Lithium ion hybrid supercapacitor nonaqueous electrolyte, preparation method and application thereof

Abstract

The application belongs to the technical field of electrochemical energy storage, and discloses a lithium ion hybrid supercapacitor non-aqueous electrolyte, a preparation method and application thereof. The lithium ion hybrid supercapacitor non-aqueous electrolyte comprises the following components in parts by weight: lithium salt 10-30 parts, organic solvent 50-110 parts, film-forming additive 0.1-5 parts, overcharge protection agent 0.5-5 parts, flame-retardant additive 1-10 parts, and low-impedance additive 0.15-5 parts. Through the multifunctional synergy of the dual lithium salt system, the organic solvent, the film-forming additive, the overcharge protection agent, the flame-retardant additive and the low-impedance additive, the application successfully constructs an electrolyte with high voltage window, excellent flame retardancy, wide working temperature range, long cycle and floating charging life and high safety. The electrolyte not only gives the lithium ion hybrid supercapacitor high energy and power density, but also significantly improves the comprehensive performance of the supercapacitor, so that the supercapacitor has great industrial application potential in the fields of new energy vehicles, power grid energy storage and special power sources.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, specifically to a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, its preparation method, and its application. Background Technology

[0002] Supercapacitors, as highly efficient electrochemical energy storage devices, possess outstanding advantages such as fast charging and discharging speeds, long cycle life, high power density, and strong environmental adaptability. They have demonstrated irreplaceable application prospects in multiple strategic emerging fields, including new energy vehicles, smart grids, rail transportation, backup power for industrial equipment, portable electronic devices, and aerospace, and have become a key research focus in the global electrochemical energy storage field. Among them, hybrid supercapacitors, as an important branch of the supercapacitor family, combine the core characteristics of high power density and long cycle life of electric double-layer capacitors with the advantages of high energy density of secondary batteries. By rationally combining battery-type electrodes and capacitor-type electrodes to construct an asymmetric electrode structure, they effectively overcome the technical limitations of the low energy density of traditional electric double-layer capacitors, becoming one of the cutting-edge directions in current energy storage device research.

[0003] Specifically, hybrid supercapacitors typically employ battery-type electrodes (such as lithium-doped carbon materials, transition metal oxides, and polyimide) as the energy storage body, relying on redox reactions to store and release charge, resulting in high specific capacity and energy storage capabilities. Meanwhile, capacitor-type electrodes (such as activated carbon, graphene, and carbon nanotubes) utilize the double-layer capacitance effect to achieve rapid charge adsorption and desorption, ensuring high power output characteristics. This electrode combination design significantly improves the operating voltage and energy density of hybrid supercapacitors compared to traditional double-layer capacitors. Particularly in lithium-ion hybrid supercapacitors, the operating voltage can be increased from 2.7V to over 3.5V, and the energy density can be increased by more than 50%, better meeting the application requirements of mid-to-high-end energy storage scenarios and becoming a current research hotspot and mainstream development trend in the supercapacitor field.

[0004] However, the improvement of energy density in hybrid supercapacitors is often accompanied by an increase in operating voltage, which in turn places more stringent requirements on the overall performance of the electrolyte. As the core medium for ion transport within the device, the electrolyte's electrochemical stability, thermal stability, safety, and wide temperature range adaptability directly determine the upper limit of operating voltage, energy density, cycle life, and application range of hybrid supercapacitors. These are key factors influencing the development of hybrid supercapacitors towards higher performance and wider application areas.

[0005] Currently, the electrolytes used in commercial lithium-ion hybrid supercapacitors are mainly conventional lithium salt electrolytes based on carbonate solvents, with the most widely used being the lithium hexafluorophosphate / ethylene carbonate + diethyl carbonate (LiPF6 / EC+DEC) system. This type of electrolyte has been widely used in low- and medium-voltage hybrid supercapacitors due to its mature preparation process, low cost, and high ionic conductivity at room temperature. However, with the continuous increase in the operating voltage of hybrid supercapacitors (breaking through 3.5V) and the continuous expansion of application scenarios, the inherent defects of these conventional carbonate-based electrolytes are becoming increasingly prominent, severely limiting further improvements in device performance and the expansion of application scope. Specifically, these defects are mainly reflected in the following aspects.

[0006] First and foremost, the most prominent issue is the insufficient safety of existing carbonate-based electrolytes. Conventional carbonate solvents (such as EC, DEC, and DMC) are flammable and have low flash points (typically between -20°C and 10°C). Under abnormal conditions such as high-voltage overcharging, internal short circuits, external impacts, and exposure to high-temperature environments, they are prone to combustion, and in severe cases, may even cause device explosions, posing significant safety hazards to equipment operation and personnel. Especially in large-scale energy storage applications such as new energy vehicles and rail transit, where safety requirements are extremely high, the risk of electrolyte combustion and explosion could trigger a chain reaction, causing enormous property damage and personal injury. This has become a crucial factor restricting the application of hybrid supercapacitors in high-end safety-demand scenarios.

