Bipolar electrode and bipolar battery

Abstract

Provided are a bipolar electrode and a bipolar battery in which warping of the electrode during charging and discharging can be suppressed. This bipolar electrode is provided with: a positive electrode base material serving as a current collector; the positive electrode composite material layer is formed on the positive electrode base material; a negative electrode base material serving as a current collector; the negative electrode composite material layer is formed on the negative electrode base material and is divided into a plurality of regions, and a groove with the negative electrode base material at the bottom is arranged between adjacent regions; and the elastic layer is formed between the negative electrode base material and the negative electrode composite material layer and has elasticity. In the electrode, a positive electrode composite material layer, a positive electrode base material, a negative electrode base material, an elastic layer and a negative electrode composite material layer are stacked in sequence.

Description

Technical Field

[0001] The present disclosure relates to bipolar electrodes and bipolar batteries. Background Art

[0002] For example, the following technology is disclosed in Japanese Patent Gazette No. 2019-0192338: In an all-solid-state battery, a slit-shaped groove is formed on the electrode surface to appropriately adjust the area of ​​the portion of the electrode surface involved in the electrode layer that participates in the electrode reaction, and the slit-shaped groove is used as a buffer portion for the expansion and contraction of the electrode layer. As a result, the expansion of the electrode layer can be suppressed.

[0003] The electrodes of bipolar batteries have composite material layers on both sides of the current collector that expand and contract differently during charge and discharge, so there is a possibility that the electrodes may warp during charge and discharge.

[0004] In addition, in the all-solid-state battery disclosed in Japanese Patent Publication No. 2019-0192338, all constituent materials including the composite material layer are solidified, so the possibility of warping in the electrode is significantly lower than that of a liquid battery using an electrolyte.

[0005] The present disclosure provides a bipolar electrode and a bipolar battery capable of suppressing warping during charge and discharge. Summary of the invention

[0006] The first type of bipolar electrode comprises: a positive electrode substrate serving as a current collector; a positive electrode composite material layer formed on the positive electrode substrate; a negative electrode substrate serving as a current collector; a negative electrode composite material layer formed on the negative electrode substrate and divided into a plurality of regions, wherein a groove having a bottom portion of the negative electrode substrate is provided between adjacent regions; and an elastic layer formed between the negative electrode substrate and the negative electrode composite material layer and having elasticity, wherein the positive electrode composite material layer, the positive electrode substrate, the negative electrode substrate, the elastic layer, and the negative electrode composite material layer are stacked in sequence.

[0007] Regarding the second type of bipolar electrode, based on the first type, the tensile shear bonding strength of the elastic layer is greater than 15 MPa and less than 40 MPa, the peel bonding strength is greater than 3 N and less than 10 N, the elastic modulus is greater than 700 MPa and less than 1200 MPa, the breaking strength is greater than 15 MPa and less than 25 MPa, and the breaking elongation is greater than 5% and less than 30%.

[0008] Regarding the bipolar electrode of a third aspect, in addition to the first aspect or the second aspect, the elastic layer has an electron conductivity of 1 mS / cm or more.

[0009] Regarding the bipolar electrode of the fourth mode, on the basis of any one of the first to third modes, the elastic layer contains a conductive additive and a polymer material.

[0010] Regarding the bipolar electrode of the fifth mode, on the basis of any one of the first to fourth modes, the thickness of the elastic layer is 10 μm or less.

[0011] Regarding the bipolar electrode of the sixth mode, on the basis of any one of the first to fifth modes, the negative composite material layer is rectangular when viewed from the stacking direction. In the negative composite material layer, when viewed from the stacking direction, a plurality of the grooves extend in directions substantially parallel to the short side and the long side of the negative composite material layer, respectively.

[0012] Regarding the bipolar electrode of the seventh mode, on the basis of any one of the first to sixth modes, the negative composite material layer contains at least a negative active material, and the negative active material contains 10% or less of silicon (Si).

[0013] Regarding the bipolar electrode of the eighth mode, on the basis of any one of the first to seventh modes, the groove width of the groove is 50 μm or more and 5 mm or less.

[0014] Regarding the bipolar electrode of the ninth mode, on the basis of any one of the first to eighth modes, the interval between adjacent grooves is 1 mm or more and 100 mm or less.

[0015] Regarding the bipolar electrode of the tenth mode, on the basis of any one of the first to ninth modes, the ratio of the groove width of the groove to the interval between adjacent grooves is 0.05.

[0016] Regarding the bipolar electrode of the eleventh mode, on the basis of any one of the first to tenth modes, the outer diameter dimension of the negative composite material layer is 1000 mm or more.

[0017] Regarding the bipolar electrode of the twelfth mode, on the basis of any one of the first to eleventh modes, compared with the outer region of the negative composite material layer, more grooves are provided in the central region.

[0018] Regarding the bipolar electrode of the thirteenth mode, on the basis of any one of the first to twelfth modes, the grooves are evenly provided in the negative composite material layer.

[0019] Regarding the bipolar electrode of the fourteenth mode, on the basis of any one of the first to thirteenth modes, the grooves are not provided in the positive composite material layer.

[0020] Regarding the bipolar battery of the fifteenth mode, a plurality of bipolar electrodes of any one of the first mode to the fourteenth mode are stacked with a spacer made of an organic material, and an electrolytic solution is included.

[0021] The bipolar electrode and the bipolar battery according to the present disclosure can suppress warping during charge and discharge. BRIEF DESCRIPTION OF THE DRAWINGS Exemplary embodiments of the present invention will be described in detail based on the following drawings.

[0022] Figure 1 It is a schematic cross-sectional view showing the configuration of the bipolar electrode according to the first embodiment of the present disclosure. Figure 2 It is viewed from the upper side in the stacking direction Figure 1 of the negative composite material layer of the bipolar electrode. Figure 3 It is a schematic cross-sectional view showing the configuration of the bipolar battery according to an embodiment of the present disclosure. Figure 4 It shows Figure 3 a schematic cross-sectional view of the internal configuration of the power storage module shown. Figure 5 It is Figure 1 an enlarged view of the portion shown by circle A in Figure 6 It is during charge and discharge corresponding to Figure 5 an enlarged view. Figure 7 It is a top view of the negative composite material layer of the bipolar electrode according to the second embodiment of the present disclosure, viewed from the upper side in the stacking direction. Figure 8 It is a schematic cross-sectional view for explaining the definition of warping. Figure 9 It is a schematic cross-sectional view showing the configuration of a conventional bipolar electrode. DETAILED DESCRIPTION OF THE INVENTION

[0023] (First Embodiment) Hereinafter, with reference to the drawings, the bipolar electrode 10 according to the first embodiment of the present disclosure will be described. In the description of the drawings, the same or equivalent elements are denoted by the same reference numerals, and repeated description is omitted.

