Method for enhancing chemical reaction of flow battery based on local ultrasonic assistance

Abstract

The invention provides a method for assisting and strengthening a chemical reaction of a flow battery based on local ultrasound, which comprises the following steps of: (1) arranging ultrasonic transducers on bipolar plates of a positive half battery and a negative half battery of the flow battery, the arrangement position of the ultrasonic transducer on the bipolar plate and the size of the ultrasonic transducer enable the action area of ultrasound applied by the ultrasonic transducer to cover the flow dead zone in the porous electrode; (2) connecting a signal generator with an ultrasonic transducer through a power amplifier; and (3) in the operation process of the flow battery, starting the signal generator and the power amplifier to apply ultrasound to the flow battery through the ultrasonic transducer, and improving the flow velocity and the flow uniformity of the electrolyte in the porous electrode by utilizing the ultrasound so as to strengthen the chemical reaction of the flow battery. According to the method, the flow uniformity of the electrolyte in the porous electrode can be effectively improved, the flexible regulation and control of the flow field in the porous electrode of the flow battery are realized, and the ultrasonic power consumption of the regulation and control of the flow field in the electrode is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of long-time energy storage and relates to a method for enhancing the chemical reaction of a liquid flow battery based on local ultrasound assistance. Background Art

[0002] Liquid flow batteries are a new type of electrochemical energy storage technology that achieves the mutual conversion of electrical energy and chemical energy through the reversible redox reaction of active substances in the positive and negative electrolytes. Liquid flow batteries have gradually become the preferred strategy for large-scale energy storage due to their high commercial value, short response time, decoupling of power and capacity, long service life, high safety, and low pollution. During the charge and discharge cycle of liquid flow batteries, the uniformity of electrolyte flow directly affects the energy efficiency of liquid flow batteries. However, the current liquid flow batteries have the problem of poor flow field uniformity, which seriously hinders the commercial development and application of liquid flow batteries.

[0003] In the prior art, the means for improving the uniformity of the internal flow field of liquid flow batteries are mainly the flow channel design of the bipolar plate and the optimization of the flow rate of the battery system. By designing flow channels on the surface of the bipolar plate of the liquid flow battery, the flow state of the electrolyte in the electrode can be changed, so that the electrolyte enters the porous electrode in the form of seepage, and the mass transfer of substances on the surface of the porous electrode is improved, thereby reducing flow losses and improving battery performance. By optimizing the flow rate, the capacity attenuation and voltage loss of the liquid flow battery can be balanced, and the battery performance can be improved. However, after designing the flow channel on the bipolar plate and optimizing the flow rate, there are still flow dead zones at the corners of the porous electrode of the liquid flow battery; in addition, the design of the bipolar plate flow channel is expensive, and once it is processed and formed, it is impossible to flexibly control the flow field under different working conditions.

[0004] In contrast, ultrasound is a good energy field auxiliary means that can perform non-contact manipulation of fluids and can be adjusted in real time at different battery operation stages; the device is simple and reliable, the layout is flexible, and it can be placed separately for the flow dead zone of the flow battery. This makes ultrasound widely used in the field of electrochemistry and begins to be used in the field of batteries. At present, low-frequency ultrasound can increase the conductivity of the electrolyte of deep eutectic solvent (DES) flow battery and reduce the viscosity of the electrolyte, reduce the internal loss of the redox battery, and thus increase the redox reaction rate (see Sun P., Lu P., Xu J., et al. Electrochimica Acta, 2021, 394: 139140.). Ultrasonic transducers can be used to pump electrolytes and improve the flow uniformity of electrolytes, thereby promoting the discharge performance of batteries (see Huang H., Liu P., Ma Q., et al. Enabling a high-performance saltwater Al-air battery via ultrasonically driven electrolyte flow [J]. Ultrasonics Sonochemistry, 2022, 88: 106-104.). However, the existing ultrasonic-assisted strategies still have the following shortcomings: (1) When applying ultrasound, thermal effects are often coupled, and the effect of acoustic flow effect on battery performance is not studied separately; (2) Ultrasound is continuously applied during the entire battery cycle, resulting in excessive energy consumption, which is not conducive to reducing the energy consumption of the battery system; (3) The ultrasonic method is applied to the entire battery, and the flow state of the local area is not improved. Although applying ultrasound to the entire battery can improve the performance of the overall electrolyte, it cannot effectively improve the flow uniformity of the electrolyte in the dead zone of the porous electrode.

[0005] In summary, the existing methods of improving battery performance based on ultrasound assistance cannot achieve efficient regulation of the flow field inside the porous electrode. In addition, the ultrasonic device has high energy consumption, which will reduce the net power of the battery system and increase the cost of regulating the flow field inside the electrode, hindering its large-scale application in long-term energy storage technology. Summary of the invention

[0006] In view of the problems that the existing methods based on ultrasound-assisted battery performance improvement cannot effectively improve the flow uniformity of the dead zone of the flow inside the porous electrode, the ultrasonic power consumption is large, which will reduce the net power of the battery system and increase the cost of regulating the internal flow field of the battery, the present invention provides a method for strengthening the chemical reaction of a liquid flow battery based on local ultrasound assistance, so as to effectively improve the flow uniformity of the electrolyte inside the porous electrode, realize the flexible regulation of the internal flow field of the porous electrode of the liquid flow battery, and reduce the ultrasonic power consumption of the internal flow field regulation of the electrode.

[0007] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0008] A method for enhancing the chemical reaction of a flow battery based on local ultrasound assistance, the steps are as follows:

[0009] (1) Mounting holes are provided on the current collector and end plate of the positive half-cell and the negative half-cell of the liquid flow battery, the mounting holes match the ultrasonic transducer, and ultrasonic transducers are provided on the bipolar plates of the positive half-cell and the negative half-cell of the liquid flow battery, the ultrasonic transducer is provided on a side of the bipolar plate close to the current collector, and the surface of the ultrasonic transducer in contact with the bipolar plate is a planar structure; the setting position of the ultrasonic transducer on the bipolar plate and the size of the ultrasonic transducer should be such that the action area of ​​the ultrasound applied by the ultrasonic transducer covers the flow dead zone inside the porous electrode;

[0010] The acoustic impedance of the bipolar plate matches the ultrasound applied by the ultrasonic transducer, and the thickness of the bipolar plate matches the half wavelength of the ultrasound applied by the ultrasonic transducer; (2) connecting the output end of the signal generator to the input end of the power amplifier, and connecting the output end of the power amplifier to the input end of the ultrasonic transducer;

[0011] (3) Turn on the electrolyte pump of the flow battery to pump electrolyte into the positive half-cell and the negative half-cell to operate the flow battery. During the operation of the flow battery, turn on the signal generator and the power amplifier to apply ultrasound to the flow battery through the ultrasonic transducer. Ultrasound is used to increase the flow rate and flow uniformity of the electrolyte in the porous electrode, thereby enhancing the chemical reaction of the flow battery.

