Thermoelectric power generation device and method for manufacturing same

Abstract

The invention relates to a thermoelectric power generation device. The thermoelectric power generation device includes an ionic gel, a first electrode in contact with the ionic gel, and a second electrode in contact with the ionic gel. The ionic gel comprises an ionic liquid, a gelling agent and an electronic conductor. The first electrode includes an inert material. The second electrode is spaced apart from the first electrode, the second electrode comprising an inert material. The invention also relates to a manufacturing method of the thermoelectric power generation device.

Description

Technical Field

[0001] This application relates to thermoelectric power generation devices. This application also relates to methods for manufacturing thermoelectric power generation devices. Technical Background

[0002] Earth possesses abundant waste heat, making the development of efficient thermoelectric (TE) technology crucial for sustainable development. Conventional thermoelectric materials are electronic materials, including inorganic semiconductors and semi-metals, conductive polymers, and their composites. However, the Seebeck coefficient of electronic materials is typically significantly lower than 1 mV·K. -1 .

[0003] Ionic thermoelectric materials are candidate materials for efficient heat harvesting, primarily because their thermal energy is two to three orders of magnitude higher than that of electronic thermoelectric materials. However, ionic thermoelectric materials cannot be directly used in conventional thermoelectric generators (TEGs) because ions cannot pass through the electrodes to reach the external circuitry. Furthermore, ionic thermoelectric materials cannot be used to harvest heat under stable temperature gradients. Summary of the Invention

[0004] This application relates to a thermoelectric power generation device. The thermoelectric power generation device includes an ion gel, a first electrode, and a second electrode. The ion gel includes an ionic liquid, a gelling agent, and an electronic conductor. The first electrode is in contact with the ion gel. The second electrode is in contact with the ion gel. The second electrode is spaced apart from the first electrode. The first electrode includes an inert material. The second electrode includes an inert material.

[0005] This application also relates to a method for manufacturing a thermoelectric power generation device. The method includes forming an ion gel. The ion gel includes an ionic liquid, a gelling agent, and an electronic conductor. The method further includes providing a first electrode in contact with the ion gel, the first electrode comprising an inert material; and providing a second electrode in contact with the ion gel, wherein the second electrode is spaced apart from the first electrode and also comprises an inert material. Attached Figure Description

[0006] In the accompanying drawings, the same reference numerals generally denote the same parts in different views. The drawings are not necessarily drawn to scale, but generally focus on illustrating the principles of various embodiments. In the following description, various embodiments of this application will be described in conjunction with the following drawings.

[0007] Figure 1AThis is a schematic diagram of a thermoelectric power generation device according to an embodiment of this application.

[0008] Figure 1B This is a schematic flowchart illustrating a method for manufacturing a thermoelectric power generation device according to an embodiment of this application.

[0009] Figure 2 The chemical structures of 1-ethyl-3-methylimidazolium dicyanamide (EMIM:DCA), sodium dodecyl sulfate (SDS), gelatin, graphene oxide (GO), and reduced graphene oxide (rGO) are shown.

[0010] Figure 3 (a) Nyquist plots and (b) ionic and electronic conductivities of rGO ionogels with different rGO loadings are shown. The values ​​of ionic and electronic conductivities were obtained by analyzing the Nyquist plots using the equivalent circuit shown in the inset.

[0011] Figure 4 The open-circuit voltage (V) of the rGO ionogel at different rGO loadings is shown. oc The curves show that the rGO loading is (a) 0 wt%, (b) 3.4 wt%, (c) 5.7 wt%, and (d) 42.1 wt%.

[0012] Figure 5 It shows (a)V oc The curve can be divided into five stages. Figure 5 The middle illustration (b) shows a schematic diagram of ion and hole accumulation in stage I. Figure 5 The inset (c) shows the potential of the ionogel under a temperature gradient. Figure 5 The inset (d) shows the equivalent circuit of the thermal voltage generated by the rGO ionogel. Figure 5 The middle illustration (e) shows stage II, Figure 5 The middle illustration (f) shows stage III, Figure 5 The middle illustration (g) shows stage IV and Figure 5 The middle inset (h) shows a schematic diagram of ion and hole accumulation during the V phase.

[0013] Figure 6This illustrates (a) a mixed ion / electron thermoelectric generator (MTEG) connected to an external load. The MTEG containing rGO ion gel is shown under rectangular thermal cycling conditions. Figure 6 The middle illustration (b) shows the output voltage (V) with an external load resistance of 10kΩ. o )curve, Figure 6 The middle illustration (c) shows the output voltage (V) with different resistances of the external load. o The curve was obtained with an rGO loading of 3.4 wt%, a temperature gradient of 3 K, and a thermal cycling duration of 1150 seconds. Figure 6 Inset (d) shows the average power density (P0.05) of MTEG using an ionogel with an rGO loading of 3.4 wt% and the control ionic thermoelectric capacitor (ITEC) using a control ionogel without rGO. av ) with R ex The change. Figure 6 The middle illustration (e) shows the optimal R ex and best P av The results of the control group ITEC without rGO and the thermoelectric generator (TEG) with rGO / SDS film are also shown for comparison as the rGO loading of the ionogel in MTEG changes. Figure 6 The middle inset (f) shows the thermal conductivity (λ) of the rGO ionogel and the P of MTEG. av / λ varies with rGO load.

[0014] Figure 7 The results show that MTEG containing 3.4 wt% rGO and the control group ITEC without rGO are linked to the same R... ex Output voltage (V) under an external load of 10kΩ o Comparison of curves.

[0015] Figure 8 The following shows V in MTEG with rGO loadings of 3.4 wt%, 5.7 wt%, and 7.9 wt%. os With R ex The change. Figure 8 Inset (b) shows V in MTEG with rGO loadings of 3.4 wt%, 5.7 wt%, and 7.9 wt%. os and P s to I os Dependency relationship (P) s =V os I os ). Figure 8The illustration (c) shows the equivalent circuit of the MTEG connected to an external load.

[0016] Figure 9 The chemical structures of (a) EMIM:DCA, PEG, and Na:DCA are shown. Figure 9 The middle illustration (b) shows a schematic diagram of the ion gel manufacturing process. Figure 9 The insets show ESPs with different mass percentages of SiO2 and ionic liquid (IL). 50% N 0.05 Ion gel, storage modulus (G′) and loss modulus (G″) (c) as a function of shear strain at 1 Hz and (d) as a function of shear frequency at 0.05% shear strain. The mass percentages of SiO2 and IL are indicated.

[0017] Figure 10 Show ESP x The thermoelectric potential and ionic conductivity of the ionogels (a) and (b) the ion power factor change with x. The SiO2 content in the ionogels was 25% by mass in IL, and the samples were tested at room temperature and 85% relative humidity (RH). The figures also show EMIM:DCA, PEG, EMIM:DCA / PEG, ES ionogels, and ESP ionogels. 100% The attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra of the ionogel are in the range of (c) 1400-800 cm⁻¹. -1 and (d) 1650-1400 cm -1 The wavenumber range.

[0018] Figure 11 A schematic diagram illustrating the mechanism of cation transport via PEG loading is shown.

[0019] Figure 12 Show ESP 100% N y (a) thermoelectric potential and ionic conductivity of ionogels and (b) ionic power factor as a function of Na + The doping level changed, with SiO2 and IL having a mass percentage of 25%. The figure also shows Na:DCA, EMIM:DCA, and ESP. 100％ N y (c) ATR-FTIR spectrum and (d) Raman spectrum of ionogel.

[0020] Figure 13 Show ESP 100% N 0.05(a) thermoelectric potential and ionic conductivity, (b) ionic power factor and (c) ZT of ionogels i The value varies with the mass percentage of SiO2 and IL. Figure 13 Illustration (d) shows pure EMIM:DCA, ES ion gel, and ESP. 100% Ion gel and ESP 100% N 0.05 Comparison of ionic conductivity and thermoelectric potential of ionogels at optimal power factor.

[0021] Figure 14 The diagram shows (a) a schematic of the TE conversion of ITEC in continuous operation mode. Figure 14 Inset (b) shows the output voltage curve of a 5kΩ external load connected to the ITEC under a rectangular thermal cycle. The temperature gradient of the thermal cycle is 3K, and the duration is 1 hour. Figure 14 The inset (c) shows the equivalent circuit of ITEC, where V oc (t) represents the thermal voltage of ITEC at time t, R in and R ex These represent the internal resistance and external resistance, respectively, and C is the total capacitance of the ITEC. Figure 14 The middle illustration (d) shows the dependence of total energy and average power on external resistance during a thermal cycle.

[0022] Figure 15 The output voltage curve of (a) connected to a 100kΩ external load of ITEC is shown. The total duration of stages II and III was extended to 10 hours. Figure 15 The inset (b) shows the output voltage curves under external loads with different resistances. Figure 15 The middle illustration (c) shows V p and V s Dependence on external resistance. Figure 15 The middle illustration (d) shows V s and output power (P) under a stable temperature gradient of 3K s The dependence of the current.

