Electrode assembly and electrochemical device

Abstract

The application discloses an electrode assembly, comprising: a winding core, comprising a positive electrode sheet, a diaphragm and a negative electrode sheet which are arranged in a mutual laminated winding mode, and both ends of the negative electrode sheet are beyond both ends of the positive electrode sheet; and a pad located at the area where both ends of the negative electrode sheet are beyond both ends of the positive electrode sheet. In addition, the application also discloses an electrochemical device. By arranging the pad in the overhanging area between the negative electrode sheet and the positive electrode sheet, the application prevents the winding core edge from contacting the shell, thereby reducing the abrasion of the shell caused by the winding core and improving the safety performance.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, and in particular to an electrode assembly and an electrochemical device. Background Technology

[0002] Lithium-ion batteries, a crucial component of electrochemical energy storage systems, contain lithium (specifically in the forms of metallic lithium, lithium alloys, lithium ions, and lithium polymers) and are widely used in numerous fields, including consumer electronics. The mainstream types of lithium-ion batteries on the market are mainly divided into two categories: stacked and wound. Wound batteries are manufactured by sequentially stacking positive and negative electrodes with a separator and then winding them together. This manufacturing method offers excellent production efficiency and helps to better control production costs, thus providing certain advantages in industrial production.

[0003] However, the structural characteristics of wound batteries lead to defects in practical applications. To ensure the normal and safe operation of lithium batteries, the negative electrode needs to be in excess of the positive electrode. Therefore, a step-like structure is formed in the overhang area between the positive and negative electrode sheets, and the edge of this step is the edge of the positive electrode sheet. During the cycling process of the wound battery, the core will undergo periodic expansion and contraction. With the repeated expansion and contraction of the core, the aforementioned step moves, and the step rubs back and forth with the casing, resulting in wear of the casing. Utility Model Content

[0004] The main objective of this application is to provide an electrode assembly and electrochemical device that aims to reduce wear on the housing by the edge of the positive electrode during cycling and improve safety performance.

[0005] To achieve the above objectives, this application proposes an electrode assembly, including a core, which includes a positive electrode sheet, a separator, and a negative electrode sheet that are stacked and wound together. The two ends of the negative electrode sheet extend beyond the two ends of the positive electrode sheet, and a pad is provided in the overhanging area of ​​the negative electrode sheet that extends beyond the positive electrode sheet.

[0006] In some implementations, the suspension areas at both ends of the negative electrode are equal, and the width of the suspension area is defined as L, satisfying 3mm≤L≤5mm.

[0007] In some implementations, the width of the pad is defined as d, satisfying 0.6L≤d≤0.8L.

[0008] In some implementations, the thickness of the positive electrode is defined as t, which satisfies 60um≤t≤120um.

[0009] In some implementations, the height of the pad is defined as h, satisfying 0.85t≤h≤0.95t.

[0010] In some embodiments, the core is cut along its thickness direction, and the cross-sectional projection of the pad is a right-angled sector.

[0011] In some implementations, the pad is made of one or more of ceramic, boehmite, and graphite.

[0012] In some embodiments, the winding core also includes a positive tab and a negative tab, with the positive tab connected to the positive electrode plate and the negative tab connected to the negative electrode plate.

[0013] Another aspect of this application provides an electrochemical device, including a housing and the aforementioned electrode assembly.

[0014] In some implementations, the core is disposed inside the housing.

[0015] This application proposes an electrode assembly and an electrochemical device. The electrochemical device is a battery. The electrode assembly is set inside the battery casing. By setting a pad on the overhanging area of ​​the negative electrode sheet that extends beyond the positive electrode sheet, continuous friction between the edge of the core and the casing is avoided, thereby reducing the wear caused by the core to the casing and improving safety performance. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the cross-sectional structure of the core in one embodiment of this application; Figure 2 This is a schematic diagram of the cross-sectional structure of the core and pad in another embodiment of this application; Figure 3 This is a schematic cross-sectional view of the negative electrode sheet and pad in another embodiment of this application; Figure 4 This is a schematic diagram of the structure of the negative electrode sheet before it is cut in another embodiment of this application; Figure 5 This is a schematic diagram of the structure of the positive electrode and the negative electrode in one embodiment of this application; Explanation of reference numerals in the attached figures: Core 100; Positive electrode 110; Negative electrode 120; Separator 130; Positive electrode tab 140; Negative electrode tab 150; Pad 200. Detailed Implementation

