Method for manufacturing secondary battery

Abstract

Provided is a method for manufacturing a secondary battery capable of reducing the power consumption of a dehumidifier for forming a low dew point environment. A secondary battery (10) is provided with: an electrode laminate (11) in which a positive electrode layer (20) and a negative electrode layer (30) are laminated; and an exterior body (14) that accommodates the electrode laminate (11). This method for manufacturing a secondary battery (10) is provided with: a positive electrode step (S100) in which a positive electrode layer (20) is formed or stored; a negative electrode step (S110) in which the negative electrode layer (30) is formed or stored; and a battery assembly step (S120) in which the positive electrode layer (20) and the negative electrode layer (30) are stacked and housed in the exterior body (14), in which, in accordance with the dew points required for each step, the dehumidified gas sent from the dehumidifier (70) is caused to sequentially flow from the step for which the dew point is low.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a secondary battery. Background Art

[0002] In recent years, in order to ensure that more people have access to affordable, reliable, and sustainable modern energy, research and development related to secondary batteries that contribute to energy efficiency has been carried out.

[0003] When moisture is mixed into the materials constituting the secondary battery, the charge and discharge performance may be reduced, so dew point management is required when manufacturing the secondary battery. For example, Patent Document 1 describes an air circulation system for manufacturing a secondary battery, which is provided with a clean room for storing a manufacturing device for the secondary battery in a drying room, and dehumidifies the interior of the drying room by a dehumidification unit.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Korean Patent Publication No. 10-2022-0046333 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In Patent Document 1, a dehumidifier is operated to maintain a constant low humidity environment in a drying room of a manufacturing apparatus in which a secondary battery is installed. Therefore, the power consumption of the dehumidifier is large, and there is room for improvement in reducing the power consumption.

[0009] The present invention provides a method for manufacturing a secondary battery capable of reducing power consumption of a dehumidifier for forming a low dew point environment, and further contributes to energy efficiency.

[0010] Means for solving problems

[0011] The present invention is a method for manufacturing a secondary battery, the secondary battery comprising: an electrode stack having a positive electrode layer and a negative electrode layer stacked thereon; and an outer casing accommodating the electrode stack, the manufacturing method comprising:

[0012] A positive electrode step of forming or storing the positive electrode layer;

[0013] A negative electrode step of forming or storing the negative electrode layer; and

[0014] A battery assembly step of stacking the positive electrode layer and the negative electrode layer and housing them in the outer casing,

[0015] Here, according to the dew point required for each process, the dehumidified gas sent out from the dehumidifier is circulated in order starting from the process having the lowest dew point.

[0016] Furthermore, the present invention is a method for manufacturing a secondary battery, the secondary battery comprising: an electrode stack having a positive electrode layer and a negative electrode layer stacked thereon; and an outer casing accommodating the electrode stack, the manufacturing method comprising:

[0017] A positive electrode step of forming or storing the positive electrode layer;

[0018] A negative electrode step, forming or storing the negative electrode layer;

[0019] a stack forming step of stacking the positive electrode layer and the negative electrode layer to form the electrode stack, and housing the electrode stack in the outer casing; and

[0020] In a liquid injection step, an electrolyte is injected into the interior of the outer body.

[0021] The manufacturing method further includes a drying step of introducing dehumidified gas sent from a dehumidifier into a drying box before the liquid injection step, and drying the electrode stack accommodated in the outer casing in the drying box.

[0022] Effects of the Invention

[0023] According to the present invention, it is possible to reduce the power consumption of a dehumidifier for forming a low dew point environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a perspective view of the appearance of a secondary battery 10 according to one embodiment of the present invention.

[0025] Figure 2 It is a schematic cross-sectional view of the secondary battery 10 .

[0026] Figure 3 It is a block diagram for explaining a method for manufacturing the secondary battery 10 .

[0027] Figure 4A , Figure 4B and Figure 4C It is a schematic diagram for explaining the drying step S122 in the drying box 80 , the transportation from the drying step S122 to the liquid injection step S123 , and the liquid injection step S123 .

[0028] Description of Reference Numerals

[0029] 10 Secondary batteries

[0030] 11 Electrode stack

[0031] 14 outer body

[0032] 20 Positive electrode layer

[0033] 30 Negative electrode layer

[0034] 70 Dehumidifier

[0035] 80 Drying Oven

[0036] 81 First Space

[0037] 82 Second Space

[0038] 83 Baffle (opening and closing part)

[0039] S100 positive electrode process

[0040] S110 Negative Electrode Process

[0041] S120 battery assembly process

[0042] S121 Laminated body forming process

[0043] S122 Drying process

[0044] S123 Liquid injection process DETAILED DESCRIPTION

[0045] First, a secondary battery according to one embodiment of the present invention will be described.

