A lignin-based self-healing thermoelectric hydrogel, a thermoelectric conversion device and a preparation method and application thereof

Abstract

The present application belongs to the technical field of thermoelectric conversion, and particularly relates to a self-repairing thermoelectric hydrogel based on lignin, a thermoelectric conversion device, and a preparation method and application thereof. The present application successfully prepares a self-repairing thermoelectric hydrogel based on lignin by compounding specific inorganic small-molecule thermoelectric materials with cyclodextrin-modified lignin sulfonate and adamantane acrylate. In the formation process of the thermoelectric hydrogel, the inorganic small-molecule thermoelectric materials are uniformly dispersed in the network structure of the hydrogel, so that the hydrogel has excellent mechanical properties; the host-guest interaction introduced by the cyclodextrin-modified lignin sulfonate enables the hydrogel to have excellent self-repairing ability; the hydrogel also has good temperature sensitivity; the above characteristics greatly improve the thermal effect, thermoelectric conversion performance and electrochemical performance of the thermoelectric conversion device prepared based on the above thermoelectric hydrogel; and the preparation method of the above thermoelectric hydrogel is simple and easy to operate, the conditions are mild, the raw materials are easy to obtain, and the thermoelectric hydrogel has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric conversion technology. More specifically, it relates to a lignin-based self-healing thermoelectric hydrogel, a thermoelectric conversion device, its preparation method, and its application. Background Technology

[0002] Against the backdrop of continuously growing global energy demand and increasingly serious environmental problems, research on energy conversion technologies has become one of the most pressing scientific issues. Low-grade heat energy, as a green and environmentally friendly new energy source, shows enormous potential among various renewable energy sources. Low-grade heat energy with a temperature difference of less than 100°C exists in living environments, industrial production processes, solar energy, and the human body, representing an energy source with immense application potential. Converting this waste heat into usable electricity helps slow down the consumption of non-renewable energy, thereby contributing to the reduction of greenhouse gas emissions. Utilizing the thermoelectric effect is an effective approach, directly converting waste heat from the environment into electrical energy to power personal medical electronic devices, which is of great significance for intelligent wearable medical devices.

[0003] In recent years, traditional thermoelectric materials have made some progress in electron diffusion and the electronic Seebeck effect. However, their widespread application is limited by problems such as the scarcity or toxicity of raw materials, complex processing, high cost, and poor mechanical flexibility. Furthermore, the electronic Seebeck coefficient of traditional thermoelectric materials is typically low, only reaching μV•K. -1 In contrast, ionic thermoelectric materials, as novel thermoelectric conversion materials, exhibit significant advantages, with an ionic Seebeck coefficient 2-3 orders of magnitude higher, enabling effective collection of low-grade heat energy. This material is low-cost, high-performance, possesses a high Seebeck coefficient, low thermal conductivity, and easy processing, thus being considered a promising green energy conversion material. However, ionic thermoelectric materials also have some shortcomings. For example, Chinese patent application CN115895158A discloses a thermoelectric conversion material and a thermoelectric conversion device. The thermoelectric conversion material exhibits temperature sensitivity and a high Seebeck coefficient, and the thermoelectric conversion device assembled with a polyaniline / carbon cloth electrode can achieve a specific area capacitance of up to 750 mF / cm². 2 However, its energy density output in 1 hour is only 88 J / m³. 2 This severely limits its electrochemical performance. In addition, Chinese patent application CN111564316A discloses a gel electrode and a fully gel-state ion thermoelectric supercapacitor, with a maximum volumetric specific capacitance of 983.6 mF / cm². 3 However, its maximum Seebeck coefficient is only 3.6 mV / K, its thermoelectric conversion efficiency is low, the device fabrication cycle is long, and the tensile properties of the electrolyte-loaded gel electrode need to be further improved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of existing hydrogel thermoelectric materials, such as the need to further improve the tensile properties and the low thermoelectric conversion efficiency, poor electrochemical performance and long preparation cycle of thermoelectric conversion devices prepared based on hydrogels. The present invention provides a method for preparing a lignin-based self-healing thermoelectric hydrogel.

[0005] Another object of the present invention is to provide the above-mentioned lignin-based self-healing thermoelectric hydrogel.

[0006] Another object of the present invention is to provide a thermoelectric conversion device.

[0007] Another object of the present invention is to provide the application of the above-mentioned lignin-based self-healing thermoelectric hydrogel or the above-mentioned thermoelectric conversion device in the fields of wearable thermoelectric conversion devices, Internet of Things, and sensing.

[0008] The above-mentioned objective of this invention is achieved through the following technical solution:

[0009] This invention protects a method for preparing a lignin-based self-healing thermoelectric hydrogel, comprising the following steps:

[0010] Cyclodextrin-modified lignin sulfonate and adamantane acrylate were added to a solvent containing inorganic small molecule thermoelectric materials and mixed well. Unsaturated carboxylic acid monomers, acrylamide monomers, metal ions and initiators were added and reacted fully to prepare a lignin-based self-healing thermoelectric hydrogel.

[0011] The inorganic small molecule thermoelectric material is selected from one or more of lithium chloride, sodium chloride, and potassium chloride.

[0012] This invention successfully prepared a lignin-based self-healing thermoelectric hydrogel by combining specific inorganic small-molecule thermoelectric materials with cyclodextrin-modified lignin sulfonate and adamantane acrylate. The inorganic small-molecule thermoelectric materials not only enhance the interactions between polymer chains (such as ionic and hydrogen bonds), helping to maintain the stability of the network structure and improve the mechanical strength of the hydrogel, but also... Specifically, the thermoelectric hydrogel uses unsaturated carboxylic acid monomers and acrylamide monomers as the hydrogel skeleton. Simultaneously, the structural characteristics of cyclodextrin-modified lignin sulfonate (LS-CD) are utilized to introduce host-guest interactions. Furthermore, the phenolic hydroxyl groups in LS-CD synergistically form redox pairs with metal ions, acting as "crosslinking agents" and "catalysts." Through the combined action of these components, the lignin-based self-healing thermoelectric hydrogel is obtained through copolymerization and crosslinking. The thermoelectric hydrogel prepared by the above method possesses excellent mechanical properties, temperature sensitivity, and self-healing capabilities.

[0013] Furthermore, the preparation method of the cyclodextrin-modified lignin sulfonate includes the following steps:

[0014] S1. Add cyclodextrin, p-toluenesulfonylimidazole and alkaline reagent to water, mix well, filter, take the filtrate, adjust the pH to 7-8, react fully, and then process to obtain the intermediate product CDOTs.

