Method for manufacturing power storage device

Abstract

To provide a method for manufacturing a power storage device that can non-destructively measure the amount of moisture in a battery module.SOLUTION: A method for manufacturing a power storage device according to the present disclosure includes a step ST6 of assembling a battery module MJ, a step ST7 of accommodating the battery module MJ in a reduced pressure chamber LC, and then venting the air in the reduced pressure chamber LC through a pipe 4 equipped with a dew point meter 2 to reduce the pressure in the reduced pressure chamber LC and measure the moisture content of the air in the reduced pressure chamber LC, a step ST8 of calculating the moisture content in the battery module MJ from the measured moisture content of the air in the reduced pressure chamber LC using a calibration curve showing the relationship between the moisture content of the air in the reduced pressure chamber LC and the moisture content in the battery module MJ, and a step ST9 of injecting an electrolyte into the battery module MJ.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing an electricity storage device. [Background technology]

[0002] In the method for manufacturing a non-aqueous electrolyte secondary battery disclosed in Patent Document 1, first, at least a negative electrode active material, a binder, and water are mixed to prepare a negative electrode active material slurry. The negative electrode active material slurry is then applied to a negative electrode core to obtain a coated electrode plate. Water is then volatilized from the coated electrode plate in an atmosphere at a temperature of 55 to 70°C and a relative humidity of 30% or less, and the applied negative electrode active material slurry becomes a negative electrode active material layer. The negative electrode active material layer is then rolled to obtain a negative electrode plate. A separately prepared positive electrode plate, a negative electrode plate, and a separator are wound together to obtain an electrode assembly. The electrode assembly is placed in a battery case, and a non-aqueous electrolyte is poured into the battery case. The opening of the battery case is sealed to obtain a battery.

[0003] On the other hand, there is an energy storage device that includes an electrode stack and a sealing body. The electrode stack is formed by stacking multiple bipolar electrodes. The sealing body seals the side surfaces of the bipolar electrodes in the electrode stack that extend in the stacking direction. The sealing body seals the space between adjacent current collectors in the stacking direction. The space is defined by the sealing body and the adjacent current collectors in the stacking direction. An electrolyte is accommodated in the space. The multiple bipolar electrodes include a pair of electrodes that are formed by a current collector and active material layers provided on a first surface and a second surface of the current collector. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-181967 Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors of the present application have discovered the following problems. In such a manufacturing method for an energy storage device, a battery module is assembled by stacking multiple battery cells, etc. Then, an electrolyte is supplied into the battery module to obtain the energy storage device. The amount of moisture in the battery module affects the performance of the energy storage device. Therefore, it is desirable to measure the amount of moisture in the battery module. The amount of moisture in the battery module can be measured by cutting some of the multiple battery modules. However, some of the battery modules are destroyed by the cutting required for measuring the amount of moisture. It has been difficult to measure the amount of moisture in a battery module non-destructively.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and provides a method for manufacturing an electricity storage device that can measure the amount of water in a battery module non-destructively. [Means for solving the problem]

[0007] A method for manufacturing an electricity storage device according to the present disclosure includes: Assembling a battery module; a step of accommodating the battery module in a decompression chamber, and then evacuating the air in the decompression chamber through a pipe provided with a dew point meter, thereby reducing the pressure in the decompression chamber, and measuring the moisture content of the air in the decompression chamber; calculating the amount of moisture in the battery module from the measured amount of moisture in the air in the decompression chamber using a calibration curve that indicates the relationship between the amount of moisture in the air in the decompression chamber and the amount of moisture in the battery module; and injecting an electrolyte into the battery module. [Effects of the Invention]

[0008] According to the present disclosure, the amount of water in a battery module can be measured non-destructively. [Brief explanation of the drawings]

[0009] [Figure 1] 5 is a flowchart showing an example of a method for manufacturing the electricity storage device according to the first embodiment. [Figure 2] 1 is a schematic diagram showing an example of the configuration of a moisture content measuring device according to a first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, the following description and drawings have been simplified as appropriate for clarity of explanation.

[0011] <First Embodiment> A first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a flowchart showing an example of a method for manufacturing an electricity storage device according to the first embodiment. Figure 2 is a schematic diagram showing an example of the configuration of a moisture content measuring device according to the first embodiment.

