Preparation method of dry-method pole piece

Abstract

A preparation method of a dry-method pole piece specifically comprises the following steps: step 1, adding an active substance, a binder and a conductive agent into a stirrer according to a mass ratio of (80-90%): (5-10%): (5-10%), heating and mixing to obtain mixed dry powder; 2, the mixed dry powder obtained in the step 1 is subjected to multiple times of negative pressure expansion operation, heating and stirring are kept in the process, a mixture is obtained, and the heating and stirring temperature is the same as the heating and mixing temperature in the step 1; step 3, adding the mixture obtained in the step 2 into a roller press, and carrying out heating and rolling treatment to prepare a dry-method pole piece membrane; 4, heating a current collector by using a laser heating device, and compounding the dry-method pole piece film on the current collector to obtain a dry-method pole piece; no solvent is introduced in the dry-method pole piece production process, and energy consumption caused by pole piece drying can be avoided.

Description

Technical Field

[0001] The present invention belongs to the field of dry-process electrode preparation, and in particular relates to a method for preparing a dry-process electrode. Background Art

[0002] Supercapacitors are a new type of electrochemical energy storage technology between traditional capacitors and secondary batteries. Compared with traditional capacitors, the active materials of supercapacitors are usually porous materials with high specific surface area, which significantly increases the effective area of ​​energy storage; the thickness of the double electric layer formed on the surface of the pole piece is nanometer-level, which is conducive to high energy storage. Compared with secondary batteries, the energy storage process of supercapacitors is highly reversible, and high-power and long-life charging and discharging processes can be achieved. Thanks to the excellent energy storage characteristics of supercapacitors, supercapacitors are particularly suitable for scenarios with instantaneous high current discharge, rapid charging and discharging, 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 the braking energy when the vehicle brakes. In addition, supercapacitors also play an important role in aerospace, machinery, military, low-temperature starting and other fields.

[0003] According to whether liquid solvent is introduced in the process of preparing the electrode, the preparation process of supercapacitor electrode can be divided into two types: wet process and dry process. The wet process has the advantages of mature technology and low production difficulty, but it also has the following defects: 1) High drying cost. A large amount of electricity is consumed for solvent volatilization during the drying process of the wet process; 2) Particle stratification occurs. During the wet process production process, due to the different densities of active materials, conductive agents, and binder particles, stratification is easy to occur in a static state. For example, in the solvent evaporation stage of the coating process, particles with low density tend to float on the upper layer, and particles with high density tend to settle to the lower layer, resulting in low bonding strength between particles and easy cracking of the electrode; 3) Solvents are difficult to remove. Since the core energy storage material (porous carbon material) of the supercapacitor has a very strong adsorption effect, the solvent remaining in the pores is difficult to completely remove, which ultimately leads to an increase in the leakage current of the supercapacitor and a decrease in the cycle life; 4) The active material loading is low, which limits the capacity of the supercapacitor, and thick electrodes are more likely to crack during the drying process, forming defects, and even causing supercapacitor failure.

[0004] Compared with the wet process, the dry process can effectively increase the active material loading, and because there is no introduction of solvent, it avoids the energy-intensive drying and solvent removal process. However, the current dry process is still not ideal. For example, CN104521033A discloses a method of using a solvent to activate a binder, which can reduce the amount of binder used, but causes problems such as residual solvent used to activate the binder and the introduction of additional pole piece drying costs. CN115207290A discloses a method of using high-speed airflow mixing technology to achieve mixing between solid powder particles and to drive the molten binder to stretch into a fiber state through high-temperature and high-pressure compressed air, but this method requires a large amount of compressed air, which is costly, and the pressure of the airflow injection is also limited, resulting in a low degree of fiberization of the binder particles. Summary of the invention

