A sodium-rich sodium polyvanadate material, a preparation method thereof, and a positive plate and a battery

Abstract

The application discloses a sodium-rich sodium polyvanadate material and a preparation method and a positive plate and a battery thereof. 2+x V6O 16 ·2.9H2O, wherein 0 + The preparation steps comprise the following steps: dissolving sodium metavanadate in deionized water, adding an acid solution, stirring until the pH is 2-3.5, continuously stirring in a water bath, naturally cooling, and collecting the sodium-rich sodium polyvanadate material through filtration, washing and drying. + The sodium-rich sodium polyvanadate material is prepared by using a simple precipitation method, and cation defects (Na + ) are introduced into the sodium polyvanadate, so that the excessive Na + The ion / electron conductivity of the sodium polyvanadate electrode material is enhanced, the actual capacity of the battery is improved, the cation defects can further serve as interlayer pillars to ensure the structural stability of the sodium polyvanadate material, the structure collapse of the sodium polyvanadate positive material is prevented, and the cycle service life of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode materials, and in particular to a sodium-rich sodium polyvanadate material, a preparation method thereof, a positive electrode sheet, and a battery. Background Art

[0002] In magnesium ion batteries, due to the divalent Mg 2+ There is a strong interaction between the host cathode material and the magnesium ion, which results in a very slow embedding / de-embedding cycle process on the cathode material, seriously affecting the electrochemical performance of the magnesium ion battery. By adding monovalent exogenous cations (such as Li + and Na + ), can effectively promote ion diffusion kinetics, improve the battery's charge storage capacity and cycle stability. This method of adding monovalent exogenous cations (such as Li + and Na + ), the energy storage system formed is called a magnesium-based hybrid ion battery. And because the abundance of lithium resources in the earth's crust is limited, magnesium-sodium hybrid ion batteries are more economical than magnesium-lithium hybrid ion batteries, and therefore have higher application potential. Although magnesium-based hybrid ion batteries exhibit superior electrochemical potential compared to magnesium-ion batteries, the positive electrode materials that can be used for magnesium-based hybrid ion batteries are still very limited. In addition, these existing positive electrode materials generally have problems of low ion conductivity and poor structural stability, resulting in low actual capacity of the battery and short cycle life. Therefore, there is an urgent need to develop advanced positive electrode materials with rapid ion diffusion channels and high structural stability to improve the performance of magnesium-sodium hybrid ion batteries.

[0003] Vanadium oxides, due to their rich redox states and VO bond distortion, have led to the development of a large number of high-capacity, structurally rich polyvanadate materials, which are widely used in various metal ion batteries. For example, CN202210724649.2 prepared copper hydroxypyrovanadate cathode materials by hydrothermal method and applied them to magnesium secondary batteries, showing excellent reversible capacity (current density of 0.2A g -1 The specific capacity is 277.31 mAh g -1 ) and excellent cycling stability (capacity retention of 96.97% after 400 cycles, and Coulombic efficiency always stable at 100%). However, the positive effect of exogenous cations in standard stoichiometric ratios on polyvanadate positive electrodes is very limited, especially in terms of structural stability and ionic conductivity, which still restricts the application of polyvanadate in magnesium secondary batteries and magnesium-based mixed ion batteries. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a sodium-rich sodium polyvanadate material to solve the problems of poor kinetic behavior, low ionic conductivity and poor structural stability when the existing polyvanadate materials are used as the positive electrode of magnesium ion batteries or magnesium-based mixed ion batteries, resulting in low battery capacity and short cycle life.

