Method for making supercapacitor diaphragm paper

Abstract

The present application relates to a method for making supercapacitor diaphragm paper, comprising the following steps: S1: selecting goose skin as the fiber raw material of supercapacitor diaphragm paper; S2: pulping goose skin; S3: making insulating pulp; S4: papermaking; S41: first concentration adjustment of insulating pulp; S42: using a high beating degree of not less than 80°SR and using a pulping machine and a nano-comb grinding disc for feathering beating to form a fiber trunk and a feathered fiber composed of nano-scale fiber filaments connected to the fiber trunk, and the fiber filament diameter is between 10nm and 40nm; S43: second concentration adjustment; S44: screening by a pulping machine; S45: papermaking by a round-net papermaking machine in combination with a dispersant. The diaphragm paper of the present application has a small fiber diameter, high strength, small thickness, high liquid absorption capacity, and relatively small supercapacitor loss, so that the supercapacitor can be made higher, and granular activated carbon with a smaller diameter can also be used to increase the capacity of the supercapacitor.

Description

Technical Field

[0001] The present application belongs to the field of papermaking technology, and in particular relates to a method for manufacturing supercapacitor diaphragm paper. Background Art

[0002] The existing supercapacitor diaphragm paper generally uses Tencel as raw material, which seriously affects its performance: 1. The low strength of paper seriously affects the high-speed operation of the subsequent process. During the manufacturing process of supercapacitors, the product may be scrapped due to paper rupture; 2. The thickness of the paper cannot be reduced, and the loss (ESR) of the supercapacitor is relatively large; 3. Paper has poor liquid absorption performance, which limits the height of supercapacitors. Summary of the invention

[0003] The technical problem solved by the present application is to overcome the above-mentioned deficiencies in the prior art and provide a method for manufacturing supercapacitor diaphragm paper.

[0004] The technical solution adopted by the present application to solve the above technical problems is: a method for making supercapacitor diaphragm paper, which is characterized by comprising the following steps: S1: Select goose skin as the fiber raw material for supercapacitor separator paper; S2: pulping of goose skin; S3: Preparation of insulation slurry: S31: spiral slurry extrusion; S32: The pulp after spiral squeezing is sent to the reaction tank via a screw conveyor; the liquid after spiral squeezing is respectively transported to the black liquor storage tank or the reverse liquid storage tank according to the concentration of the process setting parameters; S33: the pulp fibers in the reaction tank are subjected to an insulating pulp treatment process; S34: if the obtained pulp fiber meets the technical requirements, it is sent to the insulating pulp tank, otherwise it is sent to the screw extruder through the rough pulp tank to continue step S31; S4: Papermaking: S41: First concentration adjustment of the insulating slurry; S42: A high beating degree of not less than 80°SR is used and a refiner and a nano-comb grinding disc are used for feathering beating, so that the polished fibers are formed into a fiber trunk and a feathered fiber composed of fiber filaments mainly of nanometer size connected to the fiber trunk, and the diameter of the fiber filaments is between 10nm and 40nm; S43: second concentration adjustment; S44: pulp screening machine to remove fiber balls; S45: Papermaking is carried out using a cylinder paper machine in the presence of a dispersant.

[0005] The S2 step described in this application includes the following steps: S21: cutting and weighing the raw materials; S22: pre-impregnation with liquid medicine; S23: screw feed; S24: steaming with liquid medicine; S25: The pulp is sent to the blowdown pot, and the gas emission from the blowdown pot is subjected to water film dust removal, and the pulp is sent to the pulp silo.

[0006] The S3 step described in this application includes the following steps: S31: spiral slurry extrusion; S32: The pulp fibers after spiral squeezing are sent to the reaction tank via a screw conveyor; the liquid produced by the first spiral squeezing is sent to the black liquor storage tank, and the liquid produced by the second and subsequent spiral squeezing is sent to the reverse liquid storage tank; S33: the pulp fibers in the reaction tank are subjected to an insulating pulp treatment process; S34: If the prepared pulp fiber meets the technical requirements, it is sent to the insulating pulp tank, otherwise it is sent to the screw extruder through the coarse pulp tank to continue step S31.

