CN114566769B

CN114566769B - Electrochemical device, battery module, and electricity using device

Info

Publication number: CN114566769B
Application number: CN202210188280.8A
Authority: CN
Inventors: 杨超; 江静
Original assignee: Dongguan Poweramp Technology Ltd
Current assignee: Dongguan Poweramp Technology Ltd
Priority date: 2022-02-28
Filing date: 2022-02-28
Publication date: 2024-01-19
Anticipated expiration: 2042-02-28
Also published as: CN114566769A

Abstract

The application discloses an electrochemical device, a battery module and an electric device. The electrochemical device comprises a shell, an electrode assembly and a tab, wherein the electrode assembly is accommodated in the shell, the tab comprises a first part and a second part, the first part is accommodated in the shell, one end of the first part is connected with the electrode assembly, the other end of the first part is connected with the second part, the second part extends out of the shell and is used for being electrically conducted with the outside, the width of the second part is smaller than that of the first part along a first direction, and the bending resistance of the second part is 20N-300N. The bending resistance of the second part is limited in the numerical range, so that the second part has better flexibility and better mechanical strength, and the tearing of the tab when being impacted or pulled by the outside can be improved, thereby improving the yield of the electrochemical device.

Description

Electrochemical device, battery module, and electricity using device

Technical Field

The present disclosure relates to battery technology, and more particularly, to an electrochemical device, a battery module, and an electric device.

Background

The tab serves as a metal conductor for leading out the positive and negative electrodes from the electrochemical device, and is a contact point between the positive and negative electrodes when the electrodes are charged and discharged. The existing tabs are usually reserved for a certain length to be able to be electrically connected with the outside in the future in, for example, shipment transportation of electrochemical devices, tab perforation test and vibration and impact test of electrochemical devices. However, when the electrochemical device is shipped, the tab is easily bent by an external impact, and then is easily broken.

Disclosure of Invention

An object of the present application is to provide an electrochemical device that improves the ease of breakage of tabs.

An electrochemical device includes a case, an electrode assembly, and a tab. The electrode assembly is accommodated in the case. The tab includes a first portion and a second portion. One end of the first part is connected with the electrode assembly, the other end of the first part is connected with the second part, the second part extends out of the shell, and the second part is used for being electrically conducted with the outside. In the first direction, the width of the second portion is smaller than the width of the first portion. And the second portion has a bending resistance of 20N-300N. Wherein the first direction, the thickness direction of the electrode assembly and the extending direction of the second portion are perpendicular to each other. The bending strength of the second part is limited in the numerical range, so that the second part has better flexibility and better mechanical strength, and the situation that the structure is invalid due to bending when the tab is impacted by the outside can be improved, thereby improving the yield of the electrochemical device.

In some alternative embodiments, the thickness direction of the electrode assembly is referred to as a second direction, and the ratio of the width of the second portion along the first direction to the thickness of the second portion along the second direction is 0.5 to 20. The width-thickness ratio of the second part is limited in the numerical range, so that the second part is approximately linear, the contact area with external impact is reduced, and the situation of breakage when the second part is easy to be impacted by the external is improved.

In some alternative embodiments, the ratio of the width of the first portion along the first direction to the thickness of the first portion along the second direction is 10-500. The width-to-thickness ratio of the first portion is limited to the numerical range, and the thickness of the first portion of the tab metal strip during installation is reduced while the current carrying capacity of the first portion is kept unchanged, thereby improving the energy density of the electrochemical device.

In some alternative embodiments, the extending direction of the second portion is referred to as a third direction, and the tab further includes a third portion connected between the other end of the first portion and the second portion along the third direction. The third portion may be a transition portion between the first portion and the second portion of the tab, so as to facilitate manufacturing processing of the tab.

In some alternative embodiments, the third portion tapers in width along the first direction along the third direction. By the arrangement, the first part and the second part of the lug can be uniformly transited, and the manufacturing difficulty of the lug is further reduced.

In some alternative embodiments, the tab further comprises a tab glue connected between the housing and the third portion. The positions of the third part are not easy to generate relative movement after the tab adhesive is coated, so that the situation that gaps and bubbles are generated between tab metal strips is improved.

In some optional embodiments, an antioxidation layer is formed on the surface of the second portion, so that the second portion of the tab has good antioxidation, and connection stability between the second portion and the outside is improved.

Another object of the present application is to provide a battery module, which improves the situation that scraps are easily generated in the welding process of the tab and the electric connection piece.

