JP6252359B2 - Electric storage device and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electricity storage device and a manufacturing technique thereof, for example, a technique effective when applied to a lithium ion battery and a manufacturing technique thereof.

  In Japanese Patent No. 4724841 (Patent Document 1), in a lithium ion battery, after overlapping an internal electrode, a plurality of stacked tabs, and a reinforcing plate, these members are joined by friction stir welding. The technology is described.

  JP 2011-173163 A (Patent Document 2), JP 2006-289409 A (Patent Document 3), JP 2007-880 A (Patent Document 4), JP 2000-71090 A (Patent Document 5). ), Japanese Patent No. 3289650 (Patent Document 6) and the like describe a technique related to friction stir welding.

Japanese Patent No. 4724841 JP 2011-173163 A JP 2006-289409 A JP 2007-880 A JP 2000-71090 A Japanese Patent No. 3289650

  With the development of portable electronic devices, small secondary batteries that can be repeatedly charged are used as power supply sources for these portable electronic devices. Of these, lithium ion batteries are attracting attention because of their high energy density, long cycle life, low self-discharge characteristics, and high operating voltage. Lithium ion batteries have the advantages described above, and are therefore widely used in portable electronic devices such as digital cameras, notebook personal computers, and mobile phones.

  Furthermore, in recent years, research and development of large-sized lithium ion batteries capable of realizing high capacity, high output, and high energy density as batteries for electric vehicles and power storage batteries have been promoted. In particular, in the automobile industry, in order to cope with environmental problems, development of an electric vehicle that uses a motor as a power source and a hybrid vehicle that uses both an engine (internal combustion engine) and a motor as a power source are in progress. . Lithium ion batteries have attracted attention as power sources for such electric vehicles and hybrid vehicles. Similarly, importance in applications such as photovoltaic power generation and power storage for effective use of nighttime power is increasing.

  For example, a large-sized lithium ion battery for power storage includes a positive electrode plate coated with a positive electrode active material, a negative electrode plate coated with a negative electrode active material, and a separator that prevents contact between the positive electrode plate and the negative electrode plate. An electrode laminate is provided. And in this lithium ion battery, while this electrode laminated body is inserted in an exterior can (battery can), electrolyte solution is inject | poured in the exterior can.

  Here, the electrode plates constituting the positive electrode plate and the negative electrode plate are integrally formed with strip-shaped tabs (current collecting tabs), and a plurality of these tabs are stacked to form a tab laminate. . In the lithium ion battery, the tab laminate is connected to the external output terminal, thereby electrically connecting the electrode laminate disposed inside the outer can and the external output terminal fixed to the outer can. The structure to be adopted is adopted. At this time, for example, a welding technique such as arc welding has been used for the connection between the tab laminate and the external connection terminal, but in recent years, the use of a technique called friction stir welding has been studied.

  In this friction stir welding, a cylindrical tool (tool) having a protruding portion at the tip is rotated, and the protruding portion is pressed against the member with a strong force, thereby penetrating the member (base material) to which the protruding portion is bonded. As a result, in friction stir welding, frictional heat is generated to soften the member, and the periphery of the joint is plastically flowed and kneaded by the rotational force of the tool, so that the plurality of members are integrated and joined. Such friction stir welding has an advantage that the thermal influence of the joint can be suppressed because the joint can be formed without melting the member. The friction stir welding is called FSW (Friction Stir Welding) in English.

  However, in the friction stir welding, since the protruding portion of the tool is inserted into the member, the softened member is pushed out by inserting the protruding portion, and the softened member is generated as a burr near the bonded portion. Conceivable. For example, when attention is paid to a lithium ion battery, burrs may be generated in the vicinity of the joint between the tab laminate and the external output terminal.

  Therefore, when forming the joint between the tab laminate and the external output terminal by friction stir welding, the burr formed in the vicinity of the joint is peeled off, and the electrode laminate disposed inside the outer can The potential for the entry of foreign metal into the metal increases. In particular, in a normal lithium ion battery, since the positive electrode plate, the negative electrode plate, and the separator are composed of separate parts, for example, a gap exists between the positive electrode plate and the separator, and burrs are peeled off in this gap. It becomes easy for the metal foreign matter generated by the penetration. In this way, when a metal foreign object enters the inside of the electrode laminate, the metal foreign object penetrates the separator, and the positive electrode and the negative electrode are short-circuited by the metal foreign object, for example, a metal foreign object that has entered the gap between the positive electrode and the separator. When adhering to the positive electrode, a phenomenon occurs in which the adhered foreign metal is dissolved in the electrolytic solution and then deposited on the negative electrode. And when the metal which grew by precipitation from a negative electrode reaches a positive electrode, there exists a possibility that a positive electrode and a negative electrode may short-circuit.

  Therefore, in the manufacturing process of a lithium ion battery, when friction stir welding is used for joining the tab laminate and the external output terminal, there is room for improvement from the viewpoint of improving the reliability of the lithium ion battery. .

  Therefore, an object of the present invention is to provide a technique capable of improving the reliability of an electricity storage device having a structure for connecting a tab laminate and an external output terminal, as represented by, for example, a lithium ion battery. It is in.

  Other problems and novel features will become apparent from the description of the specification and the accompanying drawings.

  An electricity storage device according to an embodiment includes: (a) a cover plate having a first surface and a second surface located on the opposite side of the first surface, the cover plate having a groove on the first surface; b) a tab laminated body in contact with the second surface of the cover plate, the tab laminated body formed by stacking a plurality of tabs integrated with the electrode plate, and (c) an external output terminal in contact with the tab laminated body. . Further, the electricity storage device in one embodiment is (d) a joint formed between the cover plate, the tab laminate, and the external output terminal, the joint contacting the groove, and (e) the joint integrated with the joint. A burr joint portion formed so as to rise from the joint portion in the groove. At this time, the height of the burr joint is smaller than the depth of the groove, and the burr joint is in contact with the side surface of the groove.

