Amorphous carbon coated porous cellular VO2 / V2O5 composite material and its preparation method and application

Abstract

The invention discloses an amorphous carbon-coated porous cellular VO 2 / V 2 O 5 Composite material and preparation method and application thereof, the amorphous carbon coated porous cellular VO 2 / V 2 O 5 A composite material comprising a core material and an amorphous carbon layer covering the core material, wherein the core material comprises micron-sized VO 2 / V 2 O 5 Particles, the VO 2 / V 2 O 5 The surface of the particles is a porous cellular structure. In the present invention, vanadium pentoxide powder is delivered to the reaction chamber of a plasma device by a carrier gas, and a carbon source gas is introduced and a plasma torch is turned on to react, so that amorphous carbon-coated porous cellular VO is obtained. 2 / V 2 O 5 Composite material. It is used as the positive electrode active material of aqueous zinc battery. ‑1 120 mAh· g ‑1 The initial specific capacity is 115 mAh g after 3000 cycles. ‑1 Specific capacity.

Description

Technical Field

[0001] The present invention relates to an amorphous carbon-coated porous cellular VO 2 / V 2 O 5 The invention relates to a composite material and a preparation method and application thereof, belonging to the technical field of new energy batteries. Background Art

[0002] Based on zinc element, it has high specific capacity (820 mAh g -1 ), low redox potential (-0.76Vvs.SHE), abundant zinc resources, low price and high safety, aqueous zinc-ion batteries are considered to be one of the most promising candidates for next-generation energy storage batteries. 2 O 5 It has the advantages of high theoretical zinc storage capacity and abundant resource reserves, which has attracted great attention. 2 O 5 It has the disadvantages of low electronic conductivity and poor structural stability, usually showing poor cycle performance and capacity retention, which seriously limits the V 2 O 5 Practical application as positive electrode material for aqueous zinc-ion batteries.

[0003] In order to solve the above problems, some researchers have used modification, coating and modification methods to improve V 2 O 5 For example, Chinese invention patent application CN117096322A uses oxalic acid reduction and adds an organic carbon source for heat treatment to obtain carbon, V 4+ The composite material doped with vanadium pentoxide can still maintain about 75% of its capacity after 50 cycles at 1C current. Chinese invention patent CN114188523B in situ grows porous vanadium pentoxide nanosheets on the surface of layered graphene to obtain a graphene-supported vanadium pentoxide composite material. -1 After 1000 cycles at a current of , it still maintains about 55% of its capacity. 2 O 5 Nanobelts and polyacrylamide intercalation reaction prepared V 2 O 5 / MXene composite cathode material, the battery assembled with it has a high conductivity at 0.5 A·g -1 After 200 cycles at a current of , the capacity still remains at about 53%. However, these methods have the problem of cumbersome processing engineering and low carrying capacity of the positive electrode materials, which is difficult to meet the needs of high current fast charging and discharging in modern society. Summary of the invention

[0004] In view of the shortcomings of the existing methods, such as complicated processing engineering, small cycle current density and poor cycle performance of the prepared positive electrode materials, the first object of the present invention is to provide an amorphous carbon-coated porous cellular VO 2 / V 2 O 5 The composite material has high ion / electron transmission rate and structural stability.

[0005] The second object of the present invention is to provide an amorphous carbon-coated porous cellular VO 2 / V 2 O 5 The method for preparing a composite material has simple process, short production cycle and is conducive to large-scale production.

[0006] The third object of the present invention is to provide an amorphous carbon-coated porous cellular VO 2 / V 2 O 5 The application of composite materials, using them as positive electrode materials for aqueous zinc-ion batteries, can obtain higher current carrying density and excellent cycle performance.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention discloses an amorphous carbon-coated porous cellular VO 2 / V 2 O 5 Composite material, the amorphous carbon coated porous cellular VO 2 / V 2 O 5 A composite material comprising a core material and an amorphous carbon layer covering the core material, wherein the core material comprises micron-sized VO 2 / V 2 O 5 Particles, the VO 2 / V 2 O 5 The surface of the particles is a porous cellular structure.

