Winding-type battery cell and secondary battery
By optimizing the welding position and length of the electrode plates and tabs, the high cost and processing difficulties in improving the cycle performance of wound cells have been solved, achieving optimization of cell internal resistance and improvement of cycle performance, making it suitable for secondary batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- REPT BATTERO ENERGY CO LTD
- Filing Date
- 2023-04-14
- Publication Date
- 2026-08-04
AI Technical Summary
Improving the cycle performance of existing wound battery cells faces challenges such as high cost and processing difficulties.
By optimizing the ratio of welding offset to needle width and welding length of electrode plates and tabs, and controlling it within the range of 0.1-0.2 and 25%-65%, the distance between positive and negative tabs is ensured to be appropriate, avoiding short circuits and excessive internal resistance, and improving cell flatness.
Without changing the materials or structure, it significantly improves the cycle performance of the battery cell, reduces production costs, and is suitable for large-scale industrial production.
Smart Images
Figure CN116454412B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of secondary battery technology, and in particular to a wound battery cell and a secondary battery. Background Technology
[0002] Compared to other rechargeable batteries, lithium-ion batteries are increasingly used in a wide variety of applications due to their high energy density, low self-discharge, and high voltage platform. These range from small electronic devices to smartphones and laptops, vehicles, and many other applications. However, lithium-ion batteries do age. This depends not only on time or the calendar but also on the number of charge-discharge cycles the battery undergoes. Therefore, improving the cycle performance of batteries is crucial.
[0003] Currently, common methods to improve the cycle performance of wound cells include optimizing active materials, electrolyte composition, electrode coating structure, and electrode winding method. However, these solutions are currently limited by the materials themselves or the processing, making further improvements increasingly difficult and potentially leading to high costs or risks.
[0004] Therefore, this application is hereby submitted. Summary of the Invention
[0005] This application provides a wound-type battery cell and a secondary battery to solve the problems of high cost and difficult processing in improving the cycle performance of wound-type battery cells in related technologies.
[0006] The technical solution provided in this application is as follows:
[0007] In a first aspect, this application provides a wound battery cell, which is a flat structure formed by winding a first electrode, a second electrode, and a separator located between the first electrode and the second electrode on a winding needle. During winding, the starting end of the first electrode and the starting end of the second electrode are independently aligned with either end of the winding needle along a first direction, and the first direction is parallel to the width direction of the winding needle.
[0008] Wherein, a first empty foil area is provided on the side of the first electrode near its starting end, and a first electrode tab is connected to the first empty foil area. Along the first direction, the ratio of the distance from the first electrode tab to the starting end of the first electrode to the width of the winding needle is 0.1 to 0.2.
[0009] A second empty foil area is provided on the side of the second electrode near its starting end, and a second electrode tab is connected to the second empty foil area. Along the first direction, the ratio of the distance from the second electrode tab to the starting end of the second electrode to the width of the winding needle is 0.1 to 0.2.
[0010] In some embodiments, the point at which the first electrode first bends is the first bend point;
[0011] The point at which the second electrode first bends is the second bend, and the first bend and the second bend are located on both sides of the wound cell, respectively.
[0012] In some embodiments, the point at which the first electrode first bends is the first bend point;
[0013] The point where the second electrode first bends is the second bend, and the first bend and the second bend are located on the same side of the wound cell.
[0014] In some embodiments, the central axis of the wound cell in the width direction is taken as the cell centerline, and the first tab and the second tab are located on both sides of the cell centerline.
[0015] In some embodiments, the portion where the first tab connects to the first electrode sheet is a first welded portion, and the length of the first welded portion is 25% to 65% of the width of the first electrode sheet;
[0016] The portion where the second electrode tab connects to the second electrode sheet is the second welded portion, and the length of the second welded portion is 25% to 65% of the width of the second electrode sheet.
[0017] In some embodiments, the first electrode is a positive electrode and the second electrode is a negative electrode;
[0018] Alternatively, the first electrode can be a negative electrode and the second electrode can be a positive electrode.
[0019] In some embodiments, the width of the positive electrode is 30-100 mm, the width of the negative electrode is 32-102 mm, and the width of the negative electrode is 2-5 mm larger than the width of the positive electrode.
[0020] In some embodiments, the positive electrode includes a positive current collector and a layer of positive active material covering the positive current collector;
[0021] The negative electrode sheet includes a negative electrode current collector and a layer of negative electrode active material covering the negative electrode current collector.
