An electrochemical device and an electronic device including the same

Abstract

An electrochemical device and an electronic device comprising the same. The electrochemical device comprises at least one bipolar current collector (10) sealedly connected with an outer package (20), forming two independent sealed cavities on both sides of the bipolar current collector (10), each of which comprises an electrode assembly (30) and an electrolyte, one side of the bipolar current collector (10) is electrically connected with the outermost positive electrode tab of the adjacent electrode assembly (30), and the other side of the bipolar current collector (10) is electrically connected with the outermost negative electrode tab of the adjacent electrode assembly (30). Through the introduction of the bipolar current collector (10) and the sealed design of the bipolar current collector (10) and the inner layer of the outer package (20), the ion insulation between the multiple electrode assemblies (30) is realized, and the reliability of the high-output voltage battery and the effective output of the electric energy are realized.

Description

Technical Field

[0001] This application relates to the field of electrochemistry, and more specifically to an electrochemical device and an electronic device comprising the electrochemical device. Background Technology

[0002] Lithium-ion batteries possess numerous advantages, including high energy density, long cycle life, high nominal voltage, low self-discharge rate, small size, and light weight, making them widely used in consumer electronics. With the rapid development of electric vehicles (EVs) 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 overall performance.

[0003] In existing lithium-ion battery systems, limitations imposed by the electrochemical system, such as the limited voltage difference between the positive and negative electrode materials and the limited antioxidant capacity of the electrolyte, make it difficult for lithium-ion batteries to operate at voltages exceeding 5V. However, many practical applications require voltages exceeding 5V, such as electric vehicles (EVs), voltage transformers (PTs), and energy storage systems (ESS). Even in the mobile phone market, to meet demands such as fast charging, an increase in the open-circuit voltage of lithium-ion batteries is necessary.

[0004] Currently, some companies have proposed the concept of series-connected batteries to address this problem. Their solution involves directly connecting two lithium-ion batteries in series within the same packaging bag. However, this approach typically suffers from the following issues: Firstly, it lacks ion insulation between the two series-connected lithium-ion batteries. In this case, the increased battery voltage causes the electrolyte to decompose under high-voltage conditions, leading to battery failure. Simultaneously, internal short circuits can occur between the two lithium-ion batteries due to the voltage difference between their electrodes, also resulting in battery failure. Secondly, this series-connection method requires welding different polarity tabs of different lithium-ion batteries to achieve series connection. Poor tab welding can easily lead to increased internal resistance in the lithium-ion batteries, posing significant safety hazards and hindering power output. Furthermore, the design of multiple tab leads increases the risk of tab breakage, thereby reducing production yield. Therefore, developing a new series-connected lithium-ion battery structure that achieves high-output voltage battery reliability and efficient power output has become a pressing issue for those skilled in the art. Summary of the Invention

[0005] This application provides an electrochemical device and an electronic device including the electrochemical device to achieve high output voltage battery reliability and efficient power output.

[0006] The first aspect of this application provides an electrochemical device comprising a bipolar current collector and electrode assemblies, the electrode assemblies being located on both sides of the bipolar current collector, and the polarities of the two electrode assemblies being different near the outermost electrode of the bipolar current collector.

[0007] In some embodiments of this application, one side of the bipolar current collector is electrically connected to the outermost positive electrode of the adjacent electrode assembly, and the other side of the bipolar current collector is electrically connected to the outermost negative electrode of the adjacent electrode assembly.

[0008] In some embodiments of this application, the bipolar current collector is connected to the outer packaging, and independent sealed cavities are formed on both sides of the bipolar current collector, each sealed cavity containing an electrode assembly and an electrolyte.

[0009] In some embodiments of this application, the electrolyte includes an organic solvent.

[0010] In some embodiments of this application, the bipolar current collector further includes a sealing region that is sealed to the outer packaging. The sealing region contains a sealing material with a melting point of 100°C to 200°C.

[0011] In some embodiments of this application, the material of the bipolar current collector includes at least one of Cu-Al composite current collector, stainless steel foil current collector, or polymer conductive current collector;

[0012] The sealing material includes at least one of polypropylene (PP), polyester, or p-hydroxybenzaldehyde (PHBA).

[0013] In some embodiments of this application, the electronic resistivity in the Z direction of the bipolar current collector is 1×10⁻⁶. -11 Ω·cm to 30Ω·cm.

[0014] In some embodiments of this application, the permeability M of the bipolar current collector is ≤10. -3 g / (day·m 2 ·Pa·3mm).

[0015] In some embodiments of this application, the thickness of the bipolar current collector is from 2 μm to 100 μm.

[0016] In some embodiments of this application, at the connection between the bipolar current collector and the outer packaging, the sealing thickness T and the sealing width W satisfy T / W≤0.05, where T and W are in mm.

[0017] In some embodiments of this application, the electrochemical device has at least one of the following features:

[0018] a. The electrochemical device comprises 2 to 3 bipolar current collectors;

[0019] b. The melting point of the sealing material is 110°C to 180°C;

[0020] c. The electronic resistivity in the Z direction of the bipolar current collector is 1×10⁻⁶. -5 Ω·cm to 5Ω·cm;

[0021] d. The permeability M of the bipolar current collector is ≤10. -4 g / (day·m 2 ·Pa·3mm);

[0022] e. The thickness of the bipolar current collector is 5 μm to 50 μm;

[0023] f. The seal thickness T and the seal width W satisfy 0.02≤T / W≤0.04.

[0024] In some embodiments of this application, the electrochemical device has at least one of the following features:

[0025] 1) The melting point of the sealing material is 120°C to 160°C;

[0026] 2) The electronic resistivity in the Z direction of the bipolar current collector is 0.01 Ω·cm to 0.10 Ω·cm;

[0027] 3) The thickness of the bipolar current collector is 5 μm to 20 μm.

[0028] In some embodiments of this application, the structure of the electrode assembly includes at least one of a wound structure or a stacked structure.