[0024] Figure 1 It is a schematic cross-sectional view showing the configuration of the bipolar electrode 10. As an example, Figure 1 the bipolar electrode 10 shown is an electrode having a bipolar structure and is used for the bipolar battery 1 as a power storage device described later.

[0025] The bipolar electrode 10 is formed in a substantially rectangular parallelepiped shape. In addition, the bipolar electrode 10 includes a positive electrode substrate 12 that serves as a current collector 15, a positive electrode composite material layer 14 formed on the positive electrode substrate 12, a negative electrode substrate 16 that serves as a current collector 15, a negative electrode composite material layer 18 formed on the negative electrode substrate 16, and an elastic layer 20 formed between the negative electrode substrate 16 and the negative electrode composite material layer 18. In the present embodiment, the positive electrode substrate 12 and the negative electrode substrate 16 are fixed to form the current collector 15.

[0026] The bipolar electrode 10 is stacked with the positive electrode composite material layer 14, the positive electrode substrate 12, the negative electrode substrate 16, the elastic layer 20, and the negative electrode composite material layer 18 in this order from the lower side to the upper side of the paper surface of Figure 1 . In the present embodiment, the vertical direction of the paper surface of Figure 1 , that is, the stacking direction of the positive electrode composite material layer 14, the positive electrode substrate 12, the negative electrode substrate 16, the elastic layer 20, and the negative electrode composite material layer 18 is defined as the "stacking direction D".

[0027] As an example, the positive electrode substrate 12 is formed of a rectangular sheet-like metal foil, and specifically, it is formed of aluminum foil in the present embodiment. The positive electrode substrate 12 is, for example, a chemically inert electrical conductor that allows current to continuously flow through the positive electrode composite material layer 14 during discharge or charging of the bipolar battery 1.

[0028] The positive electrode composite material layer 14 is formed on the lower surface of the positive electrode substrate 12 on the lower side in the stacking direction D, and is formed inside the peripheral edge of the positive electrode substrate 12. That is, the peripheral edge portion 12A of the positive electrode substrate 12 has a rectangular frame shape and becomes an uncoated area where the positive electrode composite material layer 14 is not coated. The positive electrode composite material layer 14 is a positive electrode active material layer formed by coating the positive electrode active material in a substantially rectangular shape on the lower surface of the positive electrode substrate 12. As the positive electrode active material constituting the positive electrode composite material layer 14, for example, an oxide active material can be cited. As the oxide active material, for example, LiCoO 2 , LiMnO 2 , LiNiO 2 , LiVO 2 , LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 and other rock salt layer-type active materials, LiMn 2 O 4 , Li(Ni 0.5 Mn 1.5 )O 4 and other spinel-type active materials, LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCuPO4 The positive electrode active material layer forming the positive electrode composite material layer 14 may contain a conductive material and a binder in addition to the positive electrode active material.

[0029] As an example, the negative electrode substrate 16 is formed of a rectangular sheet of metal foil, and specifically, is formed of copper foil in this embodiment. The negative electrode substrate 16 is, for example, a chemically inert electrical conductor for allowing current to continue to flow through the negative electrode composite material layer 18 during discharge or charge of the bipolar battery 1. In addition, in this embodiment, as an example, the negative electrode substrate 16 is provided with a diameter of The negative electrode substrate 16 may not have pores, but may have pores with a width of 5 μm or more and 20 μm or less. The groove has a thickness of 5 μm or more and 20 μm or less.

[0030] The negative electrode composite material layer 18 is formed on the upper surface of the negative electrode substrate 16 in the stacking direction D, and is formed inside the periphery of the negative electrode substrate 16. That is, the periphery 16A of the negative electrode substrate 16 is in a rectangular frame shape, and becomes an uncoated area where the negative electrode composite material layer 18 is not coated. The negative electrode composite material layer 18 is a negative electrode active material layer formed by coating the negative electrode active material on the upper surface of the negative electrode substrate 16. Examples of the negative electrode active material constituting the negative electrode composite material layer 18 include carbon active materials, oxide active materials, and metal active materials.

[0031] In the present embodiment, specifically, the negative electrode composite material layer 18 contains silicon (Si) within 10% relative to the graphite-based negative electrode active material. In addition, in the present embodiment, the thickness of the negative electrode composite material layer 18 is formed to be greater than 100 μm and less than 200 μm. In addition, the positive electrode composite material layer 14 is formed with a thickness less than that of the negative electrode composite material layer 18. Specifically, as an example, the capacity ratio of the negative electrode composite material layer 18 to the positive electrode composite material layer 14 is set to a range of greater than 1.05 and less than 1.2.

[0032] Figure 2 It is viewed from the upper side in the stacking direction D. Figure 1 A top view of the negative electrode composite material layer 18 of the bipolar electrode 10. Figure 2 As shown, the negative electrode composite material layer 18 includes a plurality of regions 18A formed on the negative electrode substrate 16. That is, the negative electrode composite material layer 18 is divided into a plurality of regions 18A. In the present embodiment, as an example, the negative electrode composite material layer 18 is divided into a total of 48 regions 18A, which are 8 columns in the left-right direction of the paper and 6 rows in the vertical direction of the paper.

