High-voltage-resistant gel polymer electrolyte, preparation method thereof and super capacitor using high-voltage-resistant gel polymer electrolyte

Abstract

The invention discloses a high-voltage-resistant gel polymer electrolyte, a preparation method thereof and a supercapacitor using the high-voltage-resistant gel polymer electrolyte, and belongs to the technical field of supercapacitors. The high-pressure-resistant gel polymer electrolyte is formed by performing in-situ thermal polymerization reaction on a precursor solution, wherein the precursor solution comprises lithium salt, a carbonate mixed solvent, a high-pressure-resistant additive, a cross-linking agent, a flame-retardant additive and a thermal initiator; the preparation method comprises the following steps: dissolving a lithium salt in a carbonic ester mixed solvent in an inert atmosphere to form a uniform solution; adding a high-pressure-resistant additive, a cross-linking agent, a flame retardant and a thermal initiator into the solution, and stirring and mixing to form a precursor solution; and carrying out in-situ thermal polymerization reaction on the precursor solution to form the high-pressure-resistant gel polymer electrolyte. The high-voltage-resistant additive is introduced, so that the gel electrolyte not only keeps relatively high ionic conductivity, but also can be matched with a high-voltage positive electrode material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of supercapacitors, and particularly relates to a high-voltage-resistant gel polymer electrolyte and a supercapacitor prepared by a preparation method thereof and application thereof. BACKGROUND

[0002] As a new energy storage device between traditional capacitors and secondary batteries, supercapacitors have important application values in electric vehicle start-stop systems, renewable energy recovery, power grid frequency regulation, uninterruptible power supply (UPS), smart grid and aerospace, etc. due to their high power density, super-long cycle life, wide working temperature range and fast charging and discharging capability. In particular, in the field of new energy vehicles, supercapacitors combined with lithium ion batteries into hybrid energy storage systems can significantly improve the high-power response capability and braking energy recovery efficiency; in renewable energy grid connection, it can suppress the voltage sag of the power grid caused by wind and light generation fluctuations and provide millisecond active / reactive power support. However, although the power characteristics of traditional supercapacitors are excellent, the energy density is much lower than that of lithium ion batteries, which greatly limits the possibility of replacing batteries in scenarios requiring high energy continuous output. The core reason for the lack of energy density is that supercapacitors mainly rely on ion adsorption / desorption on the electrode surface (double-layer capacitor) or near-surface fast redox reaction energy storage, the utilization rate of active materials is limited, and the working voltage window is narrow due to the decomposition voltage of electrolyte.

[0003] However, traditional liquid organic electrolytes (such as acetonitrile or carbonate systems with a voltage of ≤2.7 V) are prone to continuous decomposition and gas production at high voltage, resulting in device swelling, performance degradation, and even failure, and there is a risk of leakage and combustion. Although the voltage window of some new liquid electrolytes has been improved, it is still difficult to overcome the intrinsic safety problems such as volatility and flammability. Solid-state electrolytes are safe, but they generally have low ionic conductivity and large electrode / electrolyte interface contact resistance. Therefore, developing a gel polymer electrolyte with high voltage resistance, high ionic conductivity, low interface impedance and excellent safety and flame retardation performance is the key to breaking through the energy density and safety bottleneck of supercapacitors. SUMMARY

