Battery manufacturing method

Abstract

The objective is to provide a battery manufacturing method that enables the creation of high-capacity batteries. [Solution] According to the embodiment, a method for manufacturing a battery is provided. The method for manufacturing a battery includes the steps of preparing a battery precursor and injecting an electrolyte salt-containing solution. The battery precursor includes an outer casing member and an electrode group housed in the outer casing member, which includes a first electrode and a second electrode. The step of injecting the electrolyte salt-containing solution is the step of injecting the electrolyte salt-containing solution into the outer casing member under the conditions that the temperature is 50°C or higher and 120°C or lower, and the internal pressure of the battery precursor is -70kPa or lower in gauge pressure. The electrolyte salt-containing solution has a viscosity of 10mPa·s or higher at 25°C.

Description

[Technical Field]

[0001] Embodiments of the present invention relate to a method for manufacturing a battery. [Background technology]

[0002] Ionic liquids are highly stable. Therefore, using ionic liquids as electrolytes in batteries is being considered to improve battery safety. However, because ionic liquids have high viscosity, they are difficult to impregnate electrodes and separators. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2002-246063 [Patent Document 2] Japanese Patent Publication No. 2023-53124 [Patent Document 3] Japanese Patent Publication No. 2009-218160 [Patent Document 4] Japanese Patent Publication No. 2019-32982 [Overview of the project] [Problems that the invention aims to solve]

[0004] The embodiment aims to provide a method for manufacturing a battery that can realize a high-capacity battery. [Means for solving the problem]

[0005] According to the embodiment, a method for manufacturing a battery is provided. The method for manufacturing a battery includes the steps of preparing a battery precursor and injecting an electrolyte salt-containing solution. The battery precursor includes an outer casing member and an electrode group housed in the outer casing member, which includes a first electrode and a second electrode. The step of injecting the electrolyte salt-containing solution is the step of injecting the electrolyte salt-containing solution into the outer casing member under the conditions that the temperature is 50°C or higher and 120°C or lower, and the internal pressure of the battery precursor is -70kPa or lower in gauge pressure. The electrolyte salt-containing solution has a viscosity of 10mPa·s or higher at 25°C. [Brief explanation of the drawing]

[0006] [Figure 1] A cross-sectional view of an example of a battery manufactured by the method according to the embodiment, cut in a direction perpendicular to the terminal extension direction. [Figure 2] Enlarged cross-sectional view of section A in Figure 1. [Figure 3] A partially cutaway cross-sectional view showing another example of a battery manufactured by the method according to the embodiment. [Figure 4] A side view of the battery shown in Figure 3. [Figure 5] A schematic partial cutaway perspective view showing yet another example of a battery manufactured by the method according to the embodiment. [Figure 6] An enlarged cross-sectional view of part B of the battery shown in Figure 5. [Figure 7] A perspective view showing another example of an electrode group. [Figure 8] A schematic plan view showing an example of a battery manufacturing method according to the embodiment. [Figure 9] A schematic perspective view showing another example of a battery manufacturing method according to the embodiment. [Figure 10] A schematic cross-sectional view illustrating yet another example of the battery manufacturing method according to the embodiment. [Figure 11] Front view of the battery precursor used in the manufacturing method shown in Figure 10. [Modes for carrying out the invention]

[0007] According to the embodiment, a method for manufacturing a battery is provided. The method for manufacturing a battery includes the steps of preparing a battery precursor and injecting an electrolyte salt-containing solution. The battery precursor includes an outer casing member and an electrode group housed in the outer casing member, which includes a first electrode and a second electrode. The step of injecting the electrolyte salt-containing solution is the step of injecting the electrolyte salt-containing solution into the outer casing member under the conditions that the temperature is 50°C or higher and 120°C or lower, and the internal pressure of the battery precursor is -70kPa or lower in gauge pressure. The electrolyte salt-containing solution has a viscosity of 10mPa·s or higher at 25°C.

[0008] In battery manufacturing, an electrolyte salt-containing solution is injected into the outer casing of a battery precursor, which contains an electrode group including a first electrode and a second electrode. The injected electrolyte salt-containing solution impregnates the electrode group.

[0009] However, the higher the viscosity of the electrolyte solution, the more difficult it tends to be for the electrolyte solution to impregnate the electrode group. Electrolyte solutions with a viscosity of 10 mPa·s or higher at 25°C are difficult to impregnate the electrode group with. As a result, the impregnation of the electrolyte solution into the electrode group tends to be uneven. Uneven impregnation of the electrolyte solution into the electrode group can easily lead to battery capacity loss.

[0010] The battery manufacturing method according to the embodiment includes the step of injecting an electrolyte salt-containing liquid into the outer casing member under the conditions that the temperature is 50°C or higher and 120°C or lower, and the internal pressure of the battery precursor is -70kPa or lower in gauge pressure.

[0011] At high temperatures of 50°C or above, the battery precursor can be expanded. Specifically, the first and second electrodes can be expanded, causing the voids in the electrode group to expand. Examples of voids in the electrode group include the voids that may exist between the first and second electrodes, the voids that the first electrode may contain, and the voids that the second electrode may contain. Since an electrolyte salt-containing solution can be impregnated into such voids, when the voids expand, the electrolyte salt-containing solution becomes more easily impregnated into the electrode group.

[0012] Therefore, by injecting the electrolyte salt-containing solution into the battery precursor at a high temperature of 50°C or higher, the electrolyte salt-containing solution can be more easily impregnated into the electrode group. Thus, even when injecting an electrolyte salt-containing solution with a high viscosity of 10 mPa·s or more at 25°C, the uniformity of impregnation of the electrolyte salt-containing solution into the electrode group can be improved.

[0013] By injecting the electrolyte-containing solution at a temperature of 120°C or lower, the deterioration of the electrolyte-containing solution due to heat can be suppressed.

[0014] By injecting an electrolyte-containing solution into the battery precursor at a low pressure of -70 kPa or less (gauge pressure), the electrode group can be more easily impregnated with the electrolyte-containing solution.

[0015] Therefore, according to the battery manufacturing method of the embodiment, the uniformity of impregnation of the electrolyte salt-containing solution in the electrode group can be improved. As a result, battery capacity loss can be suppressed, and a high-capacity battery can be provided.

[0016] Further details will be provided regarding the manufacturing method of the battery according to the embodiment.

[0017] The battery obtained by the manufacturing method according to the embodiment may have an electrolyte impregnated into the electrode group. The electrolyte may be an electrolyte salt-containing liquid, or for example, an electrolyte salt-containing liquid that has been modified through a chemical reaction. In other words, according to the manufacturing method according to the embodiment, a battery with good electrolyte impregnation into the electrode group can be obtained. Therefore, the battery obtained by the manufacturing method according to the embodiment can have a high capacity because of the high uniformity of electrolyte impregnation into the electrode group.

[0018] The outer casing containing the battery precursor has at least one opening. An electrolyte-containing solution can be injected into the outer casing through this opening. The opening can be sealed after the electrolyte-containing solution has been injected. This sealing allows the outer casing to be airtight.

[0019] During the process of injecting the electrolyte solution, the temperature of the battery precursor may be between 50°C and 120°C. During the process of injecting the electrolyte solution, the internal pressure of the battery precursor may be between -100kPa and -70kPa in gauge pressure.

[0020] The battery manufacturing method preferably further includes a step of heating the battery precursor before the step of injecting the electrolyte salt-containing solution. By preheating the battery precursor before injecting the electrolyte salt-containing solution, the first electrode and the second electrode can be sufficiently expanded. Therefore, the impregnation of the electrolyte salt-containing solution inside the electrode group can be made higher. In the step of heating the battery precursor, the battery precursor can be heated to, for example, a range of 50°C to 120°C.

[0021] The step of heating the battery precursor preferably includes reducing the internal pressure of the battery precursor. Specifically, for example, the step of heating the battery precursor can be carried out by housing the battery precursor in a chamber and performing heating and depressurization within the chamber. Heating and depressurization may be performed one before the other, or they may be performed simultaneously. By including the step of heating the battery precursor in reducing the internal pressure of the battery precursor, the time (cycle time) required for battery manufacturing can be shortened. In the step of heating the battery precursor, for example, the internal pressure of the battery precursor can be reduced to -70 kPa or less in gauge pressure.

