Bimetal selenide modified alkali metal negative electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of chemical power sources, in particular to a bimetallic selenide modified alkali metal negative electrode material and a preparation method and application thereof.The preparation method comprises the steps that prepared vanadium atom doped tungsten diselenide (VxWSe) powder is evenly coated on the surface of sodium / potassium metal, an adjustable interface protection layer is constructed, and the surface of the sodium / potassium metal is coated with the bimetallic selenide modified alkali metal negative electrode material; and the adsorption and transfer of sodium / potassium ions are optimized by utilizing the unique layered structure. The controllable interface protection layer can provide excellent dendrite growth prevention and desolvation functions, and the cycle life of the alkali metal battery is greatly prolonged by reducing side reactions. In addition, the preparation method has the advantages that the operation is simple, modification factors are easy to control, and large-scale production can be realized.

Description

Technical Field

[0001] This invention relates to the field of chemical power source technology, specifically to a bimetallic selenide-modified alkali metal anode material, its preparation method, and its application. Background Technology

[0002] Efficient energy storage and conversion are crucial for developing a more sustainable future. Over the past few decades, rechargeable lithium-ion batteries (LIBs) have become the focus of advanced energy storage systems due to their high energy density, low self-discharge rate, and long cycle life, and are widely used in electric vehicles (EVS), portable electronics, and grid-scale energy storage systems. However, the limited abundance and uneven global distribution of lithium resources have driven up prices in the face of increasing market demand. The growing demand for lithium-ion batteries, coupled with limited supply, has made the development of other low-cost, high-energy-density alkali metal batteries a current research hotspot. Sodium / potassium metals, belonging to the same group as lithium, are highly competitive due to their similar electrochemical properties and lower cost. In fact, sodium / potassium is far more abundant in the Earth's crust than lithium and is widely distributed worldwide. Among them, sodium metal batteries have a high theoretical specific capacity (1166 mAh·g). -1 Potassium metal batteries also exhibit a lower redox potential (-2.71 V vs. standard hydrogen electrode); similarly, they possess a higher theoretical specific capacity (687 mAh·g). -1 The sodium / potassium metal has a low redox potential (-2.93 V vs. standard hydrogen electrode). Therefore, high-energy-density alkali metal batteries can be constructed using sodium / potassium metal as the negative electrode.

[0003] However, sodium / potassium metal anodes face many problems in practical applications. The large ionic radius of sodium / potassium ions leads to sluggish transfer kinetics, limiting ion migration efficiency. Furthermore, during migration, the high electrochemical activity of sodium / potassium metals readily reacts with the contacting carbonate electrolyte to form a loose, porous solid electrolyte interphase (SEI). During repeated deposition and extraction, the unstable SEI film is punctured, causing fresh sodium / potassium to be continuously exposed to the electrolyte. This electrolyte consumption generates an uneven interface, leading to dendrite growth due to increased local current density during subsequent sodium / potassium ion deposition. The continued growth of dendrites eventually punctures the membrane, causing a short circuit.

[0004] To address these issues, researchers have undertaken various attempts and proposed different solutions. These include constructing an SEI protective layer to stabilize the electrode / electrolyte interface; optimizing the electrolyte composition to stabilize the in-situ SEI and suppress sodium / potassium dendrites; and creating a three-dimensional (3D) sodium / potassium host to reduce local current density and accommodate the significant volume expansion of sodium / potassium metals. Among these methods, constructing an SEI protective layer is considered one of the most effective due to its operability and scalability, which allows for better stabilization of the sodium / potassium anode / electrolyte interface and extends its lifespan.

[0005] However, due to the slow dissolution and transport kinetics of sodium / potassium ions, most of these protective layers are limited to high current densities and areal capacities (e.g., 1 mA·cm⁻¹). -2 and 1 mA·cm -2 Therefore, it is not possible to provide a long cycle life under these conditions. Thus, developing suitable composite artificial protective layers is crucial for promoting the desolvation of sodium / potassium ions at the electrolyte / anode interface and for providing a rapid transport channel for them to cross the protective layer during deposition.

