Bipolar electrode and bipolar type battery

Abstract

To achieve a bipolar electrode and a bipolar type battery that are capable of restraining occurrence of warping in an electrode during charging and discharging.SOLUTION: A bipolar electrode 10 includes a positive electrode substrate 12 serving as a current collector, a positive electrode composite layer 14 formed on the positive electrode substrate 12, a negative electrode substrate 16 serving as a current collector, a negative electrode composite layer 18 that is formed on the negative electrode substrate 16 and divided into a plurality of regions 18C and has a groove 18A having the negative electrode substrate 16 at the bottom portion thereof between adjacent regions 18C, and an elastic layer 20 that is formed between the negative electrode substrate 16 and the negative electrode composite layer 18 and has elasticity. In the electrode 10, the positive electrode composite layer 14, the positive electrode substrate 12, the negative electrode substrate 16, the elastic layer 20, and the negative electrode composite layer 18 are stacked in this order.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses that in an all-solid-state battery, by forming slit-shaped grooves on the electrode surface, the area of the portion involved in the electrode reaction on the electrode surface related to the electrode layer can be appropriately adjusted, and as a result, since the slit-shaped grooves serve as a buffer portion for the expansion and contraction of the electrode layer, the expansion of the electrode layer can be suppressed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The electrodes of a bipolar battery have composite layers on both sides sandwiching a current collector, and the behavior of expansion and contraction during charge and discharge is different, so there is a possibility that the electrodes may warp during charge and discharge. In the all-solid-state battery described in Patent Document 1, since all the constituent materials including the composite layer are solidified, the possibility of the electrodes warping is significantly lower compared to a liquid-based battery using an electrolytic solution.

[0005] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a bipolar electrode and a bipolar battery capable of suppressing warping during charge and discharge.

Means for Solving the Problems

[0006] The bipolar electrode according to the present invention described in claim 1 includes a positive electrode substrate serving as a current collector, a positive electrode composite layer formed on the positive electrode substrate, a negative electrode substrate serving as a current collector, and a negative electrode composite layer formed on the negative electrode substrate and divided into a plurality of regions, with grooves having bottoms on the negative electrode substrate provided between adjacent regions. It also includes an elastic layer formed between the negative electrode substrate and the negative electrode composite layer and having elasticity. The positive electrode composite layer, the positive electrode substrate, the negative electrode substrate, the elastic layer, and the negative electrode composite layer are laminated in this order.

[0007] The bipolar electrode according to the present invention described in claim 2 has, in the configuration described in claim 1, the elastic layer having a tensile shear adhesion strength of 15 MPa or more and 40 MPa or less, a peel adhesion strength of 3 N or more and 10 N or less, an elastic modulus of 700 MPa or more and 1200 MPa or less, a breaking strength of 15 MPa or more and 25 MPa or less, and an elongation at break of 5% or more and 30% or less.

[0008] The bipolar electrode according to the present invention described in claim 3 has, in the configuration described in claim 1 or claim 2, the elastic layer having an electronic conductivity of 1 mS / cm or more.

[0009] The bipolar electrode according to the present invention described in claim 4 has, in the configuration described in any one of claims 1 to 3, the elastic layer containing a conductive auxiliary agent and a polymer material.

[0010] The bipolar electrode according to the present invention described in claim 5 has, in the configuration described in any one of claims 1 to 4, the thickness of the elastic layer being 10 μm or less.

[0011] The bipolar electrode according to the present invention described in claim 6 has, in the configuration described in any one of claims 1 to 5, the negative electrode composite layer being rectangular when viewed from the lamination direction, and the grooves extending linearly in plurality along the surface of the negative electrode composite layer on the short side and the long side of the negative electrode composite layer, respectively.

[0012] The bipolar electrode according to the present invention as recited in claim 7, in the configuration recited in any one of claims 1 to 6, the negative electrode composite layer contains at least a negative electrode active material, and the negative electrode active material contains silicon (Si) within 10%.

[0013] The bipolar electrode according to the present invention as recited in claim 8, in the configuration recited in any one of claims 1 to 7, the groove width of the groove is 50 μm or more and 5 mm or less.

[0014] The bipolar electrode according to the present invention as recited in claim 9, in the configuration recited in any one of claims 1 to 8, the interval between adjacent grooves is 1 mm or more and 100 mm or less.

[0015] The bipolar electrode according to the present invention as recited in claim 10, in the configuration recited in any one of claims 1 to 9, the ratio of the groove width of the groove to the interval between adjacent grooves is 0.05.

