CN116979137A - Solid polymer electrolyte and preparation method and application thereof - Google Patents

Solid polymer electrolyte and preparation method and application thereof Download PDF

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CN116979137A
CN116979137A CN202310970655.0A CN202310970655A CN116979137A CN 116979137 A CN116979137 A CN 116979137A CN 202310970655 A CN202310970655 A CN 202310970655A CN 116979137 A CN116979137 A CN 116979137A
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lithium
solid polymer
polymer electrolyte
pdes
eutectic solvent
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何明辉
梁晓欣
刘存生
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South China University of Technology SCUT
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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
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    • 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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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F20/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
    • C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
    • C08F20/52—Amides or imides
    • C08F20/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
    • C08F20/56—Acrylamide; Methacrylamide
    • H—ELECTRICITY
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    • H01M10/00—Secondary cells; Manufacture thereof
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    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0065—Solid electrolytes
    • H01M2300/0082—Organic polymers

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Abstract

The application discloses a solid polymer electrolyte, a preparation method and application thereof, wherein the preparation method of the solid polymer electrolyte comprises the following steps: s1, mixing lithium sulfonimide salt, an amide compound containing double bonds, a nitrile compound and lithium difluoro (oxalic acid) borate according to a proportion to obtain a mixture; s2, heating the mixture and stirring the mixture at 50-80 ℃ for 1-3 hours until a transparent polymerizable eutectic solvent electrolyte solution is obtained; s3, adding an initiator into the polymerizable eutectic solvent electrolyte solution, stirring at 25+/-5 ℃ to form a transparent uniform precursor, and heating at 60-80 ℃ for 3-5 hours to obtain the solid polymer electrolyte. The novel solid polymer electrolyte prepared by using the polymerizable eutectic solvent has excellent thermal stability and incombustibility, high safety performance, high conductivity and large electrochemical window. The solid polymer electrolyte-based lithium ion battery has excellent long-term cycling stability, high safety and high energy density.

Description

Solid polymer electrolyte and preparation method and application thereof
Technical Field
The application relates to the field of battery electrolyte materials, in particular to a solid polymer electrolyte, a preparation method and application thereof.
Background
The electrolyte plays an important role in improving the safety and long-term stability of the battery as an ion transport medium. The electrolyte used in the commercial lithium ion battery contains a liquid organic solvent with high volatility and combustibility, and inevitably causes safety problems such as leakage, volatilization and explosion. And the electrochemical window of the ether electrolyte is often below 4V, which cannot be applied to a high-voltage positive electrode. The ester electrolyte can be suitable for a high-voltage positive electrode, but the ester electrolyte is unstable to a metal lithium negative electrode, and a porous solid electrolyte interface film derived from a carbonate solvent can lead to continuous decomposition of the solvent in the lithium metal deposition and stripping processes, so that the battery is rapidly disabled. Currently, the safety and cycling stability of commercial conventional electrolytes severely hamper the practical application of high energy density batteries.
Eutectic Solvents (DES) are an emerging class of ionic liquid analogues, and strong interactions between components in DES, such as hydrogen bonding, lewis acid bases and van der waals interactions, impart lower melting points to them than to each component. DES electrolytes are of particular interest because of their numerous advantages, such as low vapor pressure, nonflammability, biodegradability, low cost, and ease of preparation. The DES electrolyte has poor compatibility with lithium metal, while the solubility of high voltage cathode transition metal ions in DES results in low reversible capacity and poor cycle life of lithium metal batteries. Polymerizable eutectic solvents (PDES) as a subset of DES, PDES also inherit the advantages of DES, but PDES's thermal stability still has difficulty in fully meeting battery safety requirements.
Disclosure of Invention
Based on this, the present application aims to overcome at least one defect of the prior art and provide a solid polymer electrolyte and a preparation method thereof, and the present application prepares a novel solid polymer electrolyte having excellent thermal stability and incombustibility, high safety performance, high conductivity and a large electrochemical window by using a polymerizable eutectic solvent.
It is also an object of the present application to provide the use of said solid polymer electrolyte. The application of the solid polymer electrolyte to a lithium ion battery enables uniform deposition of lithium on the anode and effectively prevents the safety risks associated with lithium dendrite growth.