[0023] Figure 16 A schematic diagram of the sample loading method for thermoelectric potential testing is shown.

[0024] Figure 17 A schematic diagram of a self-made thermoelectric potential testing device is shown.

[0025] Figure 18 The equivalent circuit for Nyquist plot analysis in electrochemical impedance spectroscopy (EIS) testing is shown.

[0026] Figure 19 The image shows a transmission electron microscopy (TEM) image of SiO2 nanoparticles according to an embodiment of this application.

[0027] Figure 20 Show ESP 100％ N 0.05 Scanning electron microscope (SEM) images of ionogels, where the mass percentages of SiO2 and IL are (a) 0%, (b) 10%, (c) 20%, and (d) 30%.

[0028] Figure 21 ESPs with different SiO2 to IL mass percentages are shown. 100% N 0.05 The dynamic viscosity of the ionogel changes with shear frequency. The shear strain is 0.05%.

[0029] Figure 22A The open-circuit thermal voltage (ΔV) curves under the temperature gradient (ΔT) are shown, along with the linear fitting of ESP to different x values: (a, b) 0%, (c, d) 50%, and (e, f) 100%. x The ΔV-ΔT relationship of ion gels is used to determine the ionic Seebeck coefficient (S). i The mass percentage of SiO2 to IL was 25% in all samples.

[0030] Figure 22B The open-circuit thermal voltage (ΔV) curves under the temperature gradient (ΔT) are shown, along with the linear fitting of ESP to different x values ​​of (a,b)150% and (c,d)200%. x The ΔV-ΔT relationship of ion gels is used to determine the ionic Seebeck coefficient (S). i The mass percentage of SiO2 to IL was 25% in all samples.

[0031] Figure 23 Showing ESP with different x values x Nyquist plot of ionogels. The mass percentage of SiO2 to IL was 25% in all samples.

[0032] Figure 24 Showing (a) ESP x The graph shows the relationship between ionic conductivity and EMIM:DCA molar concentration in ionogels, and (b) shows the dynamic viscosity of a mixed solution of EMIM:DCA and PEG, with different molar ratios of PEG with repetitive units (-CH2O-) to IL.

[0033] Figure 25The ATR-FTIR spectra of EMIM:DCA, PEG, EMIM:DCA / PEG, ES ionogel and ESP100% ionogel are shown in the wavenumber range of 2300-2000 cm⁻¹.

[0034] Figure 26A The open-circuit thermal voltage (ΔV) curves under the temperature gradient (ΔT) are shown, and the ionic Seebeck coefficient (Si) is determined by linearly fitting the ΔV-ΔT relationship of the EP100%Ny ionomer gel to different y values ​​(a, b) 0.02, (c, d) 0.04, and (e, f) 0.05. The mass percentage of SiO2 to IL is 25% for all samples.

[0035] Figure 26B The open-circuit thermal voltage (ΔV) curves under the temperature gradient (ΔT) are shown, and the ionic Seebeck coefficient (Si) of the EP100%Ny ionomer gel is determined by linearly fitting the ΔV-ΔT relationship to different y values ​​(a, b) 0.06, (c, d) 0.07, and (e, f) 0.08. The mass percentage of SiO2 to IL is 25% for all samples.

[0036] Figure 27 Showing ESP with different y values 100% N y Nyquist plot of ionogels. The mass percentage of SiO2 to IL was 25% in all samples.

[0037] Figure 28A The open-circuit thermal voltage (ΔV) curves under the temperature gradient (ΔT) are shown, and the ionic Seebeck coefficient (Si) is determined by linearly fitting the ΔV-ΔT relationship of ESP100%N0.05 ion gel with different mass percentages of SiO2 to IL (a, b) 10% and (c, d) 15%.

[0038] Figure 28B The open-circuit thermal voltage (ΔV) curves under the temperature gradient (ΔT) are shown, and the ionic Seebeck coefficient (Si) is determined by linearly fitting the ΔV-ΔT relationship of ESP100%N0.05 ion gel with different mass percentages of SiO2 to IL at (a,b)30% and (c,d)35%.

[0039] Figure 29 Nyquist plots of ESP100%N0.05 ionogels with different SiO2 and IL mass percentages are shown.

[0040] Figure 30 The thermal conductivity of ESP100%N0.05 ionogel is shown as a function of the mass percentage of SiO2 and IL.

[0041] Figure 31 This paper shows a comparison of the ionic conductivity (σi) and thermoelectric potential (Si) of the ESP100%N0.05 ionogel of this application with those of a conventional representative ionogel.

[0042] Figure 32 The output voltage curves for the external loads are shown, where the resistances of the external loads are (a) 1 kΩ, (b) 5 kΩ, (c) 10 kΩ, (d) 30 kΩ, (e) 50 kΩ, and (f) 80 kΩ. The external loads are connected to ITEC with ESP100% NO.05 ionogel.

[0043] Figure 33 The output voltage of stage II is shown by fitting an exponential decay function, where external loads with resistances of (a) 1 kΩ, (b) 5 kΩ, (c) 10 kΩ, (d) 30 kΩ, (e) 50 kΩ and (f) 80 kΩ are connected to ITEC with ESP100%N0.05 ionogel.

[0044] Figure 34 This shows the dependence of the peak voltage (Vp), valley voltage (Vv), and voltage decay time constant (τ) on the external resistance during stage II. The relationship between τ and the external resistance is expressed by the formula... Perform fitting.

[0045] Figure 35A The output voltage curves for the external loads are shown, with resistances of (a) 100kΩ, (b) 200kΩ, (c) 300kΩ, and (d) 390kΩ. The external loads are connected to an ESP-equipped... 100% N 0.05 ITEC of ionogels.

[0046] Figure 35B The output voltage curves for the external load are shown, with resistances of (a) 520 kΩ, (b) 620 kΩ, (c) 700 kΩ, (d) 820 kΩ, and (e) 1 MΩ. The external load is connected to an ITEC containing ESP100% NO.05 ionogel. Detailed Implementation

[0047] The specific details and embodiments of this application will be described in detail below with reference to the accompanying drawings, which illustrate possible implementations of this application. These embodiments are described in detail to enable those skilled in the art to implement this application. Other embodiments may be used, and structural, logical, and electrical changes may be made without departing from the scope of this application. The various embodiments are not necessarily mutually exclusive, as some embodiments may be combined with one or more other embodiments to form new embodiments.

[0048] Features described in one embodiment may be applied accordingly to the same or similar features in other embodiments, even if not explicitly described in those other embodiments. Furthermore, additions, combinations, and / or substitutions to the feature descriptions may also be applied accordingly to the same or similar features in other embodiments.

[0049] The articles “a,” “one,” and “the” used with respect to features or elements include references to one or more features or elements.

[0050] In various embodiments, the term “about” or “approximately” when applied to numerical values ​​covers the value and a reasonable difference, such as within + / - 10% of the value.

[0051] As used herein, the term “and / or” includes any and all combinations of one or more of the listed related items.

[0052] The embodiments described in the context of one thermoelectric power generation device are equally applicable to another thermoelectric power generation device. Similarly, the embodiments described in the context of a method are equally applicable to thermoelectric power generation devices, and vice versa.

[0053] This application provides a thermoelectric power generation device 100. For example... Figure 1AAs shown, the thermoelectric power generation device 100 includes an ion gel 102, a first electrode 104, and a second electrode 106. The ion gel 102 includes an ionic liquid, a gelling agent, and an electronic conductor. The first electrode 104 is in contact with the ion gel 102. The first electrode 104 includes an inert material. The second electrode 106 is in contact with the ion gel 102. The second electrode 106 is spaced apart from the first electrode 104. The second electrode 106 also includes an inert material. In this application, "inert material" refers to a material that does not undergo redox reactions, catalytic reactions (including photocatalytic reactions, electrocatalytic reactions, electrochemical catalytic reactions, photoelectrocatalytic reactions), combination reactions, decomposition reactions, displacement reactions, metathesis reactions, or any electrochemical reactions with or with the thermoelectric power generation device 100 or itself. For example, during the operation of the thermoelectric power generation device 100, only charge accumulation occurs on the first electrode 104 and the second electrode 106, respectively, wherein no redox reactions, catalytic reactions, combination reactions, decomposition reactions, displacement reactions, metathesis reactions, or any electrochemical reactions occur on either the first electrode 104 or the second electrode 106. The inert materials of the first electrode 104 and the second electrode 106 can be the same or different. The inert material of the first electrode 104 can be any one or a combination of gold, silver, platinum, carbon nanotubes, or poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT: PSS). The inert material of the second electrode 106 can be any one or a combination of gold, silver, platinum, carbon nanotubes, or poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT: PSS). For example, the inert material of the first electrode 104 can be gold, and the inert material of the second electrode 106 can be gold. Alternatively, the inert material of the first electrode 104 can be gold, and the inert material of the second electrode 106 can be silver, platinum, carbon nanotubes, etc. In this application, "contact" refers to two physically contacting components that are electrically connected. During operation of the thermoelectric power generation device 100, no redox reaction occurs on either the first electrode 104 or the second electrode 106.

