Novel electric pile without leakage, carbon felt and bipolar plate

Abstract

The invention discloses a novel electric pile without leakage, carbon felt and bipolar plates, and belongs to the technical field of energy storage of all-vanadium redox flow batteries. According to the electric pile, a proton exchange membrane resistant to strong acidity and vanadium ion swelling serves as a core functional part, the two ends of the proton exchange membrane are fixed to a supporting pipe in a sealed mode to form a tube pass channel, a shell pass channel is formed between an electric pile shell and the proton exchange membrane, positive and negative all-vanadium electrolyte is introduced into the tube pass and the shell pass respectively, and the tube pass and the shell pass are equal in total sectional area; vanadium-corrosion-resistant conductive electrodes are arranged on the inner side and the outer side of the proton exchange membrane, a traditional carbon felt electrode and a bipolar plate structure are abandoned in the electric pile, and full-sealing design is adopted. The technical defects of bipolar plate corrosion, carbon felt vanadium adsorption, electrolyte leakage and the like of a traditional electric pile are overcome, the technical effects that the vanadium ion rejection rate is larger than or equal to 99.5%, the leakage rate is smaller than or equal to 0.01 mL / (hL), the energy efficiency is larger than or equal to 80% and the cycle life exceeds 20000 times are achieved, the whole life cycle cost is reduced by 35% or above, and the method is suitable for scenes of large-scale energy storage, new energy grid connection and the like and has remarkable economic and environmental protection values.

Description

Technical Field

[0001] This invention relates to the field of vanadium redox flow battery energy storage technology, specifically to a novel battery stack that is leak-free, carbon felt-free, and bipolar plate-free. Background Technology

[0002] Vanadium redox flow batteries, as a core technology for large-scale electrochemical energy storage, are widely used in scenarios such as new energy grid connection, grid peak shaving, and emergency power supply due to their advantages such as adjustable capacity, high safety, and environmental friendliness. However, existing vanadium redox flow battery stacks generally adopt the traditional structure of "bipolar plate-carbon felt electrode-proton exchange membrane," which has many difficult-to-solve technical defects in practical applications. First, insufficient compatibility leads to performance degradation. Bipolar plates are prone to corrosion when exposed to a strongly acidic electrolyte environment for extended periods. The corrosion products contaminate the electrolyte and reduce the efficiency of the fuel cell stack. Carbon felt electrodes are also prone to adsorbing vanadium ions, resulting in "electrode poisoning," which causes a continuous decline in the stack capacity and severely affects its service life.

[0003] Secondly, the high risk of leakage poses potential safety hazards. Traditional fuel cell stacks rely on rubber gaskets for sealing. After long-term operation, these gaskets are prone to aging and failure, leading to leakage of the positive and negative electrolytes and cross-contamination. This not only increases the cost of electrolyte regeneration but may also cause safety risks.

[0004] Furthermore, energy efficiency and economic viability are limited. The redundancy in traditional structures leads to high electrolyte mass transfer resistance, with coulombic efficiency typically below 90% and energy efficiency only 65%-75%. At the same time, the material costs of bipolar plates and carbon felt are high, and the maintenance cycle is short (usually 6 months), further increasing the total life cycle cost and hindering the commercialization of vanadium redox flow batteries.

[0005] Existing improvement technologies mostly focus on material optimization or partial structural adjustments, failing to break through the core structural framework of "bipolar plate-carbon felt" and thus unable to fundamentally solve the aforementioned technical defects. Therefore, developing a novel fuel cell stack that is carbon felt-free, bipolar plate-free, has low leakage, and high stability has become a key requirement for the development of all-vanadium redox flow battery technology. Summary of the Invention

[0006] The purpose of this invention is to provide a novel fuel cell stack that is leak-free, carbon felt-free, and bipolar plate-free, in order to solve the problem of high leakage risk and potential safety hazards in existing fuel cell stacks.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A novel, leak-free, carbon felt-free, and bipolar-plate-free fuel cell stack for vanadium redox flow batteries utilizes a tubular structure made of a proton exchange membrane resistant to strong acids and vanadium ion swelling as its core functional component. The two ends of the proton exchange membrane are sealed and fixed to supporting tubing to form a tube-side channel, and a shell-side channel is formed between the fuel cell shell and the proton exchange membrane. The tube-side channel is used to introduce the positive electrode vanadium electrolyte, and the shell-side channel is used to introduce the negative electrode vanadium electrolyte. The total cross-sectional area of ​​the tube-side channel is equal to the effective cross-sectional area of ​​the shell-side channel. Vanadium corrosion-resistant conductive electrodes are respectively provided on the inner and outer sides of the proton exchange membrane. The fuel cell stack does not contain carbon felt electrodes or bipolar plate structures, and the entire stack adopts a fully sealed design to prevent electrolyte leakage.