[0007] The thickness of the supercapacitor diaphragm paper in this application is ≤20 microns.

[0008] Compared with the prior art, the present application has the following advantages and effects: the supercapacitor diaphragm paper fiber has a small diameter, the supercapacitor diaphragm paper has high strength and small thickness, the supercapacitor loss (ESR) is relatively small, the supercapacitor diaphragm paper has high liquid absorption capacity, the supercapacitor can be made taller, and granular activated carbon with a smaller diameter can be used to increase its surface area, thereby increasing the capacity of the supercapacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a flow chart of the pulping steps of an embodiment of the present application.

[0010] Figure 2 It is a flow chart of the steps of preparing insulating slurry according to an embodiment of the present application.

[0011] Figure 3 It is a flow chart of the papermaking steps of an embodiment of the present application.

[0012] Figure 4 It is a comparative schematic diagram of the ion motion trajectory of the embodiment of the present application and the ion motion trajectory of the prior art (it is only an example, in fact, the micron fiber filaments are about a thousand times larger than the nano fiber filaments).

[0013] Figure 5 This is a schematic diagram of the scene of the capacitor diaphragm paper fiber under an electron microscope according to an embodiment of the present application.

[0014] Figure 6 yes Figure 5 A partial enlarged schematic diagram.

[0015] Figure 7 yes Figure 5 Another partial enlarged schematic diagram of .

[0016] In the figure: A-schematic diagram of ion motion trajectory in the prior art, B-schematic diagram of ion motion trajectory in the present application, C-cross section of micron fiber filaments in the prior art, D-cross section of nano fiber filaments in the present application; ZG-fiber trunk, ZG1-first fiber trunk, ZG2-second fiber trunk, ZG3-third fiber trunk, FS-fiber filaments. DETAILED DESCRIPTION

[0017] The present application will be further described in detail below in conjunction with the accompanying drawings and through examples. The following examples are intended to explain the present application but the present application is not limited to the following examples.

[0018] See also Figure 1 to Figure 7 The method for making the supercapacitor diaphragm paper of the present application embodiment comprises the following steps: S1: Selecting goose skin as the fiber raw material for supercapacitor separator paper According to the special requirements of supercapacitor diaphragm paper, especially the special requirements in the field of electrochemistry, fibers with small fiber diameter and high β-cellulose content must be selected. Since the strength of typing wax paper base made of Yanpi can reach 0.928KN / m or more for paper with a thickness of no more than 23μm, in order to achieve the strength of national standard supercapacitor diaphragm paper, the thickness of supercapacitor diaphragm paper made of Yanpi can be reduced to below 20 microns, so the best choice at present is Yanpi raw material fiber.

[0019] S2: Pulping of goose skin Pulping can be done by Figure 1 Pulping methods shown: S21: cutting and weighing the raw materials; S22: pre-impregnation with liquid medicine; S23: screw feed; S24: steaming with liquid medicine; S25: the pulp is sent to the blowdown pot, the gas emission from the blowdown pot is subjected to water film dust removal, and the pulp is sent to the pulp silo; S3: Preparation of insulation slurry Insulation slurry can be made by Figure 2 The method shown.

[0020] S31: spiral slurry extrusion; S32: The pulp fibers after spiral squeezing are sent to the reaction tank via a screw conveyor; the liquid generated by the first spiral squeezing is sent to the black liquor storage tank, and the liquid generated by the subsequent spiral squeezing of the pulp transported from the coarse pulp tank (i.e., after the second time) is sent to the reverse liquid storage tank (i.e., reusable liquid); S33: The pulp fibers in the reaction tank are subjected to conventional insulating pulp treatment process (according to the process requirements, the following steps need to be performed separately: S331 step: washing with water to remove the cooking liquid; S332 step: removing metal impurities with an acid of about PH3 and washing with pure water; S333 step: neutralizing the residual acid with alkali and washing with pure water to produce insulating pulp. S334 step is an optional step: according to user needs, if white pulp is required, bleaching with H2O2 is also required); S34: If the pulp fiber obtained in step S33 meets the technical requirements, it is sent to the insulating pulp tank, otherwise it is sent to the screw extruder through the coarse pulp tank.

