Polymer gel-state electrolyte as well as preparation method and application thereof

Abstract

The invention discloses a polymer gel-state electrolyte between a positive electrode and a negative electrode. The polymer gel-state electrolyte is obtained by carrying out polymerization reaction on a mixture containing glycidyl acrylate, polyethylene glycol diacrylate, an initiator and an electrolyte. The prepared polymer gel-state electrolyte is used as an ion conducting medium of a lithium ion battery, and can reduce the interface resistance between the positive and negative electrodes and the electrolyte and improve the ionic conductivity while separating the positive and negative electrodes from each other. The polymer gel-state electrolyte provides a new direction for the development of lithium ion batteries.

Description

Technical Field

[0001] The present application relates to a polymer gel electrolyte and its preparation method and application, belonging to the technical field of quasi-solid-state lithium-ion batteries. Background Art

[0002] In recent years, due to the exhaustion of traditional fossil energy and the increasingly serious environmental pollution, new energy storage devices that are green, safe, and efficient have attracted much attention. Among them, quasi-solid-state lithium-ion batteries are regarded as new energy batteries because of their high theoretical energy density, greenness, safety, and reliability. The commercial development of quasi-solid-state lithium-ion batteries is restricted by cathode materials, electrolytes, separators, and anode materials. Among them, most studies focus on organic solvents, resulting in serious safety problems. These traditional organic electrolytes have limitations such as decomposition, combustion, volatilization, formation of lithium dendrites, and formation of harmful by-products. The use of liquid electrolytes in lithium-ion batteries poses a serious threat to their safety and cycle stability. Therefore, it is urgent to develop safe quasi-solid electrolyte-based lithium-ion batteries. Summary of the Invention

[0003] The purpose of the present invention is to provide a polymer gel electrolyte between positive and negative electrodes. The polymer gel electrolyte is obtained by a polymerization reaction of a mixture containing glycidyl acrylate (GMA), polyethylene glycol diacrylate (PEGDA), an initiator, and an electrolyte. The prepared polymer gel electrolyte, as an ion-conducting medium for lithium-ion batteries, can reduce the interfacial resistance between the positive and negative electrodes and the electrolyte while separating the contact between the positive and negative electrodes, and improve the ionic conductivity. The polymer gel electrolyte provides a new direction for the development of lithium-ion batteries.

[0004] According to the first aspect of the present application, a polymer gel electrolyte is provided. The polymer gel electrolyte is obtained by a polymerization reaction of a mixture containing glycidyl acrylate (GMA), polyethylene glycol diacrylate (PEGDA), an initiator, and an electrolyte.

[0005] Optionally, the electrolyte in the present application is a commercially available electrolyte.

[0006] Optionally, the initiator is selected from 2,2'-azobisisobutyronitrile (AIBN).

[0007] Optionally, after the polymerization reaction of glycidyl acrylate and polyethylene glycol diacrylate, a polyethylene glycol diacrylate-glycidyl acrylate copolymer is obtained.

[0008] Optionally, the electrolyte includes a lithium salt and a solvent; the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium difluoro(oxalato)borate; the solvent is selected from at least one of ester compounds and ether compounds;

[0009] Preferably, the ester compound is selected from at least one of dimethyl ethylene carbonate, dimethyl carbonate, ethyl carbonate, and fluoroethylene carbonate; the ether compound is selected from hydrofluoroethers.

[0010] According to the second aspect of the present application, a method for preparing the above polymer gel electrolyte is provided, and the preparation method includes:

[0011] Transfer a mixture containing glycidyl acrylate, polyethylene glycol diacrylate, an initiator, and an electrolyte solution to the surface of the electrode material, and obtain the polymer gel electrolyte after heating.

[0012] Optionally, the preparation method includes:

[0013] Step S1: Mix an initiator, glycidyl acrylate, and polyethylene glycol diacrylate to obtain a polymer precursor solution;

[0014] Step S2: Add an electrolyte solution to the polymer precursor solution, transfer it to the surface of the electrode material, and obtain the polymer gel electrolyte.

[0015] As a specific embodiment, the preparation method includes:

[0016] (1) Mix a solvent and a lithium salt in a certain proportion to obtain an electrolyte solution, add two polymer monomers and an initiator to the electrolyte solution in proportion to obtain a blend, and stir to obtain a polymer precursor solution;

[0017] (2) Drop the polymer precursor solution obtained in step (1) on the surface of the electrode material, and obtain the polymer gel electrolyte after heating.

[0018] Optionally, the preparation method of the polymer precursor solution includes: adding an initiator 2,2-azobisisobutyronitrile (1-5 wt%) to a mixed solution of polyethylene glycol diacrylate and glycidyl acrylate, and stirring to obtain a polymer precursor solution.

