CN111987282B - Electrochemical device and electronic device - Google Patents
Electrochemical device and electronic device Download PDFInfo
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- CN111987282B CN111987282B CN202010932979.1A CN202010932979A CN111987282B CN 111987282 B CN111987282 B CN 111987282B CN 202010932979 A CN202010932979 A CN 202010932979A CN 111987282 B CN111987282 B CN 111987282B
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- current collector
- pole piece
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/04—Construction or manufacture in general
- H01M10/0431—Cells with wound or folded electrodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The present application relates to the field of energy storage, and more particularly, to an electrochemical device and an electronic device. The electrochemical device includes a case, an electrode assembly, a conductive sheet, an insulator, and a first connecting member. The electrode assembly is accommodated in the shell and comprises a first pole piece, a second pole piece and an isolating membrane, and the isolating membrane is arranged between the first pole piece and the second pole piece. The first pole piece comprises a first current collector, and the second pole piece comprises a second current collector. The first current collector includes a first portion that is an outermost first current collector in the electrode assembly. The conducting strip is electrically connected with the second current collector and arranged between the first part and the shell. The insulator is disposed between the first portion and the conductive sheet. The first connecting piece is connected with the conducting plate and the shell. The application provides an electrochemical device and electron device can reduce SOC under the circumstances of temperature rising to can avoid the risk that thermal runaway brought, the security is higher.
Description
Technical Field
The present application relates to the field of energy storage, and more particularly, to an electrochemical device and an electronic device.
Background
With the development of new energy technology, the application of energy storage devices is more and more extensive. In the prior art, an electrochemical device outputs electric energy by electrochemical reaction between an electrode assembly and an electrolyte. However, in the prior art, the safety of electrochemical devices at high temperatures is still to be improved.
Disclosure of Invention
The present application provides an electrochemical device and an electronic device to improve the safety of the electrochemical device at high temperatures.
A first aspect of the present application provides an electrochemical device including a case, an electrode assembly, a conductive sheet, an insulator, and a first connecting member.
The electrode assembly is accommodated in the shell and comprises a first pole piece, a second pole piece and an isolation film, and the isolation film is arranged between the first pole piece and the second pole piece. The first pole piece comprises a first current collector, the second pole piece comprises a second current collector, the first current collector comprises a first portion, and the first portion is an outermost first current collector in the electrode assembly.
The conducting strip is electrically connected with the second current collector and arranged between the first part and the shell. The insulator is disposed between the first portion and the conductive sheet. The first connecting piece is connected with the conducting plate and the shell.
The application provides an electrochemical device, under normal atmospheric temperature, electrochemical device is in normal operating condition, and it is insulating through the insulating part between first mass flow body and the second mass flow body. When the temperature of the electrochemical device rises, the insulating part loses the insulating function, and the first part of the first current collector can be conducted with the second current collector through the conducting strip. At this time, the electrochemical device starts self-discharge, and the voltage drops, thereby lowering the state of charge of the electrochemical device, and thus improving the safety of the electrochemical device at high temperatures.
After the first current collector and the second current collector are conducted, the temperature of the electrochemical device gradually rises, and a side reaction occurs in the electrochemical device to generate gas. The gas inside the shell expands, and the shell pulls the conducting strip to move through the first connecting piece under the action of the gas expansion, so that the conducting strip is disconnected from the first part, and the conduction of the first part of the first current collector and the second current collector is cut off. The electrochemical device will thus not continue to generate heat, the temperature of the electrochemical device will start to drop and the voltage will return to a certain value. Since the voltage at this moment has already decreased with respect to the starting voltage, the temperature at the conduction continues to decrease. The application provides an electrochemical device can make electrochemical device carry out self-discharge under the circumstances of temperature rising, reduces SOC to can avoid the risk that thermal runaway brought, the security is higher.
In some embodiments, the insulation comprises a heat shrinkable material having a heat shrinkage of 10% to 80%.
In the above scheme, the thermal shrinkage material with the thermal shrinkage rate of 10% to 80% is adopted, so that the insulating part can be ensured to generate certain shrinkage when the temperature rises, and the risk of too fast temperature rise caused by too large contact area of the first current collector and the second current collector due to too large shrinkage area can be avoided.
In some embodiments, the insulation is heat shrink paper.
