Tab applied to soft package battery cell and soft package battery cell

Abstract

The utility model provides a pole lug applied to a soft package battery cell and the soft package battery cell. The pole lug comprises a metal belt, a first electrode and a second electrode, tab glue is pasted on the metal belt, an exhaust groove is formed in the overlapping area of the tab glue and the metal belt, the exhaust groove is located in the side, pasted with the metal belt, of the tab glue, the thickness of the exhaust groove is smaller than that of the tab glue, and the thickness of the exhaust groove is larger than that of the tab glue. The part from one end of the exhaust groove to the other end of the exhaust groove does not penetrate through the width of the tab glue, and one end of the exhaust groove is communicated with the outside and is positioned on one side, far away from a pole piece of the soft package battery cell, in the tab glue; the phase change material is placed in the exhaust groove; the adsorbent is placed in the exhaust groove and adjacent to the phase change material, and the adsorbent is used for preventing the phase change material from being communicated with the outside and adsorbing the electrolyte of the soft package battery cell.

Description

Technical Field

[0001] This application relates to the field of battery cell technology, and in particular to a tab for use in pouch cells and a pouch cell. Background Technology

[0002] Because pouch cells lack the explosion-proof valve design of aluminum-cased or cylindrical cells, they are prone to unpredictable pressure relief, and may even explode violently due to delayed pressure relief. Currently, pressure relief is achieved by creating narrowing or thinning areas on the aluminum-plastic film, or by creating gaps in the tab adhesive layer on the surface of the rigid tab, allowing gas to break through the weak points at the tab end under high pressure. However, the following problems exist: First, the thinning method in the aluminum-plastic film area presents difficulties in equipment positioning during actual packaging due to the small sealing edge size, making precise deployment of the pressure relief position prone to misalignment; second, creating gaps on the tab adhesive layer surface shortens the width of the aluminum-plastic film and its sealing area, easily leading to poor sealing; third, when the cell depressurizes, the flammable electrolyte in the cell also splashes out with the airflow, easily causing secondary combustion; fourth, the heat from thermal runaway cannot be dissipated in time. Utility Model Content

[0003] In view of this, the purpose of this application is to provide a tab for use in pouch cells and a pouch cell, which can solve the technical problems in the prior art of difficulty in setting pressure relief positions, inability to reduce the heat of cell thermal runaway, and inability to prevent electrolyte splashing when the cell is depressurized. This achieves the technical effect of reducing the heat of cell thermal runaway and adsorbing electrolyte when the cell is depressurized.

[0004] In a first aspect, embodiments of this application provide a tab for use in a pouch cell, the tab comprising: a metal strip; tab adhesive adhered to the metal strip, wherein an venting groove is provided in the overlapping area of ​​the tab adhesive and the metal strip, the venting groove being located on the side where the tab adhesive is adhered to the metal strip, the thickness of the venting groove being less than the thickness of the tab adhesive, one end of the venting groove not penetrating the width of the tab adhesive, one end of the venting groove communicating with the outside and located on the side of the tab adhesive away from the electrode sheet of the pouch cell; a phase change material placed in the venting groove; and an adsorbent placed in the venting groove and adjacent to the phase change material, the adsorbent being used to prevent the phase change material from communicating with the outside and to adsorb the electrolyte of the pouch cell.

[0005] Optionally, the phase change material includes multiple phase change materials, each corresponding to a different melting point. The multiple phase change materials are arranged from one side of the exhaust groove to one side of the exhaust groove in ascending order of melting point. The phase change material with the highest melting point is close to the adsorbent, and the phase change material with the lowest melting point is close to the electrode of the pouch cell.

[0006] Optionally, the tab further includes a gel-like substance used to connect the sequentially arranged phase change materials and the adsorbent.

[0007] Optionally, the plurality of phase change materials include at least two of the following: carboxylic acid derivatives, paraffin-based phase change materials, and inorganic salt hydrates, wherein the carboxylic acid derivatives are fatty acids or fatty acid esters.

[0008] Optionally, the mapping area of ​​the adsorbent is greater than the mapping area of ​​the phase change material, wherein the mapping area is used to indicate the area mapped onto the plane containing one end of the exhaust groove.

[0009] Optionally, the electrode of the pouch cell includes a positive electrode and a negative electrode, the tab connected to the positive electrode is the positive tab, and the tab connected to the negative electrode is the negative tab, wherein the metal strip includes an aluminum metal strip disposed in the positive tab and a copper metal strip disposed in the negative tab.

