WO2013021640A1

WO2013021640A1 - Electrode plate for electrochemical element, method for manufacturing electrode plate for electrochemical element, and electrochemical element

Info

Publication number: WO2013021640A1
Application number: PCT/JP2012/005049
Authority: WO
Inventors: 古結　康隆; 心原口
Original assignee: パナソニック株式会社
Priority date: 2011-08-10
Filing date: 2012-08-08
Publication date: 2013-02-14
Also published as: JP2014199715A

Abstract

The present invention suppresses undesired deformation of constituent elements of an electrode group and short-circuits in an electrochemical element due to a melt portion, while electrically connecting one end portion of an electrode plate main body with an electrode lead via the melt portion. This electrode plate for an electrochemical element is provided with: an electrode plate main body, which includes a laminated body composed of a strip-like current-collecting body containing a metal, and an active material layer, which is formed on the surface of the current-collecting body, and contains an alloy-based active material; an electrode lead, which is disposed on a part of the surface of the active material layer, and includes a metal; and a melt portion, which electrically connects, at one end portion of the electrode plate main body, the electrode plate main body and the electrode lead to each other. The melt portion has a flat portion parallel to the surface of the electrode plate main body.

Description

Electrode element electrode plate, method for producing the same, and electrochemical element

The present invention relates to an electrode plate for an electrochemical element, a method for manufacturing the same, and an electrochemical element, and more particularly, to an improved bonding state between an electrode plate and an electrode lead.

In recent years, portable electronic devices have become smaller and lighter, and the demand for small, lightweight, high-output secondary batteries as power sources for these electronic devices has increased. Among them, lithium ion secondary batteries and nickel metal hydride storage batteries have high capacity and energy density, and are easy to reduce in size and weight. Therefore, mobile phones, personal digital assistants (PDAs), notebook personal computers, etc. It is widely used as a power source for various electronic devices such as computers, video cameras, and portable game machines.

Such electrochemical devices such as secondary batteries and capacitors have a pair of electrode plates with different polarities inside, and the electrode plates are electrically connected via external terminals such as sealing plates and electrode leads. Connected to. The electrode plate usually has a structure in which active material layers are formed on both surfaces of a metal foil as a current collector. The electrode plate having such a structure is provided with a current collector exposed portion on which an active material layer is not formed in order to connect strip-shaped metal pieces as electrode leads.

Thus, the electrical connection between the electrode plate and the electrode lead is conventionally performed by connecting the current collector and the electrode lead. This is because if it is attempted to connect the electrode plate and the electrode lead through the active material layer, it is difficult to ensure sufficient electrical connection. The current collector exposed portion (that is, the uncoated portion of the active material layer) is prepared without applying the electrode slurry containing the active material, or formed after the electrode slurry is applied, for example. It is produced by removing a part of the film.

In recent years, electronic devices have become more multifunctional and their power consumption has increased. On the other hand, it is desired that they can be used continuously for as long as possible with a single charge. For this reason, it is necessary to further increase the capacity of electrochemical elements such as lithium ion batteries, and the development of alloy-based active materials having a capacity higher than that of graphite has been actively conducted. Typical alloy-based active materials include silicon-containing active materials such as silicon, silicon alloys, and silicon compounds.

The active material layer containing an alloy-based active material can also be formed by depositing the active material in a film form on the surface of the current collector by a vapor phase method other than the method using the electrode slurry. However, in the case of a deposited film, it is difficult to form a current collector exposed portion on the surface of the current collector, so that it is difficult to join the electrode plate and the electrode lead as compared with the case where electrode slurry is used.

Patent Document 1 discloses a negative electrode in which a communication hole penetrating the laminated body in the thickness direction is formed by irradiating a laser on a laminated body of a negative electrode plate having an active material layer formed by a vapor phase method or the like and a negative electrode lead. Disclosure. When the laminated body is irradiated with laser, the negative electrode current collector and the negative electrode lead existing on the inner surface of the communication hole are melted and brought into contact with each other, thereby connecting the negative electrode current collector and the negative electrode lead.

Patent Document 2 discloses a negative electrode in which a negative electrode lead made of copper, a copper alloy, or a copper clad material is joined to the surface of a deposited film containing an alloy-based active material by resistance welding.

Patent Document 3 discloses arc welding of a contact portion between a negative electrode active material layer formed by a vapor phase method and a negative electrode lead.

Japanese Patent Laid-Open No. 2007-214086 JP 2007-115421 A International Publication No. 2010/041399 Pamphlet

When the active material layer is formed by the vapor phase method, unlike the case of using the electrode slurry, it is substantially impossible to form the current collector exposed portion by partially removing the formed active material layer. is there. Further, in order to form the current collector exposed portion by not partially forming the active material layer, for example, it is necessary to mask the formation region of the lead connection portion in the step of depositing the active material such as vacuum evaporation. is there. However, such a mask operation becomes very complicated in terms of the process. That is, in the case of a deposited film, it is difficult to form the current collector exposed portion on the current collector surface.

In the method of Patent Literature 1, when laser irradiation is performed, particles of an alloy-based active material flow out of the negative electrode active material layer and are mixed into the connection portion between the negative electrode current collector and the negative electrode lead. Since the alloy-based active material has a high melting point, it is difficult to melt only by laser irradiation. For this reason, the joint strength of the connection portion tends to decrease. In addition, since the alloy-based active material has a large electric resistance, the presence of particles of the alloy-based active material in the connection portion tends to lower the electrical connectivity of the connection portion.

When the surface of the deposited film and the electrode lead are to be resistance-welded as in Patent Document 2, the negative electrode current collector or the negative electrode lead may locally melt, but the negative electrode active material layer of the alloy-based active material Since almost no current flows through the negative electrode active material layer, the negative electrode active material layer does not melt. For this reason, it is difficult to sufficiently join the negative electrode current collector and the negative electrode lead by resistance welding.

In view of such a problem, the present inventors have disclosed in Patent Document 3 a current collector in which an active material layer containing a silicon-containing active material formed by a vapor phase method is formed on both sides, and nickel, copper, or A method of connecting the electrode lead containing the alloy etc. by arc welding was proposed. In this method, the active material layer and the electrode lead are overlapped, and the end of the overlapped portion is arc-welded. As a result, the active material is melted together with a part of each of the current collector and the electrode lead to form a silicon-containing alloy, and a solidified portion is formed by re-solidification. In this method, since the silicon-containing alloy layer is formed between the current collector and the electrode lead, the current collector and the electrode lead are connected with good conductivity.

FIG. 7a is a schematic cross-sectional view showing a melted portion formed at one end of an electrode plate containing an alloy-based active material by arc welding, and FIG. 7b is a melt formed at one end of the electrode plate of FIG. 7a. It is a schematic front view which shows a part. In the conventional method, at one end portion of the electrode plate body 101 including the current collector 110 and an active material layer 111 containing an alloy-based active material such as a silicon-containing active material formed on both surfaces of the current collector 110, The electrode lead 113 is disposed so as to overlap the surface, and one end of the electrode plate body 101 and one end of the electrode lead 113 are arc-welded. As a result, a melted portion 118 is formed in the welded region, and the current collector 110 of the electrode plate body 101 and the electrode lead 113 are connected via the melted portion 118.

Thus, if the end of the electrode plate body is arc welded, the current collector exposed portion is formed even in the case of an electrode plate body having a current collector and an active material layer formed on the surface thereof by a vapor phase method. Even if it does not do, since it becomes possible to firmly join the electrode plate and the electrode lead, it is industrially advantageous. However, the present inventors have found the following new problem when using arc welding.

When the electrode plate body containing an alloy-based active material such as a silicon-containing active material is welded to the electrode lead, a molten part is formed at the welded portion, that is, at the end of the portion where the electrode plate body and the electrode lead are overlapped. Is done. However, in the case of welding by arc welding, the thickness of the melted portion becomes larger than necessary, and becomes greater than the thickness of the obtained electrode plate (that is, the total thickness of the electrode plate main body and the electrode lead). For this reason, when a laminated or wound electrode group is produced using an electrode plate with such a melted portion formed, the dimensions and shape of the electrode group may be out of specification, or the electrode plate and separator The distance from the polar electrode plate may increase. Even when a battery is formed using such an electrode group, the electrode reaction becomes non-uniform, the melted part deforms the surrounding components, the electrode group deforms, or the separator is damaged, causing an internal short circuit. Inconveniences such as occurrence are likely to occur.

An object of the present invention is to provide an electrochemical device capable of suppressing deformation of an electrode group due to a melted portion and a short circuit in an electrochemical element while electrically connecting an electrode plate body to an electrode lead through a melted portion at one end thereof. It is providing a device electrode plate, a method for producing the same, and an electrochemical device.

One aspect of the present invention is an electrode plate body including a laminate of a strip-shaped current collector containing a metal and an active material layer formed on the surface of the current collector and containing an alloy-based active material. An electrode lead including a metal disposed on a part of the surface, and at one end of the electrode plate main body, the electrode plate main body and the electrode lead are provided with a melting portion that electrically connects the melting portion to the electrode plate The present invention relates to an electrode plate for an electrochemical element having a flat portion parallel to the surface of a main body.

Another aspect of the present invention provides an electrode plate body including a laminate of a strip-shaped current collector containing a metal and an active material layer formed on the surface of the current collector and containing an alloy-based active material. Step A, Step B in which the electrode lead is disposed so that one end of the electrode plate body and one end of the electrode lead containing metal are close to a part of the surface of the active material layer, and the adjacent electrode plate At one end of the main body and one end of the electrode lead, by melting a welding region including the end surface of the electrode plate main body and the end surface of the electrode lead, a melting portion that electrically connects the electrode plate main body and the electrode lead is provided. An electrode plate for an electrochemical device, comprising: a step C of forming; and a step D of compressing the melted portion in a direction perpendicular to the surface of the electrode plate body to form a flat portion parallel to the surface of the electrode plate body. It relates to the manufacturing method.

Still another aspect of the present invention is the above-described electrode plate for an electrochemical element as a first electrode, a second electrode having a polarity opposite to the first electrode, and between the first electrode and the second electrode. The present invention relates to an electrochemical element including a separator interposed between the two.

In the present invention, the electrode plate main body is electrically connected to the electrode lead through the melting portion at one end thereof, and the melting portion has a flat portion parallel to the surface of the electrode plate main body. Therefore, it is possible to suppress deformation of the electrode group due to the melting part and short circuit in the electrochemical element.

While the novel features of the invention are set forth in the appended claims, the invention will be further described by reference to the following detailed description, taken in conjunction with the other objects and features of the invention, both in terms of construction and content. It will be well understood.

FIG. 1a is a schematic cross-sectional view showing a configuration of an electrode plate for an electrochemical element according to an embodiment of the present invention. FIG. 1b is a schematic front view showing the configuration of the electrode plate for an electrochemical element in FIG. 1a. FIG. 2 a is a schematic cross-sectional view showing an electrode plate main body and electrode leads arranged in a welding jig in the method for manufacturing an electrode plate for an electrochemical element according to an embodiment of the present invention. FIG. 2B is a schematic cross-sectional view for explaining a step of forming a flat portion in the melted portion in the method for manufacturing an electrode plate for an electrochemical element according to one embodiment of the present invention. FIG. 3 is a longitudinal sectional view schematically showing a configuration of a lithium ion battery as an electrochemical element according to an embodiment of the present invention. FIG. 4 is a side view schematically showing the configuration of an electron beam evaporation apparatus for forming an active material layer containing an alloy-based active material. FIG. 5A is a schematic perspective view for explaining a method for preparing a sample for measuring the bonding strength between the electrode plate body and the electrode lead. FIG. 5B is a schematic perspective view for explaining the state of a sample for measuring the bonding strength between the electrode plate main body and the electrode lead. FIG. 6 is a schematic perspective view for explaining a method of measuring the bonding strength between the electrode plate main body and the electrode lead. FIG. 7 a is a schematic cross-sectional view showing a melted portion formed at one end of an electrode plate containing an alloy-based active material by arc welding. FIG. 7b is a schematic front view showing a melting portion formed at one end of the electrode plate of FIG. 7a.

