Battery cell, battery pack, and device comprising same

Abstract

The present invention relates to a battery cell, a battery pack, and a device comprising same. The battery cell of the present invention includes an electrode laminate that is wound, wherein the electrode laminate includes a plurality of positive electrodes and a plurality of negative electrodes, and with respect to at least two electrodes, the winding center of an electrode having a lower loading amount of active material is positioned further inward than the winding center of an electrode having a higher loading amount of active material.

Description

Battery cell, battery pack and device including the same

[0001] The present invention relates to a battery cell, a battery pack, and a device including the same. More specifically, the present invention relates to a battery cell, a battery pack, and a device including the same, having a plurality of positive electrodes and a plurality of negative electrodes.

[0002] The content described in this section merely provides background information regarding the present invention and does not constitute prior art.

[0003] As the development of automobiles, energy storage batteries, robots, and satellites accelerates, extensive research is being conducted on secondary batteries used as their driving power sources.

[0004] Secondary batteries are classified according to the shape of the battery case into cylindrical batteries, in which the electrode assembly is embedded in a cylindrical can; prismatic batteries, in which the electrode assembly is embedded in a rectangular metal can; and pouch-type batteries, in which the electrode assembly is embedded in a pouch-type case made of aluminum laminate sheets.

[0005] The electrode assembly embedded in the battery case is a rechargeable power generator composed of a stacked structure of a positive electrode, a separator, and a negative electrode, and is classified into jelly-roll type, stack type, and stack / folding type. The jelly-roll type is a form in which a separator is interposed between long sheet-type positive and negative electrodes coated with active material and wound; the stack type is a form in which multiple positive and negative electrodes of a predetermined size are sequentially stacked with a separator interposed; and the stack / folding type is a composite structure of the jelly-roll type and the stack type. Among these, the jelly-roll type electrode assembly has the advantages of being easy to manufacture and having a high energy density per unit weight.

[0006] FIG. 1 shows a jelly roll type electrode assembly. Referring to FIG. 1, the jelly roll type electrode assembly typically has a single positive electrode (11) and a single negative electrode (12) stacked and wound. However, each electrode (11, 12) is bent at a very high curvature at the center of the jelly roll type electrode assembly, and this curvature causes a large stress on the inner end of the electrode.

[0007] Meanwhile, the cathode and anode may each have a current collector and an active material layer covering the current collector. However, when the active material loading amount is large, there is a problem in that the required electrode adhesion cannot be secured or greater stress is applied due to the bending. Conversely, when the active material loading amount is small, the total length of the electrode increases to store the same amount of energy, which leads to an increase in the battery's resistance and an increase in the number of rolling cycles during the winding process.

[0008] Accordingly, the present invention is devised to solve the problems of the prior art and aims to provide a battery cell, a battery pack, and a device including the same, which can employ multiple electrodes with different specifications, such as current collector thickness or active material loading amount, while considering the stress applied to the electrodes.

[0009] The problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description below.

[0010] A battery cell according to one embodiment of the present invention comprises a wound electrode stack, wherein the electrode stack comprises a plurality of positive electrodes and a plurality of negative electrodes, and among at least two electrodes, the winding center of the electrode with a smaller active material loading amount is located inwardly from the winding center of the electrode with a larger active material loading amount.

[0011] The electrode stack can be wound such that the winding center of the negative electrode among the winding centers of each electrode is located at the innermost position.

[0012] The above electrode laminate includes a first positive electrode, a first negative electrode, a second positive electrode, and a second negative electrode, and can be wound such that the winding center of the first negative electrode, the winding center of the first positive electrode, the winding center of the second negative electrode, and the winding center of the second positive electrode are sequentially positioned from the inside to the outside of the battery cell.

[0013] At least one positive electrode comprises a positive electrode current collector, an inner positive electrode active material layer coated on the inner surface of the positive electrode current collector, and an outer positive electrode active material layer coated on the outer surface of the positive electrode current collector, and the active material loading amount of the inner positive electrode active material layer may be less than the active material loading amount of the outer positive electrode active material layer.

[0014] At least one cathode comprises a cathode current collector, an inner cathode active material layer coated on the inner surface of the cathode current collector, and an outer cathode active material layer coated on the outer surface of the cathode current collector, and the active material loading amount of the inner cathode active material layer may be less than the active material loading amount of the outer cathode active material layer.

