A wide-temperature-range electrolyte and its preparation method, battery and electrical equipment

Abstract

This invention provides a wide-temperature-range electrolyte, its preparation method, a battery, and related electrical devices. It relates to the field of lithium battery technology. The preparation method includes: reacting fluoroethylene carbonate, perfluorohexanoic acid, and diethyl tetrafluoroborate to obtain a functional solution; surface-modifying carbon nanofibers with trimethyl borate and sulfuric acid to form B-CNF materials; and embedding the B-CNF materials into the hydrogen-bonded dynamic network of the functional solution to obtain the wide-temperature-range electrolyte. This preparation method, by constructing a hydrogen-bonded dynamic network and embedding the modified B-CNF materials, achieves a balance between low viscosity at low temperatures and high stability at high temperatures, while simultaneously improving ion conductivity and significantly enhancing battery performance over a wide temperature range, meeting the requirements for high-temperature adaptability.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and more specifically, to a wide-temperature-range electrolyte and its preparation method, a battery, and electrical equipment. Background Technology

[0002] Lithium-ion batteries, as a highly efficient and rechargeable energy storage technology, have been widely used in electric vehicles, portable electronic devices, and large-scale energy storage systems in recent years. Their core advantages lie in high energy density, long cycle life, and relatively low self-discharge rate. However, with the continuous expansion of application scenarios, higher demands are being placed on the performance of lithium-ion batteries, especially their performance and lifespan under extreme temperature conditions. The battery's operating temperature range and lifespan have become key issues in current research and application, directly affecting its applicability and reliability in different environments.

[0003] In existing lithium-ion battery technologies, traditional carbonate electrolytes are widely used in battery systems. However, these electrolytes exhibit significant performance bottlenecks at low temperatures (such as below -20°C). Due to a significant increase in viscosity, conductivity drops sharply to below 0.5 mS / cm. Simultaneously, the electrolyte is prone to crystallization, disrupting the stability of the electrode interface and severely impacting the battery's low-temperature electrical performance. Furthermore, high-temperature storage life is another challenge faced by traditional lithium-ion batteries. At high temperatures, the chemical stability of the electrolyte decreases, easily triggering side reactions and accelerating battery performance degradation. These factors combined limit the low-temperature range and high-temperature storage life of electric vehicles, thus affecting the user experience and, to some extent, hindering the further promotion and application of electric vehicles and other electrification technologies.

[0004] To broaden the operating temperature range of batteries, the industry has explored various improvement methods. These include replacing lithium iron phosphate materials with ternary materials, using high-porosity separators, and employing high-conductivity electrolytes. While these methods improve low-temperature performance to some extent, they come at the cost of reduced battery life at high temperatures and decreased battery consistency. On the other hand, traditional strategies for improving high-temperature storage life rely primarily on low-reactivity designs, such as replacing ternary materials with lithium iron phosphate and introducing composite additive electrolytes. However, while these strategies enhance high-temperature performance, they significantly worsen low-temperature performance, making it difficult to achieve a balance in battery performance across a wide temperature range. Currently, no cell technology element on the market can simultaneously achieve both high and low-temperature performance, which has become a key bottleneck restricting the further development of lithium-ion battery technology.

[0005] In summary, existing lithium-ion battery technology faces numerous challenges when dealing with extreme temperature conditions. The sharp decrease in conductivity and electrode interface damage at low temperatures, coupled with reduced chemical stability and increased side reactions at high temperatures, collectively lead to performance degradation and shortened lifespan. Existing improvement methods often only achieve single-level improvements in either low-temperature or high-temperature performance, failing to achieve a balance between both, thus limiting the battery's applicability in different environments. These problems not only affect the consumer experience but also hinder the further development and widespread adoption of electrification technologies such as electric vehicles, urgently requiring an innovative technological solution that can simultaneously address both high and low-temperature performance issues.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this application is to provide a wide-temperature-range electrolyte and its preparation method, battery, and electrical device. The preparation method achieves a balance between low viscosity at low temperatures and high stability at high temperatures by constructing a dynamic hydrogen bond network and embedding modified B-CNF material, while improving ion conduction performance and significantly enhancing the battery performance in a wide temperature range, thus meeting the requirements for high temperature adaptability.

[0008] In order to achieve the above-mentioned objectives of this application, the following technical solution is adopted:

[0009] In a first aspect, this application provides a method for preparing a wide-temperature-range electrolyte, comprising:

[0010] A functional solution with a dynamic hydrogen bond network was obtained by reacting fluoroethylene carbonate, perfluorohexanoic acid and diethyl tetrafluoroborate.

[0011] Surface modification of carbon nanofibers using trimethyl borate and sulfuric acid resulted in B-CNF materials with surface defects and boron functional group modification.

[0012] The B-CNF material is embedded into the hydrogen bond dynamic network of the functional solution containing lithium salt to obtain a wide-temperature-range electrolyte with three-dimensional lithium conduction channels.

[0013] In an optional embodiment, the reaction of fluoroethylene carbonate, perfluorohexanoic acid, and diethyl tetrafluoroborate to obtain a functional solution with a dynamic hydrogen bond network includes:

[0014] Fluoroethylene carbonate, perfluorohexanoic acid, and diethyl tetrafluoroborate were mixed in a molar ratio of (0.5~1.5):(3.5~4.5):(7.5~8.5) to obtain a first mixture.

[0015] The first mixture is heated and stirred under reduced pressure to obtain the functional solution.

[0016] In an optional embodiment, the first heating and stirring treatment under reduced pressure has at least one of the following conditions: A) the stirring time is at least 8 hours; B) the heating temperature is 80°C; C) the first heating and stirring treatment is conducted under reduced pressure; D) the pressure during the first heating and stirring treatment is ≤10. -3 Pa; and / or,

[0017] The dew point in the environment during the mixing treatment is ≤-60℃; and / or,

[0018] The humidity in the environment during the mixing process is <0.1ppm.

[0019] In an optional embodiment, the surface modification treatment includes:

[0020] Carbon nanofibers were placed in a mixed solution of trimethyl borate and sulfuric acid and refluxed under heating conditions to obtain high-throughput carbon nanofibers.

[0021] The high-throughput nanocarbon is washed, dried, and ball-milled to obtain the B-CNF material.

[0022] In an optional embodiment, the heating condition is at a temperature of 120°C; and / or,

[0023] The reflux reaction time is not less than 6 hours; and / or,

[0024] The washing process consists of rinsing with water and / or an organic solvent at least three times; and / or,

[0025] The drying process is a reduced-pressure drying process; and / or,

[0026] The average particle size of the B-CNF material after ball milling is ≤200nm.

[0027] In an optional embodiment, embedding the B-CNF material into the hydrogen-bonded dynamic network of the functional solution containing lithium salt to obtain a wide-temperature-range electrolyte with three-dimensional lithium-conducting channels includes:

[0028] The lithium salt and the functional solution are premixed to obtain a second mixture;

[0029] The B-CNF material is added to the second mixture and ultrasonically treated to obtain a mixture.

[0030] The mixture is subjected to a second heating and stirring treatment under reduced pressure to obtain the wide-temperature-range electrolyte.

[0031] In an optional embodiment, the stirring speed of the mixing process is 800 rpm; and / or, the premixing time is not less than 10 minutes; and / or, the concentration of the lithium salt in the wide temperature range electrolyte is 1M~5M.