[0029] The second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application.

[0030] The electrochemical device provided in this application, through the introduction of a bipolar current collector and a sealed design around the bipolar current collector and the inner layer of the outer packaging, divides the battery into multiple independent sealed cavities. This achieves ion insulation between multiple electrode components in a liquid-state series battery, avoiding safety hazards such as internal short circuits or high-voltage electrolyte decomposition, thereby improving the safety performance of the electrochemical device and ensuring effective power output from the high-voltage battery. Furthermore, by designing different electrode component structures and bipolar current collectors, internal series connection of the electrode components is achieved, eliminating the need for welding tabs between multiple electrode components. This simplifies the process, improves production efficiency, and avoids the defects caused by welding in series connection of the electrochemical device, greatly improving the manufacturing reliability of the electrochemical device and facilitating power output. In addition, the reduction in the number of tabs effectively increases the energy density of the high-output-voltage battery. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of this application and the prior art, the drawings used in the embodiments and the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0032] Figure 1 This is a schematic diagram of the structure of an electrochemical device according to one embodiment of this application.

[0033] Figure 2 for Figure 1 A schematic diagram of the decomposed structure of an electrochemical device.

[0034] Figure 3 This is a schematic cross-sectional view of a series electrode assembly in one embodiment of this application.

[0035] Figure 4 This is a front view of an electrochemical device according to one embodiment of this application.

[0036] Figure 5 This is a top view of an electrochemical device according to one embodiment of this application. Detailed Implementation

[0037] 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. All other embodiments obtained based on the embodiments in this application are within the scope of protection of this application.

[0038] The electrochemical device described in this application is not particularly limited and can be any electrochemical device capable of using this application, such as lithium-ion batteries, sodium-ion batteries, magnesium-ion batteries, supercapacitors, etc. For ease of description, a lithium-ion battery is used as an example below, but this does not mean that the electrochemical device of this application is limited to lithium-ion batteries.

[0039] The first aspect of this application provides an electrochemical device comprising a bipolar current collector and an electrode assembly. The electrode assembly is located on both sides of the bipolar current collector, and the polarities of the outermost electrode of each electrode assembly adjacent to the bipolar current collector are different. One side of the bipolar current collector is electrically connected to the outermost positive electrode of the adjacent electrode assembly, and the other side of the bipolar current collector is electrically connected to the outermost negative electrode of the adjacent electrode assembly.

[0040] Figure 2An embodiment of this application is shown, wherein electrode assemblies 30 are located on both sides of a bipolar current collector 10, and the polarities of the two electrode assemblies 30 near the outermost electrode of the bipolar current collector 10 are different. One side of the bipolar current collector 10 is electrically connected to the outermost positive electrode of the adjacent electrode assembly 30, and the other side of the bipolar current collector 10 is electrically connected to the outermost negative electrode of the adjacent electrode assembly 30.

[0041] In this application, the aforementioned "electrical connection" includes the current collector of the positive electrode or negative electrode being connected to the circuit by physically contacting one side of the bipolar current collector or by physically contacting the conductive sheet with one side of the bipolar current collector, that is, there is no electrode active material on the surface of the electrode electrode that is electrically connected to the bipolar current collector.

[0042] In some embodiments of this application, the electrochemical device includes a number of bipolar current collectors, the specific number of which is not limited. Those skilled in the art can select the appropriate number based on actual needs, as long as the purpose of this application is achieved. For example, it may include 2 to 3 bipolar current collectors. Electrode assemblies are provided on both sides of the bipolar current collectors.

[0043] In some embodiments of this application, the bipolar current collector is sealed to the outer packaging, and independent sealed cavities are formed on both sides of the bipolar current collector, with an electrode assembly and electrolyte encapsulated in each sealed cavity. Figure 1 This invention illustrates one embodiment of the present application, wherein the bipolar current collector 10 is sealed to the outer packaging 20, and independent sealed cavities are formed on both sides of the bipolar current collector 10, each sealed cavity containing an electrode assembly 30 and an electrolyte.

[0044] In this application, the aforementioned “outer packaging” generally refers to an aluminum-plastic film, which comprises a nylon layer, an aluminum foil layer, and a PP layer. The thickness of the aluminum-plastic film can be from 60μm to 500μm, preferably from 60μm to 300μm, and more preferably from 60μm to 200μm.

[0045] In some embodiments of this application, the electrode assembly may include a separator, a positive electrode, and a negative electrode. The separator separates the positive and negative electrodes, preventing short circuits within the electrochemical device and allowing electrolyte ions to pass freely, thus completing the electrochemical charge-discharge process. In this application, the number of separators, positive and negative electrodes is not particularly limited, as long as the purpose of this application is achieved.

[0046] In some embodiments of this application, the diaphragm is not particularly limited, and any diaphragm known in the art can be used as long as it can achieve the purpose of this application. For example, at least one of the following: polyethylene (PE), polypropylene (PP) based polyolefin (PO) diaphragms, polyester films (e.g., polyethylene terephthalate (PET) films), cellulose films, polyimide films (PI), polyamide films (PA), spandex or aramid films, woven films, nonwoven films (non-woven fabrics), microporous films, composite films, diaphragm paper, rolled films, spun films, etc.

[0047] 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 be selected from at least one of 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 provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic materials.

[0048] 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).

[0049] In some embodiments of this application, the positive electrode sheet is not particularly limited, as long as it can achieve the purpose of this application. For example, the positive electrode sheet typically comprises a positive current collector and a positive active material. The positive current collector is not particularly limited and can be any positive current collector known in the art, such as aluminum foil, aluminum alloy foil, or composite current collectors. The positive active material is not particularly limited and can be any positive active material known in the art, for example, it may include at least one of NCM811, NCM622, NCM523, NCM111, NCA, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate.

