Electrochemical and electronic devices

Abstract

The present invention provides an electrochemical device including at least two electrode assemblies and a package case, the electrode assemblies being respectively disposed in independent cavities within the package case, each electrode assembly including two tabs of opposite polarity, at least one tab of one electrode assembly being connected to one of the two tabs of the other electrode assembly, the connected two tabs including an overlapping region when orthogonally projected along the thickness direction Z of the seal, the width of the overlapping region of the connected two tabs at the outer edge of the seal of the package case along the length direction X of the seal, when observed along the thickness direction Z, being 40%<α≦100% of the width of either tab. The electrochemical device provided by the present invention not only achieves high voltage output, but also improves the packaging reliability of the tab region during high voltage output.

Description

[Technical Field]

[0001] The present invention relates to the field of electrochemistry, and more particularly to an electrochemical device and an electronic device using said electrochemical device. [Background technology]

[0002] Lithium-ion batteries have many advantages, including high volumetric and mass energy density, long cycle life, low self-discharge rate, small volume, and light weight, and are therefore widely used in consumer electronics.With the rapid development of electric vehicles and mobile electronic devices in recent years, demands for battery energy density, safety, cycle characteristics, etc. are increasing, and the emergence of new lithium-ion batteries with improved overall performance is expected. Summary of the Invention

[0003] The present invention aims to provide an electrochemical device and an electronic device that achieves high voltage output while improving the welding reliability of two series-parallel tabs and the packaging reliability of the tab portion.

[0004] In a first aspect of the present invention, there is provided an electrochemical device comprising at least two electrode assemblies and a package case, the electrode assemblies being respectively provided in independent cavities within the package case; Each electrode assembly includes two tabs of opposite polarity, wherein at least one tab of one electrode assembly is connected to one of the two tabs of the other electrode assembly and includes an overlapping region of the tabs in an orthogonal projection along a thickness direction Z of the seal of the two connected tabs; The ratio of the width O1 of the overlapping region of the two connected tabs to the width W1 of either tab is 40%<α≦100%; Here, the width O1 of the overlapping region is the width of the overlapping region of the two connected tabs along the length direction X of the seal at the outer edge of the seal of the package case when observed along the thickness direction Z of the seal, When observed along the thickness direction Z of the seal, the width W1 of the tab is the width of any one of the two connected tabs along the length direction X of the seal at the outer edge of the seal of the package case.

[0005] In some embodiments of the first aspect of the present invention, each of the two connected tabs is provided with a tab tape. When observed along the length direction X of the seal at the outer edge of the seal of the package case, the width of the tab tape provided on the tab exceeds both sides of the corresponding tab, and the ratio of the shoulder width D2 of the tab tape to the width W1 of the tab satisfies D2 / W1≧1 / 60. Here, the shoulder width D2 of the tab tape is the distance at which one side of the tab tape exceeds the outer edge of the tab on the same side along the X direction at the outer edge of the seal of the package case.

[0006] In some embodiments of the first aspect of the present invention, the orthographic projection along the thickness direction Z of the seal of the tab tape on the two connected tabs includes an overlapping region of the tab tape, and the ratio of the width O2 of the overlapping region of the tab tape to the width W2 of any one of the tab tapes is 40%<β≦100%. Here, the width O2 of the overlapping region of the tab tape is the width of the overlapping region of the tab tape along the length direction X of the seal at the outer edge of the seal of the package case when observed along the thickness direction Z of the seal. The width W2 of the tab tape is the width of any one of the tab tapes along the length direction X of the seal at the outer edge of the seal of the package case when observed along the thickness direction Z of the seal.

[0007] In some embodiments of the first aspect of the present invention, at the outer edge of the seal of the package case, the distance between the two connected tabs is D5, the two connected tabs have a connection region, and the length of the tab between the connection region and the outer edge of the seal of the package case is D6. The relationship between D5 and D6 satisfies 0<D5 / D6≦1.7.

[0008] In some embodiments of the first aspect of the present invention, D6 satisfies 3 mm ≤ D6 ≤ 30 mm.

[0009] In some embodiments of the first aspect of the present invention, 0.1 mm < D5 ≤ (H1 + H2) / 2 + 5 mm, where H1 and H2 are the thicknesses of two adjacent electrode assemblies, and H1 and H2 may be the same or different.

[0010] In some embodiments of the first aspect of the present invention, the area S1 of the connection region is 1 mm

[0016] , , ,

[0014] , , , ,

[0015] , , ~200 mm 2 is.

[0011] In some embodiments of the first aspect of the present invention, along the direction away from the electrode assembly, the distance that the tab tape exceeds the upper edge of the package case along the width direction Y of the seal is 0.2 mm ≤ D1 ≤ 5 mm, the thickness of the tab tape is 0.1 mm ≤ D3 ≤ 3 mm, and the thickness of the tab is 0.2 mm ≤ D4 ≤ 5 mm.

[0012] In some embodiments of the first aspect of the present invention, α satisfies 50% ≤ α ≤ 100%.

[0013] In some embodiments of the first aspect of the present invention, the two connected tabs are two tabs with opposite polarities.

[0014] In some embodiments of the first aspect of the present invention, the electrode assembly has tabs extending from the package case in different directions.

[0015] In some embodiments of the first aspect of the present invention, the electrochemical device further includes a separator disposed between the electrode assemblies, and the thickness of the separator is 2 μm to 100 μm.

[0016] In some embodiments of the first aspect of the present invention, the structure of the electrode assembly includes at least one of a winding structure and a stacking structure.

[0017] In some embodiments of the first aspect of the present invention, the package case includes at least one of an aluminum laminate film, an aluminum case, a steel case, and a plastic case.

[0018] A second aspect of the present invention provides an electronic device comprising an electrochemical device provided by the first aspect of the present invention.

[0019] The electrochemical device provided by the present invention achieves high voltage output by connecting multiple electrode assemblies internally in series, while also reducing the total heat generated by the electrochemical device and reducing temperature rise. By placing different electrode assemblies in independent cavities, the electrode assemblies are placed in a liquid electrolyte environment, avoiding problems such as internal short circuits and electrolyte decomposition under high pressure, thereby improving the safety performance of the electrochemical device. Effective connection between the tabs of adjacent electrode assemblies improves connection reliability, ensuring effective electrical energy output and overcurrent capability of the high-voltage electrochemical device, reducing electrical energy consumption due to tab heat generation, and preventing softening or melting of the tab tape due to tab heat generation, thereby improving the packaging reliability of the electrochemical device. By extending the tabs from the package case, designing and controlling the relative position of the tabs, and designing the tabs to be consistent, the packaging reliability of high-output voltage electrochemical devices is further improved. [Brief explanation of the drawings]

[0020] In order to more clearly explain the embodiments of the present invention and the technical solutions of the prior art, the following briefly introduces the drawings necessary for the embodiments and the prior art. Obviously, the accompanying drawings described below are only some embodiments of the present invention, and those skilled in the art can further derive other drawings from these drawings without creative efforts. [Figure 1] FIG. 1 is a schematic diagram of the structure of an electrochemical device according to one embodiment of the present invention. [Figure 2]FIG. 2 is a schematic diagram of the structure of an electrochemical device according to another embodiment of the present invention. [Figure 3] FIG. 3 is a schematic diagram of the structure of an electrochemical device according to yet another embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram of a partial structure of the left side view of FIG. [Figure 5] FIG. 5 is a schematic diagram of another partial structure of the left side view of FIG. [Figure 6] FIG. 6 is a schematic diagram of yet another partial structure of the left side view of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0021] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments.

