JP2010244748A - Method for manufacturing electrode plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrode plate for obtaining an electrode plate with distortion or kink of a non-coated part restrained and with large mechanical strength at an end part. <P>SOLUTION: The method for manufacturing the electrode plate, made up by providing an active material layer at least on one face of a metal foil, includes a coating process of forming an active material layer by coating active material paste at least on one face of a belt-like metal foil (hereinafter called a foil) with a non-coated part left at an end part in a width direction, a heat treatment process of heating the foil with the active material layer formed up to a temperature higher than an annealing temperature of the foil and lower than a melting temperature of an ingredient of the active material layer, and a rolling process of pressurizing the foil in a thickness direction while conveying it in a length direction after the heat treatment process. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a manufacturing method for manufacturing a sheet-like electrode plate that is used as an electrode plate of a secondary battery, for example, and in which an electrode paste is applied to a metal current collector foil. More specifically, the present invention relates to a method for manufacturing an electrode plate including a step of rolling after applying a paste.

  Conventionally, sheet-like electrode plates have been used in, for example, lithium ion secondary batteries. The positive and negative electrode plates are manufactured by applying and rolling a paste-like active material on aluminum foil or copper foil. The positive and negative electrode plates are used by being wound, for example, with a separator interposed therebetween and immersed in an electrolytic solution.

  In the conventional manufacturing method, the electrode paste is applied while leaving both end portions in the width direction of the belt-shaped current collector foil, and rolled by passing through a pressure roll or the like. Then, it was wound after cutting the width in half. However, there is a problem in that the electrode plate is curved because the elongation amount due to rolling differs between the paste-coated part and the non-coated part at both ends. On the other hand, the present applicant has proposed a method of reducing the strain by providing a step of applying tension while heating the non-coated portion between the rolling step and the cutting step (see Patent Document 1).

JP 2005-93236 A

  However, although the strong bending of the electrode plate has been eliminated by the above-described manufacturing method, there is a case where a wavy undulation occurs in the current collecting foil at the non-coated portion due to heating. If it became like this, there existed a problem that the mechanical strength of this non-coating location fell. It has been found that, in this non-coated portion, for example, what is bonded to an electrode terminal or the like has an influence on the bonding strength of the terminal. Therefore, there has been a demand for a method of manufacturing an electrode plate that suppresses distortion and does not impair the mechanical strength of the end portion.

  The present invention has been made to solve the problems of the above-described conventional electrode plate manufacturing method. That is, an object of the present invention is to provide an electrode plate manufacturing method capable of obtaining an electrode plate in which distortion and distortion of the non-coated portion are suppressed and the end portion has high mechanical strength.

  The electrode plate manufacturing method of the present invention made for the purpose of solving this problem is an electrode plate manufacturing method in which an active material layer is provided on at least one surface of a metal foil, and is a strip-shaped metal foil (hereinafter referred to as a foil). ) On at least one surface of the width direction, leaving an uncoated portion at the end in the width direction, coating the active material paste to form an active material layer, and a foil on which the active material layer is formed, A heat treatment step of heating to a temperature higher than the annealing temperature of the foil and lower than the melting temperature of the components of the active material layer, and a rolling step of pressing the foil in the thickness direction while conveying the foil in the longitudinal direction after the heat treatment step. It is what you have.

  According to the method for manufacturing an electrode plate of the present invention, after the active material is applied to the metal foil, the heat treatment step is performed before the rolling step. By this heat treatment, the metal foil is annealed. And it becomes soft and easy to stretch. Therefore, even if a rolling process is performed after that, the entire metal foil is stretched almost uniformly and easily as much as the active material. Accordingly, it is possible to prevent the occurrence of distortion due to the difference in elongation between the coated portion and the non-coated portion, and the occurrence of kinking due to the large elongation of only the non-coated portion, thereby obtaining a good electrode plate. Therefore, the mechanical strength of the end portion where the non-coated portion is overlapped by winding or the like is large, and sufficient bonding strength can be obtained even when the electrode terminal is attached by welding or the like. The annealing temperature of the foil is the lowest temperature at which a strain releasing process such as recrystallization or phase transition occurs in the metal forming the foil.

When manufacturing a positive electrode plate of a lithium ion secondary battery as an electrode plate, an aluminum foil is used as a metal foil, and a positive electrode active material of a lithium ion secondary battery is used as an active material. Furthermore, the heating temperature in the heat treatment step is set to a temperature within the range of 150 to 400 ° C.
When manufacturing a negative electrode plate of a lithium ion secondary battery as an electrode plate, a copper foil is used as a metal foil, and a negative electrode active material of a lithium ion secondary battery is used as an active material. Furthermore, the heating temperature in the heat treatment step is set to a temperature within the range of 110 to 300 ° C.

