CN112909324B - Inorganic/organic composite solid electrolyte and preparation method and application thereof - Google Patents
Inorganic/organic composite solid electrolyte and preparation method and application thereof Download PDFInfo
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- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
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Abstract
The invention provides a preparation method of an inorganic/organic composite solid electrolyte, which comprises the following steps: mixing polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium salt, a first filler and an organic solvent to obtain first slurry; the first filler is a P2 type layered oxide fast ion conductor modified by a silane coupling agent; the particle size of the first filler is 500 nm-1.5 mu m; mixing polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium salt, a second filler and an organic solvent to obtain second slurry; the second filler is a P2 type layered oxide fast ion conductor modified by a silane coupling agent; the particle size of the second filler is less than 500nm; coating the first slurry on a substrate, and drying to obtain a layer of solid electrolyte; and coating the second slurry on the surface of the layer of solid electrolyte, and drying to obtain the inorganic/organic composite solid electrolyte.
Description
Technical Field
The invention belongs to the technical field of solid electrolytes, and particularly relates to an inorganic/organic composite solid electrolyte, a preparation method and application thereof.
Background
The sodium ion battery has the characteristics of abundant sodium resource reserves, low cost and the like, has a similar working principle as a lithium ion battery, can be used as a beneficial supplement of the lithium ion battery to be applied to low-speed electric vehicles and large-scale energy storage, is limited by the larger diameter of sodium ions, and has slower transmission dynamics in electrolyte than lithium ions, so that the sodium ion battery electrolyte material is always the key point of research in the sodium ion battery industry.
The electrolyte states of sodium ion batteries are classified into liquid electrolytes and solid electrolytes. The liquid electrolyte has relatively high ionic conductivity and is divided into three types of organic electrolyte, aqueous electrolyte and liquid ionic electrolyte, wherein the organic electrolyte consists of an organic solvent and sodium salt, and the electrolyte has the problems of flammability and easy liquid leakage, so that the application of the electrolyte is limited to a great extent; the water-based electrolyte has the ion conductivity close to that of lS-cnr1, but the decomposition voltage of water is only 1.23V, and the voltage window is difficult to widen all the time, so that the energy density of the whole battery is low; the ionic liquid electrolyte is generally composed of larger anions and cations, has high cost and certain requirements on working temperature, and is difficult to realize industrialized application. Faced with the limitations of liquid electrolytes, solid electrolytes have become a hot spot of research in order to further meet smaller, lighter, thinner demands.
Solid electrolytes are largely classified into organic polymer solid electrolytes and inorganic solid electrolytes. The organic polymer solid electrolyte has good interfacial contact and compatibility with an electrode due to good safety, film forming property and viscoelasticity, but has high crystallinity at room temperature, so that the ion conductivity at room temperature is low, resulting in poor electrochemical performance of the battery at room temperature. Therefore, it is necessary to modify the organic polymer solid electrolyte to improve the ionic conductivity thereof and to reduce the interface resistance, thereby improving the cycling stability of the organic polymer solid electrolyte.
Disclosure of Invention
The invention aims to provide an inorganic/organic composite solid electrolyte, a preparation method and application thereof. The inorganic/organic composite solid electrolyte prepared by the preparation method provided by the invention has high ionic conductivity and cycle stability, and the electrochemical performance of the prepared battery is excellent.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of an inorganic/organic composite solid electrolyte, which comprises the following steps:
(1) Mixing polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium salt, a first filler and an organic solvent to obtain first slurry; the first filler is a P2 type layered oxide fast ion conductor modified by a silane coupling agent; the particle size of the first filler is 500 nm-1.5 mu m;
(2) Mixing polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium salt, a second filler and an organic solvent to obtain second slurry; the second filler is a P2 type layered oxide fast ion conductor modified by a silane coupling agent; the particle size of the second filler is less than 500nm;
(3) Coating the first slurry obtained in the step (1) on a substrate, and drying to obtain a layer of solid electrolyte;
(4) Coating the second slurry obtained in the step (2) on the surface of the layer of solid electrolyte obtained in the step (3), and drying to obtain the inorganic/organic composite solid electrolyte;
the step (1) and the step (2) are not in sequence.
