Secondary battery and device including the same

Abstract

A secondary battery according to an embodiment of the present invention includes an electrode assembly including electrode sheets on which electrode tabs are formed and a separator disposed between the electrode sheets, a battery case in which the electrode assembly is housed, and an electrode lead connected to the electrode tab and protruding out of the battery case, the electrode lead including a flexible part that is stretchable in a direction parallel to the protruding direction of the electrode lead, the flexible part being disposed inside the battery case.

Description

[Technical field]

[0001] [Cross-reference to related applications]

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0165723 filed on December 1, 2020, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0003] The present invention relates to a secondary battery and a device including the same, and more particularly to a secondary battery that prevents breakage of electrode tabs and a device including the same. [Background technology]

[0004] Recently, as the price of energy sources rises due to the depletion of fossil fuels and concerns about environmental pollution grow, the demand for environmentally friendly alternative energy sources has become an essential factor for future life. Therefore, research into various power generation technologies such as atomic, solar, wind, and tidal power has been ongoing, and there has also been a great deal of interest in power storage devices to use the energy produced in this way more efficiently.

[0005] In particular, the demand for batteries as an energy source is rapidly increasing due to technological developments and increasing demand for mobile devices, and accordingly, much research is being conducted into batteries that can meet various demands.

[0006] 2. Description of the Related Art There is a high demand for lithium secondary batteries, such as lithium ion batteries and lithium ion polymer batteries, which have advantages such as high energy density, discharge voltage, and output stability.

[0007] Secondary batteries can also be classified according to the structure of the electrode assembly, which is a stacked structure of a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. Representative examples include a jelly roll type electrode assembly in which a long sheet-like positive electrode and a negative electrode are wound with a separator interposed therebetween, and a stack type electrode assembly in which a number of positive electrodes and negative electrodes cut into a predetermined size are stacked in sequence with a separator interposed therebetween. Recently, in order to solve the problems of the jelly roll type electrode assembly and the stack type electrode assembly, a stack / fold type electrode assembly has been developed as a hybrid of the jelly roll type and the stack type, in which unit cells in which a predetermined unit of positive electrodes and negative electrodes are stacked with a separator interposed therebetween are positioned on a separator film and wound in sequence.

[0008] In addition, secondary batteries can be classified according to the shape of the case into cylindrical secondary batteries in which the electrode assembly is built into a cylindrical case, prismatic secondary batteries in which the electrode assembly is built into a prismatic case, and pouch-type secondary batteries in which the electrode assembly is built into a pouch-type case made of a laminate sheet.

[0009] FIG. 1 is a perspective view of a conventional pouch-type secondary battery, and FIG. 2 is a cross-sectional view taken along line AA' in FIG.

[0010] 1 and 2, a conventional pouch-type secondary battery 10 may be manufactured by housing an electrode assembly 20 inside a pouch-type battery case 30 and then sealing it. The electrode assembly 20 includes electrodes and a separator disposed between the electrodes. The electrodes include electrode tabs 21t, which are joined to electrode leads 40 by a method such as welding. The electrode leads 40 are exposed to the outside of the pouch-type battery case 30, thereby providing an electrical connection to the electrode assembly 20.

[0011] In this case, the electrode assembly 20 may be a stack-type electrode assembly in which a number of electrodes cut into units of a predetermined size are stacked in sequence with a separator interposed therebetween. Each electrode tab 21t extending from each electrode may be connected to an electrode lead 40.

[0012] The electrode assembly 20 repeatedly contracts and expands as it is repeatedly charged and discharged. As shown in FIG. 2, the electrode assembly 20 expands in its thickness direction (parallel to the z-axis). The electrode lead 40 included in the conventional secondary battery 10 is not flexible and is interposed between the sealed battery cases 30, so its position can only be fixed with the electrode tabs 21t joined. At this time, when the electrode assembly 20 expands in its thickness direction (parallel to the z-axis), a large tension is generated in the electrode tabs 21t because the electrode leads 40 are fixed. In particular, in a stacked electrode assembly, the electrode tabs 21t located on the outermost side are subjected to the largest tension when the electrode assembly 20 expands, and in extreme cases, this may even lead to disconnection.

