Preparation method of amorphous silicon powder material
The amorphous silicon powder material is prepared by the melting salt electrolyte method and auxiliary cooling technology, which solves the problem of lithium loss and volume expansion in the process of lithium silicon material during lithium and de -lithium, and improves the stability of the material and the performance of the battery.
Patent Information
- Application Number
- CN202411546721.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-01
- Publication Date
- 2025-01-24
AI Technical Summary
The existing silicon-based materials have lithium loss and volume expansion problems during the lithiation and delithiation of the process of existing silicon-based materials, resulting in poor material stability and poor battery performance.
The molten salt electrolysis method is used to electrolytically reduce silicon-containing ore raw materials or biomass materials to prepare amorphous silicon powder materials, and the temperature is rapidly reduced through auxiliary cooling to obtain amorphous silicon powder materials.
Reduce lithium -silicon alloy and de -alloying consumption, improve the stability of the material in volume expansion, and improve the safety performance and efficiency of the battery.
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Abstract
Description
Technical Field
[0001] The invention discloses a method for preparing an amorphous silicon powder material, and belongs to the technical field of silicon-based material preparation. Background Art
[0002] Silicon is abundant in nature and has significant resource advantages. Thanks to its excellent physical and electrochemical properties, silicon-based materials have become an important supporting material for the development of modern science and technology. The reversible reaction of alloying and dealloying with lithium is usually accompanied by significant volume expansion, resulting in large lithiation stress, which causes the expansion, contraction and even rupture of the alloy material, causing some particles to shift. This displacement may form local electron isolation, hindering the normal deintercalation of some lithium ions, and thus causing the loss of lithium ions involved in the reaction.
[0003] In order to compensate for the loss of lithium during the lithiation and delithiation of silicon-based materials, pre-lithiation technology has emerged. At present, a variety of pre-lithiation methods have been proposed, including chemical pre-lithiation, electrochemical pre-lithiation and direct contact pre-lithiation. However, under the premise of ensuring the uniform distribution of lithium during the pre-lithiation process, it is still a technical problem to accurately control the lithium content. Pre-lithiation only stores some active lithium in advance before the battery is operated, and still cannot fundamentally solve the problem of lithium loss during lithium-silicon alloying and dealloying. Studies have shown that at room temperature, the lithiation and delithiation of crystalline silicon and amorphous silicon will eventually form amorphous lithium-silicon alloys. Therefore, using amorphous silicon as a reaction substrate at the beginning of the lithiation process will be an effective strategy to reduce the consumption of lithium sources during alloying and dealloying. On the other hand, when the amorphous silicon particle size is smaller than the critical value and there is enough space between the particles to accommodate volume expansion, amorphous silicon can remain intact without breaking under large volume changes. In addition, the higher lithium insertion voltage of amorphous silicon can effectively inhibit the formation of lithium dendrites, and has great potential in improving battery safety performance.
[0004] At present, the preparation methods of amorphous silicon powder materials mainly include liquid phase quenching method, mechanical ball milling method, vapor deposition method, etc. The liquid phase quenching method is based on the amorphous belt furnace and ball mill to prepare amorphous materials. The principle is to allow the molten metal or alloy to enter the nozzle package at a certain flow rate through the tundish flow control device, and then spray it onto the high-speed rotating cooling copper roller through the nozzle. The molten material is quickly cooled to obtain an amorphous thin strip. Therefore, the liquid phase quenching method requires extremely high supercooling to make the material disorderly arranged to form an amorphous state; the product prepared by the mechanical ball milling method has a high impurity content and low purity; the vapor deposition method has a complex process, high cost and low yield, and has no application prospects. At the same time, amorphous silicon materials are in a metastable state. During high-temperature treatment, the material is easy to change from amorphous to crystalline. The spontaneous crystallization transformation at high temperature makes the preparation of amorphous silicon materials still full of challenges. Therefore, it is of great research and application value to develop amorphous silicon powder material preparation technology suitable for industrial production and simple process. Summary of the invention
[0005] In view of the problems and shortcomings of the above-mentioned prior art, the present invention provides a method for preparing amorphous silicon powder material. The present invention has simple process, short flow, high efficiency, environmental friendliness, low production cost, and good industrial production application prospects.
[0006] The technical solution of the present invention is:
[0007] A method for preparing an amorphous silicon powder material, the steps comprising:
[0008] (1) preparing an electrolytic cathode using silicon-containing ore raw materials or biomass materials as raw materials, using a graphite carbon rod as an anode, and performing electrolysis in a pre-electrolyzed molten salt to obtain a cathode product;
[0009] (2) The cathode product is subjected to auxiliary cooling to rapidly reduce the temperature to obtain an amorphous silicon powder material.
