CN114335710B - 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 is prepared by modifying and grafting polymers forming the solid electrolyteCan assist in the transport of Li + The inorganic carbon ceramic filler is subjected to surface treatment to ensure that the surface of the inorganic carbon ceramic filler is provided with a functional group capable of transmitting Li + The similarity of the functional groups carried by the ether oligomer, polymer and ceramic filler increases the affinity of the ceramic filler to the polymer, such that Li + The interface can be quickly transmitted between organic-inorganic phase interfaces, the interfaces are strengthened, and the interface impedance is reduced; compared with an electrolyte membrane without modification, the ionic conductivity is greatly improved, the electrolyte membrane has good electrochemical performance when used for lithium ion batteries, 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 commercial liquid batteries is highly flammable, and the thermal instability of the electrolyte is a main cause of thermal runaway risk of lithium ion batteries, and only if an electrolyte system is improved and the stability of the electrolyte is improved, the safety risk of the lithium batteries can be fundamentally solved. Therefore, lithium ion batteries using solid electrolytes are widely recognized 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 defects of high interface resistance between the electrolyte and the electrode, poor electrolyte flexibility and the like severely limit the practical application. The polymer solid electrolyte has good circularity and is easy to process, but its environment of application is limited due to its low room temperature ionic conductivity.
Studies have shown that polymers with high crystallinity will be detrimental to ion migration. By adding an inorganic filler or plasticizer, the proportion of the amorphous regions of the polymer can be increased and the crystallinity can be reduced. The organic-inorganic composite solid electrolyte formed by compounding the polymer and the inorganic filler not only improves the mechanical strength, but also endows the electrolyte with flexibility and processability, but is far lower than the ionic conductivity of commercial electrolyte so that the electrolyte still does not meet the requirement of large-scale popularization. According to studies, high impedance at the interface of 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 interfacial 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, wherein the prepared solid electrolyte membrane simultaneously improves mechanical strength and ionic conductivity.
In order to achieve the above object, the present invention adopts the following technical scheme:
a method for preparing a double modified solid electrolyte membrane, comprising the steps of:
s1, modifying a polymer, and grafting the polymer to assist in Li transmission + - (-O-CH) 2 -CH 2 -) 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 plasticizer into the polymer solution, and performing ultrasonic dispersion and stirring to obtain a viscous mixed solution;
s3, transferring the viscous mixed solution into a mold, and vacuum drying and evaporating the solvent to obtain the double-modified solid electrolyte membrane.
Further, in the step S1, the polymer is modified by introducing grafts for grafting reaction after being irradiated by low-temperature plasma, and the gas used for the low-temperature plasma irradiation is SO 2 、NH 3 、H 2 O、N 2 And Ar, the irradiation treatment time is 30-120s.
Further, the functional group grafted on the polymer in the step S1 is polyethylene glycol or polyethylene oxide.
Further, the modification process of the nano ceramic particles in the step S1 is to treat the nano ceramic particles by adopting a method of exposing in air or treating a mixed gas of carbon dioxide and water vapor so that the surfaces of the nano ceramic particles are provided with a small amount of LiOH and Li 2 CO 3 Then the treated nano ceramic particles and cyclic carbonate are subjected to ring-opening grafting reaction to form the nano ceramic particles capable of transferring Li + Is lower than the ether of (2)And the cyclic carbonate is one of ethylene carbonate, propylene carbonate and vinylene carbonate.
Further, the mass concentration of the modified polymer in the solution in the step S2 is 10-35%; the mass content of the lithium salt is 10% -60% based on the total mass of the polymer and the lithium salt, the mass content of the nano ceramic particles is 2% -20% based on the total mass of the polymer and the nano ceramic particles, the mass content of the ionic liquid is 5% -40% based on the total mass of the polymer and the ionic liquid, and the mass content of the plasticizer is 5% -20% based on 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 grafted functional groups 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 (trifluoromethanesulfonic acid) imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium dioxalate borate and lithium bis (fluorosulfonyl) imide; the plasticizer is one of ethylene carbonate, polycarbonate, propylene carbonate, methyl ethyl 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) imide, N-methyl-N-propylpiperidinebis (trifluoromethylsulfonyl) imide or N-methyl-N-propylpyrrolidinediyl bis (trifluoromethylsulfonyl) imide.
