Terpyridine iron complex and its preparation method and its application in photovoltaic cell temperature control and flow battery energy storage

Abstract

The present invention relates to a terpyridine iron complex, a preparation method thereof, and applications in photovoltaic cell temperature control and liquid flow battery energy storage. Existing iron-based liquid flow batteries have the problem of generating iron dendrites during the charging process. The present invention provides a terpyridine iron complex which is a 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex. A photovoltaic cell-liquid flow battery coupling system is constructed based on the terpyridine iron complex. The terpyridine iron complex can be used as a negative electrode active material of a liquid flow battery in the photovoltaic cell-liquid flow battery coupling system, and can also exchange heat with a photovoltaic panel when passing through a flow field plate on the back of a photovoltaic module, thereby controlling the temperature of the photovoltaic panel. The present invention utilizes the nitrogen atom on the pyridine ring in terpyridine to coordinate with iron ions to form a stable complex, which effectively solves the problem of iron dendrite formation, and the application process does not require the use of organic solvents, which is safer and more environmentally friendly.

Description

Technical Field

[0001] The present invention relates to a complex, in particular to a terpyridine iron complex and a preparation method thereof, and applications in photovoltaic cell temperature control and liquid flow battery energy storage. Background Art

[0002] Iron-based flow batteries, with their low cost and environmental friendliness, have attracted widespread attention in the field of energy storage technology. The negative electrode of a traditional iron-based flow battery is iron metal. During discharge, the iron metal oxidizes into iron ions, which become free in the electrolyte. During charging, the free iron ions are reduced back to iron atoms. After forming small nuclei, iron atoms continue to deposit unevenly on the negative electrode surface, forming branch-like iron crystals called iron dendrites.

[0003] These iron dendrites are prone to breakage, producing unusable "dead iron" that reduces battery capacity. In severe cases, the iron dendrites may pierce the separator and contact the positive electrode, causing a short circuit and posing a safety hazard.

[0004] Therefore, it is necessary to propose new measures to overcome the above-mentioned defects. Summary of the Invention

[0005] The purpose of the present invention is to provide a terpyridine iron complex and its preparation method and application in photovoltaic cell temperature control and liquid flow battery energy storage, so as to solve the problem of iron dendrites generated in existing iron-based liquid flow batteries during charging.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The terpyridine iron complex is a 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex having the structure:

[0008]

[0009] On the other hand, a method for preparing the terpyridine iron complex is provided, the method comprising:

[0010] Mix dimethylformamide and thionyl chloride, then add 2-pyridinecarboxylic acid and heat to react; after cooling, add ethanol and wash to obtain a solid powder, dissolve and separate the organic phase, and extract to obtain 4-chloro-pyridine-2-carboxylic acid ethyl ester;

[0011] A mixture of ethyl 4-chloro-pyridine-2-carboxylate and acetone was diluted with anhydrous tetrahydrofuran, and added dropwise to a suspension of NaH in anhydrous tetrahydrofuran, and refluxed to obtain 4-chloro-pyridine-2-(1,3-butanedione);

[0012] 4-Chloro-pyridine-2-carboxylic acid ethyl ester, 4-chloro-pyridine-2-(1,3-butanedione) and ammonium acetate were mixed, anhydrous ethanol was used as a solvent, and refluxed for reaction; then recrystallized to obtain 4,4"-dichloro-4'-hydroxy-2,2':6',2'-terpyridine;

[0013] 4,4"-dichloro-4'-hydroxy-2,2':6',2'-terpyridine and aminosulfonic acid were mixed, the pH was adjusted to neutral, dimethylformamide was used as a solvent, and the mixture was stirred with triethylamine at room temperature to cause a nucleophilic substitution reaction, and recrystallized to obtain 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid;

[0014] 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid is dissolved in a tetrahydrofuran aqueous solution, and ferric chloride hexahydrate is dissolved in water; the ferric chloride hexahydrate aqueous solution is added dropwise to the tetrahydrofuran aqueous solution of 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid, and the mixture is refluxed to obtain a 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex.

[0015] On the other hand, the present invention provides a use of the terpyridine iron complex in liquid flow battery energy storage, wherein the terpyridine iron complex is used as a negative electrode active material of a liquid flow battery in a photovoltaic cell-liquid flow battery coupling system.

[0016] On the other hand, the application of the terpyridine iron complex as described in photovoltaic cell temperature control is provided. In the photovoltaic cell-liquid flow battery coupling system, the terpyridine iron complex exchanges heat with the photovoltaic panel when flowing through the flow field plate on the back of the photovoltaic module, thereby controlling the temperature of the photovoltaic panel.

[0017] Furthermore, the photovoltaic cell-flow battery coupling system includes a negative electrode photovoltaic assembly, a positive electrode photovoltaic assembly, a flow battery, a negative electrode liquid storage container, and a positive electrode liquid storage container;

[0018] The negative photovoltaic assembly and the positive photovoltaic assembly both include a photovoltaic panel and a flow field plate on the back thereof;

[0019] The liquid flow battery comprises a negative electrode reaction site and a positive electrode reaction site, a liquid flow battery stack is located between the negative electrode reaction site and the positive electrode reaction site, the liquid flow battery stack is connected to a liquid flow battery power supply, and the negative electrode active material of the liquid flow battery is the terpyridine iron complex;

[0020] The negative electrode liquid storage container and the positive electrode liquid storage container are both buried underground;

[0021] The flow field plate of the negative electrode photovoltaic assembly and the negative electrode liquid storage container form a circulation through a pipeline. A branch is set on the pipeline from the negative electrode liquid storage container to the flow field plate of the negative electrode photovoltaic assembly and connected to the negative electrode reaction site. The photovoltaic panel of the negative electrode photovoltaic assembly is connected to the liquid flow battery stack through a cable.