[0015] At least one positive electrode comprises a positive current collector, an inner positive active material layer applied to the inner surface of the positive current collector, and an outer positive active material layer applied to the outer surface of the positive current collector, wherein the active material loading amount of the inner positive active material layer is less than the active material loading amount of the outer positive active material layer, and at least one negative electrode comprises a negative current collector, an inner negative active material layer applied to the inner surface of the negative current collector, and an outer negative active material layer applied to the outer surface of the negative current collector, wherein the active material loading amount of the inner negative active material layer is less than the active material loading amount of the outer negative active material layer, and in mutually facing outer positive active material layer and inner negative active material layer, the capacity of the outer positive active material layer may be less than the capacity of the inner negative active material layer.

[0016] The capacity ratio (NP Ratio) of the cathode and anode of the above electrode stack may be 1 or greater.

[0017] The above electrode stack may further include a plurality of separators.

[0018] The above plurality of separation membranes may be provided of the same type.

[0019] The above plurality of separation membranes may include two separation membranes of mutually different types.

[0020] The above electrode laminate includes an SRS separator and an aramid separator, and the winding center of the SRS separator may be located inwardly from the winding center of the aramid separator.

[0021] The electrode laminate may include two different types of cathodes, and may be wound such that the winding center of the electrode with the lower volume expansion rate among the two cathodes is located inwardly compared to the winding center of the other one of the two cathodes.

[0022] The above electrode laminate includes a silicon cathode and a graphite cathode, and the graphite cathode may include one or more of a natural graphite cathode and an artificial graphite cathode.

[0023] The electrode laminate may include two different types of cathodes, and may be wound such that the winding center of the electrode with lower thermal conductivity among the two cathodes is located outside the winding center of the other of the two cathodes.

[0024] The electrode laminate may be wound such that it includes two different types of anodes, and the winding center of the electrode with the lower volume expansion rate among the two anodes is located inwardly compared to the winding center of the other of the two anodes.

[0025] The electrode laminate may be wound such that it includes two different types of anodes, and the winding center of the electrode with lower thermal conductivity among the two anodes is located outside the winding center of the other of the two anodes.

[0026] The thickness of the positive current collector of one positive electrode and the thickness of the positive current collector of another positive electrode may differ from each other.

[0027] The thickness of the current collector of one cathode and the thickness of the current collector of another cathode may differ from each other.

[0028] The battery pack of the present invention includes one or more of the above-described battery cells.

[0029] The device of the present invention includes the above-described battery pack as a power source.

[0030] The above device may be selected from mobile phones, portable computers, smartphones, smart pads, netbooks, LEVs (Light Electronic Vehicles), electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage devices.

[0031] According to the present invention, a battery cell, a battery pack, and a device including the same are provided, which can employ multiple electrodes with different specifications, such as current collector thickness or active material loading amount, taking into account the stress applied to the electrodes.

[0032] In addition, a battery cell, a battery pack, and a device including the same are provided, wherein the battery resistance performance is improved by shortening the length of the electrode in the winding direction compared to a conventional battery cell of the same capacity.

[0033] In addition, a battery cell, a battery pack, and a device including the same can employ multiple separators having different physical properties are provided.

[0034] Thus, a battery cell, a battery pack, and a device including the same are provided, with improved internal stress, resistance performance, energy density, and heat resistance.

[0035] Figure 1 shows a jelly roll type electrode assembly.

[0036] FIG. 2 briefly illustrates an electrode stack of a battery cell according to one embodiment of the present invention.

[0037] FIG. 3 is a modified example of an electrode laminate according to one embodiment of the present invention.

[0038] FIG. 4 shows an electrode stack of a battery cell according to one embodiment of the present invention.

[0039] Figure 5 is a partial enlarged view of Figure 4.

[0040] FIG. 6 is a partial enlarged view of an electrode stack according to another embodiment of the present invention.

[0041] FIG. 7 is a perspective view of a battery cell according to one embodiment of the present invention.

[0042] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention.

[0043] It should be noted that the drawings are schematic and not drawn to scale. The relative dimensions and proportions of parts in the drawings are exaggerated or reduced in size for clarity and convenience, and any dimensions are illustrative only and not limiting. Additionally, the same reference numerals are used to denote similar features for the same structure, element, or part appearing in two or more drawings.

