Gel electrolyte precursor and application thereof

Abstract

The invention relates to the technical field of electrochemistry, in particular to a gel electrolyte precursor and application thereof. A gel skeleton monomer of the gel electrolyte precursor is dicycloheptadiene, and the gel electrolyte precursor further comprises an additive, a cross-linking agent, a polymerization initiator and fluorine-containing lithium salt; the content of the dicycloheptadiene relative to the total mass of the gel electrolyte precursor accounts for 1%-10% of the total mass of the gel electrolyte precursor. The invention designs and constructs a novel cross-linked gel polymer electrolyte by regulating and controlling the contents of dicycloheptadiene and acrylate in a precursor solution. By introducing dicycloheptadiene, not only is a transmission channel of lithium ions improved, but also dissociation and transmission capabilities of the gel electrolyte to the lithium ions are enhanced. Therefore, the cross-linked copolymer gel electrolyte disclosed by the invention shows excellent lithium ion transmission performance at room temperature, and the total battery performance of the cross-linked copolymer gel electrolyte is also remarkably improved.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a gel electrolyte precursor and its application. Background Technology

[0002] With the rapid development of new energy technologies and electric vehicles, energy storage devices are facing increasingly stringent performance requirements, especially in terms of safety, charging and discharging platforms, and energy density.

[0003] Lithium-ion batteries are among the most widely used batteries today. However, the graphite anode commonly used in current lithium-ion batteries has a limited capacity for lithium ions, which restricts their energy density. Furthermore, the cathode materials in current lithium-ion secondary batteries have an upper limit on voltage; if the voltage is too high, it can easily lead to electrolyte decomposition.

[0004] To meet these needs, high-voltage lithium metal batteries are a potential solution to the aforementioned problems of lithium-ion batteries. High-voltage lithium metal batteries use metallic lithium as the negative electrode, which has extremely high theoretical specific capacity and the lowest electrochemical potential; at the same time, they are matched with high-voltage positive electrode materials in order to achieve a breakthrough increase in energy density.

[0005] High-voltage cathode materials stand out due to their high charge / discharge voltage and energy density, while lithium metal anode materials have attracted much attention for their ultra-high specific capacity and extremely low electrochemical potential. Despite the excellent performance of these two materials, there are few electrolyte materials specifically designed for high-voltage lithium metal batteries in practical applications. Liquid electrolytes perform poorly in terms of high voltage resistance and suppression of lithium dendrite growth, and are prone to causing fires; all-solid-state electrolytes are limited by high cost, environmentally unfriendly preparation processes, poor electrode wetting performance, and narrow electrochemical window, making them difficult to widely apply. Summary of the Invention

[0006] The purpose of this application is to provide a gel electrolyte precursor and its application.

[0007] According to a first aspect of this application, this application provides a gel electrolyte precursor, wherein the gel backbone monomer of the gel electrolyte precursor is dicycloheptadecene, and the gel electrolyte precursor further includes additives, crosslinking agents, polymerization initiators and fluorinated lithium salts; the content of dicycloheptadecene relative to the total mass of the gel electrolyte precursor is 1% to 10%.

[0008] In some embodiments of this application, the fluorinated lithium salt is at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, and lithium tetrafluoroborate.

[0009] In some embodiments of this application, the content of the fluorinated lithium salt relative to the total mass of the gel electrolyte precursor is 5% to 20%.

[0010] In some embodiments of the present application, the cross-linking agent is an acrylate; In some embodiments of the present application, the cross-linking agent is an acrylate containing two or more carbon-carbon double bonds; In some embodiments of the present application, the cross-linking agent is at least one of polyethylene glycol diacrylate, 1,3-butanediol diacrylate, vinyl diacrylate, triethylene glycol dimethacrylate, trimethylolpropane ethoxylate triacrylate, pentaerythritol tetraacrylate.

[0011] In some embodiments of the present application, the content of the cross-linking agent accounts for 5-10% of the total mass of the gel electrolyte precursor.

[0012] In some embodiments of the present application, the additive is a fluorine-containing carbonate; In some embodiments of the present application, the additive is at least one of fluoroethylene carbonate, difluoroethylene carbonate, and trifluoroacrylate.

[0013] In some embodiments of the present application, the polymerization initiator is an azo initiator; In some embodiments of the present application, the polymerization initiator is at least one of dimethyl azobis isobutyrate, azobis isopropyl cyanide, and azobis isobutyronitrile. In some embodiments of the present application, the content of the polymerization initiator accounts for 0.075-0.15% of the total mass of the gel electrolyte precursor.