[0008] Core functional component design: A tubular structure made of a proton exchange membrane resistant to strong acids and vanadium ion swelling is used as the core functional component of the fuel cell stack. The tubular structure replaces the traditional combination of flat sheet membrane, carbon felt, and bipolar plates, structurally eliminating the problems of carbon felt adsorbing vanadium ions and bipolar plate corrosion.

[0009] Electrolyte flow system: The proton exchange membrane is sealed and fixed at both ends to supporting tubing, forming a tube-side channel; a shell-side channel is formed between the stack shell and the proton exchange membrane. The tube-side channel is vented with the positive electrode vanadium-based electrolyte (V1). 4+ / V 5+ The shell-side channel is through which the negative electrode vanadium electrolyte (V²) is introduced. + / V³ + Furthermore, the total cross-sectional area of ​​the tube side channel is equal to the effective cross-sectional area of ​​the shell side channel to ensure electrolyte flow matching, with the flow velocity controlled at 0.2-0.4 m / s, thus reducing mass transfer resistance.

[0010] Electrode system configuration: Vanadium corrosion resistant conductive electrodes are set on the inner and outer sides of the proton exchange membrane, respectively. The electrodes are made of copper-based electrode rods and coated with a composite coating of carbon fiber, resin and graphite powder or carbon nanoparticles to ensure corrosion resistance and conductivity in a strongly acidic environment. The electrode spacing is set to 1-2 mm (inner side) and 3-5 mm (outer side) according to the channel position.

[0011] Fully sealed structural design: The fuel cell stack adopts a triple sealing design, including the adhesive seal between the proton exchange membrane and the support tubing, the double seal of "ceramic sealing ring + PTFE packing" at the electrode mounting points, and the flange fastening seal between the shell and the end caps. The sealing pressure is ≥0.3MPa, ensuring an electrolyte leakage rate ≤0.01mL / (h). L).

[0012] Shell and material selection: The stack shell is made of modified PVDF material, which has the characteristics of strong acid corrosion resistance and high mechanical strength; the stack shell is equipped with a streamlined electrolyte distribution cavity to ensure uniform electrolyte distribution and further reduce mass transfer resistance.

[0013] The present invention has the following beneficial effects: This invention, through structural innovation centered on a proton exchange membrane, abandons the traditional bipolar plate and carbon felt electrode, and combines it with a vanadium corrosion resistant electrode system, fundamentally eliminating the performance degradation problems caused by bipolar plate corrosion and dissolution and carbon felt adsorption of vanadium ions, thus significantly improving the operational stability of the fuel cell stack. By adopting a shell-and-tube layout and optimizing the matching relationship between the tube side and the shell side cross-sectional areas, the electrolyte mass transfer environment is effectively improved, the accumulation of vanadium ions on the membrane surface is reduced, and the energy conversion efficiency is improved. Combining multiple sealing designs and the selection of corrosion-resistant materials, it effectively prevents electrolyte leakage and cross-contamination of vanadium ions between the positive and negative electrodes; the modular core component design simplifies the maintenance process, and the reduction of structural redundancy lowers the total life cycle cost; at the same time, it reduces pollutant emissions in the carbon felt production process, and the low leakage characteristics avoid the corrosive impact of electrolyte on the environment, fully meeting the development needs of green energy storage. Attached Figure Description

[0014] Figure 1 This is a structural diagram of the fuel cell stack housing of the present invention.

[0015] Figure 2 This is a structural diagram of the support pipe of the present invention.

[0016] In the figure: fuel cell stack shell 100, shell-side channel 101, proton exchange membrane 102, support tube 103; Detailed Implementation The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0017] Example 1: 10kW-class all-vanadium redox flow battery stack (suitable for small and medium-sized energy storage scenarios) Core component fabrication: A perfluorosulfonic acid membrane with an equivalent weight of EW=900 was selected and proton exchange membrane tubes with an inner diameter of 5mm and a length of 800mm were manufactured by hot pressing. A total of 120 tubes were used. The support tubes were made of φ10mm food-grade PE rigid round tubes. The two ends of the proton exchange membrane tubes were bonded and fixed to the PE rigid round tubes with fluororubber sealant. After curing for 24 hours, an airtightness test was conducted (pressure 0.3MPa, pressure holding for 30 minutes with no pressure drop) to ensure reliable sealing.

