Preparation method of magnesium ion battery positive electrode material BixVS4 electrode material

Abstract

The invention belongs to the field of magnesium ion battery positive electrode materials, and particularly relates to a preparation method of a magnesium ion battery positive electrode material BixVS4 composite material, which comprises the following steps: dissolving an organic reducing agent in N-methyl pyrrolidone, and stirring at room temperature; adding ammonium metavanadate, and stirring at 50-100 DEG C; adding thioacetamide, and continuously stirring; adding hydrochloric acid and stirring until the color of the solution becomes dark green; and adding bismuth nitrate pentahydrate, stirring, carrying out a hydrothermal reaction in a reaction kettle, cooling to room temperature, centrifuging, washing with deionized water and absolute ethyl alcohol for several times, and drying to obtain the BixVS4 composite material. The method has the advantages that VS4 is subjected to cation modification, high conductivity is provided by introduction of metal ions, and charge transfer is accelerated. Bi enters a VS4 crystal lattice, local charge rearrangement is caused, Van der Waals force between VS4 layers is weakened, rapid embedding and de-embedding of Mg < 2 + > are facilitated, and more active sites for embedding of Mg < 2 + > are provided.

Description

Technical Field

[0001] This invention belongs to the field of magnesium-ion battery cathode materials, and particularly relates to a magnesium-ion battery cathode material Bi. x Preparation method of VS4 composite material. Background Technology

[0002] With rapid societal development and continuous growth in energy demand, developing high-efficiency energy storage technologies that are low-cost, highly safe, and high-performance has become an important research direction. Rechargeable batteries, due to their ease of operation and maintenance, have been widely used in various fields. Among them, rechargeable magnesium ion batteries (RMIBs) have shown significant potential following lithium-ion batteries due to their high safety, low cost, environmental friendliness, and sustainability, and are expected to provide a more cost-effective and safer solution for future energy storage devices.

[0003] Rechargeable magnesium battery systems (RMIBS) offer advantages in terms of cost and safety, but their commercial application still faces several challenges, primarily including low operating potential, short cycle life, and the limitations imposed by magnesium. 2+ The low energy density is due to the slow kinetics during charging and discharging. Additionally, Mg... 2+ The ionic radius is 0.072 nm, similar to Li. + Comparable, but due to its higher charge, Mg 2+ A strong electrostatic interaction will form between Mg and the positive electrode material, causing Mg to... 2+ The embedding process becomes more difficult and can also cause Mg to... 2+ The increased stress from insertion / extraction ultimately leads to insufficient magnesification in most magnesium-ion cathode materials, further limiting battery performance.

[0004] Currently, most of the widely studied materials are transition metal compounds with spinel, olivine, or layered structures. Examples include transition metal oxides / sulfides and some organic cathode materials (including polyaniline, PVP, and PEO). However, achieving highly reversible Mg... 2+ Intercalation / deintercalation, excellent cycle stability, and high specific capacity remain common unresolved challenges for these materials. Furthermore, most potentially valuable cathode materials are generally sulfides, such as VS4, MoS2, FeS2, and CuS. These materials offer relatively high capacity and are extremely abundant naturally, making them favorable choices for RMIB cathode materials. However, sulfides alone, as cathode materials, suffer from poor conductivity and significant volume expansion, hindering their development as cathode materials for magnesium-ion batteries.

[0005] Studies have shown that microstructure manipulation is an effective strategy for improving the magnesium storage performance of materials. As reported by Ding et al. (Strategy of cation / anion co-doping for potential elevating of VS4 cathode for magnesium ion batteries. DOI: 10.1016 / j.cej.2022.135778), when VS4 is co-doped with Mo and O, a funnel-like structure is generated. According to this report, Mo and O co-doping increases the interlayer spacing in VS4 and effectively increases the number of sulfur vacancies, while reducing Mg... 2+ Diffusion barriers and internal stresses during insertion / extraction processes. These structural modifications enhance the magnesium storage capacity of the material.

