JP2015026530A - Method of manufacturing electrode body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an electrode body in which breakage of a current collector foil during pressing can be suppressed using an electrode body in which a negative electrode mixture and a positive electrode mixture with respect to a negative electrode current collector foil and a positive electrode current collector foil are installed on both surfaces.SOLUTION: In a method of manufacturing an electrode body, when a positive electrode having a positive electrode layer and a solid electrolyte layer on both surfaces of a positive electrode current collector foil, and a negative electrode having a negative layer and the solid electrolyte layer on both surfaces of a negative electrode current collector foil and a size larger than that of the positive electrode are laminated on each other, the displacement amount of film thickness prevented from generating breakage of a current collector foil is obtained in advance by measuring the film thickness of a press part to which pressing pressure is applied and the film thickness of a non-press part which is not laminated on the positive electrode and to which the pressing pressure is not applied, and the positive electrode and the negative electrode are pressed and laminated by the pressing pressure based on the displacement amount of the film thickness.

Description

  The present invention relates to a method for manufacturing an electrode body, and more particularly, to a method for manufacturing an electrode body capable of suppressing breakage of a current collector foil during pressing.

In recent years, lithium batteries have been put into practical use as batteries having high voltage and high energy density. Due to the expansion of the use of lithium batteries in a wide range of fields and the demand for high performance, various studies have been conducted to further improve the performance of lithium batteries.
Among them, since the electrolyte is not used compared to the conventional non-aqueous electrolyte lithium battery, the system required for improving the safety when using the non-aqueous electrolyte can be simplified. Therefore, it is expected that the all-solid-state battery will be put to practical use because it can have many advantages such as an increased degree of freedom and a reduced number of auxiliary devices.

However, in order to realize the practical application of all-solid-state batteries, various improvements such as the creation of a solid electrolyte capable of providing high capacity and high output and / or the creation of electrodes capable of realizing high electrode utilization efficiency are required. It is.
The structure of an electrode body of an all-solid battery, for example, a lithium secondary battery, requires that a negative electrode that accepts Li ions be installed at a position opposite to the positive electrode in order to suppress Li deposition, and the size of the negative electrode sheet is usually the size of the positive electrode sheet. It is bigger. In this case, unlike a conventional non-aqueous electrolyte type lithium secondary battery, a Li ion path is connected by a solid electrolyte, so that a close interface needs to be formed.

  For this reason, for example, in Patent Document 1, a step of forming a positive electrode active material layer on one side of the positive electrode current collector and pressing it to a desired density, and a formation of the negative electrode active material layer on one side of the negative electrode current collector And a method of manufacturing a bipolar electrode in which the surfaces of the current collectors on which the active material layer is not formed are opposed to each other and connected by an adhesive layer having conductivity. There is no mention of cutting out of the current collector foil by pressing simultaneously.

  Patent Document 2 discloses a step of obtaining a positive electrode member by laminating a solid electrolyte on a positive electrode mixture, and a step of obtaining a negative electrode member by laminating a solid electrolyte on a negative electrode mixture and then press-molding the solid electrolyte. And a method for producing an all-solid battery comprising a step of press-molding the positive electrode member and the negative electrode member together with each solid electrolyte, and as a specific example, from the size (10 mm square) of the positive electrode mixture Although the case where the size (12 mm square) of the negative electrode mixture is large is shown, a specific example of the electrode body in which the negative electrode mixture and the positive electrode mixture are installed on both sides with respect to the negative electrode current collector foil and the positive electrode current collector foil Not shown.

  Depending on these known techniques, it is possible to suppress cutting of the current collector foil during pressing using an electrode body in which the negative electrode composite material and the positive electrode composite material are installed on both sides of the negative electrode current collector foil and the positive electrode current collector foil. It is difficult to obtain an electrode body.

JP 2005-317468 A JP 2012-69248 A

  Therefore, the object of the present invention is to suppress the cutting of the current collector foil during pressing using an electrode body in which the negative electrode mixture and the positive electrode mixture are installed on both sides of the negative electrode current collector foil and the positive electrode current collector foil. It is providing the manufacturing method of an electrode body.