[0019] Optionally, the electrode material includes a positive electrode material or a negative electrode material.

[0020] Optionally, step (2) includes:

[0021] Drop the polymer precursor solution obtained in step (1) on the surfaces of the positive electrode material and the negative electrode material, uniformly infiltrate and be able to coat the material surface, and a polymer gel electrolyte can be formed after heating.

[0022] Optionally, the solvent and the lithium salt in the electrolyte solution are in a common commercial electrolyte ratio.

[0023] Optionally, the volume ratio of the glycidyl acrylate to the polyethylene glycol diacrylate is 3 to 30:1;

[0024] The mass ratio of the total mass of the glycidyl acrylate and the polyethylene glycol diacrylate to the mass of the initiator is 100 to 20:1;

[0025] In the electrolyte, the concentration of the lithium salt is 1.0 to 2.0 mol / L;

[0026] The volume ratio of the electrolyte to the polymer precursor solution is 3 to 5:1.

[0027] Optionally, the upper limit of the volume ratio of the glycidyl acrylate to the polyethylene glycol diacrylate is selected from 30:1, 20:1, 10:1, 5:1, and the lower limit is selected from 3:1, 20:1, 10:1, 5:1.

[0028] Optionally, the upper limit of the mass ratio of the total mass of the glycidyl acrylate and the polyethylene glycol diacrylate to the mass of the initiator is selected from 100:1, 80:1, 60:1, 40:1, and the lower limit is selected from 20:1, 80:1, 60:1, 40:1.

[0029] Optionally, in the electrolyte, the upper limit of the concentration of the lithium salt is selected from 2 mol / L, 1.5 mol / L, and the lower limit is selected from 1 mol / L, 1.5 mol / L.

[0030] Optionally, the upper limit of the volume ratio of the electrolyte to the polymer precursor solution is selected from 5:1, 4:1, and the lower limit is selected from 3:1, 4:1.

[0031] Optionally, the heating conditions are: temperature is 60 - 100 °C, time is 2 - 40 min.

[0032] Optionally, the upper limit of the heating temperature is selected from 100 °C, 90 °C, 80 °C, 70 °C, and the lower limit is selected from 60 °C, 70 °C, 80 °C, 90 °C.

[0033] Optionally, the upper limit of the heating time is selected from 40 min, 30 min, 20 min, 10 min, 5 min, and the lower limit is selected from 2 min, 30 min, 20 min, 10 min, 5 min.

[0034] Optionally, the preparation of the polymer gel electrolyte is carried out under water - and oxygen - isolated conditions.

[0035] The polymer gel electrolyte provided by the present application serves as a lithium - ion transport channel, protecting the lithium negative electrode while improving the ionic conductivity.

[0036] According to the third aspect of the present application, a lithium-ion battery is provided, and the lithium-ion battery includes the above-mentioned polymer gel electrolyte.

[0037] Due to its excellent ionic conductivity and the ability to protect the lithium anode, the polymer gel electrolyte of the present application enables the lithium-ion battery assembled with this quasi-solid electrolyte to have high safety and long-term stability.

[0038] The beneficial effects that can be achieved by the present application include:

[0039] 1) The preparation method of the polymer gel electrolyte provided by the present application has a simple synthesis method, requires common instruments, is simple and easy to implement, and is easy to scale up production.

[0040] 2) The quasi-solid electrolyte provided by the present application has excellent ionic conductivity, lithium anode protection ability, and excellent charge and discharge performance and safety of the lithium-ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a high-magnification cross-sectional morphology diagram of Example 1 of the present application; Figure 1 The scale in it is 100 μm.

[0042] Figure 2 It is an optical diagram of Example 2 of the present application.

[0043] Figure 3 It is an assembled diagram of button batteries of Examples 1-4 of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] The present application will be described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0045] Unless otherwise specified, the raw materials in the embodiments of the present application are all purchased through commercial channels.

[0046] For those conditions not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0047] The morphological characteristics of the samples were analyzed by scanning electron microscopy (SEM), and the analysis instrument was a scanning electron microscope 200F (Quantu 200F).

[0048] Figure 3 It is an assembled diagram of button batteries of Examples 1-4 of the present application, from top to bottom are the negative electrode case, gasket, lithium sheet, electrolyte membrane, positive electrode material, and positive electrode case.

[0049] The features and properties of the present invention will be further described in detail below with reference to the embodiments.

