Electrochemical device, battery module and electric device

Abstract

The embodiment of the invention relates to the technical field of energy storage, and particularly discloses an electrochemical device, a battery module and a power utilization device. The electrode assembly comprises a first pole piece, a second pole piece and a diaphragm, a plurality of first tabs are arranged on the first pole piece, the diaphragm is arranged between the first pole piece and the second pole piece, the first pole piece, the diaphragm and the second pole piece are stacked and wound, and the first tabs are connected to the area, except a first inner side layer and a first outer side layer, of the first pole piece; wherein in the direction from the starting layer to the ending layer of the first pole piece, starting from the starting layer of the first pole piece to the Nth layer of the first pole piece, and all the layers jointly form a first inner side layer; from the ending layer of the first pole piece to the Mth layer in the direction from the ending layer of the first pole piece to the starting layer, all the layers jointly form a first outer side layer; wherein M > = 1, 3 < = N < = 0.6 A, N is an integer, and A is the total layer number of the first pole pieces. In this way, the problems of lithium precipitation and the like of the battery can be solved.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of energy storage technology, and in particular to an electrochemical device, a battery module, and an electrical device. Background Art

[0002] Lithium-ion batteries are widely used not only in portable electronic devices such as mobile phones, digital cameras and laptops, but also in large and medium-sized electric devices such as electric vehicles, electric bicycles and power tools due to their advantages such as high specific energy, many cycles and long storage time.

[0003] For lithium-ion batteries, during the charge and discharge process, lithium ions Li+ are intercalated and deintercalated back and forth between the two electrodes. During charging, lithium ions Li+ are deintercalated from the positive electrode and intercalated into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; while during discharge, the opposite is true.

[0004] In the process of realizing the present application, the inventors of the present application found that: in the field of new energy vehicles, higher energy density, higher rate performance, long life and safety have put forward higher requirements for lithium-ion batteries. With the increase of energy density, the volume of the battery increases. A simple single pole ear as the input and output end of the external charging and discharging device is difficult to meet the higher rate performance requirements, and then a multi-pole ear structure is introduced. However, the design of the multi-pole ear structure is prone to cause lithium precipitation inside the battery after the electrolyte is consumed in the late stage of long-term battery circulation, which then causes life attenuation and safety problems, and is difficult to be widely promoted and utilized. Summary of the invention

[0005] In view of the above problems, the embodiments of the present application provide an electrochemical device, a battery module and an electrical device, which improve the above problems such as battery lithium deposition.

[0006] According to one aspect of an embodiment of the present application, an electrochemical device is provided, including: an electrode assembly. The electrode assembly includes a first pole piece, a second pole piece and a diaphragm, a plurality of first pole ears are arranged on the first pole piece, the diaphragm is arranged between the first pole piece and the second pole piece, and the first pole piece, the diaphragm and the second pole piece are arranged in a stacked and wound manner. In addition, a plurality of first pole ears are connected to the area of ​​the first pole piece other than the first inner layer and the first outer layer; wherein, along the direction of the starting layer of the first pole piece to the ending layer, starting from the starting layer of the first pole piece and ending at the Nth layer, the first inner layer is constituted; along the direction of the ending layer of the first pole piece to the starting layer, starting from the ending layer of the first pole piece and ending at the Mth layer, the first outer layer is constituted; wherein, M≥1, 3≤N≤0.6A, N is an integer, and A is the total number of layers of the first pole piece. By setting the distribution position of the first pole ear, the electromotive force at the first inner layer and the first outer layer of the first pole piece is reduced during the charging and discharging of the electrochemical device, and the local lithium insertion rate is reduced, thereby achieving the effect of reducing the lithium deposition of the battery.

[0007] In an optional manner, the first pole piece includes a first current collector, a plurality of first pole tabs are extended from one side of the first current collector, and the plurality of first pole tabs are integrally formed with the first current collector. This arrangement facilitates the flow of current between the first pole tabs and the first current collector, and is beneficial to current density distribution.

[0008] In an optional manner, a plurality of second pole ears are provided on the second pole piece, and the plurality of second pole ears are connected to the area of ​​the second pole piece other than the second inner layer and the second outer layer. Wherein, along the direction from the starting layer to the ending layer of the second pole piece, starting from the starting layer of the second pole piece and ending at the Kth layer, the second inner layer is formed; along the direction from the ending layer to the starting layer of the second pole piece, starting from the ending layer of the second pole piece and ending at the Lth layer, the second outer layer is formed; wherein, L≥1, K≥3. By setting the distribution position of the second pole ears, the electromotive force at the second inner layer and the second outer layer of the second pole piece is reduced during the charge and discharge of the electrochemical device, and the local lithium insertion rate is reduced, thereby achieving the effect of reducing the lithium deposition of the battery.

[0009] In an optional manner, the second pole piece includes a second current collector, the plurality of second pole tabs are extended from one side of the second current collector, and the plurality of second pole tabs are integrally formed with the second current collector. This arrangement facilitates the flow of current between the second pole tab and the second current collector, and is beneficial to current density distribution.

[0010] In an optional manner, the first outer layer satisfies the following condition: 1≤M≤0.6A, where M is an integer.

[0011] In an optional manner, at least one first pole lug is connected to other layers of the first pole sheet except the first inner layer and the first outer layer.