[0022] The electrochemical device of the present invention may be any electrochemical device known to those skilled in the art, such as a lithium ion battery, a sodium ion battery, a magnesium ion battery, a supercapacitor, etc. The following description will be given taking 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 the present invention.

[0023] The present invention provides an electrochemical device including at least two electrode assemblies and a package case, wherein the electrode assemblies are respectively provided in independent cavities within the package case; Each electrode assembly includes two tabs of opposite polarity, wherein at least one tab of one electrode assembly is connected to one of the two tabs of the other electrode assembly, and an orthogonal projection of the two connected tabs along the thickness direction Z of the seal includes an overlapping region of the tabs; The ratio of the width O1 of the overlapping region of the two connected tabs to the width W1 of either tab is 40%<α≦100%; Here, the width O1 of the overlapping region is the width of the overlapping region of the two connected tabs along the length direction X of the seal at the outer edge of the seal of the package case when observed along the thickness direction Z of the seal, The tab width W1 is the width of one of the two connected tabs at the outer edge of the seal of the package case along the length direction X of the seal when observed along the thickness direction Z of the seal.

[0024] 1 shows one embodiment of the present invention, in which a three-dimensional coordinate system is constructed with the length direction, width direction, and thickness direction of the seal, with the X direction representing the length direction of the seal, the Y direction representing the width direction of the seal, and the Z direction representing the thickness direction of the seal. The electrochemical device includes electrode assemblies and a package case 1, the electrode assemblies being provided in independent cavities within the package case 1, for example, a first electrode assembly and a second electrode assembly being provided in independent cavities within the package case 1 and separated by a partition plate 8, each electrode assembly including two tabs of opposite polarity, at least one tab of one electrode assembly being connected to one of the two tabs of the other electrode assembly, and the orthogonal projection of the two connected tabs along the thickness direction Z of the seal includes an overlapping region of the tabs.

[0025] 2 , package case 1 has a sealing area 5, and a dashed line parallel to the X direction in sealing area 5 indicates the outer edge of the seal of the present invention, which is the upper boundary of sealing area 5. Each electrode assembly has two tabs of opposite polarity, of which one tab 2 is connected to one of the two tabs of the other electrode assembly, and an orthogonal projection along the thickness direction Z of the seal includes a tab overlap region 4. When observed along the thickness direction Z of the seal, the width of the overlap region of the connected two tabs along the length direction X of the seal at the outer edge of package case 1 is O1. When observed along the thickness direction Z of the seal, the width of one of the two connected tabs along the length direction X of the seal at the outer edge of package case 1 is W1, and the proportion of O1 to W1 is 40%<α≦100%.

[0026] In the electrochemical device of the present invention, each electrode assembly may include one positive electrode tab and one negative electrode tab, and adjacent electrode assemblies may be connected in series by connecting the positive and negative electrode tabs. The overlapping area of ​​the tabs affects the transport of electrical energy between adjacent electrode assemblies. Without being bound by any theory, a small width of the overlapping area may reduce the packaging reliability of the two connected tabs, further affecting the packaging reliability of the two adjacent electrode assemblies. In the electrochemical device of the present invention, the proportion α of the width O1 of the overlapping area of ​​the two connected tabs to the width W1 of either tab is 40%<α≦100%, preferably 50%≦α≦100%, which not only ensures the effective electrical energy output and overcurrent capability of the high-voltage electrochemical device, but also ensures the packaging reliability between adjacent electrode assemblies.

[0027] In some embodiments of the present invention, each of the two connected tabs is provided with a tab tape, and the width of the tab tape provided on the tab at the outer edge of the seal of the package case along the longitudinal direction X of the seal exceeds both sides of the corresponding tab, and the ratio of the shoulder width D2 of the tab tape to the width W1 of the tab satisfies D2 / W1≧1 / 60. As shown in FIG. 2 , in the present invention, the shoulder width D2 of the tab tape is the distance that one side of the tab tape exceeds the outer edge of the tab on the same side along the X direction at the outer edge of the seal of the package case, and the widths of the tab tapes on both sides may or may not be equal. By keeping the ratio D2 / W1 within the above range, the packaging reliability of the electrochemical device can be ensured.

[0028] In some embodiments of the present invention, the tab width W1 satisfies the condition 2 mm≦W1≦60 mm. Since the tab width W1 directly affects the area of ​​the overlapping region of the tabs, setting the tab width W1 within the above range can effectively improve the connection reliability between adjacent electrode assemblies.

[0029] In some embodiments of the present invention, an orthogonal projection of the seals of the tab tapes on the two connected tabs along the thickness direction Z includes an overlapping region of the tab tapes, and a proportion β of a width O2 of the overlapping region of the tab tapes to a width W2 of either tab tape is 40%<β≦100%, Here, the width O2 of the overlapping region of the tab tape is the width of the overlapping region of the tab tape along the length direction X of the seal at the outer edge of the seal of the package case when observed along the thickness direction Z of the seal, The width W2 of the tab tape is the width of any one of the tab tapes at the outer edge of the seal of the package case along the length direction X of the seal when observed along the thickness direction Z of the seal.

[0030] Figure 3 shows one embodiment of the present invention. The tab tape 3 on two connected tabs includes an overlapping region 6 of the tab tape. At the outer edge of the seal of the package case 1 along the longitudinal direction X of the seal, the ratio β of the width O2 of the overlapping region 6 of the tab tape to the width W2 at the outer edge of the seal of the package case 1 of any tab tape is 40% < β ≤ 100%. Similarly, the overlapping region 6 of the tab tape also affects the package reliability of the two connected tabs. When the width of the overlapping region 6 of the tab tape is small, when an external force is applied to the electrochemical device and bending occurs, distortion in a plane perpendicular to the tabs is likely to occur at the connection part of the two connected tabs, and stress is generated at the connection part, so cracks are likely to occur, and as a result, the package reliability of the two connected tabs decreases. By setting the ratio of the width of the overlapping region 6 of the tab tape to the width of any tab tape within the above range, the package reliability between adjacent electrode assemblies can be further enhanced.

[0031] In some embodiments of the present invention, referring to FIGS. 3 and 5, at the outer edge of the seal of the package case 1, the distance between the two connected tabs is D5, the two connected tabs have a connection region 7, and the length of the tab between the connection region 7 and the outer edge of the seal of the package case 1 is D6. The relationship between D5 and D6 satisfies 0 < D5 / D6 ≤ 1.7, preferably 3×10 -3 <D5 / D6 ≤ 1.5.

[0032] In some embodiments of the present invention, D5 satisfies 0.1 mm < D5 ≤ (H1 + H2) / 2 + 5 mm. Here, the distance D5 between the two connected tabs is the distance between the two connected tabs at the outer edge of the seal of the package case, and H1 and H2 are the thicknesses of two adjacent electrode assemblies respectively, and H1 and H2 may be the same or different. If the distance between the two tabs is too large, not only is it difficult to connect the two tabs, but the connection reliability between the two connected tabs also decreases. Therefore, by designing and controlling the relative positions of the two connected tabs, the connection reliability between adjacent electrode assemblies can be improved. In the present invention, the distance between the two connected tabs is the distance between the two tabs along the seal thickness direction Z at the outer edge of the tab and the package case seal.

