A lignin-zinc ion antifreezing hydrogel electrolyte, a preparation method and application thereof

Abstract

This invention relates to antifreeze hydrogel electrolytes, and discloses a lignin-zinc ion antifreeze hydrogel electrolyte, its preparation method, and its applications. This invention utilizes the fact that the catechol groups generated by the hydrolysis of sodium lignin sulfonate (LS) under acidic conditions are more easily oxidized to quinones, which can be converted by Zn. 2+ Complexation guides the formation of catechol, thereby establishing a redox equilibrium between catechol and quinone, promoting the conversion of APS to SO4. ‑ • It then reacts with water to generate OH•, and this autocatalytic system can also generate singlet oxygen radicals in an acidic environment ( 1 O2), along with various free radicals, jointly initiates the polymerization of ammonium acrylate (AM) monomers to form a gel. The newly developed hydrogel boasts an environmentally friendly and rapid polymerization method, excellent conductivity, strong mechanical properties, and freeze resistance. Therefore, this work will provide new insights for the design of multifunctional hydrogel solid electrolytes for flexible electronic devices and make large-scale production of hydrogels possible.

Description

Technical Field

[0001] This invention relates to antifreeze hydrogel electrolytes, and particularly to a lignin-zinc ion antifreeze hydrogel electrolyte, its preparation method, and its application. Background Technology

[0002] The scarcity of fossil fuels and increasingly severe environmental problems have spurred demand for green and environmentally friendly electronic energy storage devices. Hydrogel solid electrolytes, with their tunable mechanical properties, excellent biocompatibility, and high conductivity, have become a hot topic in the research of high-performance flexible electronic devices. However, the preparation processes of most hydrogel electrolytes are time-consuming and energy-intensive, requiring external interventions such as ultraviolet light irradiation, special compound catalysis, or prolonged heating to excite initiators to generate free radicals. This significantly limits their large-scale industrial production. Therefore, forming hydrogels at room temperature without external stimulation is challenging.

[0003] Catechol is an important chemical raw material. Due to its strong reducing, complexing, and bioadhesive properties, some catechol-containing substances have been used to prepare hydrogels with good mechanical properties and high viscosity, attracting widespread attention from researchers. Zong et al. constructed Cu... 2+ The autocatalytic system of tannic acid (an organic compound containing catechol groups) accelerates the cracking of ammonium persulfate to generate a large number of free radicals, thereby promoting the rapid polymerization of acrylate amines at ambient temperature. However, there are few attempts to use renewable catechol-containing natural polymers in autocatalytic systems, which has significant application prospects for green manufacturing and sustainable development. Plant-derived lignin contains abundant aromatic natural biopolymers in nature, and its reduced methoxy (-OCH3) and phenolic hydroxyl (-OH) groups have participated as polyphenol groups in metal ion autocatalytic systems. Compared with water-soluble modified lignin and nano-sized lignin as uniformly dispersed components, sodium lignin sulfonate (LS) has good solubility in acidic environments and can be directly applied to avoid external costs, time and energy consumption, and low yield. In addition, since acidic water contains freely migrating ions, it can be used not only for dissolution but also for conduction. Such a great motivation utilizes the multifunctional hydrogel of the LS-metal ion catalytic system.

[0004] The large amount of free water in hydrogel electrolytes inevitably freezes at temperatures below 0 °C, leading to a decrease in ionic conductivity and causing the hydrogel to lose its flexibility. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a lignin-zinc ion antifreeze hydrogel electrolyte and its preparation method.

[0006] This invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides a lignin-zinc ion antifreeze hydrogel electrolyte, which is obtained by polymerization of ammonium acrylate (AM) in the presence of sodium lignin sulfonate (LS) and Zn(BF4)2. The hydrogel electrolyte can be prepared at room temperature within 5 min without introducing any additional energy. The mechanical strength of this hydrogel electrolyte reaches a tensile stress of 0.14 MPa at 1750% strain. Alkali metal ions enable the hydrogel electrolyte to exhibit a tensile strength of 3.67 mS / cm at −40 °C. -1 Ultra-high conductivity at extreme low temperatures.

