JP2020123549A - Power storage device - Google Patents

Abstract

To provide a power storage device capable of suppressing a peeling of a negative electrode active material layer from a negative electrode metal foil while suppressing fatigue cracks in bent portions of a positive electrode tab and a negative electrode tab due to spring back.SOLUTION: In a positive electrode tab 20c, at least one surface of a bent portion 29a in a thickness direction is covered with a coating layer 30 comprising ceramic having a higher Young's modulus than the positive electrode tab 20c and a negative electrode tab 21c. A negative electrode 21 having the negative electrode tab 21c where the bent portion 29a is formed includes a tab side extension 41 as a coated extension 40 along one projecting side of the negative electrode tab 21c in the coated extension 40. The tab side extension 41 includes the tab side extension 41 that is a non-contact extension 42 not contacting with a separator 23, and the bent portion 29a and the non-contact extension 42 are covered with the coating layer 30 in the negative electrode tab 21c.SELECTED DRAWING: Figure 5

Description

The present invention relates to a power storage device.

Conventionally, a power storage device as described in Patent Document 1 is known.
The above power storage device includes an electrode assembly in which a plurality of sheet-shaped positive electrodes and a plurality of sheet-shaped negative electrodes are stacked in a state of being insulated by a plurality of separators, a case for housing the electrode assembly, and a case. It has a positive electrode terminal and a negative electrode terminal that are fixed and that exchange electricity with the electrode assembly.

The positive electrode of the above-mentioned electrode assembly has a sheet-shaped positive electrode metal foil (for example, aluminum foil), and a positive electrode active material layer provided on both surfaces of the positive electrode metal foil. The negative electrode of the above electrode assembly has a sheet-shaped negative electrode metal foil (for example, copper foil) and a negative electrode active material layer provided on both surfaces of the negative electrode metal foil.

The electrode assembly includes a positive electrode tab group in which positive electrode tabs protruding from a part of one side of the positive electrode metal foil forming the positive electrode are gathered, and a part of one side of a negative electrode metal foil forming the negative electrode. And a group of negative electrode tabs that are gathered together. The positive electrode tab group includes a positive electrode base end portion in which a plurality of positive electrode tabs are gathered toward one end in the stacking direction of the electrode assembly, and a positive electrode bent portion bent from the positive electrode base end portion to the other end in the stacking direction of the electrode assembly. And have. In addition, the positive electrode tab group extends along the tab-side end surface where the positive electrode tab group and the negative electrode tab group of the electrode assembly are present from the side opposite to the positive electrode base end portion of the positive electrode curved portion toward the other end in the stacking direction of the electrode assembly. And a positive electrode extension portion that extends and is fixed to the positive electrode terminal. The negative electrode tab group includes a negative electrode base end portion in which a plurality of negative electrode tabs are gathered toward one end in the stacking direction of the electrode assembly, and a negative electrode bending portion bent from the negative electrode base end portion toward the other end in the stacking direction of the electrode assembly. And have. The negative electrode tab group extends along the tab-side end surface of the electrode assembly from the side opposite to the negative electrode base end portion of the negative electrode curved portion toward the other end in the stacking direction of the electrode assembly and is fixed to the negative electrode terminal. And a negative electrode extension portion.

In the plurality of positive electrode tabs and the plurality of negative electrode tabs, the plurality of positive electrode tabs and the plurality of negative electrode tabs are arranged in the stacking direction of the electrode assembly in the root portion provided closer to the tab-side end surface than the positive electrode base end portion and the negative electrode base end portion. A root portion is included that has a bend that bends in a gathered manner toward one end.

In the power storage device having the above configuration, the electrode assembly is housed in the case, and the positive electrode terminal and the negative electrode terminal are fixed to the case and the positive electrode extension part and the negative electrode extension part of each tab group. Therefore, residual stress acts on the curved portions of the plurality of positive electrode tabs and the plurality of negative electrode tabs. Therefore, the plurality of positive electrode tabs and the plurality of negative electrode tabs each having the curved portion at the root part try to return from the bent state to the straight extended state. That is, springback occurs in the curved portions of the plurality of positive electrode tabs and the plurality of negative electrode tabs. Therefore, the storage device vibrates while the electrode assembly is housed in the case and the residual stress is applied to the curved portions of the plurality of positive electrode tabs and the plurality of negative electrode tabs. If a repeated load is applied to the portion, fatigue cracks may occur in the curved portions of the plurality of positive electrode tabs and the plurality of negative electrode tabs. As a result, the electrical resistance of the positive electrode tab and the negative electrode tab in which the fatigue crack has occurred increases, and the power storage performance of the power storage device deteriorates.

As a power storage device described in Patent Document 2 as a specific proposal for suppressing fatigue cracks in curved portions of a plurality of positive electrode tabs and a plurality of negative electrode tabs, a positive electrode metal foil for a positive electrode and a negative electrode metal foil for a negative electrode An insulating layer made of ceramic is provided on a non-formed portion (including the positive electrode tab and the negative electrode tab) where the active material layer is not formed. With this configuration, the plurality of positive electrode tabs and the plurality of negative electrode tabs are covered with the ceramic, which is a high Young's modulus material, and the apparent thicknesses of the plurality of positive electrode tabs and the plurality of negative electrode tabs are increased. Therefore, it is possible to suppress springback at the roots of the plurality of positive electrode tabs and the plurality of negative electrode tabs, and to suppress fatigue cracks in the curved portions of the positive electrode tabs and the negative electrode tabs.

