Silicate positive electrode material and preparation method and application thereof

Abstract

The present invention relates to the technical field of electrode materials for magnesium ion batteries, and discloses a silicate cathode material with the chemical formula MgNi x Mn 1‑x SiO4, where 0 < x ≤ 1; a preparation method of a silicate cathode material, S1: ball-milling and mixing a magnesium source, a nickel source, a manganese source, a silicon source and a flux in a certain proportion to obtain a Ni-doped precursor; S2: drying the Ni-doped precursor prepared in S1; S3: under a protective atmosphere, pre-sintering the Ni-doped precursor after drying treatment in S2, first at 300 - 400 °C for 2 - 3 h; then heating to 800 - 1000 °C and continuing to keep warm for 6 - 8 h. After cooling to room temperature, washing and drying treatments are carried out to obtain a Ni-doped silicate cathode material with the chemical formula MgNi x Mn 1‑x SiO4; this material is applied to magnesium ion batteries. The technical solution can effectively solve the problems faced by the existing MgMnSiO4 material when used as a cathode for magnesium ion batteries, such as serious agglomeration, poor electrical conductivity, structural distortion caused by manganese ions, and poor cycling performance.

Description

Technical Field

[0001] This invention relates to the field of magnesium-ion battery electrode materials technology, specifically to a silicate cathode material, its preparation method, and its application. Background Technology

[0002] In today's era of rapid technological advancement, battery energy storage systems are widely used across various fields, leading to a surge in demand for high-performance batteries. Magnesium-ion batteries, with their excellent safety and low production costs, are emerging as a promising technology for energy storage innovation and are expected to become a key force driving industry progress.

[0003] However, the strong polarization effect of magnesium ions constitutes a key obstacle to their development. When magnesium ions come into contact with the cathode material, their polarization force distorts the electron cloud of atoms or ions within the cathode material. This change first impacts the crystal structure stability of the cathode material, inducing lattice distortion and local collapse, severely hindering the insertion and extraction of magnesium ions within the cathode material. This leads to a significant decrease in ion diffusion rate and a sharp increase in charge-discharge resistance, thus negatively impacting the battery's rate performance. Secondly, due to structural damage, the number of active sites in the cathode material decreases, resulting in an actual battery capacity far lower than the theoretical value. Furthermore, the capacity decay rate accelerates significantly during cycling, drastically reducing the battery's energy density and cycle performance. Therefore, exploring cathode materials that can effectively resist magnesium ion polarization while possessing both high energy density and excellent performance has become an extremely urgent task in the current research field of magnesium-ion batteries.

[0004] Among various cathode materials, olivine silicate materials have attracted much attention due to their stable three-dimensional open framework structure, which effectively resists magnesium ion polarization reactions, and possesses high ion diffusion and a large theoretical capacity. The multivalent transition metals in their structure can reduce the damage to the host material during magnesium ion insertion / extraction, thereby maintaining stable performance during high-rate and long-cycle charge / discharge processes, significantly improving the safety and cycle performance of the battery system.

[0005] Among the olivine-type silicate materials, MgMnSiO4 stands out with its theoretical capacity exceeding 300 mAh / g. However, in practical applications, its magnesium storage capacity has been found to be relatively low. This deficiency has become a key obstacle to the large-scale application of MgMnSiO4 in magnesium-ion batteries, making it difficult to use in actual battery products. Therefore, in-depth research and improvement of magnesium-ion battery cathode materials are urgently needed. Only in this way can the shortcomings of existing technologies be effectively compensated, providing strong support and impetus for the continuous development and steady progress of magnesium-ion battery technology and commercialization, meeting the ever-growing demand for high-performance battery applications, and further expanding the application prospects of magnesium-ion batteries in new energy industries and other fields. Summary of the Invention

[0006] The present invention aims to provide a silicate cathode material, its preparation method and application, in order to solve the problem of low magnesium storage capacity of existing MgMnSiO4 materials.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a silicate cathode material with the chemical formula MgNi. x Mn 1-x SiO4, where 0 <x≤1。

[0008] This invention also provides another technical solution, a method for preparing a silicate cathode material, comprising the following steps:

[0009] S1: A magnesium source, nickel source, manganese source, silicon source and flux are ball-milled and mixed in a certain proportion to obtain a Ni-doped precursor;

[0010] S2: Ni-doped precursor prepared in drying S1;

[0011] S3: Under a protective atmosphere, the Ni-doped precursor from S2, after drying, is pre-sintered. First, it is held at 300-400℃ for 2-3 hours; then the temperature is increased to 800-1000℃ and held for another 6-8 hours. After cooling to room temperature, it is washed and dried to obtain the final product with the chemical formula MgNi. x Mn 1-x Ni-doped silicate cathode material of SiO4.

