Electrolyte precursor, flame-retardant gel electrolyte and preparation method and application thereof
By preparing a flame-retardant gel electrolyte using electrolyte precursors with specific components, the problems of poor flame retardancy and low ionic conductivity in lithium-ion batteries are solved. This achieves a comprehensive improvement in both effective flame retardancy and high ionic conductivity at high temperatures, thus constructing a dual safety barrier for lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA UNIV OF PETROLEUM (BEIJING)
- Filing Date
- 2026-02-10
- Publication Date
- 2026-06-05
AI Technical Summary
Existing lithium-ion batteries have poor flame retardant properties in their gel electrolytes, leading to safety hazards, and low ionic conductivity, making it difficult to meet the requirements of harsh environments or high safety requirements in application scenarios.
Flame-retardant gel electrolytes are prepared by thermal polymerization using an electrolyte precursor composed of phosphate monomers containing carbon-carbon double bonds, acrylate monomers containing urea bonds, cyano acrylate monomers, and phosphorus-containing crosslinking agents in a specific molar ratio. This forms a carbon layer that is crosslinked and carbonized at high temperatures to prevent the spread of combustion, and a multifunctional synergistic network is constructed at the molecular level.
This technology enables flame-retardant gel electrolytes to effectively retard at high temperatures, improves the ionic conductivity and electrochemical performance of lithium-ion batteries, constructs a dual safety barrier, and enhances the overall safety and performance of the battery.
Smart Images
Figure SMS_1 
Figure SMS_3 
Figure SMS_4
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium battery materials technology, specifically to electrolyte precursors, flame-retardant gel electrolytes, their preparation methods, and applications. Background Technology
[0002] Lithium-ion batteries, with their significant advantages such as high energy density and long cycle life, have become the core power source for electric vehicles, portable electronic devices, and other fields. However, behind their widespread application, the inherent safety hazards of traditional liquid electrolytes cannot be ignored. These electrolytes are usually composed of flammable organic solvents, and when the battery is subjected to extreme conditions such as mechanical abuse (e.g., crushing, puncture), electrical abuse (e.g., overcharging, short circuit), or thermal abuse, they are highly susceptible to combustion or even violent thermal runaway, leading to battery fire or explosion, posing a serious threat to the life and property safety of users.
[0003] To improve the intrinsic safety of batteries, solid-state electrolytes have received widespread attention from academia and industry in recent years due to their ability to completely eliminate flammable liquid components. Despite the significant safety potential of solid-state electrolytes, they still face considerable challenges in practical applications: on the one hand, the ionic conductivity of most solid-state electrolyte materials at room temperature is still significantly lower than that of liquid electrolytes, limiting the rate performance of batteries; on the other hand, poor interfacial contact and excessive interfacial impedance are common problems between solid-state electrolytes and electrode materials (especially the positive and negative electrode active materials), severely affecting the cycle stability and power output of batteries.
[0004] Gel electrolytes have emerged as a compromise, cleverly combining the advantages of liquid and solid electrolytes. Their structural feature is the immobilization or adsorption of a certain amount of liquid electrolyte within a polymer network, thus retaining the high ionic conductivity close to that of liquid electrolytes while possessing a macroscopic morphology similar to solid electrolytes and forming relatively good interfacial contact with the electrodes. However, currently widely studied aqueous gel electrolytes (hydrogels) or some organic gel electrolytes typically have poor inherent flame retardant properties, making it difficult to effectively suppress the spread of flames under high temperatures or accidental conditions. This fails to meet the requirements of high-safety lithium-ion batteries, especially for applications in harsh environments or scenarios with extremely high safety requirements.
[0005] Developing a novel gel electrolyte with inherently excellent flame-retardant properties is of urgent and significant practical importance and technical value for fundamentally improving the safety protection level and comprehensive electrochemical performance of lithium-ion batteries, constructing a dual safety barrier of "flame retardancy + thermal shutdown", and promoting their safe application in a wider range of scenarios. Summary of the Invention
[0006] The purpose of this invention is to solve the problems of poor flame retardancy leading to safety hazards and low ionic conductivity in existing lithium-ion batteries containing gel electrolytes.
[0007] To achieve the above objectives, a first aspect of the present invention provides an electrolyte precursor comprising a carbon-carbon double bond phosphate monomer, a urea-alkyl acrylate monomer, a cyano acrylate monomer, and a phosphorus-containing crosslinking agent in a molar ratio of 1:1-2:1-3:1-2. The acrylate monomers containing urea bonds are 2-urea ethyl acrylate and / or diurea dimethacrylate.
