Transfer sheet and method for manufacturing electrochemical device

Abstract

To provide a transfer sheet capable of reducing peeling of an edge of an electrolyte layer, and a manufacturing method of an electrochemical device.SOLUTION: The transfer sheet includes a support and an electrolyte layer provided on one surface of the support, the electrolyte layer includes an electrolyte and a binder that binds the electrolyte, the electrolyte layer includes a central portion and an end portion having a thickness smaller than a thickness of the central portion, and the end portion is provided at an edge of the electrolyte layer. A method of manufacturing an electrochemical device includes an operation of sandwiching a transfer sheet and an electrode between rolls such that an electrolyte layer of the transfer sheet and an active material layer of the electrode face each other, pressing a central portion against the active material layer, and pressing an end portion against a current collector.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a transfer sheet and a method for manufacturing an electrochemical device. [Background technology]

[0002] Patent Document 1 discloses a prior art technique for producing an electrochemical device by using a transfer sheet including a support and an electrolyte layer provided on one side of the support, and transferring the electrolyte layer to an electrode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-5279 Summary of the Invention [Problem to be solved by the invention]

[0004] In the transfer sheets of the prior art, the edges of the electrolyte layer may peel off from the support before the electrolyte layer is transferred to the electrode, and also after the electrolyte layer is transferred to the electrode, the edges of the electrolyte layer may peel off.

[0005] The present invention has been made to solve this problem, and has as its object to provide a transfer sheet and a method for manufacturing an electrochemical device that can reduce peeling of the edges of the electrolyte layer. [Means for solving the problem]

[0006] A first aspect for achieving this object is a transfer sheet comprising a support and an electrolyte layer provided on one side of the support, the electrolyte layer comprising an electrolyte and a binder that binds the electrolyte, the electrolyte layer comprising a central portion and end portions that are thinner than the thickness of the central portion, the end portions being provided on the edges of the electrolyte layer.

[0007] In a second aspect, in the first aspect, the end portion is provided along the longitudinal direction of the support.

[0008] In a third embodiment, in the first or second embodiment, the width of the end portion is in the range of 1 / 100 to 1 / 30 of the width of the central portion.

[0009] In a fourth aspect, in any one of the first to third aspects, the end portion includes a sloped portion where the thickness gradually decreases.

[0010] A fifth aspect is a method for manufacturing an electrochemical device having an electrode including a current collector and an active material layer attached to the current collector, and includes the steps of sandwiching the transfer sheet and the electrode between rolls so that the electrolyte layer of the transfer sheet of any of the first to fourth aspects faces the active material layer of the electrode, and pressing the center against the active material layer and the ends against the current collector. [Effects of the Invention]

[0011] According to the present invention, an edge portion that is thinner than the thickness of the central portion is provided at the edge of the electrolyte layer provided on one side of the support, which reduces the force acting on the edge of the electrolyte layer compared to when there is no edge portion, thereby reducing peeling of the edge of the electrolyte layer. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1(a) is a plan view of a transfer sheet in the first embodiment, and FIG. 1(b) is a cross-sectional view of the transfer sheet taken along line Ib-Ib. [Figure 2] 1(a) is a cross-sectional view of the transfer sheet and the electrode during roll pressing, and FIG. 1(b) is a cross-sectional view of the transfer sheet and the electrode after transfer. [Figure 3] FIG. 10(a) is a plan view of a transfer sheet in a second embodiment, and FIG. 10(b) is a cross-sectional view of the transfer sheet taken along line IIIb-IIIb. [Figure 4] FIG. 4(a) is a plan view of a transfer sheet in a third embodiment, and FIG. 4(b) is a cross-sectional view of the transfer sheet taken along line IVb-IVb. DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1(a) is a plan view of transfer sheet 10 in a first embodiment. Fig. 1(b) is a cross-sectional view of transfer sheet 10 taken along line Ib-Ib. Transfer sheet 10 includes support 11 and a strip-shaped electrolyte layer 12 provided on one side of support 11. In Fig. 1(a), a portion of support 11 in the longitudinal direction (the vertical direction in Fig. 1(a)) is omitted (the same applies to Figs. 3(a) and 4(a)).

