阅读说明：本技术 电化学装置及电子装置 (Electrochemical device and electronic device ) 是由 李学成 于 2021-06-23 设计创作，主要内容包括：本申请提供一种电化学装置及电子装置,所述电化学装置包括电极组件,电极组件包括第一极片,所述第一极片包括第一集流体、第一活性物质层和第一绝缘层。第一集流体包括相对设置的第一表面和第二表面,第一活性物质层设置在第一表面,第一绝缘层位于第一集流体和第一活性物质层之间。本申请提供的电化学装置和电子装置,通过在集流体和活性物质层之间设置绝缘层,隔断该区域的电子通道,即使发生隔膜收缩,绝缘层区域的极片由于不带电,正负极片接触也不会发生短路,进而改善了电压降失效的问题。并且,本申请提供的电化学装置的电解液含量并没有减少,电化学装置和电子装置的电性能不会受到影响。(The application provides an electrochemical device and electron device, electrochemical device includes electrode assembly, and electrode assembly includes first pole piece, first pole piece includes first mass flow body, first active material layer and first insulating layer. The first current collector comprises a first surface and a second surface which are oppositely arranged, the first active material layer is arranged on the first surface, and the first insulating layer is positioned between the first current collector and the first active material layer. The application provides an electrochemical device and electron device through set up the insulating layer between mass flow body and active substance layer, cuts off this regional electron channel, even take place the diaphragm shrink, the pole piece in insulating layer region is because uncharged, and the short circuit can not take place yet in the positive and negative pole piece contact, and then has improved the problem that the voltage drop became invalid. In addition, the electrolyte content of the electrochemical device provided by the application is not reduced, and the electrical properties of the electrochemical device and the electronic device are not affected.)

1. An electrochemical device comprising an electrode assembly including a first pole piece, a second pole piece, and a separator between the first pole piece and the second pole piece, wherein the first pole piece comprises:

a first current collector comprising first and second oppositely disposed surfaces,

a first active material layer provided on the first surface; and

a first insulating layer, wherein the first insulating layer is between the first current collector and the first active material layer.

2. The electrochemical device according to claim 1, wherein the electrode assembly is wound from the first pole piece, the second pole piece, and the separator, the first surface is disposed facing a winding center of the electrode assembly, and the second surface is disposed facing away from the winding center of the electrode assembly.

3. The electrochemical device of claim 1, further comprising a second active material layer disposed on said second surface,

the first current collector comprises a first area, a second area and a third area which are arranged along the length direction of the pole piece, and the first active material layer is arranged on the first surface of the first area and the first surface of the second area;

the second active material layer is disposed on the second surface of the first region.

4. The electrochemical device of claim 3, further comprising a tab electrically connected to said first current collector, wherein said first current collector comprises a first end and a second end disposed along a width of the pole piece, wherein said tab is disposed at said first end, and wherein said first insulating layer is disposed on at least one of:

a first end of the first region, a first end of the second region, and a first end of the third region; or

A second end of the first region, a second end of the second region, and a second end of the third region.

5. The electrochemical device according to claim 3, further comprising a tab electrically connected to the first current collector, wherein the first current collector comprises a first end and a second end disposed along the width of the pole piece, the tab disposed at the first end,

the electrochemical device further includes a second insulating layer disposed on the second surface, the second insulating layer being disposed at least in at least one of the first end portion or the second end portion of the first region, and the second insulating layer being between the first current collector and the second active material layer.

6. The electrochemical device of claim 5, wherein said second insulating layer comprises a second insulating material comprising at least one of alumina, zirconia, or chromia.

7. The electrochemical device of claim 5, wherein said second insulating layer extends no more than 10mm across the width of said pole piece.

8. The electrochemical device of claim 5, wherein said second insulating layer is further disposed on at least one of said second region or said third region.

9. The electrochemical device of claim 8, wherein said second region comprises a first portion and a second portion disposed along a length of said pole piece, said second insulating layer further disposed on said second portion.

10. The electrochemical device of claim 9, further comprising a receiving means for receiving said electrode assembly, said receiving means comprising a first receiving portion and a second receiving portion, said first receiving portion having a depth less than a depth of said second receiving portion, said first portion contacting said first receiving portion and said second portion contacting said second receiving portion when received in said receiving means.

11. The electrochemical device according to claim 8, wherein a ratio of an extension length of the second insulating layer in the width direction of the pole piece to an extension length of the first current collector in the width direction of the pole piece is not less than 50%.

12. The electrochemical device of claim 1, wherein said first insulating layer extends no more than 10mm in length across the width of said pole piece.

13. The electrochemical device of claim 1, wherein the first insulating layer comprises a first insulating material comprising at least one of alumina, zirconia, or chromia.

14. The electrochemical device according to claim 1, wherein the first pole piece is a positive pole piece, the second pole piece comprises a second current collector, and the extension length of the first current collector and the extension length of the second current collector differ by no more than 5% along the width direction of the pole piece.

15. The electrochemical device according to claim 1, wherein the electrode assembly is formed by stacking the first pole piece, the second pole piece, and the separator in the first direction, the first current collector includes a first end portion and a second end portion disposed in a second direction, a third end portion and a fourth end portion disposed in a third direction, the second direction being perpendicular to the first direction, the third direction being perpendicular to the second direction, and the first insulating layer is disposed on at least one of the first end portion, the second end portion, the third end portion, or the fourth end portion.

16. The electrochemical device of claim 15, wherein said first insulating layer extends no more than 10mm along said second direction.

17. The electrochemical device of claim 15 further comprising a second insulating layer disposed on said second surface, said second insulating layer disposed on at least one of said first end, said second end, said third end, or said fourth end.

18. The electrochemical device of claim 17, wherein said second insulating layer extends no more than 10mm along said second direction.

19. An electronic device, comprising the electrochemical device of any one of claims 1-18, wherein the electrochemical device powers the electronic device.

Technical Field

The present disclosure relates to electrochemical technologies, and particularly to an electrochemical device and an electronic device.

Background

Currently, users are increasingly looking for batteries with large capacity (for example, not less than 6Ah) and with fast charging performance, which requires that the batteries contain more electrolyte content. An increase in the electrolyte content in the battery leads to an increased risk of the battery falling out of service. Among them, the voltage drop failure is the most dominant failure mode in the drop failure, and is the most troublesome failure mode. The voltage drop failure is caused by that when the battery falls, an electrode assembly moves in a containing device (such as an aluminum plastic film), electrolyte impacts diaphragms at the head and tail parts of the electrode assembly to cause the diaphragms to shrink, and positive and negative pole pieces at the shrinking parts of the diaphragms are in contact short circuit.