[0013] Therefore, there is a need to develop a technology that can prevent the electrode tabs from breaking when the electrode assembly expands. Summary of the Invention [Problem to be solved by the invention]

[0014] An object of the present invention is to provide a secondary battery and a device including the same, which can reduce tension applied to electrode tabs and prevent breakage of the outermost electrode tabs even when an electrode assembly expands.

[0015] However, the problem to be solved by the embodiments of the present invention is not limited to the above problem, and can be variously expanded within the scope of the technical ideas included in the present invention. [Means for solving the problem]

[0016] According to an embodiment of the present invention, a secondary battery includes an electrode assembly including electrode sheets having electrode tabs and a separator disposed between the electrode sheets, a battery case in which the electrode assembly is housed, and an electrode lead connected to the electrode tab and protruding out of the battery case, the electrode lead including a flexible part having flexibility in a direction parallel to a protruding direction of the electrode lead, the flexible part being disposed inside the battery case.

[0017] The flexible portion may have a curved shape.

[0018] The flexible portion may extend in a direction parallel to a protruding direction of the electrode lead.

[0019] The flexible portion may include at least one of gold (Au) and silver (Ag).

[0020] The battery case may include an upper case and a lower case, a sealing portion of the upper case and a sealing portion of the lower case may be heat-sealed to each other, and the flexible portion may be located between a portion of the electrode lead where the sealing portion is located and the electrode assembly.

[0021] The electrode lead may include a first portion connected to the flexible portion and the electrode tab, a second portion connected to the flexible portion and protruding outside the battery case, and fixing portions connected to each of the first portion and the second portion.

[0022] The flexible portion may include a first flexible portion and a second flexible portion, and the fixed portion may be located between the first flexible portion and the second flexible portion.

[0023] The fixing portion may include at least one of a glass material, a ceramic material, graphite, and an alloy material having low flexibility.

[0024] The fixing portion may have a straight line shape.

[0025] The electrode assembly may be a stack-type electrode assembly in which the electrode sheets are stacked, and when the electrode sheets expand in a thickness direction, the flexible portion may extend in a direction perpendicular to the thickness direction. Effect of the Invention

[0026] According to an embodiment of the present invention, by forming a flexible portion in the electrode lead, it is possible to reduce tension applied to the electrode tabs even when the electrode assembly expands, and therefore, breakage of the outermost electrode tabs can be prevented.

[0027] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description of the claims. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a perspective view of a conventional pouch-type secondary battery. [Diagram 2] 2 is a cross-sectional view taken along line AA' in FIG. 1. [Diagram 3] 1 is an exploded perspective view of a secondary battery according to an embodiment of the present invention; [Figure 4] FIG. 4 is a perspective view showing the secondary battery of FIG. 3 in an assembled state. [Diagram 5] 5 is a cross-sectional view taken along line BB' in FIG. 4. [Figure 6] 6 is a plan view of an electrode lead included in the secondary battery of FIG. 5, viewed from the -z-axis direction on the xy plane. [Figure 7] 6 is a cross-sectional view showing an electrode assembly expanded relative to an electrode assembly and an electrode lead included in the secondary battery of FIG. 5. [Figure 8] FIG. 4 is a cross-sectional view showing an electrode assembly and an electrode lead according to a modified embodiment of the present invention. [Figure 9] 9 is a plan view of the electrode assembly and the electrode lead of FIG. 8 as viewed from the -z axis direction on the xy plane. [Figure 10]FIG. 13 is a plan view showing an electrode lead according to another modified embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention may, however, be embodied in various different forms and should not be construed as being limited to the embodiments set forth herein.

[0030] In order to clearly describe the present invention, parts that are not relevant to the description will be omitted, and the same reference numerals will be used throughout the specification to refer to the same or similar components.

[0031] In addition, the size and thickness of each component shown in the drawings are shown arbitrarily for convenience of explanation, and the present invention is not necessarily limited to those shown. In the drawings, the thickness is exaggerated to clearly express multiple layers and regions. In the drawings, the thickness of some layers and regions is exaggerated for convenience of explanation. In addition, when a part such as a layer, film, region, plate, etc. is said to be "on" or "above" another part, this includes not only the case where it is "directly above" the other part, but also the case where there is another part in between. Conversely, when a part is said to be "directly above" another part, it means that there is no other part in between. In addition, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "on" or "above" the opposite direction of gravity.

