Salt cavern flow battery system integrating ground-underground three-circulation path switching

Abstract

The invention belongs to the field of large-scale electrochemical energy storage, and particularly discloses a salt cavern flow battery system integrated with ground-underground three-circulation path switching, and the salt cavern flow battery system is formed by flexible switching of all-ground, all-underground and ground / underground circulation paths and collaborative design with a high-activity and high-adaptability electrolyte system. Multiple objectives of flexible adaptation of a circulation mode, great improvement of energy density, reduction of energy consumption and optimization of system stability are achieved. Overall shutdown is not needed during salt cavern overhaul, electrolyte activation or ground module maintenance, the continuous operation rate of the system is larger than or equal to 98% and is far higher than that of an existing single circulation path technology, and the strict requirement for continuous power supply of an energy storage system by a power grid can be met. The high-activity electrolyte system researched and developed in a targeted mode adapts to wide-range fluctuation of 0.1-12 MPa pressure and 10-70 DEG C temperature, the capacity retention ratio after 500 times of charge-discharge cycles is larger than or equal to 94.5%, the problems of active substance precipitation and decomposition and pipeline corrosion under the cycle working condition are effectively solved, and the service life of the electrolyte is prolonged by 10% or above.

Description

Technical Field

[0001] This invention relates to the field of large-scale electrochemical energy storage technology, specifically to a salt cavern flow battery system that integrates ground-to-underground three-cycle switching. Background Technology

[0002] With the deepening implementation of the "dual carbon" goals, the large-scale grid connection of renewable energy sources such as wind and solar power has created an urgent demand for GWh-level long-term energy storage technology. In large-scale energy storage technology, combining salt caverns with flow batteries has significant strategic importance and broad development prospects. Salt caverns, as natural or artificial geological structures, possess advantages such as large storage capacity, excellent sealing, and high safety. Furthermore, they have abundant idle underground space resources and can be directly converted into ultra-large-capacity storage tanks for flow battery electrolytes, eliminating the need for additional surface land resources and significantly reducing the construction cost and environmental impact of energy storage systems. Flow batteries, on the other hand, are highly efficient energy storage devices that store and release electrical energy through the reversible oxidation-reduction reaction of active substances in the electrolyte. They play a crucial role in addressing the volatility of renewable energy generation and improving grid stability and reliability. Salt cavern flow batteries, relying on this synergistic advantage and combining the natural storage conditions of underground salt caverns with the high-efficiency energy storage characteristics of flow batteries, have become the preferred technological route for solving the problem of renewable energy consumption. Among them, the rational design of the circulation path and the comprehensive performance of the electrolyte are the two core factors that determine the system's energy storage capacity, energy efficiency, and long-term stability, directly affecting the commercialization process of the technology.

[0003] To promote the development of salt cavern flow battery technology, existing technologies mainly explore two directions: energy storage system structure optimization and electrolyte performance improvement. However, the following technical problems still exist: 1) Single circulation path, insufficient system flexibility and continuity: Existing technologies all adopt a fixed single circulation path, which cannot flexibly switch between independent circulation on the ground and collaborative circulation between the ground and underground. When the salt cavern needs maintenance and repair, or when the electrolyte needs activation treatment and performance testing, the entire energy storage system must be shut down, resulting in low system continuous operation rate, which seriously affects the stability of power grid supply and cannot meet the core requirement of "uninterrupted service" of energy storage system. 2) The electrolyte has multiple defects and poor adaptability to actual working conditions: On the one hand, the concentration of active substances in existing electrolytes is too low, with conventional systems ≤0.5M and even optimized systems after molecular modification only ≤1.2M, resulting in an electrolyte energy density of only 20-30Wh / L, which cannot fully utilize the energy storage potential of the large volume of salt caverns and restricts the improvement of system energy storage capacity; on the other hand, the electrolyte is not optimized for the complex working conditions of salt cavern-ground circulation. Under the pressure (0.1-12MPa) and temperature (10-70℃) fluctuations encountered during circulation, problems such as active substance precipitation and oxidation decomposition are likely to occur, and the capacity retention rate is ≤85% after 100 cycles; at the same time, conventional electrolytes cannot adapt to the use requirements of long-distance underground circulation pipelines, which can easily lead to pipeline leakage risks and affect system safety and service life; 3) The system has high energy consumption and low energy utilization efficiency: The single circulation path design requires the electrolyte to flow through a long underground pipeline (≥10m) throughout the entire process. The circulation pump needs to continuously output high power to overcome the pipeline resistance, resulting in a high proportion of energy consumption of the circulation pump (20-30kW). In addition, the existing technology does not make full use of the gravitational potential energy generated by the height difference between the salt cavern and the ground (about 11m) to assist the electrolyte reflux, resulting in a large amount of energy waste and further reducing the overall energy utilization efficiency of the system. 4) Lack of synergy between structure and electrolyte limits overall system performance: Existing technologies have failed to achieve deep synergistic design between the "ground-underground circulation path structure" and the "highly active electrolyte system". Either the fixed path leads to inconvenient electrolyte maintenance and rapid performance degradation, or the electrolyte is not adapted to the pressure and temperature changes of the circulation path and the long-distance circulation requirements, so that its advantages of high solubility and high stability cannot be fully utilized. Ultimately, this results in low overall system efficiency and high operating costs, which restricts the commercialization of salt cavern flow battery technology.