[0046] [Secondary battery]

[0047] Figure 1 is a perspective view of the appearance of the secondary battery 10. Figure 2 It is a schematic cross-sectional view of the secondary battery 10 .

[0048] The secondary battery 10 includes an electrode stack 11, a positive electrode tab 12 and a negative electrode tab 13 extending from both ends of the electrode stack 11, and an outer casing 14 (e.g., a laminate film) that accommodates the electrode stack 11. The electrode stack 11 includes: a positive electrode layer 20 to which the positive electrode tab 12 is welded; a negative electrode layer 30 to which the negative electrode tab 13 is welded; and a separator 40 disposed between the positive electrode layer 20 and the negative electrode layer 30. Figure 2 In the example shown, the electrode stack 11 is composed of only one positive electrode layer 20 , one separator 40 , and one negative electrode layer 30 , but may have a structure in which a plurality of positive electrode layers 20 , separators 40 , and negative electrode layers 30 are stacked.

[0049] The secondary battery 10 is formed by sealing a stacked positive electrode layer 20 , a negative electrode layer 30 , and a separator 40 together with an electrolyte solution inside an outer casing 14 , and charging and discharging are performed by transferring lithium ions between the positive electrode layer 20 and the negative electrode layer 30 via the electrolyte solution.

[0050] The positive electrode layer 20 includes a positive electrode collector layer 21 and a positive electrode active material layer 22 which are stacked on each other.

[0051] The positive electrode current collector layer 21 is preferably composed of at least one substance having high electrical conductivity. Examples of highly conductive substances include metals or alloys containing at least one metal element of silver, palladium, gold, platinum, aluminum, copper, chromium, and nickel, or non-metals such as carbon. When considering not only high electrical conductivity but also manufacturing cost, aluminum, nickel, or stainless steel is preferred.

[0052] The positive electrode collector layer 21 may be in a foil, plate, mesh, nonwoven fabric, foam, etc. In order to improve adhesion with the positive electrode active material layer 22, carbon or the like may be disposed on the surface of the positive electrode collector layer 21, or the surface may be roughened.

[0053] The positive electrode active material layer 22 contains a positive electrode active material that transfers lithium ions and electrons. There is no particular limitation on the positive electrode active material, as long as it is a material that can reversibly release and absorb lithium ions and can transfer electrons. For example, the positive electrode active material can include lithium cobalt oxide (LiCoO2), lithium composite oxides such as lithium-manganese-nickel-cobalt oxide, etc. In addition, the positive electrode active material layer 22 can be composed of one material or two or more materials. In addition, the positive electrode active material layer 22 can also include a conductive additive, a binder, etc.

[0054] The negative electrode layer 30 includes a negative electrode collector layer 31 and a negative electrode active material layer 32 which are stacked on each other.

[0055] Similar to the positive electrode collector layer 21, the negative electrode collector layer 31 is preferably composed of at least one substance having high electrical conductivity, for example, a metal or alloy containing at least one metal element of silver, palladium, gold, platinum, aluminum, copper, chromium and nickel, or a non-metal such as carbon.

[0056] The shape of the negative electrode collector layer 31 may be, for example, foil, plate, mesh, nonwoven fabric, foam, etc. In order to improve adhesion with the negative electrode active material layer 32, carbon or the like may be disposed on the surface of the negative electrode collector layer 31, or the surface may be roughened.

[0057] The negative electrode active material layer 32 contains a negative electrode active material that transfers lithium ions and electrons. There is no particular limitation on the negative electrode active material, as long as it is a material that can reversibly release and absorb lithium ions and can transfer electrons. For example, as negative electrode active materials, metallic lithium, lithium alloys, metal oxides, metal sulfides, metal nitrides, Si, SiO, carbon materials (graphite, hard carbon, soft carbon, etc.), etc. can be listed. In addition, the negative electrode active material can be composed of one material or two or more materials. In addition, the negative electrode active material layer 32 can also include a conductive additive, a binder, etc.

[0058] The separator 40 is an insulator composed of, for example, a non-woven fabric of glass fiber, a porous resin film, etc., and is impregnated with an electrolyte. The separator 40 is between the positive electrode layer 20 and the negative electrode layer 30, thereby avoiding a short circuit between them. There is no particular limitation on the material constituting the separator 40, and examples thereof include polyolefins such as polyethylene and polypropylene, aromatic polyamides, polyimides, fluororesins, glass fibers, cellulose fibers, etc. In particular, in the separator 40 having an inorganic particle layer on the separator 40, it is necessary to dry and remove the moisture re-adsorbed on the surface of the inorganic particles, which is effective in combination with the manufacturing method of the secondary battery of the present invention described later.

