A vanadium-doped magnesium vanadate positive electrode material, a preparation method and application thereof

Abstract

This invention discloses a doped magnesium vanadate cathode material, its preparation method, and its application, belonging to the field of magnesium battery technology. The preparation of the doped magnesium vanadate cathode material includes: reacting a mixed solution of vanadium source solution, molybdenum source solution, and magnesium source solution to obtain a cathode material precursor; and calcining the cathode material precursor. This method can precisely target the doping of Mo element in magnesium vanadate. Single doping of Mo introduces strong Mo-O bonds, effectively stabilizing the structure and suppressing the spinel-to-rock salt phase transition. Furthermore, O2p-Mo4d orbital hybridization improves electronic conductivity and rate performance, effectively overcoming the difficulty of simultaneously achieving structural stability and ion-electron dynamics in spinel cathode materials for magnesium batteries. The obtained doped magnesium vanadate cathode material is a spinel system, and the magnesium metal battery further prepared from it is the first discovered spinel-based magnesium metal battery capable of cycling at room temperature.

Description

Technical Field

[0001] This invention relates to the field of magnesium battery technology, and more specifically, to a doped magnesium vanadate cathode material, its preparation method, and its application. Background Technology

[0002] Currently, the application of lithium-ion batteries (LIBs) in large-scale energy storage systems is constrained by safety issues and rising lithium resource costs. Rechargeable magnesium batteries (RMBs), due to their low manufacturing cost and good safety performance, are considered potential candidates for the next generation of energy storage technology.

[0003] Magnesium batteries have the unique advantage of directly using metallic magnesium as the negative electrode, and their volumetric capacity (approximately 3833 mAh / cm²) is significant. 3 The capacity is significantly higher than that of lithium metal anodes (approximately 2046 mAh / cm³). 3 However, Mg 2+ The charge density is much higher than that of Li + (120C / mm) 3 vs. 52C / mm 3 This results in slow diffusion kinetics and poor structural stability in most cathode materials.

[0004] Spinel structure is characterized by its unique structural properties and is a Mg 2+ The insertion and extraction of vanadate provides an effective pathway. Currently, magnesium vanadate oxides (such as MgV₂O₄) exhibit advantages in high voltage and high specific capacity due to the multi-electron redox ability of vanadium. However, Mg 2+ The strong polarization effect caused by high charge density results in a high migration barrier (approximately 560 meV~800 meV) and a low diffusion coefficient (e.g., 10) within the spinel lattice. -13 cm 2 The capacity (on the order of / s) severely limits its rate performance. More importantly, during deep demagnesiation, the spinel structure is prone to irreversible phase transition to rock salt structure, leading to rapid capacity decay.

[0005] Currently, there is no method that can simultaneously suppress the MgV2O4 phase transition and reduce Mg content. 2+ Magnesium vanadate cathode material, which can improve the electrochemical performance of magnesium-ion batteries by migrating energy barriers.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a doped magnesium vanadate cathode material, its preparation method, and its application, so as to solve or improve the above-mentioned technical problems.

[0008] This invention can be implemented as follows: In a first aspect, the present invention provides a method for preparing a magnesium vanadate-doped cathode material, comprising the following steps: reacting a mixed solution of a vanadium source solution, a molybdenum source solution, and a magnesium source solution to obtain a cathode material precursor; and calcining the cathode material precursor.

[0009] In an optional embodiment, the molar ratio of V in the vanadium source solution, Mo in the molybdenum source solution, and Mg in the magnesium source solution is (8.5~9.5):1:(9.5~10.5).

[0010] In an optional embodiment, the vanadium source in the vanadium source solution includes ammonium metavanadate; And / or, the molybdenum source in the molybdenum source solution includes molybdenum pentachloride; And / or, the magnesium source in the magnesium source solution includes magnesium acetate; And / or, the solvents in the vanadium source solution, molybdenum source solution, and magnesium source solution independently include ethylene glycol.

[0011] In an optional embodiment, the reaction is carried out at 160°C to 200°C for at least 24 hours; Preferably, the reaction is carried out at 180°C for 24 hours.

[0012] In an optional embodiment, calcination is carried out at 600°C to 700°C under a protective atmosphere for at least 2 hours.

[0013] In an optional embodiment, calcination is carried out at 600°C under a protective atmosphere for 2 hours.

[0014] In an optional embodiment, the cathode material precursor is washed and dried before calcination; Preferably, the washing process includes: washing with anhydrous ethanol at a speed of 9500 r / min to 10500 r / min for 8 min to 12 min; Preferably, the drying is carried out under vacuum at 55℃~65℃ for 10h~15h.

