A supercapacitor electrode and a preparation method thereof, and a supercapacitor
By designing a three-layer gradient structure and a polypyrrole-based self-adhesive conductive agent, the problem of balancing conductivity and energy storage capacity in supercapacitor electrodes is solved, achieving low internal resistance and high cycle retention rate, reducing production defect rate, and making it suitable for large-scale production of solvent-free dry electrodes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING LI SHEN POWER BATTERY CO LTD
- Filing Date
- 2026-03-10
- Publication Date
- 2026-06-12
AI Technical Summary
Traditional fabrication processes for supercapacitor electrodes suffer from high internal resistance, poor uniformity, and the inability of a single-layer homogeneous structure to balance conductivity and energy storage capacity. Furthermore, the addition of PTFE binder can lead to problems such as non-conductive bonding and non-adhesive bonding.
A three-layer gradient structure design is adopted, using a polypyrrole-based self-adhesive conductive agent (composed of polypyrrole, carbon nanotubes and graphene) to form a bottom layer, an intermediate layer and a top layer on the current collector surface of the electrode sheet. The content of the conductive agent gradually decreases and the specific surface area of the activated carbon gradually increases. Solvent-free dry manufacturing is achieved through low-temperature self-adhesive molding.
It achieves a balance between conductivity and energy storage capacity, reducing electrode internal resistance from 3.0mΩ to ≤2.2mΩ, increasing the 20,000-cycle retention rate from 66% to ≥90%, and reducing the production defect rate from 32% to ≤5%. It requires no additional binders or solvents and is compatible with existing production lines for large-scale production.
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Figure CN122202071A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of supercapacitor technology, and in particular to a supercapacitor electrode and its preparation method, and a supercapacitor. Background Technology
[0002] Supercapacitors are high-power, environmentally friendly energy storage devices. Compared to lithium-ion batteries, their power density is one to two orders of magnitude higher, thus they have broad application prospects in many fields such as wind power generation, smart grids, power storage, rail transportation, and power equipment. Due to their high power density, light weight, fast charging, lack of memory effect, and long service life, supercapacitor batteries have become a key research and development area for most countries.
[0003] Currently, the traditional fabrication process for supercapacitor electrodes is a wet process, which suffers from problems such as high internal resistance and poor uniformity. Furthermore, while existing mass-produced dry electrodes achieve solvent-free production, they still face technological bottlenecks. First, it is a single-layer homogeneous structure, which cannot simultaneously achieve both conductivity and energy storage capacity. Secondly, an additional PTFE (polytetrafluoroethylene) binder is required, and the industry suffers from the pain point that "the adhesive is not conductive and the conductive agent is not adhesive"; at the same time, the mass production process has poor consistency and a high defect rate.
[0004] Therefore, there is an urgent need to develop a technology that can solve the above-mentioned technical problems. Summary of the Invention
[0005] The purpose of this invention is to address the technical deficiencies of existing technologies by providing a supercapacitor electrode and its preparation method, as well as a supercapacitor.
[0006] Therefore, the present invention provides a supercapacitor electrode, including an electrode sheet current collector; The surface of the electrode sheet current collector has a three-layer gradient structure. The three-layer gradient structure consists of three layers: a bottom layer, an intermediate layer, and a top layer. The bottom layer, the middle layer, and the top layer are sequentially arranged from the inside to the outside of the current collector surface of the electrode sheet; The three-layer gradient structure layer uses a polypyrrole-based self-adhesive conductive agent; Regarding the bottom, middle, and top layers, the content of polypyrrole-based self-adhesive conductive agent in these three structural layers gradually decreases, while the specific surface area of activated carbon in these three structural layers gradually increases.
[0007] In addition, the present invention provides a method for preparing a supercapacitor electrode as described above, comprising the following steps: Step S1, raw material pretreatment: three types of activated carbon with different specific surface areas required for preparing the bottom, middle and top layers of the supercapacitor electrode, as well as polypyrrole-based self-adhesive conductive agent, are vacuum dried in advance. Step S2, gradient dry powder mixing operation: According to the preset first mass ratio, the activated carbon and polypyrrole-based self-adhesive conductive agent required for the bottom layer are mixed and stirred evenly to obtain the first mixture; according to the preset second mass ratio, the activated carbon and polypyrrole-based self-adhesive conductive agent required for the middle layer are mixed and stirred evenly to obtain the second mixture; according to the preset third mass ratio, the activated carbon and polypyrrole-based self-adhesive conductive agent required for the surface layer are mixed and stirred evenly to obtain the third mixture; then the first mixture, the second mixture, and the third mixture are extruded and molded respectively to obtain the bottom layer blank, the middle layer blank, and the surface layer blank respectively; Step S3, Low-temperature hot pressing self-adhesive molding operation: Hot pressing is performed on the bottom blank, the middle blank and the surface blank on the surface of the electrode sheet current collector, so that the bottom layer, the middle layer and the surface layer are formed from the inside to the outside of the electrode sheet current collector, thereby constructing a three-layer gradient structure layer on the surface of the electrode sheet current collector. Step S4: Perform slitting and winding operations to obtain the finished supercapacitor electrode.
[0008] In addition, the present invention also provides a supercapacitor comprising supercapacitor electrodes as described above.
[0009] As can be seen from the technical solutions provided by the present invention above, compared with the prior art, the present invention provides a supercapacitor electrode and its preparation method, and a supercapacitor with a scientific design. The supercapacitor electrode adopts a three-layer gradient functional structure layer design and a polypyrrole-based self-adhesive conductive agent, which can balance conductivity and energy storage capacity, and ensure the production quality and yield of the supercapacitor electrode, which has significant practical significance.
