Electrolyte containing imidazolyl compound and preparation method and application thereof

Abstract

The invention discloses an electrolyte containing an imidazolyl compound as well as a preparation method and application of the electrolyte. The invention provides an electrolyte containing an imidazolyl compound, which comprises the following components in percentage by mass: 15-20% of lithium salt, 1-3% of imidazolyl compound, 0.5-1% of sulfur additive, 0.2-0.5% of carbonic ester additive, 0.5-1% of lithium salt additive and the balance of organic solvent. Multifunctional protection is achieved through the synergistic effect of imidazole rings and carboxylic ester groups in molecules; uniform and compact low-impedance CEI / SEI double-interface films can be formed on the surfaces of the positive electrode and the negative electrode respectively, and continuous decomposition of an electrolyte and non-uniform Li < + > embedding are reduced; the electrolyte can be used as an electrolyte, HF generated by hydrolysis of LiPF6 in the electrolyte can be efficiently removed by virtue of alkalescence of nitrogen atoms of an imidazole ring, electrolyte acidification and electrode corrosion are inhibited, and meanwhile, positive electrode metal dissolution is remarkably reduced by virtue of coordination of the nitrogen atoms and transition metal ions such as Ni < 2 + >, Co < 3 + > and Mn < 4 + >, so that the stable electrode structure is maintained.

Description

Technical Field

[0001] This invention relates to the field of supercapacitor technology, specifically to an electrolyte containing an imidazole compound, its preparation method, and its application. Background Technology

[0002] In the rapid development of new energy vehicles, industrial energy storage, aerospace, and smart grids, supercapacitors have become key energy storage and conversion devices due to their advantages of high power density, fast charging and discharging speed, and long cycle life. However, practical applications in these fields often face challenges in high-temperature operating conditions. For example, the temperature inside the engine compartment of new energy vehicles can reach 40-80℃, and the temperature inside industrial energy storage equipment can rise to 45-75℃ during continuous operation. Traditional supercapacitors have significant performance limitations in such environments.

[0003] Specifically, the organic electrolytes in traditional supercapacitors are prone to volatilization, decomposition, or a sudden increase in viscosity, resulting in a 30%-60% decrease in ionic conductivity; electrode materials (such as activated carbon and transition metal oxides) are prone to structural collapse and loss of active sites, with a capacity decay rate exceeding 40% after 1000 cycles at 50°C; the interface between the current collector and the electrode is prone to oxidation and corrosion, causing a surge in device internal resistance and even leading to safety risks such as leakage and bulging.

[0004] The industry's demand for wide-temperature adaptability of supercapacitors is increasingly urgent, especially in highly integrated new energy vehicle electric drive systems and high-temperature industrial backup power supplies. High-temperature performance has become a core bottleneck restricting their replacement of traditional energy storage devices and expansion into high-end applications. Therefore, there is an urgent need to develop new electrolytes to improve the rate performance and safety performance of supercapacitors at high temperatures. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide an electrolyte containing imidazole compounds, a preparation method thereof, and its application, thereby improving the rate performance and safety performance of supercapacitors.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The present invention provides an electrolyte containing an imidazole compound, comprising, by mass percentage, 15-20% lithium salt, 1%-3% imidazole compound, 0.5%-1% sulfide additive, 0.2%-0.5% carbonate additive and 0.5%-1% lithium salt additive, with the balance being an organic solvent.

[0007] Furthermore, the imidazole compound includes one of the following substances:

[0008] Wherein, Formula I-1 is 2-propyl-4,5-imidazolium dicarboxylic acid dimethyl ester; Formula I-2 is 2-benzimidazole ethyl acetate; Formula I-3 is 1-triphenylmethyl-1H-imidazolium-4-carboxylic acid methyl ester.

[0009] Furthermore, the lithium salt is lithium hexafluorophosphate; the lithium salt additive includes one or more of lithium bis(fluorosulfonyl)imide and lithium bis(oxalato)borate.

[0010] Furthermore, the carbonate additive is ethylene carbonate.

[0011] Furthermore, the sulfur-based additives include one or more of vinyl sulfate and methylene methane disulfonate.

[0012] Furthermore, the organic solvent includes cyclic carbonates and chain carbonates.

[0013] Furthermore, the cyclic carbonate includes one or more of fluoroethylene carbonate and ethylene carbonate, and the chain carbonate includes one or more of diethyl carbonate and methyl ethyl carbonate.