[0033] In addition, on the upper surface of the negative electrode composite material layer 18 in the stacking direction D, grooves 19 are provided between adjacent regions 18A. In the present embodiment, as Figure 2 shown, when the negative electrode composite material layer 18 is viewed from the upper side in the stacking direction D, it is formed in a substantially rectangular shape, and a plurality of grooves 19 linearly extend along the surface of the negative electrode composite material layer 18 on the short side and the long side of the negative electrode composite material layer 18, respectively. That is, the longitudinal grooves 19A extending in the up-and-down direction of the paper surface extend substantially parallel to the short side of the negative electrode composite material layer 18, and the transverse grooves 19B extending in the left-and-right direction of the paper surface extend substantially parallel to the long side of the negative electrode composite material layer 18. In addition, in the present embodiment, the grooves 19 (longitudinal grooves 19A and transverse grooves 19B) show the portions of the upper surface of the negative electrode substrate 16 in the stacking direction D where the negative electrode composite material layer 18 is not loaded. That is, the bottom of the groove 19 is constituted by the negative electrode substrate 16.

[0034] As an example, the grooves 19 are formed by laser processing. Since the width of the grooves 19 is narrow, it is difficult to form them by coating, and laser processing is used from the viewpoint of ease of processing.

[0035] As an example, for the longitudinal grooves 19A and the transverse grooves 19B, the groove width W1 is preferably 50 μm or more and 5 mm or less, more preferably 50 μm or more and 1 mm or less. In addition, since the required size of the groove width W1 varies depending on the silicon content of the negative electrode composite material layer 18, the value is appropriately set according to the silicon content of the negative electrode composite material layer 18. Further, as an example, the interval W2 between adjacent longitudinal grooves 19A is preferably 1 mm or more and 100 mm or less, more preferably 1 mm or more and 20 mm or less. Similarly, as an example, the interval W3 between adjacent transverse grooves 19B is preferably 1 mm or more and 100 mm or less, more preferably 1 mm or more and 20 mm or less. In addition, the intervals W2 and W3 between adjacent grooves are the same as the width of the region 18A between adjacent grooves.

[0036] In addition, the ratio (W1 / W2, W1 / W3) of the groove width W1 to the intervals W2 and W3 between adjacent grooves is preferably 0.05. In addition, in the present embodiment, for convenience, the groove width W1 of the longitudinal grooves 19A and the transverse grooves 19B is denoted by the same reference numeral, but the sizes of the groove width W1 of the longitudinal grooves 19A and the transverse grooves 19B may also be different. The groove width W1 is set according to the values of the intervals W2 and W3 between adjacent grooves.

[0037] In addition, as an example, the grooves 19 are evenly set in the negative electrode composite material layer 18. That is, the longitudinal grooves 19A are provided at an equal ratio with respect to the long side of the negative electrode composite material layer 18, and the transverse grooves 19B are provided at an equal ratio with respect to the short side of the negative electrode composite material layer 18.

[0038] In addition, the horizontal width W4 and the vertical width W5 of the outer shape size of the negative electrode composite material layer 18 may also be 1000 mm or more.

[0039] In the present embodiment, the groove 19 is provided in the negative electrode composite material layer 18, but not provided in the positive electrode composite material layer 14.

[0040] The elastic layer 20 contains a conductive additive and a polymer material. The upper side in the stacking direction D is bonded to the negative electrode composite material layer 18, and the lower side is bonded to the negative electrode substrate 16. The conductive additive is contained to improve the electrical conductivity of the elastic layer 20, and for example, acetylene black, carbon black, or graphite can be used. As the polymer material, a known material can be used. As an example, polyethylene, polypropylene, polyethylene terephthalate, polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride, etc. can be used. In addition, the elastic layer 20 is formed with a thickness of 10 μm or less.

[0041] In the present embodiment, as an example, the elastic layer 20 has elasticity and adhesiveness. Specifically, as an example, the elastic layer 20 is formed such that the tensile shear adhesive strength is 15 MPa or more and 40 MPa or less, the peel adhesive strength is 3 N or more and 10 N or less, the elastic modulus is 700 MPa or more and 1200 MPa or less, the breaking strength is 15 MPa or more and 25 MPa or less, the elongation at break is 5% or more and 30% or less, and the electronic conductivity is 1 mS / cm or more. In the case of a current collector foil in which a positive electrode foil (positive electrode substrate) and a negative electrode foil (negative electrode substrate) used in a bipolar battery are paired, the negative electrode composite material layer and the negative electrode foil do not expand together originally. However, by placing such an elastic layer between the negative electrode composite material and the negative electrode foil, they can slide with each other and follow. In the case of an all-solid-state battery, the negative electrode current collector foil expands and contracts together with the negative electrode composite material, so such an elastic layer is not required.

[0042] Next, an example of a bipolar battery 1 in which a plurality of the above bipolar electrodes 10 are stacked will be described. In addition, in the description of the drawings, the same or equivalent elements are denoted by the same reference numerals, and repeated description is omitted.

[0043] Figure 3 It is a schematic cross-sectional view showing the configuration of a bipolar battery 1 according to an embodiment. Figure 1 The bipolar battery 1 shown is, for example, a device used in batteries of various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The bipolar battery 1 is, for example, a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery. In the present embodiment, the case where the bipolar battery 1 is a liquid lithium-ion secondary battery is illustrated. The bipolar battery 1 includes a module laminate 2 and a binding member 3 that applies a binding load to the module laminate 2 in the stacking direction of the module laminate 2.

[0044] The module laminate 2 includes a plurality of power storage modules 4 and a plurality of conductive plates 5. In the module laminate 2, a plurality of (here, three) power storage modules 4 and a plurality of (here, four) conductive plates 5 are alternately laminated such that the conductive plates 5 are located on both sides of the power storage modules 4. The direction in which the power storage modules 4 are laminated becomes the "lamination direction D". The power storage module 4 is a bipolar battery and has a rectangular shape when viewed in the lamination direction D.

[0045] The power storage modules 4 adjacent to each other in the lamination direction D are electrically connected to each other via the conductive plates 5. The conductive plates 5 are respectively disposed between the power storage modules 4 adjacent to each other in the lamination direction D and outside the power storage modules 4 at the lamination ends. A negative terminal 6 is connected to one of the conductive plates 5 disposed outside the power storage module 4 at the lamination end. A positive terminal 7 is connected to the other of the conductive plates 5 disposed outside the power storage module 4 at the lamination end. The negative terminal 6 and the positive terminal 7 are led out, for example, from the edge portion of the conductive plate 5 in a direction intersecting the lamination direction D. Charging and discharging of the bipolar battery 1 are performed through the negative terminal 6 and the positive terminal 7.