[0032] The concentration of the added B-CNF material in the wide-temperature-range electrolyte is 0.3wt%~0.5wt%; and / or, the ultrasonic treatment time is not less than 30 minutes; and / or, the pressure under reduced pressure is ≤10. -3 Pa; and / or, the heating temperature of the second heating and stirring treatment is 80°C; and / or, the stirring time of the second heating and stirring treatment is not less than 2 hours.

[0033] In an optional embodiment, the lithium salt is a composite lithium salt prepared from lithium bis(trifluoromethanesulfonyl)imide and lithium difluorooxalateborate;

[0034] The preparation method of the composite lithium salt includes: mixing lithium bis(trifluoromethanesulfonyl)imide and lithium difluorooxalate borate, followed by ultrasonic dispersion and stirring to obtain the composite lithium salt;

[0035] The composite lithium salt has at least one of the following characteristics:

[0036] A. The molar ratio of lithium bis(trifluoromethanesulfonyl)imide and lithium difluorooxalateborate in the composite lithium salt is (3.5~4.5):(0.5~1.5);

[0037] B. The conductivity of the composite lithium salt is >4.5 mS / cm.

[0038] Secondly, this application provides a wide-temperature-range electrolyte, which is prepared by the wide-temperature-range electrolyte preparation method described in any of the foregoing embodiments.

[0039] Thirdly, this application provides a battery including a wide-temperature-range electrolyte as described in the foregoing embodiments.

[0040] Fourthly, this application provides an electrical device including a battery as described in the foregoing embodiments.

[0041] Compared with the prior art, the beneficial effects of this application are as follows:

[0042] The method for preparing the wide-temperature-range electrolyte involves reacting fluoroethylene carbonate, perfluorohexanoic acid, and diethyl tetrafluoroborate to form a functional solution with a dynamic hydrogen-bonded network. This significantly reduces the electrolyte viscosity at low temperatures, improves lithium-ion transport efficiency, and enhances the battery's low-temperature performance. Simultaneously, surface modification of carbon nanofibers using trimethyl borate and sulfuric acid creates a B-CNF material with surface defects and boron functional group modification. This material maintains structural and performance stability at high temperatures, reduces side reactions, and improves the electrolyte's high-temperature stability. Furthermore, embedding the B-CNF material into a lithium salt-containing functional solution forms a wide-temperature-range electrolyte with three-dimensional lithium-conducting channels, providing a rapid lithium-ion transport path and further improving the electrolyte's ion conductivity. This preparation method effectively balances high and low-temperature performance, solving the problem of simultaneously meeting high and low-temperature requirements in existing technologies. It significantly improves the overall battery performance over a wide temperature range and is suitable for applications with high temperature adaptability requirements. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0044] Figure 1 This is a schematic flowchart of the preparation method of the wide-temperature-range electrolyte in the embodiments of this application. Detailed Implementation

[0045] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0046] refer to Figure 1 This application provides a method for preparing a wide-temperature-range electrolyte, comprising:

[0047] Step S1 involves mixing and reacting fluoroethylene carbonate, perfluorohexanoic acid, and diethyl tetrafluoroborate to obtain a functional solution with a dynamic hydrogen bond network.

[0048] In this step, under specific conditions, fluoroethylene carbonate (FEC), perfluorohexanoic acid (PFHA), and diethyl tetrafluoroborate (TFEB) are mixed in a certain proportion and reacted. Through this mixed reaction, a functional solution with a dynamic network of hydrogen bonds can be formed.

[0049] Hydrogen bond dynamic networks are network structures composed of multiple interconnected hydrogen bonds. A hydrogen bond is a relatively weak chemical bond, typically formed by electrostatic attraction between a highly electronegative atom (such as oxygen, nitrogen, or fluorine) and a hydrogen atom. The hydrogen bonds in a hydrogen bond dynamic network can continuously break and reform, giving the entire network a high degree of dynamism and adaptability.

[0050] The formation and breaking of hydrogen bonds are reversible, and this change is dynamic. The strength and number of hydrogen bonds vary under different temperatures and environments. For example, hydrogen bonds may become more stable at low temperatures, while they are more prone to breaking at high temperatures. Hydrogen bond dynamic networks are highly sensitive to temperature changes. At low temperatures, the strength of hydrogen bonds may increase, thereby enhancing the stability of the network; while at high temperatures, the breaking of hydrogen bonds makes the network more flexible. Furthermore, a change in one hydrogen bond in the network affects the structure and properties of surrounding hydrogen bonds. This synergistic effect gives hydrogen bond networks complex dynamic behavior.

[0051] In electrolytes, dynamic hydrogen bond networks can significantly improve the ion conductivity of the electrolyte. By designing electrolytes with dynamic hydrogen bonds, lower viscosity can be maintained at low temperatures, thereby improving lithium-ion transport efficiency; at high temperatures, the dynamic recombination ability of hydrogen bonds can reduce electrolyte volatilization and decomposition.

[0052] Hydrogen bond dynamics exhibit temperature responsiveness, meaning that hydrogen bonds can break and recombine at different temperatures. This characteristic allows the electrolyte to maintain good fluidity at low temperatures (≤30 mPa·s, -40℃), which is beneficial for lithium-ion transport; and at high temperatures (≤5 kPa, 80℃), the vapor pressure is low, which helps reduce electrolyte volatilization and decomposition, maintaining battery stability.

[0053] In the wide-temperature-range electrolyte provided in this embodiment, the dynamic hydrogen bond network is formed through a mixed reaction of fluoroethylene carbonate, perfluorohexanoic acid, and diethyl tetrafluoroborate. This network structure is temperature-responsive, capable of dynamically adjusting the strength and number of hydrogen bonds at different temperatures, thereby optimizing the electrolyte performance.

[0054] Step S2 involves surface modification of carbon nanofibers using trimethyl borate and sulfuric acid to form B-CNF materials with surface defects and boron functional group modification.

[0055] In this step, the carbon nanofibers are surface modified so that they not only have surface defects but also have boron functional group modification.

[0056] Carbon nanofibers (CNFs) are a type of carbon material with special structure and properties. They are typically one-dimensional nanomaterials composed of carbon atoms in graphitized or graphitized forms.

[0057] After this surface modification treatment, defects are formed on the surface of carbon nanofibers, which are then modified with boron functional groups, becoming B-CNF materials. The presence of these surface defects and boron functional groups can generate strong interactions with lithium ions, thereby improving the adsorption capacity of lithium ions, providing more channels and sites for lithium ion transport, and helping to improve the conductivity of the electrolyte.

[0058] Step S3: The B-CNF material is embedded into the hydrogen bond dynamic network of the functional solution containing lithium salt to obtain a wide-temperature-range electrolyte with three-dimensional lithium conduction channels.

[0059] In this step, the B-CNF material obtained after surface modification is added to a functional solution containing lithium salt, and the B-CNF material is embedded into the hydrogen bond dynamic network by means of stirring, so as to be processed by means of stirring, so as to be processed by sonication, etc.