[0004] In summary, although existing salt cavern flow battery technologies have made some progress in their respective fields, there are still many defects and shortcomings that need to be addressed, making it difficult to meet the practical application requirements of large-scale, long-term energy storage. Therefore, there is an urgent need for a new flow battery energy storage system that can solve the above-mentioned defects. Summary of the Invention

[0005] To address the shortcomings of existing technologies, such as single circulation path, low electrolyte solubility / poor adaptability to operating conditions, high system energy consumption, and lack of synergy, this invention provides a salt cavern flow battery system that integrates ground-to-underground three-circulation path switching. Through the deep synergistic design of the "three-circulation path switching structure" and the "highly active and highly adaptable electrolyte system," it achieves multiple objectives, including flexible adaptation of circulation modes, significant improvement in energy density, reduction in energy consumption, and optimization of system stability, thus solving the problems mentioned in the background technology.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a salt cavern flow battery system integrating ground-underground three-circulation path switching, the system comprising: an electrolyte storage module, an electrolyte, a flow battery stack, circulation pipelines, and a circulation pump; The electrolyte storage module includes a surface storage tank and / or an underground salt cavern with a physical solution cavity formed after salt mining, wherein the solution cavity stores electrolyte; the surface storage tank is divided into an anode storage tank and a cathode storage tank, which are spaced apart and arranged opposite each other; the underground salt cavern is divided into an underground anode salt cavern and an underground cathode salt cavern, the underground anode salt cavern including an anode salt cavern cavity and an anode solvent layer; the underground cathode salt cavern includes a cathode salt cavern cavity and a cathode solvent layer; the underground anode salt cavern and the underground cathode salt cavern are spaced apart and arranged opposite each other; The flow battery stack is connected to a ground-based liquid storage tank and / or an underground salt cavern, and the flow battery stack includes: bipolar plates, electrodes and a proton exchange membrane; The circulation pipeline forms a three-circulation path of electrolyte circulation between the ground storage tank, the underground salt cavern and the flow battery stack through the opening and closing of the valve group; The circulation pump is located in the circulation pipeline and provides a flow supply for the electrolyte circulation.

[0007] Preferably, the surface-to-underground three-circulation path includes three modes: a full surface circulation path, a full underground circulation path, and a surface-to-underground circulation path. Path switching is achieved through the linkage of valve groups in the surface-to-underground circulation switching module to adapt to different operating conditions.

[0008] Preferably, the valve assembly includes a first anode valve A1, a second anode valve A2, a third anode valve A3, a first cathode valve B1, a second cathode valve B2, and a third cathode valve B3; all valves are electric ball valves with a pressure resistance ≥10-15MPa, a response time ≤0.5-5s, corrosion resistance conforming to GB / T 21447-2018 standard, and a sealing performance level reaching ANSI Class VI; the matching circulating pump assembly is a variable frequency centrifugal pump with a rated flow rate of 60-120m³ / h. 3 / h, rated power 20-30kW, head 50-80m, with adaptive flow rate adjustment capability.

[0009] The outlet of the anode storage tank is connected to the anode inlet of the fuel cell stack via the first anode valve A1 and the third anode valve A3. The anode outlet of the fuel cell stack is connected to the inlet of the underground anode salt cave via the second anode valve A2 and the anode salt cave inlet. The outlet of the underground anode salt cave is connected to the third anode valve A3 via the anode salt cave outlet, forming an anode circulation branch. The cathode storage tank outlet is connected to the fuel cell cathode inlet via the first cathode valve B1 and the third cathode valve B3. The fuel cell cathode outlet is connected to the underground cathode salt cavern inlet via the second cathode valve B2 and the cathode salt cavern inlet. The underground cathode salt cavern outlet is connected to the third cathode valve B3 via the cathode salt cavern outlet, forming a cathode circulation branch.

[0010] The highly active electrolyte is filled in ground storage tanks, underground salt caverns and circulation pipelines. The circulation is powered by a circulation pump group, and the valve group of the circulation switching module enables precise switching between the three circulation paths.

[0011] Preferably, the all-ground circulation path is as follows: the second anode valve A2, the third anode valve A3, and the second cathode valves B2 and B3 are closed, while the first anode valve A1 and the first cathode valve B1 are opened; after the circulation pump starts, the electrolyte forms closed loops for the anode and cathode circulation branches in the paths of "anode storage tank → first anode valve A1 → fuel cell anode inlet → fuel cell anode outlet → anode storage tank" and "cathode storage tank → first cathode valve B1 → fuel cell cathode inlet → fuel cell cathode outlet → cathode storage tank"; the circulation flow rate under this path is controlled at 60-80 m³ / h. 3 / h, total pipeline length ≤50m, resistance loss ≤0.3-0.5MPa, to achieve rapid activation of electrolyte and low-load operation of system; Preferably, the underground circulation path is as follows: the first anode valve A1 and the first cathode valve B1 are closed, and the second anode valve A2, the third anode valve A3, the second cathode valve B2, and the third cathode valve B3 are opened; after the circulation pump starts, the electrolyte forms closed loops of anode and cathode circulation branches in the paths of "underground anode salt cavern → third anode valve A3 → fuel cell stack anode inlet → fuel cell stack anode outlet → second anode valve A2 → underground anode salt cavern" and "underground cathode salt cavern → third cathode valve B3 → fuel cell stack cathode inlet → fuel cell stack cathode outlet → second cathode valve B2 → underground cathode salt cavern"; the circulation flow rate under this path is controlled at 100-120 m³ / h. 3 / h, total pipeline length ≤1200-1500m, resistance loss ≤2.0-2.5Mpa; utilizing the large volume advantage of underground salt caverns to achieve large-scale energy storage and release.

[0012] Preferably, the surface-to-underground circulation path specifically involves: closing the first anode valve A1 and the first cathode valve B1, and opening the second anode valve A2, the third anode valve A3, and the second cathode valves B2 and B3, or opening the first anode valve A1, the second anode valve A2, the third anode valve A3, and the first cathode valves B1, the second cathode valves B2, and the third cathode valves B3; after the circulation pump starts, the electrolyte forms a closed loop of anode circulation branch and cathode circulation branch in the path of "anode storage tank / underground anode salt cavern → first anode valve A1 / third anode valve A3 → fuel cell anode inlet → fuel cell anode outlet → anode storage tank / [second anode valve A2 → underground anode salt cavern]" and "cathode storage tank / underground cathode salt cavern → first cathode valve B1 / third cathode valve B3 → fuel cell cathode inlet → fuel cell cathode outlet → cathode storage tank / [second cathode valve B2 → underground cathode salt cavern]"; the circulation flow rate under this path is controlled at 80-110 m³ / h. 3 The electrolyte distribution ratio between the surface storage tank and the underground salt cavern is dynamically adjusted according to the energy storage capacity requirements, with a ratio range of 1-3:1-3. The height difference between the surface and underground (100-1200m) is used to assist electrolyte reflux and reduce the energy consumption of the circulation pump.