[0008] A second aspect of the present invention provides a method for preparing a flame-retardant gel electrolyte, the method comprising: The flame-retardant gel electrolyte is obtained by thermal polymerization of a mixture containing an electrolyte precursor, a thermosetting agent, and an electrolyte. The electrolyte precursor is the electrolyte precursor described in the first aspect.
[0009] A third aspect of the present invention provides a flame-retardant gel electrolyte prepared by the method described in the second aspect.
[0010] The fourth aspect of the present invention provides the application of the flame-retardant gel electrolyte described in the third aspect in lithium-ion batteries.
[0011] Through the above technical solution, the present invention has at least the following advantages compared with the prior art: The flame-retardant gel electrolyte obtained by the technical solution of the present invention has good flame-retardant effect and good thermal stability. It can not only undergo further cross-linking when the temperature is too high, but also rapidly carbonize to form a carbon layer when the temperature continues to rise, preventing the volatilization of flammable gases and the transfer of heat, effectively preventing the combustion from spreading further. Moreover, the flame-retardant gel electrolyte can improve the ionic conductivity of lithium-ion batteries.
[0012] In summary, the lithium-ion battery obtained by the technical solution of the present invention has both excellent flame retardancy and electrochemical performance. Detailed Implementation
[0013] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0014] In this invention, the "acrylate monomer containing urea chain" refers to an acrylate monomer containing a "urea chain" functional group, but the acrylate monomer does not contain an "isocyanate group" functional group. The term "cyano-containing acrylate monomer" refers to an acrylate monomer containing a "cyano" functional group, but which does not contain a "urea-alkyl bond" functional group.
[0015] As mentioned above, a first aspect of the present invention provides an electrolyte precursor containing a carbon-carbon double bond phosphate monomer, a urea-alkyl acrylate monomer, a cyano acrylate monomer, and a phosphorus-containing crosslinking agent in a molar ratio of 1:1-2:1-3:1-2. The acrylate monomers containing urea bonds are 2-urea ethyl acrylate and / or diurea dimethacrylate.
[0016] During their research, the inventors of this invention discovered that by using an electrolyte precursor containing phosphate monomers with carbon-carbon double bonds, acrylate monomers with urea-alkyl bonds, cyano acrylate monomers, and phosphorus-containing crosslinking agents in a specific molar ratio, the flame-retardant function of the flame-retardant gel electrolyte can be constructed. This allows the flame-retardant gel electrolyte to undergo further crosslinking reactions during heating, and as the temperature continues to rise, a carbon layer is rapidly formed, preventing the volatilization of flammable gases and the transfer of heat, effectively preventing the further spread of combustion.
[0017] Preferably, the carbon-carbon double-bonded phosphate monomer is selected from at least one of 2-methyl-2-acrylate-2-hydroxyethyl phosphate, triallyl phosphate, di[2-(methacryloyloxy)ethyl] phosphate, and acrylate phosphate, preferably acrylate phosphate, and more preferably NTCADD®FM30 and / or NTCADD®FM20. The inventors of this invention have discovered that, in this preferred embodiment, a flame-retardant gel electrolyte with superior flame-retardant properties can be obtained, thereby achieving a lithium-ion battery with superior flame-retardant and electrochemical performance.
[0018] Preferably, the cyano-containing acrylate monomer is isocyanoethyl methacrylate and / or 2-isocyanoethyl acrylate. In this preferred embodiment, a flame-retardant gel electrolyte with superior flame-retardant properties can be obtained, thereby resulting in a lithium-ion battery with superior flame-retardant and electrochemical performance.
[0019] In a preferred embodiment, the phosphorus-containing crosslinking agent is obtained by a nucleophilic substitution reaction between a hydroxyl-containing acrylate derivative and a phenylphosphoyl halide derivative containing two chlorine atoms. In this preferred embodiment, the electrolyte precursor provided by the present invention further facilitates free radical capture during combustion, interrupting the chain reaction of combustion, thereby inhibiting combustion and achieving a flame-retardant effect.
[0020] Preferably, the hydroxyl-containing acrylate derivative is selected from at least one of hydroxyethyl acrylate (HEA), hydroxypropyl acrylate, hydroxyethyl methacrylate (HEMA), and hydroxypropyl methacrylate, and is more preferably hydroxyethyl acrylate and / or hydroxyethyl methacrylate.