[0014] The support 11 may be, for example, a strip-shaped synthetic resin film or paper. Examples of synthetic resins include polyimide, polyethylene terephthalate, polyamide, polysulfone, polyether ether ketone, polyetherimide, polyarylate, and polytetrafluoroethylene. Examples of paper include coated paper such as art paper and coated paper, and uncoated paper such as fine paper and book paper. The thickness of the support 11 may be, for example, 6 to 210 μm, preferably 40 to 160 μm, and more preferably 70 to 120 μm.

[0015] A release layer (not shown) may be provided on one side of the support 11 on which the electrolyte layer 12 is provided (between the support 11 and the electrolyte layer 12). Examples of the release layer include petroleum wax, vegetable wax, animal wax, and mineral wax. Waxes include, for example, esters of fatty acids with 16 to 32 carbon atoms and alcohols. The thickness of the release layer is, for example, 0.1 to 3 μm, and preferably 0.5 to 1 μm.

[0016] The electrolyte layer 12 contains an electrolyte powder and a binder that binds the powder. The electrolyte is a solid material with ion conductivity. Examples of the electrolyte include one or more types selected from sulfide-based, oxide-based, hydride-based, halide-based, and organic-based electrolytes. The electrolyte may be crystalline or amorphous. Sulfide-based electrolytes include crystalline thiolithium-type, Li 10 GeP2S 12 type, argyrodite type, Li7P3S 11Examples include glass and glass ceramic systems such as Li2S-P2S5.

[0017] Examples of oxide electrolytes include NASICON-based materials, LISICON-based materials, oxides having a perovskite structure, and oxides having a garnet structure. NASICON-based materials are represented by the general formula A x It is a material represented by M2(TO4)3. Examples of A are Na and Li, examples of M are Zr, Ti, V, Mn, Cr, Fe, Ni, Al, and Ge, and examples of T are P, Si, and As. For example, Na3V2(PO4)3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Ge x Ti 2-x (PO4)3. LISICON-based materials include Li 4-2x Zn x GeO4 (0≦x≦1). Oxides with a perovskite structure include Li x La (1-x) / 3 NbO3, La 2 / 3-X Li 3X Examples include TiO3 (0≦x≦1).

[0018] The oxide with a garnet structure is X-ray diffraction file No. 422259 (Li7La3Zr2O) in the Cambridge Structural Database (CSD). 12 ) has an XRD pattern similar to that of the electrolyte Li7La3Zr2O 12 Some of the constituent elements may be substituted with other elements, or a small amount of other elements may be added without substituting the constituent elements. Examples of other elements include at least one element selected from the group consisting of Mg, Al, Si, Ca, Ti, V, Ga, Sr, Y, Nb, Sn, Sb, Ba, Hf, Ta, W, Bi, Rb, and lanthanides (excluding La).

[0019] Examples of hydride electrolytes include solid solutions of LiBH4 with lithium halide compounds (LiI, LiBr, LiCl) and lithium amide (LiNH2). Examples of halide electrolytes include Li3YCl6. Examples of organic electrolytes include polyethylene oxide, polypropylene oxide, and polyacrylnitrile.

[0020] Examples of binders include fluorinated resins, polyolefins, polyvinylpyrrolidone, polyvinyl alcohol, cellulose ethers, polyimides, polyamides, polyamideimides, and rubber-like polymers such as styrene-butadiene rubber. Examples of fluorinated resins include vinylidene fluoride polymers, polychlorotrifluoroethylene, polyvinyl fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, ethylene-tetrafluoroethylene copolymers, and ethylene-chlorotrifluoroethylene copolymers. These may be used alone or in combination.

