A molten salt flow battery electrothermal co-storage system and method

Abstract

This invention belongs to the field of large-scale energy storage and hydrogen energy, and discloses a molten salt flow battery electrothermal co-storage system and method. The molten salt flow battery electrothermal co-storage system of this invention includes: an electrochemical reactor stack, a four-tank dual-temperature dual-electrolyte molten salt energy storage tank system, a fluid transport pipeline system, and a heat exchange system; wherein the heat exchange system is connected between the first and second tanks to form a heat exchange loop; the electrochemical reactor stack is connected to the low-temperature molten salt energy storage tank system to form an electrochemical positive and negative circulation loop; the molten salt serves simultaneously as the electrolyte for electrochemical energy storage and the heat storage medium for thermal energy storage. This invention achieves medium reuse by using the same molten salt as the electrothermal storage medium, increasing energy storage density and reducing energy storage costs; the four-tank dual-temperature structure ensures that the electrochemical reactor stack always operates in a low-temperature environment, guaranteeing stack lifespan, while the second tank can independently store thermal energy at higher temperatures.

Description

Technical Field

[0001] This invention belongs to the field of large-scale energy storage and hydrogen energy, and specifically relates to a molten salt flow battery electrothermal co-storage system and electrothermal co-storage method. Background Technology

[0002] Flow batteries, as a large-scale energy storage technology, have advantages such as high safety, long cycle life, and independent design of power and capacity, and are widely used in renewable energy grid integration and grid peak shaving. However, traditional flow batteries can only store electrical energy and cannot store thermal energy.

[0003] Currently, some solutions attempt to combine flow batteries with thermal storage functions. For example, Chinese patent document CN116487735A discloses a molten salt flow battery and energy storage system. This solution wraps the flow battery with a thermally conductive medium, which transfers heat to a separate thermal storage tank for storage. However, this solution separates the thermal storage and energy storage functions, requiring separate setups for the energy storage medium (molten salt electrolyte) and its circulation system, the thermal storage medium (thermal conductive medium) and its circulation system, and a separate thermal storage tank. This results in system redundancy and thermal resistance losses due to cross-medium heat transfer. Summary of the Invention

[0004] In view of the technical problems existing in the prior art, the purpose of this invention is to provide a molten salt flow battery electrothermal co-storage system and electrothermal co-storage method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A molten salt flow battery electrothermal co-storage system includes: Electrochemical reactor stacks are used to perform electrochemical redox reactions; A molten salt energy storage tank system includes a first storage tank and a second storage tank. The first storage tank includes a positive electrode first storage tank and a negative electrode first storage tank, and the second storage tank includes a positive electrode second storage tank and a negative electrode second storage tank. The positive electrode molten salt electrolyte circulates between the positive electrode first storage tank and the positive electrode second storage tank, and the negative electrode molten salt electrolyte circulates between the negative electrode first storage tank and the negative electrode second storage tank. The holding temperature of the first storage tank is 200-300°C lower than that of the second storage tank. Fluid delivery piping system used to drive the molten salt electrolyte to circulate between components; A heat exchange system is connected between the first and second storage tanks to exchange heat between the molten salt electrolyte and an external heat source or external heat user, forming a heat exchange circuit. The electrochemical reactor stack is connected to the molten salt energy storage tank system to form an electrochemical loop. The molten salt electrolyte serves as both the electrolyte for electrochemical energy storage and the heat storage medium for thermal energy storage.

[0006] Furthermore, the molten salt flow battery electrothermal co-storage system includes an inert gas sealing system; the inert gas sealing system is connected to the gas phase space of the molten salt energy storage tank system and is used to provide a positive pressure inert atmosphere.

[0007] Furthermore, the inert gas sealing system includes an inert gas source, a pressure control unit, and an inert gas sealing pipeline; the inert gas source provides at least one gas selected from argon, nitrogen, and helium; the pressure control unit is used to monitor and adjust the gas phase pressure inside the storage tank to maintain a slightly positive pressure inside the system and prevent outside air from penetrating the molten salt and active metal ions; the inert gas sealing pipeline connects the inert gas source and the molten salt energy storage tank system.

[0008] Furthermore, the inert gas sealing system includes a gas purification unit; the gas purification unit is used for circulating filtration and removing trace amounts of moisture and oxygen from the inert gas sealing system.

[0009] Furthermore, the molten salt electrolyte is composed of molten salt and electroactive ions dissolved therein.

[0010] Furthermore, the molten salt is a eutectic salt composed of at least one of alkali metal halide salts and alkaline earth metal halide salts; the eutectic point of the molten salt is below 450°C.

[0011] Furthermore, the alkali metal halide salt includes at least one of LiCl, NaCl, and KCl.

[0012] Furthermore, the alkaline earth metal halide salt includes at least one of MgCl2 and CaCl2.

[0013] Furthermore, the electroactive ions in the positive and negative electrode molten salt electrolytes are homologous elements; the electroactive ions in the positive electrode molten salt electrolyte include M... 3+ and M 4+ The electroactive ions in the negative electrode molten salt electrolyte include M 2+ and M 3+ M is one of Ti, Cr, Mn, Fe, Co, Ni, and V.

[0014] Furthermore, the positive electrode molten salt electrolyte and the negative electrode molten salt electrolyte are physically isolated and ion-conducting within the electrochemical reactor by means of fluid dynamics-controlled laminar interface, porous insulating partition, or density difference between the positive and negative electrode molten salt electrolytes.

[0015] Furthermore, the electrochemical reactor stack employs a non-ion-selective isolation structure, which includes one of a porous ceramic separator or a porous insulating composite material. The pore size range is configured to allow ions from the molten salt electrolyte to pass through to form a conductive circuit, while suppressing the convective mixing of active substances in the positive and negative electrode molten salt electrolytes.

[0016] Furthermore, the temperature of the first storage tank is maintained at 450-500℃; the temperature of the second storage tank is maintained at 700-750℃.

[0017] Furthermore, the molten salt energy storage tank system and the fluid transport pipeline system independently include at least one heat tracing device and a heat preservation device.

