JP2018160406A - Lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery which enables the suppression of lithium precipitation.SOLUTION: A lithium ion secondary battery according to the present invention comprises: a multilayer electrode body arranged by laminating a plurality of electrode plates in a lamination direction; and collector terminals 70 and 72 electrically connected to the multilayer electrode body. The plurality of electrode plates include all-collector foil tabs 26 and 36 provided so as to protrude from one sides of the respective electrode plates, respectively; the all-collector foil tabs and are arranged by gathering first tabs 26 and 36 in the lamination direction D, and joining the first tabs together, and they are not joined to the collector terminals 70 and 72. Of the plurality of electrode plates, electrode plates disposed on a center side in the lamination direction D include collector terminal joining tabs 28 and 38 joined to the collector terminals 70 and 72; the collector terminal joining tabs are arranged by gathering second tabs 28 and 38 provided so as to protruding from one sides of the respective electrode plates in the lamination direction D, and joining the second tabs together.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a lithium ion secondary battery. Specifically, the present invention relates to a lithium ion secondary battery including an electrode body configured by laminating a plurality of electrode plates.

  In recent years, a lithium ion secondary battery has been preferably used as a vehicle-mounted power source or a power source for personal computers and portable terminals. As one of this type of lithium ion secondary battery, a battery structure including an electrode body in which positive and negative electrodes are alternately stacked via separators is known. For example, Patent Document 1 discloses a lithium ion secondary battery having an electrode plate group including a large number of electrode plates with current collecting tabs. In the publication, a plurality of tabs of the electrode plate group are bundled so as to constitute a plurality of tab bundles arranged in the stacking direction of the electrode plate group. The tab bundle is welded onto the conductor block of the current collecting terminal that is electrically connected to the external terminal.

Japanese Patent Laying-Open No. 2015-103318

  However, in the lithium ion secondary battery configured as in Patent Document 1, when the electrode plate group moves relative to the current collecting terminal, stress concentrates on the connection portion between the tab and the current collecting terminal. Some electrode tabs may be cut. When the tabs of some of the electrode plates are cut, the electrode plates may be electrically isolated and cannot be electrically connected to the external terminals. As a result, lithium may be deposited around the isolated electrode plate.

  The present invention has been made in view of such circumstances, and its main purpose is that the electrode plates are electrically isolated even when the tabs of some electrode plates constituting the laminated electrode body are cut. It is an object to provide a lithium ion secondary battery capable of suppressing lithium deposition caused by the above.

The lithium ion secondary battery provided by the present invention includes a laminated electrode body configured by laminating a plurality of electrode plates in the laminating direction, and a current collecting terminal electrically connected to the laminated electrode body. The plurality of electrode plates are first tabs projecting from one side of the electrode plates, gathered together in the stacking direction, joined together, and all foils not joined to the current collector terminals Each tab is provided. The electrode plate arranged on the center side in the stacking direction among the plurality of electrode plates is a second tab protruding from one side of the electrode plate, and is gathered in the stacking direction and mutually A current collecting terminal joining tab joined to the current collecting terminal is provided.
According to such a configuration, even when the electrode body moves relative to the current collecting terminal and the current collecting terminal joining tabs of some of the electrode plates are cut, all the electrode plates are electrically The electrode plates from which the tabs have been cut are not electrically isolated. As a result, it is possible to suppress the precipitation of lithium resulting from the electrode plate being electrically isolated.

It is a figure for demonstrating the positive electrode, the negative electrode, and separator which comprise the electrode body which concerns on one Embodiment. It is a figure for demonstrating the positive electrode, the negative electrode, and separator which comprise the electrode body which concerns on one Embodiment. It is a perspective view which shows typically the electrode body to which the current collection terminal was joined. It is a perspective view which shows typically the electrode body to which the current collection terminal was joined.

  Embodiments according to the present invention will be described below with reference to the drawings. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention (for example, a general configuration and manufacturing process of an electrode body that does not characterize the present invention) It can be grasped as a design matter of those skilled in the art based on the prior art. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. Moreover, in the following drawings, the same code | symbol is attached | subjected and demonstrated to the member and site | part which show | plays the same effect | action. In addition, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships.

  In the present specification, the “lithium ion secondary battery” refers to a secondary battery that uses lithium ions as a charge carrier and is charged / discharged by movement of charges accompanying the lithium ions between the positive and negative electrodes.

