CN111106311A - Three-dimensional porous self-supporting electrode and preparation and application thereof - Google Patents
Three-dimensional porous self-supporting electrode and preparation and application thereof Download PDFInfo
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Abstract
The invention relates to a three-dimensional porous self-supporting electrode and preparation and application thereof, the prepared electrode does not need a current collector, a binder and extra conductive carbon, and the overall energy density of the electrode is greatly improved; the electrode has a heteroatom-doped three-dimensional conductive carbon network and a porous structure, and can ensure the rapid transmission of electrons and sodium ions, thereby showing excellent rate capability; the high molecular resin is uniformly coated on the surface of the active substance after carbonization in the preparation process, so that the volume change of the active substance in the circulation process can be inhibited, and the high molecular resin has excellent circulation performance; compared with the traditional preparation method of the self-supporting electrode (such as suction filtration film forming, electrostatic spinning and the like), the process is simpler, has lower energy consumption and is more suitable for large-scale production.
Description
Technical Field
The invention belongs to the field of electrode materials, and discloses a self-supporting electrode prepared by a film preparation process, and a preparation method and application thereof.
Background
Energy sources are important driving forces for social development, and currently used energy sources are mainly divided into renewable energy sources (wind energy, hydroenergy, solar energy and the like) and non-renewable energy sources (coal, petroleum, natural gas and the like). Due to the shortage of non-renewable energy resources and serious environmental pollution, the development of renewable energy is more and more concerned by people, but the renewable energy is discontinuous and unstable, and the direct grid connection of the renewable energy can generate great impact on a power grid. The energy storage technology is a key technology for solving the problems of discontinuity and instability of renewable energy sources. Among many energy storage technologies, lithium ion batteries have the advantages of high energy density, long cycle life and the like, and are widely applied to various portable electronic devices and electric automobiles, but the lithium ion batteries have limited storage capacity and uneven distribution of lithium resources, so that the large-scale development of the lithium ion batteries is limited. Sodium and lithium have similar chemical and physical properties, the storage amount of Na is rich (the abundance of Na is 1000 times that of Li), the distribution is wide, the cost is low, and the development of the sodium-ion battery can effectively relieve the problem of lithium resource shortage.
Currently, in view of the high cost performance of sodium ion battery materials, the positive electrode with commercial application potential is: vanadium sodium phosphate (Na)3V2(PO4)3) Sodium vanadium fluorophosphate (NaVPO)4F、Na3V2Ox(PO4)2F3-x(ii) a X is more than or equal to 0 and less than or equal to 2) and metal oxide (Na)xNiyFezMnwO2、NaxNiyFezCuwO2(ii) a X is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, w is more than or equal to 0 and less than or equal to 1), sodium ferric phosphate (NaFePO4) and the like; negative electrodes with potential for commercial applications are: sodium titanate (Na2Ti3O7), sodium titanium phosphate (NaTi2(PO4)3), titanium dioxide (TiO2), molybdenum disulfide (MoS2), tin (Sn), carbon (C), and the like. The preparation method of the electrode materials mainly adopts the traditional blade coating method, namely, the active materials, the binding agent and the conductive carbon are prepared into slurry and then coated on the current collector in a blade mode, the prepared electrode active materials have small proportion, and the whole energy density of the electrode is low. In order to improve the uniformity of the electrodeThe bulk energy density, self-supporting electrode, arises from this. The self-supporting electrode is an electrode which can be independently used as an electrode assembly battery under the condition that an electrode active material does not depend on a current collector, and has the advantages that a binder, conductive carbon and the current collector are not needed, the mass ratio of active substances in the electrode is greatly improved, and the integral energy density of the battery is improved. At present, the preparation method of the self-supporting electrode mainly comprises the following steps: cotton cloth/trees are used as self-supporting electrodes, carbon nano tubes/graphene are subjected to suction filtration to form a film, electrostatic spinning is carried out, and the like. Among these methods, electrospinning is the most commercially and industrially potential production method, but the method cannot be applied industrially on a large scale because of the high voltage of kV or more, the long production time, and the small production yield.
Disclosure of Invention
In order to realize large-scale industrial application of the self-supporting electrode, the invention prepares the high-performance three-dimensional porous self-supporting electrode without a current collector, a binder and conductive carbon.
