Battery cell and battery pack

Abstract

The utility model discloses a battery monomer and a battery pack, and relates to the technical field of batteries. The battery monomer comprises a shell and an electrode assembly arranged in the shell. The electrode assembly comprises a first pole piece, a second pole piece and a diaphragm. The first pole piece comprises a first current collector and a first active layer; the second pole piece comprises a second current collector and a second active layer; the first active layer comprises a first flat part and a first thinned part, the second active layer comprises a second flat part and a second thinned part, and the first thinned part and the second thinned part are located at the same end. The diaphragm comprises a base membrane and a first ceramic functional coating, the first ceramic functional coating is arranged at the end, close to the first thinned part, of the base membrane, and at least part of the first ceramic functional coating is located between the base membrane and the first thinned part, so that no gap exists between the first pole piece and the diaphragm. Therefore, the electrode assembly can be compounded more effectively in the hot pressing process, the phenomenon of lithium precipitation in the thinned area of the negative plate caused by too long ion transmission is avoided, and the cycle performance of the battery is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery, in particular to a battery monomer and a battery pack. BACKGROUND

[0002] With the rapid development of new energy automobile industry, lithium ion battery as one of the main power source has huge market prospect. Active lithium material as an effective active ingredient of power battery / energy storage battery, it will be consumed in the battery cycle process, thereby leading to the continuous reduction of battery capacity and cycle life, reducing the active lithium consumption in the battery cycle process is one of the effective ways to improve the cycle life of power battery. CONTENT OF THE UTILITY MODEL

[0003] The utility model aims at providing a battery monomer and a battery pack to reduce the active lithium consumption in the battery attenuation process and improve the cycle life of the battery.

[0004] In a first aspect, a battery monomer is provided, comprising: a shell; an electrode assembly arranged in the shell, the electrode assembly comprising: a first electrode tab, a second electrode tab, and a separator arranged between the first electrode tab and the second electrode tab, the first electrode tab and the second electrode tab having opposite polarities; wherein the first electrode tab comprises a first current collector and a first active layer arranged on at least one surface of the first current collector; the first active layer comprises a first flat portion and a first thinned portion, the thickness of the first thinned portion being less than the thickness of the first flat portion, the first thinned portion being arranged at one end of the first current collector in the length direction of the battery monomer; the second electrode tab comprises a second current collector and a second active layer arranged on at least one surface of the second current collector; the second active layer comprises a second flat portion and a second thinned portion, the thickness of the second thinned portion being less than the thickness of the second flat portion, the second thinned portion being arranged at one end of the second current collector in the length direction of the battery monomer, and the first thinned portion and the second thinned portion being located at the same end; the separator comprises a base film and a first ceramic functional coating layer, the base film having a first surface and a second surface arranged opposite to each other, the first ceramic functional coating layer being arranged at an end of the first surface close to the first thinned portion, and the first ceramic functional coating layer being at least partially located between the first surface and the first thinned portion in the thickness direction of the battery monomer.

[0005] In some embodiments, the first electrode tab further comprises a first tab, which is arranged on the first current collector, and the first thinned portion is arranged close to the first tab in the length direction of the battery monomer, and the first ceramic functional coating layer is arranged close to the first tab in the length direction of the battery monomer.

[0006] In some embodiments, the separator further comprises a second ceramic functional coating layer, the second ceramic functional coating layer being arranged at an end of the second surface close to the second thinned portion, and the second ceramic functional coating layer being at least partially located between the second surface and the second thinned portion in the thickness direction of the battery monomer.

[0007] In some embodiments, the second tab further comprises a second tab, disposed on the second current collector, and the second thinned portion is arranged close to the second tab in the length direction of the battery cell, and the second ceramic functional coating is arranged close to the second tab in the length direction of the battery cell.

[0008] In some embodiments, the maximum length of the second ceramic functional coating in the length direction of the battery cell is less than the maximum length of the first ceramic functional coating in the length direction of the battery cell.

[0009] In some embodiments, the maximum length of the first ceramic functional coating in the length direction of the battery cell is 5-30mm, and the maximum length of the second ceramic functional coating in the length direction of the battery cell is 5-20mm.