  1 and 2 are diagrams for explaining an electrode body 10 included in a lithium ion secondary battery 100 according to an embodiment. In addition, the code | symbol W in drawing shows the width direction of a battery, the code | symbol D shows the thickness direction of a battery, and the code | symbol H has shown the height direction of the battery. However, these are only directions for convenience of explanation, and do not limit the installation mode of the lithium ion secondary battery 100 at all.

As shown in FIGS. 1 and 2, the lithium ion secondary battery 100 includes a laminated electrode body 10, current collecting terminals 70 and 72 (FIG. 3), an electrolyte (not shown), and a battery case (not shown). .
The battery case is a container that houses the laminated electrode body 10, the electrolyte, and current collecting terminals 70 and 72. In the present embodiment, the battery case has a bottomed square (cuboid shape) outer shape. The battery case includes a flat bottomed case main body having an opening at the upper end, and a lid for closing the opening of the case main body. The material of the battery case is, for example, a metal material such as aluminum or steel.

  A positive electrode terminal and a negative electrode terminal for external connection protrude from the upper surface of the battery case, that is, the lid. The positive electrode terminal is electrically connected to the positive electrode plate 20 of the electrode body 10. The negative electrode terminal is electrically connected to the negative electrode plate 30 of the electrode body 10.

  The laminated electrode body 10, the electrolyte, and current collecting terminals 70 and 72 are accommodated inside the battery case. The laminated electrode body 10 is a laminated electrode body. The laminated electrode body 10 includes a plurality of rectangular positive plates 20 and rectangular negative plates 30. The positive electrode plate 20 and the negative electrode plate 30 are stacked in a state where they are insulated via the separator 40. Specifically, a plurality of positive electrode plates 20 and negative electrode plates 30 are repeatedly stacked in the stacking direction (here, the thickness direction D) via the separator 40. Here, FIG. 1 shows the positive electrode plate 20 and the negative electrode plate 30 arranged on the center side in the stacking direction D among the plurality of positive electrode plates 20 and negative electrode plates 30. FIG. 2 shows the positive electrode plate 20 and the negative electrode plate 30 arranged on both ends in the stacking direction D among the plurality of positive electrode plates 20 and negative electrode plates 30. The number of the positive electrode plates 20 and the negative electrode plates 30 arranged on the center side in the stacking direction D can be, for example, 2 to 10 (typically 2 to 5).

  The positive electrode plate 20 includes a positive electrode current collector 22 and a positive electrode active material layer 24 formed on the surface thereof. For the positive electrode current collector 22, for example, a metal foil suitable for the positive electrode can be suitably used. In this embodiment, an aluminum foil is used as the positive electrode current collector 22. In the illustrated example, the positive electrode active material layer 24 is held on both surfaces of the positive electrode current collector 22. In the width direction W, the positive electrode active material layer 24 is formed to have the same width as the entire width of the positive electrode current collector 22.

The positive electrode active material layer 24 contains a positive electrode active material, a conductive material, and a binder. As the positive electrode active material, one or more of materials conventionally used in lithium ion secondary batteries can be used without particular limitation. As an example, general formulas such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (lithium nickel cobalt manganese composite oxide), LiNiO ₂ (lithium nickel composite oxide), LiCoO ₂ (lithium cobalt composite oxide), etc. A lithium transition metal composite oxide having a layered structure represented by LiMeO ₂ (Me includes at least one transition metal element such as Ni, Co, and Mn) is used. In addition to the positive electrode active material described above, the positive electrode active material layer 24 can contain a conductive material such as acetylene black (AB), or a binder such as polyvinylidene fluoride (PVDF) or styrene butadiene rubber (SBR).

  The positive electrode plate 20 does not have the positive electrode active material layer 24 and has a protruding portion 26 protruding upward from the portion where the positive electrode active material layer 24 is formed. Since the positive electrode active material layer 24 is not formed in the protruding portion 26, the positive electrode current collector 22 is exposed. A first tab 26 and a second tab 28 are formed by the protruding portion 26. The first tab 26 and the second tab 28 protrude from one side of the positive electrode plate 20. The 1st tab 26 is a tab for all foil collection. The all-foil tab 26 is a positive electrode plate 20 arranged on the center side in the laminating direction D among the positive electrode plates 20 and a positive electrode plate 20 arranged on both end sides in the laminating direction D, that is, a laminated electrode body. 1 is formed on all the positive electrode plates 20 constituting 1 (see FIGS. 1 and 2). On the other hand, the 2nd tab 28 is a tab for current collection terminal joining. The current collector terminal joining tab 28 is formed only on the positive electrode plate 20 arranged on the center side in the stacking direction D among the plurality of positive electrode plates 20 (see FIG. 1). In this embodiment, the current collecting terminal joining tab 28 is arranged on the center side in the width direction W with respect to the entire foil collecting tab 26.

