Electrochemical device and electronic device

Abstract

The application discloses an electrochemical device, which comprises an electrode assembly and a bonding member. The electrode assembly is a winding structure formed by sequentially stacking and winding a first pole piece, a first separator film, a second pole piece and a second separator film; the first pole piece has a tail end located at the outermost circle of the winding structure, and the first pole piece comprises a first current collector; the bonding member comprises a substrate layer and first and second adhesive layers arranged on the surface of the substrate layer; the substrate layer comprises a first section and a second section connected with the first section; the first section is fixedly bonded with the tail end through the first adhesive layer, and the second section is fixedly bonded with the first section through the second adhesive layer, so that the substrate layer is arranged around the outer circumferential surface of the winding structure, wherein 3%F c ≤F2≤5%F c <F1. In the above manner, the safety performance of the electrochemical device can be improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to an electrochemical device and an electronic device. Background Technology

[0002] In conventional wound electrode assemblies, the outermost ring is typically finished with a current collector. While maintaining battery performance and lifespan, appropriately thinning the current collector can increase the battery's volumetric energy density. However, this affects the mechanical strength of the current collector. As the battery repeatedly expands during charging and discharging, the outermost current collector eventually experiences stress concentration and fractures. Fractures of the outermost current collector may result in burrs, posing a potential short-circuit risk and reducing safety during use. Summary of the Invention

[0003] In view of the above problems, this application provides an electrochemical device and an electronic device, which aim to improve the situation where the outermost current collector of the electrode assembly is prone to breakage.

[0004] According to a first aspect of this application, an electrochemical device is provided, including an electrode assembly and an adhesive. The electrode assembly is a wound structure formed by sequentially stacking and winding a first electrode, a first separator, a second electrode, and a second separator. The first electrode has a terminal portion located at the outermost ring of the wound structure, and the first electrode includes a first current collector.

[0005] The adhesive component includes a substrate layer and a first adhesive layer and a second adhesive layer evenly disposed on the surface of the substrate layer. The substrate layer includes a first segment and a second segment connected to the first segment. The first segment is bonded and fixed to the tail portion by the first adhesive layer, and the second segment is bonded and fixed to the first segment by the second adhesive layer, such that the substrate layer is disposed around the outer peripheral surface of the wound structure. Wherein, F c F1 is the force that the first current collector can withstand when it breaks, in N; F2 is the adhesive force between the first section and the tail section, in N; F3 is the adhesive force between the second section and the first section, in N; 3%F c ≤F2≤5%F c <F1.

[0006] In the electrochemical device involved in the embodiments of this application, firstly, the inventors discovered through research that limiting the adhesive force F1 between the second segment and the first segment to this numerical range, since the adhesive is elastic, can provide better binding force to constrain the electrode assembly within the reversible cyclic expansion range of the electrode assembly, so that the first electrode, the second electrode, the first separator and the second separator are all well attached to improve the interface problem of the electrode. This point will be explained in conjunction with subsequent experimental data.

[0007] Secondly, since the adhesive binder has a joint after binding the winding structure, and the adhesive force between the first and second sections of the joint meets the above conditions, when the expansion stress of the electrode assembly exceeds the adhesive force between the first and second sections, the joint will experience local stress concentration and fail. As a result, the interlayer force between the components in the winding structure is reduced, and the winding structure is relatively loose at this time. The first electrode adjacent to the tail of the first separator can extend along with the expansion of the electrode assembly, preventing the first current collector of this part of the first electrode from breaking, thereby improving the safety and cycle performance of the electrochemical device.

[0008] In some embodiments of this application, 5% F c <F s , of which F s The force that the substrate layer can withstand when it breaks is expressed in Newtons (N). The advantage of this design is that, during the stage where the irreversible expansion force of the electrode assembly gradually exceeds the adhesive force between the second and first sections, the structure of the adhesive remains intact. This allows the substrate layer to continue dispersing some of the expansion force of the electrode assembly, ensuring good adhesion between the first electrode, the second electrode, the first separator, and the second separator until the adhesive force between the first and second sections fails.

[0009] In some embodiments of this application, 2 < F1 / F2 ≤ 10. By limiting F1 / F2 to the above numerical range, the risk of the adhesive detaching from the electrode assembly due to excessive expansion rate can be reduced, the electrochemical device can have a better capacity retention rate, and a reasonable design redundancy can be maintained, thus saving the manufacturing cost of the electrochemical device.

[0010] In some embodiments of this application, the first section and the tail portion are bonded and fixed together by the first adhesive layer and partially overlap. The length W1 of the overlapping portion of the first section and the tail portion along the winding direction of the electrode assembly; the length W2 of the tail portion along the winding direction of the electrode assembly; W1 and W2 satisfy: 1 / 3 ≤ W1 / W2 ≤ 1. With W1 / W2 within this range, the outermost portion of the first electrode sheet and the adhesive form an integral structure, thereby improving the overall tensile strength of the outermost portion of the first electrode sheet to accommodate electrochemical devices with higher volumetric energy density.

[0011] In some embodiments of this application, the second electrode includes a second current collector and a second active material layer, the second active material layer being coated on at least one surface of the second current collector, and the coating areal density of the second active material layer being 80 mg / 1540.25 mm². 2 ~110mg / 1540.25mm 2The active material of the second active material layer includes silicon material, and the mass percentage of the silicon material is 5% to 10% based on the total mass of the active material in the second active material layer.

[0012] The force required for the first section and the overlapping portion of the tail section to break is 25N to 30N.

[0013] In some embodiments of this application, the second electrode includes a second current collector and a second active material layer, the second active material layer being coated on at least one surface of the second current collector, and the coating areal density of the second active material layer being 80 mg / 1540.25 mm². 2 ~110mg / 1540.25mm 2 The active material of the second active material layer includes silicon material, and the mass percentage of the silicon material is 10% to 15% based on the total mass of the active material in the second active material layer.

[0014] The force required for the first section and the overlapping portion of the tail section to break is 30N to 35N.

[0015] In some embodiments of this application, along the winding direction of the electrode assembly, the end of the first adhesive layer near the second adhesive layer does not extend beyond the termination end of the tail portion. This results in a larger adhesion allowance for the second adhesive layer, reducing the likelihood of the first adhesive layer being fixed to the first section, thereby improving the yield of the electrochemical device.