[0015] S2. Add the CDOTs and lignin sulfonate obtained in step S1 to water and mix well. Heat to 70~80 ℃ for full reaction. After post-treatment, obtain cyclodextrin modified lignin sulfonate.

[0016] Further, in step S1, the cyclodextrin includes one or more of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin. Cyclodextrin-modified lignin sulfonates obtained from cyclodextrins with different crystal structures can all prepare thermoelectric hydrogels with good performance. Among them, β-cyclodextrin has a moderate inner diameter, making it more suitable for encapsulating hydrophobic molecules (such as adamantane), thereby improving its solubility and stability, which is beneficial for the subsequent construction of structurally stable hydrogels. Therefore, the cyclodextrin is preferably β-cyclodextrin.

[0017] Further, in step S1, the mass ratio of the cyclodextrin to p-toluenesulfonylimidazole is (1.5~10):(1~3).

[0018] Furthermore, in step S1, the mass ratio of the cyclodextrin to p-toluenesulfonylimidazole is (1.5~10):1.

[0019] Furthermore, in step S1, the mixing is agitation.

[0020] Furthermore, the mixing time is 2-4 hours.

[0021] Furthermore, in step S1, the pH adjustment is performed using hydrochloric acid.

[0022] Furthermore, in step S1, the precipitation time is 18~36 h.

[0023] Furthermore, in step S1, the post-processing includes filtration, washing, and recrystallization.

[0024] Furthermore, the filtration process involves filtering the precipitated material and collecting the filter residue.

[0025] Furthermore, the washing process involves washing the collected filter residue with ice water and acetone 3 to 5 times in sequence.

[0026] Furthermore, the recrystallization involves removing soluble impurities by recrystallizing the washed filter residue with hot water at 80-100°C, repeating this process 2-3 times.

[0027] Specifically, in step S1, the post-processing includes filtering the precipitated material, collecting the filter residue, washing the filter residue with ice water and acetone 3 to 5 times in sequence, collecting the washed filter residue and recrystallizing it with hot water at 80 to 100 °C to remove soluble impurities, repeating this process 2 to 3 times, and the product obtained after recrystallization is the intermediate product CDOTs.

[0028] Further, in step S2, the mass ratio of CDOTs to lignin sulfonate is 1:(0.67~2.5).

[0029] Furthermore, in step S2, the mixing time is 1 to 2 hours.

[0030] Furthermore, in step S2, the time for the complete reaction is 48~72 h.

[0031] Furthermore, in step S2, the post-processing includes dialysis and drying.

[0032] Furthermore, the dialysis involves dialyzing the cooled mixture and collecting the retained solution.

[0033] Furthermore, the drying process involves drying the retained solution after dialysis, and the drying is preferably freeze-drying.

[0034] Specifically, in step S2, the post-processing includes dialyzing the cooled mixture and freeze-drying the dialysis residue to obtain cyclodextrin-modified lignin sulfonate.

[0035] Furthermore, as a preferred embodiment, the method for preparing the adamantane acrylate includes the following steps:

[0036] Si. Add adamantane alcohol and triethylamine to an organic solvent and mix well to obtain a mixed solution;

[0037] Sii. Acryloyl chloride is diluted with an organic solvent and then added dropwise to the mixed solution obtained in step Si. After mixing, it is post-treated to obtain adamantane acrylate.

[0038] Further, in step Si, the adamantanol is 1-adamantanol and / or 2-adamantanol.

[0039] Preferably, the adamantanol is 1-adamantanol, which has stronger reactivity and is more likely to undergo nucleophilic substitution reaction with acryloyl chloride to form the corresponding ester or amino compound.

[0040] Further, in step Si, the mass ratio of adamantanol to triethylamine is 1:(1~3).

[0041] Furthermore, in step Si, the mixing time is 15~40 min.

[0042] Further, in step Sii, the mass ratio of acryloyl chloride to organic solvent is 1:(1.67~10).

[0043] Furthermore, in step Sii, the mixing time is 18~36 h.

[0044] Furthermore, in step Sii, the post-processing includes filtration, washing, concentration, and purification.

[0045] Furthermore, the filtration involves filtering the mixed solution and collecting the filtrate.

[0046] Furthermore, the washing process involves washing the filtrate with ice water and acetone 1 to 3 times.

[0047] Furthermore, the concentration involves washing, collecting the organic phase, and then performing low-temperature vacuum rotary evaporation concentration at 4-15 °C.

[0048] Furthermore, the purification is performed using column chromatography to purify the concentrated substance, with V as the eluent. 乙酸乙酯 :V 正己烷 =1:(15~20).

[0049] Specifically, in step Sii, the post-processing includes filtering the mixed solution, collecting the filtrate, washing the filtrate three times with ice water and acetone, collecting the washed organic phase and concentrating it under low-temperature reduced pressure at 4-15 °C, purifying the concentrated substance using column chromatography with V as the eluent. 乙酸乙酯 :V 正己烷 =1:(15~20).

[0050] Furthermore, the mass ratio of the cyclodextrin-modified lignin sulfonate to adamantane acrylate is (1~75):1. The cyclodextrin-modified lignin sulfonate acts as a catalyst and physical crosslinking agent, while adamantane acrylate acts as a chemical crosslinking agent for the network structure. This mass ratio results in a more suitable crosslinking density and superior mechanical properties in the prepared material.

[0051] Furthermore, the mass ratio of the cyclodextrin-modified lignin sulfonate to adamantane acrylate is (1~40):1.

[0052] Preferably, the mass ratio of the cyclodextrin-modified lignin sulfonate to adamantane acrylate is 1:0.18.

[0053] Preferably, the inorganic small molecule thermoelectric material is lithium chloride. Lithium chloride exhibits excellent thermoelectric properties, specifically a high thermoelectric figure of merit (i.e., ZT, ZT=σS²T / κ, where σ is electrical conductivity, S is Seebeck coefficient, T is temperature, and κ is thermal conductivity) and good thermal stability. Furthermore, it is low-cost and readily available. Therefore, lithium chloride is the preferred inorganic small molecule thermoelectric material.

[0054] Furthermore, the concentration of the inorganic small molecule thermoelectric material is 0.1~3 mol / L.

[0055] Furthermore, the solvent is water and / or an organic solvent.

