CN116979136A - Preparation method of partially fluorinated solid electrolyte and lithium ion battery - Google Patents
Preparation method of partially fluorinated solid electrolyte and lithium ion battery Download PDFInfo
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- CN116979136A CN116979136A CN202310963205.9A CN202310963205A CN116979136A CN 116979136 A CN116979136 A CN 116979136A CN 202310963205 A CN202310963205 A CN 202310963205A CN 116979136 A CN116979136 A CN 116979136A
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- solid electrolyte
- acrylate monomer
- polymerizable
- lithium
- partially fluorinated
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- 239000007784 solid electrolyte Substances 0.000 title claims abstract description 94
- 238000002360 preparation method Methods 0.000 title claims abstract description 27
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 24
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 24
- 239000000178 monomer Substances 0.000 claims abstract description 67
- 150000001252 acrylic acid derivatives Chemical class 0.000 claims abstract description 34
- NIXOWILDQLNWCW-UHFFFAOYSA-M Acrylate Chemical compound [O-]C(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-M 0.000 claims abstract description 29
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 28
- 239000000203 mixture Substances 0.000 claims abstract description 14
- 239000002243 precursor Substances 0.000 claims abstract description 14
- 229910052744 lithium Inorganic materials 0.000 claims description 21
- -1 acrylic ester Chemical class 0.000 claims description 20
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 17
- 239000003792 electrolyte Substances 0.000 claims description 15
- 239000007788 liquid Substances 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 12
- 239000010408 film Substances 0.000 claims description 10
- 239000011159 matrix material Substances 0.000 claims description 9
- 239000004745 nonwoven fabric Substances 0.000 claims description 7
- 229910003002 lithium salt Inorganic materials 0.000 claims description 5
- 159000000002 lithium salts Chemical class 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 5
- LCGLNKUTAGEVQW-UHFFFAOYSA-N Dimethyl ether Chemical compound COC LCGLNKUTAGEVQW-UHFFFAOYSA-N 0.000 claims description 4
- 239000004744 fabric Substances 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N acetone Substances CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 2
- WURBFLDFSFBTLW-UHFFFAOYSA-N benzil Chemical compound C=1C=CC=CC=1C(=O)C(=O)C1=CC=CC=C1 WURBFLDFSFBTLW-UHFFFAOYSA-N 0.000 claims description 2
- ZTOMUSMDRMJOTH-UHFFFAOYSA-N glutaronitrile Chemical compound N#CCCCC#N ZTOMUSMDRMJOTH-UHFFFAOYSA-N 0.000 claims description 2
- MHCFAGZWMAWTNR-UHFFFAOYSA-M lithium perchlorate Chemical compound [Li+].[O-]Cl(=O)(=O)=O MHCFAGZWMAWTNR-UHFFFAOYSA-M 0.000 claims description 2
- 229910001486 lithium perchlorate Inorganic materials 0.000 claims description 2
- 229910001496 lithium tetrafluoroborate Inorganic materials 0.000 claims description 2
- IAHFWCOBPZCAEA-UHFFFAOYSA-N succinonitrile Chemical compound N#CCCC#N IAHFWCOBPZCAEA-UHFFFAOYSA-N 0.000 claims description 2
- 239000010409 thin film Substances 0.000 claims description 2
- 238000003682 fluorination reaction Methods 0.000 abstract description 5
- 230000001105 regulatory effect Effects 0.000 abstract description 3
- 239000007772 electrode material Substances 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 12
- 239000007787 solid Substances 0.000 description 11
- 229920000642 polymer Polymers 0.000 description 8
- SMBQBQBNOXIFSF-UHFFFAOYSA-N dilithium Chemical compound [Li][Li] SMBQBQBNOXIFSF-UHFFFAOYSA-N 0.000 description 7
- 239000002994 raw material Substances 0.000 description 7
- 238000012360 testing method Methods 0.000 description 5
- 238000002474 experimental method Methods 0.000 description 4
- 125000001153 fluoro group Chemical group F* 0.000 description 4
- 238000005227 gel permeation chromatography Methods 0.000 description 4
- 150000002500 ions Chemical class 0.000 description 4
- 238000004806 packaging method and process Methods 0.000 description 4
- 229920000671 polyethylene glycol diacrylate Polymers 0.000 description 3