[0046] In addition, in the present embodiment, the outermost layer of the module laminate 2 is a conductive plate 5, but the outermost layer (the outermost layer of the stack) of the module laminate 2 may also be a power storage module 4. In this case, a negative terminal 6 or a positive terminal 7 is connected to the power storage module 4 constituting the outermost layer of the stack.

[0047] Inside the conductive plate 5, a plurality of flow paths 5a through which a refrigerant such as air flows are provided. The flow paths 5a extend, for example, in a direction intersecting (orthogonal to) the lamination direction D and the lead-out directions of the negative terminal 6 and the positive terminal 7. In addition to the function of being a connection member that electrically connects the power storage modules 4 to each other, the conductive plate 5 also has the function of a heat dissipation plate that dissipates heat generated in the power storage module 4 by allowing the refrigerant to flow through these flow paths 5a.

[0048] The binding member 3 includes a pair of end plates 8 that sandwich the module laminate 2 in the lamination direction D, and fastening bolts 9A and nuts 9B that fasten the end plates 8 to each other. On the surface of the end plate 8 on the side of the module laminate 2, a film F having electrical insulation is provided, and the film F insulates between the end plate 8 and the conductive plate 5.

[0049] Next, the configuration of the power storage module 4 will be described in detail. Figure 4 is a schematic cross-sectional view showing Figure 3 the internal configuration of the power storage module 4 shown. As Figure 4 shown, the power storage module 4 includes an electrode laminate (mono-stack) 11 and a resin-made sealing body 30 that seals the electrode laminate 11. The power storage module 4 is formed, for example, in a rectangular parallelepiped shape.

[0050] The electrode stack 11 includes a plurality of electrodes stacked along a stacking direction D with a separator 13 interposed therebetween, and current collectors (metal plates 11A, 11B) located at stacking ends of the electrode stack 11. The plurality of electrodes include a positive terminal electrode 40, a negative terminal electrode 42, and a plurality of bipolar electrodes 10 stacked between the positive terminal electrode 40 and the negative terminal electrode 42. The stack of the plurality of bipolar electrodes 10 is disposed between the positive terminal electrode 40 and the negative terminal electrode 42.

[0051] The bipolar electrode 10 includes a current collector 15 including one surface 15a and another surface 15b disposed on the opposite side of the one surface 15a, a positive electrode composite material layer 14 disposed on the one surface 15a as a positive electrode, and a negative electrode composite material layer 18 disposed on the other surface 15b as a negative electrode. The one surface 15a is a surface facing one side of the stacking direction D, for example, facing downward in the direction of gravity. The other surface 15b is a surface facing the other side of the stacking direction D, for example, facing upward in the direction of gravity.

[0052] In addition, although Figure 4 Although not shown in the figure, the collector 15 of the bipolar electrode 10 is as shown in FIG. Figure 1 and Figure 2 As shown and described above, the positive electrode substrate 12 and the negative electrode substrate 16 are included. In addition, the negative electrode composite material layer 18 has grooves 19 formed therein, and an elastic layer 20 is provided between the negative electrode substrate 16 and the negative electrode composite material layer 18 .

[0053] In the electrode stack 11, the positive electrode composite material layer 14 of one bipolar electrode 10 faces the negative electrode composite material layer 18 of another bipolar electrode 10 adjacent in one direction of the stacking direction D via the separator 13. In the electrode stack 11, the negative electrode composite material layer 18 of one bipolar electrode 10 faces the positive electrode composite material layer 14 of another bipolar electrode 10 adjacent in the other direction of the stacking direction D via the separator 13.

[0054] The positive terminal electrode 40 includes a current collector 15 and a negative electrode composite material layer 18 provided on the other surface 15b of the current collector 15. The positive terminal electrode 40 is arranged on one end side of the stacking direction D so that the other surface 15b faces the center side of the stacking direction D in the electrode stack 11. A metal plate 11A is further stacked on one surface 15a of the current collector 15 of the positive terminal electrode 40, and is electrically connected to the conductive plate 5 on the side adjacent to the power storage module 4 via the metal plate 11A. The negative electrode composite material layer 18 provided on the other surface 15b of the current collector 15 of the positive terminal electrode 40 faces the positive electrode composite material layer 14 of the bipolar electrode 10 at one end of the stacking direction D via the separator 13.

[0055] The negative terminal electrode 42 has a current collector 15 and a positive composite material layer 14 provided on one surface 15a of the current collector 15. The negative terminal electrode 42 is arranged on the other end side in the stacking direction D such that the one surface 15a faces the central side in the stacking direction D of the electrode laminate 11. A metal plate 11B is further stacked on the other surface 15b of the current collector 15 of the negative terminal electrode 42, and is electrically connected to the other conductive plate 5 adjacent to the storage battery module 4 via the metal plate 11B. The positive composite material layer 14 provided on the one surface 15a of the current collector 15 of the negative terminal electrode 42 faces the negative composite material layer 18 of the bipolar electrode 10 at the other end in the stacking direction D with a spacer 13 therebetween.

[0056] In the present embodiment, the formation region of the negative composite material layer 18 in the other surface 15b of the current collector 15 is one lap larger than the formation region of the positive composite material layer 14 in the one surface 15a of the current collector 15. The electrode laminate 11 has a plurality of stacked current collectors 15, metal plates 11A, and metal plates 11B.

[0057] The spacer 13 is a component for preventing short circuits between the current collectors 15, is made of an organic material, and is formed in a sheet shape, for example. Examples of the spacer 13 include a porous film made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP), a woven fabric or non-woven fabric made of polypropylene, methyl cellulose, or the like. The spacer 13 can also be strengthened with a vinylidene fluoride resin compound. In addition, the spacer 13 is not limited to a sheet shape, and a bag shape can also be used.

