Patent ID: 12261313

DESCRIPTION OF EMBODIMENTS

Hereinafter, the present disclosure will be described on the basis of preferred exemplary embodiments with reference to the drawings. The exemplary embodiments are examples not intended to limit the present disclosure, and all features described in the exemplary embodiments and combinations thereof are not always essential to the present disclosure. The same or equivalent configuration elements, members, or processes illustrated in the drawings are denoted by the same reference marks, and a redundant description will be omitted as appropriate. The scale and shape of each part illustrated in the drawings are set for convenience in order to facilitate the description and are not limitedly interpreted unless otherwise specified. When terms such as “first” and “second” are used in the specification or claims, unless otherwise specified, these terms do not represent any order or importance but are intended to distinguish one configuration from another configuration. Furthermore, a part of a member that is not important to describe the exemplary embodiments is not illustrated in the drawings.

First Exemplary Embodiment

FIG.1is a perspective view of a power storage module according to an exemplary embodiment.FIG.2is an exploded perspective view of the power storage module. InFIG.2, illustration of buffer member40(seeFIG.6) is omitted. As an example, power storage module1includes battery stack2, a pair of binding members6, and cooling plate8. Battery stack2includes a plurality of power storage devices10, a plurality of separators12, and a pair of end plates4.

Each power storage device10is, for example, a rechargeable secondary battery such as a lithium ion battery, a nickel-hydrogen battery, and a nickel-cadmium battery, or a capacitor such as an electric double layer capacitor. Power storage device10is a so-called prismatic battery and includes exterior can14having a flat rectangular-parallelepiped shape. Exterior can14has an opening having a substantially rectangular shape on one face. Electrode body38(seeFIG.3) including a positive electrode, a negative electrode, and a porous separator, an electrolytic solution, and the like are inserted through the opening to be accommodated in exterior can14. Exterior can14is covered with an insulating film such as a shrink tube which is not illustrated. Covering the faces of exterior can14with the insulating film can suppress happening of a short circuit between neighboring power storage devices10, a short circuit between power storage device10and end plate4, and a short circuit between binding member6and cooling plate8. The opening of exterior can14is provided with sealing plate16to cover the opening and seal up exterior can14.

Sealing plate16is provided with output terminal18near one end in the longitudinal direction to be electrically connected to the positive electrode of electrode body38, and output terminal18near the other end in the longitudinal direction to be electrically connected to the negative electrode of electrode body38. Hereinafter, as necessary, output terminal18connected to the positive electrode is referred to as positive-electrode terminal18a, and output terminal18connected to the negative electrode is referred to as negative-electrode terminal18b. When it is not necessary to distinguish the polarity of output terminal18, positive-electrode terminal18aand negative-electrode terminal18bare collectively referred to as output terminal18. Exterior can14and sealing plate16are each a conductive body, and are made of metal, for example, aluminum, iron, or stainless steel. Sealing plate16and exterior can14are joined to each other by, for example, laser, friction stir bonding, or brazing.

Exterior can14has a bottom face that opposes sealing plate16. Exterior can14has four side faces connecting together the opening and the bottom face. Two of the four side faces are a pair of long side faces connected to two opposing long sides of the opening. Each of the long side faces is a face having the largest area among the faces of exterior can14, that is, a main surface. The two side faces other than the two long side faces are a pair of short side faces connected to the opening of exterior can14and short sides of the bottom face.

For convenience of describing the present exemplary embodiment, a face where sealing plate16is provided is defined as an upper face of power storage device10. The bottom face of exterior can14is defined as the bottom face of power storage device10, the long side face of exterior can14is defined as the long side face of power storage device10, and the short side face of exterior can14is defined as the short side face of power storage device10. In power storage module1, an upper face side of power storage device10is defined as the upper face of power storage module1, a bottom face side of power storage device10is defined as the bottom face of power storage module1, and a short side face of power storage device10is defined as the side face of power storage module1. The upper face side of power storage module1is defined as the upper side in the vertical direction, and the bottom face side of power storage module1is defined as the lower side in the vertical direction. These directions and positions are defined for convenience. Thus, for example, a part defined as an upper face in the present disclosure does not mean that it is always located above a part defined as a bottom face. Thus, sealing plate16is not necessarily located above bottom face of exterior can14.

Sealing plate16is provided with a safety valve (not shown) between the pair of output terminals18. The safety valve is configured to open to release the gas in exterior can14when the internal pressure of exterior can14has risen to a predetermined value or more. Safety valve includes, for example, a thin part provided at a part of sealing plate16to have a thickness smaller than the thickness of other parts, and a linear groove formed on a surface of the thin part. In this configuration, when the internal pressure of exterior can6rises, the thin part tears from the groove, and thereby safety valve14opens.

The plurality of power storage devices10is arranged side by side at predetermined intervals such that the long side faces of adjacent power storage devices10face each other. In the present exemplary embodiment, a direction in which the plurality of power storage devices10is arranged is defined as first direction X. Output terminals18of each power storage device10are disposed so as to point the same direction. In the present exemplary embodiment, output terminals18of power storage devices10are disposed to point upward in the vertical direction for convenience. Alternatively, output terminals18of power storage devices10may be disposed to point different directions.

Two adjacent power storage devices10are arranged (stacked) so as positive-electrode terminal18aof one power storage device10to be adjacent to negative-electrode terminal18bof another power storage device10. Positive-electrode terminal18aand negative-electrode terminal18bare connected in series via a bus bar (not shown). Alternatively, output terminals18of the same polarity of the plurality of power storage devices10adjacent to each other may be connected in parallel by a bus bar to form a power storage device block, and the power storage device blocks may be connected in series.

Separator12is also referred to as insulating spacer, is disposed between adjacent two power storage devices10to provide electrical insulation between adjacent two power storage devices10. Separator12is made of a resin having an insulating property, for example. Examples of the resin of which separator12is made include thermoplastic resins such as polypropylene (PP), polybutylene terephthalate (PBT), polycarbonate (PC), and Noryl (registered trademark) resin (modified PPE). The plurality of power storage devices10and the plurality of separators12are alternately stacked. Separator12is also disposed between power storage device10and end plate4.