[0022] The flow field plate of the positive photovoltaic assembly and the positive liquid storage container form a circulation through a pipeline. A branch is set on the pipeline from the positive liquid storage container to the flow field plate of the positive photovoltaic assembly and connected to the positive electrode reaction site. The photovoltaic panel of the positive photovoltaic assembly is connected to the liquid flow battery stack through a cable.

[0023] Furthermore, a power pump is provided in the pipeline circulation between the flow field plate of the negative photovoltaic assembly and the negative electrode liquid storage container, and in the pipeline circulation between the flow field plate of the positive photovoltaic assembly and the positive electrode liquid storage container.

[0024] Furthermore, two branches are provided on the pipeline from the negative electrode liquid storage container to the flow field plate of the negative electrode photovoltaic assembly, respectively connected to the negative electrode reaction site, and a shut-off valve is provided on one of the branches;

[0025] Two branches are provided on the pipeline from the positive electrode liquid storage container to the flow field plate of the positive electrode photovoltaic assembly, respectively connected to the positive electrode reaction site, and a stop valve is provided on one of the branches.

[0026] Furthermore, the negative electrode liquid storage container includes a shallow buried negative electrode liquid storage container and a deep buried negative electrode liquid storage container, and the flow field plate of the negative electrode photovoltaic assembly is connected to two pipeline switch valves through pipelines on both sides, and is respectively connected to the shallow buried negative electrode liquid storage container and the deep buried negative electrode liquid storage container;

[0027] The positive electrode liquid storage container includes a shallow buried positive electrode liquid storage container and a deep buried positive electrode liquid storage container. The flow field plate of the positive electrode photovoltaic component is connected to two pipeline switch valves through pipelines on both sides, and is respectively connected to the shallow buried positive electrode liquid storage container and the deep buried positive electrode liquid storage container.

[0028] Alternatively, the negative electrode liquid storage container is a deeply buried negative electrode liquid storage container;

[0029] The positive electrode liquid storage container is a shallow buried positive electrode liquid storage container.

[0030] Furthermore, the terpyridine iron complex exchanges heat with the photovoltaic panel when flowing through the flow field plate;

[0031] The terpyridine iron complex undergoes an oxidation-reduction reaction in the negative electrode reaction site and stores electrical energy;

[0032] The electrical energy generated by the photovoltaic panel is stored in the flow battery stack through the cable.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention provides a terpyridine iron complex, a preparation method thereof, and its application in photovoltaic cell temperature control and liquid flow battery energy storage. The nitrogen atoms on the pyridine ring in terpyridine are used to coordinate with iron ions to form a stable complex, and the iron ions are complexed in the terpyridine molecular skeleton, making it difficult for them to escape to form "free" iron ions, thereby avoiding uneven deposition of reduced iron ions during charging and effectively solving the problem of iron dendrite formation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying any creative work, they can also obtain drawings of other embodiments based on these drawings.

[0036] Figure 1 This is a structural diagram of Example 1 of the present invention.

[0037] Figure 2 This is a structural diagram of Example 2 of the present invention.

[0038] Figure 3 Schematic diagrams of different liquid storage structures of the liquid storage part in various embodiments of the present invention. In the figure, a is a cylindrical liquid storage tank, b is a vertical serpentine pipe liquid storage system, c is a horizontal serpentine pipe liquid storage system, and d is a spiral pipe liquid storage system.

[0039] Figure 4 This is an enlarged view of the structure of the photovoltaic panel and flow field plate of the present invention.

[0040] Figure 5 Schematic diagram of the flow field shape of the flow field plate of the present invention. In the figure, A is a parallel flow channel and B is a serpentine flow channel.

[0041] Figure 6 This is a graph showing the battery capacity change during the first 50 cycles of a flow battery using 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex as the negative electrode active material.

[0042] Figure 7 The first 50 charge-discharge cycles of a flow battery using 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex as the negative electrode active material are shown.

[0043] Figure 8The coulombic efficiency, voltage efficiency, and energy efficiency curves for the first 50 cycles of a flow battery using 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex as the negative electrode active material.

[0044] Figure 9 This is a comparative data chart of the present invention applied to photovoltaic cell temperature control.

[0045] The symbols in the figure are:

[0046] 001-rectifier inverter, 010-photovoltaic panel, 020-flow field plate, 030-power pump, 040-pipeline switch valve, 080-stop valve, 090-negative electrode reaction site, 091-positive electrode reaction site, 100-shallow buried negative electrode liquid storage container, 105-deep buried negative electrode liquid storage container, 110-shallow buried positive electrode liquid storage container, 105-deep buried negative electrode liquid storage container, 120-flow battery stack, 121-flow battery power supply, 130-cable, 170-electrolyte pipeline;

[0047] 050-first negative electrode pipeline, 060-second negative electrode pipeline, 070-third negative electrode pipeline, 072-fourth negative electrode pipeline, 073-fifth negative electrode pipeline;

[0048] 055-first positive electrode pipeline, 065-second positive electrode pipeline, 075-third positive electrode pipeline, 077-fourth positive electrode pipeline, 078-fifth positive electrode pipeline. DETAILED DESCRIPTION

[0049] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0050] In the description of this patent, it is to be understood that all technical and scientific terms used have the same meaning as those commonly understood by those skilled in the art to which this patent belongs. When there is a contradiction, the definitions in this specification shall prevail. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art, the reagents used in the examples are commercially available products, and the devices used in the examples are existing devices. The limitation of the means, reagents or devices cannot be understood as a limitation of this patent, and the means, reagents or devices of the same type that solve the same technical problems are all within the scope of protection of this patent.

