Application of a binary vanadium-based phosphate as an anode protective layer material

Abstract

The present invention discloses an application of a binary vanadium-based phosphate as an anode protective layer material in an aqueous zinc-ion battery. The binary vanadium-based phosphate is M x V y (PO4)3, where M is Zn, Li, Na or Mg, 0 < x < 1, 1 < y < 2; the binary vanadium-based phosphate M x V y (PO4)3 is three-dimensional honeycomb-shaped; the electrolyte in the aqueous zinc-ion battery is ZnSO4; the preparation method of M x V y (PO4)3 is: a complexing agent, phosphate, vanadium salt, and one or more of zinc salt, lithium salt, sodium salt or magnesium salt are mixed in a solvent, and stirred at room temperature and synthesized by the sol-gel method to obtain M,V-PO4 3‑ ; the vanadium salt is ammonium metavanadate; the prepared M,V-PO4 3‑ is calcined under high temperature and nitrogen atmosphere to obtain M x V y (PO4)3. In this application, the binary vanadium-based phosphate as an anode protective layer material can avoid direct contact between free water and the Zn negative electrode, further stabilize the Zn metal anode electrode-electrolyte interface, and also solve problems such as dendrite growth, hydrogen evolution reaction, corrosion and passivation in aqueous zinc-ion batteries, thereby improving the reversibility and stability of the zinc negative electrode and extending the cycle life of the battery.

Description

Technical Field

[0001] The present invention belongs to the field of application of aqueous zinc ion battery materials, and particularly relates to the application of a binary vanadium-based phosphate as an anode protective layer material. Background Art

[0002] The depletion of fossil energy and environmental deterioration are two major severe challenges faced by mankind currently. Developing advanced electrochemical energy storage devices to safely collect and store renewable clean energy is considered the key to solving the above problems.

[0003] Since the advent of aqueous batteries in 1994, due to their advantages such as safe operation, low manufacturing cost, environmental friendliness, and fast charging, they have shown broad application prospects in advanced large-scale grid energy storage systems and are considered potential competitors to LiBs. Among them, metallic zinc (Zn) has become an ideal anode material for aqueous batteries due to its high theoretical capacity (820 mA·h g -1 ), suitable redox potential (-0.76 V vs. SHE), good aqueous solution compatibility, and abundant resources. However, during the actual application process, some reactions in the aqueous electrolyte solution will affect the zinc deposition process, resulting in a decrease in the Coulombic efficiency of zinc deposition / stripping and incomplete dissolution of zinc. Therefore, zinc ions will gradually deposit unevenly on the surface of the zinc metal anode, forming needle-like and flaky zinc dendrites. As the zinc dendrites continuously form and grow, their mechanical rigidity and uneven structure will cause them to fall off from the surface of the zinc anode, forming "dead zinc", resulting in a reduction in the active material of the battery and capacity decline. Zinc dendrites may also pierce the separator, causing internal short circuit of the battery. In addition, the coexistence of zinc and water is thermodynamically unstable. Since the hydrogen evolution potential is higher than the standard electrode potential of Zn 2+ / Zn, the hydrogen evolution reaction often occurs during the electrochemical cycling process. Along with the hydrogen evolution reaction, side reactions such as corrosion pits and passivation will also occur on the surface of the zinc anode, resulting in a decrease in the Coulombic efficiency of the battery, battery swelling, and a decrease in cycle stability. And the above-mentioned adverse side reactions on the surface of the zinc anode do not occur independently and will affect and promote each other.

[0004] At present, many strategies are dedicated to improving the performance of ZIBs by optimizing the zinc electrode, including modification of the surface protection layer of the zinc metal anode, electrode structure design, electrolyte optimization, and separator modification. Among them, electrode structure design usually requires pre-depositing zinc metal through electrochemistry deposition, which increases the complexity of the preparation process and makes it difficult to achieve large-scale expansion in industrial applications. The strategies of using electrolyte additives and separator modification cannot effectively isolate the zinc anode and the electrolyte, and have limited inhibitory effects on side reactions. In addition, high-concentration electrolytes and non-liquid electrolytes often result in high viscosity and low ionic conductivity of the electrolyte, which reduces the advantages of ZIBs. In contrast, constructing an interfacial protection coating on the zinc metal anode has the advantages of a wide selection range, simple preparation, easy control, and high practical value. For example, the methods adopted in the prior art are as follows: Zhu et al. used NaTi2(PO4)3 three-dimensional porous nanoparticles as a solid-state electrolyte protection layer to induce uniform deposition of zinc ions and inhibit interfacial side reactions, resulting in a cycle life of 250 h (1 mA·cm -2 , 1mAh·cm -2 )(Liu M, Cai J, Ao H, et al. NaTi2(PO4)3 Solid‐State Electrolyte Protection Layer on ZnMetal Anode for Superior Long‐Life Aqueous Zinc-Ion Batteries[J]. AdvancedFunctional Materials, 2020.); Dai and He et al. used Na3V2(PO4)3 as a protection layer for the zinc anode, which can provide a large number of stable channels for Zn 2+ transport, thus enhancing the Zn 2+ deposition kinetics and regulating the Zn 2 + transport process through the ion confinement effect, resulting in a cycle life of 500 h (0.5 mA·cm -2 , 0.25 mAh·cm -2)(Guo N, Peng Z, Huo W, et al. Stabilizing Zn Metal Anode Through Regulation of Zn Ion Transfer and Interfacial Behavior with a Fast Ion Conductor Protective Layer[J]. Small, 2023, 19(47).). However, there is still much room for improvement in the above surface engineering for coating materials in stabilizing the Zn metal anode electrode-electrolyte interface, which will restrict its further application.