Separator12has flat surface part20and wall part22. Flat surface part20is disposed between opposing long side faces of two adjacent power storage devices10. This further reliably insulates exterior cans14of adjacent power storage devices10from each other.

Wall part22extends from a peripheral rim of flat surface part20in first direction X in which power storage devices10are arranged, and covers a part of the upper face, the side face, and a part of the bottom face of power storage device10. With this configuration, the creepage distance between adjacent power storage devices10or between power storage device10and end plate4can be secured. In addition, insulation between exterior can14of power storage device10and binding member6can further reliably provided. Furthermore, the position of power storage device10in second direction Y in which output terminals18are arranged and in third direction Z in which the upper face and the bottom face of power storage device10are arranged can be restricted or fixed. First direction X, second direction Y, and third direction Z are directions orthogonal to each other.

Wall part22includes cutout24through which the bottom face of power storage device10is exposed. With cutout24provided, hindering of thermal connection between power storage device10and cooling plate8by separator12can be avoided. Separator12has urge receiving parts26facing upward at both ends in second direction Y.

The plurality of power storage devices10and the plurality of separators12arranged side by side are sandwiched in first direction X by the pair of end plates4. Separator12is disposed between each of the pair of end plates4and corresponding power storage device10among power storage devices10disposed at both ends in first direction X. This further reliably provide insulation between exterior can14of power storage device10and end plate4. End plate4is formed of, for example, a metal sheet. End plate4is provided with screw hole4athat penetrates end plate4in first direction X and in which fastening screw28is screwed.

The pair of binding members6is also referred to as bind bars, and are elongated members of which longitudinal direction is first direction X. The pair of binding members6is disposed so as to face each other in second direction Y. Battery stack2is disposed between the pair of binding members6. Each binding member6includes body part30, supporting part32, a plurality of urging parts34, and a pair of fixing parts36.

Body part30is a rectangular part extending in first direction X. Body part30extends in parallel to the side faces of power storage devices10. Supporting part32extends in first direction X and protrudes in second direction Y from the lower end of body part30. Supporting part32is a plate-shaped body continuous in first direction X, and supports battery stack2.

The plurality of urging parts34is connected to the upper end of body part30and protrudes in second direction Y. Supporting part32and urging parts34face each other in third direction Z. The plurality of urging parts34is arranged at predetermined intervals in first direction X. Urging parts34are each disposed corresponding to respective power storage device10. Each of urging parts34has a leaf spring shape and urges power storage device10toward supporting part32.

The pair of fixing parts36is plate-shaped bodies projecting in second direction Y from both ends, in first direction X, of body part30. The pair of fixing parts36opposes each other in first direction X. Each fixing part36is provided with through-holes36athrough which fastening screws28are inserted. The pair of fixing parts36fixes binding member6to battery stack2.

Cooling plate8is a mechanism for cooling the plurality of power storage devices10. Cooling plate8is formed of a material having a heat transfer property such as metal. Battery stack2bound by the pair of binding members6is placed on a main surface of cooling plate8, and fixed to cooling plate8by fastening members (not shown) such as screws inserted through through-holes32aof supporting parts32and through-holes8aof cooling plate8. Power storage devices10are cooled by heat exchange between power storage device10and cooling plate8. Cooling plate8may be provided with a refrigerant pipe (not shown) in which refrigerant flows.

Power storage module1is assembled, for example, as follows. The plurality of power storage devices10and the plurality of separators12are alternately arranged and sandwiched between the pair of end plates4in first direction X, and thereby battery stack2is formed. Battery stack2is sandwiched between the pair of binding members6in second direction Y. Each binding member6is positioned such that through-holes36aoverlap with screw holes4aof end plates4. In this state, fastening screws28are inserted through through-holes36aand screwed into screw holes4a. The pair of binding members6engages with the pair of end plates4in this manner, thereby binding the plurality of power storage devices10. Battery stack2is fastened by binding members6with a predetermined pressure applied in first direction X.

Power storage devices10are positioned in first direction X by binding members6fastening power storage devices10in first direction X. Bottom faces of power storage devices10are supported by supporting parts32. Wall part22of separator12is disposed between the bottom face of power storage device10and supporting part32. Urging part34abuts on urge receiving part26of corresponding power storage device10. Each urging part34urges power storage device10toward supporting part32via urge receiving part26. That is, power storage devices10are sandwiched in third direction Z by supporting parts32and the plurality of urging parts34. As a result, power storage devices10are positioned in third direction Z.

Exemplarily, after the positioning is completed, bus bars are attached to output terminals18of power storage devices10, and output terminals18of the plurality of power storage devices10are electrically connected to each other. For example, bus bars are fixed to output terminals18by welding. Then, the upper face of battery stack2is covered with a cover member (not shown). The cover member prevents dew condensation water, dust, and the like from making contact with output terminal18of power storage device10, the bus bar, the safety valve, and the like. The cover member is formed of a resin having, for example, an insulating property, and can be fixed to the upper face of battery stack2by a known fixing structure (not shown) including screws and known engaging mechanisms.

Battery stack2to which binding members6and the cover member are attached is placed on cooling plate8, and fixed to cooling plate8by fastening members inserted through through-holes8aand through-holes32a. Power storage module1is obtained by the steps described above. Note that, power storage module1may be manufactured by setting battery stack2on cooling plate8and then fixing together battery stack2and cooling plate8by binding members6. In this case, cooling plate8is disposed in the inner side of the pair of binding members6.

FIG.3is a cross-sectional view schematically illustrating expanding power storage devices10. Power storage devices10are illustrated inFIG.3by a reduced number. The internal structure of power storage devices10and separators12are illustrated in a simplified manner. As illustrated inFIG.3, electrode body38is housed inside each power storage device10. In power storage device10, exterior can14repeatedly expands and contracts with charging and discharging. Exterior can14expands mainly by expansion of electrode body38. When exterior cans14of power storage devices10expand, load G1directed outward in first direction X is produced in battery stack2. Meanwhile, load G2corresponding to load G1is applied to battery stack2by binding member6. This suppresses the expansion of power storage devices10.

