A patch soft package inner series high-voltage super capacitor and a preparation method thereof

Abstract

The application provides a patch soft package inner string type high-voltage super capacitor and a preparation method thereof, and belongs to the technical field of capacitors. The super capacitor comprises a first core package and a second core package arranged in a soft package shell, and the first core package and the second core package are connected in series through an internal connecting structure; the first core package and the second core package are asymmetric structures, wherein the energy density of the first core package is higher than that of the second core package, and the power density of the second core package is higher than that of the first core package; the chemical compositions of the electrolytes filled in the first core package and the second core package are different from each other; the capacitor comprises three external pins, namely a positive pin connected with a positive electrode of the first core package, a negative pin connected with a negative electrode of the second core package, and a balance pin electrically connected with the internal connecting structure. Through the asymmetric core package, different electrolyte settings and a multi-stage segmented packaging process, the performance and stability of the capacitor can be effectively improved.

Description

Technical Field

[0001] This application relates to the field of capacitor technology, and in particular to a surface-mount soft-pack internal series high-voltage supercapacitor and its preparation method. Background Technology

[0002] Supercapacitors are a relatively new type of charge storage device that has emerged in recent years. They are characterized by long lifespan, safety, reliability, and enormous energy storage capacity, making them an ideal energy storage device. They combine the high-current, rapid charging and discharging characteristics of ordinary capacitors with the energy storage characteristics of batteries, filling the gap in specific energy and specific power between ordinary capacitors and batteries.

[0003] Currently, fully sealed supercapacitor modules mainly use small aluminum-cased supercapacitors connected in series, which are then encapsulated in a plastic shell. Existing capacitors have the following drawbacks:

[0004] 1. Limited single-cell voltage: Currently, due to the limitations of electrolyte decomposition voltage and the electrochemical stability of electrode materials, the voltage of supercapacitors is generally around 2.7V, with a maximum of no more than 3V. Therefore, multiple supercapacitor cells need to be connected in series to enable the use of supercapacitors at high voltages, which also increases the overall size of the product.

[0005] 2. Lower power density: Traditional supercapacitors form a cylindrical core package by winding electrodes and a separator. Compared with stacked, heat-bearing electrode structures, the energy density of the core package electrode of the same volume is lower. Therefore, traditional supercapacitors have a lower energy density.

[0006] 3. Traditional supercapacitors are generally cylindrical supercapacitor cells, which take up space when soldering onto circuit boards.

[0007] Patent No. 201610772313.8, concerning a high-voltage laminated aluminum electrolytic capacitor and its manufacturing method, provides a method for combining multiple core-pack units. However, in this patent, the anode and cathode conductive foils are riveted or welded to the anode and cathode foils respectively. This inevitably increases the thickness of the core-pack unit and damages the structure of the anode and cathode foils during riveting or welding. Furthermore, due to the riveting or welding, the current-collecting capacity of the anode and cathode conductive foils is weak. Therefore, it is necessary to improve the performance of the supercapacitor in the prior art. Summary of the Invention

[0008] This application is made in view of the above-mentioned problems, and its purpose is to provide a surface-mount soft-pack in-series high-voltage supercapacitor and its preparation method. The supercapacitor effectively solves the problems existing in the existing supercapacitor by adopting a first core and a second core with an asymmetric structure in series within a soft-pack package, combined with electrolytes of different chemical compositions and a unique pin design.

[0009] Specifically, the first aspect of this application provides a surface-mount soft-pack internal series high-voltage supercapacitor, comprising:

[0010] Flexible packaging shell;

[0011] The first and second core packages are disposed within the soft-pack package. The first and second core packages are connected in series through an internal connection structure, so that the external operating voltage of the capacitor is higher than the operating voltage of a single core package.

[0012] The first core pack and the second core pack are asymmetric structures, wherein the energy density of the first core pack is higher than that of the second core pack, and the power density of the second core pack is higher than that of the first core pack;

[0013] The electrolytes filled in the first and second core packages have different chemical compositions.

[0014] The capacitor includes three external pins: a positive pin connected to the positive terminal of the first core, a negative pin connected to the negative terminal of the second core, and a balance pin electrically connected to the internal connection structure.

[0015] Furthermore, the positive electrode active material of the first core package comprises a composite material of conductive polymer and porous carbon material.

[0016] Furthermore, the positive and negative electrode active materials of the second core package contain a composite network structure of one-dimensional carbon nanomaterials and two-dimensional graphene materials.

[0017] Furthermore, the conductive polymer is at least one of polyaniline, polypyrrole, or poly(3,4-ethylenedioxythiophene); the one-dimensional carbon nanomaterial is carbon nanotube, and the two-dimensional graphene material is graphene oxide or reduced graphene oxide.

[0018] Furthermore, the current collector of the first core package is an etched aluminum foil, and a porous nano-alumina transition layer formed by plasma electrolytic oxidation is provided between the etched aluminum foil and the active material layer.

