Electrochemically activated vanadium diboride, preparation method thereof and application thereof in water-based energy storage positive electrode material

Abstract

The application belongs to the technical field of electrochemical energy storage, and relates to electrochemically activated vanadium diboride, a preparation method thereof and application of the vanadium diboride in a water-based energy storage positive electrode material. The method comprises the following steps: assembling a vanadium diboride positive electrode, a separator, a negative electrode and a water-based electrolyte into an energy storage system; and activating by using a chronocoulometry method, a repeated cyclic voltammetry method, a chronopotentiometry method or a multiple constant current charge-discharge cycle method to obtain an in-situ electrochemically activated vanadium diboride positive electrode material. The electrochemically activated vanadium diboride positive electrode is applied to a Zn 2+ , Li + , NH4 + , Mg 2+ , etc. water-based energy storage system, and exhibits high electrochemical activity. For example, a zinc ion battery assembled at a current density of 0.1 A / g has a specific capacity of 331 mAh / g. The electrochemically activated vanadium diboride water-based energy storage positive electrode material provided by the application has high specific capacity and long cycle life, is low in preparation cost, simple in preparation process and suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, specifically relating to an electrochemically activated vanadium diboride, its preparation method, and its application in aqueous energy storage cathode materials. Background Technology

[0002] The development of modern society urgently requires electrochemical energy storage devices with high safety and high energy / power density. Lithium-ion batteries are widely used due to their high energy density, but the flammability of their organic electrolytes limits their application in large-scale energy storage. In contrast, the use of Zn... 2+ Li + NH 4+ Mg 2+ Aqueous energy storage devices prepared by isocation generation are expected to become an alternative solution for large-scale energy storage.

[0003] Currently, transition metal oxides (such as vanadium oxides and manganese oxides) dominate research on cathode materials for aqueous energy storage systems. Although research on metal oxides is relatively mature, their low conductivity limits electron transport in electrochemical reactions, thus affecting their electrochemical activity. Boron, which is in the same period as oxygen, can also form metal borides with metals, exhibiting good conductivity.

[0004] Vanadium diboride possesses high electrical conductivity and a high theoretical specific capacity. However, in aqueous energy storage systems, vanadium diboride exhibits poor electrochemical activity and relatively high stability, making it difficult to achieve high electrochemical activity through conventional methods. Therefore, there are currently few reports on the application of vanadium diboride as a cathode material in aqueous energy storage systems. Summary of the Invention

[0005] To address the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a simple, economical, environmentally friendly, and reproducible activation method for vanadium diboride. This invention, through electrochemical activation of vanadium diboride, yields a highly electrochemically active aqueous energy storage cathode material suitable for various ion storage applications. Furthermore, the preparation process is simple and suitable for industrial production.

[0006] This invention employs various electrochemical activation methods, such as repeated cyclic voltammetry, chronoamperometry, chronopotentialography, and repeated constant current charge-discharge cycles. These electrochemical activation methods transform vanadium diboride, which was originally unsuitable for aqueous energy storage systems, into an aqueous cathode material with high electrochemical activity. This not only improves the specific capacity but also provides excellent cycle stability, making it suitable as an aqueous energy storage cathode material supporting the storage of various ions.

[0007] Another object of the present invention is to provide an electrochemically activated vanadium diboride prepared by the above method.

[0008] Another object of the present invention is to provide the application of the above-mentioned electrochemically activated vanadium diboride in aqueous energy storage cathode materials.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A method for preparing electrochemically activated vanadium diboride includes the following steps:

[0011] Step 1: Mix vanadium diboride, conductive carbon source and binder evenly, add solvent, grind to form positive electrode slurry, coat onto current collector, dry to obtain vanadium diboride positive electrode; assemble vanadium diboride positive electrode, separator, negative electrode and aqueous electrolyte into energy storage system;

[0012] Step 2: Activate the vanadium diboride cathode material in situ using chronoamperometry, repetitive cyclic voltammetry, chronopotentialometry, or multiple constant current charge-discharge cycles to obtain the vanadium diboride cathode material.

[0013] Preferably, the chronoamperometry activation in step 2 involves applying different charging cutoff voltages during the initial charging activation process, and after charging for a certain period of time, the activation ends to obtain in-situ electrochemically activated vanadium diboride cathode material.

