Battery cell

To reduce influence of external force on a current collection tab lead and a current collection tab in a laminated cell type battery. A single film of an exterior body contacts and covers a top surface, a bottom surface, and two side surfaces of a battery perpendicular to an end surface of the battery from which a current collection tab and a current collection tab lead are provided to extend, covers the end surface of the battery from which the current collection tab and the current collection tab lead protrude, and is folded in from both short sides of the end surface such that triangular pyramid-shaped spaces are formed on both sides. A reinforcement member is arranged in and joined to each triangular pyramid-shaped space.

This application is based on and claims the benefit of priority from Japanese Patent Application 2021-024586, filed on 18 Feb. 2021, the content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a battery cell, and particularly relates to a battery cell sealed by an exterior body.

Related Art

In recent years, a demand for high-capacity high-power battery devices has rapidly grown due to popularization of various types of electric/electronic equipment with a variety of sizes, such as an automobile, a personal computer, and a mobile phone. Examples of these battery devices include a liquid battery cell using, as an electrolyte, an organic electrolytic solution between positive and negative electrodes and a solid-state battery cell using a fire-retardant solid electrolyte instead of using the organic electrolytic solution as the electrolyte.

For these battery devices, a laminated cell type battery cell configured such that a battery is sealed in a plate shape with the battery being covered with a laminated film (an exterior body) has been known. For a purpose such as an EV or an HEV, a battery cell assembly configured such that multiple laminated cell type battery cells as described above are arranged and housed in a case has been used. The battery is covered with the exterior body so that entry of atmospheric air into the battery can be prevented (e.g., Japanese Unexamined Patent Application, Publication No. 2012-169204). Note that in the present specification, the “battery” indicates a member including an electronic element stack having positive and negative electrodes and an electrolyte, a current collection tab, and a current collection tab lead, and one sealed with a battery being covered with a laminated film (an exterior body) will be referred to as a “battery cell”.

For the purpose of effectively improving the volumetric energy density of a battery module while maintaining sealability of a laminated film (an exterior body), a battery cell including an exterior body configured such that a single film is folded to house a battery is disclosed (WO2019/188825). According to WO2019/188825, this battery cell can effectively improve the volumetric energy density of the battery module while maintaining the sealability of the exterior body. Moreover, WO2019/188825 also describes a configuration in which a current collection tab lead is housed with the current collection tab lead being vertically sandwiched by the exterior body in the battery cell.Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2012-169204Patent Document 2: WO2019/188825

SUMMARY OF THE INVENTION

In a configuration in which a current collection tab and a current collection tab lead are housed with the current collection tab and the current collection tab lead being vertically sandwiched by an exterior body in a laminated cell type battery cell, there is a probability that when external force is applied to a location where the current collection tab and the current collection tab lead are housed, an electrode is cracked due to stress applied to the current collection tab and the current collection tab lead. In this case, the strength of a film of the exterior body itself is weak, and for this reason, an interior battery cannot be sufficiently protected from the external force only with the film of the exterior body.

An object of the present invention is to reduce, in a configuration in which a current collection tab and a current collection tab lead are housed with the current collection tab and the current collection tab lead being vertically sandwiched by an exterior body in a laminated cell type battery, influence of external force on the current collection tab and the current collection tab lead even in a case where the external force is applied to a location where the current collection tab and the current collection tab lead are housed.

To solve the above-described problems, the present invention is directed to a battery cell having a single film of an exterior body including: a portion contacting and covering a top surface, a bottom surface, and two side surfaces of a battery perpendicular to an end surface of the battery from which a current collection tab and a current collection tab lead are provided to extend; a portion covering the end surface of the battery, from which the current collection tab and the current collection tab lead protrude, folded in from both short sides of the end surface such that triangular pyramid-shaped spaces are formed on both sides, and folded from both long sides of the end surface such that the portion is entirely formed in a triangular prism shape to cover the end surface; and a portion provided to further extend in an axial direction from the end surface-covering portion and having opposing upper and lower surfaces joined to hold the current collection tab and the current collection tab lead between the upper and lower surfaces. The battery cell further has a reinforcement member provided in and joined to each triangular pyramid-shaped space.