[0021] The vinylidene fluoride polymer is not particularly limited as long as it contains -CH2CF2-. Examples of the vinylidene fluoride polymer include a homopolymer of vinylidene fluoride and a copolymer of vinylidene fluoride and a copolymerizable monomer. Examples of the copolymerizable monomer include a halogen-containing monomer (excluding vinylidene fluoride) and a non-halogen copolymerizable monomer. Examples of the halogen-containing monomer include a chlorine-containing monomer such as vinyl chloride; and a fluorine-containing monomer such as trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, and perfluoroalkyl vinyl ether. Examples of the non-halogen copolymerizable monomer include an olefin such as ethylene or propylene; an acrylic monomer such as acrylic acid, methacrylic acid, or an ester or salt thereof; and a vinyl monomer such as acrylonitrile, vinyl acetate, or styrene. One or more copolymerizable monomers are polymerized with vinylidene fluoride to form a copolymer.

[0022] The electrolyte layer 12 includes a central portion 13 having a substantially constant thickness and end portions 14 having a thickness thinner than the thickness of the central portion 13. The end portions 14 are portions whose thickness falls outside the range of ±20% of the average thickness of the central portion 13 and are portions whose thickness is less than 80% of the average thickness of the central portion 13. In this embodiment, the end portions 14 are provided on both edges of the electrolyte layer 12 along the longitudinal direction of the support 11. It is preferable that the width W2 of the end portions 14 be in the range of 1 / 100 to 1 / 30 of the width W1 of the central portion 13, since this allows the volume of the central portion 13 of the electrolyte layer 12 to be secured.

[0023] The edge 14 includes a sloped portion 15 adjacent to the central portion 13 where the thickness gradually decreases, and a step portion 16 adjacent to the sloped portion 15 where the thickness is approximately constant. The electrolyte layer 12 is formed by preparing a slurry containing an electrolyte and a solvent in which a binder has been dissolved, applying the slurry to the support 11 using a knife coater with depressions formed in the shapes of the central portion 13 and the edge 14 to form a membrane, and then evaporating the solvent contained in the membrane. The membrane shrinks as the solvent evaporates. The greater the force acting on the interface of the membrane in contact with the support 11 due to shrinkage, the easier the membrane will peel off from the support 11; the greater the volume of the membrane, the greater the amount of shrinkage, and therefore the greater the force.

[0024] Because the electrolyte layer 12 has the edge 14, the volume of the edge of the electrolyte layer 12 can be made smaller than that of an electrolyte layer without the edge 14. The force acting on the edge of the electrolyte layer 12 due to shrinkage can be reduced, thereby reducing peeling of the edge of the electrolyte layer 12. Furthermore, because the edge 14 includes the sloped portion 15, the force acting on the edge 14 due to shrinkage can be gradually reduced from the center portion 13 toward the step portion 16. This further reduces peeling of the edge of the electrolyte layer 12.

[0025] 2(a) is a cross-sectional view of the transfer sheet 10 and electrode 17 during roll pressing. The transfer sheet 10 is used to transfer the electrolyte layer 12 onto the electrode 17. The electrode 17 includes a current collector 18 and an active material layer 19 attached to the current collector 18.

[0026] The current collector 18 is not particularly limited as long as it is a material that has electronic conductivity and can conduct electricity to the active material layer 19. For example, conductive materials such as C, Ti, Cr, Ni, Cu, Fe, Mo, Ru, Rh, Ta, W, Os, Ir, Pt, Al, and Au, or alloys containing two or more of these conductive materials (e.g., stainless steel) can be used for the current collector 18. When Fe is used for the current collector 18, it is preferably coated with Ni, Cu, or the like to prevent oxidation. The shape of the current collector 18 is also not limited, and examples include a wire, rod, plate, foil, and porous shape.

[0027] When the electrode 17 is a positive electrode, the active material layer 19 contains a positive electrode active material. Examples of the positive electrode active material include a metal oxide containing a transition metal, a sulfur-based active material, and an organic active material. Examples of the metal oxide containing a transition metal include a metal oxide containing Li and one or more elements selected from Mn, Co, Ni, Fe, Cr, and V. Examples of the metal oxide containing a transition metal include LiCoO2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiMn2O4, LiNiVO4, LiNi 0.5 Mn 1.5 O4,LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 Examples include O2 and LiFePO4.