Hereinafter, embodiments of the present invention will be described with reference to the drawings as necessary.
(Electrode plate for electrochemical element and electrochemical element)
The electrode plate for an electrochemical element of the present invention includes an electrode plate main body including a laminate of a strip-shaped current collector containing a metal and an active material layer formed on the surface of the current collector and containing an alloy-based active material, An electrode lead including a metal disposed on a part of the surface of the active material layer, and a melting portion that electrically connects the electrode plate main body and the electrode lead are provided at one end of the electrode plate main body. And a fusion | melting part has a flat part parallel to the surface (namely, surface which an electrode plate main body and a negative electrode lead oppose) of an electrode plate main body.

The present inventors do not join the electrode plate main body and the electrode lead at the current collector exposed portion, but instead of the electrode plate main body and the electrode lead through the active material layer containing the alloy-based active material of the electrode plate main body. Attention was paid to the structure of joining the two. And as shown in patent document 3, the method which joins the electrode plate main body which has an active material layer containing an alloy type active material, and an electrode lead by arc welding in the both ends of both was discovered. According to this method, not only the current collector and electrode lead of the electrode plate main body are melted, but also the alloy-based active material contained in the active material layer of the electrode plate main body is melted, and the molten components are alloyed. It progresses and a melting part is formed. Thereby, although the electrode plate body and the electrode lead are joined through the active material layer containing the alloy-based active material, the electrode plate body and the electrode lead are joined firmly and with good conductivity.

In the joining method by arc welding, first, the surface of a part of the active material layer containing the alloy-based active material of the electrode plate body so that one end portion of the electrode plate body and one end portion of the electrode lead containing metal are close to each other. An electrode lead is disposed on the surface. Next, the electrode plate main body and the electrode lead are sandwiched with a welding jig so that the welding region including the end surface of the electrode plate main body and the end surface of the electrode lead is exposed at one end of both the electrode plate main body and the electrode lead. Then, by performing arc discharge toward the welding region, the welding region is melted to form a melted portion that electrically connects the electrode plate body and the electrode lead. The formed melted portion includes at least an alloy of an alloy-based active material and a metal component constituting the electrode lead.

However, when the melted part is formed by arc welding, the size of the melted part tends to be larger than necessary. The reason is not sufficiently clear, but is presumed as follows. When the electrode plate body and the electrode lead are joined, in order to form a melted portion containing an alloy of the alloy-based active material and the metal component constituting the electrode lead, the alloy-based activity present at the interface with the electrode lead is used. It is necessary to heat to a temperature at which a component containing an alloyable element such as silicon contained in the substance melts (1414 ° C. in the case of silicon). However, when an alloy (for example, copper-silicide alloy) of a metal component constituting the electrode lead such as copper and silicon is formed at the interface between the active material layer and the electrode lead, the melting point is lowered. Therefore, it is presumed that the melting rate of the melting region increases rapidly, and the melted portion becomes larger than necessary due to the flow of the melt.

Even when not using arc welding, when the alloy-based active material melts when welding the electrode lead and the electrode plate body, the size of the molten part is more than necessary, as in arc welding. Easy to grow.

As described above, when the alloy-based active material is melted and the size of the melted portion is increased, the bonding strength between the electrode lead and the electrode plate body can be increased. However, when the size of the melted part becomes large, when producing a laminated or wound electrode group using an electrode plate, the size of the electrode group becomes large or the shape becomes distorted. Prone. Moreover, the space | interval of an electrode plate, a separator, or an electrode plate of opposite polarity may spread. When such an electrode group is used to form an electrochemical device, the electrode reaction becomes non-uniform, the electrode group is deformed due to deformation of the surrounding components by the melting part, or an internal short circuit due to damage to the separator. Inconvenience occurs. In addition, when the melted part is formed wide in the width direction of the electrode plate body or when a plurality of melted parts are formed, the shape and dimensions of the melted part are not uniform, and the above disadvantages may become more prominent. is there.

As a result of repeated research, the inventors of the present invention are capable of plastic deformation of the melted part, and can form a flat part parallel to the surface of the electrode plate body by shaping the melted part. It has been found that inconvenience can be suppressed. When the electrode plate of the present invention is used, the electrode group can be reliably and stably wound by winding without deforming the components around the melting portion or short-circuiting the electrode plate and the electrode plate of the opposite polarity. Can be formed.

Such a flat portion can be formed by flattening the protruding portion of the melted portion in the thickness direction of the electrode plate body. Even if such a flat portion is formed in the melted portion, it is only plastically deformed, so that the joining region between the melted portion, the electrode plate body, and the electrode lead is not deformed. Furthermore, since there is no change in the composition of the melted portion, there is no change in bonding strength, and the electrode plate body and the electrode lead can be electrically connected with high bonding strength.

Moreover, since the electrode plate main body and the electrode lead can be bonded with high bonding strength in spite of using the alloy-based active material, the effect of the alloy-based active material can be easily obtained, and a high capacity and output can be obtained. Thereby, battery performance, such as cycling characteristics, can be improved. Even when the active material layer is a deposited film formed by a vapor phase method, a high bonding strength between the electrode plate main body and the electrode lead without going through a complicated process of providing a current collector exposed portion Is obtained.

FIG. 1a is a schematic cross-sectional view showing a configuration of an electrode plate for an electrochemical element according to an embodiment of the present invention. FIG. 1 b is a front view schematically showing a configuration of the electrode plate for an electrochemical element in FIG. 1. The electrode plate body 1 includes a laminate of a strip-shaped current collector 10 containing a metal, such as a metal foil, and an active material layer 11 containing an alloy-based active material formed on both surfaces of the current collector 10. . The active material layer 11 is formed over the entire surface of the current collector 10. An electrode lead 13 containing a metal such as a metal foil is adjacent to one end of the electrode plate main body 1 and one end of the electrode lead 13 on a part of the surface of one active material layer 11 of the electrode plate main body 1. Are arranged as follows.

At the one end of the electrode plate main body 1, a melting part 17 containing an alloy of the constituent components of the electrode plate main body 1 and the metal component of the electrode lead 13 is formed. The melting part 17 physically connects and electrically joins the electrode plate body 1 and the electrode lead 13 at one end of the electrode plate body 1. In the electrochemical device, the electrode lead 13 is connected to an external terminal or the like.

As shown in FIG. 1b, the electrode plate body 1 and the electrode lead 13 are overlapped so that one end portion in the longitudinal direction of the electrode plate body 1 and one end portion in the short direction of the electrode lead 13 are close to each other. Is arranged. The melting part 17 is formed at one end of the electrode plate body 1 in the longitudinal direction.

The melting part 17 has a first flat part 17a and a second flat part 17b parallel to the surface of the electrode plate body 1. The second flat portion 17b is formed on the side opposite to the first flat portion 17a. Such a flat part is obtained by flattening a portion protruding in the thickness direction of the electrode plate body of the melted part formed by melting the components of the electrode plate body and the electrode lead by welding or the like by compression or the like. It is formed by. That is, by compressing and deforming the melted portion, the melted portion has a shape in which the region protruding beyond the total thickness of the electrode plate body and the electrode lead of the melted portion is regulated in the thickness direction of the electrode plate body. Have. When the melted part is compressed from the electrode lead side or from both sides of the electrode lead side and the opposite side, the deformation equivalent amount of the melted part due to compression is the width direction and / or the length direction of the melted part (in particular, the electrode plate It projects in the length direction opposite to the main body side). The melting part 17 of FIG. 1b has shown the mode that it protrudes in the length direction (direction parallel to the longitudinal direction of an electrode plate main body) of a fusion | melting part on the opposite side to an electrode plate main body.

As shown in FIG. 1a, the melting part does not necessarily have a first flat part and a second flat part as shown in FIG. 1a, and 1 is provided on either the electrode lead side of the melting part or the opposite side of the electrode lead. You may have two flat parts. The flat portion only needs to be generally parallel to the surface of the electrode plate body, and the angle formed between the normal line of the flat portion and the normal line of the surface of the electrode plate body may be 20 ° or less. If it is such an angle, the deformation | transformation of the surrounding component by a melt | fusion part and the damage of a separator can fully be suppressed. This is because the pressure applied to the peripheral components and separators facing the melted portion from the flat portion is reduced.
The flat portion does not necessarily have to be a flat surface as a whole, and may have a gentle curved surface or unevenness in part.

The thickness t of the melting part 17 in the thickness direction of the electrode plate body 1 is equal to or greater than the total thickness T of the electrode plate body 1 and the electrode lead 13. However, since the flat part is formed in the fusion | melting part 17, the dimension of the thickness direction of an electrode plate main body does not become large more than necessary. Therefore, even when the electrode plate is wound, it is possible to suppress deformation of constituent elements around the melting portion or damage to the separator. In addition, when a fusion | melting part has a 1st flat part and a 2nd flat part, the thickness t of a fusion | melting part is the distance between a 1st flat part and a 2nd flat part.

The ratio t / T between the thickness t of the melted portion in the thickness direction of the electrode plate body and the total thickness T of the electrode plate body and the electrode lead is preferably 1 or more or greater than 1. The ratio t / T is preferably 1.3 or less, more preferably 1.2 or less. These lower limit value and upper limit value can be appropriately selected and combined. The ratio t / T may be, for example, 1 to 1.3 or 1 to 1.2. When the ratio t / T is within such a range, at one end portion of the electrode plate body, the entire end surfaces of both the electrode plate body and the electrode lead are covered with the melted portion in the thickness direction of the electrode plate body. Therefore, the electrode plate body and the electrode lead can be joined with high strength. Moreover, the deformation | transformation of the component around a fusion | melting part and the damage of a separator can be suppressed more effectively.

The melting part electrically connects the electrode plate main body including the current collector and the electrode lead, and joins the electrode plate main body and the electrode lead. The length of the melted portion (in FIGS. 1a and 1b, the length protruding in the longitudinal direction of the electrode plate body in the direction opposite to the electrode plate body) is preferably 1 mm or less, for example. Further, the width of the melted portion (in FIGS. 1a and 1b, the width of the melted portion in the direction parallel to the width direction of the electrode plate body) is substantially the same as or smaller than the width of the electrode plate body. When forming, it can suppress more effectively that the component of the circumference | surroundings of a fusion | melting part deform | transforms or damages a separator. When the width of the melted portion protrudes larger than the length of the end face of the electrode plate main body in which the melted portion is formed (the width of the electrode plate main body in FIGS. 1a and 1b), the projecting amount is 1 mm or less. It is desirable that

The melting part usually includes an alloy of the constituent components of the electrode plate body and the metal components of the electrode lead. As a component of the electrode plate main body, in addition to the alloy-based active material, when the metal component of the current collector and the active material layer include a metal component as a conductive material, the metal component as the conductive material and the like can be mentioned. . When the alloy-based active material is alloyed, it is easy to increase the bonding strength. Therefore, the melted portion preferably includes at least an alloy of the alloy-based active material and the metal component of the electrode lead. In addition, the melted portion may include an alloy of an alloy-based active material, a conductive material and / or a metal component of a current collector, and a metal component of an electrode lead. When the molten part contains an alloy containing copper, it is possible to suppress the occurrence of cracks during compression, even if the flat part is formed by compression.

