CN114678636B

CN114678636B - Electrochemical device and electricity utilization device

Info

Publication number: CN114678636B
Application number: CN202210316272.7A
Authority: CN
Inventors: 李锐
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2022-03-28
Filing date: 2022-03-28
Publication date: 2024-07-02
Anticipated expiration: 2042-03-28
Also published as: CN114678636A

Abstract

The application discloses an electrochemical device and an electric device, comprising a first shell, a second shell, a separator, a first electrode assembly and a second electrode assembly, wherein the separator is positioned between the first shell and the second shell, a first cavity is arranged between the first shell and the separator, a second cavity is arranged between the second shell and the separator, the first electrode assembly is arranged in the first cavity, the second electrode assembly is arranged in the second cavity, the separator comprises a substrate layer, the glass transition temperature of the substrate layer is Tg, and the Tg is more than or equal to 45 ℃. In this way, the electrochemical device of the present application can have improved safety.

Description

Electrochemical device and electricity utilization device

Technical Field

The present application relates to the field of battery technology, and in particular, to an electrochemical device and an electric device.

Background

Currently, batteries are widely used in electronic products such as mobile phones, tablets, notebook computers and the like.

Because in some application scenarios, a single battery cell is not capable of achieving the output of the desired power; therefore, a plurality of battery cells are generally connected in series, parallel or series-parallel with each other so that the plurality of battery cells cooperate together to achieve the desired power output.

However, although the output power can be improved by connecting a plurality of battery cells in series, parallel or series-parallel connection, the energy density of the whole battery pack is low. Therefore, the design of the in-pouch serial/parallel battery including a case and a plurality of electrode assemblies disposed in the same case, the electrode assemblies in series/parallel being separated by a separator, is proposed. However, the safety of such batteries is still insufficient and needs to be further improved.

Disclosure of Invention

In view of the above, the present application provides an electrochemical device and an electric device for improving the safety of batteries connected in series/parallel with a pouch.

According to one aspect of the present application, there is provided an electrochemical device including a first case, a second case, a separator, a first electrode assembly, and a second electrode assembly. The separator is located between the first shell and the second shell, a first cavity is arranged between the first shell and the separator, a second cavity is arranged between the second shell and the separator, the first electrode assembly is arranged in the first cavity, and the second electrode assembly is arranged in the second cavity. In addition, the separator includes a substrate layer having a glass transition temperature Tg of 45 ℃ or greater. On the one hand, the base material layer is made of an insulating polymer material, so that the risk of corrosion and short circuit caused by contact between the lug and the base material layer when the base material layer is made of metal can be avoided, and the safety performance of the electrochemical device is improved; on the other hand, tg is more than or equal to 45 ℃, at this moment, the substrate layer has good crystallinity at normal temperature, can inhibit the mutual penetration of electrolyte solvents at two sides of the separator, and reduces the risk of solvolysis gas production caused by the conduction of the electrolyte under high voltage, thereby further improving the safety of the electrochemical device.

In an alternative mode, the melting point of the substrate layer is Tm, and Tm is greater than or equal to 250 ℃. At this time, the base material layer can maintain a good form at a high temperature, and the insulation property of the separator is ensured.

In an alternative mode, the elastic modulus of the substrate layer is e, and e is greater than or equal to 1.8GPa. In an alternative mode, the tensile strength of the substrate layer is S, and S is greater than or equal to 50N/15mm. At this time, the substrate layer has good structural strength, reduces the risk of breakage during impact, and improves the safety of the electrochemical device.

In an alternative mode, tg is greater than or equal to 80 ℃. At this time, the electrochemical device has good crystallinity at high temperature, so that permeation of the electrolyte at both sides of the separator is suppressed, and safety of the electrochemical device at high temperature is further improved. In an alternative mode, tg is greater than or equal to 110 ℃.

In an alternative, the spacer further comprises an encapsulation layer on the surface of the substrate layer.

In an alternative, the electrochemical device satisfies at least one of the following conditions: the separator further comprises (a) an adhesive layer between the substrate layer and the encapsulation layer, (b) the encapsulation layer comprises at least one of polypropylene, modified polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, or ethylene-ethyl acrylate copolymer, and (c) the encapsulation layer has a thickness of 15 μm to 60 μm.