JP, 2015-32549, A JP, 2014-56673, A

Here, in general, the size of the negative electrode and the negative electrode active material layer forming the negative electrode is larger than the size of the positive electrode and the positive electrode active material layer forming the positive electrode. That is, when an electrode assembly is formed by stacking a positive electrode and a negative electrode, the negative electrode active material layer forming the negative electrode is arranged in a state of protruding outside the outer edge of the positive electrode active material layer forming the positive electrode. To be done.

By the way, as in the above-mentioned Patent Document 2, a ceramic insulating layer is provided on the non-formed portions of the positive electrode metal foil and the negative electrode metal foil to suppress fatigue cracks in the curved portions of the plurality of positive electrode tabs and the plurality of negative electrode tabs. The composition is known. In this configuration, when a plurality of negative electrode tabs are gathered at one end in the stacking direction of the electrode assembly to form a negative electrode tab group, a portion of the negative electrode active material layer protruding outside the outer edge of the positive electrode active material layer is It may bend. When the protruding portion of the negative electrode active material layer bends, the protruding portion peels off from the negative electrode metal foil. When the protruding portion of the negative electrode active material layer is peeled off from the negative electrode metal foil, peeling of the negative electrode active material layer may propagate to the entire negative electrode metal foil, and the electric capacity may be reduced.

The present invention was made by paying attention to the problems existing in such a conventional technique, and the object thereof is to suppress fatigue cracks in the curved portions of the positive electrode tab and the negative electrode tab due to springback, An object of the present invention is to provide a power storage device capable of suppressing peeling of the negative electrode active material layer from the negative electrode metal foil.

An electricity storage device that solves the above problems is an electrode assembly in which a plurality of sheet-shaped positive electrodes and a plurality of sheet-shaped negative electrodes are stacked in a state of being insulated by a separator, and a case which accommodates the electrode assembly. Provided with a positive electrode terminal and a negative electrode terminal that are fixed to the case and that exchange electricity with the electrode assembly,
The positive electrode is a sheet-shaped positive electrode metal foil, a positive electrode active material layer provided on at least one of both surfaces of the positive electrode metal foil, and a positive electrode tab protruding from a part of one side of the positive electrode metal foil. And have
The negative electrode is provided on at least one of both surfaces of the sheet-shaped negative electrode metal foil and the negative electrode metal foil, and for the negative electrode having a coating extension part that is outside the outer edge of the positive electrode active material layer. An active material layer and a negative electrode tab protruding from a part of one side of the negative electrode metal foil, and the electrode assembly includes a positive electrode tab group in which a plurality of the positive electrode tabs are gathered together, and a plurality of the positive electrode tab groups. A negative electrode tab group in which the negative electrode tabs are gathered together,
The positive electrode tab group includes a positive electrode base end portion in which the plurality of positive electrode tabs are gathered toward one end in the stacking direction of the electrode assembly, and a positive electrode base end portion from the positive electrode base end portion to the other end in the stacking direction of the electrode assembly. And a positive electrode bent portion that bends, and a stack of the electrode assembly from the side opposite to the positive electrode base end portion of the positive electrode bent portion along the tab-side end surface where the positive electrode tab group and the negative electrode tab group of the electrode assembly are present. A positive electrode extension portion fixed to the positive electrode terminal while extending toward the other end in the direction,
The negative electrode tab group includes a negative electrode base end portion in which a plurality of the negative electrode tabs are gathered toward one end in the stacking direction of the electrode assembly, and a negative electrode base end portion from the other end in the stacking direction of the electrode assembly. And a negative electrode bent portion that bends along the tab-side end surface of the electrode assembly, and extends from the side opposite to the negative electrode base end portion of the negative electrode bent portion toward the other end in the stacking direction of the electrode assembly. A negative electrode extension portion fixed to the negative electrode terminal,
In the plurality of positive electrode tabs and the plurality of negative electrode tabs, the plurality of positive electrode tabs and the plurality of negative electrode tabs are included in the root portion provided closer to the tab side end surface than the positive electrode base end portion and the negative electrode base end portion. Includes the root portion having a curved portion that is bent in a state of being gathered together at one end in the stacking direction of the electrode assembly,
In the positive electrode tab, at least one surface in the thickness direction of the curved portion is covered with a coating layer made of ceramic having a higher Young's modulus than the positive electrode tab and the negative electrode tab,
The negative electrode having the negative electrode tab in which the curved portion is formed includes a tab-side extending portion as the coating extending portion along one protruding side of the negative electrode tab among the coating extending portions, Among the tab-side extending portion, the tab-side extending portion is a non-contact extending portion that does not contact the separator,
In the negative electrode tab, the curved portion and the non-contact extending portion are covered with the coating layer.

