An electrochemical device and an electronic device

Abstract

The application provides an electrochemical device and an electronic device, wherein the electrochemical device comprises at least two electrode assemblies and a packaging shell, the electrode assemblies are arranged in respective independent cavities in the packaging shell respectively; each electrode assembly comprises two tabs with opposite polarities, at least one tab of one electrode assembly is connected with one of the two tabs of another electrode assembly, and the normal projection of the two connected tabs along the sealing thickness direction Z has a tab overlapping area; as observed along the sealing thickness direction Z at the sealing outer edge of the packaging shell, along the sealing length direction X, the proportion of the overlapping width of the two connected tabs to the width of any tab is 40% < a ≤ 100%; the two connected tabs are respectively provided with tab adhesives, and the ratio of the tab adhesive shoulder width D2 to the tab width W1 along the sealing length direction X is D2 / W1 ≥ 1 / 60. The electrochemical device provided by the application not only realizes high-voltage output, but also improves the packaging reliability of the tab area at high-voltage output.

Description

[0001] This invention is a divisional application of application number 202010937408.7, filed on September 8, 2020, entitled "An Electrochemical Device and an Electronic Device". Technical Field

[0002] This application relates to the field of electrochemistry, and in particular to an electrochemical device and an electronic device using the electrochemical device. Background Technology

[0003] Lithium-ion batteries possess numerous advantages, including high volumetric and gravimetric energy density, long cycle life, low self-discharge rate, small size, and light weight, making them widely used in consumer electronics. With the rapid development of electric vehicles and mobile electronic devices in recent years, the demands for battery energy density, safety, and cycle performance are increasing, leading to anticipation for new lithium-ion batteries with comprehensively improved performance. Summary of the Invention

[0004] The purpose of this application is to provide an electrochemical device and an electronic device that achieves high voltage output and improves the welding reliability of the series and parallel tabs and the packaging reliability of the tab area.

[0005] The first aspect of this application provides an electrochemical device comprising at least two electrode assemblies and a packaging shell, wherein the electrode assemblies are respectively disposed in their respective independent cavities within the packaging shell;

[0006] Each electrode assembly includes two tabs of opposite polarity, at least one tab of one electrode assembly is connected to one of the two tabs of the other electrode assembly, and the two connected tabs have an overlap region when projected onto the orthographic projection along the seal thickness direction Z.

[0007] The overlap width O1 of the two connected tabs is 40% < α ≤ 100% of the width W1 of any tab.

[0008] Wherein, the overlap width O1 is the overlap width of the two connected tabs at the outer edge of the packaging shell seal, viewed along the seal thickness direction Z, along the seal length direction X;

[0009] The tab width W1 is the width of any one of the two connected tabs, viewed along the seal thickness direction Z at the outer edge of the packaging shell seal and along the seal length direction X.

[0010] In some embodiments of the first aspect of this application, each of the two connected tabs is provided with tab adhesive. At the outer edge of the packaging shell seal, along the seal length direction X, the width of the tab adhesive provided on the tab extends beyond both sides of the tab, and the ratio of the tab adhesive shoulder width D2 to the tab width W1 is D2 / W1≥1 / 60.

[0011] Wherein, the tab shoulder width D2 is the distance along the X direction that one side of the tab extends beyond the edge of the tab on the same side at the outer edge of the packaging shell seal.

[0012] In some embodiments of the first aspect of this application, the tab adhesive on the two connected tabs has an overlapping area when projected along the sealing thickness direction Z, and the overlap width O2 of the tab adhesive accounts for 40% < β ≤ 100% of the width W2 of any tab adhesive.

[0013] Wherein, the overlap width O2 of the tab adhesive is the overlap width of the tab adhesive at the outer edge of the packaging shell seal, along the seal length direction X, when viewed along the seal thickness direction Z.

[0014] The tab width W2 is the width of any tab along the sealing length direction X at the outer edge of the packaging shell seal, when viewed along the sealing thickness direction Z.

[0015] In some embodiments of the first aspect of this application, at the outer edge of the packaging shell seal, the distance between the two connected tabs is D5; the two connected tabs have a connecting area, and the length of the tab between the connecting area and the outer edge of the packaging shell seal is D6; the relationship between D5 and D6 satisfies: 0 <D5 / D6≤1.7。

[0016] In some embodiments of the first aspect of this application, 3mm ≤ D6 ≤ 30mm.

[0017] In some embodiments of the first aspect of this application, 0.1mm < D5 ≤ (H1 + H2) / 2 + 5mm, where H1 and H2 are the thicknesses of two adjacent electrode assemblies, and H1 and H2 may be the same or different.

[0018] In some embodiments of the first aspect of this application, the area S1 of the connecting region is 1 mm. 2 Up to 200mm 2 .

[0019] In some embodiments of the first aspect of this application, along the direction away from the electrode assembly, the distance by which the tab adhesive extends beyond the upper edge of the packaging shell along the sealing width direction Y is 0.2mm≤D1≤5mm, the thickness of the tab adhesive is 0.1mm≤D3≤3mm, and the thickness of the tab is 0.2mm≤D4≤5mm.

[0020] In some embodiments of the first aspect of this application, 50% ≤ α ≤ 100%.

[0021] In some embodiments of the first aspect of this application, the two connected tabs are two tabs with opposite polarities.

[0022] In some embodiments of the first aspect of this application, the electrode assembly has tabs extending from the packaging shell in different directions.

[0023] In some embodiments of the first aspect of this application, the electrochemical device further includes a partition located between the electrode assemblies, the partition having a thickness of 2 μm to 100 μm.

[0024] In some embodiments of the first aspect of this application, the structure of the electrode assembly includes at least one of a wound structure and a stacked structure.

[0025] In some embodiments of the first aspect of this application, the packaging shell includes at least one of aluminum-plastic film, aluminum shell, steel shell, and plastic shell.

[0026] A second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application.

[0027] The electrochemical device provided in this application achieves high-voltage output through multiple electrode assemblies connected in series internally, while simultaneously reducing overall heat generation and temperature rise. By placing different electrode assemblies in independent chambers, the device remains in a liquid electrolyte environment, preventing internal short circuits and electrolyte decomposition under high pressure, thus improving safety. Effective connection between the tabs of adjacent electrode assemblies enhances connection reliability, ensuring efficient power output and overcurrent capacity of the high-voltage electrochemical device. This reduces heat generation from the tabs, minimizing energy consumption and preventing softening or melting of the tab adhesive due to overheating, thereby improving the packaging reliability. Furthermore, the packaging reliability of the high-output-voltage electrochemical device is further improved by extending the tabs out of the packaging shell and by designing and controlling the relative positions and consistency of the tabs. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application.

[0029] Figure 1 This is a schematic diagram of the electrochemical device structure in one embodiment of this application;

[0030] Figure 2 This is a schematic diagram of the electrochemical device structure in another embodiment of this application;

[0031] Figure 3 This is a schematic diagram of the electrochemical device structure in another embodiment of this application;

[0032] Figure 4 for Figure 2 A partial structural diagram of the left view;

[0033] Figure 5 for Figure 2 Another partial structural diagram in the left view;

[0034] Figure 6 for Figure 2 Another partial structural diagram in the left view. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments.

[0036] The electrochemical device described in this application can be any electrochemical device well known to those skilled in the art, such as lithium-ion batteries, sodium-ion batteries, magnesium-ion batteries, supercapacitors, etc. The following description uses a lithium-ion battery as an example. Those skilled in the art should understand that the following description is merely illustrative and does not limit the scope of protection of this application.