  In one embodiment, a method of manufacturing an electricity storage device includes: (a) a cover plate having a first surface and a second surface located on the opposite side of the first surface, wherein a groove is provided on the first surface. A step of preparing a cover plate, (b) a step of preparing an external output terminal, and (c) a step of stacking a plurality of tabs integrated with the electrode plate to form a tab laminate. And (d) a step of sandwiching the tab laminate between the second surface of the cover plate and the external output terminal, and (e) a step of friction stir welding the cover plate, the tab laminate and the external output terminal. Here, the step (e) includes (e1) a step of preparing a tool having a pin portion, (e2) while rotating the pin portion, penetrating the cover plate and the tab laminate from the bottom surface of the groove of the cover plate, Insert the pin part to reach the external output terminal. As a result, a joint between the cover plate, the tab laminate, and the external output terminal, which is in contact with the groove, and a burr joint integrated with the joint, the burr joint rising from the joint in the groove And forming a part. At this time, the height of the burr joint is smaller than the depth of the groove, and the burr joint contacts the side surface of the groove.

  According to one embodiment, the reliability of the electricity storage device can be improved.

It is a perspective view which shows schematic structure of a square-shaped lithium ion battery. It is a perspective view which shows the typical structure of an electrode laminated body. In related technology, it is a figure which shows typically the process of joining a cover plate, a tab laminated body, and an external output terminal by friction stir welding. In related art, it is a schematic diagram which shows the structure after joining a cover plate, a tab laminated body, and an external output terminal by friction stir welding. It is a figure explaining the detail of friction stir welding in related technology. In embodiment, it is a figure which shows typically the process of joining a cover plate, a tab laminated body, and an external output terminal by friction stir welding. In embodiment, it is a schematic diagram which shows the structure after joining a cover plate, a tab laminated body, and an external output terminal by friction stir welding. It is a figure explaining the detail of the friction stir welding in embodiment. It is a figure which shows the state inserted by the friction stir welding so that the pin part of a tool might penetrate the cover plate and tab laminated body from the bottom face of the groove | channel currently formed in the cover plate, and might reach an external output terminal. It is the graph which summarized the experimental result which this inventor performed, Comprising: It is a graph which shows the relationship between DC / DS and the depth of a groove | channel. It is the table | surface created based on the graph shown in FIG. It is sectional drawing which shows the joining structure corresponding to Comparative Examples 1-4. It is sectional drawing which shows the joining structure corresponding to Comparative Examples 5-9. It is sectional drawing which shows the joining structure corresponding to Comparative Examples 10-13. It is sectional drawing which shows the joining structure corresponding to Examples 1-14. It is a perspective view which shows the joining structure in the modification 1 of embodiment. It is a perspective view which shows the joining structure in the modification 2 of embodiment. It is a perspective view which shows the joining structure in the modification 3 of embodiment.

  In the following embodiments, when it is necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant to each other. There are some or all of the modifications, details, supplementary explanations, and the like.

  Further, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), especially when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and may be more or less than the specific number.

  Further, in the following embodiments, the constituent elements (including element steps and the like) are not necessarily indispensable unless otherwise specified and apparently essential in principle. Needless to say.

  Similarly, in the following embodiments, when referring to the shape, positional relationship, etc., of components, etc., unless otherwise specified, and in principle, it is considered that this is not clearly the case, it is substantially the same. Including those that are approximate or similar to the shape. The same applies to the above numerical values and ranges.

  In all the drawings for explaining the embodiments, the same members are denoted by the same reference symbols in principle, and the repeated explanation thereof is omitted. In order to make the drawings easy to understand, even a plan view may be hatched.

(Embodiment)
<Configuration of lithium ion battery>
In this embodiment, a lithium ion battery will be described as an example of an electricity storage device. FIG. 1 is a perspective view showing a schematic configuration of a rectangular lithium ion battery LIB. As shown in FIG. 1, for example, an electrode laminate LE including a positive electrode, a separator, and a negative electrode is formed in a rectangular outer can CS having a bottom. Specifically, the electrode laminate LE is laminated so that a separator is sandwiched between a positive electrode and a negative electrode. A tab TB is integrally formed on each of the positive electrode and the negative electrode. For example, as shown in FIG. 1, the tab TB formed integrally with the positive electrode is electrically connected to the external output terminal EOT provided on the upper surface of the outer can CS and formed integrally with the negative electrode. The tab TB is also electrically connected to another external output terminal EOT provided on the upper surface of the outer can CS.

  Inside the outer can CS, an electrolytic solution is injected from a liquid injection plug PLG provided on the upper surface of the outer can CS. Thereby, the electrode laminated body LE arrange | positioned inside the exterior can CS is satisfy | filled with electrolyte solution. A safety valve SV is provided on the upper surface of the outer can CS. The safety valve SV has a function of suppressing an increase in the internal pressure of the outer can CS based on a gas generated by, for example, a short circuit between the positive electrode and the negative electrode due to a metal foreign object, and the internal pressure of the outer can CS exceeds a reference value. In the event that it opens, the gas filled in the outer can CS is released. Thereby, destruction of the armored can CS due to an increase in internal pressure can be prevented.

