An electrolyte, an N-type thermal battery based on the electrolyte, and a preparation method

Abstract

The present invention discloses an electrolyte, an N-type thermal battery based on the electrolyte and a preparation method, and relates to the technical field of thermal batteries. The present invention provides an electrolyte, comprising deionized water, CuSO 4 NH 4 ) 2 SO 4 and ethylenediamine; CuSO in electrolyte 4 The concentration of NH 4 ) 2 SO 4 The concentration of ethylenediamine in the electrolyte is 1‑4 mol / L; the electrolyte is applied to a thermal battery using copper as an electrode, and the ethylenediamine in the electrolyte reacts with the copper at the anode to produce Cu(en) 2 2+ Chelate, forming Cu / Cu(en) 2 2+ Reaction couple; the present invention obtains a Cu / Cu(en) 2 2+ The Seebeck coefficient of the N-type thermal battery with a reaction couple reached 2.31 mV K ‑1 , effectively improving the performance of N-type ion thermal batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal batteries, and in particular to an electrolyte, an N-type thermal battery based on the electrolyte, and a preparation method thereof. Background Art

[0002] Thermoelectrochemical cells (TECs) have attracted widespread attention due to their great potential in the field of thermal energy conversion, such as waste heat collection. TECs, also known as thermal batteries, are being widely studied because of their high thermoelectric potential, high efficiency, material diversity, and repeatability. The basic structure of TECs is a reaction chamber sandwiched between two electrodes, which is filled with electrolytes. The electrolyte is usually composed of a redox pair and water. When different temperatures are applied to the electrodes at both ends, the temperature dependence of the redox pair causes oxidation / reduction reactions to occur at the hot and cold electrodes. During the entire working process, electrons move in a directed manner between the two electrodes to form an electric current, realizing the conversion of thermal energy into electrical energy.

[0003] TECs are used for device integration because they directly convert heat into stable electrical energy output. Since the voltage output of a single battery is limited by the thermoelectric potential and temperature difference, in order to obtain an effective voltage (higher than 1V) that can be used for practical applications, it is often necessary to connect multiple batteries in series. From the perspective of integration, there are two main ways. One is to connect single batteries of the same type in series into a "Z"-shaped connection; the other is to connect two different types of single batteries (N-type and P-type) in series to form a "П"-shaped connection. In thermocouples, the thermoelectrode that undergoes oxidation reaction is generally defined as P-type, while the thermoelectrode that undergoes reduction reaction is defined as N-type. For the Z-shaped connection, its advantage is that the corresponding device can use the most advanced single battery to achieve maximum power output, but its disadvantage is also obvious. The Z-shaped connection will make the device integration process complicated, and it is very likely to introduce a large contact resistance at the junction of the electrode and the Z-shaped line, which will have an adverse effect on the performance of the entire device. In contrast, the П-shaped connection effectively reduces the complexity of the device integration process. At the same time, this connection method can ensure good contact between the electrode and the current collector, thereby reducing contact resistance, reducing energy loss, and helping to improve charge transfer efficiency, thus laying a solid foundation for improving the performance and stability of the entire system. However, due to the poor performance of the current N-type TEC and the imperfect development of technology, the efficiency of the devices integrated by the П-type connection method is still at a low level, which seriously limits the output performance of the pN-type integrated device.

[0004] At present, the Seebeck coefficient (Se) of Fe(ClO4)2 / Fe(ClO4)3 as the electrolyte of N-type TEC has reached 1.76 mV K -1 , I - / I3 -The Seebeck coefficient Se of the electrolyte reaches 1.2mV K -1 In addition, other inorganic redox pairs, such as Sn 4+ / Sn 2+ and Co 2+ / Co 3+ , whose Se has 1.5 mV K -1 and 1.4 mV K -1 However, they all suffer from one or more defects, including negative concentration dependence of Se, strong counterion dependence of Se, and relatively low conductivity of non-aqueous / gel electrolytes. In addition, they mainly use expensive Pt as electrodes to ensure fast kinetics and corrosion resistance.

