Three-dimensional composite negative electrode material for magnesium ion battery as well as preparation method and application of three-dimensional composite negative electrode material

Abstract

The invention relates to the technical field of magnesium ion batteries, and discloses a three-dimensional composite negative electrode material for a magnesium ion battery, the three-dimensional composite negative electrode material comprises magnesium powder and a phosphorus material, and the mass ratio of the magnesium powder to the phosphorus material is 2: 8-20: 1; the preparation method of the three-dimensional composite negative electrode material for the magnesium ion battery comprises the following steps: S1, ball-milling and mixing magnesium powder and a phosphorus material to obtain precursor powder; s2, performing cold press molding on the precursor powder obtained in the S1 to form a three-dimensional porous precursor electrode; and S3, carrying out heat treatment on the three-dimensional porous precursor electrode obtained in the S2, so that the black phosphorus and the magnesium powder are subjected to chemical reaction to generate an Mg3P2 three-dimensional network in situ, and uniformly dispersing the Mg3P2 three-dimensional network in a magnesium matrix to prepare the three-dimensional composite negative electrode material for the magnesium ion battery. The invention relates to application of a three-dimensional composite negative electrode material for a magnesium ion battery, which is applied to the magnesium ion battery. According to the technical scheme, the problems that magnesium metal deposition / stripping is not uniform, volume expansion is caused, and the large-current performance is poor are effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium ion batteries, and in particular to a three-dimensional composite negative electrode material for magnesium ion batteries, a preparation method thereof, and applications thereof. Background Art

[0002] As global demand for clean energy continues to grow, efficient, safe, and low-cost energy storage systems have become a research hotspot. Magnesium batteries, with their significant advantages such as high theoretical capacity, abundant magnesium resources in the Earth's crust, low production costs, and high intrinsic safety, are widely considered a key development direction for next-generation energy storage technologies, demonstrating enormous potential for applications in large-scale energy storage, electric vehicles, and other fields.

[0003] However, the technical bottleneck of magnesium metal anodes has become a key factor restricting the commercialization of magnesium batteries. During the battery charge and discharge process, the electrochemical deposition / stripping process of the magnesium metal anode is uneven. Especially under high current density conditions, the magnesium metal anode will also form dendrites. Once the dendrites pierce the battery separator, they will cause the battery to short-circuit, which not only seriously threatens the safety performance of the battery but also significantly reduces its service life. At the same time, magnesium undergoes significant volume changes during the charge and discharge process. Its repeated expansion and contraction cycles are prone to structural pulverization, resulting in a large loss of active materials and, in turn, rapid battery capacity decay. In addition, the surface of traditional magnesium anodes is prone to passivation, forming a dense passivation film. As a result, the magnesium ion transport kinetics on the electrode surface are slow and polarization is very serious, which greatly limits the charge and discharge efficiency and rate performance of magnesium batteries.

[0004] In the face of the above technical challenges, it is urgent to develop new negative electrode materials to effectively solve the problems of uneven electrochemical deposition / stripping, volume expansion and poor high current performance of magnesium metal negative electrodes, and provide technical support for promoting the commercialization of magnesium batteries. Summary of the Invention

[0005] The present invention aims to provide a three-dimensional composite negative electrode material for magnesium ion batteries, a preparation method and application thereof, so as to effectively solve the problems of uneven electrochemical deposition / stripping, volume expansion and poor high current performance of magnesium metal negative electrodes.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical solution: a three-dimensional composite negative electrode material for a magnesium ion battery, comprising magnesium powder and a phosphorus material, wherein the mass ratio of the magnesium powder to the phosphorus material is 2:8 to 20:1.

[0007] Preferably, the phosphorus material is any one of black phosphorus and red phosphorus.

[0008] Preferably, the particle size of the magnesium powder is 0.05-100 μm.

[0009] The present invention also provides another technical solution, a method for preparing a three-dimensional composite negative electrode material for a magnesium ion battery, comprising the following steps: S1: ball-milling magnesium powder and phosphorus material to obtain precursor powder; S2: cold pressing the precursor powder obtained in S1 to form a three-dimensional porous precursor electrode; S3: The three-dimensional porous precursor electrode obtained in S2 is heat-treated to allow black phosphorus to react chemically with magnesium powder to in situ generate a Mg3P2 three-dimensional network, which is evenly dispersed in the magnesium matrix to produce a three-dimensional composite negative electrode material for magnesium ion batteries.