[0060] When B-CNF materials are embedded in a hydrogen bond dynamic network, they can form three-dimensional lithium-conducting channels. This three-dimensional structure provides a more convenient and efficient path for lithium-ion transport, enabling lithium ions to move more quickly in the electrolyte. This further improves the ion conductivity of the electrolyte and maintains good conductivity over a wide temperature range (from low to high temperatures), meeting the usage requirements of lithium-ion batteries under different temperature conditions and improving battery performance and lifespan.

[0061] In this embodiment, the three-dimensional lithium-conducting channel is formed by embedding surface-modified boron-doped carbon nanofibers (B-CNF) into a functional solution with a dynamic hydrogen-bonded network. This structure provides an efficient, continuous, and spatially three-dimensional channel for lithium-ion transport, thereby significantly improving the ion conductivity of the electrolyte, especially its performance under wide temperature ranges (low and high temperatures).

[0062] The mechanism of the three-dimensional lithium-conducting channel lies in providing a continuous transport path for lithium ions, thereby reducing the transport resistance of lithium ions in the electrolyte and significantly improving the ionic conductivity of the electrolyte. Simultaneously, the temperature responsiveness of the hydrogen bond dynamic network ensures that the electrolyte maintains a low viscosity at low temperatures and a low vapor pressure at high temperatures, thus maintaining the stability of the electrolyte over a wide temperature range. Furthermore, the surface defects and boron functional groups of boron-doped carbon nanofibers (B-CNF) can interact strongly with lithium ions to form a stable interface layer, further enhancing the performance of the electrolyte under high and low temperature conditions.

[0063] In some embodiments, step S1 involves reacting fluoroethylene carbonate, perfluorohexanoic acid, and diethyl tetrafluoroborate to obtain a functional solution with a dynamic hydrogen bond network, comprising:

[0064] Step S11: Fluoroethylene carbonate, perfluorohexanoic acid and diethyl tetrafluoroborate are mixed in a molar ratio of (0.5~1.5):(3.5~4.5):(7.5~8.5) to obtain a first mixture.

[0065] In this step, fluoroethylene carbonate (FEC), perfluorohexanoic acid (PFHA), and diethyl tetrafluoroborate (TFEB) are mixed in a specific molar ratio under specific reaction conditions. For example, fluoroethylene carbonate (FEC) (5 mmol), perfluorohexanoic acid (PFHA) (20 mmol), and diethyl tetrafluoroborate (TFEB) (40 mmol) are mixed.

[0066] The molar ratio of the above-mentioned fluoroethylene carbonate, perfluorohexanoic acid, and diethyl tetrafluoroborate can be (0.5~1.5):(3.5~4.5):(7.5~8.5). For example, in the ratio, fluoroethylene carbonate can be 0.5, 1, 1.5, etc.; perfluorohexanoic acid can be 3.5, 4, 4.5, etc.; and diethyl tetrafluoroborate can be 7.5, 8, 8.5, etc.

[0067] This step can be performed in a container with a protective gas, such as a glove box. This is because compounds such as fluoroethylene carbonate (FEC), perfluorohexanoic acid (PFHA), and diethyl tetrafluoroborate (TFEB) are generally sensitive to water and oxygen. Water and oxygen may react with these compounds, leading to decreased purity of the reaction products or the formation of unwanted byproducts. Conducting the reaction in an anhydrous and oxygen-free environment ensures the stability and reproducibility of the reaction. The presence of water and oxygen may interfere with hydrogen bond formation or disrupt the structure of the hydrogen bond network, thus affecting the performance of the electrolyte.

[0068] Furthermore, the dew point in the environment during the mixing process is ≤-60°C. Additionally, the humidity in the environment during the mixing process may be <0.1ppm.

[0069] Step S12: The first mixture is heated and stirred under reduced pressure to obtain the functional solution.

[0070] In this step, the first mixture can be transferred to a vacuum reactor for processing. The decompression condition can be a specific pressure condition, such as near-vacuum conditions, for stirring to obtain a functional solution.

[0071] This step ensures that the pressure inside the reactor is controlled under specific conditions, such as maintaining a reduced pressure within the reactor, with a pressure ≤10. -3 Pa. The heating temperature can be constant at 80℃ for stirring, and the stirring time can be at least 8 hours to form a dynamic hydrogen bond network with a network structure that has temperature-responsive hydrogen bond breaking / recombining ability. Its low-temperature viscosity is ≤30mPa·s (-40℃) and its high-temperature vapor pressure is ≤5kPa (80℃).

[0072] In summary, the method steps in this embodiment provide a way to convert fluoroethylene carbonate, perfluorohexanoic acid, and diethyl tetrafluoroborate into a functional solution with a hydrogen-bonded dynamic network through mixing and heating with stirring. Uniform mixing ensures thorough mixing of the three compounds, providing a homogeneous reactant for subsequent reactions. The reaction is carried out under vacuum to avoid interference from impurities and moisture. Regarding temperature and time control, constant stirring at 80°C for 8 hours ensures the full formation of the hydrogen-bonded dynamic network. The formed hydrogen-bonded dynamic network exhibits temperature responsiveness and maintains good ion conductivity over a wide temperature range, laying the foundation for subsequent embedding of B-CNF materials and the formation of three-dimensional lithium-conducting channels.

[0073] In some embodiments, step S2, surface modification treatment, includes:

[0074] Step S21: Carbon nanofibers are placed in a mixed solution of trimethyl borate and sulfuric acid and refluxed under heating conditions to obtain nano-high-throughput carbon.

[0075] In this step, carbon nanofibers are placed in a mixed solution of trimethyl borate and sulfuric acid and refluxed under heating conditions to obtain nano-high-throughput carbon.

[0076] Carbon nanofibers (CNF) can be placed in a mixed solution of trimethyl borate (B(OCH3)3) and concentrated sulfuric acid (H2SO4). The volume ratio of the mixed solution can be 3:1 (trimethyl borate to sulfuric acid).

[0077] Furthermore, the reflux reaction can be carried out at 120°C for 6 hours. The 120°C temperature promotes the chemical reaction between trimethyl borate and sulfuric acid and the carbon nanofibers. The 6-hour reflux time ensures the reaction proceeds fully, allowing sufficient surface defects and boron functional groups to form on the carbon nanofiber surface.

[0078] Surface modification treatment, involving the application of trimethyl borate and sulfuric acid, creates defects on the surface of carbon nanofibers, which are then modified with boron functional groups. These surface defects and boron functional groups enhance lithium-ion adsorption capacity, providing more active sites for lithium-ion transport. After reflux reaction, the surface structure of the carbon nanofibers changes, forming high-flux carbon nanofibers (B-CNF) with a boron content of 5-8 at%.

[0079] Step S22 involves washing, drying, and ball milling the nano-high-throughput carbon to obtain the B-CNF material.

[0080] In this step, the nano-high-throughput carbon is washed, dried, and ball-milled to obtain the B-CNF material.

[0081] The washing process can involve rinsing with water and / or an organic solvent at least three times. For example, the nano-high-flux carbon nanotubes can be washed three times with deionized water to remove impurities such as residual trimethyl borate and sulfuric acid from the surface. Then, it can be washed three times with an organic solvent (such as ethanol) to further remove surface impurities.

[0082] The above drying process can be a reduced-pressure drying process, for example, vacuum drying under an argon-protected environment (dew point ≤ -60℃).

[0083] The dried high-throughput carbon nanotubes need to be tested for their graphitization degree (Id / Ig>1) and particle size (Dv10>15nm, DV). max <100nm) and interlayer spacing (d002 is 0.35nm~0.55nm).

