Bipolar battery and power storage module

Abstract

To provide a bipolar battery and power storage module with excellent strength.SOLUTION: A bipolar battery includes a power generation element and an outer casing. The power generation element includes a bipolar electrode and a separator. The power generation element and the outer casing have an arched cross-section, and the radius of curvature of the power generation element and the outer casing is 40 mm or more and 2500 mm or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to bipolar batteries and energy storage modules. [Background technology]

[0002] Patent Document 1 (JP 2017-98365 A) discloses a lithium ion capacitor having a planar arch-shaped positive electrode, a planar arch-shaped negative electrode, and a planar arch-shaped separator interposed between them. It also discloses that this structure is realized by the positive electrode current collector and the negative electrode current collector being porous metal bodies having a three-dimensional mesh-like skeleton. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-98365 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, a bipolar electrode (bipolar battery) is known, which has a positive electrode active material layer on one side of a current collector and a negative electrode active material layer on the other side. Bipolar batteries have attracted attention from the viewpoint of improving energy density compared to conventional non-aqueous electrolyte secondary batteries.

[0005] However, the current collector described in Patent Document 1 cannot be used in bipolar batteries. Because the current collector has a three-dimensional mesh structure, the electrolyte is not isolated. For example, the positive electrode current collector may be at a low potential due to the negative electrode active material layer on the back surface, which could result in lithium intercalation. Alternatively, the electrode may be at a high potential due to a liquid junction, which could result in oxidative decomposition of the electrolyte or elution of the current collector. Furthermore, in secondary batteries, including bipolar batteries, the arched structure described in Patent Document 1 needs further consideration from the perspective of ensuring strength.

[0006] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to provide a bipolar battery and a power storage module that are excellent in strength. [Means for solving the problem]

[0007] [1] A bipolar battery including a power generating element and an exterior body, the power generating element includes a bipolar electrode and a separator; the power-generating element and the exterior body have arch-shaped cross sections, A bipolar battery, wherein the radius of curvature of the power generating element and the exterior body is 40 mm or more and 2500 mm or less.

[0008] The power generating element and the exterior body are arch-shaped and have a predetermined radius of curvature, so that they deflect along the arch shape in response to bending due to their own weight or external load, dispersing applied stress, which is expected to result in a bipolar battery with excellent strength.

[0009] [2] The power generating element and the exterior body have a longitudinal direction and a lateral direction, The bipolar battery according to [1], wherein the power generating element and the exterior body are curved in an arch shape along the short side direction.

[0010] [3] An energy storage module including the bipolar battery according to [1] or [2]. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view showing an example of a bipolar electrode included in a bipolar battery according to this embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing an example of a bipolar battery according to this embodiment. [Figure 3] FIG. 3 is a schematic diagram for calculating the radius of curvature. [Figure 4]FIG. 4 is a perspective view schematically showing the bipolar battery of this embodiment. [Figure 5] FIG. 5 is a cross-sectional view showing an example of the electricity storage module according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0013] <Bipolar battery> FIG. 1 is a cross-sectional view showing an example of a bipolar electrode included in a bipolar battery of this embodiment, and FIG. 2 is a cross-sectional view showing an example of a bipolar battery of this embodiment. Bipolar battery 100 includes a power generating element, a seal, and an exterior housing 90. The power generating element includes a bipolar electrode 20 and a separator 30. The power generating element and exterior housing 90 have an arch-shaped cross section. The radius of curvature of the power generating element and exterior housing 90 is 40 mm or more and 2500 mm or less.

[0014] The bipolar battery 100 includes a power generating element, a sealing body, and an exterior body 90. The exterior body 90 houses the power generating element, the sealing body, and the electrolyte. The exterior body 90 has a shape that follows the outer shape of the power generating element. That is, the exterior body 90 has the above-mentioned radius of curvature. The exterior body 90 may be, for example, a metal case or a pouch made of a metal foil laminate film. The exterior body 90 may contain, for example, Al.

[0015] The power generating element includes a plurality of bipolar electrodes 20 and a plurality of separators 30. The bipolar electrode 20 includes, in this order, a positive electrode active material layer 21, an electrode current collector 10, and a negative electrode active material layer 22. That is, the positive electrode active material layer 21 is bonded to one main surface of the electrode current collector 10, and the negative electrode active material layer 22 is bonded to the other main surface.

