A black phosphorene / MXene composite film electrode with piezoelectric properties and its preparation method and application
Through the self-assembly method of urea modification MXene and black phosphorene, the uniformity problem of black phosphorene/MXene composite materials is solved, the preparation process is simplified, the electrochemical performance and piezoelectric characteristics are improved, and the electrode preparation is achieved is efficient.
Patent Information
- Application Number
- CN202210726286.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-06-24
- Publication Date
- 2024-12-10
- Estimated Expiration
- 2042-06-24
AI Technical Summary
In the prior art, when preparing black phosphorene/MXene composites, its uniformity cannot be guaranteed, resulting in volume expansion effect and electrode capacity decreases, and the preparation process is complicated and energy-consuming.
The urea-modified MXene material is self-assembled with black phosphorene, and the C-O-P covalent bond is used to form urea and black phosphorene, which induces the uniform distribution of black phosphorene between the MXene layers, and combines the film-forming properties of MXene to directly form a self-supported composite The membrane electrode avoids the slurry adjustment coating step and simplifies the preparation process.
The uniform distribution of black phosphorene is achieved, the volume expansion effect is reduced, the electrochemical performance and cyclic performance is improved, the preparation process is simplified, the inactive substances are reduced, the battery energy density is improved, and significant piezoelectric characteristics are demonstrated.
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Abstract
Description
Technical Field
[0001] The present invention belongs to the field of electrode technology, and in particular refers to a black phosphorene / MXene composite film electrode with piezoelectric properties and a preparation method and application thereof. Background Art
[0002] As an emerging two-dimensional layered material, black phosphorus has attracted extensive attention from researchers due to its unique physical, chemical and electrical properties. In secondary batteries such as alkali metal ion batteries, black phosphorus has become one of the most promising negative electrode materials for alkali metal ion batteries due to its ultra-high theoretical specific capacity. For example, in lithium-ion batteries, the theoretical specific capacity of black phosphorus can reach 2596 mAh g -1 , which is much higher than the 372mAh g of commercial graphite anode materials currently used. -1 Theoretical specific capacity (Adv.EnergyMater.2016,6,1502409). However, the black phosphorus negative electrode will undergo a serious volume expansion effect (300%) during the battery charging and discharging process, which makes it impossible for the active material powder and the current collector to be in close contact, thereby increasing the internal resistance of the battery. In addition, its poor conductivity further hinders its further development as a negative electrode material. Inspired by graphene obtained by exfoliation from graphite, studies have shown that when the bulk layered black phosphorus is exfoliated into a single-layer or few-layer structure of black phosphorene (Phosphorene), its volume expansion effect during charging and discharging will be greatly reduced, and more active sites can be exposed to store alkali metal ions, effectively improving the battery capacity (Adv.EnergyMater.2018,8,1801514). In addition, few-layer black phosphorene also exhibits unique piezoelectric properties (Adv.Mater.2020,32,1905795), and theoretically has good ferroelectricity. This characteristic makes it possible for it to have both a ferroelectric spontaneous polarization electric field and an intralayer electric field due to volume changes during the process of lithium ion insertion and extraction when used as a negative electrode material. The generation of this spontaneous polarization electric field and piezoelectric field will collectively provide additional power for the transmission of ions, reduce the energy barrier for lithium ion insertion and extraction, and thus further improve the diffusion kinetics of lithium ions. At the same time, unlike the traditional graphite negative electrode, which is prone to lithium precipitation safety or dead lithium capacity decay at high rate charge and discharge cycles, the black phosphorene-based negative electrode with a slightly higher negative electrode potential (relative to lithium metal) and faster lithium ion diffusion kinetics may inhibit the easy lithium precipitation safety or dead lithium capacity decay at high rate charge and discharge cycles. Therefore, the controllable oriented growth black phosphorene-based material shows a high application potential as a high-capacity fast-charging or low-temperature fast-charging negative electrode for lithium-ion batteries.