[0014] More preferably, the activation method using chronocurrent can be selected with a charging cutoff voltage between 1.0V and 2.4V, and a charging time between 0.1h and 24h.

[0015] Preferably, the cyclic voltammetry activation in step 2 refers to performing repeated cyclic voltammetry tests on the battery multiple times. After several repetitions, the activation ends and in-situ electrochemically activated vanadium diboride cathode material is obtained.

[0016] More preferably, when activating vanadium diboride material using repetitive cyclic voltammetry, the scan rate is 0.1 mV / s to 100 mV / s, and the number of cycles is 1 to 100.

[0017] If the repetitive cyclic voltammetry method uses a battery or capacitor system, the voltage range used is within the range of 0V to 2.4V.

[0018] If the repetitive cyclic voltammetry method uses a three-electrode system, the voltage range is -1V to 0.6V, where the Pt electrode and the Ag / AgCl electrode serve as the counter electrode and the reference electrode, respectively.

[0019] A more preferred scanning speed is 20mV / s to 50mV / s, and a preferred number of repetition cycles is 50 to 80.

[0020] Preferably, the chronopotential activation method described in step 2 involves applying different charging currents during the initial charging activation process, and after charging for a certain period of time, the activation ends to obtain in-situ electrochemically activated vanadium diboride cathode material.

[0021] More preferably, when activating vanadium diboride materials using the chronopotential method, the charging current range is 0.01A / g-10A / g, and the charging time is 0.01h-12h.

[0022] Preferably, the activation method of multiple constant current charge-discharge cycles in step 2 refers to performing constant current charge-discharge tests on the battery repeatedly. After several repetitions, the activation ends and in-situ electrochemically activated vanadium diboride cathode material is obtained.

[0023] More preferably, when activating vanadium diboride material using the multiple constant current charge-discharge cycle method, the range of charge-discharge current used is 0.1A / g-20A / g, and the number of cycles is 1 to 100.

[0024] If the aforementioned constant current charge-discharge cycle method uses a battery or capacitor system, the voltage range used is within the range of 0V to 2.4V.

[0025] If the multiple constant current charge-discharge cycle method adopts a three-electrode system, the voltage range used is -1V to 0.6V, where the Pt electrode and the Ag / AgCl electrode serve as the counter electrode and the reference electrode, respectively.

[0026] Preferably, the conductive carbon source in step 1 is at least one of carbon black, conductive graphite, carbon fiber, carbon nanotubes, and acetylene black.

[0027] Preferably, the adhesive in step 1 is at least one of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), and carboxymethyl cellulose (CMC).

[0028] Preferably, the solvent in step 1 is at least one of N-methyl-2-pyrrolidone, dimethyl carbonate, ethylene carbonate, and diethylene carbonate.

[0029] Preferably, the current collector in step 1 is at least one of titanium foil, stainless steel foil (mesh), and carbon cloth.

[0030] Preferably, the diaphragm in step 1 is at least one of glass fiber diaphragm, non-woven fabric, and cellulose nanofiber diaphragm.

[0031] Preferably, the electrolyte in step 1 is an aqueous electrolyte containing a metal salt or an ammonium salt, wherein the metal salt is a zinc salt, a magnesium salt, or a lithium salt, etc.

[0032] Preferably, the negative electrode in step 1 can be activated carbon, activated carbon fiber, or zinc foil, etc.

[0033] Preferably, the drying temperature in step 1 is 50℃~100℃, and the drying time is 2h~24h.

[0034] A more preferred drying temperature is 80°C and a drying time is 6 hours.

[0035] Preferably, the loading of the positive electrode slurry on the current collector in step 1 is 0.5–15 mg / cm³. 2 .

[0036] Preferably, the concentration of the electrolyte in step 1 is 0.2–3.0 mol / L, and the pH value of the electrolyte is 3.5–8.

[0037] The in-situ electrochemically activated vanadium diboride cathode material prepared by this invention can be applied to various ion-aqueous energy storage systems as a cathode material, and assembled into various types of electrochemical energy storage devices. These electrochemical energy storage devices can take the form of cylinders, squares, pouches, buttons, three-electrode systems, etc.