In this structure, when power storage devices10expand, loads are applied to binding members6. In recent years, the amount of expansion of power storage device10has been in increase with an increase in capacity of power storage device10, and therefore the load applied to binding member6has also been in increase. An excess load applied to binding member6might damage binding member6. Raising the strength of binding member6to prevent damage may lead to an increase in size and cost of binding member6as well as power storage module1. Furthermore, suppressing the expansion of power storage devices10by binding members6may excessively press electrode bodies38(in particular, porous separators) and may deteriorate the performance of power storage devices10or shorten the life of power storage devices10.

Loosening the binding of power storage devices10by binding members6can reduce the load applied to binding members6. However, a certain level of load needs to be applied to power storage devices10to position power storage devices10in power storage module1. Thus, the binding of power storage devices10cannot be simply loosened. Typically, the amount of expansion of power storage device10gradually increases from the initial stage of life to the end stage of life. Thus, the magnitude of the load to be applied to power storage device10differs between the initial stage of life and the end stage of life of power storage device10.

In contrast, power storage module1according to the present exemplary embodiment includes buffer members40arranged with the plurality of power storage devices10in first direction X.FIG.4(A)is a front view of a hard part included in buffer member40according to the first exemplary embodiment.FIG.4(B)is a cross-sectional view taken along line A-A inFIG.4(A).FIG.5(A)is a front view of a soft part included in buffer member40.FIG.5(B)is a cross-sectional view taken along line B-B inFIG.5(A).FIG.6is a cross-sectional view of buffer member40sandwiched between two adjacent power storage devices10. Illustration of wall part22is omitted inFIG.4(A)andFIG.4(B).

Buffer members40are members that are arranged with power storage devices10and receive the load in first direction X from power storage devices10.FIG.6illustrates buffer member40disposed between adjacent first power storage device10aand second power storage device10b. Buffer member40includes hard part42having a predetermined hardness and soft part44softer than hard part42.

The shape of hard part42changes by receiving a load of a predetermined magnitude or more. By hard part42changing its shape, buffer member40changes its state from a first state in which the load is received by hard part42to a second state in which the load is received by soft part44. That is, hard part42and soft part44each receives the load in first direction X from power storage device10at different timings. Hard part42of the present exemplary embodiment has, as a structure for changing its own shape, vulnerable part46that breaks or plastically deforms by receiving a load of a predetermined magnitude or more. Thus, buffer member40changes from the first state to the second state by breakage or plastic deformation of vulnerable part46.

Hard part42can be made of, for example, a metal or a hard resin such as polypropylene (PP), polybutylene terephthalate (PBT), polycarbonate (PC), and Noryl (registered trademark) resin (modified PPE). Hard part42of the present exemplary embodiment has an insulating property, and is provided to separator12as a part of separator12. Thus, hard part42is made of a resin instead of a metal. In this case, hard part42can be integrally molded with separator12.

Hard part42is provided on flat surface part20of separator12. Separator12of the present exemplary embodiment has through-hole20apenetrating flat surface part20in first direction X. An end, close to first power storage device10a, of hard part42is disposed in through-hole20a. In a state before vulnerable part46breaks or plastically deforms, hard part42protrudes toward exterior can14of second power storage device10bfrom flat surface part20.

Hard part42of the present exemplary embodiment has first part48, second part50, and third part52. Vulnerable part46includes first vulnerable part54and second vulnerable part56. First part48to third part52, first vulnerable part54, and second vulnerable part56are integrally molded.

In a state before vulnerable part46breaks or plastically deforms, first part48is positioned closer to first power storage device10athan second part50and third part52are and separated from second power storage device10b. First part48has a cylindrical shape, and an end close to first power storage device10ais disposed in through-hole20a. In the present exemplary embodiment, first part48and flat surface part20are integrally molded. Second part50is positioned closer to second power storage device10bthan first part48is, and is separated from first power storage device10a. Second part50has a cylindrical shape having a diameter smaller than that of first part48, and is disposed into first part48as viewed in first direction X. For example, first part48and second part50are disposed such that central axes thereof overlap with each other as viewed in first direction X.

An end of first part48close to second power storage device10band an end of second part50close to first power storage device10aare connected to each other by first vulnerable part54. First vulnerable part54is a part having a lower strength in first direction X than first part48and second part50. For example, first vulnerable part54has a disk shape that is thinner in first direction X than first part48and second part50, and has a hole with a diameter larger than that of second part50. First vulnerable part54extends in parallel to the long side face of exterior can14of power storage device10, and is positioned between first part48and second part50as viewed in first direction X. Second part50is disposed inside the hole of first vulnerable part54as viewed in first direction X.

Third part52is positioned closer to second power storage device10bthan second part50is, and is separated from first power storage device10a. Third part52is disposed between second part50and second power storage device10bin first direction X. Thus, second part50is separated not only from first power storage device10abut also from second power storage device10b. Third part52has a columnar shape having a diameter smaller than that of second part50, and is disposed inside second part50as viewed in first direction X. For example, second part50and third part52are disposed such that central axes thereof overlap with each other as viewed in first direction X. The shape of third part52is not limited to a columnar shape. As long as third part52has a higher rigidity than second vulnerable part56, third part52may be, for example, a cylindrical-shaped body of which end close to second power storage device10bis closed, or a cylindrical-shaped body of which both ends in first direction X are opened.

An end of second part50close to second power storage device10band an end of third part52close to first power storage device10aare connected to each other by second vulnerable part56. Second vulnerable part56is a part having a lower strength in first direction X than second part50and third part52. For example, second vulnerable part56has a disk shape which is thinner in first direction X than second part50and third part52, and has a hole having a diameter larger than that of third part52in the center. Second vulnerable part56extends in parallel to the long side face of exterior can14of power storage device10, and is positioned between second part50and third part52as viewed in first direction X. Third part52is disposed inside the hole of second vulnerable part56as viewed in first direction X.