[0010] It should be noted that, for this invention, in response to the technical bottlenecks of existing dry electrode mass production processes, this invention provides a solvent-free, binder-free, gradient structure, and continuous mass production dry electrode manufacturing solution based on two previously unused technologies: a three-layer gradient functional structure and a polypyrrole-based self-adhesive conductive agent (composed of polypyrrole, carbon nanotubes, and graphene). This achieves a dual improvement in electrode performance and production yield, filling the gap in existing mass production technologies.
[0011] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects: 1. Structural Innovation: The three-layer gradient functional structure design of this invention is a technology not yet applied in the mass production of dry electrodes. It optimizes the ion and electron transport paths, solving the problem of difficulty in balancing conductivity and energy storage performance in single-layer electrodes. With the same 250μm thickness, it can reduce the electrode internal resistance from 3.0mΩ to ≤2.2mΩ, and increase the retention rate after 20,000 cycles from 66% to ≥90%. 2. Formulation Innovation: The polypyrrole-based self-adhesive conductive agent of this invention is a technology not used in the mass production of dry electrodes. It requires no additional binder, self-adheses at low temperature, and breaks through the bottleneck of "adhesive-conductive separation". At the same thickness of 250μm, it can reduce the electrode production defect rate from 32% to ≤5%. 3. Process innovation: Based on the above two core innovations, continuous large-scale production of dry powder is achieved with a defect rate of ≤5%, and there is no need to modify the existing production line's thickness-related equipment, making it highly adaptable to industrialization; 4. Creativity: The three-layer gradient structure design and the polypyrrole-based self-adhesive conductive agent design are both undisclosed and unapplication technologies in the field of dry electrode mass production. The combination of the two has outstanding substantive features and significant progress. Attached Figure Description
[0012] Figure 1 A simplified structural diagram of one embodiment of a supercapacitor electrode provided by the present invention; Figure 2: Relationship between the content of conductive agent in the electrode of the present invention and the thickness gradient of the coating on one side of the electrode sheet; Figure 3: Gradient relationship between the specific surface area of the activated carbon in the electrode of the present invention and the thickness gradient of the coating on one side of the electrode sheet; Figure 4: Comparison of cycle life between the present invention and existing mass-produced electrodes; Figure 5: Comparison of internal resistance and defect rate of the electrode of the present invention and existing mass-produced electrodes. Detailed Implementation
[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0014] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.
[0015] In the description of this patent, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection or setting, a detachable connection or setting, or an integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this patent according to the specific circumstances.
[0016] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.
[0017] The technical solution of the present invention will be further described below through specific embodiments. Details not specified in the embodiments are all conventional technologies in the industry.
[0018] See Figure 1 As shown, the present invention provides a supercapacitor electrode, including an electrode sheet current collector 4; The surface of the electrode sheet current collector 4 (e.g., the upper and lower two sides) has a three-layer gradient structure. The three-layer gradient structure consists of three layers: bottom layer 1, middle layer 2, and top layer 3. The bottom layer 1, the middle layer 2 and the top layer 3 are sequentially arranged from the inside to the outside of the surface 4 of the electrode sheet current collector; The three-layer gradient structure layer uses a polypyrrole-based self-adhesive conductive agent; Regarding the bottom layer 1, the middle layer 2, and the top layer 3, the content of polypyrrole-based self-adhesive conductive agent (i.e., the mass percentage in the corresponding structural layer) in these three structural layers gradually decreases, and the specific surface area of activated carbon in these three structural layers gradually increases.
[0019] In this invention, specifically, the electrode current collector is an aluminum foil or a copper foil.
[0020] In this invention, specifically, for a three-layer gradient structure, the bottom layer is distributed on the surface of the electrode sheet current collector, the middle layer is distributed on the surface of the bottom layer, and the top layer is distributed on the surface of the middle layer.
[0021] In this invention, specifically, the bottom layer, middle layer and top layer of the three-layer gradient structure all contain: polypyrrole-based self-adhesive conductive agent and activated carbon. In the bottom layer, the mass ratio between polypyrrole-based self-adhesive conductive agent and activated carbon is (10-20):(80-90); In the intermediate layer, the mass ratio between polypyrrole-based self-adhesive conductive agent and activated carbon is (10-15):(85-90); In the surface layer, the mass ratio between polypyrrole-based self-adhesive conductive agent and activated carbon is (5-10):(90-95).
[0022] In practice, activated carbon, specifically activated carbon powder.
[0023] In practice, the specific surface area of the activated carbon in the bottom layer is 1200~1500 m². 2 / g; The activated carbon in the intermediate layer has a specific surface area of 1500 m². 2 / g; The specific surface area of the activated carbon in the surface layer is 1800 m². 2 / g.
[0024] It should be noted that, in this invention, for the three-layer gradient structure, the bottom layer uses low specific surface area activated carbon (1200~1500 μm). 2 / g) is combined with a high-content conductive agent to focus on improving the conductivity of the electrode and the current collector; the intermediate layer uses activated carbon with a medium specific surface area (1500m²). 2 / g) is combined with a medium-content conductive agent as a transition layer to optimize the ion transport path; the surface layer uses high specific surface area activated carbon (1800m²). 2 / g) is combined with a low content of conductive agent to focus on improving the energy storage capacity of the electrode; For this invention, the specific surface area of the bottom activated carbon is 1200~1500 m². 2 / g; The specific surface area of the intermediate layer activated carbon is 1500m². 2 / g; the specific surface area of the surface activated carbon is 1800m². 2 / g can form a gradient distribution to achieve synergistic optimization of conductivity and energy storage performance.