[0012] Preferably, in S1, the molar ratio of magnesium source, nickel source, manganese source, silicon source, and flux is 1:x:(1-x):1:5, where 0 <x≤1。

[0013] Preferably, in S1, the ball milling speed is 250-350 rpm and the time is 6-12 h.

[0014] Preferably, in S1, the magnesium source is any one of magnesium oxide, magnesium acetate, magnesium carbonate, magnesium hydroxide, and magnesium nitrate; the nickel source is any one of nickel nitrate, nickel nitrate, and nickel acetate; the manganese source is any one of manganese carbonate, manganese acetate, manganese carbonate, manganese oxide, and manganese nitrate; the silicon source is nano-silica; and the flux is any one of potassium chloride and sodium chloride.

[0015] Preferably, in step S2, the drying temperature is 55-65℃ and the drying time is 6-8h.

[0016] Preferably, in S3, the heating rate is 2-3℃ / min.

[0017] Preferably, in step S3, deionized water is used for washing.

[0018] Preferably, in step S3, the drying temperature is 55-65℃ and the drying time is 6-12h.

[0019] The present invention also provides another technical solution, an application of a silicate cathode material, wherein the prepared silicate cathode material is used in a magnesium-ion battery.

[0020] Technical concept of the present invention: The technical concept of the present invention is based on in-depth research and innovative thinking on existing magnesium-ion battery cathode materials, aiming to overcome the limitations of traditional materials and significantly improve battery performance.

[0021] Firstly, in terms of material selection, the conventional approach of simply replacing some nickel in the existing nickel-containing silicate MgNiSiO4 system with other elements (such as copper or zinc) with similar radii or chemical properties, and then only making minor adjustments and optimizations to the internal structure, was abandoned. This traditional approach often only achieves localized and limited performance improvements within the existing structural framework, making it difficult to achieve fundamental breakthroughs and leaps in material performance. Instead, after in-depth research and comprehensive analysis, MgMnSiO4 was innovatively selected as the basic material for exploratory research on elemental doping. This choice was not accidental, but stemmed from a meticulous and comprehensive consideration of the characteristics of various different material systems. MgMnSiO4 material itself has a high theoretical capacity of over 300 mAh / g, demonstrating great potential in energy storage. However, in practical applications, its magnesium storage capacity is relatively low. Through dedicated research, the inventors discovered that this material is prone to agglomeration, and the grain size affects the movement of particles and electrons, thereby interfering with the material's conductivity. Meanwhile, as an intercalation material, the magnesium ion storage capacity of olivine silicate depends on its spatial structure. However, manganese ions in MgMnSiO4 form octahedral complexes. Due to the length difference between the two axial bonds and the four equatorial bonds, a Jahn-Teller distortion effect occurs. This not only causes structural collapse during magnesium ion extraction, severely impacting the cycle performance of the cathode material, but also significantly reduces the battery's lifespan and reliability. However, from another perspective, these existing problems provide a vast potential space for exploring sophisticated element substitution strategies to achieve a leapfrog improvement in material performance, clarifying the foundation and direction for subsequent innovative research.

[0022] In terms of element substitution strategy, nickel was chosen to replace a portion of the Mn element in MgMnSiO4. This decision is primarily based on the differences in chemical properties and ionic radii between nickel and Mn, aiming to induce a significant change in the material's crystal structure. From a structural perspective, nickel ions have a smaller radius than manganese ions, and doping with nickel will reduce the lattice constant, resulting in grain refinement and effectively mitigating the agglomeration phenomenon in MgMnSiO4, thus creating favorable conditions for improving magnesium storage performance. Simultaneously, this substitution can alter the strength and bond length of chemical bonds between different atoms in the material, affecting the degree of electron delocalization and conduction, and optimizing the material's electronic conductivity. More importantly, replacing some manganese ions with nickel ions can reduce the lateral and longitudinal chemical bond stretching or compressive deformation caused by the Jahn-Teller distortion effect of manganese ions during magnesium storage, effectively mitigating the collapse problem during electrochemical magnesium storage and demagnesiation, enhancing structural stability, and ensuring that the material maintains good performance during multiple charge-discharge cycles. In addition, nickel has a relatively low cost advantage and a good doping effect, which improves the overall performance of materials while taking into account economic feasibility, laying the foundation for large-scale application.

