A method for preparing dry electrode sheets

Abstract

A method for preparing a dry electrode sheet includes the following steps: Step 1, adding active material, binder, and conductive agent to a mixer in a mass ratio of 80-90%: 5-10%: 5-10% and heating and mixing to obtain a mixed dry powder; Step 2, subjecting the mixed dry powder obtained in Step 1 to multiple negative pressure expansion operations while maintaining heating and stirring during the process to obtain a mixture, wherein the heating and stirring temperature is the same as the heating and mixing temperature in Step 1; Step 3, adding the mixture obtained in Step 2 to a roller press for heated rolling treatment to prepare a dry electrode sheet film; Step 4, heating the current collector using a laser heating device, and then laminating the above-mentioned dry electrode sheet film onto the current collector to obtain a dry electrode sheet; The present invention avoids the introduction of solvents in the dry electrode sheet production process, thus avoiding the energy consumption caused by drying the electrode sheet.

Description

Technical Field

[0001] This invention belongs to the field of dry electrode preparation, and specifically relates to a method for preparing dry electrodes. Background Technology

[0002] Supercapacitors are a novel electrochemical energy storage technology that bridges the gap between traditional capacitors and rechargeable batteries. Compared to traditional capacitors, the active materials of supercapacitor electrodes are typically porous materials with high specific surface areas, significantly increasing the effective energy storage area. The double layer formed on the electrode surface is nanometer-thick, which is beneficial for high energy storage. Compared to rechargeable batteries, the energy storage process of supercapacitors is highly reversible, enabling high-power, long-life charge-discharge cycles. Thanks to their excellent energy storage characteristics, supercapacitors are particularly suitable for applications requiring instantaneous high-current discharge, rapid charge-discharge, long cycle life, and rapid energy recovery. For example, supercapacitors can not only provide the instantaneous high power required for vehicle starting but also recover braking energy during vehicle braking. Furthermore, supercapacitors also play an important role in aerospace, machinery, military, and cryogenic starting applications.

[0003] Based on whether liquid solvents are introduced during electrode preparation, the manufacturing processes of supercapacitor electrodes can be divided into two types: wet and dry processes. Wet processes have advantages such as mature technology and low production difficulty, but they also have the following drawbacks: 1) High drying costs: Wet processes require a large amount of electricity for solvent evaporation during drying; 2) Particle stratification: During wet process production, due to the different densities of active materials, conductive agents, and binders, stratification easily occurs under static conditions. For example, during the solvent evaporation stage of the coating process, less dense particles tend to float on the upper layer, while denser particles tend to settle to the lower layer, resulting in lower inter-particle bonding strength and easy electrode cracking; 3) Solvent removal is difficult: Because the core energy storage material of supercapacitors (porous carbon materials) has a strong adsorption effect, the solvent remaining in the pores is difficult to completely remove, ultimately leading to increased leakage current and reduced cycle life; 4) Low active material loading limits the capacity of supercapacitors, and thicker electrodes are more prone to cracking during drying, forming defects and even causing supercapacitor failure.

[0004] Compared to wet processes, dry processes can effectively increase the loading of active materials and avoid the energy-intensive drying and solvent removal process due to the absence of solvent introduction. However, current dry processes are still not ideal. For example, CN104521033A discloses a method for activating binders using solvents, which can reduce the amount of binder used, but causes problems such as solvent residue used to activate the binder and the introduction of additional electrode drying costs. CN115207290A discloses a method for mixing solid powder particles using high-speed airflow mixing technology and stretching the molten binder into a fibrous shape using high-temperature and high-pressure compressed air, but this method requires a large amount of compressed air, resulting in high costs, and the airflow injection pressure is also limited, leading to a low degree of fiberization of the binder particles. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing dry electrode sheets.

[0006] The present invention adopts the following technical solution:

[0007] A method for preparing a dry electrode sheet specifically includes the following steps:

[0008] Step 1: Add the active substance, binder and conductive agent to a mixer in a mass ratio of 80-90%: 5-10%: 5-10% and heat to mix, so as to obtain a mixed dry powder;

[0009] Step 2: Perform multiple negative pressure expansion operations on the mixed dry powder obtained in Step 1, while maintaining heating and stirring during the process to obtain a mixture. The heating and stirring temperature is the same as the heating and mixing temperature in Step 1.

