CN216085049U

CN216085049U - Battery cell and battery pack

Info

Publication number: CN216085049U
Application number: CN202121604718.3U
Authority: CN
Inventors: 申英锋; 单军; 胡春林; 李婷婷; 杨成林; 陈相; 刘平; 陈建鹏
Original assignee: Evergrande New Energy Technology Shenzhen Co Ltd
Current assignee: Evergrande New Energy Technology Shenzhen Co Ltd
Priority date: 2021-07-14
Filing date: 2021-07-14
Publication date: 2022-03-18
Anticipated expiration: 2031-07-14

Abstract

The utility model is suitable for the field of power batteries, and provides a battery monomer and a battery pack. The battery monomer comprises an aluminum-plastic film, a naked battery cell and a shell which are arranged from inside to outside, wherein the aluminum-plastic film and the shell are both in a cylindrical shape, the naked battery cell is arranged between the shell and the aluminum-plastic film, and the inner side surface of the aluminum-plastic film is enclosed to form a cooling channel; the length of the battery cell is 500-2500mm, and the outer circumference of the minimum cross section perpendicular to the length direction is 80-150 mm. The single battery provided by the utility model can improve the energy density of the battery pack.

Description

Battery cell and battery pack

Technical Field

The utility model belongs to the field of power batteries, and particularly relates to a battery monomer and a battery pack.

Background

The space under the body of the electric automobile is limited, and in order to pursue the maximized endurance mileage and the energy density of the battery pack, the blade battery is adopted in the existing design. Specifically, the battery pack includes a plurality of battery cells, which are thin and long in sheet shape and are arranged in sequence. However, a gap is left between adjacent battery cells to dissipate heat, which limits further increase in the space ratio of the battery cells.

SUMMERY OF THE UTILITY MODEL

The present invention is directed to overcoming the above-mentioned disadvantages of the prior art, and provides a battery cell and a battery pack, which are intended to improve energy density of the battery pack.

In order to achieve the above purpose, the embodiment of the present invention provides the following technical solutions:

in a first aspect, the battery monomer comprises an aluminum-plastic film, a bare cell and a shell which are arranged from inside to outside, wherein the aluminum-plastic film and the shell are both cylindrical, the bare cell is arranged between the shell and the aluminum-plastic film, and the inner side surface of the aluminum-plastic film is enclosed to form a cooling channel; the length of the battery monomer is 500-2500mm, and the outer circumference of the minimum cross section perpendicular to the length direction of the battery monomer is 80-150 mm.

By adopting the technical scheme, the length of the battery monomer is 500-2500 mm. In combination with the conventional design of the battery pack, the battery pack is cuboid, and the size of the battery pack in the length direction can only accommodate one battery monomer. The plurality of battery cells are arranged in the width and height directions of the battery pack. The arrangement of the battery monomers can be simplified under the arrangement, the number of the supporting pieces used for fixing the battery monomers in the battery pack is reduced, the space utilization rate is further improved, and the energy density of the battery pack and the cruising ability of the electric vehicle using the battery pack are improved.

The outer circumference of the cross section of the battery cell is controlled to be within 15 cm to guide heat to spread toward the end thereof rather than to be collected in the lateral direction, thereby facilitating heat dissipation.

Because the inside cooling channel that is equipped with of battery monomer, consequently, need not to leave the clearance between the battery monomer in order to dispel the heat, the battery monomer can arrange with the mode of direct butt to be favorable to improving the space utilization of battery package, improve the energy density of battery package. And because heat is leading-in and deriving from battery monomer inside, compare current outside temperature control mode, heat-conduction is more high-efficient, from another angle, can reduce liquid cooling medium quantity, reduces the pipeline volume, improves battery package energy density

In addition, the battery monomer is hollow tubular structure owing to the setting of cooling channel, combines mechanical design principle, and hollow tubular structure has higher anti ability of buckling than the solid tube structure of same cross-sectional area to be favorable to improving the structural stability of battery package.

By the aid of the battery cell, the energy density of the battery pack can be improved.

Optionally, the ratio of the length of the battery cell to the outer circumference of the smallest cross-section is 8-24.

