Method for manufacturing non-aqueous electrolyte battery

Abstract

To provide a method for manufacturing a non-aqueous electrolyte battery that can reduce the pressure inside a battery case in a short period of time while suppressing damage to an electrode body.SOLUTION: A method for manufacturing a non-aqueous electrolyte battery includes a decompression step in which a compression process in which the battery case 11 is compressed from the outside while reducing the pressure inside the battery case 11 containing the electrode body 13, and a load-relieving process in which the compression of the battery case 11 is released are repeated until the degree of decompression inside the battery case 11 reaches a predetermined degree of decompression.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a nonaqueous electrolyte battery. [Background technology]

[0002] Conventionally, various methods for manufacturing a nonaqueous electrolyte battery in which an electrode body and an electrolyte are housed in a battery case have been proposed. For example, in the method described in Patent Document 1, the battery case is compressed in the thickness direction while the pressure inside the battery case is reduced, and an electrolyte is injected while an airtight space is secured inside the electrode body, and then a step of increasing the pressure inside the battery case and a step of releasing the compression on the battery case are carried out. This promotes impregnation of the electrolyte into the inside of the electrode body based on the pressure difference between the inside and outside of the electrode body inside the battery case. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-96927 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the method described in Patent Document 1, if the compressive force on the battery case is increased in order to reduce the pressure inside the battery case in a short period of time, the electrode body cannot elastically deform in response to the compression of the battery case, and there is a risk that the electrode body will be damaged.

[0005] The present invention has been made in consideration of the above circumstances, and has an object to provide a method for manufacturing a nonaqueous electrolyte battery that can reduce the pressure inside the battery case in a short period of time while suppressing damage to the electrode body. [Means for solving the problem]

[0006] A method for manufacturing a nonaqueous electrolyte battery that solves the above problems includes a decompression process in which a compression process of compressing the battery case from the outside while reducing the pressure inside the battery case containing the electrode body and a load-relieving process of releasing the compression of the battery case are repeated until the degree of pressure reduction inside the battery case reaches a predetermined degree of pressure reduction. Effect of the Invention

[0007] According to the present invention, the pressure inside the battery case can be reduced in a short period of time while preventing damage to the electrode body. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view that illustrates a schematic internal structure of a lithium-ion secondary battery. [Diagram 2] FIG. 2 is a schematic diagram showing the configuration of an electrode body of a lithium ion secondary battery. [Diagram 3] 4 is a flowchart showing an example of a process for reducing pressure inside a battery case of a lithium ion secondary battery. [Figure 4] 1 is a diagram for explaining the operation of a lithium ion secondary battery. [Diagram 5] 1 is a graph showing characteristics of a lithium ion secondary battery. [Figure 6A] FIG. 11 is a cross-sectional view showing a schematic diagram of a modified example of the internal structure of a lithium-ion secondary battery. [Figure 6B] FIG. 11 is a cross-sectional view showing a schematic diagram of a modified example of the internal structure of a lithium-ion secondary battery. [Figure 6C] FIG. 11 is a cross-sectional view showing a schematic diagram of a modified example of the internal structure of a lithium-ion secondary battery. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 1, a lithium ion secondary battery 10, which is an example of a nonaqueous electrolyte battery according to this embodiment, is a cell battery that is combined with a plurality of lithium ion secondary batteries 10 and sealed in a resin or metal case to form a battery pack. The battery pack is used in hybrid vehicles and electric vehicles.

[0010] The lithium ion secondary battery 10 includes a battery case 11 and a lid 12. The battery case 11 has a bottomed cylindrical shape with an opening on the upper side. The lid 12 seals the upper opening of the battery case 11. The battery case 11 and the lid 12 are made of a metal such as aluminum or an aluminum alloy. The lithium ion secondary battery 10 has a battery container that contains an electrode assembly 13 and an electrolyte by attaching the lid 12 to the battery case 11.

[0011] The lid 12 is provided with a positive electrode external terminal 14 and a negative electrode external terminal 15 for external connection, and a safety valve 16. The safety valve 16 releases the internal pressure when the internal pressure of the battery case 11 rises to a predetermined level or higher. The battery case 11 is also provided with an injection port 17 for injecting an electrolyte into the battery case 11. When the battery case 11 is compressed from both sides in the thickness direction, the side walls of the compressed battery case 11 deform inwardly of the battery case 11. As an example, the material of the battery case 11 in this embodiment is aluminum, which has high thermal conductivity and appropriate rigidity.