[0037] This application provides an electrochemical device comprising at least two electrode assemblies and a packaging shell, wherein the electrode assemblies are respectively disposed in their respective independent cavities within the packaging shell;

[0038] Each electrode assembly includes two tabs of opposite polarity, at least one tab of one electrode assembly is connected to one of the two tabs of the other electrode assembly, and the two connected tabs have an overlap region when projected onto the orthographic projection along the seal thickness direction Z.

[0039] The overlap width O1 of the two connected tabs is 40% < α ≤ 100% of the width W1 of any tab.

[0040] Wherein, the overlap width O1 is the overlap width of the two connected tabs at the outer edge of the packaging shell seal, viewed along the seal thickness direction Z, along the seal length direction X;

[0041] The tab width W1 is the width of any one of the two connected tabs, viewed along the seal thickness direction Z at the outer edge of the packaging shell seal and along the seal length direction X.

[0042] Figure 1 This illustration shows one embodiment of the present application, in which a three-dimensional coordinate system is established with the seal length direction, seal width direction, and seal thickness direction, where the X direction represents the seal length direction, the Y direction represents the seal width direction, and the Z direction represents the seal thickness direction. The electrochemical device includes an electrode assembly and a packaging shell 1. The electrode assemblies are disposed in their respective independent cavities within the packaging shell 1. For example, the first electrode assembly and the second electrode assembly are disposed in their respective independent cavities within the packaging shell 1 and are separated by a partition 8. Each electrode assembly includes two tabs 2 with opposite polarities. At least one tab 2 of one electrode assembly is connected to one of the two tabs of the other electrode assembly, and the two connected tabs 2 have an overlapping area when projected onto the seal thickness direction Z.

[0043] refer to Figure 2 The packaging shell 1 has a sealing area 5. A dashed line parallel to the X direction in the sealing area 5 indicates the outer edge of the seal, which is the upper boundary of the sealing area 5. Each electrode assembly has two tabs with opposite polarities. One tab 2 is connected to one of the two tabs of the other electrode assembly, and the orthographic projection along the sealing thickness direction Z shows an overlapping area 4 of the tabs. Viewed along the sealing thickness direction Z, at the outer edge of the sealing shell 1, along the sealing length direction X, the overlap width of the two connected tabs is O1. Viewed along the sealing thickness direction Z, at the outer edge of the sealing shell 1, along the sealing length direction X, the width of any one of the two connected tabs is W1. The proportion of O1 to W1 is 40% < α ≤ 100%.

[0044] In the electrochemical device of this application, each electrode assembly may include a positive electrode tab and a negative electrode tab. Adjacent electrode assemblies can be connected in series via the connection of the positive and negative electrode tabs. The overlap region of the tabs affects the transfer of electrical energy between adjacent electrode assemblies. Without being limited to any particular theory, a small overlap width can reduce the encapsulation reliability of the two connected tabs, thus affecting the encapsulation reliability of the two adjacent electrode assemblies. In the electrochemical device of this application, the ratio α of the overlap region O1 of the two connected tabs to the width W1 of any one tab is: 40% < α ≤ 100%, preferably 50% ≤ α ≤ 100%. This not only ensures the effective electrical energy output and overcurrent capability of the high-voltage electrochemical device but also guarantees the encapsulation reliability between adjacent electrode assemblies.

[0045] In some embodiments of this application, each of the two connected tabs is provided with tab adhesive. At the outer edge of the packaging shell seal, along the seal length direction X, the width of the tab adhesive on the tab extends beyond both sides of the tab, and the ratio of the tab adhesive shoulder width D2 to the tab width W1 is D2 / W1 ≥ 1 / 60. Figure 2 As shown in this application, the tab adhesive shoulder width D2 is the distance along the X direction extending beyond the edge of the tab on one side at the outer edge of the packaging shell seal. The tab adhesive shoulder widths on both sides may be equal or unequal. A D2 / W1 ratio within the above range can ensure the packaging reliability of the electrochemical device.

[0046] In some embodiments of this application, the width W1 of the electrode tab is: 2mm ≤ W1 ≤ 60mm. The width W1 of the electrode tab directly affects the size of the overlapping area of ​​the electrode tabs. When the width W1 of the electrode tab is within the above range, the connection reliability between adjacent electrode components can be effectively improved.

[0047] In some embodiments of this application, the tab adhesive on the two connected tabs has an overlapping area when projected along the sealing thickness direction Z. The ratio β of the overlap width O2 of the tab adhesive to the width W2 of any tab adhesive is: 40% < β ≤ 100%.

[0048] Wherein, the overlap width O2 of the tab adhesive is the overlap width of the tab adhesive at the outer edge of the packaging shell seal, along the seal length direction X, when viewed along the seal thickness direction Z.

[0049] The tab width W2 is the width of any tab along the sealing length direction X at the outer edge of the packaging shell seal, when viewed along the sealing thickness direction Z.

[0050] Figure 3 This application illustrates one embodiment where the tab adhesive 3 on the two connected tabs has a tab adhesive overlap region 6. Along the sealing length direction X, at the outer edge of the sealing of the packaging shell 1, the width O2 of the tab adhesive overlap region 6 is β, which is the ratio of the width W2 of any tab adhesive at the outer edge of the sealing of the packaging shell 1 to the width O2 of either tab adhesive at the outer edge of the sealing of the packaging shell 1, in the following ratio: 40% < β ≤ 100%. The tab adhesive overlap region 6 also affects the encapsulation reliability of the two connected tabs. When the width of the tab adhesive overlap region 6 is small, when the electrochemical device is subjected to external force and bends, strain is easily generated on the tabs at the junction of the two connected tabs, resulting in stress at the junction, which can easily lead to cracks and reduce the encapsulation reliability of the two connected tabs. When the ratio of the width of the tab adhesive overlap region 6 to the width of any tab adhesive is within the above-mentioned range, the encapsulation reliability between adjacent electrode components can be further improved.

[0051] In some embodiments of this application, reference is made to Figure 3 and Figure 5At the outer edge of the sealed packaging shell 1, the distance between the two connected tabs is D5; the two connected tabs have a connecting area 7, and the length of the tab between the connecting area 7 and the outer edge of the sealed packaging shell 1 is D6; the relationship between D5 and D6 satisfies: 0 < D5 / D6 ≤ 1.7, preferably 3 × 10 -3 <D5 / D6≤1.5.

[0052] In some embodiments of this application, 0.1mm < D5 ≤ (H1 + H2) / 2 + 5mm. Here, D5 refers to the distance between the two connected tabs at the outer edge of the packaging seal, and H1 and H2 are the thicknesses of the two adjacent electrode assemblies, which can be the same or different. When the distance between the two tabs is too large, it not only increases the difficulty of connecting the two tabs but also reduces the reliability of the connection. Therefore, by designing and controlling the relative position of the two connected tabs, the connection reliability between adjacent electrode assemblies can be improved. In this application, the distance between the two connected tabs refers to the distance along the Z-direction of the seal thickness at the outer edge of the packaging seal.