[0005] Therefore, how to optimize the zinc electrode and further improve the performance of ZIBs by constructing an anode protective layer material that can not only highlight the advantages of a three-dimensional porous structure but also further stabilize the Zn metal anode electrode-electrolyte interface is a current research hotspot in this field. Summary of the Invention

[0006] The object of the present invention is to provide an application of a binary vanadium-based phosphate as an anode protective layer material; this binary vanadium-based phosphate as an anode protective layer material can avoid direct contact between free water and the Zn negative electrode, further stabilize the Zn metal anode electrode-electrolyte interface, and can also better solve problems such as dendrite growth, hydrogen evolution reaction, corrosion, and passivation existing in aqueous zinc-ion batteries, thereby improving the reversibility and stability of the zinc negative electrode and extending the cycle life of the battery.

[0007] To achieve the above invention object, the present invention provides the following technical solutions:

[0008] An application of a binary vanadium-based phosphate as an anode protective layer material in an aqueous zinc-ion battery, wherein the binary vanadium-based phosphate is M x V y (PO4)3, where M is Zn, Li, Na, or Mg, 0 < x < 1, 1 < y < 2.

[0009] In the present invention, M x V y (PO4)3 can be Zn x V y (PO4)3, Li x V y (PO4)3, Na x V y (PO4)3, or Mg x V y (PO4)3.

[0010] When the binary vanadium-based phosphate provided by the present invention is used as an anode protective layer material and as a negative electrode material for an aqueous zinc-ion battery, it can not only effectively inhibit hydrogen evolution, corrosion, and the generation of by-products, but also regulate the electric field distribution, promote the uniform and rapid transmission of zinc ions, improve the stability of the Zn metal anode electrode-electrolyte interface, and thus further improve the battery performance.

[0011] Preferably, in the binary vanadium-based phosphate M x V y (PO4)3: 0.2 ≤ x ≤ 0.8, 1.2 ≤ y ≤ 1.8. The present invention controls the ratio of metals M and V to effectively regulate the electric field distribution, promote the uniform and rapid transmission of zinc ions, and improve the cycle life of the battery (the longest cycle life ≥ 587 h).

[0012] Preferably, in the binary vanadium-based phosphate M x V y (PO4)3: 0.5 ≤ x ≤ 0.8, 1.5 ≤ y ≤ 1.2. The present invention further optimizes the ratio of metals M and V to improve the cycle life of the battery (the longest cycle life ≥ 621 h).

[0013] Preferably, M in the binary vanadium-based phosphate M x V y (PO4)3 is Zn. When 0.2 ≤ x ≤ 0.8, 1.2 ≤ y ≤ 1.8, the cycle life of the battery ≥ 608 h; when 0.5 ≤ x ≤ 0.8, 1.5 ≤ y ≤ 1.2, the cycle life of the battery ≥ 1095 h.

[0014] In the present invention, the binary vanadium-based phosphate M x V y (PO4)3 is three-dimensional honeycomb-shaped.

[0015] The binary vanadium-based phosphate M x V y (PO4)3 and PVDF are mixed and spin-coated on a zinc foil as the negative electrode of an aqueous zinc-ion battery.

[0016] Furthermore, the prepared Zn x V y (PO4)3, Li x V y (PO4)3, Na x V y (PO4)3 or Mg x V y (PO4)3 and PVDF are mixed in a ratio of 9:1, uniformly spin-coated on a zinc foil with a thickness of 100 μm and a diameter of 1 cm, and dried in a vacuum oven at 80 °C for 12 h to obtain Zn xV y (PO4)3, Li x V y (PO4)3, Na x V y (PO4)3 and Mg x V y (PO4)3 electrode.

[0017] The electrolyte in the aqueous zinc-ion battery is ZnSO4, and the positive electrode is carbon paper coated with sodium vanadate.

[0018] The present invention also provides a preparation method of the above-mentioned binary vanadium-based phosphate, and the preparation method includes:

[0019] (1) Mix a complexing agent, a phosphate, a vanadium salt, and one or more of a zinc salt, a lithium salt, a sodium salt or a magnesium salt in a solvent, and stir at room temperature to synthesize M,V-PO4 by the sol-gel method 3- , where M is Zn, Li, Na, or Mg;

[0020] (2) Calcinate the prepared M,V-PO4 3- at high temperature and in a nitrogen atmosphere to obtain three-dimensional honeycomb M x V y (PO4)3, where 0 < x < 1 and 1 < y < 2.

[0021] The preparation principle of the present invention lies in: introducing metal atoms into the vanadium-based phosphate structure framework, embedding them into the vanadium-based phosphate structure framework by high-temperature calcination, and successfully forming M x V y (PO4)3 three-dimensional honeycomb material in the vanadium-based phosphate structure framework, thereby constructing a three-dimensional interconnected porous structure. The synergistic effect of metal elements M and V in the binary vanadium-based phosphate can provide continuous ion / electron transfer, which is beneficial to regulating the electric field distribution, homogenizing the zinc ion flow, realizing the rapid transmission of zinc ions, improving the stability of the Zn metal anode electrode-electrolyte interface, and then improving the cycle life of the battery.