[0005] Furthermore, a preparation method of the sodium-rich sodium polyvanadate material, as well as a positive electrode sheet and a battery containing the sodium-rich sodium polyvanadate material are provided.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] A sodium-rich sodium polyvanadate material, whose chemical formula is Na 2+x V6O 16 2.9H2O, of which 0 <X<4,微观形貌呈各向异性单晶纳米带结构。

[0008] The preparation method of the sodium-rich sodium polyvanadate material comprises the following steps:

[0009] (1) dissolving sodium metavanadate in deionized water and stirring until the sodium metavanadate is completely dissolved to obtain a sodium metavanadate solution, which is referred to as solution A;

[0010] (2) Under stirring conditions, add acid solution to solution A and adjust the pH to 2-3.5. The resulting solution is recorded as solution B;

[0011] (3) Place solution B in a water bath, stir to allow for sufficient reaction, and then cool naturally. Filter, wash, and dry to obtain a sodium-rich sodium polyvanadate material.

[0012] The present invention utilizes a simple precipitation method to prepare a sodium-rich sodium polyvanadate material, which is simple, efficient, and low-cost. Specifically, by controlling the concentration of sodium metavanadate, the pH value of the solution, and the water bath conditions, the sodium metavanadate undergoes a condensation reaction under acidic conditions to generate the corresponding phase, thereby achieving the preparation of the sodium-rich sodium polyvanadate material.

[0013] Furthermore, the concentration of the sodium metavanadate solution in step (1) is 5 g / L to 35 g / L. If the concentration of the sodium metavanadate solution is lower than this range, the sodium ions in the original reaction solution are insufficient, and the desired sodium-rich phase cannot be formed; conversely, if the concentration of the sodium metavanadate solution is too high, the sodium metavanadate will not be completely dissolved at room temperature, resulting in a waste of raw materials.

[0014] Furthermore, the mass concentration of the acid solution in step (2) is 5% to 30%. If the concentration of the acid solution is lower than this range, the sodium ion concentration in the original reaction solution will be reduced, affecting the formation of the sodium-rich phase; while if the concentration of the acid solution is too high, the sodium metavanadate reaction will not be complete, reducing the yield of sodium-rich sodium polyvanadate and increasing the difficulty of pH control.

[0015] Furthermore, in step (3), the water bath temperature is 60-130°C, and the stirring time is 3-12 hours. A water bath temperature outside this range or a stirring time that is too short may result in decreased product purity. Experiments have shown that 8 hours is sufficient for complete reaction, and no longer reaction time is required. Therefore, a stirring time of 8 hours is preferred.

[0016] Furthermore, in step (3), the drying temperature is 60-100° C., and the drying time is 3-8 hours.

[0017] Furthermore, the acid solution in step (2) is one or more of sulfuric acid, nitric acid, hydrochloric acid, and boric acid.

[0018] Furthermore, it is preferred that the pH in step (2) is adjusted to 2.0-2.5.

[0019] A battery positive electrode sheet comprises the sodium-rich sodium polyvanadate material.

[0020] A battery comprising the positive electrode sheet, wherein the battery comprises a mixed ion battery, a sodium ion battery, a magnesium ion battery or a zinc ion battery.

[0021] A magnesium-based mixed ion battery with Na + / Mg 2+ The double salt electrolyte is used as the electrolyte, and the positive electrode sheet is used as the positive electrode.

[0022] Furthermore, the Mg 2+ / Na + The concentration of the double salt electrolyte is 0.5 to 3M.

[0023] Furthermore, in the double salt electrolyte, Na + / Mg 2+ The molar ratio is 1 to 2.5:1.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention adopts a simple precipitation method to introduce cationic defects (Na + ), increased V 5+ With V 4+The conversion ratio between vanadium and magnesium increases, which enhances electron transitions and significantly improves the conductivity of the material, thereby improving the rate performance of the positive electrode. The cation defects further act as interlayer pillars, limiting the migration path of magnesium ions, enhancing the structural stability and ion diffusion kinetics of the sodium polyvanadate material, and thus improving the cycle life and actual capacity of the battery.

[0026] 2. The sodium-rich sodium polyvanadate material prepared by the present invention has excellent ionic conductivity, electronic conductivity and structural stability. The magnesium ion battery assembled using the sodium-rich sodium polyvanadate material prepared by the present invention as the positive electrode shows excellent electrochemical performance. 2+ 、Na + It has good compatibility, and the magnesium-based mixed ion full battery assembled using the sodium-rich sodium polyvanadate material prepared by the present invention as the positive electrode still exhibits excellent charge storage performance and cycle stability.