It is also an object of the present application to provide a lithium ion battery based on a solid polymer electrolyte. The solid polymer electrolyte-based lithium ion battery has excellent long-term cycling stability, high safety and high energy density.
The technical scheme is as follows:
a method of preparing a solid polymer electrolyte comprising the steps of:
s1, mixing lithium sulfonimide salt, an amide compound containing double bonds, a nitrile compound and lithium difluoro (oxalic acid) borate according to a proportion to obtain a mixture;
s2, heating the mixture and stirring the mixture at 50-80 ℃ for 1-3 hours until a transparent polymerizable eutectic solvent electrolyte solution is obtained;
s3, adding an initiator into the polymerizable eutectic solvent electrolyte solution, stirring at 25+/-5 ℃ to form a transparent uniform precursor, and heating at 60-80 ℃ for 3-5 hours to obtain a solid polymer electrolyte;
wherein the molar ratio of the lithium sulfonyl imide salt to the amide compound containing double bonds is 1: (0.5 to 3), wherein the molar ratio of the amide compound containing a double bond to the nitrile compound is 1: (2-6), wherein the mass ratio of the lithium difluoro (oxalic acid) borate to the total amount of the lithium sulfonyl imide salt, the amide compound containing double bonds and the nitrile compound is (0.5-2%): 1, wherein the dosage of the initiator is 0.1-0.5% of the polymerizable eutectic solvent electrolyte solution.
The application uses the lithium sulfonimide salt, the amide compound containing double bonds and the nitrile compound as the components of the eutectic solvent, and adds the additive difluoro (oxalic acid) lithium borate to improve the stability of the electrolyte-electrode interface, and further adds the initiator to solidify the electrolyte solution of the polymerizable eutectic solvent to obtain the solid polymer electrolyte.
In one embodiment, the molar ratio of the lithium sulfonimide salt to the double bond containing amide compound is 1: (1-3); and/or the mass ratio of the lithium difluoro (oxalic acid) borate to the total amount of the lithium sulfonyl imide salt, the amide compound containing double bonds and the nitrile compound is (1% -2%): 1. more preferably, the molar ratio of the lithium sulfonimide salt to the double bond containing amide compound is 1: (1-2), more preferably, the molar ratio of the lithium sulfonimide salt to the double bond-containing amide compound is 1:1.5.
in one embodiment, the lithium sulfonimide salt is lithium bis (trifluorosulfonimide) or lithium bis (fluorosulfonimide).
In one embodiment, the amide compound containing double bonds is one or more of acrylamide, N-dimethylacrylamide, N-isopropylacrylamide and methylol acrylamide.
In one embodiment, the nitrile compound is one or more of malononitrile, succinonitrile, glutaronitrile.
In one embodiment, step S1 is: adding lithium sulfonimide salt and double bond-containing amide compound in proportion, then adding nitrile compound, then adding lithium difluoro (oxalic acid) borate, and uniformly mixing to obtain a mixture.
In one embodiment, the polymerizable eutectic solvent electrolyte solution has a conductivity of 3.7 to 7.9mScm -1 . More preferably, the polymerizable eutectic solvent electrolyte solution has a conductivity of 6 to 7.9mScm -1 。
The solid polymer electrolyte prepared by the preparation method.
In one embodiment, the solid polymer electrolyte has a conductivity in the range of 298K to 303K of 0.4 mScm to 1.89mScm -1 。
In one embodiment, the solid polymer electrolyte has an oxidation potential of 3.8 to 5.10V. More preferably, the oxidation potential of the solid polymer electrolyte is 4.91 to 5.10V.
The application of the solid polymer electrolyte in lithium ion batteries.
A lithium ion battery based on a solid polymer electrolyte, wherein the lithium ion battery is a lithium iron phosphate or ternary lithium battery, and the lithium ion battery comprises the solid polymer electrolyte. Further the lithium ion battery is Li|poly (PDES) |LFP or Li|poly (PDES) |NCM811.
In one embodiment, the lithium iron phosphate battery has a battery capacity retention of not less than 95% and an average coulombic efficiency of not less than 99% after 200 cycles at a current density of 1C.