[0008] Secondly, the present invention provides a method for preparing a lignin-zinc ion antifreeze hydrogel electrolyte, the preparation method being as follows:

[0009] First, HCl is dissolved in deionized water to prepare a 1 M aqueous solution;

[0010] Then, Zn(BF4)2 was dissolved in an acidic solution to prepare acidic solutions of Zn(BF4)2 with different concentrations from 0 to 5 M, and AM was added.

[0011] Dissolve LS in acidic HCl solution at different mass ratios, add N,N'-methylenebisacrylamide MBA, and stir in an ice bath for 1 hour;

[0012] Add 0.03 g of initiator APS and stir in an ice bath; inject the prepared precursor solution into a mold and seal at room temperature for polymerization.

[0013] Preferably, in step (2), the amount of AM added is 3g.

[0014] Preferably, in step (3), the mass ratio of LS is one of 0 wt%, 0.1 wt%, 0.3 wt%, and 0.5 wt%.

[0015] Preferably, in step (3), the amount of HCl acid solution is 5.0 ml and the amount of MBA added is 1 mg.

[0016] Preferably, in step (4), the amount of initiator APS added is equivalent to 1 wt% of the monomer mass.

[0017] Preferably, in step (4), the stirring time is 30s.

[0018] Thirdly, the present invention provides the application of lignin-zinc ion antifreeze hydrogel electrolyte in the preparation of sensors for detecting strain sensing signals, temperature sensing signals, and one of various motions.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] A simple, universal, and rapid gelation method based on sodium lignosulfonate and zinc ions is proposed. The complex formed by catechol and alkali metal ions promotes the equilibrium of the redox reaction. The generated SO4... - •, OH• and singlet oxygen ( 1 O2 radicals are responsible for the rapid polymerization of vinyl monomers. Alkali metal ions play a dual role in the rapid polymerization and freeze-thaw resistance of the hydrogel electrolyte. The gelation time can be adjusted by changing the lignin mass ratio and the concentration of zinc ions or acid, through regulating the mass ratio DL and metal ion concentration. The hydrogel electrolyte can be prepared within 5 min at room temperature without introducing any additional energy. The mechanical strength of the hydrogel electrolyte reaches a tensile stress of 0.14 MPa at 1750% strain. Alkali metal ions contribute to the hydrogel electrolyte's 3.67 mS / cm at −40 °C. -1 The hydrogel electrolyte sensor exhibits ultra-high conductivity at extreme low temperatures. It can detect various parts of the human body over a wide temperature range and output a stable resistance signal. This work provides a lignin-zinc ion autocatalytic method for the rapid preparation of multifunctional hydrogels.

[0021] The sensor constructed using this hydrogel electrolyte exhibits excellent electrochemical performance at both room temperature and low temperature, effectively filling the application gap in low-temperature sensors. Attached Figure Description

[0022] The invention will now be further described with reference to the accompanying drawings.

[0023] Figure 1 Schematic diagram of rapid initiation of multifunctional hydrogel polymerization by a self-catalytic system;

[0024] Figure 2 For rapid aggregation of physical images: (a) Infrared thermal image; (b) polyAM-LS 0.1 - Zn4 polymer physical image; (c) polyAM polymer physical image;

[0025] Figure 3 For the study of rapid polymerization mechanism: gelation time of (a) LS, (b) HCl and (c) Zn(BF4)2 with different contents / concentrations; XPS spectra of C1s of (d) LS and (e) LS-HCl-Zn(BF4)2; (f) electron paramagnetic spectrum;

[0026] Figure 4 For LS-Zn 2+ Mechanism diagram of autocatalytic system;

[0027] Figure 5Mechanical properties of hydrogels: (a) mechanical properties at different LS contents; (b) maximum stress-strain at different LS contents; (c) elastic modulus and toughness at different LS contents; (d) mechanical properties at different Zn(BF4)2 contents; (e) maximum stress-strain at different Zn(BF4)2 contents; (f) elastic modulus and toughness at different Zn(BF4)2 contents.