In other words, the melted portion may include a region where the elements constituting the alloy-based active material, the constituent elements of the electrode plate body such as the metal component of the current collector, and the metal elements contained in the electrode lead are uniformly dispersed. it can. Such a melted portion has good conductivity, and can more effectively electrically connect the electrode plate body and the electrode lead. Therefore, the electrode plate having such a melted portion is advantageous in that it can have both high strength bondability between the electrode plate main body and the electrode lead and good current collecting performance.

In the embodiment of FIG. 1b, an example in which one band-like continuous melting portion is formed so as to cover the entire end face of one end portion of the electrode plate main body is shown, but the embodiment is not limited thereto. For example, the melting portion may be formed in a continuous band shape so as to cover most of the end surface in the width direction (short direction) at one end portion of the electrode plate body, or may be formed intermittently like a spot. May be. Further, at least one melting part may be formed at one end of the electrode plate body, and the number of melting parts that may form two or more melting parts is not limited to one or two, for example, There may be three or more.

The weld strength can be further increased by forming the melted portion continuously in a strip shape or the like at one end of the electrode plate body or by forming a plurality of melted portions. When the electrode plate body and the electrode lead are joined with the width direction (short direction) of the electrode plate body and the longitudinal direction of the electrode lead aligned as shown in FIG. It is preferable to form a plurality of melted parts. Also, when joining the electrode plate body and the electrode lead by matching the longitudinal direction of the electrode plate body and the width direction (short direction) of the electrode lead, a melted part is formed continuously or a plurality of melts are formed. Although a part may be formed, one melting part may be formed in a spot shape.
The electrode plate of the present invention is useful as an electrode plate for various electrochemical elements because the electrode lead and the electrode plate main body are firmly joined by the melting part.

In the electrode plate of the present invention, a high bonding strength can be obtained between the electrode plate main body and the electrode lead by forming the melted portion. The bonding strength between the electrode lead and the electrode plate body is, for example, 0.5 N / mm or more, preferably 1 N / mm or more, and more preferably 1.5 N / mm or more. The bonding strength is, for example, 50 N / mm or less, 10 N / mm or less, or 5 N / mm or less. These lower limit value and upper limit value can be appropriately selected and combined. The bonding strength may be, for example, 0.5 to 50 N / mm or 1 to 5 N / mm. It is desirable to appropriately select the number and width of the melted portions and the welding conditions so that the joining strength is in such a range.

The bonding strength can be obtained as follows.
First, one end of the electrode plate body and one end of the electrode lead are overlapped with both end faces aligned and close together, and the welded area including both end faces is melted by welding or the like to form a melted portion. To join. Next, the other end of the electrode plate body and the other end of the electrode lead are set in a tensile strength measuring instrument, pulled at a predetermined speed in a direction in which both other ends are separated, and the tensile strength ( N) is measured. Then, by dividing by the width of the joint portion (joint width) (mm), the joint strength can be obtained as the tensile strength per 1 mm of the joint width.

In addition, when one fusion | melting part is formed in a joining part, joining width is the width | variety of a fusion | melting part (width in the direction parallel to the width direction of the electrode plate main body to join), and several fusion | melting parts form If it is, it is the distance between the outermost parts of the melted portions at both ends.

The electrochemical element includes the above-described electrode plate for an electrochemical element as a first electrode, a second electrode having a polarity opposite to the first electrode, and a separator interposed between the first electrode and the second electrode. Including.
Examples of the electrochemical element in which the electrode plate is used include a battery and a capacitor (for example, an electric double layer capacitor) having a current collecting structure similar to that of the secondary battery. Examples of the battery include primary batteries such as alkaline dry batteries and lithium primary batteries, alkaline secondary batteries such as nickel hydride storage batteries, and secondary batteries such as non-aqueous electrolyte secondary batteries (such as lithium ion secondary batteries).

Below, each component of an electrode plate and an electrochemical element is demonstrated.
The electrode plate main body included in the electrode plate includes a laminate of a current collector containing metal and an active material layer formed on the surface and containing an alloy-based active material.

The type of metal contained in the electrode lead, the metal contained in the current collector, and the active material can be either the type of electrochemical element or the type of electrode on which the electrode plate is used (positive electrode (or anode) or negative electrode (or cathode)). )) And so on. If the molten part is formed by alloying the metal component of the electrode lead and at least the active material (preferably the active material and the metal component of the current collector), it is included in the electrode lead that can be alloyed What is necessary is just to select suitably the combination of the metal and the metal contained in an active material or an electrical power collector.

Examples of the metal contained in the electrode lead include copper, copper alloy, nickel, nickel alloy, aluminum, aluminum alloy, silver, silver alloy, gold, and gold alloy.

From the viewpoint of uniformly dispersing an alloyable element (such as a metalloid element such as silicon) contained in the alloy-based negative electrode active material in the molten portion and increasing the bonding strength, among these, nickel and nickel alloy Copper, copper alloy or the like is preferable.

Examples of nickel alloys include alloys containing metalloid elements such as nickel-silicon alloys and nickel-tin alloys; alloys containing transition metal elements such as nickel-cobalt alloys, nickel-iron alloys and nickel-manganese alloys. Copper alloys include alloys containing alkaline earth metal elements such as copper-beryllium alloys; alloys containing transition metal elements such as copper-zirconia alloys, copper-nickel alloys, copper-iron alloys, copper-silver alloys; copper- Examples include alloys containing typical metal elements such as aluminum alloys; alloys containing metalloid elements such as copper-phosphorus alloys, copper-silicon alloys, and copper-tin alloys. Of these alloys, copper-nickel alloys are preferred.

Especially, it is preferable that the metal component contained in the electrode lead is copper or a copper alloy. As the electrode lead, an electrode lead using a clad material of copper and nickel is also preferable. The electrode lead can be obtained by molding a material such as the above metal or alloy into a general lead form.

The metal contained in the current collector is selected according to the type of electrochemical element or the type of electrode, and examples thereof include copper, copper alloy, nickel, nickel alloy, aluminum, aluminum alloy, and stainless steel. Of these, copper or a copper alloy is preferable from the viewpoint of uniformly dispersing an alloyable element (such as a metalloid element such as silicon) contained in the alloy-based negative electrode active material.

The alloy-based active material means a substance containing an element that can be alloyed and dealloyed with ions (for example, lithium ions in a lithium ion battery) that are conductive carriers in an electrochemical element. Moreover, it is preferable that the alloy-based active material can be alloyed with the metal contained in the current collector and / or the electrode lead. Therefore, the alloy-based active material preferably contains, for example, Al, Zn and / or Mg and lithium in addition to silicon and / or tin as the above-mentioned element, depending on the type of electrochemical element.

The electrode plate of the present invention is particularly useful for use in non-aqueous electrolyte secondary batteries such as lithium ion batteries among electrochemical elements. The constituent elements of the electrochemical device will be described below by taking a nonaqueous electrolyte secondary battery as an example.

The nonaqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a separator interposed therebetween, and a nonaqueous electrolyte.
In the nonaqueous electrolyte secondary battery, the electrode plate of the present invention is preferably used as a negative electrode.
The negative electrode includes a laminate of a current collector and an active material layer formed on the surface of the current collector. The active material layer may be formed on one surface of the current collector, or may be formed on both surfaces.

Examples of the material of the negative electrode current collector include stainless steel, titanium, nickel, copper, and copper alloy. The form of the negative electrode current collector is not particularly limited, and may be a nonporous metal foil, a sheet, a film, or the like, or may be porous. The thickness of the negative electrode current collector can be selected from the range of 1 to 500 μm, for example, and is, for example, 1 to 50 μm, preferably 10 to 40 μm or 10 to 30 μm.

The negative electrode active material layer may be formed only of an alloy-based active material. In addition to the alloy-based active material, other non-alloy-based active materials, binders, conductive agents, thickeners may be used as long as the characteristics are not impaired. Agents, known additives and the like.

In a non-aqueous electrolyte secondary battery, the alloy-based active material occludes lithium by alloying with lithium at the time of charging and releases lithium by de-alloying at the time of discharge under a negative electrode potential. Such an alloy-based active material is not particularly limited as an alloy-based active material, can be alloyed with a known material, for example, a metal component of an electrode lead, and reversibly occludes and releases lithium ions. Various materials containing the element to be obtained can be used.

Examples of such materials include silicon, silicon alloys, silicon compounds (silicon oxide SiO _a , silicon carbide SiC _b , silicon nitride SiN _c, etc.), tin, tin alloys, tin compounds (tin oxide SnO _a , SnO ₂ ; tin carbide SnC _b ; tin nitride SnN _c ; SnSiO ₃ , Ni ₂ Sn ₄ , Mg ₂ Sn, etc.), lithium alloys containing Al, Zn and / or Mg, etc. in addition to these partially substituted or solid solutions Examples thereof include alloy materials. In silicon oxide and tin oxide, the coefficient a is 0 <a <2, preferably 0.05 <a <1.95. In silicon carbide and tin carbide, the coefficient b is 0 <b <1. In silicon nitride and tin nitride, the coefficient c is 0 <c <4/3.

Examples of the silicon alloy include an alloy containing silicon and lithium, an alloy containing Al, Zn, and / or Mg in addition to silicon and lithium, and an alloy of silicon and a different element A1. Examples of the different element A1 include at least one element selected from the group consisting of Mg, Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, Sn, and Ti.

Examples of the tin alloy include an alloy containing tin and lithium, an alloy containing tin, lithium, an alloy containing Al, Zn, and / or Mg, an alloy of tin and a different element A2, and the like. Examples of the different element A2 include at least one element selected from the group consisting of Mg, Fe, Co, Sb, Bi, Pb, Ni, Cu, Zn, Ge, In, and Ti. Specific examples of the tin alloy include Mg—Sn alloy, Ti—Sn alloy, Fe—Sn alloy, Ni—Sn alloy, Cu—Sn alloy and the like.

As the partially substituted body, silicon, a silicon alloy, or a compound obtained by substituting a part of silicon contained in a silicon compound with a different element B1, tin, a tin alloy, or a part of tin contained in a tin compound is replaced with a different element B2. Examples include substituted compounds. The different element B1 is at least selected from the group consisting of B, Mg, Ni, Ti, Mo, Co, Ca, Cr, Cu, Fe, Mn, Nb, Ta, V, W, Zn, C, N, and Sn. One element can be used. The different element B2 is at least one selected from the group consisting of B, Mg, Ni, Ti, Mo, Co, Ca, Cr, Cu, Fe, Mn, Nb, Ta, V, W, Zn, C, and N. Two elements can be used.

These alloy-based active materials can be used singly or in combination of two or more.
Of the alloy-based active materials, active materials containing silicon and / or tin are preferable, and silicon, silicon alloys, silicon compounds, and the like are particularly preferable.

From the viewpoint of increasing the melting efficiency of the active material, a lithium foil or a lithium alloy foil may be attached to the surface of the negative electrode active material layer in the negative electrode active material layer. Lithium contained in the attached lithium foil or alloy foil is appropriately occluded in the negative electrode active material layer.

The electrode lead electrically connected to the negative electrode preferably contains copper or a copper alloy.
For example, an electrode lead containing copper or a copper alloy and an electrode plate main body containing an alloy-based active material containing an element such as silicon or tin in the active material layer are welded at one end of the electrode plate main body so that the molten portion is It is formed.

In addition, when the negative electrode current collector contains copper or a copper alloy as in the case of the electrode lead, as in the alloying of the active material and the metal component of the electrode lead, the current collector copper or copper alloy, Alloying with the active material, and hence the electrode lead, is likely to proceed.