[0018] Furthermore, the pipes in the fluid transport pipeline system include one of nickel-based alloy pipes and pipes with ceramic linings resistant to chloride ion corrosion.

[0019] Furthermore, the fluid delivery pipeline system includes control valves for switching between the following operating modes: Charge / discharge mode: The electrochemical circulation loop is activated, and the molten salt electrolyte circulates between the molten salt energy storage tank system and the electrochemical reactor stack; when the electrochemical reactor stack is connected to an external power source, electrical energy is converted into chemical energy and stored in the molten salt electrolyte, completing the charging process; when the electrochemical reactor stack is connected to an external electrical load, the chemical energy of the molten salt electrolyte is converted into electrical energy, completing the discharging process. Heat storage and release mode: When the heat exchange circuit is turned on, the molten salt electrolyte absorbs heat energy from the external heat source from the first storage tank through the heat energy exchange system and flows into the second storage tank to complete the heat storage process; the molten salt electrolyte releases heat energy from the second storage tank to the external heat user through the heat energy exchange system and then flows into the first storage tank to complete the heat release process. Synergistic mode: The electrochemical circulation loop and the heat exchange loop are simultaneously activated. The molten salt electrolyte flows from the first storage tank to the electrochemical reactor stack, and then flows into the second storage tank after absorbing heat energy from the external heat source through the heat exchange system, completing the synergistic charging / discharging and heat storage process; the molten salt electrolyte flows from the second storage tank to the heat exchange system, and then flows into the first storage tank after passing through the electrochemical reactor stack, completing the synergistic charging / discharging and heat release process.

[0020] Furthermore, in the charge / discharge mode and / or the synergistic mode, the waste heat generated by the electrochemical reactor is stored in the second storage tank along with the molten salt electrolyte.

[0021] Furthermore, in the heat storage and release mode and / or the coordinated mode, the heat exchange system absorbs heat energy from an external heat source, heats the molten salt electrolyte, and then stores it in the second storage tank.

[0022] Furthermore, the external heat source includes at least one of solar thermal power plant heat energy, nuclear power plant heat energy, or industrial heat source.

[0023] Furthermore, the fluid transport pipeline system includes a flow battery pipeline, a thermal storage pipeline, and a heat exchange pipeline; the flow battery pipeline connects the fuel cell stack, the first storage tank, and the heat exchange system, wherein the electrochemical reactor stack and the heat exchange system are connected in parallel through the flow battery pipeline; the thermal storage pipeline connects the second storage tank and the heat exchange system; and the heat exchange pipeline connects the heat exchange system to an external heat source or an external heat user.

[0024] Furthermore, the fluid transport pipeline system includes a circulation pump that provides a power source; the circulation pump is disposed on a pipeline connecting the heat exchange system, the first storage tank, and the electrochemical reactor.

[0025] Furthermore, the heat exchange system includes a heat exchanger.

[0026] A method for co-storing electrothermal energy using the above system includes the following steps: S1. Start the system and, according to the charging, discharging and heat storage requirements, switch the control valves of the fluid transport pipeline system to the corresponding working mode, so that the electrochemical circulation loop and the heat exchange loop are individually or simultaneously activated. S2. The fluid transport pipeline system drives the molten salt electrolyte to flow in the connected circuit, realizing individual charging and discharging, individual heat storage and release, or charging and discharging and heat storage and release in synergy.

[0027] The implementation of this invention has the following beneficial effects: This invention achieves medium reuse by using the same molten salt as both an energy storage medium and a heat storage medium, thereby increasing energy storage density and reducing energy storage costs. It eliminates the need for separate heat transfer media and heat storage tanks, simplifying the system structure and reducing equipment costs. Furthermore, when storing waste heat generated by electrochemistry, no heat transfer is required; the waste heat directly follows the molten salt electrolyte into the second storage tank for storage, eliminating thermal resistance loss during heat transfer.

[0028] By setting up a four-tank dual-temperature structure consisting of a positive electrode first tank, a positive electrode second tank, a negative electrode first tank, and a negative electrode second tank, the electrochemical reactor stack is always operated in a low-temperature environment, ensuring the stack's lifespan. At the same time, the second tank can independently store thermal energy at higher temperatures, and the thermal storage temperature is not limited by the stack's operating temperature, significantly improving the thermal storage density and the quality of external heat supply.

[0029] The heat exchange system can be connected to various external heat sources such as solar thermal power plant heat energy, nuclear power plant heat energy, and industrial heat sources, so as to realize the cascade utilization of energy and the improvement of comprehensive energy efficiency. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of a molten salt flow battery electrothermal co-storage system in some embodiments of the present invention.

[0031] Among them, 100-electrochemical reactor stack; 200-molten salt energy storage tank system; 201-first positive electrode storage tank; 202-first negative electrode storage tank; 203-second positive electrode storage tank; 204-second negative electrode storage tank; 300-fluid transport pipeline system; 400-inert gas sealing system; 500-heat exchange system; The letters in the diagram represent: Σ for heat exchanger; PO for circulating pump. Detailed Implementation

[0032] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the invention will now be described in detail with reference to the accompanying drawings. In the following description, it should be understood that the orientations or positional relationships indicated by terms such as "front," "rear," "upper," "lower," "left," "right," "longitudinal," "horizontal," "vertical," "horizontal," "top," "bottom," "inner," "outer," "head," and "tail" are based on the orientations or positional relationships shown in the accompanying drawings, and are constructed and operated in a specific orientation. They are only for the convenience of describing the present invention and do not indicate that the device or element referred to must have a specific orientation; therefore, they should not be construed as limitations on the present invention.

[0033] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components. When an component is referred to as being "on" or "below" another component, the component can be located "directly" or "indirectly" on the other component, or there may be one or more intermediary components. The terms "first," "second," "third," etc., are used only for the convenience of describing the present invention and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. For those skilled in the art, the specific meaning of the above terms in the present invention can be understood according to the specific circumstances.