[0084] The ball milling process described above can be used to process the dried nano-high-throughput carbon. A planetary ball mill can be used, with zirconia balls (3 mm in diameter), a ball milling speed of 500 rpm, and a ball milling time of at least 4 hours.

[0085] After ball milling, the agglomerate size (average particle size) of high-throughput nanocarbon should be ≤200nm.

[0086] For example, carbon nanofibers (CNF) are used, with a graphitization degree (Id / Ig > 1) and a particle size (Dv10 > 20 nm, dV) of 10 ... max <100nm), specific surface area 350 m²2 / g ~800 m 2 / g, d002 (0.35nm~0.55nm), the carbon nanofibers were placed in a mixed solution of trimethyl borate and concentrated sulfuric acid and refluxed at 120℃ for 6 hours to form nano-high-flux carbon. The nano-high-flux carbon was washed three times with deionized water and then three times with ethanol to remove impurities on the surface of the nano-high-flux carbon. Then, it was vacuum dried under argon protection (dew point ≤ -60℃). After drying, its graphitization degree (Id / Ig>1) and particle size (Dv10>15nm, DV max <100nm), specific surface area 370 m² 2 / g ~850m 2 / g, d002 is 0.35nm~0.55nm.

[0087] Among them, 3 wt%~5 wt% high-flux carbon nanoparticles have a boron content of 5 at%~8 at%, a diameter of 90±15 nm, and a molar volume density of boronic acid ester groups grafted on the surface of 1.6×10⁻⁶. -3 mmol / m 2 ~5.5×10 -3 mmol / m 2 Furthermore, after ball milling, a dispersion with an average size ≤200nm is formed.

[0088] In some embodiments, step S3, embedding the B-CNF material into the hydrogen-bonded dynamic network of the functional solution containing lithium salt to obtain a wide-temperature-range electrolyte with three-dimensional lithium-conducting channels, includes:

[0089] Step S31: The lithium salt and the functional solution are premixed to obtain a second mixture.

[0090] In this step, the lithium salt and the functional solution are premixed to obtain a second mixture. Lithium salts [such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium difluorooxalate borate (LiDFOB)] can be added to the prepared functional solution.

[0091] Furthermore, premixing can be performed by magnetic stirring, wherein the stirring speed of the mixing process is 800 rpm; the premixing time is not less than 10 minutes to ensure that the lithium salt and the functional solution are fully mixed.

[0092] Furthermore, the concentration of lithium salt in the wide-temperature-range electrolyte is 1M~5M;

[0093] Premixing allows the lithium salt to be uniformly dispersed in the functional solution, providing a homogeneous mixing system for subsequent steps. The premixed solution can better bind with the B-CNF material, thereby improving the overall conductivity of the electrolyte.

[0094] Step S32: Add the B-CNF material to the second mixture and sonicate to obtain a mixture.

[0095] In the above steps, B-CNF material is added to the second mixture and ultrasonically treated to obtain a mixture. Specifically, surface-modified B-CNF material (3~5wt%) can be gradually added to the second mixture to avoid excessively high local concentrations.

[0096] Furthermore, the concentration of the added B-CNF material in the wide-temperature-range electrolyte is 0.3wt% to 0.5wt%. For example, it can be 0.3wt%, 0.4wt%, 0.5wt%, etc.

[0097] The mixture can be treated with ultrasound (500W, 40kHz), and the ultrasound treatment time is no less than 30 minutes. Ultrasonic treatment can break up the secondary agglomeration of the B-CNF material, causing it to form monodisperse nanoparticles in the electrolyte. Through ultrasonic treatment, the B-CNF material can be better dispersed in the electrolyte, improving the stability and ion conductivity of the electrolyte.

[0098] Step S33: The mixture is subjected to a second heating and stirring treatment under reduced pressure to obtain the wide-temperature-range electrolyte.

[0099] In the above steps, the mixture is subjected to a second heating and stirring treatment under reduced pressure to obtain a wide-temperature-range electrolyte.

[0100] The decompression state can be a near-vacuum state; furthermore, the pressure in the decompression state is ≤10. -3 Pa.

[0101] The specific operation can be carried out in a vacuum reactor. The ultrasonically treated mixture is transferred to the vacuum reactor, ensuring that the pressure inside the reactor is controlled at ≤10. -3 Pa.

[0102] Furthermore, the heating temperature for the second heating and stirring treatment is 80°C. The stirring time for the second heating and stirring treatment is no less than 2 hours.

[0103] For example, heating and stirring at a constant temperature of 80°C for 2 hours ensures that the B-CNF material can be fully embedded in the hydrogen bond dynamic network, ensuring the reaction proceeds completely. Reduced pressure conditions allow the reaction to proceed in a vacuum environment, avoiding interference from impurities and moisture.

[0104] Through heating and stirring, B-CNF materials can be embedded into a dynamic hydrogen bond network, forming three-dimensional lithium-conducting channels. This structure provides an efficient and continuous transport path for lithium ions, significantly improving the ionic conductivity of the electrolyte. The formed three-dimensional lithium-conducting channels can improve the performance of the electrolyte over a wide temperature range, ensuring that the electrolyte maintains low viscosity at low temperatures and low vapor pressure at high temperatures, thereby enhancing the battery's low-temperature endurance and high-temperature storage life.

[0105] In summary, this embodiment embeds B-CNF material into a functional solution containing lithium salt. This includes premixing, ultrasonication, and heating / stirring to form a three-dimensional lithium-conducting channel. These steps ensure that the B-CNF material is uniformly dispersed in the electrolyte and tightly bound to the dynamic hydrogen bond network, thereby significantly improving the performance of the wide-temperature-range electrolyte.

[0106] In some embodiments, the lithium salt is a composite lithium salt prepared from lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium difluorooxalate borate (LiDFOB);

[0107] In this embodiment, a composite lithium salt consisting of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium difluorooxalate borate (LiDFOB) was chosen because this combination can significantly improve the ionic conductivity of the electrolyte over a wide temperature range while optimizing its temperature adaptability. LiTFSI exhibits high conductivity and low viscosity at low temperatures, which helps to improve lithium-ion transport efficiency; while LiDFOB demonstrates good thermal stability and the ability to reduce side reactions at high temperatures.

[0108] Furthermore, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium difluorooxalateborate (LiDFOB), as dual-coordinated lithium salts, can minimize the number of solvent coordinations, increase the redox window, and thus improve the dual stability of the high-potential positive electrode and the low-potential negative electrode.

[0109] The synergistic effect of these two compounds [lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium difluorooxalate borate (LiDFOB)] not only further enhances the ion conductivity and redox window of the electrolyte, but also forms a stable interface layer on the electrode surface, reducing interfacial impedance and thus improving the battery's cycle stability and fast charge / discharge performance. The use of this composite lithium salt allows the electrolyte to maintain high efficiency and stable performance under both low and high temperature conditions, significantly improving the overall performance and lifespan of lithium-ion batteries.

[0110] The preparation method of the composite lithium salt includes: mixing lithium bis(trifluoromethanesulfonyl)imide and lithium difluorooxalate borate, followed by ultrasonic dispersion and stirring to obtain the composite lithium salt;

[0111] The composite lithium salt has at least one of the following characteristics:

[0112] A. The molar ratio of lithium bis(trifluoromethanesulfonyl)imide and lithium difluorooxalateborate in the composite lithium salt is (3.5~4.5):(0.5~1.5).

