of high-power and high-capacity lithium secondary batteries for electric vehicles and hybrid vehicles as low-emission vehicles has been promoted. ing.

  However, the lithium secondary batteries currently on the market use an organic electrolyte that uses a flammable organic solvent as a solvent.・ Improved materials are necessary.

  In contrast, an all-solid lithium secondary battery in which the liquid electrolyte is changed to a solid electrolyte to make the battery all solid does not use a flammable organic solvent in the battery, so the safety device can be simplified and the manufacturing cost can be reduced. And is considered to be highly productive.

  In the above all-solid lithium secondary battery, for example, a three-layer pellet of positive electrode / solid electrolyte / negative electrode is formed by a powder molding method, inserted into a conventional coin-type battery case or button-type battery case, Made by sealing. Such an all-solid lithium secondary battery has a high electrochemical resistance as compared with a lithium secondary battery using an organic electrolyte because the battery constituent group consisting of the positive electrode, the negative electrode, and the electrolyte is all solid. .

  As an electrode (positive electrode and negative electrode) of a battery using such a solid electrolyte material, that is, an electrode for an all solid lithium secondary battery (hereinafter simply referred to as an electrode), an active material and a solid electrolyte material are mixed. Things need to be active material layers. In general, as shown in FIG. 3 (a), it is composed of a spherical solid electrolyte material 1 and a spherical active material 2, and Li ions move in the solid electrolyte material and charges move in the active material. . When such a spherical active material is used, the expansion and contraction of the active material is repeated with the progress of the charge / discharge cycle, thereby causing plastic deformation of the solid electrolyte material in the electrode. Therefore, a gap is generated in the electrode, the conductive path between the active materials is cut, and the active material utilization rate decreases. Further, since the contact area of the solid electrolyte material is reduced, the reaction area of the battery is reduced, and the charge / discharge capacity is reduced.

  On the other hand, a lithium secondary battery using an organic electrolyte usually needs to add a binder (binder) to the electrode in order to hold the electrode. Since this binder (binder) is contained in the electrode, in the lithium secondary battery using the organic electrolyte, the conductive path is cut even if the active material expands or contracts due to the charge / discharge cycle. The problems such as these hardly occur, and the effect of expansion / contraction of the active material accompanying the charge / discharge cycle on the charge / discharge characteristics is small. That is, the problem that the conductive path is cut by the expansion and contraction of the active material with the progress of the charge / discharge cycle described above is an all solid that does not require the addition of a binder (binder). This was a problem specific to lithium secondary batteries.

  Therefore, as shown in FIG. 3B, a method of forming a conductive path by adding a needle-like or plate-like active material 3 into an electrode has been proposed. For example, Patent Document 1 discloses that the conductivity is improved by mixing carbon whiskers or graphite whiskers having an electronic conductivity with a large aspect ratio in an active material. However, since the carbon whisker or the graphite whisker is hard to be densely packed, there are many gaps in the active material, and the packing density is lowered, so that the capacity per volume is reduced.

JP-A-2-177260 JP 11-7942 A Japanese Patent Laid-Open No. 2-87466

  The present invention has been made in view of the above problems, and by forming a good conductive path, increasing the packing density, and securing an ion conduction path, the capacity per volume is large, that is, high energy density. It is a main object of the present invention to provide an electrode for an all solid lithium secondary battery and an all solid lithium secondary battery using the same.

  In order to achieve the above object, the present invention has an active material and a solid electrolyte material in which a needle-like or plate-like active material and a spherical active material are mixed. An electrode for an all-solid lithium secondary battery is provided.

  According to the present invention, the active material and the solid electrolyte material obtained by mixing a needle-like or plate-like active material and a spherical active material cause expansion / contraction of the active material accompanying the charge / discharge cycle. However, the needle-like or plate-like active material can form a good conductive path. In addition, the inclusion of the spherical active material can increase the packing density and provide an electrode for an all solid lithium secondary battery having a large capacity per volume, that is, a high energy density.

  In the invention described in claim 1, when the all-solid-state lithium secondary battery electrode is used for a positive electrode, the active material in which the acicular or plate-like active material and the spherical active material are mixed is used. The volume fraction of the acicular or plate-like active material is preferably 10 to 40 vol%. Since the volume fraction of the acicular or plate-like active material is within the above range, the acicular or plate-like active material is good even when the active material expands or contracts due to the charge / discharge cycle. A conductive path can be formed. Moreover, since the volume fraction of the acicular or plate-like active material is within the above range, the spherical active material can be contained in a predetermined content. Therefore, it is possible to increase the packing density and obtain an electrode for an all solid lithium secondary battery having a desired high energy density.

  In the invention described in claim 1, when the all-solid-state lithium secondary battery electrode is used as a negative electrode, the active material in which the acicular or plate-like active material and the spherical active material are mixed is used. The volume fraction of the acicular or plate-like active material is preferably 10 to 20 vol%. Since the volume fraction of the acicular or plate-like active material is within the above range, the acicular or plate-like active material is good even when the active material expands or contracts due to the charge / discharge cycle. A conductive path can be formed. Moreover, since the volume fraction of the acicular or plate-like active material is within the above range, the spherical active material can be contained in a predetermined content. Therefore, it is possible to increase the packing density and obtain an electrode for an all solid lithium secondary battery having a desired high energy density.

  When the all-solid-state lithium secondary battery electrode is used for a negative electrode, the needle-like or plate-like active material and the spherical active material are preferably graphite. This is because graphite generally has good characteristics as an active material for a negative electrode and is widely used.

  In the invention described in claim 1, in the electrode for the all-solid-state lithium secondary battery, an elastic body, an active material obtained by mixing the acicular or plate-like active material and the spherical active material, and the elasticity It is preferable to contain 5-10 mass% with respect to the total mass of a body. In the present invention, if the elastic body is contained within the above range, the elastic body relieves stress generated by the expansion and contraction of the active material during charge and discharge. For this reason, the deformation of the solid electrolyte material due to the stress can be suppressed, and the decrease in the battery reaction area and the capacity decrease due to the deformation of the solid electrolyte material can be suppressed. Moreover, since it exists in the said range, a conductive path can be ensured and desired electroconductivity is obtained.