[0016] The bipolar electrode according to the present invention as recited in claim 11, in the configuration recited in any one of claims 1 to 10, the outer diameter dimension of the negative electrode composite layer is 1000 mm or more.

[0017] The bipolar electrode according to the present invention as recited in claim 12, in the configuration recited in any one of claims 1 to 11, the grooves are provided more in the central region than in the outer region of the negative electrode composite layer.

[0018] The bipolar electrode according to the present invention as recited in claim 13, in the configuration recited in any one of claims 1 to 12, the grooves are provided evenly in the negative electrode composite layer.

[0019] The bipolar electrode according to the present invention as recited in claim 14, in the configuration recited in any one of claims 1 to 13, the grooves are not provided in the positive electrode composite layer.

[0020] The bipolar battery according to the present invention described in claim 15 is a bipolar battery in which a plurality of bipolar electrodes described in any one of claims 1 to 14 are laminated via a separator made of an organic material and includes an electrolytic solution.

Advantages of the Invention

[0021] The bipolar electrode and the bipolar battery according to the present invention can suppress warping during charge and discharge.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

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

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

[0025] The bipolar electrode 10 is formed in a substantially rectangular parallelepiped shape. Further, the bipolar electrode 10 includes a positive electrode substrate 12 serving as a current collector 15, a positive electrode composite layer 14 formed on the positive electrode substrate 12, a negative electrode substrate 16 serving as a current collector 15, a negative electrode composite 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 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 laminated in the order of the positive electrode composite layer 14, the positive electrode substrate 12, the negative electrode substrate 16, the elastic layer 20, and the negative electrode composite layer 18 from the lower side to the upper side of the paper surface of FIG. 1. In the present embodiment, the vertical direction of the paper surface of FIG. 1, that is, the direction in which the positive electrode composite layer 14, the positive electrode substrate 12, the negative electrode substrate 16, the elastic layer 20, and the negative electrode composite layer 18 are laminated is defined as the "lamination direction D".

[0027] The positive electrode substrate 12 is formed of a rectangular sheet-like metal foil as an example, and is specifically formed of an aluminum foil in the present embodiment. The positive electrode substrate 12 is a chemically inert electrical conductor for continuously passing an electric current through the positive electrode composite layer 14, for example, during discharge or charge of the bipolar type battery 1.

[0028] The positive electrode composite layer 14 is formed on the lower surface of the positive electrode substrate 12 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 is an uncoated area where the positive electrode composite layer 14 is not coated. The positive electrode composite layer 14 is a positive electrode active material layer formed by coating a positive electrode active material on the lower surface of the positive electrode substrate 12 in a substantially rectangular shape. Examples of the positive electrode active material constituting the positive electrode composite layer 14 include oxide active materials. Examples of the oxide active material include rock salt layer-type active materials such as LiCoO2, LiMnO2, LiNiO2, LiVO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and other rock salt layer-type active materials, spinel-type active materials such as LiMn2O4, Li(Ni 0.5 Mn 1.5 )O4 and other spinel-type active materials, olivine-type active materials such as LiFePO4, LiMnPO4, LiNiPO4, LiCuPO4. The positive electrode active material layer forming the positive electrode composite layer 14 may contain a conductive material and a binder in addition to the positive electrode active material.

[0029] The negative electrode substrate 16 is formed of a rectangular sheet-shaped metal foil as an example, and is specifically formed of a copper foil in the present embodiment. The negative electrode substrate 16 is a chemically inert electrical conductor for continuously passing an electric current through the negative electrode composite layer 18 during discharge or charging of the bipolar battery 1, for example. In the present embodiment, the negative electrode substrate 16 is provided with pores having a diameter φ1 of 5 μm or more and 20 μm or less by an etching process as an example. Note that the negative electrode substrate 16 may be provided with grooves having a width φ2 of 5 μm or more and 20 μm or less by an etching process instead of pores as an example.

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

[0031] In this embodiment, specifically, the negative electrode composite material layer 18 contains silicon (Si) within 10% with respect to the graphite-based negative electrode active material. Also, in this embodiment, the thickness of the negative electrode composite material layer 18 is formed to be 100 μm or more and 200 μm or less. Note that the positive electrode composite material layer 14 is formed with a thickness smaller 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 with respect to the positive electrode composite material layer 14 is in the range of 1.05 or more and 1.2 or less.

