Stack battery

Abstract

To provide a stack battery which achieves both the prevention of moisture deterioration and an improvement in volume energy density.SOLUTION: A stack battery 100 of the present disclosure includes: a stack in which a plurality of unit cells 30, in each of which a negative electrode current collector 40, a negative electrode active material layer 50, a separation layer 60, a positive electrode active material layer 70, and a positive electrode current collector 80 are stacked in that order, are stacked such that the negative electrode current collectors 40 are in contact with each other and the positive electrode current collectors 80 are in contact with each other; and a sealing material 20 covering an outer side of the stack, except one outermost current collector of the stack. The one outermost current collector covers the stack other than the one current collector such that at least a part of the stack other than the one outermost current collector is enclosed by the one outermost current collector via the sealing material 20, and at least a part of an outer peripheral end-face of the other outermost current collector is covered by the sealing material 20.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to stacked batteries. [Background technology]

[0002] In lithium batteries, the negative electrode active material layer, positive electrode active material layer, and separator layer are susceptible to deterioration due to moisture, so a sealant is provided to prevent moisture from penetrating into the negative electrode active material layer, positive electrode active material layer, and separator layer.

[0003] Typically, a sealant is placed around the outer periphery of a laminate of a negative electrode active material layer, a positive electrode active material layer, and a separator layer, and the laminate and sealant are sandwiched between a negative electrode current collector and a positive electrode current collector. However, if the contact area between the negative electrode current collector and the sealant and / or the positive electrode current collector and the sealant is insufficient, moisture will penetrate through the interface between the negative electrode current collector and the sealant and / or the interface between the positive electrode current collector and the sealant near the outer peripheral edge of the negative electrode current collector and / or the positive electrode current collector. To avoid this, it is effective to increase the contact area between the negative electrode current collector and the sealant and / or the contact area between the positive electrode current collector and the sealant. However, this increases the volume fraction of the sealant that does not contribute to charge / discharge, resulting in a decrease in volumetric energy density.

[0004] Therefore, for example, Patent Document 1 discloses a thin battery in which the sealing material of the unit cells is folded so as to cover the outer peripheral end surface of the current collector of the unit cells.

[0005] Furthermore, for example, Patent Document 2 discloses a thin battery in which the entire battery is covered with a sealing material. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-21636 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-114929 Summary of the Invention [Problem to be solved by the invention]

[0007] In the thin battery disclosed in Patent Document 1, the sealing material of the unit cells is folded so as to cover the outer peripheral end faces of the current collectors of the unit cells, thereby improving sealing performance. However, because the sealing material of the unit cells is folded so as to cover the outer peripheral end faces of the current collectors of the unit cells, there are limitations to how thin the entire battery can be. In particular, when the unit cells of Patent Document 1 are stacked, it becomes difficult to thin the entire stacked battery, and a decrease in volumetric energy density is an issue.

[0008] In the thin battery disclosed in Patent Document 2, the entire battery is covered with a sealing material, and the thickness of the sealing material at both ends of the battery in the stacking direction of the constituent elements is a disadvantage in terms of thinning, resulting in a decrease in volumetric energy density.

[0009] In view of the above, the present inventors have found that there is a need for a stacked battery that can both suppress moisture deterioration and improve volumetric energy density.

[0010] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a stacked battery that achieves both suppression of moisture deterioration and improvement of volumetric energy density. [Means for solving the problem]

[0011] The present inventors have conducted extensive research to achieve the above object and have completed the stacked battery of the present disclosure, the aspects of which are as follows. <Aspect 1> A stack in which a plurality of unit cells, each having a negative electrode current collector, a negative electrode active material layer, a separator layer, a positive electrode active material layer, and a positive electrode current collector stacked in this order, are stacked such that the negative electrode current collectors are in contact with each other and the positive electrode current collectors are in contact with each other. a sealing material covering the outside of the laminate except for one outermost current collector of the laminate; It is equipped with the one outermost current collector covers the stack other than the one current collector such that at least a portion of the stack other than the one outermost current collector is enclosed by the one outermost current collector via the sealing material, and at least a portion of an outer peripheral end face of the other outermost current collector is covered by the sealing material; Stacked battery. <Aspect 2> The stacked battery according to aspect 1, wherein the negative electrode current collectors are connected to each other, or, instead of being in contact with each other, the negative electrode current collectors are shared as a single negative electrode current collector. Aspect 3: The stacked battery according to aspect 1 or 2, wherein the positive electrode current collectors are connected to each other, or, instead of being in contact with each other, the positive electrode current collectors are shared as a single positive electrode current collector. Aspect 4: The stacked battery according to aspect 1 or 2, wherein the separator layer contains a solid electrolyte. Aspect 5: The stacked battery according to aspect 3, wherein the separator layer contains a solid electrolyte. [Effects of the Invention]