  Moreover, in this invention, the all-solid-state lithium secondary battery electrode using said all-solid-state lithium secondary battery is provided.

  According to the present invention, a high energy density all solid lithium secondary battery is obtained by using the above-mentioned electrode for all solid lithium secondary battery having a large capacity per volume as described above, that is, a high energy density. Can do.

  In this invention, there exists an effect that the electrode for high energy density all the solid lithium secondary batteries can be obtained.

  The electrode for an all solid lithium secondary battery and the all solid lithium secondary battery of the present invention will be described in detail below.

A. First, an electrode for an all-solid lithium secondary battery of the present invention will be described. The all solid lithium secondary battery of the present invention is characterized by having an active material and a solid electrolyte material obtained by mixing a needle-like or plate-like active material and a spherical active material.

  According to the present invention, an electrode for an all-solid-state lithium secondary battery has an acicular or plate-like active material by having an active material mixed with a acicular or plate-like active material and a spherical active material and a solid electrolyte material. Can form a favorable conductive path. Further, by containing the spherical active material, it is possible to increase the packing density and obtain an electrode for an all solid lithium secondary battery having a large capacity per volume, that is, a high energy density.

Hereinafter, the electrode for an all-solid lithium secondary battery of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing an example of the configuration of an electrode for an all solid lithium secondary battery of the present invention. As shown in FIG. 1, the electrode for an all-solid lithium secondary battery of the present invention has a needle-like or plate-like active material 3, a spherical active material 2, and a solid electrolyte material 1 as active materials.
Hereinafter, the electrode for an all-solid lithium secondary battery of the present invention will be described in detail for each configuration.
1. Active material The present invention is characterized in that an active material is mixed with a needle-like or plate-like active material and a spherical active material. Each will be described below.
(1) Needle-like or plate-like active material The needle-like or plate-like active material used in the present invention is mixed with a spherical active material and a solid electrolyte material, which will be described later, so that the needle-like or plate-like active material has good conductivity. A path can be formed. Further, by increasing the packing density by containing a spherical active material, an electrode for an all solid lithium secondary battery having a large capacity per volume, that is, a high energy density can be obtained.

  The acicular active material in the present invention is not particularly limited as long as it is an active material having a generally acicular shape. However, when the above “acicular” is specifically defined, an aspect ratio (long (Axis length / vertical length with the long axis). In the present invention, the aspect ratio (length of major axis / length perpendicular to major axis) is 3 or more. In particular, it is preferably in the range of 4 to 100, particularly in the range of 10 to 70.

  As the length of the major axis of the acicular active material, the average value is preferably in the range of, for example, 0.1 to 1000 μm, more preferably in the range of 1 to 100 μm, and particularly preferably in the range of 5 to 20 μm.

  In addition, the vertical length of the acicular active material with respect to the major axis is, for example, in the range of 0.01 to 100 μm, in particular in the range of 0.1 to 10 μm, particularly in the range of 0.25 to 1 μm. It is preferable that

  In the present invention, the average length of the long axis of the acicular active material is described later so that the acicular active material forms a good conductive path and the spherical active material is optimal for increasing the packing density. The ratio with the average particle diameter of the spherical active material (the ratio of the average length of the long axis of the acicular active material / the average particle diameter of the spherical active material) is in the range of 1 to 100, particularly in the range of 1 to 50. In particular, it is preferably in the range of 1.5 to 30. This is because the contact between the acicular active material and the spherical active material is maintained even when the spherical active material undergoes a volume change accompanying expansion and contraction.

  In the present invention, the length and diameter of the major axis of the acicular active material may be values measured based on image analysis such as SEM.

In addition, the plate-like active material in the present invention is not particularly limited as long as it is an active material having a generally plate-like shape. However, when the above “plate-like” is specifically defined, It can be expressed by maximum width and thickness. In the present invention, the ratio of the maximum surface width to the thickness (maximum surface width / thickness) is 3 or more. In particular, it is preferably in the range of 4 to 100, particularly in the range of 10 to 70.
The maximum surface width is the diameter when the plate-shaped active material is disk-shaped, the long diameter when the plate-shaped active material is elliptical, and the length of the diagonal line when the surface is rectangular. The longest part of the surface shape is said to be said.

  As the maximum width of the surface of the plate-like active material, the average value is preferably in the range of, for example, 0.1 to 1000 μm, more preferably in the range of 1 to 100 μm, and particularly preferably in the range of 5 to 20 μm.

  Moreover, as thickness of a plate-shaped active material, the average value is in the range of 0.01-100 micrometers, for example, It is in the range of 0.1-10 micrometers especially, It is especially in the range of 0.25-1 micrometer. preferable.

  In the present invention, the maximum width of the surface of the plate-like active material described above and the spherical shape described later are used so that the plate-like active material forms an excellent conductive path and the spherical active material is optimal for increasing the packing density. The ratio with the average particle diameter of the active material (the ratio between the maximum surface width / the average particle diameter of the spherical active material) is in the range of 1 to 100, particularly in the range of 1 to 50, in particular 1.5 to 30. It is preferable to be within the range. This is because the contact between the acicular active material and the spherical active material is maintained even when the spherical active material undergoes a volume change accompanying expansion and contraction.

  In the present invention, the maximum width and thickness of the surface of the plate-like active material can be values measured based on image analysis such as SEM.

(2) Spherical active material The spherical active material used in the present invention is mixed with the above-described acicular or plate-like active material, and a solid electrolyte material described later, so that the acicular or platy active material has a good conductive path. Can be formed. Further, by containing the spherical active material, it is possible to increase the packing density and obtain an electrode for an all solid lithium secondary battery having a large capacity per volume, that is, a high energy density.

  The spherical active material in the present invention is not particularly limited as long as it is an active material having a generally spherical shape.

  The average particle diameter of the spherical active material can be, for example, 100 μm or less, and is preferably in the range of 0.1 to 20 μm, particularly preferably in the range of 1 to 10 μm.

  In the present invention, the average particle diameter of the spherical active material may be a value measured based on image analysis such as SEM.