[0005] In summary, there is currently no cost-effective N-type TEC that can compete with the P-type benchmark (Fe(CN)6 3– / Fe(CN)6 4– ), therefore, it is particularly important to develop high-performance N-type TEC and make it better cooperate with P-type TEC to improve the overall efficiency of the device. Summary of the invention

[0006] The present invention aims to solve the technical problem that the existing N-type thermal battery has poor performance, and aims to provide an electrolyte, an N-type thermal battery based on the electrolyte and a preparation method, and obtain a Cu / Cu(en)2 2+ The Seebeck coefficient of the N-type thermal battery with a reaction couple reached 2.31 mV K -1 , effectively improving the performance of N-type ion thermal batteries, with higher thermoelectric conversion efficiency and high stability.

[0007] The present invention is achieved through the following technical solutions.

[0008] The first object of the present invention is to provide an electrolyte comprising deionized water, CuSO4, (NH4)2SO4 and ethylenediamine;

[0009] The concentration of CuSO4 in the electrolyte is 0.1-0.4 mol / L, for example, the concentration of CuSO4 can be 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L;

[0010] The concentration of (NH4)2SO4 in the electrolyte is 1-4 mol / L, for example, the concentration of (NH4)2SO4 can be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L;

[0011] The concentration of ethylenediamine in the electrolyte is 1-4 mol / L, for example, the concentration of ethylenediamine can be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L;

[0012] The electrolyte is used in a thermal battery with copper as an electrode, and the ethylenediamine in the electrolyte reacts with the copper at the anode to produce Cu(en)2 2+ Chelate, forming Cu / Cu(en)2 2+ Reaction couple.

[0013] Furthermore, the concentration of CuSO4 in the electrolyte is 0.2 mol / L.

[0014] Furthermore, the concentration of (NH4)2SO4 in the electrolyte is 3 mol / L.

[0015] Furthermore, the concentration of ethylenediamine in the electrolyte is 2 mol / L.

[0016] The second object of the present invention is to provide an N-type thermal battery using the aforementioned electrolyte.

[0017] Furthermore, the N-type thermal battery includes a battery frame, copper electrodes and current collectors attached to both ends of the battery frame, and the battery frame is filled with electrolyte.

[0018] Furthermore, the current collector is made of titanium plate.

[0019] Furthermore, the battery frame is an acrylic frame.

[0020] A second object of the present invention is to provide a method for preparing an N-type thermal battery, comprising the following steps:

[0021] Copper electrodes and current collectors are attached to both ends of the battery frame in sequence and sealed with thermosetting adhesive;

[0022] injecting electrolyte into the battery frame;

[0023] The N-type thermal battery is obtained by sealing with a plug.

[0024] Furthermore, the preparation method of the electrolyte is:

[0025] Dissolve CuSO4 and (NH4)2SO4 in deionized water, stir the solution with a magnetic stirrer until the solute is completely dissolved, then slowly add ethylenediamine to the solution in a fume hood and stir evenly to obtain an electrolyte.

[0026] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0027] The present invention is based on Cu / Cu(en)2 2+ The Seebeck coefficient of the N-type TEC with the reaction couple reached 2.31 mV K -1 , effectively improving the performance of N-type ion thermal batteries, compared with the ordinary Cu / Cu 2+ The N-type ion thermal battery of the present invention has higher thermoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0029] Figure 1 It is a schematic diagram of the structure of the N-type thermal battery of the present invention;

[0030] Figure 2 Polarization curve and thermal power density curve of the N-type thermal battery prepared in Example 13 of the present invention;

[0031] Figure 3 A comparison chart of the Seebeck coefficients of the N-type thermal battery prepared in Example 13 of the present invention and the common N-type ion thermal battery of the comparative example;

[0032] Figure 4 This is a curve chart showing the change in open circuit voltage over time during a stability test of the N-type thermal battery prepared in Example 13 of the present invention. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the technical solutions in the embodiments of the present invention are clearly and completely described below in combination with the embodiments and drawings. Obviously, the schematic implementation modes of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0034] The following is a detailed description of an electrolyte, an N-type thermal battery based on the electrolyte, and an embodiment of a preparation method of the present invention with reference to the accompanying drawings as appropriate. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions and repeated descriptions of well-known matters are omitted. This is to avoid the following description from becoming unnecessarily lengthy and facilitate the understanding of those skilled in the art.

[0035] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range.

[0036] If not otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0037] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0038] Unless otherwise specified, the terms "include" and "comprising" mentioned in this application may be open-ended or closed-ended. For example, the terms "include" and "comprising" may mean that other substances not listed may also be included or only the listed substances may be included.

[0039] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0040] In thermal batteries, the Seebeck coefficient (Se) is a key parameter reflecting the output of TEC.