The reinforcement member is arranged in and joined to each of the triangular pyramid-shaped spaces on both sides, the triangular pyramid-shaped spaces being formed in such a manner that the portion covering the end surface of the battery from which the current collection tab and the current collection tab lead protrude is folded in from both short sides of the end surface. With this configuration, even in a case where external force is applied to a location where the current collection tab and the current collection tab lead are housed, influence of the external force on the current collection tab and the current collection tab lead can be reduced, and a problem that an electrode is cracked due to stress applied to the current collection tab and the current collection tab lead can be reduced.

In an aspect of the present invention, in this case, the exterior body is formed of the single film.

Since the exterior body is formed of the single film, the number of joint portions can be reduced as much as possible upon packaging and sealability can be enhanced.

In an aspect of the present invention, in this case, the battery is an all-solid-state battery cell including a stack with a solid electrolyte.

The all-solid-state battery cell is brittle and easily damaged particularly at a corner portion and an end surface. For this reason, in the present invention, the reinforcement member is arranged in and joined to each of the triangular pyramid-shaped spaces on both sides at the portion covering the end surface of the battery from which the current collection tab and the current collection tab lead protrude. Thus, the structure capable of reducing the influence of the external force on the current collection tab and the current collection tab lead even in a case where the external force is applied to the location where the current collection tab and the current collection tab lead are housed is effective for application to the all-solid-state battery cell having the end surface from which the current collection tab and the current collection tab lead protrude.

In an aspect of the present invention, in this case, the reinforcement member is a four-sided body opening on one side, the four-sided body having three surfaces including one triangular surface to be joined to the end surface, from which the current collection tab and the current collection tab lead extend, in the triangular pyramid-shaped space and two surfaces to be joined to two surfaces of the exterior body forming the triangular pyramid-shaped space without being joined to the end surface upon folding.

It can be said that such a reinforcement member has the most basic configuration for reinforcing three surfaces in the space as the reinforcement member for each of the triangular pyramid-shaped spaces on both sides, the triangular pyramid-shaped spaces being formed in such a manner that the portion covering the end surface of the battery from which the current collection tab and the current collection tab lead protrude is folded in from both short sides of the end surface. The relatively-lightweight reinforcement member can efficiently reinforce the entirety of three surfaces forming the triangular pyramid-shaped space.

In an aspect of the present invention, in this case, the reinforcement member is a hollow four-sided body having four surfaces defining four surfaces in the triangular pyramid-shaped space.

A planar reinforcement portion closing the triangular pyramid-shaped space is added to the four-sided reinforcement member opening on one side. Thus, the function of the reinforcement member can be more enhanced, and the probability that the external force enters the triangular pyramid-shaped space and acts on three surfaces defining the triangular pyramid-shaped space and the force of expanding the triangular pyramid-shaped space acts accordingly can be prevented.

In an aspect of the present invention, in this case, the reinforcement member is a solid four-sided body having four surfaces defining four surfaces in the triangular pyramid-shaped space.

Needless to say, reinforcement force is increased as compared to the hollow reinforcement member. However, because of the solid member, the reinforcement member is increased in weight and requires many materials (resources). It is effective when such a reinforcement member is employed in a case where the necessity of reinforcing the end surface of the battery from which the current collection tab and the current collection tab lead protrude.

In an aspect of the present invention, in this case, the reinforcement member is a frame body including six linear frames along six sides of the triangular pyramid-shaped space.

Such a reinforcement member is a lightest member as the reinforcement member for the triangular pyramid-shaped spaces on both sides, the triangular pyramid-shaped spaces being formed in such a manner that the portion covering the end surface of the battery from which the current collection tab and the current collection tab lead protrude is folded in from both short sides of the end surface. Thus, this reinforcement member does not require many materials (resources). Although reinforcement is necessary, it is effective when such a reinforcement member is employed in a case where a weight increase due to reinforcement needs to be suppressed as much as possible.