The application also provides a battery module, and this battery module includes battery frame, electric connection piece and electrochemical device as above, and the electric connection piece is fixed in battery frame, and the electric connection piece is equipped with the terminal, electrochemical device holding in the battery frame, the second part winding of utmost point ear is fixed in the terminal. By means of the mode, the assembly process of welding can be omitted, and the risk of puncturing the shell of the electrochemical device caused by the fact that scraps generated during welding of the tab and the connecting sheet are easy to embed into a gap between the electrochemical device and the battery frame is improved.

In some alternative embodiments, the battery module further comprises a nut. The nut is fixedly connected with the binding post in a threaded manner, and the second part is clamped between the nut and the binding post.

Another object of the present application is to provide an electric device comprising a load and a battery module as described above, the load being electrically connected with the battery module.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and that other drawings may be obtained according to the drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of an electrical device according to one embodiment of the present disclosure;

fig. 2 is a sectional view of a battery module in the power consumption device shown in fig. 1;

fig. 3 is a schematic view of the structure of an electrochemical device in the battery module shown in fig. 2;

fig. 4 is a schematic view illustrating the structure of another electrochemical device in the battery module shown in fig. 2;

fig. 5 is a schematic structural view of a battery frame in the power consumption device shown in fig. 2.

Detailed Description

In order to facilitate an understanding of the present application, the present application will be described in more detail below with reference to the accompanying drawings and specific examples. It will be understood that when an element is referred to as being "fixed" to/affixed to "another element, it can be directly on the other element or one or more intervening elements may be present therebetween. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or one or more intervening elements may be present therebetween. The terms "vertical," "horizontal," "left," "right," "inner," "outer," and the like are used in this specification for purposes of illustration only.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used in this specification includes any and all combinations of one or more of the associated listed items.

The battery module 1 disclosed in the embodiments of the present application is suitable for various electrical devices using the battery module 1, and thus, the risk of the electrochemical device 30 in the battery module 1 being punctured can be reduced, so as to improve the mechanical safety performance of the battery module 1.

Referring to an example shown in fig. 1, fig. 1 is a schematic diagram of an electrical device according to an embodiment of the present application, where the electrical device includes a battery module 1 and a load 2, the battery module 1 is electrically connected to the load 2, and the battery module 1 is configured to provide electrical energy to the load 2. In some application scenarios, the power utilization device may include a power mechanism formed by the battery module 1 and the driving motor, and other types of power mechanisms such as an engine, and electric energy and other energy sources (e.g. mechanical energy) are used to provide driving force for the load 2 of the power utilization device, for example, the power utilization device may be a vehicle, a ship, a small aircraft, and the like. In other application scenarios, the power utilization device may only include a power mechanism formed by a battery pack and a driving motor, and electric energy is used to provide all driving force for the load 2 of the power utilization device. For example, the electric device can be a pure electric vehicle, a hybrid electric vehicle, an extended range vehicle, an electric tricycle or a two-wheel electric vehicle, etc.

Referring to the example shown in fig. 2, fig. 2 is a cross-sectional view of a battery module 1 according to one embodiment of the present application, the battery module 1 includes a battery frame 10, an electrical connection sheet 20 and an electrochemical device 30, the electrochemical device 30 is accommodated in the battery frame 10, the electrical connection sheet 20 is fixed on the battery frame 10, and the electrochemical device 30 is electrically connected with the electrical connection sheet 20 to form a positive electrode or a negative electrode of the battery module 1.

In order to make it possible to clearly describe the orientations in the following, the directions are defined by means of the coordinate system in fig. 2. The coordinate axis X represents a first direction parallel to the plane of the electrode assembly 32, and in some embodiments of the present application, is also the width direction of the tab of the electrochemical device 30. In some embodiments of the present application, the relative arrangement direction of the third side plate 123 and the fourth side plate 124 of the battery frame 10 is also. The coordinate axis Y represents a second direction perpendicular to the plane of the electrode assembly, and in some embodiments of the present application, is also the thickness direction of the electrode assembly 32. In some embodiments of the present application, the arrangement direction of the respective electrochemical devices 30 in the battery module 1 is also described. Which is the relative arrangement direction of the first and second side plates 121 and 122 of the battery frame 10. The coordinate axis Z represents a third direction parallel to the plane of the electrode assembly, and in some embodiments of the present application, is also the extending direction of the tab of the electrochemical device. In some embodiments of the present application, the relative arrangement direction of the first and second pallets 111 and 112 of the battery frame 10. The third direction Z, the second direction Y and the first direction X are vertical to each other.