[0021] Pulping and insulation pulping easily bring about the pollution of sewage and waste gas. Waste gas can be solved by water film dust removal. On the one hand, low-concentration sewage is used for backwashing to reduce the amount of sewage. On the other hand, concentrated sewage is sent to chemical plants for processing as raw materials. On the other hand, a small amount of middle water (i.e. the reverse selection liquid from the screw extruder) can be sent to the reaction tank for repeated use or discharged in small quantities after conventional flotation and biochemical treatment.

[0022] S4: Papermaking Papermaking steps can be used Figure 3 The method shown.

[0023] S41: The first concentration of the insulating slurry (about 3.5~5%); S42: Use a high beating degree (beating degree is not less than 80°SR) and use a pulping machine and a nano-comb grinding disc for feathering beating, and the polished fibers are formed into a fiber trunk ZG and a feathered fiber composed of fiber filaments FS mainly at the nano level connected to the fiber trunk ZG; the pulping can be performed using a matching pulping machine and a nano-comb grinding disc in a patent application number of 202310823329.7 and a patent application name of "Feathered Fiber Diaphragm Paper and Preparation Method and Application thereof", and the fibers are subjected to a high pulping degree beating treatment for feathering beating, so that The fiber filaments FS are both tiny and connected to the fiber trunk ZG. The diameter of the fiber filaments is mainly 12nm. The paper made of these fine fibers has mainly nanometer-scale pores, forming a good "nanopore filter paper". The fine fiber filaments and the fiber trunk are kept as integrated as possible under high beating conditions, making the fiber papermaking process like the accumulation of a large number of feathers, which can not only ensure the efficient passage of ions, but also prevent the penetration short circuit of activated carbon particles, making the supercapacitor diaphragm paper more in line with the special requirements of ion movement in electrochemistry. This application upgrades the fiber beating process from "brooming" beating to "feathering" beating, so that the produced supercapacitor diaphragm paper has a large number of fiber filaments FS mainly at the nanometer level and gaps between the fiber filaments FS (see Figure 4 ) can minimize the distance of ion movement, thus further reducing the "loss" of supercapacitors. Where there is movement, there is energy loss. "Feathering" beating can effectively reduce the movement distance of ions, so that charged ions can reach their destination with the minimum movement distance, thus reducing the "loss" of supercapacitors.

[0024] S43: Second concentration adjustment (about 1-2%); S44: pulp screening machine to remove fiber balls and solve the problem of paper uniformity; S45: Papermaking is performed by a cylinder paper machine in the presence of a dispersant.

[0025] Technical points of this application: 1. The smaller the fiber diameter of supercapacitor paper, the better. Fibers with small diameters can make diaphragm paper with lower thickness, and the path of ion movement is shorter, which can make supercapacitors have lower "loss", also known as lower ESR value of supercapacitors; supercapacitors are electrochemical components, and their important material diaphragm paper must meet the basic requirements of electrochemistry. The basic principle of electrochemistry is that under the action of a DC external electric field (charging), weak electrolytes in the electrolyte are ionized into positive and negative ions. At the same time, positive ions move toward the negative electrode and negative ions move toward the positive electrode (the solvent enclosed by the electrolyte is an insulator). When the external electric field decreases or disappears (discharge), the positive and negative ions recombine into weak electrolytes. This is repeated continuously. Even if it is charged and discharged millions of times, it can still basically maintain its excellent performance. Positive and negative ions are charged tiny particles with nanometer diameters, and the sum of the distances of positive and negative ion movement is generally greater than the thickness of the diaphragm paper. The fiber filaments formed by conventional papermaking are all at the micron level. The difference between the two is more than a thousand times. These ions cannot move forward through the micron fiber filaments formed by conventional papermaking, but can only move around the micron fiber filaments, which greatly increases the movement distance of the ions. Figure 4 B, the present application, because the diameter of the nanofiber filaments is at the nanometer level, the diameter of the nanofiber filaments is small and the interval is small, the distance that the ions pass through the same paper thickness is small, and the prior art sees Figure 4 A, the distance that ions pass through the same paper thickness is large, which greatly improves the ESR value of the supercapacitor. In addition, since the supercapacitor diaphragm paper is an electrochemical component, ions are constantly moving in the diaphragm paper. Therefore, the diaphragm paper must maintain its ion movement channel. Supercapacitors are components with extremely low operating voltages, but their energy density during operation is extremely large, that is, the operating current is extremely large, and the number of ions in the internal current is large. The movement diameter of ions is not much different from the average diameter of air, which can be measured by air permeability, so supercapacitor paper must have a higher air permeability, and the small diameter of the nanofiber filaments also helps to improve the air permeability of the diaphragm paper. In addition, the electrodes of supercapacitors are generally composed of very fine granular activated carbon covered on the surface of aluminum foil. Direct contact is not allowed between the two electrodes to cause a short circuit. Therefore, supercapacitor paper must remain free of small holes to prevent the penetration of granular activated carbon. The spacing between the nanofiber filaments of the present application is small, which helps to prevent the penetration of granular activated carbon, and activated carbon with smaller particles can be used to increase its surface area, thereby increasing the capacity of the supercapacitor.