[0010] In some embodiments, the maximum thickness of the second ceramic functional coating in the thickness direction of the battery cell is less than the maximum thickness of the first ceramic functional coating in the thickness direction of the battery cell.

[0011] In some embodiments, the maximum thickness of the first ceramic functional coating in the thickness direction of the battery cell is 0-40um, and the maximum thickness of the second ceramic functional coating in the thickness direction of the battery cell is 0-30um.

[0012] In some embodiments, the material of the first ceramic functional coating comprises at least one of alumina, titanium dioxide, and silicon dioxide; and the material of the second ceramic functional coating comprises at least one of alumina, titanium dioxide, and silicon dioxide.

[0013] In a second aspect, a battery pack is provided, comprising at least two battery cells connected in series and / or in parallel.

[0014] The technical effects of the present application are to provide a battery cell and a battery pack, by arranging a first ceramic functional coating on the base film, when the separator and the first tab are stacked, the first ceramic functional coating is arranged between the base film and the first thinned portion, and the gap between the base film and the first thinned portion is completely filled, so that there is no gap between the first tab and the separator, so that the electrode assembly can be more effectively compounded during hot pressing, and the phenomenon of lithium precipitation in the thinned area caused by the too long ion transmission path is avoided, and the battery cycle performance is increased. Moreover, the use of the first ceramic functional coating can increase the high temperature resistance of the separator, increase the thermal shrinkage performance of the separator in the thinned area, avoid the shrinkage of the separator on the tab side caused by the excessive temperature of the battery in the overcharge condition, and reduce the risk of thermal runaway safety of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0015] The technical solutions and other beneficial effects of the present application will become apparent from the following detailed description of specific embodiments of the present application, combined with the accompanying drawings.

[0016] Figure 1 A structural schematic diagram of a battery cell provided for an embodiment of the present application.

[0017] Figure 2 A sectional view of an electrode assembly provided for an embodiment of the present application.

[0018] Figure 3 A sectional view of a first pole piece provided for an embodiment of the present application.

[0019] Figure 4 A sectional view of a second pole piece provided for an embodiment of the present application.

[0020] Figure 5 A structural schematic diagram of a separator provided for an embodiment of the present application. Figure 1 .

[0021] Figure 6 A structural schematic diagram of a separator provided for an embodiment of the present application. Figure 2 .

[0022] Figure 7 A sectional view of a separator provided for an embodiment of the present application.

[0023] The components in the drawings are identified as follows:

[0024] 1 housing; 2 electrode assembly; 3 end cover;

[0025] 21 first pole piece; 211 first current collector; 212 first active layer; 2121 first flat portion; 2122 first thinning portion; 2123 first tab;

[0026] 22 second pole piece; 221 second current collector; 222 second active layer; 2221 second flat portion; 2222 second thinning portion; 2223 second tab;

[0027] 23 separator; 231 base film; 232 first ceramic functional coating; 233 second ceramic functional coating;

[0028] 2311 first surface; 2312 second surface. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0030] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, 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. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" 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, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0032] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0033] The following disclosure provides many different embodiments, or examples, for implementing different structures of the present application. For purposes of explanation and simplicity, specific details of the certain examples are set forth by way of example in the following description. Of course, they are merely examples, and it is contemplated that the application can be practiced in various ways without the specific details (e.g., configurations and methodologies), that are set forth in the following description below. Further, the application provides examples of various specific components, materials, and acts which are implemented, as both of those skilled in the art will appreciate that other components, materials, and acts can be employed.

[0034] While batteries are pursuing higher energy density, the problem of thermal runaway of the battery in the working condition of overcharge needs to be solved. In this case, due to the loss of heat transfer, the temperature of the battery tab side is higher than that of the non-tab side, which leads to the thermal shrinkage of the separator near the tab side, and further causes the short circuit of the positive and negative electrodes, and triggers the thermal runaway safety problem of the battery.