Based on the above orientation definition, the specific structures of the battery frame 10, the electric connection piece 20, and the electrochemical device 30 will be described below with reference to the embodiments illustrated in the drawings. And terms such as "upper", "lower", "top", "bottom", and the like are used below to refer to an azimuth or positional relationship, all with respect to the third direction Z. It should be noted that the technical features mentioned in the different embodiments of the present application described below may be combined with each other as long as they do not conflict with each other.

With the above-described battery frame 10, the battery frame 10 is used for accommodating all the electrochemical devices 30 in the battery module 1 while the power supply connection tabs 20 are mounted. The battery frame 10 is a mounting support structure of each electrochemical device 30 and protects each electrochemical device 30. Referring to fig. 2 together with the example shown in fig. 5, the battery frame 10 has a substantially rectangular parallelepiped shape. The battery frame 10 includes a tray 11 and a side plate 12, and the side plate 12 is connected to the periphery of the tray 11 such that the battery frame 10 has a cavity for accommodating the electrochemical device 30. It is to be understood that the shape of the battery frame 10 is not limited to a rectangular parallelepiped shape, and may be, for example, a circular shape or other regular shape, and the specific shape may be set according to the shape of the electrochemical device 30.

Specifically, the support plate 11 includes a first support plate 111 and a second support plate 112, the first support plate 111 serving as a bottom plate for supporting the electrochemical device 30, and the second support plate 112 serving as a top plate for supporting the electrical connection sheet 20. The side plates 12 include a first side plate 121, a second side plate 122, a third side plate 123 and a fourth side plate 124, and the first side plate 121, the second side plate 122, the third side plate 123 and the fourth side plate 124 are sequentially connected end to form a middle frame structure, one side of the middle frame structure along the second direction Y is connected to the first supporting plate 111, and the other side of the middle frame structure along the second direction Y is connected to the second supporting plate 112, so that the cavity 10a of the battery frame 10 is formed by enclosing. The first side plate 121 and the second side plate 122 are disposed opposite to each other along the second direction Y, and the third side plate 123 and the fourth side plate 124 are disposed opposite to each other along the first direction X.

For the above-mentioned electrical connection sheet 20, the electrical connection sheet 20 is used to electrically connect different electrochemical devices 30 to realize series connection, parallel connection or series-parallel connection of the electrochemical devices 30 in the battery module 1. As shown in fig. 2, the electric connection piece 20 has a substantially rectangular plate-like structure, the electric connection piece 20 is fixed to the top plate 112 and extends in the first direction X, the electric connection piece 20 is provided with a post 21, and the post 21 is used for electric connection with the electrochemical device 30. Wherein the binding posts 21 protrude from the surface of the cavity facing the battery frame 10. It is understood that the structural form of the electric connection sheet 20 is not limited thereto, and for example, the electric connection sheet 20 may be a continuous bent structure or other irregular shape, and may be changed according to the space reserved after the arrangement of the other components of the battery module 1. In addition, the connection manner of the electrical connection sheet 20 and the top plate 112 of the battery frame 10 may be various, and is not particularly limited in the embodiment of the present application, for example, the electrical connection sheet 20 may be bonded, screwed, snap-fit, integrally connected, or the like.

Alternatively, the electrical connection pads 20 may be made of a conductive material, for example, the electrical connection pads 20 may be conductive copper bars. The electrical connection pads 20 may also be made of a non-metallic material coated with a conductive coating.

For the above-described electrochemical device 30, the electrochemical device 30 is a member for generating electric energy in the battery module 1. As shown in fig. 3, the electrochemical device 30 is substantially rectangular parallelepiped and includes a case 31, an electrode assembly 32, and tabs 33, the case 31 is fixed to a bottom plate 111 of the battery frame 10, the electrode assembly 32 is housed in the case 31, the tabs 33 are connected to the electrode assembly 32, the tabs 33 extend out of the case 31 in the third direction Z, and the portions of the tabs 33 extending out of the case 31 are electrically connected to the electrical connection pieces 20 to be in electrical communication with the load 2 of the electric device. It is to be understood that the fixing manner of the electrochemical device 30 and the battery frame 10 may be various, and the embodiment of the present application is not limited specifically, for example, the housing 31 may be fixed to the bottom plate of the battery frame 10 by means of a bolt, a limiting member, or other structural members, or one or more of glue, double-sided adhesive tape, a snap structure, or the like may be disposed on the bottom plate of the battery frame 10 to fix the housing 31 to the bottom plate of the battery frame 10. Of course, the case 31 is not limited to the bottom plate fixed to the battery frame 10.