In an alternative, the substrate layer comprises a first polymer comprising at least one of benzene rings or naphthalene rings in its molecular structure. Since the benzene ring and the naphthalene ring are rigid groups, crystallinity of the base material layer can be improved, and further permeation of the electrolyte at both sides of the separator can be suppressed, thereby improving safety of the electrochemical device.

In an alternative, the first polymer comprises at least one of polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, or derivatives thereof.

In an alternative, the electrochemical device satisfies at least one of the following conditions: (d) the spacer has a thickness of 35 μm to 145 μm; (e) the thickness of the substrate layer is 4 μm to 25 μm.

In an alternative mode, the crystallinity of the substrate layer is C at 25 ℃ and C.gtoreq.50%. At this time, the base material layer can better suppress the penetration of the electrolyte solvent, reduce the risk of the electrolyte being conducted at a high voltage, and further improve the safety of the electrochemical device.

According to another aspect of the present application, there is provided an electric device including the electrochemical device as described above.

The beneficial effects of the application are as follows: in comparison with the prior art, the separator comprises the substrate layer, the glass transition temperature of the substrate layer is Tg, and Tg is more than or equal to 45 ℃, on one hand, the substrate layer is made of insulating polymer materials, and the risk of corrosion and short circuit caused by contact between the lug and the substrate layer when the substrate layer is made of metal can be avoided, so that the safety performance of the electrochemical device is improved; on the other hand, tg is more than or equal to 45 ℃, at this moment, the substrate layer has good crystallinity at normal temperature, can inhibit the mutual penetration of electrolyte solvents at two sides of the separator, and reduces the risk of solvolysis gas production caused by the conduction of the electrolyte under high voltage, thereby further improving the safety of the electrochemical device.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are used in the description of the embodiments will be briefly described below. Like elements or portions are generally identified by like reference numerals throughout the several figures. In the drawings, elements or portions thereof are not necessarily drawn to scale.

Fig. 1 is a schematic view showing the overall structure of an electrochemical device according to an embodiment of the present application;

FIG. 2 is an exploded view of the overall structure of an electrochemical device according to an embodiment of the present application;

FIG. 3 is an exploded view of another angle of the overall structure of an electrochemical device according to an embodiment of the present application;

FIG. 4 is a schematic side view showing the structure of a case and a separator of an electrochemical device according to an embodiment of the present application;

FIG. 5 is a cross-sectional view taken along section A-A of FIG. 1;

FIG. 6 is an enlarged schematic view of the structure at B in FIG. 5;

FIG. 7 is a schematic side view of a case and a separator of another embodiment of an electrochemical device of the present application;

fig. 8 is a schematic structural diagram of an electric device according to an embodiment of the present application.

Detailed Description

In order that the application may be readily understood, a more particular description thereof will be rendered by reference to specific embodiments that are illustrated in the appended drawings. It will be understood that when an element is referred to as being "fixed" to another element, it can be directly on the other element or one or more intervening elements may be present therebetween. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or one or more intervening elements may be present therebetween. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only.

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 in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used in this specification includes any and all combinations of one or more of the associated listed items.

In addition, the technical features mentioned in the different embodiments of the application described below can be combined with one another as long as they do not conflict with one another.

Referring to fig. 1,2 and 6, the electrochemical device 1 includes a first case 100, a second case 200, a separator 300, a first electrode assembly 400 and a second electrode assembly 500. The first case 100 and the second case 200 together enclose a case portion that forms the whole of the electrochemical device 1. The spacer 300 is provided between the first housing 100 and the second housing 200. The electrochemical device 1 is provided with a first cavity 101 between the first case 100 and the separator 300, and a second cavity 102 between the second case 200 and the separator 300. The first electrode assembly 400 is disposed in the first chamber 101, and the second electrode assembly 500 is disposed in the second chamber 102. In order to facilitate a better understanding of the specific structure of the electrochemical device 1, the first case 100, the second case 200, the separator 300, the first electrode assembly 400, and the second electrode assembly 500 are specifically described below.