[0050] Optionally, the positive electrode may further include a conductive layer located between the positive current collector and the positive active material. The composition of the conductive layer is not particularly limited and can be a commonly used conductive layer in the art. For example, the conductive layer may include a conductive agent and a binder.

[0051] 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. The negative current collector is not particularly limited and can be any negative current collector known in the art, such as copper foil, copper alloy foil, or composite current collector. The negative active material is not particularly limited and can be any negative active material known in the art. For example, it can include at least one of graphite, hard carbon, soft carbon, silicon, silicon carbide, or silicon oxide.

[0052] Optionally, the negative electrode sheet may further include a conductive layer located between the negative electrode current collector and the negative electrode active material. The composition of the conductive layer is not particularly limited and can be a commonly used conductive layer in the art. For example, the conductive layer may include a conductive agent and a binder.

[0053] 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. For example, conductive carbon black (Super P) can be selected as the conductive agent. 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). For example, styrene-butadiene rubber (SBR) can be selected as the adhesive.

[0054] In this application, there are no particular limitations on the electrolyte; any electrolyte known to those skilled in the art can be used. For example, the electrolyte is selected from any of the gel, solid, and liquid states. For instance, the liquid electrolyte includes lithium salts and non-aqueous solvents.

[0055] There are no particular limitations on the lithium salt used; 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 of 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.

[0056] The non-aqueous solvent is not particularly limited, as long as it can achieve the purpose of this application. For example, the non-aqueous solvent may include at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, nitrile compounds, or other organic solvents.

[0057] 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, or trifluoromethylethylene carbonate.

[0058] In some embodiments of this application, the bipolar current collector is sealed to the outer packaging, and adjacent electrode components and electrolytes are completely separated by the bipolar current collector, thus each is in an independent sealed cavity, achieving ion isolation between different cavities. Both sides of the same bipolar current collector are electrically connected to adjacent electrode components, wherein one side of the bipolar current collector is electrically connected to the outermost positive electrode of its adjacent electrode component, and the side of the positive electrode connected to this connection has no electrode active material; the other side of the bipolar current collector is electrically connected to the outermost negative electrode of its adjacent electrode component, and the side of the negative electrode connected to this connection also has no electrode active material.

[0059] Figure 3 This is a schematic cross-sectional view of a series electrode assembly in one embodiment of this application, as shown below. Figure 3 As shown, the bipolar current collector 10 has a first electrode assembly 31 on its lower side and a second electrode assembly 32 on its upper side. The two electrode assemblies include a positive current collector 61, a positive active material 71, a negative current collector 62, a negative active material 72, and a separator 80. The bipolar current collector 10 is placed on the first electrode assembly 31, and one side of it is electrically connected to the uppermost negative current collector 62 of the first electrode assembly 31. The side of the negative current collector 62 connected to the bipolar current collector 10 does not have a negative active material 72. The second electrode assembly 32 is placed on the bipolar current collector 10, and its lowermost positive current collector 61 is electrically connected to the other side of the bipolar current collector 10. The side of the positive current collector 61 connected to the bipolar current collector 10 does not have a positive active material 71.

[0060] The aforementioned internal series structure design avoids the need to lead out and weld multiple electrode components to achieve series connection. This simplifies the process, improves production efficiency, solves the problem of poor electrode component series connection caused by welding, greatly improves the manufacturing reliability of the battery, is beneficial to the output of electrical energy, and the reduction in the number of electrode tabs effectively improves the energy density of high output voltage batteries.

[0061] In some embodiments of this application, the bipolar current collector further includes a sealing region that is sealed to the outer packaging. The sealing region also includes a sealing material, which includes at least one of polypropylene (PP), polyester, or p-hydroxybenzaldehyde (PHBA). The melting point of the sealing material is 100 to 200°C, preferably 110 to 180°C, and more preferably 120 to 160°C.

[0062] The aforementioned outer contour sealing area is sealed to the outer packaging. Specifically, it is a composite fusible sealing material around the bipolar current collector, which is heat-sealed to the inner layer of the outer packaging at a temperature of 100 to 200°C. This creates independent sealed cavities within the electrochemical device, achieving ion insulation between multiple electrode components in a liquid series battery. This avoids safety hazards such as internal short circuits or high-voltage decomposition of the electrolyte, and improves the safety performance of the electrochemical device.

[0063] In some embodiments of this application, the material of the bipolar current collector includes at least one of Cu-Al composite current collector, stainless steel foil current collector, or polymer conductive current collector. The bipolar current collector exhibits good conductivity in the thickness direction (hereinafter referred to as the Z-direction); for example, the electronic resistivity of the bipolar current collector in the Z-direction is 1 × 10⁻⁶. -11 Up to 30 Ω·cm, preferably 1×10 -5 Up to 5 Ω·cm, more preferably 0.01 to 0.10 Ω·cm.

[0064] The polymer conductive current collector comprises a composite material of polymeric material and conductive material. This application does not impose any particular limitation on the polymer conductive current collector, as long as it achieves the purpose of this invention. For example, one polymer conductive current collector includes a polymer matrix and a conductive agent, wherein the conductive agent is a one-dimensional or two-dimensional conductive material, and the conductive material is distributed in the polymer matrix at an angle of 0° to 30° with respect to the thickness direction of the polymer matrix. Another polymer conductive current collector includes conductive layers respectively disposed on two surfaces of a polymer matrix, and the two conductive layers are electrically connected. Yet another polymer conductive current collector includes a porous polymer matrix, with the conductive material located in the pores of the porous polymer matrix, enabling electronic conduction between the two surfaces of the polymer conductive current collector.

[0065] This application does not impose any particular limitation on the preparation method of the polymer conductive current collector, as long as it can achieve the purpose of this invention. For example, it can be obtained by the following method: spraying polymer material onto a stainless steel substrate to obtain a polymer material layer, heating the polymer material layer to soften it, then implanting a one-dimensional or two-dimensional conductive material, then spraying polymer material again to form a polymer material film, overheating and rolling the obtained polymer material film, using a doctor blade to remove the polymer material film from the surface of the stainless steel substrate, and winding it up to obtain the polymer conductive current collector.