[0006] In view of the above-mentioned defects, the inventors of this invention have finally obtained this invention after a long period of research and practice. Summary of the Invention

[0007] The purpose of this invention is to solve the problem that the large ionic radius of sodium / potassium ions leads to sluggish transfer kinetics that limit the migration efficiency of ions, and to provide a bimetallic selenide-modified alkali metal anode material, its preparation method, and its application.

[0008] To achieve the above objectives, this invention discloses a method for preparing a bimetallic selenide-modified alkali metal anode material, comprising the following steps:

[0009] S1, ethylenediamine diacetic acid, manganese chloride and sodium hydroxide are mixed evenly in water, and after stirring, standing, centrifugation and drying, manganese dioxide powder is obtained;

[0010] S2, the manganese dioxide powder obtained in step S1 is mixed and stirred with pyrrole and aniline in sulfuric acid solution, and then phosphotungstic acid and ammonium metavanadate are added to obtain intermediate powder.

[0011] S3, the intermediate powder obtained in step S2 and the selenium powder are subjected to a selenization reaction to obtain vanadium-doped tungsten diselenide powder.

[0012] S4. The tungsten diselenide powder obtained in step S3 is uniformly rolled onto the surface of sodium / potassium metal and subjected to spontaneous reaction. After standing, a protective layer is obtained, and finally, the bimetallic selenide-modified alkali metal anode material is obtained.

[0013] In step S1, the molar ratio of ethylenediamine diacetic acid, manganese chloride, and sodium hydroxide is 1:1:10.

[0014] In step S1, the drying temperature is 60°C and the drying time is 12 hours.

[0015] In step S2, the molar ratio of phosphotungstic acid and ammonium metavanadate is 100~97:0~3.

[0016] In step S3, the mass ratio of intermediate powder to selenium powder is 1:4.

[0017] In step S3, the selenization reaction is carried out at a temperature of 800°C for 2 hours.

[0018] In step S4, the rolling environment is a glove box filled with argon gas, the oxygen content in the glove box is less than 0.5 ppm, the spontaneous reaction temperature is 25°C, and the amount of tungsten diselenide powder used is 25 mg.

[0019] The present invention also discloses a bimetallic selenide-modified alkali metal anode material prepared by the above preparation method.

[0020] This invention also discloses the application of the above-mentioned bimetallic selenide-modified alkali metal anode material in sodium / potassium metal battery anodes.

[0021] The sodium / potassium metal battery anode includes sodium / potassium metal and an adjustable interface protective layer. The adjustable interface protective layer includes vanadium-doped tungsten diselenide powder with different interlayer spacing and a bimetallic selenide-modified alkali metal anode material formed by them. The thickness of the adjustable interface protective layer is 6 μm.

[0022] Tungsten selenide possesses a unique two-dimensional (2D) nanostructure and relatively weak interlayer van der Waals forces, allowing for tunable interlayer spacing and excellent chemical stability in organic electrolytes. However, the sodium ion transfer kinetics of tungsten selenide are significantly limited by its finite interlayer space. Heteroatom doping (such as vanadium atoms) is the most effective method to expand the interlayer spacing and maintain structural integrity. The ionic radius (~0.054 nm) and Similar in size (~0.060 nm) but with different charges, doping with vanadium atoms causes lattice distortion, typically leading to a slight increase in the interlayer spacing of tungsten selenide. The larger interlayer spacing provides more spacious channels for sodium ion insertion / extraction, lowers the diffusion barrier, and accelerates ion transport rates. The introduction of vanadium atoms alters the local electronic structure of tungsten selenide. The d-electron orbitals of vanadium can modulate the adsorption strength of the material for sodium ions. The optimal vanadium doping ratio can adjust the adsorption energy to a "just right" value—neither too strong (making sodium ion desorption difficult) nor too weak (making sodium ion adsorption ineffective), thus optimizing the charge transfer steps at the interface. Therefore, as a case study, using tungsten selenide nanosheets with controlled atomic interlayer spacing as an interfacial layer coating on the surface of a sodium metal anode holds promise for improving the interfacial stability of the anode and promoting sodium ion desolvation kinetics, thereby achieving a dendrite-free sodium metal anode. This unique protective layer provides ample sodium ion transport channels, sufficient nucleation sites, and strong sodium ion affinity.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] 1. This invention uses simple physical means to uniformly coat vanadium-doped tungsten diselenide powder onto the surface of sodium / potassium metal. Compared with existing technologies, it is simple to operate and low in cost.