[0023] In summary, this invention, through a unique basic material selection and element substitution strategy, leverages the resulting significant changes in material structure and their multifaceted positive impacts on performance to construct a novel and highly advantageous magnesium-ion battery cathode material technology solution, which is expected to bring substantial impetus and breakthroughs to the development of magnesium-ion battery technology.

[0024] Compared with existing technologies, the beneficial effects of this solution are as follows:

[0025] Regarding improvements in material performance:

[0026] (1) Grain Refinement, Improvement of Agglomeration, and Enhancement of Magnesium Storage Capacity: Based on the significant differences in ionic radius and chemical properties between nickel and manganese ions, in-situ doping with nickel to replace part of the manganese element successfully achieved effective grain refinement of the material. This process greatly reduced the originally severe agglomeration phenomenon in MgMnSiO4 material. The refined grains made the internal structure of the material more uniform and ordered, reducing internal stress concentration and electron conduction obstacles caused by agglomeration, while providing smoother diffusion channels for magnesium ions. Due to the improvement of agglomeration and the optimization of diffusion channels, more magnesium ions can be effectively embedded into the storage sites of the material, thereby significantly improving the magnesium storage capacity of the material and laying a solid foundation for subsequent performance improvements.

[0027] (2) Improved conductivity and synergistic optimization of magnesium storage: The synergistic effect of grain refinement and structural optimization significantly improves the conductivity of the material. During the charging and discharging process of magnesium-ion batteries, electrons can be conducted more smoothly within the material, reducing resistance loss. Good conductivity not only improves the charging and discharging efficiency of the battery, especially at high-rate charging and discharging, better meeting the needs of rapid charging and discharging and improving the overall performance of the battery, but also facilitates the rapid insertion and extraction of magnesium ions in the material, further promoting the effective utilization of magnesium storage capacity during actual charging and discharging, enabling the material to maintain a high magnesium storage level even under high-rate charging and discharging conditions.

[0028] (3) Enhanced structural stability and guaranteed magnesium storage stability: After nickel ions replace some manganese ions, the Jahn-Teller distortion effect generated during magnesium storage is effectively reduced. During electrochemical magnesium storage and demagnesiation, the structural collapse problem of the material is greatly alleviated, and the structural stability is significantly enhanced. The stable structure ensures the stability and continuity of magnesium ion storage sites, enabling the material to maintain good crystal structure integrity during multiple charge-discharge cycles, reducing magnesium storage capacity decay caused by structural damage, greatly extending the cycle life of the battery, improving the reliability and stability of the battery, and ensuring the stable performance of magnesium storage capacity during long-term cyclic use.

[0029] Regarding manufacturing process and cost advantages:

[0030] (1) In this technical solution, the heating rate is controlled at 2-3℃ / min during the sintering process. This effectively avoids the situation where the sintering time is too long and the production efficiency is greatly reduced due to the slow heating rate. At the same time, it can also avoid a series of problems caused by the excessively fast heating rate. That is, due to the excessively high heating rate, a significant temperature lag phenomenon is easily generated between the sample and the set program temperature. This temperature lag may cause the sample preparation to fail, or even if the sintering is successful, the internal pore diameter of the obtained sample will be abnormally large, which will have a serious negative impact on the electrochemical performance of the material and interfere with the performance of the magnesium ion battery cathode material. The heating rate range determined by this solution can ensure the smooth progress of the sintering process and guarantee the high-quality performance of the material.

[0031] (2) Simple preparation process: In-situ element doping is achieved by solid-state sintering, which is simple, easy to operate and control. It does not require complex equipment and harsh reaction conditions, which reduces the technical threshold and production cost in the preparation process, and is conducive to large-scale industrial production. It can stably prepare cathode materials with high magnesium storage capacity.

[0032] (3) Low cost: Nickel itself has a relatively low cost, which reduces the overall production cost of the cathode material while ensuring improved material performance, especially increased magnesium storage capacity. This makes the MgNi of this invention... x Mn 1-x The SiO4 nickel-doped silicate cathode material has a significant price advantage in market competition, is easier to promote and apply, and provides strong support for the industrialization of magnesium-ion batteries. It can achieve large-scale production of high magnesium storage capacity magnesium-ion battery cathode materials at a lower cost.