[0041]

[0042] Where V is voltage, T is temperature, ΔS is the entropy change of the redox reaction, n is the number of electrons transferred in the redox reaction, and F is the Faraday constant. According to theoretical analysis, the solvation structure entropy difference (ΔS) between Se and redox anions and the concentration ratio difference (ΔC) between the cold and hot ends of the TEC are closely related.

[0043] Based on this, the inventors found in their research that when ethylenediamine is added to the electrolyte, ethylenediamine will react with the cold-end Cu electrode to produce Cu(en)2 2+ The chelate increases the solvation structural entropy difference, thereby significantly improving the Seebeck coefficient of TEC, enhancing the performance of N-type TEC, and promoting its application in the field of thermoelectric conversion.

[0044] The present invention is based on Cu / Cu(en)2 2+ The Seebeck coefficient of the N-type TEC with the reaction couple reached 2.31 mV K -1 , effectively improving the performance of N-type ion thermal batteries, compared with the ordinary Cu / Cu 2+ The N-type ion thermal battery of the present invention has higher thermoelectric conversion efficiency and high stability.

[0045] Specifically, the reaction principle is:

[0046] Reduction reaction ( ) occurs at the hot electrode (cathode),

[0047] Oxidation reaction ( ) occurs at the cold electrode (anode).

[0048] When different temperatures are applied to the electrodes at both ends, the temperature dependence of the redox couple in the electrolyte causes an oxidation / reduction reaction to occur at the hot and cold electrodes. During the entire working process, electrons move in a directional manner between the two electrodes, forming a current and realizing the conversion of thermal energy into electrical energy.

[0049] The technical solution of the present invention is further described in detail below in conjunction with embodiments.

[0050] It should be noted that the experimental methods used in the examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained by those skilled in the art through commercial channels.

[0051] Example 1

[0052] An electrolyte comprises deionized water, CuSO4, (NH4)2SO4 and ethylenediamine; the concentration of CuSO4 in the electrolyte is 0.2 mol / L, the concentration of (NH4)2SO4 in the electrolyte is 3 mol / L, and the concentration of ethylenediamine in the electrolyte is 1 mol / L.

[0053] The preparation method of the electrolyte in this embodiment is as follows: weigh the raw materials according to the final preparation concentration of the electrolyte, dissolve CuSO4 and (NH4)2SO4 in deionized water, stir the solution with a magnetic stirrer until the solute is completely dissolved, and then slowly add ethylenediamine to the solution in a fume hood, stir evenly, and obtain an electrolyte.

[0054] Example 2

[0055] An electrolyte comprises deionized water, CuSO4, (NH4)2SO4 and ethylenediamine; the concentration of CuSO4 in the electrolyte is 0.2 mol / L, the concentration of (NH4)2SO4 in the electrolyte is 3 mol / L, and the concentration of ethylenediamine in the electrolyte is 2 mol / L.

[0056] The preparation method of the electrolyte in this embodiment is the same as that in Example 1.

[0057] Example 3

[0058] An electrolyte comprises deionized water, CuSO4, (NH4)2SO4 and ethylenediamine; the concentration of CuSO4 in the electrolyte is 0.2 mol / L, the concentration of (NH4)2SO4 in the electrolyte is 3 mol / L, and the concentration of ethylenediamine in the electrolyte is 3 mol / L.

[0059] The preparation method of the electrolyte in this embodiment is the same as that in Example 1.

[0060] Example 4

[0061] An electrolyte comprises deionized water, CuSO4, (NH4)2SO4 and ethylenediamine; the concentration of CuSO4 in the electrolyte is 0.2 mol / L, the concentration of (NH4)2SO4 in the electrolyte is 3 mol / L, and the concentration of ethylenediamine in the electrolyte is 4 mol / L.

[0062] The preparation method of the electrolyte in this embodiment is the same as that in Example 1.

[0063] Example 5

[0064] An electrolyte comprises deionized water, CuSO4, (NH4)2SO4 and ethylenediamine; the concentration of CuSO4 in the electrolyte is 0.1 mol / L, the concentration of (NH4)2SO4 in the electrolyte is 3 mol / L, and the concentration of ethylenediamine in the electrolyte is 2 mol / L.

[0065] The preparation method of the electrolyte in this embodiment is the same as that in Example 1.

