A high-performance, stable thermal regeneration electrochemical cyclic battery with a double membrane structure

Abstract

The application belongs to the technical field of thermo-electrochemical conversion, and particularly relates to a high-performance and stable thermal regeneration electrochemical cycle battery adopting a double-membrane structure. An intermediate electrolyte layer is arranged between positive and negative electrolytes, and anion and cation ion exchange membranes are used to separate the intermediate layer electrolyte from the positive and negative electrolytes, respectively. Solvents of the positive and negative electrolytes and the intermediate layer electrolyte are acetonitrile, water or a mixture of acetonitrile and water. The application can ensure stable pairing between positive and negative electrolytes with different pH stable ranges and active material charge signs with high thermoelectric potential, effectively improve the thermoelectric potential, power and efficiency of the TREC battery, maintain the battery capacity and improve the charge and discharge cycle life of the battery. The technical route of the application is universal, and can be applied to static batteries and also be used to construct flow batteries, so as to further improve the power and efficiency of the TREC battery and realize effective recycling of low-grade heat.

Description

Technical Field

[0001] This invention belongs to the field of thermo-electrochemical conversion technology, specifically relating to a high-performance, stable thermo-regenerative electrochemical cycle battery employing a dual-membrane structure. Background Technology

[0002] Due to the thermodynamic irreversibility of energy conversion, approximately 1.2 PWh of primary energy consumed globally each year is released into the atmosphere as heat, accounting for 72% of total energy consumption. Of this, about 63% is low-grade waste heat (<100℃). Industrial waste heat, geothermal energy, solar energy, building heating, human body heat dissipation, and electronic devices are all important and abundant sources of low-grade heat. Converting low-grade heat energy into electricity is an ideal way to address the global energy crisis and environmental challenges. However, the low energy density and dispersed distribution of these heat sources make existing thermoelectric conversion technologies uneconomical. For example, much past research has focused on semiconductor thermoelectric devices based on the Seebeck effect, but their application is limited by high cost and the use of rare elements. Furthermore, semiconductor materials typically only generate a thermoelectric potential of about 0.1 mV / K, making it difficult to generate sufficient voltage and power for effective energy harvesting under the limited temperature difference between the low-grade heat source and the environment.

[0003] In recent years, electrochemical thermoelectric conversion devices with high ionic thermoelectric potentials, such as thermally diffusing ion capacitors, thermally charged batteries, and thermally regenerative electrochemical cycles (TREC), have provided new approaches for recovering low-grade thermal energy. Among them, TREC batteries have attracted widespread research attention due to their ability to achieve high Carnot relative efficiencies exceeding 10%. A TREC battery is an isothermal device that utilizes the temperature dependence of both the anodic and cathodic reactions in its operating principle. Its open-circuit voltage V0 oc The change in battery thermoelectric potential with temperature is defined as α. cell :

[0004]

[0005] Among them, E + E- and E- are the potentials of the positive and negative electrode reaction couples, respectively; α + and α - These are the thermoelectric potentials of the positive and negative electrode reactions, respectively. Therefore, the TREC battery can convert temperature difference into electrical work output by charging and discharging it at different temperatures. Clearly, using positive and negative electrode reaction pairs with thermoelectric potentials of opposite signs can improve the battery's α-efficiency. cell The absolute value of is key to increasing battery voltage and output power.

[0006] However, the current challenge is that it is difficult to obtain high α values ​​while ensuring electrolyte stability. cellAccording to Born's solvation model, redox couples with higher positive thermoelectric potentials are typically transition metal cations, such as V. 3+ / V 2+ and Fe 3+ / Fe 2+ However, these redox couples are stable in acidic environments; while redox couples with negative thermoelectric potentials are anions, such as Fe(CN)6. 3- / Fe(CN)6 4- This anion pair is stable in neutral or alkaline environments. This pH mismatch leads to poor cycle stability in TREC batteries. Besides the pH matching issue, it is also feasible for the positive and negative electrode active materials to have the same charge sign. For example, the positive and negative electrode pairs could use I3... - / I - and Fe(CN)6 3- / Fe(CN)6 4- However, the combined thermoelectric potential of the TREC battery, at only 1.9 mV / K, leads to its low efficiency. Based on Cu(NH3)4... 2+ / Cu(NH3) 2+ and Fe(CN)6 3- / Fe(CN)6 4- TRECFB has a high thermoelectric potential |α cell |=2.9mV / K. However, the different charge signs between active ion pairs make it difficult to find the optimal ion exchange membrane to prevent cross-reaction of ions.