[0025] In this invention, specifically, the polypyrrole-based self-adhesive conductive agent includes polypyrrole, carbon nanotubes and graphene, and is formed by the composite of polypyrrole, carbon nanotubes and graphene. In specific implementation, the polypyrrole-based self-adhesive conductive agent is composed of three components: polypyrrole, carbon nanotubes, and graphene, with the following mass percentages: polypyrrole 70%~80%, carbon nanotubes 14%~22%, and graphene 5%~10%. Among them, polypyrrole is the core binding functional component, which can achieve dry powder self-bonding molding under conditions of <120℃; carbon nanotubes and graphene are conductive functional components, which work together to construct a continuous electron transport network, realizing the integration of binding and conductive functions.
[0026] In practice, the polypyrrole-based self-adhesive conductive agent is composed of polypyrrole, carbon nanotubes and graphene. A polypyrrole-based self-adhesive conductive agent, comprising the following preparation steps: Step 1, solution blending: Add deionized water (only as a dispersion medium, no other solvent) to polypyrrole powder, carbon nanotubes and graphene according to the preset mass ratio, and stir at room temperature (specifically 20-30℃) for 30-60 minutes to form a uniformly dispersed slurry; In the first step, the preset mass ratio is as follows: 70%~80% polypyrrole, 14%~22% carbon nanotubes, and 5%~10% graphene; In practice, the solid content of the mixed slurry is 20% to 30% (mass fraction).
[0027] It should be noted that the powder raw materials are weighed according to the specified ratio of the present invention (70%~80% polypyrrole, 14%~22% carbon nanotubes, and 5%~10% graphene), and the mixed slurry is prepared using deionized water as a temporary dispersion medium; the solid content of the mixed slurry is controlled to be 20%~30% (mass fraction).
[0028] The second step is vacuum drying: the mixed slurry is placed in a vacuum drying oven at 80-100℃ and dried for 2-4 hours to completely remove moisture (no solvent residue, in line with the requirements of the dry process) and obtain a blocky composite. The third step is grinding and sieving: the dried blocky composite is put into a grinder and ground, and then passed through a 200-300 mesh sieve to obtain a uniform and fine polypyrrole-based self-adhesive conductive agent powder, which can be directly used for electrode preparation.
[0029] It should be noted that the supercapacitor electrode of this invention is prepared using a solvent-free dry powder molding process, without adding solvents, slurry, or additional binders. The electrode core consists of three gradient functional layers: a bottom layer, an intermediate layer, and a top layer, sequentially arranged from the current collector to the electrode surface. From the bottom layer to the top layer, the content of the conductive agent gradually decreases, while the specific surface area of the activated carbon gradually increases. The electrode uses a polypyrrole-based polymer composite conductive agent (composed of polypyrrole, carbon nanotubes, and graphene) that combines conductivity and low-temperature self-adhesion, enabling dry powder self-adhesion molding at temperatures below 120°C. The overall thickness of the electrode is 250 μm.
[0030] It should be noted that the polypyrrole-based self-adhesive conductive agent is specifically a polypyrrole-based polymer composite conductive agent. This polypyrrole-based polymer composite conductive agent is an innovative formula, which is composed of polypyrrole and carbon-based conductive agent. It can achieve self-adhesion without the need to add additional binders. The mass ratio of polypyrrole to carbon nanotubes is (3-5):1, and the graphene content is 5-10wt%.
[0031] Based on the supercapacitor electrode provided by the present invention as described above, the present invention also provides a supercapacitor comprising the supercapacitor electrode as described above.
[0032] In order to prepare the supercapacitor electrode provided by the present invention, the present invention also provides a method for preparing the supercapacitor electrode, which is a large-scale dry manufacturing method. It is a solvent-free continuous dry powder process, which relies on a three-layer gradient innovative structural layer and an innovative formula of polypyrrole-based self-adhesive conductive agent. The method for preparing the supercapacitor electrode of the present invention specifically includes the following steps: Step S1, raw material pretreatment: three types of activated carbon with different specific surface areas required for preparing the bottom, middle and top layers of the supercapacitor electrode, as well as polypyrrole-based self-adhesive conductive agent (i.e. polypyrrole-based polymer composite conductive agent) are vacuum dried in advance. In step S1, three types of activated carbon with different specific surface areas are prepared for the bottom, middle, and surface layers of the supercapacitor electrode, specifically with specific surface areas of 1200~1500 m². 2 / g, 1500m 2 / g and 1800m 2 / g of activated carbon.
[0033] In step S1, the three types of activated carbon and the polypyrrole polymer composite conductive agent can be vacuum dried in an oven.
[0034] In step S1, the three types of activated carbon and the polypyrrole polymer composite conductive agent are vacuum dried in an oven at a temperature of 80-100℃.
[0035] It should be noted that, in this invention, step S1 involves vacuum removal of the water physically adsorbed by the powder, and only the water physically adsorbed by the raw material needs to be removed. Since the supercapacitor electrode preparation process of this invention does not require the addition of solvents, there is no need for the solvent drying process as in existing conventional supercapacitor preparation processes. This invention only requires vacuum removal of the water physically adsorbed by the powder, without solvent addition or drying processes, ensuring the flowability and self-adhesion effect of the dry powder.
[0036] In step S1, specifically, the polypyrrole-based self-adhesive conductive agent is formed by combining polypyrrole, carbon nanotubes and graphene. In step S1, specifically, the polypyrrole-based self-adhesive conductive agent is formed by combining polypyrrole, carbon nanotubes and graphene. In step S1, the polypyrrole-based self-adhesive conductive agent includes the following preparation steps: Step 1, solution blending: Add deionized water (only as a dispersion medium, no other solvent) to polypyrrole powder, carbon nanotubes and graphene according to the preset mass ratio, and stir at room temperature (specifically 20-30℃) for 30-60 minutes to form a uniformly dispersed slurry; In the first step, the preset mass ratio is as follows: 70%~80% polypyrrole, 14%~22% carbon nanotubes, and 5%~10% graphene; In practice, the solid content of the mixed slurry is 20% to 30% (mass fraction).
