CN116888793A

CN116888793A - Electrochemical device and electronic apparatus

Info

Publication number: CN116888793A
Application number: CN202280010466.2A
Authority: CN
Inventors: 郝慧; 黄矗; 尤裕哲; 林森
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2022-10-26
Filing date: 2022-10-26
Publication date: 2023-10-13
Also published as: WO2024087068A1

Abstract

The application discloses an electrochemical device, which comprises a shell, a first electrode assembly and a second electrode assembly. The first electrode assembly comprises a first pole piece assembly, a first pole lug and a third pole lug, wherein the first pole piece assembly comprises a first negative pole piece, and the graphitization degree of a first negative pole active material of the first negative pole piece is G1. The second electrode assembly comprises a second electrode plate assembly, a second electrode lug and a fourth electrode lug, the second electrode plate assembly comprises a second negative electrode plate, the graphitization degree of a second negative electrode active material of the second negative electrode plate is G2, and G2-G1 is more than or equal to 0.5%. The first electrode lug and the second electrode lug have the same polarity and are electrically connected in the shell. The electrochemical device provided by the application has high energy density and quick charge performance, and simultaneously has excellent structural stability, so that the risk of internal short circuit is reduced.

Description

Electrochemical device and electronic apparatus

Technical Field

The present application relates to the field of battery technologies, and in particular, to an electrochemical device and an electronic apparatus.

Background

With the development of technology, electronic products such as mobile phones, notebook computers, unmanned aerial vehicles and the like greatly enrich the daily life of people. Lithium ion batteries are also widely used in electronic products by virtue of their high energy density, high operating voltage, long service life, and the like. However, with the diversification of application scenes, there is a need for lithium ion batteries having excellent combination properties such as high energy density, fast charge performance, and high structural stability.

Disclosure of Invention

The present application aims to provide an electrochemical device and an electronic apparatus, which can at least improve the structural stability of the electrochemical device while simultaneously achieving high energy density and fast charge performance of the electrochemical device.

In a first aspect, the present application provides an electrochemical device comprising a case, a first electrode assembly, and a second electrode assembly. The first electrode assembly comprises a first electrode plate assembly, a first electrode lug and a third electrode lug, wherein the first electrode lug and the third electrode lug are connected with the first electrode plate assembly, the first electrode plate assembly is contained in the shell, the first electrode plate assembly comprises a first negative electrode plate, the first negative electrode plate comprises a first negative electrode active material, and the graphitization degree of the first negative electrode active material is G1. The second electrode assembly comprises a second electrode plate assembly, a second lug and a fourth lug, wherein the second lug and the fourth lug are connected with the second electrode plate assembly, the second electrode plate assembly is accommodated in the shell, the second electrode plate assembly comprises a second negative electrode plate, the second negative electrode plate comprises a second negative electrode active material, the graphitization degree of the second negative electrode active material is G2, and the requirements are met: G2-G1 is more than or equal to 0.5 percent. The first tab and the second tab have the same polarity, the third tab and the fourth tab have the same polarity, and the first tab and the second tab are electrically connected in the housing.

In the above technical solution, the graphitization degree G1 of the first negative electrode active material of the first electrode assembly is smaller than the graphitization degree G2 of the second negative electrode active material of the second electrode assembly, so that the first electrode assembly has a larger maximum charge-discharge rate, that is, the first electrode assembly can be used as a fast charge system, and the second electrode assembly can be used as a slow charge system. The quick charge system can meet the emergency charge requirement under emergency conditions and the high-rate discharge requirement under high-rate application; the slow charge system can meet the conventional use and ensure that the electrochemical device has higher capacity. And the first pole piece component and the second pole piece component are accommodated in the same shell, and when the first electrode component performs high-rate charge and discharge, the local temperature rise of the electrochemical device can be effectively reduced, so that the safety of the electrochemical device is improved. In addition, the first tab and the second tab are electrically connected in the shell, and when external impact is applied to the first tab and the second tab, dislocation and play between the first tab component and the second tab component can be restrained, so that the stability of the internal structure of the electrochemical device is improved, and the risk of internal short circuit is reduced; meanwhile, compared with the connection outside the shell, the lead wire for connection is reduced, the space is saved, and the manufacturing cost can be reduced while the energy density of the electrochemical device is improved.

In some embodiments, the first electrode assembly is stacked with the second electrode assembly, and the projections of the first tab and the second tab at least partially overlap as viewed in the stacking direction of the first electrode assembly and the second electrode assembly. At this time, the first tab and the second tab can be electrically connected in the accommodating cavity of the housing.

In some embodiments, the first electrode assembly includes a plurality of the first tabs, the second electrode assembly includes a plurality of the second tabs, and the electrochemical device further includes a first transfer tab connected with the plurality of the first tabs and the plurality of the second tabs in the case and extending out of the case. The polarity is led out through the first transfer tab, so that the occupied space of the first tab and the second tab can be reduced, and the energy density of the electrochemical device can be improved; meanwhile, the first transfer tab can be used as a positive electrode or a negative electrode contact point when the electrochemical device is charged and discharged, so that the electrochemical device can be connected with an external circuit conveniently.

In some embodiments, the first electrode assembly includes a plurality of the third tabs, the second electrode assembly includes a plurality of the fourth tabs, the electrochemical device further includes a second switching tab and a third switching tab, the second switching tab and the third tabs are connected in the case and extend out of the case, and the third switching tab and the fourth tabs are connected in the case and extend out of the case. The structure design can reduce the space occupied by the third lug and the fourth lug, thereby improving the energy density of the electrochemical device.

In some embodiments, the first pole piece assembly is selected from a lamination stack or a winding structure.

In some embodiments, the second pole piece assembly is selected from a lamination stack or a winding structure.

In some embodiments, the first electrode assembly has an internal resistance of R1 and the second electrode assembly has an internal resistance of R2, satisfying R1< R2.

In some embodiments, the electrochemical device satisfies: g1 is less than or equal to 95 percent, and/or G2 is more than or equal to 95.5 percent. Further, the electrochemical device satisfies: g1 is more than or equal to 94% and less than or equal to 95%; and/or G2 is more than or equal to 95.5% and less than or equal to 96.5%.

In some embodiments, the electrochemical device further comprises a first connection member connecting the first and second pole piece assemblies. At this time, can make the connection between first pole piece subassembly and the second pole piece subassembly fixed, inhibit dislocation drunkenness between the two, improve electrochemical device inner structure's stability.

In some embodiments, the first connection member includes a first bond, a second bond, and a third bond. The first bonding part and the third bonding part are oppositely arranged at two ends of the second bonding part, and the first pole piece component and the second pole piece component are positioned between the first bonding part and the third bonding part. At this time, the connection fixing effect between the first pole piece component and the second pole piece component can be improved.