Dimensions of third part52, second part50, and first part48in a direction perpendicular to first direction X, that is, in a direction along a YZ plane, are in descending order. That is, with respect to the dimension in the direction perpendicular to first direction X of the hard part42, the dimension of a part close to second power storage device10bis smaller than the dimension of a part close to first power storage device10a. With this configuration, third part52can be separated from soft part44further than second part50and first part48are. In addition, second part50can be separated from soft part44further than first part48is. More specifically, the distance from the inner peripheral surface of through-hole58described later to third part52can be set longer than the distance from the inner peripheral surface to second part50and the distance from the inner peripheral surface to first part48. In addition, the distance from the inner peripheral surface to second part50can be made longer than the distance from the inner peripheral surface to first part48. With this configuration, a chance of hard part42of which shape has changed pressing soft part44can be reduced. As a result, when soft part44compressively deforms in the second state, happening of hard part42hindering the deformation of soft part44can be suppressed. Thus, the change in compression margin of soft part44is suppressed.

Buffer member40includes a plurality of hard parts42. Each of hard parts42of the present exemplary embodiment is disposed so as to overlap with electrode body38included in power storage device10as viewed in first direction X. In addition, the plurality of hard parts42is arranged so as to be uniformly dispersed on flat surface part20at predetermined distances therebetween.

Soft part44can be made of a soft resin such as urethane foam. Soft part44is, for example, a sheet body, and is disposed parallel to flat surface part20of separator12. Soft part44is disposed closer to second power storage device10bthan flat surface part20is. A part of soft part44overlapping with flat surface part20in first direction X is separated from first power storage device10a, because flat surface part20is disposed between the part and first power storage device10a. Soft part44has at least one through-hole58at a location overlapping with hard part42as viewed in first direction X. Soft part44of the present exemplary embodiment has through-holes58of which number is the same as the number of hard parts42. Each through-hole58penetrates the sheet body in first direction X. Hard part42is inserted in through-hole58, and a distal end close to second power storage device10bprotrudes from soft part44in first direction X. The part of hard part42except the distal end is disposed in through-hole58.

Entire hard part42of the present exemplary embodiment is separated from the inner peripheral surface of through-hole58. With this configuration, hard part42of which shape has been changed pressing the inner peripheral surface of through-hole58can be suppressed. Accordingly, in the second state, hindering of deformation of soft part44can be suppressed. When hard part42is separated from at least a part of inner peripheral surface of through-hole58, hard part42hindering the deformation of soft part44can be suppressed at some degree. Soft part44may not have a sheet shape, and may be formed of, for example, a plurality of block bodies disposed around hard part42.

No soft part44is disposed between hard part42and power storage device10in first direction X. In the present exemplary embodiment, no soft part44is disposed between hard part42and first power storage device10anor between hard part42and second power storage device10b. This configuration can suppress, in the first state, soft part44taking up a load which is to be applied to hard part42.

FIG.7(A)toFIG.7(C)are cross-sectional views schematically illustrating buffer member40changing its shape by receiving loads from power storage devices10.FIG.7(B)exemplarily illustrates a state in which second vulnerable part56is broken, andFIG.7(C)exemplarily illustrates a state in which first vulnerable part54is broken. InFIG.7(A)toFIG.7(C), illustration of electrode body38is omitted.

First vulnerable part54and second vulnerable part56are designed such that one has lower strength than the other. In the present exemplary embodiment, second vulnerable part56is thinner in first direction X than first vulnerable part54and has a lower strength than first vulnerable part54. Thus, when hard part42receives a load in first direction X due to the expansion of power storage device10, second vulnerable part56breaks or plastically deforms first, and then, first vulnerable part54breaks or plastically deforms.

With respect to the dimension (thickness) in first direction X, the dimension of hard part42is larger than the dimension of soft part44in a state before vulnerable part46breaks or plastically deforms. Thus, as illustrated inFIG.7(A), before first vulnerable part54and second vulnerable part56break or plastically deform, third part52abuts on exterior can14of second power storage device10b, and hard part42receives the load from power storage device10. That is, buffer member40is in the first state, and hard part42restricts first power storage device10aand second power storage device10bapproaching each other.

As illustrated inFIG.7(B), when second vulnerable part56breaks or plastically deforms, third part52falls into the inside of second part50, and the dimension of hard part42decreases. That is, hard part42contracts in first direction X by breakage or plastic deformation of second vulnerable part56. However, in a state where first vulnerable part54has broken or plastically deformed, the dimension of hard part42is still larger than the dimension of soft part44. Thus, exterior can14of second power storage device10babuts on second part50, and hard part42receives the load from power storage device10. Thus, buffer member40continues to be in the first state, and hard part42restricts first power storage device10aand second power storage device10bapproaching each other. In this state, distance L between first power storage device10aand second power storage device10bis smaller than before first vulnerable part54and second vulnerable part56breaks or plastically deforms.

As illustrated inFIG.7(C), when first vulnerable part54also breaks or plastically deforms in addition to the breakage or plastic deformation of second vulnerable part56, second part50falls into the inside of first part48, and the dimension of hard part42further decreases. That is, hard part42contracts in first direction X by breakage or plastic deformation of first vulnerable part54. Accordingly, hard part42of the present exemplary embodiment contracts by two steps by second vulnerable part56having a low strength breaking or plastically deforming, and then first vulnerable part54having a high strength breaking or plastically deforming. As a result, the dimension of hard part42becomes smaller than the dimension of soft part44, and exterior can14of second power storage device10babuts on soft part44, so that soft part44receives the load from power storage device10. That is, buffer member40is in the second state, and soft part44restricts first power storage device10aand second power storage device10bapproaching each other. At this time, distance L between first power storage device10aand second power storage device10bis smaller than before second vulnerable part56breaks or plastically deforms.

As described above, regarding the dimensions in first direction X of hard part42and soft part44, hard part42is larger than soft part44in the first state, and soft part44is larger than hard part42in the second state. Thus, in the first state, soft part44is separated from second power storage device10b, and in the second state, hard part42is separated from second power storage device10b. That is, in the first state, distance L between first power storage device10aand second power storage device10bis defined by the dimension of hard part42, and in the second state, distance L is defined by the dimension of soft part44. Accordingly, when buffer member40is in the first state, hard part42can further reliably receive the load from power storage device10. When buffer member40is in the second state, soft part44can further reliably receive the load from power storage device10.

Dimensions of first part48to third part52are smaller than the dimension of soft part44. This configuration can suppress, in the second state where soft part44abuts on second power storage device10b, hard part42of which shape has changed abutting on second power storage device10b. As a result, uneven distribution of the load applied to soft part44can be suppressed.