[0025] 2. This invention utilizes vanadium-doped tungsten diselenide powder (V2) with suitable interlayer spacing. x A modified negative electrode (Na@V) composed of WSe and sodium / potassium metal is formed. x WSe or K@V x WSe, due to its high sodium / potassium affinity, low sodium ion diffusion barrier, and excellent ion migration efficiency, is conducive to inducing sodium / potassium ions to pass rapidly and uniformly through the interface layer, achieving uniform deposition of sodium / potassium beneath the interface layer; furthermore, V x The adjustable interface protective layer constructed from WSe has strong mechanical strength and can effectively suppress dendrite growth during repeated peeling / coating processes, protecting the negative electrode and improving the cycle life of alkali metal batteries. Attached Figure Description

[0026] Figure 1 X-ray electron diffraction analysis pattern of sodium metal surface coated with 1% vanadium-doped tungsten diselenide powder (VWSe) in Example 1 of the present invention;

[0027] Figure 2 This is a high-resolution transmission scanning electron microscope image of sodium metal coated with 1% vanadium-doped tungsten diselenide powder (VWSe) in Example 1 of the present invention.

[0028] Figure 3The images show a comparison before and after of coating the sodium metal surface with 1% vanadium-doped tungsten diselenide powder (VWSe) in Example 1 of the present invention. A is pure sodium, and B is the powder coated on the sodium metal surface.

[0029] Figure 4 Temperature-dependent electrochemical impedance spectroscopy of sodium metal surface coated with 1% vanadium-doped tungsten diselenide powder (VWSe) in Example 1 of this invention;

[0030] Figure 5 The exchange current density spectrum of sodium metal surface coated with 1% vanadium-doped tungsten diselenide powder (VWSe) in Example 1 of the present invention;

[0031] Figure 6 This is a nucleation overpotential diagram of sodium metal surface coated with 1% vanadium-doped tungsten diselenide powder (VWSe) in Example 1 of the present invention;

[0032] Figure 7 In Example 1 of this invention, sodium sheets coated with 1% vanadium-doped tungsten diselenide powder (VWSe) were assembled into a symmetrical cell and measured at 1 mA·cm⁻¹. -2 Current density and capacity are 1 mAh·cm -2 The following is a time-voltage diagram;

[0033] Figure 8 This is a comparison of the cycle performance curves of the full cell assembled with the sodium metal anode protected by the adjustable protective layer and the unprotected sodium metal anode and sodium vanadium phosphate cathode obtained in Example 1 of the present invention.

[0034] Figure 9 This is a comparison of the charge-discharge curves of a full battery assembled with an adjustable protective layer-protected sodium metal anode and an unprotected sodium metal anode and sodium vanadium phosphate cathode, obtained in Example 1 of the present invention.

[0035] Figure 10 This is a high-resolution transmission scanning electron microscope image of sodium metal coated with vanadium-free tungsten diselenide powder (WSe) in Example 2 of the present invention.

[0036] Figure 11 Temperature-dependent electrochemical impedance spectroscopy of sodium metal surface coated with vanadium-free tungsten diselenide powder (WSe) in Example 2 of this invention;

[0037] Figure 12 The exchange current density spectrum of sodium metal surface coated with vanadium-free tungsten diselenide powder (WSe) in Example 2 of the present invention;

[0038] Figure 13 This is a nucleation overpotential diagram of sodium metal surface coated with vanadium-free tungsten diselenide powder (WSe) in Example 2 of the present invention;

[0039] Figure 14In Example 2 of this invention, sodium sheets coated with vanadium-free tungsten diselenide powder (WSe) were assembled into a symmetrical cell, and the cell measured at 1 mA·cm⁻¹. -2 Current density and capacity are 1 mAh·cm -2 The following is a time-voltage diagram;