  The positive electrode is formed by applying a coating liquid containing a positive electrode active material and a binder (binder) to a positive electrode plate (positive electrode current collector), drying it, and then applying pressure. A plurality of rectangular tabs (positive electrode current collecting tabs) TB are integrally formed on the positive electrode, and the plurality of tabs TB are connected to one external output terminal EOT. Therefore, the positive electrode is electrically connected to one external output terminal EOT via a plurality of tabs TB. The plurality of tabs TB are provided in order to reduce the resistance of the positive electrode and expedite current extraction.

  The positive electrode active material constituting the positive electrode is formed of a lithium-containing transition metal oxide capable of inserting and removing lithium ions. Specifically, the above-described materials represented by lithium cobaltate, lithium nickelate, lithium manganate and the like can be used as the positive electrode active material, for example. As the binder, for example, polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene, or the like can be used. Furthermore, for the positive electrode plate, for example, a metal foil or a net-like metal made of a conductive metal such as aluminum is used.

  The negative electrode is formed by applying a coating liquid containing a negative electrode active material and a binder (binder) to a negative electrode plate (negative electrode current collector), drying it, and then applying pressure. A plurality of rectangular tabs (negative electrode current collecting tabs) TB are formed integrally with the negative electrode, and the plurality of tabs TB are connected to the other external output terminal EOT. Therefore, the negative electrode is electrically connected to the other external output terminal EOT via the plurality of tabs TB. The plurality of tabs TB are provided in order to reduce the resistance of the negative electrode and to quickly extract current.

  The negative electrode active material constituting the negative electrode is made of a material typified by a carbon material that can insert and desorb lithium ions. As the binder, for example, polyvinylidene fluoride, polytetrafluoroethylene, or the like can be used. Furthermore, for the negative electrode plate, for example, a metal foil made of a conductive metal such as copper or a mesh metal is used.

  The separator functions as a spacer that allows lithium ions to pass through while preventing electrical contact between the positive electrode and the negative electrode. In recent years, a high-strength and thin microporous membrane has been used as the separator. This microporous membrane also has a function of preventing abnormal current due to a short circuit of the battery, rapid increase in internal pressure and temperature, and ignition. In other words, the current separator has a function as a thermal fuse for preventing a short circuit and overcharge in addition to a function of preventing electrical contact between the positive electrode and the negative electrode and allowing lithium ions to pass therethrough. Become. The safety of the lithium ion battery can be maintained by the shutdown function of the microporous membrane. For example, when a lithium ion battery causes an external short circuit for some reason, a large current flows instantaneously, and the temperature may rise abnormally due to Joule heat. At this time, if a microporous membrane is used as a separator, the microporous membrane blocks pores (microporous) in the vicinity of the melting point of the membrane material, thus preventing lithium ion permeation between the positive electrode and the negative electrode. can do. In other words, by using a microporous membrane as a separator, current can be interrupted when an external short circuit occurs, and the temperature rise inside the lithium ion battery can be stopped. As a separator comprised from this microporous membrane, it is comprised from the combination of polyethylene (PE), polypropylene (PP), or these materials, for example.

  As the electrolyte, a non-aqueous electrolyte is used. A lithium ion battery is a battery that performs charging / discharging by using insertion / extraction of lithium ions in an active material, and lithium ions move in an electrolytic solution. Lithium is a strong reducing agent and reacts violently with water to generate hydrogen gas. Therefore, in a lithium ion battery in which lithium ions move in the electrolytic solution, an aqueous solution cannot be used as the electrolytic solution as in a conventional battery. For this reason, in the lithium ion battery, a nonaqueous electrolytic solution is used as the electrolytic solution.

Specifically, as _the electrolyte of the nonaqueous _{electrolyte, LiPF 6, LiClO 4, LiAsF} 6, LiBF 4, LiB (C 6 H 5) 4, CH 3 SO 3 Li, CF 3 SO 3 Li , etc., and mixtures thereof Can be used. Examples of the organic solvent include ethylene carbonate, dimethyl carbonate, propylene carbonate, diethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-methyl- 1,3 dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, etc., or a mixture thereof can be used.

<Mechanism of charge / discharge>
The lithium ion battery is configured as described above, and the charging / discharging mechanism will be described below. First, the charging mechanism will be described. For example, when charging a lithium ion battery, a charger is connected between one external output terminal EOT connected to the positive electrode and the other external output terminal EOT connected to the negative electrode. In this case, in the lithium ion battery, lithium ions inserted in the positive electrode active material are desorbed and released into the electrolytic solution. At this time, the lithium ions are desorbed from the positive electrode active material, whereby electrons flow from the positive electrode to the charger. Then, the lithium ions released into the electrolytic solution move in the electrolytic solution, pass through a separator made of a microporous film, and reach the negative electrode. The lithium ions that have reached the negative electrode are inserted into the negative electrode active material constituting the negative electrode. At this time, when lithium ions are inserted into the negative electrode active material, electrons flow into the negative electrode. In this way, charging is completed as electrons move from the positive electrode to the negative electrode via the charger.

  Next, the discharge mechanism will be described. For example, an external load is connected between one external output terminal EOT connected to the positive electrode and the other external output terminal EOT connected to the negative electrode. Then, lithium ions inserted into the negative electrode active material are desorbed and released into the electrolytic solution. At this time, electrons are emitted from the negative electrode. Then, the lithium ions released into the electrolytic solution move in the electrolytic solution, pass through a separator made of a microporous film, and reach the positive electrode. The lithium ions reaching the positive electrode are inserted into the positive electrode active material constituting the positive electrode. At this time, when lithium ions are inserted into the positive electrode active material, electrons flow into the positive electrode. In this way, discharge is performed by the movement of electrons from the negative electrode to the positive electrode. In other words, a current can flow from the positive electrode to the negative electrode to drive the load. As described above, in a lithium ion battery, charging / discharging can be performed by inserting / extracting lithium ions between the positive electrode active material and the negative electrode active material.

