JP2012146512A - Method for manufacturing battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a battery, which is capable of easily manufacturing a battery having a structure in which bipolar electrodes are provided and a plurality of unit cells are laminated.SOLUTION: The method for manufacturing a battery comprises: a lamination step of producing a laminate including a structure in which a plurality of collector substrates and a plurality of power generating elements each comprising a cathode layer, an anode layer, and a solid electrolyte layer disposed between the cathode layer and the anode layer are alternately laminated; and a pressurization step of pressurizing the laminate in a laminating direction.

Description

  The present invention relates to a battery manufacturing method.

  A lithium ion secondary battery has the characteristics that it has a higher energy density than other secondary batteries and can operate at a high voltage. For this reason, it is used as a secondary battery that can be easily reduced in size and weight in information equipment such as a mobile phone, and in recent years, there is an increasing demand for large motive power such as for electric vehicles and hybrid vehicles.

  A lithium ion secondary battery includes a positive electrode layer and a negative electrode layer, and an electrolyte layer disposed therebetween. As the electrolyte provided in the electrolyte layer, for example, a non-aqueous liquid or solid is used. When a liquid (hereinafter referred to as “electrolytic solution”) is used as the electrolyte, the electrolytic solution easily penetrates into the positive electrode layer and the negative electrode layer. Therefore, an interface between the active material contained in the positive electrode layer or the negative electrode layer and the electrolytic solution is easily formed, and the performance is easily improved. However, since the widely used electrolyte is flammable, it is necessary to mount a system for ensuring safety. On the other hand, since the solid electrolyte (hereinafter referred to as “solid electrolyte”) is nonflammable, the above system can be simplified. Therefore, a lithium ion secondary battery (hereinafter referred to as “solid battery”) in a form provided with a layer containing a solid electrolyte that is nonflammable (hereinafter referred to as “solid electrolyte layer”) has been proposed. Yes.

  As a technique related to such a battery, for example, Patent Document 1 discloses a solid battery including a solid electrolyte layer having a structure in which two or more layers are stacked. Patent Document 1 discloses that metallic lithium is used for the negative electrode and oxide is used for the solid electrolyte layer.

JP 2007-066693 A

  In order to obtain a battery having a high energy density by using a solid battery as disclosed in Patent Document 1 or the like, a battery having a structure in which a so-called bipolar electrode is provided and a plurality of unit cells are stacked is preferable. The bipolar electrode is a laminate in which a positive electrode layer is formed on one surface side of a sheet-like current collecting substrate and a negative electrode layer is formed on the other surface side. However, conventionally, when a battery in which a plurality of unit cells are stacked is manufactured, the layers constituting the unit cell are sequentially formed, so that there is a problem that man-hours required for manufacturing the battery increase. .

  Therefore, an object of the present invention is to provide a battery method that can easily manufacture a battery including a bipolar electrode and having a structure in which a plurality of single cells are stacked.

In order to solve the above problems, the present invention has the following configuration. That is,
The present invention relates to a current collector substrate and a laminate having a structure in which a plurality of power generation elements each including a positive electrode layer, a negative electrode layer, and a positive electrode layer and a solid electrolyte layer disposed between the negative electrode layer are alternately stacked. Is a method for producing a battery having a laminating step for producing a laminate and a pressurizing step for pressurizing the laminate in the laminating direction.

  In the battery manufacturing method of the present invention, it is preferable that the stacking step includes a step of forming a positive electrode layer on the current collector substrate by an aerosol deposition method or a chemical vapor deposition method.

  In the battery manufacturing method of the present invention, it is preferable to use an oxide-based solid electrolyte for the solid electrolyte layer and a metal lithium foil for the negative electrode layer.

  According to the method for producing a battery of the present invention, a plurality of power generation elements including a current collecting substrate and a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer are alternately provided. After producing a laminated body having a laminated structure, a battery having a structure in which a plurality of unit cells are provided with bipolar electrodes can be easily manufactured by pressurizing the laminated body in the lamination direction.

  Further, in the battery manufacturing method of the present invention, by forming the positive electrode layer by the aerosol deposition method or the chemical vapor deposition method, it becomes easy to form a positive electrode layer having a thickness of several tens of μm. It becomes easy to improve the energy density.

  Further, in the battery manufacturing method of the present invention, even if an oxide-based solid electrolyte is used for the solid electrolyte layer and a metal lithium foil is used for the negative electrode layer, fine irregularities are formed on the surface of the solid electrolyte layer. The negative electrode layer can be brought into close contact with the unevenness, and the interface resistance between the negative electrode layer and the solid electrolyte layer can be reduced.