[0038] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0039] 1. The technical method of the present invention is simple, low-cost, environmentally friendly and safe, and can achieve mass production. It is expected to be used in the commercial production of various ion storage aqueous energy storage cathode materials.

[0040] 2. In the electrochemical activation process, this invention transforms vanadium diboride, which is originally unsuitable for aqueous energy storage systems due to its poor electrochemical activity, into an aqueous energy storage cathode material with excellent electrochemical performance, supporting the storage of multiple ions. After activation, the interatomic gaps in vanadium diboride provide abundant diffusion channels and numerous active sites for ions, thereby enhancing its ion storage capacity and resulting in superior electrochemical performance and high specific capacity. Attached Figure Description

[0041] Figure 1 a) is the constant current charge-discharge curve of the aqueous zinc-ion battery in Example 1; b) is a comparison of the cyclic voltammetry curves of vanadium diboride before and after electrochemical activation in Example 1 at a scan rate of 0.5 mV / s; c) is the constant current charge-discharge curve of the electrochemically activated vanadium diboride cathode at different current densities. In the figure, VB2 represents vanadium diboride before electrochemical activation, and VB2-ECA represents vanadium diboride after electrochemical activation.

[0042] Figure 2 The image shown is a transmission electron microscope image of vanadium diboride in the example.

[0043] Figure 3The image shows the X-ray powder diffraction pattern of vanadium diboride in the example.

[0044] Figure 4 a, b, c, and d are, in order, the cyclic voltammetry curves of the electrochemically activated vanadium diboride cathode in different ion-based aqueous electrolytes in Examples 5, 6, 7, and 8 (where the cathode is the electrochemically activated vanadium diboride and the anode is activated carbon fiber).

[0045] Figure 5 a, b, c, and d are, in order, the constant current charge-discharge curves of the electrochemically activated vanadium diboride cathode in different ion-based aqueous electrolytes in Examples 5, 6, and 7 (where the cathode is the electrochemically activated vanadium diboride and the anode is the activated carbon fiber). Detailed Implementation

[0046] To further illustrate the present invention, some preferred embodiments of the present invention will be described below, with the aim of making the technical solution of the present invention clearer. However, these descriptions are only for further illustrating the features and advantages of the present invention, and are not intended to limit the claims of the present invention. Moreover, the described embodiments are only some embodiments of this application, and not all embodiments are listed.

[0047] Unless otherwise specified, and where specific conditions are not indicated in the examples, use the equipment under standard operating conditions or as recommended by the manufacturer. Furthermore, all experimental reagents and instruments used, unless otherwise specified, are commercially available products.

[0048] Example 1

[0049] Aqueous zinc-ion batteries based on electrochemically activated vanadium diboride cathode and metallic zinc anode.

[0050] (I) Preparation of vanadium diboride cathode

[0051] (1) Weigh 20mg of vanadium diboride powder, 2.5mg of acetylene black powder and 2.5mg of polyvinylidene fluoride in a mass ratio of 8:1:1. Add all materials to an agate mortar and grind manually for 5 minutes to mix the materials evenly. Then add an appropriate amount of N-methyl-2-pyrrolidone and continue grinding for more than 30 minutes until the slurry is viscous and no obvious particles are visible.

[0052] (2) The ground slurry was coated onto a stainless steel foil current collector, with a vanadium diboride loading of 2 mg / cm³. 2 The stainless steel foil current collector coated with slurry is placed in a vacuum drying oven at 80°C for thorough drying. After drying, an unactivated vanadium diboride cathode can be obtained.

[0053] (II) Preparation of electrochemically activated vanadium diboride cathode and aqueous zinc-ion battery

[0054] Using the unactivated vanadium diboride cathode prepared in the previous step as the working electrode, an aqueous zinc-ion battery was assembled in the following order: zinc anode, separator, electrolyte, and vanadium diboride cathode current collector. Activation was performed using a chronoamperometry method, and the voltage of the zinc-ion battery was kept constant at 2.0V for 24 hours by constant voltage charging. After constant voltage activation, a zinc-ion battery containing an in-situ electrochemically activated vanadium diboride cathode was obtained, and electrochemical testing of the zinc-ion battery could be performed directly.