[0035] In the existing battery, the edge of the active material coating on the pole piece is generally thinned to prevent the edge of the pole piece from warping during the rolling process. After the positive and negative pole pieces are laminated or wound into an electrode assembly, the electrode assembly needs to be hot-pressed. However, the thickness of the thinned area of the positive and negative pole pieces is less than that of the pole pieces in the non-thinned area, which leads to the fact that the thinned area of the positive and negative pole pieces cannot be effectively hot-combined with the separator during the hot-pressing process, that is, the positive pole piece and the negative pole piece in the thinned area cannot be completely attached to form a gap. Therefore, during the charging process of the battery, the lithium ion transmission path becomes longer, resulting in an increase in transmission impedance. Thus, the negative pole piece appears to be lithium precipitation, which reduces the cycle performance of the battery.

[0036] To reduce the technical problem of active lithium consumption in battery attenuation, the embodiments of the present application provide a battery monomer, which comprises a shell and an electrode assembly arranged in the shell, the electrode assembly comprising: a first pole piece, a negative pole piece and a separator, the separator being arranged between the first pole piece and the second pole piece, and the polarity of the first pole piece and the second pole piece being opposite; wherein the first pole piece comprises a first current collector and a first active layer arranged on at least one surface of the first current collector; the first active layer comprises a first flat part and a first thinned part, the thickness of the first thinned part is less than the thickness of the first flat part, and the first thinned part is arranged at one end of the first current collector in the length direction of the battery monomer; the second pole piece comprises a second current collector and a second active layer arranged on at least one surface of the second current collector; the second active layer comprises a second flat part and a second thinned part, the thickness of the second thinned part is less than the thickness of the second flat part, and the second thinned part is arranged at one end of the second current collector in the length direction of the battery monomer, and is located at the same end as the first thinned part; the separator comprises a base film and a first ceramic functional coating, the base film has a first surface and a second surface opposite to each other, the first ceramic functional coating is arranged at the end of the first surface close to the first thinned part, and the first ceramic functional coating is at least partially located between the first surface and the first thinned part in the thickness direction of the battery monomer. Therefore, by arranging the first ceramic functional coating on the base film, when the separator and the first pole piece are stacked, the first ceramic functional coating is arranged between the base film and the first thinned part, and the gap between the base film and the first thinned part is completely filled, so that there is no gap between the first pole piece and the separator, so that the electrode assembly can be more effectively compounded during hot pressing, and the lithium precipitation phenomenon in the thinned area caused by long ion transmission is avoided, and the battery cycle performance is increased. Moreover, the use of the first ceramic functional coating can increase the high temperature resistance of the separator, increase the thermal shrinkage performance of the separator, avoid the shrinkage of the separator on the tab side caused by the high temperature in the overcharge and other thermal safety tests, reduce the risk of battery thermal runaway safety, and the like. The following will be described in detail.

[0037] As shown in Figure 1 The embodiments of the present application provide a battery monomer, which has intersecting first direction X, second direction Y and third direction Z, and the first direction X is the length direction, the second direction Y is the thickness direction, and the third direction Z is the height direction.

[0038] The battery monomer can be a secondary battery, which refers to a monomer battery that can be activated by charging after discharging. For example, the battery monomer can be a lithium ion battery, a sodium ion battery, a sodium lithium ion battery, a lithium metal battery, a sodium metal battery, a lithium sulfur battery, a magnesium ion battery, a nickel hydrogen battery or a nickel cadmium battery, but is not limited thereto.

[0039] As shown in Figures 1 to 7As shown, the battery cell includes a shell 1, an electrode assembly 2, and an end cover 3. The electrode assembly 2 is arranged in the shell 1, and the end cover 3 is arranged at one end of the shell 1 in the first direction X.

[0040] The shell 1 can be made of a metal or the like strength material, but is not limited thereto. For example, the shell 1 is made of an aluminum profile, but is not limited thereto.

[0041] The end cover 3 can be integrally formed with the shell 1, that is, the end cover 3 and the shell 1 are in an integrated structure; or the end cover 3 can be fixedly connected with the shell 1, for example, the end cover 3 is fixedly connected with the shell 1 at one end in the first direction X by welding or the like process. In the present application, no specific limitation is made, and the arrangement can be specifically set according to the actual situation. For example, in the present application, the end cover 3 is arranged separately from the shell 1, and the end cover 3 is fixedly connected with the shell 1 by welding.

