Active metal powder and preparation method thereof

Abstract

The invention provides active metal powder and a preparation method thereof. The preparation method comprises the steps that active metal is dissolved in a Lewis alkaline solvent under the condition of first stirring to obtain a solution, the solution is heated under the condition of second stirring, solvent components in the solution are removed in a reduced pressure evaporation mode, and active metal powder is obtained; the speed of the second stirring is greater than or equal to 1000rpm; in the reduced pressure evaporation process, the vacuum degree is less than or equal to 1kPa. Active metal can be effectively dissolved by utilizing a specific Lewis alkaline solvent, sufficiently strong disturbance and convection are provided for the solution by stirring at a high speed of more than or equal to 1000rpm, active metal powder with abundant dendritic crystal or needle-shaped structures and crystal defects is promoted to be formed, evaporation is carried out at a low vacuum degree of less than or equal to 1kPa, a stable dendritic or needle-shaped form is favorably formed, and the active metal powder can be used for preparing active metal powder. The active metal powder with high specific surface area and high activity is obtained, and the preparation process is simple and low in energy consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation methods of metal powders, and in particular, to an active metal powder and a preparation method thereof. Background Art

[0002] Active metal materials have wide application values in many fields such as energy, material chemistry, catalytic chemistry, synthetic chemistry, medicine, environmental protection, etc. For example, lithium powder commonly used in the lithium supplementation technology of lithium-ion batteries, organolithium reagents, organomagnesium reagents, metallic sodium, etc. commonly used in organic synthesis. However, since the reactions all occur from the metal surface, the physical form and surface morphology of the metal will greatly affect its chemical properties and functions. Although metals with different physical forms and morphologies are applied in various fields, the demand for more efficient production and faster reaction rates is increasing during the industrialization process. Active metal powders with high specific surface area and high activity provide a series of solutions for such challenges.

[0003] The preparation methods of metal powders can be mainly divided into physical methods and chemical methods, and can be directly refined from solid and liquid metals through atomization methods and mechanical crushing methods; they can also be obtained by reducing, pyrolyzing, electrolyzing, etc. of metal compounds in different states. However, for active metals, especially alkali metals such as lithium metal and sodium metal, due to their high reactivity and high viscosity, it is difficult to obtain powders by conventional methods. Currently, the vacuum melting and dispersion method is usually adopted. This method is to heat the metal to melting in a vacuum or inert medium, and then spray or disperse it into particles. However, this method has problems such as high manufacturing cost, low efficiency, high requirements for equipment, and impure products. In addition, most of the metal powders obtained by the existing preparation methods are spherical particles, with a relatively single morphology and a relatively limited specific surface area, which are difficult to meet the different requirements of industrialization. Summary of the Invention

[0004] The main object of the present invention is to provide an active metal powder and a preparation method thereof to solve the problems in the prior art that the preparation methods of active metal powders have high costs, low efficiency, high requirements for equipment, impure metal powder products, relatively single morphology of metal powder products, and relatively limited specific surface area of metal powder products.

[0005] To achieve the above object, according to one aspect of the present invention, there is provided a preparation method of an active metal powder, the preparation method including: Step S1, dissolving an active metal in a Lewis basic solvent under the condition of first stirring to obtain a solution; Step S2, heating the solution under the condition of second stirring, and removing the solvent component in the solution by means of reduced-pressure evaporation to obtain an active metal powder; wherein the rate of the second stirring ≥ 1000 rpm; during the reduced-pressure evaporation process, the vacuum degree ≤ 1 kPa.

[0006] Furthermore, the rate of the second stirring ≥ 2500 rpm, preferably the rate of the second stirring is 2500 rpm to 8000 rpm.

[0007] Furthermore, the water content in the above-mentioned Lewis basic solvent is < 50 ppm, and the dissolved oxygen content in the Lewis basic solvent is < 0.05 mg / L.