[0010] Secondly, embodiments of this application also provide a pouch cell, the pouch cell comprising a plurality of stacked electrodes and a plurality of separators, the plurality of electrodes comprising a plurality of positive electrodes and a plurality of negative electrodes, the positive electrodes and the negative electrodes being arranged alternately, the separators being located between adjacent positive electrodes and negative electrodes, wherein tabs as described in the first aspect or any possible implementation of the first aspect are respectively connected to the positive electrodes and the negative electrodes.

[0011] Optionally, the arrangement of the plurality of electrodes includes: arranging them in descending order of polarization degree from the center position after stacking as the center of symmetry to both sides.

[0012] Optionally, the polarization of the electrode can be reduced by decreasing the coating amount and / or reducing the compaction density of the electrode.

[0013] Optionally, the tab connected to the positive electrode plate is a positive tab, and the tab connected to the negative electrode plate is a negative tab, wherein the metal strip includes an aluminum metal strip disposed in the positive tab and a copper metal strip disposed in the negative tab.

[0014] This application provides an embodiment of a tab for a pouch cell and a pouch cell. The tab includes: a metal strip; tab adhesive adhered to the metal strip, wherein an venting groove is provided in the overlapping area of ​​the tab adhesive and the metal strip, the venting groove is located on the side where the tab adhesive is adhered to the metal strip, the thickness of the venting groove is less than the thickness of the tab adhesive, one end of the venting groove to the other end does not penetrate the width of the tab adhesive, one end of the venting groove communicates with the outside and is located on the side of the tab adhesive away from the electrode sheet of the pouch cell; a phase change material placed in the venting groove; and an adsorbent placed in the venting groove and adjacent to the phase change material, the adsorbent being used to prevent the phase change material from communicating with the outside and to adsorb the electrolyte of the pouch cell. This application solves the technical problems in the prior art of difficulty in setting pressure relief positions, inability to reduce the heat of thermal runaway of the battery cell, and inability to prevent electrolyte splashing when the battery cell is depressurized. It achieves the technical effect of reducing the heat of thermal runaway of the battery cell and adsorbing electrolyte when the battery cell is depressurized. The venting groove is located on the side of the tab adhesive where the metal strip is attached to the tab adhesive, and the thickness of the venting groove is less than the thickness of the tab adhesive. It does not penetrate the width of the tab adhesive from one end to the other end. One end of the venting groove is connected to the outside and is located on the side of the tab adhesive away from the electrode sheet of the soft-pack battery cell. The venting groove is filled with phase change material and adsorbent in sequence.

[0015] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This illustration shows a schematic diagram of the structure of a tab for a pouch cell provided in an embodiment of this application.

[0018] Figure 2 The diagram shows a top view of the tab provided in an embodiment of this application. Figure 1 .

[0019] Figure 3 A front view of the tab provided in an embodiment of this application is shown.

[0020] Figure 4 The diagram shows a top view of the tab provided in an embodiment of this application. Figure 1 .

[0021] Figure 5 A schematic diagram of the structure of a pouch cell provided in an embodiment of this application is shown.

[0022] Figure 6 This illustration shows a schematic diagram of multiple electrode sheets stacked in a pouch cell provided in an embodiment of this application. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. Based on the embodiments of this application, every other embodiment obtained by those skilled in the art without inventive effort falls within the scope of protection of this application.

[0024] In existing technologies, high-energy-density battery cells generate a significant amount of gas during thermal runaway, posing a certain risk. Furthermore, pouch cells, lacking the explosion-proof valve design found in aluminum-cased or cylindrical cells, are prone to unpredictable pressure release, potentially leading to violent explosions due to delayed pressure relief. Current solutions involve creating narrowing or thinning areas on the aluminum-plastic film as pressure relief sections, or creating gaps in the adhesive layer on the hard tab surface, allowing gas to breach weak points at the tab end under high pressure. However, these solutions present several problems: First, thinning the aluminum-plastic film area presents difficulties in equipment positioning during actual packaging due to the small sealing edge size, making precise deployment of the pressure relief location prone to misalignment; second, creating gaps on the tab adhesive layer surface shortens the width of the aluminum-plastic film and its sealing area, easily leading to poor sealing; third, during pressure relief, the flammable electrolyte in the cell splashes with the gas flow, potentially causing secondary combustion; and fourth, the heat generated during thermal runaway cannot be dissipated in a timely manner.