In some embodiments, the first electrode assembly includes a first surface, a second surface, and a third surface connected, the first surface and the third surface being disposed opposite each other in a lamination direction of the first electrode assembly and the second electrode assembly, the second surface being connected between the first surface and the third surface. The second electrode assembly includes a fourth surface, a fifth surface, and a sixth surface connected to each other, the fourth surface and the sixth surface being disposed opposite to each other in a lamination direction of the first electrode assembly and the second electrode assembly, the fifth surface being connected between the fourth surface and the sixth surface. The first bonding part is bonded to the first surface, the second bonding part is bonded to the second surface and the fifth surface, and the third bonding part is bonded to the sixth surface. The first connecting component adopts the bending connecting structure, so that dislocation and play between the first pole piece component and the second pole piece component can be restrained, and the stability of the internal structure of the electrochemical device is improved.

In some embodiments, the first pole piece assembly comprises a first diaphragm and the second pole piece assembly comprises a second diaphragm, and the first pole piece assembly and the second pole piece assembly are connected through the first diaphragm and the second diaphragm. Through the mode that first diaphragm and second diaphragm are connected for connect fixedly between first pole piece subassembly and the second pole piece subassembly, do not need extra coupling assembling, can save space, in order to improve electrochemical device's energy density.

In some embodiments, a second connecting component is disposed between the first pole piece assembly and the second pole piece assembly, and the first pole piece assembly and the second pole piece assembly are connected by the second connecting component. The second connecting part is positioned between the first pole piece component and the second pole piece component, so that dislocation and play between the first pole piece component and the second pole piece component can be well restrained, and the risk of internal short circuit can be reduced.

In some embodiments, the adhesive strength between the first pole piece assembly and the second pole piece assembly is F, satisfying: f is more than or equal to 5N/m. At this time, the connection stability between the first electrode assembly and the second electrode assembly is good, and the dislocation and play between the two can be better restrained.

In some embodiments, the first pole piece assembly is a lamination structure, the first separator includes a first Z-fold and a first winding, the first pole piece assembly further includes a first positive pole piece, the first Z-fold is disposed between adjacent first positive pole piece and first negative pole piece, and the first winding is wound on an outer ring of the lamination structure. By adopting the first diaphragm comprising the first Z-shaped folding part and the first winding part, dislocation and play between the first positive pole piece and the first negative pole piece can be well restrained, so that the risk of internal short circuit is reduced.

In some embodiments, the second separator comprises a second Z-fold and a second winding, the second separator further comprises a second positive pole piece, the second Z-fold is disposed between adjacent second positive pole piece and second negative pole piece, and the second winding is wound around an outer ring of the lamination. By adopting the second diaphragm comprising the second Z-shaped folding part and the second winding part, dislocation and play between the second positive pole piece and the second negative pole piece can be well restrained, so that the risk of internal short circuit is reduced.

In some embodiments, the first separator and the second separator each independently comprise a substrate layer, an optional ceramic layer, and an optional bonding layer.

In some embodiments, the substrate layer comprises at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide.

In some embodiments, the ceramic layer is located on a surface of the substrate layer.

In some embodiments, the ceramic layer includes inorganic particles and a binder.

In some embodiments, the inorganic particles comprise at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate.

In some embodiments, the binder comprises at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, an acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polytetrafluoroethylene, or polyhexafluoropropylene.

In some embodiments, the bonding layer is located on a surface of the substrate layer and/or the ceramic layer.

In some embodiments, the tie layer comprises at least one of a polyamide, a polyacrylonitrile, an acrylate polymer, a polyacrylic acid, a polyacrylate, a polyvinylpyrrolidone, a polyvinyl ether, a polyvinylidene fluoride, or a copolymer of vinylidene fluoride-hexafluoropropylene.

In some embodiments, the electrochemical device includes at least two first electrode assemblies and at least one second electrode assembly, the second electrode assembly being disposed between two adjacent first electrode assemblies. The first electrode assembly is a quick-charging system, the second electrode assembly is arranged between the first electrode assemblies of the quick-charging system, and when the high-rate charging and discharging are carried out through the first electrode assembly, the diffusion of heat of the first electrode assembly of the quick-charging system can be facilitated, so that the local temperature rise of the electrochemical device is reduced, and the safety of the electrochemical device is improved. Or the electrochemical device comprises at least one first electrode assembly and at least two second electrode assemblies, and the first electrode assembly is arranged between two adjacent second electrode assemblies. The first electrode component of the quick charge system is arranged in the middle, which is beneficial to the diffusion of heat generated by the electrode component of the quick charge system to the left and right sides.

In a second aspect, the application also proposes an electronic device comprising an electrochemical apparatus as described in any one of the above.

Drawings

One or more embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements, and in which the figures of the drawings are not to scale, unless expressly stated otherwise.

Fig. 1 is a schematic view illustrating the structure of an electrochemical device according to some embodiments of the present application;

fig. 2 is an exploded view of an electrochemical device according to some embodiments of the present application;

FIG. 3 is a schematic illustration of the structure of a first pole piece assembly and a second pole piece assembly according to some embodiments of the present application;

FIG. 4 is a schematic view of a winding structure of a first pole piece assembly according to some embodiments of the present application;

fig. 5 is a schematic structural diagram of a first negative electrode tab according to some embodiments of the present application;

FIG. 6 is a schematic diagram of a lamination of a first electrode assembly and a second electrode assembly according to some embodiments of the present application;

fig. 7 is an exploded view of an electrochemical device according to some embodiments of the present application;

FIG. 8 is a schematic view of a first connecting member connecting a first pole piece assembly and a second pole piece assembly according to some embodiments of the present application;

FIG. 9 is a schematic view of a first connecting member connecting a first pole piece assembly and a second pole piece assembly according to some embodiments of the present application

FIG. 10 is a schematic illustration of the structure of a first pole piece assembly and a second pole piece assembly according to some embodiments of the present application;

FIG. 11 is a schematic illustration of the structure of a first pole piece assembly and a second pole piece assembly according to some embodiments of the present application;

fig. 12 is an exploded view of an electrochemical device according to some embodiments of the present application.