[0010] Step 3: Add the mixture obtained in Step 2 to a roller press for heating and rolling treatment to prepare a dry electrode film;

[0011] Step 4: After heating the current collector using a laser heating device, the above-mentioned dry electrode film is laminated onto the current collector to obtain the dry electrode.

[0012] Furthermore, in step 2, the multiple negative pressure expansion operations include multiple vacuuming operations to form negative pressure and nitrogen replenishment operations for the mixed dry powder. The negative pressure is (-100) - (-10) kPa, the negative pressure is maintained for 180-300 s, the nitrogen replenishment pressure is (-5) - (0) kPa, the nitrogen is maintained for 180-300 s, and the number of negative pressure expansion operations is 10-20 times.

[0013] Furthermore, in step 1, before heating and mixing, the raw materials are dried. The drying process involves placing the active material and conductive agent into a blower oven for baking and drying. The baking temperature is set to 60-120℃ and the baking time is set to 6-12h.

[0014] Furthermore, the active material is selected from at least one of graphene, activated carbon powder, activated carbon fiber, and activated carbon balls; the conductive agent is selected from at least one of metal powder, conductive graphite, carbon nanotubes, acetylene black, Ketjen black, and Super P; and the binder is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, polyvinyl alcohol, or polyacrylic acid.

[0015] Furthermore, in step 1, the heating and mixing are carried out in a double planetary mixer at a heating temperature of 150-200℃, a mixing speed of 5-10Hz, and a mixing time of 6-12h.

[0016] Furthermore, in step 3, when the roller press is working, the roller pressing pressure is 100-150 Bar, the roller pressing speed is 1-3 m / min, and the roller pressing temperature is 80-120℃.

[0017] Furthermore, in step 4, the surface of the current collector is coated with conductive adhesive, and at least one side of the current collector surface is provided with conductive adhesive.

[0018] Furthermore, in step 4, when the laser heating device is working, the heating time is 1-5 seconds and the heating temperature is 200-300℃. Within this range, the conductive adhesive on the surface of the current collector melts, thereby bonding the dry electrode film to the current collector.

[0019] Furthermore, in step 4, the compounding process is carried out in a roller press with a roller pressure of 50-80 Bar and a roller speed of 1-3 m / min.

[0020] As can be seen from the above description of the present invention, compared with the prior art, the beneficial effects of the present invention are:

[0021] First, this invention utilizes negative pressure expansion combined with heating and stirring to achieve more complete fiberization of the binder. The principle is as follows: the porous nature of the active material allows gas to easily accumulate within the pores and between the active material particles. During physical mixing, the binder powder and active material particles disperse, forming a mixed dry powder rich in gas. Negative pressure treatment is then applied, lowering the internal gas pressure of the dry powder to atmospheric pressure, thus increasing its volume. During this process, the softened binder is drawn into fibers, i.e., fiberization. Repeated negative pressure application and nitrogen replenishment improve the uniformity of binder fiberization, making it more complete. In other words, the binder undergoes fiberization under negative pressure, and stirring effectively distributes the fiberized binder across the surface of the active material and conductive agent particles, cross-linking into a network. Heating further softens the binder, facilitating fiberization.

[0022] Secondly, the laser heating device rapidly heats the current collector coated with conductive adhesive, melting the conductive adhesive and improving the adhesion between the current collector and the dry electrode film. This solves problems such as wrinkles caused by the difference in elongation between the dry electrode film and the current collector, and the low bonding strength between the current collector and the dry electrode film. Furthermore, the rapid heating brought by the laser heating device can effectively improve production efficiency.

[0023] Third, the absence of solvents in the dry electrode production process of this invention avoids the energy consumption associated with drying electrodes. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the composite of dry electrode film and current collector;

[0025] Figure 2 Optical image of the dry electrode film prepared in Example 2;

[0026] In the figure, 1-dry electrode film, 2-current collector, 3-laser heating device. Detailed Implementation

[0027] The present invention will be further described below through specific embodiments.

[0028] A method for preparing a dry electrode sheet specifically includes the following steps:

[0029] Step 1: Place the active material and binder in a forced-air oven and bake them at 60-120℃ for 6-12 hours. Then, add the dried active material, binder and conductive agent to a double planetary mixer in a mass ratio of 80-90%: 5-10%: 5-10% and heat to mix them to obtain a mixed dry powder. The heating temperature is 150-200℃, the stirring speed is 5-10Hz, and the stirring time is 6-12 hours.