[0007] Secondly, existing carbonate-based electrolytes have poor high-temperature performance and cannot adapt to high-temperature operating environments. Under high-temperature operating conditions (typically exceeding 60°C), lithium salts (such as LiPF6) in carbonate-based electrolytes are prone to decomposition reactions, generating corrosive gases and harmful substances such as HF and PF5. These decomposition products not only corrode electrode materials and device casings but also damage the interfacial film between the electrode and the electrolyte, leading to structural collapse and performance degradation of the electrode materials. Simultaneously, carbonate solvents are prone to oxidative decomposition reactions under high temperatures and voltages, generating gases such as carbon dioxide and olefins. This results in severe internal gas generation and a sharp increase in internal pressure, potentially causing leakage, bulging, or even rupture, significantly shortening the device's cycle life and service life. Especially in high-temperature operating conditions of industrial equipment and outdoor driving scenarios in new energy vehicles during summer, the internal temperature of devices can easily exceed 60°C. Therefore, the high-temperature instability of conventional electrolytes is even more pronounced, seriously affecting the reliability and safety of the devices.

[0008] Furthermore, existing carbonate-based electrolytes exhibit poor low-temperature performance, making them unsuitable for low-temperature applications. In the low-temperature operating environment of devices (typically below -20°C), the viscosity of carbonate-based electrolytes increases dramatically, and the molecular motion rate slows down, leading to a significant decrease in the electrolyte's ionic conductivity (usually dropping to less than 1 / 10 of the room temperature conductivity), resulting in a significant increase in ion migration resistance. Simultaneously, the degree of lithium salt dissociation in carbonate-based electrolytes decreases at low temperatures, further reducing the number of free ions in the electrolyte. This causes a sharp increase in the internal resistance of hybrid supercapacitors, exacerbating polarization during charging and discharging, and significantly reducing or even completely eliminating the device's power output capability, thus failing to meet energy storage requirements in low-temperature environments. Especially in low-temperature applications such as outdoor smart grids, rail transit, and portable electronic devices in northern winters, the low-temperature performance defects of carbonate-based electrolytes severely limit the application and promotion of hybrid supercapacitors, causing devices to fail to start up normally and operate stably.

[0009] In summary, the electrolytes currently used in commercially available hybrid supercapacitors suffer from numerous inherent defects, including insufficient safety, poor high-temperature performance, and suboptimal low-temperature performance. These limitations fail to meet the application requirements of high-voltage, wide-temperature-range, high-safety, and long-life hybrid supercapacitors, severely hindering their development towards higher energy density and wider applications. Therefore, developing a non-aqueous electrolyte that balances high voltage tolerance, excellent wide-temperature-range performance, and high safety, and overcoming the core technological bottlenecks of existing electrolytes, has become a critical technical issue urgently needing resolution in the field of hybrid supercapacitors. This has significant practical implications and industrial value for promoting the upgrading and development of the hybrid supercapacitor industry. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art and provide a non-aqueous electrolyte for lithium-ion hybrid supercapacitors, its preparation method, and its application.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, comprising the following components in parts by weight: 10-30 parts lithium salt, 50-110 parts organic solvent, 0.1-10 parts film-forming additive, 0.5-5 parts overcharge protectant, 1-10 parts flame retardant additive, and 0.15-5 parts low impedance additive. The lithium salt includes at least two of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide. The low-impedance additive includes a first low-impedance additive and a second low-impedance additive. The first low-resistance additive includes vinyl sulfate and / or ethylene carbonate; The structural formula of the second low-resistivity additive is shown in formula (I): Formula (I).

[0012] This invention successfully constructs a non-aqueous electrolyte that combines a high voltage window, excellent flame retardancy, a wide operating temperature range, long cycle and float charge life, and high safety through the multi-functional synergy of a dual lithium salt system, organic solvent, film-forming additive, overcharge protectant, flame retardant additive, and low impedance additive. This electrolyte not only endows lithium-ion hybrid supercapacitors with high energy and power density, but also significantly improves the overall performance of the capacitor, making it a promising candidate for industrial applications and a promising market prospect in high-requirement fields such as new energy vehicles, grid energy storage, and special power supplies.

[0013] The dual lithium salt system of this invention balances conductivity and temperature characteristics, enabling the electrolyte to maintain high ion migration capability over a wide temperature range. It also synergistically participates in the formation of a stable passivation layer at the electrode interface, providing a foundation for high-rate performance and wide-temperature operation, effectively expanding the application range of lithium-ion supercapacitors. Furthermore, the flame-retardant additive of this invention further forms a synergistic flame-retardant effect with the organic solvent, giving the electrolyte excellent flame-retardant or even non-flammable properties, fundamentally improving the intrinsic safety of the device and greatly enhancing its operational safety. Secondly, the overcharge protectant of this invention, in conjunction with other components, can generate a high-resistance conductive polymer film in situ on the positive electrode surface when the voltage abnormally rises to its polymerization potential. This film rapidly increases the battery's internal resistance, limits overcharge current, and dissipates excess energy as controllable heat, thereby effectively preventing uncontrolled voltage and temperature increases and avoiding thermal runaway. Furthermore, the film-forming additive and the low-impedance additive of the present invention work synergistically to undergo reduction and oxidative decomposition on the surfaces of the negative and positive electrodes, constructing a dense, stable solid electrolyte interface film and a positive electrode electrolyte interface film with low impedance. This effectively inhibits the continuous decomposition of the electrolyte and the damage to the electrode structure. Moreover, the composite film also has good ionic conductivity, high mechanical strength and moderate flexibility, which can buffer the volume change of the electrode material during cycling, maintain the structural integrity and electrochemical stability of the interface, thereby significantly reducing the interface impedance and extending the cycle life.

