Anti-freezing hydrogel electrolyte and preparation method, and supercapacitor and preparation method

Abstract

The application belongs to the field of supercapacitor preparation, and discloses a kind of anti-freezing hydrogel electrolyte and preparation method and supercapacitor and preparation method.The anti-freezing hydrogel electrolyte includes lithium chloride, water, acrylamide, proline, crosslinking agent and initiator.The supercapacitor of the application has excellent anti-freezing property, excellent electrochemical performance, high safety and low economic cost.

Description

Technical Field

[0001] This invention belongs to the field of supercapacitor preparation, and more specifically, relates to an antifreeze hydrogel electrolyte and its preparation method, as well as a supercapacitor and its preparation method. Background Technology

[0002] With the booming development of the new energy field, corresponding power-consuming equipment has placed higher demands on energy storage devices. Besides excellent electrochemical performance, they also need to withstand harsh application environments such as low temperatures to meet the needs of higher-level production and daily life. Therefore, in recent years, various low-temperature resistant energy storage devices have been widely reported. Supercapacitors, as an important energy storage device, are extremely suitable for fabricating low-temperature resistant energy sources due to their high power density, fast charge and discharge speeds, and especially their wide operating temperature range. To endow supercapacitors with excellent low-temperature adaptability, the electrolyte material, as a key component, should possess freeze resistance.

[0003] As is well known, ice is the result of hydrogen bonding aggregation of water molecules. Currently, the main strategies for preparing antifreeze electrolytes fall into two categories: preparing high-concentration salts and adding organic liquids. High-concentration salt electrolytes contain almost no water and therefore have high viscosity, resulting in low ionic conductivity. Furthermore, strong corrosiveness is a major drawback of this type of electrolyte, posing significant risks during preparation and use. In addition, these electrolytes face the problem of high preparation costs, thus limiting their practical application value. Organic liquids used as electrolyte additives mainly include ethylene glycol, glycerol, and dimethyl sulfoxide. In these binary / ternary systems, the interaction between organic liquids and water molecules is considered the main reason for inhibiting ice crystal formation. Electrolytes containing these organic liquids can achieve low freezing points. However, the presence of organic liquids also significantly reduces the ionic conductivity of the electrolyte. Moreover, the volatility and high self-ignition properties of organic liquids pose serious safety hazards to energy storage devices.

[0004] As can be seen from the methods for preparing antifreeze electrolytes described above, maintaining high ionic conductivity while achieving a low freezing point is a significant challenge. In recent years, zwitterionic materials have been widely used as an emerging material in the preparation of antifreeze hydrogel electrolytes, simultaneously addressing the challenges faced by antifreeze electrolytes. Zwitterionic ions disrupt the hydrogen bond network in water molecules through electrostatically induced hydration, transforming freezeable free water molecules into non-freezeable strongly bound water, thereby lowering the freezing point. Simultaneously, the charged functional groups on the zwitterionic monomer chains can provide separate migration channels for electrolyte ions, thus improving the ionic conductivity of the electrolyte. However, the types of zwitterionic materials currently used are relatively limited, mainly based on sulfonated betaine. Therefore, the development of more adaptable zwitterionic materials is an urgent need in this field. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing an antifreeze hydrogel electrolyte and its preparation method, as well as a supercapacitor and its preparation method. The supercapacitor of this invention possesses excellent antifreeze properties, superior electrochemical performance, high safety, and low economic cost.

[0006] To achieve the above objectives, the first aspect of the present invention provides an antifreeze hydrogel electrolyte, the antifreeze hydrogel electrolyte comprising lithium chloride, water, acrylamide, proline, a crosslinking agent and an initiator.

[0007] According to the present invention, preferably, based on the total weight of the antifreeze hydrogel electrolyte, the content of lithium chloride is 20-30 wt%, the content of water is 20-59 wt%, the content of acrylamide is 5-20 wt%, the content of proline is 15-30 wt%, the content of crosslinking agent is 0.005-0.02 wt%, and the content of initiator is 0.05-0.2 wt%.