[0022] An electrolyte salt-containing solution may have a viscosity of 10 mPa·s to 3000 mPa·s at 25°C, for example. Examples of electrolyte salt-containing solutions with a viscosity of 10 mPa·s or more at 25°C include electrolyte salt-containing solutions containing ionic liquids and concentrated electrolyte salt-containing solutions. In this specification, a concentrated electrolyte salt-containing solution refers to an electrolyte salt-containing solution containing a solvent and an electrolyte salt as a solute, in which the molar concentration of the electrolyte salt is 2 mol / L or more. Since the viscosity of an electrolyte salt-containing solution tends to increase with increasing electrolyte salt concentration, concentrated electrolyte salt-containing solutions can have high viscosity.

[0023] When using a concentrated electrolyte solution, it is preferable to heat the battery precursor to a temperature of 100°C or lower in order to suppress deterioration of the electrolyte solution caused by solvent volatilization or the like during the heating process of the battery precursor.

[0024] The electrolyte salt-containing solution preferably contains an ionic liquid. Ionic liquids are preferable in that they have high stability, but they tend to have high viscosity. Generally, ionic liquids with a viscosity of 10 mPa·s or more at 25°C, for example, make it difficult to improve the impregnation of the electrode group. According to the battery manufacturing method of this embodiment, even if the electrolyte salt-containing solution contains a highly viscous ionic liquid, the uniformity of the impregnation of the electrolyte salt-containing solution into the electrode group can be improved. Therefore, according to this manufacturing method, safety is improved because it contains a highly stable ionic liquid, and a high-capacity battery can be manufactured.

[0025] It is preferable to preheat the electrolyte salt-containing solution before injecting it into the outer casing. Preheating the electrolyte salt-containing solution reduces its viscosity at the time of injection. It is preferable that the electrolyte salt-containing solution is injected at a temperature of 50°C to 120°C, as this facilitates impregnation of the electrode group. This further improves the uniformity of impregnation of the electrode group with the electrolyte salt-containing solution. When using a concentrated electrolyte salt-containing solution, it is preferable to heat the concentrated electrolyte salt-containing solution to 100°C or lower in order to suppress deterioration of the electrolyte salt-containing solution due to solvent volatilization, etc.

[0026] If the impregnation of the electrode group with the electrolyte salt-containing solution is uneven, the resistance may increase in areas where impregnation is insufficient. Furthermore, localized degradation of the battery may occur in areas where impregnation is insufficient. When such localized degradation occurs, the resistance may increase further, and the battery capacity tends to decrease. According to the battery manufacturing method of this embodiment, the uniformity of the impregnation of the electrode group with the electrolyte salt-containing solution can be improved, thereby improving the battery capacity and input / output performance.

[0027] A method for manufacturing a battery according to an embodiment, and a battery manufactured by the manufacturing method according to an embodiment, will be further described below with reference to the drawings.

[0028] The battery manufactured by the manufacturing method according to the embodiment is not particularly limited as long as it includes a first electrode, a second electrode, an outer casing, and an electrolyte, and may be, for example, a primary battery or a secondary battery. In other words, the battery manufacturing method according to the embodiment may be used to manufacture either a primary battery or a secondary battery.

[0029] The first electrode can be either the positive or negative electrode of the battery. The second electrode can be the other of the positive or negative electrode of the battery. For example, if the first electrode is the negative electrode, the second electrode can be the positive electrode. If the first electrode is the positive electrode, the second electrode can be the negative electrode.

[0030] It is preferable to manufacture a secondary battery by the battery manufacturing method according to the embodiment. In other words, it is preferable that the battery manufacturing method according to the embodiment is a method for manufacturing a secondary battery.

[0031] Localized degradation of a battery caused by uneven impregnation of the electrolyte into the electrodes and / or separators is more likely to progress with repeated charge-discharge cycles. According to the manufacturing method of the embodiment, a secondary battery with good electrolyte impregnation into the electrode group can be obtained, and a secondary battery with excellent cycle performance can be provided that can maintain high battery capacity and input / output performance even after charge-discharge cycles.

[0032] When manufacturing a secondary battery by the battery manufacturing method according to the embodiment, the type of secondary battery can be, for example, a lithium secondary battery or a lithium-ion secondary battery.

[0033] Figures 1 and 2 show an example of a battery manufactured by the manufacturing method according to the embodiment, which uses a laminate film exterior component.

[0034] As shown in Figures 1 and 2, the electrode group 1 is a flat wound electrode group. The wound electrode group 1 is housed in a bag-shaped outer casing member 12 made of a laminate film with a metal layer interposed between two resin films. The flat wound electrode group 1 is formed by stacking a first electrode 4, a separator 5, a second electrode 3, and a separator 5 in that order from the outside, winding the stack in a spiral shape around an axis parallel to the short side direction, and then press-molding this stack. The outermost first electrode 4 has a configuration in which a first active material containing a first active material layer (first composite layer) 4b is formed on one side of the inner surface of the first current collector 4a, as shown in Figure 2, while the other first electrodes 4 are configured with the first active material containing layer 4b formed on both sides of the first current collector 4a. The second electrode 3 is configured with a second active material containing layer (second composite layer) 3b formed on both sides of the second current collector 3a.

[0035] Near the outer peripheral end of the wound electrode group 1, the first terminal 13 is connected to the first current collector 4a of the outermost first electrode 4, and the second terminal 14 is connected to the second current collector 3a of the inner second electrode 3. These first terminals 13 and second terminals 14 extend outward from the opening of the bag-shaped outer casing member 12. The wound electrode group 1 is sealed by heat-sealing the opening of the bag-shaped outer casing member 12. When heat-sealing, the first terminals 13 and second terminals 14 are sandwiched by the bag-shaped outer casing member 12 at this opening.

[0036] In addition to the batteries described above, the batteries manufactured by the manufacturing method according to the embodiment may also be the batteries shown in Figures 3 and 4.

[0037] Figures 3 and 4 show an example of a battery using a metal container. The X-axis direction is aligned with the thickness direction of the battery. The Y-axis direction is perpendicular to the X-axis direction and aligned with the width direction of the battery. The Z-axis direction is perpendicular to the X-axis and Y-axis directions and aligned with the height direction of the battery.

[0038] The electrode group 1 is housed in a metal container comprising a rectangular cylindrical metal can 2 and a lid member 10. The electrode group 1 is formed, for example, by winding a second electrode 3 and a first electrode 4 in a flat spiral shape around an axis parallel to their short sides, with a separator 5 interposed between them. As shown in Figure 4, multiple strip-shaped second leads 6 are electrically connected to each of the multiple ends of the second electrode 3 located on the end face of the electrode group 1 intersecting the electrode stacking direction. Similarly, multiple strip-shaped first leads 7 are electrically connected to each of the multiple ends of the first electrode 4 located on this end face. These multiple second leads 6 are electrically connected to a second current collector tab 8 when bundled together. The second terminal is formed from the second leads 6 and the second current collector tab 8. The first lead 7 is connected to a first current collector tab 9 when bundled together. The first terminal is formed from the first lead 7 and the first current collector tab 9. The metal lid member 10 is fixed to the opening of the metal can 2 by welding or the like. The second current collector tab 8 and the first current collector tab 9 are each pulled out to the outside through outlet holes provided in the lid member 10. The inner circumferential surface of each outlet hole in the lid member 10 is covered with an insulating member 11 to prevent short circuits caused by contact with the second current collector tab 8 and the first current collector tab 9. A liquid filling port 28 is formed in the lid member 10. In addition, a sealing plate 29 that closes the liquid filling port 28 is welded to the outer surface of the lid member 10.

[0039] The batteries manufactured by the manufacturing method according to the embodiment are not limited to the batteries with the configurations shown in Figures 1 and 2, and Figures 3 and 4, but may also be batteries with configurations such as those shown in Figures 5 and 6.

[0040] Figure 5 is a schematic partial cutaway perspective view showing another example of a battery. Figure 6 is an enlarged cross-sectional view of part B of the battery shown in Figure 5.

[0041] The battery shown in Figures 5 and 6 comprises an electrode group 1 shown in Figures 5 and 6, an outer casing member 12 shown in Figure 5, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed within the outer casing member 12. The electrolyte is held within the electrode group 1.

[0042] The exterior component 12 consists of a laminate film comprising two resin layers and a metal layer interposed between them.

