A polymer electrolyte based on bis(vinylsulfone)-methane and a method for preparing the same

Abstract

This invention relates to the field of lithium-ion battery technology, and particularly to a method for preparing a polymer electrolyte based on bis(ethylene sulfone)methane. The method includes: dissolving bis(ethylene sulfone)methane, a soluble metal salt, a plasticizer, and a second monomer by stirring; adding an initiator and stirring until dissolved to obtain an electrolyte; injecting the obtained electrolyte into a battery and encapsulating it; and then performing in-situ polymerization at 50-120°C for 1-10 hours to obtain the polymer electrolyte. This method for preparing a polymer electrolyte based on bis(ethylene sulfone)methane retains the processing and encapsulation advantages of liquid electrolytes while also achieving the safety performance of polymer electrolytes. The addition of sulfone groups to the polymer molecular chain effectively promotes lithium-ion transport and improves the ionic conductivity of the polymer electrolyte. Simultaneously, the addition of sulfone groups to the molecular chain increases the oxidation potential of the polymer electrolyte, thereby improving the battery's cycle performance and capacity retention.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and specifically relates to a polymer electrolyte based on bis(ethylene sulfone)methane and its preparation method. Background Technology

[0002] Lithium-ion batteries are widely used due to their numerous advantages, including high energy density, long cycle life, high operating voltage, no memory effect, low self-discharge rate, rapid charge and discharge capability, and environmental friendliness. Currently, commercially available lithium-ion batteries generally use organic carbonate-based liquid electrolytes. However, traditional liquid lithium-ion batteries contain a large amount of organic electrolyte, which has disadvantages such as easy leakage, flammability, and explosion, posing significant safety hazards. These safety issues limit the further application of this type of electrolyte. In addition, under high-voltage operating conditions, traditional battery systems suffer from poor electrode / electrolyte interface stability, severe electrolyte decomposition, damage to the positive electrode material structure, and dissolution of transition metal ions, all of which severely restrict the improvement of lithium-ion battery operating voltage.

[0003] Polymer electrolytes possess numerous advantages over inorganic and organic solvent electrolytes, including light weight, corrosion resistance, excellent safety performance, and ease of processing, making them ideal materials for electrolytes. They hold broad application prospects in the field of micro-mobile power supplies. However, their low room-temperature conductivity limits their application. For many years, researchers have focused on developing an ionic conductor with good mechanical properties and high ionic conductivity at room temperature. Lithium-ion transport in polymer electrolytes is accomplished through the movement of chain segments in the internal amorphous regions. For polymers with high crystallinity at room temperature, the ionic conductivity is relatively low, failing to meet the room-temperature conductivity requirements of lithium-ion batteries. Furthermore, the low oxidation potential of polymer electrolytes leads to severe decomposition when applied to high-voltage cathode materials, hindering the development of lithium-ion batteries with high output voltage and energy density.

[0004] Chinese patent CN 108258314 A discloses a method for preparing a lithium-ion battery electrolyte adapted to ternary materials, comprising the following steps: (1) purifying and removing impurities and water from a non-aqueous organic solvent; (2) adding an electrolyte lithium salt to the solvent obtained in step (1) at room temperature, stirring until the lithium salt is completely dissolved to obtain a common electrolyte; (3) adding a bis(ethylene sulfone)methane functional additive to the common electrolyte obtained in step (2), stirring and mixing, and letting it stand for 24 hours to obtain an electrolyte adapted to high-voltage nickel-cobalt-manganese ternary cathode material. With the addition of the functional additive, when applied to ternary materials, under a high-voltage working condition of 4.5V, the electrolyte containing the functional additive exhibits good interfacial compatibility with the ternary material, forming a high-performance solid electrolyte interfacial film at the material interface, effectively stabilizing the electrolyte, protecting the stability of the electrode material structure, and thus improving the cycle life of the ternary lithium-ion battery. However, liquid lithium secondary batteries contain a large amount of organic electrolyte, which has disadvantages such as easy leakage, easy combustion, and easy explosion, posing significant safety hazards.

[0005] Chinese patent CN 109449491 A discloses a method for preparing a gel polymer electrolyte material, comprising the following steps: (1) dissolving polyethylene oxide (PEO), tetraol tetra-3-mercaptopropionate (PETT), 1,6-bis(ethylene sulfone)hexane and a thermal initiator in DMF, then adding triethylene glycol dimethyl ether (TEGDME) and lithium salt, and stirring to form a homogeneous mixed solution; (2) coating the mixed solution obtained in step (1) onto a glass plate, heating and polymerizing to obtain a white, semi-transparent electrolyte wet film; (3) vacuum drying the wet film at room temperature for 12-48 hours to obtain the gel polymer electrolyte material. The gel polymer electrolyte material prepared by this invention has good cycle performance in lithium batteries, and its application in lithium-sulfur full batteries can suppress the shuttle effect and improve battery capacity. However, the sulfur loading per unit area is not high, making it impossible to obtain a high-performance lithium-sulfur battery.

