Electrolyte containing pyridyl compound as well as preparation method and application of electrolyte

Abstract

The invention discloses an electrolyte containing a pyridyl compound as well as a preparation method and application of the electrolyte. The invention provides an electrolyte containing a pyridyl compound, which is prepared from the following components in percentage by mass: 15 to 25 percent of lithium salt, 2 to 4 percent of 3-bromo-5-fluoropyridylaldehyde, 0.5 to 1 percent of sulfur additive, 0.2 to 0.5 percent of carbonic ester additive, 0.5 to 1 percent of lithium salt additive and the balance of organic solvent. In the electrolyte provided by the invention, the 3-bromine-5-fluoropyridylaldehyde can form a stable interfacial film, and electrolyte decomposition and metal ion dissolution are inhibited; the bromine and fluorine electricity absorption groups can improve the stability of an electrode / electrolyte interface and assist uniform deposition of lithium; and acid can be removed, high-temperature gas production can be reduced, and battery circulation and storage performance can be enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of supercapacitors, in particular to an electrolyte containing a pyridyl compound, a preparation method and application thereof. BACKGROUND

[0002] The cycle performance of a hybrid supercapacitor is a key technical indicator and core competitiveness for adapting to long-term stable application scenarios, and is particularly important in high-frequency and high-intensity charge-discharge fields such as new energy vehicles, large-scale energy storage and industrial energy recovery.

[0003] Due to the integration of battery-type electrode materials that undergo Faraday reactions, the hybrid device is prone to volume deformation, structure collapse or active material dissolution during repeated charge-discharge processes, which significantly limits the durability and reliability of the device, and further affects the service life, economic benefits and market competitiveness of the energy storage system.

[0004] Current industry has been committed to improving the cycle life of hybrid supercapacitors through material nanocrystallization, composite electrode structure design and other technical approaches, and has achieved remarkable results in improving the cycle performance of the device, providing a feasible technical approach to solve the cycle stability problem.

[0005] The existing technical solutions still have obvious limitations, and cannot achieve the synergistic optimization of electrode interface stability, nor effectively inhibit the capacity decay phenomenon in long-term cycling. This core technical bottleneck has not been broken through, which not only restricts the large-scale application of high-performance hybrid supercapacitors, but also is the direction that needs to be focused on in the current field. SUMMARY

[0006] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide an electrolyte containing a pyridyl compound, a preparation method and application thereof, which solves the technical problem of rapid increase of direct current resistance in the prior art, thereby causing cycle diving.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions: The present application provides an electrolyte containing a pyridyl compound, which comprises 15-25% of lithium salt, 2-4% of 3-bromo-5-fluoropyridine formaldehyde, 0.5-1% of sulfur-based additive, 0.2-0.5% of carbonate-based additive and 0.5-1% of lithium salt additive, and the balance is organic solvent.

[0008] Further, the lithium salt is lithium hexafluorophosphate.

[0009] Further, the sulfur-based additive includes at least one of vinyl sulfate and methanedimethanesulfonate.

[0010] Further, the carbonate-based additive is vinyl carbonate.

[0011] Further, the lithium salt additive includes one or more of lithium bisfluorosulfonylimide, lithium bis(oxalato)borate.

[0012] Further, the organic solvent includes a cyclic carbonate and a chain carbonate.

[0013] Further, 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 ethyl methyl carbonate.

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

[0015] The present application also provides a preparation method of the electrolyte containing the pyridyl compound, comprising: In an inert environment, the electrolyte containing the pyridyl compound is prepared by adding the sulfur additive, the carbonate additive, and the 3-bromo-5-fluoropyridine formaldehyde into the organic solvent according to the mass fraction, and then adding the lithium salt and the lithium salt additive, and mixing uniformly at a temperature of 10-20°C.

[0016] The present application also provides a supercapacitor, comprising a positive electrode, a negative electrode, a separator, and the electrolyte containing the pyridyl compound.