Preferably, the molar ratio of the monomeric ethylene oxide of the polyethylene oxide to the sodium salt in step (1) and step (2) is independently 8 to 20.
Preferably, the mass ratio of the polyethylene oxide to the polyvinylidene fluoride-hexafluoropropylene copolymer in the step (1) and the step (2) is independently (1 to 4): 1.
preferably, the sodium salt in the step (1) and the step (2) is sodium perchlorate, sodium hexafluorophosphate or NaTFSI.
Preferably, the P2 type layered oxide fast ion conductor in the step (1) and the step (2) is independently Na 2 Mg 2 TeO 6 、Na 1.9 Ni 1.9 Fe 0.1 TeO 6 Or Na (or) 2 Ni 2 TeO 6 。
Preferably, the mass of the first filler in the step (1) is 10 to 100% of the mass of the polyethylene oxide.
Preferably, the mass of the second filler in step (2) is less than 10% of the mass of the polyethylene oxide.
Preferably, the organic solvent in step (1) and step (2) is independently dimethylformamide or acetonitrile.
The invention also provides the inorganic/organic composite solid electrolyte prepared by the preparation method of the technical scheme, and the inorganic/organic composite solid electrolyte has a two-layer structure.
The invention also provides application of the inorganic/organic composite solid electrolyte in sodium ion batteries.
The invention provides a preparation method of an inorganic/organic composite solid electrolyte, which comprises the following steps: mixing polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium salt, a first filler and an organic solvent to obtain first slurry; the first filler is a P2 type layered oxide fast ion conductor modified by a silane coupling agent; the particle size of the first filler is 500 nm-1.5 mu m; mixing polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium salt, a second filler and an organic solvent to obtain second slurry; the second filler is a P2 type layered oxide fast ion conductor modified by a silane coupling agent; the particle size of the second filler is less than 500nm; coating the first slurry on a substrate, and drying to obtain a layer of solid electrolyte; and coating the second slurry on the surface of the layer of solid electrolyte, and drying to obtain the inorganic/organic composite solid electrolyte. According to the invention, a polyethylene oxide matrix is used as a main body, PVDF-HFP copolymer with low HOMO (highest occupied molecular orbital) value and good compatibility with a positive electrode is introduced, a three-dimensional cross-linked porous network structure is formed by the interaction of hydrogen bonds, and a P2 type layered oxide fast ion conductor is used as an inorganic filler, so that the ionic conductivity and mechanical property of the composite solid electrolyte are improved, and the cycle stability of the electrolyte is improved; the silane coupling agent and the fast ion conductor are adopted to perform bonding action, so that the fast ion conductor is uniformly dispersed in the polymer matrix, and the ion conductivity of the composite solid electrolyte is further improved; the first slurry and the second slurry are sequentially coated on the substrate, the prepared composite solid electrolyte membrane is provided with the inorganic filler with larger particle size in the bottom layer, so that the mechanical property can be further enhanced, the effect of inhibiting metal dendrites is achieved, the risk of short circuit caused by the penetration of the metal dendrites through the membrane is avoided, the circulation stability of the electrolyte is improved, the upper layer is provided with the inorganic filler with smaller particle size, the flexibility of the composite solid electrolyte is better, the interface compatibility between the electrode and the electrolyte is improved, the interface side reaction is reduced, and the circulation stability of the electrolyte is further improved. The results of the examples show that after the inorganic/organic composite solid electrolyte prepared by the preparation method of the invention is stood for 8 days at room temperature, the impedance is obviously reduced, which indicates that the interface compatibility is better; the Na-symmetric battery constant current circulation prepared by the inorganic/organic composite solid electrolyte prepared by the preparation method still has good stability for 250 hours.