[0027] 3. Na obtained by the present invention 2+x V6O 16 When 2.9H2O material is used as the positive electrode material of magnesium ion battery, it has a high -1 The specific capacity is as high as 155 mAh g at a current density of -1 ; Increase the current density to 5.0Ag -1 Time 2+x V6O 16 The specific capacity of the 2.9H2O cathode remains at 39mAh g -1 ; at 0.5Ag -1 The capacity retention rate is as high as 78% after 300 cycles at the current density, showing excellent rate performance and long-cycle stability. It is a highly promising high-capacity, long-life magnesium-ion battery positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of the preparation process of the sodium-rich sodium polyvanadate material of the present invention;

[0029] Figure 2 TEM and SAED patterns of the sodium-rich sodium polyvanadate material prepared in Example 1 of the present invention;

[0030] Figure 3 This is the XRD pattern of the sodium-rich sodium polyvanadate material prepared in Example 1 of the present invention;

[0031] Figure 4 This is a TGA graph of the sodium-rich sodium polyvanadate material prepared in Example 1 of the present invention;

[0032] Figure 5This is a graph of the specific capacity at different current densities when the sodium-rich sodium polyvanadate material prepared in Example 1 of the present invention is used as a positive electrode material for a magnesium ion battery;

[0033] Figure 6 When the sodium-polyvanadate material prepared in Example 1 of the present invention is used as the positive electrode material of magnesium ion battery, the -1 Long cycle test diagram under current density;

[0034] Figure 7 When the sodium-polyvanadate material prepared in Example 1 of the present invention is used as the positive electrode material of the magnesium-sodium mixed ion full battery, the magnesium-sodium mixed ion full battery has a positive electrode at 8.0 mV s -1 Cyclic voltammetry curves at different scan rates;

[0035] Figure 8 For the application example 1, the magnesium-sodium mixed ion full battery is used in 0.1Ag -1 Long cycle test diagram under current density;

[0036] Figure 9 For the application example 2, the magnesium-sodium mixed ion full battery is used in 0.1Ag -1 Long cycle test diagram under current density;

[0037] Figure 10 For the application of Example 3, the magnesium-sodium mixed ion full battery is used in 0.1Ag -1 Long cycle test diagram under current density. DETAILED DESCRIPTION

[0038] The specific implementation methods of the present invention are further described in detail below with reference to specific examples.

[0039] The numerical ranges herein are understood to specifically disclose every intervening value between the upper and lower limits of the range. Each smaller range between any stated value or intervening value in a stated range and any other stated value or intervening value in that stated range is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0040] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art. Although the present invention has only described preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail. As used herein, "comprising", "including", "having", "containing", etc. are all open-ended terms, meaning including but not limited to.

[0041] Unless otherwise specified, the experimental methods used in the present invention are all conventional methods.

[0042] Unless otherwise specified, the materials, reagents, etc. used in the present invention can be purchased or synthesized by known methods.

[0043] The quantitative tests in the present invention were repeated three times and the results were averaged.

[0044] See also Figure 1 The present invention provides a method for preparing a sodium-rich sodium polyvanadate material, comprising the following steps:

[0045] (1) dissolving sodium metavanadate in deionized water and stirring until the sodium metavanadate is completely dissolved to obtain a sodium metavanadate solution;

[0046] (2) adding an acid solution to the sodium metavanadate solution obtained in step (1) under stirring until the pH is 2 to 3.5;

[0047] (3) placing the solution obtained in step (2) in a water bath, stirring to allow it to react fully, cooling naturally, filtering, washing, and drying to obtain a sodium-rich sodium polyvanadate material.

