CN114784370A - Three-dimensional polymer composite solid electrolyte and preparation method thereof - Google Patents
Three-dimensional polymer composite solid electrolyte and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a three-dimensional polymer composite solid electrolyte and a preparation method thereof, and relates to the technical field of solid electrolytes, wherein the three-dimensional polymer composite solid electrolyte comprises a polymer matrix, a cross-linking agent, a photoinitiator, an inorganic filler and lithium salt, wherein the polymer matrix is a mixture of PVDF, PEO and PAA; wherein the mass ratio of the PVDF, the PEO, the PAA, the cross-linking agent, the photoinitiator, the inorganic filler and the lithium salt is 10-20: 10-20: 10-20: 5-10: 0.3-0.5: 2-5: 3-7. Compared with a pure PEO or PVDF-based polymer composite solid electrolyte, the three-dimensional polymer composite solid electrolyte can provide more lithium ion transmission channels, improve the normal-temperature conductivity and mechanical strength of the polymer solid electrolyte, and prolong the cycle life of a battery.
Description
Technical Field
The invention relates to the technical field of solid electrolytes, in particular to a three-dimensional polymer composite solid electrolyte and a preparation method thereof.
Background
An all-solid-state lithium battery is a lithium secondary battery using a solid electrode and a solid electrolyte, and is safer to use and capable of being used as compared with a conventional lithium ion battery using a liquid organic electrolyteThe bulk density is higher. At present, all-solid-state lithium batteries mainly include two major categories, distinguished by electrolyte: the first type is an all solid-state lithium battery composed of an organic polymer electrolyte, which is called a polymer all solid-state lithium battery; the second type is a lithium ion battery composed of an inorganic solid electrolyte, called an inorganic all-solid-state lithium battery, mainly including oxides and sulfides. In the using process of the inorganic all-solid-state lithium battery, because the interface resistance of the inorganic solid electrolyte is large, the inorganic all-solid-state lithium battery is unstable to a lithium metal negative electrode, and the critical current density of the battery short circuit caused by the penetration of lithium dendrites through the solid electrolyte is small, so that the application of the inorganic solid electrolyte in the all-solid-state lithium battery is limited. Meanwhile, since the inorganic solid electrolyte is fragile, the thickness is generally 200 μm or more, which in turn greatly reduces the rate performance and energy density of the battery. Compared with a fragile inorganic solid electrolyte, the polyethylene oxide (PEO) polymer solid electrolyte has better flexibility and good interfacial contact with an electrode, and can reduce the interfacial resistance of a solid battery, but the polymer solid electrolyte usually has about 10 parts at room temperature-6S·cm-1Thereby increasing the overpotential of the battery and limiting the battery service temperature to about 60 deg.f. C
With the continuous development of lithium battery technology, the inorganic/polymer composite electrolyte has higher Li than the polymer electrolyte at room temperature+Electrical conductivity has become a hotspot of research in recent years. For example, chinese patent application publication No. CN111613833A, application No. cn202010415819.x, which discloses a polymer solid electrolyte and a method for preparing the same, utilizes a lithium salt containing bulky anions and an inorganic filler to improve the conductivity and interfacial stability of PVDF and PVDF/PEO based polymer electrolytes. However, in the patent application, the interaction between the anion with large volume and the lithium ion is reduced, so that the lithium salt is easy to dissociate, the conductivity of the solid electrolyte is improved, and the negative charge delocalization degree is increased only by improving the volume of the anion, so that the defects of limited influence on the dissociation of the lithium salt, low conductivity at normal temperature, poor mechanical property of the solid electrolyte at high temperature, poor lithium dendrite resistance and the like exist.
Disclosure of Invention
1. Technical problems to be solved by the invention
The invention provides a three-dimensional polymer composite solid electrolyte and a preparation method thereof, aiming at the technical problems of lower normal-temperature conductivity and poor high-temperature mechanical property of the polymer solid electrolyte in the prior art, and the three-dimensional polymer composite solid electrolyte can obviously improve the lithium ion transmission performance of the polymer solid electrolyte, improve the normal-temperature conductivity and high-temperature mechanical strength of the polymer solid electrolyte and prolong the cycle life of a battery.
2. Technical scheme
In order to solve the problems, the technical scheme provided by the invention is as follows:
a three-dimensional polymer composite solid electrolyte comprises a polymer matrix, a cross-linking agent, a photoinitiator, an inorganic filler and a lithium salt, wherein the polymer matrix is a mixture of PVDF, PEO and PAA; wherein the mass ratio of the PVDF, the PEO, the PAA, the cross-linking agent, the photoinitiator, the inorganic filler and the lithium salt is 10-20: 10-20: 10-20: 5-10: 0.3-0.5: 2-5: 3-7.