[0004] The purpose of the present application is to overcome the above problems, and to provide a high-voltage-resistant gel polymer electrolyte and a supercapacitor prepared by a preparation method thereof and application thereof, which can solve the problems of easy decomposition and gas production of traditional liquid electrolytes at high voltage, unstable interface and risk of leakage and combustion, and avoid the defects of low ionic conductivity and large interface impedance of solid-state electrolytes.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: In a first aspect, the present application provides a high-pressure-resistant gel polymer electrolyte formed by in-situ thermal polymerization of a precursor solution, wherein the precursor solution comprises a lithium salt, a carbonate mixed solvent, a high-pressure-resistant additive, a cross-linking agent, a flame-retardant additive, and a thermal initiator. The lithium salt is any one or two of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorophosphate, lithium bisfluorosulfonylimide, and lithium bis-trifluoromethylsulfonylimide. The carbonate mixed solvent comprises a cyclic carbonate and a chain carbonate, wherein the cyclic carbonate comprises fluoroethylene carbonate and ethylene carbonate, and the chain carbonate comprises at least one of diethyl carbonate and dimethyl carbonate. The high-pressure-resistant additive is one or both of 1,1,2,2,3,3,4,4,4-nonafluorobutane-1-sulfonic acid 2,2,2-trifluoro-1-methylethyl ester and 1,1,2,2-tetrafluoroethane-1-sulfonic acid 2,2,2-trifluoroethyl ester. The cross-linking agent is any one of tetrapropenyl pentaerythritol, pentaerythritol tetraacrylate, polyethylene glycol diacrylate, and pentaerythritol triacrylate. The flame-retardant additive is tris(2,2,2-trifluoroethyl) phosphate.

[0006] In a further improvement of the present application, the lithium salt accounts for 10-15% of the total mass of the precursor solution.

[0007] In a further improvement of the present application, the total volume of the cyclic carbonate accounts for 20-25% of the total volume of the carbonate mixed solvent, the volume of the diethyl carbonate accounts for 10-20%, and the volume of the methyl ethyl carbonate accounts for 55-65%.

[0008] In a further improvement of the present application, the high-pressure-resistant additive accounts for 1-3% of the total mass of the precursor solution.

[0009] In a further improvement of the present application, the cross-linking agent accounts for 1-3% of the total mass of the precursor solution, and the flame-retardant additive accounts for 1-4% of the total mass of the precursor solution.

[0010] In a further improvement of the present application, the thermal initiator is any one of azobisdimethyl isobutyl nitrile, azobisdimethyl isohexyl nitrile, dibenzoyl peroxide, and potassium persulfate, and accounts for 0.3-1% of the total mass of the precursor solution.

[0011] In a further improvement of the present application, the volume ratio of fluoroethylene carbonate to ethylene carbonate in the cyclic carbonate is 1:3 to 1:5.

[0012] In a second aspect, the present application further provides a preparation method of a high-pressure-resistant gel polymer electrolyte, comprising the following steps: S1, dissolving a lithium salt in a carbonate mixed solvent under an inert atmosphere to form a uniform solution; S2, adding a high-pressure resistant additive, a crosslinking agent, a flame retardant and a thermal initiator into the solution obtained in step S1, and stirring and mixing to form a precursor solution; S3, performing in-situ thermal polymerization of the precursor solution to form the high-pressure resistant gel polymer electrolyte.

[0013] Further improvement of the present application is that in step S3, the temperature of the in-situ thermal polymerization is 60-80℃, and the reaction time is 2-4 hours.

[0014] In a third aspect, the present application also provides a supercapacitor, which comprises a positive electrode shell, a positive electrode sheet, a separator, a negative electrode sheet and a negative electrode shell, and the high-pressure resistant gel polymer electrolyte is arranged between the positive electrode sheet and the negative electrode sheet.