[0037] It should be noted that the powder raw materials are weighed according to the specified ratio of the present invention (70%~80% polypyrrole, 14%~22% carbon nanotubes, and 5%~10% graphene), and the mixed slurry is prepared using deionized water as a temporary dispersion medium; the solid content of the mixed slurry is controlled to be 20%~30% (mass fraction).
[0038] The second step is vacuum drying: the mixed slurry is placed in a vacuum drying oven at 80-100℃ and dried for 2-4 hours to completely remove moisture (no solvent residue, in line with the requirements of the dry process) and obtain a blocky composite. The third step is grinding and sieving: the dried blocky composite is put into a grinder and ground, and then passed through a 200-300 mesh sieve to obtain a uniform and fine polypyrrole-based self-adhesive conductive agent powder, which can be directly used for electrode preparation.
[0039] In step S1, specifically, the polypyrrole-based self-adhesive conductive agent is composed of three components: polypyrrole, carbon nanotubes, and graphene, with the following mass percentages: polypyrrole 70%~80%, carbon nanotubes 14%~22%, and graphene 5%~10%. Among them, polypyrrole is the core binding functional component, which can achieve dry powder self-bonding molding under conditions of <120℃; carbon nanotubes and graphene are conductive functional components, which work together to construct a continuous electron transport network, realizing the integration of binding and conductive functions.
[0040] Step S2, gradient dry powder mixing operation: According to the preset first mass ratio, the activated carbon and polypyrrole-based self-adhesive conductive agent required for the bottom layer are mixed and stirred evenly to obtain the first mixture; according to the preset second mass ratio, the activated carbon and polypyrrole-based self-adhesive conductive agent required for the middle layer are mixed and stirred evenly to obtain the second mixture; according to the preset third mass ratio, the activated carbon and polypyrrole-based self-adhesive conductive agent required for the surface layer are mixed and stirred evenly to obtain the third mixture; then the first mixture, the second mixture, and the third mixture are extruded and molded respectively to obtain the bottom layer blank, the middle layer blank, and the surface layer blank respectively; In step S2, in the bottom layer, the first mass ratio between the polypyrrole-based self-adhesive conductive agent and the activated carbon is (10-20):(80-90); In the intermediate layer, the second mass ratio between the polypyrrole-based self-adhesive conductive agent and the activated carbon is (10-15):(85-90); In the surface layer, the third mass ratio between the polypyrrole-based self-adhesive conductive agent and the activated carbon is (5-10):(90-95).
[0041] In step S2, the extrusion molding process adopted is a mature and widely applied dry powder continuous molding process.
[0042] In step S2, the first mixture, the second mixture, and the third mixture are extruded using existing, technologically mature extrusion molding equipment (such as an extruder).
[0043] In practice, extrusion molding equipment (such as extruders) is a mature equipment that has been widely used. For example, the equipment used in the extrusion molding operation of this invention can be the SF-35 (or other models) dry electrode continuous twin-screw extrusion molding machine produced by Shenzhen Shangshui Intelligent Co., Ltd. This equipment is a general standardized mass production equipment in the field of supercapacitor dry electrodes. It is used for continuous low-temperature extrusion molding of bottom, middle and surface gradient formulation dry powder materials, and can prepare a continuous strip-shaped single-layer electrode preform with uniform thickness (the electrode preform specifically includes bottom preform, middle preform and surface preform).
[0044] In practice, the first mixture is extruded to obtain the bottom preform, which includes the following bottom preform extrusion molding operations: The first step is to mix the pre-mixed, evenly prepared bottom dry powder (1400m). 2 / g of low specific surface area activated carbon and polypyrrole-based self-adhesive conductive agent, with a mass ratio of 85:15 (corresponding to the optimal embodiment ratio in the patent), are placed into the loss-in-weight closed-loop metering feed hopper of an SF-35 (or other model) twin-screw extruder; The second step involves constant feeding of the equipment, which uniformly conveys the bottom dry powder mixture to the closed twin-screw extrusion chamber. The twin screws continuously mix, degas, and compact the material, and the temperature of the chamber and die is stably controlled at 90℃ (<120℃, to match the low-temperature characteristics of polypyrrole self-adhesive conductive agent). The third step involves the continuous extrusion of a continuous, uninterrupted long strip-shaped bottom blank with a thickness of 38.3 μm (three layers of equal thickness) from the slit die at the front end of the twin-screw extruder, thus obtaining the bottom blank. This blank is then pulled at a constant speed by traction rollers, and the thickness deviation is controlled to ≤±1 μm by an online laser thickness gauge. Once qualified, it is conveyed to the subsequent lamination and composite station.
[0045] In practice, the second mixture is extruded to obtain an intermediate layer preform, which includes the following intermediate layer preform extrusion molding operations: The first step is to mix the pre-mixed intermediate layer dry powder (1500m). 2 / g of low specific surface area activated carbon and polypyrrole-based self-adhesive conductive agent, with a mass ratio of 88:12 (corresponding to the optimal embodiment ratio in the patent), are placed into the loss-in-weight closed-loop metering feed hopper of an SF-35 (or other model) twin-screw extruder; The second step involves constant feeding of the equipment, which uniformly conveys the intermediate layer dry powder mixture to the closed twin-screw extrusion chamber. The twin screws continuously mix, degas, and compact the material, and the temperature of the chamber and die head is stably controlled at 90℃ (<120℃, to match the low-temperature characteristics of polypyrrole self-adhesive conductive agent). The third step involves the continuous extrusion of a continuous, uninterrupted long strip-shaped bottom layer preform with a thickness of 38.3 μm (three layers of equal thickness) from the slit die at the front end of the twin-screw extruder, thus obtaining the middle layer preform. This preform is then pulled at a constant speed by traction rollers, and the thickness deviation is controlled to ≤±1 μm by an online laser thickness gauge. Once qualified, it is conveyed to the subsequent lamination and composite station.