In the application, the polymer matrix is a mixture of PVDF, PEO and PAA, under the irradiation of a photoinitiator and ultraviolet light, the PEO and the PAA are crosslinked with a crosslinking agent to form an amphiphilic block copolymer, and are crosslinked with the PVDF to form a polymer with an interpenetrating three-dimensional structure, so that the three-dimensional PVDF-PEO-PAA based polymer composite solid electrolyte, namely the three-dimensional polymer composite solid electrolyte, is obtained, and the electric conductivity and the mechanical property of the composite solid electrolyte are improved. Because PEO has stronger hydrophilicity and PAA has strong hydrophobicity, after the copolymer is formed after crosslinking, compared with other systems, on one hand, the PEO has good compatibility with an organic solvent and can improve the dispersion uniformity of the raw material in the preparation process; on the other hand, the affinity with lithium ions is enhanced, and the lithium ion transmission performance of the composite solid electrolyte is enhanced. Meanwhile, the PVDF is introduced, so that the surface flatness, the thermal stability and the chemical stability of the composite solid electrolyte can be enhanced, and the service life of the solid electrolyte is prolonged. In addition, by adding the lithium salt and the inorganic filler, the inorganic filler and the lithium salt have strong adsorption effect, and the dissociation of the lithium salt is effectively promoted, so that the polymer solid electrolyte is activatedMore mobile Li in+Further, the normal-temperature conductivity of the polymer solid electrolyte is obviously improved, the internal resistance of the solid battery is reduced, and the cycle life is prolonged. Therefore, compared with a pure PEO or PVDF-based polymer composite solid electrolyte, the three-dimensional polymer composite solid electrolyte can provide more lithium ion transmission channels, and the normal-temperature conductivity and the mechanical strength of the polymer solid electrolyte are improved.
Optionally, the lithium salt is selected from one or more of lithium bistrifluoromethanesulfonimide, lithium bistriflurosulfonate, lithium bisoxalato borate, lithium tetrafluoroborate, lithium hexafluoroborate, lithium perchlorate, lithium difluorobisoxalato borate, lithium triethylborohydride, lithium diisopropylamide, lithium acetoacetate, lithium bistrimethylsilyl, lithium pentamethylcyclopentadiene, 4, 5-dicyano-2-trifluoromethylimidazole, lithium fluorosulfonate (n-perfluorobutylsulfonyl) imide, and tert-butyllithium.
Optionally, the inorganic filler is any one of gadolinium oxide doped ceria, cerium stabilized scandium doped zirconia and yttrium oxide stabilized zirconia.
Optionally, the cross-linking agent is selected from one or more of acrylate, trimethyl carbonate, divinylbenzene and diisocyanate, N-methylenebisacrylamide, polyalkylacrylate, benzoyl peroxide, di-t-butyl peroxide, diisopropylbenzene hydroperoxide, diethylenetriamine, 2-ethyl-4 methylimidazole, 2-phenylimidazole, 2-isopropylimidazole, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, triethylenetetramine, dimethylaminopropylamine, diethylaminopropylamine.
Optionally, the photoinitiator is one or more of 2-hydroxy-2-methyl propyl benzene ketone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1- [4- (2-hydroxyethoxy) phenyl ] -1-acetone, and 2-methyl-2- (4-morpholinyl) -1- [4- (methylthio) phenyl ] -1-acetone.
Meanwhile, the application also provides a preparation method of the three-dimensional polymer composite solid electrolyte, which is used for preparing the three-dimensional polymer composite solid electrolyte and comprises the following steps:
s1, dissolving a polymer matrix, a cross-linking agent, a photoinitiator, an inorganic filler and lithium salt in acetonitrile, and uniformly stirring in a protective atmosphere to obtain a precursor mixed solution;
s2, coating the precursor mixed solution obtained in the step S1 on a glass plate, and then curing the coated precursor mixed solution by ultraviolet irradiation in a protective atmosphere to obtain a polymer solid electrolyte membrane;
and S3, peeling the polymer solid electrolyte membrane obtained in the step S2 from a glass plate, washing, and drying in vacuum to obtain the three-dimensional polymer composite solid electrolyte.
Optionally, the step S1 is specifically as follows: dissolving PVDF in acetonitrile at normal temperature, then adding PEO, PAA, a cross-linking agent, a photoinitiator, an inorganic filler and lithium salt, and stirring for 3-8h under an argon atmosphere or a nitrogen atmosphere to obtain a precursor mixed solution.
Optionally, the mass ratio of the PVDF, the PEO, the PAA, the cross-linking agent, the photoinitiator, the inorganic filler, and the lithium salt is 10-20: 10-20: 10-20: 5-10: 0.3-0.5: 2-5: 3-7; the crosslinking agent is acrylate, the photoinitiator is 2-hydroxy-2-methyl propyl benzene ketone, the inorganic filler is gadolinium oxide doped cerium oxide, and the lithium salt is lithium bis (trifluoromethanesulfonimide). By providing the inorganic filler as gadolinium oxide-doped cerium oxide (Gd)0.1Ce0.9O1.95Simplified to GDC), the lithium salt is bis (trifluoromethanesulfonimide) Lithium (LITFSI), so that strong adsorption effect is achieved between GDC and LITFSI lithium salt anions, dissociation of the lithium salt is effectively promoted, and more movable Li in the polymer solid electrolyte is activated+The normal-temperature conductivity of the polymer solid electrolyte is obviously improved, the internal resistance of the solid battery is reduced, and the cycle life is prolonged.