[0044] In this specification, terms such as first, second, third, etc., may be used to describe various components, but these components are not limited by these terms. The terms are used for the purpose of distinguishing one component from other components. For example, without departing from the scope of the present invention, the first component may be named the second or third component, and similarly, the second or third component may be named alternately.

[0045] The present invention relates to a battery cell comprising a wound electrode stack, wherein the electrode stack comprises a plurality of positive electrodes and a plurality of negative electrodes. Herein, among at least two electrodes, the winding center of the electrode with a lower active material loading amount is located inwardly from the winding center of the electrode with a higher active material loading amount.

[0046] Hereinafter, a battery cell according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 2 briefly shows an electrode stack of a battery cell according to an embodiment of the present invention. FIG. 3 is a modified example of a battery cell according to an embodiment of the present invention. FIG. 4 shows an electrode stack of a battery cell according to an embodiment of the present invention. FIG. 5 is a partial enlarged view of FIG. 4. Hereinafter, the winding center of an electrode refers to the innermost end of the corresponding electrode that has been wound. Referring to FIG. 2 to FIG. 5, a battery cell according to an embodiment of the present invention includes a wound electrode stack. The electrode stack includes a plurality of positive electrodes (110, 130) and a plurality of negative electrodes (120, 140). Here, for at least two electrodes, the winding center of the electrode with a smaller active material loading amount is located inwardly compared to the winding center of the electrode with a larger active material loading amount. According to this configuration, stress due to curvature during winding of the inner end of the electrode with a larger active material loading amount can be reduced.

[0047] The electrode stack (100) can be wound such that the winding center of the negative electrode (120) among the winding centers of each electrode (110, 120, 130, 140) is located at the innermost position. The capacity ratio (NP Ratio) of the negative electrode (120, 140) and the positive electrode (110, 130) of the electrode stack (100) may be 1 or greater. In one embodiment, the electrode stack (100) may include a first positive electrode (110), a first negative electrode (120), a second positive electrode (130), and a second negative electrode (140). For example, the electrode stack may be wound such that the winding center of the first negative electrode (120), the winding center of the first positive electrode (110), the winding center of the second negative electrode (140), and the winding center of the second positive electrode (130) are sequentially located from the inner side to the outer side of the battery cell. Meanwhile, the concept of the present invention is not limited to the above examples and the drawings of this specification, and as another example, the electrode laminate (100) may be wound such that the winding center of the anode (110) is located at the innermost side. In other words, the winding order of the anode and cathode is not limited to a specific winding order.

[0048] At least one positive electrode may include a positive current collector, an inner positive active material layer applied to the inner surface of the positive current collector, and an outer positive active material layer applied to the outer surface of the positive current collector. Here, the amount of active material loading in the inner positive active material layer may be less than the amount of active material loading in the outer positive active material layer. This takes into account that the inner surface of each electrode (110, 120, 130, 140) at the inner end has a higher curvature than the outer surface. In one embodiment, the first positive electrode (110) and the second positive electrode (130) each include a positive current collector (111, 131), an inner positive active material layer (112, 132), and an outer positive active material layer (113, 133).

[0049] At least one cathode may include a cathode current collector, an inner cathode active material layer applied to the inner surface of the cathode current collector, and an outer cathode active material layer applied to the outer surface of the cathode current collector. Here, the active material loading amount of the inner cathode active material layer may be less than the active material loading amount of the outer cathode active material layer. This takes into account that the inner surface of each electrode (110, 120, 130, 140) at the inner end has a higher curvature than the outer surface. In one embodiment, the first cathode (120) and the second cathode (140) each include a cathode current collector (121, 141), an inner cathode active material layer (122, 142), and an outer cathode active material layer (123, 143).

[0050] In the outer positive active material layer and the inner negative active material layer facing each other (this arrangement assumes that the positive having the corresponding positive active material layer is wound outwardly from the negative having the corresponding negative active material layer, and the electrode having the negative active material layer is wound one more turn), the capacity ratio (NP Ratio) must satisfy 1 or more such that the capacity of the outer positive active material layer is less than the capacity of the inner negative active material layer. In addition, the inner loading amount of each positive and negative active material layer must be less than the outer loading amount, taking into account that the inner end of the wound active material layer has a higher curvature than the outer end.

[0051] The electrode laminate (100) of the present invention is not limited to being wound in the shape of a circular spiral, and may be wound in the shape of an elliptical spiral, for example, as shown in FIG. 3.