[0021] Preferably, the phenylphosphonic halide derivative containing two chlorine atoms is selected from at least one of phenylphosphonic dichloride (PPDC), phenyl dichlorophosphate, p-tolylphosphonic dichloride, o-methoxyphenylphosphonic dichloride, and p-chlorophenylphosphonic dichloride, and is more preferably phenylphosphonic dichloride and / or phenyl dichlorophosphate.
[0022] According to a preferred embodiment, the phosphorus-containing crosslinking agent is prepared by a method comprising the following steps: (1) A hydroxyl-containing acrylate derivative is contacted with an alkaline solution and a portion of an organic solvent to obtain a mixture I; and The phenylphosphoyl halide derivative containing two chlorine atoms is contacted with the remaining organic solvent to obtain mixture II; (2) Mix the mixture I and the mixture II to obtain the phosphorus-containing crosslinking agent.
[0023] Under the above preferred conditions, a flame-retardant gel electrolyte with superior flame-retardant properties can be obtained, thereby obtaining a lithium-ion battery with superior flame-retardant and electrochemical properties.
[0024] Preferably, the organic solvent is dichloromethane. More preferably, the amount of the organic solvent used is 660-720 mL relative to 1 mol of the derivative combination; the derivative combination is a combination of a hydroxyl-containing acrylate derivative and the phenylphosphoyl halide derivative containing two chlorine atoms.
[0025] Preferably, the volume ratio of the partial organic solvent to the remaining partial organic solvent is 1-3:1.
[0026] Preferably, the alkaline solution is triethylamine (TEA). More preferably, the molar ratio of the hydroxyl-containing acrylate derivative to the alkaline solution is 1:1-1.5.
[0027] Preferably, the molar ratio of the hydroxyl-containing acrylate derivative to the phenylphosphoyl halide derivative containing two chlorine atoms is 1-3:1.
[0028] This invention does not impose any particular restrictions on the conditions for contact I and contact II in step (1). Those skilled in the art can conduct experiments using conventional mixing methods, as long as the reactants are uniformly mixed. Further details will not be elaborated here, and those skilled in the art should not interpret this as a limitation of the invention.
[0029] In a preferred embodiment, in step (2), the conditions for the mixing reaction include: a temperature of -5°C to 5°C, a time of 10-15 h, and a rotation speed of 10-40 rpm.
[0030] According to a particularly preferred embodiment, the method for preparing the phosphorus-containing crosslinking agent further includes: in step (2), the material obtained by the mixing reaction is subjected to impurity removal treatment and drying treatment in sequence to obtain the phosphorus-containing crosslinking agent.
[0031] The method for preparing the phosphorus-containing crosslinking agent described in this invention does not have any particular limitations on the methods of impurity removal and drying. Exemplarily, the impurity removal method includes vacuum filtration, adjusting the pH value of the filtrate, and vacuum distillation. The pH adjuster used to adjust the pH value of the filtrate is selected from at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, and ammonia water. The amount of the pH adjuster added is such that the pH value of the adjusted filtrate is 6-7. The material obtained after the impurity removal treatment is subjected to a first drying using a desiccant, and then the material after the first drying is subjected to a second drying at 40-80°C. Further details are omitted here, and those skilled in the art should not construe this as a limitation of the invention.
[0032] According to a preferred embodiment, the electrolyte precursor is prepared by a method comprising the following steps: The electrolyte precursor is obtained by contact mixing of phosphate ester monomers containing carbon-carbon double bonds, acrylate monomers containing urea-alkyl bonds, cyano acrylate monomers, and phosphorus-containing crosslinking agents. In this preferred embodiment, phosphorus-containing flame retardants, phosphorus-containing crosslinking agents, acrylate functional monomers containing urea-alkyl bonds, and bifunctional functional monomers containing active double bonds and isocyanates can be more precisely integrated into the same molecular framework or electrolyte system through chemical bonding. This method is not a simple physical blending, but rather designs and constructs a multifunctional synergistic network at the molecular level. Specifically, the phosphorus-containing flame retardant can efficiently exert gas-phase and condensation mechanisms at high temperatures or in the early stages of thermal runaway, effectively capturing free radicals and interrupting chain reactions. The introduction of the phosphorus-containing crosslinking agent forms a stable three-dimensional network structure in the system, effectively fixing the active components and preventing their migration or loss. After introducing urea and isocyanate functional groups, the material undergoes secondary crosslinking under heating conditions, thereby effectively inhibiting the runaway reaction process of the system.