[0032] FIG. 2 is a plan view of the negative electrode composite material layer 18 of the bipolar electrode 10 in FIG. 1 as viewed from above in the stacking direction D. As shown in FIG. 2, 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 this embodiment, as an example, the negative electrode composite material layer 18 is divided into a total of 48 regions 18A arranged in 8 columns in the left-right direction of the drawing sheet and 6 rows in the up-down direction of the drawing sheet.

[0033] Also, 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 this embodiment, as shown in FIG. 2, the negative electrode composite material layer 18 is formed in a substantially rectangular shape as viewed from above in the stacking direction D, and the grooves 19 extend linearly 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 vertical grooves 19A extending in the up-down direction of the drawing sheet extend substantially parallel to the short side of the negative electrode composite material layer 18, and the horizontal grooves 19B extending in the left-right direction of the drawing sheet extend substantially parallel to the long side of the negative electrode composite material layer 18. Note that in this embodiment, the grooves 19 (vertical grooves 19A and horizontal grooves 19B) indicate portions where the negative electrode composite material layer 18 is not supported on the upper surface of the negative electrode substrate 16 in the stacking direction D. That is, the bottom of the groove 19 is constituted by the negative electrode substrate 16.

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

[0035] The longitudinal grooves 19A and the transverse grooves 19B preferably have a groove width W1 of 50 μm or more and 5 mm or less, more preferably 50 μm or more and 1 mm or less, as an example. Note that 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. Also, as an example, for the longitudinal grooves 19A, the interval W2 between adjacent grooves is preferably 1 mm or more and 100 mm or less, more preferably 1 mm or more and 20 mm or less. Similarly, for the transverse grooves 19B, as an example, the interval W3 between adjacent grooves is preferably 1 mm or more and 100 mm or less, more preferably 1 mm or more and 20 mm or less. Note that the intervals W2 and W3 between adjacent grooves are the same as the width of the region 18A interposed between the adjacent grooves.

[0036] Also, 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 this 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 be different. The groove width W1 is set according to the values of the intervals W2 and W3 between adjacent grooves.

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

[0038] Also, the lateral width W4 and the longitudinal width W5, which are the outer dimensions of the negative electrode composite material layer 18, may be 1000 mm or more.

[0039] In this embodiment, the grooves 19 are provided in the negative electrode composite material layer 18 but not in the positive electrode composite material layer 14.

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

[0041] In this embodiment, the elastic layer 20 has elasticity and adhesiveness as an example. Specifically, the elastic layer 20 has, as an example, a tensile shear adhesion strength of 15 MPa or more and 40 MPa or less, a peel adhesion strength of 3 N or more and 10 N or less, an elastic modulus of 700 MPa or more and 1200 MPa or less, a breaking strength of 15 MPa or more and 25 MPa or less, an elongation at break of 5% or more and 30% or less, and an electronic conductivity of 1 mS / cm or more. For 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 set, originally, the negative electrode composite layer and the negative electrode foil cannot expand together. However, by inserting such an elastic layer between the negative electrode composite and the negative electrode foil, they can follow each other while sliding. In the case of an all-solid-state battery, since the negative electrode current collector foil and the negative electrode composite expand and contract together, such an elastic layer is unnecessary.

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

[0043] FIG. 3 is a schematic cross-sectional view showing the configuration of the bipolar battery 1 according to one embodiment. The bipolar battery 1 shown in FIG. 1 is a device used for batteries of various vehicles such as forklifts, hybrid vehicles, and electric vehicles. The bipolar battery 1 is a secondary battery such as a nickel-metal hydride secondary battery or a lithium-ion secondary battery. In this embodiment, the case where the bipolar battery 1 is a liquid-based lithium-ion secondary battery is exemplified. The bipolar battery 1 includes a module laminate 2 and a restraint member 3 that applies a restraint 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 (here, three) of power storage modules 4 and a plurality (here, four) of conductive plates 5 are alternately stacked such that the conductive plates 5 are positioned on both sides of the power storage module 4. The direction in which the power storage modules 4 are stacked is the “stacking direction D”. The power storage module 4 is a bipolar battery and has a rectangular shape when viewed from the stacking direction D.

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

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

[0047] Inside the conductive plate 5, a plurality of flow paths 5a for allowing a refrigerant such as air to flow are provided. The flow paths 5a extend along directions that intersect (are orthogonal to) the stacking direction D and the drawing-out directions of the negative terminal 6 and the positive terminal 7, respectively. The conductive plate 5 functions not only as a connection member for electrically connecting the power storage modules 4 to each other, but also as a heat dissipation plate for dissipating the heat generated in the power storage module 4 by allowing the refrigerant to flow through these flow paths 5a.