[0034] like Figure 1As shown, in some embodiments, a molten salt flow battery electrothermal co-storage system is provided, including an electrochemical reactor stack 100, a molten salt energy storage tank system 200, a fluid transport pipeline system 300, and a heat exchange system 500, to achieve electrothermal co-storage. The electrochemical reactor stack 100 is used to perform electrochemical redox reactions to realize the mutual conversion of electrical energy and chemical energy. The electrochemical reactor stack 100 is connected to an external power source or an electricity user.

[0035] The molten salt energy storage tank system 200 includes a first storage tank and a second storage tank. The first storage tank includes a positive electrode first storage tank 201 and a negative electrode first storage tank 202, and the second storage tank includes a positive electrode second storage tank 203 and a negative electrode second storage tank 204. The positive electrode molten salt electrolyte circulates between the positive electrode first storage tank 201 and the positive electrode second storage tank 203, and the negative electrode molten salt electrolyte circulates between the negative electrode first storage tank 202 and the negative electrode second storage tank 204. The holding temperature of the first storage tank is 200-300℃ lower than that of the second storage tank. Through the four-tank dual-temperature structure design, the second storage tank and the electrochemical reactor 100 can operate decoupled, and the heat storage temperature is not limited by the temperature resistance of the materials of the electrochemical reactor 100. At the same time, the connection design between the electrochemical reactor 100 and the molten salt energy storage tank system 200 ensures that the temperature of the electrolyte entering the electrochemical reactor 100 is stable and is not affected by the temperature fluctuation of the second storage tank, effectively extending the service life of the electrochemical reactor 100 and improving the reliability of system operation.

[0036] The fluid delivery pipeline system 300 is used to drive the molten salt electrolyte to circulate between the components.

[0037] The heat exchange system 500 is connected between the first and second storage tanks and is used to exchange heat between the molten salt electrolyte and an external heat source or external heat user, forming a heat exchange loop. Specifically, the heat exchange system 500 includes a heat exchanger ( Figure 1 Σ in the middle.

[0038] The electrochemical reactor 100 is connected to the molten salt energy storage tank system 200 to form an electrochemical loop.

[0039] Molten salt electrolyte serves as both the electrolyte for electrochemical energy storage and the heat storage medium for thermal energy storage. By utilizing this dual function of a single medium, the energy storage system is upgraded from a single power storage medium to a combined electro-thermal carrier, significantly improving the overall energy utilization efficiency and economy of the system without adding additional heat storage facilities. Furthermore, the waste heat generated during the charge-discharge reaction of the electrochemical reactor 100 is stored in the molten salt electrolyte. Then, along with the molten salt electrolyte, this waste heat is transferred to the second storage tank during the heat storage process. In other words, the waste heat generated by electrochemistry is stored in the second storage tank via mass transfer through the molten electrolyte, eliminating the need for heat transfer and thus avoiding thermal resistance losses.

[0040] In some embodiments, the molten salt flow battery electrothermal co-storage system includes an inert gas sealing system 400; the inert gas sealing system 400 is connected to the gas phase space of the molten salt energy storage tank system 200 to provide a positive pressure inert atmosphere. Specifically, the inert gas sealing system 400 includes an inert gas source, a pressure control unit, and an inert gas sealing pipeline; the inert gas source provides at least one gas selected from argon, nitrogen, and helium; the pressure control unit monitors and regulates the gas phase pressure inside the tank to maintain a slight positive pressure inside the system and prevent outside air from penetrating into the oxidized molten salt and active metal ions; the inert gas sealing pipeline connects the inert gas source and the molten salt energy storage tank system 200. The inert gas sealing system 400 also includes a gas purification unit; the gas purification unit is used to circulate and filter to remove trace amounts of moisture and oxygen from the inert gas sealing system 400. Understandably, the inert gas sealing system 400 can prevent the transition metal ions from undergoing unintended oxidation reactions and suppress corrosive gases that may be generated by the molten chloride salt at high temperatures, thereby improving the operational stability of the entire co-storage system.

[0041] In some embodiments, the molten salt electrolyte consists of a molten salt (as an ionic conductor / solvent) and electroactive ions dissolved therein (as reactants). The molten salt is a eutectic salt composed of at least one of alkali metal halide salts and alkaline earth metal halide salts, and a possible combination includes an alkali metal halide salt + an alkaline earth metal halide salt; the eutectic point of the molten salt is below 450°C. The alkali metal halide salt includes at least one of LiCl, NaCl, and KCl, and a possible combination includes LiCl + KCl, etc. The alkaline earth metal halide salt includes at least one of MgCl2 and CaCl2. In general, as long as the eutectic point of the specific combination of molten salts is below 450°C, the corresponding effect can be achieved, that is, it not only meets the minimum temperature requirement for the first row of transition metals (such as Ti, V, Cr, etc.) to maintain liquid electrochemical activity in the molten salt system, but also crosses the operating range of high-quality thermodynamic cycling. For example, a mixed molten salt of NaCl-MgCl2-KCl (19 mol%-29 mol%-52 mol%) chlorides has a melting point of 400℃, a maximum operating temperature not exceeding 800℃, and a specific heat capacity of 1.0-1.20 kJ / (kg·K). This system abandons traditional nitrates or single-component salts, adopting a mixed molten salt system composed of a series of alkali metal halide salts and alkaline earth metal halide salts. This type of molten salt possesses extremely high thermal stability and a wide liquid phase region, enabling the system to operate at high temperatures above 700°C. It serves as the mainstream carrier for next-generation solar thermal power plants and advanced industrial heat source recovery. For example, when the heat exchange system of this invention is integrated with a supercritical CO2 Brayton cycle, the heat storage temperature of the second tank at 750℃ can generate a supercritical CO2 working fluid at temperatures above 650℃, achieving an energy conversion efficiency of >50%. This structural design (direct matching of the high-temperature section with the supercritical CO2 heat exchange channel) can be considered a core differentiating feature from other thermo-electric coupling systems. This system not only has advantages such as low cost and high specific heat capacity, but also has good engineering compatibility with existing industrial thermal equipment.