Further, the nano ceramic particles are Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO)、Li 6.3 La 3 Zr 1.65 W 0.35 O 12 (LLZWO)、Li 7 La 3 Zr 2 O 12 (LLZO)、Li 6.25 A l0.25 La 3 Zr 2 O 12 (LLZAO) and Li 6.20 Ga 0.30 La 2.95 Rb 0.05 Zr 2 O 12 (LLZGRO) and the average radius of the nano ceramic particles is 5-200nm.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention can assist in Li transportation by modifying both the polymer and the inorganic ceramic filler, which are raw materials for preparing the solid electrolyte, and by modifying the polymer composing the solid electrolyte, as shown in figure 4 + - (-O-CH) 2 -CH 2 -) n Functional groups, carrying out surface treatment on the inorganic carbon ceramic filler to lead the surface of the inorganic carbon ceramic filler to carry lithium hydroxide and lithium carbonate, and further inducing the cyclic carbonate to open loop on the surface of the inorganic ceramic filler to form a catalyst capable of transferring Li + The similarity of the functional groups carried by the ether oligomer, polymer and ceramic filler increases the affinity of the ceramic filler to the polymer, such that Li + Can be rapidly transmitted between organic-inorganic phase interfaces, strengthen the interfaces and reduce interface impedance.
3. The invention provides a composite electrolyte membrane, which takes inorganic ceramic particles as solid fillers, and compared with single inorganic solid electrolyte or polymer solid electrolyte, the composite electrolyte membrane fully ensures that the electrolyte membrane has better electrochemical stability and thermal stability, and a polymer matrix ensures that the electrolyte membrane has stronger processing and forming properties, and both ionic liquid and plasticizer play a plasticizing role, so that the segment movement capacity of the polymer is enhanced, the migration rate of lithium ions is accelerated, the ionic conductivity of the material is improved, and the interface impedance is reduced.
4. The preparation method of the solid electrolyte provided by the invention is simple, 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, and the solid electrolyte membrane can be prepared by a simple process and can be applied to large-scale production.
5. The solid electrolyte membrane can be applied to solid lithium batteries, in particular to solid lithium metal batteries, and the solid batteries applying the solid electrolyte have better cycle performance and rate performance. Taking lithium iron phosphate/lithium half cell as an example, the capacity retention rate after 200 times of circulation is 99.6%, and the lithium iron phosphate/lithium half cell has better circulation stability. Compared with an electrolyte membrane without modification, the ionic conductivity is greatly improved, and the electrolyte membrane has good electrochemical performance when used for lithium ion batteries.
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 showing the cycle performance of an all-solid lithium battery prepared according to example 1 of the present invention
FIG. 4 modified electrolyte membrane transport Li+ mechanism diagram
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 connection with the drawings and the specific preferred embodiments, which are not intended to limit the scope of the invention. The examples are preferred during the experimental process and are only used for more complete description of the present invention, but are not to be construed as limiting the scope of the invention.
Both the instruments and the drug materials used in the present invention are commercially available.
First, the solid electrolyte of the present invention will be described.
In the present invention, a dual modified high strength solid polymer electrolyte is proposed, which consists of: the lithium ion battery comprises a polymer, lithium salt, nano ceramic particles, 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 grafted active groups on the polymer is 0.02-20 ten thousand.
More preferably, the average molecular weight of the polymer is 50 to 80 ten thousand.
More preferably, the average molecular weight of the grafted reactive groups on the polymer is from 0.2 to 2 tens of thousands.
The lithium salt to be added is not particularly limited and may be selected according to actual requirements. For example, the lithium salt is lithium bis (trifluoromethanesulfonate) (LiTFSI), lithium hexafluorophosphate (LiPF) 6 ) Lithium tetrafluoroborate (LiBF) 4 ) Lithium perchlorate (LiClO) 4 ) A mixture of any one or more of lithium dioxaborate (LiBOB) and lithium bis-fluorosulfonimide (LiFSI).
The selected nano ceramic filler can be Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO)、Li 6.3 La 3 Zr 1.65 W 0.35 O 12 (LLZWO)、Li 7 La 3 Zr 2 O 12 (LLZO)、Li 6.25 A l0.25 La 3 Zr 2 O 12 (LLZAO) and Li 6.20 Ga 0.30 La 2.95 Rb 0.05 Zr 2 O 12 (LLZGRO). The average radius of the nano ceramic particles is 5-200nm.