[0006] Chinese patent CN 114512713 A discloses a single-ion conductor polymer solid electrolyte, its preparation method, and its application. The raw materials for preparing the single-ion conductor polymer solid electrolyte include a combination of anion acceptor, metal salt, framework material, and initiator. The anion acceptor includes a combination of borate ester molecules and sulfone compounds. By selecting borate ester molecules and sulfone compounds as anion acceptors, and then further reacting them with the framework material in situ, the prepared single-ion conductor polymer solid electrolyte can have high ionic conductivity, thereby enabling solid-state batteries containing it to have high cycle stability, capacity retention, and excellent rate performance. However, this invention uses a monovinyl sulfone compound, resulting in a low sulfone content. Furthermore, the patent requires the preparation of borate ester molecules, which is relatively complex. Borate ester molecules are easily hydrolyzed to generate methanol as a byproduct, leading to low utilization of borate ester molecules during polymerization. Summary of the Invention

[0007] The purpose of this invention is to provide a polymer electrolyte based on bis(ethylene sulfone)methane and its preparation method, which overcomes the defects of traditional battery systems such as poor electrode / electrolyte interface stability, unstable battery structure, and insufficient battery cycle performance under high voltage operating conditions.

[0008] To achieve the above objectives, the present invention provides a method for preparing a polymer electrolyte based on bis(ethylene sulfone)methane, comprising the following steps:

[0009] (1) Dissolve bis(ethylene sulfone)methane, soluble metal salt, plasticizer and second monomer by stirring, then add initiator and stir until dissolved to obtain electrolyte;

[0010] (2) Inject the electrolyte obtained in step (1) into the battery and encapsulate it; then keep it at 50-120℃ for 1-10h and carry out in-situ polymerization to obtain polymer electrolyte.

[0011] Preferably, in the above-described method for preparing the polymer electrolyte based on bis(ethylene sulfonyl)methane, the soluble metal salt is a lithium salt or a sodium salt, wherein the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide; the sodium salt is one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium difluorooxalate borate, sodium difluorosulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide; and the mass ratio of the soluble metal salt to bis(ethylene sulfonyl)methane is 1 to 7:1.

[0012] Preferably, in the above-described method for preparing the polymer electrolyte based on bis(ethylene sulfone)methane, the second monomer is ethylene glycol diacrylate, polyethylene glycol diacrylate, acrylonitrile, or ethyl acrylate; and the mass ratio of the second monomer to bis(ethylene sulfone)methane is 2 to 7:1.

[0013] Preferably, in the above-described method for preparing the polymer electrolyte based on bis(ethylene sulfone)methane, the second monomer is polyethylene glycol diacrylate.

[0014] Preferably, in the above-mentioned method for preparing the polymer electrolyte based on bis(ethylene sulfone)methane, the plasticizer is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl acetate, ethylene glycol diacetate, triethyl glycerol, sulfolane, oxadionitrile, and succinate, and the mass ratio of the plasticizer to bis(ethylene sulfone)methane is 10 to 36:1.

[0015] Preferably, in the above-described method for preparing the polymer electrolyte based on bis(ethylene sulfone)methane, the plasticizer is ethylene glycol diacetate.

[0016] Preferably, in the above-mentioned method for preparing the polymer electrolyte based on bis(ethylene sulfonyl)methane, the initiator is azobisisobutyronitrile, benzoyl peroxide, or diisopropylbenzene peroxide, and the mass ratio of the initiator to bis(ethylene sulfonyl)methane is 0.001 to 0.02:1.

[0017] Preferably, in the above-mentioned method for preparing the polymer electrolyte based on bis(ethylene sulfone)methane, in step (2), the temperature is maintained at 50-60°C for 8-10 hours.

[0018] Preferably, in the above-described method for preparing a polymer electrolyte based on bis(ethylene sulfone)methane, the battery is a lithium-ion battery or a sodium-ion battery.

[0019] A polymer electrolyte based on bis(ethylene sulfone)methane, wherein the polymer electrolyte is prepared by the above-described method for preparing a polymer electrolyte based on bis(ethylene sulfone)methane.