(3) For positive electrode

  When the electrode for the all-solid-state lithium secondary battery is a positive electrode, the volume fraction of the acicular or plate-like active material in the active material obtained by mixing the acicular or plate-like active material and the spherical active material is It is preferable that it is 10-40 vol%. Among these, it is preferable to be in the range of 15-30 vol%, particularly in the range of 20-25 vol%. Since the volume fraction of the acicular or plate-like active material is within the above range, the acicular or plate-like active material is good even when the active material expands or contracts due to the charge / discharge cycle. A conductive path can be formed. Moreover, since the volume fraction of the acicular or plate-like active material is within the above range, the spherical active material can be contained in a predetermined content. Therefore, it is possible to increase the packing density and obtain an electrode for an all solid lithium secondary battery having a desired high energy density.

  The acicular or plate-like active material used for the positive electrode is not particularly limited as long as it has a function as the acicular or plate-like active material used for the positive electrode of the present invention. Examples include α-FeOOH.

Examples of the spherical active material used for the positive electrode include LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiFePO _{4, and the} like, among which LiCoO ₂ , LiNiO ₂ , and particularly LiCoO ₂ are preferable. This is because LiCoO ₂ generally has good characteristics as an active material for a positive electrode and is widely used.

(4) For negative electrode

  When the electrode for the all-solid-state lithium secondary battery is a negative electrode, the volume fraction of the acicular or plate-like active material in the active material obtained by mixing the acicular or plate-like active material and the spherical active material is It is preferable that it is 10-20 vol%. Among these, it is preferable to be in the range of 12-18 vol%, particularly in the range of 14-16 vol%. Since the volume fraction of the acicular or plate-like active material is within the above range, the acicular or plate-like active material is good even when the active material expands or contracts due to the charge / discharge cycle. A conductive path can be formed. Moreover, since the volume fraction of the acicular or plate-like active material is within the above range, the spherical active material can be contained in a predetermined content. Therefore, it is possible to increase the packing density and obtain an electrode for an all solid lithium secondary battery having a desired high energy density.

  Examples of the acicular or plate-like active material used for the negative electrode include plate-like graphite and acicular graphite. Of these, plate-like graphite is preferable. This is because graphite generally has good characteristics as an active material for a negative electrode and is widely used.

  The spherical active material used for the negative electrode is not particularly limited as long as it has a function as the spherical active material used for the negative electrode of the present invention, and examples thereof include spherical graphite. .

2. Solid Electrolyte Material The solid electrolyte material used in the present invention mainly has a good ion conduction path because ions such as Li in the electrode easily pass through the solid electrolyte material rather than in the active material.

  In the present invention, examples of the solid electrolyte material include sulfide-based crystallized glass, thiolithicone, oxide-based solid electrolyte, and the like. Among them, sulfide-based crystallized glass, thiosilicon, particularly sulfide-based crystals. A vitrified glass is preferred.

  In the present invention, the shape of the solid electrolyte material is not particularly limited as long as it has a function as a solid electrolyte, but a spherical material is usually used. The spherical solid electrolyte material in the present invention is not particularly limited as long as it is a solid electrolyte material having a generally spherical shape.

  The average particle diameter of the solid electrolyte material can be, for example, 50 μm or less, and is preferably in the range of 0.01 to 20 μm, particularly preferably in the range of 0.1 to 10 μm. In the present invention, the average particle diameter of the solid electrolyte material may be a value measured based on image analysis such as SEM.

  The mass ratio of the mixed active material (a mixture of the needle-like or plate-like active material and the spherical active material) and the solid electrolyte material varies greatly depending on the active material, electrolyte shape, particle size, etc. There is no particular limitation.

  The method for producing the solid electrolyte material used in the present invention is not particularly limited as long as it is a method capable of obtaining a desired solid electrolyte material. Specifically, a raw material containing Li or the like is used as a planetary ball mill. And the like obtained by vitrification and subsequent heat treatment.

3. Elastic body In this invention, it is preferable to contain 5-10 mass% of elastic bodies in the said electrode for all-solid-state lithium secondary batteries. Among these, it is preferable to be in the range of 7 to 10% by mass, particularly in the range of 8 to 10% by mass. If it contains an elastic body in the said range, the said elastic body will relieve | moderate the stress which generate | occur | produces by the expansion / contraction of the active material at the time of charging / discharging. For this reason, the deformation of the solid electrolyte material due to the stress can be suppressed, and the decrease in the battery reaction area and the capacity decrease due to the deformation of the solid electrolyte material can be suppressed. Moreover, it is because a conductive path can be secured and desired conductivity can be obtained.

  The elastic body is only required to be electrically stable and have a predetermined elastic value width, and its Young's modulus obtained by a stress-strain test is specifically within a range of 0.1 to 50 MPa. In particular, it is preferable to be in the range of 1 to 10 MPa, particularly in the range of 1.5 to 5.0 MPa. If the elastic body has a Young's modulus within the above range, the elastic body relieves stress generated by expansion and contraction of the active material during charge and discharge. For this reason, the deformation of the solid electrolyte material due to the stress can be suppressed, and the decrease in the battery reaction area and the capacity decrease due to the deformation of the solid electrolyte material can be suppressed. Moreover, it is because a conductive path can be secured and desired conductivity can be obtained. The elastic body may be a conductive elastic body or an elastic body having a function of transmitting ions such as Li ions.

  The elastic body is not particularly limited as long as it has a function as an elastic body, but has an optimum Young's modulus as an elastic body in the present invention, high electrochemical stability, etc. For this reason, for example, styrene butadiene rubber (SBR), silicon rubber and the like can be mentioned.

  In the present invention, the shape of the elastic body is not particularly limited as long as it has a function as an elastic body, but a spherical shape is usually used. The spherical elastic body in the present invention is not particularly limited as long as it is an elastic material having a generally spherical shape.

  The average particle diameter of the elastic body is, for example, 50 μm or less, preferably 0.1 to 10 μm, more preferably 1 to 5 μm. In the present invention, the average particle diameter of the elastic body may be a value measured based on image analysis such as SEM or particle size distribution measurement by laser diffraction.