The melted portion thus formed preferably contains an alloy of copper and silicon or tin. In a more preferred embodiment, the molten part contains an alloy of copper and silicon. The composition of such an alloy is not particularly limited, but the alloy preferably contains Cu ₅ Si.

The negative electrode active material layer can be formed using a negative electrode slurry containing an alloy-based active material, a binder and a dispersion medium. The negative electrode slurry may further contain a thickener, a conductive material, a known additive and the like as necessary. The negative electrode active material layer can be formed by preparing a negative electrode slurry containing these components and applying it to the surface of the negative electrode current collector. The coating film of the negative electrode slurry is usually dried and subjected to rolling.

As binders, various resin materials, for example, fluororesins (polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyhexafluoropropylene, etc.); polyolefin resins (polyethylene, polypropylene, etc.); polyamide resins such as aromatic polyamides, etc. Polyimide resin such as polyimide and polyamideimide; acrylic resin such as polymethyl acrylate and ethylene-methyl methacrylate copolymer; polyvinyl pyrrolidone; rubber-like material such as styrene-butadiene rubber, acrylic rubber or modified products thereof it can. These binders can be used individually by 1 type or in combination of 2 or more types.
The ratio of the binder is, for example, 0.1 to 10 parts by mass, preferably 1 to 5 parts by mass, per 100 parts by mass of the active material.

Examples of the dispersion medium contained in the negative electrode slurry include water; alcohols such as ethanol; ketones such as acetone and cyclohexanone; amides such as dimethylformamide, dimethylacetamide and methylformamide; N-methyl-2-pyrrolidone (NMP); dimethyl Examples thereof include amines such as amines; or mixed solvents thereof.

Examples of non-alloy active materials include carbonaceous materials such as natural or artificial graphite. The amount of the non-alloy type active material is, for example, 30 parts by mass or less, preferably 10 parts by mass or less, per 100 parts by mass of the alloy type active material.

Examples of the conductive agent include carbon black; conductive fibers such as metal fibers and carbon fibers; metal powders such as aluminum; and carbon fluoride. These electrically conductive agents can be used individually by 1 type or in combination of 2 or more types. The ratio of the conductive agent is, for example, 0.1 to 7 parts by mass per 100 parts by mass of the active material.

Examples of the thickener include cellulose derivatives such as carboxymethyl cellulose (CMC); poly C _2-4 alkylene glycol such as polyethylene glycol. The ratio of the thickener is, for example, 0.1 to 10 parts by mass per 100 parts by mass of the active material.

Also, by vapor deposition methods such as vacuum deposition, sputtering, ion plating, laser ablation, chemical vapor deposition (CVD), plasma chemical vapor deposition, and thermal spraying The negative electrode active material layer may be formed by depositing an alloy-based active material on the surface of the current collector to form a thin film of the negative electrode active material. Among these, it is preferable to form a negative electrode active material layer by a vacuum evaporation method. When the active material layer is a deposited film of an alloy-based active material by a vapor phase method, a current collector exposed portion is provided as in the conventional method, and an electrode lead is joined to this current collector exposed portion. Difficult to do. In the present invention, since the electrode plate and the electrode lead can be joined by the melting portion, it is particularly effective when the active material layer is a deposited film.

Formation of the negative electrode active material layer by vacuum deposition can be performed, for example, as follows.
In the electron beam vacuum deposition apparatus, a current collector is disposed above the silicon target in the vertical direction. The silicon target is irradiated with an electron beam to generate silicon vapor, and this silicon vapor is deposited on the surface of the negative electrode current collector. Thereby, a thin-film negative electrode active material layer made of silicon is formed on the surface of the current collector. At this time, when oxygen or nitrogen is supplied into the electron beam vacuum deposition apparatus, a negative electrode active material layer containing silicon oxide or silicon nitride is formed.

The negative electrode active material layer thus obtained is formed as a thin solid film, but is not limited thereto, and is formed by a gas phase method as a pattern shape such as a lattice or an aggregate of a plurality of columnar bodies. Also good. Each of the plurality of columnar bodies contains an alloy-based active material, and is formed to extend outward from the surface of the negative electrode current collector and to be separated from each other.

In this case, it is preferable to form a plurality of convex portions regularly or irregularly on the surface of the negative electrode current collector and to form one columnar body on the surface of one convex portion. Examples of the shape in the orthographic projection from above in the vertical direction of the convex portion include a rhombus, a circle, an ellipse, and a polygon (triangle, octagon, etc.). When the convex portions are regularly formed, the arrangement of the convex portions on the negative electrode current collector surface includes a grid-like arrangement, a lattice arrangement, a staggered arrangement, a close-packed arrangement, and the like. Further, the convex portion is formed on one surface or both surfaces in the thickness direction of the negative electrode current collector. The height of the columnar body is preferably 3 μm to 30 μm.

The thickness of the negative electrode active material layer is, for example, 3 to 200 μm, preferably 5 to 100 μm. The thickness of the negative electrode active material layer formed by deposition is, for example, 3 to 50 μm or 5 to 30 μm.
The negative electrode active material layer in a preferred form is an amorphous or low crystalline deposited film containing an alloy-based active material and having a thickness of 3 to 50 μm.

The positive electrode includes a current collector and an active material layer formed on the surface of the current collector. The active material layer may be formed on one surface of a current collector (such as a belt-shaped or sheet-shaped current collector), or may be formed on both surfaces.

Examples of the material of the positive electrode current collector include stainless steel, aluminum, aluminum alloy, and titanium. The form and thickness of the positive electrode current collector are the same as those of the negative electrode current collector. As the positive electrode current collector, it is also preferable to use a porous material, and examples of the porous current collector include a mesh body, a net body, a punching sheet, a lath body, a porous body, a foam, and a nonwoven fabric. It can be illustrated.

The positive electrode active material layer may contain a binder, a conductive agent, a thickener and the like in addition to the positive electrode active material. The positive electrode active material layer can be formed by the same method as in the case of forming a negative electrode active material layer using a negative electrode slurry using a positive electrode slurry containing these components. As each component contained in a positive electrode slurry, what was illustrated by the term of the negative electrode slurry can be used, and content of each component can be selected from the same range as the case of a negative electrode slurry. As the conductive agent added to the positive electrode slurry, graphite such as natural graphite or artificial graphite can be used in addition to those exemplified in the section of the negative electrode slurry. The thickness of the positive electrode active material layer can be selected from the same range as the thickness of the negative electrode active material layer.

As the positive electrode active material, a known non-aqueous electrolyte secondary battery positive electrode active material can be used, and among these, lithium transition metal composite oxide, olivine type lithium phosphate and the like are preferably used. A positive electrode active material can be used individually by 1 type or in combination of 2 or more types.

Examples of the lithium transition metal composite oxide include a metal oxide containing lithium and a transition metal element, and a metal oxide in which a part of the transition metal element in such a metal oxide is substituted with a different element. Specific examples of the transition metal element include Sc, Y, Cr, Mn, Fe, Co, Ni, and Cu. The lithium transition metal composite oxide may contain one of these transition metal elements or a combination of two or more. Of these transition metal elements, Mn, Co and / or Ni are preferred.

Examples of the different elements include alkali metal elements, alkaline earth metal elements, typical metal elements, and semimetal elements. Specific examples of the different elements include Na, Mg, Zn, Al, Pb, Sb, and B. The lithium transition metal composite oxide may contain one kind of these different elements or two or more kinds. Among the different elements, Mg and / or Al are preferable.

Examples of the lithium transition metal composite oxides, for _{_{_{example, Li l CoO 2, Li l}}} NiO 2, Li l MnO 2, Li l Co m Ni 1-m O 2, Li l Co m A 1-m O n, Li l _{_{_{Ni 1-m A m O n}}} , Li l Mn 2 O 4, Li l like Mn _2-m A _n O ₄ and the like. In these formulas, A represents at least one element selected from the group consisting of the transition metal element and the heterogeneous element, and 0 <l ≦ 1.2, 0 ≦ m ≦ 0.9, 2 ≦ n ≦ 2. 3.

Examples of the olivine type lithium phosphate include LiXPO ₄ and Li ₂ XPO ₄ F. In these formulas, X represents a transition metal element, for example, at least one element selected from the group consisting of Co, Ni, Mn and Fe.
In the positive electrode active material exemplified above, the molar ratio of lithium is a value immediately after the production of the positive electrode active material, and increases or decreases due to charge / discharge.

The positive electrode further includes at least a positive electrode lead electrically connected to the current collector. Depending on the type of active material, the positive electrode lead can be electrically connected to the current collector and the active material layer in the same manner as the electrode lead connection method in the negative electrode. Preferably, one end of the positive electrode lead is bonded to the current collector by resistance welding, ultrasonic welding, or the like. The other end of the positive electrode lead is electrically connected to the positive electrode terminal.
Examples of the material for the positive electrode lead include aluminum and aluminum alloys.

As the separator, a sheet having a predetermined ion permeability, mechanical strength, insulation and the like can be used. As the separator, it is preferable to use a porous sheet such as a resin microporous film, a woven fabric or a non-woven fabric. From the viewpoint of durability, shutdown function, etc., it is preferable to use a polyolefin resin such as polyethylene or polypropylene as the resin material constituting the separator.

The thickness of the separator is, for example, 10 to 300 μm, preferably 10 to 30 μm, and more preferably 10 to 25 μm. Further, the porosity of the separator is preferably 30 to 70%, more preferably 35 to 60%. The porosity is a percentage of the total volume of pores of the separator with respect to the volume of the separator.

In the non-aqueous electrolyte secondary battery, a non-aqueous electrolyte having lithium ion conductivity is used as the non-aqueous electrolyte. The non-aqueous electrolyte includes a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent as a solute (or supporting salt). At least the separator is impregnated with the nonaqueous electrolyte.

Non-aqueous solvents include cyclic carbonates such as propylene carbonate and ethylene carbonate (EC); chain carbonates such as diethyl carbonate, ethylmethyl carbonate (EMC) and dimethyl carbonate; cyclic esters such as γ-butyrolactone and γ-valerolactone Examples thereof include carboxylic acid esters. These non-aqueous solvents can be used alone or in combination of two or more.

Examples of the lithium _{_{salt, LiPF 6, LiSbF 6, LiAsF}} 6, LiBF 4, LiBCl 4, LiB 10 Cl 10, LiAlCl 4, LiClO 4, LiCF 3 SO 3, LiC (SO 2 CF 3) 3, imidates [ LiN etc. _{_{_{(SO 2 CF 3) 2,}}} LiN (SO 2 C 2 F 5) 2], halide (LiCl, LiBr, etc. LiI), boric acid salts, LiCF ₃ CO _2, LiSCN, lower aliphatic carboxylic acid lithium, etc. Is mentioned. A lithium salt can be used individually by 1 type or in combination of 2 or more types. The concentration of the lithium salt in the nonaqueous electrolyte is, for example, 0.5 to 2 mol / L.

A known additive may be added to the nonaqueous electrolyte. Additives that improve charge and discharge efficiency such as fluorine atom-containing cyclic carbonates (fluorinated ethylene carbonate, etc.) and cyclic carbonates with unsaturated bonds (vinylene carbonate, vinylethylene carbonate, divinylethylene carbonate, etc.) An additive that inactivates a battery such as an aromatic compound such as cyclohexylbenzene, biphenyl, and diphenyl ether; An additive can be used individually by 1 type or in combination of 2 or more types.