[0051] In the description of this patent, it should be understood that when an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood to specifically disclose all ranges formed by any pairing of any upper range limit or preferred value with any lower range limit or preferred value, regardless of whether the range is disclosed separately. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0052] In the description of this patent, it should be understood that multiple steps are involved in the description of the method, which should not be understood as a limitation on the order of the method steps. Technical solutions obtained by simply changing the order of the steps when solving the same technical problem are also within the scope of protection of this patent.

[0053] At the same time, in the description of the present invention, the terms "first," "second," etc. are used only to distinguish descriptions and should not be understood as indicating or implying relative importance. Of course, such terms can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0054] Inhibiting the growth of iron dendrites is the key to achieving high capacity and safe iron-based flow batteries. To solve the problem of iron dendrite growth, flow batteries can use complexes that are soluble in the electrolyte in both the oxidized and reduced states as negative electrode active materials. The positive electrode active materials of flow batteries often use potassium ferrocyanide / potassium ferrocyanide with excellent stability. – It can form a strong coordination bond with iron ions. Similarly, the negative electrode can also use a suitable stable complex as an active material. The present invention intends to use the nitrogen atom on the pyridine ring in terpyridine to coordinate with iron ions to form a stable complex, complexing the iron ions in the terpyridine molecular skeleton, making it difficult for them to escape to form "free" iron ions, thereby avoiding the uneven deposition of iron ions being reduced during the charging process, thereby avoiding the formation of iron dendrites during the charging process, resulting in reduced capacity and even battery short circuit. Specifically, the present invention provides a terpyridine iron complex, specifically a 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex, the structure of which is:

[0055]

[0056] The terpyridine-iron complex formed by terpyridine and iron can be used as the negative electrode active material of the all-iron liquid flow battery. However, the negative electrode active material can only be dissolved in organic solvents and is almost insoluble in water. It is not only expensive, but also brings potential toxicity and safety risks such as combustion and explosion. Therefore, in the process of preparing the above-mentioned terpyridine-iron complex, in order to avoid the use of organic solvents, the present invention first synthesizes 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid, and then combines it with iron to form a 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex with better water solubility. Specifically, the preparation method of the terpyridine-iron complex comprises the following steps:

[0057] S1: Dimethylformamide (DMF) and thionyl chloride (SOCl2) were mixed, followed by the addition of 2-pyridinecarboxylic acid. The mixture was heated at 70°C for 24 hours. The mixture was cooled to room temperature, and ethanol (C2H5OH) was added and washed to obtain a solid powder. The powder was dissolved in deionized water, the pH was adjusted to neutral, the organic phase was separated, and the mixture was extracted with ethyl acetate. The solvent was evaporated to obtain ethyl 4-chloro-pyridine-2-carboxylate.

[0058]

[0059] S2: Under nitrogen, a mixture of ethyl 4-chloropyridine-2-carboxylate and acetone was diluted with anhydrous tetrahydrofuran (THF) and added dropwise to a suspension of NaH in anhydrous THF. The mixture was refluxed for 4 hours. After the reaction, the pH was adjusted to neutral to yield 4-chloro-pyridine-2-(1,3-butanedione).

[0060]

[0061] S3: Mix ethyl 4-chloropyridine-2-carboxylate, 4-chloro-pyridine-2-(1,3-butanedione), and an excess of ammonium acetate (CH3COONH4) in anhydrous ethanol as the solvent and reflux for 8 hours. After the reaction, recrystallize from anhydrous ethanol to obtain 4,4"-dichloro-4'-hydroxy-2,2':6',2'-terpyridine.

[0062]

[0063] S4: 4,4"-dichloro-4'-hydroxy-2,2':6',2'-terpyridine is mixed with aminosulfonic acid, and dimethylformamide is used as a solvent. 3-5 equivalents of triethylamine (TEA) are stirred at room temperature to cause a nucleophilic substitution reaction.

[0064] After the reaction is completed, 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid is obtained by recrystallization.

[0065]

[0066] S5: Weigh 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid and dissolve it in a tetrahydrofuran aqueous solution. Dissolve ferric chloride hexahydrate (FeCl3·6H2O) in water. Under nitrogen protection, slowly add the FeCl3·6H2O aqueous solution dropwise to the tetrahydrofuran aqueous solution of 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid (molar ratio of 1:2). Reflux the mixture to obtain an iron complex of 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid.

[0067]

[0068] The 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex obtained by the above method is an ideal complex with stable electrochemical properties and excellent water solubility. It can be used in an aqueous all-iron liquid flow battery energy storage device as a negative electrode active material. It can not only effectively avoid the formation of iron dendrites, but also the introduced hydrophilic groups such as hydroxyl and sulfonic acid groups greatly improve the solubility of the complex in water, so that water can be used as a solvent in its preparation process, greatly reducing costs, high safety, and green and pollution-free.