  For example, as shown in a schematic diagram showing an example of the configuration of the electrode for an all-solid lithium secondary battery shown in FIG. 2, the elastic body 4 includes the spherical active material 2, the acicular active material 3 and the solid in the electrode. It is preferable to relax the stress generated by the expansion and contraction of the active material by entering the electrolyte material 1 and the like. For this purpose, the ratio between the average particle size of the elastic body and the average particle size of the spherical active material (Average particle diameter of elastic body / average particle diameter of spherical active material) is in the range of 0.1 to 0.5, particularly in the range of 0.1 to 0.3, particularly in the range of 0.1 to 0.2. It is preferable to be within.

  The method for producing the elastic body used in the present invention is not particularly limited as long as it can obtain a desired elastic body. Specifically, the aqueous solution containing the raw material is dried and pulverized. And a method obtained by sieving, a method obtained by sieving the bulk material after washing, drying and pulverizing.

4). Conductive agent In the present invention, an additive such as a conductive agent may be contained as a conductive aid. By adding this conductive agent, the conductivity can be improved. Specific examples of the conductive agent include acetylene black, ketjen black (trade name, manufactured by Lion Corporation), carbon fiber, and the like, and carbon fiber is particularly preferable.

5. Method for producing electrode for all solid lithium secondary battery The method for producing the electrode for all solid lithium secondary battery of the present invention is particularly limited as long as it is a method capable of obtaining the electrode for all solid lithium secondary battery. Although not, for example, the above needle-like or plate-like active material, the above-mentioned spherical active material, the above-mentioned solid electrolyte material, the above-mentioned elastic body, the above-mentioned conductive agent powder etc. are mixed in a mortar etc. After adjusting the mixed powder, it can be obtained by a manufacturing method such as a method for forming an electrode layer for an all-solid lithium secondary battery by uniaxial compression molding with a solid electrolyte pellet obtained by uniaxial compression molding of a solid electrolyte material. .

B. Next, the all solid lithium secondary battery of the present invention will be described. The all solid lithium secondary battery of the present invention is characterized by having the above-mentioned electrode for an all solid lithium secondary battery.

  According to the present invention, an all-solid lithium secondary battery having a high energy density is obtained by using any electrode for an all-solid lithium secondary battery described in “A. Electrode for all-solid lithium secondary battery”. Obtainable.

Next, the all solid lithium secondary battery of the present invention will be described with reference to the drawings. FIG. 4 is a schematic sectional view showing an example of the all solid lithium secondary battery of the present invention. As shown in FIG. 4, in the all solid lithium secondary battery of the present invention, the solid electrolyte layer 8 is sandwiched between the positive electrode layer 9 and the negative electrode layer 7, and the current collector 5 is disposed on the outside thereof. An insulating portion 6 is disposed so as to cover the side surface.
Hereinafter, such an all-solid lithium secondary battery of the present invention will be described for each configuration.

1. Positive electrode layer The positive electrode layer used in the present invention will be described. The positive electrode layer used in the present invention uses the electrode for an all solid lithium secondary battery described in “(3) In the case of the positive electrode” in “A. Electrode for an all solid lithium secondary battery” above. The electrode for an all solid lithium secondary battery of the present invention may be used for either the positive electrode or the negative electrode. That is, when the electrode for an all-solid lithium secondary battery of the present invention is used for the negative electrode layer, the electrode obtained by mixing the normally used positive electrode active material such as LiCoO ₂ and the solid electrolyte material is used as the positive electrode. It may be used as a layer.

  The film thickness of the positive electrode layer used in the present invention is not particularly limited, and a film having the same thickness as that of the positive electrode layer used in an ordinary all-solid lithium secondary battery can be used.

2. Negative electrode layer The negative electrode layer used in the present invention will be described. The negative electrode layer used in the present invention uses the electrode for an all solid lithium secondary battery described in “(4) In the case of the negative electrode” in “A. Electrode for all solid lithium secondary battery” above. The electrode for an all solid lithium secondary battery of the present invention may be used for either the positive electrode or the negative electrode. That is, when the electrode for an all-solid lithium secondary battery of the present invention is used for the positive electrode layer, an electrode obtained by mixing a commonly used negative electrode active material such as graphite and the above solid electrolyte material is used as the negative electrode layer. It may be used.

  The thickness of the negative electrode layer used in the present invention is not particularly limited, and can be the same as the thickness of the negative electrode layer used in a normal all-solid lithium secondary battery.

3. Solid electrolyte layer The solid electrolyte layer used in the present invention will be described. The solid electrolyte layer used in the present invention uses the solid electrolyte material described in “2. Solid electrolyte material” of “A. Electrode for all-solid lithium secondary battery”. Specifically, the above solid electrolyte material may be formed into a pellet form by uniaxial compression molding.

  In addition, the thickness of the solid electrolyte layer used in the present invention is not particularly limited, and may be the same as the thickness of the solid electrolyte layer used in a normal all-solid lithium secondary battery.

4). Current collector Next, the current collector used in the present invention will be described. The current collector used in the present invention has a function of transmitting electrons generated by the reaction. The current collector is not particularly limited as long as it has conductivity, and examples thereof include metal foils such as Al, Ni, and Ti, or carbon paper. Moreover, the current collector used in the present invention may have a function of a battery cell. Specifically, a case where a battery cell made of SUS is prepared and a part of the battery cell is used as a current collector can be exemplified.

5. Insulating part Next, the insulating part used in the present invention will be described. The insulating part is not particularly limited as long as it has electrical insulation, and examples thereof include polyethylene terephthalate (PET), polypropylene (PP), and tetrafluoroethylene resin (PTFE). it can.

6). Production method of all solid lithium secondary battery The production method for the all solid lithium secondary battery of the present invention is not particularly limited as long as it is a method capable of obtaining the above all solid lithium secondary battery. However, for example, the mixed powder was prepared by mixing the needle-like or plate-like active material, the spherical active material, the solid electrolyte material, the elastic body, the conductive agent, etc. with a mortar or the like. Then, the solid electrolyte secondary battery pellet formed into a pellet form by uniaxial compression molding so that the positive electrode layer and the negative electrode layer are sandwiched between the solid electrolyte layers is sandwiched by a conductive current collector, and the side surfaces are insulated. It can be obtained by a production method such as a method of coating with a material.