[0006] However, unmodified VS4 suffers from poor cycle life and low rate capacity due to its inherently low conductivity, unavoidable volume expansion, and irreversible polysulfide formation. Therefore, it is necessary to create more electrochemical active sites and construct multidimensional diffusion pathways to improve the magnesium storage performance of VS4. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, the purpose of this invention is to provide a magnesium-ion battery cathode material, Bi. x A method for preparing VS4 electrode materials, using Bi-modified VS4 to prepare Bi cathode materials for magnesium-ion batteries. x VS4 effectively suppresses the problems of low conductivity and volume expansion that exist when VS4 is used alone as the positive electrode material of magnesium-ion batteries.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] Bi, a magnesium-ion battery cathode material x The preparation method of VS4 composite material includes the following steps:

[0010] 1) Preparation of solution A: Dissolve 0.2~0.5g of organic reducing agent in 10~100ml of N-methylpyrrolidone and stir until dissolved at room temperature;

[0011] 2) Preparation of solution B: Dissolve 0.1~0.5g of ammonium metavanadate in solution A and stir at 400~600r / min at 50~100℃ for 10~60min;

[0012] 3) Preparation of solution C: Dissolve 1.0~2.0g of thioacetamide in solution B and stir at 100~300r / min at 50~100℃ for 10~60min;

[0013] 4) Preparation of solution D: Add 1-10 ml of 3 mol / L hydrochloric acid to solution C, and stir at 100-300 r / min for 10-60 min at 50-100℃ until the solution turns dark green.

[0014] 5) Preparation of solution E: Dissolve 10-40 mg of bismuth nitrate pentahydrate in solution D and stir at 100-300 r / min for 10-60 min at 20-30℃.

[0015] 6) Place the obtained E solution into a reaction vessel and hydrothermally react at a temperature of 100~200℃ for 10~24h;

[0016] 7) After removing the reaction vessel and cooling it to room temperature, centrifuge it, wash it several times with deionized water and anhydrous ethanol, and then dry it to obtain Bi. x VS4 composite material.

[0017] The organic reducing agent mentioned in step 1) is one of ascorbic acid, butenal, ethylene, glucose, and citric acid.

[0018] The stirring described in step 1) is stirring at a speed of 100~300 r / min.

[0019] In this invention, ammonium metavanadate is used as the vanadium source; thioacetamide is used as the sulfur source; bismuth nitrate pentahydrate is used as the bismuth source; N-methylpyrrolidone is used as the solvent; dilute hydrochloric acid not only affects the hydrolysis reaction of thioacetamide but also affects the preferred growth orientation of the crystal nuclei. During the reaction, thioacetamide generates H2S, which reacts with ammonium metavanadate in a suitable acidic environment. Furthermore, thioacetamide generates CH3CONH2 during hydrolysis, and CH3CONH2 further hydrolyzes to produce NH4 under continuous heating. + In moderately acidic media, these NH4 + It tends to selectively anchor on the (110) crystal plane and is the connection factor connecting adjacent (110) lattices. The addition of an organic reducing agent can control the reduced valence state of vanadium. Without a reducing agent or with insufficient reducing agent, V 5+ It may not be fully reduced, resulting in a mixture of vanadium oxide (such as V2O5) and vanadium sulfide, or vanadium sulfide with impure valence state, affecting the purity of the material. In addition, some reducing agents with multiple hydroxyl groups (such as glucose and ascorbic acid) can adsorb onto specific crystal faces through coordination, changing the growth rate of different crystal faces, thereby controlling the formation, anisotropic growth, or self-assembly of nanosheets into specific three-dimensional structures (such as flower-like or hollow spheres).

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This invention modifies VS4 with cations (Bi) to obtain Bi. x The VS4 electrode material was studied, and results showed that the introduction of metal ions provided higher conductivity and accelerated charge transfer. Furthermore, Bi entered the VS4 lattice, replacing some of the V. 4+ This caused local charge rearrangement, weakening the van der Waals forces between VS4 layers, which is beneficial to Mg. 2+ Rapid insertion and extraction provide a wide range of options for Mg 2+ The embedded active site. Bi x VS4 electrode material is used as the positive electrode material in magnesium-ion batteries at a current density of 50 mA g. -1 At that time, the maximum capacity after 100 cycles is 10-150 mAh g. -1 This indicates that Bi x VS4 composite materials have promising applications in electrochemical energy storage. Attached Figure Description

[0022] Figure 1 It's Bi x Flowchart of VS4 composite material preparation.

[0023] Figure 2 It's Bi x XRD pattern of VS4 composite material.

[0024] Figure 3 It's Bi x SEM and EDS images of VS4 composite material.

[0025] Figure 3 In the image: (a) and (b) are SEM images of VS4 material; (c) and (d) are SEM images of Bi. 0.01 SEM images of VS4 material; (e) and (f) are Bi 0.02 SEM images of VS4 material; (g) and (h) are Bi 0.03 SEM images of VS4 material; (i)-(l) are Bi 0.02 EDS plot of VS4 material.

