CN114335710A - Preparation method and application of double-modified solid electrolyte membrane - Google Patents
Preparation method and application of double-modified solid electrolyte membrane Download PDFInfo
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Abstract
The invention discloses a preparation method and application of a double-modified solid electrolyte membrane, which can assist in Li transmission by modifying a polymer forming a solid electrolyte and grafting the polymer+The inorganic carbon ceramic filler is subjected to surface treatment to enable the surface of the inorganic carbon ceramic filler to be provided with functional groups capable of transferring Li+The similarity of the functional groups carried by the ether oligomer, polymer and ceramic filler of (a) improves the affinity of the ceramic filler for the polymer, so that Li+The organic-inorganic phase interface can be rapidly transmitted, the interface is strengthened, and the interface impedance is reduced; compared with an electrolyte membrane which is not modified, the ionic conductivity is greatly improved, the electrolyte membrane has good electrochemical performance when being used for a lithium ion battery, and the preparation method is simple and can be applied to large-scale production.
Description
Technical Field
The invention belongs to a power battery electrolyte preparation technology, and relates to a preparation method and application of a double-modified solid electrolyte membrane.
Background
Lithium batteries are widely used in electronic devices and electric vehicles due to their excellent electrochemical properties. However, the electrolyte in the commercialized liquid battery is highly flammable, the thermal instability of the organic electrolyte is the main reason for the thermal runaway risk of the lithium ion battery, and the safety risk of the lithium battery can be fundamentally solved only by improving the electrolyte system and improving the stability of the electrolyte. Therefore, lithium ion batteries using solid state electrolytes are widely considered as a promising next generation advanced battery technology.
Currently, common solid electrolytes are classified into inorganic solid electrolytes and polymer solid electrolytes. The inorganic solid electrolyte material has high ionic conductivity and high-voltage resistance, but the practical application of the inorganic solid electrolyte material is severely limited by the defects of high interface resistance between the electrolyte and the electrode, poor electrolyte flexibility and the like. The polymer solid electrolyte possesses good cyclability and is easy to process, but its application environment is limited due to its low room temperature ionic conductivity.
Studies have shown that polymers with high crystallinity will be detrimental to ion transport. By adding an inorganic filler or plasticizer, the proportion of the amorphous region of the polymer can be increased, and the crystallinity can be reduced. The organic-inorganic composite solid electrolyte compounded by the polymer and the inorganic filler improves the mechanical strength and endows the electrolyte with flexibility and processability, but the ionic conductivity of the organic-inorganic composite solid electrolyte is far lower than that of a commercial electrolyte, so that the organic-inorganic composite solid electrolyte still cannot meet the requirement of large-scale popularization. According to research, high impedance at the interface between the polymer and the inorganic filler inside the composite electrolyte is a main cause of low ionic conductivity. Therefore, there is an urgent need to solve the problem of poor organic-inorganic interface properties inside the composite solid electrolyte.
Disclosure of Invention
The invention aims to solve the defects in the prior art and provides a preparation method and application of a double-modified solid electrolyte membrane, and the prepared solid electrolyte membrane simultaneously improves the mechanical strength and the ionic conductivity.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a preparation method of a double-modified solid electrolyte membrane comprises the following steps:
s1, modification of polymer, grafting of polymer to assist in Li transport+Of (e) - (-O-CH)2-CH2-)n-a functional group; modifying the nano ceramic particles to enable the surfaces of the nano ceramic particles to be provided with ether oligomers;
s2, dissolving the polymer modified in the step S1 in an organic solvent, adding lithium salt, modified nano ceramic particles, ionic liquid and a plasticizer into the polymer solution, and performing ultrasonic dispersion and stirring to obtain a viscous mixed solution;
and S3, transferring the viscous mixed solution into a mould, and drying in vacuum to evaporate the solvent to obtain the double-modified solid electrolyte membrane.
Further, the step S1 of modifying the polymer is to irradiate low-temperature plasma and then introduce the graft to perform grafting reaction, wherein the gas used for the irradiation of the low-temperature plasma is SO2、NH3、H2O、N2And Ar, the irradiation treatment time is 30-120 s.
Further, the functional group grafted on the polymer in the step S1 is polyethylene glycol or polyethylene oxide.
Further, the modifying process of the nano ceramic particles in the step S1 is to treat the nano ceramic particles by exposing in air or treating with carbon dioxide and water vapor mixed gas to make the surfaces of the nano ceramic particles have a small amount of LiOH and Li2CO3Then the processed nano ceramic particles and cyclic carbonate are subjected to ring-opening grafting reaction to form the material capable of transferring Li+The cyclic carbonate is one of ethylene carbonate, propylene carbonate and vinylene carbonate.