  The negative electrode plate 30 includes a negative electrode current collector 32 and a negative electrode active material layer 34 formed on the surface thereof. For the negative electrode current collector 32, for example, a metal foil suitable for the negative electrode can be suitably used. In this embodiment, a copper foil is used as the negative electrode current collector 32. In the illustrated example, the negative electrode active material layer 34 is held on both surfaces of the negative electrode current collector 32. In the width direction W, the negative electrode active material layer 34 is formed to have the same width as the entire width of the negative electrode current collector 32.

  The negative electrode active material layer 34 includes a negative electrode active material, a thickener, a binder, and the like. As the negative electrode active material, one type or two or more types of materials conventionally used in lithium ion secondary batteries can be used without any particular limitation. Examples thereof include carbon-based materials such as graphite carbon and amorphous carbon, lithium transition metal oxides, lithium transition metal nitrides, and the like. In addition to the negative electrode active material, a binder such as polyvinylidene fluoride (PVDF) and styrene butadiene rubber (SBR), and a thickener such as carboxymethyl cellulose (CMC) can be added.

  The negative electrode plate 30 does not have the negative electrode active material layer 34 and has a protruding portion 36 that protrudes upward from the portion where the negative electrode active material layer 34 is formed. Since the negative electrode active material layer 34 is not formed in the protruding portion 36, the negative electrode current collector 32 is exposed. The protruding portion 36 forms a first tab 36 and a second tab 38. The first tab 36 and the second tab 38 protrude from one side of the negative electrode plate 30. The 1st tab 36 is a tab for all the foil collection. The tabs 36 for the entire foil collection are both the negative electrode plate 30 arranged on the center side in the laminating direction D among the plurality of negative electrode plates 30 and the negative electrode plate 30 arranged on both end sides in the laminating direction D, that is, a laminated electrode body. 1 is formed on all the negative electrode plates 30 constituting 1 (see FIGS. 1 and 2). On the other hand, the second tab 38 is a current collecting terminal joining tab. The current collecting terminal joining tab 38 is formed only on the negative electrode plate 30 disposed on the center side in the stacking direction D among the plurality of negative electrode plates 30 (see FIG. 1). In this embodiment, the current collecting terminal joining tab 38 is disposed closer to the center in the width direction W than the entire foil collecting tab 36.

  The separator 40 is a member that separates the positive electrode plate 20 and the negative electrode plate 30. In this example, the separator 40 is made of a sheet material having a predetermined width having a plurality of minute holes. As the separator 40, for example, a single layer structure separator or a multilayer structure separator made of a porous polyolefin-based resin can be used.

  As described above, the laminated electrode body 10 is formed by laminating a plurality of positive plates 20, a plurality of negative plates 30, and a plurality of separators 40. The laminated electrode body 10 has a laminated portion in which the positive electrode active material layer 24 and the negative electrode active material layer 34 overlap with a separator 40 interposed therebetween. The stacked portion is a portion where charge carriers (here, lithium ions) are exchanged between the positive electrode active material layer 24 and the negative electrode active material layer 34 via the separator 40, and a portion contributing to charge / discharge of the battery. It is.

  3 and 4 are perspective views schematically showing the laminated electrode body 10 to which the current collecting terminals 70 and 72 are joined. As shown in FIG. 3 and FIG. 4, the tabs 26 for all the foils of the plurality of positive electrode plates 20 that are repeatedly stacked are stacked in the stacking direction (here, the thickness direction D) of the stacked electrode body 10, and the end face (here It protrudes from the upper surface. The plurality of all foil collecting tabs 26 are stacked in the stacking direction D to constitute a tab 26 group. The tabs 26 are gathered to the center side in the stacking direction D and joined (for example, welded) to each other. Thus, all the positive plates 20 constituting the electrode body 10 are electrically connected to each other through the tab 26 group. The tabs 26 are not joined to the current collecting terminals 70 and are not electrically connected to the current collecting terminals 70. In this embodiment, the tip portions 26 a of the collected foil tabs 26 are folded back in a direction perpendicular to the protruding direction of the tabs 26 (here, the thickness direction D). On the other hand, in the positive electrode plate 20 arranged on the center side in the stacking direction D, a plurality of current collecting terminal joining tabs 28 are stacked in the stacking direction D to constitute a tab 28 group. The tabs 28 are gathered together on the center side in the stacking direction D and joined (for example, welded) to the current collecting terminals 70. Thereby, the positive electrode plate 20 arranged on the center side in the stacking direction D is electrically connected to the current collecting terminal 70 and the positive electrode terminal. Further, the positive plates 20 arranged on both ends in the stacking direction D are electrically connected to the current collecting terminal 70 and the positive terminal via the tab 28 group and the tab 26 group.