[0007] Patent CN117747896A discloses a rechargeable thermal regeneration electrochemical battery based on a dual-film structure and its usage method. It achieves regulation of the positive electrode potential and thermoelectric potential by changing three schemes: the proportion of Prussian blue analogue metal material, the electrolyte concentration, and the intercalation of ions. Furthermore, the dual-film structure effectively blocks Fe from the negative electrode. 2+ / Fe 3+ and ClO 4- The effect on the insertion and extraction processes of positive electrode ions is investigated to achieve long-term stable cycling. However, the thermoelectric potential of this scheme is -2.5 to -3 mV / K, which needs further improvement. Summary of the Invention

[0008] The purpose of this invention is to provide a high-performance, stable thermal regenerative electrochemical cycle battery with a dual-membrane structure. By optimizing the battery structure and electrolyte composition, the battery thermoelectric potential is significantly improved, thereby achieving efficient recovery and utilization of low-grade thermal energy.

[0009] To achieve the above objectives, the present invention provides a thermal regenerative electrochemical cycle battery with a dual-membrane structure, comprising a positive electrode, a positive electrode electrolyte, an intermediate layer electrolyte, a negative electrode electrolyte, a negative electrode, an anion exchange membrane, and a cation exchange membrane; wherein the positive electrode electrolyte and the negative electrode electrolyte are two different redox couples with opposite thermoelectric potential signs; the cations in the intermediate layer electrolyte are selected from the cations in the positive electrode electrolyte, and the anions are selected from the anions in the negative electrode electrolyte, or the cations in the intermediate layer electrolyte are selected from the cations in the negative electrode electrolyte, and the anions are selected from the anions in the positive electrode electrolyte;

[0010] When the cations of the intermediate layer electrolyte and the positive electrode electrolyte are the same, the intermediate layer electrolyte and the positive electrode electrolyte are separated by a cation exchange membrane, and the intermediate layer electrolyte and the negative electrode electrolyte are separated by an anion exchange membrane.

[0011] When the anions of the intermediate layer electrolyte and the positive electrode electrolyte are the same, the intermediate layer electrolyte and the positive electrode electrolyte are separated by anion exchange membrane, and the intermediate layer electrolyte and the negative electrode electrolyte are separated by cation exchange membrane.

[0012] The solvents for the positive electrode electrolyte, the intermediate layer electrolyte, and the negative electrode electrolyte are each independently selected from acetonitrile, water, or a mixture of acetonitrile and water. Preferably, the solvents for the positive electrode electrolyte, the intermediate layer electrolyte, and the negative electrode electrolyte are the same. This invention has found that when a solvent containing acetonitrile is used, the thermoelectric potential is significantly increased.

[0013] The intermediate electrolyte layer is separated from the positive and negative electrode electrolytes by ion exchange membranes to prevent the charging and discharging cycle life of the high thermoelectric potential positive and negative electrode electrolytes from being reduced due to pH mismatch or redox ion cross-linking.

[0014] Furthermore, the mass fraction of acetonitrile in the mixture of acetonitrile and water is 0% to 100%, preferably 60% to 100%.