Further, the mass concentration of the modified polymer in the solution of the step S2 is 10-35%; the mass content of the lithium salt is 10-60% by the total mass of the polymer and the lithium salt, the mass content of the nano ceramic particles is 2-20% by the total mass of the polymer and the nano ceramic particles, the mass content of the ionic liquid is 5-40% by the total mass of the polymer and the ionic liquid, and the mass content of the plasticizer is 5-20% by the total mass of the polymer and the plasticizer.
Further, the polymer is at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), Polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyethylene oxide (PEO), or polyethylene glycol (PEG); the average molecular weight of the polymer is 10-110 ten thousand; the average molecular weight of the functional group grafted on the polymer is 0.02-20 ten thousand.
Further, the organic solvent is one of N, N-dimethylformamide, N-dimethylacetamide, N-dimethylpropionamide, N-methylpyrrolidone, acetonitrile, acetone, and tetrahydrofuran.
Further, the lithium salt is at least one of lithium bis (trifluoromethyl) sulfonate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium dioxalate borate and lithium bis (fluoro) sulfonyl imide; the plasticizer is one of ethylene carbonate, polycarbonate, propylene carbonate, ethyl methyl carbonate, dimethyl carbonate and diethyl phthalate; the ionic liquid is 1-ethyl-3-methylimidazole bis (trifluoromethylsulfonyl), N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imine, N-methyl-N-propylpiperidine bis (trifluoromethylsulfonyl) imine or N-methyl-N-propylpyrrole bis (trifluoromethylsulfonyl) imine.
Further, the nano ceramic particles are Li6.4La3Zr1.4Ta0.6O12(LLZTO)、Li6.3La3Zr1.65W0.35O12(LLZWO)、Li7La3Zr2O12(LLZO)、Li6.25Al0.25La3Zr2O12(LLZAO) and Li6.20Ga0.30La2.95Rb0.05Zr2O12(LLZGRO) with a mean radius of the ceramic nanoparticles of 5-200 nm.
Compared with the prior art, the invention has the beneficial effects that:
1. the present invention modifies both polymer and inorganic ceramic filler, which are raw materials for preparing the solid electrolyte, as shown in fig. 4, and the polymer constituting the solid electrolyte is modified to graft thereon a polymer capable of assisting in the transport of Li+Of (e) - (-O-CH)2-CH2-)n-functional groups, which are used for surface treatment of the inorganic carbon ceramic filler, so that the surface of the inorganic carbon ceramic filler is provided with lithium hydroxide and lithium carbonate, and the lithium hydroxide and the lithium carbonate further initiate ring opening of cyclic carbonate on the surface of the inorganic ceramic filler to form a functional group capable of transferring Li+The similarity of the functional groups carried by the ether oligomer, polymer and ceramic filler of (A) improves the similarity of the functional groups carried by the ceramic filler with the polymerAffinity of the compound such that Li+Can be rapidly transmitted between organic-inorganic phase interfaces, strengthens the interfaces and reduces the interface impedance.
3. The invention provides a composite electrolyte membrane, which takes inorganic ceramic particles as solid fillers, compared with a single inorganic solid electrolyte or a polymer solid electrolyte, the composite electrolyte membrane fully ensures that the electrolyte membrane has better electrochemical stability and thermal stability, the polymer matrix ensures that the electrolyte membrane has stronger processing and forming properties, and ionic liquid and a plasticizer both play a plasticizing role, thereby enhancing the chain segment movement capability of the polymer, accelerating the migration rate of lithium ions, improving the ionic conductivity of the material and reducing the interface impedance.
4. The solid electrolyte provided by the invention is simple in preparation method, the polymer is dissolved in the solvent, the polymer solution is obtained by stirring, then the lithium salt, the inorganic nano ceramic filler, the ionic liquid and the plasticizer are added to obtain a uniform viscous mixed solution, the mixed solution is poured into a mould, and then the solvent is evaporated to obtain the solid electrolyte membrane.
5. The solid electrolyte membrane can be applied to a solid lithium battery, in particular to a solid lithium metal battery, and the solid battery applying the solid electrolyte membrane has better cycle performance and rate capability. Taking a lithium iron phosphate/lithium half-cell as an example, the capacity retention rate after 200 cycles is 99.6%, and the lithium iron phosphate/lithium half-cell shows better cycle stability. Compared with an electrolyte membrane which is not modified, the ionic conductivity is greatly improved, and the electrolyte membrane has good electrochemical performance when being used for a lithium ion battery.