[0008] Furthermore, during the above-mentioned vacuum evaporation, the vacuum degree ≤ 0.01 kPa, and / or the average heating rate is 1 to 50 °C / min.

[0009] Furthermore, the above-mentioned Lewis basic solvent is selected from any one or more of liquid ammonia, organic amines, and ether compounds; preferably, the Lewis basic solvent is selected from any one or more of liquid ammonia, hexamethylphosphoramide, ethylene glycol dimethyl ether, tetrahydrofuran, and crown ether.

[0010] Furthermore, the rate of the first stirring is 1000 rpm to 8000 rpm.

[0011] Furthermore, the above-mentioned active metal is selected from any one of alkali metals and alkaline earth metals, or the active metal is selected from an alloy formed by any several of alkali metals and / or alkaline earth metals; and / or the alkali metal is selected from any one or more of lithium, sodium, potassium, and cesium; and / or the alkaline earth metal is selected from any one or more of magnesium, calcium, strontium, and barium; and / or the physical form of the active metal is selected from any one or more of metal ingots, metal blocks, metal foils, metal wires, and metal powders.

[0012] According to another aspect of the present invention, an active metal powder is provided, and the active metal powder is prepared by the above-mentioned preparation method.

[0013] Furthermore, the above-mentioned active metal powder is dendritic crystals or needle-like crystals.

[0014] Furthermore, the specific surface area of the above-mentioned active metal powder is 10000 to 150000 m 2 / g.

[0015] Applying the technical solution of the present application, a specific Lewis basic solvent can effectively dissolve active metals. On the one hand, the Lewis basic solvent can only dissolve active metals without dissolving their surface passivation layers and non-active impurities therein, effectively ensuring that the finally prepared active metal powder has a high purity. On the other hand, after the active metal is dissolved in the solvent and exists in the form of metal ions in the solution, it can effectively avoid unnecessary side reactions caused by the high activity of the metal, providing guarantee for the purity of the finally prepared metal powder. Moreover, the Lewis basic solvent can usually dissolve active metals at a relatively low temperature, reducing the heat energy consumption in the preparation process, and at the same time helping to reduce the thermal load of the equipment and lower the production cost.

[0016] The crystal form and surface defects of active metal M depend on the concentration of active metal in the solution, temperature, the second stirring rate, and the evaporation rate of the Lewis basic solvent. Through the selection of the Lewis basic solvent, the regulation of the second stirring speed, and the vacuum degree during the vacuum evaporation process in the present application, the crystal size, physical form, surface morphology, and crystal defects of the active metal powder can be freely regulated, so as to obtain active metal powder with a dendritic fractal structure or a needle-like structure, and with a large number of lattice defects, dislocations, or grain boundaries, thereby effectively preparing active metal powder with a high specific surface area, high activity, high purity, easy preservation, and high reactivity. Specifically, during the process of heating the solution and vacuum evaporation in the present application, a second stirring speed of ≥1000 rpm provides strong enough disturbance and convection for the solution, promoting the formation of active metal powder with rich dendritic or needle-like structures and crystal defects, and these structures greatly increase the specific surface area of the active metal powder and improve its reactivity. Evaporation is carried out at a low vacuum degree of ≤1 kPa, which not only accelerates the removal of the solvent but also controls the crystallization rate, helps to form a stable dendritic or needle-like morphology, and at the same time reduces the chance of contact between the metal and air, ensuring the purity of the active metal powder. And the above preparation process is simple (such as no need for inert solvent cleaning), low in energy consumption, and mild in requirements for equipment. Detailed implementation manners

[0017] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0018] As analyzed in the background technology of the present application, the existing methods for preparing active metal powder have problems such as high cost, low efficiency, high requirements for equipment, impure metal powder products, relatively single morphology of metal powder products, and relatively limited specific surface area of metal powder products. To solve this problem, the present application provides an active metal powder and a preparation method thereof.