Reference numerals illustrate:

100. an electrochemical device;

10. a housing; 11. a first housing; 111. a first cavity; 12. a second housing;

20. a first electrode assembly; 21. a first pole piece assembly; 211. a first positive electrode sheet; 212. a first negative electrode tab; 2121. a first negative electrode current collector; 2122. a first anode active layer; 213. a first diaphragm; 2131. a first Z-shaped fold; 2132. a first winding section; 22. a first tab; 23. a third ear; 24. a first surface; 25. a second surface; 26. a third surface; 27. a first single-sided positive electrode sheet;

30. a second electrode assembly; 31. a second pole piece assembly; 311. a second positive electrode sheet; 312. a second negative electrode tab; 313. a second diaphragm; 3131. a second Z-shaped folded portion; 3132. a second winding section; 32. a second lug; 33. a fourth ear; 34. a fourth surface; 35. a fifth surface; 36. a sixth surface; 37. a second single-sided positive pole piece;

40. A first switching tab;

50. the second switching lug;

60. a third switching tab;

70. a first connecting member; 71. a first adhesive part; 72. a second adhesive portion; 73. a third adhesive part;

80. and a second connection member.

Detailed Description

Embodiments of the technical scheme of the present application will be described in detail below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present application, and thus are merely examples, and are not intended to limit the scope of the present application.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having" and any variations thereof in the description of the application and the claims and the description of the drawings above are intended to cover a non-exclusive inclusion.

In the description of embodiments of the present application, the technical terms "first," "second," and the like are used merely to distinguish between different objects and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated, a particular order or a primary or secondary relationship. In the description of the embodiments of the present application, the meaning of "plurality" is two or more unless explicitly defined otherwise.

In the description of the embodiments of the present application, the term "and/or" is merely an association relationship describing an association object, and indicates that three relationships may exist, for example, a and/or B may indicate: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

In a first aspect, embodiments of the present application provide an electrochemical device 100, the electrochemical device 100 being a site for specific electrical energy and chemical energy conversion. Referring to fig. 1 and 2, the electrochemical device 100 includes a case 10, a first electrode assembly 20, and a second electrode assembly 30.

With respect to the case 10, the case 10 is used to package the first electrode assembly 20 and the second electrode assembly 30. Referring to fig. 1 and 2, the case 10 encloses a receiving chamber (not shown) in which the first electrode assembly 20 and the second electrode assembly 30 can be received. Alternatively, the housing 10 has a square structure as a whole, and the thickness of each side wall of the housing 10 may be set to 40 micrometers to 200 micrometers; the housing 10 includes a first housing 11 and a second housing 12, the first housing 11 is concavely provided with a first cavity 111, the second housing 12 is concavely provided with a second cavity (not shown in the drawings), the first housing 11 is spliced with the second housing 12 and edges of the first housing 11 and the second housing 12 are heat-sealed, so that the first housing 11 and the second housing 12 are connected as the housing 10, wherein the first cavity 111 communicates with the second cavity to form a receiving cavity. The case 10 may be a multi-layer composite film containing a metal layer or a stainless steel case, for example, an aluminum plastic film containing a PP layer and an aluminum layer laminated structure, so as to sufficiently increase the energy density of the electrochemical device 100 on the premise of playing a packaging role.

For the first electrode assembly 20, referring to fig. 2, the first electrode assembly 20 includes a first electrode tab assembly 21, a first electrode tab 22 and a third electrode tab 23.

For the first pole piece assembly 21 described above, referring to fig. 3 and 4, the first pole piece assembly 21 includes a first positive pole piece 211, a first negative pole piece 212, and a first separator 213. The first pole piece assembly 21 may be stacked using a lamination structure, that is, the first positive pole piece 211, the first separator 213, and the first negative pole piece 212, and fig. 3 illustrates the stacked structure of the first pole piece assembly 21. The first pole piece assembly 21 may also adopt a winding structure, that is, the first positive pole piece 211, the first separator 213, and the first negative pole piece 212 are laminated and wound to form, and fig. 4 shows the winding structure of the first pole piece assembly 21. Referring further to fig. 5, the first negative electrode tab 212 includes a first negative electrode current collector 2121 and a first negative electrode active layer 2122, and the first negative electrode active layer 2122 is coated on at least one surface of the first negative electrode current collector 2121. The first anode active layer 2122 includes a first anode active material, a binder, and optionally a conductive agent, etc., wherein the first anode active material includes graphite, and the degree of graphitization of the first anode active material is G1.

For the first tab 22 and the third tab 23, referring to fig. 2 and 3, the first tab 22 and the third tab 23 are connected to the first pole piece assembly 21, the first tab 22 and the third tab 23 are metal conductors for leading out the positive and negative poles of the first pole piece assembly 21, for example, the first tab 22 is connected to the first negative pole piece 212, and the second tab 32 is connected to the first positive pole piece 211; in other embodiments, the first tab 22 may be further connected to the first positive electrode tab 211, and the second tab 32 is connected to the first negative electrode tab 212.

For the second electrode assembly 30, referring to fig. 2, the second electrode assembly 30 includes a second electrode tab assembly 31, a second electrode tab 32, and a fourth electrode tab 33.

For the second electrode assembly 31, referring to fig. 3, the second electrode assembly 31 includes a second positive electrode tab 311, a second negative electrode tab 312, and a second separator 313. The second electrode sheet assembly 31 may adopt a lamination structure, that is, the second positive electrode sheet 311, the second separator 313 and the second negative electrode sheet 312 are stacked; the second electrode sheet assembly 31 may also adopt a winding structure, that is, the second positive electrode sheet 311, the second separator 313, and the second negative electrode sheet 312 are stacked and wound to form. The second negative electrode tab 312 includes a second negative electrode current collector (not shown in the drawing) and a second negative electrode active layer (not shown in the drawing) coated on at least one surface of the second negative electrode current collector. The second anode active layer includes a second anode active material, a binder, an optional conductive agent, and the like; wherein the second negative electrode active material comprises graphite, and the graphitization degree of the second negative electrode active material is G2, wherein G2-G1 is more than or equal to 0.5%.

The lower the graphitization degree of the negative electrode active material, the higher the maximum charge-discharge rate setting of the corresponding electrode assembly can be, and therefore, in the electrochemical device 100 of the present application, the maximum charge-discharge rate (the maximum charge-discharge rate acceptable to the electrode assembly, for example, the maximum charge rate does not cause precipitation of lithium) of the first electrode assembly 20 can be set to be greater than the maximum charge-discharge rate of the second electrode assembly 30, that is, the first electrode assembly 20 is a fast charge system, the second electrode assembly 30 is a slow charge system, and the fast charge system can meet the emergency charge requirement in the emergency case and the large-rate discharge requirement in the large-rate application, but the capacity in the full charge state is generally lower; the slow charge system can satisfy the conventional use and can increase the capacity of the electrochemical device 100 as a whole. For example, the maximum charge rate of the first electrode assembly 20 is > 2C, the full charge capacity is less than or equal to 2000mAh, and the rapid charging system part can be charged in emergency, so as to meet the emergency requirement; the maximum charge rate of the second electrode assembly 30 is less than or equal to 2C, the full charge capacity is less than or equal to 3000mAh, and the electrochemical device 100 can be ensured to have a high capacity as a whole in the case of satisfying the conventional use. In addition, the first electrode assembly 21 and the second electrode assembly 31 are housed in the same case 10, and when the first electrode assembly 20 is charged and discharged at a high rate, the local temperature rise of the electrochemical device 100 can be effectively reduced, thereby improving the safety of the electrochemical device 100.