By adopting the technical scheme, the energy density of the battery pack is further improved.

Optionally, the thickness of the bare cell between the outer shell and the aluminum-plastic film is 5-15 mm.

By adopting the technical scheme, the requirement of the energy density of the battery pack can be met, and the strength and the heat dissipation performance of the battery monomer are taken into consideration.

Optionally, the cross section of the cooling channel is rectangular, and the length of the short side of the cooling channel is not less than 2 mm.

By adopting the technical scheme, the minimum winding radius of the positive pole piece/the negative pole piece is ensured.

Optionally, the bare cell includes a positive electrode plate and a negative electrode plate, and the positive electrode plate and the negative electrode plate are wound on the outer side of the aluminum-plastic film.

By adopting the technical scheme, the winding device has higher initial winding radius when being produced in a winding mode so as to reduce the bending and damage of the positive pole piece and the negative pole piece. Compared with a lamination mode, the winding process reduces a plurality of times of slicing, and is beneficial to process simplification and yield improvement. The battery cell provided by the application has the short-circuit discharge characteristic similar to that of a blade battery and has high safety similar to that of the blade battery.

Optionally, the outer side surface of the outer shell is coated with a thermal insulation layer.

Through adopting above-mentioned technical scheme, effective isolation is close to battery monomer in order to avoid the run away to spread when battery monomer appears unusual intensification.

Optionally, the positive electrode tab and the negative electrode tab of the battery cell are respectively located on two opposite sides of the bare cell in the length direction.

Through adopting above-mentioned technical scheme, compare in anodal utmost point ear and negative pole utmost point ear homonymy setting, current density's homogeneity when can guaranteeing battery monomer normal discharge. When the battery monomer is subjected to acupuncture or local short circuit, the distance between the negative pole lug and the positive pole lug is far, and the power supply resistance is increased, so that the short-circuit current and the discharge intensity can be effectively reduced.

In a second aspect, a battery pack is provided, which includes a plurality of battery cells as described above.

Through adopting above-mentioned technical scheme, reduce the quantity that is used for the free support piece of fixed battery in the battery package, and then improve space utilization, improve the energy density of battery package and use the electric motor car duration of this battery package.

Optionally, a plurality of the battery cells are arranged along the thickness and/or height direction thereof, and two adjacent battery cells are abutted against each other.

Optionally, the shells of two adjacent battery cells in the thickness and/or height direction of the battery cells are glued to each other.

Through adopting above-mentioned technical scheme to increase battery monomer whole rigidity and intensity.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a battery cell according to an embodiment of the present invention;

fig. 2 is a schematic cross-sectional view of a battery cell according to an embodiment of the present invention;

fig. 3 is a first schematic layout diagram of a battery cell according to an embodiment of the present invention;

fig. 4 is a second schematic layout diagram of a battery cell according to an embodiment of the present invention;

fig. 5 is a third schematic layout diagram of a battery cell according to an embodiment of the present invention;

fig. 6 is a fourth schematic arrangement diagram of the battery cells according to the embodiment of the present invention.

Wherein, in the figures, the respective reference numerals:

10. a battery cell; 11. an aluminum-plastic film; 12. a naked battery cell; 13. a housing; 101. a cooling channel.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the utility model and are not intended to limit the utility model.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.

It will be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, as used herein, refer to an orientation or positional relationship indicated in the drawings, which is solely for the purpose of facilitating the description and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and is therefore not to be construed as limiting the utility model.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

Referring to fig. 1 to 6, a battery cell 10 and a battery pack using the battery cell 10 provided in the present application will now be described.

Referring to fig. 1, a battery cell 10 has a narrow and long sheet shape, and has a length, a width and a height. For convenience of description, the length direction of the battery cell 10 is defined as a front-rear direction, the width direction of the battery cell 10 is defined as a left-right direction, and the height direction of the battery cell 10 is defined as a top-bottom direction.

