JP5262143B2 - Positive electrode body and method for producing the same - Google Patents

Description

  The present invention relates to a positive electrode body that does not require a binder and a conductive material and has a positive electrode layer having a high energy density.

  With the miniaturization of personal computers, video cameras, mobile phones, etc., in the fields of information-related equipment and communication equipment, lithium secondary batteries have been put into practical use because of their high energy density as the power source used for these equipment. It has become widespread. On the other hand, in the field of automobiles, the development of electric vehicles has been urgently caused by environmental problems and resource problems, and lithium secondary batteries have been studied as power sources for the electric vehicles.

  A lithium secondary battery generally includes a positive electrode layer containing a positive electrode active material, a negative electrode layer containing a negative electrode active material, an insulating separator disposed between the positive electrode layer and the negative electrode layer, and a positive electrode layer and a negative electrode layer. And an electrolyte that conducts Li ions. The electrolyte has forms such as liquid, solid, and gel depending on the type of lithium secondary battery.

  A positive electrode layer used for a lithium secondary battery usually includes a positive electrode active material that absorbs and releases Li ions, a conductive material that improves conductivity, and a binder that binds the positive electrode active material. Here, it is preferable to reduce the content of the conductive material and the binder because they do not contribute to the improvement of the electric capacity. However, there is a problem that the rate characteristic is lowered when the content of the conductive material is reduced, and the cycle characteristic is lowered when the content of the binder is reduced. For this reason, it has been difficult to reduce the contents of the conductive material and the binder in the positive electrode layer.

  On the other hand, attempts have been made to improve the volume capacity density of the positive electrode active material. For example, in Patent Document 1, a method for producing a positive electrode active material in which a powder containing a constituent element of a positive electrode active material is mixed and slurried in an aqueous solution in which a part of the constituent metal of the positive electrode active material is dissolved, and the slurry is dried and granulated. Is disclosed. In this method, a positive electrode active material having an improved volume capacity density can be obtained. However, when a positive electrode layer of a lithium secondary battery is formed, a conductive material and a binder are not added as in the prior art. It was necessary and there was a limit to increasing the energy density.

JP 2007-95571 A JP 2001-143688 A

  This invention is made | formed in view of the said situation, and it aims at providing the positive electrode body which has a positive electrode layer with a high energy density without requiring a binder and a electrically conductive material.

  In order to achieve the above object, in the present invention, a positive electrode current collector, a binder formed on the positive electrode current collector, and bound to the particulate positive electrode active material and the adjacent particulate positive electrode active material are bound. And a positive electrode layer containing a positive electrode active material.

  According to the present invention, the binder positive electrode active material is formed so as to bind the adjacent particulate cathode active material, and the contact area between the particulate cathode active material and the binder cathode active material is increased. There is no need to add a material and a conductive material. Therefore, the capacity per unit volume can be improved, and a positive electrode layer having a high energy density can be obtained. Furthermore, since the positive electrode body of the present invention has a large contact area between the particulate positive electrode active material and the binder positive electrode active material, it is equivalent to the conventional positive electrode layer using the binder and the conductive material. Rate characteristics can be maintained.

  In the present invention, a positive electrode layer forming composition containing a particulate positive electrode active material and a binder positive electrode active material synthesis material is applied on the positive electrode current collector, and the applied positive electrode layer forming A positive electrode body comprising a binder positive electrode active material synthesis step of synthesizing a binder positive electrode active material that binds the adjacent particulate positive electrode active material by subjecting the composition to a wet method A manufacturing method is provided.

  According to the present invention, a positive electrode layer having a large film thickness can be easily formed by applying a wet method using a positive electrode layer forming composition containing a particulate positive electrode active material.

  In the above invention, the wet method is preferably a sol-gel method. This is because the binder positive electrode active material can be easily synthesized.

  In the above invention, a solid electrolyte supporting step of supporting the solid electrolyte on the surfaces of the particulate positive electrode active material and the binder positive electrode active material by applying and drying a solid electrolyte-containing composition in which the solid electrolyte is dissolved It is preferable to have. This is because the lithium ion conductivity inside the positive electrode layer can be easily improved by supporting the solid electrolyte on the inner surface of the positive electrode layer.