[0010] Preferably, in S1, before ball-milling the magnesium powder and the phosphorus material, the phosphorus material is first subjected to a stripping treatment to obtain phosphorus nanosheets.

[0011] Preferably, the mixed ball milling in S1 is carried out under an inert atmosphere, the ball milling time is 2-48 hours, and the ball milling speed is 50-1000 rpm.

[0012] Preferably, the pressure of the cold pressing in S2 is 1-50 MPa.

[0013] Preferably, the heat treatment temperature in S3 is 200-600° C., and the holding time is 1-12 h.

[0014] Preferably, the heating rate of the heat treatment is 1-20°C / min.

[0015] The present invention also provides another technical solution, an application of a three-dimensional composite negative electrode material for a magnesium ion battery, which is applied to a magnesium ion battery.

[0016] Compared with the existing technology, the beneficial effects of this solution are: (1) The process is simple and easy to scale up: the process route of ball milling mixing, cold pressing and heat treatment does not require complex equipment or special conditions. The process is short and highly controllable, which is suitable for industrial mass production and lays the technological foundation for the practical application of three-dimensional composite magnesium negative electrode.

[0017] (2) Interface bonding enhancement and component uniformity: The ball milling process achieves nano-scale dispersion and close contact between magnesium powder and phosphorus materials (such as black phosphorus nanosheets) through mechanical force, forming a "magnesium-phosphorus" composite interface layer, avoiding the stratification or agglomeration problems caused by component density differences in traditional physical mixing, and ensuring that phosphorus and magnesium fully react to form a Mg3P2 skeleton during subsequent heat treatment.

[0018] (3) Improved electrolyte wettability and reduced interface impedance: The three-dimensional porous structure formed by cold pressing significantly increases the specific surface area of the electrode. The electrolyte can quickly penetrate into the interior of the material through the pores, greatly improving the electrolyte wettability and achieving good contact with the negative electrode.

[0019] (4) Volume expansion buffer and structural stability enhancement: The porosity of the porous structure provides "expansion space" for magnesium deposition, and absorbs the volume change stress during charge and discharge through pore deformation, thus avoiding electrode cracking and powdering. SEM shows that the three-dimensional composite negative electrode has a high conductivity at 0.1 mA / cm 2 and 1mA / cm 2 After cycling for 500 h at the same current density, the pore structure remains intact.

[0020] (5) Optimization of ion transport kinetics: The Mg3P2 three-dimensional network generated by heat treatment has high chemical stability and ion conductivity, and can serve as a "high-speed channel" for magnesium ion transport. The initial overpotential of the three-dimensional composite negative electrode is significantly lower than that of the pure magnesium negative electrode, indicating that the Mg3P2 skeleton effectively improves the insertion / deinsertion kinetics of magnesium ions.

[0021] (6) Current density uniformity and dendrite suppression: The Mg3P2 skeleton is evenly distributed in the magnesium matrix, forming a "rigid support network" that forces the current density to be evenly distributed and avoids excessive deposition of magnesium ions in local areas. 2 After cycling for 500 h at high current density, the interface morphology of the three-dimensional composite anode remained uniform, while the surface of the pure magnesium anode short-circuited due to uneven deposition / stripping.

[0022] (7) Synergistic effect of electronic conductivity and chemical stability: The magnesium matrix provides high electronic conductivity, and the Mg3P2 skeleton inhibits the side reactions at the electrode / electrolyte interface through chemical stability, reducing the generation of "dead magnesium". The synergistic effect of the two enables the three-dimensional composite negative electrode to maintain low impedance and high capacity retention during long-term cycling.

[0023] (8) Practical application significance: The three-dimensional composite negative electrode material for magnesium ion batteries has significantly improved the practicality of magnesium batteries in large-scale energy storage, electric vehicles and other scenarios due to its high performance such as symmetrical battery cycle life of over 2000h and high capacity retention rate of the whole battery. At the same time, it takes advantage of the abundance and low cost of magnesium and phosphorus resources to alleviate the dependence on lithium resources and supply chain pressure. Its environmentally friendly and recyclable characteristics are in line with the development trend of green energy. In addition, the design concept of the three-dimensional composite structure can be extended to other multivalent metal battery systems, promoting the diversified transformation of energy storage technology and providing important support for the global clean energy revolution with both technological innovation and industrial feasibility.