[0003] Liquid phase exfoliation has become the mainstream preparation method for preparing single-layer and few-layer structure two-dimensional materials, including MoS2, WS2 and black phosphorene, by virtue of its high yield and simple and efficient steps. Many researchers can prepare a large amount of black phosphorene or black phosphorene quantum dots by using N-methylpyrrolidone (NMP) solvent (Adv. Funct. Mater. 2015, 25, 6996; Angew. Chem. Int. Ed. 2015, 54, 3653). However, the prepared black phosphorene cannot be directly used as the negative electrode material of ion batteries, because they are very easy to be stacked in the absence of a carrier, so that the prepared black phosphorene is stacked into a multilayer black phosphorus structure, thereby losing the meaning of exfoliation. Therefore, the current modification of black phosphorene is usually to find a suitable ligand to form a composite material with it. This ligand should meet the characteristics of high conductivity and the ability to be closely connected with black phosphorene. In view of this, the ligand materials currently studied are mainly divided into two categories: carbon-based materials represented by carbon nanotubes (CNT) and graphene (Adv. Funct. Mater. 2020, 30, 1909372; Small 2017, 13, 1700758), and Ti3C2T x MXene materials represented by (ACS Nano 2020, 14, 3651). These ligands can provide a good conductive framework for black phosphorene, and can tightly link black phosphorene with the ligand itself through chemical bonds (carbon-based materials and black phosphorene can form CP covalent bonds, and MXene can form Ti-P covalent bonds with black phosphorene). In this way, the service stability of the active substance few-layer black phosphorus can be well protected, and the electrochemical properties of few-layer black phosphorus can be fully utilized. Therefore, these composite materials show good performance in subsequent electrochemical tests.
[0004] At present, the preparation methods of these composites are all achieved through simple physical mixing methods or self-assembly methods. For example, the composite of black phosphorene and carbon-based materials is mostly achieved through high-energy ball milling. Long-term high-energy ball milling not only easily generates high temperature and high mechanical force, which makes black phosphorus easy to damage and the consistency of electrode quality cannot be guaranteed, but also requires liquid nitrogen cooling, which is energy-consuming and increases the preparation cost; while the composite of black phosphorene and MXene is achieved through a self-assembly process of ultrasonic stirring. However, these synthesis methods cannot guarantee the uniformity of the composite between black phosphorene and the ligand, making it easy for black phosphorene to be unevenly distributed on the surface or layer of the ligand and to easily aggregate and stack again, causing a serious volume expansion effect and shielding some active sites, resulting in a decrease in electrode capacity and cycle performance. In addition, after the usual composite material is prepared, it is necessary to go through processes such as slurry coating to prepare the electrode sheet. During the slurry adjustment process, the composite material also needs to be mixed with conductive carbon black (Super P), binder (PVDF), etc., and the insufficient mixing process will further aggravate the heavy accumulation of black phosphorene, seriously affecting the electrical performance of the battery. At the same time, the volume expansion effect caused will also make it impossible for the active material and the current collector to be in close contact, increase the internal resistance of the battery, and further reduce the cycle performance of the battery. Summary of the invention
[0005] In order to solve the above technical problems, the present invention provides a black phosphorene / MXene composite membrane electrode with piezoelectric properties and its preparation method and application. The present invention is a simple and efficient composite solid-state membrane method of black phosphorene and MXene materials in a green water environment. The method is to self-assemble black phosphorene and urea-modified MXene materials, and urea can be spontaneously adsorbed between MXene layers. When composited with black phosphorene, these ureas located between MXene layers can in situ induce black phosphorene to enter the interlayer of MXene by forming COP covalent bonds with black phosphorene, so that black phosphorene is more inclined to be evenly distributed between MXene layers rather than accumulated on the surface during the self-assembly process, effectively ensuring its high capacity and cycle performance. At the same time, utilizing the film-forming characteristics of MXene, MXene containing embedded black phosphorene can form a self-supporting composite film after vacuum filtration and freeze-drying, which can be directly used as the membrane electrode of the negative electrode of the battery, avoiding the slurry coating steps required for the preparation of conventional battery negative electrodes, and further shortening the preparation process.
