A method for regulating the performance of paper-based microfluidic fuel cells based on papermaking technology

Abstract

This invention discloses a method for regulating the performance of paper-based microfluidic fuel cells (PMFCs) based on papermaking technology, belonging to the field of paper-based microfluidic fuel cell technology. This invention improves the pore structure of the paper substrate by using papermaking technology, making it more conducive to capillary flow of the electrolyte, diffusion and transport of reactants, and ion conduction between electrodes. This replaces commercially available filter paper widely used in existing PMFCs, thereby improving the low performance of PMFCs caused by slow liquid absorption and high ohmic resistance of paper-based substrates. It meets the mass transfer and conductivity requirements of PMFCs, providing a structural basis for improving PMFC performance and increasing the power output of PMFCs. This invention combines papermaking technology with PMFCs, and has broad application prospects and practical value.

Description

Technical Field

[0001] This invention relates to the field of paper-based microfluidic fuel cell technology, and in particular to a method for regulating the performance of paper-based microfluidic fuel cells based on papermaking technology. Background Technology

[0002] Microfluidic fuel cells utilize the laminar flow characteristics of microfluidics, allowing two electrolyte solutions containing fuel or oxidant to naturally stratify without the need for expensive polymer electrolyte membranes for separation. This design eliminates the complex hydrothermal management problems of polymer membrane fuel cells, significantly reducing manufacturing costs, increasing design flexibility, and broadening the range of fuel options. However, traditional microfluidic fuel cells still require external pumps to drive the flow of the electrolyte solution, inevitably increasing system complexity. Furthermore, their low energy density is a pressing issue that needs to be addressed.

[0003] In recent years, research on paper-based microfluidic fuel cells (PMFCs) has gradually moved to the forefront. These fuel cells typically use filter paper as a substrate to carry electrodes, current collectors, and electrolyte solutions. They offer advantages such as small size, light weight, and high flexibility, making them easy to integrate into small detection systems, such as medical test strips for blood glucose and pregnancy tests, as well as various wearable devices. Furthermore, paper is biodegradable, inexpensive, and can be easily folded to change its shape and structure. Simultaneously, as a substrate for transporting the electrolyte, the porous fibrous structure of paper allows the electrolyte to flow within it via capillary action, thus eliminating the need for an external pump. These advantages make PMFCs highly applicable, especially in small portable electronic devices, where they can further reduce device size, making them more environmentally friendly and easier to use. However, currently, the power output of PMFCs remains generally low.

[0004] To date, research on improving PMFC power output has mostly focused on connecting multiple individual cells in series or parallel. While this method effectively increases battery output, it also increases the overall complexity of the device structure. Furthermore, the performance of a single PMFC has long been limited by the low liquid absorption rate of commercial filter paper, leading to insufficient fuel supply on the anode side and hindered ion conduction between electrodes. This is primarily attributed to the unoptimized pore structure of commercial filter paper.

[0005] Therefore, improving the power output of a single PMFC cell in a low-cost and effective manner is a technical problem that needs to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a method for regulating the performance of paper-based microfluidic fuel cells based on papermaking technology. The aim is to improve the pore structure of the paper substrate through papermaking technology, thereby replacing the commercial filter paper widely used in existing PMFCs and improving the power output of PMFCs.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] This invention provides a method for preparing paper-based microfluidic fuel cells based on papermaking technology, comprising the following steps:

[0009] (1) Preparation of paper-based materials:

[0010] a. Prepare pulp; b. Filter out water from the pulp to achieve preliminary paper formation; c. Dry the paper; d. Smooth the paper to obtain the paper base material;

[0011] (2) Fabrication of paper-based microfluidic fuel cells:

[0012] The paper-based material obtained in step (1) is processed into a predetermined shape, and the battery assembly is fixed on the surface of the paper-based material to prepare a paper-based microfluidic fuel cell.

[0013] Furthermore, the pore structure of the paper-based material is controlled by adjusting the stirring time during the pulp preparation process.

[0014] Furthermore, the pore structure of the paper-based material is controlled by adjusting the fiber areal density.