[0008] According to the present invention, preferably, the crosslinking agent is at least one selected from N,N-methylenebisacrylamide, tetraethylene glycol dimethacrylate, and ethylene glycol dimethacrylate.

[0009] According to the present invention, preferably, the initiator is at least one selected from ammonium persulfate, potassium persulfate, and azobisisobutylamidine hydrochloride.

[0010] According to the present invention, preferably, the antifreeze hydrogel electrolyte is in the form of a sheet with a thickness of 10μm-30μm.

[0011] A second aspect of this invention provides a method for preparing the aforementioned antifreeze hydrogel electrolyte. This invention prepares the antifreeze hydrogel electrolyte via free radical polymerization, comprising the following steps:

[0012] S1: Mix the lithium chloride with water until homogeneous to obtain a lithium chloride solution;

[0013] S2: Mix the acrylamide, lithium chloride solution and proline evenly to obtain a precursor solution;

[0014] S3: After the precursor solution, crosslinking agent and initiator are mixed evenly, they are subjected to ultrasonic treatment and heat treatment in sequence to obtain the antifreeze hydrogel electrolyte.

[0015] According to the present invention, preferably, in step S2, the stirring time is 0.5h-10h and the stirring speed is 200-500r / min.

[0016] According to the present invention, preferably, in step S3, acrylamide is polymerized as the heat treatment proceeds, the heat treatment temperature is 50℃-90℃, preferably 60℃, and the time is 4h-12h (that is, the polymerization reaction time).

[0017] A third aspect of the present invention provides a supercapacitor containing an antifreeze hydrogel electrolyte, the supercapacitor comprising electrode plates, stainless steel gaskets, a stainless steel battery casing and the antifreeze hydrogel electrolyte;

[0018] The electrode sheets are attached to both sides of the antifreeze hydrogel electrolyte.

[0019] According to the present invention, preferably, the thickness of the stainless steel gasket is 400μm-600μm.

[0020] According to the present invention, preferably, based on the total weight of the electrode slurry of the electrode sheet, the content of polyvinylidene fluoride is 3-10% and the content of activated carbon is 90-97%.

[0021] The current collector of the electrode sheet is at least one of titanium foil, stainless steel foil, and copper foil;

[0022] Preferably, the titanium foil is a rectangular sheet with a thickness of 5μm-15μm.

[0023] According to the present invention, preferably, the method for preparing the electrode sheet includes:

[0024] (1) Mix the polyvinylidene fluoride, activated carbon and solvent evenly to obtain an electrode slurry;

[0025] (2) The electrode paste is coated on the surface of the current collector, vacuum dried, and cut into pieces to obtain the electrode sheet.

[0026] According to the present invention, preferably, in step (1):

[0027] The stirring time is 0.5h-10h, and the stirring speed is 200-500r / min;

[0028] The solvent is at least one of N-methylpyrrolidone solvent, N,N-dimethylformamide, and dimethyl sulfoxide.

[0029] According to the present invention, preferably, in step (2), the vacuum drying temperature is 100℃-140℃ and the time is 10h-16h.

[0030] A fourth aspect of this invention provides a method for preparing the supercapacitor containing the antifreeze hydrogel electrolyte, comprising:

[0031] The electrode sheet is attached to both sides of the antifreeze hydrogel electrolyte;

[0032] The stainless steel gasket is placed on the outside of the positive electrode plate and the inside of the stainless steel battery casing, and then encapsulated in the stainless steel battery casing. The stainless steel battery casing is then sealed using a press to obtain the supercapacitor containing the antifreeze hydrogel electrolyte.

[0033] According to the present invention, preferably, the pressure of the press is 1-3 MPa.