[0066] Example 6

[0067] An electrolyte comprises deionized water, CuSO4, (NH4)2SO4 and ethylenediamine; the concentration of CuSO4 in the electrolyte is 0.15 mol / L, the concentration of (NH4)2SO4 in the electrolyte is 3 mol / L, and the concentration of ethylenediamine in the electrolyte is 2 mol / L.

[0068] The preparation method of the electrolyte in this embodiment is the same as that in Example 1.

[0069] Example 7

[0070] An electrolyte comprises deionized water, CuSO4, (NH4)2SO4 and ethylenediamine; the concentration of CuSO4 in the electrolyte is 0.25 mol / L, the concentration of (NH4)2SO4 in the electrolyte is 3 mol / L, and the concentration of ethylenediamine in the electrolyte is 2 mol / L.

[0071] The preparation method of the electrolyte in this embodiment is the same as that in Example 1.

[0072] Example 8

[0073] An electrolyte comprises deionized water, CuSO4, (NH4)2SO4 and ethylenediamine; the concentration of CuSO4 in the electrolyte is 0.3 mol / L, the concentration of (NH4)2SO4 in the electrolyte is 3 mol / L, and the concentration of ethylenediamine in the electrolyte is 2 mol / L.

[0074] The preparation method of the electrolyte in this embodiment is the same as that in Example 1.

[0075] Example 9

[0076] An electrolyte comprises deionized water, CuSO4, (NH4)2SO4 and ethylenediamine; the concentration of CuSO4 in the electrolyte is 0.4 mol / L, the concentration of (NH4)2SO4 in the electrolyte is 3 mol / L, and the concentration of ethylenediamine in the electrolyte is 2 mol / L.

[0077] The preparation method of the electrolyte in this embodiment is the same as that in Example 1.

[0078] Example 10

[0079] An electrolyte comprises deionized water, CuSO4, (NH4)2SO4 and ethylenediamine; the concentration of CuSO4 in the electrolyte is 0.2 mol / L, the concentration of (NH4)2SO4 in the electrolyte is 1 mol / L, and the concentration of ethylenediamine in the electrolyte is 2 mol / L.

[0080] The preparation method of the electrolyte in this embodiment is the same as that in Example 1.

[0081] Embodiment 11

[0082] An electrolyte comprises deionized water, CuSO4, (NH4)2SO4 and ethylenediamine; the concentration of CuSO4 in the electrolyte is 0.2 mol / L, the concentration of (NH4)2SO4 in the electrolyte is 2 mol / L, and the concentration of ethylenediamine in the electrolyte is 2 mol / L.

[0083] The preparation method of the electrolyte in this embodiment is the same as that in Example 1.

[0084] Example 12

[0085] An electrolyte comprises deionized water, CuSO4, (NH4)2SO4 and ethylenediamine; the concentration of CuSO4 in the electrolyte is 0.2 mol / L, the concentration of (NH4)2SO4 in the electrolyte is 4 mol / L, and the concentration of ethylenediamine in the electrolyte is 2 mol / L.

[0086] The preparation method of the electrolyte in this embodiment is the same as that in Example 1.

[0087] Embodiment 13

[0088] An N-type thermal battery, using the electrolyte of Example 2, has a structure as follows Figure 1 As shown, it includes an acrylic frame, copper electrodes attached to both ends of the battery frame and a current collector, and the battery frame has a reaction chamber, and the reaction chamber is filled with the electrolyte of Example 2. The preparation method thereof includes the following steps:

[0089] The copper electrode was placed in a reaction chamber with a volume of 1 mL (1 × 1 × 1 cm 3 ) on an acrylic frame with an effective reaction area of ​​1 cm 2 Next, a 4 mm thick, 2.5 × 2.5 cm 2 The graphite sheet is tightly attached to the copper electrode, and the frame is sealed with a thermosetting adhesive to connect the battery frame as a whole and prevent the electrolyte in the reaction chamber from leaking out and affecting the test performance. Then, the electrolyte is injected into the reaction chamber to fill the battery. Finally, it is sealed with a plug to obtain a Cu / Cu(en)2 based battery. 2+ N-type thermal battery with a reaction couple.

[0090] Comparative example.

[0091] This comparative example is based on Cu / Cu 2+ The ordinary N-type ion thermal battery of Example 13 is different from Example 13 in that the electrolyte does not contain ethylenediamine.

[0092] Polarization tests were performed on Example 13 and the comparative example N-type thermal battery to measure performance parameters such as thermoelectric potential (Se), polarization curve, and thermal power density curve. The results are as follows.