[0022] In step (1), the solvent is deionized water.

[0023] In step (1), 2 - 20 mmol of a complexing agent, 1 - 10 mmol of a vanadium salt and 1 - 14 mmol of a phosphate, and one of 1 - 18 mmol of a zinc salt, 1 - 18 mmol of a lithium salt, 1 - 18 mmol of a sodium salt or 1 - 18 mmol of a magnesium salt are added to the solvent, and the molar mass ratio of the vanadium salt to the zinc salt, lithium salt, sodium salt or magnesium salt is 1:1 - 4.

[0024] Preferably, in step (1), the complexing agent is selected from anhydrous citric acid, the phosphate is selected from ammonium dihydrogen phosphate, the vanadium salt is selected from ammonium metavanadate, the zinc salt is selected from zinc nitrate hexahydrate, the lithium salt is selected from lithium nitrate, the sodium salt is selected from sodium nitrate, and the magnesium salt is selected from magnesium nitrate hexahydrate.

[0025] Preferably, step (1) is specifically as follows:

[0026] (1-1) Add 2-20 mmol of anhydrous citric acid to 20-200 mL of deionized water and stir at a speed of 400-800 r / min at room temperature for 15-30 min to obtain a mixed solution A for standby;

[0027] (1-2) Put 1-10 mmol of ammonium metavanadate into the mixed solution A and stir at a speed of 400-800 r / min at room temperature for 15-30 min to obtain a mixed solution B for standby;

[0028] (1-3) Put 1-14 mmol of ammonium dihydrogen phosphate and 1-18 mmol of zinc nitrate hexahydrate / 1-18 mmol of lithium nitrate / 1-18 mmol of sodium nitrate / 1-18 mmol of magnesium nitrate hexahydrate into the mixed solution B, continue to stir for 5-10 h, evaporate the solvent to obtain a blue gel-like substance, and put the prepared product into a vacuum oven at 75-85 °C for drying for 12-24 h to obtain the final M, V-PO4 3- powder. Appropriate molar mass ratio and reaction time will make M, V-PO4 3- form more uniformly.

[0029] Preferably, 1-10 mmol of ammonium metavanadate and 1-18 mmol of zinc nitrate hexahydrate or 1-18 mmol of lithium nitrate or 1-18 mmol of sodium nitrate or 1-18 mmol of magnesium nitrate hexahydrate are added, and the molar mass ratio of ammonium metavanadate to zinc nitrate hexahydrate or lithium nitrate or sodium nitrate or magnesium nitrate hexahydrate is 1:1-4. By further regulating the types and proportions of metals in the three-dimensional honeycomb binary vanadium-based phosphate material, the present invention can further uniformly construct a three-dimensional interconnected porous structure, so that the finally prepared three-dimensional honeycomb binary vanadium-based phosphate anode protective layer material can effectively regulate the electric field distribution when applied to an aqueous zinc-ion battery, promote the uniform and rapid transmission of zinc ions, and improve the cycle life of the battery.

[0030] In step (2), the M, V-PO4 prepared in step (1) 3- is calcined at 300-900 °C in a nitrogen atmosphere for 2-15 h, and the heating rate is 2-7 °C·min -1 . Appropriate calcination temperature, calcination time and heating rate will make M x Vy (PO4)3 three-dimensional honeycomb materials have better structures and properties, which are beneficial to improving the prepared M x V y (PO4)3 three-dimensional honeycomb materials can effectively regulate the electric field distribution when applied in aqueous zinc-ion batteries, promote the uniform and rapid transmission of zinc ions, and improve the cycle life of the batteries.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. Aiming at the problems of dendrites, hydrogen evolution, and corrosion of the zinc anode during the cyclic use of current aqueous zinc-ion batteries, the present invention proposes to use M x V y (PO4)3 three-dimensional honeycomb materials as coatings to prepare electrode protection coatings. The appropriate ratio of metal M to V can homogenize the electric field distribution, inhibit dendrite growth, accelerate the transport kinetics of zinc ions, and the Zn 2+ transference number can reach 0.76, effectively improving the electrochemical performance of the zinc anode;

[0033] 2. The M x V y (PO4)3 three-dimensional honeycomb materials provided by the present invention as coatings can effectively reduce the direct contact between the zinc anode and the electrolyte, and to a certain extent, avoid the generation of hydrogen evolution, corrosion, and by-products, thereby improving the cycle stability of the aqueous zinc-ion battery;

[0034] 3. The preparation method of the binary vanadium-based phosphate provided by the present invention has the advantages of simple preparation process, environmental friendliness, high repeatability, and low-cost raw materials. Description of the Drawings

[0035] Figure 1 is the morphology diagram of the Zn 0.5 V 1.5 (PO4)3 material prepared in Example 1 observed by the S-4800 type field emission scanning electron microscope (FE-SEM) of Hitachi, Japan;

[0036] Figure 2 is the elemental distribution diagram of the Zn 0.5 V 1.5 (PO4)3 material prepared in Example 1 observed by the S-4800 type field emission scanning electron microscope (FE-SEM) of Hitachi, Japan;

[0037] Figure 3 is the Zn of Example 1 measured by the D8 type X-ray diffractometer of Bruker, USA 0.5 V 1.5The refined XRD pattern of (PO4)3, where the abscissa X is the diffraction angle (2θ) and the ordinate Y is the relative diffraction intensity;