[0012] In step (3) of the above technical solution, in order to alleviate the problem of excessive temperature of the flow battery caused by the application of ultrasound, during the operation of the flow battery, the temperature of the positive electrolyte and the negative electrolyte is regulated by a temperature control device, mainly by lowering the temperature of the positive electrolyte and the negative electrolyte. Further, during the operation of the flow battery, it is preferred that the temperature of the positive electrolyte and the negative electrolyte be regulated at 0 to 50°C by the temperature control device. More preferably, during the operation of the flow battery, the temperature of the positive electrolyte and the negative electrolyte be regulated at 0 to 35°C by the temperature control device.

[0013] In the above technical solution, in order to achieve flexible regulation of the positive half-cell and the negative half-cell in practical applications and avoid unnecessary energy consumption, the ultrasonic transducers arranged on the bipolar plates of the positive half-cell and the negative half-cell are preferably operated independently of each other.

[0014] Furthermore, in the above technical solution, in order to carry out targeted regulation and enhancement of the flow field in a local area (e.g., a flow dead zone) of a half-cell in practical applications, at least one ultrasonic transducer should be arranged on the bipolar plate of the positive half-cell, and preferably at least two ultrasonic transducers should be arranged on the bipolar plate of the positive half-cell. When the number of ultrasonic transducers arranged on the bipolar plate of the positive half-cell is ≥2, each ultrasonic transducer works independently; similarly, at least one ultrasonic transducer should be arranged on the bipolar plate of the negative half-cell, and preferably at least two ultrasonic transducers should be arranged on the bipolar plate of the negative half-cell. When the number of ultrasonic transducers arranged on the bipolar plate of the negative half-cell is ≥2, each ultrasonic transducer works independently.

[0015] In the above technical solution, the ultrasonic transducer includes at least one of a piezoelectric ultrasonic transducer and an electromagnetic acoustic transducer. Further, the piezoelectric ultrasonic transducer includes a piezoelectric ceramic sheet, a sandwich ultrasonic transducer or an interdigital transducer.

[0016] In the above technical solution, in order to ensure that the ultrasound emitted by the ultrasonic transducer plays an effective role in strengthening the chemical reaction of the flow battery, the ultrasonic transducer is arranged on the bipolar plate and the size of the ultrasonic transducer should be such that the action area of ​​the ultrasound applied by the ultrasonic transducer covers the flow dead zone inside the porous electrode. The flow dead zone refers to the area where the flow rate of the electrolyte in the electrode does not exceed 1.15 mm / s.

[0017] Furthermore, in the above technical solution, the setting position of the ultrasonic transducer on the bipolar plate and the size of the ultrasonic transducer preferably meet the following requirements: the ultrasonic transducer is set on the bipolar plate corresponding to the flow dead zone of the porous electrode, and the total contact area of ​​all ultrasonic transducers set on the same bipolar plate and the bipolar plate is recorded as A1, the area of ​​the surface of the porous electrode in contact with the bipolar plate is recorded as A0, and the flow dead zone area inside the porous electrode in contact with the bipolar plate is recorded as A2, A1:A0=(A2 / A0~1.2):1.

[0018] In the above technical solution, during the operation of the liquid flow battery, the vibration frequency of the ultrasonic transducer is controlled to be 0.02-10 MHz, and the vibration frequency of the ultrasonic transducer can be adjusted by adjusting the input voltage of the signal generator.

[0019] In the above technical solution, ultrasound can be applied continuously or intermittently during the operation of the liquid flow battery. In order to reduce ultrasonic energy consumption, it is preferred to apply ultrasound intermittently during the operation of the liquid flow battery.

[0020] In the above technical solution, the bipolar plate should have good electrical conductivity, and the acoustic impedance of the bipolar plate should match the ultrasound applied by the ultrasonic transducer, and the thickness of the bipolar plate should match the half-wavelength of the ultrasound applied by the ultrasonic transducer. Feasible bipolar plates include metal bipolar plates, graphite bipolar plates or carbon-plastic composite bipolar plates, and feasible carbon-plastic composite bipolar plates include polypropylene bipolar plates, where the material of the polypropylene bipolar plate is polypropylene containing conductive fillers. In the art, bipolar plates of this type of material are commonly referred to as polypropylene bipolar plates.

[0021] In the above technical solution, during the operation of the flow battery, the flow rate of the electrolyte pumping to the positive half-cell and the negative half-cell is controlled to be 5 to 200 mL min -1 .

[0022] In the above technical solution, during the operation of the flow battery, the current density of the flow battery is controlled to be 50-500 mA cm -2 .

[0023] In the above technical solution, the flow battery includes any one of an all-vanadium flow battery, an iron-chromium flow battery, a zinc-bromine flow battery, a zinc-iron flow battery, an organic flow battery and a hydrogen-bromine flow battery.