[0025] Furthermore, because the energy density of each electrode in a laminated cell remains consistent, during actual charging and discharging, the electrode at the center experiences the most heat due to heat dissipation issues. This results in a lower degree of polarization between the positive and negative electrodes at this location compared to the two ends, leading to a higher depth of charge and discharge. Over long-term cycling, this can easily affect the consistency of each electrode.

[0026] To address the aforementioned problems, this application provides an electrode tab and a pouch cell for use in pouch cells. By creating an venting groove on the electrode adhesive in the overlapping area of ​​the adhesive and the metal strip, the venting groove is located on the side of the adhesive where the metal strip is attached, and its thickness is less than that of the adhesive. The venting groove does not penetrate the width of the adhesive from one end to the other. One end of the venting groove is connected to the outside and located on the side of the adhesive away from the electrode sheet of the pouch cell. A phase change material and an adsorbent are sequentially filled into the venting groove. This solves the technical problems in the prior art, such as the difficulty in setting a pressure relief location, the inability to reduce the heat of thermal runaway of the cell, and the inability to prevent electrolyte splashing during cell pressure relief. It achieves the technical effect of reducing the heat of thermal runaway of the cell and adsorbing electrolyte during cell pressure relief, as detailed below:

[0027] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of a tab used in a pouch cell, provided as an embodiment of this application. Figure 1As shown in the embodiment of this application, the tab for a pouch cell includes: a metal strip 101; tab adhesive 102 adhered to the metal strip, wherein an venting groove 1021 is provided on the overlapping area of ​​the tab adhesive and the metal strip, the venting groove is located on the side where the tab adhesive is adhered to the metal strip, the thickness h1 of the venting groove is less than the thickness h2 of the tab adhesive, one end A1 of the venting groove to the other end A2 of the venting groove does not penetrate the width of the tab adhesive, one end A1 of the venting groove communicates with the outside and is located on the side of the tab adhesive away from the electrode sheet of the pouch cell; a phase change material 1022, the phase change material is placed in the venting groove; and an adsorbent 1023, the adsorbent is placed in the venting groove and adjacent to the phase change material, the adsorbent is used to prevent the phase change material from communicating with the outside and to adsorb the electrolyte of the pouch cell.

[0028] like Figure 1 As shown, in the coordinate system where the tabs are located, a point is randomly selected as the origin O. The xoy plane is parallel to the horizontal plane of the metal strip. The horizontal plane can be used to attach either the electrode sheet or the tab adhesive. The z-axis direction is the direction in which the electrode sheets are stacked sequentially. That is, tab adhesive is attached to the horizontal plane on both sides of the metal strip. A venting groove is carved out in the overlapping area of ​​the metal strip and the tab adhesive. One end A1 of the venting groove is parallel to the xoz plane, so that the end of the venting groove away from the electrode sheet is connected to the outside. Thus, the venting groove serves as the pressure relief position of the cell. Furthermore, phase change material is first filled into the venting groove, followed by adsorbent. This allows the phase change material to absorb heat first when thermal runaway occurs in the cell. The phase change material absorbs heat and transforms into liquid or gas to reduce the heat of the cell, thereby lowering the maximum temperature during thermal runaway. At the same time, because the phase change material vaporizes or liquefies, gaps will exist in the venting groove. When thermal runaway reaches a certain stage and the internal pressure of the cell exceeds atmospheric pressure, the gas and liquid inside the cell will be ejected from the venting groove. However, due to the adsorbent placed between the phase change material and the outside, the adsorbent will adsorb the liquid during the gas and liquid injection process, playing a role in gas-liquid separation. During the gas-liquid injection process, the liquid will be adsorbed by the adsorbent to prevent secondary hazards caused by the electrolyte being ejected with the gas.