[0056] Furthermore, the organic solvent includes one or more of glycerol, propylene glycol, sugar ammonium salt ionic liquids, pyridine ionic liquids, and phosphate-based ionic liquids. Adding an organic solvent to the hydrogel can effectively enhance its moisturizing properties and slow down water loss, thereby improving the stability and efficiency of the thermoelectric conversion device.

[0057] Preferably, the solvent is an aqueous solution of glycerol.

[0058] More preferably, in the glycerol aqueous solution, the mixing ratio of glycerol and water is as follows: V 甘油 :V 水 =1: (1~5).

[0059] Furthermore, the mixing time is 30-60 min.

[0060] Furthermore, the unsaturated carboxylic acid monomer is a C3-C8 olefinic acid and / or a C3-C8 alkynetic acid.

[0061] Furthermore, the unsaturated carboxylic acid monomer is a C3-C5 olefinic acid and / or a C3-C5 alkynetic acid.

[0062] Furthermore, the unsaturated carboxylic acid monomers include one or more of acrylic acid, methacrylic acid, butenoic acid, propionic acid, and butynic acid.

[0063] Furthermore, the acrylamide monomer includes one or more of acrylamide, methacrylamide, and ethylacrylamide.

[0064] Furthermore, the mass ratio of the unsaturated carboxylic acid monomer to the acrylamide monomer is 1:(0.8~1.5).

[0065] Furthermore, the metal ions are derived from one or more of the following: stannous chloride, ferric chloride, calcium chloride, barium chloride, aluminum chloride, cobalt chloride, nickel chloride, copper chloride, and silver chloride.

[0066] Preferably, the metal ion is stannous chloride. In the method for rapid preparation of multifunctional thermoelectric hydrogels in a metal-phenolic chemical system, compared with other transition metals (such as iron, cobalt, nickel, etc.), the introduction of stannous ions not only makes the hydrogel more uniform, but also significantly enhances its tensile properties.

[0067] Furthermore, the initiator is ammonium persulfate and / or potassium persulfate.

[0068] Furthermore, the fully reacted cyclodextrin-modified lignin and metal ions form a redox coordination system that can activate the initiator and rapidly prepare a hydrogel.

[0069] This invention protects the lignin-based self-healing thermoelectric hydrogel prepared by the above preparation method.

[0070] This invention utilizes the reducing properties of lignin to rapidly and efficiently construct self-healing hydrogels, solving the problem of balancing self-healing properties and mechanical properties in self-healing hydrogels. At the same time, it utilizes specific inorganic small molecule thermoelectric materials to directly prepare hydrogels with phase transition behavior, giving them good self-healing properties, mechanical properties, and temperature-sensitive properties.

[0071] This invention protects a thermoelectric conversion device, which includes a lignin-based self-healing thermoelectric hydrogel and an electrode; the lignin-based self-healing thermoelectric hydrogel is connected to the electrode as a thermoelectric conversion material.

[0072] The lignin-based self-healing thermoelectric hydrogel used in this invention exhibits high Seebeck coefficient and high thermoelectric conversion efficiency as an ionic thermoelectric material due to its volume phase transition behavior. Assembling the self-healing thermoelectric hydrogel and electrodes into a thermoelectric conversion device can effectively convert thermal energy into electrical energy, achieving high thermal power and output power, and demonstrating excellent electrochemical performance.

[0073] Furthermore, the thermoelectric conversion device includes a stacked structure arranged in sequence: a first electrode, a thermoelectric conversion material, and a second electrode.

[0074] Furthermore, as a preferred embodiment, the lignin-based self-healing thermoelectric hydrogel is placed in a cylindrical quartz mold for in-situ molding.

[0075] Furthermore, the electrode is preferably a polyaniline carbon fiber cloth electrode. The polyaniline in the polyaniline carbon fiber cloth electrode not only enhances the electrode's conductivity but also undergoes redox reactions.

[0076] Furthermore, the thermoelectric conversion device further includes a polymer film and a temperature measuring element, and the thermoelectric conversion device includes a stacked structure arranged in sequence: a temperature measuring element, a polymer film, a first electrode, a thermoelectric conversion material, a second electrode, a polymer film, and a temperature measuring element.

[0077] Further, the polymer film includes one or more of polyimide film (PI film), polyester film (PET film), polytetrafluoroethylene film (PTFE film), and polyurethane film (PU film), preferably PI film. Encapsulating the thermoelectric conversion device with a polymer film effectively prevents solvent leakage, and the polymer film also has electrical insulation properties, effectively isolating the electrodes from the temperature measuring element. PI film, in particular, has excellent electrical insulation properties, effectively isolating the electrodes from the temperature measuring element and preventing short circuits in the thermoelectric conversion device; therefore, PI film is preferred.

[0078] Furthermore, the polyaniline carbon fiber cloth electrode is prepared by chemical oxidation deposition and includes polyaniline and carbon fiber cloth, wherein the polyaniline is coated on the surface of the carbon fiber cloth.

[0079] Furthermore, the preparation method of the polyaniline carbon fiber cloth electrode includes the following steps:

[0080] The aniline monomer and initiator were dissolved separately in an acidic reagent. The carbon fiber cloth was immersed in the aniline solution, and then the initiator solution was added to the aniline solution. The reaction was carried out at low temperature and then post-treated to obtain the polyaniline carbon fiber cloth electrode (PANI@CWF).

[0081] Furthermore, the initiator is ammonium persulfate and / or potassium persulfate.

[0082] Furthermore, the molar ratio of the aniline monomer to the initiator is 1:(0.25~1).

[0083] Furthermore, the molar ratio of the aniline monomer to the initiator is 1:1.

[0084] Furthermore, the low temperature is an ice-water bath.

[0085] Furthermore, the time for the full reaction is 4 to 16 hours, preferably 12 hours.

[0086] Furthermore, the post-processing includes washing and drying.

[0087] Furthermore, the washing process involves rinsing the carbon fiber cloth electrode containing polyaniline with deionized water 3 to 6 times.

[0088] Furthermore, the drying process involves annealing in a vacuum oven at 60-80 °C for 2-4 hours.

[0089] Specifically, the post-treatment includes rinsing the polyaniline-containing carbon fiber cloth electrode three times with deionized water, and then annealing it in a vacuum oven at 60-80 °C for 2-4 h.

[0090] Furthermore, the temperature measuring element is preferably a thermocouple. The temperature measuring element can provide different temperature signals to the thermoelectric conversion device, thereby determining the thermoelectric conversion efficiency of the thermoelectric conversion device.