[0043] As shown in Figure 6, electrode group 1 is a stacked electrode group. The stacked electrode group 1 has a structure in which the first electrode 4 and the second electrode 3 are stacked alternately with a separator 5 interposed between them.

[0044] Electrode group 1 includes a plurality of first electrodes 4. Each of the plurality of first electrodes 4 comprises a first current collector 4a and a first active material-containing layer 4b supported on both sides of the first current collector 4a. Electrode group 1 also includes a plurality of second electrodes 3. Each of the plurality of second electrodes 3 comprises a second current collector 3a and a second active material-containing layer 3b supported on both sides of the second current collector 3a.

[0045] Each first electrode 4's first current collector 4a includes a portion on one side where the first active material-containing layer 4b is not supported on any surface. This portion functions as a first current collector tab 4c. As shown in Figure 6, the first current collector tabs 4c do not overlap with the second electrode 3. Furthermore, multiple first current collector tabs 4c are electrically connected to a strip-shaped first terminal 13. The tip of the strip-shaped first terminal 13 is extended to the outside of the exterior member 12.

[0046] Although not shown in the diagram, the second current collector 3a of each second electrode 3 includes a portion on one side where the second active material-containing layer 3b is not supported on any surface. This portion functions as a second current collector tab. The second current collector tab, like the first current collector tab 4c, does not overlap with the first electrode 4. In the electrode group 1, the tip of the second current collector tab is in the same direction as the first current collector tab 4c and is extended to the outside of the outer casing member 12 in a position where it does not come into contact with the first current collector tab 4c. The second current collector tab is electrically connected to the strip-shaped second terminal 14.

[0047] In addition, in the batteries shown in Figures 1 to 6, the electrode group exemplified in Figure 7 may be used instead of the electrode group described above. The electrode group 1 shown in Figure 7 is constructed by folding a separator 5 in a zigzag pattern and alternately arranging the first electrode 4 and the second electrode 3 at the folded parts. Specifically, the second electrode 3, first electrode 4, second electrode 3, and first electrode 4 are arranged in this order so as to be sandwiched between the separators 5 in the zigzag-folded separator 5. The second current collector tab 3c and the first current collector tab 4c protrude from one of the long sides of the zigzag-folded separator 5. The second current collector tab 3c and the first current collector tab 4c are arranged so as not to overlap each other.

[0048] Note that the order of the first electrode 4 and the second electrode 3 is not limited to the order shown in Figure 7; they may also be arranged in the order of first electrode 4, second electrode 3, first electrode 4, second electrode 3.

[0049] When the stacked electrode group 1 described above with reference to Figure 7 is applied as the electrode group 1 of the battery shown in Figures 3 and 4, each of the multiple second current collection tabs 3c can be electrically connected to the second lead 6. In addition, each of the multiple first current collection tabs 4c can be electrically connected to the first lead 7.

[0050] As an example of a battery manufacturing method in the embodiment, a method for manufacturing a battery equipped with a wound electrode group will be described with reference to Figures 1, 2, and 8. Figure 8 is a schematic diagram showing the outline of a battery manufacturing method using a bag-shaped outer casing made of laminate film.

[0051] First, the first electrode 4 and the second electrode 3 are fabricated.

[0052] The first electrode can be manufactured, for example, by the following method. First, a slurry is prepared by suspending the first active material, a conductive agent, and a binder in a solvent. This slurry is applied to one or both sides of the first current collector. Next, the applied slurry is dried to obtain a laminate of the first active material-containing layer and the first current collector. After that, this laminate is pressed. In this way, the first electrode is manufactured. Alternatively, the first electrode may be manufactured by the following method. First, the first active material, a conductive agent, and a binder are mixed to obtain a mixture. Next, this mixture is formed into pellets. Then, the first electrode can be obtained by placing these pellets on the first current collector.

[0053] The second electrode can be fabricated in the same manner as the first electrode, for example, by using the second active material instead of the first active material and the second current collector instead of the first current collector.

[0054] An electrode group 1 is fabricated by placing a separator 5 between the second electrode 3 and the first electrode 4. The second terminal 14 is electrically connected to the second electrode 3 of electrode group 1, and the first terminal 13 is electrically connected to the first electrode 4 of electrode group 1.

[0055] An electrode group 1 having a first terminal 13 and a second terminal 14 is sandwiched between an outer casing member 12 made of a pair of laminate films. Each of the pair of laminate films constituting the outer casing member 12 is rectangular. The four ends corresponding to the four sides of the rectangle are designated as the first end 12a, second end 12b, third end 12c, and fourth end 12d, respectively, as shown in Figure 8.

[0056] After housing the electrode group 1 within the outer casing member 12, the second end 12b, the third end 12c, and the fourth end 12d are sealed by heat sealing. At this time, the first terminal 13 and the second terminal 14 are sandwiched between the outer casing member 12 at the second end 12b. As a result, the first terminal 13 and the second terminal 14 extend to the outside of the outer casing member 12. Thus, the battery precursor 100 can be manufactured.

[0057] Next, under conditions where the temperature is between 50°C and 120°C and the internal pressure of the battery precursor is -70kPa or less in gauge pressure, an electrolyte salt-containing solution is injected into the outer casing member 12 from the first end 12a. After that, the outer casing member 12 is sealed by heat-sealing the first end 12a. This gives rise to a battery. After sealing the first end 12a, the battery may undergo initial charge-discharge and aging.

[0058] As another example of a battery manufacturing method according to the embodiment, a method for manufacturing a battery equipped with a wound electrode group will be described with reference to Figures 2, 3, and 9. Figure 9 is a schematic diagram showing the general method of manufacturing a battery using a rectangular cylindrical metal container as described in Figures 2 and 3.

[0059] First, electrode group 1 is fabricated in the same manner as described above. The second terminal is electrically connected to the second electrode 3 of electrode group 1, and the first terminal is electrically connected to the first electrode 4 of electrode group 1.

[0060] After housing the electrode group 1, which has a first terminal and a second terminal, in a metal can 2, the metal can 2 and the lid member 10 are welded together. In this way, a battery precursor 100 can be manufactured.

[0061] In the example shown in Figure 9, a gas release valve 27 and an injection port 28 are formed in the lid member 10. The gas release valve 27 and the injection port 28 are positioned between the current collector tabs 8 and 9 in the Y-axis direction of the battery precursor 100. Under conditions where the temperature is between 50°C and 120°C and the internal pressure of the battery precursor is -70kPa or less in gauge pressure, an electrolyte salt-containing solution is injected into the metal container, which serves as the outer casing, through the injection port 28. After that, a sealing plate 29 that closes the injection port 28 is welded to the outer surface of the lid member 10. This seals the metal container consisting of the metal can 2 and the lid member 10. This allows a battery to be obtained. After sealing, the battery may undergo initial charge / discharge and aging.

[0062] A battery manufacturing method according to this embodiment may use, for example, an apparatus that includes a chamber and has the function of reducing pressure and heating the inside of the chamber. An example of such an apparatus is a vacuum oven.

[0063] An example of a battery manufacturing method using the apparatus will be described with reference to Figure 10. Figure 10 shows the chamber portion of a vacuum oven, which is equipped with a metal chamber and capable of reducing pressure and heating the inside of the chamber, as an example of the apparatus 200. Figure 10 is a cross-sectional view showing the state in which a battery precursor 100, including a rectangular cylindrical metal container as described with reference to Figures 2, 3 and 9, is housed inside the chamber.

[0064] Figure 10 shows an example where one battery precursor 100 is housed in the apparatus, but multiple battery precursors 100 may be housed in the apparatus. By housing multiple battery precursors 100 in the apparatus, multiple batteries can be manufactured simultaneously.

[0065] The device 200 has an exhaust port 201. By releasing the gas inside the chamber to the outside through the exhaust port 201, the pressure inside the chamber can be reduced.

[0066] The space inside the device 200, outside the exterior member 2 (inside the device), is indicated by the symbol i200. The space inside the exterior member 2 (inside the exterior member) is indicated by the symbol i2.

[0067] When manufacturing a battery using the apparatus 200, with the battery precursor 100 housed inside the apparatus i200, the apparatus is used to maintain a temperature of 50°C to 120°C and an internal pressure of -70kPa or less (gauge pressure). Under these conditions, an electrolyte salt-containing solution with a viscosity of 10mPa·s or more at 25°C is injected into the outer casing. Thus, a battery can be manufactured.