[0013] Preferably, the electrolyte is a highly active electrolyte system. This highly active electrolyte system uses deionized water as a solvent and is designed to meet the pressure (0.1-12 MPa), temperature (10-70℃) fluctuations and long-distance circulation requirements of the surface-to-underground circulation path. It features high solubility, high stability, and high compatibility, and is deeply adapted to the surface-to-underground circulation structure. Its formulation, preparation process, and core performance are as follows: Formulation: The electrolyte contains positive electrode active material, negative electrode active material, supporting electrolyte, synergistic co-solvent, environmentally adaptable stabilizer, anti-precipitation agent and deionized water.

[0014] Preparation: The preparation of the electrolyte includes the following: S1. First, heat the supporting electrolyte to 40-50℃, add the co-solvent and stir evenly at a stirring speed of 300 rpm. S2. Slowly add the positive electrode active material and stir continuously for 12 hours; then add the negative electrode active material and use 300-500W ultrasonic dispersion for 2-4 hours to break up the active material agglomerates and ensure uniform dissolution; after cooling to 25℃, add the environmental compatibility stabilizer and anti-precipitation agent and stir for 6 hours. S3. The electrolyte is aged in a nitrogen atmosphere (nitrogen purity ≥ 99.99%) for 24-48 hours to remove dissolved oxygen and prevent oxidation of active substances. Then, the electrolyte is placed in a 15MPa autoclave and treated at 60℃ for 8 hours. Qualified electrolytes without precipitation or decomposition are screened. The qualified electrolytes are placed in a clean container, sealed and protected from light, and stored at a temperature controlled between 5-35℃ to obtain a highly active electrolyte.

[0015] Preferably, the positive electrode active material is one of the following: DIS-TEMPO (a disulfonated TEMPO derivative), Tri-SO3Na-Xanthenone (a trisulfonated xanthenone derivative), SO3Na-COOH-Phenazine (a sulfonate-carboxyl dual-modified phenazine), or HP-SO3Na-Anthraquinone (a hydroxypropyl-sulfonate dual-modified anthraquinone), with a mass percentage of 15%-22% in the electrolyte, corresponding to a concentration of 1.5-2.2M; the sulfonation group modification improves water solubility and ion conductivity.

[0016] The negative electrode active material is one of hydroxyethyl-sulfonate double-modified viologen (HEV-SO3Na) or dihydroxyethyl-sulfonate tri-modified bipyridine (Di-HE-SO3Na-Bipyridine), with a mass percentage of 18%-25% in the electrolyte, corresponding to a concentration of 1.8-2.5M. The introduction of hydroxyethyl groups enhances the steric hindrance effect and avoids dimer formation, while the sulfonate groups enhance water solubility, resulting in a 120% increase in solubility compared to conventional alkyl-modified viologen.

[0017] The supporting electrolyte is a saturated NaCl solution, with a mass percentage of 55%-60% in the electrolyte, corresponding to a concentration of 5.5-6.0 M; it provides a high ionic strength environment, promotes the dissolution of active substances and charge transfer, and inhibits the dissolution of salt caverns.

[0018] Preferably, the synergistic co-solvent is one or more of ethylene glycol (EG) and N-methylpyrrolidone (NMP), with a mass percentage of 8%-12% in the electrolyte; the volume ratio of the two is 2:1; EG improves the low-temperature stability of the electrolyte (does not freeze at -10℃), and NMP enhances the solubility of active substances. Under the synergistic effect, the solubility of active substances is increased by 30% compared with the single solvent system.

[0019] The environmental adaptability stabilizer is one or more of vitamin C phosphate magnesium VC-PMg and benzotriazole BTA, wherein the concentration of VC-PMg is 0.03-0.06M and the concentration of BTA is 0.005-0.01M; VC-PMg inhibits the oxidative decomposition of active substances, and BTA forms a passivation film with 316L stainless steel, thereby reducing the corrosion rate.

[0020] The anti-deposition agent is polyethylene glycol PEG-2000, with a mass percentage of 0.5%-1.0% in the electrolyte; it prevents the deposition of active substances under high voltage through steric hindrance.

[0021] The beneficial effects of this invention are: 1) Significantly improved system continuous operation rate: Through flexible switching between three paths—all-ground, all-underground, and ground / underground circulation—no overall shutdown is required during salt cavern maintenance, electrolyte activation, or ground module maintenance. The system continuous operation rate is ≥98%, far exceeding the existing single circulation path technology, which can meet the stringent requirements of the power grid for continuous power supply to the energy storage system. 2) Significantly reduced operating energy consumption: On the one hand, the 100-1200m height difference between the ground and the underground salt cavern assists in electrolyte reflux, reducing the power demand of the circulation pump; on the other hand, it adapts to the resistance differences of different circulation paths, realizing dynamic flow adjustment. The average energy consumption of the circulation pump is reduced by more than 10% compared with traditional fixed power pumps. Combined with the low viscosity characteristics of highly active electrolyte, the friction resistance along the pipeline is further reduced, and the long-term operating economy is significantly improved. 3) Electrolyte stability and compatibility optimization: The specially developed high-activity electrolyte system can adapt to a wide range of pressure fluctuations of 0.1-12MPa and temperature fluctuations of 10-70℃. After adding environmentally compatible stabilizers and anti-deposition agents, the capacity retention rate is ≥94.5% after 500 charge-discharge cycles, effectively avoiding the problems of active material precipitation, decomposition and pipeline corrosion under surface-to-underground circulation conditions, and extending the service life of the electrolyte by more than 10%. The active material concentration of the electrolyte in this patent is 1.5-2.2M, and the energy density can reach 43 Wh / L. 4) Enhanced energy storage capacity and operational flexibility: Leveraging the large volume of underground salt caverns, a single salt cavern can achieve an energy storage capacity of up to 500MWh, meeting the long-term energy storage requirements at the GWh level; three circulation paths adapt to diverse operating conditions such as electrolyte activation, salt cavern maintenance, and large-scale energy storage / release; the electrolyte distribution ratio between the ground and underground storage modules can be adjusted within the range of 1:3 to 3:1, taking into account both long-term energy storage and short-term peak shaving capabilities. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the flow battery system structure in the ground-to-underground circulation path of the embodiment; Figure 2 This is a schematic diagram of the flow battery system structure with a fully underground circulation path in the embodiment; Figure 3 This is a schematic diagram of the flow battery system structure with an all-terrain circulation path in the embodiment; Figure 4 This is a schematic diagram showing the concentration and viscosity data of the positive electrode electrolyte in Examples 1-3; Figure 5This is a schematic diagram showing the concentration and viscosity data of the negative electrode electrolyte in Examples 1-3; In the diagram, 11-flow battery stack; 110-bipolar plate; 111-electrode; 112-proton exchange membrane; 120-anode reservoir; 121-cathode reservoir; 210-anode salt cavern; 220-anode solvent layer; 230-anode salt cavern inlet; 240-anode salt cavern outlet; 211-cathode salt cavern; 221-cathode solvent layer; 231-cathode salt cavern inlet; 241-cathode salt cavern outlet; A1-first anode valve; A2-second anode valve; A3-third anode valve; B1-first cathode valve; B2-second cathode valve; B3-third cathode valve. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. It should also be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0025] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0026] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] This invention provides a technical solution: a salt cavern flow battery system integrating ground-underground three-circulation path switching, the system comprising: an electrolyte storage module, an electrolyte, a flow battery stack 11, circulation pipelines, and a circulation pump.