[0042] In an embodiment, as shown in Figures 2 to 7 The electrode assembly 2 includes a first electrode tab 21, a second electrode tab 22, and a separator 23 arranged between the first electrode tab 21 and the second electrode tab 22, and the first electrode tab 21 and the second electrode tab 22 have opposite polarities.

[0043] The first electrode tab 21 can be a positive electrode tab or a negative electrode tab. For example, in the embodiment of the present application, the first electrode tab 21 is a positive electrode tab, and the second electrode tab 22 is a negative electrode tab.

[0044] In an embodiment, as shown in Figure 3 The first electrode tab 21 includes a first current collector 211 and a first active layer 212 arranged on at least one surface of the first current collector 211.

[0045] The first current collector 211 can be a positive current collector or a negative current collector; the first active layer 212 can be a positive active layer or a negative active layer, and no specific limitation is made in the present application, and the arrangement can be specifically selected according to the actual situation. For example, in the embodiment of the present application, the first current collector 211 is a positive current collector, and the first current collector 211 can include aluminum, composite aluminum foil, titanium, tantalum, or the like metal material.

[0046] The first active layer 212 is a positive active layer, and the first active layer 212 includes a positive active material, a positive binder, and a positive conductive agent. The positive active material includes lithium cobaltate, lithium manganate, lithium iron phosphate, lithium nickel cobalt manganate, or lithium nickel cobalt aluminum, and the above-mentioned positive active material can be used alone or in any combination.

[0047] The positive binder includes polyvinylidene fluoride or polytetrafluoroethylene, and the above-mentioned positive binder can be used alone or in any combination.

[0048] Positive electrode conductive agents include carbon black, conductive graphite, carbon fiber, or carbon nanotubes. These positive electrode conductive agents can be used alone or in any combination.

[0049] In one embodiment, such as Figure 3 As shown, with the dashed line a as the boundary, the first active layer 212 includes a first flat portion 2121 and a first thinned portion 2122. The thickness of the first thinned portion 2122 is less than the thickness of the first flat portion 2121. The first thinned portion 2122 is disposed at one end of the first current collector 211 along the length direction of the battery cell. The thicknesses of the first thinned portion 2122 and the first flat portion 2121 in the second direction can be measured using a two-dimensional micrometer-scale image measuring instrument to ensure that the thickness of the first thinned portion 2122 is less than the thickness of the first flat portion 2121. Of course, the specific measurement method can be determined according to the actual situation and is not limited here.

[0050] In one embodiment, such as Figure 4 As shown, the second electrode 22 includes a second current collector 221 and a second active layer 222 disposed on at least one surface of the second current collector 221.

[0051] The second current collector 221 can be either a positive or negative current collector; the second active layer 222 can be either a positive or negative active layer, and this application does not impose specific limitations, but can be selected according to the actual situation. For example, in an embodiment of this application, the second current collector 221 is a negative current collector, and the second current collector 221 includes metal foil, metal cylinder, metal strip roll, metal plate, metal film, metal mesh, stamped metal, foamed metal, etc. In one embodiment, the second current collector 221 is copper foil or composite copper foil. As used herein, the term "copper foil" includes copper alloy foil.

[0052] The first active layer 212 is the negative electrode active layer, and the first active layer 212 includes artificial graphite, natural graphite, soft carbon, hard carbon, amorphous carbon, carbon nanotubes, mesophase carbon microspheres, silicon-based materials, etc. The above-mentioned negative electrode active materials can be used alone or in any combination.

[0053] In one embodiment, such as Figure 3As shown, the second active layer 222 includes a second flat portion 2221 and a second thinned portion 2222, the thickness of the second thinned portion 2222 is less than the thickness of the second flat portion 2221, the second thinned portion 2222 is arranged at one end of the second current collector 221 in the length direction of the battery cell, and is located at the same end as the first thinned portion 2122. The thickness of the second thinned portion 2222 and the second flat portion 2221 in the second direction can be measured by a two-dimensional micrometer image measuring instrument to obtain that the thickness of the second thinned portion 2222 is less than the thickness of the second flat portion 2221. Of course, the specific measurement method can be determined according to the actual situation, which is not limited here.