[0015] Compared with the prior art, the present application has the following beneficial effects: The present application provides a high-pressure resistant gel polymer electrolyte, by introducing a specific high-pressure resistant additive, due to its low HOMO energy level, it can be preferentially oxidized and decomposed on the surface of the positive electrode under high pressure than the carbonate solvent, and its decomposition products can form a dense and uniform positive electrolyte interface film, which can effectively isolate the positive active material from the electrolyte, thereby significantly inhibiting the continuous decomposition and gas production of the electrolyte under high pressure, widening the electrochemical stability window of the electrolyte to above 4.5V, and ensuring the high-pressure working stability of the device. The crosslinking agent used forms a three-dimensional polymer network with moderate crosslinking density through in-situ thermal polymerization, which on the one hand provides an effective channel for lithium ion transmission, and on the other hand maintains the ionic conductivity at 8×10 -3The high S / cm level provides sufficient mechanical strength to suppress gas generation and enhance the structural stability of the electrolyte. The introduced specific flame retardant, with its fluorinated groups ensuring good electrochemical compatibility with high-voltage systems, and the phosphorus-based structure, through a synergistic mechanism of forming a glassy capping layer in the condensed phase and capturing free radicals in the gas phase at high temperatures, exhibits highly efficient flame retardancy, giving the electrolyte self-extinguishing properties (self-extinguishing time reduced to less than 50 seconds). Simultaneously, the gel-like nature solves the leakage and volatilization problems of liquid electrolytes, improving thermal stability and enhancing overall safety in multiple dimensions. Furthermore, the in-situ polymerization process enables close molecular-level contact between the final gel electrolyte and the electrode, significantly reducing interfacial impedance (down to below 50Ω). Combined with the stable CEI film and cross-linked network, it effectively suppresses electrode interfacial side reactions and the dissolution of transition metal ions during cycling. Thus, after 1000 cycles at a high operating voltage of 3.5V, it retains more than 85% of its capacity with a gas generation rate of less than 5%, demonstrating excellent long-cycle cycling stability. In summary, this technical solution successfully achieves synergistic optimization of high voltage tolerance, high ionic conductivity, excellent safety and flame retardant performance, and long cycle life.

[0016] This invention also provides a method for preparing a high-voltage resistant gel polymer electrolyte. The method first involves dissolving a lithium salt in a carbonate mixed solvent under an inert atmosphere. This step ensures the complete dissociation of the lithium salt and the homogeneity of the solution, laying the foundation for high ionic conductivity. Subsequently, a high-voltage resistant additive, a crosslinking agent, a flame retardant, and a thermal initiator are added sequentially to form a precursor solution. This order of addition and mixing process ensures that the various additives, which play a crucial role in gas generation suppression, ion transport, and safety, are uniformly dispersed and maintain chemical stability, avoiding potential premature reactions or phase separation. The core in-situ thermal polymerization step directly transforms the precursor solution into a gel electrolyte within the final device. This process promotes the formation of a tightly bound molecular-level encapsulation and bonding between the crosslinked polymer network and the electrode surface, significantly reducing the electrode / electrolyte interfacial impedance and effectively solving the capacity decay problem caused by poor interfacial contact. Simultaneously, the mild one-step thermal polymerization process conditions are easy to precisely control, which is conducive to forming a three-dimensional network structure with uniform crosslinking density and stable mechanical properties. This effectively immobilizes electrolyte molecules to suppress decomposition and gas generation, while also providing a smooth channel for ion migration. The entire preparation method is simple and highly controllable. It transforms the liquid precursor into a solid electrolyte in one step through in-situ polymerization technology, which cleverly avoids the complex film formation, cutting and assembly process of traditional pre-prepared gel membranes, as well as the problems of high interfacial impedance and high risk of mechanical damage. It provides a reliable and efficient process route for preparing supercapacitors with high voltage tolerance, high safety and long cycle life. Detailed Implementation

[0017] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0018] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0019] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0020] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0021] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0022] This invention provides a high-pressure resistant gel polymer electrolyte, which is formed by in-situ thermal polymerization of a precursor solution. The precursor solution contains lithium salt, carbonate mixed solvent, high-pressure resistant additive, crosslinking agent, flame retardant additive, and thermal initiator. The lithium salt is any one or two of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide. The carbonate mixed solvent includes cyclic carbonates and chain carbonates, the cyclic carbonates include fluoroethylene carbonate and ethylene carbonate, and the chain carbonates include at least one of diethyl carbonate and dimethyl carbonate. The high-pressure resistant additive is one or two of 1,1,2,2,3,3,4,4,4-nonafluorobutane-1-sulfonic acid 2,2,2-trifluoro-1-methyl ethyl ester and 1,1,2,2-tetrafluoroethane-1-sulfonic acid 2,2,2-trifluoro ethyl ester. The crosslinking agent is any one of isoprene tetraacrylate, pentaerythritol tetraacrylate, polyethylene glycol diacrylate, and pentaerythritol triacrylate. The flame retardant is tris(2,2,2-trifluoroethyl) phosphate.