  In this invention, since it is not necessary to make a positive electrode layer contain a binder and a electrically conductive material, there exists an effect that high energy density can be achieved.

  Hereinafter, the positive electrode body and the method for producing the positive electrode body of the present invention will be described in detail.

A. First, the positive electrode body of the present invention will be described. The positive electrode body of the present invention contains a positive electrode current collector, a particulate positive electrode active material formed on the positive electrode current collector, and a binder positive electrode active material that binds the adjacent particulate positive electrode active material. And a positive electrode layer.

  According to the present invention, the binder positive electrode active material is formed so as to bind the adjacent particulate cathode active material, and the contact area between the particulate cathode active material and the binder cathode active material is increased. There is no need to add a material and a conductive material. Therefore, the capacity per unit volume can be improved, and a positive electrode layer having a high energy density can be obtained. Furthermore, since the positive electrode body of the present invention has a large contact area between the particulate positive electrode active material and the binder positive electrode active material, it is equivalent to the conventional positive electrode layer using the binder and the conductive material. Rate characteristics can be maintained. Further, in the conventional positive electrode layer, the conductivity becomes insufficient only by the contact between the particles of the positive electrode active material, so that it is necessary to add a conductive material. Further, a binder is added to improve the adhesion between the particles of the positive electrode active material. However, since the binder is usually insulative, it is necessary to add a conductive material. On the other hand, the positive electrode layer of the positive electrode body of the present invention can solve all of these problems by using a binder positive electrode active material.

FIG. 1 is a schematic cross-sectional view showing an example of the positive electrode body of the present invention. A positive electrode body 10 shown in FIG. 1 includes a positive electrode current collector 1 and a positive electrode layer 2 formed on the positive electrode current collector. Furthermore, the positive electrode layer 2 contains a particulate positive electrode active material 3 and a binding positive electrode active material 4 that binds the adjacent particulate positive electrode active material 3.
Hereinafter, the positive electrode body of the present invention will be described for each configuration.

1. Positive electrode layer The positive electrode layer used in the present invention is a layer formed on a positive electrode current collector, and contains a particulate positive electrode active material and a binder positive electrode active material that binds adjacent particulate positive electrode active materials. It is a layer to do.

(1) Particulate cathode active material The particulate cathode active material used in the present invention is not particularly limited as long as it has a function as a cathode active material. For example, when the positive electrode body of the present invention is used for a lithium secondary battery, the particulate positive electrode active material only needs to have a function of occluding and releasing lithium ions. Specifically, the layered positive electrode active material, spinel Type positive electrode active material and olivine type positive electrode active material. Examples of the layered positive electrode active material include LiCoO ₂ , LiNiO ₂ , LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , and LiNi _1/2 Mn _1/2 O ₂ . Examples of the spinel positive electrode active material include LiMn ₂ O ₄ , LiCoMnO ₄ , Li ₂ NiMn ₃ O ₈ , and LiNi _0.5 Mn _1.5 O ₄ . Examples of the olivine-type positive electrode active material include LiCoPO ₄ , LiMnPO ₄ , LiFePO _{4 and the} like.

  The shape of the particulate positive electrode active material is not particularly limited as long as it has a function as a positive electrode active material, and examples thereof include spheres such as a true sphere and an oval sphere, among which a true sphere is preferable. . This is because a dense positive electrode layer can be obtained by regularly arranging the particulate positive electrode active materials.

  The average particle diameter of the particulate positive electrode active material is preferably selected as appropriate according to the required characteristics of the positive electrode layer. For example, when the energy density is improved, the positive electrode layer is preferably a dense body. In the case of obtaining a positive electrode layer that is a dense body, the average particle diameter of the particulate positive electrode active material is preferably small. In this case, the average particle diameter of the particulate positive electrode active material is, for example, preferably 50 μm or less, and more preferably in the range of 0.05 μm to 10 μm. In addition, the average particle diameter of the particulate positive electrode active material in the present invention can be measured by, for example, an X-ray small angle scattering method, a laser diffraction method, or the like.