[0033] FIG. 3 shows one embodiment of the present invention. The two connected tabs have a connection region 7, and D6 is the length of the tab between the lower edge of the connection region 7 and the outer edge of the seal of the package case 1. When the ratio of D5 / D6 is relatively small, D6 is relatively large, that is, the connection region 7 is far from the electrode assembly and the distance from the electrode assembly is relatively large. When the electrochemical device is subjected to an external force, the tab 2 with sufficient length relaxes the stress, reduces the stress on the end seal location and the connection location, and improves the seal reliability and connection reliability between two adjacent electrode assemblies. When the ratio of D5 / D6 is relatively large, D5 is relatively large, that is, the distance between the two connected tabs is too large. When the electrochemical device is subjected to an external force, a certain breakage is caused in the seal region due to the tearing of the tab 2, which affects the package reliability of the electrochemical device and the stability of the connection region 7. On the other hand, the ratio of D5 / D6 in the electrochemical device provided by the present invention satisfies the above range, which can not only improve the connection reliability between two adjacent electrode assemblies, but also improve the package reliability of the electrochemical device.

[0034] In some embodiments of the present invention, D6 satisfies the condition 3 mm≦D6≦30 mm. If D6 is relatively small, the tab tape on the tabs is easily damaged when connecting the two tabs, affecting the packaging reliability of the electrochemical device and making the connection operation more difficult. Second, because the distance between the connection area and the package case is short, cracks are easily generated under the action of external force, resulting in reduced connection reliability between two adjacent electrode assemblies. Furthermore, because the distance between the connection area and the package case is short and the electrode assemblies have a certain thickness, this affects the connection strength of the connection area and reduces the connection reliability between the two adjacent electrode assemblies. Furthermore, if the connection strength of the connection area is low and the connection is not tight, the resistance of the connection area increases during use of the electrode assembly, which increases the temperature rise of the tabs during charging, resulting in softening or melting of the tab tape and reduced packaging reliability of the electrochemical device. If D6 is relatively large, when the electrochemical device is subjected to external force, the connection area is easily broken, reducing the connection reliability between two adjacent electrode assemblies. Also, if D6 is relatively large, the volume of the electrochemical device will be increased by the connection area, and since the connection area is an inactive material area, it will not provide energy, resulting in a reduction in the volumetric energy density of the electrochemical device. Therefore, when D6 is within the above range, the resulting electrochemical device will have excellent packaging reliability and usage reliability.

[0035] In some embodiments of the present invention, the area S1 of the connection region is 1 mm 2 ~200mm 2The area S1 of the connection area is equal to or less than the area of ​​the overlapping area of ​​the tabs. That is, the entire overlapping area of ​​the tabs may be connected, or only a portion of the overlapping area of ​​the tabs may be connected. It is sufficient to ensure the connection reliability of the two tabs and achieve the objectives of the present invention. If the area of ​​the connection area is too small, the connection reliability between the two connected tabs will decrease, and at the same time, the current-carrying capacity of the connection area will be reduced. Within the area of ​​the connection area provided by the present invention, the connection reliability between adjacent electrode assemblies and the normal operation of the electrochemical device can be effectively ensured. Increasing the area S1 of the connection area improves the current-carrying capacity and ensures the effective electrical energy output and overcurrent capability of the high-voltage electrochemical device. In addition, increasing the area S1 of the connection area reduces electrical energy consumption due to heat generation of the tabs, thereby avoiding softening or melting of the tab tape due to heat generation of the tabs and improving the packaging reliability of the electrochemical device.

[0036] Furthermore, when the area S1 of the connection region is constant, the width of the overlapping region of the tab becomes smaller, and the width of the connection region along the longitudinal direction X of the seal becomes smaller, which reduces the connection strength of the connection region and also reduces the connection reliability of adjacent electrode assemblies.

[0037] In some embodiments of the present invention, the distance that the tab tape 3 extends beyond the upper edge of the package case along the width direction Y of the seal in the direction away from the electrode assembly is 0.2 mm≦D1≦5 mm, the shoulder width of the tab tape 3 is 1 mm≦D2≦8 mm, and the thickness of the tab tape 3 is 0.1 mm≦D3≦3 mm, and the thickness of the tab 2 is 0.2 mm≦D4≦5 mm, as shown in Figure 4. When D1 to D4 are within the above ranges, the resulting electrochemical device has good packaging reliability and usage reliability, and adjacent electrode assemblies have good connection reliability.

[0038] In the present invention, the tab tape provided on the tab may be coupled to the package case, and the coupling may be a hermetic connection between the tab and the package case by the tab tape.

[0039] In some embodiments of the present invention, the two tabs of each electrode assembly may extend from the package case in the same or different directions, either along one side of the package case or along each of two sides of the package case.

[0040] As shown in FIG. 5, in some embodiments of the present invention, the electrochemical device can further include a separator 8 positioned between the electrode assemblies. The cavities can be located on both sides of the separator 8, with each electrode assembly being disposed in a separate cavity. The separator thickness is 2 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm. In an electrochemical device, the separator must not only have ionic insulation properties but also a certain level of mechanical strength. Therefore, if the separator is too thin, its mechanical strength will be poor, leading to breakage and affecting the performance and safety of the electrochemical device. If the separator is too thick, the weight of the electrochemical device will increase, limiting its performance. In other embodiments of the present invention, as shown in FIG. 6, the separator 8 also includes a bonding material 9 to ensure effective bonding between the tab tape 3 and the separator 8.

[0041] In some embodiments of the present invention, the structure of the electrode assembly includes at least one of a wound structure and a stacked structure.

[0042] In some embodiments of the present invention, the cavity is a sealed cavity, which is an independent cavity formed on each side of the separator by hermetically connecting the separator and the package case, and completely separates the electrode assemblies and electrolyte on both sides of the separator, ensuring normal operation of the electrode assemblies on both sides. Good sealing properties are also beneficial for improving the safety and environmental stability of the electrochemical device.

[0043] In the present invention, the method of connecting the two connected tabs is not particularly limited as long as the object of the present invention can be achieved. For example, welding is an example. The method of the welding connection is not particularly limited as long as the object of the present invention can be achieved. For example, laser welding, ultrasonic welding, resistance welding, etc. can be used.

[0044] In the present invention, when the connection method of the two connected tabs is a welding connection, the area of ​​the connection region is the area surrounded by the outermost welding spots, and the welding spots are distributed in the connection region.

[0045] The electrode assembly described in the present invention may be an electrode assembly including a positive electrode piece, a negative electrode piece, and a separator, and the above-mentioned electrode assembly will be taken as an example for description. Those skilled in the art should understand that the following description is merely an illustrative description and does not limit the scope of protection of the present invention.

[0046] In the present invention, the thickness of the electrode assembly is not particularly limited as long as the object of the present invention can be achieved, for example, the thickness of the electrode assembly is 3 mm.

[0047] In some embodiments of the present invention, the positive electrode piece is not particularly limited, as long as the objectives of the present invention are achieved. For example, the positive electrode piece typically includes a positive electrode current collector and a positive electrode active material. In the present invention, the positive electrode current collector is not particularly limited and may be any positive electrode current collector known in the art. For example, copper foil, aluminum foil, aluminum alloy foil, composite current collector, etc. are included. The positive electrode active material is not particularly limited, and may be any positive electrode active material used in the prior art. For example, the positive electrode active material may include at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, and lithium iron manganese phosphate. In the present invention, the thickness of the positive electrode current collector and the positive electrode active material is not particularly limited, as long as the objectives of the present invention are achieved. For example, the thickness of the positive electrode current collector is 8 μm to 12 μm, and the thickness of the positive electrode active material is 30 μm to 120 μm.