[0059] The electrolyte solution is, for example, an organic electrolyte solution in which an electrolyte is dissolved in an organic solvent. The organic solvent may be a cyclic carbonate, a chain carbonate, a cyclic ether, a chain ether, a hydrofluoroether, an aromatic ether, a sulfone, a cyclic ester, a chain carboxylic acid ester, or a nitrile, and examples thereof include propylene carbonate, ethylene carbonate, diethyl carbonate, methyl ethyl carbonate, and diethylene glycol dimethyl ether. Examples of cyclic ethers include tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, and 4-methyl 1,3-dioxolane. Examples of chain ethers include 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane, and diethyl ether. As examples of hydrofluoroethers, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane, etc. can be cited. These organic solvents can be used alone or in a variety of mixed forms. In addition, electrolytes can include lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethanesulfonyl imide), etc. These electrolytes can be used alone or in a variety of mixed forms.

[0060] [Method for producing secondary battery]

[0061] Next, regarding a method for manufacturing a secondary battery according to an embodiment of the present invention, first, an overview of the manufacturing method will be described, and then, dew point management during manufacturing will be described.

[0062] (Outline of Manufacturing Method)

[0063] Figure 3 The manufacturing method of the secondary battery 10 of the present embodiment comprises: a positive electrode step S100 for forming or storing the positive electrode layer 20; a negative electrode step S110 for forming or storing the negative electrode layer 30; a battery assembly step S120 for stacking the positive electrode layer 20 and the negative electrode layer 30 and storing them in the outer body 14; and a formation step S130 for forming the secondary battery 10.

[0064] The positive electrode step S100 includes, for example, a coating step of coating the positive electrode active material on the positive electrode collector layer 21 to form the positive electrode active material layer 22; a stamping step of pressing the stacked positive electrode collector layer 21 and the positive electrode active material layer 22 using a roller press or the like to form the positive electrode layer 20; and a cutting step of cutting the positive electrode layer 20 after the stamping step into a predetermined size, etc. In addition, the positive electrode step S100 may also include a storage step of storing (including temporary storage) the positive electrode layer 20 after the positive electrode layer 20 is formed and before the battery assembly step S120, or storing the purchased positive electrode layer 20 when the positive electrode layer 20 is purchased separately without providing a step for forming the positive electrode layer 20 on the production line.

[0065] Similar to the positive electrode step S100, the negative electrode step S110 also includes, for example: a coating step of coating the negative electrode active material on the negative electrode collector layer 31 to form the negative electrode active material layer 32; a stamping step of pressing the stacked negative electrode collector layer 31 and the negative electrode active material layer 32 using a roller press or the like to form the negative electrode layer 30; and a cutting step of cutting the negative electrode layer 30 after the stamping step into a predetermined size, etc. In addition, the negative electrode step S110 may also include: a storage step of storing (including temporary storage) the negative electrode layer 30 after the negative electrode layer 30 is formed and before the battery assembly step S120, or storing the purchased negative electrode layer 30 when the negative electrode layer 30 is purchased separately without providing a step for forming the negative electrode layer 30 on the production line.

[0066] The battery assembly process S120 includes: a stack forming process S121, stacking the positive electrode layer 20 and the negative electrode layer 30 to form an electrode stack 11, and housing the electrode stack 11 in an outer casing 14; a drying process S122, drying the electrode stack 11 housed in the outer casing 14; and a liquid injection process S123, injecting the electrolyte into the interior of the outer casing 14.

[0067] The stack forming process S121 includes, for example: an electrode stacking process, stacking the positive electrode layer 20 and the negative electrode layer 30 via the separator 40 to form the electrode stack 11; a tab welding process, welding the positive electrode tab 12 and the negative electrode tab 13 to the positive electrode layer 20 and the negative electrode layer 30 respectively; and a housing process, housing the electrode stack 11 in the outer casing 14, etc.

[0068] The drying step S122 is a step of drying the electrode stack 11 housed in the outer body 14 under an extremely low dew point environment before the liquid injection step S123 is performed. Although the details will be described later, in the drying step S122, the electrode stack 11 is left to stand for a predetermined time in the drying box 80 into which the dehumidified air sent from the dehumidifier 70 is introduced and dried. The drying box 80 does not include a stacking machine, a welding device, a laminating seal, and other devices and equipment groups, so the inside of the drying box 80 can be minimized, and the gas replacement speed is high, so the electrode stack 11 can be dried in a shorter residence time. In addition, the dehumidified air in the drying box 80 is preferably higher than the room temperature, for example, by passing dehumidified air at 30°C to 80°C, the drying time can be shortened. In addition, not only the dehumidified air, but also when a low-moisture gas such as dry nitrogen and argon flows into the drying box 80, the drying time can be further shortened.

[0069] In the liquid injection step S123, the electrolyte is injected into the interior of the outer body 14 under an extremely low dew point environment, and the outer body 14 is sealed. In this embodiment, the liquid injection step S123 is also performed in the drying box 80, similarly to the drying step S122. Before the liquid injection step S123, the electrode stack 11 is dried in the drying step S122, so that water can be suppressed from mixing into the electrolyte. After the liquid injection, the opening of the outer body 14 is temporarily sealed by thermal welding.

