Method for manufacturing electrode plates, method for manufacturing energy storage devices, and drying apparatus

Abstract

It is possible to manufacture electrode plates with good bonding strength between the electrode foil surface and the electrode layer. [Solution] The method for manufacturing the electrode plate 1 comprises a surface coating step of applying an active material paste 12P to the surface 11a of a strip-shaped electrode foil 11 to form an undried electrode plate 10M, and a surface drying step of drying the active material paste 12P of the undried electrode plate 10M to form an electrode plate 10 having an electrode layer 11 on the surface 11a of the electrode foil 11, while the back surface 11b of the electrode foil 11 does not have an electrode layer 11. In the surface drying step, the back surface of the undried electrode plate 10M (the back surface 11b of the electrode foil 11) is supported by a conveyor belt 33 and conveyed in the longitudinal direction DA, while the undried electrode plate 10M is dried from the surface side. The conveyor belt 33 has a belt surface 33X capable of supporting the back surface of the undried electrode plate 10M, and the belt surface 33X is composed of a heat-resistant surface resin layer 33a that suppresses heat radiation from the back surface of the undried electrode plate 10M over its entire circumference.

Description

Technical Field

[0001] The disclosed technology relates to a method for manufacturing an electrode plate, a method for manufacturing a power storage device, and a drying device.

Background Art

[0002] Patent Document 1 describes applying an active material paste to the surface of a strip-shaped electrode foil and drying the active material paste using a drying device. Specifically, an active material paste containing active material particles, a binder, and a solvent is applied to the surface of the electrode foil. Then, the active material paste applied to the surface of the electrode foil is heated and dried from the surface side using a drying device, so that an electrode plate having an electrode layer on the surface of the electrode foil and no electrode layer on the back surface of the electrode foil is formed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the active material paste is heated and dried from the surface side, the solvent evaporates from the surface of the active material paste, and a flow occurs in which the solvent also moves from the lower side (electrode foil side) to the upper side (surface side of the active material paste) inside the active material paste. At this time, the binder dissolved in the solvent also moves from the lower side to the upper side, causing a so-called migration phenomenon. When the migration phenomenon occurs, inside the dried active material paste (electrode layer), the amount of the binder on the lower side becomes relatively small, so there is a risk of problems such as a decrease in the bonding strength between the surface of the electrode foil and the electrode layer and the electrode layer being easily peeled off.

[0005] In particular, when the electrode foil does not have an electrode layer on its back surface, and the active material paste applied to the surface of the electrode foil is heated and dried from the surface side, the temperature of the back surface of the electrode foil drops significantly compared to the surface temperature of the active material paste due to thermal radiation from the back surface of the electrode foil. In other words, the temperature difference between the surface temperature of the active material paste and the back surface temperature of the electrode foil becomes large. As a result, strong convection of the solvent occurs inside the active material paste, which promotes the migration phenomenon.

[0006] This disclosure is made in view of the current situation and aims to provide a method for manufacturing an electrode plate, a method for manufacturing an energy storage device, and a drying apparatus that can produce an electrode plate with good bonding strength between the surface of the electrode foil and the electrode layer. [Means for solving the problem]

[0007] One aspect of this disclosure is, A surface coating process involves applying an active material paste containing active material particles, a binder, and a solvent to the surface of a strip-shaped electrode foil to form an undried electrode plate. A method for manufacturing an electrode plate comprising: a surface-side drying step of drying the active material paste of the undried electrode plate to form an electrode plate having an electrode layer on the surface of the electrode foil and not having the electrode layer on the back surface of the electrode foil, In the aforementioned surface drying process, The undried electrode plate is supported on its back surface by a conveyor belt and transported in the longitudinal direction, while the undried electrode plate is heated from the front side to dry it. The conveyor belt has a belt surface capable of supporting the back surface of the undried electrode plate, The aforementioned belt surface is composed of a heat-resistant resin layer that suppresses heat radiation from the back surface of the undried electrode plate to the outside of the undried electrode plate over its entire circumference, and is a method for manufacturing an electrode plate.

