Patent Publication Number: US-2023155103-A1

Title: Electrode manufacturing apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-185892 filed on Nov. 15, 2021, incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The disclosure relates to an electrode manufacturing apparatus. 
     2. Description of Related Art 
     Japanese Unexamined Patent Application Publication No. 2017-103015 (JP 2017-103015 A) discloses an electrode plate manufacturing apparatus having a first roll and a second roll that are opposed to each other at a first position, and a third roll opposed to the second roll at a second position. In the electrode plate manufacturing apparatus, while the first to third rolls are rotated, an electrode material is supplied to the first position, and a current collecting foil is passed through the second position. The electrode plate manufacturing apparatus has a flow channel roll having a flow channel formed therein and an outer circumferential surface that is in contact with an outer circumferential surface of at least one of the first to third rolls, and a circulating unit that circulates fluid in the flow channel. During manufacturing of electrode plates, the circulating unit circulates the fluid through the flow channel of the flow channel roll, so as to curb temperature changes in the roll that is in contact with the flow channel roll. 
     SUMMARY 
     In the apparatus described in the above-identified publication, when a large-area battery is produced, it is difficult to maintain the uniformity of the thickness of the electrode in the width direction. 
     This disclosure proposes an electrode manufacturing apparatus capable of maintaining the uniformity of the thickness of an electrode. 
     According to a first aspect of the disclosure, an electrode manufacturing apparatus including a film forming device configured to form an electrode layer on a surface of a substrate is proposed. The film forming device includes a first roll configured to rotate, a second roll that is spaced apart from and opposed to the first roll and configured to rotate in an opposite direction of the first roll, a third roll that is spaced apart from and opposed to the second roll and configured to rotate in the opposite direction of the second roll, and a temperature adjusting unit. The temperature adjusting unit is configured to reduce a temperature difference between a central portion and an end portion in an axial direction of at least one roll of the first roll, the second roll, and the third roll. 
     The temperature adjusting unit is configured to reduce the temperature difference between the central portion and the end portion of the roll, so that the uniformity of the thermal expansion between the central portion and the end portion of the roll can be improved, and the uniformity of the outside diameter of the roll between the central portion and the end portion of the roll can be improved. Accordingly, the uniformity of the thickness of the electrode in the width direction can be maintained. 
     In the above electrode manufacturing apparatus, the temperature adjusting unit may be configured to adjust the temperature of at least the second roll. By adjusting the temperature of the second roll, the uniformity of the thickness of the electrode can be efficiently maintained. 
     In the above electrode manufacturing apparatus, the temperature adjusting unit may be configured to adjust the temperature of at least the third roll. By adjusting the temperature of the third roll, the uniformity of the thickness of the electrode can be efficiently maintained. 
     In the above electrode manufacturing apparatus, the temperature adjusting unit may have a cooling device that cools the end portion. With this arrangement, the temperature difference between the central portion and the end portion of the roll can be reliably reduced. 
     In the above electrode manufacturing apparatus, the temperature adjusting unit may have a heating device that heats the central portion. With this arrangement, the temperature difference between the central portion and the end portion of the roll can be reliably reduced. 
     In the above electrode manufacturing apparatus, the film forming device may further include temperature sensors that detect temperatures of the central portion and the end portion. The temperature adjusting unit can efficiently reduce the temperature difference between the central portion and the end portion of the roll, based on the temperature difference between the central portion and the end portion of the roll. 
     A second aspect of the disclosure relates to an electrode manufacturing apparatus including a film forming device configured to form an electrode layer on a surface of a substrate. The film forming device includes a first roll configured to rotate; a second roll that is spaced apart from and opposed to the first roll and configured to rotate in an opposite direction of the first roll; a third roll that is spaced apart from and opposed to the second roll and configured to rotate in the opposite direction of the second roll; and a temperature adjusting unit configured to heat only a central portion in an axial direction of at least one roll of the first roll, the second roll, and the third roll. 