[0040] Figure 15 In Example 3 of this invention, a sodium metal surface is coated with 3% vanadium-doped tungsten diselenide powder (V). 0.03 High-resolution transmission scanning electron microscope (SEM) images of WSe;

[0041] Figure 16 In Example 3 of this invention, a sodium metal surface is coated with 3% vanadium-doped tungsten diselenide powder (V). 0.03 Variable-temperature electrochemical impedance spectroscopy of WSe;

[0042] Figure 17 In Example 3 of this invention, a sodium metal surface is coated with 3% vanadium-doped tungsten diselenide powder (V). 0.03 The exchange current density spectrum of WSe;

[0043] Figure 18 In Example 3 of this invention, a sodium metal surface is coated with 3% vanadium-doped tungsten diselenide powder (V). 0.03 Nucleation overpotential diagram of WSe;

[0044] Figure 19 Example 3 of the present invention is a 3% vanadium-doped tungsten diselenide powder coated with (V 0.03 After the sodium sheets obtained from WSe were assembled into a symmetrical cell, the temperature was 1 mA·cm⁻¹. -2 Current density and capacity are 1 mAh·cm -2 The following is a time-voltage diagram;

[0045] Figure 20 In Example 4 of this invention, potassium sheets coated with 1% vanadium-doped tungsten diselenide powder (VWSe) were assembled into a symmetrical cell, and the cell measured at 1 mA·cm⁻¹ -2 Current density and capacity are 5 mAh·cm -2 Nucleation overpotential diagram below;

[0046] Figure 21 In Example 4 of this invention, potassium sheets coated with 1% vanadium-doped tungsten diselenide powder (VWSe) were assembled into a symmetrical cell, and the cell measured at 1 mA·cm⁻¹ -2 Current density and capacity are 1 mAh·cm -2 The following is a time-voltage diagram;

[0047] Figure 22 In Example 5 of this invention, potassium sheets coated with vanadium-free tungsten diselenide powder (WSe) were assembled into a symmetrical cell, and the cell measured at 1 mA·cm⁻¹ -2Current density and capacity are 5 mAh·cm -2 Nucleation overpotential diagram below;

[0048] Figure 23 In Example 5 of this invention, potassium sheets coated with vanadium-free tungsten diselenide powder (WSe) were assembled into a symmetrical cell, and the cell measured at 1 mA·cm⁻¹ -2 Current density and capacity are 1 mAh·cm -2 The following is a time-voltage diagram. Detailed Implementation

[0049] The above-mentioned and other technical features and advantages of the present invention will be described in more detail below with reference to the accompanying drawings.

[0050] Example 1

[0051] 25 mg of 1% vanadium-doped tungsten diselenide powder (VWSe) was weighed in a glove box and uniformly coated onto a rectangular sodium metal sheet 3 cm wide and 10 cm long. The sodium sheet was then left to stand for 2 minutes to allow for a chemical reaction at room temperature. After the reaction, the sodium sheet was punched into 10 mm diameter discs, which were used as positive and negative electrodes to assemble a coin cell. The electrolyte used in the sodium metal battery was 1 M NaClO4-EC / DEC / 5% FEC. After assembly, the coin cell was tested at a current density of 1 mA·cm⁻¹. -2 Capacity is 1 mAh·cm -2 Under certain conditions, its cycle stability during charge and discharge processes was tested.

[0052] The aforementioned sodium metal anode with adjustable interface protection was applied to a full cell assembled with a sodium vanadium phosphate cathode. The ratio of the cathode material sodium vanadium phosphate (Na3V2(PO4)3), conductive carbon black (super P), and binder polytetrafluoroethylene (5% PVDF) was 7:2:1, which was then coated onto double-sided carbon-coated aluminum foil to serve as the cathode. The resulting sodium metal with adjustable interface protection was used as the anode to assemble the full cell.

[0053] Figure 1 The image shows the X-ray electron diffraction pattern of VWSe. From the image, we can see that the diffraction peaks are consistent with the standard PDF card of WSe2. The match proves that VWSe was successfully synthesized.

[0054] Figure 2 The image shows a high-resolution transmission scanning electron microscope (TEM) image of VWSe. As can be seen from the image, the (002) interplanar spacing of VWSe is increased.