[0017] Compared with the prior art, the present application has the following beneficial effects: The electrolyte containing the 3-bromo-5-fluoropyridine formaldehyde provided by the present application can form a tight and stable interface film containing LiXNYOY on the surface of the positive and negative electrodes in the electrolyte containing the pyridyl compound, can inhibit the decomposition of the electrolyte, can block the corrosion of HF to the positive electrode, can reduce the dissolution of transition metal ions, can improve the cycle performance of the battery, and the effect is particularly prominent at high temperature. Meanwhile, the strong electron-withdrawing groups of bromine and fluorine in the molecule of the 3-bromo-5-fluoropyridine formaldehyde can increase the molecular dipole moment, promote the adsorption of the molecule on the surface of lithium metal, reduce the concentration of other molecules at the interface, reduce the charge density of pyridine-N and the binding energy of the additive-lithium ion, reduce the desolvation energy of lithium ions at the interface, improve the conversion kinetics, help the uniform deposition of lithium, and enhance the stability of the electrode / electrolyte interface. The weak basicity of the pyridyl group can neutralize the acid, can complex the metal ions in the electrolyte, can inhibit the dissolution of the metal ions, can reduce the adverse effects on the performance of the battery, can prolong the cycle life and improve the capacity retention rate. In addition, it also has the effect of removing acid, can relieve the gas generation of the electrolyte at high temperature, the N and F containing passivation film formed by it can enhance the stability at high temperature, reduce the side reactions during storage at high temperature, reduce the consumption of active lithium by the electrolyte, and improve the recovery capacity after storage of the battery.

[0018] The electrolyte provided by the application is used for supercapacitors, and makes the supercapacitors maintain stable performance output in long-term cycles, and solves the problem of cycle diving. The stable interface protection film formed by the electrolyte containing the pyridine-based compound can long-term inhibit the increase of the electrode / electrolyte interface resistance; the high stability of the electrolyte body can maintain the ionic conductivity after long-term cycles, avoid the increase of the ion transmission resistance caused by electrolyte degradation, and ensure that the supercapacitor still maintains a low overall direct current resistance under large current cycles, and further ensures the cycle performance consistency. The electrolyte containing the pyridine-based compound can also inhibit the self-discharge phenomenon of the supercapacitor, reduce the side reaction of the electrode and the electrolyte when idle; and at the same time, the working temperature range is widened, and the abnormal increase of the resistance under extreme temperature is avoided. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the following will be further described in detail in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0020] In the present application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which can mean that A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents that the associated objects before and after it are in an "or" relationship.

[0021] In the present application, "at least one" means one or more, and "a plurality of" means two or more. "At least one of the following" or the like means any combination of these items, including any combination of single item or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple.

[0022] It should be understood that in various embodiments of the present application, the size of the sequence number of the above processes does not mean the order of execution, and part or all of the steps can be executed in parallel or in sequence, and the execution order of the processes should be determined according to their functions and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0023] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0024] The weight of the related components mentioned in the embodiment of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of each component, therefore, as long as the content of the related components in the embodiment of the present application is enlarged or reduced in proportion, it is within the scope disclosed in the embodiment of the present application. Specifically, the mass mentioned in the embodiment of the present application can be μg, mg, g, kg and other mass units commonly known in the chemical field.

[0025] In the research and industrialization process of hybrid supercapacitors, excellent cycle performance is a key technical indicator for measuring whether it can meet long-term and stable application scenarios, and is also an important element for determining the core competitiveness of the market. Traditional supercapacitors generally have a long cycle life, but hybrid supercapacitors, due to the introduction of battery-type electrode materials that can undergo Faraday reactions, are more prone to problems such as electrode material volume change, structure collapse and active material dissolution during repeated charging and discharging. These problems seriously affect the durability and reliability of the device, and greatly limit the development and application of the device.

[0026] In application scenarios such as new energy vehicles, large-scale energy storage and industrial energy recovery that require high frequency and high intensity charging and discharging, the cycle stability of the electrode material of the hybrid supercapacitor is crucial, as it directly determines the service life, economic benefits and market competitiveness of the entire energy storage system.

[0027] Currently, researchers have made significant progress in improving the cycle life of hybrid supercapacitors through material nanocrystallization and composite electrode design, and the performance of the device has been improved to some extent. However, how to further optimize the stability of the electrode interface and suppress the capacity decay during long-term cycling remains a core technical bottleneck that restricts the widespread application of high-performance hybrid supercapacitors. It is also a direction that needs to be focused on in current research in this field, and relevant research has important practical significance for the development of the hybrid supercapacitor industry.

[0028] The present application provides a kind of electrolyte containing pyridyl compound, by mass percentage, including 15~25% of lithium salt, 2%~4% of 3-bromo-5-fluoropyridine formaldehyde, 0.5%~1% of sulfur additive, 0.2%~0.5% of carbonate additive and 0.5%~1% of lithium salt additive, the rest is organic solvent.