It should be noted that the electrochemical device 30 in the embodiment of the present application includes all devices in which the reactive electrochemical reaction occurs. Illustratively, the electrochemical device 30 includes, but is not limited to, all kinds of primary, secondary, fuel, solar, and capacitor (e.g., supercapacitor) electrochemical devices. The electrochemical device 30 may be selected from lithium secondary batteries including, but not limited to, lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, and lithium ion polymer secondary batteries.

The shell 31 may be a soft shell 31, for example, the shell 31 may be made of an aluminum plastic film, and the soft shell 31 made of a polymer such as an aluminum plastic film has the characteristics of light weight, small thickness, high installation performance, and the like. It is understood that the case 31 of the electrochemical device is not limited thereto, and for example, the case 31 may be a hard case 31 made of aluminum alloy or stainless steel, etc., and may be specifically set according to the structural use requirements of the battery module 1.

The electrode assembly 32 is a member of the electrochemical device 30 that realizes a charge and discharge function, the electrode assembly 32 may include a positive electrode tab, a negative electrode tab, and a separator that separates the positive electrode tab from the negative electrode tab, the positive electrode tab includes a positive electrode current collector and a positive electrode active material layer coated on a surface of the positive electrode current collector, the positive electrode current collector may be an aluminum foil, and the positive electrode active material layer may include a ternary material, lithium manganate, or lithium iron phosphate. The negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer coated on the surface of the negative electrode current collector, wherein the negative electrode current collector can be copper foil, and the negative electrode active material layer can comprise graphite or silicon. The present application is not limited to the members of the electrochemical device, for example, the materials of the positive electrode active material, the negative electrode active material, and the like. Specifically, the electrode assembly 32 may be a wound electrode assembly, that is, the positive electrode sheet and the negative electrode sheet are both one, and the positive electrode sheet and the negative electrode sheet are both in a ribbon structure. The positive electrode sheet, the separator and the negative electrode sheet are sequentially laminated and wound for two or more turns to form the aforementioned wound electrode assembly, which may be flat. Alternatively, the electrode assembly 32 may be a laminated electrode assembly, specifically, a plurality of positive electrode sheets and a plurality of negative electrode sheets are provided, the plurality of positive electrode sheets and the plurality of negative electrode sheets are alternately laminated along the thickness direction of the electrode assembly 32, and a separator separates the positive electrode sheets and the negative electrode sheets.

The tab 33 is a metal conductor for leading out the positive and negative electrodes in the electrochemical device 30, the tab 33 includes a first portion 331, a second portion 332 and a tab adhesive 334, the tab adhesive 334 is thermally pressed and compounded on the second portion 332, and the tab adhesive 334 is sandwiched between the housing 31 and the tab and isolates the interior of the housing 31 from the external environment. The first portion 331 is integrally connected to the second portion 332, and the first portion 331 is a portion where the tab is received in the case 31 of the electrochemical device 30 and is connected to the electrode assembly 32. The second portion 332 is a portion of the tab that protrudes outside the electrochemical device 30 and is connected to the electrical connection pad 20. The portion of the second portion 332 of the tab extending out of the housing 31 is wrapped around the terminal 21 fixed to the electrical connection pad 20.

In the embodiment of the present application, on one hand, since the tab and the binding post 21 are connected and fixed by winding, the welding assembly process can be omitted, the situation that the tab and the electric connection piece 20 are easy to generate scraps when being welded is improved, that is, the risk of the scraps being embedded into the gap between the electrochemical device 30 and the battery frame 10 to puncture the casing 31 of the electrochemical device 30 is reduced. On the other hand, the winding force applied to the terminal 21 by the tab increases the friction between the tab and the terminal 21, thereby enhancing the connection stability of the connection between the tab and the terminal 21. In still another aspect, the tab can be sufficiently bonded to the outer peripheral surface of the terminal 21, i.e., the contact area between the tab and the terminal 21 is increased, thereby improving the current carrying capacity at the junction of the tab and the terminal 21.