[0093] like Figure 2 The polarization curve and power density curve of the N-type thermal battery prepared in Example 13 are shown in FIG. Figure 2 It can be seen that the present invention is based on Cu / Cu(en)2 2+ N-type thermal battery with a reaction couple, Cu in the electrolyte 2+When the concentration is 0.2 mol / L, the concentration of ethylenediamine is 2 mol / L, and the concentration of (NH4)2SO4 is 3 mol / L, the corresponding thermal power of the battery exceeds 600 μW·m -2 ·K -2 .

[0094] like Figure 3 is a comparison chart of the Seebeck coefficients of the N-type thermal battery prepared in Example 13 and the ordinary N-type ion thermal battery of the comparative example. Figure 3 It can be seen that the present invention is based on Cu / Cu(en)2 2+ N-type thermal battery with a reaction couple, Cu in the electrolyte 2+ When the concentration was 0.2 mol / L, the concentration of ethylenediamine was 2 mol / L, and the concentration of (NH4)2SO4 was 3 mol / L, the Seebeck coefficient reached 2.31 mV K -1 , while the common Cu / Cu based 2+ The N-type ion thermal battery is only 0.45 mV K -1 It can be seen that the use of the electrolyte of the present invention can effectively improve the performance of the N-type ion thermal battery and has a higher thermoelectric conversion efficiency.

[0095] In order to further test the stability of the N-type thermal battery of the present invention, the temperature difference between the two ends of the electrode was maintained at 30K, and the linear sweep voltammetry (LSV) test was performed. The battery was turned over after 5 hours of working test and the test was continued. The whole process was tested for 10 hours. The results are as follows: Figure 4 As shown, from Figure 4 It can be seen that the open circuit voltage is always stable at the same level, which shows that the N-type thermal battery of the present invention has good stability.

[0096] Finally, it should be noted that the above specific embodiments are only used to explain in detail the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific implementation method of the present invention and is not used to limit the protection scope of the present invention. Although the present invention is described in detail with reference to the above specific embodiments, ordinary technicians in this field should understand that it is still possible to modify the technical solutions recorded in the above embodiments, or to replace or improve some or all of the technical features therein. These modifications, equivalent replacements and improvements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. An electrolyte, characterized in that: including deionized water, CuSO4, (NH4)2SO4 and ethylenediamine; The concentration of CuSO4 in the electrolyte is 0.1-0.4 mol / L; The concentration of (NH4)2SO4 in the electrolyte is 1-4 mol / L; The concentration of ethylenediamine in the electrolyte is 1-4 mol / L; The electrolyte is used in a thermal battery with copper as an electrode, and the ethylenediamine in the electrolyte reacts with the copper at the anode to produce Cu(en)2 2+ Chelate, forming Cu / Cu(en)2 2+ Reaction couple.

2. An electrolyte according to claim 1, characterized in that: The concentration of CuSO4 in the electrolyte is 0.2 mol / L.

3. An electrolyte according to claim 1, characterized in that: The concentration of (NH4)2SO4 in the electrolyte is 3 mol / L.

4. An electrolyte according to claim 1, characterized in that: The concentration of ethylenediamine in the electrolyte is 2 mol / L.

5. An N-type thermal battery, characterized in that: The electrolyte according to any one of claims 1 to 4 is used.

6. An N-type thermal battery according to claim 5, characterized in that: The N-type thermal battery comprises a battery frame, copper electrodes attached to both ends of the battery frame and a current collector, and the battery frame is filled with electrolyte.

7. An N-type thermal battery according to claim 6, characterized in that: The current collector is a titanium plate.

8. An N-type thermal battery according to claim 6, characterized in that: The battery frame adopts an acrylic frame.

9. The method for preparing an N-type thermal battery according to any one of claims 5 to 8, characterized in that: The following steps are involved: Copper electrodes and current collectors are attached to both ends of the battery frame in sequence and sealed with thermosetting adhesive; injecting electrolyte into the battery frame; The N-type thermal battery is obtained by sealing with a plug.

10. The method for preparing an N-type thermal battery according to claim 9, characterized in that: The preparation method of the electrolyte is: Dissolve CuSO4 and (NH4)2SO4 in deionized water, stir the solution with a magnetic stirrer until the solute is completely dissolved, then slowly add ethylenediamine to the solution in a fume hood and stir evenly to obtain an electrolyte.

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