[0029] The structural formula of 3-bromo-5-fluoropyridine formaldehyde is as follows: .

[0030] The 3-bromo-5-fluoropyridine formaldehyde in the electrolyte provided by the application forms a dense, uniform and high ion selectivity protective film at the electrode / electrolyte interface by the coordination of the pyridine ring nitrogen atom and the electrode active site, which isolates the direct contact between the two, reduces the interface side reactions such as electrode dissolution and electrolyte decomposition, and avoids the interface resistance increase caused by the accumulation of by-products. At the same time, the lithium salt additive participates in the formation of the protective film, supplements the film defects, and enhances the mechanical strength and cycle resistance of the film; at the same time, the sulfur-based additive can capture free radicals generated by side reactions, inhibit the cycle degradation of the electrolyte, and cooperatively broaden the redox potential window with 3-bromo-5-fluoropyridine formaldehyde, reduce the electrolyte decomposition probability at high voltage, and avoid the decrease of ion concentration and the increase of viscosity caused by decomposition products, thereby preventing the increase of bulk resistance. In addition, the reasonable proportion of lithium salt and organic solvent can maintain high ionic conductivity for a long time, ensure smooth ion migration, and avoid the increase of ion transmission resistance to cause the increase of overall direct current resistance.

[0031] In some embodiments, the lithium salt is lithium hexafluorophosphate (LiPF6). Lithium hexafluorophosphate has excellent dissociation energy and can efficiently release lithium ions in organic solvents, ensuring high ionic conductivity of the battery and improving charge-discharge efficiency. It can also react with the electrode surface to form a stable passivation film, reduce electrode and electrolyte side reactions, and enhance the cycle stability of the battery.

[0032] In some embodiments, the sulfur-based additive includes one or more of vinyl sulfate (DTD) and methylene methane disulfonate (MMDS). DTD and MMDS can preferentially undergo redox reactions on the electrode surface to form a dense and ionically conductive SEI film. This film can prevent further decomposition of the electrolyte, reduce the loss of active materials, and improve the cycle life of the battery.

[0033] In some embodiments, the carbonate-based additive is vinyl carbonate (VC). As a film-forming additive, VC can form a thin and stable SEI film on the negative electrode surface, which can effectively block solvent molecules from intercalating into the graphite layer, preventing the expansion of the graphite structure and protecting the integrity of the negative electrode structure.

[0034] In some embodiments, the lithium salt additive includes one or more of lithium bisfluorosulfonylimide (LiFSi) and lithium bis(oxalato)borate (LiBOB). LiFSi and LiBOB can optimize the ionic conductivity of the electrolyte, improve the lithium ion transport efficiency, and enhance the rate performance of the battery. LiFSi can improve the low-temperature discharge capability of the battery, and LiBOB can form a stable SEI film on the electrode surface to reduce side reactions.

[0035] In some embodiments, the organic solvent includes cyclic carbonates and chain carbonates. Cyclic carbonates have high dielectric constant for dissociating lithium salts and high viscosity; chain carbonates have lower viscosity and are used as co-solvents with cyclic carbonates.

[0036] In some embodiments, 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 ethyl methyl carbonate.

[0037] In some embodiments, the ratio of the total mass of fluoroethylene carbonate and ethylene carbonate, the mass of diethyl carbonate, and the mass of ethyl methyl carbonate is (15-25):(10-20):(50-70).

[0038] The application provides a preparation method of an electrolyte containing a pyridyl compound, comprising: In an inert environment, an organic solvent is prepared according to the mass fraction of the electrolyte containing the pyridyl compound described above, and then a sulfur additive, a carbonate additive, and 3-bromo-5-fluoropyridine formaldehyde are added to the organic solvent, followed by the addition of a lithium salt and a lithium salt additive, and mixing uniformly at a temperature of 10-20°C to obtain the electrolyte containing the pyridyl compound.

[0039] The application provides a supercapacitor, comprising a positive electrode, a negative electrode, a separator, and the electrolyte containing the pyridyl compound described above. The positive electrode uses NCM622 as an active material; the NCM622, a conductive agent acetylene black, a binder polyvinylidene fluoride, and a carbon nanotube are mixed to prepare a positive electrode slurry, the positive electrode slurry is coated on an aluminum foil current collector, and vacuum drying is performed to obtain the positive electrode; the negative electrode uses graphite as an active material; the graphite, a conductive agent acetylene black, a binder carboxymethyl cellulose, and a binder polyacrylic acid are mixed to prepare a negative electrode slurry, the negative electrode slurry is coated on a copper foil current collector, and vacuum drying is performed to obtain the negative electrode.