[0053] Figure 3 This application illustrates one embodiment where two connected tabs have a connection region 7. D6 refers to the tab length between the lower edge of the connection region 7 and the outer edge of the sealing of the packaging shell 1. When the ratio of D5 / D6 is small, D6 is large, meaning the connection region 7 is far from the electrode assembly and the distance between it and the electrode assembly is large. When the electrochemical device is subjected to external forces, the tabs 2 of sufficient length can alleviate stress, reducing stress on the end seal and connection, thereby improving the sealing reliability and connection reliability between adjacent electrode assemblies. When the ratio of D5 / D6 is large, D5 is large, meaning the distance between the two connected tabs is too large. When the electrochemical device is subjected to external forces, tearing of the tabs 2 can cause some damage to the sealing region, thus affecting the packaging reliability and the stability of the connection region 7. In the electrochemical device provided in this application, the ratio of D5 / D6 meets the above-mentioned range, which not only improves the connection reliability between adjacent electrode assemblies but also improves the packaging reliability of the electrochemical device.

[0054] In some embodiments of this application, 3mm ≤ D6 ≤ 30mm. When D6 is small, the tab adhesive on the tabs is easily damaged when connecting the two tabs, affecting the packaging reliability of the electrochemical device and making the connection operation difficult. Secondly, because the connection area is close to the packaging shell, it is prone to cracking under external force, resulting in a decrease in the connection reliability of the two adjacent electrode components. Thirdly, the close distance between the connection area and the packaging shell, due to the certain thickness of the electrode components, affects the connection strength of the connection area, thus reducing the connection reliability of the two adjacent electrode components. Furthermore, when the connection strength of the connection area is low and the connection is not tight enough, the resistance of the connection area will increase during the use of the electrode components, thereby increasing the temperature rise of the tabs during charging, causing the tab adhesive to soften or melt, reducing the packaging reliability of the electrochemical device. When D6 is large, the connection area is more easily damaged when the electrochemical device is subjected to external forces, reducing the connection reliability between the two adjacent electrode components. In addition, when D6 is large, the connection area will increase the volume of the electrochemical device. Since the connection area is a non-active material area and does not provide energy, it will lead to a decrease in the volumetric energy density of the electrochemical device. Therefore, when D6 is within the above range, the resulting electrochemical device exhibits excellent packaging reliability and operational reliability.

[0055] In some embodiments of this application, the area S1 of the connecting region is 1 mm. 2 Up to 200mm 2 The area S1 of the connection region is less than or equal to the area of ​​the overlapping tab region. That is, the overlapping tab region can be fully connected or partially connected, as long as the connection reliability of the two tabs is guaranteed, achieving the purpose of this application. When the area of ​​the connection region is too small, the connection reliability between the two tabs decreases, and the current carrying capacity of the connection region also decreases. Within the area range of the connection region provided in this application, the connection reliability between adjacent electrode components and the normal operation of the electrochemical device can be effectively guaranteed. As the area S1 of the connection region increases, the current carrying capacity increases accordingly, ensuring the effective power output and overcurrent capability of the high-voltage electrochemical device. Furthermore, increasing the area S1 of the connection region can also reduce the heat generated by the tabs and the resulting power consumption, thereby preventing the tab adhesive from softening or melting due to heat generation, and improving the encapsulation reliability of the electrochemical device.

[0056] Furthermore, when the area S1 of the connection region remains unchanged, the width of the overlapping area of ​​the electrode tabs decreases, the width of the connection region along the sealing length direction X becomes smaller, the connection strength of the connection region decreases, and the connection reliability of adjacent electrode components also decreases accordingly.

[0057] In some embodiments of this application, along the direction away from the electrode assembly, the distance by which the tab adhesive 3 extends beyond the upper edge of the packaging shell along the sealing width direction Y is 0.2mm ≤ D1 ≤ 5mm, and the shoulder width of the tab adhesive 3 is 1mm ≤ D2 ≤ 8mm. Figure 4 As shown, the thickness of the tab adhesive 3 is 0.1mm ≤ D3 ≤ 3mm, and the thickness of the tab 2 is 0.2mm ≤ D4 ≤ 5mm. When D1 to D4 are within the above ranges, the resulting electrochemical device has good packaging reliability and operational reliability, as well as good connection reliability between adjacent electrode components.

[0058] In this application, the tab adhesive provided on the tab can be combined with the packaging shell. The combination can be a sealing connection between the tab and the packaging shell through the tab adhesive.

[0059] In some embodiments of this application, the two tabs of each electrode assembly can extend out of the packaging shell in the same or different directions. The two tabs can extend out along one side of the packaging shell, or one tab can extend out from each of any two sides of the packaging shell.

[0060] like Figure 5 As shown, in some embodiments of this application, the electrochemical device may further include a partition 8 located between the electrode assemblies, with cavities located on both sides of the partition 8, and each electrode assembly may be disposed in its own independent cavity. The thickness of the partition is 2 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm. In the electrochemical device, the partition not only has ion-insulating properties but should also possess a certain mechanical strength. Therefore, if the partition is too thin, its mechanical strength is poor, making it prone to breakage and affecting the performance and even safety of the electrochemical device. If the partition is too thick, it will increase the weight of the electrochemical device, thus limiting its performance. Figure 6 As shown, in some other embodiments of this application, in order to achieve an effective bond between the tab adhesive 3 and the separator 8, the separator 8 also includes a bonding material 9.

[0061] In some embodiments of this application, the structure of the electrode assembly includes at least one of a wound structure and a stacked structure.

[0062] In some embodiments of this application, the cavity is a sealed cavity. The sealed cavity is formed by a partition and a packaging shell that are sealed together, with independent cavities formed on both sides of the partition. The electrode assemblies and electrolytes on both sides of the partition are completely separated, which not only ensures the normal operation of the electrode assemblies on both sides, but also improves the safety and environmental stability of the electrochemical device due to the good sealing performance.

[0063] In this application, the connection method of the two electrodes is not particularly limited, as long as it achieves the purpose of this application. For example, welding connection. The welding connection method is not particularly limited, as long as it achieves the purpose of this application. For example, laser welding, ultrasonic welding, or resistance welding, etc.

[0064] In this application, when the two electrodes are connected by welding, the area of ​​the connection region is the area surrounded by the outermost weld point, and the weld point is distributed in the connection region.

[0065] The electrode assembly mentioned in this application may be an electrode assembly comprising a positive electrode, a negative electrode, and a separator, and the above-mentioned electrode assembly is used as an example for illustration. Those skilled in the art should understand that the following description is merely illustrative and does not limit the scope of protection of this application.

[0066] In this application, there are no particular limitations on the thickness of the electrode assembly, as long as it achieves the purpose of this application. For example, the thickness of the electrode assembly is 3 mm.

[0067] In some embodiments of this application, the positive electrode sheet is not particularly limited, as long as it achieves the purpose of this application. For example, the positive electrode sheet typically comprises a positive current collector and a positive active material. In this application, the positive current collector is not particularly limited and can be any positive current collector known in the art, such as copper foil, aluminum foil, aluminum alloy foil, and composite current collectors. The positive active material is not particularly limited and can be any prior art positive active material; for example, the positive active material includes at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, or lithium manganese iron phosphate. In this application, the thickness of the positive current collector and the positive active material is not particularly limited, as long as it achieves the purpose of this application. For example, the thickness of the positive current collector is 8 μm to 12 μm, and the thickness of the positive active material is 30 μm to 120 μm.

[0068] In some preferred embodiments of this application, the positive electrode sheet may further include a conductive layer located between the positive current collector and the positive active material layer. The composition of the conductive layer is not particularly limited and can be any conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder.