[0055] The electrolyte used is a 2 mol / L ZnSO4 aqueous solution, and the separator is a commercially available glass fiber membrane. The constant current charge-discharge curve of this aqueous zinc-ion battery is shown below. Figure 1 As shown. Based on the mass of the cathode material, the specific capacity of this aqueous zinc-ion battery at a current density of 0.1 A / g is 331 mAh / g.

[0056] Figure 2 This is a transmission electron microscope image of vanadium diboride in the embodiment. Figure 3 The image shows the X-ray powder diffraction pattern of vanadium diboride in the examples. The XRD peak positions of vanadium diboride are consistent with those of the standard card PDF#38-1463, and there are no impurity peaks, indicating that the prepared vanadium diboride has high purity.

[0057] Figure 1 Figure 'a' in Example 1 shows a comparison of the cyclic voltammetry curves of vanadium diboride and electrochemically activated vanadium diboride as cathode materials in an aqueous zinc-ion battery at a scan rate of 0.5 mV / s. The figure shows that the area enclosed by the cyclic voltammetry curve of the unactivated vanadium diboride cathode is much smaller than that of the electrochemically activated vanadium diboride. This indicates that vanadium diboride has poor electrochemical activity. Furthermore, during constant current charge-discharge testing, the voltage of vanadium diboride fails to increase, making it unsuitable as a direct cathode material for aqueous zinc-ion batteries. Figure 1 In Figure b, the constant current charge-discharge curve of vanadium diboride after electrochemical activation in Example 1 is shown. The charge-discharge curve reveals that the electroactivated vanadium diboride exhibits a higher specific capacity, indicating that compared to the unactivated vanadium diboride electrode, electrochemically activated vanadium diboride transforms from an electrochemically inert material into an electrochemically active material.

[0058] Example 2

[0059] Aqueous zinc-ion batteries based on electrochemically activated vanadium diboride cathode and metallic zinc anode.

[0060] (I) Preparation of vanadium diboride cathode

[0061] (1) Weigh 40mg of vanadium diboride powder, 5mg of acetylene black powder and 5mg of polyvinylidene fluoride in a mass ratio of 8:1:1. Add all materials to an agate mortar and grind manually for 5 minutes to mix the materials evenly. Then add an appropriate amount of N-methyl-2-pyrrolidone and continue grinding for more than 30 minutes until the slurry is viscous and no obvious particles are visible.

[0062] (2) The ground slurry was coated onto a stainless steel foil current collector, with a vanadium diboride loading of 2 mg / cm³. 2 The stainless steel foil current collector coated with slurry is placed in a vacuum drying oven at 80°C for thorough drying. After drying, an unactivated vanadium diboride cathode can be obtained.

[0063] (II) Preparation of electrochemically activated vanadium diboride cathode

[0064] The activation process of vanadium diboride electrode materials can be completed using a three-electrode system. A Pt electrode and an Ag / AgCl electrode serve as the counter and reference electrodes, respectively, while the unactivated vanadium diboride cathode serves as the working electrode. A 2 mol / L zinc sulfate electrolyte is used as the activation electrolyte. Activation is achieved through repeated cyclic voltammetry, with a cyclic voltage range of -1V to 0.6V, 20 cycles, and a voltage scan rate of 0.5 mV / s. After cyclic voltammetry, the material can be directly tested in the three-electrode system. Alternatively, the electroactivated vanadium diboride cathode can be repeatedly washed with deionized water 3–5 times, followed by vacuum drying in a vacuum drying oven at 80℃ for 6 hours. After drying, the electrochemically activated vanadium diboride cathode material is obtained. Different sizes of cathodes can be obtained through stamping or cutting for use in assembling other ion-based aqueous energy storage devices.

[0065] (III) Preparation of aqueous zinc-ion batteries

[0066] An aqueous zinc-ion battery was assembled in the following order: zinc anode, separator, and electrochemically activated vanadium diboride cathode. A 2 mol / L ZnSO4 aqueous solution was used as the electrolyte, and a commercially available glass fiber separator was employed. Based on the mass of the cathode materials, the aqueous zinc-ion battery exhibited a discharge specific capacity of 301 mAh / g at a current density of 0.1 A / g.

[0067] Example 3

[0068] Aqueous zinc-ion batteries based on electrochemically activated vanadium diboride cathode and metallic zinc anode.