[0030] Step 2: Perform multiple negative pressure expansion operations on the mixed dry powder obtained in Step 1, while maintaining heating and stirring during the process to obtain a mixture. The heating and stirring temperature is the same as the heating and mixing temperature in Step 1.

[0031] Step 3: Add the mixture obtained in step 2 to a roller press for heating and rolling treatment to prepare dry electrode film 1;

[0032] Step 4: After heating the current collector 2 using the laser heating device 3, the above-mentioned dry electrode film 1 is laminated onto the current collector 2 to obtain the dry electrode.

[0033] The active material is selected from at least one of graphene, activated carbon powder, activated carbon fiber, and activated carbon balls; the conductive agent is selected from at least one of metal powder, conductive graphite, carbon nanotubes, acetylene black, Ketjen black, and Super P; and the binder is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, polyvinyl alcohol, or polyacrylic acid.

[0034] In step 2, the multiple negative pressure expansion operations include multiple vacuuming operations to form negative pressure and nitrogen replenishment operations for the mixed dry powder. The negative pressure is (-100) - (-10) kPa, the negative pressure is maintained for 180-300 s, the nitrogen replenishment pressure is (-5) - (0) kPa, the nitrogen is maintained for 180-300 s, and the number of negative pressure expansion operations is 10-20 times.

[0035] In step 3, when the roller press is working, the roller pressing pressure is 100-150 Bar, the roller pressing speed is 1-3 m / min, and the roller pressing temperature is 80-120℃.

[0036] In step 4, the surface of the current collector is coated with conductive adhesive, and at least one side of the current collector surface is provided with conductive adhesive; when the laser heating device is working, the heating time is 1-5s, the heating temperature is 200-300℃, within this range, the conductive adhesive on the surface of the current collector melts, thereby bonding the dry electrode film to the current collector; the composite process is carried out in a roller press, the roller pressing pressure is 50-80 Bar, and the roller pressing speed is 1-3 m / min.

[0037] Example 1

[0038] A method for preparing a dry electrode includes the following steps:

[0039] Step 1: Weigh 900g of activated carbon powder and 50g of Super P powder and place them in a forced-air oven for baking and drying. The baking temperature is set to 60℃ and the baking time is set to 12h. Then, add the dried activated carbon powder, Super P powder and 50g of polytetrafluoroethylene powder to a double planetary mixer for heating and stirring. The heating temperature is 200℃, the stirring speed is 5Hz, and the stirring time is 12h.

[0040] Step 2: The mixed dry powder obtained in Step 1 is subjected to multiple negative pressure expansion operations to achieve the purpose of fiberization of the binder, while maintaining heating and stirring during the process to obtain a mixture. Stirring speed: 30Hz, heating temperature: 200℃, negative pressure: -100kPa, negative pressure holding time: 300s, nitrogen replenishment pressure: -5kPa, nitrogen holding time: 300s, number of negative pressure expansions: 10.

[0041] Step 3: The mixture obtained in Step 2 is added to a roller press for heating and rolling treatment. The rolling pressure is 100 Bar, the rolling speed is 1 m / min, and the rolling temperature is 80℃ to prepare a dry electrode film.

[0042] Step 4: The current collector coated with conductive adhesive on both sides is heated using a laser heating device for 5 seconds at a temperature of 200°C. Then, the dry electrode film is laminated onto the current collector in a roller press at a pressure of 50 Bar and a speed of 1 m / min to obtain the dry electrode.

[0043] Example 2

[0044] A method for preparing a dry electrode includes the following steps:

[0045] Step 1: Weigh 800g of activated carbon powder and 100g of Super P powder and place them in a forced-air oven for baking and drying. The baking temperature is set to 120℃ and the baking time is set to 12h. Then, add the dried activated carbon powder, 100g of Super P powder and 100g of polytetrafluoroethylene powder to a double planetary mixer for heating and stirring. The heating temperature is 200℃, the stirring speed is 10Hz, and the stirring time is 6h.

[0046] Step 2: The mixed dry powder obtained in Step 1 is subjected to multiple negative pressure expansion operations to achieve the purpose of fiberization of the binder, while maintaining heating and stirring during the process to obtain a mixture. Stirring speed: 30Hz, heating temperature: 200℃, negative pressure: -50kPa, negative pressure holding time: 300s, nitrogen replenishment pressure: -5kPa, nitrogen holding time: 300s, number of negative pressure expansions: 20.

[0047] Step 3: The mixture obtained in Step 2 is added to a roller press for heating and rolling treatment. The rolling pressure is 150 Bar, the rolling speed is 1 m / min, and the rolling temperature is 120℃ to prepare a dry electrode film.