It is a flowchart which shows the process included in the manufacturing method of the battery of this invention. It is sectional drawing which shows the process roughly about an example of the manufacturing method of the battery of this invention. It is sectional drawing which shows the process roughly about an example of the manufacturing method of the conventional battery.

  After describing the conventional battery manufacturing method, the battery manufacturing method of the present invention will be described. FIG. 3 is a cross-sectional view schematically showing the process of an example of a conventional battery manufacturing method.

  When manufacturing a battery 28 in which a plurality of unit cells 27 are stacked as shown in FIG. 3D, conventionally, a plurality of unit cells 27 are stacked by sequentially forming each layer. 3 is a bipolar electrode in which the positive electrode layer 22 is formed on one surface side of the current collecting substrate 21 and the negative electrode layer 24 is formed on the other surface side of the current collecting substrate 21. The battery 28 shown in FIG. The adjacent unit cells 27, 27 share the current collecting substrate 21 provided between the unit cells 27, 27. A specific example of a conventional method for manufacturing such a battery 28 is as follows.

  For example, in the conventional battery manufacturing method, as shown in FIG. 3A, first, the positive electrode layer 22 is formed on the current collecting substrate 21, and the solid electrolyte layer 23 is further formed on the positive electrode layer 22. Thus, the laminate 25 was produced. Next, a laminate 26 in which the negative electrode layer 24 is formed on the current collector substrate 21 is prepared, and the laminate is arranged so that the solid electrolyte layer 23 and the negative electrode layer 24 face each other as shown in FIG. 25 and the laminated body 26 were laminated. Here, the unit cell 27 was manufactured by pressurizing the obtained laminated body in the laminating direction for the purpose of bringing the layers into close contact with each other or reducing the voids contained in each layer. Thereafter, as shown in FIGS. 3C and 3D, the battery 28 in which the plurality of single cells 27 are stacked is manufactured by repeating the same operation as before.

  In the conventional battery manufacturing method as described above, when a battery in which a plurality of unit cells are stacked is manufactured, the layers constituting the unit cell are sequentially formed. There was a problem of increasing. The present invention has been completed in view of such problems. The present invention will be described below with reference to the drawings.

  FIG. 1 is a flowchart showing steps included in the battery manufacturing method of the present invention. FIG. 2 is a cross-sectional view schematically showing the process of an example of the battery manufacturing method of the present invention.

  As shown in FIG. 1, the battery manufacturing method of the present invention may be described as a lamination process (hereinafter sometimes referred to as “S11”) and a pressurizing process (hereinafter referred to as “S12”). ). Hereinafter, these steps will be described.

<Lamination process (S11)>
S11 is a laminate including a current collecting substrate and a structure in which a plurality of power generation elements each including a positive electrode layer, a negative electrode layer, and a positive electrode layer and a solid electrolyte layer disposed between the negative electrode layer are alternately stacked. It is a manufacturing process. The positive electrode layer, the negative electrode layer, the electrolyte layer, and the current collecting substrate that can be used in the present invention are not particularly limited, and known materials can be appropriately used. Moreover, these lamination methods are not particularly limited.

  In S11, for example, as shown in FIG. 2A, a plurality of laminated bodies 5 in which the positive electrode layer 2 is formed on the current collecting substrate 1 are prepared, and as shown in FIG. The positive electrode layer 2, the negative electrode layer 4, and the solid electrolyte layer disposed between the positive electrode layer 2 and the negative electrode layer 4 are laminated so that the negative electrode layer 4 is disposed between the laminate 5. 3 and the laminated body 15 having a structure in which a plurality of current collecting substrates 1 are alternately laminated. In addition, as shown in FIG.2 (b), the current collection board | substrate 1 is arrange | positioned in the outermost surface of the lamination direction of the laminated body 15 as shown in FIG.2 (b).

(Collector board 1)
The material constituting the current collecting substrate 1 is not particularly limited as long as it has conductivity, and is preferably selected appropriately in consideration of the potentials of the positive electrode active material and the negative electrode active material. Specifically, aluminum, aluminum alloy, copper, nickel, silver, stainless steel (SUS), etc. can be mentioned. Moreover, about the thickness of the current collection board | substrate 1, it is the same as that of the current collection board | substrate in a general solid battery.