The application has the beneficial effects that: the solid polymer electrolyte has excellent thermal stability and incombustibility, also has better conductivity and a large electrochemical window, can be applied to a lithium ion battery, can uniformly deposit lithium on an anode, and effectively prevents safety risks related to growth of lithium dendrites; lithium ion batteries based on solid polymer electrolytes have excellent long-term cycling stability, high safety and high energy density.
Drawings
FIG. 1 is a DSC graph of a polymerizable eutectic solvent electrolyte solution PDES-X of some examples.
FIG. 2 is an infrared spectrum of a comparison of PDES-3 and LiTFSI, AM, SN.
FIG. 3 shows nuclear magnetic resonance hydrogen spectra of PDES-3 and AM, SN contrast.
FIG. 4 is a linear plot of Poly (PDES) -3 temperature dependent ionic conductivity.
FIG. 5 is an electrochemical window test pattern of PDES-3 and Poly (PDES) -3.
FIG. 6 is a cyclic voltammetry test pattern of PDES-3 and Poly (PDES) -3.
FIG. 7 is a lithium deposition diagram of Poly (PDES) -3.
FIG. 8 is a thermogravimetric analysis of PDES-3, poly (PDES) -3 and conventional commercial electrolytes.
FIG. 9 is an ignition test chart of PDES-3, poly (PDES) -3 and conventional commercial electrolytes.
Fig. 10 is a graph of the capacity retention test and average coulombic efficiency for 200 cycles under three Li LFP batteries 1C of PDES-3, poly (PDES) -3, and a conventional commercial electrolyte.
Fig. 11 is a graph showing capacity retention test after 100 cycles of three Li NCM811 cells of PDES-3, poly (PDES) -3 and the constitution of the conventional commercial electrolyte at a current density of 1C.
Detailed Description
The present embodiments are to be considered in all respects as illustrative and not restrictive.
For simplicity, only a few numerical ranges are explicitly disclosed herein. However, any lower limit may be combined with any upper limit to form a range not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and any upper limit may be combined with any other upper limit to form a range not explicitly recited. Furthermore, each point or individual value between the endpoints of the range is included within the range, although not explicitly recited. Thus, each point or individual value may be combined as a lower or upper limit on itself with any other point or individual value or with other lower or upper limit to form a range that is not explicitly recited.
The above summary of the present application is not intended to describe each disclosed embodiment or every implementation of the present application. The following description more particularly exemplifies illustrative embodiments. Guidance is provided throughout this application by a series of embodiments, which may be used in various combinations. In the various examples, the list is merely a representative group and should not be construed as exhaustive.
Example 1
A solid polymer electrolyte, which is prepared by the following steps:
s1, mixing lithium bistrifluoro sulfonyl imide (LiTFSI) and Acrylamide (AM) according to a proportion, then adding Succinonitrile (SN), then adding lithium difluoro (oxalic acid) borate, and uniformly mixing to obtain a mixture; wherein the molar ratio of the lithium bis (trifluorosulfonimide) to the acrylamide is 1:0.5, the molar ratio of the acrylamide to the succinonitrile is 1:4, and the dosage of the lithium difluoro (oxalic acid) borate (LiODFB) is 2wt% of the total mass of the lithium bis (trifluorosulfonimide), the acrylamide and the succinonitrile;
s2, heating the mixture and stirring the mixture at 50-80 ℃ for 1-3 hours until a transparent polymerizable eutectic solvent electrolyte solution is obtained, which is named as PDES-1;
s3, adding 0.2wt% of initiator Azodiisobutyronitrile (AIBN) into the polymerizable eutectic solvent electrolyte solution, stirring at 20-30 ℃ to form a transparent uniform precursor, and heating at 60-80 ℃ for 3-5 hours to obtain a solid polymer electrolyte, namely Poly (PDES) -1.