[0019] In a typical embodiment of the present application, a method for preparing an active metal powder is provided. The preparation method includes: dissolving an active metal in a Lewis basic solvent under the condition of first stirring to obtain a solution; heating the solution under the condition of second stirring, and removing the solvent component in the solution by means of vacuum evaporation to obtain an active metal powder; the rate of the second stirring ≥ 1000 rpm; during the vacuum evaporation, the vacuum degree ≤ 1 kPa.

[0020] The use of a specific Lewis basic solvent can effectively dissolve the active metal. On the one hand, the Lewis basic solvent can only dissolve the active metal, but not dissolve its surface passivation layer and non-active impurities therein, which can effectively ensure that the finally prepared active metal powder has a high purity; on the other hand, after the active metal is dissolved in the solvent, it exists in the solution in the form of metal ions, which can effectively avoid unnecessary side reactions caused by the high activity of the metal, and can provide guarantee for the purity of the finally prepared metal powder. And the Lewis basic solvent can usually dissolve the active metal at a relatively low temperature, reducing the heat energy consumption in the preparation process, and at the same time also helping to reduce the heat load of the equipment and lower the production cost.

[0021] The crystal form and surface defects of the active metal M depend on the concentration of the active metal in the solution, temperature, the rate of the second stirring and the evaporation rate of the Lewis basic solvent. In the present application, by selecting the Lewis basic solvent, controlling the speed of the second stirring, and the vacuum degree during the vacuum evaporation, the crystal size, physical form, surface morphology and crystal defects of the active metal powder can be freely controlled, so as to obtain an active metal powder with a dendritic fractal structure or a needle-like structure, and having a large number of lattice defects, dislocations or grain boundaries, and then effectively preparing an active metal powder with a high specific surface area, high activity, high purity, easy storage and high reaction activity. Specifically, in the process of heating the solution and vacuum evaporating, the second stirring speed of ≥ 1000 rpm provides strong enough disturbance and convection for the solution, promoting the formation of an active metal powder with a rich dendritic or needle-like structure and crystal defects, and these structures greatly increase the specific surface area of the active metal powder and improve its reaction activity. Evaporation is carried out under a low vacuum degree of ≤ 1 kPa, which not only accelerates the removal of the solvent, but also controls the crystallization rate, helps to form a stable dendritic or needle-like morphology, and at the same time reduces the chance of the metal contacting with air, ensuring the purity of the active metal powder. And the above preparation process is simple (such as no need for inert solvent cleaning), low in energy consumption, and mild in requirements for equipment.

[0022] In some embodiments of the present application, the rate of the second stirring ≥ 2500 rpm, and preferably the rate of the second stirring is 2500 rpm - 8000 rpm.

[0023] Preferably, the above stirring rate helps to apply sufficient strong disturbance to the solution and accelerate the controllable evaporation of the solvent, which can promote the formation of dendritic or needle-like structures and crystal defects, and improve the specific surface area and reactivity of the powder. Specifically, under strong disturbance, the solution crystallization process is in a non-equilibrium process with more nuclei inside, which helps to form finer crystals and more crystal defects, avoid the formation of regular and large-sized crystals, and finally form dendritic or needle-like structures and a large number of crystal defects, improving the specific surface area and reactivity of the active metal powder. At the same time, it can effectively remove the bubbles in the solution and control the solvent evaporation rate, further optimizing the surface morphology of the active metal powder, which is beneficial to improving the specific surface area and reactivity of the active metal powder.

[0024] In addition, the rate of the second stirring can be 2500 rpm, 2600 rpm, 3000 rpm, 3500 rpm, 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm or 8000 rpm. Of course, the rate of the second stirring can be any point value within 2500 rpm to 8000 rpm. Preferably, the rate of the second stirring can be any point value within 4000 rpm to 8000 rpm. Further preferably, the rate of the second stirring can be any point value within 5000 rpm to 8000 rpm, which will not be elaborated here.

