JP6036107B2 - Electricity storage element - Google Patents

Description

  In the present invention, electrode plates each having an active material layer formed on the surface and separators are alternately stacked, and the separator extends at least at one end of the electrode plate from the edge of the electrode plate. The present invention relates to a power storage element.

Such an electric storage element has a separator between the electrode plate on which the positive electrode active material layer is formed and the electrode plate on which the negative electrode active material layer is formed. The movement of ions by infiltration is ensured.
In many cases, the separator is formed of a resin. Therefore, as described in Patent Document 1 below, when the power storage element becomes high temperature, the separator may contract. When the separator contracts, the active materials contact each other or the active material and the electrode plate of the counter electrode at the contracted portion, thereby causing a short circuit failure.
As a technique for suppressing such shrinkage of the separator, a technique for forming a shrinkage inhibiting layer mainly composed of an inorganic compound on the surface of the separator is also considered.

JP 2007-073317 A

However, even if a method for forming a shrinkage suppression layer on the surface of the separator is used, although there is a certain degree of shrinkage suppression effect, depending on the temperature of the power storage element, the shrinkage suppression effect is not always sufficient. May contact the negative electrode plate and cause a short-circuit failure.
This invention is made | formed in view of this situation, The objective is to fully suppress the shrinkage | contraction of a separator at the time of high temperature, and to improve safety | security.

  According to a first aspect of the present application, an electrode plate having an active material layer formed on a surface and a separator are alternately stacked, and the separator is at least at one end of the electrode plate from an edge of the electrode plate. In the power storage element that also extends, the separator has a coating layer that is coated with a coating material, and a portion that extends beyond the edge of the electrode plate in the separator is not coated with the coating material. An uncovered portion is disposed.

That is, the separators adjacent in the stacking direction are arranged in a separated state in the stacking direction at least in a state where the power storage element is operating normally.
In the state where the power storage element is operating normally, as described above, the end portions of the separators adjacent in the stacking direction remain separated in the stacking direction, but the power storage element is in an abnormally high temperature state. The ends are welded together.
However, this welding does not occur effectively in a simple configuration in which the electrode plate is simply sandwiched between the separators, and the surface of the separator is covered with the above-mentioned coating material in order to realize effective welding between the separator ends. Cover.
In a simple configuration in which the electrode plate is sandwiched between the separators without the covering material, the separators that are adjacent to each other in the stacking direction have a rapid contraction rate when the storage element is in a high temperature state that deviates from the normal use state. Even if the ends of each of the electrodes shrink toward the inner side of the electric storage element, or even if the ends are slightly welded, the separator cannot resist the force that the separator tries to shrink. End up.

Therefore, a coating material is coated on the surface of the separator to reduce the shrinkage rate of the separator in the high temperature state.
Further, the region of the separator covered with the coating material is located between the separator base materials and hinders the welding of the separator. A region where the covering material is not covered is set in the extending portion.
As a result, when the power storage element is in an abnormally high temperature state, the end portions of the separators adjacent in the stacking direction are welded to each other while the separator shrinkage is suppressed by the coating material coated on the separator surface. It becomes a shape. The bag-shaped portion of the separator comes into contact with the edge of the electrode plate and prevents further contraction of the separator.

  According to the present invention, the shrinkage of the separator at a high temperature can be sufficiently suppressed, and the safety of the power storage element can be improved.

1 is an external perspective view of a secondary battery according to an embodiment of the present invention. The perspective view which shows the inside of the secondary battery concerning embodiment of this invention. The perspective view which shows the structure of the electric power generation element concerning embodiment of this invention. The perspective view which shows the manufacturing process of the secondary battery concerning embodiment of this invention. The perspective view which shows the manufacturing process of the secondary battery concerning embodiment of this invention. The expanded sectional view which shows the lamination | stacking state of the electric power generation element concerning embodiment of this invention The expanded sectional view which shows the lamination | stacking state of the electric power generation element concerning embodiment of this invention The expanded sectional view which shows the lamination | stacking state of the electric power generation element concerning embodiment of this invention The expanded sectional view which shows the lamination | stacking state of the electric power generation element concerning another embodiment of this invention

Hereinafter, an embodiment in which a power storage element of the present invention is configured as a secondary battery will be described with reference to the drawings.
In the present embodiment, a nonaqueous electrolyte secondary battery (more specifically, a lithium ion battery) will be described as an example of the secondary battery.