(Negative electrode layer 4)
The negative electrode layer 4 is a layer containing at least a negative electrode active material, and may contain at least one of a solid electrolyte, a conductive material, and a binder as necessary. Examples of the negative electrode active material that can be used for the negative electrode layer 4 include a metal active material and a carbon active material. Examples of the metal active material that can be used for the negative electrode layer 4 include Li, In, Al, Si, Sn, and alloys thereof. On the other hand, examples of the carbon active material that can be used for the negative electrode layer 4 include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. An oxide active material may be used as the negative electrode active material. Examples of the oxide active material include Li ₄ Ti ₅ O ₁₂ and Li ₃ V ₂ (PO ₄ ) ₃ .

  As described above, the negative electrode layer 4 can contain a solid electrolyte. By adding a solid electrolyte to the negative electrode layer 4, the ion conductivity of the negative electrode layer 4 can be improved. As the said solid electrolyte, the material similar to the solid electrolyte used for the solid electrolyte layer 3 mentioned later can be mentioned. Further, as described above, the negative electrode layer 4 can contain a conductive material. By adding a conductive material to the negative electrode layer 4, the conductivity of the negative electrode layer 4 can be improved. Examples of the conductive material include acetylene black, ketjen black, and carbon fiber. Further, as described above, the negative electrode layer 4 can contain a binder. Examples of the binder include fluorine-containing binders such as polytetrafluoroethylene (PTFE).

  Moreover, the negative electrode layer 4 may be a metal film of a metal-based active material, or may be a compression-molded powder containing a metal-based active material or a carbon-based active material. Specific examples of the metal film of the metal-based active material include metal foils, plating foils, vapor-deposited foils, and the like of the above-described metal-based active materials. Among these, metal foils of the metal-based active material are preferable.

  Although the thickness of the negative electrode layer 4 is not specifically limited, For example, it is preferable that it exists in the range of 0.1 micrometer or more and 1000 micrometers or less.

  As the negative electrode layer 4, a known negative electrode layer that can be used in the conventional battery as described above can be used. However, as will be described later, from the viewpoint of reducing the interfacial resistance between the solid electrolyte layer 3 and the negative electrode layer 4, the rigidity of the negative electrode layer 4 is preferably 0.1 GPa or more and 10 GPa or less. Examples of the material having such a rigidity and usable for the negative electrode layer 4 include a metal lithium foil, a metal lithium alloy foil, a layer formed by compression molding a powder of a solid electrolyte and a carbon active material, and the like.

(Solid electrolyte layer 3)
The solid electrolyte layer 3 is a layer including a solid electrolyte formed between the positive electrode layer 2 and the negative electrode layer 4. Examples of the solid electrolyte that can be used for the solid electrolyte layer 3 include Li ₃ PS ₄ and Li ₂ S: P ₂ S ₅ = 50: 50 to 100 in addition to an oxide solid electrolyte such as Li ₃ PO _4. : 0. the way Li ₂ S and _P 2 _S sulfide ₅ were mixed was produced solid electrolyte (e.g., by mass _ratio, Li _{2 S:} P 2 S 5 = 70: 30 to become as Li ₂ A known solid electrolyte such as a sulfide solid electrolyte prepared by mixing S and P ₂ S ₅ can be appropriately used. The thickness of the solid electrolyte layer 3 can be, for example, in the range of 0.1 μm or more and 1000 μm or less, and preferably in the range of 0.1 μm or more and 300 μm or less.

(Positive electrode layer 2)
The positive electrode layer 2 is a layer containing at least a positive electrode active material, and may contain at least one of a solid electrolyte, a conductive material, and a binder as necessary. Specific examples of the positive electrode active material can be used for the positive electrode layer _{2, LiCo x Mn y O 2} , LiNi x Co y O 2, LiNi x Mn y O 2, LiNi x Co y Mn z O 2, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), iron olivine (LiFePO ₄ ), cobalt olivine (LiCoPO ₄ ), manganese olivine (LiMnPO ₄ ), lithium titanate (Li ₄ Ti ₅ Examples thereof include lithium transition metal oxides such as O ₁₂ ); chalcogenides such as copper subrel (Cu ₂ Mo ₆ S ₈ ), iron sulfide (FeS), cobalt sulfide (CoS), and nickel sulfide (NiS). Since the solid electrolyte, the conductive material, and the binder that can be used for the positive electrode layer 2 are the same as those of the negative electrode layer 4, the description thereof is omitted.