[0014] The second aspect of the present application provides a preparation method of a gel electrolyte, wherein the precursor of the first aspect is processed as follows: the fluorine-containing lithium salt is dissolved in the additive, mixed uniformly, then the dicycloheptadiene and the cross-linking agent are added, mixed uniformly, the polymerization initiator is added and mixed uniformly to obtain the solution for preparing the gel electrolyte, and the solution for preparing the gel electrolyte is polymerized and gelled, then heated and solidified to obtain the gel electrolyte.

[0015] The third aspect of the present application provides a gel electrolyte prepared by the method of the second aspect.

[0016] The fourth aspect of the present application provides a battery, which comprises the gel electrolyte of the third aspect and a positive electrode, a separator, and a negative electrode. In some embodiments of the present application, the separator is any one of a cellulose separator, a polyethylene battery separator, a polypropylene battery separator, and a polyethylene / polypropylene composite battery separator. In some embodiments of the present application, the positive electrode comprises a positive electrode current collector, and the positive electrode current collector is a carbon-coated aluminum foil. In some embodiments of the present application, the positive electrode comprises a positive electrode active material, which is any one of a lithium iron phosphate positive electrode, a lithium iron manganese phosphate positive electrode, a lithium cobaltate positive electrode, a nickel cobalt manganese 811 positive electrode.

[0017] The fifth aspect of the present application provides an electronic device comprising the battery according to the fourth aspect.

[0018] Beneficial effects: By adjusting the content of dicycloheptadiene and acrylate in the precursor solution, a new cross-linked gel polymer electrolyte is designed and constructed. By introducing dicycloheptadiene, not only the transmission channel of lithium ions is improved, but also the dissociation and transmission capacity of gel electrolyte to lithium ions is enhanced. Therefore, the cross-linked copolymer gel electrolyte of the present application exhibits excellent lithium ion transmission performance at room temperature, and the performance of the full battery is also significantly improved. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present application will be described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art based on the present application belong to the scope of protection of the present application.

[0020] Although gel electrolyte effectively integrates the mechanical stability of polymer matrix and the ionic conductivity of electrolyte, it exhibits unique advantages in inhibiting lithium dendrite growth and improving battery safety. However, due to the poor internal ion migration channel, low lithium ion migration number, and often unsatisfactory electrode / electrolyte interface compatibility, the overall lithium ion transmission kinetics is slow. Therefore, systematically improving the lithium ion transmission performance has become the core issue to promote the development of high-performance gel electrolyte.

[0021] According to the first aspect of the present application, the present application provides a gel electrolyte precursor, the gel skeleton monomer of the gel electrolyte precursor is dicycloheptadiene, and the gel electrolyte precursor further comprises an additive, a cross-linking agent, a polymerization initiator and a fluorine-containing lithium salt; the content of the dicycloheptadiene accounts for 1% to 10% of the total mass of the gel electrolyte precursor. In some specific embodiments, the content of the dicycloheptadiene relative to the total mass of the gel electrolyte precursor can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a value within the range formed by any two of these values.

[0022] This application uses dicycloheptadiene as the gel backbone monomer. Therefore, this application achieves the introduction of tension rings through dicycloheptadiene, realizing the polymerization of highly active gels and facilitating the preparation of cross-linked copolymers. As a gel backbone monomer, the polymer formed by dicycloheptadiene has regular lithium-ion transport channels, reduces the cross-linking point density, adjusts the lithium-ion transport channels, and is conducive to rapid lithium-ion conduction.

[0023] In addition, the introduction of alkyl groups into dicycloheptadecene can reduce the crystallinity of the gel electrolyte and enhance its toughness.

[0024] The dicycloheptadecene content in the gel electrolyte precursor used in this application enables the final gel electrolyte to improve the lithium-ion transport capacity of the electrolyte, thereby avoiding internal polarization of the battery during charging and discharging and improving the charging and discharging performance of the battery. At the same time, it avoids the reduction in the solubility of lithium salt caused by excessive cycloheptadecene content, thereby avoiding the deterioration of the overall performance of the battery.

[0025] In some embodiments of this application, the fluorinated lithium salt is at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, and lithium tetrafluoroborate.

[0026] In some embodiments of this application, the content of the fluorinated lithium salt relative to the total mass of the gel electrolyte precursor is 5% to 20%. In some specific embodiments, the content of the fluorinated lithium salt relative to the total mass of the gel electrolyte precursor can be 5%, 6%, 8%, 10%, 12%, 15%, 18%, 20%, or a value within any range of two of these values.