[0026] 2. By using diaphragm paper with lower thickness, a shell of the same volume can achieve a larger capacity; the thickness of the diaphragm paper in this application is ≤20 microns.

[0027] 3. The paper made from goose skin pulping has another important characteristic: the liquid absorption height is particularly good. Referring to the liquid absorption height test of stylus wax paper base paper, its liquid absorption height can exceed the test range of the instrument (150mm). Even under the condition of low beating degree, stylus wax paper base paper has no pinholes, but the air permeability is still high. These properties are very suitable for supercapacitor diaphragm paper.

[0028] See also Figure 5~Figure 7 , Schematic diagram of the fiber state of the paper sample of this application scanned under the femtosecond / FM5269-SEM / 3-07 system, Figure 5 The parameters of three fiber trunks ZG and nine fiber sub-filaments FS were statistically calculated, and the specific data are as follows: The minimum diameter of fiber FS is 16.5nm, the maximum diameter is 30.9nm, and the average diameter is 24.47nm; The fiber trunk ZG1 has a diameter of 252.6 nm at the indicated position; The fiber trunk ZG2 has a diameter of 164.8 nm at the indicated position; The diameter of the fiber trunk ZG3 at the indicated position is 281.1 nm, which indicates that under the condition of high beating degree, the diameter of the fiber trunk is significantly reduced.

[0029] The present application forms feathered fibers with a fiber trunk ZG as the main component and nano-scale fiber filaments FS attached to the fiber trunk ZG as the auxiliary component, which reduces the ESR value of the supercapacitor, has good air permeability, and helps prevent the penetration of activated carbon. The thickness of the diaphragm paper can be made smaller, and activated carbon with smaller particles can be used to increase its surface area, thereby increasing the capacity of the supercapacitor.

[0030] The pulp made from Yanpi has a small fiber diameter and a particularly long fiber length (length 2.36-5.67 mm, diameter 4.4-22 μm), with an average aspect ratio of up to 421 (the aspect ratio of high-quality wood pulp fiber is less than 100). Therefore, the aspect ratio of the fiber is particularly large. During the papermaking process of the iron pen wax paper base paper, it is easy for the fibers to cross-link with each other, resulting in fiber balling, which has an adverse effect on the uniformity of the paper. The iron pen wax paper base paper is produced by a side wave papermaking machine, which basically imitates the manual production method to solve the problem of fiber cross-linking and balling. The longitudinal and transverse arrangement of the fibers of the side wave papermaking machine is opposite to that of the commonly used garden net paper machine, long net and inclined net paper machine, and does not meet the actual requirements of supercapacitor paper. The present application adopts high beating degree beating, and the length of the Yanpi fiber can be shortened during the beating process to reduce the aspect ratio and prevent the problem of fiber balling; the additional pulp screening machine can remove the fiber balling problem, thereby solving the problem of paper uniformity. Raw materials with high β-cellulose content, high pulp concentration and short fiber cutting will not reduce the strength of paper. Instead, more hydroxyl groups will be exposed, which will form hydrogen bonds with water molecules and make the paper stronger.