[0042] In some embodiments, the electroactive ions in the positive and negative electrode molten salt electrolytes are homologous elements, and the electroactive ions in the positive electrode molten salt electrolyte include M. 3+ and M 4+ Electroactive ions in the negative electrode molten salt electrolyte include M 2+ and M 3+M is one of Ti, Cr, Mn, Fe, Co, Ni, and V. The abundance of electrochemically active materials provides a more cost-effective and resource-secure option for large-scale, long-term energy storage systems while maintaining efficient charge storage. Furthermore, an intrinsically safe system capable of self-repairing capacity loss is established by utilizing the self-disproportionation and reverse disproportionation chemical equilibrium mechanism of the active materials. Since the positive and negative electrodes use homologous metal elements as active centers, the irreversible contamination problem caused by cross-mixing of dissimilar elements is fundamentally eliminated. Even when a small amount of active species (divalent metal ions M) occurs under conditions allowing ion diffusion through the porous membrane... 2+ With tetravalent metal ions M 4+ Through cross-linking, these species can also rapidly transform into stable intermediate valence states (trivalent metal ions M) via spontaneous disproportionation reactions (i.e., reverse disproportionation reactions) at the contact interface or after mixing. 3+ This unique chemical self-regulating behavior ensures that even with trace amounts of cross-mixing, the overall chemical composition and average valence state of the electrolyte remain in dynamic equilibrium. Furthermore, through the selection of specific active species (M... 2+ / M 3+ / M 4+ The intrinsic high stability of this electrolyte eliminates the risk of hydrolysis or polymerization of high-oxidation-state species, resulting in precipitation. Simultaneously, both the positive and negative electrodes contain the same intermediate-valence ion (M). 3+ The properties of this basic component significantly reduce the capacity imbalance problem caused by cross-contamination of different active materials in traditional batteries.

[0043] In some embodiments, the positive and negative molten salt electrolytes are physically isolated and ion-conducting within the electrochemical reactor 100 through fluid dynamics-controlled laminar interface, porous insulating separators, or density differences between the positive and negative molten salt electrolytes. The electrochemical reactor 100 employs a non-ion-selective isolation structure, including a porous ceramic separator or a porous insulating composite material. The pore size is configured to allow ions from the molten salt electrolyte to pass through to form a conductive circuit, while suppressing convective mixing of active materials in the positive and negative molten salt electrolytes. This non-ion-selective membrane design effectively reduces the system's internal resistance and maintenance costs.

[0044] In some embodiments, the electrochemical reactor stack 100 employs an alumina-based porous ceramic material as a non-ion-selective physical separator to separate the positive and negative electrode chambers. While this design utilizes a solid ceramic material, it differs fundamentally from the dense beta-alumina ceramic tubes used as solid electrolytes in traditional high-temperature sodium-sulfur batteries. Traditional beta-alumina relies on its crystal lattice to conduct specific sodium ions and must maintain a tight, airtight seal. In contrast, the porous ceramic material used in this embodiment does not possess ion conductivity; it serves only as a physical support framework, utilizing the molten salt electrolyte filling the pores to achieve non-selective ion migration and conduction. The alumina material acts only as a physical porous separator to block macroscopic convection and does not perform the function of selectively conducting specific ions, thus significantly reducing manufacturing difficulty and cost. This structure, while significantly reducing separator costs, leverages the excellent high-temperature stability of alumina ceramics to ensure the mechanical strength and long-term operational reliability of the electrochemical reactor stack 100 in a high-temperature molten salt environment.

[0045] In some embodiments, the temperature of the first storage tank is maintained at 450-500°C, and any temperature within this range can be selected, including 450°C, 460°C, 500°C, etc.; the temperature of the second storage tank is maintained at 700-750°C, and any temperature within this range can be selected, including 700°C, 720°C, 750°C, etc. In the co-storage system, the molten salt electrolyte operates within a temperature range of 450-750°C, which not only meets the minimum temperature requirements for maintaining the liquid electrochemical activity of the first row of transition metals (such as Ti, V, Cr, etc.) in the chlorinated molten salt system, but also extends into the operating range of high-quality thermodynamic cycling. The low-temperature range of 450-500°C focuses on ensuring the charge-discharge efficiency of the battery and the long lifespan of the membrane material, while the high-temperature range of 700-750°C greatly improves the total energy storage density of the system through the heat exchange pipeline. This independent regulation and efficient coupling of both electrical and thermal energy enables the system to flexibly respond to power load fluctuations, demonstrating extremely high engineering practical value, especially in supporting large-capacity, long-term energy storage scenarios such as deep peak shaving for nuclear power. The molten salt energy storage tank system 200 includes at least one heat tracing device and an insulation device to maintain the temperature of the corresponding storage tank. Preferably, it may include both a heat tracing device and an insulation device.

[0046] In some embodiments, the fluid transport piping system 300 includes at least one heat tracing device and a heat insulation device; preferably, it may include both a heat tracing device and a heat insulation device. The pipes in the fluid transport piping system 300 include one of nickel-based alloy pipes and pipes with a ceramic lining resistant to chloride ion corrosion.

[0047] Furthermore, the fluid delivery piping system 300 includes control valves for switching the following operating modes: Charge / discharge mode: The electrochemical circulation loop is activated, and the molten salt electrolyte circulates between the molten salt energy storage tank system 200 and the electrochemical reactor stack 100. When the electrochemical reactor stack 100 is connected to an external power source, it converts electrical energy into chemical energy and stores it in the molten salt electrolyte, completing the charging process. When the electrochemical reactor stack 100 is connected to an external electrical load, it converts the chemical energy of the molten salt electrolyte into electrical energy, completing the discharging process. The electrochemical waste heat generated by the electrochemical reactor stack 100 flows into the second storage tank with the molten salt electrolyte during the next heat storage and is stored in the second storage tank. Before the next heat storage, this waste heat is stored in the molten salt electrolyte in the first storage tank, which can delay the temperature drop of the first storage tank.