Specifically, in some embodiments, the graphitization degree G1 of the first negative electrode active material is less than or equal to 95%, and/or the graphitization degree G2 of the second negative electrode active material is less than or equal to 95.5%; further, the graphitization degree G1 of the first anode active material satisfies: 94% or more and 95% or less of G1, and/or the graphitization degree G2 of the second anode active material satisfies: g2 is more than or equal to 95.5 percent and less than or equal to 96.5 percent.

For the second tab 32 and the fourth tab 33, referring to fig. 2 and 3, the second tab 32 and the fourth tab 33 are connected to the second tab assembly 31, the second tab 32 and the fourth tab 33 are metal conductors for leading out the positive and negative poles of the second tab assembly 31, for example, the second tab 32 is connected to the second negative pole piece 312, and the fourth tab 33 is connected to the second positive pole piece 311; in other embodiments, the second tab 32 may be further connected to the second positive electrode tab 311, and the fourth tab 33 is connected to the second negative electrode tab 312.

The polarities of the first tab 22 and the second tab 32 are the same, and the polarities of the third tab 23 and the fourth tab 33 are the same, for example, the first tab 22 and the second tab 32 are both negative tabs; alternatively, the first tab 22 and the second tab 32 are both positive pole pieces. The first tab 22 and the second tab 32 are electrically connected in the accommodating cavity of the housing 10. The first tab 22 and the second tab 32 are electrically connected in the housing cavity of the case 10, and when external impact is applied, the dislocation movement between the first tab assembly 21 and the second tab assembly 31 can be suppressed, so that the stability of the internal structure of the electrochemical device 100 is improved, and the risk of internal short circuit is reduced, compared with external connection of the case 10.

Specifically, as shown in fig. 2, the first electrode assembly 20 is stacked under the second electrode assembly 30, the first tab 22 and the third tab 23 are disposed near the upper edge of the first electrode assembly 20, and the second tab 32 and the fourth tab 33 are disposed near the lower edge of the second electrode assembly 30, so that the first tab 22 and the second tab 32 are stacked and connected.

In some embodiments, referring to fig. 6, the first electrode assembly 20 and the second electrode assembly 30 are stacked, and the projections of the first tab 22 and the second tab 32 at least partially overlap when viewed along the stacking direction of the first electrode assembly 20 and the second electrode assembly 30. This structure can facilitate the connection of the first tab 22 and the second tab 32 in the accommodating cavity of the housing 10. For example, the laser welding is used to weld the laminate of the first tab 22 and the second tab 32 together in the lamination direction of the first electrode assembly 20 and the second electrode assembly 30, so that the stability of the connection of the first electrode assembly 20 and the second electrode assembly 30 can be improved.

In some embodiments, referring to fig. 1 and 7, the first electrode assembly 20 includes a plurality of first tabs 22, the second electrode assembly 30 includes a plurality of second tabs 32, and the electrochemical device 100 further includes a first switching tab 40. One end of the first switching tab 40 is disposed in the accommodating cavity of the housing 10 and connected to the first tabs 22 and the second tabs 32, and the other end of the first switching tab 40 extends out of the housing 10. The polarities of the first tab 22 and the second tab 32 are the same, and the polarities are led out through the first switching tab 40, so that the space occupied by the first tab 22 and the second tab 32 can be reduced, and the energy density of the electrochemical device 100 can be improved; meanwhile, the first tab 40 may serve as a positive or negative contact point when the electrochemical device 100 is charged and discharged, so as to facilitate connection of the electrochemical device 100 to an external circuit.

Alternatively, referring to fig. 1 and 7, the first electrode assembly 20 includes a plurality of third tabs 23, the second electrode assembly 30 includes a plurality of fourth tabs 33, and the electrochemical device 100 further includes a second switching tab 50 and a third switching tab 60. One end of the second switching tab 50 is connected with the third tabs 23 in the accommodating cavity of the housing 10, and the other end of the second switching tab 50 extends out of the housing 10 to serve as a contact point for connection with an external circuit. One end of the third switching tab 60 is connected to the plurality of fourth tabs 33 in the accommodating cavity of the housing 10, and the other end of the third switching tab 60 extends out of the housing 10 to serve as a contact point for connection with an external circuit. In the present embodiment, the space occupied by the third tab 23 and the fourth tab 33 can be reduced by such a structural design, so that the energy density of the electrochemical device 100 can be improved.

In some embodiments, the first switching tab 40 is welded to the first tabs 22 and the second tabs 32, the second switching tab 50 is welded to the third tabs 23, and the third switching tab 60 is welded to the fourth tabs 33.

In some embodiments, the internal resistance of the first electrode assembly 20 is R1, and the internal resistance of the second electrode assembly 30 is R2, satisfying R1< R2. Optionally, R2-R1 is less than or equal to 30mΩ. The fast charge requirement is satisfied by setting the internal resistance of the first electrode assembly 20 to be smaller than the internal resistance of the second electrode assembly 30 in order to increase the current through the first electrode assembly 20.

In order to further fix the first electrode assembly 20 to the second electrode assembly 30, referring to fig. 8, in an embodiment of the present application, the electrochemical device 100 further includes a first connection member 70, and the first connection member 70 connects the first electrode assembly 21 and the second electrode assembly 31 to fix the first electrode assembly 21 to the second electrode assembly 31, thereby preventing misalignment and play therebetween and reducing the risk of internal short circuit.

Alternatively, referring to fig. 8 and 9, the first connection member 70 includes a first adhesive portion 71, a second adhesive portion 72, and a third adhesive portion 73. The first bonding portion 71 and the third bonding portion 73 are disposed at opposite ends of the second bonding portion 72, and the first pole piece assembly 21 and the second pole piece assembly 31 are located between the first bonding portion 71 and the third bonding portion 73.