[0048] In some preferred embodiments of the present invention, the positive electrode piece may further include a conductive layer, which is located between the positive electrode current collector and the positive electrode active material layer. The composition of the conductive layer is not particularly limited and may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and an adhesive.

[0049] In some embodiments of the present invention, the negative electrode piece is not particularly limited as long as the objectives of the present invention are achieved. For example, the negative electrode piece typically includes a negative electrode current collector and a negative electrode active material. In the present invention, the negative electrode current collector is not particularly limited and may be any negative electrode current collector known in the art. Examples include copper foil, aluminum foil, aluminum alloy foil, and composite current collectors. The negative electrode active material is not particularly limited and may be any negative electrode active material known in the art. For example, it may include at least one of artificial graphite, natural graphite, mesocarbon microbeads, silicon, silicon-carbon, silicon oxide, soft carbon, hard carbon, lithium titanate, and niobium titanate. In the present invention, the thickness of the negative electrode current collector and the negative electrode active material is not particularly limited as long as the objectives of the present invention are achieved. For example, the thickness of the negative electrode current collector is 6 μm to 10 μm, and the thickness of the negative electrode active material is 30 μm to 120 μm.

[0050] In some preferred embodiments of the present invention, the negative electrode piece may further include a conductive layer, the conductive layer being 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 may be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and an adhesive.

[0051] The conductive agent is not particularly limited, and any conductive agent known in the art may be used as long as the objectives of the present invention are achieved. For example, the conductive agent may include at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fiber, graphene, etc. The adhesive is not particularly limited, and any adhesive known in the art may be used as long as the objectives of the present invention are achieved. For example, the adhesive may include at least one of styrene butadiene rubber (SBR), polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), carboxymethyl cellulose sodium (CMC-Na), etc.

[0052] In some embodiments of the present invention, the separator is not particularly limited as long as it can achieve the object of the present invention. For example, the separator has a thickness of 5 μm to 15 μm, and can include a polymer or inorganic material formed from a material stable in the electrolyte of the present invention. In the present invention, the separator can also be called a separation film.

[0053] For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric, a membrane, or a composite membrane having a porous structure. The material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer formed by mixing a polymer and an inorganic material.

[0054] For example, the inorganic layer may contain inorganic particles and a binder. The inorganic particles may be at least one selected from the group consisting of alumina, silica, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder may be at least one selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylic acid ester, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer includes a polymer, and the polymer material includes at least one of polyamide, polyacrylonitrile, polymer of acrylic ester, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0055] The tabs described in this invention are metal conductors extending from the positive or negative electrode pieces for connecting other parts of the electrochemical device in series or parallel. The positive electrode tabs extend from the positive electrode pieces, and the negative electrode tabs extend from the negative electrode pieces.

[0056] In the present invention, the material of the tab tape is not particularly limited, and any tab tape known in the art may be used as long as the objectives of the present invention are achieved. For example, the tab tape material may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc., and may further include a composite material containing the above polymer, such as a PP / PET / PP composite, a PP / PEN / PP composite, a PP / nonwoven fabric / PP composite, or a PP / high-temperature barrier layer / PP composite. The width of the tab tape is not particularly limited, and may be any material that achieves the objectives of the present invention. For example, the width of the tab tape is 4 mm to 76 mm. The nonwoven fabric is not particularly limited, and may be any material that achieves the objectives of the present invention, such as a polypropylene nonwoven fabric or a polyethylene nonwoven fabric. The high-temperature barrier layer is not particularly limited, and may be any material that achieves the objectives of the present invention, such as an aramid layer.

[0057] In the present invention, the diaphragm is not particularly limited, and any diaphragm known in the art may be used as long as it can achieve the objectives of the present invention. Generally, the diaphragm must have ionic insulation properties to prevent high-voltage decomposition of the electrolyte and short-circuiting within the electrode assembly. For example, the diaphragm material may include at least one of a polymer material, a metal material, a carbon material, and a composite material thereof.

[0058] The polymer material is not particularly limited as long as it can achieve the object of the present invention. Any material known to those skilled in the art can be used, and for example, the polymer material can include at least one of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyether ether ketone, polyimide, polyamide, polyethylene glycol, polyamideimide, 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, acid anhydride-modified polypropylene, polyethylene, ethylene-ethylene 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 derivatives thereof.

[0059] The metal material is not particularly limited, and any material known to those skilled in the art can be used as long as the object of the present invention can be achieved, and can include, for example, 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 compositions or alloys thereof. Preferably, a metal material with excellent anti-oxidation and reduction properties in a lithium-ion battery environment can be selected.

[0060] The carbon material may include at least one of carbon felt, carbon film, carbon black, acetylene black, fullerene, conductive graphite film, and graphene film. In some embodiments of the present invention, the ion insulating layer is preferably made of a polymer material. The low density of the polymer material reduces the weight of inert materials, thereby increasing the mass energy density of the electrode assembly. Furthermore, the polymer material used for the ion insulating layer reduces the likelihood of debris generation in the event of mechanical abuse (such as nailing, impact, or squeezing), and provides a stronger covering effect on mechanically damaged surfaces, thereby improving the safety boundary in the event of such mechanical abuse and increasing the pass rate of safety tests.

[0061] In some embodiments of the present invention, the separator further includes a packaging layer, which may be disposed on both sides of the ion insulating layer, and which is disposed around the periphery of the surface of the ion insulating layer or over the entire surface thereof, and which is used to hermetically connect the ion insulating layer with the package case.

[0062] In the present invention, the material of the packaging layer is not particularly limited, and any material known to those skilled in the art can be used as long as it can achieve the object of the present invention. For example, the material of the packaging layer includes at least one of polypropylene, acid anhydride-modified polypropylene, polyethylene, ethylene-ethylene 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 derivatives thereof.

[0063] Of course, the packaging layer of the present invention still provides ionic insulation even when it covers the entire surface of the ion insulating layer. For convenience, the separator is divided into an ion insulating layer and a packaging layer in the present invention, but this does not mean that the packaging layer does not have ion insulating properties. For example, when the packaging layer covers both sides of the ion insulating layer, the ion insulating layer and the packaging layer function as ion insulating layers.

[0064] In the present invention, the bonding material between the partition plate and the tab tape is not particularly limited, and any material known to those skilled in the art may be used as long as it achieves the object of the present invention. For example, the bonding material may include at least one of polypropylene, polyester, p-hydroxybenzaldehyde, polyamide, polyphenylene ether, polyurethane, etc.

[0065] The electrolyte described in the present invention may include a lithium salt and a non-aqueous solvent. In the present invention, the lithium salt is not particularly limited, and any lithium salt known in the art may be used as long as the objectives of the present invention are achieved. For example, the lithium salt may include at least one of LiPF, LiBF, LiAsF, LiClO, LiB(CH), LiCHSO, LiCFSO, LiN(SOCF), LiC(SOCF), and LiPOF. For example, LiPF may be selected as the lithium salt. In the present invention, the non-aqueous solvent is not particularly limited, and as long as the objectives of the present invention are achieved. For example, the non-aqueous solvent may include at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, nitrile compounds, and other organic solvents.