The nonaqueous electrolyte secondary battery can be manufactured by a known method according to the shape of the battery. In a cylindrical battery or a rectangular battery, for example, a positive electrode, a negative electrode, and a separator disposed between them are wound to form an electrode group, and the electrode group and the electrolyte can be accommodated in a battery case. .

The electrode group is not limited to a wound one, but may be a laminated one or a zigzag folded one. The shape of the electrode group may be a cylindrical shape or a flat shape having an oval end surface perpendicular to the winding axis, depending on the shape of the battery or battery case.

As the battery case material, aluminum, an aluminum alloy (such as an alloy containing a trace amount of a metal such as manganese or copper), a steel plate, or the like can be used.

FIG. 3 is a longitudinal sectional view schematically showing a configuration of a lithium ion battery as an electrochemical element according to an embodiment of the present invention. The lithium ion battery 25 has the same configuration as a conventional lithium ion battery except that the electrode plate for electrochemical elements of the present invention is included as the negative electrode 28.
The lithium ion battery 25 includes a bottomed cylindrical battery case 32, a wound electrode group 26 accommodated in the battery case 32, and a non-aqueous electrolyte (not shown), and the opening of the battery case 32 has a sealing plate. 34 is sealed.

More specifically, the electrode group 26 is formed by laminating a belt-like positive electrode 27 and a belt-like negative electrode 28 with a belt-like separator 29 interposed therebetween, and winding one end portion in the longitudinal direction of the laminate. It is formed by winding around a rotation axis. The electrode group 26 is housed inside the battery case 32 with the upper insulating plate 30 disposed on the upper surface and the lower insulating plate 31 disposed on the bottom surface.

The positive electrode lead 36 led out from the upper part of the electrode group 26 is electrically connected to a sealing plate 34 that seals the opening of the battery case 32 and supports the positive electrode terminal 33.
The negative electrode 28 includes a plurality of melts that electrically connect the electrode plate body 1 and the electrode lead 13, and the electrode plate body 1 and the negative electrode lead, each including a laminate of a current collector and an active material layer formed on both sides thereof. Unit 17. The electrode lead 13 is led out from the electrode group 26 and is electrically connected to the inner bottom surface of the battery case 32.

The nonaqueous electrolyte is injected into the battery case 32 after the electrode group 26 is stored in a predetermined amount. After injecting the nonaqueous electrolyte, a sealing body 34 that supports the positive terminal 33 is inserted into the opening of the battery case 32. The lithium ion battery 25 can be obtained by caulking and sealing the opening of the battery case 32 so as to be bent inward.

The upper insulating plate, the lower insulating plate, and the sealing plate are produced by molding an electrically insulating material, preferably a resin material, a rubber material, or the like into a predetermined shape. The battery case and the positive terminal are produced by molding a metal material such as iron or stainless steel into a predetermined shape.

Although an example of a cylindrical battery is shown in FIG. 3, the shape or type of the nonaqueous electrolyte secondary battery is not particularly limited, and may be a square battery, a flat battery, a coin battery, a laminated film pack battery, or the like. .
Although the wound electrode group is used in FIG. 3, the present invention is not limited to this, and a stacked electrode group, a flat electrode group, or the like may be used.

Thus, an electrochemical element such as a non-aqueous electrolyte secondary battery including the electrode plate of the present invention has a high capacity and a high output, and is excellent in battery performance such as output characteristics and cycle characteristics. Further, the electrode plate and the electrode lead are bonded to the melted portion more firmly and with high conductivity. On the other hand, since the flat part is formed in the melting part, it is possible to suppress a short circuit due to undesired deformation of the constituent elements of the electrode group around the melting part or damage to the separator. Thereby, the current collection performance of the electrode plate, the output characteristics of the battery, etc. are maintained at a high level over a long period of time. Therefore, the electrochemical element has a long service life.

(Method for producing electrode plate for electrochemical element)
The method for producing an electrode plate for an electrochemical element used as an electrode for a nonaqueous electrolyte secondary battery includes the following steps A to D.
(I) A step of preparing an electrode plate body including a laminate of a band-shaped current collector containing a metal and an active material layer formed on the surface of the current collector and containing an alloy-based active material,
(Ii) Step B of arranging the electrode lead so that one end of the electrode plate body and one end of the electrode lead containing metal are close to a part of the surface of the active material layer,
(Iii) At one end of the electrode plate body and one end of the electrode lead that are close to each other, the electrode plate body and the electrode lead are electrically connected by melting a welding region including the end surface of the electrode plate body and the end surface of the electrode lead. A step C of forming a fusion part to be connected in general, and (iv) a step D of compressing the fusion part in a direction perpendicular to the surface of the electrode plate body to form a flat part parallel to the surface of the electrode plate body.

In step A, the electrode plate body can be prepared by laminating an active material layer containing an alloy-based active material on the surface of the current collector to form a laminate. A laminated body can be formed according to the formation method of the negative electrode in said nonaqueous electrolyte secondary battery. The active material layer may be formed on one surface of the current collector, or may be formed on both surfaces.

When the electrode plate is used as a negative electrode of a non-aqueous electrolyte secondary battery, a step (hereinafter referred to as “lithium storage step”) in which lithium is stored in the active material layer is provided between step A and step B. Also good. Thereby, the uniform dispersibility of the alloy in the fusion | melting part obtained at the process C can be improved further. The lithium occlusion process is particularly effective when the alloy-based active material contains silicon.

Further, when the lithium occlusion process is provided, the bonding strength can be ensured without impairing the uniformity of the shape of the melted part as compared with the case where the lithium occlusion process is not provided. Thereby, the contact area of a fusion | melting part, an electrode plate main body, and an electrode lead can be enlarged in the width direction whole region of a fusion | melting part. As a result, it is possible to more effectively improve the bondability and electrical connectivity between the electrode plate body and the electrode lead by the melted portion.

The occlusion of lithium into the active material layer can be performed, for example, by vacuum deposition, an electrochemical method, sticking of lithium foil on the surface of the active material layer, or the like. For example, according to the vacuum deposition method, when metal lithium is attached to a target of a vacuum deposition apparatus and vacuum deposition is performed, lithium is occluded in the active material layer. The amount of lithium occluded is not particularly limited, but it is preferable to occlude lithium for the irreversible capacity of the active material layer.

In step B, electrode leads are arranged on a part of the surface of the active material layer of the electrode plate body prepared in step A. At this time, the electrode lead is disposed on the surface of the active material layer so that the one end portion of the electrode plate body and the one end portion of the electrode lead containing metal are close to each other so that the melted portion can be easily formed in the next step C. . In the next step C, the end surface of the electrode plate main body and the end surface of the electrode lead are welded, and in step B, the end surface of the electrode plate main body and the end surface of the electrode lead are brought close to each other. In a preferred embodiment, both the end face of the electrode plate body and the end face of the electrode lead are formed so as to form the same plane (a flat weld end face formed by the end face of the electrode plate body and the end face of the electrode lead). Arranged in the thickness direction of the electrode plate body.

In step B, the electrode lead may be arranged so that one end in the longitudinal direction and one end in the longitudinal direction of the electrode plate body are close to each other, and one end in the short direction and one end in the longitudinal direction of the electrode plate body. They may be arranged so that they are close to each other, or may be arranged so that one end in the longitudinal direction is close to one end in the short direction of the electrode plate body. In a preferred embodiment, one end part of the electrode lead in the longitudinal direction or the short side direction and one end part of the electrode plate body in the longitudinal direction are brought close to each other. The electrode lead and the electrode plate body are overlapped with each other in the thickness direction.

In step C, a melted portion is formed by melting a welded region including the end face of the electrode plate body and the end face of the electrode lead at one end portion of the electrode plate body and the one end portion of the electrode lead that are close to each other. When the welding region is melted, the constituent components of the electrode plate main body and the constituent components of the electrode lead are melted in the welding region to form a molten portion. In the welding region, at least the metal component of the current collector (preferably the metal component of the current collector and the alloy-based active material of the active material layer) and the metal component of the electrode lead among the constituent components of the electrode plate main body are melted. Is preferred. It is considered that when the constituent components of the electrode plate main body and the metal components of the electrode lead are melted, the constituent elements contained therein are uniformly dispersed in the melt and alloying occurs. Alloying preferably takes place throughout the melt.

The welding is not particularly limited as long as the melted part can be formed by melting the end face of the electrode plate body and the end face of the electrode lead, and a known welding method can be used. However, since the alloy-based active material has low conductivity, when resistance welding is used, it is difficult for current to flow through the active material layer. Therefore, a part of the current collector is locally melted near the interface between the current collector and the active material layer, or a part of the electrode lead is locally localized at the contact point between the active material layer and the electrode lead. The end surface of the electrode plate body and the end surface of the electrode lead cannot be melted only by melting. In particular, in resistance welding, it is difficult to melt the alloy-based active material. Therefore, resistance welding may not be able to form a melted part that can electrically connect the electrode plate body and the electrode lead. In the case of ultrasonic welding, the same result as that obtained by resistance welding is easily obtained.

It is advantageous to use arc welding to melt the end face of the electrode plate body and the end face of the electrode lead to form a melted portion that can electrically join the electrode plate body and the electrode lead. In arc welding, an arc discharge is performed toward a welding region including the end surface of the electrode plate main body and the end surface of the electrode lead, and the molten region is melted and arc-welded to form a fusion zone. When forming the melted part by arc welding, the alloy active material is melted and alloyed with the metal component of the current collector and / or the metal component of the electrode lead to form the alloy active material in the melted part. It is easy to disperse the elements to be dispersed. Therefore, the electrode plate body and the electrode lead can be firmly joined.

In addition, depending on the type of welding method and welding conditions, the alloy-based active material may remain as it is in the molten part without melting. However, in arc welding, one end of the electrode plate body and one end of the electrode lead are melted in a relatively wide range to form a melted portion. Therefore, even if the alloy-based active material remains in the melted part, the electrode plate body and the electrode lead can be firmly joined by the melted part. In addition, the electrical connectivity between the electrode plate body and the electrode lead is not impaired.

In step C, it is preferable to arrange the electrode plate body and the electrode lead so that the welding region is exposed between a pair of plates of a welding jig including the pair of plates prior to arc discharge. The welding region may be exposed from the end of the welding jig, and a space is formed between the pair of plates and the electrode plate main body or the electrode lead at one end of the electrode plate main body and the electrode lead adjacent to each other. Thus, the welding region may be exposed. An example of the latter case is shown in FIG.

FIG. 2 a is a schematic cross-sectional view showing an electrode plate main body and electrode leads arranged in a welding jig in the method for manufacturing an electrode plate for an electrochemical element according to an embodiment of the present invention.
In FIG. 2a, an electrode plate body 1 including a laminate of a current collector 10 and an active material layer 11 containing an alloy-based active material formed on both sides thereof, and an electrode lead 13 The end surface 1 a of the plate body 1 and the end surface 13 a of the electrode lead 13 are aligned and overlapped in the surface direction of the electrode plate body 1 and the electrode lead 13. In this state, the electrode plate body 1 and the electrode lead 13 are sandwiched by a welding jig having a pair of plates 14 including a first plate 20 and a second plate 21. The pair of plates 14 of the welding jig is produced by forming a metal material such as copper into a predetermined shape.

At one end of the electrode lead 13, a space (or a depression) is formed between the first plate 20 of the welding jig and the electrode lead 13 by the first recess 20 x formed in the first plate 20. . Similarly, at one end of the electrode plate body 1, a space (or a depression) is formed between the second plate 21 of the welding jig and the active material layer 11 by the second recess 21 x formed in the second plate 21. Is formed.