     A second aspect of the disclosure relates to an electrode manufacturing apparatus including a film forming device configured to form an electrode layer on a surface of a substrate. The film forming device includes a first roll configured to rotate; a second roll that is spaced apart from and opposed to the first roll and configured to rotate in an opposite direction of the first roll; a third roll that is spaced apart from and opposed to the second roll and configured to rotate in the opposite direction of the second roll; and a temperature adjusting unit configured to cool only opposite end portions in an axial direction of at least one roll of the first roll, the second roll, and the third roll. 
     According to the electrode manufacturing apparatus of this disclosure, even when a large-area battery is produced, the uniformity of the thickness of the electrode can be maintained. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein: 
         FIG.  1    is a perspective view schematically showing the configuration of an electrode in one embodiment; 
         FIG.  2    is a conceptual diagram showing an electrode manufacturing apparatus according to the embodiment; 
         FIG.  3    is a conceptual diagram showing details of the configuration of a film forming device; 
         FIG.  4    is a conceptual, perspective view showing details of the configuration of the film forming device; 
         FIG.  5    is a schematic view showing a first example of a temperature adjusting unit; 
         FIG.  6    is a schematic view showing a second example of the temperature adjusting unit; 
         FIG.  7    is a graph showing the temperature difference and the thickness difference between a central portion and end portions of a roll in a comparative example; and 
         FIG.  8    is a graph showing the temperature difference and the thickness difference between a central portion and end portions of a roll in an example. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     One embodiment will be described based on the drawings. In the following description, the same reference signs are assigned to the same components. The names and functions of these components are identical. Thus, detailed description of the components will not be repeated. 
     Electrode  100   
       FIG.  1    is a perspective view schematically showing the configuration of an electrode  100  in the embodiment. The electrode  100  is used, for example, as an electrode of a lithium-ion secondary battery (non-aqueous electrolyte secondary battery). The lithium-ion secondary battery can be used, for example, as a power supply of a hybrid electric vehicle (HEV), battery electric vehicle (BEV), plug-in hybrid electric vehicle (PHEV), or the like. However, the electrode  100  of this disclosure is not limited to such automotive applications, but can be applied to any use. 
     As shown in  FIG.  1   , the electrode  100  has a substrate  110  and an electrode layer  120 . The substrate  110  is a support for the electrode layer  120 . The substrate  110  may be in the form of a sheet, for example. The substrate  110  may be in the form of a strip, for example. The substrate  110  may have electrical conductivity. The substrate  110  may function as a current collector. The substrate  110  may include, for example, a metal foil. When the electrode  100  is a positive electrode, the substrate  110  may include, for example, an aluminum foil. When the electrode  100  is a negative electrode, the substrate  110  may include, for example, a copper foil. 
     The electrode layer  120  is formed on a surface of the substrate  110 . The electrode layer  120  may be formed on only one surface of the substrate  110  as shown in  FIG.  1   , or may be formed on both the front and back surfaces of the substrate  110 . 
     The electrode layer  120  is an electrode active material layer containing electrode active material. The electrode active material may be a positive-electrode active material or a negative-electrode active material. The positive-electrode active material may be selected from, for example, lithium-containing metal oxides, lithium-containing phosphates, etc. The negative-electrode active material may be selected from, for example, carbon-based negative-electrode active materials such as graphite, easily graphitizable carbon, and non-graphitizable carbon, and alloy-based negative-electrode active materials containing silicon, tin, etc. 
     Recesses  121  (grooves) are formed in the electrode layer  120 . At least one recess  121  is formed in the electrode layer  120 . The recess  121  has any cross-sectional shape. The bottom of the recess  121  may be flat, curved, or inclined. The recess  121  may be U-shaped or V-shaped in cross-section. Raised portions  122  are formed between adjacent ones of the recesses  121 . 