[0008] Another aspect of this disclosure is an electrode body forming step of forming an electrode body using an electrode plate manufactured by the electrode plate manufacturing method of this disclosure, A method for manufacturing an energy storage device, comprising a housing step of housing the electrode body in a case.

[0009] Another aspect of this disclosure relates to a drying apparatus for drying an undried electrode plate in which an active material paste containing active material particles, a binder, and a solvent is applied to the surface of a strip-shaped electrode foil, A heating unit that heats the active material paste of the undried electrode plate from the surface side of the undried electrode plate, The system includes a conveyor belt that supports the back surface of the undried electrode plate and transports it in the longitudinal direction, The conveyor belt has a belt surface capable of supporting the back surface of the undried electrode plate, The drying apparatus is configured such that the surface of the belt is made of a heat-resistant resin layer that suppresses heat radiation from the back surface of the undried electrode plate to the outside of the undried electrode plate over its entire circumference. [Effects of the Invention]

[0010] The present invention provides a method for manufacturing an electrode plate, a method for manufacturing an energy storage device, and a drying apparatus, which can produce an electrode plate with good bonding strength between the surface of the electrode foil and the electrode layer. [Brief explanation of the drawing]

[0011] [Figure 1] This is a plan view of the electrode plate in the embodiment. [Figure 2] This is a cross-sectional view of the electrode plate shown in Figure 1, along line AA. [Figure 3] This is a cross-sectional view of the electrode plate shown in Figure 1, along the BB line. [Figure 4] This figure illustrates the surface drying process in the embodiment. [Figure 5] This is a cross-sectional view along the CC line shown in Figure 4. [Figure 6] This is a schematic diagram of the battery in the embodiment. [Figure 7] This is a perspective view showing the conveyor belt in the first modified example. [Figure 8] This is a rear view as seen from arrow D, as shown in Figure 7. [Figure 9]It is a perspective view showing the conveyor belt in the second modification. [Figure 10] It is a cross-sectional view of the conveyor belt in the second modification.

Mode for Carrying Out the Invention

[0012] Next, a method for manufacturing an electrode plate, a method for manufacturing a power storage device, and a drying device according to the embodiment will be described. As shown in FIGS. 1 to 3, the electrode plate 10 of the present embodiment includes a strip-shaped electrode foil 11 extending in the longitudinal direction DA and an electrode layer 12 formed on the surface 11a of the electrode foil 11. As described above, the electrode layer 12 is formed on the surface 11a of the electrode foil 11, but the electrode layer 12 is not formed on the back surface 11b of the electrode foil 11. The electrode layer 12 is obtained by heating and drying the active material paste 12P described later. The electrode layer 12 is provided at the central portion in the width direction DB of the surface 11a of the electrode foil 11, while not provided at both end portions in the width direction DB of the surface 11a of the electrode foil 11. The line that bisects the electrode layer 12 in the width direction DB and the line that bisects the electrode foil 11 in the width direction DB coincide.

[0013] Subsequently, the method for manufacturing the electrode plate 10 described above will be described in detail. In the present embodiment, as shown in FIG. 4, the electrode plate 10 is manufactured using a coating device 20 and a drying device 30. The method for manufacturing this electrode plate 10 includes a surface-side coating step of applying the active material paste 12P to the surface 11a of the electrode foil 11 and a surface-side drying step of heating and drying the active material paste 12P applied to the surface 11a of the electrode foil 11 from the surface side. The electrode foil 11 is, for example, an aluminum foil, and the active material paste 12P is, for example, a paste formed by mixing a positive electrode active material that is lithium transition metal composite oxide particles, a conductive material that is acetylene black, a binder that is PVDF, and a solvent that is NMP (N-methylpyrrolidone).

[0014] The coating device 20 is a known die coater and, as shown in FIG. 4, has a support roll 21 and a die 22. The support roll 21 rotates around the axis center O1 to convey the strip-shaped electrode foil 11 in the conveyance direction DL. The conveyance direction DL coincides with the longitudinal direction DA described above. The die 22 discharges the active material paste 12P onto the electrode foil 11 conveyed in the conveyance direction DL. Thus, in the surface-side coating step, while the active material paste 12P is being applied to the surface 11a of the electrode foil 11 by the coating device 20, an undried electrode plate 10M is formed in which the active material paste 12P is not applied to the back surface 11b of the electrode foil 11. Note that the dried active material paste 12P is the electrode layer 12 described above.