In order to realize the purpose, the adopted specific technical scheme is as follows:
a method for preparing a three-dimensional porous self-supporting electrode, the self-supporting electrode being prepared by the steps of:
1) adding one or more than two of organic polymer resins into a solvent, and fully stirring for 0.5-48 h at the temperature of 20-100 ℃ to prepare a solution A; and then dispersing an electrode material in the solution A, wherein the mass ratio of the electrode material to the polymer resin is 1: 10-20: 1 (preferably 1: 2-8: 1), and uniformly mixing and dispersing to obtain a solution B;
2) pouring the solution B prepared in the step (1) on a non-woven fabric substrate or directly on a flat plate, volatilizing the solvent for 0-20 minutes, then soaking the whole solution B in a poor solvent of resin for 1-300 minutes, and preparing a porous membrane at the temperature of 0-60 ℃;
3) drying the membrane prepared in the step (2) at 0-200 ℃ for 1-24 h to prepare a composite membrane;
4) calcining the composite membrane prepared in the step (3) at high temperature to obtain a self-supporting electrode;
the organic polymer resin in the step 1) is one or more than two of polysulfone, polyketone, polyimide, polybenzimidazole, polyvinyl pyridine, polymethyl methacrylate and polyacrylonitrile.
When the organic polymer resin in the step 4) is polysulfone, polyketone, polyimide, polybenzimidazole, polyvinylpyridine or polymethyl methacrylate, the high-temperature calcination process is to calcine the organic polymer resin for 1-24 hours at 600-1000 ℃ under the protection of inert atmosphere;
when the organic polymer resin is polyacrylonitrile, the high-temperature calcination process comprises the steps of pre-oxidizing for 0.5-12 hours in an oxygen atmosphere at 200-400 ℃, and then calcining for 1-24 hours at 600-1000 ℃ under the protection of an inert atmosphere.
The solvent of the organic polymer resin in the step 1) is one or more than two of DMSO, DMAC, NMP and DMF; wherein the concentration of the organic polymer resin in the solution is 2-70 wt%, preferably
5～20wt％。
The electrode material in the step 1) comprises sodium vanadium phosphate (Na)3V2(PO4)3) Sodium vanadium fluorophosphate (NaVPO)4F、Na3V2Ox(PO4)2F3-xWherein x is more than or equal to 0 and less than or equal to 2), sodium ferric phosphate (NaFePO)4) Sodium-based transition metal oxide (NaCrO)2,NaVO2) Sodium titanate (Na)2Ti3O7) Sodium titanium phosphate (NaTi)2(PO4)3) Titanium dioxide (TiO)2) Molybdenum disulfide (MoS)2) One or more of tin (Sn) and carbon (C).
The poor solvent of the resin in the step 2) is one or more than two of methanol, ethanol, propanol, isopropanol and carbon tetrachloride.
The solvent in the step 2) is volatilized for 0-60 minutes, preferably 0-10 minutes, and the resin is immersed in the poor solvent for 1-300 minutes, preferably 5-100 minutes.
The thickness of the electrode is 10-150 μm (preferably 20-80 μm).
The self-supporting electrode is used as a positive electrode or a negative electrode in a sodium ion battery.
The invention has the advantages of
1) The electrode is a self-supporting electrode, a current collector, a binder and extra conductive carbon are not needed, the mass ratio of active materials in the electrode is greatly improved, and the overall energy density of the electrode is greatly improved;
2) the continuity of the high polymer resin can be ensured through phase transformation, the connectivity among the high polymer resins is good, and after high-temperature carbonization, the connected high polymer resins are transformed into a continuous highly-graphitized three-dimensional conductive carbon network, so that a rapid transmission channel is provided for the transmission of electrons;
3) the polymer resin used in the invention is nitrogen or oxygen-containing polymer resin, and a carbon layer with defects is easily formed after carbonization, the defects not only can further improve the conductivity of the three-dimensional conductive carbon network, but also nitrogen or oxygen atoms at the defects can be effectively combined with an active material, so that the binding force of the whole electrode is improved, and electrons can be rapidly conducted between the carbon network and the active material;
4) after phase inversion, a membrane electrode with a porous structure can be obtained, and the size of the pores is about 1 μm. The porous structure with macropores can ensure the full infiltration of the electrolyte and provide a rapid diffusion channel for the diffusion of sodium ions;
5) compared with a non-defective carbon network, the defective carbon network can ensure that sodium ions can rapidly pass through the carbon layer due to the existence of vacancies;
6) after the polymer is carbonized, the polymer can be uniformly coated on the surface of the active substance, the volume change of the active substance in the circulation process can be inhibited, the good structural stability can be kept in the long-term circulation process, and the high reversible capacity can be kept;
7) the polymer resin is uniformly coated on the surface of the active substance, so that the active substance is uniformly dispersed in the polymer, and the particle agglomeration can be effectively prevented in the carbonization process, so that the active substance is kept at a nanometer level. Due to the smaller particles, the transmission path of sodium ions and electrons is shortened, so that the self-supporting electrode has excellent rate performance;
8) the electrode has excellent rate performance due to rapid sodium ion diffusion and electron conduction, and the electrode has excellent cycle performance due to the carbon layer coating structure;
9) the self-supporting electrode prepared by the process has a three-dimensional conductive carbon network and a porous structure, can ensure sufficient electrolyte infiltration, rapid electron conduction and ion diffusion even under high load, and is easy to prepare high-load electrode materials;
10) compared with the traditional preparation method of the self-supporting electrode (preparation processes such as suction filtration film formation, electrostatic spinning and the like), the process is simpler, shorter in flow, lower in energy consumption and more suitable for large-scale production.