[0048] The restraining member 3 includes a pair of end plates 8 that sandwich the module laminate 2 in the stacking 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. FIG. 4 is a schematic cross-sectional view showing the internal configuration of the power storage module 4 shown in FIG. 3. As shown in FIG. 4, the power storage module 4 includes an electrode laminate (cell stack) 11 and a resin sealing body 30 that seals the electrode laminate 11. The power storage module 4 is formed in a rectangular parallelepiped shape, for example.

[0050] The electrode laminate 11 includes a plurality of electrodes laminated along the stacking direction D with a separator 13 interposed therebetween, and current collectors (metal plates 11A, 11B) located at the laminated ends of the electrode laminate 11. The plurality of electrodes include a positive terminal electrode 40, a negative terminal electrode 42, and a plurality of bipolar electrodes 10 laminated between the positive terminal electrode 40 and the negative terminal electrode 42. The laminate of the plurality of bipolar electrodes 10 is provided 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 the other surface 15b provided on the opposite side of the one surface 15a, a positive electrode composite layer 14 as a positive electrode provided on the one surface 15a, and a negative electrode composite layer 18 as a negative electrode provided on the other surface 15b. The one surface 15a is a surface facing one direction of the stacking direction D, for example, facing downward in the direction of gravity. The other surface 15b is a surface facing the other direction of the stacking direction D, for example, facing upward in the direction of gravity.

[0052] Although not shown in FIG. 4, the current collector 15 of the bipolar electrode 10 includes a positive electrode substrate 12 and a negative electrode substrate 16 as described above with reference to FIGS. 1 and 2. Further, a groove 19 is formed in the negative electrode composite layer 18, and an elastic layer 20 is provided between the negative electrode substrate 16 and the negative electrode composite layer 18.

[0053] In the electrode laminate 11, the positive electrode composite layer 14 of one bipolar electrode 10 faces the negative electrode composite layer 18 of another bipolar electrode 10 adjacent to one side in the stacking direction D with the separator 13 interposed therebetween. In the electrode laminate 11, the negative electrode composite layer 18 of one bipolar electrode 10 faces the positive electrode composite layer 14 of another bipolar electrode 10 adjacent to the other side in the stacking direction D with the separator 13 interposed therebetween.

[0054] The positive terminal electrode 40 includes a current collector 15 and a negative electrode composite layer 18 provided on the other surface 15b of the current collector 15. The positive terminal electrode 40 is disposed on one end side in the stacking direction D such that the other surface 15b faces the central side in the stacking direction D in the electrode laminate 11. A metal plate 11A is further laminated on the one surface 15a of the current collector 15 of the positive terminal electrode 40, and is electrically connected to one conductive plate 5 adjacent to the power storage module 4 through the metal plate 11A. The negative electrode composite layer 18 provided on the other surface 15b of the current collector 15 of the positive terminal electrode 40 faces the positive electrode composite layer 14 of the bipolar electrode 10 at one end in the stacking direction D with the separator 13 interposed therebetween.

[0055] The negative terminal electrode 42 has a current collector 15 and a positive electrode composite layer 14 provided on one surface 15a of the current collector 15. The negative terminal electrode 42 is disposed on the other end side in the stacking direction D such that one surface 15a faces the center side in the stacking direction D in 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 power storage module 4 through this metal plate 11B. The positive electrode composite layer 14 provided on one surface 15a of the current collector 15 of the negative terminal electrode 42 faces the negative electrode composite layer 18 of the bipolar electrode 10 at the other end in the stacking direction D through the separator 13.

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

[0057] The separator 13 is a member for preventing short circuit between current collectors 15, is made of an organic material, and is formed in a sheet shape, for example. Examples of the separator 13 include a porous film made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP), a woven fabric or a non-woven fabric made of polypropylene, methyl cellulose, or the like. The separator 13 may be reinforced with a vinylidene fluoride resin compound. Note that the separator 13 is not limited to a sheet shape, and a bag-shaped one may be used.

[0058] The metal plates 11A and 11B are substantially the same members as the current collector 15. The metal plates 11A and 11B are uncoated electrodes with no active material layer coated on both sides. By the metal plate 11A, the positive terminal electrode 40 is disposed between the metal plate 11A and the bipolar electrode 10 along the stacking direction D. The metal plate 11A and the current collector 15 of the positive terminal electrode 40 are electrically connected by directly contacting each other without any intervening member therebetween. By the metal plate 11B, the negative terminal electrode 42 is disposed between the metal plate 11B and the bipolar electrode 10 along the stacking direction D. The metal plate 11B and the current collector 15 of the negative terminal electrode 42 are electrically connected by directly contacting each other without any intervening member therebetween.