[0029] For example, please refer to Figure 2 and Figure 3 , Figure 2 Top view of the tabs provided in the embodiments of this application Figure 1 , Figure 3 This is a front view of the electrode provided in an embodiment of this application. Figure 2As shown, a top view is obtained by viewing the tab from above along the z-axis of the coordinate system in which the tab is located. The tab adhesive 102 is attached to the metal strip 101. The thickness of the venting groove can be adjusted according to the thickness of the tab adhesive. It is only necessary to control that the thickness of the venting groove is less than the thickness of the tab adhesive. Furthermore, the venting groove 1021 is not visible in the tab adhesive from the top view perspective, to prevent gaps in the tab adhesive from reducing the contact area with the aluminum-plastic film of the battery cell. This avoids the problem in the prior art where gaps are made on the surface of the tab adhesive layer, resulting in a shortened width of the aluminum-plastic film and its sealing area. Figure 3 As shown, a front view is obtained by looking at the electrode head-on along the y-axis of the coordinate system in which the electrode is located. The electrode adhesive 102 is attached to the metal strip 101, and the venting groove 1021 is provided at the connection between the electrode adhesive and the metal strip.

[0030] Specifically, the phase change material includes multiple phase change materials, each corresponding to a different melting point. The multiple phase change materials are arranged from one side of the exhaust groove to one side of the exhaust groove in ascending order of melting point. The phase change material with the highest melting point is close to the adsorbent, and the phase change material with the lowest melting point is close to the electrode of the soft-pack battery cell.

[0031] In other words, by arranging the phase change materials (PCMs) closest to the electrode in ascending order of melting point, and then to the PCM closest to the adsorbent, multiple PCMs are arranged in ascending order of melting point. Therefore, when the temperature of the battery cell's electrodes rises abnormally, the PCM closest to the electrode absorbs heat and converts to a liquid state first, followed by the PCM closest to the adsorbent. This sequential conversion of multiple PCMs into liquid states achieves heat absorption, thereby reducing the maximum temperature of thermal runaway in the battery cell. Furthermore, as the temperature gradually rises within the battery cell, the PCMs that initially become liquid will vaporize and turn into gas, resulting in the possibility that the PCMs in the exhaust grooves may be in both liquid and gaseous states.

[0032] For example, the plurality of phase change materials includes at least two of the following: carboxylic acid derivatives, paraffin-based phase change materials, and inorganic salt hydrates, wherein the carboxylic acid derivatives are fatty acids or fatty acid esters. Fatty acid esters refer to esters and their derivatives formed by the reaction of fatty acids and alcohols. Furthermore, each phase change material is solid within the venting groove of the insert tab adhesive.

[0033] For example, please refer to Figure 4 , Figure 4 Top view of the tabs provided in the embodiments of this application Figure 1A top view is obtained by viewing the tab from above along the z-axis of the coordinate system in which the tab is located. Tab adhesive 102 is attached to the metal strip 101. Multiple phase change materials are filled in the exhaust groove 1021 in ascending order of melting point. These multiple phase change materials can be referred to as first phase change material 201, second phase change material 202, and third phase change material 203, with the third phase change material having the highest melting point being the one closest to the adsorbent 204. Furthermore, the mapping area of ​​the adsorbent 204 can be larger than the mapping area of ​​the phase change materials. The mapping area indicates the area mapped onto the plane containing one end of the exhaust groove. That is, the mapping area is the area obtained by projecting the phase change material onto the xoz plane along the y-axis; the mapping area of ​​the phase change material is the area obtained by projecting the phase change material onto the xoz plane along the y-axis; and the mapping area of ​​the adsorbent is the area obtained by projecting the adsorbent onto the xoz plane along the y-axis. The mapping area of ​​the phase change material and the mapping area of ​​the adsorbent are not limited to rectangles and can be any shape. However, the mapping area of ​​each phase change material needs to coincide with the mapping area of ​​the adsorbent so that the exhaust groove is a through channel, naturally forming a weak area of ​​the battery cell, which facilitates pressure relief in case of thermal runaway of the battery cell.

[0034] In this process, the adsorbent can perform gas-liquid separation by adsorbing the electrolyte. Generally, the adsorbent is embedded horizontally in the exhaust groove, meaning that the mapping area of ​​the adsorbent can be larger than the mapping area of ​​each phase change material, so as to ensure that the adsorbent at the defect will not be blown out by the gas during thermal runaway.

[0035] For example, the material of the adsorption block includes any of the following: activated carbon and molecular sieve. This application does not limit the material of the adsorption block, as long as it can adsorb electrolyte.