[0015] Furthermore, the pore structure of the paper-based material is controlled by adjusting the pressure of the leveling process.

[0016] Further, the stirring time for preparing the pulp is 1-15 min, more preferably 6 min; the concentration of the pulp is 0.83-6.67 mg / mL, more preferably 3.33 mg / mL; and the fiber areal density of the paper base material is 0.01-0.08 g / cm³. 2 More preferably 0.04 g / cm 2 The pressure for the paper leveling process is 1-2.5 MPa, more preferably 1 MPa.

[0017] Furthermore, the methods for preparing pulp include chemical methods, mechanical methods, chemimechanical methods, semi-chemical methods, or waste paper pulping; the methods for removing moisture include flat screen filtration, press screen filtration, cylinder screen filtration, sieve filtration, or filter cloth filtration; the methods for drying paper include natural drying, high-temperature drying, or freeze-drying; and the methods for paper leveling include cold pressing, hot pressing, or ironing.

[0018] Furthermore, the paper-based material is a multilayer composite material.

[0019] Furthermore, the preparation method of the multilayer composite material includes the following steps:

[0020] a. Prepare pulp to obtain pulps with different fiber lengths:

[0021] b. Pulp of different fiber lengths is added to the filtration device to filter out the water in the paper and obtain wet paper. Then, the different wet papers are stacked to form a multi-layer structure. After that, the paper is pressed in the filtration device with a pressure plate to remove the remaining water and ensure that the different layers are tightly bonded, so as to achieve the initial formation of the multi-layer paper structure.

[0022] c. Paper drying;

[0023] d. The paper is flattened to obtain the paper-based material.

[0024] Furthermore, in the preparation of multilayer paper, pulp with short fiber length is used as the outer layer pulp material, and pulp with long fiber length is used as the middle layer pulp material.

[0025] The present invention also provides a paper-based microfluidic fuel cell prepared by the above method.

[0026] Figure 1 This is a flowchart illustrating the technical solution of the present invention.

[0027] like Figure 2 As shown, the PMFC manufacturing process based on papermaking technology in this invention mainly consists of two major steps: papermaking and battery manufacturing. The papermaking process mainly comprises the following four steps: First, pulp is manufactured, using techniques including chemical methods, mechanical methods, chemimechanical methods, semi-chemical methods, and waste paper pulping; second, water is filtered out of the pulp to achieve preliminary paper formation, using techniques including flat screen filtration, press screen filtration, cylinder screen filtration, sieve filtration, and filter cloth filtration; then, water is completely removed from the formed wet paper, using drying techniques including natural drying, high-temperature drying, and freeze-drying; finally, the dried paper is flattened, using techniques including cold pressing, hot pressing, and ironing.

[0028] Using the aforementioned paper as the battery substrate for PMFC, the first step is to define flow channels of appropriate size. Available techniques include mechanical cutting, laser cutting, photoresist etching, batik, and flexographic printing. Next, electrodes are loaded into the corresponding areas of the flow channels. Available techniques include separate electrode patch mounting, electrode ink deposition, screen printing, roll-to-roll printing, and 3D printing. Then, the electrodes are connected to the current collectors. Available techniques include separate current collector patch mounting, current collector ink deposition, screen printing, roll-to-roll printing, and 3D printing. Finally, the entire battery is encapsulated. Available techniques include thermoforming encapsulation, adhesive encapsulation, injection molding encapsulation, and mechanical encapsulation.

[0029] This invention regulates the pore structure of the paper base by controlling the pulp properties (fiber size, fiber concentration, type of additives, etc.) and process parameters (fiber loading, drying conditions, leveling conditions, etc.) during the papermaking process. This makes the paper base more conducive to the capillary flow of the electrolyte, the diffusion of reactants, and the conduction of ions between electrodes, thereby greatly improving the performance of the paper-based microfluidic fuel cell, far exceeding that of existing batteries of the same type based on commercial filter paper.

