Method and system for suppressing magnetohydrodynamic instability of liquid metal battery

Abstract

The invention belongs to the technical field of electrochemical energy storage batteries, and particularly relates to a method and a system for inhibiting magnetohydrodynamic instability of a liquid metal battery. Conductive buses parallel to the side wall of the liquid metal battery are uniformly distributed outside the liquid metal battery; the direction of current passing through the conductive buses is the same as the direction of current in the liquid metal battery, so that the direction of an induced magnetic field formed by all the conductive buses is opposite to the direction of a magnetic field generated by the liquid metal battery, and the flowing of electrolyte of the liquid metal battery is hindered under the action of the induced magnetic field; the magnetic field intensity in the battery is effectively weakened, the Lorentz force pointing to the axis is reduced, and the critical current density and the stability of the liquid metal battery are improved. The invention aims to provide the method for inhibiting the MHDI, which has the advantages of saving energy cost and improving the space utilization rate of the battery module group by optimizing the configuration of the battery bus on the premise of not damaging the internal structure of the battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy storage batteries, and particularly relates to a method and a system for suppressing the magnetohydrodynamic instability of a liquid metal battery. Background Art

[0002] A liquid metal battery is a new type of electrochemical energy storage technology with broad development potential and is considered one of the systems that can be used for grid-scale electrochemical energy storage. It mainly consists of three layers of molten liquids with different densities inside. The liquid positive electrode and the liquid negative electrode are separated by a thin layer of molten metal salt. Since the three layers are immiscible and have different densities, the internal layers automatically separate, with a simple structure and good self-healing and scalability. The liquid metal battery has a stable structure and will not have problems such as electrode structure deformation and dendrite formation caused by long-term operation of solid batteries, resulting in a reduction in battery operation efficiency.

[0003] In order to meet the requirements of large-scale grid-scale energy storage and control costs at the same time, the development of larger-capacity single liquid metal batteries has become an inevitable trend. However, large-size liquid metal batteries are more likely to encounter magnetohydrodynamic flow instability (MHDI) problems during high-current charge and discharge processes, such as Taylor instability, interface sloshing instability, etc. Taking Taylor instability as an example, as the internal current of the liquid metal battery increases, the azimuthal magnetic field intensity generated by the current increases. When the azimuthal magnetic field is large enough, Taylor instability will inevitably occur, resulting in the liquid metal battery losing stability and short-circuiting in a short time.

[0004] In large-scale energy storage systems, the design of battery packs usually adopts a combination of series and parallel connections. Among them, battery parallel connection can increase the current capacity of the entire battery pack and improve the energy density of the system; while battery series connection can increase the charge and discharge voltage of the battery pack, which is more suitable for the application of power grids and energy storage systems. In the entire battery pack system, as long as an unstable phenomenon occurs inside one of the battery monomers, it will affect the charge and discharge process of the entire system, and further affect the normal operation of the energy storage system. Therefore, it is of great significance to propose a new method that can weaken the growth rate of MHDI in a single battery. Summary of the Invention

[0005] In order to solve the existing MHDI problem, the present invention aims to provide a method for suppressing MHDI without damaging the internal structure of the battery. By optimizing the battery bus configuration, the magnetohydrodynamic instability of the liquid metal battery is suppressed, and thus the critical current density under normal battery operation conditions is increased. The specific technical solution adopted is as follows: A method for suppressing the magnetohydrodynamic instability of a liquid metal battery, comprising the following steps:

[0006] Step 1. A number of conductive busbars are evenly distributed outside the liquid metal battery. The conductive busbars are parallel to the side wall of the liquid metal battery, and the direction of the current passing through the conductive busbars is the same as the direction of the current inside the liquid metal battery. The perpendicular distance from each conductive busbar to the center of the liquid metal battery is the same;

[0007] Step 2. The conductive busbars are energized, and the direction of the induced magnetic field formed by all the conductive busbars is opposite to the direction of the magnetic field generated by the liquid metal battery itself;

[0008] Step 3. The action of the induced magnetic field in Step 2 hinders the flow of the electrolyte of the liquid metal battery, and improves the critical current density of the liquid metal battery.

[0009] Moreover, in Step 1, the liquid metal battery is in a cuboid shape, and one conductive busbar is arranged outside each of the four side walls of the cuboid-shaped liquid metal battery, and the perpendicular distance from the two side lines parallel to the conductive busbar on each side wall to the corresponding conductive busbar is the same.

[0010] Moreover, in Step 1, the perpendicular distance from the conductive busbar to the side wall of the liquid metal battery is within 0.15 meters.