[0070] The chemical conversion step S130 includes, for example, an aging step of allowing the battery to stand for a predetermined period of time while being charged, etc. After the chemical conversion step S130 , the temporarily sealed opening of the outer casing 14 is resealed.

[0071] (Dew point management)

[0072] When manufacturing the secondary battery 10, if moisture is mixed into the materials constituting the secondary battery 10, the charge and discharge performance of the secondary battery 10 may be reduced, so it is necessary to manage the dew point in each process included in the production line of the secondary battery 10. Here, the dew point substantially indicates the dryness of the space, and the lower the dew point, the higher the dryness of the space, and the higher the dew point, the lower the dryness of the space.

[0073] For example, when manufacturing a lithium ion battery using graphite as the negative electrode active material, the entire manufacturing process is usually formed into an environment with a low dew point (for example, a dew point of -40°C or less). In addition, when manufacturing a lithium metal secondary battery using lithium metal as the negative electrode active material, since lithium metal has a high ionization tendency and high reactivity with water, an environment with a lower dew point (for example, a dew point of -50°C or less) is required in the step of exposing the negative electrode layer 30 in the manufacturing process.

[0074] The environment with a low dew point (hereinafter also referred to as a low dew point environment) is formed by supplying and discharging dehumidified air generated by dehumidifying to a low dew point by the dehumidifier 70 to the production line of the secondary battery 10. The production line is an environment where moisture is always generated by workers working in each process, so the dehumidifier 70 continuously supplies dehumidified air. In addition, the dehumidifier 70 is configured to be able to adjust the air volume of the dehumidified air (the amount of dehumidified air passing per unit time), and the dew point of the dehumidified air supplied to the production line is adjusted by adjusting the air volume. In the manufacture of the secondary battery 10, the power consumption generated by the operation of the dehumidifier 70 is relatively large.

[0075] In order to achieve the same low dew point environment for the entire production line, the volume of dehumidified air delivered from the dehumidifier needs to be increased due to the large space volume of the dehumidified air supply destination, and the power consumption of the dehumidifier further increases. In addition, equipment investment is required, such as increasing the number of dehumidifiers installed, and accordingly, the power consumption generated by the operation of multiple dehumidifiers also increases further. As a result, the manufacturing cost of the secondary battery 10 increases.

[0076] Therefore, in the manufacturing method of the secondary battery 10 of the present embodiment, the dehumidified air sent from the dehumidifier 70 is circulated in order from the process with the lowest required dew point according to the dew point required by each process. As a result, it is not necessary to form all processes into the same low dew point environment according to the process requiring the lowest dew point, so that the power consumption generated by the operation of the dehumidifier 70 can be reduced. In addition, the increase in the equipment investment of the dehumidifier 70 can be suppressed. Therefore, the manufacturing cost of the secondary battery 10 can be reduced.

[0077] The dew point management will be described in more detail below. In the following description, a case where the secondary battery 10 is a lithium metal secondary battery having a high energy density is taken as an example, and a specific dew point value is described as an example.

[0078] Lithium metal secondary batteries contain lithium metal in the negative electrode active material, which has a high reactivity with water. Therefore, the dew point is strictly managed in the negative electrode process S110 to form a low dew point environment. The positive electrode process S100 does not need to be managed as a low dew point as the negative electrode process S110, and its dew point is managed to be higher than the dew point of the negative electrode process S110. The battery assembly process S120 is a downstream process in the manufacturing process of the secondary battery 10. In order to prevent moisture from mixing in before the assembly of the secondary battery 10 is about to be completed, the dew point management is more strictly performed to form a dew point lower than that of the negative electrode process S110. That is, in the order of the positive electrode process S100, the negative electrode process S110 and the battery assembly process S120, the required dew point decreases successively.

[0079] Therefore, the dehumidifier 70 circulates the dehumidified air in the order of the battery assembly process S120, the negative electrode process S110, and the positive electrode process S100. At this time, the dew point of the dehumidified air is the lowest in the battery assembly process S120 on the side close to the dehumidifier 70, and gradually increases in the order of the negative electrode process S110 and the positive electrode process S100. By circulating the dehumidified air in this order, the dew point required by each process can be met without forming all processes into the same low dew point environment, so the power consumption generated by the operation of the dehumidifier 70 can be reduced.

[0080] More specifically, the dehumidifier 70 circulates the dehumidified air from the drying step S122 and the liquid injection step S123 in the manufacturing process. In other words, the dehumidifier 70 first supplies the dehumidified air to the drying box 80 .