Drawings
FIG. 1 is a macroscopic view of an inorganic/organic composite solid electrolyte prepared in example 1;
FIG. 2 is a flexibility test chart of the inorganic/organic composite solid electrolyte prepared in example 1;
fig. 3 is an SEM image of the inorganic/organic composite solid electrolyte prepared in example 1;
FIG. 4 is an LSV curve of the inorganic/organic composite solid electrolyte prepared in example 1;
FIG. 5 is an AC impedance spectrum of the symmetrical battery Na|SPE|Na prepared in application example 1 at different standing times;
FIG. 6 shows a symmetrical cell Na|SPE|Na prepared in application example 1 and a symmetrical cell Na|celgard-NaClO prepared in comparative example 1 4 EC-DMC|Na at 0.1mAcm -2 Sodium deposition-stripping voltage curve at current density;
FIG. 7 is a battery Na prepared in comparative example 2 3 V 2 (PO 4 ) 3 |celgard-NaClO 4 -charge-discharge curve of EC-dmc|na at room temperature;
FIG. 8 is a view of battery Na prepared in application example 2 3 V 2 (PO 4 ) 3 Charge-discharge curve of SPE Na at room temperature.
Detailed Description
The invention provides a preparation method of an inorganic/organic composite solid electrolyte, which comprises the following steps:
(1) Mixing polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium salt, a first filler and an organic solvent to obtain first slurry; the first filler is a P2 type layered oxide fast ion conductor modified by a silane coupling agent; the particle size of the first filler is 500 nm-1.5 mu m;
(2) Mixing polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium salt, a second filler and an organic solvent to obtain second slurry; the second filler is a P2 type layered oxide fast ion conductor modified by a silane coupling agent; the particle size of the second filler is less than 500nm;
(3) Coating the first slurry obtained in the step (1) on a substrate, and drying to obtain a layer of solid electrolyte;
(4) Coating the second slurry obtained in the step (2) on the surface of the layer of solid electrolyte obtained in the step (3), and drying to obtain the inorganic/organic composite solid electrolyte;
the step (1) and the step (2) are not in sequence.
The invention mixes polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium salt, first filler and organic solvent to obtain first slurry.
In the present invention, the viscosity average molecular weight of the polyethylene oxide is preferably 100000 ～ 1000000, more preferably 500000 ～ 600000. In the present invention, the viscosity average molecular weight of the polyethylene oxide is within the above range, so that the polyethylene oxide can be ensured to have a moderate viscosity. The source of the polyethylene oxide is not particularly limited, and commercially available products known to those skilled in the art may be used. In the present invention, the polyethylene oxide PEO serves as a matrix for the composite solid electrolyte.
The source of the polyvinylidene fluoride-hexafluoropropylene copolymer is not particularly limited in the present invention, and may be prepared by commercially available products known to those skilled in the art or by a known preparation method. In the present invention, the mass ratio of the polyethylene oxide to the polyvinylidene fluoride-hexafluoropropylene copolymer is preferably (1 to 4): 1, more preferably (2 to 3): 1. in the invention, the polyvinylidene fluoride-hexafluoropropylene copolymer has good compatibility with the positive electrode, has low HOMO (highest occupied molecular orbital) value, can form a three-dimensional crosslinked porous network structure with polyethylene oxide through the interaction of hydrogen bonds, and improves the mechanical property of the composite solid electrolyte, thereby improving the cycle stability of the electrolyte.
In the present invention, the sodium salt is preferably sodium perchlorate, sodium hexafluorophosphate or naffsi. The source of the sodium salt is not particularly limited in the present invention, and commercially available products known to those skilled in the art may be used. In the present invention, the molar ratio of the monomer ethylene oxide of the polyethylene oxide to the sodium salt is preferably 8 to 20, more preferably 10 to 16. In the invention, when the sodium salt is the substance, the electrochemical stability of the solid electrolyte can be improved, and the transportation speed of sodium ions can be enhanced.