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 selected imidazole ionic liquid is 1-ethyl-3-methylimidazole bis (trifluoromethyl sulfonyl) imine; the quaternary ammonium ionic liquid is N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethyl sulfonyl) imine; the piperidine ionic liquid is N-methyl-N-propyl piperidine bis (trifluoromethyl sulfonyl) imine; the pyrrole ionic liquid is N-methyl-N-propyl pyrrole bis (trifluoromethyl sulfonyl) imine.
The plasticizer is one of ethylene carbonate, polycarbonate, propylene carbonate, methyl ethyl carbonate, dimethyl carbonate and diethyl phthalate.
The mass content of the nano ceramic particles is 2-20% based on the total mass of the polymer and the nano ceramic particles, the mass content of the lithium salt is 10-60% based on the total mass of the polymer and the lithium salt, the mass content of the ionic liquid is 0-40% based on the total mass of the polymer and the ionic liquid, and the mass content of the plasticizer is 0-20% based on the total mass of the polymer and the plasticizer.
Next, a process for producing a composite solid polymer electrolyte membrane according to the second aspect of the present invention is described.
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. Freezing and degassing the polymer, putting the polymer into a reaction cavity, vacuumizing, and ventilating for replacement; performing plasma excitation under set conditions; and closing the plasma and introducing the grafts to carry out grafting reaction, taking out the grafts after a certain time, and carrying out aftertreatment and drying. The inorganic filler is exposed to air and has a small amount of LiOH and Li on its surface 2 CO 3 Mixing 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 10-35wt%. The choice of the organic solvent is not particularly limited and can be selected according to actual requirements. For example, in an 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 is subjected to ultrasonic dispersion so as to be sufficiently dissolved. The time of ultrasonic dispersion is not particularly required and can be adjusted according to actual requirements. For example, in embodiments of the present invention, the ultrasonic dispersion time is 10-60 minutes. The solution comprising the polymer is stirred to allow for thorough mixing. The stirring method is not particularly limited, 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 embodiments of the present invention, the preferred agitation time is 4-12 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 10-60wt%. The content of the nano ceramic particles in the total mass of the polymer and the nano ceramic particles is 2-20wt%. The content of the ionic liquid in the total mass of the polymer and the ionic liquid is 5-40wt%, and the content of the plasticizer in the total mass of the polymer and the plasticizer is 5-20wt%. In this step, the time of the ultrasonic treatment is 10-60min, the stirring time is 6-12h, and the stirring is performed at 40-65deg.C.
S4, transferring the stirred mixed solution into a mold, and vacuum drying and evaporating the solvent to obtain the composite solid electrolyte membrane with the thickness of 100-300 mu m. According to the embodiment of the present invention, the conditions of vacuum drying are not particularly required, and may be selected according to actual requirements. For example, according to an embodiment of the present invention, the temperature of the vacuum drying is 30-100 ℃ and the time of the vacuum drying is 5-24 hours.
Again, the assembly of the all-solid lithium battery according to the third aspect of the present invention is explained.
An all-solid 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, a positive active material coated on the positive current collector, a positive conductive agent and a binder.
In an all-solid-state lithium battery according to the application of the present invention, the positive electrode current collector may be selected from aluminum foil, nickel foil, carbon foil or stainless steel sheet.
In the all-solid lithium battery applied according to the present invention, the positive electrode active material may be selected from LiCoO according to actual selection 2 、LiFePO 4 Or nickel-cobalt-manganese ternary anode material.
In the all-solid lithium battery applied according to the present invention, the positive electrode conductive agent may be selected from acetylene black, graphite, super P, or carbon nanotubes according to the actual use.
In the all-solid lithium battery according to the application of the present invention, the negative electrode material may be selected according to the actual use. For example, the negative electrode is metallic lithium and a metallic lithium-based negative electrode material or a carbon-based negative electrode material.
The following is a more detailed description of the present invention with reference to examples.
Example 1
A high strength solid electrolyte is prepared from modified polyvinylidene fluoride (PVDF), lithium perchlorate (LIClO) 4 ) Modified LLZTO (Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 ) 1-ethyl-3-methylimidazole bis (trifluoromethylsulfonyl) (EMITFSI), and dimethyl carbonate (DMC).