[0015] As shown in FIG. 4, the drying device 30 includes an upstream drying chamber 31A, a downstream drying chamber 31B, a number of conveying rolls 32A, 32B, 32C, each conveyor belt 33, a gas supply device 34, a duct 35, and a number of air supply nozzles 36. Since the internal configuration of the upstream drying chamber 31A is the same as the internal configuration of the downstream drying chamber 31B, the configuration of the upstream drying chamber 31A will be described as representative.

[0016] As shown in FIG. 4, a first conveying roll 32A, a second conveying roll 32B, and a third conveying roll 32C are arranged side by side in the conveyance direction DL below the inside of the upstream drying chamber 31A. The first conveying roll 32A, the second conveying roll 32B, and the third conveying roll 32C span the conveyor belt 33 in an oval shape and are rotatable around the axis center O2 by a motor not shown. Thus, when the motor is driven, the conveyor belt 33 rotates in an oval shape as the conveying rolls 32A, 32B, 32C rotate.

[0017] As shown in FIG. 4, the conveyor belt 33 supports the back surface of the undried electrode plate 10M (the back surface 11b of the electrode foil 11) and can convey the undried electrode plate 10M in the conveyance direction DL (the longitudinal direction DA) by rotating. As shown in FIG. 5, the conveyor belt 33 supports the entire width direction DB of the electrode foil 11. The detailed configuration of the conveyor belt 33 will be described later.

[0018] As shown in Figure 4, the gas supply device 34 is located outside the upstream drying chamber 31A and the downstream drying chamber 31B and is in communication with the duct 35. The gas supply device 34 has a heater and a blower fan (not shown), and the hot air heated by the heater is sent to the duct 35 by the blower fan.

[0019] The duct 35 is a connecting pipe that extends in the transport direction DL inside the upper part of the upstream drying chamber 31A and the upper part of the downstream drying chamber 31B, and is fitted with a number of air blowing nozzles 36. In this way, the hot air sent from the gas supply device 34 to the duct 35 passes through the duct 35 and is supplied to each air blowing nozzle 36.

[0020] Each air blower nozzle 36 is positioned at intervals in the transport direction DL inside the upstream drying chamber 31A and the downstream drying chamber 31B. Each air blower nozzle 36 is positioned above the conveyor belt 33 and can blow hot air supplied from the duct 35 toward the surface of the undried electrode plate 10M (the surface of the active material paste 12P) being transported in the transport direction DL. The hot air blown from each air blower nozzle 36 blows over the entire width DB of the surface of the undried electrode plate 10M (the surface of the active material paste 12P). In the drying apparatus 30, the gas supply device 34, the duct 35, and each air blower nozzle 36 correspond to the "heating section".

[0021] Thus, in the surface drying process, the drying apparatus 30 supports the back surface (back surface 11b of the electrode foil 11) of the undried electrode plate 10M with the conveyor belt 33 and transports it in the longitudinal direction DA (transport direction DL), while simultaneously heating and drying the undried electrode plate 10M from the surface side (upper side in Figure 4) with hot air. As a result, the active material paste 12P applied to the surface 11a of the electrode foil 11 dries, forming an electrode plate 10 (see Figures 1 to 3) that has an electrode layer 12 on the surface 11a of the electrode foil 11, but does not have an electrode layer 12 on the back surface 11b of the electrode foil 11.

[0022] Incidentally, during the surface drying process, the solvent evaporates from the surface of the active material paste 12P, creating a flow where the solvent moves from the bottom (electrode foil 11 side) to the top (surface side of the active material paste 12P). At this time, the binder dissolved in the solvent also moves from the bottom to the top, causing a so-called migration phenomenon. When the migration phenomenon occurs, the amount of binder on the bottom side becomes relatively smaller inside the dried active material paste 12P (electrode layer 12), which can lead to a decrease in the bonding strength between the electrode foil 11 and the electrode layer 12, potentially causing problems such as the electrode layer 12 becoming more prone to peeling.