[0028] Figure 6 For polyAM-LS 0.3 - Zn4 hydrogel actual product image

[0029] Figure 7 For PolyAM and polyAM-LS 0.3 -Image of Zn4 hydrogel at room temperature and -40 °C;

[0030] Figure 8 Study on the antifreeze properties of hydrogel electrolytes: (a) polyAM-LS 0.3 -Zn y (a) DSC of hydrogel electrolytes; (b) polyAM-LS 0.3 -Zn y Ionic conductivity of hydrogels at different temperatures; (c) polyAM-LS 0.3 -Zn y Temperature dependence of hydrogel ionic conductivity;

[0031] Figure 9 For the performance study of the hydrogel sensor: (a) the change of relative resistance under different strains; (b) the response time and recovery time of the sensor; (c) the change of relative resistance of the sensor over time when subjected to cyclic stretching under tensile strain; (d) the change of resistance of the sensor at different temperatures; (e) a schematic diagram of the monitored sensor position; (f) the change of relative resistance over time when subjected to cyclic stretching of the finger at -20 °C; and (g) the change of relative resistance over time when subjected to cyclic stretching of the finger, (h) elbow, and (i) knee at room temperature. Detailed Implementation

[0032] The invention will now be further described with reference to the accompanying drawings. Example

[0033] Raw materials and reagents

[0034] Table 1 Main raw materials and reagents

[0035] .

[0036] Experimental instruments and equipment

[0037] Table 2 Main Experimental Instruments and Equipment

[0038] .

[0039] Experimental sample preparation

[0040] Antifreeze zwitterionic polyAM-LS x -Zn y Preparation of electrolytes

[0041] polyAM-LS was obtained by polymerization of AM in the presence of sodium lignosulfonate (LS) and Zn(BF4)2. x -Zn y Hydrogel electrolyte. First, HCl was dissolved in deionized water to prepare a 1 M aqueous solution. Then, Zn(BF4)2 was dissolved in an acidic solution to prepare acidic solutions of Zn(BF4)2 with different concentrations from 0 to 5 M, and 3 g of AM was added. Then, LS at different mass ratios (0 wt%, 0.1 wt%, 0.3 wt%, 0.5 wt%) was dissolved in 5.0 ml of acidic HCl solution, 1 mg of MBA was added, and the mixture was stirred in an ice bath for 1 hour. 0.03 g of initiator APS (equivalent to 1 wt% of the monomer mass) was added, and the mixture was stirred in an ice bath for 30 s. The precursor solution was injected into a mold and sealed at room temperature for several minutes to allow polymerization.

[0042] Example 2 Test Characterization

[0043] Characterization of rapid gelation

[0044] The polymerization time was calculated after the addition of APS (0 s). The polymerization reaction was complete when the temperature reached its maximum. LS and LS-Zn were determined using an electron spectrometer (Escalab 250Xi). 2+ X-ray photoelectron spectroscopy (XPS) of the self-catalytic system was used to determine the DL-Zn content. 2+ The degree of oxidation in the autocatalytic system was recorded on an ESR spectrometer (Bruker EMXnano). 2+ Spin trapped electron spin resonance (ESR) spectra of 5,5-dimethyl-1-pyrrolline-orthooxide (DMPO) in an autocatalytic system were used to determine sulfuric acid and hydroxyl radicals as well as singlet oxygen.

[0045] Mechanical performance test

[0046] The mechanical properties of the sample were tested using a general-purpose mechanical testing instrument (Hensgrand, WDW-02, Jinan). The tensile sample was a cuboid with a length of 50 mm, a width of 7 mm, and a thickness of 3 mm. The strain rate was 50 mm / min. -1 .

[0047] Measurement of the conductivity of hydrogel electrolytes

[0048] The ionic conductivity (σ) of the hydrogel electrolyte was measured by electrochemical impedance spectroscopy (EIS) using a CHI660E electrochemical workstation. First, the hydrogel electrolyte was filled into a CR927 battery case, and the electrolyte-filled case was stabilized at different temperatures for 2 to 4 hours. Impedance was then measured at the corresponding temperatures. It is best to perform three measurements for each sample to reduce error. Ionic conductivity (σ, mS / cm) -1 ) is calculated using the following formula.

[0049] .

[0050] Where L is the thickness of the sample to be tested (cm), R is the resistance (Ω), and S is the contact area of ​​the electrolyte (cm²). 2 ).

[0051] Feature testing

[0052] Differential scanning calorimetry (DSC) was performed using a TA2500 instrument. The sample was first cooled from 40 °C to -80 °C, and then heated from -80 °C to 40 °C. Both cooling and heating rates were 5 °C / min. -1 The sample mass was between 8 and 10 mg. The sample was tested under nitrogen protection.