[0069] (I) Preparation of vanadium diboride cathode

[0070] (1) Weigh 20mg of vanadium diboride powder, 2.5mg of acetylene black powder and 2.5mg of polyvinylidene fluoride in a mass ratio of 8:1:1. Add all materials to an agate mortar and grind manually for 5 minutes to mix the materials evenly. Then add an appropriate amount of N-methyl-2-pyrrolidone and continue grinding for more than 30 minutes until the slurry is viscous and no obvious particles are visible.

[0071] (2) The ground slurry is coated onto a stainless steel foil current collector with a vanadium diboride loading of 2 mg / cm2. The stainless steel foil current collector coated with the slurry is placed in a vacuum drying oven at 80°C for thorough drying. After drying, an unactivated vanadium diboride cathode can be obtained.

[0072] (II) Preparation of electrochemically activated vanadium diboride cathode and aqueous zinc-ion battery

[0073] Using the unactivated vanadium diboride cathode prepared in the previous step as the working electrode, an aqueous zinc-ion battery was assembled in the following order: zinc anode, separator, electrolyte, and vanadium diboride cathode current collector. Activation was performed using a chronopotential method, by constant current charging at 5 A / g for 0.4 h. After constant current charging, activation was completed, yielding a zinc-ion battery containing an in-situ electrochemically activated vanadium diboride cathode, which could then be directly subjected to electrochemical testing. The electrolyte used was a 2 mol / L ZnSO4 aqueous solution, and the separator was a commercially available glass fiber separator. Based on the mass of the cathode material, the specific capacity of this aqueous zinc-ion battery at a current density of 0.2 A / g was 130 mAh / g.

[0074] Example 4

[0075] Aqueous zinc-ion batteries based on electrochemically activated vanadium diboride cathode and metallic zinc anode.

[0076] (I) Preparation of vanadium diboride cathode

[0077] (1) Weigh 20mg of vanadium diboride powder, 2.5mg of acetylene black powder and 2.5mg of polyvinylidene fluoride in a mass ratio of 8:1:1. Add all materials to an agate mortar and grind manually for 5 minutes to mix the materials evenly. Then add an appropriate amount of N-methyl-2-pyrrolidone and continue grinding for more than 30 minutes until the slurry is viscous and no obvious particles are visible.

[0078] (2) The ground slurry is coated onto a stainless steel foil current collector with a vanadium diboride loading of 2 mg / cm2. The stainless steel foil current collector coated with the slurry is placed in a vacuum drying oven at 80°C for thorough drying. After drying, an unactivated vanadium diboride cathode can be obtained.

[0079] (II) Preparation of electrochemically activated vanadium diboride cathode and aqueous zinc-ion battery

[0080] Using the unactivated vanadium diboride cathode prepared in the previous step as the working electrode, an aqueous zinc-ion battery was assembled in the following order: zinc anode, separator, electrolyte, and vanadium diboride cathode current collector. Activation was performed using a multiple constant current charge-discharge cycle method, involving 50 charge-discharge cycles at a constant current of 5 A / g, with a voltage range of 0.2 V–1.4 V. After the constant current charge-discharge cycles, activation was completed, yielding a zinc-ion battery containing an in-situ electrochemically activated vanadium diboride cathode, which could then be directly subjected to electrochemical testing. The electrolyte used was a 2 mol / L ZnSO4 aqueous solution, and the separator was a commercially available glass fiber separator. Based on the mass of the cathode material, the specific capacity of this aqueous zinc-ion battery at a current density of 0.2 A / g was 123 mAh / g.

[0081] Example 5

[0082] A zinc ion hybrid capacitor based on an electrochemically activated vanadium diboride cathode, an activated carbon fiber anode, and an aqueous zinc sulfate electrolyte.

[0083] (I) Preparation of vanadium diboride cathode

[0084] (1) Weigh 40mg of vanadium diboride powder, 5mg of acetylene black powder and 5mg of polyvinylidene fluoride in a mass ratio of 8:1:1. Add all materials to an agate mortar and grind manually for 5 minutes to mix the materials evenly. Then add an appropriate amount of N-methyl-2-pyrrolidone and continue grinding for more than 30 minutes until the slurry is viscous and no obvious particles are visible.