Referring to fig. 2, a battery cell 10 includes an aluminum-plastic film 11, a bare cell 12 and a housing 13, which are arranged from inside to outside, the aluminum-plastic film 11 and the housing 13 are both in a cylindrical shape extending from front to back, the cylindrical shape may be a cylindrical structure with uniform cross sections or a similar cylindrical structure with different cross sections but smaller differences, the bare cell 12 is disposed between the housing 13 and the aluminum-plastic film 11, and the inner side surface of the aluminum-plastic film 11 is enclosed to form a cooling channel 101.

The length (i.e., the dimension in the front-rear direction) of the battery cell 10 is 500-.

The length of the battery cell 10 is 500-2500 mm. The design that combines the battery package, the battery package is the cuboid form, and for some battery package structures of standard length, its length direction's size can only hold a battery monomer 10, and the battery monomer accumulates along the width direction of battery package, and the length direction of battery monomer is unanimous with the length direction of battery package. The battery monomers can also be arranged in the battery pack in other arrangement modes, and are not listed one by one. The plurality of battery cells 10 are arranged in the width and height directions of the battery pack. This arrangement can simplify the arrangement of battery monomer 10 to reduce the quantity that is used for the support piece of fixed battery monomer 10 in the battery package, and then improve space utilization, improve the energy density of battery package and use the electric motor car duration of this battery package.

Further, the outer circumference of the cross section of the battery cell 10 is controlled to be within 15 cm, which is related to the width of the battery cell, and is controlled to be within 15 cm, which is smaller in proportion to the length of the battery cell, so as to guide heat to propagate toward the end thereof rather than being collected in the lateral direction, thereby facilitating heat dissipation.

The space enclosed by the inner side of the aluminum-plastic film 11 forms a cooling channel 101, and the temperature of the battery cell 10 can be adjusted by air cooling or water cooling, so that the battery cell 10 is within the designed working temperature range. It is understood that temperature regulation includes temperature increase and cool down. When air cooling is adopted, cold air can directly flow through the cooling channel 101 to dissipate heat of the battery cell 10. When water cooling is adopted, the liquid cooling medium directly flows through the cooling channel 101, or a pipeline for the liquid cooling medium to flow through is arranged in the cooling channel 101, so as to dissipate heat of the battery cell 10. In this embodiment, the battery cells 10 are cooled by water. Specifically, the battery pack further includes a thermal management system including a duct provided in the cooling passage 101. The plurality of battery cells 10 are arranged in rows and columns, and the pipes in the cooling channels 101 are connected in series, in parallel, or in combination to allow a liquid cooling medium to flow.

Because the inside cooling channel 101 that is equipped with of battery monomer 10, consequently, need not to leave the clearance between battery monomer 10 in order to dispel the heat, battery monomer 10 can arrange with the mode of direct butt to be favorable to improving the space utilization of battery package, improve the energy density of battery package. And because the heat is leading-in and derived from battery monomer 10 inside, compare current outside temperature control mode, heat-conduction is more high-efficient, from another angle, can reduce the liquid cooling medium quantity, reduces the pipeline volume, improves battery package energy density.

In addition, the battery cell 10 is a hollow tubular structure due to the arrangement of the cooling channel 101, and the hollow tubular structure has higher bending resistance compared with a solid tube structure with the same sectional area by combining a mechanical design principle, so that the structural stability of the battery pack is improved.

By last, the battery cell 10 that this embodiment provided, through the design of battery cell 10 overall dimension in order to improve the energy density of battery package, the design of the cooling channel 101 through battery cell 10 is favorable to improving the space utilization of battery package, and then improves the energy density of battery package, through the design of battery cell 10 cavity in order to improve the anti ability of buckling of battery cell 10.