[0048] Heat storage and release mode: With the heat exchange circuit open, the molten salt electrolyte flows from the first storage tank, absorbs heat energy from an external heat source via the heat exchange system 500, and then flows into the second storage tank, completing the heat storage process. The molten salt electrolyte then flows from the second storage tank, releases heat energy to an external heat user via the heat exchange system 500, and then flows back into the first storage tank, completing the heat release process. Understandably, when the electrochemical reactor 100 is in an open-circuit or standby state, the fluid transport pipeline system 300 continuously drives the molten salt electrolyte to circulate between the molten salt energy storage tank system 200 and the heat exchange system 500, independently storing and releasing heat energy. The heat exchange system 500 absorbs heat energy from an external heat source, heats the molten salt electrolyte, and stores it in the second storage tank; the external heat source includes at least one of the following: solar thermal power plant heat energy, nuclear power plant heat energy, or industrial heat source.

[0049] Synergistic Mode: The electrochemical circulation loop and heat exchange loop are simultaneously activated. Molten salt electrolyte flows from the first storage tank to the electrochemical reactor 100, then absorbs heat energy from an external heat source via the heat exchange system 500 before flowing into the second storage tank, completing the synergistic charging / discharging and heat storage process. Waste heat generated by the electrochemical reactor 100 is stored in the second storage tank along with the molten salt electrolyte. The heat exchange system 500 absorbs heat energy from an external heat source, heats the molten salt electrolyte, and stores it in the second storage tank. Specifically, when the electrochemical reactor 100 is connected to an external power source, it operates as a charging and heat storage synergistic mode; when the electrochemical reactor 100 is connected to an external electrical load, it operates as a discharging and heat storage synergistic mode.

[0050] Simultaneously, the electrochemical circulation loop and heat exchange loop are activated. Molten salt electrolyte flows from the second storage tank through the heat exchange system 500, releasing heat energy to external heat users before flowing into the electrochemical reactor stack. It then enters the first storage tank, completing the coordinated charging / discharging and heat release process. The electrochemical waste heat generated by the electrochemical reactor stack 100 flows into the second storage tank along with the molten salt electrolyte during the next heat storage cycle and is stored there. When the electrochemical reactor stack 100 is connected to an external electrical load, it exhibits coordinated discharge and heat release; when it is connected to an external power source, it exhibits coordinated charging and heat release.

[0051] In some embodiments, the fluid transport pipeline system 300 includes a flow battery pipeline, a heat storage pipeline, and a heat exchange pipeline. The flow battery pipeline connects the electrochemical reactor 100, the first storage tank, and the heat exchange system 500, wherein the electrochemical reactor 100 and the heat exchange system 500 are connected in parallel via the flow battery pipeline. Specifically, the flow battery pipeline includes a first pipeline and a second pipeline. The first pipeline connects the electrochemical reactor 100 and the first storage tank, and there are two first pipelines in total. One end of the second pipeline is connected to one of the first pipelines, and the other end is connected to the heat exchange system 500. The heat storage pipeline connects the second storage tank and the heat exchange system 500. The heat exchange pipeline connects the heat exchange system 500 to an external heat source or an external heat user. The fluid transport pipeline system 300 includes a circulating pump that provides a power source. Figure 1 The circulating pump (PO) is installed on the pipeline connecting the heat exchange system 500, the first storage tank and the electrochemical reactor 100.

[0052] Specifically, the core operating environment of the flow battery pipeline is maintained at 450-500℃. This pipeline connects the first storage tank to the central electrochemical reactor stack 100. Specifically, the left-side pipeline is responsible for circulating M... 2+ With M 3+ The reducing electrolyte is located on the right side, while the right-side tubing is responsible for circulating M. 3+ With M 4+ The molten salt electrolyte is at the oxidation end. A circulating pump (PO) serves as the power source, ensuring that the molten salt electrolyte passes through the battery plates at a constant flow rate for oxidation-reduction reactions, thereby storing or releasing electrical energy.

[0053] The thermal storage pipeline forms a high-temperature thermal storage circulation loop at 700-750℃. This pipeline connects to a molten salt storage tank with an even higher temperature rating, where the stored medium has extremely high thermal quality. The heat exchange pipeline acts as a thermal bridge, thermally coupling the 700-750℃ high-temperature heat source with the 450-500℃ battery circulation loop through a high-efficiency heat exchanger (Σ). When the system is in thermal storage mode, heat from external sources (such as solar thermal energy or waste heat from nuclear power plant peak shaving) enters the molten salt system through the heat exchanger (Σ); when heat release is required, the high-quality thermal energy can be output to industrial steam or power generation terminals, realizing the storage and utilization of sensible heat beyond electrochemical energy.

[0054] The following embodiments detail the electrothermal co-storage method for the molten salt flow battery electrothermal co-storage system proposed in this invention, including the following steps: S1. Start the system and switch the control valves of the fluid transport pipeline system to the corresponding working mode according to the charging, discharging and heat storage requirements, so that the electrochemical circulation loop and the heat exchange loop are individually or simultaneously turned on; S2. The fluid transport pipeline system drives the molten salt electrolyte to flow in the connected circuit, realizing individual charging and discharging, individual heat storage and release, or charging and discharging and heat storage and release in tandem.

[0055] Specifically, this system can flexibly switch between charging / discharging mode, thermal storage / discharge mode, and coordinated mode based on power peak-shaving demand. In some implementation methods: During off-peak electricity hours (when the grid is at its lowest electricity price), the electrochemical reactor stack is connected to an external power source, and the system switches to charge-discharge mode. Molten salt electrolyte flows from the first storage tank to the electrochemical reactor stack, where it converts electrical energy from the external power source into chemical energy stored in the molten salt electrolyte, thus achieving charging. The molten salt electrolyte is then returned to the first storage tank for further storage. The heat generated during charging is temporarily stored in the molten salt electrolyte in the first storage tank before the next heat storage process, which slows down the temperature drop in the first storage tank. During subsequent heat storage processes, the heat is further increased as the molten salt electrolyte heats up and is then transferred to the second storage tank.

[0056] During peak hours (when the power grid is operating at peak electricity prices), the electrochemical reactor stack connects to external electrical loads, and the system switches to a coordinated mode. Molten salt electrolyte flows from the second storage tank to the heat exchange system, releasing heat energy to external heat users. It then flows back into the electrochemical reactor stack, converting the chemical energy stored in the molten salt electrolyte into electrical energy, which is output to the external electrical loads and then stored in the first storage tank. Specifically, the external heat users are thermal power generation devices, further supplementing the electricity supply.