[0012] In an optional manner, the number of first pole tabs connected to each layer of the first pole sheet except the first inner layer and the first outer layer is no more than 5. For example, the number of first pole tabs in each layer may be 1, 2, 3, 4 or 5.

[0013] In an optional manner, the total number of layers A of the first pole piece is 5 to 80 layers.

[0014] In an optional manner, the second inner layer satisfies the following condition: 3≤K≤0.6B, where K is an integer and B is the total number of layers of the second pole piece.

[0015] In an optional manner, the second outer layer satisfies the following condition: 1≤L≤0.6B, where L is an integer and B is the total number of layers of the second pole piece.

[0016] In an optional manner, at least one second pole lug is connected to other layers of the second pole sheet except the second inner layer and the second outer layer.

[0017] In an optional manner, the number of second pole tabs connected to each layer of the second pole sheet except the second inner layer and the second outer layer is no more than 5. For example, the number of second pole tabs in each layer may be 1, 2, 3, 4 or 5.

[0018] In an optional manner, the total number of layers B of the second pole piece is 5 to 80 layers.

[0019] According to another aspect of an embodiment of the present application, a battery module is provided, comprising the electrochemical device as described above.

[0020] According to another aspect of an embodiment of the present application, there is provided an electrical device comprising the battery module as described above.

[0021] The beneficial effects of the embodiment of the present application are as follows: Different from the prior art, the embodiment of the present application is provided with an electrode assembly, wherein the electrode assembly includes a first pole piece, a second pole piece and a diaphragm, a plurality of first pole ears are provided on the first pole piece, the diaphragm is provided between the first pole piece and the second pole piece, the first pole piece, the diaphragm and the second pole piece are stacked and wound, and in addition, the plurality of first pole ears are connected to the area of ​​the first pole piece except the first inner layer and the first outer layer, wherein, in the direction from the starting layer of the first pole piece to the ending layer, Starting from the starting layer of the first pole piece and ending at the Nth layer, the first inner layer is formed; along the direction from the ending layer of the first pole piece to the starting layer, starting from the ending layer of the first pole piece and ending at the Mth layer, the first outer layer is formed, wherein M≥1, 3≤N≤0.6A, N is an integer, A is the total number of layers of the first pole piece, and by setting the distribution positions of a plurality of first pole ears, the electromotive force at the first inner layer and the first outer layer of the first pole piece is reduced during charging and discharging of the electrochemical device, and the local lithium insertion rate is reduced, thereby achieving the effect of reducing lithium plating of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the prior art description. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0023] Figure 1 is a schematic diagram of the structure of the electrochemical device of an embodiment of the present application;

[0024] Figure 2 yes Figure 1 Sectional view at AA;

[0025] Figure 3 is a schematic structural diagram of a first pole piece of an embodiment of an electrochemical device of the present application;

[0026] Figure 4 is a side cross-sectional view of a first pole piece of an embodiment of the electrochemical device of the present application;

[0027] Figure 5 is a cross-sectional view of an embodiment of the electrochemical device of the present application;

[0028] Figure 6 is a cross-sectional view of another embodiment of the electrochemical device of the present application;

[0029] Figure 7 is a schematic structural diagram of a second pole piece of an embodiment of the electrochemical device of the present application;

[0030] Figure 8 is a side cross-sectional view of a second pole piece of an embodiment of the electrochemical device of the present application;

[0031] Fig. 9 is a cross-sectional view of another embodiment of the electrochemical device of the present application;

[0032] Fig.10 is a cross-sectional view of another embodiment of the electrochemical device of the present application. DETAILED DESCRIPTION

[0033] In order to facilitate the understanding of the present application, the present application is described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is described as "fixed to" another element, it can be directly on the other element, or there can be one or more centered elements therebetween. When an element is described as "connected to" another element, it can be directly connected to the other element, or there can be one or more centered elements therebetween. The terms "vertical", "horizontal", "left", "right" and similar expressions used in this specification are for illustrative purposes only.

[0034] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in this specification and in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0035] See also Figure 1 and Figure 2 The electrochemical device 01 includes a housing 10 and an electrode assembly 20. The electrode assembly 20 is disposed in the housing 10. The electrode assembly 20 is a winding structure.

[0036] For the above-mentioned housing 10, if Figure 1 and Figure 2 As shown, the shell 10 is in the shape of a flat rectangular parallelepiped as a whole, and a receiving cavity 10a is provided inside the shell, and the receiving cavity 10a is used to receive the electrode assembly 20 and the electrolyte. In this embodiment, the electrochemical device is a soft-pack battery, that is, the shell 10 is an aluminum-plastic film. It can be understood that in other embodiments of the present application, the electrochemical device can also be a hard-shell battery, and accordingly, the shell 10 is a metal shell.

[0037] For the electrode assembly 20, Figure 2As shown, it is accommodated in the above-mentioned accommodation cavity 10a, and the electrode assembly 20 includes a first pole piece 201, a second pole piece 202, and a diaphragm 203. A plurality of first pole tabs 204 are arranged on the first pole piece 201. The first pole piece 201 and the second pole piece 202 have opposite polarities and are arranged at intervals, one of which is a positive pole piece and the other is a negative pole piece; the diaphragm 203 is arranged between the above-mentioned two pole pieces and is used to separate the two pole pieces; the first pole tab 204 is obtained by extending from one side of the first pole piece 201, and one end of the first pole tab 204 away from the first pole piece 201 extends from the shell 10. The first pole piece 201, the second pole piece 202 and the diaphragm 203 are stacked and wound into a columnar structure with an oblong or elliptical cross section, so as to be accommodated in the above-mentioned accommodation cavity 10a. The shell 10 is also filled with an electrolyte, and the electrode assembly 20 is immersed in the electrolyte. The electrolyte is used to provide an environment for lithium ion conduction so that the lithium ions can be embedded in the first electrode 201 or the second electrode 202 in a timely manner, thereby realizing the charge and discharge process of the electrochemical device.