Example 2
A solid polymer electrolyte, which is prepared by the following steps:
s1, mixing lithium bistrifluoro sulfonyl imide (LiTFSI) and Acrylamide (AM) according to a proportion, then adding Succinonitrile (SN), then adding lithium difluoro (oxalic acid) borate, and uniformly mixing to obtain a mixture; wherein the molar ratio of the lithium bis (trifluoro-sulfonimide) to the acrylamide is 1:1, the molar ratio of the acrylamide to the succinonitrile is 1:4, and the dosage of the lithium difluoro (oxalic acid) borate (LiODFB) is 2wt% of the total mass of the lithium bis (trifluoro-sulfonimide), the acrylamide and the succinonitrile;
s2, heating the mixture and stirring the mixture at 50-80 ℃ for 1-3 hours until a transparent polymerizable eutectic solvent electrolyte solution is obtained, which is named as PDES-2;
s3, adding 0.2wt% of initiator Azodiisobutyronitrile (AIBN) into the polymerizable eutectic solvent electrolyte solution, stirring at 20-30 ℃ to form a transparent uniform precursor, and heating at 60-80 ℃ for 3-5 hours to obtain a solid polymer electrolyte, namely Poly (PDES) -2.
Example 3
A solid polymer electrolyte, which is prepared by the following steps:
s1, mixing lithium bistrifluoro sulfonyl imide (LiTFSI) and Acrylamide (AM) according to a proportion, then adding Succinonitrile (SN), then adding lithium difluoro (oxalic acid) borate, and uniformly mixing to obtain a mixture; wherein the molar ratio of the lithium bis (trifluorosulfonimide) to the acrylamide is 1:1.5, the molar ratio of the acrylamide to the succinonitrile is 1:4, and the dosage of the lithium difluoro (oxalic acid) borate (LiODFB) is 2wt% of the total mass of the lithium bis (trifluorosulfonimide), the acrylamide and the succinonitrile;
s2, heating the mixture and stirring the mixture at 50-80 ℃ for 1-3 hours until a transparent polymerizable eutectic solvent electrolyte solution is obtained, which is named as PDES-3;
s3, adding 0.2wt% of initiator Azodiisobutyronitrile (AIBN) into the polymerizable eutectic solvent electrolyte solution, stirring at 20-30 ℃ to form a transparent uniform precursor, and heating at 60-80 ℃ for 3-5 hours to obtain a solid polymer electrolyte, namely Poly (PDES) -3.
Example 4
A solid polymer electrolyte, which is prepared by the following steps:
s1, mixing lithium bistrifluoro sulfonyl imide (LiTFSI) and Acrylamide (AM) according to a proportion, then adding Succinonitrile (SN), then adding lithium difluoro (oxalic acid) borate, and uniformly mixing to obtain a mixture; wherein the molar ratio of the lithium bis (trifluoro-sulfonimide) to the acrylamide is 1:2, the molar ratio of the acrylamide to the succinonitrile is 1:4, and the dosage of the lithium difluoro (oxalic acid) borate (LiODFB) is 2wt% of the total mass of the lithium bis (trifluoro-sulfonimide), the acrylamide and the succinonitrile;
s2, heating the mixture and stirring the mixture at 50-80 ℃ for 1-3 hours until a transparent polymerizable eutectic solvent electrolyte solution is obtained, which is named as PDES-4;
s3, adding 0.2wt% of initiator Azodiisobutyronitrile (AIBN) into the polymerizable eutectic solvent electrolyte solution, stirring at 20-30 ℃ to form a transparent uniform precursor, and heating at 60-80 ℃ for 3-5 hours to obtain a solid polymer electrolyte, namely Poly (PDES) -4.
Example 5
A solid polymer electrolyte, which is prepared by the following steps:
s1, mixing lithium bistrifluoro sulfonyl imide (LiTFSI) and Acrylamide (AM) according to a proportion, then adding Succinonitrile (SN), then adding lithium difluoro (oxalic acid) borate, and uniformly mixing to obtain a mixture; wherein the molar ratio of the lithium bis (trifluoro-sulfonimide) to the acrylamide is 1:3, the molar ratio of the acrylamide to the succinonitrile is 1:4, and the dosage of the lithium difluoro (oxalic acid) borate (LiODFB) is 2wt% of the total mass of the lithium bis (trifluoro-sulfonimide), the acrylamide and the succinonitrile;
s2, heating the mixture and stirring the mixture at 50-80 ℃ for 1-3 hours until a transparent polymerizable eutectic solvent electrolyte solution is obtained, which is named as PDES-5;
s3, adding 0.2wt% of initiator Azodiisobutyronitrile (AIBN) into the polymerizable eutectic solvent electrolyte solution, stirring at 20-30 ℃ to form a transparent uniform precursor, and heating at 60-80 ℃ for 3-5 hours to obtain a solid polymer electrolyte, namely Poly (PDES) -5.