[0031] Supercapacitor diaphragm paper is an electrochemical component, and the continuous movement of ions in the diaphragm paper is its greatest feature. Therefore, the diaphragm paper must maintain the channel for the movement of ions. Supercapacitors are components with extremely low working voltages. However, their energy density during operation is extremely high, that is, the working current is extremely high, and the number of ions in the internal current is large. The movement diameter of ions is not much different from the average diameter of air, which can be measured by air permeability. Therefore, supercapacitor paper must have a high air permeability. However, the electrodes of supercapacitors are generally composed of very fine particles of activated carbon covered on the surface of aluminum foil. Direct contact between the two electrodes is not allowed to cause a short circuit. Therefore, supercapacitor paper must be kept free of small holes to prevent the penetration of activated carbon and cause a short circuit. The above two points are contradictory. Conventional papermaking processes use high pulping to produce a large number of fine fibers and fragments, which will be broken and peeled off from the fiber trunk. These broken and peeled fine fibers and fragments have only two ways out in the papermaking process: one is to lose with white water and have nothing to do with paper. The other is to be mounted on the fiber trunk and together with the fiber trunk, they form a part of the paper. However, these fine fibers and fragments not only affect the dehydration process during the papermaking process, but more importantly, they block the gaps between paper fibers and reduce the air permeability of the paper (paper with a high beating degree is generally paper with very low air permeability). The traditional beating method is difficult to overcome the above contradictions, which will inevitably cause the ESR value of the supercapacitor to remain high. This application upgrades the "brooming" beating to "feathering" beating, that is, retaining the fine fibers under high beating degree conditions and the fiber trunk as much as possible to keep them as one, so that the fiber papermaking process is like the accumulation of a large number of feathers, which can not only ensure the efficient passage of ions, but also prevent the penetration short circuit of activated carbon particles.

[0032] Brooming and feathering pulping have little impact on ordinary papermaking, but have a huge impact in the field of electrochemistry.

[0033] Impact 1, Impact on supercapacitor loss: With the development of modern technology, electric cars, subways, high-speed rail, solar and wind power generation, aircraft catapults, laser and electromagnetic weapons and other new energy sources, supercapacitors are an indispensable power system. As we all know, electrical energy cannot be stored! Only supercapacitors can quickly charge and discharge large currents in a very short time and store a large amount of electrical energy.

[0034] Supercapacitors are a new type of energy storage system that has higher energy density than electrolytic capacitors and higher power density than batteries. They are particularly suitable for areas that require energy pulses in a short time (several seconds to tens of seconds). Due to its low operating voltage, it is very important to reduce the "loss" index of supercapacitors (main index: equivalent series resistance ESR), which is also very difficult. The loss of supercapacitors is not only related to paper, but also to electrolyte. Papermakers can only work hard to reduce the loss of diaphragm paper in supercapacitors. According to relevant information, the current diaphragm accounts for about 30% of the total loss.

[0035] The so-called loss of supercapacitor can be understood as follows: The interior of a supercapacitor is made up of two sides of conductive material (including leads) and supercapacitor diaphragm paper that has absorbed electrolyte.

[0036] The main working mode of supercapacitors is: under the action of a DC external electric field (charging), the weak electrolyte inside the two electrodes separates into positive ions and negative ions. Positively charged ions move toward the negative electrode, and negatively charged ions move toward the positive electrode (the solvent surrounding the electrolyte is an insulator) until the internal and external charges are equal and the signs are opposite (charging energy storage). When the external electric field voltage drops or disappears (discharging), the ions on the two sides of the electrode attract each other and the weak electrolyte returns to its original state.

[0037] Where there is movement, there is bound to be energy loss. The amount of energy consumed by ions in motion determines the size of the capacitor's "loss". The so-called "loss" is the ratio of the active power (Ur) to the reactive power (Uc) of the capacitor's electrical energy loss, expressed as a tangent value.

