VxOy-coated V2O5 composite material as well as preparation method and application thereof

Abstract

The invention provides a preparation method of a VxOy-coated V2O5 in-situ composite material. The preparation method comprises the following steps: step 1, heating a muffle furnace to a target temperature; step 2, weighing a certain amount of VO2; step 3, putting the weighed VO2 into the muffle furnace which is preheated; and 4, carrying out heat preservation in a muffle furnace for a certain time, and cooling to prepare the high-performance V2O5 in-situ composite electrode material VxOy-coated V2O5. The invention further provides the VxOy-coated V2O5 composite material and application of the VxOy-coated V2O5 composite material. The VxOy-coated V2O5 aqueous zinc ion battery composite positive electrode material is prepared by using VO2 in-situ oxidation for the first time, the process is simple, the cost is low, the reproducibility is good, the morphology is controllable, additional reagents are not needed, and calcination can be completed at low temperature, so that the reaction cost and the energy consumption are saved, and industrialization is easy.

Description

Technical Field

[0001] The present invention relates to a positive electrode material for an aqueous zinc-ion battery and a preparation method thereof, and particularly relates to an in-situ composite method that can significantly improve the zinc storage performance of VO2 in aqueous solution. Background Art

[0002] Since the advent of lithium-ion batteries in the late 1990s of the 20th century, they have almost occupied the entire rechargeable battery technology market with their advantages such as high energy density and long cycle life. However, such lithium-ion batteries based on organic electrolytes generally have disadvantages such as high preparation cost, high safety risk, limited lithium resource reserves, and difficult recycling. Therefore, aqueous rechargeable zinc-ion batteries (AZIBs) are recognized as ideal candidates for future energy storage and conversion to replace lithium-ion batteries. On the one hand, metallic zinc has advantages such as rich reserves, low price, high chemical stability, and relatively low redox potential (-0.76 V vs. SHE); meanwhile, metallic zinc can achieve the transfer of two electrons, which gives it a mass specific capacity as high as 820 mAh g -1 and a volume specific capacity of 5855 mAh cm -3 . In addition, the aqueous electrolyte system has an ionic conductivity two orders of magnitude higher than that of the organic electrolyte system and has no disadvantages such as flammability and explosiveness.

[0003] However, the aqueous electrolyte has problems such as slow Zn deposition / dissolution kinetics, low Coulomb efficiency, and narrow electrochemical window; at the same time, due to the high charge / ionic radius ratio of Zn 2+ , its insertion and extraction kinetics in the positive electrode are relatively slow, resulting in poor ionic kinetic performance of AZIBs. VO2 can not only provide open migration channels for , but also can better alleviate the self-structural deformation caused by the insertion and extraction of Zn 2+ . Therefore, VO2 has good crystal structure stability while having the advantages of high specific capacity and low cost of other vanadium-based AZIBs positive electrodes, and is a relatively promising positive electrode for AZIBs. However, there are still problems such as low intrinsic electronic conductivity, unsatisfactory rate performance and specific capacity retention rate, which seriously limit its practical application. Summary of the Invention

[0004] In view of this, the present invention provides a positive electrode composite material for an aqueous zinc-ion battery and a preparation method thereof. The preparation method of the present invention is simple, and the morphology of the obtained composite positive electrode material is controllable; the obtained positive electrode material is applied to an aqueous zinc-ion battery and has electrochemical performance characteristics such as high discharge specific capacity, charge-discharge rate, and cycle stability.

[0005] The technical solution of the present invention is as follows:

[0006] A x O y preparation method of VO@V2O5 composite material, comprising the following steps:

[0007] Step 1: Heat the muffle furnace to the target temperature;

[0008] Step 2: Weigh a certain amount of VO2;

[0009] Step 3: Place the weighed VO2 into the pre-heated muffle furnace above;

[0010] Step 4: Keep it warm in the muffle furnace for a certain time, and after cooling down, a high-performance V2O5 in-situ composite electrode material V x O y @V2O5 can be prepared.

[0011] A further scheme is:

[0012] In Step 1, the target temperature is 200 - 500 °C, preferably 200 - 400 °C; the temperature error does not exceed ±5 °C.