[0023] In some embodiments, the lithium salt accounts for 10%-15% of the total mass of the precursor solution. As a key component providing lithium ions, the concentration of the lithium salt directly affects the conductivity of the electrolyte: if the concentration is too low (e.g., below 10%), the number of mobile lithium ions is insufficient, leading to a decrease in ionic conductivity and affecting the rate performance and power density of the supercapacitor; if the concentration is too high (e.g., above 15%), ion migration may be hindered due to ion association or increased viscosity, and may even result in some lithium salt remaining undissolved, reducing the chemical stability of the electrolyte. A lithium salt content of 10%-15% ensures sufficient charge carriers while maintaining suitable liquid-phase fluidity, helping to maintain low interfacial impedance and efficient ion transport at high voltages, thereby supporting rapid charge-discharge and long cycle life of the device.

[0024] In some embodiments, based on the total volume of the carbonate mixed solvent as 100%, the total volume of the cyclic carbonates accounts for 20% to 25%, the volume of diethyl carbonate accounts for 10% to 20%, and the volume of dimethyl carbonate accounts for 55% to 65%. Cyclic carbonates (such as ethylene carbonate) have high dielectric constants, which can effectively promote lithium salt dissociation and improve ionic conductivity, but their viscosity is high, and using them alone will limit ion migration. Chain carbonates such as diethyl carbonate and dimethyl carbonate have lower viscosity, which can improve flowability, but their dielectric constant is lower. 20%-25% of cyclic carbonates ensures sufficient solubility, while the complementary ratio of chain carbonates (diethyl carbonate provides moderate volatility, and dimethyl carbonate balances viscosity and electrochemical window) allows the mixed solvent to have both high ionic conductivity and wide electrochemical stability, which helps to suppress solvent decomposition at high voltages and reduce the risk of gas generation.

[0025] In some embodiments, the high-voltage resistant additive accounts for 1%-3% of the total mass of the precursor solution. Due to its low highest occupied molecular orbital (HOMO) energy level, this additive can preferentially oxidize under high voltage, forming a dense CEI film (cathode-electrolyte interface film) on the cathode surface. If the addition amount is less than 1%, the formed CEI film may be incomplete, failing to effectively isolate the electrode from the electrolyte, leading to persistent side reactions; if it exceeds 3%, it may introduce excessive fluorine or sulfur-containing species, increasing interfacial impedance or triggering unnecessary side reactions. An addition amount of 1%-3% is sufficient to promote the formation of a uniform and stable CEI film, inhibit electrolyte decomposition and transition metal dissolution, while avoiding significant damage to ionic conductivity. This content range is crucial for achieving a balance between high-voltage withstand capability and electrochemical performance.

[0026] In some embodiments, the crosslinking agent accounts for 1%-3% of the total mass of the precursor solution; the flame retardant accounts for 1%-4% of the total mass of the precursor solution. The crosslinking agent constructs the gel framework through polymerization. If the addition amount is too low (e.g., below 1%), the network structure may be too loose, failing to effectively fix the liquid components and affecting the mechanical strength and interfacial stability of the electrolyte. If it is too high (e.g., exceeding 3%), excessive crosslinking will make the gel brittle, reducing toughness and potentially blocking ion transport pathways, affecting conductivity. An addition amount of 1%-3% ensures good mechanical integrity of the gel, inhibiting electrode expansion and dendrite growth, while maintaining high ion mobility, improving device safety and cycle stability. The range of flame retardant addition ensures its effective flame retardant efficiency in both the gas and condensed phases, while avoiding negative impacts on the electrochemical performance of the electrolyte system.