[0019] The current collector of the second core package is a smooth aluminum foil, and a vertically oriented graphene layer is grown on the surface of the smooth aluminum foil by chemical vapor deposition.

[0020] Furthermore, the electrolyte in the first core pack is a solution containing an organic solvent and a quaternary ammonium salt, as well as a fluoroethylene carbonate film-forming additive; the electrolyte in the second core pack is a mixed electrolyte containing an ionic liquid, a lithium salt, and a boron-based anodizing accelerator.

[0021] Furthermore, the organic solvent of the first core electrolyte comprises a mixed solvent of propylene carbonate and acetonitrile, and the quaternary ammonium salt is tetraethylammonium tetrafluoroborate with a concentration range of 1.0M-1.8M; the ionic liquid in the second core electrolyte is an imidazole ionic liquid, and the lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

[0022] Furthermore, an insulating and thermally conductive layer is provided between the first core package and the second core package, the insulating and thermally conductive layer being composed of a polymer matrix and a highly thermally conductive insulating filler dispersed therein.

[0023] Furthermore, the polymer matrix is ​​polyimide, polyetheretherketone, or polytetrafluoroethylene; the high thermal conductivity insulating filler is aluminum nitride, boron nitride, or aluminum oxide, with a filling volume ratio of 30%-60%.

[0024] Furthermore, the internal connection structure is a welded metal guide plate;

[0025] A positive temperature coefficient resistor is connected in series between the internal connection structure and the balancing pin.

[0026] The second aspect of this application provides a method for fabricating a patch-mount soft-pack internal series high-voltage supercapacitor, comprising the following steps:

[0027] S1: Prepare asymmetric first and second core packages;

[0028] S2: Stack the first core package, the insulating and thermally conductive layer and the second core package in sequence and pre-assemble them;

[0029] S3: Perform the first encapsulation, heat-seal the edges except for the internal core packing spacer area and the injection port to form at least two independent sealed chambers;

[0030] S4: Electrolytes with different chemical compositions are injected into the chambers containing the first and second core packages respectively through an independent injection system;

[0031] S5: Perform a second encapsulation to completely seal the injection port and the internal core packing spacer area.

[0032] Furthermore, in step S3, during the first encapsulation, the heat sealing temperature is 155℃-175℃ and the pressure is 0.3MPa-0.5MPa.

[0033] Furthermore, in step S5, during the second encapsulation, the heat sealing temperature is 175℃-195℃ and the pressure is 0.4MPa-0.6MPa.

[0034] Furthermore, in step S4, the order of injecting electrolytes into the first core pack and the second core pack is as follows: first, inject the organic solvent electrolyte into the first core pack, let it stand for 5-15 minutes, and then inject the ionic liquid electrolyte into the second core pack.

[0035] Further, in step S5, after injecting the electrolyte and completing the second encapsulation, electrochemical formation is performed. The formation process includes: first, constant current charging at a small rate not exceeding 0.2C to the rated voltage of a single core, then constant current charging to the rated voltage of the entire capacitor, and then constant voltage aging.

[0036] The present invention has the following beneficial effects:

[0037] This invention, by employing a first and second core package with a series asymmetric structure within a soft-pack enclosure, effectively increases the external operating voltage of the supercapacitor, overcoming the limitation of single-cell voltage in existing supercapacitors. Due to the high energy density of the first core package and the high power density of the second core package, their combined performance enables the supercapacitor to possess both high energy storage capacity and excellent power output performance.

[0038] Electrolytes with different chemical compositions are filled into the first and second core packs, respectively, which can better adapt to the electrode materials and performance requirements of different core packs, further improving the overall performance of the supercapacitor. For example, the electrolyte solution containing organic solvents and quaternary ammonium salts, as well as fluoroethylene carbonate film-forming additives, in the first core pack helps to improve the energy storage efficiency of the first core pack; the mixed electrolyte containing ionic liquids, lithium salts, and boron-based anodizing promoters in the second core pack can enhance the ion conduction capacity of the second core pack, thereby increasing its power density.

[0039] The unique design with three external pins—positive, negative, and balance—offers greater possibilities for the use and performance adjustment of supercapacitors. The balance pin, electrically connected to the internal connection structure, allows for monitoring and adjustment of the voltage balance within the capacitor, ensuring its stability and safety during use.

[0040] In summary, the patch-mount soft-pack in-series high-voltage supercapacitor of the present invention, through its innovative structural design, effectively solves the problems of limited single-cell voltage, low power density, and large volume of existing supercapacitors, and has broad application prospects and market value. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this drawing or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this drawing. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the first core package structure;

[0043] Figure 2 This is a schematic diagram of the second core package structure;

[0044] Figure 3 This is a schematic diagram of the connection structure between the first core package and the second core package.

[0045] The purpose, features, and advantages of this accompanying drawing will be further explained in conjunction with the embodiments and with reference to the accompanying drawing. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this application clearer, the following description and illustration are provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0047] Obviously, the following description is merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios without any inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0048] An embodiment of the first aspect of this application provides a surface-mount flexible-pack internal series high-voltage supercapacitor, comprising:

[0049] Flexible packaging shell;

[0050] The first and second core packages are disposed within the soft-pack package. The first and second core packages are connected in series through an internal connection structure, so that the external operating voltage of the capacitor is higher than the operating voltage of a single core package.