Optionally, in S2, the precursor mixed solution is coated on a glass plate by a doctor blade method, where the coating thickness is 20 to 80 μm; the protective atmosphere is argon atmosphere or nitrogen atmosphere; the illumination intensity is 1500--2The curing time is 60-120S. The mechanical strength and the conductivity of the polymer solid electrolyte membrane can be ensured by setting the coating thickness to be 20-80 mu m; if the coating thickness is less than 20The micron-sized electrolyte can reduce the mention and mass energy density of the solid battery, increase the battery cost, is not beneficial to large-scale application, and can weaken the mechanical strength of the electrolyte due to too low thickness, thereby reducing the safety of the solid battery; when the thickness is more than 80 μm, the lithium ion transport path increases, the internal resistance of the battery increases, and the performance of the power performance of the battery is not facilitated. Meanwhile, the illumination intensity is 1500--2The curing time is 60-120S, which can fully ensure that the components are crosslinked to form a polymer, and avoid the problem that the long-time high-intensity radiation can cause the grading of the polymer and generate adverse effects on the electrochemical and mechanical properties of the polymer solid electrolyte.
Optionally, in S3, washing with methanol or isopropanol for 3-5 times, vacuum drying at 30-70 deg.C for 10-24 h. By washing 3-5 times with methanol or isopropanol, unpolymerized monomer, cross-linking agent and excess photoinitiator on the polymer solid electrolyte membrane can be removed, and the quality of the polymer solid electrolyte membrane can be improved.
3. Advantageous effects
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
(1) according to the three-dimensional polymer composite solid electrolyte provided by the embodiment of the application, the polymer matrix is a mixture of PVDF, PEO and PAA, under the irradiation of a photoinitiator and ultraviolet light, PEO and PAA are crosslinked with a crosslinking agent to form an amphiphilic block copolymer, and are crosslinked with PVDF to form a polymer with an interpenetrating three-dimensional structure, so that the three-dimensional PVDF-PEO-PAA based polymer composite solid electrolyte, namely the three-dimensional polymer composite solid electrolyte, is obtained, and the electric conductivity and the mechanical property of the composite solid electrolyte are improved. Because PEO has stronger hydrophilicity and PAA has strong hydrophobicity, after the copolymer is formed after crosslinking, compared with other systems, on one hand, the PEO has good compatibility with an organic solvent and can improve the dispersion uniformity of the raw material in the preparation process; on the other hand, the affinity with lithium ions is enhanced, and the lithium ion transmission performance of the composite solid electrolyte is enhanced. Meanwhile, the introduction of PVDF can enhance the surface flatness, thermal stability and chemical stability of the composite solid electrolyte and prolong the service life of the composite solid electrolyteThe service life of the solid electrolyte. In addition, by adding the lithium salt and the inorganic filler, the inorganic filler and the lithium salt have strong adsorption effect, and the dissociation of the lithium salt is effectively promoted, so that more movable Li in the polymer solid electrolyte is activated+Further, the normal-temperature conductivity of the polymer solid electrolyte is obviously improved, the internal resistance of the solid battery is reduced, and the cycle life is prolonged. Therefore, compared with a pure PEO or PVDF-based polymer composite solid electrolyte, the three-dimensional polymer composite solid electrolyte can provide more lithium ion transmission channels, and the normal-temperature conductivity and the mechanical strength of the polymer solid electrolyte are improved.
(2) According to the preparation method of the three-dimensional polymer composite solid electrolyte, the three-dimensional polymer composite solid electrolyte prepared by the method can provide more lithium ion transmission channels, and the normal-temperature conductivity and the mechanical strength of the polymer solid electrolyte are improved.
(3) In the preparation method of the three-dimensional polymer composite solid electrolyte provided by the embodiment of the application, the inorganic filler is gadolinium oxide doped cerium oxide (Gd)0.1Ce0.9O1.95And simplified to GDC), the lithium salt is bis (trifluoromethanesulfonyl) imide Lithium (LITFSI), so that strong adsorption is achieved between GDC and LITFSI lithium salt anions, dissociation of the lithium salt is effectively promoted, and more movable Li in the polymer solid electrolyte is activated+The normal-temperature conductivity of the polymer solid electrolyte is obviously improved, the internal resistance of the solid battery is reduced, and the cycle life is prolonged.