[0016] In some embodiments of this application, along the winding direction of the electrode assembly, the end of the first adhesive layer near the second adhesive layer extends beyond the termination end of the tail portion. Besides being bonded and fixed to the termination end of the tail portion via the first adhesive layer, the first section is also bonded and fixed to the termination end of the second winding portion, the termination end of the first separator, and the termination end of the second separator. Thus, the aforementioned four components form an integrated stress-bearing structure under the adhesive action of the first adhesive layer, thereby reducing the impact of uneven stress on the various components of the electrode assembly on shortening the lifespan of the electrochemical device.

[0017] In some embodiments of this application, the first electrode further has a first winding portion located in the inner circle of the winding structure, and the first winding portion is connected to the tail portion. The first section and a portion of the first winding portion are both bonded and fixed by the first adhesive layer. The adhesive can directly cover the end of the single-sided first active material layer of the first winding portion, eliminating the need to apply a protective adhesive to the end of the single-sided first active material layer of the first winding portion 2, thereby improving the situation where lithium plating occurs due to increased gap at the end interface of the first electrode and the second electrode caused by uneven thickness of the protective adhesive.

[0018] In some embodiments of this application, the substrate layer includes at least one of polypropylene, polyethylene, and polyethylene terephthalate.

[0019] In some embodiments of this application, the first adhesive layer and the second adhesive layer each independently comprise at least one of the following: acrylic compounds, acrylate compounds, phosphate compounds, polyurethane compounds, rosin resins, terpene resins, phenolic resins, petroleum resins, epoxy resins, vinyl acetate compounds, polyvinyl acetal compounds, polyamide compounds, vulcanized silicone rubber, furan resins, formaldehyde resins, polyimide compounds, urea-formaldehyde resins, acetate compounds, styrene, microcrystalline wax, or copolymers of styrene with C2-C5 olefins.

[0020] According to a second aspect of this application, an electronic device is provided, comprising the electrochemical device described above. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0022] Figure 1 This is a schematic diagram of the structure of an electrochemical device provided according to the first aspect of this application;

[0023] Figure 2 This is a schematic diagram of a structure in an electrochemical device according to the present application, in which an adhesive element is disposed around the outer peripheral surface of an electrode assembly;

[0024] Figure 3 for Figure 2 The image shows a cross-sectional view along line AA of the overall structure where the adhesive is bonded and fixed to the electrode assembly.

[0025] Figure 4 for Figure 3 The figure shows a partial cross-sectional view along line aa of the overall structure of the adhesive component bonded and fixed to the electrode assembly.

[0026] Figure 5 for Figure 3 The image shows a partial enlarged view of the adhesive component being bonded and fixed to the electrode assembly at point A'.

[0027] Figure 6 This is another structural schematic diagram of the adhesive component surrounding the outer peripheral surface of the electrode assembly in the electrochemical device according to this application;

[0028] Figure 7 for Figure 3A schematic diagram of the overall structure in which the middle adhesive component is bonded and fixed to the electrode assembly, taken from the end of the first electrode plate and in an unfolded state.

[0029] Reference numerals: 10, housing; 20, electrode assembly; 20a, center hole; 21, first electrode; 211, first winding portion; 212, tail portion; 21a, first active material layer; 21b, first current collector; 22, first separator; 23, second electrode; 231, starting portion; 232, second winding portion; 23a, second active material layer; 23b, second current collector; 24, second separator; 30, first tab; 40, second tab; 50, adhesive; 51, substrate layer; 511, first section; 512, second section; 52, first adhesive layer; 53, second adhesive layer. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its application or use.

[0031] Figure 1 This is a schematic diagram of the structure of an electrochemical device according to the first aspect of this application. Figure 2 This is a schematic diagram of the structure of the electrochemical device according to this application, in which the adhesive is disposed around the outer peripheral surface of the electrode assembly. Figure 3 for Figure 2 A cross-sectional view along line AA. For ease of description, a three-dimensional Cartesian coordinate system is established with the thickness direction of the electrochemical device as the X direction (first direction), the width direction of the electrochemical device as the Y direction (second direction), and the height direction of the electrochemical device as the Z direction (third direction). In some embodiments of this application, the thickness direction of the electrode assembly and the thickness direction of the adhesive are the same as the thickness direction of the electrochemical device; in some embodiments of this application, the stacking direction of each electrode in the electrode assembly is the same as the thickness direction of the electrochemical device; in some embodiments of this application, the width direction of the electrode assembly and the width direction of the adhesive are the same as the width direction of the electrochemical device; in some embodiments of this application, the height direction of the electrode assembly and the height direction of the adhesive are the same as the height direction of the electrochemical device; in some embodiments of this application, the protrusion direction of each tab in the electrochemical device is the same as or opposite to the height direction of the electrochemical device.

[0032] In the description of this application, it should be noted that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0033] Next, the specific structure of the electrochemical device will be described in conjunction with the embodiments illustrated in the accompanying drawings. Unless otherwise specified, the technical features involved in the different embodiments of this application described below can be combined with each other.

[0034] First, please refer to the following: Figures 1 to 3 As illustrated in some embodiments of this application, the electrochemical device includes: a housing 10, an electrode assembly 20, a first tab 30, a second tab 40, an adhesive 50, and an electrolyte (not shown); wherein, the housing 10 is a mounting support structure for the aforementioned components, the electrode assembly 20 and the electrolyte are both housed within the housing 10, and the electrode assembly 20 is immersed in the electrolyte; the electrode assembly 20 is a generally flat wound structure formed by sequentially stacking and winding a first electrode 21, a first separator 22, a second electrode 23, and a second separator 24; the adhesive 50 is disposed around the outer peripheral surface of the wound structure along the winding direction S of the electrode assembly 20, and constrains the state of the inward constraint load acting on the wound structure; the first tab 30 and / or the second tab 40 are at least partially disposed within the housing 10, the first tab 30 is electrically connected to the first electrode 21, and the second tab 40 is electrically connected to the second electrode 23. The electrochemical device is configured to be connected to an external circuit via a first tab 30 and a second tab 40. Specifically, the external circuit can be a load circuit in an electronic device, so that the electrochemical device can output its stored electrical energy; or it can be a power input circuit of an electronic device, so that external input can supplement the electrochemical device with electrical energy.