FIG.8(A)is a view illustrating the relationship between the compressive load and the compression ratio of buffer member40when hard part42is in the state illustrated inFIG.7(A).FIG.8(B)is a view illustrating the relationship between the compressive load and the compression ratio of buffer member40when hard part42is in the state illustrated inFIG.7(B).FIG.8(C)is a view illustrating the relationship between the compressive load and the compression ratio of buffer member40when hard part42is in the state illustrated inFIG.7(C).

As illustrated inFIG.8(A)toFIG.8(C), the absorption amount (accepted amount) of expansion required of buffer member40, that is, required absorption amount M1is determined according to the amount of expansion of power storage devices10. Lower limit compressive load N1and upper limit compressive load N2are defined for buffer member40. Lower limit compressive load N1is a load applied to buffer member40when the minimum load necessary for positioning power storage device10, that is, a lower limit binding load, is applied to power storage devices10. Upper limit compressive load N2is the maximum load under which no damage to binding member6nor degradation in performance of power storage device10occurs, that is, a load applied to buffer member40when an upper limit binding load is applied to power storage devices10. Thus, buffer member40is required to absorb necessary absorption amount M1in the range from lower limit compressive load N1to upper limit compressive load N2.

Load absorption characteristics of buffer member40differ among the state where third part52abuts on exterior can14of second power storage device10b, the state where second part50abuts on exterior can14of second power storage device10b, and the state where soft part44abuts on exterior can14of second power storage device10b. The load absorption characteristics are determined based on the stress-strain curve unique to the material of the member receiving the load, the shape of the member receiving the load, and the like.

Hard part42is hard and has a small deformation amount compared to soft part44. Thus, as illustrated inFIG.8(A), in a state where third part52abuts on second power storage device10b, lower limit compressive load N1can be reached with a small compression ratio, whereas the compression ratio to reach upper limit compressive load N2is also small. Thus, only absorption amount M2within necessary absorption amount M1can be absorbed. Similarly, as illustrated inFIG.8(B), even in a state where second part50abuts on second power storage device10b, lower limit compressive load N1can be reached with a small compression ratio, whereas the compression ratio to reach upper limit compressive load N2is also small. Thus, only absorption amount M3within necessary absorption amount M1can be absorbed.

In contrast, soft part44is soft and has a large deformation amount compared to hard part42. Thus, in a state where soft part44abuts on second power storage device10b, a compression ratio larger than that of hard part42is required until lower limit compressive load N1is reached, whereas the compression ratio to reach upper limit compressive load N2is also large. Thus, absorption amount M4that is within necessary absorption amount M1but larger than absorption amount M2and absorption amount M3can be absorbed.

FIG.9is a view illustrating the relationship between the compressive load and the compression ratio of buffer member40in the first state and the second state. For example, buffer member40is designed such that second vulnerable part56breaks when compression ratio m1is reached, and first vulnerable part54breaks when compression ratio m2is reached. While the amount of expansion of power storage devices10is relatively small and buffer member40is repeatedly compressed and released from compression in a range up to compression ratio m1, buffer member40is in the first state of receiving the load from second power storage device10bby third part52. Such a state can be observed, for example, at the initial stage of life of power storage device10. The relationship between the compressive load applied to buffer member40and the compression ratio in this stage conforms to the relationship illustrated inFIG.8(A).

When the load applied to buffer member40increases and the compression ratio of buffer member40reaches compression ratio m1, second vulnerable part56breaks. As a result, buffer member40changes its state to the first state in which second part50receives the load from second power storage device10b. Then, while the amount of expansion of power storage devices10is at around a medium level and buffer member40is repeatedly compressed and released from compression in a range up to compression ratio m2, buffer member40is kept in the first state. Such a state is observed, for example, in the middle stage of life of power storage device10. The relationship between the compressive load applied to buffer member40and the compression ratio in this stage conforms to the relationship illustrated inFIG.8(B).

When the load applied to buffer member40increases and the compression ratio of buffer member40reaches compression ratio m2, first vulnerable part54breaks. As a result, buffer member40changes its state to the second state in which soft part44receives the load from second power storage device10b. Then, while the amount of expansion of each power storage device10is large and buffer member40is repeatedly compressed and released from compression in a range from compression ratio m2and higher, buffer member40is kept in the second state. Such a situation is observed, for example, in the end stage of life of power storage device10. At this time, the relationship between the compressive load applied to buffer member40and the compression ratio conforms to the relationship illustrated inFIG.8(C).

As described above, buffer member40of the present exemplary embodiment has a structure that changes it shape by the load from power storage device10, and receives a relatively small load by hard part42and a relatively large load by soft part44. That is, buffer member40switches, by steps, the flexibility and the amount of dimensional change of a part receiving the load according to the magnitude of the load. As a result, as illustrated inFIG.9, necessary absorption amount M1required of buffer member40is secured while maintaining the load range from lower limit compressive load N1to upper limit compressive load N2.

As described above, power storage module1according to the present exemplary embodiment includes at least one power storage device10, and buffer member40arranged with power storage device10in first direction X. Buffer member40includes hard part42and soft part44which receive a load in first direction X from power storage device10. The shape of hard part42changes by receiving a load of a predetermined magnitude or more. By hard part42changing its shape, buffer member40changes its state from the first state in which the load is received by hard part42to the second state in which the load is received by soft part44. With this configuration, in the initial stage of life where power storage device10is thin, hard part42of which deformation amount is small receives the load, so that the binding force necessary for positioning power storage device10can be maintained. In contrast, in the end stage of life where power storage device10is thick, soft part44of which deformation amount is large receives the load, and power storage device10can be held with a low binding force within such a range that does not cause damage to binding member6.

Thus, according to the present exemplary embodiment, even when the amount of expansion of power storage device10increases with the increase in capacity of power storage device10, both absorption of expansion and positioning of power storage device10can be achieved at a high level. In addition, even when the amount of expansion of power storage device10differs between the initial stage of life and the end stage of life, power storage device10can be held with an appropriate binding force in accordance with the amount of expansion in each step. Consequently, reliability of power storage module1can be enhanced.