The preparation method comprises the following steps: firstly, placing PVDF in a plasma reaction cavity, introducing argon for replacement, wherein the plasma irradiation time is 30s, introducing PEG-300, 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 in air for 15 days, then dispersed in ethylene carbonate, reacted for 3 hours at 100 ℃, filtered and dried in vacuum at 200 ℃.
Then, 1.8 g of PVDF was dissolved in 16.2 g of DMF solvent at a mass concentration of 10%, dispersed by ultrasound for 10min, and magnetically stirred at 55℃for 6h to obtain a mixed solution. LiClO is added to PVDF solution in sequence 4 LLZTO, EMITFSI, DMC. Added LiClO 4 Occupy LiClO 4 And 30% of the total weight of PVDF, the added LLZTO accounts for 1% of the total weight of LLZTO and PVDF0wt% of the weight of the added EMITFSI was 10wt% of the total weight of the mixture of EMITFSI and PVDF, and the weight of the added DMC was 5wt% of the total weight of the mixture of DMC and PVDF, followed by further stirring for 12 hours, and stirring was carried out sufficiently to form a mixed solution.
Finally, the mixed solution after stirring is transferred into a mould, and the solvent is dried and evaporated at the temperature of 80 ℃ in vacuum, so that the composite solid electrolyte membrane with the thickness of 220 mu m is obtained.
Calculated from FIG. 1, the sample obtained in example 1 can reach 1.145×10 at room temperature -3 S/cm ionic conductivity.
As can be seen from fig. 2, the electrochemical window of the electrolyte membrane is 4.8V, and has good electrochemical stability.
As can be seen from fig. 3, the lithium iron phosphate battery using the electrolyte membrane did not see significant capacity fade 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 introduced 2 The replacement, the plasma irradiation time is 30s, the PEG-200 is introduced, the grafting time is 1h, and the PVDF-HFP after grafting is washed with acetone for more than three times to remove unreacted PEG-200. The LLZWO powder was left to stand in air for 15 days, dispersed in ethylene carbonate, reacted at 100℃for 3 hours, filtered and dried under vacuum at 200 ℃.
Then, 1.8 g of PVDF-HFP was dissolved in 16.2 g of acetonitrile solvent at a mass concentration of 10%, dispersed by ultrasound for 10min, and magnetically stirred at 60℃for 4 hours to obtain a mixed solution. LiClO was added sequentially to PVDF-HFP solution 4 LLZWO, EMITFSI, PC. Added LiClO 4 Occupy LiClO 4 And 30% of the total weight of PVDF-HFP, wherein the added LLZWO accounts for 10% by weight of the total weight of the LLZWO and PVDF-HFP, the added EMITFSI accounts for 5% by weight of the total weight of the mixture of EMITFSI and PVDF-HFP, the added PC accounts for 5% by weight of the total weight of the mixture of PC and PVDF, and then stirring is continued for 12 hours, and the mixture is fully reacted to form a slurry.
Finally, the mixed solution after stirring is transferred into a mould, and the solvent is dried and evaporated at the temperature of 60 ℃ in vacuum, so that the composite solid electrolyte membrane with the thickness of 220 mu m is obtained.
Example 3
The preparation method comprises the following steps: firstly, PAN is placed in a plasma reaction cavity, and N is introduced 2 The plasma irradiation time is 60s, PEG-200 is introduced, the grafting time is 1h, and the PAN after grafting is washed with acetone for more than three times to remove unreacted PEG-200.LLZO powder in CO 2 And the mixture is treated by water vapor mixed gas for 12 hours, then dispersed in vinylene carbonate, reacted for 6 hours at 100 ℃, and the product is dried in vacuum at 150 ℃ after centrifugation.
Then, 1.8 g of PAN was dissolved in 16.2 g of DMA solvent at a mass concentration of 10%, and the mixture was ultrasonically dispersed for 10 minutes, and magnetically stirred at 50℃for 8 hours to obtain a mixed solution. Sequentially adding LiPF into the solution in sequence 6 LLZO, N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imide, DMC. Added LiPF 6 Occupy LiPF 6 And 25% of the total mass of PAN, wherein LLZO is added in an amount of 10% by weight based on the total mass of LLZO and PAN, and N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imide is added in an amount of N-methyl-N, 10wt% of the total mass of the mixture of N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imide and PAN, the mass of DMC added was 5wt% of the total mass of DMC and PAN, and stirring was continued for 6 hours, and the reaction was completed to form a slurry.