[0033] This invention does not impose particular limitations on the contact mixing conditions. Those skilled in the art can conduct experiments using conventional mixing methods, such as mechanical stirring or ultrasonic treatment, as long as the reactants are uniformly mixed. Further details are omitted here and should not be construed as limiting the invention.
[0034] Preferably, the weight ratio of the phosphate monomer containing carbon-carbon double bonds, the acrylate monomer containing urea bonds, the acrylate monomer containing cyano groups, and the phosphorus-containing crosslinking agent is 1:0.2-0.5:0.125-0.25:0.2-0.5.
[0035] As previously described, a second aspect of the present invention provides a method for preparing a flame-retardant gel electrolyte, the method comprising: The flame-retardant gel electrolyte is obtained by thermal polymerization of a mixture containing an electrolyte precursor, a thermosetting agent, and an electrolyte. The electrolyte precursor is the electrolyte precursor described in the first aspect.
[0036] Preferably, the thermosetting agent is selected from at least one of diaminodiphenylmethane, azobisisobutyronitrile (AIBN), and 2-methylimidazole.
[0037] In a preferred embodiment, the electrolyte is a lithium salt electrolyte.
[0038] Preferably, the weight ratio of the electrolyte precursor, the thermosetting agent, and the electrolyte is 1:0.05-0.1:1-9.
[0039] Preferably, the conditions for the thermal polymerization reaction include: a temperature of 60-80°C and a time of 30-120 min.
[0040] As previously stated, a third aspect of the present invention provides a flame-retardant gel electrolyte prepared by the method described in the second aspect.
[0041] As previously stated, the fourth aspect of the present invention provides the application of the flame-retardant gel electrolyte described in the third aspect in lithium-ion batteries.
[0042] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the instruments, medicines and reagents used are all conventional commercially available products.
[0043] Hydroxyl-containing acrylate derivatives: Hydroxyethyl acrylate: purchased from Shanghai Aladdin Technology Co., Ltd., CAS No. 818-61-1; Hydroxyethyl methacrylate: Purchased from Shanghai Aladdin Technology Co., Ltd., CAS No. 868-77-9.
[0044] Phenylphosphonohalide derivatives containing two chlorine atoms: Phenylephrine dichloro: purchased from Shanghai Aladdin Technology Co., Ltd., CAS No. 824-72-6; Phenylacetic dichlorophosphate: purchased from Shanghai Aladdin Technology Co., Ltd., CAS No. 770-12-7.
[0045] Phosphate ester monomers containing carbon-carbon double bonds: NTCADD®FM30 (phosphate acrylate): purchased from Beijing Baiyuan Chemical Co., Ltd.; NTCADD®FM20 (phosphate acrylate): purchased from Beijing Baiyuan Chemical Co., Ltd.; 2-(methacryloyloxy)ethyl-2-(trimethylamino)ethyl phosphate: purchased from Shanghai Aladdin Technology Co., Ltd., CAS No. 67881-98-5.
[0046] Acrylate monomers containing urea bonds: Diurea dimethacrylate: purchased from Shanghai Aladdin Technology Co., Ltd., CAS No. 72869-86-4.
[0047] 1,3-Diallylurea: Purchased from Shanghai Aladdin Technology Co., Ltd., CAS No. 1801-72-5.
[0048] Diallyl isocyanurate: purchased from Shanghai Aladdin Technology Co., Ltd., CAS No. 6294-79-7.
[0049] Cyano-containing acrylate monomers: Ethyl isocyanate methacrylate: purchased from Shanghai Aladdin Technology Co., Ltd., CAS No. 30678-80-7; 2-Isocyanoethyl acrylate: purchased from Shanghai Aladdin Technology Co., Ltd., CAS No. 13641-96-8.
[0050] Phosphorus-containing crosslinking agent: Triallyl phosphate, purchased from Shanghai Aladdin Technology Co., Ltd., CAS No. 1623-19-4.
[0051] In the following examples, room temperature refers to a temperature of 23±2℃.