[0066] The polymer film comprises at least one of the following: polyethylene terephthalate (PET), 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 resin, vinylon, polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene ether, polysulfone, or derivatives thereof.

[0067] The conductive material includes at least one of carbon materials or metallic materials.

[0068] The carbon material may include at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes (MWCNTs), conductive carbon fibers, conductive carbon black, fullerenes, conductive graphite, or graphene.

[0069] The metallic material may include at least one of Cu, Al, Ni, Ti, Ag, Au, Pt, or stainless steel and their alloys.

[0070] The polymer conductive current collector can also be formed by other methods, such as dispersing conductive agent particles in a polymer material.

[0071] In some embodiments of this application, the permeability M of the bipolar current collector is ≤10. -3 g / (day·m 2 ·Pa·3mm), preferably M≤10 -4 g / (day·m 2 •Pa·3mm), thereby avoiding excessive water content in lithium-ion batteries during their lifespan after packaging.

[0072] In some embodiments of this application, the thickness of the bipolar current collector is 2 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 5 to 20 μm. When the thickness of the bipolar current collector is less than 2 μm, the mechanical strength of the bipolar current collector may be insufficient; when its thickness is greater than 100 μm, the mass of the introduced inactive material increases, reducing the energy density of the lithium-ion battery.

[0073] In some embodiments of this application, at the connection between the bipolar current collector and the outer packaging, the sealing thickness T and the sealing width W satisfy T / W≤0.05, preferably 0.02≤T / W≤0.04.

[0074] In this application, "seal" refers to the sealed area of ​​the outer packaging. For example, Figure 4 This is a front view of one embodiment of the present application, where the thickness T of the sealing area 40 of the outer packaging is the seal thickness T; Figure 5 This is a top view of one embodiment of the present application. The width W of the sealing area 40 of the outer packaging is the sealing width W. When T / W ≤ 0.05, excellent packaging reliability can be achieved; otherwise, the packaging effect will be reduced due to unsuitable sealing thickness and sealing width. In this application, there are no particular limitations on the sealing width and sealing thickness, as long as the ratio meets the requirements. Those skilled in the art can select according to the specific battery size; for example, the sealing width is preferably 1mm to 7mm.

[0075] In this application, the type of electrode assembly is not particularly limited, and may include at least one of a wound structure or a stacked structure.

[0076] In some embodiments of this application, the structure of the electrode assembly includes a wound structure, and the electrode assembly leads out at least one positive electrode tab and one negative electrode tab from the positive electrode sheet and the negative electrode sheet, respectively.

[0077] In some embodiments of this application, the electrode assembly has a stacked structure and includes multiple tabs. A positive tab and a negative tab can be drawn from each layer of positive and negative electrode sheets, and finally, a stacked electrode assembly includes multiple sets of positive and negative tabs. Then, metal sheets are drawn out through the adapter tabs.

[0078] In this application, the welding method for the electrode tabs is not particularly limited, as long as it achieves the purpose of this application. For example, at least one of laser welding, ultrasonic welding, or resistance welding.

[0079] In some embodiments of this application, the bipolar current collector may or may not have tabs. When the bipolar current collector has tabs, it can be used to monitor the voltage of a single electrode assembly.

[0080] In this application, the direction in which the electrode tabs are led out is not particularly limited, as long as it achieves the purpose of this application. For example, the direction in which the electrode tabs are led out can be in the same direction or in opposite directions.

[0081] A second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application.

[0082] The electronic devices described in this application include general electronic devices in the art, such as laptops, mobile phones, electric motorcycles, electric cars, electric toys, energy storage systems, drones, power tools, robotic vacuum cleaners, tablets, power grids, electric boats, etc.

[0083] The terminology used in this field is generally the terminology commonly used by those skilled in the art. If there is any inconsistency with the commonly used terminology, the terminology in this application shall prevail.

[0084] Test method:

[0085] Output voltage test method:

[0086] When testing the output voltage of 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 1 hour, the open circuit voltage was measured.

[0087] When testing the output voltage of Comparative Examples 2-3 and Examples 1-25, the test temperature was 25±3℃. The lithium-ion battery was charged to 8.4V at a constant current of 0.5C, and then charged to 0.05C at a constant voltage of 8.4V. After standing for 1 hour, the open circuit voltage was measured.

[0088] Method for testing the discharge capacity / initial discharge capacity η after 50 charge-discharge cycles:

[0089] 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 / initial discharge capacity retention rate after 50 charge-discharge cycles is: η(%) = Q50D / Q1D × 100%.

[0090] In tests of Comparative Examples 2-3 and Examples 1-25, 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%.

[0091] Method for measuring the electronic resistivity of bipolar current collectors in the Z-direction:

[0092] Take a 10cm × 10cm bipolar current collector sample. Clamp the positive and negative sides of the bipolar current collector between two metal clamps of fixed area, where the area of ​​the clamps is the same as that of the bipolar current collector. Apply a voltage of 0.1V between the two clamps and measure the current value between them. Then calculate the resistance value R. Finally, calculate the electronic resistivity in the Z direction using the following formula: ρ = RS / L. In the formula, R represents the resistance value, S represents the area of ​​the bipolar current collector, and L represents the thickness of the bipolar current collector.

[0093] Test method for permeability of bipolar current collectors:

[0094] A bipolar current collector of a certain thickness is placed on a clamping mechanism, and its edges are pressed tightly with rubber pressure. A fixed temperature and humidity environment is created on one side (A) of the device, while a water vapor mass spectrometry probe is placed on the other side (B). Gas exchange between the two sides is only possible through the bipolar current collector. The testing process begins by fixing the bipolar current collector and evacuating cavity B to remove internal water vapor. The mass spectrometer is then turned on, continuously receiving water vapor permeating through cavity A and converting it into an electrical signal output. This test is continued for 24 hours or longer, yielding the total water permeation m during this period. The water vapor permeability (g / (day·m)) is obtained by dividing the total permeation m by the time, water vapor partial pressure, permeation area, and thickness of the bipolar current collector. 2 ·Pa·3mm).