[0006] The first object of the present invention is to provide a method for preparing a black phosphorene / MXene composite film electrode with piezoelectric properties, comprising the following steps:
[0007] (1) Under inert conditions, dispersing block black phosphorus in an organic solvent, performing ultrasonic exfoliation for 4-8 hours to obtain black phosphorene, and dispersing the black phosphorene in the solvent to obtain a black phosphorene dispersion;
[0008] (2) Add urea to the MXene solution, mix and stir to obtain a urea-adsorbed MXene solution;
[0009] (3) Under inert conditions, the black phosphorene dispersion obtained in step (1) and the urea-adsorbed MXene solution prepared in step (2) are mixed, stirred and ultrasonically treated, and filtered and dried to obtain the black phosphorene / MXene composite film, which is directly used as a self-supporting electrode (after filtration and drying, it can be directly used as a negative electrode of a lithium battery), i.e., the black phosphorene / MXene composite film electrode.
[0010] In one embodiment of the present invention, in step (1), ultrasonic exfoliation is a physical process, not a chemical reaction process. It is a process in which additional energy is given to the raw material by ultrasound or other means, so that the van der Waals force between the blocky black phosphorus is broken, so that it is exfoliated from the block (hundreds or thousands of layers or more are called a block) into a single layer or a few layers of black phosphorus (generally less than 10 layers, which can be called black phosphorene).
[0011] In one embodiment of the present invention, in step (1), the inert condition is argon.
[0012] In one embodiment of the present invention, in step (1), the organic solvent is selected from one or more of N-methylpyrrolidone, ethanol, isopropanol and N,N-dimethylformamide.
[0013] In one embodiment of the present invention, in step (1), the solvent is selected from water; the dispersion in water is mainly for the subsequent composite with MXene, because MXene generally requires water as a solvent.
[0014] In one embodiment of the present invention, in step (1), the concentration of the blocky black phosphorus in the organic solvent is 1-5 mg / mL.
[0015] In one embodiment of the present invention, in step (2), the mass ratio of the urea to the MXene in the MXene solution is 1:15-1:20.
[0016] In one embodiment of the present invention, in step (3), the mass ratio of black phosphorene in the black phosphorene dispersion to MXene in the urea-adsorbed MXene solution is 1:2-1:5.
[0017] In one embodiment of the present invention, in step (3), the filter paper used for suction filtration is selected from Celgard 3501, polyethersulfone microporous filter membrane or polypropylene microporous filter membrane.
[0018] In one embodiment of the present invention, step (3) further comprises freeze-drying for 10-24 hours after filtration.
[0019] The second object of the present invention is to provide a black phosphorene / MXene composite membrane electrode obtained by the preparation method.
[0020] The third object of the present invention is to provide the application of the black phosphorene / MXene composite film electrode in the preparation of nanogenerators and piezoelectric electronic products.
[0021] The above technical solution of the present invention has the following advantages compared with the prior art:
[0022] 1. The present invention uses urea as an intermediate to induce the directional assembly process of black phosphorene. MXene itself has the property of adsorbing urea, which allows urea to reach the interlayer of MXene through a simple stirring process. In the subsequent self-assembly process, urea anchors black phosphorene in the interlayer of MXene by forming COP covalent bonds with black phosphorene, ensuring that black phosphorene is evenly distributed in the interlayer of MXene, effectively avoiding its heavy stacking or uneven distribution in a certain place, and greatly reducing its volume expansion effect during the charge and discharge process.
[0023] 2. The black phosphorene embedded in the interlayer is protected by MXene layers above and below. This sandwich structure can effectively suppress the volume expansion of black phosphorene during the charging and discharging process, and build a good conductive skeleton for it, effectively improving the electrochemical properties of the composite material.
[0024] 3. After vacuum filtration and freeze-drying, the prepared black phosphorene / MXene composite film can be directly used as a membrane electrode for the negative electrode of alkali metal ion batteries without the need for subsequent slurrying and coating with conductive carbon black and binder. This not only avoids the possibility of re-deposition of the added black phosphorene in the subsequent uneven slurrying process, but also simplifies the electrode preparation process, providing a simpler and more convenient electrode preparation method.
[0025] 4. Since the prepared composite membrane can be used directly as a membrane electrode, the entire membrane electrode is composed of active composite materials. Compared with the conventional battery negative electrode, there is no need to add conductive agents, binders and current collectors, which can greatly reduce the mass of inactive substances in the electrode and effectively improve the overall energy density of the battery.