[0081] A plurality of pipes (not shown) are provided in the production line of the secondary battery 10 to circulate the dehumidified air sent from the dehumidifier 70. The plurality of pipes are provided between the air supply port of the dehumidifier 70 and the drying box 80 (i.e., the space where the drying step S122 and the liquid injection step S123 are performed), between the drying box 80 and the space 91 where the negative electrode step S110 and the laminate forming step S121 are performed, between the space 91 and the space 92 where the positive electrode step S100 is performed, and between the space 92 and the air inlet of the dehumidifier 70.

[0082] The dehumidified air generated by the dehumidifier 70 has a dew point of, for example, -80°C, and the moisture content of the dehumidified air is 1 ppm or less. When the dehumidified air is supplied to the drying box 80, the dew point of the drying box 80 is, for example, -60°C or less, forming an extremely low dew point environment. Thus, the dew point required in the drying step S122 and the liquid injection step S123 is satisfied.

[0083] The dew point of the dehumidified air discharged from the drying box 80 and supplied to the space 91 where the negative electrode step S110 and the laminate forming step S121 are performed is substantially the same as the dew point in the drying box 80, for example, -60°C. When the dehumidified air is supplied to the space 91, the dew point of the space 91 is, for example, -60°C to -50°C. Although the dew point of the space 91 is higher than that of the drying box 80, since the negative electrode step S110 and the laminate forming step S121 are performed in a state where the negative electrode layer 30 is exposed (that is, the negative electrode layer 30 is not sealed by the outer body 14), a low dew point environment is required. As a result, the dew point required in the negative electrode step S110 and the laminate forming step S121 is satisfied.

[0084] The dew point of the dehumidified air discharged from the space 91 and introduced into the space 92 where the positive electrode step S100 is performed is substantially the same as the dew point of the space 91, for example, -50° C. When the dehumidified air is supplied to the space 92, the dew point of the space 92 is, for example, -50° C. to -40° C. Thus, the dew point required in the positive electrode step S100 is satisfied.

[0085] Dehumidified air (eg, dew point -40°C) exhausted from space 92 is introduced into dehumidifier 70, dehumidified to a dew point of -80°C, and then supplied to drying box 80 again. Dehumidifier 70 circulates the dehumidified air from downstream to upstream of the production line of secondary batteries 10.

[0086] Figure 4A , Figure 4B and Figure 4C This is a schematic diagram for explaining the drying box 80. The drying box 80 is a local space where no one enters or leaves, and prevents moisture generated by the human body from mixing into the electrode stack 11.

[0087] The drying box 80 has a first space 81 and a second space 82 separated by an openable and closable baffle 83. The second space 82 is located downstream of the production line relative to the first space 81. The first space 81 and the second space 82 are separated by the baffle 83, but dehumidified air is introduced from the dehumidifier 70 to each other, and the dew points are substantially the same.

[0088] After the stack forming step S121, the electrode stack 11 housed in the outer package 14 is transported to the first space 81, and a drying step S122 is performed in the first space 81 ( Figure 4A In the drying step S122, the dew point and drying time of the first space 81 are managed so as to remove as much water as possible contained in the electrode stack 11 before the liquid injection step S123.

[0089] As described above, the dew point of the first space 81 is below -60°C, and the drying time is, for example, more than 1 minute and within 72 hours. More specifically, the drying time is adjusted according to the dew point of the first space 81. For example, when the dew point of the first space 81 is -70°C, if the drying time is set to 3 hours, the electrode stack 11 can be fully dried. In this embodiment, dehumidified air is circulated not only in the drying process S122, but also in the processes (positive electrode process S100, negative electrode process S110, and stack forming process S121) upstream of the drying process S122 to form a low dew point environment, so that the drying time in the drying process S122 can be shortened, and the power consumption of the dehumidifier 70 can be reduced.

[0090] After the drying step S122, the shutter 83 is opened to transfer the electrode stack 11 housed in the outer package 14 from the first space 81 to the second space 82 ( Figure 4B). After the electrode stack 11 is transported to the second space 82, the baffle 83 is closed. Although not shown in the figure, after the electrode stack 11 is transported from the first space 81 to the second space 82, a new electrode stack 11 is transported to the first space 81, and the electrode stack 11 is subjected to the drying step S122.

[0091] In the second space 82, the liquid injection step S123 is performed ( Figure 4C ). Like the drying step S122, the liquid injection step S123 is also performed under an extremely low dew point environment. In this way, the drying step S122 and the liquid injection step S123 are performed continuously in the drying box 80.

[0092] When the secondary battery 10 is a lithium metal secondary battery, a water-insoluble organic electrolyte is injected into the interior of the outer casing 14. The water content of the electrolyte at this time is, for example, 50 ppm or less, and an electrolyte having an extremely low water content is injected.