Example 6
A solid polymer electrolyte, which is prepared by the following steps:
s1, mixing lithium bistrifluoro sulfonyl imide (LiTFSI) and Acrylamide (AM) according to a proportion, then adding Succinonitrile (SN), then adding lithium difluoro (oxalic acid) borate, and uniformly mixing to obtain a mixture; wherein the molar ratio of the lithium bis (trifluorosulfonimide) to the acrylamide is 1:1.5, the molar ratio of the acrylamide to the succinonitrile is 1:2, and the dosage of the lithium difluoro (oxalic acid) borate (LiODFB) is 1wt% of the total mass of the lithium bis (trifluorosulfonimide), the acrylamide and the succinonitrile;
s2, heating the mixture and stirring the mixture at 50-80 ℃ for 1-3 hours until a transparent polymerizable eutectic solvent electrolyte solution is obtained, which is named as PDES-6;
s3, adding 0.1wt% of initiator Azodiisobutyronitrile (AIBN) into the polymerizable eutectic solvent electrolyte solution, stirring at 20-30 ℃ to form a transparent uniform precursor, and heating at 60-80 ℃ for 3-5 hours to obtain a solid polymer electrolyte, namely Poly (PDES) -6.
Example 7
A solid polymer electrolyte, which is prepared by the following steps:
s1, mixing lithium bistrifluoro sulfonyl imide (LiTFSI) and Acrylamide (AM) according to a proportion, then adding Succinonitrile (SN), then adding lithium difluoro (oxalic acid) borate, and uniformly mixing to obtain a mixture; wherein the molar ratio of the lithium bis (trifluorosulfonimide) to the acrylamide is 1:1.5, the molar ratio of the acrylamide to the succinonitrile is 1:6, and the dosage of the lithium difluoro (oxalic acid) borate (LiODFB) is 1wt% of the total mass of the lithium bis (trifluorosulfonimide), the acrylamide and the succinonitrile;
s2, heating the mixture and stirring the mixture at 50-80 ℃ for 1-3 hours until a transparent polymerizable eutectic solvent electrolyte solution is obtained, which is named as PDES-7;
s3, adding 0.5wt% of initiator Azodiisobutyronitrile (AIBN) into the polymerizable eutectic solvent electrolyte solution, stirring at 20-30 ℃ to form a transparent uniform precursor, and heating at 60-80 ℃ for 3-5 hours to obtain a solid polymer electrolyte, namely Poly (PDES) -7.
Example 8
A solid polymer electrolyte, which is prepared by the following steps:
s1, mixing lithium difluorosulfimide and N-isopropyl acrylamide in proportion, then adding malononitrile, then adding lithium difluoroborate (oxalic acid), and uniformly mixing to obtain a mixture; wherein the molar ratio of the lithium bis (trifluoro-sulfonimide) to the acrylamide is 1:0.5, the molar ratio of the acrylamide to the succinonitrile is 1:4, and the dosage of the lithium difluoro (oxalic acid) borate (LiODFB) is 0.5wt% of the total mass of the lithium bis (trifluoro-sulfonimide), the N isopropyl acrylamide and the malononitrile;
s2, heating the mixture and stirring the mixture at 50-80 ℃ for 1-3 hours until a transparent polymerizable eutectic solvent electrolyte solution is obtained, which is named as PDES-8;
s3, adding 0.2wt% of initiator Azodiisobutyronitrile (AIBN) into the polymerizable eutectic solvent electrolyte solution, stirring at 20-30 ℃ to form a transparent uniform precursor, and heating at 60-80 ℃ for 3-5 hours to obtain a solid polymer electrolyte, namely Poly (PDES) -8.