According to this, the curved portion of the positive electrode tab is covered with the coating layer, and the curved portion of the negative electrode tab and the non-contact extension portion of the coating extension portion of the negative electrode are coated with the coating layer. Since the coating layer is made of a ceramic having a higher Young's modulus than the positive electrode tab and the negative electrode tab, the apparent Young's modulus of the curved portion of the positive electrode tab and the negative electrode tab can be improved. Therefore, the springback amount of the curved portions of the positive electrode tab and the negative electrode tab becomes small. In addition, the curved portions of the positive electrode tab and the negative electrode tab have an apparent thickness increased by the coating layer. Therefore, the apparent second moment of area of the curved portions of the positive electrode tab and the negative electrode tab increases. The second moment of area is an index indicating the difficulty of bending. Therefore, the curved portions of the positive electrode tab and the negative electrode tab are less likely to bend, and thus the curved portions of the positive electrode tab and the negative electrode tab are less likely to be deformed from the bent state. Therefore, the springback amount of the curved portions of the positive electrode tab and the negative electrode tab becomes small. Therefore, fatigue cracks in the curved portions of the positive electrode tab and the negative electrode tab due to springback can be suppressed.

Further, the coating layer is also provided on the non-contact extending portion of the negative electrode active material layer. Therefore, it is possible to improve the strength of the portion of the negative electrode active material layer that extends outside the outer edge of the positive electrode active material layer. Therefore, the negative electrode active material layer is less likely to bend than in the case of covering only the non-formed portion of the conventional negative electrode with ceramics, and the peeling of the negative electrode active material layer from the negative electrode metal foil is suppressed. You can Therefore, peeling of the negative electrode active material layer from the negative electrode metal foil can be suppressed while suppressing fatigue cracks in the curved portions of the positive electrode tab and the negative electrode tab due to springback.

In the above power storage device, the coating layer may cover a mountain fold portion that is bent so that the curved portion is mountain fold.
In the curved portions of the positive electrode tab and the negative electrode tab, there are a mountain fold portion that bends to form a mountain fold and a valley fold portion that bends to form a valley fold. Tensile residual stress is generated in the mountain folds, and compressive residual stress is generated in the valley folds. It is considered that the spring back of the curved portions of the positive electrode tab and the negative electrode tab is mainly due to the tensile residual stress generated in the mountain fold portion.

In that respect, according to this, the coating layer covers the mountain folds of the curved portions of the positive electrode tab and the negative electrode tab. Therefore, compressive stress is applied to the mountain folds by the coating layer. Therefore, the tensile residual stress generated in the curved portion is reduced by the compressive stress due to the coating layer. Therefore, fatigue cracks in the curved portions of the positive electrode tab and the negative electrode tab due to springback can be suppressed.

In the above power storage device, the coating layer may be provided on both surfaces in the thickness direction of the curved portion.
According to this, since both surfaces of the positive electrode tab and the negative electrode tab are covered with the coating layer, fatigue cracks in the curved portions of the positive electrode tab and the negative electrode tab due to springback can be suitably suppressed.

In the above power storage device, the coating layer may be provided up to the positive electrode curved portion in the positive electrode tab group and the negative electrode curved portion in the negative electrode tab group.
It is conceivable that springback may also occur in the positive electrode bent portion of the positive electrode tab group and the negative electrode bent portion of the negative electrode tab group.

According to this, the positive electrode curved portion in the positive electrode tab group and the negative electrode curved portion in the negative electrode tab group are covered with the coating layer. Therefore, the coating layer improves the apparent Young's modulus of the positive electrode curved portion in the positive electrode tab group and the negative electrode curved portion in the negative electrode tab group, and also increases the apparent thickness. Therefore, the springback amount of the positive electrode bent portion of the positive electrode tab group and the negative electrode bent portion of the negative electrode tab group can be reduced, and fatigue cracks of the positive electrode tab group and the negative electrode tab group can be suppressed.

According to the present invention, peeling of the negative electrode active material layer from the negative electrode metal foil can be suppressed while suppressing fatigue cracks in the curved portions of the positive electrode tab and the negative electrode tab due to springback.

FIG. 3 is an exploded perspective view of the first embodiment of the power storage device. The exploded perspective view of an electrode assembly. FIG. 3 is a cross-sectional view of a power storage device. FIG. 3 is a cross-sectional view of a power storage device. (A) is an enlarged sectional view showing a coating layer that covers the curved portion of the positive electrode tab, and (b) is an enlarged sectional view that shows a coating layer that covers the curved portion of the negative electrode tab. Schematic which showed the coating method at the time of coating a curved part with a coating layer. (A) is an enlarged cross-sectional view showing a coating layer that covers the curved portion of the positive electrode tab in the second embodiment of the electricity storage device, and (b) covers the curved portion of the negative electrode tab in the second embodiment. The expanded sectional view which showed the coating layer. (A), (b) is an expanded sectional view which shows the position where the coating layer in 3rd Embodiment of an electrical storage apparatus is provided.

<First Embodiment>
Hereinafter, a first embodiment in which a power storage device is embodied as a secondary battery will be described with reference to FIGS. 1 to 6.