[0068] When the internal pressure of the battery precursor is reduced using the device 200, the liquid injection port 28 is open. Therefore, the pressure inside the outer casing i2, which is the internal pressure of the battery precursor, the pressure inside the device i200, and the pressure at the exhaust port 201 can be equal. Thus, the internal pressure of the battery precursor may be measured by measuring the pressure inside the outer casing i2, by measuring the pressure inside the device i200, or by measuring the pressure at the exhaust port 201.

[0069] To measure the pressure inside the outer casing member i2, for example, a pipe can be connected to an open portion of the outer casing member 2, and the gauge pressure inside the pipe can be measured with a vacuum gauge. For example, in the example shown in Figure 10, a pipe (not shown) can be connected to the liquid injection port 28.

[0070] When measuring the pressure inside the apparatus i200, a vacuum gauge can be used to measure the gauge pressure inside the apparatus. Alternatively, a vacuum gauge may be installed at the exhaust port 201, and the gauge pressure at the exhaust port 201 may be measured using this vacuum gauge.

[0071] Furthermore, the temperature of the battery precursor 100 and the temperature of the inside of the device i200 can be equal. Therefore, when measuring the temperature, either the temperature of the battery precursor 100 or the temperature of the inside of the device i200 can be measured. When measuring the temperature of the battery precursor 100, a thermocouple can be installed on the exterior component to measure the temperature. When measuring the temperature of the inside of the device i200, the temperature inside the device can be measured using a temperature sensor.

[0072] The temperature measurement position when measuring the temperature of the battery precursor 100 will be explained with reference to Figure 11. Figure 11 is a front view of the battery precursor shown in Figure 10. The diagonals when observing the battery precursor 100 from the front are denoted as yz1 and yz2, respectively. The intersection of the diagonals yz1 and yz2 is denoted as P.

[0073] When measuring the temperature of the battery precursor 100, it is preferable to place a thermocouple at intersection P and measure the temperature there. Since intersection P is located near the center of the battery precursor, it may be the part where heat is least easily transferred. Therefore, when the temperature at intersection P is the desired temperature, the entire battery precursor may be at the desired temperature.

[0074] As explained with reference to Figure 10, when manufacturing a battery by housing multiple battery precursors inside the device, it is preferable to measure the temperature of the battery precursor located closest to the center of the housing. It is most preferable to install a thermocouple on each of the multiple battery precursors and measure their temperatures. The battery precursor located near the center of the multiple battery precursors is the least susceptible to heat transfer. Therefore, when the temperature of that battery precursor reaches the desired temperature, all of the multiple battery precursors may also be at the desired temperature.

[0075] Details of the conditions for the battery manufacturing method according to the embodiment are described below.

[0076] The steps of injecting the electrolyte salt-containing solution and sealing the outer casing are preferably carried out in an atmosphere with a low oxygen gas concentration. As a specific example of such a manufacturing method, it is preferable to inject the electrolyte salt-containing solution in a chamber with a temperature of 50°C to 120°C and a gauge pressure of -70kPa or less, and then seal the outer casing in the same chamber under the same conditions.

[0077] The following describes the first electrode, second electrode, and outer casing members included in the battery precursor used in the battery manufacturing method according to the embodiment, as well as the electrolyte salt-containing liquid. Separators that may be included in the battery precursor used in the battery manufacturing method according to the embodiment, in addition to the above members, will also be described below.

[0078] (1st electrode) The first electrode may include a first current collector and a first active material-containing layer. The first active material-containing layer may be formed on one or both sides of the first current collector. The first active material-containing layer may include a first active material and optionally a conductive agent and a binder.

[0079] The thickness of the first active material-containing layer is preferably, for example, 20 μm or more. The thicker the first active material-containing layer, the higher the battery capacity can be. However, generally speaking, the thicker the first active material-containing layer, the more difficult it becomes to impregnate the first electrode with the electrolyte salt-containing solution. According to the battery manufacturing method of this embodiment, even when the first active material-containing layer is thick, such as 20 μm or more, good impregnation of the electrolyte salt-containing solution into the first electrode can be achieved.

[0080] The electrolyte salt-containing solution can impregnate the voids that the first electrode may contain. Specifically, it can impregnate the pores that the first active material-containing layer may contain.

[0081] The lower the porosity of the first active material-containing layer, or the smaller the median diameter in the pore distribution, the more difficult it tends to be to impregnate the first electrode with the electrolyte salt-containing solution. According to the battery manufacturing method of the embodiment, even when the porosity of the first active material-containing layer is low, between 20% and 40%, good impregnation of the electrolyte salt-containing solution into the first electrode can be achieved. Furthermore, even when the median diameter in the pore distribution is small, between 0.1 μm and 0.5 μm, good impregnation of the electrolyte salt-containing solution into the first electrode can be achieved.

[0082] When the first electrode is used as the negative electrode of a lithium-ion secondary battery, an example of the first active material is lithium titanate having a ramsdelite structure (e.g., Li 2+y Li3O7 (0≦y≦3), lithium titanate having a spinel structure (e.g., Li 4+x Ti5O 12 Examples include titanium dioxide (TiO2), anatase-type titanium dioxide, rutile-type titanium dioxide, niobium pentoxide (Nb2O5), hollandite-type titanium composite oxide, orthorhombic titanium composite oxide, and monoclinic niobium titanium oxide. The first active material can be one or more types.

[0083] As an example of the above orthorhombic titanium-containing composite oxide, Li 2+a MI 2-b Ti 6-c M II d O 14+σ Examples of the compounds represented by are as follows. Here, M I is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. M II is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. Each subscript in the composition formula satisfies 0 ≦ a ≦ 6, 0 ≦ b < 2, 0 ≦ c < 6, 0 ≦ d < 6, and -0.5 ≦ σ ≦ 0.5. Specific examples of the orthorhombic titanium-containing composite oxide include Li 2+a Na2Ti6O 14 (0 ≦ a ≦ 6).

[0084] Examples of the above monoclinic niobium titanate oxide include Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δ Examples of the compounds represented by are as follows. Here, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. Each subscript in the composition formula satisfies 0 ≦ x ≦ 5, 0 ≦ y < 1, 0 ≦ z < 2, and -0.3 ≦ δ ≦ 0.3. Specific examples of the monoclinic niobium titanate oxide include Li x Nb2TiO7(0 ≦ x ≦ 5).

[0085] Other examples of the monoclinic niobium titanate oxide include Li x Ti 1-y M3 y+z Nb 2-z O 7-δ Examples of the compounds represented by are as follows. Here, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. Each subscript in the composition formula satisfies 0 ≦ x ≦ 5, 0 ≦ y < 1, 0 ≦ z < 2, and -0.3 ≦ δ ≦ 0.3.

[0086] Conductive agents are added to enhance current collection performance and reduce contact resistance between the active material and the current collector. Examples of conductive agents include carbonaceous materials such as vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, graphite, carbon nanotubes, and carbon nanofibers. One of these may be used as a conductive agent, or two or more may be used in combination. Alternatively, instead of using a conductive agent, the surface of the active material particles may be coated with a carbon coating or an electronically conductive inorganic material coating.

[0087] Binding agents are added to fill the gaps between dispersed active materials and to bind the active materials to the current collector. Examples of binding agents include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, styrene-butadiene rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as a binding agent, or two or more may be used in combination. CMC and salts of CMC can also function as dispersants, for example, in slurry preparation.

[0088] The blending ratio of the first active material, conductive agent, and binder in the first active material-containing layer can be appropriately changed depending on the application of the first electrode. For example, when the first electrode is used as the negative electrode of a secondary battery, it is preferable to blend the first active material (negative electrode active material), conductive agent, and binder in the following proportions: 68% to 96% by mass, 2% to 30% by mass, and 2% to 30% by mass, respectively. By setting the amount of conductive agent to 2% by mass or more, the current collection performance of the first active material-containing layer can be improved. Furthermore, by setting the amount of binder to 2% by mass or more, sufficient bonding between the first active material-containing layer and the current collector can be achieved, and excellent cycle performance can be expected. On the other hand, it is preferable to set the amount of conductive agent and binder to 30% by mass or less in order to achieve high capacity.