[0009] The amorphous carbon-coated porous VO provided by the present invention 2 / V 2 O 5 Composite material, the core material of which is VO 2 / V 2 O 5 particles; compared to simple V 2 O 5 , doped VO 2It has a higher energy density and exhibits better cycle and rate performance. In addition, the VO 2 / V 2 O 5 The particles have a unique three-dimensional porous cellular structure. The evenly distributed micropores and cellular surface can fully increase the contact area between the active material and the solution, improve the utilization rate of the active material and fully expose the active sites; the three-dimensional conductive network formed by the cross-linking between the outer layer of amorphous carbon can effectively improve the ionic conductivity and electronic conductivity of the electrode system, and at the same time inhibit the structural collapse caused by volume changes during the charge and discharge process of the electrode, effectively improving the battery's carrying current and cycle life.

[0010] In a preferred embodiment, the core material is composed of micron-sized VO 2 / V 2 O 5 Particles and diffuse adsorption on VO 2 / V 2 O 5 Nano-VO on the particle surface 2 / V 2 O 5 composition.

[0011] Due to the large amount of nano-VO dispersed on the surface of the core material 2 / V 2 O 5 It can provide a large number of preferential nucleation sites for zinc ion adsorption, effectively promote the uniform nucleation deposition of zinc, improve the structural stability of the material during the cycle to a certain extent, and enhance the cycle performance of the positive electrode.

[0012] The preferred solution is the VO 2 / V 2 O 5 The particles are spherical or nearly spherical.

[0013] The preferred solution is the VO 2 / V 2 O 5 The particle size is 0.5 μm~20 μm.

[0014] In a preferred embodiment, the amorphous carbon coated porous cellular VO 2 / V 2 O 5 In the composite material, the mass fraction of the amorphous carbon layer is 0.07 wt.% to 0.2 wt.%. In the present invention, the mass fraction of the amorphous carbon layer is within the above preferred range, which can completely cover the core material and avoid the amorphous carbon layer being too thick, thereby reducing the ion transmission rate or even hindering the passage of ions.

[0015] The present invention also provides an amorphous carbon-coated porous cellular VO 2 / V 2 O 5 The preparation method of the composite material comprises the following steps: delivering vanadium pentoxide powder to a reaction chamber of a plasma device through a carrier gas, introducing a carbon source gas and starting a plasma torch to react, thereby obtaining amorphous carbon-coated porous cellular VO 2 / V 2 O 5 Composite materials.

[0016] The key to the technical solution of the present invention is to use plasma to introduce carbon source gas to prepare amorphous carbon modified cellular porous spherical VO 2 @V 2 O 5 Composite materials, on the one hand, under the high temperature conditions of plasma, commercial vanadium pentoxide powder will undergo a remelting-spheroidization process, changing from an irregular shape to a spherical / near-spherical shape. At the same time, due to the ultra-fast cooling rate, the powder surface presents a porous cellular structure, which is conducive to improving the utilization rate of active substances while fully exposing active sites. At the same time, due to the complex gas flow field in the plasma sub-device, the first solidified nanopowder will diffuse and adsorb on the surface of the micron powder after contacting the incompletely solidified micron powder, which can provide a large number of preferential nucleation sites for zinc ion adsorption; on the other hand, the carbon source gas undergoes a cracking reaction under the high temperature conditions of plasma to form a carbon atom cluster structure and adsorb on the surface of the porous cellular vanadium pentoxide particles, in which some carbon atoms undergo a reduction reaction with vanadium pentoxide at high temperature to convert V 2 O 5 Convert to VO 2 The remaining carbon atoms grow in situ at a lower temperature to form an amorphous carbon coating on its surface. The in situ growth behavior greatly improves the bonding stability between the porous vanadium pentoxide nanosheets and the carbon coating, which is beneficial to improving the cycle stability of the positive electrode material.

[0017] In a preferred embodiment, the carrier gas is selected from argon and nitrogen.

[0018] In a preferred embodiment, the flow rate of the carrier gas is 40 slpm to 60 slpm. In the present invention, by controlling the flow rate of the carrier gas within the above range, the final material performance is optimal. If the flow rate of the carrier gas is too large, the powder feeding rate is too fast, which will cause V 2 O 5 The particles are not completely melted, and there is no time for them to react and be coated. If the flow rate of the carrier gas is too small, the pressure in the reaction chamber will be too low and the powder feeder will not be able to deliver powder normally.