[0054] The first and second pole pieces 21 and 22 of the battery cell can be prepared by any known method, which will not be described here.

[0055] In an embodiment, as shown in Figure 5 and Figure 7 The separator 23 includes a base film 231 and a first ceramic functional coating layer 232, the base film 231 has a first surface 2311 and a second surface 2312 opposite to each other, the first ceramic functional coating layer 232 is arranged at the end of the first surface 2311 close to the first thinned portion 2122, and the first ceramic functional coating layer 232 is at least partially located between the first surface 2311 and the first thinned portion 2122 in the thickness direction of the battery cell.

[0056] When the separator 23 is arranged in layers with the first pole piece 21, the first ceramic functional coating layer 232 is arranged between the base film 231 and the first thinned portion 2122, and completely fills the gap between the base film 231 and the first thinned portion 2122, so that there is no gap between the first pole piece 21 and the separator 23, so that the electrode assembly 2 can be more effectively compounded during hot pressing, avoiding the phenomenon of lithium precipitation in the negative thinned area due to long ion transmission, increasing the battery cycle performance. And, using the first ceramic functional coating layer 232 can increase the high temperature resistance of the separator 23, increase the thermal shrinkage performance of the separator 23, avoid the shrinkage of the separator 23 on the tab side caused by the high temperature of the battery in the overcharge condition, reduce the risk of battery thermal runaway safety.

[0057] In an embodiment, as shown in Figure 6 and Figure 7 The separator 23 further includes a second ceramic functional coating layer 233, the second ceramic functional coating layer 233 is arranged at the end of the second surface 2312 close to the second thinned portion 2222, and the second ceramic functional coating layer 233 is at least partially located between the second surface 2312 and the second thinned portion 2222 in the thickness direction of the battery cell.

[0058] When the diaphragm 23 is stacked with the second pole piece 22, the second ceramic functional coating 233 is arranged between the base film 231 and the second thinned portion 2222, and completely fills the gap between the base film 231 and the second thinned portion 2222, so that there is no gap between the second pole piece 22 and the diaphragm 23, so that the electrode assembly 2 can be more effectively compounded during the hot pressing process, avoiding the phenomenon of lithium precipitation in the negative thinned area due to long ion transmission, and increasing the battery cycle performance. Moreover, the use of the second ceramic functional coating 233 can increase the high temperature resistance of the diaphragm 23, increase the thermal shrinkage performance of the diaphragm 23, avoid the shrinkage of the diaphragm 23 on the tab side caused by the temperature being too high in the battery under the working condition of overcharging, and reduce the risk of battery thermal runaway safety.

[0059] In an embodiment, the maximum length of the second ceramic functional coating 233 in the length direction of the battery monomer is less than the maximum length of the first ceramic functional coating 232 in the length direction of the battery monomer.

[0060] The maximum length of the first ceramic functional coating 232 in the length direction of the battery monomer is 5-30mm, and the maximum length of the second ceramic functional coating 233 in the length direction of the battery monomer is 5-20mm. It can be understood that the maximum length of the first ceramic functional coating 232 in the length direction of the battery monomer (unit: mm) is any one of 5, 10, 15, 20, 25, 30 or a value between any two values. The maximum length of the second ceramic functional coating 233 in the length direction of the battery monomer (unit: mm) is any one of 5, 10, 15, 20 or a value between any two values.

[0061] In an embodiment, the maximum thickness of the second ceramic functional coating 233 in the thickness direction of the battery monomer is less than the maximum thickness of the first ceramic functional coating 232 in the thickness direction of the battery monomer.

[0062] The maximum thickness of the first ceramic functional coating 232 in the thickness direction of the battery monomer is 0-40um, and the maximum thickness of the second ceramic functional coating 233 in the thickness direction of the battery monomer is 0-30um. It can be understood that the maximum thickness of the first ceramic functional coating 232 in the thickness direction of the battery monomer (unit: um) is any one of 1, 5, 10, 15, 20, 25, 30, 35, 40 or a value between any two values. The maximum thickness of the second ceramic functional coating 233 in the thickness direction of the battery monomer (unit: um) is any one of 1, 5, 10, 15, 20, 25, 30 or a value between any two values.