[0091] Furthermore, as a preferred embodiment, the method for manufacturing the thermoelectric conversion device includes the following steps:

[0092] An electrode (preferably a polyaniline carbon fiber cloth electrode) is attached to the bottom surface of a custom-made cylindrical quartz glass mold (12 mm inner diameter, 16 mm outer diameter, 15 mm height). Then, a lignin-based self-healing thermoelectric hydrogel is poured into the cylindrical mold to form it in situ. After forming, another electrode (preferably a polyaniline carbon fiber cloth electrode) is attached to the top surface of the cylindrical mold. Two polymer films (preferably PI films) are then attached to the electrodes on both sides. Finally, a temperature measuring element is attached to the polymer films on both sides, thus forming the thermoelectric conversion device. The assembled thermoelectric conversion device structure consists of, in sequence, a temperature measuring element, a polymer film, a first electrode, a lignin-based self-healing thermoelectric hydrogel, a first electrode, a polymer film, and a temperature measuring element.

[0093] This invention protects the application of the above-mentioned lignin-based self-healing thermoelectric hydrogel or the above-mentioned thermoelectric conversion device in the fields of wearable thermoelectric devices, Internet of Things, and sensing.

[0094] Compared with the prior art, the present invention has the following beneficial effects:

[0095] This invention successfully prepared a lignin-based self-healing thermoelectric hydrogel by combining specific inorganic small-molecule thermoelectric materials with cyclodextrin-modified lignin sulfonate and adamantane acrylate. During the formation of the thermoelectric hydrogel, the inorganic small-molecule thermoelectric material is uniformly dispersed in the hydrogel's network structure, giving it excellent mechanical properties; the host-guest interaction introduced by the cyclodextrin-modified lignin sulfonate endows it with excellent self-healing capabilities; the hydrogel also exhibits good temperature-sensitive properties. These characteristics greatly enhance the thermal effect, thermoelectric conversion performance, and electrochemical performance of thermoelectric conversion devices prepared based on the aforementioned thermoelectric hydrogel. Furthermore, the preparation method of the above-mentioned thermoelectric hydrogel is simple and easy to implement, with mild conditions and readily available raw materials, showing broad application prospects. Attached Figure Description

[0096] Figure 1 These are comparison images of the hydrogels prepared in Example 1 and Comparative Examples 2-6;

[0097] Figure 2 This is an SEM image of the hydrogel prepared in Example 1;

[0098] Figure 3 These are the tensile stress-strain curves of the hydrogels prepared in Example 1 and Comparative Example 1;

[0099] Figure 4 These are diagrams illustrating the self-healing properties of the hydrogels prepared in Example 1 and Comparative Example 1.

[0100] Figure 5 These are optical images of the phase transition of the hydrogel prepared in Example 1;

[0101] Figure 6 This is the permeability-temperature curve of the hydrogel prepared in Example 1;

[0102] Figure 7 (a) Mass change curve and (b) optical image of the antifreeze properties of the hydrogel prepared in Example 2;

[0103] Figure 8 This is a SEM image of the polyaniline carbon fiber cloth electrode prepared in Example 1;

[0104] Figure 9 This is a digital image of the polyaniline carbon fiber cloth electrode prepared in Example 1;

[0105] Figure 10 This is a cyclic voltammetry curve of the polyaniline carbon fiber cloth electrode prepared in Example 1;

[0106] Figure 11 These are schematic diagrams of the thermoelectric conversion devices prepared in Examples 1-3;

[0107] Figure 12 These are the open-circuit voltage-time curves of the thermoelectric conversion devices prepared in Examples 1-2 and Comparative Examples 7-8;

[0108] Figure 13 These are the power density-time curves of the thermoelectric conversion devices prepared in Examples 1-2 and Comparative Example 8;

[0109] Figure 14 These are the specific capacitance curves calculated for different current densities of the thermoelectric conversion devices prepared in Examples 1-2 and Comparative Example 8. Detailed Implementation

[0110] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0111] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0112] The unmodified lignin was provided by Zhejiang Jiefa Technology Co., Ltd.

[0113] Figure 7 a represents Figure 7 Figure a in the middle; Figure 7 b represents Figure 7 The naming of the other plots follows the same pattern, starting with plot b.

[0114] Example 1: Preparation of a lignin-based self-healing thermoelectric hydrogel and thermoelectric conversion device

[0115] 1. Preparation of cyclodextrin-modified lignin sulfonate (LS-CD)

[0116] 36.3 g of β-cyclodextrin and 6.67 g of 1-p-toluenesulfonylimidazole were added to 250 mL of deionized water and stirred vigorously at room temperature for 3 h. 50 mL of 10 wt% NaOH solution was added, and stirring continued for 30 min. Unreacted insoluble matter was removed by filtration, and then 1 M HCl solution was added to adjust the pH of the filtrate to 7.5. The resulting mixture was precipitated at low temperature for 18 h, then filtered to collect the residue, which was washed three times with ice water and acetone to obtain the crude product. The crude product was recrystallized three times in hot water to obtain CDOTs. 6.5 g of lignin sulfonate was dissolved in 150 mL of deionized water and stirred thoroughly to obtain a clear solution. 6.5 g of CDOTs was added, and the mixture was stirred vigorously at room temperature for 2 h, then refluxed at 80 °C for 72 h. After cooling, the solution was transferred to a dialysis bag in a MWC 3500 and dialyzed for 3 days. The retentate was freeze-dried to obtain a yellow or pale yellow product, LS-CD.

[0117] 2. Preparation of Adamantane Acrylate (ADA)

[0118] 3.04 g of 1-adamantanol and 60 mL of anhydrous dichloromethane were added to the reactor and stirred until fully dissolved. Then, 3 g of triethylamine was added. The mixture was kept at 0 °C and stirred for 40 min. 3.62 g of acryloyl chloride diluted with 25 mL of anhydrous dichloromethane was added dropwise to the mixture at 0 °C using a constant-pressure dropping funnel. After the addition was complete, the mixture was slowly brought to room temperature and stirred for 18 h. After the reaction, the insoluble matter was filtered off, and the filtrate was collected. The filtrate was washed three times each with 0.1 M HCl aqueous solution, 0.5 wt% NaHCO3 solution, and distilled water, respectively. The organic phase was collected and concentrated by rotary evaporation under reduced pressure at 4 °C. The solution was then purified by column chromatography, with V as the eluent. 乙酸乙酯 :V 正己烷=1:15, to obtain the product ADA, which is stored at low temperature for later use.