Drawings
FIG. 1 is a graph showing rate capability of example 1, comparative example 1 and comparative example 2 at a voltage of 2 to 4.5V.
FIG. 2 is a graph of 1C cycle performance at voltages of 2-4.5V for example 1, comparative example 1, and comparative example 2.
FIG. 3 is a SEM photograph of a cross-section of example 1.
FIG. 4 is a Raman diagram of example 1.
FIG. 5 is an XPS survey of example 1.
Fig. 6 is an XPS chart of N1s of example 1.
Detailed Description
Example 1: (preparation of Na)3V2(PO4)3@3DPC-1 self-supporting electrode)
0.8g of polyacrylonitrile (organic polymer resin) was weighed into 9.2g of DMF, and stirred for 4 hours to be completely dissolved, to form an 8% resin solution. To the resin solution was added 1.0g of Na3V2(PO4)3(electrode material), stirring for 12h, then carrying out ultrasonic treatment for 3h, and stirring for 24h to obtain a uniformly dispersed mixed solution. And flatly paving the mixed solution on a glass plate, volatilizing for 5mins, setting the paving thickness to be 100 microns, then quickly soaking in 5L of ethanol for 10 minutes, and curing to form the porous composite membrane. Pre-calcining the composite membrane for 3h at 300 ℃ in the air atmosphere, and then calcining for 4h at 800 ℃ in the argon atmosphere to obtain Na with the thickness of 30 mu m3V2(PO4)3@3DPC-1 self-supporting electrode. The prepared Na3V2(PO4)3The self-supporting electrode @3DPC-1 is used as a working electrode, the metal sodium sheet is used as a negative electrode, the glass fiber membrane is used as a diaphragm, the solute is 1MNaClO4, the mixture of a solvent EC (ethylene carbonate) and a DEC (diethyl carbonate) (the mass ratio is 1:1), the additive is FEC (Forward error correction) with the mass fraction of 2% and is used as electrolyte, and the sodium ion battery is assembled by sequentially stacking and compressing a negative electrode shell, a negative electrode, the electrolyte, the diaphragm, the electrolyte, a positive electrode and a positive electrode shell through a CR2016 button shell in sequence.
Example 2: (preparation of Na)3V2(PO4)3@3DPC-2 self-supporting electrode)
0.8g of polyacrylonitrile (organic polymer resin) was weighed into 9.2g of DMF, and stirred for 6 hours to be completely dissolved, to form an 8% resin solution. To the resin solution was added 0.1g of Na3V2(PO4)3(electrode material), stirring for 12h, then carrying out ultrasonic treatment for 3h, and stirring for 24h to obtain a uniformly dispersed mixed solution. And flatly paving the mixed solution on a glass plate, volatilizing for 5mins, setting the paving thickness to be 100 microns, then quickly soaking in 5L of ethanol for 10 minutes, and curing to form the porous composite membrane. Pre-calcining the composite membrane for 3h at 300 ℃ in the air atmosphere, and then calcining for 4h at 800 ℃ in the argon atmosphere to obtain Na with the thickness of 30 mu m3V2(PO4)3@3DPC-2 self-supporting electrode. The cell assembly was the same as in example 1.
Example 3: (preparation of Na)3V2(PO4)3@3DPC-3 self-supporting electrode)
0.8g of polyacrylonitrile (organic polymer resin) was weighed into 9.2g of DMF, and stirred for 7 hours to be completely dissolved, to form an 8% resin solution. To the resin solution was added 1.0g of Na3V2(PO4)3(electrode material), stirring for 12h, then carrying out ultrasonic treatment for 3h, and stirring for 24h to obtain a uniformly dispersed mixed solution. And flatly paving the mixed solution on a glass plate, volatilizing for 30mins, setting the paving thickness to be 100 microns, then quickly soaking in 5L of ethanol for 10 minutes, and curing to form the porous composite membrane. Will be compoundedThe film was pre-calcined at 300 ℃ for 3h in an air atmosphere and then at 800 ℃ for 4h in an argon atmosphere to give 30 μm thick Na3V2(PO4)3@3DPC-3 self-supporting electrode. The cell assembly was the same as in example 1.
Example 4: (preparation of Na)3V2(PO4)3@3DPC-4 self-supporting electrode)
0.8g of polyacrylonitrile (organic polymer resin) was weighed into 9.2g of DMF, and stirred for 6 hours to be completely dissolved, to form an 8% resin solution. To the resin solution was added 1.0g of Na3V2(PO4)3(electrode material), stirring for 12h, then carrying out ultrasonic treatment for 3h, and stirring for 24h to obtain a uniformly dispersed mixed solution. And flatly paving the mixed solution on a glass plate, volatilizing for 5mins, setting the paving thickness to be 100 microns, then quickly soaking the glass plate into 5L of ethanol for 2 minutes, and curing to form the porous composite membrane. Pre-calcining the composite membrane for 3h at 300 ℃ in the air atmosphere, and then calcining for 4h at 800 ℃ in the argon atmosphere to obtain Na with the thickness of 30 mu m3V2(PO4)3@3DPC-4 self-supporting electrode. The cell assembly was the same as in example 1.