     The electrode  100  has a long-side or longitudinal direction (Y-direction) and a short-side direction (X-direction). The longitudinal direction corresponds to the conveying direction in the manufacturing process of the electrode  100 . The short-side direction is perpendicular to the longitudinal direction, and may also be referred to as the “width direction” of the electrode  100 . The electrode  100  also has a thickness direction (Z-direction). The thickness direction is perpendicular to the XY plane. The recess  121  is formed such that a part of the electrode layer  120  is recessed from the surface of the electrode layer  120 , to extend in the Z-direction. 
     In the example shown in  FIG.  1   , the recesses  121  and the raised portions  122  extend in the short-side direction. The recesses  121  are formed at equal intervals in the longitudinal direction. The recesses  121  extending in the short-side direction of the electrode  100  are formed in the electrode layer  120 , to give flexibility to the electrode  100 . Thus, cracking of the electrode layer  120  during conveyance of the electrode  100  is curbed, and the conveyability of the electrode  100  is improved. 
     The electrode  100  may have recesses  121  and raised portions  122  extending in the longitudinal direction. The electrode  100  may have both recesses  121  and raised portions  122  extending in the longitudinal direction and recesses  121  and raised portions  122  extending in the short-hand direction. 
     The shape of each of the recesses  121  is not limited to the straight line shown in  FIG.  1   , but may be curved, wavy, or dotted. The planar pattern of the recesses  121  may be a set of numerous parallel lines or a grid. 
     Electrode Manufacturing Apparatus  1   
       FIG.  2    is a conceptual diagram showing the electrode manufacturing apparatus  1  according to the embodiment. As shown in  FIG.  2   , the electrode manufacturing apparatus  1  includes a conveyor device  10 , film forming device  20 , shaping device  40 , and drying device  50 . 
     The conveyor device  10  has a feed roll  11  and a take-up roll  12 . The feed roll  11  is formed such that the substrate  110  is wound around its core material. The substrate  110  is rolled out from the feed roll  11 . The take-up roll  12  takes up the substrate  110  (electrode  100 ). The conveyor device  10  conveys the substrate  110  such that it passes through the film forming device  20 , shaping device  40 , and drying device  50  in this order, and conveys the electrode  100  as a laminate formed by laminating the electrode layer  120  on the substrate  110 . 
     The film forming device  20  forms the electrode layer  120  on the surface of the substrate  110 . Details of the film forming device  20  will be described later. 
     The shaping device  40  forms an uneven shape on the surface of the electrode layer  120 . The shaping device  40  forms the recesses  121  and the raised portions  122  in the electrode layer  120 . The shaping device  40  has a shaping roll  41  and an opposed roll  42 , for example. One or more protrusion molds are formed on the outer circumferential surface of the shaping roll  41 . The shaping device  40  forms the recesses  121  and the raised portions  122  on the surface of the electrode layer  120 , by sandwiching the electrode  100  carried by the conveyor device  10  in the longitudinal direction (Y-direction) with the shaping roll  41  and the opposed roll  42 , and pressing the protrusion molds of the shaping roll  41  against the surface of the electrode layer  120  at this time. The shaping device  40  is located on the upstream side of the drying device  50  in the conveying direction of the electrode  100 , and is arranged to process the surface of the electrode layer  120  that is in a wet state before drying. This makes it easy to form the uneven shape. 
     The drying device  50  dries the electrode layer  120  after the uneven shape is formed. The drying device  50  can dry the electrode layer  120  by any given method. For example, the drying device  50  may include a hot air dryer, an infrared dryer, etc. Drying conditions (drying temperature, drying time, etc.) in the drying device  50  are adjusted so that the electrode layer  120  is brought into a dry state. 
     After the electrode layer  120  is dried, the electrode  100  is cut to a predetermined size using, for example, a slitter, to produce a sheet-like electrode  100  as shown in  FIG.  1   . 
     Film Forming Device  20   
     In the film forming device  20 , the electrode material is supplied between a pair of rolls that are arranged in parallel with each other with a spacing therebetween and are respectively driven to be rotated, and the electrode material is compressed and formed by the pair of rolls to form a sheet-like coating film. 
