Layered cuprous tetrathiotungstate positive electrode material for rechargeable magnesium battery as well as specific crystal face regulation and control method and application of layered cuprous tetrathiotungstate positive electrode material

Abstract

The invention belongs to the technical field of electrochemical energy storage materials, and particularly discloses a layered-structure cuprous tetrathiotungstate positive electrode material for a rechargeable magnesium battery, a regulation and control method of a specific crystal face of the layered-structure cuprous tetrathiotungstate positive electrode material and application of the layered-structure cuprous tetrathiotungstate positive electrode material. Effective regulation and control on the exposure proportion of the high-activity crystal face (such as (101) crystal face) of the Cu2WS4 crystal are realized, and the magnesium storage specific capacity and the rate capability of the material are remarkably improved. The preparation method is simple and controllable in process, mild in condition, rich in raw material source and low in cost, and has good repeatability and application prospects.

Description

A layered cuprous tetrathiotungstate cathode material for rechargeable magnesium batteries, its specific crystal plane modulation method, and its application. Technical Field

[0001] This invention belongs to the field of electrochemical energy storage materials technology, specifically relating to a layered structured cuprous tetrathiotungstate cathode material for rechargeable magnesium batteries, a method for controlling specific crystal planes, and its application in rechargeable magnesium batteries. Background Technology

[0002] Rechargeable magnesium batteries, as an emerging multivalent metal-ion energy storage system, have significant advantages in terms of resource availability and intrinsic safety. Magnesium has a high abundance in the Earth's crust, reaching 2.09%, approximately 320 times that of lithium. Furthermore, the magnesium metal anode exhibits a negative redox potential (-2.36 V vs. SHE) and a high volumetric capacity (3832 mAh mL). -1 More importantly, metallic magnesium is less prone to dendrite formation during electrochemical deposition, thus significantly improving the operational safety of the battery system.

[0003] However, the practical application of rechargeable magnesium batteries is still limited by the scarcity of high-performance cathode materials. This is because divalent magnesium ions (Mg...) 2+ Magnesium ions (MgO) have a high charge density and exhibit strong Coulomb interactions with anions in the host lattice, resulting in a high solid-state diffusion barrier in the inorganic lattice and sluggish ion migration kinetics, which in turn limits their electrochemical energy storage performance. Currently, the most representative cathode material is Chevrel-phase Mo6S8, which, despite its good reversible magnesium ion intercalation / deintercalation, has a relatively low theoretical specific capacity (approximately 120 mAh g⁻¹). -1 This makes it difficult to meet the needs of high-energy-density energy storage systems.

[0004] Layered transition metal disulfides (such as MoS2 and WS2) have attracted widespread attention due to their open two-dimensional ion diffusion channels. However, these materials generally suffer from limited interlayer spacing and low intrinsic electronic conductivity, resulting in limited practical magnesium storage capacity and poor rate performance. Cuprous tetrathiotungstate (Cu2WS4), as a uniquely structured layered thiometallic acid salt, [WS4]... 2- In the tetrahedron, the 5d orbital of W has an energy close to that of the 3p orbital of S, which causes the negative charge to delocalize into the W atom, thus helping to weaken the Mg atom. 2+ The electrostatic interaction between Cu and lattice anions helps to lower the ion diffusion barrier and improve magnesium storage kinetics. Furthermore, Cu... + It has high migration ability in the crystal lattice, can participate in redox reactions, and provides additional electrochemical active sites, which is expected to enhance the overall magnesium storage capacity and reactivity of the material.