As shown in fig. 2 and 3, the first housing 100 and the second housing 200 are disposed opposite to each other along a first predetermined direction X as shown in the drawings, and define a receiving space therebetween. The first housing 100 is generally approximately box-like in structure and includes a first cavity portion 110 and a first peripheral portion 120. Wherein the first cavity 110 is recessed toward a side facing away from the second housing 200 to form a cavity. Specifically, the first cavity 110 includes a first bottom wall and a first sidewall extending from an edge of the first bottom wall along the first preset direction X, where the first bottom wall and the first sidewall together enclose the cavity; the cavity of the first cavity portion 110 is disposed toward the second housing 200. The first peripheral portion 120 is in a sheet-like structure, and is disposed around the first cavity portion 110; the first peripheral portion 120 is formed to extend outwardly from an open end of the first cavity portion 110. Similarly, the second housing 200 is also an overall approximately box-shaped structure, and includes a second cavity portion 210 and a second peripheral portion 220. Wherein the second cavity 210 is recessed toward a side facing away from the first housing 100 to form a cavity. In this embodiment, the second cavity 210 includes a second bottom wall and a second side wall extending from an edge of the second bottom wall along the first preset direction X, and the second bottom wall and the second side wall together enclose a cavity of the second cavity 210; the cavity of the second cavity portion 210 is disposed toward the first housing 100. The second peripheral portion 220 is in a sheet-like structure, and is disposed around the second cavity portion 210; the second peripheral portion 220 is formed to extend outwardly from an open end of the second cavity portion 210. In this embodiment, the first housing 100 and the second housing 200 have two independent structures, the cavities of the first cavity 110 and the second cavity are respectively formed by punching, and the first housing 100 and the second housing 200 are respectively fixed to the spacer 300. It should be understood that, in other embodiments of the present application, the first housing 100 and the second housing 200 may be integrally formed; specifically, the same sheet structure is folded after two cavities are punched, so as to form the first housing 100 and the second housing 200 that are disposed opposite to each other.

As for the materials of the first and second cases 100 and 200, they are various. Taking the first housing 100 as an example, as shown in fig. 4, in the present embodiment, the first housing 100 includes a first insulating material layer 130, a first metal layer 140, and a second insulating material layer 150 that are stacked. The first metal layer 140 is disposed between the first insulating material layer 130 and the second insulating material layer 150 along the thickness direction of the sheet of the first case 100, and the second insulating material layer 150 is disposed facing the spacer 300. Optionally, the material of the first metal layer 140 includes aluminum, and the material of the first insulating material layer 130 and/or the second insulating material layer 150 includes polypropylene; of course, other embodiments of the present application can also be adapted to be modified based on the first metal layer 140 comprising an aluminum alloy, a copper alloy, or the like, and the first insulating material layer 130 and/or the second insulating material layer 150 comprising at least one of modified polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, or ethylene-ethyl acrylate copolymer. The second case 200 includes a third insulating material layer 230, a second metal layer 240, and a fourth insulating material layer 250. The second metal layer 240 is disposed between the third insulating material layer 230 and the fourth insulating material layer 250 along the thickness direction of the sheet material of the second housing 200, and the fourth insulating material layer 250 is disposed facing the spacer 300, and the material of the second housing 200 is substantially the same as that of the first housing 100, which will not be described in detail herein.

For the separator 300, please refer to fig. 5 and 6, which respectively show a schematic sectional view of the electrochemical device 1 along the line A-A and a partially enlarged schematic view of the electrochemical device 1 at the point B, the separator 300 is disposed between the first housing 100 and the second housing 200, so that the separator 300 separates the accommodating spaces defined by the first housing 100 and the second housing 200, and further forms a first cavity 101 and a second cavity 102 respectively located at two sides of the separator 300 along the thickness direction; that is, the electrochemical device 1 is provided with the first cavity 101 and the second cavity 102 on both sides of the separator 300. The first cavity 101 is defined by the spacer 300 and the first housing 100, and the second cavity 102 is defined by the spacer 300 and the second housing 200. Specifically, the spacer 300 has a sheet-like structure, which includes a spacer portion and a packaging portion. The isolation part is accommodated in the accommodating space and is arranged opposite to the first cavity part 110. The packaging part is disposed around the isolation part and located between the first peripheral part 120 and the second peripheral part 220; the package portion is fixedly connected to the first peripheral portion 120 and the second peripheral portion 220, respectively. Alternatively, the fixing connection manner between the package portion and the first peripheral portion 120 and the second peripheral portion 220 may be a hot-melt fixing manner, a glue fixing manner, or the like.