[0053] Electrochemical performance testing of the sensor

[0054] The electrochemical signal of the hydrogel was recorded on a CHI660E workstation using impedance-time measurements to depict the change in the hydrogel electrolyte impedance over time. The strain coefficient, representing the strain sensitivity of the hydrogel sensor, was calculated using the following formula:

[0055] .

[0056] The corresponding changes in resistance are measured, where R0 and R are the initial resistance and the real-time resistance, respectively. It is a response.

[0057] Example 3

[0058] Results Discussion

[0059] Rapid polymerization mechanism

[0060] This invention uses acrylamide (AM) monomer for hydrogel polymerization in this system, verifying the synergistic autocatalytic effect of lignin and zinc ions. In this system, sodium lignin sulfonate (LS) and Zn(BF4)2 are used to construct the autocatalytic system. To enhance the catalytic effect of LS, hydrochloric acid (…) was also added to the system. Figure 1).

[0061] The final multifunctional hydrogel is abbreviated as polyAM-LS. x -Zn y Where x is the mass fraction of LS and y is the molar concentration of Zn(BF4)2 in the system. LS and Zn 2+ This is the decisive factor in the rapid polymerization of AM monomers. Various components in the precursor solution work synergistically to achieve the rapid preparation of multifunctional hydrogel electrolytes within 5 minutes. This is as observed by infrared thermography. Figure 2 a) After APS, LS, and Zn(BF4)2 were added to the precursor solution, the solution began to release heat at an ambient temperature of 20–25°C for 3 minutes, reaching a heat peak at 5 minutes, and then gradually began to cool, indicating that the hydrogel reactive polymerization was essentially completed within 5 minutes. Figure 2 As shown in b, compared to the precursor solution containing LS and Zn(BF4)2, which was able to form a gel in 5 min, the precursor solution without LS and Zn(BF4)2 could not form a gel. Figure 2 c). These experimental results confirm that LS and Zn(BF4)2 can promote the rapid gelation of precursor solutions at ambient temperature, which greatly facilitates large-scale preparation.

[0062] In addition, further experimental data from this invention show that the gelation rate of the hydrogel is positively correlated with both the content of LS and the concentration of HCl / Zn(BF4)2. Figure 3 As shown in Figure a, when the precursor solution was controlled with 1 M HCl and 4 M Zn(BF4)2, the gelation time decreased from 3 hours to 8 minutes as the LS content increased from 0 to 0.1 wt%. With further increases in LS content, the gelation time gradually shortened to 3 minutes. Increasing the acid concentration in the system also significantly promoted the gelation time. When the HCl concentration changed from 0 M to 0.5 M, the gelation time decreased from 11.5 minutes to 6 minutes. Figure 3 b). Furthermore, by increasing the Zn(BF4)2 concentration from 0 to 4 M, the gelation time of the hydrogel could be reduced from 24 min to 5 min. Figure 3 c). Experimental results show that increasing the content / concentration of LS, HCl, and Zn(BF4)2 is beneficial for rapid gelation, and the absence of any one component cannot reduce the gelation time to below 10 min. Therefore, this indicates that the LS-Zn system is a method capable of achieving rapid polymerization, where the catechol groups obtained after LS acid hydrolysis can promote monomer polymerization in Zn. 2+ Fast aggregation is achieved in the presence of an object.