[0034] In this invention, such as Figure 1 As shown, the supercapacitor uses zwitterionic proline as an effective antifreeze agent, lithium chloride as an electrolyte salt and antifreeze aid, acrylamide as a polymer mechanical framework, and activated carbon as the active material in the electrode. Proline is a naturally occurring amino acid, therefore it is safe and environmentally friendly. Specifically:

[0035] For electrolytes: Due to proline's strong hydration capacity, it can disrupt the hydrogen bond network structure between water molecules, converting free water molecules in hydrogel electrolytes into strongly bound water, thereby altering the state of water within the electrolyte and achieving a low freezing point. Simultaneously, the charged functional groups on the proline molecule can provide dedicated migration channels for electrolyte ions, thus increasing the electrolyte's ionic conductivity.

[0036] For the electrodes: Activated carbon is used as the active material in the electrodes. Activated carbon has low-temperature adaptability, so the supercapacitor assembled from it has antifreeze properties.

[0037] The beneficial effects of the technical solution of the present invention are as follows:

[0038] 1. The supercapacitor of the present invention uses a proline / polyacrylamide / lithium chloride hydrogel with antifreeze properties as the electrolyte and activated carbon as the active material in the electrode, and is assembled in a traditional sandwich structure.

[0039] 2. This invention utilizes a proline-containing antifreeze hydrogel as the electrolyte, thereby obtaining not only an antifreeze electrolyte but also an antifreeze supercapacitor energy storage device. This is the first time proline has been applied to the field of supercapacitors using an antifreeze hydrogel electrolyte. Due to its unique properties, proline can simultaneously lower the freezing point of the hydrogel electrolyte and increase its ionic conductivity, characteristics not found in traditional hydrogel electrolytes. Extensive practical testing shows that the proline added in this invention has a good effect on disrupting the hydrogen bond network in the hydrogel electrolyte, lowering the freezing point to -43℃. Among currently reported related materials, this freezing point is already quite low, indicating that proline is an effective antifreeze electrolyte additive. Furthermore, the supercapacitor based on this antifreeze hydrogel electrolyte retains 80% of its capacity at -30℃, demonstrating excellent low-temperature adaptability.

[0040] 3. The main raw materials involved in this invention, namely proline, acrylamide, lithium chloride, activated carbon, etc., are all inexpensive reagents that are non-toxic and harmless. Furthermore, the electrolyte has strong adhesive properties, eliminating the need for additional binders and diaphragms. Therefore, the entire process is relatively simple, low-cost, and environmentally friendly. Consequently, this invention is particularly suitable for large-scale commercial production and has excellent commercial application prospects.

[0041] 4. This invention specifically studies and designs the entire fabrication process of supercapacitors (including the preparation of the antifreeze hydrogel electrolyte) and its key parameters. Through this invention, an antifreeze supercapacitor with excellent antifreeze properties, superior electrochemical performance, high safety, and low cost can be obtained. Compared with traditional supercapacitors, the obtained capacitor does not require a separator, resulting in a simplified device structure. The antifreeze supercapacitor of this invention is not only suitable for room temperature environments but is also particularly suitable for fields with special antifreeze requirements, such as electric vehicles, aerospace, and military applications.

[0042] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0043] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0044] Figure 1 This diagram illustrates a supercapacitor structure based on the component design and assembly of an antifreeze hydrogel electrolyte provided by the present invention.

[0045] Figure 2 (a)-(d) are optical images showing the various deformations and adhesion properties of an antifreeze hydrogel electrolyte provided in Embodiment 1 of the present invention.

[0046] Figure 3 Differential scanning calorimetry (DSC) spectrum of an antifreeze hydrogel electrolyte provided in Embodiment 1 of the present invention.

[0047] Figure 4 The graph shows the ionic conductivity of an antifreeze hydrogel electrolyte provided in Embodiment 1 of the present invention at different temperatures.

[0048] Figure 5 The graph shows the cyclic voltammetry test results of a supercapacitor containing an antifreeze hydrogel electrolyte provided in Embodiment 1 of the present invention at different temperatures.

[0049] Figure 6The graph shows the charge and discharge test results of a supercapacitor containing an antifreeze hydrogel electrolyte provided in Embodiment 1 of the present invention at different temperatures.

[0050] Figure 7 This is a schematic diagram illustrating the rate performance of a supercapacitor containing an antifreeze hydrogel electrolyte at different temperatures, as provided in Embodiment 1 of the present invention.