[0119] 3. Preparation of lignin-based self-healing thermoelectric hydrogel (LAM-1)

[0120] 0.0144 g of LS-CD and 80 μL of methanol solution containing ADA (0.01 g / mL) were added to 7 mL of 1.5 mol / L lithium chloride solution (i.e., lithium chloride aqueous solution), and the mixture was stirred at room temperature for 30 min. Then, 0.02 g of stannous chloride (SnCl2) was added, followed by 0.96 g of acrylamide (AM) and 0.96 g of acrylic acid (AA), and finally 0.024 g of ammonium persulfate (APS) was added to obtain hydrogel LAM-1.

[0121] 4. Preparation of polyaniline carbon fiber cloth electrodes

[0122] First, carbon fiber cloth (CWF) was ultrasonically cleaned for 30 min using ethanol and deionized water. Then, 0.025 mol of ANI monomer was dissolved in 2.0 mol / L H2SO4 solution (25 mL) with magnetic stirring and reacted in an ice-water bath for 1 h to obtain solution A. Next, 0.025 mol of APS was dissolved in 2.0 mol / L H2SO4 solution (25 mL) to prepare solution B. Using the cleaned CWF as a support substrate, polyaniline nanorod arrays were directly assembled on it using a simple chemical oxidation deposition process. The CWF was vertically immersed in solution A, and then solution B was added to solution A, and the reaction was carried out with magnetic stirring in an ice-water bath for 12 h. The resulting polyaniline-containing CWF was rinsed several times with deionized water and then annealed in a vacuum oven at 60 °C for 2 h to obtain the final product, labeled as polyaniline carbon fiber cloth electrode (PANI@CWF).

[0123] 5. Fabrication of thermoelectric conversion devices

[0124] The PANI@CWF electrode is attached to the bottom surface of a custom-made cylindrical quartz mold (12 mm inner diameter, 16 mm outer diameter, 15 mm height). LAM-1 hydrogel is then poured into the cylindrical mold to allow it to form in situ. After forming, another PANI@CWF electrode is attached to the top surface of the cylindrical mold. Two PI films are then attached to the electrodes on both sides. Finally, thermocouples are attached to the polymer films on both sides, thus creating the thermoelectric conversion device.

[0125] Example 2: Preparation of a lignin-based self-healing thermoelectric hydrogel and thermoelectric conversion device

[0126] The difference from Example 1 is that the solvent for the lithium chloride solution in step 3 is changed from water to glycerol / water, wherein V甘油 V 水 =1:2.

[0127] The other steps and conditions are the same as in Example 1, and the lignin-based self-healing thermoelectric hydrogel LAM-2 and the thermoelectric conversion device prepared based on LAM-2 are obtained in sequence.

[0128] Example 3: Preparation of a lignin-based self-healing thermoelectric hydrogel and thermoelectric conversion device

[0129] The difference from Example 1 is that the inorganic small molecule thermoelectric material lithium chloride in step 3 is replaced with sodium chloride.

[0130] The other steps and conditions are the same as in Example 1, and the lignin-based self-healing thermoelectric hydrogel LAM-3 and the thermoelectric conversion device prepared based on LAM-3 are obtained in sequence.

[0131] Comparative Example 1: Preparation of a lignin-based thermoelectric hydrogel

[0132] The difference from Example 1 is that the cyclodextrin-modified lignin sulfonate in step 1 is replaced with commercially available unmodified lignin.

[0133] The other steps and conditions are the same as in Example 1, and the lignin-based self-healing thermoelectric hydrogel LAM-4 is obtained.

[0134] Comparative Example 2: Preparation of a lignin-based self-healing thermoelectric hydrogel

[0135] The difference from Example 1 is that the inorganic small molecule thermoelectric material lithium chloride in step 3 is replaced with lithium bromide.

[0136] The other steps and conditions are the same as in Example 1, and a lignin-based self-healing thermoelectric hydrogel, LAM-5, is obtained.

[0137] Comparative Example 3: Preparation of a lignin-based self-healing thermoelectric hydrogel

[0138] The difference from Example 1 is that the inorganic small molecule thermoelectric material lithium chloride in step 3 is replaced with potassium iodide.

[0139] The other steps and conditions are the same as in Example 1, and a lignin-based self-healing thermoelectric hydrogel, LAM-6, is obtained.

[0140] Comparative Example 4: Preparation of a lignin-based self-healing thermoelectric hydrogel

[0141] The difference from Example 1 is that the inorganic small molecule thermoelectric material lithium chloride in step 3 is replaced with potassium bromide.

[0142] The other steps and conditions are the same as in Example 1, and a lignin-based self-healing thermoelectric hydrogel, LAM-7, is obtained.

[0143] Comparative Example 5: Preparation of a lignin-based self-healing thermoelectric hydrogel

[0144] The difference from Example 1 is that the inorganic small molecule thermoelectric material lithium chloride in step 3 is replaced with sodium iodide.

[0145] The other steps and conditions are the same as in Example 1, and the lignin-based self-healing thermoelectric hydrogel LAM-8 is obtained.

[0146] Comparative Example 6: Preparation of a lignin-based self-healing thermoelectric hydrogel

[0147] The difference from Example 1 is that the inorganic small molecule thermoelectric material lithium chloride in step 3 is replaced with sodium bromide.

[0148] The other steps and conditions are the same as in Example 1, and a lignin-based self-healing thermoelectric hydrogel, LAM-9, is obtained.

[0149] Comparative Example 7: Preparation of a lignin-based self-healing thermoelectric hydrogel and thermoelectric conversion device

[0150] The difference from Example 1 is that the inorganic small molecule thermoelectric material lithium chloride in step 3 was not added.

[0151] The other steps and conditions are the same as in Example 1, and the lignin-based self-healing thermoelectric hydrogel LAM-10 and the thermoelectric conversion device based on LAM-10 are obtained in sequence.

