CN111261936A - Composite electrolyte and preparation method thereof - Google Patents
Composite electrolyte and preparation method thereof Download PDFInfo
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- CN111261936A CN111261936A CN201811450081.XA CN201811450081A CN111261936A CN 111261936 A CN111261936 A CN 111261936A CN 201811450081 A CN201811450081 A CN 201811450081A CN 111261936 A CN111261936 A CN 111261936A
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- Prior art keywords
- lithium
- sodium
- high molecular
- carbon quantum
- electrolyte
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a composite electrolyte and a preparation method thereof, wherein the polymer electrolyte comprises a high molecular polymer, carbon quantum dots and organic lithium salt or organic sodium salt, and the high molecular polymer is selected from one of polyoxyethylene, polyacrylonitrile or polymethyl methacrylate. The preparation method is that the carbon quantum dots are prepared by taking organic ketone or organic aldehyde as raw materials and then are compounded with a high molecular polymer matrix and organic lithium/sodium salt. The invention can effectively reduce the crystalline phase of the polymer matrix in the electrolyte, improve the dissociation rate of lithium/sodium salt, and obviously improve the electrochemical properties of the polymer electrolyte, such as ionic conductivity and the like.
Description
Technical Field
The invention relates to a polymer electrolyte and a preparation method thereof, in particular to a lithium/sodium ion battery composite solid polymer electrolyte and a preparation method thereof.
Background
The electrolyte is an essential component of the lithium/sodium ion battery, plays a role in ion transmission between the positive electrode and the negative electrode, and plays a vital role in the aspects of specific energy density, safety, cycling stability, high rate performance, cost and the like of the battery.
Most of the electrolytes used in the conventional lithium/sodium ion batteries are organic liquid electrolytes. Because the liquid electrolyte contains organic solvents with low ignition points and low boiling points, the electrolyte is easy to combust under the condition of large current or overcharge of the battery, so that the battery is ignited and exploded. In addition, the organic liquid is also liable to leak, resulting in poor cycle performance and safety performance of the battery. Therefore, it is extremely important to develop and study an electrolyte having high safety performance.
In recent years, research on electrolytes is gaining favor, not only because of their solid-state structure, they overcome the safety problems associated with the use of organic electrolytes, but also they have advantages such as low reactivity with electrode materials, light weight, flexible and variable shape, and easy processing. However, the electrolyte has limited ion conductivity, and the low conductivity results in poor cycle and rate performance of the battery, which hinders the practical application of the battery in lithium/sodium ion batteries.
Disclosure of Invention
The invention mainly aims to provide a composite electrolyte and a preparation method thereof, which can effectively solve the problem of limited ion conduction capability in the electrolyte and improve the ion conductivity of the electrolyte. The invention is realized by the following scheme:
a composite electrolyte comprises a high molecular polymer, a carbon quantum dot and an organic lithium salt or an organic sodium salt, wherein the lithium salt is selected from one or more of lithium perchlorate, lithium trifluoromethanesulfonate and lithium bistrifluoromethanesulfonylimide, and the sodium salt is selected from one or more of sodium perchlorate, sodium trifluoromethanesulfonate and sodium bistrifluoromethanesulfonylimide; the high molecular polymer is selected from one of polyoxyethylene, polyacrylonitrile or polymethyl methacrylate polymer.
The solid electrolyte performs better under the following conditions:
(1) the average diameter of the carbon quantum dots is 3-5 nm, and the mass ratio of the carbon quantum dots to the high molecular polymer is not higher than 10%.
(2) The molecular weight of the high molecular polymer is 100,000-1,000,000 g/mol.
(3) The thickness of the electrolyte membrane is 50 to 500 μm.
A preparation method for preparing a composite electrolyte comprises the following steps:
mixing an alkali metal hydroxide with a ketone organic matter or aldehyde organic matter solution for at least 1 hour, and reacting at room temperature for at least 3 days, wherein the concentration of the alkali metal hydroxide in the solution is 0.1-0.5 g/mL; after the reaction is finished, adjusting the pH value of the solution to 6-8, and then carrying out dispersion, separation, cleaning and vacuum drying to obtain carbon quantum dot solid particles with the average diameter of 3-5 nm; the dispersion can be carried out by ultrasonic dispersion method, and the separation is generally centrifugal separation.
(II) dissolving the carbon quantum dots, the high molecular polymer and lithium salt or sodium salt prepared in the step I in an organic solvent, stirring for at least 12 hours, pouring into a mold, and performing vacuum drying to obtain an electrolyte; the lithium salt is selected from one or more of lithium perchlorate, lithium trifluoromethanesulfonate and lithium bistrifluoromethanesulfonylimide, and the sodium salt is selected from one or more of sodium perchlorate, sodium trifluoromethanesulfonate and sodium bistrifluoromethanesulfonylimide; the high molecular polymer is selected from one of polyoxyethylene, polyacrylonitrile or polymethyl methacrylate polymer.