Finally, the mixed solution after stirring is transferred into a mould, and the solvent is dried and evaporated at the temperature of 60 ℃ in vacuum, so that the composite solid electrolyte membrane with the thickness of 220 mu m is obtained.
Example 4
The preparation method comprises the following steps: PVDF and PEO are mixed and ball milled in a mass ratio of 20:1, and the temperature is controlled below 120 ℃. Placing the ball-milled mixture into a plasma reaction cavity, and introducing N 2 The replacement, the plasma irradiation time was 60s and the grafting time was 1h. LLZO powder in CO 2 And the mixture is treated by water vapor mixed gas for 12 hours, then dispersed in ethylene carbonate, reacted for 6 hours at 100 ℃, and the product is dried in vacuum at 200 ℃ after centrifugation.
Then 1.8 g PVDF-PEO is dissolved in 16.2 g DMA solvent with the mass concentration of 10 percent, dispersed for 10min by ultrasonic, stirred magnetically for 8h at 50 ℃ to obtain mixed solution. Sequentially adding LiPF into the solution in sequence 6 LLZO, N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imide, ethylene carbonate. Added LiPF 6 Occupy LiPF 6 And 25% by weight of the total mass of PAN, the added LLZO accounting for 10% by weight of the total mass of LLZO and PAN, the added N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imide accounting for 10% by weight of the total mass of the mixture of N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imide and PAN, and the added ethylene carbonate accounting for 5% by weight of the total mass of the mixture of ethylene carbonate and PAN, followed by continuing stirring for 6 hours, and fully reacting to form a slurry.
Finally, the mixed solution after stirring is transferred into a mould, and the solvent is dried and evaporated at the temperature of 60 ℃ in vacuum, so that the composite solid electrolyte membrane with the thickness of 220 mu m is obtained.
Example 5
The preparation method comprises the following steps: firstly, PMMA is placed in a plasma reaction cavity, and SO is introduced 2 The replacement, the plasma irradiation time is 120s, the PEG-200 is introduced, the grafting time is 1h, and the PMMA after grafting is washed by acetone for more than three times to remove unreacted PEG-200.LLZGRO powder in CO 2 And the mixture is treated by water vapor mixed gas for 12 hours, then dispersed in propylene carbonate, reacted for 6 hours at 100 ℃, and the product is dried in vacuum at 150 ℃ after centrifugation.
Then, 1.8 g of PMMA was dissolved in 3.34 g of N, N-dimethylformamide solvent at a mass concentration of 35%, and the mixture was ultrasonically dispersed for 10 minutes and magnetically stirred at 50℃for 8 hours to obtain a mixed solution. Lithium dioxalate borate, LLZGRO, N-methyl-N-propylpiperidinebis (trifluoromethylsulfonyl) imide and DMC were added to the solution in order. The added lithium dioxalate borate accounts for 10% of the total mass of the lithium dioxalate borate and the PMMA, the added LLZGRO accounts for 2% of the total mass of the LLZGRO and the PMMA, the added N-methyl-N-propylpiperidyl bis (trifluoromethylsulfonyl) imide accounts for 40% of the total mass of the mixture of the N-methyl-N-propylpiperidyl bis (trifluoromethylsulfonyl) imide and the PMMA, the added DMC accounts for 20% 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 a slurry.
Finally, the mixed solution after stirring is transferred into a mould, and the solvent is dried and evaporated at the temperature of 60 ℃ in vacuum, so that the composite solid electrolyte membrane with the thickness of 220 mu m is obtained.
Example 6
The preparation method comprises the following steps: firstly, PEG is placed in a plasma reaction cavity, and NH is introduced 3 Or H 2 O replacement, wherein the plasma irradiation time is 80s, PEG-300 is introduced, the grafting time is 1h, and the grafted PEG is washed with acetone for more than three times to remove unreacted PEG-200.LLZGRO powder in CO 2 And the mixture is treated by water vapor mixed gas for 12 hours, then dispersed in propylene carbonate, reacted for 6 hours at 100 ℃, and the product is dried in vacuum at 150 ℃ after centrifugation.