[0028] The electrolyte storage module includes a surface storage tank and / or an underground salt cavern with a physical solution cavity formed after salt mining, wherein the solution cavity stores electrolyte. The surface storage tank is divided into an anode storage tank 120 and a cathode storage tank 121, which are spaced apart and arranged opposite each other. The underground salt cavern is divided into an underground anode salt cavern and an underground cathode salt cavern. The underground anode salt cavern includes an anode salt cavern cavity 210 and an anode solvent layer 220; the underground cathode salt cavern includes a cathode salt cavern cavity 211 and a cathode solvent layer 221; the underground anode salt cavern and the underground cathode salt cavern are spaced apart and arranged opposite each other. Considering the multi-layered and sedimentary characteristics of the salt cavern, the cavity modification should focus on eliminating the risk of uneven settlement, and layered grouting reinforcement technology should be used to enhance the structural stability of the salt cavern. The sealing process requires the selection of a high-polymer sealing material that is compatible with salt rock. A multi-level sealing device is set at the entrance of the salt cave, which, combined with the natural barrier of the rock strata, forms a three-dimensional protection system. The salt cave, cavity, and solvent layer in this patent are all existing technologies and are not specifically limited in this patent.

[0029] The flow battery stack 11 is connected to a ground-based liquid storage tank and / or an underground salt cavern. The flow battery stack 11 includes a bipolar plate 110, an electrode 111, and a proton exchange membrane 112.

[0030] The circulation pipeline forms a three-circulation path of electrolyte circulation between the ground storage tank, the underground salt cavern, and the flow battery stack through the opening and closing of the valve group.

[0031] The circulation pump is located in the circulation pipeline and provides a flow supply for the electrolyte circulation.

[0032] Furthermore, the surface-to-underground three-circulation path includes three modes: a fully surface circulation path, a fully underground circulation path, and a surface-to-underground circulation path. Path switching is achieved through valve group linkage of the surface-to-underground circulation switching module to adapt to different operating conditions.

[0033] The valve assembly includes a first anode valve A1, a second anode valve A2, a third anode valve A3, a first cathode valve B1, a second cathode valve B2, and a third cathode valve B3; all valves are electric ball valves, with a pressure resistance ≥10-15MPa, a response time ≤0.5-5s, corrosion resistance conforming to GB / T 21447-2018 standard, and a sealing performance level reaching ANSI Class VI; the matching circulating pump set is a variable frequency centrifugal pump with a rated flow rate of 60-120m³ / h. 3 / h, rated power 20-30kW, head 50-80m, with adaptive flow rate adjustment capability.

[0034] The outlet of the anode storage tank is connected to the anode inlet of the fuel cell stack via the first anode valve A1 and the third anode valve A3. The anode outlet of the fuel cell stack is connected to the inlet of the underground anode salt cave via the second anode valve A2 and the anode salt cave inlet 230. The outlet of the underground anode salt cave is connected to the third anode valve A3 via the anode salt cave outlet 240, forming an anode circulation branch. The cathode storage tank outlet is connected to the cathode inlet of the fuel cell stack via the first cathode valve B1 and the third cathode valve B3. The cathode outlet of the fuel cell stack is connected to the inlet of the underground cathode salt cave via the second cathode valve B2 and the cathode salt cave inlet 231. The outlet of the underground cathode salt cave is connected to the third cathode valve B3 via the cathode salt cave outlet 241, forming a cathode circulation branch.

[0035] The highly active electrolyte is filled in ground storage tanks, underground salt caverns and circulation pipelines. The circulation is powered by a circulation pump group, and the valve group of the circulation switching module enables precise switching between the three circulation paths.

[0036] Preferred, such as Figure 3 As shown, the specific all-ground circulation path is as follows: close the second anode valve A2, the third anode valve A3, and the second cathode valves B2 and B3, and open the first anode valve A1 and the first cathode valve B1; after the circulation pump starts, the electrolyte forms a closed loop of anode circulation branch and cathode circulation branch in the path of "anode storage tank 120 → first anode valve A1 → fuel cell anode inlet → fuel cell anode outlet → anode storage tank 120" and "cathode storage tank 121 → first cathode valve B1 → fuel cell cathode inlet → fuel cell cathode outlet → cathode storage tank 121"; the circulation flow rate under this path is controlled at 60-80m³. 3 With a capacity of / h, a total pipeline length of ≤50m, and a resistance loss of ≤0.3-0.5MPa, the system achieves rapid activation of the electrolyte and low-load operation. Preferred, such as Figure 2As shown, the specific underground circulation path is as follows: The first anode valve A1 and the first cathode valve B1 are closed; the second anode valve A2, the third anode valve A3, the second cathode valve B2, and the third cathode valve B3 are opened. After the circulation pump starts, the electrolyte forms closed loops for the anode and cathode circulation branches in the paths of "underground anode salt cavern → third anode valve A3 → fuel cell stack anode inlet → fuel cell stack anode outlet → second anode valve A2 → underground anode salt cavern" and "underground cathode salt cavern → third cathode valve B3 → fuel cell stack cathode inlet → fuel cell stack cathode outlet → second cathode valve B2 → underground cathode salt cavern". The circulation flow rate under this path is controlled at 100-120 m³ / h. 3 / h, total pipeline length ≤1200-1500m, resistance loss ≤2.0-2.5Mpa; utilizing the large volume advantage of underground salt caverns to achieve large-scale energy storage and release.