[0038] A plurality of second pole tabs 205 are disposed on the second pole piece 202 . The second pole tab 205 is extended from one side of the second pole piece 202 . One end of the second pole tab 205 away from the second pole piece 202 extends out from the housing 10 .

[0039] In some embodiments, Figure 3-Figure 4 As shown, the first pole piece 201 includes a first current collector 2011 and a first active material layer 2012 , the first active material layer 2012 is disposed on the first current collector 2011 , the plurality of first pole tabs 204 are extended from one side of the first current collector 2011 , and the plurality of first pole tabs 204 are integrally formed with the first current collector 2011 . It should be noted that: the first current collector 2011 includes a first surface 2011a and a second surface 2011b, the first active material layer 2012 can be coated on the first surface 2011a and / or the second surface 2011b, the first current collector 2011 whose first surface 2011a and the second surface 2011b are not symmetrically coated with the first active material layer 2012 is a single-sided area first pole piece 201, for example: a section of the first surface 2011a is not coated with the first active material layer 2012, and the second surface 2011b symmetrical to the section is coated with the first active material layer 2012, then the first current collector 2011 of the corresponding section is a single-sided area first pole piece 201; the first current collector 2011 whose first surface 2011a and the second surface 2011b are symmetrically coated with the first active material layer 2012 is a double-sided area first pole piece 201. In some embodiments, the single-sided area first pole piece 201 is usually provided at the winding start layer and / or the end layer of the wound electrode assembly 20.

[0040] In some embodiments, Figure 5 and Figure 6 As shown, the first pole piece 201 includes a first inner layer (not marked) and a first outer layer (not marked), wherein, along the direction of the starting layer to the ending layer of the first pole piece 201, starting from the starting layer of the first pole piece 201 and ending at the Nth layer, each layer together constitutes the above-mentioned first inner layer; along the direction of the ending layer to the starting layer of the first pole piece 201, starting from the ending layer of the first pole piece 201 and ending at the Mth layer, each layer together constitutes the above-mentioned first outer layer, and M≥1, N≥3, and N is an integer.

[0041] In some embodiments, the first inner layer satisfies the following conditions: 3≤N≤0.6A, wherein N is an integer, and A is the total number of layers of the first pole piece 201. For example, when A=15, 3≤N≤9, that is, from the starting layer to the ending layer of the first pole piece 201, starting from the starting layer of the first pole piece 201, the first pole piece 201 has at least 3 layers and at most 9 layers without the first pole ear 204, and if the value of N is equal to 5, it means that from the starting layer to the ending layer of the first pole piece 201, the first pole piece 201 has no first pole ear 204 between the first layer (that is, the starting layer of the first pole piece 201, which is also the innermost layer of the first pole piece 201) and the fifth layer.

[0042] In some embodiments, the first outer layer satisfies the following conditions: 1≤M≤0.6A, M is an integer, wherein A is the total number of layers of the first pole piece 201. For example: when A=15, 1≤M≤9, that is, from the end layer of the first pole piece 201 to the starting layer, starting from the end layer of the first pole piece 201, at least 1 layer and at most 9 layers of the first pole piece 201 are not provided with the first pole ear 204. If the value of M is equal to 3, it means that from the end layer of the first pole piece 201 to the starting layer, the first pole piece 201 is not provided with the first pole ear 204 from the first layer (that is, the end layer of the first pole piece 201, which is also the outermost layer of the first pole piece 201) to the third layer.

[0043] In some embodiments, the total number of layers A of the first pole piece 201 is 5 to 80 layers.

[0044] It should be noted that: the electrode assembly in this embodiment is a winding structure. When defining the total number of layers A of the first electrode sheet 201, the first straight section of the first electrode sheet 201 located at the innermost side of the electrode assembly that has not been wound to the midpoint of the first bending end is defined as the first fold of the first electrode sheet as the starting layer of the first electrode sheet 201, and along the winding direction, from the midpoint of the first bending end to the midpoint of the second bending end is defined as the second fold of the first electrode sheet as the second layer, that is, each time the first electrode sheet 201 is bent, the total number of layers of the first electrode sheet 201 increases by 1 layer, and the remaining layers are similar.