[0032] Also, throughout the specification, when a part "comprises" a certain element, this means that it may further include other elements, but not excluding other elements, unless specifically stated to the contrary.

[0033] Also, throughout the specification, "in a plane" means when the subject part is viewed from above, and "in cross section" means when the subject part is cut vertically and viewed from the side.

[0034] Fig. 3 is an exploded perspective view of a secondary battery according to an embodiment of the present invention, Fig. 4 is a perspective view showing an assembled state of the secondary battery of Fig. 3, Fig. 5 is a cross-sectional view taken along line BB' of Fig. 4.

[0035] 3 to 5, a secondary battery 100 according to an embodiment of the present invention includes an electrode assembly 200, a battery case 300 in which the electrode assembly 200 is housed, and electrode leads 400, 500 protruding outside the battery case 300.

[0036] The electrode assembly 200 includes electrode sheets 210, 220 on which electrode tabs 210t are formed, and a separator 230 disposed between the electrode sheets 210, 220. In particular, the electrode assembly 200 according to this embodiment may be a stacked type electrode assembly, a jelly roll type electrode assembly, or a stacked / folded type electrode assembly, but is preferably a stacked type electrode assembly. Specifically, the stacked type electrode assembly may have a structure in which a number of electrode sheets 210, 220 are stacked with a separator 230 interposed therebetween.

[0037] Each of the electrode sheets 210 and 220 may be formed by applying an electrode active material onto an electrode collector, and a portion of the electrode collector may protrude to provide an electrode tab 210t. The electrode sheets 210 and 220 may be divided into a positive electrode sheet and a negative electrode sheet, and a separator 230 may be interposed between the positive electrode sheet and the negative electrode sheet. For example, the electrode sheet 210 may be a positive electrode sheet, and the electrode tab 210t protruding therefrom may be a positive electrode tab. The other electrode sheet 220 may be a negative electrode sheet, and the electrode tab (not shown) protruding therefrom may be a negative electrode tab.

[0038] In addition, the electrode tabs according to the present embodiment may be connected to electrode leads. For example, an electrode tab 210t of one polarity may be connected to one electrode lead 400, and an electrode tab of the other polarity (not shown) may be connected to the other electrode lead 500. Such electrode leads 400, 500 may protrude from both ends of the battery case 300. Although two electrode leads 400, 500 are shown protruding in directions opposite to each other in Figs. 3 and 4, the protruding directions are not particularly limited. That is, a structure in which two electrode leads 400, 500 protrude in the same direction from one side of the secondary battery 100 is also possible. One of the two electrode leads 400, 500 may be a positive electrode lead, and the other may be a negative electrode lead.

[0039] Meanwhile, the battery case 300 according to the present embodiment may be a pouch-type case. Such a battery case 300 may include an upper case 310 and a lower case 320 that are heat-sealed to each other. Although not specifically shown, the battery case 300 including the upper case 310 and the lower case 320 may be a laminate sheet including a resin layer and a metal layer. Specifically, each of the upper case 310 and the lower case 320 may include an inner resin layer for sealing, a metal layer for preventing penetration of a material, and an outermost outer resin layer.

[0040] The outer resin layer may have excellent tensile strength and weather resistance and electrical insulation properties relative to its thickness in order to protect the pouch-type secondary battery 100 from the outside. The outer resin layer may include PolyEthylene Terephthalate (PET) resin or nylon resin. The metal layer may prevent air, moisture, etc. from entering the pouch-type secondary battery 100. The metal layer may include aluminum (Al). The inner resin layers may be thermally fused to each other by heat and pressure applied with the electrode assembly 200 embedded inside. The inner resin layer may include Casted PolyPropylene (CPP) or PolyPropylene (PP).

[0041] The upper case 310 and the lower case 320 are formed with recessed receiving portions 310R and 320R in which the electrode assembly 200 can be seated, respectively, and the electrode assembly 200 is received in the receiving portions 310R and 320R. There is no particular limitation on the method for forming the receiving portions 310R and 320R, and a deep drawing method using a pressurizing punch may be applied.