In an aspect of the present invention, in this case, the reinforcement member includes a plurality of reinforcement members combined and integrally joined to fix the positions of a plurality of battery cells when the plurality of battery cells is stacked on each other.

In a case where the reinforcement members of the present invention are integrally connected to each other, the integrated reinforcement members are inserted into and joined to the triangular pyramid-shaped spaces at four upper, lower, right, and left (upper right, upper left, lower right, and lower left) locations of each of the battery cell stacked on each other from the front side to the back side in the horizontal direction in module formation. In this manner, the stacked battery cells can be joined to each other with the positions of these battery cells being fixed. That is, the reinforcement members for the battery cells of the present invention can function as position fixing members in a case where the battery cells are stacked on each other.

As described above, the present invention has the following advantageous effects. The reinforcement member is arranged in and joined to each of the triangular pyramid-shaped spaces on both sides, the triangular pyramid-shaped spaces being formed in such a manner that the exterior body housing the battery from which the current collection tab and the current collection tab lead protrude is folded in from both short sides of the end surface of the battery from which the current collection tab and the current collection tab lead protrude. With this configuration, even in a case where the external force is applied to the location where the current collection tab and the current collection tab lead are housed, a problem that the external force influences the end surface and also influences the current collection tab and the current collection tab lead and an electrode connected to the current collection tab and the current collection tab lead is cracked due to the stress applied to the current collection tab and the current collection tab lead can be reduced.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

A battery1of the present invention is an all-solid-state battery in the embodiment, and is in a rectangular parallelepiped shape as shown inFIG.1. The battery1has six surfaces including a top surface11a, a bottom surface11b, side surfaces12a,12b, and end surfaces13a,13b. Assuming that a center axis15connects the centers of the end surfaces13a,13bto each other, each of current collection tabs/current collection tab leads14a,14bis provided to extend in the direction of the center axis15from a corresponding one of the end surfaces13a,13b. The all-solid-state battery is brittle and easily damaged particularly at a corner portion and a surface portion (an end surface portion), and for this reason, is more suitable for application of the configuration of each embodiment of the present invention.

FIG.2shows a battery cell2configured such that the battery1of the present invention is packaged in an exterior body3(FIG.3) with the battery1being covered with the exterior body3. In the battery cell2, a top surface21a, a bottom surface21b, and side surfaces22a,22bare defined corresponding to the battery1. Portions corresponding to the end surfaces13a,13bof the battery1are end surface folding portions23a-1,23a-2,23b-1,23b-2in such a form that the exterior body3is folded, and have appearances in a triangular prism shape. At the end surface folding portions23a-1,23a-2,23b-1,23b-2, the total of four triangular pyramid-shaped spaces25a-1,25a-2,25b-1,25b-2formed by folding-in of the portions23a-1,23a-2,23b-1,23b-2from side surface22a,22bsides are formed two on each side. Current collection tab/current collection tab lead housing portions24a-1,24a-2,24b-1,24b-2vertically sandwiching and housing the current collection tabs/current collection tab leads14a,14bare provided to extend in the direction of the center axis15from the end surface folding portions23a-1,23a-2,23b-1,23b-2.

FIG.3shows a development view of the exterior body3. The exterior body3has a top surface covering portion31aand a bottom surface covering portion31bas portions each covering the top surface11aand the bottom surface11bof the battery1, has a side surface covering portion32aas a portion covering the side surface12a, and has side surface covering portions32b-1,32b-2as portions covering the side surface12b. The side surface covering portions32b-1,32b-2are joint portions overlapping with and joined to each other when the battery1is covered with the exterior body3. Thus, the side surface12aof the battery1is doubly covered with the side surface covering portions32b-1,32b-2of the exterior body3.