As shown in FIG. 1, a secondary battery 10 as a power storage device includes a case 11. The secondary battery 10 includes an electrode assembly 12 housed in a case 11 and an electrolytic solution (not shown). The case 11 includes a case body 13 in the shape of a square cylinder with a bottom, and a plate-like lid 14 that closes the opening 13 a of the case body 13. The case main body 13 and the lid 14 that form the case 11 are both made of metal (for example, stainless steel or aluminum). Further, the secondary battery 10 of the present embodiment is a prismatic battery having a prismatic appearance. Further, the secondary battery 10 of the present embodiment is a lithium ion secondary battery.

The secondary battery 10 includes a positive electrode terminal 15 and a negative electrode terminal 16 that exchange electricity with the electrode assembly 12. The positive electrode terminal 15 and the negative electrode terminal 16 are exposed to the outside of the case 11 through a pair of holes 14a that are arranged in parallel in the lid 14 at a predetermined interval. Further, the positive electrode terminal 15 and the negative electrode terminal 16 are attached with ring-shaped insulating rings 17 a for insulating the case 11 from each other. Thereby, the positive electrode terminal 15 and the negative electrode terminal 16 are fixed to the case 11. The positive electrode terminal 15 and the negative electrode terminal 16 have a positive electrode conductive member and a negative electrode conductive member having the same polarity, respectively.

The lid 14 is provided with a round hole-shaped injection port 14c penetrating in the thickness direction. The injection port 14c is used to inject the electrolytic solution into the case 11. The liquid injection port 14c is sealed by the sealing member 19, and the sealing property of the liquid injection port 14c is maintained.

As shown in FIGS. 2, 3, and 4, the electrode assembly 12 includes a plurality of sheet-shaped positive electrodes 20, a plurality of sheet-shaped negative electrodes 21, and a plurality of sheet-shaped separators 23. Have The electrode assembly 12 is configured by stacking a plurality of positive electrodes 20 and a plurality of negative electrodes 21 in a state of being insulated by a separator 23. The stacking direction of the positive electrode 20, the negative electrode 21, and the separator 23 is the stacking direction of the electrode assembly 12.

As shown in FIG. 2, the positive electrode 20 includes a sheet-shaped positive electrode metal foil (for example, aluminum foil) 20a, a positive electrode active material layer 20b provided on both surfaces of the positive electrode metal foil 20a, and a positive electrode metal foil. 20 a and a strip-shaped positive electrode tab 20 c protruding from a part of one side. The positive electrode tab 20c is composed of the positive electrode metal foil 20a itself.

The negative electrode 21 includes a sheet-shaped negative electrode metal foil (for example, copper foil) 21a, negative electrode active material layers 21b provided on both surfaces of the negative electrode metal foil 21a, and a part of one side of the negative electrode metal foil 21a. It has a protruding negative electrode tab 21c. The negative electrode tab 21c is composed of the negative electrode metal foil 21a itself. The plurality of positive electrode tabs 20c and the plurality of negative electrode tabs 21c are present at positions where the positive electrode tab 20c and the negative electrode tab 21c do not overlap each other in a state where the positive electrode 20 and the negative electrode 21 are stacked.

As shown in FIGS. 3 and 4, in the secondary battery 10, the negative electrode active material layer 21b of the negative electrode 21 should face the positive electrode active material layer 20b of the positive electrode 20 in the stacking direction of the electrode assembly 12. I have to. Therefore, the negative electrode active material layer 21b is formed larger than the positive electrode active material layer 20b. Specifically, in the stacking direction of the electrode assembly 12, the positive electrode active material layer 20b provided on the positive electrode metal foil 20a can be covered with the negative electrode active material layer 21b provided on the negative electrode metal foil 21a. Thus, the negative electrode active material layer 21b is set larger than the positive electrode active material layer 20b. For this reason, in the electrode assembly 12, the outer edge portion of the negative electrode active material layer 21b of the negative electrode 21 constitutes the coating extension portion 40 that extends outside the outer edge of the positive electrode active material layer 20b.

As shown in FIG. 3, the electrode assembly 12 includes a positive electrode tab group 25. The positive electrode tab group 25 is configured by collecting a plurality of positive electrode tabs 20c in the stacking direction of the electrode assembly 12.

The positive electrode tab group 25 includes a positive electrode base end portion 27a in which a plurality of positive electrode tabs 20c are gathered toward one end in the stacking direction of the electrode assembly 12, and a positive electrode base end portion 27a from the other end in the stacking direction of the electrode assembly 12. It has a positive electrode bent portion 24a that is bent toward. In addition, the positive electrode tab group 25 is arranged along the tab-side end surface 12a where the positive electrode tab group 25 and the negative electrode tab group 26 of the electrode assembly 12 are present, from the side opposite to the positive electrode base end portion 27a of the positive electrode bent portion 24a. Has a positive electrode extension portion 28a extending toward the other end in the stacking direction. The tab-side end surface 12a of the electrode assembly 12 is configured by gathering one side of the negative electrode metal foil 21a on which the negative electrode tab 21c is provided and one side of the separator 23 along the stacking direction of the electrode assembly 12. Has been done. The positive electrode conductive member of the positive electrode terminal 15 is fixed to the positive electrode extension portion 28 a of the positive electrode tab group 25.