[0042] Sealing parts 310S, 320S are provided along the outer periphery of the storage parts 310R, 320R of the upper case 310 and the lower case 320. The sealing part 310S of the upper case 310 and the sealing part 320S of the lower case 320 are heat-sealed to each other to seal the battery case 300. More specifically, the inner resin layer of the sealing part 310S of the upper case 310 and the inner resin layer of the sealing part 320S of the lower case 320 may be heat-sealed in a state where they face each other. Meanwhile, while FIG. 3 illustrates the upper case 310 and the lower case 320 separated from each other with the storage parts formed therein, one side of the upper case and one side of the lower case may be a laminate sheet integrally formed, or only one of the upper case and the lower case may have a storage part formed therein and the other may have a plate-like structure without the storage part formed therein.

[0043] Hereinafter, the flexible portion formed in the electrode lead according to the embodiment of the present invention will be described in detail with reference to Figures 5 and 6. In order to avoid repetitive explanation, the flexible portion will be described based on one of the two electrode leads 400, 500. However, the flexible portion structure according to the present embodiment can be formed in the other electrode lead 500 as well.

[0044] FIG. 6 is a plan view of the electrode lead included in the secondary battery of FIG. 5 as viewed from the -z axis direction on the xy plane.

[0045] 3, 5 and 6, the electrode lead 400 according to this embodiment includes a flexible part (400f) having elasticity in a direction parallel to the protruding direction of the electrode lead 400 (direction parallel to the y-axis), and the flexible part 400f is located inside the battery case 300.

[0046] Specifically, the flexible portion 400f according to this embodiment has a bent shape and can extend in a direction parallel to the protruding direction (direction parallel to the y-axis) of the electrode lead 400. In other words, the flexible portion 400f according to this embodiment can be in a form compressed in a direction parallel to the protruding direction (direction parallel to the y-axis) of the electrode lead 400.

[0047] The flexible portion 400f is preferably made of a material having excellent flexibility, malleability, elasticity, and toughness, and may contain at least one of gold (Au) and silver (Ag) as an example. The flexible portion 400f may be formed in the middle of the electrode lead 400, and specifically, as shown in Figs. 5 and 6, an existing plate-shaped metal material constituting the electrode lead 400 may be joined to both ends of the metal material constituting the flexible portion 400f by a method such as welding. That is, the electrode lead 400 including the flexible portion 400f may be manufactured by welding metal members containing aluminum (Al) or copper (Cu) to both ends of a metal member containing silver (Ag).

[0048] FIG. 7 is a cross-sectional view showing a state in which the electrode assembly expands with respect to the electrode assembly and the electrode lead included in the secondary battery of FIG.

[0049] In the conventional electrode assembly (20, see FIG. 2), the electrode lead 40 is not flexible and is fixed in position, so that the electrode tab 21t is subjected to a large tension when the electrode assembly 20 expands, and the outermost electrode tab 21t is at risk of being broken. On the other hand, referring to FIG. 7 together with FIG. 5 and FIG. 6, the flexible portion 400f of the electrode lead 400 according to the present embodiment has elasticity, so that when the electrode assembly 200 expands in the thickness direction (direction parallel to the z-axis), it can extend in a direction perpendicular to the thickness direction. That is, when the electrode assembly 200 expands, the flexible portion 400f according to the present embodiment can extend in a direction parallel to the protruding direction of the electrode lead 400 (direction parallel to the y-axis), particularly in the direction in which the electrode assembly 200 is located (-y-axis direction).

[0050] It is possible to prevent excessive tension from being generated in the electrode tabs 210t due to the stretching of the flexible portion 400f, and it is possible to prevent breakage of the outermost electrode tabs 210t.