To solve the above problem, one approach is to suppress the shrinkage of the separator by increasing the adhesive force of the separator, thereby improving the voltage drop failure. However, increasing the adhesion of the separator leads to deterioration in the electrical properties of the battery, which is more pronounced especially in a high-rate rapid charge system (for example, a charge system having a charge rate of not less than 3C). The other method is to reduce the impact of free electrolyte on the diaphragm by reducing the content of the electrolyte in the battery, but if the content of the electrolyte is too low, the later cycle of the battery is influenced, the aging of the battery is accelerated, and the service life is shortened. Therefore, it is desirable to provide a design to solve the aforementioned problems.

Disclosure of Invention

Accordingly, the present application provides an electrochemical device that can improve the voltage drop failure problem without affecting the electrical performance.

In addition, it is also necessary to provide an electronic device.

In a first aspect of the present application, an electrochemical device is provided that includes an electrode assembly including a first pole piece, a second pole piece, and a separator between the first pole piece and the second pole piece. First pole piece includes first mass flow body, first active material layer and first insulating layer, first mass flow body is including relative first surface and the second surface that sets up, first active material layer sets up first surface, first insulating layer is located first mass flow body with between the first active material layer.

The insulating layer is arranged on the current collector and then coated with the active substance layer, and the insulating layer can prevent electrons in the area from flowing to the active substance layer from the current collector, so that the pole piece in the area is uncharged. In the dropping process, the contact short circuit of the positive and negative pole pieces at the head and the tail of the outermost circle of the battery can be prevented after the diaphragm shrinks, so that the risk of dropping voltage drop failure is improved. If the active material layer is coated on the current collector and then the insulating layer is arranged on the active material layer, the active material layer is in contact with the current collector, and the active material layer can normally gain and lose electrons and generate lithium intercalation and deintercalation. At this time, the electrode plate in this region is in a charged state, and when the insulating layer provided on the active material layer is too thin or is left uncoated, there is still a risk of contact short-circuiting of the positive and negative electrode plates. In addition, the interface bonding force between the active material layer and the current collector is weaker than that between the insulating layer and the current collector, and in the process of falling, an electrochemical device which is provided with the active material layer firstly and then coated with the insulating layer is easy to cause the phenomenon that the active material layer falls off, so that the current collector is exposed, the positive and negative pole pieces are in short circuit, heat is rapidly generated, the voltage is reduced, and the safety performance is reduced. Therefore, the problem of voltage drop failure can be solved only by arranging the insulating layer on the current collector and then coating the active material layer. In addition, the content of the electrolyte is not reduced, and the electrical property of the electrochemical device is not affected.

In some embodiments, the electrode assembly is wound from a first pole piece, a second pole piece, and a separator, with the first surface disposed facing the winding center and the second surface disposed away from the winding center.

In some embodiments, the electrochemical device further comprises a second active material layer disposed on the second surface, the first current collector comprises a first region and a second region disposed along the length of the pole piece, and the first active material layer is disposed on the first surface of the first region and the first surface of the second region; the second active material layer is disposed on the second surface of the first region.

In some embodiments, the electrochemical device further comprises a tab electrically connected to the first current collector, the first current collector comprising a first end and a second end disposed along the width of the pole piece, the tab disposed at the first end. The first insulating layer is disposed on at least one of: a first end of the first region, a first end of the second region, and a first end of the third region; or a second end of the first region, a second end of the second region, and a second end of the third region. Generally, the separator shrinks mainly in the width direction of the pole piece toward the middle of the separator, that is, the separator at the first end or the second end is easy to shrink, so that the risk of voltage drop failure at the positions of the first end of the first region, the first end of the second region, the first end of the third region, the second end of the first region, the second end of the second region and the second end of the third region is relatively high, and the first insulating layer is arranged at the positions, so that the effect of better preventing the risk of voltage drop failure can be achieved, and the safety performance of the electrochemical device can be improved.

In some embodiments, the first insulating layer extends no more than 10mm in the width direction of the pole piece. The longer the extension length of the first insulating layer in the width direction of the pole piece is, the better the voltage drop failure can be prevented, but at the same time, the first insulating layer occupies the inner space of the electrode assembly, which reduces the energy density of the electrode assembly. The applicant has found through experiments that the risk of voltage drop failure can be well prevented when the extension length of the first insulating layer is not more than 10mm, while the influence on the energy density of the electrode assembly is within an acceptable range.

In some embodiments, the first insulating layer comprises a first insulating material comprising at least one of alumina, zirconia, or chromia. In some embodiments, the first insulating material comprises at least one of an alumina ceramic, a zirconia ceramic, or a chromia ceramic.

In some embodiments, the electrochemical device further comprises a second insulating layer disposed on the second surface, the second insulating layer being disposed at least in at least one of the first end or the second end of the first region, and the second insulating layer being between the first current collector and the second active material layer. The second insulating layer is arranged in the first area of the second surface, when the diaphragm close to the second surface shrinks, the second insulating layer can prevent electrons of the current collector at the position of the second insulating layer from being transmitted to the second active material layer, so that the pole piece in the area is uncharged, short circuit can not occur even if the first pole piece and the second pole piece are in contact, and the safety performance of the electrochemical device is improved. The diaphragm shrinks mainly towards the middle of the diaphragm along the width direction of the pole piece, namely the diaphragm positioned at the first end or the second end is easy to shrink, so that voltage drop failure is easy to occur at the positions of the first end of the first area and the second end of the first area, and the second insulating layer is arranged at the positions, so that the effect of better preventing the risk of voltage drop failure can be achieved, and the safety performance of the electrochemical device is further improved.

In some embodiments, the second insulating layer disposed in the first region extends no more than 10mm in the width direction of the pole piece. The longer the extension length of the second insulating layer in the width direction of the pole piece is, the better the voltage drop failure can be prevented, but at the same time, the second insulating layer occupies the inner space of the electrode assembly, which reduces the energy density of the electrode assembly. The applicant has found through experiments that the risk of voltage drop failure can be well prevented when the extension length of the second insulating layer ranges from 2mm to 10mm, while the influence on the energy density of the electrode assembly is within an acceptable range.

In some embodiments, the second insulating layer is further disposed on at least one of the second region or the third region. It is understood that the separator corresponding to the empty foil region (region not coated with the active material layer) at the tail of the electrode assembly is easily shrunk, and the risk of voltage drop failure in this region is relatively high. And after the second insulating layer is arranged on the second area and/or the third area, the second insulating layer can prevent the electron transfer between the first current collector and the second pole piece, and even if the first pole piece is in contact with the second pole piece, the short circuit can not occur, so that the safety performance of the electrochemical device is improved.

