Patent Application
20230140763
This application relates to the technical field energy storage, and in particular, to an electrochemical device and an electronic device containing the electrochemical device.
With the progress of science and technology and higher requirements imposed on environment protection, electrochemical devices have penetrated everyday life. Due to the universal application of lithium-ion batteries, most mobile devices such as mobile phones, notebook computers, and electric vehicles are powered by electrochemical devices (such as lithium-ion batteries) nowadays. Therefore, structural stability and cycle performance of the electrochemical devices are attracting more and more attention.
An electrode assembly of an electrochemical device includes a positive electrode plate and a negative electrode plate. An ion transmission distance at edges of the positive electrode plate and the negative electrode plate is longer than that in a middle position of the electrochemical device because the positive electrode plate and the negative electrode plate are not in close contact. An interface between the positive electrode plate and the negative electrode plate at the edges is prone to be abnormal. Consequently, problems such as lithium plating at the edge of the negative electrode plate or black-fleck-induced failure are prone to occur during charge-and-discharge cycles, ending in a decline of overall performance of the electrochemical device.
Therefore, a technical solution to such problems is urgently needed in this field.
This application provides an electrochemical device and an electronic device that contains the electrochemical device in an attempt to solve at least one problem in the related art to at least some extent.
According to an aspect of this application, some embodiments of this application provide an electrochemical device, including:
an electrode assembly, where the electrode assembly includes a body portion and a first metal portion, the body portion includes a first surface and a second surface opposite to the first surface, the first metal portion includes a third surface and a fourth surface opposite to the third surface, the body portion includes a first part and a second part in a first direction, the first part is electrically connected to the first metal portion, a junction between the first part and the first metal portion in the first direction is a first boundary line, a junction between the first part and the second part is a second boundary line, a thickness of the first part is h (mm), a thickness of the second part is H (mm) and is a constant, and h is less than H; and
a first adhesive tape, where the first adhesive tape includes a first tape edge and a third tape edge opposite to the first tape edge, the first adhesive tape is disposed on the first surface of the first part and the third surface of the first metal portion, and, viewed from a direction perpendicular to the first surface of the second part, the first tape edge is located between the first boundary line and the second boundary line.
According to another aspect of this application, some embodiments of this application provide an electronic device. The electronic device contains the electrochemical device.
In the electrochemical device according to this application, the first adhesive tape is disposed on the body portion of the electrode assembly, and a position relationship between the first tape edge and the body portion is adjusted, so as to optimize the interface of an electrode plate edge in the electrode assembly and alleviate lithium plating at the edge, and in turn, improve safety performance and cycle performance. Moreover, the disposed first adhesive tape can coat a bonding region between the adapter strip and the first metal portion, thereby preventing weld-induced burrs in the bonding region from piercing a packaging shell of the electrochemical device, protecting integrity of the electrochemical device, and in turn, improving safety performance of the electrochemical device and the electronic device.
Additional aspects and advantages of some embodiments of this application will be partly described or illustrated later herein or expounded through implementation of an embodiment of this application.
For ease of describing an embodiment of this application, the following outlines the drawings needed for describing an embodiment of this application or the prior art. Evidently, the drawings outlined below are merely a part of embodiments in this application.
Some embodiments of this application are described in detail below. Throughout the specification of this application, the same or similar components and the components serving the same or similar functions are represented by similar reference numerals. An embodiment described herein with reference to the drawings is descriptive and illustrative in nature, and is intended to enable a basic understanding of this application. No embodiment of this application is to be construed as a limitation on this application.
In this specification, unless otherwise specified or defined, relative terms such as “central”, “longitudinal”, “lateral”, “front”, “rear”, “right”, “left”, “internal”, “external”, “lower”, “higher”, “horizontal”, “vertical”, “higher than”, “lower than”, “up”, “down”, “top”, “bottom”, and derivatives thereof (such as “horizontally”, “downward”, and “upward”) are intended to be construed as a reference to a direction described in the context or a direction illustrated in the drawings. Such relative terms are merely used for ease of description, but not intended to require a structure to be constructed or an operation to be performed in a given direction according to this application.