[0015] Furthermore, the redox couple OR(+)||OR(-) in the positive and negative electrolytes are selected from one of the following combinations: Fe 3+ / Fe 2+ (+)||Fe(CN)6 3- / Fe(CN)6 4- (-), Fe(CN)6 3- / Fe(CN)6 4- (+)||Zn / Zn 2+ (-), V 3+ / V 2+ (+)||Fe(CN)6 3- / Fe(CN)64- OR(-) ; where OR(+) is the redox couple of the positive electrode electrolyte and OR(-) is the redox couple of the negative electrode electrolyte.

[0016] Furthermore, when the solvent is acetonitrile or a mixture of acetonitrile and water, the electrolyte of the positive electrode electrolyte is a mixed solution of Fe(ClO4)3 and Fe(ClO4)2; the electrolyte of the negative electrode electrolyte is a mixed solution of Li4Fe(CN)6 and Li4Fe(CN)6; and the electrolyte of the intermediate layer electrolyte is LiClO4. This electrolyte combination, paired with acetonitrile solvent, can further increase the thermoelectric potential to 3.2-4.7 mV / K.

[0017] Furthermore, the concentration range of the positive electrode electrolyte is 0.1-1M, preferably 0.1-0.4M; the concentration range of the negative electrode electrolyte is 0.1-1M, preferably 0.1-0.4M; and the concentration range of the intermediate layer electrolyte is 0.1-3M, preferably 1-3M. The determination of the concentration range of the redox couple in the positive and negative electrode electrolytes in this invention can simultaneously consider electrolyte concentration and solubility, and is determined based on the relationship between electrolyte concentration and battery capacity, and electrolyte concentration and battery thermoelectric potential.

[0018] Furthermore, the concentration, storage volume, or flow rate of the positive and negative electrode electrolytes and the intermediate layer electrolyte can be adjusted to optimize the energy conversion rate.

[0019] Furthermore, the electrolyte in the intermediate layer is an alkali metal salt. In a preferred embodiment of the present invention, the alkali metal salt includes one of potassium chloride, sodium chloride, sodium sulfate, lithium chloride, lithium perchlorate, lithium sulfate, ammonium chloride, and ammonium sulfate.

[0020] Furthermore, the positive and negative electrodes are selected from one of the following: platinum sheet, graphite felt, carbon paper, carbon cloth material, and carbon nanotubes.

[0021] Furthermore, the positive and negative electrolytes also include a co-solvent and / or a supporting electrolyte;

[0022] The co-solvent is an acidic or alkaline co-solvent, and the supporting electrolyte is a salt.

[0023] Furthermore, the acidic co-solvent includes hydrochloric acid, sulfuric acid, and perchloric acid; the alkaline co-solvent includes one of potassium hydroxide, sodium hydroxide, and lithium hydroxide; and the supporting electrolyte includes one of potassium chloride, sodium chloride, sodium sulfate, lithium chloride, lithium sulfate, and lithium perchlorate.

[0024] Furthermore, in the ion exchange membrane, when the charge carriers of the positive electrode electrolyte are cations, a cation exchange membrane is used between the positive electrode electrolyte and the intermediate layer; otherwise, an anion exchange membrane is used. Similarly, when the charge carriers of the negative electrode electrolyte are cations, a cation exchange membrane is used between the negative electrode electrolyte and the intermediate layer; otherwise, an anion exchange membrane is used. In a preferred embodiment of the present invention, the cation exchange membrane includes, but is not limited to, selections from the Nafion series, Fumasep series, and Selemion series, as well as their treated types; the anion exchange membrane includes, but is not limited to, selections from the Fumasep series and Selemion series, as well as their pretreated types. Preferably, both the anion and cation exchange membranes are soaked in the intermediate layer electrolyte for 1-48 hours before use.

[0025] Furthermore, the thermal regenerative electrochemical cycle battery is a static battery or a flow battery; when the thermal regenerative electrochemical cycle battery is a flow battery, the positive and negative electrodes of the battery are respectively provided with electrolyte flow channels to ensure efficient electrolyte flow.