In some embodiments, the second region comprises a first portion and a second portion disposed along a length of the pole piece, and the second insulating layer is further disposed on the second portion. The second insulating layer arranged on the second part can prevent the electron transfer between the first current collector and the second pole piece, and the short circuit can not occur even if the first pole piece is in contact with the second pole piece, so that the safety performance of the electrochemical device is improved.

In some embodiments, the second insulating layer disposed in the second region or the third region has a ratio of an extension length of the first current collector in the width direction of the electrode sheet to an extension length of the second current collector in the width direction of the electrode sheet of not less than 50%.

In some embodiments, the second insulating layer comprises a second insulating material comprising at least one of alumina, zirconia, or chromia. In some embodiments, the second insulating material comprises at least one of an alumina ceramic, a zirconia ceramic, or a chromia ceramic.

In some embodiments, the electrochemical device further comprises a receiving means for receiving the electrode assembly, the receiving means comprising a first receiving portion and a second receiving portion, the first receiving portion having a depth less than a depth of the second receiving portion. When the container is accommodated in the accommodating device, the first part is in contact with the first accommodating part, and the second part is in contact with the second accommodating part.

In some embodiments, the first electrode sheet is a positive electrode sheet, the second electrode sheet includes a second current collector, and the difference between the extension length of the first current collector and the extension length of the second current collector along the width direction of the electrode sheet is not greater than 5%. It can be understood that the difference between the two is not more than 5%, and the extension length of the first current collector in the width direction of the pole piece is considered to be equal to the extension length of the second current collector in the width direction of the pole piece. So, the diaphragm can be cliied to the edge of first mass flow body and second mass flow body, and the diaphragm is more difficult to slide, the voltage drop of preventing that can be better inefficacy risk.

In some embodiments, an electrode assembly is formed by stacking a first pole piece, a second pole piece, and a separator in a first direction. The first current collector includes first and second ends disposed in the second direction, and third and fourth ends disposed in the third direction. The second direction is perpendicular to the first direction, the third direction is perpendicular to the second direction, and a first insulating layer is disposed on at least one of the first end portion, the second end portion, the third end portion, or the fourth end portion. It can be understood that when the separator shrinks, the risk of voltage drop failure at the first end portion, the second end portion, the third end portion or the fourth end portion of the stacked electrode assembly is relatively high, and the first insulating layer is disposed at these positions, so that the risk of voltage drop failure can be prevented better, and the safety performance of the electrochemical device can be improved.

In some embodiments, the first insulating layer extends along the second direction by no more than 10 mm. So set up, can better take precautions against the voltage drop risk of failing, simultaneously, the influence to electrode subassembly's energy density can be almost ignored.

In some embodiments, the electrochemical device further comprises a second insulating layer disposed on the second surface, the second insulating layer disposed on at least one of the first end, the second end, the third end, or the fourth end. And a second insulating layer is further arranged, so that voltage drop failure can be prevented better, and the safety performance of the electrochemical device is improved.

In some embodiments, the second insulating layer extends along the second direction by no more than 10 mm. So set up, can better take precautions against the voltage drop risk of failing, simultaneously, the influence to electrode subassembly's energy density can be almost ignored.

The present application also provides an electronic device comprising an electrochemical device as described above, which supplies power to the electronic device.

The application provides an electrochemical device and electron device through set up the insulating layer between mass flow body and active substance layer, cuts off this regional electron channel, even take place the diaphragm shrink, the pole piece in insulating layer region is because uncharged, and the short circuit can not take place yet in the positive and negative pole piece contact, and then has improved the problem that the voltage drop became invalid. In addition, the electrolyte content of the electrochemical device provided by the application is not reduced, and the electrical properties of the electrochemical device and the electronic device are not affected.

Drawings

The present application will be described in further detail with reference to the following drawings and detailed description.

Fig. 1 is a schematic structural view of an electrochemical device according to an embodiment of the present disclosure.

Fig. 2 is a schematic structural diagram of a first current collector according to an embodiment of the present disclosure.

Fig. 3 is a schematic structural diagram of an accommodating apparatus according to an embodiment of the present application.

Fig. 4a is a schematic structural diagram of a first pole piece according to an embodiment of the present disclosure.

Fig. 4b is a schematic structural diagram of the first pole piece in fig. 4a after being coated with an active material layer.

Fig. 5a is a schematic structural diagram of a first pole piece according to an embodiment of the present disclosure.

Fig. 5b is a schematic structural diagram of the first pole piece in fig. 5a after being coated with an active material layer.

Fig. 6 is a schematic structural view of an electrochemical device according to an embodiment of the present disclosure.

Fig. 7a is a schematic structural diagram of a first pole piece according to an embodiment of the present disclosure.

Fig. 7b is a schematic structural diagram of the first pole piece in fig. 7a after being coated with an active material layer.

Fig. 8 is a schematic structural view of an electrochemical device according to an embodiment of the present disclosure.

Fig. 9 is a schematic structural view of an electrochemical device according to an embodiment of the present disclosure.

Fig. 10 is a schematic structural diagram of a first current collector according to an embodiment of the present disclosure.

Fig. 11a is a schematic structural diagram of a first pole piece according to an embodiment of the present disclosure.

Fig. 11b is a schematic structural diagram of the first pole piece in fig. 11a after the active material layer is coated on the first pole piece.

Fig. 12 is an enlarged view at a in fig. 9.

Description of the main element symbols:

electrochemical device 100

Electrode assembly 10

Tab 30

Accommodating device 50

First housing part 51

Second receiving part 52

First pole piece 101

Second pole piece 103

Diaphragm 105

First current collector 1011

First surface 1012

Second surface 1014

First active material layer 1013

First insulating layer 1015

Second active material layer 1017

Second insulating layer 1019

First region 102

Second region 104

Third region 106

First end 1016

Second end 1018

Third end 1020

Fourth end part 1022

First portion 1041

Second part 1042

Pole piece length direction X

Pole piece width direction Y

Thickness direction Z

In the first direction Z'

Second direction X'

Third Direction Y'

The following detailed description will further describe embodiments of the present application in conjunction with the above-described figures.

Detailed Description

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 the embodiments of this application belong. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the embodiments of the present application.

It should be noted that all the directional indications (such as up, down, left, right, front, and rear … …) in the embodiment of the present application are only used to explain the relative position relationship between the components, the movement situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indication is changed accordingly.

It will be understood that when a layer is referred to as being "on" another layer, it can be directly on the other layer or intervening layers may be present. In contrast, when a layer is referred to as being "directly on" another layer, there are no intervening layers present.