[0027] In this application, fluorinated lithium salts serve as the main source of active lithium ions in the gel electrolyte, and fluorinated lithium salts can participate in the construction of artificial solid electrolyte interface films, thereby optimizing the electrode-electrolyte interface performance.

[0028] In some embodiments of this application, the crosslinking agent is an acrylate.

[0029] In this application, the polymer matrix obtained by copolymerizing dicycloheptadecene and acrylate has a higher elastic modulus, resulting in a better effect on mitigating the volume expansion of the positive and negative electrode materials. Furthermore, the crosslinked copolymer gel electrolyte of this application can be applied to lithium metal batteries.

[0030] In some embodiments of this application, the crosslinking agent is an acrylate containing two or more carbon-carbon double bonds.

[0031] The acrylates containing multiple carbon-carbon double bonds in this application can spontaneously form cross-linked structures during polymerization. These cross-linked structures can more effectively fix fluorocarbon plasticizers, inhibit side reactions of gel electrolytes on the positive and negative electrode surfaces, and enhance the electrochemical stability of the battery.

[0032] In some embodiments of this application, the crosslinking agent is at least one selected from polyethylene glycol diacrylate, 1,3-butanediol diacrylate, ethylene diacrylate, triethylene glycol dimethacrylate, trimethylolpropane ethoxylated triacrylate, and pentaerythritol tetraacrylate.

[0033] In some embodiments of this application, the crosslinking agent accounts for 5% to 10% of the total mass of the gel electrolyte precursor. In some specific embodiments, the crosslinking agent accounts for 5%, 6%, 7%, 8%, 9%, 10%, or any value within the range of any two of these values.

[0034] In some embodiments of this application, the additive is a fluorocarbonate.

[0035] This application contains fluorocarbonate, which can co-form a lithium fluoride-rich solid electrolyte interface film with acrylate. This film can induce uniform lithium ion deposition and stripping, inhibit lithium dendrite formation, and alleviate the volume expansion of the lithium metal anode. Simultaneously, the small-molecule fluorocarbonate can participate in lithium ion transport, thereby improving the lithium ion transport performance of the electrolyte.

[0036] In some embodiments of this application, the additive is at least one of fluoroethylene carbonate, difluoroethylene carbonate, and trifluoropropylene carbonate.

[0037] In some embodiments of this application, the polymerization initiator is an azo initiator.

[0038] In some embodiments of this application, the polymerization initiator is at least one of dimethyl azobisisobutyrate, azobisisoheptanenitrile, and azobisisobutyronitrile.

[0039] In some embodiments of this application, the content of the polymerization initiator relative to the total mass of the gel electrolyte precursor is 0.075%-0.15%. In some specific embodiments, the content of the polymerization initiator relative to the total mass of the gel electrolyte precursor can be 0.075%, 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, or a value within any range of two of these values.

[0040] This application uses fluorocarbonate as a film-forming additive and plasticizer, and acrylate and dicycloheptadecene as polymer monomers as a gel electrolyte precursor. The gel electrolyte prepared using this precursor exhibits good room-temperature lithium-ion transport capability, high-voltage resistance, stability to lithium metal, and electrode-electrolyte interface performance. Furthermore, this application is compatible with existing battery electrolyte filling and battery formation processes and equipment, and has broad application prospects.

[0041] The second aspect of this application provides a method for preparing a gel electrolyte, wherein the precursor described in the first aspect is processed as follows: a fluorinated lithium salt is dissolved in an additive and mixed, then dicycloheptadecene and a crosslinking agent are added and mixed, a polymerization initiator is added and mixed to obtain a solution for preparing the gel electrolyte, and the solution for preparing the gel electrolyte is polymerized and gelled and then heated and cured to obtain the gel electrolyte.

[0042] In some embodiments of this application, the preparation method of the gel electrolyte includes dissolving a fluorinated lithium salt into an additive, mixing it thoroughly, and then stirring for 30-120 minutes.

[0043] In some embodiments of this application, the preparation method of the gel electrolyte includes dissolving a fluorinated lithium salt into an additive, mixing it, adding dicycloheptadecene and a crosslinking agent, mixing it, and stirring for 30-60 minutes.

[0044] In some embodiments of this application, the preparation method of the gel electrolyte includes dissolving a fluorinated lithium salt in an additive, mixing it, adding dicycloheptadecene and a crosslinking agent, mixing it, adding a polymerization initiator and mixing it, and stirring for 10-30 minutes to obtain a solution for preparing the gel electrolyte.