[0057] During the flat period of thermal storage (when grid electricity prices are flat and solar thermal resources are abundant), the system switches to thermal storage and release mode, only conducting the heat exchange circuit. Molten salt electrolyte flows from the first storage tank to the heat energy exchange system, storing the thermal energy of the external heat source in the molten salt electrolyte through heat transfer, and then flows into the second storage tank for storage.

[0058] Example 1 A 500W pilot-scale system was built according to the above system structure. The molten salt in the electrolyte is a mixed molten salt of NaCl-MgCl2-KCl (19 mol%-29 mol%-52 mol%) chlorides, with a melting point of 400℃, a maximum operating temperature not exceeding 800℃, and a specific heat capacity of 1.0-1.20 kJ / (kg·K). The temperature of the first storage tank is maintained at 450℃ to avoid direct thermal shock to the fuel cell stack materials and sealing structure from the high-temperature molten salt, resulting in higher system stability. The temperature of the second storage tank is maintained at 750℃. In this embodiment, 1 ton of molten salt electrolyte is used as the energy carrier for continuous circulation of both the positive and negative electrode electrolytes, totaling 2 tons. The positive electrode electrolyte contains Ti. 3+ / Ti 4+The relevant high-valence titanium active species are preferably maintained within the first storage tank and electrochemical circulation loop during operation, and their temperature is controlled at approximately 450°C to reduce the risk of high-valence titanium active species forming volatile TiCl4; the electrolyte on the negative electrode side mainly involves Ti. 2+ / Ti 3+ Due to the relatively low risk of valence changes and volatilization, this embodiment preferably uses 1 ton of molten salt electrolyte on the negative electrode side for high-temperature thermal storage cycling. Based on the molten salt specific heat capacity of 1.20 kJ / (kg·K) and a temperature difference of 300℃, the system can theoretically store approximately 100 kWh of thermal energy; considering the heat exchange efficiency and pipeline heat loss, the system can achieve effective thermal storage and release of 90.5 kWh in a single cycle. Meanwhile, the total electroactive titanium species concentration in both the positive and negative electrode electrolytes is 2 mol Ti / kg, calculated as titanium element. The electroactive titanium species on the positive electrode side include Ti... 3+ / Ti 4+ Redox pairs based on valence state changes; electroactive titanium species on the negative electrode side include Ti 2+ / Ti 3+ Redox pairs based on valence state changes. Furthermore, LiF is added to the positive electrode electrolyte as a fluorine complexing agent; the amount of LiF added is 4 mol / kg of molten salt electrolyte, causing F... - The molar ratio of total electroactive titanium species, calculated as titanium, is 2:1. The system voltage can reach 1.6 V, and the theoretical electrical energy storage capacity is approximately 85.8 kWh. After actual charge-discharge operation, the coulombic efficiency is 96.2%, corresponding to an energy efficiency of 83.6%, and the effective electrical energy output in a single cycle is 71.7 kWh.

[0059] In this embodiment, the electroactive titanium species are introduced in situ by reacting TiCl4 with metallic titanium in a molten salt to generate TiCl3: Under an inert atmosphere, metallic titanium is placed in a molten salt electrolyte, and TiCl4 is introduced into the molten salt electrolyte in a gaseous phase to generate TiCl3 in situ. The remaining TiCl4 is discharged from the system, and the metallic titanium is removed. Thus, both the positive and negative electrodes are titanium-containing mother salts of NaCl-MgCl2-KCl-TiCl3. After electrochemical pretreatment, the resulting titanium-containing molten salt forms a TiCl3-based structure on the positive electrode side. 3 + / Ti 4+ A redox pair based on valence state change forms a Ti-based structure on the negative electrode side. 2+ / Ti 3+ Redox pairs based on valence state changes.

[0060] Test results show that this system can achieve a high level of both electrical and thermal energy storage under single molten salt medium conditions. Specifically, considering the system as a whole, with approximately 2 tons of molten salt electrolyte for both positive and negative electrodes, the system can achieve a combined effective electrothermal energy of approximately 162.2 kWh per cycle. The thermal energy portion is stored as sensible heat from the molten salt, and its further conversion into electrical energy output depends on the thermoelectric conversion efficiency of the external thermal power generation device. These results indicate that the single molten salt in this system functions as both an electrochemical energy storage medium and a thermal storage medium, significantly improving the overall energy storage density of the system and reducing equipment redundancy and cross-medium heat transfer losses caused by independent thermal storage media and independent thermal storage loops.

[0061] Furthermore, during 15 consecutive co-charge-discharge cycles, the inlet temperature of the electrochemical reactor stack remained stable at 450±20℃, and the temperature of the second storage tank remained in the range of 730~750℃. No obvious deactivation of active materials, abnormal deposition, or circulation blockage was observed. This indicates that the four-tank dual-temperature structure can effectively achieve decoupled operation of the high-temperature thermal storage unit and the lower-temperature reactor stack unit, which is beneficial to ensuring the life of the reactor stack and the long-term operational stability of the system. This verifies the feasibility of the technical solution of this application in the field of co-thermal power storage.

[0062] In addition, this system has significant characteristics of flow batteries: the electrochemical reaction stack and the molten salt storage tank are set separately, and the electrolyte actively circulates between the storage tank and the stack through a circulation pump. The energy storage capacity is independently determined by the volume of the storage tank and the concentration of active materials in the electrolyte, and the capacity can be flexibly expanded without changing the stack specifications. In contrast, the electrolyte and electrode materials of existing molten salt batteries are fixed inside the battery casing, and the energy storage capacity is limited by the volume of the casing. Capacity expansion must be achieved by increasing the number of batteries or the number of stacked layers.

[0063] Comparative Example 1 The same electrochemical reactor, the same molten salt electrolyte composition and the same active material concentration as in Example 1 were used, but no second storage tank was provided. Instead, external heat was stored in the molten salt of the first storage tank, and the temperature of the first storage tank was maintained at 450°C.