[0051] The first core pack and the second core pack are asymmetric structures, wherein the energy density of the first core pack is higher than that of the second core pack, and the power density of the second core pack is higher than that of the first core pack;

[0052] The electrolytes filled in the first and second core packages have different chemical compositions.

[0053] The capacitor includes three external pins: a positive pin connected to the positive terminal of the first core, a negative pin connected to the negative terminal of the second core, and a balance pin electrically connected to the internal connection structure.

[0054] The soft-pack supercapacitor of this application has its internal core package formed by stacked electrodes and separators, with the positive and negative electrodes of each core package led out by spot welding aluminum foil. To achieve internal series connection, each supercapacitor cell contains two individual core packages, and the positions of the positive and negative electrodes need to be staggered, such as... Figure 1 and Figure 2 As shown, the positive electrode aluminum foil of the first core package needs to be led out from the upper right of the lead-out surface, and the negative electrode is led out from the middle. The negative electrode aluminum foil of the second core package needs to be led out from the lower left of the lead-out surface, and the positive electrode is led out from the middle.

[0055] This invention, by employing a first and second core package with a series asymmetric structure within a soft-pack enclosure, effectively increases the external operating voltage of the supercapacitor, overcoming the limitation of single-cell voltage in existing supercapacitors. Due to the high energy density of the first core package and the high power density of the second core package, their combined performance enables the supercapacitor to possess both high energy storage capacity and excellent power output performance.

[0056] Electrolytes with different chemical compositions are filled into the first and second core packs, respectively, which can better adapt to the electrode materials and performance requirements of different core packs, further improving the overall performance of the supercapacitor. For example, an electrolyte solution containing organic solvents and quaternary ammonium salts in the first core pack helps to improve the energy storage efficiency of the first core pack; while an ionic liquid or a mixed electrolyte containing ionic liquids and lithium salts in the second core pack can enhance the ion conduction capability of the second core pack, thereby increasing its power density.

[0057] The unique design with three external pins—positive, negative, and balance—offers greater possibilities for the use and performance adjustment of supercapacitors. The balance pin, electrically connected to the internal connection structure, allows for monitoring and adjustment of the voltage balance within the capacitor, ensuring its stability and safety during use.

[0058] In this embodiment, the positive electrode active material of the first core package comprises a composite material of conductive polymer and porous carbon material.

[0059] Specifically, the first core pack is used to provide high capacity, laying the foundation for energy density. The positive electrode contains the following active material: porous activated carbon (YP-50F), accounting for 85 wt%; conductive polymer: at least one of polyaniline, polypyrrole, or poly(3,4-ethylenedioxythiophene), preferably polyaniline (PANI), accounting for 5 wt%, the composite of polyaniline and activated carbon enhances capacity through its pseudocapacitive effect; conductive agent: Super P, accounting for 5 wt%; binder: polyvinylidene fluoride (PVDF), accounting for 5 wt%; current collector: 20 μm thick etched aluminum foil, on which a porous nano-alumina transition layer of about 200 nm thickness is grown in situ through a plasma electrolytic oxidation process. The etched aluminum foil is placed in an electrolytic cell, with the aluminum foil as the anode and a stainless steel plate as the cathode, and treated in a 2% sodium phosphate electrolyte at 300V and 500Hz for 2 minutes. After that, it is washed with deionized water and dried at 120°C. The porous nano-alumina transition layer acts like an "anchor" to form a strong mechanical interlock with the active material layer, thereby improving the electrode peel strength and significantly reducing the interfacial contact resistance.

[0060] The negative electrode of the first core pack contains: active material: high specific surface area activated carbon (ASC-20), accounting for 90 wt%; conductive agent: carbon nanotubes (CNT), accounting for 5 wt%, used to construct a three-dimensional conductive network and reduce internal resistance; binder: sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) mixed in a 1:1 mass ratio, accounting for a total of 5 wt%; current collector: 20 μm thick etched aluminum foil, which is treated in the same way as the current collector of the positive electrode.

[0061] The positive and negative electrodes of the first core pack are separated by a separator. The separator is a ceramic-coated polypropylene separator with good ion conductivity and chemical stability, and its thickness is 20 μm. In the preparation of the first core pack, the positive electrode active material, conductive agent, and binder are first mixed evenly in a specific ratio, and an appropriate amount of solvent is added to prepare a positive electrode slurry. The slurry is then evenly coated onto a current collector, and the positive electrode sheet is formed through processes such as drying and rolling. The negative electrode sheet is prepared using the same method. The positive electrode sheet, separator, and negative electrode sheet are then stacked sequentially and hot-pressed to ensure a tight bond between the layers, forming the first core pack with good structural stability. This structure ensures sufficient contact between the electrode materials and the electrolyte during charging and discharging, improving ion transport efficiency and further enhancing the energy storage capacity and charge / discharge performance of the first core pack.