[0017] The solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments in this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0018] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0019] It should also be noted that when a component is described as "fixed to" or "set on" another component, it can be directly on the other component or there may be an intervening component present. When a component is described as "connected to" another component, it can be directly connected to the other component or there may be an intervening component present.

[0020] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0021] Please see Figure 1 , Figure 1 This is a schematic diagram of the cross-sectional structure of the core 100. This application provides an electrode assembly including a core 100. The core 100 includes a positive electrode sheet 110, a diaphragm 130, and a negative electrode sheet 120, which are stacked and wound around each other. The two ends of the negative electrode sheet 120 extend beyond the two ends of the positive electrode sheet 110. A pad 200 is provided in the overhanging area of ​​the negative electrode sheet 120 extending beyond the positive electrode sheet 110.

[0022] In this embodiment, the electrode assembly includes a core 100 and pads 200. Specifically, the core 100 is formed by winding a positive electrode 110, a separator 130, and a negative electrode 120 together in a specific order. At the edge of the core 100, since the two ends of the negative electrode 120 extend beyond the two ends of the positive electrode 110, a stepped structure is formed on the outermost side of the core 100, and the edge of this step is the edge of the outermost positive electrode 110. To eliminate this step difference and prevent the edge of the positive electrode 110 from contacting the housing, pads 200 are provided at both ends of the negative electrode 120. Specifically, looking along the length of the core 100, the length of the negative electrode 120 is greater than the length of the positive electrode 110. There is a hanging area between the two ends of the positive electrode 110 and the two ends of the negative electrode 120. The spacer 200 is disposed in this hanging area. By placing the spacer 200 in the area where the negative electrode 120 extends beyond the positive electrode 110, the aforementioned step difference is filled, thereby preventing the edge of the positive electrode 110 from contacting the casing and avoiding damage to the casing. In this embodiment, the spacer 200 can be formed in the hanging area of ​​the negative electrode 120 by coating or dispensing.

[0023] In some embodiments, the suspension areas at both ends of the negative electrode 120 are equal, and the width of the suspension area is defined as L, satisfying 3mm≤L≤5mm.

[0024] In some embodiments, the width of the pad 200 is defined as d, satisfying 0.6L≤d≤0.8L.

[0025] In a preferred embodiment, such as Figure 1 As shown, looking along the length of the core 100, there is a hanging area at each end of the negative electrode 120. The distance from the left end of the negative electrode 120 to the left end of the positive electrode 110 is equal to the distance from the right end of the negative electrode 120 to the right end of the positive electrode 110. The width of this hanging area is denoted as L, and the value of L is set within the range of 3mm to 5mm. For example, in actual production, the distance L between the ends of the positive electrode 110 and the ends of the negative electrode 120 can be set to different values ​​such as 3mm, 4mm, and 5mm according to different design requirements. Specifically, setting the distance L between the ends of the positive electrode 110 and the ends of the negative electrode 120 to 5mm improves battery safety performance; setting the distance L between the ends of the positive electrode 110 and the ends of the negative electrode 120 to 3mm reduces the overall volume and increases energy density; setting the distance L between the ends of the positive electrode 110 and the ends of the negative electrode 120 to 4mm reduces the volume while ensuring battery safety performance.

