Ionic hydrogel, ionic thermoelectric device and preparation method and application thereof

Abstract

The present application belongs to the technical field of thermoelectric conversion materials, and particularly relates to an ionic hydrogel, an ionic thermoelectric device and a preparation method and application thereof. The ionic hydrogel comprises a hydrogel base material, and conductive ions and phytic acid dispersed in the hydrogel base material. The addition of the conductive ions can endow the hydrogel with conductivity, reduce the saturated vapor pressure of water, and improve the water retention of the ionic hydrogel; the hydrolysis of the phytic acid generates H + and C6H6O 24 P6 12‑ , a large number of free hydrogen ions enhance the conductivity; the phytic acid has rich hydrogen bond donor and acceptor sites, forms strong hydrogen bond action with water molecules, prevents the crystallization and evaporation of water, and further improves the water retention of the ionic hydrogel; and H + and C6H6O 24 P6 12‑ have a large difference in volume and a significant difference in transmission rate, and a high Seebeck coefficient can be obtained, and a high voltage can be output under a small temperature difference.

Description

Technical Field

[0001] This invention belongs to the technical field of thermoelectric conversion materials, specifically relating to an ion hydrogel, an ion thermoelectric device, its preparation method and application. Background Technology

[0002] Thermal energy is the most common form of energy in nature and a potential energy source. From basic generators to modern data centers and even the human body, a large amount of waste heat is constantly being generated. More specifically, more than half of primary energy is released into the environment as heat, with waste heat with a heat source temperature below 100°C accounting for about 63%. However, this waste heat is difficult to collect and utilize. There are generally three ways to convert this waste heat into electrical energy. First, mechanical heat engines have high energy conversion efficiency, but the presence of their mechanical components makes the entire system unsuitable for dispersed heat sources. Second, thermoelectric devices based on semiconductors or conductive polymers have significant advantages in capturing dispersed heat energy, but their conversion efficiency is low in the waste heat range with a heat source temperature below 100°C. Emerging ion thermoelectric generators, on the other hand, excel in flexibility and high-voltage output. By incorporating multiple thermoelectric effects, such as the Thermogalvanic effect and the Soret effect, and optimizing the electrodes, the Seebeck coefficient, current density, power density, and energy density of ion thermoelectric generators can be effectively improved.

[0003] Waste heat occurs in almost every step of the energy conversion process and is often directly released into the environment, such as waste heat generated by industrial processes, transportation processes, and solar photovoltaic power generation. Existing thermoelectric devices based on semiconductors or conductive polymers generally have low Seebeck coefficients, require large temperature differences, or involve connecting thousands of thermoelectric devices in series to output a useful voltage, resulting in low conversion efficiency. Therefore, it is of great significance to develop an ion thermoelectric generator capable of efficiently converting this series of environmental waste heat directly into electrical energy.

[0004] Existing thermoelectric devices based on semiconductors or conductive polymers generally have low Seebeck coefficients, requiring large temperature differences or thousands of thermoelectric devices connected in series to output a useful voltage, resulting in low conversion efficiency. The key to improving conversion efficiency lies in the thermoelectric conversion material within the thermoelectric device. Therefore, there is a need to develop a new thermoelectric conversion material that can improve the efficiency of directly converting environmental waste heat into electrical energy. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes an ionic hydrogel with a high Seebeck coefficient, good electrical conductivity, water retention and excellent mechanical properties.

[0006] The present invention also proposes a method for preparing the above-mentioned ionic hydrogel and its application.

[0007] The present invention further proposes an ion thermoelectric device containing the above-mentioned ion hydrogel, its preparation method and application.

[0008] In a first aspect, the present invention provides an ionic hydrogel comprising a hydrogel matrix material and conductive ions and phytic acid dispersed in the hydrogel matrix material.