7). Application of the all-solid lithium secondary battery The application of the fuel cell of the present invention is not particularly limited, and can be used as, for example, an all-solid lithium secondary battery for automobiles.
8). Other Examples of the shape of the all-solid lithium secondary battery obtained by the present invention include a coin type, a button type, a square type, a cylindrical type, a laminate type, and the like. Is preferred.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described in more detail with reference to examples.

[Example 1]
(All-solid lithium secondary battery production)
Spherical active material LiCoO ₂ (D10 manufactured by Toda Kogyo Co., Ltd.) so that the volume ratio of the spherical active material and the acicular active material in the positive electrode is 90:10 (the volume fraction of the acicular or plate-like active material is 10 vol%). ) And an acicular active material α-FeOOH (FEI16PB manufactured by Kojundo Chemical Co., Ltd.). In addition, a sulfide-based crystallized glass (as the solid electrolyte material) is used so that the mass ratio of the active material in the positive electrode (the active material in which the spherical active material and the acicular active material are mixed) and the solid electrolyte material is 70:30. According to the method of JP 2005-228570 A, Li ₂ S and P ₂ S ₅ were vitrified with a planetary ball mill at a molar ratio of Li ₂ S: P ₂ S ₅ = 70: 30, and then heat-treated. The mixture for the positive electrode was obtained by dry mixing. Next, the negative electrode active material (graphite (TIMcal KS15)) is used as the solid electrolyte material so that the mass ratio of the active material in the negative electrode (graphite (TIMcal KS15)) to the solid electrolyte material is 50:50. Sulfide-based crystallized glass was added and dry mixed to obtain a negative electrode mixture. Moreover, the solid electrolyte pellet was obtained by processing the sulfide type crystallized glass obtained by the method of Unexamined-Japanese-Patent No. 2005-228570 into a pellet form. The solid electrolyte pellet was integrally molded so as to be sandwiched between the positive electrode mixture and the negative electrode mixture, and an all solid lithium secondary battery pellet having a diameter of about 10 mm and a thickness of about 1 mm was obtained. The capacity ratio was positive electrode: negative electrode = 1: 1.2, and the charge / discharge capacity was regulated to be positive.

  The all solid lithium secondary battery pellet was sandwiched between SUS current collectors, and the side surfaces thereof were covered with a PET insulator to obtain an all solid lithium secondary battery.

[Example 2]
In Example 1 above, except that the volume ratio of the spherical active material and the acicular active material in the positive electrode is 75:25 (the volume fraction of the acicular or plate-like active material is 25 vol%), In the same manner as in Example 1, an all solid lithium secondary battery was obtained.

[Example 3]
In Example 1 above, except that the volume ratio of the spherical active material and the acicular active material in the positive electrode is 60:40 (the volume fraction of the acicular or plate-like active material is 40 vol%), In the same manner as in Example 1, an all solid lithium secondary battery was obtained.

[Example 4]
In Example 1 above, except that the volume ratio of the spherical active material and the acicular active material in the positive electrode was 50:50 (the volume fraction of the acicular or plate-like active material was 50 vol%) In the same manner as in Example 1, an all solid lithium secondary battery was obtained.

[Comparative Example 1]
In Example 1 above, except that the volume ratio of the spherical active material and the acicular active material in the positive electrode was 100: 0 (the volume fraction of the acicular or plate-like active material was 0 vol%), In the same manner as in Example 1, an all solid lithium secondary battery was obtained.

[Example 5]
Spherical graphite (KS15 manufactured by Timcal) and acicular shape so that the volume ratio of the spherical active material and acicular active material in the negative electrode is 90:10 (volume fraction of acicular or plate-like active material is 10 vol%). Graphite (KFG15 manufactured by Timcal) was mixed. In addition, a sulfide-based crystallized glass as a solid electrolyte material (Japanese Patent Application Laid-Open (JP-A) No. 2003-26853) is used so that the mass ratio of the active material in the negative electrode (the active material obtained by mixing spherical graphite and acicular graphite) to the solid electrolyte material is 50:50. According to the method of JP 2005-228570 A, Li ₂ S and P ₂ S ₅ were vitrified with a planetary ball mill at a molar ratio of Li ₂ S: P ₂ S ₅ = 70: 30, and then heat-treated) Was added and dry mixed to obtain a negative electrode mixture. Next, the positive electrode active material (LiCoO ₂ (D10 manufactured by Toda Kogyo Co., Ltd., D10)) is adjusted so that the mass ratio of the active material in the positive electrode (LiCoO ₂ (D10 manufactured by Toda Kogyo Co., Ltd.)) and the solid electrolyte material is 70:30. A sulfide-based crystallized glass was added as a solid electrolyte material, and dry mixing was performed to obtain a positive electrode mixture. Moreover, the solid electrolyte pellet was obtained by processing the sulfide type crystallized glass obtained by the method of Unexamined-Japanese-Patent No. 2005-228570 into a pellet form. The solid electrolyte pellet was integrally molded so as to be sandwiched between the positive electrode mixture and the negative electrode mixture, and an all solid lithium secondary battery pellet having a diameter of about 10 mm and a thickness of about 1 mm was obtained. The capacity ratio was positive electrode: negative electrode = 1.2: 1, and the charge / discharge capacity was regulated to be negative.

  The all solid lithium secondary battery pellet was sandwiched between SUS current collectors, and the side surfaces thereof were covered with a PET insulator to obtain an all solid lithium secondary battery.

[Example 6]
In Example 5 above, except that the volume ratio of the spherical active material and the acicular active material in the negative electrode was 80:20 (the volume fraction of the acicular or plate-like active material was 20 vol%), In the same manner as in Example 5, an all solid lithium secondary battery was obtained.

[Example 7]
In Example 5 above, except that the volume ratio of the spherical active material and the acicular active material in the negative electrode was 70:30 (the volume fraction of the acicular or plate-like active material was 30 vol%) In the same manner as in Example 5, an all solid lithium secondary battery was obtained.