Specifically, referring to fig. 8 and 9, the first electrode assembly 21 includes a first surface 24, a second surface 25 and a third surface 26 that are connected, the first surface 24 and the third surface 26 are disposed opposite to each other along the lamination direction of the first electrode assembly 20 and the second electrode assembly 30, and the second surface 25 is connected between the first surface 24 and the third surface 26. The second electrode sheet member 31 includes a fourth surface 34, a fifth surface 35 and a sixth surface 36 connected, the fourth surface 34 and the sixth surface 36 being disposed opposite to each other in the lamination direction of the first electrode member 20 and the second electrode member 30, the fifth surface 35 being connected between the fourth surface 34 and the sixth surface 36. The first adhesive portion 71 is adhered to the first surface 24, the second adhesive portion 72 is adhered to the second surface 25 and the fifth surface 35, and the third adhesive portion 73 is adhered to the sixth surface 36. In this embodiment, the two ends of the first connecting member 70 are bent to form a U-shaped structure, so that the first bonding portion 71 bonds the first surface 24 of the first electrode assembly 20, the third bonding portion 73 bonds the sixth surface 36 of the second electrode assembly 30, and the second bonding portion 72 bonds the second surface 25 of the first electrode assembly 20 and the fourth surface 34 of the second electrode assembly 30, so that the first electrode assembly 20 and the second electrode assembly 30 are connected as a whole, and misalignment and play between the first pole piece assembly 21 and the second pole piece assembly 31 can be prevented, thereby improving the stability of connection. In this embodiment, the first connecting member 70 may be adhesive tape, and at this time, the thickness of the first connecting member 70 is relatively small, so that the space occupied by the first connecting member 70 can be reduced, thereby facilitating the improvement of the energy density of the electrochemical device 100.

In some embodiments, referring to fig. 3, a first membrane 213 is disposed on an end surface of the first pole piece assembly 21 facing the second pole piece assembly 31, a second membrane 313 is disposed on an end surface of the second pole piece assembly 31 facing the first pole piece assembly 21, and each of the first membrane 213 and the second membrane 313 independently includes a substrate layer, an optional ceramic layer, and an optional adhesive layer, and the first pole piece assembly 21 and the second pole piece assembly 31 are connected through the first membrane 213 and the second membrane 313. Specifically, the first membrane 213 and the second membrane 313 may be bonded between the first pole piece assembly 21 and the second pole piece assembly 31 by hot pressing. In this embodiment, the first pole piece assembly 21 and the second pole piece assembly 31 are bonded and connected through the first membrane 213 and the second membrane 313 by direct hot pressing, so that no additional bonding assembly is needed, and space can be saved, so as to improve the energy density of the electrochemical device 100. It will be appreciated that the first membrane 213 or the second membrane 313 of different materials and structures may provide different bonding forces during hot pressing, and in the embodiment of the present application, the first membrane 213 and the second membrane 313 of suitable materials and structures may be selected according to specific situations. In some embodiments, the substrate layer comprises at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. In some embodiments, the ceramic layer is located on the surface of the substrate layer. In some embodiments, the ceramic layer includes inorganic particles and a binder. In some embodiments, the inorganic particles comprise at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. In some embodiments, the binder comprises at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, an acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polytetrafluoroethylene, or polyhexafluoropropylene. In some embodiments, the bonding layer is located on the surface of the substrate layer and/or the ceramic layer, at which point the bonding layer may facilitate bonding of the first pole piece assembly 21 to the second pole piece assembly 31. In some embodiments, the tie layer comprises at least one of a polyamide, a polyacrylonitrile, an acrylate polymer, a polyacrylic acid, a polyacrylate, a polyvinylpyrrolidone, a polyvinyl ether, a polyvinylidene fluoride, or a copolymer of vinylidene fluoride-hexafluoropropylene.

Alternatively, referring to fig. 10, a second connecting member 80 is disposed between the first pole piece assembly 21 and the second pole piece assembly 31, and the first pole piece assembly 21 and the second pole piece assembly 31 are connected by the second connecting member 80. In this embodiment, the first pole piece assembly 21 and the second pole piece assembly 31 are connected by the second connecting component 80, and according to the requirement, the second connecting component 80 with different viscosity can be selected to bond the first pole piece assembly 21 and the second pole piece assembly 31, for example, adhesive tape with stronger viscosity is used to improve the bonding stability of the first pole piece assembly 21 and the second pole piece assembly 31.

In some embodiments, the adhesion force between the first pole piece assembly 21 and the second pole piece assembly 31 is F, satisfying: f is more than or equal to 5N. At this time, the connection stability between the first pole piece assembly 21 and the second pole piece assembly 31 is good, and the dislocation and play between the two can be better restrained.

Alternatively, referring to fig. 10 and 11, the first pole piece assembly 21 is a laminated structure, the first diaphragm 213 includes a first Z-shaped folded portion 2131 and a first winding portion 2132, the first pole piece assembly 21 includes a plurality of first positive pole pieces 211 and a plurality of first negative pole pieces 212, the first Z-shaped folded portion 2131 is disposed between adjacent first positive pole pieces 211 and first negative pole pieces 212 to isolate the adjacent first positive pole pieces 211 from the first negative pole pieces 212, and the first winding portion 2132 is wound around an outer ring of the laminated structure. With the first separator 213 including the first Z-shaped folded portion 2131 and the first wound portion 2132, misalignment play between the first positive electrode tab 211 and the first negative electrode tab 212 can be better suppressed, thereby reducing the risk of occurrence of an internal short circuit.

Further, the second separator 313 includes a second Z-shaped folded portion 3131 and a second winding portion 3132, the second separator 31 includes a plurality of second positive electrode pieces 311 and a plurality of second negative electrode pieces 312, the second Z-shaped folded portion 3131 is disposed between the adjacent second positive electrode pieces 311 and second negative electrode pieces 312 to isolate the adjacent second positive electrode pieces 311 from the second negative electrode pieces 312, and the second winding portion 3132 is wound around an outer ring of the laminated structure. With the second separator 313 including the second Z-shaped folded portion 3131 and the second wound portion 3132, misalignment play between the second positive electrode tab 311 and the second negative electrode tab 312 can be better suppressed, thereby reducing the risk of occurrence of an internal short circuit.

Referring to fig. 11, the outermost layer of the first pole piece assembly 21 is a first single-sided positive pole piece 27, that is, only one side of the first positive current collector of the outermost layer is coated with a positive active layer, and the positive active layer faces the inner layer of the first pole piece assembly 21; also, the outermost layer of the second electrode assembly 31 is the second single-sided positive electrode sheet 37, and this structure can fully utilize each active layer to increase the energy density of the electrochemical device 100.