[0018] Electrode rod preparation: A φ2mm copper rod is used as the substrate, and a composite layer of carbon fiber and resin is wound around the outer surface. An appropriate amount of graphite powder and carbon nanoparticles are added to the resin to ensure conductivity. Positive and negative electrode rods (with the same structure) are made. No corrosion is observed after soaking in 1.5mol / L LOSO4 + 3mol / L H2SO4 electrolyte for 1000h.

[0019] Fuel cell stack assembly: The fuel cell stack shell is made of modified PVDF material, with an inner diameter of φ50mm and a length of 900mm; 120 proton exchange membrane tube assemblies are evenly distributed in a ring inside the shell. According to calculation, the total cross-sectional area of ​​the tube side = 120×π×(5 / 2)² = 2943.75mm², and the effective cross-sectional area of ​​the shell side = π×(50 / 2)² - 2943.75 = 2945.25mm², which meets the design requirement of "equal cross-sectional areas of the tube side and the shell side"; the positive electrode rod is coaxially inserted into the center of the proton exchange membrane tube (1-2mm away from the inner wall of the membrane tube), and the negative electrode rod is fixed on the shell side axis (3-5mm away from the inner wall of the shell side). The two ends of the electrode rod are led out of the shell through a double seal of "ceramic sealing ring + polytetrafluoroethylene filler". The end caps are fastened to the shell with bolts, and the sealing pressure is ≥0.3MPa.

[0020] Electrolyte preparation and performance testing: The positive electrode electrolyte is 1.5 mol / L V. 4+ / V 5+ (Concentration ratio 1:1) + 3 mol / L H2SO4, negative electrode electrolyte is 1.5 mol / L V² + / V³ + (Concentration ratio 1:1) + 3 mol / L H2SO4; electrolyte flow rate controlled at 0.3 m / s, charge / discharge current density at 80 mA / cm². Test results: stack energy efficiency 82%, coulombic efficiency 96.5%, capacity decay rate of 0.8% after 3000 hours of continuous operation, no electrolyte leakage, meeting the power and stability requirements of small and medium-sized energy storage scenarios.

[0021] Example 2: 50kW-class all-vanadium redox flow battery stack (suitable for large-scale energy storage power stations) Core component preparation: A perfluorosulfonic acid membrane with an equivalent weight of EW=900 (consistent with Example 1, but can be adjusted to 800-1000 as needed) was selected to make a proton exchange membrane tube with an inner diameter of 6mm and a length adapted to the shell, totaling 300 tubes; the support tubes still use food-grade PE rigid round tubes, and the bonding and sealing process is the same as in Example 1 to ensure that the airtightness meets the standard.

[0022] Electrode rod fabrication: The positive electrode rod is made of φ2.5mm copper rod, and the negative electrode rod is made of φ5mm copper rod. The outer surface of both rods is wrapped with a composite coating of carbon fiber-graphite powder + carbon nanoparticle powder + resin, which meets the design requirements for corrosion resistance and conductivity.

[0023] Electron stack assembly: The modified PVDF shell has an inner diameter of φ80mm and a length adapted to the proton exchange membrane tubes; 300 proton exchange membrane tube assemblies are evenly distributed, and calculations ensure that the total cross-sectional area of ​​the tube side is equal to the effective cross-sectional area of ​​the shell side; the electrode spacing design is the same as in Example 1 (internal spacing of 1-2mm in the membrane tubes and internal spacing of 3-5mm in the shell side), and the sealing structure adopts the same double sealing + flange fastening scheme as in Example 1, with a sealing pressure ≥0.3MPa.

[0024] Electrolyte preparation and performance testing: The electrolyte system was the same as in Example 1 (1.5 mol / L vanadium ions + 3 mol / L H₂SO₄); the electrolyte flow rate was controlled at 0.35 m / s, and the charge / discharge current density was 100 mA / cm². Test results: Stack energy efficiency 81%, coulombic efficiency 95.8%, cycle life 16,000 cycles, electrolyte leakage rate 0.008 mL / (h) L), adapted to the high power and long life requirements of large-scale energy storage power stations.