[0026] Figure 4 It's Bi x Cycle diagram of VS4 composite material.

[0027] Figure 5 It's Bi x Magnification diagram of VS4 composite material. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0029] Example 1:

[0030] See Figure 1 First, 0.3523 g of ascorbic acid was weighed and dissolved in 50 ml of N-methylpyrrolidone. The solution was stirred at 200 r / min at room temperature until dissolved and named A. Ascorbic acid not only acts as a reducing agent, but also plays an important role in the VC bond, because the VC bond is beneficial to improving conductivity and enhancing structural stability.

[0031] Subsequently, 0.2340 g of ammonium metavanadate was weighed and dissolved in solution A, and stirred at 400 r / min for 30 min at 80 °C to obtain solution B; 1.5027 g of thioacetamide was weighed and dissolved in solution B, and stirred at 200 r / min for 40 min at 80 °C to obtain solution C; 5 ml of 3 mol / L hydrochloric acid was added to solution C, and stirred at 200 r / min for 30 min at 80 °C until the solution turned dark green, which was named solution D; 13.9 mg of bismuth nitrate pentahydrate was weighed and dissolved in solution D, and stirred at 200 r / min for 1 h at 25 °C to obtain solution E; solution E was placed in a 100 ml reaction vessel and reacted at 170 °C for 18 h; after removing the reaction vessel and cooling to room temperature, it was centrifuged, washed several times with deionized water and anhydrous ethanol, and then dried to obtain Bi. 0.01 VS4 composite material (atomic ratio of bismuth nitrate pentahydrate to ammonium metavanadate is 0.01).

[0032] The assembly process of a magnesium-ion battery, including the preparation of electrode sheets and the assembly of the magnesium-ion battery, is as follows:

[0033] Weigh out Bi in a mass ratio of 7:2:1. x The VS4 composite material, conductive agent (Super-P), and binder (PVDF) are ground and mixed evenly. N-methylpyrrolidone (NMP) is added to form a viscous slurry, which is then evenly coated onto the surface of the current collector (carbon paper) using a coating applicator.

[0034] Carbon paper coated with slurry was baked in a 120°C vacuum oven for 12 hours to remove NMP solvent. Finally, copper foil was cut into 11mm diameter circular electrode sheets for later use. The order of battery encapsulation is as follows: negative electrode shell, magnesium sheet, separator, negative electrode sheet, gasket, spring sheet, positive electrode shell. In the entire test element, the magnesium sheet serves as both the counter electrode and the reference electrode. The entire process of encapsulating the magnesium-ion battery was carried out in an argon-filled glove box, with water and oxygen content both less than 0.1 ppm.

[0035] Preparation of standard card PDF#72-1294: First, weigh 0.3523 g of ascorbic acid and dissolve it in 50 ml of N-methylpyrrolidone. Stir at 200 rpm at room temperature until dissolved, and name this solution A. Then, weigh 0.2340 g of ammonium metavanadate and dissolve it in solution A. Continue stirring at 400 rpm for 30 min at 80 °C to obtain solution B. Weigh 1.5027 g of thioacetamide and dissolve it in solution B. Stir at 200 rpm for 40 min at 80 °C. Solution C was obtained by stirring at 200 rpm for 30 minutes at 80°C until the solution turned dark green. Solution D was then stirred at 200 rpm for 1 hour at 25°C to obtain solution E. Solution E was then placed in a 100 ml reactor and reacted at 170°C for 18 hours. After removing the reactor and cooling to room temperature, the solution was centrifuged, washed several times with deionized water and anhydrous ethanol, and then dried to obtain the VS4 composite material.

[0036] Depend on Figure 2 As can be seen, this corresponds to the standard card PDF#72-1294, indicating that Bi was successfully prepared. 0.01 VS4 composite material. Figure 3 The SEM images in (c) and (d) show the morphology of microspheres aggregated with multiple spheres, but at 200 nm, it was found that they are not all large sheet-like structures. Figure 4 It can be seen that Bi 0.01 VS4 electrode material at a current density of 50 mA g -1 After 100 cycles, the reversible capacity is 68.7 mAh g. -1 . Figure 5 It can be seen that Bi 0.01 The VS4 electrode material exhibits performance at different current densities, ranging from 0.05 to 2.0 A g. -1 The capacities were 54.35, 52.00, 46.48, 42.38, 38.10, and 35.19 mAh g, respectively. -1 .