[0062] In this embodiment, the positive and negative electrodes of the second core package contain active materials: a composite network structure of one-dimensional carbon nanomaterials and two-dimensional graphene materials. Preferably, the one-dimensional carbon nanomaterials are carbon nanotubes, and the two-dimensional graphene materials are graphene oxide or reduced graphene oxide, forming a three-dimensional conductive network that provides a large specific surface area and electron / ion channels; the mass ratio of graphene oxide to carbon nanotubes is 8:2; and the total proportion of active materials is 88 wt%. The process also includes a binder: a polytetrafluoroethylene (PTFE) emulsion, comprising 12 wt%; and a current collector: a 15 μm thick smooth aluminum foil. A 1-2 μm thick, vertically oriented few-layer graphene is grown on the surface of this foil via low-pressure chemical vapor deposition (CVD) at 600°C in a CH4 / H2 atmosphere. Specifically, the smooth aluminum foil is placed in a CVD apparatus, a mixture of methane and hydrogen is introduced, the volume ratio of methane to hydrogen is controlled at 1:5, the chamber pressure is adjusted to 200 Pa, and the temperature is raised to 600°C and maintained for 20 minutes. Under these conditions, carbon atoms generated from the decomposition of methane are deposited layer by layer on the aluminum foil surface to form vertically oriented few-layer graphene. By adjusting the growth time, the thickness of the graphene can be precisely controlled within the 1-2 μm range, ultimately obtaining a graphene layer with excellent electrical and mechanical properties.

[0063] This VFG layer provides a vertical highway for charge transfer from a two-dimensional plane to three-dimensional space, maximizing the rate performance and cycle life of the electrode.

[0064] The positive and negative electrodes of the second core pack are also separated by a separator. A ceramic-coated polypropylene separator with a thickness of 20 μm is used, which effectively promotes rapid ion migration between the electrodes while preventing direct contact and short circuits. In the preparation of the second core pack, one-dimensional carbon nanomaterials and two-dimensional graphene materials are first mixed in a specific ratio and a uniform composite network structure is formed through ultrasonic dispersion and other methods. A binder is then added and thoroughly stirred to prepare an electrode slurry. The slurry is uniformly coated onto a current collector, and after drying and calendering, electrode sheets are obtained. The positive electrode sheet, separator, and negative electrode sheet are then stacked sequentially and firmly bonded together using a hot-pressing process to form the second core pack. This structure of the second core pack, due to its unique composite network structure and active material, provides a rapid electron conduction channel, giving it excellent power output capability and enabling rapid response during high-current charging and discharging, reducing energy loss. Furthermore, the asymmetric structural design of the second and first core packs complements each other in performance, further enhancing the overall performance of the supercapacitor.

[0065] In this embodiment, the electrolyte in the first core pack is a solution containing an organic solvent and a quaternary ammonium salt, as well as a fluoroethylene carbonate film-forming additive. Preferably, the organic solvent of the electrolyte in the first core pack contains a mixed solvent of propylene carbonate and acetonitrile, wherein propylene carbonate (PC) and acetonitrile (AN) are mixed in a 7:3 ratio. Propylene carbonate provides high voltage stability, while acetonitrile provides low viscosity. The quaternary ammonium salt in the solution is tetraethylammonium tetrafluoroborate, with a concentration range of 1.0M-1.8M. High concentration improves the voltage window and ion concentration. The fluoroethylene carbonate is added at 0.5 wt%, preferentially forming a stable and dense solid electrolyte interface film on the negative electrode surface, effectively inhibiting the continuous decomposition of the electrolyte and improving the cycle life of the first core pack.

[0066] The electrolyte in the second core pack is a mixed electrolyte of ionic liquid and lithium salt, along with a boron-based anodizing promoter. Preferably, the ionic liquid in the electrolyte of the second core pack is an imidazole ionic liquid, such as 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM-BF4), which is inherently non-volatile, has a wide electrochemical window, and extremely high thermal stability. The lithium salt is lithium bis(trifluoromethanesulfonyl)imide, added at 5% of the ionic liquid mass, introducing lithium ions to slightly increase capacity and improve low-temperature performance. The boron-based anodizing promoter is 1.0 wt% tris(trimethylsilane)borate, used to electrochemically polymerize on the positive electrode surface to form a robust boron-oxygen-silicon composite protective layer, which can increase the anodic decomposition potential of the ionic liquid, thereby allowing the second core pack to operate stably at higher voltages and indirectly increasing the voltage limit of the entire device.