[0026] Along the length of the core 100, the width of the pad 200 is denoted as d. The value of the width d of the pad 200 is set according to the distance L between the two ends of the negative electrode 120 and the two ends of the positive electrode 110, and satisfies 0.6L≤d≤0.8L. Taking a distance L of 3mm between the two ends of the positive electrode 110 and the two ends of the negative electrode 120 as an example, the width d of the pad 200 can be set between 1.8mm and 2.4mm. Depending on different needs, the width d of the pad 200 can be set to 1.8mm, 2mm, or 2.4mm. Specifically, if the width d of the pad 200 is less than 0.6 times the distance L between the two ends of the positive electrode 110 and the two ends of the negative electrode 120, the pad 200 will not be able to effectively compensate for the step difference; if the width d of the pad 200 is greater than 0.8 times the distance L between the two ends of the positive electrode 110 and the two ends of the negative electrode 120, the core 100 will deform during cycling, affecting the safety performance of the battery. Setting the width d of the pad 200 to 1.8mm is to ensure that the pad 200 can compensate for the step difference between the positive electrode 110 and the negative electrode 120; setting the width d of the pad 200 to 2.4mm is to avoid the pad 200 affecting the safety performance of the battery; setting the width d of the pad 200 to 1.8mm allows the pad 200 to effectively compensate for the step difference between the positive electrode 110 and the negative electrode 120, and ensures that the pad 200 will not cause the core 100 to deform during cycling.

[0027] It is understandable that the value of the width d of the pad 200 is set according to the value of the distance L between the two ends of the negative electrode 120 and the two ends of the positive electrode 110. In another embodiment, when the distance L between the two ends of the negative electrode 120 and the two ends of the positive electrode 110 is set to 5mm, the value of the width d of the pad 200 is set in the range of 3mm to 4mm; in yet another embodiment, when the distance L between the two ends of the negative electrode 120 and the two ends of the positive electrode 110 is set to 4mm, the value of the width d of the pad 200 is set in the range of 2.4mm to 3.2mm; and so on, as long as 0.6L≤d≤0.8L is satisfied.

[0028] In this embodiment, by limiting the distance L between the two ends of the positive electrode 110 and the two ends of the negative electrode 120 to between 3mm and 5mm, and limiting the width d of the pad 200 to between 0.6 times and 0.8 times the distance L between the two ends of the positive electrode 110 and the two ends of the negative electrode 120, the pad 200 can effectively compensate for the step difference between the positive electrode 110 and the negative electrode 120 while ensuring safety performance, thus preventing the outermost edge of the positive electrode 110 from directly contacting the shell and reducing shell wear.

[0029] In some embodiments, the thickness of the positive electrode 110 is defined as t, which satisfies 60um≤t≤120um.

[0030] In some embodiments, the height of the pad 200 is defined as h, satisfying 0.85t≤h≤0.95t.

[0031] In a preferred embodiment, such as Figure 1 As shown, looking along the thickness direction of the core 100, the thickness of the positive electrode 110 is denoted as t, and the value of t is set in the range of 60um to 120um. For example, the thickness t of the positive electrode 110 can be set to different values ​​such as 60um, 98um, and 120um. Specifically, if the thickness t of the positive electrode 110 is too small, it will lead to a decrease in the energy density of the battery; if the thickness t of the positive electrode 110 is too large, the internal resistance of the battery will increase, which will lead to a decrease in the charge and discharge rate performance of the battery. Setting the thickness t of the positive electrode 110 to 60um is to avoid adverse effects on the energy density of the battery; setting the thickness t of the positive electrode 110 to 120um is to avoid adverse effects on the internal resistance of the battery; setting the thickness t of the positive electrode 110 to 98um can balance the internal resistance and energy density of the battery.