[0026] Furthermore, the electrolyte flow channel is a serpentine flow channel, a comb-shaped flow channel, or a spiral flow channel; the positive electrode electrolyte, the intermediate layer electrolyte, and the negative electrode electrolyte are respectively connected to the electrolyte storage tank to form an electrolyte circulation loop, and the flow rate of the electrolyte is controlled by a flow pump.

[0027] When using a flow battery, the flow rate range of the positive and negative electrolytes in this invention can be determined based on parameters such as the current density during the charging and discharging process, the concentration of the redox couple, and the pump power consumed. Typically, the electrolyte flow rate that meets the maximum battery power density or efficiency is selected.

[0028] The design method of the thermal regenerative electrochemical cycle battery of this invention is as follows:

[0029] Select matching positive and negative electrode electrolytes, intermediate layer electrolyte, anion and cation exchange membranes, and set the parameters of the electrolytes. Based on the sign of the battery's thermoelectric potential and the set high and low temperatures, the battery is sequentially charged or discharged, and then cycled according to the set battery temperature. Specifically, taking a static battery with a thermoelectric potential greater than 0 as an example, the battery discharges at a high temperature and charges at a low temperature. The portion of electrical energy that is higher during high-temperature discharge than low-temperature charging during the entire cycle is the total electrical work output by the battery. For flow batteries, a flow pump is used to facilitate the transfer of electrolyte between the battery and the storage tank.

[0030] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages:

[0031] 1. The dual-membrane structure proposed in this invention ensures stable pairing between positive and negative electrode electrolytes with different pH stability ranges and active material charge signs, resulting in high thermoelectric potential. This effectively improves the thermoelectric potential, power, and efficiency of TREC batteries while maintaining battery capacity and extending charge-discharge cycle life. It addresses the current challenge of balancing high thermoelectric potential and cycle stability in TREC batteries, enabling stable operation with high performance. Furthermore, by optimizing the electrolyte composition, this invention significantly enhances the thermoelectric potential of the system, thereby improving energy harvesting and utilization.

[0032] 2. The present invention preferably uses a solvent containing acetonitrile to prepare the electrolyte. Studies have found that this solvent can significantly improve the thermoelectric potential. Furthermore, when the positive electrode electrolyte is a mixed solution of Fe(ClO4)3 and Fe(ClO4)2, and the negative electrode electrolyte is a mixed solution of Li4Fe(CN)6 and Li4Fe(CN)6, the thermoelectric potential can reach a maximum of 4.7 mV / K.

[0033] 3. The technical approach of this invention is universal. In addition to being applied to static batteries, it can also be used to construct flow batteries, thereby further improving the power and efficiency of TREC batteries and realizing the effective recovery and utilization of low-grade heat. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the TREC static battery provided by the present invention.

[0035] Figure 2 This is a schematic diagram of the TREC flow battery provided by the present invention.

[0036] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0037] 1-Current collector; 2-Electrode; 3-Negative electrode electrolyte or storage tank; 4-Positive electrode electrolyte or storage tank; 5-Intermediate layer electrolyte or storage tank; 6-Anion exchange membrane; 7-Cation exchange membrane; 8-Load or power supply; 9-Flow pump. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0039] This invention provides a thermo-regenerative electrochemical cycle battery with a dual-membrane structure. The battery consists of positive and negative electrodes 2, a current collector 1, a positive electrolyte, a negative electrolyte, an intermediate electrolyte layer, an anion exchange membrane 6, and a cation exchange membrane 7. The positive and negative electrolytes contain two different redox couples with opposite thermoelectric potentials. The intermediate electrolyte layer is composed of anion or cation carriers from the positive and negative electrolytes and is located between the positive and negative electrolytes. The intermediate electrolyte layer is separated from the positive and negative electrolytes by ion exchange membranes to prevent charge-discharge cycle life degradation due to pH mismatch or redox ion cross-linking in the high thermoelectric potential of the positive and negative electrolytes. The solvents for the positive electrolyte, intermediate electrolyte layer, and negative electrolyte are acetonitrile, water, or a mixture of acetonitrile and water.