[0063] The first ceramic functional coating 232 and the second ceramic functional coating 233 are both ceramic materials, which mainly include at least one of aluminum oxide, titanium dioxide, and silicon dioxide, and can be doped with PVDF glue and the like. Specifically, the first ceramic functional coating 232 includes at least one of aluminum oxide, titanium dioxide, and silicon dioxide. The second ceramic functional coating 233 includes at least one of aluminum oxide, titanium dioxide, and silicon dioxide.

[0064] In the second direction Y, by arranging the first ceramic functional coating 232 and the second ceramic functional coating 233 at the end portions of the two surfaces of the diaphragm 23, the high-temperature resistance of the diaphragm 23 can be improved, the thermal shrinkage of the diaphragm 23 can be improved, the diaphragm 23 on the tab side can be prevented from shrinking to cause internal short circuit of the positive and negative electrode sheets, and the safety risk of thermal runaway of the battery can be reduced.

[0065] The first electrode sheet 21 further includes a first tab 2123 arranged on the first current collector 211, and the first thinned portion 2122 is arranged close to the first tab 2123 in the length direction of the battery monomer, and the first ceramic functional coating 232 is arranged close to the first tab 2123 in the length direction of the battery monomer, so as to facilitate the processing and forming of the first electrode sheet 21.

[0066] The second electrode sheet 22 further includes a second tab 2223 arranged on the second current collector 221, and the second thinned portion 2222 is arranged close to the second tab 2223 in the length direction of the battery monomer, and the second ceramic functional coating 233 is arranged close to the second tab 2223 in the length direction of the battery monomer, so as to facilitate the processing and forming of the first electrode sheet 21.

[0067] The battery monomer further includes an electrolyte, a pole, and other functional components. The electrolyte can be a conventional electrolyte or a special electrolyte added with an additive, and the electrolyte is used to soak the electrode assembly 2. The electrode assembly 2 is a component in which an electrochemical reaction occurs in the battery monomer, and the electrode assembly 2 can be one or more. The part of the first electrode sheet 21 and the second electrode sheet 22 with active material constitutes an electrode body, and the part of the first electrode sheet 21 and the second electrode sheet 22 without active material constitutes a tab. In the charging and discharging process of the battery monomer, the active material reacts with the electrolyte, and the tab is electrically connected with the pole to form a current loop, so that the battery monomer can be normally used.

[0068] The current density on the tab side of the battery cell is too large, which is easy to cause the lithium precipitation of the tab side of the tab. By arranging the first ceramic functional coating 232 on the first surface 2311 of the base film 231, and arranging the second ceramic functional coating 233 on the second surface 2312, when the first tab 21 and the second tab 22 are arranged in layers, and the diaphragm 23 is located between the first tab 21 and the second tab 22, the first ceramic functional coating 232 is arranged between the first surface 2311 and the first thinning portion 2122, so as to completely fill the gap between the first surface 2311 and the first thinning portion 2122, so that there is no gap between the first tab 21 and the first surface 2311, and the second ceramic functional coating 233 is arranged between the second surface 2312 and the second thinning portion 2222, so as to completely fill the gap between the second surface 2312 and the second thinning portion 2222, so that there is no gap between the second tab 22 and the first surface 2311. The first ceramic functional coating 232 and the second ceramic functional coating 233 can effectively absorb free electrolyte, reduce the transmission impedance of lithium ions in the thinning area to meet the local excessive current density on the tab side, and reduce the risk of lithium precipitation on the negative tab on the tab side.

[0069] The application also provides a battery pack comprising at least two battery cells as described above, and the at least two battery cells are connected in series and / or in parallel. The battery pack can be a battery module, a battery pack, or a battery cluster. All battery cells in the battery pack can be connected in series or in parallel. Of course, part of the battery cells in the battery pack can be connected in series, and the other part can be connected in parallel, which is not particularly limited here and can be set as needed. The battery pack is provided with a ceramic functional coating on at least one side surface of the base film, and when the diaphragm and the tab are arranged in layers, the ceramic functional coating is arranged between the base film and the thinning portion, and the gap between the base film and the thinning portion is completely filled, so that there is no gap between the tab and the diaphragm, so that the electrode assembly can be more effectively compounded during hot pressing, and the lithium precipitation phenomenon in the thinning area caused by long ion transmission is avoided, and the battery cycle performance is increased. Moreover, the use of the ceramic functional coating can increase the high-temperature resistance of the diaphragm, increase the thermal shrinkage performance of the diaphragm, avoid the shrinkage of the diaphragm on the tab side caused by the overcharging of the battery under the working condition, and reduce the risk of thermal runaway of the battery.