[0069] Liquid flow battery energy storage technology holds enormous potential for large-scale, long-term energy storage in the solar power generation sector. In the photovoltaic power generation process, the impact of temperature on power generation efficiency, as well as the intermittent and unstable nature of sunlight, are significant obstacles hindering its development. The optimal power generation temperature for photovoltaic panels is approximately 25°C, at which they operate at peak efficiency. When the panel temperature deviates from this temperature, output power decreases. For example, in the hot summer, in regions with abundant solar resources such as Xinjiang, Qinghai, and Tibet, the highest temperature can reach 47.8°C, with the highest surface temperature exceeding 70°C. This can significantly increase the temperature of photovoltaic panels, leading to a decrease in power generation and a serious impact on power generation efficiency. Conversely, in the cold winter, the lowest temperature can reach -52.3°C, causing the temperature of photovoltaic panels to drop significantly. This is especially true when snow accumulates on the panels, significantly reducing the time they can generate electricity and lowering their efficiency. The terpyridine iron complex of the present invention can not only be used as the negative electrode active material of the liquid flow battery in the photovoltaic cell-liquid flow battery coupling system, but can also be used to control the temperature of the photovoltaic cell. In the photovoltaic cell-liquid flow battery coupling system, the terpyridine iron complex exchanges heat with the photovoltaic panel 010 when flowing through the flow field plate 020 on the back of the photovoltaic module, thereby controlling the temperature of the photovoltaic panel 010.

[0070] Based on the above application, a photovoltaic cell-liquid flow battery coupling system can be constructed. Specifically, the photovoltaic cell-liquid flow battery coupling system includes a negative photovoltaic component, a positive photovoltaic component, a flow battery, a negative electrode liquid storage container and a positive electrode liquid storage container.

[0071] In photovoltaic cell-flow battery coupling system:

[0072] 1. Both the negative and positive photovoltaic modules include a photovoltaic panel 010 and a flow field plate 020 on the back thereof. Figure 4 The photovoltaic module further includes a rectifier inverter 001 and an electrolyte pipeline 170. Figure 5 The flow channels of flow field plate 020 are designed as either parallel or serpentine channels. Parallel channels, which are numerous and connected in parallel, offer advantages such as low flow resistance and simplified manufacturing. Furthermore, parallel channels can reduce pressure loss to a certain extent, thereby improving heat exchange efficiency. Serpentine channels offer advantages such as space savings, strong adaptability, and high customization. Their tortuous paths can fully utilize limited space and accommodate complex layouts.

[0073] 2. The liquid flow battery includes a negative electrode reaction site 090 and a positive electrode reaction site 091 . A liquid flow battery stack 120 is located between the negative electrode reaction site 090 and the positive electrode reaction site 091 . The liquid flow battery stack 120 is connected to a liquid flow battery power supply 121 .

[0074] The negative electrode active material of the flow battery is a terpyridine iron complex. Electrode materials in flow batteries are selected from graphite felt, conventional graphite plates, flow channel graphite plates, glassy carbon electrodes, platinum electrodes, and iridium oxide electrodes. The diaphragm can be a cation exchange membrane (Nafion series proton exchange membrane, SPEEK membrane), an anion exchange membrane (PBI membrane), or a microporous membrane (Daramic membrane).

[0075] The terpyridine iron complex undergoes an oxidation-reduction reaction between trivalent and divalent states in the negative electrode reaction site 090:

[0076]

[0077] 3. Both the negative electrode liquid storage container and the positive electrode liquid storage container are buried underground and can be made of stainless steel, polyvinyl chloride (PVC), high-density polyethylene (HDPE), fiberglass reinforced plastic (RPM), etc. The negative electrode liquid storage container contains the electrolyte of the iron-4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid complex, and the positive electrode liquid storage container contains the electrolyte of potassium ferrocyanide / potassium ferrocyanide.

[0078] The preparation process of the negative electrode electrolyte is as follows: adding a supporting electrolyte to a 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex solution, stirring, and mixing uniformly to obtain the negative electrode electrolyte.

[0079] The preparation process of the positive electrode electrolyte is as follows: potassium ferrocyanide / potassium ferrocyanide is mixed with water to form a solution, and a supporting electrolyte is added to obtain the positive electrode electrolyte; the supporting electrolyte of the above-mentioned positive and negative electrode electrolytes is selected from KCl, NaCl, NH4Cl, KNO3, and Na2SO4.

[0080] like Figure 3 The liquid storage container can adopt different structural forms, including cylindrical liquid storage tank a, vertical serpentine pipe liquid storage system b, horizontal serpentine pipe liquid storage system c, and spiral pipe liquid storage system d, to facilitate better heat exchange with the formation.

[0081] The above structural components are connected by pipes and cables to form a photovoltaic cell-flow battery coupling system. Specifically:

[0082] The flow field plate 020 of the negative photovoltaic module and the negative electrode liquid storage container form a loop through a pipeline. A branch is set on the pipeline from the negative electrode liquid storage container to the flow field plate 020 of the negative photovoltaic module and is connected to the negative electrode reaction site 090. The photovoltaic panel 010 of the negative photovoltaic module is connected to the liquid flow battery stack 120 via cable 130. The flow field plate 020 of the positive photovoltaic module and the positive electrode liquid storage container form a loop through a pipeline. A branch is set on the pipeline from the positive electrode liquid storage container to the flow field plate 020 of the positive photovoltaic module and is connected to the positive electrode reaction site 091. The photovoltaic panel 010 of the positive photovoltaic module is connected to the liquid flow battery stack 120 via cable 130.