[0048] The obtained sodium-polyvanadate material has the chemical formula Na 2+x V6O 16 2.9H2O, of which 0 <X<4,微观形貌呈各向异性纳米带结构,为典型单晶结构。

[0049] 1. Implementation

[0050] Example 1

[0051] This embodiment provides a method for preparing a sodium-rich sodium polyvanadate material, comprising the following steps:

[0052] Dissolve 15g of sodium metavanadate in 2000mL of deionized water and stir at room temperature until homogeneous. Then, add 10% sulfuric acid solution while stirring until a uniform orange-red transparent solution with a pH of 2.0 is obtained. Place the resulting uniform orange-red transparent solution in a water bath at 70°C and stir for 9 hours. After the reaction is complete, allow it to cool naturally and filter. The resulting precipitate is washed three times with deionized water by suction and dried in a drying oven at 70°C for 8 hours to obtain a sodium-rich sodium polyvanadate material.

[0053] Example 2

[0054] This embodiment provides a method for preparing a sodium-rich sodium polyvanadate material, comprising the following steps:

[0055] Dissolve 30 g of sodium metavanadate in 2000 mL of deionized water, stir at room temperature until uniform; then under stirring conditions, add a 5% mass concentration of sulfuric acid solution until a uniform orange-red transparent solution with pH = 2.0 is obtained. Place the obtained uniform orange-red transparent solution in a water bath, stir at 60°C for 12 h under water bath conditions, and after the reaction is completed, filter it after natural cooling. The prepared precipitated product is washed with deionized water by suction filtration three times, and is placed in a drying oven at 80°C for 6 h to obtain a sodium-rich sodium polyvanadate material.

[0056] Example 3

[0057] The present example provides a method for preparing a sodium-rich sodium polyvanadate material, comprising the following steps:

[0058] Dissolve 15 g of sodium metavanadate in 2000 mL of deionized water, stir at room temperature until uniform; then under stirring conditions, add a 15% mass concentration of nitric acid solution until a uniform orange-red transparent solution with pH = 2.5 is obtained. Place the obtained uniform orange-red transparent solution in a water bath, stir at 80°C for 7 h under water bath conditions, and after the reaction is completed, filter it after natural cooling. The prepared precipitated product is washed with deionized water by suction filtration three times, and is placed in a drying oven at 80°C for 6 h to obtain a sodium-rich sodium polyvanadate material.

[0059] Example 4

[0060] The present example provides a method for preparing a sodium-rich sodium polyvanadate material, comprising the following steps:

[0061] Dissolve 20 g of sodium metavanadate in 2000 mL of deionized water, stir at room temperature until uniform; then under stirring conditions, add a 30% mass concentration of boric acid solution until a uniform orange-red transparent solution with pH = 2.8 is obtained. Place the obtained uniform orange-red transparent solution in a water bath, stir at 130°C for 3 h under water bath conditions, and after the reaction is completed, filter it after natural cooling. The prepared precipitated product is washed with deionized water by suction filtration three times, and is placed in a drying oven at 100°C for 3 h to obtain a sodium-rich sodium polyvanadate material.

[0062] Example 5

[0063] The present example provides a method for preparing a sodium-rich sodium polyvanadate material, comprising the following steps:

[0064] Dissolve 15g of sodium metavanadate in 2000mL of deionized water and stir at room temperature until homogeneous. Then, add 10% hydrochloric acid solution while stirring until a uniform orange-red transparent solution with a pH of 3.5 is obtained. Place the resulting uniform orange-red transparent solution in a water bath at 70°C and stir for 9 hours. After the reaction is complete, allow it to cool naturally and filter. The resulting precipitate is washed three times with deionized water by suction and dried in a drying oven at 70°C for 8 hours to obtain a sodium-rich sodium polyvanadate material.

[0065] 2. Results and Analysis

[0066] (1) Structural characterization of the prepared sodium-rich sodium polyvanadate material

[0067] (1) TEM characterization

[0068] Figure 2 The transmission electron microscope image (TEM image) and selected area electron diffraction image (SAED image) of the sodium-rich sodium polyvanadate material obtained in Example 1 are shown in FIG. Figure 2 It can be seen that the microscopic morphology of the sodium-rich sodium polyvanadate material obtained in Example 1 is an anisotropic nanoribbon structure and a typical single crystal structure with good crystallinity.