[0051] Figure 8 This is a schematic diagram of the AC impedance test of a supercapacitor containing an antifreeze hydrogel electrolyte at different temperatures, provided in Embodiment 1 of the present invention (where Z'(Ohm) is the real part of the impedance; -Z"(Ohm) is the imaginary part of the impedance).

[0052] Figure 9 This is a schematic diagram illustrating the cycle life analysis of a supercapacitor containing an antifreeze hydrogel electrolyte at different temperatures, as provided in Embodiment 1 of the present invention. Detailed Implementation

[0053] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0054] In the following embodiments, the stainless steel battery casing is model 2016.

[0055] Example 1

[0056] This embodiment provides an antifreeze hydrogel electrolyte, which, based on the total weight of the antifreeze hydrogel electrolyte, contains 24 wt% lithium chloride, 43.89 wt% deionized water, 10 wt% acrylamide, 22 wt% proline, 0.01 wt% N,N-methylenebisacrylamide, and 0.1 wt% ammonium persulfate.

[0057] The antifreeze hydrogel electrolyte is in the form of a thin sheet with a thickness of 20 μm.

[0058] The preparation method of the antifreeze hydrogel electrolyte includes the following steps:

[0059] S1: Mix the lithium chloride with deionized water until homogeneous to obtain a lithium chloride solution;

[0060] S2: Slowly add acrylamide to the lithium chloride solution in step S1, then add proline and stir for 0.5 h to form a homogeneous precursor solution;

[0061] S3: N,N-methylenebisacrylamide and ammonium persulfate are then added sequentially to the precursor solution. After mixing evenly, the mixture is transferred to a clean petri dish and sonicated. The petri dish is then sealed and placed in a 60°C drying oven for 8 hours to allow the acrylamide to polymerize, thus obtaining the antifreeze hydrogel electrolyte.

[0062] This embodiment also provides a supercapacitor containing an antifreeze hydrogel electrolyte, the supercapacitor comprising electrode plates, stainless steel gaskets, a stainless steel battery casing and the aforementioned antifreeze hydrogel electrolyte;

[0063] The electrode sheets are attached to both sides of the aforementioned antifreeze hydrogel electrolyte.

[0064] The thickness of the stainless steel gasket is 500 μm;

[0065] Based on the total weight of the electrode slurry in the electrode sheet, the content of polyvinylidene fluoride is 5%, and the content of activated carbon is 95%; the current collector of the electrode sheet is titanium foil, which is a rectangular thin sheet with a thickness of 10 μm. The preparation method of the electrode sheet includes:

[0066] (1) Mix the polyvinylidene fluoride, activated carbon and an appropriate amount of N-methylpyrrolidone solvent evenly to obtain an electrode slurry;

[0067] (2) The electrode slurry is transferred to a clean titanium foil current collector, and then the electrode slurry is uniformly coated on the surface of the titanium foil current collector using a coating machine. After that, it is placed in a vacuum drying oven at 120°C and heated to remove the N-methylpyrrolidone solvent. The electrode is then cut into pieces to obtain the electrode.

[0068] The method for preparing the supercapacitor containing the antifreeze hydrogel electrolyte includes:

[0069] The electrode sheet is attached to both sides of the antifreeze hydrogel electrolyte;

[0070] The stainless steel gasket is placed on the outside of the positive electrode plate and the inside of the stainless steel battery casing, and then encapsulated in the stainless steel battery casing. The stainless steel battery casing is then sealed by applying a pressure of 1 MPa using a press to obtain the supercapacitor containing the antifreeze hydrogel electrolyte.

[0071] like Figure 2 The image shown is an optical diagram illustrating various deformations and adhesion properties of an antifreeze hydrogel electrolyte provided in Example 1. Wherein:

[0072] from Figure 2 As can be seen in (a), the antifreeze hydrogel electrolyte of this embodiment has excellent stretchability, with an elongation rate of up to 409%.

[0073] from Figure 2As can be seen in (b), the antifreeze hydrogel electrolyte of this embodiment can also be twisted arbitrarily.