[0015] Secondly, the present invention provides a magnesium vanadate-doped cathode material, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0016] In an optional embodiment, the doped magnesium vanadate cathode material has at least one of the following characteristics: Feature 1: The doped magnesium vanadate cathode material exhibits a spinel structure; Feature 2: In magnesium vanadate-doped cathode materials, molybdenum atoms occupy some of the vanadium lattice sites in the spinel framework; Feature 3: In the magnesium vanadate cathode material, the molar percentage of Mo does not exceed 30% of V; preferably 10% to 25% of V, more preferably 10% to 15% of V.

[0017] Thirdly, the present invention provides a battery containing the doped magnesium vanadate cathode material of the aforementioned embodiments.

[0018] The beneficial effects of this invention include: This invention precisely targets and dops Mo into magnesium vanadate. Single Mo doping introduces strong Mo-O bonds, effectively stabilizing the structure and suppressing the spinel-to-rock salt phase transition. Furthermore, O2p-Mo4d orbital hybridization enhances electronic conductivity and rate performance, effectively overcoming the challenge of simultaneously achieving structural stability and ion-electron dynamics in spinel cathode materials for magnesium batteries. The resulting doped magnesium vanadate cathode material is a spinel system, and the magnesium metal battery further prepared from it represents the first discovery of a spinel-based magnesium metal battery capable of cycling at room temperature. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The XRD patterns of MVMO and MVO in Experimental Example 1 are shown below. Figure 2 The TEM and HAADF-STEM images of MVMO in Experiment Example 1 are shown. Figures 3 to 7 The graphs show the charge-discharge curves, cycle performance results, rate performance results, long-cycle performance results, and electrochemical impedance results of the half-cell in Experiment Example 1. Figures 8 to 11 The graphs show the cycle performance, charge-discharge curves, rate performance, and CV results of the full cell in Experiment Example 1. Figure 12 The images show the in-situ XRD pattern of MVMO in Experimental Example 1, and the off-situ XRD patterns of MVO and MVMO. Figure 13 The XRD patterns are of the magnesium vanadate cathode materials doped with Mo and the undoped magnesium vanadate cathode materials in Comparative Examples 2-1 to 2-4 of Experimental Example 2. Figures 14 to 18 SEM images of the undoped magnesium vanadate cathode material in Experimental Example 2 and the doped magnesium vanadate cathode materials in Comparative Examples 2-1 to 2-4. Figure 19 The graph shows the electrochemical performance results of the half-cell in Experiment Example 2; Figure 20 XRD patterns of various doped magnesium vanadate cathode materials in Experiment Example 3; Figure 21 The graph shows the electrochemical performance results of each doped magnesium vanadate cathode material obtained in Experiment Example 3. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0022] The following is a detailed description of the doped magnesium vanadate cathode material, its preparation method, and its application provided by the present invention.

[0023] This invention provides a method for preparing a magnesium vanadate-doped cathode material, comprising the following steps: reacting a mixed solution of vanadium source solution, molybdenum source solution and magnesium source solution to obtain a cathode material precursor; and calcining the cathode material precursor.

[0024] It should be noted that this invention specifically uses Mo for doping, which allows for more precise doping compared to other common doping elements (such as Cr, W, Ta, and Nb). Furthermore, after precursor calcination, it effectively maintains the complete spinel structure while ensuring superior electrochemical performance of the resulting magnesium-ion battery. Regarding common doping elements, Nb is difficult to dope in magnesium vanadate; Cr and Nb have large atomic radii, which alter the spinel structure of magnesium vanadate after doping; and W has an excessively large relative atomic mass, which reduces the theoretical capacity of the final magnesium-ion battery after doping.

[0025] In some optional embodiments, the molar ratio of V in the vanadium source solution, Mo in the molybdenum source solution, and Mg in the magnesium source solution is (8.5~9.5):1:(9.5~10.5), such as 8.5:1:9.5, 9:1:10, or 9.5:1:10.5, or other values ​​within the range of (8.5~9.5):1:(9.5~10.5).

[0026] By controlling the V, Mo, and Mg in the raw materials within the above molar range, the Mo doping amount in the magnesium vanadate cathode material can be appropriately controlled. If the Mo doping amount is too low, it is not conducive to the structural stability of magnesium vanadate spinel; if the Mo doping amount is too high, it is easy to cause a decrease in the theoretical capacity of magnesium vanadate and structural changes.