[0027] In some embodiments, the thermal initiator is any one of azobisisobutyronitrile, azobisisobutyronitrile, benzoyl peroxide, and potassium persulfate, and accounts for 0.3%-1% of the total mass of the precursor solution. The thermal initiator (such as azobisisobutyronitrile) decomposes under heating to generate free radicals, initiating the polymerization of the crosslinking agent. If the addition amount is too low, the reaction may be incomplete, leading to insufficient gel formation or localized solidification failure; if it is too high, rapid polymerization may generate hot spots or byproducts, affecting the electrolyte uniformity and purity. An addition amount of 0.3%-1% ensures a stable polymerization process, guaranteeing the formation of a dense and uniform crosslinked structure of the electrolyte in situ on the electrode surface, reducing interfacial impedance, and compatibility with large-scale production processes.

[0028] In some embodiments, the volume ratio of fluoroethylene carbonate to ethylene carbonate in the cyclic carbonate is 1:3 to 1:5. This specific ratio enhances the overall performance of the electrolyte by synergistically optimizing interfacial film-forming properties and bulk transport performance: fluoroethylene carbonate (FEC), with its fluorinated groups, preferentially participates in the formation of a stable LiF-rich CEI film at the electrode interface, enhancing its high-voltage tolerance; while ethylene carbonate (EC) mainly contributes a high dielectric constant, ensuring effective dissociation of the lithium salt. If the FEC ratio is too high (e.g., greater than 1:3), although it is beneficial for film formation, the fluorinated groups will increase the system viscosity, which is detrimental to ion transport; if the ratio is too low (e.g., less than 1:5), the interfacial modification effect of FEC is insufficient, making it difficult to effectively suppress electrolyte decomposition. A volume ratio of 1:3 to 1:5 balances the requirements for interfacial protection and ionic conductivity, forming a dense CEI film to suppress side reactions under high voltage while maintaining good ion migration efficiency, thus contributing to improved cycle stability and high-voltage performance.

[0029] This invention also provides a method for preparing a high-pressure resistant gel polymer electrolyte, comprising the following steps: S1, under an inert atmosphere, lithium salt is dissolved in a carbonate mixed solvent to form a homogeneous solution; S2, add high-pressure resistant additive, crosslinking agent, flame retardant and thermal initiator to the solution obtained in step S1, and stir to form the precursor solution; S3, the precursor solution is subjected to in-situ thermal polymerization to form the high-pressure resistant gel polymer electrolyte.

[0030] In step S3, the temperature of the in-situ thermal polymerization reaction is 60-80℃, and the reaction time is 2-4 hours.

[0031] The present invention also provides a supercapacitor, comprising a positive electrode shell, a positive electrode plate, a separator, a negative electrode plate, and a negative electrode shell, wherein the above-mentioned high-voltage resistant gel polymer electrolyte is disposed between the positive electrode plate and the negative electrode plate.

[0032] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0033] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0034] Example 1 This embodiment provides a method for preparing a high-voltage resistant gel polymer electrolyte and its application in supercapacitors, specifically including the following steps: Step 1: In an argon atmosphere glove box (water and oxygen content both below 0.1 ppm), dissolve lithium hexafluorophosphate (LiPF6) in a carbonate mixed solvent at a ratio of 13% of the total mass of the precursor solution, and stir at 25°C for 40 minutes to form a homogeneous and transparent solution; the carbonate mixed solvent is composed of fluoroethylene carbonate (FEC), ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC), with the following volume percentages of each component relative to the total volume of the mixed solvent: FEC 5%, EC 18%, DEC 15%, and DMC 62%.