- 239000002202 Polyethylene glycol Substances 0.000 description 2
- 239000011203 carbon fibre reinforced carbon Substances 0.000 description 2
- 238000009831 deintercalation Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 125000004386 diacrylate group Chemical group 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229920002313 fluoropolymer Polymers 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 238000009830 intercalation Methods 0.000 description 2
- 230000002687 intercalation Effects 0.000 description 2
- 239000011244 liquid electrolyte Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229920001223 polyethylene glycol Polymers 0.000 description 2
- 229910001251 solid state electrolyte alloy Inorganic materials 0.000 description 2
- VBHXIMACZBQHPX-UHFFFAOYSA-N 2,2,2-trifluoroethyl prop-2-enoate Chemical compound FC(F)(F)COC(=O)C=C VBHXIMACZBQHPX-UHFFFAOYSA-N 0.000 description 1
- FTALTLPZDVFJSS-UHFFFAOYSA-N 2-(2-ethoxyethoxy)ethyl prop-2-enoate Chemical compound CCOCCOCCOC(=O)C=C FTALTLPZDVFJSS-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000012983 electrochemical energy storage Methods 0.000 description 1
- 238000005538 encapsulation Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229920000058 polyacrylate Polymers 0.000 description 1
- 239000005518 polymer electrolyte Substances 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000004626 scanning electron microscopy Methods 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- 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
-
- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
- D06M10/00—Physical treatment of fibres, threads, yarns, fabrics, or fibrous goods made from such materials, e.g. ultrasonic, corona discharge, irradiation, electric currents, or magnetic fields; Physical treatment combined with treatment with chemical compounds or elements
- D06M10/04—Physical treatment combined with treatment with chemical compounds or elements
- D06M10/08—Organic compounds
-
- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
- D06M10/00—Physical treatment of fibres, threads, yarns, fabrics, or fibrous goods made from such materials, e.g. ultrasonic, corona discharge, irradiation, electric currents, or magnetic fields; Physical treatment combined with treatment with chemical compounds or elements
- D06M10/04—Physical treatment combined with treatment with chemical compounds or elements
- D06M10/08—Organic compounds
- D06M10/10—Macromolecular compounds
-
- D—TEXTILES; PAPER
- D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
- D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
- D06M14/00—Graft polymerisation of monomers containing carbon-to-carbon unsaturated bonds on to fibres, threads, yarns, fabrics, or fibrous goods made from such materials
- D06M14/18—Graft polymerisation of monomers containing carbon-to-carbon unsaturated bonds on to fibres, threads, yarns, fabrics, or fibrous goods made from such materials using wave energy or particle radiation
-
- 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
- H01M10/052—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
Abstract
The invention discloses a preparation method of a partially fluorinated solid electrolyte and a lithium ion battery, and belongs to the field of electrode materials. The invention provides a strategy of partial fluorination, which discovers that the mechanical property and the ionic conductivity of the finally obtained solid electrolyte can be regulated and controlled by changing the proportion of a monofunctional polymerizable acrylate monomer and a difunctional polymerizable acrylate monomer in a polymerization precursor solution and the proportion of the polymerizable fluorinated acrylate monomer in a polymerizable acrylate monomer composition; the partially fluorinated solid electrolyte prepared by the preparation method provided by the invention has the advantages of reliable stability, higher safety, excellent mechanical property and higher ionic conductivity. The partially fluorinated solid electrolyte provided by the invention can be used for preparing lithium ion batteries with better safety performance and excellent electrochemical performance.
