A method for preparing a composite plastic-crystalline electrolyte with molecular brushes

Abstract

The application relates to a preparation method and application of a composite plastic crystal electrolyte with a molecular brush. The application belongs to the technical field of electrolyte materials. The composite plastic crystal polymer electrolyte material with the molecular brush is characterized in that the composite plastic crystal polymer electrolyte material is composed of a diaphragm with a molecular brush and a plastic crystal electrolyte obtained by in-situ polymerization in the diaphragm. A mixed solution of polymer monomers, lithium salt, additives and plastic crystal materials is heated to obtain the plastic crystal electrolyte. The application aims to solve the problem of uncontrollable side reactions in the plastic crystal electrolyte, so that the assembled battery can be stably and long-term cycled at room temperature. The preparation method comprises the following steps: (1) preparing the diaphragm with the molecular brush; (2) preparing a mixed solution of the polymer monomers, the lithium salt and the plastic crystal material, and mixing the mixed solution with the treated diaphragm. The application has the advantages of simple preparation process, good mechanical strength, long cycle life of the assembled battery and the like.

Description

Technical Field

[0001] This invention belongs to the field of electrolyte materials technology, and in particular relates to a method for preparing a composite plastic crystal electrolyte and its application. Background Technology

[0002] As electric vehicles, mobile phones, and other products gradually become an indispensable part of people's lives, the demand for high energy density batteries is becoming increasingly strong. However, with the increase in battery energy density, especially when using electrolytes, battery safety issues have become uncontrollable.

[0003] To address battery safety concerns, solid-state electrolytes, especially polymer solid-state electrolytes, are increasingly becoming an alternative to flammable electrolytes. However, solid-state electrolytes often suffer from low conductivity and narrow conductivity windows. Plastic crystal electrolytes, as a type of polymer solid-state electrolyte, possess high ionic conductivity, a wide conductivity window, and excellent thermal stability; however, the side reactions between them and the lithium anode limit their application in solid-state batteries.

[0004] One common method to mitigate side reactions between the crystalline electrolyte and the lithium anode is to introduce a polymer network into the crystalline electrolyte for fixation (e.g., CN 116247289 A). However, the introduction of polymers can reduce the conductivity of the electrolyte to some extent. Introducing fillers for fixation (e.g., CN 113410523 A) is also a common method, but the introduction of fillers may trigger polymerization of the crystalline material on the filler surface. Summary of the Invention

[0005] One of the objectives of this invention is to solve the problems of uncontrollable side reactions in plastic crystal electrolytes, and to provide a composite plastic crystal polymer electrolyte with high ionic conductivity, wide chemical stability window and good mechanical strength. The assembled battery can still have good cycle performance at a high current density.

[0006] The preparation method of the composite plastic crystal electrolyte with molecular brush of the present invention is carried out according to the following steps:

[0007] I. Preparation of a membrane with a molecular brush: 2-Acrylamido-2-methylpropanesulfonic acid and lithium carbonate were mixed in N,N-dimethylformamide at room temperature and stirred for 10-60 min. Then, the membrane, which had been treated with UV / ozone for 0.5-2 h, was added to the above solution, followed by benzoyl peroxide, 2,2-bipyridine, copper chloride, and toluene. The mixture was stirred under argon atmosphere for 6-16 h. The membrane was then removed, washed, and dried for further experimental use. The mass ratio of 2-acrylamido-2-methylpropanesulfonic acid to lithium carbonate was (6-4):1; the mass ratio of benzoyl peroxide, 2,2-bipyridine, and copper chloride was (20-15):(8-4):1; and the mass ratio of N,N-dimethylformamide to toluene was (8-4):1.

[0008] II. Preparation of Composite Plastic Crystal Electrolyte with Molecular Brush and its Application in Batteries: Polymer monomers, lithium salts, additives, and plastic crystal materials were mixed and stirred for 0.5-1 h. Azobisisobutyronitrile was added and stirred until completely dissolved. The mixture was then dropped onto a treated separator, and the electrodes were stacked and assembled into a battery. The assembled battery was heated at 40-100 °C for 0.5-1 h.