[0035] Step 2: Add the following to the solution obtained in Step 1 in sequence: high pressure resistant additive A (1,1,2,2,3,3,4,4,4-nonafluorobutane-1-sulfonic acid 2,2,2-trifluoro-1-methyl ethyl ester, added at 1% of the total mass of the precursor solution), crosslinking agent polyethylene glycol diacrylate (PEGDA, Mn=400, added at 2%), flame retardant additive tris(2,2,2-trifluoroethyl) phosphate (TFEP, added at 2%), and thermal initiator azobisisobutyronitrile (AIBN, added at 0.5%). Stir continuously at 25°C for 60 minutes to obtain a homogeneous and stable precursor solution.

[0036] Step 3: Measure 70 μL of the above precursor solution and drop it onto the surface of the NCM811 positive electrode. Then assemble the CR2032 coin cell supercapacitor in the following order: "positive electrode shell → NCM811 positive electrode sheet → polypropylene separator → precursor solution → natural graphite negative electrode sheet → stainless steel current collector → spring sheet → negative electrode shell".

[0037] Step 4: Place the assembled supercapacitor in a 70℃ constant temperature oven and carry out an in-situ thermal polymerization reaction for 3 hours to form a cross-linked high-voltage resistant gel polymer electrolyte at the electrode interface, thus completing the preparation of the supercapacitor.

[0038] Example 2 The difference between this embodiment and Example 1 is that the lithium salt is a mixture of lithium hexafluorophosphate (LiPF6) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in a mass ratio of 2:1, and the total mass of the lithium salt accounts for 13% of the total mass of the precursor solution. The remaining steps and parameters are exactly the same as in Example 1.

[0039] Example 3 The difference between this embodiment and Example 1 is that the high-pressure resistant additive is replaced with 2% (by mass) of 1,1,2,2-tetrafluoroethane-1-sulfonic acid 2,2,2-trifluoroethyl ester (additive B). The remaining steps and parameters are exactly the same as in Example 1.

[0040] Example 4 The difference between this embodiment and Example 1 is that the crosslinking agent is replaced with 3% (by mass) pentaerythritol tetraacrylate (PETTA). The remaining steps and parameters are exactly the same as in Example 1.

[0041] Example 5 The difference between this embodiment and Example 1 is that the thermal initiator is replaced with 0.8% (mass percentage) benzoyl peroxide (BPO), and the temperature of the in-situ thermal polymerization reaction is adjusted to 75°C. The remaining steps and parameters are exactly the same as in Example 1.

[0042] Example 6 The difference between this embodiment and Example 1 is that the amount of the flame retardant additive tris(2,2,2-trifluoroethyl) phosphate (TFEP) added is 3% of the total mass of the precursor solution. The remaining steps and parameters are exactly the same as in Example 1.

[0043] Example 7 The difference between this embodiment and Example 1 is that the composition of the carbonate mixed solvent is as follows, by total volume percentage: 4% fluoroethylene carbonate (FEC), 20% ethylene carbonate (EC), 10% diethyl carbonate (DEC), and 66% dimethyl carbonate (DMC). The remaining steps and parameters are exactly the same as in Example 1.

[0044] Example 8 The difference between this embodiment and Example 1 is that the lithium salt is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and its addition amount is 14% of the total mass of the precursor solution. The remaining steps and parameters are exactly the same as in Example 1.

[0045] Example 9 The difference between this embodiment and Embodiment 1 is that the high-pressure resistant additive is a mixture of 1% (by mass) additive A and 1% (by mass) additive B. The remaining steps and parameters are exactly the same as in Embodiment 1.

[0046] Example 10 The difference between this embodiment and Example 1 is that the crosslinking agent is replaced with 1.5% (by mass) pentaerythritol triacrylate (PETA). The remaining steps and parameters are exactly the same as in Example 1.

[0047] Example 11 The difference between this embodiment and Embodiment 1 is that the temperature of the in-situ thermal polymerization reaction is adjusted to 65°C, and the reaction time is adjusted to 3.5 hours. The remaining steps and parameters are exactly the same as in Embodiment 1.