[0037] Example 2:

[0038] See Figure 1 The difference from Example 1 is that, in the preparation process, the amount of bismuth nitrate pentahydrate added was 19.4 mg, resulting in Bi... 0.02 VS4 composite material.

[0039] The XRD, SEM, EDS, cycling performance, and rate capability diagrams of the prepared materials are as follows: Figures 2-5 As shown, hydrothermal treatment at 170℃ for 18 hours still successfully prepared Bi with a denser surface and a smoother spherical surface. 0.02VS4 material; Figure 3 (i)-(l) Energy dispersive spectroscopy (EDS) was used to study the electrode material Bi. 0.02 The elemental distribution in VS4 showed that V, S, and Bi were uniformly distributed on the microspheres; at a current density of 50 mA g -1 After 100 cycles, the reversible capacity is 92.54 mAh g. -1 ; at different current densities, in the range of 0.05-2.0 A g -1 The capacities were 83.70, 72.78, 66.28, 57.68, 52.21, and 45.96 mAh g, respectively. -1 .

[0040] Example 3:

[0041] See Figure 1 The difference from Example 1 is that, in the preparation process, the amount of bismuth nitrate pentahydrate added was 32.3 mg, resulting in Bi... 0.03 VS4 composite material.

[0042] The XRD, SEM, cycling performance, and rate capability diagrams of the prepared materials are as follows: Figures 2-5 As shown, this indicates that Bi microspheres with rough surfaces were successfully prepared even after hydrothermal treatment at 170℃ for 18 hours. 0.03 VS4 material; at a current density of 50 mA g -1 After 100 cycles, the reversible capacity was 59.3 mAh g. -1 ; at different current densities in the range of 0.05-2.0 A g -1 The capacities were 60.79, 45.44, 40.08, 36.07, 30.44 and 25.67 mAh g, respectively. -1 .

[0043] Example 4:

[0044] See Figure 1 The difference from Example 1 is that the amount of bismuth nitrate pentahydrate added during the preparation process is 0 mg, resulting in the VS4 composite material.

[0045] The XRD, SEM, cycling performance, and rate capability diagrams of the prepared materials are as follows: Figures 2-5 As shown, microspheres of VS4 composed of ultrathin nanosheets were successfully prepared by hydrothermal treatment at 170℃ for 18 h; at a current density of 50 mA g -1 After 100 cycles, the reversible capacity is 18.3 mAh g. -1 ; at different current densities in the range of 0.05-2.0 A g -1The capacities were 51.75, 33.34, 22.45, 19.43, 16.39, and 13.70 mAh g, respectively. -1 .

Claims

1. A magnesium-ion battery cathode material Bi x A method for preparing a composite material of BiVS4, characterized in that, The method comprises the following steps: 1) preparing solution A: 0.2-0.5 g of an organic reducing agent is dissolved in 10-100 ml of N-methyl pyrrolidone, and stirring is carried out at room temperature until dissolution; 2) preparing solution B: 0.1-0.5 g of ammonium metavanadate is dissolved in solution A, and stirring is carried out at 50-100 DEG C at a rotating speed of 400-600 r / min for 10-60 min; 3) preparing solution C: 1.0-2.0 g of thioacetamide is dissolved in solution B, and stirring is carried out at 50-100 DEG C at a rotating speed of 100-300 r / min for 10-60 min; 4) preparing solution D: 1-10 ml of 3 mol / L hydrochloric acid is added to solution C, and stirring is carried out at 50-100 DEG C at a rotating speed of 100-300 r / min for 10-60 min, and the color of the solution changes to dark green; 5) preparing solution E: 10-40 mg of bismuth nitrate pentahydrate compound is dissolved in solution D, and stirring is carried out at 20-30 DEG C at a rotating speed of 100-300 r / min for 10-60 min; 6) the obtained solution E is put into a reaction kettle, and hydrothermal reaction is carried out at a temperature of 100-200 DEG C for 10-24 h; 7) After cooling to room temperature, centrifugation was performed, and washing with deionized water and anhydrous ethanol was performed several times, and drying was performed to obtain Bi x VS4 composite material.

2. A magnesium-ion battery cathode material BiVS4 according to claim 1. x A method for producing a VS4 composite material, characterized by, The organic reducing agent in step 1) is one of ascorbic acid, crotonaldehyde, ethylene, glucose and citric acid.

3. A magnesium-ion battery cathode material BiVS4 according to claim 1. x A method for producing a VS4 composite material, characterized by, The stirring in step 1) is carried out at a rotating speed of 100-300 r / min.

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