[0005] Currently, research on Cu2WS4 mainly focuses on photocatalysis, with its application in electrochemical energy storage, particularly magnesium storage, remaining largely unexplored. The macroscopic electrochemical performance of a material is typically closely related to the exposure characteristics of its microscopic crystal facets. Different crystal facets exhibit different atomic arrangements and surface energies, directly affecting the magnesium content. 2+ Adsorption, solid-phase diffusion, and reactivity. In layered Cu2WS4 crystals, the dominant crystal planes are (001) and (101). From the perspective of crystal growth orientation, Cu2WS4 tends to grow preferentially along the layered direction, resulting in the (001) crystal plane becoming the dominant exposed surface. According to theoretical calculations, the (101) crystal plane has a lower ion adsorption energy than the (001) crystal plane, indicating that it may have higher electrochemical interfacial reactivity. Therefore, by controlling the dominant exposure of the highly active (101) crystal plane, it is expected to significantly improve the magnesium storage performance of Cu2WS4 cathode materials. However, there are no reports to date on the selective exposure of specific crystal planes of Cu2WS4 to optimize its electrochemical performance, and there is also a lack of mature and effective crystal plane control methods. Summary of the Invention

[0006] This invention provides a layered cuprous tetrathiotungstate (Cu2WS4) cathode material, a method for controlling its specific crystal planes, and its application in rechargeable magnesium batteries. Specifically, this invention solves the following technical problems: overcoming the low capacity of existing magnesium battery cathode materials and the poor rate performance of traditional layered sulfides due to slow ion migration kinetics, thereby obtaining a rechargeable magnesium battery cathode material with higher capacity and rate performance.

[0007] The present invention adopts the following technical solution: a positive electrode material for rechargeable magnesium batteries, wherein the active material is a layered structure of cuprous tetrathiotungstate (Cu2WS4).

[0008] This invention further provides a method for controlling specific crystal planes of the above-mentioned cathode material. The specific crystal plane refers to the dominant exposed surface of Cu2WS4, which is conducive to the exposure of divalent magnesium ions (Mg²⁺). 2+The highly active crystal faces that can be rapidly embedded and extracted include, but are not limited to, the (101) crystal face and the (001) crystal face. Specifically, the following steps are included: (1) Dissolve copper source, tungsten source and sulfur source in a certain molar ratio in a hydrophilic solvent, add the sulfur source solution dropwise to the mixed solution of copper source and tungsten source, and mix evenly by ultrasonic treatment and stirring to obtain a precursor solution; (2) Transfer the precursor solution to a hydrothermal reactor, seal it and carry out a solvothermal reaction at a certain temperature; After the reaction is completed, cool it naturally to room temperature, centrifuge to collect the precipitate, wash it (preferably: wash it three times with deionized water and anhydrous ethanol in sequence), and vacuum dry it to obtain the target Cu2WS4 cathode material; wherein, by controlling the type and ratio of hydrophilic solvent, the (101) crystal face and the (001) crystal face of the finally obtained layered structure of copper tetrathiotungstate are controlled.

[0009] Furthermore, in step (1): the copper source is one or more of CuCl2, Cu(CH3COO)2, Cu(NO3)2, and CuSO4 (preferably CuCl2); the tungsten source is Na2WO4·2H2O or (NH4)6H2W 12 O 40 One or more of WCl4 (preferably Na2WO4·2H2O); the sulfur source is one or more of thioacetamide, thiourea, and L-cysteine ​​(preferably thioacetamide); further, in step (1), the molar ratio of copper source, tungsten source and sulfur source is 2:1:6~2:1:12 (preferably 2:1:8).

[0010] Furthermore, in step (1), the hydrophilic solvent is a mixture of ethylene glycol and water or a mixture of ethanol and water; the volume ratio of ethylene glycol to water in the hydrophilic solvent is 1:0 to 1:1, and the volume ratio of ethanol to water is 1:1 to 1:2 (preferably a mixture of ethanol and water with a volume ratio of 1:1).

[0011] Furthermore, when the hydrophilic solvent is a mixture of ethylene glycol and water, the specific crystal plane is the (001) crystal plane; when the hydrophilic solvent is a mixture of ethanol and water, the specific crystal plane is the (101) crystal plane.