Drawings
FIG. 1 is an AC impedance spectrum of a composite electrolyte membrane prepared according to example 1
FIG. 2 is a linear scan of a composite electrolyte membrane prepared according to example 1
FIG. 3 is a graph of cycle performance of an all solid-state lithium battery prepared according to example 1 of the present invention
FIG. 4A diagram of the Li + transport mechanism of a modified electrolyte membrane
FIG. 5 is an AC impedance spectrum of a composite electrolyte membrane prepared according to comparative example 1
Detailed Description
The invention is further described in the following description with reference to the figures and specific preferred embodiments, but without thereby limiting the scope of protection of the invention. The examples are preferred in the experimental process and are only used for more complete illustration of the present invention, but are not to be construed as limiting the scope of the present invention.
The instruments and drug materials used in the present invention are commercially available.
First, the solid electrolyte of the present invention will be explained.
In the present invention, a dual modified high strength solid polymer electrolyte is proposed, which is composed of: the lithium ion battery comprises a polymer, lithium salt, nano ceramic particles, an ionic liquid and a plasticizer.
The selection of the high molecular polymer in the invention has no special requirement, and can be selected according to actual requirements. For example, one or more of polyvinylidene fluoride (PVDF), Polyacrylonitrile (PAN), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and polymethyl methacrylate (PMMA), polyethylene oxide (PEO), and polyethylene glycol (PEG) may be selected. The average molecular weight of the polymer is 10-110 ten thousand. The active group grafted on the polymer is one of polyethylene glycol and polyethylene oxide. The average molecular weight of the active group grafted on the polymer is 0.02-20 ten thousand.
More preferably, the average molecular weight of the polymer is from 50 to 80 ten thousand.
More preferably, the active groups grafted onto the polymer have an average molecular weight of from 0.2 to 2 ten thousand.
The lithium salt added is not particularly required, and can be selected according to actual requirements. Examples of the lithium salt include lithium bistrifluoromethylsulfonate imide (LiTFSI) and lithium hexafluorophosphate (LiPF)6) Lithium tetrafluoroborate (LiBF)4) Lithium perchlorate (LiClO)4) Lithium bis (oxalato) borate (LiBOB) and lithium bis (fluorosulfonyl) imide (LiFSI).
The selected nanoceramic filler may be Li6.4La3Zr1.4Ta0.6O12(LLZTO)、Li6.3La3Zr1.65W0.35O12(LLZWO)、Li7La3Zr2O12(LLZO)、Li6.25Al0.25La3Zr2O12(LLZAO) and Li6.20Ga0.30La2.95Rb0.05Zr2O12(LLZGRO). The average radius of the nano ceramic particles is 5-200 nm.
More preferably, the exposure time of the nanoceramic filler to air is adjusted according to the local air humidity and carbon dioxide concentration.
More preferably, the inorganic ceramic filler is treated with a mixed gas of CO2 and water vapor for a period of 2 to 24 hours.
The selected ionic liquid is one of imidazole ionic liquid, quaternary ammonium ionic liquid, piperidine ionic liquid and pyrrole ionic liquid. The imidazole ionic liquid is 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide; the quaternary ammonium ionic liquid is N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imide; the piperidine ionic liquid is N-methyl-N-propyl piperidine bi (trifluoromethyl sulfonyl) imine; the pyrrole ionic liquid is N-methyl-N-propyl pyrrole bi (trifluoromethyl sulfonyl) imine.
The plasticizer is one of ethylene carbonate, polycarbonate, propylene carbonate, ethyl methyl carbonate, dimethyl carbonate and diethyl phthalate.
The mass content of the nano ceramic particles is 2-20% of the total mass of the polymer and the nano ceramic particles, the mass content of the lithium salt is 10-60% of the total mass of the polymer and the lithium salt, the mass content of the ionic liquid is 0-40% of the total mass of the polymer and the ionic liquid, and the mass content of the plasticizer is 0-20% of the total mass of the polymer and the plasticizer.
Next, a process for producing the composite solid polymer electrolyte membrane according to the second aspect of the invention is explained.
The invention provides a preparation method of a composite solid electrolyte membrane, which specifically comprises the following steps:
s1, modifying the polymer and the inorganic filler. For the polymer, after freezing and degassing the graft, putting the polymer into a reaction cavity, vacuumizing, and ventilating for replacement; carrying out plasma excitation under set conditions; and closing the plasma and introducing the graft to carry out grafting reaction, taking out after a certain time, and carrying out post-treatment and drying. For the inorganic filler, the surface of the inorganic filler is provided with a small amount of LiOH and Li after the air exposure treatment2CO3Mixing the treated inorganic filler with cyclic carbonate for reaction at 80-120 deg.c for 2-12 hr.