[0045] For the second pole piece 202, in some embodiments, as Figure 7-Figure 8 As shown, the second pole piece 202 includes a second current collector 2021 and a second active material layer 2022 , wherein the second active material layer 2022 is disposed on the second current collector 2021 , and the plurality of second pole tabs 205 are extended from one side of the second current collector 2021 , and the plurality of second pole tabs 205 are integrally formed with the second current collector 2021 . It should be noted that: the second current collector 2021 includes a third surface 2021a and a fourth surface 2021b, the second active material layer 2022 can be coated on the third surface 2021a and / or the fourth surface 2021b, the second current collector 2021 on which the third surface 2021a and the fourth surface 2021b are not symmetrically coated with the second active material layer 2022 is a single-sided second pole piece 202, for example: a section of the third surface 2021a is not coated with the second active material layer 2022, and the fourth surface 2021b symmetrical to the section is coated with the second active material layer 2022, then the second current collector 2021 in the corresponding section is a single-sided second pole piece 202; the second current collector 2021 on which the third surface 2021a and the fourth surface 2021b are symmetrically coated with the second active material layer 2022 is a double-sided second pole piece 202. In some embodiments, the single-sided second electrode sheet 202 is generally disposed at a winding start layer and / or a winding end layer of the wound electrode assembly 20 .

[0046] In some embodiments, Fig. 9 and Fig.10 As shown, the second pole piece 202 includes a second inner layer (not marked) and a second outer layer (not marked), wherein, along the direction from the starting layer to the ending layer of the second pole piece 202, starting from the starting layer of the second pole piece 202 and ending at the Kth layer, each layer together constitutes the above-mentioned second inner layer; along the direction from the ending layer to the starting layer of the second pole piece 202, starting from the ending layer of the second pole piece 202 and ending at the Lth layer, each layer together constitutes the above-mentioned second outer layer; wherein, L≥1, K≥3.

[0047] In some embodiments, the second inner layer satisfies the following conditions: 3≤K≤0.6B, where K is an integer and B is the total number of layers of the second pole piece 202. For example, when B=15, 3≤K≤9, that is, from the starting layer to the ending layer of the second pole piece 202, starting from the starting layer of the second pole piece 202, at least 3 layers and at most 9 layers of the second pole piece 202 are not provided with the second pole ear 205. If the value of K is equal to 5, it means that from the starting layer to the ending layer of the second pole piece 202, the second pole piece 202 has no second pole ear 205 from the first layer (that is, the starting layer of the second pole piece 202, which is also the innermost layer of the second pole piece 201) to the fifth layer.

[0048] In some embodiments, the second outer layer satisfies the following conditions: 1≤L≤0.6B, L is an integer, where B is the total number of layers of the second pole piece 202. For example: when B=15, 1≤L≤9, that is, from the end layer of the second pole piece 202 to the starting layer, starting from the end layer of the second pole piece 202, at least 1 layer and at most 9 layers of the second pole piece 202 are not provided with the second pole ear 205. If the value of M is equal to 3, it means that from the end layer of the second pole piece 202 to the starting layer, the second pole piece 202 has no second pole ear 205 between the first layer (that is, the end layer of the second pole piece 202, which is also the outermost layer of the second pole piece 202) and the third layer.

[0049] In some embodiments, the total number of layers B of the second pole piece 202 is 5 to 80 layers.

[0050] It should be noted that: the electrode assembly in this embodiment is a winding structure. When defining the total number of layers B of the second electrode sheet 202, the midpoint from the first straight section of the second electrode sheet 202 located at the innermost side of the electrode assembly to the first bent end is defined as the first fold of the second electrode sheet as the starting layer of the second electrode sheet 202, and along the winding direction, the midpoint from the first bent end to the midpoint of the second bent end is defined as the second fold of the second electrode sheet as the second layer, that is, every time the second electrode sheet 202 is bent, the total number of layers of the second electrode sheet 202 increases by 1, and the remaining layers are similar.

[0051] For the above-mentioned first tabs 204, Figure 1 As shown, the plurality of first pole tabs 204 are connected to the area of ​​the first pole piece 201 except the first inner layer and the first outer layer. By setting the distribution position of the first pole tabs 204, the electromotive force at the first inner layer and the first outer layer of the first pole piece 201 is reduced during the charge and discharge of the electrochemical device, and the local lithium insertion rate is reduced, thereby achieving the effect of reducing the lithium deposition of the battery. It can be understood that the polarity of the first pole tab 204 is closely related to the polarity of the first pole piece 201, and is not specifically limited here. For example, when the first pole piece 201 is a negative electrode, the material of the first pole tab 204 can be a metal material such as copper and nickel.

[0052] In some embodiments, at least one first pole lug 204 is connected to other layers of the first pole piece 201 except the first inner layer and the first outer layer. It can be understood that when the number of the first pole lug 204 is one, the first pole lug 204 can be arranged in any layer of the first pole piece 201 except the first inner layer and the first outer layer, and when the number of the first pole lug 204 is two or more, the arrangement of the two or more first pole lugs 204 on the first pole piece 201 can be continuous arrangement or discontinuous arrangement, which is not specifically limited here.

[0053] In some embodiments, the number of first pole tabs 204 connected to each layer of the first pole piece 201 except the first inner layer and the first outer layer is no more than 5. For example, the number of first pole tabs 204 connected to each layer may be 1, 2, 3, 4 or 5.

[0054] For the above-mentioned plurality of second tabs 205, as Fig.10 As shown, the plurality of second pole tabs 205 are connected to the area of ​​the second pole piece 202 except the second inner layer and the second outer layer. By setting the distribution position of the second pole tabs 205, the electromotive force at the second inner layer and the second outer layer of the second pole piece 202 is reduced during the charge and discharge of the electrochemical device, and the local lithium insertion rate is reduced, thereby achieving the effect of reducing lithium deposition in the battery cell. It can be understood that the polarity of the second pole tab 205 is closely related to the polarity of the second pole piece 202, and is not specifically limited here. For example, when the second pole piece 202 is a positive electrode, the material of the second pole tab 205 can be a metal material such as aluminum.