The polymerizable eutectic solvent electrolyte solutions PDES-X of examples 1 to 8 were prepared
(x=1, 2,3,4,5,6,7 or 8) all have been subjected to Differential Scanning Calorimetry (DSC) tests for their melting point Tm. The melting points of PDES-1, PDES-2, PDES-3, PDES-4, PDES-5, PDES-6, PDES-7, PDES-8 were 5.2 ℃, -0.7 ℃, -10.9 ℃, 18.2 ℃, 23.1 ℃, 2.3 ℃, 20.1 ℃ and 15.1 ℃ respectively, indicating that PDES-X (X=1,2,3,4,5,6,7 or 8) a melting point (T) in the range of-10.9 ℃ to 23.1 DEG C m ) Below the melting point of the individual components (LiTFSI: 238 ℃, AM:86 ℃, SN: malononitrile at 54 ℃): 32 ℃ and thus, it was found that PDES was successfully prepared, and that the DSC curve of the partially polymerizable eutectic solvent electrolyte solution PDES-X was as shown in FIG. 1.
The polymerizable eutectic solvent electrolyte solutions PDES-X of examples 1 to 8 were subjected to infrared spectroscopy and nuclear magnetic resonance hydrogen spectroscopy, and the results showed that no chemical reaction occurred during the sample preparation. This means successful preparation of PDES. The infrared spectrogram of PDES-3 and LiTFSI, AM, SN is shown in FIG. 2, and the nuclear magnetic resonance hydrogen spectrogram of PDES-3 and AM and SN is shown in FIG. 3.
The polymerizable eutectic solvent electrolyte solutions PDES-X and the solid polymer electrolyte Poly (PDES) -X of examples 1 to 8 were subjected to conductivity tests using a conductivity instrument, and the conductivities of the polymerizable eutectic solvent electrolyte solutions of examples 1 to 8 were 3.7mScm, respectively -1 ，6.0mScm -1 ，7.9mScm -1 、7.8mS cm -1 、7.2mScm -1 、5.7mScm -1 、7.5mScm -1 、2.1mScm -1 The conductivities (room temperature) of the solid polymer electrolytes were 0.40mScm, respectively -1 ，0.98mScm -1 ，1.89mScm -1 、1.39mScm -1 、0.46mScm -1 、0.85mS cm -1 、1.42mScm -1 、0.21mScm -1 . It can be seen that although the conductivity of the solid polymer electrolyte is lower than that of the polymerizable eutectic solvent electrolyte solution, the conductivity is still better and still meets the requirements of the lithium battery.
The temperature-dependent ion conductivity test of samples was performed on the solid polymer electrolytes Poly (PDES) -X of examples 1 to 8, and the results showed that the solid polymer electrolytes Poly (PDES) -X of examples 1 to 7 had good lithium ion conductivity over a wide temperature range (298 to 363K), and the conductivity was 0.4 to 4.87mScm -1 . In particular, the Poly (PDES) -3 sample has the highest lithium ion conductivity at room temperature (1.89 mScm at 25 ℃) -1 ). Wherein the implementation is thatA linear plot of the temperature dependent ionic conductivity of Poly (PDES) -3 of example 3 is shown in FIG. 4.
Electrochemical window test oxidation potentials of polymerizable eutectic solvent electrolyte solutions PDES-X and solid polymer electrolytes Poly (PDES) -X, PDES-1, PDES-2, PDES-3, PDES-4, PDES-5, PDES-6, PDES-7, PDES-8 were 4.68V, 4.64V, 4.75V, 4.64V, 4.69V, 4.15V, 4.21V, 3.51V, poly (PDES) -1, poly (PDES) -2, poly (PDES) -3, poly (PDES) -4, poly (PDES) -5, poly (PDES) -6, poly (PDES) -7, poly (PDES) -8 were 5.04V, 5.05V, 5.10V, 4.91V, 4.92V, 4.66V, 4.75V, 3.8V, respectively. The results show that the oxidation potential of the solid polymer electrolyte Poly (PDES) -X is higher than that of the polymerizable eutectic solvent electrolyte solution PDES-X. An oxidation potential test chart of the polymerizable eutectic solvent electrolyte solution PDES-3 and the solid polymer electrolyte Poly (PDES) -3 is shown in FIG. 5. Solid polymer electrolytes have higher oxidation potentials than the polymerizable eutectic solvent electrolyte solutions, due primarily to the high oxidation resistance of the polymer chains. From this, it is known that the solid polymer Poly (PDES) has a higher oxidation potential than the liquid polymerizable eutectic solvent electrolyte solution PDES, and is more suitable as a high-voltage electrode material.