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

[0006] The present invention adopts the following technical solution: A method for preparing a dry electrode comprises the following steps: Step 1, adding active material, binder and conductive agent in a mass ratio of 80-90%: 5-10%: 5-10% into a blender, heating and mixing to obtain a mixed dry powder; Step 2, performing multiple negative pressure expansion operations on the mixed dry powder obtained in step 1, and maintaining heating and stirring during the process to obtain a mixture, wherein the temperature of heating and stirring is the same as the temperature of heating and mixing in step 1; Step 3, adding the mixture obtained in step 2 into a roller press for heating and roller pressing to prepare a dry electrode film; Step 4, after heating the current collector by using a laser heating device, compounding the above-mentioned dry electrode film on the current collector to obtain the dry electrode; Furthermore, in step 2, the multiple negative pressure expansion operations include multiple vacuuming of the mixed dry powder to form negative pressure and nitrogen replenishment operations, wherein the negative pressure is: (-100) - (-10) kPa, the negative pressure is maintained for 180-300s, the nitrogen replenishment pressure is: (-5) - (0) kPa, the nitrogen is maintained for 180-300s, and the number of negative pressure expansions is: 10-20 times.

[0007] Furthermore, in step 1, the raw material drying is also included before the heating and mixing. The raw material drying is: putting the active material and the conductive agent into a blast oven for baking and drying. The baking temperature is set to: 60-120°C, and the baking time is set to: 6-12h.

[0008] 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; the binder is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, polyvinyl alcohol, or polyacrylic acid.

[0009] Furthermore, in step 1, the heating and mixing is carried out in a double planetary mixer, the heating temperature is 150-200° C., the stirring speed is 5-10 Hz, and the stirring time is 6-12 h.

[0010] Furthermore, in step 3, when the roller press is working, the roller pressure is: 100-150 Bar, the roller speed is: 1-3 m / min, and the roller temperature is: 80-120°C.

[0011] Furthermore, the surface of the current collector in step 4 is coated with a conductive adhesive, and at least one side of the current collector surface is provided with a conductive adhesive.

[0012] Furthermore, in step 4, when the laser heating device is working, the heating time is: 1-5s, and the heating temperature is: 200-300°C. Within this range, the conductive glue on the surface of the current collector melts, thereby bonding the dry electrode film to the current collector.

[0013] Furthermore, in step 4, the compounding process is carried out in a roller press, and the roller pressure is 50-80 Bar and the roller speed is 1-3 m / min.

[0014] It can be seen from the above description of the present invention that, compared with the prior art, the present invention has the following beneficial effects: First, the present invention uses a negative pressure expansion method in combination with a heating and stirring method to make the binder fiberized more fully. The principle is that the porous nature of the active material makes it very easy for gas to gather inside the pores and between the active material particles. During the physical mixing process, the binder powder and the active material particles are dispersed with each other to form a mixed dry powder rich in gas inside. Then, negative pressure treatment is performed to make the gas pressure inside the dry powder less than the atmospheric pressure, thereby achieving a process of increasing the volume. During this process, the heated and softened binder is drawn into fibers, that is, fiberized. Repeated operations of pumping negative pressure and supplementing nitrogen improve the uniformity of the binder fiberization and make the fiberization more complete. That is, the binder undergoes fiberization under the action of negative pressure, and the stirring action enables the fiberized binder to effectively distribute the active material and the surface of the conductive agent particles, cross-linking into a network. In this process, heating is used to soften the binder, which is conducive to the fiberization. Second, the laser heating device is used to quickly heat the current collector coated with conductive glue to melt the conductive glue, thereby improving the fit between the current collector and the dry electrode film. The wrinkles caused by the different elongation of the dry electrode film and the current collector, and the low bonding strength between the current collector and the dry electrode film are solved. In addition, the rapid heating brought by the laser heating device can effectively improve production efficiency. Thirdly, the dry-process electrode production process of the present invention does not involve the introduction of solvents, thereby avoiding the energy consumption caused by drying the electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the composite of dry electrode film and current collector; Figure 2 This is an optical image of the dry electrode film prepared in Example 2; In the figure, 1-dry electrode film, 2-current collector, 3-laser heating device. DETAILED DESCRIPTION

[0016] The present invention is further described below through specific implementation modes.