[0030] Furthermore, the present invention obtains a composite paper substrate with a multi-level pore structure through papermaking technology. The electrolyte flow region in the middle layer is selected with large pores to promote its capillary flow, while the electrode deposition region in the outermost layer is selected with small pores to prevent catalyst permeation and waste and internal short circuits of the battery. This balances catalyst utilization and capillary flow rate, and effectively avoids internal short circuits of the battery.

[0031] Furthermore, the papermaking technology of this invention can be used to encapsulate the anode inside the paper substrate, thereby isolating it from the outside air and preventing the generation of mixed potentials and parasitic currents at the anode.

[0032] The present invention discloses the following technical effects:

[0033] This invention relates to a novel paper-based microfluidic fuel cell (PMFC) technology. By using papermaking technology to improve the pore structure of the paper substrate, it makes it more conducive to the capillary flow of electrolyte, the diffusion and transport of reactants, and the conduction of ions between electrodes. This replaces the commercial filter paper widely used in existing PMFCs, thereby improving the low performance of PMFCs caused by the slow liquid absorption rate and high ohmic resistance of paper-based substrates. It meets the mass transfer and conductivity requirements of PMFCs, provides a structural basis for improving PMFC performance, and increases the power output of PMFCs.

[0034] This invention combines papermaking technology with PMFC, thereby effectively improving the power output of PMFC, and has broad application prospects and practical value. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a flowchart illustrating the technical solution of the present invention;

[0037] Figure 2 This is a flowchart illustrating the preparation process of the technical solution of this invention;

[0038] Figure 3 This is a schematic diagram of the structure of a paper-based microfluidic fuel cell in Embodiment 1 of the present invention;

[0039] Figure 4 This is a schematic diagram of the structure of the paper-based microfluidic fuel cell in Embodiment 2 of the present invention;

[0040] Figure 5 This is a schematic diagram of the structure of the paper-based microfluidic fuel cell in Embodiment 3 of the present invention;

[0041] Figure 6 This is a schematic diagram of the structure of the paper-based microfluidic fuel cell in Embodiment 4 of the present invention;

[0042] Figure 7 This is a schematic diagram of the structure of the paper-based microfluidic fuel cell in Embodiment 5 of the present invention;

[0043] Figure 8 This is a schematic diagram of the structure of the paper-based microfluidic fuel cell in Embodiment 6 of the present invention;

[0044] Among them, 1-paper base, 2-current collector, 3-cathode, 4-anode, 5-conductive silver grid;

[0045] Figure 9 This document presents a comparison of the performance of PMFCs based on self-made paper and commercial filter paper in Example 2 of the present invention. Specifically, a) is a comparison curve of current density and power density of the paper-based microfluidic fuel cells based on the self-made paper and commercial filter paper (slow-speed and fast-speed filter paper) of Example 2; b) is a comparison curve of single-electrode performance of the paper-based microfluidic fuel cells based on the self-made paper and commercial filter paper (slow-speed and fast-speed filter paper) of Example 2; c) is a comparison curve of activation time of the paper-based microfluidic fuel cells based on the self-made paper and commercial filter paper (slow-speed and fast-speed filter paper) of Example 2; and d) is a comparison curve of impedance of the paper-based microfluidic fuel cells based on the self-made paper and commercial filter paper (slow-speed and fast-speed filter paper) of Example 2.

[0046] Figure 10 The battery performance in Example 2 was tested using different stirring times;

[0047] Figure 11 The battery performance of Example 2 was tested using batteries with different cellulose areal densities.

[0048] Figure 12 The battery performance in Example 2 is shown using different hot-pressing pressures. Detailed Implementation

[0049] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0050] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0051] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0052] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0053] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0054] Currently, PMFC has two structures: a split type and an integrated type. The former uses independent electrode and current collector modules, so it requires external packaging to provide assembly pressure to press them onto the paper base surface. The latter completely deposits the electrodes and current collectors on or inside the paper base surface, so it does not require external packaging to provide assembly pressure.

[0055] Example 1

[0056] Figure 3 This is a schematic diagram of the PMFC single cell structure of Embodiment 1 of the present invention. The cell adopts a split structure and a typical Y-shaped flow channel, with two electrolytes drawn in from the two antennae of the Y.