[0083] In the system, a power pump 030 is provided in the pipeline circulation between the flow field plate 020 of the negative photovoltaic module and the negative liquid storage container, as well as in the pipeline circulation between the flow field plate 020 of the positive photovoltaic module and the positive liquid storage container. The flow rate of the electrolyte is controlled by adjusting the pump speed of the power pump 030, thereby adjusting the heat exchange rate between the electrolyte and the photovoltaic panel.

[0084] Furthermore, the pipeline from the negative electrode liquid storage container to the flow field plate 020 of the negative photovoltaic module has two branches, each connected to the negative electrode reaction site 090. One of the branches is equipped with a shutoff valve 080. Similarly, the pipeline from the positive electrode liquid storage container to the flow field plate 020 of the positive photovoltaic module has two branches, each connected to the positive electrode reaction site 091. One of the branches is equipped with a shutoff valve 080. The electrolyte in the positive and negative electrode liquid storage containers is separated into two parts by the power pump 030. One part directly passes through the flow field plate on the back of the photovoltaic panel to control the temperature of the photovoltaic panel; the other part, under the control of the shutoff valve 080, participates in the positive and negative electrode reactions of the liquid flow battery stack, storing and releasing electrical energy.

[0085] There are three main operating processes in the above system: ① The terpyridine iron complex exchanges heat with the photovoltaic panel 010 when flowing through the flow field plate 020; ② The terpyridine iron complex undergoes an oxidation-reduction reaction in the negative electrode reaction site 090 and stores electrical energy; ③ The electrical energy generated by the photovoltaic panel 010 is stored in the liquid flow battery stack 120 through the cable 130.

[0086] During operation (1), the electrolyte of the flow battery flows through the back of the photovoltaic panel 010, controlling its temperature. During high temperatures in the summer, the panel is cooled by the liquid medium in a relatively low-temperature storage container (10-15°C, buried 3-5 meters underground). During sub-zero temperatures or snow accumulation in the winter, the panel is heated by the liquid medium in a higher-temperature storage container (20-25°C, buried 15-20 meters underground), bringing the panel to its optimal power generation temperature and achieving optimal power generation efficiency.

[0087] The positive and negative electrode liquid storage containers of the flow battery are buried at different depths underground, maintaining constant temperatures. During operation, electrolytes of varying temperatures flow through the photovoltaic panels to control their temperature and maintain optimal power generation efficiency. In summer, a low-temperature electrolyte is used to cool the high-temperature panels; in winter, a higher-temperature electrolyte is used to heat them. Finally, the electricity generated by photovoltaic power generation is stored in an aqueous all-iron flow battery using an iron complex of 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid as the negative electrode active material. This effectively addresses the issues of solar photovoltaic power generation being affected by factors such as temperature, time, and season, as well as curtailment of solar power and electricity.

[0088] According to the depth requirements, the photovoltaic cell-flow battery coupling system of the present invention can adopt two structural forms:

[0089] Example 1: The system includes four liquid storage containers

[0090] like Figure 1The negative electrode liquid storage container includes a shallow buried negative electrode liquid storage container 100 and a deep buried negative electrode liquid storage container 105. The flow field plate 020 of the negative electrode photovoltaic module is connected to two pipeline switch valves 040 through pipelines on both sides, and is respectively connected to the shallow buried negative electrode liquid storage container 100 and the deep buried negative electrode liquid storage container 105. The positive electrode liquid storage container includes a shallow buried positive electrode liquid storage container 110 and a deep buried positive electrode liquid storage container 115. The flow field plate 020 of the positive electrode photovoltaic module is connected to two pipeline switch valves 040 through pipelines on both sides, and is respectively connected to the shallow buried positive electrode liquid storage container 110 and the deep buried positive electrode liquid storage container 115.

[0091] During the hot summer months, photovoltaic panels 010 are exposed to the sun. The immense heat causes the surface temperature of photovoltaic panels 010 to rise significantly, causing them to deviate from their optimal power generation temperature of 25°C, resulting in a significant decrease in photovoltaic power generation efficiency. At this point, by switching pipeline switch valve 040, the flow battery stack 120 uses a shallowly buried (3-5 meters) negative electrode liquid storage container 100 (maintained at a temperature of 10-15°C). Under the action of power pump 030, the negative electrode electrolyte flows through pipeline loop 050→070, passing through flow field plate 020 on the back of photovoltaic panel 010, removing the waste heat generated by the photovoltaic panel and maintaining photovoltaic panel 010 at the optimal power generation temperature of 25°C, thereby achieving optimal power generation efficiency. A portion of the electrolyte is then transported to the negative electrode of the flow battery via pipeline 073, while the remaining portion flows directly to pipeline switch valve 040 via pipeline 072. The portion of electricity flowing to the flow battery's negative electrode undergoes a redox reaction at negative electrode reaction site 090. The novel flow battery negative electrode active material, 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex, undergoes a redox reaction between trivalent and divalent states, storing electrical energy. After the reaction is complete, the participating negative electrode electrolyte passes through shut-off valve 080, flows concurrently with the negative electrode electrolyte from pipeline 072, then passes through the switched pipeline switch valve 040 and, via pipeline 050, returns to the negative electrode storage container 100. Simultaneously, the electricity generated by the photovoltaic panel 010 is stored in the flow battery stack 120 via cable 130. Furthermore, the flow rate of the electrolyte in the negative electrode storage container can be controlled by adjusting the pump speed of the power pump 030, thereby controlling the heat exchange rate between the electrolyte and the photovoltaic panel. The flow rate of the electrolyte participating in the flow battery's negative electrode reaction can be adjusted by controlling shut-off valve 080.