[0038] Figure 4 is the Zn of Example 1 measured by an X-ray photoelectron spectrometer of model ESCALAB MKΙΙ 0.5 V 1.5 The X-ray photoelectron spectrum (XPS) of (PO4)3, where the abscissa X is the binding energy (eV) and the ordinate Y is the relative intensity (a.u.);

[0039] Figure 5 is the cross-sectional elemental distribution map of the Zn 0.5 V 1.5 (PO4)3 material spin-coated on the surface of zinc foil after;

[0040] Figure 6 is the Zn of Example 1 tested by the CT3001A electrochemical workstation of Wuhan Blue Electric Co., Ltd. 0.5 V 1.5 (PO4)3 material assembled button battery, at a current density of 1 mA·cm -2 , with an areal capacity of 1 mAh·cm -2 under, the time-voltage graph of the aqueous zinc-ion battery symmetric cell;

[0041] Figure 7 is the Zn of Example 2 tested by the CT3001A electrochemical workstation of Wuhan Blue Electric Co., Ltd. 0.2 V 1.8 (PO4)3 material assembled button battery, at a current density of 1 mA·cm -2 , with an areal capacity of 1 mAh·cm -2 under, the time-voltage graph of the aqueous zinc-ion battery symmetric cell;

[0042] Figure 8 is the Zn of Example 3 tested by the CT3001A electrochemical workstation of Wuhan Blue Electric Co., Ltd. 0.8 V 1.2 (PO4)3 material assembled button battery, at a current density of 1 mA·cm -2 , with an areal capacity of 1 mAh·cm -2 under, the time-voltage graph of the aqueous zinc-ion battery symmetric cell;

[0043] Figure 9 is the Mg of Example 4 tested by the CT3001A electrochemical workstation of Wuhan Blue Electric Co., Ltd. 0.5 V 1.5The time - voltage graph of a symmetric aqueous zinc - ion battery using a button battery assembled with (PO4)3 material at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 ;

[0044] Figure 10 is the Na 0.5 V 1.5 (PO4)3 - material - assembled button battery tested by the CT3001A electrochemical workstation of Wuhan Blue - Electric Co., Ltd. at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 ;

[0045] Figure 11 is the Li 0.5 V 1.5 (PO4)3 - material - assembled button battery tested by the CT3001A electrochemical workstation of Wuhan Blue - Electric Co., Ltd. at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 ;

[0046] Figure 12 is the time - voltage graph of a symmetric aqueous zinc - ion battery using a button battery assembled with V2(PO4)3 material tested by the CT3001A electrochemical workstation of Wuhan Blue - Electric Co., Ltd. at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 ;

[0047] Figure 13 is the time - voltage graph of a symmetric aqueous zinc - ion battery using a button battery assembled with Zn3(PO4)2 material tested by the CT3001A electrochemical workstation of Wuhan Blue - Electric Co., Ltd. at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 ;

[0048] Figure 14 is the Zn 1.2 V 0.8 (PO4)3 - material - assembled button battery tested by the CT3001A electrochemical workstation of Wuhan Blue - Electric Co., Ltd. at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 ;

[0049] Figure 15It is a button battery assembled with the unmodified zinc foil directly used as the negative electrode in the electrochemical workstation CT3001A of Wuhan Blue Electric Co., Ltd. for the test of Comparative Example 4. At a current density of 1 mA·cm -2 , and an areal capacity of 1 mAh·cm -2 , the time-voltage graph of the aqueous zinc-ion battery symmetric cell. Detailed Description of the Invention

[0050] The above content of the present invention will be further described in detail below through examples, but it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples. All technologies implemented based on the above content of the present invention belong to the scope of the present invention.

[0051] Example 1

[0052] 18 mmol of anhydrous citric acid was added to 200 mL of deionized water and stirred at a rotation speed of 500 r / min for 20 min at room temperature to obtain a mixed solution A; then 8 mmol of ammonium metavanadate was added to the mixed solution A and stirred at a rotation speed of 500 r / min for 20 min at room temperature to obtain a mixed solution B; then 12 mmol of ammonium dihydrogen phosphate and 16 mmol of zinc nitrate hexahydrate were added to the mixed solution B, stirred at 50 °C for 3 h first, and then stirred at 88 °C for 3.5 h. The solvent was evaporated to obtain a blue gel-like substance. The prepared product was placed in a vacuum oven at 80 °C and dried for 12 h to obtain the final Zn,V-PO4 3- powder. Then the prepared Zn,V-PO4 3- was calcined at 400 °C for 4 h first and then at 750 °C for 8 h under a nitrogen atmosphere, and the heating rate was 5 °C·min -1 to obtain the Zn 0.5 V 1.5 (PO4)3 three-dimensional honeycomb material. Finally, the prepared Zn 0.5 V 1.5 (PO4)3 was mixed with PVDF in a ratio of 9:1, and it was uniformly spin-coated on a zinc foil with a thickness of 100 um and a diameter of 1 cm, and dried in a vacuum oven at 80 °C for 12 h to obtain the Zn 0.5 V 1.5 (PO4)3 electrode.