  On the other hand, when the positive electrode body of the present invention is used for a lithium secondary battery having an electrolytic solution, the positive electrode layer is preferably a porous body. This is because the electrolytic solution can sufficiently penetrate into the positive electrode layer. Similarly, when the positive electrode body of the present invention is used for an all-solid lithium secondary battery and the lithium ion conductivity of the positive electrode layer is improved, the positive electrode layer is preferably a porous body. This is because the lithium ion conductivity inside the positive electrode layer can be easily improved by supporting the solid electrolyte on the inner surface of the porous body. Thus, when obtaining the positive electrode layer which is a porous body, it is preferable that the average particle diameter of a particulate-form positive electrode active material is large. In this case, the average particle diameter of the particulate positive electrode active material is, for example, preferably in the range of 0.01 μm to 50 μm, and more preferably in the range of 0.1 μm to 5 μm.

  Moreover, the positive electrode layer used in the present invention may contain two or more kinds of particulate positive electrode active materials having different average particle diameters. This is because a positive electrode layer that is a dense body can be obtained. This is considered to be because a dense positive electrode layer can be obtained by arranging the particulate positive electrode active material having a small average particle diameter in the gap between the particulate positive electrode active materials having a large average particle diameter. Among them, in the present invention, it is preferable to use two or three types of particulate positive electrode active materials having different average particle diameters, and more preferably two types of particulate positive electrode active materials having different average particle diameters. This is because if the number of types of the particulate positive electrode active material increases, the production may become complicated and the cost may increase. When two types of particulate positive electrode active materials having different average particle diameters are used, the difference in average particle diameter is preferably in the range of 0.01 μm to 45 μm, for example. In the present invention, when two or more types of particulate positive electrode active materials having different average particle diameters are used, each of the particulate positive electrode active materials may be a particulate positive electrode active material having the same chemical composition, and are different. It may be a particulate positive electrode active material having a chemical composition.

  Moreover, the positive electrode layer used in the present invention may contain a particulate positive electrode active material having a small particle size distribution range. This is because a positive electrode layer that is a dense body can be obtained. This is presumably because the particulate positive electrode active material having a small particle size distribution range has a uniform particle shape, and a dense positive electrode layer can be obtained by arranging the particulate positive electrode active material regularly. . In this case, it is preferable that the 50% volume average particle diameter of the particulate positive electrode active material is, for example, in the range of 0.01 to 10 μm, and more preferably in the range of 0.1 to 5 μm. In addition, the particle size distribution of the particulate positive electrode active material in the present invention can be measured by, for example, an X-ray small angle scattering method, a laser diffraction method, or the like.

(2) Binding cathode active material Next, the binding cathode active material used in the present invention will be described. The binder positive electrode active material used in the present invention binds the particulate positive electrode active material described above. In the present invention, the binder positive electrode active material usually does not cover the entire surface of the particulate positive electrode active material, but covers the surface to the extent that a part of the particulate positive electrode active material is exposed.

  The binder positive electrode active material used in the present invention is not particularly limited as long as it can bind the adjacent particulate cathode active material and has a function as a cathode active material. Especially, in this invention, it is preferable that a binder positive electrode active material is synthesize | combined by the wet method as described in the "B. manufacturing method of a positive electrode body" mentioned later. This is because the binder positive electrode active material can be easily synthesized.

  For example, when the positive electrode body of the present invention is used for a lithium secondary battery, the binder positive electrode active material specifically includes a layered positive electrode active material, a spinel positive electrode active material, an olivine positive electrode active material, and the like. Can do. Since these positive electrode active materials are the same as the contents described in the above “(1) particulate positive electrode active material”, description thereof is omitted here. In the present invention, the particulate positive electrode active material and the binder positive electrode active material may have the same chemical composition or different chemical compositions. For example, if the particulate positive electrode active material and the binder positive electrode active material have the same chemical composition, unnecessary stress is less likely to occur when the positive electrode active material expands and contracts, and the mechanical strength of the positive electrode layer There is an advantage that it is possible to suppress a decrease in.

  In the present invention, the positive electrode layer may contain two or more types of binder positive electrode active materials having different chemical compositions. Especially, in this invention, it is preferable to contain 2 types or 3 types of binder positive electrode active materials from which a chemical composition differs, and it is more preferable to contain 2 types of binder positive electrode active materials from which a chemical composition differs. This is because if the types of the binder positive electrode active material are increased, the production may become complicated and the cost may be increased.