[0037] Preferred, such as Figure 1 As shown, the specific surface-to-underground circulation path is as follows: First anode valve A1 and first cathode valve B1 are closed; second anode valve A2, third anode valve A3, and second cathode valves B2 and third cathode valves B3 are opened, or first anode valve A1, second anode valve A2, third anode valve A3, and first cathode valves B1, second cathode valves B2, and third cathode valves B3 are opened. After the circulation pump starts, the electrolyte forms a closed loop of anode and cathode circulation branches in the following paths: "Anode storage tank 120 / underground anode salt cavern → first anode valve A1 / third anode valve A3 → fuel cell stack anode inlet → fuel cell stack anode outlet → anode storage tank 120 / [second anode valve A2 → underground anode salt cavern]" and "Cathode storage tank 121 / underground cathode salt cavern → first cathode valve B1 / third cathode valve B3 → fuel cell stack cathode inlet → fuel cell stack cathode outlet → cathode storage tank 121 / [second cathode valve B2 → underground cathode salt cavern]". The circulation flow rate under this path is controlled at 80-110 m³ / h. 3 The electrolyte distribution ratio between the surface storage tank and the underground salt cavern is dynamically adjusted according to the energy storage capacity requirements, with a ratio range of 1-3:1-3. The height difference between the surface and underground (100-1200m) is used to assist electrolyte reflux and reduce the energy consumption of the circulation pump.

[0038] Example 1: Surface-subsurface circulation system based on disulfonated TEMPO-hydroxyethylsulfonate viologen electrolyte In this embodiment, the electrolyte uses deionized water as the solvent and is designed for pressure fluctuations of 0.1-12 MPa and temperature fluctuations of 10-70°C in the surface-to-underground circulation path. During electrolyte preparation, the positive electrode active material is a disulfonated TEMPO derivative (DIS-TEMPO), with a mass percentage of 18% and a corresponding concentration of 1.8 M; the negative electrode active material is hydroxyethyl-sulfonate double-modified viologen (HEV-SO3Na), with a mass percentage of 22% and a corresponding concentration of 2.2 M; the supporting electrolyte is a saturated NaCl solution, with a mass percentage of 55% and a corresponding concentration of 5.5 M; the co-solvent is a mixture of ethylene glycol (EG) and N-methylpyrrolidone (NMP) (volume ratio 2:1), with a mass percentage of 4%; and the environmental compatibility stabilizer is 0.04 M magnesium vitamin C phosphate (VC-PMg) + 0. 008M benzotriazole (BTA); the anti-precipitation agent is polyethylene glycol (PEG-2000), 1% by mass. The electrolyte preparation steps are as follows: Take the prescribed amount of saturated NaCl solution, heat to 45℃, add the synergistic co-solvent, stir at 300rpm until uniformly mixed, slowly add DIS-TEMPO, continue stirring for 12h until completely dissolved, then add HEV-SO3Na, use 400W ultrasonic dispersion for 3h to break the active material aggregates, then cool to 25℃, add VC-PMg, BTA and PEG-2000 in sequence, stir for 6h, mature in a nitrogen atmosphere with a purity ≥99.99% for 36h to remove dissolved oxygen, finally place in a 15MPa autoclave and treat at 60℃ for 8h, filter through a 0.22μm microporous membrane to obtain a qualified electrolyte.

[0039] Utilizing a surface-to-underground circulation path: equipped with a variable frequency circulation pump with a rated flow rate of 60-120 m³ / h. 3 / h; Flow control 80-110m 3 / h, with a surface and underground electrolyte distribution ratio of 1:2, suitable for conventional energy storage / release.

[0040] Operational Performance Verification: After 100 hours of system operation, the core indicators are as follows: continuous operation rate of the system is 98.2%; average energy consumption of the circulating pump is reduced by 10% compared to the traditional method; electrolyte capacity retention rate is 95.8% after 500 charge-discharge cycles. The concentration and viscosity data of the positive and negative electrolytes are as follows: Figure 4 and Figure 5 As shown in the figure, the concentration of the positive electrode active material is 1.8 mol / L and the viscosity is 8.6 mPa·s; the concentration of the negative electrode active material is 2.2 mol / L and the viscosity is 8.6 mPa·s; the system energy density is 39.3 Wh / L.

[0041] Example 2: Surface-subsurface circulation system based on high-concentration disulfonated TEMPO-hydroxyethylsulfonate viologen electrolyte In this embodiment, the electrolyte uses deionized water as the solvent and is designed for pressure fluctuations of 0.1-12 MPa and temperature fluctuations of 10-60℃ in the surface-to-underground circulation path. During electrolyte preparation, the positive electrode active material is a disulfonated TEMPO derivative (DIS-TEMPO), with a mass percentage of 22% and a concentration of 2.2 M; the negative electrode active material is hydroxyethyl-sulfonate double-modified viologen (HEV-SO3Na), with a mass percentage of 25% and a concentration of 2.5 M; the supporting electrolyte is a saturated NaCl solution, with a mass percentage of 50% and a concentration of 5.8 M; the co-solvent is a mixture of ethylene glycol (EG) and N-methylpyrrolidone (NMP) (volume ratio 2:1), with a mass percentage of 2%; and the environmental compatibility stabilizer is 0.06 M magnesium vitamin C phosphate (VC-PMg) + 0... 0.01M benzotriazole (BTA); the anti-precipitation agent is polyethylene glycol (PEG-2000), 1% by mass. The electrolyte preparation steps are as follows: Take the prescribed amount of saturated NaCl solution, heat to 45℃, add the synergistic co-solvent, stir at 300rpm until uniformly mixed, slowly add DIS-TEMPO, continue stirring for 12h until completely dissolved, then add HEV-SO3Na, use 400W ultrasonic dispersion for 3h to break the active material aggregates, then cool to 25℃, add VC-PMg, BTA and PEG-2000 in sequence, stir for 6h, mature in a nitrogen atmosphere with a purity ≥99.99% for 36h to remove dissolved oxygen, finally place in a 15MPa autoclave and treat at 60℃ for 8h, filter through a 0.22μm microporous membrane to obtain a qualified electrolyte.