[0048] Example 12 The difference between this embodiment and Embodiment 1 is that the positive electrode material of the supercapacitor is replaced with NCM622. The remaining steps and parameters are exactly the same as in Embodiment 1.

[0049] Example 13 The difference between this embodiment and Example 1 is that the flame retardant additive tris(2,2,2-trifluoroethyl) phosphate (TFEP) was not added. The remaining steps and parameters are exactly the same as in Example 1.

[0050] Example 14 The difference between this embodiment and Example 1 is that the thermal initiator is replaced with 0.6% (mass percentage) of azobisisobutyronitrile (ABVN), and the initiation temperature of the in-situ thermal polymerization reaction is adjusted to 60°C. The remaining steps and parameters are exactly the same as in Example 1.

[0051] Example 15 The difference between this embodiment and Embodiment 1 is that the lithium salt is a mixture of lithium hexafluorophosphate (LiPF6) and lithium difluorophosphate (LiDFOB) in a mass ratio of 3:1, and the total mass of the lithium salt accounts for 12% of the total mass of the precursor solution. The remaining steps and parameters are exactly the same as in Embodiment 1.

[0052] Comparative Example 1 The difference between this comparative example and Example 1 is that no high-pressure resistant additives were added. The remaining steps and parameters are exactly the same as in Example 1.

[0053] Comparative Example 2 The difference between this comparative example and Example 1 is that no crosslinking agent or thermal initiator was added in step two. The mixed solution obtained in step S2 was directly used as a liquid electrolyte in step three for assembling the supercapacitor, and the in-situ thermal polymerization reaction in step four was not performed. The remaining steps and parameters are exactly the same as in Example 1.

[0054] Comparative Example 3 This comparative example provides a conventional liquid electrolyte supercapacitor as an example, and its preparation method is as follows: Step 1: Dissolve lithium hexafluorophosphate (LiPF6) in acetonitrile solvent at a ratio of 13% of the total electrolyte mass, and stir at 25°C for 30 minutes to form a homogeneous liquid electrolyte.

[0055] Step 2: Measure 70 μL of the above liquid electrolyte and drop it onto the surface of the NCM811 positive electrode. Then assemble the CR2032 button supercapacitor in the following order: "positive electrode shell → NCM811 positive electrode sheet → polypropylene separator → liquid electrolyte → natural graphite negative electrode sheet → stainless steel current collector → spring sheet → negative electrode shell", without performing any polymerization reaction.

[0056] Table 1 Performance test parameters of the supercapacitors prepared in the embodiments and comparative examples of the present invention

[0057] As shown in Table 1, the high-voltage gel polymer electrolyte prepared in this invention achieves synergistic optimization in its core performance. First, the electrochemical window is significantly broadened to above 4.5 V, mainly due to the low HOMO energy level of the high-voltage resistant additives (A / B), which preferentially oxidize and form a dense CEI film on the cathode surface. Simultaneously, this film synergistically enhances the oxidation resistance of the interface with the mixed lithium salt system. Second, the ionic conductivity remains consistently at 8.5 × 10⁻⁶. -3 The high S / cm ratio is attributed to the fact that the carbonate mixed solvent, with its high dielectric constant and low viscosity, promotes the complete dissociation of the lithium salt. Furthermore, the moderately cross-linked network constructed by the cross-linking agent provides a good pathway for ion transport. Additionally, the TFEP flame retardant additive exhibits excellent compatibility with the system, without significantly hindering ion migration. Third, the interfacial impedance is reduced to below 50 Ω, thanks to the in-situ polymerization process that achieves a molecular-level "seamless connection" between the gel network and the electrode. Simultaneously, the stable CEI film effectively suppresses interfacial side reactions. Finally, regarding safety performance, the TFEP flame retardant additive achieves a synergistic flame retardant effect by forming a polyphosphoric acid glassy capping layer in the condensed phase and promoting carbonization, as well as by capturing active free radicals in the gas phase using fluorine-containing free radicals. This shortens the self-extinguishing time of the electrolyte to less than 50 s; while the self-extinguishing time of the system without flame retardant is extended to 67 s. This fully demonstrates that through synergistic design, the components achieve a comprehensive improvement in high-pressure tolerance, ion transport efficiency, interfacial compatibility, and safe flame retardant performance.