[0014] Therefore, the electrolyte system of the present invention achieves comprehensive optimization from bulk electrolyte to electrode interface through the synergistic effect of the above-mentioned multiple mechanisms, ultimately ensuring the excellent performance of lithium-ion hybrid supercapacitors in terms of high operating voltage, wide temperature range, long cycle and float charge life, and excellent overcharge and needle penetration safety, providing a key electrolyte solution for its industrial promotion in high energy density, high power density and high reliability application scenarios.

[0015] As a preferred embodiment of the non-aqueous electrolyte for the lithium-ion hybrid supercapacitor of the present invention, the lithium salt includes lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide; the mass ratio of the lithium bis(fluorosulfonyl)imide to the lithium bis(trifluoromethanesulfonyl)imide is (0.5-1.5):1.

[0016] Preferably, the mass ratio of lithium bis(fluorosulfonyl)imide to lithium bis(trifluoromethanesulfonyl)imide is 1:1.

[0017] In a preferred embodiment of the non-aqueous electrolyte for the lithium-ion hybrid supercapacitor of the present invention, the organic solvent includes a first organic solvent and a second organic solvent; the first organic solvent includes ethylene carbonate and / or propylene carbonate; the second organic solvent includes at least one of acetonitrile, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl acetate, propyl acetate, ethyl propionate, and propyl propionate; the mass ratio of the first organic solvent to the second organic solvent is 1:(1-5).

[0018] Preferably, the first organic solvent includes ethylene carbonate.

[0019] Preferably, the second organic solvent comprises dimethyl carbonate and ethyl methyl carbonate; the mass ratio of dimethyl carbonate to ethyl methyl carbonate is (0.5-1):1.

[0020] More preferably, the mass ratio of dimethyl carbonate to ethyl methyl carbonate is 0.6:1.

[0021] Preferably, the mass ratio of the first organic solvent to the second organic solvent is 1:4.

[0022] As a preferred embodiment of the non-aqueous electrolyte for the lithium-ion hybrid supercapacitor of the present invention, the film-forming additive includes at least one of vinylene carbonate, fluoroethylene carbonate, tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, methylene disulfonate, 1,3-propane sulpholactone, and ethylene ethylene carbonate.

[0023] Preferably, the film-forming additive comprises fluoroethylene carbonate and 1,3-propanesulfonyl lactone; the mass ratio of the fluoroethylene carbonate and the 1,3-propanesulfonyl lactone is (1-10):1.

[0024] More preferably, the mass ratio of the fluoroethylene carbonate to the 1,3-propanesulfonyl lactone is 8:1.5.

[0025] In a preferred embodiment of the non-aqueous electrolyte for the lithium-ion hybrid supercapacitor of the present invention, the overcharge protection agent includes biphenyl and / or cyclohexylbenzene.

[0026] Preferably, the overcharge protectant includes biphenyl.

[0027] In a preferred embodiment of the non-aqueous electrolyte for the lithium-ion hybrid supercapacitor of the present invention, the first low-impedance additive includes ethylene sulfate.

[0028] In a preferred embodiment of the non-aqueous electrolyte for the lithium-ion hybrid supercapacitor of the present invention, the mass ratio of the first low-impedance additive to the second low-impedance additive is (1-2):1.

[0029] Preferably, the mass ratio of the first low-impedance additive to the second low-impedance additive is 1.5:1.

[0030] Secondly, the present invention provides a method for preparing the non-aqueous electrolyte of the lithium-ion hybrid supercapacitor, comprising the following steps: Under a protective atmosphere, the lithium salt is dissolved in the organic solvent, and then the film-forming additive, overcharge protectant, flame retardant additive, and low impedance additive are added and mixed to obtain the non-aqueous electrolyte of the lithium-ion hybrid supercapacitor.

[0031] As a preferred embodiment of the preparation method described in this invention, the organic solvent is stored at a temperature of -20°C to -10°C for 1-5 hours before adding the lithium salt.

[0032] Thirdly, the present invention provides a lithium-ion hybrid supercapacitor, the lithium-ion hybrid supercapacitor comprising a positive electrode, a negative electrode and a non-aqueous electrolyte of the lithium-ion hybrid supercapacitor.

[0033] In a preferred embodiment of the lithium-ion hybrid supercapacitor of the present invention, the positive electrode comprises activated carbon and ternary lithium material; the negative electrode comprises at least one of hard carbon, soft carbon, porous carbon, and graphite.