[0033] In summary, this invention addresses the key issues faced by MgMnSiO4 materials as positive electrodes in magnesium-ion batteries, including severe agglomeration, poor conductivity, structural distortion caused by manganese ions, and poor cycle performance, by focusing on both material properties and preparation processes. Through multiple mechanisms, it effectively improves the magnesium storage capacity of the material, providing a highly valuable technical solution for the further development and application of magnesium-ion battery technology. Attached Figure Description

[0034] Figure 1 (a) is a SEM image of the silicate cathode material MgMnSiO4 prepared in Comparative Example 2 of this invention;

[0035] Figure 1 (b) is a SEM image of the silicate cathode material MgMnSiO4 prepared in Comparative Example 1 of this invention;

[0036] Figure 1 (c) MgNi silicate cathode material prepared in Example 1 of this invention. 0.1 Mn 0.9 SEM image of SiO4;

[0037] Figure 1 (d) is the silicate cathode material MgNi prepared in Example 2 of this invention. 0.3 Mn 0.7 SEM image of SiO4;

[0038] Figure 1 (e) MgNi silicate cathode material prepared in Example 3 of this invention. 0.5 Mn 0.5 SEM image of SiO4;

[0039] Figure 1 (f) is the silicate cathode material MgNi prepared in Example 4 of this invention. 0.7 Mn 0.3 SEM image of SiO4;

[0040] Figure 2XRD patterns of the silicate cathode material MgMnSiO4 prepared in Comparative Example 1 and Comparative Example 2 of the present invention;

[0041] Figure 3 XRD patterns of the silicate cathode materials prepared in Examples 1-4 and Comparative Example 3 of the present invention;

[0042] Figure 4 Cycling performance comparison graphs of the silicate cathode materials prepared in Examples 1-4 and Comparative Examples 1-2 using the 0.5 moL / L Mg(TFSI)2 / MgCl2 / DME solution prepared in Example 5 of the present invention as the electrolyte;

[0043] Figure 5 First-cycle performance comparison graphs of the silicate cathode materials prepared in Examples 1-4 and Comparative Examples 1-2 using the 0.5 moL / L Mg(TFSI)2 / MgCl2 / DME solution prepared in Example 5 of the present invention as the electrolyte;

[0044] Figure 6 Specific capacity-voltage graph of the silicate cathode material prepared in Example 1 of the present invention in a commercially available APC electrolyte;

[0045] Figure 7 Cycling performance graph of the silicate cathode material prepared in Example 1 of the present invention in the 0.5 moL / L Mg(TFSI)2 / MgCl2 / DME electrolyte prepared in Example 5 at a current density of 0.5 C. Detailed Description of the Specific Embodiments

[0046] The following is a further detailed description through specific embodiments:

[0047] Example 1

[0048] A silicate cathode material with the chemical formula MgNi x Mn 1-x SiO4, where 0 < x ≤ 1. In this example, the value of x is 0.1, and its chemical formula is MgNi 0.1 Mn 0.9 SiO4

[0049] A preparation method of a silicate cathode material, comprising the following steps:

[0050] S1: Magnesium source, nickel source, manganese source, silicon source, and flux are weighed out in a molar ratio of 1:0.1:0.9:1:5 and placed in a ball mill for ball milling and mixing at a speed of 250-350 rpm for 6-12 hours to obtain a Ni-doped precursor. The magnesium source is any one of magnesium oxide, magnesium acetate, magnesium carbonate, magnesium hydroxide, and magnesium nitrate; the nickel source is any one of nickel suboxide, nickel nitrate, and nickel acetate; the manganese source is any one of manganese carbonate, manganese acetate, manganese carbonate, manganese oxide, and manganese nitrate; the silicon source is nano-silica; and the flux is any one of potassium chloride and sodium chloride. In this embodiment, the ball milling speed is 300 rpm for 8 hours, the magnesium source is magnesium oxide, the nickel source is nickel suboxide, the manganese source is manganese carbonate, and the flux is potassium chloride.

[0051] S2: Drying the Ni-doped precursor prepared in S1. The drying temperature is 55-65℃, and the drying time is 6-8 hours. In this embodiment, the drying temperature is 60℃, and the drying time is 6 hours. The purpose of drying is to minimize the water content in the ball-milled product and avoid affecting the temperature during sintering. Failure to dry may lead to unsuccessful sintering in the next step.