[0009] According to a first aspect of the present invention, at least the following beneficial effects are achieved:

[0010] As the matrix material for ion-gel hydrogels, the addition of conductive ions imparts conductivity to the hydrogel, while effectively reducing the saturated vapor pressure of water and improving the water retention capacity of the ion-gel hydrogel; phytic acid can hydrolyze to produce H+. + and C6H6O 24 P6 12- A large number of free hydrogen ions can improve the conductivity of ionized hydrogels; phytic acid, with six phosphate groups, has abundant hydrogen bond donor and acceptor sites, improving the mechanical properties of ionized hydrogels; at the same time, it can form strong hydrogen bonds with water molecules, interfering with the hydrogen bonding between water molecules, effectively preventing water crystallization and evaporation, further improving the water retention of ionized hydrogels; and H + and C6H6O 24 P6 12- The volumes of these components differ significantly, resulting in a marked difference in transmission rates. This allows for the achievement of a high Seebeck coefficient and the output of high voltage under small temperature differences.

[0011] Preferably, the conductive ions are derived from a water-soluble metal salt, which includes at least one of lithium chloride, potassium chloride, sodium chloride, magnesium chloride, lithium nitrate, potassium nitrate, and sodium nitrate.

[0012] Preferably, the mass ratio of the water-soluble metal salt to phytic acid is 1.0 to 1.5:1, more preferably 1.0 to 1.3:1, and even more preferably around 1.1:1.

[0013] Preferably, the ionic hydrogel further includes water; the mass-to-volume ratio of the water-soluble metal salt to water is 1g:30-50mL, more preferably 1g:30-40mL, and even more preferably 1g:38-40mL.

[0014] Preferably, the raw materials for preparing the hydrogel matrix material include acrylamide and its derivatives, crosslinking agents, and initiators.

[0015] Preferably, the molar ratio of acrylamide and its derivatives to the crosslinking agent is 1200–1500:1, more preferably 1300–1500:1, and even more preferably 1400–1450:1. Adding a small amount of a crosslinking agent containing two or more unsaturated bonds allows the hydrogel to solidify and form a crosslinked network, giving the hydrogel both flexibility and mechanical strength.

[0016] Preferably, the mass-to-volume ratio of the acrylamide and its derivatives to the initiator is 1g:2-8μL, more preferably 1g:3-6μL, and even more preferably about 1g:5μL.

[0017] Preferably, the acrylamide and its derivatives include at least one of acrylamide, isopropylacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid.

[0018] Preferably, the crosslinking agent is a monomer containing two or more unsaturated bonds, including N,N-methylenebisacrylamide.

[0019] Preferably, the initiator comprises at least one selected from 2-hydroxy-2-methylphenylacetone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-2-(4-morpholino)-1-[4-(methylthio)phenyl]-1-propanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and 2-dimethylamino-2-benzyl-1-[4-(4-morpholino)phenyl]-1-butanone.

[0020] In a second aspect, the present invention provides a method for preparing the ionic hydrogel, wherein the hydrogel matrix material, conductive ions, and phytic acid are mixed and solidified to obtain the ionic hydrogel.

[0021] Preferably, the preparation method of the ionic hydrogel includes the following steps:

[0022] S1, first mix water-soluble metal salt, phytic acid, and water to obtain a solution;

[0023] S2, the solution obtained in step S1 is mixed with the hydrogel matrix material, and after solidification, the ionic hydrogel is obtained.

[0024] Preferably, the curing is ultraviolet (UV) curing, and the curing time is 1–8 min, more preferably 2–6 min, and even more preferably 4 min; the wavelength of the UV light is 350–420 nm, more preferably 365–395 nm, and even more preferably around 365 nm; the power density of the UV light is 1–10 W·cm⁻¹. -2 More preferably 2-5 W·cm -2 Further optimization of 2W·cm -2 about.

[0025] Preferably, the curing process specifically involves mixing the solution obtained in step S1 with the hydrogel matrix material and pouring the mixture into a mold, followed by curing to obtain the ionic hydrogel. The mold is a cylindrical quartz mold with a radius and height of 0.1–2 cm, more preferably with a radius and height of approximately 1.5 cm.