[0016] The power generating element may also be referred to as an electrode body or an electrode group. The power generating element may be formed by alternately stacking bipolar electrodes 20 and separators 30 in the Z direction. The power generating element includes a positive terminal electrode at one end in the Z direction and a negative terminal electrode at the other end. The positive terminal electrode has a configuration in which the negative electrode active material layer 22 has been removed from the bipolar electrode 20. The negative terminal electrode has a configuration in which the positive electrode active material layer 21 has been removed from the bipolar electrode 20.

[0017] The positive electrode active material layer 21 contains a positive electrode active material. The positive electrode active material layer 21 may further contain, for example, a conductive material, a binder, and the like.

[0018] The positive electrode active material may be, for example, particulate. The positive electrode active material may have a D50 of, for example, 1 to 30 μm. The positive electrode active material may contain, for example, at least one selected from the group consisting of LiCoO2, LiNiO2, LiMnO2, Li(NiCoMn)O2, Li(NiCoAl)O2, LiFePO4, and Li(MnFe)PO4. For example, "(NiCoMn)" in "Li(NiCoMn)O2" indicates that the sum of the composition ratios in parentheses is 1. The amounts of each component are arbitrary as long as the sum is 1.

[0019] The conductive material may include, for example, acetylene black (AB), etc. The binder may include, for example, polyvinylidene fluoride (PVdF), etc. The conductive material and the binder may be, for example, 0.1% by mass or more and 10% by mass or less with respect to the positive electrode active material layer 21.

[0020] The negative electrode active material layer 22 contains a negative electrode active material. The negative electrode active material layer 22 may further contain, for example, a binder, a thickener, and the like.

[0021] The negative electrode active material may include, for example, at least one selected from the group consisting of graphite, soft carbon, and hard carbon.

[0022] The binder may include, for example, styrene butadiene rubber (SBR), etc. The thickener may include, for example, carboxymethyl cellulose (CMC), etc. The binder and the thickener may be present in an amount of, for example, 0.1% by mass or more and 10% by mass or less with respect to the negative electrode active material layer 22.

[0023] The electrode current collector 10 may contain at least one selected from the group consisting of aluminum (Al), stainless steel, nickel (Ni), chromium (Cr), platinum (Pt), niobium (Nb), iron (Fe), titanium (Ti), copper (Cu), and zinc (Zn). The electrode current collector 10 may also be a metal foil whose surface has been plated.

[0024] The separator 30 is porous. The separator 30 is permeable to an electrolyte. The separator 30 separates the positive electrode active material layer 21 and the negative electrode active material layer 22. The separator 30 is electrically insulating. The separator 30 may contain, for example, a polyolefin resin such as polyethylene (PE) or polypropylene (PP). The separator 30 may have, for example, a single-layer structure or a multi-layer structure. The separator 30 may, for example, be substantially composed of a PE layer, or may be formed by laminating a PP layer, a PE layer, and a PP layer in this order.

[0025] The electrolyte solution includes a solvent and a Li salt. The solvent is aprotic. The solvent may include any component. For example, the solvent may include at least one selected from the group consisting of ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC).

[0026] The Li salt is a supporting electrolyte. The Li salt is dissolved in a solvent. The Li salt may include, for example, at least one selected from the group consisting of LiPF6 and LiBF4. The Li salt may have a molar concentration of, for example, 0.5 mol / L or more and 2.0 mol / L or less.

[0027] The electrolytic solution may further contain an optional additive. For example, the electrolytic solution may contain 0.01% by mass or more and 5% by mass or less of the additive. The additive may include, for example, at least one selected from the group consisting of vinylene carbonate (VC) and vinyl ethylene carbonate (VEC).

[0028] The sealing body seals the power generating element. The sealing body may include a first sealing material, a spacer, and a second sealing material. The first sealing material is arranged on both sides in the Z direction of the end of the bipolar electrode 20 in the X direction. The spacer is arranged between a pair of first sealing materials arranged between adjacent electrode current collectors 10 in the Z direction. The first sealing material and the spacer seal the space between the bipolar electrodes 20. Part of the first sealing material and part of the spacer are embedded in the second sealing material. The exterior body 90 further covers the outside of the second sealing material. The first sealing material, the spacer, and the second sealing material may contain insulating resin.

[0029] The bipolar electrode 20, separator 30, positive terminal electrode, negative terminal electrode, and outer casing 90 included in the power generating element have an arch-shaped cross section. Specifically, the radius of curvature of the power generating element and outer casing 90 is 40 mm or more and 2500 mm or less. This structure allows the power generating element and outer casing 90 to bend along the arch shape in response to bending due to their own weight, thereby suppressing deformation and gaps due to residual stress that occurs when smoothed. Furthermore, the arch shape of the bipolar battery 100 forms a convex shape, which is resistant to external loads. As a result, a bipolar battery 100 with excellent strength is expected to be obtained. Furthermore, the power generating element and outer casing 90 are curved in the same direction in an arch shape, as shown in Figures 1 and 2.

