Battery cell and power consuming device using battery cell

Abstract

To provide a battery cell that can reduce the risk of lithium deposition due to installation of tab grooves, reduce a thickness of the battery cell, and increase the energy density.SOLUTION: An electrode assembly 10 is formed by sequentially stacking and winding a first electrode sheet 11, a separator, and a second electrode sheet 12. In a winding direction of the electrode assembly, each layer of the first electrode sheet from a second layer to a next outer layer includes a first flat stage 113 and a first folded stage 114 and a second folded stage 115 respectively provided on both sides of the first flat stage. The first folded stage and the second folded stage are respectively portions where both sides of each layer of the first electrode sheet are folded. A first bare foil region 110 is provided on the first flat stage, and in a longitudinal direction of the electrode assembly, the first bare foil region does not have a first active material layer 112.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present application relates to the technical field of batteries, and more particularly to battery cells and power consuming devices using battery cells. [Background technology]

[0002] With the commercial development of lithium-ion batteries, the market has increasingly higher requirements for the charging speed, charge / discharge temperature rise, energy density and multiplying discharge performance of battery cells, which has led to the birth of tab-mounted battery cells.

[0003] The most common battery cells with tabs in the middle are mainly constructed as follows: One is to provide a tab groove on the active material layer of the tab to expose the void collecting fluid, and then fix the tab in the tab groove. However, in battery cells with a width of less than 30mm, the tab grooves of the anode and cathode overlap, and when the tab grooves overlap, the thickness of the battery cell does not match, and at the same time, lithium is precipitated in the grooves, which further deteriorates the circulation and leads to a decrease in performance such as remaining capacity and circulation expansion. The other is to open a tab groove on the electrode sheet, but the width of the tab groove in the width direction of the electrode sheet is a short groove that is slightly larger than the tab fixing end, and this groove is prone to lithium precipitation. At the same time, the area where the active material is not applied in this area corresponds to the area on the negative electrode sheet where lithium is precipitated. In order to prevent lithium precipitation in this area, it is necessary to attach insulating rubber to the negative electrode sheet corresponding to the positive tab groove to prevent the release of lithium ions. At the position of the positive tab, generally at least two layers of protective tape are installed, which increases the thickness of the electric battery cell.

[0004] How to solve the above problems needs to be considered by those skilled in the art. Summary of the Invention [Problem to be solved by the invention]

[0005] This solves the problems of lithium deposition, uneven thickness of the battery cell, and low energy density caused by the provision of tab grooves in conventional technology. [Means for solving the problem]

[0006] An embodiment of the present application provides a battery cell, the battery cell comprising an electrode assembly, the electrode assembly comprising: a first current collector having a first bare foil area where a first active material layer is not provided, a first electrode sheet comprising the first active material layer provided on a surface of the first current collector, a second current collector having a second bare foil area where a second active material layer is not provided, a second electrode sheet comprising the second active material layer provided on a surface of the second current collector, and a separator provided between the first electrode sheet and the second electrode sheet, the electrode assembly being formed by sequentially stacking and winding the first electrode sheet, the separator, and the second electrode sheet; a first flat step and a first folded step and a second folded step respectively provided on both sides of the first flat step, each of the layers of the first electrode sheet from the second layer to the next outer layer in the winding direction of the electrode assembly, the first folded step and the second folded step being portions where both sides of each layer of the first electrode sheet are folded, the first bare foil region is provided on the first flat step, and both sides of the first bare foil region are connected to the first folded step and the second folded step, respectively, and the first active material layer is not provided in the first bare foil region in the longitudinal direction of the electrode assembly.

[0007] In a possible embodiment, in the winding direction of the electrode assembly, each layer from the second layer to the next outer layer of the second electrode sheet includes a second flat step and a third folding step and a fourth folding step respectively provided on both sides of the second flat step, the third folding step and the fourth folding step are portions where both sides of each layer of the second electrode sheet are folded, the second bare foil area is provided on the second flat step, both sides of the second bare foil area are connected to the third folding step and the fourth folding step, respectively, and in the longitudinal direction of the electrode assembly, the second bare foil area is not provided with the second active material layer.