[0026] Preferably, the method for preparing the ionic hydrogel further includes immersing the ionic hydrogel in a mixed solution of water-soluble metal salt and phytic acid until it is completely swollen; the immersion time is 24 to 72 hours, more preferably 40 to 50 hours, and even more preferably about 48 hours.

[0027] Preferably, the water-soluble metal salt used in the soaking process includes at least one of lithium chloride, potassium chloride, sodium chloride, magnesium chloride, lithium nitrate, potassium nitrate, and sodium nitrate. It can be the same type or a different type of water-soluble metal salt as the one used in step S1; more preferably, it is the same type as the one used in step S1. Soaking treatment can increase the content of lithium chloride and phytic acid in the ionic hydrogel, further improving the Seebeck coefficient and mechanical properties of the ionic hydrogel.

[0028] Preferably, the concentration of the water-soluble metal salt in the mixed solution used during the soaking process is 0.4–0.8 mol·L⁻¹. -1 More preferably 0.5–0.7 mol·L -1 Further optimization of 0.6 mol·L -1 The concentration of phytic acid is approximately 0.2–0.7 mol·L⁻¹. -1 More preferably 0.4–0.6 mol·L -1 Further optimization of 0.5 mol·L -1 about.

[0029] A third aspect of the present invention provides an ion thermoelectric device comprising the ion hydrogel.

[0030] Preferably, the ion thermoelectric device further includes a composite electrode, and the ion hydrogel is disposed between the composite electrodes.

[0031] Preferably, the composite electrode comprises phytic acid iron and carbon material; the mass ratio of phytic acid iron to carbon material is 1 to 10:1, more preferably 3.5 to 8:1, and even more preferably 3.5:1.

[0032] Preferably, the carbon material includes at least one of carbon black, carbon sponge, and carbon aerogel.

[0033] Preferably, the composite electrode further includes at least one of a binder and a solvent.

[0034] Preferably, the binder comprises at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyacrylic acid, sodium carboxymethyl cellulose, polyacrylamide, and cyclodextrin.

[0035] Preferably, the mass ratio of the binder to ferrous phytate is 1:5 to 10, more preferably 1:5 to 8, and even more preferably about 1:7.

[0036] Preferably, the solvent includes at least one of N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0037] Preferably, the mass-to-volume ratio of ferrous phytate to solvent is 1g:2-10mL, more preferably 1g:5-10mL, and even more preferably 1g:8-9mL.

[0038] Preferably, the preparation process of the composite electrode includes the following steps: mixing ferric phytate, carbon material, binder and solvent to obtain a slurry, coating the slurry onto the surface of the current collector to obtain the composite electrode.

[0039] Preferably, the current collector includes at least one of carbon cloth, carbon foil, aluminum foil, and copper foil.

[0040] Preferably, the step of mixing phytic acid iron, carbon material, binder, and solvent to obtain a slurry specifically involves grinding phytic acid iron and carbon material into powder, mixing the powder with binder and solvent to obtain a slurry; the mixing time is 2 to 5 hours, more preferably about 4 hours.

[0041] Preferably, the slurry is coated on the surface of the current collector and dried to obtain the composite electrode; the drying includes at least one of room temperature drying and vacuum drying, the temperature of the vacuum drying is 30-50°C, more preferably around 40°C; the vacuum drying time is 1-3 hours, more preferably around 2 hours.

[0042] Preferably, the preparation process of the phytic acid iron includes the following steps: mixing an iron source and phytic acid, and reacting to obtain the phytic acid iron.

[0043] Preferably, the iron source includes at least one of ferric chloride, ferric nitrate, and ferric sulfate.

[0044] Preferably, the mass ratio of phytic acid to iron source is 1 to 5:1, more preferably 1 to 3:1, and even more preferably around 1.7:1.

[0045] Preferably, the preparation process of the ferrous phytate includes the following steps: adding an iron source to water, adding phytic acid dropwise, stirring, centrifuging, and washing to obtain the ferrous phytate; the stirring time is 20-50 min, more preferably 30-50 min; the centrifugation time is 5-20 min, more preferably 10-20 min; the centrifugation speed is 5000-10000 r / min, more preferably 5000-8000 r / min; the centrifugation and washing operations are repeated 2-6 times, more preferably about 3 times.