[0034] Compared with existing technologies, the beneficial effects of this invention are as follows: The non-aqueous electrolyte of the lithium-ion hybrid supercapacitor of this invention possesses a wide electrochemical window and excellent high-voltage oxidation stability, maintaining effective ion conduction and interface stability under both extremely low and high temperature conditions, ensuring the reliability of the device under complex and harsh environments. Secondly, the non-aqueous electrolyte of the lithium-ion hybrid supercapacitor of this invention itself has excellent flame-retardant properties, significantly improving the safety threshold of the capacitor and maintaining high safety even under extreme abuse conditions such as overcharging and mechanical puncture. Simultaneously, the electrochemical system constructed by the non-aqueous electrolyte of the lithium-ion hybrid supercapacitor of this invention can form a stable low-impedance interface, endowing the capacitor with excellent high-power output capability and outstanding long-cycle stability. Furthermore, the bulk and interfacial film structure of the non-aqueous electrolyte of the lithium-ion hybrid supercapacitor of this invention are stable, effectively suppressing side reactions under continuous high-temperature and high-pressure stress, ensuring the long-term storage and float-charge lifespan of the device. Detailed Implementation

[0035] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0036] The following description, in conjunction with specific embodiments, illustrates the practical effects of the present invention.

[0037] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials, reagents, equipment, etc. used are all commercially available unless otherwise specified.

[0038] The raw materials used in the following embodiments and comparative examples are described below, but are not limited to these materials: Vinyl sulfate (additive A), purchased from Suzhou Qitian New Materials Co., Ltd.; its specific structural formula is shown below: ; Ethylene carbonate (additive B), purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; its specific structural formula is shown below: ; 1,5,2,4-Dioxadithiane,6,6-difluoro-,2,2,4,4-tetraoxide (additive C), purchased from Merck Life Sciences, Inc.; the specific structural formula is shown below: .

[0039] Example 1: This embodiment provides a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, the raw materials for which are prepared include the following components in parts by weight, and the specific raw material ratio is shown in Table 1.

[0040] Table 1. Raw material ratio (parts by weight) of the non-aqueous electrolyte for the lithium-ion hybrid supercapacitor in Example 1. The preparation method of the non-aqueous electrolyte for the lithium-ion hybrid supercapacitor in this embodiment includes the following steps: S1. In an argon glove box with a moisture content of less than 10 ppm, weigh diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC), mix them evenly, and prepare a mixed solvent.

[0041] S2. Store the above mixed solvent at -20℃ for 6 hours, and then add lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in sequence, and stir until completely dissolved.

[0042] S3. After lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are completely dissolved, functional additives are added in sequence: fluoroethylene carbonate (FEC), 1,3-propanesulfonyl lactone (PS), biphenyl (BP), tri(2,2,2-trifluoroethyl) phosphate (TFEP), ethylene sulfate (low impedance additive A), and 1,5,2,4-Dioxadithiane,6,6-difluoro-2,2,4,4-tetraoxide (low impedance additive C). After all components are added, the mixture is stirred continuously to obtain the non-aqueous electrolyte for lithium-ion hybrid supercapacitors.

[0043] Example 2: This embodiment provides a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, the raw materials for which are prepared include the following components in parts by weight, and the specific raw material ratio is shown in Table 2.

[0044] Table 2. Raw material ratio (parts by weight) of non-aqueous electrolyte for lithium-ion hybrid supercapacitor in Example 2. The preparation method of the non-aqueous electrolyte for the lithium-ion hybrid supercapacitor in this embodiment includes the following steps: S1. In an argon glove box with a moisture content of less than 10 ppm, weigh diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC), mix them evenly, and prepare a mixed solvent.

[0045] S2. Store the above mixed solvent at -20℃ for 6 hours, and then add lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6) in sequence, stirring until completely dissolved.

[0046] S3. After lithium difluorosulfonylimide (LiFSI) and lithium hexafluorophosphate (LiPF6) are completely dissolved, functional additives are added in sequence: fluoroethylene carbonate (FEC), 1,3-propanesulfonyl lactone (PS), biphenyl (BP), tri(2,2,2-trifluoroethyl) phosphate (TFEP), ethylene sulfate (low impedance additive A), and 1,5,2,4-Dioxadithiane,6,6-difluoro-2,2,4,4-tetraoxide (low impedance additive C). After all components are added, the mixture is stirred continuously to obtain the non-aqueous electrolyte for lithium-ion hybrid supercapacitors.

[0047] Example 3: This embodiment provides a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, the raw materials for which are prepared include the following components in parts by weight, and the specific raw material ratio is shown in Table 3.

[0048] Table 3. Raw material ratio (parts by weight) of non-aqueous electrolyte for lithium-ion hybrid supercapacitor in Example 3. The preparation method of the non-aqueous electrolyte for the lithium-ion hybrid supercapacitor in this embodiment includes the following steps: S1. In an argon glove box with a moisture content of less than 10 ppm, weigh ethyl propionate (EP), ethyl methyl carbonate (EMC), and ethylene carbonate (EC), mix them evenly, and prepare a mixed solvent.

[0049] S2. Store the above mixed solvent at -20℃ for 6 hours, and then add lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in sequence, and stir until completely dissolved.

[0050] S3. After lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are completely dissolved, functional additives are added in sequence: fluoroethylene carbonate (FEC), 1,3-propanesulfonyl lactone (PS), biphenyl (BP), tri(2,2,2-trifluoroethyl) phosphate (TFEP), ethylene sulfate (low impedance additive A), and 1,5,2,4-Dioxadithiane,6,6-difluoro-2,2,4,4-tetraoxide (low impedance additive C). After all components are added, the mixture is stirred continuously to obtain the non-aqueous electrolyte for lithium-ion hybrid supercapacitors.