[0023] In particular, when an undried electrode plate 10M, which does not have an electrode layer 12 on the back surface 11b of the electrode foil 11, is heated and dried from the surface side, the back surface 11b of the electrode foil 11 is exposed, making it easy for heat radiation to occur on the back surface 11b of the electrode foil 11. As a result, the temperature of the back surface 11b of the electrode foil 11 drops significantly compared to the surface temperature of the active material paste 12P. In other words, the difference between the surface temperature of the active material paste 12P and the temperature of the back surface 11b of the electrode foil 11 becomes large. As a result, strong convection of the solvent occurs inside the active material paste 12P, promoting the migration phenomenon. That is, when strong convection of the solvent occurs, even binders that could remain on the lower side (electrode foil 11 side) inside the active material paste 12P when strong convection of the solvent was not occurring are more likely to move to the upper side (surface side).

[0024] Here, the inventors found that when an undried electrode plate having an active material paste 12P applied to the surface 11a of the electrode foil 11 and an electrode layer 12 on the back surface 11b of the electrode foil 11 is heated and dried from the surface side, the migration phenomenon is not promoted. This is thought to be because, since the back surface 11b of the electrode foil 11 is not exposed, heat radiation is less likely to occur on the back surface 11b of the electrode foil 11, and as described above, the temperature of the back surface 11b of the electrode foil 11 does not drop significantly compared to the surface temperature of the active material paste 12P. In other words, when an electrode layer 12 is provided on the back surface 11b of the electrode foil 11, the difference between the surface temperature of the active material paste 12P and the temperature of the back surface 11b of the electrode foil 11 does not become large. Therefore, when an electrode layer 12 is present on the back surface 11b of the electrode foil 11, strong convection of the solvent inside the active material paste 12P is less likely to occur during the surface-side drying process, and the migration phenomenon is not promoted.

[0025] Therefore, in order to reduce the temperature difference between the surface temperature of the active material paste 12P and the temperature of the back surface 11b of the electrode foil 11 during the surface drying process, the inventors configured the conveyor belt 33 as shown in Figure 5. Figure 5 is a cross-sectional view along the CC line in Figure 4. As shown in Figure 5, the conveyor belt 33 has a surface resin layer 33a, a back resin layer 33b, an adhesive rubber layer 33c, and a number of steel cords 33d. The length DB in the width direction of this conveyor belt 33 is greater than the length in the width direction of the electrode foil 11.

[0026] The surface resin layer 33a and the back resin layer 33b are each made of a heat-resistant resin, such as Teflon (registered trademark). The surface of the surface resin layer 33a is in contact with the back surface of the undried electrode plate 10M (the back surface 11b of the electrode foil 11), and the back surface of the surface resin layer 33a is bonded to the surface of the adhesive rubber layer 33c. The surface of the back resin layer 33b is bonded to the back surface of the adhesive rubber layer 33c, and the back surface of the back resin layer 33b is in contact with the circumferential surface of the first conveyor roll 32A. The adhesive rubber layer 33c interposes a large number of steel cords 33d between the surface resin layer 33a and the back resin layer 33b. The large number of steel cords 33d are high-strength core materials extending in the conveying direction DL (longitudinal direction DA), and are arranged at intervals in the width direction DB to reinforce the conveyor belt 33.

[0027] As described above, the belt surface 33X of the conveyor belt 33 can support the entire width DB of the back surface (back surface 11b of the electrode foil 11) of the undried electrode plate 10M. Furthermore, this belt surface 33X is composed of a heat-resistant surface resin layer 33a that suppresses heat radiation from the back surface (back surface 11b of the electrode foil 11) of the undried electrode plate 10M to the outside (bottom) of the undried electrode plate 10M over its entire circumference.Therefore, in the surface drying process, the belt surface 33X can suppress heat radiation from the back surface of the undried electrode plate 10M, thereby reducing the temperature difference between the surface temperature of the active material paste 12P and the temperature of the back surface of the undried electrode plate 10M.As a result, convection occurring inside the active material paste 12P can be suppressed.