In the above scheme, the insulating piece is the thermal contraction adhesive tape, the insulating piece can be directly fixed between the first part and the conducting strip without other additional fixing structures, the space of the electrochemical device is saved, and the energy density of the electrochemical device is improved. Wherein the insulator is a part of the isolation film. The scheme has the advantages of simple structure, high space utilization rate of the electrochemical device and improvement on the energy density of the electrochemical device.
In some embodiments, the insulating member is provided with a through hole, the through hole is provided with an insulating material, the melting point of the insulating material ranges from 70 ℃ to 90 ℃, and the diameter of the through hole ranges from 1mm to 100mm.
In the above scheme, through set up the through-hole on the insulating part, can come the insulating area of contact between control first mass flow body and the conducting strip through the size of design through-hole, and then control electrochemical device's temperature rising speed.
In some embodiments, the electrochemical device further comprises a resistive member, the resistive member being a negative temperature coefficient thermistor, the resistive member being disposed between the insulating member and the first portion, or the resistive member being disposed between the insulating member and the conductive sheet.
In the above-mentioned scheme, along with the rising of electrochemical device temperature, because above-mentioned resistance spare is negative temperature coefficient thermistor, it can be along with the temperature rise resistance and be the exponential relation and reduce, consequently can accelerate the speed of discharging, and set up the resistance spare that has certain resistance between first mass flow body and the second mass flow body, can not lead to the direct contact of first mass flow body and second mass flow body for discharge current is too big, produces the safety risk.
In some embodiments, the electrochemical device further includes a second connection member connecting the electrode assembly and the case, the first connection member and the second connection member being located at opposite sides of the electrode assembly.
After the first current collector and the second current collector are connected, the temperature of the connected part is continuously increased, the gas inside the shell expands, and the shell pulls the conducting strip through the first connecting piece under the action of the gas expansion, so that the conducting strip is disconnected from the first part. Since the second connector is provided at a side of the electrode assembly remote from the first connector, the second connector can fixedly connect the case and the electrode assembly. Under the tensile force of the second connecting piece, the electrode assembly does not deviate towards the direction of the first connecting piece, so that the electrode assembly can be stably fixed in the shell, and the safety performance of the electrochemical device is further improved.
In some embodiments, at least one of the first connecting member or the second connecting member includes an adhesive material, the adhesive material being a double-sided tape or a hot melt adhesive.
The scheme has the advantages of convenient material taking and firm bonding.
In some embodiments, the electrode assembly is a wound structure, and the conductive sheet is a portion of the second current collector from which the wound end extends, and has a width smaller than that of the second current collector in a vertical winding direction.
The width of the conducting strip is smaller than that of the second current collector, so that the overlarge contact area between the first part of the first current collector and the second current collector can be avoided. Therefore, the temperature of the electrochemical device does not increase too fast to be high, so that the safety of the electrochemical device is improved. Simultaneously, also can make first connecting piece pull open conducting strip and first mass flow body more easily when the casing flatulence.
A second aspect of the present application provides an electronic device comprising an electrochemical device according to any one of the above.
The application provides an electron device under normal atmospheric temperature, electrochemical device are in normal operating condition, and it is insulating through the insulating part between first mass flow body and the second mass flow body. When the temperature of the electrochemical device rises, the insulating part loses the insulating function, the first part of the first current collector can be conducted with the second current collector through the conducting strip, the electrochemical device starts to perform self-discharge at the moment, the voltage is reduced, the charge state of the electrochemical device is reduced, and therefore the safety of the electrochemical device at high temperature can be improved.
After the first current collector and the second current collector are conducted, the temperature of the electrochemical device gradually rises, and a side reaction occurs in the electrochemical device to generate gas. The gas inside the shell expands, and the shell pulls the conducting strip to move through the first connecting piece under the action of the gas expansion, so that the conducting strip is disconnected from the first part, and the conduction of the first part of the first current collector and the second current collector is cut off. The electrochemical device will thus not continue to generate heat, the temperature of the electrochemical device will start to drop and the voltage will return to a certain value. Since the voltage at this moment has decreased with respect to the starting voltage, the temperature at the conduction continues to decrease. The application provides an electrochemical device and electron device can make electrochemical device carry out self-discharge under the circumstances of temperature rising, reduces SOC to can avoid the risk that thermal runaway brought, the security is higher.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application.