  As a result of investigations to achieve the above object, the present inventors have conducted a laminating press with electrodes provided on both sides of the current collector foil, and when the current collector foil thickness is reduced, the current collector foil breaks. As a result of finding out and conducting further studies, the present invention was completed.

The present invention provides a positive layer having a positive electrode layer on both sides of a positive electrode current collector foil and a solid electrolyte layer thereon, a negative electrode layer on both sides of the negative electrode current collector foil, and a positive electrode size having a solid electrolyte layer thereon. A method for producing an electrode body in which a negative electrode having a larger size is laminated and solid electrolyte layers are adhered to each other to form a laminated structure. The film thickness displacement amount that does not cause the current collector foil to break is measured in advance by measuring the film thickness of the non-pressed portion that is not stacked on the positive electrode and is not subjected to the press pressure, and is pressed with the press pressure based on the film thickness displacement amount. It is related with the said manufacturing method laminated | stacked.
In the present invention, the film thickness displacement can be determined by the measurement method described in detail in the column of Examples described later.

  ADVANTAGE OF THE INVENTION According to this invention, the electrode body which can suppress the cutting | disconnection of the current collection foil at the time of press using the electrode body by which the negative electrode compound material and the positive electrode compound material were installed in both surfaces with respect to the negative electrode current collector foil and the positive electrode current collector foil Can be easily obtained.

FIG. 1 is a schematic diagram showing a part of the steps in the method of manufacturing an electrode body according to the embodiment of the present invention. FIG. 2 is a partial schematic view for explaining the positive electrode and the negative electrode in the steps of the method for producing an electrode body according to the embodiment of the present invention. FIG. 3 is a partially enlarged schematic view for explaining a pressed portion and a non-pressed portion of the negative electrode in the process of the method for manufacturing an electrode body according to the embodiment of the present invention. FIG. 4 is a graph showing the relationship between the film thickness displacement amount and the press pressure in the negative electrode. FIG. 5 is a table collectively showing the relationship between the film thickness displacement amount and the press pressure in the negative electrode. FIG. 6 is a copy of a cross-sectional SEM photograph of the negative electrode pressed at a press pressure of 1.0 t. FIG. 7 is a copy of a cross-sectional SEM photograph of the negative electrode pressed at a press pressure of 2.0 t. FIG. 8 is a copy of a cross-sectional SEM photograph of the negative electrode pressed at a press pressure of 3.0 t. FIG. 9 is a copy of a cross-sectional SEM photograph of the negative electrode pressed at a pressure of 4.0 t. FIG. 10 is a schematic diagram for explaining a method of measuring the film thickness displacement of the negative electrode in the process of the method for manufacturing an electrode body according to the embodiment of the present invention. FIG. 11 is a table collectively showing the pressing pressure and the peel strength of the obtained electrode body by changing the temperature during pressing.

In particular, in the present invention, the following embodiments can be mentioned.
1) The said manufacturing method with which the said press is performed by a hot press.
2) The production method described above, wherein the positive electrode includes a positive electrode active material and a solid electrolyte, and the negative electrode includes a negative electrode active material and a solid electrolyte.
3) The manufacturing method as described above, wherein the electrode body has a peeling strength at which delamination between the electrodes / current collector foil occurs, and the current collector foil does not have a break.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the method for producing an electrode body according to an embodiment of the present invention, a positive electrode having a positive electrode layer on both sides of the positive electrode current collector foil and a solid electrolyte layer thereon, a negative electrode layer on both sides of the negative electrode current collector foil, and a solid material thereon In an electrode body manufacturing method in which a negative electrode having an electrolyte layer and a size larger than the size of the positive electrode is laminated and the solid electrolyte layers are adhered to each other to form a laminated structure, the negative electrode is laminated on the positive electrode at the time of lamination. The film thickness displacement amount that does not cause current collector foil breakage is determined in advance by measuring the film thickness of the pressed portion where the pressing pressure is applied and the non-pressed portion where the pressing pressure is not applied to the positive electrode. The peel strength is high enough to prevent the current collector foil from being cut by pressing, preferably hot-pressing, and laminating, and preferably causing separation between the electrode and current collector foil in the peel test. Considered a solid electrolyte with each other can be obtained to a stacked electrode body contact.