[0014] Furthermore, the ratio of the total mass of the fluoroethylene carbonate and ethylene carbonate, the mass of diethyl carbonate, and the mass of methyl ethyl carbonate is (15~25):(10~20):(50~70).

[0015] This invention also provides a method for preparing an electrolyte containing an imidazole group, comprising: In an inert environment, according to the mass fraction of the electrolyte containing imidazole compounds mentioned above, sulfur-based additives, carbonate additives, and imidazole compounds are added to an organic solvent, followed by lithium salts and lithium salt additives. The mixture is then stirred evenly at a temperature of 10~20℃ to obtain an electrolyte containing imidazole compounds.

[0016] The present invention also provides a supercapacitor, comprising a positive electrode, a negative electrode, a separator, and an electrolyte containing an imidazole compound as described above.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: In the electrolyte containing imidazole compounds provided by this invention, the imidazole compounds achieve multifunctional protection through the synergistic effect of the imidazole ring and carboxylic acid ester groups in the molecule: they can form uniform and dense low-resistance CEI / SEI dual-interface films on the positive and negative electrode surfaces respectively, reducing the continuous decomposition of the electrolyte and Li. + The intercalation is uneven; it can also efficiently remove HF generated by the hydrolysis of LiPF6 in the electrolyte by virtue of the weak basicity of the nitrogen atom in the imidazole ring, inhibiting electrolyte acidification and electrode corrosion, while simultaneously interacting with Ni atoms. 2 + Co 3+ Mn 4+The coordination effect of transition metal ions significantly reduces the dissolution of positive electrode metal to maintain the stability of electrode structure. In addition, it can also improve the antioxidant capacity of electrolyte, preferentially consume active oxygen under high voltage, capture free radicals, reduce electrolyte decomposition and gas generation at high temperature, so that the capacity retention rate of the battery can still reach more than 91% after 400 cycles in a high temperature environment such as 55℃ (far better than the 73% of the battery without additives), while reducing the risk of thermal runaway.

[0018] When the electrolyte provided by this invention is applied to supercapacitors, the combination of sufficient lithium salt and appropriate additives ensures efficient ion migration. Imidazole compounds inhibit the rapid increase in electrolyte viscosity at high temperatures, ensuring rapid ion transport in high-power charging and discharging scenarios, reducing internal resistance losses, and improving rate response speed. Imidazole compounds enhance the high-temperature stability of the electrolyte, reducing the risk of leakage caused by the volatilization and decomposition of organic electrolytes. Sulfide-based additives and carbonate additives optimize the electrode-electrolyte interface, inhibit current collector oxidation corrosion and electrode material structure collapse, reduce capacity decay rate, and avoid safety hazards such as bulging. This allows the supercapacitor to operate stably under high-temperature conditions, meeting the dual requirements of device safety and performance in fields such as new energy vehicles and industrial energy storage. Detailed Implementation

[0019] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0020] In this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0021] In this invention, "at least one" refers to one or more items, and "more than one" refers to two or more items. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c," or "at least one of a, b, and c," can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or multiple.

[0022] It should be understood that in various embodiments of the present invention, the order of the above-mentioned processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0023] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0024] The weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope disclosed in the embodiments of this invention. Specifically, the mass described in the embodiments of this invention can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0025] The electrolyte containing an imidazole compound provided by the present invention comprises, by mass percentage, 15-20% lithium salt, 1%-3% imidazole compound, 0.5%-1% sulfide additive, 0.2%-0.5% carbonate additive and 0.5%-1% lithium salt additive, with the balance being an organic solvent.

[0026] In some embodiments, the imidazole compound comprises one of the following substances:

[0027] Wherein, Formula I-1 is 2-propyl-4,5-imidazolium dicarboxylic acid dimethyl ester; Formula I-2 is 2-benzimidazole ethyl acetate; Formula I-3 is 1-triphenylmethyl-1H-imidazolium-4-carboxylic acid methyl ester.

[0028] The electrolyte containing imidazole compounds of this invention provides a sufficient ion source for the electrolyte by including 10%–15% lithium salt, ensuring basic ion conductivity. 0.2%–0.7% imidazole compounds (such as dimethyl 2-propyl-4,5-imidazolium dicarboxylate) play a stabilizing role, improving the chemical stability of the electrolyte under high-temperature conditions and reducing the risk of volatilization and decomposition. Simultaneously, 0.5%–1% sulfur-based additives, 0.2%–0.5% carbonate additives, and 0.5%–1% lithium salt additives form an auxiliary system. Sulfur-based additives optimize interfacial properties, carbonate additives adjust electrolyte viscosity to accommodate ion migration, and lithium salt additives further replenish ions and enhance the overall compatibility of the electrolyte. The synergistic effect of these components gives the electrolyte both good ionic conductivity and chemical stability, avoiding performance defects caused by the shortcomings of a single component.