As shown in FIG. 4, the electrode assembly 12 includes a negative electrode tab group 26. The negative electrode tab group 26 is configured by collecting a plurality of negative electrode tabs 21c in the stacking direction of the electrode assembly 12.

The negative electrode tab group 26 includes a negative electrode base end portion 27b in which a plurality of negative electrode tabs 21c are gathered toward one end in the stacking direction of the electrode assembly 12, and a negative electrode base end portion 27b from the other end in the stacking direction of the electrode assembly 12. It has a negative electrode bent portion 24b that is bent toward. The negative electrode tab group 26 extends along the tab-side end surface 12a of the electrode assembly 12 from the side opposite to the negative electrode base end portion 27b of the negative electrode bent portion 24b in the stacking direction of the electrode assembly 12. It has a portion 28b. Further, the negative electrode conductive member of the negative electrode terminal 16 is fixed to the negative electrode extension portion 28 b of the negative electrode tab group 26.

As shown in FIGS. 3 and 4, the plurality of positive electrode tabs 20c and the plurality of negative electrode tabs 21c have a plurality of root portions 29 closer to the tab-side end surface 12a than the positive electrode base end portions 27a and the negative electrode base end portions 27b. ing. The plurality of root portions 29 includes a root portion 29 having a curved portion 29a that is bent in a state where the plurality of positive electrode tabs 20c and the plurality of negative electrode tabs 21c are gathered together at one end in the stacking direction of the electrode assembly 12. There is. In the present embodiment, the root portions 29 (see FIG. 3) of all the positive electrode tabs 20c have the curved portion 29a. Of the root parts 29 of the negative electrode tab 21c, the root parts 29 of the plurality of negative electrode tabs 21c have a curved part 29a, except for the one located at one end in the stacking direction of the electrode assembly 12 (see FIG. 4). The negative electrode tab 21c located at one end of the electrode assembly 12 in the stacking direction extends straight toward the lid 14 along the side wall of the case body 13 (see FIG. 4).

As shown in FIGS. 5A and 5B, the curved portion 29a of the root portion 29 of the positive electrode tab 20c is a mountain fold portion 20d that is bent so that the positive electrode tab 20c is a mountain fold, and a valley fold. And a valley fold portion 20e that bends. The curved portion 29a of the root portion 29 of the negative electrode tab 21c has a mountain fold portion 21d that is bent so that the negative electrode tab 21c is mountain-folded and a valley fold portion 21e that is bent so as to be valley-folded. Here, the mountain folds 20d and 21d are bent so as to be mountain folds when viewed from the other end of the electrode assembly 12 in the stacking direction along the stacking direction of the electrode assembly 12. The valley folds 20e and 21e are bent from one end in the stacking direction of the electrode assembly 12 so as to form a valley fold when viewed along the stacking direction of the electrode assembly 12.

As shown in FIG. 5A, in the positive electrode tab 20c, one surface in the thickness direction of the curved portion 29a is covered with a coating layer 30 made of ceramic having a Young's modulus higher than that of the positive electrode tab 20c. .. The coating layer 30 is provided on the surface of the curved portion 29a of the positive electrode tab 20c on the mountain fold portion 20d side. The coating layer 30 is provided from a boundary portion with the positive electrode active material layer 20b on a surface of the curved portion 29a of the positive electrode tab 20c where the mountain folded portion 20d is provided to a position that covers the mountain folded portion 20d of the curved portion 29a. .. The coating layer 30 does not reach the positive electrode base end portion 27 a of the positive electrode tab group 25. Note that aluminum oxide, silicon nitride, zirconium oxide, aluminum nitride, or the like is used as the ceramic.

As shown in FIG. 5B, among the coating extension portions 40 of the negative electrode active material layer 21b, the coating extension portion 40 along one side from which the negative electrode tab 21c projects is referred to as a tab side extension portion 41. .. Among the plurality of tab-side extending portions 41, the tab-side extending portion 41 that is the non-contact extending portion 42 that is not in contact with the separator 23 in the stacking direction of the electrode assembly 12 is included. The negative electrode tab 21c continuous with the negative electrode metal foil 21a coated with the non-contact extending portion 42 has a curved portion 29a. The non-contact extending portion 42 is one of the tab-side extending portions 41 that sandwich the negative electrode metal foil 21a. The non-contact extending portion 42 is the tab side extending portion 41 on the mountain fold portion 21d side of the negative electrode tab 21c among the tab side extending portions 41 that sandwich the negative electrode metal foil 21a. That is, a gap is provided between one of the tab-side extending portions 41 and the separator 23.

The curved portion 29a and the non-contact extending portion 42 of the negative electrode tab 21c are covered with the coating layer 30. The coating layer 30 is provided on the surface of the curved portion 29a of the negative electrode tab 21c on the mountain fold portion 21d side. The coating layer 30 is provided between the non-contact extending portion 42 and the separator 23 to a position that covers the mountain fold portion 21d of the curved portion 29a of the negative electrode tab 21c. The coating layer 30 does not reach the negative electrode base end portion 27b of the negative electrode tab group 26.