[0022] In some embodiments, the positive electrode active material layer includes a positive electrode active substance, which includes lithium iron phosphate or ternary materials;
[0023] The negative electrode active material layer includes a negative electrode active substance, which includes one or more of graphite, soft carbon, hard carbon, silicon oxide, and silicon carbon.
[0024] Secondly, this application also provides a secondary battery comprising the wound cell as described above.
[0025] The beneficial effects of the technical solution provided in this application include:
[0026] The inventors discovered through research that the ratio of the welding offset between the positive and negative tabs (i.e., the distance from the tab to the starting end of the electrode) to the width of the winding needle affects the internal resistance of the battery cell. If the ratio is less than 0.1, the distance between the positive and negative tabs becomes too large, resulting in poor contact between the positive and negative electrodes and the separator at the center of the winding core, leading to excessive internal resistance and affecting the cell's cycle performance. If the ratio is greater than 0.2, the unsupported area at the edge of the electrode foil is larger, making the inner ring prone to wrinkling during winding, resulting in unevenness inside the winding core and increased internal resistance. Furthermore, due to the insufficient distance between the positive and negative tabs, the tabs are prone to short-circuiting during testing.
[0027] This application has made fine optimizations to the original wound cell structure, controlling the ratio of the welding offset of the positive and negative tabs to the width of the winding needle to be between 0.1 and 0.2, which can further improve the cycle performance of the cell. It does not require major modifications to the cell material or structure and can still be produced using existing production equipment and processes. It has the advantage of low cost. In actual production, the above purpose can be achieved by adjusting the welding position of the tabs or the width of the winding needle. It is simple to operate and suitable for large-scale industrial production. Attached Figure Description
[0028] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0029] Figure 1 This is a schematic diagram of the structure of the first electrode provided in an embodiment of this application;
[0030] Figure 2 A cross-sectional view of the battery cell provided in an embodiment of this application;
[0031] Figure 3 This is a schematic diagram of the battery cell structure provided in an embodiment of this application;
[0032] Figure 4 The room temperature cycling capacity retention rate diagrams of the battery cells provided in Examples 1-2 and Comparative Examples 1-2 of this application;
[0033] Figure 5 The diagram shows the room temperature cycling capacity retention rate of the battery cells provided in Embodiment 3 and Comparative Examples 3-4 of this application.
[0034] In the figure: 1. First electrode; 100. First tab; 101. First bend; 102. First weld; 103. First empty foil area; 2. Second electrode; 200. Second tab; 201. Second bend; 2. Diaphragm. Detailed Implementation
[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings and embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0036] See Figure 1 , Figure 2 and Figure 3 As shown, in a first aspect, embodiments of this application provide a wound battery cell, which is a flat structure formed by winding a first electrode 1, a second electrode 2, and a separator 3 located between the first electrode 1 and the second electrode 2 onto a winding needle. During winding, the starting end of the first electrode 1 and the starting end of the second electrode 2 are independently aligned with either end of the winding needle along a first direction, which is parallel to the width direction of the winding needle. It should be noted that after winding, the winding needle is removed and high-temperature pressing is performed, so there is no winding needle in the formed wound battery cell. Furthermore, the first direction... Figure 2 The left and right directions in the middle.
[0037] Wherein, a first empty foil area 103 is provided on the side of the first electrode 1 near its starting end, and a first electrode tab 100 is connected to the first empty foil area 103. Along the first direction, the ratio of the distance from the first electrode tab 100 to the starting end of the first electrode 1 to the width of the winding needle is 0.1 to 0.2.
[0038] A second empty foil area is provided on the side of the second electrode 2 near its starting end, and a second electrode tab 200 is connected to the second empty foil area. Along the length extension direction of the second electrode 2, the ratio of the distance from the second electrode tab 200 to the starting end of the second electrode 2 to the width of the winding needle is 0.1 to 0.2.
[0039] It should be noted that the empty foil area is part of the electrode sheet, but this part is not coated with an active material layer. In other words, the electrode sheet consists of two parts: the part coated with an active material layer and the empty foil area without an active material layer. The empty foil area can be used to solder tabs, for example, see [reference needed]. Figure 1 As shown, the gray portion of the first electrode 1 is coated with an active material layer, while the white portion is the first empty foil area 103 without an active material layer. This allows for better adhesion... Figure 1 As can be seen, the starting end of the first electrode 1 is the end of the first empty foil region 103 that is far away from the active material layer.