With respect to "greater than" and "less than" in the present application. It will be understood that, unless otherwise specified, the terms "greater than" and "less than" in this application mean "substantially greater than" and "substantially less than", respectively. When comparing the size of one object (denoted as first object) and the other object (denoted as second object), there are errors in the calculation and measurement, as well as errors caused by the process (e.g. coating process induced coating inhomogeneity), e.g. the error may be at or 2%, etc. To eliminate this error, the ratio of the difference between the first object and the second object to the second object is limited to be greater than 5%, and the difference due to the error can be eliminated, indicating that the first object is substantially larger or smaller than the second object. It should be understood that the ratio may be adjusted to 10%, 15%, 20%, etc., depending on the actual situation.

In addition, descriptions in this application as to "first", "second", etc. are for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicit to the technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the feature. In the description of the present application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

The technical scheme of this application sets up the insulating layer through setting up on at least one in the positive pole piece and the negative pole piece of battery to set up the insulating layer between mass flow body and active substance layer, can improve the security performance of battery.

The insulating layer is arranged on a certain area of the pole piece. By disposing the insulating layer between the current collector and the active material layer, the insulating layer can prevent electrons from flowing from the current collector in this region to the active material layer in this region, and the pole piece in this region is insulated as a whole. Therefore, in the falling process, the contact short circuit of the positive and negative pole pieces can be prevented after the diaphragm contracts, and the risk of falling voltage drop failure is improved. If the active material layer is coated on the current collector and the insulating layer is arranged on the active material layer, the active material layer is in contact with the current collector, and the active material layer can normally gain and lose electrons and generate lithium intercalation and deintercalation. At this time, the electrode plate in this region is in a charged state, and when the insulating layer provided on the active material layer is too thin or is left uncoated, there is still a risk of contact short-circuiting of the positive and negative electrode plates. In addition, the interface bonding force between the active material layer and the current collector is weaker than that between the insulating layer and the current collector, and in the process of falling, an electrochemical device which is coated with the active material layer firstly and then provided with the insulating layer is easy to cause the phenomenon that the active material layer falls off, so that the current collector is exposed, the positive and negative pole pieces are in short circuit, heat is rapidly generated, the voltage is reduced, and the safety performance is reduced. Therefore, the problem of voltage drop failure can be improved only by directly coating an insulating layer on the current collector and then coating an active material layer. In addition, the technical scheme does not reduce the content of the electrolyte, and the electrical property of the electrochemical device is also ensured.

Referring to fig. 1, the present application provides an electrochemical device 100 including an electrode assembly 10. The direction Z shown in the drawing is the thickness direction of the electrode assembly 10. The electrochemical device 100 may be a battery, for example, a secondary battery (e.g., a lithium ion secondary battery, a sodium ion battery, a magnesium ion battery, etc.), a primary battery (e.g., a lithium primary battery, etc.), etc., but is not limited thereto. The electrochemical device 100 may include an electrode assembly 10 and an electrolyte.

The electrode assembly 10 comprises a first pole piece 101, a second pole piece 103 and a separator 105 located between said first pole piece 101 and said second pole piece 103. The first pole piece 101 includes a first current collector 1011, a first active material layer 1013, and a first insulating layer 1015.

The first pole piece 101 may be a positive pole piece or a negative pole piece. When the first pole piece 101 is a positive pole piece, the second pole piece 103 is a negative pole piece, and when the first pole piece 101 is a negative pole piece, the second pole piece 103 is a positive pole piece. Correspondingly, the first current collector 1011 may be a positive electrode current collector or a negative electrode current collector. The first active material layer 1013 may be a positive electrode active material layer or a negative electrode active material layer.

The positive electrode current collector may be an Al foil, but of course, other current collectors commonly used in the art may be used. In some embodiments, the thickness of the current collector of the positive electrode tab may be 1 μm to 50 μm. In some embodiments, the current collector of the negative electrode sheet may employ at least one of a copper foil, a nickel foil, or a carbon-based current collector. In some embodiments, the current collector of the negative electrode tab may have a thickness of 1 μm to 50 μm.

The negative electrode collector may be a negative electrode collector commonly used in the art. The negative electrode collector may be made of a metal foil or a porous metal plate, for example, a foil or a porous plate made of a metal such as copper, nickel, titanium, or iron, or an alloy thereof, such as copper foil. The positive electrode active material layer is disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer contains a positive electrode active material including a compound that reversibly intercalates and deintercalates lithium ions (i.e., a lithiated intercalation compound). In some embodiments, the positive active material may include a lithium transition metal composite oxide. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese and nickel. In some embodiments, the positive active material is selected from at least one of: lithium cobaltate (LiCoO)₂) Ternary lithium nickel manganese cobalt (NCM) and lithium manganate (LiMn)₂O₄) Lithium nickel manganese oxide (LiNi)_0.5Mn_1.5O₄) Or lithium iron phosphate (LiFePO)₄)。

The negative electrode active material layer is disposed on at least one surface of the negative electrode current collector. The negative electrode active material layer contains a negative electrode active material, and a negative electrode active material capable of reversibly intercalating and deintercalating active ions known in the art is used, and the present application is not limited thereto. For example, a combination including, but not limited to, one or more of graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials, tin-based materials, lithium titanate, or other metals capable of alloying with lithium, and the like may be used. Wherein, the graphite can be selected from one or more of artificial graphite, natural graphite and modified graphite; the silicon-based material can be selected from one or more of simple substance silicon, silicon oxygen compound, silicon carbon compound and silicon alloy; the tin-based material may be selected from elemental tin, tin-oxygen compounds, tin alloys, and the like, in one or more combinations.

The diaphragm comprises at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide or aramid. For example, the polyethylene includes at least one selected from high density polyethylene, low density polyethylene, or ultra high molecular weight polyethylene. Particularly polyethylene and polypropylene, which have a good effect on preventing short circuits and can improve the stability of the battery through a shutdown effect. In some embodiments, the membrane has a thickness in the range of about 5 μm to 50 μm.

The first insulating layer 1015 is disposed on the first electrode sheet 101, and can prevent electrons of the current collector at the position from transferring to the first active material layer 1013. In some embodiments, the conductivity of the first insulating layer 1015 is not greater than 1010 Ω · m.

The first insulating layer 1015 may include a first insulating material including at least one of an alumina ceramic, a zirconia ceramic, or a chromia ceramic. As an example, the first insulating material includes an alumina ceramic. In some embodiments, the first insulating layer 1015 may further include an adhesive to better adhere the first insulating material to the first pole piece 101. The binder may include at least one of carboxymethyl cellulose (CMC), polyacrylic acid, polyvinyl pyrrolidone, polyaniline, polyimide, polyamideimide, polysiloxane, styrene-butadiene rubber, epoxy resin, polyester resin, polyurethane resin, or polyfluorene.

