Gel electrolyte precursor and use thereof

Abstract

This application relates to the field of electrochemical technology, and in particular to a gel electrolyte precursor and its application. The gel electrolyte precursor's gel backbone monomer is dicycloheptadecene, and the precursor also includes additives, crosslinking agents, polymerization initiators, and fluorinated lithium salts; the dicycloheptadecene accounts for 1% to 10% of the total mass of the gel electrolyte precursor. This application designs and constructs a novel crosslinked gel polymer electrolyte by controlling the content of dicycloheptadecene and acrylate in the precursor solution. By introducing dicycloheptadecene, this application not only improves the lithium-ion transport channel but also enhances the gel electrolyte's ability to dissociate and transport lithium ions. Therefore, the crosslinked copolymer gel electrolyte of this application exhibits excellent lithium-ion transport performance at room temperature, and its full-cell performance is also significantly 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 this application, the crosslinking agent is an acrylate;

[0011] In some embodiments of this application, the crosslinking agent is an acrylate containing two or more carbon-carbon double bonds;

[0012] 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.

[0013] In some embodiments of this application, the crosslinking agent accounts for 5% to 10% of the total mass of the gel electrolyte precursor.

[0014] In some embodiments of this application, the additive is a fluorocarbonate;

[0015] In some embodiments of this application, the additive is at least one of fluoroethylene carbonate, difluoroethylene carbonate, and trifluoropropylene carbonate.

[0016] In some embodiments of this application, the polymerization initiator is an azo initiator;

[0017] In some embodiments of this application, the polymerization initiator is at least one selected from dimethyl azobisisobutyrate, azobisisoheptanenitrile, and azobisisobutyronitrile.

[0018] 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%.

[0019] 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 the 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.

[0020] A third aspect of this application provides a gel electrolyte prepared by the method described in the second aspect.

[0021] 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;

[0022] 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;

[0023] In some embodiments of this application, the positive electrode includes a positive current collector, which is a carbon-coated aluminum foil;

[0024] 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.

[0025] The fifth aspect of this application provides an electronic device comprising a battery as described in the fourth aspect.

[0026] Beneficial Effects: This application designs and constructs a novel cross-linked gel polymer electrolyte by controlling the content of dicycloheptadecene and acrylate in the precursor solution. By introducing dicycloheptadecene, this application not only improves the lithium-ion transport channel but also enhances the gel electrolyte's ability to dissociate and transport lithium ions. Therefore, the cross-linked copolymer gel electrolyte of this application exhibits excellent lithium-ion transport performance at room temperature, and its full-cell performance is also significantly improved. Detailed Implementation

[0027] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art based on this application are within the scope of protection of this application.

[0028] While gel electrolytes effectively integrate the mechanical stability of the polymer matrix with the ionic conductivity of the electrolyte, exhibiting unique advantages in suppressing lithium dendrite growth and improving battery safety, their overall lithium-ion transport kinetics are sluggish due to obstructed internal ion migration channels, low lithium-ion transference numbers, and often unsatisfactory electrode / electrolyte interface compatibility. Therefore, systematically improving their lithium-ion transport performance has become a core issue driving the development of high-performance gel electrolytes.

[0029] According to a first aspect of this application, a gel electrolyte precursor is provided. The gel backbone monomer of the gel electrolyte precursor is dicycloheptadecene. 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%. In some specific embodiments, the content of dicycloheptadecene 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 any range of two of these values.

[0030] 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.

[0031] In addition, the introduction of alkyl groups into dicycloheptadecene can reduce the crystallinity of the gel electrolyte and enhance its toughness.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] In some embodiments of this application, the crosslinking agent is an acrylate.

[0037] 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.

[0038] In some embodiments of this application, the crosslinking agent is an acrylate containing two or more carbon-carbon double bonds.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] In some embodiments of this application, the additive is a fluorocarbonate.

[0043] 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.

[0044] In some embodiments of this application, the additive is at least one of fluoroethylene carbonate, difluoroethylene carbonate, and trifluoropropylene carbonate.

[0045] In some embodiments of this application, the polymerization initiator is an azo initiator.

[0046] In some embodiments of this application, the polymerization initiator is at least one of dimethyl azobisisobutyrate, azobisisoheptanenitrile, and azobisisobutyronitrile.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] In some embodiments of this application, the positive electrode includes a positive current collector, which is a carbon-coated aluminum foil.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] Example

[0065] 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.

[0066] 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.

[0067] The test methods and equipment used in the embodiments and comparative examples of this application are as follows:

[0068] 1. Ionic conductivity test

[0069] 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.

[0070] 2. Electrochemical window upper limit test

[0071] 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.

[0072] 3. Lithium-ion transference number

[0073] Lithium-ion transport 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 )];

[0074] 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.

[0075] Example 1

[0076] (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;

[0077] (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;

[0078] (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;

[0079] (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.

[0080] Example 2

[0081] (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;

[0082] (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;

[0083] (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;

[0084] (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.

[0085] Example 3

[0086] (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;

[0087] (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;

[0088] (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;

[0089] (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.

[0090] Example 4

[0091] (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;

[0092] (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;

[0093] (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;

[0094] (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.

[0095] Example 5

[0096] (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;

[0097] (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;

[0098] (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;

[0099] (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.

[0100] Example 6

[0101] (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;

[0102] (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;

[0103] (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;

[0104] (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.

[0105] Example 7

[0106] (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;

[0107] (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;

[0108] (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;

[0109] (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.

[0110] Example 8

[0111] (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;

[0112] (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;

[0113] (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;

[0114] (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.

[0115] Example 9

[0116] (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;

[0117] (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;

[0118] (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;

[0119] (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.

[0120] Example 10

[0121] (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;

[0122] (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;

[0123] (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;

[0124] (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.

[0125] Example 11

[0126] (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;

[0127] (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;

[0128] (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;

[0129] (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.

[0130] Example 12

[0131] (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;

[0132] (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;

[0133] (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;

[0134] (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.

[0135] Comparative Example 1

[0136] (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;

[0137] (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;

[0138] (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;

[0139] (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.

[0140] Comparative Example 2

[0141] (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;

[0142] (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;

[0143] (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;

[0144] (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.

[0145] Battery assembly methods used in each embodiment and comparative example:

[0146] <Preparation of Negative Electrode Sheets>

[0147] 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.

[0148] <Preparation of the positive electrode>

[0149] 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.

[0150] <Preparation of Electrolyte>

[0151] 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.

[0152] <Preparation of the diaphragm>

[0153] A polyethylene film with a thickness of 7μm was used as the diaphragm.

[0154] <Preparation of Lithium-ion Batteries>

[0155] 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.

[0156] The preparation parameters for the examples and comparative examples are shown in Table 1 below.

[0157] Table 1

[0158]

[0159] 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.

[0160] Table 2

[0161]

[0162] 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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] 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%. The additives are fluorocarbonates and the crosslinking agents are acrylates.

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 any one of claims 1-4, characterized in that, The polymerization initiator accounts for 0.075%-0.15% of the total mass of the gel electrolyte precursor.

6. A method for preparing a gel electrolyte, characterized in that, The precursor as described in any one of claims 1-5 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.

7. A gel electrolyte prepared by the method of claim 6.

8. A battery, characterized in that, The battery comprises the gel electrolyte as described in claim 7, 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.

9. An electronic device, characterized in that, The electronic device includes the battery as described in claim 8.

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