  The amount of the binder positive electrode active material used with respect to the particulate cathode active material is particularly limited as long as it can bind the adjacent particulate cathode active material and does not cover the entire surface of the particulate cathode active material. It is not something. When the content of the particulate positive electrode active material in the positive electrode layer is 100 parts by weight, the content of the binder positive electrode active material in the positive electrode layer is, for example, in the range of 0.1 part by weight to 40 parts by weight, especially 1 part by weight. It is preferable to be within the range of ˜20 parts by weight.

(3) Positive Electrode Layer As described above, the positive electrode layer used in the present invention is a layer formed on the positive electrode current collector, and binds the particulate positive electrode active material and the adjacent particulate positive electrode active material. It is a layer containing a binder positive electrode active material. The film thickness of the positive electrode layer used in the present invention varies depending on the use of the positive electrode body, but is preferably in the range of, for example, 1 μm to 100 μm, and more preferably in the range of 10 μm to 30 μm.

  The positive electrode layer used in the present invention may be a dense body or a porous body. If the positive electrode layer is a dense body, a lithium secondary battery having a higher energy density can be obtained. On the other hand, if the positive electrode layer is a porous body, the lithium ion conductivity can be improved by, for example, infiltrating the electrolytic solution into the porous portion. For example, a lithium secondary battery excellent in lithium ion conductivity can be obtained by carrying a solid electrolyte in a porous portion.

That is, in the present invention, it is preferable that a solid electrolyte is supported on the surfaces of the particulate positive electrode active material and the binder positive electrode active material. This is because a lithium secondary battery excellent in lithium ion conductivity can be obtained as described above. When the positive electrode body of the present invention is used, for example, in an all-solid-state lithium secondary battery, specifically, as a solid electrolyte, a sulfide-based solid electrolyte such as Li ₂ S—P ₂ S ₅ , a nitrided Li ₃ PO ₄ , oxide-based solid electrolytes such as Li ₂ O—V ₂ O ₅ —SiO ₂ , LiO—Li ₂ OB ₂ O ₃ , perovskite solid electrolytes such as (Li, La) TiO ₃ , Li ₅ La ₃ Ta ₂ Garnet-type solid electrolytes such as O ₁₂ and Li ₆ BaLa ₂ Ta ₂ O ₁₂ can be used. The amount of the solid electrolyte supported is not particularly limited, and is preferably selected as appropriate according to the use of the positive electrode body of the present invention.

2. Positive electrode current collector The positive electrode current collector used in the present invention has a function of collecting current in the positive electrode layer. Examples of the material for the positive electrode current collector include aluminum, SUS, nickel, iron, and titanium. Of these, aluminum and SUS are preferable. Moreover, as a shape of a positive electrode electrical power collector, foil shape, plate shape, mesh shape etc. can be mentioned, for example, Foil shape is preferable. Further, when the battery case has a function of a positive electrode current collector, the battery case may be used as the positive electrode current collector.

3. Positive electrode body The positive electrode body of the present invention has the positive electrode layer and the positive electrode current collector described above. The use of the positive electrode body of the present invention is not particularly limited, and examples thereof include battery use. Especially, it is preferable to use the positive electrode body of this invention for a secondary battery use, and it is preferable to use it for a lithium secondary battery especially. That is, the present invention can provide a lithium secondary battery using the positive electrode body. The configuration of the lithium secondary battery is not particularly limited, and is the same as the configuration of a general lithium secondary battery. Specifically, a positive electrode current collector formed on the positive electrode current collector and the positive electrode current collector and containing a positive electrode active material, a negative electrode current collector, and the negative electrode current collector formed on the negative electrode active material A lithium secondary battery having a negative electrode body containing a cathode, a separator disposed between the positive electrode body and the negative electrode body, and an electrolyte that conducts Li ions between the positive electrode layer and the negative electrode layer. be able to. The electrolyte used for the lithium secondary battery may be liquid, solid, or gel. The method for producing a positive electrode body of the present invention is not particularly limited as long as it can produce the above-described positive electrode body. For example, the method described in “B. Method for producing positive electrode body” described later is given. be able to.