[0012] Naturally, the right-handed XYZ coordinate system shown in Figure 2 is a convenient way to explain the positional relationships of the components. Normally, the positive Z axis is vertically upward, and the XY plane is a horizontal plane, which is common among all drawings.

[0013] The power storage device manufactured using this manufacturing method may be a non-aqueous battery. A non-aqueous battery is a battery that does not contain water in the electrolyte. Examples of non-aqueous batteries include lithium ion secondary batteries, nickel-metal hydride secondary batteries, and sodium ion secondary batteries. The power storage device according to the first embodiment is a lithium ion secondary battery. The power storage device manufactured using this manufacturing method may be a bipolar battery. The power storage device manufactured using this manufacturing method may be an electric double layer capacitor or an all-solid-state battery.

[0014] Specifically, the energy storage device manufactured using this manufacturing method includes an electrode stack and a sealing body. The electrode stack is formed by stacking multiple bipolar electrodes. The sealing body seals the side surfaces of the bipolar electrodes in the electrode stack, which extend in the stacking direction. The sealing body also seals the space between adjacent current collectors in the stacking direction. The space is defined by the sealing body and the adjacent current collectors in the stacking direction. An electrolyte is accommodated in the space. The multiple bipolar electrodes include a pair of electrodes each composed of a current collector and active material layers provided on a first surface and a second surface of the current collector. The electrode stack includes multiple battery cells. Each battery cell includes a positive electrode, a negative electrode, and a separator.

[0015] More specifically, the sealing body may include a plurality of frame-shaped sealing members welded to the edges of the current collectors, and a plurality of frame-shaped spacers arranged between adjacent sealing members in the stacking direction. The outer surface of the sealing body may be formed by welding together an outer edge portion of each spacer that extends outward beyond the edges of the current collectors and an outer edge portion of each sealing member that extends outward beyond the edges of the current collectors, adjacent to each spacer in the stacking direction.

[0016] The melt mass-flow rate is a measure of the fluidity of a resin material when melted. The melt mass-flow rates of the resin material constituting the spacer and the resin material constituting the sealing member can each be selected from a wide range and are not particularly limited.

[0017] First, active materials are kneaded to form a kneaded body (step ST1). The active materials, binders, and conductive additives may be kneaded together. The active materials are positive electrode active materials or negative electrode active materials. The positive electrode active materials may be capable of absorbing and releasing charge carriers such as lithium ions. Examples of the positive electrode active materials include composite oxides, metallic lithium, and sulfur. The composite oxides may contain at least one of iron, manganese, titanium, nickel, cobalt, and aluminum, and lithium. Examples of the composite oxides include olivine-type lithium iron phosphate (LiFePO4), LiCoO2, and LiNiMnCoO2. The negative electrode active materials may absorbing and releasing charge carriers such as lithium ions. Examples of the negative electrode active materials include carbon such as graphite, artificial graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, and soft carbon, metal compounds, elements or compounds thereof that can be alloyed with lithium, and boron-doped carbon. Examples of elements that can be alloyed with lithium are silicon and tin.

[0018] Next, the kneaded material is applied to a current collector (step ST2). The current collector may be, for example, a plate, foil, sheet, film, mesh, or the like. The current collector may be made of, for example, aluminum, copper, nickel, titanium, iron, or an alloy thereof. The alloy may be, for example, stainless steel. The current collector may also be a clad made by bonding together members made of these metals or alloys thereof.

[0019] Next, the current collector coated with the kneaded body is pressed (step ST3) and baked (step ST4). Active material layers are formed on the first and second surfaces of the current collector. The baking conditions in step ST4 include, for example, temperature and time. When this manufacturing method is performed multiple times, the baking conditions in step ST4 may be appropriately changed by feedback control using the amount of moisture in the battery module MJ calculated in step ST8, which will be described later. This makes it possible to change the baking conditions in step ST4, such as temperature and time, depending on the amount of moisture in the battery module MJ. As a result, the performance of the power storage device can be maintained or improved.

[0020] Next, separators and the like are arranged to form battery cells (step ST5). Next, a battery module MJ is assembled using multiple battery cells (step ST6). Specifically, a sealing member is welded to each of the first and second surfaces of the edge of each current collector. The current collectors with the sealing members welded are stacked with spacers interposed between them. The outer edge of each stacked spacer and the outer edge of each sealing member are welded to each other to form welded parts, and a sealed body is formed by the spacers and sealing members.