According to some embodiments of the present application, there are at least two first electrode assemblies 20, at least one second electrode assembly 30, and a second electrode assembly 30 is disposed between two adjacent first electrode assemblies 20. The first electrode assemblies 20 are a fast charge system, and the second electrode assemblies 30 are disposed between the first electrode assemblies 20 of the fast charge system, so that heat diffusion of the first electrode assemblies 20 of the fast charge system can be facilitated when the first electrode assemblies 20 are charged and discharged at a high rate, thereby reducing local temperature rise of the electrochemical device 100 and improving safety of the electrochemical device 100. According to some embodiments of the present application, at least one first electrode assembly 20, at least two second electrode assemblies 30, and a first electrode assembly 20 disposed between two adjacent second electrode assemblies 30. The first electrode assembly 20 of the rapid charging system is disposed in the middle, and heat generated from the first electrode assembly 20 of the rapid charging system can be easily diffused to the left and right sides. For example, referring to fig. 12, there are two first electrode assemblies 20, and a second electrode assembly 30 is sandwiched between the two first electrode assemblies 20.

In the embodiment of the application, the lithium ion battery with three systems of fast charge, slow charge, fast charge and slow charge is taken as an example, and is subjected to charge and discharge test, graphitization degree test, drop test and bonding strength test.

Preparation of lithium ion batteries

Example 1

(1) Preparing a fast charge system and a slow charge system negative electrode plate: the quick charge system selects artificial graphite with the graphitization degree G1 of 94.8% as a negative electrode active material, the slow charge system selects artificial graphite with the graphitization degree G2 of 95.5% as a negative electrode active material, the negative electrode active material artificial graphite, a binder Styrene Butadiene Rubber (SBR) and a thickener sodium carboxymethyl cellulose (CMC) are mixed according to the weight ratio of 96:2:2, deionized water is added as a solvent, slurry with the solid content of 70wt% is prepared, and the slurry is uniformly stirred. And uniformly coating the slurry on one surface of a negative current collector copper foil with the thickness of 10 mu m, and drying to obtain the negative electrode plate with the negative electrode active layer coated on one side. And repeating the steps on the other surface of the negative current collector copper foil to obtain the negative electrode plate with the negative electrode active layer coated on both sides. After cold pressing, the negative pole piece is cut into the specification of 41mm multiplied by 61mm for standby.

(2) Preparing a positive electrode plate: the positive electrode active materials of lithium cobaltate (LiCoO 2), conductive carbon black (Super P) and polyvinylidene fluoride (PVDF) are mixed according to the weight ratio of 97.5:1.0:1.5, N-methyl pyrrolidone (NMP) is added as a solvent, and the mixture is prepared into slurry with the solid content of 75 weight percent and stirred uniformly. And uniformly coating the slurry on one surface of an aluminum foil of the positive electrode current collector with the thickness of 12 mu m, and drying to obtain the positive electrode plate with the single-sided coating of the positive electrode active layer. And repeating the steps on the other surface of the aluminum foil of the positive electrode current collector to obtain the positive electrode plate with the positive electrode active layer coated on both sides. After cold pressing, the positive pole piece is cut into the specification of 38mm multiplied by 58mm for standby.

(3) Preparation of electrolyte: in a dry argon atmosphere, firstly, mixing Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) according to a mass ratio EC:EMC: DEC=30:50:20 to form a basic organic solvent, and then adding lithium salt lithium hexafluorophosphate (LiPF 6) into the basic organic solvent to dissolve and uniformly mix to obtain an electrolyte with the mass concentration of LiPF6 of 12.5%.

(4) Preparation of a separation film: the porous polyethylene film is used as a substrate layer, and a ceramic layer containing alumina ceramic and PVDF binder is coated on one side surface of the substrate layer to be used as a diaphragm (CCS), wherein the mass percentage of the alumina ceramic in the ceramic layer is 95%.

(5) Preparation of fast-charge and slow-charge electrode assemblies: and Z-shaped folding the diaphragm is arranged between the laminated negative pole piece and positive pole piece, and the tail end of the diaphragm is wound and wrapped on the whole electrode assembly to form the electrode assembly with the laminated structure for later use.

(6) Assembly of fast-charge and slow-charge electrode assemblies: placing the aluminum-plastic film formed by punching the pits in an assembly fixture, placing the fast-charging system electrode assembly in the pits with the pits facing upwards, then placing the slow-charging system electrode assembly on the fast-charging system electrode assembly, enabling the edges to be aligned, applying external force to compress, wherein a plurality of negative electrode lugs of the fast-charging system electrode assembly and the slow-charging system electrode assembly are overlapped, welding the overlapped negative electrode lugs together through laser, leading out the overlapped negative electrode lugs, respectively welding a plurality of positive electrode lugs overlapped by the fast-charging system electrode assembly and a plurality of positive electrode lugs overlapped by the slow-charging system electrode assembly through laser, leading out the electrode lugs, covering the pit face of the aluminum-plastic film formed by punching the pits downwards on the slow-charging system electrode assembly, and heat-sealing the periphery in a hot-pressing mode to obtain the assembled electrode assembly.

(7) And (5) filling liquid and packaging: and (3) injecting electrolyte into the assembled electrode assembly, and performing vacuum packaging, standing, thermocompression forming, shaping and other procedures to obtain the lithium ion battery.

Example 2 differs from example 1 in that the fast charge system selects an artificial graphite having a graphitization degree G1 of 94.6% as the negative electrode active material. In the preparation of the isolating membrane, the mass percentage of the alumina ceramic in the ceramic layer is 90 percent.

Example 3 is different from example 1 in that an artificial graphite having a graphitization degree G1 of 94.4% is selected as the negative electrode active material for the fast charge system. In the preparation of the isolating membrane, the mass percentage of the alumina ceramic in the ceramic layer is 85 percent.

Example 4 differs from example 1 in that the fast charge system selects an artificial graphite having a graphitization degree G1 of 94.1% as the negative electrode active material; in the preparation of the isolating film, the mass percentage of the alumina ceramic in the ceramic layer is 40 Percent (PCCS).

Example 5 differs from example 1 in that the fast charge system selects an artificial graphite having a graphitization degree G1 of 94.1% as the negative electrode active material, and the slow charge system selects an artificial graphite having a graphitization degree G2 of 96.1% as the negative electrode active material; in the preparation of the release film, the ceramic layer was replaced with a tie layer (PCS) containing only PVDF.

Example 6 differs from example 3 in that the fast charge system selects an artificial graphite having a graphitization degree G1 of 94.0% as the negative electrode active material, and the slow charge system selects an artificial graphite having a graphitization degree G2 of 96.1% as the negative electrode active material. In the assembling step of the fast-charging system electrode assembly and the slow-charging system electrode assembly, firstly, bonding adhesive paper is used as a first connecting component, the fast-charging system electrode assembly and the slow-charging system electrode assembly are stacked and then bonded and fixed, and then the stacked fast-charging system electrode assembly and the slow-charging system electrode assembly are placed in a pit of an aluminum plastic film.