[0064] The single-tank constant temperature (450℃) operation mode adopted in Comparative Example 1 is essentially similar to the thermal management strategy of existing general molten salt batteries (such as sodium-sulfur batteries and liquid metal batteries), that is, it only maintains the minimum operating temperature required for electrochemical reaction, without actively utilizing the heat capacity of molten salt for high-density storage of external heat energy.

[0065] The results show that, compared with Comparative Example 1, this system combines the scalability of flow batteries with a thermal-electric decoupled dual-temperature thermal storage design, adding 90.5 kWh of effective thermal energy storage while maintaining the electrochemical energy storage function. This breaks through the technical bottleneck of existing molten salt batteries, which only have a single electrical energy storage function and limited capacity expansion.

[0066] Comparative Example 2 The same electrochemical reactor, the same molten salt electrolyte composition and the same active material concentration as in Example 1 were used, but no second storage tank was set up. Instead, external heat was stored in the molten salt of the first storage tank, and the temperature of the first storage tank was raised from 450°C to 750°C.

[0067] Test results show that Comparative Example 2 has serious defects compared to Example 1. Specifically, the Ti in the positive electrode electrolyte... 4+ High-valence titanium active species pose a risk of forming volatile TiCl4 at 750℃. Since TiCl4 is a low-boiling-point, volatile titanium chloride, it readily vaporizes from the molten salt at 750℃ and escapes into the system's gas phase, subsequently condensing or remaining in the low-temperature zone of the pipeline, causing irreversible loss of effective active material on the positive electrode side. After 5 charge-discharge cycles, the active material that can participate in Ti... 3+ / Ti 4+ The effective concentration of titanium active material in the redox reaction rapidly decreased from an initial 2.0 mol / kg to below 0.3 mol / kg, resulting in a battery capacity decay of over 80%. Simultaneously, the molten salt at 750°C caused severe corrosion to the structural materials, leading to multiple leaks after five charge-discharge cycles. In contrast, Example 1 employed a four-tank, dual-temperature design, stably controlling the operating temperature of the electrochemical reactor stack at 450°C ± 20°C. At this temperature, the vapor pressure of TiCl4 in the molten salt was reduced by approximately four orders of magnitude compared to 750°C, resulting in no loss of active material through volatilization, eliminating the need for frequent refueling, and avoiding high-temperature corrosion and pipeline blockage. The system could operate in a closed system for extended periods, significantly improving cycle life and reliability.

[0068] Example 2 The system employs the same four-tank dual-temperature thermal storage system, electrochemical reactor stack, and titanium-based molten salt electrolyte as in Example 1. The electrochemical reactor stack and the heat exchange system are connected in parallel. The electrochemical circulation loop and the heat exchange loop can be independently or simultaneously activated, thereby enabling flexible switching between charge / discharge mode, heat storage / release mode, and synergistic mode. Based on the complete 24-hour power peak-shaving demand, the system switches modes and operates according to the following sequence.

[0069] Off-peak electricity hours (20:00-5:00, 9 hours): During off-peak hours, electricity prices are lowest, and there are no external heat sources. The electrochemical reactor stack is connected to an external power source, and the system switches to charge / discharge mode, only conducting the electrochemical circulation loop while the heat exchange loop is closed. Molten salt electrolyte flows out from the first storage tank (450℃), is charged by the electrochemical reactor stack, and then returns directly to the first storage tank, forming a closed loop that does not flow through the second storage tank. The electrochemical reactor stack is charged at approximately 9.5kW, with an external power input of approximately 85.8 kWh. The Joule heat generated during charging accounts for approximately 5% of the charging energy, or approximately 4.3 kWh. This portion of heat is temporarily stored in the molten salt electrolyte in the first storage tank before the next heat storage, which can slow down the temperature drop of the first storage tank; during subsequent heat storage, it is further heated by the molten salt and then transferred to the second storage tank.

[0070] Peak Hours (8:00-11:00 and 17:00-20:00, a total of 6 hours): The power grid operates during peak electricity price periods. The electrochemical reactor stack is connected to external electrical loads, and the system switches to coordinated mode, with the electrochemical circulation loop and heat exchange loop connected in parallel. Molten salt electrolyte flows out from the second storage tank, releases heat energy to the thermal power generation unit through the heat exchange system, and replenishes the peak electricity demand through thermal power generation. It then flows into the electrochemical reactor stack, converting the chemical energy stored in the molten salt electrolyte into electrical energy, which is output to the external electrical loads and then stored in the first storage tank. The electrochemical reactor stack discharges at approximately 12.0 kW, operating for 3 hours each during the morning and evening peak hours, with a total discharge of approximately 71.7 kWh. This corresponds to an output of 85.8 kWh of output energy at an energy efficiency of 83.6% during off-peak charging input. During the discharge process, the active materials remain reversible.

[0071] During the flat-period thermal storage period (5:00-8:00 and 11:00-17:00, a total of 9 hours): Electricity prices are stable, and solar thermal resources are abundant. The system switches to thermal storage and release mode, with only the heat exchange circuit open. Molten salt electrolyte flows out from the first storage tank, absorbs external solar heat through the heat exchanger, and is heated to 750°C before entering the high-temperature tank. During this period, 1 ton of molten salt is heated from 450°C to 750°C, theoretically storing approximately 100 kWh of heat. Considering heat exchange efficiency and pipeline heat loss, a single cycle can achieve effective thermal storage and release of approximately 90.5 kWh. In this mode, the electrochemical reactor stack is in an open-circuit state with no molten salt flowing through, and the concentration of active materials remains constant.

[0072] Test results show that after 30 complete 24-hour peak-shaving cycles, the output electrical energy in the 30th cycle decreased by less than 2% compared to the initial cycle; the coulombic efficiency remained above 95.8%, and the energy efficiency was above 83.0%. These results demonstrate that, through on-demand switching between three modes, this system achieves coordinated storage and release of electrical and thermal energy during a complete 24-hour peak-shaving cycle, thereby improving the overall energy utilization efficiency of the system.

[0073] Comparative Example 3 The system uses the same four-tank dual-temperature system and molten salt electrolyte as in Example 2, but the electrochemical reactor and the heat exchange system are connected in series. That is, the electrochemical circulation loop and the heat exchange loop are the same and neither loop can be independently connected. The system can only operate in a single cooperative mode: at any time, the molten salt electrolyte flows through the electrochemical reactor and the heat exchange system simultaneously.