As portions covering the end surfaces13a,13bof the battery1, end surface covering portions33a-1,33a-2,33b-1,33b-2forming the triangular prism-shaped end surface folding portions23a-1,23a-2,23b-1,23b-2of the battery cell2in the form that the exterior body3is folded are provided corresponding to an upper-lower direction of the end surface on each side. As extensions of the end surface covering portions33a-1,33a-2,33b-1,33b-2in the center axis15direction, current collection tab/current collection tab lead sandwiching portions34a-1,34a-2,34b-1,34b-2vertically sandwiching the current collection tabs and the current collection tab leads on both sides are provided. As portions forming the triangular pyramid-shaped spaces25a-1,25a-2,25b-1,25b-2formed folded in from the side surface22a,22bsides, triangular pyramid-shaped space formation portions35a-1,35a-21,35a-22,35b-1,35b-21,35b-22are formed. The triangular pyramid-shaped space formation portions35a-21,35a-22overlap with each other to form the triangular pyramid-shaped space by double layers of the film of the exterior body3, and the triangular pyramid-shaped space formation portions35b-21,35b-22overlap with each other to form the triangular pyramid-shaped space by double layers of the film of the exterior body3.

Note that the exterior body3is formed of the single film as described above so that the number of joint portions can be reduced as much as possible upon covering and packaging of the battery1and sealability can be enhanced accordingly. The exterior body3as shown in the development view ofFIG.3is suitable for covering and packaging the battery1configured such that the current collection tabs and the current collection tab leads protrude from the end surfaces ofFIG.1, particularly the all-solid-state battery which is brittle and easily damaged at the end surface or corner portion. With the exterior body3of the development view ofFIG.3formed of the single film, the efficiency of manufacturing the battery cell2is improved.

As shown inFIG.4, in one embodiment of the present invention, reinforcement members4are arranged in and joined to the shaded triangular pyramid-shaped spaces at the end portions. The reinforcement members4include those provided on at least some surfaces or sides forming the triangular pyramid-shaped spaces25a-1,25a-2,25b-1,25b-2. The reinforcement members4are arranged in and joined to the triangular pyramid-shaped spaces25a-1,25a-2,25b-1,25b-2so that even in a case where external force is applied to locations where the current collection tabs and the current collection tab leads are housed, influence of such external force on the current collection tabs and the current collection tab leads can be reduced and a problem that the battery is cracked due to stress applied to the current collection tabs and the current collection tab leads can be reduced.

One example of the reinforcement member4in one embodiment of the present invention is a four-sided reinforcement member41opening on one side as shown inFIG.5. The reinforcement member41has three surfaces including one triangular surface to be joined to the end surface13a,13bof the battery1, from which the current collection tabs and the current collection tab leads protrude, in the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2and two surfaces to be joined to two surfaces of the exterior body3forming the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2without being joined to the end surface13a,13bupon folding. This four-sided reinforcement member41opening on one side has the most basic configuration among the reinforcement members4for reinforcing three surfaces in each of the triangular pyramid-shaped spaces25a-1,25a-2,25b-1,25b-2, and is relatively lightweight and can efficiently reinforce the entirety of three surfaces defining each of the triangular pyramid-shaped spaces25a-1,25a-2,25b-1,25b-2.

The four-sided reinforcement member41opening on one side can be, as shown inFIGS.6to8, a reinforcement member41′ in a further-developed form. For the reinforcement member41′ in the developed form,FIG.6shows a perspective view, andFIG.7shows a top view, a left view, a front view, a right view, and a bottom view. Moreover,FIG.8shows a development view.

As shown inFIGS.6to8, in the reinforcement member41′ in the developed form, slits41aare formed at some of ridge portions, and holes41bare each provided at tip ends of the slits41a. Moreover, a flat surface41cis formed at a top portion, and folded-back portions41dfolded back to the outside are provided on the lower side.

The slits41aproduce a plate spring effect, and can reduce not only the external force but also vibration. This point will be supplementarily described. The technique of using a plate bent in a stress direction is generally employed as the technique of providing a plate spring structure. If the four-sided reinforcement member41opening on one side has a structure with bent surfaces, the area of contact with the exterior body3is small and the exterior body3is damaged due to stress concentration on such a small contact area. For this reason, the technique of bending the surfaces of the reinforcement member41to provide the bent surface structure as described above cannot be employed.