  On the other hand, in the conventional method for producing an electrode body, single-side coating, that is, a positive electrode having a positive electrode layer and a solid electrolyte layer thereon on one side of the positive electrode current collector foil, and a negative electrode layer on one side of the negative electrode current collector foil and its The current collector foil is a method of obtaining an electrode body by laminating a negative electrode having a solid electrolyte layer thereon and having a size larger than the size of the positive electrode and bringing the solid electrolyte layers into close contact to form a laminated structure. Since one of these is free, it is considered that no shear stress is applied and the problem of foil breakage in the electrode body has not been realized.

  However, double-sided coating by a production method outside the scope of the present invention, that is, a positive electrode having a positive electrode layer and a solid electrolyte layer thereon on both sides of the positive electrode current collector foil, and a negative electrode layer on both sides of the negative electrode current collector foil In accordance with the method for obtaining an electrode body by laminating a solid electrolyte layer and a negative electrode having a size larger than the size of the positive electrode and bringing the solid electrolyte layers into close contact to form a laminated structure, Since the layer is constrained to the electrode, it is considered that the problem of foil breakage in the electrode body has become apparent depending on conditions.

As shown in FIG. 1, the manufacturing method of the all solid state battery of the embodiment of the present invention is as follows.
(1) Densification of the positive electrode layer on both sides of the positive electrode current collector foil, and densification of the negative electrode layer on both sides of the negative electrode current collector foil,
(2) Transfer of a coarse solid electrolyte layer (sometimes abbreviated as a crude SE layer) on both surfaces of the positive electrode layer, and a coarse solid electrolyte layer (abbreviated as a coarse SE layer) on both sides of the negative electrode layer. ) Transcription process,
(3) Displacement of film thickness that does not cause current collector foil breakage by measuring the film thickness of the negative electrode and the non-pressed part that is not laminated to the positive electrode and is not pressed at the positive electrode during lamination. A step of determining the amount in advance (not shown), and
(4) A step of laminating by uniaxial pressing with a pressing pressure based on the film thickness displacement amount to form an interface between the rough SEs.
In the step (4), in order to enhance the adhesion between the solid electrolytes, the pressing can be performed by hot pressing. Said hot pressing can be carried out at temperatures of 100 ° C. or higher, preferably in the range of 100 to 200 ° C., in particular in the range of 100 to 180 ° C.

In the embodiment of the present invention, as shown in FIG. 2, a positive electrode having a positive electrode layer on both sides of the positive electrode current collector foil and a solid electrolyte layer thereon, and a negative electrode layer on both surfaces of the negative electrode current collector foil. Using a negative electrode having a solid electrolyte layer and a size larger than the size of the positive electrode, both electrode layers are pressed to form a solid electrolyte (SE) interface.
The size of the positive electrode and the negative electrode may vary depending on the use of the all-solid battery using the electrode body. However, the size of the negative electrode is larger than the size of the negative electrode, and typically the positive electrode has a diameter of 11.28 mm. Can be 13 mm in diameter.

In the embodiment of the present invention, as shown in FIG. 3, in the negative electrode, there are a press part that is laminated on the positive electrode during lamination and a press pressure is applied, and a non-pressed part that is not laminated on the positive electrode and is not subjected to a press pressure.
Then, by changing the press pressure to the negative electrode, the displacement amount of the film thickness: the thickness of the non-pressed portion−the thickness of the pressed portion (μm) was obtained, and the relationship with the press pressure (t) was plotted in FIG. FIG. 5 summarizes the above.
The present invention measures the film thickness change of the negative electrode in a non-destructive manner within the process, and predicts before the current collector foil cracks based on the correlation between the press pressure and the film thickness change. This is based on the finding that the production yield of the body can be improved.

  This is because when electrodes (sheets) with different diameter sizes are laminated by uniaxial pressing, a displacement difference occurs between the portion where the pressing pressure is applied and the portion where the pressing pressure is not applied at the end of the electrode, and the current collector foil is sheared. Force is generated and the current collector foil is cut off, but by measuring the change in the film thickness of the negative electrode, it can be predicted before the foil breakage occurs in the electrode body, thereby improving the yield. it is conceivable that. Moreover, when there is almost no film thickness displacement of the negative electrode, the cause of the foil breakage is reduced, so that the production yield of the electrode body can be further improved.