[0035] Next, an example of a secondary battery using an electrochemical device will be used for illustration. It is understood that the embodiments of this application do not particularly limit the type of secondary battery, which can include any device in which an electrochemical reaction occurs. For example, in some other embodiments of this application, the secondary battery may include, but is not limited to: lithium metal secondary batteries, lithium-ion secondary batteries (lithium-ion batteries), lithium polymer secondary batteries, or lithium-ion polymer secondary batteries, etc. Furthermore, for ease of description, the electrode assembly 20 will be described using the first electrode 21 as the cathode and the second electrode 23 as the anode; however, the first electrode 21 can also be an anode, and correspondingly, the second electrode 23 can also be a cathode.

[0036] In the description of this application, it should be noted that the terms "first," "second," etc., in the specification, claims, and drawings are used to distinguish different objects, not to describe a specific order, and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0037] For the first electrode 21, please refer to... Figure 4 See also Figure 3 As illustrated in some embodiments of this application, the first electrode 21 includes a first winding portion 211 and a tail portion 212 integrally connected to the first winding portion 211 along the winding direction S of the electrode assembly 20. The first winding portion 211 is located on the inner ring of the winding structure and is electrically connected to the first electrode tab 30. The tail portion 212 is located on the outermost ring of the winding structure and is bonded and fixed to the adhesive member 50. Specifically, both the first winding portion 211 and the tail portion 212 include a first active material layer 21a and a first current collector 21b; the common feature of the first winding portion 211 and the tail portion 212 is that both are formed by coating the first active material layer 21a onto the first current collector 21b. The difference between the first winding portion 211 and the tail portion 212 is that the first winding portion 211 is formed by coating the first active material layer 21a onto two surfaces of the first current collector 21b that are opposite to each other in the first direction X, while the tail portion 212 is formed by coating the first active material layer 21a onto one surface of the first current collector 21b in the first direction X. As an example, the first active material layer 21a on the first winding portion 211 is coated on the surface of the first current collector 21b facing the center hole 20a of the winding structure and the surface of the first current collector 21b facing away from the center hole 20a of the winding structure, respectively. The first active material layer 21a on the tail portion 212 is coated only on the surface of the first current collector 21b facing the center hole 20a of the winding structure. The surface of the tail portion 212 facing away from the center hole 20a of the winding structure is bonded and fixed to the adhesive 50 so that the adhesive 50 is attached to the outer peripheral surface of the winding structure along the winding direction S of the electrode assembly 20. It should be noted here that the outer peripheral surface of the winding structure mentioned here refers to the surface of the tail portion 212 facing away from the center hole 20a of the winding structure, that is, the other side of the winding structure except for the side that is electrically connected to the first tab 30 and the second tab 40. The first current collector 21b of the first winding portion 211 and the first current collector 21b of the tail portion 212 are integrally formed, and the first active material layer 21a of the first winding portion 211 and the first active material layer 21a of the tail portion 212 are integrally formed.

[0038] It is understood that the type of the first current collector 21b is not specifically limited in the various embodiments of this application, as long as it has good corrosion resistance and electrical conductivity. For example, the first current collector 21b may include, but is not limited to, at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In, Zn, and combinations thereof (alloys). As an example, the first current collector 21b may be made of aluminum foil or nickel foil.

[0039] It is also understood that, in the various embodiments of this application, the components of the first active material layer 21a are not specifically limited, as long as they possess good electrochemical performance and durability. For example, the first active material in the first active material layer 21a may include, but is not limited to, LiNi. 1 / 3 Mn 1 / 3 Co 1 / 3 Lithium metal oxides such as O2, LiCoO2, LiNiO2, LiMn2O4, LiCoMnO4, and Li2NiMn3O8. Alternatively, lithium metal phosphates such as LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, Li3Fe2(PO4)3, and Li3V2(PO4)3. As an example, the positive electrode active material uses LiNi... 1 / 3 Mn 1 / 3 Co 1 / 3 Made from O2.

[0040] For the second electrode 23, please continue to combine Figure 4 See also Figure 3As illustrated in some embodiments of this application, the second electrode 23 includes a starting portion 231 and a second winding portion 232 integrally connected to the starting portion 231 along the winding direction S of the electrode assembly 20. The starting portion 231 is located at the innermost loop of the winding structure and is disposed opposite to the first winding portion 211 of the first electrode 21 along the first direction X; the second winding portion 232 is located at the inner loop of the winding structure and is disposed opposite to the ending portion 212 of the first electrode 21 along the first direction X, and the second winding portion 232 is electrically connected to the second electrode tab 40. Specifically, both the starting portion 231 and the second winding portion 232 include a second active material layer 23a and a second current collector 23b; the similarity between the starting portion 231 and the second winding portion 232 is that both are formed by coating the first current collector 21b with the second active material layer 23a. The difference between the starting portion 231 and the second winding portion 232 is that the starting portion 231 is formed by coating a second active material layer 23a onto one surface of the second current collector 23b in the first direction X, while the second winding portion 232 is formed by coating the second active material layer 23a onto two opposing surfaces of the second current collector 23b in the first direction X. As an example, the second active material layer 23a on the starting portion 231 is only coated on the surface of the second current collector 23b facing away from the center hole 20a of the winding structure, while the second active material layer 23a on the second winding portion 232 is coated on both the surface of the second current collector 23b facing the center hole 20a of the winding structure and the surface of the first current collector 21b facing away from the center hole 20a of the winding structure. The second current collector 23b of the starting portion 231 and the second current collector 23b of the second winding portion 232 are integrally formed, and the second active material layer 23a of the starting portion 231 and the second active material layer 23a of the second winding portion 232 are also integrally formed.

[0041] It is understood that the type of the second current collector 23b is not specifically limited in the various embodiments of this application, as long as it has good corrosion resistance and electrical conductivity. For example, the second current collector 23b may include, but is not limited to, at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Si, Ge, Sb, Pb, In, Zn, and combinations thereof (alloys). As an example, the second current collector 23b may be made of copper foil.