Wherein, the thickness of the first portion 331 along the second direction Y is greater than the thickness of the second portion 332 along the second direction Y. The width w1 of the first portion 331 along the first direction X and the width w2 of the second portion 332 along the first direction X satisfy: w1 > w2 in mm. As can be seen from the calculation formula of the current carrying capacity of the tab 33, the current carrying capacity of the tab 33 is independent of the length of the tab 33, and can only be related to the width and thickness of the tab 33, so that the current carrying capacities of the first portion 331 and the second portion 332 of the tab are approximately converged by changing the thickness and width setting of the tab 33, thereby reducing the impedance of the tab and improving the aging condition of the tab material caused by heat radiation accumulation generated by the increase of the impedance. Reflecting the electrolyte on the electrochemical device 30 can improve the situation that the electrolyte leakage is easy to occur at the packaging position of the tab glue 334 and the tab caused by the reduction of the packaging strength.

Lug current carrying capacity formula:

wherein: i is the current carrying capacity of the tab 33;

b is the width of the tab 33 in millimeters;

t is the thickness of the tab 33 in microns;

P _o -resistance ratio;

alpha- -temperature coefficient of resistance;

h, heat dissipation coefficient;

the temperature difference between the temperature of the T-shaped pole piece and the normal temperature.

Further, the ratio of the width w1 of the first portion 331 along the first direction X to the thickness t1 of the first portion 331 along the second direction Y is as follows: the thickness required for installation is reduced under the condition that the current carrying capacity of the first part 331 is ensured to be unchanged, so that the energy density of the electrochemical device 30 is improved, and the welding difficulty of the first part 331 and the current collector of the pole piece is reduced due to the fact that the surface area of the first part 331 is increased. Alternatively, the cross-sectional shape of the first portion 331 may be wedge-shaped or oval as viewed in the third direction Z.

Further, the ratio of the width w2 of the second portion 332 along the first direction X to the thickness t2 of the second portion 332 along the second direction Y satisfies: the w2/t2 is more than 0.5 and less than or equal to 20, namely the second part 332 of the tab is narrower and thicker, and the second part 332 is easy to bend under the condition of ensuring that the current carrying capacity of the second part 332 is unchanged, so that the assembly difficulty of the second part 332 and the binding post 21 of the electric connection sheet 20 is reduced. Alternatively, the cross-sectional shape of the second portion 332 may be rectangular, square, circular, oval, or prismatic, as viewed in the third direction Z.

Referring to the experimental results in table 1, the tab is evaluated by a three-point bending test method, and the bending resistance f of the second portion 332 of the tab can satisfy: f is more than or equal to 20N and less than 300N. When the bending resistance of the second portion of the tab is less than 20N, for example, when the bending resistance of the second portion of the tab is 10N, the rate of deformation fracture of the tab is large at this time. When the bending resistance of the second portion of the tab is greater than 300N, for example, when the bending resistance of the second portion of the tab is 400N, the rate of deformation and fracture of the tab at this time further increases, and the failure rate of connection of the second portion of the tab with the module is also further increased. Illustratively, the bending resistance of the second portion 332 of the tab may be 20N, 100N, 200N, or 300N. The bending resistance of the second part of the tab is limited in the range, and besides the reduction of the deformation and fracture ratio of the tab, the minimum overcurrent ratio of the second part of the tab is also increased, so that the electric performance of the part is improved. It should be noted that the bending resistance in the embodiment of the present application is a force applied between two fulcrums of the tab until the tab starts to deform.

Further, an antioxidation layer is formed on the surface of the second part of the tab, so that the second part of the tab can have good antioxidation, and connection stability between the second part and the outside is improved. For example, the oxidation resistant layer comprises at least one of chromium, tin, copper, nickel, aluminum, or copper nickel plated alloy.

Further, the first portion 331 of the tab has a first conductivity σ1, and the second portion 332 of the tab has a second conductivity σ2, the second conductivity σ2 and the first conductivity σ1 satisfying: sigma 2/Sigma 1 is more than or equal to 1. The cross-sectional area of the tab is equal to the conductivity sigma/product, and the maximum charge-discharge current allowed by the product is more than 20%.