[0095] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "%" refers to weight.

[0096] Example 1

[0097] <Preparation of Negative Electrode Sheets>

[0098] A mixture of graphite (anode active material), Super P conductive carbon black, and SBR (styrene-butadiene rubber) at a weight ratio of 96:1.5:2.5 was prepared, and deionized water was added as a solvent to form a slurry with a solid content of 70%, which was then stirred evenly. The slurry was uniformly coated onto one surface of an 8 μm thick copper foil current collector and dried at 110°C to obtain a single-sided coated negative electrode sheet with a coating thickness of 130 μm. This completes the single-sided coating of the negative electrode sheet. The above steps were then repeated on the other surface of the negative electrode sheet to obtain a double-sided coated negative electrode sheet. After coating, the electrode sheet was cut into 41 mm × 61 mm dimensions for later use.

[0099] <Preparation of the positive electrode>

[0100] 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%, and the mixture was stirred evenly. The slurry was uniformly coated onto one surface of a 10 μm thick aluminum foil used as a positive electrode current collector, and dried at 90°C to obtain a positive electrode sheet with a coating thickness of 110 μm. This completes the single-sided coating of the positive electrode sheet. The same steps were then repeated on the other surface of the positive electrode sheet to obtain a double-sided coated positive electrode sheet. After coating, the electrode sheets were cut into 38 mm × 58 mm dimensions for later use.

[0101] <Preparation of Electrolyte>

[0102] 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.

[0103] <Preparation of Electrode Components>

[0104] A 15μm PP diaphragm is placed between the positive and negative electrode sheets prepared above. After stacking, the four corners are fixed to form a stacked electrode assembly. The number of layers of the positive and negative electrode sheets are 13 and 14, respectively. The two outermost electrodes of the stacked cell are single-sided electrodes, and the rest are double-sided electrodes.

[0105] <Preparation of Polymer Conductive Current Collectors>

[0106] A PET layer is obtained by spraying PET material onto a stainless steel substrate. The PET layer is then heated to soften it, and conductive material MWCNT is implanted. Subsequently, PET material is sprayed again to form a PET film. The PET film is then heated and rolled to obtain a PET film. The PET film is then removed from the surface of the stainless steel substrate using a doctor blade and wound up to obtain a polymer conductive current collector composed of PET and MWCNT.

[0107] <Preparation of Lithium-ion Batteries>

[0108] A polymer conductive current collector composed of PET and MWCNT composites was selected as the bipolar current collector. The polymer conductive current collector has a thickness of 100 μm, an electronic resistivity in the Z direction of 0.06 Ω·cm, and a water permeability of 5 × 10⁻⁶. -5 g / (day·m 2 The bipolar current collector has a sealing layer at its perimeter (·Pa·3mm), where T / W is 0.025.

[0109] A piece of outer packaging (aluminum-plastic film with a thickness of 150μm) with the dented surface is placed in the assembly fixture with the dented surface facing upwards. An electrode assembly (hereinafter referred to as electrode assembly A) is placed in the dent, with the uppermost layer being the negative electrode sheet, the upper surface of which has no negative electrode active material. The positive electrode tab of electrode assembly A is then led out.

[0110] Then, the bipolar current collector is placed on electrode assembly A, so that it contacts the negative electrode plate of electrode assembly A, and external force is applied to press it down.

[0111] An electrode assembly (hereinafter referred to as electrode assembly B) is placed on a bipolar current collector, with its positive electrode plate in contact with the bipolar current collector. The lower surface of the positive electrode plate is not coated with positive active material, and external force is applied to press it firmly. Then, another outer packaging (a 150μm thick aluminum-plastic film) is placed on top of electrode assembly B with the pitted side facing down. The negative electrode tab of electrode assembly B is led out, leaving the liquid injection port side open. The remaining positions of the outer packaging are then heat-sealed to obtain the assembled electrode assembly, in which two independent cavities are formed on both sides of the bipolar current collector. The heat-sealing temperature is 180℃, and the heat-sealing pressure is 0.5MPa.

[0112] Electrolyte was injected separately into the two cavities of the assembled electrode assembly, and then the cavities were sealed.

[0113] The charging and discharging process only requires connecting the positive electrode tab of electrode assembly A to the negative electrode tab of electrode assembly B.

[0114] Example 2

[0115] Except for the fact that the thickness of the bipolar current collector is 15 μm as shown in Table 1, everything else is the same as in Example 1.

[0116] Example 3

[0117] Except for the fact that the thickness of the bipolar current collector is 5 μm as shown in Table 1, everything else is the same as in Example 1.

[0118] Example 4

[0119] In addition to using a Cu-Al composite current collector as shown in Table 1, the electronic resistivity of this bipolar current collector in the Z direction is 5.2 × 10⁻⁶. -10 Except for Ω·cm, the rest is the same as in Example 2.

[0120] Example 5

[0121] Except for the stainless steel foil current collector used as shown in Table 1, the electronic resistivity of this bipolar current collector in the Z direction is 9.3 × 10⁻⁶. -10 Except for Ω·cm, the rest is the same as in Example 2.

[0122] Example 6

[0123] Except for the electronic resistivity of the bipolar current collector in the Z direction being 30 Ω·cm as shown in Table 1, the rest is the same as in Example 2.

[0124] Example 7

[0125] Except for the bipolar current collector, whose electronic resistivity in the Z direction is 1×10⁻⁶ as shown in Table 1. -4 Except for Ω·cm, the rest is the same as in Example 2.