Example 5: (preparation of Na)3V2(PO4)3@3DPC-5 self-supporting electrode)
0.8g of polyacrylonitrile (organic polymer resin) was weighed into 9.2g of DMF, and stirred for 8 hours to be completely dissolved, to form an 8% resin solution. To the resin solution was added 1.0g of Na3V2(PO4)3(electrode material), stirring for 12h, then carrying out ultrasonic treatment for 3h, and stirring for 24h to obtain a uniformly dispersed mixed solution. And flatly paving the mixed solution on a glass plate, volatilizing for 5mins, setting the paving thickness to be 500 microns, then quickly soaking the glass plate into 5L of ethanol for 10 minutes, and curing to form the porous composite membrane. Pre-calcining the composite membrane for 3h at 300 ℃ in the air atmosphere, and then calcining for 4h at 800 ℃ in the argon atmosphere to obtain Na with the thickness of 150 mu m3V2(PO4)3@3DPC-5 self-supporting electrode. The cell assembly was the same as in example 1.
Example 6: (preparation of Na)3V2(PO4)3@3DPC-6 self-supporting electrode)
2.4g of polyacrylonitrile (organic polymer resin) was weighed into 7.6g of DMF, and stirred for 4 hours to be completely dissolved, thereby forming a 24% resin solution. To the resin solution was added 1.0g of Na3V2(PO4)3(electrode material), stirring for 12h, then carrying out ultrasonic treatment for 3h, and stirring for 24h to obtain a uniformly dispersed mixed solution. And flatly paving the mixed solution on a glass plate, volatilizing for 5mins, setting the paving thickness to be 100 microns, then quickly soaking in 5L of ethanol for 10 minutes, and curing to form the porous composite membrane. Pre-calcining the composite membrane for 3h at 300 ℃ in the air atmosphere, and then calcining for 4h at 800 ℃ in the argon atmosphere to obtain Na with the thickness of 30 mu m3V2(PO4)3@3DPC-6 self-supporting electrode. The cell assembly was the same as in example 1.
Example 7: (preparation of Na)3V2(PO4)2F3@3DPC self-supporting electrode)
1.5g of polybenzimidazole (organic polymer resin) was weighed into 8.5g of NMP, and stirred for 6 hours to be completely dissolved to form a 15% resin solution. To the resin solution was added 1.5g of Na3V2(PO4)2F3(electrode material), stirring for 12h, then carrying out ultrasonic treatment for 3h, and stirring for 24h to obtain a uniformly dispersed mixed solution. And flatly paving the mixed solution on a glass plate, setting the film paving thickness to be 150 mu m, volatilizing for 5mins, quickly immersing in 5L of propanol for 10 minutes, and curing to form the porous composite film. Calcining the composite membrane at 800 ℃ for 5h in argon atmosphere to obtain Na with the thickness of 45 mu m3V2(PO4)2F3@3DPC self-supporting electrode. The cell assembly was the same as in example 1.
Example 8: (preparation of NaFePO)4@3DPC self-supporting electrode)
1.0g of polyvinylpyrrolidone (organic polymer resin) was weighed into 9g of DMAC, and stirred for 4 hours until completely dissolved to form a 10% resin solution. 2.0g NaFePO was added to the resin solution4(electrode material), stirring for 12h, then carrying out ultrasonic treatment for 3h, and stirring for 24h to obtain a uniformly dispersed mixed solution. The mixed solution is spread on a PVC plate,the thickness of the spread film is set to be 150 mu m, the spread film is volatilized for 5mins, then the spread film is quickly immersed into 5L of propanol for 10 minutes and solidified to form the porous composite film. Calcining the composite membrane for 4 hours at 800 ℃ in an argon atmosphere to obtain NaFePO with the thickness of 35 mu m4@3DPC self-supporting electrode. The cell assembly was the same as in example 1.
Example 9: (preparation of NaVPO4F @3DPC self-supporting electrode)
1.2g of polyimide (organic polymer resin) was weighed out and added to 8.8g of DMF, and stirred for 6 hours until complete dissolution to give a 12% resin solution. To the resin solution was added 1.8g of NaVPO4And F (electrode material), stirring for 12 hours, then carrying out ultrasonic treatment for 3 hours, and stirring for 24 hours to obtain a uniformly dispersed mixed solution. And flatly paving the mixed solution on a glass plate, setting the film paving thickness to be 150 mu m, volatilizing for 5mins, quickly immersing in 5L of propanol for 10 minutes, and curing to form the porous composite film. Calcining the composite membrane for 4 hours at 750 ℃ in an argon atmosphere to obtain NaVPO with the thickness of 35 mu m4F @3DPC self-supporting electrode. The battery assembly is the same
Example 1.