[0052] S3: The dried Ni-doped precursor from S2 is placed in an alumina crucible and pre-sintered in a tube furnace under a protective atmosphere at a heating rate of 2-3℃ / min. First, it is held at 300-400℃ for 2-3 hours; then, the temperature is increased to 800-1000℃ and held for another 6-8 hours. After cooling to room temperature, the resulting material is washed 3-5 times with deionized water and dried at 55-65℃ for 6-12 hours, finally yielding the chemical formula MgNi. 0.1 Mn 0.9 In this embodiment, a Ni-doped silicate cathode material of SiO4 is prepared under an argon protective atmosphere. The dried Ni-doped precursor from S2 is placed in an alumina crucible and pre-sintered in a tube furnace under an argon atmosphere at a heating rate of 2°C / min. The material is first held at 350°C for 2 hours, then heated to 900°C and held for another 6 hours. After cooling to room temperature, the resulting material is washed three times with deionized water and dried at 60°C for 12 hours, ultimately yielding a material with the chemical formula MgNi. 0.1 Mn 0.9 Ni-doped silicate cathode material of SiO4.

[0053] Example 2

[0054] Unlike Example 1, a silicate cathode material is used, where x is 0.3, and its chemical formula is MgNi. 0.3 Mn 0.7 SiO4.

[0055] A method for preparing a silicate cathode material includes the following steps: In step S1, magnesium oxide, nickel oxide, manganese carbonate, nano-silica, and potassium chloride are weighed out in a molar ratio of 1:0.3:0.7:1:5. In step S3, the final product is MgNi 0.3 Mn 0.7 Ni-doped silicate cathode material of SiO4.

[0056] Example 3

[0057] Unlike Example 1, a silicate cathode material is used, where x is 0.5, and its chemical formula is MgNi. 0.5 Mn 0.5 SiO4.

[0058] A method for preparing a silicate cathode material includes the following steps: In step S1, magnesium oxide, nickel oxide, manganese carbonate, nano-silica, and potassium chloride are weighed out in a molar ratio of 1:0.5:0.5:1:5. In step S3, the final product is MgNi 0.5 Mn 0.5 Ni-doped silicate cathode material of SiO4.

[0059] Example 4

[0060] Unlike Example 1, a silicate cathode material is used, where x is 0.7, and its chemical formula is MgNi. 0.7 Mn 0.3 SiO4.

[0061] A method for preparing a silicate cathode material includes the following steps: In step S1, magnesium oxide, nickel oxide, manganese carbonate, nano-silica, and potassium chloride are weighed out in a molar ratio of 1:0.7:0.3:1:5. In step S3, the final product is MgNi 0.5 Mn 0.5 Ni-doped silicate cathode material of SiO4.

[0062] Example 5

[0063] A MgNi x Mn 1-x The electrolyte for SiO4 silicate cathode material has the molecular formula Mg(TFSI)2 / MgCl2 / DME and a concentration of 0.5 mol / L.

[0064] A MgNi x Mn 1-xThe preparation method of the electrolyte for SiO4 silicate cathode material is as follows: First, Mg(TFSI)2 and MgCl2 are weighed in a molar ratio of 1:2. The weighed MgCl2 is added to an appropriate amount of 1,2-dimethoxyethane (DME). Then, a magnetic stirrer is turned on and stirred at a speed of 500-600 r / min for 3-15 min. Mg(TFSI)2 is then slowly added while stirring continuously. After stirring for 12 h, the Mg(TFSI)2 / MgCl2 / DME electrolyte, i.e., the MCT electrolyte, is obtained. In this embodiment, the weighed MgCl2 is added to an appropriate amount of 1,2-dimethoxyethane (DME). Then, a magnetic stirrer is turned on and stirred at a speed of 550 r / min for 5 min. Mg(TFSI)2 is then slowly added while stirring continuously. After stirring for 12 h, the Mg(TFSI)2 / MgCl2 / DME electrolyte is obtained.

[0065] Example 6

[0066] A magnesium-ion battery includes a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode is a magnesium metal sheet, and the positive electrode comprises MgNi x Mn 1-x SiO4 silicate cathode material, conductive agent and binder, MgNi x Mn 1-x The mass ratio of SiO4 silicate cathode material, conductive agent, and binder is 7:2:1, and MgNi x Mn 1-x The SiO4 silicate cathode material was prepared using the preparation method of this application. The conductive agent was Super P, the binder was PVDF dissolved in N-methylpyrrolidone (NMP) dispersant, and the electrolyte was the 0.5 mol / L Mg(TFSI)2 / MgCl2 / DME electrolyte prepared in Example 5, with a volume of 90 μL.

[0067] Comparative Example 1

[0068] Unlike Example 1, this is a silicate cathode material with the chemical formula MgMnSiO4.