In order to improve the connection stability between the electrochemical device 30 and the electrical connection pad 20, the outer circumferential surface of the terminal 21 is provided with threads (not shown), and optionally, the battery module 1 further includes a nut (not shown) screwed to the terminal 21, and the second portion 332 of the electrochemical device 30 is sandwiched between the terminal 21 and the nut. Further, the outer circumferential surface of the post 21 is provided with a groove (not shown) having a shape adapted to the shape of the second portion 332, and the second portion 332 is fixed to the groove under the force applied by the nut. On the one hand, the force generated when the nut is screwed on the post 21 can be reduced, so that the second portion 332 is not easy to stretch, and the impedance of the second portion 332 is reduced. On the other hand, the surfaces of the second portion 332 are fitted with the grooves, further increasing the contact area between the second portion 332 and the electrical connection pad 20, so that the electrical resistance between the second portion 332 and the electrical connection pad 20 is smaller and the connection is more reliable.

Optionally, the tab further includes a third portion 333, and the third portion 333 is a transition portion between the first portion 331 and the second portion 332 of the tab. In the third direction Z, the cross-sectional area of the third portion 333 near the end of the first portion 331 gradually decreases to the cross-sectional area of the third portion 333 near the end of the second portion 332. Specifically, the tab adhesive 334 is disposed on the third portion 333, and the third portion 333 can be encapsulated in the housing 31 through the tab adhesive 334. Further, the width t3 at any position of the third portion 333 in the first direction X satisfies: 0.01 (w 1-w 2) < t3 < 3%

(w 1-w 2). Illustratively, 2mm < t3 < 20mm, such that the positions of the third portion 333 after the tab adhesive 334 is coated are not easily moved relative to each other, thereby improving the occurrence of gaps and bubbles between the tabs to enhance the sealability of the electrochemical device 30. It can be understood that the connection position of the tab adhesive 334 is not limited thereto, and the coating position of the tab adhesive 334 can be adjusted according to the actual use situation, so that the amount of the tab adhesive 334 required for packaging the tab and the housing 31 is less, and the manufacturing cost of the electrochemical device 30 is more easily saved.

The tab 33 includes a positive tab and a negative tab, and the positive current collectors of the positive tab and the positive plate may be welded and fixed by transfer welding, and optionally, the positive tab may be made of an aluminum material. The negative electrode lug 33 and the negative electrode current collector of the negative electrode sheet can be welded and fixed through transfer welding, and the material of the negative electrode lug can be copper, nickel or copper nickel plating material. The arrangement modes of the positive electrode lug and the negative electrode lug can be various. For example, as shown in fig. 2, the positive electrode tab and the negative electrode tab are both located on the same side of the electrode assembly 32, and at this time, the lengths required for connection between the positive electrode tab and the negative electrode tab and the terminal 21 of the electrical connection sheet 20 are substantially the same, so that the manufacturing cost of the battery module 1 is saved. Of course, the positive and negative tabs may also protrude from opposite sides of the electrode assembly 32.

Alternatively, the tabs 33 of each electrochemical device 30 are wound around the posts 21 fixed to the electrical connection pieces 20. With continued reference to the example shown in fig. 2, the positive electrode tab 33 of one electrochemical device 30 and the negative electrode tab 33 of another electrochemical device 30 adjacent thereto are wound around the same terminal 21 fixed to the electrical connection sheet 20, i.e., the electrochemical devices 30 are connected in series. It can be appreciated that, unlike the foregoing embodiments, the tabs 33 of the same polarity of each electrochemical device 30 are all wound around the same terminal 21 fixed on one electric connection piece 20, i.e. the electrochemical devices 30 are connected in parallel, which has the advantage of reducing the welding process between the tabs 33 of each electrochemical device 30 and the electric connection piece 20, thereby reducing the assembly difficulty of the battery module 1.

For easy understanding, the assembly process of the battery module 1 is given as follows: first, the electrode lug and the electrode lug glue are subjected to hot pressing and compounding to form an independent structural member. And secondly, fixing the empty foil area of the current collector on the electrode assembly and the tab through transfer welding, and adjusting the position of the tab to enable the tab adhesive to be placed at the packaging opening of the shell for hot-pressing packaging, so that the electrochemical device is formed. Finally, a plurality of electrochemical devices are stacked along the second direction Y, the orientation of each electrochemical device is the same, and a battery frame and other structural members are added to assemble the battery module.

In addition, some examples using the scheme of the present application and comparative examples not using the scheme of the present application for comparison of effects are given below.

Comparative example 1

The thickness and the width of the first part and the second part of the tab are the same, the width of the tab is 20mm, the thickness of the tab is 0.2 mm, and the connection rate and the leakage failure rate of the package of the electrochemical device are tested.