As shown in the perspective view of FIG. 1, the nonaqueous electrolyte secondary battery RB includes a battery casing BC (hereinafter referred to as “casing”) formed by welding a cover 1 on the open surface of a can 1. BC ”). The lid portion 2 is formed of a strip-shaped rectangular plate material, and a terminal bolt 5 that is a positive electrode terminal and a terminal bolt 7 that is a negative electrode terminal are attached to a surface on the outer side of the casing BC. It has been.
The can 1 is a flat rectangular parallelepiped in accordance with the shape of the lid portion 2, and thus has a flat and substantially rectangular parallelepiped shape as a whole of the casing BC, and the internal space of the casing BC is also flat and substantially rectangular. It has become.

On the inner side of the casing BC, the power generation element 3 and current collectors 4 and 6 indicated by a two-dot chain line in FIG. 2 are housed and arranged in a state of being partially immersed in the electrolyte. FIG. 2 shows the inner side of the casing BC as a perspective view looking up from the lower side with the can 1 removed.
The current collectors 4 and 6 are members for electrically connecting the power generation element 3 and the terminal bolts 5 and 7, and both are formed of a conductor.
The current collector 4 and the current collector 6 have a relationship in which substantially the same shape is arranged symmetrically, but the materials are different, and the current collector 4 on the positive electrode side is mainly composed of aluminum. The current collector 6 on the negative electrode side is formed of a material mainly composed of copper.

  The schematic shape of the current collectors 4 and 6 is such that the above-described metal material plate-like member is bent and formed in a posture along the side surface on the short side of the casing BC to have a substantially L shape. A portion extending along the surface of the lid portion 2 that is an arrangement surface of the lid portion, and a vertical posture portion that is bent 90 degrees downward near the longitudinal end portion of the lid portion 2 and extends in the normal direction of the lid portion 2. It has a continuous shape. Bifurcated connecting portions 4a and 6a for connecting to the power generation element 3 are formed by bending the current collectors 4 and 6 to the power generation element 3 side.

As shown in FIG. 3, the power generating element 3 includes a pair of electrode plates 31, 32 each composed of a foil-like positive electrode plate 31 formed in a long strip shape and a foil-like negative electrode plate 32 formed in a long strip shape. The active material layers 31a and 32a are formed on both the front and back surfaces by coating, and are stacked in a state where the separators 33 formed in a long belt-like sheet are sandwiched between the active material layers 31a and 32a. Has been. That is, the electrode plates 31 and 32 and the separators 33 are alternately stacked. In this embodiment, as an active material to form on the positive electrode side of the electrode plate (foil positive electrode plate 31), Ni, active material _{(LiNi x} ternary containing Co and _{Mn Mn y Co z O 2,} x + y + z = 1) is used.

The foil-like positive electrode plate 31 and the like are wound around a flat winding axis, and the wound one has a flat shape in accordance with the shape of the battery casing BC. In FIG. 3, the application area | region of an active material is shown with the double diagonal line.
The separator 33 is formed as a resin microporous film, and is one surface of the separator 33 facing the positive and negative electrode plates (more specifically, the surface facing the foil-like positive electrode plate 31 which is a positive electrode plate). ) Is coated with a thin layer of a coating material made of a high-resistance inorganic compound mainly composed of aluminum oxide or silicon oxide. The inorganic compound coating layer (hereinafter referred to as “inorganic compound layer”) formed on the surface of the separator 33 is oxidized by the resin surface of the separator 33 being in direct contact with the high-potential positive electrode active material. The purpose is to prevent this from happening. Therefore, it is not necessary to coat the inorganic compound layer on the surface of the separator 33 that is in contact with the active material layer on the foil-like negative electrode plate 32 side, and as described above, the positive electrode plate (foil-like positive electrode plate 31) and An inorganic compound layer is formed only on the opposite surface. As described above, in this embodiment, since LiNi _x Mn _y Co _z O ₂ is used as the positive electrode active material, the positive electrode potential is higher than when a positive electrode active material such as lithium iron phosphate is used. It is particularly effective to form the inorganic compound layer on the surface of the separator 33.
The foil-shaped positive electrode plate 31 is formed of the same material as the main component of aluminum as the current collector 4, and the foil-shaped negative electrode plate 32 is formed of the same material as the main component of copper as the current collector 6. Has been.