[0058] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A high-pressure resistant gel polymer electrolyte, characterized in that, It is formed by in-situ thermal polymerization of a precursor solution, wherein the precursor solution contains lithium salt, carbonate mixed solvent, high pressure resistant additive, crosslinking agent, flame retardant additive and thermal initiator; The lithium salt is any one or two of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide. The carbonate mixed solvent includes cyclic carbonates and chain carbonates, the cyclic carbonates include fluoroethylene carbonate and ethylene carbonate, and the chain carbonates include at least one of diethyl carbonate and dimethyl carbonate. The high-pressure resistant additive is one or two of 1,1,2,2,3,3,4,4,4-nonafluorobutane-1-sulfonic acid 2,2,2-trifluoro-1-methyl ethyl ester and 1,1,2,2-tetrafluoroethane-1-sulfonic acid 2,2,2-trifluoro ethyl ester. The crosslinking agent is any one of isoprene tetraacrylate, pentaerythritol tetraacrylate, polyethylene glycol diacrylate, and pentaerythritol triacrylate. The flame retardant is tris(2,2,2-trifluoroethyl) phosphate.

2. The high-pressure resistant gel polymer electrolyte according to claim 1, characterized in that, The lithium salt accounts for 10%-15% of the total mass of the precursor solution.

3. The high-pressure resistant gel polymer electrolyte according to claim 1, characterized in that, With the total volume of the carbonate mixed solvent being 100%, the total volume of the cyclic carbonate accounts for 20% to 25%, the volume of the diethyl carbonate accounts for 10% to 20%, and the volume of the methyl ethyl carbonate accounts for 55% to 65%.

4. The high-pressure resistant gel polymer electrolyte according to claim 1, characterized in that, The high-pressure resistant additive accounts for 1%-3% of the total mass of the precursor solution.

5. The high-pressure resistant gel polymer electrolyte according to claim 1, characterized in that, The crosslinking agent accounts for 1%-3% of the total mass of the precursor solution; the flame retardant accounts for 1%-4% of the total mass of the precursor solution.

6. The high-pressure resistant gel polymer electrolyte according to claim 1, characterized in that, The thermal initiator is any one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, and potassium persulfate, and accounts for 0.3%-1% of the total mass of the precursor solution.

7. The high-pressure resistant gel polymer electrolyte according to claim 1, characterized in that, The volume ratio of fluoroethylene carbonate to ethylene carbonate in the cyclic carbonate is 1:3 to 1:

5.

8. A method for preparing a high-pressure resistant gel polymer electrolyte according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1, under an inert atmosphere, lithium salt is dissolved in a carbonate mixed solvent to form a homogeneous solution; S2, add high-pressure resistant additive, crosslinking agent, flame retardant and thermal initiator to the solution obtained in step S1, and stir to form the precursor solution; S3, the precursor solution is subjected to in-situ thermal polymerization to form the high-pressure resistant gel polymer electrolyte.

9. The method for preparing a high-pressure resistant gel polymer electrolyte according to claim 8, characterized in that, In step S3, the temperature of the in-situ thermal polymerization reaction is 60-80℃, and the reaction time is 2-4 hours.

10. A supercapacitor, characterized in that, It includes a positive electrode shell, a positive electrode sheet, a separator, a negative electrode sheet, and a negative electrode shell, wherein a high-voltage resistant gel polymer electrolyte as described in any one of claims 1 to 7 is disposed between the positive electrode sheet and the negative electrode sheet.

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