An arc welding electrode (not shown) is arranged in a welding region including the end surface 1 a of the electrode plate body 1 and the end surface 13 a of the electrode lead 13, particularly in a direction perpendicular to the flat welding end surface 16. Then, energy is irradiated in the direction of the arrow 19 from the welding torch of the electrode for arc welding. The energy irradiated from the welding torch is irradiated to the welding end surface 16. The welding region including the weld end surface 16 is the energy of arc discharge in the electrode plate main body 1 and the electrode lead 13 when arc discharge is performed from a direction 19 perpendicular to the weld end surface 16 under the conditions described later. This is the area covered by

The thermal energy generated by the arc discharge does not escape to the welding jig due to the depressions formed in the first concave portion 20x and the second concave portion 21x of the pair of plates 14 of the welding jig, and the electrode plate main body and the electrode lead, and the electrode plate main body 1 and the electrode lead 13 are used for melting without waste.

However, when the melted part is formed by arc welding, the melting of the alloy-based active material is facilitated, and the alloy-based active material and the metal component of the current collector and / or electrode lead are alloyed to form an alloy-based active material. The melting point of the substance tends to decrease. When the melting point of the alloy-based active material is lowered, melting of the welding region proceeds rapidly, the size of the molten part increases, and the thickness of the molten part may become larger than the thickness of the obtained electrode plate. Thus, when a wound electrode group is formed using the obtained electrode plate or an electrochemical element is assembled, the constituent elements around the melted portion are deformed or the separator is damaged.

It is also possible to control the welding conditions in step C so that the thickness of the melted part does not become larger than necessary. However, if the degree of melting in the weld region is reduced and the thickness of the melted portion is reduced, the joint strength is likely to be lowered. In addition, if the degree of melting of the weld region is small, the alloy-based active material is likely to remain without melting, and a barrier including active material particles is formed between the electrode plate body and the electrode lead, and alloying proceeds. The bonding strength is likely to decrease from the point of difficulty.

In order to form a stable melted part with high joint strength, it is necessary to perform arc welding with sufficient strength and to reliably melt and join the electrode plate body and the electrode lead in the welding region. When such bonding is performed, the thickness of the melted portion becomes large, and thus the formed melted portion is flattened in step D, thereby controlling the thickness of the melted portion within an appropriate range.

In step C, the weld region including the weld end face is uniformly melted by arc welding, and then solidified to form a melted portion. The cross-sectional shape of the solidified molten part is rounded. This is presumably because the melt obtained by melting the electrode plate body and the electrode lead is spheroidized by the surface tension and solidifies in that state.

In arc welding, arc discharge is performed while moving the electrode for arc welding in the width direction of the electrode plate body at predetermined intervals. If the arc discharge is continuously performed in the width direction while appropriately adjusting the arc discharge conditions, depending on the conditions, a continuous belt-like molten part is formed, or the molten metal is partially agglomerated in the width direction to form a spherical shape. And the melted portion solidified into a spherical shape is intermittently formed. When the melted portion is intermittently formed in the width direction of the electrode plate body, the arc welding may be performed intermittently while moving the electrode for arc welding in the width direction of the electrode plate body. By performing arc welding, it is possible to easily form a melted portion at an arbitrary position in one end portion of the electrode plate main body and the electrode lead that are close to each other.

In order to ensure a strong joint strength between the electrode plate body and the electrode lead, arc welding is performed with sufficient strength to ensure melting of the current collector and / or active material layer of the electrode plate body and the electrode lead. Need to be joined together. At this time, the thickness t1 of the melted portion tends to be thicker than the total thickness T of the electrode plate body and the electrode lead. In order to securely bond the electrode plate main body and the electrode lead, it is preferable to form a melting portion having a size sufficient to cover the entire end surface of the electrode plate main body and the end surface of the electrode lead.

Therefore, the ratio t1 / T between the thickness t1 of the melted portion after welding (before step D) and the total thickness T of the electrode plate body 1 and the electrode lead is, for example, 1 or more, preferably 1.3 or more, Preferably it is 1.5 or more. Further, the ratio t1 / T is, for example, 4 or less, preferably 3 or less. These lower limit value and upper limit value can be appropriately selected and combined. The ratio t1 / T may be, for example, 1 to 3 or 1.3 to 3.

Examples of arc welding include TIG (Tungsten Inert Gas) welding, plasma welding, and covering arc welding. Among these welding methods, non-consumable electrode type arc welding such as TIG welding or plasma welding is preferable. From the viewpoint of uniformly dispersing the constituent elements of the electrode plate main body and the electrode lead in the melted portion, plasma is particularly preferable. Welding is preferred. When the dispersibility of the constituent elements of the electrode plate main body and the electrode lead in the melted portion is increased, the bondability and electrical connectivity between the electrode plate main body and the electrode lead by the melted portion can be improved. It is guessed. Plasma welding and TIG welding can be performed using a commercially available plasma welding machine and TIG welding machine, respectively.

Plasma welding can be performed, for example, by appropriately selecting conditions such as welding current value, welding speed (moving speed of the welding torch), welding time, types of plasma gas and shield gas, and their flow rates. By selecting these conditions, it is possible to control the bondability and electrical connectivity between the electrode plate main body and the electrode lead by the melting portion to be generated.

The welding current value is, for example, 1 to 100A, preferably 5 to 50A. The sweep speed of the welding torch is, for example, 1 to 100 mm / second, preferably 5 to 50 mm / second. As the plasma gas, an inert gas such as an argon gas can be used. The plasma gas flow rate is, for example, 10 mL / min to 10 L / min, preferably 0.05 to 5 L / min. Argon, hydrogen, etc. can be used for the shielding gas. The shield gas flow rate is, for example, 10 mL / min to 10 L / min, preferably 0.1 to 5 L / min.

In step D, a flat portion parallel to the surface of the electrode plate body is formed in the melted portion formed in step C.
The flat part can be formed by flattening the melted part. Specifically, the flat part forms a generally flat surface by cutting or pressing at least a part of the melted part region protruding beyond the thickness of the electrode plate body and electrode lead laminate. Can be formed. By forming the flat portion, the melted portion is processed so as to be thin.

In a preferred embodiment, the flat portion is formed by compressing the melted portion in a direction perpendicular to the surface of the electrode plate body (that is, deformation by pressurization). The compression can be performed by a known compression processing apparatus such as a flat pressing means. FIG. 2b shows an example of a method for forming the flat portion.
FIG. 2B is a schematic cross-sectional view for explaining a step of forming a flat portion in the melted portion in the method for manufacturing an electrode plate for an electrochemical element according to one embodiment of the present invention.

As shown in FIG. 2b, specifically, in step D, first, in step C, the melted portion 18 formed at one end of the electrode plate main body 1 and the electrode lead 13 is replaced with a pair of planar pressing jigs 23. Is sandwiched between a pair of flat surface pressing jigs 23 of the flat surface pressing means. And the area | region which protruded from the surface of the laminated body of the electrode plate main body 1 and the electrode lead 13 of the fusion | melting part 18 is compressed by applying a load to the plane pressurization jig | tool 23. FIG.

At this time, a load is applied to the topmost portion (and the bottommost portion) in the thickness direction of the melted portion 18, and the vicinity of the topmost portion (and the vicinity of the bottommost portion) is pressed. In this manner, the vicinity of the top part (and the vicinity of the bottom part) of the melted part 18 is subjected to pressure deformation so that the thickness of the melted part 18 becomes thin, and a flat part as shown in FIG. 1a is formed.

When a load is applied mainly to the topmost part, a flat part is formed near the topmost part. Further, the melted portion is compressed from both directions in a direction perpendicular to the surface of the electrode plate body to form a first flat portion and a second flat portion opposite to the first flat portion as shown in FIG. 1a. May be. A first flat portion is formed by applying a weight to the topmost portion, and a second flat portion is formed by applying a weight to the bottommost portion.
The relationship between the thickness t of the melted portion having a flat portion and the total thickness T of the electrode plate body and the electrode lead is as described above.

The melting part 18 is preferably sandwiched between the flat pressing jigs 23 so that the pressing surface of the flat pressing jig 23 is generally parallel to the surface of the electrode plate body. Thereby, the fusion | melting part 18 can be compressed substantially perpendicularly with respect to the surface of an electrode plate main body using the plane pressurization jig | tool 23, and a flat part is made substantially parallel with respect to the surface of an electrode plate main body. Can do. As described above, the flat portion may be generally parallel to the surface of the electrode plate body.

When compressing the melted portion with a flat pressure jig, the electrode plate body and the electrode lead may or may not be fixed. When not fixed, the pressing surface of the flat pressing jig and the surface of the electrode plate main body are likely to shift from parallel. However, if the angle of the flat portion is within a certain range as described above, the effects of the present invention can be sufficiently obtained.

As described above, even if the flat portion is formed, the bonding strength between the electrode plate body and the electrode lead does not decrease. This is because the boundary region between the electrode plate main body and the electrode lead and the melted part is separated from the topmost part (and the bottommost part) of the melted part. This is presumed to be unaffected.

In Step C, even if arc discharge is continuously performed in the width direction at one end portion of the electrode plate body, the formed melted portions are a plurality of melted portions that are discontinuously aggregated into a spherical shape or the like. There is a case. In this case, the formed melted portion tends to increase in thickness. Therefore, when a flat part is formed by compressing such a melted part, as shown in FIG. 1b, the degree of protrusion of the melted part from the electrode plate body tends to increase. In some cases, the melted portion protrudes greatly due to the planarization, but the protruding direction is parallel to the longitudinal direction of the electrode plate body. Therefore, even if an electrode group is formed or an electrochemical element is formed, it is possible to suppress deformation of peripheral components and damage to the separator. However, the amount of protrusion is preferably not so large, and the amount of protrusion from one end of the electrode plate body (that is, the length of the melted portion) is desirably 1 mm or less as described above.

In step D, the load applied when compressing the melted part is, for example, 3 N / mm or more, preferably 5 N / mm or more, and more preferably 15 N / mm or more. Moreover, a load is 1000 N / mm or less, for example, Preferably it is 200 N / mm or less, More preferably, it is 80 N / mm or less. These lower limit value and upper limit value can be appropriately selected and combined. When the weight is in such a range, the flat portion can be formed more effectively, and the thickness of the melted portion can be in an appropriate range. In addition, a load can be applied only to the melted portion, which is advantageous for suppressing damage to the electrode plate body and the electrode lead and cracking in the melted portion.

In addition, since the thickness of the fusion | melting part formed at the process C is larger than the total thickness of an electrode plate main body and an electrode lead, a load is added only to a fusion | melting part in the case of planarization. In order to convert the load of the plane press into a pressure, it is necessary to measure the contact area between the melting part 18 and the plane pressure jig 23. However, since the contact area changes due to pressure deformation, it is possible to measure this. Have difficulty. Therefore, as described above, the weight at the time of compression is defined as the weight per 1 mm of the welding width of the welded portion.

Hereinafter, the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to the following examples.

Example 1
(1) Preparation NiSO ₄ aqueous solution of the positive electrode active material, Ni: Co = 8.5: 1.5 ( molar ratio) metal ion concentration by the addition of cobalt sulfate so as to have to prepare an aqueous solution of 2 mol / L. A ternary precipitate having a composition represented by Ni _0.85 Co _0.15 (OH) ₂ was coprecipitated by gradually dropping a 2 mol / L sodium hydroxide aqueous solution into the aqueous solution while stirring to neutralize the solution. It was generated by the method. This precipitate was separated by filtration, washed with water, and dried at 80 ° C. to obtain a composite hydroxide.