[0046] Preferably, the mass-to-volume ratio of the iron source to water is 1g:10-20mL, more preferably 1g:10-15mL, and even more preferably 1g:12-13mL.

[0047] In a fourth aspect of the present invention, the ion gel or ion thermoelectric device is used in the fabrication of thermoelectric power generation devices and wearable devices.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects:

[0049] 1. This invention uses a hydrogel substrate material as the framework of the ionic hydrogel. Adding water-soluble metal salts imparts conductivity to the hydrogel and reduces the saturated vapor pressure of water in the system, thereby improving the water retention capacity of the ionic hydrogel. Phytic acid can hydrolyze to produce H₂. + and C6H6O 24 P6 12- Free hydrogen ions can improve the conductivity of ionized hydrogels; phytic acid, containing six phosphate groups, has abundant hydrogen bond donor and acceptor sites, which improves the mechanical properties of ionized hydrogels; at the same time, it can form strong hydrogen bonds with water molecules, interfering with the hydrogen bonding between water molecules, effectively preventing water crystallization and evaporation, and further improving the water retention of ionized hydrogels. The resulting ionized hydrogels have excellent mechanical properties, conductivity, and water retention.

[0050] 2. The composite electrode of the present invention contains ferric phytate, which has redox capabilities, and the mechanism is: C6H6O 24 P6Fe4+4e - =C6H6O 24 Fe4 4- C6H6O 24 Fe4 4- -4e - =C6H6O 24 P6Fe4, and iron phytate is a chelate, sparingly soluble in water and insoluble in ion-gel, thus maintaining the stability of ion-thermoelectric devices; compared to common redox pairs (such as Fe... 3+ / Fe 2+ Fe(CN)6 3- / Fe(CN)6 4-By directly adding it to the ion hydrogel, the ion thermoelectric device prepared by this invention has higher stability and better continuous output capability.

[0051] 3. Phytic acid in ionic hydrogels hydrolyzes to produce H₂. + and C6H6O 24 P6 12- The significant differences in volume and transport rate, along with the excellent conductivity and water retention of the ion hydrogel, combined with the phytic acid-containing iron composite electrode, result in an ion thermoelectric device with a high Seebeck coefficient (26.7 mV·K). -1 ), current density, power density, and energy density.

[0052] 4. The preparation process of the ion hydrogel and ion thermoelectric device of the present invention is simple and easy to realize industrial production.

[0053] 5. The ionized hydrogel and ionized thermoelectric device of the present invention can be used to prepare thermoelectric power generation devices and wearable devices, especially for thermoelectric conversion in the waste heat range with low temperature differences and heat source temperatures below 100°C. Applied to wearable devices, it exhibits good flexibility and utilizes the temperature difference between the human body and the surrounding environment to convert it into electrical energy, directly powering wearable devices and electronic skin. Attached Figure Description

[0054] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0055] Figure 1 This is a schematic diagram of the preparation process of the ion hydrogel and carbon cloth / iron phytate composite electrode in Example 1 of the present invention.

[0056] Figure 2 The tensile stress-strain curve of the ionic hydrogel prepared in Example 1 of this invention;

[0057] Figure 3 The open-circuit voltage of the ion thermoelectric generator of Embodiment 1 of the present invention at temperature differences of 15-20°C, 15-25°C, 15-30°C and 15-35°C respectively;

[0058] Figure 4 The instantaneous output current density and power density of the ion thermoelectric generator of Embodiment 1 of the present invention at a temperature difference of 15-30°C;

[0059] Figure 5 The instantaneous output current density and power density of the ion thermoelectric generator of Comparative Example 1 of the present invention at a temperature difference of 15-30°C.

[0060] Figure 6The power density of the ion thermoelectric generator of Example 1 connected in series with resistance boxes of 1000Ω, 2000Ω, 3000Ω, 4000Ω and 5000Ω respectively for 2 hours under a temperature difference of 15-30℃.