B. Next, a method for producing a positive electrode body according to the present invention will be described. The method for producing a positive electrode body of the present invention comprises a coating step of coating a positive electrode layer-forming composition containing a particulate positive electrode active material and a binder positive electrode active material synthesis material on a positive electrode current collector, and a coated positive electrode A binder positive electrode active material synthesis step of synthesizing a binder cathode active material that binds the adjacent particulate cathode active material by applying a wet method to the layer forming composition. To do.

  According to the present invention, a positive electrode layer having a large film thickness can be easily formed by applying a wet method using a positive electrode layer forming composition containing a particulate positive electrode active material. Conventional film growth means in a vacuum / low pressure environment such as a sputtering method or a PLD (Pulsed Lase Deposition) method has a problem of high cost. On the other hand, in the conventional wet method, a positive electrode layer is formed using a composition for forming a positive electrode layer that contains only the synthetic material of the target positive electrode active material. If it is repeated, there is a problem that stress is accumulated in the film and the film is peeled off. On the other hand, in this invention, a positive electrode layer with a large film thickness can be easily formed at low cost by previously adding a particulate positive electrode active material to the positive electrode layer forming composition. Further, according to the present invention, since the binder positive electrode active material is formed so as to bind adjacent particulate cathode active materials, the contact area between the particulate cathode active material and the binder cathode active material is increased. In addition, there is an advantage that it is not necessary to add a binder and a conductive material.

FIG. 2 is a schematic cross-sectional view showing an example of the method for producing a positive electrode body of the present invention. In the method of manufacturing a positive electrode body shown in FIG. 2, first, a positive electrode current collector 1 is prepared (FIG. 2 (a)). Next, the positive electrode layer forming composition 5 containing the particulate positive electrode active material 3 and the binder positive electrode active material synthesis material 4a is applied onto the positive electrode current collector 1 (FIG. 2B). Next, the applied positive electrode layer-forming composition 5 is subjected to a wet method such as a sol-gel method to synthesize a binder positive electrode active material 4 that binds the adjacent particulate positive electrode active material 3 ( FIG. 2 (c)).
Hereafter, the manufacturing method of the positive electrode body of this invention is demonstrated for every process.

1. Application Step The application step in the present invention is a step of applying a positive electrode layer forming composition containing a particulate positive electrode active material and a binder positive electrode active material synthesis material onto a positive electrode current collector.

  The positive electrode layer forming composition used in the present invention contains at least a particulate positive electrode active material and a binder positive electrode active material synthesis material. In addition, about the particulate positive electrode active material used for this invention, since it is the same as that of the content described in said "A. positive electrode body", description here is abbreviate | omitted.

The binder positive electrode active material synthesis material used in the present invention is a material for synthesizing the binder positive electrode active material by a chemical reaction in a wet method described later. For example, when the positive electrode body of the present invention is used for a lithium secondary battery, the binder positive electrode active material synthesis material is a material for synthesizing a positive electrode active material having a function of occluding and releasing lithium ions. As will be described later, for example, when the wet method in the present invention is a sol-gel method, the binder positive electrode active material synthesis material usually contains a Li source and a transition metal source. Examples of the Li source include a lithium compound having an organic group. Examples of the organic group include carboxylic acids, alcohols, esters, ketones, ethers, cycloalkanes, and aromatics. Specific examples of such a Li source include lithium acetate. In the present invention, two or more types of Li sources may be used. The transition metal source varies depending on the chemical composition of the target binder positive electrode active material. For example, it has a cobalt compound having an organic group, a nickel compound having an organic group, a manganese compound having an organic group, and an organic group. An iron compound etc. can be mentioned. The organic group is the same as the organic group in the Li source described above. Specific examples of such a transition metal source include cobalt acetate, nickel acetate, manganese acetate, iron acetate and the like. Moreover, when the target binder positive electrode active material is an olivine type positive electrode active material, the binder positive electrode active material synthesis material further contains a P source. Examples of the P source include NH ₄ H ₂ PO ₄ and H ₃ PO ₄ .

  In addition, it is preferable to select suitably the composition ratio of the material for binder positive electrode active material synthesis | combination according to the composition ratio of the target binder positive electrode active material. The amount of the binder positive electrode active material used with respect to the particulate cathode active material is such that the adjacent cathode active material can be bound and does not cover the entire surface of the particulate cathode active material. The amount is preferably such that can be synthesized. The contents of the particulate positive electrode active material and the binder positive electrode active material contained in the positive electrode layer are the same as those described in “A. Positive electrode body”.