[0028] Examples of sulfur-based active materials include S, TiS2, NiS, FeS2, Li2S, MoS3, and sulfur-carbon composites. Examples of organic active materials include radical compounds such as 2,2,6,6-tetramethylpiperidinoxyl-4-yl methacrylate and polytetramethylpiperidinoxyl vinyl ether, quinone compounds, radialene compounds, tetraciaquinodimethane, and phenazine oxide.

[0029] When the electrode 17 is a negative electrode, the active material layer 19 contains a negative electrode active material. The negative electrode active material is not particularly limited as long as it is a material capable of reversibly absorbing and releasing cations. The ion absorption and release mechanism may be dissolution and precipitation of the material, or insertion and desorption of ions between crystalline layers. The negative electrode active material may be, for example, one or more elements selected from the group consisting of Li, Na, K, C, Mg, Al, Si, P, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Nb, Mo, Pd, Ag, Cd, In, Sn, Sb, W, Pb, and Bi, or an alloy, composite, oxide, chalcogenide, or halide containing these elements. From the viewpoint of increasing energy density, the negative electrode active material preferably contains elements such as Al, Si, Zn, Ge, Ag, and Sn.

[0030] The alloys used as the negative electrode active material are preferably Si-Al, Al-Zn, Si-Mg, Si-La, Al-Ge, Si-Ge, Si-Ag, Si-Sn, Si-Ti, Si-Y, Si-Cr, Si-Ni, Si-Zr, Si-V, Si-Nb, Si-Mo, Zn-Sn, Ge-Ag, Ge-Sn, Ge-Sb, Ag-Sn, Ag-Ge, Sn-Sb, etc., and may be complete solid solution alloys, eutectic alloys, hypoeutectic alloys, hypereutectic alloys, or peritectic alloys. The oxides used are Fe2O3, CuO, MnO2, NiO, Li4Ti5O 12 , H2Ti 12 O 25 , Na2Ti3O7, etc. are preferred. The negative electrode active material may be coated with a material or ceramics having excellent electronic conductivity. Two or more materials may be used as the negative electrode active material. The shape of the negative electrode active material is not particularly limited, and may be spherical, elliptical, faceted, strip-shaped, fibrous, scale-shaped, torus-shaped, or hollow.

[0031] The active material layer 19 may contain a conductive additive to reduce the resistance of the active material layer 19. Examples of conductive additives include carbon black, acetylene black, ketjen black, carbon fiber, Ni, Pt, and Ag. The active material layer 19 may contain an electrolyte to increase the ionic conductivity of the active material layer 19. The active material layer 19 may contain a binder that binds the positive electrode active material and the negative electrode active material. The binder is the same as the binder contained in the electrolyte layer 12. The size of the active material layer 19 is smaller than that of the electrolyte layer 12. The size of the current collector 18 is approximately the same as that of the electrolyte layer 12.

[0032] As shown in FIG. 2( a), the electrolyte layer 12 is transferred to the electrode 17 by roll pressing. The transfer sheet 10 and the electrode 17 are sandwiched between rotating rolls 20 so that the electrolyte layer 12 of the transfer sheet 10 and the active material layer 19 of the electrode 17 face each other, and the transfer sheet 10 and the electrode 17 are moved to press the central portion 13 against the active material layer 19. After pressing the central portion 13 against the active material layer 19, the rolls 20 press the edge portions 14 against the current collector 18. Because the edge portions 14 are thinner than the central portion 13, the force applied by the edge portions 14 to the current collector 18 can be reduced compared to when the edge portions 14 are not present. This reduces deformation and damage to the current collector 18 during roll pressing due to the force applied by the edge portions 14 to the current collector 18.

[0033] 2(b) is a cross-sectional view of the transfer sheet 10 and electrode 17 after transfer. When the support 11 is peeled off from the transfer sheet 10 after transfer, a laminate of the electrode 17 and the electrolyte layer 12 is formed. Since the force applied to the end 14 during roll pressing can be reduced, the adhesion force between the support 11 and the end 14 can be reduced. Since the end 14 can be prevented from adhering to the support 11, peeling of the end 14 from the current collector 18 when the support 11 is peeled off can be reduced.