[0152] Comparative Example 8: Preparation of a lignin-based self-healing thermoelectric hydrogel and thermoelectric conversion device

[0153] The difference from Example 1 is that the method of adding the inorganic small molecule thermoelectric material lithium chloride in step 3 is changed from an integrated method to a substitution method, thereby obtaining a lignin-based self-healing thermoelectric hydrogel LAM-11, and a thermoelectric conversion device based on LAM-11. The specific preparation method includes the following steps:

[0154] 1. Preparation of cyclodextrin-modified lignin sulfonate (LS-CD)

[0155] 36.3 g of β-cyclodextrin and 6.67 g of 1-p-toluenesulfonylimidazole were added to 250 mL of deionized water and stirred vigorously at room temperature for 3 h. 50 mL of 10 wt% NaOH solution was added, and stirring continued for 30 min. Unreacted insoluble matter was removed by filtration, and then 1 M HCl solution was added to adjust the pH of the filtrate to 7.5. The resulting mixture was precipitated at low temperature for 18 h, then filtered to collect the residue, which was washed three times with ice water and acetone to obtain the crude product. The crude product was recrystallized three times in hot water to obtain CDOTs. 6.5 g of lignin sulfonate was dissolved in 150 mL of deionized water and stirred thoroughly to obtain a clear solution. 6.5 g of CDOTs was added, and the mixture was stirred vigorously at room temperature for 2 h, then refluxed at 80 °C for 24 h. After cooling, the solution was transferred to a dialysis bag in a MWC 3500 and dialyzed for 3 days. The retentate was freeze-dried to obtain a yellow or pale yellow product, LS-CD.

[0156] 2. Preparation of Adamantane Acrylate (ADA)

[0157] 3.04 g of 1-adamantanol and 60 mL of anhydrous dichloromethane were added to the reactor and stirred until fully dissolved. Then, 3 g of triethylamine was added. The mixture was kept at 0 °C and stirred for 40 min. 3.62 g of acryloyl chloride diluted with 25 mL of anhydrous dichloromethane was added dropwise to the mixture at 0 °C using a constant-pressure dropping funnel. After the addition was complete, the mixture was slowly brought to room temperature and stirred for 18 h. After the reaction, the insoluble matter was filtered off, and the filtrate was collected. The filtrate was washed three times each with 0.1 M HCl aqueous solution, 0.5 wt% NaHCO3 solution, and distilled water, respectively. The organic phase was collected and concentrated by rotary evaporation under reduced pressure at 4 °C. The solution was then purified by column chromatography, with V as the eluent. 乙酸乙酯 :V 正己烷 =1:15, to obtain the product ADA, which is stored at low temperature for later use.

[0158] 3. Preparation of lignin-based self-healing thermoelectric hydrogel (LAM-11)

[0159] 0.0144 g LS-CD and 80 μL of methanol solution containing ADA (0.01 g / mL) were added to 7 mL of ultrapure water and stirred at room temperature for 30 min. Then 0.02 g stannous chloride (SnCl2) was added, followed by 0.96 g acrylamide (AM) and 0.96 g acrylic acid (AA), and finally 0.024 g ammonium persulfate (APS) to obtain P(AA-AM) hydrogel. Finally, the P(AA-AM) hydrogel was immersed in 1.5 mol / L lithium chloride aqueous solution to obtain hydrogel LAM-11.

[0160] 4. Preparation of polyaniline carbon fiber cloth electrodes

[0161] First, carbon fiber fabric (CWF) was ultrasonically cleaned for 30 min using ethanol and deionized water. Then, 0.025 mol of ANI monomer was dissolved in 2.0 mol / L H₂SO₄ solution (25 mL) with magnetic stirring and reacted in an ice-water bath for 1 h to obtain solution A. Next, 0.025 mol of APS was dissolved in 2.0 mol / L H₂SO₄ solution (25 mL) to prepare solution B. Using the cleaned CWF as a support substrate, polyaniline nanorod arrays were directly assembled on it using a simple chemical oxidation deposition process. The CWF was vertically immersed in solution A, and then solution B was added to solution A, reacting with magnetic stirring in an ice-water bath for 12 h. The resulting polyaniline-containing CWF was rinsed several times with deionized water and then annealed in a vacuum oven at 60 °C for 2 h to obtain the final product, labeled PANI@CWF.

[0162] 5. Fabrication of thermoelectric conversion devices

[0163] The bottom surface of a custom-made cylindrical quartz mold (12 mm inner diameter, 16 mm outer diameter, 15 mm height) is attached with a PANI@CWF electrode. LAM-11 hydrogel is then poured into the cylindrical mold to form it in situ. After forming, another PANI@CWF electrode is attached to the top surface of the cylindrical mold. Two PI films are then attached to the electrodes on both sides. Finally, thermocouples are attached to the polymer films on both sides, thus completing the thermoelectric conversion device.

[0164] Example 1: Performance Characterization of Thermoelectric Hydrogels and Electrodes

[0165] (1) A picture of the hydrogel

[0166] By comparing the gelation process of the hydrogels in Example 1 and Comparative Examples 2-6, such as... Figure 1 As shown, the precursor solution containing lithium chloride in Example 1 formed a hydrogel network structure. However, the precursor solutions containing lithium bromide, potassium iodide, potassium bromide, sodium iodide, and sodium bromide in Comparative Examples 2-6 failed to form a network structure. This may be because iodide ions (I₂O₃, I₂O₃, I₂O₃, I₂O₃, I₂O₃)... - ) and bromide ions (Br - The ionic radius of ions is relatively large compared to that of chloride ions (Cl). - These factors can affect the arrangement and cross-linking structure of polymer chains, thus preventing the formation of stable three-dimensional networks.

[0167] (2) SEM images of the hydrogel

[0168] The hydrogel in Example 1 was characterized by SEM, such as... Figure 2 As shown, at low temperatures, the hydrogel network exhibits numerous interchain / intrachain hydrogen bonds between carboxyl (-COOH) and amide (-CONH2) groups. These molecular interactions lead to polymer chain aggregation, which in turn forms a "sieve-like" network. Under the temperature gradient provided by the temperature measuring element (thermocouple) (hot end temperature 318 K, cold end temperature 298 K), a temperature difference is generated within the hydrogel, and the pore size increases with increasing temperature, exhibiting volumetric phase transition behavior. Furthermore, due to the negative charge of the carboxyl / amino groups in the hydrogel, the hydrogel network gradually suppresses large Cl- groups in lithium chloride (LiCl) through electrostatic repulsion. - Heat diffuses towards the hot end, while Li + Its smaller volume and relatively higher fluidity and diffusion rate compared to Cl - Large, therefore Li + It will migrate from the hot end to the cold end. Ultimately, high concentrations of Li... + and Cl - The particles aggregate on both sides of the hydrogel in the cold and hot directions, respectively, thereby generating a thermoelectric potential and enhancing the ionic Seebeck coefficient of the prepared thermoelectric material.