[0069] In some embodiments of this application, the negative electrode sheet is not particularly limited, as long as it achieves the purpose of this application. For example, the negative electrode sheet typically comprises a negative current collector and a negative active material. In this application, the negative current collector is not particularly limited, and any negative current collector known in the art can be used, such as copper foil, aluminum foil, aluminum alloy foil, and composite current collectors. The negative active material is not particularly limited, and any negative active material known in the art can be used. For example, it may include at least one of artificial graphite, natural graphite, mesophase carbon microspheres, silicon, silicon-carbon, silicon oxides, soft carbon, hard carbon, lithium titanate, or niobium titanate. In this application, the thickness of the negative current collector and the negative active material is not particularly limited, as long as it achieves the purpose of this application. For example, the thickness of the negative current collector is 6 μm to 10 μm, and the thickness of the negative active material is 30 μm to 120 μm.

[0070] In some preferred embodiments of this application, the negative electrode sheet may further include a conductive layer located between the negative electrode current collector and the negative electrode active material layer. The composition of the conductive layer is not particularly limited and can be any conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder.

[0071] The conductive agent described above is not particularly limited, and any conductive agent known in the art can be used, as long as it achieves the purpose of this application. For example, the conductive agent may include at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, or graphene. The adhesive described above is not particularly limited, and any adhesive known in the art can be used, as long as it achieves the purpose of this application. For example, the adhesive may include at least one of styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), or sodium carboxymethyl cellulose (CMC-Na).

[0072] In some embodiments of this application, the diaphragm is not particularly limited, as long as it can achieve the purpose of this application. For example, the thickness of the diaphragm can be from 5 μm to 15 μm, and the diaphragm can include polymers or inorganic materials formed from materials that are stable to the electrolyte of this application. In this application, the diaphragm can also be referred to as a separating membrane.

[0073] For example, the diaphragm may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer may include at least one selected from polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is disposed on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic materials.

[0074] For example, the inorganic layer comprises inorganic particles and a binder. The inorganic particles are not particularly limited and may be selected from at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is not particularly limited and may be selected from one or a combination of several of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer contains a polymer, the polymer material of which includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0075] The term "tab" as used in this application refers to a metal conductor drawn from the positive or negative electrode plate, used for series or parallel connection to other parts of the electrochemical device. The positive electrode tab is drawn from the positive electrode plate, and the negative electrode tab is drawn from the negative electrode plate.

[0076] This application does not impose any particular limitation on the material of the tab adhesive; any tab adhesive known in the art can be used, as long as it achieves the purpose of this application. For example, the tab adhesive material may include at least one of polypropylene (PP), polyethylene terephthalate (PET), or polyethylene naphthalate (PEN), and may also include composite materials containing the above polymers, such as PP / PET / PP composites, PP / PEN / PP composites, PP / nonwoven fabric / PP composites, or PP / high-temperature barrier layer / PP composites. The width of the tab adhesive is not particularly limited, as long as it achieves the purpose of this application. For example, the width of the tab adhesive can be 4 mm to 76 mm. The nonwoven fabric is not particularly limited, as long as it achieves the purpose of this application; for example, polypropylene nonwoven fabric, polyethylene nonwoven fabric, etc. The high-temperature barrier layer is not particularly limited, as long as it achieves the purpose of this application; for example, an aramid layer, etc.

[0077] This application does not impose any particular limitation on the separator; any separator known in the art can be used, as long as it achieves the purpose of this application. Typically, the separator needs to be ionicly insulating to prevent high-voltage electrolyte decomposition and short circuits within the electrode assembly. For example, the separator material includes at least one of polymeric materials, metallic materials, carbon materials, or composite materials thereof.

[0078] There are no particular limitations on the polymeric materials used; any material known to those skilled in the art can be used, as long as it can achieve the purpose of this application. For example, the polymeric materials may include at least one of the following: polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyetheretherketone, polyimide, polyamide, polyethylene glycol, polyamide-imide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polyethylene naphthalate, polypropylene carbonate, poly(vinylidene fluoride-hexafluoropropylene), poly(vinylidene fluoride-co-trifluorochloroethylene), silicone, vinylon, polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-vinyl alcohol copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene ether, polyester, polysulfone, amorphous α-olefin copolymer, and their derivatives.

[0079] The metallic material is not particularly limited, and any material known to those skilled in the art can be used, as long as it can achieve the purpose of this application. For example, it may include 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, stainless steel, and combinations or alloys thereof. Preferably, a metallic material with good oxidation and reduction resistance in a lithium-ion battery environment can be selected.

[0080] The carbon material includes at least one of carbon felt, carbon film, carbon black, acetylene black, fullerene, conductive graphite film, or graphene film. In some embodiments of this application, the ion-insulating layer is preferably made of a polymer material. Because polymer materials have a low density, the weight of inactive substances can be reduced, thereby increasing the mass energy density of the electrode assembly. Furthermore, using a polymer material for the ion-insulating layer reduces the probability of debris generation under mechanical abuse conditions (piercing, impact, compression, etc.) and provides better protection for mechanically damaged surfaces. Therefore, it can improve the safety boundary under such mechanical abuse conditions and increase the pass rate of safety tests.

[0081] In some embodiments of this application, the partition further includes an encapsulation layer, which may be disposed on both sides of the ion-insulating layer. The encapsulation layer is disposed at the periphery of the surface of the ion-insulating layer or on its entire surface, and is used to seal the ion-insulating layer to the packaging shell.

[0082] In this application, the material of the encapsulation layer is not particularly limited, as long as it can achieve the purpose of this application, materials known to those skilled in the art can be used. For example, the encapsulation layer material includes at least one of polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-vinyl alcohol copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyamide, polyester, amorphous α-olefin copolymer and its derivatives.

[0083] Of course, the encapsulation layer in this application also has ion-insulating function when it covers the entire surface of the ion-insulating layer. In this application, for convenience, the separator is divided into an ion-insulating layer and an encapsulation layer, but this does not mean that the encapsulation layer has no ion-insulating properties. For example, when the encapsulation layer completely covers both sides of the ion-insulating layer, the ion-insulating layer and the encapsulation layer together provide ion insulation.

[0084] In this application, there are no particular limitations on the bonding material between the separator and the tab adhesive. As long as the purpose of this application can be achieved, any material known to those skilled in the art can be used. For example, the bonding material includes at least one of polypropylene, polyester, p-hydroxybenzaldehyde, polyamide, polyphenylene ether, polyurethane, etc.

[0085] The electrolyte described in this application may comprise lithium salts and non-aqueous solvents. In this application, the lithium salt is not particularly limited; any lithium salt known in the art can be used, as long as it achieves the purpose of this application. For example, the lithium salt may include at least one selected from LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, or LiPO2F2. For example, LiPF6 may be selected as the lithium salt. In this application, the non-aqueous solvent is not particularly limited; it may be used as long as it achieves the purpose of this application. For example, the non-aqueous solvent may include at least one selected from carbonate compounds, carboxylic acid ester compounds, ether compounds, nitrile compounds, and other organic solvents.

[0086] For example, carbonate compounds may include at least one of diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, and trifluoromethylethylene carbonate.