In addition, an increase in strength of binding member6can be avoided, so that an increase in size, weight, cost, and the like of binding member6and hence those of power storage module1can be suppressed. In addition, deterioration in the performance and shortening of the life of power storage device10due to an increase in the load applied to power storage device10can be suppressed. Furthermore, for example, when necessary absorption amount M1is to be absorbed only by soft part44, the thickness in first direction X of buffer member40needs to be increased, which leads to an increase in size of entire power storage module1. In contrast, according to buffer member40of the present exemplary embodiment, the necessary absorption amount M1can be absorbed without increasing the thickness of buffer member40. Accordingly, buffer member40can be made thinner, and hence power storage module1can be downsized.

Regarding the thicknesses of hard part42and soft part44in first direction X, hard part42is thicker than soft part44in the first state, and soft part44is thicker than hard part42in the second state. Thus, when buffer member40is in the first state, hard part42can more reliably receive the load, and when buffer member40is in the second state, soft part44can more reliably receive the load. Accordingly, both absorption of expansion and positioning of power storage device10can be further reliably achieved.

Hard part42has vulnerable part46that breaks or plastically deforms by receiving a load of a predetermined magnitude or more. Buffer member40changes its state from the first state to the second state by breakage or plastic deformation of vulnerable part46. Accordingly, both absorption of expansion and positioning of power storage device10can be achieved with a simple configuration.

Furthermore, power storage module1includes first power storage device10aand second power storage device10bwhich are adjacent to each other. Hard part42before breaking or plastically deforming includes first part48located close to first power storage device10a, among first power storage device10aand second power storage device10b, and separated from second power storage device10b, and second part50that is located closer to second power storage device10bthan first part48is and separated from first power storage device10a. Vulnerable part46includes first vulnerable part54that connects first part48to second part50and has a strength lower than that of first part48and second part50. Hard part42contracts in first direction X by first vulnerable part54breaking or plastically deforming. Accordingly, both absorption of expansion and positioning of power storage device10can be achieved with a simple configuration.

In the present exemplary embodiment, hard part42before breaking or plastically deforming has third part52that is located closer to second power storage device10bthan second part50is and separated from first power storage device10a. Vulnerable part46includes second vulnerable part56that connects second part50to third part52and has a strength lower than that of second part50and third part52. One of first vulnerable part54and second vulnerable part56has a lower strength than that of the other. Hard part42contracts by two steps by vulnerable part46having a low strength breaking or plastically deforming, followed by vulnerable part46having a high strength breaking or plastically deforming. Accordingly, both absorption of expansion and positioning of power storage device10can be achieved at a higher level.

When second vulnerable part56breaks, third part52separates from second part50and is accommodated in second part50or first part48. When first vulnerable part54breaks, second part50separates from first part48, and third part52and second part50are accommodated in first part48. As a result, when buffer member40changes its state from the first state to the second state, the dimension of hard part42more reliably becomes smaller than the dimension of soft part44. When second vulnerable part56plastically deforms, third part52is accommodated in second part50or first part48with third part52connected to second part50. When first vulnerable part54plastically deforms, third part52and second part50are accommodated in first part48with second part50connected to first part48.

Hard part42of the present exemplary embodiment has an insulating property, is provided on separator12which insulates power storage device10from the outside (for example, adjacent power storage device10, end plate4, binding member6, etc.), and constitutes a part of separator12. Thus, hard part42can be installed easily. In addition, an increase in the number of parts of power storage module1provided with buffer member40can be suppressed. Furthermore, hard part42is disposed so as to overlap with electrode body38as viewed in first direction X. Accordingly, the expansion of power storage device10can be more reliably absorbed by buffer member40. Thus, the load applied to binding member6can be more reliably reduced.

First Modified Example

In the first exemplary embodiment, hard part42includes first vulnerable part54and second vulnerable part56, and contracts by two steps, but the present invention is not limited to such a configuration. Hard part42may have first part48, second part50, and first vulnerable part54, and first part48may abut on first power storage device10aand second part50may abut on second power storage device10b. In this case, hard part42contracts by a single step by breakage or plastic deformation of first vulnerable part54.

Second Modified Example

In the first exemplary embodiment, in a state where only second vulnerable part56has broken or plastically deformed, the dimension of hard part42is larger than the dimension of soft part44, but the present invention is not limited to this configuration. The dimension of soft part44may be larger than the dimension of hard part42in a state where only second vulnerable part56has broken or plastically deformed.

Third Modified Example

In the first exemplary embodiment, the strength of second vulnerable part56is lower than that of first vulnerable part54, and after third part52is displaced by the breakage or the like of second vulnerable part56, second part50is displaced by the breakage or the like of first vulnerable part54, but the present invention is not limited to this configuration. It may be configured that first vulnerable part54has a lower strength than second vulnerable part56, and after second part50and third part52are displaced by breakage or the like of first vulnerable part54, third part52is displaced by breakage or the like of second vulnerable part56.

Second Exemplary Embodiment

A second exemplary embodiment has a configuration common to that of the first exemplary embodiment except for the shape of hard part42. Hereinafter, the present exemplary embodiment will be described mainly on a configuration different from that of the first exemplary embodiment, and common configurations will be briefly described or not described.

FIG.10(A)is a front view of hard parts42included in buffer member40according to the second exemplary embodiment.FIG.10(B)is a cross-sectional view taken along line C-C inFIG.10(A).FIG.10(C)is a front view of soft part44included in buffer member40.FIG.10(D)is a cross-sectional view taken along line D-D inFIG.10(C).FIG.11is a cross-sectional view of buffer member40sandwiched between two adjacent power storage devices10. Illustration of wall part22is omitted inFIG.10(A)andFIG.10(B).

Buffer member40includes hard parts42and soft part44. By hard part42changing its shape, buffer member40changes its state from a first state in which the load is received by hard part42to a second state in which the load is received by soft part44. Hard part42of the present exemplary embodiment has vulnerable part46as a structure for changing the shape of hard part42.