[0169] (3) Mechanical performance testing

[0170] Tensile tests were performed on the hydrogels at room temperature using a computer-controlled universal testing machine (CMT6203; SensTest, Shenzhen, China) equipped with a 100 N load cell. The tensile strain capacity of the hydrogels was determined by uniaxial tensile testing, where hydrogel samples were cut into rectangles approximately 2 mm thick, 15 mm long, and 4 mm wide, and stretched at a speed of 50 mm / min. Four equilibrium samples were measured for each group of samples. The mechanical properties of the hydrogels were compared between the tensile strength and tensile strain capacity of the hydrogels in Example 1 and Comparative Example 1. Figure 3 As shown, compared to the LAM-4 hydrogel in Comparative Example 1 (tensile strength 119 kPa and tensile strain 802%), the LAM-1 hydrogel with added LS-CD in Example 1 achieved a tensile strength of 264 kPa and a tensile strain of 1208%, indicating that the thermoelectric hydrogel in Example 1 has excellent mechanical properties.

[0171] (4) Self-healing performance test

[0172] The self-healing performance was compared by comparing the load-bearing capacity of the hydrogel cross-section in Example 1 and Comparative Example 1. Figure 4As shown, the LAM-1 hydrogel prepared in Example 1 can still withstand 175% tension without breaking after 1 hour of self-healing at the fracture surface, while the LAM-4 hydrogel prepared in Comparative Example 1 cannot withstand tension after 1 hour of self-healing at the fracture surface. This proves that after introducing host-guest interaction, the LAM-1 hydrogel prepared in this application has superior self-healing properties.

[0173] (5) Temperature-sensitive performance test

[0174] The upper critical eutectic temperature (UCST) of hydrogels was determined using a UV-VIS spectrophotometer and an ultra-constant temperature water bath to characterize the hydrogel's temperature-sensitive properties. The transmittance of the hydrogel sample was measured within the range of 298–368 K by placing the sample in the UV-VIS spectrophotometer equipped with a constant temperature water bath. The wavelength parameter of the UV-VIS spectrophotometer was set to 600 nm, and the measurement range parameter was 3 cm. After each temperature increase, the transmittance was allowed to stabilize before the next temperature increase, and temperature-transmittance curves were prepared. Figure 5 As shown, in Example 1, the LAM-1 hydrogel can transition between a white opaque state and a transparent state within a temperature range of 278–318 K, preliminarily demonstrating that the hydrogel exhibits phase transition behavior. To further investigate the temperature sensitivity of the hydrogel, in-situ variable temperature UV detection was performed on the LAM-1 hydrogel. The phase transition temperature was the 50% transmittance of the LAM hydrogel during the heating process. Figure 6 As shown, during the test, the transmittance increased with increasing temperature, reaching 50% at 325 K. The critical dissolution temperature (UCST) was 313 K, indicating that when the LAM-1 hydrogel sample was below 313 K (278 K), hydrogen bonds formed between the amide and carboxyl groups in the hydrogel sample, causing the molecular chains to shrink, the gel to dehydrate and become turbid. When the temperature was above 313 K (318 K), the hydrogen bonds between the amide and carboxyl groups opened, the gel absorbed water and became transparent. The thermosensitive nature of the thermoelectric conversion material provides a way to construct gradient ion channels.

[0175] (6) Test of freeze resistance and water retention performance

[0176] The antifreeze and water retention properties of the hydrogel in Example 2 were tested, such as... Figure 7 As shown in Figure a, after being stored at 25 °C for 7 days, the LAM-2 hydrogel still retains more than 70% of its initial weight. To investigate the antifreeze properties of the LAM-2 hydrogel... Figure 7As shown in b, we verified the conductivity of the hydrogel at low temperatures. Whether at room temperature or -20 °C, the small light bulb in the hydrogel circuit remained lit, demonstrating that it can still maintain electron transport at low temperatures. This indicates that adding glycerol as a solvent during the preparation of the hydrogel can give it good antifreeze and water-retention properties.

[0177] (7) Morphology of polyaniline carbon fiber cloth electrode

[0178] like Figure 8 As shown in the digital image, a dark green deposit was observed on the polyaniline carbon fiber cloth electrode (PANI@CWF) prepared in Example 1, which well covered the underlying CWF electrode. SEM characterization of the polyaniline carbon fiber cloth electrode (PANI@CWF) revealed... Figure 9 As shown, a dense array of nanorods forms on the surface of PANI@CWF. The formation of the nanorod array significantly increases the surface area of ​​the electrode, thereby improving the contact area between it and the thermoelectric material and enhancing the electrochemical performance of the electrode.

[0179] (8) Electrochemical performance of polyaniline carbon fiber cloth electrode

[0180] The PANI@CWF electrode prepared in Example 1 was characterized by cyclic voltammetry at different scan rates in 1 M H2SO4 solution using a two-electrode testing system. Figure 10 As shown, the results indicate that with the increase of scan rate, the oxidation peak and reduction peak of the PANI@CWF electrode shift to the positive and negative potentials, respectively, indicating that the electrode has good reversibility and fast charge and discharge response.

[0181] Experimental Example 2: Performance Characterization of Thermoelectric Conversion Devices

[0182] (1) Structural diagram

[0183] Schematic diagrams of the thermoelectric conversion devices prepared in Examples 1-3 are shown below. Figure 11 As shown, its overall stacked structure, arranged sequentially from bottom to top, consists of: thermocouple, PI film, polyaniline carbon fiber cloth electrode (PANI@CWF), lignin-based self-healing thermoelectric hydrogel, polyaniline carbon fiber cloth electrode, PI film, and thermocouple.