The peak current densities of PDES-X and Poly (PDES) -X were measured by cyclic voltammetry over 25 cycles, and the results indicate that the peak current density of PDES-X of the polymerizable eutectic solvent electrolyte solution rapidly decreased over 25 cycles, mainly due to side reactions of AM and SN molecules with lithium metal anodes, with an increase in interfacial impedance. The rate of change of Poly (PDES) -X peak current density over 25 cycles was not evident, demonstrating good compatibility of Poly (PDES) -X with lithium metal anodes. As shown in FIG. 6, which shows cyclic voltammetry test curves of PDES-3 and Poly (PDES) -3, the peak current density does not change substantially over 25 cycles.
Application of the solid polymer electrolytes of examples 1 to 8 in lithium|lithium symmetric batteries, the use of the solid electrolyte Poly (PDES) -X maintains a dense smooth surface with a hillock-like lithium morphology on lithium metal, which results demonstrate that Poly (PDES) is able to deposit lithium uniformly on the anode and effectively prevents the safety risks associated with lithium dendrite growth. A lithium deposition pattern of Poly (PDES) -3 is shown in fig. 7.
Thermogravimetric analysis is carried out on the polymerizable eutectic solvent electrolyte solution PDES-X and the solid polymer electrolyte Poly (PDES) -X, and analysis results show that the stability of the PDES-X and the stability of the Poly (PDES) -X are good, and the thermal decomposition temperature of the Poly (PDES) -X is higher than that of the PDES-X. As shown in FIG. 8, which shows thermogravimetric analysis curves for PDES-3 and Poly (PDES) -3, poly (PDES) -3 and PDES-3 show negligible weight loss at temperatures up to 176℃and 117℃respectively. In contrast, the conventional commercial electrolyte (commercial electrolyte) Ethylene Carbonate (EC)/ethylmethyl carbonate (EMC)/dimethyl carbonate (DEC) (volume ratio 1:1:1) in 1m LiPF6 in liquid electrolyte evaporates rapidly even at room temperature, mainly due to the lower boiling point of the carbonate solvent.
The traditional electrolyte is easy to ignite, namely in 3s, PDES-3 is ignited in 30s, and Poly (PDES) -X electrolyte cannot be ignited even if the ignition time is prolonged to 120s, so that the flame retardant property is very excellent, and the safety of the battery can be remarkably improved. The ignition experiment measurement chart is shown in fig. 9. This suggests that Poly (PDES) electrolytes are intrinsically safer than commercial electrolytes and PDES electrolytes, contributing to safe operation of high energy lithium batteries.
The PDES-X and Poly (PDES) -X of examples 2 to 4, conventional commercial electrolytes, were applied to lithium ion batteries, assembled into three lithium iron phosphate (li||lfp) batteries. The method for assembling the Li I LFP battery by Poly (PDES) -X comprises the following steps: and injecting PDES-X into the battery to fully infiltrate the positive electrode and the negative electrode, and placing the battery into a 70 ℃ oven for in-situ polymerization for 4 hours after the battery is packaged. The battery capacity retention rates of different electrolytes after 200 cycles at 1C current density were tested, and the results show that the battery capacity retention rates of Poly (PDES) -2, poly (PDES) -3 and Poly (PDES) -4 after 200 cycles at 1C current density are not lower than 95% and the average coulombic efficiency is not lower than 99%. As shown in fig. 10, the li|lfp battery capacity retention rate using Poly (PDES) -3 after 200 cycles at 1C was 96.1%, corresponding to a li|lfp battery (94.3%) using a commercial electrolyte. Poly (PDES) -3 (average coulombic efficiency 99.96%) has a higher average coulombic efficiency than the commercial conventional electrolyte (average coulombic efficiency 96.80%). However, the capacity retention of the li|lfp battery using PDES-3 after 200 cycles was only 44.9%.
PDES-3 and Poly (PDES) -3 and conventional commercial electrolytes were applied to high energy density lithium ion batteries to assemble Li NCM811 batteries. The battery capacity retention of different electrolytes after 100 cycles at 1C current density was tested, and the results showed that the battery capacity retention of Poly (PDES) -3 after 100 cycles at the next 1C current density was not lower than 90%. As shown in fig. 11, the NCM811 cell using Poly (PDES) -3 maintained 91.9% of its capacity after 100 cycles at a current density of 1C, which was higher than the cell using a commercial electrolyte, and the li|ncm 811 cell using PDES-3 maintained only 55.4% of its capacity.