[0013] A further scheme is:

[0014] In Step 2, the VO2 is any one of VO2(A), VO2(B), VO2(D), VO2(M) and VO2(R), preferably VO2(B) and VO2(M).

[0015] A further scheme is:

[0016] In Step 4, the calcination time in the muffle furnace is 1 - 16 min, preferably 2 - 9 min, and the time error does not exceed ±1 min.

[0017] A further scheme is:

[0018] In Step 4, the cooling is to cool down to room temperature.

[0019] The present invention also provides a x O y VO@V2O5 composite material, which is prepared by the preparation method of the foregoing VO@V2O5 composite material. x O y @V2O5 composite material.

[0020] The present invention also provides the application of VO@V2O5 composite material, which is to use the VO@V2O5 composite material as the positive electrode material to prepare an aqueous zinc-ion battery. x O y @V2O5 composite material. x O y @V2O5 composite material as the positive electrode material to prepare an aqueous zinc-ion battery.

[0021] A further solution is as follows:

[0022] The zinc-ion battery is a button-type aqueous zinc-ion battery.

[0023] According to the present invention, the positive electrode material can be applied to the preparation of a rechargeable aqueous zinc-ion battery according to the existing technology; preferably, the preparation of a rechargeable aqueous zinc-ion battery includes the following steps:

[0024] A. Preparation of the positive electrode: Dissolve the active material and conductive carbon black in polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP), mix evenly to form a slurry, coat it on a stainless steel mesh, and obtain a positive electrode sheet through vacuum drying; the mass ratio of the active material, activated carbon, and polyvinylidene fluoride is 7:2:1, the vacuum drying temperature is 80°C, and the drying time is 8 - 12 h;

[0025] B. Preparation of the negative electrode: The negative electrode is a zinc foil, which is polished to remove the oxide layer, washed, and vacuum dried to obtain a negative electrode sheet;

[0026] C. Preparation of the aqueous electrolyte: Dissolve zinc trifluoromethanesulfonate in triple deionized water to obtain an electrolyte; the concentration of zinc trifluoromethanesulfonate in the electrolyte is preferably 3 M;

[0027] D. Assembly of the battery: Place the electrode sheets into the positive and negative cases of the button battery respectively, separate the two electrode sheets with a glass fiber membrane, add an appropriate amount of the electrolyte, and then encapsulate the battery to obtain a rechargeable aqueous zinc-ion button battery.

[0028] According to the present invention, the addition amount of NMP in step A can be carried out according to the existing technology.

[0029] E. Electrochemical performance test: The amplitude of the AC impedance test is 0.05 mV, the frequency is 100 KHz - 10 mHz, and the electrochemical test voltage window is 0.2 - 1.4 V (vs. Zn 2+ / Zn)

[0030] The beneficial effects of the present invention are as follows:

[0031] 1. The present invention for the first time uses in-situ oxidation of VO2 to prepare a V x O y @V2O5 aqueous zinc-ion battery composite positive electrode material, which has a simple process, low cost, good reproducibility, controllable morphology, does not require additional reagents, and can be completed by calcination at low temperature, thus saving reaction costs and energy consumption and being easy to industrialize.

[0032] 2. The in-situ composite of V2O5 alleviates the stress of volume change of the V x O y electrode, gives full play to the synergistic effect of the two, and increases the Zn 2+The reversibility of insertion and extraction, so when it is used as the aqueous zinc ion positive electrode, it can not only improve the actual electrochemical specific capacity of the zinc ion battery, but also enhance the rate performance and extend the cycle service life.

[0033] 3. The V x O y @V2O5 composite positive electrode material for aqueous zinc ion batteries prepared in the present invention is an ideal candidate for high specific capacity, high rate and long cycle life zinc ion positive electrode materials applied to various portable electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to make the objectives, technical solutions and beneficial effects of the present invention clearer, the present invention provides the following drawings for description:

[0035] Figure 1 XRD patterns of the positive electrode materials VO2(M)@V2O5 and VO2(M) for aqueous zinc ion batteries prepared in Example 1 and Comparative Example 1.