[0045] This application describes the preparation of a crosslinked copolymer gel electrolyte via in-situ polymerization using fluorocarbonate as a film-forming additive and plasticizer, and acrylate and dicycloheptadecene as polymer monomers. This electrolyte exhibits good room-temperature lithium-ion transport capability, high-voltage resistance, stability to lithium metal, and excellent electrode-electrolyte interface performance. Furthermore, this application is compatible with existing battery electrolyte filling and battery formation processes and equipment, demonstrating broad application prospects.

[0046] A third aspect of this application provides a gel electrolyte prepared as described in the second aspect. The electrolyte exhibits good room-temperature lithium-ion transport capability, high-voltage resistance, stability to lithium metal, and electrode-electrolyte interface performance. Furthermore, this application is compatible with existing battery electrolyte filling and battery formation processes and equipment, and has broad application prospects.

[0047] A fourth aspect of this application provides a battery comprising a gel electrolyte as described in the third aspect, as well as a positive electrode, a separator, and a negative electrode.

[0048] The battery is prepared by the following method: adding dicycloheptadecene and a crosslinking agent, mixing well, adding a polymerization initiator and mixing well to obtain the solution for preparing the gel electrolyte, injecting the solution for preparing the gel electrolyte into the battery, and then heating and solidifying after polymerization and gelation to obtain the battery containing the gel electrolyte.

[0049] In some embodiments of this application, the separator is any one of a cellulose separator, a polyethylene battery separator, a polypropylene battery separator, or a polyethylene / polypropylene composite battery separator.

[0050] In some embodiments of this application, the positive electrode includes a positive current collector, which is a carbon-coated aluminum foil.

[0051] In some embodiments of this application, the positive electrode includes a positive electrode active material, which is any one of lithium iron phosphate positive electrode, lithium manganese iron phosphate positive electrode, lithium cobalt oxide positive electrode, and nickel cobalt manganese 811 positive electrode.

[0052] The battery described in this application exhibits good room-temperature lithium-ion transport capability, high-voltage resistance, stability to lithium metal, and electrode-electrolyte interface performance. Furthermore, this application is compatible with existing battery electrolyte filling and formation processes and equipment, demonstrating broad application prospects.

[0053] The battery of this application also includes a packaging bag for containing the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the art for secondary batteries. This application does not limit the scope of these other components. This application does not impose any particular limitation on the packaging bag; it can be any packaging bag known in the art, as long as it achieves the purpose of this application. For example, an aluminum-plastic film packaging bag can be used.

[0054] This application provides a fifth aspect of an electronic device comprising a battery as described in the fourth aspect. The electronic device of this application exhibits good room-temperature lithium-ion transport capability, high-voltage resistance, stability to lithium metal, and electrode-electrolyte interface performance.

[0055] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries or lithium-ion capacitors, etc.

[0056] Example The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0057] Unless otherwise specified, the raw materials and equipment used in this application are commonly used in the field; unless otherwise specified, the methods used in this application are conventional methods in the field.

[0058] The test methods and equipment used in the embodiments and comparative examples of this application are as follows: 1. Ionic conductivity test Ionic conductivity was determined by alternating current impedance spectroscopy. The test frequency range was 1 Hz to 1 MHz, and the AC voltage amplitude was 10 mV. The bulk resistance (R6) of the electrolyte was obtained from the Nyquist plot. Ionic conductivity (σ) was calculated using the formula σ = L / (R6·A), where L is the electrolyte film thickness (cm) and A is the effective contact area of ​​the electrode (cm²). 2 The test results are the average of three parallel samples.

[0059] 2. Electrochemical window upper limit test Oxidation stability was determined by linear sweep voltammetry (LSV). The scan range was from open circuit potential to 6.0 V (vs. Li). + / Li), with a scan rate of 0.5 mV / s. The upper limit of the electrochemical window is defined as the current density increasing to 0.1 mA / cm². 2 The corresponding voltage value. Each group of samples was tested three times and the average value was taken.

[0060] 3. Lithium-ion transference number The lithium-ion transference number was determined by combining constant voltage polarization and AC impedance spectroscopy. First, a 10mV DC voltage was applied for polarization, and the initial current (I0) and steady-state current (I0) were recorded. ss AC impedance tests were performed before and after polarization to obtain the initial resistance (R0) and steady-state resistance (R). ss Lithium-ion transport number (t) + ) Calculated according to the Bruce–Vincent–Evans formula, i.e.: t + =[Iss(V-I0R0)] / [I0(VI ss R ss )]; Where V is the polarization voltage (10mV). Each group of samples was tested at least three times, and the average value was taken as the final result.