[0008] In a possible embodiment, the first current collector is provided with the first active material layer on its other side opposite the first bare foil area, or the second current collector is provided with the second active material layer on its other side opposite the second bare foil area.

[0009] In a possible embodiment, in the width direction of the electrode assembly, the distance between the central symmetry line of the first bare foil area or the second bare foil area and the central symmetry line of the electrode assembly is respectively 2 mm or less.

[0010] In a possible embodiment, the first bare foil area and the second bare foil area are arranged opposite each other.

[0011] In a possible embodiment, in the width direction of the electrode assembly, both sides of the first bare foil area exceed the width of both sides of the second bare foil area corresponding to the first bare foil area by 0 to 4 mm.

[0012] In a possible embodiment, the electrode assembly further comprises a first tab electrically connecting to the first bare foil area, a second tab electrically connecting to the second bare foil area, a first insulating layer provided on the first bare foil area, and a second insulating layer provided on the second bare foil area.

[0013] In a possible embodiment, the first tab is fixed to the first bare foil area by welding and the first insulating layer is coated on a surface of the first tab, or the second tab is fixed to the second bare foil area by welding and the second insulating layer is coated on a surface of the second tab.

[0014] In a possible embodiment, the first active material layer is provided on each of both surfaces of the winding start section of the first current collector, and the second active material layer is provided on each of both surfaces of the winding end section of the second current collector.

[0015] In a possible embodiment, the winding start section of the second current collector includes a fifth folding section, and the fifth folding section does not overlap with the winding start section of the first current collector in the thickness direction of the electrode assembly.

[0016] In a possible embodiment, the first active material layer is provided on the surface of the first folded section and the surface of the second folded section.

[0017] In a possible embodiment, the surfaces of the first and second fold stages extending from the first bare foil region are free of the first active material layer.

[0018] In a possible embodiment, a first planar step of the first electrode sheet adjacent the first bare foil area is provided with the first active material layer.

[0019] An embodiment of the present application provides a power consuming device comprising an operational module and a battery for supplying power to said operational module, said battery comprising a battery cell as described above. Effect of the Invention

[0020] Compared to the conventional technology, the battery cell of the present application has the following advantages: on the one hand, the tab and the bare foil area for installing the tab are provided on the flat stage of the battery cell; in other words, the tab and the bare foil area for installing the tab are not provided on the winding stage of the battery cell, thereby avoiding variations in the thickness of the battery cell and reducing the risk of lithium precipitation in the battery cell; and on the other hand, the bare foil area for installing the tab has a single-sided structure, and by simply attaching a layer of insulating rubber to the bare foil area, it is possible to cover burrs on the current collector and reduce the risk of short circuits. By reducing the number of insulating rubber layers, the thickness of the battery cell can be reduced, and by providing an active material layer on the back side of the bare foil area where the tab is provided, the energy density of the battery cell can be increased. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic diagram of a battery cell according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing an enlarged portion of a first bare foil area of ​​a battery cell according to one embodiment of the present application. [Diagram 3] FIG. 3 is a schematic diagram showing an enlarged portion of a second bare foil area of ​​a battery cell according to one embodiment of the present application. [Figure 4] FIG. 4 is a schematic plan view of the front and back surfaces of a first bare foil region of a battery cell according to one embodiment of the present application. [Diagram 5] FIG. 5 is a schematic plan view of the front and back surfaces of the second bare foil region of a battery cell according to one embodiment of the present application. [Figure 6] FIG. 6 is a schematic diagram showing an enlarged portion of a first bare foil area of ​​a battery cell according to another embodiment of the present application. [Figure 7] FIG. 7 is a schematic diagram showing an enlarged view of a portion of a second bare foil area of ​​a battery cell according to another embodiment of the present application. [Figure 8] FIG. 8 is a schematic diagram showing an enlarged view of a portion of a first bare foil region of a battery cell according to still another embodiment of the present application. [Figure 9] FIG. 9 is a schematic diagram showing an enlarged view of a portion of a second bare foil region of a battery cell according to still another embodiment of the present application. [Figure 10] FIG. 10 is a schematic diagram of a power consuming device according to an embodiment of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The present application will now be described more comprehensively with reference to the drawings. In the drawings, exemplary embodiments of the present application are shown. However, the present application may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. These embodiments are provided so that the present application will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art. Like reference numerals refer to the same or similar elements.