Then 1.8 g PEG was dissolved in a mass concentration of 20% in 7.2 g N-methylpyrrolidone solvent, and the mixture was subjected to ultrasonic dispersion for 10min and magnetic stirring at 50℃for 8 hours to obtain a mixed solution. Lithium bis (fluorosulfonyl) imide, LLZGRO, N-methyl-N-propylpyrrole bis (trifluoromethylsulfonyl) imide, and propylene carbonate are sequentially added to the solution in order. 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% of the total mass of the LLZGRO and the PEG, the added N-methyl-N-propylpyrrole bis (trifluoromethylsulfonyl) imide accounts for 20% of the total mass of the mixture of the N-methyl-N-propylpyrrole bis (trifluoromethylsulfonyl) imide and the PEG, the added propylene carbonate accounts for 10% of the total mass of the mixture of the propylene carbonate and the PEG, and then stirring is continued for 6 hours to fully react to form a slurry.
Finally, the mixed solution after stirring is transferred into a mould, and the solvent is dried and evaporated at the temperature of 60 ℃ in vacuum, so that the composite solid electrolyte membrane with the thickness of 220 mu m is obtained.
Comparative example 1: unmodified composite electrolyte membrane
Comparative example 1 the procedure was exactly the same as in example 1, except that the starting material was not modified, 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. LIClO4, LLZTO, EMITFSI, DMC are then added sequentially to the PVDF solution. Added LIClO 4 Occupy LIClO 4 And 30% of the total mass of PVDFThe added LLZTO accounts for 10wt% of the total mass of the LLZTO and the PVDF, the added EMITFSI accounts for 10wt% of the total mass of the mixture of the EMITFSI and the PVDF, the added DMC accounts for 5wt% of the total mass of the mixture of the DMC and the PVDF, and then stirring is continued for 12 hours, and the mixture is fully reacted to form slurry. After casting the slurry with a mold, vacuum drying was performed at 60℃for 8 hours to obtain a solid electrolyte membrane having a thickness of 180. Mu.m.
As shown in fig. 1 and 5, the ac impedance diagram 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:
(1) the impedance is significantly lower, decreasing from 30Ω to 17Ω.
(2) The conductivity was significantly higher, increasing from 0.53mS/cm to 1.15mS/cm.
The data above show that our modification of the electrolyte membrane is significant in improving 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 lithium battery uses a half battery with NCM523 as a positive electrode and lithium metal 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 in NMP at a mass ratio NCM523:super P: pvdf=8:1:1 to obtain a positive electrode slurry, which was coated on an aluminum foil, and then vacuum-dried at 105 ℃ for 24 hours to obtain a positive electrode.
In this example, a positive electrode was cut into a positive electrode sheet using a microtome, a negative electrode was a lithium sheet using the electrolyte membrane of example 1, and a coin cell was assembled in a glove box under an argon atmosphere.
Performance test:
(1) Conductivity test
The electrolyte membrane prepared in example 1 was punched using a sheet punching machine to obtain a sample having a diameter of 12mm and a thickness of 220. Mu.m. The sample is tested for room temperature ionic conductivity, and the specific process is as follows: and clamping the sample in the middle of a stainless steel sheet in a blocking type die to obtain electrochemical impedance data, and obtaining the total conductivity according to the thickness and the electrode area after fitting. The sample obtained in example 1 can reach an ion conductivity of 0.8mS/cm at room temperature, and the composite electrolyte membrane has high room temperature conductivity.
(2) Electrochemical window testing
The electrolyte membrane prepared in example 1 was punched using a sheet punching machine to obtain a sample having a diameter of 12mm and a thickness of 220. Mu.m. Under argon atmosphere, the sample, the stainless steel sheet and the lithium sheet form a button cell (wherein the stainless steel sheet is used as a working electrode, the lithium sheet is used as a reference electrode and a counter electrode), and an electrochemical window of the button cell is tested on an electrochemical workstation within a test range of 2.5-6V.
(3) Charge and discharge test
The sample obtained in example 1 was tested, with a charge-discharge interval of 2.0 to 4.0V, and charged and discharged at a current of 0.1C. As shown in fig. 3, the lithium metal battery prepared by setting the electrolyte membrane prepared in example 1 between the positive electrode and the negative electrode with lithium iron phosphate as the positive electrode and lithium metal as the negative electrode has a specific discharge capacity of 155mAh/g after 200 charge and discharge cycles at a current density of 0.1C, which indicates that the electrolyte membrane has high ionic conductivity and good interfacial compatibility.