  Similar to the positive electrode side, all the foil collecting tabs 36 of the plurality of negative electrode plates 30 that are repeatedly stacked are stacked in the stacking direction (here, the thickness direction D) of the electrode body 10, and from the end surface (here, the upper surface) of the stack portion. It protrudes. The plurality of all foil collecting tabs 36 are stacked in the stacking direction D to constitute a tab 36 group. The tabs 36 are gathered to the center side in the stacking direction D and joined (for example, welded) to each other. Thereby, all the negative electrode plates 30 constituting the electrode body 10 are electrically connected to each other through the tab 36 group. The tab group 36 is not joined to the current collecting terminal 72 and is not electrically connected to the current collecting terminal 72. In this embodiment, the front end portions 36a of the collected foil collecting tabs 36 are folded back in a direction perpendicular to the protruding direction of the tabs 36 (in this case, the thickness direction D). On the other hand, in the negative electrode plate 30 disposed on the center side in the stacking direction D, a plurality of current collecting terminal joining tabs 38 are stacked in the stacking direction D, thereby forming a tab 38 group. The tabs 38 are gathered together on the center side in the stacking direction D and joined (for example, welded) to the current collecting terminals 72. Thereby, the negative electrode plate 30 arrange | positioned at the center side of the lamination direction D is electrically connected with the current collection terminal 72 and the negative electrode terminal. Further, the negative plates 30 arranged on both ends in the stacking direction D are electrically connected to the current collecting terminal 72 and the negative terminal through the tab 38 group and the tab 36 group.

  As described above, as shown in FIGS. 1 to 4, the lithium ion secondary battery 100 includes a laminated electrode body 10 configured by laminating a plurality of positive electrode plates 20 and negative electrode plates 30 in the lamination direction D, and a laminated electrode body 10. Current collecting terminals 70 and 72 electrically connected to the electrode body 10 are provided. The plurality of positive electrode plates 20 and negative electrode plates 30 are first tabs 26 and 36 protruding from one side of the electrode plates 20 and 30, gathered in the stacking direction D and joined together, All the foil collecting tabs 26 and 36 which are not joined to the electric terminals 70 and 72 are provided. In addition, among the plurality of positive plates 20 and negative plates 30, the electrode plates 20, 30 arranged on the center side in the stacking direction D are second tabs 28, 38 protruding from one side of the electrode plates 20, 30. In addition, current collecting terminal joining tabs 28 and 38 which are gathered in the stacking direction D and joined to each other and joined to the current collecting terminals 70 and 72 are provided. According to this configuration, even when the laminated electrode body 10 moves relative to the current collecting terminals 70 and 72 and the current collecting terminal joining tabs 28 and 38 of some of the positive and negative plates 20 and 30 are cut. Since all the positive electrode plates 20 and all the negative electrode plates 30 are electrically connected to each other by the foil collecting tabs 26 and 36, the positive electrode plate 20 and the negative electrode plate 30 from which the tabs 28 and 38 are cut are electrically connected. Not isolated. Thereby, it is possible to suppress the precipitation of lithium due to the electrical isolation of the positive electrode plate 20 and the negative electrode plate 30.

  Further, according to the present embodiment, the positive electrode plate 20 and the negative electrode plate 30 are bundled together at two locations of the current collecting terminal joining tabs 28 and 38 and the all foil collecting tabs 26 and 36, so that the electrodes The strength of the body 10 itself is improved as compared with the conventional case. Therefore, it is possible to suppress a short circuit due to the stacking deviation of the electrode plates 20 and 30. Moreover, workability (for example, retainability) when the laminated electrode body 10 is accommodated in the battery case is improved.