[0087] This application does not impose any particular limitation on the packaging shell, as long as it achieves the purpose of this application. The packaging shell includes at least one of aluminum-plastic film, aluminum shell, steel shell, and plastic shell. For example, the packaging shell may include an inner layer and an outer layer, with the inner layer sealed to the partition. Therefore, the material of the inner layer may include a polymer material to achieve a good sealing effect; simultaneously, the combination of the inner and outer layers effectively protects the internal structure of the electrochemical device. In this application, the material of the inner layer is not particularly limited, as long as it achieves the purpose of this application. For example, the material of the inner layer includes at least one of polypropylene, polyester, p-hydroxybenzaldehyde, polyamide, polyphenylene ether, and polyurethane. In this application, the material of the outer layer is not particularly limited, as long as it achieves the purpose of this application. For example, the material of the outer layer includes at least one of aluminum foil, an alumina layer, and a silicon nitride layer.

[0088] This application does not impose any particular limitation on the thickness of the packaging shell, as long as it achieves the purpose of this application. For example, the thickness of the packaging shell is 60 μm to 500 μm, preferably 60 μm to 300 μm, and more preferably 60 μm to 200 μm. The packaging shell of the above thickness can effectively protect the internal structure of the electrochemical device.

[0089] In this application, the sealing thickness T (in mm) and sealing width W (in mm) of the separator and the sealing area of ​​the packaging shell satisfy 0.01 ≤ T / W ≤ 0.05. A T / W ratio within this range ensures good battery sealing and improves battery life. In this application, the sealing thickness and sealing width are not particularly limited, as long as they achieve the purpose of this application; for example, the sealing width is preferably 1 mm to 7 mm.

[0090] This application does not impose any particular limitation on the sealing connection method between the partition and the packaging shell, as long as it achieves the purpose of this application. For example, the sealing method includes one of hot pressing, adhesive sealing, and welding. In this application, the hot pressing conditions are not particularly limited, as long as they achieve the purpose of this application. For example, for polypropylene inner layer materials, the hot pressing temperature is 150°C to 220°C, and the hot pressing pressure is 0.1 MPa to 0.6 MPa.

[0091] In some embodiments of this application, the electrode assembly has a wound structure, comprising a single tab or multiple tabs. A single tab is formed by leading one positive tab and one negative tab from the positive electrode and the negative electrode, respectively. Multiple tabs can be formed by leading one positive tab and one negative tab from each turn of the positive and negative electrode, or by leading one positive tab and one negative tab from two or more turns of the positive and negative electrode. Ultimately, a wound electrode assembly comprises multiple sets of positive and negative tabs, which are then connected by soldering adapter leads.

[0092] In some embodiments of this application, the electrode assembly has a stacked structure and includes multiple tabs. One positive tab and one negative tab can be led out from each layer of positive and negative electrode sheets, and finally, a stacked electrode assembly includes multiple sets of positive and negative tabs, and then the tab leads are soldered to the adapter.

[0093] In this application, the distances D1-D6, W1, W1, O1, O2, etc. mentioned above are all measured using a micrometer. Figure 1 The measurements are taken in the X, Y, or Z directions as shown. The average value of 10 measurements is taken as the final result.

[0094] This application also provides an electronic device that includes the electrochemical device provided in this application. The electronic device in this application is not particularly limited and can be any electronic device known in the prior art. For example, display devices include, but are 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.

[0095] There are no particular limitations on the method for preparing the electrochemical device of this application; any method known in the art can be used. For example, in one embodiment, this application can be prepared using the following method:

[0096] (1) Preparation of the negative electrode sheet: The negative electrode active material and solvent are mixed into a slurry and stirred evenly. The slurry is uniformly coated onto the negative electrode sheet and dried to obtain a single-sided coated negative electrode sheet. The above steps are repeated on the other surface of the negative electrode sheet to obtain a double-sided coated negative electrode sheet. Then, the negative electrode sheet is cut for use. The coating thickness of the negative electrode active material on one surface is 70 μm.

[0097] (2) Preparation of the positive electrode sheet: The positive active material and solvent are mixed into a slurry and stirred evenly. The slurry is uniformly coated onto the positive electrode sheet and dried to obtain a single-sided coated positive electrode sheet. The above steps are repeated on the other surface of the positive electrode sheet to obtain a double-sided coated positive electrode sheet. Then, the positive electrode sheet is cut for use. The coating thickness of the positive active material on one surface is 65 μm.

[0098] (3) Preparation of electrolyte: Lithium salt and non-aqueous solvent are mixed and stirred evenly to obtain an electrolyte containing 30% lithium salt.

[0099] (4) Preparation of electrode assembly: The negative electrode sheet, the separator, and the positive electrode sheet are stacked and the layers are fixed together for later use. Each electrode assembly contains a positive electrode tab and a negative electrode tab. Repeating the above steps can yield multiple electrode assemblies. The structure of the electrode assembly can be a wound structure or a stacked structure.

[0100] (5) Partition: Any partition known in the art may be used.

[0101] (6) Electrode assembly: Place the packaging shell in the assembly fixture, then set the electrode assembly and the partition plate at intervals, with the packaging shell and the electrode assembly adjacent to each other, and finally seal to obtain the assembled electrode assembly.

[0102] (7) Liquid injection and encapsulation: Electrolyte is injected separately into the two cavities of the assembled electrode assembly, and all the tabs of the electrode assembly are led out of the aluminum-plastic film for subsequent processing.

[0103] (8) Series connection: The positive electrode tab of one electrode assembly and the negative electrode tab of another electrode assembly are welded together by laser welding to achieve series connection, and the battery assembly is completed.

[0104] The electrochemical device provided in this application may include two electrode assemblies, or three or more electrode assemblies. The preparation methods for electrochemical devices containing two or more electrode assemblies can refer to the preparation methods described above. Electrochemical devices containing three or more electrode assemblies are also within the scope of protection defined in the claims of this application.

[0105] The terminology used in this application is generally the same as that commonly used by those skilled in the art. If there is any discrepancy with commonly used terminology, the terminology used in this application shall prevail. In this application, unless otherwise specified, "%" and "parts" are based on weight.

[0106] Test method:

[0107] Series tab area package strength test:

[0108] The tab sealing area of ​​the electrode assembly was removed and used as sample 1;

[0109] Sample 1 was cut into a strip with a width L of 8mm to ensure that the entire sealing area was preserved intact, and the packaging shells on both sides of the sealing area were also intact, thus obtaining Sample 2.

[0110] Using a high-speed rail tensile testing machine, the packaging shells on both sides are torn open at a 180° angle, causing the two layers of packaging shells within the sealed area to separate from each other;

[0111] Record the stable tensile force F when the two packaging shells separate, and calculate the packaging strength σ = F / L.

[0112] Discharge capacity / initial discharge capacity test after 50 charge-discharge cycles:

[0113] In Comparative Example 1, the test temperature was 25±3℃. The lithium-ion battery was charged to 4.2V with a constant current of 0.5C, and then charged to 0.05C with a constant voltage of 4.2V. After standing for 10 minutes, it was discharged to 3.0V with a current of 0.5C. The initial discharge capacity was recorded as Q1D. This cycle was repeated 50 times, and the discharge capacity at this time was recorded as Q50D. The discharge capacity after 50 charge-discharge cycles / initial discharge capacity retention rate: η(%) = Q50D / Q1D × 100%;

[0114] In tests of Comparative Examples 2-4 and Examples 1-22, the test temperature was 25±3℃. The lithium-ion battery was charged to 8.4V with a constant current of 0.5C, then charged to 0.05C with a constant voltage of 8.4V, left to stand for 10 minutes, and then discharged to 6.0V with a current of 0.5C. The initial discharge capacity was recorded as Q1D. This cycle was repeated 50 times, and the discharge capacity at this time was recorded as Q50D. The discharge capacity / initial discharge capacity retention rate after 50 charge-discharge cycles is: η(%) = Q50D / Q1D × 100%.