[0036] For example, the melting point of the first phase change material is between 65°C and 70°C, and a paraffin-based phase change material can be selected; the melting point of the second phase change material is between 80°C and 90°C, and a fatty acid or fatty acid ester can be selected; the melting point of the third phase change material is between 90°C and 100°C, and an inorganic salt hydrate can be selected. Furthermore, after the temperature of the electrode reaches the melting point of the third phase change material, all phase change materials have been transformed into their corresponding liquid or gaseous states. Moreover, this application does not limit the specific materials of the multiple phase change materials; it only requires that the melting points of each phase change material be different, and the melting points should be less than or equal to the temperature at which the electrolyte sprays out due to temperature rise, so that the sprayed electrolyte can be adsorbed by the adsorbent.

[0037] For example, inorganic salt hydrates include magnesium nitrate hexahydrate Mg(NO)·6H2O, potassium nitrate trihydrate KNO·3H2O, and ammonium dihydrogen phosphate tetrahydrate NHHPO·4H2O.

[0038] Specifically, the tab also includes a gel-like substance, which is used to connect the multiple phase change materials arranged in sequence and the adsorbent.

[0039] For example, the adhesive material is PP adhesive (polypropylene), and the material of the tab adhesive is also generally polypropylene. Furthermore, after multiple electrodes and films are stacked, an aluminum-plastic film is needed to encapsulate the pouch cell. The inner side of the aluminum-plastic film includes a PP layer. At the tab positions, the aluminum-plastic film is heat-sealed using the tab adhesive, while at other positions, the aluminum-plastic film is heat-sealed using the PP layer on its inner side, thus achieving encapsulation of the pouch cell using the aluminum-plastic film.

[0040] In other words, multiple phase change materials (PCMs) are sequentially bonded together using an adhesive substance, with the PCM closest to the adsorbent adhering to it. Then, after the PCM closest to the adsorbent becomes liquid, the adsorbent directly contacts the liquid PCM in the venting groove. This allows the PCMs, along with electrolyte and gas generated during thermal runaway within the battery cell, to be more effectively expelled from the venting groove, resulting in directional pressure relief. Furthermore, the adsorbent effectively absorbs the electrolyte ejected during thermal runaway pressure relief, preventing electrolyte splashing and avoiding greater safety hazards, and also achieving gas-liquid separation.

[0041] The electrode of the soft-pack battery cell includes a positive electrode and a negative electrode. The tab connected to the positive electrode is the positive tab, and the tab connected to the negative electrode is the negative tab. The metal strip includes an aluminum metal strip disposed in the positive tab and a copper metal strip disposed in the negative tab.

[0042] In other words, the metal strips in the tabs corresponding to the positive and negative electrodes in a pouch cell are made of different materials. The metal strip in the positive tab connecting the positive electrode is made of aluminum, while the metal strip in the negative tab connecting the negative electrode is made of copper.

[0043] Based on the same application concept, this application also provides a soft-pack battery cell corresponding to the tabs of the soft-pack battery cells provided in the above embodiments. Since the principle of solving the problem by the soft-pack battery cell in this application is similar to that of the tabs of the soft-pack battery cells in the above embodiments of this application, the implementation of the soft-pack battery cell can refer to the implementation of the above embodiments, and the repeated parts will not be described again.

[0044] Please see Figure 5 , Figure 5 This is a schematic diagram of the structure of a pouch cell provided in an embodiment of this application. Figure 5As shown, the pouch cell includes multiple stacked electrode sheets and multiple separators 301. The multiple electrode sheets include multiple positive electrode sheets 302 and multiple negative electrode sheets 303. The positive electrode sheets and the negative electrode sheets are arranged alternately. The separators are located between adjacent positive electrode sheets and negative electrode sheets. The positive electrode sheets and the negative electrode sheets are respectively provided with tabs as described in the above embodiments.

[0045] For example, such as Figure 5 As shown, the tab connected to the positive electrode plate is a positive tab 3021, and the tab connected to the negative electrode plate is a negative tab 3031. The metal strip includes an aluminum metal strip 30211 disposed in the positive tab 3021 and a copper metal strip 30311 disposed in the negative tab 3031.

[0046] The arrangement of the plurality of electrodes includes: arranging them in descending order of polarization degree from the center position after stacking as the center of symmetry to both sides.

[0047] In other words, the number of electrodes on both sides of the center position is the same, and the electrodes on both sides are arranged symmetrically with the center position as the center of symmetry according to their polarization degree. The electrodes on both sides of the center position are arranged in ascending order of polarization degree, from the electrode furthest from the center position to the electrode closest to the center position. That is, the closer the electrode is to the center position, the higher the polarization degree, and the farther away the electrode is from the center position, the lower the polarization degree.