[0058] The metal plates 11A and 11B are components substantially the same as the current collector 15. The metal plates 11A and 11B are uncoated electrodes with no active material layer coated on both surfaces. Through the metal plate 11A, the positive terminal electrode 40 is in a state of being arranged between the metal plate 11A and the bipolar electrode 10 along the stacking direction D. The current collector 15 of the positive terminal electrode 40 and the metal plate 11A are electrically connected by direct contact without any component intervening therebetween. Through the metal plate 11B, the negative terminal electrode 42 is in a state of being arranged between the metal plate 11B and the bipolar electrode 10 along the stacking direction D. The current collector 15 of the negative terminal electrode 42 and the metal plate 11B are electrically connected by direct contact without any component intervening therebetween.

[0059] In the electrode laminate 11, the central region of the electrode laminate 11 (the region where the active material layer is arranged in the bipolar electrode 10, the positive terminal electrode 40, and the negative terminal electrode 42) bulges in the stacking direction D more than the surrounding region. Therefore, the metal plates 11A and 11B are bent in a direction in which the central regions of the metal plates 11A and 11B are separated from each other. The central regions of the lower side surface of the metal plate 11A and the upper side surface of the metal plate 11B are in contact with the conductive plate 5.

[0060] The sealing body 30 is integrally formed, for example, of an insulating resin into a rectangular cylindrical shape. The sealing body 30 is formed, for example, into a rectangular cylindrical shape having a pair of short side portions 30a and a pair of long side portions (not shown). The sealing body 30 is provided to surround the side surface 11a of the electrode laminate 11. The sealing body 30 holds the edge portion 15c of the current collector 15 on the side surface 11a.

[0061] The sealing body 30 has a plurality of frame-shaped first sealing portions 31 (resin portions) respectively provided at the edge portions of the metal plates included in the electrode laminate 11 (that is, the edge portion 15c of the current collector 15 and the edge portions 11c of the metal plates 11A and 11B), and a second sealing portion 32 that surrounds the first sealing portions 31 from the outside along the side surface 11a and is respectively joined to the first sealing portions 31. The first sealing portions 31 and the second sealing portion 32 are, for example, insulating resins, and examples of the constituent materials of the resin include polypropylene (PP), polyphenylene sulfide (PPS), modified polyphenylene ether (modified PPE), and the like.

[0062] The first sealing portions 31 are continuously provided over the entire circumference of the edge portion 15c of the current collector 15 and the edge portions 11c of the metal plates 11A and 11B, and have a rectangular frame shape when viewed from the stacking direction D. The first sealing portions 31 are hermetically joined to the current collector 15 and the first sealing portions 31 are hermetically joined to the metal plates 11A and 11B, respectively. When viewed from the stacking direction D, the first sealing portions 31 extend to the outside of the edge portion 15c of the current collector 15 or the edge portion 11c of the metal plates 11A and 11B. The first sealing portions 31 include an outer portion 31a that protrudes to the outside of the edge of the current collector 15 or the metal plates 11A and 11B, and an inner portion 31b that is located inside the edge of the current collector 15 or the metal plates 11A and 11B. A fusion layer 33 is formed at the tip portion (outer edge portion) of the outer portion 31a of the first sealing portions 31.

[0063] In the present embodiment, the first sealing portions 31 are formed in a double-layer structure by folding a single film in half. The outer edge portion of the first sealing portions 31 embedded in the second sealing portion 32 is a folded-back portion (bent portion) of the film. The edge portions of the metal plates included in the electrode laminate 11 (that is, the edge portion 15c of the current collector 15 and the edge portions 11c of the metal plates 11A and 11B) are held from both sides in the stacking direction D by the inner portions 31b of the first layer film and the second layer film that constitute the first sealing portions 31. Specifically, the plurality of first sealing portions 31 are respectively joined to one surface 15a of the current collector 15 and the outer side surfaces of the metal plates 11A and 11B. In addition, the plurality of first sealing portions 31 may also be respectively joined to one surface 15a of the current collector 15 and the inner side surfaces of the metal plates 11A and 11B.

[0064] In addition, in the present embodiment, the first sealing portion 31 is formed of one film, but the present disclosure is not limited thereto, and it may also be formed of two films. That is, the first layer film and the second layer film may also be formed separately. In this case, the peripheral edge portions of the first layer film and the second layer film are joined together.

[0065] The second sealing portion 32 holds the outer peripheral portions of a plurality of first sealing portions 31. Specifically, the second sealing portion 32 integrates the outer peripheral portions of the plurality of first sealing portions 31 by fusing the overlapping portions of the plurality of first sealing portions 31 in the stacking direction using the fusion layer 33.

[0066] A plurality of internal spaces V are provided in the electrode laminate 11. Each internal space V is provided between adjacent metal plates. The internal space V is a space hermetically and liquid-tightly separated by the metal plate and the seal 30 between adjacent metal plates in the stacking direction D. For example, an electrolytic solution (not shown) is accommodated in the internal space V. The electrolytic solution contains, for example, a non-aqueous solvent and a supporting salt. Examples of the non-aqueous solvent include organic solvents such as carbonates, ethers, esters, nitriles, sulfones, and lactones. Examples of the supporting salt include lithium salts such as LiPF6. The electrolytic solution is impregnated in the spacer 13, the positive composite layer 14, and the negative composite layer 18.

[0067] In addition, on the bipolar battery 1, a liquid injection port (not shown) is provided in one short side portion 30a of the seal 30. The liquid injection port penetrates the seal 30 in the long side direction of the seal 30. The liquid injection port communicates with the internal space V and the external space. The position where the liquid injection port is provided in one short side portion 30a of the seal 30 varies according to the position of the corresponding internal space V in the stacking direction D (refer to Figure 4 ). The liquid injection ports are provided offset from each other in the short side direction of the seal 30 so that the liquid injection ports adjacent to each other in the stacking direction D (refer to Figure 4 ) do not overlap each other.

[0068] Next, the operation and effects of the bipolar battery 1 in the first embodiment will be described.

[0069] Here, a conventional bipolar battery will be described. Figure 9 FIG. is a schematic cross-sectional view showing the configuration of a conventional bipolar electrode 100. The conventional bipolar electrode 100 has composite material layers (a positive composite layer 114 and a negative composite layer 118) with different expansion and contraction behaviors during charge and discharge on both sides in the stacking direction D with the current collector 115 interposed therebetween. Specifically, during charging of the bipolar battery, the amount of expansion of the bipolar electrode 100 on the negative composite layer 118 side increases, while the bipolar electrode 100 on the positive composite layer 114 side contracts. In addition, the "amount of expansion" indicates the amount of elongation in the plane direction (a direction substantially orthogonal to the stacking direction D).