[0025] In some embodiments of the present application, the water content in the Lewis basic solvent is <50 ppm, and the dissolved oxygen content in the Lewis basic solvent is <0.05 mg / L.

[0026] Controlling the water content in the Lewis basic solvent at the above extremely low level and maintaining the dissolved oxygen content within the above range can effectively reduce the side reactions (such as oxidation reaction and hydrolysis reaction) during the dissolution and recrystallization of the active metal, and improve the purity and activity of the final active metal powder.

[0027] In some embodiments of the present application, during the vacuum evaporation process, the vacuum degree ≤0.01 kPa, and / or the average heating rate is 1 - 50 °C / min.

[0028] At a low vacuum degree, the evaporation rate of the solvent is significantly accelerated, which is beneficial to the formation of lattice defects, dislocations or grain boundaries while improving production efficiency, thereby enhancing the reactivity of the active metal powder. At the same time, the evaporation under low vacuum conditions reduces the contact of the metal with impurities such as oxygen and water, reduces the risk of side reactions, and helps to improve the purity of the active metal powder.

[0029] In addition, the above average heating rate can not only reduce the risk of instantaneous evaporation of solvent and excessive agglomeration of metal powder due to excessive temperature, but also enable the solvent to be removed smoothly, which is conducive to maintaining the dendritic or needle-like structure of the metal powder and increasing the specific surface area of ​​the powder. The above control of the heating rate helps to keep the active metal in a non-steady state during the crystallization process, prompting it to form smaller and more defective crystals, increasing the specific surface area and active sites of the active metal powder and improving its reaction activity; at the same time, a faster heating rate can achieve more efficient production efficiency, allowing the solvent to be completely removed in a shorter time.

[0030] In addition, the average rate of heating can be 1°C / min, 2°C / min, 3°C / min, 5°C / min, 10°C / min, 15°C / min, 20°C / min, 25°C / min, 30°C / min, 35°C / min, 40°C / min, 45°C / min or 50°C / min. Of course, the average rate of heating can be any point value within the range of 1 to 50°C / min. Preferably, the average rate of heating can be any point value within the range of 5 to 30°C / min. Further, preferably, the rate of the second stirring can be any point value within the range of 10 to 30°C / min, which will not be repeated here.

[0031] In some embodiments of the present application, the Lewis alkaline solvent is selected from any one or more of liquid ammonia, organic amines and ether compounds; preferably, the Lewis alkaline solvent is selected from any one or more of liquid ammonia, hexamethylphosphoric acid triamide, ethylene glycol dimethyl ether, tetrahydrofuran and crown ether.

[0032] Strong Lewis alkaline solvents such as liquid ammonia can dissolve active metals to form solutions of metal cations and solvated electrons. Preferred solvents such as liquid ammonia, hexamethylphosphoric acid triamide, etc. can form relatively stable solutions with active metals, and can promote the formation of unique morphologies of metal crystals, especially dendritic or needle-like structures, by regulating the recrystallization conditions during the recrystallization process. These structural features help to increase the specific surface area of ​​active metal powders and improve their reactivity. The selection of solvents also takes into account the removability after evaporation. For example, liquid ammonia and ether solvents are not easy to remain after evaporation, which improves the high purity of metal powders. At the same time, considering the lower volatility and milder operating conditions, the use of solvents such as hexamethylphosphoric acid triamide can help to further reduce the safety risks and costs of the preparation process compared to liquid ammonia.

[0033] In some embodiments of the present application, the first stirring rate is 1000 rpm to 8000 rpm.

[0034] The above first stirring rate helps to accelerate the dissolution rate and uniformity of the active metal in the Lewis alkaline solvent.

[0035] In addition, the rate of the first stirring can be 1000 rpm, 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, 4000 rpm, 4500 rpm, 5000 rpm, 5500 rpm, 6000 rpm, 6500 rpm, 7000 rpm, 7500 rpm or 8000 rpm. Of course, the rate of the first stirring can be any point value within 1000 rpm to 8000 rpm. Preferably, the rate of the first stirring can be any point value within 3000 rpm to 8000 rpm. Further preferably, the rate of the first stirring can be any point value within 5000 rpm to 8000 rpm, which will not be elaborated here.