Further, in the present invention, in the coating process, coating is performed leaving both ends in the width direction of the foil, and the foil is longitudinally arranged at one place in the width direction after the coating process and before the heat treatment process. It is desirable to have a cutting step for cutting.
In this way, coating is easy. And since it can cut | disconnect in a state without distortion, it can cut | disconnect easily and appropriately.

  According to the method for manufacturing an electrode plate of the present invention, an electrode plate can be obtained in which distortion and twist of the non-coated portion are suppressed and the mechanical strength of the end portion is large.

It is process drawing which concerns on this form. It is explanatory drawing which shows the state which the coating process was complete | finished. It is explanatory drawing which shows the state which the cutting process completed. It is explanatory drawing which shows the heat processing process. It is explanatory drawing which shows a rolling process.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a manufacturing method for manufacturing an electrode plate used in a lithium ion secondary battery.

In the present embodiment, the present invention will be described by taking as an example a method for manufacturing an electrode plate used for a positive electrode of a lithium ion secondary battery. In this electrode plate, for example, layers of a positive electrode active material capable of inserting and extracting lithium ions are provided on both surfaces of a metal foil such as aluminum. Examples of the positive electrode active material include lithium composite oxides such as lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), and lithium cobaltate (LiCoO ₂ ).

  As shown in the process diagram of FIG. 1, the manufacturing method of the electrode plate according to this embodiment includes a preparation step (S1), a coating step (S2), a cutting step (S3), a heat treatment step (S4), and a rolling step (S5). ). First, a metal foil and a paste-form active material are prepared (preparation process). As the metal foil, a strip-shaped aluminum foil having a width twice that of the electrode plate to be manufactured is prepared. This preparation process may be the same as the conventional one.

  Next, as shown in FIG. 2, the active material 20 is coated on both surfaces of the aluminum foil 10 to produce a coated aluminum foil 30 (coating process). In this step, uncoated portions 12 having an appropriate width are left on both the front and back surfaces at both ends of the aluminum foil 10 in the width direction (vertical direction in the drawing). This non-coating part 12 is a place where an electrode terminal is attached later by welding or the like.

  Next, the central portion in the width direction of the coated aluminum foil 30 is cut in the longitudinal direction (cutting step). Thereby, as shown in FIG. 3, two coated aluminum foils 31 and 32 having the same shape are obtained. It should be noted that since no heat or pressure is applied after the active material 20 is applied to the aluminum foil 10 until this step, there is no reason for new distortion such as bending in the aluminum foil 10. Therefore, appropriate division can be easily performed.

  Next, as shown in FIG. 4, a heat treatment process is performed on the cut and coated aluminum foils 31 and 32. That is, it is simply heated without applying pressure. For example, the heating roller 40 is heated in the width direction (depth direction in FIG. 4) wider than the width of the coated aluminum foils 31 and 32 (size in the vertical direction in FIG. 3). By this step, the aluminum foil 10 is heated to a temperature higher than the annealing temperature of aluminum (the lowest temperature at which a strain releasing process such as recrystallization or phase transition occurs) and lower than the melting temperature of the components of the coated active material 20 layer. As described above, the temperature of the heating roller 40 is adjusted. No preheating is required. Also, no special cooling means is required after heating. It only has to be allowed to cool to the atmosphere. Thereby, since it cools slowly, the aluminum foil 10 becomes soft and becomes easy to extend. On the other hand, the active material 20 is not particularly affected.

  In this embodiment, the temperature of the heating roller 40 is preferably 150 ° C. or higher and 400 ° C. or lower. For example, about 300 ° C. is suitable. At temperatures below 150 ° C, the effect is small. Further, at a temperature higher than 400 ° C., the components of the layer of the active material 20 may be dissolved. Then, as shown in FIG. 4, for example, aluminum foils 31 and 32 are placed on a heating roller having a diameter of about 50 cm and run at a peripheral speed of about 5 m / min, whereby each portion of the aluminum foil is heated for about 10 seconds.

Next, as shown in FIG. 5, it rolls by passing between the two rolling rollers 50 (rolling process). Thereby, the layer of the active material 20 is compressed and becomes a dense state, and is securely crimped to the aluminum foil 10. The layer of the active material 20 is, for example, about 1.29 g / cm ³ before rolling, but is about 2.29 g / cm ³ . Further, the electrode plate is stretched by about 1 to 3% in the longitudinal direction. Thereby, the manufacturing method of the electrode plate according to the present embodiment is completed.

  In this embodiment, since the heat treatment process is performed before this rolling process, the aluminum foil 10 is considerably softer than before the heat treatment. And it becomes easy to extend to such an extent that it does not change so much as compared with the layer of the active material 20 being coated. Therefore, depending on the thickness of the active material 20, the non-coated portion 12 that is not directly pressed by the rolling roller 50 extends almost in the same manner as the coated area. Accordingly, even when the rolling process is performed, the aluminum foil 10 is not bent or twisted.