[0019] In the present invention, the vanadium pentoxide powder used is commercial vanadium pentoxide powder.

[0020] In a preferred embodiment, the feeding rate of the vanadium pentoxide powder is 1 g / min to 3 g / min.

[0021] In a preferred embodiment, the carbon source gas is selected from methane and / or acetylene. The inventors have found that the reaction effect is best when methane and / or acetylene are selected as the carbon source gas.

[0022] In a preferred embodiment, the flow rate of the carbon source gas is 0.1 slpm to 0.2 slpm. In the present invention, the flow rate of the carbon source gas needs to be effectively controlled. If it is too little, the reduction and coating will be incomplete, while if it is too much, the carbon atom clusters will be increased, so that the thickness of the surface amorphous carbon coating layer will be greatly increased, which will increase the difficulty of Zn ion adsorption and cause a slight decrease in cycle performance.

[0023] In a preferred embodiment, the plasma power is 10 KW to 15 KW, and the pressure of the reaction chamber is 7 psig to 9 psig.

[0024] The present invention also provides an amorphous carbon-coated porous cellular VO 2 / V 2 O 5 Application of composite materials: the amorphous carbon is coated with porous cellular VO 2 / V 2 O 5 The composite material is used as a positive electrode material for aqueous zinc-ion batteries.

[0025] In practical applications, amorphous carbon is coated with porous VO 2 / V 2 O 5 The composite material, conductive carbon black and polyvinylidene fluoride (PVDF) were weighed in a mass ratio of 8:1:1 and placed in a mixing box. Then, an appropriate amount of 1-methyl 2-pyrrolidone (NMP) was added and mixed continuously until a uniform slurry was obtained. The obtained slurry was coated on a 300-mesh stainless steel mesh and vacuum dried at 65°C for 12 h to obtain a positive electrode sheet. A glass fiber membrane was used as a separator. 3 mol / L Zn(CF 3 SO 3 ) 2 The aqueous solution was used as the electrolyte; the commercial 100 μm metal zinc foil was used as the negative electrode to construct a CR2016 button-type aqueous zinc ion battery.

[0026] Compared with the prior art, the advantages of the present invention are:

[0027] (1) The amorphous carbon-coated porous VO 2 / V 2 O 5The composite material has a unique three-dimensional porous cellular structure. The evenly distributed micropores and cellular surface on the surface of the porous sphere can fully increase the contact area between the active substance and the solution, improve the utilization rate of the active substance and fully expose the active sites; the three-dimensional conductive network formed by the cross-linking between the outer layer of coated carbon can effectively improve the ionic conductivity and electronic conductivity of the electrode system, and at the same time inhibit the structural collapse caused by volume changes during the charge and discharge process of the electrode, effectively improving the battery's carrying current and cycle life.

[0028] (2) The amorphous carbon-coated porous cellular VO of the present invention 2 / V 2 O 5 The performance of aqueous zinc-ion batteries assembled with the composite material is better than that of aqueous zinc-ion batteries assembled with commercial vanadium pentoxide zinc battery cathode sheets. -1 140 mAh g -1 The initial specific capacity is 115 mAh g after 3000 cycles. -1 The specific capacity of commercial vanadium zinc pentoxide battery cathode assembled aqueous zinc ion battery has about 110 mAh g at the same current density. -1 The initial specific capacity is only about 50 mAh·g after 3000 cycles. -1 Specific capacity.

[0029] (3) The preparation method of the present invention has a simple process, a short preparation cycle, and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a macroscopic image of the powder in Example 1: Figure 1 (a) is a picture of commercial vanadium pentoxide powder. Figure 1 (b) Amorphous carbon coated porous VO 2 / V 2 O 5 Macroscopic image of composite powder.