The present invention provides a double-modified solid electrolyte, a preparation method and an application thereof, the above examples are only preferred embodiments, the present invention is not limited to the above examples, and any modification, replacement, improvement, etc. made on the premise of consistent with the principles of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. The preparation method of the double-modified solid electrolyte membrane is characterized by comprising the following steps of:
s1, modifying a polymer, and grafting the polymer to assist in Li transmission + - (-O-CH) 2 -CH 2 -） n -a functional group; modifying the nano ceramic particles to enable the surfaces of the nano ceramic particles to be provided with ether oligomers;
the modification process of the nano ceramic particles comprises the steps of exposing in air or carbon dioxide waterThe method for treating the steam mixed gas treats the nano ceramic particles to ensure that the surfaces of the nano ceramic particles are provided with a small amount of LiOH and Li 2 CO 3 Then the treated nano ceramic particles and cyclic carbonate are subjected to ring-opening grafting reaction to form the nano ceramic particles capable of transferring Li + The cyclic carbonate is one of ethylene carbonate, propylene carbonate and vinylene carbonate;
s2, dissolving the polymer modified in the step S1 in an organic solvent, adding lithium salt, modified nano ceramic particles, ionic liquid and plasticizer into the polymer solution, and performing ultrasonic dispersion and stirring to obtain a viscous mixed solution;
s3, transferring the viscous mixed solution into a mold, and vacuum drying and evaporating 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, wherein: the polymer in the step S1 is modified by introducing grafts for grafting reaction after low-temperature plasma irradiation, and the gas used for the low-temperature plasma irradiation is SO 2 、NH 3 、H 2 O、N 2 And Ar, the irradiation treatment time is 30-120s.
3. The method for producing a double modified solid electrolyte membrane according to claim 1, wherein: the functional group grafted on the polymer in the step S1 is polyethylene glycol or polyethylene oxide; the average molecular weight of the grafted functional groups on the polymer is 0.02-20 ten thousand.
4. The method for producing a double modified solid electrolyte membrane according to claim 1, wherein: the mass concentration of the modified polymer in the solution in the step S2 is 10-35%; the mass content of the lithium salt is 10% -60% based on the total mass of the polymer and the lithium salt, the mass content of the nano ceramic particles is 2% -20% based on the total mass of the polymer and the nano ceramic particles, the mass content of the ionic liquid is 5% -40% based on the total mass of the polymer and the ionic liquid, and the mass content of the plasticizer is 5% -20% based on the total mass of the polymer and the plasticizer.
5. The method for producing a double modified solid electrolyte membrane according to claim 1, wherein: 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.
6. The method for producing a double modified solid electrolyte membrane according to claim 1, wherein: the organic solvent is one of N, N-dimethylformamide, N-dimethylacetamide, N-dimethylpropionamide, N-methylpyrrolidone, acetonitrile, acetone and tetrahydrofuran.
7. The method for producing a double modified solid electrolyte membrane according to claim 1, wherein: the lithium salt is at least one of lithium bis (trifluoromethanesulfonic acid) imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium dioxalate borate and lithium bis (fluorosulfonyl) imide; the plasticizer is one of ethylene carbonate, polycarbonate, propylene carbonate, methyl ethyl carbonate, dimethyl carbonate and diethyl phthalate; the ionic liquid is one of 1-ethyl-3-methylimidazole bis (trifluoromethylsulfonyl) imide, N-methyl-N, N-diethyl-N- (2-methoxyethyl) ammonium bis (trifluoromethylsulfonyl) imide, N-methyl-N-propylpiperidinebis (trifluoromethylsulfonyl) imide or N-methyl-N-propylpyrrolidinyl bis (trifluoromethylsulfonyl) imide.
8. The method for producing a double modified solid electrolyte membrane according to claim 1, wherein: the nano ceramic particles are Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 、Li 6.3 La 3 Zr 1.65 W 0.35 O 12 、Li 7 La 3 Zr 2 O 12 、Li 6.25 A l0.25 La 3 Zr 2 O 12 And Li (lithium) 6.20 Ga 0.30 La 2.95 Rb 0.05 Zr 2 O 12 The average radius of the nano ceramic particles is 5-200nm.
9. Use of a double modified solid electrolyte membrane prepared according to the method of any one of claims 1 to 8 in a lithium battery.
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