[0059] In the electrode laminate 11, the central region of the electrode laminate 11 (the region where the active material layer is disposed in the bipolar electrode 10, the positive terminal electrode 40, and the negative terminal electrode 42) bulges in the stacking direction D compared to the surrounding region. For this reason, the metal plates 11A and 11B bend 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 surface of the metal plate 11A and the upper surface of the metal plate 11B contact the conductive plate 5.

[0060] The sealing body 30 is formed, for example, of an insulating resin into a rectangular cylindrical shape as a whole. 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 so as 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 at the side surface 11a.

[0061] The sealing body 30 includes a plurality of frame-shaped first sealing portions 31 (resin portions) provided at the edges of the metal plates included in the electrode laminate 11 (i.e., the edges 15c of the current collector 15 and the edges 11c of the metal plates 11A and 11B), and a second sealing portion 32 that surrounds the first sealing portion 31 from the outside along the side surface 11a and is coupled to each of the first sealing portions 31. The first sealing portion 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 portion 31 is continuously provided over the entire circumference of the edge 15c of the current collector 15 and the edges 11c of the metal plates 11A and 11B, and forms a rectangular frame shape when viewed in the stacking direction D. The first sealing portion 31 and the current collector 15, and the first sealing portion 31 and the metal plates 11A and 11B are hermetically joined to each other. The first sealing portion 31 extends outward beyond the edge 15c of the current collector 15 or the edges 11c of the metal plates 11A and 11B when viewed in the stacking direction D. The first sealing portion 31 includes an outer portion 31a that protrudes outward beyond the edge of the current collector 15 or the metal plates 11A and 11B, and an inner portion 31b that is located inward of the edge of the current collector 15 or the metal plates 11A and 11B. A welding layer 33 is formed at the tip (outer edge portion) of the outer portion 31a of the first sealing portion 31.

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

[0064] In addition, in the present embodiment, the first sealing portion 31 is constituted by a single film, but the present invention is not limited to this, and it may be constituted by two films. That is, the first-layer film and the second-layer film may 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 the plurality of first sealing portions 31. Specifically, the second sealing portion 32 welds the overlapping portions of the plurality of first sealing portions 31 in the stacking direction by a welding layer 33, thereby integrating the outer peripheral portions of the plurality of first sealing portions 31.

[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 partitioned by the metal plate and the sealing body 30 between adjacent metal plates in the stacking direction D. For example, an electrolytic solution (not shown) is accommodated in this 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 into the separator 13, the positive electrode composite layer 14, and the negative electrode composite layer 18.

[0067] In addition, a liquid injection port (not shown) is provided in one short side portion 30a of the sealing body 30 of the bipolar battery 1. The liquid injection port penetrates the sealing body 30 in the long side direction of the sealing body 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 sealing body 30 varies depending on the position in the stacking direction D (see FIG. 4) of the corresponding internal space V. The liquid injection ports are provided offset in the short side direction of the sealing body 30 so that the liquid injection ports adjacent to each other in the stacking direction D (see FIG. 4) do not overlap.

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

[0070] In the bipolar electrode 100, since the positive electrode composite layer 114 and the negative electrode composite layer 118 are directly disposed on the current collector 115, when a stress difference due to the difference in expansion amount across the current collector 115 occurs, a force that stretches the current collector 115 in accordance with the expansion and contraction of the composite layer acts, and there was a possibility that the bipolar electrode 100 warps during charge and discharge of the bipolar battery. In particular, when the composite layer (the positive electrode composite layer 114 and the negative electrode composite layer 118) is thick, since the displacement amount of the composite layer becomes large, it is assumed that the warping due to the pressure difference becomes particularly prominent.

[0071] On the other hand, the electrode 10 of the present embodiment includes a positive electrode base material 12 serving as a current collector 15, a positive electrode composite layer 14 formed on the positive electrode base material 12, a negative electrode base material 16 serving as a current collector 15, a negative electrode composite layer 18 formed on the negative electrode base material 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 base material 16 and the negative electrode composite layer 18 and having elasticity. Further, the electrode 10 is laminated in the stacking direction D in the order of the positive electrode composite layer 14, the positive electrode base material 12, the negative electrode base material 16, the elastic layer 20, and the negative electrode composite layer 18.