[0046] In practice, the third mixture is extruded to obtain a surface preform, which includes the following surface preform extrusion molding operations: The first step is to mix the pre-mixed surface dry powder (1800m). 2 / g of low specific surface area activated carbon and polypyrrole-based self-adhesive conductive agent, with a mass ratio of 92:8 (corresponding to the optimal embodiment ratio in the patent), are placed into the loss-in-weight closed-loop metering feed hopper of an SF-35 (or other model) twin-screw extruder; The second step involves constant feeding of the equipment, which uniformly conveys the surface dry powder mixture to the closed twin-screw extrusion chamber. The twin screws continuously mix, degas, and compact the material, and the temperature of the chamber and die head is stably controlled at 90℃ (<120℃, to match the low-temperature characteristics of polypyrrole self-adhesive conductive agent). The third step involves the continuous extrusion of a continuous, uninterrupted long strip-shaped bottom layer preform with a thickness of 38.3 μm (three layers of equal thickness) from the slit die at the front end of the twin-screw extruder, thus obtaining the top layer preform. This preform is then uniformly pulled by traction rollers, and the thickness deviation is controlled to ≤±1 μm by an online laser thickness gauge. Once qualified, it is conveyed to the subsequent lamination and composite station.
[0047] In step S2, specifically, the bottom blank, the middle blank, and the surface blank are elongated (specifically, continuously distributed elongated or rectangular shapes); the thickness of these three structural layers is the same.
[0048] It should be noted that, in this invention, in step S2, the materials required for the bottom layer, the middle layer and the surface layer are mixed into dry powder and then extruded through dry powder gradient preforming to form a continuous dry powder gradient preform. It should be noted that in step S2, a gradient dry powder pre-extrusion operation is performed: this prepares the materials required for the bottom, middle, and top layers (corresponding to a specific surface area of 1200~1500 m²). 2 / g, 1500m 2 / g、1800m 2 After mixing activated carbon ( / g) and polypyrrole-based self-adhesive conductive agent separately, continuous extrusion can achieve simultaneous preforming of three layers of dry powder to form a uniform gradient green body.
[0049] Step S3, Low-temperature hot pressing self-adhesive molding operation: Hot pressing is performed on the bottom blank, the middle blank and the surface blank on the surface of the electrode sheet current collector, so that the bottom layer, the middle layer and the surface layer are formed from the inside to the outside of the electrode sheet current collector, thereby constructing a three-layer gradient structure layer on the surface of the electrode sheet current collector. In step S3, specifically, for the three-layer gradient structure, the bottom layer is distributed on the surface of the electrode sheet current collector, the middle layer is distributed on the surface of the bottom layer, and the top layer is distributed on the surface of the middle layer; the bottom layer, the middle layer, and the top layer are arranged sequentially from the inside to the outside of the surface of the electrode sheet current collector.
[0050] In step S3, a hot pressing operation is performed at a preset low temperature; In specific implementation, in step S3, the bottom blank, the middle blank and the surface blank are hot-pressed at a temperature range of 100-120℃. The molding is achieved by relying on the self-adhesive function of the polypyrrole-based composite conductive agent in the bottom blank, the middle blank and the surface blank. A three-layer gradient structure layer including the bottom layer, the middle layer and the surface layer is obtained on the surface of the electrode sheet current collector, and no additional adhesive is required.
[0051] Step S4: Perform slitting and winding operations to obtain the finished supercapacitor electrode.
[0052] It should be noted that the slitting and winding processes are mature electrode processing technologies and will not be elaborated upon here.
[0053] After step S4, the present invention can further perform intelligent closed-loop control on the electrode: online detection of electrode parameters, real-time adjustment of process parameters, and improvement of electrode product consistency.
[0054] In addition, after step S4, a non-conforming product recycling operation can be carried out: the non-conforming electrodes are crushed and reused to ensure no waste and no solvent discharge.
[0055] In summary, the supercapacitor electrode preparation method provided by this invention is a large-scale dry manufacturing method that adopts a continuous dry powder forming process. It relies on a three-layer gradient innovative structural layer and a polypyrrole-based self-adhesive conductive agent, which is different from the existing traditional intermittent powder pressing process and is suitable for industrial mass production.
[0056] To better understand the technical solution of the present invention, the technical principle of the supercapacitor electrode provided by the present invention will be explained below.
[0057] I. Solvent-free gradient composite dry supercapacitor electrode.
[0058] The core innovation of the electrode of this invention lies in the use of a three-layer gradient functional structure and a polypyrrole-based self-adhesive conductive agent (composed of polypyrrole, carbon nanotubes, and graphene). The entire process is solvent-free, pulp-free, and requires no additional binders. These two innovations are technologies not yet applied in the mass production of dry-process electrodes for capacitors. 1. Core Innovation 1: The invention employs a three-layer gradient functional structure design: from the current collector to the surface layer, the content of the conductive agent decreases while the specific surface area of the activated carbon increases (bottom layer 1200~1500m²). 2 / g→Intermediate layer 1500m 2 / g→Surface layer 1800m 2 / g), the bottom layer focuses on conductivity, the middle layer focuses on ion transport, and the surface layer focuses on energy storage capacity, which solves the pain point that existing single-layer electrodes cannot take into account both conductivity and energy storage performance. The three-layer gradient functional structure design of this invention achieves a synergistic balance between low internal resistance and high energy storage through spatial partitioning. The bottom layer, with a high content of conductive agent, forms a continuous electron transport network at the current collector-electrode interface, reducing contact and bulk resistance. The middle layer serves as a transition layer, matching electron and ion transport rates, eliminating polarization loss, and reducing polarization resistance. The surface layer, with a low content of conductive agent, avoids encapsulating the active sites of the activated carbon, achieving a 1800m... 2 / g High specific surface area activated carbon is fully exposed to improve energy storage capacity, and polypyrrole-based self-adhesive conductive agent can still form a continuous conductive path even at a low proportion, thus taking into account both energy storage and conductivity.