<Configuration of electrode laminate>
FIG. 2 is a perspective view showing a schematic configuration of the electrode laminate LE. As shown in FIG. 2, the electrode laminate LE has a configuration in which a positive electrode, a negative electrode, and a separator are stacked. A plurality of tabs TB formed integrally with the positive electrode are formed on the positive electrode, and the plurality of tabs TB are bundled and connected to the external output terminal EOT. Similarly, a plurality of tabs TB formed integrally with the negative electrode are also formed on the negative electrode, and the plurality of tabs TB are bundled and connected to another external output terminal EOT.

  Here, in the present embodiment, friction stir welding is used for connection between the plurality of tabs TB and the external output terminals EOT. Since this friction stir welding can form a joint without melting the member, it has an advantage of suppressing the thermal effect of the joint, while the friction stir welding is connected to a plurality of tabs TB in the lithium ion battery and the outside. When used for joining to the output terminal EOT, there is room for improvement specific to the electricity storage device. Below, first, the room for improvement accompanying friction stir welding will be described in the related art.

<Room for improvement in related technologies>
FIG. 3 is a diagram schematically showing a process of joining the cover plate CPLT, the tab laminate TL, and the external output terminal EOT by friction stir welding in the related art. As shown in FIG. 3, first, a flat cover plate CPLT and an external output terminal EOT are prepared. Moreover, the tab laminated body TL is formed by overlapping a plurality of tabs. Then, the tab laminate TL is sandwiched between the cover plate CPLT and the external output terminal EOT, and in this state, the cover plate CPLT, the tab laminate TL, and the external output terminal EOT are joined by friction stir welding. As a result, the joint CU is formed across the cover plate CPLT, the tab laminate TL, and the external output terminal EOT.

  Next, details of the friction stir welding used in the related art will be described. FIG. 4 is a schematic diagram showing a configuration after the cover plate CPLT, the tab laminate TL, and the external output terminal EOT are joined by friction stir welding in the related art. As shown in FIG. 4, it can be seen that a circular joint CU is formed on the surface of the cover plate CPLT.

  Here, the details of the friction stir welding in the related art will be described below with reference to a cross-sectional view taken along line AA of FIG. FIG. 5 is a diagram illustrating details of friction stir welding in the related art. As shown in FIG. 5, the tab laminate TL is sandwiched between the cover plate CPLT and the external output terminal EOT. Then, a tool (tool) TOL is arranged above the cover plate CPLT. A projecting pin portion PU is formed at the tip of the tool TOL.

  Next, the pin portion PU is pressed against the cover plate CPLT with a strong force while rotating the pin portion PU, thereby penetrating the member to which the pin portion PU is joined. Specifically, while rotating the pin portion PU, the pin portion PU is inserted so as to penetrate the cover plate CPLT and the tab laminate TL from the upper surface of the cover plate CPLT and reach the external output terminal EOT. As a result, in the related technology, frictional heat is generated to soften the member, and the periphery of the joint CU is plastically flowed and mixed by the rotational force of the tool TOL, so that the cover plate CPLT, the tab laminate TL, and the external A joint CU is formed integrally with the output terminal EOT.

  However, in the related art, as shown in FIG. 5, since the pin portion PU of the tool TOL is inserted into the member, the softened member is pushed out by inserting the pin portion PU, and this softened member is joined to the joint portion. It is conceivable that a burr BR is generated in the vicinity of. Specifically, as shown in FIG. 5, the burr BR may protrude from the surface of the cover plate CPLT.

  Since the protruding burr BR is very easy to peel off, the burr BR formed on the upper surface of the cover plate CPLT is peeled off to become a metal foreign object, and the metal foreign object is formed on the electrode laminate disposed inside the outer can. There is a possibility of intrusion. In particular, in a lithium ion battery, since the positive electrode, the negative electrode, and the separator are composed of separate parts, for example, a gap exists between the positive electrode and the separator, and the burr BR is peeled off in this gap. It becomes easy for metal foreign objects to enter. In this way, when a metal foreign object enters the inside of the electrode laminate, the metal foreign object penetrates the separator, and the positive electrode and the negative electrode are short-circuited by the metal foreign object, for example, a metal foreign object that has entered the gap between the positive electrode and the separator. When adhering to the positive electrode, a phenomenon occurs in which the adhered foreign metal is dissolved in the electrolytic solution and then deposited on the negative electrode. And when the metal which grew by precipitation from a negative electrode reaches a positive electrode, there exists a possibility that a positive electrode and a negative electrode may short-circuit.

  Therefore, in the related art, when friction stir welding is used for joining the cover plate CPLT, the tab laminate TL, and the external output terminal, the reliability of the lithium ion battery may be lowered. That is, it can be seen that there is room for improvement in the related art from the viewpoint of improving the reliability of the lithium ion battery. Therefore, in this embodiment, even if the friction stir welding is used for joining the cover plate CPLT, the tab laminate TL, and the external output terminal, a device for suppressing a decrease in the reliability of the lithium ion battery is applied. Yes. Below, the technical idea in this Embodiment which gave this device is demonstrated.

<Method for Manufacturing Lithium Ion Battery in Embodiment>
FIG. 6 is a diagram schematically showing a process of joining the cover plate CPLT, the tab laminate TL, and the external output terminal EOT by friction stir welding in the present embodiment. As shown in FIG. 6, first, for example, a cover plate CPLT in which a circular groove DIT is formed and an external output terminal EOT are prepared. Moreover, the tab laminated body TL is formed by overlapping a plurality of tabs. Then, the tab laminate TL is sandwiched between the cover plate CPLT in which the groove DIT is formed and the external output terminal EOT. In this state, the cover plate CPLT, the tab laminate TL, and the external output terminal EOT are joined by friction stir welding. Join. As a result, the joint CU is formed across the cover plate CPLT, the tab laminate TL, and the external output terminal EOT. In particular, in the present embodiment, the joint CU is formed at the bottom of the groove DIT.