[0026] 5. The prepared black phosphorene / MXene composite film has obvious piezoelectric properties. The internal electric field generated in the layer can effectively promote the diffusion dynamics of lithium ions, so that it still has good electrochemical properties at room temperature and low temperature.
[0027] 6. Since black phosphorene can alloy with a variety of alkali metals to provide capacity, the prepared black phosphorene / MXene composite film can be directly used in a variety of alkali metal ion battery systems, including lithium ion batteries, sodium ion batteries, potassium ion batteries, etc. Similarly, the piezoelectric properties of the composite also make it have great application potential in the fields of self-charging electrodes and nanogenerators that use pressure / deformation as charging. Since these new piezoelectric devices have high requirements on the piezoelectricity and conductivity of the electrodes, and it is difficult for common electrodes to meet the above conditions at the same time, the composite electrode we prepared can better meet the above conditions, and thus play a huge application potential in these fields. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein
[0029] Figure 1 This is an atomic force microscope image of black phosphorene prepared in Example 1 of the present invention;
[0030] Figure 2 This is the XPS graph of P 2p of the black phosphorene / MXene composite film prepared in Example 1 of the present invention;
[0031] Figure 3 The cross-sectional SEM image and HRTEM image of the black phosphorene / MXene composite film prepared in Example 2 of the present invention;
[0032] Figure 4 The piezoelectric properties of the black phosphorene / MXene composite film prepared in Example 2 of the present invention are tested;
[0033] Figure 5 The four black phosphorus ene / MXene composite films with different ratios prepared in Examples 1-4 of the present invention and the bulk black phosphorus electrode and MXene electrode in the comparative example were heated at 100 mAg. -1 Comparison of electrochemical performance under different current densities;
[0034] Figure 6 The charge and discharge curves of Example 3 of the present invention under different low temperature conditions are shown. DETAILED DESCRIPTION
[0035] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.
[0036] Example 1
[0037] (1) 0.5 g of blocky black phosphorus powder was dispersed in 100 mL of N-methylpyrrolidone solvent and ultrasonically treated for 6 hours. The entire stripping process was carried out in an ice bath and under argon atmosphere protection to prevent oxidation of black phosphorus. Then the unstripped black phosphorus residue was removed by centrifugation at 1500 r / min, followed by another centrifugation at 14000 r / min for 30 minutes to collect the few-layered black phosphorus ene, which was then washed three times with ethanol and deionized water (14000 r / min, 30 minutes), and then redispersed in 50 ml of deionized water for later use. The specific concentration of black phosphorus ene can be calculated by subtracting the dry weight of the unstripped black phosphorus removed in the first centrifugation from the total mass.
[0038] (2) 2 g of LiF was placed in 40 mL of hydrochloric acid (9 M) and stirred for 30 minutes, and then 2 g of Ti3AlC2 powder was slowly added. After etching at 35 ° C for 24 hours, the suspension was removed, and the residue was washed by centrifugation at 3500 r / min in deionized water until its pH value was about 6 and multilayer MXene was obtained. Subsequently, it was further ultrasonically treated for 2 hours in an ice bath and under argon protection. The solution was then centrifuged at 3500 r / min for 30 minutes, and the filter residue was removed to obtain a few-layer MXene solution. The specific concentration of the solution can be calculated by weighing the mass of the dry MXene film made from a known volume of the prepared MXene solution.
[0039] (3) Urea was then added to the MXene solution and magnetically stirred for 1 hour, with the mass ratio of urea to MXene being 1:15. After the urea was dispersed, the black phosphorene solution was added, wherein the mass ratio of black phosphorene to MXene was 1:2. This was followed by 4 hours of magnetic stirring and 4 hours of ultrasonic treatment. An argon atmosphere and an ice bath were used throughout the self-assembly process to prevent oxidation. Vacuum filtration was then performed and Celgard 3501 membrane was selected as the filter paper. After a 24-hour freeze-drying process after filtration, the Celgard 3501 membrane was removed to obtain a self-supporting black phosphorene / MXene nanocomposite film.