4 to 9 show the occurrence of cracks in the current collector foil of the electrode body due to pressing by changing the pressing pressure based on FIG.
From comparison between FIGS. 6 and 7 and FIGS. 8 and 9, foil breakage occurred at press pressures of 3.0 t and 4.0 t, and current collector foil breakage occurred at press pressures of 1.0 t and 2.0 t. Not.
This result shows that the occurrence of breakage of the current collector foil can be prevented or suppressed if the pressing pressure is 2.0 t or less.

In the embodiment of the present invention, the positive electrode and the negative electrode in the first step for obtaining the electrode body can be obtained as follows. For example, a positive electrode slurry containing an active material, a solid electrolyte such as a solid electrolyte material, a binder and a solvent is applied to one side of the positive electrode current collector foil, and the positive electrode slurry is applied to the other side in the same procedure to obtain a positive electrode layer. Next, a solid electrolyte slurry containing a solid electrolyte material, a binder and a solvent is applied to both surfaces of the positive electrode layer to obtain a positive electrode. On the other hand, a negative electrode slurry containing an active material, a solid electrolyte material, a binder and a solvent is applied to one side of a negative electrode current collector foil, and a negative electrode slurry is applied to the other side in the same procedure to obtain a negative electrode layer, and then a solid electrolyte material Then, a solid electrolyte slurry containing a binder and a solvent is applied to both sides of the negative electrode layer to obtain a negative electrode.
A metal foil such as SUS foil or Al foil can be used as the positive electrode current collector foil, and a metal foil such as SUS foil or Cu foil can be used as the negative electrode current collector foil.

In an embodiment of the present invention, the active material includes lithium cobaltate (Li _x CoO ₂ ), lithium nickelate (Li _x NiO ₂ ), nickel manganese lithium cobaltate (Li _{1 + x} Ni _1/3 Mn _1/3). Co _1/3 O ₂ ), nickel lithium cobaltate (LiCo _0.3 Ni _0.7 O ₂ ), lithium manganate (Li _x Mn ₂ O ₄ ), lithium titanate (Li _4/3 Ti _5/3 O) _4), lithium manganese oxide compound _{(Li 1 + x M y Mn} 2-x-y O 4; M = Al, Mg, Fe, Cr, Co, Ni, Zn), lithium titanate _(Li x _TiO y), phosphoric acid metallic lithium _{(LiMPO 4, M = Fe,} Mn, Co, Ni), vanadium oxide _{(V 2 O} 5), molybdenum oxide (MoO3), titanium sulfide ( iS _2), lithium cobalt nitride (LiCoN), lithium silicon nitride (LiCoN), lithium metal, lithium alloy (LiM, M = Sn, Si , Al, Ge, Sb, P), lithium storage intermetallic compound ( (MgxM, M = Sn, Ge, Sb, or XySb, X = In, Cu, Mn) and their derivatives, carbon materials (C) such as graphite and hard carbon. Here, there is no clear distinction between the positive electrode active material and the negative electrode active material, and the positive and negative potentials are compared for the positive electrode and the negative potential is used for the negative electrode by comparing the charge and discharge potentials of the two types of compounds. Thus, an electrode having an arbitrary voltage can be formed.
For example, Li _x CoO ₂ , Li _x NiO ₂ , Li _x Mn ₂ O ₄ , Li _x Ni _1/2 Mn _1/2 O ₂ , Li _x Ni _1/3 Co _1/3 Mn _1/3 O ₂ , Li _x [Ni _y Li _{1 / 3-2y / 3} ] O ₃ (0 ≦ x ≦ 1, 0 <y <1/2) and lithium or transition metal of these lithium transition metal oxides were substituted with other elements Lithium transition metals such as LiNiMnCoO ₂ can be mentioned as the positive electrode active material.
Moreover, carbon materials (C), such as graphite and hard carbon, are preferably used as the negative electrode active material.