[0025] Summary of Implementation Schemes 1. Common core solutions Both types of embodiments strictly follow the core technical framework of this invention, and their core commonalities include: Core membrane modules: All are made of perfluorosulfonic acid membranes in tubular structure, which are bonded and sealed to rigid PE round tubes to ensure vanadium ion rejection rate ≥99.5%; Structural design: All adopt a shell-and-tube layout, strictly ensuring that the total cross-sectional area of ​​the tube side is equal to the effective cross-sectional area of ​​the shell side, thus optimizing electrolyte mass transfer; Electrode system: Carbon felt is abandoned in all cases. Copper-based + carbon fiber-graphite powder + carbon nanopowder + resin coating electrode rods are used, which have vanadium corrosion resistance. Sealing and materials: Both adopt modified PVDF shell and "ceramic sealing ring + polytetrafluoroethylene filler" double seal, with sealing pressure ≥0.3MPa; Electrolyte system: All systems use 1.5 mol / L vanadium ions + 3 mol / L H2SO4 to ensure compatibility with the characteristics of vanadium redox flow batteries.

[0026] 2. Key differences (adapting to different power requirements) 3. Implementation effect verification Both types of embodiments achieved the design goal of the present invention: electrolyte leakage rate ≤ 0.01 mL / (h) With an energy efficiency of ≥80%, a coulombic efficiency of ≥95%, and a long cycle life (the capacity decay rate of 10kW-level continuous operation for 3000h is only 0.8%, and the cycle life of 50kW-level is 16000 times), it verifies the technical advantages of "no carbon felt, no bipolar plate, low leakage, and high stability". Moreover, by adjusting the number, size and electrode parameters of the membrane tubes, it can be flexibly adapted to the energy storage needs of different power levels and has a wide range of application scenarios.

[0027] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A novel fuel cell stack with no leakage, no carbon felt, and no bipolar plates, characterized in that, A tubular structure made of a proton exchange membrane (102) that is resistant to strong acids and vanadium ion swelling is used as the core functional component. The two ends of the proton exchange membrane (102) are sealed and fixed to the supporting tube (103) to form a tube-side channel. A shell-side channel (101) is formed between the proton exchange membrane (102) and the stack shell (100). The tube-side channel is used to introduce the positive electrode vanadium electrolyte, and the shell-side channel (101) is used to introduce the negative electrode vanadium electrolyte. The total cross-sectional area of ​​the tube-side channel is equal to the effective cross-sectional area of ​​the shell-side channel (101). The proton exchange membrane (102) is provided with vanadium corrosion resistant conductive electrodes on its inner and outer sides respectively. The stack does not include carbon felt electrodes and bipolar plate structures, and the entire stack adopts a fully sealed design to prevent electrolyte leakage.

2. The novel fuel cell stack with no leakage, no carbon felt, and no bipolar plates according to claim 1, characterized in that, The proton exchange membrane (102) is a perfluorosulfonic acid membrane with an equivalent weight (EW) of 800-1000. The inner diameter of the proton exchange membrane is 3-6 mm and the wall thickness is 0.1-0.15 mm.

3. The novel fuel cell stack with no leakage, no carbon felt, and no bipolar plates according to claim 1, characterized in that, The vanadium corrosion resistant conductive electrode is a copper-based electrode rod, and the surface of the copper-based electrode rod is coated with a composite coating of carbon fiber, resin and graphite powder or carbon nanoparticles.

4. The novel fuel cell stack with no leakage, no carbon felt, and no bipolar plates according to claim 1, characterized in that, The fully sealed design includes a triple sealing structure, namely the adhesive seal between the proton exchange membrane and the support tube, the double seal at the electrode mounting point, and the flange fastening seal between the stack housing (100) and the end cap.

5. The novel fuel cell stack with no leakage, no carbon felt, and no bipolar plates according to claim 4, characterized in that, The double seal at the electrode mounting point uses a combination of a ceramic sealing ring and polytetrafluoroethylene packing, with a sealing pressure ≥0.3MPa.

6. The novel fuel cell stack according to claim 1, characterized in that: The ratio of the total cross-sectional area of ​​the tube side channel to the effective cross-sectional area of ​​the shell side channel (101) is 1:1, and the flow velocity of the electrolyte in the channel is 0.2-0.4 m / s.

7. The novel fuel cell stack according to claim 1, characterized in that: The stack housing (100) is made of modified PVDF material, and a streamlined electrolyte distribution cavity is provided inside the stack housing (100).

8. The novel fuel cell stack according to claim 1, characterized in that: The inner electrode spacing of the proton exchange membrane is 1-2 mm, and the outer electrode spacing is 3-5 mm.

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