[0063] In the system of this invention, the mechanism triggering rapid polymerization is completely different from the reported rapid polymerization mechanism of redox systems formed by high-valence oxidized metal ions and lignin. To explore LS, Zn 2+ The mechanism of rapid polymerization of acids was analyzed by X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) spectroscopy. Figure 3 XPS spectra in c show that DL has a high CO / C-OH peak at 286.3 eV and a low C=O peak at 288.9 eV. When LS is treated with HCl and Zn(BF4)2, the area of ​​the CO / C-OH peak increases, while the area of ​​the C=O peak decreases significantly. Figure 3 e), indicating that the -OH and -OCH3 groups of LS are acidically hydrolyzed to form a catechol structure. In the system of the present invention, the methoxy group of lignin is hydrolyzed under acidic conditions to form catechol from lignin, and these catechol salts are readily converted to S2O8 by APS. 2- It is oxidized to the quinone group of lignin. Simultaneously, APS is reduced to produce sulfate radicals (SO4). - • Sulfate radicals can interact with water molecules (H2O) to produce hydroxyl radicals (OH•), and four signals with relative intensities of 1:2:2:1 confirm the presence of OH•. Figure 3 f). It should be noted that the present invention also detected typical triple-line EPR spectra with the same intensity (f). Figure 3 f), this spectrum is attributed to singlet oxygen (f). 1 O2) Therefore, OH• and 1 O2 is generally considered to facilitate rapid polymerization of monomers. In summary, this invention proposes that sodium lignin sulfonate more readily generates easily oxidized catechol groups under acidic conditions. Notably, zinc ions and the catechol groups of lignin can form stable complexes, which effectively improves the reversibility of the redox reaction between catechol and quinone. This zinc ion-catechol complex is less stable than the zinc salt of catechol, thereby promoting the reduction of the quinone groups in lignin. Figure 4 Furthermore, acidic environments and Zn 2+ The synergistic effect makes this autocatalytic system more likely to generate more free radicals. Therefore, sodium lignosulfonate-Zn 2+ It can achieve rapid gelation within 5 minutes in an acidic environment.

[0064] Mechanical properties of hydrogel electrolytes

[0065] Excellent mechanical properties are crucial for the application of hydrogel electrolytes. Therefore, polyAM-LS was evaluated through a series of tensile and rheological tests. x -Zn yMechanical properties of hydrogel electrolytes. The addition of sodium lignosulfonate (LS) did not significantly increase the tensile strain of the hydrogel at 0.1 wt%. However, with gradually increasing the LS content, the tensile strain value increased significantly, indicating that LS, as a component of the gel, contributes to the tensile strain. Figure 5 a) Regarding the ultimate tensile strength, the sample without DL showed a significant decrease after the addition of LS, indicating that the addition of LS disrupted the original hydrogel structure, leading to a sharp drop in strain. Figure 5 As shown in b, the stress intensity is at its maximum of 0.25 MPa without LS, gradually decreasing to 0.11 MPa with increasing LS content. The ultimate tensile strain is 1750% without LS, gradually increasing to 2200% with increasing LS content. This indicates that increasing LS content impairs the mechanical strength of the hydrogel and makes it more easily stretchable. Figure 5 As shown in Figure c, the elastic modulus reaches its highest value of 32.8 kPa without LS. With increasing LS content, the elastic modulus gradually decreases to 13.8 kPa. The toughness value is also highest at 201.28 KJ / m² without LS. -3 However, the toughness initially decreases and then increases with increasing LS, reaching a minimum of 107.5 KJ / m. -3 It was later increased to 130.68 kJ / m³ -3 .

[0066] The effect of Zn(BF4)2 concentration on the mechanical properties of polyAM hydrogels was also investigated. The addition of HCl decreased both the tensile strength and strain of the hydrogel, indicating that the addition of Zn(BF4)2 significantly affects the mechanical properties of the polyAM hydrogel. Regarding tensile strength, with increasing Zn(BF4)2 concentration, the ultimate tensile strength decreased from 0.242 ± 0.01 MPa at 0 M to 0.057 ± 0.01 MPa at 5 M. Figure 5 d). Similarly, with the addition of Zn(BF4)2, the tensile strain decreased from 1929% to 1169% ( Figure 5 d). For example Figure 5 As shown in Figure e, the maximum stress intensity is 0.242 MPa in the absence of Zn(BF4)2, and gradually decreases to 0.057 MPa with increasing Zn(BF4)2 concentration. Meanwhile, the ultimate tensile strain is 1929% in the absence of Zn(BF4)2, and gradually decreases to 1169% with increasing Zn(BF4)2 concentration. This indicates that increasing Zn(BF4)2 concentration impairs the mechanical properties of the hydrogel. Figure 5As shown in Figure c, the elastic modulus reaches its highest value of 42.4 kPa when Zn(BF4)2 is absent. With increasing Zn(BF4)2 concentration, the elastic modulus gradually decreases to 12.45 kPa. The toughness value also reaches its highest value of 258.7 kJ / m when Zn(BF4)2 is absent. -3 As the Zn(BF4)2 concentration increases, the toughness gradually decreases to 33 kJ / m. -3 .like Figure 6 The representative example shown is polyAM-LS. 0.3 -Zn4 hydrogel electrolytes possess sufficient flexibility to withstand various types of deformation, such as load-bearing, twisting, and knotting. Notably, polyAM-LS weighing 1.2 g... 0.3 -Zn4 hydrogel electrolyte can be successfully lifted to 200 g, which is 167 times its own weight, indicating that the hydrogel has excellent mechanical load-bearing capacity.