Drawings
In order to more clearly illustrate the detailed description of the present application or the technical solutions in the prior art, the drawings that are required in the detailed description of the present application or the technical solutions in the prior art will be briefly described below. It is apparent that the drawings in the following description are of some embodiments of the application, and that other drawings may be derived from those drawings by a person skilled in the art.
Fig. 1 is a structural sectional view of an electrochemical device according to an embodiment of the present application;
FIG. 2 is a schematic view of a partial structure of an electrochemical device according to an embodiment of the present application;
FIG. 3 is an enlarged view taken at A in FIG. 2;
fig. 4 is a top structural view of an insulating member in an electrochemical device according to an embodiment of the present application;
fig. 5 is a structural sectional view of an electrochemical device according to an embodiment of the present application;
FIG. 6 is a perspective view of an electrochemical device according to an embodiment of the present application;
fig. 7 is a sectional view of an electrochemical device according to an embodiment of the present application;
FIG. 8 is a perspective view of an electrochemical device according to an embodiment of the present application;
fig. 9 is a sectional view of an electrochemical device according to an embodiment of the present application;
fig. 10 is a graph showing temperature and voltage changes of an electrochemical device according to an embodiment of the present application.
Reference numerals are as follows:
1-a shell;
2-an electrode assembly;
21-a first pole piece;
211-a first current collector;
211 a-first portion;
212 — first active material layer;
22-a second pole piece;
221-a second current collector;
222-a second active material layer;
23-a barrier film;
3, conducting strips;
4-an insulator;
41-through holes;
5-a first connecting member;
6-a second connector;
7-a resistive member;
8-electrode terminals.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and, together with the description, serve to explain the principles of the application.
Detailed Description
The technical solutions of the present application will be described clearly and completely with reference to the accompanying drawings, and it is to be understood that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments.
The terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the examples of this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.
It should be noted that the terms "upper", "lower", "left", "right", and the like used in the embodiments of the present application are described in terms of the angles shown in the drawings, and should not be construed as limiting the embodiments of the present application. In addition, in this context, it will also be understood that when an element is referred to as being "on" or "under" another element, it can be directly on "or" under "the other element or be indirectly on" or "under" the other element via an intermediate element.
The embodiment of the application provides an electronic device, and this electronic device can be cell-phone, computer, wearable equipment, unmanned aerial vehicle, electric tool, energy memory, electric bicycle or electric automobile etc. and this electronic device includes electrochemical device for produce the electric energy.
As shown in fig. 1, the present embodiment provides an electrochemical device including a case 1 and an electrode assembly 2. The housing 1 may have a hexahedral shape or other shapes. A receiving chamber for receiving the electrode assembly 2 and an electrolyte (not shown in the drawings) may be formed in the case 1. The shell 1 has a certain deformation capacity, and when gas expands in the shell 1, the shell 1 can deform.
In one embodiment, the case 1 is a packaging film including a protective layer, a metal layer, and a heat seal layer. The protective layer can be made of nylon materials, the metal layer can be made of metal materials such as iron foils or aluminum foils, and the heat sealing layer can be made of polypropylene or polyethylene hot-melt materials.
The electrode assembly 2 includes a first pole piece 21, a second pole piece 22, and a separator 23, the separator 23 being disposed between the first pole piece 21 and the second pole piece 22. Specifically, the first pole piece 21 may be a positive pole piece, and the second pole piece 22 may be a negative pole piece. Alternatively, the first pole piece 21 is a negative pole piece, and the second pole piece 22 is a positive pole piece. The isolation film 23 is used to separate the first pole piece 21 and the second pole piece 22, and prevent the first pole piece 21 and the second pole piece 22 from short-circuiting.
In one embodiment, three of the first pole piece 21, the isolation film 23 and the second pole piece 22 are sequentially stacked and wound, i.e. the electrode assembly 2 is a winding structure. In another embodiment, the first pole piece 21, the separator 23 and the second pole piece 22 are stacked in sequence, and the electrode assembly 2 has a laminated structure. Meanwhile, the electrode assembly 2 has a gap after being formed, and the electrolyte can enter the electrode assembly 2 through the gap to wet the first pole piece 21 and the second pole piece 22.