[0011] Moreover, after energization in Step 2, the magnitude of the current passing through the conductive busbar is 0.02 to 1.2 times the magnitude of the current inside the liquid metal battery.

[0012] Moreover, when the conductive busbar is closely attached to the outer surface of the side wall of the liquid metal battery, the magnitude of the current passing through the conductive busbar is 0.044 times the magnitude of the current inside the liquid metal battery, and the critical current density of the liquid metal battery is increased by 25%.

[0013] Moreover, when multiple rows of liquid metal batteries are arranged in series in the vertical direction, the conductive busbars outside the liquid metal batteries belonging to the same row are connected in parallel, and the conductive busbars of the liquid metal batteries belonging to different rows are connected in series every other row in the vertical direction.

[0014] A liquid metal battery busbar system configured according to the above method, which consists of a conductive busbar device and a current regulating device. The conductive busbar device includes a number of conductive busbars evenly distributed outside the liquid metal battery. The conductive busbars are parallel to the side wall of the liquid metal battery and the perpendicular distance from each conductive busbar to the center of the liquid metal battery is the same; the current regulating device is connected to the conductive busbar, and the current regulating device can control and adjust the direction and magnitude of the current passing through the conductive busbar, so that the direction of the current passing through the conductive busbar is the same as the direction of the current inside the liquid metal battery.

[0015] Moreover, the conductive busbar is made of copper, aluminum or their alloy materials, and the cross-section of the conductive busbar is circular or polygonal.

[0016] Compared with the prior art, the beneficial effects of the present technical solution are as follows:

[0017] 1. The present invention provides a method and system for suppressing the magnetohydrodynamic instability of a liquid metal battery. A conductive busbar is arranged outside the liquid metal battery, and the direction of the current passing through the conductive busbar is the same as the direction of the current inside the liquid metal battery, so that the induced magnetic field generated by the busbar is opposite to the direction of the magnetic field of the battery itself, generating a cancellation effect inside the battery, effectively weakening the magnetic field intensity inside the battery, reducing the Lorentz force pointing to the axis, and improving the stability of the battery.

[0018] 2. The present invention can further adjust the intensity and distribution of the magnetic field inside the battery by optimizing the busbar configuration position, adjusting the distance between the busbar and the center of the liquid metal battery, and adjusting the magnitude and direction of the busbar adjustment current, etc., weakening the vorticity shear velocity at the electrode-electrolyte interface, suppressing the occurrence of MHDI, and improving the stability of the liquid metal battery.

[0019] 3. The present invention can flexibly and quickly adjust the voltage and current of the battery pack by setting a busbar layout of horizontal parallel connection and vertical series connection: (1) For the batteries on the same horizontal plane, a parallel connection method is adopted, which means that the positive electrodes of these batteries are all connected together to form a total positive electrode; at the same time, their negative electrodes are also all connected together to form a total negative electrode. The advantage of the parallel design is that it can provide a higher current output because multiple batteries can discharge simultaneously. In addition, if one of the batteries fails, the other batteries can still continue to work, enhancing the reliability of the system. (2) For the vertically distributed batteries, a series connection method is adopted every other row. Such a design can ensure the superposition of voltages, thereby increasing the total voltage of the entire battery pack. This configuration method not only ensures the overall performance of the battery pack but also improves the reliability of the system, providing a solution for the large-scale application of liquid metal batteries, ensuring the overall performance of the battery pack and improving the reliability of the system, and realizing the large-scale application of liquid metal batteries.

[0020] 4. The optimized busbar configuration in the present invention significantly improves the critical parameters of the liquid metal battery. When the magnitude of the current passing through the busbar is 0.02 - 1.2 times the magnitude of the current inside the liquid metal battery, the maximum value of the induced magnetic field generated by the busbar is 0.002 - 0.006 Tesla, increasing the critical parameters of the liquid metal battery by 12% - 50%, the critical current density reaching 8 - 20 A / cm², and the Hartmann number reaching 20 - 30, enabling the liquid metal battery to withstand a larger charge and discharge current without instability, greatly improving the power density and energy conversion rate of the battery. At the same time, the increase in the critical current also expands the working range of the battery, enabling it to adapt to more high-power demand application scenarios, providing important technical support for the practical application of large-scale energy storage systems. Brief Description of the Drawings

[0021] Figure 1 FIG. 1 is a schematic cross-sectional view of the liquid metal battery busbar device provided by the present invention and a schematic diagram of the circuit connection mode of the busbar;

[0022] Figure 2 FIG. 2 is a physical model of a liquid metal battery used in the numerical simulation of the comparative example;

[0023] Figure 3 (a) is a 3D morphology diagram of the electrolyte layer at the operating time t = 4s under the working conditions of the comparative example;