[0028] In other words, during the surface drying process, heat is not easily transferred from the back surface of the undried electrode plate 10M (the back surface 11b of the electrode foil 11) to the belt surface 33X of the conveyor belt 33, and the temperature of the back surface 11b of the electrode foil 11 does not drop significantly relative to the surface temperature of the active material paste 12P. As a result, strong convection of the solvent within the active material paste 12P is less likely to occur, as is the case when an undried electrode plate having an electrode layer 12 on the back surface 11b of the electrode foil 11 is heated and dried from the surface side. As a result, migration phenomena can be suppressed, and an electrode plate 10 with good bonding strength between the surface 11a of the electrode foil 11 and the electrode layer 12 can be manufactured.

[0029] In conventional drying apparatuses for drying the active material paste 12P, it is common practice to make the path for transporting the undried electrode plate 10M in the longitudinal direction DA sufficiently long, thereby slowly heating and drying the active material paste 12P. This is because migration phenomena can be suppressed as much as possible. In contrast, in this embodiment, as described above, migration phenomena can be suppressed by reducing the temperature difference between the surface temperature of the active material paste 12P and the temperature of the back surface of the undried electrode plate 10M. Therefore, unlike conventional drying apparatuses, it is not necessary to make the path for transporting the undried electrode plate 10M in the longitudinal direction DA sufficiently long, and the drying apparatus 30 can be configured compactly.

[0030] In this embodiment, the belt surface 33X is made of Teflon, a heat-resistant resin layer, so that in the surface drying process, the temperature difference between the surface temperature of the active material paste 12P and the temperature of the back surface of the undried electrode plate 10M is, for example, 15 degrees or less. However, the composition of the belt surface 33X is not limited to Teflon; any heat-resistant resin layer such as polypropylene or EPDM (ethylene propylene rubber) may be used, and can be changed as appropriate.

[0031] Next, a method for manufacturing a battery 1 (an example of an energy storage device), which is a lithium-ion secondary battery according to the embodiment, will be described. First, the configuration of the battery 1 will be described with reference to Figure 6. As shown in Figure 6, the battery 1 comprises a case 2, an electrode body 3 housed inside the case 2, and an electrolyte 4. The case 2 is a rectangular box shape and comprises a bottomed rectangular cylindrical case body 2a and a lid 2b. The periphery of the lid 2b is joined to the upper end of the case body 2a by laser welding. A positive electrode terminal 6P is fixed to one end of the lid 2b (right side in Figure 6) via an insulating member 5, and a negative electrode terminal 6N is fixed to the other end of the lid 2b (left side in Figure 6) via an insulating member 5.

[0032] The electrode body 3 is formed by winding a strip-shaped positive electrode plate 3P and a strip-shaped negative electrode plate 3N around a pair of separators 3S, and is thinned and flattened in the direction perpendicular to the plane of the paper in Figure 6. One end of the electrode body 3 (the right end in Figure 6) is a positive electrode current collector section 3a where the electrode foils of each positive electrode plate 3P are overlapped. The lower end 6Pa of the positive electrode terminal 6P is joined to the positive electrode current collector section 3a. On the other hand, the other end of the electrode body 3 (the left end in Figure 6) is a negative electrode current collector section 3b where the electrode foils of each negative electrode plate 3N are overlapped. The lower end 6Na of the negative electrode terminal 6N is joined to the negative electrode current collector section 3b. The electrolyte 4 is housed inside the case 2. A portion of the electrolyte 4 is impregnated into the inside of the electrode body 3, and the remainder of the electrolyte is accumulated at the bottom of the case 2.