[0023] The terms used herein are used only to describe certain exemplary embodiments and are not intended to limit the present application. As used herein, the singular forms "a", "one" and "it" are intended to include the plural forms unless the context clearly indicates otherwise. Furthermore, as used herein, "including" and / or "comprising" and / or "having" refer to integers, steps, operations, components and / or components, but do not exclude the presence or addition of one or more other features, regions, integers, steps, operations, components, components and / or groups thereof.

[0024] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which this application belongs. Furthermore, terms as defined in common dictionaries should be interpreted as having a meaning consistent with the meaning in the relevant art and the context of this application, and should not be interpreted as being more ideal or formal than usual.

[0025] Exemplary embodiments are described below with reference to the drawings, in which components are not necessarily drawn to scale, and in which identical or similar components are labeled with identical or similar reference numerals and similar technical terms.

[0026] Hereinafter, specific embodiments of the present invention will be described in more detail with reference to the drawings.

[0027] FIG. 1 is a schematic diagram of the configuration of a battery cell 1 according to an embodiment of the present application, FIG. 2 is a schematic diagram of an enlarged portion of a first bare foil area 110 of a battery cell 1 according to an embodiment of the present application, and FIG. 3 is a schematic diagram of an enlarged portion of a second bare foil area 120 of a battery cell 1 according to an embodiment of the present application.

[0028] The battery cell 1 includes an electrode assembly 10, which includes a first electrode sheet 11, a second electrode sheet 12, and a separator 13. Here, the first electrode sheet 11 includes a first current collector 111 and a first active material layer 112 provided on the surface of the first current collector 111, the first current collector 111 includes a first bare foil region 110 where the first active material layer 112 is not provided, the second electrode sheet 12 includes a second current collector 121 and a second active material layer 122 provided on the surface of the second current collector 121, the second current collector 121 further includes a second bare foil region 120 where the second active material layer 122 is not provided, and the separator 13 is provided between the first electrode sheet 11 and the second electrode sheet 12.

[0029] The electrode assembly 10 is formed by laminating a first electrode sheet 11, a separator 13, and a second electrode sheet 12 in this order and winding them.

[0030] In one embodiment, in the winding process, the first electrode sheet 11 and the second electrode sheet 12 are arranged with a gap between them, and a separator 13 is provided between the first electrode sheet 11 and the second electrode sheet 12 to insulate the first electrode sheet 11 and the second electrode sheet 12 and prevent a short circuit due to contact between the first electrode sheet 11 and the second electrode sheet 12.

[0031] In the winding direction of the electrode assembly 10, each layer of the first electrode sheet 11 from the second layer to the next outer layer includes a first flat stage 113 and a first folded stage 114 and a second folded stage 115 respectively provided on both sides of the first flat stage 113, the first folded stage 114 and the second folded stage 115 being portions where both sides of each layer of the first electrode sheet 11 are folded, the first bare foil region 110 is provided on the first flat stage 113, and both sides of the first bare foil region 110 are connected to the first folded stage 114 and the second folded stage 115 respectively, and in the longitudinal direction of the electrode assembly 10, the first bare foil region 110 does not have a first active material layer 112 provided therein.