[0074] After 30 complete 24-hour peak-shaving cycles, the shell and internal flow channels of the electrochemical reactor stack in this comparative example showed significant pitting corrosion compared to Example 2. The sealing surfaces lost their airtightness due to the accumulation of corrosion products, leading to molten salt leakage and loss of active materials through volatilization. This is because in the system of Comparative Example 3, the molten salt electrolyte flows through the electrochemical reactor stack regardless of whether charging or discharging is required. Consequently, the electrochemical reactor stack is subjected to prolonged exposure to molten salt at 450°C, resulting in corrosion of the electrochemical reactor stack by the molten salt electrolyte.

[0075] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A molten salt flow battery electrothermal co-storage system, characterized in that, include: An electrochemical reactor (100) is used for electrochemical redox reactions; A molten salt energy storage tank system (200) includes a first storage tank and a second storage tank. The first storage tank includes a positive electrode first storage tank (201) and a negative electrode first storage tank (202). The second storage tank includes a positive electrode second storage tank (203) and a negative electrode second storage tank (204). The positive electrode molten salt electrolyte circulates between the positive electrode first storage tank (201) and the positive electrode second storage tank (203), and the negative electrode molten salt electrolyte circulates between the negative electrode first storage tank (202) and the negative electrode second storage tank (204). The holding temperature of the first storage tank is 200-300°C lower than that of the second storage tank. A fluid delivery piping system (300) is used to drive the molten salt electrolyte to circulate between the components; A heat exchange system (500) is connected between the first storage tank and the second storage tank to exchange heat between the molten salt electrolyte and an external heat source or external heat user to form a heat exchange circuit. The electrochemical reactor (100) is connected to the molten salt energy storage tank system (200) to form an electrochemical loop; The molten salt serves as both the electrolyte for electrochemical energy storage and the heat storage medium for thermal energy storage.

2. The molten salt flow battery electrothermal co-storage system of claim 1, wherein: The molten salt flow battery electrothermal co-storage system includes an inert gas sealing system (400); the inert gas sealing system (400) is connected to the gas phase space of the molten salt energy storage tank system (200) and is used to provide a positive pressure inert atmosphere.

3. The molten salt flow battery electrothermal co-storage system according to claim 1 or 2, characterized in that: The molten salt in the molten salt electrolyte is a eutectic salt composed of at least one of alkali metal halide salts and alkaline earth metal halide salts; the eutectic point of the molten salt is below 450°C.

4. The fused salt flow battery electrothermal co-storage system according to claim 1 or 2, characterized in that: The electroactive ions in the positive and negative molten salt electrolyte are homologous elements; the electroactive ions in the positive molten salt electrolyte include M 3+ and M 4+ ; the electroactive ions in the negative molten salt electrolyte include M 2+ and M 3+ ; the M is one of Ti, Cr, Mn, Fe, Co, Ni, and V.

5. The fused salt flow battery electrothermal co-storage system according to claim 1 or 2, characterized in that: The electrochemical reactor (100) employs a non-ion-selective isolation structure, which includes one of a porous ceramic separator or a porous insulating composite material.

6. The fused salt flow battery electrothermal co-storage system according to claim 1 or 2, characterized in that: The temperature of the first storage tank is maintained at 450-500℃; the temperature of the second storage tank is maintained at 700-750℃.

7. The fused salt flow battery electrothermal co-storage system according to claim 1 or 2, characterized in that: The molten salt storage tank system (200) and the fluid transport pipeline system (300) each independently include at least one heat tracing device and a heat insulation device; And / or, the fluid delivery pipeline system (300) includes a circulation pump that provides a power source; the circulation pump is disposed on a pipeline connecting the heat exchange system (500), the first storage tank and the electrochemical reactor (100).

8. The fused salt flow battery electrothermal co-storage system according to claim 1 or 2, characterized in that: The fluid delivery piping system (300) includes control valves for switching the following operating modes: Charge / discharge mode: The electrochemical circulation loop is activated, and the molten salt electrolyte circulates between the molten salt energy storage tank system (200) and the electrochemical reactor (100); when the electrochemical reactor (100) is connected to an external power source, electrical energy is converted into chemical energy and stored in the molten salt electrolyte to complete the charging process; when the electrochemical reactor (100) is connected to an external electrical load, the chemical energy of the molten salt electrolyte is converted into electrical energy to complete the discharging process. Heat storage and release mode: When the heat exchange circuit is turned on, the molten salt electrolyte absorbs heat energy from the external heat source from the first storage tank through the heat exchange system (500) and flows into the second storage tank to complete the heat storage process; the molten salt electrolyte releases heat energy from the second storage tank to the external heat user through the heat exchange system (500) and then flows into the first storage tank to complete the heat release process. Synergistic mode: The electrochemical circulation loop and the heat exchange loop are simultaneously connected. The molten salt electrolyte flows from the first storage tank to the electrochemical reactor (100), and then flows into the second storage tank after absorbing the heat energy from the external heat source through the heat exchange system (500), thus completing the synergistic charging / discharging and heat storage process; the molten salt electrolyte flows from the second storage tank to the heat exchange system (500), and then flows into the first storage tank through the electrochemical reactor (100), thus completing the synergistic charging / discharging and heat release process.

9. The molten salt flow battery electrothermal co-storage system according to claim 1 or 2, characterized in that: The external heat source includes at least one of the following: solar thermal power plant heat energy, nuclear power plant heat energy, or industrial heat source.

10. A method for co-storing electrothermal energy, utilizing the molten salt flow battery co-storage system according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Start the system and, according to the charging, discharging and heat storage requirements, switch the control valves of the fluid transport pipeline system to the corresponding working mode, so that the electrochemical circulation loop and the heat exchange loop are individually or simultaneously activated. S2. The fluid transport pipeline system drives the molten salt electrolyte to flow in the connected circuit, realizing individual charging and discharging, individual heat storage and release, or charging and discharging and heat storage and release in synergy.

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