[0029] In some embodiments, the lithium salt is lithium hexafluorophosphate; the lithium salt additive includes one or more of lithium bis(fluorosulfonyl)imide (LiFSi) and lithium bis(oxalato)borate (LiBOB).

[0030] In some embodiments, the sulfur-based additive includes one or more of vinyl sulfate (DTD) and methylene methane disulfonate (MMDS). The sulfur-based additive can form a stable passivation film on the electrode surface, reducing side reactions between the electrode material and the electrolyte, thereby ensuring the rate performance and cycle stability of the supercapacitor during charge and discharge.

[0031] In some embodiments, the carbonate additive is ethylene carbonate (VC). Ethylene carbonate has a high dielectric constant and good solubility, which can significantly improve the electrolyte's ability to dissolve lithium salts and increase the concentration of free ions in the electrolyte.

[0032] In some embodiments, the organic solvent includes cyclic carbonates and linear carbonates. Cyclic carbonates have a high dielectric constant, which is beneficial for lithium salt dissolution; linear carbonates have low viscosity, which can improve ion migration rate. The synergistic effect of the two can balance the high ionic conductivity and good fluidity of the electrolyte, ensuring that the supercapacitor can efficiently transport ions under different operating conditions and improve the overall performance of the device.

[0033] In some embodiments, the cyclic carbonates include one or more of fluoroethylene carbonate and ethylene carbonate, and the chain carbonates include one or more of diethyl carbonate and methyl ethyl carbonate.

[0034] In some embodiments, the ratio of the total mass of fluoroethylene carbonate and ethylene carbonate, the mass of diethyl carbonate, and the mass of methyl ethyl carbonate is (15~25):(10~20):(50~70). This ratio ensures that the organic solvent has a suitable dielectric constant and solubility in the electrolyte, while also controlling the electrolyte viscosity within a reasonable range to ensure efficient ion migration. Simultaneously, it improves the compatibility between the electrolyte and electrode materials, significantly enhancing the rate performance, cycle life, and safety performance of the supercapacitor.

[0035] The method for preparing an electrolyte of an imidazole compound provided by the present invention includes: In an inert environment, according to the mass fraction of the electrolyte containing imidazole compounds mentioned above, sulfur-based additives, carbonate additives, and imidazole compounds are added to an organic solvent, followed by lithium salts and lithium salt additives. The mixture is then stirred evenly at a temperature of 10~20℃ to obtain an electrolyte containing imidazole compounds.

[0036] The supercapacitor provided by the present invention includes a positive electrode, a negative electrode, a separator, and an electrolyte containing an imidazole compound as described above.

[0037] 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 this description, 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.

[0038] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under standard conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications in the art, unless otherwise stated.

[0039] Example 1 Prepare an organic solvent by adding 10% fluoroethylene carbonate, 15% ethylene carbonate, 10% diethyl carbonate, and 65% methyl ethyl carbonate to a reaction vessel and stirring for 10 minutes, with the total mass of the organic solvent being 100%.

[0040] Based on the mass percentage of the components, in an inert environment (a glove box with water and oxygen content both less than 0.1 ppm), 0.8% DTD was added to the organic solvent and stirred for 20 min to ensure complete dissolution of DTD. Then, 0.2% VC was added and stirred for 20 min. Next, 2% dimethyl 2-propyl-4,5-imidazolium dicarboxylate was added and stirred for 30 min to form a homogeneous mixture. 18% LiPF6 and 1% LiFSi were added to the mixture and stirred at 10°C for 3 h to obtain the electrolyte of this embodiment.

[0041] Example 2 Prepare an organic solvent by adding 10% fluoroethylene carbonate, 15% ethylene carbonate, 10% diethyl carbonate, and 65% methyl ethyl carbonate to a reaction vessel and stirring for 10 minutes, with the total mass of the organic solvent being 100%.