The obtained composite hydroxide was heated in the atmosphere at 900 ° C. for 10 hours to obtain a composite oxide having a composition represented by Ni _0.85 Co _0.15 O ₂ . Lithium hydroxide monohydrate was added to the obtained composite oxide so that the sum of the number of Ni and Co atoms and the number of Li atoms were equal, and heated in air at 800 ° C. for 10 hours. Thus, a lithium nickel-containing composite metal oxide having a composition represented by LiNi _0.85 Co _0.15 O ₂ was obtained. In this way, a positive electrode active material having a secondary particle volume average particle size of 10 μm was obtained.

(2) Preparation of positive electrode A positive electrode mixture slurry was prepared by thoroughly mixing 93 g of the positive electrode active material powder obtained above, 3 g of acetylene black (conductive agent), 4 g of PVDF powder (binder) and 50 ml of NMP. did. The positive electrode mixture slurry was applied to both surfaces of a 15 μm thick aluminum foil (positive electrode current collector), and the resulting coating film was dried and rolled to form a positive electrode active material layer having a thickness of 50 μm per side, 56 mm A positive electrode plate of × 205 mm was produced. A part (56 mm × 5 mm) of the positive electrode active material layer on both sides of the positive electrode plate is excised to form a positive electrode current collector exposed portion, and an aluminum positive electrode lead is welded to the positive electrode current collector exposed portion by ultrasonic welding. As a result, a positive electrode was produced.

(3) Production of Negative Electrode FIG. 4 is a side view schematically showing the configuration of the electron beam type vacuum vapor deposition apparatus 40. In FIG. 4, members inside the electron beam vacuum deposition apparatus 40 are indicated by solid lines. The vacuum chamber 41 is a pressure-resistant container, and accommodates a transfer means 42, a gas supply means 48, a plasma generating means 49,

silicon targets

50a and 50b, a shielding plate 51, and an electron beam generator (not shown).

The conveying means 42 includes an unwinding roller 43, a can 44, a winding roller 45, and guide

rollers

46 and 47. A strip-shaped current collector 10 is wound around the unwinding roller 43. The strip-shaped current collector 10 is conveyed via the guide roller 46, the can 44 and the guide roller 47, and is taken up by the take-up roller 45 as the electrode plate body 1.

When the strip-shaped current collector 10 is transported on the surface of the can 44, silicon vapor is supplied to the surface of the strip-shaped current collector 10. The silicon vapor is cooled by a cooling means (not shown) inside the can 44 and deposited on the surface of the strip-shaped current collector 10 to form the solid active material layer 11. The silicon vapor is generated by irradiating the silicon targets 50a and 50b with an electron beam from an electron beam generator.

The gas supply means 48 supplies the source gas into the vacuum chamber 41. When the source gas is oxygen, a mixture of silicon vapor and oxygen is supplied to the surface of the strip-shaped current collector 10 to form an active material layer 11 containing silicon oxide. When the gas supply means 48 does not supply the source gas, the active material layer 11 containing silicon is formed. The plasma generating means 49 converts the raw material gas into plasma. The horizontal position of the shielding plate 51 is adjusted according to the formation state of the active material layer 11 on the surface of the current collector 10.

A thin-film negative electrode active material layer (silicon thin film) having a thickness of 5 μm was formed on both surfaces of the strip-shaped negative electrode current collector using the electron beam vacuum vapor deposition apparatus 40 under the following conditions to produce a negative electrode plate.

Pressure in the vacuum chamber: 8.0 × 10 ⁻⁵ Torr
Strip-shaped negative electrode current collector: roughened electrolytic copper foil (Furukawa Electric Co., Ltd.)
Winding speed of belt-shaped negative electrode current collector by winding roller: 2 cm / min Raw material gas: Not supplied Silicon target: Silicon single crystal of purity 99.9999% (manufactured by Shin-Etsu Chemical Co., Ltd.)
Electron beam acceleration voltage: -8 kV
Electron beam emission: 300 mA
The obtained negative electrode plate (electrode plate main body) was cut into 58 mm × 210 mm. This electrode plate body was fixed in a resistance heating vapor deposition apparatus (manufactured by ULVAC, Inc.) so that the tantalum board and the active material layer face each other. The tantalum board was loaded with lithium metal. An argon atmosphere was introduced into the resistance heating vapor deposition apparatus, a 50 A current was passed through the tantalum boat, and lithium was deposited on the active material layer. The deposition time was 10 minutes. As a result, the irreversible capacity of lithium stored during the first charge / discharge was supplemented in the active material layer.

(4) Bonding of negative electrode lead The electrode plate body obtained above was cut from a copper foil (tough pitch copper, manufactured by Hitachi Cable Co., Ltd.), having a width of 5 mm, a length of 70 mm, and a thickness of 0.1 mm. The negative electrode lead was joined by plasma welding as follows to produce a negative electrode.

First, the electrode plate main body and the negative electrode lead are formed such that one end surface in the longitudinal direction of the electrode plate main body and one end surface in the width direction of the negative electrode lead are in one continuous plane and a flat weld end surface is formed. Are superimposed. The direction perpendicular to the weld end face was made to coincide with the vertical direction, and the weld end face was arranged so as to face upward in the vertical direction. These were sandwiched between a pair of plates of a welding jig including a pair of plates as shown in FIG. 2a, and further fixed by a single-axis robot (manufactured by IAI Corporation).

The welding jig includes a pair of plates of a first plate and a second plate, and the dimensions of the first plate and the second plate are 100 mm × 40 mm × 10 mm, respectively, and both are made of copper. Moreover, the cross-sectional shape of the notch which is the 1st recessed part formed in the 1st board and the 2nd recessed part formed in the 2nd board is a taper shape, and the cross-sectional dimension of a notch is a 1st board or a 2nd board. The length in the direction along the end surface of the first plate was 0.5 mm, and the length in the direction along the mating surface of the first plate or the second plate was 0.5 mm.

Next, a plasma welding machine (trade name: PW-50NR, manufactured by Koike Oxygen Industry Co., Ltd.) was placed vertically above the weld end face. Energy was irradiated from the torch of this plasma welding machine perpendicularly to the welding end face in the welding region. The torch was moved at equal intervals in the width direction of the electrode plate body. At the location where the torch was stopped, energy was applied to the weld end face under the following conditions, and the end face of the electrode plate body and the negative electrode lead was melted to form a melted portion, thereby producing a negative electrode.

Electrode bar: 1.0mm in diameter
Electrode nozzle: 1.6mm in diameter
Torch distance: 2.0mm
Torch sweep speed: 30 mm / s
Plasma gas: Argon Plasma gas flow rate: 100 (sccm)
Shield gas: hydrogen, argon Shield gas flow rate (hydrogen): 500 (sccm)
Shielding gas flow rate (argon): 1 (slm)
Welding current: 8.0A

After the plasma welding, the negative electrode was allowed to cool naturally, and the weld end face was observed with a scanning electron microscope (trade name: 3D Real Surface View, manufactured by Keyence Corporation). As a result, it was confirmed that a continuous melted portion was formed at one end of the electrode plate body and the negative electrode lead. On the weld end face, a plurality of fused portions aggregated in a spherical shape at indefinite intervals in the width direction of the electrode plate body were formed. Moreover, in the cross section of the fusion | melting part in the thickness direction of an electrode plate main body, the maximum thickness is 0.4 mm, The ratio of thickness is 2 with respect to the total thickness 0.2mm of the electrode plate main body and negative electrode lead before plasma welding. 0.0.

Using a scanning electron microscope (3D real surface view), an elemental map of copper and silicon in the cross section of the molten part was examined using an energy dispersive X-ray analyzer (trade name: Genesis XM2, manufactured by EDAX). As a result, copper and silicon were present in almost the entire region of the melted section. Moreover, as a result of measuring the element molar ratio of copper and silicon in the predetermined part of the fusion | melting part with the energy dispersive X-ray analyzer (Genesis XM2), copper was 90 mol% and silicon was 10 mol%. From these results, it was found that silicon diffused in copper to form an alloy.

The cross section of the melted part was qualitatively analyzed by a micro part X-ray diffractometer (trade name: RINT2500, manufactured by Rigaku Corporation). From a peak of components contained in the molten portion, components contained in the molten portion, it was identified as copper and Cu ₅ Si. Therefore, it was found that the molten portion contains a Cu ₅ Si alloy.

Further, the elemental map of lithium was examined with respect to the cross section of the melted portion by an Auger electron spectrometer (trade name: MODEL670, manufactured by ULVAC PHI). At the periphery of the cross section of the melted portion, there were a cross section of the active material layer and a cross section of the silicon layer, which had very small dimensions compared to the cross section of the melted portion. The active material layer is a portion that remains without melting. The silicon layer is a portion that has been melted once and resolidified without being alloyed. Although lithium was present in these cross sections, lithium was not present in the cross sections of copper and copper alloys.

From the above analysis results, it was found that copper and a copper-silicon alloy containing Cu ₅ Si exist in the molten part, and silicon and lithium exist in the peripheral part of the cross section of the molten part.

Next, the melted part was placed between a pair of opposed plane pressure jigs and subjected to pressure deformation. A precision press (manufactured by Nippon Automatic Machine Co., Ltd., SSP1000) was used as a flat press machine. Each of the pair of flat surface pressing jigs has a size of 150 mm × 150 mm × 20 mm and is made of stainless steel. The melted part was subjected to pressure deformation by setting the press load condition to 1000N. The width of the melted part is 30 mm, and the load per melted width is 33.3 N / mm.

In the cross section of the melted portion in the thickness direction of the electrode plate body, the maximum thickness is 0.23 mm, and the ratio of the thickness is 1.15 with respect to the total thickness of 0.2 mm of the electrode plate body and the negative electrode lead before plasma welding. Met. As a result of observing the cross-sectional shape, the flat portion generated by the pressure deformation of the melted portion was substantially parallel to the surface of the electrode plate body. The dimension in which the melted portion protruded in the same plane as the negative electrode lead to the opposite side was 0.2 mm at the maximum from the end of the negative electrode lead.

(5) Production of Battery The polyethylene microporous membrane (separator, trade name: Hypore, thickness 20 μm, manufactured by Asahi Kasei Co., Ltd.) is interposed between the positive electrode and the negative electrode obtained above, and the resulting laminate is obtained. By winding the object, a wound electrode group was produced. The other end of the positive electrode lead was welded to a stainless steel positive electrode terminal, and the other end of the negative electrode lead was connected to the inner bottom surface of a bottomed cylindrical iron battery case. An upper insulating plate and a lower insulating plate made of polyethylene were attached to one end and the other end in the longitudinal direction of the wound electrode group, respectively, and accommodated in a battery case.

Next, a nonaqueous electrolyte in which LiPF ₆ was dissolved at a concentration of 1.0 mol / L in a mixed solvent containing ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 1 was poured into the battery case. Furthermore, a sealing plate was attached to the opening of the battery case via a polyethylene gasket, and the battery case was sealed by caulking the opening end of the battery case to the inside to produce a cylindrical lithium ion battery.

Comparative Example 1
A cylindrical lithium ion battery was produced in the same manner as in Example 1 except that the negative electrode was produced without being subjected to pressure deformation by a flat press.

After the plasma welding, the negative electrode was allowed to cool naturally, and the weld end face was observed with a scanning electron microscope (trade name: 3D real surface view). As a result, in the cross section of the melted portion in the thickness direction of the negative electrode plate of plasma welding, the maximum thickness is 0.4 mm, with respect to the total thickness of 0.2 mm of the electrode plate main body and the negative electrode lead before plasma welding. The ratio was 2.0. The cross-sectional shape of the maximum melting part is a shape that is almost a semicircle as a whole, and protrudes relatively large from the surface of the electrode plate body.