[0055] Figure 3The image shows a comparison between the original sodium sheet and the sodium sheet coated with VWSe powder. As can be seen from the image, the original sodium sheet has a metallic luster, while the sodium metal surface turns black after being coated with VWSe powder, indicating that the sodium metal reacted with the VWSe powder.

[0056] Figure 4 The temperature-dependent electrochemical impedance spectroscopy (TIS) of the tunable interfacial protective layer shows that the VWSe-modified anode exhibits very low interfacial impedance and charge transfer impedance at different temperatures, significantly lower than the impedance of the pure sodium metal symmetric battery in the control group. This demonstrates that the 1% vanadium-doped tungsten diselenide powder (VWSe) plays a role in regulating interfacial impedance and desolvation in the modified anode.

[0057] Figure 5 The figure shows the exchange current density spectrum of the tunable interface protective layer. As can be seen from the figure, the VWSe-modified anode has a much higher exchange current density than the pure sodium metal anode. This proves that the interface layer of the modified anode, in which sodium ions participate through 1% vanadium-doped tungsten diselenide powder (VWSe), forms a faster current density.

[0058] Figure 6 Time-voltage diagrams of symmetrical cells assembled with sodium metal as both positive and negative electrodes, with adjustable interface layer protection, at a current density of 1 mA·cm⁻¹. -2 The capacity is 5 mAh·cm -2 The nucleation overpotential diagram was obtained under cycling conditions. It can be seen from the diagram that the VWSe-coated sodium metal anode has a smaller nucleation overpotential compared to pure sodium metal, indicating that the VWSe layer can effectively reduce the nucleation barrier during sodium ion deposition.

[0059] Figure 7 The following are time-voltage diagrams of sodium metal discs with adjustable interface layer protection obtained in Example 1, used as positive and negative electrodes in the assembly of symmetrical cells, at a current density of 1 mA·cm⁻¹. -2 The capacity is 1 mAh·cm -2 Under the same cycling conditions, the cycle life was extended from 70 hours to over 850 hours. Under the same conditions, a pure sodium metal symmetric battery failed after approximately 70 hours, exhibiting poor cycle stability. The figure shows severe voltage fluctuations and dendrite formation during the initial cycling period, which may be the cause of its early failure. This indicates that the tunable interface protective layer, through a VWSe with appropriate interlayer spacing, modulates the sodium ion transfer kinetics, not only promoting uniform sodium ion deposition but also inhibiting sodium dendrite growth, thereby improving the battery's cycle life.

[0060] Figure 8The figures show the cycle performance curves of the full cell assembled with a sodium metal anode with an adjustable protective layer and an unprotected sodium metal anode, along with a sodium vanadium phosphate cathode, as obtained in Example 1. It can be seen that the full cell assembled with the sodium metal anode with an adjustable protective layer and a sodium vanadium phosphate cathode achieves a cycle count of around 20C (1C=110). Under normal conditions, the battery can achieve over 2100 cycles with a capacity retention rate of 91%, demonstrating excellent cycle performance. In contrast, a full cell assembled with an unprotected sodium metal electrode and a sodium vanadium phosphate cathode experiences capacity decay after 180 cycles, exhibiting poor long-term cycle performance and resulting in insufficient cycle life.

[0061] Figure 9 The figures show the charge-discharge curves of the full cell assembled with the sodium metal anode with the adjustable protective layer obtained in Example 1 and the unprotected sodium metal anode and sodium vanadium phosphate cathode. A clear difference in polarization voltage and specific capacity can be observed between the two.

[0062] Example 2

[0063] 25 mg of vanadium-free tungsten diselenide powder (WSe2) was weighed in a glove box and uniformly coated onto the surface of a rectangular sodium metal sheet 3 cm wide and 10 cm long. The sodium sheet was then left to stand for 2 minutes to allow for a chemical reaction at room temperature. After the reaction, the sodium sheet was punched into 10 mm diameter discs, which were used as positive and negative electrodes to assemble coin cells. The electrolyte used in the sodium metal battery was 1 M NaClO4-EC / DEC / 5% FEC. After assembly, the coin cells were tested at a current density of 1 mA·cm⁻¹. -2 Capacity is 1 mAh·cm -2 Under certain conditions, its cycle stability during charge and discharge processes was tested.