[0048] Step 4: The current collector coated with conductive adhesive on both sides is heated using a laser heating device for 1 second at a temperature of 300°C. The dry electrode film is then laminated onto the current collector in a roller press at a pressure of 80 Bar and a speed of 3 m / min to obtain the dry electrode.

[0049] Comparative Example 1

[0050] A method for preparing a dry electrode includes the following steps:

[0051] Step 1: Weigh 800g of activated carbon powder and 100g of Super P powder and put them into a forced-air oven for baking and drying. The baking temperature is set to 120℃ and the baking time is set to 12h. Then, add the dried activated carbon powder, Super P powder and 100g of polytetrafluoroethylene powder into a double planetary mixer and stir at a speed of 10Hz for 6h.

[0052] Step 2: The mixed dry powder obtained in Step 1 is subjected to multiple negative pressure expansion operations to achieve the purpose of fiberization of the binder, while stirring is maintained during the process to obtain a mixture. The stirring speed is 30Hz, no heating is performed, the negative pressure is -50kPa, the negative pressure is maintained for 300s, the nitrogen supply pressure is -5kPa, the nitrogen is maintained for 300s, and the number of negative pressure expansions is 20.

[0053] Step 3: The mixture obtained in Step 2 is added to a roller press for heating and rolling treatment. The rolling pressure is 150 Bar, the rolling speed is 1 m / min, and the rolling temperature is 120℃ to prepare a dry electrode film.

[0054] Step 4: The current collector coated with conductive adhesive on both sides is heated using a laser heating device for 1 second at a temperature of 300°C. The dry electrode film is then laminated onto the current collector in a roller press at a pressure of 80 Bar and a speed of 3 m / min to obtain the dry electrode.

[0055] Comparative Example 2

[0056] A method for preparing a dry electrode includes the following steps:

[0057] Step 1: Weigh 800g of activated carbon powder and 100g of Super P powder and place them in a forced-air oven for baking and drying. The baking temperature is set to 120℃ and the baking time is set to 12h. Then, add the dried activated carbon powder, Super P powder and 100g of polytetrafluoroethylene powder to a double planetary mixer for heating and stirring. The heating temperature is 200℃, the stirring speed is 10Hz, and the stirring time is 6h.

[0058] Step 2: The mixed dry powder obtained in Step 1 is subjected to multiple negative pressure expansion operations to achieve the purpose of fiberization of the binder, while maintaining heating and stirring during the process to obtain a mixture. The stirring speed is 30 Hz, the heating temperature is 200℃, the negative pressure is -50kPa, the negative pressure holding time is 300s, the nitrogen replenishment pressure is -5kPa, the nitrogen holding time is 300s, and the number of negative pressure expansion operations is 20.

[0059] Step 3: The mixture obtained in Step 2 is added to a roller press for heating and rolling treatment. The rolling pressure is 150 Bar, the rolling speed is 1 m / min, and the rolling temperature is 120℃ to prepare a dry electrode film.

[0060] Step 4: The above-mentioned dry electrode film is laminated onto the current collector. The lamination process is carried out in a roller press with a rolling pressure of 80 Bar and a rolling speed of 3 m / min to obtain the dry electrode.

[0061] Comparative Example 3

[0062] A method for preparing a dry electrode includes the following steps:

[0063] Step 1: Weigh 800g of activated carbon powder and 100g of Super P powder and place them in a forced-air oven for baking and drying. The baking temperature is set to 120℃ and the baking time is set to 12h. Then, add the dried activated carbon powder, Super P powder and 100g of polytetrafluoroethylene powder to a double planetary mixer for heating and stirring. The heating temperature is 200℃, the stirring speed is 10Hz, and the stirring time is 6h.

[0064] Step 2: The mixed dry powder obtained in Step 1 is heated and stirred only to obtain a mixture. The stirring speed is 30 Hz, and the heating temperature is 200℃.

[0065] Step 3: The mixture obtained in Step 2 is added to a roller press for heating and rolling treatment. The rolling pressure is 150 Bar, the rolling speed is 1 m / min, and the rolling temperature is 120℃ to prepare a dry electrode film.

[0066] Step 4: The above-mentioned dry electrode film is laminated onto the current collector. The lamination process is carried out in a roller press with a rolling pressure of 80 Bar and a rolling speed of 3 m / min to obtain the dry electrode.