[0032] Looking along the thickness direction of the core 100, let the height of the pad 200 be denoted as h. The height h of the pad 200 is set according to the thickness t of the positive electrode 110, and satisfies 0.85t≤h≤0.95t. Taking a thickness t of 98um for the positive electrode 110 as an example, the height h of the pad 200 can be set within the range of 83.3um to 93.1um. For example, the height h of the pad 200 can be set to different values ​​such as 83.3um, 93um, and 93.1um. Specifically, if the height h of the pad 200 is greater than 0.95 times the thickness t of the positive electrode 110, the pad 200 will exceed the height of the positive electrode 110 during the cycle of the core 100, causing the core 100 to deform; if the height h of the pad 200 is less than 0.85 times the thickness t of the positive electrode 110, the pad 200 will not be able to fully compensate for the step difference between the positive electrode 110 and the negative electrode 120. Setting the height h of the pad 200 to 83.3 μm ensures that the pad 200 can fully fill the step difference between the positive electrode 110 and the negative electrode 120; setting the height h of the pad 200 to 93.1 μm ensures that the pad 200 will not exceed the height of the positive electrode 110 during the circulation of the core 100; setting the height h of the pad 200 to 93 μm avoids deformation of the core 100 while ensuring that the pad 200 can fully fill the step difference between the positive electrode 110 and the negative electrode 120.

[0033] It is understandable that the value range of the height h of the pad 200 is set according to the thickness t of the positive electrode 110. In another embodiment, if the thickness t of the positive electrode 110 is 60 μm, the value of the height h of the pad 200 is set in the range between 51 μm and 57 μm; in yet another embodiment, if the thickness of the positive electrode 110 is 120 μm, the value of the height h of the pad 200 is set in the range between 102 μm and 114 μm; and so on, satisfying 0.85t ≤ h ≤ 0.95t.

[0034] In this embodiment, by limiting the thickness t of the positive electrode 110 to between 60 μm and 120 μm, and limiting the height h of the pad 200 to between 0.85 times and 0.95 times the thickness t of the positive electrode 110, it is possible to prevent the core 100 from deforming while ensuring that the pad 200 fully fills the step difference between the positive electrode 110 and the negative electrode 120, thereby preventing the edge of the positive electrode 110 from directly contacting the housing and reducing the wear of the housing.

[0035] In other embodiments, as the number of turns of the core 100 increases, the thickness of the core 100 also increases. With the increase in the thickness of the core 100, the compressive force on the steps at the edges of the core 100 increases during cycling, which can cause the outermost pad 200 of the core 100 to easily fold over. To solve this problem, such as... Figure 2 As shown, Figure 2 The diagram shows a cross-sectional view of the core 100 and the pad 200. A pad 200 can be added to the edge of the second ring of the negative electrode sheet 120 to support the outermost pad 200 of the core 100, preventing the pad 200 from folding over and preventing wear on the shell from the edge of the core 100. In other embodiments not shown, it is understood that as the thickness of the core 100 increases, to ensure that the pad 200 at the edge of the core 100 does not fold over, pads 200 can also be provided at the edges of the second, third, or even more rings of the negative electrode sheet 120.

[0036] In some embodiments, the cross-sectional shape of the pad 200 is a right-angled sector along the length direction of the core 100.

[0037] In this embodiment, as Figure 3 and Figure 4 As shown, Figure 3 This is a schematic diagram of the cross-sectional structure of the negative electrode 120 and the pad 200. Figure 4This is a schematic diagram of the negative electrode 120 before slitting, with the dashed lines representing the slitting lines. The pad 200 is coated before the negative electrode 120 is wound up, and then slit along the slitting lines using a slitting knife after winding. This design allows for the pad 200 to be coated onto the unwound negative electrode 120 before winding, and then the negative electrode 120 is cut along the pad 200 after winding. This eliminates the need for coating in the narrow areas at the edges of the negative electrode 120, effectively reducing the precision requirements of the coating process and facilitating manufacturing.

[0038] like Figure 3 As shown, after the negative electrode 120 is cut, the cross-section of the cut pad 200 presents a right-angled fan shape. Since the pad 200 has the largest thickness on the side closest to the edge of the negative electrode 120, it can more effectively compensate for the step difference between the positive electrode 110 and the negative electrode 120, and at the same time play a role in assisting the positioning of the positive electrode 110.

[0039] In some embodiments, the pad 200 is made of one or more of ceramic, boehmite, and graphite. The specific process for coating ceramic, boehmite, and graphite is as follows: first, the relevant materials are dispersed, then a stirring operation is performed, followed by coating on the negative electrode 120, then baking, and finally winding.