[0069] The sodium-rich sodium polyvanadate materials prepared in Examples 2 to 5 were tested using the same method, and the results were basically consistent with those of Example 1.

[0070] (2) XRD characterization

[0071] Figure 3 The X-ray diffraction analysis diagram (XRD diagram) of the sodium-rich sodium polyvanadate material obtained in Example 1 is shown in FIG. Figure 3 It can be seen that the sodium-rich sodium polyvanadate material prepared in Example 1 is consistent with the X-ray diffraction standard card JCPDS#16-0601 (chemical formula is Na2V6O 16 ·3H2O) for comparison, the two phases are completely consistent, and all diffraction peaks are consistent with monoclinic crystal Na2V6O 16 The 3H2O standard peak is completely consistent, indicating that the introduced interlayer cation defects do not change the original sodium polyvanadate phase composition.

[0072] Compared with the peak position of the (001) crystal plane of the standard card JCPDS#16-0601, the XRD curve of the sample in this embodiment has an obvious rightward angle shift, corresponding to a decrease in the interlayer spacing, indicating that the excess sodium is located between the layers and acts as an interlayer pillar, enhancing the interlayer connection, resulting in a decrease in the interlayer spacing, thereby enhancing the structural stability of the positive electrode material.

[0073] The sodium-rich sodium polyvanadate materials prepared in Examples 2 to 5 were tested using the same method, and the results were basically consistent with those of Example 1.

[0074] (3) TGA and ICP characterization

[0075] Figure 4 Thermogravimetric analysis (TGA) of the sodium-polyvanadate material obtained in Example 1 is shown in FIG. Figure 4 It can be seen that the sodium-rich sodium polyvanadate material prepared in Example 1 contains about 2.9 water molecules in each product molecule.

[0076] The sodium-rich sodium polyvanadate materials prepared in Examples 2 to 5 were subjected to thermogravimetric analysis, and the results were substantially consistent with those of Example 1.

[0077] Table 1 is the ICP test results of the sodium-rich sodium polyvanadate material prepared in the present invention.

[0078] Table 1 ICP test results of sodium-rich sodium polyvanadate materials.

[0079] Example element Na / V (atomic ratio) Example 1 Na / V 3.7：6 Example 2 Na / V 4.5：6 Example 3 Na / V 3.8：6 Example 4 Na / V 4.0：6 Example 5 Na / V 3.7：6

[0080] Combining the thermogravimetric analysis results of the sodium-rich sodium polyvanadate material and Table 1, it can be seen that the chemical formulas of the sodium-rich sodium polyvanadate materials prepared in different embodiments are shown in Table 2.

[0081] Table 2 Chemical formula of sodium-rich sodium polyvanadate material prepared in Example

[0082] Example Chemical formula Example 1 <![CDATA[Na 3.7 V6O 16 2.9H2O Example 2 <![CDATA[Na 4.5 V6O 16 2.9H2O Example 3 <![CDATA[Na 3.8 V6O 16 2.9H2O Example 4 Na 4.0 V6O 16 ·2.9H2O]]> Example 5 <![CDATA[Na 3.7 V6O 16 2.9H2O

[0083] (2) Electrochemical performance test of sodium-rich sodium polyvanadate materials

[0084] (1) Magnesium ion battery

[0085] The sodium-rich sodium polyvanadate material prepared in Example 1 was loaded onto a carbon paper current collector as the positive electrode, activated carbon loaded onto a carbon cloth current collector as the negative electrode, and 0.5 M Mg(TFSI)₂ as the electrolyte. These cells were assembled into 2032 coin cells for electrochemical performance testing. Galvanostatic charge-discharge (GCD) testing of the sodium-rich sodium polyvanadate positive electrode was performed using a Neware-CT8000 charge-discharge test system.