[0074] from Figure 2 As can be seen in (c), the antifreeze hydrogel electrolyte of this embodiment can be compressed to 80% of the strain.

[0075] from Figure 2 As can be seen from (d), the antifreeze hydrogel electrolyte of this embodiment also has good adhesion and can be firmly adhered to the glass surface.

[0076] like Figure 3 The image shows a differential scanning calorimeter of an antifreeze hydrogel electrolyte provided in Example 1. The image shows that the freezing point of the electrolyte is -43℃.

[0077] like Figure 4 The figure shows the ionic conductivity of the antifreeze hydrogel electrolyte provided in Example 1 at different temperatures. It can be seen that even at -30°C, the electrolyte still exhibits a conductivity of 7.1 mS / cm. -1 ionic conductivity.

[0078] like Figure 5 As shown, this embodiment 1 provides a supercapacitor containing an antifreeze hydrogel electrolyte, operating at 10 mV / s at different temperatures. -1 The cyclic voltammetry test results, from Figure 5 As can be seen, all curves at different temperatures exhibit a rectangular shape, indicating that the capacitor has significant double-layer capacitance characteristics. Even at -30℃, the area under the CV curve does not decrease significantly. This demonstrates that the capacitor still exhibits good capacitive behavior at low temperatures.

[0079] like Figure 6 The image shows the charge-discharge test results of a supercapacitor containing an antifreeze hydrogel electrolyte provided in Example 1 at different temperatures. Figure 6 As can be seen from this, at a current density of 0.5Ag -1 Below, the charge-discharge curves exhibit good symmetry across all temperatures.

[0080] like Figure 7 The figure shows the rate performance of a supercapacitor containing an antifreeze hydrogel electrolyte provided in Example 1 at different temperatures. Figure 7 As can be seen from this, at 25℃, the specific capacitance is 145.8 F g. -1 At -30℃, the specific capacitance is 116.1 F g. -1The capacity retention rate can reach 80%, which is higher than most reported supercapacitors based on activated carbon electrodes and containing antifreeze hydrogel electrolytes. Moreover, the rate performance at -30°C is generally poor, mainly due to the hindered ion diffusion of the antifreeze hydrogel electrolyte at low temperatures.

[0081] like Figure 8 The figure shows the AC impedance test results of a supercapacitor containing an antifreeze hydrogel electrolyte provided in Example 1 at different temperatures. It can be seen that the equivalent series internal resistance of the capacitor in this example is relatively small, but its charge transfer resistance increases as the temperature decreases. This is mainly because the charge transport rate at the interface decreases with decreasing temperature. However, overall, the increase in charge transfer resistance is not very significant. This is mainly due to the superior properties of proline as a zwitterionic additive, which can accelerate the migration of electrolyte ions while lowering the freezing point.

[0082] like Figure 9 The figure shown is a cycle life analysis graph of a supercapacitor containing an antifreeze hydrogel electrolyte provided in Example 1 at different temperatures. Figure 9 It can be seen that the capacitor of this embodiment has an ideal cycle life at 25°C, with a capacitance retention of 92% even after 12,000 cycles. At -30°C, the capacitor retains 74% of its initial capacitance after 12,000 cycles. This retention rate is excellent for a supercapacitor operating at -30°C, indicating that the supercapacitor has good low-temperature adaptability.

[0083] Example 2

[0084] This embodiment provides an antifreeze hydrogel electrolyte. The only difference between this embodiment and Embodiment 1 is that:

[0085] Based on the total weight of the antifreeze hydrogel electrolyte, the content of lithium chloride is 24 wt%, the content of deionized water is 43.89 wt%, the content of acrylamide is 8 wt%, the content of proline is 24 wt%, the content of N,N-methylenebisacrylamide is 0.02 wt%, and the content of ammonium persulfate is 0.09 wt%.

[0086] The stirring time in step S2 of the method for preparing the antifreeze hydrogel electrolyte is 1 hour;

[0087] In the preparation method of the supercapacitor containing antifreeze hydrogel electrolyte, the stainless steel battery casing is sealed by applying a pressure of 2MPa using a press to obtain the supercapacitor containing antifreeze hydrogel electrolyte.