[0089] The first current collector is made of a material that is electrochemically stable at the potential in which lithium (Li) is inserted into and removed from the active material. For example, when the first active material is used as the negative electrode active material, the first current collector is preferably made of copper, nickel, stainless steel, or aluminum, or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the first current collector is preferably 5 μm to 20 μm. A first current collector with such a thickness can balance the strength and weight reduction of the first electrode.

[0090] Furthermore, the first current collector may include portions on its surface where the first active material-containing layer is not formed. These portions can function as the first current collector tab.

[0091] (2nd electrode) The second electrode may include a second current collector and a second active material-containing layer. The second active material-containing layer may be formed on one or both sides of the second current collector. The second active material-containing layer may optionally include a second active material and a conductive agent and a binder.

[0092] The thickness of the second active material-containing layer is preferably, for example, 20 μm or more. The thicker the second active material-containing layer, the higher the battery capacity can be. However, the thicker the second active material-containing layer, the more difficult it becomes to impregnate the second electrode with the electrolyte salt-containing solution. According to the battery manufacturing method of this embodiment, even when the second active material-containing layer is thick, such as 20 μm or more, good impregnation of the electrolyte salt-containing solution into the second electrode can be achieved.

[0093] The electrolyte salt-containing solution can impregnate the voids that the second electrode may contain. Specifically, it can impregnate the pores that the second active material-containing layer may contain.

[0094] The lower the porosity of the second active material-containing layer or the smaller the median diameter in the pore size distribution, the more difficult it tends to be to impregnate the second electrode with the electrolyte salt-containing solution. According to the method for manufacturing a battery according to the embodiment, even when the porosity of the second active material-containing layer is as low as 20% or more and 40% or less, the impregnation property of the electrolyte salt-containing solution into the second electrode can be made good. Further, even when the median diameter in the pore size distribution is as small as 0.1 μm or more and 0.5 μm or less, the impregnation property of the electrolyte salt-containing solution into the second electrode can be made good.

[0095] When the second electrode is used as the positive electrode of a lithium-ion secondary battery, as the second active material, for example, an oxide or a sulfide can be used. The second electrode may contain, as the second active material, one type of compound alone or a combination of two or more types of compounds. Examples of oxides and sulfides include compounds into which Li or Li ions can be inserted and desorbed.

[0096] Examples of such compounds include, for example, manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (e.g., Li x Mn2O4 or Li x MnO2; 0 < x ≦ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≦ 1, 0 < y < 2), lithium phosphate having an olivine structure (e.g., Li x FePO4; 0 < x ≦ 1, Li x Fe1-y Mn y PO4; 0 < x ≤ 1, 0 < y ≤ 1, Li x CoPO4; 0 < x ≤ 1), iron sulfate (Fe2(SO4)3), vanadium oxide (e.g., V2O5), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1) is included.

[0097] Among the above, examples of more preferable compounds as the second active material include lithium manganese composite oxide having a spinel structure (e.g., Li x Mn2O4; 0 < x ≤ 1), lithium nickel composite oxide (e.g., Li x NiO2; 0 < x ≤ 1), lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≤ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≤ 1, 0 < y < 2), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; 0 < x ≤ 1, 0 < y < 1), lithium iron phosphate (e.g., Li x FePO4; 0 < x ≤ 1), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1) is included. Using these compounds as the second active material can increase the potential of the second electrode.

[0098] When using an electrolyte salt-containing liquid containing an ionic liquid (room temperature molten salt) as the electrolyte salt-containing liquid, lithium iron phosphate, Li xIt is preferable to use a second active material containing VPO4F (0 ≤ x ≤ 1), lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, or a mixture thereof. These compounds have low reactivity with room-temperature molten salts, thus improving cycle life. Details of the room-temperature molten salts will be described later.

[0099] The primary particle size of the second active material is preferably between 100 nm and 1 μm. A second active material with a primary particle size of 100 nm or more is easy to handle in industrial production. A second active material with a primary particle size of 1 μm or less allows for smooth diffusion of lithium ions within the solid.

[0100] The specific surface area of ​​the second active material is 0.1 m². 2 / g or more 10m 2 It is preferable that it is less than or equal to / g. 0.1m 2 A second active material having a specific surface area of ​​10m or more can adequately secure sites for Li ion absorption and release. 2 A second active material having a specific surface area of ​​less than / g is easy to handle in industrial production and ensures good charge-discharge cycle performance.

[0101] A binder is added to fill the gaps between the dispersed second active material and to bond the second active material to the second current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as a binder, or two or more may be used in combination.

[0102] Conductive agents are added to enhance current collection performance and reduce contact resistance between the second active material and the second current collector. Examples of conductive agents include vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, and carbonaceous materials such as graphite. One of these may be used as a conductive agent, or two or more may be used in combination. Conductive agents may also be omitted.

[0103] In the second active material-containing layer, it is preferable that the second active material and the binder are blended in proportions of 80% to 98% by mass and 2% to 20% by mass, respectively.

[0104] Sufficient electrode strength can be obtained by using a binder amount of 2% by mass or more. Furthermore, the binder can function as an insulator. Therefore, reducing the binder amount to 20% by mass or less reduces the amount of insulator contained in the electrode, thereby reducing internal resistance.

[0105] When a conductive agent is added, it is preferable that the second active material, binder, and conductive agent are blended in proportions of 77% to 95% by mass, 2% to 20% by mass, and 3% to 15% by mass, respectively.

[0106] The above-mentioned effects can be achieved by increasing the amount of conductive agent to 3% by mass or more. Furthermore, by reducing the amount of conductive agent to 15% by mass or less, the proportion of conductive agent in contact with the electrolyte can be reduced. This lower proportion reduces electrolyte decomposition even when the manufactured batteries are stored at high temperatures.

[0107] The second current collector is preferably an aluminum foil, or an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si.

[0108] The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, and more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

[0109] Furthermore, the second current collector may include portions on its surface where the second active material-containing layer is not formed. These portions can function as second current collector tabs.

[0110] (Exterior components) For example, the outer packaging material can be a container made of laminate film or a metal container.

[0111] The thickness of the laminating film is, for example, 0.5 mm or less, and preferably 0.2 mm or less.

[0112] As the laminate film, a multilayer film is used that includes multiple resin layers and a metal layer interposed between these resin layers. The resin layers include polymer materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layer is preferably made of aluminum foil or aluminum alloy foil for weight reduction. The laminate film can be molded into the shape of an exterior component by sealing it by heat fusion.

[0113] The thickness of the metal container wall is, for example, 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0114] Metal containers are made from, for example, aluminum or aluminum alloys. Aluminum alloys preferably contain elements such as magnesium, zinc, and silicon. If aluminum alloys contain transition metals such as iron, copper, nickel, and chromium, their content is preferably 100 ppm by mass or less.

[0115] The shape of the exterior components is not particularly limited. For example, the exterior components may be flat (thin), rectangular, cylindrical, coin-shaped, or button-shaped. The exterior components can be appropriately selected according to the battery dimensions and intended use.

[0116] (Electrolyte-containing salt solution) The electrolyte salt-containing solution may, for example, include an ionic liquid or a liquid non-aqueous electrolyte.

[0117] The battery produced by the manufacturing method according to this embodiment may contain an ionic liquid, a liquid non-aqueous electrolyte, or a gel-like non-aqueous electrolyte as the electrolyte. The gel-like non-aqueous electrolyte is prepared by compounding a liquid non-aqueous electrolyte with a polymer material.

[0118] The electrolyte may include an ionic liquid and / or a liquid non-aqueous electrolyte as an electrolyte salt-containing solution. When manufacturing a battery in which the electrolyte includes a gel-like non-aqueous electrolyte, the electrolyte salt-containing solution may be a mixture of a liquid non-aqueous electrolyte and a precursor of a polymer material such as a monomer. Such an electrolyte salt-containing solution may gel after being injected into the outer casing to form a gel-like non-aqueous electrolyte. For example, gelation may occur when the monomer precursor polymerizes to form a polymer material.

[0119] Even when the electrolyte salt-containing solution contains the precursor described above, its viscosity at 25°C is 10 mPa·s or higher.

[0120] Ionic liquids (room-temperature molten salts) refer to organic salts consisting of a combination of organic cations and anions that can exist as a liquid at room temperature (15°C to 25°C).