[0053] The SEM of the obtained product is shown in Figure 1 , and it can be observed that Zn 0.5 V 1.5 (PO4)3 presents a three-dimensional honeycomb structure, and it can be observed from Figure 2 that the contained elements Zn, V, P, and O are evenly distributed; according to Figure 3XRD and its refined pattern (PDF#01-076-0604), the physical degree of conformity (profile residual factor, R p ) is equal to 4.04%, and the mathematical degree of conformity (weighted profile residual factor, R wp ) is equal to 2.95%, both of which are far less than the maximum fitting error allowed for XRD refinement (15.00%), indicating the successful preparation of Zn 0.5 V 1.5 (PO4)3; This can be further proved by the XPS according to Figure 4 , and as Figure 5 shows, the thickness of the prepared zinc anode coating material is 33 μm, and the elements Zn, V, P, and O contained are evenly distributed. The Zn 0.5 V 1.5 (PO4)3 electrode prepared in this example has the following electrochemical performance: at a current density of 1 mA·cm -2 and a surface capacity of 1 mAh·cm -2 , the assembled symmetric battery can stably cycle for 3457 hours; the Zn 2+ transference number is as high as 0.76.

[0054] Example 2

[0055] 18 mmol of anhydrous citric acid was added to 200 mL of deionized water and stirred at a rotation speed of 500 r / min for 20 min at room temperature to obtain a mixed solution A; then 4 mmol of ammonium metavanadate was put into the mixed solution A and stirred at a rotation speed of 500 r / min for 20 min at room temperature to obtain a mixed solution B; then 12 mmol of ammonium dihydrogen phosphate and 16 mmol of zinc nitrate hexahydrate were put into the mixed solution B, stirred at 50 °C for 3 h first, and then stirred at 88 °C for 3.5 h, and the solvent was evaporated to obtain a blue gel-like substance. The prepared product was placed in a vacuum oven at 80 °C and dried for 12 h to obtain the final Zn,V-PO4 3- powder. Then the prepared Zn,V-PO4 3- was calcined in a nitrogen atmosphere at 400 °C for 4 h first, and then at 750 °C for 8 h, with a heating rate of 5 °C·min -1 to obtain the Zn 0.2 V 1.8 (PO4)3 three-dimensional honeycomb material. Finally, the prepared Zn 0.2 V 1.8 (PO4)3 was mixed with PVDF in a ratio of 9:1, and it was uniformly spin-coated on a zinc foil with a thickness of 100 μm and a diameter of 1 cm, and dried in a vacuum oven at 80 °C for 12 h to obtain the Zn 0.2 V 1.8 (PO4)3 electrode.

[0056] The Zn 0.2 V 1.8 (PO4)3 electrode prepared in this example has the following electrochemical performance: at a current density of 1 mA·cm -2 and areal capacity of 1 mAh·cm -2 , the symmetric cell assembled with it can stably cycle for 608 hours.

[0057] Example 3

[0058] 18 mmol of anhydrous citric acid was added to 200 mL of deionized water and stirred at a speed of 500 r / min for 20 min at room temperature to obtain a mixed solution A; then 8 mmol of ammonium metavanadate was put into the mixed solution A and stirred at a speed of 500 r / min for 20 min at room temperature to obtain a mixed solution B; then 12 mmol of ammonium dihydrogen phosphate and 12 mmol of zinc nitrate hexahydrate were put into the mixed solution B, stirred at 50 °C for 3 h first, and then stirred at 88 °C for 3.5 h, and the solvent was evaporated to obtain a blue gel-like substance. The prepared product was placed in a vacuum oven at 80 °C and dried for 12 h to obtain the final Zn,V-PO4 3- powder. Then the prepared Zn,V-PO4 3- was calcined at 400 °C for 4 h first and then at 750 °C for 8 h under a nitrogen atmosphere, and the heating rate was 5 °C·min -1 to obtain Zn 0.8 V 1.2 (PO4)3 three-dimensional honeycomb material. Finally, the prepared Zn 0.8 V 1.2 (PO4)3 was mixed with PVDF in a ratio of 9:1, and it was uniformly spin-coated on a zinc foil with a thickness of 100 um and a diameter of 1 cm, and dried in a vacuum oven at 80 °C for 12 h to obtain the Zn 0.8 V 1.2 (PO4)3 electrode.

[0059] The Zn 0.8 V 1.2 (PO4)3 electrode prepared in this example has the following electrochemical performance: at a current density of 1 mA·cm -2 and areal capacity of 1 mAh·cm -2 , the symmetric cell assembled with it can stably cycle for 1095 hours.

[0060] Example 4

[0061] 18 mmol of anhydrous citric acid was added to 200 mL of deionized water and stirred at a speed of 500 r / min for 20 min at room temperature to obtain a mixed solution A; then 8 mmol of ammonium metavanadate was added to the mixed solution A and stirred at a speed of 500 r / min for 20 min at room temperature to obtain a mixed solution B; then 12 mmol of ammonium dihydrogen phosphate and 16 mmol of magnesium nitrate hexahydrate were added to the mixed solution B, stirred at 50 °C for 3 h first, and then stirred at 88 °C for 3.5 h, and the solvent was evaporated to dryness to obtain a blue gel-like substance. The prepared product was placed in a vacuum oven at 80 °C and dried for 12 h to obtain the final Mg,V-PO4 3- powder. Then the prepared Mg,V-PO4 3- was calcined at 400 °C for 4 h first and then at 750 °C for 8 h in a nitrogen atmosphere, and the heating rate was 5 °C·min -1 to obtain Mg 0.5 V 1.5 (PO4)3 three-dimensional honeycomb material. Finally, the prepared Mg 0.5 V 1.5 (PO4)3 was mixed with PVDF in a ratio of 9:1, and it was evenly spin-coated on a zinc foil with a thickness of 100 um and a diameter of 1 cm, and dried in a vacuum oven at 80 °C for 12 h to obtain a Mg 0.5 V 1.5 (PO4)3 electrode.