[0057] (1) Paper base manufacturing: A mechanical method is used to mix a certain amount of cellulose fiber with an appropriate amount of water, then use a mixer to stir and break it into a uniformly dispersed fiber solution (3.33 mg / mL) for 6 min. Then, the fiber solution is poured into a filter device with a fixed filtration area and then filtered out most of the water with a pressure plate to obtain a wet paper base. Then, the wet paper base is thoroughly dried in a 60°C oven to obtain a dry paper base. Finally, the dry paper base is placed in a hot press and hot-pressed at 90°C with a pressure of 1 MPa for 5 min to obtain the finished paper base.

[0058] (2) Battery manufacturing:

[0059] First, the finished paper base obtained from papermaking is cut into Y-shaped paper base 1 using a mechanical cutting method; then, the current collector 2, cathode 3 and anode 4 are installed onto the same side surface of the paper base 1 using a patch mounting method under external pressure; finally, all battery components are fixed between the two end plates using a mechanical encapsulation method.

[0060] The main feature of this battery is that the cathode 3 and anode 4 are located on the same side of the paper substrate, and a certain electrode spacing is maintained between them.

[0061] In actual operation, the two contacts at the bottom of the battery are immersed in different electrolytes. Once the corresponding electrolytes have wetted the electrode areas, the battery is activated and can supply power. This battery has good electrode conductivity and high power density; however, its structure is relatively complex and requires external packaging to provide assembly pressure, thus it is mostly lacking in flexibility. This battery structure is more suitable for some high power density applications.

[0062] Examples 2-4 provide a PMFC with an integrated structure, and the electrode placement can be in three ways: the two electrodes are located on the same surface of the paper substrate (Example 2), the two electrodes are located on different surfaces of the paper substrate (Example 3), and some or all of the electrodes are located inside the paper substrate (Example 4).

[0063] Example 2

[0064] Figure 4 This is a schematic diagram of the PMFC single cell structure of Embodiment 2 of the present invention. The cell adopts a typical Y-shaped flow channel, and two electrolytes are drawn in from the two antennae of the Y.

[0065] (1) Paper base manufacturing: Same as in Example 1;

[0066] (2) Battery manufacturing:

[0067] First, the finished paper base obtained by papermaking is cut into Y-shaped paper base 1 by mechanical cutting method; then, the current collector 2 is loaded onto the surface of paper base 1 by patch mounting method; then, the cathode 3, anode 4 and conductive silver grid 5 are directly deposited onto the same side surface of paper base 1 by deposition method; finally, all battery components are fixed inside the plastic film by thermo-pressing encapsulation method.

[0068] The main feature of this battery is that the cathode 3 and anode 4 are located on the same side of the paper substrate, and a certain electrode spacing is maintained between them.

[0069] In actual operation, the two electrodes at the bottom of the battery are immersed in different electrolytes. Once the corresponding electrolytes have wetted the electrode areas, the battery is activated and can supply power. This type of battery effectively avoids internal short circuits caused by electrode ink penetration, requires no external packaging to provide assembly pressure, and has high compactness and flexibility. However, due to the relatively large electrode spacing (especially for batteries with larger electrodes), the ion transport resistance between electrodes is relatively high, resulting in a higher internal resistance and lower power density. This electrode design is more suitable for PMFCs with smaller electrodes.

[0070] Example 3

[0071] Figure 5 This is a schematic diagram of the PMFC single cell structure of Embodiment 3 of the present invention. The battery adopts an integrated structure and uses a typical strip-shaped flow channel, with only one stream of electrolyte drawn in from the bottom.

[0072] (1) Paper base manufacturing: Same as in Example 1;

[0073] (2) Battery manufacturing:

[0074] First, the finished paper base obtained from papermaking is cut into strips 1 using laser cutting. Then, a current collector 2 is mounted onto the surface of the paper base 1 using a patch mounting method. Next, a cathode 3, anode 4, and conductive silver grid 5 are directly deposited onto both sides of the paper base 1 using a deposition method. Finally, all battery components are fixed inside a plastic film using a thermo-press encapsulation method. The main feature of this battery is that the cathode 3 and anode 4 are located on different side surfaces of the paper base 1, and their surfaces face to face.