[0061] Example 1 (1) Dissolve 1.0 g of lithium tetrafluoroborate in 8.0 g of propylene trifluorocarbonate and stir continuously at room temperature for 30 min until completely dissolved to obtain a clear solution A; (2) Add 0.7g of polyethylene glycol diacrylate and 0.3g of dicycloheptadecene to the clear solution A, and stir continuously at room temperature for 30min to obtain clear solution B; (3) Add 7.5 mg of dimethyl azobisisobutyrate to the clear solution C and stir continuously at room temperature for 30 min to obtain clear solution D, which is the gel electrolyte precursor solution; (4) Inject the clear solution C into the battery, let it stand, and finally heat it to solidify to obtain the cross-linked copolymer gel electrolyte.

[0062] Example 2 (1) Dissolve 1.0 g of lithium difluorosulfonylimide in 8.0 g of difluoroethylene carbonate and stir continuously at room temperature for 60 min until completely dissolved to obtain a clear solution A; (2) Add 0.7 g of 1,3-butanediol diacrylate and 0.3 g of dicycloheptadecene to the clear solution A, and stir continuously at room temperature for 30 min to obtain clear solution B; (3) Add 7.5 mg of azobisisoheptanenitrile to the clear solution B and stir continuously at room temperature for 10 min to obtain clear solution C, which is the gel electrolyte precursor solution; (4) Inject the clear solution C into the battery, let it stand, and finally heat it to solidify to obtain the cross-linked copolymer gel electrolyte.

[0063] Example 3 (1) Dissolve 1.0 g of lithium bis(trifluoromethanesulfonylimide) in 8.0 g of propylene trifluorocarbonate and stir continuously at room temperature for 60 mins until completely dissolved to obtain a clear solution A; (2) Add 0.7g of vinyl acrylate and 0.3g of dicycloheptadecene to the clear solution A, and stir continuously at room temperature for 30min to obtain clear solution B; (3) Add 7.5 mg of dimethyl azobisisobutyrate to the clear solution C and stir continuously at room temperature for 10 min to obtain clear solution C, which is the gel electrolyte precursor solution; (4) Inject the clear solution C into the battery, let it stand, and finally heat it to solidify to obtain the cross-linked copolymer gel electrolyte.

[0064] Example 4 (1) Dissolve 1.0 g of lithium difluorooxalate borate in 8.0 g of fluoroethylene carbonate and stir continuously at room temperature for 30 min until completely dissolved to obtain a clear solution A; (2) Add 0.7g of triethylene glycol dimethacrylate and 0.3g of dicycloheptadecene to the clear solution A, and stir continuously at room temperature for 30min to obtain clear solution B; (3) Add 7.5 mg of azobisisobutyronitrile to the clear solution C and stir continuously at room temperature for 10 mins to obtain clear solution C, which is the gel electrolyte precursor solution; (4) Inject the clear solution C into the battery, let it stand, and finally heat it to solidify to obtain the cross-linked copolymer gel electrolyte.

[0065] Example 5 (1) Dissolve 1.0 g of lithium hexafluorophosphate in 8.0 g of ethylene difluorocarbonate and stir continuously at room temperature for 60 min until completely dissolved to obtain a clear solution A; (2) Add 0.7g of trimethylolpropane ethoxylated triacrylate and 0.3g of dicycloheptadecene to the clear solution A, and stir continuously at room temperature for 30min to obtain clear solution B; (3) Add 7.5 mg of azobisisoheptanenitrile to the clear solution C and stir continuously at room temperature for 10 min to obtain clear solution C, which is the gel electrolyte precursor solution; (4) Inject the clear solution C into the battery, let it stand, and finally heat it to solidify to obtain the cross-linked copolymer gel electrolyte.

[0066] Example 6 (1) Dissolve 1.0 g of lithium hexafluorophosphate in 8.0 g of ethylene difluorocarbonate and stir continuously at room temperature for 60 min until completely dissolved to obtain a clear solution A; (2) Add 0.7g of pentaerythritol tetraacrylate and 0.3g of dicycloheptadecene to the clear solution A, and stir continuously at room temperature for 30min to obtain clear solution B; (3) Add 7.5 mg of azobisisoheptanenitrile to the clear solution C and stir continuously at room temperature for 10 min to obtain clear solution C, which is the gel electrolyte precursor solution; (4) Inject the clear solution C into the battery, let it stand, and finally heat it to solidify to obtain the cross-linked copolymer gel electrolyte.