[0036] Figure 2 XRD pattern of the positive electrode material VO2(B) for aqueous zinc ion batteries prepared in Comparative Example 2.

[0037] Figure 3 XRD pattern of the positive electrode material V3O7@H x V2O5 for aqueous zinc ion batteries prepared in Example 2.

[0038] Figure 4 XRD patterns of the positive electrode materials VO2(D)@V2O5 and VO2(D) for aqueous zinc ion batteries prepared in Example 3 and Comparative Example 3.

[0039] Figure 5 a is the TEM image of the sample in Example 1; Figure 5 b is the high-resolution characteristic lattice fringe image of M-phase VO2 and V2O5.

[0040] Figure 6 XPS image of the sample in Example 1.

[0041] Figure 7 Specific capacity - cycle number curves of the electrodes prepared in Example 1 and Comparative Example 1 at the same discharge rate. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The present invention will be further described below with reference to the drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the embodiments given are not intended to limit the present invention.

[0043] Example 1

[0044] A V of Example 1 x O y @V2O5 composite material and its preparation method and application include the following steps:

[0045] 1) Grind VO2(M) thoroughly and evenly;

[0046] 2) Calcinate in a muffle furnace preheated to 345 °C for 4 min;

[0047] 3) After naturally cooling to room temperature with the furnace, a grayish-black VO2(M)@V2O5 aqueous zinc-ion battery composite cathode material is obtained.

[0048] Comparative Example 1

[0049] A V of Comparative Example 1 x O y @V2O5 composite material and its preparation method and application include the following steps:

[0050] 1) Weigh 1.286 g of NH4VO3 into a mixed solution of 40 mL of deionized water and 20 mL of ethylene glycol, and stir at room temperature for 1 h;

[0051] 2) Transfer the suspension obtained in step 1) to a 100 mL reaction kettle, and carry out hydrothermal reaction at 180 °C for 12 h;

[0052] 3) The product obtained in step 2) is centrifugally washed 2 - 3 times with deionized water and ethanol respectively, and then vacuum dried at 70 °C for 12 h to obtain a black VO2(M) material. This material has not undergone the in-situ oxidation treatment in air in Example 1 above, and this material is used as the implementation material in Example 1 for the in-situ oxidation preparation of VO2(M)@V2O5 composite material in this example.

[0053] Example 2

[0054] A V of Example 2 x O y @V2O5 composite material and its preparation method and application include the following steps:

[0055] 1) Grind VO2(B) thoroughly and evenly;

[0056] 2) Calcinate in a muffle furnace preheated to 350 °C for 8 min;

[0057] 3) After naturally cooling to room temperature with the furnace, a grayish-black V3O7@H x V2O5 aqueous zinc-ion battery composite cathode material is obtained.

[0058] Comparative Example 2

[0059] A V of Comparative Example 2x O y V@V2O5 composite material, its preparation method and application, comprising the following steps:

[0060] 1) Weigh 2 g of V2O5 and place it in a mixed solution of 30 mL of deionized water and 20 mL of ethylene glycol, and stir at room temperature for 1 h;

[0061] 2) Transfer the suspension obtained in step 1) to a 100 mL autoclave and carry out hydrothermal reaction at 180 °C for 6 h;

[0062] 3) After centrifugally washing the product obtained in step 2) with deionized water and ethanol 2 - 3 times respectively, vacuum dry it at 70 °C for 12 h to obtain a gray - black VO2(B) material. This material has not undergone the in - situ oxidation treatment in air in Example 2 above. This material is used as the implementation material in Example 2 for the in - situ oxidation preparation of V3O7@H x V2O5 composite material.

[0063] Example 3

[0064] A V in Example 3 x O y V@V2O5 composite material, its preparation method and application, comprising the following steps:

[0065] 1) Grind VO2(D) thoroughly and evenly;

[0066] 2) Calcinate in a muffle furnace pre - heated to 350 °C for 6 min;

[0067] 3) After naturally cooling to room temperature with the furnace, a gray - black VO2(D)@V2O5 composite positive electrode material for aqueous zinc - ion batteries is obtained.