[0055] In some embodiments, at least one second pole lug 205 is connected to other layers of the second pole piece 202 except the second inner layer and the second outer layer. It can be understood that when the number of the second pole lug 205 is one, the one second pole lug 205 can be arranged in any layer of the second pole piece 202 except the second inner layer and the second outer layer, and when the number of the second pole lug 205 is two or more, the arrangement of the two or more second pole lugs 205 on the second pole piece 202 can be continuous arrangement or intermittent arrangement, which is not specifically limited here.

[0056] In some embodiments, the number of second pole tabs 205 connected to each layer of the second pole piece 202 except the second inner layer and the second outer layer is no more than 5. For example, the number of second pole tabs 205 connected to each layer may be 1, 2, 3, 4 or 5.

[0057] In addition, in order to facilitate the reader to understand the technical effects brought about by the technical solution, the embodiments of the present application also carried out comparative tests, in which the lithium deposition of the anode was tested for illustration. The embodiments and comparative examples in the present application were all made by packaging the electrode assembly in a shell aluminum-plastic film, perfusing the electrolyte, and then packaging it into a lithium-ion battery. Of course, the embodiment of the present application is not limited to this, and the test process is as follows:

[0058] Comparative Example 1

[0059] The electrode assembly is wound by the cathode electrode sheet, the anode electrode sheet and the isolation film. The number of winding layers of the cathode and anode electrodes is 28, that is, A=28, B=28, then 3≤N≤16, 1≤M≤16, 3≤K≤16, 1≤L≤16, take N=3, M=1, K=3, L=1, set the number of layers where the cathode ear is located to 2-26 layers, and the number of cathode ear per layer is 1, the number of layers where the anode ear is located to 2-28 layers, and the number of anode ear per layer is 1, set the ambient temperature to 25°C, charge the battery first, and then let it stand for 5 minutes. The charging process is: 6C 4.2V, 5C 4.32V, 3C 4.5V, then the battery was discharged and then left to stand for 5 minutes. The discharge process was: discharge from 0.7C to 3.0V. Finally, the test cycle numbers reached 300, 500, 700, 900 and 1100 respectively, and the lithium plating of the anode was measured after the battery was fully charged and disassembled.

[0060] Comparative Example 2

[0061] The electrode assembly is wound by the cathode electrode sheet, the anode electrode sheet and the isolation film. The number of winding layers of the cathode and anode electrodes is 28, that is, A=28, B=28, then 3≤N≤16, 1≤M≤16, 3≤K≤16, 1≤L≤16, take N=3, M=1, K=3, L=1, set the number of layers where the cathode ear is located to 4-28 layers, the number of cathode ear per layer is 1, the number of layers where the anode ear is located to 4-28 layers, the number of anode ear per layer is 1, set the ambient temperature to 25°C, first charge the battery, and then let it stand for 5 minutes. The charging process is: 6C 4.2V, 5C 4.32V, 3C 4.5V, then the battery was discharged and then left to stand for 5 minutes. The discharge process was: discharge from 0.7C to 3.0V. Finally, the test cycle numbers reached 300, 500, 700, 900 and 1100 respectively, and the lithium plating of the anode was measured after the battery was fully charged and disassembled.

[0062] Comparative Example 3

[0063] The electrode assembly is wound by the cathode electrode sheet, the anode electrode sheet and the isolation film. The number of winding layers of the cathode and anode electrodes is 28, that is, A=28, B=28, then 3≤N≤16, 1≤M≤16, 3≤K≤16, 1≤L≤16, take N=3, M=1, K=3, L=1, set the number of layers where the cathode electrode ear is located to 2-24 layers, and the number of cathode electrode ears per layer is 1, and the number of layers where the anode electrode ear is located to 2-24 layers, and the number of anode electrode ears per layer is 1, set the ambient temperature to 25°C, first charge the battery, and then let it stand for 5 minutes. The charging process is: 6C 4.2V, 5C 4.32V, 3C 4.5V, then the battery was discharged and then left to stand for 5 minutes. The discharge process was: discharge from 0.7C to 3.0V. Finally, the test cycle numbers reached 300, 500, 700, 900 and 1100 respectively, and the lithium plating of the anode was measured after the battery was fully charged and disassembled.

[0064] Comparative Example 4

[0065] The electrode assembly is wound by the cathode electrode sheet, the anode electrode sheet and the isolation film. The number of winding layers of the cathode and anode electrodes is 28, that is, A=28, B=28, then 3≤N≤16, 1≤M≤16, 3≤K≤16, 1≤L≤16, take N=3, M=1, K=3, L=1, set the number of layers where the cathode ear is located to 2-9 layers, and the number of cathode ear per layer is 1, the number of layers where the anode ear is located to 2-9 layers, and the number of anode ear per layer is 1, set the ambient temperature to 25°C, charge the battery first, and then let it stand for 5 minutes. The charging process is: 6C 4.2V, 5C 4.32V, 3C 4.5V, then the battery was discharged and then left to stand for 5 minutes. The discharge process was: discharge from 0.7C to 3.0V. Finally, the test cycle numbers reached 300, 500, 700, 900 and 1100 respectively, and the lithium plating of the anode was measured after the battery was fully charged and disassembled.