Example 7 differs from example 5 in that the fast charge system selects an artificial graphite having a graphitization degree G1 of 94.2% as the negative electrode active material, and the slow charge system selects an artificial graphite having a graphitization degree G2 of 96.2% as the negative electrode active material. In the assembling step of the fast-charging system electrode assembly and the slow-charging system electrode assembly, firstly, bonding adhesive paper is used as a first connecting component, the fast-charging system electrode assembly and the slow-charging system electrode assembly are stacked and then bonded and fixed, and then the stacked fast-charging system electrode assembly and the slow-charging system electrode assembly are placed in a pit of an aluminum plastic film.

Example 8 differs from example 2 in that the fast charge system selects an artificial graphite having a graphitization degree G1 of 94.5% as the negative electrode active material, and the slow charge system selects an artificial graphite having a graphitization degree G2 of 95.8% as the negative electrode active material. In the assembling steps of the fast-charging system electrode assembly and the slow-charging system electrode assembly, the fast-charging electrode assembly is further placed on the slow-charging system electrode assembly, and a fast-charging, slow-charging and fast-charging structure is formed.

Example 9 differs from example 1 in that the fast charge system selects an artificial graphite having a graphitization degree G1 of 94.3% as the negative electrode active material, and the slow charge system selects an artificial graphite having a graphitization degree G2 of 95.9% as the negative electrode active material. In the assembling step of the fast-charging system electrode assembly and the slow-charging system electrode assembly, bonding adhesive paper is used as a second connecting part, the bonding adhesive paper is arranged between the fast-charging system electrode assembly and the slow-charging system electrode assembly, and after stacking, the bonding adhesive paper is bonded and fixed to form a fast-charging structure, the slow-charging structure and the fast-charging structure are arranged in a pit of an aluminum plastic film.

Example 10 differs from example 7 in that the fast charge system selects an artificial graphite having a graphitization degree G1 of 94.6% as the negative electrode active material, and the slow charge system selects an artificial graphite having a graphitization degree G2 of 96.0% as the negative electrode active material. In the assembling steps of the fast charge system electrode assembly and the slow charge system electrode assembly, a fast charge, slow charge and fast charge structure is formed.

Example 11 differs from example 10 in that the fast charge system selects an artificial graphite having a graphitization degree G1 of 94.8% as the negative electrode active material, and the slow charge system selects an artificial graphite having a graphitization degree G2 of 95.7% as the negative electrode active material. In the assembling steps of the fast-charging system electrode assembly and the slow-charging system electrode assembly, a slow-charging, fast-charging and slow-charging structure is formed.

Comparative example 1 is different from example 1 in that in the assembling steps of the fast-charge system electrode assembly and the slow-charge system electrode assembly, a plurality of negative electrode tabs of the fast-charge system electrode assembly and a plurality of negative electrode tabs of the slow-charge system electrode assembly are each welded together by laser and each of the negative electrode tabs is led out through the respective transfer tabs.

Test method

And (3) quick temperature rise test: and (3) charging the electrode assembly of the quick-charging system, charging to 4.45V at a constant current of 10C multiplying power at 25 ℃, charging to 0.05C at a constant voltage, and monitoring the maximum temperature rise of the surface of the battery in the charging process.

And (3) testing slow charging temperature rise: and (3) charging the electrode assembly of the slow charging system, charging to 4.45V at a constant current with a 1C multiplying power at the temperature of 25 ℃, charging to 0.02C at a constant voltage, and monitoring the maximum temperature rise of the surface of the battery in the charging process.

Graphitization degree test: XRD testing was performed using a Brookfield tester, in which XRD reference standard is JIS K0131-1996 general rule of ray diffraction analysis method General rules of X-ray diffractometric analysis X. The mass ratio of the silicon powder to the graphite anode active material to be tested is 1:5. the target material is Cu K alpha, the voltage is 40KV, the current is 40mA, the scanning angle range is 52-58 degrees, the scanning step length is 0.008 degrees, and the time per step length is 0.3s.

Drop test: on the cement falling ground, the battery is dropped for 1 time along the 6 faces from the 1m falling height, and is dropped for 1 time at the 4 angles, and 5 rounds of tests are carried out in total; determination criteria: the width direction dislocation between the electrode assemblies is less than or equal to 0.2mm, and no dislocation is judged; the width direction dislocation between the electrode assemblies is more than 0.2mm and less than or equal to 0.5mm, and the slight dislocation is judged; the width direction dislocation between the electrode assemblies is more than 0.5mm and less than or equal to 1.0mm, and the middle dislocation is judged; the displacement in the width direction between the electrode assemblies was >1.0mm, and the displacement was determined as a heavy displacement.

And (3) adhesive strength test: (1) before testing, a power supply of the high-speed rail tension machine is turned on, whether an upper clamp and a lower clamp of the tension machine are in a horizontal position or not is confirmed, whether a tension rod can normally go up and down or not is confirmed, and the speed of the tension machine is controlled to be 50mm/min; (2) manufacturing a sample, and cutting a sample of the bonding area with the width W; (3) the sample is put on the clamp, and the clamp clamps the materials on two sides of the sample in the bonding area; (4) and (3) tensile testing, namely clicking a zero clearing button and operating the button to start testing, and outputting a tensile value P, wherein the bonding strength F=P/W.

The test results are shown in Table 1 below

TABLE 1

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According to the above test results, it can be found that the graphitization degree G1 of the fast charge system electrode assembly is smaller than the graphitization degree G2 of the slow charge system electrode assembly, and it can be seen from examples 1 to 11 that the fast charge and slow charge requirements of the electrochemical device 100 can be satisfied when G2-G1 is greater than or equal to 0.5%.

Further, when G1 is less than or equal to 95%, and/or G2 is more than or equal to 95.5%, the temperature rise of the battery is smaller when the fast-charge system electrode assembly is fast charged and the slow-charge system electrode assembly is slow charged. Still further, G1 is more than or equal to 94% and less than or equal to 95%; and/or G2 is more than or equal to 95.5% and less than or equal to 96.5%, and in the range, the battery temperature rise under the condition of fast charge and slow charge can achieve better effect.

In addition, in the drop test, as is clear from the combination of examples 1 to 11 and comparative example 1, the negative electrode tabs of the fast-charge system electrode assembly and the slow-charge system electrode assembly are welded and connected in the case, and the degree of misalignment during the drop test can be suppressed, thereby reducing the risk of internal short-circuiting. As is apparent from the combination of examples 1 to 5 and examples 6 to 7, when the electrode assemblies are fixedly connected using the first connecting member 70, the degree of misalignment during the drop test can be further reduced. Therefore, in the embodiment of the present application, the first tab 22 and the second tab 32 are preferably connected in the accommodating cavity, and further, the first electrode assembly 20 and the second electrode assembly 30 are bonded by thermocompression bonding with the first separator 213 and the second separator 313, and the first electrode assembly 20 and the second electrode assembly 30 are integrally connected by the first connecting member 70, so that dislocation and play between the first electrode assembly 20 and the second electrode assembly 30 are suppressed, and the risk of occurrence of short circuits inside the electrochemical device 100 is reduced.