[0040] Example 2
[0041] (1) 0.5 g of blocky black phosphorus powder was dispersed in 100 mL of isopropanol solvent and ultrasonically treated for 6 hours. The entire stripping process was carried out in an ice bath and under argon atmosphere protection to prevent oxidation of black phosphorus. Then the unstripped black phosphorus residue was removed by centrifugation at 1500 r / min, followed by another centrifugation at 14000 r / min for 30 minutes to collect the few-layered black phosphorus ene, which was then washed three times with ethanol and deionized water (14000 r / min, 30 minutes), and then redispersed in 50 ml of deionized water for later use. The specific concentration of black phosphorus ene can be calculated by subtracting the dry weight of the unstripped black phosphorus removed in the first centrifugation from the total mass.
[0042] (2) 2 g of LiF was placed in 40 mL of hydrochloric acid (9 M) and stirred for 30 minutes, and then 2 g of Ti3AlC2 powder was slowly added. After etching at 35 ° C for 24 hours, the suspension was removed, and the residue was washed by centrifugation at 3500 r / min in deionized water until its pH value was about 6 and multilayer MXene was obtained. Subsequently, it was further ultrasonically treated for 2 hours in an ice bath and under argon protection. The solution was then centrifuged at 3500 r / min for 30 minutes, and the filter residue was removed to obtain a few-layer MXene solution. The specific concentration of the solution can be calculated by weighing the mass of the dry MXene film made from a known volume of the prepared MXene solution.
[0043] (3) Urea was then added to the MXene solution and magnetically stirred for 1 hour, with the mass ratio of urea to MXene being 1:15. After the urea was dispersed, the black phosphorene solution was added, with the mass ratio of black phosphorene to MXene being 1:3. This was followed by 4 hours of magnetic stirring and 4 hours of ultrasonic treatment. An argon atmosphere and an ice bath were used throughout the self-assembly process to prevent oxidation. Vacuum filtration was then performed and Celgard 3501 membrane was selected as filter paper. After 12 hours of freeze drying after filtration, the Celgard 3501 membrane was removed to obtain a self-supporting black phosphorene / MXene nanocomposite film.
[0044] Example 3
[0045] (1) 0.5 g of blocky black phosphorus powder was dispersed in 100 mL of N-methylpyrrolidone solvent and ultrasonically treated for 6 hours. The entire stripping process was carried out in an ice bath and under argon atmosphere protection to prevent oxidation of black phosphorus. Then the unstripped black phosphorus residue was removed by centrifugation at 1500 r / min, followed by another centrifugation at 14000 r / min for 30 minutes to collect the few-layered black phosphorus ene, which was then washed three times with ethanol and deionized water (14000 r / min, 30 minutes), and then redispersed in 50 ml of deionized water for later use. The specific concentration of black phosphorus ene can be calculated by subtracting the dry weight of the unstripped black phosphorus removed in the first centrifugation from the total mass.
[0046] (2) 2 g of LiF was placed in 40 mL of hydrochloric acid (9 M) and stirred for 30 minutes, and then 2 g of Ti3AlC2 powder was slowly added. After etching at 35 ° C for 24 hours, the suspension was removed, and the residue was washed by centrifugation at 3500 r / min in deionized water until its pH value was about 6 and multilayer MXene was obtained. Subsequently, it was further ultrasonically treated for 2 hours in an ice bath and under argon protection. The solution was then centrifuged at 3500 r / min for 30 minutes, and the filter residue was removed to obtain a few-layer MXene solution. The specific concentration of the solution can be calculated by weighing the mass of the dry MXene film made from a known volume of the prepared MXene solution.
[0047] (3) Urea was then added to the MXene solution and magnetically stirred for 1 hour, with the mass ratio of urea to MXene being 1:15. After the urea was dispersed, the black phosphorene solution was added, with the mass ratio of black phosphorene to MXene being 1:5. This was followed by 4 hours of magnetic stirring and 4 hours of ultrasonic treatment. An argon atmosphere and an ice bath were used throughout the self-assembly process to prevent oxidation. Vacuum filtration was then performed and a polyethersulfone microporous filter membrane was selected as the filter paper. After 16 hours of freeze drying after filtration, the polyethersulfone microporous filter membrane was removed to obtain a self-supporting black phosphorene / MXene nanocomposite film.