S2, dissolving the polymer in an organic solvent, performing ultrasonic dispersion, and uniformly stirring to obtain a uniform polymer solution. The concentration of the polymer in the mixed solution is 10 to 35 wt%. The selection of the organic solvent is not particularly required, and can be selected according to actual requirements. For example, in the embodiment of the present invention, the organic solvent is one of N, N-dimethylformamide, N-dimethylacetamide, N-dimethylpropionamide, N-methylpyrrolidone, acetonitrile, acetone, and tetrahydrofuran.
The mixed solution containing the polymer was subjected to ultrasonic dispersion for sufficient dissolution. The time of ultrasonic dispersion has no special requirements and can be adjusted according to actual requirements. For example, in the embodiment of the present invention, the ultrasonic dispersion time is 10 to 60 min. The solution including the polymer was stirred for thorough mixing. The stirring method is not particularly required, and may be selected according to the actual conditions. For example, in embodiments of the present invention, mechanical agitation is used. The stirring time and temperature are not particularly limited and may be selected according to the actual conditions. For example, in the examples of the present invention, the preferred stirring time is 4 to 12 hours; stirring is carried out at 40-65 ℃.
S3, adding lithium salt, nano ceramic particles, ionic liquid and plasticizer into the uniform polymer solution in sequence, and performing ultrasonic dispersion and stirring to obtain a uniform viscous mixed solution; the content of lithium salt in the total mass of the polymer and the lithium salt is 10-60 wt%. In the total mass of the polymer and the nano ceramic particles, the content of the nano ceramic particles is 2-20 wt%. The content of the ionic liquid in the total mass of the polymer and the ionic liquid is 5-40 wt%, and the content of the plasticizer in the total mass of the polymer and the plasticizer is 5-20 wt%. In the step, the ultrasonic treatment time is 10-60min, the stirring time is 6-12h, and the stirring is carried out at 40-65 ℃.
S4, transferring the stirred mixed solution into a mold, and performing vacuum drying to evaporate the solvent to obtain the composite solid electrolyte membrane with the thickness of 100-300 mu m. According to the embodiment of the invention, the vacuum drying condition is not particularly required, and can be selected according to actual requirements. For example, according to the embodiment of the present invention, the temperature of vacuum drying is 30 to 100 ℃ and the time of vacuum drying is 5 to 24 hours.
Again, the assembly of the all solid-state lithium battery according to the third aspect of the invention is explained.
The all-solid-state lithium battery applied according to the present invention includes a positive electrode sheet, a negative electrode sheet, and a high-strength solid electrolyte membrane interposed between the positive electrode sheet and the negative electrode sheet. The positive plate comprises a positive current collector, and a positive active material, a positive conductive agent and a binder which are coated on the positive current collector.
In the all solid-state lithium battery applied according to the present invention, the positive electrode current collector may be selected from an aluminum foil, a nickel foil, a carbon foil, or a stainless steel sheet.
In the all solid-state lithium battery applied according to the present invention, the positive active material may be selected according to the actual choice of LiCoO2、LiFePO4Or a nickel-cobalt-manganese ternary cathode material.
In the all solid-state lithium battery applied according to the present invention, the positive electrode conductive agent may be acetylene black, graphite, Super P, or carbon nanotube according to actual use.
In the all solid-state lithium battery to which the present invention is applied, the negative electrode material may be selected according to the actual use. For example, the negative electrode is a metallic lithium and metallic lithium-based negative electrode material or a carbon-based negative electrode material.
The present invention will be described in more detail with reference to examples.
Example 1
A kind ofHigh-strength solid electrolyte composed of modified polyvinylidene fluoride (PVDF), lithium perchlorate (LICLO)4) Modified LLZTO (Li)6.4La3Zr1.4Ta0.6O12) 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) (EMITFSI) and dimethyl carbonate (DMC).
The preparation method comprises the following steps: firstly, placing PVDF in a plasma reaction chamber, introducing argon for replacement, introducing PEG-300 when the plasma irradiation time is 30s, wherein the grafting time is 1h, and washing the grafted PVDF with acetone for more than three times to remove unreacted PEG. The LLZTO powder is exposed to air for 15 days, dispersed in ethylene carbonate, reacted at 100 deg.C for 3h, filtered, and vacuum dried at 200 deg.C.