Examples of the solid electrolyte include Li ₂ S—SiS ₂ , LiI—Li ₂ S—SiS ₂ , liI-li ₂ S—P ₂ S ₅ , LiI—Li ₂ S—B ₂ S ₃ , Li ₃ PO ₄ —. _{Li 2 S-Si 2 S,} Li 3 PO 4 -Li 2 S-SiS 2, LiPO 4 -Li 2 S-SiS, LiI-Li 2 S-P 2 O 5, LiI-Li 3 PO 4 -P 2 S ₅ , sulfide-type amorphous solid electrolytes such as Li ₃ PS ₄ and Li ₂ S—P ₂ S ₅ .

The Li ₂ S—P ₂ S ₅ can be obtained from lithium sulfide and diphosphorus pentasulfide and / or simple phosphorus and simple sulfur. For example, these raw materials are melt-reacted and then rapidly cooled or the raw materials are used. It can be obtained by heat-treating sulfide glass obtained by processing by a mechanical milling method. The mixing molar ratio of lithium sulfide to diphosphorus pentasulfide or simple phosphorus and simple sulfur is usually 50:50 to 80:20, preferably 60:40 to 75:25, and preferably Li ₂ S: P _2. S ₅ = 70: 30~75: is about 25 (mole ratio).

In the embodiment of the present invention, the active material, the solid electrolyte, and a commonly used conductive agent can be used.
Examples of the conductive agent include carbon materials and metals that are difficult to be alloyed with lithium, such as aluminum and conductive polymer materials, and aluminum and carbon materials are preferable. As the carbon material, graphite, carbon black, carbon nanotube, carbon nanofiber, fullerene and the like can be used alone or in combination of two or more.
Examples of the binder include polybutadiene rubber (BR rubber), styrene butadiene rubber (SBR), polyacrylate, and polyvinylidene fluoride (PVdF).
The proportion of each component in the total solid content in the positive electrode and the negative electrode material is 60% by mass or more and 98.5% by mass or less, the solid electrolyte is 10 to 35% by mass, and the binder is 1% by mass or more and 20% by mass. % Or less, and the conductive agent may be 0 to 30% by mass or less.

  In the above process, the description was made based on typical examples of the size of the positive electrode, the size of the negative electrode, and the thickness of the negative electrode (double-sided coating + current collector foil), but in the manufacturing method of the embodiment of the present invention, Even when the positive and negative electrode sizes and the negative electrode thickness (double-sided coating + current collector foil) are different, the above steps (1) to (4) are laminated by uniaxial press with the press pressure based on the film thickness displacement amount, An electrode body in which cutting of the current collector foil during pressing is suppressed can be obtained by the step of forming the interface between the rough SEs.

Examples of the present invention will be described below.
The following examples are for illustrative purposes only and are not intended to limit the invention.
In each of the following examples, the measurement was performed by the following measurement method.

1. Measurement of Displacement The displacement of the negative electrode is obtained by punching out a sample pressed at 392 MPa with a diameter of 11.28 mm and using an autograph manufactured by Shimadzu Corporation by the following method.
A. The baseline is measured by measuring the displacement during pressing and the displacement of the autograph device in the left diagram of FIG.
B. Insert the negative electrode coated on both sides into the press jig, measure the displacement, and determine the value of sample + baseline.
Measurement range: 0 to 5 t (5 t / cm ² )
Negative electrode thickness used (double-sided coating + 10 μm current collector foil): 120 μm

2. 2. Confirmation of cracking of current collector foil Cut the cross section of the laminated electrode body with Microtrome and confirm with SEM Peel strength test Both surfaces of the laminated electrode body were fixed with an adhesive tape, a tensile stress was applied to the electrode body, and a peel test was performed.

Reference example 1
1. Solid electrolyte synthesized Li ₂ S and (Nippon Chemical Industrial Co., Ltd.) _P 2 _{S 5} and (Aldrich) as a starting _material, P ₂ S 5 _0.7656g, a P 2 _{S 5} and 1.2344g weighed, Denka there Add 0.016 g of black (DENKA), mix for 5 minutes in an agate mortar, then add 4 g of heptane, and use a planetary ball mill (container: 45 ml of ZrO ₂ , ball: 53 g of φ 5 mm made of ZrO ₂ ), 500 rpm Was mechanically milled for 20 hours and heated at 110 ° C. for 1 hour to remove heptane and obtain a solid electrolyte.