[0030] Here, "curvature" is an index indicating the degree of bending, and the reciprocal of the curvature is the "radius of curvature." Referring to Fig. 3, the radius of curvature R is calculated by the following formula (1). The smaller the radius of curvature R, the greater the degree of bending of the power generating element and exterior body 90.

[0031] R=((w / 2) 2 +h 2 ) / 2h (1) The applied stress tends to be more dispersed by reducing the radius of curvature R. On the other hand, if the radius of curvature R is too large, the power generating element and exterior body 90 may not be able to maintain their shapes.

[0032] "w" and "h" in the above formula (1) can be measured, for example, by length measurement or X-ray CT imaging. The w and h are measured at 10 or more locations on each of the power generating element and the exterior body 90, and the average value of the radii of curvature R calculated from each w and h is regarded as the "radius of curvature R" in this embodiment. The radius of curvature R of the power generating element and the radius of curvature R of the exterior body 90 may be the same or different.

[0033] The power generating element and the exterior body 90 preferably have a longitudinal direction and a lateral direction. In this case, the power generating element and the exterior body 90 are preferably curved in an arch shape along the lateral direction (in FIG. 4, the X direction is the lateral direction, and the Y direction is the longitudinal direction). This is expected to result in a bipolar battery with superior strength. It is also expected to improve the efficiency of the manufacturing process.

[0034] The bipolar battery 100 can have any capacity and size. The bipolar battery 100 can be, for example, a small battery for a portable device. The bipolar battery 100 can be, for example, a large battery for an automobile.

[0035] <Bipolar battery manufacturing method> The bipolar battery of this embodiment is manufactured, for example, as follows: However, this is merely an example and the present invention is not limited to this.

[0036] An electrode current collector is prepared, and a positive electrode paint containing a positive electrode active material is applied to one surface of the electrode current collector, and a negative electrode paint containing a negative electrode active material is applied to the other surface, thereby producing a bipolar electrode having a positive electrode active material layer, an electrode current collector, and a negative electrode active material layer in this order.

[0037] A separator is prepared. A bipolar electrode, a separator, and another bipolar electrode are stacked so that the separator separates the positive electrode active material layer and the negative electrode active material layer. Depending on the desired performance of the bipolar battery, bipolar electrodes and separators can be further stacked. A power generating element is fabricated by forming a positive electrode terminal electrode at one end in the stacking direction and a negative electrode terminal electrode at the other end. The power generating element has a radius of curvature of 40 mm or more and 2500 mm or less. The power generating element is fabricated, for example, by performing the above process on a curved stacking table having a predetermined radius of curvature.

[0038] An electrolyte solution is prepared, and the obtained power generating element is filled with the electrolyte solution. After filling with the electrolyte solution, the power generating element is sealed with a sealer.

[0039] An exterior body is prepared. The exterior body has a curvature radius of 40 mm or more and 2500 mm or less. A power generating element is housed in the exterior body. After the power generating element is housed, the exterior body is sealed to produce a bipolar battery.

[0040] <Energy storage module> 5 is a cross-sectional view showing an example of an electric storage module according to this embodiment. The electric storage module 200 includes a plurality of bipolar batteries 100.

[0041] As shown in Fig. 5, the energy storage module 200 may include, for example, a cooling member 110, a control member 120, and the like. As described above, the bipolar battery 100 in this embodiment is a battery that is curved in an arch shape with a predetermined curvature. A energy storage module 200 that includes a plurality of such bipolar batteries 100 may have a gap V. By installing the above-described members in such a gap V, the space can be used effectively.

[0042] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0043] 10 electrode current collector, 20 bipolar electrode, 21 positive electrode active material layer, 22 negative electrode active material layer, 30 separator, 90 exterior body, 100 bipolar battery, 110 cooling member, 120 control member, 200 energy storage module

Claims

1. A bipolar battery including a power generating element and an exterior body, the power generating element includes a bipolar electrode and a separator; the power-generating element and the exterior body have arch-shaped cross sections, A bipolar battery, wherein the radius of curvature of the power generating element and the exterior body is 40 mm or more and 2500 mm or less.

2. the power-generating element and the exterior body have a longitudinal direction and a lateral direction, The bipolar battery according to claim 1 , wherein the power generating element and the exterior body are curved in an arch shape along the short-side direction.

3. A storage module comprising the bipolar battery according to claim 1 or 2.

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