[0042] It is also understood that, in the various embodiments of this application, the components of the second active material layer 23a are not specifically limited, as long as they possess good electrochemical performance and durability. For example, the second active material in the second active material layer 23a may include, but is not limited to, carbon materials such as graphite and hard carbon, or Si, Si alloys, and Li4Ti5O. 12Etc. As an example, the second active material includes silicon material, and based on the total mass of the active material in the second active material layer 23a, the mass percentage of silicon material is 5% to 10%, wherein the coating surface density of the second active material layer 23a is 80 mg / 1540.25 mm. 2 ~110mg / 1540.25mm 2 .

[0043] When winding the electrode assembly 20, the second electrode 23 can be wound first. After the starting portion 231 of the second electrode 23 is wound in, the first winding portion 211 of the first electrode 21 is then wound in. Therefore, during winding, the winding phase of the second electrode 23 around the winding center leads the winding phase of the first electrode 21 around the winding center, just as... Figure 3 or Figure 6 As shown, the beginning of the starting part 231 and the beginning of the second winding part 232 both extend beyond the beginning of the first winding part 211 by a certain distance; therefore, the cutoff phase of the second pole piece 23 around the center hole 20a of the winding structure leads the cutoff phase of the second pole piece 23 around the winding center, just as... Figure 3 or Figure 6 As shown, the end of the second winding portion 232 also extends beyond the end of the tail portion 212 and the end of the first winding portion 211 by a certain distance. The advantage of this arrangement is that, on the one hand, along the winding direction S of the electrode assembly 20, the second electrode 23 has an overhang area to improve the lithium plating situation at the end of the second electrode 23; on the other hand, the two ends of the second electrode 23 along the winding direction S are offset from the two ends of the first electrode 21 along the winding direction S, which also improves the situation where a short circuit occurs when the electrochemical device is under impact conditions due to the burrs at the ends of the two electrodes piercing the separator. It should be noted that the coating area of ​​the active material layer on the second electrode 23 should be larger than the coating area of ​​the active material layer on the first electrode 21. This is because during the secondary battery charging process, metal ions on the first electrode 21 will migrate to the second electrode 23 via the electrolyte. If the coating area of ​​the first electrode 21 is larger, more metal ions will enter the electrolyte. If they cannot completely migrate to the second electrode 23, metal ion deposition may occur on the surface of the second electrode 23. Of course, it is understandable that the winding methods of the first separator 22, the first electrode 21, the second separator 24, and the second electrode 23 are actually diverse. Users can make adaptive adjustments according to actual usage needs, and are not limited to the aforementioned winding methods.

[0044] For adhesive part 50, please refer to Figure 5 and Figure 6 See you again Figure 3As illustrated in some embodiments of this application, the adhesive 50 is generally a flexible sheet structure, comprising a substrate layer 51 and a first adhesive layer 52 and a second adhesive layer 53 disposed on the surface of the substrate layer 51. The substrate layer 51 includes a first segment 511 and a second segment 512 integrally connected to the first segment 511 along the winding direction S of the electrode assembly 20. It should be noted that the first segment 511 specifically refers to the segment from the starting end of the substrate layer 51 along the winding direction S of the electrode assembly 20 to the point where it overlaps with the starting point in the next turn. The second segment 512 specifically refers to the segment from the point overlapping with the starting point along the winding direction S of the electrode assembly 20 to the ending end of the substrate layer 51. The first segment 511 and the tail portion 212 are bonded and fixed by the first adhesive layer 52, and the second segment 512 and the first segment 511 are bonded and fixed by the second adhesive layer 53, so that the substrate layer 51 is disposed around the outer peripheral surface of the winding structure.

[0045] Adhesive component 50 satisfies: 3% F c ≤F2≤5%F c <F1, where F c F1 is the force that the first current collector 21b can withstand when it breaks, in N; F2 is the adhesive force between the first section 511 and the tail section 212, in N; F3 is the adhesive force between the second section 512 and the first section 511, in N.

[0046] In the electrochemical device involved in the embodiments of this application, firstly, the inventors discovered through research that limiting the adhesive force F1 between the second segment 512 and the first segment 511 to this numerical range, since the adhesive 50 is elastic, it can provide better binding force to constrain the electrode assembly 20 within the reversible cyclic expansion range of the electrode assembly 20, so that the first electrode 21, the second electrode 23, the first separator 22 and the second separator 24 are all well attached to improve the interface problem of the electrode. This point will be explained in conjunction with subsequent experimental data.

[0047] Second, since the adhesive 50 has a joint after binding the winding structure, and the bonding force between the first section 511 and the second section 512 at the joint meets the above conditions, when the expansion stress of the electrode assembly 20 exceeds the bonding force between the first section 511 and the second section 512, the joint will experience local stress concentration and fail. As a result, the interlayer force between the components in the winding structure is reduced, and the winding structure is relatively loose at this time. The portion of the first electrode 21 adjacent to the tail portion 212 of the first separator 22 can extend along with the expansion of the electrode assembly 20, preventing the first current collector 21b of this portion of the first electrode 21 from breaking, thereby improving the safety and cycle performance of the electrochemical device.

[0048] Third, when the first electrode 21 in the electrochemical device is made of aluminum foil and the housing 10 is made of aluminum-plastic film, because the adhesive 50 is insulating, even if the polypropylene layer of the housing 10 is locally damaged during the processing such as punching, the first current collector 21b is unlikely to provide an electron channel when it comes into contact with the aluminum layer of the housing 10. This improves the situation where water vapor enters the interior of the housing 10 through the corroded aluminum-plastic film due to the corrosion of the aluminum layer of the housing 10 and reacts with the electrolyte, causing gas expansion.

[0049] Furthermore, in some embodiments of this application, the adhesive 50 also satisfies: 2 < F1 / F2 ≤ 10. For example, the value of F1 / F2 can be 2, 3, 4, 5, 6, 7, 8, 9, 10, or any range thereof. When the value of F1 / F2 is too small (e.g., less than 2), it means that the difference between the adhesive force between the first segment 511 and the tail portion 212 and the adhesive force between the second segment 512 and the first segment 511 is small. If the irreversible expansion force of the electrode assembly 20 increases rapidly by a large margin, the risk of the adhesive 50 directly detaching from the electrode assembly 20 increases. When the value of F1 / F2 is too large (e.g., greater than 10), it means that the difference between the adhesive force between the first segment 511 and the tail portion 212 and the adhesive force between the second segment 512 and the first segment 511 is large. In other words, the design redundancy of F1 / F2 is too large, thereby increasing the manufacturing cost of the electrochemical device.