In order to prepare the composite electrolyte with better performance, the following optimized process parameters can be adopted:
(1) in the step I, the ketone organic matter is acetone, and the aldehyde organic matter solution adopts 40% acetaldehyde aqueous solution.
(2) And II, using the carbon quantum dots in the step II in an amount which is not more than 10% of the mass of the high molecular polymer.
(3) The molecular weight of the high molecular polymer used in the step II is 100,000-1,000,000 g/mol.
(4) The molar ratio of the lithium salt or the sodium salt in the step II to the polar functional group unit in the high molecular polymer is 1 (1-40). For example, the functional group unit of polyoxyethylene is an oxyethylene segment, the functional group unit of polyacrylonitrile is an acrylonitrile segment, and the functional group unit of polymethyl methacrylate is a methyl methacrylate segment.
(5) The temperature of vacuum drying in the step I is 70-150 ℃.
(6) And (3) controlling the thickness of the electrolyte membrane to be 50-100 mu m by controlling the amount of the mixture poured into the mould in the step (II).
Compared with the prior art, the carbon quantum dots are compounded with the high molecular polymer and the organic lithium/sodium salt to obtain the novel composite electrolyte membrane, and the carbon quantum dots have small size and good dispersibility, can be uniformly dispersed in the high molecular polymer, and can effectively reduce the crystallinity of a polymer matrix in the electrolyte; meanwhile, the carbon quantum dots can interact with organic lithium and sodium salt, so that the dissociation rate is improved, the ion conduction capability of the polymer electrolyte is further improved, and the result shows that the electrochemical performance of the composite electrolyte synthesized by the method is effectively improved.
Detailed Description
The following description is presented to disclose the invention so as to enable any person skilled in the art to practice the invention. The preferred embodiments in the following description are given by way of example only, and other obvious variations will occur to those skilled in the art.
Example 1
The preparation method comprises the following steps:
mixing 8g of sodium hydroxide and 40ml of acetone, stirring for 1 hour, stopping stirring, and reacting the mixed solution at room temperature for 5 days in a dry environment; then adding a proper amount of 1mol/L diluted hydrochloric acid into the reacted solution, adjusting the pH value of the solution to 7, then carrying out ultrasonic dispersion, centrifugal separation and deionized water washing for 5 times, and finally carrying out vacuum drying at 100 ℃ for 12 hours to obtain a carbon quantum dot solid with the average diameter of 3-5 nm;
(II) dissolving the carbon quantum dots, the polyoxyethylene with the molecular weight of 600,000g/mol and the lithium perchlorate prepared in the step I in acetonitrile solution, stirring at room temperature for 12 hours, pouring the mixture into a polytetrafluoroethylene mold, controlling the amount of the mixed solution poured into the mold, and performing vacuum drying to obtain the composite solid electrolyte with the thickness of 100 microns; wherein the molar ratio of the lithium perchlorate to the oxyethylene chain segment in the polyoxyethylene is 1:20, and the mass of the added carbon quantum dots is 5 percent of the mass of the polyoxyethylene.
The composite solid electrolyte prepared by the method has the thickness of 100 mu m, and consists of polyoxyethylene, a carbon quantum dot and lithium perchlorate, wherein the mass of the carbon quantum dot is 5% of that of the polyoxyethylene, the molecular weight of the polyoxyethylene is 600,000g/mol, and the average diameter of the carbon quantum dot is 3-5 nm.
The polymer electrolyte was tested to have an ionic conductivity of 1.39X 10-4S/cm at 25 ℃. Under the same condition, the ionic conductivity of the electrolyte which is composed of polyoxyethylene and lithium perchlorate and does not contain carbon quantum dots is 6.39 multiplied by 10 < -6 > S/cm, and the ionic conductivity of the composite solid electrolyte synthesized by the invention is obviously improved.
Example 2
The preparation method comprises the following steps:
mixing 8g of sodium hydroxide and 40ml of 40% acetaldehyde aqueous solution, stirring for 1 hour, stopping stirring, and reacting the mixed solution at room temperature in a dry environment for 5 days; then adding a proper amount of 1mol/L diluted hydrochloric acid into the reacted solution, adjusting the pH value of the solution to 7, then carrying out ultrasonic dispersion, centrifugal separation and deionized water washing for 5 times, and finally carrying out vacuum drying at 100 ℃ for 12 hours to obtain a carbon quantum dot solid with the average diameter of 3-5 nm;
(II) dissolving the carbon quantum dots, the polyoxyethylene with the molecular weight of 600,000g/mol and the sodium perchlorate prepared in the step I in an acetonitrile solution, stirring at room temperature for 12 hours, pouring the mixture into a polytetrafluoroethylene mold, controlling the amount of the mixed solution poured into the mold, and performing vacuum drying to obtain a composite solid electrolyte with the thickness of 100 mu m; wherein the molar ratio of sodium perchlorate to the oxyethylene segment in polyoxyethylene is 1:20, and the mass of the added carbon quantum dots is 5% of the mass of polyoxyethylene.