  Next, the details of the friction stir welding used in the present embodiment will be described. FIG. 7 is a schematic diagram showing a configuration after the cover plate CPLT, the tab laminate TL, and the external output terminal EOT are joined by friction stir welding in the present embodiment. As shown in FIG. 7, a groove DIT is formed in the cover plate CPLT, and, for example, a circular joint CU is formed in the groove DIT.

  Here, the details of the friction stir welding in the present embodiment will be described below with reference to a cross-sectional view taken along line AA in FIG.

  FIG. 8 is a diagram for explaining the details of the friction stir welding in the present embodiment. In FIG. 8, first, a cover plate CPLT having a front surface (first surface) and a back surface (second surface) located on the opposite side of the front surface, and having a groove DIT on the front surface, is prepared. . The cover plate CPLT has a function of pressing the tab laminate TL. An external output terminal EOT is also prepared. Furthermore, a tab laminate TL is formed by stacking a plurality of tabs integrated with the electrode plate.

  Next, as shown in FIG. 8, the tab laminate TL is sandwiched between the back surface of the cover plate CPLT and the external output terminal EOT, and then the cover plate CPLT, the tab laminate TL, and the external output terminal EOT are subjected to friction stir welding. Specifically, a tool (tool) TOL is disposed above the surface of the cover plate CPLT. A projecting pin portion PU is formed at the tip of the tool TOL.

  Subsequently, the pin portion PU is pressed against the cover plate CPLT with a strong force while rotating the pin portion PU, thereby penetrating the member to which the pin portion PU is joined. Specifically, while rotating the pin portion PU, the pin portion extends from the bottom surface of the groove DIT formed in the cover plate CPLT through the cover plate CPLT and the tab laminate TL to reach the external output terminal EOT. Insert the PU. Accordingly, in the present embodiment, frictional heat is generated to soften the member, and the periphery of the joint CU is plastically flowed and mixed by the rotational force of the tool TOL, so that the cover plate CPLT and the tab laminate TL are mixed. And the external output terminal EOT are integrally formed with the joint CU.

  Here, in the present embodiment, as shown in FIG. 8, since the pin portion PU of the tool TOL is inserted into the member, the concave portion CAV is formed in the joint portion CU by inserting the pin portion PU, and the concave portion CAV Is formed, the softened member is pushed out from the recess CAV. For this reason, a burr joint BCU integrated with the joint CU is formed, and the burr joint BCU is formed so as to rise from the joint CU in the groove DIT. At this time, in this embodiment, since the groove DIT is formed in the cover plate CPLT, the burr joint BCU is formed in the groove DIT. Specifically, in the present embodiment, the height of the burr joint BCU is formed smaller than the depth of the groove DIT, and the burr joint BCU is formed so as to be in contact with the side surface of the groove DIT.

  As described above, in the friction stir welding in the present embodiment, the joint CU is integrally formed across the cover plate CPLT, the tab laminate TL, and the external output terminal EOT, and is integrated with the joint CU. The burr joint BCU thus formed is formed inside the groove DIT.

<Features in Embodiment>
Then, the feature point in the manufacturing method of the lithium ion battery in this Embodiment mentioned above is demonstrated. As shown in FIG. 8, the feature point in the present embodiment is that a groove DIT is provided on the surface of the cover plate CPLT. In this case, as shown in FIG. 8, the insertion of the pin portion PU in the friction stir welding forms a concave portion CAV in the joint portion CU, and the softened member is pushed out from the concave portion CAV. According to this, the groove DIT is formed in the cover plate CPLT. As a result, since this groove DIT functions as a protective wall, the scattering of metal scraps is suppressed, and therefore, according to the present embodiment, the generation of metal foreign matter is suppressed.

  Further, according to the present embodiment, since the groove DIT is formed in the cover plate CPLT, the member pushed out from the recess CAV forms the burr joint BCU that rises integrally from the joint CU. The burr joint BCU does not protrude from the inside of the groove DIT. That is, according to the present embodiment, since the burr joint BCU does not protrude from the surface of the cover plate CPLT, the potential that the burr joint BCU peels off and becomes a metal foreign object can be reduced. In particular, in the present embodiment, the burr joint BCU formed inside the groove DIT is in contact with the side surface of the groove DIT. In other words, the burr joint BCU formed in the present embodiment is not only in close contact with the bottom surface of the groove DIT but also in close contact with the side surface of the groove DIT, so that the adhesion strength between the burr joint BCU and the cover plate CPLT is high. growing. This means that the burr joint BCU peels off from the cover plate CPLT and does not easily become a metal foreign object, thereby suppressing the generation of metal foreign objects due to the peeling of the burr joint BCU.

  For example, as shown in FIG. 5, the burr BR formed by the related technique has a small contact area with the cover plate CPLT and protrudes from the surface of the cover plate CPLT. It is easy to receive and is easy to peel from the cover plate CPLT.