[0067] Example 7 (1) Dissolve 1.0 g of lithium hexafluorophosphate in 8.0 g of ethylene difluorocarbonate and stir continuously at room temperature for 60 min until completely dissolved to obtain a clear solution A; (2) Add 1.0 g of dicycloheptadiene to the clear solution A and stir continuously at room temperature for 30 min to obtain clear solution B; (3) Add 7.5 mg of azobisisoheptanenitrile to the clear solution C and stir continuously at room temperature for 10 min to obtain clear solution C, which is the gel electrolyte precursor solution; (4) Inject the clear solution C into the battery, let it stand, and finally heat it to solidify to obtain the cross-linked copolymer gel electrolyte.

[0068] Example 8 (1) Dissolve 1.0 g of lithium hexafluorophosphate in 8.0 g of ethylene difluorocarbonate and stir continuously at room temperature for 60 min until completely dissolved to obtain a clear solution A; (2) Add 0.9 g of pentaerythritol tetraacrylate and 0.1 g of dicycloheptadecene to the clear solution A, and stir continuously at room temperature for 30 min to obtain clear solution B; (3) Add 7.5 mg of azobisisoheptanenitrile to the clear solution C and stir continuously at room temperature for 10 min to obtain clear solution C, which is the gel electrolyte precursor solution; (4) Inject the clear solution C into the battery, let it stand, and finally heat it to solidify to obtain the cross-linked copolymer gel electrolyte.

[0069] Example 9 (1) Dissolve 1.0 g of lithium hexafluorophosphate in 8.0 g of ethylene difluorocarbonate and stir continuously at room temperature for 60 min until completely dissolved to obtain a clear solution A; (2) Add 0.3g of pentaerythritol tetraacrylate and 0.7g of dicycloheptadecene to the clear solution A, and stir continuously at room temperature for 30min to obtain clear solution B; (3) Add 7.5 mg of azobisisoheptanenitrile to the clear solution C and stir continuously at room temperature for 10 min to obtain clear solution C, which is the gel electrolyte precursor solution; (4) Inject the clear solution C into the battery, let it stand, and finally heat it to solidify to obtain the cross-linked copolymer gel electrolyte.

[0070] Example 10 (1) Dissolve 1.0 g of lithium hexafluorophosphate in 8.0 g of ethylene difluorocarbonate and stir continuously at room temperature for 60 min until completely dissolved to obtain a clear solution A; (2) Add 1.0 g of pentaerythritol tetraacrylate to the clear solution A and stir continuously at room temperature for 30 min to obtain clear solution B; (3) Add 7.5 mg of azobisisoheptanenitrile to the clear solution C and stir continuously at room temperature for 10 min to obtain clear solution C, which is the gel electrolyte precursor solution; (4) Inject the clear solution C into the battery, let it stand, and finally heat it to solidify to obtain the cross-linked copolymer gel electrolyte.

[0071] Example 11 (1) Dissolve 1.0 g of lithium hexafluorophosphate in 8.0 g of ethylene difluorocarbonate and stir continuously at room temperature for 60 min until completely dissolved to obtain a clear solution A; (2) Add 0.8 g of pentaerythritol tetraacrylate and 0.2 g of dicycloheptadecene to the clear solution A, and stir continuously at room temperature for 30 min to obtain clear solution B; (3) Add 7.5 mg of azobisisoheptanenitrile to the clear solution C and stir continuously at room temperature for 10 min to obtain clear solution C, which is the gel electrolyte precursor solution; (4) Inject the clear solution C into the battery, let it stand, and finally heat it to solidify to obtain the cross-linked copolymer gel electrolyte.

[0072] Example 12 (1) Dissolve 1.0 g of lithium hexafluorophosphate in 8.0 g of ethylene difluorocarbonate and stir continuously at room temperature for 60 min until completely dissolved to obtain a clear solution A; (2) Add 0.5g of pentaerythritol tetraacrylate and 0.5g of dicycloheptadecene to the clear solution A, and stir continuously at room temperature for 30min to obtain clear solution B; (3) Add 7.5 mg of azobisisoheptanenitrile to the clear solution C and stir continuously at room temperature for 10 min to obtain clear solution C, which is the gel electrolyte precursor solution; (4) Inject the clear solution C into the battery, let it stand, and finally heat it to solidify to obtain the cross-linked copolymer gel electrolyte.