[0031] Figure 2 Amorphous carbon coated porous VO 2 / V 2 O 5 The overall SEM image of the composite material powder and the magnified SEM image of its partial area; Figure 2 (a) Amorphous carbon coated porous VO 2 / V 2 O 5 Overall SEM image of the composite material powder. Figure 2 (b) Amorphous carbon coated porous VO 2 / V 2 O5 A magnified scanning electron microscope image of a part of the composite material powder;

[0032] Figure 3 Commercial vanadium pentoxide and amorphous carbon coated porous cellular VO 2 / V 2 O 5 XRD pattern of composite powder.

[0033] Figure 4 The amorphous carbon-coated porous VO in Example 1 2 / V 2 O 5 Rate performance diagram of composite material powder used as positive electrode.

[0034] Figure 5 The amorphous carbon-coated porous VO in Example 1 2 / V 2 O 5 Composite powder as positive electrode at 5 A·g -1 Cycling performance diagram under current.

[0035] Figure 6 The amorphous carbon-coated porous VO in Example 1 2 / V 2 O 5 Composite material powder as positive electrode at 10 A·g -1 Cycling performance diagram under current.

[0036] Figure 7 The amorphous carbon-coated porous VO in Example 1 2 / V 2 O 5 The charge and discharge curves of the composite material powder as the positive electrode.

[0037] Figure 8 The commercial vanadium pentoxide powder used as the positive electrode in Comparative Example 1 was 5 A·g -1 Cycling performance diagram under current.

[0038] Fig. 9 The commercial vanadium pentoxide powder used as the positive electrode in Comparative Example 1 was used at 10 A·g -1 Cycling performance diagram under current. DETAILED DESCRIPTION

[0039] In order to facilitate the understanding of the present invention, the present invention will be described in more comprehensive and detailed manner below in conjunction with the accompanying drawings and preferred embodiments of the specification, but the protection scope of the present invention is not limited to the following specific embodiments.

[0040] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0041] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0042] Example 1

[0043] Step 1: Powder preparation: Using argon as carrier gas, commercial vanadium pentoxide precursor is delivered to the reaction chamber of the plasma device, and methane gas is introduced at the same time and the plasma torch is turned on for reaction. During the preparation process, the plasma power is maintained at 12.5 KW, the carrier gas flow rate is 40 slpm, the methane gas flow rate is 0.1 slpm, the pressure of the reaction chamber is 9 psig, and the vanadium pentoxide raw material powder feeding rate is 1 g / min, so that amorphous carbon-coated porous cellular VO 2 / V 2 O 5 Composite material powder.

[0044] Step 2: Positive electrode preparation: Amorphous carbon coated porous VO 2 / V 2 O 5 The composite material, conductive carbon black and polyvinylidene fluoride (PVDF) were weighed in a mass ratio of 8:1:1 and placed in a mixing box. Then, an appropriate amount of 1-methyl 2-pyrrolidone (NMP) was added and mixed continuously until a uniform slurry was obtained. The obtained slurry was coated on a 300-mesh stainless steel mesh and vacuum dried at 65 °C for 12 h to obtain a positive electrode sheet. A glass fiber membrane was used as a separator. 2 mol / L Zn(CF 3 SO 3 ) 2 The aqueous solution was used as the electrolyte and the commercial 100 μm metal zinc foil was used as the negative electrode to construct a CR2016 button-type aqueous zinc-ion battery. The battery was charged and discharged at a constant current on the Xinwei test system.

[0045] The powder macroscopic image in this embodiment is as follows Figure 1 As shown, Figure 1 (a) is a picture of commercial vanadium pentoxide powder. Figure 1 (b) Amorphous carbon coated porous VO 2 / V 2 O 5 Composite material powder image. It can be seen from the figure that the commercial vanadium pentoxide powder is yellow and slightly agglomerated, while the vanadium pentoxide powder after plasma treatment is gray and non-agglomerated. The color change indicates the successful coating of amorphous carbon.

[0046] The amorphous carbon-coated porous VO prepared in this embodiment 2 / V 2 O 5 Composite material powder scanning image Figure 2 As shown in the figure, it can be seen that amorphous carbon coated porous cellular VO 2 / V 2 O 5 The composite material powder is spherical in shape and has a particle size of about 20 μm. At a large magnification in Figure (b), it can be found that the powder surface is a porous cellular structure with a large number of nanoparticles diffusely adsorbed.