[0042] Utilizing a surface-to-underground circulation path: equipped with a variable frequency circulation pump with a rated flow rate of 60-120 m³ / h. 3 / h; Flow control 80-110m 3 / h, with a surface and underground electrolyte distribution ratio of 1:2, suitable for conventional energy storage / release.

[0043] Operational performance verification: After 100 hours of system operation, the core indicators are as follows: continuous operation rate of the system is 98.0%; the average energy consumption of the circulating pump is reduced by 11% compared with the traditional method; the electrolyte capacity retention rate is 94.5% after 500 charge-discharge cycles. The concentration of the positive electrode active material is 2.2 mol / L, and the viscosity is 12.2 mPa·s; the concentration of the negative electrode active material is 2.5 mol / L, and the viscosity is 12.12 mPa·s; the system energy density is 43 Wh / L.

[0044] Example 3: Surface-subsurface circulation system based on low-concentration disulfonated TEMPO-hydroxyethyl sulfonate viologen electrolyte In this embodiment, the electrolyte uses deionized water as the solvent and is designed for pressure fluctuations of 0.1-12 MPa and temperature fluctuations of 10-60℃ in the surface-to-underground circulation path. During the electrolyte preparation process, the positive electrode active material is a disulfonated TEMPO derivative (DIS-TEMPO), with a mass percentage of 15% and a corresponding concentration of 1.5M; the negative electrode active material is hydroxyethyl-sulfonate double-modified viologen (HEV-SO3Na), with a mass percentage of 18% and a corresponding concentration of 1.8M; the supporting electrolyte is a saturated NaCl solution, with a mass percentage of 62% and a corresponding concentration of 6.0M; the co-solvent is a mixture of ethylene glycol (EG) and N-methylpyrrolidone (NMP) (volume ratio 2:1), with a mass percentage of 4%; and the environmental compatibility stabilizer is 0.03M magnesium vitamin C phosphate (VC-PMg) + 0. 005M benzotriazole (BTA); the anti-precipitation agent is polyethylene glycol (PEG-2000), 1% by mass. The electrolyte preparation steps are as follows: Take the prescribed amount of saturated NaCl solution, heat to 45℃, add the synergistic co-solvent, stir at 300rpm until uniformly mixed, slowly add DIS-TEMPO, continue stirring for 12h until completely dissolved, then add HEV-SO3Na, use 400W ultrasonic dispersion for 3h to break the active material agglomerates, then cool to 25℃, add VC-PMg, BTA and PEG-2000 in sequence, stir for 6h, mature in a nitrogen atmosphere with a purity ≥99.99% for 36h to remove dissolved oxygen, finally place in a 15MPa autoclave and treat at 60℃ for 8h, filter through a 0.22μm microporous membrane to obtain a qualified electrolyte.

[0045] Utilizing a surface-to-underground circulation path: equipped with a variable frequency circulation pump with a rated flow rate of 60-120 m³ / h. 3 / h; Flow control 80-110m 3 / h, with a surface and underground electrolyte distribution ratio of 1:2, suitable for conventional energy storage / release.

[0046] Operational Performance Verification: After 100 hours of system operation, the core indicators are as follows: continuous operation rate of the system is 98.5%; the average energy consumption of the circulating pump is reduced by 10.5% compared to the traditional method; the electrolyte capacity retention rate is 96.2% after 500 charge-discharge cycles; the low-temperature stability of the electrolyte is improved, with no precipitation at -10℃. The concentration of the positive electrode active material is 1.5 mol / L, and the viscosity is 6.8 mPa·s; the concentration of the negative electrode active material is 1.8 mol / L, and the viscosity is 6.7 mPa·s; the system energy density is 34 Wh / L.

[0047] Example 4: All-terrain single-loop path system based on standard concentration electrolyte In this embodiment, deionized water is used as the electrolyte, designed for ambient temperature and pressure conditions in a single-loop ground-based system. During electrolyte preparation, the positive electrode active material is a disulfonated TEMPO derivative (DIS-TEMPO), 18% by mass, corresponding to a concentration of 1.8M; the negative electrode active material is hydroxyethyl-sulfonate double-modified viologen (HEV-SO3Na), 22% by mass, corresponding to a concentration of 2.2M; the supporting electrolyte is a saturated NaCl solution, 56% by mass, corresponding to a concentration of 5.6M; the co-solvent is a mixture of ethylene glycol (EG) and N-methylpyrrolidone (NMP) (volume ratio 2:1), 3% by mass; and the environmental stabilizer is 0.04M magnesium vitamin C phosphate (VC-PMg) + 0.008M benzotriazole. (BTA); the anti-precipitation agent is polyethylene glycol (PEG-2000), 1% by mass. The electrolyte preparation steps are as follows: Take the prescribed amount of saturated NaCl solution, heat it to 45℃, add the synergistic co-solvent, stir at 300rpm until it is mixed evenly, slowly add DIS-TEMPO, continue stirring for 12h until completely dissolved, then add HEV-SO3Na, use 400W ultrasonic dispersion for 3h to break the active material agglomerates, then cool to 25℃, add VC-PMg, BTA and PEG-2000 in sequence, stir for 6h, mature in a nitrogen atmosphere with a purity ≥99.99% for 36h to remove dissolved oxygen, finally place it in a 15MPa autoclave and treat at 60℃ for 8h, filter through a 0.22μm microporous membrane to obtain a qualified electrolyte.