[0042] Based on the mass percentage of the components, in an inert environment (a glove box with water and oxygen content both less than 0.1 ppm), 0.8% DTD was added to the organic solvent and stirred for 20 min to ensure complete dissolution of DTD. Then, 0.2% VC was added and stirred for 20 min. Next, 1% dimethyl 2-propyl-4,5-imidazolium dicarboxylate was added and stirred for 30 min to form a homogeneous mixture. 18% LiPF6 and 1% LiFSi were added to the mixture and stirred at 10°C for 3 h to obtain the electrolyte of this embodiment.

[0043] Example 3 Prepare an organic solvent by adding 10% fluoroethylene carbonate, 15% ethylene carbonate, 10% diethyl carbonate, and 65% methyl ethyl carbonate to a reaction vessel and stirring for 10 minutes, with the total mass of the organic solvent being 100%.

[0044] Based on the mass percentage of the components, in an inert environment (a glove box with water and oxygen content both less than 0.1 ppm), 0.8% DTD was added to the organic solvent and stirred for 20 min to ensure complete dissolution of DTD. Then, 0.2% VC was added and stirred for 20 min. Next, 3% 2-propyl-4,5-imidazolium dicarboxylate was added and stirred for 30 min to form a homogeneous mixture. 18% LiPF6 and 1% LiFSi were added to the mixture, and the mixture was stirred and mixed at 10°C for 3 h to obtain the electrolyte of this embodiment.

[0045] Example 4 Prepare an organic solvent by adding 5% fluoroethylene carbonate, 10% ethylene carbonate, 15% diethyl carbonate and 70% methyl ethyl carbonate to a reaction vessel and stirring for 10 minutes, with the total mass of the organic solvent being 100%.

[0046] Based on the mass percentage of the components, in an inert environment (glove box with water and oxygen content both less than 0.1 ppm), 1% DTD was added to the organic solvent and stirred for 20 min to ensure complete dissolution of DTD. Then, 0.3% VC was added and stirred for 20 min. Next, 2% 2-propyl-4,5-imidazolium dicarboxylate was added and stirred for 30 min to form a homogeneous mixture. 15% LiPF6 and 0.5% LiFSi were added to the mixture and stirred at 10°C for 3 h to obtain the electrolyte of this embodiment.

[0047] Example 5 Prepare an organic solvent by adding 10% fluoroethylene carbonate, 15% ethylene carbonate, 20% diethyl carbonate, and 55% methyl ethyl carbonate to a reaction vessel and stirring for 10 minutes, with the total mass of the organic solvent being 100%.

[0048] Based on the mass percentage of the components, in an inert environment (a glove box with water and oxygen content both less than 0.1 ppm), 1% DTD was added to the organic solvent and stirred for 20 min to ensure complete dissolution of DTD. Then, 0.4% VC was added and stirred for 20 min, followed by 2% ethyl 2-benzimidazole and stirring for 30 min to form a homogeneous mixture. 20% LiPF6 and 0.8% LiFSi were added to the mixture, and the mixture was stirred at 10°C for 3 h to obtain the electrolyte of this embodiment.

[0049] Example 6 Prepare an organic solvent by adding 10% fluoroethylene carbonate, 15% ethylene carbonate, 20% diethyl carbonate, and 55% methyl ethyl carbonate to a reaction vessel and stirring for 10 minutes, with the total mass of the organic solvent being 100%.

[0050] Based on the mass percentage of the components, in an inert environment (a glove box with water and oxygen content both less than 0.1 ppm), 0.5% DTD was added to the organic solvent and stirred for 20 min to ensure complete dissolution of DTD. Then, 0.5% VC was added and stirred for another 20 min. Next, 2% methyl 1-triphenylmethyl-1H-imidazolium-4-carboxylate was added and stirred for 30 min to form a homogeneous mixture. 20% LiPF6 and 0.8% LiFSi were added to the mixture, and the mixture was stirred and mixed at 10°C for 3 h to obtain the electrolyte of this embodiment.

[0051] Comparative Example 1 An electrolyte differs from Example 1 only in that it does not contain imidazole compounds; all other components are the same as in Example 1.