As shown in fig. 1, the bent cross-sectional shape of the electrode assembly 2 after winding is specifically shown. In the embodiment shown in fig. 2, the electrode assembly 2 is wound to form a shape having an elliptical cross-section. In other embodiments, the electrode assembly 2 may be formed into other shapes after being wound, and is not further limited herein.
As shown in fig. 3, which illustrates a partial structure of the electrode assembly 2, the first electrode sheet 21 includes a first current collector 211, and the second electrode sheet 22 includes a second current collector 221. The first current collector 211 and the second current collector 221 may be a positive current collector and a negative current collector, respectively, the negative current collector may be a copper foil, and a negative active material layer (for example, a carbon material or a silicon material, etc.) is coated on a surface of the copper foil, that is, the second active material layer 222 in fig. 3, to form a negative electrode tab. The positive electrode current collector may be an aluminum foil, and a positive electrode active material layer (for example, a nickel-cobalt-manganese ternary material, lithium iron phosphate, or lithium cobaltate, etc.) is coated on the surface of the aluminum foil, that is, the first active material layer 212 in fig. 3, to form a positive electrode sheet.
Referring to fig. 1, the first current collector 211 of the first electrode piece 21 includes a first portion 211a, and the first portion 211a is an outermost first current collector 211 in the electrode assembly 2. The electrochemical device provided by the embodiment of the present application further includes a conductive sheet 3, an insulating member 4, and a first connecting member 5.
In one embodiment, no active material layer is provided on both the first portion 211a and the conductive sheet 3.
The conductive sheet 3 is electrically connected to the second current collector 221 of the second pole piece 22, the conductive sheet 3 being disposed between the first portion 211a and the case 1. The insulator 4 is disposed between the first portion 211a and the conductive plate 3, and the first connector 5 connects the conductive plate 3 and the case 1.
At normal temperature, the electrochemical device is in a normal working state, the first current collector 211 and the second current collector 221 are insulated by the insulating member 4, and the voltage of the electrochemical device is not changed. When the temperature of the electrochemical device increases, for example, the temperature reaches between 70 ℃ and 90 ℃ or is higher than 90 ℃, the insulating member 4 loses its insulating effect, and the first portion 211a of the first current collector 211 can be conducted with the second current collector 221 through the conductive sheet 3. At this time, the electrochemical device starts self-discharge, the voltage curve changes, the voltage drops, and the state of charge (SOC) of the electrochemical device is reduced, whereby the safety of the electrochemical device at high temperature can be improved.
As the temperature of the electrochemical device gradually increases after the first current collector 211 and the second current collector 221 are connected, for example, when the temperature increases to 200 ℃, since the connected portion of the first current collector 211 and the second current collector 221 continuously generates heat, there is a risk of thermal runaway occurring, which may cause the electrochemical device to catch fire or explode. According to the electrochemical device provided by the embodiment of the application, as the temperature of the electrochemical device continues to rise, a side reaction occurs in the electrochemical device to generate gas. The gas inside the casing 1 expands, and the casing 1 pulls the conductive sheet 3 to move through the first connector 5 under the action of the gas expansion, so that the conductive sheet 3 is disconnected from the first portion 211a, and the conduction between the first portion 211a of the first current collector 211 and the second current collector 221 is cut off. The electrochemical device will thus not continue to generate heat, the temperature of the electrochemical device will start to drop and the voltage will return to a certain value. Since the voltage at this moment has been reduced with respect to the starting voltage, the temperature at the point of conduction continues to decrease, reducing the risk of thermal runaway and making the electrochemical device more safe.
In one embodiment, the insulating member 4 includes a heat shrinkable material having a heat shrinkage rate of 10% to 80%.
In one embodiment, the insulating member 4 may be a portion of the separation film 23 in the electrode assembly 2.
In one embodiment, the insulating member 4 may also be a heat-shrinkable adhesive tape.
Specifically, for the case where the heat shrinkable material is a separator, a separator sample of 100X 100mm was cut out from the separator, and the longitudinal length (MD) thereof was measured Front side ) And transverse length (TD) Front side ) Baking at 70 deg.C for 1 hr in a vacuum oven, taking out the diaphragm sample, cooling to room temperature, and measuring its longitudinal length (M)D Rear end ) And transverse length (TD) Rear end ) The heat shrinkage factor δ was calculated as follows to characterize the heat resistance of the separator (the smaller the heat shrinkage factor, the better the heat resistance).