[0047] In this embodiment, commercial vanadium pentoxide and prepared amorphous carbon-coated porous cellular VO 2 / V 2 O 5 The XRD results of the composite powder are shown in Figure 3 As shown in the figure, it can be seen that amorphous carbon coated porous cellular VO 2 / V 2 O 5 In addition to the vanadium pentoxide peak, there are also a large number of VO 2 phase, indicating that part of the vanadium pentoxide phase was successfully reduced to VO during the high temperature plasma treatment. 2 Mutually.

[0048] The amorphous carbon-coated porous VO prepared in this embodiment 2 / V 2 O 5 The rate performance of composite material powder as positive electrode is shown in the figure Figure 4 As shown in the figure, at 10 A· g -1 Under the condition of -1 , maintained at a high level. The amorphous carbon-coated porous cellular VO prepared in this embodiment 2 / V 2 O 5 Composite material powder as positive electrode at 5A·g -1 and 10 A·g -1 The cycle performance diagrams are as follows Figure 5 and Figure 6 As shown in the figure, it can be seen that it is used as a positive electrode active material for aqueous zinc batteries at 5 A·g -1 The current is about 120 mAh g -1 The initial specific capacity is 115 mAh g after 3000 cycles. -1 The specific capacity of -1 120 mAh g-1 The initial specific capacity is 1.38kWh, and it still maintains the original specific capacity after 3000 cycles. Figure 7 Amorphous carbon coated porous VO 2 / V 2 O 5 The change in the charge capacity of the material from 1000 to 3000 cycles in the charge and discharge curve of the composite material powder as the positive electrode further proves that the material has excellent cycle stability.

[0049] Example 2

[0050] The steps are roughly the same as those in Example 1, except that the parameters in step 1 are different:

[0051] Step 1: Powder preparation: The commercial vanadium pentoxide precursor is delivered to the reaction chamber of the plasma device using argon as the carrier gas, and methane gas is introduced at the same time and the plasma torch is turned on for reaction. During the preparation process, the plasma power is maintained at 12.5 KW, the carrier gas flow rate is 40 slpm, the methane gas flow rate is adjusted to 0.15 slpm, the pressure of the reaction chamber is 9 psig, and the vanadium pentoxide raw material powder feeding rate is 1 g / min, so that amorphous carbon-coated porous cellular VO is obtained. 2 / V 2 O 5 Composite materials.

[0052] This embodiment 2 increases the flow rate of methane gas and slightly increases VO 2 The amount of carbon and the thickness of the amorphous carbon coating layer on the surface. The positive electrode prepared in this comparative example was measured at 10 A· g -1 120 mAh g -1 The initial specific capacity of the battery is only 112 mAh·g after 1000 cycles. -1 Specific capacity.

[0053] Comparative Example 1

[0054] The raw material powder was not subjected to modification and spheroidization treatment, and the positive electrode preparation process was the same as that in Example 1, using commercial vanadium pentoxide raw material to prepare the positive electrode for testing:

[0055] The positive electrode prepared in this comparative example was measured at 5 A·g -1 122 mAh g -1 The initial specific capacity of 10A·g -1 At high current, it has about 110 mAh g -1 The initial specific capacity is only about 50 mAh·g after 3000 cycles. -1This comparative example uses raw material powder for testing without reduction and coating process, and the electrochemical performance of the material drops sharply.

[0056] Comparative Example 2

[0057] The steps are roughly the same as those in Example 1, except that the parameters in step 1 are different:

[0058] Step 1: Powder preparation: The commercial vanadium pentoxide precursor is delivered to the reaction chamber of the plasma device using argon as the carrier gas, and methane gas is introduced at the same time and the plasma torch is turned on for reaction. During the preparation process, the plasma power is maintained at 12.5 KW, the carrier gas flow rate is 40 slpm, the methane gas flow rate is adjusted to 0 slpm, the pressure of the reaction chamber is 9 psig, and the vanadium pentoxide raw material powder feeding rate is 1 g / min, so that amorphous carbon-coated porous cellular VO 2 / V 2 O 5 Composite materials.