Here, the manufacture of the coating layer 30 will be described.
The coating layer 30 is formed by a powder jet deposition method which is one of low temperature thermal spraying methods.
As shown in FIG. 2, in the coating layer 30, before the positive electrode 20 and the negative electrode 21 are laminated, the mountain fold portion 20d in the curved portion 29a is formed from the boundary portion between the positive electrode tab 20c and the positive electrode active material layer 20b. It is formed by spraying ceramic particles onto the corresponding covering region R1 up to the covering position. In addition, the coating layer 30 includes the entire area of the non-contact extending portion 42 of the negative electrode active material layer 21b and the curved portion of the non-contact extending portion 42 to the negative electrode tab 21c before the lamination of the positive electrode 20 and the negative electrode 21. It is formed by spraying ceramic particles to the covering region R2 corresponding to the position where the mountain fold portion 21d of 29a is covered.

As shown in FIG. 6, the coating layer 30 is formed by causing the ceramic particles 31 to bite into the surfaces of the positive electrode tab 20c, the negative electrode tab 21c, and the non-contact extension portion 42 of the coating extension portion 40. Each ceramic particle 31 is finely pulverized (crushed), and is closely adhered to another ceramic particle 31 so that an oxide is not present. The average particle diameter of the ceramic particles 31 is, for example, 50 nm to 10 μm.

In this embodiment, the following actions and effects can be obtained.
(1-1) In the present embodiment, the curved portion 29a of the positive electrode tab 20c is covered with the coating layer 30, and the curved portion 29a of the negative electrode tab 21c and the non-contact extending portion 42 in the coating extending portion 40 of the negative electrode 21 are formed. It is covered with the coating layer 30. Since the coating layer 30 is made of a ceramic having a higher Young's modulus than the positive electrode tab 20c and the negative electrode tab 21c, the apparent Young's modulus of the curved portion 29a of the positive electrode tab 20c and the negative electrode tab 21c can be improved. Therefore, the springback amount of the curved portions 29a of the positive electrode tab 20c and the negative electrode tab 21c becomes small. Further, the curved portions 29a of the positive electrode tab 20c and the negative electrode tab 21c have an apparent thickness increased by the coating layer 30. Therefore, the apparent moment of inertia of area of the curved portions 29a of the positive electrode tab 20c and the negative electrode tab 21c increases. The second moment of area is an index indicating the difficulty of bending. Therefore, the curved portions 29a of the positive electrode tab 20c and the negative electrode tab 21c are less likely to bend, and thus the curved portions 29a of the positive electrode tab 20c and the negative electrode tab 21c are less likely to be deformed from the bent state. Therefore, the springback amount of the curved portion of the positive electrode tab 20c and the negative electrode tab 21c becomes small. Therefore, fatigue cracks in the curved portions 29a of the positive electrode tab 20c and the negative electrode tab 21c due to springback can be suppressed.

Further, the coating layer 30 is also provided on the non-contact extending portion 42 of the negative electrode active material layer 21b. Therefore, the strength of the tab-side extending portion 41, which is a portion of the negative electrode active material layer 21b protruding outside the outer edge of the positive electrode active material layer 20b, can be improved. Therefore, the negative electrode active material layer 21b is less likely to bend as compared with the conventional case where only the non-formed portion of the negative electrode is coated with ceramic, and the negative electrode active material layer 21b is separated from the negative electrode metal foil 21a. Can be suppressed. Therefore, peeling of the negative electrode active material layer 21b from the negative electrode metal foil 21a can be suppressed while suppressing fatigue cracks in the curved portions 29a of the positive electrode tab 20c and the negative electrode tab 21c due to springback.

(1-2) The bent portions 29d of the positive electrode tab 20c and the negative electrode tab 21c have the mountain folds 20d and 21d and the valley folds 20e and 21e. Tensile residual stress is generated in the mountain folds 20d and 21d, and compressive residual stress is generated in the valley folds 20e and 21e. It is considered that the springback of the curved portions 29a of the positive electrode tab 20c and the negative electrode tab 21c is mainly due to the tensile residual stress generated in the mountain folds 20d and 21d.

The coating layer 30 covers the mountain folds 20d and 21d of the curved portion 29a of the positive electrode tab 20c and the negative electrode tab 21c. Therefore, compressive stress is applied to the mountain folds 20d and 21d by the coating layer 30. Therefore, the tensile residual stress generated in the curved portion 29a is reduced by the compressive stress of the coating layer 30. Therefore, fatigue cracks in the curved portions 29a of the positive electrode tab 20c and the negative electrode tab 21c due to springback can be suppressed. In particular, since the notch effect of the boundary portion of the coating is mitigated in the coating thickness direction, it is effective in suppressing fatigue cracks.

<Second Embodiment>
A second embodiment in which the power storage device is embodied as a secondary battery will be described below with reference to FIG. 7. The same components as those in the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIG. 7A, in the plurality of positive electrode tabs 20c, both surfaces in the thickness direction of the curved portion 29a are covered with the covering layer 30. The coating layer 30 is provided from a boundary portion with the positive electrode active material layer 20b on a surface of the curved portion 29a of the positive electrode tab 20c where the mountain folded portion 20d is provided to a position that covers the mountain folded portion 20d of the curved portion 29a. .. In addition, the coating layer 30 extends from the boundary with the positive electrode active material layer 20b on the surface of the curved portion 29a of the positive electrode tab 20c on which the valley folded portion 20e is provided to a position that covers the valley folded portion 20e of the curved portion 29a. It is provided.