[0024] Figure 3 (b) is a 2D morphology diagram of the electrolyte layer on the YOZ coordinate plane at the operating time t = 4s under the working conditions of the comparative example;

[0025] Figure 3 (c) is a fluid streamline diagram on the YOZ coordinate plane at the operating time t = 4s under the working conditions of the comparative example;

[0026] Figure 4 (a) is a 3D morphology diagram of the electrolyte layer at the operating time t = 4s under the working conditions of Example 1;

[0027] Figure 4 (b) is a 2D morphology diagram of the electrolyte layer on the YOZ coordinate plane at the operating time t = 4s under the working conditions of Example 1;

[0028] Figure 4 (c) is a fluid streamline diagram on the YOZ coordinate plane at the operating time t = 4s under the working conditions of Example 1;

[0029] Figure 5 (a) is a 3D morphology diagram of the electrolyte layer at the operating time t = 8s under the working conditions of Example 1;

[0030] Figure 5 (b) is a fluid streamline diagram on the YOZ coordinate plane at the operating time t = 8s under the working conditions of Example 1;

[0031] Figure 6 (a) is a 3D morphology diagram of the electrolyte layer at the operating time t = 8s under the working conditions of Example 2;

[0032] Figure 6 (b) is a fluid streamline diagram on the YOZ coordinate plane at the operating time t = 8s under the working conditions of Example 2. Detailed Description of the Invention

[0033] The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments, and the content of the present invention is not limited to the following embodiments.

[0034] A method for suppressing the magnetohydrodynamic instability of a liquid metal battery, comprising the following steps:

[0035] Step 1. A plurality of conductive busbars are uniformly distributed outside the liquid metal battery. The conductive busbars are parallel to the side wall of the liquid metal battery (the side wall of the liquid metal battery is also parallel to the perpendicular line passing through the center of the liquid metal battery). The current direction in the conductive busbars is the same as the current direction inside the liquid metal battery, and the perpendicular distance from each conductive busbar to the center of the liquid metal battery is the same;

[0036] Step 2. The conductive busbars are energized, and the direction of the induced magnetic field formed by all the conductive busbars is opposite to the direction of the magnetic field generated by the liquid metal battery itself;

[0037] Step 3. The electrolyte flow of the liquid metal battery is hindered by the action of the induced magnetic field in Step 2, and the critical current density of the liquid metal battery is increased.

[0038] Based on the actual situation of a company's container energy storage system, this method configures a liquid metal battery busbar device as shown in Figure 1 (a). The liquid metal battery of the company's container energy storage system is a regular quadrangular prism. Figure 1 (a) is a cross-sectional schematic diagram of the liquid metal battery. One busbar is configured on each of the 4 side surfaces of the liquid metal battery, and the current direction flowing through each busbar is the same as the current direction of the single battery; the distance between the busbar and the center of the liquid metal battery is a, the current inside the liquid metal battery is I, and its own magnetic field is B. The currents passing through the 4 busbars are respectively I add , and the induced magnetic field formed by the 4 conductive busbars is B add . The current in the conductive busbar can change the magnitude and direction of the current through the current regulating device.

[0039] When there are multiple rows of liquid metal batteries connected in series in the vertical direction, the conductive busbars outside the liquid metal batteries belonging to the same row are connected in parallel, and the conductive busbars belonging to different rows of liquid metal batteries are connected in series every other row in the vertical direction. The circuit connection mode of the conductive busbars is as shown in Figure 1 (b).

[0040] This solution uses numerical simulation to verify whether the method and the configured busbar device are effective in suppressing various instabilities inside the liquid metal battery.

[0041] I. Comparative example (only including liquid metal battery):

[0042] As shown inFigure 2 As shown in Figure 2 , the physical model of the liquid metal battery used in this solution consists of Li||LiCl-KCl||Pb-Bi and automatically stratifies due to different densities. The size of the model is set to 100×100×450 mm 3 , and the specific structural parameters and physical property parameters are given in Table 1:

[0043] Table 1 shows the structural parameters and physical property parameters of the liquid metal battery at a temperature of 500 °C.

[0044]

[0045] During the numerical simulation process, Figure 3 (a) is a three-dimensional diagram of the electrolyte morphology inside the liquid metal battery when the charging current I = 2.264 kA and the running time t = 4 s. Figure 3 (b) is the corresponding two-dimensional diagram in the YOZ coordinate system. It can be seen from the figure that when the busbar system and method configured in this solution are not used, the electrolyte morphology inside the battery has deformed at t = 4 s, the electrolyte layer structure has been completely destroyed, and contact has occurred between the positive and negative electrodes, which means that the battery has been in an unstable state. This phenomenon is explained in Figure 3 (c). Figure 3 (c) is the streamline diagram of the liquid metal battery in the YOZ coordinate plane in this state. At this time, the distribution of the eddy current structure inside the battery has become completely disordered.