[0052] The electrolytes of the above embodiments and comparative examples are assembled into a supercapacitor, specifically as follows: Using graphite as the negative electrode active material, a negative electrode slurry was prepared by mixing graphite, conductive agent acetylene black, binder carboxymethyl cellulose (CMC), and binder polyacrylic acid (PAA) in a ratio of (97.5:0.7:1.0:0.8). The negative electrode slurry was coated onto a copper foil current collector and dried under vacuum to obtain a negative electrode sheet. Using NCM622 as the positive electrode active material, a positive electrode slurry was prepared by mixing the positive electrode active material, conductive agent acetylene black, binder polyvinylidene fluoride (PVDF), and carbon nanotubes (CNT) in a ratio of (96.8:1.2:1:1). The positive electrode slurry was coated onto an aluminum foil current collector and dried under vacuum to obtain a positive electrode sheet. The electrolytes prepared in the examples and comparative examples were used to assemble the above-mentioned positive electrode sheet, negative electrode sheet, and separator into a supercapacitor.

[0053] The electrical performance of the prepared supercapacitors was tested, and the results are shown in Table 1: Table 1. Electrical Performance Test Results

[0054] As shown in Table 1, compared with Examples 1-6 and Comparative Example 1, the addition of imidazole compounds to the electrolyte improved the high-temperature cycling performance at 55°C and the high-temperature storage performance at 60°C. The capacity retention rate after 400 cycles at 55°C was over 91%, and the capacity retention rate after 30 days of storage at 60°C was over 90%. This is mainly due to the synergistic effect of the imidazole ring and the carboxylic acid ester group, which achieves multifunctional protection: it can form a uniform and dense low-resistance CEI / SEI dual-interface film on the positive and negative electrode surfaces respectively, reducing the continuous decomposition of the electrolyte and Li. + The intercalation is uneven; it can also efficiently remove HF generated by the hydrolysis of LiPF6 in the electrolyte by virtue of the weak basicity of the nitrogen atom in the imidazole ring, inhibiting electrolyte acidification and electrode corrosion, while simultaneously interacting with Ni atoms. 2+ Co 3+ Mn 4+ The coordination effect of transition metal ions significantly reduces the dissolution of positive electrode metal to maintain the stability of the electrode structure.

[0055] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the claims of the present invention pending approval.

Claims

1. An electrolyte containing an imidazole group compound, characterized in that, By mass percentage, it includes 15-20% lithium salt, 1-3% imidazole compounds, 0.5-1% sulfide additives, 0.2-0.5% carbonate additives and 0.5-1% lithium salt additives, with the balance being organic solvents.

2. The electrolyte containing an imidazole group according to claim 1, characterized in that, The imidazole compound includes one of the following substances: Wherein, Formula I-1 is 2-propyl-4,5-imidazolium dicarboxylic acid dimethyl ester; Formula I-2 is 2-benzimidazole ethyl acetate; Formula I-3 is 1-triphenylmethyl-1H-imidazolium-4-carboxylic acid methyl ester.

3. The electrolyte containing an imidazole group according to claim 1, characterized in that, The lithium salt is lithium hexafluorophosphate; the lithium salt additive includes one or more of lithium bis(fluorosulfonyl)imide and lithium bis(oxalato)borate.

4. The electrolyte containing an imidazole group according to claim 1, characterized in that, The carbonate additive is ethylene carbonate.

5. The electrolyte containing an imidazole group according to claim 1, characterized in that, The sulfur-based additives include one or more of vinyl sulfate and methylene disulfonate.

6. The electrolyte containing an imidazole compound according to claim 1, characterized in that, The organic solvents include cyclic carbonates and chain carbonates.

7. The electrolyte containing an imidazole compound according to claim 6, characterized in that, The cyclic carbonates include one or more of fluoroethylene carbonate and ethylene carbonate, and the chain carbonates include one or more of diethyl carbonate and methyl ethyl carbonate.

8. The electrolyte containing an imidazole group according to claim 7, characterized in that, The ratio of the total mass of the fluoroethylene carbonate and ethylene carbonate, the mass of diethyl carbonate, and the mass of methyl ethyl carbonate is (15~25):(10~20):(50~70).

9. A method for preparing an electrolyte containing an imidazole group, characterized in that, include: In an inert environment, according to the mass fraction of the electrolyte containing imidazole compounds as described in any one of claims 1-8, sulfur-based additives, carbonate additives, and imidazole compounds are added to an organic solvent, followed by the addition of lithium salts and lithium salt additives. The mixture is then stirred uniformly at a temperature of 10-20°C to obtain an electrolyte containing imidazole compounds.

10. A supercapacitor, characterized in that, The electrolyte includes a positive electrode, a negative electrode, a separator, and an electrolyte containing an imidazole compound as described in any one of claims 1-8.

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