[0113] B. The conductivity of the composite lithium salt is >4.5 mS / cm.

[0114] For example, LiTFSI (1.2M) and LiDFOB (0.3M) were added in batches, and the mixture was treated with alternating ultrasonic dispersion (500W power, 40kHz frequency) and magnetic stirring (800rpm speed) for 3 hours to ensure that the conductivity was >4.5ms / cm, thus obtaining a composite lithium salt.

[0115] The above describes the molar ratio of lithium bis(trifluoromethanesulfonyl)imide to lithium difluorooxalate borate as (3.5~4.5):(0.5~1.5). For example, the ratio of lithium bis(trifluoromethanesulfonyl)imide can be 3.5, 4, 4.5, etc.; the ratio of lithium bis(trifluoromethanesulfonyl)imide can be 0.5, 1, 1.5, etc.

[0116] In this embodiment, a wide-temperature-range electrolyte is provided, which is prepared by the wide-temperature-range electrolyte preparation method described in any of the foregoing embodiments.

[0117] In this application embodiment, a battery is provided, including a wide-temperature-range electrolyte as described in the foregoing embodiments.

[0118] In addition to the wide-temperature-range electrolyte, the aforementioned battery may also include, but is not limited to, a positive electrode (including active material, conductive agent, binder, and aluminum foil current collector), a negative electrode (including active material, conductive agent, binder, and copper foil current collector), a separator (for separating the positive and negative electrodes and allowing lithium ions to pass through), a casing (providing encapsulation and physical protection), current collectors (for current collection and conduction), and other components (such as tabs, safety valves, temperature sensors, etc.). These components work together to ensure the battery operates efficiently and safely over a wide temperature range, while improving its overall performance and lifespan.

[0119] In this application embodiment, an electrical device is provided, including a battery as described in the foregoing embodiments.

[0120] The aforementioned "electrical equipment" refers to devices that use batteries (especially batteries containing wide-temperature-range electrolytes) as their primary or auxiliary power source. These devices are widely used in various fields, including but not limited to electric vehicles, hybrid vehicles, portable electronic devices (such as smartphones, tablets, and laptops), wearable devices (such as smartwatches and health monitoring bracelets), medical devices (such as portable medical monitoring devices and pacemakers), energy storage systems (for grid energy storage, solar / wind energy storage), drones, power tools, and other devices requiring efficient and reliable power support. By using batteries with wide-temperature-range electrolytes, these electrical equipment can maintain high performance and high safety over a wider temperature range, thus meeting the stringent requirements of different application scenarios.

[0121] The present invention will be further illustrated below with specific embodiments. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.

[0122] Table 1. Comparison of key parameters in the comparative examples of the embodiments.

[0123]

[0124] In Table 1, FEC represents fluoroethylene carbonate; PFHA represents perfluorohexanoic acid; TFEB represents diethyl tetrafluoroborate; LiTFSI represents lithium bis(trifluoromethanesulfonyl)imide; LiDFOB represents lithium difluorooxalate borate; M represents molar concentration, which represents the amount of substance contained in each liter of solution.

[0125] Example 1

[0126] In this embodiment, a wide-temperature-range electrolyte was prepared, and a battery cell was prepared based on the wide-temperature-range electrolyte.

[0127] Experimental methods:

[0128] (1) Preparation of functional solution: Mix fluoroethylene carbonate (FEC), perfluorohexanoic acid (PFHA), and diethyl tetrafluoroborate (TFEB), under argon protection (dew point ≤ -60℃), in a vacuum reactor (pressure ≤ 10). -3 Stirring at 80°C for 8 hours in a solution containing a dynamic hydrogen bond cross-linking network forms a functional solution.

[0129] Fourier Transform Infrared Spectroscopy (FTIR): at 3200 cm⁻¹ -1 ~3500cm -1 A broad peak appears (hydrogen bond OH stretching vibration), and the peak position shifts by 10 cm at low temperature (-40℃). -1 This indicates that the hydrogen bond flexibility is enhanced.

[0130] Molecular dynamics simulations (MD) showed that the average hydrogen bond lifetime decreased from 12 ps at 25 °C to 4 ps at -40 °C, demonstrating the improved dynamic reconstruction capability of hydrogen bonds at low temperatures.

[0131] (2) Preparation of composite lithium salt: In a glove box (water and oxygen content less than 10 ppm), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) and LiDFOB (lithium difluorooxalate borate) were compounded to obtain a composite lithium salt with a total molar concentration of 4 M. Alternating sonication (500 W, 40 kHz) and magnetic stirring (800 rpm) for 3 hours were performed to ensure complete dissociation of the lithium salt. The concentration was 6.8 mS / cm at -40℃ (conventional electrolyte: 0.1 mS / cm); and 14.2 mS / cm at 80℃ (conventional system: 18.5 mS / cm).

[0132] (3) Preparation of B-CNF material: In the reaction vessel, 12g of carbon nanofibers (CNF) were taken, with graphitization degree (Id / Ig=1.52) and particle size (Dv10=20nm, dV) max =80nm), d002=0.4lnm, specific surface area=560m 2 / g , the carbon nanofibers were refluxed at 120℃ for 6 hours in a mixed solution of 60mL trimethyl borate and 20mL concentrated sulfuric acid (the volume ratio of trimethyl borate to concentrated sulfuric acid in the mixed solution was 3:1) to obtain high-flux carbon nanofibers with a boron doping content of 6at%. The B-CNF nanofibers were washed three times with deionized water and then three times with ethanol to remove surface impurities. Under argon protection (dew point ≤ -60℃), they were vacuum dried. After drying, their graphitization degree (Id / Ig = 1.53), particle size (Dv10 = 18nm, dVmax = 75nm), d002 = 0.41nm, and specific surface area = 580m² were measured. 2 / g.

[0133] B-CNF material was obtained after planetary ball milling (zirconia balls, 3 mm, 500 rpm, 4 hours). The aggregate size was ≤200 nm (dynamic light scattering detection), and the Raman spectroscopy showed Id / Ig = 0.92, indicating that surface defect sites and borate ester groups synergistically enhance lithium-ion adsorption capacity.

[0134] X-ray photoelectron spectroscopy analysis: The B1s peak is located at 192.5 eV (BO bond), which is related to the F in the electrolyte. - The interaction energy is reduced to 0.25 eV (density functional theory calculation).

[0135] (4) Preparation of wide temperature range electrolyte: The functional solution obtained in step (1) and the composite lithium salt obtained in step (2) are premixed with magnetic stirring (800 rpm) for 10 minutes, and then B-CNF material (0.4 wt%) is gradually added to avoid excessive local concentration.

[0136] The secondary aggregation of B-CNF was disrupted by ultrasonic treatment at 500W / 40kHz for 30 minutes, which promoted its monodispersity in the electrolyte.

[0137] Transfer the mixture to a vacuum reactor (pressure ≤10). -3 By stirring at 80℃ for 2 hours, B-CNF is embedded into a dynamic hydrogen bond network to form a three-dimensional lithium conduction channel, thus obtaining a wide-temperature-range electrolyte.