[0064] Figure 10 The image shows a high-resolution transmission scanning electron microscope image of WSe. As can be seen from the image, the (002) interplanar spacing of WSe is relatively small.

[0065] Figure 11 The figure shows the temperature-varying electrochemical impedance spectroscopy of the WSe interface protective layer. As can be seen, the WSe-modified anode still exhibits very low interfacial layer impedance and charge transfer impedance at different temperatures, but these are greater than those of Example 1 and significantly less than the impedance of the pure sodium metal symmetric battery in the control group. This demonstrates that the vanadium-free tungsten diselenide powder (WSe)-modified anode effectively regulates interfacial impedance and desolvates the electrolyte, but its effect is not as good as that of the VWSe-modified anode.

[0066] Figure 12The figure shows the exchange current density spectrum of the tunable interface protective layer. As can be seen, the WSe-modified anode has a much higher exchange current density than the pure sodium metal anode, but lower than the VWSe-modified anode. This demonstrates that sodium ions pass through the interface layer of the WSe-modified anode relatively quickly, but not as quickly as in Example 1.

[0067] Figure 13 Time-voltage diagrams of symmetrical cells assembled with sodium metal as both positive and negative electrodes, with adjustable interface layer protection, at a current density of 1 mA·cm⁻¹. -2 The capacity is 5 mAh·cm -2 The nucleation overpotential diagram was obtained under cycling conditions. It can be seen from the diagram that the WSe-coated sodium metal anode has a smaller nucleation overpotential compared to pure sodium metal, but is greater than that of the VWSe-modified anode. This indicates that the WSe layer can effectively reduce the nucleation barrier during sodium ion deposition, but not as effectively as in Example 1.

[0068] Figure 14 The following are time-voltage diagrams of sodium metal discs with adjustable interface layer protection obtained in Example 2, used as positive and negative electrodes in the assembly of symmetrical cells, at a current density of 1 mA·cm⁻¹. -2 The capacity is 1 mAh·cm -2 Under the given cycling conditions, it was found that its cycle life was longer than that of the pure sodium symmetric cell, but its cycle stability was not as strong as that of Example 1. Therefore, it can be concluded that the smaller (002) interplanar spacing of WSe has a less significant impact on ion migration than the (002) interplanar spacing of VWSe.

[0069] Example 3

[0070] Weigh 25 mg of 3% vanadium-doped tungsten diselenide powder (V) into a glove box. 0.03 WSe was uniformly coated onto the surface of a rectangular sodium metal sheet 3 cm wide and 10 cm long. The sodium sheet was then left to stand for 2 minutes to allow for a chemical reaction at room temperature. After the reaction, the sodium sheet was punched into 10 mm diameter discs, which were used as positive and negative electrodes to assemble a coin cell. The electrolyte used in the sodium metal battery was 1 M NaClO4-EC / DEC / 5% FEC. After assembly, the coin cell was tested at a current density of 1 mA·cm⁻¹. -2 Capacity is 1 mAh·cm -2 Under certain conditions, its cycle stability during charge and discharge processes was tested.

[0071] Figure 15 For V 0.03 High-resolution transmission scanning electron microscope (SEM) images from WSe. As can be seen from the figures, V 0.03 WSe has a larger (002) interplanar spacing.

[0072] Figure 16 For V0.03 Temperature-dependent electrochemical impedance spectroscopy of the WSe interface protective layer. As can be seen from the figure, V 0.03 The modified WSe anode still exhibits very low interfacial layer impedance and charge transfer impedance at different temperatures, but these are greater than those of Example 1 and much smaller than the impedance of the pure sodium metal symmetric cell in the control group. This demonstrates that 3% vanadium-doped tungsten diselenide powder (V... 0.03 The modified anode involving WSe played a role in adjusting interfacial impedance and desolvation, but its effect was not as good as that of the modified anode involving VWSe.