[0009] The composite plasticized polymer electrolyte material with molecular brush of the present invention can also adopt the following technical solutions:

[0010] The composite plastic crystal electrolyte with molecular brush is characterized in that: the polymer monomer is one or a mixture of two of ethoxylated trimethylolpropane triacrylate, ethylene glycol dimethacrylate, polyethylene glycol methyl ether methacrylate, and methyl acrylate.

[0011] The composite plastic crystal electrolyte with molecular brush is characterized in that: the lithium salt is one or a mixture of several of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonylimide), and lithium dioxoborate.

[0012] The composite plastic crystal electrolyte with molecular brush is characterized in that: the additive is one or a mixture of several of fluoroethylene carbonate, thioethylene carbonate, and methyltrifluoroethyl carbonate.

[0013] The composite plasticized electrolyte with molecular brush is characterized in that the plasticized material is succinic anionyl nitrile.

[0014] The composite plastic crystal electrolyte with molecular brush is characterized in that: the amount of lithium salt is 0.2-2 times the mass of polymer monomer, the amount of plastic crystal material is 0.05-2 times the mass of polymer matrix, and the amount of additives is 0.1-1 times the mass of polymer matrix.

[0015] Advantages and beneficial effects of the present invention:

[0016] This invention combines a membrane with molecular brushes and a crystalline electrolyte. Compared with existing technologies, the composite crystalline electrolyte with molecular brushes of this invention has advantages such as high conductivity, good interfacial stability, and high tensile strength. The lithium 2-acrylamide-2-methylpropanesulfonate molecular brushes grafted onto the membrane surface not only complex the crystalline structure but also provide a lithium-ion transport path. This dual design ensures that the battery assembled with this composite electrolyte exhibits good interfacial stability at the negative electrode, guaranteeing good cycle performance even at high rates. The composite crystalline electrolyte with molecular brushes prepared in this way can be widely used in power supplies for computers and mobile phones, and even in power supplies for drones and electric vehicles. Attached Figure Description

[0017] Figure 1 The charge-discharge curves of the assembled solid-state battery under 3C conditions;

[0018] Figure 2 The assembled solid-state battery and its cycling performance under 3C conditions. Detailed Implementation

[0019] Specific Implementation Method 1: The preparation of a composite plastic crystal electrolyte with molecular brushes and its application in batteries according to this embodiment are carried out according to the following steps:

[0020] I. Preparation of the membrane with molecular brush: 2 g of 2-acrylamido-2-methylpropanesulfonic acid and 0.37 g of lithium carbonate were mixed in N,N-dimethylformamide at room temperature and stirred for 30-60 min. Then, the membrane, which had been treated with UV / ozone for 1 h, was added to the above solution, followed by 6.06 mg of benzoyl peroxide, 1.17 mg of 2,2-bipyridine, 0.34 mg of copper chloride, and 1 mL of toluene. The mixture was stirred under argon atmosphere for 5-10 h. The membrane was then removed, washed, and dried for further experimental use.

[0021] II. Preparation of Composite Plastic Crystal Electrolyte with Molecular Brush and its Application in Batteries: 50 μL of ethoxylated trimethylolpropane triacrylate, 10 μL of fluoroethylene carbonate, 200 μg of lithium bis(trifluoromethanesulfonyl)imide, and 250 μg of succinate were mixed and stirred for 0.5–1 h. Then, 70 μg of azobisisobutyronitrile was added and stirred until completely dissolved to obtain a precursor solution. This precursor solution was dropped onto a treated separator, and the electrodes were stacked and assembled into a battery. The assembled battery was heated at 50–100 °C for 0.8–1 h to obtain solid-state battery 1. The charge-discharge curves and cycle performance of the assembled solid-state battery at 3C are shown below. Figure 1 and Figure 2 As shown.

[0022] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that 10 μL of methyl acrylate is added to the precursor solution described in step one. Everything else is the same as in Specific Implementation Method One.