[0050] Optionally, in some embodiments of this application, the adhesive 50 further satisfies: 5% F c <F s ,F s =K s ×σ s , of which F s The force that the substrate layer 51 can withstand when it fractures, in N.

[0051] With this configuration, when the irreversible expansion force of the electrode assembly 20 gradually exceeds the adhesive force between the second section 512 and the first section 511, the structure of the adhesive 50 remains intact. As a result, the substrate layer 51 can continue to disperse part of the expansion force of the electrode assembly 20, ensuring that the first electrode 21, the second electrode 23, the first separator 22, and the second separator 24 are well bonded until the adhesive force between the first section 511 and the second section 512 fails.

[0052] In some embodiments of this application, the first adhesive layer 52 and the second adhesive layer 53 each independently comprise at least one of the following: acrylic compounds, acrylate compounds, phosphate ester compounds, polyurethane compounds, rosin resins, terpene resins, phenolic resins, petroleum resins, epoxy resins, vinyl acetate compounds, polyvinyl acetal compounds, polyamide compounds, vulcanized silicone rubber, furan resins, formaldehyde resins, polyimide compounds, urea-formaldehyde resins, acetate compounds, styrene, microcrystalline wax, or copolymers of styrene with C2-C5 olefins. Preferably, the acrylate compounds may include, but are not limited to, at least one of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, or 2-ethylhexyl acrylate; the acetate compounds may include, but are not limited to, at least one of methyl acetate, ethyl acetate, propyl acetate, or butyl acetate; and the copolymers of styrene with C2-C5 olefins may include, but are not limited to, at least one of styrene-isoprene copolymers, styrene-isoprene-styrene block copolymers, styrene-butadiene copolymers, and hydrogenated styrene-butadiene copolymers. The C2-C5 olefins can be ethylene, propylene, butene, isomers of butene, pentene, or isomers of pentene. By selecting the above compounds, the adhesion force F1 between the first segment 511 and the tail portion 212 at the outermost loop of the winding structure, and the adhesion force F2 between the second segment 512 and the first segment 511, can meet the requirements of this application, thereby improving the safety performance of the electrochemical device.

[0053] It is understood that the molecular weight of the materials of the first adhesive layer 52 and the second adhesive layer 53 in the various embodiments of this application is not particularly limited, as long as the purpose of this application can be achieved. For example, the molecular weights of polyurethane compounds, rosin resins, terpene resins, petroleum resins, epoxy resins, polyvinyl alcohol acetal compounds, polyamide compounds, vulcanized silicone rubber, furan resins, formaldehyde resins, polyimide compounds, urea-formaldehyde resins, and microcrystalline waxes can be 40,000 to 60,000, 250 to 350, 800 to 1300, 500 to 1000, 400 to 600, 30,000 to 50,000, 600 to 700, 30,000 to 50,000, 500 to 1000, 12,000 to 17,000, 40,000 to 50,000, 8,000 to 15,000, and 400 to 600, respectively. In addition, the materials of the first adhesive layer 52 and the second adhesive layer 53 may also be commercially available materials that meet the requirements of this application.

[0054] In some embodiments of this application, the material of the substrate layer 51 includes, but is not limited to, at least one of polypropylene, polyethylene, and polyethylene terephthalate. By selecting the above materials, the substrate of the resulting adhesive 50 has good elasticity and can stretch or shrink with the reversible expansion of the electrode assembly 20, thereby improving the safety performance of the electrochemical device.

[0055] It is also understood that the specific structure of the adhesive 50 is not specifically limited in the embodiments of this application, as long as it can provide a good binding force to constrain the electrode assembly 20 within a certain expansion range, and the adhesive force between the first segment 511 and the second segment 512 fails when the expansion force of the electrode assembly 20 exceeds the adhesive force between the first segment 511 and the second segment 512. For example, as Figure 3 As shown, the first adhesive layer 52 is disposed on the surface of the first section 511 facing the center hole 20a of the winding structure, and is bonded and fixed to the surface of the tail section 212 facing the center hole 20a of the winding structure; the second adhesive layer 53 is disposed on the surface of the second section 512 facing the center hole 20a of the winding structure, and is bonded and fixed to the surface of the first section 511 facing away from the center hole 20a of the winding structure, wherein the second adhesive layer 53 and the first adhesive layer 52 are partially bonded along the winding direction S of the electrode assembly 20. As an example, the adhesive 50 is an insulating adhesive paper, so that the adhesive 50 can be easily manufactured and applied to the winding structure. For example, as... Figure 6 As shown, in some other embodiments of this application, the first adhesive layer 52 is disposed on the surface of the first section 511 facing the center hole 20a of the winding structure, and the second adhesive layer 53 is disposed on the part of the surface of the first section 511 that overlaps with the second section 512 that faces away from the center hole 20a of the winding structure. At this time, the second section 512 is no longer provided with the second adhesive layer 53, that is to say, the second section 512 no longer has adhesiveness. In this way, after stretching the adhesive member 50, the second section 512 can be directly attached to the second adhesive layer 53. Since the second adhesive layer 53 is initially bonded and fixed with the second section 512, the effective contact area between the first section 511 and the second section 512 is large, and the adhesion force between the first section 511 and the second section 512 is also high.

[0056] like Figure 7As shown, in some embodiments of this application, the first section 511 and the tail portion 212 are bonded and fixed together by the first adhesive layer 52 and partially overlap. Along the winding direction S of the electrode assembly 20, the length of the overlapping portion of the first section 511 and the tail portion 212 is W1; the length of the tail portion 212 along the winding direction S of the electrode assembly 20 is W2. W1 and W2 satisfy the condition: 1 / 3 ≤ W1 / W2 ≤ 1. For example, the value of W1 / W2 can be 1 / 3, 1 / 2, 4 / 5, 2 / 3, 1, or any range thereof. Within this range, W1 / W2 ensures that the outermost portion of the first electrode 21 and the adhesive member 50 form an integral structure, thereby increasing the overall tensile strength of the outermost portion of the first electrode 21 to accommodate electrochemical devices with higher volumetric energy density.