[0024] Compared with the prior art, the technical solution of the present invention can produce the following beneficial technical effects:

[0025] 1. The present invention provides a method for strengthening the chemical reaction of a liquid flow battery based on local ultrasound assistance. The method is performed by arranging an ultrasonic transducer bonded to the bipolar plate on one side of the bipolar plate of the positive half-cell and the negative half-cell of the liquid flow battery close to the current collector. The arrangement position of the ultrasonic transducer on the bipolar plate and the size of the ultrasonic transducer should be such that the action area of ​​the ultrasound applied by the ultrasonic transducer covers the flow dead zone inside the porous electrode. The signal generator is connected to the ultrasonic transducer via a power amplifier. During the operation of the liquid flow battery, the signal generator and the power amplifier are turned on to apply ultrasound to the liquid flow battery through the ultrasonic transducer. The ultrasound is used to increase the flow velocity and flow uniformity of the electrolyte in the porous electrode, especially to strengthen the flow state of the electrolyte in the flow dead zone of the porous electrode, thereby strengthening the chemical reaction of the liquid flow battery. The method provided by the present invention is a strategy for regulating the flow velocity of the flow field inside the electrode of a liquid flow battery. The ultrasonic action process is flexible and efficient, and the flow field can be adjusted for a specific electrode area (such as a flow dead zone), and the area of ​​ultrasonic action can be adjusted. It can also be combined with an ultrasonic application strategy to reduce battery energy consumption (such as continuous or intermittent application of ultrasound, time interval for intermittent application of ultrasound, etc.). The method described in the present invention can regulate the flow field for a specific flow dead zone, which can greatly improve the efficiency of ultrasonic action. With the appropriate ultrasonic application strategy, it can reduce battery energy consumption, improve economic efficiency, and be conducive to commercial application. It solves the problem of high battery energy consumption caused by the continuous application of ultrasound to the battery in the prior art, and the problem of low ultrasonic efficiency when ultrasound is applied to the entire liquid flow battery.

[0026] 2. The method of the present invention can also cool the positive electrode electrolyte and the negative electrode electrolyte through a temperature control device to avoid the problem of excessive battery temperature due to the application of ultrasonic coupled thermal effect, thereby avoiding adverse effects on the performance of the liquid flow battery due to excessive battery temperature.

[0027] 3. The method of the present invention is an active control strategy that can be flexibly and specifically adjusted according to different operating conditions of the flow battery. For example, the intensity, action position, action time, and application method of ultrasound, as well as the temperature of the electrolyte, can be flexibly controlled according to the operating conditions of the battery to specifically strengthen the chemical reaction of the flow battery. Compared with the prior art method of strengthening by designing flow channels on bipolar plates, the method of the present invention has a wider range of applicable conditions for flow batteries, a more flexible control method, and strong scalability, and is very suitable for the commercial application of large-scale flow batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram of the structure of the ultrasound-assisted all-vanadium liquid flow battery in Example 1, Figure 1 In the figure, 1 is an end plate, 2 is a current collector, 3 is an ion membrane, 4 is a bipolar plate, 5 is an electrode frame, 6 is a porous electrode, and 7 is an ultrasonic transducer.

[0029] Figure 2 This is a schematic diagram of the principle of ultrasound acting on the all-vanadium liquid flow battery in Example 1.

[0030] Figure 3 It is a comparison diagram of the flow field distribution on the middle cross section of the negative electrode in Example 2 with and without ultrasound.

[0031] Figure 4 It is a comparison diagram of the electrolyte flow rate distribution in the negative electrode with and without ultrasound drawn along the diagonal line.

[0032] Figure 5 Schematic diagram of the experimental device described in Example 3, in which 8 is an ultrasound-assisted all-vanadium liquid flow battery, 9 is a signal generator, 10 is a power amplifier, 11 is a charge and discharge tester, 12 is a temperature control device, 13 is a digital thermometer, and 14 is a peristaltic pump.

[0033] Figure 6 This is a photo of the ultrasound-assisted all-vanadium liquid flow battery in Example 3 (taken from one end plate).

[0034] Figure 7 This is a curve showing the change of the battery temperature with the ultrasonic action time when different intensities of ultrasound are applied when there is no temperature control in Example 3.

[0035] Figure 8 It is a relationship diagram between the set temperature of the temperature control device and the actual temperature of the battery under ultrasonic and non-ultrasonic conditions when temperature control is performed in Example 3.

[0036] Fig. 9 The effect of the battery operating temperature on the battery efficiency in Example 4 with or without ultrasound.

[0037] Fig.10 This is a schematic diagram of the model of ultrasound acting on a battery established using COMSOL Multiphysics software in Example 5.

[0038] Fig.11 It is a schematic diagram of the effect of acoustic flow in the electrode in Example 5.

[0039] Fig.12 These are the acoustic field distribution and flow field distribution when ultrasound propagates in the electrode in Example 5.

[0040] Fig.13 is the V on the middle cross section of the negative electrode in Example 5 with and without ultrasound 2+ Distribution map.

[0041] Fig.14 is the V at different measurement cross sections of the negative electrode in Example 5 with and without ultrasound 2+ Distribution uniformity factor.

[0042] Fig.15 is the V on the middle cross section of the negative electrode in Example 5 under different current density conditions with and without ultrasound 2+ Distribution uniformity factor.

[0043] Fig.16 is the V on the middle cross section of the negative electrode with and without ultrasound under different SOC conditions in Example 5 2+ Distribution uniformity factor.

[0044] Fig.17 3 is a graph showing the relationship between the input voltages of different signal generators and the actual output voltages of the piezoelectric ceramic piece in Example 6.

[0045] Fig.18 This is the effect of different signal generator input voltages on battery efficiency in Example 6.

[0046] Fig.19 This is the effect of different current densities on battery efficiency in Example 7 with and without ultrasound.

[0047] Fig. 20 This is a photo of the piezoelectric ceramic sheet installed on the bipolar plate in the experimental device of Example 8.

[0048] Fig.21 Schematic diagram of different ultrasound application positions in Example 8.

[0049] Fig. 22 This is the effect of not applying ultrasound and applying ultrasound at different positions on battery efficiency in Example 8.

[0050] Fig.23 It is a schematic diagram of the ultrasonic application method in Example 9, the temperature change during battery operation, and the battery power consumption.

[0051] Fig.24 The following is the effect of different ultrasound application methods on battery efficiency in Example 9.

[0052] Fig.25 This is a schematic diagram of the dimensions of the industrial-scale and laboratory-scale porous electrodes in Example 10.

[0053] Fig.26 This is a schematic diagram of a model of ultrasound acting on an industrial-scale battery constructed using COMSOL Multiphysics software in Example 10.

[0054] Fig. 27 It is a comparison diagram of the flow field and streamlines on the middle section of the negative electrode when there is ultrasound and when there is no ultrasound in Example 10.