It should be noted that the battery cell 10 according to the present embodiment dissipates heat from the inside. Compared with the external heat dissipation mode of the traditional battery cell, the heat dissipation area is reduced to some extent, and the internal temperature rise is possibly caused. Therefore, it is necessary to compare whether the charging and discharging temperature rise is acceptable under the same heat dissipation surface temperature condition. Steady state thermal conductivity value simulations were performed on the discharge heating of the same cell 10 in the same physical dimensions and the results are shown in table 1:

	internal heat dissipation	External heat dissipation
			Positive electrode material	Lithium iron phosphate	Lithium iron phosphate
Negative electrode material	Graphite	Graphite
			Discharge current, C	15	15
Heat generation power, W/m3	120958	120958
			Coefficient of thermal conductivity, W/(mK. cndot.)	29.557	29.557
Heat capacity, J/(kgK. the product of the design is)	1399.1	1399.1
			Outer boundary temperature,. degree.C	Thermal insulation	Constant temperature
Inner layer boundary temperature,. degree.C	Constant temperature	Thermal insulation
			Temperature difference between the inner and outer layers,. deg.C	0.31	0.14

TABLE 1 comparison of internal and external Heat dissipation modes

In another embodiment of the present application, the ratio of the length of the battery cell 10 in the front-rear direction to the outer circumference of the smallest cross section is 8 to 24. This arrangement can further improve the energy density of the battery pack. Those skilled in the art can set the ratio to 8, 9, 10, 12, 13, 14, 15, 16, 18, 19, 20, 21, 22, 23, 24, etc. according to practical situations, and the ratio is not limited herein.

In another embodiment of the present application, the thickness of the bare cell 12 between the outer shell 13 and the aluminum-plastic film 11 layer is 5-15 mm. It can be understood that the thickness of the bare cell 12 affects the energy density of the battery pack and also affects the heat dissipation effect of the battery cell 10. Through multiple experiments, under the condition that the outer circumference is 80-150mm, the thickness of the bare cell 12 is 5-15mm, the requirement of the energy density of a battery pack can be met, and the strength and the heat dissipation performance of the battery monomer 10 are considered. The thickness of the bare cell 12 can be set to 5mm, 6mm, 8mm, 8.6mm, 8.8mm, 9mm, 10mm, 10.2mm, 11mm, 12mm, 13mm, 14mm, 15mm, etc. by those skilled in the art according to actual conditions, which is not limited herein.

In another embodiment of the present application, referring to fig. 2, the cross section of the cooling channel 101 is rectangular, and the length of the short side (i.e. the height of the cooling channel 101 in the vertical direction) is not less than 2 mm. Preferably, the cooling channel 101 has a rectangular cross section, and four inner corners are rounded, and the radius of the rounded corner is 0.5 mm or more.

After the combination, the bare cell 12 is formed by a winding process, and the height of the cooling channel 101 is set to be more than 2mm, so as to ensure the minimum winding radius of the positive electrode plate/the negative electrode plate. Preferably, the height of the cooling channel 101 is less than 5 mm. Too high a thickness of the cooling channel 101 and the battery cell 10 may reduce the effective packing density of the battery cell 10. The height of the cooling channel 101 may be set to 2.0mm, 2.2mm, 2.8mm, 3.0mm, 3.2mm, 3.5mm, 3.6mm, 3.8mm, 4.0mm, 4.4mm, 5mm, etc. by those skilled in the art according to practical circumstances, and is not limited herein.

In this embodiment, the positive electrode tab and the negative electrode tab of the battery cell 10 are respectively located on two opposite sides of the bare cell 12.

The relative both sides (can understand, for length direction's both sides) of naked electric core 12 are located to negative pole utmost point ear and positive pole utmost point ear, compares in positive pole utmost point ear and negative pole utmost point ear homonymy setting, and the homogeneity of current density when can guaranteeing battery monomer 10 normally discharges on the one hand. On the other hand, when the battery cell 10 is subjected to a needle-prick or a local short circuit, the distance between the negative electrode tab and the positive electrode tab is relatively long, and the power supply resistance increases, so that the short-circuit current and the discharge intensity can be effectively reduced.

In another embodiment of the present application, the bare cell 12 includes a positive electrode plate and a negative electrode plate, and the positive electrode plate and the negative electrode plate are wound on the outer side of the aluminum-plastic film 11. The positive pole piece adopts lithium iron phosphate as an active material. The negative pole piece is a graphite electrode. Bare cell 12 may also include a separator. The positive pole piece and the negative pole piece which are coated on the two sides and the diaphragm in the middle are wound and formed to a given thickness on a reel which is externally sleeved with an aluminum plastic film 11 to form a naked electric core 12. Because the hollow structure is adopted, the winding device has higher initial winding radius in the winding mode production so as to reduce the bending and damage of the positive pole piece and the negative pole piece. However, if the existing solid battery cell adopts a winding process, a part of the initial winding space is inevitably wasted (for example, the center of the cylindrical battery cannot be completely filled with the pole piece). In addition, compared with a lamination mode, the winding process reduces a plurality of times of slicing, and is beneficial to process simplification and yield improvement.