[0066] Comparative Example 5

[0067] The electrode assembly is wound by the cathode electrode sheet, the anode electrode sheet and the isolation film. The number of winding layers of the cathode and anode electrodes is 28 layers, that is, A=28, B=28, then 3≤N≤16, 1≤M≤16, 3≤K≤16, 1≤L≤16, take N=3, M=1, K=3, L=1, set the number of layers where the cathode ear is located to 21-28 layers, the number of cathode ear per layer is 1, the number of layers where the anode ear is located to 21-28 layers, the number of anode ear per layer is 1, set the ambient temperature to 25°C, first charge the battery, and then let it stand for 5 minutes. The charging process is: 6C 4.2V, 5C 4.32V, 3C 4.5V, then the battery was discharged and then left to stand for 5 minutes. The discharge process was: discharge from 0.7C to 3.0V. Finally, the test cycle numbers reached 300, 500, 700, 900 and 1100 respectively, and the lithium plating of the anode was measured after the battery was fully charged and disassembled.

[0068] Example 1

[0069] The electrode assembly is wound by the cathode electrode sheet, the anode electrode sheet and the isolation film. The number of winding layers of the cathode and anode electrodes is 28, that is, A=28, B=28, then 3≤N≤16, 1≤M≤16, 3≤K≤16, 1≤L≤16, take N=3, M=1, K=3, L=1, set the number of layers where the cathode ear is located to 10-18 layers, and the number of cathode ear per layer is 1, the number of layers where the anode ear is located to 10-18 layers, and the number of anode ear per layer is 1, set the ambient temperature to 25°C, charge the battery first, and then let it stand for 5 minutes. The charging process is: 6C 4.2V, 5C 4.32V, 3C 4.5V, then the battery was discharged and then left to stand for 5 minutes. The discharge process was: discharge from 0.7C to 3.0V. Finally, the test cycle numbers reached 300, 500, 700, 900 and 1100 respectively, and the lithium plating of the anode was measured after the battery was fully charged and disassembled.

[0070] Example 2

[0071] The electrode assembly is wound by the cathode electrode sheet, the anode electrode sheet and the isolation film. The number of winding layers of the cathode and anode electrodes is 28, that is, A=28, B=28, then 3≤N≤16, 1≤M≤16, 3≤K≤16, 1≤L≤16, take N=3, M=1, K=3, L=1, set the number of layers where the cathode ear is located to 10-18 layers, the number of cathode ear ears per layer is 3, the number of layers where the anode ear is located to 10-18 layers, the number of anode ear ears per layer is 3, set the ambient temperature to 25°C, charge the battery first, and then let it stand for 5 minutes. The charging process is: 6C 4.2V, 5C 4.32V, 3C 4.5V, then the battery was discharged and then left to stand for 5 minutes. The discharge process was: discharge from 0.7C to 3.0V. Finally, the test cycle numbers reached 300, 500, 700, 900 and 1100 respectively, and the lithium plating of the anode was measured after the battery was fully charged and disassembled.

[0072] Example 3

[0073] The electrode assembly is wound by the cathode electrode sheet, the anode electrode sheet and the isolation film. The number of winding layers of the cathode and anode electrodes is 28, that is, A=28, B=28, then 3≤N≤16, 1≤M≤16, 3≤K≤16, 1≤L≤16, take N=3, M=1, K=3, L=1, set the number of layers where the cathode ear is located to 6-22 layers, the number of cathode ear per layer is 1, the number of layers where the anode ear is located to 6-22 layers, the number of anode ear per layer is 1, set the ambient temperature to 25°C, charge the battery first, and then let it stand for 5 minutes. The charging process is: 6C 4.2V, 5C 4.32V, 3C 4.5V, then the battery was discharged and then left to stand for 5 minutes. The discharge process was: discharge from 0.7C to 3.0V. Finally, the test cycle numbers reached 300, 500, 700, 900 and 1100 respectively, and the lithium plating of the anode was measured after the battery was fully charged and disassembled.

[0074] Example 4

[0075] The electrode assembly is wound by the cathode electrode sheet, the anode electrode sheet and the isolation film. The number of winding layers of the cathode and anode electrodes is 28, that is, A=28, B=28, then 3≤N≤16, 1≤M≤16, 3≤K≤16, 1≤L≤16, take N=3, M=1, K=3, L=1, set the number of layers where the cathode electrode ear is located to 6-22 layers, the number of cathode electrode ear per layer is 1, the number of layers where the anode electrode ear is located to 10-18 layers, the number of anode electrode ear per layer is 1, set the ambient temperature to 25°C, first charge the battery, and then let it stand for 5 minutes. The charging process is: 6C 4.2V, 5C 4.32V, 3C 4.5V, then the battery was discharged and then left to stand for 5 minutes. The discharge process was: discharge from 0.7C to 3.0V. Finally, the test cycle numbers reached 300, 500, 700, 900 and 1100 respectively, and the lithium plating of the anode was measured after the battery was fully charged and disassembled.