[0051] At this time, as described above, the flexible portion 400f included in the electrode lead 400 is located inside the battery case 300. Specifically, referring again to FIG. 5, the sealing portion 310S of the upper case 310 and the sealing portion 320S of the lower case 320 are heat-sealed to each other, and the flexible portion 400f is located between the electrode assembly 200 and the portion of the electrode lead 400 where the sealing portions 310S, 320S are located. If the flexible portion 400f is formed in an outer portion outside the portion of the electrode lead 400 where the sealing portions 310S, 320S are located, the tension applied to the electrode tab 210t when the electrode assembly 200 expands cannot be reduced because it is the outer portion of the portion fixed by the sealing portions 310S, 320S. Therefore, it is preferable that the flexible portion 400fs according to this embodiment is formed inside the battery case 300.

[0052] Hereinafter, a fixing portion according to a modified embodiment of the present invention will be described in detail with reference to FIGS.

[0053] Fig. 8 is a cross-sectional view showing an electrode assembly and an electrode lead according to a modified embodiment of the present invention. Fig. 9 is a plan view of the electrode assembly and the electrode lead of Fig. 8 as seen from the -z axis direction on the xy plane. In particular, Fig. 8 corresponds to a cross section cut along the yz plane like the cut sections of Figs. 5 and 7.

[0054] 8 and 9, the electrode lead 400' according to the modified embodiment of the present invention has a flexible portion 400f' as described above, but a fixed portion 430 may be further formed.

[0055] Specifically, the electrode lead 400' according to this embodiment may include a first portion 410 connected to the flexible portion 400f' and the electrode tab 210t, a second portion 420 connected to the flexible portion 400f' and protruding outside the battery case, and a fixing portion 430 connected to each of the first portion 410 and the second portion 420.

[0056] More specifically, the flexible portion 400f' according to the present embodiment may include a first flexible portion 400f1 and a second flexible portion 400f2. The first portion 410 may be joined to one end of each of the first flexible portion 400f1 and the second flexible portion 400f2, and the second portion 420 may be joined to the other end of each of the first flexible portion 400f1 and the second flexible portion 400f2. As described above, the joining method may be welding.

[0057] At this time, the fixing part 430 is connected to each of the first part 410 and the second part 420 while being located between the first flexible part 400f1 and the second flexible part 400f2. At this time, the fixing part 430 is also connected to each of the first part 410 and the second part 420 by a method such as welding.

[0058] As long as the material is easily cut or broken, it can be applied to the fixing part 430 without any particular limitation. For example, the fixing part 430 can include at least one of a glass material, a ceramic material, carbon (graphite), and an alloy material having low flexibility. Also, unlike the flexible part 400f' having a bent shape, the fixing part 430 can have a straight shape.

[0059] Since the flexible portion 400f' includes a material having excellent softness, malleability, elasticity, and toughness, the flexible portion 400f' is not fixed during the process of welding the electrode tab 210t to the electrode lead 400', and the welding is not performed smoothly. Therefore, in the present embodiment, a linear fixing portion 430 is provided to fix the compressed shape of the flexible portion 400f'. In addition, since the fixing portion 430 can maintain a constant distance between the first portion 410 and the second portion 420, it is possible to prevent the flexible portion 400f' from expanding before the electrode assembly 200 expands. Instead, since the fixing portion 430 according to the present embodiment includes a metal material having a somewhat weak strength, it does not break due to the expansion of the electrode assembly 200 and thus does not prevent the flexible portion 400f' from expanding.

[0060] Meanwhile, FIG. 10 is a plan view showing an electrode lead according to another modified embodiment of the present invention, specifically showing the position of a modified fixing portion 430. The electrode lead 400″ according to this embodiment may include a first portion 410, a second portion 420, and a fixing portion 430. The fixing portion 430 according to this embodiment is not particularly limited in its position and number as long as it connects the first portion 410 and the second portion 420. As an example, referring to FIG. 10, one flexible portion 400f″ is formed to connect the first portion 410 and the second portion 420, and two fixing portions 430 are connected to the first portion 410 and the second portion 420, respectively, with one flexible portion 400f″ therebetween. That is, two fixing portions 430 are disposed on both sides of the flexible portion 400f″ in the x-axis direction. The fixing portion 430 shown in FIG. 10 can also fix the compressed form of the flexible portion 400f″ and maintain a constant distance between the first portion 410 and the second portion 420 before the electrode assembly expands.