[0070] In the bipolar electrode 100, the positive composite material layer 114 and the negative composite material layer 118 are directly disposed on the current collector 115. Therefore, if a stress difference is generated due to the difference in the amount of expansion across the current collector 115, a stretching force acts on the current collector 115 corresponding to the expansion and contraction of the composite material layer, and warping (undulation) may occur in the bipolar electrode 100 during charge and discharge of the bipolar battery. In particular, when the composite material layer (the positive composite material layer 114 and the negative composite material layer 118) is thick, the displacement amount of the composite material layer becomes large, and thus it is conceivable that the warping caused by the pressure difference is particularly significant.

[0071] In contrast, the electrode 10 of the present embodiment includes: a positive electrode substrate 12 serving as the current collector 15; a positive composite material layer 14 formed on the positive electrode substrate 12; a negative electrode substrate 16 serving as the current collector 15; a negative composite material layer 18 formed on the negative electrode substrate 16 and divided into a plurality of regions 18A, with grooves 19 provided between adjacent regions 18A; and an elastic layer 20 formed between the negative electrode substrate 16 and the negative composite material layer 18 and having elasticity. In addition, the electrode 10 is laminated with the positive composite material layer 14, the positive electrode substrate 12, the negative electrode substrate 16, the elastic layer 20, and the negative composite material layer 18 in this order in the stacking direction D.

[0072] Figure 5 is Figure 1 an enlarged view of the portion shown by the circle A in Figure 6 and is an enlarged view corresponding to Figure 5 during charge and discharge. As Figure 5 shown, the bipolar electrode 10 of the present embodiment includes the elastic layer 20 between the negative electrode substrate 16 and the negative composite material layer 18. Thus, as Figure 6 shown, when the negative composite material layer 18 extends, the elastic layer 20 extends accordingly. Thereby, the influence of the extension of the negative composite material layer 18 can be suppressed from being transmitted to the negative electrode substrate 16, that is, the current collector 15.

[0073] In this way, by suppressing the influence of the extension of the negative composite material layer 18 from being transmitted to the current collector 15, warping (undulation) of the bipolar electrode 10 during charge and discharge of the bipolar battery 1 can be suppressed.

[0074] In addition, in the present embodiment, the thickness of the elastic layer 20 is formed to be 10 μm or less. In the bipolar electrode 10, if the thickness of the elastic layer 20 is thicker than 10 μm, the transfer of electrons between the negative electrode substrate 16 and the negative composite material layer 18 via the elastic layer 20 becomes difficult, and if the thickness of the elastic layer 20 is 10 μm or less, the transfer of electrons between the negative electrode substrate 16 and the negative composite material layer 18 via the elastic layer 20 becomes easy.

[0075] In addition, in the present embodiment, the elastic layer 20 contains a conductive additive and a polymer material. In this way, by making the elastic layer 20 contain a conductive additive and a polymer material, the transfer of electrons between the negative electrode substrate 16 and the negative electrode composite layer 18 via the elastic layer 20 becomes easier. As a result, the high-rate charge-discharge performance of the negative electrode can be improved, and as a result, the negative electrode capacity can be further increased.

[0076] In addition, the elastic layer 20 is formed such that the tensile shear adhesion strength is 15 MPa or more and 40 MPa or less, the peel adhesion strength is 3 N or more and 10 N or less, the elastic modulus is 700 MPa or more and 1200 MPa or less, the fracture strength is 15 MPa or more and 25 MPa or less, the elongation at break is 5% or more and 30% or less, and the electronic conductivity is 1 mS / cm or more. By interposing the elastic layer 20 formed in this way between the negative electrode substrate 16 and the negative electrode composite layer 18, the elongation rate of the negative electrode composite layer 18 in the planar direction can be appropriately absorbed.

[0077] In addition, in the present embodiment, as described above, a groove 19 is provided on the upper surface in the stacking direction D of the negative electrode composite layer 18 (see Figure 1 and Figure 2 ). The purpose of the groove 19 in the present embodiment is to reduce the amount of expansion of the negative electrode composite layer 18. Therefore, for example, compared with the groove for injecting liquid described in the above Patent Document 1, more grooves are required. Thus, the shape, number, size, etc. of the grooves are different from those of the grooves described in Patent Document 1, for example. That is, by increasing the area of the groove 19, the area of each region 18A in the negative electrode composite layer 18 can be further reduced, so that the amount of expansion in each region 18A can be further reduced.

[0078] In addition, in the present embodiment, the negative electrode composite layer 18 contains 10% or less of silicon (Si) relative to the graphite-based negative electrode active material. As a result of research by the inventors of the present application, in the negative electrode composite layer 18 containing 10% or less of silicon relative to the graphite-based negative electrode active material, the expansion rate in the planar direction during charging of the bipolar battery 1 is about 2.5%. Therefore, when the rectangular coating area of the negative electrode composite layer 18 on the negative electrode substrate 16 is 10 mm on one side, the groove width W1 needs to be about 5% of 10 mm. By reducing the above coating area, the groove width W1 can be reduced, but if the coating area becomes too small, the processing difficulty of the groove 19 increases, and the negative electrode composite layer 18 is divided more finely. As a result, unevenness of the battery reaction may occur due to an increase in the edges at the unopposed portions between the negative electrode composite layer 18 and the positive electrode composite layer 14. Therefore, the size of the groove 19 is set in consideration of the contradictions and effects.

[0079] In the present embodiment, the thickness of the negative composite material layer 18 is formed to be 100 μm or more and 200 μm or less. In addition, the horizontal width W4 and the vertical width W5 of the outer shape dimensions of the negative composite material layer 18 are formed to be 1000 mm or more. In addition, the capacity ratio of the negative composite material layer 18 with respect to the positive composite material layer 14 is set in the range of 1.05 or more and 1.2 or less. In addition, the negative composite material layer 18 is divided into 48 regions 18A. As an example, for the grooves 19, that is, the longitudinal grooves 19A and the transverse grooves 19B, it is preferable that the groove width W1 is 50 μm or more and 5 mm or less, and more preferably 50 μm or more and 1 mm or less. As an example, for the longitudinal grooves 19A, it is preferable that the interval W2 between adjacent grooves is 1 mm or more and 100 mm or less, and more preferably 1 mm or more and 20 mm or less.