[0069] A method for preparing a silicate cathode material includes the following steps: In step S1, magnesium oxide, manganese carbonate, nano-silica, and potassium chloride are weighed out in a molar ratio of 1:1:1:5 and then ball-milled at 300 rpm for 8 hours to obtain a precursor without Ni doping. After steps S2 and S3, in step S3, a silicate cathode material with the chemical formula MgMnSiO4 is finally obtained.

[0070] Comparative Example 2

[0071] Unlike Comparative Example 1, in a method for preparing a silicate cathode material, in step S3, the undoped Ni precursor after drying in step S2 is placed in an alumina crucible and pre-sintered in a tube furnace under an argon atmosphere at a heating rate of 2℃ / min. It is first held at 350℃ for 2 hours, then heated to 800℃ and held for 6 hours. After cooling to room temperature, the obtained material is washed three times with deionized water and dried at 60℃ for 12 hours to finally obtain a silicate cathode material with the chemical formula MgMnSiO4.

[0072] Comparative Example 3

[0073] Unlike Example 1, a silicate cathode material is used, where x is 1, and its chemical formula is MgNiSiO4.

[0074] A method for preparing a silicate cathode material, wherein in S1, magnesium oxide, nickel oxide, nano-silica and potassium chloride are weighed in a molar ratio of 1:1:1:5, and in S3, a silicate cathode material with the chemical formula MgNiSiO4 is finally obtained.

[0075] Comparative Example 4

[0076] Unlike Example 1, in a method for preparing a silicate cathode material, in S1, magnesium oxide, nickel oxide, manganese carbonate, and nano-silica are weighed in a molar ratio of 1:0.1:0.9:1:5 and ball-milled at 300 rpm for 8 hours to obtain a Ni-doped precursor. After S2-S3, the silicate cathode material is obtained in S3. XRD analysis of the prepared silicate cathode material revealed that no flux was added during the sintering of the precursor, which prevented the formation of MgNi at 900°C. 0.1 Mn 0.9 SiO4 pure phase.

[0077] The silicate cathode materials prepared in Examples 1-4 and Comparative Examples 1-2 were observed using a scanning electron microscope, and the results are as follows: Figure 1 As shown in the figure, by comparing Comparative Example 1 and Comparative Example 2, it can be found that the MgMnSiO4 silicate cathode material obtained under sintering conditions of 900℃ exhibits finer grains and a more perfect crystal structure. This uniform and fine surface morphology has a positive promoting effect on improving the conductivity of the material; conversely, the silicate cathode material synthesized at 800℃ shows a more significant agglomeration phenomenon, with a significantly larger particle size. Therefore, the sintering condition of 900℃ can effectively improve the agglomeration phenomenon of MgMnSiO4 silicate cathode material.

[0078] Figure 1 (c) to Figure 1 (f) presents a Ni-doped silicate cathode material. Due to the relatively small radius of Ni ions, their doping into the material lattice reduces the lattice constant, thus refining the grain size. Differences in material performance are related to surface micromorphology; finer particles and higher dispersion result in a larger contact area with the electrolyte during electrochemical cycling, leading to superior electrochemical performance. When the Ni doping concentration is between 0.1 and 0.7, the particles exhibit a clear dispersion, indicating that nickel plays an effective role in mitigating material agglomeration. As the Ni doping concentration gradually increases, the material's micromorphology undergoes a regular change, evolving from an initial rod-like shape to a mixed plate-like and rod-like morphology at x = 0.1, then to a blocky shape at x = 0.3, followed by a more elongated plate-like shape at x = 0.5, until finally forming a uniform, fine, elongated rod-like structure at x = 0.7.

[0079] In summary, sintering at 900℃ helps to improve the agglomeration of silicate cathode materials. Ni doping concentrations of 0.1-0.7% can improve the agglomeration of materials, with the best effect observed at 0.7%. At this concentration, the uniform and fine rod-shaped material alleviates the agglomeration of MgMnSiO4 particles and improves magnesium storage performance by increasing the contact area with the electrolyte.

[0080] The silicate cathode materials prepared in Comparative Examples 1 and 2 were analyzed by X-ray diffraction spectroscopy, and the results are as follows: Figure 2 As shown, the main characteristic peaks of the silicate cathode material MgMnSiO4 sintered at 800℃ and 900℃ are consistent with those of the standard card (#83-1546), indicating that the main phase of the synthesized silicate cathode material is MgMnSiO4.