Example 10: (preparation of Na)3V2O2(PO4)2F @3DPC self-supporting electrode)
0.6g of polyvinylpyrrolidone (organic polymer resin) was weighed into 9.4g of DMAC, and stirred for 7 hours to be completely dissolved, thereby forming a 6% resin solution. To the resin solution was added 1.2g of Na3V2O2(PO4)2And F (electrode material), stirring for 12 hours, then carrying out ultrasonic treatment for 3 hours, and stirring for 24 hours to obtain a uniformly dispersed mixed solution. And flatly paving the mixed solution on a glass plate, setting the paving thickness to be 150 mu m, volatilizing for 5mins, quickly immersing in 5L of propanol for 10 minutes, quickly immersing in 5L of methanol, and curing to form the porous composite membrane. Calcining the composite membrane at 800 ℃ for 4h in argon atmosphere to obtain Na with the thickness of 25 mu m3V2O2(PO4)2F @3DPC self-supporting electrode. The cell assembly was the same as in example 1.
Example 11: (preparation of Na)3V2(PO4)2OF2@3DPC self-supporting electrode)
1.0g of polybenzimidazole (organic polymer resin) was weighed into 9g of DMAC, and stirred for 6 hours to be completely dissolved, to form a 10% resin solution. To the resin solution was added 1.0g of Na3V2(PO4)2O F2(electrode material), stirring for 12h, then carrying out ultrasonic treatment for 3h, and stirring for 24h to obtain a uniformly dispersed mixed solution. And flatly paving the mixed solution on a glass plate, setting the film paving thickness to be 150 mu m, volatilizing for 5mins, quickly immersing in 5L of propanol for 10 minutes, and curing to form the porous composite film. Calcining the composite membrane at 800 ℃ for 4h in argon atmosphere to obtain Na with the thickness of 35 mu m3V2(PO4)2O F2@3DPC self-supporting electrode. The cell assembly was the same as in example 1.
Example 12: (preparation of MoS2@3DPC self-supporting electrode)
1.5g of polyvinylpyrrolidone (organic polymer resin) was weighed into 8.5g of NMP, and stirred for 8 hours to be completely dissolved to form a 15% resin solution. To the resin solution was added 1.5g of MoS2(electrode material), stirring for 12h, then carrying out ultrasonic treatment for 3h, and stirring for 24h to obtain a uniformly dispersed mixed solution. And flatly paving the mixed solution on a glass plate, setting the film paving thickness to be 150 mu m, volatilizing for 5mins, quickly immersing in 5L of propanol for 10 minutes, and curing to form the porous composite film. Calcining the composite membrane for 5 hours at 800 ℃ in an argon atmosphere to obtain MoS with the thickness of 30 mu m2@3DPC self-supporting electrode. The cell assembly was the same as in example 1.
Example 13: (preparation of TiO)2@3DPC self-supporting electrode)
1.0g of polybenzimidazole (organic polymer resin) was weighed into 9g of DMAC, and stirred for 4 hours to be completely dissolved, to form a 10% resin solution. 1.0g of TiO was added to the resin solution2(electrode material), stirring for 12h, then carrying out ultrasonic treatment for 3h, and stirring for 24h to obtain a uniformly dispersed mixed solution. And flatly paving the mixed solution on a glass plate, setting the film paving thickness to be 150 mu m, volatilizing for 5mins, quickly immersing in 5L of propanol for 10 minutes, and curing to form the porous composite film. Calcining the composite membrane for 4 hours at 800 ℃ in an argon atmosphere to obtain TiO with the thickness of 25 mu m2@3DPC self-supporting electrode.The cell assembly was the same as in example 1.
Example 14: (preparation of Na2Ti3O7@3DPC self-supporting electrode)
0.6g of polyvinylpyrrolidone (organic polymer resin) was weighed into 9.4g of DMAC, and stirred for 5 hours to be completely dissolved, thereby forming a 6% resin solution. To the resin solution was added 1.2g of Na2Ti3O7(electrode material), stirring for 12h, then carrying out ultrasonic treatment for 3h, and stirring for 24h to obtain a uniformly dispersed mixed solution. And flatly paving the mixed solution on a glass plate, setting the film paving thickness to be 150 mu m, volatilizing for 5mins, quickly immersing in 5L of propanol for 10 minutes, and curing to form the porous composite film. Calcining the composite membrane at 800 ℃ for 4h in argon atmosphere to obtain Na with the thickness of 20 mu m2Ti3O7@3DPC self-supporting electrode. The cell assembly was the same as in example 1.