In addition, the battery cell 10 provided in the present embodiment has a short-circuit discharge characteristic similar to that of a blade battery. The positive electrode sheet, the diaphragm and the negative electrode sheet are stacked and then wound around a shaft in the length direction to obtain the bare cell 12. The outer perimeter of the cross section of the bare cell 12 is equivalent to the width of the narrow side of the blade battery, and thus, although the winding process is adopted by the bare cell 12 instead of the lamination process in the battery cell 10 provided by the embodiment, the short-circuit discharge circuit is almost the same. And therefore has similarly high security.

In this embodiment, the housing 13 may be a highly insulating material. When the abnormal temperature rise of the battery cell 10 occurs, the adjacent battery cells 10 are effectively isolated to avoid the runaway propagation.

In another embodiment of the present application, the outer side surface of the outer case 13 is coated with a thermal insulation layer to effectively isolate the adjacent battery cells 10 from runaway propagation when abnormal temperature rise occurs in the battery cells 10.

The housing 13 is made of a high-strength material to limit the inward expansion of the battery cell 10 during the charging and discharging processes, thereby reducing the load of the pressure plate in the conventional battery pack or reducing the usage amount of the pressure plate, and improving the energy density of the battery pack. When the internal battery monomer 10 is out of control, the combustion object is prevented from being transmitted to other battery monomers 10, and meanwhile, the aluminum-plastic film 11 with lower strength on the inner side is combined, high-pressure gas is led into the cooling channel 101 after the aluminum-plastic film 11 is broken, and then the high-pressure gas is discharged from a controllable area, so that the safety of the battery pack is improved.

Preferably, the housing 13 is made of a fiber-reinforced composite material (a reinforcing material such as aramid fiber, glass fiber-reinforced plastic, or carbon fiber), a nanocellulose-based material, a foamed metal, stainless steel, or an aluminum alloy.

Referring to fig. 3 to 6, the battery pack includes a plurality of battery cells 10, and the plurality of battery cells 10 are arranged in rows and columns along the thickness and height directions thereof. The battery pack is rectangular in shape, and has a length dimension that can accommodate only one battery cell 10. The plurality of battery cells 10 are arranged in the width and height directions of the battery pack. This arrangement can simplify the arrangement of battery monomer 10 to reduce the quantity that is used for the support piece of fixed battery monomer 10 in the battery package, and then improve space utilization, improve the energy density of battery package and use the electric motor car duration of this battery package.

In the present embodiment, the outer cases 13 of two battery cells 10 adjacent in the thickness and/or height direction of the battery cell 10 abut against each other. Since the battery cells 10 are arranged in a hollow (cooling channel 101), no gap is required between the battery cells 10 to dissipate heat. Adjacent battery cells 10 can be stacked in close packing to further increase the energy density of the battery pack. In addition, since the adjacent battery cells 10 are in surface-to-surface contact with each other, the contact stress is uniform, which is advantageous to disperse stress caused by external impact or vibration. The combination of the hollow tubular structure can increase the rigidity of the battery cell, and the close packing of the battery cells 10 can also significantly reduce the amount of system support. In the battery pack, the total volume of all the battery cells 10 accounts for more than 70% or 80% of the volume of the battery pack, and a heat dissipation space is already included.

It is understood that the battery cells 10 may be arranged in an array or may be staggered.

Preferably, a structural adhesive is coated between adjacent battery cells 10 to increase overall rigidity and strength.

Fig. 3 to 5 show the arrangement of three different sizes of battery cells 10.