δ MD ＝(MD Front part －MD Rear end )/MD Front part ×100％
δ TD ＝(TD Front side －TD Rear end )/TD Front side ×100％
The thermal shrinkage of the heat-shrinkable gummed paper before and after baking can be measured by the same procedure as the above test procedure.
The heat shrinkable material has a characteristic of shrinking when heated, and in a normal state, the first current collector 211 and the second current collector 221 are insulated and isolated by the insulator 4. The insulator 4 is thermally shrunk with the increase of the temperature so that the first current collector 211 and the second current collector 221 can be conducted through the conductive sheet 3. The thermal shrinkage material with the thermal shrinkage rate of 10% -80% is adopted, so that the insulating part 4 can be ensured to shrink to a certain extent when the temperature rises, and the risk that the contact area of the first current collector 211 and the second current collector 221 is too large to cause too fast temperature rise due to too large shrinkage area is avoided.
In one embodiment, the insulating member 4 is a heat-shrinkable adhesive tape. Through setting up insulating part 4 for the thermal contraction adhesive tape, can be with insulating part 4 direct fixation between first portion 211a and conducting strip 3, and need not other extra fixed knot structure, practiced thrift electrochemical device's space, improved electrochemical device's energy density.
In one embodiment, the insulator 4 is a part of the isolation film 23. That is, in the process of forming the electrode assembly 2, a portion of the separation film 23 located between the first portion 211a of the first current collector 211 and the second current collector 221 is processed to have different properties from the other portions of the separation film 23. The separator 23 has a heat shrinkage characteristic with respect to a portion between the first portion 211a of the first current collector 211 and the second current collector 221.
In one embodiment, the material of the partial separation film 23 of the insulating member 4 may include a porous substrate, and the porous substrate is not coated with a heat-resistant coating such as a ceramic layer. The porous substrate may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid.
As the temperature within the case 1 of the electrochemical device increases, the portion of the separator 23 between the first portion 211a of the first current collector 211 and the second current collector 221 thermally contracts, causing conduction of the first current collector 211 and the second current collector 221 through the conductive sheet 3, thereby lowering the SOC of the electrochemical device.
Further, in order to avoid a slow reaction time of the thermal shrinkage of the portion of the separator 23 between the first portion 211a of the first current collector 211 and the second current collector 221, a through hole 41 may be provided on the insulating member 4, as shown in fig. 4, in which an insulating material is provided in the through hole 41, the insulating material having a melting point ranging from 70 ℃ to 90 ℃.
In a normal working state of the electrochemical device, the first current collector 211 and the second current collector 221 are insulated by the insulating member 4, and the voltage of the electrochemical device is not changed. When the temperature of the electrochemical device increases, for example, to between 70 ℃ and 90 ℃, the insulating material inside the through-hole 41 melts, and the first portion 211a of the first current collector 211 and the second current collector 221 are electrically connected at the through-hole 41. In the present embodiment, the through hole 41 may be formed directly on a part of the isolation film 23 as the insulator 4.
The aperture of the through hole 41 may be 1mm to 100mm. Specifically, the aperture of the through-hole 41 may be 1mm, 10mm, 30mm, 50mm, 85mm, 100mm, or the like. If the aperture of the through hole 41 is smaller than 1mm, it is not only inconvenient to perform the filling process of the insulating material, but also affects the conduction effect of the first current collector 211 and the second current collector 221. If the diameter of the through-hole 41 is larger than 100mm, it is disadvantageous in designing the overall structure and size of the separation membrane 23.
In one embodiment, the electrochemical device according to the present embodiment further includes a resistive member 7, and referring to fig. 5, the resistive member 7 is a negative temperature coefficient thermistor, and the resistive member 7 is disposed between the insulating member 4 and the conductive sheet 3. In other embodiments, the resistive member 7 may also be disposed between the insulating member 4 and the first portion 211 a.
At normal temperature, the insulator 4 insulates the first current collector 211 and the second current collector 221, and the electrochemical device does not self-discharge. When the temperature of the electrochemical device increases, the first current collector 211 and the second current collector 221 are conducted through the conductive sheet 3 and the resistor 7, and at this time, the electrochemical device starts to discharge, the voltage curve changes, the voltage drops, and the SOC of the electrochemical device is reduced, thereby improving the safety of the electrochemical device at high temperature.