[0093] After the liquid injection step S123, the outer casing 14 is temporarily sealed in the second space 82 by heat welding or the like. Thus, the electrode stack 11 and the electrolyte are sealed inside the outer casing 14, and moisture does not penetrate into the electrode stack 11 and the electrolyte, so that dew point management is not required in the subsequent steps (i.e., the formation step S130).

[0094] The dew point management in the method for manufacturing the secondary battery 10 described above is applicable regardless of whether the secondary battery 10 is a liquid battery including a liquid electrolyte, a semi-solid battery including a semi-solid electrolyte, or an all-solid battery including a solid electrolyte.

[0095] When the secondary battery 10 is a semi-solid battery, in the injection step S123, a semi-solid electrolyte is injected into the outer casing 14. Here, the semi-solid electrolyte is a mixture of a liquid phase and a solid phase such as slurry, particle suspension, colloidal suspension, emulsion, gel, or micelle.

[0096] When the secondary battery 10 is an all-solid-state battery, the electrode stack 11 of the secondary battery 10 includes a solid electrolyte layer provided between the positive electrode layer 20 and the negative electrode layer 30 instead of the separator 40. The above-mentioned liquid injection step S123 is omitted, and the outer body 14 is sealed after the drying step S122.

[0097] Above, one embodiment of the present invention has been described with reference to the accompanying drawings, but the present invention is certainly not limited to this embodiment. Obviously, those skilled in the art can think of various variations or modifications within the scope of the technical solution, and it should be understood that these variations and modifications also belong to the technical scope of the present invention. In addition, the various constituent elements in the above-mentioned embodiment can also be arbitrarily combined within the scope of the main purpose of the invention.

[0098] For example, in the case where the secondary battery 10 is a lithium metal secondary battery, a passivation layer containing lithium carbonate (Li2CO3) can be formed on the surface of the negative electrode layer 30 containing metallic lithium. In this way, by forming a passivated layer on the surface of the negative electrode layer 30, the reaction between metallic lithium and water can be further suppressed. When the surface of the lithium metal negative electrode is modified, the reaction with water can be reduced, so that water is not easy to react with lithium to form an adsorbed state. As a result, water can be removed faster. In this case, the residence time of the electrode stack 11 in the drying box 80 with a low dew point can be further shortened, so the production speed of the secondary battery 10 can be further increased.

[0099] In the above embodiment, the dew point management is described by taking the case where the secondary battery 10 is a lithium metal secondary battery as an example, but the secondary battery 10 is not limited to a lithium metal secondary battery, and the dew point management can be applied to various types of batteries.

[0100] At least the following matters are described in this specification: In parentheses, corresponding components in the above-mentioned embodiment are shown as an example, but the present invention is not limited to this.

[0101] (1) A method for manufacturing a secondary battery (secondary battery 10), the secondary battery comprising: an electrode stack (electrode stack 11) in which a positive electrode layer (positive electrode layer 20) and a negative electrode layer (negative electrode layer 30) are stacked; and an outer casing (outer casing 14) that houses the electrode stack, the manufacturing method comprising:

[0102] A positive electrode step (positive electrode step S100 ), forming or storing the positive electrode layer;

[0103] A negative electrode step (negative electrode step S110 ), forming or storing the negative electrode layer; and

[0104] a battery assembly step (battery assembly step S120 ) of stacking the positive electrode layer and the negative electrode layer and housing them in the outer casing;

[0105] Here, according to the dew point required for each process, the dehumidified gas sent from the dehumidifier (dehumidifier 70) is circulated in order from the process having the lowest dew point.

[0106] According to (1), dehumidified gas is circulated in order from the process with the lowest dew point according to the dew point required by each process, so that the power consumption generated by the operation of the dehumidifier can be reduced compared with the case where the same low dew point environment is achieved in all processes when manufacturing secondary batteries. Therefore, the manufacturing cost of the secondary batteries can be reduced.

[0107] (2) The method for manufacturing a secondary battery according to (1), wherein:

[0108] According to the order of the positive electrode process, the negative electrode process and the battery assembly process, the required dew point decreases successively.

[0109] The dehumidified gas sent from the dehumidifier is circulated in the order of the battery assembly process, the negative electrode process, and the positive electrode process.

[0110] According to (2), the dehumidified gas is circulated from the battery assembly process near the downstream side in the manufacturing process, so that the mixing of moisture before the secondary battery is completed can be suppressed. In addition, compared with the positive electrode process, the dehumidified gas is preferentially circulated to the negative electrode process where the negative electrode layer with high reactivity with moisture is exposed and a low dew point is required, so that the mixing of moisture into the negative electrode layer can be suppressed.

[0111] (3) The method for manufacturing a secondary battery according to (2), wherein:

[0112] The battery assembly process includes:

[0113] a stack forming step (stack forming step S121 ) of stacking the positive electrode layer and the negative electrode layer to form the electrode stack, and housing the electrode stack in the outer casing; and

[0114] In a drying step (drying step S122 ), the electrode stack accommodated in the outer package is dried in a drying oven (drying oven 80 ).