[0067] The appearance inspection results of the dry-process electrode sheets obtained in the above embodiments and comparative examples are shown in Table 1.

[0068] Table 1

[0069] project Electrode appearance inspection results Example 1 Smooth, no powdering, no wrinkles Example 2 Smooth, no powdering, no wrinkles Comparative Example 1 The electrode surface sheds powder, resulting in poor uniformity. Comparative Example 2 The electrode sheets are wrinkled, some are deformed, and they are prone to breakage. Comparative Example 3 The mixture cannot form a complete film and instead appears as a dispersed powder.

[0070] As shown in Table 1, the dry electrode prepared by the method of using negative pressure expansion treatment combined with heating and stirring fiberization process, and simultaneously using a laser heating device to rapidly heat the current collector coated with conductive adhesive, has a good appearance with flatness, no powder shedding, and no wrinkles. Comparing Example 2 with Comparative Example 1, it can be seen that the dry electrode obtained without the heating fiberization process has problems with surface powder shedding and poor uniformity. Comparing Example 2 with Comparative Example 2, it can be seen that the dry electrode obtained without the laser heating device to rapidly heat the current collector coated with conductive adhesive has problems with wrinkles, even deformation, and easy breakage. Comparing Example 2 with Comparative Example 3, it can be seen that the mixture obtained without the negative pressure expansion step cannot be rolled into a complete dry electrode film and appears as a dispersed powder. This is because the unfiberized binder cannot cross-link the active material and conductive agent particles into a network.

[0071] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing a dry electrode, characterized in that: Specifically, the following steps are included: Step 1: Add the active substance, binder and conductive agent to a mixer in a mass ratio of 80-90%: 5-10%: 5-10% and heat to mix, so as to obtain a mixed dry powder; Step 2: Perform multiple negative pressure expansion operations on the mixed dry powder obtained in Step 1, while maintaining heating and stirring during the process to obtain a mixture. The heating and stirring temperature is the same as the heating and mixing temperature in Step 1. Step 3: Add the mixture obtained in Step 2 to a roller press for heating and rolling treatment to prepare a dry electrode film; Step 4: After heating the current collector using a laser heating device, the above-mentioned dry electrode film is laminated onto the current collector to obtain the dry electrode. In step 2, the multiple negative pressure expansion operations include multiple vacuuming operations to form negative pressure and nitrogen replenishment operations for the mixed dry powder. The negative pressure is (-100) - (-10) kPa, the negative pressure is maintained for 180-300 s, the nitrogen replenishment pressure is (-5) - (0) kPa, the nitrogen is maintained for 180-300 s, and the number of negative pressure expansion operations is 10-20 times. In step 1, before heating and mixing, the raw materials are dried. The drying process involves placing the active material and conductive agent into a blower oven for baking and drying. The baking temperature is set to 60-120℃ and the baking time is set to 6-12h.

2. The method for preparing a dry electrode sheet according to claim 1, characterized in that: The active material is selected from at least one of graphene, activated carbon powder, activated carbon fiber, and activated carbon balls; the conductive agent is selected from at least one of metal powder, conductive graphite, carbon nanotubes, acetylene black, Ketjen black, and Super P; and the binder is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, polyvinyl alcohol, or polyacrylic acid.

3. The method for preparing a dry electrode sheet according to claim 1, characterized in that: In step 1, heating and mixing are carried out in a double planetary mixer at a heating temperature of 150-200℃, a mixing speed of 5-10Hz, and a mixing time of 6-12h.

4. The method for preparing a dry electrode sheet according to claim 1, characterized in that: In step 3, when the roller press is working, the roller pressing pressure is 100-150 Bar, the roller pressing speed is 1-3 m / min, and the roller pressing temperature is 80-120℃.

5. The method for preparing a dry electrode sheet according to claim 1, characterized in that: In step 4, the surface of the current collector is coated with conductive adhesive, and at least one side of the current collector surface is provided with conductive adhesive.

6. The method for preparing a dry electrode sheet according to claim 5, characterized in that: In step 4, when the laser heating device is working, the heating time is 1-5 seconds and the heating temperature is 200-300℃. Within this range, the conductive adhesive on the surface of the current collector melts, thereby bonding the dry electrode film to the current collector.

7. The method for preparing a dry electrode sheet according to claim 1, characterized in that: In step 4, the compounding process is carried out in a roller press with a roller pressure of 50-80 Bar and a roller speed of 1-3 m / min.

Images