[0050] Preparation method of lithium-ion battery in the embodiment of the present application: Lithium cobaltate LCO, graphene (mixed solution, graphene solid content of 5%), multi-walled carbon nanotubes MWCNT, and polyvinylidene fluoride PVDF are added to an agate mortar in a mass ratio of 12:1:1:1 and ground for 30 min, and then ground with NMP as the solvent (ground evenly) until it presents a uniform viscous state. After carefully wiping and cleaning the coater with anhydrous ethanol, turn on the vacuum pump, lay the aluminum foil flat on the coater, adjust the coating thickness of the coater, then carefully scrape off the ground positive electrode material with a spoon, spread it at one end of the aluminum foil, adjust the speed of the doctor blade, turn on the coater, and slowly spread and coat the positive electrode. Put the prepared positive electrode (aluminum foil) into a vacuum drying oven, and the drying conditions are a temperature of 120 °C and vacuum drying for 24 h. Obtain the dried positive electrode, lay it flat on a slicer with a diameter of 14 mm, and cut it at a flat and uniform surface to obtain the positive electrode sheet of the button battery. Before assembling the battery, the positive electrode material must be weighed and recorded, and then put into the glove box to prepare for assembling the battery. The assembly of the battery is carried out in the glove box. According to the test requirements, assemble a button-type battery of model 2016 (control in the glove box: O2 < 0.1 ppm, H2O < 0.1 ppm), and stack the materials used for assembling the battery in order in the glove box and align them with the center of the positive electrode case. Figure 3 Put the assembled battery into a manual hydraulic button battery pressing machine with tweezers, manually press the pressure to 50 Mpa, and keep it for 2 - 3 seconds to press it into a button battery. Label the prepared button battery for subsequent detection of battery performance.

[0051] Example 1

[0052] Take 30 mL of GMA, add 1 mL of PEGDA, stir for 5 min, and then add 350 mg of AIBN and continue to stir for 30 min to obtain a polymer precursor solution.

[0053] Take 30 mL of electrolyte (1 M LiPF6 in DEC:DMC:EC = 1:1:1 V% with 5% FEC), add 10 mL of the polymer precursor solution, and stir for 30 min to obtain polymer precursor sample 1. Figure 1 This is the high-magnification cross-sectional morphology diagram of Example 1 of the present application; Figure 1 The scale in is 100 μm. Drop sample 1 on the surfaces of the positive and negative electrode materials, drop 3 - 10 drops at one time, so that sample 1 fully infiltrates the electrode materials and covers the surface. After placing it on a heating table at 75 °C and heating for 5 min, sample 1 will form a polymer gel electrolyte layer on the electrode surface. When assembling a button battery with the heated positive and negative electrode materials, it can not only isolate the positive and negative electrodes, but also solve the problem of poor interface contact between the electrode materials and the electrolyte layer, and improve the charge and discharge performance of the battery. The above operations are all carried out under oxygen and water isolation conditions.

[0054] Example 2

[0055] 10 mL of GMA was added to 1 mL of PEGDA and stirred for 5 min, then 150 mg of AIBN was added and stirring was continued for 30 min to obtain a pre-polymer solution.

[0056] 30 mL of electrolyte solution (1 M LiPF6 in DEC:DMC:EC = 1:1:1 V% with 5% FEC) was added to 10 mL of the pre-polymer solution and stirred for 30 min to obtain polymer precursor sample 2. Figure 2 This is the optical diagram of Example 2 of this application. Taking sample 2 as an example, sample 2 was dropped on the surfaces of the positive and negative electrode materials. For the first time, 2 drops of sample 2 were dropped to allow sample 2 to fully infiltrate the electrode materials. After being placed on a heating table at 75 °C and heated for 3 min, 4 drops of sample 2 were dropped again on the above electrode surfaces. After the electrode surfaces were evenly covered with sample 2, heating was continued on the heating table at 75 °C for 5 min. Then, sample 2 would form a polymer gel electrolyte layer on the electrode surfaces. When assembling a button battery with the heated positive and negative electrode materials, it could not only isolate the positive and negative electrodes, but also solve the problem of poor interface contact between the electrode materials and the electrolyte layer, and improve the charge and discharge performance of the battery. The above operations were all carried out under oxygen- and water-proof conditions.

[0057] Example 3

[0058] 8 mL of GMA was added to 1 mL of PEGDA and stirred for 5 min, then 75 mg of AIBN was added and stirring was continued for 30 min to obtain a pre-polymer solution.

[0059] 15 mL of electrolyte solution (1 M LiPF6 in DEC:DMC:EC = 1:1:1 V% with 5% FEC) was added to 5 mL of the pre-polymer solution and stirred for 30 min to obtain polymer precursor sample 3. Sample 3 was dropped on the surfaces of the positive and negative electrode materials. For the first time, 2 drops of sample 3 were dropped to allow sample 3 to fully infiltrate the electrode materials. After being placed on a heating table at 75 °C and heated for 3 min, 4 drops of sample 3 were dropped again on the above electrode surfaces. After the electrode surfaces were evenly covered with sample 3, heating was continued at 75 °C for 3 min. Then, a button battery was assembled with the heated positive and negative electrode materials. After assembly, it was placed on a heating table at 75 °C and heated for 3 min. Then, sample 3 would form a polymer gel electrolyte layer on the electrode surfaces. This electrolyte layer could not only isolate the positive and negative electrodes, but also solve the problem of poor interface contact between the electrode materials and the electrolyte layer, and improve the charge and discharge performance of the battery. The above operations were all carried out under oxygen- and water-proof conditions.