The formation state of the active material layers 31a and 32a in the foil-like positive electrode plate 31 and the foil-like negative electrode plate 32 is set to a narrow band-like region where the active material layers 31a and 32a are not formed by coating at the respective end portions in the width direction. These regions are uncoated portions 3a and 3b for connection to the current collectors 4 and 6.
The uncoated part 3a of the foil-like positive electrode plate 31 and the uncoated part 3b of the foil-like negative electrode plate 32 are opposite to each other in the width direction (the direction indicated by arrow A in FIG. 3) of the foil-like positive electrode plate 31 and the like. The uncoated portion 3 a of the foil-like positive electrode plate 31 is located at the end of the (reverse side) and protrudes in the width direction from the edges of the foil-like negative electrode plate 32 and the separator 33, and the foil-like negative electrode plate 32. The uncoated portion 3 b protrudes in the width direction from the edges of the foil-like positive electrode plate 31 and the separator 33. Therefore, in the state where the foil-like positive electrode plate 31, the foil-like negative electrode plate 32 and the separator 33 are wound, as shown in FIG. 3, the uncoated portions 3a and 3b are located at both ends in the winding axis direction. Moreover, the length of the separator 33 in the width direction is set to be slightly wider than the active material application width of the foil-like positive electrode plate 31 and the foil-like negative electrode plate 32, and the uncoated portion of the foil-like positive electrode plate 31. It arrange | positions ranging from the edge part located in the uncoated part 3b side of the foil-shaped negative electrode plate 32 to the edge part located in the 3a side.

The joining mode between the uncoated portions 3a and 3b of the power generating element 3 and the connecting portions 4a and 6a of the current collectors 4 and 6 will be described in more detail while following the manufacturing process.
FIG. 6 shows a schematic laminated section in which a part of the foil-like positive electrode plate 31, the foil-like negative electrode plate 32, and the separator 33 that have been laminated by winding is extracted. 6 shows an end of the negative electrode uncoated portion 3b side in a state where the foil-like positive electrode plate 31 or the like is wound as shown in FIG. 3 in the manufacturing process of the secondary battery RB. In order to make the drawing easy to see, the description of the parallel oblique lines indicating the cross section is omitted.
As described above, the separator 33 is set to be slightly wider than the existing width of the active material layers 31a and 32a in the width direction (the direction indicated by the arrow A in FIG. 3), and the uncoated portion on the negative electrode side. Also on the side where 3b is present, the end in the width direction of the separator 33 extends in the width direction from the edges of the active material layers 31a and 32a. Of course, as is apparent from FIG. 3, the extending length of the separator 33 is sufficiently smaller than the width of the uncoated portion 3b.
Further, the above-described inorganic compound layer 33 a is formed on the positive electrode side surface of the separator 33.
However, the inorganic compound layer 33 a is not formed on the entire surface of the separator 33 on the positive electrode active material layer 31 a side, but rather than the edge of the foil-like positive electrode plate 31 at the end in the width direction of the separator 33. The extending portion is provided with an uncoated portion in which the resin surface of the separator 33 is exposed without forming the inorganic compound layer 33a.

The power generating element 3 in a state wound as described above and the connection portions 4a and 6a of the current collectors 4 and 6 are connected with a pair of welding auxiliary plates 21 shown in FIG. 4 interposed therebetween.
In FIG. 4, although the welding auxiliary plate 21 for joining with the uncoated part 3b and the connection part 6a of a negative electrode is shown, welding for joining with the uncoated part 3a and the connection part 4a on the positive electrode side is shown. The auxiliary plate 21 has substantially the same shape, and the welding auxiliary plate 21 on the negative electrode side is formed of the same material as the main component of the current collector 6 and the foil-like negative electrode plate 32, and the welding auxiliary plate 21 on the positive electrode side. Is formed of the same material as the main component of the current collector 4 and the foil-like positive electrode plate 31.

Each of the welding auxiliary plates 21 provided as a pair on each of the positive electrode side and the negative electrode side is formed by bending a thin plate member into a U shape with a narrow interval between the opposing surfaces. As shown in FIG. 4, the uncoated portions 3a and 3b in a bundled state are sandwiched and fixed by caulking.
In the state where the uncoated portions 3a and 3b are bundled as shown in FIG. 4, the separator 33 positioned between the uncoated portions 3b is as shown in FIG. The end portions of the separators 33 adjacent to each other in the stacking direction come into contact with each other in the uncoated portion 3b. Although in contact, they are separated from each other in the stacking direction.
In addition, in FIG. 7, although the uncoated part 3b side of a negative electrode is shown, it will be in the same state also on the uncoated part 3a side of a positive electrode.