[0066] For example, the carbonate ester compound may be 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), butylene carbonate (BC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate (PEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate (VEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), ethylene carbonate (VEC), ethylene carbonate (F ... The fluorocarbon polymer may include at least one of ethylene 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, and trifluoromethylethylene carbonate.

[0067] The present invention is not particularly limited to a package case, as long as it achieves the objectives of the present invention. The package case may include at least one of an aluminum laminate film, an aluminum case, a steel case, and a plastic case. For example, the package case may include an inner layer and an outer layer. Since the inner layer is hermetically connected to the separator, the material of the inner layer may include a polymer material, thereby achieving a good sealing effect. At the same time, the bond between the inner layer and the outer layer can effectively protect the internal structure of the electrochemical device. In the present invention, the material of the inner layer is not particularly limited, as long as it achieves the objectives of the present invention. For example, the material of the inner layer may include at least one of polypropylene, polyester, p-hydroxybenzaldehyde, polyamide, polyphenylene ether, polyurethane, etc. In the present invention, the material of the outer layer is not particularly limited, as long as it achieves the objectives of the present invention. For example, the material of the outer layer may include at least one of aluminum foil, an alumina layer, a silicon nitride layer, etc.

[0068] In the present invention, the thickness of the package case is not particularly limited as long as the object of the present invention can be achieved. For example, the thickness of the package case is 60 μm to 500 μm, preferably 60 μm to 300 μm, and more preferably 60 μm to 200 μm, and a package case of the above thickness can effectively protect the internal structure of the electrochemical device.

[0069] In the present invention, the seal thickness T (unit: mm) and seal width W (unit: mm) of the seal area between the separator and the package case satisfy the relationship 0.01≦T / W≦0.05. By keeping the T / W ratio within the above range, good sealing of the battery can be ensured, and the battery life can be improved. In the present invention, the seal thickness and seal width are not particularly limited as long as they achieve the object of the present invention. For example, the seal width is preferably 1 mm to 7 mm.

[0070] The present invention is not particularly limited by the sealing method between the separator and the package case, as long as the objective of the present invention can be achieved. For example, the sealing method can include one of heat pressing, adhesive sealing, and welding. In the present invention, the heat pressing conditions are not particularly limited, as long as the objective of the present invention can be achieved. For example, for a polypropylene inner layer material, the heat pressing temperature is 150°C to 220°C, and the heat pressing pressure is 0.1 MPa to 0.6 MPa.

[0071] In some embodiments of the present invention, the electrode assembly has a wound structure and includes a single tab or multiple tabs. When the electrode assembly includes a single tab, one positive tab and one negative tab are drawn from the positive and negative pole pieces, respectively. When the electrode assembly includes multiple tabs, one positive tab and one negative tab may be drawn from each round of the positive and negative pole pieces, respectively, or one positive tab and one negative tab may be drawn from two or more rounds of the positive and negative pole pieces, respectively. Finally, a wound electrode assembly includes multiple sets of positive and negative tabs, and the tab leads are then wound by spin welding.

[0072] In some embodiments of the present invention, the electrode assembly has a laminated structure. When the electrode assembly includes multiple tabs, one positive electrode tab and one negative electrode tab may be drawn out from each layer of positive electrode pieces and negative electrode pieces, respectively, so that one laminated electrode assembly ultimately includes multiple sets of positive electrode tabs and negative electrode tabs, and then the tab leads are wound by spin welding.

[0073] In the present invention, the distances D1 to D6, W1, W2, O1, and O2 are all measured using a micrometer along the X, Y, or Z direction shown in FIG. 1, and the average of 10 measurements is used as the final result.

[0074] The present invention further provides an electronic device comprising the electrochemical device of the present invention. The electronic device of the present invention is not particularly limited and may be any electronic device known in the prior art. For example, display devices include, but are not limited to, laptops, pen-input computers, mobile computers, electronic book players, mobile phones, portable facsimiles, portable copiers, portable printers, stereo headsets, video recorders, LCD televisions, portable vacuum cleaners, portable CD players, minidiscs, walkie-talkies, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, power-assisted bicycles, bicycles, lighting equipment, toys, game consoles, watches, power tools, flashlights, cameras, large-scale household storage batteries, and lithium-ion capacitors.

[0075] The method for preparing the electrochemical device of the present invention is not particularly limited, and any method known in the art can be employed. For example, in one embodiment, the present invention can be prepared using the following preparation method.

[0076] (1) Preparation of negative electrode pieces: The negative electrode active material and solvent are mixed into a slurry and stirred uniformly. The slurry is evenly applied to the negative electrode pieces and dried to obtain a single-sided coated negative electrode piece. The above procedure is repeated on the other surface of the negative electrode piece to obtain a double-sided coated negative electrode piece. The negative electrode piece is then cut for later use. The thickness of the coating on one surface of the negative electrode active material is 70 μm.

[0077] (2) Preparation of positive electrode pieces: The positive electrode active material and solvent are mixed into a slurry and stirred uniformly. The slurry is evenly coated on the positive electrode pieces and dried to obtain single-sided coated positive electrode pieces. The above procedure is repeated on the other surface of the positive electrode pieces to obtain double-sided coated positive electrode pieces. The positive electrode pieces are then cut for later use. The thickness of the coating on one surface of the positive electrode active material is 65 μm.

[0078] (3) Preparation of electrolyte: A lithium salt and a non-aqueous solvent are mixed and stirred uniformly to obtain an electrolyte with a lithium salt concentration of 30%.

[0079] (4) Preparation of electrode assembly: Anode pieces, separators, and cathode pieces are stacked and fixed for later use. Each electrode assembly contains one cathode tab and one anode tab. By repeating the above steps, multiple electrode assemblies can be obtained. The electrode assembly structure can be a wound structure or a stacked structure.

[0080] (5) Diaphragm: Any diaphragm known in the art can be employed.

[0081] (6) Assembling the electrode assembly: The package case is placed in the assembly clip, and the electrode assembly and the separator are spaced apart, and the package case and the electrode assembly are adjacent to each other, and finally sealed to obtain the assembled electrode assembly.

[0082] (7) Injection and packaging: Inject electrolyte into each of the two cavities of the assembled electrode assembly, and pull out all the tabs of the electrode assembly from the aluminum laminate film for subsequent processing.

[0083] (8) Series connection: The positive electrode tab of one electrode assembly and the negative electrode tab of the other electrode assembly are welded and connected by laser welding to achieve a series connection, thereby completing the assembly of the battery.

[0084] The electrochemical device provided by the present invention may include two electrode assemblies or three or more electrode assemblies. The preparation method for an electrochemical device including two electrode assemblies or three or more electrode assemblies can refer to the preparation method for an electrochemical device described above. Electrochemical devices including three or more electrode assemblies are also within the scope of protection defined in the claims of the present invention.

[0085] The terms used in the present invention are those commonly used by those skilled in the art, and if they do not match the commonly used terms, the terms used in the present invention shall prevail. In the present invention, unless otherwise specified, "%" and "parts" are all based on weight.

[0086] Measurement method:

[0087] Series Tab Area Package Strength Test: The sealed area of ​​the tab was removed from the electrode assembly and designated as Sample 1. Sample 1 was cut into a test piece with a width L of 8 mm, and the test piece was ensured to completely retain the entire sealing area, and the package case on both sides of the sealing area was also completely intact, to obtain Sample 2. Using a universal material testing machine, both sides of the package case were torn at an angle of 180° so that the two layers of the package case in the seal area were separated from each other. The stable tensile force F when the two-layer package case was separated was recorded, and the resulting package strength σ=F / L was calculated.