In the structure shown in fig. 3, the winding starting radius (the inner corner radius of the cooling channel 101) is 0.3mm, the height of the cooling channel 101 is 3.6mm, the width of the cooling channel 101 is 31mm, the thickness of the bare cell 12 is 5mm, the thickness of the outer shell 13 is 0.2mm, and the length of the battery cell 10 is 1000 mm. From this, the cross-sectional outer circumference of the single battery 10 is 100mm, the aspect ratio of 3:1 and the volume of the single battery 10 is 580cm³The theoretical maximum bulk density of the battery cell 10 in the battery pack is 72.8%. In the battery pack, a plurality of battery cells 10 are arranged in an array. The contact surfaces of the adjacent battery cells 10 are coated with a structural adhesive to increase the strength of the entire battery cell 10.

In the structure shown in fig. 4, the winding starting radius is 0.3mm, the height of the cooling channel 101 is 3.6mm, the width of the cooling channel 101 is 23mm, the thickness of the bare cell 12 is 8mm, the thickness of the outer shell 13 is 0.2mm, and the length of the battery cell 10 is 1000 mm. Thereby can countThe cross section outer circumference of the single battery 10 is 100mm, the width-height ratio of the single battery 10 is 2:1, and the solid volume of the single battery 10 is 580cm³The theoretical maximum bulk density of the battery cell 10 in the battery pack is 78.5%. In the battery pack, a plurality of battery cells 10 are arranged in an array. The contact surfaces of the adjacent battery cells 10 are coated with a structural adhesive to increase the strength of the entire battery cell 10.

In the structure shown in fig. 5, the initial winding radius is 0.3mm, the height of the cooling channel 101 is 3.6mm, the width of the cooling channel 101 is 16mm, the thickness of the bare cell 12 is 10mm, the thickness of the outer shell 13 is 0.2mm, and the length of the battery cell 10 is 1000 mm. From this, the cross-sectional outer circumference of the single battery 10 is 100mm, the aspect ratio of 1.5:1 and the solid volume of the single battery 10 is 852cm³The theoretical maximum bulk density of the battery cell 10 in the battery pack is 80.1%. In the battery pack, a plurality of battery cells 10 are arranged in an array. The contact surfaces of the adjacent battery cells 10 are coated with a structural adhesive to increase the strength of the entire battery cell 10.

Fig. 3 and 6 show different arrangements of the battery cells 10 of the same size. In the structure of fig. 3, the battery cells 10 are arranged in an array. In the structure shown in fig. 6, two adjacent rows of the battery cells 10 are arranged with a shift.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the utility model, and any modifications, equivalents or improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A battery monomer comprises an aluminum plastic film, a naked battery cell and a shell which are arranged from inside to outside, and is characterized in that the aluminum plastic film and the shell are both in a cylindrical shape, the naked battery cell is arranged between the shell and the aluminum plastic film, and the inner side surface of the aluminum plastic film is enclosed to form a cooling channel; the length of the battery monomer is 500-.

2. The battery cell of claim 1, wherein a ratio of a length of the battery cell to an outer perimeter of the smallest cross-section is 8-24.

3. The battery cell of claim 1, wherein the bare cell has a thickness between the outer shell and the aluminum-plastic film of 5-15 mm.

4. The battery cell of claim 1, wherein the cooling channel is rectangular in cross section and has a short side length of not less than 2 mm.

5. The battery cell of claim 1, wherein the bare cell comprises a positive pole piece and a negative pole piece, and the positive pole piece and the negative pole piece are wound on the outside of the aluminum-plastic film.

6. The battery cell of claim 1, wherein an outside surface of the housing is coated with a thermal insulation layer.

7. The battery cell of any one of claims 1 to 6, wherein a positive electrode tab and a negative electrode tab of the battery cell are respectively located on two opposite sides of the bare cell in the length direction.

8. A battery pack comprising a plurality of battery cells according to any one of claims 1 to 7.

9. The battery pack according to claim 8, wherein a plurality of the battery cells are arranged in a thickness and/or height direction thereof, and adjacent two of the battery cells abut against each other.

10. The battery pack according to claim 8, wherein the outer cases of two of the battery cells adjacent in the thickness and/or height direction of the battery cells are adhesively bonded to each other.