[0138] (5) Preparation of battery cells: The positive electrode is a lithium manganese oxide system (active material loading of 97% + conductive agent of 1.5% + PVDF of 1.5%), and the negative electrode is graphite (active material loading of 96.5% + conductive agent of 0.5% + (SBR + CMC) total of 3.0%) to make a 20Ah square-shell dry cell. Among them, SBR is Styrene-Butadiene Rubber, CMC is Carboxymethyl Cellulose, and PVDF is Polyvinylidene Fluoride.

[0139] Example 2

[0140] In the embodiments, a wide-temperature-range electrolyte was prepared, and a battery cell was prepared based on the wide-temperature-range electrolyte.

[0141] Experimental methods:

[0142] The method used in this embodiment is basically the same as that in Embodiment 1. The differences are shown in the process parameters in Table 1.

[0143] Example 3

[0144] In this embodiment, a wide-temperature-range electrolyte was prepared, and a battery cell was prepared based on the wide-temperature-range electrolyte.

[0145] The experimental method is basically the same as that used in Example 1, with the differences being the process parameters in Table 1.

[0146] Example 4

[0147] In this embodiment, a wide-temperature-range electrolyte was prepared, and a battery cell was prepared based on the wide-temperature-range electrolyte.

[0148] The experimental method is basically the same as that used in Example 1. The difference is that in step (3), 72g of carbon nanofibers (CNF) are refluxed at 120°C for 6 hours in 60mL of trimethyl borate / 20mL of concentrated sulfuric acid (volume ratio 3:1) to obtain nano high-throughput carbon, and the boron doping amount becomes 1at.

[0149] Example 5

[0150] In this embodiment, a wide-temperature-range electrolyte was prepared, and a battery cell was prepared based on the wide-temperature-range electrolyte.

[0151] The experimental method is basically the same as that used in Example 1. The difference is that in step (3), 6g of carbon nanofibers (CNF) are refluxed at 120°C for 6 hours in 60mL of trimethyl borate / 20mL of concentrated sulfuric acid (volume ratio 3:1) to obtain nano high-throughput carbon, and the boron doping amount becomes 12at.

[0152] Example 6

[0153] In this embodiment, a wide-temperature-range electrolyte was prepared, and a battery cell was prepared based on the wide-temperature-range electrolyte.

[0154] The experimental method is basically the same as that used in Example 1, except that the process parameters are referenced in Table 1.

[0155] Comparative Example 1

[0156] The comparative example uses a method that is basically the same as that used in Example 1. The difference is that in step (3), 12g of carbon nanofibers (CNF) were refluxed at 120°C for 6 hours in 60mL of trimethyl borate / 60mL of concentrated sulfuric acid (volume ratio 1:1) to obtain nano-high-flux carbon. In this example, due to the excessive amount of concentrated sulfuric acid, the local temperature was too high during the preparation process, resulting in uneven boron doping in the material, with different parts having doping amounts of 3at% to 30at%.

[0157] Comparative Example 2

[0158] The comparative example uses a method that is basically the same as that used in Example 1. The differences are shown in Table 1.

[0159] Comparative Example 3

[0160] The comparative example uses a method that is basically the same as that used in Example 1, the only difference being the use of a single lithium salt, 4.95 mol LiTFSI.

[0161] Comparative Example 4

[0162] The comparative example uses a method that is basically the same as that used in Example 1. The differences are shown in Table 1.

[0163] Comparative Example 5

[0164] In this embodiment, an electrolyte was prepared, and a battery cell was obtained based on the electrolyte.

[0165] The experimental method used a conventional lithium manganese oxide electrolyte (the mass ratio of each component was: EC:EMC:VC:LiPF6=25.5:59.4:2:13.1), and the parameters such as the molar concentration of lithium salt are shown in Table 1. The conductivity was 8.1 mS / cm.

[0166] Comparative Example 6

[0167] In this embodiment, an electrolyte was prepared, and a battery cell was obtained based on the electrolyte.

[0168] The experimental method used a conventional low-temperature electrolyte of lithium manganese oxide (the mass ratio of each component is: EC:EMC:DMC:VC:LiPF6:LiFSi=25:33.4:25:2:10.0:4.6), and the parameters such as the molar concentration of lithium salt are referred to Table 1. The conductivity is 9.8 mS / cm.

[0169] Test experiment:

[0170] 1. Experimental materials and equipment:

[0171] (1) Battery cells: Battery cells prepared in Examples 1-6 and Comparative Examples 1-6 respectively.

[0172] (2) Testing equipment:

[0173] Electrochemical testing system: used to measure electrochemical performance parameters of batteries such as discharge DC internal resistance (DCR) and discharge capacity retention rate. It can accurately control the current, voltage and other conditions during the charging and discharging process and record relevant data.

[0174] Temperature chamber: Used to simulate different temperature environments, such as -20℃, 45℃, 60℃, etc., to test the performance of batteries at different temperatures, ensure temperature stability and accuracy, and keep the batteries in the set temperature environment during the test.

[0175] Charge-discharge cycle tester: Used in conjunction with an electrochemical testing system to perform cyclic charge-discharge tests on batteries in order to evaluate performance indicators such as capacity retention during multiple charge-discharge cycles.

[0176] 2. Testing Method:

[0177] (1) Low temperature performance test: Each group of battery cells was placed in a constant temperature chamber set to -20℃. After the battery cell temperature stabilized, the electrochemical test system was used to perform a discharge test at a discharge rate of 1C.

[0178] Record the discharge DC internal resistance (DCR) of each group of batteries. By comparing it with the initial internal resistance (R0) of the battery, obtain the ratio of the discharge DC internal resistance to R0. This ratio is used to evaluate the change of the battery's internal resistance at low temperatures and reflects the ease or difficulty of processes such as ion transport inside the battery.

[0179] Simultaneously, the capacity retention rate of each group of batteries when discharged to the termination voltage at -20℃ is recorded, i.e., the percentage of discharge capacity to rated capacity, to measure the battery's discharge performance in low-temperature environments and understand the proportion of electricity that the battery can release under low-temperature conditions. The -20℃ 1C discharge test method is to charge the battery cell at room temperature (25±2℃) to 4.2V at 1C, cut off at 0.05C, let it rest for 30 minutes, discharge it at 1C to 2.7V, let it rest for 30 minutes, record the initial capacity, then fully charge it, and after full charging, place it in a -20℃±2℃ constant temperature charge-discharge machine and let it stand for 6 hours before discharging it at 1C to 2.7V, and record the discharge capacity. The discharge capacity at -20℃ is compared with the discharge capacity at room temperature to obtain the capacity retention rate.

[0180] The -20℃ DCR ​​test involves charging the battery cell at room temperature (25±2℃) to 4.2V using 1C, stopping at 0.05C, letting it rest for 30 minutes, discharging it at 1C to 2.7V, letting it rest for 30 minutes, recording the initial capacity, then fully charging it again. After full charging, the cell is placed in a -20℃±2℃ constant temperature charge-discharge machine and left to stand for 6 hours. Then, it is discharged at 0.2C for 10 seconds, discharged at 1C for 1 second, and cycled to 2.7V. The discharge DC internal resistance of the full discharge SOC process is recorded, and the discharge DC internal resistance at 50% SOC is compared.