Then, 1.8 g of PVDF was dissolved in 16.2 g of DMF solvent at a mass concentration of 10%, ultrasonically dispersed for 10min, and magnetically stirred at 55 ℃ for 6h to obtain a mixed solution. Sequentially adding LiClO into PVDF solution according to sequence4LLZTO, EMITFSI, DMC. Added LiClO4Account for LiClO4And 30% of the total mass of PVDF, the added LLZTO accounting for 10 wt% of the total mass of LLZTO and PVDF, the added EMITFSI accounting for 10 wt% of the total mass of the mixture of EMITFSI and PVDF, and the added DMC accounting for 5 wt% of the total mass of the mixture of DMC and PVDF, and then stirring is continued for 12h and sufficient stirring is carried out to form a mixed solution.
And finally, transferring the stirred mixed solution into a mold, and drying and evaporating the solvent at the temperature of 80 ℃ in vacuum to obtain the composite solid electrolyte membrane with the thickness of 220 mu m.
From FIG. 1, it was calculated that the sample obtained in example 1 could reach 1.145X 10 at room temperature-3Ion conductivity of S/cm.
As can be seen from FIG. 2, the electrolyte membrane has an electrochemical window of 4.8V and has good electrochemical stability.
As can be seen from fig. 3, the lithium iron phosphate battery using the electrolyte membrane has no significant capacity fading after 200 charge and discharge cycles.
Example 2
The preparation method comprises the following steps: firstly, PVDF-HFP is placed in a plasma reaction cavity, and N is introduced2And (3) displacement, wherein the duration of plasma irradiation is 30s, PEG-200 is introduced, the grafting time is 1h, and the grafted PVDF-HFP is washed with acetone for more than three times to remove the unreacted PEG-200. The LLZWO powder is exposed in the air for 15 days, dispersed in ethylene carbonate, reacted at 100 ℃ for 3 hours, filtered and vacuum-dried at 200 ℃.
Then, 1.8 g of PVDF-HFP was dissolved in 16.2 g of acetonitrile solvent at a mass concentration of 10%, ultrasonically dispersed for 10min, and magnetically stirred at 60 ℃ for 4 hours to obtain a mixed solution. Sequentially adding LiClO to the PVDF-HFP solution according to the sequence4LLZWO, EMITFSI, PC. Added LiClO4Account for LiClO4And 30% of the total mass of PVDF-HFP, the added LLZWO accounting for 10 wt% of the total mass of LLZWO and PVDF-HFP, the added EMITFSI accounting for 5 wt% of the total mass of the mixture of EMITFSI and PVDF-HFP, and the added PC accounting for 5 wt% of the total mass of the mixture of PC and PVDF, followed by further stirring for 12 hours to sufficiently react to form a slurry.
And finally, transferring the stirred mixed solution into a mold, and drying and evaporating the solvent at the temperature of 60 ℃ in vacuum to obtain the composite solid electrolyte membrane with the thickness of 220 mu m.
Example 3
The preparation method comprises the following steps: firstly, PAN is placed in a plasma reaction chamber, and N is introduced2And (3) replacing, wherein the plasma irradiation time is 60s, introducing PEG-200, the grafting time is 1h, and washing the grafted PAN with acetone for more than three times to remove the unreacted PEG-200. LLZO powder in CO2Treating with mixed gas of water vapor for 12h, dispersing in vinylene carbonate, reacting at 100 deg.C for 6h, centrifuging, and vacuum drying at 150 deg.C.
Then, 1.8 g of PAN was dissolved in 16.2 g of DMA solvent at a mass concentration of 10%, ultrasonically dispersed for 10min, and magnetically stirred at 50 ℃ for 8 hours to obtain a mixed solution. Sequentially adding LiPF into the solution according to the sequence6LLZO, N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imide, DMC. Added LiPF6Account for LiPF6And 25% by mass of PAN, the added LLZO being 10% by mass of the total mass of LLZO and PAN, and the added N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imideThe mass of amine was 10 wt% of the total mass of the mixture of N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imide and PAN, and the mass of DMC added was 5 wt% of the total mass of the mixture of DMC and PAN, followed by stirring for 6h to react well to form a slurry.
And finally, transferring the stirred mixed solution into a mold, and drying and evaporating the solvent at the temperature of 60 ℃ in vacuum to obtain the composite solid electrolyte membrane with the thickness of 220 mu m.