[0048] For example, Figure 6 This is a schematic diagram of multiple electrode sheets stacked in a pouch cell provided in an embodiment of this application. Figure 6 As shown, there are one hundred electrodes, and they are numbered from 1 to 100 according to their arrangement. The center position after stacking can be the diaphragm between electrodes numbered 50 and 51. The polarization degree of the electrodes numbered 1 to 50 is equal to the descending order of the polarization degree of the electrodes numbered 51 to 100. If the polarization degree of the electrodes is divided into a first polarization degree and a second polarization degree, and the first polarization degree is different from the second polarization degree and the first polarization degree is higher than the second polarization degree, then the polarization degree of the electrodes numbered 1 to 30 and the polarization degree of the electrodes numbered 71 to 100 are both the second polarization degree, and the polarization degree of the electrodes numbered 31 to 50 and the polarization degree of the electrodes numbered 51 to 70 are both the first polarization degree.

[0049] For example, the polarization of an electrode can be reduced by decreasing the coating amount and / or reducing the compaction density of the electrode.

[0050] In conventional stacked batteries, the positive and negative electrodes are formed by stacking each other, and the design state of each positive or negative electrode is consistent. In order to balance the polarization effect caused by temperature, the surface density or compaction of the positive or negative electrode near the center is artificially increased to increase the polarization of the initially designed electrode, and then the polarization is reduced stepwise towards both sides.

[0051] In other words, due to heat dissipation issues, the electrodes closer to the center generate more heat, resulting in lower polarization. Therefore, the stacked electrodes are pre-designed with a gradient of polarization symmetrically around the center. This ensures that electrodes with a polarization gradient closer to the center have higher polarization, while those with a polarization gradient farther from the center have lower polarization. Furthermore, there can be two or more polarization gradients on either side of the center to balance the issue of lower polarization towards the center during cell use. This polarization balance improves the consistency of the electrodes within the cell.

[0052] Furthermore, by designing a gradient in the coating amount of the multiple electrodes stacked on the pouch cell, or a gradient in the compaction density of the multiple electrodes stacked on the pouch cell, or a gradient in both the coating amount and compaction density of the multiple electrodes stacked on the pouch cell, the polarization gradient of the electrodes closer to the center is higher, and the polarization gradient of the electrodes farther from the center is lower, in order to balance the problem of uneven polarization caused by uneven heat during charging and discharging.

[0053] For example, such as Figure 6 As shown, if the gradient design is based solely on the coating amount, the first polarization degree closest to the center includes: the coating amount of multiple electrodes numbered 31 to 50 and multiple electrodes numbered 51 to 70 is a; the second polarization degree farther from the center includes: the coating amount of multiple electrodes numbered 1 to 30 and multiple electrodes numbered 71 to 100 is b, and the coating amount a is greater than the coating amount b.

[0054] For example, such as Figure 6 As shown, if gradient design is based solely on compaction density, the first polarization degree closest to the center includes: the compaction density of the positive electrode among multiple electrodes numbered 31 to 50 and multiple electrodes numbered 51 to 70, which is 2.55 g / cm³. 3 The compaction density of the negative electrode in multiple electrodes numbered 31 to 50 and multiple electrodes numbered 51 to 70 is 1.55 g / cm³. 3The second degree of polarization, located away from the center, includes: the compaction density of the positive electrode in multiple electrodes numbered 1 to 30 and multiple electrodes numbered 71 to 100, which is 2.50 g / cm³. 3 The compaction density of the negative electrode in multiple electrodes numbered 1 to 30 and multiple electrodes numbered 71 to 100 is 1.50 g / cm³. 3 ).