[0075] In actual operation, the bottom of the battery is immersed in the electrolyte. Once the corresponding electrolyte wets the electrode area, the battery is activated and can supply power. This method simplifies electrolyte preparation and effectively reduces battery internal resistance; however, the cathode and anode inks may penetrate into the paper substrate and come into contact with each other, potentially causing an internal short circuit. This electrode design is more suitable for PMFCs with large electrodes.

[0076] Example 4

[0077] Figure 6This is a schematic diagram of the PMFC single cell structure of Embodiment 4 of the present invention. The cell adopts an integrated structure and uses a typical strip-shaped flow channel, with only one stream of electrolyte drawn in from the bottom.

[0078] (1) Paper base manufacturing: Same as in Example 1;

[0079] (2) Battery manufacturing:

[0080] First, the finished paper base obtained from papermaking is cut into strips 1 using laser cutting. Then, a current collector 2 is mounted onto the surface of the paper base 1 using a patch mounting method. Next, the cathode 3, anode 4, and conductive silver grid 5 are directly deposited onto both sides of the paper base 1 using a deposition method. Afterward, another layer of paper base 1 is added to one side of the anode 4 using papermaking techniques and combined with the paper base 1, thus embedding the anode 4 within the paper base. Finally, a thermosetting encapsulation method is used to fix all battery components inside a plastic film. Its main feature is that the cathode 3 and anode 4 of the battery are located on different side surfaces of the paper base 1, facing each other, and the anode 4 is embedded within two layers of paper base 1.

[0081] In actual operation, the bottom of the battery is immersed in the electrolyte. Once the corresponding electrolyte wets the electrode area, the battery is activated and can supply power. This electrode design simplifies electrolyte preparation and effectively reduces battery internal resistance. Furthermore, the paper base, having absorbed the electrolyte, isolates the anode from air and provides a more sufficient fuel supply to the anode. However, its battery manufacturing process is more complex, and the cathode and anode inks may penetrate into the paper base and come into contact with each other, potentially causing an internal short circuit. This design is more suitable for PMFCs where the anode cannot be exposed to air.

[0082] For the integrated PMFC structure in Examples 2-4, large-pore paper substrates can easily cause electrode ink to penetrate into the paper substrate during electrode deposition, leading to catalyst waste or even short circuits within the battery. Small-pore paper substrates can easily result in excessively low electrolyte capillary flow rates, leading to untimely reactant supply. By adjusting the pulp stirring time parameter in papermaking, the pore size of the finished paper substrate can be controlled, thereby constructing a special paper substrate with a composite pore structure. Small pores are used on the surface of the paper substrate where the electrodes are deposited, while large pores are used inside the paper substrate where the electrolyte is absorbed.

[0083] Example 5

[0084] Figure 7 The diagram shows the PMFC single cell structure of Embodiment 5 of the present invention. The cell adopts an integrated structure and a two-stage composite paper substrate (small hole-large hole). The two electrodes are located on the same surface of the paper substrate (small hole side) and a typical Y-shaped flow channel is adopted. The two electrolytes are drawn in from the two antennae of the Y respectively.

[0085] (1) Manufacturing of two-stage composite paper base:

[0086] First, a mechanical method is used. A certain amount of cellulose fibers are mixed with an appropriate amount of water, then dispersed and cut into uniformly dispersed fiber solutions using a mixer. One fiber solution is stirred for a short time (1 min), while the other is stirred for a long time (6 min). Next, a screen filtration method is used. The fiber solution with the longer stirring time is poured into a filter device with a fixed filtration area, and then the fiber solution with the shorter stirring time is poured onto the surface of the former. A pressing plate is then used to filter out most of the water, resulting in a wet paper base. Then, a high-temperature drying method is used. The wet paper base is placed in an oven and thoroughly dried at 60°C. Finally, a hot-pressing method is used. The dried paper base is placed in a hot press and pressed at 90°C with a pressure of 1 MPa for 5 minutes to obtain the finished paper base, which has a two-level composite pore structure (micropores-macropores).