[0059] This invention, through an overall gradient design, allows each region of the electrode to undertake the functions of conduction, transition, and energy storage respectively. It achieves an overall internal resistance of ≤2.2mΩ from three dimensions: contact internal resistance, bulk internal resistance, and polarization internal resistance. At the same time, it fully releases the energy storage potential of activated carbon, solving the technical pain point of "conductivity and energy storage cannot be achieved simultaneously" in traditional single-layer structures.
[0060] 2. Core Innovation 2: The polypyrrole-based self-adhesive conductive agent of the present invention is composed of polypyrrole and carbon-based conductive agent. It can achieve low-temperature self-adhesion without the need for additional binder, thus solving the pain point of existing mass-produced dry electrodes where "the binder does not conduct electricity and the conductive agent does not adhere". The polypyrrole-based self-adhesive conductive agent of the present invention uses polypyrrole, carbon nanotubes and graphene, which are all commercially available conventional raw materials in the field of new materials, and are not scarce and do not require customized development; The polypyrrole-based self-adhesive conductive agent of the present invention can be obtained on a large scale in two ways. The first way is to prepare the agent by simple solution blending (the preparation process of polypyrrole-based self-adhesive conductive agent requires the use of deionized water as a temporary dispersion medium) – vacuum drying – grinding process according to the specified ratio of the present invention. The formula is controllable and no complex production equipment is required, which is suitable for laboratory research and development and small-batch production. It should be noted that the manufacturing process of polypyrrole-based self-adhesive conductive agent uses only deionized water as a temporary dispersion medium, which is only used to improve the dispersion uniformity of multi-component powders. It is completely removed by vacuum drying. The finished conductive agent has no liquid phase residue. This is fundamentally different from the traditional wet electrode process that uses water and other solvents to make slurry and relies on solvents to complete the electrode forming. This invention belongs to the solvent-free dry electrode preparation method.
[0061] The second approach is to purchase conductive agents from specialized manufacturers according to the formulation requirements of this invention, eliminating the need for new production lines and meeting the demands of industrial-scale mass production. Both methods ensure that the performance and formulation of the conductive agent meet the requirements of this invention, guaranteeing the industrial feasibility of manufacturing and use of the technical solution.
[0062] 3. Innovative optimization of formulation and performance: This invention achieves synergistic optimization of electron and ion transport by limiting the mass ratio of conductive agent to activated carbon in each layer. Specifically, the overall thickness of the electrode of this invention is 250 μm, the capacitance retention rate after 20,000 cycles is ≥90%, the internal resistance is ≤2.2 mΩ, and the production defect rate is ≤5%. Its performance is superior to existing mass-produced single-layer dry electrode of the same thickness (the existing single-layer dry electrode has an internal resistance of 3.0 mΩ, a retention rate of 66% after 20,000 cycles, and a production defect rate of 32%).
[0063] Therefore, addressing the technical bottlenecks of existing traditional mass-production dry electrode single-layer structure processes, such as the need for additional binders, high internal resistance, and high defect rate, this invention employs two innovative designs: a three-layer gradient functional structure and a polypyrrole-based self-adhesive conductive agent (composed of polypyrrole, carbon nanotubes, and graphene). The electrode has a bottom layer, an intermediate layer, and a top layer along the current collector to the surface, with decreasing conductive agent content and an activated carbon specific surface area (1200~1500 m²). 2 / g→1500m 2 / g→1800m 2 The electrode thickness increases by an increment of / g, maintaining the mainstream 250μm thickness of traditional dry-process electrodes. It achieves low-temperature self-bonding at <120℃ using this conductive agent, with no solvents, no pulping, and no additional binders added throughout the process, only removing physically adsorbed water from the raw materials. Mass production is achieved through a continuous dry powder molding process. The electrode of this invention has an internal resistance ≤2.2mΩ, a capacitance retention rate ≥90% after 20,000 cycles, and a production defect rate ≤5%. These innovations are all undisclosed and unapplication technologies in the existing dry-process electrode mass production field, and require no modification to existing production line equipment related to thickness, demonstrating strong industrial adaptability.
[0064] To better understand the technical solution of the present invention, the following describes the technical solution of the present invention in conjunction with specific embodiments.
[0065] The following embodiments further illustrate the present invention, focusing on different proportions of the three-layer gradient functional structure to demonstrate the industrial feasibility of the core innovation of the present invention. The core protection points of the present invention are the three-layer gradient functional structure (i.e., the three-layer gradient structure layer) and the polypyrrole-based self-adhesive conductive agent. The overall thickness of the electrode (i.e., the electrode sheet) is 250 μm (the mainstream thickness of traditional dry process). All embodiments use conventional dry process parameters, namely, vacuum drying at 80-100℃, dry powder mixing + gradient preforming extrusion, hot pressing at 100-120℃ and 0.5-1.0MPa for 5-10 min, and online detection and control.
[0066] Table 1: Schematic diagram of core parameters of supercapacitor electrodes in various embodiments
[0067] Example 1 In Embodiment 1 of the present invention, the three-layer gradient electrode core structure (i.e., the three-layer gradient structure layer) corresponding to Table 1 is used and prepared according to the general dry process of the present invention (i.e. the supercapacitor preparation method described above).