[0054] Preferably, the thermoelectric power generation device 100 is configured to generate a non-zero and stable or relatively stable voltage under a stable temperature gradient. For example, the thermoelectric power generation device 100 is configured to generate a non-zero output voltage greater than, for example, 4 mV over a 24-hour period under a stable temperature gradient. This non-zero output voltage can also be referred to as a non-zero steady-state voltage. In this document, "non-zero and stable or relatively stable voltage" and "non-zero steady-state voltage" can be used interchangeably.

[0055] Preferably, the thermoelectric power generation device 100 is configured to generate a non-zero voltage under a changing temperature gradient.

[0056] Preferably, the electronic conductor is composed of any one or more of the following materials: reduced graphene oxide (rGO) sheets, silver (Ag) nanoparticles, silver (Ag) nanowires, gold (Au) nanoparticles, gold (Au) nanowires, bismuth telluride (Bi₂Te₃) nanoparticles, bismuth telluride (Bi₂Te₃) nanowires, silicon dioxide (SiO₂) nanowires, titanium dioxide (TiO₂) nanoparticles, titanium dioxide (TiO₂) nanowires, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) chains (PEDOT: PSS chains), poly(3-hexylthiophene) chains (P₃HT chains), MXene fibers, or carbon nanotubes. In one example, the electronic conductor can be, for example, an rGO sheet, and the ion gel 102 can be in the form of an ion gel film. The rGO nanosheets can be uniformly dispersed in the ion gel film substantially parallel to the main surface of the ion gel film, wherein each rGO nanosheet forms a supercritical electronic conduction network. This supercritical electron conduction network enables electrons to tunnel through rGO sheets dispersed in an ionic liquid. Within this network, the thermoelectric generator 100 can produce a non-zero and stable or relatively stable voltage under both stable and varying temperature gradients. For example, the thermoelectric generator 100 can produce a non-zero output voltage, for instance, greater than 4 mV, over a period of up to 24 hours under both stable and varying temperature gradients. The supercritical electron conduction network can also be composed of any one or more of the following materials: rGO sheets, silver nanoparticles, silver nanowires, gold nanoparticles, gold nanowires, bismuth telluride nanoparticles, bismuth telluride nanowires, silica nanowires, titanium dioxide nanoparticles, titanium dioxide nanowires, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) chains (PEDOT: PSS chains), poly(3-hexylthiophene) chains (P3HT chains), MXene fibers, or carbon nanotubes. The supercritical electron conduction network enables electrons to tunnel through an electron conductor dispersed in an ionic liquid, allowing the thermoelectric power generation device 100 to produce a non-zero and stable or relatively stable voltage under both stable and changing temperature gradients. In contrast, conventional thermoelectric power generation devices do not possess a supercritical electron conduction network.

[0057] Preferably, the mass percentage of the electronic conductor in the ionogel 102 is greater than the percolation threshold. The "percolation threshold" refers to the critical mass percentage of the electronic conductor in the ionogel that enables the formation of a supercritical electronic conduction network. For example, when the mass percentage is equal to or higher than the percolation threshold, a supercritical electronic conduction network will form in the ionogel; conversely, when the mass percentage is lower than the percolation threshold, a supercritical electronic conduction network will not form in the ionogel.

[0058] Preferably, the ionic liquid is 1-ethyl-3-methylimidazolium dicyandiamide, ethyl-3-methylimidazolium trifluoromethanesulfonate, ethyl-3-methylimidazolium tetrafluoroborate, or ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium chloride, pyridine hexafluorophosphate, pyrazole tetrafluoroborate, or any combination thereof.

[0059] Preferably, the inert material of the first electrode 104 is any one or a combination of gold, silver, platinum, carbon nanotubes, or poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT: PSS). The inert material of the second electrode 106 is any one or a combination of gold, silver, platinum, carbon nanotubes, or poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT: PSS).

[0060] Preferably, the ionogel 102 further includes a surfactant. Alternatively, the ionogel 102 may not include a surfactant.

[0061] Preferably, the surfactant is composed of any one or more of the following materials: sodium dodecyl sulfate, sodium lauryl sulfate, sodium myristyl sulfate, sodium stearate, sodium lauroyl sarcosinate, hexadecyltrimethylammonium bromide, hexadecylpyridine chloride, benzalkonium chloride, benzyl chloride, dimethyl dioctadecyl ammonium chloride, dioctadecyl dimethyl ammonium bromide, sulfobetaine, 3-[(3-cholamidopropyl)dimethylammonium]-1-propanesulfonate (CHAPS), cocamidopropyl hydroxysulfobetaine, cocamidopropyl betaine, phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, sphingomyelin, dodecyl dimethylamine oxide, myristamine oxide, octaethylene glycol monododecyl ether, pentaethylene glycol monododecyl ether, or 2-[4-(2,4,4-trimethylpentane-2-yl)phenoxy]ethanol (Triton X-100).

[0062] Preferably, the gelling agent is a silica nanostructure.

[0063] Preferably, the gelling agent is gelatin.

[0064] Preferably, the ionogel 102 is in the form of a self-supporting membrane or a slurry.

[0065] On the other hand, this application provides a method 200 for manufacturing a thermoelectric power generation device. For example... Figure 1BAs shown, method 200 includes steps 202, 204, and 206. In step 202, an ionic gel is formed, comprising an ionic liquid, a gelling agent, and an electronic conductor. In step 204, a first electrode is provided in contact with the ionic gel, the first electrode comprising an inert material. In step 206, a second electrode, comprising an inert material, is provided in contact with the ionic gel and spaced apart from the first electrode. During operation of the thermoelectric power generation device, no redox reactions, catalytic reactions (including photocatalysis, electrocatalysis, electrochemical catalysis, photoelectrocatalysis), combination reactions, decomposition reactions, displacement reactions, metathesis reactions, or any electrochemical reactions occur on either the first or second electrode. The inert material of the first electrode can be any one or a combination of gold, silver, platinum, carbon nanotubes, or poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT: PSS). The inert material of the second electrode can also be any one or a combination of gold, silver, platinum, carbon nanotubes, or poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT: PSS). For example, the inert material of both the first and second electrodes can be gold. Alternatively, the inert material of the first electrode can be gold, and the inert material of the second electrode can be silver, platinum, carbon nanotubes, etc.

[0066] Preferably, step 202 includes: mixing an electronic conductor and a surfactant to form a dispersion; mixing a liquid containing a gelling agent and an ionic liquid to form a solution; and mixing the dispersion and the solution to form an ionic gel.

[0067] Preferably, the dispersion is sonicated before being mixed with the solution to form an ionic gel.

[0068] Preferably, the gelling agent comprises silica nanostructures.

[0069] Preferably, the gelling agent is gelatin.

[0070] Preferably, the electronic conductor is composed of any one or more of the following materials: reduced graphene oxide sheets, silver nanoparticles, silver nanowires, gold nanoparticles, gold nanowires, bismuth telluride nanoparticles, bismuth telluride nanowires, silicon dioxide nanowires, titanium dioxide nanoparticles, titanium dioxide nanowires, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) chains (PEDOT: PSS chains), poly(3-hexylthiophene) chains (P3HT chains), MXene fibers, or carbon nanotubes.

[0071] Preferably, the ionic liquid comprises one or more of 1-ethyl-3-methylimidazolium dicyandiamide, ethyl-3-methylimidazolium trifluoromethanesulfonate, ethyl-3-methylimidazolium tetrafluoroborate, or ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium chloride, pyridine hexafluorophosphate, pyrazole tetrafluoroborate, or any combination thereof.

[0072] Preferably, the inert material of the first electrode is gold, silver, platinum, carbon nanotubes, or poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT: PSS). The inert material of the second electrode is gold, silver, platinum, carbon nanotubes, or poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT: PSS). Example 1: Ionic gel with reduced graphene oxide (rGO) Material

[0073] Graphene oxide (GO) aqueous solution (GO wafer size: 0.5 μm to 5 μm, monolayer GO >80%) was purchased from Graphene Supermarket. 1-Ethyl-3-methylimidazolium dicyandiamide (EMIM:DCA), gelatin (gel strength 300, type A), L-ascorbic acid (L-AA), and sodium dodecyl sulfate (SDS) were purchased from Sigma-Aldrich. Silver paste (Leitsiber 200) was purchased from Ted Pella Inc. Silicon wafers were purchased from Guangzhou Fangdao Semiconductor Co., Ltd. Sample manufacturing

[0074] The method for producing reduced graphene oxide (rGO) involves reducing an aqueous GO solution with ascorbic acid. The rGO is then separated and purified by centrifugation, filtration, and rinsing with deionized water. The rGO dispersion is then mixed with SDS powder to prepare an rGO / SDS dispersion.