The composite solid electrolyte prepared by the method has the thickness of 100 mu m and consists of polyoxyethylene, carbon quantum dots and sodium perchlorate, wherein the mass of the carbon quantum dots is 5% of that of the polyoxyethylene, the molecular weight of the polyoxyethylene is 600,000g/mol, and the average diameter of the carbon quantum dots is 3-5 nm.
The polymer electrolyte was tested to have an ionic conductivity of 7.17X 10-5S/cm at 25 ℃. Under the same condition, the ionic conductivity of the electrolyte which is composed of polyoxyethylene and sodium perchlorate and does not contain carbon quantum dots is 2.21 multiplied by 10 < -6 > S/cm, and the ionic conductivity of the composite solid electrolyte synthesized by the invention is obviously improved.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (5)
1. A composite electrolyte characterized by: the organic lithium ion battery comprises a high molecular polymer, a carbon quantum dot and an organic lithium salt or an organic sodium salt, wherein the lithium salt is selected from one or more of lithium perchlorate, lithium trifluoromethanesulfonate and lithium bistrifluoromethanesulfonylimide, and the sodium salt is selected from one or more of sodium perchlorate, sodium trifluoromethanesulfonate and bistrifluoromethanesulfonylimide; the high molecular polymer is selected from one of polyoxyethylene, polyacrylonitrile or polymethyl methacrylate polymer.
2. The composite electrolyte of claim 1, wherein: the average diameter of the carbon quantum dots is 3-5 nm, and the mass ratio of the carbon quantum dots to the high molecular polymer is not higher than 10%.
3. The composite electrolyte of claim 1, wherein: the molecular weight of the high molecular polymer is 100,000-1,000,000 g/mol.
4. The composite electrolyte of claim 1, wherein: the thickness of the electrolyte membrane is about 50 to 500 μm.
5. A method for producing the composite electrolyte according to any one of claims 1 to 4, characterized in that: mixing an alkali metal hydroxide with a ketone or aldehyde organic solution for at least 1 hour, and reacting at room temperature for at least 3 days, wherein the concentration of the alkali metal hydroxide in the solution is 0.1-0.5 g/mL; after the reaction is finished, adjusting the pH value of the solution to 6-8, and then performing dispersion, separation, cleaning and vacuum drying to obtain carbon quantum dot solid particles with the average diameter of 3-5 nm; (II) dissolving the carbon quantum dots, the high molecular polymer and lithium salt or sodium salt prepared in the step I in an organic solvent, stirring for at least 12 hours, pouring into a mold, and drying in vacuum to obtain an electrolyte; the lithium salt is selected from one or more of lithium perchlorate, lithium trifluoromethanesulfonate and lithium bistrifluoromethanesulfonylimide, and the sodium salt is selected from one or more of sodium perchlorate, sodium trifluoromethanesulfonate and sodium bistrifluoromethanesulfonylimide; the high molecular polymer is selected from one of polyoxyethylene, polyacrylonitrile or polymethyl methacrylate polymer.
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| CN201811450081.XA CN111261936A (en) | 2018-11-30 | 2018-11-30 | Composite electrolyte and preparation method thereof |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111607389A (en) * | 2020-07-08 | 2020-09-01 | 大连工业大学 | Oil-soluble carbon quantum dot-based ionic gel material and preparation method thereof |
| CN112133962A (en) * | 2020-09-25 | 2020-12-25 | 天津大学 | Preparation method of bis (trifluoromethyl) sulfimide lithium-glucose carbon quantum dot solid electrolyte |
| CN113224384A (en) * | 2021-04-12 | 2021-08-06 | 中南大学 | Composite polymer solid electrolyte and preparation method thereof |
-
2018
- 2018-11-30 CN CN201811450081.XA patent/CN111261936A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111607389A (en) * | 2020-07-08 | 2020-09-01 | 大连工业大学 | Oil-soluble carbon quantum dot-based ionic gel material and preparation method thereof |
| CN112133962A (en) * | 2020-09-25 | 2020-12-25 | 天津大学 | Preparation method of bis (trifluoromethyl) sulfimide lithium-glucose carbon quantum dot solid electrolyte |
| CN113224384A (en) * | 2021-04-12 | 2021-08-06 | 中南大学 | Composite polymer solid electrolyte and preparation method thereof |
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