[0057] Furthermore, the force required for the overlapping portion of the first section 511 and the tail section 212 to break is 25N to 30N. This is because a force lower than 25N is insufficient to protect the first current collector 21b of the tail section 212, while a force higher than 30N would make it difficult to release the expansion stress of the electrode assembly 20, causing deformation of the internal electrode structure and affecting safety. Of course, the tensile strength of the overlapping portion of the first section 511 and the tail section 212 is not always constant; it can be adaptively adjusted according to the ease of expansion of the electrochemical device. For example, in some other embodiments of this application, when other conditions remain constant, the silicon material mass percentage in the second active material layer 23a is 10% to 15%, and the force required for the overlapping portion of the first section 511 and the tail section 212 to break is 30N to 35N. This is because as the silicon content in the electrochemical device increases, the expansion stress becomes greater, requiring an increase in the force needed to break the overlapping portion of the first section 511 and the tail section 212 in order to improve the fracture of the first current collector 21b of the tail section 212.

[0058] Continue as Figure 5 As shown, in some embodiments of this application, the first end of the substrate layer 51 is adjacent to the end of the first winding portion 211 of the first electrode 21, and the end of the substrate layer 51 is attached to the portion overlapping the first end of the substrate layer 51 after wrapping around the winding structure at least once. Along the winding direction S of the electrode assembly 20, the end of the first adhesive layer 52 near the second adhesive layer 53 does not extend beyond the end of the tail portion 212. The advantage of this arrangement is that the adhesion allowance of the second adhesive layer 53 is larger, reducing the situation where the first adhesive layer 52 is bonded and fixed to the first section 511, thereby improving the yield of the electrochemical device. Alternatively, as Figure 6As shown, in some other embodiments of this application, along the winding direction S of the electrode assembly 20, one end of the first adhesive layer 52 near the second adhesive layer 53 extends beyond the termination end of the tail portion 212. The advantage of this arrangement is that, in addition to the first section 511 being bonded and fixed to the termination end of the tail portion 212 via the first adhesive layer 52, the first section 511 is also bonded and fixed to the termination ends of the second winding portion 232, the first separator 22, and the second separator 24. Thus, these four components form an integrated stress-bearing structure under the bonding action of the first adhesive layer 52, reducing the impact of uneven stress on the components of the electrode assembly 20 on shortening the lifespan of the electrochemical device.

[0059] Furthermore, the first section 511 is not only bonded and fixed to the tail portion 212 of the first electrode 21 through the first adhesive layer 52, but also bonded and fixed to a portion of the first winding portion 211 through the first adhesive layer 52. The advantage of this arrangement is that the adhesive 50 can directly cover the end of the single-sided first active material layer 21a of the first winding portion 211, eliminating the need to apply protective adhesive to the end of the single-sided first active material layer 21a of the first winding portion 211, thereby improving the situation of lithium plating caused by the increased gap at the end interface of the first electrode 21 and the second electrode 23 due to uneven thickness of the protective adhesive.

[0060] It should be noted that the terminator, end, start, and first end mentioned for each component in the above embodiments are all referenced to the center hole 20a of the winding structure. The end of each component that is close to the center hole 20a of the winding structure is the start end or first end, and the end of each component that is far from the center hole 20a of the winding structure is the end or end.

[0061] Regarding the shape and structure of the housing 10, the shape of the housing 10 should match the shape of the electrode assembly 20 to achieve good electrical contact and structural stability; the structure of the housing 10 should isolate moisture from the external environment from the electrolyte inside the housing 10 and prevent the electrolyte from corroding the packaging. As an example, such as... Figure 1 As shown, in some embodiments of this application, the housing 10 is also generally flat and can be made of composite materials such as, but not limited to, aluminum-plastic film and steel-plastic film. Preferably, the housing 10 is made of aluminum-plastic film. However, the structure of the housing 10 is not limited to this, and the housing 10 can also be made of hard metal materials such as steel alloy and aluminum alloy.

[0062] This application does not impose any particular limitation on the preparation method of the adhesive 50, as long as it can achieve the purpose of this application. For example, it may include, but is not limited to, the following steps: dissolving the substance used in the first adhesive layer 52 in a solvent to obtain a first adhesive layer 52 slurry, dissolving the substance used in the second adhesive layer 53 in a solvent to obtain a second adhesive layer 53 slurry, coating the first adhesive layer 52 slurry and the second adhesive layer 53 slurry onto the same surface of the substrate layer 51 along its own thickness direction, and drying to obtain the adhesive 50.

[0063] The preparation process of the electrochemical device is well known to those skilled in the art, and this application does not impose any particular limitations. For example, it may include, but is not limited to, the following steps: the first electrode 21, the first separator 22, the second electrode 23, and the second separator 24 are stacked sequentially from top to bottom, and then wound and folded as needed to obtain a wound electrode assembly 20. After the outermost ring of the electrode assembly 20 is fixed by the adhesive 50, the electrode assembly 20 is placed in a packaging bag, the electrolyte is injected into the packaging bag, and the bag is sealed to obtain the electrochemical device. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the packaging bag as needed to prevent pressure rise and overcharging / discharging inside the electrochemical device. The materials and preparation methods for the positive electrode, separator, negative electrode, and electrolyte in this application may use materials and preparation methods known in the art, and this application does not limit them.

[0064] A second aspect of this application provides an electronic device that includes the electrochemical device in any of the foregoing embodiments. The electrochemical device provided by this application has good safety performance, thereby providing the electronic device with good safety performance.

[0065] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0066] The present application is further illustrated below with reference to embodiments and comparative examples. Various tests and evaluations were performed according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0067] F c F1, F2 and F s Test

[0068] F c To determine the force that the first current collector can withstand upon fracture, a 20mm × 100mm sample was punched out using a punching machine. The sample was then fixed to the test fixture of a high-speed rail tensile testing machine to measure the force it could withstand upon fracture. The tensile speed was 5mm / min, and the standard distance between the two fixtures was 50mm. The force at fracture of the first current collector was recorded. Ten parallel samples were tested for each sample, and the final average value was recorded as F. c The test sample is the first current collector. During sample preparation, the active material layer on the first electrode needs to be removed to obtain the first current collector before testing.