[0034] When the active material layer 19 contains a positive electrode active material, the electrode 17 is a positive electrode. After the support 11 is peeled off, an active material layer (not shown) containing a negative electrode active material is laminated on the electrolyte layer 12, thereby obtaining an electrochemical device in which the electrolyte layer 12 separates the positive electrode from the negative electrode.

[0035] When the active material layer 19 contains a negative electrode active material, the electrode 17 is a negative electrode. After the support 11 is peeled off, an active material layer (not shown) containing a positive electrode active material is laminated on the electrolyte layer 12, thereby obtaining an electrochemical device in which the electrolyte layer 12 separates the positive electrode and the negative electrode.

[0036] Examples of electrochemical devices include secondary batteries such as lithium ion batteries, sodium ion batteries, and magnesium ion batteries, electrochemical capacitors, fuel cells, and electrolytic cells. Examples of electrochemical capacitors include redox capacitors that utilize redox reactions and hybrid capacitors that are asymmetric cells that combine an electric double layer capacitor with an electrolyte layer 12.

[0037] A second embodiment will be described with reference to Figure 3. In the first embodiment, transfer sheet 10 was described in which end portions 14 were provided on both edges of electrolyte layer 12. In contrast, in the second embodiment, transfer sheet 21 will be described in which end portion 24 is provided on one edge of electrolyte layer 22. In the second embodiment, the same parts as those described in the first embodiment are designated by the same reference numerals, and the following description will be omitted.

[0038] Fig. 3(a) is a plan view of transfer sheet 21 in the second embodiment. Fig. 3(b) is a cross-sectional view of transfer sheet 21 taken along line IIIb-IIIb. Transfer sheet 21 includes support 11 and a strip-shaped electrolyte layer 22 provided on one side of support 11. Electrolyte layer 22 includes a central portion 23 having a substantially constant thickness and end portions 24 having a thickness thinner than that of central portion 23.

[0039] In this embodiment, the edge 24 is provided on one edge of the electrolyte layer 22 along the longitudinal direction of the support 11. The edge 24 consists of a sloping portion that is adjacent to the central portion 23 and gradually becomes thinner. As in the first embodiment, the electrolyte layer 22 is produced by applying a slurry to the support 11 using a knife coater in which recesses in the shapes of the central portion 23 and the edge 24 are made.

[0040] Because the electrolyte layer 22 has the end portions 24, the volume of the edge of the electrolyte layer 22 can be made smaller than that of an electrolyte layer without the end portions 24. The force acting on the edge of the electrolyte layer 22 due to shrinkage can be reduced, thereby reducing peeling of the edge of the electrolyte layer 22. Furthermore, because the end portions 24 are inclined, the force acting on the end portions 24 due to shrinkage can be gradually reduced with increasing distance from the central portion 13. This further reduces peeling of the edge of the electrolyte layer 22.

[0041] As in the first embodiment, the presence of the end portion 24 reduces deformation and damage to the current collector 18 during transfer by roll press. Furthermore, peeling of the end portion 24 from the current collector 18 when the support 11 is peeled off can be reduced.

[0042] A third embodiment will be described with reference to Figure 4. In the first and second embodiments, the case was described in which end portions 14, 24 are provided along the longitudinal direction of support 11, and no end portions are provided in the lateral direction of support 11. In contrast, the third embodiment describes a transfer sheet 25 in which end portions 28 are provided in both the longitudinal and lateral directions of support 11. In the third embodiment, the same parts as those described in the first embodiment are assigned the same reference numerals, and the following description will be omitted.

[0043] Fig. 4(a) is a plan view of transfer sheet 25 in the third embodiment. Fig. 4(b) is a cross-sectional view of transfer sheet 25 taken along line IVb-IVb. Transfer sheet 25 includes support 11 and rectangular electrolyte layer 26 provided on one side of support 11. Electrolyte layer 26 includes central portion 27 having a substantially constant thickness and end portions 28 having a thickness thinner than that of central portion 27.