[0020] Compared with existing technologies, the present invention has the following advantages:

[0021] 1. The present invention provides a method for preparing a polymer electrolyte based on bis(ethylene sulfone)methane. The polymer electrolyte is obtained by injecting bis(ethylene sulfone)methane, a soluble metal salt, a second monomer, etc. into a battery and then encapsulating them, followed by in-situ polymerization. This method retains the processing and encapsulation advantages of liquid electrolytes while also achieving the safety performance of polymer electrolytes. The polymer electrolyte and the separator in the battery form an integrated structure with good interfacial bonding and a more stable electrode material structure.

[0022] 2. The method for preparing bis(ethylene sulfone)methane-based polymer electrolytes of the present invention provides a new direction for the use of bis(ethylene sulfone)methane in electrolytes, enabling it to be used not only as an additive but also as a matrix material for polymer electrolytes.

[0023] 3. The method for preparing a polymer electrolyte based on bis(ethylene sulfone)methane of the present invention overcomes the low ionic conductivity of polymers with high crystallinity at room temperature. By adding sulfone groups to the polymer molecular chain, its crystalline structure is disrupted, which effectively promotes lithium-ion transport and improves the ionic conductivity of the polymer electrolyte. Furthermore, bis(ethylene sulfone)methane belongs to the sulfone-containing alkene monomer class, and its sulfone content is higher than that of most monomers, maximizing the sulfone content in the polymer. Simultaneously, the addition of sulfone groups to the molecular chain increases the oxidation potential of the polymer electrolyte, thereby improving the battery's cycle performance and capacity retention.

[0024] 4. The preparation method of the polymer electrolyte based on bis(ethylene sulfone)methane of the present invention is simple in preparation process, has low production cost, and is suitable for large-scale production. Attached Figure Description

[0025] Figure 1 The AC impedance test results are for the battery in Embodiment 1 of this invention.

[0026] Figure 2 The results are from the linear voltammetric scan of the battery in Embodiment 1 of this invention.

[0027] Figure 3 This is a battery cycle performance diagram at a 0.1C rate in Embodiment 1 of the present invention. Detailed Implementation

[0028] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0029] Example 1

[0030] A method for preparing a polymer electrolyte based on bis(ethylene sulfone)methane includes the following steps: 0.1 g of bis(ethylene sulfone)methane (BVSM), 1.75 g of ethylene glycol diacetate (EGDA), and 0.34 g of polyethylene glycol diacrylate (PEGDA600) are weighed and added to a transparent glass bottle, and mixed evenly with magnetic stirring at 40°C. Then, 0.32 g of lithium difluorooxalate borate (LiDFOB) is added and stirred until completely dissolved. The solution is cooled to room temperature (30°C), and then 0.001 g of azobisisobutyronitrile (AIBN) is added and stirred until completely dissolved to obtain the electrolyte. The electrolyte is dropwise added to a coin cell in a glove box and packaged according to the coin cell assembly process. The battery structure is positive electrode / polymer electrolyte / negative electrode, wherein the positive electrode is LiNi0.6Mn0.2Co0.2O2, the negative electrode is lithium metal, and the separator is a nanocellulose membrane. Polymer electrolyte 1 can be obtained by in-situ polymerization after being kept at 60℃ for 10 hours in a constant temperature oven.

[0031] The battery ionic conductivity, oxidation potential, and cycle performance of the polymer electrolyte prepared in Example 1 were tested, and the specific test results are as follows:

[0032] (1) Polymer electrolyte ionic conductivity test

[0033] The polymer electrolyte battery prepared in Example 1 was subjected to AC impedance testing at a voltage amplitude of 10mV and a frequency range of 0.1 to 105Hz. Figure 1 Based on the EIS test results, the impedance spectrum was fitted, and the intercept of the linear axis with the real axis represents the resistance of the electrolyte. The ionic conductivity of the electrolyte was calculated using the formula: σ = L / RS, where L is the thickness of the polymer electrolyte, R is the resistance of the electrolyte, and S is the effective area of ​​the electrolyte. The calculated ionic conductivity of polymer electrolyte 1 at 30℃ is 0.405 mS / cm.

[0034] (2) Oxidation potential test of polymer electrolyte battery

[0035] The polymer electrolyte battery prepared in Example 1 was subjected to linear voltammetry scanning test, and the results are shown in [Figure 1]. Figure 2 The range of -0.5V to 0.5V represents the deposition and stripping process of lithium ions. The linear voltammetric scan curves from 1V to 5V are all stable curves with no significant oxidation peaks. However, when the oxidation potential exceeds 5V, an oxidation peak begins to appear, indicating that the electrolyte has undergone oxidative decomposition. Analysis using the cross-section method yields an oxidation potential of 5.98V for electrolyte G.