[0069] F1 represents the adhesive force between the first section of the adhesive component and the tail end of the first electrode. During sample preparation, the overlapping portion of the adhesive component and the adjacent tail end of the first electrode is removed as a whole and then cut into 20mm × 100mm test specimens (if the specimen length is insufficient, a piece of paper of equal width can be used and glued to the tensile end of the test specimen to extend the total length of the test specimen and facilitate clamping the specimen end with the fixture). The side of the test specimen facing the first termination section is fixed to the test fixture of the high-speed rail tensile testing machine using high-adhesion adhesive paper (3M adhesive paper) for adhesive force testing. The peel angle is 90°, the tensile speed is 50mm / min, and the single tensile displacement is 30mm. Ten parallel samples are tested for each sample, and the final average value is recorded as F1.

[0070] F2 represents the adhesive force between the second and first sections of the bonded component. During sample preparation, the second section and the overlapping portion of the adjacent first section are removed as a single unit and cut into 20mm x 100mm test specimens. (If the specimen length is insufficient, a piece of paper of equal width can be used, bonded to the tensile end of the test specimen to extend its total length and facilitate clamping.) The side of the test specimen facing the second termination section is fixed to the test fixture of the high-speed rail tensile testing machine using high-adhesion adhesive tape (3M tape). The adhesive force is tested with a peel angle of 90°, a tensile speed of 50mm / min, and a single tensile displacement of 30mm. Ten parallel samples are tested for each specimen, and the final average value is recorded as F2.

[0071] F sTo determine the force that the substrate layer can withstand upon fracture, a 20mm × 100mm sample was punched out using a punching machine. Then, using a thickness gauge (or micrometer), the distance between the two large surfaces of the substrate layer was measured without load. The sample was then fixed to the testing fixture of a high-speed rail tensile testing machine to test the force that the sample could withstand upon fracture. The tensile speed was 5mm / min, and the standard distance between the two fixtures of the tensile testing machine was 50mm. The force that the substrate layer could withstand upon fracture was recorded. Ten parallel samples were tested for each sample, and the final average value was recorded as F. S， Since the test sample is a substrate layer, during sample preparation, the first and second adhesive layers on the surface of the adhesive part need to be removed to obtain the substrate layer. Organic solvents such as alcohol are used to remove the substrate layer before testing.

[0072] Fracture test

[0073] At 25°C, the lithium-ion battery was charged to 4.25V at a constant current of 1.0C, then charged to 0.05C at a constant voltage of 4.25V, and allowed to rest for 10 minutes; then discharged to 2.0V at a constant current of 4.0C, and allowed to rest for 15 minutes. This constitutes one cycle, and the cycle was repeated 400 times. After the 400th cycle, the cell was disassembled to check the condition of the first current collector at the outermost end of the electrode assembly.

[0074] Capacity retention test

[0075] The capacity retention rate of each secondary battery prepared above was tested. At 25°C, the secondary battery was charged at a constant current of 1.5C to 4.48V, then charged at a constant voltage to 0.05C, and left to stand for 10 minutes. After that, it was discharged at a constant current of 0.5C to 3.0V. This was the first cycle. The above process was repeated to measure the capacity retention rate of the lithium-ion battery after 400 cycles. The capacity retention rate (%) = discharge capacity after 400 cycles / discharge capacity after the first cycle × 100%.

[0076] Example 1-1

[0077] Preparation of the first electrode

[0078] The first active material is ternary lithium (LiNi). 1 / 3 Mn 1 / 3 Co 1 / 3 O2, binder, conductive agent, and conductive carbon black (Super P) are dissolved in dispersant N-methylpyrrolidone (NMP) at a mass ratio of 94:3:3 and stirred evenly to prepare a positive electrode slurry. The first active slurry is then evenly coated onto both sides of the first current collector aluminum foil using a coating machine, and subsequently dried at 85°C to obtain the first active material layer. The positive electrode sheet is then rolled under a certain pressure. Afterwards, it is cold-pressed, slit, and cut into sheets to obtain the first electrode sheet. The compacted density of the first active slurry is 3.5 g / cm³.3 .

[0079] Preparation of the second electrode

[0080] A negative electrode slurry was prepared by uniformly mixing artificial graphite (second active material), nano-silicon, styrene-butadiene rubber (binder), and conductive carbon black (Super P) in a mass ratio of 74:20:5:1 with deionized water. The negative electrode slurry was then uniformly coated onto both sides of the second current collector copper foil using a coating machine, and subsequently dried at 85°C to form the second active material layer. The second electrode sheet was then rolled, cold-pressed, slit, and cut into sheets to obtain the final second electrode sheet. The compacted density of the second active slurry was 1.6 g / cm³. 3 .

[0081] Preparation of electrolyte

[0082] Under a dry argon environment, LiPF6 is dissolved at 1 mol / L in a non-aqueous solvent consisting of ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) at 20 wt%, 30 wt%, 40 wt%, and 10 wt%, respectively. Then, 1 wt% ethylene carbonate and 5 wt% fluoroethylene carbonate are added to obtain the electrolyte.

[0083] Preparation of the first and second separating membranes

[0084] A porous polyethylene film with a thickness of 7μm is used.

[0085] Preparation of lithium-ion batteries

[0086] The first electrode, the first separator, the second electrode, and the second separator are stacked sequentially from top to bottom. They are then wound and folded as needed to obtain a wound electrode assembly. After the outermost ring of the electrode assembly is fixed with adhesive, the electrode assembly is placed in a packaging bag. Electrolyte is injected into the packaging bag and the bag is sealed. After formation and degassing, a lithium-ion battery is obtained.

[0087] Comparative Examples 1-1 to 1-2, Comparative Examples 2-1 to 2-2, Examples 1-1 to 1-5, and Examples 2-1 to 2-8 are the same as Example 1-1, except that the relevant parameters are adjusted according to Table 1.

[0088] The relevant preparation parameters and performance tests for each embodiment and comparative example are shown in Table 1.

[0089] Table 1

[0090]

[0091]

[0092] Comparing Examples 1-1 to 1-5 with Comparative Example 1-1, it can be seen that when at least one of F1 and F2 is less than F... c In this case, F2 will be the first to be affected by the expansion stress of the electrode assembly and fail. Therefore, the spacing between the layers inside the electrode assembly can increase with the increase of the expansion stress of the electrode assembly, so that the first current collector of the outermost ring of the electrode assembly will not break. This can also be seen by comparing Examples 2-1 to 2-6 with Comparative Example 2-1.