In some embodiments, as shown in fig. 4, the spacer 300 includes a substrate layer 310 and an encapsulation layer 320, the encapsulation layer 320 being located on a surface of the substrate layer 310. The spacer 300 is thermally fused and fixed to the first case 100 through the encapsulation layer 320; in this embodiment, the encapsulation layer 320 is further thermally fused and fixed to the second housing 200, and at this time, the encapsulation layer 320 is located on two surfaces of the substrate layer 310. In this way, the edges of the first and second cases 100 and 200 can be sealed while the first and second cases 100 and 200 are fixed, including the spacer 300. Optionally, the material of the encapsulation layer 320 includes at least one of polypropylene, modified polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, or ethylene-ethyl acrylate copolymer. Alternatively, the thickness of the single-sided encapsulation layer 320 is 15 μm to 60 μm, and the single-sided encapsulation layer refers to an encapsulation layer located on a surface of the substrate layer 310, where the surface may be a surface of the substrate layer 310 near the first housing 100, and the surface may be a surface of the substrate layer 310 near the second housing 200. In some embodiments, the thickness of the spacer 300 is 35 μm to 145 μm.

In some embodiments, the glass transition temperature of the substrate layer 310 is Tg, and Tg is 45 ℃.

It should be noted that: the glass transition temperature refers to the critical temperature at which the polymeric material changes from a glassy state to a highly elastic state, wherein the glassy state is a rigid solid state at a lower temperature, similar to glass, and undergoes very little deformation under the action of an external force, and the highly elastic state is a state in which the deformation of the material increases significantly after the temperature continues to rise to a certain range and is relatively stable at a certain subsequent temperature interval.

Through the above arrangement, on the one hand, the material of the base material layer 310 is an insulating polymer material, so that the risk of corrosion and short circuit caused by contact between the tab module 700 and the base material layer 310 when the base material layer 310 is metal can be avoided, thereby improving the safety performance of the electrochemical device 1; on the other hand, tg is not less than 45 ℃, and at this time, the base material layer 310 has good crystallinity at normal temperature, and can suppress the mutual penetration of the electrolyte solvents on both sides of the separator 300, and reduce the risk of solvolysis and gas production caused by the conduction of the electrolyte under high voltage, thereby further improving the safety of the electrochemical device 1.

In some embodiments, tg is greater than or equal to 80 ℃. At this time, the base material layer 310 has good crystallinity at high temperature of the electrochemical device 1, thereby suppressing permeation of the electrolyte at both sides of the separator 300, and further improving the safety of the electrochemical device 1 at high temperature. In some embodiments, tg is greater than or equal to 110 ℃.

In some embodiments, the melting point of the substrate layer 310 is Tm, and Tm is greater than or equal to 250 ℃, so that, on one hand, since the melting point of the encapsulation layer 320 is generally in the range of 120-170 ℃, the breakage of the substrate layer 310 can be reduced when the encapsulation layer 320 is thermally fused and fixed with the first housing 100 or the second housing 200. On the other hand, the base material layer 310 can maintain a good form at a high temperature, and the insulation of the separator 300 is ensured.

In some embodiments, the elastic modulus of the substrate layer 310 is e, and e is ≡1.8GPa. In some embodiments, the tensile strength of the substrate layer 310 is S, and S is 50N/15mm or greater. At this time, the base material layer 310 has good structural strength, reduces the risk of breakage during impact, and improves the safety of the electrochemical device 1.

In some embodiments, the thickness of the substrate layer 310 is 4 μm to 25 μm.

In some embodiments, the substrate layer 310 includes a first polymer including at least one of benzene rings or naphthalene rings in a molecular structure. Since the benzene ring and the naphthalene ring are rigid groups, crystallinity of the base material layer 310 can be improved, and permeation of the electrolyte solution on both sides of the separator 300 can be suppressed, thereby improving safety of the electrochemical device 1. Optionally, the first polymer comprises at least one of polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, or derivatives thereof.