[0062] The electrochemical performance of the Mg 0.5 V 1.5 (PO4)3 electrode prepared in this example is as follows: at a current density of 1 mA·cm -2 and a surface capacity of 1 mAh·cm -2 , the assembled symmetric battery can stably cycle for 833 hours.

[0063] Example 5

[0064] The difference from Example 4 is that the molar amount of ammonium metavanadate is 4 mmol, and a Mg 0.2 V 1.8 (PO4)3 electrode is obtained.

[0065] The electrochemical performance of the Mg 0.2 V 1.8 (PO4)3 electrode prepared in this example is as follows: at a current density of 1 mA·cm -2 and a surface capacity of 1 mAh·cm -2 , the assembled symmetric battery can stably cycle for 600 hours.

[0066] Example 6

[0067] Differing from Example 4, the number of moles of magnesium nitrate hexahydrate is 12 mmol, obtaining Mg 0.8 V 1.2 (PO4)3 electrode.

[0068] The Mg 0.8 V 1.2 (PO4)3 electrode prepared in this example has the following electrochemical performance: at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 , the symmetric cell assembled with it can stably cycle for 782 hours.

[0069] Example 7

[0070] 18 mmol of anhydrous citric acid was added to 200 mL of deionized water and stirred at a speed of 500 r / min for 20 min at room temperature to obtain a mixed solution A; then 8 mmol of ammonium metavanadate was added to the mixed solution A and stirred at a speed of 500 r / min for 20 min at room temperature to obtain a mixed solution B; then 12 mmol of ammonium dihydrogen phosphate and 16 mmol of sodium nitrate were added to the mixed solution B, stirred at 50 °C for 3 h first, and then stirred at 88 °C for 3.5 h. The solvent was evaporated to obtain a blue gel-like substance. The prepared product was placed in a vacuum oven at 80 °C and dried for 12 h to obtain the final Na,V-PO4 3- powder. Then the prepared Na,V-PO4 3- was calcined at 400 °C for 4 h first and then at 750 °C for 8 h in a nitrogen atmosphere, with a heating rate of 5 °C·min -1 to obtain Na 0.5 V 1.5 (PO4)3 three-dimensional honeycomb material. Finally, the prepared Na 0.5 V 1.5 (PO4)3 was mixed with PVDF in a ratio of 9:1, and it was uniformly spin-coated on a zinc foil with a thickness of 100 μm and a diameter of 1 cm, and dried in a vacuum oven at 80 °C for 12 h to obtain the Na 0.5 V 1.5 (PO4)3 electrode.

[0071] The Na 0.5 V 1.5 (PO4)3 electrode prepared in this example has the following electrochemical performance: at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 , the symmetric cell assembled with it can stably cycle for 750 hours.

[0072] Example 8

[0073] Differing from Example 7, the number of moles of ammonium metavanadate is 4 mmol, obtaining Na 0.2 V 1.8 (PO4)3 electrode.

[0074] The Na 0.2 V 1.8 (PO4)3 electrode prepared in this example has the following electrochemical performance: at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 , the symmetric cell assembled with it can stably cycle for 592 hours.

[0075] Example 9

[0076] Differing from Example 7, the number of moles of sodium nitrate is 12 mmol, obtaining Na 0.8 V 1.2 (PO4)3 electrode.

[0077] The Na 0.8 V 1.2 (PO4)3 electrode prepared in this example has the following electrochemical performance: at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 , the symmetric cell assembled with it can stably cycle for 660 hours.

[0078] Example 10

[0079] Add 18 mmol of anhydrous citric acid to 200 mL of deionized water and stir at a speed of 500 r / min for 20 min at room temperature to obtain a mixed solution A; then add 8 mmol of ammonium metavanadate to the mixed solution A and stir at a speed of 500 r / min for 20 min at room temperature to obtain a mixed solution B; then add 12 mmol of ammonium dihydrogen phosphate and 16 mmol of lithium nitrate to the mixed solution B, stir at 50 °C for 3 h first, and then stir at 88 °C for 3.5 h, evaporate the solvent to obtain a blue gel-like substance, put the prepared product into a vacuum oven at 80 °C and dry for 12 h to obtain the final Li,V-PO4 3- powder. Then calcine the prepared Li,V-PO4 3- under a nitrogen atmosphere, first calcine at 400 °C for 4 h, and then calcine at 750 °C for 8 h, with a heating rate of 5 °C·min -1 to obtain Li 0.5 V 1.5 (PO4)3 three-dimensional honeycomb material. Finally, the prepared Li 0.5 V 1.5(PO4)3 and PVDF are mixed in a ratio of 9:1, and it is evenly spin-coated on a zinc foil with a thickness of 100 um and a diameter of 1 cm, and dried in a vacuum oven at 80 °C for 12 h to obtain Li 0.5 V 1.5 (PO4)3 electrode.

[0080] The Li 0.5 V 1.5 (PO4)3 electrode prepared in this example has the following electrochemical performance: at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 , the symmetric cell assembled with it can stably cycle for 728 hours.