[0012] Furthermore, in step (2), the temperature of the solvothermal reaction is 140~200℃ and the reaction time is 12~48h (preferably 24h at 160℃).

[0013] Furthermore, in step (2), the vacuum drying temperature is 60~80℃ and the reaction time is 12~48h (preferably drying at 70℃ for 12h).

[0014] This invention also provides the application of Cu2WS4 cathode material obtained by the above-mentioned specific crystal plane modulation method in rechargeable magnesium battery cathode materials.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The present invention is the first to apply copper tetrathiotungstate (Cu2WS4) to the cathode material of rechargeable magnesium battery, and significantly improves its electrochemical performance through a specific crystal plane control strategy, thus expanding the application prospects of this type of material in the field of multivalent ion energy storage.

[0016] (2) The crystal plane control method provided is based on solvothermal synthesis technology. By precisely controlling key parameters such as the composition of mixed solvent, reaction temperature and time, the optimal exposure of the highly active crystal plane of Cu2WS4 crystal (101) is achieved, which provides an effective way to control the surface structure of layered electrode materials.

[0017] (3) The Cu2WS4 material with crystal facet modulation has higher surface reactivity and lower magnesium ion diffusion barrier, exhibiting excellent reversible magnesium storage specific capacity (>200 mAh g). -1 With good rate capability, it effectively alleviates the problem caused by Mg 2+ The problem of dynamic hysteresis caused by strong electrostatic effects.

[0018] (4) The raw materials for this preparation method are widely available and inexpensive. The process is simple, the conditions are mild and the repeatability is good. It is easy to achieve large-scale production and has significant practical value and industrial application potential. Attached Figure Description

[0019] Figure 1 is a schematic diagram of the cell structure of copper tetrathiotungstate (Cu2WS4) and its crystal structure model with the (001) and (101) crystal planes predominantly exposed.

[0020] Figure 2 shows the XRD patterns of Cu2WS4 prepared in Examples 1-7 of this invention.

[0021] Figure 3 shows SEM and TEM images of Cu2WS4 prepared in Examples 1 (a–c) and 5 (d–f) of the present invention.

[0022] Figure 4 shows the magnesium storage performance of the Cu2WS4 magnesium storage cathode prepared in Examples 1-7 of this invention at different current densities and the comparison with the electrochemical performance of existing embedded magnesium storage cathode materials. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] In Example 1, 0.34 g of CuCl2·2H2O and 0.33 g of Na2WO4·2H2O were sequentially dissolved in 30 ml of ethylene glycol. The solutions were then sonicated (in specific embodiments, sonication was performed to ensure rapid and uniform mixing of the components under the same conditions: 25°C, 35W, 15 min) and stirred until homogeneous, yielding a blue-green solution, denoted as solution A. 0.6 g of thioacetamide was sonicated and dissolved in 30 ml of ethylene glycol, followed by sonication to form a clear solution, denoted as solution B. Under continuous stirring, solution B was added dropwise to solution A. The solution gradually turned pale yellow, accompanied by the formation of a flocculent precipitate. After the addition was complete, sonication was continued for 30 min. The resulting suspension was then transferred to a 100 mL stainless steel hydrothermal reactor lined with polytetrafluoroethylene (PTFE), sealed, and reacted in a 140°C forced-air drying oven for 24 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature (25℃, the same below), centrifuged at 8000 rpm for 10 min and the product was collected. After being washed three times each with water and ethanol, it was vacuum dried at 70℃ for 12 h to obtain Cu2WS4 cathode material with a high (001) crystal plane exposure ratio.