[0087] (2) Battery manufacturing:

[0088] First, a paper substrate with a two-level composite pore structure (small pores-large pores) obtained by papermaking is cut into Y-shaped paper substrates 1 using a mechanical cutting method. Then, a current collector 2 is mounted onto the surface of the paper substrate 1 using a patch mounting method. Next, a cathode 3, anode 4, and conductive silver grid 5 are directly deposited onto the small pore side of the paper substrate 1 using a deposition method. Finally, a thermo-press encapsulation method is used to fix all battery components inside a plastic film. The main feature of this battery is that the cathode 3 and anode 4 are located on the same surface of the paper substrate with smaller pores, maintaining a certain electrode spacing between them.

[0089] In actual operation, the two electrodes at the bottom of the battery are immersed in different electrolytes. Once the corresponding electrolytes have wetted the electrode areas, the battery is activated and can supply power. This composite porous paper base effectively prevents electrode ink from penetrating into the paper base, thus avoiding catalyst waste.

[0090] Example 6

[0091] Figure 8 The diagram below shows the structure of a PMFC single cell in Embodiment 6 of the present invention. The cell adopts an integrated structure and a three-stage composite paper substrate (small hole-large hole-small hole). The two electrodes are located on different side surfaces of the paper substrate and a typical strip-shaped flow channel is used, with only one stream of electrolyte drawn in from the bottom.

[0092] (1) Manufacturing of three-level composite paper base:

[0093] First, a mechanical method is used to mix a certain mass of cellulose fibers with an appropriate amount of water, then use a mixer to disperse and cut the mixture into a uniformly dispersed fiber solution. One fiber solution is stirred for a short time (1 min), and the other for a long time (6 min). Next, a screen filtration method is used. The fiber solution with the longer stirring time is poured into a filter device with a fixed filtration area, and then the fiber solution with the shorter stirring time is poured onto its surface. Then, the fiber solution with the longer stirring time is poured onto both surfaces. Finally, a pressing plate is used to filter out most of the water, resulting in a wet paper base. Then, a high-temperature drying method is used, placing the wet paper base in an oven and drying it thoroughly at 60°C. Finally, a hot-pressing method is used, placing the dry paper base in a hot press at 90°C and a pressure of 1 MPa for 5 minutes to obtain the finished paper base, which has a three-level composite pore structure (micropore-macropore-micropore).

[0094] (2) Battery manufacturing:

[0095] First, a paper substrate with a three-level composite pore structure (small pore-large pore-small pore) obtained by papermaking is cut into strips 1 using laser cutting. Then, a current collector 2 is mounted onto the surface of the paper substrate 1 using a patch mounting method. Next, a cathode 3, anode 4, and conductive silver grid 5 are deposited onto the two sides of the small pores of the paper substrate 1 using a deposition method. Finally, a thermo-press encapsulation method is used to fix all battery components inside a plastic film. The main feature of this battery is that the cathode 3 and anode 4 are located on both sides of the small pores of the paper substrate 1, and their surfaces face to face.

[0096] In actual operation, the bottom of the battery is immersed in the electrolyte. Once the corresponding electrolyte wets the electrode area, the battery is activated and can supply power. This composite porous paper base effectively prevents electrode ink from penetrating into the paper base, thereby avoiding catalyst waste and internal short circuits in the battery.

[0097] Battery performance testing:

[0098] This invention combines papermaking with PMFC, adjusting the pore structure of the paper by controlling various parameters in the papermaking process, thereby optimizing the battery's power generation performance.

[0099] This paper presents a detailed example of an integrated battery structure where the anode and cathode are distributed on the same surface of a paper substrate with a single porous structure. The cathode and anode electrode areas are 10mm × 2mm, and the electrode spacing is 4mm. The cathode catalyst is MnO2 (6mg / cm³). 2 The anode catalyst is Pt-Ru / C (0.1 mg / cm³). 2The cathode electrolyte is 3M KOH, and the anode electrolyte is 3M KOH + 2M ethanol. The paper substrates used include two types of commercial filter paper (slow-speed and fast-speed) and various types of self-made paper with different pore structures. In the papermaking process, the pore structure is mainly controlled by controlling the pulp stirring time, cellulose surface density and paper hot pressing pressure.