[0067] In this embodiment, when the first and second core packages are connected in series, an insulating layer is required between them to prevent short circuits and ensure that the insulating film does not deform or degrade in insulation performance under temperature conditions ranging from -55℃ to 125℃. An insulating and thermally conductive layer is provided between the first and second core packages. This insulating and thermally conductive layer is composed of a polymer matrix and a highly thermally conductive insulating filler dispersed therein. Preferably, the polymer matrix is ​​polyimide, polyetheretherketone, or polytetrafluoroethylene; the highly thermally conductive insulating filler is aluminum nitride, boron nitride, or aluminum oxide, with a volume ratio of 30%-60%. More preferably, the matrix is ​​a 25μm thick polyimide (PI) film, and the filler is aluminum nitride (AlN) ceramic powder with a particle size of 1-3μm and a filling ratio of 40 vol.

[0068] Furthermore, the internal connection structure is a welded metal guide plate. The metal guide plate can be made of metals such as copper or aluminum, which have good conductivity and mechanical strength. When connecting the first core package and the second core package, the metal guide plate is welded to the negative electrode of the first core package and the positive electrode of the second core package, respectively.

[0069] The leads of the supercapacitor in this application are made of gold-plated nickel alloy. The entire lead consists of aluminum foil strip, nickel strip and lead. Since direct welding of aluminum foil and nickel is not strong and there is a risk of lead falling off, the aluminum foil strip and nickel strip are first bonded together with tab adhesive inside the product, and then the nickel strip is welded to the gold-plated lead to form the positive and negative terminals of the capacitor.

[0070] A positive temperature coefficient resistor is connected in series between the internal connection structure and the balance pin. In this invention, a ceramic PTC resistor with a resistance of 0.1Ω at 25°C and an operating temperature of 85°C is connected in series between the internal connection point and the balance pin. The PTC resistor is attached and soldered to the conductive path connecting the nickel strip and the balance pin using conductive silver paste. This PTC acts as a resettable fuse; when an abnormally large current causes the connection point to overheat, it can automatically disconnect the balancing circuit, preventing thermal runaway and providing passive safety protection.

[0071] In another preferred embodiment, the present invention further includes a voltage monitoring unit for monitoring a first voltage between the positive pin and the balance pin, and a second voltage between the balance pin and the negative pin; and an equalization control unit for controlling the equalization circuit to discharge the higher voltage cell through the balance pin when the difference between the first voltage and the second voltage exceeds a preset threshold (30mV-70mV) to achieve voltage equalization.

[0072] An embodiment of the second aspect of this application provides a method for fabricating a patch-mount soft-pack internal series high-voltage supercapacitor, comprising the following steps:

[0073] S1: Prepare asymmetric first and second core packages;

[0074] S2: Stack the first core package, the insulating and thermally conductive layer and the second core package in sequence and pre-assemble them;

[0075] S3: Perform the first encapsulation, heat-seal the edges except for the internal core packing spacer area and the injection port to form at least two independent sealed chambers;

[0076] S4: Electrolytes with different chemical compositions are injected into the chambers containing the first and second core packages respectively through an independent injection system;

[0077] S5: Perform a second encapsulation to completely seal the injection port and the internal core packing spacer area.

[0078] In step S1, the preparation of the first core package includes: mixing the active material, conductive agent, and binder with N-methylpyrrolidone (NMP) solvent in a certain proportion, and stirring at 500 rpm for 120 minutes in a vacuum planetary mixer to obtain a slurry;

[0079] The preparation of the second core package includes: mixing graphene oxide and carbon nanotube composite with polytetrafluoroethylene emulsion in ethanol, and shearing and mixing them at 80°C using a twin-screw extruder to form a viscous slurry;

[0080] The slurries for the first and second core packages were coated onto the current collector using a microgravure coating method, with the coating density accuracy controlled within ±1.5%. After drying at 120℃, the electrodes were compacted using a roller mill under a pressure of 10 MPa. The electrode compaction density of the first core package was 0.75 g / cm³. 3 The electrode compaction density of the second core package is 0.55 g / cm³. 3 .

[0081] The prepared electrodes and separators were stacked in a dust-free environment according to the "positive electrode-separator-negative electrode" structure. A precision resistance spot welder was used to spot weld a 0.1mm thick, 5mm wide nickel strip to the electrode aluminum foil. Welding parameters: current 3000A, time 5ms, pressure 50N.

[0082] Step S2 involves stacking the core packages in the following order: first core package → insulation layer → second core package. The edge of the insulation layer extends 2.0 mm beyond the core package to ensure proper sealing with the aluminum-plastic film.

[0083] like Figure 3 An insulating layer is placed between the first and second core packages, and this insulating layer is larger than both the first and second core packages. During the side-sealing process, it is heat-sealed together with the aluminum-plastic film of the outer casing, ensuring the fixation of the insulating layer. Simultaneously, the first core package (negative electrode) and the second core package (positive electrode) have their intermediate leads overlapping. The positive electrode of the first core package is the positive electrode of the entire surface-mount supercapacitor, and the negative electrode of the second core package is the negative electrode of the entire surface-mount supercapacitor.

[0084] In step S3, during the first encapsulation, an aluminum-plastic film is used, the vacuum degree is -95 kPa, the heat sealing temperature is 155℃-175℃, the pressure is 0.3MPa-0.5MPa, and the heat sealing time is 2-5s. The three sides, excluding the injection port and the internal core packing spacer area, are encapsulated to form two independent sealed chambers.