(4) According to the preparation method of the three-dimensional polymer composite solid electrolyte, the mechanical strength and the conductivity of the polymer solid electrolyte membrane can be ensured by setting the coating thickness to be 20-80 mu m; if the coating thickness is less than 20 mu m, the mention and mass energy density of the solid battery can be reduced, the battery cost is increased, the large-scale application is not facilitated, and the mechanical strength of the electrolyte is weakened due to too low thickness, so that the safety of the solid battery is reduced; when the thickness is more than 80 μm, the lithium ion transport path increases, the internal resistance of the battery increases, and the performance of the power performance of the battery is not facilitated. At the same time, the user can select the desired position,the illumination intensity is 1500--2The curing time is 60-120S, which can fully ensure that each component is crosslinked to form a polymer, and avoid the adverse effects on the electrochemical and mechanical properties of the polymer solid electrolyte caused by the grading of the polymer due to long-term high-intensity radiation.
Drawings
Fig. 1 is a schematic flow chart of a method for preparing a three-dimensional polymer composite solid electrolyte according to an embodiment of the present invention.
Detailed Description
For a further understanding of the present invention, reference will now be made in detail to the embodiments illustrated in the drawings.
The present application will be described in further detail with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings. The terms first, second, and the like in the present invention are provided for convenience of describing the technical solution of the present invention, have no specific limiting function, are all general terms, and do not limit the technical solution of the present invention. It should be noted that, in the present application, the embodiments and features of the embodiments may be combined with each other without conflict. In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in a specific case to those of ordinary skill in the art.
In the present application, it is to be noted that all reagent components referred to in the present application belong to the existing reagents and can be obtained by purchase. Wherein PVDF is polyvinylidene fluoride, PEO is polyethylene oxide, PAA is polyacrylic acid, LITFSI is lithium bistrifluoromethanesulfonylimide, and GDC is gadolinium oxide-doped cerium oxide Gd0.1Ce0.9O1.95。
The application provides a three-dimensional polymer composite solid electrolyte, which comprises a polymer matrix, a cross-linking agent, a photoinitiator, an inorganic filler and a lithium salt, wherein the polymer matrix is a mixture of PVDF, PEO and PAA; wherein the mass ratio of the PVDF, the PEO, the PAA, the cross-linking agent, the photoinitiator, the inorganic filler and the lithium salt is 10-20: 10-20: 10-20: 5-10: 0.3-0.5: 2-5: 3-7. Under the irradiation of a photoinitiator and ultraviolet light, PEO, PAA and a cross-linking agent are cross-linked to form an amphiphilic block copolymer, and are cross-linked with PVDF to form a polymer with an interpenetrating three-dimensional structure, so that the three-dimensional PVDF-PEO-PAA based polymer composite solid electrolyte, namely the three-dimensional polymer composite solid electrolyte, is obtained, and the electric conductivity and the mechanical property of the composite solid electrolyte are improved. Because PEO has stronger hydrophilicity and PAA has strong hydrophobicity, after the copolymer is formed after crosslinking, compared with other systems, on one hand, the PEO has good compatibility with an organic solvent and can improve the dispersion uniformity of the raw material in the preparation process; on the other hand, the affinity with lithium ions is enhanced, and the lithium ion transmission performance of the composite solid electrolyte is enhanced. Meanwhile, the PVDF is introduced to enhance the surface flatness, thermal stability and chemical stability of the composite solid electrolyte and prolong the service life of the solid electrolyte. In addition, by adding the lithium salt and the inorganic filler, the inorganic filler and the lithium salt have strong adsorption effect, and the dissociation of the lithium salt is effectively promoted, so that more movable Li in the polymer solid electrolyte is activated+Further remarkably improveThe normal temperature conductivity of the polymer solid electrolyte is improved, the internal resistance of the solid battery is reduced, and the cycle life is prolonged. Therefore, compared with a pure PEO or PVDF-based polymer composite solid electrolyte, the three-dimensional polymer composite solid electrolyte can provide more lithium ion transmission channels, and the normal-temperature conductivity and the mechanical strength of the polymer solid electrolyte are improved.
Specifically, the lithium salt is selected from one or more of lithium bistrifluoromethanesulfonylimide, lithium bistrifluorosulfonylimide, lithium bisoxalateborate, lithium tetrafluoroborate, lithium hexafluoroborate, lithium perchlorate, lithium difluorobisoxalateborate, lithium triethylborohydride, lithium diisopropylamide, lithium acetoacetate, lithium bistrimethylsilyl, lithium pentamethylcyclopentadiene, 4, 5-dicyano-2-trifluoromethylimidazole, lithium fluorosulfonate (n-perfluorobutylsulfonyl) imide and tert-butyllithium; the inorganic filler is any one of gadolinium oxide doped cerium oxide, cerium stabilized scandium doped zirconia and yttrium oxide stabilized zirconia; the cross-linking agent is selected from one or more of acrylate, trimethyl carbonate, divinylbenzene and diisocyanate, N-methylenebisacrylamide, polyalkylacrylate, benzoyl peroxide, di-tert-butyl peroxide, hydrogen peroxide diisopropylbenzene, diethylenetriamine, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-isopropylimidazole, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, triethylenetetramine, dimethylaminopropylamine and diethylaminopropylamine; the photoinitiator is one or more of 2-hydroxy-2-methyl propyl benzene ketone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1- [4- (2-hydroxyethoxy) phenyl ] -1-acetone and 2-methyl-2- (4-morpholinyl) -1- [4- (methylthio) phenyl ] -1-acetone.