[0052] Referring to FIGS. 4 and 5, for example, the amount of active material loaded in the inner positive active material layer (112) of the first positive electrode (110) may be less than the amount of active material loaded in the outer positive active material layer (113) of the first positive electrode (110). The amount of active material loaded in the inner negative active material layer (142) of the second negative electrode (140) may be less than the amount of active material loaded in the outer negative active material layer (143) of the second negative electrode (140). Likewise, the amount of active material loaded in the inner positive active material layer (132) of the second positive electrode (130) may be less than the amount of active material loaded in the outer positive active material layer (133) of the second positive electrode (130).

[0053] For example, referring to FIG. 5, the ratio can be “'active material capacity of the inner cathode active material layer (122) of the first cathode' : 'active material capacity of the outer cathode active material layer (123) of the first cathode' : 'active material capacity of the inner anode active material layer (112) of the first anode' : 'active material capacity of the outer anode active material layer (113) of the first anode' : 'active material capacity of the inner cathode active material layer (142) of the second cathode' : 'active material capacity of the outer anode active material layer (143) of the second cathode' : 'active material capacity of the inner anode active material layer (132) of the second anode' : 'active material capacity of the outer anode active material layer (133) of the second anode' = 5 : 6 : 5 : 6 : 7 : 8 : 7 : 4”, and based on the loading amount, it can be “5 : 6 : 10 : 12 A ratio of 7 : 8 : 14 : 8 can be achieved. As such, the capacity reference ratio and the loading amount reference ratio between the inner and outer sides of each electrode may differ from one another. In this regard, generally, when configuring the electrode, the specific capacity of the positive electrode active material is formed to be smaller than the specific capacity of the negative electrode active material. However, since capacity and loading amount have a directly proportional relationship, the relationship between the inner and outer sides within the same electrode (e.g., the relationship between the inner side of the positive electrode and the outer side of the positive electrode, the relationship between the inner side of the negative electrode and the outer side of the negative electrode) can be expressed as both the loading amount ratio and the capacity ratio, but for the relationship between different electrodes (positive and negative electrodes (e.g., the relationship between the first positive electrode and the first negative electrode, the relationship between the second positive electrode and the second negative electrode)), it may be preferable to express it only as a capacity ratio.

[0054] FIG. 6 is a partial enlarged view of an electrode stack according to another embodiment of the present invention.

[0055] Referring to FIG. 6, an electrode laminate (100) according to another embodiment of the present invention may be configured such that the innermost part (winding start area) of the inner negative electrode active material layer (122) of the first negative electrode is located radially outward from the outer positive electrode active material layer (133) of the second positive electrode. In this case, the ratio can be “'active material capacity of the inner cathode active material layer (122) of the first cathode' : 'active material capacity of the outer cathode active material layer (123) of the first cathode' : 'active material capacity of the inner anode active material layer (112) of the first anode' : 'active material capacity of the outer anode active material layer (113) of the first anode' : 'active material capacity of the inner cathode active material layer (142) of the second cathode' : 'active material capacity of the outer anode active material layer (143) of the second cathode' : 'active material capacity of the inner anode active material layer (132) of the second anode' : 'active material capacity of the outer anode active material layer (133) of the second anode' = 9 : 6 : 5 : 6 : 7 : 8 : 7 : 8”. That is, in order to form a larger capacity of the outer positive active material layer (133) of the second positive electrode, the electrode laminate (100) according to another embodiment of the present invention may be configured such that the capacity of the inner negative active material layer (122) of the first negative electrode is formed larger than that of the outer positive active material layer (133) of the second positive electrode, and at the same time, the winding starting point of the inner negative active material layer (122) of the first negative electrode (the innermost part of the inner negative active material layer (122) of the first negative electrode) is located radially outward from the outer positive active material layer (133) of the second positive electrode.

[0056] The electrode stack (100) further comprises a plurality of separators (150, 160), wherein the plurality of separators (150, 160) may comprise two separators (150, 160) of mutually different types. The electrode stack (100) may comprise a first separator (150) and a second separator (160). A virtual plane passing through the stack winding center (C), which is the winding center of the electrode stack (100), and perpendicular to the radial direction of the electrode stack (100) may be named a reference plane, and a cut surface obtained by cutting the electrode stack (100) with respect to the reference plane may be named a reference cut surface. When looking at a cut surface located on one side or the other side in the radial direction relative to the stack winding center (C) among the reference cut surfaces, the first separator (150) and the second separator (160) may be arranged to alternate with each other along the radial direction.