[0067] Antifreeze properties and conductivity of hydrogel electrolytes

[0068] The essence of water freezing is a phase transition from disordered to ordered water driven by hydrogen bonds. Researchers typically achieve this by adding high concentrations of salts, ionic liquids, organic solvents, or antifreeze proteins to the aqueous solvent. These methods disrupt the hydrogen bond network between water molecules, thereby achieving an antifreeze effect. In the case of this invention, the addition of Zn(BF4)2 not only accelerates the polymerization of the hydrogel but also endows the hydrogel with antifreeze properties and high conductivity. Figure 7 As shown, after freezing at −30 °C for 4 hours, the polyAM hydrogel lost its flexibility. Conversely, the polyAM-LS... 0.3 -Zn4 hydrogels retain a certain degree of flexibility and can be stretched up to five times their initial size.

[0069] Differential scanning calorimetry (DSC) is also used to measure the effect of HCl concentration on the freezing point of electrolytes. For example... Figure 8 As shown in Figure a, the freezing points of the electrolyte are -6.2, -19.7, -27.2, and -35.6 °C when the Zn(BF4)2 concentration is 0, 2, 4, and 5 M, respectively. Notably, when the HCl concentration is 5 M, the DSC curve shows an exothermic peak only at -35.6 °C, indicating no heat flow in the -35 to 40 °C temperature range. In addition to the aforementioned antifreeze properties, the conductivity of the electrolyte with different Zn(BF4)2 concentrations was also measured at different temperatures. Figure 8 As shown in b, polyAM-LS 0.3 -Zn0 exhibits poor low-temperature conductivity. In contrast, polyAM-LS 0.3 -Zn4 and polyAM-LS 0.3-Zn5 exhibits good ionic conductivity between −40 °C and 25 °C. At 25 °C, the conductivity reaches 40.07 mS / cm. -1 and 45.2 mS cm -1 Even at a low temperature of -40 °C, polyAM-LS 0.3 -Zn4 and polyAM-LS 0.3 The conductivity of Zn5 can also reach 3.67 mS / cm. -1 and 3.9 mS cm -1 It is well known that the relationship between the ionic conductivity of an electrolyte and the reciprocal of its absolute temperature is always linear and follows Arrhenius's law (…). Figure 8 c). The lower the activation energy (Ea), the more favorable the ion migration. polyAM-LS 0.3 -Zn5 electrolyte has the lowest Ea at 12.05 eV, which is consistent with the ionic conductivity data.

[0070] Electrical sensing characteristics of the sensor

[0071] Considering the above properties, polyAM-LS 0.3 -Zn4 hydrogel electrolytes can be rapidly polymerized (gelation at room temperature for 5 min) and exhibit strong mechanical properties (stress: 0.14 MPa, strain: ~1760%) and low-temperature conductivity (3.67 mS cm⁻¹ at −40°C). -1 This is superior to hydrogel electrolytes reported in the literature. To better develop polyAM-LS... 0.3 The practical application value of Zn4 hydrogel electrolyte lies in its fabrication into sensors for detecting strain and temperature signals. Furthermore, the hydrogel electrolyte exhibits high sensitivity and rapid response. With increasing strain (ɛ), the strain coefficients are 0.01 and 0.013 for ɛ ≤ 400% and 400% < ɛ ≤ 900%, respectively. Figure 9 a). In addition, the response time and recovery time of the sensor made of this hydrogel ( Figure 9 b) These are 4 s and 5 s, respectively, indicating that polyAM-LS 0.3 -Zn4 hydrogel sensors can sensitively detect various movements. For example... Figure 9 As shown in Figure c, no significant signal fluctuations were observed within the tensile strain range of 100% to 600%, demonstrating that the designed sensor possesses stable signal output capability. This is due to the polyAM-LS... 0.3 -Zn4 hydrogel electrolyte has excellent antifreeze properties, and this invention can also apply it to temperature sensors that respond to different temperature changes. For example... Figure 9As shown in d, this sensor maintains a stable output signal at temperatures below 0 °C and can operate normally at temperatures as low as −30 °C. Subsequently, the polyAM-LS... 0.3 -Zn4 hydrogel sensors are attached to various parts of the human body to detect human movement. Figure 9 e). For example Figure 9 As shown in f and 9g, the sensor, when mounted on a finger, exhibits stable signal fluctuations at -20 and 25 °C, respectively. This indicates that the hydrogel sensor can effectively monitor various human movements at low temperatures. In addition to the finger, resistance changes during flexion were also monitored at the elbow and knee. The sensor easily detected resistance signals under different conditions, demonstrating that the hydrogel sensor can adhere to various parts of the body to detect relevant human activities.