  The solvent used in the positive electrode layer forming composition is not particularly limited as long as it can disperse the particulate positive electrode active material and dissolve the binder positive electrode active material synthesis material. Specific examples include water, acetic acid, isopropyl alcohol and the like.

  The composition for positive electrode layer formation used for this invention may contain the solid electrolyte as needed. This is because a positive electrode layer having excellent ion conductivity can be obtained. In the present invention, a wet method is applied in the binder positive electrode active material synthesis step described later. For example, when the wet method is a sol-gel method, the binder positive electrode active material is synthesized by performing normal firing. Therefore, when a solid electrolyte is added to the positive electrode layer forming composition, it is preferably a material that is not affected by the wet method. For example, when the wet method is a sol-gel method, any heat-resistant solid electrolyte can be added.

  The composition for positive electrode layer formation used for this invention may contain the viscosity modifier as needed. The viscosity of the positive electrode layer forming composition is preferably selected as appropriate according to the coating method. Examples of the viscosity modifier include polyvinyl pyrrolidone (PVP), paraffin, polyethylene, polyoctanium, polyvinyl alcohol, palmitic acids, celluloses, PEGs, amides, polyacrylic acids and the like.

  The method for applying the composition for forming a positive electrode layer on the positive electrode current collector is not particularly limited, and examples thereof include a general application method. Specifically, a spin coating method, a dip coating method, an ink jet method, a spray coating method, and the like can be given, and among these, the spin coating method is preferable.

2. Next, the binder positive electrode active material synthesis step in the present invention will be described. In the binder positive electrode active material synthesis step in the present invention, a wet method is applied to the applied positive electrode layer forming composition to synthesize a binder positive electrode active material that binds adjacent particulate positive electrode active materials. It is a process.

  In the present invention, the wet method means that a positive electrode layer forming composition is applied onto a positive electrode current collector, and a binder positive electrode active material synthetic material dissolved in the positive electrode layer forming composition is chemically changed to thereby bind the positive electrode. A method for synthesizing an active material. The wet method in the present invention is not particularly limited as long as a desired positive electrode layer can be obtained. For example, a sol-gel method, a MOD (Metal-Organic Deposition) method, a hydrothermal synthesis method, and a liquid phase precipitation method are used. Among them, the sol-gel method is preferable. This is because the binder positive electrode active material can be easily synthesized.

  In the present invention, for example, a positive electrode layer forming composition is applied onto a positive electrode current collector, and the applied positive electrode layer forming composition is baked to synthesize a binder positive electrode active material. Although it does not specifically limit as a calcination temperature in that case, For example, it is preferable to exist in the range of 200 to 800 degreeC. Moreover, it is preferable to select suitably as atmosphere at the time of baking according to the target positive electrode active material, and an oxidizing atmosphere may be sufficient and a reducing atmosphere may be sufficient.

3. Other Steps In the present invention, after the step of synthesizing the positive electrode active material, the composition for synthesizing the positive electrode active material containing the synthetic material for synthesizing the positive electrode active material is applied again and the wet method is applied. A binder-made positive electrode active material may be synthesized. Thereby, a binder cathode active material can be further formed on the surfaces of the particulate cathode active material and the binder cathode active material formed up to the binder cathode active material synthesis step, and a denser cathode layer can be formed. Can be obtained. At this time, the binder positive electrode active material synthesis material may be the same as or different from the binder positive electrode active material synthesis material used in the coating step described above. That is, in the present invention, after the above-mentioned binder positive electrode active material synthesis step, for the synthesis of a binder cathode active material containing the same or different binder cathode active material synthesis material as the above-mentioned binder cathode active material synthesis material. Applying the composition and applying a wet method to perform a binder cathode active material addition step of synthesizing an additional binder cathode active material on the surface of the particulate cathode active material and the binder cathode active material. Can do. In the present invention, the step of adding the binder positive electrode active material can be repeated twice or more.