[0073] Comparative Example 1 (1) Dissolve 1.0 g of lithium hexafluorophosphate in 8.0 g of ethylene difluorocarbonate and stir continuously at room temperature for 60 min until completely dissolved to obtain a clear solution A; (2) Add 0.5g of pentaerythritol tetraacrylate and 0.5g of cyclopentene to the clear solution A, and stir continuously at room temperature for 30min to obtain clear solution B; (3) Add 7.5 mg of azobisisoheptanenitrile to the clear solution C and stir continuously at room temperature for 10 min to obtain clear solution C, which is the gel electrolyte precursor solution; (4) Inject the clear solution C into the battery, let it stand, and finally heat it to solidify to obtain the cross-linked copolymer gel electrolyte.

[0074] Comparative Example 2 (1) Dissolve 1.0 g of lithium hexafluorophosphate in 8.0 g of ethylene difluorocarbonate and stir continuously at room temperature for 60 min until completely dissolved to obtain a clear solution A; (2) Add 0.5g of pentaerythritol tetraacrylate and 0.5g of norbornene to the clear solution A, and stir continuously at room temperature for 30min to obtain clear solution B; (3) Add 7.5 mg of azobisisoheptanenitrile to the clear solution C and stir continuously at room temperature for 10 min to obtain clear solution C, which is the gel electrolyte precursor solution; (4) Inject the clear solution C into the battery, let it stand, and finally heat it to solidify to obtain the cross-linked copolymer gel electrolyte.

[0075] Battery assembly methods used in each embodiment and comparative example: <Preparation of Negative Electrode Sheets> The negative electrode active material, graphite, silicon carbide, conductive agent, and binder were mixed uniformly at a mass ratio of 76:20:1:3 to obtain the negative electrode material. Based on the total mass of the negative electrode material, the mass fraction of silicon carbide was 20%. The negative electrode material was uniformly dispersed in deionized water to form a black slurry, which was then coated on both sides of a copper foil. After baking, rolling, and cutting, the negative electrode sheet was obtained, with a compaction density of 1.65 g / cm³ for the negative electrode active material layer. 3 The compaction density of the negative electrode active material layer is controlled by the electrode manufacturing process, specifically by the electrode coating weight and the electrode roll forming thickness parameters.

[0076] <Preparation of the positive electrode> LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, conductive agent, and binder are mixed evenly at a mass ratio of 97:2:1, and then uniformly dispersed in N-methyl-2-pyrrolidone to form a black slurry. This slurry is then coated onto both sides of an aluminum foil, and after baking, rolling, and cutting, a positive electrode sheet is obtained. The compaction density of the positive electrode active material layer is 3.5 g / cm³. 3 The compaction density of the positive electrode active material layer is controlled by the electrode manufacturing process, specifically by the electrode coating weight and the electrode roll forming thickness parameters.

[0077] <Preparation of Electrolyte> In a dry argon atmosphere glove box, the lithium salt is first dissolved in a fluorocarbonate solvent. Then, a crosslinking agent and monomer are added to the dissolved solution, and the solution is fully dissolved to obtain a homogeneous, transparent solution. Finally, an azo initiator is added to the solution to obtain the electrolyte. The proportions of the added components are adjusted according to specific embodiments.

[0078] <Preparation of the diaphragm> A polyethylene film with a thickness of 7μm was used as the diaphragm.

[0079] <Preparation of Lithium-ion Batteries> The prepared positive electrode, separator, and negative electrode are stacked sequentially, with the separator positioned between the positive and negative electrodes to act as a separator. The electrodes are then wound to obtain the electrode assembly. After welding the tabs, the electrode assembly is placed in an aluminum-plastic film packaging bag and baked at high temperature until the moisture content reaches the required level. The prepared electrolyte is then injected, and the lithium-ion battery is obtained through vacuum sealing, settling, formation, degassing, and shaping processes.

[0080] The preparation parameters for the examples and comparative examples are shown in Table 1 below.

[0081] Table 1

[0082] The relevant parameters and properties of the electrolytes prepared in the above embodiments and comparative examples were tested using the above testing methods, and the results are shown in Table 2.