[0100] The pulp mixing time was 3 minutes, and the cellulose surface density was 0.02 g / cm³. 2 Under the same manufacturing conditions of 1 MPa hot-pressing pressure, the performance comparison of PMFC using its self-made paper and commercial filter paper in Example 2 is shown in [reference needed]. Figure 9 Among them, the battery assembly method is Figure 4 As shown.

[0101] Experimental results show that PMFCs using homemade filter paper perform significantly better than PMFCs using commercial filter paper. Specifically, from Figure 9 As can be seen, the performance of fast-speed filter paper is slightly better than that of slow-speed filter paper, with peak power density (PPD) and maximum current density (MCD) increasing from 1.2 mW / cm². 2 and 4.6 mA / cm 2 Increased to 1.8 mW / cm 2 and 6.5mA / cm 2 This is primarily due to the faster capillary flow, which results in a more efficient fuel supply to the anode. However, this positive effect is very limited, with significant mass transfer losses observed in both cases. For self-made paper, PPD and MCD further increased to 5.4 mW / cm². 2 and 42.3 mA / cm 2 These figures are 4.5 times and 9.2 times that of low-speed filter paper, respectively, indicating a significant improvement in mass transfer loss. From Figure 9 b shows that the anode performance of PMFC based on commercial filter paper is significantly lower than that of PMFC based on homemade paper, indicating that homemade paper is superior to commercial filter paper in terms of fuel supply. Figure 9 c shows the activation time of different PMFCs, measured from the moment the bottom of the battery contacts the electrolyte until the open-circuit voltage stabilizes. The activation times of PMFCs using slow filter paper, fast filter paper, and homemade paper were 2940 seconds, 1700 seconds, and 350 seconds, respectively, demonstrating that the capillary flow rate in homemade paper was faster. Figure 9 The ohmic resistances (intercepts of the impedance curves on the X-axis) of the self-made paper were compared, yielding 65.1 Ω, 47.8 Ω, and 13 Ω, respectively, demonstrating lower ion conduction resistance in the self-made paper. These results indicate that paper with specific pore parameters obtained through papermaking is more suitable as a substrate for PMFCs than existing commercial filter papers.

[0102] Furthermore, in Example 2 ( Figure 4Based on the structure shown, in order to demonstrate the effect of different pulp stirring times in the papermaking process on battery performance, a hot-pressing pressure of 1 MPa and a cellulose areal density of 0.04 g / cm³ were used. 2 Under these conditions, five stirring times were selected: 1 min, 3 min, 6 min, 9 min, and 15 min. Figure 10 The battery performance was compared under different stirring times. Experimental results show that the battery performs best when the stirring time is around 6 minutes, with an MCD of 48.9 mA / cm². 2 The PPD is 6.3 mW / cm². 2 However, further extending the stirring time led to a decrease in battery performance. This is because a longer stirring time cuts the paper fibers into shorter pieces, resulting in lower porosity and thinner paper. The former weakens the paper's liquid absorption rate, leading to slower fuel supply and reduced anode performance, but it also prevents excessive penetration of the catalyst ink, concentrating the catalytic active sites near the current collector and improving catalyst utilization. The latter affects the battery's ion transport; thicker paper provides more ion transport paths (for electrodes on the same surface), thereby reducing the battery's ohmic impedance and improving battery performance. Therefore, due to the combined effect of both factors, a stirring time of 6 minutes yielded the optimal battery performance.