[0085] (2) The ground slurry was coated onto a stainless steel foil current collector, with a vanadium diboride loading of 2 mg / cm³. 2 The stainless steel foil current collector coated with slurry is placed in a vacuum drying oven at 80°C for thorough drying. After drying, an unactivated vanadium diboride cathode can be obtained.

[0086] (II) Preparation of electrochemically activated vanadium diboride cathode

[0087] The activation process of vanadium diboride electrode material can be completed using a three-electrode system. A Pt electrode and an Ag / AgCl electrode serve as the counter and reference electrodes, respectively, while the unactivated vanadium diboride cathode serves as the working electrode. A 2 mol / L zinc sulfate electrolyte is used as the activation electrolyte. Activation is achieved using a chronoamperometry method. The voltage of the system is maintained at 1.1V for 12 hours using constant-voltage charging. After constant-voltage activation, the obtained electroactivated vanadium diboride cathode is repeatedly washed with deionized water 3–5 times. Then, the washed vanadium diboride cathode is placed in a vacuum drying oven for vacuum drying at 80℃ for 6 hours. After drying, the electrochemically activated vanadium diboride cathode material is obtained. Different sizes of cathode current collectors can be obtained by stamping or cutting for use in assembling other energy storage devices.

[0088] (III) Preparation of Aqueous Zinc Ion Hybrid Capacitors

[0089] An aqueous zinc-ion hybrid capacitor was assembled in the following order: commercially available activated carbon fiber anode, separator, and electrochemically activated vanadium diboride cathode. A 2 mol / L ZnSO4 aqueous solution was used as the electrolyte, and a commercially available glass fiber separator was employed. Based on the mass of the cathode material, the discharge specific capacity of this aqueous zinc-ion hybrid capacitor at a current density of 1 A / g is 110 mAh / g.

[0090] Example 6

[0091] A magnesium ion hybrid capacitor based on an electrochemically activated vanadium diboride cathode, an activated carbon fiber anode, and an aqueous magnesium sulfate electrolyte.

[0092] (I) Preparation of vanadium diboride cathode

[0093] (1) Weigh 20mg of vanadium diboride powder, 2.5mg of acetylene black powder and 2.5mg of polyvinylidene fluoride in a mass ratio of 8:1:1. Add all materials to an agate mortar and grind manually for 5 minutes to mix the materials evenly. Then add an appropriate amount of N-methyl-2-pyrrolidone and continue grinding for more than 30 minutes until the slurry is viscous and no obvious particles are visible.

[0094] (2) The ground slurry was coated onto a stainless steel foil current collector, with a vanadium diboride loading of 2 mg / cm³. 2 The stainless steel foil current collector coated with slurry is placed in a vacuum drying oven at 80°C for thorough drying. After drying, an unactivated vanadium diboride cathode can be obtained.

[0095] (II) Preparation of electrochemically activated vanadium diboride cathode and aqueous magnesium ion hybrid capacitor

[0096] Using the unactivated vanadium diboride cathode prepared in the previous step as the working electrode, an aqueous magnesium ion hybrid capacitor was assembled in the following order: commercial activated carbon fiber anode, separator, electrolyte, and unactivated vanadium diboride cathode. Activation was achieved using a repetitive cyclic voltammetry method. The cyclic voltage range of the magnesium ion hybrid capacitor was 0.2V–1.8V, with 20 cycles and a voltage scan rate of 0.5mV / s. After electrochemical activation, a magnesium ion hybrid capacitor containing the in-situ electrochemically activated vanadium diboride cathode was obtained, allowing for direct electrochemical testing. The electrolyte used was a 2mol / L MgSO4 aqueous solution, and the separator was a commercially available glass fiber separator. Based on the mass of the cathode material, the specific capacity of this aqueous magnesium ion hybrid capacitor at a current density of 1A / g was 98mAh / g.

[0097] Example 7

[0098] Ammonium ion hybrid capacitor based on electrochemically activated vanadium diboride cathode, activated carbon fiber anode, and aqueous ammonium sulfate electrolyte.