  In the present invention, after the step of synthesizing the binder positive electrode active material, the solid electrolyte-containing composition in which the solid electrolyte is dissolved is applied to the positive electrode layer and dried, whereby the particulate positive electrode active material and the A solid electrolyte supporting step of supporting the solid electrolyte on the surface of the binder positive electrode active material can be performed. By supporting the solid electrolyte on the inner surface of the positive electrode layer, the lithium ion conductivity inside the positive electrode layer can be easily improved.

  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]
(1) Preparation of composition for forming positive electrode layer The following materials were mixed and stirred for 1 hour to prepare a composition in which a material for synthesizing a binder positive electrode active material was dispersed.
_{· (CH 3 COO) Li (} 99.9%, manufactured by WAKO Co., Ltd.) ... 0.73g (1.1 molar parts)
_{· (CH 3 COO) 2 Co} · 4H 2 O (99.9%, manufactured by WAKO Co.) ... 2.49 g (1 part by mole)
・ H ₂ O: 15.02 g (83 mol parts)
CH ₃ COOH (99.9%, manufactured by WAKO) ... 12.02 g (20 mole parts)
_{· I-C 3 H 7 OH} (99.9%, manufactured by WAKO Co., Ltd.) ... 6.01g (10 molar parts)
・ (C ₆ H ₉ NO) _n (PVP, manufactured by WAKO) ... 1.51 g (1 mol part)

1.0 g of a particulate positive electrode active material (LiCoO ₂ ) having an average particle size of 4 μm was added to 1.0 ml of the obtained composition, and the mixture was stirred for 1 hour to obtain a positive electrode layer forming composition.

(2) Production of positive electrode body 50 μL of the obtained composition for forming a positive electrode layer was dropped onto a positive electrode current collector (metal substrate, 15 mmΦ × 2 mmt), and spin coated at 4,000 rpm for 20 seconds. Next, the positive electrode layer forming composition on the metal substrate was temporarily fired at 400 ° C. for 10 minutes, and then finally fired at 800 ° C. for 1 hour to obtain a positive electrode body.

  A laser micrograph of the positive electrode layer of the positive electrode obtained is shown in FIG. As shown in FIG. 3, it was confirmed that the particulate positive electrode active material was disposed on the positive electrode current collector without any defects. Further, according to image analysis, the average film thickness of the positive electrode layer was 7.2 μm, and it was a thickness in which about two layers of a particulate positive electrode active material having an average particle diameter of 4 μm were laminated.

[Comparative Example 1]
A positive electrode layer forming composition having 87 parts by weight of LiCoO ₂ , 10 parts by weight of a conductive material (acetylene black), and 3 parts by weight of a binder (PTFE) was prepared. This positive electrode layer forming composition was applied to a positive electrode current collector (metal substrate, 15 mmΦ × 2 mmt) and dried to obtain a positive electrode body. The coating of the positive electrode layer forming composition, the amount of LiCoO ₂ contained per positive electrode layer unit area was adjusted to be the same as in Example 1. Moreover, the average film thickness of the obtained positive electrode layer was 30 μm.

[Evaluation]
Using the positive electrode bodies obtained in Example 1 and Comparative Example 1, lithium secondary batteries for evaluation were produced, and charge / discharge characteristics were evaluated.
(Constitution)
Positive electrode: positive electrode body of Example 1 or Comparative Example 1 Electrolyte: 1 mol / l LiClO ₄ dissolved in an ethylene carbonate system Negative electrode: Li metal (manufactured by Honjo Metal Co., Ltd.)
Separator: UP3025 (manufactured by Ube Industries)
Battery case: Jig manufactured by Tom Cell Japan (charge / discharge test conditions)
(A) Charging start (b) Charging CV4.3V 5μA Rest 10min
(C) Discharge CV3.5V 5μA Rest 10min

The obtained result is shown in FIG. As shown in FIG. 4A, the rate maintenance rates of Example 1 and Comparative Example 1 were the same. As described above, in Example 1 and Comparative Example 1, the amount of LiCoO ₂ contained per positive electrode layer unit area is the same. Therefore, it was confirmed that the same rate maintenance rate can be obtained even under conditions where there are no conductive material and binder. Further, when Example 1 and Comparative Example 1 are compared, the energy density is equivalent per unit area. However, since Example 1 does not use a conductive material or binder, the film thickness of Comparative Example 1 is 4 It is less than 1 / min. That is, when compared per unit volume, it was confirmed that Example 1 had a larger energy density than Comparative Example 1 (see FIG. 4B).