[0055] Fig.28It is a comparison chart of the average flow rate of the electrolyte in the negative electrode before and after applying ultrasound under the porous electrode conditions of the laboratory scale of Example 2 and the industrial scale of Example 10. DETAILED DESCRIPTION

[0056] The following examples further illustrate the method for enhancing the chemical reaction of liquid flow batteries based on local ultrasound assistance provided by the present invention. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention according to the above invention content and implement them specifically, which still falls within the scope of protection of the present invention.

[0057] Since the principle of strengthening the chemical reaction of all types of liquid flow batteries and strengthening the chemical reaction of all-vanadium liquid flow batteries is the same, the following embodiments take all-vanadium liquid flow batteries as an example to explain the method of the present invention in detail.

[0058] In the following embodiments, the piezoelectric ceramic sheet made of PZT-4 material is purchased from Shandong Xinming Electronics Co., Ltd., the length × width × thickness of the piezoelectric ceramic sheet made of PZT-4 material used in Example 9 is 20 × 20 × 2 mm, and the length × width × thickness of the piezoelectric ceramic sheet made of PZT-4 material used in the remaining embodiments is 40 × 40 × 2 mm. The model of the signal generator is DG1022Z, purchased from Puyuan Jingdian Technology Co., Ltd.; the model of the power amplifier is ATA-1222A, purchased from Xi'an Antai Electronic Technology Co., Ltd.; the model of the charge and discharge tester is A211-BTS-4S-1U, purchased from Shenzhen Xinwei Electronics Co., Ltd.; the model of the digital thermometer is HH806AU, purchased from OMEGA Industrial Measurement Company; the model of the low-temperature constant temperature water bath is DC-1015, purchased from Shanghai Hengping Instrument Factory; the end plate is purchased from Dalian Deyue Co., Ltd.; the polypropylene (PP) bipolar plate is provided by Jiaxing Naco New Materials Co., Ltd. The electrolyte solution was purchased from Dalian BoRong New Materials Co., Ltd.

[0059] Example 1

[0060] In this example, an ultrasound-assisted all-vanadium liquid flow battery was assembled and its performance was tested.

[0061] (1) Figure 1 The schematic diagram of the structure of the ultrasonic-assisted all-vanadium liquid flow battery is shown. The structure of the battery is basically the same as that of the ordinary all-vanadium liquid flow battery. The only difference is that an ultrasonic transducer is fixedly arranged on the side of the bipolar plate close to the current collector of the positive half-cell and the negative half-cell, as follows:

[0062] according to Figure 1The structure shown in the figure is used for battery assembly. The ultrasound-assisted all-vanadium liquid flow battery consists of a positive half-cell and a negative half-cell, and the positive half-cell and the negative half-cell are separated by an ion membrane. The positive half-cell and the negative half-cell both include a porous electrode 6, an electrode frame 5, a bipolar plate 4, a current collector 2, an end plate 1 and an ultrasonic transducer 7. The bottom and top of the end plate 7 are respectively provided with an electrolyte inlet and an electrolyte outlet.

[0063] The ion membrane used is 115 ion exchange membrane (DuPont Co.), the ultrasonic transducer used is specifically a piezoelectric ceramic piece made of PZT-4 material, with a length × width × thickness of 40 × 40 × 2 mm, the end plate used is made of aluminum alloy, the current collector is made of copper material, the electrode frame is a polyvinyl chloride (PVC) electrode frame, the bipolar plate is a polypropylene (PP) bipolar plate with a thickness of 0.9 mm, and the porous electrode used is a carbon felt electrode.

[0064] A carbon felt electrode without any activation is inserted into the electrode frame and compressed to a thickness of 3.5 mm. The length and width of the carbon felt electrode are 40×40 mm. The carbon felt electrode is bonded to the ion membrane, and the bipolar plate is bonded to the carbon felt electrode. Mounting holes matching the shape and size of the piezoelectric ceramic sheet are set on the current collector and the end plate. A piezoelectric ceramic sheet is respectively pasted and fixed on the outer side surface of each bipolar plate (the middle position of the side of the bipolar plate close to the current collector, so that the piezoelectric ceramic sheet is bonded to the bipolar plate, and the current collector is bonded to the bipolar plate on the outer side surface of the bipolar plate. An end plate is set on the outer side surface of the current collector (the side where the current collector is not in contact with the bipolar plate), and the two piezoelectric ceramic sheets can act independently on the two half-cells.

[0065] (2) After the battery is assembled, use a peristaltic pump to pump 35 mL of electrolyte solution at a rate of 10 mL min. -1 is delivered to the electrode reaction zone at a flow rate.

[0066] (3) Use a charge and discharge tester to test the battery performance.

[0067] Figure 2 This is a schematic diagram of the principle of ultrasound acting on an all-vanadium liquid flow battery. The ultrasound in the fluid causes the particles of the fluid to oscillate around their equilibrium position. By applying ultrasound of appropriate intensity, acoustic flow will be generated in the sound field.

[0068] Example 2

[0069] In this embodiment, the flow field distribution in the negative electrode of the battery described in Example 1 with and without ultrasound is provided.

[0070] The COMSOL simulation software was used to calculate the electrolyte concentration at 20 mL min -1Under the condition that the electrolyte is transported to the electrode reaction zone of the battery described in Example 1 at a flow rate of 1 MHz, the velocity distribution of the electrolyte in the negative electrode with ultrasound (the simulated frequency of ultrasound is 1 MHz) and without ultrasound, and the flow field distribution comparison diagram on the middle cross section of the negative electrode with ultrasound and without ultrasound are shown in the figure below: Figure 3 shown.

[0071] Depend on Figure 3 It can be seen that compared with the case without ultrasound, after ultrasound was applied, the streamlines of the electrolyte in the negative electrode changed significantly, the flow rate of the electrolyte generally increased, the dead zone in the flow field decreased, and the flow uniformity and average flow rate of the electrolyte in the negative electrode were improved. Figure 3 The diagonal line shown by the dotted line in Figure (A) is used to draw a comparison diagram of the electrolyte flow rate distribution in the negative electrode with and without ultrasound. The results are shown in Figure 4 As shown. Figure 4 It can be seen that the acoustic flow can increase the flow rate of the flow field in the negative electrode, especially can effectively improve the flow rate of the electrolyte in the negative electrode along the diagonal line and the flow dead zone, which is very beneficial to reduce concentration polarization. From this embodiment, it can be seen that by applying ultrasound in the method described in the present invention, the acoustic flow can increase the overall flow rate of the negative electrode flow field, reduce the flow dead zone, thereby improving the distribution uniformity of the electrolyte, and then help reduce the internal concentration polarization of the battery and improve the battery performance.