The current collectors 4 and 6 to be joined to the uncoated portions 3a and 3b of the power generation element 3 are in a state of being assembled to the lid portion 2 in advance.
The terminal bolt 5 on the positive electrode side attached to the lid 2 is electrically connected to the current collector 4 on the positive electrode side, and the terminal bolt 7 on the negative electrode side is electrically connected to the current collector 6 on the negative electrode side. Yes.
The current collector 4 on the positive electrode side is electrically connected to the terminal bolt 5 via a rivet 8 integrally formed on the head side of the terminal bolt 5, and the rivet 8 includes the current collector 4, the current collector 4, and the current collector 4. Lower gasket 12 for electrical insulation between rivet 8 and lid 2, upper gasket 11 for electrical insulation between lid 2 and terminal bolt 5 including lid 2 and rivet 8 and lid 2 In this state, the current collector 4 is caulked at the inner end portion of the casing BC, thereby fixing the current collector 4 to the lid portion 2.
The negative electrode side has the same configuration, and the negative electrode side current collector 6 is electrically connected to the terminal bolt 7 via a rivet 15 integrally formed on the head side of the terminal bolt 7. The electrical current between the terminal 6 including the electrical current 6, the current collector 6 and the lower gasket 18 for electrical insulation between the rivet 15 and the lid 2, the lid 2 and the rivet 15 and the lid 2 The current collector 6 is fixed to the lid portion 2 by being caulked at the inner end of the casing BC in a state of passing through the upper gasket 17 for insulation.

As shown in FIG. 5, a pair of auxiliary welding plates sandwiching the uncoated portions 3a and 3b as shown in FIG. 5 in the connecting portions 4a and 6a of the current collectors 4 and 6 assembled on the lid 2 side as described above. 21. The welding auxiliary plate 21, the uncoated portions 3a and 3b and the connection portions 4a and 6a of the current collectors 4 and 6 sandwiched between the welding auxiliary plates 21 and Weld by sonic welding.
More specifically, an anvil is arranged on the side of the connecting portions 4a and 6a, and a horn is pressed at a position indicated by a two-dot chain line C in FIG.
As described above, the current collectors 4 and 6 and the power generation element 3 joined together are inserted into the can 1, and the edge of the lid 2 and the open end of the can 1 are welded.

The secondary battery RB having the above configuration is not so hot in a normal use state, and the separator 33 of the power generation element 3 maintains the state shown in FIG.
However, for example, when the secondary battery RB is externally short-circuited with a tool or the like, or an accident occurs in a device or the like equipped with the secondary battery RB, an extremely strong external force is applied to the secondary battery RB. In such a case, for example, there may be an abnormally high temperature state such as 140 ° C. or higher.
In such an abnormally high temperature state, the end portions of the separators 33 adjacent in the stacking direction are welded by the abnormally high temperature, as shown in FIG. As shown in FIG. 7, the end portions of the separators 33 adjacent in the stacking direction are in contact with each other even in a normal state, so that this welding is particularly likely to occur.

8 is a separator 33 arranged with the foil-like positive electrode plate 31 interposed therebetween, and in the case where the inorganic compound layer 33a is formed on the entire surface of the separator 33 on the foil-like positive electrode 31 side. The inorganic compound layer 33a obstructs the welding of the end portions of the separators 33 adjacent in the stacking direction. However, as shown in FIG. 8 and the like, the width direction end portion of the separator 33 is replaced with the inorganic compound layer 33a. By setting it as the area | region which does not form, the edge part of the separator 33 adjacent in the lamination direction is welded in the area | region which has not formed the inorganic compound layer 33a.
At this time, the inorganic compound layer 33a formed on the surface of the separator 33 has a function of suppressing the shrinkage of the separator 33 due to an abnormally high temperature, and before the end portions of the separator 33 are welded due to the abnormally high temperature. In addition, a situation in which each separator 33 contracts greatly and is drawn into the power generation element 3 is avoided.

When the end portions of the separator 33 are welded as shown in FIG. 8, even if the separator 33 further shrinks as shown by the arrow B due to the abnormal high temperature, the welded portion is a foil-like positive electrode plate. It is caught by the edge part of 31 and the further contraction of the separator 33 is prevented, and the short circuit failure accompanying the contraction of the separator 33 can be avoided.
In order to prevent the shrinkage of the separator 33 by welding the end portions of the separator 33, it is conceivable that the end portions of the separator 33 are welded in advance in the manufacturing process of the secondary battery RB.
However, considering that the electrolytic solution is injected after the end portions of the separator 33 are welded to each other, the bag-like separator 33 delays the entry of the electrolytic solution into the power generation element 3, and the electrolytic solution This will reduce the efficiency of liquid injection work.
In this regard, as described above, the above-described configuration in which the end portions of the separator 33 are welded for the first time when the secondary battery RB reaches an abnormally high temperature does not reduce the electrolyte injection efficiency.