[0115] Bending stability test:

[0116] The two connected tabs were subjected to a 360° bending test, that is, the tabs were bent towards the XY plane of the electrochemical device with the separator and the top seal area of ​​the packaging shell as the axis (XY plane as shown). Figure 1(As shown) Bend the tab until it adheres to the XY plane; this is recorded as one bend. Then bend it 360° in the opposite direction until it adheres to the XY plane on the other side of the electrochemical device; this is recorded as a second bend. Repeat this process until cracks appear at the outer edge of the tab adhesive and the packaging shell; record the number of tab bends at this point.

[0117] Battery output voltage test:

[0118] At a test temperature of 25±3℃, the lithium-ion battery was charged to N×4.2V (where N is the number of series electrode components) at a constant current of 0.5C, and then charged to 0.05C at a constant voltage of N×4.2V. After standing for 1 hour, the open circuit voltage was measured, which is the output voltage of the battery.

[0119] Welding pull test of series tabs:

[0120] Remove the tab portion containing the tab connection area from the electrode assembly as a test sample. Ensure that the entire connection area is preserved intact, and that the tabs on both sides are also undamaged. Using a small tensile testing machine, tear the tabs on both sides at a 180° angle to separate the two tabs in the welding area; record the stable tensile force at which the two tabs separate as the welding tensile force.

[0121] Temperature rise test of 2C charging tabs:

[0122] At a test temperature of 25℃, the electrode was charged at a constant current of 0.5C to 4.45V, then charged at a constant voltage of 4.45V to 0.025C, and left to stand for 5 minutes. Then it was discharged at 0.5C to 3.0V and left to stand for 5 minutes. The tab temperature at this point was measured as T1 using a multi-channel temperature gauge. After charging at a constant current of 2C to 4.45V, the tab temperature was measured as T2 using a multi-channel temperature gauge. Therefore, the tab temperature rise during 2C charging is ΔT = T2 - T1.

[0123] Example 1

[0124] (1) Preparation of the negative electrode sheet: The negative electrode active materials, artificial graphite, conductive carbon black (Super P), and styrene-butadiene rubber (SBR), were mixed in a weight ratio of 96:1.5:2.5. Deionized water was added as a solvent to prepare a slurry with a solid content of 70 wt%, and the mixture was stirred evenly. The slurry was uniformly coated on one surface of a 10 μm thick copper foil for the negative electrode current collector and dried at 110 °C to obtain a negative electrode sheet with a single-sided coating of negative electrode active material layer with a coating thickness of 150 μm. The above steps were repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a double-sided coating of negative electrode active material layer. Then, the negative electrode sheet was cut into 41 mm × 61 mm dimensions for later use.

[0125] (2) Preparation of the positive electrode sheet: Lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97.5:1.0:1.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 75 wt%, and the mixture was stirred evenly. The slurry was uniformly coated on one surface of a 12 μm thick aluminum foil for the positive electrode current collector and dried at 90 °C to obtain a positive electrode sheet with a positive electrode active material layer thickness of 100 μm. The above steps were repeated on the other surface of the aluminum foil for the positive electrode current collector to obtain a positive electrode sheet with a positive electrode active material layer coated on both sides. Then, the positive electrode sheet was cut into 38 mm × 58 mm dimensions for later use.

[0126] (3) Preparation of electrolyte: In a dry argon atmosphere, the organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC = 30:50:20. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0127] (4) Preparation of electrode assembly A and electrode assembly B: The separator, the double-sided coated negative electrode sheet, the separator, and the double-sided coated positive electrode sheet are stacked in sequence to form a stack. Then, the four corners of the entire stack structure are fixed for later use. Each electrode assembly includes one positive electrode tab and one negative electrode tab. The positive electrode tab is made of aluminum (Al) and the negative electrode tab is made of nickel (Ni). The two tabs are arranged side by side. The thickness D4 of the tab is 0.3 mm and the width W1 of the tab is 5 mm. The separator is a polyethylene (PE) film with a thickness of 15 μm.

[0128] (5) Separator preparation: Polypropylene (PP, melting point 140℃) encapsulation layer material was uniformly dispersed in N-methylpyrrolidone (NMP) dispersant to prepare a PP suspension; the PP suspension was coated on both sides of a 15μm thick polyimide (PI) film using a coating machine; then, the NMP dispersant was removed from the suspension by drying at 130℃, thus completing the preparation of the separator. The separator thickness was 15μm.

[0129] (6) Assembly of Electrode Assembly A: Place the punched aluminum-plastic film (150μm thick) in the assembly fixture with the punched surface facing upwards. Place the electrode assembly A in the punch with the diaphragm surface facing upwards. Apply an 11mm wide tab adhesive strip to the area corresponding to the tab of the electrode assembly A at the edge of the aluminum-plastic film. Then place the diaphragm on the electrode assembly A, aligning the edges, and apply external force to press it down to obtain the assembled semi-finished product. The distance D1 between the upper edge of the tab adhesive and the upper edge of the packaging shell is 1mm, the tab adhesive shoulder width D2 is 3mm, and the tab adhesive thickness D3 is 0.2mm.

[0130] (7) Assembly of Electrode Assembly B: Place the semi-finished assembly in the assembly fixture with the partition side facing upwards. Place the electrode assembly B with the diaphragm side facing downwards on the partition, aligning the edges. Apply external force to press it firmly. Then, cover the electrode assembly B with another punched aluminum-plastic film with the pitted side facing downwards. Set an 11mm wide tab adhesive at the edge of the aluminum-plastic film corresponding to the tab of the electrode assembly B. Heat seal the perimeter using a hot-pressing method to obtain the assembled electrode assembly. The distance D1 between the upper edge of the tab adhesive and the upper edge of the packaging shell is 1mm, the tab adhesive shoulder width D2 is 3mm, and the tab adhesive thickness D3 is 0.2mm.

[0131] (8) Electrolyte injection and encapsulation: Electrolyte is injected into each cavity of the assembled electrode assembly separately, and all tabs of electrode assemblies A and B are led out of the aluminum-plastic film. The width of the overlap area between the negative tab of electrode assembly A and the positive tab of electrode assembly B is 4.75 mm, and the width of the overlap area between the tab adhesive of the negative tab of electrode assembly A and the positive tab of electrode assembly B is 10.67 mm.

[0132] (9) Series connection: The negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B are welded together by laser welding to achieve a series connection, and the battery assembly is completed. The area S1 of the connection region is 20 mm². 2 The distance D5 between the two connected tabs is 3mm, and the distance D6 between the connecting area and the aluminum-plastic film is 5mm.

[0133] Example 2

[0134] The width of the overlapping area between the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B is 2.5 mm, and the width of the overlapping area between the tab adhesive of the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B is 5.61 mm. The rest is the same as in Example 1.

[0135] Example 3

[0136] Except for the distance D1 between the upper edge of the tab adhesive and the upper edge of the packaging shell, which is 5mm, the rest is the same as in Example 1.