Description
Technical Field
The invention relates to the technical field of electrode materials, in particular to a preparation method of a solid electrolyte, and specifically relates to a preparation method of a partially fluorinated solid electrolyte and a lithium ion battery.
Background
Lithium ion batteries have been developed at a high rate in the past decades as the most widely used products for electrochemical energy storage, and have many advantages such as high energy density, long cycle life, and wide use temperature range. At present, the commonly used lithium ion battery generally uses organic liquid as electrolyte, and the liquid electrolyte has high ionic conductivity, but the safety problem caused by the characteristics of easy volatilization, inflammability and the like becomes a bottleneck for restricting the rapid development of the lithium ion battery. Therefore, the use of solid electrolytes instead of liquid electrolytes has become a future development trend in the lithium ion battery industry.
Polymer electrolytes are a widely focused class of solid state electrolyte types because of their excellent processability and flexibility. In the polymer solid electrolyte, the fluorinated polymer can form a stable solid electrolyte interface film (SEI film) through the introduction of fluorine atoms, thereby remarkably reducing the interface impedance of a system and increasing the cycling stability. However, fluorinated polymerizable monomers can have difficulties in-situ polymerization due to the greater steric hindrance of the fluorine atoms, ultimately resulting in lower polymerization levels of the resulting polymers. Based on this, it is necessary to develop a fluorinated solid electrolyte having a high degree of polymerization, capable of forming a stable SEI interface, and thus it is also important to prepare a solid battery having excellent charge and discharge properties and safety.
Disclosure of Invention
An object of the present invention is to provide a method for preparing a partially fluorinated solid electrolyte, which overcomes the disadvantages of the prior art, such as low polymerization degree, poor mechanical properties or low ionic conductivity, of the fluorinated electrolyte;
it is another object of the present invention to provide a lithium ion battery assembled using a partially fluorinated solid electrolyte to overcome the disadvantage of the prior art of poor electrochemical performance of solid state batteries assembled using a solid state electrolyte prepared using a fluorinated polymer.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the invention provides a preparation method of a partially fluorinated solid electrolyte, which comprises the following steps in sequence:
s1, uniformly mixing a polymerizable acrylic ester monomer composition, a nitrile compound, lithium salt and a photoinitiator to prepare a polymerization precursor solution;
s2, infiltrating the non-woven fabric into a polymerization precursor liquid to prepare an infiltrated matrix;
s3, carrying out in-situ polymerization on the infiltrated matrix under ultraviolet light to obtain a partially fluorinated solid electrolyte;
wherein in step S1, the polymerizable acrylate monomer composition includes a polymerizable fluorinated acrylate monomer and a polymerizable non-fluorinated acrylate monomer, the polymerizable fluorinated acrylate monomer is a monofunctional polymerizable fluorinated acrylate monomer, and the polymerizable non-fluorinated acrylate monomer includes at least one difunctional polymerizable non-fluorinated acrylate monomer and one monofunctional polymerizable non-fluorinated acrylate monomer.
As a first limitation to the above preparation method, in step S1, the difunctional polymerizable non-fluorinated acrylate monomer is also referred to herein as a difunctional polymerizable acrylate monomer; the monofunctional polymerizable fluorinated acrylate monomer and the monofunctional polymerizable non-fluorinated acrylate monomer are collectively referred to herein as a monofunctional polymerizable acrylate monomer; the mass of the difunctional polymerizable acrylate monomer is not less than 5wt% of the mass of the monofunctional polymerizable acrylate monomer;
the monofunctional polymerizable acrylate monomer is a polymerizable acrylate monomer containing one carbon-carbon double bond in a monomer molecule; the difunctional polymerizable acrylate monomer refers to a polymerizable acrylate monomer containing two carbon-carbon double bonds in the monomer molecule.