Example 4
The preparation method comprises the following steps: PVDF and PEO were first mixed and ball milled at a mass ratio of 20:1, with the temperature controlled below 120 ℃. Placing the mixture after ball milling in a plasma reaction chamber, and introducing N2The plasma irradiation time was 60s and the grafting time was 1 h. LLZO powder in CO2Treating with mixed gas of water vapor for 12h, dispersing in ethylene carbonate, reacting at 100 deg.C for 6h, centrifuging, and vacuum drying at 200 deg.C.
Then, 1.8 g of PVDF-PEO was dissolved in 16.2 g of DMA solvent at a mass concentration of 10%, ultrasonically dispersed for 10min, and magnetically stirred at 50 ℃ for 8 hours to obtain a mixed solution. Sequentially adding LiPF into the solution according to the sequence6LLZO, N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imide, ethylene carbonate. Added LiPF6Account for LiPF6And 25% of the total mass of PAN, the added LLZO accounts for 10 wt% of the total mass of the LLZO and PAN, the added N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imide accounts for 10 wt% of the total mass of the mixture of N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imide and PAN, the added ethylene carbonate accounts for 5 wt% of the total mass of the mixture of ethylene carbonate and PAN, and then stirring is continued for 6h, and the mixture is fully reacted to form slurry.
And finally, transferring the stirred mixed solution into a mold, and drying and evaporating the solvent at the temperature of 60 ℃ in vacuum to obtain the composite solid electrolyte membrane with the thickness of 220 mu m.
Example 5
The preparation method comprises the following steps: firstly, PMMA is placed in a plasma reaction chamber, and SO is introduced2Replacement, plasmaThe irradiation time of the daughter was 120s, PEG-200 was introduced, the grafting time was 1h, and the grafted PMMA was washed three or more times with acetone to remove the unreacted PEG-200. LLZGRO powder in CO2Treating with mixed gas of water vapor for 12h, dispersing in propylene carbonate, reacting at 100 deg.C for 6h, centrifuging, and vacuum drying at 150 deg.C.
Then, 1.8 g of PMMA was dissolved in 3.34 g of N, N-dimethylpropionamide solvent at a mass concentration of 35%, ultrasonically dispersed for 10min, and magnetically stirred at 50 ℃ for 8 hours to obtain a mixed solution. Adding lithium dioxalate borate, LLZGRO, N-methyl-N-propyl piperidine bi (trifluoromethyl sulfonyl) imine and DMC into the solution in sequence. The added lithium dioxalate borate accounts for 10 percent of the total mass of the lithium dioxalate borate and the PMMA, the added LLZGRO accounts for 2 percent of the total mass of the LLZGRO and the PMMA, the added N-methyl-N-propyl piperidine bis (trifluoromethyl sulfonyl) imide accounts for 40 percent of the total mass of the mixture of the N-methyl-N-propyl piperidine bis (trifluoromethyl sulfonyl) imide and the PMMA, the added DMC accounts for 20 percent of the total mass of the mixture of the DMC and the PMMA, and then stirring is continued for 6 hours to fully react to form slurry.
And finally, transferring the stirred mixed solution into a mold, and drying and evaporating the solvent at the temperature of 60 ℃ in vacuum to obtain the composite solid electrolyte membrane with the thickness of 220 mu m.
Example 6
The preparation method comprises the following steps: firstly, PEG is placed in a plasma reaction cavity, NH is introduced3Or H2And (3) performing O replacement, wherein the plasma irradiation time is 80s, introducing PEG-300, the grafting time is 1h, and washing the grafted PEG with acetone for more than three times to remove the unreacted PEG-200. LLZGRO powder in CO2Treating with mixed gas of water vapor for 12h, dispersing in propylene carbonate, reacting at 100 deg.C for 6h, centrifuging, and vacuum drying at 150 deg.C.
Then, 1.8 g of PEG was dissolved in 7.2 g of N-methylpyrrolidone solvent at a mass concentration of 20%, ultrasonically dispersed for 10min, and magnetically stirred at 50 ℃ for 8 hours to obtain a mixed solution. Adding the lithium bis (fluorosulfonyl) imide, LLZGRO, N-methyl-N-propyl pyrrole bis (trifluoromethanesulfonyl) imide and propylene carbonate into the solution in sequence. The added lithium bis (fluorosulfonyl) imide accounts for 60% of the total mass of the lithium bis (fluorosulfonyl) imide and the PEG, the added LLZGRO accounts for 20 wt% of the total mass of the LLZGRO and the PEG, the added N-methyl-N-propyl pyrrole bis (trifluoromethanesulfonyl) imide accounts for 20 wt% of the total mass of the mixture of the N-methyl-N-propyl pyrrole bis (trifluoromethanesulfonyl) imide and the PEG, the added propylene carbonate accounts for 10 wt% of the total mass of the mixture of the propylene carbonate and the PEG, and then stirring is continued for 6h to fully react to form slurry.