[0075] Next, gelatin powder was added to deionized water and stirred to prepare a gelatin aqueous solution. Then, EMIM:DCA was stirred and mixed with the gelatin solution. Then, the rGO dispersion was added to the mixture of gelatin and EMIM:DCA and stirred. The mixture was immediately drop-cast onto a glass substrate to form an rGO ionogel film. After drying, the rGO ionogel film was obtained. Characterization

[0076] The thermal voltage and Seebeck coefficient were measured using a self-made system. A Keithley 2000 power supply / meter, thermocouples (Type T), and a thermometer (UT325) were used to measure voltage and temperature. The hot and cold sinks were identical in size, both 4 × 4 cm. 2 The distance between the heat sink and the cold sink is 2 cm, and the glass substrate acts as a bridge between them. Silver electrodes with a length of 13 mm and a width of 1 mm are fabricated by coating the glass substrate with silver paste. The distance between the two electrodes is 1 mm. The silver electrodes are then placed on a heating plate and heated at 60°C for 5 minutes.

[0077] Impedance spectroscopy was measured using an electrochemical workstation (PGSTAT 302N, Autolab) at a voltage amplitude of 10 mV and frequencies ranging from 100 kHz to 0.1 Hz. RGO ionogel films with different rGO loadings were sandwiched between two stainless steel sheets. Ionic and electronic conductivity were then calculated from the resistance using the formula σ = l / RA, where σ represents ionic or electronic conductivity, l represents film thickness, R represents electronic or ionic resistance, and A represents area. The distance between the silver electrodes of the MTEG was 1.4 mm.

[0078] Scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements were performed on spin-coated rGO slides using a Thermo Scientific Helios 5 Hydra CX Dual Beam instrument and a Bruker Dimension Icon AFM instrument, respectively. The slides were treated with sonication at a concentration of 5 mg / mL. -1 rGO and 2.5 mg·mL -1 The aqueous dispersion of SDS was prepared at a concentration of 0.2 mg / mL. -1 rGO and 0.1 mg·mL -1 A diluted dispersion of SDS was spin-coated (2000 rpm, 40 s) onto a silicon wafer to prepare well-dispersed rGO sheets. SEM images of the drop-cast rGO / SDS membrane, the ionogel containing 11.8 wt% rGO, and the rGO aerogel were captured using a Zeiss SUPRA 40 SEM. 5 mg·mL⁻¹ -1 rGO and 2.5 mg·mL -1An aqueous dispersion of SDS was droplet-cast onto polished stainless steel to prepare an rGO / SDS membrane with an rGO loading of 66.7%. The rGO / SDS membrane was rinsed with hot deionized water at 60°C to remove SDS. The SDS, ionic liquid, and gelatin in the rGO ionogel were then rinsed with hot deionized water at 60°C to prepare an rGO aerogel. Dynamical mechanical analysis (DMA) was performed using an Anton Paar MCR302 rheometer. Raman spectra were collected using a LabRAM HR Evolution (Horiba Scientific) with a 514.5 nm argon laser as the excitation source. The thermal conductivity of the ionogel was measured using a thermal constant analyzer (TPS 2500S) employing the transient plane source (TPS) method. The sensor was clamped between two identical ionogels, and the thermal conductivity was calculated based on transient temperature data. Structure and properties of rGO ionogel membranes

[0079] The chemical structures of 1-ethyl-3-methylimidazolium dicyandiamide (EMIM:DCA, an ionic liquid (IL)), gelatin, sodium dodecyl sulfate (SDS), graphene oxide (GO), and rGO are as follows: Figure 2 As shown. rGO was prepared by chemically reducing GO with L-ascorbic acid. rGO tablets in water were stabilized using SDS. An rGO / SDS dispersion was mixed with an aqueous solution of EMIM:DCA and gelatin. A self-supporting rGO ionogel membrane was prepared by drop casting the mixture and drying.

[0080] The ionic conductivity and electronic conductivity of rGO ion gel were studied using AC impedance spectroscopy. Figure 3 (Illustration (a)). The ionic conductivity of the control group ionogel without rGO was 1.05 S·m. -1 This value was estimated based on the intercept of the curve with the Z' axis. The electronic and ionic conductivity of rGO ionogels with different rGO loadings were obtained by analyzing the Nyquist plot. The electronic and ionic conductivity were plotted as a function of the rGO loading. Figure 3 Illustration (b)). As the rGO loading increased from 1.7 wt% to 42.1 wt%, the electronic conductivity of the rGO ionogel increased from 2.06 × 10⁻⁶. -5 mS·m -1 Increased to 0.53 mS·m -1 The ionic conductivity decreased from 1.00 S·m. -1 Reduced to 4.92×10 -3 S·m -1Electron conduction is attributed to the rGO network formed in the ionogel, and therefore increases with increasing rGO loading. Ionic conductivity decreases with increasing rGO loading, which can be attributed to the decrease in IL loading and the reinforcement of the gel by rGO. Thermoelectric properties of rGO ionogels

[0081] The thermoelectric properties of rGO ionogels were characterized by applying a temperature gradient across the sample. The open-circuit voltage (Voc) of the rGO ionogel membrane varied with rGO loading from 0 wt% to 42.1 wt%. Figure 4 Without rGO, after applying a temperature gradient, Voc gradually increases and eventually reaches a steady-state value of 12.8 mV at a temperature gradient of 0.5 K. Figure 4 (Illustration (a)). The corresponding thermoelectric potential is 25.6 mV·K⁻¹. After the heater is turned off, the temperature gradient drops to zero, and Voc correspondingly drops slowly to zero. The change in Voc can be attributed to ion accumulation at both ends of the temperature gradient, i.e., the Soret effect.

[0082] The presence of rGO significantly affects the V of the ionogel under the temperature gradient. oc Curve. When the rGO loading is 3.4 wt%, the thermal voltage reaches a steady-state value of 12.1 mV under a temperature gradient of 0.5 K. Figure 4 Illustration (b)). When the rGO loading was further increased to 5.7 wt%, the V of the ionogel oc The curves become very different, and transient behavior with peak voltage can be observed. Figure 4 (Illustration (c)). Upon heater activation, the thermal voltage increases. After 485 seconds, it reaches a peak of 11.5 mV. The thermal voltage then decays under a stable temperature gradient, eventually reaching a steady-state value of 9.6 mV. This can be attributed to the conductive rGO network formed in the ionogel. The peak voltage disappears when the rGO loading reaches 42.1 wt%. The steady-state thermal voltage at a 42.1% rGO loading is 17.6 μV·K. -1 The Seebeck voltage of the rGO / SDS film is close to that of the rGO / SDS film (17.5 μV·K). -1 Seebeck voltage of either the pure rGO membrane or the pure rGO membrane (17.6 μV·K⁻¹) Transient and steady-state voltage behavior

[0083] The transient Voc behavior is due to the presence of rGO sheets in the ionogel. Under the influence of a temperature gradient, ion accumulation at both ends creates a potential gradient from the cold end to the hot end. The potential of the rGO sheets at lower temperatures is higher than that of the rGO sheets at higher temperatures. However, since the Seebeck coefficient of rGO is about three orders of magnitude lower than the thermoelectric potential of ionic liquids, the potential within the same rGO sheet can be considered uniform. When the rGO sheets are far apart, they do not significantly affect Voc. oc The curve shows that when the rGO loading exceeds the percolation threshold, charge is transported between rGO sheets via tunneling, forming a conductive network. The charge carriers in rGO are holes, as it exhibits a positive Seebeck coefficient. Voltage decay can be attributed to charge transport through the rGO conductive network.

[0084] This model can be used to understand the transient and steady-state V of rGO ion gels. oc Behavior. For example... Figure 5 As shown in illustration (a), V oc The curve can be divided into 5 stages. In stage I, V oc The temperature rises after a temperature gradient is applied. This can be attributed to the accumulation of cations and anions at both ends, i.e., the Sorey effect. Figure 5 Illustration (b)). Simultaneously, due to the Seebeck effect, holes accumulate at the hot end of the rGO sheet. Since the ionic thermoelectric potential is much higher than the Seebeck coefficient of rGO, the thermal voltage between the two ends is controlled by the Soray effect of the ions. Due to the thermal voltage between the two ends, the potential of the rGO sheet should be from the cold end (φ). c ) to hot end (φ h Decreasing () Figure 5 Illustration (c)).

[0085] When the potential difference between two adjacent rGO plates is low and the distance between them is small, holes can tunnel through the gap between the rGO plates. Figure 5 (Illustration (e)). Furthermore, a capacitance exists at the interface between the rGO sheet, which acts as an electronic conductor, and the ionic liquid, which acts as an ionic conductor, similar to the electrochemical interface between an electrode and an electrolyte. Additionally, since the thermal voltage of the ionic liquid is much higher than the Seebeck voltage of rGO, electrons (holes) in the rGO sheet are transported to the interface between rGO and IL to partially balance the accumulated cations (anions). The presence of the resistance (R) of charge transport through the rGO network and the interfacial capacitance (C) between the rGO sheet and the ionic liquid leads to V oc Attenuation. This is stage II. Based on this model, an equivalent circuit is proposed ( Figure 5 Illustration (d)).