Examples 1-16
2. Preparation of Battery Element 2-1 Positive Electrode LiNi1 / 3Co1 / 3Mn1 / 3O ₂ (Nichia Chemical Co., Ltd.) 12.03 mg, VGCF (Showa Denko Co., Ltd.) 0.51 mg, and the above solid electrolyte 5.03 mg as a positive electrode active material What weighed and mixed with heptane as a solvent was coated on an aluminum current collector foil, dried, and coated on the other side in the same manner. The dried one was used as a positive electrode coating film.
2-2 Negative electrode A graphite (Mitsubishi Chemical Corporation) 9.06 mg as a negative electrode active material and 8.24 mg of the above solid electrolyte were weighed, and a mixture of heptane as a solvent and applied to a copper current collector foil was dried. The negative electrode coating film was coated and dried on the other surface.
2-3 Solid Electrolyte Layer Weighing 18 mg of the above solid electrolyte, applying a mixture of 3.6 mg of 5% by weight heptane solution of BR rubber as a binder and 30.3 mg of heptane on aluminum foil and drying, What peeled aluminum foil was used as the BR electrolyte coating film.

3. Sample Preparation Sample preparation was performed according to the steps shown in FIG.
1) Press each electrode sheet at 329 MPa using CIP (Cold Isostatic Press) 2) Press both sides of the electrode sheet and press the electrolyte layer at 98 MPa 3) Press the electrode sheet and the positive electrode is φ11 Punching at 28 and negative electrode punching at φ13 4) Electrolyte layers are bonded to each electrode sheet and bonded by uniaxial pressing. Preliminary Measurement of Relationship between Negative Electrode Displacement and Pressing Pressure Preliminary measurement of the relationship between negative electrode displacement and press pressure was performed in the procedure shown in FIG.
The results are summarized in the graph of FIG. 4 and the table of FIG.

5. Production of Electrode Body Based on the results of FIGS. 4 to 5 and FIGS. 6 to 9, an electrode body was produced by uniaxial pressing (pressing and hot pressing) under the following conditions.
Press pressure: 0.2, 0.5, 1.0, 2.0 t / cm ²
Temperature: Room temperature (about 25 ° C), 100 ° C, 140 ° C, 180 ° C
The measurement results of the obtained electrode body are summarized and shown in the table of FIG.
In the table of FIG. 11, when peeled at the electrode / foil, the peel strength at the SE / SE interface is greater than the peel strength at the electrode / foil.
From FIG. 11, it is understood that the lamination press pressure can be reduced by hot pressing.

Comparative Examples 1-2
An electrode body was produced in the same manner as in Example 1 except that uniaxial pressing was performed under the following conditions.
Pressing pressure: Each pressing pressure (t / cm ² ) of 3.0 (Comparative Example 1) and 4.0 (Comparative Example ² )
Temperature: Room temperature (about 25 ° C)
The cross-sectional SEM photograph about the obtained electrode body is shown in FIG. 8, FIG.

  By this invention, the electrode body which can suppress the cutting | disconnection of the current collection foil at the time of a press using the electrode which has a solid electrolyte on both surfaces of a positive electrode layer and a negative electrode layer can be obtained easily.

Claims (4)

  A positive electrode having a positive electrode layer on both sides of the positive electrode current collector foil and a solid electrolyte layer thereon, and a negative electrode layer on both sides of the negative electrode current collector foil and a solid electrolyte layer thereon, and having a size larger than the size of the positive electrode A method of manufacturing an electrode body in which a solid electrolyte layer is laminated and formed into a laminated structure by laminating a negative electrode having a negative electrode, and the negative electrode is laminated on a positive electrode and a press portion on which a press pressure is applied at the time of lamination. The film thickness displacement amount that does not cause current collector foil breakage is determined in advance by measuring the film thickness of the non-pressed portion where no pressing pressure is applied, and is pressed and laminated by the pressing pressure based on the film thickness displacement amount, Production method.   The manufacturing method according to claim 1, wherein the pressing is performed by hot pressing.   The manufacturing method according to claim 1, wherein the positive electrode includes a positive electrode active material and a solid electrolyte, and the negative electrode includes a negative electrode active material and a solid electrolyte.   The manufacturing method according to claim 1, wherein the electrode body has a peel strength at which delamination between electrodes / current collector foil occurs, and the current collector foil does not have a break.