[Comparative Example 2]
In Example 5 above, except that the volume ratio of the spherical active material and the acicular active material in the negative electrode was 100: 0 (the volume fraction of the acicular or plate-like active material was 0 vol%), In the same manner as in Example 5, an all solid lithium secondary battery was obtained.

[Evaluation]
(Charge / discharge characteristics)
For the all solid lithium secondary batteries obtained in Examples 1 to 7 and Comparative Examples 1 and 2, the current density was 130 μA / cm ² , and the voltage range was the volume ratio of the spherical active material and the acicular active material in the positive electrode. In the case of Example 1, Example 2, Example 3, Example 4, and Comparative Example 1, which are all-solid lithium secondary batteries that have been changed, the spherical activity in the negative electrode is in the range of 1.5 to 4.2 V. In the case of Example 5, Example 6, Example 7, and Comparative Example 2, which are all solid lithium secondary batteries in which the volume ratio of the substance and the acicular active material was changed, 3.0 to 4.2 V A charge / discharge test was performed in the range, and the capacity was measured. Per positive electrode volume of Example 1, Example 2, Example 3, Example 4 and Comparative Example 1, which are all solid lithium secondary batteries in which the volume ratio of the spherical active material and the acicular active material in the positive electrode is changed The capacity is shown in FIG. Moreover, the capacity | capacitance per negative electrode volume of Example 5, Example 6, Example 7, and the comparative example 2 which are all the solid lithium secondary batteries which changed the volume ratio of the spherical active material and acicular active material in a negative electrode Is shown in FIG.

  As shown in FIG. 5, the capacity per positive electrode volume (mAh / cc) is 90:10 (the volume fraction of the acicular or plate-like active material is the volume ratio of the spherical active material and the acicular active material in the positive electrode). In Example 1, which was 10 vol%), 121 mAh / cc, and the volume ratio of the spherical active material to the acicular active material in the positive electrode was 75:25 (the volume fraction of the acicular or plate active material was 25 vol%). In Example 2, 125 mAh / cc, and in Example 3, the volume ratio of the spherical active material and the acicular active material in the positive electrode was 60:40 (the volume fraction of acicular or plate-like active material was 40 vol%). In Example 4, in which the volume ratio of the spherical active material to the acicular active material in the positive electrode was 50:50 (the volume fraction of the acicular or plate-like active material was 50 vol%), it was 96 mAh / cc, and the spherical The volume ratio of the active material to the acicular active material is set to 100: 0 (acicular or Volume fraction of plate-like active material became 0 vol%) and the Comparative Example 1 104 mAh / cc. That is, the capacity per positive electrode volume was higher than that of Comparative Example 1 in Examples 1 to 3 in which the volume fraction of the acicular active material in the positive electrode active material was in the range of 10 to 40 vol%.

  Further, as shown in FIG. 6, the capacity per negative electrode volume (mAh / cc) is 90:10 (volume fraction of acicular or plate-like active material) of the volume ratio of spherical active material to acicular active material in the negative electrode. In Example 5 where the rate was 10 vol%), the volume ratio of the spherical active material to the acicular active material in the negative electrode was 245 mAh / cc, and the volume ratio of the acicular or platy active material was 20 vol%. Example 6 was 242 mAh / cc, and in Example 7 the volume ratio of the spherical active material and the acicular active material in the negative electrode was 70:30 (the volume fraction of the acicular or plate-like active material was 30 vol%). In Comparative Example 2 in which the volume ratio of the spherical active material and the acicular active material in the negative electrode was 100: 0 (the volume fraction of the acicular or plate-like active material was 0 vol%), it was 226 mAh / cc. It was. That is, the capacity per volume of the negative electrode was higher than that of Comparative Example 2 in Example 5 and Example 6 in which the volume fraction of the acicular active material in the negative electrode active material was in the range of 10 to 20 vol%.

  From the above results, the all-solid lithium secondary battery obtained in the examples shows the volume fraction of the acicular active material in the cathode active material when the electrode for the all-solid lithium secondary battery of the present invention is used as the cathode. When the rate is in the range of 10 to 40 vol%, and the volume fraction of the acicular active material in the negative electrode active material is in the range of 10 to 20 vol% when used for the negative electrode, the expansion of the active material accompanying the charge / discharge cycle Even when contraction occurs, the needle-like or plate-like active material can form a good conductive path. Moreover, since the volume fraction of the acicular or plate-like active material is within the above range, the spherical active material can be contained in a predetermined content. Therefore, it was possible to increase the packing density and obtain an all solid lithium secondary battery having a desired high energy density.

[Example 8]
(All-solid lithium secondary battery production)
Spherical active material LiCoO ₂ (D10 manufactured by Toda Kogyo Co., Ltd.) so that the volume ratio of the spherical active material and the acicular active material in the positive electrode is 75:25 (volume fraction of the acicular or plate-like active material is 25 vol%). ) And an acicular active material α-FeOOH (FEI16PB manufactured by Kojundo Chemical Co., Ltd.). In addition, a sulfide-based crystallized glass (as the solid electrolyte material) is used so that the mass ratio of the active material in the positive electrode (the active material in which the spherical active material and the acicular active material are mixed) and the solid electrolyte material is 70:30. According to the method of JP 2005-228570 A, Li ₂ S and P ₂ S ₅ were vitrified with a planetary ball mill at a molar ratio of Li ₂ S: P ₂ S ₅ = 70: 30, and then heat-treated. In addition, the styrene butadiene rubber (SBR), which is an elastic body, is added to the total mass of the active material in the positive electrode (the active material in which the spherical active material and the acicular active material are mixed) and the styrene butadiene rubber (SBR). On the other hand, 5 mass% was added, and the mixture for positive electrodes was obtained by dry-mixing. Styrene rubber was obtained by drying the aqueous solution and pulverizing and passing through a 50 μm sieve. Next, the negative electrode active material (graphite (TIMcal KS15)) is used as the solid electrolyte material so that the mass ratio of the active material in the negative electrode (graphite (TIMcal KS15)) to the solid electrolyte material is 50:50. Sulfide-based crystallized glass was added and dry mixed to obtain a negative electrode mixture. Moreover, the solid electrolyte pellet was obtained by processing the sulfide type crystallized glass obtained by the method of Unexamined-Japanese-Patent No. 2005-228570 into a pellet form. The solid electrolyte pellet was integrally molded so as to be sandwiched between the positive electrode mixture and the negative electrode mixture, and an all solid lithium secondary battery pellet having a diameter of about 10 mm and a thickness of about 1 mm was obtained. The capacity ratio was positive electrode: negative electrode = 1: 1.2, and the charge / discharge capacity was regulated to be positive.