[0115] The drying process requires the lowest dew point.

[0116] The dehumidified gas sent out from the dehumidifier is circulated from the drying step.

[0117] According to (3), by partially drying the electrode stack in a drying oven in a drying process close to the downstream side of the manufacturing process, it is possible to more reliably suppress the mixing of moisture into the electrode stack. In addition, since the dew point gradually decreases toward the downstream side of the manufacturing process, the drying time in the drying process can be shortened, and the power consumption of the dehumidifier can be further reduced.

[0118] (4) The method for manufacturing a secondary battery according to (3), wherein:

[0119] The battery assembly process further includes: a liquid injection process (liquid injection process S123), in which electrolyte is injected into the interior of the outer casing after the drying process.

[0120] The liquid injection process is performed in the drying oven.

[0121] According to (4), since the drying step is performed before the liquid injection step, mixing of water into the electrolyte can be suppressed.

[0122] (5) The method for manufacturing a secondary battery according to (4), wherein:

[0123] The drying box includes a first space (first space 81) and a second space (second space 82) partitioned by an opening and closing member (damping plate 83) that can be opened and closed.

[0124] In the first space, the drying process is performed in a state where the opening and closing member is closed.

[0125] After the drying step, the opening and closing member is opened to transport the electrode stack accommodated in the outer casing from the first space to the second space.

[0126] In the second space, the liquid injection step is performed in a state where the opening and closing member is closed.

[0127] According to (5), the drying step and the liquid injection step can be continuously performed in the drying oven.

[0128] (6) The method for manufacturing a secondary battery according to (4) or (5), wherein:

[0129] The water content of the electrolyte injected into the interior of the outer casing in the liquid injection step is 50 ppm or less.

[0130] According to (6), the electrolyte having an extremely low water content is injected into the interior of the outer casing in the liquid injection step.

[0131] (7) The method for manufacturing a secondary battery according to any one of (3) to (6), wherein:

[0132] In the drying step, the electrode stack accommodated in the outer casing is dried at a predetermined dew point for a predetermined time.

[0133] According to (7), by managing the dew point and the drying time in the drying step, it is possible to more reliably suppress the incorporation of moisture into the electrode stack.

[0134] (8) The method for manufacturing a secondary battery according to (7), wherein:

[0135] The prescribed dew point is -60°C or lower.

[0136] According to (8), the electrode stack is locally dried in an environment with an extremely low dew point, so that it is possible to more reliably suppress the incorporation of moisture into the electrode stack and to desorb adsorbed moisture in a short time.

[0137] (9) The method for manufacturing a secondary battery according to (7) or (8), wherein:

[0138] The predetermined time is greater than or equal to 1 minute and less than or equal to 72 hours.

[0139] According to (9), the drying process is performed in a short time, so the power consumption of the dehumidifier can be greatly reduced.

[0140] (10) The method for manufacturing a secondary battery according to any one of (3) to (9), wherein:

[0141] The moisture content of the dehumidified gas introduced into the drying oven is 1 ppm or less.

[0142] According to (10), the electrode stack is locally dried in an environment with an extremely low dew point, so that mixing of moisture into the electrode stack can be more reliably suppressed.

[0143] (11) The method for manufacturing a secondary battery according to any one of (3) to (10), wherein:

[0144] The drying box is a space where no one enters or leaves.

[0145] According to (11), it is possible to prevent moisture generated by the human body from entering the drying box, and the interior of the drying box can be made into an environment with an extremely low dew point.

[0146] (12) The method for manufacturing a secondary battery according to any one of (1) to (11), wherein:

[0147] The secondary battery is a lithium metal secondary battery in which the negative electrode active material of the negative electrode layer includes lithium metal.

[0148] According to (12), the negative electrode active material contains lithium metal which is highly reactive with water. Even when an extremely low dew point environment is required, the power consumption and the number of dehumidifiers installed can be reduced, and the manufacturing cost of the secondary battery can be reduced.

[0149] (13) The method for manufacturing a secondary battery according to (12), wherein:

[0150] A passivation layer containing lithium carbonate is formed on the surface of the negative electrode layer.

[0151] According to (13), in the lithium metal secondary battery, the moisture reaction in the negative electrode layer can be suppressed.

[0152] (14) A method for manufacturing a secondary battery (secondary battery 10), the secondary battery comprising: an electrode stack (electrode stack 11) in which a positive electrode layer (positive electrode layer 20) and a negative electrode layer (negative electrode layer 30) are stacked; and an outer casing (outer casing 14) that houses the electrode stack, the manufacturing method comprising:

[0153] A positive electrode step (positive electrode step S100 ), forming or storing the positive electrode layer;

[0154] A negative electrode step (negative electrode step S110 ), forming or storing the negative electrode layer;

[0155] a stack forming step (stack forming step S121 ) of stacking the positive electrode layer and the negative electrode layer to form the electrode stack, and housing the electrode stack in the outer casing; and

[0156] In a liquid injection step (liquid injection step S123), an electrolyte is injected into the interior of the outer body.