[0073] Figure 17 The figure shows the exchange current density spectrum of the tunable interface protective layer. As can be seen from the figure, V 0.03 The modified anode of WSe exhibits an exchange current density much greater than that of the pure sodium metal anode, but less than that of the modified anode of VWSe. This demonstrates that sodium ions pass through V 0.03 The interface layer of the modified anode with WSe participation is faster, but not as fast as in Example 1.

[0074] Figure 18 Time-voltage diagrams of symmetrical cells assembled with sodium metal as both positive and negative electrodes, with adjustable interface layer protection, at a current density of 1 mA cm⁻¹. -2 The capacity is 5 mAh·cm -2 The nucleation overpotential diagram was obtained under the condition of cycling. It can be seen from the diagram that V... 0.03 The WSe-coated sodium metal anode exhibits a smaller nucleation overpotential compared to pure sodium metal, but a higher one than the VWSe-modified anode. This indicates that V 0.03 The WSe layer can effectively reduce the nucleation barrier during sodium ion deposition, but not as effectively as in Example 1.

[0075] Figure 19 The following are time-voltage diagrams of sodium metal discs with adjustable interface layer protection obtained in the examples, used as positive and negative electrodes in the assembly of symmetrical cells, at a current density of 1 mA·cm⁻¹. -2 The capacity is 1 mAh·cm -2 Under the conditions of cycling, it was found that its cycle life was longer than that of the pure sodium symmetric cell, but its cycle stability was not as strong as that of Example 1. Therefore, V 0.03 The (002) interplanar spacing of WSe has a less significant impact on ion migration than the (002) interplanar spacing of VWSe, and a larger interplanar spacing is not necessarily better.

[0076] Example 4

[0077] 25 mg of 1% vanadium-doped tungsten diselenide powder (VWSe) was weighed in a glove box and uniformly coated onto a rectangular potassium metal sheet 3 cm wide and 10 cm long. The potassium sheet was then left to stand for 2 minutes to allow for an in-situ reaction at room temperature. The sheet was rolled into a disc and then punched into 10 mm diameter discs, which were used as positive and negative electrodes to assemble a coin cell. The electrolyte used in the potassium metal battery was 1 M KFSI-EC / DEC. After assembly, the coin cell was tested at a current density of 1 mA·cm⁻¹. -2 The capacity is 1mAh·cm -2 Under certain conditions, its cycle stability during the charge and discharge process was tested.

[0078] Figure 20 The following are time-voltage diagrams of potassium metal discs with adjustable interface layer protection obtained in the examples, used as positive and negative electrodes in the assembly of symmetrical cells, at a current density of 1 mA·cm⁻¹. -2 The capacity is 5 mAh·cm -2 The nucleation overpotential diagram was obtained under cycling conditions. It can be seen from the diagram that the VWSe-coated potassium metal anode has a smaller nucleation overpotential compared to pure potassium metal, indicating that the VWSe layer can effectively reduce the nucleation barrier during potassium ion deposition.

[0079] Figure 21 The following are time-voltage diagrams of potassium metal discs with adjustable interface layer protection obtained in the examples, used as positive and negative electrodes in the assembly of symmetrical cells, at a current density of 1 mA·cm⁻¹. -2 The capacity is 1 mAh·cm -2 Under cycling conditions, the cycle life was extended from 200 hours to over 1200 hours. This indicates that the VWSe interface protective layer still has a good modifying effect on potassium. It not only promotes the uniform deposition of potassium ions but also inhibits the growth of potassium dendrites, thereby improving the cycle life of the battery.

[0080] Example 5

[0081] 25 mg of vanadium-free tungsten diselenide powder (WSe) was weighed in a glove box and uniformly coated onto a rectangular potassium metal sheet 3 cm wide and 10 cm long. The potassium sheet was then left to stand for 2 minutes to allow for a chemical reaction at room temperature. After the reaction, the potassium sheet was punched into 10 mm diameter discs, which were used as positive and negative electrodes to assemble a coin cell. The electrolyte used in the potassium metal battery was 1 M KFSI-EC / DEC. After assembly, the coin cell was tested at a current density of 1 mA·cm⁻¹. -2 The capacity is 1mAh·cm -2 Under certain conditions, its cycle stability during the charge and discharge process was tested.