  Although the thickness of the positive electrode layer 2 is not particularly limited, it is preferably formed with a thickness of the order of several tens of μm from the viewpoint of realizing a solid battery having a high energy density. In addition, when the positive electrode layer 2 is formed on the current collecting substrate 1 as shown in FIG. 2A, the method of forming the positive electrode layer 2 is not particularly limited. However, when the positive electrode layer 2 is formed with a thickness of the order of several tens of μm. However, it is not practical to form the film by physical vapor deposition (CVD) such as sputtering as in the prior art. On the other hand, when the positive electrode layer 2 is formed by another method with a high film formation rate (for example, aerosol deposition (AD method), chemical vapor deposition (CVD method), etc.), a sputtering method or the like is formed on the surface of the positive electrode layer 2. As compared with the case where the positive electrode layer 2 is formed by the PVD method, large irregularities may be formed. In FIG. 2, the unevenness on the surface of the positive electrode layer 2 is exaggerated.

  When unevenness is formed on the surface of the positive electrode layer 2, if the solid electrolyte layer 3 is formed on the positive electrode layer 2, the unevenness on the surface of the positive electrode layer 2 may be reflected on the surface of the solid electrolyte layer 3. At this time, when a relatively soft substance such as a sulfide-based solid electrolyte is used for the solid electrolyte layer 3, the surface of the solid electrolyte layer 3 can be flattened to some extent by applying pressure in the stacking direction in S12. . However, when a relatively hard substance such as an oxide-based solid electrolyte is used for the solid electrolyte layer 3, it is difficult to flatten the unevenness on the surface of the solid electrolyte layer 3 even if the solid electrolyte layer 3 is pressurized in S12. Met. When the negative electrode layer 4 is laminated on the solid electrolyte layer 3 with the irregularities remaining on the surface in this way, the adhesion between the solid electrolyte layer 3 and the negative electrode layer 4 is lowered, and the solid electrolyte layer 3 and the negative electrode layer 4 are not bonded. In some cases, the interface resistance was high.

  On the other hand, in order to obtain a high energy density, it is preferable to use a battery having a structure in which a plurality of unit cells are stacked as in the battery obtained by the present invention. When a plurality of unit cells are stacked in this way, the number of interfaces between the solid electrolyte layer and the negative electrode layer included in one battery increases, so that it is possible to reduce the interface resistance between the solid electrolyte layer and the negative electrode layer. It becomes important.

  When irregularities remain on the surface of the solid electrolyte layer 3 as described above, the rigidity of the negative electrode layer 4 is preferably 0.1 GPa or more and 10 GPa or less. When the negative electrode layer 4 has a rigidity of 0.1 GPa or more and 10 GPa or less, the negative electrode layer 4 is stacked on the solid electrolyte layer 3 and pressed in the stacking direction in S12, as shown in FIG. As described above, the surface on the solid electrolyte layer 3 side of the negative electrode layer 4 is recessed according to the unevenness of the surface of the solid electrolyte layer 3, so that the solid electrolyte layer 3 and the negative electrode layer 4 are in close contact with each other. Interfacial resistance with the layer 4 can be reduced. At this time, as shown in FIG. 2C, the surface of the negative electrode layer 4 in contact with the current collector substrate 1 is flat, so that the interface resistance between the negative electrode layer 4 and the current collector substrate 1 is increased. Can be prevented.

  Actually, three samples (samples A to C) were prepared as described below, and AC impedance evaluation was performed. The results are shown in Table 1. The interface resistance ratio shown in Table 1 is based on Sample A.

As a preparation procedure of Sample A, first, a positive electrode layer containing LiCoO ₂ was formed to a thickness of 50 μm by aerosol deposition on a current collecting substrate made of an aluminum foil having a flat surface. Next, a solid electrolyte layer was formed into a thickness of 10 μm by aerosol deposition using an oxide-based solid electrolyte (Li _1.5 Al _0.5 Ti _1.5 (PO ₄ ) ₃ ). At this time, the surface roughness of the solid electrolyte layer was Ra (arithmetic mean roughness defined in JIS B0601-2001) = 5 μm. Next, a negative electrode layer made of a metal lithium foil having a thickness of 50 μm is disposed on the solid electrolyte layer, and a current collecting substrate made of an aluminum foil similar to the above current collecting substrate is further disposed thereon, and then, these are formed. The laminated body was pressurized in the lamination direction at 0.5 MPa to produce a single cell. This unit cell was subjected to AC impedance evaluation.