[0086] Because the individual rGO sheets are separated by the ionic liquid, the open-circuit voltage does not decay to zero. The open-circuit voltage tends to stabilize in stage III. Figure 5 (Illustration (f)). The higher the rGO loading, the less ionic liquid between the rGO sheets, which results in a lower steady-state open-circuit voltage.

[0087] In stage IV, the heater is turned off. Since the temperature gradient is now zero, the accumulated ions and holes retreat to their initial positions. The ions retreat much faster than the charge balance of the electrons / holes, resulting in a negative voltage. Figure 5 Illustration (g)). Finally, electrons / holes used for charge balance at the rGO / IL interface retreat to rGO, which leads to a decrease in thermal voltage (e.g. Figure 5 The illustration (h) shows stage V.

[0088] When the rGO loading was 42.1 wt%, the open-circuit thermoelectric potential did not exhibit transient behavior. At such a high rGO loading, the rGO network exhibited good electronic conductivity between the sample ends. Therefore, the Soray effect of the ions no longer contributed to the thermoelectric potential. Thermoelectric properties of MTEG

[0089] MTEG was fabricated by coating silver electrodes onto rGO ion gel. Figure 6 Illustration (a)).

[0090] Similar to open-circuit thermal voltage, transient and steady-state behavior of the external load output voltage can be observed for ionogels with rGO loadings ranging from 3.4 wt% to 20.0 wt%. Figure 6 Illustration (b) shows the Vo of a 10kΩ external load connected to MTEG with a 3.4wt% rGO loading during a rectangular thermal cycle with a temperature gradient of 3K for 1150 seconds. o The curve shows the transient and steady-state output voltages. (V) o The curve can also be divided into five stages. For example... Figure 6 As shown in illustration (c), the output peak voltage (V) op ) and steady-state voltage (V os It depends on the resistance (R) of the external load. ex R ex The higher, V op Value and V os The higher the value, the better. When the rGO loading is in the range of 3.4 wt% to 20.0 wt%, V can be observed under a stable temperature gradient. os This indicates that the device can generate electrical energy under a stable temperature gradient.

[0091] Average power density (P) on external load av It can be calculated using the following formula: Among them, R ex VOL represents the resistance of the external load, VOL represents the volume of the rGO ion gel between the electrodes, and Δt represents the total duration of the thermal cycle. Figure 6 Illustration (d) shows the P of ionogels with different rGO loadings. av With R ex The change. Figure 6 Illustration (e) shows the optimal P av With the corresponding R ex Relationship diagram. Optimal R ex The R value decreased with increasing rGO loading. The control group ionomer gel without rGO showed a lower R value. ex The R-resistance of the rGO ionogel is 50 kΩ, while the rGO loading is 66.7 wt%. ex The resistance decreased to 0.2 kΩ. The optimal P value was achieved when the rGO loading increased from 0 wt% to 3.4 wt%. av From 4.1 W·m -3 Increased to 18.6 W·m -3 However, when the rGO loading further increased to 66.7 wt%, P av Then it drops to 3.7 mW·m -3 When the rGO loading is 3.4 wt%, P av It has reached its maximum value.

[0092] The thermal conductivity (λ) of the rGO ionogel increases with increasing rGO loading. The thermal conductivity of the control group ionogel without rGO is 0.186 W·m. -1 ·K -1 When the rGO loading increased to 20.0 wt%, the thermal conductivity increased to 0.369 W·m. -1 ·K -1 ( Figure 6 Illustration (f)). Since thermal conductivity is not very sensitive to rGO loading, the P of MTEG av / λ changes with rGO load and optimal P av Similar to changes in rGO load ( Figure 6 Illustration (f)). MTEG with an rGO loading of 3.4 wt% exhibited the highest P. av / λ value 64.6 K·m -2 This is the control group ITEC (21.8 K·m). -2 Three times that of ).

[0093] MTEG's V o The curve and the V of the control group ITEC without rGO oThe significant difference between the curves lies in the steady-state output voltage under a stable temperature gradient. Figure 7 Under a stable temperature gradient, the output voltage of the ITEC drops to zero. Therefore, the MTEG can generate electricity continuously because it can harvest heat from temperature fluctuations and a stable temperature gradient. In contrast, the ITEC can only harvest heat from temperature fluctuations.

[0094] By using the exponential decay function V o = V1 e -(t-t0) / τ1 + V os Fitting V o The curve can be used to obtain the steady-state output voltage (V). os The value is given by V1, where V1 represents the peak output voltage and τ1 represents the time constant. Figure 8 Illustration (a) shows the V of MTEG with rGO loadings of 3.4 wt%, 5.7 wt%, and 7.9 wt%, respectively. os With R ex The change. V os With R ex It increases with the increase of.

[0095] Since the output voltage is stable under a stable temperature gradient, the TE performance of the MTEG should be similar to that of a conventional TEG. Figure 8 Illustration (b) shows V os For the corresponding current (I) os The dependence of V is similar to that of a conventional TEG. The corresponding steady-state power density can be determined based on V. os and I os Calculations show that P s =V os I os P s and I os The arched relationship between them is also similar to that of a regular TEG.

[0096] Based on these results and the open-circuit thermal voltage results, the equivalent circuit of MTEG was constructed. Figure 8 (Illustration (c)). Due to electron tunneling through the rGO sheets, the thermal voltage generated by the rGO ionogel can maintain a steady-state value under a stable temperature gradient. The internal resistance mainly originates from the ionic resistance of the rGO ionogel in MTES, which is connected in series with the external load. According to this model, the Voss value of MTEG is similar to the Seebeck voltage of conventional TEG.

[0097] MTEG differs significantly from combined devices consisting of ITEC and TEG. ITEC's V... o It decays to zero under a stable temperature gradient. Only TEG can produce a Seebeck voltage, which does not exceed several hundred μV·K. -1MTEG also differs significantly from thermal galvanic cells (TGCs). TGCs can generate electricity under a stable temperature gradient, but their output voltage decays to zero within hours.

[0098] In this example, the active material of MTEG is an ionogel containing rGO. Since ionic liquids are ionic conductors and rGO is an electronic conductor, the ionogel containing rGO is a hybrid ionic / electronic conductor. MTEG can harvest heat from both temperature fluctuations and stable temperature gradients. Specifically, MTEG can provide a stable output voltage to an external load under a stable temperature gradient. Under a stable temperature gradient, the thermal conductivity (TE) of MTEG is similar to that of conventional TEG. The thermoelectric potential of MTEG can reach 7.0 mV·K. -1 The Seebeck coefficient is one to two orders of magnitude higher than that of the best electronic thermoelectric materials. Its mechanism of action is attributed to electron tunneling between rGO sheets dispersed in the ionic liquid, and its higher thermoelectric potential is related to the Soray effect of ions. Example 2: Ion gel containing SiO2 nanoparticles Material

[0099] 1-Ethyl-3-methylimidazolium dicyandiamide (EMIM:DCA, ≥98%), sodium dicyandiamide (Na:DCA), polyethylene glycol (PEG, Mn≈300), and isopropanol (IPA) were all purchased from Sigma-Aldrich. SiO2 nanoparticles with an average particle size of 20 nm were supplied by Aerosil Co. Ltd. Conductive silver paste (product number 16035) was purchased from Ted Pella Inc. Silica was dried at 120°C for 10 hours and then stored at 60°C for later use; other chemicals were used as is. Manufacturing of SiO2 ion gel

[0100] A PEG- and Na+-doped ionic liquid (IL) was prepared by mixing PEG, Na:DCA, and EMIM:DCA. The solution was then mixed with SiO2 nanoparticles and ground in an agate mortar for 20 minutes. Based on the molar ratio of PEG repeating units to EMIM:DCA and the molar ratio of sodium salt to EMIM:DCA, the prepared SiO2 / PEG ionic gel was designated ESP. x And SiO2 / PEG / Na + Ion gel is abbreviated as ESP x N y Where x and y represent the molar ratio of the repeating unit (-CH2O-) of PEG to IL, and the molar ratio of Na⁺ to IL, respectively. That is, x = n PEG / n EMIM:DCA y=nNa+ / nEMIM:DCA , where n PEG n EMIM:DCA and n Na+ These are PEG units, EMIM:DCA, and Na, respectively. + The molar amounts of SiO2 and IL are both 20% by mass, unless otherwise specified. All ionogels were dried at 60°C for 20 hours to remove adsorbed moisture. For thermoelectric testing, the ionogel was scraped onto a 13mm × 26mm glass substrate, using five layers of polypropylene tape as a spacer, with a total tape thickness of 250μm. Silver electrodes with a length of 13mm and a width of 1mm were fabricated by screen printing silver paste onto the glass substrate. A schematic diagram of the sample loading method is shown below. Figure 16 As shown. Thermoelectric property characterization

[0101] The thermoelectric potential of ions was measured using a homemade device consisting of two Peltier devices fixed to an alumina radiator, such as... Figure 17 As shown. The thermoelectric output (ΔU) and temperature difference (ΔT) of the samples were measured using a Keithley 2000 multimeter and a thermocouple (type T). For each sample, the ΔU value was measured at four different ΔT values. The ionic thermoelectric potential (S) was calculated using the following formula. i ), Each sample was tested in triplicate, and the average S was calculated. i Values ​​and corresponding error bars. An ionic thermoelectric capacitor (ITEC) is an energy harvesting device that converts heat into electrical energy. The sample preparation process is similar when measuring the ionic thermoelectric potential. Unless otherwise stated, all tests were performed at approximately 85% relative humidity and approximately 25°C.