Since the resistance member 7 is a negative temperature coefficient thermistor that decreases exponentially with temperature increase as the temperature of the electrochemical device increases, the discharge speed can be increased. The resistive member 7 may be obtained by providing a conductive coating having a resistance of 1 to 100 ohms when the temperature in the case of the electrochemical device rises to 200 ℃, so that the voltage of the electrochemical device can be rapidly reduced to a certain value.
With the continuous rise of the temperature of the electrochemical device, the gas generated in the housing 1 gradually expands, the first connecting member 5 pulls the conductive sheet 3 to disconnect the conductive sheet 3 from the first portion 211a, the SOC at this time has been reduced, the first current collector 211 and the second current collector 221 are not conducted after being disconnected, the electrochemical device avoids thermal runaway under the condition that heat is not generated any more, and the safety of the electrochemical device is higher.
In one embodiment, the electrochemical device further includes a second connection member 6, the second connection member 6 connecting the electrode assembly 2 and the case 1, and the first connection member 5 and the second connection member 6 are located at opposite sides of the electrode assembly 2. In this embodiment, after the first current collector 211 and the second current collector 221 are conducted, the temperature at the conducting position continues to increase. The gas generated by the side reaction in the electrochemical device expands inside the case 1, and the case 1 pulls the conductive sheet 3 through the first connector 5 under the expansion of the gas, so that the conductive sheet 3 is disconnected from the first portion 211 a. Since the second connector 6 is provided at a side of the electrode assembly 2 remote from the first connector 5, the second connector 6 can fixedly connect the case 1 and the electrode assembly 2. The electrode assembly 2 is not biased toward the first connecting member 5 by the tensile force of the second connecting member 6, so that the electrode assembly 2 can be stably fixed in the case 1, thereby further improving the safety of the electrochemical device.
Specifically, at least one of the first connecting member 5 or the second connecting member 6 includes an adhesive material, which is a double-sided tape or a hot melt adhesive. By connecting the case 1 with the conductive sheet 3 and the electrode assembly 2 by the adhesive material, it is possible to save more space to improve the energy density of the electrochemical device. Meanwhile, the electrode assembly 2 and the shell can be bonded into a whole, so that the electrode assembly 2 is prevented from bouncing when the electrochemical device falls, and the safety performance is improved.
In one embodiment, the electrode assembly 2 is in a wound structure, and the conductive sheet 3 is a portion of the second current collector 221 from which the wound end extends. The width of the conductive sheet 3 is smaller than the width of the second current collector 221 in the vertical winding direction. In this embodiment, the winding end of the second current collector 221 is directly used as the conductive sheet 3, and there is no need to add additional components to the conductive sheet 3, which can further save the component arrangement space of the electrochemical device and improve the energy density of the electrochemical device.
The width of the conductive sheet 3 is less than the width of the second current collector 221, which can prevent an excessively large contact area of the first portion 211a of the first current collector 211 and the second current collector 221. Therefore, the temperature of the electrochemical device does not increase too fast to be high, so that the safety of the electrochemical device is improved.
In one embodiment, the second current collector 221 is a negative electrode current collector, which may be a copper foil. After the first current collector 211 and the second current collector 221 are conducted, heat is generated more, the temperature rise is larger, the melting point of the copper foil is higher, the conducting strip 3 is used as a part of the second current collector 221 and is not easy to fuse, and therefore the effect of pulling the conducting strip 3 open when the shell 1 expands is not lost.
In a specific embodiment, the insulating member 4 may also be an insulating layer disposed between the first pole piece 21 and the second pole piece 22.
Fig. 6 to 9 illustrate some embodiments of the electrochemical device in which the conductive sheet 3 is disposed at a side close to the electrode terminal 8 and is connected to the case 1 by the first connection member 5 in the electrochemical device illustrated in fig. 6 to 8. It will be appreciated by those skilled in the art that in other embodiments the conductive sheet 3 may also be provided on the other side in the width direction of the electrochemical device.
The first current collector 211 is located at the outermost circle of the electrode assembly, and the conductive sheet 3 is electrically connected to the second current collector 221 near the inner circle.
In one embodiment, the conductive sheet 3 is a portion of the second current collector 221.
In another embodiment, the conductive sheet 3 may also be separately disposed and then electrically connected to the second current collector 221.