In addition, a quantity, a ratio, or another numerical value herein is sometimes expressed in the format of a range. Understandably, such a range format is set out for convenience and brevity, and needs to be flexibly understood to include not only the numerical values explicitly specified and defined by the range, but also all individual numerical values or sub-ranges covered in the range as if each individual numerical value and each sub-range were explicitly specified.
Further, for ease of description, “first”, “second”, “third”, and the like may be used herein to distinguish between different components in one drawing or a series of drawings. Unless otherwise expressly specified or defined, the terms “first”, “second”, “third”, and the like are not intended to describe the corresponding components.
In the field of electrochemical devices, an existing manufacturing process is limited in some aspects, for example, the coating amount at the edge of an electrode plate during the coating is relatively low, or the active material layer is broken at the edge of the electrode plate, and therefore, a thickness of an active material layer of the electrode plate at the edge of the electrode plate is prone to decline gradually. Consequently, the thickness of the active material layer at the edge of the electrode plate is less than the thickness of the active material layer in the middle of the electrode plate. At the same time, some regions at the edge of the electrode plate are not coated with the active material layer, so that an thinned region of the electrode plate is formed at the edge of the electrode plate.
As shown in
In addition, the surface of the metal portion (not shown in
According to an aspect of this application, some embodiments of this application provide an electrochemical device. By limiting the position and thickness of the protective adhesive tape on the electrode assembly, this application improves the interface stability at the edge of the electrode assembly.
As shown in
In some embodiments, the electrode assembly 30 further includes a second metal portion (not shown in
By disposing the first adhesive tape 31 on the first part 303a of the body portion 303 in the electrode assembly 30 and the surface of the first metal portion 304, or on the first part 303a and the surface of the second metal portion, this application protects and fixes the edge part of the electrode assembly 30, enables the thinned regions of the first electrode plates and the second electrode plates to bond more firmly, shortens the ion transmission distance, makes the interface more stable at the edge of the electrode assembly, and in turn, enhances the cycle performance and safety performance of the electrochemical device.
In this application, the first part of the electrode assembly, which is affected by the thinned region of the electrode plate, is defined by the following method: measuring the thickness of the electrode assembly in the middle of the electrode assembly with an instrument (such as a small-probe micrometer), where the probe is 1 mm in diameter, and H represents the thickness of the body portion of the electrode assembly (equivalent to the thickness of the second part); subsequently, measuring points at intervals of 1 mm in the first direction of the electrode assembly, and, when the thickness of a test point is less than (H−0.01) mm, defining this point as a boundary point between the first part and the second part.
Understandably, the first adhesive tape according to this application may be disposed at all edges that may be affected by the thinned regions of the electrode plates on the electrode assembly, including the edge in the length direction of the electrochemical device and the edge in the width direction of the electrochemical device. In some embodiments, the first direction is the length direction or width direction of the electrode assembly. In some other embodiments, the first direction may be any planar direction perpendicular to a corresponding edge in the electrode assembly.
In some embodiments, the electrode assembly is a jelly-roll type structure or a stacked type structure.
Understandably, as shown in
As shown in
As shown in
In some embodiments, the third surface 304c of the first metal portion 304 is fully provided with the first adhesive tape 301. In some embodiments, the third surface 304c of the first metal portion 304 is partly provided with the first adhesive tape 31.
As shown in
Referring to
In some embodiments, the second adhesive tape may be further disposed on the fourth surface of the first metal portion. In some embodiments, the second adhesive tape may be further disposed on the sixth surface of the second metal portion. Understandably, the first metal portion or the second metal portion may be a combination of curved or irregular tab bundles. To the extent not departing from the spirit of this application, the second adhesive tape may fully or partly overlay the fourth surface of the first metal portion or the sixth surface of the second metal portion to fix or coat the first metal portion or the second metal portion. In some embodiments, the fourth surface of the first metal portion is fully provided with the second adhesive tape. In some embodiments, the fourth surface of the first metal portion is partly provided with the second adhesive tape. In some embodiments, the first adhesive tape and the second adhesive tape each independently include a substrate layer and an bonding layer. The material of the substrate layer may include a polymer substrate such as polyethylene terephthalate, polyethylene, polypropylene, polyimide, polytetrafluoroethylene, or polyvinyl chloride. The material of the bonding layer may include one or more of acrylate, polyurethane, rubber, or silicone. In some embodiments, the bonding layer is disposed on one side or both sides of the substrate layer, and the first adhesive tape or the second adhesive tape bonds and fixes the electrode assembly through the bonding layer.