[0088] Example 3

[0089] This embodiment provides an antifreeze hydrogel electrolyte. The only difference between this embodiment and Embodiment 1 is that:

[0090] Based on the total weight of the antifreeze hydrogel electrolyte, the content of lithium chloride is 22 wt%, the content of deionized water is 43.87 wt%, the content of acrylamide is 10 wt%, the content of proline is 24 wt%, the content of N,N-methylenebisacrylamide is 0.03 wt%, and the content of ammonium persulfate is 0.1 wt%.

[0091] The stirring time in step S2 of the method for preparing the antifreeze hydrogel electrolyte is 1.5 h; the heating temperature in step S3 is 70 °C and the time is 6 h.

[0092] In the preparation method of the supercapacitor containing antifreeze hydrogel electrolyte, the stainless steel battery casing is sealed by applying a pressure of 3MPa using a press to obtain the supercapacitor containing antifreeze hydrogel electrolyte.

[0093] Example 4

[0094] This embodiment provides an antifreeze hydrogel electrolyte. The only difference between this embodiment and Embodiment 1 is that:

[0095] Based on the total weight of the antifreeze hydrogel electrolyte, the content of lithium chloride is 26 wt%, the content of deionized water is 43.79 wt%, the content of acrylamide is 8 wt%, the content of proline is 22 wt%, the content of N,N-methylenebisacrylamide is 0.01 wt%, and the content of ammonium persulfate is 0.2 wt%.

[0096] The stirring time in step S2 of the method for preparing the antifreeze hydrogel electrolyte is 1.5 h; the heating temperature in step S3 is 60 °C and the time is 7 h.

[0097] In the preparation method of the supercapacitor containing antifreeze hydrogel electrolyte, the stainless steel battery casing is sealed by applying a pressure of 1.5 MPa using a press to obtain the supercapacitor containing antifreeze hydrogel electrolyte.

[0098] Example 5

[0099] This embodiment provides an antifreeze hydrogel electrolyte. The only difference between this embodiment and Embodiment 1 is that:

[0100] Based on the total weight of the antifreeze hydrogel electrolyte, the content of lithium chloride is 22 wt%, the content of deionized water is 43.88 wt%, the content of acrylamide is 12 wt%, the content of proline is 22 wt%, the content of N,N-methylenebisacrylamide is 0.02 wt%, and the content of ammonium persulfate is 0.1 wt%.

[0101] The stirring time in step S2 of the method for preparing the antifreeze hydrogel electrolyte is 2 hours; the heating temperature in step S3 is 80°C and the time is 8 hours.

[0102] In the preparation method of the supercapacitor containing antifreeze hydrogel electrolyte, the stainless steel battery casing is sealed by applying a pressure of 2.5 MPa using a press to obtain the supercapacitor containing antifreeze hydrogel electrolyte.

[0103] Example 6

[0104] This embodiment provides an antifreeze hydrogel electrolyte. The only difference between this embodiment and Embodiment 1 is that:

[0105] Based on the total weight of the antifreeze hydrogel electrolyte, the content of lithium chloride is 20 wt%, the content of deionized water is 45.87 wt%, the content of acrylamide is 14 wt%, the content of proline is 20 wt%, the content of N,N-methylenebisacrylamide is 0.03 wt%, and the content of ammonium persulfate is 0.1 wt%.

[0106] The stirring time in step S2 of the method for preparing the antifreeze hydrogel electrolyte is 2.5 h; the heating temperature in step S3 is 60 °C and the time is 8 h.

[0107] In the preparation method of the supercapacitor containing antifreeze hydrogel electrolyte, the stainless steel battery casing is sealed by applying a pressure of 3MPa using a press to obtain the supercapacitor containing antifreeze hydrogel electrolyte.