[0137] Example 4

[0138] The tab width is 8mm, the tab shoulder width D2 is 1.5mm, and the rest is the same as in Example 1.

[0139] Example 5

[0140] Except for the thickness D3 of the tab adhesive, which is 3mm, the rest is the same as in Example 1.

[0141] Example 6

[0142] Except for the thickness D4 of the tab, which is 2mm, the rest is the same as in Example 1.

[0143] Example 7

[0144] Except for the width W1 of the tab, which is 10mm, the rest is the same as in Example 1.

[0145] Example 8

[0146] Except for the distance D5 between the two connected tabs, which is 6mm, the rest is the same as in Example 1.

[0147] Example 9

[0148] Except for the distance D6 between the connecting area and the aluminum-plastic film, which is 30mm, the rest is the same as in Example 1.

[0149] Example 10

[0150] Except for the partition thickness being 200 μm, it is the same as in Example 1.

[0151] Example 11

[0152] The width of the overlapping area between the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B is 3 mm, and the width of the overlapping area between the tab adhesive of the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B is 6.6 mm. The rest is the same as in Example 1.

[0153] Example 12

[0154] Except for the distance D5 between the two connected tabs, which is 1 mm, the rest is the same as in Example 1.

[0155] Example 13

[0156] Except for the tab shoulder width D2 being 1.5mm and the distance D6 between the connection area and the aluminum-plastic film being 3mm, the rest is the same as in Example 1.

[0157] Example 14

[0158] Except for the distance D5 between the two connected tabs being 6mm and the distance D6 between the connecting area and the aluminum-plastic film being 4mm, the rest is the same as in Example 1.

[0159] Example 15

[0160] In addition to the fact that the area S1 of the connecting region is 4mm 2 The electrode assembly has a rated capacity of 10A at 0.2C and a maximum discharge rate of 2C; otherwise, it is the same as in Example 3. The current carrying capacity per unit area of ​​the connection region is 5A / mm². 2 .

[0161] Example 16

[0162] In addition to the fact that the area S1 of the connecting region is 3mm 2 The maximum discharge rate is 3C, and the rest is the same as in Example 15.

[0163] Example 17

[0164] In addition to the fact that the area S1 of the connecting region is 10mm 2 The electrode assembly has a rated capacity of 50A at 0.2C, and the rest is the same as in Example 15.

[0165] Example 18

[0166] According to step (4) of Example 1, electrode assembly C is prepared; when encapsulating the electrode assembly, electrode assembly B is placed on the partition with the diaphragm side facing down, so that the edges are aligned, and after applying external force to press it, the partition is set on electrode assembly B, and then electrode assembly C is placed on the partition with the diaphragm side facing down, so that the edges are aligned, and after applying external force to press it; then another aluminum-plastic film with the dented side facing down is covered on electrode assembly C, and an electrode tab adhesive with a width of 11mm is set in the area corresponding to the electrode tab of electrode assembly C at the edge of the aluminum-plastic film, and the four sides are heat-sealed by hot pressing to obtain the assembled electrode assembly.

[0167] All the tabs of electrode assembly C are led out of the aluminum-plastic film, and then the negative electrode tab of electrode assembly B is welded to the positive electrode tab of electrode assembly C by laser welding to achieve series connection, and the battery assembly is completed.

[0168] The rest is the same as in Example 15.

[0169] Example 19

[0170] Except that the positive and negative electrodes of electrode assemblies A and B extend out of the packaging shell in opposite directions, the rest is the same as in Example 15.

[0171] Example 20

[0172] (1) Preparation of negative electrode sheet: Cut the negative electrode sheet into 41mm×550mm size for later use, and the rest is the same as in Example 1.

[0173] (2) Preparation of positive electrode sheet: The positive electrode sheet is cut into 35mm×547mm size for later use, and the rest is the same as in Example 1.

[0174] (3) Preparation of electrolyte: In a dry argon atmosphere, the organic solvents ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are first mixed in a mass ratio of EC:EMC:DEC = 30:50:20. Then, lithium salt lithium hexafluorophosphate (LiPF6) is added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0175] (4) Preparation of electrode assembly A and electrode assembly B: The diaphragm, the double-sided coated negative electrode sheet, the diaphragm, and the double-sided coated positive electrode sheet are stacked and then wound from one end to form a wound electrode assembly. Each electrode assembly includes one positive electrode tab and one negative electrode tab, which are arranged side by side. The thickness D4 of the electrode tab is 0.3 mm and the width W1 of the electrode tab is 5 mm. The diaphragm is a 15 μm thick polyethylene (PE) film.

[0176] (5) Separator preparation: Polypropylene (PP, melting point 140℃) encapsulation layer material was uniformly dispersed in N-methylpyrrolidone (NMP) dispersant to prepare a PP suspension; the PP suspension was coated on both sides of a 15μm thick polyimide (PI) film using a coating machine; then, the NMP dispersant was removed from the suspension by drying at 130℃, thus completing the preparation of the separator. The separator thickness was 15μm.

[0177] (6) Assembly of Electrode Assembly A: Place the punched aluminum-plastic film (150μm thick) in the assembly fixture with the punched surface facing upwards. Place electrode assembly A in the punch, then place the partition on electrode assembly A. Apply 11mm wide tab adhesive to the area corresponding to the tab of electrode assembly B at the edge of the aluminum-plastic film to align the edges. Apply external force to press and obtain the assembled semi-finished product. The distance D1 between the upper edge of the tab adhesive and the upper edge of the packaging shell is 5mm, the tab adhesive shoulder width D2 is 3mm, and the tab adhesive thickness D3 is 0.2mm.

[0178] (7) Assembly of Electrode Assembly B: Place the semi-finished assembly in the assembly fixture with the partition facing upwards. Place Electrode Assembly B on the partition, aligning the edges, and apply external force to press it firmly. Then, cover Electrode Assembly B with another punched aluminum-plastic film, pitted side down. Place an 11mm wide tab adhesive strip on the edge of the aluminum-plastic film corresponding to the tab of Electrode Assembly B. Heat seal the perimeter using a hot-pressing method to obtain the assembled electrode assembly. The distance D1 between the upper edge of the tab adhesive and the upper edge of the packaging shell is 5mm, the tab adhesive shoulder width D2 is 3mm, and the tab adhesive thickness D3 is 0.2mm.

[0179] (8) Electrolyte injection and encapsulation: Electrolyte is injected into each cavity of the assembled electrode assembly separately, and all tabs of electrode assemblies A and B are led out of the aluminum-plastic film. The width of the overlap area between the negative tab of electrode assembly A and the positive tab of electrode assembly B is 4.75 mm, and the width of the overlap area between the tab adhesive of the negative tab of electrode assembly A and the positive tab of electrode assembly B is 10.67 mm.

[0180] (9) Series connection of electrode components: The negative electrode tab of electrode component A and the positive electrode tab of electrode component B are welded together by laser welding to achieve series connection, and the battery assembly is completed. The area S1 of the connection region is 30 mm². 2 The distance D5 between the two electrodes connected by welding is 3mm, and the distance D6 between the connection area and the aluminum-plastic film is 5mm.