Hard part42includes first part48and second part50. Vulnerable part46includes first vulnerable part54. First part48, first vulnerable part54, and second part50are integrally molded. Separator12has through-holes20aeach having a substantially square shape and penetrating flat surface part20in first direction X, and the peripheral rim of through-hole20aconstitutes first part48. Thus, first part48is positioned closer to first power storage device10athan second part50is, and is separated from second power storage device10b. In the present exemplary embodiment, first part48abuts on exterior can14of first power storage device10a.

Second part50is positioned closer to second power storage device10bthan first part48is, and is separated from first power storage device10a. In the present exemplary embodiment, second part50abuts on exterior can14of second power storage device10b. Second part50is a small, substantially square-shaped, flat plate having a shape similar to that of through-hole20a, and is disposed into through-hole20aas viewed in first direction X with its posture determined such that each side thereof is parallel to a side of through-hole20a.

First part48and second part50are connected to each other by first vulnerable parts54. First vulnerable part54is a part having a lower strength in first direction X than first part48and second part50. Hard part42of the present exemplary embodiment has four first vulnerable parts54. Each first vulnerable part54is a flat plate thinner than first part48and second part50, and has one side connected to a rim (side) of the peripheral rim of through-hole20aand the other side connected to a rim of second part50, the rim facing the rim of through-hole20ato which first vulnerable part54is connected. Each first vulnerable parts54extends from first part48toward second power storage device10bso as to be nearer, as approaching second power storage device10b, to the center of through-hole20a. Each rim of second part50is connected to the distal end of corresponding first vulnerable part54.

Soft part44can be made of a material similar to that of soft part44of the first exemplary embodiment. The shape of soft part44is similar to that of soft part44of the first exemplary embodiment.

FIG.12(A)toFIG.12(D)are cross-sectional views schematically illustrating buffer member40changing its shape by receiving loads from power storage devices10.FIG.12(C)exemplarily illustrates a state in which first vulnerable part54has broken. InFIG.12(A)toFIG.12(D), illustration of electrode body38is omitted.

With respect to the dimension in first direction X, the dimension of hard part42is larger than the dimension of soft part44in a state before vulnerable part46breaks or plastically deforms. Thus, as illustrated inFIG.12(A), in a state before first vulnerable part54breaks or plastically deforms, second part50abuts on exterior can14of second power storage device10b, and hard part42receives a load from power storage device10. That is, buffer member40is in the first state.

As illustrated inFIG.12(B), when the load from power storage device10increases, first vulnerable part54curves, and displacement of first part48and second part50starts in first direction X to approach each other. That is, buffer member40starts to change its state from the first state to the second state. Now, exterior can14of second power storage device10babuts also on soft part44, and a load may be applied also to soft part44. The load received by soft part44is smaller than the load received by hard part42.

As curving of first vulnerable part54progresses, first vulnerable part54breaks or plastically deforms as illustrated inFIG.12(C). As a result, hard part42contracts in first direction X, and the dimension of hard part42becomes smaller than the dimension of soft part44. As a result, as illustrated inFIG.12(D), buffer member40is now in the second state in which soft part44receives the load from power storage device10.

An effect similar to that of the first exemplary embodiment can be obtained also by buffer member40of the present exemplary embodiment. Note that, buffer member40of the present exemplary embodiment may also have a structure that contracts by two steps as in the first exemplary embodiment.

Fourth Modified Example

In the second exemplary embodiment, first vulnerable parts54are connected to the four sides of substantially square shaped second part50, but the present invention is not limited to this configuration. For example, first vulnerable parts54may be connected only to two opposing sides of second part50.

Third Exemplary Embodiment

A third exemplary embodiment has a configuration common to that of the first exemplary embodiment except for the shape of hard part42. Hereinafter, the present exemplary embodiment will be described mainly on a configuration different from that of the first exemplary embodiment, and common configurations will be briefly described or not described.

FIG.13is a cross-sectional view of buffer member40according to the third exemplary embodiment sandwiched between two adjacent power storage devices10. Buffer member40includes hard parts42and soft part44. By hard part42changing its shape, buffer member40changes its state from a first state in which the load is received by hard part42to a second state in which the load is received by soft part44. Hard part42of the present exemplary embodiment has hollow protrusion60as a structure for changing the shape of hard part42.

Protrusion60can be made of an elastic material such as rubber. Protrusion60of the present exemplary embodiment has a hollow truncated cone shape, and includes top part62, base part64, side wall part66, and hollow part68. Protrusion60is disposed on flat surface part20of separator12so as top part62and base part64to be arranged in first direction X. Flat surface part20has through-hole20a, and protrusion60protrudes from flat surface part20toward exterior can14of second power storage device10bwith base part64disposed in through-hole20a. In the present exemplary embodiment, base part64abuts on exterior can14of first power storage device10a, and top part62abuts on exterior can14of second power storage device10b.

Top part62and base part64are connected to each other by side wall part66. Side wall part66is a part having a strength in first direction X lower than those of top part62and base part64. Thus, side wall part66corresponds to vulnerable part46. Hollow part68is a space defined by top part62, base part64, and side wall part66. Hollow part68is opened via through-hole20a. That is, protrusion60has a protruding part protruding toward second power storage device10b, and the surface of the protruding part facing first power storage device10ais recessed toward second power storage device10b. This recess constitutes hollow part68.

Soft part44can be made of a material similar to that of soft part44of the first exemplary embodiment. The shape of soft part44is similar to that of soft part44of the first exemplary embodiment.

FIG.14(A)toFIG.14(C)are cross-sectional views schematically illustrating buffer member40changing its shape by receiving loads from power storage devices10. InFIG.14(A)toFIG.14(C), illustration of electrode body38is omitted.

With respect to the dimension in first direction X, the dimension of protrusion60before deforming is larger than the dimension of soft part44. Thus, as illustrated inFIG.14(A), in a state before protrusion60deforms, top part62abuts on exterior can14of second power storage device10b, and protrusion60receives a load from power storage device10. That is, buffer member40is in the first state.

As illustrated inFIG.14(B), when the load from power storage device10increases, side wall part66curves, and displacement of top part62and base part64starts in first direction X to approach each other. That is, buffer member40starts to change its state from the first state to the second state. Now, exterior can14of second power storage device10babuts also on soft part44, and a load may be applied also to soft part44. The load received by soft part44is smaller than the load received by hard part42.