[0068] In Example 1, the mass ratio of the components in the polypyrrole-based self-adhesive conductive agent is as follows: 78% polypyrrole, 16% carbon nanotubes, and 6% graphene.
[0069] Example 2 In Embodiment 2 of the present invention, the three-layer gradient electrode core structure corresponding to the one in Table 1 below is adopted and prepared according to the general dry process of the present invention (i.e. the supercapacitor preparation method described above), which is the optimal implementation of the three-layer gradient structure.
[0070] In Example 2, the mass ratio of the components in the polypyrrole-based self-adhesive conductive agent is as follows: 78% polypyrrole, 16% carbon nanotubes, and 6% graphene.
[0071] Example 3 In Embodiment 3 of the present invention, the three-layer gradient electrode core structure corresponding to Table 1 is adopted and prepared according to the general dry process of the present invention (i.e. the supercapacitor preparation method described above). The conductive agent has the highest proportion and the internal resistance reduction effect is the most significant.
[0072] In Example 3, the mass ratio of the components in the polypyrrole-based self-adhesive conductive agent is as follows: 78% polypyrrole, 16% carbon nanotubes, and 6% graphene.
[0073] Comparative experiment (control group) The existing traditional mass-produced single-layer dry electrode (the overall thickness of the electrode is 250μm, with added PTFE (polytetrafluoroethylene) binder, no three-layer gradient ratio, and no polypyrrole self-adhesive conductive agent) has the following performance parameters: internal resistance 3.0mΩ, 66% retention rate after 20,000 cycles, and 32% defect rate.
[0074] It should be noted that existing traditional mass-produced single-layer dry-process electrodes, including activated carbon (specific surface area of approximately 1500 m²), 2 The mixture consists of a conductive agent (SP conductive carbon black) and a binder (PTFE polytetrafluoroethylene), in a mass ratio of approximately 88:5:7.
[0075] As shown in Table 1, Examples 1-3 of the present invention (with an overall electrode thickness of 250 μm) exhibit a cycle retention rate of 92%-95%, an internal resistance of 1.9-2.2 mΩ, and a defect rate of 3.5-4.2%, all of which are superior to existing commercially available electrodes of the same thickness. This performance improvement is unaffected by thickness variations and is solely attributable to the three-layer gradient conductive agent + activated carbon formulation design and the application of a polypyrrole-based self-adhesive conductive agent. Both of these technologies, individually and in combination, are undisclosed and unapplications in the prior art, demonstrating outstanding inventiveness and practicality.
[0076] Figure 2: Relationship between the content of conductive agent in the electrode of the present invention and the thickness gradient of the coating on one side of the electrode sheet; See Figure 2 The horizontal axis represents the thickness of the coating on one side of the electrode (μm), and the vertical axis represents the content of the conductive agent (wt%). The figure contains four curves, representing Example 1, Example 2, Example 3, and the control group (existing single-layer dry electrode of the same thickness). Figure 2 The data clearly shows that from the current collector (aluminum foil) side to the electrode surface, the conductive agent content in Examples 1-3 decreases gradually with the increase of the coating thickness on one side, while the conductive agent content in the control group has no gradient and is uniformly distributed throughout, which intuitively demonstrates the design advantages of the three-layer gradient structure of the present invention in terms of conductive agent ratio. Figure 3: Gradient relationship between the specific surface area of the activated carbon in the electrode of the present invention and the thickness gradient of the coating on one side of the electrode sheet; See Figure 3 x-axis: coating thickness on one side of the electrode (μm), y-axis: specific surface area of activated carbon (m²) 2 / g); The figure contains four curves, representing Example 1, Example 2, Example 3, and the control group (existing single-layer dry electrode of the same thickness); Figure 3 The data clearly shows that, from the current collector (aluminum foil) side to the electrode surface, the specific surface area of the activated carbon in Examples 1-3 exhibits a gradient increasing trend with the increase of the coating thickness on one side (1200~1500 μm²). 2 / g→1500m 2 / g→1800m 2 / g), the control group has no gradient in specific surface area and is homogeneously distributed throughout, which complements the conductive agent gradient in Figure 2, demonstrating the synergistic design of conductivity and energy storage in this invention; in Figure 3 In the middle, the inner layer is the bottom layer; Figure 4: Comparison of cycle life between the present invention and existing mass-produced electrodes See Figure 4The graph shows four curves: x-axis: number of cycles (times), y-axis: capacitance retention (%). These curves represent Example 1, Example 2, Example 3, and the control group (existing single-layer dry electrode with the same 250μm thickness). The curve trends show that as the number of cycles increases, the capacitance retention of the control group rapidly decreases, reaching only 66% after 20,000 cycles. In contrast, the capacitance retention of Examples 1-3 remains stable, reaching 92%, 93%, and 95% respectively after 20,000 cycles, showing no significant decrease. This clearly demonstrates the cycling stability advantage of the electrode of this invention. Figure 5: Comparison of internal resistance and defect rate of the electrode of the present invention and existing mass-produced electrodes; See Figure 5 The horizontal axis represents the experimental groups (Example 1, Example 2, Example 3, and Control Group), and the vertical axis represents the internal resistance (mΩ) on the left and the defect rate (%) on the right. The graph shows the internal resistance and defect rate data of each group in the form of a bar chart. It clearly shows that the internal resistance (1.9~2.2mΩ) and defect rate (3.5~4.2%) of Examples 1-3 are much lower than those of the control group (internal resistance 3.0mΩ, defect rate 32%). Among them, Example 2 is the optimal ratio, with an internal resistance of 2.0mΩ and a defect rate of 3.8%, which fully verifies the technical effect of the present invention in reducing electrode internal resistance and improving production yield.