[0072] FIG. 5 is an enlarged view of the portion shown by circle A in FIG. 1, and FIG. 6 is an enlarged view corresponding to FIG. 5 during charge and discharge. As shown in FIG. 5, the bipolar electrode 10 of the present embodiment includes an elastic layer 20 between the negative electrode substrate 16 and the negative electrode composite material layer 18. Therefore, as shown in FIG. 6, when the negative electrode composite material layer 18 is stretched, the elastic layer 20 is stretched in accordance with the stretching of the negative electrode composite material layer 18. Thereby, it is possible to suppress the influence of the stretching of the negative electrode composite material layer 18 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 stretching of the negative electrode composite material layer 18 from being transmitted to the current collector 15, it is possible to suppress the occurrence of warping in the bipolar electrode 10 during charge and discharge of the bipolar battery 1.

[0074] 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 greater than 10 μm, it becomes difficult for electrons to be transferred between the negative electrode substrate 16 and the negative electrode composite material layer 18 through the elastic layer 20. If the thickness of the elastic layer 20 is 10 μm or less, it becomes easier for electrons to be transferred between the negative electrode substrate 16 and the negative electrode composite material layer 18 through the elastic layer 20.

[0075] Further, in the present embodiment, the elastic layer 20 contains a conductive assistant and a polymer material. By containing the conductive assistant and the polymer material in the elastic layer 20 in this way, it becomes easier for electrons to be transferred between the negative electrode substrate 16 and the negative electrode composite material layer 18 through the elastic layer 20. Thereby, the high-rate charge and discharge performance of the negative electrode can be enhanced, and as a result, the negative electrode capacity can be further increased.

[0076] Further, the elastic layer 20 is formed such that its tensile shear adhesion strength is 15 MPa or more and 40 MPa or less, its peel adhesion strength is 3 N or more and 10 N or less, its elastic modulus is 700 MPa or more and 1200 MPa or less, its breaking strength is 15 MPa or more and 25 MPa or less, its elongation at break is 5% or more and 30% or less, and its electronic conductivity is 1 mS / cm or more. By interposing the thus formed elastic layer 20 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 preferably absorbed.

[0077] Also, in the present embodiment, as described above, the groove 19 is provided on the upper surface of the negative electrode composite layer 18 in the stacking direction D (see FIGS. 1 and 2). Since the groove 19 of the present embodiment is intended to reduce the expansion amount of the negative electrode composite layer 18, more grooves are required as compared with, for example, the grooves for injecting electrolyte described in Patent Document 1 above. Therefore, for example, the shape, number, size, etc. of the grooves are different from those of the grooves described in Patent Document 1. 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 made smaller, so that the expansion amount in each region 18A can be made smaller.

[0078] Also, in the present embodiment, the negative electrode composite layer 18 contains silicon (Si) within 10% with respect to the graphite-based negative electrode active material. As a result of investigations by the inventors of the present application, in the negative electrode composite layer 18 containing silicon within 10% with respect to the graphite-based negative electrode active material, the expansion rate in the planar direction during charging of the bipolar battery 1 was about 2.5%. From this, 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 is required to be about 5% of 10 mm. By reducing the coating area, it is possible to reduce the groove width W1. However, if the coating area becomes too small, the processing difficulty of the groove 19 increases, and the negative electrode composite layer 18 is finely divided, resulting in an increase in the edges in the unopposed portion between the negative electrode composite layer 18 and the positive electrode composite layer 14, raising concerns about unevenness in the battery reaction. Therefore, the dimensions of the groove 19 are set in consideration of the trade-off and effects.

[0079] In this embodiment, the thickness of the negative electrode composite material layer 18 is formed to be 100 μm or more and 200 μm or less. Further, the lateral width W4 and the longitudinal width W5, which are the outer dimensions of the negative electrode composite material layer 18, are formed to be 1000 mm or more. Further, the capacity ratio of the negative electrode composite material layer 18 to the positive electrode composite material layer 14 is in the range of 1.05 or more and 1.2 or less. Further, the negative electrode composite material layer 18 is divided into 48 regions 18A. Further, for the groove 19, that is, the vertical groove 19A and the horizontal groove 19B, as an example, 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. Further, for the vertical groove 19A, as an example, 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, for the horizontal groove 19B, as an example, 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. Further, the ratio (W1 / W2, W1 / W3) of the groove width W1 to the intervals W2, W3 between adjacent grooves is preferably 0.05. Thus, by setting the groove 19, it is more preferable in terms of reducing the amount of expansion in the negative electrode composite material layer 18, workability, and suppressing unevenness in the battery reaction.