[0040] The thermal regenerative electrochemical cycle battery of this invention can be a static battery or a flow battery, such as... Figure 1 This is a schematic diagram of the TREC static battery structure. Figure 2 This is a schematic diagram of a flow battery. When it is a flow battery, it also includes an electrolyte storage tank and a flow pump 9 to form an electrolyte circulation loop, and the flow rate of the electrolyte is controlled by the flow pump.

[0041] Example 1: High Thermoelectric Potential Organic All-Iron TREC Battery

[0042] The electrolyte solvent was pure acetonitrile. The positive electrode electrolyte was a mixed solution containing 0.1M Fe(ClO4)3 / Fe(ClO4)2, the negative electrode electrolyte was 0.1M Li3Fe(CN)6 / Li4Fe(CN)6, and the intermediate layer electrolyte was 2M LiClO4. An anion exchange membrane, Fumasep FAA-70, was used between the positive electrode electrolyte and the intermediate layer electrolyte, and a proton exchange membrane, Nafion 115, was used between the negative electrode electrolyte and the intermediate layer electrolyte. Both the anion and cation exchange membranes were soaked in 1M LiClO4 solution for 24 hours before use. Graphite felt electrodes were used. The thermoelectric potential of the all-iron TREC battery constructed in this embodiment was 4.7 mV / K.

[0043] Example 2: High Thermoelectric Potential Organic All-Iron TREC Battery

[0044] The difference from Example 1 is that the electrolyte solvent is a mixture of acetonitrile and water, with acetonitrile accounting for 80% by mass. All other aspects are the same as in Example 1 and will not be repeated here. The thermoelectric potential of the all-iron TREC battery constructed in this example is 4.2 mV / K.

[0045] Example 3: High Thermoelectric Potential Organic All-Iron TREC Battery

[0046] The difference from Example 2 is that the positive electrode electrolyte uses a mixed solution containing 0.4M Fe(ClO4)3 / Fe(ClO4)2, and the negative electrode electrolyte uses 0.4M Li3Fe(CN)6 / Li4Fe(CN)6. Everything else is the same as in Example 2 and will not be repeated here. The thermoelectric potential range of the all-iron TREC battery constructed in this example is 3.5mV / K.

[0047] Example 4: High Thermoelectric Potential All-Iron TREC Battery

[0048] The difference from Example 1 is that the electrolyte solvent is water; otherwise, it is the same as Example 1 and will not be repeated here. The thermoelectric potential of the all-iron TREC battery constructed in this example is 3.1 mV / K.

[0049] Example 5: High thermoelectric potential, high capacity all-iron TREC battery

[0050] The electrolyte solvent is water. The positive electrode electrolyte is a mixed solution containing 2.3M Fe(ClO4)3 / 1M HClO4, the negative electrode electrolyte is 2.3M Li4Fe(CN)6, and the intermediate layer electrolyte is 3M LiClO4. An anion exchange membrane (Fumasep FAA-70) is used between the positive electrode electrolyte and the intermediate layer electrolyte, and a proton exchange membrane (Nafion 115) is used between the negative electrode electrolyte and the intermediate layer electrolyte. Both the anion and cation exchange membranes are soaked in 1M LiClO4 solution for 24 hours before use. Graphite felt electrodes are used. The all-iron TREC battery constructed in this embodiment has a thermoelectric potential of 3.2 mV / K and a theoretical capacity as high as 61.6 Ah / L.

[0051] Example 6: High Thermoelectric Potential Iron-Vanadium TREC Battery

[0052] The electrolyte solvent is water. The positive electrode electrolyte is 0.4M K3Fe(CN)6 / K4Fe(CN)6, the negative electrode electrolyte is a mixed solution containing 0.4M V2Cl3 / VCl2 / 2M H2SO4, and the intermediate layer electrolyte is 3M KCl. A proton exchange membrane Nafion 115 is used between the positive electrode electrolyte and the intermediate layer electrolyte, and an anion exchange membrane Selemion AMV is used between the negative electrode electrolyte and the intermediate layer electrolyte. Both the anion and cation exchange membranes are soaked in 1M KCl solution for 24 hours before use. Graphite felt electrodes are used. The thermoelectric potential of the all-iron TREC battery constructed in this embodiment is -3.1mV / K.