In the invention, the first filler is a P2 type layered oxide fast ion conductor modified by a silane coupling agent; the particle size of the first filler is 500nm to 1.5. Mu.m, preferably 800nm to 1.3. Mu.m, more preferably 900nm to 1.2. Mu.m; the type of the P2 type layered oxide fast ion conductor is preferably Na 2 Mg 2 TeO 6 、Na 1.9 Ni 1.9 Fe 0.1 TeO 6 Or Na (or) 2 Ni 2 TeO 6 The method comprises the steps of carrying out a first treatment on the surface of the The mass of the first filler is preferably 10 to 100% of the mass of polyethylene oxide, more preferably 20 to 80%, and still more preferably 30 to 50%. The source of the P2 type layered oxide fast ion conductor is not particularly limited, and the P2 type layered oxide fast ion conductor is prepared by a preparation method well known to those skilled in the art. In the invention, the P2 type layered oxide fast ion conductor of the silane coupling agent is used as an inorganic filler, so that the ion conductivity and the mechanical property of the composite solid electrolyte can be improved, and the cycle stability of the electrolyte is improved; the particle size of the first filler can further enhance mechanical properties when the particle size is in the range, plays a role in inhibiting metal dendrites, avoids the risk of short circuit caused by penetration of the metal dendrites through a diaphragm, and improves the cycle stability of the electrolyte; the mass of the first filler can further enhance mechanical properties when it is within the above range.
In the present invention, the preparation method of the first filler preferably includes the steps of:
1) Mixing a silane coupling agent with an alcohol solution to obtain a mixed solution;
2) And (2) mixing the mixed solution obtained in the step (1) with the P2 type layered oxide rapid ion conductor, and then sequentially filtering, drying and crushing to obtain the first filler.
In the present invention, the silane coupling agent is preferably mixed with an alcohol solution to obtain a mixed solution.
In the present invention, the concentration of the alcohol solution is preferably 15 to 25%, more preferably 20%. The kind of the alcohol solution is not particularly limited, and alcohol solutions well known to those skilled in the art may be used. The source of the silane coupling agent is not particularly limited, and commercially available products known to those skilled in the art may be used. In the present invention, the mixing of the silane coupling agent with the alcohol solution is preferably performed under stirring conditions; the concentration of the silane coupling agent in the mixed solution is preferably 1 to 5%, more preferably 2%. The stirring rate and time are not particularly limited in the present invention, as long as a uniformly dispersed mixed solution is ensured. In the invention, the silane coupling agent is mixed with the alcohol solution, so that the silane coupling agent is dispersed on the surface of the P2 type layered oxide fast ion conductor, and the modification effect is improved.
After the mixed solution is obtained, the mixed solution is preferably mixed with the P2 type layered oxide rapid ion conductor and then sequentially filtered, dried and crushed to obtain the first filler.
In the present invention, the mixing of the mixed solution with the P2 type layered oxide fast ion conductor is preferably performed under stirring conditions; the stirring time is preferably 15 to 25 minutes, more preferably 20 minutes. The stirring rate is not particularly limited in the present invention, as long as it is ensured that a uniformly dispersed mixed solution is obtained. In the present invention, the mass of the silane coupling agent is preferably 0.2 to 1.5% of the mass of the P2 type layered oxide fast ion conductor, more preferably 1.0 to 1.5%. In the invention, when the mixed solution is mixed with the P2 type layered oxide fast ion conductor, a silane coupling agent containing an alkoxy group capable of being hydrolyzed is introduced, and the inorganic fast ion conductor with uniform size is uniformly dispersed in a polymer matrix through the bonding action of the hydrolysis group and the fast ion conductor.