In some embodiments, as shown in fig. 7, the spacer 300 further includes an adhesive layer 330, where the adhesive layer 330 is located between the substrate layer 310 and the encapsulation layer 320, and the adhesive layer 330 is used to connect the substrate layer 310 and the encapsulation layer 320, so that the connection between the two layers is more firm. Optionally, the adhesive layer 330 includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl alkoxy, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene butadiene rubber, carboxymethyl cellulose, or polyacrylate alcohol.

In some embodiments, the crystallinity of the substrate layer 310 is C at 25 ℃ and C.gtoreq.50%. Wherein, the crystallinity refers to the proportion of the crystalline region in the polymer. At this time, the base material layer 310 can better suppress permeation of the electrolyte solvent, reduce the risk of the electrolyte being conducted at a high voltage, and further improve the safety of the electrochemical device 1.

For the first electrode assembly 400 and the second electrode assembly 500, please continue to refer to fig. 6, the first electrode assembly 400 is received in the first cavity 101, and the second electrode assembly 500 is received in the second cavity 102, which are core elements of the electrochemical device 1. The first electrode assembly 400 includes a first electrode sheet, a second electrode sheet, and a separator disposed therebetween. One of the first pole piece and the second pole piece is an anode piece, and the other is a cathode piece; the isolation film is arranged between the first pole piece and the second pole piece so as to avoid the first pole piece from being electrically contacted with the second pole piece. In this embodiment, the first electrode assembly 400 has a winding structure, and is wound in a flat shape, so as to be conveniently accommodated in the first cavity 101; it is understood that, in other embodiments of the present application, the first electrode assembly 400 may also be a laminated structure, i.e. stacked along a predetermined direction, for example, the thickness direction, and a separator is disposed between the adjacent first electrode sheet and the second electrode sheet. The second electrode assembly 500 is substantially identical to the first electrode assembly 400 in structure, and is not described herein.

In addition, the electrochemical device further includes a plurality of tab modules 700, and the first electrode assembly 400 and the second electrode assembly 500 are respectively and correspondingly connected to at least one tab module 700. The tab module 700 includes a first tab 710 and a second tab 720. In the tab module 700 connected to the first electrode assembly 400, one end of the first tab 710 is connected to the first electrode sheet of the first electrode assembly 400, and the other end thereof protrudes out of the above-mentioned case part through the heat-fusible area between the first case 100 and the separator 300; one end of the second tab 720 is connected to the second electrode sheet of the first electrode assembly 400, and the other end protrudes out of the above-mentioned case part through the heat-fused region between the first case 100 and the separator 300. The connection relationship between the second electrode assembly 500 and the tab module 700 is substantially the same as that of the first electrode assembly 400; specifically, in the tab module 700 connected to the second electrode assembly 500, one end of the first tab 710 is connected to the first electrode sheet of the second electrode assembly 500, and the other end protrudes out of the above-mentioned case portion through the heat-fusible area between the second case 200 and the separator 300; one end of the second tab 720 is connected to the second electrode tab of the second electrode assembly 500, and the other end protrudes out of the above-mentioned case part through the heat-fused region between the second case 200 and the separator 300. The second tab connected to the first electrode assembly 400 is electrically connected to the first tab connected to the second electrode assembly 500 such that the first electrode assembly 400 and the second electrode assembly 500 are connected in series. It is understood that in other embodiments of the present application, the first electrode assembly 400 and the second electrode assembly 500 may be connected in parallel; at this time, the first tab connected to the first electrode assembly 400 is electrically connected to the first tab connected to the second electrode assembly 500, and the second tab connected to the first electrode assembly 400 is electrically connected to the second tab connected to the second electrode assembly 500.

In addition, in order to facilitate readers to more clearly understand the technical effects brought by the technical scheme, the application also carries out a comparison test, and the test process is as follows:

The high-temperature storage permeability test method comprises the following steps: cutting a spacer sample with the length of 150mm and the width of 75mm, packaging the side edges and the bottom edges by a heat sealing machine after folding, weighing, sealing after injecting 4ml of solution from the top edge, weighing to obtain the total weight of the injected solution, calculating the weight of the injected solution, and finally continuously storing for seven days at the temperature of 60 ℃, weighing the total weight of the injected solution every day, and calculating the weight change rate of the injected solution, wherein the weight change rate of the solution is = (total weight of the day-total weight of the injected solution)/the weight of the injected solution.