[0081] The silicate cathode materials prepared in Examples 1-4 and Comparative Example 3 were analyzed by X-ray diffraction spectroscopy, and the results are as follows: Figure 3 As shown. Five silicate cathode materials, MgNi, sintered at 900℃. 0.1 Mn 0.9 SiO4, MgNi 0.3 Mn 0.7 SiO4, MgNi 0.5 Mn 0.5 SiO4, MgNi 0.7 Mn 0.3The XRD cards for SiO4 and MgNiSiO4 are shown in the figure. The main characteristic peaks of the cards with doping levels of 0.1-0.7% match those of the standard cards (#83-1546), indicating that the Ni-doped silicate cathode material MgMnSiO4 has been successfully synthesized. However, MgNiSiO4 with a doping level of 1.0% does not match the standard cards, indicating that a pure phase of MgNiSiO4 cannot be synthesized under the conditions of this invention.

[0082] The silicate cathode materials prepared in Examples 1-4 and Examples 1-2 were used as cathode materials for magnesium-ion batteries to verify their performance.

[0083] (1) Using commercially available APC electrolyte as the electrolyte, the silicate cathode material prepared in Example 1 was assembled into a button cell. The specific assembly steps are as follows:

[0084] First, the silicate cathode material prepared in Example 1 was thoroughly mixed with Super P (as a conductive agent) and PVDF (binder) dissolved in N-methylpyrrolidone (NMP) dispersant at a mass ratio of 7:2:1 until homogeneous. Then, the homogeneous mixture was coated onto the surface of carbon cloth cut to 12mm diameter after ultrasonic treatment. Next, the coated cathode sheet was placed in a vacuum drying oven and dried at 60°C for 10 hours to remove volatile components such as solvents, thereby obtaining a cathode sheet that meets the requirements.

[0085] Then, using the fabricated positive electrode as the positive electrode and a magnesium sheet as the negative electrode, Whatman GF / A glass fiber filter paper as the separator, and commercially available APC electrolyte as the electrolyte, the battery was assembled in an argon atmosphere glove box environment with water pressure <0.01ppm and oxygen <0.01ppm. The electrolyte volume was 90uL. Finally, the assembled button cell was placed on a sealing machine and sealed under 80MPa pressure to ensure the airtightness and integrity of the battery assembly for subsequent battery performance testing and evaluation.

[0086] Figure 6 The figure shows the specific capacity voltage of the silicate cathode material prepared in Example 1 in commercially available APC electrolyte. As can be seen from the figure, the silicate cathode material prepared in Example 1 is not compatible with the electrolyte, which makes the battery prone to short circuit and prevents the battery from working properly.

[0087] (2) Using the 0.5 mol / L Mg(TFSI)₂ / MgCl₂ / DME solution prepared in Example 5 as the electrolyte, the silicate cathode material prepared in Example 1 was assembled into a button cell. The assembly process was the same as that using commercially available APC electrolyte, and will not be described again here. Tests were conducted at a current density of 0.5C. Figure 7 It was found that using the 0.5 mol / L Mg(TFSI)₂ / MgCl₂ / DME electrolyte prepared in Example 5 resulted in a continuous increase in the specific capacity of the battery at a current density of 0.5C, and it remained in an activated state even after 500 cycles, failing to stabilize at a fixed value. The reason for this is likely that the MCT electrolyte contains a large number of functional groups, leading to a long activation time at high current densities. The solution was to activate the battery by cycling it for 10 cycles at a low current of 0.05C before cycling it at a high current of 0.5C, which successfully stabilized the battery's specific capacity at a fixed level.

[0088] (3) Using the 0.5 mol / L Mg(TFSI)₂ / MgCl₂ / DME solution prepared in Example 5 as the electrolyte, the silicate cathode material prepared in Example 1 was assembled into a button cell. The assembly process was the same as that using commercially available APC electrolyte, except that the amount of electrolyte used was 60-70 μL. After testing, the battery could not be charged and discharged normally.

[0089] (4) Using the 0.5 mol / L Mg(TFSI)2 / MgCl2 / DME solution prepared in Example 5 as the electrolyte, the silicate cathode materials prepared in Examples 1-4 and Comparative Examples 1-2 were assembled into button cells. The assembly process was the same as that using commercially available APC electrolyte, and will not be described again.