  The all solid lithium secondary battery pellet was sandwiched between SUS current collectors, and the side surfaces thereof were covered with a PET insulator to obtain an all solid lithium secondary battery.

[Example 9]
In Example 8 above, the styrene butadiene rubber (SBR), which is an elastic body, in the positive electrode is mixed with the active material in the positive electrode (the active material in which the spherical active material and the acicular active material are mixed) and the styrene butadiene rubber (SBR). An all solid lithium secondary battery was obtained in the same manner as in Example 8 except that 10% by mass was added to the total mass.

[Example 10]
In the above Example 8, instead of styrene butadiene rubber (SBR), instead of styrene butadiene rubber (SBR), the bulk body was washed, dried, pulverized, and then silicon rubber, which was an elastic body obtained by passing through a 50 μm sieve, All solid lithium secondary in the same manner as in Example 8 except that 5% by mass of the active material (active material obtained by mixing spherical active material and needle-like active material) and silicon rubber was added in an amount of 5% by mass. A battery was obtained.

[Example 11]
In the above Example 8, instead of styrene butadiene rubber (SBR), instead of styrene butadiene rubber (SBR), the bulk body was washed, dried, pulverized, and then silicon rubber, which was an elastic body obtained by passing through a 50 μm sieve, All solid lithium secondary in the same manner as in Example 8, except that 10% by mass of the active material (active material obtained by mixing spherical active material and acicular active material) and silicon rubber was added in an amount of 10% by mass. A battery was obtained.

[Example 12]
In Example 8 above, an all-solid lithium secondary battery was obtained in the same manner as in Example 8 except that no elastic body was added to the positive electrode (the amount of elastic body added was 0%).

[Example 13]
In Example 8 above, the styrene butadiene rubber (SBR), which is an elastic body, in the positive electrode is mixed with the active material in the positive electrode (the active material in which the spherical active material and the acicular active material are mixed) and the styrene butadiene rubber (SBR). An all-solid lithium secondary battery was obtained in the same manner as in Example 8 except that 15% by mass was added relative to the total mass.

[Example 14]
In the above Example 8, instead of styrene butadiene rubber (SBR), instead of styrene butadiene rubber (SBR), the bulk body was washed, dried, pulverized, and then silicon rubber, which was an elastic body obtained by passing through a 50 μm sieve, All solid lithium secondary in the same manner as in Example 8 except that 15% by mass of the active material (active material obtained by mixing spherical active material and needle-shaped active material) and silicon rubber was added in an amount of 15% by mass. A battery was obtained.

[Example 15]
Spherical graphite (KS15 manufactured by Timcal) and acicular shape so that the volume ratio of the spherical active material and acicular active material in the negative electrode is 90:10 (volume fraction of acicular or plate-like active material is 10 vol%). Graphite (KFG15 manufactured by Timcal) was mixed. In addition, a sulfide-based crystallized glass as a solid electrolyte material (Japanese Patent Application Laid-Open (JP-A) No. 2003-26853) is used so that the mass ratio of the active material in the negative electrode (the active material obtained by mixing spherical graphite and acicular graphite) to the solid electrolyte material is 50:50. According to the method of JP 2005-228570 A, Li ₂ S and P ₂ S ₅ were vitrified with a planetary ball mill at a molar ratio of Li ₂ S: P ₂ S ₅ = 70: 30, and then heat-treated) And 5 masses of styrene butadiene rubber (SBR), which is an elastic body, with respect to the total mass of the active material in the negative electrode (active material in which spherical graphite and acicular graphite are mixed) and styrene butadiene rubber (SBR). % Was added and dry-mixed to obtain a negative electrode mixture. Styrene rubber was obtained by drying the aqueous solution and pulverizing and passing through a 50 μm sieve. Next, the above-described sulfide crystallized glass is added as a solid electrolyte material so that the mass ratio of the active material in the positive electrode (LiCoO ₂ (D10 manufactured by Toda Kogyo Co., Ltd. D10)) and the solid electrolyte material is 70:30, A positive electrode mixture was obtained by dry mixing. Moreover, the solid electrolyte pellet was obtained by processing the sulfide type crystallized glass obtained by the method of Unexamined-Japanese-Patent No. 2005-228570 into a pellet form. The solid electrolyte pellet was integrally molded so as to be sandwiched between the positive electrode mixture and the negative electrode mixture, and an all solid lithium secondary battery pellet having a diameter of about 10 mm and a thickness of about 1 mm was obtained. The capacity ratio was positive electrode: negative electrode = 1.2: 1, and the charge / discharge capacity was regulated to be positive.

  The all solid lithium secondary battery pellet was sandwiched between SUS current collectors, and the side surfaces thereof were covered with a PET insulator to obtain an all solid lithium secondary battery.

[Example 16]
In Example 15, the total mass of styrene butadiene rubber (SBR), which is an elastic body, in the negative electrode and the active material in the negative electrode (active material in which spherical graphite and acicular graphite are mixed) and styrene butadiene rubber (SBR). An all solid lithium secondary battery was obtained in the same manner as in Example 15 except that 10% by mass was added.

[Example 17]
In Example 15 above, all solid lithium was added in the same manner as in Example 15 except that styrene butadiene rubber (SBR), which is an elastic body, was not added to the negative electrode (the addition amount of the elastic body was 0%). A secondary battery was obtained.

[Example 18]
In Example 15 above, the styrene butadiene rubber (SBR), which is an elastic body in the negative electrode, is replaced with the total mass of the active material (LiCoO ₂ (D10 manufactured by Toda Kogyo Co., Ltd.)) and the styrene butadiene rubber (SBR) in the negative electrode. An all solid lithium secondary battery was obtained in the same manner as in Example 15 except that 15% by mass was added.