[0033] In this battery 1, the positive electrode plate 3P is manufactured by the electrode plate manufacturing method described above. Specifically, the active material paste 12P described above is applied to the surface 11a of the electrode foil 11, which is aluminum foil, and this active material paste 12P is heated and dried. Subsequently, the active material paste 12P described above is applied to the back surface 11b of the electrode foil 11, and this active material paste 12P is heated and dried. In this way, electrode layers 12 are formed on the surface 11a and back surface 11b of the electrode foil 11, respectively, thereby manufacturing the positive electrode plate 3P.

[0034] Similarly, the negative electrode plate 3N is also manufactured using the electrode plate manufacturing method described above. However, in the case of the negative electrode plate 3N, copper foil is used as the electrode foil 11, and the active material paste 12P is a mixture of, for example, graphite particles as the negative electrode active material, SBR (styrene-butadiene rubber) as the binder, CMC (carboxymethylcellulose) as the thickener, and deionized water as the solvent. Thus, the active material paste 12P is applied to the surface 11a of the copper foil electrode foil 11, and the active material paste 12P is heated and dried. Subsequently, the active material paste 12P is applied to the back surface 11b of the electrode foil 11, and the active material paste 12P is heated and dried. In this way, the electrode layer 12 is formed on the surface 11a and the back surface 11b of the electrode foil 11, respectively, thereby manufacturing the negative electrode plate 3P.

[0035] The manufacturing method for the battery 1 described above comprises an electrode body formation step and a housing step. In the electrode body formation step, an electrode body 3 is formed using a known method with a positive electrode plate 3P manufactured by the electrode plate manufacturing method described above, a negative electrode plate 3N manufactured by the electrode plate manufacturing method described above, and a separator 3S. Then, in the housing step, the electrode body 3 is housed inside the case 2 (case body 2a) using a known method, and the periphery of the lid 2b is joined to the upper end of the case body 2a. In summary, this manufacturing method for the battery 1 makes it possible to suppress the migration phenomenon in the positive electrode plate 3P and negative electrode plate 3N, which are prone to migration. Therefore, a highly reliable battery 1 can be manufactured using a positive electrode plate 3P and negative electrode plate 3N that have good bonding strength between the surface 11a of the electrode foil 11 and the electrode layer 12.

[0036] Next, the first modified example will be described with reference to Figures 7 and 8. Figure 7 is a perspective view showing the conveyor belt 33A in the first modified example. In the first modified example, the configuration of the conveyor belt 33A differs from the configuration of the conveyor belt 33 in the embodiment described above. As shown in Figure 7, the conveyor belt 33A of the first modified example incorporates a bellows-shaped heating element 37 (heater).

[0037] The heating element 37 is for heating the back surface (back surface 11b of the electrode foil 11) of the undried electrode plate 10M via the conveyor belt 33A, and is built into the surface resin layer 33a of the conveyor belt 33A. As shown in Figure 7, the drying apparatus 30A of the first modified example is provided with a positive electrode side power supply roller 32A1 and a negative electrode side power supply roller 32A2 in place of the first transport roll 32A of the embodiment. The drying apparatus 30A is also provided with a power supply 38. The positive electrode side power supply roller 32A1 and the negative electrode side power supply roller 32A2 are spaced apart in the width direction DB. The positive electrode side power supply roller 32A1 is connected to the positive electrode side of the power supply 38, and the negative electrode side power supply roller 32A2 is connected to the negative electrode side of the power supply 38. The positive electrode side power supply roller 32A1 and the negative electrode side power supply roller 32A2 are rotatable around the axis center O2.

[0038] Here, Figure 8 is a rear view as seen from arrow D shown in Figure 7. As shown in Figure 8, on the back surface of the conveyor belt 33A, a positive terminal plate 33f1 is provided on one end of the width direction DB (upper side in Figure 8), and a negative terminal plate 33f2 is provided on the other end of the width direction DB (lower side in Figure 8). The positive terminal plate 33f1 and the negative terminal plate 33f2 extend in the longitudinal direction DA and are arranged around the entire circumference on the back surface of the conveyor belt 33A. Therefore, even when the conveyor belt 33A rotates, the positive terminal plate 33f1 and the negative terminal plate 33f2 are always in contact with the positive power supply roller 32A1 and the negative power supply roller 32A2.