The embodiment of the present application also proposes an electronic device comprising the electrochemical device 100 according to any one of the embodiments described above. The electronic device of the embodiment of the present application is not particularly limited, and may be any electronic device known in the art. For example, electronic devices include, but are not limited to, bluetooth headsets, cell phones, tablets, notebook computers, electric toys, electric tools, battery cars, electric cars, boats, spacecraft, and the like.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and are not limiting; the technical features of the above embodiments or in the different embodiments may also be combined within the idea of the application, the steps may be implemented in any order, and there are many other variations of the different aspects of the application as described above, which are not provided in detail for the sake of brevity; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the application.

Claims

1. An electrochemical device, comprising:

a housing;

the first electrode assembly comprises a first electrode plate assembly, a first electrode lug and a third electrode lug which are connected with the first electrode plate assembly, wherein the first electrode plate assembly is accommodated in the shell, the first electrode plate assembly comprises a first negative electrode plate, the first negative electrode plate comprises a first negative electrode active material, and the graphitization degree of the first negative electrode active material is G1;

the second electrode assembly comprises a second electrode plate assembly, a second lug and a fourth lug, wherein the second lug and the fourth lug are connected with the second electrode plate assembly, the second electrode plate assembly is accommodated in the shell, the second electrode plate assembly comprises a second negative electrode plate, the second negative electrode plate comprises a second negative electrode active material, the graphitization degree of the second negative electrode active material is G2, and the requirements are met: G2-G1 is more than or equal to 0.5%;

the first tab and the second tab have the same polarity, the third tab and the fourth tab have the same polarity, and the first tab and the second tab are electrically connected in the housing.

2. The electrochemical device of claim 1, wherein the electrochemical device satisfies at least one of the following conditions:

(1) The first electrode assembly and the second electrode assembly are arranged in a stacked mode, and the projection of the first tab and the projection of the second tab at least partially coincide when viewed along the stacking direction of the first electrode assembly and the second electrode assembly;

(2) The first electrode assembly comprises a plurality of first lugs, the second electrode assembly comprises a plurality of second lugs, the electrochemical device further comprises a first switching lug, and the first switching lug is connected with the plurality of first lugs and the plurality of second lugs in the shell and extends out of the shell;

(3) The first electrode assembly comprises a plurality of third lugs, the second electrode assembly comprises a plurality of fourth lugs, the electrochemical device further comprises a second switching lug and a third switching lug, the second switching lug and the third lugs are connected in the shell and extend out of the shell, and the third switching lug and the fourth lugs are connected in the shell and extend out of the shell;

(4) The first pole piece assembly is selected from a lamination structure or a winding structure;

(5) The second pole piece assembly is selected from a lamination stack or a winding structure;

(6) The internal resistance of the first electrode assembly is R1, and the internal resistance of the second electrode assembly is R2, so that R1< R2 is satisfied.

3. The electrochemical device of claim 1, wherein the electrochemical device satisfies: g1 is less than or equal to 95 percent, and/or G2 is more than or equal to 95.5 percent.

4. The electrochemical device of claim 3, wherein the electrochemical device satisfies: g1 is more than or equal to 94% and less than or equal to 95%; and/or G2 is more than or equal to 95.5% and less than or equal to 96.5%.

5. The electrochemical device of claim 1, further comprising a first connecting member connecting the first pole piece assembly and the second pole piece assembly.

6. The electrochemical device of claim 5, wherein the first connection member comprises a first adhesive portion, a second adhesive portion, and a third adhesive portion;

the first bonding part and the third bonding part are oppositely arranged at two ends of the second bonding part, and the first pole piece component and the second pole piece component are positioned between the first bonding part and the third bonding part.

7. The electrochemical device according to claim 6, wherein,

the first pole piece assembly comprises a first surface, a second surface and a third surface which are connected, the first surface and the third surface are oppositely arranged along the lamination direction of the first electrode assembly and the second electrode assembly, and the second surface is connected between the first surface and the third surface;

The second electrode assembly comprises a fourth surface, a fifth surface and a sixth surface which are connected, the fourth surface and the sixth surface are oppositely arranged along the lamination direction of the first electrode assembly and the second electrode assembly, and the fifth surface is connected between the fourth surface and the sixth surface;

the first bonding part is bonded to the first surface, the second bonding part is bonded to the second surface and the fifth surface, and the third bonding part is bonded to the sixth surface.

8. The electrochemical device of claim 1, wherein the electrochemical device satisfies at least one of the following conditions:

(1) The first pole piece assembly comprises a first diaphragm, the second pole piece assembly comprises a second diaphragm, and the first pole piece assembly is connected with the second pole piece assembly through the first diaphragm and the second diaphragm;

(2) The first pole piece component and the second pole piece component are connected through the second connecting component.

9. The electrochemical device of claim 8, wherein the electrochemical device satisfies at least one of the following conditions:

(1) The bonding strength between the first pole piece component and the second pole piece component is F, and the following conditions are satisfied: f is more than or equal to 5N/m;

(2) The first pole piece assembly is of a lamination structure, the first diaphragm comprises a first Z-shaped folding part and a first winding part, the first pole piece assembly further comprises a first positive pole piece, the first Z-shaped folding part is arranged between the adjacent first positive pole piece and first negative pole piece, and the first winding part is wound on the outer ring of the lamination structure;

(3) The second diaphragm comprises a second Z-shaped folding part and a second winding part, the second diaphragm further comprises a second positive pole piece, the second Z-shaped folding part is arranged between the adjacent second positive pole piece and second negative pole piece, and the second winding part is wound on the outer ring of the lamination structure;

(4) The first separator and the second separator each independently include a substrate layer, an optional ceramic layer, and an optional bonding layer.

10. The electrochemical device according to claim 1, comprising at least two of the first electrode assemblies and at least one of the second electrode assemblies, the second electrode assemblies being disposed between adjacent two of the first electrode assemblies; or alternatively, the process may be performed,

The electrochemical device comprises at least one first electrode assembly and at least two second electrode assemblies, wherein the first electrode assembly is arranged between two adjacent second electrode assemblies.

11. An electronic device comprising the electrochemical apparatus according to any one of claims 1 to 10.