[0085] In step S4, within a -98 kPa vacuum glove box, using two independent high-precision injection pumps, the customized electrolyte is first injected into the chamber of the first core package at a volume of 105% of the theoretical saturation absorption volume calculated based on the electrode porosity. After standing for 5-15 minutes, the ionic liquid electrolyte is injected into the chamber of the second core package at a volume of 103% of the theoretical amount to prevent cross-contamination.

[0086] Step S5: Immediately perform final sealing at a heat sealing temperature of 175℃-195℃, a pressure of 0.4MPa-0.6MPa, and a time of 3-5 seconds.

[0087] After the electrolyte is injected and the second encapsulation is completed, electrochemical formation is performed. The formation process includes: first, constant current charging at a small rate not exceeding 0.2C to the rated voltage of a single core, then constant current charging to the rated voltage of the entire capacitor, and then constant voltage aging.

[0088] Specifically:

[0089] Charge at a constant current of 0.1C to 2.7V and let stand for 30 minutes; then charge at a constant current of 0.2C to 5.4V.

[0090] Charge at a constant voltage of 5.4V until the current drops to 0.05C; discharge at a constant current of 0.5C to 0V.

[0091] The formed capacitors were then placed in a 70°C oven for 48 hours to age. Products with a capacitance decrease of >2% or an internal resistance increase of >5% after aging were discarded.

[0092] Example

[0093] The following examples describe the disclosure of this invention in more detail. These examples are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight. Unless otherwise stated, all reagents used in the examples are available commercially or synthesized using conventional methods and are ready for use without further processing. Unless otherwise stated, all instruments used in the examples are available commercially.

[0094] Example 1

[0095] A surface-mount flexible-pack internal series high-voltage supercapacitor includes:

[0096] Flexible packaging shell;

[0097] The first and second core packages are disposed within the soft-pack package. The first and second core packages are connected in series through an internal connection structure, so that the external operating voltage of the capacitor is higher than the operating voltage of a single core package.

[0098] The first core pack and the second core pack are asymmetric structures, wherein the energy density of the first core pack is higher than that of the second core pack, and the power density of the second core pack is higher than that of the first core pack;

[0099] The positive electrode of the first core package contains 85 wt% of porous activated carbon as active material, 5 wt% of polyaniline as conductive polymer, 5 wt% of Super P as conductive agent, and 5 wt% of polyvinylidene fluoride as binder; the negative electrode contains 90 wt% of activated carbon as active material, 5 wt% of carbon nanotubes as conductive agent, and 5 wt% of a mixture of sodium carboxymethyl cellulose and styrene-butadiene rubber in a 1:1 mass ratio as binder.

[0100] The second core-packed positive and negative electrodes contain 88 wt% active materials carbon nanotubes and graphene oxide, and 12 wt% polytetrafluoroethylene emulsion.

[0101] The electrolyte in the first core pack is a mixed solvent containing the organic solvents propylene carbonate and acetonitrile, and 0.5 wt% of fluoroethylene carbonate, wherein propylene carbonate (PC) and acetonitrile (AN) are mixed in a 7:3 ratio, and tetraethylammonium tetrafluoroborate, with a concentration range of 1.5 M; the electrolyte in the second core pack is 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid and lithium bis(trifluoromethanesulfonyl)imide, and the functional additive tris(trimethylsilane)borate.

[0102] An insulating and thermally conductive layer is disposed between the first core packing and the second core packing, with polyimide as the matrix and aluminum nitride as the filler, and the filling ratio is 40 vol%.

[0103] The capacitor includes three external pins: a positive pin connected to the positive terminal of the first core, a negative pin connected to the negative terminal of the second core, and a balance pin electrically connected to the internal connection structure; a positive temperature coefficient resistor is connected in series between the internal connection structure and the balance pin.

[0104] The fabrication method of the patch-mount soft-pack in-series high-voltage supercapacitor includes the following steps:

[0105] S1: Prepare an asymmetric first core bag and a second core bag, wherein:

[0106] The preparation of the first core package includes: mixing active material, conductive agent, binder with N-methylpyrrolidone (NMP) solvent in proportion, and stirring at 500 rpm for 120 minutes in a vacuum planetary mixer to obtain a slurry;

[0107] The preparation of the second core package includes: mixing graphene oxide and carbon nanotube composite with polytetrafluoroethylene emulsion in ethanol, and shearing and mixing them at 80°C using a twin-screw extruder to form a viscous slurry;

[0108] The slurries for the first and second core packages were coated onto the current collector using a microgravure coating method, with the coating density accuracy controlled within ±1.5%. After drying at 120℃, the electrodes were compacted using a roller mill under a pressure of 10 MPa. The electrode compaction density of the first core package was 0.75 g / cm³. 3 The electrode compaction density of the second core package is 0.55 g / cm³. 3 .