[0102] The ionic conductivity of the ionogel was measured using electrochemical impedance spectroscopy (EIS) on a Metrohm Autolab electrochemical workstation. The voltage amplitude was 10 mV, and the frequency scan range was 1 Hz to 5000 kHz. Circular samples with a diameter of 16.5 mm and a thickness of 2.0 mm were clamped between two polished stainless steel electrodes. A silicone elastic gasket was used to maintain the distance between the two electrodes. Figure 18 As shown, the Nyquist plot in the EIS test was analyzed using equivalent circuit analysis. The ionic resistance (R0) of the ionogel was determined by extrapolating the real axis curve from the EIS data. i ), σ is obtained from the following equation i value, Where ι is the thickness of the ionogel, A is the contact area between the ionogel and the stainless steel electrode, and R... i (Ω) represents the ionic resistance, which is obtained by extrapolating the Nyquist plot using the abscissa. In this example, σ is performed three times for each ionogel. i Parallel measurements were performed, and then σ was calculated. i The average value and the corresponding error bar.

[0103] The electrochemical behavior of the ion supercapacitor was tested using the ECO HEMIE Autolab system. The voltage scan rate for cyclic voltammetry (CV) was 20 mV / s. -1 The thermal conductivity of the ionogel was measured using the transient hot wire method with a XIATECH-TC3000E. All measurements were performed at room temperature. Characterization of other properties

[0104] Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images were obtained using a field emission electron microscope (JEM-2010F, JEOL) and a field emission scanning electron microscope (Zeiss supra40), respectively. Fourier-transform infrared (FTIR) spectra were obtained using a Carry 600 (Agilent Technologies). FTIR and Raman spectra were obtained using a PerkinElmer Fourier transform infrared spectrometer (FTIR, ATR mode) and a Renishaw Via-Reflex Raman microspectrometer, respectively, under a 532 nm laser. Rheological analysis was performed using a Thermo HAAKEMARS 60 rheometer with a parallel plate geometry of 25 mm in diameter and a gap of 1 mm. Relationship between carrier concentration C and ionic conductivity

[0105] The addition of PEG can dilute the ion concentration and further reduce the ionic conductivity of the ionogel. Therefore, to intuitively study the relationship between them, ESP... x The molar concentration of the ionic liquid in the ionic gel is calculated using the following formula. Where V total Let m be the total volume, ρ be the weight, M be the density, n be the molar mass, and C be the number of moles. IL q is the molar concentration of IL, μ is the charge carrier, and x is the molar percentage of repeating units (-CH2O-) in PEG relative to IL. Manufacturing and Structure of Ion Gels

[0106] Figure 9 The chemical structures of EMIM:DCA, PEG, and Na:DCA are shown. EMIM:DCA exhibits high ionic conductivity and low viscosity. SiO2 nanoparticles are used as a gelling agent because they can generate high ionic conductivity. Transmission electron microscopy (TEM) shows that the diameter of the SiO2 nanoparticles is approximately 20 nm. Figure 19 The molecular weight is approximately 300 gmol. -1 PEG and Na:DCA were used as additives for EMIM:DCA / SiO2 ion gels.

[0107] EMIM:DCA, PEG, and Na:DCA were mixed and then ground together with SiO2 nanoparticles to prepare an ionogel. Figure 9 Illustration (b)). Based on the molar ratio of PEG repeating units to EMIM:DCA and the molar ratio of sodium salt to EMIM:DCA, the EMIM:DCA / SiO2 / PEG ionogel is represented as ESP. x And EMIM: DCA / SiO2 / PEG / Na + Ionogel is referred to as ESP x N y Where x and y are the molar ratios of PEG repeating unit (-CH2O-) to IL and Na, respectively. + The molar ratio with IL, i.e., x=n PEG / n EMIM：DCA y=n Na+ / n EMIM:DCA Where n PEG， n EMIM:DCA and n Na+ These are PEG units, EMIM:DCA, and Na, respectively. + The molar number. The mass percentage of SiO2 to IL is 20%, unless otherwise stated. Iongels can be self-supporting. Figure 20 ESPs with different SiO2 loadings are shown. 100% N 0.05 Scanning electron microscope (SEM) images of ionomers. When the mass percentage of SiO2 to IL is less than 20%, no obvious features are observed, while when the mass percentage of SiO2 to IL is 30%, obvious aggregates can be observed.

[0108] The mixture exhibits gel-like properties, which can be confirmed by dynamic mechanical analysis. Figure 9 Illustrations (c and d) show ESPs with different SiO2 to IL mass percentages. 100% N 0.05The strain- and frequency-dependent relationships of the storage modulus (G') and loss modulus (G'') of the ionogel. In the absence of SiO2 nanoparticles, G' is comparable to G'', in other words, the mixture of EMIM:DCA, PEG, and Na:DCA is a viscous fluid. The presence of SiO2 nanoparticles immobilizes the IL. G' is consistently higher than G'', which indicates its gelling properties. Furthermore, both G' and G'' increase with increasing SiO2 nanoparticle loading. Figure 21 As shown, all samples exhibited significant shear thinning behavior; in other words, the dynamic viscosity decreased with increasing shear frequency. Furthermore, the dynamic viscosity increased with increasing SiO2 loading. This indicates an interaction between EMIM:DCA and SiO2 nanoparticles. PEG enhances thermoelectric potential

[0109] pass Figure 16 and Figure 17 The ionic thermoelectric potential (Si) of the ionogel in the system shown is measured. The PEG-free EMIM:DCA / SiO2 ionogel is referred to as the ES ionogel, with a Si of 15.5 mVK⁻¹ and a σi of 39.3 mScm⁻¹. The ionic power factor (PFi) is calculated based on the ionic thermoelectric potential and ionic conductivity. The corresponding ion power factor is 942.2 μWm⁻¹K⁻².

[0110] Adding PEG to ES ionogels can significantly increase the thermoelectric potential, thereby improving the overall TE characteristics. For example... Figure 10 Illustration (a) Figure 22A and Figure 22B As shown, ESP x The thermoelectric potential of the ionogel increases with increasing PEG content, reaching a maximum of 26.7 mVK at x=100%. -1 Then, with further increases in PEG content, the thermoelectric potential decreases. In contrast, by adding PEG, the thermoelectric potential of conventional PVDF-HFP / EMIM:TFSI ionogels can be increased from -4 mVK. -1 Increased to +14 mVK -1 The thermoelectric potential of this application is higher than that of conventional ion gels, which can be attributed to the fact that the anions of the ion liquid are different from those of conventional ion gels.

[0111] The ionic conductivity of ionogels was studied using AC impedance spectroscopy. For example... Figure 23 As shown, in ESP xIn the Nyquist plot of ionogels, the real part of impedance (Z') and the imaginary part of impedance (Z”) are substantially linearly related. This is significantly different from some common polymeric electrolytes, which typically exhibit a semi-circular shape in the high-frequency region. The absence of a semi-circular shape in the high-frequency range can be attributed to the relaxation of the dielectric response of the bulk electrolyte by moving ions, thus weakening the capacitive properties. The σ of ES ionogels... i 39.3 mScm -1 σ is higher than that of pure EMIM:DCA i (31.8 mScm -1 This can be attributed to the channels provided by SiO2 nanoparticles for ion transport. Although As shown in Figure 10(a), the ionic conductivity decreases monotonically with increasing PEG content. At x=200%, the ionic conductivity is 22.3 mS / cm. -1 There are two possible reasons why PEG causes a decrease in ionic conductivity. One reason is that the concentration of EMIM:DCA decreases with increasing PEG content. Figure 24 (Illustration (a)). Another reason is the reinforcement of ionic gels by PEG. For example... Figure 24 As shown in Figure (b), the dynamic viscosity increases with decreasing EIM:DCA concentration. For the ES ionogel, the dynamic viscosity is 22.7 mPa·s, while for the ESP... 100% The ionogel exhibits an increased dynamic viscosity of 43.9 mPa·s.

[0112] The ionic power factor (PF) initially increases with increasing PEG content. Figure 10 Illustration (b)). When x=100%, the ion power factor reaches its optimal value of 2205 μWm. -1 K -2 However, it decreases with further increases in PEG content.