[Evaluation]
(Charge / discharge characteristics)
A charge / discharge test was performed on the all-solid lithium secondary batteries obtained in Examples 8 to 18 at a current density of 130 μA / cm ² and a voltage range of 3.0 to 4.2 V, and the capacity was measured. Capacity retention rate (%) (discharge of X cycle) with the number of cycles of Examples 8, 9 and 12 which are all solid lithium secondary batteries in which the amount of elastic body added in the positive electrode is changed FIG. 7 shows the change of capacity / discharge capacity at the first cycle) × 100). Further, FIG. 8 shows the change in capacity retention rate with the number of cycles of Examples 15, 16, and 17 which are all solid lithium secondary batteries in which the amount of elastic body added in the negative electrode is changed.

  As shown in FIG. 7, when an elastic body is added to the positive electrode, the capacity retention rate with the number of cycles is determined based on the styrene-butadiene rubber as the elastic material and the active material in the positive electrode (a mixture of a spherical active material and an acicular active material). In Example 8 in which 5% by mass was added to the total mass of (material) and styrene-butadiene rubber (SBR), the capacity retention rate at 20 cycles was 52%, and the addition amount of styrene-butadiene rubber was 10% by mass. In Example 12, 53% and 47% in Example 12 in which the addition amount of styrene-butadiene rubber was 0% by mass. Moreover, Example 13 which made said addition amount 15 mass% became 40% or less. This tendency is the same even when the elastic material is silicon rubber. The total mass of the silicon rubber as the elastic material, the active material in the positive electrode (the active material obtained by mixing the spherical active material and the acicular active material) and the silicon rubber. In Example 10 in which 5% by mass was added, the capacity retention rate at 20 cycles was 50%, in Example 11 in which the addition amount of silicon rubber was 10% by mass, 52% and the addition amount of silicon rubber was 15% by mass. In Example 14, it was 40% or less. That is, when an elastic body was added to the positive electrode, the capacity maintenance ratio accompanying the number of cycles was particularly improved in the examples in which the amount of elastic body added was in the range of 5 to 10% by mass.

  In addition, as shown in FIG. 8, when an elastic body is added to the negative electrode, the capacity maintenance ratio accompanying the number of cycles is determined by using styrene butadiene rubber as an elastic material and an active material in the negative electrode (a mixture of spherical graphite and acicular graphite). In Example 15 in which 5% by mass was added to the total mass of the material and styrene butadiene rubber (SBR), the capacity retention rate at 20 cycles was 49%, and the amount of styrene butadiene rubber added was 10% by mass. No. 16 was 53% and Example 17 in which the addition amount of styrene butadiene rubber was 0% by mass was 44%. Further, in Example 18 in which the addition amount of styrene-butadiene rubber was 15% by mass, it was 40% or less. That is, when an elastic body was added to the negative electrode, the capacity retention ratio accompanying the number of cycles was particularly improved in the examples where the amount of elastic body added was in the range of 5 to 10% by mass.

  From the above results, the all-solid-state lithium secondary battery obtained in the examples is obtained by adding the elastic body in the range of 5 to 10% by mass, so that the elastic body is expanded and contracted by the active material during charging and discharging. Relieve the generated stress. Moreover, a conductive path could be secured and desired conductivity could be obtained. For this reason, the deformation of the solid electrolyte material due to the stress can be suppressed, and the decrease in the battery reaction area and the capacity decrease due to the deformation of the solid electrolyte material can be suppressed. The next battery could be obtained.

It is a schematic diagram which shows an example of a structure of the electrode for all-solid-state lithium secondary batteries of this invention. It is a schematic diagram which shows an example of a structure of the electrode for all-solid-state lithium secondary batteries of this invention. It is a schematic diagram which shows an example of a structure of the conventional electrode for all-solid-state lithium secondary batteries. It is a schematic sectional drawing which shows an example of a structure of the all-solid-state lithium secondary battery of this invention. It is the graph which showed the capacity | capacitance per positive electrode volume of Example 1, Example 2, Example 3, Example 4, and the comparative example 1 with respect to the volume fraction of the acicular active material in an active material. It is the graph which showed the capacity | capacitance per negative electrode volume of Example 5, Example 6, Example 7, and Comparative Example 2 with respect to the volume fraction of the plate-shaped active material in an active material. It is the graph which showed the discharge capacity maintenance factor of Example 8, Example 9, and Example 12 with respect to the cycle number. It is the graph which showed the discharge capacity maintenance factor of Example 15, Example 16, and Example 17 with respect to the cycle number.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Solid electrolyte material 2 ... Spherical active material 3 ... Acicular or plate-shaped active material 4 ... Elastic body 5 ... Current collection part 6 ... Insulation part 7 ... Negative electrode layer 8 ... Solid electrolyte layer 9 ... Positive electrode layer

Claims (6)

  An electrode for an all-solid-state lithium secondary battery, comprising an active material obtained by mixing a needle-like or plate-like active material and a spherical active material and a solid electrolyte material.   The volume fraction of the acicular or plate-like active material in the active material used for the positive electrode and mixed with the acicular or plate-like active material and the spherical active material is 10 to 40 vol%. The electrode for an all-solid-state lithium secondary battery according to claim 1.   The volume fraction of the acicular or plate-like active material in the active material used for the negative electrode and mixed with the acicular or plate-like active material and the spherical active material is 10 to 20 vol%. The electrode for an all-solid-state lithium secondary battery according to claim 1.   The electrode for an all-solid-state lithium secondary battery according to claim 3, wherein the needle-like or plate-like active material and the spherical active material are graphite.   In the electrode for the all-solid-state lithium secondary battery, the elastic body is 5 to 10 based on the total mass of the active material obtained by mixing the acicular or plate-like active material and the spherical active material and the elastic body. The electrode for an all-solid-state lithium secondary battery according to any one of claims 1 to 4, wherein the electrode is contained by mass%.   An all-solid lithium secondary battery comprising the electrode for an all-solid lithium secondary battery according to any one of claims 1 to 5.

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