[0060] Example 4

[0061] 8 mL of GMA was added to 1 mL of PEGDA and stirred for 5 min. Then 75 mg of AIBN was added and stirring was continued for 30 min to obtain a pre-polymer solution.

[0062] 15 mL of electrolyte (1 M LiPF6 in DEC:DMC:EC = 1:1:1 V% with 5% FEC) was taken and 3 mL of the pre-polymer solution was added, followed by stirring for 30 min to obtain a polymer precursor sample 4. Sample 4 was dropped into a polytetrafluoroethylene circular mold with a diameter of 30 cm. Each time 1.0 mL of sample 4 was dropped to make sample 1 evenly distributed on the inner surface of the mold. The mold was placed on a heating table at 75 °C and heated for 5 min, and a polymer gel electrolyte membrane was formed inside the mold. The electrolyte membrane was removed from the mold and cut into circular pieces with a diameter of 16 mm. When assembling the button cell, the circular piece was placed between the positive and negative electrode materials, serving as both a separator to isolate the positive and negative electrodes and a conductor of lithium ions to provide an ion channel, thus solving safety problems such as electrolyte leakage of the battery. The above operations were all carried out under oxygen- and water-proof conditions.

[0063] As described above, only several embodiments of the present application are provided, and no any form of limitation is imposed on the present application. Although the present application is disclosed with preferred embodiments as above, it is not intended to limit the present application. Any person skilled in the art, without departing from the scope of the technical solution of the present application, makes some changes or modifications using the disclosed technical content, which are equivalent to equivalent embodiments and all fall within the scope of the technical solution.

Claims

1. A polymer gel electrolyte, characterized in that, The polymer gel electrolyte is obtained by a polymerization reaction of a mixture containing glycidyl acrylate, polyethylene glycol diacrylate, an initiator, and an electrolyte solution.

2. The polymer gel electrolyte according to claim 1, characterized in that, The initiator is selected from 2,2-azobisisobutyronitrile.

3. The polymer gel electrolyte according to claim 1, characterized in that, After the glycidyl acrylate and polyethylene glycol diacrylate undergo a polymerization reaction, a polyethylene glycol diacrylate-glycidyl acrylate copolymer is obtained.

4. The polymer gel electrolyte according to claim 1, characterized in that, The electrolyte solution includes a lithium salt and a solvent; the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, and lithium difluoro(oxalato)borate; the solvent is selected from at least one of ester compounds and ether compounds. Preferably, the ester compound is selected from at least one of dimethyl ethylene carbonate, dimethyl carbonate, ethyl carbonate, and vinyl fluorocarbonate; the ether compound is selected from hydrofluoroether.

5. A method for preparing the polymer gel electrolyte according to any one of claims 1 to 4, characterized in that, The preparation method includes: Transferring the mixture containing glycidyl acrylate, polyethylene glycol diacrylate, an initiator, and an electrolyte solution to the surface of the electrode material, and obtaining the polymer gel electrolyte after heating.

6. The preparation method according to claim 5, characterized in that, The preparation method includes: Step S1, mixing the initiator, glycidyl acrylate, and polyethylene glycol diacrylate to obtain a polymer precursor solution. Step S2, adding the electrolyte solution to the polymer precursor solution, transferring it to the surface of the electrode material, and obtaining the polymer gel electrolyte.

7. The preparation method according to claim 6, characterized in that, The volume ratio of the glycidyl acrylate to the polyethylene glycol diacrylate is 3 to 30:

1. The mass ratio of the total mass of the glycidyl acrylate and the polyethylene glycol diacrylate to the mass of the initiator is 100 to 20:

1. In the electrolyte solution, the concentration of the lithium salt is 1.0 to 2.0 mol / L. The volume ratio of the electrolyte solution to the polymer precursor solution is 3 to 5:

1.

8. The preparation method according to claim 5, characterized in that, The heating conditions are: the temperature is 60 - 100 °C, and the time is 2 - 40 min.

9. The preparation method according to claim 5, characterized in that, The preparation of the polymer gel electrolyte is carried out under conditions of water isolation and oxygen isolation.

10. A lithium-ion battery, characterized in that, The lithium ion battery includes the polymer gel electrolyte according to any one of claims 1 to 4.

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