The extension length of the first insulating layer 1015 along the width direction Y of the pole piece is not more than 10 mm. In some embodiments, the first insulating layer 1015 extends for a length of between 2mm and 10mm, e.g., 4mm to 8mm, 4mm to 6mm, etc. In some embodiments, the first insulating layer 1015 extends no less than 2mm in length. Generally, the longer the extension length of the first insulating layer 1015 in the width direction Y of the pole piece, the better the prevention of voltage drop failure, but at the same time, the first insulating layer 1015 occupies the inner space of the electrode assembly 10, which reduces the energy density of the electrode assembly 10. The applicant has found through experiments that the first insulating layer 1015 having an extended length in a range of 2mm to 10mm can prevent the risk of voltage drop failure (e.g., more than 90%) well while having an influence on the energy density of the electrode assembly 10 within an acceptable range. Further, when the extension length of the first insulating layer 1015 is not more than 2mm, the risk of voltage drop failure (for example, about 70%) can be well prevented, and at the same time, the influence on the energy density of the electrode assembly 10 can be almost negligible.

The first current collector 1011 includes a first surface 1012 and a second surface 1014 disposed opposite to each other, the first active material layer 1013 is disposed on the first surface 1012, and the first insulating layer 1015 is located between the first current collector 1011 and the first active material layer 1013.

A first insulating layer 1015 is formed on the first current collector 1011 and then the first active material layer 1013 is coated. The first insulating layer 1015 is provided on the first pole piece 101, and a portion of the first pole piece 101 on which the first insulating layer 1015 is provided is referred to as a region corresponding to the first insulating layer 1015. Correspondingly, the first current collector 1011 in this area is referred to as a current collector corresponding to the first insulating layer 1015, and the first active material layer 1013 in this area is referred to as an active material layer corresponding to the first insulating layer 1015. In the region corresponding to the first insulating layer 1015, the first insulating layer 1015 can prevent electrons from flowing from the current collector corresponding thereto to the active material layer corresponding thereto, so that the pole piece in the region is uncharged, thereby improving the safety performance of the battery. In some embodiments, the first insulating layer 1015 is disposed directly on the first pole piece 101. Since the active material layer generally contains components with poor adhesion such as a conductive agent and an active material, the first insulating layer 1015 and the first current collector 1011 have better adhesion and are less likely to fall off than the active material layer.

As shown in fig. 1, the electrode assembly 10 is wound from a first pole piece 101, a second pole piece 103, and a separator 105. The first surface 1012 is disposed facing the winding center (or simply, the winding center) of the electrode assembly 10, and the second surface 1014 is disposed away from the winding center. Electrochemical device 100 also includes a second active material layer 1017 disposed on second surface 1014.

Referring to fig. 2, the electrochemical device 100 further includes a tab 30 electrically connected to the first current collector 1011, the first current collector 1011 includes a first end 1016 and a second end 1018 arranged along the pole piece width direction Y, and the tab 30 is arranged at the first end 1016. The first current collector 1011 includes a first region 102, a second region 104, and a third region 106 disposed along the pole piece length direction X. In some embodiments, the second region 104 and the third region 106 are located at the trailing end of the first current collector 1011. In some embodiments, the terminating end of the first current collector 1011 is located at the outermost circle of the electrode assembly 10. In some embodiments, the terminating ends of the first current collector 1011 are located at the outermost and the next outermost rings of the electrode assembly 10.

The second region 104 includes a first portion 1041 and a second portion 1042 disposed along the pole piece length direction X. When received in a receiving device (e.g., receiving device 50), second portion 1042 is received in a well of the receiving device. The description of the pit section can be found in other relevant parts of the present application.

A first active material layer 1013 is provided on the first surface 1012 of the first region 102 and on the first surface 1012 of the second region 104, and a second active material layer 1017 is provided on the second surface 1014 of the first region 102.

By "end" is meant in this application the area extending 30% inwards from the edge. For example, the first end 1016 of the first pole piece 101 has a first edge, and the first end 1016 of the first pole piece 101 refers to an area extending 30% from the first edge towards the inside of the first pole piece 101.

The first insulating layer 1015 is provided at least on at least one of the following areas: a first end 1016 of the first region 102, a first end 1016 of the second region 104, and a first end 1016 of the third region 106; alternatively, the second end 1018 of the first region 102, the second end 1018 of the second region 104, and the second end 1018 of the third region 106. Generally, when the membrane 105 contracts, the risk of voltage drop failure at the positions of the first end 1016 of the first region 102, the first end 1016 of the second region 104, the first end 1016 of the third region 106, the second end 1018 of the first region 102, the second end 1018 of the second region 104 and the second end 1018 of the third region 106 is relatively high, and the first insulating layer 1015 is arranged at the positions to play a role in better preventing the risk of voltage drop failure and improve the safety performance of the electrochemical device.

In some embodiments, the first insulating layer 1015 penetrates the first pole piece 101 along the pole piece length direction (X-direction). Specifically, the length of the first insulating layer 1015 in the pole piece length direction is substantially equal to the length of the first pole piece 101 in the pole piece length direction. It is noted that the width of the first insulating layer 1015 in different areas of the first pole piece 101 along the length of the pole piece can be approximately equal. For example, the first insulating layer 1015 on at least two of the first region 102, the second region 104, and the third region 106 of the first pole piece 101 have the same width — length in the pole piece width direction Y. For example, at least two of the width of the first insulating layer 1015 provided on the first surface of the first region 102, the width of the first insulating layer 1015 provided on the first surface of the second region 104, and the width of the first insulating layer 1015 provided on the first surface of the third region 106 are substantially equal. The two values are substantially the same, meaning that the two values differ by a degree within 20%. It should be understood that two values are substantially the same, and that the difference between the two values is within 15%, within 10%, within 5%, etc. depending on the measurement method. The degree of difference between two values refers to the ratio of the absolute value of the difference between the two values to the smaller of the two values.

Referring to fig. 3, the electrochemical device 100 further includes a receiving device 50 for receiving the electrode assembly 10. The receiving device 50 includes a first receiving portion 51 and a second receiving portion 52, and the depth of the first receiving portion 51 is smaller than that of the second receiving portion 52. The receiving device 50 may be an aluminum plastic film commonly used in the art, and the application is not limited thereto.

As shown in fig. 3, the depth of first receiving portion 51 and the depth of second receiving portion 52 are the lengths extending in the direction M.