[0024] In summary, this technical solution breaks through the performance bottleneck of traditional magnesium negative electrodes from multiple dimensions of "ion transport-structural stability-interface regulation" through preparation process innovation and composite structure design. It not only provides a technical path with both high performance and low cost for the commercialization of magnesium batteries, but also lays a theoretical and practical foundation for the development of the field of multivalent metal batteries through the dual innovation of material system and mechanism research. It has significant scientific value and industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the XRD pattern of the three-dimensional composite negative electrode material for magnesium ion batteries prepared in Example 1 of the present invention; Figure 2 This is a comparison chart of the electrolyte wettability of the three-dimensional composite negative electrode material for magnesium ion batteries prepared in Example 1 of the present invention and the magnesium metal negative electrode material of Comparative Example 1; Figure 3 This is a comparison chart of the impedance of a symmetrical battery assembled with the three-dimensional composite negative electrode material for a magnesium ion battery prepared in Example 1 of the present invention and the magnesium metal negative electrode material of Comparative Example 1; Figure 4 (a) is a comparison of the long cycle overpotential and cycle time of the three-dimensional composite negative electrode material for magnesium ion batteries prepared in Examples 1-3; Figure 4 (bd) is Figure 4 (a) Local magnified images at different time periods; Figure 5 (a) SEM image of a symmetrical battery assembled with a three-dimensional composite negative electrode material for magnesium ion batteries prepared in Example 1 before cycling; Figure 5 (b) A symmetrical battery assembled with the three-dimensional composite negative electrode material for the magnesium ion battery prepared in Example 1 at 0.1 mA / cm 2 SEM image of the battery after 500 h of cycling at the same current density; Figure 5 (c) A symmetrical battery assembled with the three-dimensional composite negative electrode material for magnesium ion batteries prepared in Example 1 at 1 mA / cm 2 SEM image of the battery after 500 h of cycling at the same current density; Figure 6 (a) is a comparison of the rate performance of a full cell (VS4||APC||MBP) assembled with the three-dimensional composite negative electrode material for magnesium ion batteries prepared in Example 1 of the present invention and a full cell (VS4||APC||Mg) assembled with the magnesium metal negative electrode material of Comparative Example 1; Figure 6 (b) is a charge and discharge curve diagram of a full cell (VS4||APC||MBP) assembled with the three-dimensional composite negative electrode material for magnesium ion batteries prepared in Example 1 of the present invention; Figure 6 (c) A comparison of the long cycle performance of a full cell (VS4||APC||MBP) assembled with the three-dimensional composite negative electrode material for a magnesium ion battery prepared in Example 1 of the present invention and a full cell (VS4||APC||Mg) assembled with the magnesium metal negative electrode material of Comparative Example 1 at a current density of 50 mA / g. Figure 7(a) is a charge-discharge curve diagram of a full battery (Mo6S8||APC||Mg) assembled with the magnesium metal negative electrode material of Comparative Example 1 of the present invention at room temperature; Figure 7 (b) is a charge and discharge curve diagram of a full cell (Mo6S8||APC||MBP) assembled with a three-dimensional composite negative electrode material for a magnesium ion battery prepared in Example 1 of the present invention at room temperature; Figure 7 (c) A long cycle comparison chart of a full cell (Mo6S8||APC||MBP) assembled with a three-dimensional composite negative electrode material for a magnesium ion battery prepared in Example 1 of the present invention and a full cell (Mo6S8||APC||Mg) assembled with a magnesium metal negative electrode material of Comparative Example 1 at a current density of 50 mA / g. DETAILED DESCRIPTION

[0026] The following is further described in detail through specific implementation methods: Example 1 A three-dimensional composite negative electrode material for a magnesium-ion battery comprises magnesium powder and a phosphorus material, wherein the mass ratio of the magnesium powder to the phosphorus material is 2:8 to 20:1, wherein the phosphorus material is either black phosphorus or red phosphorus; and the particle size of the magnesium powder is 0.05-100 μm. In this embodiment, the mass ratio of the magnesium powder to the phosphorus material is 7:3, black phosphorus is selected as the phosphorus material, and the particle size of the magnesium powder is 0.05 μm.

