Preparation method of high-conductivity zinc-bromine flow battery bipolar plate

Abstract

The invention discloses a preparation method of a bipolar plate of a high-conductivity zinc-bromine flow battery. The preparation method comprises the following steps: respectively taking compounds of polythiol and polyisocyanate as raw materials; an initiator accounting for 2-5 wt% of the mixture is added; a conductive agent polypyrrole accounting for 2-5 wt% of the mixture is added; performing ultrasonic treatment on the mixture, and stirring for 3-5 minutes to ensure uniform mixing; and placing the mixture in a polytetrafluoroethylene mold, heating in a blast oven at 100-120 DEG C, and cooling to room temperature to obtain the polythionocarbamate high-molecular polymer with excellent conductivity, which can be used as a bipolar plate of a zinc-bromine flow battery. The bipolar plate can be effectively prevented from being corroded by electrolyte, the overall service life of the battery is prolonged, and then the reliability and stability of the whole battery are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of zinc-bromine flow batteries, and particularly relates to a preparation method of a bipolar plate for a zinc-bromine flow battery with high conductivity. Background Art

[0002] With the continuous growth of the global demand for sustainable energy, energy storage technology has become a research hotspot. Zinc-bromine flow batteries have shown great potential in the energy storage field due to their many significant advantages. First of all, they have high safety. Compared with some traditional energy storage batteries, such as lithium-ion batteries, zinc-bromine flow batteries do not have serious safety hazards such as thermal runaway, which makes them have high application value in large-scale energy storage scenarios, such as power grid energy storage, distributed energy storage, etc. Secondly, the maintenance cost is low. Due to its relatively simple structure and the recyclable electrolyte, the maintenance cost during long-term operation is reduced. Moreover, the output voltage is relatively high, which can meet various different electricity consumption requirements.

[0003] As an important component of a zinc-bromine flow battery stack, the bipolar plate has a decisive impact on the energy storage characteristics of the battery. At present, bipolar plates are mainly formed by pressing a polymer with a conductive agent. However, there are many problems with this traditional preparation method. On the one hand, the conductivity of the bipolar plate is limited. The existing conductive agents have unsatisfactory dispersion in the polymer matrix, resulting in obstacles in the electron transport path and unable to fully exert the conductive performance of the conductive agent, thus restricting the energy efficiency of the zinc-bromine flow battery. The reduction of energy efficiency means more energy loss during the energy storage and release processes, which not only reduces the actual available power of the battery but also increases the usage cost. On the other hand, the polymer itself has some defects. Its preparation process is complex, involving multiple steps and strict control of reaction conditions, which not only increases the production cost but also places high requirements on production equipment and the technical level of operators. Moreover, the polymer performance is unstable, and its physical and chemical properties are prone to change under different environmental conditions, such as temperature and humidity changes, which cause many adverse effects on the practical application of the bipolar plate. For example, it may lead to a decrease in the mechanical properties of the bipolar plate, affecting the overall structural stability of the battery, or cause fluctuations in its electrochemical properties, reducing the charge-discharge efficiency and cycle life of the battery.

[0004] In summary, the problems existing in the existing bipolar plates of zinc-bromine flow batteries in terms of conductivity and polymer performance seriously restrict the further popularization and application of zinc-bromine flow batteries in the energy storage field, and there is an urgent need to develop a new type of bipolar plate and its preparation method that can effectively solve these problems. Summary of the Invention

[0005] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a bipolar plate for a zinc-bromine flow battery with high conductivity and a preparation method thereof, including the following steps:

[0006] 1) Take the compounds of raw material polythiol and polyisocyanate respectively, where the molar ratio of mercapto group to isocyanate group is 1:1;

[0007] 2) Add 2%wt - 5%wt of initiator such as TBD, DBU, etc. to the mixture in step 1);

[0008] 3) Add 2%wt - 5%wt of conductive agent polypyrrole to the mixture in step 1);

[0009] 4) Ultrasonic and stir the above mixture for 5 min to ensure uniform mixing;

[0010] 5) Place the mixture in a polytetrafluoroethylene mold, heat it in a forced air oven at 100 °C for 2 h, and cool it to room temperature to obtain a polythiourethane polymer with excellent conductivity, which can be used as a bipolar plate for zinc - bromine flow batteries.

[0011] The polythiol compound can be trimethylolpropane trithioglycolate, pentaerythritol tetra(3 - mercaptopropionate), 1,6 - hexanedithiol, triphenylene - 2,3,6,7,10,11 - hexathiol, etc.;

[0012] The polyisocyanate compound can be toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate, etc.;

[0013] The thiol and isocyanate react under the initiator to form the following structure (in this example, the thiol is trimethylolpropane trithioglycolate and the isocyanate is isophorone diisocyanate):

[0014]

[0015] The present invention also provides a bipolar plate for zinc - bromine flow batteries with high - conductivity polythiourethane prepared by the above method.