[0086] Figure 5 The Na prepared in Example 1 of the present invention 3.7 V6O 16 ·Specific capacity diagram of 2.9H2O material as the positive electrode material of magnesium ion battery at different current densities. Figure 5 It can be seen that at 0.05Ag -1 At current density, Na 3.7 V6O 16 2.9H2O cathode specific capacity up to 155mAh g -1 ; Increase the current density to 5.0Ag-1 When, Na 3.7 V6O 16 The specific capacity of the 2.9H2O cathode remains at 39mAh g -1 It can be seen that the Na prepared by the present invention 3.7 V6O 16 ·2.9H2O material has excellent rate performance when used as the positive electrode of magnesium ion batteries.

[0087] Figure 6 The Na obtained in Example 1 of the present invention 3.7 V6O 16 When 2.9H2O material is used as the positive electrode material of magnesium ion battery, at 0.5Ag -1 Long cycle test diagram under current density. Figure 6 It can be seen that Na 3.7 V6O 16 ·2.9H2O positive electrode at 0.5Ag -1 After 300 cycles at the same current density, the capacity retention rate reached 78%, showing the Na 3.7 V6O 16 ·2.9H2O cathode has excellent long-cycle stability.

[0088] (2) Magnesium-sodium mixed ion battery

[0089] The present invention uses the sodium-rich sodium polyvanadate material prepared in Example 1 to be loaded on a carbon paper current collector as the positive electrode, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) to be loaded on a carbon cloth current collector as the negative electrode, and 1.5M NaTFSI / Mg(TFSI)2 as the electrolyte (in the electrolyte, Na + / Mg 2+ The molar ratio was 1:1) and the 2032 coin cells were assembled for electrochemical performance testing. Cyclic voltammetry (CV) tests were performed on the sodium-rich sodium polyvanadate cathode using an electrochemical workstation (CHI660e).

[0090] Figure 7 The Na obtained in Example 1 of the present invention 3.7 V6O 16 When 2.9H2O material is used as the positive electrode material of magnesium-sodium mixed ion full battery, the magnesium-sodium mixed ion full battery has a high -1 The cyclic voltammetry curves of the first three cycles at the scan rate. Figure 7 It can be seen that in the first three cycles, the area and shape of the cyclic voltammetry curve did not change significantly, indicating that Mg 2+ 、Na + In Na 3.7 V6O 16 ·2.9H2O can undergo reversible insertion / extraction cycles in the positive electrode, with good reversibility.

[0091] The sodium-rich sodium polyvanadate materials prepared in Examples 2 to 5 were used to perform the above electrochemical performance test and had similar electrochemical properties.

[0092] This shows that the Na 2+x V6O 16 ·2.9H2O material exhibits excellent electrochemical performance when used as cathode material for magnesium-ion batteries and magnesium-based mixed-ion batteries, providing a direction for the research of cathode materials for high-capacity and long-life magnesium-ion batteries and magnesium-based mixed-ion batteries.

[0093] 3. Application Examples

[0094] Application Example 1

[0095] A magnesium-sodium mixed ion battery, comprising:

[0096] Na prepared in Example 1 of the present invention 3.7 V6O 16 ·2.9H2O material is loaded on carbon paper current collector as positive electrode, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) is loaded on carbon cloth current collector as negative electrode, and 1.5M NaTFSI / Mg(TFSI)2 electrolyte is used as electrolyte to assemble a magnesium-sodium mixed ion full battery. + / Mg 2+ The molar ratio is 1:1.

[0097] The battery capacity and coulombic efficiency of the battery assembled in this embodiment are as follows: Figure 8 As shown by Figure 8 It can be seen that in Na + / Mg 2+ In the NaTFSI / Mg(TFSI)2 electrolyte with a molar ratio of 1:1, the hybrid ion battery -1 Provides 28mAh g -1 The initial specific capacity is as high as 100%, and its average coulombic efficiency is as high as 90% after 200 cycles.