[0025] In Example 2, 0.34 g of CuCl2·2H2O and 0.33 g of Na2WO4·2H2O were dissolved sequentially in 30 ml of ethylene glycol. After ultrasonic treatment and stirring, a blue-green solution was obtained, denoted as solution A. 0.6 g of thioacetamide was ultrasonically dissolved in 30 ml of ethylene glycol, and after ultrasonic treatment, a clear solution was formed, denoted as solution B. Under continuous stirring, solution B was added dropwise to solution A. The solution gradually turned pale yellow, accompanied by the formation of flocculent precipitate. After the addition was complete, ultrasonic stirring was continued for 30 min. The resulting suspension was transferred to a polytetrafluoroethylene-lined stainless steel hydrothermal reactor, sealed, and reacted in a 160℃ forced-air drying oven for 24 h. After the reaction, the reactor was allowed to cool naturally to room temperature, centrifuged at 8000 rpm for 10 min, and the product was collected. After washing three times each with water and ethanol, the product was vacuum dried at 70℃ for 12 h to obtain Cu2WS4 cathode material with a moderate (001) crystal plane exposure ratio.

[0026] In Example 3, 0.34 g of CuCl2·2H2O and 0.33 g of Na2WO4·2H2O were dissolved sequentially in 30 ml of ethylene glycol. After ultrasonic treatment and stirring, a blue-green solution was obtained, denoted as solution A. 0.6 g of thioacetamide was ultrasonically dissolved in 30 ml of ethylene glycol, and after ultrasonic treatment, a clear solution was formed, denoted as solution B. Under continuous stirring, solution B was added dropwise to solution A. The solution gradually turned pale yellow, accompanied by the formation of flocculent precipitate. After the addition was complete, ultrasonic stirring was continued for 30 min. The resulting suspension was transferred to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene (PTFE), sealed, and reacted in a 160°C forced-air drying oven for 48 h. After the reaction, the reactor was allowed to cool naturally to room temperature, centrifuged at 8000 rpm for 10 min, and the product was collected. After washing three times each with water and ethanol, the product was vacuum dried at 70°C for 12 h to obtain Cu2WS4 cathode material with a moderate (001) crystal plane exposure ratio.

[0027] In Example 4, 0.34 g of CuCl₂·2H₂O and 0.33 g of Na₂WO₄·2H₂O were dissolved sequentially in a mixed solvent of 15 ml ethylene glycol and 15 ml water. After sonication and stirring, a blue-green solution was obtained, denoted as solution A. 0.6 g of thioacetamide was sonicated and dissolved in a mixed solvent of 15 ml ethylene glycol and 15 ml water. After sonication, a clear solution was formed, denoted as solution B. Under continuous stirring, solution B was added dropwise to solution A. The solution gradually turned pale yellow, accompanied by the formation of flocculent precipitate. After the addition was complete, sonication was continued for 30 min. The resulting suspension was transferred to a polytetrafluoroethylene-lined stainless steel hydrothermal reactor, sealed, and reacted in a 160°C forced-air drying oven for 24 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The product was centrifuged at 8000 rpm for 10 min and collected. After being washed three times each with water and ethanol, the product was vacuum dried at 70℃ for 12 h to obtain Cu2WS4 cathode material with a moderate (001) crystal plane exposure ratio.

[0028] In Example 5, 0.34 g of CuCl2·2H2O and 0.33 g of Na2WO4·2H2O were dissolved sequentially in a mixed solvent of 15 ml of ethanol (all ethanol used in this invention is anhydrous ethanol) and 15 ml of water. After ultrasonic treatment and stirring until homogeneous, a blue-green solution was obtained, denoted as solution A. 0.6 g of thioacetamide was ultrasonically dissolved in a mixed solvent of 15 ml of ethanol and 15 ml of water. After ultrasonic treatment, a clear solution was formed, denoted as solution B. Under continuous stirring, solution B was added dropwise to solution A. The solution gradually turned brown, accompanied by the formation of flocculent precipitate. After the addition was complete, ultrasonic stirring was continued for 30 min. The resulting suspension was transferred to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene, sealed, and reacted in a 160°C forced-air drying oven for 24 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The product was centrifuged at 8000 rpm for 10 min and collected. After being washed three times each with water and ethanol, the product was vacuum dried at 70℃ for 12 h to obtain Cu2WS4 cathode material with a high (101) crystal plane exposure ratio.