[0184] (2) Thermal effect

[0185] The thermal effect was measured on an integrated instrument with an electrochemical workstation (Bio-logic-VMP-3e) and a temperature controller (TLTP-TEC2415D), with a temperature deviation of ±0.1 K. A temperature gradient was set, and thermal charging was performed. The changes in thermal voltage were recorded using the electrochemical workstation until the thermal voltage reached equilibrium, at which point the open-circuit voltage was recorded. After measuring the saturation voltage under different temperature gradients, the ionic Seebeck coefficient was calculated using the formula S. i =△ V / △ T Calculations show that the thermal effect of the thermoelectric conversion devices is characterized by comparing the open-circuit voltage and Seebeck coefficient of the thermoelectric conversion devices in Examples 1-2 and Comparative Examples 7-8. Figure 12 As shown, under a temperature difference of 20 K, the thermoelectric conversion device in Comparative Example 7 exhibits a maximum open-circuit voltage of 0.2 V and a Seebeck coefficient of 10 mV•K. -1 The thermoelectric conversion device in Comparative Example 8 showed an open-circuit voltage as high as 0.109 V, with a Seebeck coefficient of 5.45 mV•K. -1 The "sandwich" structure thermoelectric conversion device assembled from the LAM hydrogel and polyaniline carbon fiber cloth electrode prepared in Example 1 showed a maximum open-circuit voltage of 0.395V and a Seebeck coefficient of 19.75 mV•K under the same temperature difference conditions. -1 The thermoelectric conversion device in Example 2 exhibited an open-circuit voltage as high as 0.404 V, with a Seebeck coefficient of 20.2 mV•K. -1 This strongly demonstrates that the addition of lithium chloride can significantly improve the thermal effect of thermoelectric conversion devices.

[0186] (3) Thermoelectric conversion performance

[0187] The thermoelectric conversion performance of the thermoelectric conversion devices in Examples 1-2 and Comparative Example 8 was characterized by testing their energy density, using ≤0.3 mV min. -1 The voltage near-saturation state is defined by the changing voltage rate. Then, various external resistors are connected to obtain the power output stage, and the energy density during a 1-hour discharge process is calculated using the integral output power curve, and P=E / Δ t The equation calculates the average power density under external load, where ∆ t This is the total duration of the discharge phase within a thermal cycle; the instantaneous output power is obtained by multiplying the voltage and current. For example... Figure 13 As shown, under a temperature difference of 20 K, the power-time curves of the thermoelectric conversion devices of Examples 1-2 and Comparative Example 8 connected in series with a 3 kΩ resistance box are displayed. Among them, the energy density of Comparative Example 8 is 117.4 J•m in 1 h. -2 Examples 1 and 2 can achieve 616.04 J•m respectively.-2 and 676 J•m -2 This indicates that only thermoelectric conversion devices prepared by directly preparing specific inorganic small molecule thermoelectric materials into thermoelectric hydrogels and then integrating them with polyaniline carbon fiber cloth electrodes can have excellent thermoelectric conversion performance.

[0188] (4) Electrochemical performance

[0189] Cyclic voltammetry (CV) testing first establishes a voltage window (0–1 V), and tests the electrode at different scan rates, repeatedly scanning in a triangular waveform over time, recording the current-potential curve. The electrochemical performance of the thermoelectric conversion device is reflected by comparing the maximum specific areal capacitance of Examples 1–2 and Comparative Example 8. Figure 14 As shown, the maximum specific areal capacitance of the thermoelectric conversion device in Comparative Example 8 is 76 mF•cm. -2 Examples 1 and 2 can achieve 764 mF•cm, respectively. -2 and 355 mF•cm -2 This demonstrates that, compared to the solution substitution method commonly used in existing studies (i.e., preparing the gel first and then replacing it with LiCl), the advantage of directly preparing the gel using LiCl solution lies in the ability to directly pour it into the device and achieve "integrated" bonding with the polyaniline carbon fiber cloth electrode while the gel is still in the precursor solution state. This method effectively solves the problem of poor contact between the thermoelectric gel and the electrode, ensuring that the thermoelectric conversion device prepared in this application has superior interfacial contact and electrochemical performance.

[0190] In summary, this invention successfully prepared a lignin-based self-healing thermoelectric hydrogel by combining specific inorganic small-molecule thermoelectric materials with cyclodextrin-modified lignin sulfonate and adamantane acrylate. During the formation of the thermoelectric hydrogel, the inorganic small-molecule thermoelectric material is uniformly dispersed within the hydrogel's network structure, giving it excellent mechanical properties; the host-guest interaction introduced by the cyclodextrin-modified lignin sulfonate endows it with excellent self-healing capabilities; and the hydrogel also exhibits good temperature-sensitive properties. These characteristics significantly enhance the thermal effect, thermoelectric conversion performance, and electrochemical performance of thermoelectric conversion devices prepared based on the aforementioned thermoelectric hydrogel.

[0191] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A lignin-based self-healing thermoelectric hydrogel, characterized in that, The preparation method of the lignin-based self-healing thermoelectric hydrogel includes the following steps: Cyclodextrin-modified lignin sulfonate and adamantane acrylate were added to a solvent containing inorganic small molecule thermoelectric materials and mixed well. Unsaturated carboxylic acid monomers, acrylamide monomers, metal ions and initiators were added and reacted fully to prepare a lignin-based self-healing thermoelectric hydrogel. The inorganic small molecule thermoelectric material is selected from one or more of lithium chloride, sodium chloride, and potassium chloride. The concentration of the inorganic small molecule thermoelectric material is 0.1~3 mol / L; the mass ratio of the cyclodextrin-modified lignin sulfonate and adamantane acrylate is (1~75):1; the mass ratio of the unsaturated carboxylic acid monomers and acrylamide monomers is 1:(0.8~1.5).

2. The lignin-based self-healing thermoelectric hydrogel according to claim 1, characterized in that, The metal ions are derived from one or more of the following: stannous chloride, ferric chloride, calcium chloride, barium chloride, aluminum chloride, cobalt chloride, nickel chloride, copper chloride, and silver chloride.

3. The lignin-based self-healing thermoelectric hydrogel according to claim 1, characterized in that, The unsaturated carboxylic acid monomers are C3-C8 olefinic acids and / or C3-C8 alkynetic acids.

4. The lignin-based self-healing thermoelectric hydrogel according to claim 1, characterized in that, The acrylamide monomers include one or more of acrylamide, methacrylamide, and ethylacrylamide.

5. A thermoelectric conversion device, characterized in that, The thermoelectric conversion device includes the lignin-based self-healing thermoelectric hydrogel and electrode as described in any one of claims 1 to 4; the lignin-based self-healing thermoelectric hydrogel is connected to the electrode as a thermoelectric conversion material.

6. The thermoelectric conversion device according to claim 5, characterized in that, The thermoelectric conversion device includes a stacked structure arranged in sequence: a first electrode, a thermoelectric conversion material, and a second electrode.

7. The application of the lignin-based self-healing thermoelectric hydrogel according to any one of claims 1 to 4 in the fields of wearable thermoelectric conversion devices, the Internet of Things, and sensing.

8. The application of the thermoelectric conversion device according to claim 5 or 6 in the fields of wearable thermoelectric conversion devices, the Internet of Things, and sensing.

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