As a second limitation on the above preparation method, in step S1, the nitrile compound includes succinonitrile or glutaronitrile; the lithium salt is one of lithium bis (trifluoromethanesulfonyl imide), lithium bis (fluorosulfonyl imide), lithium oxalyldifluoroborate, lithium dioxaborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate or lithium perchlorate; the photoinitiator comprises benzil dimethyl ether, 2-hydroxy-2-methyl-1-phenyl-1-acetone or 2-methyl-1- (4-methylthiophenyl) -2-morpholin-1-one.
As a third limitation to the above-mentioned production method, in step S2, the nonwoven fabric is at least one of a fibrous film, a meltblown fabric, or a nonwoven fabric separator.
As a fourth limitation on the above preparation method, the components in step S1 are mixed according to the following weight:
the mass ratio of the polymerizable fluorinated acrylate monomer in the polymerizable acrylate monomer composition is 30-70%.
As a further limitation to the above preparation method, in the step S3, the wavelength of the ultraviolet light is 350-400 nm.
As another further limitation of the above preparation method, in step S3, the partially fluorinated solid electrolyte is in the form of a thin film having a thickness of 10 to 200 μm.
The invention also provides a lithium ion battery, and the electrolyte of the lithium ion battery is prepared by the preparation method of the partially fluorinated solid electrolyte.
By adopting the technical scheme, compared with the prior art, the invention has the following technical progress:
(1) based on the defects of low polymerization degree, poor mechanical property, low ionic conductivity and the like of the fluorinated electrolyte in the prior art, the invention provides a partially fluorinated strategy and provides a preparation method of the partially fluorinated acrylate polymer solid electrolyte, and the solid electrolyte prepared by the method has the advantages of reliable stability, less influence by factors such as water, oxygen and the like, excellent mechanical property and higher ionic conductivity;
(2) in the preparation method of the partially fluorinated solid electrolyte, the polymerization degree of the polymer obtained after the polymerizable acrylate monomer is mixed can be regulated by changing the proportion of the polymerizable acrylate monomer with single functionality and the polymerizable acrylate monomer with double functionality and the proportion of the polymerizable fluorinated acrylate monomer in the polymerizable acrylate monomer composition, so that the mechanical property and the ionic conductivity of the finally obtained solid electrolyte can be further regulated;
(3) in the preparation process of the partially fluorinated solid electrolyte provided by the invention, the invention also discovers that the mass of the difunctional polymerizable acrylate monomer is not less than 5wt% of the mass of the monofunctional polymerizable acrylate monomer, otherwise, the obtained polymerized precursor liquid is not easy to form a film;
(4) in the preparation method of the partially fluorinated solid electrolyte, the nitrile compound is introduced as an ion conductivity additive, and has a certain promotion effect on improving the ion conductivity of the obtained solid electrolyte; the non-woven fabric is used as a matrix, and the raw materials are cheap and easy to obtain, and can also improve the mechanical properties of the solid electrolyte film;
(5) compared with the existing lithium ion battery, the lithium ion battery assembled by the partially fluorinated solid electrolyte prepared by the invention has smaller potential safety hazard and better electrochemical performance; the potential safety hazard is smaller, namely the property of the solid electrolyte selected by the battery is more stable, and combustion or explosion is not easy to occur; the electrochemical performance is more excellent, and the lithium ion battery provided by the invention has the discharge specific capacity of 141.2mAh/g under the current density of 1C, and the discharge specific capacity of 119.6mAh/g is still maintained after 750 circles of circulation.
The preparation method of the partially fluorinated solid electrolyte provided by the invention can be used for preparing the solid electrolyte and further applied to preparing lithium ion batteries.
Drawings
The invention will be described in more detail below with reference to the accompanying drawings and specific examples.