[0039] As shown in Figure 8, one end 37a of the heating element 37 is exposed from the conveyor belt 33A (backside resin layer 33b) and connected to the positive terminal plate 33f1. The other end 37b of the heating element 37 is also exposed from the conveyor belt 33A and connected to the negative terminal plate 33f2. As a result, current flows from the positive side of the power supply 38 to the negative side of the power supply 38 via the positive terminal supply roller 32A1, the positive terminal plate 33f1, the heating element 37, the negative terminal plate 33f2, and the negative terminal supply roller 32A2, allowing the heating element 37 to generate heat.

[0040] According to the first modified example, in the surface drying process, the belt surface 33X, which is composed of a heat-resistant surface resin layer 33a, can suppress heat radiation from the back surface of the undried electrode plate 10M (the back surface 11b of the electrode foil 11). Furthermore, since the conveyor belt 33A has a heating element 37 built in, the back surface of the undried electrode plate 10M is heated by the heat generated by the belt surface 33X. This makes it possible to further reduce the temperature difference between the surface of the active material paste 12P and the back surface of the undried electrode plate 10M, thereby further suppressing heat radiation from the back surface of the undried electrode plate 10M.

[0041] Next, a second modified example will be described with reference to Figures 9 and 10. Figure 9 is a perspective view showing the conveyor belt 33B in the second modified example. In the second modified example, the configuration of the conveyor belt 33B of the drying apparatus 30B is different from the configuration of the conveyor belt 33 of the drying apparatus 30 in the embodiment described above. As shown in Figure 9, the conveyor belt 33B of the second modified example has a number of recesses 33g on its surface side. Each recess 33g is arranged in a grid pattern, spaced apart in the longitudinal direction DA and spaced apart in the width direction DB. Each of these recesses 33g is formed, for example, by embossing the surface resin layer 33a of the conveyor belt 33.

[0042] Thus, as shown in Figure 10, the surface resin layer 33a of the conveyor belt 33B of the second modified example has numerous protrusions 33h that support the back surface of the undried electrode plate 10M (the back surface 11b of the electrode foil 11) in a scattered manner with numerous recesses 33g. In other words, the surface resin layer 33a of the conveyor belt 33B is an uneven resin layer that forms an insulating air layer DK between itself and the back surface of the undried electrode plate 10M (the back surface 11b of the electrode foil 11).

[0043] According to the second modified example, in the surface drying process, since the surface resin layer 33a of the conveyor belt 33B is an uneven resin layer, there is less contact with the back surface of the undried electrode plate 10M (the back surface 11b of the electrode foil 11), and the transfer of heat from the back surface 11b of the electrode foil 11 to the conveyor belt 33B is suppressed. Furthermore, since an insulating air layer DK is formed between the back surface of the undried electrode plate 10M and the uneven resin layer, heat radiation from the back surface of the undried electrode plate 10M can be further suppressed.

[0044] Although the present disclosure has been described above in relation to the embodiments and their respective modifications, it goes without saying that the present disclosure is not limited to the embodiments and their respective modifications, and can be modified and applied as appropriate without departing from its essence.

[0045] In this embodiment, the belt surface 33X was configured such that the temperature difference between the surface temperature of the active material paste 12P and the temperature of the back surface of the undried electrode plate 10M was 15 degrees or less during the surface drying process. However, the temperature difference between the surface temperature of the active material paste 12P and the temperature of the back surface of the undried electrode plate 10M is not limited to 15 degrees or less; for example, the belt surface 30X may be configured so that the temperature difference is 20 degrees or less or 10 degrees or less. However, from the viewpoint of suppressing heat radiation from the back surface of the undried electrode plate 10M, it is preferable to configure the belt surface 33X so that the temperature difference between the surface temperature of the active material paste 12P and the temperature of the back surface of the undried electrode plate 10M is as small as possible.