[0012] As shown in Fig. 2, the electrode body 13 is a flat wound body in which a long positive electrode sheet 20, a long negative electrode sheet 21, a long first separator 22, and a long second separator 23 are overlapped and wound. The positive electrode sheet 20, the first separator 22, the negative electrode sheet 21, and the second separator 23 are stacked so as to coincide with their respective longitudinal directions. In the laminate before winding, the positive electrode sheet 20, the first separator 22, the negative electrode sheet 21, and the second separator 23 are stacked in the thickness direction in this order.

[0013] The positive electrode sheet 20 is formed by coating both sides of a long positive electrode collector 24 with a positive electrode active material layer 25. The positive electrode sheet 20 also has an uncoated portion 20A which is a portion where the positive electrode collector 24 is exposed without being coated with the positive electrode active material layer 25. A positive electrode external terminal 14 is electrically connected to the uncoated portion 20A.

[0014] The positive electrode active material is a lithium-containing composite metal oxide capable of absorbing and releasing lithium ions, which are charge carriers in the lithium-ion secondary battery 10. The lithium-containing composite oxide is an oxide containing lithium and a metal element other than lithium. The metal element other than lithium is at least one selected from the group consisting of nickel, cobalt, manganese, vanadium, magnesium, molybdenum, niobium, titanium, tungsten, aluminum, and iron contained in the lithium-containing composite oxide as iron phosphate.

[0015] For example, the lithium-containing composite oxide is lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or lithium manganese oxide (LiMn2O4). For example, the lithium-containing composite oxide is a ternary lithium-containing composite oxide containing nickel, cobalt, and manganese, and is lithium nickel cobalt manganese oxide (LiNiCoMnO2). For example, the lithium-containing composite oxide is lithium iron phosphate (LiFePO4).

[0016] The negative electrode sheet 21 has a negative electrode active material layer 27 applied to both sides of a long negative electrode current collector 26. The negative electrode sheet 21 also has an uncoated portion 21A that is a portion where the negative electrode active material layer 27 is not applied and the negative electrode current collector 26 is exposed. A negative electrode external terminal 15 is electrically connected to the uncoated portion 21A.

[0017] The negative electrode active material is a material capable of absorbing and releasing lithium ions. For example, carbon materials such as graphite, non-graphitizable carbon, easily graphitizable carbon, and carbon nanotubes are used as the negative electrode active material. An example of the negative electrode solvent is water. An example of the negative electrode dispersant is carboxymethyl cellulose (CMC). An example of the negative electrode binder is the same as the positive electrode binder. An example of the negative electrode binder is SBR.

[0018] The first separator 22 and the second separator 23 prevent contact between the positive electrode sheet 20 and the negative electrode sheet 21, and retain the nonaqueous electrolyte between the positive electrode sheet 20 and the negative electrode sheet 21. When the electrode body 13 is immersed in the nonaqueous electrolyte, the nonaqueous electrolyte permeates from the ends of the first separator 22 and the second separator 23 toward the center.

[0019] The first separator 22 and the second separator 23 are nonwoven fabrics made of polypropylene, etc. As the first separator 22 and the second separator 23, for example, a porous polymer membrane such as a porous polyethylene membrane, a porous polyolefin membrane, or a porous polyvinyl chloride membrane, an ion-conductive polymer electrolyte membrane, etc. can be used.

[0020] The non-aqueous electrolyte is a composition in which a supporting salt is contained in a non-aqueous solvent. As the non-aqueous solvent, one or more materials selected from the group consisting of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, etc. can be used. In addition, as the supporting salt, one or more lithium compounds (lithium salts) selected from LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiC4F9SO3, LiN(CF3SO2)2, LiC(CF3SO2)3, LiI, etc. can be used.

[0021] Next, the process of reducing pressure inside the battery case 11 in the lithium ion secondary battery 10 according to this embodiment will be described with reference to the flowchart shown in FIG.

[0022] As shown in FIG. 3, first, pressure reduction inside the battery case 11 starts (step S10).

[0023] Next, the battery case 11 is compressed from both sides in the thickness direction (step S11).