FIG. 1 is a structural formula of TFEA-EA in example 1 of the present invention;
FIG. 2 is a structural formula of DECS-EA in example 1 of the present invention;
FIG. 3 is a structural formula of polyethylene glycol diacrylate according to example 1 of the present invention;
FIG. 4 is a scanning electron microscope image of a partially fluorinated solid electrolyte I according to example 1 of the present invention;
FIG. 5 shows the results of gel permeation chromatography for three different degrees of fluorination of solid state electrolytes according to example 1 of the present invention, wherein FIG. 5a shows the results of gel permeation chromatography for non-fluorinated solid state electrolyte and partially fluorinated solid state electrolyte I, and FIG. 5b shows the results of gel permeation chromatography for perfluorinated solid state electrolyte;
FIG. 6 is a graph showing the ionic conductivity as a function of temperature for three solid state electrolytes of varying degrees of fluorination in example 1 of the present invention;
FIG. 7 shows a lithium-lithium symmetrical battery I, a lithium-lithium symmetrical battery pair I and a lithium-lithium symmetrical battery pair II in example 8 of the present invention at 0.1mA/cm 2 The test result of lithium ion intercalation and deintercalation experiments at the current density;
fig. 8 is a graph showing the battery cycle performance of the lithium ion battery I of example 8 of the present invention at a current density of 1C.
Detailed Description
The invention is further illustrated by the following examples. It should be understood that the described embodiments are preferred examples of the present invention and are merely for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Materials, reagents, and the like used in the examples of the present invention are commercially available unless otherwise specified.
Example 1A method for preparing a partially fluorinated solid electrolyte
The present embodiment is a method for producing a partially fluorinated solid electrolyte, comprising the steps of, in order:
s1, mixing 2, 2-trifluoroethyl acrylate (TFEA-EA), ethoxyethoxyethyl acrylate (DECS-EA), polyethylene glycol diacrylate (PEGDA), a nitrile compound, lithium salt and a photoinitiator according to the proportion shown in the table 1, placing the mixture on an oscillator for oscillation for 5min, then placing the mixture in an ultrasonic dispersing device for dispersing ultrasonic waves for 20min, and finally obtaining a uniformly mixed polymerization precursor liquid which is marked as a polymerization precursor liquid I;
s2, the area is 10 multiplied by 10cm 2 Soaking the melt-blown cloth with the thickness of 120 mu m in a 500mL screw bottle filled with 200mL of polymer precursor liquid I for 3 hours to obtain a soaked matrix, and marking the soaked matrix as a soaked matrix I;
s3, taking out the infiltrated matrix I from the polymerization precursor liquid I, and polymerizing for 10min under ultraviolet light with the wavelength of 365nm to obtain a partially fluorinated solid electrolyte, which is marked as the partially fluorinated solid electrolyte I;
in the step S1, TFEA-EA is a single-functionality polymerizable fluorinated acrylate monomer, and the structural formula of the TFEA-EA is shown in figure 1; DECS-EA is a monofunctional polymerizable non-fluorinated acrylate monomer with a structural formula shown in figure 2; PEGDA is a difunctional polymerizable non-fluorinated acrylate monomer with a structural formula shown in figure 3, wherein n is a positive integer from 3 to 6.
TABLE 1 raw materials proportioning table of polymerization precursor liquid I
As can be seen from Table 1, the ratio of the mass of the difunctional polymerizable acrylate monomer (PEGDA) to the mass of the monofunctional polymerizable acrylate monomers (TFEA-EA and DECS-EA) was 5.3:100; the mass ratio of the polymerizable fluorinated acrylate monomer in the polymerizable acrylate monomer composition was 47.5%.
(II) this example also characterizes the thickness, microcosmic morphology of the partially fluorinated solid electrolyte I, and the average molar mass and ionic conductivity of the partially fluorinated solid electrolyte I were determined as follows:
(1) Thickness of partially fluorinated solid electrolyte I
The thickness of the partially fluorinated solid electrolyte I was measured to be 200. Mu.m.