Referring to
0.47×H≤0.5×(T1+t1)≤0.52×H.
In the formula above, T1 represents the thickness of the first part corresponding to the first tape edge, and t1 represents the thickness of the first adhesive tape.
Understandably, the structural diagram shown in
0.47×H≤0.5×(T2+t2)≤0.52×H.
In the formula above, T2 represents the thickness of the first part corresponding to the second tape edge, and t2 represents the thickness of the second adhesive tape.
In some embodiments, a sum of the thickness of the first adhesive tape and the thickness of the second adhesive tape of the electrochemical device, the thickness of the first part of the electrode assembly corresponding to the first tape edge or the second tape edge, and the thickness of the body portion of the electrode assembly also satisfy the relation, that is,
0.47×H≤0.5×(T1+T2+t1+t2)≤0.52×H.
In some embodiments, the thickness of the first adhesive tape and the thickness of the second adhesive tape range from 0.01 mm to 0.5 mm.
As shown in
As shown in
Understandably, although the metal portion 304 of the electrode assembly 30 in
In some embodiments, the first metal portion or the second metal portion is a single-tab structure. In some embodiments, the first metal portion or the second metal portion is a dual-tab structure. In some embodiments, the first metal portion or the second metal portion is a multi-tab structure. In some embodiments, the shape of the tab in the first metal portion or the second metal portion may be strip-like, sheet-like, plate-like, bundle-like, and so on, without being limited herein.
Referring to
In some embodiments, the thickness of the inorganic material layer 42 is less than or equal to a maximum thickness of a single-side active material layer 401 or 402 of the first electrode plate 40 or second electrode plate 41.
In some embodiments, the it material layer 42 is contiguous to the positive active material layer 401 or negative active material layer 411. In some embodiments, when the first electrode plate and the second electrode plate are stacked or wound to form an electrode assembly, the length of the inorganic material layer disposed on the second electrode plate in the first direction is greater than or equal to a distance between a first electrode plate edge and a second electrode plate edge that are adjacent to the inorganic material layer.
In some embodiments, when the first electrode plate and the second electrode plate are stacked or wound to form an electrode assembly, the edge of the inorganic material layer 41 disposed on the second electrode plate, which is away from the second active material layer, extends beyond the first electrode plate edge of the adjacent first electrode plate 40.
In some embodiments, the inorganic material layer includes an inorganic material. The inorganic material includes at least one of aluminum oxide, dioxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium dioxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate.
Understandably, to the extent not departing from the spirit of this application, the method for preparing the electrochemical device according to this application may be any appropriate preparation method in the art, and is not limited to the illustrated method.
Some embodiments of this application further provide an electronic device. The electronic device includes the electrochemical device according to an embodiment of this application.
The electronic device according to an embodiment of this application is not particularly limited, and may be any electronic device known in the prior art. In some embodiments, the electronic device may include, but without being limited to, an electronic cigarette device, electronic vaporizer, wireless headset, robot cleaner, unmanned aerial vehicle, notebook computer, pen-inputting computer, mobile computer, e-book player, portable phone, portable fax machine, portable photocopier, portable printer, stereo headset, video recorder, liquid crystal display television set, handheld cleaner, portable CD player, mini CD-ROM, transceiver, electronic notepad, calculator, memory card, portable voice recorder, radio, backup power supply, motor, automobile, motorcycle, power-assisted bicycle, bicycle, lighting appliance, toy, game console, watch, electric tool, flashlight, camera, large household battery, lithium-ion capacitor, and the like.
Some specific embodiments are enumerated below on which a cycle performance test and a lithium plating test are performed to describe this application more clearly. A person skilled in the art understands that the preparation methods described in this application are merely exemplary, and any other appropriate preparation methods still fall within the scope of this application.