[0072] In summary, the invention has discovered a lignin macromolecule-zinc ion autocatalytic system (DL-Zn). 2+ A simple method for preparing hydrogels with good antifreeze properties and high conductivity in a short time. Specifically, the catechol groups generated by the hydrolysis of sodium lignosulfonate (LS) under acidic conditions are more easily oxidized to quinones, which can be converted by Zn. 2+ Complexation guides the formation of catechol, thereby establishing a redox equilibrium between catechol and quinone, promoting the conversion of APS to SO4. - • It then reacts with water to generate OH•, and this autocatalytic system can also generate singlet oxygen radicals in an acidic environment ( 1 O2), along with various free radicals, jointly initiates the polymerization of ammonium acrylate (AM) monomers to form a gel. The newly developed hydrogel boasts an environmentally friendly and rapid polymerization method, excellent conductivity, strong mechanical properties, and freeze resistance. Therefore, this work will provide new insights for the design of multifunctional hydrogel solid electrolytes for flexible electronic devices and make large-scale production of hydrogels possible.

Claims

1. A lignin-zinc ion antifreezing hydrogel electrolyte, characterized in that, The hydrogel electrolyte is obtained by polymerization of acrylic amine AM in the presence of sodium lignosulfonate LS and Zn(BF4)2; the hydrogel electrolyte can be prepared in 5 min at room temperature without introducing any additional energy, the mechanical strength of the hydrogel electrolyte can reach a tensile stress of 0.14 MPa at a strain of 1750%, and the alkali metal ions enable the hydrogel electrolyte to have an ultrahigh and extremely low temperature conductivity of 3.67 mS cm -1 at −40°C; the preparation method of the lignin-zinc ion antifreezing hydrogel electrolyte is as follows: (1) First, HCl was dissolved in deionized water to prepare a 1 mol / L HCl solution; (2) Then Zn(BF4)2 was dissolved in the 1 mol / L HCl solution to prepare a 4-5 mol / L Zn(BF4)2 acidic solution of different concentrations, and AM was continuously added; (3) LS of different mass ratios was dissolved in the 1 mol / L HCl solution, and N,N'-methylenebisacrylamide MBA was added, and stirred in an ice bath for 1 hour; the mass ratio is one of 0.3 wt%, 0.5 wt%; (4) 0.03 g of initiator APS was added, and then stirred in an ice bath; the precursor solution was injected into a mold, and sealed at room temperature for polymerization.

2. The lignin-zinc ion antifreezing hydrogel electrolyte according to claim 1, characterized in that, In step (2), the amount of AM added is 3 g.

3. The lignin-zinc ion antifreezing hydrogel electrolyte according to claim 1, characterized in that, In step (3), the amount of HCl solution is 5.0 ml, and the amount of MBA added is 1 mg.

4. The lignin-zinc ion antifreezing hydrogel electrolyte according to claim 1, characterized in that, In step (4), the amount of initiator APS added is 1 wt% of the mass of the monomer.

5. The lignin-zinc ion antifreezing hydrogel electrolyte according to claim 1, wherein, In step (4), the stirring time is 30 s.

6. Use of the lignin-zinc ion anti-freezing hydrogel electrolyte of claim 1 in the preparation of a sensor for detecting one of a strain sensing signal, a temperature sensing signal.

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