[0023] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 in that 10 μL of ethylene glycol dimethacrylate is added to the precursor solution described in step 1. Everything else is the same as in Specific Implementation Method 1.

[0024] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method One in that 10 μg of lithium dioxoborate is added to the precursor solution described in step one. Everything else is the same as in Specific Implementation Method One.

[0025] The invention was verified using the following experiments:

[0026] Experiment: The solid-state lithium iron phosphate battery assembled in Experiment 1 was used for testing:

[0027] A constant current charge-discharge test was performed using a charge-discharge tester to measure the cycle performance curve of the solid-state battery. The charge-discharge voltage range was 2.8V to 4.0V. Figure 1 As shown.

[0028] The assembled solid-state battery can stably cycle 1500 times at a 3C current density, such as... Figure 2 As shown.

Claims

1. A method for preparing a composite plastic crystal electrolyte with a molecular brush, characterized in that, The preparation method of the composite plastic crystal electrolyte with molecular brush is carried out according to the following steps: I. Preparation of a membrane with molecular brushes: 2-Acrylamido-2-methylpropanesulfonic acid and lithium carbonate are mixed in N,N-dimethylformamide at room temperature and stirred for 10-60 min; then, the membrane treated with UV / ozone for 0.5-2 h is added to the above solution, followed by the addition of benzoyl peroxide, 2,2-bipyridine, copper chloride, and toluene, and stirred under argon atmosphere for 6-16 h; then, the membrane is removed, washed, and dried; wherein, the mass ratio of 2-acrylamido-2-methylpropanesulfonic acid to lithium carbonate is (6-4):1; the mass ratio of benzoyl peroxide, 2,2-bipyridine, and copper chloride is (20-15): (8-4):1; and the mass ratio of N,N-dimethylformamide to toluene is (8-4):

1. II. Preparation of composite plastic crystal electrolyte with molecular brush and its application in batteries: Polymer monomers, lithium salts, additives and plastic crystal materials are mixed and stirred for 0.5-1 h. Azobisisobutyronitrile is added to the mixture and stirred until completely dissolved. The mixture is then dropped onto the treated separator, and the electrodes are stacked and assembled into a battery. The assembled battery is heated at 40-100 °C for 0.5-1 h. The plastic crystal material is butadiene nitrile.

2. The method for preparing a composite plastic crystal electrolyte with a molecular brush according to claim 1, characterized in that, The mass ratio of 2-acrylamide-2-methylpropanesulfonic acid to lithium carbonate is 5.4:

1.

3. The method for preparing a composite plastic crystal electrolyte with a molecular brush according to claim 1, characterized in that, The mass ratio of benzoyl peroxide, 2,2-bipyridine, and copper chloride is 18:4:

1.

4. The method for preparing a composite plastic crystal electrolyte with a molecular brush according to claim 1, characterized in that, The polymer monomer is one or a mixture of two of the following: ethoxylated trimethylolpropane triacrylate, ethylene glycol dimethacrylate, polyethylene glycol methyl ether methacrylate, and methyl acrylate.

5. The method for preparing a composite plastic crystal electrolyte with a molecular brush according to claim 1, characterized in that, The lithium salt is one or a mixture of several of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonylimide), and lithium dioxoborate.

6. The method for preparing a composite plastic crystal electrolyte with a molecular brush according to claim 1, characterized in that, The additive is one or a mixture of several of the following: fluoroethylene carbonate, thioethylene carbonate, and methyltrifluoroethyl carbonate.

7. The method for preparing a composite plastic crystal electrolyte with a molecular brush according to claim 1, characterized in that, The plasticizing material is succinic anhydride.

8. The method for preparing the composite plastic crystal electrolyte with molecular brush according to any one of claims 1 to 6, characterized in that, The amount of lithium salt is 0.2-2 times the mass of the polymer monomer, the amount of plastic crystal material is 0.05-2 times the mass of the polymer monomer, and the amount of additives is 0.1-1 times the mass of the polymer monomer.

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