[0072] Example 3

[0073] In this embodiment, the entire experimental device of ultrasound-assisted all-vanadium liquid flow battery is provided. The schematic diagram of the experimental device is as follows: Figure 5 As shown, it includes an ultrasound-assisted all-vanadium liquid flow battery 8, a signal generator 9, a power amplifier 10, a charge and discharge tester 11, a temperature control device 12 (the temperature control device is a constant temperature low-temperature water bath), a digital thermometer 13, and a peristaltic pump 14.

[0074] First, the ultrasound-assisted all-vanadium redox flow battery is assembled according to the operation of Example 1. After the assembly is completed, the photo of the ultrasound-assisted all-vanadium redox flow battery (taken from one end plate) is as follows: Figure 6 As shown. Connect the output end of the signal generator to the input end of the power amplifier, and connect the output end of the power amplifier to the input end of the ultrasonic transducer; connect the electrolyte outlet of the positive half-cell to the positive electrolyte storage tank through a pipe fitting, and then connect it to the electrolyte inlet of the positive half-cell through a peristaltic pump and a pipe fitting; connect the electrolyte outlet of the negative half-cell to the negative electrolyte storage tank through a pipe fitting, and then connect it to the electrolyte inlet of the negative half-cell through a peristaltic pump and a pipe fitting; place the positive electrolyte storage tank and the negative electrolyte storage tank in a temperature control device; connect the positive and negative output ends of the charge and discharge tester to the positive and negative poles of the ultrasonic-assisted all-vanadium liquid flow battery respectively; and place the probe of the digital thermometer at the electrolyte outlet of the positive half-cell and the negative half-cell.

[0075] After the entire experimental device was built, a peristaltic pump was used to pump 35 mL of electrolyte solution (1.65 MV and 4.12 MH2SO4) at a rate of 10 mL min -1 The flow rate is delivered to the electrode reaction area. The experimental device is operated and the battery performance is tested using a charge and discharge tester. When the temperature control device is not used to control the temperature of the electrolyte, the temperature of the battery changes with the ultrasonic action time when different intensities of ultrasound are applied. Figure 7 When the temperature control device is used to control the temperature of the electrolyte, the temperature of the temperature control device is set under ultrasonic and non-ultrasonic conditions ( Figure 8 The relationship between the water bath temperature in the battery and the actual battery temperature is shown in the figure below. Figure 8 shown.

[0076] Combination Figures 7-8 It can be seen that when temperature control is not performed, the temperature of the battery will increase as the ultrasonic application time increases, and the greater the ultrasonic intensity applied, the higher the battery temperature and the faster the temperature rises. When the temperature control device is turned on for temperature control, the temperature difference between the battery when ultrasound is applied and when ultrasound is not applied is not particularly obvious, indicating that when the temperature control device is turned on for temperature control, strengthening by applying ultrasound will not cause a significant increase in the battery temperature.

[0077] Example 4

[0078] In this embodiment, a method for enhancing the chemical reaction of an all-vanadium liquid flow battery based on local ultrasound assistance is provided, and the steps are as follows:

[0079] (1) Build the experimental device according to the operation of Example 3.

[0080] (2) The battery was operated without ultrasound and the electrolyte flow rate was controlled to 10 mL min -1 , current density is 110 mA cm -2 , turn on the temperature control device to control the operating temperature of the battery to 25°C, and obtain the coulombic efficiency (CE), voltage efficiency (VE) and energy efficiency (EE) of the battery after the battery runs to a stable cycle; then adjust the set temperature of the temperature control device to control the operating temperature of the battery to 5°C, 15°C, 35°C and 45°C respectively, and obtain the CE, VE and EE of the battery after the battery runs to a stable cycle.

[0081] (3) The battery was operated under ultrasonic conditions and the electrolyte flow rate was controlled to 10 mL min -1 , current density is 110 mA cm -2, turn on the temperature control device to control the operating temperature of the battery to 25°C, control the input voltage of the signal generator to 800mVpp, and the power amplifier gain multiple to 40dB, and obtain the CE, VE and EE of the battery after the battery runs to a stable cycle; then adjust the set temperature of the temperature control device to control the operating temperature of the battery to 5°C, 15°C, 35°C and 45°C respectively, and obtain the CE, VE and EE of the battery after the battery runs to a stable cycle.

[0082] In this embodiment, the test results of CE, VE and EE of the battery when applying and adding ultrasound at different battery operating temperatures are as follows: Fig. 9 As shown. With the increase of operating temperature, regardless of whether ultrasound is applied or not, the coulombic efficiency shows a downward trend, while the voltage efficiency and energy efficiency show an upward trend. This is due to the influence of temperature on the thermodynamics and kinetics of electrochemical reactions. With the increase of temperature, the movement of vanadium ions also becomes more intense, resulting in an increase in the permeability of vanadium ions through the membrane, thereby reducing the coulombic efficiency. The acoustic streaming effect brought about by applying ultrasound at low temperatures helps the mixing of the electrolyte, thereby reducing the concentration polarization of the electrolyte and promoting the improvement of the energy efficiency and voltage efficiency of the battery. At high temperatures, applying ultrasound will cause the coulombic efficiency to drop rapidly, while the voltage efficiency will increase relatively slowly, which directly leads to a decrease in energy efficiency. It can be seen from this embodiment that applying ultrasound at low temperatures can more effectively improve the performance of the battery, while at high temperatures, the effect of ultrasound will be limited.

[0083] Example 5

[0084] In this embodiment, the negative electrode V is investigated under different states of charge (SOC) and current densities with or without ultrasound. 2+ Variation of flow uniformity factor.