[0098] Application Example 2

[0099] A magnesium-sodium mixed ion battery, comprising:

[0100] Na prepared in Example 1 of the present invention 3.7 V6O 16·2.9H2O material is loaded on carbon paper current collector as positive electrode, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) is loaded on carbon cloth current collector as negative electrode, and 1.5M NaTFSI / Mg(TFSI)2 electrolyte is used as electrolyte to assemble a magnesium-sodium mixed ion full battery. + / Mg 2+ The molar ratio is 2:1.

[0101] The battery capacity and coulombic efficiency of the battery assembled in this embodiment are as follows: Figure 9 As shown by Figure 9 It can be seen that in Na + / Mg 2+ In the NaTFSI / Mg(TFSI)2 electrolyte with a molar ratio of 2:1, the hybrid ion battery -1 Provides 28mAh g -1 The initial specific capacity of the battery decreased to about 70% after 200 cycles.

[0102] Application Example 3

[0103] A magnesium-sodium mixed ion battery, comprising:

[0104] Na prepared in Example 1 of the present invention 3.7 V6O 16 ·2.9H2O material is loaded on carbon paper current collector as positive electrode, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) is loaded on carbon cloth current collector as negative electrode, and 1.5M NaTFSI / Mg(TFSI)2 electrolyte is used as electrolyte to assemble a magnesium-sodium mixed ion full battery. + / Mg 2+ The molar ratio is 2.5:1.

[0105] The battery capacity and coulombic efficiency of the battery assembled in this embodiment are as follows: Figure 10 As shown by Figure 10 It can be seen that in Na + / Mg 2 + In the NaTFSI / Mg(TFSI)2 electrolyte with a molar ratio of 2.5:1, the average coulombic efficiency of the hybrid ion battery is about 90% after 200 cycles, but it is -1 The initial specific capacity was reduced to 21 mAh g -1 .

[0106] By comparative analysis, Na + / Mg 2+When the molar ratio is 1:1, the magnesium-sodium mixed ion full battery has both optimal capacity and optimal coulombic efficiency.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the technical solutions. Those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present invention that do not depart from the purpose and scope of the technical solutions of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A sodium-rich sodium polyvanadate material, characterized in that: Its chemical formula is Na 2+x V6O 16 ·2.9H2O, where 0 < X < 4, and the microscopic morphology is an anisotropic single-crystal nanobelt structure.

2. The method for preparing the sodium-rich sodium polyvanadate material according to claim 1, wherein The following steps are involved: (1) dissolving sodium metavanadate in deionized water and stirring until the sodium metavanadate is completely dissolved to obtain a sodium metavanadate solution, which is referred to as solution A; (2) Under stirring conditions, add acid solution to solution A and adjust the pH to 2-3.

5. The resulting solution is recorded as solution B; (3) Place solution B in a water bath, stir to allow for sufficient reaction, and then cool naturally. Filter, wash, and dry to obtain a sodium-rich sodium polyvanadate material.

3. The method for preparing a sodium-rich sodium polyvanadate material according to claim 2, wherein The concentration of the sodium metavanadate solution in step (1) is 5 g / L to 35 g / L.

4. The method for preparing a sodium-rich sodium polyvanadate material according to claim 2, wherein The mass concentration of the acid solution in step (2) is 5% to 30%.

5. The method for preparing a sodium-rich sodium polyvanadate material according to claim 2, wherein: In step (3), the water bath temperature is 60-130° C., and the stirring time is 3-12 h.

6. A battery positive electrode sheet, characterized in that: The invention comprises the sodium-rich sodium polyvanadate material according to claim 1.

7. A battery, characterized in that: Including the positive electrode sheet as claimed in claim 6.

8. A magnesium-based mixed ion battery with Na + / Mg 2+ The double salt electrolyte is an electrolyte characterized by: The positive electrode sheet according to claim 6 is used as the positive electrode.

9. The magnesium-based hybrid ion battery according to claim 8, characterized in that: The Mg 2+ / Na + The concentration of the double salt electrolyte is 0.5 to 3M.

10. The magnesium-based hybrid ion battery according to claim 8, characterized in that: In the double salt electrolyte, Na + / Mg 2+ The molar ratio is 1 to 2.5:1.

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