[0088] Discharge capacity after 50 charge / discharge cycles / initial discharge capacity test: When measuring Comparative Example 1, the measurement temperature was 25±3°C, and the lithium ion battery was charged to 4.2 V at a constant current of 0.5 C, then charged to a current of 0.05 C at a constant voltage of 4.2 V, allowed to stand for 10 minutes, and then discharged to 3.0 V at a current of 0.5 C. 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%. When measuring Comparative Examples 2 to 4 and Examples 1 to 22, the measurement temperature was 25±3°C, and the lithium ion battery was charged to 8.4 V at a constant current of 0.5 C, then charged to a current of 0.05 C at a constant voltage of 8.4 V, allowed to stand for 10 minutes, and then discharged to 6.0 V at a current of 0.5 C. 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%.

[0089] Bending stability test: The two connected tabs were subjected to a 360° bending test. That is, the tab was bent around the sealing area between the separator and the top seal of the package case, along the axis, onto the XY plane of the electrochemical device (the XY plane is shown in Figure 1) until the connected tab and the XY plane were bonded together. This was recorded as the first bend. Next, the tab was bent 360° in the opposite direction until it was bonded to the opposite XY plane of the electrochemical device, which was recorded as the second bend. This was repeated until cracks appeared on the outer edge of the package between the tab tape and the package case, and the number of times the corresponding tab was bent was recorded.

[0090] Battery output voltage test: Under the test temperature condition of 25±3°C, the lithium-ion battery was charged at a constant current of 0.5C up to N×4.2V (N is the number of series electrode assemblies), then charged at a constant voltage of N×4.2V up to a current of 0.05C, left to stand for 1 hour, and the open circuit voltage, which is the output voltage of the battery, was measured.

[0091] Series Tab Weld Pull Test: The tab portion, including the tab connection area, was removed from the electrode assembly to serve as a test sample. This sample retained the entire connection area, ensuring that both tabs were completely intact. Using a small tensile tester, the tabs on both sides were torn at a 180° angle, separating the two tabs in the welded area from each other. The stable tensile force required to separate the two tabs was recorded and used as the weld tensile force.

[0092] Temperature rise test of the tab during 2C charging: At a test temperature of 25°C, the battery was charged to 4.45V at a constant current of 0.5C, then charged to 0.025C at a constant voltage of 4.45V, and allowed to rest for 5 minutes. It was then discharged to 3.0V at 0.5C and allowed to rest for 5 minutes. The tab temperature at this time was measured as T1 using a multiplex thermometer. The battery was then charged to 4.45V at a constant current of 2C, and the tab temperature at this time was measured as T2 using a multiplex thermometer. Therefore, the temperature rise of the tab during 2C charging is △T = T2 - T1.

[0093] Example 1 (1) Preparation of negative electrode pieces: 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, and deionized water was added as a solvent to prepare a slurry with a solids content of 70 wt%. The mixture was then uniformly stirred. The slurry was then uniformly coated on one surface of a 10 μm-thick copper foil negative electrode current collector and dried at 110°C to obtain a negative electrode piece with a 150 μm-thick coating layer of negative electrode active material on one side. The same procedure was repeated on the other surface of this negative electrode piece to obtain a negative electrode piece with a double-coated negative electrode active material layer. The negative electrode piece was then cut to a size of 41 mm x 61 mm for later use.

[0094] (2) Preparation of Positive Electrode Pieces: The positive electrode active materials, lithium cobalt oxide (LiCoO), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF), were mixed in a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solids content of 75 wt%. The slurry was then uniformly mixed. The slurry was then uniformly coated on one surface of a 12 μm thick aluminum foil positive electrode current collector and dried at 90°C to obtain positive electrode pieces with a 100 μm thick positive electrode active material layer. The above procedure was repeated on the other surface of the aluminum foil positive electrode current collector to obtain positive electrode pieces with positive electrode active material layers coated on both sides. The positive electrode pieces were then cut to a size of 38 mm x 58 mm for later use.

[0095] (3) Preparation of electrolyte: In a dry argon gas atmosphere, first, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed as organic solvents in a mass ratio of EC:EMC:DEC = 30:50:20. Then, lithium hexafluorophosphate (LiPF6), a lithium salt, was added to the organic solvent, dissolved, and mixed uniformly to obtain an electrolyte solution with a lithium salt concentration of 1.15 mol / L.

[0096] (4) Preparation of electrode assembly A and electrode assembly B: Separator, double-sided coated negative electrode piece, separator, double-sided coated positive electrode piece were stacked in this order and assembled into a laminate. The four corners of the entire laminate structure were then fixed for later use. Each electrode assembly contained one positive electrode tab and one negative electrode tab. The positive electrode tab was aluminum (Al) and the negative electrode tab was nickel (Ni). The two tabs were placed side by side, with a tab thickness D4 of 0.3 mm and a tab width W1 of 5 mm. The separator was a 15 μm thick polyethylene (PE) film.

[0097] (5) Preparation of the partition: Polypropylene (PP, melting point 140°C), a packaging layer material, was uniformly dispersed in N-methylpyrrolidone (NMP), a dispersant, to prepare a PP suspension. The PP suspension was then applied to both sides of a 15 μm-thick polyimide (PI) film using a coater, and the suspension was then dried at 130°C to remove the NMP dispersant from the suspension, completing the preparation of the partition. The thickness of the partition was 15 μm.

[0098] (6) Assembly of electrode assembly A: A press-formed aluminum laminate film (thickness 150 μm) was placed in an assembly grip with the pit side facing up, and electrode assembly A was placed in the pit with the separator side facing up. An 11 mm-wide tab tape was then attached to the outer edge of the aluminum laminate film in the area corresponding to the tab of electrode assembly A. A separator was then placed on electrode assembly A, the outer edges were aligned, and an external force was applied to press to obtain an assembled semi-finished product. Here, the distance D1 between the upper edge of the tab tape and the upper edge of the package case was 1 mm, the shoulder width D2 of the tab tape was 3 mm, and the thickness D3 of the tab tape was 0.2 mm.

[0099] (7) Assembly of electrode assembly B: The semi-finished assembly was placed in an assembly grip, one side of the separator was placed facing up, and electrode assembly B was placed on the separator with its separator side facing down. The outer edges were aligned and pressed together. Next, another press-formed aluminum laminate film was placed on electrode assembly B with its pit side facing down. An 11 mm-wide tab tape was attached to the outer edge of the aluminum laminate film in the area corresponding to the tab of electrode assembly B, and the periphery was heat-sealed using a heat press to obtain an assembled electrode assembly. The distance D1 between the upper edge of the tab tape and the upper edge of the package case was 1 mm, the shoulder width D2 of the tab tape was 3 mm, and the thickness D3 of the tab tape was 0.2 mm.

[0100] (8) Injection and packaging: Electrolyte was injected into each cavity of the assembled electrode assembly, and all tabs of electrode assemblies A and B were pulled out of the aluminum laminate film. The width of the overlapping area between the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B was 4.75 mm, and the width of the overlapping area between the tab tape of the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B was 10.67 mm.

[0101] (9) Series connection: The negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B are welded and connected in series by laser welding, and the battery assembly is completed. The area S1 of the connection area is 20 mm 2 The distance D5 between the two connected tabs was 3 mm, and the distance D6 between the connection area and the aluminum laminate film was 5 mm.