The filtering operation is not particularly limited in the present invention, and filtering operations well known to those skilled in the art may be employed. In the present invention, the drying temperature is preferably 30 to 120 ℃, more preferably 40 to 60 ℃. The drying time is not particularly limited, and the filtered product is dried to constant weight. The operation of the pulverization is not particularly limited as long as the particle size requirement of the first filler is satisfied.
In the present invention, the organic solvent is preferably dimethylformamide or acetonitrile. The source of the organic solvent is not particularly limited, and commercially available products known to those skilled in the art may be used. The amount of the organic solvent used in the present invention is not particularly limited as long as the first slurry is in the form of a slurry. In the present invention, the organic solvent is used to dissolve the raw material.
In the present invention, the operation of mixing the polyethylene oxide, the polyvinylidene fluoride-hexafluoropropylene copolymer, the sodium salt, the first filler and the organic solvent is preferably to mix the polyethylene oxide with the organic solvent, then add the first filler to mix, and finally add the sodium salt and the polyvinylidene fluoride-hexafluoropropylene copolymer to mix, thereby obtaining the first slurry.
In the present invention, the mixing of the polyethylene oxide with the organic solvent, the mixing with the first filler, and the mixing with the sodium salt and the polyvinylidene fluoride-hexafluoropropylene copolymer are preferably performed under stirring conditions; the temperature of the stirring is independently preferably 60 to 90 ℃. The stirring time is not particularly limited in the present invention, as long as it is ensured that a uniform slurry is obtained.
The invention mixes polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium salt, second filler and organic solvent to obtain second slurry.
In the invention, the second filler is a P2 type layered oxide fast ion conductor modified by a silane coupling agent; the particle size of the second filler is less than 500nm, preferably 100 to 450nm, more preferably 200 to 300nm. In the invention, the second filler with smaller particle size can make the flexibility of the composite solid electrolyte better, improve the interface compatibility between the electrode and the electrolyte, reduce the interface side reaction, and further improve the cycle stability of the electrolyte.
In the present invention, the mass of the second filler is less than 10% of the mass of polyethylene oxide, preferably 2 to 8%, more preferably 4 to 6%. In the present invention, the mass of the second filler in the above range can further secure the flexibility of the composite solid electrolyte, thereby further improving the cycle stability of the electrolyte.
In the present invention, other raw materials and operations for preparing the second slurry are preferably the same as those for preparing the first slurry, and will not be described herein.
After the first slurry is obtained, the first slurry is coated on a substrate, and a layer of solid electrolyte is obtained after drying.
In the present invention, the method of the first slurry coating is preferably a casting method. The specific operation of the casting method is not particularly limited in the present invention, and the operation of preparing the polymer solid electrolyte by the casting method, which is well known to those skilled in the art, may be employed. In the present invention, the substrate is preferably a polytetrafluoroethylene plate. The size of the substrate is not particularly limited, and the substrate may be adjusted according to actual conditions. In the present invention, the drying operation is preferably the same as the drying operation used in the preparation of the first filler, and will not be described herein. In the invention, the drying can avoid the influence of moisture on the battery performance; the solid electrolyte layer obtained at the drying temperature of 40-60 ℃ is softer and is more beneficial to the contact of the composite solid electrolyte with the anode.
After a layer of solid electrolyte and a second slurry are obtained, the second slurry is coated on the surface of the layer of solid electrolyte, and the inorganic/organic composite solid electrolyte is obtained after drying.
In the present invention, the volumes of the first slurry and the second slurry are preferably the same; the method of the second slurry coating is preferably a casting method. The specific operation of the casting method is not particularly limited in the present invention, and the operation of preparing the polymer solid electrolyte by the casting method, which is well known to those skilled in the art, may be employed. In the present invention, the drying operation is preferably the same as the drying operation used in the preparation of the first filler, and will not be described herein. In the invention, the drying can avoid the influence of moisture on the battery performance; the composite solid electrolyte obtained at the drying temperature of 40-60 ℃ is softer and is more beneficial to contact with the anode.