And finally, transferring the stirred mixed solution into a mold, and drying and evaporating the solvent at the temperature of 60 ℃ in vacuum to obtain the composite solid electrolyte membrane with the thickness of 220 mu m.
Comparative example 1: non-modified composite electrolyte membrane
Comparative example 1 the procedure was exactly the same as in example 1 except that the raw material was not modified, and 1.8 g of PVDF was first dissolved in 16.2 g of DMF solvent at a mass concentration of 10%, ultrasonically dispersed for 10min, and magnetically stirred at 55 ℃ for 6h to obtain a mixed solution. Then, the PVDF solution was sequentially added with LICLO4, LLZTO, EMITFSI, and DMC. Added LICLO4Occupy LICLO4And 30% of the total mass of PVDF, the added LLZTO accounting for 10 wt% of the total mass of LLZTO and PVDF, the mass of EMITFSI added accounting for 10 wt% of the total mass of the mixture of EMITFSI and PVDF, and the mass of DMC added accounting for 5 wt% of the total mass of the mixture of DMC and PVDF, and then stirring is continued for 12h, and the mixture is fully reacted to form slurry. After the slurry was cast in a mold, it was dried in vacuo at 60 ℃ for 8 hours to obtain a solid electrolyte membrane having a thickness of 180 μm.
As shown in fig. 1 and 5, the ac impedance plots of the solid electrolyte membrane prepared according to comparative example 1 can be seen that the electrolyte membrane after modification is compared with that before modification:
the impedance is significantly lower, from 30 Ω to 17 Ω.
② the conductivity is obviously higher and is improved to 1.15mS/cm from 0.53 mS/cm.
The data show that the modification of the electrolyte membrane obviously improves the electrochemical performance of the electrolyte membrane.
Preparing an all-solid-state lithium battery:
the high-strength solid electrolyte membrane prepared by the invention is applied to a solid lithium battery, the solid battery uses a half battery with NCM523 as a positive electrode and metal lithium as a negative electrode, and the high-strength solid electrolyte membrane is applied between the positive electrode and the negative electrode.
The electrolyte membrane may be the high-strength electrolyte membrane in examples 1 to 4.
In this example, the positive electrode was mixed with NMP at a mass ratio of NCM523: Super P: PVDF of 8:1:1 to obtain a positive electrode slurry, and the positive electrode slurry was coated on an aluminum foil and then vacuum-dried at 105 ℃ for 24 hours to obtain a positive electrode.
In this example, the positive electrode was cut into a positive electrode sheet using a slicer, the negative electrode was a lithium sheet, the electrolyte membrane of example 1 was used, and the coin cell was assembled in a glove box under an argon atmosphere.
And (3) performance testing:
(1) conductivity test
The electrolyte membrane prepared in example 1 was punched using a punching machine to obtain a sample having a diameter of 12mm and a thickness of 220 μm. The method is used for testing the room-temperature ionic conductivity of the sample, and comprises the following specific steps: the sample was clamped between stainless steel plates in a blocking mold to obtain electrochemical impedance data, and then the total conductivity was obtained by fitting according to thickness and electrode area. The sample obtained in the example 1 can reach the ionic conductivity of 0.8mS/cm at room temperature, and the room-temperature conductivity of the composite electrolyte membrane is high.
(2) Electrochemical window testing
The electrolyte membrane prepared in example 1 was punched using a punching machine to obtain a sample having a diameter of 12mm and a thickness of 220 μm. And (3) under the argon atmosphere, forming the button cell by the sample, a stainless steel sheet and a lithium sheet (wherein the stainless steel sheet is used as a working electrode, and the lithium sheet is used as a reference electrode and a counter electrode), and testing an electrochemical window of the button cell on an electrochemical workstation, wherein the testing range is 2.5-6V.
(3) Charge and discharge test
The sample obtained in example 1 was tested, and the charge and discharge interval was 2.0 to 4.0V, and the charge and discharge were carried out at a current of 0.1C. As shown in fig. 3, the lithium metal battery prepared by using lithium iron phosphate as the positive electrode and lithium metal as the negative electrode and disposing the electrolyte membrane prepared in example 1 between the positive electrode and the negative electrode still has a specific discharge capacity of 155mAh/g after 200 charge-discharge cycles at a current density of 0.1C, which indicates that the electrolyte membrane has high ionic conductivity and good interface compatibility.