[0181] (2) High temperature storage performance test: Each group of fully charged battery cells was placed in a constant temperature chamber set at 60°C for a 7-day high temperature storage test.

[0182] After storage, the battery cells are removed and their capacity retention rate is measured using an electrochemical testing system. This is the percentage of battery capacity after storage compared to the battery capacity before storage, in order to assess the capacity loss of the battery after long-term storage in a high-temperature environment.

[0183] Then, the battery is subjected to charge-discharge cycles to restore it to normal operating conditions. The capacity recovery rate is measured again, which is the percentage of the battery capacity after recovery compared to the initial capacity before storage. This is used to understand the proportion of capacity that the battery can recover after high-temperature storage and a certain recovery process, reflecting the battery's reversibility. The test method for 7 days of fully charged storage at 60℃ involves charging the cell at room temperature (25±2℃) at 1C to 4.2V, stopping at 0.05C, resting for 30 minutes, discharging at 1C to 2.7V, resting for 30 minutes, recording the initial capacity, then fully charging again. After full charging, the cell is placed in a 60℃±2℃ constant temperature chamber for 7 days. After storage, it is cooled to room temperature for 6 hours. The cycle is repeated 3 times according to the initial capacity steps. The smaller capacity from the 2nd or 3rd cycle is taken as the maintenance capacity, and compared with the initial capacity to obtain the capacity retention rate.

[0184] (3) Cycle life test: Each group of battery cells is subjected to cycle charge and discharge test under the set temperature conditions (e.g., 45℃). The cycle is carried out at a certain charge and discharge rate (e.g., 1C charge to 4.2V, 0.05C cut off, rest for 30 minutes, 1C discharge to 2.7V, rest for 30 minutes) until the battery capacity retention rate reaches 80%.

[0185] The number of cycles when each group of batteries reaches 80% capacity retention is recorded to evaluate the cycle life of the battery under specific temperature conditions, reflecting the stability of the battery during repeated charge and discharge processes.

[0186] 3. Test Results:

[0187] Table 2. Comparison of battery performance between the examples and comparative examples.

[0188]

[0189] In Table 2, at -20℃, DCR(SOC50%)R0=36mΩ.

[0190] analyze:

[0191] (1) Low temperature performance test:

[0192] Discharge DC internal resistance (DCR): The discharge DC internal resistance of Examples 1-6 is all below 1 R0, with Example 2 having the lowest discharge DC internal resistance at 0.41 R0. The discharge DC internal resistance of Comparative Examples 1-6 is all above 0.63 R0, with Comparative Example 5 having the highest discharge DC internal resistance at R0. This indicates that the wide-temperature-range electrolyte of this application can significantly reduce the battery's internal resistance and improve ion transport efficiency at low temperatures. This is because this application achieves a balance between low viscosity and high ion conductivity at low temperatures by constructing a hydrogen bond dynamic network and embedding modified B-CNF material. The hydrogen bond dynamic network can disintegrate hydrogen bonds at low temperatures, promoting the solvation of lithium ions at low temperatures. It has good flexibility and can quickly respond to the needs of ion transport. LiTFSI has a high degree of dissociation, high ionic conductivity, and high kinetics, while the embedding of B-CNF material further optimizes the ion transport path and reduces the resistance to ion transport.

[0193] 1C discharge capacity retention: The 1C discharge capacity retention rates of Examples 1-6 are all above 86%, with Example 2 exhibiting the highest 1C discharge capacity retention rate at 99%. In contrast, the 1C discharge capacity retention rates of Comparative Examples 1-6 are all below 92%, with Comparative Example 6 showing the lowest at 77%. This demonstrates that the wide-temperature-range electrolyte of this application can effectively maintain the battery's discharge capacity at low temperatures, improving the battery's low-temperature performance. This is because the electrolyte of this application has low viscosity and high ionic conductivity at low temperatures, ensuring rapid and stable lithium-ion transport at low temperatures, thereby improving the battery's discharge capacity retention rate.

[0194] (2) High-temperature storage performance test:

[0195] 7-day storage capacity retention at 60℃: The 7-day storage capacity retention rates of Examples 1-6 at 60℃ are all above 91.2%, with Example 2 showing the highest retention rate at 96.9%. In contrast, the retention rates of Comparative Examples 1-6 are all below 93.6%, with Comparative Example 3 showing the lowest retention rate at 89.1%. This indicates that the wide-temperature-range electrolyte of this application can effectively maintain battery capacity and reduce capacity loss at high temperatures. This is because the presence of a dynamic hydrogen bond network in this application increases the boiling point of the electrolyte at high temperatures, preventing gas generation due to side reactions. The use of LiTFSI and LiDFOB dual lithium salts forms a relatively stable double coordination structure, effectively suppressing lithium salt decomposition at high temperatures. Furthermore, the B-CNF material formed by surface modification treatment exhibits good stability at high temperatures, reducing the occurrence of side reactions and thus improving the high-temperature stability of the electrolyte, thereby enhancing the high-temperature storage performance of the battery.

[0196] 60℃ 7-day storage capacity recovery rate: The 60℃ 7-day storage capacity recovery rates of Examples 1-6 were all above 93.3%, with Example 2 showing the highest recovery rate at 98.6%. In contrast, the recovery rates of Comparative Examples 1-6 were all below 93.6%, with Comparative Example 3 showing the lowest at 90.9%. This indicates that the wide-temperature-range electrolyte of this application can better restore battery capacity and improve battery reversibility after high-temperature storage. This is because the electrolyte of this application has a low vapor pressure and good chemical stability at high temperatures, which reduces electrolyte volatilization and decomposition, thus better restoring battery capacity after high-temperature storage.

[0197] (3) Cycle life test: The number of cycles at 45°C to 80% capacity retention in Examples 1-6 were all above 532. Among them, Example 2 had the most cycles at 45°C to 80% capacity retention, at 690 cycles. In contrast, the number of cycles at 45°C to 80% capacity retention in Comparative Examples 1-6 were all below 530 cycles, with Comparative Example 3 having the fewest cycles at 45°C to 80% capacity retention, at 420 cycles. This indicates that the wide-temperature-range electrolyte of this application can significantly improve the cycle life of the battery at 45°C and reduce capacity decay during cycling. This is because the electrolyte of this application can maintain stable ion conduction performance and electrode interface stability during cycling, reducing side reactions and irreversible lithium-ion loss during cycling, thereby improving the cycle life of the battery.

[0198] in conclusion:

[0199] (1) Adjustment of solvent ratio affects the formation of hydrogen bond network: As can be seen from Examples 1-6, the functional solutions obtained by mixing fluoroethylene carbonate (FEC), perfluorohexanoic acid (PFHA), and diethyl tetrafluoroborate (TFEB) in different molar ratios have a significant impact on battery performance. When the molar ratio of FEC:PFHA:TFEB is 1:4:8 (Example 2), the battery's low-temperature performance and high-temperature storage performance are both optimal, indicating that the dynamic hydrogen bond network formed at this time has the best ion conduction performance and temperature adaptability. In Comparative Example 4, the molar ratio of FEC:PFHA:TFEB is 4:5:4. Compared with the examples, all battery performances have decreased, which further proves the importance of solvent ratio for hydrogen bond network formation.