[0077] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A supercapacitor electrode, characterized in that, Including electrode sheet current collector (4); The surface of the electrode sheet current collector (4) has a three-layer gradient structure layer; The three-layer gradient structure consists of a bottom layer (1), an intermediate layer (2), and a top layer (3). The bottom layer (1), the middle layer (2) and the top layer (3) are arranged sequentially from the inside to the outside of the surface (4) of the electrode sheet current collector. The three-layer gradient structure layer uses a polypyrrole-based self-adhesive conductive agent; Regarding the bottom layer (1), the middle layer (2), and the top layer (3), the content of polypyrrole self-adhesive conductive agent in these three structural layers gradually decreases, and the specific surface area of activated carbon in these three structural layers gradually increases.
2. The supercapacitor electrode as described in claim 1, characterized in that, For a three-layer gradient structure, the bottom layer is distributed on the current collector surface of the electrode sheet, the middle layer is distributed on the bottom layer surface, and the top layer is distributed on the middle layer surface.
3. The supercapacitor electrode as described in claim 1, characterized in that, The bottom, middle and top layers of the three-layer gradient structure all contain: polypyrrole-based self-adhesive conductive agent and activated carbon; In the bottom layer, the mass ratio between polypyrrole-based self-adhesive conductive agent and activated carbon is (10-20):(80-90); In the intermediate layer, the mass ratio between polypyrrole-based self-adhesive conductive agent and activated carbon is (10-15):(85-90); In the surface layer, the mass ratio between polypyrrole-based self-adhesive conductive agent and activated carbon is (5-10):(90-95).
4. The supercapacitor electrode as described in claim 1, characterized in that, The specific surface area of the activated carbon in the bottom layer is 1200~1500 m². 2 / g; The activated carbon in the intermediate layer has a specific surface area of 1500 m². 2 / g; The specific surface area of the activated carbon in the surface layer is 1800 m². 2 / g.
5. The supercapacitor electrode as described in claim 1, characterized in that, Polypyrrole-based self-adhesive conductive agent, comprising polypyrrole, carbon nanotubes and graphene; the mass percentage of each component is: polypyrrole 70%~80%, carbon nanotubes 14%~22%, graphene 5%~10%.
6. A method for preparing a supercapacitor electrode as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step S1, raw material pretreatment: three types of activated carbon with different specific surface areas required for preparing the bottom, middle and top layers of the supercapacitor electrode, as well as polypyrrole-based self-adhesive conductive agent, are vacuum dried in advance. Step S2, gradient dry powder mixing operation: According to the preset first mass ratio, the activated carbon and polypyrrole-based self-adhesive conductive agent required for the bottom layer are mixed and stirred evenly to obtain the first mixture; according to the preset second mass ratio, the activated carbon and polypyrrole-based self-adhesive conductive agent required for the middle layer are mixed and stirred evenly to obtain the second mixture; according to the preset third mass ratio, the activated carbon and polypyrrole-based self-adhesive conductive agent required for the surface layer are mixed and stirred evenly to obtain the third mixture; then the first mixture, the second mixture, and the third mixture are extruded and molded respectively to obtain the bottom layer blank, the middle layer blank, and the surface layer blank respectively; Step S3, Low-temperature hot pressing self-adhesive molding operation: Hot pressing is performed on the bottom blank, the middle blank and the surface blank on the surface of the electrode sheet current collector, so that the bottom layer, the middle layer and the surface layer are formed from the inside to the outside of the electrode sheet current collector, thereby constructing a three-layer gradient structure layer on the surface of the electrode sheet current collector. Step S4: Perform slitting and winding operations to obtain the finished supercapacitor electrode.
7. The method for preparing a supercapacitor electrode as described in claim 6, characterized in that, In step S1, three types of activated carbon with different specific surface areas are prepared for the bottom, middle, and surface layers of the supercapacitor electrode, specifically with specific surface areas of 1200~1500 m². 2 / g, 1500m 2 / g and 1800m 2 / g of activated carbon; In step S1, the polypyrrole-based self-adhesive conductive agent includes the following preparation steps: Step 1, solution blending: Add deionized water to polypyrrole powder, carbon nanotubes and graphene according to the preset mass ratio, and stir at room temperature for 30-60 minutes to form a uniformly dispersed slurry; In the first step, the preset mass ratio is as follows: 70%~80% polypyrrole, 14%~22% carbon nanotubes, and 5%~10% graphene; The second step is vacuum drying: the mixed slurry is placed in a vacuum drying oven at 80-100℃ and dried for 2-4 hours to completely remove moisture and obtain a blocky composite. The third step is grinding and sieving: the dried blocky composite is put into a grinder and ground, and then passed through a 200-300 mesh sieve to obtain a uniform and fine polypyrrole-based self-adhesive conductive agent powder, which can be directly used for electrode preparation.
8. The method for preparing a supercapacitor electrode as described in claim 6, characterized in that, In step S1, the three types of activated carbon and the polypyrrole polymer composite conductive agent are vacuum dried in an oven at a temperature of 80-100℃. In step S3, the bottom blank, the middle blank, and the surface blank are hot-pressed at a temperature range of 100-120℃.
9. The method for preparing a supercapacitor electrode as described in claim 6, characterized in that, In step S2, in the bottom layer, the first mass ratio between the polypyrrole-based self-adhesive conductive agent and the activated carbon is (10-20):(80-90); In the intermediate layer, the second mass ratio between the polypyrrole-based self-adhesive conductive agent and the activated carbon is (10-15):(85-90); In the surface layer, the third mass ratio between the polypyrrole-based self-adhesive conductive agent and the activated carbon is (5-10):(90-95).
10. A supercapacitor, characterized in that, Includes the supercapacitor electrode as described in any one of claims 1 to 5.