In one embodiment, the electrochemical device 100 further comprises a second insulating layer 1019 disposed on the second surface 1014, the second insulating layer 1019 being disposed at least at one of the first end 1016 of the first region 102 or the second end 1018 of the first region 102, and the second insulating layer 1019 being between the first current collector 1011 and the second active material layer 1017. The second insulating layer 1019 is disposed in the first region 102 of the second surface 1014, and when the separator 105 near the second surface 1014 shrinks, the second insulating layer 1019 can prevent electrons of the current collector at the position of the second insulating layer from being transferred to the second active material layer 1017, so that the pole piece in the region is uncharged, and even if the first pole piece 101 and the second pole piece 103 are in contact, a short circuit does not occur, and the safety performance of the electrochemical device 100 is improved. Since the separator 105 shrinks mainly in the pole piece width direction Y toward the middle of the separator 105, that is, the separator 105 at the first end 1016 or the second end 1018 easily shrinks, voltage drop failure easily occurs at the first end 1016 of the first region 102 and the second end 1018 of the first region 102, and the second insulating layer 1019 is disposed at these positions, which can better prevent the risk of voltage drop failure, and further improve the safety performance of the electrochemical device 100.

In some embodiments, the second insulating layer 1019 penetrates the second pole piece 103 along the pole piece length direction (X-direction). Specifically, the length of the second insulating layer 1019 in the pole piece length direction is substantially equal to the length of the second pole piece 103 in the pole piece length direction. It is noted that the arrangement of the second insulating layer 1019 in different areas of the second pole piece 103 may be different along the length of the pole piece. For example, the second insulating layer 1019 on at least two of the first region 102, the second region 104, and the third region 106 of the second pole piece 103 have different widths — lengths in the pole piece width direction Y. For example, the width of the second insulating layer 1019 provided on the second surface of the third region 106 is greater than the width of the second insulating layer 1019 provided on the second surface of the first region 102. For another example, the width of the second insulating layer 1019 provided on the second surface of the third region 106 is larger than the width of the second insulating layer 1019 provided on the second surface of the second region 104.

Referring to fig. 2 and 4a, the electrochemical device 100 includes a first insulating layer disposed on the first surface 1012 and a second insulating layer 1019 disposed on the second surface 1014. A first insulating layer 1015 is disposed over the first end 1016 of the first region 102, the first end 1016 of the second region 104, the first end 1016 of the third region 106, the second end 1018 of the first region 102, the second end 1018 of the second region 104, and the second end 1018 of the third region 106, and a second insulating layer 1019 is disposed over the first end 1016 of the first region 102 and the second end 1018 of the first region 102. The first pole piece 101 shown in fig. 4a is coated with an active material layer to obtain the first pole piece 101 shown in fig. 4 b. Referring to fig. 4b, a first active material layer 1013 is disposed on the first surface 1012 of the first region 102 and the first surface 1012 of the second region 104, and a second active material layer 1017 is disposed on the second surface 1014 of the first region 102.

The first region 102 is a double-coated region, and both the side facing the winding center and the side facing away from the winding center are coated with an active material layer. The second region 104 is a single-side coated region, and has one side facing the winding center coated with an active material layer and the other side facing away from the winding center uncoated with an active material layer. After the first pole piece 101, the separator 105 and the second pole piece 103 shown in fig. 4b are wound, the wound structure shown in fig. 1 is obtained.

The electrode assembly 10 shown in fig. 1 is housed in the housing device 50. The first portion 1041 is received in at least the first receiving portion 51, and the second portion 1042 is received in the second receiving portion 52. A part of the first portion 1041 is accommodated in the first accommodating portion 51, the first accommodating portion 51 covers a part of the first portion 1041, and a part of the first portion 1041 is in direct contact with the first accommodating portion 51 or in contact with the first accommodating portion through other intermediate members. Second portion 1042 is accommodated in second accommodating portion 52, second accommodating portion 52 covers second portion 1042, and second portion 1042 is in direct contact with second accommodating portion 52 or in contact with the first accommodating portion through other intermediate members.

A portion of first portion 1041 contacts first receiving portion 51, and second portion 1042 contacts second receiving portion 52. Correspondingly, in some embodiments, the first portion 1041 and the second portion 1042 are referred to as a shallow pit surface and a deep pit surface, respectively. It is understood that first insulating layer 1015 disposed on first end 1016 of second region 104 and second end 1018 of second region 104 is located in both first receiving portion 51 and second receiving portion 52.

When the electrode assembly 10 moves in the containing device 50 during dropping and the electrolyte impacts the membrane 105 at the head and tail of the electrode assembly 10 to cause the membrane 105 to shrink, since the first insulating layer 1015 can prevent electrons from flowing from the current collector to the active material layer, the first pole piece 101 in the area corresponding to the first insulating layer 1015 is not electrified, and even if the area is in contact with the second pole piece 103, short circuit does not occur in the area, so that the risk of voltage drop failure can be improved. Similarly, the second insulating layer 1019 can prevent electrons from flowing from the current collector to the active material layer, the first pole piece 101 in the region corresponding to the second insulating layer 1019 is not charged, and even if the region is in contact with the second pole piece 103, short circuit does not occur in the region, so that the risk of voltage drop failure is further improved.

In one embodiment, a second insulating layer 1019 is further disposed on at least one of the second region 104 or the third region 106.

Referring to fig. 2 and 5a, a first insulating layer 1015 is disposed over the first end 1016 of the first region 102, the first end 1016 of the second region 104, the first end 1016 of the third region 106, the second end 1018 of the first region 102, the second end 1018 of the second region 104, and the second end 1018 of the third region 106, and a second insulating layer 1019 is disposed over the first end 1016 of the first region 102, the second end 1018 of the first region 102, and the second portion 1042. It is understood that the second insulating layer 1019 may also be disposed on the first end 1016 of the first region 102, the second end 1018 of the first region 102, and the first portion 1041.

The first pole piece 101 shown in fig. 5a is coated with an active material layer to obtain the first pole piece 101 shown in fig. 5 b. Referring to fig. 5b, a first active material layer 1013 is disposed on the first surface 1012 of the first region 102 and the first surface 1012 of the second region 104, and a second active material layer 1017 is disposed on the second surface 1014 of the first region 102. After the first pole piece 101, the separator 105 and the second pole piece 103 shown in fig. 5b are wound, a wound structure as shown in fig. 6 is obtained.

When electrode assembly 10 shown in fig. 6 is housed in housing device 50, first portion 1041 contacts first housing portion 51, and second portion 1042 contacts second housing portion 52. It is understood that first insulating layer 1015 disposed over first end 1016 of second region 104 and second end 1018 of second region 104 is located in both first receiving portion 51 and second receiving portion 52; the second insulating layer 1019 disposed on the second portion 1042 is located in the second receiving portion 52.