Thus, the stress is received by the entirety of the surfaces of the reinforcement member41each contacting the surfaces of the exterior body3in the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2, and in this manner, stress concentration is eliminated. In addition, the technique of forming the slits41aat some of the ridge portions of the reinforcement member41to provide the plate spring structure is employed as the technique of absorbing the external force and the vibration. Bending stress is mainly on each surface in the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2, but the plate spring structure in which the slits41aare formed at some of the ridge portions of the reinforcement member41effectively provides a bending stress relaxing function.

The hole41bprovided at the tip end of the slit41ais for relaxing stress generated at the tip end of the slit41a. That is, the hole41bprevents damage of the reinforcement member41′ from the tip end of the slit41adue to stress concentration on the tip end of the slit41a. Moreover, the holes41balso provide additional features and advantageous effects that the accuracy of dimension in plate bending is improved in a case where the reinforcement member41′ is made of metal.

In the reinforcement member41′ in the developed form, the flat surface41cis formed at the top portion on a tip end side in an insertion direction. When the reinforcement member41′ is attached, stress detaching welded portions of the exterior body3is generated in an attachment direction. However, the flat surface41ccan reduce such stress detaching the welded portions, and contributes to retention of the sealability.

The folded-back portions41dfolded back to the outside are provided at locations corresponding to the sides of the exterior body3positioned outside the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2. With the folded-back portions41d, position retention of the reinforcement member41′ is improved. With the folded-back portions41d, the exterior body3can be sandwiched between the folded-back portion41dand an outer surface of the reinforcement member41′, and therefore, an adhesive or a double-sided tape is not necessary and a manufacturing process is simplified.

As one embodiment, in a case where the reinforcement member4is used for the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2of the exterior body3, a reinforcement plate (not shown) can be arranged on the surface of the exterior body3in the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2. In this case, the exterior body3and the reinforcement plate can be sandwiched between the folded-back portion41dand the outer surface of the reinforcement member41′. With this configuration, the surface, which is a lowest-strength portion, of the exterior body3outside the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2can be strongly reinforced. Moreover, influence of external force vertically on the reinforcement plate can be also reduced, and therefore, the stress on the welded portions of the exterior body3can be reduced and the sealability can be improved. As a result, influence of moisture on the battery1can be reduced, and gas discharging can be prevented even in a case where gas is generated inside the exterior body3.

Another example of the reinforcement member4in one embodiment of the present invention is a reinforcement member42as a hollow four-sided body having four surfaces defining four sides of the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2, as shown inFIG.9. The reinforcement member42as the hollow four-sided body having four surfaces additionally includes a planar reinforcement portion closing the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2. This can make the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2stronger, and can also prevent the external force from entering the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2and acting on three surfaces defining such a triangular pyramid-shaped space, thereby preventing the force of deforming the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2from acting on such a triangular pyramid-shaped space.

Still another example of the reinforcement member4in one embodiment of the present invention is a reinforcement member43as a solid four-sided body having four surfaces defining four sides of the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2, as shown inFIG.10. It can be said that the reinforcement member43as the solid four-sided body is stronger because the reinforcement member43is the solid body. However, in other aspects, the reinforcement member43is increased in weight, and requires many materials (resources). It is effective when the reinforcement member43is employed in a case where the necessity of reinforcing the end surfaces13a,13bof the battery1and four corner portions at intersections between the end surface13a,13band the side surface12a,12bis high.

Still another example of the reinforcement member4in one embodiment of the present invention is a reinforcement member44as a frame body including six linear members along six sides of the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2, as shown inFIG.11. The reinforcement member44as the frame body is a lightest member as compared to those described above as the examples, and therefore, does not require many materials (resources). Although it is necessary to reinforce the end surfaces13a,13bof the battery1and four corner portions at the intersections between the end surface13a,13band the side surface12a,12b, it is effective when the reinforcement member44is employed in a case where an increase in the weight of the battery cell2due to reinforcement needs to be suppressed as much as possible.