[0157] The manufacturing method further includes a drying step (drying step S122 ) in which dehumidified gas sent from a dehumidifier (dehumidifier 70 ) is introduced into a drying box (drying box 80 ) before the liquid injection step, and the electrode stack accommodated in the outer casing is dried in the drying box.

[0158] According to (14), by partially drying the electrode stack in a drying oven in the downstream drying step in the manufacturing process, it is possible to more reliably suppress the incorporation of water into the electrode stack. In addition, since the drying step is performed before the liquid injection step, it is possible to suppress the incorporation of water into the electrolyte.

Claims

1. A method for manufacturing a secondary battery, the secondary battery comprising: an electrode stack having a positive electrode layer and a negative electrode layer stacked thereon; and an outer casing housing the electrode stack, wherein: The secondary battery manufacturing method comprises: A positive electrode step of forming or storing the positive electrode layer; A negative electrode step of forming or storing the negative electrode layer; and A battery assembly step of stacking the positive electrode layer and the negative electrode layer and housing them in the outer casing, According to the dew point required for each process, the dehumidified gas sent out from the dehumidifier is circulated in order starting from the process having the lowest dew point.

2. The method for manufacturing a secondary battery according to claim 1, wherein: According to the order of the positive electrode process, the negative electrode process and the battery assembly process, the required dew point decreases successively. The dehumidified gas sent from the dehumidifier is circulated in the order of the battery assembly process, the negative electrode process, and the positive electrode process.

3. The method for manufacturing a secondary battery according to claim 2, wherein: The battery assembly process includes: a stack forming step of stacking the positive electrode layer and the negative electrode layer to form the electrode stack, and housing the electrode stack in the outer casing; and a drying step of drying the electrode stack housed in the outer casing in a drying oven, The drying process requires the lowest dew point. The dehumidified gas sent out from the dehumidifier is circulated from the drying step.

4. The method for manufacturing a secondary battery according to claim 3, wherein: The battery assembly process further includes: a liquid injection process of injecting electrolyte into the interior of the outer body after the drying process; The liquid injection process is performed in the drying oven.

5. The method for manufacturing a secondary battery according to claim 4, wherein: The drying box has a first space and a second space separated by an opening and closing member that can be opened and closed. In the first space, the drying process is performed in a state where the opening and closing member is closed. After the drying step, the opening and closing member is opened to transport the electrode stack accommodated in the outer casing from the first space to the second space. In the second space, the liquid injection step is performed in a state where the opening and closing member is closed.

6. The method for manufacturing a secondary battery according to claim 4, wherein: The water content of the electrolyte injected into the interior of the outer casing in the liquid injection step is 50 ppm or less.

7. The method for manufacturing a secondary battery according to claim 3, wherein: In the drying step, the electrode stack accommodated in the outer casing is dried at a predetermined dew point for a predetermined time.

8. The method for manufacturing a secondary battery according to claim 7, wherein: The prescribed dew point is -60°C or lower.

9. The method for manufacturing a secondary battery according to claim 7, wherein: The predetermined time is greater than or equal to 1 minute and less than or equal to 72 hours.

10. The method for manufacturing a secondary battery according to claim 3, wherein: The moisture content of the dehumidified gas introduced into the drying oven is 1 ppm or less.

11. The method for manufacturing a secondary battery according to claim 3, wherein: The drying box is a space where no one enters or leaves.

12. The method for manufacturing a secondary battery according to any one of claims 1 to 11, wherein: The secondary battery is a lithium metal secondary battery in which the negative electrode active material of the negative electrode layer includes lithium metal.

13. The method for manufacturing a secondary battery according to claim 12, wherein: A passivation layer containing lithium carbonate is formed on the surface of the negative electrode layer.

14. A method for manufacturing a secondary battery, the secondary battery comprising: an electrode stack having a positive electrode layer and a negative electrode layer stacked thereon; and an outer casing housing the electrode stack, wherein: The secondary battery manufacturing method comprises: A positive electrode step of forming or storing the positive electrode layer; A negative electrode step, forming or storing the negative electrode layer; a stack forming step of stacking the positive electrode layer and the negative electrode layer to form the electrode stack, and housing the electrode stack in the outer casing; as well as In a liquid injection step, an electrolyte is injected into the interior of the outer body. The secondary battery manufacturing method further includes a drying step of introducing dehumidified gas sent from a dehumidifier into a drying box before the liquid injection step, and drying the electrode stack accommodated in the outer casing in the drying box.

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