Referring to fig. 2 and 7a, a first insulating layer 1015 is disposed over the first end 1016 of the first region 102, the first end 1016 of the second region 104, the first end 1016 of the third region 106, the second end 1018 of the first region 102, the second end 1018 of the second region 104, and the second end 1018 of the third region 106, and a second insulating layer 1019 is disposed over the first end 1016 of the first region 102, the second end 1018 of the first region 102, the second region 104, and the third region 106. The first pole piece 101 shown in fig. 7a is coated with an active material layer to obtain the first pole piece 101 shown in fig. 7 b. Referring to fig. 7b, a first active material layer 1013 is disposed on the first surface 1012 of the first region 102 and the first surface 1012 of the second region 104, and a second active material layer 1017 is disposed on the second surface 1014 of the first region 102. After the first pole piece 101, the separator 105 and the second pole piece 103 shown in fig. 7b are wound, a wound structure as shown in fig. 8 is obtained.

When electrode assembly 10 shown in fig. 8 is housed in housing device 50, first portion 1041 contacts first housing portion 51, and second portion 1042 contacts second housing portion 52. It is understood that first insulating layer 1015 disposed over first end 1016 of second region 104 and second end 1018 of second region 104 is located in both first receiving portion 51 and second receiving portion 52; the second insulating layer 1019 provided in the second region 104 is located in both the first receiving portion 51 and the second receiving portion 52.

The material composition of the second insulating layer 1019 can be referred to the material composition of the first insulating layer 1015, and is not repeated here. In some embodiments, the second insulating layer 1019 and the first insulating layer 1015 comprise the same material, and the composition content of the corresponding same material is substantially the same. In the present application, the component content of the material in the insulating layer refers to the mass percentage content of the component in the insulating layer. In the present application, two values are substantially the same, meaning that the degree of difference between the two values is within 20%. It should be understood that two values are substantially the same, and that the difference between the two values is within 15%, within 10%, within 5%, etc. depending on the measurement method. The degree of difference between two values refers to the ratio of the absolute value of the difference between the two values to the smaller of the two values. In some embodiments, the second insulating layer 1019 and the first insulating layer 1015 comprise different materials.

Further, the extension length of the second insulating layer 1019 on the first region 102 in the width direction of the pole piece is not more than 10 mm. In some embodiments, the first insulating layer 1015 extends for a length of between 2mm and 10mm, e.g., 4mm to 8mm, 4mm to 6mm, etc. In some embodiments, the first insulating layer 1015 extends no less than 2mm in length. Generally, the longer the extension length of the second insulating layer 1019 along the width direction Y of the pole piece is, the better the voltage drop failure can be prevented, but at the same time, the second insulating layer 1019 occupies the inner space of the electrode assembly 10, which reduces the energy density of the electrode assembly 10. The applicant has found through experiments that the second insulating layer 1019 may extend over a length ranging from 2mm to 10mm, so as to better protect against the risk of voltage drop failure (e.g., over 90%), while having an effect on the energy density of the electrode assembly 10 within an acceptable range. Further, when the extension length of the second insulating layer 1019 is not more than 2mm, the risk of voltage drop failure (for example, about 70%) can be prevented well, and at the same time, the influence on the energy density of the electrode assembly 10 is almost negligible.

Further, the ratio of the extension length of the second insulating layer 1019 on the second region 104 or the third region 106 in the pole piece width direction Y to the extension length of the first current collector 1011 in the pole piece width direction Y is not less than 50%.

In one embodiment, the first electrode sheet 101 is a positive electrode sheet, and the second electrode sheet 103 includes a second current collector, and the extension length (width) of the first current collector 1011 differs from the extension length (width) of the second current collector by no more than 5% along the width direction Y of the electrode sheet. Due to measurement errors, when the difference between the widths of the first current collector 1011 and the second current collector is not greater than 5%, the widths of the first current collector 1011 and the second current collector are considered to be equal or substantially equal, and the difference is calculated by: (width of second current collector-width of first current collector 1011)/width of first current collector 1011. Therefore, the difference between the width of the first current collector 1011 and the width of the second current collector is not greater than 5%, and the extension length of the first current collector 1011 in the width direction Y of the pole piece is considered to be equal to the extension length of the second current collector in the width direction Y of the pole piece. Thus, the edges of the first current collector 1011 and the second current collector can clamp the diaphragm 105, the diaphragm 105 is not easy to slide, and the risk of voltage drop failure can be better prevented.

Further, the first and second electrode sheets 101 and 103 may be prepared by a method conventional in the art, for example, the first and second active material layers 1013 and 1017 may be made of lithium cobaltate (LiCoO)₂) Conductive carbon black (Super P), polyvinylidene fluoride (PVDF), N-methylpyrrolidone (NMP), and the like, and the present application is not limited thereto. The separator 105 may be a separator commonly used in the art, such as a Polyethylene (PE) separator or a Polypropylene (PE) separator, and the like, and the present application is not limited thereto.

Referring to fig. 9, the electrode assembly 10 may be further formed by stacking a first pole piece 101, a second pole piece 103, and a separator 105 along the first direction Z'. The first direction Z ' is defined as a thickness direction of the electrode assembly 10, the second direction X ' is perpendicular to the first direction Z ', and the third direction Y ' is perpendicular to the second direction X '. The second direction X' may be a length direction of the pole pieces in the stacked electrode assembly 10, and may also be a width direction of the pole pieces. When the second direction X 'is a length direction of the pole pieces in the stacked electrode assembly 10, the third direction Y' is a width direction of the pole pieces in the electrode assembly 10. And vice versa.

The contents of the first pole piece 101, the second pole piece 103, the diaphragm 105, the first insulating layer 1015 and the second insulating layer 1019 can be found in the description above. And will not be described in detail herein.

Referring to fig. 10, the first current collector 1011 includes a first end 1016 and a second end 1018 disposed along the second direction X ', and a third end 1020 and a fourth end 1022 disposed along the third direction Y'. A first insulating layer 1015 is disposed on at least one of the first end portion 1016, the second end portion 1018, the third end portion 1020, or the fourth end portion 1022.

In one embodiment, the electrochemical device 100 further comprises a second insulating layer 1019 disposed on the second surface 1014. A second insulating layer 1019 is disposed on at least one of the first end 1016, second end 1018, third end 1020, or fourth end 1022.