[Comparative Example 2]
A composition for forming a positive electrode layer was produced in the same manner as in Example 1 except that a particulate positive electrode active material (LiCoO ₂ ) having an average particle diameter of 4 μm was not used.
50 μL of the obtained composition for forming a positive electrode layer was dropped onto a positive electrode current collector (metal substrate, 15 mmΦ × 2 mmt), and spin-coated at 4,000 rpm for 20 seconds. Next, the positive electrode layer forming composition on the metal substrate was temporarily fired at 400 ° C. for 10 minutes. This coating / pre-baking operation was the first operation, and the same operation was repeated 5 times in total. Thereafter, the main body was fired at 800 ° C. for 1 hour to obtain a positive electrode body.

  FIG. 5 shows the relationship between the number of coatings and the average film thickness of the positive electrode layer. As shown in FIG. 5, the average film thickness of the positive electrode layer when the number of coatings is 5 is about 0.6 μm, which is 7.2 μm, which is the average film thickness of the positive electrode layer obtained in Example 1. Was also significantly smaller. Furthermore, it was confirmed that peeling was occurring in the obtained positive electrode layer. For this reason, it was confirmed that when the number of coatings is increased, the mechanical strength is reduced although the thickness of the positive electrode layer can be slightly increased. This decrease in mechanical strength is considered to be a result of stress accumulated in the film by repeated pre-sintering.

It is a schematic sectional drawing which shows an example of the positive electrode body of this invention. It is a schematic sectional drawing which shows an example of the manufacturing method of the positive electrode body of this invention. 2 is a laser micrograph of the positive electrode layer of the positive electrode body obtained in Example 1. FIG. 3 is a graph showing charge / discharge characteristics of an evaluation lithium secondary battery using the positive electrode bodies obtained in Example 1 and Comparative Example 1. In the comparative example 2, it is a graph which shows the relationship between the frequency | count of application | coating and the average film thickness of a positive electrode layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Positive electrode collector 2 ... Positive electrode layer 3 ... Particulate positive electrode active material 4 ... Binder positive electrode active material 4a ... Binder positive electrode active material synthesis material 5 ... Positive electrode layer forming composition 10 ... Positive electrode body

Claims (2)

And positive electrode current collector, wherein formed on the positive electrode current collector, to perforated a positive electrode layer containing a binder positive electrode active material for binding the particulate positive electrode active material particulate positive electrode active material, and adjacent, the A positive electrode body,
The particulate positive electrode active material is a layered positive electrode active material, LiCoO ₂ , LiNiO ₂ , LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiNi _1/2 Mn _1/2 O ₂ , spinel-type positive electrode active material. Selected from the materials LiMn ₂ O ₄ , LiCoMnO ₄ , Li ₂ NiMn ₃ O ₈ , LiNi _0.5 Mn _1.5 O ₄ , or the olivine-type positive electrode active material LiCoPO ₄ , LiMnPO ₄ , LiFePO ₄ ,
The positive electrode layer, wherein the positive electrode layer contains two or more kinds of the particulate positive electrode active materials having different average particle diameters . Two or more kinds of particulate positive electrode active materials having different average particle diameters , and LiCoO ₂ , LiNiO ₂ , LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , and LiNi _1/2 Mn _{1 / 2} O _2, LiMn ₂ O ₄ spinel-type cathode active _{material, LiCoMnO 4, Li 2 NiMn 3} O 8, LiNi 0.5 Mn 1.5 O 4 LiCoPO 4 or olivine positive electrode active material,, LiMnPO ₄ Applying a positive electrode layer-forming composition containing a binder positive electrode active material synthesis material selected from LiFePO ₄ on a positive electrode current collector;
A binder cathode active material synthesis step of synthesizing a binder cathode active material that binds the adjacent particulate cathode active material by applying a wet method to the applied cathode layer forming composition;
A solid electrolyte supporting step of supporting the solid electrolyte on the surfaces of the particulate positive electrode active material and the binder positive electrode active material by applying and drying a solid electrolyte-containing composition in which the solid electrolyte is dissolved;
A method for producing a positive electrode body comprising:
The method for producing a positive electrode body , wherein the wet method is a sol-gel method.