[0036] (3) Cyclic performance testing of polymer electrolyte batteries

[0037] The polymer electrolyte battery prepared in Example 1 was tested for charge-discharge cycle performance at room temperature, at a rate of 0.1C and a voltage range of 3–4.3V. Figure 3 The charge-discharge cycle diagram obtained from the test shows that the initial discharge specific capacity of the polymer electrolyte battery is 152.4 mAh / g, and after 100 cycles, the discharge specific capacity of the polymer electrolyte lithium-ion battery is 143.2 mAh / g, with a capacity retention of 93.9%.

[0038] Example 2

[0039] A method for preparing a polymer electrolyte based on bis(ethylene sulfone)methane includes the following steps: 0.05 g of bis(ethylene sulfone)methane (BVSM), 1.75 g of ethylene glycol diacetate (EGDA), and 0.34 g of polyethylene glycol diacrylate (PEGDA600) are weighed and added to a transparent glass bottle, and mixed evenly with magnetic stirring at 40°C. Then, 0.32 g of lithium difluorooxalate borate (LiDFOB) is added and stirred until completely dissolved. The solution is cooled to room temperature (30°C), and then 0.0005 g of azobisisobutyronitrile (AIBN) is added and stirred until completely dissolved to obtain the electrolyte. The electrolyte is dropwise added to a coin cell in a glove box and packaged according to the coin cell assembly process. The battery structure is positive electrode / polymer electrolyte / negative electrode, wherein the positive electrode is LiNi0.6Mn0.2Co0.2O2, the negative electrode is lithium metal, and the separator is a nanocellulose membrane. Polymer electrolyte 2 can be obtained by in-situ polymerization after being kept at 60℃ for 10 hours in a constant temperature oven.

[0040] Example 3

[0041] A method for preparing a polymer electrolyte based on bis(ethylene sulfone)methane includes the following steps: 0.1 g of bis(ethylene sulfone)methane (BVSM), 1.75 g of ethylene carbonate (EC), and 0.34 g of polyethylene glycol diacrylate (PEGDA600) are weighed and added to a transparent glass bottle, and mixed evenly with magnetic stirring at 40°C. Then, 0.32 g of lithium difluorooxalate borate (LiDFOB) is added and stirred until completely dissolved. The solution is cooled to room temperature (30°C), and then 0.001 g of azobisisobutyronitrile (AIBN) is added and stirred until completely dissolved to obtain the electrolyte. The electrolyte is dropwise added to a coin cell in a glove box and packaged according to the coin cell assembly process. The battery structure is positive electrode / polymer electrolyte / negative electrode, wherein the positive electrode is LiNi0.6Mn0.2Co0.2O2, the negative electrode is lithium metal, and the separator is a nanocellulose membrane. Polymer electrolyte 3 can be obtained by in-situ polymerization after being kept at 60℃ for 10 hours in a constant temperature oven.

[0042] Example 4

[0043] A method for preparing a polymer electrolyte based on bis(ethylene sulfone)methane includes the following steps: 0.1 g of bis(ethylene sulfone)methane (BVSM), 1.75 g of ethylene glycol diacetate (EGDA), and 0.34 g of ethylene glycol diacrylate are weighed and added to a transparent glass bottle, and mixed evenly with magnetic stirring at 40°C. Then, 0.32 g of lithium difluorooxalate borate (LiDFOB) is added and stirred until completely dissolved. The solution is cooled to room temperature (30°C), and then 0.001 g of azobisisobutyronitrile (AIBN) is added and stirred until completely dissolved to obtain the electrolyte. The electrolyte is dropwise added to a coin cell in a glove box and packaged according to the coin cell assembly process. The battery structure is positive electrode / polymer electrolyte / negative electrode, wherein the positive electrode is LiNi0.6Mn0.2Co0.2O2, the negative electrode is lithium metal, and the separator is a nanocellulose membrane. Polymer electrolyte 4 can be obtained by in-situ polymerization after being kept at 60℃ for 10 hours in a constant temperature oven.

[0044] Comparative Example 1

[0045] Weigh 1.75g ​​of ethylene glycol diacetate (EGDA) and 0.34g of polyethylene glycol diacrylate (PEGDA600) and add them to a transparent glass bottle. Mix thoroughly with magnetic stirring at 40°C. Then add 0.32g of LiDFOB and stir until completely dissolved. Cool the solution to room temperature (30°C), then add 0.001g of AIBN and stir until completely dissolved to obtain the electrolyte. Add the electrolyte dropwise to a coin cell in a glove box and seal it according to the coin cell assembly process. The battery structure is positive electrode / polymer electrolyte / negative electrode, where the positive electrode is LiNi0.6Mn0.2Co0.2O2, the negative electrode is lithium metal, and the separator is a nanocellulose membrane. Incubate at 60°C for 10 hours in a constant temperature oven. The electrolyte without BVSM is designated as polymer electrolyte 5.