[0061] Figure 7 The power density of the ion thermoelectric generator in Comparative Example 1 connected in series with resistance boxes of 1000Ω, 2000Ω, 3000Ω, 4000Ω and 5000Ω respectively for 2 hours under a temperature difference of 15-30℃.

[0062] Figure 8 The energy density of the ion thermoelectric generator of Example 1 connected in series with resistance boxes of 1000Ω, 2000Ω, 3000Ω, 4000Ω and 5000Ω respectively for 2 hours at a temperature difference of 15-30℃.

[0063] Figure 9 The energy density of the ion thermoelectric generator of Comparative Example 1 connected in series with resistance boxes of 1000Ω, 2000Ω, 3000Ω, 4000Ω and 5000Ω for 2 hours at a temperature difference of 15-30℃ is calculated.

[0064] Figure 10 The current-voltage cycle curve of the ion thermoelectric generator in Example 1;

[0065] Figure 11 These are application images of the ion thermoelectric generator from Example 1;

[0066] Figure 12 This is a schematic diagram of the open-circuit voltage test of the ion thermoelectric generator in Example 1. Detailed Implementation

[0067] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0068] Unless otherwise specified, the raw materials used in this invention are conventional in the art; the testing / testing methods are commonly used in the art.

[0069] The preparation process of the ion hydrogel and composite electrode of the present invention is as follows: Figure 1As shown, acrylamide and N,N-Methylenebis(acrylamide) hydrogel matrix materials are mixed with water-soluble metal salt lithium chloride and phytic acid. Under the action of an initiator and 365nm ultraviolet light, acrylamide undergoes a free radical polymerization reaction to obtain polyacrylamide hydrogel (PAAm chain). Lithium ions, chloride ions and hydrogen ions are dispersed in the hydrogel to obtain an ionic hydrogel.

[0070] Ferric phytate and carbon black are mixed to obtain a slurry, which is then coated onto the surface of carbon cloth to obtain a carbon cloth / ferric phytate composite electrode. An ion-hydrogel is sandwiched between two carbon cloth / ferric phytate composite electrodes to obtain an ion thermoelectric generator.

[0071] Example 1

[0072] (1) Preparation of ionized hydrogel: First, 0.773 g of lithium chloride and 1 mL of 70% phytic acid were added to 30 mL of deionized water and stirred for 30 min. Then, 10 g of acrylamide (monomer), 0.015 g of N,N-methylenebisacrylamide (crosslinking agent) and 50 μL of 2-hydroxy-2-methylphenylacetone (initiator) were added to the solution and stirred for another 30 min. Next, the solution was poured into a cylindrical quartz mold with a radius and height of 1.5 cm and heated with a power density of 2 W·cm⁻¹. -2 Irradiation with 365nm ultraviolet light for 4 min yielded an ionic hydrogel; finally, the ionic hydrogel was immersed in 0.6 mol·L⁻¹ water. -1 Lithium chloride and 0.05 mol·L -1 Swell completely in a mixed solution of phytic acid for 48 hours.

[0073] (2) Preparation of carbon cloth / ferric phytate composite electrode: First, 1.23 g of ferric chloride (iron source) was added to 15 mL of deionized water, and 3 mL of 70% phytic acid (chelating agent) was added dropwise while stirring. The stirring was continued for 30 min, and the suspension was transferred to a centrifuge tube and centrifuged at 8000 r / min for 10 min. Then, it was washed with 20 mL of deionized water. This cycle was repeated 3 times to obtain ferric phytate (C6H6O). 24 P6Fe4); then, 0.35g of phytic acid iron and 0.10g of carbon black are mixed evenly and ground into powder (active material). Next, 0.05g of polyvinylidene fluoride (binder) is added to 3mL of N-methylpyrrolidone (solvent) and stirred until completely dissolved. The powder is then added and stirred for 4 hours to obtain a slurry. Finally, the slurry is evenly coated on the surface of carbon cloth and dried at room temperature to obtain a carbon cloth / phytic acid iron composite electrode.