  On the other hand, in the present embodiment, (1) the groove DIT functions as a protective wall that suppresses the scattering of metal foreign matters, because of the feature that the groove DIT is provided on the surface of the cover plate CPLT. The portion BCU fits in the groove DIT and does not protrude from the surface of the cover plate CPLT. (3) As a result of the burr joint BCU not only contacting the bottom surface of the groove DIT but also the side surface of the groove DIT, the burr joint BCU and the cover The point where the contact area with the plate CPLT increases is realized. Thereby, according to this Embodiment, even if it is a case where friction stir welding is used by generation | occurrence | production of the synergistic effect of (1)-(3) mentioned above, generation | occurrence | production of a metal foreign material can be suppressed effectively. . From this, in particular, in the lithium ion battery, the occurrence of metal foreign matter tends to cause a short circuit between the positive electrode and the negative electrode, but according to the friction stir welding in the present embodiment, the metal foreign matter that causes the short circuit in the lithium ion battery. Since generation | occurrence | production can be suppressed effectively, according to this Embodiment, the reliability of a lithium ion battery can be improved. That is, according to the present embodiment, it is possible to provide a highly reliable lithium ion battery while ensuring the advantage of friction stir welding.

<Joint structure in the embodiment>
Next, a junction structure manufactured by the method for manufacturing a lithium ion battery in the present embodiment will be described. That is, in the present embodiment, as shown in FIG. 8, a joint structure of the cover plate CPLT, the tab laminate TL, and the external output terminal EOT is formed by friction stir welding. Below, this junction structure is explained.

  As shown in FIG. 8, the lithium ion battery according to the present embodiment is a cover plate CPLT having a front surface (first surface) and a back surface (second surface) located on the opposite side of the front surface. A cover plate CPLT provided with a DIT, a tab laminate TL in contact with the back surface of the cover plate CPLT, a tab laminate TL formed by stacking a plurality of tabs integrated with an electrode plate, and a tab laminate TL And an external output terminal EOT in contact with.

  Furthermore, as shown in FIG. 8, the lithium ion battery according to the present embodiment is a joint CU formed between cover plate CPLT, tab laminate TL, and external output terminal EOT, and is a joint that contacts groove DIT. A CU and a burr joint BCU integrated with the joint CU, and a burr joint BCU formed so as to rise from the joint CU in the groove DIT. At this time, the height of the burr joint BCU is smaller than the depth of the groove DIT. Therefore, the burr joint BCU does not protrude from the surface of the cover plate CPLT, and the burr joint BCU does not protrude from the groove DIT. It touches the side.

  And as shown in FIG. 8, the recessed part CAV is formed toward the inside of the junction part CU from the bottom face of the groove | channel DIT. This is because the pin portion PU of the tool TOL penetrates the cover plate CPLT and the tab laminate TL from the bottom surface of the groove DIT formed in the cover plate CPLT and reaches the external output terminal EOT by friction stir welding. It is formed as an inserted trace.

  Although not specifically stated in the present embodiment, the joint structure in the present embodiment may be applied to a connection structure that connects the tab formed integrally with the positive electrode plate and the external output terminal EOT. In addition, it can be applied to a connection structure for connecting a tab formed integrally with the negative electrode plate and the external output terminal EOT.

  Further, the cover plate CPLT, the tab laminate TL, and the external output terminal EOT can be made of different materials. From the viewpoint of ease of application of friction stir welding, for example, the cover plate CPLT, the tab, The stacked body TL and the external output terminal EOT can also be configured from the same member. In this case, for example, in the bonding structure with respect to the positive electrode, the same member is a member whose main component is aluminum, and in the bonding structure with respect to the negative electrode, the same member is a member whose main component is copper.

  Here, in this specification, the “main component” means a material component that is contained most among the constituent materials constituting the member. For example, the “member mainly composed of aluminum” This means that the material of the member contains the most aluminum (Al). Similarly, the “member mainly composed of copper” means that the material of the member contains the most copper (Cu). The intention to use the term “main component” in this specification is to express that, for example, the member is basically composed of aluminum or copper, but does not exclude the case where other impurities are included. It is used for.

  Although the technical idea in the present embodiment has been described above, the present inventor has described the feature of the present embodiment in that the friction stir welding is performed in a state where the groove DIT is provided on the surface of the cover plate CPLT. An experiment was conducted to further investigate. As a result, the present inventor has acquired the following knowledge, and this knowledge will be described in the form of examples.

<Example>
FIG. 9 shows that the pin portion PU of the tool TOL passes through the cover plate CPLT and the tab laminate TL from the bottom surface of the groove DIT formed in the cover plate CPLT and reaches the external output terminal EOT by friction stir welding. It is a figure which shows the state inserted in.

  In FIG. 9, the diameter DC of the groove DIT and the shoulder diameter DS of the tool TOL are illustrated. In particular, the shoulder diameter DS of the tool TOL is generally a portion other than the pin portion PU in the portion of the tool TOL. Therefore, it is defined as a portion inserted below the bottom surface of the groove DIT formed in the cover plate CPLT. FIG. 9 shows a case where the diameter DC of the groove DIT is larger than the shoulder diameter DS of the tool TOL.

  Here, the inventor pays attention to the relationship between the diameter D of the groove DIT / the shoulder diameter DS (= DC / DS) of the tool TOL and the depth of the groove DIT, and when these parameters are changed, An example of conditions for realizing the feature points in the embodiment was studied. That is, the present inventor conducted an experiment on a condition example in which the feature point that the height of the burr joint BCU is smaller than the depth of the groove DIT and the burr joint BCU is in contact with the side surface of the groove DIT is realized. This experiment result will be described.

  FIG. 10 is a graph summarizing the results of experiments conducted by the present inventor, showing the relationship between DC / DS and groove depth. In FIG. 10, the horizontal axis indicates DC / DS, and the vertical axis indicates the depth (mm) of the groove DIT. In FIG. 10, ◯ indicates an example of a condition for realizing a feature point in the present embodiment, and x indicates an example of a condition for not realizing a feature point in the present embodiment. In other words, ◯ indicates “OK” in which burr does not occur as a burr evaluation, and × indicates “NG” in which burr occurs as a burr evaluation.