When protrusion60receives a load of a predetermined magnitude or more from power storage device10, as illustrated inFIG.14(C), side wall part66curves so as to be bent inward, and top part62falls into hollow part68. That is, protrusion60contracts in first direction X by top part62entering hollow part68, resulting in the shape of protrusion60partially inverting. As a result, the dimension of hard part42becomes smaller than the dimension of soft part44, and buffer member40is now in the second state in which soft part44receives the load from power storage device10.

An effect similar to that of the first exemplary embodiment can be obtained also by buffer member40of the present exemplary embodiment. Note that, buffer member40of the present exemplary embodiment may also have a structure that contracts by two steps as in the first exemplary embodiment.

Fourth Exemplary Embodiment

A fourth exemplary embodiment has a configuration common to that of the first exemplary embodiment except for the shape of hard part42. Hereinafter, the present exemplary embodiment will be described mainly on a configuration different from that of the first exemplary embodiment, and common configurations will be briefly described or not described.

FIG.15is a cross-sectional view of buffer member40according to the fourth exemplary embodiment sandwiched between two adjacent power storage devices10. Buffer member40includes hard parts42and soft part44. By hard part42changing its shape, buffer member40changes its state from a first state in which the load is received by hard part42to a second state in which the load is received by soft part44. Hard part42of the present exemplary embodiment has hollow protrusion60as a structure for changing the shape of hard part42.

Protrusion60can be made of a metal or the like. Protrusion60of the present exemplary embodiment has a hollow dome shape and includes top part62, base part64, side wall part66, and hollow part68. Protrusion60is disposed on flat surface part20of separator12so as top part62and base part64to be arranged in first direction X. Flat surface part20has through-hole20a, and protrusion60protrudes from flat surface part20toward exterior can14of second power storage device10bwith base part64disposed in through-hole20a. In the present exemplary embodiment, base part64abuts on exterior can14of first power storage device10a, and top part62abuts on exterior can14of second power storage device10b.

Top part62and base part64are connected to each other by side wall part66. Side wall part66is a part having a strength in first direction X lower than those of top part62and base part64. Thus, side wall part66corresponds to vulnerable part46. Base part64extends parallel to first direction X, and side wall part66extends obliquely with respect to first direction X from the end of base part64. Hollow part68is a space defined by top part62, base part64, and side wall part66. Hollow part68is opened via through-hole20a.

Soft part44can be made of a material similar to that of soft part44of the first exemplary embodiment. The shape of soft part44is similar to that of soft part44of the first exemplary embodiment.

FIG.16(A)toFIG.16(C)are cross-sectional views schematically illustrating buffer member40changing its shape by receiving loads from power storage devices10. InFIG.16(A)toFIG.16(C), illustration of electrode body38is omitted.

With respect to the dimension in first direction X, the dimension of protrusion60before deforming is larger than the dimension of soft part44. Thus, as illustrated inFIG.16(A), in a state before protrusion60deforms, top part62abuts on exterior can14of second power storage device10b, and protrusion60receives a load from power storage device10. That is, buffer member40is in the first state.

As illustrated inFIG.16(B), when the load from power storage device10increases, base part64and side wall part66fall inward, and displacement of top part62starts in first direction X to approach first power storage device10a. That is, buffer member40starts to change its state from the first state to the second state. Now, exterior can14of second power storage device10babuts also on soft part44, and a load may be applied also to soft part44. The load received by soft part44is smaller than the load received by hard part42.

When protrusion60receives a load of a predetermined magnitude or more from power storage device10, as illustrated inFIG.16(C), top part62enters hollow part68, resulting in the shape of the protrusion60partially inverting. As a result, protrusion60contracts in first direction X, and thereby the dimension of hard part42becomes smaller than the dimension of soft part44. As a result, buffer member40is now in the second state in which soft part44receives the load from power storage device10.

An effect similar to that of the first exemplary embodiment can be obtained also by buffer member40of the present exemplary embodiment. Note that, buffer member40of the present exemplary embodiment may also have a structure that contracts by two steps as in the first exemplary embodiment. An insulating sheet (not shown) may be provided between protrusion60and first power storage device10aand between protrusion60and second power storage device10b.

The exemplary embodiments of the present disclosure have been described in detail above. The above-described exemplary embodiments are merely specific examples for implementing the present disclosure. The contents of the exemplary embodiments do not limit the technical scope of the present disclosure, and many design changes such as modifications, additions, and deletions of configuration elements can be made without departing from the spirit of the invention defined in the claims. Any new exemplary embodiment to which design change has been made has an effect of the combined exemplary embodiments and of modified examples. In the above-described exemplary embodiments, with respect to the contents where such design changes can be made, the contents are emphasized with expressions such as “of the present exemplary embodiment” and “in the present exemplary embodiment”. However, design changes are allowed even with respect to the contents without such expressions. Furthermore, any combination of configuration elements included in exemplary embodiments is also effective as an aspect of the present disclosure. Hatching in a cross section in the drawings does not limit the material of the object to which the hatching is applied.

Fifth Modified Example

Buffer member40may be provided to every combination of two adjacent power storage devices10, or may be provided to some of the combinations. Buffer member40may be provided, in addition to that provided between two power storage devices10, between power storage device10and end plate4. Furthermore, buffer member40may be provided only between power storage device10and end plate4.

Sixth Modified Example

Hard part42may be provided separately from separator12. In an example of such a structure, hard part42is integrally molded with a support substrate (not shown). Then, the support substrate is joined to separator12. Examples of a method of bonding the support substrate to separator12include a method of insert-molding the support substrate and separator12, and a method of welding individually formed separator12to the support substrate using ultrasonic waves.

Other Modified Examples

The number of power storage devices10included in power storage module1is not particularly limited. Power storage module1needs to include at least one power storage device10. The structure of each part of power storage module1including the structure of end plate4and that of binding member6is not limited.

REFERENCE MARKS IN THE DRAWINGS

1power storage module10power storage device10afirst power storage device10bsecond power storage device12separator38electrode body40buffer member42hard part44soft part46vulnerable part48first part50second part52third part54first vulnerable part56second vulnerable part60protrusion62top part64base part68hollow part