[0081] Further, the groove 19 is provided uniformly in the negative electrode composite material layer 18 as an example. Thus, by providing the groove 19 uniformly, the electrolyte is likely to spread evenly when the electrolyte is injected, which is preferable in terms of injectability.

[0082] Further, in this embodiment, the groove 19 is not provided in the positive electrode composite material layer 14. Since the groove 19 is not provided in the positive electrode composite material layer 14, the amount of expansion in the positive electrode composite material layer 14 is not suppressed, so the difference in expansion and contraction between the positive electrode composite material layer 14 and the negative electrode composite material layer 18 during charge and discharge can be suppressed, and 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 invention will be described. In the bipolar electrode 10-2 of the second embodiment, the same components as those of the bipolar electrode 10 of the first embodiment described above are denoted by the same reference numerals and the description thereof is omitted, and only the different parts will be described in detail. The bipolar electrode 10-2 of the second embodiment is different from the bipolar electrode 10 of the first embodiment in that the configuration of the negative electrode composite layer 18-2 is different from that of the negative electrode composite layer 18 of the first embodiment. FIG. 7 is a plan view of the negative electrode composite layer 18-2 of the bipolar electrode 10-2 according to the second embodiment as viewed from the upper side in the stacking direction.

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

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

[0086] Note that, as shown in FIG. 7, the negative electrode composite layer 18-2 of the second embodiment has different numbers of grooves 19 in the outer region and the inner region of the negative electrode composite layer 18-2, but the present invention is not limited thereto. For example, the number of grooves 19 may increase toward the inside. Also, more grooves 19 may be provided in at least one of the vertical grooves 19A and the horizontal grooves 19B in the central region than in the outer region.

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

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

[0089] Examples and comparative examples are shown below to more specifically explain the present invention. Note that the present invention 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 layer 18.

[0091] (Comparative Example 1)[ First, a negative electrode active material (artificial zinc), a silicon active material, a binder (styrene-butadiene rubber: SBR), a thickener (carboxymethyl cellulose: CMC), and a conductive assistant (carbon nanotube: CNT) were mixed at a weight ratio of 92.95:5:1:1:0.05%. After adding distilled water, the materials were thoroughly kneaded using a kneader to obtain a negative electrode paste. The negative electrode paste was applied onto a copper foil as a current collector (negative electrode substrate 16) using a doctor blade, and dried in an environment at 100°C for 15 minutes to completely evaporate the water, thereby producing the negative electrode composite layer 18. At this time, the loading amount of the dried negative electrode composite layer 18 was adjusted to be 26 mg / cm 2 The produced negative electrode was subjected to a biaxial roll press to obtain a negative electrode with a density of 1.2 to 1.4 g / cc.

[0092] (Comparative Example 2)[ A perforated negative electrode substrate 16 having openings with a diameter of φ5 to 20 μm at intervals of 20 to 30 μm was prepared as the current collector (negative electrode substrate 16). The aperture ratio was set to about 10% per unit area. As a method for forming the openings, laser processing is typical, but various means such as punch press processing using a needle-shaped stamp are possible. Laser processing was used as Comparative Example 2. Note that the method for producing the negative electrode composite layer 18 was the same as that in Comparative Example 1 to obtain a negative electrode.

[0093] (Comparative Example 3)[ Laser processing was performed on the negative electrode composite layer 18 of the negative electrode prepared in Comparative Example 1 to form grooves 19. As the processing method, laser processing is typical, but methods such as masking during coating and cutting by a prop can also be selected. The groove width W1 was set to 500 μm, and the intervals W2 and W3 between adjacent grooves were set to 10 mm for processing.

[0094] (Example) Laser processing was performed on the negative electrode composite layer 18 of the negative electrode prepared in Comparative Example 2 to form grooves 19. The groove width W1 was set to 500 μm, and the intervals W2 and W3 between adjacent grooves were set to 10 mm for 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] LiNi, which is a transition metal oxide 0.6 Mn 0.2 Co 0.2 O2 was used as the positive electrode active material. The positive electrode active material, a conductive assistant (acetylene black: AB), and a binder (polyvinylidene fluoride: PVdF) were mixed so that the weight ratio was 95:2.5:2.5%, and N-methylpyrrolidone: NMP was added as a solvent, and the particles were sufficiently dispersed using a kneader to obtain a positive electrode paste. The positive electrode paste was applied onto an aluminum foil as a current collector (positive electrode substrate 12) using a doctor blade, and dried in an 80°C environment for 15 minutes or more to produce the positive electrode composite layer 14. At this time, the loading amount of the dried positive electrode composite layer 14 was adjusted to be 38 mg / cm 2 And the positive electrode was obtained by subjecting the produced positive electrode to a biaxial roll press so that the density became 3.2 g / cc.