[0057] One of these first membrane (150) and second membrane (160) may be provided as an SRS membrane, and the other as an aramid membrane. For example, the first membrane (150) may be provided as an SRS membrane, and the second membrane (160) may be provided as an aramid membrane.

[0058] Additionally, referring again to FIG. 5, with respect to the laminated winding center (C), the winding center of the SRS separator (150) may be located inwardly compared to the winding center of the aramid separator (160). In other words, the winding center of the SRS separator (150) may be located closer to the laminated winding center (C) than to the winding center of the aramid separator (160). That is, the radial distance between the winding center of the SRS separator (150) and the laminated winding center (C) may be smaller than the radial distance between the winding center of the aramid separator (160) and the laminated winding center (C).

[0059] Although aramid membranes possess excellent heat resistance, they can cause winding process issues when bent at high curvature due to friction with winding equipment; however, this arrangement allows one to take advantage of the aramid membranes while suppressing these problems.

[0060] The electrode laminate (100) may include two different types of cathodes (120, 140), and may be wound such that the winding center of the electrode with the lower volume expansion rate among the two cathodes (120, 140) is located inward than the winding center of the other of the two cathodes (120, 140). For example, the electrode laminate (100) may include a silicon cathode (140) and a graphite cathode (120). As a detailed example, the graphite cathode (120) included in the electrode laminate (100) may be provided with one or more of an artificial graphite cathode and a natural graphite cathode. As a more detailed example, the graphite cathode (120) may be understood as a concept comprising only artificial graphite, only natural graphite, or both artificial graphite and natural graphite. Here, a silicon cathode (140) with a high volume expansion rate can be placed on the outside of an artificial graphite cathode (120) with a lower volume expansion rate.

[0061] Likewise, the electrode laminate (100) may include two different types of anodes (110, 130), and may be wound such that the winding center of the electrode with the lower volume expansion rate among the two anodes (110, 130) is located inwardly compared to the winding center of the other anode (110, 130).

[0062] The electrode laminate (100) may include two different types of cathodes (120, 140), and may be wound such that the winding center of the electrode with lower thermal conductivity among the two cathodes (120, 140) is located outside the winding center of the other one of the two cathodes (120, 140).

[0063] Likewise, the electrode laminate (100) may include two different types of anodes (110, 130), and may be wound such that the winding center of the electrode with lower thermal conductivity among the two anodes (110, 130) is located outside the winding center of the other of the two anodes (110, 130).

[0064] FIG. 7 is a perspective view showing a battery cell according to an embodiment of the present invention. Referring to FIG. 7, the battery cell of the present invention may include the electrode stack (100) described above and a can that accommodates the electrode stack (100). Although the can is depicted as being cylindrical in the drawing, the shape of the can is not particularly limited, such as the can being approximately rectangular.

[0065]

[0066] The battery pack according to the present invention may include one or more of the above-described battery cells.

[0067]

[0068] The device according to the present invention may include the above-described battery pack as a power source.

[0069] The device may be selected from mobile phones, portable computers, smartphones, smart pads, netbooks, LEVs (Light Electronic Vehicles), electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage devices.

[0070] The above description is merely an illustrative explanation of the technical concept of the present invention, and those skilled in the art to which the present invention pertains will be able to make various modifications, changes, and substitutions within the scope of the essential characteristics of the present invention. Accordingly, the present embodiment is intended to explain, not limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by such embodiment. The scope of protection of the present invention shall be interpreted by the claims below, and all technical concepts within an equivalent scope shall be interpreted as being included within the scope of rights of the present invention.

[0071] [Explanation of the symbol]

[0072] 1: Battery cell

[0073] 100: Electrode laminate

[0074] 110: First anode

[0075] 120: First cathode

[0076] 130: Second anode

[0077] 140: Second cathode

[0078] 150: First separator

[0079] 160: Second separator

Claims

1. A battery cell comprising a wound electrode laminate, The above electrode stack includes a plurality of positive electrodes and a plurality of negative electrodes, A battery cell having at least two electrodes, wherein the winding center of the electrode with a lower active material loading amount is located inwardly from the winding center of the electrode with a higher active material loading amount.