Comparative example 1
A solid polymer electrolyte was prepared in substantially the same manner as in example 1, except that the molar ratio of lithium bistrifluorosulfonylimide, acrylamide and succinonitrile in comparative example 1 was 1:6:2.
The solid polymer electrolyte prepared in comparative example 1 was tested to have a conductivity of only 0.02mScm -1 Cannot satisfy the solid electrolyte conductivity of more than 0.1mScm -1 Is not limited.
It should be understood that the foregoing examples of the present application are merely illustrative of the present application and are not intended to limit the present application to the specific embodiments thereof. Any modification, equivalent replacement, improvement, etc. that comes within the spirit and principle of the claims of the present application should be included in the protection scope of the claims of the present application.

Claims (10)

1. A method for preparing a solid polymer electrolyte, comprising the steps of:
s1, mixing lithium sulfonimide salt, an amide compound containing double bonds, a nitrile compound and lithium difluoro (oxalic acid) borate according to a proportion to obtain a mixture;
s2, heating the mixture and stirring the mixture at 50-80 ℃ for 1-3 hours until a transparent polymerizable eutectic solvent electrolyte solution is obtained;
s3, adding an initiator into the polymerizable eutectic solvent electrolyte solution, stirring at 25+/-5 ℃ to form a transparent uniform precursor, and heating at 60-80 ℃ for 3-5 hours to obtain a solid polymer electrolyte;
wherein the molar ratio of the lithium sulfonyl imide salt to the amide compound containing double bonds is 1: (0.5 to 3), wherein the molar ratio of the amide compound containing a double bond to the nitrile compound is 1: (2-6), wherein the mass ratio of the lithium difluoro (oxalic acid) borate to the total amount of the lithium sulfonyl imide salt, the amide compound containing double bonds and the nitrile compound is (0.5-2%): 1, wherein the dosage of the initiator is 0.1-0.5% of the polymerizable eutectic solvent electrolyte solution.
2. The method according to claim 1, wherein the molar ratio of the lithium sulfonimide salt to the double bond-containing amide compound is 1: (1-3); and/or the mass ratio of the lithium difluoro (oxalic acid) borate to the total amount of the lithium sulfonyl imide salt, the amide compound containing double bonds and the nitrile compound is (1% -2%): 1.
3. the method according to claim 1, wherein the lithium sulfonimide salt is lithium bis (trifluorosulfonimide) or lithium bis (fluorosulfonyl imide); and/or the amide compound containing double bonds is one or more of acrylamide, N-dimethylacrylamide, N-isopropylacrylamide and methylol acrylamide; and/or the nitrile compound is one or more of malononitrile, succinonitrile and glutaronitrile.
4. The method of preparing according to claim 1, wherein the polymerizable eutectic solvent electrolyte solution has a conductivity of 3.7 to 7.9mS cm -1 。
5. A solid polymer electrolyte prepared by the preparation method of claims 1 to 4.
6. According toThe solid polymer electrolyte of claim 5, wherein said solid polymer electrolyte has a conductivity in the range of 298K to 363K of 0.4 mS cm to 4.87mS cm -1 。
7. The solid polymer electrolyte of claim 5 wherein the oxidation potential of the solid polymer electrolyte is 3.8 to 5.10V.
8. Use of a solid polymer electrolyte as claimed in any one of claims 5 to 7 in a lithium ion battery.
9. A lithium ion battery based on a solid polymer electrolyte, characterized in that the lithium ion battery is a lithium iron phosphate or ternary lithium battery comprising the solid polymer electrolyte according to any one of claims 5 to 7.
10. The solid polymer electrolyte based lithium ion battery of claim 9, wherein the lithium iron phosphate battery has a battery capacity retention of not less than 95% and an average coulombic efficiency of not less than 99% after 200 cycles at a current density of 1C.
CN202310970655.0A 2023-08-03 2023-08-03 Solid polymer electrolyte and preparation method and application thereof Pending CN116979137A (en)

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