[0093] Continuing to compare Examples 1-1 to 1-5 with Comparative Examples 1-2 and 1-3, it can be seen that F1 and F2 satisfy 3% F c ≤F2≤5%F c At <F1, the retention rate of the electrochemical device after 400 cycles is significantly better than that of the comparative example. This is mainly because the inventors found that the expansion stress of this type of electrochemical device is within 3% F. c ~5% F c When F1 is within this numerical range, the expansion stress of the electrode assembly changes from reversible expansion force to irreversible expansion force. Therefore, setting F1 within this range allows the adhesive to detach promptly from the electrode assembly during the irreversible cyclic expansion range, while also providing better binding force to constrain the electrode assembly during the reversible cyclic expansion range. This can also be seen by comparing Examples 2-1 to 2-6 with Comparative Examples 2-2 and 2-3.

[0094] Furthermore, a comparison of Examples 1-1 and 1-2 shows that changing F1, even with all other conditions remaining constant, does not affect the capacity retention rate of the electrochemical device after 400 cycles. Moreover, a comparison of the data from Examples 1-2 to 1-5 shows that the capacity retention rate of the electrochemical device after 400 cycles is mainly affected by F2; specifically, as F2 increases, the capacity retention rate of the electrochemical device after 400 cycles gradually increases. This is also evident from the data analysis of Examples 2-2 to 2-6.

[0095] Finally, comparing Comparative Examples 1-3 and Examples 1-5 separately reveals that if F1 / F2≤2, it means F2>1N, which means F2 exceeds the normal expansion stress range of the electrochemical device. This will cause the electrode assembly to be affected by irreversible expansion force, reducing the capacity retention rate of the electrochemical device after 400 cycles. Alternatively, it means F1<2N, which means the difference between F1 and F2 is small, and the adhesive is prone to detachment as the expansion stress of the electrode assembly increases rapidly. The same logic applies to comparing Comparative Examples 2-3 and Examples 2-2 separately. Therefore, 2<F1 / F2≤10 can reduce the risk of the adhesive detaching from the electrode assembly due to excessive expansion rate and also ensure that the electrochemical device has a better capacity retention rate.

[0096] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. An electrochemical device, comprising an electrode assembly and an adhesive, wherein the electrode assembly is a wound structure formed by sequentially stacking and winding a first electrode, a first separator, a second electrode, and a second separator, wherein the first electrode has a tail portion located at the outermost ring of the wound structure, and the first electrode includes a first current collector. The adhesive includes a substrate layer and a first adhesive layer and a second adhesive layer evenly disposed on the surface of the substrate layer. The substrate layer includes a first segment and a second segment connected to the first segment, wherein... The first segment refers to the segment from the starting end of the substrate layer along the winding direction of the electrode assembly to the point where the next turn overlaps with the starting point; the second segment refers to the segment from the point overlapping with the starting point along the winding direction of the electrode assembly to the ending end of the substrate layer; the first segment and the tail portion are bonded and fixed together by the first adhesive layer; the second segment and the first segment are bonded and fixed together by the second adhesive layer, so that the substrate layer is disposed around the outer peripheral surface of the winding structure; characterized in that... 3%F c ≤F2≤5%F c <F1, where, F c The force that the first current collector can withstand when it breaks is expressed in N; F1 is the adhesive force between the first section and the tail section, expressed in N; F2 is the adhesive force between the second segment and the first segment, expressed in N.

2. The electrochemical device according to claim 1, characterized in that, 5%F c <F s , of which F s The force that the substrate layer can withstand when it breaks is expressed in N.

3. The electrochemical device according to claim 1, characterized in that, 2 < F1 / F2 ≤ 10.

4. The electrochemical device according to claim 1, characterized in that, The first section and the tail section are bonded and fixed together by the first adhesive layer and partially overlap. The length W1 of the overlapping portion of the first section and the tail section along the winding direction of the electrode assembly. The length W2 of the tail portion in the winding direction of the electrode assembly, W1 and W2 satisfy: 1 / 3≤W1 / W2≤1.

5. The electrochemical device according to claim 4, characterized in that, The second electrode includes a second current collector and a second active material layer. The second active material layer is coated on at least one surface of the second current collector, and the coating surface density of the second active material layer is 80 mg / 1540.25 mm². 2 ~110mg / 1540.25mm 2 The active material in the second active material layer includes silicon material, and the mass percentage of the silicon material is 5% to 10% based on the total mass of the active material in the second active material layer. The force required for the first section and the overlapping portion of the tail section to break is 25N to 30N.

6. The electrochemical device according to claim 4, characterized in that, The second electrode includes a second current collector and a second active material layer. The second active material layer is coated on at least one surface of the second current collector, and the coating surface density of the second active material layer is 80 mg / 1540.25 mm². 2 ~110mg / 1540.25mm 2 The active material in the second active material layer includes silicon material, and the mass percentage of the silicon material is 10% to 15% based on the total mass of the active material in the second active material layer. The force required for the first section and the overlapping portion of the tail section to break is 30N to 35N.

7. The electrochemical device according to claim 4, characterized in that, Along the winding direction of the electrode assembly, the end of the first adhesive layer near the second adhesive layer does not extend beyond the termination end of the tail portion; or Along the winding direction of the electrode assembly, the end of the first adhesive layer near the second adhesive layer extends beyond the termination end of the tail portion.

8. The electrochemical device according to claim 1, characterized in that, The first electrode also has a first winding portion located in the inner circle of the winding structure, and the first winding portion is connected to the tail portion; The first section and part of the first winding portion are both bonded and fixed by the first adhesive layer.

9. The electrochemical device according to any one of claims 1 to 8, characterized in that, The substrate layer comprises at least one of polypropylene, polyethylene, and polyethylene terephthalate; and / or The first adhesive layer and the second adhesive layer each independently comprise acrylic compounds, acrylate compounds, phosphate ester compounds, polyurethane compounds, rosin resins, terpene resins, phenolic resins, petroleum resins, epoxy resins, vinyl acetate compounds, polyvinyl acetal compounds, polyamide compounds, vulcanized silicone rubber, furan resins, formaldehyde resins, polyimide compounds, urea-formaldehyde resins, acetate compounds, styrene, microcrystalline wax, or styrene mixed with C2 At least one of the copolymers of C5 olefins.

10. An electronic device, characterized in that, Includes the electrochemical device as described in any one of claims 1 to 9.

Images