[0055] For example, such as Figure 6 As shown, if a gradient design is performed based on coating amount and compaction density, the first polarization degree closest to the center includes: the coating amount of multiple electrodes numbered 31 to 50 and multiple electrodes numbered 51 to 70 is 'a', and the compaction density of the positive electrode among the multiple electrodes numbered 31 to 50 and multiple electrodes numbered 51 to 70 is 2.55 g / cm³. 3 The compaction density of the negative electrode in multiple electrodes numbered 31 to 50 and multiple electrodes numbered 51 to 70 is 1.55 g / cm³. 3 The second polarization, located away from the center, includes: multiple electrodes numbered 1 to 30 and multiple electrodes numbered 71 to 100, all having a coating amount of b, a coating amount greater than coating amount b, and the compaction density of the positive electrode among the multiple electrodes numbered 1 to 30 and multiple electrodes numbered 71 to 100 being 2.50 g / cm³. 3 The compaction density of the negative electrode in multiple electrodes numbered 1 to 30 and multiple electrodes numbered 71 to 100 is 1.50 g / cm³. 3 ).

[0056] Furthermore, by increasing the coating amount and / or compaction density of the electrodes near the center and then gradually decreasing towards both ends, the heating phenomenon effectively balances the polarization of the electrodes at each polarization gradient, while simultaneously reducing the overall cell thickness, thus increasing the cell's energy density. This application does not limit the measures that affect the degree of polarization and energy density, as long as a gradient design can be achieved.

[0057] In the description of this application, it should be noted that the terms "inner" and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and for 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. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0058] It should also be noted that, unless otherwise explicitly specified and limited, the terms "setup" and "connection" 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 direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0059] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A tab for use in pouch cells, characterized in that, The electrode includes: Metal strip; A tab adhesive is attached to the metal strip, wherein an venting groove is provided in the overlapping area of ​​the tab adhesive and the metal strip. The venting groove is located on the side where the tab adhesive is attached to the metal strip. The thickness of the venting groove is less than the thickness of the tab adhesive. One end of the venting groove does not penetrate the width of the tab adhesive. One end of the venting groove communicates with the outside and is located on the side of the tab adhesive away from the electrode sheet of the pouch cell. A phase change material, wherein the phase change material is placed in the exhaust groove; An adsorbent is placed in the venting groove and adjacent to the phase change material. The adsorbent is used to prevent the phase change material from communicating with the outside and to adsorb the electrolyte of the pouch cell.

2. The electrode tab according to claim 1, characterized in that, The phase change material includes multiple phase change materials, each corresponding to a different melting point. In this arrangement, multiple phase change materials are arranged from one side of the venting groove to the other side of the venting groove in ascending order of melting point. The phase change material with the highest melting point is close to the adsorbent, and the phase change material with the lowest melting point is close to the electrode of the pouch cell.

3. The electrode tab according to claim 2, characterized in that, The tab also includes a gel-like substance used to connect the sequentially arranged phase change materials and the adsorbent.

4. The electrode tab according to claim 2, characterized in that, The plurality of phase change materials includes at least two of the following: carboxylic acid derivatives, paraffin-based phase change materials, and inorganic salt hydrates. The carboxylic acid derivative is a fatty acid or a fatty acid ester.

5. The electrode tab according to claim 1, characterized in that, The mapping area of ​​the adsorbent is larger than that of the phase change material. The mapped area is used to indicate the area mapped onto the plane containing one end of the exhaust groove.

6. The electrode tab according to claim 1, characterized in that, The electrode plates of the pouch cell include a positive electrode plate and a negative electrode plate. The tab connected to the positive electrode plate is the positive tab, and the tab connected to the negative electrode plate is the negative tab. The metal strip includes an aluminum metal strip disposed in the positive electrode tab and a copper metal strip disposed in the negative electrode tab.

7. A pouch cell, characterized in that, The pouch cell includes multiple stacked electrodes and multiple separators. The multiple electrodes include multiple positive electrodes and multiple negative electrodes, which are arranged alternately. The separators are located between adjacent positive and negative electrodes. The positive electrode and the negative electrode are respectively connected to the tabs as described in any one of claims 1 to 6.

8. The soft-pack battery cell according to claim 7, characterized in that, The arrangement of the multiple electrodes includes: arranging them in descending order of polarization degree, with the center position after stacking as the center of symmetry.

9. The soft-pack battery cell according to claim 8, characterized in that, Reduce the polarization of the electrode in the following ways: The polarization of the electrode is reduced by decreasing the coating amount and / or reducing the compaction density of the electrode.

10. The soft-pack battery cell according to claim 9, characterized in that, The tab connected to the positive electrode plate is the positive tab, and the tab connected to the negative electrode plate is the negative tab. The metal strip includes an aluminum metal strip disposed in the positive electrode tab and a copper metal strip disposed in the negative electrode tab.

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