[0126] Example 8

[0127] In addition to the bipolar current collector having a permeability rate of 10 as shown in Table 1, -3 g / (day·m 2 Except for Pa·3mm), the rest is the same as in Example 2.

[0128] Example 9

[0129] In addition to the bipolar current collector having a permeability rate of 10 as shown in Table 1, -7 g / (day·m 2 Except for Pa·3mm), the rest is the same as in Example 2.

[0130] Example 10

[0131] Except that the sealing material is p-hydroxybenzaldehyde (PHBA) as shown in Table 1 and the melting point of the sealing material is 115°C, everything else is the same as in Example 2.

[0132] Example 11

[0133] Except that the melting point of the sealing material is 100°C as shown in Table 1, everything else is the same as in Example 2.

[0134] Example 12

[0135] Except that the melting point of the sealing material is 200°C as shown in Table 1, everything else is the same as in Example 2.

[0136] Example 13

[0137] Except for the aluminum-plastic film thickness of 60 μm as shown in Table 1, everything else is the same as in Example 2.

[0138] Example 14

[0139] Except for the aluminum-plastic film thickness of 500 μm as shown in Table 1, everything else is the same as in Example 2.

[0140] Example 15

[0141] Except that T / W is 0.005 as shown in Table 1, everything else is the same as in Example 2.

[0142] Example 16

[0143] Except that T / W is 0.05 as shown in Table 1, everything else is the same as in Example 2.

[0144] Example 17

[0145] Except for the preparation process of the lithium-ion battery, which is different from that in Example 1, everything else is the same as in Example 1.

[0146] <Preparation of Lithium-ion Batteries>

[0147] Except for bringing out the tabs of the bipolar current collector, everything else is the same as in Example 1.

[0148] Example 18

[0149] Except for the preparation process of the lithium-ion battery, which is different from that in Example 1, everything else is the same as in Example 1.

[0150] <Preparation of Lithium-ion Batteries>

[0151] A polymer conductive current collector composed of PET and MWCNT composites was selected as the bipolar current collector. The polymer conductive current collector has a thickness of 15 μm, an electronic resistivity in the Z direction of 0.06 Ω·cm, and a water permeability of 5 × 10⁻⁶. -5 g / (day·m 2 The bipolar current collector has a sealing layer at its perimeter (·Pa·3mm), where T / W is 0.025, and the tabs of the bipolar current collector are led out.

[0152] A piece of outer packaging (aluminum-plastic film with a thickness of 150μm), formed by punching a groove, is placed in the assembly fixture with the groove facing upwards. Then, an electrode assembly (hereinafter referred to as electrode assembly A) is placed in the groove, with the top layer being the negative electrode sheet, the upper surface of which has no negative electrode active material. The multiple positive electrode tabs of electrode assembly A are welded together into a single positive electrode tab using a transfer welding method, and this positive electrode tab is then led out.

[0153] Then, the bipolar current collector is placed on electrode assembly A, so that it contacts the negative electrode plate of electrode assembly A, and external force is applied to press it down.

[0154] An electrode assembly (hereinafter referred to as electrode assembly B) is placed on a bipolar current collector, with its positive electrode plate in contact with the bipolar current collector. The lower surface of the positive electrode plate has no positive active material, and external force is applied to press it firmly. Then, another outer packaging piece (a 150μm thick aluminum-plastic film) is placed on top of electrode assembly B with the pitted side facing down. Multiple negative electrode tabs of electrode assembly B are welded together to form a single negative electrode tab. This negative electrode tab is then led out, leaving the injection port side exposed. The remaining positions of the outer packaging are then heat-sealed to obtain the assembled electrode assembly, in which two independent cavities are formed on either side of the bipolar current collector. The heat-sealing temperature is 180℃, and the heat-sealing pressure is 0.5MPa.

[0155] Electrolyte is injected separately into the two cavities of the assembled electrode assembly, and then the cavities are sealed. The charging and discharging process only requires connecting the positive electrode tab of electrode assembly A to the negative electrode tab of electrode assembly B.

[0156] Example 19

[0157] Except for the preparation process of the lithium-ion battery, which is different from that in Example 1, everything else is the same as in Example 1.

[0158] <Preparation of Lithium-ion Batteries>

[0159] A polymer conductive current collector composed of PET and MWCNT composites was selected as the bipolar current collector. The polymer conductive current collector has a thickness of 15 μm, an electronic resistivity in the Z direction of 0.06 Ω·cm, and a water permeability of 5 × 10⁻⁶. -5 g / (day·m 2 The bipolar current collector has a sealing layer at its perimeter (·Pa·3mm), where T / W is 0.025, and the tabs of the bipolar current collector are led out.

[0160] A piece of outer packaging (aluminum-plastic film with a thickness of 200μm) with the dented surface is placed in the assembly fixture with the dented surface facing upwards. Then, an electrode assembly (hereinafter referred to as electrode assembly A) is placed in the dent, with the uppermost layer being the negative electrode sheet, the upper surface of which has no negative electrode active material. The positive electrode tab of electrode assembly A is then led out.

[0161] Then, a bipolar current collector (hereinafter referred to as bipolar current collector A) is placed on electrode assembly A, so that it contacts the negative electrode plate of electrode assembly A, and external force is applied to press it tightly.

[0162] An electrode assembly (hereinafter referred to as electrode assembly C) is placed on a bipolar current collector A, so that its positive electrode plate is in contact with the bipolar current collector A. The lower surface of the positive electrode plate has no positive active material, and an external force is applied to press it down.

[0163] Then, a bipolar current collector (hereinafter referred to as bipolar current collector B) is placed on the electrode assembly C, so that the bipolar current collector B comes into contact with the negative electrode of the electrode assembly C, and an external force is applied to press it down. There is no negative electrode active material on the upper surface of the negative electrode.