[0027] In some optional embodiments, the vanadium source in the vanadium source solution may include ammonium metavanadate, the molybdenum source in the molybdenum source solution may include molybdenum pentachloride, and the magnesium source in the magnesium source solution may include magnesium acetate. The solvents in the aforementioned vanadium source solution, molybdenum source solution, and magnesium source solution may each independently include ethylene glycol.

[0028] It should be noted that vanadium chloride can be used as a vanadium source and dissolved in water to synthesize doped magnesium vanadate cathode materials, along with molybdenum and magnesium sources. However, the doped magnesium vanadate cathode materials synthesized in this way have very high crystallinity, which can actually reduce the electrochemical performance of the materials.

[0029] In some optional embodiments, the vanadium source solution can be prepared by stirring 8.5 mmol to 9.5 mmol of ammonium metavanadate with 180 mL of ethylene glycol at 55°C to 65°C for 10 to 15 hours using a heated magnetic stirrer to obtain a light yellow vanadium source solution.

[0030] For the preparation of the molybdenum source solution, refer to the following: using a heated magnetic stirrer, stir 1 mmol of molybdenum pentachloride with 20 mL of ethylene glycol at 55℃~65℃ for 10h~15h to obtain a green molybdenum source solution.

[0031] The preparation of the magnesium source solution can be found by stirring 9.5 mmol to 10.5 mmol of magnesium acetate with 40 mL of ethylene glycol at 55 °C to 65 °C for 10 to 15 hours using a heated magnetic stirrer to obtain a colorless magnesium source solution.

[0032] The vanadium source solution, molybdenum source solution and magnesium source solution are mixed and stirred for 25 min to 40 min to obtain a mixed solution, which is then transferred to a stainless steel reactor for reaction to obtain a green cathode material precursor.

[0033] In some alternative implementations, the reaction can be carried out at 160°C to 200°C for at least 24 hours.

[0034] The reaction temperature can be 160℃, 165℃, 170℃, 175℃, 180℃, 185℃, 190℃, 195℃ or 200℃, or other values ​​within the range of 160℃ to 200℃.

[0035] The reaction time can be 24h, 28h, 32h, 36h or 40h, etc.

[0036] In some preferred embodiments, the reaction is carried out at 160°C to 200°C for 24 to 36 hours. In some even preferred embodiments, the reaction is carried out at 180°C for 24 hours.

[0037] If the reaction temperature is below 160℃, the reaction is prone to incompleteness. If the reaction time is less than 24 hours, the precursor particles will be larger, affecting the electrochemical performance of the material.

[0038] Furthermore, the cathode material precursor can be washed and dried before calcination.

[0039] In some optional embodiments, washing can be performed using anhydrous ethanol at a speed of 9500 r / min to 10500 r / min (e.g., 9500 r / min, 10000 r / min, or 10500 r / min) for 8 min to 12 min (e.g., 8 min, 10 min, or 12 min). The number of washing cycles can be once, twice, three times, or more.

[0040] In some alternative embodiments, drying can be performed under vacuum at 55°C to 65°C (e.g., 55°C, 60°C, or 65°C) for 10 to 15 hours (e.g., 10 hours, 12 hours, or 15 hours).

[0041] In some alternative embodiments, calcination can be carried out at 600°C to 700°C under a protective atmosphere for at least 2 hours.

[0042] The calcination temperature can be 600℃, 650℃ or 700℃, or other values ​​within the range of 600℃ to 700℃.

[0043] The calcination time can be 2 hours, 4 hours, or 6 hours, etc.

[0044] The calcination atmosphere can be nitrogen or argon, etc.

[0045] In some preferred embodiments, calcination is carried out at 600°C under a protective atmosphere for 2 hours.

[0046] It should be noted that the calcination temperature has a direct impact on the structure of the doped magnesium vanadate cathode material. If the calcination temperature is below 600℃, the doped magnesium vanadate cathode material will not transform into a spinel structure and will contain precursor impurities. If the calcination temperature is above 700℃, it is prone to material decomposition. In addition, if the calcination time is less than 2 hours, it is not conducive to the formation of the spinel structure.

[0047] By calcining under the above conditions, a doped magnesium vanadate cathode material derived from the cathode material precursor is obtained.