[0017] A method for preparing a dry electrode comprises the following steps: Step 1, placing the active material and the binder in a blast oven at 60-120°C for baking and drying for 6-12h, adding the dried active material, binder and conductive agent in a mass ratio of 80-90%: 5-10%: 5-10% to a double planetary mixer for heating and mixing to obtain a mixed dry powder, wherein the heating temperature is 150-200°C, the stirring speed is 5-10Hz, and the stirring time is 6-12h; Step 2, performing multiple negative pressure expansion operations on the mixed dry powder obtained in step 1, and maintaining heating and stirring during the process to obtain a mixture, wherein the temperature of heating and stirring is the same as the temperature of heating and mixing in step 1; Step 3, adding the mixture obtained in step 2 into a roller press for heating and roller pressing to prepare a dry electrode film 1; Step 4, after heating the current collector 2 by using the laser heating device 3, the above-mentioned dry electrode film 1 is compounded on the current collector 2 to obtain the dry electrode; Among them, 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; the binder is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, polyvinyl alcohol, or polyacrylic acid.

[0018] In step 2, multiple negative pressure expansion operations include multiple vacuuming of the mixed dry powder to form negative pressure and nitrogen replenishment operations, wherein the negative pressure is: (-100) - (-10) kPa, the negative pressure is maintained for 180-300s, the nitrogen replenishment pressure is: (-5) - (0) kPa, the nitrogen is maintained for 180-300s, and the number of negative pressure expansions is: 10-20 times.

[0019] In step 3, when the roller press is working, the roller pressure is: 100-150 Bar, the roller speed is: 1-3 m / min, and the roller temperature is: 80-120°C.

[0020] The surface of the current collector in step 4 is coated with a conductive glue, and at least one side of the current collector surface is provided with a conductive glue; when the laser heating device is working, the heating time is: 1-5s, and the heating temperature is: 200-300°C. Within this range, the conductive glue 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 rolling pressure is: 50-80 Bar, and the rolling speed is: 1-3 m / min.

[0021] Example 1 A method for preparing a dry electrode comprises the following steps: Step 1: Weigh 900g of activated carbon powder and 50g of Super P powder in turn and put them into a blast oven for baking and drying. The baking temperature is set to 60°C and the baking time is set to 12h. Then, add the dried activated carbon powder, Super P powder and 50g of polytetrafluoroethylene powder into a double planetary mixer for heating and stirring. The heating temperature is 200°C, the stirring speed is 5Hz, and the stirring time is 12h. Step 2: The mixed dry powder obtained in step 1 is subjected to multiple negative pressure expansion operations to achieve the purpose of binder fiberization, and heating and stirring are maintained during the process to obtain a mixture. The stirring speed is: 30 Hz, the heating temperature is: 200°C, the negative pressure is: -100 kPa, the negative pressure time is: 300 s, the nitrogen supplement pressure is: -5 kPa, the nitrogen time is: 300 s, and the number of negative pressure expansions is: 10 times; Step 3: Add the mixture obtained in step 2 into a roller press for heating and rolling treatment, with a rolling pressure of 100 Bar, a rolling speed of 1 m / min, and a rolling temperature of 80° C. to prepare a dry electrode film; Step 4: Use a laser heating device to heat the current collector coated with conductive glue on both sides. The heating time is 5s and the heating temperature is 200°C. Then, the above-mentioned dry electrode film is composited on the current collector. The composite process is carried out in a roller press with a rolling pressure of 50 Bar and a rolling speed of 1 m / min to obtain the dry electrode.