[0102] Example 2 The same as in Example 1 was performed except that the width of the overlapping region between the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B was 2.5 mm, and the width of the overlapping region of the tab tape between the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B was 5.61 mm.

[0103] Example 3 The same as in Example 1 was performed except that the distance D1 between the upper edge of the tab tape and the upper edge of the package case was 5 mm.

[0104] Example 4 The same as in Example 1 was used except that the width of the tab tape was 8 mm and the shoulder width D2 of the tab tape was 1.5 mm.

[0105] Example 5 The same as in Example 1, except that the thickness D3 of the tab tape was 3 mm.

[0106] Example 6 The same as in Example 1, except that the thickness D4 of the tab was 2 mm.

[0107] Example 7 The same as in Example 1, except that the width W1 of the tab was 10 mm.

[0108] Example 8 This was the same as Example 1, except that the distance D5 between the two connected tabs was 6 mm.

[0109] Example 9 The results were the same as in Example 1, except that the distance D6 between the connection region and the aluminum laminate film was 30 mm.

[0110] Example 10 The same as in Example 1, except that the thickness of the partition plate was 200 μm.

[0111] Example 11 The same as in Example 1 was performed except that the width of the overlapping region between the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B was 3 mm, and the width of the overlapping region of the tab tape between the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B was 6.6 mm.

[0112] Example 12 This was the same as Example 1, except that the distance D5 between the two connected tabs was 1 mm.

[0113] Example 13 The same as in Example 1 was used except that the shoulder width D2 of the tab tape was 1.5 mm and the distance D6 between the connection area and the aluminum laminate film was 3 mm.

[0114] Example 14 The same as in Example 1 was performed except that the distance D5 between the two connected tabs was 6 mm and the distance D6 between the connection area and the aluminum laminate film was 4 mm.

[0115] Example 15 The area of ​​the connection area S1 is 4 mm 2The electrode assembly had a 0.2C rated capacity of 10A and a maximum discharge rate of 2C, which was the same as in Example 3. The current carrying capacity per unit area of ​​the connection region was 5A / mm 2 It was.

[0116] Example 16 The area of ​​the connection area S1 is 3 mm 2 The results were the same as in Example 15, except that the maximum discharge rate was 3C.

[0117] Example 17 The area of ​​the connection area S1 is 10 mm 2 The results were the same as in Example 15, except that the rated capacity of the electrode assembly at 0.2 C was 50 A.

[0118] Example 18 Electrode assembly C was prepared according to procedure (4) of Example 1. When packaging the electrode assembly, electrode assembly B was placed on a partition plate with the separator side facing down, the outer edges were aligned, and external force was applied to press the assembly. After that, a partition plate was placed on electrode assembly B, and electrode assembly C was placed on the partition plate with the separator side facing down, the outer edges were aligned, and external force was applied to press the assembly. Then, another press-formed aluminum laminate film was placed on electrode assembly C with the pit side facing down. An 11 mm-wide tab tape was then attached to the outer edge of the aluminum laminate film in the area corresponding to the tab of electrode assembly C, and the periphery was heat-sealed using a heat press to obtain an assembled electrode assembly. All of the tabs of electrode assembly C were pulled out of the aluminum laminate film, and then the negative electrode tabs of electrode assembly B and the positive electrode tabs of electrode assembly C were welded together using laser welding, achieving a series connection and completing the assembly of the battery. Other than that, the procedure was the same as in Example 15.

[0119] Example 19 The same as in Example 15, except that the positive and negative electrode tabs of electrode assemblies A and B extended in opposite directions from the package case.

[0120] Example 20

[0121] (1) Preparation of negative electrode pole pieces: Same as in Example 1, except that the negative electrode pole pieces were cut to the specifications of 41 mm x 550 mm for later use.

[0122] (2) Preparation of positive pole pieces: Same as in Example 1, except that the positive pole pieces were cut to the specifications of 35 mm x 547 mm for later use.

[0123] (3) Preparation of electrolyte: In a dry argon gas atmosphere, first, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed as organic solvents in a mass ratio of EC:EMC:DEC = 30:50:20. Then, lithium hexafluorophosphate (LiPF6), a lithium salt, was added to the organic solvent, dissolved, and mixed uniformly to obtain an electrolyte solution with a lithium salt concentration of 1.15 mol / L.

[0124] (4) Preparation of electrode assembly A and electrode assembly B: A separator, a double-sided coated negative electrode piece, a separator, and a double-sided coated positive electrode piece were stacked and then wound from one end to form a wound electrode assembly. Each electrode assembly contained one positive electrode tab and one negative electrode tab, with the two tabs arranged side by side. The tab thickness D4 was 0.3 mm and the tab width W1 was 5 mm. The separator was a 15 μm thick polyethylene (PE) film.

[0125] (5) Preparation of the separator: The packaging material, polypropylene (PP, melting point 140°C), was uniformly dispersed in the dispersant, N-methylpyrrolidone (NMP), to prepare a PP suspension. The PP suspension was then applied to both sides of a 15 μm-thick polyimide (PI) film using a coater, and the NMP dispersant in the suspension was removed by drying at 130°C, completing the preparation of the separator. The thickness of the separator was 15 μm.

[0126] (6) Assembly of electrode assembly A: A press-formed aluminum laminate film (thickness 150 μm) was placed in an assembly grip, with the pit side facing up, and electrode assembly A was placed in the pit. Next, a separator was placed on electrode assembly A. Then, an 11 mm-wide tab tape was attached to the outer edge of the aluminum laminate film in the area corresponding to the tab of electrode assembly A. The outer edges were aligned, and an external force was applied to press to obtain an assembled semi-finished product. The distance D1 between the upper edge of the tab tape and the upper edge of the package case was 5 mm, the shoulder width D2 of the tab tape was 3 mm, and the thickness D3 of the tab tape was 0.2 mm.

[0127] (7) Assembly of electrode assembly B: The semi-finished assembly was placed in an assembly grip with the separator facing up. Electrode assembly B was placed on the separator, the outer edges were aligned, and pressed together with external force. Another press-formed aluminum laminate film was then placed on electrode assembly B with the pit side facing down. An 11 mm-wide tab tape was then attached to the outer edge of the aluminum laminate film in the area corresponding to the tab of electrode assembly B, and the periphery was heat-sealed using a heat press to obtain an assembled electrode assembly. The distance D1 between the upper edge of the tab tape and the upper edge of the package case was 5 mm, the shoulder width D2 of the tab tape was 3 mm, and the thickness D3 of the tab tape was 0.2 mm.

[0128] (8) Injection and packaging: Electrolyte was injected into each cavity of the assembled electrode assembly, and all tabs of electrode assemblies A and B were pulled out of the aluminum laminate film. The width of the overlapping area between the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B was 4.75 mm, and the width of the overlapping area between the tab tape of the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B was 10.67 mm.

[0129] (9) Serial connection of electrode assemblies: The negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B are connected by laser welding to achieve a serial connection, completing the battery assembly. The area S1 of the connected area is 30 mm2 The distance D5 between the two welded tabs was 3 mm, and the distance D6 between the connection area and the aluminum laminate film was 5 mm.