[0040] The inventors discovered through research that the ratio of the welding offset L (i.e., the distance from the tab to the starting end of the electrode) to the width of the coiling needle affects the internal resistance of the battery cell. For example... Figure 1 In wound battery cells, a ratio of the tab welding offset L to the winding needle width of less than 0.1 results in an excessively large distance between the positive and negative tabs, leading to poor contact between the positive and negative electrodes and the separator at the center of the core. This causes excessive internal resistance and affects the cell's cycle performance. Conversely, a ratio greater than 0.2 results in a large unsupported area at the starting foil region of the electrode, making the inner ring prone to wrinkling during winding, causing unevenness inside the core, poor contact between the positive and negative electrodes, and increasing internal resistance. Furthermore, the small distance between the positive and negative tabs makes them highly susceptible to short-circuiting during testing. It should be noted that the starting end of the electrode refers to the end of the electrode located inside the cell.
[0041] Since the starting end of the first electrode 1 and the starting end of the second electrode 2 are independently aligned with either end of the winding needle along the first direction, that is, the starting end of the first electrode 1 can be aligned with either end of the winding needle along the first direction, and the starting end of the second electrode 2 can also be aligned with either end of the winding needle along the first direction, and the two do not affect each other, there are multiple layouts for the positions of the first bending point of the first electrode 1 and the second bending point of the second electrode 2.
[0042] For example, see Figure 2 As shown, in some embodiments, the first bending point of the first electrode 1 is the first bending point 101; the first bending point of the second electrode 2 is the second bending point 201, and the first bending point 101 and the second bending point 201 are located on both sides of the wound cell, respectively.
[0043] The solution provided in this application is applicable to various existing conventional wound cell structures. As an example, Figure 2 One example is shown, specifically, with the central axis of the wound cell in the width direction as the cell centerline AA. Figure 2 In the displayed wound cell structure, the first bend 101 and the second bend 201 are located on both sides of the cell centerline AA, respectively.
[0044] For example, as another example, the first bend 101 and the second bend 201 are located on the same side of the cell centerline AA.
[0045] See Figure 2As shown, in some embodiments, the central axis of the wound cell in the width direction is taken as the cell centerline AA, and the first tab 100 and the second tab 200 are located on both sides of the cell centerline.
[0046] The above configuration ensures that the first tab 100 and the second tab 200 have sufficient distance to avoid short circuits caused by contact between them.
[0047] See Figure 1 As shown, in some embodiments, the portion of the first electrode tab 100 connected to the first electrode plate 1 is a first welding portion 102, and the length of the first welding portion 102 is 25% to 65% of the width of the first electrode plate 1.
[0048] The portion of the second electrode tab 200 that connects to the second electrode plate 2 is the second welding portion, and the length of the second welding portion is 25% to 65% of the width of the second electrode plate 2.
[0049] The inventors discovered through research that the welding length d of the positive and negative tabs (i.e., the length of the first or second welding part) affects the cycle performance of the battery cell. If the welding length d of the tab is less than 25% of the electrode width D, the welding length is too short, resulting in a small contact area between the tab and the electrode, which leads to excessive internal resistance of the battery cell and reduces the cycle performance. If the welding length d of the tab is greater than 65% of the electrode width D, the surface of the battery cell will be uneven, the contact between the positive and negative electrodes will be poor, and the cycle performance of the battery cell will be affected. Therefore, by controlling the welding length d of the tab within 25%-65% of the electrode width D, the cycle performance of the wound battery cell can be improved.
[0050] In some embodiments, the first electrode 1 is a positive electrode and the second electrode 2 is a negative electrode;
[0051] Alternatively, the first electrode 1 can be a negative electrode, and the second electrode 2 can be a positive electrode.
[0052] In some embodiments, the width of the positive electrode is 30-100 mm, the width of the negative electrode is 32-102 mm, and the width of the negative electrode is 2-5 mm larger than the width of the positive electrode.
[0053] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active material layer covering the positive current collector;
[0054] The negative electrode sheet includes a negative electrode current collector and a layer of negative electrode active material covering the negative electrode current collector.
[0055] In some embodiments, the positive electrode active material layer includes a positive electrode active substance, which includes lithium iron phosphate or ternary materials;
[0056] The negative electrode active material layer includes a negative electrode active substance, which includes one or more of graphite, soft carbon, hard carbon, silicon oxide, and silicon carbon.
[0057] Secondly, embodiments of this application also provide a secondary battery, which includes the wound cell as described above.
[0058] The present application will be further described below through specific embodiments.