[0103] Furthermore, in Example 2 ( Figure 4 Based on the structure shown, to demonstrate the effect of different cellulose areal densities on battery performance during the papermaking process, four cellulose areal densities were selected under the conditions of a stirring time of 3 min and a hot-pressing pressure of 1 MPa: 0.01 g / cm³. 2 0.02g / cm 2 0.04g / cm 2 and 0.08g / cm 2 . Figure 11 The battery performance under different cellulose areal densities was investigated. Experimental results showed that the optimal cellulose areal density was 0.04 g / cm³. 2 Battery performance reaches its optimal level at this time, with an MCD of 47.1 mA / cm². 2 PPD is 6mW / cm 2Increasing the areal density of cellulose did not have a better effect on the battery. This is because as the areal density increases, the porosity of the paper decreases slightly, reducing the fuel supply rate and weakening the anode performance. On the other hand, the paper thickness increases almost proportionally with the areal density, providing more ion transport paths and reducing the ohmic impedance of the battery. Furthermore, as the thickness increases, the lateral diffusion of fuel from positions perpendicular to the anode direction to the anode surface is enhanced, which can compensate to some extent for the slow fuel supply caused by the reduced liquid absorption rate. Therefore, under the combined influence of these two factors, a cellulose areal density of 0.04 g / cm³ is optimal. 2 At this time, the battery performance is optimal.

[0104] Furthermore, based on Example 2, to demonstrate the effect of different hot-pressing pressures in the papermaking process on battery performance, a stirring time of 3 minutes and a cellulose areal density of 0.02 g / cm³ were used. 2 Under these conditions, three hot-pressing pressures were selected: 1 MPa, 2 MPa, and 2.5 MPa. Figure 12 To evaluate battery performance under different thermal pressure conditions, experimental results show that the battery performs best under a thermal pressure of 1 MPa, with an MCD of 42.3 mA / cm². 2 The PPD is 5.4 mW / cm 2 Increasing the hot-pressing pressure further weakens battery performance. This is because higher pressure compresses the paper fibers more tightly, reducing the paper's liquid absorption rate and resulting in poorer fuel supply. Therefore, the battery performance is optimal at a hot-pressing pressure of 1 MPa.

[0105] This invention combines papermaking technology with paper-based microfluidic fuel cells. The optimized paper-based pore structure is more conducive to the capillary flow of electrolyte, the diffusion and transport of reactants, and the conduction of ions between electrodes, thereby greatly improving the power output of the battery.

[0106] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing paper-based microfluidic fuel cells based on papermaking technology, characterized in that, Includes the following steps: (1) Preparation of paper-based materials: a. Prepare pulp; b. Filter out water from the pulp to achieve preliminary paper formation; c. Dry the paper; d. Smooth the paper to obtain the paper base material; (2) Fabrication of paper-based microfluidic fuel cells: The paper-based material obtained in step (1) is processed into a predetermined shape, and the battery assembly is fixed on the surface of the paper-based material to prepare a paper-based microfluidic fuel cell. The pore structure of the paper-based material is controlled by adjusting the stirring time during the pulp preparation process; The pore structure of the paper-based material can be controlled by adjusting the fiber areal density; The pore structure of the paper-based material is controlled by adjusting the pressure of the leveling process. The methods for preparing pulp include chemical methods, mechanical methods, chemimechanical methods, semi-chemical methods, or waste paper pulping; the methods for removing moisture include flat screen filtration, press screen filtration, cylinder screen filtration, sieve filtration, or filter cloth filtration; the methods for drying paper include natural drying, high-temperature drying, or freeze-drying; and the methods for paper leveling include cold pressing, hot pressing, or ironing. The paper base material is a multi-layered paper; In preparing the multilayer paper, pulp with short fiber length is used as the outer layer pulp material, and pulp with long fiber length is used as the middle layer pulp material.

2. The method according to claim 1, characterized in that, The method for preparing the multi-layered paper includes the following steps: a. Prepare pulp to obtain pulps with different fiber lengths: b. Pulp of different fiber lengths is added to the filtration device to filter out the water in the paper and obtain wet paper. Then, the different wet papers are stacked to form a multi-layer structure. After that, the paper is pressed in the filtration device with a pressure plate to remove the remaining water and ensure that the different layers are tightly bonded, so as to achieve the initial formation of the multi-layer paper structure. c. Paper drying; d. The paper is flattened to obtain the multi-layered paper structure.

3. A paper-based microfluidic fuel cell prepared by the method according to any one of claims 1-2.

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