Putting a lithium-ion battery in each of the following embodiments and comparative embodiments into a 25° C.±2° C. thermostat, leaving the battery to stand for 2 hours, charging the battery at a constant current of 0.5 C. until the voltage reaches 4.4 V, charging the battery at a constant voltage of 4.4 V until the current reaches 0.02 C., and leaving the battery to stand for 15 minutes; and discharging the battery at a constant current of 0.5 C. until the voltage reaches 3.0 V, thereby completing one charge-and-discharge cycle. Recording a first-cycle discharge capacity of the lithium-ion battery. Repeating the charge-and-discharge cycle according to the foregoing method, recording a discharge capacity at the end of each charge-and-discharge cycle, and then comparing the discharge capacity with the first-cycle discharge capacity to obtain a cycle capacity curve.
Testing the batteries in groups, where each group includes 4 lithium-ion batteries, and calculating an average of cycle capacity retention rates of the lithium-ion batteries: cycle capacity retention rate of each lithium-ion battery=(500th-cycle discharge capacity (mAh)/first-cycle discharge capacity (mAh)×100%.
Putting a lithium-ion battery in each of the following embodiments and comparative embodiments into a 25° C.±2° C. thermostat, and leaving the battery to stand for 2 hours. Charging the battery at a constant current of 3 C. until the voltage reaches 4.4 V, and then charging the battery at a constant voltage of 4.4 V until the current reaches 0.02 C., leaving the battery to stand fore 15 minutes, and then discharging the battery at a constant current of 0.5 C. until the voltage reaches 3.0 V, thereby completing one lithium plating test cycle. Repeating the lithium plating test cycle for 100 cycles, and then discharging the lithium-ion battery at a constant current of 0.5 C. until the voltage reaches 3.00 V. Subsequently, disassembling the lithium-ion battery, and checking whether lithium plating occurs on the surface of the negative active material layer. A gray position indicates lithium plating, and absence of gray positions indicates no lithium plating.
Stacking a positive electrode plate, a separator, and a negative electrode plate in sequence, and then winding the stacked structure to form an electrode assembly. Measuring the electrode assembly with a small-probe micrometer to obtain the relevant parameters affected by thinned regions of the electrode plates: the length of the first part of the body portion is 12 mm, and the thickness of the second part of the body portion is 4.5 mm.
Disposing a first adhesive tape on a surface of the electrode assembly near the edge of the electrode assembly in the length direction (perpendicular to the winding direction). To be specific, affixing the first adhesive tape to a part of the surface of the first part of the body portion of the electrode assembly and the surface of the metal portion connected thereto, where the first tape edge is located between the first boundary line and the second boundary line. Table 1 shows specific settings of parameters such as the thickness of the electrode assembly corresponding to the first tape edge, the thickness of the adhesive tape, and the overlay length on the body portion. Putting the electrode assembly with the adhesive tape into a housing, and injecting an electrolytic solution. Performing steps such as vacuum sealing, static standing, chemical formation, and shaping to obtain a finished-product lithium-ion battery.
In Embodiments 2 to 5 and Embodiments 8 to 11, the preparation method is identical to that in Embodiment 1, but differs from Embodiment 1 in the thickness of the electrode assembly corresponding to the first tape edge, the thickness of the adhesive tape, or the overlay length on the body portion, as detailed in Table 1.
In Embodiments 6 to 7 and Embodiment 12, the preparation method is identical to that in Embodiment 1 except that, during the disposition of the first adhesive tape, a second adhesive tape is further disposed on the surface back from the surface on which the first adhesive tape is disposed, where the specific settings of parameters are shown in Table 1, such as the thickness of the electrode assembly corresponding to the first tape edge or second tape edge, the thickness of the adhesive tape, the overlay length on the body portion, and the final position relationship.
In Embodiment 13, the preparation method is identical to that in Embodiment 12 except that a gel is further disposed on the overlap part between the tab and the adapter strip.
Identical to Embodiment 1 in terms of the preparation method except that, in Comparative Embodiment 1, no first adhesive tape is disposed on the electrode assembly in the lithium-ion battery.