  The above describes the state of the negative electrode on the uncoated portion 3b side. On the uncoated portion 3a side of the positive electrode, the surface of the separator 33 on which the inorganic compound layer 33a is not formed sandwiches the foil-shaped negative electrode plate 32. In the same manner, the ends of the separators 33 adjacent in the stacking direction are welded to each other on the uncoated part 3a side of the positive electrode, and the separators are separated by interference with the end of the foil-like negative electrode plate 32. 33 contraction is prevented.

[Another embodiment]
Hereinafter, other embodiments of the present invention will be listed.
(1) In the above embodiment, the end portions of the separator 33 are in contact with each other even in a normal state by bundling the uncoated portions 3a and 3b, and welding is likely to occur when an abnormally high temperature state occurs. However, as described above, there are various methods for bringing the separators to be welded into contact with each other even in a normal state. For example, as shown in FIG. 9 which is a laminated sectional view corresponding to FIG. Next, the separator 33 extending from the edge of the electrode plate (foil-like positive electrode plate 31 in FIG. 9) is pressed by a tape member 35 formed of an electrically insulating material, so that they are adjacent in the stacking direction. It is good also as a structure which makes the edge parts of the separator 33 contact.
Furthermore, it is good also as a structure which arrange | positions the housing | casing BC of the secondary battery RB in the position of the tape member 35 in FIG. 9, and presses the separator 33 with housing | casing BC itself.
In addition, it is not necessarily an essential condition that the end portions of the separator are in contact with each other in a normal state, and it is sufficient that the separators are disposed at a position sufficiently close to the extent that welding can occur.

(2) In the above embodiment, the uncoated portions 3a and 3b are arranged at the widthwise ends of the positive and negative electrode plates (the foil-shaped positive plate 31 and the foil-shaped negative plate), and the uncoated portions. Although the configuration in which the electrical connection with the current collectors 4 and 6 is illustrated by 3a and 3b is illustrated, the present invention can also be applied to the power generation element 3 having no uncoated portions 3a and 3b.
(3) In the above embodiment, the winding type power generating element 3 in which a long belt-like electrode plate or separator is wound and laminated is illustrated, but a simple sheet-like positive and negative electrode plate and separator, The present invention can also be applied to a power generation element of a type in which a plurality of layers are alternately stacked.
(4) In the above embodiment, the non-aqueous electrolyte secondary battery RB is described as an example of the power storage element, but the present invention can be applied to various power storage elements such as capacitors.

(5) In the above embodiment, the inorganic compound layer 33a is formed only on the surface of the separator 33 on the positive electrode active material layer 31a side, but the above three-component active material is used as the positive electrode active material or phosphorous is used. Regardless of whether an active material such as lithium iron oxide is used, an inorganic compound layer 33a may be formed on both sides of the separator 33 to increase the shrinkage suppressing effect of the separator 33.
(6) In the above embodiment, the case where the three-component active material is used as the positive electrode active material is exemplified, but a so-called iron-based active material such as lithium iron phosphate may be used.
When the iron-based active material is used, the oxidation of the separator 33 by the positive electrode active material is difficult to proceed. Therefore, it is not always necessary to form the inorganic compound layer 33a on the surface of the separator 33 on the positive electrode active material layer 31a side. The inorganic compound layer 33a may be formed on the surface on the negative electrode active material layer 32a side of 33, and may be formed on both the front and back surfaces of the separator 33 as described above.

31a, 32a Active material layer 31, 32 Electrode plate 33 Separator 33a Coating layer

Claims (1)

Electrode plates with active material layers formed on the surface and separators are alternately stacked,
The separator is a power storage element extending at least at one end of the electrode plate from the edge of the electrode plate,
The electrode plate comprises a foil-like positive electrode plate formed in a long strip shape and a foil-like negative electrode plate formed in a long strip shape, and is wound with the long strip-shaped separator interposed therebetween,
The separator extends in the winding axis direction of the separator from the edge of the electrode plate,
The separator has a coating layer coated with a coating material,
A portion that extends beyond the edge of the electrode plate in the separator is disposed with a non-covering portion that does not cover the covering material ,
The electrical storage element with which the edge parts side of the said separator adjacent in the lamination direction is contacting in the said non-coating part .

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