[0113] To understand the mechanism by which PEG enhances thermoelectric potential, Fourier transform infrared spectroscopy (FTIR) was used to study the ion gel and its components. PEG at 1062 cm⁻¹... -1 The broader spectral band at that location is caused by the stretching vibration of the C−O bond. Figure 10 Illustration (c)). After mixing EMIM:DCA with PEG, the band shifted significantly to 1088 cm⁻¹. -1 .like Figure 10 As shown in illustration (d), pure EMIM:DCA at 1568 cm⁻¹ -1 The spectral band at that location can be attributed to EMIM + The C−N stretching vibration of cations. This feature also appears at the same location in EMIM:DCA / SiO2 ionomer gels, while in ESP... 100% In ionogels, this band shifts to 1572 cm⁻¹.-1 These results indicate that PEG and EMIM + There is an interaction between them. This may be related to EMIM. + The positive charge on the PEG atom and the partially negative charge on the oxygen atom are related. Pure EMIM:DCA at 2123 cm⁻¹ -1 The spectral band at that location is attributed to DCA - C≡N stretching vibration of anions ( Figure 25 When EMIM:DCA was mixed with PEG, the spectral band did not shift significantly. This indicates that PEG reacts with DCA... - The interaction between them is very weak.

[0114] PEG can promote lithium-ion migration in solid polymer electrolytes because PEG can coordinate with lithium ions through ether oxygen atoms. This can be understood as... (EMIM) + The cation can coordinate with the oxygen atom of PEG. This coordination facilitates the dissociation of EMIM:DCA and promotes EMIM... + The migration. Figure 11 This illustrates PEG and EMIM. + The coordination mechanism. Although the addition of PEG can strengthen the ionogel, thereby reducing ion mobility, PEG can promote the coordination mechanism of EMIM. + Cation migration. Therefore, PEG can increase DCA. - With EMIM + The difference in mobility enhances the thermoelectric potential. Na + Cation doping

[0115] To further enhance the thermoelectric potential, Na:DCA was added to the ESP ionogel. This is because Na+ has a strong Coulombic attraction to DCA-, which can slow down the migration of DCA-. Figure 12 Illustration (a) Figure 26A and Figure 26B As shown, the thermoelectric potential of the ESP100%Ny ionomer gel initially increases with increasing Na+ doping concentration. At a Na+ doping concentration of 5 mol%, the thermoelectric potential reaches a maximum of 34.4 mV K⁻¹, and then decreases with further increases in Na+ doping concentration. This optimal thermoelectric potential is significantly higher than that of the undoped ESP100% ionomer gel (27 mV K⁻¹). The ionic conductivity of the ionomer gel decreases with increasing Na+ doping concentration. Figure 27 and Figure 12 Illustration (a) shows that the ionic conductivity is 22.9 mScm-1 when the Na+ doping level is 8 mol%.

[0116] For the ion power factor, the optimal Na +The doping concentration is 5 mol%. Figure 12 Illustration (b)). ESP 100% N 0.05 Ion gels can exhibit a 26.2 mS / cm² pattern. -1 High ionic conductivity and 34.4 mVK -1 It has a high thermoelectric potential. The optimal power factor is 3,106 μW / m². -1 K -2 The ion power factor is higher than that of doped Na. + The EMIM:DCA / PVDF-HFP ionogel is selected because its ionic conductivity is much higher than that of doped Na. + EMIM:DCA / PVDF-HFP ionogel.

[0117] Na in ion gel was studied using FTIR and Raman spectroscopy. + and DCA - The interaction between them. For example... Figure 12 As shown in illustration (c), the C≡N stretching band appears at 2163 cm⁻¹ in the FTIR spectrum of pure Na:DCA. -1 At this point, it is much higher than the C≡N stretching band of pure EMIM:DCA (2123 cm⁻¹). -1 This can be attributed to Na. + With DCA - The coulomb attraction between them is higher than that between EMIM. + With DCA - The Coulomb attraction between them. Na + Doping shifts the C≡N stretching band of EMIM:DCA into the blue region. A similar shift of the C≡N stretching band is also observed in the Raman spectra of Na:DCA, EMIM:DCA, and mixtures of Na:DCA and EMIM:DCA. Figure 12 Illustration (d)).

[0118] Optimization of SiO2 nanoparticle loading

[0119] Regarding the power factor of the EMIM:DCA / SiO2 ionogel, the optimal SiO2-ionic liquid loading was 20%. The optimal SiO2 nanoparticle loading changed with the addition of PEG and Na+. ESP100%N0.05 ionogels with different mass percentages of SiO2-ionic liquid were fabricated and tested. Figure 13 Illustration (a) Figure 28A and Figure 28B As shown, the loading of SiO2 nanoparticles has a slight effect on the ionic thermoelectric potential. When SiO2 accounts for 20% of the ionic liquid by mass, the ionic thermoelectric potential is 34.7 mVK. -1The value is essentially equal to that when SiO2 accounts for 25% of the ionic liquid (34.4 mVK). -1 The loading of SiO2 nanoparticles also affects the ionic conductivity. Figure 13 Illustration (a) and Figure 29 When the mass percentage of SiO2 in the ionic liquid increases from 10 wt% to 25 wt%, the ionic conductivity remains substantially unchanged. When the mass percentage of SiO2 in the ionic liquid is 10%, the ionic conductivity is 27.0 mS / cm. -1 When SiO2 accounts for 25% of the mass percentage of the ionic liquid, the ionic conductivity decreases slightly to 26.2 mS / cm. -1 .

[0120] Figure 13 Illustration (b) shows the relationship between the ionic power factor and the mass percentage of SiO2 in the ionic liquid. This dependence is similar to that of the ionic thermoelectric potential. The optimal power factor is 3218.1 μWm⁻¹K⁻² when the mass percentage of SiO2 in the ionic liquid is 20%. The thermal conductivity of ESP100%N0.05 ionic gels with different mass percentages of SiO2 in the ionic liquid was measured using the hot-wire method. Figure 30 As shown, the thermal conductivity increases slightly with increasing SiO2 loading. The ionic figure of merit (ZTi) is calculated based on ionic conductivity, ionic thermoelectric potential, and thermal conductivity. Figure 13 As shown in illustration (c), ZTi depends on the SiO2 loading. The optimal ZTi value is 3.94 when SiO2 accounts for 20% of the ionic liquid by mass.

[0121] Figure 13 Illustration (d) shows EMIM:DCA, ES ion gel, and ESP. 100% Ion gel and ESP 100% N 0.05 Ionic conductivity and thermoelectric potential of ionogels. The ionic conductivity of ES ionogels can reach 39.3 mS / cm. -1 It is even higher than the ionic conductivity of pure EMIM:DCA (31.8 mS / cm). -1 Although PEG and / or Na are added + It will reduce ionic conductivity, but ESP 100% N 0.05 The ionogel still achieved 26.7 mS / cm. -1 The ionic conductivity. Adding PEG significantly increases the thermoelectric potential to 26.7 mVK. -1 Na + Doping can be further increased to 34.7 mVK.-1 Compared to conventional ionogels, ESP... 100% N 0.05 Ion gels can exhibit both high thermoelectric potential and high ionic conductivity, while conventional ion gels only have one of either high ionic conductivity or high thermoelectric potential. Figure 31 ). Continuous power generation

[0122] Conventional ionic thermoelectric materials cannot be used directly in thermoelectric power generation devices because ions cannot pass through the electrodes to reach the external circuit. Instead, conventional ionic thermoelectric materials are typically used in ionic TE capacitors (ITECs) to harvest heat. 100% N 0.05 The ionogel ITEC was tested while always connected to an external load. Figure 14 Illustration (a)). Figure 14 Illustration (b) shows the output voltage curve of a 5kΩ external load connected to the ITEC under rectangular thermal cycling. The output voltage curve can be divided into five stages. After the heater is turned on, the temperature gradient increases, the output voltage increases, and finally reaches a peak value (V). p 8.3mV. This is the first stage. The output voltage rise is due to the Sorey effect of anions and cations. After reaching the peak, the output voltage decays over time, which is the second stage. The voltage decay is due to charge compensation caused by the migration of electrons and holes from the external circuit to the two electrodes. It should be noted that the output voltage decays to zero. Under a stable temperature gradient, the output voltage becomes a steady-state voltage. This is the third stage. Then, in the fourth stage, the heater is turned off. In this stage, the accumulated anions and cations migrate back to their initial positions, and the electrons and holes used to maintain charge balance at the two electrodes also tend to flow back to the external circuit. However, the migration rate of electrons and holes is much slower than that of cations and anions, which results in a negative voltage. Valley output voltage (V v The voltage is -2.3mV. After reaching the valley voltage, electrons and holes retreat, and the absolute voltage gradually decreases to zero. This is the fifth stage. Throughout these five stages, the ITEC continuously performs work on the external load.

[0123] The output voltage of the second stage can be fitted using an exponential decay function, as shown in the formula: Where τ is the decay time constant, and Vs is the steady-state output voltage of the third stage. The output voltage curve depends on the external resistor ( Figure 32 The τ value was obtained by fitting the output voltage decay of the second stage. Figure 33 ). Figure 34 V is shown p V v and τ to external resistance (R) exThe dependence of these parameters on the external resistance increases. They all increase with increasing external resistance. Figure 14 For the equivalent circuit shown in illustration (c), τ and R ex The relationship between them can be expressed by formulas. Fit, where R in C is the internal resistance, and C is the total capacitance of the ITEC. According to the fitting results, the capacitance is 4.28mF.