[0032] In one embodiment, each layer from the second layer to the next outer layer of the first electrode sheet 11 includes a first flat section 113, which extends horizontally during the winding process of the battery cell 1 and is not curved by the winding of the battery cell 1, and a first folding section 114 and a second folding section 115 provided on both sides of the first flat section 113 are sections where the first electrode sheet 11 is folded during the winding process of the battery cell 1 to realize the winding of the battery cell 1. The thickness of the first electrode sheet 11 in the first bare foil region 110 is thinner than the thickness of the first electrode sheet 11 adjacent to the first bare foil region 110, and by providing the first bare foil region 110 in the first flat section 113, it is possible to prevent the thin part of the first electrode sheet 11 from extending into the winding and folding region, which would cause the thickness of the battery cell 1 to vary.

[0033] In one embodiment, the first bare foil region 110 is provided on at least one first flat step 113, and a first folded step 114 and a second folded step 115 are connected to both sides of the first bare foil region 110, so that the first bare foil region 110 can occupy one first flat step 113. In another embodiment, the first active material layer 112 is provided on the surfaces of the first folded step 114 and the second folded step 115, and the first active material layer 112 is not provided on the surfaces of the first folded step 114 and the second folded step 115 extending from the first bare foil region 110. In another embodiment, the first active material layer 112 is provided on the first flat step 113 of the first electrode sheet 11 adjacent to the first bare foil region 110.

[0034] In the winding direction of the electrode assembly 10, each layer of the second electrode sheet 12 from the second layer to the next outer layer includes a second flat stage 123 and a third folded stage 124 and a fourth folded stage 125 respectively provided on both sides of the second flat stage 123, the third folded stage 124 and the fourth folded stage 125 being portions where both sides of each layer of the second electrode sheet 12 are folded, the second bare foil region 120 is provided on the second flat stage 123, and both sides of the second bare foil region 120 are connected to the third folded stage 124 and the fourth folded stage 125, respectively, and in the longitudinal direction of the electrode assembly 10, the second bare foil region 120 is not provided with a second active material layer 122.

[0035] In one embodiment, each layer from the second layer to the next outer layer of the second electrode sheet 12 includes a second flat step 123, and the second flat step 123 is a portion where the battery cell 1 extends horizontally during the winding process and does not bend due to the winding of the battery cell 1, and the third folding step 124 and the fourth folding step 125 provided on both sides of the second flat step 123 are portions where the second electrode sheet 12 is folded during the winding process of the battery cell 1 to realize the winding of the battery cell 1. The thickness of the second electrode sheet 12 in the second bare foil region 120 is thinner than the thickness of the second electrode sheet 12 adjacent to the second bare foil region 120, and by providing the second bare foil region 120 in the second flat step 123, it is possible to prevent the thin part of the second electrode sheet 12 from extending into the winding and folding region, which causes the thickness of the battery cell 1 to vary.

[0036] In one embodiment, the second bare foil region 120 is provided on at least one second flat step 123, and a third folded step 124 and a fourth folded step 125 are connected to both sides of the second bare foil region 120, and the second bare foil region 120 can occupy one second flat step 123. In another embodiment, the second active material layer 122 is provided on the surfaces of the third folded step 124 and the fourth folded step 125, and the second active material layer 122 is not provided on the surfaces of the third folded step 124 and the fourth folded step 125 that extend from the second bare foil region 120. In another embodiment, the second active material layer 122 is provided on the second flat step 123 of the second electrode sheet 12 adjacent to the second bare foil region 120.

[0037] The first bare foil area 110 and the second bare foil area 120 are arranged opposite each other. In one embodiment, the first bare foil area 110 and the second bare foil area 120 are arranged on adjacent first electrode sheet 11 and second electrode sheet 12, respectively. The first bare foil area 110 is arranged facing the second bare foil area 120, and the second bare foil area 120 is also arranged facing the first bare foil area 110. The first bare foil area 110 on which the first active material layer 112 is not provided corresponds to the second bare foil area 120 on which the second active material layer 122 is not provided, thereby avoiding problems such as uneven thickness of the battery cell and lithium precipitation due to misalignment.