After the drying is completed, the invention preferably peels off the substrate from the product obtained by the drying to obtain the inorganic/organic composite solid electrolyte. The operation of peeling the substrate is not particularly limited, and may be any operation known to those skilled in the art.
According to the invention, a polyethylene oxide matrix is taken as a main body, PVDF-HFP copolymer with low HOMO (highest occupied molecular orbital) value and good compatibility with a positive electrode is introduced, a three-dimensional cross-linked porous network structure is formed by the interaction of hydrogen bonds, and a P2 type layered oxide fast ion conductor is taken as an inorganic filler to improve the ionic conductivity and mechanical property of the composite solid electrolyte, so that the cycle stability of the electrolyte is improved; the silane coupling agent and the fast ion conductor are adopted to perform bonding action, so that the fast ion conductor is uniformly dispersed in the polymer matrix, and the ion conductivity of the composite solid electrolyte is further improved; in the prepared composite solid electrolyte, the bottom layer is the inorganic filler with larger particle size, so that the mechanical property can be further enhanced, the effect of inhibiting metal dendrites is achieved, the risk of short circuit caused by the penetration of the metal dendrites through a diaphragm is avoided, the circulation stability of the electrolyte is improved, the upper layer is the inorganic filler with smaller particle size, the flexibility of the composite solid electrolyte is better, the interface compatibility between an electrode and the electrolyte is improved, the interface side reaction is reduced, and the circulation stability of the electrolyte is further improved.
According to the invention, the inorganic ion conductor is added into the polymer solid electrolyte to construct the inorganic/organic composite solid electrolyte, so that on one hand, the soft characteristic of the polymer electrolyte can be effectively utilized to improve the interface compatibility between the electrode and the electrolyte, and on the other hand, the synergistic advantages of the ion conductivity and the strong mechanical property of the inorganic ion conductor are utilized to improve the ion conductivity and the mechanical property of the composite solid electrolyte.
The invention constructs the three-dimensional inorganic/organic composite functional solid electrolyte based on the in-situ bonding effect, can effectively solve the problem of solid-solid interface contact between inorganic electrolyte powder and polymer electrolyte in the solid electrolyte by the in-situ bonding effect, and promotes the uniform dispersion of inorganic filler in a polymer matrix, thereby obtaining the flexible composite solid electrolyte with high ionic conductivity and electrochemical stability.
The invention also provides the inorganic/organic composite solid electrolyte prepared by the preparation method of the technical scheme, and the inorganic/organic composite solid electrolyte has a two-layer structure.
The inorganic/organic composite solid electrolyte provided by the invention has a gradient structure, the bottom layer is the composite solid electrolyte distributed by the first filler with larger particle size, and the upper layer is the composite solid electrolyte with the second filler with small particle size and mainly made of polymer matrix uniformly dispersed, and the composite solid electrolyte has high ionic conductivity, excellent mechanical property and cycle stability.
The invention also provides application of the inorganic/organic composite solid electrolyte in sodium ion batteries.
The application of the inorganic/organic composite solid electrolyte in the sodium ion battery is not particularly limited, and the application operation of the solid electrolyte known to those skilled in the art can be adopted.