[0048] Building upon the above, this invention, through the precise replacement of V sites with Mo doping, overcomes two key technical challenges in the field of magnesium battery cathode materials (structural stability and ion / electron dynamics of magnesium battery spinel cathode materials), and solves the problem of improving rate performance (requiring a reduction in Mg content). 2+This solution addresses the often contradictory issues of migrating energy barriers and improving cycle stability (which requires suppressing irreversible phase transitions), achieving a "two birds with one stone" effect.

[0049] Specifically, this invention uses Mo as a single dopant element, simultaneously introducing strong Mo-O bonds and O2p-Mo4d orbitals. The Mo-O bonds play a role in stabilizing the structure and inhibiting the transformation of the material from the spinel phase to the rock salt phase; specifically, Mo... 6+ The bond energy of the -O bond is approximately 607 kJ / mol, V 3+ The bond energy of the -O bond is approximately 464 kJ / mol, therefore, Mo 6+ -O bond is more V 3+ The -O bond has a higher bond energy, and this strong bond energy mechanism can stabilize the vanadium octahedral framework, thus effectively suppressing the transformation from spinel phase to rock salt phase during charge and discharge. The π-electron donation effect of the O2p-Mo4d orbitals can effectively narrow the band gap and enhance the intrinsic electronic conductivity of the material (EIS shows a decrease in charge transfer resistance Rct), thereby improving the rate performance of the material. Simultaneously, the increase in specific surface area can contribute to the growth of Mg. 2+ It provides more diffusion channels, ensuring unobstructed ion transport paths.

[0050] Accordingly, the present invention also provides a magnesium vanadate-doped cathode material, which is prepared by the above-described preparation method.

[0051] In some alternative implementations, the magnesium vanadate-doped cathode material has a spinel structure.

[0052] In some alternative implementations, in the magnesium vanadate cathode material, molybdenum atoms occupy some of the vanadium lattice sites in the spinel framework.

[0053] In some alternative embodiments, the average particle size of the magnesium vanadate-doped cathode material is 3.4 μm to 3.6 μm.

[0054] In some alternative implementations, the molar percentage of Mo in the magnesium vanadate cathode material does not exceed 30% of V, such as 30%, 25%, 20%, 15%, 10%, 5%, or 1% of V, or other values ​​within the range not exceeding 30%.

[0055] In some preferred embodiments, the Mo content in the doped magnesium vanadate cathode material is 10% to 25% of V, by mole percentage. In some more preferred embodiments, the Mo content in the doped magnesium vanadate cathode material is 10% to 15% of V, by mole percentage. At this doping ratio, the doped magnesium vanadate cathode material can possess both superior structural morphology and electrochemical performance.

[0056] Continuing on the above, this invention successfully obtained spinel-structured doped magnesium vanadate cathode materials (such as MgV₂O₄) by doping Mo into magnesium vanadate (MgV₂O₄). 1.1 V 1.7 Mo 0.4 O4) significantly improves the rate performance and cycle stability of magnesium vanadate cathode materials. On the one hand, the strong bond energy mechanism of Mo-O bonds in the doped magnesium vanadate cathode material effectively slows down the transformation of the material from spinel structure to rock salt structure, improving the cycle performance of the material; on the other hand, the π-donation mechanism of O2p-Mo4d in the doped magnesium vanadate cathode material can enhance the electron transfer between energy bands, improving the conductivity and rate performance of the material.

[0057] In addition, the present invention also provides a battery containing the above-mentioned doped magnesium vanadate cathode material, which has better electrochemical performance.

[0058] The battery containing the above-mentioned doped magnesium vanadate cathode material is the first magnesium metal battery discovered in the spinel system that can achieve good cycling at room temperature.

[0059] In some alternative implementations, the battery can provide a high specific capacity of not less than 285 mAh / g at a current density of 100 mA / g and exhibit no capacity decay after 100 cycles.

[0060] In some alternative implementations, the battery retains at least 93% capacity after 600 cycles at a high current density of 2 A / g.

[0061] In some alternative implementations, the battery capacity decreases by no more than 25% as the current density increases from 100 mA / g to 1000 mA / g.

[0062] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0063] Example 1 This embodiment provides a doped magnesium vanadate cathode material, the preparation method of which includes the following steps: S1: Preparation of cathode material precursor.

[0064] Using a heated magnetic stirrer, 9 mmol of ammonium metavanadate and 180 mL of ethylene glycol were stirred at 60 °C for 12 h to obtain a light yellow vanadium source solution.

[0065] A green molybdenum source solution was obtained by stirring 1 mmol of molybdenum pentachloride with 20 mL of ethylene glycol at 60 °C for 12 h using a heated magnetic stirrer.