[0046] II. Example 1

[0047] Using the Figure 1 of the present invention and the aforementioned method to configure the busbar, observe the state change of the internal fluid of the liquid metal battery when the charging current I = 2.264 kA. At this time, the busbar current is the same as the monomer charging current, I = 2.264 kA, and the distance between the busbar and the battery center is a = 0.1 m.

[0048] Figure 4 (a) is a three-dimensional diagram of the electrolyte morphology inside the liquid metal battery when the running time t = 4 s in this case. Figure 4 (b) is the corresponding two-dimensional diagram in the YOZ coordinate plane. It can be seen from the figure that when the busbar system and method configured in this solution are used, the electrolyte morphology inside the battery hardly deforms. In Figure 4 (c), the maximum flow velocity in the streamline diagram is also reduced by 75% compared with the comparative example. This is because the direction of the induced magnetic field generated by the busbar is opposite to the direction of the magnetic field generated by the liquid metal battery itself, suppressing the electrolyte flow, and thus increasing its critical current density. Compared with the comparative example, the critical current density is increased by about 12%.

[0049] Figure 5 (a) andFigure 5 (b) shows the internal situation of the liquid metal battery when the running time t = 8 s in this case, which is used as the comparative example of Example 2.

[0050] III. Example 2

[0051] Using the Figure 1 of the present invention and the foregoing method to configure the busbar. The difference from Example 1 is that at this time, the busbar is closely attached to the outer wall surface of the liquid metal battery, the distance of the busbar from the center of the battery is a = 0.051 m, and the busbar current is I = 0.1 kA; still observe the state change of the internal fluid of the liquid metal battery under the charging current I = 2.264 kA. Compared with Example 1, the busbar current in this example is only 0.044 times (about 1 / 20) of the internal current of the battery, and at this time the busbar is closely attached to the outer wall surface of the battery, which not only greatly saves the energy cost, but also greatly improves the space utilization rate of the battery module group.

[0052] Figure 6 (a) is a three-dimensional diagram of the electrolyte inside the liquid metal battery when the running time t = 8 s under this configuration method. It can be seen that, compared with Figure 5 (a), the morphology of the electrolyte inside the battery is stable. As can also be seen from the Figure 6 (b) streamline diagram, although the streamline structures of each layer inside the battery have become chaotic and disordered, the flow of each layer of fluid still remains in each layer area and no mixing phenomenon occurs, so the battery will not short-circuit.

[0053] Example 2 makes the critical current density of the liquid metal battery increase by about 25% compared with the comparative example, and the value of the busbar current is only 1 / 20 of the charging current. It can be seen that when the conductive busbar is closer to the center of the battery, not only the critical current density of the liquid metal battery increases more significantly, but also it has the advantages of saving energy cost and improving the space utilization rate of the battery module group.

[0054] After further experiments, it is found that when the busbar is closely attached to the outer wall surface of the liquid metal battery and the busbar current is the same as the charging current I = 2.264 kA, the increase in the critical current density of the liquid metal battery can reach about 50%.

[0055] In summary, the beneficial effects of this technical solution are as follows:

[0056] 1. The present invention provides a method and system for suppressing the magnetohydrodynamic instability of a liquid metal battery. A conductive busbar is arranged outside the liquid metal battery, and the direction of the current passing through the conductive busbar is the same as the direction of the current inside the liquid metal battery, so that the induced magnetic field generated by the busbar is opposite to the direction of the magnetic field of the battery itself, generating a cancellation effect inside the battery, effectively weakening the magnetic field intensity inside the battery, reducing the Lorentz force pointing to the axis, and realizing the improvement of the battery stability.

[0057] 2. The present invention can further adjust the intensity and distribution of the magnetic field inside the battery by optimizing the busbar configuration position, adjusting the distance between the busbar and the center of the liquid metal battery, and adjusting the magnitude and direction of the current in the busbar, weakening the vorticity shear velocity at the electrode-electrolyte interface, suppressing the occurrence of MHDI, and improving the stability of the liquid metal battery.