[0121] Room temperature molten salts include room temperature molten salts that exist as liquids on their own, room temperature molten salts that become liquid when mixed with electrolyte salts, room temperature molten salts that become liquid when dissolved in organic solvents, or mixtures thereof. Generally, the melting point of room temperature molten salts used in batteries is 25°C or lower. Also, organic cations generally have a quaternary ammonium skeleton.

[0122] A specific example of an ionic liquid is a mixture of triethylsulfonium salt represented as S222TFSI and lithium bis(fluorosulfonyl)imide (LiFSI) as an electrolyte salt. The mole fraction of LiFSI in a mixture of S222TFSI and LiFSI can be between 0.05 and 0.65. More specifically, the mixing ratio of S222TFSI and LiFSI can be, for example, 0.40:0.60 in mole fraction.

[0123] The higher the mole fraction of the electrolyte salt, the higher the viscosity of the ionic liquid tends to be. For example, when using LiFSI as the electrolyte salt, if the mole fraction of LiFSI is 0.30 or higher, it becomes difficult to impregnate the electrodes and separators. According to the battery manufacturing method of the embodiment, even when the electrolyte salt-containing liquid contains a highly viscous ionic liquid, the uniformity of impregnation of the electrolyte salt-containing liquid with the electrode group can be improved.

[0124] In addition to the above, other cation species that ionic liquids may contain include, for example, those having imidazolium, pyridinium, pyrrolidinium, piperidinium, ammonium, and phosphonium skeletons.

[0125] An example of anion species that an ionic liquid may contain is AlCl4. - NO2 - NO3 - , I - BF4 - PF6 - AsF6 - SbF6 - , NbF6 - TaF6- 、 F(HF) 2.3 - 、 p-CH3PhSO3 - 、 CH3CO2 - 、 CF3CO2 - 、 CH3SO3 - 、 CF3SO3 - 、 (CF3SO2)3C - 、 C3F7CO2 - 、 C4F9SO3 - 、 (CF3SO2)2N - 、 (C2F5SO2)2N - 、 (CF3SO2)(CF3CO)N - 、 (CN)2N - etc. can be cited. The types of cations and anions contained in the ionic liquid can be one type or two or more types, respectively.

[0126] The liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt as a solute in an organic solvent. The molar concentration of the electrolyte salt in the liquid non-aqueous electrolyte is preferably 2 mol / L or more and 5 mol / L or less. The higher the electrolyte salt concentration, the higher the viscosity of the liquid non-aqueous electrolyte tends to be. Therefore, when the molar concentration of the electrolyte salt is as high as 2 mol / L or more, the effects of the manufacturing method of the battery according to the embodiment are easily obtained. The mole fraction of the electrolyte salt in the liquid non-aqueous electrolyte may be 0.20 or more, for example, it may be 0.30.

[0127] Examples of the electrolyte salt include lithium salts such as lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), and lithium bis(trifluoromethylsulfonyl)imide (LiN(CF3SO2)2), and mixtures thereof. The electrolyte salt is preferably one that is difficult to oxidize even at high potentials, and LiPF6 is most preferred.

[0128] Examples of organic solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC); linear carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), and dioxolane (DOX); linear ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); and γ-butyrolactone (GBL), acetonitrile (AN), and sulfolane (SL). These organic solvents can be used alone or as mixed solvents.

[0129] Examples of polymer materials that may contain gel-like non-aqueous electrolytes include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or mixtures thereof.

[0130] The battery manufactured by the manufacturing method according to this embodiment may contain, as an electrolyte, a polymer solid electrolyte, an inorganic solid electrolyte, and the like, in addition to an ionic liquid, a liquid non-aqueous electrolyte, and a gel-like non-aqueous electrolyte.

[0131] (Separator) A separator may be interposed between the first electrode and the second electrode. When the electrode group includes a separator, the electrolyte salt-containing solution injected during the electrolyte salt-containing solution injection process may also impregnate the separator. Specifically, it may impregnate voids that the separator may have, such as pores. Furthermore, the electrolyte salt-containing solution may also impregnate voids that may exist between the first electrode and the separator, and voids that may exist between the second electrode and the separator.

[0132] The lower the porosity of the separator, or the smaller the median diameter in the pore distribution, the more difficult it tends to be to impregnate the separator with the electrolyte salt-containing solution. According to the battery manufacturing method of the embodiment, even when the porosity of the separator is low, between 40% and 60%, good impregnation of the electrolyte salt-containing solution into the separator can be achieved. Furthermore, even when the median diameter in the pore distribution is small, between 0.05 μm and 0.2 μm, good impregnation of the electrolyte salt-containing solution into the separator can be achieved.

[0133] The thickness of the separator can be, for example, in the range of 5 μm to 50 μm. More preferably, the thickness of the separator is in the range of 10 μm to 35 μm. According to the battery manufacturing method of the embodiment, even when the thickness of the separator is thick, the impregnation of the electrolyte salt-containing solution into the separator can be made good. Therefore, the thicker the separator, the easier it is to obtain the effect of improving the impregnation of the electrolyte salt-containing solution into the separator.

[0134] The separator may include, for example, a porous film containing polyethylene (PE), polypropylene (PP), cellulose, polyvinylidene fluoride (PVdF), polyimide, polyamide-imide, or aramid, or a nonwoven fabric made of synthetic resin. From a safety standpoint, separators containing polyimide, polyamide-imide, or aramid are preferred because they have high heat resistance. Therefore, the stability of the separator can be improved when the battery precursor is heated to 80°C or higher during battery manufacturing, and when an electrolyte salt-containing solution that has been preheated to 80°C or higher is injected.

[0135] The separator preferably further comprises a layer containing inorganic particles, laminated on the porous film or synthetic resin nonwoven fabric described above. A separator containing a layer of inorganic particles may be less susceptible to shrinkage due to heat. Therefore, it is preferable in battery manufacturing because it is less susceptible to shrinkage even when heated or impregnated with a high-temperature electrolyte salt-containing solution. The layer containing inorganic particles can be formed, for example, by coating a slurry in which inorganic particles are dispersed in a dispersion medium onto the porous film or synthetic resin nonwoven fabric described above, and then removing the dispersion medium.

[0136] Examples of inorganic particles include oxides (e.g., oxides of groups IIA-VA, transition metals, IIIB, IVB, such as Li2O, BeO, B2O3, Na2O, MgO, Al2O3, SiO2, P2O5, CaO, Cr2O3, Fe2O3, ZnO, ZrO2, TiO2, magnesium oxide, silicon oxide, alumina, zirconia, titanium oxide, etc.), zeolites (M 2 / n O·Al2O3·xSiO2·yH2O (wherein M is a metal atom such as Na, K, Ca, and Ba, and n is a metal cation Mn) + A number corresponding to the charge, where x and y are the number of moles of SiO2 and H2O, and 2 ≤ x ≤ 10, 2 ≤ y), nitrides (e.g., BN, AlN, Si3N4 and Ba3N2), silicon carbide (SiC), zircon (ZrSiO4), carbonates (e.g., MgCO3 and CaCO3), sulfates (e.g., CaSO4 and BaSO4), and composites thereof (e.g., types of porcelain such as steatite (MgO·SiO2), forsterite (2MgO·SiO2), and cordierite (2MgO·2Al2O3·5SiO2), tungsten oxide, or mixtures thereof can be used.

[0137] (Measurement method) Of the battery manufacturing conditions, the temperature during battery manufacturing and the internal pressure of the battery precursor can be measured using the method described above.

[0138] The following describes methods for measuring the viscosity of an electrolyte-containing solution, and for measuring the porosity and pore distribution of electrodes and separators.

[0139] (Method for measuring the viscosity of electrolyte-containing solutions) The viscosity of an electrolyte-containing solution can be measured using a rotational viscometer. A predetermined amount of the electrolyte-containing solution to be measured is placed in the apparatus. A plate or cylinder is placed in the sample and rotated, and the viscosity is determined by measuring the shear stress. The measurement should be performed in a non-air-exposed environment.

[0140] (Measurement of porosity and pore distribution) The porosity and pore distribution of the active material-containing layer and separator can be measured by the mercury intrusion method described below.

[0141] First, cut the electrode or separator to be measured to obtain multiple test pieces. The size of the test pieces should be, for example, a strip with a short side of 1.25 cm and a long side of 2.5 cm.