[0051] Example 4: This embodiment provides a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, the raw materials for which are prepared include the following components in parts by weight, and the specific raw material ratio is shown in Table 4.

[0052] Table 4. Raw material ratio (parts by weight) of non-aqueous electrolyte for lithium-ion hybrid supercapacitor in Example 4. The preparation method of the non-aqueous electrolyte for the lithium-ion hybrid supercapacitor in this embodiment includes the following steps: S1. In an argon glove box with a moisture content of less than 10 ppm, weigh diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC), mix them evenly, and prepare a mixed solvent.

[0053] S2. Store the above mixed solvent at -20℃ for 6 hours, and then add lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in sequence, and stir until completely dissolved.

[0054] S3. After lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are completely dissolved, functional additives are added in sequence: fluoroethylene carbonate (FEC), 1,3-propanesulfonyl lactone (PS), biphenyl (BP), tri(2,2,2-trifluoroethyl) phosphate (TFEP), ethylene ethylene carbonate (low impedance additive B), and 1,5,2,4-Dioxadithiane,6,6-difluoro-2,2,4,4-tetraoxide (low impedance additive C). After all components are added, the mixture is stirred continuously to obtain the non-aqueous electrolyte for lithium-ion hybrid supercapacitors.

[0055] Example 5: This embodiment provides a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, the raw materials for which are prepared include the following components in parts by weight, and the specific raw material ratio is shown in Table 5.

[0056] Table 5. Raw material ratio (parts by weight) of the non-aqueous electrolyte for the lithium-ion hybrid supercapacitor in Example 5. The preparation method of the non-aqueous electrolyte for the lithium-ion hybrid supercapacitor in this embodiment includes the following steps: S1. In an argon glove box with a moisture content of less than 10 ppm, weigh diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC), mix them evenly, and prepare a mixed solvent.

[0057] S2. Store the above mixed solvent at -20℃ for 6 hours, and then add lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in sequence, and stir until completely dissolved.

[0058] S3. After lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are completely dissolved, functional additives are added in sequence: fluoroethylene carbonate (FEC), 1,3-propanesulfonyl lactone (PS), biphenyl (BP), tri(2,2,2-trifluoroethyl) phosphate (TFEP), ethylene sulfate (low impedance additive A), and 1,5,2,4-Dioxadithiane,6,6-difluoro-2,2,4,4-tetraoxide (low impedance additive C). After all components are added, the mixture is stirred continuously to obtain the non-aqueous electrolyte for lithium-ion hybrid supercapacitors.

[0059] Example 6: This embodiment provides a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, the raw materials for which are prepared include the following components in parts by weight, and the specific raw material ratio is shown in Table 6.

[0060] Table 6. Raw material ratio (parts by weight) of non-aqueous electrolyte for lithium-ion hybrid supercapacitor in Example 6. The preparation method of the non-aqueous electrolyte for the lithium-ion hybrid supercapacitor in this embodiment includes the following steps: S1. In an argon glove box with a moisture content of less than 10 ppm, weigh diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC), mix them evenly, and prepare a mixed solvent.

[0061] S2. Store the above mixed solvent at -20℃ for 6 hours, and then add lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in sequence, and stir until completely dissolved.

[0062] S3. After lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are completely dissolved, functional additives are added in sequence: fluoroethylene carbonate (FEC), 1,3-propanesulfonyl lactone (PS), biphenyl (BP), tri(2,2,2-trifluoroethyl) phosphate (TFEP), ethylene sulfate (low impedance additive A), and 1,5,2,4-Dioxadithiane,6,6-difluoro-2,2,4,4-tetraoxide (low impedance additive C). After all components are added, the mixture is stirred continuously to obtain the non-aqueous electrolyte for lithium-ion hybrid supercapacitors.

[0063] Comparative Example 1: This comparative example provides a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, the preparation method of which includes the following steps: S1. In an argon glove box with a moisture content of less than 10 ppm, weigh diethyl carbonate (DEC), methyl ethyl carbonate (EMC), and ethylene carbonate (EC), mix them evenly, and prepare a mixed solvent (the mass ratio of DMC, EMC, and EC is 3:5:2).

[0064] S2. Store the above mixed solvent at -20℃ for 6 hours, then add lithium hexafluorophosphate (LiPF6) (the concentration of LiPF6 in the mixed solvent is 1 mol / L), and stir until completely dissolved to obtain the non-aqueous electrolyte for lithium-ion hybrid supercapacitors.

[0065] Comparative Example 2: This comparative example provides a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, which differs from Example 1 only in that: Free of fluoroethylene carbonate (FEC) and 1,3-propanesulfonyl lactone (PS); The remaining components and steps are the same as in Example 1.

[0066] Comparative Example 3: This comparative example provides a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, which differs from Example 1 only in that: It does not contain vinyl sulfate or 1,5,2,4-Dioxadithiane,6,6-difluoro-2,2,4,4-tetraoxide; The remaining components and steps are the same as in Example 1.

[0067] Comparative Example 4: This comparative example provides a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, which differs from Example 1 only in that: Free of biphenyl (BP) and tri(2,2,2-trifluoroethyl) phosphate (TFEP); The remaining components and steps are the same as in Example 1.