[0066] A colorless magnesium source solution was obtained by stirring 10 mmol of magnesium acetate with 40 mL of ethylene glycol at 60 °C for 12 h using a heated magnetic stirrer.

[0067] The vanadium source solution, molybdenum source solution and magnesium source solution were mixed and stirred for 30 minutes to obtain a mixed solution. The mixed solution was transferred to a stainless steel reactor and reacted at 180°C for 24 hours to obtain a green cathode material precursor.

[0068] S2: Preparation of magnesium vanadate-doped cathode material.

[0069] The cathode material precursor was washed with anhydrous ethanol for 10 min in a centrifuge at a speed of 10000 r / min, and the washing was repeated 3 times. Then it was vacuum dried at 60℃ for 12 h.

[0070] The dried material was calcined at 600℃ for 2 hours in an argon atmosphere to obtain magnesium vanadate-doped cathode material (Mg). 1.1 V 1.7 Mo 0.2 O4, abbreviated as MVMO or Mo-MVO, the elemental molar ratio is determined by ICP-MS.

[0071] Example 2 This embodiment provides a doped magnesium vanadate cathode material, the preparation method of which includes the following steps: S1: Preparation of cathode material precursor.

[0072] Using a heated magnetic stirrer, 8.5 mmol of ammonium metavanadate and 180 mL of ethylene glycol were stirred at 55 °C for 15 h to obtain a light yellow vanadium source solution.

[0073] A green molybdenum source solution was obtained by stirring 1 mmol of molybdenum pentachloride with 20 mL of ethylene glycol at 55 °C for 15 h using a heated magnetic stirrer.

[0074] A colorless magnesium source solution was obtained by stirring 9.5 mmol of magnesium acetate with 40 mL of ethylene glycol at 55 °C for 15 h using a heated magnetic stirrer.

[0075] The vanadium source solution, molybdenum source solution and magnesium source solution were mixed and stirred for 25 minutes to obtain a mixed solution. The mixed solution was transferred to a stainless steel reactor and reacted at 160°C for 32 hours to obtain a green cathode material precursor.

[0076] S2: Preparation of magnesium vanadate-doped cathode material.

[0077] The cathode material precursor was washed with anhydrous ethanol for 12 min in a centrifuge at a speed of 9500 r / min, and the washing was repeated 3 times. Then it was vacuum dried at 55℃ for 15 h.

[0078] The dried material was calcined at 600℃ for 4 hours in an argon atmosphere to obtain magnesium vanadate-doped cathode material.

[0079] Example 3 This embodiment provides a doped magnesium vanadate cathode material, the preparation method of which includes the following steps: S1: Preparation of cathode material precursor.

[0080] Using a heated magnetic stirrer, 9.5 mmol of ammonium metavanadate and 180 mL of ethylene glycol were stirred at 65 °C for 10 h to obtain a light yellow vanadium source solution.

[0081] A green molybdenum source solution was obtained by stirring 1 mmol of molybdenum pentachloride with 20 mL of ethylene glycol at 65 °C for 10 h using a heated magnetic stirrer.

[0082] A colorless magnesium source solution was obtained by stirring 10.5 mmol of magnesium acetate with 40 mL of ethylene glycol at 65 °C for 10 h using a heated magnetic stirrer.

[0083] The vanadium source solution, molybdenum source solution and magnesium source solution were mixed and stirred for 40 minutes to obtain a mixed solution. The mixed solution was transferred to a stainless steel reactor and reacted at 190°C for 24 hours to obtain a green cathode material precursor.

[0084] S2: Preparation of magnesium vanadate-doped cathode material.

[0085] The cathode material precursor was washed with anhydrous ethanol for 8 min in a centrifuge at a speed of 10500 r / min, and the washing was repeated 3 times. Then it was vacuum dried at 65℃ for 10 h.

[0086] The dried material was calcined at 700℃ for 2 hours in an argon atmosphere to obtain magnesium vanadate-doped cathode material.

[0087] Experimental Example 1 Taking the doped magnesium vanadate cathode material prepared in Example 1 as an example, its structure and performance were tested. A control example was also set up; the only difference between the control example and Example 1 was that it was not doped with Mo. The magnesium vanadate cathode material prepared in the control example was denoted as MVO.

[0088] (1) XRD tests were performed on the MVMO prepared in Example 1 and the MVO prepared in the control group, and the results are as follows: Figure 1 As shown. Figure 1(a) shows the XRD pattern corresponding to MVO. Figure 1 (b) is the XRD diagram corresponding to MVMO.