[0061] 3 and 5, a lead film 600 is disposed on each of the electrode leads 400 and 500. The lead film 600 is disposed between the upper case 310 and the lower case 320 in a shape that wraps the electrode leads 400 and 500, respectively.

[0062] Such a lead film 600 can prevent short circuits from occurring between the electrode leads 400, 500 and the metal layer of the battery case 300, and can also improve the sealing of the pouch-type battery case 300. When the electrode leads 400, 500 made of a metal material are heat-sealed to the inner resin layer of the pouch-type battery case 300, contact resistance is somewhat large and surface adhesion may decrease. However, when the lead film 600 is provided as in the present embodiment, such a decrease in adhesion can be prevented. In addition, the lead film 600 includes an insulating material, and can block current from being applied to the pouch-type battery case 300 by the electrode leads 400, 500.

[0063] The lead film 600 is made of a film having insulating properties and heat-sealing properties, and may include at least one of polyimide (PI), polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET), for example.

[0064] In this embodiment, terms indicating directions such as front, back, left, right, up, and down are used, but these terms are used for convenience of explanation and may change depending on the position of the target object or the position of the observer, etc.

[0065] A plurality of secondary batteries according to the present embodiment may be assembled to form a battery module, and the battery module may be attached to various control and protection systems, such as a battery management system (BMS) and a cooling system, to form a battery pack.

[0066] The secondary battery, the battery module, or the battery pack may be applied to various devices, specifically, to transportation means such as electric bicycles, electric cars, and hybrid vehicles, but is not limited thereto, and may be applied to various devices that can use secondary batteries.

[0067] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention. [Explanation of symbols]

[0068] 10 Secondary battery 20 Electrode assembly 21t Electrode tab 30 Battery case 40 Electrode Lead 100 Secondary battery 200 electrode assembly 210,220 Electrode sheet 210t Electrode tab 230 Separation membrane 300 Battery Case 310 Upper Case 310R, 320R Storage area 310S, 320S sealing part 320 Lower Case 400,500,400' electrode leads 400f,400f' Flexible part 410 Part 1 420 Part 2 430 Fixed part 600 Lead Film

Claims

1. An electrode assembly including an electrode sheet having an electrode tab formed thereon and a separator disposed between the electrode sheets; a battery case in which the electrode assembly is housed; and an electrode lead connected to the electrode tab and protruding outside the battery case; The electrode lead includes a flexible part having elasticity in a direction parallel to a protruding direction of the electrode lead, the flexible portion is located inside the battery case, The electrode lead includes a first portion coupled to the flexible portion and the electrode tab; a second portion connected to the flexible portion and protruding outward from the battery case; and A secondary battery comprising: a fixing portion connected to each of the first portion and the second portion, the fixing portion being cut by the expansion of the electrode assembly so as not to prevent the flexible portion from extending.

2. The secondary battery according to claim 1 , wherein the flexible portion has a curved shape.

3. The secondary battery according to claim 1 , wherein the flexible portion is capable of extending in a direction parallel to the protruding direction of the electrode lead.

4. The secondary battery according to claim 1 , wherein the flexible portion contains at least one of gold (Au) and silver (Ag).

5. the battery case includes an upper case and a lower case, The sealing portion of the upper case and the sealing portion of the lower case are heat-sealed to each other, The secondary battery of claim 1 , wherein the flexible portion is located between the electrode assembly and a portion of the electrode lead where the sealing portion is located.

6. The flexible portion includes a first flexible portion and a second flexible portion, The secondary battery according to claim 1 , wherein the fixed portion is located between the first flexible portion and the second flexible portion.

7. The secondary battery according to claim 1 or 6, wherein the fixing portion includes at least one of a glass material, a ceramic material, graphite, and an alloy material having low flexibility.

8. The secondary battery according to claim 1 , wherein the fixing portion has a straight line shape.

9. the electrode assembly is a stack-type electrode assembly in which the electrode sheets are stacked, The secondary battery according to claim 1 , wherein when the electrode sheet expands in a thickness direction, the flexible portion extends in a direction perpendicular to the thickness direction.

10. A device comprising a secondary battery according to any one of claims 1 to 9.

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