[0142] Next, multiple test specimens are placed in the measuring cell of the measuring device, and mercury is introduced into the pores of the test specimens. The number of test specimens is, for example, between 16 and 32. As the measuring cell, for example, a 5cc cell for large specimens with a stem volume of 0.4cc is used. As the measuring device, for example, a Shimadzu Autopore 9520 (Autopore 9520 model manufactured by Shimadzu Corporation) is used. For the measurement, for example, the initial pressure is set to 7kPa and the final pressure to 414MPa. 7kPa corresponds to 1.0 psia (pounds per square inch absolute pressure), which corresponds to a pore with a diameter of approximately 180μm. Also, 414MPa corresponds to approximately 6 psia, which corresponds to a pore with a diameter of approximately 0.003μm. The mercury contact angle is set to 130 degrees, and the mercury surface tension is set to 485 dynes / cm. By processing the obtained data, the porosity and pore distribution of the test specimen can be obtained.

[0143] (Examples) Examples are given below to explain the present invention in more detail. However, the present invention is not limited to the embodiments described below as long as it does not exceed the gist of the invention.

[0144] (Example 1) (Fabrication of the first electrode) As the first active material, niobium titanate (TNO) was used. To 100 parts by mass of the first active material, 2 parts by mass of acetylene black and 2 parts by mass of graphite powder were added as conductive agents, 2 parts by mass of CMC as a dispersant, 2 parts by mass of CMC and 2 parts by mass of SBR as binders, respectively, and dispersed in water as a solvent to prepare a slurry. The slurry was applied to both sides of a first current collector made of an aluminum foil with a thickness of 12 μm, dried, and pressed. At this time, portions where the slurry was not applied were left on both sides of the first current collector to form the first current collector tabs. After pressing, the first electrode was fabricated by punching out a piece with a size of 75 mm × 85 mm. The density of the first active material-containing layer in the first electrode was 2.6 g / cm 3 It was.

[0145] (Fabrication of the second electrode) As the second active material, lithium nickel cobalt manganese oxide (LiNi 0.5 Co 0.3 Mn 0.2 O2) with an average particle diameter of 3 μm was used. To 100 parts by mass of the second active material, 2 parts by mass of acetylene black and 6 parts by mass of graphite powder were added as conductive agents, and 3 parts by mass of PVdF as a binder, respectively, and dispersed in n-methylpyrrolidone (NMP) as a solvent to prepare a slurry. The slurry was applied to both sides of a current collector made of an aluminum foil with a thickness of 12 μm, dried, and then pressed. At this time, portions where the slurry was not applied were left on both sides of the current collector to form the second current collector tabs. After pressing, the second electrode was fabricated by punching out a piece with a size of 70 mm × 80 mm. The density of the second active material-containing layer in the second electrode was 3.2 g / cm 3 It was.

[0146] (Fabrication of the electrode group) The first and second electrodes were dried at 100°C for 5 hours. A porous polyimide separator with a thickness of 30 μm was prepared as a separator, and this separator was folded into a zigzag pattern. The first and second electrodes were inserted into the space defined by the opposing surfaces of the zigzag-folded separator so that the first and second electrodes faced each other with the separator in between. At this time, the first and second current-collecting tabs were made to extend in the same direction. Thus, the electrode group was fabricated.

[0147] (Preparation of electrolyte-containing solution) An ionic liquid was prepared by mixing triethyl sulfonium bis(trifluoromethylsulfonyl imide) represented by S222TFSI and lithium salt represented by LiFSI, with their respective mole fractions being 0.40 and 0.60. This ionic liquid was used as the electrolyte salt-containing solution. The prepared electrolyte salt-containing solution was heated to 70°C.

[0148] (Preparation of battery precursor) The first terminal was connected to the first current-collecting tab of the electrode group, and the second terminal was connected to the second current-collecting tab. A cylindrical pack made of aluminum laminate sheet with two openings was prepared as the outer casing. The electrode group prepared as described above was housed in the outer casing, so that the first and second terminals extended from one of the two openings of the outer casing. The aluminum laminate pack was heat-sealed at that opening, with the first and second terminals sandwiched between the pack. Thus, a battery precursor was prepared.

[0149] (Heating process and injection process) The battery precursor was subjected to a heating process (heating step) with the other of the two openings in the exterior member described above left open. The heating process was carried out by placing the battery precursor in a vacuum oven chamber, setting the temperature to 80°C, and reducing the gauge pressure to -97kPa, and leaving the battery precursor in the chamber for 2 hours. After 2 hours, an injection process (injection step) was carried out by injecting an electrolyte salt-containing solution at 70°C into the chamber under the same conditions as described above. After that, it was left to stand in the chamber under the same conditions as described above for 1 hour. Then, the other opening in the exterior member was heat-sealed under the same conditions. Thus, a battery was manufactured. The manufactured battery was a secondary battery.

[0150] (Example 2) As an electrolyte salt-containing solution, propylene carbonate (PC) as the solvent and LiPF6 as the electrolyte salt were mixed so that their respective mole fractions were 0.70 and 0.30, respectively, to prepare a concentrated electrolyte salt-containing solution with an electrolyte salt concentration of 3.2 mol / L. The gauge pressure during the heating process was changed to -70 kPa. Except for the above, the battery was manufactured in the same manner as in Example 1.

[0151] (Example 3) A battery was fabricated in the same manner as in Example 1, except that the mole fractions of S222TFSI and LiFSI were set to 0.70 and 0.30, respectively, in the preparation of the ionic liquid as the electrolyte salt solution.

[0152] (Example 4) A battery was fabricated in the same manner as in Example 1, except that a separator consisting of a 12 μm thick polyethylene separator laminated with a layer containing inorganic particles was used as the separator.

[0153] (Examples 5 and 6) A battery was fabricated in the same manner as in Example 1, except that the heating temperature of the battery precursor in the heating process was as shown in Table 2.

[0154] (Example 7) The battery was manufactured in the same manner as in Example 1, except that the gauge pressure during the heating process was changed to -70kPa.

[0155] (Example 8) The electrolyte solution was not heated. The injection process was carried out by injecting the electrolyte solution at 25°C. Except for the above, the battery was manufactured in the same manner as in Example 1.

[0156] (Examples 9, 10) A battery was fabricated in the same manner as in Example 1, except that a 12 μm thick polyethylene separator was used as the separator and the heating temperature of the battery precursor in the heating process was as shown in Table 2.

[0157] (Comparative Example 1) The battery precursor was not heated. Therefore, the electrolyte solution was injected at a battery precursor temperature of 25°C and a gauge pressure of 0 kPa. Except for the above, the battery was fabricated in the same manner as in Example 1.

[0158] (Comparative Example 2) The electrolyte solution was injected under conditions of a battery precursor temperature of 25°C and a gauge pressure of 0 kPa. After the electrolyte solution was injected, the battery precursor was placed in a vacuum oven chamber and left to stand for 2 hours in a chamber set to a temperature of 80°C and a gauge pressure of -97 kPa. After that, it was left to stand for another hour under the same conditions. Subsequently, the other opening of the outer casing was heat-sealed under the same conditions. Except for the above, the battery was manufactured in the same manner as in Example 1.

[0159] (Comparative Example 3) The battery precursor was left to stand for 2 hours in a chamber at a temperature of 25°C and a gauge pressure of -97kPa. Then, under the same conditions as described above, the injection process was carried out by injecting an electrolyte salt-containing solution at 70°C. Except for the above, the battery was manufactured in the same manner as in Example 1.

[0160] (Comparative Example 4) The battery was manufactured in the same manner as in Example 1, except that the gauge pressure during the heating process was changed to -50kPa.

[0161] (Discharge capacity test) The batteries according to the examples and comparative examples were charged to 3.0V at 25°C with a constant current equivalent to 0.2C, and then discharged to 1.5V with a constant current equivalent to 0.2C. The discharge capacity at this time was defined as the initial discharge capacity. A high initial discharge capacity may indicate that the battery has a high capacity.

[0162] Subsequently, the battery was charged to 3.0V with a constant current equivalent to 1C at 25°C, and then discharged to 1.5V with a constant current equivalent to 1C. This cycle was repeated, and the discharge capacity retention rate was determined after 100 cycles. The discharge capacity retention rate serves as an indicator of the battery's cycle performance.