[0059] In Examples 1 and 2, and Comparative Examples 1 and 2, the types of positive and negative active materials and coating thicknesses are the same between the positive and negative electrodes. The positive active material is lithium iron phosphate, and the negative active material is artificial graphite with a coin cell capacity of 340 mAh / g. In Examples 3 and Comparative Examples 3-4, the types of positive and negative active materials and coating thicknesses are the same between the positive and negative electrodes. The positive active material is lithium iron phosphate, and the negative active material is artificial graphite with a coin cell capacity of 350 mAh / g.
[0060] Example 1
[0061] like Figure 2 The image shows a type of wound battery cell, which is a flat structure formed by winding a positive electrode plate, a negative electrode plate, and a separator located between the positive electrode plate and the negative electrode plate onto a winding needle;
[0062] Among them, a positive electrode tab is connected to the positive electrode sheet, the distance from the positive electrode tab to the starting end of the positive electrode sheet is 5mm, the width of the coiling needle is 42mm, and the ratio of the electrode tab welding offset L to the width of the coiling needle is 0.12.
[0063] The negative electrode sheet is connected to a negative electrode tab. The distance from the negative electrode tab to the starting end of the negative electrode sheet is 5mm. The width of the coiled needle is 42mm. The ratio of the electrode tab welding offset L to the width of the coiled needle is 0.12.
[0064] The positive electrode has a width of 70mm, the negative electrode has a width of 73mm, the welding length of the positive electrode tab is 30mm, accounting for 43% of the width of the positive electrode, and the welding length of the negative electrode tab is 31mm, accounting for 43% of the width of the negative electrode.
[0065] Example 2
[0066] like Figure 2 The image shows a type of wound battery cell, which is a flat structure formed by winding a positive electrode plate, a negative electrode plate, and a separator located between the positive electrode plate and the negative electrode plate onto a winding needle;
[0067] Among them, a positive electrode tab is connected to the positive electrode sheet, the distance from the positive electrode tab to the starting end of the positive electrode sheet is 8mm, the width of the coiling needle is 42mm, and the ratio of the electrode tab welding offset L to the width of the coiling needle is 0.19.
[0068] The negative electrode plate is connected to a negative electrode tab. The distance from the negative electrode tab to the starting end of the negative electrode plate is 8mm. The width of the coiled needle is 42mm. The ratio of the electrode tab welding offset L to the width of the coiled needle is 0.19.
[0069] The positive electrode has a width of 70mm, the negative electrode has a width of 73mm, the welding length of the positive electrode tab is 30mm, accounting for 43% of the width of the positive electrode, and the welding length of the negative electrode tab is 31mm, accounting for 43% of the width of the negative electrode.
[0070] Comparative Example 1
[0071] like Figure 2 The image shows a type of wound battery cell, which is a flat structure formed by winding a positive electrode plate, a negative electrode plate, and a separator located between the positive electrode plate and the negative electrode plate onto a winding needle;
[0072] Among them, a positive electrode tab is connected to the positive electrode sheet, the distance from the positive electrode tab to the starting end of the positive electrode sheet is 3mm, the width of the coiling needle is 42mm, and the ratio of the electrode tab welding offset L to the width of the coiling needle is 0.07.
[0073] The negative electrode sheet is connected to a negative electrode tab. The distance from the negative electrode tab to the starting end of the negative electrode sheet is 3mm. The width of the coiled needle is 42mm. The ratio of the electrode tab welding offset L to the width of the coiled needle is 0.07.
[0074] The positive electrode has a width of 70mm, the negative electrode has a width of 73mm, the welding length of the positive electrode tab is 30mm, accounting for 43% of the width of the positive electrode, and the welding length of the negative electrode tab is 31mm, accounting for 43% of the width of the negative electrode.
[0075] Comparative Example 2
[0076] like Figure 2 The image shows a type of wound battery cell, which is a flat structure formed by winding a positive electrode plate, a negative electrode plate, and a separator located between the positive electrode plate and the negative electrode plate onto a winding needle;
[0077] Among them, a positive electrode tab is connected to the positive electrode sheet, the distance from the positive electrode tab to the starting end of the positive electrode sheet is 12mm, the width of the coiling needle is 42mm, and the ratio of the electrode tab welding offset L to the width of the coiling needle is 0.29.
[0078] The negative electrode sheet is connected to a negative electrode tab. The distance from the negative electrode tab to the starting end of the negative electrode sheet is 12mm. The width of the coiled needle is 42mm. The ratio of the electrode tab welding offset L to the width of the coiled needle is 0.29.