(2) Microcosmic morphology of partially fluorinated solid electrolyte I
This example characterizes the surface structure of a partially fluorinated solid electrolyte i by scanning electron microscopy, and an SEM image of the partially fluorinated solid electrolyte i is shown in fig. 4.
As can be seen from fig. 4, the partially fluorinated solid electrolyte i retains the crosslinked network structure of the meltblown while possessing a relatively flat polymer surface; the structure can further enhance the interface performance of the relatively flexible and flat surface on the premise of ensuring the stability of the mechanical property and the mechanical strength of the solid electrolyte.
(3) Preparation of comparative examples
To explore the effect of the mass ratio of polymerizable fluorinated acrylate monomers in the polymerizable acrylate monomer composition on the overall degree of polymerization and ionic conductivity of the solid state electrolyte, this example separately prepared two comparative examples based on a non-fluorinated strategy, perfluorinated strategy, as follows.
Comparative example 1: based on the preparation method of the embodiment 1, TFEA-EA is not added in a raw material proportion table of the polymerization precursor liquid I, and the mass ratio of DECS-EA is adjusted from 15% to 30%, so that the mass ratio of the polymerizable acrylate monomer composition in the polymerization precursor liquid I is ensured to be 31.6%, the consumption of the rest raw materials and preparation process parameters are kept unchanged, and the prepared solid electrolyte is marked as a non-fluorinated solid electrolyte.
Comparative example 2: based on the preparation method of example 1, the mass ratio of DECS-EA in the raw material proportion table of the polymerization precursor liquid I is only added to the mass ratio of TFEA-EA, namely, the mass ratio of TFEA-EA is adjusted from 15% to 30% without adding DECS-EA, and the consumption and preparation process parameters of the rest raw materials are kept unchanged, so that the prepared solid electrolyte is named as perfluorinated solid electrolyte.
(3) Determination of the average molar mass of the three solid electrolytes
The partially fluorinated solid electrolyte I prepared in example 1, the non-fluorinated solid electrolyte prepared in comparative example 1 and the perfluorinated solid electrolyte prepared in comparative example 2 were subjected to gel permeation chromatography experiments, and the results of the measurements are shown in FIG. 5 by measuring the polymerization degree of the polymer in the average molar mass reaction system of the systems.
As can be seen from fig. 5, the average molar mass of the perfluorinated solid-state electrolyte is only 23.8kg/mol, which may be due to excessive fluorine atom incorporation, resulting in a significant decrease in the degree of polymerization; the resulting partially fluorinated solid state electrolyte I and non-fluorinated solid state electrolyte based on the partially fluorinated strategy and non-fluorinated strategy achieve relatively high molar masses of about 74.2kg/mol and 78.6kg/mol, respectively. Higher molar mass means higher degree of polymerization and more desirable mechanical properties, which can provide a basis for subsequent stable electrochemical properties.
(4) Determination of ion conductivity of three solid electrolytes
To determine the ionic conductivity of the partially fluorinated solid electrolyte i prepared in example 1, the non-fluorinated solid electrolyte prepared in comparative example 1, and the perfluorinated solid electrolyte prepared in comparative example 2, the three solid electrolytes were first assembled into a battery. The assembly was performed in a glove box according to the sequence of the negative electrode case-leaf spring-gasket-solid electrolyte-gasket-positive electrode case, followed by the button cell packaging using a pressure-controllable manual packaging machine. After the encapsulation, the ion conductance was measured by the ac impedance method, and the measurement result is shown in fig. 6.
As can be seen from FIG. 6, the ionic conductivity of the non-fluorinated solid electrolyte at room temperature is 0.5mS/cm, which is much lower than that of the partially fluorinated solid electrolyte I (1.0 mS/cm) and the perfluorinated solid electrolyte (1.1 mS/cm), which is due in part to the low degree of polymerization and high oligomer content of the polymer.