[0021] Next, the moisture content of the air in the reduced pressure chamber LC is measured (step ST7). Specifically, as shown in FIG. 2, the battery module MJ is placed on a flat surface FS. The cover 1 of the moisture content measuring device 10 is placed on the flat surface FS so that it covers the battery module MJ. The cover 1 and the flat surface FS are brought into tight contact. The space enclosed by the cover 1 and the flat surface FS is sealed and functions as a reduced pressure chamber LC. The reduced pressure chamber LC houses the battery module MJ. The reduced pressure chamber LC is connected to a pump 3 via a pipe 4. A dew point meter 2 is provided midway through the pipe 4. The pump 3 exhausts the air in the reduced pressure chamber LC through the pipe 4, reducing the pressure inside the reduced pressure chamber LC. As a result, at least a portion of the moisture in the battery module MJ moves along the flow FF, in other words, from the battery module MJ to the reduced pressure chamber LC, the pipe 4, and the dew point meter 2. The dew point meter 2 measures the moisture content of the air in the reduced pressure chamber LC. For example, the Karl Fischer method can be used to measure the moisture content.

[0022] Next, the moisture content in the battery module MJ is calculated (step ST8). A calibration curve showing the relationship between the moisture content of the air in the reduced pressure chamber LC and the moisture content in the battery module MJ is obtained in advance. This calibration curve can be obtained by measuring the correlation between the moisture content in the battery module MJ and the moisture content of the air in the reduced pressure chamber LC. Using this calibration curve, the moisture content in the battery module MJ is calculated from the moisture content of the air in the reduced pressure chamber LC measured in step ST7.

[0023] Next, the electrolyte is poured into the filling port Mb of the battery module MJ to form a power storage device (step ST9). The electrolyte passes through the filling port Mb and is supplied into the main body Ma of the battery module MJ. The electrolyte contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous solvent is a known solvent such as cyclic carbonates, cyclic esters, chain carbonates, chain esters, or ethers. The non-aqueous solvent may be a combination of two or more of these known solvent materials. The electrolyte salt is a known lithium salt such as LiClO4, LiAsF6, LiPF6, LiBF4, LiCF3SO3, LiN(FSO2)2, or LiN(CF3SO2)2.

[0024] Finally, the energy storage device is repeatedly charged and discharged to activate it (step ST10). The activation conditions in this step ST10 include the initial charge time and the high-temperature aging time. When this manufacturing method is performed multiple times in succession, the activation conditions in this step ST10 may be changed as appropriate by feedforward control using the amount of moisture in the battery module MJ calculated in step ST8. The performance of the energy storage device may be maintained or improved by changing the activation conditions in this step ST10 according to the amount of moisture in the battery module MJ calculated in step ST8. When the amount of moisture in the battery module MJ calculated in step ST8 is an upper limit value, the performance of the energy storage device may be guaranteed by changing the activation conditions in this step ST10, specifically, the initial charge time and the high-temperature aging time, by feedforward control.

[0025] As described above, an energy storage device can be manufactured. After calculating the amount of moisture in the battery module MJ, an energy storage device using the battery module MJ can be obtained. That is, the amount of moisture in the battery module MJ can be measured non-destructively. This prevents the battery module MJ from being destroyed, thereby increasing the yield in the manufacture of energy storage devices. Furthermore, each manufactured battery module MJ can be guaranteed, thereby increasing reliability.

[0026] The present invention is not limited to the above-described embodiment, and can be appropriately modified without departing from the spirit and scope of the present invention. Furthermore, the present invention may be implemented by appropriately combining the above-described embodiment and examples thereof. [Explanation of symbols]

[0027] 10. Moisture content measuring device 1 cover 2 Dew point meter 3. Pump 4 tubes FS plane LC decompression chamber FF Flow MJ battery module Ma body Mb filling port

Claims

[Claim 1] Assembling a battery module; a step of accommodating the battery module in a decompression chamber, and then evacuating the air in the decompression chamber through a pipe provided with a dew point meter, thereby reducing the pressure in the decompression chamber, and measuring the moisture content of the air in the decompression chamber; calculating the amount of moisture in the battery module from the measured amount of moisture in the air in the decompression chamber using a calibration curve that indicates the relationship between the amount of moisture in the air in the decompression chamber and the amount of moisture in the battery module; and injecting an electrolyte into the battery module. A method for manufacturing an electricity storage device.

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