[0076] Example 5

[0077] The electrode assembly is wound by the cathode electrode sheet, the anode electrode sheet and the isolation film. The number of winding layers of the cathode and anode electrodes is 28, that is, A=28, B=28, then 3≤N≤16, 1≤M≤16, 3≤K≤16, 1≤L≤16, take N=3, M=1, K=3, L=1, set the number of layers where the cathode ear is located to 10-18 layers, and the number of cathode ear per layer is 1, the number of layers where the anode ear is located to 6-22 layers, and the number of anode ear per layer is 1, set the ambient temperature to 25°C, first charge the battery, and then let it stand for 5 minutes. The charging process is: 6C 4.2V, 5C 4.32V, 3C 4.5V, then the battery was discharged and then left to stand for 5 minutes. The discharge process was: discharge from 0.7C to 3.0V. Finally, the test cycle numbers reached 300, 500, 700, 900 and 1100 respectively, and the lithium plating of the anode was measured after the battery was fully charged and disassembled.

[0078] Example 6

[0079] The electrode assembly is wound by the cathode electrode sheet, the anode electrode sheet and the isolation film. The number of winding layers of the cathode and anode electrodes is 28 layers, that is, A=28, B=28, then 3≤N≤16, 1≤M≤16, 3≤K≤16, 1≤L≤16, take N=3, M=1, K=3, L=1, set the number of layers where the cathode ear is located to 10-17 layers, and the number of cathode ear per layer is 1, the number of layers where the anode ear is located to 10-17 layers, and the number of anode ear per layer is 1, set the ambient temperature to 25°C, first charge the battery, and then let it stand for 5 minutes, where the charging process is: 6C 4.2V, 5C 4.32V, 3C 4.5V, then the battery was discharged and then left to stand for 5 minutes. The discharge process was: discharge from 0.7C to 3.0V. Finally, the test cycle numbers reached 300, 500, 700, 900 and 1100 respectively, and the lithium plating of the anode was measured after the battery was fully charged and disassembled.

[0080] Example 7

[0081] The electrode assembly is wound by the cathode electrode sheet, the anode electrode sheet and the isolation film. The number of winding layers of the cathode and anode electrodes is 28, that is, A=28, B=28, then 3≤N≤16, 1≤M≤16, 3≤K≤16, 1≤L≤16, take N=3, M=1, K=3, L=1, set the number of layers where the cathode ear is located to 14-21 layers, and the number of cathode ear per layer is 1, the number of layers where the anode ear is located to 14-21 layers, and the number of anode ear per layer is 1, set the ambient temperature to 25°C, first charge the battery, and then let it stand for 5 minutes, where the charging process is: 6C 4.2V, 5C 4.32V, 3C 4.5V, then the battery was discharged and then left to stand for 5 minutes. The discharge process was: discharge from 0.7C to 3.0V. Finally, the test cycle numbers reached 300, 500, 700, 900 and 1100 respectively, and the lithium plating of the anode was measured after the battery was fully charged and disassembled.

[0082] Example 8

[0083] The electrode assembly is wound by the cathode electrode sheet, the anode electrode sheet and the isolation film. The number of winding layers of the cathode and anode electrodes is 28, that is, A=28, B=28, then 3≤N≤16, 1≤M≤16, 3≤K≤16, 1≤L≤16, take N=3, M=1, K=3, L=1, set the number of layers where the cathode ear is located to 4-27 layers, the number of cathode ear per layer is 1, the number of layers where the anode ear is located to 4-27 layers, the number of anode ear per layer is 1, set the ambient temperature to 25°C, first charge the battery, and then let it stand for 5 minutes. The charging process is: 6C 4.2V, 5C 4.32V, 3C 4.5V, then the battery was discharged and then left to stand for 5 minutes. The discharge process was: discharge from 0.7C to 3.0V. Finally, the test cycle numbers reached 300, 500, 700, 900 and 1100 respectively, and the lithium plating of the anode was measured after the battery was fully charged and disassembled.

[0084] Example 9

[0085] The electrode assembly is wound by the cathode electrode sheet, the anode electrode sheet and the isolation film. The number of winding layers of the cathode and anode electrodes is 28, that is, A=28, B=28, then 3≤N≤16, 1≤M≤16, 3≤K≤16, 1≤L≤16, take N=3, M=1, K=3, L=1, set the number of layers where the cathode electrode ear is located to 4-27 layers, the number of cathode electrode ear per layer is 1, the number of layers where the anode electrode ear is located to 10-18 layers, the number of anode electrode ear per layer is 1, set the ambient temperature to 25°C, first charge the battery, and then let it stand for 5 minutes. The charging process is: 6C 4.2V, 5C 4.32V, 3C 4.5V, then the battery was discharged and then left to stand for 5 minutes. The discharge process was: discharge from 0.7C to 3.0V. Finally, the test cycle numbers reached 300, 500, 700, 900 and 1100 respectively, and the lithium plating of the anode was measured after the battery was fully charged and disassembled.

[0086] The experimental results are shown in the following table:

[0087]

[0088] It can be seen from the test data in the table that: in comparative examples 1-5, when the number of cycles of the battery is 500 or 700, slight lithium deposition will occur, but in embodiments 1-9, when the number of cycles of the battery is 500 or 700, no lithium deposition will occur, indicating that when the number of cycles of the battery is between 300-500, embodiments 1-9 are more conducive to slow lithium deposition than comparative examples 1-5; in comparative examples 1-5, when the number of cycles of the battery is 900, slight or moderate lithium deposition will occur, and in embodiments 1, 2 and embodiment 7, when the number of cycles of the battery is 900, no lithium deposition will occur, indicating that when the number of cycles of the battery is 900, the technical scheme of the embodiment has a mitigating effect on reducing lithium deposition.