[0089] XRD refinement ( Figure 1 The results showed that both MVO and MVMO crystallized into space group Fd. The m-type pure spinel structure shows a slight shift in diffraction peaks at higher angles in the MVMO sample, reflecting a minor contraction in the lattice spacing (from 8.42 Å to 8.40 Å). In MVMO, Mg occupies the tetrahedral 8a sites, while the octahedral 16d sites are partially occupied by Mg, along with all of the Mo and V.

[0090] (2) The MVMO prepared in Example 1 was scanned by transmission electron microscopy, and the results are as follows: Figure 2 As shown in (a). Figure 2 (b) and (c) are high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) images, and (c) is a magnified view of the boxed area in (b).

[0091] Depend on Figure 2 As can be seen in (a), Mo is uniformly doped in MVMO; Figure 2 As can be seen in (b) and (c), some atomic pillars in MVMO exhibit higher intensity than their adjacent atomic pillars, confirming that Mo precisely occupies the V sites.

[0092] (3) The MVMO prepared in Example 1 and the MVO prepared in the control group were assembled into a half-cell in the following manner and their electrochemical performance was tested. The results are as follows: Figures 3 to 7 As shown.

[0093] Assembly Method: A CR2032 magnesium-ion battery was assembled to test its electrochemical performance. First, the positive electrode was prepared by mixing active material, acetylene black, and binder in a weight ratio of 6:3:1. Next, the above materials were uniformly mixed with N-methylpyrrolidone as a solvent to form a homogeneous slurry, which was then coated onto carbon paper and dried in a vacuum oven at 60°C for 12 hours. Finally, the active material loading was approximately 1.5 mg / cm³. 2 The electrodes were matched with activated carbon cloth as counter electrodes, and the button cell was assembled in an argon-filled glove box. The electrodes in the cell were separated by porous glass fibers and immersed in 80 μL of electrolyte dissolved in anhydrous acetonitrile in 0.3 mol / L MgTFSI.

[0094] Test conditions: Constant current charge-discharge tests were conducted on the Xinwei Battery Test System, with potential ranges from -1.2V to -1.5V (vs. AC) under different conditions. Electrochemical impedance spectroscopy was studied using a CHI760E electrochemical workstation, with a frequency range of 100kHz to 100mHz and an AC voltage of 1mV (relative to open circuit voltage).

[0095] Figure 3 The graph shows the charge-discharge curves. It can be seen from the graph that the half-cell with Mo doping has a smaller decay and smaller polarization change in the first 100 cycles. Figure 4 The graph shows the cycling performance results. As can be seen from the graph, the half-cell with Mo doping has less degradation and better capacity retention. Figure 5 The graph shows the rate performance results. As can be seen from the graph, the half-cell with Mo doping has better rate performance. Figure 6 The graph shows the long-cycle performance results. As can be seen from the graph, the capacity retention of the half-cell doped with Mo is about 93% after 600 cycles. Figure 7 The figure shows the electrochemical impedance spectroscopy results. As can be seen from the figure, the impedance of the half-cell is reduced and the conductivity is improved after doping with Mo.

[0096] Continuing from the above, the half-cell corresponding to the MVMO cathode material provided in Example 1 exhibits excellent capacity retention, providing a high specific capacity of 285.3 mAh / g at a current density of 100 mA / g, with no capacity decay after 100 cycles. After 600 cycles at a high current density of 2 A / g, the capacity remains at 93.3%. When the current density increases from 100 mA / g to 1000 mA / g, the capacity decreases by only about 23%.

[0097] (4) The MVMO prepared in Example 1 and the MVO prepared in the control group were assembled into a full cell in the following manner and their electrochemical performance was tested. The results are as follows: Figures 8 to 11 As shown.

[0098] Assembly method: Using metallic magnesium as the negative electrode and a non-corrosive Mg(hfip)2 / DME electrolyte, a full battery system is assembled with the above-mentioned positive electrode material.

[0099] Test conditions: Constant current charge-discharge tests were conducted on the Xinwei Battery Test System, with potential ranges of 0.1V~3.5V under different conditions (vs. Mg / Mg). 2+ ).

[0100] Figure 8The graph shows the cycling performance results. As can be seen from the graph, the charging voltage of the full cell without Mo doping cannot reach 3.5V, and the cycle fails. The reason is that the MVO without Mo doping produces a vanadium dioxide phase, which is not resistant to high voltage. Figure 9 The graph shows the charge-discharge curves. As can be seen from the graph, at a current density of 50 mA / g, the initial discharge capacity of the MVMO cathode is 106.7 mAh / g, which increases to 196.5 mAh / g in the second cycle, indicating that the electrode activation is incomplete during the initial cycle.