[0130] Comparative Example 1 The press-formed aluminum laminate film was placed in an assembly grip with the pit side facing up, and electrode assembly A was placed in the pit with the separator side facing up. Next, electrode assembly B was placed on electrode assembly A, and the outer edges were aligned and pressed with external force. Next, another press-formed aluminum laminate film was placed on electrode assembly B with the pit side facing down, and the periphery was heat-sealed using a heat press method to obtain an assembled electrode assembly. The process was the same as in Example 1, except that the tab tape shoulder width D2 was 3 mm, the tab tape thickness D3 was 0.2 mm, the distance D1 between the upper edge of the tab tape and the upper edge of the package case was 1 mm, the distance between the two connected tabs was 3 mm, and the tab thickness D4 was 0.3 mm.

[0131] Comparative Example 2 The same as in Example 1 was performed except that the width of the overlapping area between the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B was 1 mm, and the width of the overlapping area between the tab tapes of the negative electrode tab of electrode assembly A and the positive electrode tab of electrode assembly B was 2.31 mm.

[0132] Comparative Example 3 The same as in Example 1 was used, except that the distance D5 between the two connected tabs was 1 mm, and the distance D6 between the connection area and the aluminum laminate film was 1 mm.

[0133] Comparative Example 4 The same as in Example 1 was performed except that the distance D5 between the two connected tabs was 6 mm and the distance D6 between the connection area and the aluminum laminate film was 3.5 mm.

[0134] Tables 1 and 2 show the data and test results for each of the examples and comparative examples.

[0135] [Table 1]

[0136] [Table 2]

[0137] From Examples 1 to 14 and Comparative Examples 2 to 3 in Table 1, it was found that the bending stability of the electrochemical device of the present invention clearly improved as the ratio of the width of the overlapping region of two connected tabs to the width of either tab, and the ratio of the width of the overlapping region of the tab tape to the width of either tab tape, increased.

[0138] From Examples 1 to 14 and Comparative Example 2 in Table 1, it was found that the package strength of the connection area of ​​the electrochemical device of the present invention was clearly improved, and the discharge capacity after 50 cycles / initial discharge capacity was improved.

[0139] From Examples 1 to 14 and Comparative Examples 3 and 4 in Table 1, it was found that as long as the value of D6 and the value of D5 / D6 are within the range of the present invention, the bending stability of the electrochemical device of the present invention is significantly improved.

[0140] From Examples 1 to 14 and Comparative Example 4 in Table 1, it was found that as long as the D5 / D6 ratio was within the range of the present invention, the bending stability of the electrochemical device was improved, thereby improving the usage reliability of the electrochemical device.

[0141] From Examples 15 to 20 and Comparative Examples 2 and 3 in Table 2, it can be seen that the welding tensile strength of the connection area of ​​the electrochemical device of the present invention was significantly improved, the output voltage was almost unchanged, and the temperature rise of the tab during 2C charging was reduced, indicating that the electrochemical device of the present invention has good connection reliability and usage reliability.

[0142] From Examples 15 to 20 and Comparative Examples 3 and 4 in Table 2, it can be seen that as long as the D5 / D6 ratio is within the range of the present invention, the welding tensile strength of the connection area in the electrochemical device can be significantly increased and the temperature rise of the tab during 2C charging can be reduced, thereby improving the reliability of the electrochemical device.

[0143] The ratio α of the overlapping area between two connected tabs to the width of either tab and the ratio β of the overlapping area between two tab tapes to the width of either tab typically affect the packaging strength and bending stability of an electrochemical device. The area S1 of the connection area typically affects the connection strength of the connection area and the temperature rise of the tab. The design and control of the relative positions of the two connected tabs typically affect the connection reliability between adjacent electrode assemblies and the packaging reliability of the electrochemical device, which is achieved by adjusting the distances D1 to D6. Examples 1 to 20 demonstrate that, as long as the above parameters are within the ranges of the present invention, the resulting electrochemical device not only achieves improved output voltage, but also improves connection reliability and packaging reliability, demonstrating excellent industrial applicability.

[0144] The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection of the present invention.

Claims

1. An electrochemical device comprising at least two electrode assemblies and a packaging case; The electrode assemblies are respectively installed in independent cavities within the package case, Each electrode assembly includes two tabs of opposite polarity, wherein at least one tab of one electrode assembly is connected to one of the two tabs of the other electrode assembly, and an orthogonal projection of the two connected tabs along the thickness direction Z of the seal includes an overlapping region of the tabs; a ratio α of a width O1 of the overlapping region of the two connected tabs to a width W1 of either tab is 60%≦α≦100%, Here, when observing along the thickness direction Z of the seal, the width O1 of the overlapping region is the width of the overlapping region of the two connected tabs at the outer edge of the seal of the package case in the longitudinal direction X of the seal, When observing along the thickness direction Z of the seal, the width W1 of the tab is the width of one of the two connected tabs at the outer edge of the seal of the package case in the longitudinal direction X of the seal, At the outer edge of the seal of the package case, the distance between the two connected tabs is D5; the two connected tabs have a connection area; The length of the tab between the connection area and the outer edge of the seal of the package case is D6; The D5 satisfies 3 mm < D5 ≦ (H1 + H2) / 2 + 5 mm, where H1 and H2 are the thicknesses of the two connected electrode assemblies, respectively; The D6 satisfies 3 mm≦D6≦30 mm, The relationship between D5 and D6 satisfies 0<D5 / D6≦1.7, The two connected tabs are each provided with a tab tape, The width of the tab tape provided on the tab at the outer edge of the seal of the package case along the length direction X of the seal exceeds both sides of the corresponding tab, a ratio of a shoulder width D2 of the tab tape to a width W1 of the tab satisfies D2 / W1≧1 / 60, a shoulder width D2 of the tab tape is a distance that one side of the tab tape exceeds the outer edge of the tab on the same side along the X direction at the outer edge of the seal of the package case, an orthogonal projection of the seal of the tab tape on the two connected tabs along the thickness direction Z includes an overlapping region of the tab tape; a ratio β of the width O2 of the overlapping region of the tab tape to the width W2 of either tab tape is 60%≦β≦100%, a width O2 of the overlapping region of the tab tape is a width of the overlapping region of the tab tape along the length direction X of the seal at the outer edge of the seal of the package case when observed along the thickness direction Z of the seal, the width W2 of the tab tape is the width of any one of the tab tapes at the outer edge of the seal of the package case along the length direction X of the seal when observed along the thickness direction Z of the seal.

2. The area S1 of the connection area is 1 mm ２ ~200mm ２ 2. The electrochemical device of claim 1 , wherein:

3. a distance D1 of the tab tape extending beyond the upper edge of the package case along the width direction Y of the seal in a direction away from the electrode assembly is 0.2 mm≦D1≦5 mm; The thickness of the tab tape is 0.1 mm≦D3≦3 mm, 2. The electrochemical device of claim 1, wherein the thickness of the tab is 0.2 mm≦D4≦5 mm.

4. 10. The electrochemical device of claim 1, wherein the two connected tabs are two tabs of opposite polarity.

5. 10. The electrochemical device of claim 1, wherein the electrode assembly has tabs extending in different directions from a package case.

6. The electrode assembly further includes a partition disposed between the electrode assemblies, 2. The electrochemical device according to claim 1, wherein the thickness of the separator is 2 μm to 100 μm.

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

8. 2. The electrochemical device according to claim 1, wherein the package case comprises at least one of an aluminum laminate film, an aluminum case, a steel case, and a plastic case.

9. An electronic device comprising the electrochemical device according to any one of claims 1 to 8.

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