[0068] Comparative Example 5: This comparative example provides a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, which differs from Example 1 only in that: Lithium bis(trifluoromethanesulfonylimide) (LiTFSI) is free of lithium bis(trifluoromethanesulfonylimide). The remaining components and steps are the same as in Example 1.

[0069] Comparative Example 6: This comparative example provides a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, which differs from Example 1 only in that: Replace ethylene carbonate (EC) with an equal amount of ethyl acetate (EA); The remaining components and steps are the same as in Example 1.

[0070] Comparative Example 7: This comparative example provides a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, which differs from Example 1 only in that: Does not contain 1,5,2,4-Dioxadithiane,6,6-difluoro-2,2,4,4-tetraoxide; The remaining components and steps are the same as in Example 1.

[0071] Comparative Example 8: This comparative example provides a non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, which differs from Example 1 only in that: Replace 1,5,2,4-Dioxadithiane,6,6-difluoro-2,2,4,4-tetraoxide with an equal amount of 4-methylvinyl sulfate; The remaining components and steps are the same as in Example 1.

[0072] Test Example 1: Intrinsic Performance Test of Electrolyte The following performance tests were conducted on the non-aqueous electrolytes of the lithium-ion hybrid supercapacitors in the above embodiments and comparative examples.

[0073] (1) Electrochemical window test Test Method: The electrochemical stability of the electrolyte under high voltage was tested using linear sweep voltammetry (LSV). Specifically, a platinum electrode was used as the working electrode, and lithium metal was used as both the counter and reference electrodes. The scan rate was 0.01 V / s, and the voltage scan range was 0 V–6 V. An electrode potential that varied linearly with time was applied between the working and reference electrodes, and the current flowing through the working and auxiliary electrodes was recorded simultaneously. This yielded the voltammetric curve between the electrode current and electrode potential. The potential at which the anodic current began to increase significantly was recorded as the oxidation decomposition potential.

[0074] Table 7. Oxidation potential test results of non-aqueous electrolyte in lithium-ion hybrid supercapacitors. As shown in Table 7, the anodic decomposition potentials of the non-aqueous electrolyte in the lithium-ion hybrid supercapacitors of the embodiments of the present invention are all higher than 5.0V, indicating that they can maintain structural stability under high voltage and have excellent resistance to oxidation decomposition. This high oxidation stability is of great significance for the stable operation of the device under high potential windows, extending cycle life and improving energy density. In contrast, the anodic decomposition potentials of the non-aqueous electrolytes in Comparative Examples 1-6 are all less than 5.0V (vs. Li / Li + This indicates that oxidation and decomposition begin at relatively low voltages, potentially leading to gas generation, increased internal pressure, and deterioration of the electrode / electrolyte interface, thereby affecting the electrochemical performance and safety of the capacitor. In particular, the conventional electrolyte without additives in Comparative Example 1 and the electrolyte without TFEP and BP in Comparative Example 4 exhibit extremely low oxidation potentials, which are detrimental to overcharge safety.

[0075] (2) Flame retardant performance test Test method: An open flame ignition experiment was conducted. An igniter was used to directly contact the electrolyte sample with an open flame to observe whether it could be ignited and whether it continued to burn in order to evaluate the flame retardant properties of the electrolyte.

[0076] Table 8. Test results of flame retardant properties of non-aqueous electrolyte in lithium-ion hybrid supercapacitors. As shown in Table 8, the non-aqueous electrolyte of the lithium-ion hybrid supercapacitor in the embodiments of the present invention could not be ignited in the open flame test, exhibiting excellent flame-retardant properties. This effectively blocks the combustion chain under extreme abuse conditions (such as internal short circuits and thermal runaway), fundamentally improving the intrinsic safety of the device. In contrast, the conventional electrolyte without additives in Comparative Example 1, the electrolyte without TFEP and BP in Comparative Example 4, and the electrolyte in Comparative Example 6 could all be easily ignited by an open flame and continue to burn, exhibiting typical flammability.

[0077] Test Example 2: Capacitor Performance Test 1. Preparation of capacitor sample for testing The non-aqueous electrolytes of the lithium-ion hybrid supercapacitors described in the above embodiments and comparative examples were used to assemble soft-pack lithium-ion hybrid supercapacitors.

[0078] The specific assembly process for capacitors is as follows: (1) Electrode preparation Positive electrode: Activated carbon and ternary NCM622 lithium material are mixed as active material (the mass ratio of activated carbon to ternary lithium material is 2:8), and then mixed with conductive agent (Super P, carbon nanotubes) and binder polyvinylidene fluoride (PVDF) to form a slurry (the mass ratio of active material, conductive agent and binder is 88:10:2). After that, it is coated on aluminum foil current collector, dried, rolled and punched into shape.

[0079] Negative electrode: Graphite and pre-lithiated hard carbon (purchased from Guoke Tanmei New Materials (Huzhou) Co., Ltd., model RK-02) are mixed as active material (the mass ratio of graphite to pre-lithiated hard carbon is 7:3), and then mixed with binder sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) (the mass ratio of active material, sodium carboxymethyl cellulose and styrene-butadiene rubber is 94:3:3). The mixture is coated on copper foil current collector, dried, rolled and then die-cut into shape.