[0101] Figure 10 The figure shows the rate performance results. As can be seen from the figure, although the half-cell performance is excellent, the rate performance of the MVMO full cell is compromised, which indicates that there is a challenge to maintaining consistent kinetics across different cell architectures.

[0102] Figure 11 The figure shows the CV results. As can be seen from the figure, the cyclic voltammetry (CV) peaks correspond to the redox reaction of vanadium, indicating the reversibility of the surface reaction.

[0103] As mentioned above, the MVO full cell failed after 15 cycles because it could not reach the 3.5V cutoff voltage. This is closely related to the formation of the irreversible rock salt phase, which will destroy the high-voltage cycling stability.

[0104] (5) The MVMO prepared in Example 1 and the MVO prepared in the control group were subjected to in-situ and in-situ XRD tests, and the results are as follows: Figure 12 As shown.

[0105] Depend on Figure 12 It can be seen that the (111) / ((311) / (400) peak positions are stable during cycling with negligible angular displacement, while maintaining their intensity and phase purity (no second phase), which is characteristic of solid solution behavior. In-situ XRD shows that molybdenum doping can suppress the occurrence of cumulative phase transitions.

[0106] Experimental Example 2 This experimental example provides different Mo doping levels, denoted as Comparative Example 2-1 to Comparative Example 2-2. Among them, Comparative Example 2-1 (denoted as MgV) 1.8 Mo 0.2 The difference between Comparative Example 2-2 (O4) and Example 1 is that the molar amount of Mo is approximately 11% of V; Comparative Example 2-2 (denoted as MgV) 1.6 Mo 0.4 The difference between O4 and Example 1 is that the molar amount of Mo is 25% of V; Comparative Examples 2-3 (denoted as MgV) 1.4 Mo 0.6 The difference between O4 and Example 1 is that the molar amount of Mo is approximately 43% of V; Comparative Examples 2-4 (denoted as MgV)1.2 Mo 0.8 The difference between O4 and Example 1 is that the molar amount of Mo is approximately 66% of V.

[0107] (1) The magnesium vanadate cathode materials doped with Mo and the undoped magnesium vanadate cathode materials of Comparative Examples 2-1 to 2-4 were subjected to XRD tests, and the results are as follows: Figure 13 As shown.

[0108] Depend on Figure 13 It can be seen that when the Mo doping content exceeds 40%, the material undergoes a phase transition and vanadium dioxide is generated.

[0109] (2) The magnesium vanadate cathode materials doped with Mo and the undoped magnesium vanadate cathode materials of Comparative Examples 2-1 to 2-4 were subjected to SEM testing, and the results are as follows: Figures 14 to 18 As shown.

[0110] Figure 14 The above are SEM results for undoped MgV2O4. Figure 14 (b) is a magnified view of a portion of (a); Figure 15 For MgV 1.8 Mo 0.2 SEM results for O4 Figure 15 (b) is a magnified view of a portion of (a); Figure 16 For MgV 1.6 Mo 0.4 SEM results for O4 Figure 16 (b) is a magnified view of a portion of (a); Figure 17 For MgV 1.4 Mo 0.6 SEM results for O4 Figure 17 (b) is a magnified view of a portion of (a); Figure 18 For MgV 1.2 Mo 0.8 SEM results for O4 Figure 18 (b) is a magnified view of (a).

[0111] Depend on Figures 14 to 18 It can be seen that after doping magnesium vanadate with Mo, the morphology of the resulting cathode material shrinks while the specific surface area increases. Figure 14 The particle size of (b) is 8.47 μm; Figure 15 The particle size in (b) is 3.5 μm. When the Mo doping amount exceeds 25%, the morphology begins to change; when the Mo doping amount reaches more than 40%, the resulting cathode material no longer exhibits a spinel morphology.

[0112] (3) The magnesium vanadate cathode materials doped with Comparative Examples 2-1 to 2-3 and the undoped magnesium vanadate cathode materials were assembled into half-cells as described in Experimental Example 1, and their electrochemical performance was tested. The results are as follows: Figure 19 As shown.