[0040] The application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the application and not used to limit the scope of the application. In addition, it should be understood that those skilled in the art can make various modifications or changes to the application after reading the description of the application, and these equivalent forms also fall within the scope defined by the claims attached hereto.

[0041] The following examples use conventional equipment in the art. The experimental methods in the following examples are not specified, and are usually carried out according to conventional conditions, or according to the conditions recommended by the manufacturer. Various raw materials are used in the following examples, unless otherwise specified, and conventional commercially available products are used, which are conventional specifications in the art.

[0042] Example 1 An organic solvent is prepared, and 10% of fluoroethylene carbonate, 15% of ethylene carbonate, 10% of diethyl carbonate, and 65% of ethyl methyl carbonate are added to a reaction vessel, and stirred for 10 min to obtain the organic solvent, with the total mass of the organic solvent being 100%.

[0043] According to the mass percentage of components, 0.8% of DTD was added to the organic solvent and stirred for 20 min in an inert environment (a glove box with water and oxygen content less than 0.1 ppm) to ensure complete dissolution of DTD, 0.2% of VC was continuously added and stirred for 20 min, 3% of 3-bromo-5-fluoropyridine formaldehyde was continuously stirred for 30 min to form a uniform mixture, 18% of LiPF6 and 1% of LiFSi were added to the mixture, and the mixture was stirred at 10°C for 3h to obtain the electrolyte of the example.

[0044] Example 2 The organic solvent was configured, and 10% of fluoroethylene carbonate, 15% of ethylene carbonate, 10% of diethyl carbonate and 65% of methyl ethyl carbonate were added to the reaction container and stirred for 10 min to obtain the organic solvent.

[0045] According to the mass percentage of components, 0.8% of DTD was added to the organic solvent and stirred for 20 min in an inert environment (a glove box with water and oxygen content less than 0.1 ppm) to ensure complete dissolution of DTD, 0.2% of VC was continuously added and stirred for 20 min, 2% of 3-bromo-5-fluoropyridine formaldehyde was continuously stirred for 30 min to form a uniform mixture, 18% of LiPF6 and 1% of LiFSi were added to the mixture, and the mixture was stirred at 10°C for 3h to obtain the electrolyte of the example.

[0046] Example 3 The organic solvent was configured, and 10% of fluoroethylene carbonate, 15% of ethylene carbonate, 10% of diethyl carbonate and 65% of methyl ethyl carbonate were added to the reaction container and stirred for 10 min to obtain the organic solvent.

[0047] According to the mass percentage of components, 0.8% of DTD was added to the organic solvent and stirred for 20 min in an inert environment (a glove box with water and oxygen content less than 0.1 ppm) to ensure complete dissolution of DTD, 0.2% of VC was continuously added and stirred for 20 min, 4% of 3-bromo-5-fluoropyridine formaldehyde was continuously stirred for 30 min to form a uniform mixture, 18% of LiPF6 and 1% of LiFSi were added to the mixture, and the mixture was stirred at 10°C for 3h to obtain the electrolyte of the example.

[0048] Example 4 The organic solvent was configured, and 5% of fluoroethylene carbonate, 10% of ethylene carbonate, 15% of diethyl carbonate and 70% of methyl ethyl carbonate were added to the reaction container and stirred for 10 min to obtain the organic solvent.

[0049] According to the mass percentage of components, 1% of DTD was added to the organic solvent and stirred for 20 min in an inert environment (a glove box with water and oxygen content less than 0.1 ppm) to ensure complete dissolution of DTD, 0.3% of VC was continuously added and stirred for 20 min, 3% of 3-bromo-5-fluoropyridine formaldehyde was continuously stirred for 30 min to form a uniform mixture, 15% of LiPF6 and 0.5% of LiFSi were added to the mixture, and the mixture was stirred at a temperature of 10°C for 3h to obtain the electrolyte of the example.

[0050] Example 5 The organic solvent was configured, and 10% of fluoroethylene carbonate, 15% of ethylene carbonate, 20% of diethyl carbonate and 55% of methyl ethyl carbonate were added to the reaction container and stirred for 10 min to obtain the organic solvent.