[0052] Preparation Example 1 (1) At room temperature, in a fume hood, a hydroxyl-containing acrylate derivative (hydroxyethyl acrylate, 0.2 mol) was contacted with an alkaline solution (triethylamine) and a portion of an organic solvent (dichloromethane) in a three-necked flask on a magnetic stirrer for contact I (time 5 min) to obtain mixture I; and The remaining organic solvent (dichloromethane) was contacted with a phenylphosphonic halide derivative (phenylphosphonic dichloro) containing two chlorine atoms in a second contact (for 30 min) to obtain a mixture II. (2) In a fume hood, mix I and mix II are mixed and reacted (temperature 0℃, time 12h, rotation speed 30rpm); the obtained material is vacuum filtered to remove byproducts such as triethylamine hydrochloride salt, and pH adjuster is added to the filtrate to adjust the pH of the aqueous phase to 6.5 to remove residual byproduct impurities; then vacuum distillation is performed to remove solvent and unreacted raw materials, and then anhydrous MgSO4 is added to the treated material and allowed to stand for 6h, and the anhydrous MgSO4 is filtered out. Then it is placed in a vacuum drying oven at 60℃ and dried for 6h to obtain phosphorus-containing crosslinking agent-1. The amount of organic solvent used relative to 1 mol of the derivative combination (the combination of hydroxyethyl acrylate and phenylphosphonic dichloride) is 700 mL; the volume ratio of the partial organic solvent to the remaining organic solvent is 2.5:1. The molar ratio of hydroxyethyl acrylate to triethylamine is 1:1.1; The molar ratio of hydroxyethyl acrylate to phenylphosphonic dichloride is 2:1.
[0053] Preparation Example 2 The preparation of phosphorus-containing crosslinking agent-1 was carried out using a similar method as described above, except that an equimolar amount of hydroxyethyl methacrylate was used instead of hydroxyethyl acrylate. Everything else is the same, resulting in phosphorus-containing crosslinking agent-2.
[0054] Preparation Example 3 The preparation of phosphorus-containing crosslinking agent-1 was carried out using a similar method as described above, except that an equimolar amount of phenyl dichlorophosphate was used instead of phenylphosphono dichloro. Everything else is the same, resulting in phosphorus-containing crosslinking agent-3.
[0055] The following examples illustrate the preparation method of the electrolyte precursor provided by the present invention. Example 1 At room temperature, 0.95 g of phosphate monomers containing carbon-carbon double bonds, acrylate monomers containing urea bonds, cyano acrylate monomers and phosphorus-containing crosslinking agents were placed in a mixing container and mixed (at a speed of 30 rpm) to obtain electrolyte precursor-1.
[0056] Examples 2 to 4 were carried out using a method similar to that of Example 1, except that the types and proportions of raw materials were different, as detailed in Table 1.
[0057] Table 1
[0058] Note: Molar ratio of dosage 1It refers to the molar ratio of phosphate ester monomers containing carbon-carbon double bonds, acrylate monomers containing urea bonds, acrylate monomers containing cyano groups, and phosphorus-containing crosslinking agents.
[0059] Example 5 The procedure was carried out in a similar manner to that of Example 1, except that an equimolar amount of 2-(methacryloyloxy)ethyl-2-(trimethylamino)ethyl phosphate was used to replace NTCADD®FM30; Everything else was the same, and electrolyte precursor-5 was obtained.
[0060] Example 6 The procedure was carried out in a similar manner to that of Example 1, except that an equimolar amount of triallyl phosphate was used to replace phosphorus-containing crosslinking agent-1. Everything else was the same, and electrolyte precursor-6 was obtained.
[0061] Comparative Example 1 The procedure was carried out in a similar manner to that of Example 1, except that an equimolar amount of 1,3-diallylurea was used to replace diurea dimethacrylate. Everything else was the same, and the electrolyte precursor -D1 was obtained.
[0062] Comparative Example 2 The procedure was carried out in a similar manner to that of Example 1, except that an equimolar amount of diallyl isocyanurate was used instead of diurea dimethacrylate. Everything else was the same, and the electrolyte precursor -D2 was obtained.
[0063] Comparative Example 3 The process was carried out in a similar manner to Example 1, except that the amount of phosphate ester monomers containing carbon-carbon double bonds was kept constant, and the amounts of phosphate ester monomers containing carbon-carbon double bonds, acrylate monomers containing urea bonds, acrylate monomers containing cyano groups and phosphorus-containing crosslinking agents were adjusted so that the molar ratio of the three in the electrolyte precursor was 1:4:6:2. Everything else was the same, and the electrolyte precursor -D3 was obtained.