[0012] In the stacked battery of the present disclosure, one outermost current collector covers the stacked body other than one current collector such that at least a portion of the stacked body other than one outermost current collector is enclosed by the one outermost current collector via a sealing material, and at least a portion of the outer peripheral end face of the other outermost current collector is covered by the sealing material. Therefore, according to the present disclosure, it is possible to provide a stacked battery that achieves both suppression of moisture degradation and improvement of volumetric energy density. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing an example of the cross-sectional structure of a stacked battery according to the present disclosure. [Figure 2] FIG. 2 is a schematic diagram illustrating an example of a method for manufacturing a stacked battery according to the present disclosure. [Figure 3] FIG. 3 is a cross-sectional view showing the vicinity of one of the outermost negative electrode current collectors in FIG. [Figure 4]FIG. 4 is a cross-sectional view showing the vicinity of one of the negative electrode current collectors other than the outermost negative electrode current collector in FIG. [Figure 5] FIG. 5 is a cross-sectional view showing the state immediately before the sealing material is fully fused. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the stacked battery according to the present disclosure will be described in detail. Note that the stacked battery according to the present disclosure is not limited to the embodiments described below.

[0015] Without being bound by theory, the inventors will now describe their findings regarding why the stacked battery of the present disclosure achieves both suppression of moisture degradation and improvement in volumetric energy density.

[0016] In the stacked battery of the present disclosure, one outermost current collector covers the stack other than one current collector such that at least a portion of the stack other than the outermost current collector is enclosed by the one outermost current collector via a sealing material, and at least a portion of the outer peripheral end face of the other outermost current collector is covered by the sealing material. That is, with respect to the other outermost current collector, at least a portion of a surface on which no active material is laminated, extending from at least a portion of the outer peripheral end face of the other outermost current collector, is covered by the one outermost current collector via a sealing material.

[0017] As a result, at least a portion of the outer peripheral end face of all current collectors except for one outermost current collector is covered with the sealing material, which improves the sealing property of the interface between the current collector and the sealing material in all current collectors except for one outermost current collector.

[0018] In contrast, the outer peripheral end surface of the one outermost current collector is not covered with a sealant, and therefore has poor sealing properties. However, even if moisture penetrates through the interface between the one outermost current collector and the sealant, the interface between the one outermost current collector and the sealant is on the opposite side of the laminate from the interface that contains everything except the one outermost current collector. Therefore, moisture degradation of the negative electrode active material layer, the positive electrode active material layer, and the separator layer present in the laminate is not affected.

[0019] Furthermore, because the sealing material is folded only in the portion that covers the outer peripheral end face of the other outermost current collector, the increase in the volume occupied by the sealing material due to the folding of the sealing material can be minimized, thereby improving the volumetric energy density of the stacked battery.

[0020] For these reasons, the stacked battery of the present disclosure can achieve both suppression of moisture deterioration and improvement of volumetric energy density.

[0021] The constituent elements of the stacked battery of the present disclosure, which have been completed based on the findings and the like described above, will be described with reference to the drawings.

[0022] 《Stacked battery》 1 is a schematic diagram showing an example of an outline of the cross-sectional structure of a laminated battery according to the present disclosure. The laminated battery 100 according to the present disclosure includes a laminate 10 and a sealing material 20. The laminate 10 and the sealing material 20 will be described below.

[0023] <Laminate> The laminate 10 includes a plurality of unit cells 30a, 30b, 30c, and 30d stacked together. In the unit cell 30a, a negative electrode current collector 40a, a negative electrode active material layer 50a, a separator layer 60a, a positive electrode active material layer 70a, and a positive electrode current collector 80a are stacked in this order. The same is true for the unit cells 30b, 30c, and 30d.

[0024] In the embodiment shown in FIG. 1 , the multiple single cells 30a, 30b, 30c, and 30d are stacked with their negative electrode current collectors and positive electrode current collectors in contact with each other, but this is not limited thereto. For example, the negative electrode current collectors may be connected to each other and stacked as a single shared negative electrode current collector. Similarly, the positive electrode current collectors may be connected to each other and stacked as a single shared positive electrode current collector. The connection method is not particularly limited, and examples include pressure welding and welding. Alternatively, instead of the negative electrode current collectors being in contact with each other, they may be stacked as a single shared negative electrode current collector. Similarly, instead of the positive electrode current collectors being in contact with each other, they may be stacked as a single shared positive electrode current collector.