The solution may be dimethyl carbonate (DMC) or an electrolyte, wherein the electrolyte is a solution of which the mass ratio of Ethylene Carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) is EC: DEC: dmc=1:1:1, and the mass percentage of LiPF ₆ is 12.5% based on the mass of the electrolyte.

Example 1

Selecting a polyethylene naphthalate (PEN) material with a glass transition temperature of 121 ℃ as a base material layer material of the spacer, and setting the PEN-1 as a base material layer material with a thickness of 12 mu m; the packaging layer is made of polypropylene and has a thickness of 30 μm.

Example 2

The difference from example 1 is that a polyethylene naphthalate (PEN) material having a glass transition temperature of 117℃was selected as a material of the base material layer of the separator, and PEN-2 was used.

Example 3

The difference from example 1 was that a polyethylene naphthalate (PEN) material having a glass transition temperature of 113℃was selected as a material of the base material layer of the separator, and PEN-3 was used.

Example 4

The difference from example 1 is that a polyethylene terephthalate (PET) material having a glass transition temperature of 81℃was selected as the base material layer material of the separator, and PET-1 was used.

Example 5

The difference from example 1 is that a polyethylene terephthalate (PET) material having a glass transition temperature of 75℃was selected as the base material layer material of the separator, and PET-2 was used.

Example 6

The difference from example 1 was that a polyethylene terephthalate (PET) material having a glass transition temperature of 67℃was selected as the base material layer material of the separator, and PET-3 was used.

Example 7

The difference from example 1 is that a polyethylene terephthalate (PET) material having a glass transition temperature of 60℃was selected as the base material layer material of the separator, and PET-4 was used.

Example 8

The difference from example 1 is that a polybutylene terephthalate (PBT) material having a glass transition temperature of 60℃was selected as the base material layer material of the separator, and PBT-1 was used.

Example 9

The difference from example 1 is that a polybutylene terephthalate (PBT) material having a glass transition temperature of 55℃was selected as the base material layer material of the separator, and PBT-2 was used.

Example 10

The difference from example 1 is that a polybutylene terephthalate (PBT) material having a glass transition temperature of 45℃was selected as the base material layer material of the separator, and PBT-3 was used.

Comparative example 1

The difference from example 1 is that a polypropylene (PP) material having a glass transition temperature of-10 ℃ was selected as a base material layer material of the separator, and the separator was used as a sample of the separator in the test method, with a thickness of 20 μm.

Comparative example 2

The difference from example 1 is that a polybutylene terephthalate (PBT) material having a glass transition temperature of 35℃was selected as the base material layer material of the separator, and PBT-4 was used.

Comparative example 3

The difference from example 1 is that an Al material was selected as a material of the base material layer of the separator, and the thickness was 20 μm, and the separator was used as a sample of the separator in the test method.

The experimental results are shown in table 1 below:

TABLE 1

As can be seen from the data in Table 1, examples 1 to 10 were smaller in the weight change rate of the electrolyte in examples 1 to 10 in seven days at 60℃than comparative examples 1 and 2, and the weight change rate of the electrolyte in comparative example 1 was as high as 29.5%, and furthermore, the weight change rate of the solvent DMC in examples 1 to 10 was also smaller, indicating that the separator in examples 1 to 10 was effective in suppressing permeation of the electrolyte and the solvent DMC. The test results of examples 1-10 are similar to the test results of the electrolyte in comparative example 3, which shows that the materials can replace the common aluminum materials of the substrate layer in the separator, and can avoid the risk of corrosion and short circuit caused by contact between the tab and the substrate layer when the substrate layer is metal, thereby improving the safety performance of the electrochemical device.

Meanwhile, as can be seen from comparison of examples 1 to 4 and examples 5 to 10, the separator having Tg of 80 or more is further satisfied, and the DMC weight change rate after high-temperature storage can be further significantly reduced. This is because the base material layer has good crystallinity at high temperature of the electrochemical device, thereby suppressing permeation of the electrolyte at both sides of the separator, and further improving the safety of the electrochemical device at high temperature.