[0097] <Configuration of Bipolar Electrode>[ A lithium-ion battery according to an embodiment of the present invention 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 via a current collector 15. When forming the bipolar structure, the positive electrode and the negative electrode may be manufactured separately and then bonded together at the end. Alternatively, a current collector 15 (current collecting foil) obtained by bonding a positive electrode substrate 12 (aluminum foil) and a negative electrode substrate 16 (copper foil), a clad current collecting foil, etc. may be prepared in advance, and the positive electrode composite layer 14 and the negative electrode composite layer 18 may be applied to this current collecting foil respectively to manufacture it. In this embodiment, as an example, the bipolar electrode 10 was manufactured by separately manufacturing the positive electrode and the negative electrode and then bonding them together at the end.

[0098] <Manufacture of Lithium-Ion Battery> A lithium-ion battery was manufactured using the bipolar electrode 10 manufactured by the method described above. The bipolar electrodes 10 were stacked so that the positive electrode composite layer 14 and the negative electrode composite layer 18 faced each other, and a separator 13 was disposed between the bipolar electrodes 10 to electrically insulate them. A film with polyethylene as the base material was used for the separator 13. The manufactured laminate was wrapped with a laminate film, and after injecting an electrolytic solution, it was sealed under a vacuum of -80 kPa. As the electrolytic solution, a carbonate-based solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed at a volume ratio of EC:DMC:EMC = 3:4:3 was used, and a solution in which 6 lithium fluoride:LiPF6 (electrolyte) was dissolved at 1.2 (g / mol) as a lithium salt was used.

[0099] <Evaluation Method> FIG. 8 is a schematic cross-sectional view for explaining the definition of warpage (T). The charged lithium-ion battery was disassembled, and as shown in FIG. 8, the bipolar electrode 10 was taken out and left standing on a horizontal plane, and the height of the thickest part of the bipolar electrode 10 was measured and defined as the magnitude of warpage (T).

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

[0101]

Table 1

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

Explanation of Signs

[0103] 1 bipolar battery 10 bipolar electrode 12 positive electrode base material 13 separator 14 positive electrode composite material layer 15 current collector 16 negative electrode base material 18 negative electrode composite material layer 19 groove 20 elastic layer D stacking direction W1 groove width W2 interval between adjacent grooves W4 lateral width (outer diameter dimension of negative electrode composite material layer) W5 longitudinal width (outer diameter dimension of negative electrode composite material layer)

Claims

1. A positive electrode substrate serving as a current collector, A positive electrode composite layer formed on the positive electrode substrate, A negative electrode substrate serving as a current collector, A negative electrode composite layer formed on the negative electrode substrate and divided into a plurality of regions, and a groove having a bottom on the negative electrode substrate is provided between adjacent regions, An elastic layer formed between the negative electrode substrate and the negative electrode composite layer and having elasticity, and A bipolar electrode in which the positive electrode composite layer, the positive electrode substrate, the negative electrode substrate, the elastic layer, and the negative electrode composite layer are laminated in this order.

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

3. The bipolar electrode according to claim 1, wherein the elastic layer has an electronic 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 thickness of the elastic layer is 10 µm or less.

6. The negative electrode composite layer is rectangular when viewed from the stacking direction, The bipolar electrode according to claim 1, wherein the grooves extend linearly along the surface of the negative electrode composite layer on the short side and the long side of the negative electrode composite layer, respectively.

7. The negative electrode composite layer contains at least a negative electrode active material, The bipolar electrode according to claim 1, wherein the negative electrode active material contains 10% or less 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 distance between the 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 distance between the adjacent grooves is 0.

05.

11. The bipolar electrode according to claim 1, wherein the outer diameter dimension of the negative electrode composite layer is 1000 mm or more.

12. The bipolar electrode according to claim 1, wherein more grooves are provided in the central region than in the outer region of the negative electrode composite layer.

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

14. The bipolar electrode according to claim 1, wherein the grooves are not provided in the positive electrode composite layer.

15. A bipolar battery including a plurality of bipolar electrodes according to any one of claims 1 to 14 laminated via a separator made of an organic material and containing an electrolytic solution.

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