[0025] (Negative electrode current collector) The material used for the negative electrode current collectors 40a, 40b, 40c, and 40d is not particularly limited, and any material that can be used as a negative electrode current collector for a battery can be appropriately used. Examples of materials that can be used for the negative electrode current collectors 40a, 40b, 40c, and 40d include, but are not limited to, stainless steel (SUS), aluminum, copper, nickel, iron, titanium, carbon, and conductive resins. The material used for the negative electrode current collectors 40a, 40b, 40c, and 40d is preferably reduction-resistant, such as nickel.

[0026] (Negative electrode active material layer) The negative electrode active material layers 50a, 50b, 50c, and 50d contain a negative electrode active material and, optionally, a conductive additive and a binder. When the laminated battery of the present disclosure is a solid-state battery, it may optionally contain a solid electrolyte. In this case, the solid electrolyte constituting the separator layer can be used.

[0027] The material of the negative electrode active material is not particularly limited, and may be metallic lithium or a material capable of absorbing and releasing metal ions such as lithium ions. Examples of materials capable of absorbing and releasing metal ions such as lithium ions include, but are not limited to, alloy-based negative electrode active materials and carbon materials.

[0028] The alloy-based negative electrode active material is not particularly limited, and examples thereof include Si alloy-based negative electrode active materials and Sn alloy-based negative electrode active materials. Examples of Si alloy-based negative electrode active materials include silicon, silicon oxide, silicon carbide, silicon nitride, and solid solutions thereof. The Si alloy-based negative electrode active material may contain elements other than silicon, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, and Ti. Examples of Sn alloy-based negative electrode active materials include tin, tin oxide, tin nitride, and solid solutions thereof. The Sn alloy-based negative electrode active material may contain elements other than tin, such as Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Ti, and Si. Among these, Si alloy-based negative electrode active materials are preferred.

[0029] The carbon material is not particularly limited, and examples thereof include hard carbon, soft carbon, and graphite.

[0030] (separate layer) The materials used for the separator layers 60a, 60b, 60c, and 60d are not particularly limited, and any material that can be used as a separator layer in a battery can be appropriately used. When the laminated battery of the present disclosure is a solid-state battery, the separator layer may contain a solid electrolyte and, optionally, a binder. Since a hot press is used in the manufacturing process of the laminated battery of the present disclosure to adhere the sealing material 20 described below to the required locations, the separator layer is preferably a solid electrolyte with high heat resistance, particularly a sulfide-based or oxide-based solid electrolyte.

[0031] The material of the solid electrolyte is not particularly limited, and examples thereof include a sulfide solid electrolyte, an oxide solid electrolyte, and a polymer electrolyte.

[0032] Examples of sulfide solid electrolytes include, but are not limited to, sulfide-based amorphous solid electrolytes, sulfide-based crystalline solid electrolytes, and argyrodite-type solid electrolytes. Specific examples of sulfide solid electrolytes include Li2S-P2S5-based (Li7P3S 11, Li3PS4, Li8P2S9, etc.), Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-P2S5-GeS2(Li 13 GeP3S 16 , Li 10 GeP2S 12 etc.), LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li 7-x PS 6-x Cl x etc.; or combinations thereof, but are not limited to these.

[0033] An example of an oxide solid electrolyte is Li7La3Zr2O 12、 Li 7-x La3Zr 1-x Nb x O 12、 Li 7-3x La3Zr2Al x O 12 , Li 3x La 2 / 3-x TiO3, Li 1+x Al x Ti 2-x (PO4)3, Li 1+x Al x Ge 2-x (PO4)3, Li3PO4, or Li 3+x PO 4-x N x (LiPON), etc., but are not limited to these.

[0034] The sulfide solid electrolyte and the oxide solid electrolyte may be glass or crystallized glass (glass ceramic).

[0035] Examples of polymer electrolytes include, but are not limited to, polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof.

[0036] (Cathode active material layer) The positive electrode active material layers 70a, 70b, 70c, and 70d contain a positive electrode active material and, optionally, a conductive additive and a binder. When the laminated battery of the present disclosure is a solid-state battery, it may optionally contain a solid electrolyte. In this case, the solid electrolyte constituting the separator layer can be used.

[0037] The material of the positive electrode active material is not particularly limited. For example, the positive electrode active material may be lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), lithium manganese oxide (LiMnO), LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 O2, Li 1+x Mn 2-x-y M y The material may be, but is not limited to, a different element-substituted Li-Mn spinel having a composition represented by O4 (M is one or more metal elements selected from Al, Mg, Co, Fe, Ni, and Zn).