[0083] Table 2

[0084] Table 2 shows that the room temperature ionic conductivity of the composite gel electrolyte changes by adjusting the type and content of raw materials. Using fluorinated lithium salts with strong dissociation capabilities, low-viscosity fluorocarbonate plasticizers, and introducing dicycloheptadecene can improve the room temperature ionic conductivity of the composite gel electrolyte. The difference between Example 6 and Example 7 lies in the content of dicycloheptadecene. Because Example 7 does not contain the crosslinking agent acrylate, the high content of dicycloheptadecene leads to reduced lithium salt solubility and lithium-ion transport capacity, resulting in low ionic conductivity. The difference between Example 6 and Example 10 lies in the content of acrylate. Example 10 contains only acrylate, resulting in excessive crosslinking, which is detrimental to lithium-ion transport and leads to low conductivity. The difference between Example 6 and Comparative Examples 1 and 2 lies in the different types of monomers, leading to irregular polymer formation and a more complex lithium-ion transport pathway, resulting in low conductivity.

[0085] As shown in Table 2, the upper limit of the electrochemical window of Examples 1 to 4 is higher than 5.0V, which shows good electrochemical stability and can be adapted to high voltage cathode materials.

[0086] Table 2 shows the lithium-ion transference number data for Examples 1-12 and Comparative Examples 1-2. The difference between Example 6 and Comparative Example 7 lies in the dicycloheptadecene content. Due to the excessively high dicycloheptadecene content in Comparative Example 1, the solubility of the lithium salt in the gel electrolyte is reduced, hindering its rapid migration within the gel electrolyte, resulting in a lower lithium-ion transference number. The difference between Example 6 and Example 10 lies in the acrylate content. Example 10 contains only acrylate, leading to a stronger interaction with negative ions and a relatively higher lithium-ion transference number.

[0087] In summary, the cross-linked copolymer gel electrolyte involved in this application, with fluorinated lithium salt, fluorocarbon plasticizer, dicycloheptadecene, and acrylate as its main components, exhibits good room-temperature lithium-ion transport capability, high-voltage resistance, stability to lithium metal, and excellent electrode-electrolyte interface performance. By compounding and controlling the proportion of dicycloheptadecene, the specific properties of the gel electrolyte can be enhanced, enabling the preparation of electrolytes for various types and applications. Furthermore, it is compatible with existing battery electrolyte filling and battery formation processes and equipment, showing broad application prospects.

[0088] It is understood that this application has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the scope of this application. Furthermore, based on the teachings of this application, these features and embodiments can be modified to adapt to specific situations and materials without departing from the scope of this application. Therefore, this application is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are protected by this application.

Claims

1. A gel electrolyte precursor, characterized in that, The gel electrolyte precursor has a gel skeleton monomer of dicycloheptadecene and also includes additives, crosslinking agents, polymerization initiators and fluorinated lithium salts; the content of dicycloheptadecene relative to the total mass of the gel electrolyte precursor is 1% to 10%.

2. The precursor according to claim 1, characterized in that, The fluorinated lithium salt is at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, and lithium tetrafluoroborate.

3. The precursor according to claim 1, characterized in that, The content of the fluorinated lithium salt relative to the total mass of the gel electrolyte precursor is 5% to 20%.

4. The precursor according to claim 1, characterized in that, The crosslinking agent accounts for 5% to 10% of the total mass of the gel electrolyte precursor.

5. The precursor according to claim 1, characterized in that, The additive is a fluorocarbonate.

6. The precursor according to any one of claims 1-5, characterized in that, The polymerization initiator accounts for 0.075%-0.15% of the total mass of the gel electrolyte precursor.

7. A method for preparing a gel electrolyte, characterized in that, The precursor as described in any one of claims 1-6 is processed as follows: a fluorinated lithium salt is dissolved in an additive and mixed, then dicycloheptadecene and a crosslinking agent are added and mixed, a polymerization initiator is added and mixed to obtain a solution for preparing a gel electrolyte, and the solution for preparing the gel electrolyte is polymerized and gelled and then heated and cured to obtain the gel electrolyte.

8. A gel electrolyte prepared by the method of claim 7.

9. A battery, characterized in that, The battery comprises the gel electrolyte as described in claim 8, as well as a positive electrode, a separator, and a negative electrode; The separator is any one of cellulose separator, polyethylene battery separator, polypropylene battery separator, or polyethylene / polypropylene composite battery separator; The positive electrode includes a positive electrode current collector, which is a carbon-coated aluminum foil. The positive electrode includes a positive electrode active material, which is any one of lithium iron phosphate positive electrode, lithium manganese iron phosphate positive electrode, lithium cobalt oxide positive electrode, and nickel cobalt manganese 811 positive electrode.

10. An electronic device, characterized in that, The electronic device includes the battery as described in claim 9.

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