In summary, it can be seen from the tests of average molar mass and ionic conductivity of the solid electrolyte prepared under the non-fluorination strategy, the perfluorinated strategy and the partially fluorinated strategy respectively, that the single-functionality acrylate monomer in the polymerizable acrylate monomer composition fully uses the fluorinated acrylate monomer shown in fig. 1, which results in lower polymerization degree and poorer mechanical properties; if the monofunctional acrylate monomer is used as a non-fluorinated acrylate monomer like that shown in fig. 2, there is a problem in that it is difficult to form a stable solid electrolyte interface film (SEI film) after the subsequent battery assembly, which also results in poor electrochemical performance. The use of a partially fluorinated strategy balances the relationship between mechanical and electrochemical properties.
Examples 2 to 7 preparation of partially fluorinated solid electrolytes
Examples 2 to 7 are respectively a method for preparing a partially fluorinated solid electrolyte, and the prepared partially fluorinated solid electrolytes are sequentially labeled as a partially fluorinated solid electrolyte II to a partially fluorinated solid electrolyte VIII, and the preparation methods are basically the same as those of example 1, except that the raw materials, the amounts and the process parameters are different, and the details are shown in Table 2.
Table 2 list of control parameters for examples 2 to 7
During the experiments of examples 2 to 7, it was found that the mass of the difunctional polymerizable fluorinated acrylate monomer was not less than 5wt% of the mass of the monofunctional polymerizable fluorinated acrylate monomer, otherwise film formation was not easy.
The determination of the average molar mass and ionic conductivity of the partially fluorinated solid electrolytes II through VIII shows that the partially fluorinated solid electrolytes II through VIII have good polymerization degree and ionic conductivity.
Example 8 use of partially fluorinated solid electrolytes in the preparation of lithium ion batteries
In view of the excellent electrochemical and mechanical properties of fluorinated solid electrolytes, the partially fluorinated solid electrolytes prepared in examples 1 to 7 can be used to assemble lithium ion batteries. This example only assembled a lithium ion battery with the partially fluorinated solid electrolyte I prepared in example 1 and examined its electrochemical properties further.
The specific method comprises the following steps:
(1) Electrochemical performance of solid electrolyte assembled lithium symmetric batteries made under different fluorination degree strategies
The partially fluorinated solid electrolyte i prepared in example 1, the non-fluorinated solid electrolyte prepared in comparative example 1, and the perfluorinated solid electrolyte prepared in comparative example 2 were respectively used as solid electrolytes to assemble a button cell. The assembly process is as follows: and assembling in a glove box according to the sequence of the negative electrode shell, the lithium sheet, the solid electrolyte, the lithium sheet, the gasket, the spring sheet and the positive electrode shell, and then packaging the button cell by using a pressure-controllable manual packaging machine to obtain the lithium-lithium symmetrical cell. Lithium symmetrical batteries assembled using the partially fluorinated solid electrolyte I, the non-fluorinated solid electrolyte prepared in comparative example 1, and the perfluorinated solid electrolyte prepared in comparative example 2 were sequentially referred to as lithium symmetrical battery I, lithium symmetrical battery II, and lithium symmetrical battery III.
The three assembled lithium symmetrical batteries are subjected to lithium ion intercalation and deintercalation experiments, and the test current density is 0.1mA/cm 2 The test results are shown in fig. 7.
As can be seen from fig. 7, the lithium-lithium symmetric battery II is relatively unstable in cycle, and short-circuits occur in about fifty hours of cycle, which may be because the non-fluorinated solid electrolyte does not form a stable SEI film because of no introduction of fluorine atoms, further resulting in unstable cycle of the assembled battery; after 50 hours, the voltage of the lithium-lithium symmetrical battery III is gradually increased from 50mV to 5V, because the interface is still unstable due to the low polymerization degree of the polymer in the perfluorinated solid-state electrolyte in the system; and the lithium-lithium symmetrical battery I can stably circulate for more than 800 hours and shows excellent electrochemical stability.