[0070] In the above embodiments, the description of each embodiment has its own focus, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0071] The above has carried out the detailed introduction to the battery monomer and the battery pack provided by the embodiment of the application, the principle and the implementation mode of the application are described by applying specific examples, the above embodiment is only used for helping understanding the technical scheme of the application and its core idea; the ordinary skilled in the art should understand that: it can still modify the technical scheme recorded by the foregoing each embodiment, or equivalent replacement is carried out to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical scheme deviate from the scope of the technical scheme of the embodiments of the application.

Claims

1. A battery cell, characterized by, The battery cell comprises: a housing; an electrode assembly arranged in the housing, the electrode assembly comprising: a first electrode tab, a second electrode tab, and a separator arranged between the first electrode tab and the second electrode tab, the first electrode tab and the second electrode tab having opposite polarities; wherein the first electrode tab comprises a first current collector and a first active layer arranged on at least one surface of the first current collector; the first active layer comprises a first flat portion and a first thinned portion, the thickness of the first thinned portion being less than the thickness of the first flat portion, the first thinned portion being arranged at one end of the first current collector in a length direction of the battery cell; the second electrode tab comprises a second current collector and a second active layer arranged on at least one surface of the second current collector; the second active layer comprises a second flat portion and a second thinned portion, the thickness of the second thinned portion being less than the thickness of the second flat portion, the second thinned portion being arranged at one end of the second current collector in the length direction of the battery cell, and the second thinned portion is located at the same end as the first thinned portion; the separator comprises a base film having a first surface and a second surface arranged opposite to each other, and a first ceramic functional coating arranged on an end of the first surface close to the first thinned portion, and the first ceramic functional coating is at least partially located between the first surface and the first thinned portion in a thickness direction of the battery cell.

2. The battery cell according to claim 1, wherein the first electrode tab further comprises a first tab arranged on the first current collector, and the first thinned portion is arranged close to the first tab in the length direction of the battery cell, and the first ceramic functional coating is arranged close to the first tab in the length direction of the battery cell.

3. The battery cell according to claim 1, wherein the separator further comprises a second ceramic functional coating arranged on an end of the second surface close to the second thinned portion, and the second ceramic functional coating is at least partially located between the second surface and the second thinned portion in the thickness direction of the battery cell.

4. The battery cell according to claim 3, wherein the second electrode tab further comprises a second tab arranged on the second current collector, and the second thinned portion is arranged close to the second tab in the length direction of the battery cell, and the second ceramic functional coating is arranged close to the second tab in the length direction of the battery cell.

5. The battery cell according to claim 3, wherein a maximum length of the second ceramic functional coating in the length direction of the battery cell is less than a maximum length of the first ceramic functional coating in the length direction of the battery cell.

6. The battery cell according to claim 5, wherein the maximum length of the first ceramic functional coating in the length direction of the battery cell is 5-30 mm, and the maximum length of the second ceramic functional coating in the length direction of the battery cell is 5-20 mm.

7. The battery cell according to claim 3, wherein The maximum thickness of the second ceramic functional coating in the thickness direction of the battery cell is less than the maximum thickness of the first ceramic functional coating in the thickness direction of the battery cell.

8. The battery cell according to claim 7, wherein The maximum thickness of the first ceramic functional coating in the thickness direction of the battery cell is 0-40 um, and the maximum thickness of the second ceramic functional coating in the thickness direction of the battery cell is 0-30 um.

9. A battery pack characterized by comprising: A battery cell comprising at least two battery cells according to any one of claims 1 to 8, wherein the at least two battery cells are connected in series or in parallel.

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