Referring to fig. 11a, a first insulating layer 1015 is disposed on the first end portion 1016, the second end portion 1018, the third end portion 1020, and the fourth end portion 1022, and a second insulating layer 1019 is disposed on the first end portion 1016, the second end portion 1018, the third end portion 1020, and the fourth end portion 1022. The first pole piece shown in fig. 11a was further coated with an active material layer to obtain a first pole piece as shown in fig. 11 b. Referring to fig. 11b, a first active material layer 1013 is disposed on the first surface 1012 and a second active material layer 1017 is disposed on the second surface 1014. The first pole piece 101, the separator 105 and the second pole piece 103 shown in fig. 11b are stacked to obtain the electrode assembly 10 shown in fig. 9.

Fig. 12 is an enlarged view of a point a of the first pole piece 101 at the fourth end 1022 in fig. 9. As shown in fig. 12, along the third direction Z', the first pole piece 101 includes a first current collector 1011, a first insulating layer 1015 and a second insulating layer 1019 respectively disposed on both surfaces of the first current collector 1011, a first active material layer 1013 disposed on the first insulating layer 1015, and a second active material layer 1017 disposed on the second insulating layer 1019.

Further, along the second direction X', the extension length of the first insulating layer 1015 is not more than 10 mm. Preferably, the first insulating layer 1015 extends along the second direction X' in a length ranging from 2mm to 10 mm.

Further, along the second direction X', the second insulating layer 1019 extends no more than 10 mm. Preferably, the second insulating layer 1019 extends along the second direction X' in a length range of 2mm to 10 mm.

The present application will be further described with reference to specific examples and comparative examples.

Example 1

(1) Preparation of Positive electrode sheet (first electrode sheet)

A layer of strip-shaped alumina ceramic (first insulating layer) with the width of 4mm is coated on the end portions of the first area, the second area and the third area of the aluminum foil first surface of the positive electrode current collector (first current collector), and a layer of strip-shaped alumina ceramic (second insulating layer) with the width of 4mm is coated on the end portion of the first area of the second surface, so as to obtain the positive electrode piece shown in fig. 4 a.

The positive electrode active material lithium cobaltate (LiCoO)₂) Mixing conductive carbon black (Super P) and polyvinylidene fluoride (PVDF) according to the weight ratio of 97.5:1.0:1.5, adding N-methylpyrrolidone (NMP) as a solvent, preparing into slurry with the solid content of 0.75, and uniformly stirring. And uniformly coating the slurry on the second area and the third area of the first surface coated with the first insulating layer, drying at 90 ℃, and then coating the slurry on the second area of the second surface. After coating, the positive active material layer of the pole piece is cold-pressed to 4.0g/cm³And then carrying out auxiliary processes such as tab welding, gummed paper pasting and the like, namely the preparation flow of the positive pole piece.

(2) Preparation of negative pole piece

Mixing Graphite (Graphite) as a negative active material, conductive carbon black (Super P) and Styrene Butadiene Rubber (SBR) according to a weight ratio of 96:1.5:2.5, and adding deionized water as a solventAnd (4) preparing the agent into slurry with the solid content of 0.7, and uniformly stirring. Uniformly coating the slurry on a second current collector copper foil, wherein the weight of the negative active substance on the second pole piece is 95g/m². Drying at 110 ℃ to finish the single-side coating of the negative pole piece, and finishing the coating of the other side by the same method. After coating, the negative active material layer of the pole piece is cold-pressed to 1.7g/cm³The compacted density of (a). And then carrying out auxiliary processes such as tab welding, gummed paper pasting and the like, thus completing the preparation process of the double-sided coated negative pole piece.

(3) Preparation of the electrolyte

In a dry argon atmosphere, organic solvents of Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) were first mixed in a mass ratio of EC: EMC: DEC: 30:50:20, and then lithium salt lithium hexafluorophosphate (LiPF) was added to the organic solvent₆) Dissolved and mixed uniformly to obtain an electrolyte solution with the concentration of lithium salt of 1.15M.

(4) Preparation of electrochemical devices

Polyethylene (PE) with the thickness of 15 mu m is selected as a diaphragm, and the prepared positive pole piece, the diaphragm and the negative pole piece are sequentially stacked and wound to obtain a winding structure as shown in figure 1, wherein one surface of the positive pole piece, which is coated with the first insulating layer, faces to the winding center, and the other surface of the positive pole piece faces away from the winding center. The electrode assembly is placed in a receiving device (aluminum plastic film) in which the first insulating layer is located in both the first receiving portion (shallow pit surface) and the second receiving portion (deep pit surface). And (3) sealing the top and the side, injecting liquid, and forming (charging to 3.3V at a constant current of 0.02C and then charging to 3.6V at a constant current of 0.1C) to obtain the electrochemical device with the length of 90mm, the width of 66mm and the thickness of 4.8 mm.

Example 2

The difference from example 1 is that: the structure of the electrochemical device is a laminated structure, and strip-shaped alumina ceramics (a first insulating layer) with the width of 4mm is arranged at the first end part, the second end part, the third end part and the fourth end part of the positive pole piece. The rest is the same as the embodiment 1, and the description is omitted.

Comparative example 1

The difference from example 1 is that: the preparation process of the positive pole piece does not comprise the step of coating the first insulating layer and the second insulating layer. The rest is the same as the embodiment 1, and the description is omitted.

The electrochemical devices prepared in the above-described examples 1 and 2 and comparative example 1 were subjected to a drop test: the fully charged electrochemical device was dropped from a height of 1.2m onto a hard rubber plate and observed for breakage, leakage, deformation and explosion. If none of the above occurs, the drop test is passed. The test results are: all of the 10 electrochemical devices of example 1 passed the drop test, all of the 10 electrochemical devices of example 2 passed the drop test, and only 4 of the 10 electrochemical devices of comparative example 1 passed the drop test.

From the drop test results, the drop voltage drop failure of the electrochemical device of the embodiment group is significantly improved, which shows that the drop voltage drop failure and other performances can be effectively improved by arranging the insulating layer between the current collector and the active material layer.

The application provides an electrochemical device and electron device through set up the insulating layer between mass flow body and active substance layer, cuts off this regional electron channel, even take place the diaphragm shrink, the pole piece in insulating layer region is because uncharged, and the short circuit can not take place yet in the positive and negative pole piece contact, and then has improved the problem that the voltage drop became invalid. In addition, the electrolyte content of the electrochemical device provided by the application is not reduced, and the electrical properties of the electrochemical device and the electronic device are not affected.

The above description is a few specific embodiments of the present application, but in practical applications, the present application is not limited to these embodiments. Other modifications and variations to the technical concept of the present application should fall within the scope of the present application for those skilled in the art.