[0090] Figure 4 Comparison of the cycle performance of silicate cathode materials prepared in Examples 1-4 and Comparative Examples 1-2, using the 0.5 mol / L Mg(TFSI)2 / MgCl2 / DME solution prepared in Example 5 as the electrolyte; Figure 5 The image shows a comparison of the first-cycle performance of the silicate cathode materials prepared in Examples 1-4 and Comparative Examples 1-2, using the 0.5 mol / L Mg(TFSI)₂ / MgCl₂ / DME solution prepared in Example 5 as the electrolyte. Figure 4 and Figure 5 It can be seen that after activation by cycling at a low current of 0.05C for 10 cycles, followed by cycling at a high current of 0.5C, the magnesium storage performance of the material is significantly improved after Ni doping. The sample with a doping amount of 0.7% exhibits the highest specific capacity, with an initial discharge capacity of 128.06 mAh / g. After 150 cycles, the capacity retention is 90%, and the coulombic efficiency remains stable at around 100%, with slow capacity decay and more stable charge-discharge performance. In contrast, the undoped silicate cathode material MgMnSiO4 exhibits a first-cycle capacity of 63.3 mAh / g. -1 The discharge specific capacity is nearly twice that of the other two.

[0091] The performance verification results of the silicate cathode materials prepared in Examples 1-4 and Comparative Examples 1-2 are shown in Table 1.

[0092] Table 1

[0093] sample First discharge capacity / mAh / g First Coulomb efficiency / % Capacity retention rate / % Example 1 95.8 89.89 88.31 Example 2 77.5 103.81 93.42 Example 3 88.07 105.16 85.12 Example 4 128.06 103.7 90 Comparative Example 1 63.3 144.29 43.99 Comparative Example 2 49.08 171.5 44.0

[0094] The performance verification results of Examples 1 to 4 show that the Ni-doped silicate cathode material MgMnSiO4 provided by this invention has excellent initial coulombic efficiency and discharge capacity, and good cycle stability. In particular, when the doping amount is 0.7%, the specific capacity of the magnesium battery can be increased to twice that of the undoped type. However, as the doping amount increases, the energy required for synthesis also increases, making it impossible to synthesize MgNiSiO4 material with a doping amount of 1.0 at 900℃. Nickel ion doping can effectively mitigate the adverse effects of collapse and coarse grain agglomeration caused by the Jahn-Teller distortion effect in silicate cathode materials during use, making it suitable for application in the field of magnesium batteries and showing broad development prospects.

[0095] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A silicate cathode material, characterized in that: Its chemical formula is MgNi x Mn 1-x SiO4, in which And x≠0.

5.

2. A method for preparing the silicate cathode material according to claim 1, characterized in that: Includes the following steps: S1: A magnesium source, nickel source, manganese source, silicon source and flux are ball-milled and mixed in a certain proportion to obtain a Ni-doped precursor; S2: Ni-doped precursor prepared in drying S1; S3: Under a protective atmosphere, the Ni-doped precursor after drying treatment in S2 is pre-sintered, first at 300-400°C, holding for 2-3h; then heated to 800-1000°C, continuing to hold for 6-8h, after cooling to room temperature, washing and drying treatment, finally obtaining the Ni-doped silicate cathode material of chemical formula MgNi x Mn 1-x SiO4.

3. The method for preparing a silicate cathode material according to claim 2, characterized in that: In S1, the molar ratio of magnesium source, nickel source, manganese source, silicon source and flux is 1:x:(1-x):1:

5.

4. The method for preparing a silicate cathode material according to claim 3, characterized in that: In S1, the ball mill speed is 250-350 rpm and the time is 6-12 hours.

5. The method for preparing a silicate cathode material according to claim 4, characterized in that: In S1, the magnesium source is any one of magnesium oxide, magnesium acetate, magnesium carbonate, magnesium hydroxide, and magnesium nitrate; the nickel source is any one of nickel oxide, nickel nitrate, and nickel acetate; the manganese source is any one of manganese carbonate, manganese acetate, manganese carbonate, manganese oxide, and manganese nitrate; the silicon source is nano-silica; and the flux is any one of potassium chloride and sodium chloride.

6. The method for preparing a silicate cathode material according to claim 5, characterized in that: In S2, the drying temperature is 55-65℃ and the drying time is 6-8h.

7. The method for preparing a silicate cathode material according to claim 6, characterized in that: In S3, the heating rate is 2-3℃ / min.

8. The method for preparing a silicate cathode material according to claim 7, characterized in that: In S3, deionized water is used for washing.

9. The method for preparing a silicate cathode material according to claim 8, characterized in that: In S3, the drying temperature is 55-65℃ and the drying time is 6-12h.

10. An application of a silicate cathode material, characterized in that: The silicate cathode material prepared by any one of claims 2-9 is used in magnesium-ion batteries.

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