[0064] Test case Flame-retardant gel electrolytes (corresponding numbers are flame-retardant gel electrolyte-1 to flame-retardant gel electrolyte-6 and flame-retardant gel electrolyte-D1 to flame-retardant gel electrolyte-D3) were prepared using the electrolyte precursors (electrolyte precursor-1 to electrolyte precursor-6 and electrolyte precursor-D1 to flame-retardant gel electrolyte-D3) obtained in the examples. Then, lithium-ion batteries (corresponding numbers are lithium-ion battery-1 to lithium-ion battery-6 and lithium-ion battery-D1 to lithium-ion battery-D3) were prepared using the aforementioned flame-retardant gel electrolytes. The specific steps are as follows: (1) Take 0.1g of electrolyte precursor and add 0.9g of electrolyte. The electrolyte is prepared by dissolving 1.0mol / L LiPF6 in a mixed solvent of EC (ethylene carbonate) and DEC (diethyl carbonate) in a volume ratio of 1:1. Then add 0.01g of thermosetting agent (AIBN), mix evenly, and place in an oven at 60℃ for 30min to carry out thermal polymerization reaction to obtain flame-retardant gel electrolyte.
[0065] (2) At room temperature, weigh 4g of lithium iron phosphate powder, 0.5g of polyvinylidene fluoride and 0.5g of conductive carbon black and dry them in a vacuum environment at 80℃ for 12h. Then pour the dried materials into a mortar and grind for 15min. After ensuring that the three materials are mixed evenly, add an appropriate amount of NMP solvent and continue grinding for 10min. Observe the material under a light and there is no obvious particle feel, which means that the positive electrode slurry is formed. Finally, coat the positive electrode slurry onto the aluminum foil with a gap of 50μm by a scraper. After coating, let the solvent dry naturally and then transfer it to a vacuum drying oven and vacuum dry at 100℃ for 12h to obtain the positive electrode sheet.
[0066] (3) The flame-retardant gel electrolyte is coated on the battery separator and then assembled with the above positive electrode and negative electrode (lithium sheet, size 12.5mm) in the order of negative electrode shell, lithium sheet, separator, electrolyte injection, positive electrode sheet, steel sheet, spring sheet, and positive electrode shell. After assembly, it is laid flat and left to stand for 12 hours, and then placed in a 70℃ oven for 1.5 hours to obtain a lithium-ion battery.
[0067] Subsequently, the flame retardant properties of the above-mentioned flame-retardant gel electrolyte were tested, as were the flame retardant properties and electrochemical properties of the above-mentioned lithium-ion battery. The test results are shown in Tables 2 and 3, respectively.
[0068] The testing methods involved are as follows: Self-extinguishing performance after flame removal: This was evaluated using a spray gun combustion test. Specifically, the flame-retardant gel electrolyte sample was placed in a spray gun flame and ignited for a certain period of time. The flame source was then quickly removed, and the duration of continuous combustion and self-extinguishing time were recorded. If the sample extinguished rapidly without any afterflame after the flame was removed, it was determined to have good self-extinguishing performance, indicating that the electrolyte material possesses effective flame-retardant properties.
[0069] Needle penetration safety test: Place the lithium-ion battery in a 25℃ environment, discharge it at 0.2C to the lower limit voltage, and let it stand for 10 minutes; then charge it at a constant current of 0.5C to the upper limit voltage (4.3V), and then charge it at a constant voltage of 4.3V to a current of 0.05C, and let it stand for 5 minutes; use a high-temperature resistant steel needle with a diameter of (2.0±0.2) mm to penetrate it at a speed of (25±2.5 mm / s) from a direction perpendicular to the battery plates, and the puncture point should be close to the geometric center of the punctured surface (the steel needle stays in the battery); observe for 30 minutes whether the battery catches fire or explodes.
[0070] Coulombic efficiency and capacity retention after 100 cycles were obtained using a WHW-200L-0C-220V-5V50mA-160CH constant temperature test chamber. The test conditions were as follows: the lithium metal battery was left to stand for 12 hours, then charged at a constant current rate of 0.2C, followed by constant current charge and discharge at a constant current rate of 0.2C for five cycles, with the voltage range between 3-4.3V. After that, the battery was left to stand for 5 minutes, then charged and discharged at a constant current rate of 1C for 100 cycles, with the temperature maintained at 25℃.
[0071] Ion transport impedance: obtained by testing with a CS350Pro electrochemical workstation.