The technical solutions of the present invention will be clearly and completely described in the following in connection with the embodiments of the present invention. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
(1) Adding a silane coupling agent into a 20% ethanol solution under stirring to obtain a mixed solution; the concentration of the silane coupling agent in the mixed solution is 2%;
(2) The P2 type layered oxide fast ion conductor Na 2 Ni 2 TeO 6 Adding the mixture into the mixed solution obtained in the step (1) under stirring, stirring for 20min, filtering, drying at 80 ℃, and ball milling to a particle size of 900 nm-1.2 mu m to obtain a first filler; wherein the silane coupling agent is the P2 type lamellar oxidation1.5% of the mass of the ion conductor;
(3) Dispersing polyethylene oxide with viscosity average molecular weight of 600000 in dimethylformamide at 1.6wt%, and stirring at 60deg.C to obtain uniform polymer slurry liquid; adding a first filler with the mass of 100% of that of the polyethylene oxide under the stirring condition of 60 ℃, uniformly mixing, adding sodium hexafluorophosphate and PVDF-HFP copolymer under the stirring condition of 60 ℃, and uniformly mixing to obtain a first slurry; wherein, the mol ratio of the monomer ethylene oxide of the polyethylene oxide to the sodium hexafluorophosphate is 16, and the mass ratio of the polyethylene oxide to the PVDF-HFP copolymer is 1:1, a step of;
(4) Coating the first slurry obtained in the step (3) on a smooth polytetrafluoroethylene plate by adopting a tape casting method, and vacuum drying at 60 ℃ to obtain a layer of solid electrolyte, wherein the coating thickness is 500 mu m;
(5) Preparing a second filler according to the step (1) and the step (2), wherein the second filler is ball-milled after being dried until the particle size is 200-300 nm, and other conditions are unchanged; preparing a second slurry with the same volume according to the step (3), wherein the second filler is 2% of the mass of the polyethylene oxide, and other conditions are unchanged;
(6) And (3) coating the second slurry obtained in the step (5) on the surface of the layer of solid electrolyte obtained in the step (4) by adopting a tape casting method, and peeling the polytetrafluoroethylene plate after vacuum drying at 60 ℃ to obtain the inorganic/organic composite solid electrolyte SPE, wherein the coating thickness is 500 mu m.
Performance testing was performed on the inorganic/organic composite solid electrolyte prepared in example 1, wherein fig. 1 is a macroscopic view of the inorganic/organic composite solid electrolyte prepared in example 1; FIG. 2 is a flexibility test chart of the inorganic/organic composite solid electrolyte prepared in example 1; fig. 3 is an SEM image of the inorganic/organic composite solid electrolyte prepared in example 1; fig. 4 is an LSV curve of the inorganic/organic composite solid electrolyte prepared in example 1.
As can be seen from fig. 2, the inorganic/organic composite solid electrolyte prepared in this example has good flexibility. As can be seen from fig. 3, the filler in the inorganic/organic composite solid electrolyte prepared in this example was uniformly dispersed. As can be seen from fig. 4, the electrochemical stability window of the inorganic/organic composite solid electrolyte prepared in this example is much higher than that of pure PEO solid electrolyte, and the 4.2V cathode material commonly used in the art can be matched with it.
Application example 1
The inorganic/organic composite solid electrolyte SPE, the metal sodium positive electrode and the metal sodium negative electrode prepared in example 1 were assembled into a symmetrical battery na|spe|na, and the battery na|spe|na was tested for ac impedance for different periods of time, and the results are shown in fig. 5. As can be seen from fig. 5, the impedance of the symmetrical battery na|spe|na was significantly reduced after standing at room temperature for 8 days, indicating that the interface compatibility was improved.
Application example 2
The inorganic/organic composite solid electrolyte SPE and the positive electrode material Na prepared in the example 1 3 V 2 (PO 4 ) 3 Assembled with metal sodium cathode to form battery Na 3 V 2 (PO 4 ) 3 |SPE|Na。
Comparative example 1
With organic liquid electrolyte NaClO 4 The EC-DMC is used as electrolyte, metal sodium positive electrode and metal sodium negative electrode to assemble the symmetrical battery Na|cellgard-NaClO 4 -EC-DMC|Na。
Comparative example 2
With organic liquid electrolyte NaClO 4 EC-DMC as electrolyte, positive electrode material Na 3 V 2 (PO 4 ) 3 Assembled with metal sodium cathode to form battery Na 3 V 2 (PO 4 ) 3 |celgard-NaClO 4 -EC-DMC|Na。
Symmetrical cell Na|SPE|Na prepared in application example 1 and symmetrical cell Na|celgard-NaClO prepared in comparative example 1 were combined 4 EC-DMC|Na at 0.1mAcm -2 Electrochemical performance testing was performed at current density and the results are shown in fig. 6. As can be seen from FIG. 6, the deposition-stripping voltage curve cycle 250h of the symmetrical cell prepared in application example 1 still has good stability, while comparative example 1 uses the liquid electrolyte system celgard-NaClO 4 The symmetrical cells of the EC-DMC are short-circuited.