[0080] Similarly, as an example, for the transverse grooves 19B, it is preferable that the interval W3 between adjacent grooves is 1 mm or more and 100 mm or less, and more preferably 1 mm or more and 20 mm or less. In addition, the ratio (W1 / W2, W1 / W3) of the groove width W1 to the intervals W2 and W3 between adjacent grooves is preferably 0.05. By setting the grooves 19 in this way, it is more preferable in terms of further reducing the expansion amount of the negative composite material layer 18, workability, and suppressing the unevenness of the battery reaction.

[0081] In addition, as an example, the grooves 19 are equally provided in the negative composite material layer 18. By equally providing the grooves 19 in this way, the electrolyte is likely to be evenly distributed when injecting the electrolyte, so it is preferable in terms of liquid injection property.

[0082] In addition, in the present embodiment, the grooves 19 are not provided in the positive composite material layer 14. By not providing the grooves 19 in the positive composite material layer 14, the expansion amount is not suppressed in the positive composite material layer 14, so the expansion and contraction difference between the positive composite material layer 14 and the negative composite material layer 18 during charge and discharge can be suppressed, and thus warping of the bipolar electrode 10 can be suppressed.

[0083] (Second Embodiment) Hereinafter, with reference to the drawings, the bipolar electrode 10-2 according to the second embodiment of the present disclosure will be described. In addition, for the components of the bipolar electrode 10-2 in the second embodiment that are the same as those of the bipolar electrode 10 in the above-described first embodiment, the same reference numerals are used and the description is omitted, and only the different parts will be described in detail. In the bipolar electrode 10-2 of the second embodiment, the configuration of the negative composite material layer 18-2 is different from the configuration of the negative composite material layer 18 in the above-described first embodiment. Figure 7 It is a top view of observing the negative composite material layer 18-2 of the bipolar electrode 10-2 according to the second embodiment from the upper side in the stacking direction.

[0084] In the negative electrode composite material layer 18 of the first embodiment described above, the grooves 19 are provided evenly. In contrast, in the negative electrode composite material layer 18-2 of the second embodiment, as Figure 7 shown, compared to the outer region of the negative electrode composite material layer 18-2, more grooves 19 are provided in the central region. That is, in the plurality of regions 18A divided in the negative electrode composite material layer 18-2, the regions 18A located in the central region are formed smaller than the outer region of the negative electrode composite material layer 18-2.

[0085] The grooves 19 are preferably provided evenly in terms of liquid injection property. However, by providing more grooves 19 in the central region than in the outer region of the negative electrode composite material layer 18-2 as in this embodiment, the amount of swelling in the central region of the negative electrode composite material layer 18-2 can be further suppressed, and thus it is preferable in terms of suppressing warping during charge and discharge.

[0086] In addition, the negative electrode composite material layer 18-2 of the second embodiment is formed as Figure 7 shown, such that the number of grooves 19 is different between the outer region and the inner region of the negative electrode composite material layer 18-2, but the present disclosure is not limited thereto. For example, the number of grooves 19 may increase toward the inner side. Additionally, it may be that for at least one of the longitudinal grooves 19A and the transverse grooves 19B, more grooves 19 are provided in the central region than in the outer region.

[0087] In addition, the dimensions of the bipolar electrodes 10, 10-2 in the bipolar battery 1 according to the embodiment of the present disclosure are not particularly limited.

[0088] In addition, the configuration of the present disclosure is not limited to the above embodiments, and the configuration can be appropriately changed as long as the problems can be solved.

[0089] Hereinafter, examples and comparative examples are shown to describe the present disclosure more specifically. In addition, the present disclosure is not limited by these examples.

[0090] <Manufacture of Negative Electrode>[ Here, the negative electrode is an electrode having a negative electrode substrate 16 and a negative electrode composite material layer 18.

[0091] (Comparative Example 1)[ First, the negative electrode active material (artificial zinc), silicon active material, adhesive (styrene-butadiene rubber: SBR), thickener (carboxymethyl cellulose: CMC), and conductive additive (carbon nanotube: CNT) are mixed in a weight ratio of 92.95:5:1:1:0.05%, and after adding distilled water, the materials are thoroughly kneaded using a kneader to obtain a negative electrode paste. The negative electrode paste is coated on a copper foil serving as a current collector (negative electrode substrate 16) using a spatula and dried in an environment of 100 °C for 15 minutes to completely evaporate the water, thereby producing a negative electrode composite layer 18. At this time, the loading amount of the dried negative electrode composite layer 18 is adjusted to 26 mg / cm 2 . The produced negative electrode is subjected to biaxial roll pressing to make the density 1.2 g / cc to 1.4 g / cc, thereby obtaining a negative electrode.

[0092] (Comparative Example 2) Prepare a perforated negative electrode substrate 16 obtained by perforating a copper foil serving as a current collector (negative electrode substrate 16) at intervals of 20 μm to 30 μm. The aperture ratio per unit area is about 10%. As the perforating method, laser processing is representative, but various means such as stamping using a needle-shaped die can be used. As Comparative Example 2, laser processing was used. In addition, the negative electrode composite layer 18 was produced in the same manner as in Comparative Example 1 to obtain a negative electrode.

[0093] (Comparative Example 3) Laser processing is performed on the negative electrode composite layer 18 of the negative electrode produced in Comparative Example 1 to form a groove 19. As the processing method, laser processing is representative, but methods such as a mask during coating and cutting using a probe can also be selected. The groove width W1 is made 500 μm, and the intervals W2 and W3 between adjacent grooves are made 10 mm for the processing.

[0094] (Example) Laser processing is performed on the negative electrode composite layer 18 of the negative electrode produced in Comparative Example 2 to form a groove 19. The groove width W1 is made 500 μm, and the intervals W2 and W3 between adjacent grooves are made 10 mm for the processing.

[0095] (Manufacture of Positive Electrode) Here, the positive electrode is an electrode having a positive electrode substrate 12 and a positive electrode composite layer 14.