[0163] Table 1 shows the type, composition, viscosity at 25°C, and separator material of the batteries in each example and comparative example. Table 2 shows the temperature and internal pressure (gauge pressure) of the battery precursor, the temperature of the electrolyte solution, the initial discharge capacity, and the discharge capacity retention rate. The initial discharge capacity and discharge capacity retention rate are shown as relative values ​​with the test results for Example 1 set to 100. For Examples 1 to 10 and Comparative Examples 1, 3, and 4, the temperature and internal pressure (gauge pressure) of the battery precursor refer to the temperature and internal pressure of the battery precursor when the electrolyte solution is injected into the outer casing. For Comparative Example 2, the temperature and internal pressure refer to the temperature and internal pressure of the battery precursor after the electrolyte solution has been injected into the outer casing.

[0164] [Table 1]

[0165] [Table 2]

[0166] The batteries in Examples 1-10 showed superior initial discharge capacity and discharge capacity retention rate compared to Comparative Examples 1-4.

[0167] Examples 1 to 3 demonstrate that even when the type and concentration of the electrolyte solution are changed, it is possible to achieve both a high initial discharge capacity and a high discharge capacity retention rate.

[0168] Examples 1, 4, and 9 demonstrated that high initial discharge capacity and discharge capacity retention can be achieved simultaneously even when the type of separator is varied. In particular, Example 1, which included a separator containing polyimide with high heat resistance, and Example 4, which included a separator with a layer containing inorganic particles, showed superior initial discharge capacity and discharge capacity retention.

[0169] Examples 1, 5, 6, and Comparative Example 3 revealed that even when varying the temperature of the battery precursor when injecting the electrolyte salt-containing solution into the outer casing, a battery with both high initial discharge capacity and discharge capacity retention rate can be obtained as long as the temperature of the battery precursor is within the range of 50°C to 120°C. Comparative Example 3, where the temperature of the battery precursor when injecting the electrolyte salt-containing solution into the outer casing was low, showed inferior initial discharge capacity and discharge capacity retention rate.

[0170] The results from Examples 1 and 7 and Comparative Example 4 revealed that even when varying the internal pressure of the battery precursor when injecting the electrolyte salt-containing solution into the outer casing, a battery with both high initial discharge capacity and discharge capacity retention rate can be obtained when the internal pressure is -70 kPa or less in gauge pressure. Comparative Example 4, where the internal pressure of the battery precursor when injecting the electrolyte salt-containing solution into the outer casing was high, showed inferior initial discharge capacity and discharge capacity retention rate.

[0171] From the results of Examples 1 and 8, it became clear that Example 1, in which the temperature of the electrolyte salt-containing solution was higher when injected into the outer casing, yielded a battery with superior initial discharge capacity and discharge capacity retention rate.

[0172] In Comparative Example 1, where the temperature was low at 25°C and the internal pressure of the battery precursor was high at 0 kPa gauge pressure during the electrolyte salt solution injection process, the initial discharge capacity and discharge capacity retention rate were inferior compared to Examples 1-10. Similarly, in Comparative Example 4, where the internal pressure of the battery precursor was high at -50 kPa gauge pressure during the electrolyte salt solution injection process, the initial discharge capacity and discharge capacity retention rate were also inferior compared to Examples 1-10.

[0173] Comparative Example 2 is an example in which the temperature of the battery precursor was set to 80°C and the gauge pressure to -97kPa after injecting the electrolyte salt-containing solution. In Comparative Example 2, the initial discharge capacity and discharge capacity retention rate were inferior to those of Example 1, in which the temperature of the battery precursor was 80°C and the gauge pressure to -97kPa at the time of injection of the electrolyte salt-containing solution. This is thought to be because the expansion of the electrode group due to the high temperature of the battery precursor and the low gauge pressure is greater before the injection of the electrolyte salt-containing solution than after the injection of the electrolyte salt-containing solution. In other words, it is thought that the expansion of the electrode group is greater when only the electrode group is present in the outer casing than when both the electrode group and the electrolyte salt-containing solution are present in the outer casing. Therefore, it is thought that Example 1 was able to expand the gaps in the electrode group more than Comparative Example 2, thereby improving the impregnation of the electrode group with the electrolyte salt-containing solution, and as a result, the initial discharge capacity and discharge capacity retention rate were good.

[0174] Comparative Example 3 is an example in which an electrolyte salt-containing solution at 70°C was injected into a battery precursor at a temperature of 25°C. In Comparative Example 3, the initial discharge capacity and discharge capacity retention rate were inferior to those of Example 1, in which an electrolyte salt-containing solution at 70°C was injected into a battery precursor at a temperature of 80°C. In Example 1, it is thought that the high temperature of the battery precursor at the time of injection of the electrolyte salt-containing solution resulted in uniform expansion of the voids in the electrode group during injection. In contrast, in Comparative Example 3, it is thought that the low temperature of the battery precursor at the time of injection of the electrolyte salt-containing solution resulted in insufficient expansion of the voids in the electrode group during injection. Therefore, even when an electrolyte salt-containing solution preheated to 70°C was injected, the uniformity of the impregnation of the electrolyte salt-containing solution was low, resulting in inferior initial discharge capacity and discharge capacity retention rate.

[0175] A method for manufacturing a battery is provided according to at least one embodiment or example described above. The method for manufacturing a battery includes the steps of preparing a battery precursor and injecting an electrolyte salt-containing solution. The battery precursor includes an outer casing member and an electrode group housed in the outer casing member, including a first electrode and a second electrode. The step of injecting the electrolyte salt-containing solution is to inject the electrolyte salt-containing solution into the outer casing member under the conditions that the temperature is 50°C or higher and 120°C or lower, and the internal pressure of the battery precursor is -70kPa or lower in gauge pressure. The electrolyte salt-containing solution has a viscosity of 10mPa·s or higher at 25°C. Therefore, a method for manufacturing a battery that can realize a high-capacity battery can be provided.

[0176] The invention according to the embodiment is described below.

[0177] [1] A step of preparing a battery precursor which includes an exterior member and an electrode group housed in the exterior member and which includes a first electrode and a second electrode, A method for manufacturing a battery, comprising the step of injecting an electrolyte salt-containing liquid having a viscosity of 10 mPa·s or more at 25°C into the outer casing member, under the conditions that the temperature is 50°C or more and 120°C or less, and the internal pressure of the battery precursor is -70 kPa or less in gauge pressure.

[0178] [2] The method for manufacturing a battery according to [1], further comprising the step of heating the battery precursor before the step of injecting the electrolyte salt-containing solution.

[0179] [3] The method for manufacturing a battery according to [2], wherein the step of heating the battery precursor is to reduce the internal pressure of the battery precursor.

[0180] [4] The method for manufacturing a battery according to any one of [1] to [3], wherein the electrolyte salt-containing solution comprises an ionic liquid having a viscosity of 10 mPa·s or more at 25°C.

[0181] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0182] 1... Electrode group, 2... Container (outer material), 3... Second electrode, 4... First electrode, 5... Separator, 6... Second lead, 7... First lead, 8... Second current collector tab, 9... First current collector tab, 10... Lid material, 11... Insulating material, 12... Outer material, 13... First terminal, 14... Second terminal, 100... Battery precursor, 3a... Second current collector, 3b... Second composite layer, 4a... First current collector, 4b... First composite layer, 28... Injection port, 29... Sealing plate, 12a... First end, 12b... Second end, 12c... Third end, 12d... Fourth end, 27... Gas release valve.

Claims

1. A step of preparing a battery precursor including an exterior member and an electrode group housed in the exterior member, which includes a first electrode and a second electrode, A method for manufacturing a battery, comprising the step of injecting an electrolyte salt-containing liquid having a viscosity of 10 mPa·s or more at 25°C into the outer casing member, under the conditions that the temperature is 50°C or higher and 120°C or lower, and the internal pressure of the battery precursor is -70 kPa or less in gauge pressure.

2. The method for manufacturing a battery according to claim 1, further comprising the step of heating the battery precursor before the step of injecting the electrolyte salt-containing solution.

3. The method for manufacturing a battery according to claim 2, wherein the step of heating the battery precursor includes reducing the internal pressure of the battery precursor.

4. The method for manufacturing a battery according to any one of claims 1 to 3, wherein the electrolyte salt-containing solution includes an ionic liquid having a viscosity of 10 mPa·s or more at 25°C.

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