  In this embodiment, the cutting process is arranged between the coating process and the heat treatment process, but may be performed after the heat treatment process. Alternatively, it can be performed after the rolling process. According to the manufacturing method of the present embodiment, since the aluminum foil 10 is not deformed, the order of the cutting steps can be freely selected.

Note that the electrode plate for the negative electrode can be appropriately manufactured by the same manufacturing method. The negative electrode plate is a copper foil coated with a negative electrode active material capable of inserting and extracting lithium ions. As the negative electrode active material, carbon-based materials such as amorphous carbon, non-graphitizable carbon, graphitizable carbon, and graphite are used. In the case of the negative electrode plate, the temperature of the heating roller in the heat treatment step is preferably in the range of 110 to 300 ° C. For example, about 190 ° C. is suitable. Further, the density of the layer made of the active material was about 0.75 g / cm ³ before rolling, but became about 1.41 g / cm ³ by the rolling process.

  The positive and negative electrode plates manufactured in this way are wound or laminated through a separator, and electrode terminals are welded to the respective non-coated portions 12. In the electrode plate manufactured in this embodiment, since the metal foil does not have a strong curve, it can be easily wound or laminated without distortion. Furthermore, since no deflection is generated by the non-coated portion 12, the electrode terminal can be easily welded, and the welded portion has sufficient mechanical strength.

  As described above in detail, according to the manufacturing method of this embodiment, after the active material is applied to the metal foil, heat treatment is performed before rolling. Therefore, even in the range where the active material is not coated in the metal foil, the metal foil can be easily stretched to the same extent as the layer made of the active material. Therefore, even after the rolling process, the metal foil is prevented from being bent or twisted. Thereby, it is a manufacturing method which does not impair the mechanical strength of an edge part, suppressing the distortion and distortion of a non-coating part.

In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, the present invention is applicable not only to lithium ion secondary batteries but also to methods for manufacturing electrode plates for various batteries. In addition, the metal used for the current collector foil and the material of the electrode paste can be appropriately selected. The active material layer may be provided only on one side of the metal foil. In the case of coating only on one side, the metal foil side should be in contact with the heating roller. Further, for example, the processing method and processing time of the heat treatment process can be changed as appropriate according to the material and size of the electrode plate. In addition, if a metal foil having a width suitable for the electrode plate is prepared and applied so that an uncoated portion is left only in one side in the width direction, a cutting step is unnecessary.

10 Aluminum foil 20 Active material S2 Coating process S3 Cutting process S4 Heat treatment process S5 Rolling process

Claims (4)

In an electrode plate manufacturing method comprising an active material layer on at least one surface of a metal foil,
A coating step of forming an active material layer by applying an active material paste on at least one surface of a strip-shaped metal foil (hereinafter referred to as a foil), leaving an uncoated portion at the end in the width direction;
A heat treatment step of heating the foil on which the active material layer is formed to a temperature higher than an annealing temperature of the foil and lower than a melting temperature of components of the active material layer;
A method of manufacturing an electrode plate, comprising: a rolling step of pressing the foil in the thickness direction while conveying the foil in the longitudinal direction after the heat treatment step. In an electrode plate manufacturing method comprising an active material layer on at least one surface of an aluminum foil,
Form the active material layer by applying the positive electrode active material paste of the lithium ion secondary battery, leaving the uncoated part at the end in the width direction on at least one side of the strip-shaped aluminum foil (hereinafter referred to as foil) Coating process,
A heat treatment step of heating the foil on which the active material layer is formed to a temperature within a range of 150 to 400 ° C .;
A method of manufacturing an electrode plate, comprising: a rolling step of pressing the foil in the thickness direction while conveying the foil in the longitudinal direction after the heat treatment step. In an electrode plate manufacturing method comprising an active material layer on at least one surface of a copper foil,
Form the active material layer by applying the negative electrode active material paste of the lithium ion secondary battery, leaving the uncoated part at the end in the width direction on at least one side of the strip-shaped copper foil (hereinafter referred to as foil) Coating process,
A heat treatment step of heating the foil on which the active material layer is formed to a temperature within a range of 110 to 300 ° C .;
A method of manufacturing an electrode plate, comprising: a rolling step of pressing the foil in the thickness direction while conveying the foil in the longitudinal direction after the heat treatment step. In the manufacturing method of the electrode plate as described in any one of Claim 1- Claim 3,
In the coating step, coating is performed leaving both ends in the width direction of the foil,
A method for producing an electrode plate, comprising: a cutting step of cutting the foil in the longitudinal direction at one place in the width direction after the coating step and before the heat treatment step.

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