[0074] (3) Preparation of ion thermoelectric generator: The ion hydrogel is sandwiched between two carbon cloth / iron phytate composite electrodes to obtain the ion thermoelectric generator.

[0075] Example 2

[0076] The main difference between this embodiment and Example 1 lies in the different ratio of phytic acid to carbon black used in the preparation of the carbon cloth / ferric phytate composite electrode. The specific process is as follows:

[0077] (1) The preparation of the ion hydrogel is similar to step (1) of Example 1;

[0078] (2) Preparation of carbon cloth / ferric phytate composite electrode: First, 1.23 g of ferric chloride (iron source) was added to 15 mL of deionized water, and 3 mL of 70% phytic acid (chelating agent) was added dropwise while stirring. The mixture was stirred for 30 min, and the suspension was transferred to a centrifuge tube and centrifuged at 8000 r / min for 10 min. Then, it was washed with 20 mL of deionized water. This process was repeated 3 times to obtain ferric phytate (C6H6O). 24 P6Fe4); then, 0.40g of phytic acid iron and 0.05g of carbon black are mixed evenly and ground into powder (active material). Next, 0.05g of polyvinylidene fluoride (binder) is added to 3mL of N-methylpyrrolidone (solvent) and stirred until completely dissolved. The above powder is added and stirring is continued for 4h to obtain a slurry. Finally, the slurry is evenly coated on the surface of carbon cloth and dried at room temperature to obtain a carbon cloth / phytic acid iron composite electrode.

[0079] (3) The preparation of the ion thermoelectric generator is similar to step (3) of Example 1.

[0080] Example 3

[0081] The main difference between this embodiment and Embodiment 1 is that carbon aerogel is used instead of carbon black in the preparation of the carbon cloth / ferric phytate composite electrode. The specific process is as follows:

[0082] (1) The preparation of the ion hydrogel is similar to step (1) of Example 1;

[0083] (2) Preparation of carbon cloth / ferric phytate composite electrode: First, 1.23 g of ferric chloride (iron source) was added to 15 mL of deionized water, and 3 mL of 70% phytic acid (chelating agent) was added dropwise while stirring. The mixture was stirred for 30 min, and the suspension was transferred to a centrifuge tube and centrifuged at 8000 r / min for 10 min. Then, it was washed with 20 mL of deionized water. This process was repeated 3 times to obtain ferric phytate (C6H6O). 24P6Fe4); then, 0.35g of phytic acid iron and 0.10g of carbon aerogel are mixed evenly and ground into powder (active material). Next, 0.05g of polyvinylidene fluoride (binder) is added to 3mL of N-methylpyrrolidone (solvent) and stirred until completely dissolved. The powder is then added and stirred for 4 hours to obtain a slurry. Finally, the slurry is evenly coated on the surface of carbon cloth and dried at room temperature to obtain a carbon cloth / phytic acid iron composite electrode.

[0084] (3) The preparation of the ion thermoelectric generator is similar to step (3) of Example 1.

[0085] Example 4

[0086] The main difference between this embodiment and Embodiment 2 is that carbon sponge is used instead of carbon black in the process of preparing the carbon cloth / ferric phytate composite electrode. The specific process is as follows:

[0087] (1) The preparation of the ion hydrogel is similar to step (1) of Example 2;

[0088] (2) Preparation of carbon cloth / ferric phytate composite electrode: First, 1.23 g of ferric chloride (iron source) was added to 15 mL of deionized water, and 3 mL of 70% phytic acid (chelating agent) was added dropwise while stirring. The mixture was stirred for 30 min, and the suspension was transferred to a centrifuge tube and centrifuged at 8000 r / min for 10 min. Then, it was washed with 20 mL of deionized water. This process was repeated 3 times to obtain ferric phytate (C6H6O). 24 P6Fe4); then, 0.40g of phytic acid iron and 0.05g of carbon sponge are mixed evenly and ground into powder (active material). Next, 0.05g of polyvinylidene fluoride (binder) is added to 3mL of N-methylpyrrolidone (solvent) and stirred until completely dissolved. The powder is then added and stirred for 4 hours to obtain a slurry. Finally, the slurry is evenly coated on the surface of carbon cloth and dried at room temperature to obtain a carbon cloth / phytic acid iron composite electrode.