[0051] According to the mass percentage of components, 1% of DTD was added to the organic solvent and stirred for 20 min in an inert environment (a glove box with water and oxygen content less than 0.1 ppm) to ensure complete dissolution of DTD, 0.3% of VC was continuously added and stirred for 20 min, 3% of 3-bromo-5-fluoropyridine formaldehyde was continuously stirred for 30 min to form a uniform mixture, 15% of LiPF6 and 0.5% of LiFSi were added to the mixture, and the mixture was stirred at a temperature of 10°C for 3h to obtain the electrolyte of the example.

[0052] Example 6 The organic solvent was configured, and 10% of fluoroethylene carbonate, 15% of ethylene carbonate, 20% of diethyl carbonate and 55% of methyl ethyl carbonate were added to the reaction container and stirred for 10 min to obtain the organic solvent.

[0053] According to the mass percentage of components, 1% of DTD was added to the organic solvent and stirred for 20 min in an inert environment (a glove box with water and oxygen content less than 0.1 ppm) to ensure complete dissolution of DTD, 0.3% of VC was continuously added and stirred for 20 min, 3% of 3-bromo-5-fluoropyridine formaldehyde was continuously stirred for 30 min to form a uniform mixture, 15% of LiPF6 and 0.5% of LiFSi were added to the mixture, and the mixture was stirred at a temperature of 10°C for 3h to obtain the electrolyte of the example.

[0054] Comparative Example 1 An electrolyte, which is different from Example 1 only in that it does not contain 3-bromo-5-fluoropyridine formaldehyde, and other components are the same as Example 1.

[0055] 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 (96.5:1.2:1.5:0.8). The negative electrode slurry was coated onto a copper foil current collector and vacuum dried 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 (97.8:1.2:0.6:0.4). The positive electrode slurry was coated onto an aluminum foil current collector and vacuum dried 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.

[0056] The electrical performance of the prepared supercapacitors was tested, and the results are shown in Table 1: Table 1. Electrical Performance Test Results

[0057] 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.

[0058] 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 solution containing a pyridyl group, characterized by comprising: The lithium salt, the 3-bromo-5-fluoropyridine formaldehyde, the sulfur-based additive, the carbonate-based additive, and the lithium salt additive are included in the electrolyte in a mass percentage of 15-25%, 2-4%, 0.5-1%, 0.2-0.5%, and 0.5-1%, respectively, and the balance is the organic solvent.

2. The electrolyte solution containing a pyridyl group according to claim 1, characterized by The lithium salt is lithium hexafluorophosphate.

3. The electrolyte solution containing a pyridyl group according to claim 1, wherein The sulfur-based additive includes one or more of vinyl sulfates and methane disulfonate methylene.

4. The electrolyte solution containing a pyridyl group according to claim 1, wherein The carbonate-based additive is vinyl carbonate.

5. The electrolyte solution containing a pyridyl group according to claim 1, wherein The lithium salt additive includes one or more of lithium bisfluorosulfonimide and lithium bisoxalate borate.

6. The electrolyte solution containing a pyridyl group according to claim 1, wherein The organic solvent includes a cyclic carbonate and a chain carbonate.

7. The electrolyte solution containing a pyridyl group according to claim 6, wherein The cyclic carbonate includes one or more of fluorinated vinyl carbonate and vinyl carbonate, and the chain carbonate includes one or more of diethyl carbonate and methyl ethyl carbonate.

8. The electrolyte solution containing a pyridyl group according to claim 7, wherein The ratio of the total mass of the fluorinated vinyl carbonate and the vinyl carbonate, the mass of the diethyl carbonate, and the mass of the methyl ethyl carbonate is (15-25):(10-20):(50-70).

9. A method for preparing an electrolyte solution containing a pyridyl group, characterized by, The electrolyte includes: In an inert environment, the electrolyte including the pyridine-based compound according to any one of claims 1-8 is added to the organic solvent, and then the sulfur-based additive, the carbonate-based additive, and the 3-bromo-5-fluoropyridine formaldehyde are added, and then the lithium salt and the lithium salt additive are added, and the mixture is uniformly mixed at a temperature of 10-20°C to obtain the electrolyte including the pyridine-based compound.

10. An ultracapacitor, characterized by, The battery includes a positive electrode, a negative electrode, a separator, and the electrolyte including the pyridine-based compound according to any one of claims 1-8.

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