As shown in FIG. 7B, the non-contact extending portions 42 are both the tab-side extending portions 41 that sandwich the negative electrode metal foil 21a. The non-contact extending portion 42 is the tab-side extending portion 41 that sandwiches the negative electrode metal foil 21a.

The curved portion 29a of the negative electrode tab 21c and the two non-contact extending portions 42 that sandwich the negative electrode metal foil 21a are covered with the coating layer 30. The coating layer 30 is provided between the two non-contact extending portions 42 and the separator 23 to a position that covers the mountain fold portion 21d and the valley fold portion 21e of the curved portion 29a of the negative electrode tab 21c.

According to this embodiment, the same effects as those of the first embodiment can be obtained, and the following effects can be obtained.
(2-1) In the present embodiment, since both surfaces of the curved portion 29a of the positive electrode tab 20c and the negative electrode tab 21c are covered with the coating layer 30, fatigue cracks in the curved portion 29a of the positive electrode tab 20c and the negative electrode tab 21c due to springback. Can be suitably suppressed.

<Third Embodiment>
Hereinafter, a third embodiment in which the power storage device is embodied as a secondary battery will be described with reference to FIG. The same components as those in the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIG. 8A, the coating layer 30 includes a positive electrode bent portion of the positive electrode tab group 25 from the boundary portion with the positive electrode active material layer 20b on the mountain folded portion 20d side surface of the curved portion 29a of the positive electrode tab 20c. It is provided up to the portion 24a.

As shown in FIG. 8B, the coating layer 30 is provided from between the non-contact extending portion 42 and the separator 23 to the negative electrode bent portion 24b of the negative electrode tab group 26.
According to this embodiment, the same effects as those of the first embodiment can be obtained, and the following effects can be obtained.

(3-1) It is considered that springback also occurs in the positive electrode bent portion 24a of the positive electrode tab group 25 and the negative electrode bent portion 24b of the negative electrode tab group 26.
In the present embodiment, the positive electrode bent portion 24a of the positive electrode tab group 25 and the negative electrode bent portion 24b of the negative electrode tab group 26 are covered with the coating layer 30. Therefore, the coating layer 30 improves the apparent Young's modulus of the positive electrode curved portion 24a in the positive electrode tab group 25 and the negative electrode curved portion 24b in the negative electrode tab group 26, and also increases the apparent thickness. Therefore, the springback amount of the positive electrode bent portion 24a of the positive electrode tab group 25 and the negative electrode bent portion 24b of the negative electrode tab group 26 can be reduced, and fatigue fatigue cracks of the positive electrode tab group 25 and the negative electrode tab group 26 can be suppressed.

In addition, each of the above-described embodiments can be modified and implemented as follows. The above embodiments and the following modifications can be implemented in combination with each other within a technically consistent range.

In the third embodiment, the coating layer 30 is provided up to the positive electrode bent portion 24a of the positive electrode tab group 25 and the negative electrode bent portion 24b of the negative electrode tab group 26, but the present invention is not limited to this. For example, the coating layer 30 is provided so as to cover only the mountain folds 20d and 21d of the curved portion 29a, and is provided only on the positive electrode bent portion 24a of the positive electrode tab group 25 and the negative electrode bent portion 24b of the negative electrode tab group 26. You may change to.

In each of the above embodiments, the surface of the curved portion 29a on which the mountain folds 20d and 21d are provided is covered with the coating layer 30, but, for example, the valley folds 20e and 21e of the curved portion 29a are provided. Only the surface may be covered with the coating layer 30.

In each of the above embodiments, the coating layer 30 may be modified so as to cover only the valley folds 20e and 21e of the curved portion 29a.
In the positive electrode 20, the positive electrode active material layer 20b may be present only on one surface of the positive electrode metal foil 20a. In the negative electrode 21, the negative electrode active material layer 21b may be present only on one surface of the negative electrode metal foil 21a. That is, the positive electrode active material layer 20b and the negative electrode active material layer 21b may be provided on at least one of the positive electrode metal foil 20a and the negative electrode metal foil 21a.

The curved portion 29a was not provided in the root portion 29 of the negative electrode tab 21c, which is located at one end in the stacking direction of the electrode assembly 12 among the plurality of negative electrode tabs 21c constituting the negative electrode tab group 26, but is not limited thereto. Absent. For example, the position of forming the negative electrode base end portion 27b of the negative electrode tab group 26 is slightly moved from the present embodiment toward the central portion of the electrode assembly 12 so that the negative electrode tab located at one end of the electrode assembly 12 in the stacking direction is located. A curved portion 29a is also formed on 21c. Also in this case, it is preferable to cover the curved portion 29a with the coating layer 30. The configurations of the positive electrode tab group 25 and the negative electrode tab group 26 may be reversed.