  Further, according to the present lithium ion secondary battery 100, the current collector terminal joining tabs 28, 38 are provided only on the electrode plates 20, 30 arranged on the center side in the stacking direction D among the plurality of electrode plates 20, 30. Since the current collector terminals 70 and 72 are joined, the size of the collected tabs 28 and 38 group can be made smaller than when the current collector terminal joining tabs 28 and 38 are provided on all the electrode plates 20 and 30. can do. For example, the size of the side surface (triangular portion) in the height direction H when the tabs 28 and 38 are viewed from the width direction W is smaller than the conventional size, and the space required for current collection can be reduced. This makes it possible to increase the occupation ratio of the electrode body 10 (laminated portion) that contributes to charging / discharging in the battery case. As a result, a space (dead space) that does not contribute to charging / discharging in the battery case can be reduced, and high energy density can be realized. Further, in the conventional mode in which the current collecting terminal joining tabs 28 and 38 are provided on all the electrode plates 20 and 30, when the tabs 28 and 38 are gathered to the center side in the laminating direction D, both end sides in the laminating direction D are provided. The electrode plate is pulled more than the electrode plate on the center side, and therefore, the electrode plate is liable to be misaligned. Can be done.

  Further, according to the present embodiment, since the tip portions of the collected foil collecting tabs 26 and 36 are folded back in the direction perpendicular to the protruding direction of the tabs 26 and 36 (here, the thickness direction D), The size of the foil tabs 26 and 36 in the height direction H can be reduced, and the space required for current collection can be reduced. This makes it possible to increase the occupation ratio of the electrode body 10 (laminated portion) that contributes to charging / discharging in the battery case. As a result, a space (dead space) that does not contribute to charging / discharging in the battery case can be reduced, and high energy density can be realized.

  As mentioned above, although this invention was demonstrated in detail, the said embodiment and Example are only illustrations and what changed and changed the above-mentioned specific example is contained in the invention disclosed here.

  For example, in the above-described embodiment, the case where all the tabs 26 and 36 for collecting foil and the tabs 28 and 38 for connecting current collecting terminals are respectively provided on the positive electrode plate 20 and the negative electrode plate 30 is illustrated. The number of is not limited to this. A plurality of all foil collecting tabs 26, 36 and current collecting terminal joining tabs 28, 38 may be formed on the positive electrode plate 20 and the negative electrode plate 30, respectively. In the above-described embodiment, the case where the current collecting terminal joining tabs 28 and 38 are provided only on the electrode plates 20 and 30 arranged on the center side in the stacking direction D among the plurality of electrode plates is illustrated. It is not limited. The current collecting terminal joining tabs 28 and 38 may be provided on the electrode plates 20 and 30 arranged on both ends of the lamination direction D in addition to the electrode plates 20 and 30 arranged on the center side in the lamination direction D. . However, as in the above-described embodiment, the tabs 28 and 38 grouped together when the current collector terminal joining tabs 28 and 38 are formed only on the electrode plates 20 and 30 arranged on the center side in the stacking direction D are arranged. The space required for current collection can be reduced by reducing the size of the battery.

  The lithium ion secondary battery 100 can be used for various applications, but is characterized in that lithium is hardly deposited even when the tab is cut. Therefore, taking advantage of such characteristics, for example, it can be suitably used as a power source (drive power source) for a motor mounted on a vehicle. The type of vehicle is not particularly limited, but typically includes automobiles such as plug-in hybrid cars (PHV), hybrid cars (HV), electric cars (EV), and the like.

DESCRIPTION OF SYMBOLS 10 Stacked electrode body 20 Positive electrode plates 26 and 36 Tabs 28 and 38 for collecting all current collectors Tab 30 for collecting current collector terminals Negative electrode plates 70 and 72 Current collecting terminals 100 Lithium ion secondary battery

Claims (1)

A laminated electrode body formed by laminating a plurality of electrode plates in the laminating direction;
A current collecting terminal electrically connected to the laminated electrode body,
The plurality of electrode plates are first tabs projecting from one side of the electrode plates, gathered together in the stacking direction, joined together, and all foils not joined to the current collector terminals Each has a tab for
Of the plurality of electrode plates, the electrode plate disposed on the center side in the stacking direction is a second tab protruding from one side of the electrode plate, and is gathered in the stacking direction and joined to each other. And a collector terminal joining tab joined to the current collector terminal.

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