[0085] Use COMSOL Multiphysics software to build a model of ultrasound acting on a battery. Fig.10 As shown in Figure 2, COMSOL simulation software was then used to calculate the electrolyte transport to the electrode reaction area of ​​the battery. The ultrasonic frequency was controlled to be 1 MHz and the electrolyte flow rate was 20 mL min -1 , SOC is 0.15, current density is 80mA cm -2 Under the condition of , the acoustic field distribution and flow field distribution when ultrasound propagates in the electrode, and the schematic diagram of the effect of acoustic flow in the electrode are shown in Fig.11 As shown in Figure 2, the acoustic field distribution and flow field distribution when ultrasound propagates in the electrode are as follows: Fig.12 As shown in Figures (A) and (B). Fig.13 It is the V in the middle section of the negative electrode with and without ultrasound. 2+ Distribution comparison chart. Fig.13 It can be seen that by applying ultrasound through the method of the present invention, the acoustic flow enhances the V2+ The distribution uniformity of the negative electrode is improved, and the mass transfer in the flow dead zone of the negative electrode is effectively improved.

[0086] like Fig.14 As shown in the small figure in the upper left corner, three measurement sections are taken along the thickness direction of the negative electrode. The three measurement sections are numbered as position 1, position 2 and position 3 according to the distance from the ion membrane from near to far. The V on the three measurement sections is calculated under the conditions of applying and not applying ultrasound. 2+ Distribution uniformity factor, the result is as follows Fig.14 As shown. Fig.14 It can be seen that after applying ultrasound, the acoustic streaming can enhance the flow uniformity on all three measurement sections, that is, increase the V 2+ The distribution is uniform, and the closer the distance to the piezoelectric ceramic piece PZT-4 where ultrasound is applied is, the more obvious the acoustic streaming effect is.

[0087] COMSOL simulation software was used to calculate the electrolyte transport to the electrode reaction area of ​​the battery. The ultrasonic frequency was controlled to be 1 MHz and the electrolyte flow rate was 20 mL min -1 , SOC is 0.15, and the current density is 20, 60, and 100 mA cm -2 Under the condition of V 2+ Distribution uniformity factor, the result is as follows Fig.15 shown.

[0088] COMSOL simulation software was used to calculate the electrolyte transport to the electrode reaction area of ​​the battery. The ultrasonic frequency was controlled to be 1 MHz and the electrolyte flow rate was 20 mL min -1 , current density is 80 mA cm -2 The V in the middle section of the negative electrode under the conditions of SOC of 0.15, 0.45, and 0.75 respectively 2+ Distribution uniformity factor, the result is as follows Fig.16 shown.

[0089] Depend on Figures 15-16 It can be seen that under high current density and low SOC conditions, the application of ultrasound shows a more excellent flow field regulation ability, which is mainly due to the intensified concentration polarization in the electrode at this time.

[0090] Example 6

[0091] In this embodiment, a method for enhancing the chemical reaction of an all-vanadium liquid flow battery based on local ultrasound assistance is provided, and the steps are as follows:

[0092] (1) Build the experimental device according to the operation of Example 3.

[0093] (2) The battery was operated without ultrasound and the electrolyte flow rate was controlled to 10 mL min -1 , current density is 110 mA cm -2 , turn on the temperature control device to control the operating temperature of the battery to 25°C, and obtain the CE, VE and EE of the battery after the battery runs to a stable cycle.

[0094] (3) The battery was operated under ultrasonic conditions and the electrolyte flow rate was controlled to 10 mL min -1 , current density is 110 mA cm -2 , control the input voltage of the ultrasonic signal generator to 100-1500mVpp, control the gain of the power amplifier to 40dB, turn on the temperature control device to control the operating temperature of the battery to 25℃, and the relationship between the output voltage of the signal generator and the output voltage of the piezoelectric ceramic piece PZT-4 is as follows Fig.17 When the input voltage of the ultrasonic signal generator is 400mVpp, 600mVpp, 800mVpp, 1000mVpp, and 1200mVpp, the CE, VE, and EE of the battery are obtained after the battery runs to cycle stability. The results are as follows: Fig.18 shown.

[0095] Example 7

[0096] In this embodiment, a method for enhancing the chemical reaction of an all-vanadium liquid flow battery based on local ultrasound assistance is provided, and the steps are as follows:

[0097] (1) Build the experimental device according to the operation of Example 3.

[0098] (2) The battery was operated without ultrasound and the electrolyte flow rate was controlled to 10 mL min -1 , respectively control the current density to 50 mA cm -2 , 100mA cm -2 , 150mA cm -2 , 200mA cm -2 , 250mA cm -2 , turn on the temperature control device to control the operating temperature of the battery to 25°C, and obtain the CE, VE and EE of the battery after the battery runs to a stable cycle.

[0099] (3) The battery was operated under ultrasonic conditions and the electrolyte flow rate was controlled to 10 mL min -1 , respectively control the current density to 50 mA cm -2 、100mAcm -2 , 150mA cm -2 、200mAcm -2 , 250mA cm -2, the input voltage of the control signal generator is 800mVpp, the gain of the power amplifier is 40dB, and the CE, VE and EE of the battery are obtained after the battery runs to cycle stability. The results are as follows Fig.19 shown.

[0100] Example 8

[0101] In this embodiment, the position of the piezoelectric ceramic sheet to which ultrasound is applied is adjusted to investigate the effect of the ultrasound application position on the battery efficiency.

[0102] (1) The experimental device was built according to the operation of Example 3. The difference between this embodiment and Example 3 is that when assembling the ultrasonic-assisted all-vanadium liquid flow battery, the piezoelectric ceramic sheet made of PZT-4 with a length × width × thickness of 40 × 40 × 2 mm was replaced by four piezoelectric ceramic sheets with a length × width × thickness of 20 × 20 × 2 mm, that is, the place where a piezoelectric ceramic sheet with a size of 40 × 40 × 2 mm was installed in Example 1 was replaced by four piezoelectric ceramic sheets with a size of 20 × 20 × 2 mm, and the four piezoelectric ceramic sheets were allowed to work independently, such as Fig. 20 shown.

[0103] (2) The battery was operated without ultrasound and the electrolyte flow rate was controlled to 10 mL min -1 , the current density was controlled to be 110 mA cm -2 , turn on the temperature control device to control the operating temperature of the battery to 25°C, and obtain the CE, VE and EE of the battery after the battery runs to cycle stability. No ultrasound is applied in this step, such as Fig.21 As shown in Figure (A).