[0036] In some embodiments of the present application, the active metal is selected from any one of alkali metals and alkaline earth metals, or the active metal is an alloy formed by any several selected from alkali metals and / or alkaline earth metals; and / or the alkali metal is selected from any one or more of lithium, sodium, potassium and cesium; and / or the alkaline earth metal is selected from any one or more of magnesium, calcium, strontium and barium; and / or the physical form of the active metal is selected from any one or more of metal ingots, metal blocks, metal foils, metal wires and metal powders.

[0037] In another typical embodiment of the present application, the active metal powder is prepared by the above preparation method.

[0038] The present application adopts a special preparation process. By adjusting the specific preparation conditions, the size, crystallinity and surface properties of the active metal powder can be precisely controlled, and dendritic or needle-shaped active metal powder with high reaction activity and high specific surface area can be obtained. In addition, the active metal powder obtained by the method adopted in the present application has the characteristic of high purity, reduces the negative impact of impurities on the performance of the active metal powder, improves its reliability and efficiency in high-demand industrial applications, and is beneficial to its application in fields such as battery lithium supplementation and catalytic reactions.

[0039] In some embodiments of the present application, the active metal powder is dendritic crystal or needle-shaped crystal.

[0040] The dendritic or needle-shaped crystal structure improves the specific surface area of the active metal powder and also makes the surface of the active metal powder have more active sites, significantly enhancing its activity in electrochemical reactions and catalytic processes. This structure also improves the fluidity of the active metal powder, facilitates its uniform dispersion in industrial processes such as battery manufacturing, and further optimizes the performance of the material.

[0041] In some embodiments of the present application, the specific surface area of the active metal powder is 10000 - 150000 m 2 / g.

[0042] The specific surface area is as high as 10,000 - 150,000 m 2 / g, which helps to further improve the reaction activity and the number of active sites of the active metal powder, speeds up the chemical reaction rate, improves the energy conversion efficiency, means that the active metal powder has a higher material utilization rate and better industrial processability, reduces the usage amount of active components, and lowers the production cost.

[0043] In addition, the specific surface area of the active metal powder can be 10,000 m 2 / g, 20,000 m 2 / g, 30,000 m 2 / g, 40,000 m 2 / g, 50,000 m 2 / g, 60,000 m 2 / g, 70,000 m 2 / g, 80,000 m 2 / g, 90,000 m 2 / g, 100,000 m 2 / g, 120,000 m 2 / g, 130,000 m 2 / g, 140,000 m 2 / g or 150,000 m 2 / g. Of course, the specific surface area of the active metal powder can be any point value within 10,000 - 150,000 m 2 / g, preferably, the specific surface area of the active metal powder can be any point value within 40,000 - 150,000 m 2 / g. Further preferably, the specific surface area of the active metal powder can be any point value within 100,000 - 150,000 m 2 / g, which will not be elaborated here.

[0044] The beneficial effects of the present application will be further described below in conjunction with embodiments.

[0045] Example 1

[0046] (1) Scrape off the impurity layer on the surface of the lithium metal block with a knife in a high-purity argon environment to expose the smooth and silver-white lithium metal;

[0047] (2) Add the lithium block to liquid ammonia with a water content < 10 ppm and a dissolved oxygen content of < 0.01 mg / L at -78 °C and a rotation speed of 5000 rpm until it dissolves to form a bronze-colored or golden solution S;

[0048] (3) Transfer the solution S to a round-bottom flask, maintain a rotation speed of 6000 rpm and a vacuum degree of 5 Pa, with an average heating rate of 10 °C / min, heat up to room temperature and hold until the solution has completely evaporated, obtaining dendritic crystalline lithium metal on the flask wall;

[0049] (4) Scrape off the lithium metal on the flask wall with a spatula and store it in a high-purity argon atmosphere to obtain the final high specific surface area and high-activity lithium metal powder.