  Sample B was the same as Sample A until the solid electrolyte layer was formed. At this time, the surface roughness of the solid electrolyte layer was Ra = 5 μm. The negative electrode layer was produced as follows. That is, 50 parts by mass of carbon and 50 parts by mass of a polymer solid electrolyte were mixed and dispersed using a solvent, and then coated on a PTFE sheet and dried to prepare a negative electrode layer having a thickness of 50 μm after drying. . Next, after arranging a negative electrode layer on the solid electrolyte layer and pressurizing in the laminating direction, the PTFE sheet was peeled off. Next, a current collector substrate made of the same aluminum foil as sample A was placed on the negative electrode layer, and then pressed in the stacking direction in the same manner as sample A to produce a single cell. This unit cell was subjected to AC impedance evaluation.

Sample C was the same as Sample A until the solid electrolyte layer was formed. At this time, the surface roughness of the solid electrolyte layer was Ra = 5 μm. Next, a negative electrode layer containing Li ₄ TiO ₁₂ was formed to a thickness of 50 μm by aerosol deposition on a current collector substrate made of the same aluminum foil as Sample A. Next, after laminating | stacking so that a solid electrolyte layer and a negative electrode layer might face, it pressurized in the lamination direction similarly to the sample A, and the single battery was produced. This unit cell was subjected to AC impedance evaluation.

  The rigidity of the negative electrode layer of sample A was 4 GPa, and the rigidity of the negative electrode layer of sample B was 8 GPa. On the other hand, in Sample C, the rigidity of the negative electrode layer was 86 GPa, and the interface resistance of Sample C was extremely high, 1000 times or more compared to Sample A and Sample B.

<Pressurizing step (S12)>
S12 is a process of pressurizing the laminated body produced in S11 in the laminating direction.

  S12 can be a step of pressing the laminate 15 produced in S11 in the laminating direction as indicated by arrows P1 and P1 shown in FIG. 2B, for example. By pressing the laminated body 15 produced in S11 in the laminating direction, a battery 17 in which a plurality of unit cells 16 are laminated as shown in FIG. 2C can be manufactured. The battery 17 includes a bipolar electrode in which the positive electrode layer 2 is formed on one surface side of the current collecting substrate 1 and the negative electrode layer 4 is formed on the other surface side of the current collecting substrate 1, and is adjacent thereto. The unit cells 16 and 16 share the current collector board 1 provided between the unit cells 16 and 16.

  In the case of manufacturing a battery including a bipolar electrode and having a structure in which a plurality of unit cells are stacked, as described above, in the conventional manufacturing method, the layers are formed by sequentially forming the layers constituting the unit cell. The number of man-hours required for manufacturing the battery has increased. On the other hand, according to the battery manufacturing method of the present invention, as described above, a battery can be easily manufactured by simply applying pressure at once after a plurality of elements constituting a single battery are stacked. As described above, according to the present invention, a battery having a high energy density in which a plurality of bipolar electrodes are provided and a plurality of unit cells are stacked can be easily manufactured.

  The present invention has been described with reference to the most practical and preferred embodiments at the present time. However, the present invention is not limited to the embodiments disclosed in the present specification, and can be appropriately changed within the scope of the claims and the gist or idea of the invention that can be read from the entire specification. It should be understood that a method for manufacturing a battery with such a change is also included in the technical scope of the present invention.

  The method for producing a battery of the present invention can be applied to the production of a battery used as a power source for portable devices, electric vehicles, hybrid vehicles, and the like.

DESCRIPTION OF SYMBOLS 1 Current collection board | substrate 2 Positive electrode layer 3 Solid electrolyte layer 4 Negative electrode layer 5 Laminated body 10 Electric power generation element 15 Laminated body 16 Cell 17 Battery

Claims (3)

Producing a current collector substrate, and a laminate having a structure in which a plurality of power generation elements including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer are alternately stacked; Lamination process;
A pressurizing step of pressurizing the laminate in the laminating direction;
The manufacturing method of the battery which has this.   The battery manufacturing method according to claim 1, wherein the stacking step includes a step of forming the positive electrode layer on the current collector substrate by an aerosol deposition method or a chemical vapor deposition method.   The method for producing a battery according to claim 1, wherein an oxide-based solid electrolyte is used for the solid electrolyte layer and a metal lithium foil is used for the negative electrode layer.

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