[0082] Figure 22The following are time-voltage diagrams of potassium metal discs with adjustable interface layer protection obtained in the examples, used as positive and negative electrodes in the assembly of symmetrical cells, at a current density of 1 mA·cm⁻¹. -2 The capacity is 5 mAh·cm -2 The nucleation overpotential diagram was obtained under cycling conditions. It can be seen from the diagram that the potassium metal anode coated with WSe still has a smaller nucleation overpotential than that of pure potassium metal, but it is not as small as that of Example 4. This indicates that the modification of the nucleation barrier by the WSe layer is not as obvious as that of VWSe.

[0083] Figure 23 The following are time-voltage diagrams of potassium metal discs with interface layer protection obtained in Example 5 of this invention, used as positive and negative electrodes to assemble a symmetrical cell, at a current density of 1 mA·cm⁻¹. -2 The capacity is 1 mAh·cm -2 Under the operating conditions, it was found that its cycle life was extended from 200 hours to more than 560 hours, but it was not as strong as the cycle stability of Example 4.

[0084] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.

Claims

1. A method for preparing a bimetallic selenide-modified alkali metal anode material, characterized in that, Includes the following steps: S1, ethylenediamine diacetic acid, manganese chloride and sodium hydroxide are mixed evenly in water, and after stirring, standing, centrifugation and drying, manganese dioxide powder is obtained; S2, the manganese dioxide powder obtained in step S1 is mixed and stirred with pyrrole and aniline in sulfuric acid solution, and then phosphotungstic acid and ammonium metavanadate are added to obtain intermediate powder. S3, the intermediate powder obtained in step S2 and the selenium powder are subjected to a selenization reaction to obtain vanadium-doped tungsten diselenide powder. S4. The tungsten diselenide powder obtained in step S3 is uniformly rolled onto the surface of sodium / potassium metal and subjected to spontaneous reaction. After standing, a protective layer is obtained, and finally, the bimetallic selenide-modified alkali metal anode material is obtained.

2. The method for preparing a bimetallic selenide-modified alkali metal anode material as described in claim 1, characterized in that, In step S1, the molar ratio of ethylenediamine diacetic acid, manganese chloride, and sodium hydroxide is 1:1:

10.

3. The method for preparing a bimetallic selenide-modified alkali metal anode material as described in claim 1, characterized in that, In step S1, the drying temperature is 60°C and the drying time is 12 hours.

4. The method for preparing a bimetallic selenide-modified alkali metal anode material as described in claim 1, characterized in that, In step S2, the molar ratio of phosphotungstic acid and ammonium metavanadate is 100~97:0~3.

5. The method for preparing a bimetallic selenide-modified alkali metal anode material as described in claim 1, characterized in that, In step S3, the mass ratio of intermediate powder to selenium powder is 1:

4.

6. The method for preparing a bimetallic selenide-modified alkali metal anode material as described in claim 1, characterized in that, In step S3, the selenization reaction is carried out at a temperature of 800°C for 2 hours.

7. The method for preparing a bimetallic selenide-modified alkali metal anode material as described in claim 1, characterized in that, In step S4, the rolling environment is a glove box filled with argon gas, the oxygen content in the glove box is less than 0.5 ppm, the spontaneous reaction temperature is 25°C, and the amount of tungsten diselenide powder used is 25 mg.

8. A bimetallic selenide-modified alkali metal anode material prepared by the preparation method according to any one of claims 1 to 7.

9. The application of a bimetallic selenide-modified alkali metal anode material as described in claim 8 in the anode of a sodium / potassium metal battery.

10. The application of the bimetallic selenide-modified alkali metal anode material as described in claim 9 in the anode of a sodium / potassium metal battery, characterized in that, The sodium / potassium metal battery anode includes sodium / potassium metal and an adjustable interface protective layer. The adjustable interface protective layer includes vanadium-doped tungsten diselenide powder with different interlayer spacing and a bimetallic selenide-modified alkali metal anode material formed by them. The thickness of the adjustable interface protective layer is 6 μm.

Images