[0109] S2: Stack the first core package, the insulating and thermally conductive layer and the second core package in sequence and pre-assemble them;

[0110] S3: Perform the first encapsulation using aluminum-plastic film, with a vacuum degree of -95 kPa, a heat sealing temperature of 165℃, a pressure of 0.4MPa, and a heat sealing time of 3s. Heat seal the edges except for the internal core packing spacer area and the liquid injection port to form at least two independent sealed chambers.

[0111] S4: Through an independent liquid injection system, the customized electrolyte is first injected into the chamber of the first core pack, and the injection volume is 105% of the theoretical saturated liquid absorption volume calculated based on the electrode porosity; after standing for 10 minutes, the ionic liquid electrolyte is injected into the chamber of the second core pack, and the injection volume is 103% of the theoretical amount to prevent cross-contamination.

[0112] S5: Perform the second sealing process, with a heat sealing temperature of 185℃, a pressure of 0.5MPa, and a time of 4 seconds, to completely seal the injection port and the internal core packing spacer area.

[0113] After the electrolyte is injected and the second encapsulation is completed, electrochemical formation is performed. The formation process includes: first, constant current charging at a small rate not exceeding 0.2C to the rated voltage of a single core, then constant current charging to the rated voltage of the entire capacitor, and then constant voltage aging.

[0114] Example 2

[0115] This embodiment and implementation

[0116] Example 1 is basically the same, except that the concentration of tetraethyltetrafluoroborate ammonium in the electrolyte of the first core is adjusted to 1.2M.

[0117] Example 3

[0118] This embodiment is basically the same as Embodiment 1, except that the second core electrolyte is only 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid.

[0119] Example 4

[0120] This embodiment is basically the same as embodiment 1, except that the insulating and thermally conductive layer between the first core package and the second core package, consisting of polyimide and boron nitride, has a volume ratio of 40%.

[0121] Comparative Example 1

[0122] Two commercially available 2.7V / 2.2F cylindrical supercapacitors are connected in series on a circuit board to form a 5.4V / 1.1F module.

[0123] Comparative Example 2

[0124] This comparative example is basically the same as Example 1, except that the first and second core packs use the same electrodes and electrolytes as the first core pack in Example 1.

[0125] Comparative Example 3

[0126] This comparative example is basically the same as Example 1, except that the first core pack and the second core pack both use the same ionic liquid electrolyte as the second core pack in Example 1.

[0127] Comparative Example 4

[0128] This comparative example is basically the same as Example 1, except that the first core package and the second core package are separated only by a common PP diaphragm, and no functional insulating and thermally conductive layer is used.

[0129] Comparative Example 5

[0130] This comparative example is basically the same as Example 1, except that the multi-stage segmented packaging is eliminated in the preparation process, and the traditional one-time vacuum liquid injection and full sealing process is adopted.

[0131] Experimental Case

[0132] Capacity and internal resistance testing: Using a charge-discharge tester, the capacitor was charged to 5.4V at a constant current of 1A at 25℃, then the voltage was kept constant until the current dropped to 0.1A. After resting for 1 minute, it was discharged to 2.7V at a constant current of 1A. The capacity was calculated from the discharge curve, and the internal resistance (ESR) was measured at 1kHz using the DC internal resistance method (DCIR).

[0133] High and low temperature performance test: The capacitor is placed in a high and low temperature test chamber and kept at +70℃ and -40℃ for 2 hours respectively. Its capacitance and internal resistance are measured and compared with the 25℃ reference value to calculate the rate of change.

[0134] Cycle life test: At 25℃, charge and discharge cycles were performed at a constant current of 5A between 2.7V and 5.4V, and the number of cycles when the capacity decayed to 80% of the initial capacity was recorded.

[0135] The capacitors of Examples 1-4 and Comparative Examples 1-5 were subjected to the above tests, and the test results are shown in Table 1.

[0136]

[0137] As shown in Table 1, the patch-type soft-pack series-connected high-voltage supercapacitors prepared in Examples 1-4 exhibit excellent overall performance. Compared with the comparative examples, the examples show significant advantages in capacity, internal resistance, high and low temperature performance, and cycle life. Comparative Example 1 uses commercial cylindrical supercapacitors in series. Although the initial capacity is high, the internal resistance is extremely high, the high and low temperature performance is poor, and the cycle life is short, indicating that the traditional series connection method has significant defects in high-voltage applications. Comparative Examples 2 and 3, because the core packs use the same electrodes and electrolytes, show certain performance characteristics, but not as diverse as the examples, highlighting the importance of asymmetric structures and different electrolyte combinations. This may be because the asymmetric structure allows the first and second core packs to leverage their respective advantages. The high energy density of the first core pack ensures the overall energy storage capacity of the capacitor, while the high power density of the second core pack improves the charging and discharging speed and power response capability. The combination of different electrolytes also plays a crucial role. The rational use of customized electrolytes and ionic liquid electrolytes avoids cross-contamination problems and meets the different core packs' requirements for electrolyte performance, such as ion conductivity and stability. In Comparative Example 4, only a standard PP diaphragm was used for insulation, without a functional insulating and thermally conductive layer. This resulted in a significant decrease in performance at high temperatures and a markedly shortened cycle life. This demonstrates that a functional insulating and thermally conductive layer is crucial for maintaining the stability and performance of capacitors in high-temperature environments. It can effectively conduct heat, reduce internal temperature, and minimize the adverse effects of heat on the electrodes and electrolyte, thereby improving the reliability and lifespan of the capacitor.