[0080] (2) Core assembly and packaging Using a "Z"-shaped stacking method, the positive electrode, cellulose separator, and negative electrode are stacked sequentially to ensure complete isolation between each layer of positive and negative electrodes by the separator. Then, all the positive electrode tabs are welded together, and all the negative electrode tabs are welded together to form a concentrated current conduction path. Subsequently, the stacked core is placed in a stamped aluminum-plastic film bag, and the non-aqueous electrolyte of the lithium-ion hybrid supercapacitor of the examples and comparative examples is injected into an argon glove box. After standing and soaking (45℃ / 48h, 25℃ / 24h), formation, vacuum secondary packaging, and capacity testing are performed to obtain the capacitor to be tested.

[0081] 2. Performance Testing The following performance tests were performed on the test capacitors prepared with non-aqueous electrolytes for the lithium-ion hybrid supercapacitors of the above embodiments and comparative examples: (1) DC internal resistance (DCIR) test Test method: Charge the battery cell to full charge at 25℃ (cutoff current 0.05C), let it stand for 10 minutes, discharge it at 0.5C for 1 hour, let it stand for 10 minutes, and record the voltage V1; then discharge it at 3C current for 10 seconds, and record the voltage V2 at the 10th second; calculate the DC internal resistance (DCIR) according to the following formula: DCIR = (V2-V1) / I, where I is the 3C discharge current.

[0082] Table 9. Test results of DC internal resistance of capacitors As shown in Table 9, the capacitors prepared with non-aqueous electrolytes in the lithium-ion hybrid supercapacitors of the embodiments of the present invention exhibit relatively low DC internal resistance. This indicates that the electrolyte system of the present invention can form a stable, low-impedance solid electrolyte interface film with the electrode material, thereby ensuring the excellent high-power performance and long cycle life of the capacitors. In contrast, the DC internal resistances of Comparative Examples 1 and 3 are as high as 34.49 mΩ and 35.95 mΩ, respectively, significantly higher than those of the embodiments.

[0083] (2) Cyclic performance test Test method: In an environment of 25℃, the capacitor is discharged at a constant current of 5C to the cutoff voltage of 2.5V, left to stand for 10 minutes, and then charged at a constant current of 5C to 4.0V, and then switched to constant voltage charging until the current drops to 0.05C cutoff. The capacitance retention rate is recorded after 5000 cycles.

[0084] Table 10 Results of Cyclic Performance Tests for Capacitors As shown in Table 10, the capacitors prepared with the non-aqueous electrolyte of the lithium-ion hybrid supercapacitor in the embodiments of the present invention all exhibited a capacity retention rate of over 91% after 5000 cycles. This indicates that the electrolyte system of the present invention can maintain the stability of the electrode interface and bulk structure for a long time, demonstrating excellent long cycle life. In contrast, the cycle performance of Comparative Examples 1-6 was significantly reduced due to the lack of key additives or the use of single salts and different solvent systems.

[0085] (3) High and low temperature performance test Test method: Using the capacitance measured at 25℃ as the benchmark (its retention rate is 100%), the capacitor was charged and discharged under low temperature conditions of -40℃ and high temperature conditions of 70℃ respectively, and its capacitance retention rate under high and low temperature conditions was recorded.

[0086] Table 11 Test results of high and low temperature performance of capacitors As shown in Table 11, the capacitors prepared with non-aqueous electrolytes for lithium-ion hybrid supercapacitors in the embodiments of the present invention exhibit significantly better capacity retention rates than all comparative examples at both low temperatures of -40°C and high temperatures of 70°C. This demonstrates that the electrolyte system of the present invention has excellent temperature adaptability and can maintain effective electrochemical reactions and ion transport in both frigid and hot environments, thereby ensuring the reliability of the device in complex environments.

[0087] (4) High-temperature float life test Test method: The capacitor was placed in a 65°C high-temperature environment, charged to the upper limit voltage (4.0V), and maintained in a constant voltage charging state for up to 140 days. During this period, the electrolyte and electrode interface were continuously subjected to the dual stress of high temperature and high voltage redox potential. After the test, its remaining capacity was tested under standard conditions, and the capacity retention rate was calculated.

[0088] Table 12 High-Temperature Float Life Test Results of Capacitors As shown in Table 12, the capacitor prepared by the non-aqueous electrolyte of the lithium-ion hybrid supercapacitor of the present invention retained its capacity between 81% and 86% after 140 days of continuous constant voltage float charging at 65°C and 4.0V. This proves that the electrolyte and the interfacial film formed on the electrode surface have extremely high chemical and electrochemical inertness, and can withstand the dual stress of high temperature and high pressure for a long time. It effectively suppresses continuous interfacial side reactions and electrolyte decomposition, and ensures the long-term storage and standby reliability of the device.

[0089] (5) Overcharge safety test Test method: Based on the GB31241-2022 standard, simulate the behavior of capacitors when charged beyond their rated voltage to detect whether dangerous situations such as overheating, expansion or explosion will occur.

[0090] Table 13 Overcharge safety test results for capacitors As shown in Table 13, the lithium-ion hybrid supercapacitors of the present invention, prepared with non-aqueous electrolytes, all exhibited "no gas production, no fire, and no explosion" in overcharge tests, demonstrating a balance between high performance in daily use and high safety under extreme abuse. In contrast, the lithium-ion hybrid supercapacitors in the comparative examples, prepared with non-aqueous electrolytes, lacked sufficient safety performance, exhibiting gas production, fire, and explosion after overcharging.