[0099] (I) Preparation of vanadium diboride cathode

[0100] (1) Weigh 20mg of vanadium diboride powder, 2.5mg of acetylene black powder and 2.5mg of polyvinylidene fluoride in a mass ratio of 8:1:1. Add all materials to an agate mortar and grind manually for 5 minutes to mix the materials evenly. Then add an appropriate amount of N-methyl-2-pyrrolidone and continue grinding for more than 30 minutes until the slurry is viscous and no obvious particles are visible.

[0101] (2) The ground slurry was coated onto a stainless steel foil current collector, with a vanadium diboride loading of 2 mg / cm³. 2 The stainless steel foil current collector coated with slurry is placed in a vacuum drying oven at 80°C for thorough drying. After drying, an unactivated vanadium diboride cathode can be obtained.

[0102] (II) Preparation of electrochemically activated vanadium diboride cathode and aqueous ammonium ion mixed capacitor

[0103] Using the unactivated vanadium diboride cathode prepared in the previous step as the working electrode, an aqueous ammonium ion hybrid capacitor was assembled in the following order: commercial activated carbon fiber anode, separator, electrolyte, and vanadium diboride cathode. Activation was achieved using a chronoamperometry method. The voltage of the ammonium ion hybrid capacitor was kept constant at 1.8V for 8 hours using constant voltage charging. After constant voltage activation, an ammonium ion hybrid capacitor containing an in-situ electrochemically activated vanadium diboride cathode was obtained, and electrochemical testing of the ammonium ion hybrid capacitor could be performed directly. The electrolyte used was a 2 mol / L (NH4)2SO4 aqueous solution, and the separator was a commercially available glass fiber separator. Based on the mass of the cathode material, the specific capacity of this aqueous ammonium ion hybrid capacitor at a current density of 1 A / g was 78 mAh / g.

[0104] Example 8

[0105] A lithium-ion hybrid capacitor based on an electrochemically activated vanadium diboride cathode, an activated carbon fiber anode, and an aqueous lithium sulfate electrolyte.

[0106] (I) Preparation of vanadium diboride cathode

[0107] (1) Weigh 20mg of vanadium diboride powder, 2.5mg of acetylene black powder and 2.5mg of polyvinylidene fluoride in a mass ratio of 8:1:1. Add all materials to an agate mortar and grind manually for 5 minutes to mix the materials evenly. Then add an appropriate amount of N-methyl-2-pyrrolidone and continue grinding for more than 30 minutes until the slurry is viscous and no obvious particles are visible.

[0108] (2) The ground slurry was coated onto a stainless steel foil current collector, with a vanadium diboride loading of 2 mg / cm³. 2 The stainless steel foil current collector coated with slurry is placed in a vacuum drying oven at 80°C for thorough drying. After drying, an unactivated vanadium diboride cathode can be obtained.

[0109] (II) Preparation of electrochemically activated vanadium diboride cathode and aqueous lithium-ion hybrid capacitor

[0110] Using the unactivated vanadium diboride cathode prepared in the previous step as the working electrode, an aqueous lithium-ion hybrid capacitor was assembled in the following order: activated carbon fiber anode, separator, electrolyte, and vanadium diboride cathode current collector. Activation was achieved using a chronoamperometry method. The voltage of the lithium-ion hybrid capacitor was kept constant at 2.0V for 10 hours using constant voltage charging. After constant voltage activation, a lithium-ion hybrid capacitor containing an in-situ electrochemically activated vanadium diboride cathode was obtained, which could be directly subjected to electrochemical testing. The electrolyte used was a 2mol / L Li₂SO₄ aqueous solution, and the separator was a commercially available glass fiber separator. Based on the mass of the cathode material, the specific capacitance of this aqueous magnesium-ion hybrid capacitor was 97mAh / g at a current density of 1A / g.

[0111] Figure 4 The figures show the cyclic voltammetry curves of the electrochemically activated vanadium diboride cathodes in Examples 5-8 in aqueous electrolytes with different ions. Figure 5 The figures show the galvanostatic charge-discharge curves of the electrochemically activated vanadium diboride cathodes from Examples 5-8 in aqueous electrolytes with different ions. As can be seen from the figures, in Zn-containing... 2+ Mg 2+ Li + or NH4 + In aqueous electrolytes, activated vanadium diboride exhibits high electrochemical activity.