[0029] In Example 6, 0.34 g of CuCl₂·2H₂O and 0.33 g of Na₂WO₄·2H₂O were dissolved sequentially in a mixed solvent of 10 ml ethanol and 20 ml water. After sonication and stirring, a blue-green solution was obtained, denoted as solution A. 0.6 g of thioacetamide was sonicated and dissolved in a mixed solvent of 10 ml ethanol and 20 ml water. After sonication, a clear solution was formed, denoted as solution B. Under continuous stirring, solution B was added dropwise to solution A. The solution gradually turned pale yellow, accompanied by the formation of flocculent precipitate. After the addition was complete, sonication was continued for 30 min. The resulting suspension was transferred to a polytetrafluoroethylene-lined stainless steel hydrothermal reactor, sealed, and reacted in a 160°C forced-air drying oven for 24 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The product was centrifuged at 8000 rpm for 10 min and collected. After being washed three times each with water and ethanol, the product was vacuum dried at 70℃ for 12 h to obtain Cu2WS4 cathode material with a high (101) crystal plane exposure ratio.

[0030] In Example 7, 0.34 g of CuCl₂·2H₂O and 0.33 g of Na₂WO₄·2H₂O were dissolved sequentially in a mixed solvent of 15 ml ethanol and 15 ml water. After sonication and stirring, a blue-green solution was obtained, denoted as solution A. 0.6 g of thioacetamide was sonicated and dissolved in a mixed solvent of 15 ml ethanol and 15 ml water. After sonication, a clear solution was formed, denoted as solution B. Under continuous stirring, solution B was added dropwise to solution A. The solution gradually turned brown, accompanied by the formation of a flocculent precipitate. After the addition was complete, sonication was continued for 30 min. The resulting suspension was transferred to a polytetrafluoroethylene-lined stainless steel hydrothermal reactor, sealed, and reacted in a 180°C forced-air drying oven for 24 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The product was centrifuged at 8000 rpm for 10 min and collected. After being washed three times each with water and ethanol, the product was vacuum dried at 70℃ for 12 h to obtain Cu2WS4 cathode material with a high (101) crystal plane exposure ratio.

[0031] Figure 1 shows a schematic diagram of the unit cell structure of Cu2WS4 and its crystal structure model with the (101) and (001) crystal planes predominantly exposed. As shown in Figure 1a, Cu2WS4 has a typical layered crystal structure with an interlayer spacing of 0.503 nm. Figure 1b shows the crystal structure with the (001) crystal plane as the predominant exposed surface. This crystal plane has a significant growth advantage along the layer plane direction, leading to a tendency for the grains to form a two-dimensional plate-like morphology. Figure 1c shows the crystal structure with the (101) crystal plane as the predominant exposed surface. Due to the preferential growth and exposure of the lateral crystal planes, the crystal exhibits a typical decahedral geometry. The above structural models show that the preferred growth behavior of different crystal planes has a significant regulatory effect on the microstructure of the grains.

[0032] Figure 2 shows the XRD patterns of the Cu2WS4 cathode materials prepared in Examples 1 to 7. As shown in the figure, the characteristic diffraction peaks of each sample are in perfect agreement with the standard diffraction card (JCPDS: 96-711-7864) of tetragonal Cu2WS4, confirming the successful synthesis of the target product. In Examples 1 to 4, pure ethylene glycol or a mixture of water and ethylene glycol was used as the reaction medium. The XRD patterns showed that the (002) crystal plane diffraction peak intensity was high, indicating that the crystal preferentially grew along the