  In FIG. 10, the area indicated by the arrow A indicates an area where the diameter DC of the groove DIT is smaller than the shoulder diameter DS of the tool TOL. In this area, the groove DIT is crushed when the tool TOL is pushed in. It is an area. For this reason, the area indicated by the arrow A is an area where it is difficult to realize the feature points in the present embodiment.

  Subsequently, a region indicated by an arrow B indicates a region where the diameter of the groove DIT is too larger than the shoulder diameter DS of the tool TOL, and the burr does not adhere to the side surface of the groove DIT. This is an area where it is difficult to realize feature points in the form.

  Further, a region indicated by an arrow C indicates a region where the depth of the groove DIT is shallow and a burr protrudes from the groove DIT. This region is a feature point in the present embodiment because the burr protrudes from the groove DIT. This is an area where it is difficult to realize.

  On the other hand, as shown in FIG. 10, when the value of DC / DS and the value of the depth of the groove DIT are the example of the condition indicated by ◯ in FIG. 10, the feature point in the present embodiment is realized. Is done. Therefore, depending on the value of DC / DS and the value of the depth of the groove DIT, even if the groove DIT is provided on the surface of the cover plate CPLT, the feature point in the present embodiment is not realized, and the present embodiment It can be seen that the DC / DS value and the depth value of the trench DIT need to be set to appropriate values in order to realize the feature point in the form.

FIG. 11 is a table created based on the graph shown in FIG. 10, and examples of conditions for realizing the feature points in the present embodiment are described as Examples 1 to 14, while in the present embodiment. Examples of conditions in which the feature points are not realized are described as Comparative Examples 1 to 13. Specifically, FIG. 11 shows the shape parameters (DC / DS value, shoulder diameter DS value, groove DIT diameter DC value, groove diameter, when the tool indentation volume V is kept constant at 88 (mm ³ ). DIT depth value) and burr evaluation are shown.

Since the generation of burrs depends on the tool indentation volume V, in FIG. 11, for example, when the tool indentation volume V is kept constant at 88 (mm ³ ), the shape parameter shown in FIG. Is evaluated. That is, if the tool indentation volume V is the same, the generation of burrs basically depends on the shape parameters, and other conditions (for example, the material (positive electrode and negative electrode), the number of stacked tabs, the number of rotations of the tool and the indentation speed Etc.), these conditions are not limited in FIG. That is, the burr evaluation shown in FIG. 11 can be applied regardless of the material (positive electrode or negative electrode), the number of stacked tabs, the number of rotations of the tool, the pushing speed, and the like.

  Looking at the burr evaluation column in the table shown in FIG. 11, it is understood that at least the DC / DS value needs to be within an appropriate range in order to realize the feature point in the present embodiment. . Specifically, in order to realize the feature point in the present embodiment, when the diameter DC of the groove DIT / the shoulder diameter DS = A, it is necessary that 1.05 ≦ A ≦ 1.2.

  As shown in FIG. 11, even if this condition example is satisfied, there is a condition example in which the burr evaluation is “x” depending on the depth of the groove DIT, so that the condition of 1.05 ≦ A ≦ 1.2 This is not a necessary and sufficient condition for realizing the feature point in the present embodiment, but it is understood that it is a necessary condition that must be satisfied at least in order to realize the feature point in the present embodiment.

  Next, the presence / absence of burrs will be described with reference to schematic cross-sectional views of joint structures corresponding to Comparative Examples 1 to 13 and Examples 1 to 14 shown in FIG.

  FIG. 12 is a cross-sectional view illustrating a bonding structure corresponding to Comparative Examples 1 to 4. In FIG. 12, a junction structure corresponding to DC / DS = 1 is shown. As shown in FIG. 12, it can be seen that the end of the groove DIT is crushed and a burr BR protruding from the surface of the cover plate CPLT is formed. As a result, it can be seen that the burr BR is not housed in the groove DIT, and the feature point in the present embodiment is not realized. In the joining structure shown in FIG. 12, the burrs BR are formed so as to protrude from the surface of the cover plate CPLT, and the burrs BR are easily peeled off. It can be said that it is a structure.

  Next, FIG. 13 is a cross-sectional view showing a joint structure corresponding to Comparative Examples 5 to 9. As shown in FIG. 13, the height HB of the burr BR is larger than the depth LC of the groove DIT, and it can be seen that the burr BR protrudes from the surface of the cover plate CPLT. Also in the joining structure shown in FIG. 13, it can be seen that the burrs BR are not housed in the trench DIT, and the feature points in the present embodiment are not realized. Also in the joining structure shown in FIG. 13, the burr BR is formed so as to protrude from the surface of the cover plate CPLT. Since this burr BR is easily peeled off, the burr BR is peeled off and the metal foreign matter is likely to be generated. It can be said that it is a structure.

  Then, FIG. 14 is sectional drawing which shows the joining structure corresponding to Comparative Examples 10-13. As shown in FIG. 14, since the height of the burr BR is smaller than the depth of the groove DIT, the burr BR does not protrude from the surface of the cover plate CPLT, but the diameter DIT of the groove DIT is too large. Is not in contact with the side surface of the groove DIT. From this, it can be seen that the feature points in the present embodiment are not realized in the joint structure shown in FIG. In the joining structure shown in FIG. 14, since the burr BR formed on the bottom surface of the groove DIT is not in contact with the side surface of the groove DIT, the contact area between the burr BR and the groove DIT cannot be increased. , Burr BR is easy to peel off. From this, it can be said that the joining structure shown in FIG. 14 is also a joining structure in which the burr BR is peeled off and metal foreign matter is easily generated.