[0081] Example 11

[0082] The difference from Example 10 is that the number of moles of ammonium metavanadate is 4 mmol, and Li 0.2 V 1.8 (PO4)3 electrode is obtained.

[0083] The Li 0.2 V 1.8 (PO4)3 electrode prepared in this example has the following electrochemical performance: at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 , the symmetric cell assembled with it can stably cycle for 587 hours.

[0084] Example 12

[0085] The difference from Example 10 is that the number of moles of lithium nitrate is 12 mmol, and Li 0.8 V 1.2 (PO4)3 electrode is obtained.

[0086] The Li 0.8 V 1.2 (PO4)3 electrode prepared in this example has the following electrochemical performance: at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 , the symmetric cell assembled with it can stably cycle for 621 hours.

[0087] Comparative Example 1

[0088] 18 mmol of anhydrous citric acid was added to 200 mL of deionized water and stirred at a speed of 500 r / min for 20 min at room temperature to obtain a mixed solution A; then 8 mmol of ammonium metavanadate was put into the mixed solution A and stirred at a speed of 50 r / min for 20 min at room temperature to obtain a mixed solution B; then 12 mmol of ammonium dihydrogen phosphate was put into the mixed solution B, stirred at 50 °C for 3 h first, and then stirred at 88 °C for 3.5 h. The solvent was evaporated to dryness to obtain a blue gel-like substance. The prepared product was placed in a vacuum oven at 80 °C and dried for 12 h to obtain the final V-PO4 3- powder. Then the prepared V-PO4 3- was calcined at 400 °C for 4 h under a nitrogen atmosphere, and then calcined at 750 °C for 8 h with a heating rate of 5 °C·min -1 to obtain a V2(PO4)3 three-dimensional honeycomb material. Finally, the prepared V2(PO4)3 was mixed with PVDF in a ratio of 9:1, and it was uniformly spin-coated on a zinc foil with a thickness of 100 μm and a diameter of 1 cm, and dried in a vacuum oven at 80 °C for 12 h to obtain a V2(PO4)3 electrode.

[0089] The electrochemical performance of the V2(PO4)3 electrode prepared in this comparative example was as follows: at a current density of 1 mA·cm -2 and a specific capacity of 1 mAh·cm -2 the symmetric battery assembled with it could stably cycle for 579 hours.

[0090] Comparative Example 2

[0091] 18 mmol of anhydrous citric acid was added to 200 mL of deionized water and stirred at a speed of 500 r / min for 20 min at room temperature to obtain a mixed solution A; then 12 mmol of ammonium dihydrogen phosphate and 16 mmol of zinc nitrate hexahydrate were put into the mixed solution A, stirred at 50 °C for 3 h first, and then stirred at 88 °C for 3.5 h. The solvent was evaporated to dryness to obtain a blue gel-like substance. The prepared product was placed in a vacuum oven at 80 °C and dried for 12 h to obtain the final Zn-PO4 3- powder. Then the prepared Zn-PO4 3- was calcined at 400 °C for 4 h under a nitrogen atmosphere, and then calcined at 750 °C for 8 h with a heating rate of 5 °C·min -1 to obtain a Zn3(PO4)2 three-dimensional honeycomb material. Finally, the prepared Zn3(PO4)2 was mixed with PVDF in a ratio of 9:1, and it was uniformly spin-coated on a zinc foil with a thickness of 100 μm and a diameter of 1 cm, and dried in a vacuum oven at 80 °C for 12 h to obtain a Zn3(PO4)2 electrode.

[0092] The electrochemical performance of the Zn3(PO4)2 electrode prepared in this comparative example is as follows: at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 , the symmetric cell assembled with it can stably cycle for 583 hours.

[0093] Comparative Example 3

[0094] The difference from Example 1 is that the number of moles of ammonium metavanadate is 12 mmol, and the number of moles of zinc nitrate hexahydrate is 8 mmol, obtaining a Zn 1.2 V 0.8 (PO4)3 electrode.

[0095] The Zn 1.2 V 0.8 (PO4)3 electrode prepared in this comparative example has the following electrochemical performance: at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 , the symmetric cell assembled with it can stably cycle for 453 hours.

[0096] Comparative Example 4

[0097] The method for assembling a water-based zinc-ion symmetric button battery with an unmodified zinc foil electrode is different from that of Example 1 only in that: both the positive and negative electrode plates use unmodified zinc foil.

[0098] The electrochemical performance of the symmetric button battery obtained in this comparative example is as follows: at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 , it can stably cycle for 175 hours.

[0099] Application Example

[0100] Electrochemical Test

[0101] The materials obtained in Examples 1 to 12 were used for electrochemical tests and compared with Comparative Examples 1 to 4. All electrochemical tests were completed in button cells.

[0102] The carbon paper and the unmodified zinc foil were cut into the size of electrode sheets by a cutting machine, and the M x V y (PO4)3 three-dimensional honeycomb materials prepared in Examples 1 to 12 and the materials prepared in Comparative Examples 1 to 3 were spin-coated on the unmodified zinc foil as the negative electrode, the carbon paper coated with sodium vanadate was used as the positive electrode, and 2M-ZnSO4 was used as the electrolyte to assemble a button cell. The assembly method of the symmetric button battery in Comparative Example 4 is that both the positive and negative electrode plates use unmodified zinc foil. At a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2Under the following conditions, cyclic charge-discharge tests of symmetric button cells were carried out, as Figures 6 to 15 shown. Among them, Example 1 had the best performance, with the longest cycle life of 3457 h, greatly enhancing the cycle durability of the aqueous zinc-ion battery (as Figure 6 shown).