[0072] Electrochemical window: Linear scan voltammetry (LSV) was performed using the CHI660E electrochemical workstation from Shanghai Chenhua Instruments Co., Ltd. The test conditions were: voltage range of 0-6V and scan rate of 0.1mV / s.
[0073] Ionic conductivity: AC impedance was measured using a CHI660E electrochemical workstation from Shanghai Chenhua Instruments Co., Ltd. The test conditions were: test voltage 0V, test frequency range 0.1Hz-1MHz, and test amplitude 5mV. Ionic conductivity was calculated according to equation (1): Equation (1); In equation (1), δ is the ionic conductivity, L is the electrolyte thickness, R is the measured resistance, and S is the working electrode area.
[0074] Table 2
[0075] Table 3
[0076] The results above show that the flame-retardant gel electrolyte obtained by the electrolyte precursor provided by this invention can efficiently exert the gas phase and condensation mechanism at high temperature or in the early stage of thermal runaway, effectively capture free radicals, interrupt chain reactions, and form a stable three-dimensional network structure, thereby suppressing side reactions at the electrode-electrolyte interface, effectively fixing active components, and preventing their migration or loss.
[0077] The lithium-ion battery prepared by the flame-retardant gel electrolyte provided by this invention cleverly balances the relationship between ion transport and safety protection. The stable cross-linked network in the flame-retardant gel electrolyte provides a continuous and efficient transport channel for lithium ions, thereby ensuring the high ionic conductivity of the lithium-ion battery. At the same time, the components in the electrolyte precursor work together to fundamentally and significantly improve the fire resistance and thermal runaway protection capabilities of the lithium-ion battery.
[0078] In summary, this invention provides key technical support for the development of next-generation lithium batteries that combine high performance and high safety. The lithium metal battery made from the flame-retardant gel electrolyte provided by this invention can withstand high voltage, has high ionic conductivity, and also has excellent flame retardancy.
[0079] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. An electrolyte precursor, characterized in that, The electrolyte precursor contains phosphate monomers containing carbon-carbon double bonds, acrylate monomers containing urea bonds, acrylate monomers containing cyano groups, and phosphorus-containing crosslinking agents in a molar ratio of 1:1-2:1-3:1-2. The acrylate monomers containing urea bonds are 2-urea ethyl acrylate and / or diurea dimethacrylate.
2. The electrolyte precursor according to claim 1, wherein, The phosphate monomer containing carbon-carbon double bonds is selected from at least one of 2-methyl-2-acrylate-2-hydroxyethyl phosphate, triallyl phosphate, di[2-(methacryloyloxy)ethyl] phosphate, and acrylate phosphate.
3. The electrolyte precursor according to claim 1, wherein, The cyano-containing acrylate monomers are isocyanoethyl methacrylate and / or 2-isocyanoethyl acrylate.
4. The electrolyte precursor according to any one of claims 1-3, wherein, The phosphorus-containing crosslinking agent is obtained by a nucleophilic substitution reaction between a hydroxyl-containing acrylate derivative and a phenylphosphoryl halide derivative containing two chlorine atoms.
5. The electrolyte precursor according to claim 4, wherein, The hydroxyl-containing acrylate derivative is selected from at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate; And / or, the phenylphosphonic halide derivative containing two chlorine atoms is selected from at least one of phenylphosphonic dichloride, phenyl dichlorophosphate, p-tolylphosphonic dichloride, o-methoxyphenylphosphonic dichloride, and p-chlorophenylphosphonic dichloride.
6. A method for preparing a flame-retardant gel electrolyte, characterized in that, The method includes: The flame-retardant gel electrolyte is obtained by thermal polymerization of a mixture containing an electrolyte precursor, a thermosetting agent, and an electrolyte. The electrolyte precursor is the electrolyte precursor according to any one of claims 1-5.
7. The method according to claim 6, wherein, The thermosetting agent is selected from at least one of diaminodiphenylmethane, azobisisobutyronitrile, and 2-methylimidazole; And / or, the electrolyte is a lithium salt electrolyte.
8. The method according to claim 6 or 7, wherein, The weight ratio of the electrolyte precursor, the thermosetting agent, and the electrolyte is 1:0.05-0.1:1-9.
9. The flame-retardant gel electrolyte prepared by the method according to any one of claims 6-8.
10. The application of the flame-retardant gel electrolyte of claim 9 in lithium-ion batteries.