Meanwhile, the application also provides a preparation method of the three-dimensional polymer composite solid electrolyte, which comprises the following steps:
s1, dissolving the polymer matrix, the cross-linking agent, the photoinitiator, the inorganic filler and the lithium salt in acetonitrile, and uniformly stirring in a protective atmosphere to obtain a precursor mixed solution.
Specifically, PVDF is dissolved in acetonitrile at normal temperature, and then PEO, PAA and Croton agent are addedThe composite material comprises a cross-linking agent, a photoinitiator, an inorganic filler and a lithium salt, wherein the mass ratio of the PVDF, the PEO, the PAA, the cross-linking agent, the photoinitiator, the inorganic filler and the lithium salt is 10-20: 10-20: 10-20: 5-10: 0.3-0.5: 2-5: 3-7, wherein the cross-linking agent is acrylate, the photoinitiator is 2-hydroxy-2-methyl propyl phenyl ketone, the inorganic filler is gadolinium oxide doped cerium oxide, and the lithium salt is lithium bis (trifluoromethanesulfonyl) imide; and then stirring for 3-8h in an argon atmosphere or a nitrogen atmosphere to obtain a precursor mixed solution. By setting the lithium salt to be lithium bistrifluoromethanesulfonylimide (LITFSI), the inorganic filler is gadolinium oxide-doped cerium oxide (Gd)0.1Ce0.9O1.95Simplified to GDC) so that strong adsorption effect is achieved between GDC and LITFSI lithium salt anions, lithium salt dissociation is effectively promoted, and more movable Li in polymer solid electrolyte is activated+The normal-temperature conductivity of the polymer solid electrolyte is obviously improved, the internal resistance of the solid battery is reduced, and the cycle life is prolonged. Meanwhile, under the argon atmosphere or the nitrogen atmosphere, the interference of other pollutants on the reaction can be prevented.
And S2, coating the precursor mixed solution obtained in the step S1 on a glass plate, and then curing by ultraviolet irradiation in a protective atmosphere to obtain the polymer solid electrolyte membrane.
Specifically, the precursor mixed solution is coated on a glass plate by a scraper method, and the coating thickness is 20-80 μm; then curing the cured product by ultraviolet irradiation in the protective atmosphere of argon or nitrogen, wherein the irradiation intensity is 1500-2500W-cm-2The curing time is 60-120S. The mechanical strength and the conductivity of the polymer solid electrolyte membrane can be ensured by setting the coating thickness to be 20-80 mu m; if the coating thickness is less than 20 mu m, the mention and mass energy density of the solid battery can be reduced, the battery cost is increased, the large-scale application is not facilitated, and the mechanical strength of the electrolyte is weakened due to too low thickness, so that the safety of the solid battery is reduced; when the thickness is more than 80 μm, the lithium ion transport path increases, the internal resistance of the battery increases, and the performance of the power performance of the battery is not facilitated. Meanwhile, the illumination intensity is 1500--2Curing time of 60-120S, the components can be fully crosslinked to form a polymer, and the polymer is prevented from being classified due to long-time high-intensity radiation, so that the electrochemical and mechanical properties of the polymer solid electrolyte are adversely affected.
And S3, peeling the polymer solid electrolyte membrane obtained in the step S2 from a glass plate, washing, and drying in vacuum to obtain the three-dimensional polymer composite solid electrolyte.
Specifically, the polymer solid electrolyte membrane is peeled from a glass plate, washed 3-5 times by methanol or isopropanol, and dried in vacuum at the temperature of 30-70 ℃ for 10-24h to obtain the three-dimensional polymer composite solid electrolyte. By washing 3-5 times with methanol or isopropanol, unpolymerized monomer, cross-linking agent and excess photoinitiator on the polymer solid electrolyte membrane can be removed, and the quality of the polymer solid electrolyte membrane can be improved.
In practical application, when the lithium salt is lithium bistrifluoromethanesulfonimide (LITFSI), the inorganic filler is gadolinium oxide-doped cerium oxide (Gd)0.1Ce0.9O1.95Abbreviated as GDC), the PVDF, the PEO, and the PAA are subjected to a crosslinking agent and a photoinitiator to prepare a three-dimensional polymer composite solid electrolyte. The flow diagram of the three-dimensional polymer composite solid electrolyte is shown in fig. 1, wherein the value range of n is 80000-.