[0103] The zinc negative electrode protected by the Zn 0.2 V 1.8 (PO4)3 coating can stably cycle for 608 hours when assembled into a symmetric cell at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 ; the zinc negative electrode protected by the Zn 0.5 V 1.5 (PO4)3 coating can stably cycle for 3457 hours when assembled into a symmetric cell at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 ; the zinc negative electrode protected by the Zn 0.8 V 1.2 (PO4)3 coating can stably cycle for 1095 hours when assembled into a symmetric cell at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 . From this, the optimal molar mass ratio of the metal elements Zn and V was determined to be 1:2, and the optimal structural formula was Zn 0.5 V 1.5 (PO4)3 (space group P21 / c). The zinc negative electrode protected by the Mg 0.5 V 1.5 (PO4)3 coating can stably cycle for 833 hours when assembled into a symmetric cell at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 ; the zinc negative electrode protected by the Na 0.5 V 1.5 (PO4)3 coating can stably cycle for 750 hours when assembled into a symmetric cell at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 ; the zinc negative electrode protected by the Li 0.5 V 1.5 (PO4)3 coating can stably cycle for 728 hours when assembled into a symmetric cell at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2 ; the cycle lives are all higher than those of symmetric cells assembled with zinc negative electrodes without coating at a current density of 1 mA·cm -2 and an areal capacity of 1 mAh·cm -2Under the same conditions, the cycle life of the symmetric battery assembled with a zinc anode protected by a monovanadium-based phosphate V2(PO4)3 coating is 579 hours, the cycle life of the symmetric battery assembled with a zinc anode protected by a monophosphate Zn3(PO4)2 coating is 453 hours, and the cycle life of the symmetric battery assembled with an unmodified zinc foil is 175 hours.

[0104] The above results show that the three-dimensional honeycomb-like binary vanadium-based phosphate anode protective layer material prepared in the present invention has a three-dimensional interconnected porous structure. When this material is applied to an aqueous zinc-ion battery, due to the synergistic effect of metal M and V, it can provide continuous ion / electron transfer, which is beneficial to regulating the electric field distribution, homogenizing the zinc ion flow, realizing the rapid transmission of zinc ions, improving the stability of the Zn metal anode electrode-electrolyte interface, and then increasing the cycle life of the battery; the present invention promotes the research of the three-dimensional honeycomb-like binary vanadium-based phosphate anode protective layer material in aqueous zinc-ion batteries, which plays a certain role in promoting the development of high-cycle-life, green and safe aqueous zinc-ion batteries.

Claims

1. Application of a binary vanadium-based phosphate as an anode protective layer material in an aqueous zinc-ion battery, characterized in that, The binary vanadium-based phosphate is M x V y (PO4)3, where M is Zn, Li, Na or Mg, 0 < x < 1, 1 < y < 2; the binary vanadium-based phosphate M x V y (PO4)3 is three-dimensional honeycomb-shaped; The electrolyte in the aqueous zinc-ion battery is ZnSO4; The preparation method of the binary vanadium-based phosphate includes: (1) Mix a complexing agent, a phosphate, a vanadate, and one or more of a zinc salt, a lithium salt, a sodium salt, or a magnesium salt in a solvent and stir at room temperature to synthesize M,V-PO4 by the sol-gel method 3- , where M is Zn, Li, Na, or Mg; the vanadate is ammonium metavanadate; (2) The prepared M,V-PO4 3- is calcined under high temperature and nitrogen atmosphere to obtain three-dimensional honeycomb M x V y (PO4)3, where 0 < x < 1 and 1 < y < 2.

2. The application according to claim 1, wherein The binary vanadium-based phosphate M x V y (PO4)3, where 0.2 ≤ x ≤ 0.8 and 1.2 ≤ y ≤ 1.

8.

3. The application according to claim 1, characterized in that, The binary vanadium-based phosphate M x V y (PO4)3 where: 0.5 ≤ x ≤ 0.8 and 1.5 ≤ y ≤ 1.

2.

4. The application according to claim 1, characterized in that, The binary vanadium-based phosphate M x V y In (PO4)3, M is Zn.

5. The application according to claim 1, wherein The binary vanadium-based phosphate M x V y (PO4)3 and PVDF are mixed and spin-coated on a zinc foil as the negative electrode of an aqueous zinc-ion battery.

6. The application according to claim 5, characterized in that, The positive electrode in the aqueous zinc-ion battery is carbon paper coated with sodium vanadate.

7. The application according to claim 1, wherein In step (1), 2 to 20 mmol of complexing agent, 1 to 10 mmol of vanadium salt, 1 to 14 mmol of phosphate, and one of 1 to 18 mmol of zinc salt, 1 to 18 mmol of lithium salt, 1 to 18 mmol of sodium salt or 1 to 18 mmol of magnesium salt are added to the solvent, and the molar mass ratio of the vanadium salt to the zinc salt, lithium salt, sodium salt or magnesium salt is 1:1 to 4.

8. The application according to claim 7, wherein In step (2), the M,V-PO4 prepared in step (1) 3- is calcined at 300 to 900 °C under a nitrogen atmosphere for 2 to 15 h, and the heating rate is 2 to 7 °C min -1 .

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