[0048] Example 4
[0049] The experimental steps are the same as those in Example 1, except that the mass ratio of black phosphorene to MXene is 1:4.
[0050] Comparative Example
[0051] The bulk black phosphorus electrode was prepared by slurry coating method. The bulk black phosphorus, acetylene black and PVDF were mixed in a mass ratio of 8:1:1 and dissolved in N-methylpyrrolidone (NMP). After mixing and stirring, the mixture was coated on copper foil and placed in a vacuum oven at 120 °C for 12 h. After being rolled, the electrode sheets were cut into 12 mm diameter sheets for use. The average active material mass loaded was 1.5 mg cm -2 The MXene membrane electrode was obtained by direct filtration of the MXene solution, dried in a vacuum oven at 70°C for 12 h, and then sliced into pieces with a diameter of 12 mm and used directly as the negative electrode.
[0052] Performance Test:
[0053] The composite films obtained in Examples 1-3 were directly used as negative electrodes of lithium-ion batteries to assemble batteries, and the electrochemical performance was tested on a BlueDian 5V-10mA battery tester.
[0054] Battery assembly method: Use a slicer to cut the above composite membrane into 16 mm diameter discs, weigh and record the mass of the electrode sheet in a glove box, then use it directly as a membrane electrode and place it in the center of the battery positive electrode shell, add 0.2 mL of electrolyte, put in a 19 mm diameter Celgard 2400 diaphragm, add 0.2 mL of electrolyte again, then put in the lithium sheet, gasket, and spring sheet in turn, cover the negative electrode shell, seal the battery with a pneumatic sealing machine, and test it after standing for one day.
[0055] Test method: The battery was tested on a Blue Power 5V-10mA battery tester at 100mAg -1 The charge and discharge experiments were carried out in a certain voltage range with a current density of 1.
[0056] Test results:
[0057] Figure 1 Atomic force microscopy images of black phosphorene prepared in Example 1. These atomic force microscopy images clearly show that the thickness of the prepared black phosphorene nanosheets is between 2 and 4 nm (about 4 to 7 layers) and the lateral size is 100 to 500 nm, indicating the successful exfoliation of bulk black phosphorus by liquid phase exfoliation.
[0058] Figure 2 This is the XPS graph of P 2p of the black phosphorene / MXene composite film prepared in Example 1. As shown in the figure, two obvious peaks can be observed at 133.1eV and 134.8eV. This is because black phosphorus can form a PO-Ti bond with MXene, so the peak at 133.1eV can be attributed to this, rather than P x O y In addition, the peak at 134.8 eV is due to the formation of POC bonds by the addition of urea, which proves the successful bonding between urea and black phosphorene.
[0059] Figure 3 The cross-sectional scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM) images of the black phosphorene / MXene composite film prepared in Example 2 show a typical cross-sectional scanning electron microscope image of the black phosphorene / MXene composite film. Since MXene accounts for the majority, the nanocomposite film after filtration can still maintain its typical layered structure. The HRTEM image clearly shows the effective compounding of the two materials, and it can be observed that the black phosphorene is successfully embedded in the interlayer of the MXene.
[0060] Figure 4 is the piezoelectric coefficient d of the black phosphorene / MXene composite film obtained in Example 2 33 Test picture. Under the external force of 0.2N-2N, it can show a relatively stable 33 Piezoelectric coefficient (9.7-10pC / N). Thanks to the stable piezoelectric properties of the composite film, the volume change caused by the insertion / extraction of lithium ions can ensure the generation of an internal electric field, thereby providing an additional electric field power source for ion conduction, effectively increasing the ion diffusion rate and thus improving its rate performance and low-temperature performance.