  Finally, FIG. 15 is a cross-sectional view showing a joint structure corresponding to Examples 1-14. As shown in FIG. 15, in the joint structure corresponding to Examples 1 to 14, the burr joint BCU fits in the groove DIT and does not protrude from the surface of the cover plate CPLT, and the burr joint BCU is the bottom surface of the groove DIT. In addition, it can be seen that, as a result of the close contact with the side surface of the groove DIT, the contact area between the burr joint BCU and the cover plate CPLT is increased.

  Thereby, according to the joining structure shown in FIG. 15 corresponding to Examples 1-14, even if it is a case where friction stir welding is used, generation | occurrence | production of a metal foreign material can be suppressed effectively. That is, according to the junction structure corresponding to Examples 1 to 14 shown in FIG. 15, it is possible to effectively suppress the occurrence of metallic foreign matters that cause a short circuit of the lithium ion battery. Can be improved.

<Modification Example of Joining Structure in Embodiment>
Next, a modified example of the joint structure in the present embodiment will be described. FIG. 16 is a perspective view showing a joint structure in Modification 1 of the embodiment. As shown in FIG. 16, in the joint structure in the first modification, the shape of the groove DIT provided in the cover plate CPLT is an oval shape, and thus the shape of the joint portion CU is also an oval shape. Become. As a result, according to the first modification, the area of the joint CU can be increased, thereby improving the joint strength of the joint CU across the cover plate CPLT, the tab laminate TL, and the external output terminal EOT. Can be made.

  Next, FIG. 17 is a perspective view showing a joint structure in Modification 2 of the embodiment. As shown in FIG. 17, the joint structure of the second modification is a structure in which the tab laminate TL is drawn out from only one side of the external output terminal EOT. The technical idea in the embodiment can also be applied to the joining structure of the second modification. That is, the technical idea in the embodiment can be applied regardless of the form of pulling out the tab laminate TL from the external output terminal EOT.

  Further, FIG. 18 is a perspective view showing a joint structure in Modification 3 of the embodiment. As shown in FIG. 18, the joint structure of Modification 3 is a structure in which the tab laminate TL is joined to the side surface of the external output terminal EOT. The technical idea in the embodiment can also be applied to the joint structure of the third modification.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  In the embodiment, the lithium ion battery has been described as an example of the electricity storage device. However, the technical idea in the embodiment is not limited to this, and for example, the cover plate and the tab laminate are formed by friction stir welding. It can be widely applied to an electricity storage device that forms a joint portion extending between and an external output terminal.

  The present invention can be widely applied to, for example, a manufacturing industry that manufactures an electricity storage device represented by a lithium ion battery.

BCU Burr joint CPLT Cover plate CU joint DIT Groove EOT External output terminal

Claims (10)

(A) a cover plate having a first surface and a second surface located on the opposite side of the first surface, wherein the cover plate is provided with a groove on the first surface;
(B) a tab laminate in contact with the second surface of the cover plate, the tab laminate formed by overlapping a plurality of tabs integrated with an electrode plate;
(C) an external output terminal in contact with the tab laminate,
(D) a joint formed between the cover plate, the tab laminate, and the external output terminal, wherein the joint is in contact with the groove;
(E) a burr joint integrated with the joint, the burr joint formed so as to rise from the joint in the groove;
With
The height of the burr joint is smaller than the depth of the groove,
The burr junction is a power storage device in contact with a side surface of the groove. The electricity storage device according to claim 1,
The electrical storage device in which the recessed part is formed toward the inside of the said junction part from the bottom face of the said groove | channel. The electricity storage device according to claim 1,
The burr joint is an electricity storage device that does not protrude from the first surface of the cover plate. The electricity storage device according to claim 1,
The power storage device, wherein the cover plate, the tab laminate, and the external output terminal are formed of the same member. The electricity storage device according to claim 4,
The electrical storage device, wherein the same member is a member mainly composed of aluminum. The electricity storage device according to claim 4,
The electric storage device, wherein the same member is a member mainly composed of copper. The electricity storage device according to claim 1,
The electricity storage device is a lithium ion battery. (A) a step of preparing a cover plate having a first surface and a second surface located on the opposite side of the first surface, wherein the cover plate is provided with a groove on the first surface;
(B) preparing an external output terminal;
(C) a step of stacking a plurality of tabs integrated with the electrode plate to form a tab laminate,
(D) a step of sandwiching the tab laminate between the second surface of the cover plate and the external output terminal;
(E) After the step (d), the step of friction stir welding the cover plate, the tab laminate, and the external output terminal;
With
The step (e)
(E1) preparing a tool having a pin portion;
(E2) While rotating the pin portion, by inserting the pin portion so as to penetrate the cover plate and the tab laminate from the bottom surface of the groove of the cover plate and reach the external output terminal ,
A joint extending over the cover plate, the tab laminate, and the external output terminal, the joint contacting the groove;
A burr joint integrated with the joint, and forming the burr joint raised from the joint in the groove;
Have
The height of the burr joint is smaller than the depth of the groove,
The method for manufacturing an electricity storage device, wherein the burr joint is in contact with a side surface of the groove. In the manufacturing method of the electrical storage device according to claim 8,
The method for manufacturing an electricity storage device, wherein a diameter of the groove is larger than a shoulder diameter of the tool. In the manufacturing method of the electrical storage device according to claim 9,
When the diameter of the groove / the shoulder diameter = A,
The manufacturing method of the electrical storage device which is 1.05 <= A <= 1.2.

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