[0050] Example 2

[0051] (1) In a high-purity argon environment, use sandpaper to polish off the oxide layer on the surface of the magnesium strip to expose the smooth silver-white metallic magnesium;

[0052] (2) Add the magnesium strip to liquid ammonia with a water content < 10 ppm and a dissolved oxygen content of < 0.01 mg / L at -78 °C and a rotation speed of 5000 rpm until it dissolves, forming a bronze-colored or golden solution S;

[0053] (3) Transfer the solution S to a round-bottom flask, maintain a rotation speed of 6000 rpm and a vacuum degree of 5 Pa, with an average heating rate of 20 °C / min, heat up to room temperature and hold until the solution has completely evaporated, obtaining dendritic crystalline magnesium metal on the flask wall;

[0054] (4) Scrape off the magnesium metal on the flask wall with a spatula and store it in a high-purity argon atmosphere to obtain the final high specific surface area and high-activity magnesium metal powder.

[0055] Example 3

[0056] (1) In a high-purity argon environment, use a knife to scrape off the impurity layer on the surfaces of the sodium metal block and potassium metal block to expose the smooth silver-white sodium metal and potassium metal;

[0057] (2) Add the lithium block and sodium block to liquid ammonia with a water content < 10 ppm and a dissolved oxygen content < 0.01 mg / L at -78 °C and a rotation speed of 5000 rpm until they dissolve, forming a bronze-colored or golden solution S;

[0058] (3) Transfer the solution S to a round-bottom flask, maintain a rotation speed of 6000 rpm and a vacuum degree of 5 Pa, with an average heating rate of 50 °C / min, heat up to room temperature and hold until the solution has completely evaporated, obtaining dendritic crystalline sodium-potassium alloy on the flask wall;

[0059] (4) Scrape off the sodium-potassium alloy on the flask wall with a spatula and store it in a high-purity argon atmosphere to obtain the final high specific surface area and high-activity sodium-potassium alloy powder.

[0060] Example 4

[0061] (1) In a high-purity argon environment, use a small knife to scrape off the impurity layer on the surface of the lithium metal block, exposing the smooth silver-white lithium metal;

[0062] (2) Add the lithium block to hexamethylphosphoramide at 10 °C and a rotation speed of 5000 rpm until it dissolves to form a bronze or golden solution S;

[0063] (3) Transfer solution S to a round-bottom flask, maintain a rotation speed of 6000 rpm and a vacuum of 5 Pa, with an average heating rate of 10 °C / min. Heat it to room temperature and hold until the solution evaporates completely, obtaining dendritic crystalline lithium metal on the flask wall;

[0064] (4) Scrape off the lithium metal on the flask wall with a spatula and store it in a high-purity argon atmosphere to obtain the final high specific surface area and high-activity lithium metal powder.

[0065] Example 5

[0066] The difference from Example 1 is that solution S is transferred to a round-bottom flask, maintained at a rotation speed of 2500 rpm until the solution completely evaporates, obtaining dendritic crystalline lithium metal on the flask wall, and finally obtaining high specific surface area and high-activity lithium metal powder.

[0067] Example 6

[0068] The difference from Example 1 is that solution S is transferred to a round-bottom flask, maintained at a rotation speed of 1000 rpm until the solution completely evaporates, obtaining dendritic crystalline lithium metal on the flask wall, and finally obtaining high specific surface area and high-activity lithium metal powder.

[0069] Example 7

[0070] The difference from Example 1 is that solution S is transferred to a round-bottom flask, maintained at a rotation speed of 6000 rpm and a vacuum of 0.01 kPa until the solution evaporates completely, obtaining dendritic crystalline lithium metal on the flask wall, and finally obtaining high specific surface area and high-activity lithium metal powder.