Identical to Embodiment 1 in terms of the preparation method except that in Comparative Embodiment 2, the first adhesive tape is affixed onto the surface of the first part of the electrode assembly and partly affixed onto a part of the surface of the second part, with the first tape edge extending beyond the second boundary line. The specific settings of parameters are shown in Table 1.
Table 1 shows settings of parameters of the adhesive tape and the electrode assembly in different embodiments.
After a finished-product lithium-ion battery in an embodiment or comparative embodiment is measured, the capacity, thickness, width, and length of the finished product is recorded, so as to determine the volumetric energy density of the lithium-ion battery. Subsequently, a cycle performance test and a lithium plating test are performed on the finished-product lithium-ion batteries in the foregoing embodiments. Table 2 shows experimental parameters and measurement results in each embodiment and comparative embodiment.
As can be seen from Comparative Embodiment 1 versus Embodiments 1 to 3 as shown in Table 1 and Table 2 above, by disposing the adhesive tape in the thinned region of the electrode plate of the electrode assemble and controlling the position and other parameters of the adhesive tape, this application effectively enhances the cycle performance of the electrochemical device and alleviates the lithium plating of the electrochemical device during the cycling.
As can be seen from the comparison between Embodiments 1 to 5, when the thickness t1 of the first adhesive tape, and the thickness T1 of the first part of the body portion corresponding to the position of the first tape edge, and the thickness H of the body portion of the electrode assembly satisfy 0.47×H±0.5×(T1+t1)≤0.52×H, the lithium plating of the electrode assembly can be effectively suppressed, and the lithium-ion battery achieves a relatively high cycle capacity retention rate. In contrast, in Embodiment 4, a half of the sum of the thickness t1 of the first adhesive tape and the thickness T1 of the first part of the body portion corresponding to the position of the first tape edge is not greater than 0.47 H, so that the first adhesive tape is not enough to protect the first part of the electrode assembly, and in turn, lithium plating occurs on the first part. In Embodiment 5, a half of the sum of the thickness t1 of the first adhesive tape and the thickness T1 of the first part of the body portion corresponding to the position of the first tape edge is not less than 0.52 H, so that the first adhesive tape presses the second part of the body portion during sealing and leads to lithium plating of the second part.
As can be seen from Embodiments 1 and 8 to 11 versus Comparative Embodiment 2, when the position of the first tape edge satisfies the range specified in embodiment of this application, a relatively stable interface is formed at the electrode plate edge in the electrode assembly, so that the lithium-ion battery achieves a high cycle capacity retention rate and a high volumetric energy density. When the adhesive tape is disposed on the surface of the second part of the electrode assembly, the thickness is not evenly distributed at the boundary of the electrode assembly due to the protruding adhesive tape, thereby leading to a plunge in the energy density of the lithium-ion battery.
As shown in Embodiments 6, 7, and 12, the lithium-ion batteries coated with the adhesive tape on both sides also achieve high cycle capacity retention rates and energy densities.
As shown in Embodiments 12 and 13, a drop test that is further performed on the batteries in Embodiments 12 and 13 shows that the lithium-ion batteries with a gel achieve relatively high anti-drop performance. When impacted b an external force, the lithium-ion batteries (8/10) in Embodiment 13 exhibit higher safety performance than the lithium-ion batteries (4/10) in Embodiment 12.
A person skilled in the art understands that although the lithium-ion battery is used as an example for describing the foregoing embodiments and comparative embodiments, a person skilled in the art who has read this application can learn that the adhesive tape arrangement in this application is applicable to other appropriate electrochemical devices. Through comparison between the foregoing embodiments, it is clearly understood that the electrochemical devices equipped with the adhesive tape according to this application exhibit higher safety performance and cycle performance.
Although illustrative embodiments have been demonstrated and described above, a person skilled in the art understands that the foregoing embodiments are not to be construed as a limitation on this application, and changes, replacements, and modifications may be made to the embodiments without departing from the spirit, principles, and scope of this application.
This application is a continuation of PCT application PCT/CN2020/099308, filed on Jun. 30, 2020, the disclosure of which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2020/099308 | Jun 2020 | US |
| Child | 18090808 | US |