As can be seen from fig. 1, under the irradiation of a photoinitiator and ultraviolet light, PEO and PAA are crosslinked with a crosslinking agent to form an amphiphilic block copolymer, and are crosslinked with PVDF to form a polymer with an interpenetrating three-dimensional structure, i.e., a three-dimensional polymer composite solid electrolyte, so that the electrical conductivity and the mechanical properties of the composite solid electrolyte are improved. Meanwhile, the lithium salt is lithium bis (trifluoromethanesulfonyl) imide (LITFSI), and the inorganic filler is gadolinium oxide doped cerium oxide (Gd)0.1Ce0.9O1.95Simplified to GDC), so that the GDC and the LITFSI lithium salt anion have strong adsorption, the dissociation of lithium salt is effectively promoted, more movable Li + in the polymer solid electrolyte is activated, the normal-temperature conductivity of the polymer solid electrolyte is obviously improved, the internal resistance of the solid battery is reduced, and the extension of the internal resistance of the solid battery is realizedAnd (4) the cycle life is prolonged. In addition, because PEO has stronger hydrophilicity and PAA has strong hydrophobicity, after the copolymer is formed after crosslinking, compared with other systems, on one hand, the PEO has good compatibility with an organic solvent and can improve the dispersion uniformity of the raw material in the preparation process; on the other hand, the affinity with lithium ions is enhanced, and the lithium ion transmission performance of the composite solid electrolyte is enhanced; and the introduction of PVDF can enhance the surface flatness, thermal stability and chemical stability of the composite solid electrolyte and prolong the service life of the solid electrolyte. Therefore, compared with a single PEO or PVDF-based polymer composite solid electrolyte, the three-dimensional polymer composite solid electrolyte prepared by the method can provide more lithium ion transmission channels, and the normal-temperature conductivity and the mechanical strength of the polymer solid electrolyte are improved.
In addition, in order to determine the polymers cross-linked between PEO, PAA and PVDF to form interpenetrating three-dimensional structures after uv irradiation, the present application uses acetone or acetonitrile as an etching solution to remove PVDF, PEO and PAA. And (2) soaking the prepared three-dimensional composite polymer solid electrolyte in an acetone or acetonitrile solution at normal temperature for 15-30h, taking out, washing with methanol for 3-5 times, and finally, drying in vacuum at 30-70 ℃ for 10-15h, and weighing. As a result, it was found that the three-dimensional composite polymer solid electrolyte prepared in example 1 did not significantly change before and after immersion, and the three-dimensional composite polymer solid electrolyte remained intact. It is thus understood that after UV curing, the PEO, PAA and PVDF are photocured and polymerized, and are insoluble and crosslinked.
Example 1
Dissolving PVDF in acetonitrile at normal temperature to form a transparent solution, and then adding PEO, PAA, acrylic ester, 2-hydroxy-2-methyl propyl ketone, GDC powder and LITFSI, wherein the mass ratio of the PVDF, the PEO, the PAA, the acrylic ester, the 2-hydroxy-2-methyl propyl ketone, the GDC and the LITFSI is 14: 15: 14: 8: 0.4: 4: 6; and continuously stirring for 5 hours under the argon atmosphere to obtain a uniformly dispersed precursor mixed solution. Then, the precursor mixed solution was uniformly coated on a glass plate by a doctor blade method to a coating thickness of 60 μm in an argon atmosphereUltraviolet light irradiation curing is carried out, the curing time is 90S, and the illumination intensity is 2200W cm-2And obtaining the polymer solid electrolyte membrane. Next, the cured polymer solid electrolyte membrane was peeled off from the glass, washed 4 times with methanol, and vacuum-dried at 55 ℃ for 16 hours to obtain a three-dimensional polymer composite solid electrolyte.
Example 2
Dissolving PVDF in acetonitrile at normal temperature to form a transparent solution, and then adding PEO, PAA, acrylic ester, 2-hydroxy-2-methyl propyl phenyl ketone, GDC powder and LITFSI, wherein the mass ratio of the PVDF, the PEO, the PAA, the acrylic ester, the 2-hydroxy-2-methyl propyl phenyl ketone, the GDC and the LITFSI is 10: 20: 10: 5: 0.5: 2: 3; and continuously stirring for 8 hours under the argon atmosphere to obtain a uniformly dispersed precursor mixed solution. Then, the precursor mixed solution is uniformly coated on a glass plate by a scraper method, the coating thickness is 80 μm, and ultraviolet irradiation curing is carried out in an argon atmosphere, the curing time is 120S, and the illumination intensity is 1500W-cm-2And obtaining the polymer solid electrolyte membrane. Next, the cured polymer solid electrolyte membrane was peeled off from the glass, washed 5 times with isopropyl alcohol, and vacuum-dried at 70 ℃ for 24 hours to obtain a three-dimensional polymer composite solid electrolyte.
Example 3
Dissolving PVDF in acetonitrile at normal temperature to form a transparent solution, and then adding PEO, PAA, divinylbenzene, diisocyanate, 2-hydroxy-2-methyl propyl ketone, GDC powder and lithium bis (oxalato) borate, wherein the mass ratio of the PVDF, the PEO, the PAA, the divinylbenzene, the diisocyanate, the 2-hydroxy-2-methyl propyl ketone, the GDC and the lithium bis (oxalato) borate is 14: 15: 14: 8: 0.4: 4: 6; and continuously stirring for 5 hours under the argon atmosphere to obtain a uniformly dispersed precursor mixed solution. Then, the precursor mixed solution is uniformly coated on a glass plate by a scraper method, the coating thickness is 60 mu m, and ultraviolet irradiation curing is carried out in an argon atmosphere, the curing time is 90S, and the illumination intensity is 2200W-cm-2And obtaining the polymer solid electrolyte membrane. Next, the cured polymer solid electrolyte membrane was peeled off from the glass, washed 4 times with methanol, and vacuum-dried at 55 deg.CAnd air-drying for 16h to obtain the three-dimensional polymer composite solid electrolyte.