[0040] In other embodiments, the material of the pad 200 can also be one or more of PP (polypropylene), PE (polyethylene), and PET (polyethylene terephthalate). The specific process is as follows: first, the material is subjected to hot melt treatment to achieve a suitable coating state; then, the material is uniformly extruded through an extrusion operation; subsequently, a coating operation is carried out to uniformly coat the material onto the surface of the negative electrode sheet 120; then, a cooling treatment is performed to quickly set the coating layer; finally, the winding process is completed.

[0041] like Figure 5 As shown, Figure 5 This is a schematic diagram of the structure of the positive electrode tab 140 and the negative electrode tab 150. In some embodiments, the core 100 further includes a positive electrode tab 140 and a negative electrode tab 150, with the positive electrode tab 140 connected to the positive electrode plate 110 and the negative electrode tab 150 connected to the negative electrode plate 120. The positive electrode tab 140 and the negative electrode tab 150 are disposed at the top of the core 100.

[0042] This application further proposes an electrochemical device comprising a housing and the aforementioned electrode assembly. The specific structure of the electrode assembly is as described in the above embodiments. Since the electrochemical device employs all the technical solutions of all the above embodiments, it possesses at least all the technical effects brought about by the technical solutions of the above embodiments, and will not be elaborated upon here. Specifically, the housing is preferably an aluminum-plastic film, and the core 100 is disposed inside the housing. By providing a pad 200 to fill the step difference at the edge of the core 100, the edge of the core 100 is prevented from scratching the aluminum-plastic film.

[0043] In summary, this application proposes an electrode assembly and an electrochemical device. The electrochemical device is a battery, and the electrode assembly is disposed inside the battery casing. By providing a pad 200 on the overhanging area of ​​the negative electrode 120 beyond the positive electrode 110, continuous friction between the step at the edge of the core 100 and the casing is avoided, thereby reducing the wear caused by the core 100 to the casing and improving safety performance.

[0044] The above description is only a part or preferred embodiment of this application. Neither the text nor the drawings should limit the scope of protection of this application. All equivalent structural transformations made using the content of this application's specification and drawings under the overall concept of this application, or direct / indirect applications in other related technical fields, are included within the scope of protection of this application.

Claims

1. An electrode assembly comprising a jelly-roll, the jelly-roll comprising a positive electrode sheet, a separator, and a negative electrode sheet, which are disposed in a state of being laminated on each other, both ends of the negative electrode sheet exceeding both ends of the positive electrode sheet, characterized in that, A pad is provided in the overhanging area of ​​the negative electrode extending beyond the positive electrode.

2. The electrode assembly of claim 1, wherein, The suspension areas at both ends of the negative electrode are equal, and the width of the suspension area is defined as L, satisfying 3mm≤L≤5mm.

3. The electrode assembly of claim 2, wherein, The width of the pad is defined as d, which satisfies 0.6L≤d≤0.8L.

4. The electrode assembly of claim 3, wherein, The thickness of the positive electrode is defined as t, which satisfies 60um≤t≤120um.

5. The electrode assembly of claim 4, wherein, The height of the pad is defined as h, which satisfies 0.85t≤h≤0.95t.

6. The electrode assembly of any one of claims 1 to 5, wherein, When the core is cut along its thickness direction, the cross-sectional projection of the pad is a right-angled sector.

7. The electrode assembly of claim 6, wherein, The pad is made of one or more of ceramic, boehmite, and graphite.

8. The electrode assembly of claim 7, wherein, The winding core also includes a positive electrode tab and a negative electrode tab, wherein the positive electrode tab is connected to the positive electrode plate and the negative electrode tab is connected to the negative electrode plate.

9. An electrochemical device, characterized by, It includes a housing and the electrode assembly as described in any one of claims 1 to 8.

10. The electrochemical device of claim 9, wherein, The core is disposed inside the housing.

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