[0038] (Positive electrode current collector) The material used for the positive electrode current collectors 80a, 80b, 80c, and 80d is not particularly limited, and any material that can be used as a positive electrode current collector for a battery can be appropriately used. Examples of materials used for the positive electrode current collectors 80a, 80b, 80c, and 80d include, but are not limited to, stainless steel (SUS), aluminum, copper, nickel, iron, titanium, carbon, and conductive resins. The material used for the positive electrode current collectors 80a, 80b, 80c, and 80d is preferably oxidation-resistant, such as aluminum.

[0039] (Conductive additive) The conductive additive is not particularly limited, and may be, for example, a carbon material such as VGCF (Vapor Grown Carbon Fiber) or carbon nanofiber, or a metal material, but is not limited thereto.

[0040] (binder) The binder is not particularly limited, and may be, for example, but not limited to, a material such as polyvinylidene fluoride (PVdF), butadiene rubber (BR), polytetrafluoroethylene (PTFE), or styrene butadiene rubber (SBR), or a combination thereof.

[0041] <Sealing material> The sealing material 20 covers the outside of the laminate 10 except for one outermost negative electrode current collector 40a of the laminate 10. In the embodiment shown in FIG. 1 , one outermost current collector is the negative electrode current collector 40a and the other outermost current collector is the negative electrode current collector 40d, but this is not limited to this. For example, one outermost current collector may be a positive electrode current collector and the other outermost current collector may be a positive electrode current collector, or one outermost current collector may be a negative electrode current collector and the other outermost current collector may be a positive electrode current collector.

[0042] The laminate 10 is enclosed by the one outermost negative electrode current collector 40a via the sealing material 20. The parts other than the one outermost negative electrode current collector 40a refer to the negative electrode current collectors 40b, 40c, and 40d, the negative electrode active material layers 50a, 50b, 50c, and 50d, the separator layers 60a, 60b, 60c, and 60d, the positive electrode active material layers 70a, 70b, 70c, and 70d, and the positive electrode current collectors 80a, 80b, 80c, and 80d, excluding the negative electrode current collector 40a. The one outermost negative electrode current collector 40a covers (encloses) the laminate 10 except for the one negative electrode current collector 40a, such that the outer peripheral end surface 42d of the other outermost negative electrode current collector 40d is covered by the sealing material 20. As a result, at least a portion of the surface of the other outermost current collector on which no active material is laminated, extending from the outer peripheral end surface 42d of the other outermost negative electrode current collector 40d, is covered by the one outermost negative electrode current collector 40a via the sealing material 20.

[0043] There are no particular limitations on the sealing material 20, as long as it is a resin that can seal the stack 10 except for one outermost negative electrode current collector 40a.

[0044] Such materials include thermoplastic resins such as polyethylene terephthalate (PET), polypropylene (PP), polyvinylidene chloride (PVDC), polyvinylidene fluoride (PVDF), polycarbonate (PC), or polyetherimide (PEI), rubbers such as acrylonitrile butadiene rubber (ABR) or butadiene rubber (BR), or non-conductive binders such as epoxy or acrylic binders, etc. Polypropylene (PP) is particularly preferred.

[0045] The manufacturing method of the stacked battery described so far is not particularly limited, but a typical manufacturing method will be described with reference to the drawings. Fig. 2 is a schematic diagram illustrating an example of the manufacturing method of the stacked battery of the present disclosure. Fig. 3 is a cross-sectional view showing the vicinity of one of the outermost negative electrode current collectors 40d in Fig. 2. Fig. 4 is a cross-sectional view showing the vicinity of one of the negative electrode current collectors 40b other than the one of the outermost negative electrode current collectors 40d in Fig. 2. Fig. 5 is a cross-sectional view showing the state immediately before the sealing material 20 is fully fused.

[0046] The negative electrode current collectors 40a, 40b, 40c, and 40d each have a connecting portion 44a, 44b, and 44c and a tab portion 46. The positive electrode current collectors 80a, 80b, 80c, and 80d each have a connecting portion 84a, 84b, and 84c and a tab portion 86. The components of the cells 30a, 30b, 30c, and 30d and the sealing material 20 are disposed between the negative electrode current collectors 40a, 40b, 40c, and 40d, respectively, and the positive electrode current collectors 80a, 80b, 80c, and 80d, respectively. The structure shown in FIG. 2 is heated to temporarily fuse the sealing material 20.