Comparative example 1
The difference compared to example 1 is that the polymer matrix of comparative example 1 does not contain the component PVDF, the remaining conditions being the same as in example 1.
Comparative example 2
The difference compared to example 1 is that the polymer matrix in comparative example 2 does not contain the component PEO, the other conditions being the same as in example 1.
Comparative example 3
The difference compared to example 1 is that the polymeric matrix in comparative example 3 does not contain the component PAA, the other conditions being the same as in example 1.
Comparative example 4
The difference compared to example 1 is that the polymer matrix in comparative example 4 was only pure PEO, and the remaining conditions were the same as in example 1.
Comparative example 5
The difference from example 1 is that no inorganic filler GDC was added to the composition of comparative example 5, and the other conditions were the same as example 1.
Comparative example 6
The difference from example 1 is that in comparative example 6, the curing time was 180S and the light intensity was 3000W cm-2The remaining conditions were the same as in example 1.
Evaluation of various performance tests
The three-dimensional polymer composite solid electrolyte prepared in the examples 1 to 3 and the solid electrolyte prepared in the comparative examples 1 to 6 are respectively subjected to a tensile test under the condition of 10mm/min according to GB1040-92 plastic tensile property test method, the test temperatures are respectively 30 ℃ and 60 ℃, each sample is repeatedly tested for 5 times, and the average value of the three intermediate numbers is taken; and simultaneously, respectively carrying out alternating current internal resistance test on the pressed solid electrolyte at 30 ℃ and 60 ℃ by adopting a double-probe method, wherein the frequency range is 1-106HZ, the alternating current impedance directly reflects the lithium ion transmission resistivity, and the bottom and the top of the sample are sprayed with gold before testing in order to reduce the measurement error. In addition, a composite positive electrode sheet was prepared using a ternary material NCM, a lithium indium alloy sheet (lithium atomic ratio: 55%) was used as a negative electrode, and the three-dimensional polymer composite solid electrolyte prepared in examples 1 to 3 and the solid electrolyte prepared in comparative examples 1 to 6 were respectively pressed at 35 standard atmospheres to prepare corresponding solid full cells. And then, the solid full batteries respectively prepared by the above steps are subjected to charge-discharge test for cycle life at a rate of 0.1C and at a temperature of 30 ℃ and 60 ℃ within an electric range of 2.8-4.1V. As shown in Table 1, the results of the performance tests of the three-dimensional polymer composite solid electrolytes obtained in examples 1 to 3 and the solid electrolytes obtained in comparative examples 1 to 6.
Table 1.
As shown in table 1, the three-dimensional polymer composite solid electrolytes prepared in examples 1 to 3 exhibited significantly lower ac impedance, significantly higher tensile strength, and increased number of battery cycle life, compared to comparative examples 1 to 6, regardless of the temperatures at 30 ℃ (room temperature) and 60 ℃ (high temperature). Therefore, the three-dimensional polymer composite solid electrolyte prepared by the method can obviously improve the performance of the solid electrolyte, reduce the internal resistance of a solid battery, improve the normal-temperature conductivity and prolong the cycle life.
Specifically, combining example 1 and comparative examples 1 to 4, it can be seen that the three-dimensional polymer composite solid electrolyte prepared by the present invention has better mechanical properties and electrochemical properties compared with pure PEO, and the main mechanism is that the polymer matrix is a mixture of PVDF, PEO and PAA, so that after the PVDF-PEO-PAA is compounded, more lithium ion transport channels, mechanical strength and chemical stability are provided.
Meanwhile, it is known that, by combining example 1 and comparative example 6, the ultraviolet light irradiation time is too long or the intensity is too high, which causes the polymer material to be aged, and rather, leads to the degradation of the battery performance.
In addition, it can be seen from the combination of example 1 and comparative example 5 that the anion TFSI of GDC and LITFSI is added-Form strong bonding force between them, TFSI-With cations Li+The interaction between the two is weakened, and more Li is released+Increase the electrolyteLi in (1)+The transfer number reduces the internal resistance of the battery and prolongs the cycle life of the solid battery.
Therefore, the three-dimensional polymer composite solid electrolyte prepared by the method can obviously improve the lithium ion transmission performance and the mechanical strength of the polymer solid electrolyte, and provides a way reference for developing high-performance polymer solid electrolytes.