[0053] Example 7: Low-cost zinc-iron TREC battery

[0054] The electrolyte solvent is water. The positive electrode electrolyte is 0.4M K3Fe(CN)6 / K4Fe(CN)6, the negative electrode electrolyte is a mixed solution containing 0.4M ZnCl / 1M KCl, and the intermediate layer electrolyte is 3M KCl. A proton exchange membrane Nafion 115 is used between the positive electrode electrolyte and the intermediate layer electrolyte, and an anion exchange membrane Selemion AMV is used between the negative electrode electrolyte and the intermediate layer electrolyte. Both the anion and cation exchange membranes are soaked in 1M KCl solution for 24 hours before use. Graphite felt electrodes are used. The thermoelectric potential of the all-iron TREC battery constructed in this embodiment is -2.1mV / K.

[0055] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A thermal regenerative electrochemical cycle battery employing a dual-membrane structure, characterized in that, It includes a positive electrode, a positive electrode electrolyte, an intermediate layer electrolyte, a negative electrode electrolyte, a negative electrode, an anion exchange membrane, and a cation exchange membrane; the positive electrode electrolyte and the negative electrode electrolyte are two different redox couples with opposite thermoelectric potential signs; the cations in the intermediate layer electrolyte are selected from the cations in the negative electrode electrolyte, and the anions are selected from the anions in the positive electrode electrolyte; When the anions of the intermediate layer electrolyte and the positive electrode electrolyte are the same, the intermediate layer electrolyte and the positive electrode electrolyte are separated by anion exchange membrane, and the intermediate layer electrolyte and the negative electrode electrolyte are separated by cation exchange membrane. The positive electrode electrolyte is a mixed solution of Fe(ClO4)3 and Fe(ClO4)2; the negative electrode electrolyte is a mixed solution of Li3Fe(CN)6 and Li4Fe(CN)6; and the electrolyte of the intermediate layer electrolyte is LiClO4. The solvents for the positive electrode electrolyte, the intermediate layer electrolyte, and the negative electrode electrolyte are selected from acetonitrile or a mixture of acetonitrile and water; The concentration range of the positive electrode electrolyte is 0.1-1M, the concentration range of the negative electrode electrolyte is 0.1-1M, and the concentration range of the intermediate layer electrolyte is 0.1-3M.

2. The thermal regenerative electrochemical cycle battery according to claim 1, characterized in that, The positive and negative electrolytes also include a co-solvent and / or a supporting electrolyte; The co-solvent is an acidic co-solvent or an alkaline co-solvent, and the supporting electrolyte is a salt; The acidic co-solvent includes one of hydrochloric acid, sulfuric acid, and perchloric acid; the alkaline co-solvent includes one of potassium hydroxide, sodium hydroxide, and lithium hydroxide; and the supporting electrolyte includes one of potassium chloride, sodium chloride, sodium sulfate, lithium chloride, lithium sulfate, and lithium perchlorate.

3. The thermal regenerative electrochemical cycle battery according to any one of claims 1-2, characterized in that, The thermal regenerative electrochemical cycle battery is either a static battery or a flow battery; when the thermal regenerative electrochemical cycle battery is a flow battery, the positive and negative electrodes of the battery are respectively provided with electrolyte flow channels.

4. The thermal regenerative electrochemical cycle battery according to claim 3, characterized in that, The electrolyte flow channel is a serpentine flow channel, a comb-shaped flow channel, or a spiral flow channel; the positive electrode electrolyte, the intermediate layer electrolyte, and the negative electrode electrolyte are respectively connected to the electrolyte storage tank to form an electrolyte circulation loop.

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