       FIG.  3    is a conceptual diagram showing details of the configuration of the film forming device  20 .  FIG.  4    is a conceptual perspective view showing details of the configuration of the film forming device  20 . As shown in  FIG.  3    and  FIG.  4   , the film forming device  20  has a first roll  21 , second roll  22 , and third roll  23 . The first roll  21 , second roll  22 , and third roll  23  have a generally cylindrical shape having substantially the same diameter. 
     The first roll  21 , second roll  22 , and third roll  23  are respectively driven to be rotated. In  FIG.  3    and  FIG.  4   , a curved arrow depicted in each roll indicates the rotational direction of the roll. The second roll  22  rotates in the opposite direction of the first roll  21 . The third roll  23  rotates in the opposite direction of the second roll  22 . In  FIG.  3    and  FIG.  4   , the first roll  21  rotates in the clockwise direction, the second roll  22  rotates in the counterclockwise direction, and the third roll  23  rotates in the clockwise direction. 
     The second roll  22  is spaced apart from and arranged in parallel with the first roll  21 . The outer circumferential surfaces of the first roll  21  and the second roll  22  are opposed to each other via a first gap, which is a gap between the first roll  21  and the second roll  22 . The axes of the first roll  21  and the second roll  22  are fixed so that the distance between these rolls is kept constant. 
     The third roll  23  is spaced apart from and arranged in parallel with the second roll  22 . The outer circumferential surfaces of the second roll  22  and the third roll  23  are opposed to each other via a second gap, which is a gap between the second roll  22  and the third roll  23 . The axis of the third roll  23  is fixed so that the distance between the third roll  23  and the second roll  22  is kept constant. 
     A feeder  25  is located right above the first gap between a pair of rolls, specifically, between the first roll  21  and the second roll  22 . The feeder  25  supplies an electrode material  91  to the first gap between the first roll  21  and the second roll  22 . The electrode material  91  is, for example, powder. 
     As shown in  FIG.  4   , the film forming device  20  further has a pair of partition walls  24 . The partition walls  24  are arranged in parallel with each other, with a given spacing in the axial direction of each roll. The partition walls  24  put a limit to the width dimension of the electrode material  91  supplied to the gap between the first roll  21  and the second roll  22 . 
     As the first roll  21  and the second roll  22  rotate, the electrode material  91  passes through the first gap between the first roll  21  and the second roll  22 , and is drawn downward of the first gap. The electrode material  91  is consolidated (compressed) and formed into a sheet as it passes through the first gap between the first roll  21  and the second roll  22 . In this manner, a thin coating film  92  is formed from the electrode material  91 . By changing the dimensions of the first gap between the first roll  21  and the second roll  22 , it is possible to adjust the thickness of the coating film  92  and the mass per unit area of the coating film  92 . 
     After passing through the first gap between the first roll  21  and the second roll  22 , the coating film  92  is conveyed while adhering to the second roll  22 , and fed to the second gap between the second roll  22  and the third roll  23 . 
     The substrate  110  is conveyed to the third roll  23  after it is rolled out from the feed roll  11  ( FIG.  2   ). The substrate  110  is conveyed on the third roll  23 , and fed to the second gap between the second roll  22  and the third roll  23 . 
     The coating film  92  and the substrate  110  are supplied between the second roll  22  and the third roll  23 . In the second gap, the coating film  92  is pressed against the substrate  110 , and the coating film  92  is pressed onto the surface of the substrate  110 , away from the second roll  22 . Namely, the coating film  92  is transferred from the second roll  22  to the substrate  110 . In this manner, the electrode  100  is formed in which the sheet-like electrode layer  120  is laminated at a predetermined position on the surface of the substrate  110 . The second roll  22  and the third roll  23  constitute a pair of rolls rotating in opposite directions while sandwiching the electrode  100  therebetween. 