The positive electrode metal foil 20a was an aluminum foil and the negative electrode metal foil 21a was a copper foil, but the invention is not limited to this. The positive electrode metal foil 20a and the negative electrode metal foil 21a may be made of any material as long as it is made of a metal having a high conductivity and a Young's modulus lower than that of the ceramic forming the coating layer 30.

The secondary battery 10 may be a secondary battery other than the lithium ion secondary battery. In short, any material can be used as long as the ions move between the positive electrode active material layer 20b and the negative electrode active material layer 21b, and the charge is transferred.

The power storage device may be applied to another power storage device such as an electric double layer capacitor instead of the secondary battery 10.

10... Secondary battery as power storage device, 11... Case, 12... Electrode assembly, 12a... Tab side end surface, 15... Positive electrode terminal, 16... Negative electrode terminal, 20... Positive electrode, 20a... Metal foil for positive electrode, 20b... Positive electrode Active material layer, 20c... Positive electrode tab, 20d... Mountain fold portion, 21... Negative electrode, 21a... Negative electrode metal foil, 21b... Negative electrode active material layer, 21c... Negative electrode tab, 21d... Mountain fold portion, 23... Separator, 24a... Positive electrode curved portion, 24b... Negative electrode curved portion, 25... Positive electrode tab group, 26... Negative electrode tab group, 27a... Positive electrode base end portion, 27b... Negative electrode base end portion, 28a... Positive electrode extension portion, 28b... Negative electrode extension Part, 29... Root part, 29a... Curved part, 30... Coating layer, 40... Coating extension part, 41... Tab side extension part, 42... Non-contact extension part.

Claims (4)

An electrode assembly in which a plurality of sheet-shaped positive electrodes and a plurality of sheet-shaped negative electrodes are stacked in a state of being insulated by a separator,
A case accommodating the electrode assembly,
The positive electrode terminal and the negative electrode terminal fixed to the case and transmitting and receiving electricity to and from the electrode assembly are provided.
The positive electrode is a sheet-shaped positive electrode metal foil, a positive electrode active material layer provided on at least one of both surfaces of the positive electrode metal foil, and a positive electrode tab protruding from a part of one side of the positive electrode metal foil. And have
The negative electrode is provided on at least one of both surfaces of the sheet-shaped negative electrode metal foil and the negative electrode metal foil, and for the negative electrode having a coating extension part that is outside the outer edge of the positive electrode active material layer. An active material layer, and a negative electrode tab protruding from a part of one side of the negative electrode metal foil,
The electrode assembly includes a positive electrode tab group in which the plurality of positive electrode tabs are gathered together, and a negative electrode tab group in which the plurality of negative electrode tabs are gathered together,
The positive electrode tab group includes a positive electrode base end portion in which the plurality of positive electrode tabs are gathered toward one end in the stacking direction of the electrode assembly, and a positive electrode base end portion from the positive electrode base end portion to the other end in the stacking direction of the electrode assembly. And a positive electrode bent portion that bends, and a stack of the electrode assembly from the side opposite to the positive electrode base end portion of the positive electrode bent portion along the tab-side end surface where the positive electrode tab group and the negative electrode tab group of the electrode assembly are present. A positive electrode extension portion fixed to the positive electrode terminal while extending toward the other end in the direction,
The negative electrode tab group includes a negative electrode base end portion in which a plurality of the negative electrode tabs are gathered toward one end in the stacking direction of the electrode assembly, and a negative electrode base end portion from the other end in the stacking direction of the electrode assembly. And a negative electrode bent portion that bends along the tab-side end surface of the electrode assembly, and extends from the side opposite to the negative electrode base end portion of the negative electrode bent portion toward the other end in the stacking direction of the electrode assembly. A negative electrode extension portion fixed to the negative electrode terminal,
In the plurality of positive electrode tabs and the plurality of negative electrode tabs, the plurality of positive electrode tabs and the plurality of negative electrode tabs are included in the root portion provided closer to the tab side end surface than the positive electrode base end portion and the negative electrode base end portion. Includes the root portion having a curved portion that is bent in a state of being gathered together at one end in the stacking direction of the electrode assembly,
In the positive electrode tab, at least one surface in the thickness direction of the curved portion is covered with a coating layer made of ceramic having a higher Young's modulus than the positive electrode tab and the negative electrode tab,
The negative electrode having the negative electrode tab in which the curved portion is formed includes a tab-side extending portion as the coating extending portion along one protruding side of the negative electrode tab among the coating extending portions, Among the tab-side extending portion, the tab-side extending portion is a non-contact extending portion that does not contact the separator,
In the negative electrode tab, the curved portion and the non-contact extending portion are covered with the coating layer, which is an electric storage device. The power storage device according to claim 1, wherein the coating layer covers a mountain fold portion that is bent so that the curved portion is a mountain fold. The power storage device according to claim 1, wherein the coating layer is provided on both surfaces in the thickness direction of the curved portion. The said coating layer is provided even to the said positive electrode curved part in the said positive electrode tab group and the said negative electrode curved part in the said negative electrode tab group, The any one of the Claims 1-3 characterized by the above-mentioned. Power storage device.