[0047] Thereafter, the positive electrode current collector 80a of the cell 30a and the positive electrode current collector 80b of the cell 30b, the negative electrode current collector 40b of the cell 30b and the negative electrode current collector 40c of the cell 30c, and the positive electrode current collector 80c of the cell 30c and the positive electrode current collector 80d of the cell 30d are folded so as to be in contact with each other, and a sealing material 20 is placed on the surface of the negative electrode current collector 40d of the cell 30d where the negative electrode active material layer 50d is not laminated. Furthermore, the outermost negative electrode current collector 40a is folded so as to enclose the cells 30a, 30b, 30c, and 30d to which the sealing material 20 has been temporarily fused, and to cover, via the sealing material 20, the surface of the negative electrode current collector 40d of the cell 30d where the negative electrode active material layer 50d is not laminated (see FIG. 5 ). The structure is heated in the state shown in FIG. 5 to permanently fuse the sealing material 20.

[0048] The temperatures and times for pre-fusion and final fusion may be appropriately determined taking into consideration the type of resin of the sealing material 20, etc., so that the sealing material 20 is properly fused. It is preferable to set the final fusion temperature higher than the pre-fusion temperature. The pre-fusion temperature may be, for example, 120°C or higher, 130°C or higher, or 135°C or higher, and 150°C or lower, 145°C or lower, or 140°C or lower. The pre-fusion time may be, for example, 30 seconds or higher, 45 seconds or higher, or 60 seconds or higher, and 180 seconds or lower, 120 seconds or lower, or 90 seconds or lower. The final fusion temperature may be, for example, 130°C or higher, 140°C or higher, or 145°C or higher, and 160°C or lower, 155°C or lower, or 150°C or lower. The final fusion time may be, for example, 30 seconds or higher, 45 seconds or higher, or 60 seconds or higher, and 180 seconds or lower, 120 seconds or lower, or 90 seconds or lower.

[0049] When one positive electrode current collector and one negative electrode current collector are shared, the following method may be used: A component unit (first unit) of the cell shown in Fig. 3, a component unit (second unit) obtained by removing the negative electrode current collector from the components of the cell shown in Fig. 4, and a component unit (third unit) obtained by removing the positive electrode current collector from the components of the cell shown in Fig. 4 are prepared. The sheet materials of the first unit, second unit, and third unit are temporarily fused to obtain a first temporarily fused unit, a second temporarily fused unit, and a third temporarily fused unit.

[0050] The second temporary fusion unit, the third temporary fusion unit, and the second temporary fusion unit are stacked on the first temporary fusion unit so that they share one negative electrode current collector and one positive electrode current collector. The stack (excluding the negative electrode current collector of the first temporary fusion unit) is then folded to encase the stack and cover, via a sealing material, the surface of the top negative electrode current collector that is not laminated with the negative electrode active material layer. Heat is applied in this state to permanently fuse the sealing material.

[0051] Transformation In addition to what has been described so far, the manufacturing method of the present disclosure can be modified in various ways within the scope of the claims. For example, the entire exterior of the stacked battery 100 in FIG. 1 may be further covered with resin. [Explanation of symbols]

[0052] 100 stacked battery 10 Laminate 20 Sealing material 30, 30a, 30b, 30c, 30d single cell 40,40a, 40b, 40c, 40d negative electrode current collector 42d Outer edge 44a, 44b, 44c connection part 46 Tab section 50,50a, 50b, 50c, 50d negative electrode active material layer 60, 60a, 60b, 60c, 60d Separate layer 70,70a, 70b, 70c, 70d Cathode active material layer 80,80a, 80b, 80c, 80d positive electrode current collector 84a, 84b, 84c connection part 86 Tab section

Claims

1. a stack in which a plurality of unit cells, each having a negative electrode current collector, a negative electrode active material layer, a separator layer, a positive electrode active material layer, and a positive electrode current collector stacked in this order, are stacked such that the negative electrode current collectors are in contact with each other and the positive electrode current collectors are in contact with each other; a sealing material covering the outside of the laminate except for one outermost current collector of the laminate; It is equipped with the one outermost current collector covers the stack other than the one current collector such that at least a portion of the stack other than the one outermost current collector is enclosed by the one outermost current collector via the sealing material, and at least a portion of an outer peripheral end face of the other outermost current collector is covered by the sealing material; Stacked battery.

2. 2. The stacked battery according to claim 1, wherein the negative electrode current collectors are connected to each other, or instead of being in contact with each other, the negative electrode current collectors are shared as one negative electrode current collector.

3. 3. The stacked battery according to claim 1, wherein the positive electrode current collectors are connected to each other, or instead of being in contact with each other, the positive electrode current collectors are shared as one positive electrode current collector.

4. The laminated battery according to claim 1 or 2, wherein the separator layer contains a solid electrolyte.

5. The laminated battery according to claim 3 , wherein the separator layer contains a solid electrolyte.

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