[0071] Example 8

[0072] The difference from Example 1 is that solution S is transferred to a round-bottom flask, maintained at a rotation speed of 6000 rpm and a vacuum of 0.8 kPa until the solution evaporates completely, obtaining dendritic crystalline lithium metal on the flask wall, and finally obtaining high specific surface area and high-activity lithium metal powder.

[0073] Example 9

[0074] The difference from Example 1 is that under the conditions of -40°C and a rotation speed of 5000 rpm, lithium blocks are added to ethylene glycol dimethyl ether with a water content of <10 ppm and a dissolved oxygen content of <0.01 mg / L until dissolved, forming a bronze or golden solution S, and finally obtaining high specific surface area and highly active lithium powder.

[0075] Example 10

[0076] The difference from Example 1 is that under the conditions of -78°C and a rotation speed of 5000 rpm, sodium blocks are added to tetrahydrofuran with a water content of <10 ppm and a dissolved oxygen content of <0.01 mg / L until dissolved, forming a bronze or golden solution S, and finally obtaining high specific surface area and highly active sodium powder.

[0077] Example 11

[0078] The difference from Example 1 is that under the conditions of -78°C and a rotation speed of 5000 rpm, cesium blocks are added to 15-crown-5 with a water content of <10 ppm and a dissolved oxygen content of <0.01 mg / L until dissolved, forming a bronze or golden solution S, and finally obtaining high specific surface area and highly active cesium powder.

[0079] Example 12

[0080] The difference from Example 1 is that solution S is transferred to a round-bottom flask, maintaining a rotation speed of 6000 rpm and a vacuum of 5 Pa, and the heating rate is 2°C / min until the solution has completely evaporated, obtaining dendritic crystalline lithium on the flask wall, and finally obtaining high specific surface area and highly active lithium powder.

[0081] Example 13

[0082] The difference from Example 1 is that lithium blocks are replaced with lithium powder, and finally obtaining high specific surface area and highly active lithium powder.

[0083] Comparative Example 1

[0084] The difference from Example 1 is that under the conditions of -78°C and a rotation speed of 5000 rpm, lithium blocks are added to dichloromethane with a water content of <10 ppm and a dissolved oxygen content of <0.01 mg / L, and the lithium metal is completely insoluble.

[0085] Comparative Example 2

[0086] The difference from Example 1 is that solution S is transferred to a round-bottom flask, maintaining a rotation speed of 500 rpm and a vacuum of 5 Pa until the solution has completely dried, obtaining dendritic crystalline lithium on the flask wall, and finally obtaining lithium powder.

[0087] Comparative Example 3

[0088] The difference from Example 1 is that the solution S is transferred to a round-bottom flask, and the rotation speed is maintained at 6000 rpm and the vacuum degree is 5 Pa until the solution is completely evaporated to dryness, and dendritic crystalline lithium metal is obtained on the bottle wall, and finally lithium metal powder is obtained.

[0089] The specific surface areas of the active metal powders obtained after the preparation of the above examples and comparative examples are listed in Table 1.

[0090] Table 1

[0091]

[0092]

[0093] From the test results of Examples 1 to 4, it can be seen that the active metal powder provided by the present invention greatly increases the specific surface area of the powder and improves its reaction activity.

[0094] Comparing Example 1 with Comparative Example 2, it can be seen that if the rotation speed during evaporation to dryness of the solvent does not reach ≥1000 rpm, it will seriously affect the specific surface area of the final powder and greatly affect the reaction activity of the metal.

[0095] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0096] Using a specific Lewis basic solvent can effectively dissolve the active metal. On the one hand, the Lewis basic solvent can only dissolve the active metal without dissolving its surface passivation layer and non-active impurities therein, which can effectively ensure that the finally prepared active metal powder has a high purity; on the other hand, after the active metal is dissolved in the solvent, it exists in the solution in the form of metal ions, which can effectively avoid unnecessary side reactions caused by the high activity of the metal and provide guarantee for the purity of the finally prepared metal powder. And the Lewis basic solvent can usually dissolve the active metal at a relatively low temperature, reducing the heat energy consumption in the preparation process, and at the same time helping to reduce the heat load of the equipment and lowering the production cost.