Comparative example 1 (self-supporting Na prepared by electrospinning)3V2(PO4)3Electrode):
reacting NaH with2PO4、NH4VO3And citric acid in a mass ratio of 3:2:2 in deionized water to give solution a. Dissolving PVP into deionized water, and stirring for 4h to form a uniform solution to obtain a solution B, wherein the content of the PVP in the solution is 10 wt%. Solution a was then slowly added to solution B and stirred for two hours to give the final electrospun solution. Adding the electrostatic spinning into a 5ml syringe with a stainless steel needle, placing an aluminum foil as a collector at a distance of 15cm from the needle, and then carrying out electrostatic spinning at a voltage of 15kV to obtain an electrospun membrane. Pre-sintering the obtained electrospun membrane at 300 ℃ for 3h in argon atmosphere, and sintering the electrospun membrane at 800 ℃ for 8h to obtain the final self-supporting Na with the thickness of 30 mu m3V2(PO4)3And an electrode. The cell assembly was the same as in example 1.
Comparative example 2 (non self-supporting Na)3V2(PO4)3Electrode):
NVP (electrode material), Super P and PVDF are added into 2.5% PVDF solution, and the mass ratio of NVP to Super P to PVDF is 7: 2: 1, stirring for 5 hours to prepare uniform slurry, and thenThe slurry was drawn down on an aluminum foil to a thickness of 80 μm. The electrode was dried in an oven at 100 ℃ for 12h to give 30 μm thick non-self-supporting Na3V2(PO4)3And an electrode. The cell assembly was the same as in example 1.
TABLE 1
As can be seen from table 1, the self-supporting examples and comparative example 1 have a low mass of the electrode, resulting in a higher overall energy density, relative to the unsupported comparative example 2, due to the absence of the current collector, conductive carbon and binder. Meanwhile, the electrode has a three-dimensional conductive carbon network and a porous electrode structure, so that the electrolyte is favorably infiltrated, sodium ions are favorably diffused, and electrons are conducted, and the electrode has excellent rate capability and cycle performance. In the aspect of preparation process, the electrostatic spinning process of comparative example 1 is not suitable for industrial application and large-scale production due to relatively complicated process, long time consumption and high energy consumption, and in contrast, the embodiment adopts the membrane preparation process, so the process is simple, the preparation time is short, the energy consumption is low, and the large-scale application and the industrial production are easier. Also, the examples showed more excellent performance than comparative example 1 and comparative example 2.
As can be seen from fig. 1, the rate performance of example 1 is significantly better than the rate performance of comparative examples 1 and 2. At 0.5C, example 1 showed 117mAh g-1The specific capacity of (A) is close to the theoretical specific capacity, and comparative examples 1 and 2 respectively show 111mAh g-1、107mAh g-1The specific capacity of (a), the initial specific capacity of example, is higher than that of comparative example. At a high rate of 40C, the specific capacity of example 1 was 110mAh g-1The 94% of the 0.5C specific capacity is still maintained, and the excellent capacity retention rate is achieved, which is mainly that the embodiment 1 has a porous structure and a three-dimensional conductive network, and the ion diffusion and the electron conduction are fast, so that the high rate performance is shown. While comparative examples 1 and 2 showed specific capacities of 15mAh g-1 and 66mAh g-1, respectively, it can be seen that the specific capacities of the examples were 40CThe amount is much higher than comparative examples 1 and 2, and example 1 has excellent rate performance.
As can be seen from fig. 2, the cycle performance of example 1 is significantly better than the rate performance of comparative examples 1 and 2. At 1C, example 1 showed 91mAh g-1After 100 circles of activation, the specific capacity reaches 106mAh g-1The specific capacity is improved to a certain extent, and after 1000 times of circulation, the specific capacity reaches 114mAhg-1The specific capacity of (a) is close to the theoretical specific capacity, and the capacity does not have any attenuation within 1000 cycles. After 1000 cycles, the specific capacity of the material in example 1 can be close to the theoretical specific capacity, and the material shows extremely excellent cycling performance. While comparative examples 1 and 2 showed 104mAh g at 1C-1、103mAh g-1After 200 cycles, the initial specific capacity shows the specific capacities of 33mAh g-1 and 39mAh g-1, and the capacity retention rates are respectively 32% and 38%, which are obviously different from those of the embodiment 1. It can be seen that comparative example 1 exhibited much higher cycle performance than comparative example 1 and comparative example 2.
Example 2 showed 114mAh g at 0.5C-1The initial specific capacity of the resin is 76mAh g under the high multiplying power of 40C-1. At 1C, example 2 showed 109mAh g-1The specific capacity of the resin shows 102mAh g after 1000 cycles-1The capacity retention ratio of (2) was 94%. The ratio of the polymeric resin to the active material of example 2 was changed from that of preferred example 1 and was not within the preferred range. The rate capability and cycle performance of example 2 are somewhat reduced, mainly because the ratio of the active material in example 2 is reduced, the carbon content is much higher than that in example 1, and the thicker carbon layer can obstruct the diffusion of sodium ions, thereby limiting Na3V2(PO4)3The electrochemical performance of (2) is exerted.