[0096] Use LiNi as a transition metal oxide 0.6 Mn 0.2 Co 0.2 O 2As the positive electrode active material. The positive electrode active material, a conductive assistant (acetylene black: AB), and an adhesive (polyvinylidene fluoride: PVdF) are mixed in a weight ratio of 95:2.5:2.5%, and N-methylpyrrolidone: NMP is added as a solvent. A kneader is used to fully disperse the particles to obtain a positive electrode paste. The positive electrode paste is applied to an aluminum foil as a current collector (positive electrode substrate 12) using a doctor blade, and dried at 80°C for 15 minutes or more to produce a positive electrode composite layer 14. At this time, the loading amount of the dried positive electrode composite layer 14 is adjusted to 38 mg / cm 2 . The produced positive electrode is subjected to biaxial roll pressing to make the density 3.2 g / cc to obtain a positive electrode.

[0097] <Configuration of bipolar electrode> As a lithium-ion battery according to an embodiment of the present disclosure, it includes a bipolar electrode 10 having a bipolar structure in which a positive electrode composite layer 14 and a negative electrode composite layer 18 are arranged with a current collector 15 interposed therebetween. In the case of forming a bipolar structure, the positive electrode and the negative electrode can be separately produced and finally bonded together. Alternatively, a current collector 15 (current collecting foil) formed by bonding a positive electrode substrate 12 (aluminum foil) and a negative electrode substrate 16 (copper foil) and a clad current collecting foil or the like can be prepared in advance, and the positive electrode composite layer 14 and the negative electrode composite layer 18 are respectively applied to the current collecting foil to manufacture. In this embodiment, as an example, the bipolar electrode 10 is manufactured by separately producing the positive electrode and the negative electrode and finally bonding them together.

[0098] <Manufacture of lithium-ion battery> A lithium-ion battery is manufactured using the bipolar electrode 10 manufactured by the above method. The bipolar electrodes 10 are stacked with the positive electrode composite layer 14 and the negative electrode composite layer 18 facing each other, and a spacer 13 is disposed between the bipolar electrodes 10 to electrically insulate them. As the spacer 13, a film based on polyethylene is used. The produced laminate is wrapped with a laminated film, and after injecting an electrolyte, it is sealed under a vacuum of -80 kPa. The electrolyte used is an electrolyte that uses a carbonate-based solvent obtained by mixing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of EC:DMC:EMC = 3:4:3, and dissolves 1.2 (g / mol) of lithium hexafluoride: LiPF6 as a lithium salt (electrolyte).

[0099] <Evaluation method> Figure 8 It is a schematic cross-sectional view for explaining the definition of warpage (T). After disassembling the charged lithium-ion battery, as Figure 8As shown, the bipolar electrode 10 is taken out and placed statically on a horizontal plane, and the height of the portion with the maximum thickness of the bipolar electrode 10 is measured, and this value is defined as the magnitude of the warpage (T).

[0100] The evaluation results of the warpage (T) are shown in Table 1.

[0101] [Table 1]

[0102] As can be seen from Table 1, in the examples satisfying the requirements that the groove 19 is provided in the negative composite material layer 18 and the elastic layer 20 is provided between the negative electrode substrate 16 and the negative composite material layer 18, the warpage can be reduced compared with Comparative Examples 1 to 3 that do not satisfy this requirement. From this, it can be known that in the examples, the warpage generated during charge and discharge is successfully suppressed.

Claims

1. A bipolar electrode comprising: Become the positive electrode substrate of the current collector; A positive electrode composite material layer formed on the positive electrode substrate; Become the negative electrode substrate of the current collector; a negative electrode composite material layer formed on the negative electrode substrate and divided into a plurality of regions, wherein a groove having a bottom portion of the negative electrode substrate is provided between adjacent regions; and The elastic layer is formed between the negative electrode substrate and the negative electrode composite material layer and has elasticity. The positive electrode composite material layer, the positive electrode substrate, the negative electrode substrate, the elastic layer, and the negative electrode composite material layer are stacked in sequence.

2. The bipolar electrode according to claim 1, wherein: The elastic layer has a tensile shear bonding strength of 15 MPa to 40 MPa, a peel bonding strength of 3 N to 10 N, an elastic modulus of 700 MPa to 1200 MPa, a breaking strength of 15 MPa to 25 MPa, and a breaking elongation of 5% to 30%.

3. The bipolar electrode according to claim 1, wherein: The elastic layer has an electron conductivity of 1 mS / cm or more.

4. The bipolar electrode according to claim 1, wherein: The elastic layer contains a conductive auxiliary agent and a polymer material.

5. The bipolar electrode according to claim 1, wherein: The elastic layer has a thickness of 10 μm or less.

6. The bipolar electrode according to claim 1, wherein: The negative electrode composite material layer is rectangular when viewed from the stacking direction. In the negative electrode mixture layer, a plurality of grooves extend in directions substantially parallel to the short sides and the long sides of the negative electrode mixture layer when viewed in the stacking direction.

7. The bipolar electrode according to claim 1, wherein: The negative electrode composite material layer at least contains a negative electrode active material. The negative electrode active material contains less than 10% of silicon.

8. The bipolar electrode according to claim 1, wherein: The groove width of the groove is 50 μm or more and 5 mm or less.

9. The bipolar electrode according to claim 1, wherein: The interval between adjacent grooves is 1 mm or more and 100 mm or less.

10. The bipolar electrode according to claim 1, wherein: The ratio of the groove width of the groove to the interval between adjacent grooves is 0.

05.

11. The bipolar electrode according to claim 1, wherein: The outer diameter of the negative electrode composite material layer is greater than 1000 mm.

12. The bipolar electrode according to claim 1, wherein: The grooves are arranged more in the central area than in the outer area of ​​the negative electrode composite material layer.

13. The bipolar electrode according to claim 1, wherein: The grooves are evenly arranged in the negative electrode composite material layer.

14. The bipolar electrode according to claim 1, wherein: The groove is not provided in the positive electrode composite material layer.

15. A bipolar battery, A plurality of bipolar electrodes according to any one of claims 1 to 14 are stacked with a separator made of an organic material interposed therebetween, and an electrolyte solution is contained.

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