[0059] The positive electrode prepared in this comparative example was measured at 10 A·g -1 120 mAh g -1 The initial specific capacity is only about 60 mAh·g after 3000 cycles. -1 In this comparative example, methane gas was removed, and the vanadium pentoxide raw material only underwent melting and rapid condensation crystallization in the plasma, without reduction and coating processes, and the electrochemical performance of the material dropped sharply.

[0060] Comparative Example 3

[0061] The steps are roughly the same as those in Example 1, except that the parameters in step 1 are different:

[0062] Step 1: Powder preparation: The commercial vanadium pentoxide precursor is delivered to the reaction chamber of the plasma device using argon as the carrier gas, and methane gas is introduced at the same time and the plasma torch is turned on for reaction. During the preparation process, the plasma power is maintained at 12.5 KW, the carrier gas flow rate is 40 slpm, the methane gas flow rate is adjusted to 0.35 slpm, the pressure of the reaction chamber is 9 psig, and the vanadium pentoxide raw material powder feeding rate is adjusted to 0.5 g / min, so that amorphous carbon-coated porous cellular VO 2 / V 2 O 5 Composite materials.

[0063] This comparative example increases the methane gas flow rate and reduces V 2 O 5The powder feeding rate, after the vanadium pentoxide raw material is reduced and coated in the plasma, the surface amorphous carbon layer is too thick (submicron thickness), which hinders the ion transmission and causes a sharp drop in the electrochemical performance of the material. It is measured that the positive electrode prepared in this comparative example has a high conductivity at 10 A·g -1 100 mAh g -1 The initial specific capacity is low and it fails after 300 cycles.

Claims

1. A method for preparing an amorphous carbon-coated porous cellular VO2 / V2O5 composite material, characterized in that: Vanadium pentoxide powder is delivered to the reaction chamber of a plasma device by a carrier gas, and a carbon source gas is introduced at the same time and a plasma torch is turned on to react, thereby obtaining an amorphous carbon-coated porous cellular VO2 / V2O5 composite material; The amorphous carbon-coated porous cellular VO2 / V2O5 composite material is composed of a core material and an amorphous carbon layer coating the core material. The core material contains micron-sized VO2 / V2O5 particles, and the surface of the VO2 / V2O5 particles is a porous cellular structure. In the amorphous carbon-coated porous cellular VO2 / V2O5 composite material, the mass fraction of the amorphous carbon layer is 0.07wt.%~0.2wt.%.

2. The method for preparing an amorphous carbon-coated porous cellular VO2 / V2O5 composite material according to claim 1, characterized in that: The carrier gas is selected from one of argon and nitrogen; The flow rate of the carrier gas is 40 slpm~60 slpm.

3. The method for preparing an amorphous carbon-coated porous cellular VO2 / V2O5 composite material according to claim 1, characterized in that: The feeding rate of the vanadium pentoxide powder is 1 g / min to 3 g / min.

4. The method for preparing an amorphous carbon-coated porous cellular VO2 / V2O5 composite material according to claim 1, characterized in that: The carbon source gas is selected from methane and / or acetylene; The flow rate of the carbon source gas is 0.1 slpm to 0.2 slpm.

5. The method for preparing an amorphous carbon-coated porous cellular VO2 / V2O5 composite material according to claim 1, characterized in that: The power of the plasma is 10 KW~15 KW, and the pressure of the reaction chamber is 7 psig~9 psig.

6. A method for preparing an amorphous carbon-coated porous cellular VO2 / V2O5 composite material according to any one of claims 1 to 5, characterized in that: The core material consists of micron-sized VO2 / V2O5 particles and nano-VO2 / V2O5 dispersedly adsorbed on the surface of the VO2 / V2O5 particles.

7. A method for preparing an amorphous carbon-coated porous cellular VO2 / V2O5 composite material according to any one of claims 1 to 5, characterized in that: The VO2 / V2O5 particles are spherical or nearly spherical; The particle size of the VO2 / V2O5 particles is 0.5 μm~20 μm.

8. Application of an amorphous carbon-coated porous cellular VO2 / V2O5 composite material prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The amorphous carbon-coated porous cellular VO2 / V2O5 composite material is used as a positive electrode material for an aqueous zinc-ion battery and applied to an aqueous zinc-ion battery.

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