[0046] Comparative Example 2

[0047] Weigh 0.1g of vinyl sulfone, 1.75g ​​of ethylene glycol diacetate (EGDA), and 0.34g of polyethylene glycol diacrylate (PEGDA600) and add them to a transparent glass bottle. Mix thoroughly with magnetic stirring at 40°C. Then add 0.32g of lithium difluorooxalate borate (LiDFOB) and stir until completely dissolved. Cool the solution to room temperature (30°C), then add 0.001g of azobisisobutyronitrile (AIBN) and stir until completely dissolved to obtain the electrolyte. Add the electrolyte dropwise to a coin cell in a glove box and encapsulate it according to the coin cell assembly process. The battery structure is positive electrode / polymer electrolyte / negative electrode, where the positive electrode is LiNi0.6Mn0.2Co0.2O2, the negative electrode is lithium metal, and the separator is a nanocellulose membrane. In-situ polymerization is carried out in a constant temperature oven at 60°C for 10 hours to obtain polymer electrolyte 6.

[0048] The performance (ionic conductivity, electrolyte oxidation potential, specific capacity, and cycle performance) of the batteries containing polymer electrolytes prepared in the examples and comparative examples were tested, and the test results are shown in Table 1.

[0049] As shown in Table 1, compared with the comparative example, the polymer electrolyte prepared in the embodiments of the present invention has significantly improved ionic conductivity and oxidation potential, and the cycle performance and capacity retention of the battery are improved.

[0050] Table 1 shows the battery performance data of the polymer electrolytes prepared in the examples and comparative examples.

[0051]

[0052] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing a polymer electrolyte based on bis(ethylene sulfone)methane, characterized in that, Includes the following steps: (1) Dissolve bis(ethylene sulfone)methane, soluble metal salt, plasticizer and second monomer by stirring. The mass ratio of the second monomer to bis(ethylene sulfone)methane is 2~7:1 to obtain a mixed solution. The second monomer is ethylene glycol diacrylate, polyethylene glycol diacrylate, acrylonitrile or ethyl acrylate. Then add an initiator and stir until dissolved to obtain an electrolyte. (2) Inject the electrolyte obtained in step (1) into the battery and seal it; Then, the polymer electrolyte is obtained by in-situ polymerization after being kept at 50~120℃ for 1~10 hours.

2. The method for preparing a polymer electrolyte based on bis(ethylenesulfone) methane according to claim 1, characterized by, The soluble metal salt is a lithium salt or a sodium salt, wherein the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide; the sodium salt is one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium difluorooxalate borate, sodium difluorosulfonylimide, and sodium bis(trifluoromethanesulfonyl)imide; and the mass ratio of the soluble metal salt to bis(ethylene sulfone)methane is 1 to 7:

1.

3. The method for preparing a polymer electrolyte based on bis(ethylenesulfone) methane according to claim 1, characterized by, The second monomer is polyethylene glycol diacrylate.

4. The method for preparing a polymer electrolyte based on bis(vinylsulfone group)-methane according to claim 1, characterized by, The plasticizer is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl acetate, ethylene glycol diacetate, triethyl glycerol, sulfolane, oxadionitrile, and succinate, and the mass ratio of the plasticizer to bis(ethylene sulfone)methane is 10~36:

1.

5. The method for preparing a polymer electrolyte based on bis(ethylenesulfone) methane according to claim 4, characterized by, The plasticizer is ethylene glycol diacetate.

6. The method for preparing a polymer electrolyte based on bis(ethylenesulfone) methane according to claim 1, characterized by, The initiator is azobisisobutyronitrile, benzoyl peroxide, or diisopropylbenzene peroxide, and the mass ratio of the initiator to bis(ethylene sulfone)methane is 0.001~0.02:

1.

7. The method for preparing a polymer electrolyte based on bis(vinylsulfone group)-methane according to claim 1, characterized by, In step (2), the temperature is maintained at 50~60℃ for 8~10 hours.

8. The method for preparing the polymer electrolyte based on bis(ethylene sulfone)methane according to claim 1, characterized in that, The battery is a lithium-ion battery or a sodium-ion battery.

9. A polymer electrolyte based on bis(vinylsulfone group)-methane, characterized by, The polymer electrolyte is prepared by the method for preparing the polymer electrolyte based on bis(ethylene sulfone)methane as described in any one of claims 1 to 8.

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