     Since the film forming device  20  has the partition walls  24 , which put a limit to the width dimension of the electrode layer  120 , exposed portions (see  FIG.  1   ) on which the electrode layer  120  is not formed are provided in the electrode  100  on the opposite sides of the electrode layer  120  in the width direction (X-direction) of the electrode  100 . 
     In the example shown in  FIG.  3    and  FIG.  4   , the first roll  21 , second roll  22 , and third roll  23  are arranged side by side, and the rotation axes of the first roll  21 , second roll  22 , and third roll  23  are on the same plane. The first roll  21 , second roll  22 , and third roll  23  are not limited to those of the example shown in  FIG.  3    and  FIG.  4   , but may be located as desired. For example, the third roll  23  may be located right below the second roll  22  with a spacing between the third roll  23  and the second roll  22 . 
     Temperature Adjusting Unit 
     The film forming device  20  of the embodiment further has a temperature adjusting unit. The temperature adjusting unit has the function of reducing a temperature difference between a central portion and an end portion in the axial direction, of at least one roll of the first roll  21 , second roll  22  and third roll  23 . 
       FIG.  5    is a schematic view showing a first example of the temperature adjusting unit. The temperature adjusting unit shown in  FIG.  5    adjusts the temperature of the second roll  22 , and adjusts the temperature of the third roll  23 . More specifically, the temperature adjusting unit has cooling devices  60 . The cooling devices  60  cool the opposite end portions of the second roll  22 . The cooling devices  60  cool the opposite end portions of the third roll  23 . 
     The cooling device  60  is realized, for example, by a flow channel of cooling medium formed in a housing that supports each end portion of the roll. The cooling medium is, for example, water. The housing rotatably supports the end portion of the roll via a bearing. The flow channel of the cooling medium is formed around the bearing, and the cooling medium circulates in the flow channel. The cooling medium of which the temperature was increased by heat transferred from the end portion of the roll is cooled at a position away from the end portion of the roll, and returns to the end portion of the roll. The cooling device  60  is not limited to this example, but may cool the end portion of the roll by any means, for example, a Peltier element, heat pipe, etc. 
       FIG.  6    is a schematic view showing a second example of the temperature adjusting unit. The temperature adjusting unit shown in  FIG.  6    adjusts the temperature of the second roll  22  and adjusts the temperature of the third roll  23 . More specifically, the temperature adjusting unit has heating devices  70 . The heating device  70  heats the central portion of the second roll  22 . The heating device  70  heats the central portion of the third roll  23 . 
     The heating device  70  is realized, for example, by an electric heater. The heating device  70  may have two or more heaters arranged in the axial direction of the roll. Which one or ones of the two or more heaters are caused to generate heat, or the amount of heat generated by the heater or heaters, may be controlled according to the temperature distribution of the roll in the axial direction. 
     As shown in  FIG.  5    and  FIG.  6   , the film forming device  20  further has temperature sensors  80 . The temperature sensor  80  may be a non-contact sensor such as an infrared sensor. The temperature sensor  80  that detects the temperature of the central portion of the roll and the temperature sensors  80  that detect the temperature of the end portions of the roll may be provided. The temperature sensor  80  that scans in the axial direction may detect the temperatures of the central portion and end portions of the roll. A controller  200  obtains the detection results of the temperature sensors  80 . A temperature difference between the central portion and the end portions of the roll is obtained from the detection results of the temperature sensors  80 . The controller  200  performs feedback control on the temperature adjusting unit based on the temperature difference between the central portion and the end portions of the roll, so that the temperature adjusting unit can efficiently reduce the temperature difference between the central portion and the end portions of the roll. For example, the controller  200  may control the temperature adjusting unit (cooling devices  60 , heating devices  70 ) so that the temperature difference between the central portion and the end portions of the roll becomes equal to or smaller than a predetermined value. 
     Operation and Effects 
     The characteristic configuration and effects of the above embodiment will be summarized and described as follows. 