[0061] Figure 5 The three black phosphorene / MXene composite films with different ratios prepared in Examples 1-4, the bulk black phosphorus electrode and the MXene electrode in the comparative example were charged at room temperature at 100 mA g -1 Comparison of electrochemical performance under current density. It can be seen from the figure that bulk black phosphorus exhibits the highest first-cycle discharge capacity, which is about 2110 mAh g -1However, due to the lack of ligand material to inhibit its volume expansion, it showed a rapid capacity decay in the initial 10 cycles, and its reversible specific capacity was only 102.7 mAh g after 100 cycles. -1 , showing poor cycle performance. The first cycle capacity of pure MXene is 320 mAh g -1 After 100 cycles, it can maintain 81.7 mAh g -1 The specific capacity of MXene / Phosphorus ene is too small to meet the capacity requirements of practical applications, but its highly conductive layered structure can serve as a framework for accommodating black phosphorene. For the prepared black phosphorene / MXene composite electrode, it can be seen that its electrical performance is related to the mass ratio between the two.
[0062] Generally speaking, since black phosphorene is the main contributor to capacity, a high black phosphorene content tends to have a higher initial capacity. However, it is difficult for too many black phosphorene nanosheets to find enough space to accommodate them, and they may restack or agglomerate, resulting in poor cycling performance. On the contrary, when MXene occupies a higher dominant position, the composite film electrode exhibits relatively stable cycling performance similar to that of the pure MXene electrode. In view of its excellent specific capacity and cycling performance, we selected the composite film with a ratio of black phosphorene to MXene of 1:3 as the best electrode for other electrochemical characterizations and tests. At 100mAg -1 At this current density, its initial discharge capacity can reach 1985.6 mAh g -1 , it can still maintain 848.3mAh g after 100 cycles -1 This indicates that the prepared black phosphorene / MXene film electrode with a mass ratio of 1:3 has good cycling performance.
[0063] Figure 6 The charge and discharge curves of the black phosphorene / MXene composite film prepared in Example 2 under different low temperature conditions. Due to the acceleration of the internal electric field generated by the piezoelectric property, the slow ion diffusion rate under low temperature conditions is improved. Even at -20°C, it still has a charge and discharge capacity of 567.8 mAh g -1 The discharge specific capacity shows that it can still maintain good performance under low temperature conditions.
[0064] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.
Claims
1. A method for preparing a black phosphorene / MXene composite film electrode with piezoelectric properties, characterized in that: The following steps are involved: (1) Under inert conditions, dispersing block black phosphorus in an organic solvent, performing ultrasonic exfoliation for 4-8 hours to obtain black phosphorene, and dispersing the black phosphorene in the solvent to obtain a black phosphorene dispersion; (2) Add urea to the MXene solution, mix and stir to obtain a urea-adsorbed MXene solution; (3) Under inert conditions, the black phosphorene dispersion obtained in step (1) and the urea-adsorbed MXene solution prepared in step (2) are mixed, stirred and ultrasonically treated, and filtered and dried to obtain the black phosphorene / MXene composite film, which is directly used as a self-supporting electrode, i.e., the black phosphorene / MXene composite film electrode.
2. The preparation method according to claim 1, characterized in that: In step (1), the inert condition is argon gas.
3. The preparation method according to claim 1, characterized in that: In step (1), the organic solvent is selected from one or more of N-methylpyrrolidone, ethanol, isopropanol and N,N-dimethylformamide.
4. The preparation method according to claim 1, characterized in that: In step (1), the concentration of the blocky black phosphorus in the organic solvent is 1-5 mg / mL.
5. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of the urea to the MXene in the MXene solution is 1:15-1:
20.
6. The preparation method according to claim 1, characterized in that: In step (3), the mass ratio of black phosphorene in the black phosphorene dispersion to MXene in the urea-adsorbed MXene solution is 1:2-1:
5.
7. The preparation method according to claim 1, characterized in that: In step (3), the filter paper used for suction filtration is selected from Celgard 3501, polyethersulfone microporous filter membrane or polypropylene microporous filter membrane.
8. The preparation method according to claim 1, characterized in that: Step (3) also includes freeze-drying for 10-24 hours after filtration.
9. A black phosphorene / MXene composite film electrode obtained by the preparation method according to any one of claims 1 to 8.
10. Use of the black phosphorene / MXene composite film electrode according to claim 9 in the preparation of nanogenerators and piezoelectric electronic products.