[0104] (3) The battery was operated under ultrasonic conditions and the electrolyte flow rate was controlled to 10 mL min -1 , the current density was controlled to be 110 mA cm -2 , turn on the temperature control device to control the operating temperature of the battery to 25℃, control the input voltage of the signal generator to 800mVpp, and the power amplifier gain to 40dB. Fig.21 Ultrasound is applied to the dead zone of electrode flow in the manner of Figure (B), and the CE, VE and EE of the battery are obtained after the battery runs to cycle stability.

[0105] (3) The battery was operated under ultrasonic conditions and the electrolyte flow rate was controlled to 10 mL min -1 , the current density was controlled to be 110 mA cm -2 , turn on the temperature control device to control the operating temperature of the battery to 25℃, control the input voltage of the signal generator to 800mVpp, and the power amplifier gain to 40dB. Fig.21Ultrasound is applied to the dead zone of electrode flow in the manner of Figure (C), and the CE, VE and EE of the battery are obtained after the battery runs to cycle stability.

[0106] The CE, VE and EE test results of the battery in this embodiment when no ultrasound is applied and ultrasound is applied at different positions are as follows: Fig. 22 As shown, Fig. 22 a, b, and c in the figure represent the test results when ultrasound is not applied in step (1), step (2), and step (3), respectively. Fig. 22 It can be seen that the application position of ultrasound has a more obvious effect on the voltage efficiency and energy efficiency of the battery. When ultrasound acts more fully on the flow dead zone of the electrode, the voltage efficiency and energy efficiency are more significantly improved.

[0107] Example 9

[0108] In this embodiment, the influence of the ultrasound application strategy on the battery temperature and energy consumption is investigated by adjusting the ultrasound application strategy.

[0109] (1) Build the experimental device according to the operation of Example 3.

[0110] (2) Fig.23 As shown in the application method a in Figure (A), in this step, no ultrasound is applied during the charging and discharging stages, and the electrolyte flow rate is controlled to be 10 mL min -1 , the current density was controlled to be 110 mA cm -2 The temperature control device is not turned on for temperature control. After the battery runs to a stable cycle, the CE, VE and EE of the battery, as well as the temperature change of the battery and the energy consumption (power consumption) of the battery are obtained.

[0111] (3) Fig.23 As shown in the application method b in Figure (A), ultrasound is continuously applied during the charging stage, and no ultrasound is applied during the discharging stage. The electrolyte flow rate is controlled to be 10 mL min -1 , the current density was controlled to be 110 mA cm -2 The temperature control device was not turned on for temperature control. When ultrasound was applied, the input voltage of the control signal generator was controlled to be 800mVpp and the gain multiple of the power amplifier was 40dB. After the battery ran to cycle stability, the CE, VE and EE of the battery, as well as the temperature change of the battery and the energy consumption of the battery were obtained.

[0112] (4) Fig.23 As shown in the application method c in Figure (A), in this step, ultrasound is not applied during the charging stage, and ultrasound is continuously applied during the discharging stage, and the electrolyte flow rate is controlled to be 10 mL min -1 , the current density was controlled to be 110 mA cm -2The temperature control device was not turned on for temperature control. When ultrasound was applied, the input voltage of the control signal generator was controlled to be 800mVpp and the gain multiple of the power amplifier was 40dB. After the battery ran to cycle stability, the CE, VE and EE of the battery, as well as the temperature change of the battery and the energy consumption of the battery were obtained.

[0113] (5) Fig.23 As shown in the application method d in Figure (A), this step applies ultrasound in a pulsed manner during the charging stage, does not apply ultrasound during the discharging stage, and controls the electrolyte flow rate to 10 mL min -1 , the current density was controlled to be 110 mA cm -2 The temperature control device was not turned on for temperature control. When ultrasound was applied, the input voltage of the control signal generator was controlled to be 800mVpp and the gain multiple of the power amplifier was 40dB. After the battery ran to cycle stability, the CE, VE and EE of the battery, as well as the temperature change of the battery and the energy consumption of the battery were obtained.

[0114] (6) Fig.23 As shown in the application method e in Figure (A), in this step, ultrasound is not applied during the charging stage, and ultrasound is applied in a pulsed manner during the discharging stage, and the electrolyte flow rate is controlled to be 10 mL min -1 , the current density was controlled to be 110 mA cm -2 The temperature control device was not turned on for temperature control. When ultrasound was applied, the input voltage of the control signal generator was controlled to be 800mVpp and the gain multiple of the power amplifier was 40dB. After the battery ran to cycle stability, the CE, VE and EE of the battery, as well as the temperature change of the battery and the energy consumption of the battery were obtained.

[0115] (7) Fig.23 As shown in the application method f in Figure (A), ultrasound is continuously applied during both the charging and discharging stages, and the electrolyte flow rate is controlled to be 10 mL min -1 , the current density was controlled to be 110 mA cm -2 The temperature control device was not turned on for temperature control. When ultrasound was applied, the input voltage of the control signal generator was controlled to be 800mVpp and the gain multiple of the power amplifier was 40dB. After the battery ran to cycle stability, the CE, VE and EE of the battery, as well as the temperature change of the battery and the energy consumption of the battery were obtained.

[0116] In this embodiment, when the temperature control device is not turned on for temperature control, the temperature change of the battery and the battery energy consumption under different ultrasonic application strategies are as follows: Fig.23 As shown in Figures (B) and (C), the test results of CE, VE and EE of the battery under different ultrasonic application strategies are as follows Fig.24 As shown. Figures 23-24It can be seen that when the temperature control device is not turned on to control the temperature of the battery, the temperature of the battery increases with the application of ultrasound, and when the application of ultrasound stops, the temperature of the battery will decrease; the energy consumption of the battery will increase with the increase of the application time of ultrasound. In general, when ultrasound is applied in a pulsed manner, the voltage efficiency and energy efficiency of the battery can be improved while effectively reducing the power consumption.

[0117] Example 10

[0118] In this embodiment, the flow field distribution inside the negative electrode of the battery is tested with and without ultrasound at the industrial scale porous electrode size. Fig.25 As shown, the size (length × width) of the porous electrode in the laboratory (Examples 1 to 9) is 40 mm × 40 mm, while the size (length × width) of the porous electrode in the industrial scale is 600 mm × 240 mm. The battery model of ultrasound acting on the industrial-scale porous electrode was established using COMSOL Multiphysics software (the battery structure is basically the same as in Example 1, but the size is larger), as shown in FIG. Fig.26 As shown, the electrolyte flow rate is controlled at 20 mL min -1 , under the condition of ultrasonic frequency of 1MHz, the flow field distribution in the negative electrode with and without ultrasound is simulated. The flow field and streamline comparison on the middle section of the negative electrode are shown in the figure below. Fig. 27 shown.