[0016] A bipolar plate for zinc - bromine flow batteries with high conductivity and its preparation method disclosed by the present invention have the following advantages:

[0017] 1) Optimization of the selection of conductive agent: The present invention innovatively uses polypyrrole as the conductive agent. Polypyrrole itself has good conductivity, especially when the preparation process is optimized and the material purity is high, its conductive performance is more prominent. Compared with traditional conductive agents, the molecular structure of polypyrrole contains groups such as amino (-NH2) and carboxylic acid (-COOH), and hydrogen bonds can be formed between these groups. In the mixed solution for preparing the bipolar plate, polypyrrole can be evenly dispersed through hydrogen bond interaction, thereby improving the conductivity uniformity of the bipolar plate. The improvement of conductivity uniformity is crucial for zinc-bromine flow batteries. It can ensure uniform current distribution inside the battery, reduce local overheating or overcooling phenomena, and thus help improve the battery energy efficiency, avoid local aging and performance degradation of the battery caused by uneven current distribution, and extend the overall service life of the battery.

[0018] 2) Innovative selection of raw materials: Thiol and isocyanate are selected as the raw materials for preparing the bipolar plate. Both thiol and isocyanate are common industrial products with wide sources, which makes it easier to obtain raw materials, greatly reducing the raw material procurement cost and supply risk. At the same time, the reaction conditions between thiol and isocyanate are mild, without requiring harsh reaction conditions such as temperature and pressure. The reaction can occur under relatively conventional experimental conditions, and the reaction rate is fast. This not only simplifies the preparation process, reduces the energy consumption and time cost during production, but also improves production efficiency, which has a significant improvement significance for the efficient and simple preparation of high-conductivity bipolar plates.

[0019] 3) Formation of a new polymer matrix: By reacting thiol and isocyanate under the action of an initiator, a polythiourethane polymer matrix is obtained. This polymer matrix has excellent physical and chemical properties and can still maintain stability under high temperature, strong acid and strong base conditions. This stability enables the bipolar plate to adapt to the complex electrochemical environment inside the zinc-bromine flow battery and will not deteriorate in performance due to the heat generated during battery operation and the acid-base properties of the electrolyte. Its good corrosion resistance can effectively prevent the bipolar plate from being corroded by the electrolyte, extend the service life of the bipolar plate, and thus improve the reliability and stability of the entire battery. The low swelling rate ensures that the bipolar plate will not undergo excessive swelling and deformation after absorbing the electrolyte, maintaining the stability of the internal structure of the battery. In addition, the polythiourethane material has good processing stability and can be subjected to various processing techniques such as stretching, forming, and injection molding, which is suitable for different bipolar plate forming requirements, improving the processability and production flexibility of the product. Description of the Drawings

[0020] Figure 1 is the SEM photograph of the high-conductivity bipolar plate of the zinc-bromine flow battery of the present invention. Detailed Embodiments

[0021] Example 1

[0022] A preparation method of a bipolar plate for a high-conductivity zinc-bromine flow battery, and the raw material components and dosages are as follows:

[0023] Take 10 g of trimethylolpropane trithioglycolate, 6.55 g of toluene diisocyanate, add 0.33 g of TBD, add 0.33 g of conductive agent polypyrrole, ultrasonically stir the above mixture for 5 min to ensure uniform mixing; then place the mixture in a polytetrafluoroethylene mold and heat it in a forced-air oven at 100 °C for 2 h, and cool it to room temperature to obtain a polythiourethane polymer with excellent conductivity;

[0024] Example 2

[0025] A preparation method of a bipolar plate for a high-conductivity zinc-bromine flow battery, and the raw material components and dosages are as follows:

[0026] Take 10 g of trimethylolpropane trithioglycolate, 8.37 g of isophorone diisocyanate, add 0.37 g of TBD, add 0.37 g of conductive agent polypyrrole, ultrasonically stir the above mixture for 5 min to ensure uniform mixing; then place the mixture in a polytetrafluoroethylene mold and heat it in a forced-air oven at 100 °C for 2 h, and cool it to room temperature to obtain a polythiourethane polymer with excellent conductivity;

[0027] Example 3

[0028] A preparation method of a bipolar plate for a high-conductivity zinc-bromine flow battery, and the raw material components and dosages are as follows:

[0029] Take 10 g of pentaerythritol tetrakis(3-mercaptopropionate), 9.10 g of isophorone diisocyanate, add 0.38 g of TBD, add 0.38 g of conductive agent polypyrrole, ultrasonically stir the above mixture for 5 min to ensure uniform mixing; then place the mixture in a polytetrafluoroethylene mold and heat it in a forced-air oven at 100 °C for 2 h, and cool it to room temperature to obtain a polythiourethane polymer with excellent conductivity;

[0030] Example 4

[0031] A preparation method of a bipolar plate for a high-conductivity zinc-bromine flow battery, and the raw material components and dosages are as follows:

[0032] Take 10 g of pentaerythritol tetrakis(3-mercaptopropionate), 7.12 g of toluene diisocyanate, add 0.34 g of TBD, add 0.34 g of conductive agent polypyrrole, ultrasonically stir the above mixture for 5 min to ensure uniform mixing; then place the mixture in a polytetrafluoroethylene mold and heat it in a forced-air oven at 100 °C for 2 h, and cool it to room temperature to obtain a polythiourethane polymer with excellent conductivity;