[0058] 3. The present invention can flexibly and quickly adjust the voltage and current of the battery pack by setting a busbar layout of horizontal parallel connection and vertical series connection: (1) For the batteries on the same horizontal plane, a parallel connection method is adopted, which means that the positive electrodes of these batteries are all connected together to form a total positive electrode; at the same time, their negative electrodes are also all connected together to form a total negative electrode. The advantage of the parallel design is that it can provide a higher current output because multiple batteries can discharge simultaneously. In addition, if one of the batteries fails, the other batteries can still continue to work, enhancing the reliability of the system. (2) For the vertically distributed batteries, a series connection method is adopted every other row. Such a design can ensure the superposition of voltages, thereby increasing the total voltage of the entire battery pack. This configuration method not only ensures the overall performance of the battery pack but also improves the reliability of the system, providing a solution for the large-scale application of liquid metal batteries, ensuring the overall performance of the battery pack and improving the reliability of the system, and realizing the large-scale application of liquid metal batteries.

[0059] 4. The optimized busbar configuration in the present invention significantly improves the critical parameters of the liquid metal battery. When the magnitude of the current passing through the busbar is 0.02 - 1.2 times the magnitude of the current inside the liquid metal battery, the maximum value of the induced magnetic field generated by the busbar is 0.002 - 0.006 Tesla, increasing the critical parameters of the liquid metal battery by 12% - 50%, the critical current density reaching 8 - 20 A / cm², and the Hartmann number reaching 20 - 30, enabling the liquid metal battery to withstand a larger charge-discharge current without instability, greatly improving the power density and energy conversion rate of the battery. At the same time, the increase in the critical current also expands the working range of the battery, enabling it to adapt to more application scenarios with high power requirements, providing an important technical support for the practical application of large-scale energy storage systems.

Claims

1. A method for suppressing the magnetohydrodynamic instability of a liquid metal battery, characterized in that, It includes the following steps: Step 1. A number of conductive busbars are evenly distributed outside the liquid metal battery. The conductive busbars are parallel to the side wall of the liquid metal battery, and the current direction passing through the conductive busbars is the same as the current direction inside the liquid metal battery. The perpendicular distance from each conductive busbar to the center of the liquid metal battery is the same; Step 2. The conductive busbars are energized, and the direction of the induced magnetic field formed by all the conductive busbars is opposite to the direction of the magnetic field generated by the liquid metal battery itself; Step 3. The action of the induced magnetic field in Step 2 hinders the flow of the electrolyte of the liquid metal battery, and improves the critical current density of the liquid metal battery.

2. A method for suppressing the magnetohydrodynamic instability of a liquid metal battery according to claim 1, characterized in that: In Step 1, the liquid metal battery is in a cuboid shape, and one conductive busbar is arranged outside each of the four side walls of the cuboid-shaped liquid metal battery, and the perpendicular distance from the two side lines parallel to the conductive busbar on each side wall to the corresponding conductive busbar is the same.

3. A method for suppressing the magnetohydrodynamic instability of a liquid metal battery according to claim 1, characterized in that: In Step 1, the perpendicular distance from the conductive busbar to the side wall of the liquid metal battery is within 0.15 meters.

4. A method for suppressing the magnetohydrodynamic instability of a liquid metal battery according to claim 1, characterized in that: After energization in Step 2, the magnitude of the current passing through the conductive busbar is 0.02 - 1.2 times the magnitude of the current inside the liquid metal battery.

5. A method for suppressing the magnetohydrodynamic instability of a liquid metal battery according to claim 1, characterized in that: When the conductive busbar is closely attached to the outer surface of the side wall of the liquid metal battery, the magnitude of the current passing through the conductive busbar is 0.044 times the magnitude of the current inside the liquid metal battery, and the critical current density of the liquid metal battery is increased by 25%.

6. A method for suppressing the magnetohydrodynamic instability of a liquid metal battery according to claim 1, characterized in that: When multiple rows of liquid metal batteries are arranged in series in the vertical direction, the conductive busbars outside the liquid metal batteries belonging to the same row are connected in parallel, and the conductive busbars belonging to different rows of liquid metal batteries are connected in series every other row in the vertical direction.

7. A liquid metal battery busbar system configured according to the method described in claim 1, characterized in that: It is composed of a conductive busbar device and a current regulating device. The conductive busbar device includes a number of conductive busbars evenly distributed outside the liquid metal battery. The conductive busbars are parallel to the side wall of the liquid metal battery and the perpendicular distance from each conductive busbar to the center of the liquid metal battery is the same; the current regulating device is connected to the conductive busbar, and the current regulating device can control and adjust the current direction and magnitude passing through the conductive busbar so that the current direction passing through the conductive busbar is the same as the current direction inside the liquid metal battery.

8. The liquid metal battery busbar system according to claim 7, wherein: The conductive busbar is made of copper, aluminum or their alloy materials, and the cross-section of the conductive busbar is circular or polygonal.

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