The present invention and its embodiments have been described above schematically, without limitation, and what is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Therefore, if the person skilled in the art receives the teaching, without departing from the spirit of the invention, the person skilled in the art shall not inventively design the similar structural modes and embodiments to the technical solution, but shall fall within the scope of the invention.
Claims (10)
1. The three-dimensional polymer composite solid electrolyte is characterized by comprising a polymer matrix, a cross-linking agent, a photoinitiator, an inorganic filler and a lithium salt, wherein the polymer matrix is a mixture of PVDF, PEO and PAA; wherein the mass ratio of the PVDF, the PEO, the PAA, the cross-linking agent, the photoinitiator, the inorganic filler and the lithium salt is 10-20: 10-20: 10-20: 5-10: 0.3-0.5: 2-5: 3-7.
2. The three-dimensional polymer composite solid electrolyte according to claim 1, wherein the lithium salt is selected from one or more of lithium bistrifluoromethylsulfonyl imide, lithium bistrifluorosulfonate, lithium bisoxalato borate, lithium tetrafluoroborate, lithium hexafluoroborate, lithium perchlorate, lithium difluorobisoxalato borate, lithium triethylborohydride, lithium diisopropylamide, lithium acetoacetate, lithium bistrimethylsilyl, lithium pentamethylcyclopentadiene, 4, 5-dicyano-2-trifluoromethylimidazole, lithium fluorosulfonate (n-perfluorobutylsulfonyl) imide, and t-butyllithium.
3. The three-dimensional polymer composite solid electrolyte according to claim 1, wherein the inorganic filler is any one of gadolinium oxide-doped ceria, cerium-stabilized scandium-doped zirconia, and yttrium oxide-stabilized zirconia.
4. The three-dimensional polymer composite solid electrolyte according to claim 1, wherein the cross-linking agent is selected from one or more of acrylates, trimethyl carbonate, divinyl benzene and diisocyanates, N-methylenebisacrylamide, polyalkylacrylates, benzoyl peroxide, di-t-butyl peroxide, diisopropylbenzene hydroperoxide, diethylenetriamine, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-isopropylimidazole, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, triethylenetetramine, dimethylaminopropylamine, diethylaminopropylamine.
5. The three-dimensional polymer composite solid electrolyte according to claim 1, wherein the photoinitiator is one or more of 2-hydroxy-2-methyl propyl ketone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1- [4- (2-hydroxyethoxy) phenyl ] -1-propanone, and 2-methyl-2- (4-morpholinyl) -1- [4- (methylthio) phenyl ] -1-propanone.
6. A method for preparing a three-dimensional polymer composite solid electrolyte according to any one of claims 1 to 5, comprising the steps of:
s1, dissolving a polymer matrix, a cross-linking agent, a photoinitiator, an inorganic filler and lithium salt in acetonitrile, and uniformly stirring in a protective atmosphere to obtain a precursor mixed solution;
s2, coating the precursor mixed solution obtained in the step S1 on a glass plate, and then curing the coated precursor mixed solution by ultraviolet irradiation in a protective atmosphere to obtain a polymer solid electrolyte membrane;
and S3, peeling the polymer solid electrolyte membrane obtained in the step S2 from a glass plate, washing, and drying in vacuum to obtain the three-dimensional polymer composite solid electrolyte.
7. The method for preparing a three-dimensional polymer composite solid electrolyte according to claim 6, wherein the step of S1 is specifically as follows: and dissolving PVDF in acetonitrile at normal temperature, adding PEO, PAA, a cross-linking agent, a photoinitiator, an inorganic filler and lithium salt, and stirring for 3-8 hours in an argon atmosphere or a nitrogen atmosphere to obtain a precursor mixed solution.
8. The method for preparing the three-dimensional polymer composite solid electrolyte according to claim 7, wherein the mass ratio of the PVDF, the PEO, the PAA, the cross-linking agent, the photoinitiator, the inorganic filler and the lithium salt is 10-20: 10-20: 10-20: 5-10: 0.3-0.5: 2-5: 3-7; the crosslinking agent is acrylate, the photoinitiator is 2-hydroxy-2-methyl propyl phenyl ketone, the inorganic filler is gadolinium oxide doped cerium oxide, and the lithium salt is lithium bis (trifluoromethanesulfonyl) imide.
9. The method for preparing a three-dimensional polymer composite solid electrolyte according to claim 6, wherein in S2, the precursor mixed solution is coated on a glass plate by a doctor blade method to a coating thickness of 20 to 80 μm; the protective atmosphere is argon atmosphere or nitrogen atmosphere; the illumination intensity is 1500--2The curing time is 60-120S.
10. The method for preparing the three-dimensional polymer composite solid electrolyte according to claim 6, wherein in S3, methanol or isopropanol is used for washing for 3-5 times, the vacuum drying temperature is 30-70 ℃, and the drying time is 10-24 h.
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| CN116231068B (en) * | 2023-05-09 | 2023-07-21 | 长江三峡集团实业发展(北京)有限公司 | Solid electrolyte membrane, preparation method thereof and solid lithium metal battery |
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