[0089] (3) The preparation of the ion thermoelectric generator is similar to step (3) of Example 2.

[0090] Example 5

[0091] The main difference between this embodiment and Embodiment 1 is that the preparation process of the carbon cloth / ferric phytate composite electrode has been adjusted. The specific process is as follows:

[0092] (1) The preparation of the ion hydrogel is similar to step (1) of Example 1;

[0093] (2) Preparation of carbon cloth / ferric phytate composite electrode: First, 1.23 g of ferric chloride (iron source) was added to 15 mL of deionized water, and 3 mL of 70% phytic acid (chelating agent) was added dropwise while stirring. The mixture was stirred for 30 min, and the suspension was transferred to a centrifuge tube and centrifuged at 8000 r / min for 10 min. Then, it was washed with 20 mL of deionized water. This process was repeated 3 times to obtain ferric phytate (C6H6O). 24 P6Fe4); then, 0.35g of phytic acid iron and 0.10g of carbon black are mixed evenly and ground into powder (active material). Next, 0.05g of polyvinylidene fluoride (binder) is added to 3mL of N-methylpyrrolidone (solvent) and stirred until completely dissolved. The above powder is added and stirring is continued for 4h to obtain a slurry. Finally, the slurry is evenly coated on the surface of carbon cloth and vacuum dried at 40℃ for 2h to obtain a carbon cloth / phytic acid iron composite electrode.

[0094] (3) The preparation of the ion thermoelectric generator is similar to step (3) of Example 1.

[0095] Comparative Example 1

[0096] This comparative example prepared an ion thermoelectric generator. The difference from Example 1 is that a carbon cloth electrode was used instead of a carbon cloth / ferric phytate composite electrode. The specific process is similar to that of Example 1.

[0097] Test case

[0098] This experiment tested the performance of the ionized hydrogel prepared in Example 1, as well as the thermoelectric generators prepared in the examples and comparative examples.

[0099] 1. Ionized hydrogel

[0100] like Figure 2 As shown, Example 1 of this invention uses acrylamide as a monomer, which is mixed with N,N-methylenebisacrylamide, 2-hydroxy-2-methylphenylacetone, lithium chloride, and phytic acid. The resulting ionic hydrogel exhibits excellent mechanical properties, with a tensile strength reaching 2.2 MPa and an elongation at break of 1100%. The Seebeck coefficient of the thermoelectric generator prepared from this ionic hydrogel reaches 26.7 mV·K. -1 .

[0101] 2. Ion thermoelectric generator

[0102] Continuous output power density and energy density testing method: First, the ionized hydrogel is tightly sandwiched between carbon cloth / ferric phytate composite electrodes to form a sandwich-like ionized thermoelectric device. Then, the device is fixed on a temperature control platform and connected to an electrochemical workstation to measure its open-circuit voltage. After the voltage stabilizes, an external resistance box is connected to continue measuring its open-circuit voltage. The test schematic diagram is shown below. Figure 12Finally, voltage is converted into power density and energy density using the following formula.

[0103] P d =U 2 / (R·S)

[0104] E d =U 2 / (R·S)·t

[0105] Where U is the open-circuit voltage, P d For power density, E d Where is the energy density, R is the resistance, S is the contact area between the gel and the electrode, and t is the continuous output time.

[0106] Instantaneous output current density and power density test method: LSV is measured using an electrochemical workstation, and scanning is performed at a scan rate of 0.1V / s within the voltage range of 0 to 0.42V.

[0107] Cyclic voltammetry characteristic curve testing method: CV is measured using an electrochemical workstation, and scanning is performed at a scan rate of 5mV / s within the voltage range of -0.6 to 0.6V.

[0108] Depend on Figure 3 It can be seen that the ion thermoelectric generator prepared in Example 1 of the present invention has a high open-circuit voltage at temperature differences of 15-20℃, 15-25℃, 15-30℃ and 15-35℃, and the voltage increases with the increase of temperature difference; the open-circuit voltage of a single ion thermoelectric generator at 15-35℃ can reach more than 500mV.