[0164] An electrode assembly (hereinafter referred to as electrode assembly B) is placed on a bipolar current collector B, with its positive electrode plate in contact with the bipolar current collector B. The lower surface of the positive electrode plate has no positive active material, and external force is applied to press it firmly. Then, another outer packaging piece (a 200μm thick aluminum-plastic film) is placed on top of electrode assembly B with the pitted side facing down. The negative electrode tab of electrode assembly B is led out, leaving the injection port side exposed. The remaining positions of the outer packaging are then heat-sealed to obtain the assembled electrode assembly, in which three independent cavities are formed on both sides of the bipolar current collectors A and B. The heat-sealing temperature is 180℃, and the heat-sealing pressure is 0.5MPa.

[0165] Electrolyte was injected separately into the three cavities of the assembled electrode assembly, and then the cavities were sealed.

[0166] The charging and discharging process only requires connecting the positive electrode tab of electrode assembly A to the negative electrode tab of electrode assembly B.

[0167] Example 20

[0168] Except for the opposite lead-out directions of the positive and negative electrodes, the rest is the same as in Example 2.

[0169] Example 21

[0170] Except for the electronic resistivity of the bipolar current collector in the Z direction being 4 Ω·cm as shown in Table 1, the rest is the same as in Example 2.

[0171] Example 22

[0172] The preparation of the negative electrode, positive electrode, electrolyte, and electrode assembly are the same as in Example 1.

[0173] <Preparation of Polymer Conductive Current Collectors>

[0174] Except for the fact that the conductive material is graphene, everything else is the same as in Example 2.

[0175] <Preparation of Lithium-ion Batteries>

[0176] Except for the use of a polymer conductive current collector composed of PET and graphene as a bipolar current collector, which has an electronic resistivity of 0.1 Ω·cm in the Z direction as shown in Table 1, the rest is the same as in Example 2.

[0177] Example 23

[0178] Except that the sealing material is polyester as shown in Table 1, everything else is the same as in Example 2.

[0179] Example 24

[0180] <Preparation of Negative Electrode Sheets>

[0181] Except for cutting the negative electrode sheet into 465mm×92mm dimensions for later use, the rest is the same as in Example 1.

[0182] <Preparation of the positive electrode>

[0183] Except for cutting the positive electrode sheet into 480mm×90mm dimensions for later use, the rest is the same as in Example 1.

[0184] <Preparation of Electrolyte>

[0185] Same as Example 1.

[0186] <Preparation of Electrode Components>

[0187] The positive and negative electrode sheets prepared above, along with a 15μm PP separator, are stacked in the order of positive electrode sheet, separator, and negative electrode sheet, with the separator positioned between the positive and negative electrode sheets to provide isolation. The resulting coiled electrode assembly is then obtained.

[0188] <Preparation of Polymer Conductive Current Collectors>

[0189] Same as Example 1.

[0190] <Preparation of Lithium-ion Batteries>

[0191] Except for the electrode assembly being the aforementioned wound electrode assembly, everything else is the same as in Example 2.

[0192] Example 25

[0193] The preparation of the negative electrode, positive electrode, electrolyte, electrode assembly, and polymer conductive current collector are the same as in Example 24.

[0194] <Preparation of Lithium-ion Batteries>

[0195] Except for the electrode assembly being the aforementioned wound electrode assembly, everything else is the same as in Example 17.

[0196] The data and test results for Examples 1-25 are shown in Table 1.

[0197] Comparative Example 1

[0198] The preparation of the negative electrode, positive electrode, electrolyte, and electrode assembly are the same as in Example 1.

[0199] <Preparation of Lithium-ion Batteries>

[0200] A piece of outer packaging (150μm thick aluminum-plastic film) with the perforated surface is placed in the assembly fixture with the perforated surface facing upwards. An electrode assembly (hereinafter referred to as electrode assembly A) is then placed in the perforation. Next, another piece of outer packaging (150μm thick aluminum-plastic film) with the perforated surface facing downwards is placed over electrode assembly A. The positive and negative electrode tabs of electrode assembly A are led out, leaving the injection port side exposed. The remaining positions of the outer packaging are then heat-sealed to obtain the assembled electrode assembly. The heat-sealing temperature is 180℃, and the heat-sealing pressure is 0.5MPa.

[0201] The charging and discharging process only requires connecting the positive and negative electrodes of electrode assembly A.

[0202] Comparative Example 2

[0203] The preparation of the negative electrode, positive electrode, electrolyte, and electrode assembly are the same as in Example 1.

[0204] <Preparation of Lithium-ion Batteries>

[0205] A piece of outer packaging (aluminum-plastic film with a thickness of 150μm) with the dented surface is placed in the assembly fixture with the dented surface facing upwards. An electrode assembly (hereinafter referred to as electrode assembly A) is placed in the dent, with the uppermost layer being the negative electrode sheet, the upper surface of which has no negative electrode active material. The positive electrode tab of electrode assembly A is then led out.

[0206] An electrode assembly (hereinafter referred to as electrode assembly B) is placed on electrode assembly A, with the positive electrode of electrode assembly B in contact with the negative electrode of electrode assembly A. The lower surface of the positive electrode of electrode assembly B has no positive active material, and external force is applied to press it firmly. Then, another outer packaging sheet (a 150μm thick aluminum-plastic film) is placed on top of electrode assembly B with the concave side facing down. The negative electrode tab of electrode assembly B is led out, leaving the injection port side exposed. The remaining positions of the outer packaging are then heat-sealed to obtain the assembled electrode assembly. The heat-sealing temperature is 180℃, and the heat-sealing pressure is 0.5MPa.

[0207] Electrolyte is injected into the assembled electrode assembly, and then the assembly is sealed.

[0208] The charging and discharging process only requires connecting the positive electrode tab of electrode assembly A to the negative electrode tab of electrode assembly B.

[0209] Comparative Example 3

[0210] The preparation of the negative electrode, positive electrode, electrolyte, and electrode assembly are the same as in Example 1.