2. In Paragraph 1, A battery cell in which the electrode stack is wound such that the winding center of the negative electrode among the winding centers of each electrode is located at the innermost position.

3. In Paragraph 2, The above electrode stack is, It includes a first anode, a first cathode, a second anode and a second cathode, and A battery cell wound such that the winding center of the first negative electrode, the winding center of the first positive electrode, the winding center of the second negative electrode, and the winding center of the second positive electrode are positioned sequentially from the inside to the outside of the battery cell.

4. In Paragraph 1, At least one positive electrode comprises a positive electrode current collector, an inner positive electrode active material layer applied to the inner surface of the positive electrode current collector, and an outer positive electrode active material layer applied to the outer surface of the positive electrode current collector. A battery cell in which the active material loading amount of the inner positive active material layer is less than the active material loading amount of the outer positive active material layer.

5. In Paragraph 1, At least one cathode comprises a cathode current collector, an inner cathode active material layer coated on the inner surface of the cathode current collector, and an outer cathode active material layer coated on the outer surface of the cathode current collector. A battery cell in which the active material loading amount of the inner negative active material layer is less than the active material loading amount of the outer negative active material layer.

6. In Paragraph 1, At least one positive electrode comprises a positive electrode current collector, an inner positive electrode active material layer applied to the inner surface of the positive electrode current collector, and an outer positive electrode active material layer applied to the outer surface of the positive electrode current collector. The active material loading amount of the inner positive active material layer is less than the active material loading amount of the outer positive active material layer, and At least one cathode comprises a cathode current collector, an inner cathode active material layer coated on the inner surface of the cathode current collector, and an outer cathode active material layer coated on the outer surface of the cathode current collector. The active material loading amount of the inner cathode active material layer is less than the active material loading amount of the outer cathode active material layer, and A battery cell having an outer positive active material layer and an inner negative active material layer facing each other, wherein the capacity of the outer positive active material layer is less than the capacity of the inner negative active material layer.

7. In Paragraph 1, A battery cell in which the capacity ratio (NP Ratio) of the negative electrode and the positive electrode of the above electrode stack is 1 or greater.

8. In Paragraph 1, The above electrode laminate is a battery cell further comprising a plurality of separators.

9. In Paragraph 8, A battery cell in which the above plurality of separators are provided of the same type.

10. In Paragraph 8, A battery cell comprising the above plurality of separators, each comprising two separators of mutually different types.

11. In Paragraph 10, The above electrode laminate includes an SRS separator and an aramid separator, and A battery cell in which the winding center of the above-mentioned SRS separator is located inwardly to the winding center of the above-mentioned aramid separator.

12. In Paragraph 1, The above electrode stack comprises two cathodes of mutually different types, A battery cell wound such that the winding center of the electrode with the lower volume expansion rate among the two cathodes is located inwardly compared to the winding center of the other of the two cathodes.

13. In Paragraph 8, The above electrode laminate includes a silicon cathode and a graphite cathode, and The graphite cathode above is, A battery cell comprising one or more of a natural graphite cathode and an artificial graphite cathode.

14. In Paragraph 1, The above electrode stack comprises two cathodes of mutually different types, A battery cell wound such that the winding center of the electrode with lower thermal conductivity among the two cathodes is located outward from the winding center of the other of the two cathodes.

15. In Paragraph 1, The above electrode stack comprises two anodes of mutually different types, A battery cell wound such that the winding center of the electrode with the lower volume expansion rate among the two anodes is located inwardly compared to the winding center of the other of the two anodes.

16. In Paragraph 1, The above electrode stack comprises two anodes of mutually different types, A battery cell wound such that the winding center of the electrode with lower thermal conductivity among the two anodes is located outward from the winding center of the other of the two anodes.

17. In Paragraph 1, A battery cell in which the thickness of the positive current collector of one positive and the thickness of the positive current collector of another positive are different from each other.

18. In Paragraph 1, A battery cell in which the thickness of the current collector of one negative electrode and the thickness of the current collector of another negative electrode are different from each other.

19. A battery pack comprising one or more battery cells according to any one of paragraphs 1 through 18.

20. A device comprising a battery pack according to paragraph 19 as a power source.

21. In paragraph 20, the device is a device selected from a mobile phone, a portable computer, a smartphone, a smart pad, a netbook, an LEV (Light Electronic Vehicle), an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage device.

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