     As shown in  FIG.  2   , the electrode manufacturing apparatus  1  includes the film forming device  20 . As shown in  FIG.  5    and  FIG.  6   , the film forming device  20  has the temperature adjusting unit that reduces the temperature difference between the central portion and the end portions in the axial direction of at least one roll of the first roll  21 , second roll  22 , and third roll  23 . 
     The end portions of the roll are supported by the housing. When the roll rotates relative to the housing, friction heat is generated. The friction heat is transferred to the roll, and the temperature at the end portions of the roll is more likely to rise to be higher than at the central portion of the roll. When an electrode  100  having a large width is produced, the temperature difference between the central portion and the end portions of the roll may become significantly large, and the thermal expansion of the end portions of the roll may become larger than that of the central portion of the roll due to the influence of the temperature difference. The diameter of the end portions of the roll becomes larger than that of the central portion, and the gap between the pair of opposed rolls in the end portions is narrowed. As a result, the thickness of the electrode layer  120  in the end portions of the roll may be reduced, and the uniformity of the thickness of the electrode layer  120  between the central portion and the end portions in the width direction of the electrode  100  may not be maintained. 
     In the electrode manufacturing apparatus  1  of the embodiment, the film forming device  20  has the temperature adjusting unit, which is configured to reduce the temperature difference between the central portion and the end portions of the roll. The uniformity of the thermal expansion between the central portion and the end portions of the roll can be improved, and the uniformity of the outside diameter of the roll between the central portion and the end portions of the roll can be improved. Accordingly, the electrode manufacturing apparatus  1  of the embodiment can maintain the uniformity of the thickness of the electrode layer  120  in the width direction even when wide electrodes  100  are manufactured. 
     As shown in  FIG.  5    and  FIG.  6   , the temperature adjusting unit may adjust the temperature of the second roll  22 . The coating film  92  is formed in the first gap between the first roll  21  and the second roll  22 , and the coating film  92  is transferred from the second roll  22  onto the substrate  110  in the second gap between the second roll  22  and the third roll  23 . The highest load is applied to the second roll  22 , resulting in increase of the friction heat generated at the end portions of the second roll  22 , and the temperature difference between the central portion and the end portions of the second roll  22  is likely to be large. By adjusting the temperature of the second roll  22 , the uniformity of the outside diameter between the central portion and the end portions of the second roll  22  is improved, so that the uniformity of the thickness of the electrode layer  120  can be efficiently maintained. 
     As shown in  FIG.  5    and  FIG.  6   , the temperature adjusting unit may adjust the temperature of the third roll  23 . By compressing the coating film  92  in the second gap between the second roll  22  and the third roll  23 , the coating film  92  is stretched thin and transferred to the substrate  110 . The load applied to the third roll  23  is relatively high, resulting in increase of the friction heat generated at the end portions of the third roll  23 , and the temperature difference between the central portion and the end portions of the third roll  23  is likely to be large. By adjusting the temperature of the third roll  23 , the uniformity of the outside diameter between the central portion and the end portions of the third roll  23  is improved, so that the uniformity of the thickness of the electrode layer  120  can be efficiently maintained. 
     As shown in  FIG.  5   , the temperature adjusting unit may have the cooling devices  60  for cooling the end portions of the rolls. The cooling devices  60  cool the end portions of the roll, so that the temperature difference between the central portion and the end portions of the roll can be reliably reduced. In the film forming device  20 , the electrode material  91 , which is slightly moistened with water, is formed in powder form into the coating film  92 , to form the electrode layer  120 . If the roll is heated, the water in the electrode layer  120  evaporates faster, and the moisture content of the electrode layer  120  may be reduced, thus making it difficult to handle the electrode layer  120 . When the end portions of the roll are cooled to adjust the temperature of the roll, the water in the electrode layer  120  is less likely or unlikely to evaporate, and changes in the properties of the electrode  100  due to changes in the moisture content of the electrode  100  can be reduced. 