[0089] In the embodiment of the present application, an electrode assembly and a plurality of first pole tabs are provided. The electrode assembly includes a first pole piece, a second pole piece and a diaphragm, the diaphragm is provided between the first pole piece and the second pole piece, the first pole piece, the diaphragm and the second pole piece are stacked and wound, and one end of the plurality of first pole tabs is connected to the area of ​​the first pole piece other than the first inner layer and the first outer layer, wherein, along the direction of the starting layer of the first pole piece to the ending layer, starting from the starting layer of the first pole piece and ending at the Nth layer, wherein each layer together constitutes the first inner layer; along the direction of the ending layer of the first pole piece to the starting layer, starting from the ending layer of the first pole piece and ending at the Mth layer, wherein each layer together constitutes the first outer layer, wherein M≥1, 3≤N≤0.6A, N is an integer, and A is the total number of layers of the first pole piece, and by setting the distribution position of the plurality of first pole tabs, the electromotive force at the first inner layer and the first outer layer of the first pole piece during the charging and discharging of the electrochemical device is reduced, and the local lithium insertion rate is reduced, thereby achieving the effect of reducing the lithium deposition of the battery.

[0090] The present application also provides an embodiment of a battery module, wherein the battery module includes the electrochemical device as described above. The function and structure of the electrochemical device can be referred to the above embodiments, and will not be described in detail here.

[0091] The present application also provides an embodiment of an electric device, which includes the battery module as described above. The function and structure of the battery module can be found in the above embodiments, and will not be described in detail here.

[0092] The above descriptions are merely embodiments of the present application and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. An electrochemical device, comprising an electrode assembly, wherein the electrode assembly comprises a first electrode sheet, a second electrode sheet and a diaphragm, wherein the diaphragm is disposed between the first electrode sheet and the second electrode sheet, and the first electrode sheet, the diaphragm and the second electrode sheet are stacked and wound, characterized in that: A plurality of first pole ears are arranged on the first pole sheet, and the plurality of first pole ears are connected to the area of ​​the first pole sheet excluding the first inner layer and the first outer layer; wherein, along the direction from the starting layer to the ending layer of the first pole sheet, starting from the starting layer of the first pole sheet and ending at the Nth layer, each layer together constitutes the first inner layer; along the direction from the ending layer to the starting layer of the first pole sheet, starting from the ending layer of the first pole sheet and ending at the Mth layer, each layer together constitutes the first outer layer; wherein, M≥1, 3≤N≤0.6A, N is an integer, and A is the total number of layers of the first pole sheet.

2. The electrochemical device according to claim 1, characterized in that The first pole piece includes a first current collector, the plurality of first pole tabs are extended from one side of the first current collector, and the plurality of first pole tabs are integrally formed with the first current collector.

3. The electrochemical device according to claim 1, characterized in that A plurality of second pole ears are arranged on the second pole piece, and the plurality of second pole ears are connected to the area of ​​the second pole piece excluding the second inner layer and the second outer layer; wherein, along the direction from the starting layer to the ending layer of the second pole piece, starting from the starting layer of the second pole piece and ending at the Kth layer, each layer together constitutes the second inner layer; along the direction from the ending layer to the starting layer of the second pole piece, starting from the ending layer of the second pole piece and ending at the Lth layer, each layer together constitutes the second outer layer; wherein, L≥1, K≥3.

4. The electrochemical device according to claim 3, characterized in that The second pole piece includes a second current collector, the plurality of second pole tabs are extended from one side of the second current collector, and the plurality of second pole tabs are integrally formed with the second current collector.

5. The electrochemical device according to claim 1, characterized in that The first outer layer satisfies the following condition: 1≤M≤0.6A, where M is an integer.

6. The electrochemical device according to claim 1, characterized in that At least one first pole lug is connected to other layers of the first pole sheet except the first inner layer and the first outer layer.

7. The electrochemical device according to claim 6, characterized in that The number of first pole tabs connected to each layer of the first pole sheet except the first inner layer and the first outer layer is no more than 5.

8. The electrochemical device according to any one of claims 1 to 7, characterized in that: The total number of layers A of the first pole piece is 5 to 80 layers.

9. The electrochemical device according to claim 3, characterized in that The second inner layer satisfies the following condition: 3≤K≤0.6B, where K is an integer and B is the total number of layers of the second pole piece.

10. The electrochemical device according to claim 3, characterized in that The second outer layer satisfies the following condition: 1≤L≤0.6B, where L is an integer and B is the total number of layers of the second pole piece.

11. The electrochemical device according to claim 1, characterized in that At least one second pole lug is connected to the other layers of the second pole sheet except the second inner layer and the second outer layer.

12. The electrochemical device according to claim 11, characterized in that The number of the second pole tabs connected to each layer of the second pole sheet except the second inner layer and the second outer layer is no more than 5.

13. The electrochemical device according to any one of claims 9 to 12, characterized in that: The total number of layers B of the second pole piece is 5 to 80 layers.

14. A battery module, characterized in that: An electrochemical device comprising any one of 1-13.

15. An electrical device, characterized in that: Comprising the battery module as claimed in claim 14.

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