[0124] The total energy density (Et) and average power (Pav) during the rectangular thermal cycle were calculated, where and Where Vout is the output voltage across the external load (resistor) during one thermal cycle, Rex is the external resistance, A is the cross-sectional area of ​​the ionogel, and ∆t is the duration of one complete thermal cycle. Figure 14 As shown in illustration (d), the specific energy increases with increasing Rex. The average power density initially increases, then decreases with increasing external resistance. The optimal average power density is 2.13 mW / m³. -2 .

[0125] It should be noted that the output voltage remains stable under the steady temperature gradient of stage III. This is quite different from conventional ITECs. Typically, conventional ITECs only have four stages in the rectangular thermal cycle because the output voltage decays to zero in stage II. Therefore, conventional ITECs can only harvest heat intermittently and cannot generate electricity under a steady temperature gradient. Figure 15 Illustration (a) shows the output voltage curves of a 100kΩ external load connected to the ITEC with extended durations in stages II and III. The steady-state voltage can be obtained by fitting the output voltage curves of stages II and III using a decay function, where... After 10 hours, the steady-state voltage (Vs) was still 15.9mV.

[0126] The higher the external resistance, the more pronounced the steady-state output voltage of the ITEC in ESP100%N0.05 ionogel. Figure 15 Illustration (b) shows the output voltage curve for an external load, where the resistance of the external load ranges from 100 kΩ to 1 MΩ. Figure 15 As shown in illustration (c), the steady-state output voltage increases with increasing external resistance. According to Ohm's law, the steady-state current (Ist) flowing through the external load can be calculated. s ),in It can also calculate the power (P) under steady-state output voltage. s ), . Figure 15 Illustration (d) shows V s and P s with I sRelationship diagram. V s and I s The relationship between them is almost linear, while P s -I s The relationship exhibits a downward parabolic curve, which closely resembles the standard IVP curve of TEG (Thermoelectric Genetic Engineering) materials. At a temperature gradient of 3 K and an external resistance of 1 MΩ, the steady-state output voltage is 39.7 mV. The corresponding temperature coefficient is 13.2 mVK. -1 It has a Seebeck coefficient that is 1-2 orders of magnitude higher than that of TEG, which has the best electronic thermoelectric material.

[0127] An ionogel with high thermoelectric potential and high ionic conductivity was prepared using SiO2 nanoparticles as a gelling agent and PEG and Na+ as additives. SiO2 nanoparticles provide ion transport channels, thereby improving ionic conductivity. PEG can strengthen the ES ionogel, thus reducing ionic conductivity. However, due to EMIM... + Cations and DCA - Lewis acid-base interactions exist between anions, and PEG can promote EMIM. + Cation migration. Therefore, the presence of PEG can increase EMIM. + Cations and DCA - The difference in anion mobility increases the ionic thermoelectric potential. Due to the difference in Na... + With DCA - There is a strong Coulomb attraction between anions, Na + It can also slow down DCA - Anion migration. ESPN ionogels exhibit a high ionic figure of merit (ZT) at room temperature. i The value is 3.94, and the relatively high thermoelectric potential is 35 mVK. -1 And a high ionic conductivity of 27 mS / cm -1 Unlike conventional ITECs, ITECs with ESPN ion gel exhibit a higher steady-state output voltage when connected to an external load under a stable temperature gradient. Their thermoelectric behavior under a stable temperature gradient is similar to that of conventional thermoelectric generators (TEGs). Therefore, ITECs with ESPN ion gel can harvest not only intermittent heat but also continuous heat. Since the thermoelectric potential of ESPN ion gel is much higher than that of electronic thermoelectric materials, ion gels have significant practical application value.

Claims

1. A thermoelectric power generator comprising: an ionic gel, the ionic gel comprising: an ionic liquid; a gelling agent; and an electronic conductor; a first electrode in contact with the ionic gel, the first electrode comprising an inert material; and a second electrode in contact with the ionic gel, the second electrode spaced apart from the first electrode, the second electrode comprising an inert material.

2. The thermoelectric power generation device according to claim 1, wherein the thermoelectric power generator is configured to produce a non-zero voltage under a steady temperature gradient.

3. The thermoelectric power generation device of claim 1, wherein, the thermoelectric power generator is configured to produce a non-zero voltage under a changing temperature gradient.

4. The thermoelectric power generation device of claim 1, wherein, the electronic conductor consists of any combination of one or more of: reduced graphene oxide sheets, silver nanoparticles, silver nanowires, gold nanoparticles, gold nanowires, bismuth telluride nanoparticles, bismuth telluride nanowires, silicon dioxide nanowires, titanium dioxide nanoparticles, titanium dioxide nanowires, poly(3,4- ethylenedioxythiophene)-poly(styrenesulfonate) chains, poly(3-hexylthiophene) chains, meijoene fibers, and carbon nanotubes.

5. The thermoelectric power generation device of claim 1, wherein, a mass percentage of the electronic conductor in the ionic gel is greater than a percolation threshold.

6. The thermoelectric power generation device of claim 1, wherein, the ionic liquid consists of any combination of one or more of: 1-ethyl-3-methylimidazolium dicyanamide, ethyl-3-methylimidazolium triflate, ethyl-3-methylimidazolium tetrafluoroborate, ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium chloride, pyridinium hexafluorophosphate, and pyrazolium tetrafluoroborate.

7. The thermoelectric power generation device of claim 1, wherein, the inert material of the first electrode comprises any combination of one or more of: gold, silver, platinum, carbon nanotubes, and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate); and the inert material of the second electrode comprises any combination of one or more of: gold, silver, platinum, carbon nanotubes, and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate).

8. The thermoelectric power generation device of claim 1, wherein, the ionic gel further comprises a surfactant.

9. The thermoelectric power generation device of claim 1, wherein, the surfactant consists of any combination of one or more of: sodium dodecyl sulfate, sodium lauryl sulfate, sodium myristyl sulfate, sodium stearate, sodium lauroyl sarcosinate, cetyltrimethylammonium bromide, cetylpyridinium chloride, benzalkonium chloride, benzethonium chloride, dimethdialkylammonium chloride, dioctadecyldimethylammonium bromide, sulfobetaine, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, cocamidopropyl hydroxysultaine, cocamidopropyl betaine, phospholipids phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, sphingomyelin, dodecyldimethylamine oxide, myristyl amine oxide, octaethylene glycol monododecyl ether, pentaethylene glycol monododecyl ether, and 2-[4-(2,4,4-trimethylpentan-2-yl)phenoxy]ethanol.

10. The thermoelectric power generation device of claim 1, wherein, the gelling agent comprises a silica nanostructure.

11. The thermoelectric power generation device of claim 1, wherein, the gelling agent is gelatin.

12. The thermoelectric power generation device of claim 1, wherein, the ionic gel is in the form of a self-supporting film or a slurry.

13. A method of manufacturing a thermoelectric power generator, the method comprising: forming an ionic gel including an ionic liquid, a gelling agent, and an electronic conductor; providing a first electrode in contact with the ionic gel, the first electrode including an inert material; and providing a second electrode in contact with the ionic gel, the second electrode spaced apart from the first electrode, the second electrode including an inert material.

14. The method of claim 13, wherein, the forming the ionic gel includes: mixing the electronic conductor and a surfactant to form a dispersion; mixing a liquid including the gelling agent and the ionic liquid to form a solution; and mixing the dispersion and the solution to form the ionic gel.

15. The method of claim 14, wherein, the dispersion is sonicated prior to the mixing the dispersion and the solution to form the ionic gel.

16. The method of claim 13, wherein, the gelling agent includes a silica nanostructure.

17. The method of claim 13, wherein, the gelling agent is gelatin.

18. The method of claim 13, wherein, the electronic conductor consists of any combination of one or more of: reduced graphene oxide sheets, silver nanoparticles, silver nanowires, gold nanoparticles, gold nanowires, bismuth telluride nanoparticles, bismuth telluride nanowires, silica nanowires, titanium dioxide nanoparticles, titanium dioxide nanowires, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) chains, poly(3-hexylthiophene) chains, meijoene fibers, and carbon nanotubes.

19. The method of claim 13, wherein, the ionic liquid consists of any combination of one or more of: 1-ethyl-3-methylimidazolium dicyanamide, ethyl-3-methylimidazolium triflate, ethyl-3-methylimidazolium tetrafluoroborate, or ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium chloride, pyridine hexafluorophosphate, and pyrazole tetrafluoroborate.

20. The method of claim 13, wherein, the inert material of the first electrode includes a combination of one or more of: gold, silver, platinum, carbon nanotubes, and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate); and the inert material of the second electrode includes a combination of one or more of: gold, silver, platinum, carbon nanotubes, and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate).

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