[0211] <Preparation of Lithium-ion Batteries>

[0212] A piece of outer packaging (150μm thick aluminum-plastic film) with the dented surface is placed in the assembly fixture, with the dented surface facing upwards. Then, an electrode assembly (hereinafter referred to as electrode assembly A) is placed in the dent, with the diaphragm as the top layer. The positive and negative electrodes of electrode assembly A are then led out.

[0213] An electrode assembly (hereinafter referred to as electrode assembly B) is placed on electrode assembly A, with the diaphragm of electrode assembly B in contact with the diaphragm side of electrode assembly A. The positive electrode plate is located above the diaphragm, and external force is applied to press it firmly. Then, another outer packaging piece (a 150μm thick aluminum-plastic film) is placed on top of electrode assembly B with the pitted side facing down. The positive and negative electrode tabs of electrode assembly B are led out, leaving the liquid injection port side exposed. The remaining positions of the outer packaging are then heat-sealed to obtain the assembled electrode assembly. The heat-sealing temperature is 180℃, and the heat-sealing pressure is 0.5MPa.

[0214] Electrolyte is injected into the assembled electrode assembly, and then the assembly is sealed.

[0215] The negative electrode tab of electrode assembly A is laser welded to the positive electrode tab of electrode assembly B, so that electrode assemblies A and B are connected in series.

[0216] The charging and discharging process only requires connecting the positive electrode tab of electrode assembly A to the negative electrode tab of electrode assembly B.

[0217] The data and test results for Comparative Examples 1-3 are shown in Table 1.

[0218] Table 1. Preparation parameters and test results for each embodiment and comparative example.

[0219]

[0220]

[0221]

[0222] As can be seen from Examples 1-25 and Comparative Examples 1-3 of this application, the electrochemical device connected in series with the bipolar current collector (e.g., Examples 1-25) has a higher output voltage, and the discharge capacity / initial discharge capacity of the electrochemical device in Examples 1-25 of this application is significantly improved after 50 charge-discharge cycles.

[0223] As can be seen, the electrochemical device provided in this application, through the bipolar current collector connecting electrode components in series and the bipolar current collector being sealed around the outer packaging, divides the battery into multiple independent sealed cavities. This achieves ion isolation between the multiple electrode components in a liquid-state series battery, avoiding safety hazards such as internal short circuits or high-voltage electrolyte decomposition, thereby improving the safety performance of the electrochemical device and ensuring effective power output from the high-voltage battery. Furthermore, the internal series connection of the electrode components is achieved through a wound or stacked structure and the design of the bipolar current collector, eliminating the need for welding the tabs between multiple electrode components. This simplifies the process, improves production efficiency, and avoids the problem of poor series connection caused by welding, greatly improving the manufacturing reliability of the electrochemical device and facilitating power output. In addition, the reduction in the number of tabs effectively increases the energy density of the high-output-voltage battery to a certain extent.

[0224] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrochemical device comprising a bipolar current collector and electrode assemblies, the electrode assemblies being located on both sides of the bipolar current collector, and the polarities of the two electrode assemblies being different near the outermost electrode of the bipolar current collector; One side of the bipolar current collector is electrically connected to the outermost positive electrode of the adjacent electrode assembly, and the other side of the bipolar current collector is electrically connected to the outermost negative electrode of the adjacent electrode assembly. The side of the positive electrode where the electrical connection is made has no active electrode material, and the side of the negative electrode where the electrical connection is made also has no active electrode material. The electrical connection refers to the current collector of either the positive or negative electrode being physically connected to one side of the bipolar current collector to achieve a circuit connection. The bipolar current collector is connected to the outer packaging, and independent sealed cavities are formed on both sides of the bipolar current collector. Each sealed cavity contains an electrode assembly and an electrolyte.

2. The electrochemical device according to claim 1, wherein, The electrolyte includes an organic solvent.

3. The electrochemical device according to claim 1, wherein, The bipolar current collector also includes a sealing region, which is sealed to the outer packaging. The sealing region contains a sealing material with a melting point of 100°C to 200°C.

4. The electrochemical device according to claim 3, wherein, The bipolar current collector includes at least one of Cu-Al composite current collector, stainless steel foil current collector, or polymer conductive current collector; The sealing material includes at least one of polypropylene, polyester, or p-hydroxybenzaldehyde.

5. The electrochemical device according to claim 1, wherein, The electronic resistivity in the Z direction of the bipolar current collector is 1×10⁻⁶. -11 Ω·cm to 30Ω·cm.

6. The electrochemical device according to claim 1, wherein, The permeability M of the bipolar current collector is ≤10. -3 g / (day·m 2 ·Pa·3mm).

7. The electrochemical device according to claim 1, wherein, The thickness of the bipolar current collector is 2 mm to 100 mm.

8. The electrochemical device according to claim 1, wherein, At the connection between the bipolar current collector and the outer packaging, the sealing thickness T and sealing width W satisfy T / W≤0.05, where T and W are in mm.

9. The electrochemical device according to claim 8, wherein it has at least one of the following features: a. The electrochemical device comprises 2 to 3 bipolar current collectors; b. The melting point of the sealing material is 110°C to 180°C; c. The electronic resistivity in the Z direction of the bipolar current collector is 1×10⁻⁶. -5 Ω·cm to 5Ω·cm; d. The permeability M of the bipolar current collector is ≤10. -4 g / (day·m 2 ·Pa·3mm); e. The thickness of the bipolar current collector is 5 mm to 50 mm; f. The seal thickness T and the seal width W satisfy 0.02≤T / W≤0.

04.

10. The electrochemical device according to claim 9, wherein it has at least one of the following features: 1) The melting point of the sealing material is 120°C to 160°C; 2) The electronic resistivity in the Z direction of the bipolar current collector is 0.01 Ω·cm to 0.10 Ω·cm; 3) The thickness of the bipolar current collector is 5 mm to 20 mm.

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

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

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