[001] direction, making the (001) crystal plane the main exposed surface (the atomic arrangement of the (002) and (001) crystal planes is exactly the same, and the layers are periodically arranged, only the interplanar spacing is different). The absence of the (001) crystal plane diffraction signal on the XRD is due to the extinction of X-rays (diffraction signal cancellation) of this set of crystal planes. That is, this crystal plane itself exists, but there is no X-ray diffraction signal. Therefore, the (002) crystal plane is used to describe the XRD diffraction intensity, while the (001) crystal plane is used to describe the exposed crystal plane of the material itself. The corresponding (101) / (002) crystal plane diffraction intensity ratio is significantly less than 1, indicating that the (001) crystal plane has a high degree of exposure. With increasing solvent water content, reaction temperature, and reaction time, the exposure ratio of the (001) crystal plane decreased, but it still dominated overall. In contrast, Examples 5 to 7, using a mixed solvent of ethanol and water as the reaction system, exhibited significantly enhanced (101) crystal plane diffraction peaks, with the (101) / (002) crystal plane diffraction intensity ratio significantly greater than 1, indicating that preferential exposure of the (101) crystal plane was achieved under these conditions. Further changes in solvent ratio, increases in reaction temperature, or extension of reaction time had little effect on the exposure ratio of the (101) crystal plane, indicating that the choice of solvent system is a key factor in controlling crystal plane orientation.

[0033] Figure 3 shows SEM and TEM images of the Cu2WS4 materials prepared in Examples 1 (a–c) and 5 (d–f). As shown in Figures 3a–c, when ethylene glycol is used as the reaction solvent, the Cu2WS4 material synthesized in Example 1 exhibits a two-dimensional flake morphology with a size of about 1 μm. The tilting feature of the (101) crystal plane at the edge of the flake is not obvious, and the main exposed surface of the grain is the (001) crystal plane, indicating that this crystal plane has a preferential growth trend. In contrast, as shown in Figures 3d–f, under the condition of using a mixed solvent of ethanol and water as the reaction medium, the product obtained in Example 5 exhibits a characteristic structure dominated by the growth of the (101) crystal plane, forming a decahedral geometry with obvious oblique facets, showing the preferential exposure characteristics of the (101) crystal plane.

[0034] Electrochemical performance tests were conducted on the materials obtained in Examples 1-7 and existing rechargeable magnesium battery intercalation cathode materials MoS2, VS2, Mo6S8, V2O5, VSe2, VS4, and MoS3 (all commonly available rechargeable magnesium battery intercalation cathode materials, purchased and used as active materials): The electrode was prepared by mixing the active material, conductive agent (Super P), and binder (5wt% PVDF, NMP solvent) in a mass ratio of 60:30:10, adding NMP dropwise to form a slurry, coating it onto carbon cloth, vacuum drying at 80°C for 12 h, and then cutting it into 12 mm diameter discs (with a loading of approximately 1 mg cm⁻¹). -2 The positive electrode is a magnesium sheet; the negative electrode is a glass fiber membrane; and the electrolyte contains 0.5 mol / L of [unspecified substance]. -1 Mg(TFSI)2 and 1.0 mol L -1 A MgCl2 solution in ethylene glycol dimethyl ether was used to assemble a 2032 coin cell in an argon glove box (H2O < 0.1 ppm, O2 < 0.1 ppm).

[0035] Figure 4a–c shows the magnesium storage performance of the Cu2WS4 cathode materials prepared in Examples 1 to 7 at different current densities.

[0036] Battery testing was conducted on a LAND system with a voltage range of 0.1–2.5 V and current densities of 100, 200, and 1000 mA g. -1 . at 100 mA g -1 After 50 cycles, the specific capacity of Examples 1–4 was close to 150 mAh g. -1 Examples 5–7 all showed significantly higher specific capacities, with Example 5 exhibiting the highest specific capacity at 255 mAh g⁻¹. -1 . at 200 mA g -1 and 1000 mA g -1 Even at high current densities, this performance advantage remains consistent; the magnesium storage performance of Examples 5–7 is significantly better than that of Examples 1–4, with Example 5 showing superior performance at 1000 mA g. -1 The highest magnesium storage capacity reaches 157 mAh g. -1 Significantly higher than Example 1 (91mAh g) -1 ).