[0119] Depend on Fig. 27 It can be seen that for industrial-scale porous electrodes, compared with the case without ultrasound application, the electrolyte flow rate has been significantly improved after ultrasound application, the electrolyte streamline has changed significantly, the dead zone area in the flow field has been reduced, and the flow uniformity and average flow rate of the electrolyte have been improved, which will significantly reduce the concentration polarization inside the battery.

[0120] Under the conditions of the porous electrode of the laboratory scale of Example 2 and the industrial scale of this example, the average flow rate of the electrolyte in the negative electrode before and after the application of ultrasound is compared as shown in the figure: Fig.28As shown. Due to the size limitation of the porous electrode on a laboratory scale, the uneven concentration of the electrolyte in the porous electrode is not obvious, so the effect of applying ultrasound on promoting the flow of the electrolyte is relatively limited. The average flow rate of the electrolyte in the negative electrode only increases from 1.44 mm / s without ultrasound to 3.26 mm / s. Under the size of the porous electrode on an industrial scale, the uneven flow of the electrolyte in the negative electrode is even worse. At this time, applying ultrasound can significantly increase the flow rate of the electrolyte. After applying ultrasound, the average flow rate of the electrolyte in the porous electrode can be increased from 1.23 mm / s to 18.19 mm / s. It can be seen from this embodiment that applying ultrasound by the method described in the present invention can also effectively increase the overall flow rate of industrial-scale liquid flow batteries, reduce flow dead zones, thereby improving the uniformity of the electrolyte, and thus improving the performance of liquid flow batteries at industrial scales.

Claims

1. A method for enhancing the chemical reaction of a liquid flow battery based on local ultrasound assistance, characterized in that: Here are the steps: (1) Mounting holes are provided on the current collector and end plate of the positive half-cell and the negative half-cell of the liquid flow battery, the mounting holes match the ultrasonic transducer, and ultrasonic transducers are provided on the bipolar plates of the positive half-cell and the negative half-cell of the liquid flow battery, the ultrasonic transducer is provided on a side of the bipolar plate close to the current collector, and the surface of the ultrasonic transducer in contact with the bipolar plate is a planar structure; the setting position of the ultrasonic transducer on the bipolar plate and the size of the ultrasonic transducer should be such that the action area of ​​the ultrasound applied by the ultrasonic transducer covers the flow dead zone inside the porous electrode; The acoustic impedance of the bipolar plate matches the ultrasound applied by the ultrasonic transducer, and the thickness of the bipolar plate matches the half wavelength of the ultrasound applied by the ultrasonic transducer; (2) connecting the output end of the signal generator to the input end of the power amplifier, and connecting the output end of the power amplifier to the input end of the ultrasonic transducer; (3) Turn on the electrolyte pump of the flow battery to pump electrolyte into the positive half-cell and the negative half-cell to operate the flow battery. During the operation of the flow battery, turn on the signal generator and the power amplifier to apply ultrasound to the flow battery through the ultrasonic transducer. Ultrasound is used to increase the flow rate and flow uniformity of the electrolyte in the porous electrode, thereby enhancing the chemical reaction of the flow battery.

2. The method for enhancing the chemical reaction of a flow battery based on local ultrasound assistance according to claim 1, characterized in that: In step (3), during the operation of the liquid flow battery, the temperature of the positive electrode electrolyte and the negative electrode electrolyte is regulated by a temperature control device.

3. The method for enhancing the chemical reaction of a flow battery based on local ultrasound assistance according to claim 2, characterized in that: During the operation of the flow battery, the temperature of the positive electrode electrolyte and the negative electrode electrolyte is regulated at 0-50°C by a temperature control device.

4. The method for enhancing the chemical reaction of a flow battery based on local ultrasound assistance according to claim 1, characterized in that: The ultrasonic transducers arranged on the bipolar plates of the positive electrode half-cell and the negative electrode half-cell work independently.

5. The method for enhancing the chemical reaction of a flow battery based on local ultrasound assistance according to claim 4 is characterized in that: At least one ultrasonic transducer is arranged on the bipolar plate of the positive half-cell, and when the number of ultrasonic transducers arranged on the bipolar plate of the positive half-cell is ≥2, each ultrasonic transducer operates independently; at least one ultrasonic transducer is arranged on the bipolar plate of the negative half-cell, and when the number of ultrasonic transducers arranged on the bipolar plate of the negative half-cell is ≥2, each ultrasonic transducer operates independently.

6. The method for enhancing the chemical reaction of a flow battery based on local ultrasound assistance according to any one of claims 1 to 5, characterized in that: The ultrasonic transducer includes at least one of a piezoelectric ultrasonic transducer and an electromagnetic acoustic transducer.

7. The method for enhancing the chemical reaction of a flow battery based on local ultrasound assistance according to claim 6, characterized in that: The piezoelectric ultrasonic transducer includes a piezoelectric ceramic sheet, a sandwich ultrasonic transducer or an interdigital transducer.

8. The method for enhancing the chemical reaction of a liquid flow battery based on local ultrasound assistance according to any one of claims 1 to 5, characterized in that: The ultrasonic transducer is set on the bipolar plate corresponding to the flow dead zone of the porous electrode, and the total contact area of ​​all ultrasonic transducers set on the same bipolar plate and the bipolar plate is recorded as A1, the area of ​​the surface of the porous electrode in contact with the bipolar plate is recorded as A0, and the flow dead zone area inside the porous electrode in contact with the bipolar plate is recorded as A2, A1:A0=(A2 / A0~1.2):

1.

9. The method for enhancing the chemical reaction of a liquid flow battery based on local ultrasound assistance according to any one of claims 1 to 5, characterized in that: During the operation of the flow battery, the vibration frequency of the ultrasonic transducer is controlled to be 0.02 to 10 MHz.

10. The method for enhancing the chemical reaction of a liquid flow battery based on local ultrasound assistance according to any one of claims 1 to 5, characterized in that: Ultrasound is applied intermittently during the operation of the flow battery.

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