In the reinforcement member44as the frame body, a flat surface can be also formed at a top portion on a tip end side in an insertion direction as in the reinforcement member41′ in the developed form. In this case, the reinforcement member44is in such a form that the tip end portion in the insertion direction is cut parallel with a bottom surface. At the cut portion, frames connecting the cut frames on each side are arranged, and the flat surface including the frames in a triangular shape is formed.

In addition to the linear (rod-shaped) frame, an L-shaped frame having an L-shaped section or a U-shaped frame having a U-shaped section can be also used as the frame of the reinforcement member44as the frame body. In the case of the L-shaped frame, such a frame is arranged such that an intersection between two flat surfaces of the L-shape is on the outside of the reinforcement member44, and a slit and a hole at a tip end of the slit can be provided at such an intersection. The L-shaped frame is used as at least some of the frames of the reinforcement member44as the frame body so that the slit and the hole at the tip end of the slit can be formed at some of ridge portions of the reinforcement member44.

Alternatively, the U-shaped frame can be also used as at least some of the frames of the reinforcement member44as the frame body. The U-shaped frame is employed as a frame at a location, which corresponds to the side of the exterior body3positioned outside the triangular pyramid-shaped space25a-1,25a-2,25b-1,25b-2, of the reinforcement member44as the frame body. The reinforcement member44is arranged such that one flat surface of the U-shape is positioned on the outside, and in this manner, folded-back portions folded back to the outside can be provided. With these folded-back portions, position retention of the reinforcement member44can be improved, and the exterior body3can be sandwiched between the folded-back portion and an outer surface of the reinforcement member44.

In another embodiment of the present invention, a plurality of reinforcement members4is combined and integrally joined as shown inFIG.12. In a case where the reinforcement members4are integrally connected to each other, the integrated reinforcement members4are inserted into and joined to the triangular pyramid-shaped spaces25a-1,25a-2,25b-1,25b-2at four upper, lower, right, and left (upper right, upper left, lower right, and lower left) locations of each of battery cells2stacked on each other from the front side to the back side in the horizontal direction in module formation. In this manner, the stacked battery cells2can be joined to each other with the positions of these battery cells2being fixed. That is, the reinforcement members4for the battery cells2of the present invention can be combined and integrally joined to function as position fixing members in a case where the battery cells2are stacked on each other.

Resin or metal is used as the material of the reinforcement member4,41,41′,42,43,44of the present invention. The resin is a preferred material because the resin can be used for integral molding by injection molding, is low in cost and light weight, and can provide a sufficient reinforcement effect in terms of strength.

The embodiments of the present invention have been described above with reference to the examples, but the present invention is not limited to these examples. Needless to say, various forms can be made without departing from the gist of the present invention.

EXPLANATION OF REFERENCE NUMERALS

1Battery11aTop Surface11bBottom Surface12a,12bSide Surface13a,13bEnd Surface14a,14bCurrent collection Tab/Current collection Tab Lead15Center Axis2Battery Cell21aTop Surface21bBottom Surface22a,22bSide Surface23a-1,23a-2,23b-1,23b-2End Surface Folding Portion24a-1,24a-2,24b-1,24b-2Current collection Tab/Current collection Tab Lead Housing Portion25a-1,25a-2,25b-1,25b-2Triangular Pyramid-Shaped Space3Exterior Body31aTop Surface Covering Portion31bBottom Surface Covering Portion32a,32b-1,32b-2Side Surface Covering Portion33a-1,33a-2,33b-1,33b-2End Surface Covering Portion34a-1,34a-2,34b-1,34b-2Current collection Tab/Current collection Tab Lead Sandwiching Portion35a-1,35a-21,35a-22,35b-1,35b-21,35b-22Triangular Pyramid-Shaped Space Formation Portion4Reinforcement Member41Four-Sided Reinforcement Member Opening on One Side41′ Reinforcement Member in Developed Form of Four-Sided Reinforcement Member Opening on One Side41aSlit41bHole at Tip End of Slit41cFlat Surface at Top Portion41dFolded-Back Portion42Reinforcement Member as Hollow Four-Sided Body Having Four Surfaces43Reinforcement Member as Solid Four-Sided Body44Reinforcement Member as Frame Body Including Six Linear Members