The present invention provides a double modified solid electrolyte, a method for preparing the same and applications thereof, the above examples are only preferred embodiments, the present invention is not limited to the above examples, and any modifications, substitutions, improvements and the like made in the same principle shall be included in the scope of the present invention.
Claims (10)
1. A preparation method of a double-modified solid electrolyte membrane is characterized by comprising the following steps:
s1, modification of polymer, grafting of polymer to assist in Li transport+Of (e) - (-O-CH)2-CH2-)n-a functional group; modifying the nano ceramic particles to enable the surfaces of the nano ceramic particles to be provided with ether oligomers;
s2, dissolving the polymer modified in the step S1 in an organic solvent, adding lithium salt, modified nano ceramic particles, ionic liquid and a plasticizer into the polymer solution, and performing ultrasonic dispersion and stirring to obtain a viscous mixed solution;
and S3, transferring the viscous mixed solution into a mould, and drying in vacuum to evaporate the solvent to obtain the double-modified solid electrolyte membrane.
2. The method for producing a double modified solid electrolyte membrane according to claim 1, characterized in that: the step S1 is to modify the polymer by irradiating with low temperature plasma and introducing the graft to perform grafting reaction, wherein the gas used for irradiating with low temperature plasma is SO2、NH3、H2O、N2And Ar, the irradiation treatment time is 30-120 s.
3. The method for producing a double modified solid electrolyte membrane according to claim 1, characterized in that: the functional group grafted on the polymer in the step S1 is polyethylene glycol or polyethylene oxide; the average molecular weight of the functional group grafted on the polymer is 0.02-20 ten thousand.
4. The method for producing a double modified solid electrolyte membrane according to claim 1, characterized in that: the step S1 of modifying the nano-ceramic particles is to treat the nano-ceramic particles by exposing in the air or treating with carbon dioxide and water vapor mixed gas to make the surfaces of the nano-ceramic particles carry a small amount of LiOH and Li2CO3Then the processed nano ceramic particles and cyclic carbonate are subjected to ring-opening grafting reaction to form the material capable of transferring Li+The cyclic carbonate is one of ethylene carbonate, propylene carbonate and vinylene carbonate.
5. The method for producing a double modified solid electrolyte membrane according to claim 1, characterized in that: the mass concentration of the modified polymer in the solution of the step S2 is 10-35%; the mass content of the lithium salt is 10-60% by the total mass of the polymer and the lithium salt, the mass content of the nano ceramic particles is 2-20% by the total mass of the polymer and the nano ceramic particles, the mass content of the ionic liquid is 5-40% by the total mass of the polymer and the ionic liquid, and the mass content of the plasticizer is 5-20% by the total mass of the polymer and the plasticizer.
6. The method for producing a double modified solid electrolyte membrane according to claim 1, characterized in that: the polymer is at least one of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), Polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyethylene oxide (PEO) or polyethylene glycol (PEG); the average molecular weight of the polymer is 10-110 ten thousand.
7. The method for producing a double modified solid electrolyte membrane according to claim 1, characterized in that: the organic solvent is one of N, N-dimethylformamide, N-dimethylacetamide, N-dimethylpropionamide, N-methylpyrrolidone, acetonitrile, acetone and tetrahydrofuran.
8. The method for producing a double modified solid electrolyte membrane according to claim 1, characterized in that: the lithium salt is at least one of lithium bis (trifluoromethyl) sulfonate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium dioxalate borate and lithium bis (fluoro) sulfonyl imide; the plasticizer is one of ethylene carbonate, polycarbonate, propylene carbonate, ethyl methyl carbonate, dimethyl carbonate and diethyl phthalate; the ionic liquid is one of 1-ethyl-3-methylimidazole bis (trifluoromethylsulfonyl) imine, N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imine, N-methyl-N-propyl piperidine bis (trifluoromethylsulfonyl) imine or N-methyl-N-propyl pyrrole bis (trifluoromethylsulfonyl) imine.
9. The method for producing a double modified solid electrolyte membrane according to claim 1, characterized in that: the nano ceramic particles are Li6.4La3Zr1.4Ta0.6O12(LLZTO)、Li6.3La3Zr1.65W0.35O12(LLZWO)、Li7La3Zr2O12(LLZO)、Li6.25Al0.25La3Zr2O12(LLZAO) and Li6.20Ga0.30La2.95Rb0.05Zr2O12(LLZGRO) with a mean radius of the ceramic nanoparticles of 5-200 nm.
10. Use of a dual modified solid electrolyte membrane prepared according to the method of any one of claims 1 to 9 in a lithium battery.
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