[0027] A method for preparing a three-dimensional composite negative electrode material for a magnesium ion battery comprises the following steps: S1: exfoliating bulk black phosphorus using liquid-phase ultrasonic exfoliation to obtain phosphorus nanosheets with a lateral size of 100-500 nm and a thickness of 5-20 nm; ball-milling magnesium powder and phosphorus nanosheets in a mass ratio of 2:8 to 20:1 under an inert atmosphere for 2-48 hours at a speed of 50-1000 rpm to obtain a precursor powder; wherein the inert atmosphere is either argon or nitrogen; In this embodiment, bulk black phosphorus was exfoliated into phosphorus nanosheets with a lateral size of 100 nm and a thickness of 8 nm using liquid-phase ultrasonic exfoliation. Under an argon atmosphere, magnesium powder and the phosphorus nanosheets were ball-milled in a mass ratio of 7:3 for 12 h at a speed of 600 rpm to obtain a precursor powder. S2: cold pressing the precursor powder obtained in S1 under a pressure of 1-50 MPa to form a three-dimensional porous precursor electrode; In this embodiment, the precursor powder obtained in S1 is cold pressed under a pressure of 10 MPa to form a three-dimensional porous precursor electrode; S3: heat treating the three-dimensional porous precursor electrode obtained in S2: heating the three-dimensional porous precursor obtained in S2 to 200-600°C at a heating rate of 1-20°C / min in a vacuum or inert atmosphere quartz tube, and keeping the temperature for 1-12 hours, so that black phosphorus reacts with magnesium powder to form a three-dimensional Mg3P2 network in situ, which is uniformly dispersed in the magnesium matrix, thereby preparing a three-dimensional composite negative electrode material (MBP) for magnesium ion batteries; In this example, the three-dimensional porous precursor obtained in S2 was heated to 400°C in a vacuum quartz tube at a heating rate of 10°C / min and kept at this temperature for 6 hours, so that black phosphorus and magnesium powder reacted chemically to form an in situ Mg3P2 three-dimensional network, which was uniformly dispersed in the magnesium matrix, to produce a three-dimensional composite negative electrode material for magnesium ion batteries, which was recorded as MBP-7.

[0028] The invention discloses an application of a three-dimensional composite negative electrode material for a magnesium ion battery, which is applied in the magnesium ion battery.

[0029] Example 2 Different from Example 1, a three-dimensional composite negative electrode material for a magnesium ion battery has a mass ratio of magnesium powder to phosphorus material of 6:4; A method for preparing a three-dimensional composite negative electrode material for a magnesium ion battery comprises: in step S1, ball-milling magnesium powder and phosphorus nanosheets in a mass ratio of 6:4, and preparing a three-dimensional composite negative electrode material for a magnesium ion battery in step S3, which is designated as MBP-6.

[0030] Example 3 Different from Example 1, a three-dimensional composite negative electrode material for a magnesium ion battery has a mass ratio of magnesium powder to phosphorus material of 8:2; A method for preparing a three-dimensional composite negative electrode material for a magnesium ion battery comprises: in step S1, ball-milling magnesium powder and phosphorus nanosheets at a mass ratio of 8:2, and preparing the three-dimensional composite negative electrode material for a magnesium ion battery in step S3, which is designated as MBP-8.

[0031] Comparative Example 1 A magnesium metal negative electrode is used, denoted as Mg.

[0032] The various properties of the negative electrode materials prepared in Examples 1-3 and the magnesium metal negative electrode of Comparative Example 1 were tested.

[0033] (1) XRD analysis was performed on the three-dimensional composite negative electrode material (MBP-7) for magnesium ion batteries prepared in Example 1.

[0034] Depend on Figure 1It can be seen that the main diffraction peaks of the three-dimensional composite negative electrode material for magnesium ion batteries (MBP-7) prepared in Example 1 are highly consistent with the standard card data for magnesium metal (Mg, PDF#35-0821) and magnesium phosphide (Mg3P2, PDF#74-1155), and no characteristic diffraction peaks of other impurity phases are detected. This indicates that the phase composition of the three-dimensional composite negative electrode material for magnesium ion batteries (MBP-7) prepared in Example 1 is primarily composed of two phases: magnesium metal (Mg) and magnesium phosphide (Mg3P2). The material is of high purity, with no obvious impurity phases.