[0109] Figures 4-5 The instantaneous output current density and power density of the ion thermoelectric generators prepared in Example 1 and Comparative Example 1 of this invention are shown respectively. Compared with Comparative Example 1, which uses carbon cloth as the electrode of the ion thermoelectric generator, this invention uses a carbon cloth / ferric phytate composite electrode. Because ferric phytate can undergo a redox reaction, C6H6O... 24 P6Fe4+4e - =C6H6O 24 Fe4 4- C6H6O 24 Fe4 4- -4e - =C6H6O 24 P6Fe4; iron phytate is insoluble in the ion hydrogel, maintaining the stability of the ion thermoelectric generator. The prepared ion thermoelectric generator has higher instantaneous output current density and power density, with a maximum power density as high as 4.5 W / m³. -2 The comparative example 1 was only 0.4 W m -2 about.

[0110] The ion thermoelectric generators prepared in Example 1 and Comparative Example 1 of this invention were connected in series with resistance boxes of 1000Ω, 2000Ω, 3000Ω, 4000Ω, and 5000Ω respectively for 2 hours to test their power density and energy density. Figures 6-9 It can be seen that the power density of the ion thermoelectric generator prepared in Example 1 of the present invention is significantly higher; under the same series resistance, the energy density of Example 1 of the present invention is greater than that of the comparative example, and the energy density reaches a maximum of 2451 J·m when the resistance is 2000 Ω. -2 .

[0111] Depend on Figure 10 It can be seen that the ion thermoelectric generator prepared by the carbon cloth / ferric phytate composite electrode of the present invention undergoes a redox reaction during the discharge process; Comparative Example 1 uses a carbon cloth electrode instead of the carbon cloth / ferric phytate composite electrode, which does not contain ferric phytate, and therefore does not undergo a redox reaction. The discharge process mainly originates from capacitor discharge, with a short duration, rapid voltage drop, and low energy density; while the ion thermoelectric generator prepared in Example 1 has a discharge process originating from capacitor discharge and redox discharge, with high voltage, high energy density, and long duration; at a temperature difference of 15°C, connecting six thermoelectric generators from Example 1 in series can generate a voltage exceeding 2.3V and successfully light up an LED lamp, such as... Figure 11 .

[0112] The performance of the ion thermoelectric generators prepared in Examples 2 to 5 of this invention is similar to that in Example 1, and will not be described again here.

[0113] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. An ion thermoelectric device, characterized in that, The ion thermoelectric device includes an ion hydrogel and a composite electrode; the ion hydrogel is disposed between the composite electrodes. The ionic hydrogel comprises a hydrogel matrix material, and conductive ions and phytic acid dispersed in the hydrogel matrix material; the raw materials for preparing the hydrogel matrix material include acrylamide and its derivatives, crosslinking agents, and initiators; the conductive ions are derived from water-soluble metal salts, and the water-soluble metal salts include at least one of lithium chloride, potassium chloride, sodium chloride, magnesium chloride, lithium nitrate, potassium nitrate, and sodium nitrate; The composite electrode comprises iron phytate and carbon material; the mass ratio of iron phytate to carbon material is 1~10:

1.

2. The ion thermoelectric device according to claim 1, characterized in that: The mass ratio of the water-soluble metal salt to phytic acid is 1.0~1.5:

1.

3. The ion thermoelectric device according to claim 1, characterized in that: The ionic hydrogel is prepared by a method including the following steps: mixing the hydrogel matrix material, conductive ions, and phytic acid, and then solidifying the mixture to obtain the ionic hydrogel.

4. The ion thermoelectric device according to claim 3, characterized in that, It also includes immersing the ionic hydrogel in a mixed solution of water-soluble metal salt and phytic acid until it is fully swollen.

5. The application of the ion thermoelectric device according to any one of claims 1-4 in the preparation of thermoelectric power generation devices and wearable devices.

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