[0079] The positive electrode has a width of 70mm, the negative electrode has a width of 73mm, the welding length of the positive electrode tab is 30mm, accounting for 43% of the width of the positive electrode, and the welding length of the negative electrode tab is 31mm, accounting for 43% of the width of the negative electrode.
[0080] Example 3
[0081] like Figure 2 The image shows a type of wound battery cell, which is a flat structure formed by winding a positive electrode plate, a negative electrode plate, and a separator located between the positive electrode plate and the negative electrode plate onto a winding needle;
[0082] Among them, a positive electrode tab is connected to the positive electrode sheet, the distance from the positive electrode tab to the starting end of the positive electrode sheet is 5mm, the width of the coiling needle is 42mm, and the ratio of the electrode tab welding offset L to the width of the coiling needle is 0.12.
[0083] The negative electrode sheet is connected to a negative electrode tab. The distance from the negative electrode tab to the starting end of the negative electrode sheet is 5mm. The width of the coiled needle is 42mm. The ratio of the electrode tab welding offset L to the width of the coiled needle is 0.12.
[0084] The positive electrode has a width of 83mm, the negative electrode has a width of 86mm, the welding length of the positive electrode tab is 42mm, accounting for 51% of the width of the positive electrode, and the welding length of the negative electrode tab is 44mm, accounting for 51% of the width of the negative electrode.
[0085] Comparative Example 3
[0086] like Figure 2 The image shows a type of wound battery cell, which is a flat structure formed by winding a positive electrode plate, a negative electrode plate, and a separator located between the positive electrode plate and the negative electrode plate onto a winding needle;
[0087] Among them, a positive electrode tab is connected to the positive electrode sheet, the distance from the positive electrode tab to the starting end of the positive electrode sheet is 5mm, the width of the coiling needle is 42mm, and the ratio of the electrode tab welding offset L to the width of the coiling needle is 0.12.
[0088] The negative electrode sheet is connected to a negative electrode tab. The distance from the negative electrode tab to the starting end of the negative electrode sheet is 5mm. The width of the coiled needle is 42mm. The ratio of the electrode tab welding offset L to the width of the coiled needle is 0.12.
[0089] The positive electrode has a width of 83mm, the negative electrode has a width of 86mm, the welding length of the positive electrode tab is 18mm, accounting for 22% of the width of the positive electrode, and the welding length of the negative electrode tab is 20mm, accounting for 23% of the width of the negative electrode.
[0090] Comparative Example 4
[0091] like Figure 2 The image shows a type of wound battery cell, which is a flat structure formed by winding a positive electrode plate, a negative electrode plate, and a separator located between the positive electrode plate and the negative electrode plate onto a winding needle;
[0092] Among them, a positive electrode tab is connected to the positive electrode sheet, the distance from the positive electrode tab to the starting end of the positive electrode sheet is 5mm, the width of the coiling needle is 42mm, and the ratio of the electrode tab welding offset L to the width of the coiling needle is 0.12.
[0093] The negative electrode sheet is connected to a negative electrode tab. The distance from the negative electrode tab to the starting end of the negative electrode sheet is 5mm. The width of the coiled needle is 42mm. The ratio of the electrode tab welding offset L to the width of the coiled needle is 0.12.
[0094] The positive electrode has a width of 83mm, the negative electrode has a width of 86mm, the welding length of the positive electrode tab is 58mm, accounting for 70% of the width of the positive electrode, and the welding length of the negative electrode tab is 60mm, accounting for 70% of the width of the negative electrode.
[0095] Performance testing
[0096] The wound cells obtained in Examples 1-3 and Comparative Examples 1-4 were used to make secondary batteries, and the batteries were subjected to the following performance tests.
[0097] (1) Battery internal resistance: The internal resistance of the cells after capacity grading was tested using an internal resistance meter. The test results are shown in Table 1.
[0098] (2) Battery cycle performance: 1C constant current and constant voltage charging to 3.65V; resting for 10 minutes; 1C discharge to 2.0V. Capacity retention rate = capacity after N cycles / initial capacity. The capacity retention rate curve at room temperature is shown in [reference needed]. Figure 4 and Figure 5 .