[0048] A single-loop path is adopted across the entire ground: the flow rate is stably controlled at 70m³. 3 / h, suitable for electrolyte activation and small-scale energy storage needs.

[0049] Operational Performance Verification: After 100 hours of continuous operation, the core indicators are as follows: Continuous operation rate of the system is 98.0% (no salt cavern maintenance required); average energy consumption of the circulating pump is reduced by 11% compared to traditional methods (short path, low resistance); electrolyte capacity retention rate is 96.0% after 500 charge-discharge cycles; no active material precipitation or pipeline leakage is observed. The concentration of the positive electrode active material is 1.8 mol / L, and the viscosity is 8.6 mPa·s; the concentration of the negative electrode active material is 2.2 mol / L, and the viscosity is 8.6 mPa·s; the system energy density is 40.2 Wh / L.

[0050] Example 5: A fully underground single-circulation path system based on a highly stable electrolyte This embodiment is designed for underground high-pressure conditions of 12 MPa. The remaining preparation steps are the same as in Example 1. Deionized water is used as the electrolyte, designed for high-pressure, long-distance circulation in a single underground loop. During electrolyte preparation, the positive electrode active material is a disulfonated TEMPO derivative (DIS-TEMPO), 20% by mass, corresponding to a concentration of 2.0 M; the negative electrode active material is hydroxyethyl-sulfonate double-modified viologen (HEV-SO3Na), 23% by mass, corresponding to a concentration of 2.3 M; the supporting electrolyte is a saturated NaCl solution, 52% by mass, corresponding to a concentration of 5.7 M; the co-solvent is a mixture of ethylene glycol (EG) and N-methylpyrrolidone (NMP) (volume ratio 2:1), 4% by mass; and the environmental stabilizer is 0.05 M magnesium vitamin C phosphate (VC). -PMg) + 0.01M benzotriazole (BTA); the anti-precipitation agent is polyethylene glycol (PEG-2000), 1% by mass. The electrolyte preparation steps are as follows: Take the prescribed amount of saturated NaCl solution, heat to 45℃, add the synergistic co-solvent, stir at 300rpm until mixed evenly, slowly add DIS-TEMPO, continue stirring for 12h until completely dissolved, then add HEV-SO3Na, use 400W ultrasonic dispersion for 3h to break the active material agglomerates, then cool to 25℃, add VC-PMg, BTA and PEG-2000 in sequence, stir for 6h, mature in a nitrogen atmosphere with a purity ≥99.99% for 36h to remove dissolved oxygen, finally place in a 15MPa autoclave and treat at 60℃ for 8h, filter through a 0.22μm microporous membrane to obtain a qualified electrolyte.

[0051] A fully underground single-loop path is adopted: the flow rate is stably controlled at 110m³. 3 / h, adaptable to large-scale, long-term energy storage needs.

[0052] Operational Performance Verification: After 100 hours of continuous system operation, the core indicators are as follows: System continuous operation rate 97.8% (shutdown during regular maintenance of ground modules); Average energy consumption of the circulating pump reduced by 10.8% compared to traditional methods (altitude difference assisted reflux); Electrolyte capacity retention rate 94.8% after 500 charge-discharge cycles; No active material precipitation under 12MPa high-pressure conditions, and stable pipeline sealing performance. The concentration of the positive electrode active material is 2.0 mol / L, and the viscosity is 10.3 mPa·s; the concentration of the negative electrode active material is 2.3 mol / L, and the viscosity is 10.5 mPa·s; the system energy density is 41.1 Wh / L.

[0053] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A salt cavern flow battery system integrating surface-to-underground three-circulation path switching, characterized in that, The system includes: an electrolyte storage module, an electrolyte, a flow battery stack (11), a circulation pipeline, and a circulation pump; The electrolyte storage module includes a surface storage tank and / or an underground salt cavern with a physical solution cavity formed after salt mining, wherein the solution cavity stores electrolyte; the surface storage tank is divided into an anode storage tank (120) and a cathode storage tank (121), which are spaced apart and arranged opposite to each other; the underground salt cavern is divided into an underground anode salt cavern and an underground cathode salt cavern, the underground anode salt cavern including an anode salt cavern cavity (210) and an anode solvent layer (220); the underground cathode salt cavern includes a cathode salt cavern cavity (211) and a cathode solvent layer (221); the underground anode salt cavern and the underground cathode salt cavern are spaced apart and arranged opposite to each other; The flow battery stack (11) is connected to the ground storage tank and / or the underground salt cavern respectively. The flow battery stack (11) includes: bipolar plate (110), electrode (111) and proton exchange membrane (112). The circulation pipeline forms a three-circulation path of electrolyte circulation between the ground storage tank, the underground salt cavern and the flow battery stack through the opening and closing of the valve group; The circulation pump is located in the circulation pipeline and provides a flow supply for the electrolyte circulation.

2. The salt cavern flow battery system with integrated surface-underground three-circulation path switching according to claim 1, characterized in that: The ground-underground three-loop path includes three modes: a fully ground-loop path, a fully underground-loop path, and a ground-underground-loop path.

3. The salt cavern flow battery system with integrated surface-underground three-circulation path switching according to claim 1, characterized in that: The valve group includes a first anode valve A1, a second anode valve A2, a third anode valve A3, a first cathode valve B1, a second cathode valve B2, and a third cathode valve B3; The outlet of the anode storage tank is connected to the anode inlet of the fuel cell stack through the first anode valve A1 and the third anode valve A3. The anode outlet of the fuel cell stack is connected to the inlet of the underground anode salt cave through the second anode valve A2 and the anode salt cave inlet (230). The outlet of the underground anode salt cave is connected to the third anode valve A3 through the anode salt cave outlet (240), forming an anode circulation branch. The cathode storage tank outlet is connected to the cathode inlet of the fuel cell stack via the first cathode valve B1 and the third cathode valve B3. The cathode outlet of the fuel cell stack is connected to the inlet of the underground cathode salt cave via the second cathode valve B2 and the cathode salt cave inlet (231). The underground cathode salt cave outlet is connected to the third cathode valve B3 via the cathode salt cave outlet (241), forming a cathode circulation branch.