[0091] (6) Needle prick safety test Test method: According to GB31485-2015 standard, the external damage such as puncture or impact that the capacitor may suffer during use is simulated to evaluate its safety.

[0092] Table 14 Results of the nail penetration safety test for capacitors As shown in Table 14, the capacitors prepared with non-aqueous electrolytes in the lithium-ion hybrid supercapacitors of the present invention all achieved "no fire and no explosion" in the needle penetration test. This indicates that the electrolyte system of the present invention has an excellent ability to effectively suppress the spread of thermal runaway from the bulk to the interface. It can control the violent internal short circuit energy and heat caused by needle penetration within the safe range that the system can withstand, thus preventing the spread of thermal runaway. In contrast, the capacitors prepared with non-aqueous electrolytes in the comparative lithium-ion hybrid supercapacitors have insufficient safety performance. In particular, the conventional electrolyte without additives in Comparative Example 1 and the electrolyte without TFEP and BP in Comparative Example 4 are flammable in bulk and have extremely poor interfacial thermal stability. The local high temperature caused by needle penetration can instantly ignite the electrolyte vapor and trigger a violent chain exothermic reaction between the electrode and the electrolyte, leading to uncontrollable thermal runaway.

[0093] In summary, this invention successfully prepared a non-aqueous electrolyte with a high voltage window, excellent flame retardancy, wide operating temperature range (-40℃ to 70℃), long cycle and float charge life, and high safety through the multi-functional synergy of a dual lithium salt system, optimized solvent combination and film-forming additives, low impedance additives, overcharge protectants, and flame retardants. This electrolyte not only endows lithium-ion hybrid supercapacitors with high energy and power density, but also significantly improves the overall performance of the capacitor, making it have great industrial application potential and market prospects in high-requirement fields such as new energy vehicles, grid energy storage, and special power supplies.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A non-aqueous electrolyte for a lithium-ion hybrid supercapacitor, characterized in that, It includes the following components in parts by weight: 10-30 parts lithium salt, 50-110 parts organic solvent, 0.1-10 parts film-forming additive, 0.5-5 parts overcharge protectant, 1-10 parts flame retardant additive, and 0.15-5 parts low impedance additive. The lithium salt includes at least two of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide. The low-impedance additive includes a first low-impedance additive and a second low-impedance additive. The first low-resistance additive includes vinyl sulfate and / or ethylene carbonate; The structural formula of the second low-resistivity additive is shown in formula (I): Equation (I).

2. The non-aqueous electrolyte for the lithium-ion hybrid supercapacitor as described in claim 1, characterized in that, The lithium salt comprises lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide; the mass ratio of lithium bis(fluorosulfonyl)imide to lithium bis(trifluoromethanesulfonyl)imide is (0.5-1.5):

1.

3. The non-aqueous electrolyte for the lithium-ion hybrid supercapacitor as described in claim 1, characterized in that, The organic solvent includes a first organic solvent and a second organic solvent; the first organic solvent includes ethylene carbonate and / or propylene carbonate; the second organic solvent includes at least one of acetonitrile, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl acetate, propyl acetate, ethyl propionate, and propyl propionate; the mass ratio of the first organic solvent to the second organic solvent is 1:(1-5).

4. The non-aqueous electrolyte for the lithium-ion hybrid supercapacitor as described in claim 1, characterized in that, The film-forming additive includes at least one of fluoroethylene carbonate, tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, methylene disulfonate, and 1,3-propane sulpholactone.

5. The non-aqueous electrolyte for the lithium-ion hybrid supercapacitor as described in claim 4, characterized in that, The film-forming additive includes fluoroethylene carbonate and 1,3-propane sulfonyl lactone; the mass ratio of the fluoroethylene carbonate and the 1,3-propane sulfonyl lactone is (1-10):

1.

6. The non-aqueous electrolyte for the lithium-ion hybrid supercapacitor as described in claim 1, characterized in that, The overcharge protectant includes biphenyl and / or cyclohexylbenzene.

7. The non-aqueous electrolyte for the lithium-ion hybrid supercapacitor as described in claim 1, characterized in that, The mass ratio of the first low-impedance additive to the second low-impedance additive is (1-2):

1.

8. A method for preparing the non-aqueous electrolyte of the lithium-ion hybrid supercapacitor according to any one of claims 1-7, characterized in that, Includes the following steps: Under a protective atmosphere, the lithium salt is dissolved in the organic solvent, and then the film-forming additive, overcharge protectant, flame retardant additive, and low impedance additive are added and mixed to obtain the non-aqueous electrolyte of the lithium-ion hybrid supercapacitor.

9. A lithium-ion hybrid supercapacitor, characterized in that, It includes a positive electrode, a negative electrode, and the non-aqueous electrolyte of the lithium-ion hybrid supercapacitor as described in any one of claims 1-7.

10. The lithium-ion hybrid supercapacitor as described in claim 9, characterized in that, The positive electrode comprises activated carbon and ternary lithium materials; the negative electrode comprises at least one of hard carbon, soft carbon, porous carbon, and graphite.

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