[0092] During cold winter months, the temperature of photovoltaic panel 010 drops significantly, deviating from its optimal power generation temperature of 25°C, resulting in a decrease in photovoltaic power generation efficiency. At this time, by switching pipeline switch valve 040, the flow battery stack 120 uses a deep-buried (15-20 meters) negative electrode liquid storage container 105 (where the temperature is maintained at 20-25°C year-round). Under the action of power pump 030, the negative electrode electrolyte in the container flows through pipeline loop 060→070, passing through flow field plate 020 on the back of photovoltaic panel 010. Heat from the negative electrode electrolyte is transferred to photovoltaic panel 010 through heat exchange, raising the temperature of photovoltaic panel 010 and maintaining the optimal power generation temperature of 25°C, thereby maintaining its optimal power generation efficiency. A portion of the electrolyte is then transported to the negative electrode of the flow battery via pipeline 073; the remaining portion flows directly to pipeline switch valve 040 via pipeline 072. The portion of electricity flowing to the flow battery's negative electrode undergoes a redox reaction at negative electrode reaction site 090. The novel flow battery negative electrode active material, 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex, converts between trivalent and divalent states, enabling electrical energy storage. After the reaction is complete, the electrolyte involved in the reaction passes through shut-off valve 080, flows parallel to the negative electrode electrolyte from 072, and then passes through the switching pipeline switch valve 040, through pipeline 060, and finally returns to the negative electrode liquid storage container 105. Simultaneously, the electricity generated by the photovoltaic panel 010 is stored in the flow battery stack 120 via cable 130. The flow rate of the electrolyte in the negative electrode liquid storage container can be controlled by adjusting the pump speed of the power pump 030, thereby controlling the heat exchange rate between the electrolyte and the photovoltaic panel. The flow rate of the electrolyte involved in the flow battery's negative electrode reaction can be adjusted by controlling shut-off valve 080.

[0093] The operating principle of the positive electrode part is the same as that of the negative electrode part mentioned above.

[0094] Example 2: The system includes two liquid storage containers

[0095] like Figure 2 The negative electrode liquid storage container is a deeply buried negative electrode liquid storage container 105 (the temperature of which is maintained at 20-25°C all year round), and the positive electrode liquid storage container is a shallowly buried positive electrode liquid storage container 110 (the temperature of which is maintained at 10-15°C all year round).

[0096] Taking the negative electrode operation as an example, during the hot summer months, the intense heat from the sun's scorching sun causes the surface temperature of the photovoltaic panel 010 to rise significantly. This causes the power generation to deviate from the optimal power generation temperature of 25°C during photovoltaic power generation, resulting in a significant decrease in power generation efficiency. The electrolyte in the negative electrode reservoir, driven by a power pump 030, circulates through a pipe loop 060, passing through the flow field plate 020 on the back of the photovoltaic panel 010. This removes the waste heat generated by the photovoltaic panel, maintaining the optimal power generation temperature of 25°C and, in turn, achieving optimal power generation efficiency. A portion of the electrolyte is then transported to the negative electrode of the flow battery via pipe 063; the remaining portion flows directly to the negative electrode reservoir via pipe 062. The portion flowing to the negative electrode of the liquid flow battery undergoes an oxidation-reduction reaction at the negative electrode reaction site 090. The new liquid flow battery negative electrode active material 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex undergoes an oxidation-reduction reaction between trivalent and divalent, realizing the storage of electrical energy. After the reaction is completed, the electrolyte participating in the reaction passes through the shut-off valve 080 and flows in parallel with the negative electrode electrolyte from 062 and returns to the negative electrode storage container 105. Finally, the electrical energy generated by the photovoltaic panel 010 is stored in the liquid flow battery stack 120 through the cable 130. At the same time, the flow rate of the electrolyte in the negative electrode storage container can be controlled by adjusting the pump speed of the power pump 030, thereby controlling the heat exchange rate between the electrolyte and the photovoltaic panel. The speed of the electrolyte participating in the liquid flow battery negative electrode reaction can be adjusted by controlling the shut-off valve 080.

[0097] The operation process of the positive electrode part is the same as described above, the difference is that the temperature (10-15°C) of the positive electrode liquid storage container 110 buried shallower (3-5 meters) is lower than the temperature (20-25°C) of the negative electrode liquid storage container 100 buried deeper (15-20 meters), so that the cooling effect on the photovoltaic panel 010 is more obvious.