[0038] If an electrochemical reaction is carried out in a laboratory beaker (supercapacitor paper is not required), both positive and negative ions can move in a straight line in the solvent toward the target. The power consumed in the movement is the minimum "loss" (intrinsic loss) of the original device. In a supercapacitor, the electrolyte is adsorbed in the supercapacitor paper. The fibers of supercapacitor paper are all compounds composed of covalent bonds, which cannot allow charged ions to pass through. Charged ions can only bypass the fibers to move toward the target. The increase in movement distance will inevitably increase the energy loss of ion movement (see Figure 4 ).

[0039] The working voltage of a single supercapacitor is very low, so the input power U is small, and the reactive power Uc is also small, so multiple supercapacitors need to be used in series and parallel. Because of the low working voltage and low movement speed, the inherent loss of tgα1 is not small. At present, the influence of fibers accounts for about 30% of the total loss. The task of papermakers is to reduce the influence of fibers as much as possible to reduce the total loss Ur. There are two ways to reduce the influence of fibers: the first is to select raw materials with the smallest fiber diameter; the second is to use nano-comb grinding discs to perform "three-dimensional feathering" treatment on the fibers, so that the distance that ions originally need to bypass the micron scale is reduced to the distance that only needs to bypass the nanometer scale. This can effectively reduce the resistance to ion movement and enable the movement of ions to reach the destination at the smallest possible distance (the diameter of the double-layer particles of positive and negative ions in motion is less than or approximately 1nm).

[0040] Impact 2, the impact on the air permeability of supercapacitor paper: Paper made from pulp treated with feathering will inevitably block the pores of the paper with a large number of stripped fragments and capillary fibers, especially paper with high pulp density, which has only a small air permeability. The molecular diameters of oxygen and nitrogen in the air are generally slightly smaller than the diameters of ions (mainly negative ions). The small air permeability will inevitably affect the movement of ions, increase the movement resistance, and increase the "ESR" of the product. However, paper produced from feathered fibers has a large number of nanopores and a large air permeability, so ions can pass smoothly, which can greatly reduce the resistance to ion movement and reduce the "ESR" value.

Claims

1. A method for making supercapacitor diaphragm paper, characterized in that The following steps are involved: S1: Select goose skin as the fiber raw material for supercapacitor separator paper; S2: pulping of goose skin; S3: Preparation of insulation slurry: S4: Papermaking: S41: First concentration adjustment of the insulating slurry; S42: A high beating degree of not less than 80°SR is used and a refiner and a nano-comb grinding disc are used for feathering beating, so that the polished fibers are formed into a fiber trunk and a feathered fiber composed of fiber filaments mainly of nanometer size connected to the fiber trunk, and the diameter of the fiber filaments is between 10nm and 40nm; S43: second concentration adjustment; S44: pulp screening machine to remove fiber balls; S45: Papermaking is carried out using a cylinder paper machine in the presence of a dispersant.

2. The method for making supercapacitor diaphragm paper according to claim 1, characterized in that: The S2 step comprises the following steps: S21: cutting and weighing the raw materials; S22: pre-impregnation with liquid medicine; S23: screw feed; S24: steaming with liquid medicine; S25: The pulp is sent to the blowdown pot, and the gas emission from the blowdown pot is subjected to water film dust removal, and the pulp is sent to the pulp silo.

3. The method for making supercapacitor diaphragm paper according to claim 1, characterized in that: The S3 step includes the following steps: S31: spiral squeeze; S32: The pulp fibers after spiral squeezing are sent to the reaction tank via a screw conveyor; the liquid produced by the first spiral squeezing is sent to the black liquor storage tank, and the liquid produced by the second and subsequent spiral squeezing is sent to the reverse liquid storage tank; S33: the pulp fibers in the reaction tank are subjected to an insulating pulp treatment process; S34: If the prepared pulp fiber meets the technical requirements, it is sent to the insulating pulp tank, otherwise it is sent to the screw extruder through the coarse pulp tank to continue step S31.

4. The method for making supercapacitor diaphragm paper according to claim 1, characterized in that: Supercapacitor diaphragm paper thickness ≤ 20 microns.

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