[0035] (2) Electrolyte wettability test The three-dimensional composite negative electrode material (MBP-7) for magnesium ion batteries prepared in Example 1 and the magnesium metal negative electrode material (Mg) prepared in Comparative Example 1 were placed in a commercial APC electrolyte (0.4M (MgPhCl)2-AlCl3 / THF) to observe the infiltration of the electrolyte on the electrode surface. Figure 2 It can be seen that the contact angle between the three-dimensional composite negative electrode material (MBP-7) for magnesium ion batteries prepared in Example 1 and the electrolyte is 6.6°C, while the contact angle between the magnesium metal negative electrode (Mg) in Comparative Example 1 and the electrolyte is 34.2°C, proving that the three-dimensional porous structure greatly improves the wettability of the electrolyte and promotes good contact between the electrode and the electrolyte.

[0036] (3) Symmetrical battery impedance test The three-dimensional composite negative electrode material (MBP-7) for magnesium ion batteries prepared in Example 1 and the magnesium metal negative electrode material (Mg) of Comparative Example 1 were assembled into symmetrical batteries, and their impedances were tested.

[0037] Taking Example 1 as an example, the specific operation is as follows: A symmetrical cell was assembled using MBP-7 as the positive and negative electrode materials, a glass fiber separator (GF) as the separator material, and a commercial APC electrolyte (0.4M (MgPhCl)₂-AlCl₃ / THF). This cell is referred to as an MBP||MBP symmetrical cell. The assembly process for the symmetrical cell in Comparative Example 1 is identical to that in Example 1 and is not further described here. The symmetrical cell assembled in Comparative Example 1 is referred to as an Mg||Mg symmetrical cell.

[0038] Depend on Figure 3 It can be seen that the interface impedance of the MBP||MBP symmetric battery assembled with the three-dimensional composite negative electrode material for the magnesium ion battery prepared in Example 1 is 629.7Ω, while the interface impedance of the Mg||Mg symmetric battery assembled with the magnesium metal negative electrode material of Comparative Example 1 is 18010Ω, indicating that the presence of the porous structure and the magnesium phosphide skeleton can significantly reduce the interface impedance.

[0039] (4) Long cycle overpotential test The magnesium ion battery prepared in Example 2-3 was assembled into a symmetrical battery using a three-dimensional composite negative electrode material. The assembly method was the same as that in Example 1 and will not be described again here.

[0040] The symmetrical battery assembled with the three-dimensional composite negative electrode material for the magnesium ion battery prepared in test examples 1-3 was tested at 0.01 mA / cm 2 Current density and 0.005mAh / cm 2 Electrochemical performance under surface capacity. Figure 4 It can be seen that at 0.01mA / cm 2 The current density is 0.005 mAh / cm 2 Under the areal capacity test conditions, the three-dimensional composite negative electrode materials for magnesium ion batteries prepared in Examples 1-3 all exhibited significantly different electrochemical properties. Among them, MBP-6 (Mg:BP = 6:4) exhibited the highest initial overpotential (70mV), which gradually increased to 500mV with cycling, and eventually short-circuited and failed after 1362h of cycling. MBP-7 (Mg:BP = 7:3) exhibited the best electrochemical performance, with an initial overpotential of only 20mV, which stabilized at around 30mV after cycling for more than 2000h. While MBP-8 (Mg:BP = 8:2) exhibited a lower initial overpotential of 40mV, its cycling stability was poor, with the overpotential increasing to 300mV after 950h of cycling.

[0041] (5) SEM morphology analysis The symmetrical battery assembled with the three-dimensional composite negative electrode material (MBP-7) for magnesium ion batteries prepared in Example 1 was subjected to SEM analysis. The results are as follows: Figure 5 As shown: Original structural characteristics: MBP-7 has a three-dimensional porous structure with large specific surface area and rich porosity, which provides ample channels for electrolyte penetration and magnesium ion transport.

[0042] Cyclic stability verification: at 0.1mA / cm 2 and 1mA / cm 2 After cycling for 500 h at the same current density, the electrode interface morphology remained uniform and stable, and a large amount of pore structure was retained.