[0108] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. An antifreeze hydrogel electrolyte, characterized in that, The antifreeze hydrogel electrolyte includes lithium chloride, water, acrylamide, proline, a crosslinking agent, and an initiator; Based on the total weight of the antifreeze hydrogel electrolyte, the content of lithium chloride is 20-30 wt%, the content of water is 20-59 wt%, the content of acrylamide is 5-20 wt%, the content of proline is 15-30 wt%, the content of crosslinking agent is 0.005-0.02 wt%, and the content of initiator is 0.05-0.2 wt%.

2. The antifreeze hydrogel electrolyte according to claim 1, wherein, The crosslinking agent is at least one of N,N-methylenebisacrylamide, tetraethylene glycol dimethacrylate, and ethylene glycol dimethacrylate. The initiator is at least one of ammonium persulfate, potassium persulfate, and azobisisobutylamidine hydrochloride.

3. The antifreeze hydrogel electrolyte according to claim 1, wherein, The antifreeze hydrogel electrolyte is in the form of thin sheets with a thickness of 10μm-30μm.

4. The method for preparing the antifreeze hydrogel electrolyte according to any one of claims 1-3, characterized in that, The preparation method includes the following steps: S1: Mix the lithium chloride with water until homogeneous to obtain a lithium chloride solution; S2: Mix the acrylamide, lithium chloride solution and proline evenly to obtain a precursor solution; S3: After the precursor solution, crosslinking agent and initiator are mixed evenly, they are subjected to ultrasonic treatment and heat treatment in sequence to obtain the antifreeze hydrogel electrolyte.

5. The method for preparing the antifreeze hydrogel electrolyte according to claim 4, wherein, In step S2, the stirring time is 0.5h-10h, and the stirring speed is 200-500r / min; In step S3, the heating temperature is 50℃-90℃ and the time is 4h-12h.

6. A supercapacitor containing an antifreeze hydrogel electrolyte, characterized in that, The supercapacitor includes electrode plates, stainless steel gaskets, a stainless steel battery casing, and an antifreeze hydrogel electrolyte as described in any one of claims 1-3; The electrode sheets are attached to both sides of the antifreeze hydrogel electrolyte.

7. The supercapacitor containing an antifreeze hydrogel electrolyte according to claim 6, wherein, The thickness of the stainless steel gasket is 400μm-600μm; Based on the total weight of the electrode slurry of the electrode sheet, the content of polyvinylidene fluoride is 3-10%, and the content of activated carbon is 90-97%. The current collector of the electrode sheet is at least one of titanium foil, stainless steel foil, and copper foil.

8. The supercapacitor containing an antifreeze hydrogel electrolyte according to claim 7, wherein, The titanium foil is a rectangular sheet with a thickness of 5μm-15μm.

9. The supercapacitor containing an antifreeze hydrogel electrolyte according to claim 7, wherein, The method for preparing the electrode sheet includes: (1) Mix the polyvinylidene fluoride, activated carbon and solvent evenly to obtain an electrode slurry; (2) The electrode paste is coated on the surface of the current collector, vacuum dried, and cut into pieces to obtain the electrode sheet.

10. The supercapacitor containing an antifreeze hydrogel electrolyte according to claim 9, wherein, In step (1): The stirring time is 0.5h-10h, and the stirring speed is 200-500r / min; The solvent is at least one of N-methylpyrrolidone solvent, N,N-dimethylformamide and dimethyl sulfoxide; In step (2), the vacuum drying temperature is 100℃-140℃ and the time is 10h-16h.

11. A method for preparing a supercapacitor containing an antifreeze hydrogel electrolyte according to any one of claims 6-10, characterized in that, include: The electrode sheet is attached to both sides of the antifreeze hydrogel electrolyte; The stainless steel gasket is placed on the outside of the positive electrode plate and the inside of the stainless steel battery casing, and then encapsulated in the stainless steel battery casing. The stainless steel battery casing is then sealed using a press to obtain the supercapacitor containing the antifreeze hydrogel electrolyte.

12. The method for preparing a supercapacitor containing an antifreeze hydrogel electrolyte according to claim 11, wherein, The pressure of the press is 1-3 MPa.

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