[0097] The crystal morphology and surface defects of the active metal M depend on the concentration of the active metal in the solution, temperature, the second stirring rate, and the evaporation rate of the Lewis basic solvent. In this application, by selecting the Lewis basic solvent, regulating the speed of the second stirring, and controlling the vacuum degree during the vacuum evaporation process, the size, physical form, surface morphology, and crystal defects of the active metal powder crystals can be freely regulated, thereby obtaining active metal powders with dendritic fractal structures or needle-like structures, and having a large number of lattice defects, dislocations, or grain boundaries, and then effectively preparing active metal powders with a high specific surface area, high activity, high purity, easy storage, and high reactivity. Specifically, during the process of heating the solution and vacuum evaporation, a second stirring rate of ≥1000 rpm provides strong enough disturbance and convection for the solution, promoting the formation of active metal powders with rich dendritic or needle-like structures and crystal defects, and these structures greatly increase the specific surface area of the active metal powders and enhance their reactivity. Evaporation is carried out at a low vacuum degree of ≤1 kPa, which not only accelerates the removal of the solvent but also controls the crystallization rate, helps to form stable dendritic or needle-like morphologies, and at the same time reduces the chance of the metal contacting the air, ensuring the purity of the active metal powder. And the above preparation process is simple (such as no need for inert solvent cleaning), low in energy consumption, and mild in equipment requirements.

[0098] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various modifications and changes can be made to the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a reactive metal powder, characterized in that, The preparation method includes the following: Step S1: Dissolve an active metal in a Lewis basic solvent under the condition of first stirring to obtain a solution; Step S2: Heat up the solution under the condition of second stirring, and remove the solvent component in the solution by means of vacuum evaporation to obtain the active metal powder; The rate of the second stirring ≥ 1000 rpm; During the vacuum evaporation process, the vacuum degree ≤ 1 kPa.

2. The preparation method according to claim 1, wherein, The rate of the second stirring ≥ 2500 rpm, preferably the rate of the second stirring is 2500 rpm - 8000 rpm.

3. The preparation method according to claim 1 or 2, characterized in that The water content in the Lewis basic solvent is < 50 ppm, and the dissolved oxygen content in the Lewis basic solvent is < 0.05 mg / L.

4. The preparation method according to any one of claims 1 to 3, characterized in that, During the vacuum evaporation process, the vacuum degree ≤ 0.01 kPa, and / or the average rate of heating up is 1 - 50 °C / min.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The Lewis basic solvent is selected from any one or more of liquid ammonia, organic amines and ether compounds; preferably the Lewis basic solvent is selected from any one or more of liquid ammonia, hexamethylphosphoramide, ethylene glycol dimethyl ether, tetrahydrofuran and crown ether.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The rate of the first stirring is 1000 rpm - 8000 rpm.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The active metal is selected from any one of alkali metals and alkaline earth metals, or the active metal is selected from an alloy formed by any several of the alkali metals and / or the alkaline earth metals; and / or the alkali metal is selected from any one or more of lithium, sodium, potassium and cesium; and / or the alkaline earth metal is selected from any one or more of magnesium, calcium, strontium and barium; and / or the physical form of the active metal is selected from any one or more of metal ingots, metal blocks, metal foils, metal wires and metal powders.

8. A reactive metal powder, characterized in that, The active metal powder is prepared by the preparation method described in any one of claims 1 to 7.

9. The active metal powder according to claim 8, wherein The active metal powder is dendritic crystals or needle-like crystals.

10. The active metal powder according to claim 8 or 9, characterized in that, The specific surface area of the active metal powder is 10,000 to 150,000 m 2 / g.

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