[0181] Comparative Example 1

[0182] The perforated aluminum-plastic film is placed in the assembly fixture with the perforated surface facing upwards. Electrode assembly A is placed in the perforation with the diaphragm surface facing upwards. Then, electrode assembly B is placed on top of electrode assembly A, aligning the edges. External force is applied to press it firmly. Then, another perforated aluminum-plastic film is placed on top of electrode assembly B with the perforated surface facing downwards. The perimeter is then heat-sealed using a hot-pressing method to obtain the assembled electrode assembly. The tab shoulder width D2 is 3mm, the tab thickness D3 is 0.2mm, the distance D1 between the upper edge of the tab and the upper edge of the packaging shell is 1mm, the distance between the two connected tabs is 3mm, and the tab thickness D4 is 0.3mm. The rest is the same as in Example 1.

[0183] Comparative Example 2

[0184] The width of the overlapping area between the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B is 1 mm, and the width of the overlapping area between the tab adhesive of the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B is 2.31 mm. The rest is the same as in Example 1.

[0185] Comparative Example 3

[0186] Except for the distance D5 between the two connected tabs being 1mm and the distance D6 between the connecting area and the aluminum-plastic film being 1mm, the rest is the same as in Example 1.

[0187] Comparative Example 4

[0188] Except for the distance D5 between the two connected tabs being 6mm and the distance D6 between the connecting area and the aluminum-plastic film being 3.5mm, the rest is the same as in Example 1.

[0189] The data and test results for each embodiment and comparative example are shown in Table 1 and Table 2.

[0190]

[0191]

[0192] As can be seen from Examples 1-14 and Comparative Examples 2-3 in Table 1, as the ratio of the overlap width of the two connected tabs to the width of any tab and the ratio of the width of the overlap area of ​​the tab adhesive to the width of any tab adhesive increase, the bending stability of the electrochemical device of this application is significantly improved.

[0193] As can be seen from Examples 1-14 and Comparative Example 2 in Table 1, the encapsulation strength of the connection area of ​​the electrochemical device of this application is significantly improved, and the discharge capacity / first discharge capacity after 50 cycles is improved.

[0194] As can be seen from Examples 1-14 and Comparative Examples 3 and 4 in Table 1, as long as the values ​​of D6 and D5 / D6 are within the range of this application, the bending stability of the electrochemical device of this application is greatly improved.

[0195] As can be seen from Examples 1-14 and Comparative Example 4 in Table 1, as long as the ratio of D5 / D6 is within the range of this application, the bending stability of the electrochemical device is improved, thereby improving the reliability of the electrochemical device.

[0196] As can be seen from Examples 15-20 and Comparative Examples 2 and 3 in Table 2, the welding pull force of the connection area of ​​the electrochemical device of this application is significantly improved, the output voltage remains basically unchanged, and the temperature rise of the 2C charging tab decreases, indicating that the electrochemical device of this application has good connection reliability and usage reliability.

[0197] As can be seen from Examples 15-20 and Comparative Examples 3 and 4 in Table 2, as long as the ratio of D5 / D6 is within the range of this application, the welding pull force in the welded connection area of ​​the electrochemical device is significantly increased, the temperature rise of the 2C charging tab is reduced, thereby improving the reliability of the electrochemical device.

[0198] The ratio α of the overlap width of the two connected tabs to the width of any one tab, and the ratio β of the overlap area of ​​the tab adhesive to the width of any one tab adhesive, typically affect the encapsulation strength and bending stability of the electrochemical device; the area S1 of the connection region typically affects the connection strength of the connection region and the temperature rise of the tabs; the design and adjustment of the relative positions of the two connected tabs typically affect the connection reliability between adjacent electrode components and the encapsulation reliability of the electrochemical device, which is achieved by adjusting the distance between D1 and D6. As can be seen from Examples 1-20, as long as the above parameters are within the range of this application, the obtained electrochemical device not only improves the output voltage but also improves the connection reliability and encapsulation reliability, exhibiting excellent industrial applicability.

[0199] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An electrochemical device comprising at least two electrode assemblies and a packaging shell, wherein the electrode assemblies are respectively disposed in their respective independent cavities within the packaging shell; Each electrode assembly includes two tabs of opposite polarity, at least one tab of one electrode assembly is connected to one of the two tabs of the other electrode assembly, and the two connected tabs have an overlap region when projected onto the orthographic projection along the seal thickness direction Z. The overlap width O1 of the two connected electrodes is 50% ≤ α ≤ 100% of the width W1 of any electrode. in, The overlap width O1 is the overlap width of the two connected tabs at the outer edge of the packaging shell seal, viewed along the seal thickness direction Z, and along the seal length direction X; the tab width W1 is the width of any one of the two connected tabs at the outer edge of the packaging shell seal, viewed along the seal thickness direction Z, and along the seal length direction X. Each of the two connected tabs is provided with tab adhesive. At the outer edge of the packaging shell seal, along the seal length direction X, the width of the tab adhesive provided on the tab extends beyond both sides of the tab. The ratio of the tab adhesive shoulder width D2 to the tab width W1 is D2 / W1≥1 / 60. Wherein, the tab shoulder width D2 is the distance that one side of the tab extends beyond the edge of the same tab along the X direction at the outer edge of the packaging shell seal; At the outer edge of the packaging shell seal, the distance between the two connected tabs is D5; the two connected tabs have a connecting area, and the length of the tab between the connecting area and the outer edge of the packaging shell seal is D6; the relationship between D5 and D6 satisfies: 0.1≤D5 / D6≤1.

5.

2. The electrochemical device according to claim 1, wherein, The tab adhesive on the two connected tabs has an overlapping area when projected along the sealing thickness direction Z. The overlap width O2 of the tab adhesive accounts for 40% < β ≤ 100% of the width W2 of any tab adhesive. Wherein, the overlap width O2 of the tab adhesive is the overlap width of the tab adhesive at the outer edge of the packaging shell seal, along the seal length direction X, when viewed along the seal thickness direction Z. The tab width W2 is the width of any tab along the sealing length direction X at the outer edge of the packaging shell seal, when viewed along the sealing thickness direction Z.

3. The electrochemical device according to claim 1, wherein, 3mm≤D6≤30mm.

4. The electrochemical device according to claim 1, wherein, 0.1mm<D5≤(H1+H2) / 2+5mm, where H1 and H2 are the thicknesses of the two connecting electrode assemblies, respectively.

5. The electrochemical device according to claim 1, wherein, The area S1 of the connecting region is 1 mm. 2 Up to 200mm 2 .

6. The electrochemical device according to claim 1, wherein, Along the direction away from the electrode assembly, the distance of the tab adhesive extending beyond the upper edge of the packaging shell along the sealing width direction Y is 0.2mm≤D1≤5mm, the thickness of the tab adhesive is 0.1mm≤D3≤3mm, and the thickness of the tab is 0.2mm≤D4≤5mm.

7. The electrochemical device according to claim 1, wherein, The two connected tabs are tabs with opposite polarities.

8. The electrochemical device according to claim 1, wherein, The electrode assembly has tabs that extend from the packaging shell in different directions.

9. The electrochemical device according to claim 1, further comprising a partition located between the electrode assemblies, wherein, The thickness of the partition is from 2µm to 100µm.

10. The electrochemical device according to claim 1, wherein, The structure of the electrode assembly includes at least one of a wound structure and a stacked structure.

11. The electrochemical device according to claim 1, wherein, The packaging shell includes at least one of aluminum-plastic film, aluminum shell, steel shell, and plastic shell.

12. An electronic device comprising the electrochemical device according to any one of claims 1 to 11.

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