[0022] Example 2 A method for preparing a dry electrode comprises the following steps: Step 1: Weigh 800g of activated carbon powder and 100g of Super P powder in turn and put them into a blast oven for baking and drying. The baking temperature is set to 120°C 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 into a double planetary mixer for heating and stirring. The heating temperature is 200°C, the stirring speed is 10Hz, and the stirring time is 6h. Step 2: The mixed dry powder obtained in step 1 is subjected to multiple negative pressure expansion operations to achieve the purpose of binder fiberization, and heating and stirring are maintained during the process to obtain a mixture. The stirring speed is: 30 Hz, the heating temperature is: 200°C, the negative pressure is: -50 kPa, the negative pressure time is: 300 s, the nitrogen supplement pressure is: -5 kPa, the nitrogen time is: 300 s, and the number of negative pressure expansions is: 20 times; Step 3: Add the mixture obtained in step 2 into a roller press for heating and rolling treatment, with a rolling pressure of 150 Bar, a rolling speed of 1 m / min, and a rolling temperature of 120° C. to prepare a dry electrode film; Step 4: Use a laser heating device to heat the current collector coated with conductive glue on both sides. The heating time is 1s and the heating temperature is 300°C. Then, the above-mentioned dry electrode film is composited on the current collector. The composite process is carried out in a roller press. The rolling pressure is 80 Bar and the rolling speed is 3m / min to obtain the dry electrode.

[0023] Comparative Example 1 A method for preparing a dry electrode comprises the following steps: Step 1: Weigh 800g of activated carbon powder and 100g of Super P powder in turn and put them into a blast oven for baking and drying. The baking temperature is set to 120°C 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 for stirring. The stirring speed is 10Hz and the stirring time is 6h. Step 2: The mixed dry powder obtained in step 1 is subjected to multiple negative pressure expansion operations to achieve the purpose of binder fiberization, and stirring is maintained during the process to obtain a mixture. The stirring speed is: 30 Hz, no heating operation, the negative pressure is: -50 kPa, the negative pressure time is: 300 s, the nitrogen supplement pressure is: -5 kPa, the nitrogen time is: 300 s, and the number of negative pressure expansions is: 20 times; Step 3: Add the mixture obtained in step 2 into a roller press for heating and rolling treatment, with a rolling pressure of 150 Bar, a rolling speed of 1 m / min, and a rolling temperature of 120° C. to prepare a dry electrode film; Step 4: Use a laser heating device to heat the current collector coated with conductive glue on both sides. The heating time is 1s and the heating temperature is 300°C. Then, the above-mentioned dry electrode film is composited on the current collector. The composite process is carried out in a roller press. The rolling pressure is 80 Bar and the rolling speed is 3m / min to obtain the dry electrode.

[0024] Comparative Example 2 A method for preparing a dry electrode comprises the following steps: Step 1: Weigh 800g of activated carbon powder and 100g of Super P powder in turn and put them into a blast oven for baking and drying. The baking temperature is set to 120°C 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 for heating and stirring. The heating temperature is 200°C, the stirring speed is 10Hz, and the stirring time is 6h. Step 2: The mixed dry powder obtained in step 1 is subjected to multiple negative pressure expansion operations to achieve the purpose of binder fiberization, and heating and stirring are maintained during the process to obtain a mixture. The stirring speed is: 30 Hz, the heating temperature is: 200°C, the negative pressure is: -50kPa, the negative pressure time is: 300s, the nitrogen supplement pressure is: -5kPa, the nitrogen time is: 300s, and the number of negative pressure expansions is: 20 times; Step 3: Add the mixture obtained in step 2 into a roller press for heating and rolling treatment, with a rolling pressure of 150 Bar, a rolling speed of 1 m / min, and a rolling temperature of 120° C. to prepare a dry electrode film; Step 4: Compound the above-mentioned dry electrode film on the current collector. The compounding process is carried out in a roller press. The rolling pressure is 80 Bar and the rolling speed is 3 m / min to obtain the dry electrode.

[0025] Comparative Example 3 A method for preparing a dry electrode comprises the following steps: Step 1: Weigh 800g of activated carbon powder and 100g of Super P powder in turn and put them into a blast oven for baking and drying. The baking temperature is set to 120°C 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 for heating and stirring. The heating temperature is 200°C, the stirring speed is 10Hz, and the stirring time is 6h. Step 2: Heat and stir the mixed dry powder obtained in step 1 to obtain a mixture. The stirring speed is 30 Hz and the heating temperature is 200°C; Step 3: Add the mixture obtained in step 2 into a roller press for heating and rolling treatment, with a rolling pressure of 150 Bar, a rolling speed of 1 m / min, and a rolling temperature of 120° C. to prepare a dry electrode film; Step 4: Compound the above-mentioned dry electrode film on the current collector. The compounding process is carried out in a roller press. The rolling pressure is 80 Bar and the rolling speed is 3 m / min to obtain the dry electrode.