In addition, as is clear from the comparison of examples 1 to 6, 8 to 9 and examples 7 and 10, the separator having a crystallinity C.gtoreq.50% is further satisfied, and the weight change rate of the electrolyte and DMC after high-temperature storage can be further reduced, because the more regions in the crystalline state are, the better the penetration of the electrolyte solvent can be suppressed, thereby reducing the risk of conducting the electrolyte at high voltage, and further improving the safety of the electrochemical device.

Further, test data of example 1, example 4, example 8, and comparative examples 1 and 3 were selected and compared in detail, and specific data are shown in tables 2 and 3.

TABLE 2

TABLE 3 Table 3

As is clear from tables 2 and 3, example 1 has a smaller weight change rate of the electrolyte and DMC than example 4 and example 8, indicating that the effect of inhibiting the permeation of the electrolyte by using the PEN material as the material of the base material layer in the separator is better. The rate of change of weight of the electrolyte and DMC in example 1 was substantially the same as that in comparative example 3, indicating that under certain conditions the PEN material may replace the aluminum material commonly used for the substrate layer in separators. Of these, the weight change rates of the electrolyte and DMC in comparative example 1 are most remarkable, indicating that the suppression effect of electrolyte permeation by using PP material as the base material layer material in the separator is poor.

By providing the spacer 300, the embodiment of the application comprises a substrate layer 310, wherein the glass transition temperature of the substrate layer 310 is Tg, and Tg is more than or equal to 45 ℃. The electrode tab is arranged on the surface of the substrate layer, and the electrode tab is arranged on the surface of the substrate layer; on the other hand, tg is more than or equal to 45 ℃, at this moment, the substrate layer has good crystallinity at normal temperature, can inhibit the mutual penetration of electrolyte solvents at two sides of the separator, and reduces the risk of solvolysis gas production caused by the conduction of the electrolyte under high voltage, thereby further improving the safety of the electrochemical device.

The present application also provides an embodiment of an electric device 2, as shown in fig. 8, which includes the electrochemical device described above, and the functions and structures of the electrochemical device can be referred to the above embodiment, and will not be described herein.

The foregoing description is only illustrative of the present application and is not intended to limit the scope of the application, and all equivalent structures or equivalent processes or direct or indirect application in other related technical fields are included in the scope of the present application.

Claims

1. An electrochemical device, comprising:

a first housing and a second housing;

the separator is positioned between the first shell and the second shell, a first cavity is arranged between the first shell and the separator, and a second cavity is arranged between the second shell and the separator;

The first electrode assembly is arranged in the first cavity, and the second electrode assembly is arranged in the second cavity;

The separator comprises a substrate layer, wherein the glass transition temperature of the substrate layer is Tg, and Tg is more than or equal to 45 ℃;

the crystallinity of the substrate layer at 25 ℃ is C, and C is more than or equal to 50%.

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

(1) The melting point of the substrate layer is Tm, and Tm is more than or equal to 250 ℃;

(2) The elastic modulus of the substrate layer is e, and e is more than or equal to 1.8GPa;

(3) The tensile strength of the substrate layer is S, and S is more than or equal to 50N/15mm.

3. The electrochemical device of claim 1, wherein Tg is greater than or equal to 80 ℃.

4. The electrochemical device of claim 1, wherein the separator further comprises an encapsulation layer on a surface of the substrate layer.

5. The electrochemical device of claim 4, wherein at least one of the following conditions is satisfied:

(a) The separator further includes an adhesive layer between the substrate layer and the encapsulation layer;

(b) The packaging layer comprises at least one of polypropylene, modified polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer;

(c) The thickness of the encapsulation layer on one side is 15 to 60 μm.

6. The electrochemical device of claim 4, wherein the substrate layer comprises a first polymer comprising at least one of a benzene ring or a naphthalene ring in its molecular structure.

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

The first polymer comprises at least one of polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, or derivatives thereof.

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

(d) The thickness of the spacer is 35-145 μm;

(e) The thickness of the substrate layer is 4 μm to 25 μm.

9. An electrical device comprising the electrochemical device of any one of claims 1-8.