[0200] (2) Advantages of combining lithium salts LiTFSI and LiDFOB: Examples 1-6 all used composite lithium salts combining lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium difluorooxalate borate (LiDFOB). Compared with Comparative Examples 2 and 3, the low-temperature performance and high-temperature storage performance of the batteries were significantly better than those using only a single lithium salt, LiTFSI, or conventional lithium salts. This indicates that LiTFSI has a high degree of dissociation and ionic conductivity, but its anion-solvent double coordination is unstable and easily triggers side reactions; while LiDFOB can form a stable double coordination structure with LiTFSI, inhibiting the decomposition of lithium salt, thereby improving the electrochemical stability window at high voltage and high temperature and enhancing the overall performance of the battery.

[0201] (3) Effects of boron doping and addition amount of B-CNF material on performance: In Examples 1-6, the boron doping amount of B-CNF material was approximately 6 at%, and the addition amount was between 0.3 wt% and 0.5 wt%, resulting in good battery performance. However, in Comparative Example 1, the boron doping amount was uneven, leading to a decrease in battery performance; in Comparative Examples 4 and 5, the boron doping amounts were 1 at% and 12 at%, respectively, and the battery performance also decreased. This indicates that when the boron doping amount is too low, the B-CNF material's improvement effect on the interface is not significant and cannot effectively improve ion conductivity; when the boron doping amount is too high, the porous structure of the B-CNF material may collapse and lose its function. At the same time, the addition amount of B-CNF material also affects the performance of the electrolyte. Too little addition will affect the ionic conductivity, while too much addition will cause electrolyte sedimentation and affect stability. The addition amount of B-CNF material in Examples 1-6 was optimized to fully exert its effect on improving electrolyte performance and enhance the low-temperature performance and high-temperature stability of the battery.

[0202] (4) As can be seen from the above analysis, the wide-temperature-range electrolyte and its preparation method of this application can effectively solve the problem of poor performance of existing lithium-ion batteries under extreme temperature conditions. By constructing a dynamic hydrogen bond network and embedding modified B-CNF materials, a balance between low viscosity at low temperatures and high stability at high temperatures is achieved, while improving ion conduction performance and significantly enhancing the battery performance in a wide temperature range, thus meeting the requirements for high temperature adaptability. The electrolyte of this application has low internal resistance and high discharge capacity retention at low temperatures, good capacity retention and recovery rate at high temperatures, and can maintain stable performance during cycling, extending the battery's service life and providing strong technical support for the application of lithium-ion batteries in a wider temperature range.

[0203] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a wide-temperature-range electrolyte, characterized in that, include: A functional solution with a dynamic hydrogen bond network is obtained by mixing and reacting fluoroethylene carbonate, perfluorohexanoic acid and diethyl tetrafluoroborate; wherein the functional solution comprises fluoroethylene carbonate, perfluorohexanoic acid and diethyl tetrafluoroborate in a molar ratio of (0.5~1.5):(3.5~4.5):(7.5~8.5). Carbon nanofibers were surface-modified using trimethyl borate and sulfuric acid to form a B-CNF material with surface defects and boron functional group modification; the boron content of the B-CNF material was 5 at%~8 at% The B-CNF material is embedded into the hydrogen bond dynamic network of the functional solution containing lithium salt to obtain a wide-temperature-range electrolyte with three-dimensional lithium conduction channels; the concentration of the added B-CNF material in the wide-temperature-range electrolyte is 0.3wt%~0.5wt%; the lithium salt is a composite lithium salt prepared from lithium bis(trifluoromethanesulfonyl)imide and lithium difluorooxalateborate.

2. The method for preparing the wide-temperature-range electrolyte as described in claim 1, characterized in that, The reaction of fluoroethylene carbonate, perfluorohexanoic acid, and diethyl tetrafluoroborate to obtain a functional solution with a dynamic hydrogen bond network includes: Fluoroethylene carbonate, perfluorohexanoic acid, and diethyl tetrafluoroborate were mixed in a specific molar ratio to obtain the first mixture. The first mixture is heated and stirred under reduced pressure to obtain the functional solution.

3. The method for preparing the wide-temperature-range electrolyte as described in claim 2, characterized in that, The first heating and stirring treatment under reduced pressure conditions has at least one of the following conditions: A. The stirring time is at least 8 hours; B. The heating temperature is 80°C; C. The first heating and stirring treatment is conducted under reduced pressure; D. The pressure during the first heating and stirring treatment is ≤10. -3 Pa; and / or, The dew point in the environment during the mixing treatment is ≤-60℃; and / or, The humidity in the environment during the mixing process is <0.1ppm.

4. The method for preparing the wide-temperature-range electrolyte as described in claim 1, characterized in that, The surface modification treatment includes: Carbon nanofibers were placed in a mixed solution of trimethyl borate and sulfuric acid and refluxed under heating conditions to obtain high-throughput carbon nanofibers. The high-throughput nanocarbon is washed, dried, and ball-milled to obtain the B-CNF material.

5. The method for preparing the wide-temperature-range electrolyte as described in claim 4, characterized in that, The heating condition is at a temperature of 120°C; and / or, The reflux reaction time is not less than 6 hours; and / or, The washing process consists of rinsing with water and / or an organic solvent at least three times; and / or, The drying process is a reduced-pressure drying process; and / or, The average particle size of the B-CNF material after ball milling is ≤200nm.

6. The method for preparing the wide-temperature-range electrolyte as described in claim 1, characterized in that, The step of embedding the B-CNF material into the hydrogen bond dynamic network of the functional solution containing lithium salt to obtain a wide-temperature-range electrolyte with three-dimensional lithium conduction channels includes: The lithium salt and the functional solution are premixed to obtain a second mixture; The B-CNF material is added to the second mixture and ultrasonically treated to obtain a mixture. The mixture is subjected to a second heating and stirring treatment under reduced pressure to obtain the wide-temperature-range electrolyte.

7. The method for preparing the wide-temperature-range electrolyte as described in claim 6, characterized in that, The mixing speed during the mixing process is 800 rpm; and / or, The premixing treatment time is not less than 10 minutes; and / or, The concentration of the lithium salt in the wide-temperature-range electrolyte is 1M~5M; and / or, The ultrasonic treatment time is not less than 30 minutes; and / or, The pressure under the decompression state is ≤10. -3 Pa; and / or, The heating temperature for the second heating and stirring treatment is 80°C; and / or, The stirring time for the second heating and stirring treatment is no less than 2 hours.

8. The method for preparing the wide-temperature-range electrolyte as described in claim 1, characterized in that, The preparation method of the composite lithium salt includes: mixing lithium bis(trifluoromethanesulfonyl)imide and lithium difluorooxalate borate, followed by ultrasonic dispersion and stirring to obtain the composite lithium salt; The composite lithium salt has at least one of the following characteristics: A. The molar ratio of lithium bis(trifluoromethanesulfonyl)imide and lithium difluorooxalateborate in the composite lithium salt is (3.5~4.5):(0.5~1.5); B. The conductivity of the composite lithium salt is >4.5 mS / cm.

9. A wide-temperature-range electrolyte, characterized in that, It is prepared by the method for preparing a wide temperature range electrolyte as described in any one of claims 1-8.

10. A battery, characterized in that, Includes the wide-temperature-range electrolyte as described in claim 9.

11. An electrical-related device, characterized in that, Includes the battery as described in claim 10.

Images