[0113] Depend on Figure 19 It can be seen that MgV with a Mo doping content of about 10% 1.8 Mo 0.2 The electrochemical performance corresponding to O4 is better than that of MgV corresponding to other doping levels. 1.6 Mo 0.4 O4 and MgV 1.4 Mo 0.6 O4.

[0114] Based on the morphology and electrochemical performance results, the best performance is achieved when Mo is about 10% of V in the magnesium vanadate cathode material, expressed as a molar percentage.

[0115] Experimental Example 3 This experimental example provides various cases of doping with different elements, referred to as Comparative Examples 1-1 to 1-5. The difference between Comparative Example 1-1 and Example 1 is that Nb is used to replace Mo in an equal amount; the difference between Comparative Example 1-2 and Example 1 is that Cr is used to replace Mo in an equal amount; the difference between Comparative Example 1-3 and Example 1 is that Ta is used to replace Mo in an equal amount; the difference between Comparative Example 1-4 and Example 1 is that W is used to replace Mo in an equal amount; and the difference between Comparative Example 1-5 and Example 1 is that half of the Mo is replaced with W, i.e., a co-doping method of Mo and W is used.

[0116] The XRD patterns of the various doped magnesium vanadate cathode materials are as follows: Figure 20 As shown, the results indicate that all elements except niobium (whose precursor failed to react due to dissolution problems) were successfully introduced, resulting in a pure spinel phase.

[0117] The electrochemical performance of the obtained doped magnesium vanadate cathode materials was tested using the methods described in the aforementioned experimental examples, and the results are as follows: Figure 21 As shown, by Figure 21 It can be seen that molybdenum doping can achieve the best battery performance.

[0118] In summary, this invention, through precise doping of Mo into magnesium vanadate, achieves two key benefits. Firstly, the introduction of strong Mo-O bonds effectively stabilizes the structure and suppresses the spinel-to-rock salt phase transition. Secondly, the O2p-Mo4d orbital hybridization enhances electronic conductivity and improves rate performance, effectively overcoming the challenge of simultaneously achieving structural stability and ion-electron dynamics in spinel cathode materials for magnesium batteries. The resulting doped magnesium vanadate cathode material is a spinel system, and the magnesium metal battery further prepared from it represents the first discovery of a spinel-based magnesium metal battery capable of cycling at room temperature.

[0119] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a magnesium vanadate-doped cathode material, characterized in that, Includes the following steps: A mixture of vanadium source solution, molybdenum source solution and magnesium source solution is reacted to obtain a cathode material precursor; the cathode material precursor is then calcined.

2. The preparation method according to claim 1, characterized in that, The molar ratio of V in the vanadium source solution, Mo in the molybdenum source solution, and Mg in the magnesium source solution is (8.5~9.5):1:(9.5~10.5).

3. The preparation method according to claim 2, characterized in that, The vanadium source in the vanadium source solution includes ammonium metavanadate. And / or, the molybdenum source in the molybdenum source solution includes molybdenum pentachloride; And / or, the magnesium source in the magnesium source solution includes magnesium acetate; And / or, the solvents in the vanadium source solution, molybdenum source solution, and magnesium source solution independently include ethylene glycol.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The reaction was carried out at 160℃~200℃ for 24h~36h; Preferably, the reaction is carried out at 180°C for 24 hours.

5. The preparation method according to any one of claims 1 to 3, characterized in that, Calcination is carried out at 600℃~700℃ under a protective atmosphere for at least 2 hours.

6. The preparation method according to claim 5, characterized in that, Calcination was carried out at 600℃ under a protective atmosphere for 2 hours.

7. The preparation method according to any one of claims 1 to 3, characterized in that, Before calcination, the cathode material precursor is washed and dried. Preferably, the washing process includes: washing with anhydrous ethanol at a speed of 9500 r / min to 10500 r / min for 8 min to 12 min; Preferably, the drying is carried out under vacuum at 55℃~65℃ for 10h~15h.

8. A magnesium vanadate-doped cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. The doped magnesium vanadate cathode material according to claim 8, characterized in that, The doped magnesium vanadate cathode material has at least one of the following characteristics: Feature 1: The doped magnesium vanadate cathode material has a spinel structure; Feature 2: In the doped magnesium vanadate cathode material, molybdenum atoms occupy some of the vanadium lattice sites in the spinel framework; Feature 3: In the doped magnesium vanadate cathode material, Mo does not exceed 30% of V by mole percentage; preferably 10% to 25% of V, more preferably 10% to 15% of V.

10. A battery, characterized in that, The battery contains the doped magnesium vanadate cathode material as described in claim 8 or 9.

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