[0043] Performance improvement mechanism: Charge transport advantage: The Mg metal phase in MBP-7 has high electronic conductivity, providing an efficient charge transfer path for the electrode. At the same time, the excellent magnesium ion transport capacity can improve the ion conduction kinetics.

[0044] Interface stability: The high chemical stability of the Mg3P2 framework can effectively inhibit side reactions at the electrode / electrolyte interface, reduce the formation of "dead magnesium", and avoid the loss of active substances.

[0045] Current homogenization: The Mg3P2 phase is evenly distributed in the three-dimensional structure, which can make the current density distribution more uniform and avoid excessive magnesium ion deposition and dendrite growth in local areas due to current concentration.

[0046] Volume expansion suppression: The large specific surface area and reasonable pore size distribution of the three-dimensional porous structure provide ample space for magnesium deposition, which can buffer the volume change during charge and discharge (about 300% theoretical expansion rate), effectively suppress the pulverization of the electrode structure, and achieve uniform deposition of magnesium ions.

[0047] Synergistic effect: The high conductivity of Mg and the chemical stability of the Mg3P2 skeleton form a synergistic effect, which not only reduces the overall impedance of the electrode, but also significantly inhibits dendrite growth and structural degradation through uniform current distribution and buffering volume expansion, ultimately improving the cycle stability and electrochemical performance of the electrode.

[0048] (6) Full battery performance test using vanadium tetrasulfide (VS4) as the positive electrode active material To further explore the practical application performance of the three-dimensional composite anode material for magnesium-ion batteries prepared in Example 1, it was assembled into full batteries with the magnesium metal anode prepared in Comparative Example 1, and performance tests were conducted. The full battery assembly was performed using Example 1 as an example: the MBP-7 prepared in Example 1 was used as the anode, vanadium tetrasulfide (VS4) as the positive electrode active material, copper foil as the positive electrode current collector, a glass fiber separator (GF) as the separator material, and a commercial APC electrolyte (0.4M (MgPhCl)2-AlCl3 / THF) as the electrolyte. The assembly method of the full battery in Comparative Example 1 was the same as that in Example 1 and is not further described.

[0049] Through rate performance and constant current long cycle tests, the magnesium storage capacity, interface stability and cycle reversibility of the MBP-7 composite magnesium anode under actual working conditions were systematically studied. Figure 6 As shown in (a), at the same current density, the MBP-7 prepared in Example 1 exhibits better rate performance and reversible capacity than the magnesium metal negative electrode of Comparative Example 1: at a low current density of 50 mA / g, the discharge specific capacity of MBP-7 reaches 185 mAh / g; when the current density is increased to 100 mA / g, 200 mA / g and 500 mA / g respectively, the discharge specific capacity is stable at 145 mAh / g, 125 mAh / g and 115 mAh / g; especially when the current density is gradually reduced from 500 mA / g to 50 mA / g, the discharge specific capacity at each current density can be restored to the initial value without obvious capacity attenuation or fluctuation, which fully verifies the excellent rate performance and cycle stability of MBP-7 in a wide current density range.

[0050] Further analysis of the constant current charge and discharge curve shows that Figure 6(b) It can be seen that the charge and discharge platform of the full battery assembled by MBP-7 is clear and symmetrical, indicating that it has low polarization overpotential and efficient magnesium ion transport kinetics during rapid charge and discharge.

[0051] Comparing the long cycle performance of the two at a current density of 100mA / g, Figure 6 (c) It can be seen that the discharge specific capacity of MBP-7 is stably maintained at 140 mAh / g, while that of the magnesium metal negative electrode is only 80 mAh / g, highlighting the significant advantages of MBP-7 in long-term cycling.

[0052] (7) Full battery performance test using Mo6S8 as the positive electrode active material Mo6S8 cathodes are widely used in magnesium batteries due to their unique crystal structure, excellent electrochemical performance, good electrolyte compatibility, and mature research foundation. Their high stability, low polarization, and excellent cycling performance make them an ideal cathode material for magnesium-ion batteries. Therefore, we further compared the electrochemical performance of Mo6S8||APC||MBP-7 and Mo6S8||APC||Mg full cells.