[0038] In one embodiment, in the width direction of the electrode assembly 10, the distance between the central symmetry line of the first bare foil area 110 or the second bare foil area 120 and the central symmetry line of the electrode assembly 10 is 2 mm or less, respectively. In other words, the first bare foil area 110 and the second bare foil area 120 are provided in the central area of ​​the battery cell 1, thereby improving the flatness of the battery cell 1.

[0039] In the width direction of the electrode assembly 10, both sides of the first bare foil region 110 exceed the width of both sides of the second bare foil region 120 corresponding to the first bare foil region 110 by 0 to 4 mm. In one embodiment, the first electrode sheet 11 is the cathode of the battery cell 1, and the second electrode sheet 12 is the anode of the battery cell 1, and by having both edges of the first bare foil region 110 exceed both edges corresponding to the second bare foil region 120, electrode analysis lithium is avoided and the safety of the battery cell 1 is improved.

[0040] As shown in Figures 4 and 5, Figure 4 is a schematic plan view of the front and back surfaces of the first bare foil area 110 of a battery cell 1 according to an embodiment of the present application, and Figure 5 is a schematic plan view of the front and back surfaces of the second bare foil area 120 of a battery cell 1 according to an embodiment of the present application.

[0041] The first current collector 111 has a first active material layer 112 provided on the other surface opposite the first bare foil area 110, and the second current collector 121 has a second active material layer 122 provided on the other surface opposite the second bare foil area 120. In one embodiment, a first active material layer 112 and a second active material layer 122 are provided on the back side of the first bare foil area 110 and the second bare foil area 120, respectively. That is, the first bare foil area 110 and the second bare foil area 120 are provided on one side. The thickness of the first electrode sheet 11 provided with the first bare foil area 110 and the thickness of the second electrode sheet 12 provided with the second bare foil area 120 have a smaller impact on the uniformity of the overall thickness of the battery cell 1 when wound or stacked than the thickness of a conventional double-sided grooved bare foil area. Furthermore, the first electrode sheet 11 is provided with the first active material layer 112 on the back side corresponding to the first bare foil area 110, and the second electrode sheet 12 is provided with the second active material layer 122 on the back side corresponding to the second bare foil area 120. This increases the total amount of active material in the battery cell 1 and further increases the energy density of the battery cell 1 when the volume does not change.

[0042] In one embodiment, in the longitudinal direction of the electrode assembly 10, the first bare foil area 110 is free of the first active material layer 112, and in the longitudinal direction of the electrode assembly 10, the second bare foil area 120 is free of the second active material layer 122, i.e., the opposing sides of the first bare foil area 110 and the second bare foil area 120 extend to the edges of the first current collector 111 and the second current collector 121, respectively, and both the first bare foil area 110 and the second bare foil area 120 have openings on both sides, providing a complete stress relief window for the expansion of the first electrode sheet 11 and the second electrode sheet 12 during the electrochemical cycle.

[0043] The electrode assembly 10 further includes a first tab 15 electrically connected to the first bare foil area 110, a second tab 16 electrically connected to the second bare foil area 120, a first insulating layer 17 disposed on the first bare foil area 110, and a second insulating layer 18 disposed on the second bare foil area 120. The first tab 15 is secured to the first bare foil area 110 by welding, with the first insulating layer 17 covering at least a surface of the first tab 15, and the second tab 16 is secured to the second bare foil area 120 by welding, with the second insulating layer 18 covering at least a surface of the second tab 16.

[0044] In one embodiment, the first current collector 111 and the second current collector 121 may be made of a material with good conductive ability and ductility, such as copper foil, aluminum foil, etc., and the first tab 15 may be fixed to the first current collector 111 by resistance welding, ultrasonic welding, laser welding, conductive rubber adhesion, etc. to realize an electrical connection, and the second tab 16 may be fixed to the first current collector 111 by resistance welding, ultrasonic welding, laser welding, conductive rubber adhesion, etc. to realize an electrical connection. A first insulating layer 17 is provided on the first bare foil area 110, covering at least the first tab 15 and the connection area between the first tab 15 and the first current collector 111, and covering at least burrs that may occur when connecting between the first tab 15 and the first current collector 111, thereby avoiding a short circuit of the battery cell 1, and a second insulating layer 18 is provided on the second bare foil area 120, covering at least the second tab 16 and the connection area between the second tab 16 and the second current collector 121, and covering at least burrs that may occur when connecting between the second tab 16 and the second current collector 121, thereby avoiding a short circuit of the battery cell 1.