[0138] Comparative Example 5, employing a traditional one-time vacuum injection and full-sealing process, exhibited significant dispersion in various performance indicators, demonstrating the crucial importance of multi-stage segmented packaging technology in ensuring consistent product quality and performance. Multi-stage segmented packaging allows for better control of the injection volume and packaging quality, avoiding issues such as electrolyte cross-contamination and poor packaging, thereby improving product yield and stability.

[0139] In summary, this invention, through asymmetric core-pack design, the use of different electrolytes, the setting of functional insulating and thermally conductive layers, and multi-stage segmented packaging process, can effectively improve the performance and stability of capacitors, meeting the application requirements of high voltage, long life and wide temperature range.

[0140] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A patch soft-pack intra-series high voltage supercapacitor, characterized in that, The patch soft package in-series high-voltage supercapacitor comprises: a soft package shell; a first core package and a second core package arranged in the soft package shell, the first core package and the second core package are connected in series through an internal connecting structure, so that the external working voltage of the capacitor is higher than the working voltage of a single core package; the first core package and the second core package are asymmetric structures, wherein the energy density of the first core package is higher than that of the second core package, and the power density of the second core package is higher than that of the first core package; the chemical compositions of the electrolytes filled in the first core package and the second core package are different from each other; the capacitor comprises three external pins, namely a positive pin connected with the positive electrode of the first core package, a negative pin connected with the negative electrode of the second core package, and a balance pin electrically connected with the internal connecting structure; a preparation method of the patch soft package in-series high-voltage supercapacitor, comprising the following steps: S1: preparing asymmetric first core package and second core package; S2: sequentially stacking the first core package, the insulating and heat-conducting layer and the second core package and pre-assembling; S3: performing first packaging, heat-sealing the edges except the internal core package spacing area and the liquid injection port to form at least two independent sealed cavities; S4: injecting electrolytes with different chemical compositions into the cavities where the first core package and the second core package are located through independent liquid injection systems; S5: performing second packaging to completely seal the liquid injection port and the internal core package spacing area.

2. The patch soft-packaged in-series high voltage supercapacitor of claim 1, wherein, The positive electrode active material of the first core package comprises a composite material of conductive polymer and porous carbon material; and / or The positive electrode and negative electrode active material of the second core package comprises a composite network structure of one-dimensional carbon nanomaterial and two-dimensional graphene material.

3. The patch soft-packaged in-series high voltage supercapacitor of claim 1, wherein, The current collector of the first core package is etched aluminum foil, and a porous nano-aluminum oxide transition layer formed by plasma electrolytic oxidation is arranged on the surface of the etched aluminum foil; The current collector of the second core package is a smooth aluminum foil, and a vertically oriented graphene layer is grown on the surface of the smooth aluminum foil by chemical vapor deposition.

4. The patch soft-packaged in-series high voltage supercapacitor of claim 1, wherein, The electrolyte in the first core package is a solution comprising organic solvent and quaternary ammonium salt, and fluorinated ethylene carbonate film-forming additive; the electrolyte in the second core package is a mixed electrolyte comprising ionic liquid, lithium salt and boron-based anode oxidation promoter.

5. The patch soft-packaged in-line high voltage supercapacitor of claim 1, wherein, An insulating and heat-conducting layer is arranged between the first core package and the second core package, and the insulating and heat-conducting layer is composed of a polymer matrix and high-thermal-conductivity insulating fillers dispersed therein.

6. The patch-lithium-ion battery of claim 1, wherein, The internal connecting structure is a welded metal flow guide sheet; A positive temperature coefficient resistor is connected in series between the internal connecting structure and the balance pin.

7. The patch soft-packaged in-series high voltage supercapacitor of claim 1, wherein, In the first packaging of step S3, the heat-sealing temperature is 155-175°C, and the pressure is 0.3-0.5 MPa; and / or in the second packaging of step S5, the heat-sealing temperature is 175-195°C, and the pressure is 0.4-0.6 MPa.

8. The patch-lithium-ion battery of claim 1, wherein, In step S4, the order of injecting electrolytes into the first core package and the second core package is to inject organic solvent electrolyte into the first core package first, and then to inject ionic liquid electrolyte into the second core package after standing for 5-15 minutes.

9. The patch-lithium-ion battery of claim 1, wherein, Step S5, after injecting the electrolyte and completing the second encapsulation, electrochemical formation is carried out, the formation procedure including: first constant current charging to the rated voltage of the single core package at a small rate current not more than 0.2C, then constant current charging to the rated voltage of the entire capacitor, and constant voltage aging.

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