Comparative example 2

The thickness and the width of the first part and the second part of the tab are the same, the width of the tab is 2mm, the thickness of the tab is 0.3 mm, and the connection rate and the leakage failure rate of the package of the electrochemical device are tested.

Example 1

The thickness and the width of the first part and the second part of the tab are different, the width of the first part of the tab is 0.5 millimeter, and the thickness of the first part of the tab is 0.5 millimeter. The width of the second part of the electrode tab is 20mm, the width of the second part of the electrode tab is 0.2 mm, and the connection rate and the leakage failure ratio of the package of the electrochemical device are tested.

Example 2

The thickness and the width of the first part and the second part of the tab are different, the width of the first part of the tab is 1 millimeter, and the thickness of the first part of the tab is 0.5 millimeter. The width of the second part of the electrode tab is 10 mm, the width of the second part of the electrode tab is 0.2 mm, and the connection rate and the leakage failure ratio of the package of the electrochemical device are tested.

The experimental results are shown in table 2 below:

from the experimental data in the table, it can be seen that:

when other structures of the electrochemical device were kept unchanged, the smaller the thickness and width of the tab metal tape in comparative example 2 was, the lower the leakage failure ratio of the electrochemical device was, and accordingly, the connection yield of the tab was lowered, as compared with comparative example 1.

In example 1, compared with comparative example 1, the thickness and width of the first portion of the tab remained unchanged, the thickness and width of the second portion of the tab metal strip became smaller, the leakage failure rate of the electrochemical device was greatly reduced, and the connection rate of the tab was improved. In this application, the connection rate of the tab refers to the connection success rate of the tab with the connected component, such as a terminal post. The lug is connected with the binding post, and when current is conducted to the binding post, the lug is considered to be successfully connected with the binding post.

In example 2, the width of the first portion of the tab was reduced and the thickness was not changed, and the width of the second portion of the tab was increased and the thickness was increased, compared to example 1. The second portion of the tab has a reduced width and a constant thickness, the leakage failure rate of the electrochemical device is further reduced, the tab connection rate is maintained constant, and the minimum overcurrent ratio of the tab is increased.

The foregoing description is only of embodiments of the present application, and is not intended to limit the scope of the patent application, and all equivalent structures or equivalent processes using the descriptions and the contents of the present application or other related technical fields are included in the scope of the patent application.

Claims

1. The electrochemical device comprises a shell, an electrode assembly and a tab, wherein the electrode assembly is accommodated in the shell, the tab comprises a first part and a second part, the first part is accommodated in the shell, one end of the first part is connected with the electrode assembly, the other end of the first part is connected with the second part, the second part extends out of the shell and is used for being electrically communicated with the outside, and the electrochemical device is characterized in that the width of the second part is smaller than the width of the first part along a first direction, and the bending resistance of the second part is 20N-300N, wherein the thickness direction of the first direction, the thickness direction of the electrode assembly and the extending direction of the second part are perpendicular to each other.

2. The electrochemical device according to claim 1, wherein a thickness direction of the electrode assembly is referred to as a second direction, and a ratio of a width of the second portion in the first direction to a thickness of the second portion in the second direction is 0.5 to 20.

3. The electrochemical device of claim 2, wherein a ratio of a width of the first portion along the first direction to a thickness of the first portion along the second direction is 10-500.

4. An electrochemical device according to any one of claims 1 to 3, wherein the direction of extension of the second portion is referred to as a third direction, and the tab further comprises a third portion connected between the other end of the first portion and the second portion in the third direction.

5. The electrochemical device of claim 4, wherein the third portion has a width in the first direction that gradually decreases in the third direction.

6. The electrochemical device of claim 5, wherein the tab further comprises a tab glue, the tab glue being connected between the housing and the third portion.

7. An electrochemical device according to any one of claims 1 to 3, wherein the surface of the second portion is formed with an oxidation-resistant layer.

8. A battery module comprising a battery frame, an electrical connection tab and the electrochemical device of any one of claims 1-7, wherein the electrical connection tab is secured to the battery frame, the electrical connection tab is provided with a terminal post, the electrochemical device is housed within the battery frame, and the second portion of the tab is secured to the terminal post.

9. The battery module of claim 8, further comprising a nut threadably secured to the post;

the second portion is sandwiched between the nut and the post.

10. An electrical device comprising a load and the battery module of claim 8 or 9, the load being electrically connected to the battery module.