[0053] The three-dimensional composite anode material for magnesium-ion batteries prepared in Example 1 and the magnesium metal anode material in Comparative Example 1 were assembled into full cells. The assembly process for the full cells was as follows: The MBP-7 prepared in Example 1 was used as the anode, Mo6S8 as the cathode, a glass fiber separator (GF) was used as the separator material, and a commercial APC electrolyte (0.4M (MgPhCl)2-AlCl3 / THF) was used as the electrolyte to form a Mo6S8||APC||MBP-7 full cell. Comparative Example 1 used magnesium metal as the anode, and all other components were the same, forming a Mo6S8||APC||Mg full cell.

[0054] Depend on Figure 7 The Mo6S8||APC||MBP-7 full cell exhibits superior charge-discharge platform and capacity retention. After 400 cycles at a 1C rate, the cell capacity remains above 80 mAh / g, while the Mo6S8||APC||Mg full cell capacity is only approximately 50 mAh / g. These results demonstrate that the uniform network structure of MBP-7 significantly enhances interfacial stability, ion transport kinetics, and structural strength, resulting in superior electrochemical performance in the Mo6S8 full cell.

[0055] In summary, the three-dimensional composite negative electrode material (MBP-7) for magnesium ion batteries prepared in Example 1 has excellent performance for the following reasons: 1. Excellent interface wettability: The three-dimensional structure increases the specific surface area and porosity, promotes full infiltration of the electrolyte, and reduces the interface impedance.

[0056] 2. Strong structural stability: The in-situ generated Mg3P2 three-dimensional skeleton is evenly dispersed in the magnesium matrix, which alleviates volume expansion, inhibits dendrite growth, improves cycle stability and rate performance, and provides a new direction for the development of high-performance magnesium battery negative electrodes.

[0057] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A three-dimensional composite negative electrode material for a magnesium ion battery, characterized in that: The invention comprises magnesium powder and phosphorus material, wherein the mass ratio of the magnesium powder to the phosphorus material is 2:8 to 20:

1.

2. The three-dimensional composite negative electrode material for a magnesium ion battery according to claim 1, characterized in that: The phosphorus material is either black phosphorus or red phosphorus.

3. The three-dimensional composite negative electrode material for a magnesium ion battery according to claim 2, characterized in that: The particle size of the magnesium powder is 0.05-100 μm.

4. A method for preparing a three-dimensional composite negative electrode material for a magnesium ion battery, characterized in that: The following steps are involved: S1: ball-milling magnesium powder and phosphorus material to obtain precursor powder; S2: cold pressing the precursor powder obtained in S1 to form a three-dimensional porous precursor electrode; S3: The three-dimensional porous precursor electrode obtained in S2 is heat-treated to allow black phosphorus to react chemically with magnesium powder to in situ generate a Mg3P2 three-dimensional network, which is evenly dispersed in the magnesium matrix to produce a three-dimensional composite negative electrode material for magnesium ion batteries.

5. The method for preparing a three-dimensional composite negative electrode material for a magnesium ion battery according to claim 4, characterized in that: In S1, before the magnesium powder and the phosphorus material are ball-milled and mixed, the phosphorus material is firstly subjected to a stripping treatment to obtain phosphorus nanosheets.

6. The method for preparing a three-dimensional composite negative electrode material for a magnesium ion battery according to claim 5, characterized in that: The mixed ball milling in S1 is carried out under an inert atmosphere, the ball milling time is 2-48 hours, and the ball milling speed is 50-1000 rpm.

7. The method for preparing a three-dimensional composite negative electrode material for a magnesium ion battery according to claim 6, characterized in that: The pressure of cold pressing in S2 is 1-50MPa.

8. The method for preparing a three-dimensional composite negative electrode material for a magnesium ion battery according to claim 7, wherein: The heat treatment temperature in S3 is 200-600°C, and the holding time is 1-12h.

9. The method for preparing a three-dimensional composite negative electrode material for a magnesium ion battery according to claim 8, characterized in that: The heating rate of the heat treatment is 1-20°C / min.

10. An application of a three-dimensional composite negative electrode material for a magnesium ion battery, characterized in that: The three-dimensional composite negative electrode material for magnesium ion batteries according to claims 1-3 and the three-dimensional composite negative electrode material for magnesium ion batteries prepared according to claims 4-9 are both used in magnesium ion batteries.

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