[0033] Example 5

[0034] A preparation method of a bipolar plate for a high-conductivity zinc-bromine flow battery, and the raw material components and dosages are as follows:

[0035] Take 10 g of trimethylolpropane trithioglycolate, 6.55 g of toluene diisocyanate, add 0.33 g of DBU, add 0.33 g of conductive agent polypyrrole, ultrasonically stir the above mixture for 5 min to ensure uniform mixing; then place the mixture in a polytetrafluoroethylene mold and heat it in a forced-air oven at 100 °C for 2 h, and cool it to room temperature to obtain a polysulfide polyurethane polymer with excellent conductivity;

[0036] Example 6

[0037] A preparation method of a bipolar plate for a high-conductivity zinc-bromine flow battery, and the raw material components and dosages are as follows:

[0038] Take 10 g of trimethylolpropane trithioglycolate, 8.37 g of isophorone diisocyanate, add 0.37 g of DBU, add 0.37 g of conductive agent polypyrrole, ultrasonically stir the above mixture for 5 min to ensure uniform mixing; then place the mixture in a polytetrafluoroethylene mold and heat it in a forced-air oven at 100 °C for 2 h, and cool it to room temperature to obtain a polysulfide polyurethane polymer with excellent conductivity;

[0039] Example 7

[0040] A preparation method of a bipolar plate for a high-conductivity zinc-bromine flow battery, and the raw material components and dosages are as follows:

[0041] Take 10 g of pentaerythritol tetrakis(3-mercaptopropionate), 9.10 g of isophorone diisocyanate, add 0.38 g of DBU, add 0.38 g of conductive agent polypyrrole, ultrasonically stir the above mixture for 5 min to ensure uniform mixing; then place the mixture in a polytetrafluoroethylene mold and heat it in a forced-air oven at 100 °C for 2 h, and cool it to room temperature to obtain a polysulfide polyurethane polymer with excellent conductivity;

[0042] Example 8

[0043] A preparation method of a bipolar plate for a high-conductivity zinc-bromine flow battery, and the raw material components and dosages are as follows:

[0044] Take 10 g of pentaerythritol tetrakis(3-mercaptopropionate), 7.12 g of toluene diisocyanate, add 0.34 g of DBU, add 0.34 g of conductive agent polypyrrole, ultrasonically stir the above mixture for 5 min to ensure uniform mixing; then place the mixture in a polytetrafluoroethylene mold and heat it in a forced-air oven at 100 °C for 2 h, and cool it to room temperature to obtain a polysulfide polyurethane polymer with excellent conductivity.

Claims

1. A preparation method of a bipolar plate for a high-conductivity zinc-bromine flow battery, characterized in that It includes the following steps: 1) Take the compounds of raw material polythiol and polyisocyanate respectively; 2) Add an initiator accounting for 2%wt - 5%wt of the mixture in step 1); 3) Add polypyrrole as a conductive agent accounting for 2%wt - 5%wt of the mixture in step 1); 4) Ultrasonically agitate the above mixture for 3 - 5 min to ensure uniform mixing; 5) Place the mixture in a polytetrafluoroethylene mold, heat it in a forced-air oven at 100 - 120 °C, and cool it to room temperature to obtain a polythiourethane polymer with excellent conductivity, which can be used as a bipolar plate for zinc-bromine flow batteries.

2. The preparation method of the bipolar plate of the high-conductivity zinc-bromine flow battery according to claim 1, characterized in that, In step 1), for the compounds of raw material polythiol and polyisocyanate, the molar ratio of mercapto group to isocyanate group is 1:

1.

3. The preparation method of the bipolar plate of the high-conductivity zinc-bromine flow battery according to claim 1, characterized in that, In step 5), heat it in the forced-air oven for 2 - 4 h.

4. The preparation method of the bipolar plate of the high-conductivity zinc-bromine flow battery according to claim 1, characterized in that, The initiator is TBD or DBU.

5. The preparation method of the bipolar plate of the high-conductivity zinc-bromine flow battery according to claim 1, wherein, The polythiol compound is trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate), 1,6-hexanedithiol, triphenylene-2,3,6,7,10,11-hexanethiol.

6. The preparation method of the bipolar plate of the high-conductivity zinc-bromine flow battery according to claim 1, characterized in that, The polyisocyanate compound is toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate.

7. The preparation method of the bipolar plate for the high-conductivity zinc-bromine flow battery according to claim 1, characterized in that, The thiol and isocyanate react under the initiator to form the following structure:

8. The preparation method of the bipolar plate of the high-conductivity zinc-bromine flow battery according to claim 7, wherein The thiol is trimethylolpropane tris(3-mercaptopropionate).

9. The preparation method of the bipolar plate of the high-conductivity zinc-bromine flow battery according to claim 7, characterized in that The isocyanate is isophorone diisocyanate.

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