4. The salt cavern flow battery system with integrated surface-underground three-circulation path switching according to claim 2, characterized in that: The specific all-ground circulation path is as follows: close the second anode valve A2, the third anode valve A3, and the second cathode valve B2 and the third cathode valve B3, and open the first anode valve A1 and the first cathode valve B1; after the circulation pump starts, the electrolyte forms a closed loop of anode circulation branch and cathode circulation branch in "anode storage tank (120) → first anode valve A1 → fuel cell anode inlet → fuel cell anode outlet → anode storage tank (120)" and "cathode storage tank (121) → first cathode valve B1 → fuel cell cathode inlet → fuel cell cathode outlet → cathode storage tank (121)"; the circulation flow rate under this path is controlled at 60-80m³. 3 / h, total pipeline length ≤50m, resistance loss ≤0.3-0.5MPa, to achieve rapid activation of electrolyte and low-load operation of system.

5. The salt cavern flow battery system with integrated surface-underground three-circulation path switching according to claim 2, characterized in that: The specific underground circulation path is as follows: The first anode valve A1 and the first cathode valve B1 are closed; the second anode valve A2, the third anode valve A3, the second cathode valve B2, and the third cathode valve B3 are opened. After the circulation pump starts, the electrolyte forms closed loops for the anode and cathode circulation branches in the paths of "underground anode salt cavern → third anode valve A3 → fuel cell stack anode inlet → fuel cell stack anode outlet → second anode valve A2 → underground anode salt cavern" and "underground cathode salt cavern → third cathode valve B3 → fuel cell stack cathode inlet → fuel cell stack cathode outlet → second cathode valve B2 → underground cathode salt cavern". The circulation flow rate under this path is controlled at 100-120 m³ / h. 3 / h, total pipeline length ≤1200-1500m, resistance loss ≤2.0-2.5Mpa.

6. The salt cavern flow battery system with integrated surface-underground three-circulation path switching according to claim 2, characterized in that: The specific ground-to-underground circulation path is as follows: close the first anode valve A1 and the first cathode valve B1, and open the second anode valve A2, the third anode valve A3 and the second cathode valve B2 and the third cathode valve B3, or open the first anode valve A1, the second anode valve A2, the third anode valve A3 and the first cathode valve B1, the second cathode valve B2 and the third cathode valve B3; after the circulation pump starts, the electrolyte forms a closed loop of anode circulation branch and cathode circulation branch in "anode storage tank (120) / underground anode salt cavern → first anode valve A1 / third anode valve A3 → stack anode inlet → stack anode outlet → anode storage tank (120) / [second anode valve A2 → underground anode salt cavern]" and "cathode storage tank (121) / underground cathode salt cavern → first cathode valve B1 / third cathode valve B3 → stack cathode inlet → stack cathode outlet → cathode storage tank (121) / [second cathode valve B2 → underground cathode salt cavern]"; the circulation flow rate under this path is controlled at 80-110m³. 3 / h, the electrolyte distribution ratio between the ground storage tank and the underground salt cavern is dynamically adjusted according to the energy storage capacity requirements, with a distribution ratio range of 1-3:1-3.

7. The salt cavern flow battery system with integrated surface-underground three-circulation path switching according to claim 1, characterized in that: The electrolyte comprises a positive electrode active material, a negative electrode active material, a supporting electrolyte, a synergistic co-solvent, an environmentally compatible stabilizer, an anti-precipitation agent, and deionized water; the preparation of the electrolyte includes the following steps: S1. First, heat the supporting electrolyte to 40-50℃, add the co-solvent and stir evenly at a stirring speed of 300 rpm. S2. Slowly add the positive electrode active material and stir continuously for 12 hours; then add the negative electrode active material and disperse it using ultrasonication at 300-500W for 2-4 hours. After cooling to 25℃, add the environmental compatibility stabilizer and anti-precipitation agent and stir for 6 hours. S3. The electrolyte is aged in a nitrogen atmosphere for 24-48 hours to remove dissolved oxygen and prevent oxidation of active substances. Then, the electrolyte is placed in a 15MPa autoclave and treated at 60℃ for 8 hours. Electrolytes without precipitation or decomposition are screened to obtain highly active electrolytes.

8. The salt cavern flow battery system with integrated surface-underground three-circulation path switching according to claim 7, characterized in that: The positive electrode active material is one of the following: DIS-TEMPO (a disulfonated TEMPO derivative), Tri-SO3Na-Xanthenone (a trisulfonated xanthenone derivative), SO3Na-COOH-Phenazine (a sulfonate-carboxyl dual-modified phenazine), or HP-SO3Na-Anthraquinone (a hydroxypropyl-sulfonate dual-modified anthraquinone), with a mass percentage of 15%-22% in the electrolyte, corresponding to a concentration of 1.5-2.2M. The negative electrode active material is one of hydroxyethyl-sulfonate double-modified viologen HEV-SO3Na or dihydroxyethyl-sulfonate triple-modified bipyridine Di-HE-SO3Na-Bipyridine, with a mass percentage of 18%-25% in the electrolyte, corresponding to a concentration of 1.8-2.5M. The supporting electrolyte is a saturated NaCl solution, with a mass percentage of 55%-60% in the electrolyte, corresponding to a concentration of 5.5-6.0 M.

9. The salt cavern flow battery system with integrated surface-underground three-circulation path switching according to claim 7, characterized in that: The co-solvent is one or more of ethylene glycol (EG) and N-methylpyrrolidone (NMP), and its mass percentage in the electrolyte is 8%-12%. The environmental adaptability stabilizer is one or more of vitamin C phosphate magnesium VC-PMg and benzotriazole BTA, wherein the concentration of VC-PMg is 0.03-0.06M and the concentration of BTA is 0.005-0.01M; The anti-exudant is polyethylene glycol PEG-2000, with a mass percentage of 0.5%-1.0% in the electrolyte.

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