[0068] Comparative Example 3

[0069] A V in Comparative Example 3 x O y V@V2O5 composite material, its preparation method and application, comprising the following steps:

[0070] 1) Weigh 1.04 g of vanadyl acetylacetonate and place it in a mixed solution of 4 mL of 30% H2O2 solution and 45 mL of isopropanol, and stir at room temperature for 30 min;

[0071] 2) Transfer the suspension obtained in step 1) to a 100 mL autoclave and carry out hydrothermal reaction at 200 °C for 6 h;

[0072] 3) After centrifugally washing the product obtained in step 2) with deionized water and ethanol 2 - 3 times respectively, it is vacuum dried at 60 °C for 8 h to obtain a black VO2(D) material. This material has not undergone the in-situ oxidation treatment in air in Example 3 above. This material is used as the implementation material in Example 3 for the in-situ oxidation preparation of the VO2(D)@V2O5 composite material in this example.

[0073] As can be seen from the above examples, the V x O y @V2O5 composite material provided by this application, where V x O y represents different types of vanadium oxides.

[0074] Figure 1 XRD patterns of the aqueous zinc-ion battery cathode materials VO2(M)@V2O5 and VO2(M) prepared in Example 1 and Comparative Example 1 are shown. The sample prepared in Comparative Example 1 has extremely high crystallinity and certain preferred orientation, and its phase corresponds to the standard peaks of VO2(M2); while the main characteristic peaks at 2θ = 12.40°, 18.95°, 27.92° and 40.55° respectively correspond to the (200), (221), (240) and (035) crystal planes of tetragonal V2O5 (PDF#45 - 1074).

[0075] Figure 2 XRD pattern of the aqueous zinc-ion battery cathode material VO2(B) prepared in Comparative Example 2 is shown. The sample prepared in Comparative Example 2 has good crystallinity and no other impurity peaks, and it is a pure phase of VO2(B).

[0076] Figure 3 XRD pattern of the aqueous zinc-ion battery cathode material V3O7@H x V2O5 obtained in Example 2 is shown. The sample prepared in Example 2 is a composite, and its main phase corresponds to the standard peaks of orthorhombic H x V2O5 (PDF#45 - 0429); while the main characteristic peaks at 2θ = 19.77°, 21.82°, 49.93° and 51.17° respectively correspond to the (402), (204), (001) and (101) crystal planes of monoclinic V3O7 (PDF#27 - 0940).

[0077] Figure 4XRD patterns of the aqueous zinc-ion battery cathode materials VO2(D)@V2O5 and VO2(D) prepared in Example 3 and Comparative Example 3. The sample prepared in Comparative Example 3 corresponds to the standard peaks of monoclinic VO2(D) (PDF#15-0755); while the main characteristic peaks of the sample prepared in Example 3 at 2θ = 24.99°, 27.92°, 45.07° and 48.21° correspond to the (400), (240), (026) and (055) crystal planes of tetragonal V2O5 (PDF#45-1074), respectively.

[0078] Figure 5 a is the TEM image of the sample in Example 1. After the composite, the sample VO2(M)@V2O5 in Example 1 basically does not change the flower-like structure of the VO2(M) sample, and its morphology only has slightly curled nanosheets at high temperature. Figure 5 b is the high-resolution characteristic lattice fringes of M-phase VO2 and V2O5, which confirm that the sample in Example 1 is a VO2(M)@V2O5 composite.

[0079] Figure 6 XPS image of the sample in Example 1. In the figure, two split peaks at 516.44 and 517.42 eV can be well simulated for V 2p3 / 2, corresponding to the characteristic split peaks of V 4+ and V 5+ respectively, which also confirm that the VO2@V2O5 composite has been successfully prepared, in line with the above analysis results of XRD and TEM.