[0099] Table 1
[0100]
[0101] See Figure 4 As shown, Figure 4 The room-temperature cycling performance of the wound cells prepared in Examples 1-2 and Comparative Examples 1-2 is shown. As can be seen from the figures, in Comparative Example 1, the ratio of the tab welding offset to the winding needle width is less than 0.1, resulting in an excessively large center distance between the tabs, poor contact between the positive and negative electrodes and the separator, thus increasing the internal resistance of the cell and reducing its cycle performance. In Comparative Example 2, the ratio of the tab welding offset to the winding needle width is greater than 0.2, resulting in a large unsupported area in the empty foil region at the beginning of the electrode, making the inner ring prone to wrinkling during winding, causing unevenness inside the core, and further increasing the internal resistance of the cell due to poor contact between the positive and negative electrodes. Simultaneously, due to the excessively small distance between the positive and negative tabs, the tabs are prone to short-circuiting during testing. Therefore, it is necessary to control the ratio of the tab welding offset to the winding needle width within 0.1-0.2.
[0102] See Figure 5 As shown, Figure 5The room-temperature cycle performance of the wound cells prepared in Example 3 and Comparative Examples 3-4 is shown. As can be seen from the figures, in Comparative Example 3, the tab welding length is less than 25% of the electrode width, resulting in an excessively small contact area between the tab and the electrode, leading to excessive internal resistance after capacity grading and reduced battery cycle performance. In Comparative Example 4, the tab welding length is greater than 65% of the electrode width, causing unevenness on the core surface and poor contact between the positive and negative electrodes and the separator, which is also detrimental to improving battery cycle performance. Therefore, it is necessary to control the tab welding length within 25%-65% of the electrode width.
[0103] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.
[0104] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0105] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. A wound battery cell, characterized in that, It is a flat structure formed by winding a first electrode (1), a second electrode (2) and a diaphragm (3) located between the first electrode (1) and the second electrode (2) on a winding needle. During winding, the starting end of the first electrode (1) and the starting end of the second electrode (2) are independently aligned with either end of the winding needle along a first direction. The first direction is parallel to the width direction of the winding needle. Wherein, a first empty foil area (103) is provided on the side of the first electrode (1) near its starting end, and a first electrode tab (100) is connected to the first empty foil area (103). Along the first direction, the ratio of the distance from the first electrode tab (100) to the starting end of the first electrode (1) to the width of the winding needle is 0.1 to 0.
2. The second electrode (2) has a second empty foil area on one side near its starting end, and a second electrode tab (200) is connected to the second empty foil area. Along the first direction, the ratio of the distance from the second electrode tab (200) to the starting end of the second electrode (2) to the width of the winding needle is 0.1 to 0.
2. With the central axis of the wound cell in the width direction as the cell centerline, the first tab (100) and the second tab (200) are located on both sides of the cell centerline; The first empty foil region (103) is part of the first electrode (1), and the second empty foil region is part of the second electrode (2). The first empty foil region (103) and the second empty foil region are not coated with an active material layer.
2. The wound battery cell as described in claim 1, characterized in that, The first bending point of the first electrode (1) is the first bending point (101). The first bending point of the second electrode (2) is the second bending point (201), and the first bending point (101) and the second bending point (201) are located on both sides of the wound cell.
3. The wound battery cell as described in claim 1, characterized in that, The portion of the first electrode tab (100) connected to the first electrode plate (1) is the first welding part (102), and the length of the first welding part (102) is 25% to 65% of the width of the first electrode plate (1); The part where the second electrode tab (200) is connected to the second electrode plate (2) is the second welding part, and the length of the second welding part is 25% to 65% of the width of the second electrode plate (2).
4. The wound battery cell as described in claim 1, characterized in that, The first electrode (1) is a positive electrode, and the second electrode (2) is a negative electrode; Alternatively, the first electrode (1) can be a negative electrode and the second electrode (2) can be a positive electrode.
5. The wound battery cell as described in claim 4, characterized in that, The width of the positive electrode is 30-100 mm, the width of the negative electrode is 32-102 mm, and the width of the negative electrode is 2-5 mm larger than the width of the positive electrode.
6. The wound battery cell as described in claim 4, characterized in that, The positive electrode sheet includes a positive current collector and a positive active material layer covering the positive current collector; The negative electrode sheet includes a negative electrode current collector and a layer of negative electrode active material covering the negative electrode current collector.
7. The wound battery cell as described in claim 6, characterized in that, The positive electrode active material layer includes a positive electrode active substance, which includes lithium iron phosphate or ternary materials. The negative electrode active material layer includes a negative electrode active substance, which includes one or more of graphite, soft carbon, hard carbon, silicon oxide, and silicon carbon.
8. A secondary battery, characterized in that, It includes the wound battery cell as described in any one of claims 1-7.