Comparative Example 2
A cylindrical lithium ion battery was produced in the same manner as in Comparative Example 1 except that the negative electrode was produced by changing the joining method of the negative electrode lead to the negative electrode current collector from plasma welding to resistance welding. The negative electrode was produced as follows.

[Production of negative electrode]
First, an electrode plate main body and a copper negative electrode lead (width 4 mm, length 70 mm, thickness 100 μm) obtained in the same manner as in Example 1 were combined, and the end surface in the longitudinal direction of the electrode plate main body and the end surface in the width direction of the negative electrode lead Are arranged close to each other so as to form one continuous plane. The electrode plate body and the negative electrode lead are sandwiched between electrode rods having a tip diameter of 2 mm, and spot welding is performed using a resistance welding machine (manufactured by Miyachi Technos Co., Ltd.) with the current value set to 1.3 kA. Was joined to prepare a negative electrode.

[Joint strength between negative electrode current collector and negative electrode lead]
For the negative electrodes obtained in Example 1 and Comparative Examples 1 and 2, the bonding strength between the current collector and the negative electrode lead was measured as the tensile strength of the negative electrode lead with respect to the current collector as follows. FIG. 5a is a schematic perspective view for explaining a method for preparing a sample for measuring the bonding strength between the electrode plate main body and the electrode lead, and FIG. 5b shows the bonding strength between the electrode plate main body and the electrode lead. It is a schematic perspective view for demonstrating the state of the sample for doing. FIG. 6 is a schematic perspective view for explaining a method of measuring the bonding strength between the electrode plate main body and the electrode lead.

As shown in FIG. 5 a, first, the electrode lead 13 was cut so that the length of the electrode lead (negative electrode lead) 13 was the same as the width of the electrode plate body 1. Next, the electrode plate body 1 was cut so that the length of the electrode plate body 1 was 30 mm from the end where the electrode lead 13 was joined. At this time, the bonding width d was measured. The joining width d is the length of the melting part 17 in the width direction of the electrode plate body 1.

When a plurality of melting portions 17 are formed at a predetermined interval as shown in FIG. 5a, the bonding width d is formed at the other end from the melting portion 17 formed at one end in the width direction of the electrode plate body 1. It is the length to the melted part 17 made. In this case, the length of the melting part 17 formed at one end and the other end is included in the joining width d. The junction width d of each of the negative electrodes obtained in Example 1 and Comparative Examples 1 and 2 was cut to 30 mm.

Subsequently, as shown in FIG. 5b, the electrode lead 13 was folded back in the direction of the arrow 66 so as to peel off the electrode plate body 1, and a sample 65 for measuring tensile strength was produced.
Using the obtained sample 65, the tensile strength was measured by the measuring method shown in FIG. A universal testing machine (manufactured by Shimadzu Corp.) 70 is fixed to the lower fixing jig 71 with the end of the electrode plate body 1 on the side where the melted portion 17 is not formed being sandwiched. The lead 13 was fixed by sandwiching the end portion on the side where the melted portion 17 is not formed (end portion on the folded side).

At room temperature of 25 ° C., the upper fixing jig 72 was moved at a speed of 5 mm / min in the direction of the arrow 73 to pull the electrode lead 13. And the tensile strength (N) when the junction part (melting part 17) of the electrode plate main body 1 and the electrode lead 13 fractured | ruptured was measured. The tensile strength (N / mm) per 1 mm of the bonding width was determined from the measured value of the tensile strength and the measured value of the bonding width d. The results are shown in Table 1.

[Conductivity between negative electrode current collector and negative electrode lead]
For the negative electrodes obtained in Example 1 and Comparative Examples 1 and 2, the junction resistance between the current collector and the negative electrode lead was measured as follows.
First, the active material layer near the negative electrode lead was peeled off using sandpaper. Next, the junction resistance between the exposed current collector and the negative electrode lead was measured using a milliohm meter (trade name: milliohm high tester 3540, manufactured by Hioki Electric Co., Ltd.). The results are shown in Table 1.

[Electrode deformation during electrode group configuration]
About 20 cylindrical lithium ion batteries obtained in Example 1 and Comparative Examples 1 and 2, a cross-sectional observation by CT (Computer Tomography) was performed to measure the presence or absence of electrode deformation due to protrusion of the melted portion. An X-ray CT observation apparatus (SMX-225CT-f manufactured by Shimadzu Corporation) was used for CT cross-sectional observation. In the battery with a large protrusion of the melting part relative to the thickness direction of the electrode plate body and negative electrode lead, the shape of the electrode that circulates on the opposite surface of the melting part is deformed so as to avoid the melting part inside or outside is confirmed. It was.

From the results in Table 1, it can be seen that in Example 1, the melted portion can obtain good jointability between the electrode plate body and the negative electrode lead and can be electrically connected effectively. Also in Comparative Example 1, good bondability and electrical connectivity can be obtained between the electrode plate body and the negative electrode lead. However, since the melted part of Comparative Example 1 does not have a flat part, the shape is larger than that of the melted part of Example 1, and an electrode that circulates adjacent to the melted part when producing a wound electrode group. Was deformed.

Thus, when a battery is manufactured using a negative electrode having a melting part as in Comparative Example 1, the space around the melting part for suppressing the occurrence of defects such as an internal short circuit in the battery. It is necessary to provide it. This is disadvantageous in implementing high density and high capacity designs that need to eliminate as much extra space in the battery as possible.

On the other hand, in Comparative Example 2 in which resistance welding was performed, it was clear that a melted portion for electrically connecting the electrode plate main body and the negative electrode lead was not formed, and sufficient bonding could not be performed.

(Test Example 2)
[Cycle characteristics]
The lithium ion batteries of Example 1 and Comparative Examples 1 and 2 were each housed in a constant temperature bath at 20 ° C., and the batteries were charged by the following constant current and constant voltage method.

Each battery was charged at a constant current of 1C rate (1C is a current value that can use up the entire battery capacity in 1 hour) until the battery voltage reaches 4.2V. After the battery voltage reached 4.2V, each battery was charged at a constant voltage of 4.2V until the current value reached 0.05C. Next, after resting for 20 minutes, the charged battery was discharged at a constant rate of 1C rate until the battery voltage reached 2.5V. Such charge and discharge was repeated 100 cycles.

The ratio of the total discharge capacity at the 100th cycle to the total discharge capacity at the first cycle was determined as a percentage value. The obtained values are shown in Table 2 as capacity retention rates.

The batteries of Example 1 and Comparative Example 1 were found to have a high capacity retention rate and good cycle characteristics. In particular, the battery of Example 1 exhibited a higher capacity retention rate. In the battery of Comparative Example 1, the distance between the positive electrode and the negative electrode was changed in the region due to the weld part deforming a part of the electrode group, so that the electrode reaction became non-uniform and the capacity retention rate was slightly reduced. The On the other hand, the battery of Comparative Example 2 could not be energized, and the resistance was infinite. It is presumed that when the battery was assembled, the lead peeled off from the negative electrode active material, making it impossible to conduct electricity.

Although the present invention has been described in terms of the presently preferred embodiments, such disclosure should not be construed as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains after reading the above disclosure. Accordingly, the appended claims should be construed to include all variations and modifications without departing from the true spirit and scope of this invention.

The electrode plate of the present invention can be suitably used as an electrode plate for electrochemical elements such as non-aqueous electrolyte secondary batteries. The electrochemical device of the present invention is useful as a power source for portable electronic devices. Examples of portable electronic devices include personal computers, mobile phones, mobile devices, personal digital assistants (PDAs), portable game devices, and video cameras. In addition, the electrochemical element of the present invention is used as a main power source and auxiliary power source for hybrid electric vehicles, electric vehicles, fuel cell vehicles, etc., driving power sources for electric tools, vacuum cleaners, robots, etc., power sources for plug-in HEVs, etc. Use is also expected.

DESCRIPTION OF SYMBOLS 1 Electrode plate main body 1a End surface of electrode plate main body 10 Current collector 11 Active material layer 13 Electrode lead 13a End surface of electrode lead 14 A pair of plates of welding

jig

17, 18 Melting portion 20 First plate 20x First concave portion 21 Second Plate 21x Second concave portion 23 Flat pressing jig 25 Lithium ion battery 40 Electron beam vacuum deposition device

Claims

An electrode plate body comprising a laminate of a strip-shaped current collector containing metal and an active material layer formed on the surface of the current collector and containing an alloy-based active material;
An electrode lead including a metal disposed on a part of the surface of the active material layer, and a melting portion that electrically connects the electrode plate body and the electrode lead at one end of the electrode plate body. And
The melting part is an electrode plate for an electrochemical element having a flat part parallel to the surface of the electrode plate body.
2. The electrode plate for an electrochemical element according to claim 1, wherein the melting part has a first flat part and a second flat part opposite to the first flat part as the flat part.
The ratio t / T between the thickness t of the melted portion in the thickness direction of the electrode plate body and the total thickness T of the electrode plate body and the electrode lead is 1 or more and 1.3 or less. The electrode plate for electrochemical elements according to 2.
The electrode plate for an electrochemical element according to any one of claims 1 to 3, wherein a bonding strength between the electrode lead and the electrode plate main body is 0.5 N / mm or more and 50 N / mm or less.
The electrode plate for an electrochemical element according to any one of claims 1 to 4, wherein the flat portion is formed by compression of the melted portion.
The electrode plate for an electrochemical element according to any one of claims 1 to 5, wherein the molten part contains at least an alloy of the alloy-based active material and a metal component of the electrode lead.
The electrode plate for an electrochemical element according to any one of claims 1 to 6, wherein the active material layer is a deposited film of the alloy-based active material.
The alloy-based active material is at least one selected from the group consisting of silicon, silicon alloys and silicon compounds;
The metal component of the electrode lead is copper or a copper alloy;
The electrode plate for an electrochemical element according to any one of claims 1 to 7, wherein the molten part contains an alloy of silicon and copper.
The electrode plate for an electrochemical element according to claim 8, wherein the alloy of silicon and copper contains Cu 5 Si.
Preparing an electrode plate body including a laminate of a strip-shaped current collector containing a metal and an active material layer formed on a surface of the current collector and containing an alloy-based active material; and
A step B of disposing the electrode lead so that one end of the electrode plate body and one end of the electrode lead containing metal are close to a part of the surface of the active material layer;
By melting a welding region including an end surface of the electrode plate body and an end surface of the electrode lead at one end portion of the electrode plate body and one end portion of the electrode lead that are close to each other, the electrode plate body, the electrode lead, A step C of forming a melted portion to be electrically connected;
A process D for compressing the melted portion in a direction perpendicular to the surface of the electrode plate main body to form a flat portion parallel to the surface of the electrode plate main body. .
In the step C, the electrode plate main body and the electrode lead are arranged so that the welding region is exposed between a pair of plates, and the welding region is melted by performing arc discharge toward the welding region. Item 11. A method for producing an electrode plate for an electrochemical element according to Item 10.
In the step D, the melting portion is compressed from both directions in a direction perpendicular to the surface of the electrode plate body, and the first flat portion and the second flat portion on the opposite side of the first flat portion are used as the flat portion. The manufacturing method of the electrode plate for electrochemical devices of Claim 10 or 11 which forms a part.
The method for producing an electrode plate for an electrochemical element according to any one of claims 10 to 12, wherein in the step D, the melted portion is compressed with a load of 3 N / mm or more and 1000 N / mm or less.
The electrode plate for an electrochemical element according to any one of claims 1 to 9, as a first electrode;
A second electrode having a polarity opposite to that of the first electrode;
An electrochemical device comprising a separator interposed between the first electrode and the second electrode.