[0037] Figure 4d shows a comparison of the electrochemical performance of Example 5 with existing rechargeable magnesium battery intercalation cathode materials, demonstrating that Cu2WS4 with crystal facet modulation has significant performance advantages. The above results confirm that controlling the crystal facet orientation can effectively improve the magnesium storage activity and rate performance of Cu2WS4. When the (001) crystal facet is the dominant exposed surface, the strong interlayer interaction may hinder magnesium ion intercalation, resulting in relatively low magnesium storage activity. In contrast, when the (101) crystal facet is the dominant exposed surface, multiple highly active lateral crystal faces not only have lower magnesium ion adsorption energy but also provide abundant edge sites, which is beneficial for promoting the adsorption process of magnesium ions and interfacial charge transfer, significantly improving the magnesium storage performance of the material.

Claims

1. A positive electrode material for rechargeable magnesium batteries, wherein the active material is cuprous tetrathiotungstate Cu2WS4 with a layered structure.

2. The method for controlling specific crystal planes of the cathode material according to claim 1, characterized in that, The specific crystal facet refers to the dominant exposed facet of Cu2WS4, which is a highly active crystal facet that facilitates the rapid insertion and extraction of divalent magnesium ions, including but not limited to the (101) crystal facet and the (001) crystal facet. Specifically, the following steps are included: (1) Dissolve a certain molar ratio of copper source, tungsten source and sulfur source in a hydrophilic solvent, add the sulfur source solution dropwise to the mixed solution of copper source and tungsten source, and mix evenly by ultrasonic treatment and stirring to obtain a precursor solution; (2) Transfer the precursor solution to a hydrothermal reactor, seal it and carry out a solvothermal reaction at a certain temperature; After the reaction is completed, cool it naturally to room temperature, centrifuge to collect the precipitate, wash it, and vacuum dry it to obtain the target Cu2WS4 cathode material; wherein, by controlling the type and ratio of hydrophilic solvent, the (101) crystal facet and the (001) crystal facet of the finally obtained layered structure of tetrathiotungstate cuprous oxide are controlled.

3. The method for controlling specific crystal planes according to claim 2, characterized in that, In step (1): the copper source is one or more of CuCl2, Cu(CH3COO)2, Cu(NO3)2, and CuSO4; and / or the tungsten source is Na2WO4·2H2O or (NH4)6H2W 12 O 40 One or more of WCl4; the sulfur source is one or more of thioacetamide, thiourea, and L-cysteine.

4. The method for controlling specific crystal planes according to claim 2, characterized in that, In step (1), the molar ratio of copper source, tungsten source and sulfur source is 2:1:6~2:1:

12.

5. The method for controlling specific crystal planes according to claim 2, characterized in that, In step (1), the hydrophilic solvent is a mixture of ethylene glycol and water with a volume ratio of 1:0 to 1:1 or a mixture of ethanol and water with a volume ratio of 1:1 to 1:

2.

6. The method for controlling specific crystal planes according to claim 5, characterized in that, When the hydrophilic solvent is a mixture of ethylene glycol and water, the specific crystal plane is (001) crystal plane; when the hydrophilic solvent is a mixture of ethanol and water, the specific crystal plane is (101) crystal plane.

7. The method for controlling specific crystal planes according to claim 2, characterized in that, In step (2), the temperature of the solvothermal reaction is 140~200℃ and the reaction time is 12~48h.

8. The method for controlling specific crystal planes according to claim 2, characterized in that, In step (2), the vacuum drying temperature is 60~80℃ and the reaction time is 12~48h.

9. The application of Cu2WS4 cathode material obtained by the specific crystal plane control method according to any one of claims 2-8 in the cathode material of rechargeable magnesium batteries.

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