In the embodiment shown in fig. 7, an insulator 4 is provided between the conductive plate 3 and the first portion 221 a.
In the embodiment shown in fig. 8, the insulating member 4 and the resistive member 7 are provided between the conductive plate 3 and the first portion 221 a.
In the embodiment shown in fig. 9, the winding end of the second current collector 221 serves as the conductive sheet 3.
As shown in fig. 10, in one embodiment, when the first portion 211a and the second current collector 221 are connected, the electrochemical device is discharged, the voltage is rapidly decreased, and the temperature at the connection is increased. When the temperature rises to about 200 ℃, the first connecting piece 5 pulls the conducting strip 3 to be disconnected from the first part 211a due to gas expansion, heat is not generated at the conducting part any more, the temperature slowly drops, and the voltage is recovered to a certain value (about 4.1V). Since the voltage at this moment has been reduced with respect to the starting voltage, the temperature at the point of conduction continues to decrease, reducing the risk of thermal runaway and making the electrochemical device more safe.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (10)
1. An electrochemical device, comprising:
a housing;
an electrode assembly housed within the case, the electrode assembly including a first pole piece, a second pole piece, and a separator disposed between the first pole piece and the second pole piece;
the first pole piece comprises a first current collector, the second pole piece comprises a second current collector, the first current collector comprises a first part, and the first part is an outermost first current collector in the electrode assembly;
a conductive sheet electrically connected to the second current collector, the conductive sheet disposed between the first portion and the housing;
an insulator disposed between the first portion and the conductive sheet;
the first connecting piece is used for pulling the conducting strip under the action of expansion of gas in the shell;
the first connecting piece comprises an adhesive material which is double-sided adhesive tape or hot melt adhesive.
2. The electrochemical device according to claim 1, wherein the insulating member comprises a heat-shrinkable material having a heat shrinkage ratio of 10% to 80%.
3. The electrochemical device according to claim 2, wherein the insulating member is a heat-shrinkable gummed paper.
4. The electrochemical device according to claim 1, wherein the insulator is a part of the separation film.
5. The electrochemical device according to claim 4, wherein the insulating member is provided with a through hole, an insulating material is provided in the through hole, the insulating material has a melting point ranging from 70 ℃ to 90 ℃, and the through hole has a hole diameter ranging from 1mm to 100mm.
6. The electrochemical device according to claim 1, wherein the electrochemical device further comprises a resistive member, the resistive member being a negative temperature coefficient thermistor,
the resistive member is disposed between the insulator and the first portion, or the resistive member is disposed between the insulator and the conductive tab.
7. The electrochemical device according to claim 1, further comprising a second connection member connecting the electrode assembly and the case, the first and second connection members being located at opposite sides of the electrode assembly.
8. The electrochemical device of claim 7, the second connection member comprising an adhesive material, the adhesive material being a double-sided tape or a hot melt adhesive.
9. The electrochemical device according to claim 1, wherein the electrode assembly is a wound structure, the conductive sheet is a portion of the second current collector from which a wound end extends, and a width of the conductive sheet is smaller than a width of the second current collector in a vertical winding direction.
10. An electronic device comprising the electrochemical device according to any one of claims 1 to 9.
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| WO2022204982A1 (en) * | 2021-03-30 | 2022-10-06 | 宁德新能源科技有限公司 | Electrode assembly, battery, and electrical apparatus |
| CN115347285A (en) * | 2021-05-12 | 2022-11-15 | 宁德新能源科技有限公司 | Electrochemical device and electronic device |
| CN113782870B (en) * | 2021-08-19 | 2023-03-24 | 宁德新能源科技有限公司 | Electrochemical device and electric equipment |
| CN114094281A (en) * | 2021-11-19 | 2022-02-25 | 宁德新能源科技有限公司 | Electrochemical device and electronic device |
| CN114243122A (en) * | 2021-12-08 | 2022-03-25 | 宁德新能源科技有限公司 | Electrochemical device and electricity utilization device |
| CN114447399A (en) * | 2022-01-28 | 2022-05-06 | 宁德新能源科技有限公司 | Electrochemical device and electronic apparatus |
| CN114335692B (en) * | 2022-03-08 | 2022-06-21 | 宁德新能源科技有限公司 | Electrochemical device and electronic device |
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