[0098] During cold winter months, the temperature of photovoltaic panel 010 drops significantly, causing photovoltaic power generation to deviate from the optimal power generation temperature of 25°C. This significantly reduces power generation efficiency during photovoltaic power generation. Taking the negative electrode operation process as an example, the negative electrode electrolyte in the negative electrode storage container 105, which is buried deep (15 to 20 meters) and maintains a temperature of 20 to 25°C year-round, flows through the flow field plate 020 on the back of photovoltaic panel 010 through pipeline loop 060 under the action of power pump 030. Heat from the negative electrode electrolyte is transferred to photovoltaic panel 010 through heat exchange, raising the temperature of photovoltaic panel 010 and maintaining the optimal power generation temperature of 25°C, thereby maintaining the optimal power generation efficiency of photovoltaic panel 010. A portion of the electrolyte is then transported to the negative electrode of the flow battery through pipeline 063; the other portion flows directly to the negative electrode storage container 105 through pipeline 062. The part flowing to the negative electrode of the liquid flow battery undergoes an oxidation-reduction reaction in the negative electrode reaction site 090, and the new liquid flow battery negative electrode active material 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex is converted between trivalent and divalent to achieve electrical energy storage. After the reaction is completed, the electrolyte participating in the reaction passes through the shut-off valve 080 and flows in parallel with the negative electrode electrolyte from 062 and returns to the negative electrode storage container 105. Finally, the electrical energy generated by the photovoltaic panel 010 is stored in the liquid flow battery stack 120 through the cable 130. At the same time, The flow rate of the electrolyte in the negative electrode storage container can be controlled by adjusting the pump speed of the power pump 030, thereby controlling the heat exchange rate between the electrolyte and the photovoltaic panel. The speed of the electrolyte participating in the negative electrode reaction of the liquid flow battery can be adjusted by controlling the shut-off valve 080. The operation process of the positive electrode is the same as described above, except that the temperature of the negative electrode storage container 100 buried deeper (15-20 meters) (20-25°C) is higher than the temperature of the positive electrode storage container 110 buried shallower (3-5 meters) (10-15°C), resulting in a more significant warming effect on the photovoltaic panel 010.

[0099] Example 1 and Example 2 are suitable for different operational requirements. Example 1 requires the use of four liquid storage containers, multiple valves, and more pipes. Regardless of the season, the electrolyte in the positive and negative liquid storage containers has the same effect on cooling (increasing) the temperature of the photovoltaic panels, which is conducive to achieving system temperature control of multiple photovoltaic panels at the same time to achieve the maximum power generation efficiency of the entire system. Example 2 is cheaper than Example 1, only two liquid storage containers are required, and no complicated piping design, valves, and other devices are required. In actual application, the selection can be made by comprehensively considering factors such as photovoltaic power generation efficiency, burial depth of liquid storage containers, system construction cost, and site selection.

[0100] The iron dendrites produced during the operation of the iron-based flow battery will cause the battery capacity to decay rapidly. Figure 6, by calculation, the battery capacity of the first 50 cycles of the liquid flow battery using 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex as the negative electrode active material of the present invention is maintained at 7.82mAh within 50 cycles without attenuation, which proves that the present invention solves the iron dendrite problem.

[0101] The present invention can be applied to negative electrode active materials of liquid flow batteries. Figure 7 The first 50 charge-discharge curves of a flow battery using 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex as the negative electrode active material are shown. Figure 8 This is a graph showing the coulombic efficiency, voltage efficiency, and energy efficiency of the battery in the first 50 cycles.

[0102] Figure 9 Comparative data on the present invention's use of photovoltaic cell temperature control: (a) compares the panel temperature before and after cooling using the present invention from 8:00 AM to 6:00 PM in summer; (b) compares the panel temperature before and after cooling from 8:00 AM to 6:00 PM in winter. This demonstrates that the present invention can control the panel temperature at approximately 25°C, maintaining optimal power generation efficiency.

[0103] In summary, the present invention provides a 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex, which is a new type of negative electrode active material for liquid flow batteries. Among them, not only is the iron element low in cost, high in safety, and has mild reaction conditions, but also no dendrites are generated during the charging process and the cycle life is long. Using 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid as a ligand can effectively solve the problems of cross-contamination of the existing positive and negative active materials in all-iron liquid flow batteries, and the need to inhibit the formation of iron hydroxide precipitation under alkaline conditions. In addition, hydroxyl and sulfonic acid groups, as hydrophilic groups, can significantly improve the solubility of negative electrode active materials in water. Using water as a solvent can reduce costs, increase safety, and be green and environmentally friendly.

[0104] The photovoltaic cell-liquid flow battery coupling system provided by the present invention integrates photovoltaic, energy storage, and temperature control functions. It can achieve efficient temperature control while storing energy. The heat exchange rate can be controlled by adjusting the pump speed to maintain or stabilize the optimal power generation efficiency of the solar photovoltaic cell. In addition, this device changes the unstable and highly random power generation characteristics of traditional solar photovoltaic cells. It uses a liquid flow battery with 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid as the negative electrode active material for energy storage. It has outstanding advantages such as high safety, long cycle life, and low cost. The battery capacity can also be controlled by adjusting the concentration or volume of the liquid storage container.

[0105] The above examples are used to illustrate the present invention, which are only used to help understand the present invention and are not intended to limit the present invention. Those skilled in the art can make several simple deductions, modifications or substitutions based on the concept of the present invention.

Claims

1. A terpyridine iron complex, characterized in that: The terpyridine iron complex is a 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex, and the structure is:

2. The method for preparing the terpyridine iron complex according to claim 1, wherein: The method comprises: Mix dimethylformamide and thionyl chloride, then add 2-pyridinecarboxylic acid and heat to react; after cooling, add ethanol and wash to obtain a solid powder, dissolve and separate the organic phase, and extract to obtain 4-chloro-pyridine-2-carboxylic acid ethyl ester; A mixture of ethyl 4-chloro-pyridine-2-carboxylate and acetone was diluted with anhydrous tetrahydrofuran, and added dropwise to a suspension of NaH in anhydrous tetrahydrofuran, and refluxed to obtain 4-chloro-pyridine-2-(1,3-butanedione); 4-Chloro-pyridine-2-carboxylic acid ethyl ester, 4-chloro-pyridine-2-(1,3-butanedione) and ammonium acetate were mixed, anhydrous ethanol was used as a solvent, and refluxed for reaction; then recrystallized to obtain 4,4"-dichloro-4'-hydroxy-2,2':6',2'-terpyridine; 4,4"-dichloro-4'-hydroxy-2,2':6',2'-terpyridine and aminosulfonic acid were mixed, the pH was adjusted to neutral, dimethylformamide was used as a solvent, and the mixture was stirred with triethylamine at room temperature to cause a nucleophilic substitution reaction, and recrystallized to obtain 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid; 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid is dissolved in a tetrahydrofuran aqueous solution, and ferric chloride hexahydrate is dissolved in water; the ferric chloride hexahydrate aqueous solution is added dropwise to the tetrahydrofuran aqueous solution of 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid, and the mixture is refluxed to obtain a 4'-hydroxy-2,2':6',2'-terpyridine-4,4"-diaminosulfonic acid iron complex.

3. The use of the terpyridine iron complex according to claim 1 in liquid flow battery energy storage, characterized in that: The terpyridine iron complex is used as a negative electrode active material of a flow battery in a photovoltaic cell-flow battery coupling system.

4. The use of the terpyridine iron complex according to claim 1 in photovoltaic cell temperature control, characterized in that: In a photovoltaic cell-liquid flow battery coupling system, the terpyridine iron complex exchanges heat with the photovoltaic panel (010) when flowing through the flow field plate (020) on the back of the photovoltaic module, thereby controlling the temperature of the photovoltaic panel (010).

5. The use according to claim 3 or 4, characterized in that: The photovoltaic cell-liquid flow battery coupling system includes a negative electrode photovoltaic assembly, a positive electrode photovoltaic assembly, a liquid flow battery, a negative electrode liquid storage container and a positive electrode liquid storage container; The negative electrode photovoltaic assembly and the positive electrode photovoltaic assembly both include a photovoltaic panel (010) and a flow field plate (020) on the back thereof; The liquid flow battery comprises a negative electrode reaction site (090) and a positive electrode reaction site (091); a liquid flow battery stack (120) is located between the negative electrode reaction site (090) and the positive electrode reaction site (091); the liquid flow battery stack (120) is connected to a liquid flow battery power source (121); and the negative electrode active material of the liquid flow battery is the terpyridine iron complex; The negative electrode liquid storage container and the positive electrode liquid storage container are both buried underground; The flow field plate (020) of the negative electrode photovoltaic assembly and the negative electrode liquid storage container form a circulation through a pipeline, a branch is set on the pipeline from the negative electrode liquid storage container to the flow field plate (020) of the negative electrode photovoltaic assembly and connected to the negative electrode reaction site (090), and the photovoltaic panel (010) of the negative electrode photovoltaic assembly is connected to the liquid flow battery stack (120) through a cable (130); The flow field plate (020) of the positive photovoltaic assembly and the positive electrode liquid storage container form a circulation through a pipeline. A branch is set on the pipeline from the positive electrode liquid storage container to the flow field plate (020) of the positive photovoltaic assembly and connected to the positive electrode reaction site (091). The photovoltaic panel (010) of the positive photovoltaic assembly is connected to the liquid flow battery stack (120) through a cable (130).

6. The use according to claim 5, characterized in that: A power pump (030) is provided in the pipeline circulation between the flow field plate (020) of the negative electrode photovoltaic assembly and the negative electrode liquid storage container, and in the pipeline circulation between the flow field plate (020) of the positive electrode photovoltaic assembly and the positive electrode liquid storage container.

7. The use according to claim 6, characterized in that: Two branches are provided on the pipeline from the negative electrode liquid storage container to the flow field plate (020) of the negative electrode photovoltaic assembly, respectively connected to the negative electrode reaction site (090), and a stop valve (080) is provided on one of the branches; Two branches are provided on the pipeline from the positive electrode liquid storage container to the flow field plate (020) of the positive electrode photovoltaic assembly, respectively connected to the positive electrode reaction site (091), and a stop valve (080) is provided on one of the branches.

8. The use according to claim 7, characterized in that: The negative electrode liquid storage container comprises a shallow buried negative electrode liquid storage container (100) and a deep buried negative electrode liquid storage container (105); the flow field plate (020) of the negative electrode photovoltaic assembly is connected to two pipeline switch valves (040) through pipelines on both sides, and is respectively connected to the shallow buried negative electrode liquid storage container (100) and the deep buried negative electrode liquid storage container (105); The positive electrode liquid storage container comprises a shallow buried positive electrode liquid storage container (110) and a deep buried positive electrode liquid storage container (115); the flow field plate (020) of the positive electrode photovoltaic assembly is respectively connected to two pipeline switch valves (040) through pipelines on both sides, and is respectively connected to the shallow buried positive electrode liquid storage container (110) and the deep buried positive electrode liquid storage container (115).

9. The use according to claim 7, characterized in that: The negative electrode liquid storage container is a deeply buried negative electrode liquid storage container (105); The positive electrode liquid storage container is a shallow buried positive electrode liquid storage container (110).

10. The use according to claim 7, characterized in that: The terpyridine iron complex exchanges heat with the photovoltaic panel (010) when flowing through the flow field plate (020); The terpyridine iron complex undergoes an oxidation-reduction reaction in the negative electrode reaction site (090) and stores electrical energy; The electrical energy generated by the photovoltaic panel (010) is stored in the flow battery stack (120) via the cable (130).

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