[0045] In this embodiment, as shown in Figures 2 and 3, the first insulating layer 17 can cover only the first tab 15 and the welding area between the first tab 15 and the first current collector 111, and the second insulating layer 18 can cover only the second tab 16 and the welding area between the second tab 16 and the second current collector 121.

[0046] In another embodiment, as shown in Figures 6 and 7, the first insulating layer 17 can cover the first tab 15 and other areas on the surface of the first current collector 111 corresponding to the first bare foil area 110 where the first tab 15 is not provided, and the second insulating layer 18 can cover the second tab 16 and other areas on the surface of the second current collector 121 corresponding to the second bare foil area 120 where the second tab 16 and second current collector 121 are not provided.

[0047] In another embodiment, as shown in Figures 8 and 9, the first insulating layer 17 covers the first bare foil area 110 and covers the first tab 15, and both ends of the first insulating layer 17 can overlap the surface of the first active material layer 112 to cover the first bare foil area 110, and the second insulating layer 18 covers the second bare foil area 120 and covers the second tab 16, and both ends of the second insulating layer 18 can overlap the surface of the second active material layer 122 to cover the second bare foil area 120.

[0048] In one embodiment, a first active material layer 112 is provided on each of the two surfaces of the first current collector 111 at the start of winding, and a second active material layer 122 is provided on each of the two surfaces of the second current collector 121 at the end of winding.

[0049] In one embodiment, the winding start section of the second current collector 121 includes a fifth folding section 1210 that does not overlap with the winding start section of the first current collector 111 in the thickness direction of the electrode assembly 10.

[0050] In one embodiment, the winding start section of the second electrode sheet 12 may be provided with a third bare foil region 1211 connected to a fifth folding section 1210, and the fifth folding section 1210 may be a pre-folded structure, and the fifth folding section 1210 is further connected to the tile section of the second electrode sheet 12. The fifth folding section 1210 is provided toward the winding center of the battery cell 1, and the length of the third bare foil region 1211 may be less than half the winding core width, so that the fifth folding section 1210 and the winding start section of the first current collector 111 do not overlap in the thickness direction of the electrode assembly 10, preventing the occurrence of a folding phenomenon in one-sided region of the first electrode sheet 11, and the pre-folded fifth folding section 1210 can compensate for the thickness difference of the battery cell 1 and make the thickness of the battery cell 1 flatter.

[0051] As shown in Fig. 10, it is a schematic diagram of a power consumption device 100 according to an embodiment of the present application. The present application further provides a power consumption device 100, which includes an operation module 101 and a battery 102 for supplying power to the operation module 101, and the battery 102 includes the above-mentioned battery cell 1. In Fig. 10, the power consumption device 100 is only a mobile phone, and in other embodiments, the power consumption device 100 may be a personal computer, a smart home appliance, an industrial controller, an electric car, a hybrid oil-electric vehicle, etc.

[0052] Specific embodiments of the present application have been described with reference to the above-mentioned drawings. However, modifications and substitutions of the specific embodiments of the present application may be made without departing from the spirit and scope of the present application. All of these modifications and substitutions are within the scope limited in the present application. [Explanation of symbols]

[0053] 1 Battery Cell 10 Electrode Assembly 11 First electrode sheet 110 1st bare foil area 111 First current collector 112 First active material layer 113 1st flat stage 114 First folding stage 115 Second folding stage 12 Second electrode sheet 120 2nd bare foil area 121 Second current collector 1210 5th folding stage 1211 3rd bare foil area 122 Second active material layer 123 2nd flat step 124 Third folding stage 125 4th folding stage 13 Separator 15 First Tab 16 Second Tab 17 First insulating layer 18 Second insulating layer 100 Power consumption equipment 101 Operation Module 102 Batteries