[0044] In this embodiment, the end portions 28 are provided around the central portion 27 along the longitudinal and lateral directions of the support 11. The end portions 28 are adjacent to the central portion 27 and have a stepped shape such that the thickness thereof is thinner. The thickness of the end portions 28 is, for example, 4 / 5 or less of the thickness of the central portion 27, and more preferably 1 / 5 or less. The electrolyte layer 26 is produced by stencil printing using a screen, metal mask, or the like, by printing the portion having the thickness of the end portions 28 and then printing the portion having the thickness of the central portion 27 on top of that.

[0045] Because the electrolyte layer 26 has the edge 28, the volume of the edge of the electrolyte layer 26 can be made smaller than that of an electrolyte layer without the edge 28. The force acting on the edge of the electrolyte layer 26 due to shrinkage can be reduced, thereby reducing peeling of the edge of the electrolyte layer 26. Furthermore, because the edge 28 is present, deformation and damage to the current collector 18 during transfer by roll press can be reduced, as in the first embodiment. Furthermore, peeling of the edge 28 from the current collector 18 when the support 11 is peeled off can be reduced.

[0046] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention.

[0047] In the embodiment, an electrochemical device has been described that includes an electrode in which an active material layer 19 is provided on one side of a current collector 18, but the present invention is not necessarily limited to this. For example, it is of course possible to apply each element in the embodiment to an electrochemical device that includes an electrode (a so-called bipolar electrode) in which a negative electrode active material layer and a positive electrode active material layer are provided on both sides of a current collector 18. If bipolar electrodes and electrolyte layers 12, 22, and 26 are alternately stacked and housed in a case (not shown), a so-called bipolar structure electricity storage device (electrochemical device) can be obtained.

[0048] In the third embodiment, the end portion 28 has one step at the boundary between the central portion 27 and the end portion 28, but this is not necessarily limited to this. In addition to the step at the boundary between the central portion 27 and the end portion 28, it is of course possible to provide one or more steps at the end portion 28. According to this modification, the thickness of the end portion 28 gradually decreases with increasing distance from the central portion 27, so that the force acting on the end portion 28 due to contraction can be gradually reduced with increasing distance from the central portion 27. This can further reduce peeling of the edge of the electrolyte layer 26.

[0049] It is of course possible to change the shape of the end 14 in the first embodiment to any of the shape of the end 24 in the second embodiment, the shape of the end 28 in the third embodiment, and the shape of the end 28 in the modified example. Similarly, it is of course possible to change the shape of the end 24 in the second embodiment to any of the shape of the end 14 in the first embodiment, the shape of the end 28 in the third embodiment, and the shape of the end 28 in the modified example. [Explanation of symbols]

[0050] 10, 21, 25 Transfer sheet 11 Support 12,22,26 Electrolyte layer 13,23,27 central part 14, 24, 28 End 15 Slope 17 electrodes 18 Current collector 19 Active material layer 20 rolls 24 End (slope) W1 Center width W2 End width

Claims

1. a support and an electrolyte layer provided on one surface of the support, the electrolyte layer is a transfer sheet including an electrolyte and a binder that binds the electrolyte, the electrolyte layer includes a central portion and an end portion having a thickness thinner than the thickness of the central portion; The transfer sheet has an end portion provided on the edge of the electrolyte layer.

2. 2. The transfer sheet according to claim 1, wherein the edge portion is provided along the longitudinal direction of the support.

3. 3. The transfer sheet according to claim 2, wherein the width of the end portion is in the range of 1 / 100 to 1 / 30 of the width of the central portion.

4. 2. The transfer sheet according to claim 1, wherein the edge portion includes a sloped portion in which the thickness gradually decreases.

5. A method for manufacturing an electrochemical device including an electrode including a current collector and an active material layer attached to the current collector, the method comprising:

5. A method for manufacturing an electrochemical device, comprising: sandwiching the transfer sheet and the electrode between rolls so that the electrolyte layer of the transfer sheet according to claim 1 faces the active material layer of the electrode; and pressing the central portion against the active material layer and the end portion against the current collector.

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