Preparation of application example 2Is of the battery Na 3 V 2 (PO 4 ) 3 SPE Na and comparative example 2 battery Na 3 V 2 (PO 4 ) 3 |celgard-NaClO 4 The charge and discharge performance test was performed at room temperature with EC-dmc|na, and the results are shown in fig. 7 and 8, and fig. 7 is a battery Na prepared in comparative example 2 3 V 2 (PO 4 ) 3 |celgard-NaClO 4 -charge-discharge curve of EC-dmc|na at room temperature; FIG. 8 is a view of battery Na prepared in application example 2 3 V 2 (PO 4 ) 3 Charge-discharge curve of SPE Na at room temperature.
As can be seen by comparing fig. 7 and 8, battery Na prepared in application example 2 3 V 2 (PO 4 ) 3 Coulombic efficiency of spe|na was higher than that of the liquid organic system (NaClO) prepared in comparative example 2 4 EC-DMC) is high in coulombic efficiency and the polarization voltage is reduced.
As can be seen from the above examples and application examples, the inorganic/organic composite solid electrolyte prepared by the preparation method provided by the present invention has high ionic conductivity and cycle stability.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (7)
1. A method for preparing an inorganic/organic composite solid electrolyte, comprising the steps of:
(1) Mixing polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium salt, a first filler and an organic solvent to obtain first slurry; the first filler is a P2 type layered oxide fast ion conductor modified by a silane coupling agent; the particle size of the first filler is 500 nm-1.5 mu m;
(2) Mixing polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, sodium salt, a second filler and an organic solvent to obtain second slurry; the second filler is a P2 type layered oxide fast ion conductor modified by a silane coupling agent; the particle size of the second filler is less than 500nm;
(3) Coating the first slurry obtained in the step (1) on a substrate, and drying to obtain a layer of solid electrolyte;
(4) Coating the second slurry obtained in the step (2) on the surface of the layer of solid electrolyte obtained in the step (3), and drying to obtain the inorganic/organic composite solid electrolyte;
the step (1) and the step (2) are not in sequence;
the P2 type layered oxide rapid ion conductor in the step (1) and the step (2) is independently Na 2 Mg 2 TeO 6 、Na 1.9 Ni 1.9 Fe 0.1 TeO 6 Or Na (or) 2 Ni 2 TeO 6 ；
The mass of the first filler in the step (1) is 10-100% of the mass of the polyethylene oxide;
the mass of the second filler in the step (2) is less than 10% of the mass of the polyethylene oxide.
2. The process according to claim 1, wherein the molar ratio of the monomeric ethylene oxide of the polyethylene oxide to the sodium salt in step (1) and step (2) is independently 8 to 20.
3. The method according to claim 1, wherein the mass ratio of the polyethylene oxide to the polyvinylidene fluoride-hexafluoropropylene copolymer in the step (1) and the step (2) is independently (1 to 4): 1.
4. the method according to claim 1, wherein the sodium salt in the step (1) and the step (2) is sodium perchlorate, sodium hexafluorophosphate or naffsi.
5. The process according to claim 1, wherein the organic solvent in step (1) and step (2) is dimethylformamide or acetonitrile.
6. The inorganic/organic composite solid electrolyte prepared by the preparation method according to any one of claims 1 to 5, wherein the inorganic/organic composite solid electrolyte has a two-layer structure.
7. Use of the inorganic/organic composite solid-state electrolyte according to claim 6 in sodium ion batteries.
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