Claims

1. An electrode assembly, The electrode assembly comprises: A first electrode sheet including a first current collector and a first active material layer provided on a surface of the first current collector, the first current collector including a first bare foil region on which the first active material layer is not provided; A second electrode sheet including a second current collector and a second active material layer provided on a surface of the second current collector, the second current collector including a second bare foil region on which the second active material layer is not provided; The first tab, a separator provided between the first electrode sheet and the second electrode sheet, The electrode assembly is a battery cell formed by sequentially stacking and winding the first electrode sheet, the separator, and the second electrode sheet, In the winding direction of the electrode assembly, each layer from the second layer to the next outer layer of the first electrode sheet includes a first flat section and a first folded section and a second folded section provided on both sides of the first flat section, The first folding section and the second folding section are each a portion where both sides of each layer of the first electrode sheet are folded, a first bare foil area provided on the first flat step, the first tab electrically connected to the first bare foil area, and the first active material layer not being provided on the first bare foil area in the longitudinal direction of the electrode assembly.

2. In the winding direction of the electrode assembly, each layer from the second layer to the next outer layer of the second electrode sheet includes a second flat section and a third folded section and a fourth folded section respectively provided on both sides of the second flat section, 2. The battery cell according to claim 1, wherein the third folding step and the fourth folding step are portions where both sides of each layer of the second electrode sheet are folded, the second bare foil area is provided on the second flat step, both sides of the second bare foil area are connected to the third folding step and the fourth folding step, respectively, and the second active material layer is not provided on the second bare foil area in the longitudinal direction of the electrode assembly.

3. 2. The battery cell of claim 1, wherein the first current collector has the first active material layer provided on a surface opposite the first bare foil area, or the second current collector has the second active material layer provided on a surface opposite the second bare foil area.

4. 2. The battery cell according to claim 1 , wherein in the width direction of the electrode assembly, a distance between a central symmetric line of the first bare foil region or the second bare foil region and a central symmetric line of the electrode assembly is 2 mm or less.

5. The battery cell according to claim 1 , wherein the first bare foil area and the second bare foil area are provided opposite each other.

6. The battery cell according to claim 5, wherein in the width direction of the electrode assembly, the width of both sides of the first bare foil region is 0 to 4 mm greater than the width of both sides of the second bare foil region corresponding to the first bare foil region.

7. 2. The battery cell of claim 1, wherein the electrode assembly further comprises: a second tab electrically connected to the second bare foil area; a first insulating layer provided on the first bare foil area; and a second insulating layer provided on the second bare foil area.

8. the first tab is fixed to the first bare foil region by welding, and the first insulating layer is coated on a surface of the first tab; Alternatively, the second tab is fixed to the second bare foil area by welding, and a surface of the second tab is coated with the second insulating layer.

9. 2. The battery cell according to claim 1, wherein the first active material layer is provided on each of both surfaces of the first current collector at the start of winding, and the second active material layer is provided on each of both surfaces of the second current collector at the end of winding.

10. 2 . The battery cell according to claim 1 , wherein the winding start portion of the second current collector includes a fifth folding portion, and the fifth folding portion does not overlap with the winding start portion of the first current collector in a thickness direction of the electrode assembly.

11. The battery cell according to claim 1 , wherein the first active material layer is provided on a surface of the first folded section and a surface of the second folded section.

12. The battery cell according to claim 11 , wherein the first active material layer is not provided on the surfaces of the first folded section and the second folded section that extend from the first bare foil region.

13. 2 . The battery cell according to claim 1 , wherein the first active material layer is provided on a first flat step of the first electrode sheet adjacent to the first bare foil region.

14. A power consuming device comprising an operating module and a battery for supplying power to said operating module, said battery comprising a battery cell according to any one of claims 1 to 13.

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