[0024] Next, when the amount of compressive displacement of the battery case 11 has not reached the specified value (step S12=NO), the process returns to step S11, and compression of the battery case 11 is continued until the amount of compressive displacement of the battery case 11 reaches the specified value. On the other hand, when the amount of compressive displacement of the battery case 11 reaches the specified value (step S12=YES), the compression of the battery case 11 is released (step S13).

[0025] Next, when the degree of reduced pressure inside the battery case 11 has not reached the target value (step S13=NO), the process returns to step S10, and steps S10 to S13 are repeated until the degree of reduced pressure inside the battery case 11 reaches the target value. On the other hand, when the degree of reduced pressure inside the battery case 11 reaches the target value (step S14=YES), the depressurization process of the battery case 11 shown in FIG. 3 is terminated.

[0026] Next, the operation of the lithium ion secondary battery 10 according to this embodiment will be described.

[0027] As shown in FIG. 4, before the pressure inside the battery case 11 is reduced, air is present in the gaps between the positive electrode sheet 20, the separators 22 and 23, and the negative electrode sheet 21.

[0028] Here, when the battery case 11 is compressed from both sides in the thickness direction while the pressure inside the battery case 11 is reduced, the gaps in each of the positive electrode sheet 20, the separators 22, 23, and the negative electrode sheet 21 are compressed, and the unreduced-pressure air that has entered the gaps is expelled to the outside of the electrode body 13.

[0029] Next, when the compression of the battery case 11 is released, the reduced pressure air inside the battery case 11 enters the respective gaps of the positive electrode sheet 20 , the separators 22 and 23 , and the negative electrode sheet 21 in the electrode body 13 .

[0030] Thereafter, by repeatedly compressing and releasing the battery case 11 while reducing the pressure inside the battery case 11, air with a high degree of reduced pressure enters the gaps in the positive electrode sheet 20, the separators 22, 23, and the negative electrode sheet 21 in the electrode body 13, and the degree of reduced pressure inside the battery case 11 is increased.

[0031] FIG. 5 is a graph showing the transition of the characteristics of the lithium ion secondary battery 10 when the decompression process of the battery case 11 is performed.

[0032] As shown in the figure, in the battery case 11 of the embodiment, the pressure inside the battery case 11 is reduced more quickly during the decompression process than in the battery case of the conventional example. That is, in this embodiment, the time required for the degree of decompression inside the battery case 11 to reach the target value is shortened. Therefore, the inside of the battery case 11 can be decompressed in a short time while preventing damage to the electrode body 13.

[0033] The above embodiment can also be implemented in the following forms.

[0034] In the above embodiment, as shown in Fig. 6A, the side wall of the battery case 11 may be curved in a convex shape toward the inside of the battery case 11. As shown in Fig. 6B, the side wall of the battery case 11 may be bellows-shaped extending in the thickness direction of the battery case 11. As shown in Fig. 6C, the side wall of the battery case 11 may be curved in a convex shape toward the inside of the battery case 11. In these cases, for example, the bottom wall and the side wall of the battery case 11 may be formed of separate members and joined by welding or the like.

[0035] The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The present invention may be modified / improved without departing from the spirit thereof, and equivalents are also included in the present invention. That is, those in which a person skilled in the art appropriately changes the design of each embodiment are also included in the scope of the present invention as long as they have the characteristics of the present invention. For example, the elements and their arrangements, materials, conditions, shapes, sizes, etc. of each embodiment are not limited to those exemplified, and can be appropriately changed. In addition, each embodiment is an example, and it goes without saying that partial replacement or combination of the configurations shown in different embodiments is possible, and these are also included in the scope of the present invention as long as they include the characteristics of the present invention. [Explanation of symbols]

[0036] 10...lithium ion secondary battery, 11...battery case, 12...lid body, 13...electrode body, 14...positive electrode external terminal, 15...negative electrode external terminal, 16...safety valve, 20...positive electrode sheet, 20A...uncoated portion, 21...negative electrode sheet, 21A...uncoated portion, 22...first separator, 23...second separator, 24...positive electrode current collector, 25...positive electrode active material layer, 26...negative electrode current collector, 27...negative electrode active material layer.

Claims

[Claim 1] a decompression process in which a compression process of compressing the battery case from the outside while reducing the pressure inside the battery case in which the electrode body is housed and a load-removal process of releasing the compression of the battery case are repeated until the degree of decompression inside the battery case reaches a predetermined degree of decompression, A method for manufacturing a non-aqueous electrolyte battery.

Images