Example 3 at 0.5C showed 116mAh g-1The initial specific capacity of the resin is 83mAh g under the high multiplying power of 40C-1. At 1C, example 3 showed 110mAh g-1Specific capacity of (2) after 1000 cyclesAfter the ring, 109mAh g was exhibited-1The capacity retention rate is close to 100 percent. The solvent volatilization time for example 3 was increased compared to the preferred example 1 and was not within the preferred range. The rate performance of example 3 is somewhat degraded while the cycle performance is essentially unchanged. This is mainly because the pores of the electrode shrink after the volatilization time is prolonged beyond the preferable range, so that the diffusion rate of sodium ions is reduced and the rate performance is attenuated to a certain extent.
Example 4 showed 113mAh g at 0.5C-1The initial specific capacity of the resin is 73mAh g under the high multiplying power of 40C-1. At 1C, example 4 showed 111mAh g-1The specific capacity of the resin shows 101mAh g after 1000 cycles-1The capacity retention rate is close to 91 percent. The immersion time of example 4 in the poor solvent was shorter than that of preferred example 1, and was not within the preferred range. The rate capability and cycle performance of example 4 were somewhat degraded. This is mainly because the immersion time in the poor solvent is shortened, the curing time of the film is shortened, and the curing of the film is insufficient, so that the pore distribution of the finally obtained electrode is not uniform, and the diffusion rate of sodium ions and the diffusion rate of electrons are reduced, thereby deteriorating the rate capability.
Example 5 showed 112mAh g at 0.5C-1The initial specific capacity of the resin is 44mAh g under the high multiplying power of 40C-1. At 1C, example 5 showed 108mAh g-1The specific capacity of the resin shows 89mAh g after 1000 cycles-1The capacity retention rate is close to 82 percent. Example 5 the thickness of the electrode was increased by a factor of 5 to that of example 1 and was outside the preferred range. The rate capability and cycle capability of example 5 showed a more significant decrease. The thickness of the electrode has a great influence on the performance of the electrode, when the thickness of the electrode is increased, the diffusion path of sodium ions and electrons is increased, the diffusion time of the sodium ions and the electrons is increased, the relative diffusion speed of the sodium ions and the electrons is reduced, and the electrochemical performance of the electrode is reduced.
Example 6 at 0.5C showed 105mAh g-1At an initial specific capacity of40C high rate, the specific capacity is 52mAh g-1. At 1C, example 6 showed 100mAh g-1The specific capacity of the resin shows 78mAh g after 1000 cycles-1The capacity retention rate is close to 78 percent. Example 6 the thickness of the electrode was increased by a factor of 5 to that of example 1 and was outside the preferred range. Example 6 used a higher concentration of polymeric resin than example 1, and was outside the preferred range. The rate capability and cycle capability of example 6 showed a more significant decrease. The concentration of the polymer resin has a great influence on the performance of the electrode, and when the concentration of the polymer resin is increased beyond a preferable range, the carbon content of the electrode after carbonization is increased, the carbon layer becomes high, and the transmission of sodium ions is hindered, so that the electrochemical performance is reduced.
As can be seen from the SEM image of fig. 3, example 1 has a uniform three-dimensional conductive carbon network, which facilitates electron conduction. Meanwhile, the cross section of the embodiment 1 is represented by uniform spongy holes, the size of each hole is about 1um, the continuous through macropores can ensure the sufficient infiltration of the electrolyte, and a continuous sodium ion transmission channel is formed inside the electrode, so that the rapid diffusion of sodium ions in the electrode is ensured, and the rapid diffusion of the sodium ions can also be ensured even under high multiplying power. In addition, as can be seen from the Raman diagram of FIG. 4, I of example 1D/IGThis means that, in the carbon layer of the electrode of example 1, graphitized carbon is dominant, and such highly graphitized carbon can effectively improve the conductivity of the conductive carbon. From the XPS survey in FIG. 5, it can be seen that example 1 contains not only carbon but also certain amounts of N and O. The N and O-containing positions are easy to form carbon layers with defects, the defects can further improve the conductivity of the three-dimensional conductive carbon network, nitrogen or oxygen atoms at the defects can be effectively combined with an active material, the binding force of the whole electrode is improved, and electrons can be rapidly conducted between the carbon network and the active material. As can be seen from the N1s spectrum of fig. 6, N is mainly present in the form of pyridine N and pyrrole N, which form defects on the carbon layer, and the defect sites ensure that sodium ions rapidly pass through the carbon layer. Moreover, the carbon coating can also inhibit the material from being charged and dischargedThe volume change of the structure is ensured, and the cycle performance of the material is improved. Overall, example 1 exhibited excellent rate performance and cycling performance due to rapid sodium ion diffusion, electron conduction, and good carbon coating. The method for preparing the sodium-ion battery electrode is very suitable for large-scale production due to excellent performance, simple preparation process and high energy density of the embodiment.