[0112] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing electrochemically activated vanadium diboride, characterized in that, Includes the following steps: Step 1: Mix vanadium diboride, conductive carbon source, and binder evenly, add solvent, grind to form a positive electrode slurry, coat it onto the current collector, and dry to obtain a vanadium diboride positive electrode; assemble the vanadium diboride positive electrode, separator, negative electrode, and aqueous electrolyte into an energy storage system; the loading of the positive electrode slurry on the current collector is 0.5~15 mg / cm³. 2 The concentration of the electrolyte is 0.2 ~ 3.0 mol / L, and the pH value of the electrolyte is 3.5 ~ 8; Step 2: Activate the vanadium diboride cathode material in situ using chronoamperometry, repetitive cyclic voltammetry, chronopotentialometry, or multiple constant current charge-discharge cycles to obtain the vanadium diboride cathode material with in situ electrochemical activation. The chronoamperometry activation method involves applying different charging cutoff voltages during the initial charging activation process. After charging for a certain period of time, the activation ends, resulting in in-situ electrochemically activated vanadium diboride cathode material. The chronoamperometry method has a charging cutoff voltage of 1.0-2.4V and a charging time of 0.1-24h. The repetitive cyclic voltammetry activation refers to performing repeated cyclic voltammetry tests on the battery multiple times. After several repetitions, the activation ends, yielding in-situ electrochemically activated vanadium diboride cathode material. If a battery or capacitor system is used in the repetitive cyclic voltammetry, the voltage range is 0 V to 2.4 V. If a three-electrode system is used, the voltage range is -1 V to 0.6 V, where the Pt electrode and Ag / AgCl electrode serve as the counter electrode and reference electrode, respectively. The repetitive cyclic voltammetry has a scan rate of 0.1-100 mV / s and is repeated 1-100 times. The chronopotential activation method involves applying different charging currents during the initial charging activation process. After charging for a certain period of time, the activation ends, resulting in in-situ electrochemically activated vanadium diboride cathode material. The chronopotential method involves a charging current of 0.01-10 A / g and a charging time of 0.01-12 h. The activation method of repeated constant current charge-discharge cycles refers to repeatedly performing constant current charge-discharge tests on the battery. After several repetitions, the activation ends, yielding in-situ electrochemically activated vanadium diboride cathode material. If a battery or capacitor system is used in the repeated constant current charge-discharge cycle method, the voltage range is 0 V to 2.4 V. If a three-electrode system is used, the voltage range is -1 V to 0.6 V, where the Pt electrode and Ag / AgCl electrode serve as the counter electrode and reference electrode, respectively. The repeated constant current charge-discharge cycle method involves a charge-discharge current of 0.1-20 A / g and 1-100 cycles.

2. The preparation method according to claim 1, characterized in that, In the repetitive cyclic voltammetry: the scan rate is 20 mV / s to 50 mV / s, and the number of repetitions is 50 to 80.

3. The preparation method according to claim 1, characterized in that, The conductive carbon source mentioned in step 1 is at least one of carbon black, conductive graphite, carbon fiber, carbon nanotubes, and acetylene black. The adhesive mentioned in step 1 is at least one of polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, and carboxymethyl cellulose; The solvent mentioned in step 1 is at least one of N-methyl-2-pyrrolidone, dimethyl carbonate, ethylene carbonate, and diethylene carbonate; The current collector mentioned in step 1 is at least one of titanium foil, stainless steel foil, stainless steel mesh, and carbon cloth; The diaphragm mentioned in step 1 is at least one of glass fiber diaphragm, non-woven fabric, and cellulose nanofiber diaphragm; The aqueous electrolyte mentioned in step 1 is an aqueous electrolyte containing a metal salt or ammonium salt, wherein the metal salt is a zinc salt, magnesium salt or lithium salt; The negative electrode mentioned in step 1 is activated carbon, activated carbon fiber, or zinc foil.

4. The preparation method according to claim 1, characterized in that, In step 1, the drying temperature is 50 ℃~100 ℃ and the drying time is 2 h~24 h.

5. An electrochemically activated vanadium diboride, characterized in that, It is prepared by the method described in any one of claims 1-4.

6. The application of the electrochemically activated vanadium diboride as described in claim 5 in aqueous energy storage cathode materials.

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