[0046] In the first modified example, the heating element 37 embedded in the conveyor belt 33A was heated, but the amount of heat generated by the heating element 37 may be controlled based on the temperature of the back surface of the undried electrode plate 10M, or based on the difference between the surface temperature of the active material paste 12P and the temperature of the back surface of the undried electrode plate 10M. Specifically, a temperature sensor for detecting the temperature of the back surface of the undried electrode plate 10M and a temperature sensor for detecting the surface temperature of the active material paste 12P may be provided, and the amount of heat generated by the heating element 37 may be controlled based on the values ​​detected by these temperature sensors. Although a heating element 37 was used as the heater for heating the conveyor belt 33A, a thermoelectric element may also be used, for example, and can be changed as appropriate.

[0047] In this embodiment, a lithium-ion secondary battery, battery 1, was manufactured as the energy storage device. However, the energy storage device may also be a sodium-ion secondary battery, a calcium-ion secondary battery, or a capacitor such as a lithium-ion capacitor, and can be changed as appropriate. [Explanation of Symbols]

[0048] 1 battery 2 cases 3 Electrode body 10 Electrode plate 10M undried electrode plate 11 Electrode foil 11a surface 11b Back side 12 Electrode layer 12P Active Material Paste 20 Coating equipment 30, 30A, 30B drying equipment 30X Belt surface 33A, 33B, 33C Conveyor Belts 33a Surface side resin layer 33g recess 33h protrusion DK Insulation Air Layer

Claims

1. A surface coating process involves applying an active material paste containing active material particles, a binder, and a solvent to the surface of a strip-shaped electrode foil to form an undried electrode plate. A method for manufacturing an electrode plate comprising: a surface-side drying step of drying the active material paste of the undried electrode plate to form an electrode plate having an electrode layer on the surface of the electrode foil and not having the electrode layer on the back surface of the electrode foil, In the aforementioned surface drying process, The undried electrode plate is supported on its back surface by a conveyor belt and transported in the longitudinal direction, while the undried electrode plate is heated from the front side to dry it. The conveyor belt has a belt surface capable of supporting the back surface of the undried electrode plate, A method for manufacturing an electrode plate, wherein the surface of the belt is composed of a heat-resistant resin layer that suppresses heat radiation from the back surface of the undried electrode plate to the outside of the undried electrode plate over its entire circumference.

2. In the method for manufacturing an electrode plate according to claim 1, The conveyor belt has a built-in heater that heats the back surface of the undried electrode plate. In the aforementioned surface drying process, A method for manufacturing an electrode plate, comprising using the conveyor belt to support the back surface of the undried electrode plate while transporting it in the longitudinal direction, and heating the back surface of the undried electrode plate.

3. In the method for manufacturing an electrode plate according to claim 1 or claim 2, The resin layer of the conveyor belt is The undried electrode plate has numerous protrusions that support the back surface in a scattered manner, A method for manufacturing an electrode plate, which is an uneven resin layer that forms an insulating air layer between itself and the back surface of the undried electrode plate.

4. An electrode body forming step of forming an electrode body using an electrode plate manufactured by the electrode plate manufacturing method described in claim 1 or claim 2, A method for manufacturing an energy storage device, comprising a housing step of housing the electrode body in a case.

5. In a drying apparatus for drying an undried electrode plate in which an active material paste containing active material particles, a binder, and a solvent is applied to the surface of a strip-shaped electrode foil, A heating unit that heats the active material paste of the undried electrode plate from the surface side of the undried electrode plate, The system includes a conveyor belt that supports the back surface of the undried electrode plate and transports it in the longitudinal direction, The conveyor belt has a belt surface capable of supporting the back surface of the undried electrode plate, The drying apparatus is configured such that the surface of the belt is made of a heat-resistant resin layer that suppresses heat radiation from the back surface of the undried electrode plate to the outside of the undried electrode plate over its entire circumference.

6. In the drying apparatus according to claim 5, The conveyor belt is a drying device that incorporates a heater for heating the back surface of the undried electrode plate.

7. In the drying apparatus according to claim 5 or claim 6, The resin layer of the conveyor belt is The undried electrode plate has numerous protrusions that support the back surface in a scattered manner, A drying apparatus comprising a textured resin layer that forms an insulating air layer between itself and the back surface of the undried electrode plate.

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