Claims (8)
1. A preparation method of a three-dimensional porous self-supporting electrode is characterized by comprising the following steps: the self-supporting electrode is prepared by the following steps:
1) adding one or more than two of organic polymer resins into a solvent, and fully stirring for 0.5-48 h at the temperature of 20-100 ℃ to prepare a solution A; and then dispersing an electrode material in the solution A, wherein the mass ratio of the electrode material to the polymer resin is 1: 10-20: 1 (preferably 1: 2-8: 1), and uniformly mixing and dispersing to obtain a solution B;
2) pouring the solution B prepared in the step (1) on a non-woven fabric substrate or directly on a flat plate, volatilizing the solvent for 0-60 minutes, then soaking the whole solution B in a poor solvent of resin for 1-300 minutes, and preparing a porous membrane at the temperature of 0-60 ℃;
3) drying the membrane prepared in the step (2) at 0-200 ℃ for 1-24 h to prepare a composite membrane;
4) calcining the composite membrane prepared in the step (3) at high temperature to obtain a self-supporting electrode;
the organic polymer resin in the step 1) is one or more than two of polysulfone, polyketone, polyimide, polybenzimidazole, polyvinyl pyridine, polymethyl methacrylate and polyacrylonitrile.
2. The method of claim 1, wherein: when the organic polymer resin in the step 1) is polysulfone, polyketone, polyimide, polybenzimidazole, polyvinyl pyridine or polymethyl methacrylate, the high-temperature calcination process in the step 4) is to calcine for 1-24 hours at 600-1000 ℃ under the protection of inert atmosphere;
when the organic polymer resin in the step 1) is polyacrylonitrile, the high-temperature calcination process comprises the steps of pre-oxidizing for 0.5-12 hours in an oxygen atmosphere at 200-400 ℃, and then calcining for 1-24 hours at 600-1000 ℃ under the protection of an inert atmosphere.
3. The method of claim 1, wherein: the solvent of the organic polymer resin in the step 1) is one or more than two of DMSO, DMAC, NMP and DMF; wherein the concentration of the organic polymer resin in the solution is 2-70 wt%, preferably 5-20 wt%.
4. The method of claim 1, wherein: the electrode material in the step 1) comprises sodium vanadium phosphate (Na)3V2(PO4)3) Sodium vanadium fluorophosphate (NaVPO)4F、Na3V2Ox(PO4)2F3-xWherein x is more than or equal to 0 and less than or equal to 2), sodium ferric phosphate (NaFePO)4) Sodium-based transition metal oxide (NaCrO)2,NaVO2) Sodium titanate (Na)2Ti3O7) Sodium titanium phosphate (NaTi)2(PO4)3) Titanium dioxide (TiO)2) Molybdenum disulfide (MoS)2) One or more of tin (Sn) and carbon (C).
5. The method of claim 1, wherein: the poor solvent of the resin in the step 2) is one or more than two of methanol, ethanol, propanol, isopropanol and carbon tetrachloride.
6. The method of claim 1, wherein: the solvent in the step 2) is volatilized for 0-60 minutes, preferably 0-10 minutes, and the resin is immersed in the poor solvent for 1-300 minutes, preferably 5-100 minutes.
7. A self-supporting electrode obtainable by the process according to any one of claims 1 to 6, said electrode having a thickness of from 10 to 150 μm (preferably from 20 to 80 μm).
8. Use of the self-supporting electrode of claim 7 as a positive or negative electrode in a sodium ion battery.
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| CN111900373A (en) * | 2020-08-04 | 2020-11-06 | 大连理工大学 | Preparation method of lithium dendrite-resistant lithium metal battery cathode side separator material |
| CN111900373B (en) * | 2020-08-04 | 2021-08-06 | 大连理工大学 | Preparation method of lithium dendrite-resistant lithium metal battery cathode side separator material |
| CN112349881A (en) * | 2020-11-17 | 2021-02-09 | 河南电池研究院有限公司 | Manufacturing method of flexible current collector-free electrode |
| CN112837942A (en) * | 2021-01-18 | 2021-05-25 | 武汉工程大学 | Preparation method of composite electrode material |
| CN112837942B (en) * | 2021-01-18 | 2022-09-27 | 武汉工程大学 | Preparation method of composite electrode material |
| CN114530573A (en) * | 2022-02-23 | 2022-05-24 | 广东工业大学 | Flexible self-supporting anode for sodium ion battery and preparation method and application thereof |
| CN114530573B (en) * | 2022-02-23 | 2023-12-12 | 广东工业大学 | Flexible self-supporting positive electrode for sodium ion battery and preparation method and application thereof |
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