     As shown in  FIG.  6   , the temperature adjusting unit may have the heating devices  70  for heating the central portions of the rolls. The heating device  70  heats the central portion of the roll, so that the temperature difference between the central portion and the end portions of the roll can be reliably reduced. By controlling the amount of heat generated by the heating device  70 , the temperature difference between the central portion and the end portions of the roll can be precisely reduced. When the heating device  70  consists of two or more heaters arranged in the axial direction of the roll, and the two or more heaters are controlled according to the temperature distribution in the axial direction of the roll, the temperature difference between the central portion and the end portions of the roll can be further reduced. 
     As shown in  FIG.  5    and  FIG.  6   , the film forming device  20  may have the temperature sensors  80  for detecting the temperatures of the central portions and the end portions of the rolls. By feedback controlling the temperature adjusting unit based on the temperature difference between the central portion and the end portions of each roll, the temperature adjusting unit can efficiently reduce the temperature difference between the central portion and the end portions of the roll. 
     In the description of the embodiment, the example in which the temperature adjusting unit has the cooling devices  60  is shown in  FIG.  5   , and the example in which the temperature adjusting unit has the heating devices  70  is shown in  FIG.  6   . The temperature adjusting unit may have both the cooling devices  60  and the heating devices  70 . 
     In the examples shown in  FIG.  5    and  FIG.  6   , the temperature adjusting unit for adjusting the temperatures of the second roll  22  and the third roll  23  is provided. The temperature adjusting unit may further adjust the temperature of the first roll  21 . With the temperature adjusting unit thus provided for all of the three rolls, i.e., the first roll  21 , second roll  22 , and third roll  23 , that constitute the film forming device  20 , the uniformity of the thickness of the electrode layer  120  can be further improved. 
     While the film forming device  20  has the temperature sensors  80  in the examples of  FIG.  5    and  FIG.  6   , the temperature sensors  80  may not necessarily be provided. For example, by verifying in advance how the temperature of the roll varies according to film forming conditions, and controlling the temperature adjusting unit according to a program created based on the verification result to reduce the temperature difference between the central portion and the end portions of the roll, it is possible to similarly achieve the effects of the above embodiment. 
     An example will be described. By using the film forming device  20  equipped with the temperature adjusting unit, as described above in the embodiment, the electrode layer  120  was formed on the surface of the substrate  110 . The roll temperature during film forming and the thickness difference in the electrode layer  120  between the central portion and the end portions of the roll were measured. As a comparative example, an electrode layer was formed in a similar manner, using a film forming device that is not equipped with the temperature adjusting unit, and the roll temperature during film forming and the thickness difference were measured. 
       FIG.  7    is a graph showing the temperature difference between the central portion and the end portions of the roll and the thickness difference in the comparative example. In the comparative example, a temperature difference appeared between the central portion and the end portions of the roll after a lapse of  10  min. from the start of film forming. The outside diameter of the end portions of the roll became larger than the outside diameter of the central portion due to thermal expansion. As a result, the thickness difference between the central portion and the end portions exceeded 2 μm, and the uniformity of the thickness of the electrode layer  120  could not be maintained. 
       FIG.  8    is a graph showing the temperature difference between the central portion and the end portions of the roll and the thickness difference in the example of the embodiment. In the example, the temperature difference between the central portion and the end portions of the roll during the temperature increase was smaller than that of the comparative example. The difference in the outside diameter between the central portion and the end portions of the roll was reduced; as a result, the thickness difference between the central portion and the end portions was kept smaller than  1  pm. Accordingly, it became apparent that the uniformity of the thickness of the electrode layer  120  can be maintained by reducing the temperature difference between the central portion and the end portions of the roll. 
     It is to be understood that the embodiment disclosed herein is exemplary in all respects, and is not restrictive. The scope of this disclosure is indicated by the claims, rather than the above description, and is intended to include all changes within the claims and the meaning and range of equivalents thereof