(2) Electrochemical performance of partially fluorinated solid electrolyte assembled lithium metal full cells
A lithium sheet having a diameter of 12mm was used as a negative electrode of a button cell, a lithium iron phosphate paste (LFP) was used as a positive electrode of the button cell, and the partially fluorinated solid electrolyte I obtained in example 1 was used as a solid electrolyte for battery assembly, and the assembled button cell was designated as a lithium metal full cell I and was subjected to an electrochemical performance test, and the test results thereof are shown in fig. 8.
As can be seen from fig. 8, at a current density of 1C, the lithium metal full battery I exhibited a specific discharge capacity of 141.2mAh/g, and a specific discharge capacity of 119.6mAh/g was maintained after 750 cycles, thus it was seen that the lithium metal full battery I exhibited excellent electrochemical properties.
It is to be understood that the above examples of the present invention are provided by way of illustration only and not by way of limitation of the embodiments of the present invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. Not all embodiments are exhaustive. All obvious changes or modifications which come within the spirit of the invention are desired to be protected.
Claims (8)
1. A method of preparing a partially fluorinated solid electrolyte, comprising the steps of, in order:
s1, uniformly mixing a polymerizable acrylic ester monomer composition, a nitrile compound, lithium salt and a photoinitiator to prepare a polymerization precursor solution;
s2, infiltrating the non-woven fabric into a polymerization precursor liquid to prepare an infiltrated matrix;
s3, placing the infiltrated matrix under ultraviolet light for polymerization to obtain a partially fluorinated solid electrolyte;
wherein in step S1, the polymerizable acrylate monomer composition includes a polymerizable fluorinated acrylate monomer and a polymerizable non-fluorinated acrylate monomer, the polymerizable fluorinated acrylate monomer is a monofunctional polymerizable fluorinated acrylate monomer, and the polymerizable non-fluorinated acrylate monomer includes at least one difunctional polymerizable non-fluorinated acrylate monomer and one monofunctional polymerizable non-fluorinated acrylate monomer.
2. The method for producing a partially fluorinated solid electrolyte according to claim 1, wherein in step S1, the mass of the difunctional polymerizable non-fluorinated acrylate monomer is denoted as a, the total mass of the monofunctional polymerizable fluorinated acrylate monomer and the monofunctional polymerizable non-fluorinated acrylate monomer is denoted as B, and a is not less than 5wt% of B.
3. The method for producing a partially fluorinated solid electrolyte according to claim 1, wherein in step S1,
the nitrile compound comprises succinonitrile or glutaronitrile;
the lithium salt is one of lithium bis (trifluoromethanesulfonyl imide), lithium bis (fluorosulfonyl imide), lithium oxalyldifluoroborate, lithium dioxaborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate or lithium perchlorate;
the photoinitiator comprises benzil dimethyl ether, 2-hydroxy-2-methyl-1-phenyl-1-acetone or 2-methyl-1- (4-methylthiophenyl) -2-morpholin-1-one.
4. The method of producing a partially fluorinated solid electrolyte according to claim 1, wherein in step S2, the nonwoven fabric is at least one of a fibrous film, a meltblown fabric, or a nonwoven fabric separator.
5. The method for producing a partially fluorinated solid electrolyte according to any one of claims 1 to 4, wherein the components in step S1 are mixed in the following amounts by weight:
the mass ratio of the polymerizable fluorinated acrylate monomer in the polymerizable acrylate monomer composition is 30-70%.
6. The method according to claim 5, wherein in the step S3, the ultraviolet light has a wavelength of 350 to 400nm.
7. The method according to claim 5, wherein the partially fluorinated solid electrolyte in step S3 is in the form of a thin film having a thickness of 10 to 200 μm.
8. A lithium ion battery, characterized in that the electrolyte of the lithium ion battery is prepared by the preparation method of the partially fluorinated solid electrolyte according to any one of claims 1 to 6.
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