[0026] The appearance inspection results of the dry-process electrodes of the above-mentioned embodiments and comparative examples are shown in Table 1.

[0027] Table 1 project Pole appearance inspection results Example 1 Smooth, no powdering, no wrinkles Example 2 Smooth, no powdering, no wrinkles Comparative Example 1 The surface of the pole piece is powdery and the uniformity is poor Comparative Example 2 The pole piece is wrinkled, some pole pieces are deformed, and the belt is easy to break. Comparative Example 3 The mixture cannot form a complete film and appears as dispersed powder As can be seen from Table 1, the dry-process electrode sheet preparation method using a fiberization process supplemented by negative pressure expansion treatment and heating and stirring, and simultaneously, using a laser heating device to quickly heat the current collector coated with a conductive adhesive, has a good appearance of being flat, free of powder and wrinkles; by comparing Example 2 with Comparative Example 1, it can be seen that the dry-process electrode sheet obtained by the fiberization process without heating has problems of surface powder loss and poor uniformity; by comparing Example 2 with Comparative Example 2, it can be seen that the dry-process electrode sheet obtained by the lack of a laser heating device to quickly heat the current collector coated with a conductive adhesive has wrinkles, even deformation, and easy to break the belt; by comparing Example 2 with Comparative Example 3, it can be seen that the mixture obtained by lacking the negative pressure expansion step cannot be rolled into a complete dry-process electrode sheet film, and appears as a dispersed powder. This is because the unfiberized binder cannot cross-link the active material and the conductive agent particles into a network.

[0028] The above description is only a preferred embodiment of the present invention, and therefore cannot be used to limit the scope of implementation of the present invention. That is, equivalent changes and modifications made according to the application 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: The specific steps include: Step 1, adding active material, binder and conductive agent in a mass ratio of 80-90%: 5-10%: 5-10% into a blender, heating and mixing to obtain a mixed dry powder; Step 2, performing multiple negative pressure expansion operations on the mixed dry powder obtained in step 1, and maintaining heating and stirring during the process to obtain a mixture, wherein the temperature of heating and stirring is the same as the temperature of heating and mixing in step 1; Step 3, adding the mixture obtained in step 2 into a roller press for heating and roller pressing to prepare a dry electrode film; Step 4, after heating the current collector by using a laser heating device, the above-mentioned dry-process electrode film is compounded on the current collector to obtain the dry-process electrode.

2. The method for preparing a dry electrode according to claim 1, characterized in that: In step 2, multiple negative pressure expansion operations include multiple vacuuming of the mixed dry powder to form negative pressure and nitrogen replenishment operations, wherein the negative pressure is: (-100) - (-10) kPa, the negative pressure is maintained for 180-300s, the nitrogen replenishment pressure is: (-5) - (0) kPa, the nitrogen is maintained for 180-300s, and the number of negative pressure expansions is: 10-20 times.

3. The method for preparing a dry electrode according to claim 1, characterized in that: In step 1, the raw material drying is also included before the heating and mixing. The raw material drying is: putting the active material and the conductive agent into a blast oven for baking and drying. The baking temperature is set to: 60-120° C., and the baking time is set to: 6-12 hours.

4. The method for preparing a dry electrode 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; the binder is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, polyvinyl alcohol, or polyacrylic acid.

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

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

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

8. The method for preparing a dry electrode according to claim 7, characterized in that: In step 4, when the laser heating device is working, the heating time is: 1-5s, and the heating temperature is: 200-300°C. Within this range, the conductive glue on the surface of the current collector melts, thereby bonding the dry electrode film to the current collector.

9. The method for preparing a dry electrode 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.

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