[0080] Figure 7 Charge-discharge specific capacity - cycle number curves of the electrodes prepared in Example 1 and Comparative Example 1 at the same discharge rate. After the initial 100-week activation cycle, the discharge specific capacity of the electrode in Comparative Example 1 is only 148.81 mAh / g, while the discharge specific capacity of the electrode in Example 1 can be as high as 205.67 mAh / g. As the number of cycles increases, its specific capacity is still increasing, from 205.67 mAh / g to 228.76 mAh / g. The specific capacity of the electrode in Comparative Example 1 reaches the maximum value of 148.81 mAh / g at the 193rd cycle, and then the specific capacity slowly decreases. The capacity decays at the 500th cycle, only 138.52 mAh / g, and the discharge specific capacity drops sharply after 750 cycles, only 124.82 mAh / g, corresponding to a capacity retention rate of 83.88%. While Example 1 can still provide a capacity of 219.35 mAh / g after 1200 cycles, with a Coulomb efficiency close to 100% and a capacity retention rate as high as 111.23%, indicating its ultra-high cycle stability and good application prospects in high-performance aqueous zinc-ion battery cathode materials.

[0081] Table 1 is a statistical table of the comparison of the discharge specific capacity data of the electrodes prepared in Example 1, Comparative Example 1, Example 2, and Comparative Example 2 at different discharge rates. It can be seen from Table 1 that as the current density increases, the examples show higher reversible discharge specific capacities than the corresponding comparative examples, indicating that the method of in-situ composite V2O5 in the present invention can significantly improve the rate performance of the comparative example electrodes.

[0082] Table 1

[0083]

[0084] Through the above comparative experiments, it can be proved that the VO2@V2O5 cathode material prepared by the in-situ air calcination oxidation method is more conducive to the reversibility of the insertion and extraction of aqueous zinc ions compared with the comparative example samples, and thus can significantly improve the electrochemical zinc storage performance of aqueous zinc ion batteries, including higher actual electrochemical specific capacity, higher rate performance, and longer cycle service life.

[0085] Although the present invention has been described herein with reference to its explanatory embodiments, the above embodiments are only the preferred embodiments of the present invention, and the embodiments of the present invention are not limited by the above embodiments. It should be understood that those skilled in the art can design many other modifications and embodiments, and these modifications and embodiments will fall within the scope and spirit of the principles disclosed in this application.

Claims

1. A V x O y @V2O5 composite material preparation method, characterized in that It includes the following steps: Step 1: Heat the muffle furnace to the target temperature; Step 2: Weigh a certain amount of VO2; Step 3: Place the weighed VO2 into the pre-heated muffle furnace above; Step 4: Keep it warm in a muffle furnace for a certain period of time, and after cooling down, a high-performance V2O5 in-situ composite electrode material V x O y @V2O5 can be prepared.

2. The preparation method of the V x O y @V2O5 composite material, characterized in that: In Step 1, the target temperature is 200 to 500 °C, and the temperature error does not exceed ±5 °C.

3. The preparation method of the V x O y @V2O5 composite material, characterized in that: In Step 1, the target temperature is 200 to 400 °C.

4. The preparation method of the V x O y @V2O5 composite material, characterized in that: In Step 2, VO2 is any one of VO2(A), VO2(B), VO2(D), VO2(M) and VO2(R).

5. The preparation method of the V x O y @V2O5 composite material according to claim 4, characterized in that: In Step 2, VO2 is any one of VO2(B) and VO2(M).

6. The preparation method of the V x O y @V2O5 composite material, characterized in that: In Step 4, the calcination time in the muffle furnace is 1 to 16 min, the time error does not exceed ±1 min, and the cooling is to room temperature.

7. The preparation method of the V x O y @V2O5 composite material according to claim 6, characterized in that: In Step 4, the calcination time in the muffle furnace is 2 to 9 min.

8. A V x O y @V2O5 composite material, characterized in that it is Prepared by the method for preparing the V x O y @V2O5 composite material according to any one of claims 1 to 7.

9. The application of the V x O y @V2O5 composite material, characterized in that it is Prepare a water-based zinc-ion battery using the V x O y @V2O5 composite material as the positive electrode material.

10. The application of the V x O y @V2O5 composite material, characterized in that: The zinc ion battery is a button-type aqueous zinc ion battery.

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