[0010] The biomass material in (1) is one or a mixture of any proportion of silicon dioxide, silicon monoxide, calcium silicate, montmorillonite and quartz.
[0011] A binder is added to the silicon-containing ore raw material or biomass material to prepare an electrode material, the electrode material is wrapped with nickel foam, and the electrode material wrapped with nickel foam is tied to a molybdenum rod with molybdenum wire as a cathode.
[0012] The electrode material can be in any one or more of porous, tubular, linear, and spherical shapes, or can be directly used as a cathode.
[0013] The electrolysis in (1) is performed under an argon atmosphere at an electrolysis temperature of 650-850° C. using stage constant voltage and stage constant current segmented electrolysis. The first 0.5 h of the electrolysis is performed using constant current electrolysis with a current of 1.2A-1.8A; the last 0.5-2.5 h of the electrolysis is performed using constant voltage electrolysis with a voltage of 2.8-3.2V. The total electrolysis time is 1-3 h.
[0014] The auxiliary cooling in (2) is a rapid cooling process in which the cathode is quickly transferred to an atmosphere of cold air, ice, dry ice, liquid nitrogen, liquid ammonia, liquid argon, liquid helium, etc. for rapid cooling at the end of electrolysis.
[0015] Compared with the prior art, the present invention is characterized in that:
[0016] In the present invention, molten salt electrolysis is used to electrolytically reduce silicon-containing ore raw materials or biomass materials to successfully prepare amorphous silicon powder material, which is of great significance for reducing lithium source consumption in the alloying and de-alloying process of lithium silicon and improving material volume expansion.
[0017] The beneficial effects of the present invention are:
[0018] The present invention can reduce silicon-containing ore raw materials or biomass materials directly at the cathode through molten salt electrolysis to obtain amorphous silicon powder materials. The amorphous silicon will reduce the consumption of active lithium during the alloying process with lithium, and will expand and shrink more uniformly than the crystalline silicon material, which will improve the volume expansion problem in this process (>300%) and improve the material stability.
[0019] The amorphous silicon powder material prepared by the present invention requires a short experimental process and low energy consumption. It has low requirements for electrolysis equipment and can select a cheap molten salt system to achieve low-cost continuous industrial production, providing a potential idea for solving the key technologies of lithium-ion batteries and large-scale preparation of silicon-based negative electrode materials.
[0020] The cathode product of the present invention can obtain amorphous silicon powder material only through auxiliary cooling (transfer to one of the atmospheres of cold air, ice, dry ice, liquid nitrogen, liquid ammonia, liquid argon, liquid helium, etc. for rapid cooling). Compared with the conventional spray cooling of molten metal or alloy, the cooling equipment and process are simpler and more convenient. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 This is the X-ray diffraction pattern of the amorphous silicon powder material prepared in Example 1. DETAILED DESCRIPTION
[0022] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. It should be noted that the embodiments in this application and the features in the embodiments can be combined with each other arbitrarily without conflict.
[0023] A method for preparing an amorphous silicon powder material, the specific steps of which are:
[0024] (1) pre-electrolyzing the molten salt;
[0025] (2) preparing an electrolytic cathode using silicon-containing ore raw materials or biomass materials as raw materials, using a graphite carbon rod as an anode, and performing electrolysis in a pre-electrolyzed molten salt to obtain a cathode product;
[0026] (3) The cathode product is subjected to auxiliary cooling to rapidly reduce the temperature to obtain an amorphous silicon powder material.
[0027] The molten salt is CaCl with a molar ratio of 1:1 2 and NaCl.
[0028] The molten salt in (1) is pretreated before pre-electrolysis, and the pretreatment process is as follows: heating the molten salt at a heating rate of 5°C / min, keeping it at 100°C for 1-3h to remove free water in the molten salt; and then keeping it at 400°C for 2-4h to remove bound water in the molten salt.
[0029] The pre-electrolysis in (1) is as follows: using a graphite carbon rod as an anode, using molybdenum wire to wind nickel foam onto the molybdenum rod as a cathode, immersing the cathode and the anode in molten salt at the same time, and performing pre-electrolysis in an argon environment using a DC regulated power supply, controlling the voltage to 2.0-3.2V, and the electrolysis time to 2-4h.
[0030] Embodiment 1: A method for preparing the amorphous silicon powder material, comprising the steps of:
[0031] (1) Pretreatment of molten salt; wherein the molten salt is NaCl and CaCl in a molar ratio of 1:1 2 The pretreatment process of the mixed molten salt is as follows: the molten salt is heated at a heating rate of 5°C / min, and kept at 100°C for 2 hours to remove the free water in the molten salt; then kept at 400°C for 3 hours to remove the bound water in the molten salt;
[0032] (2) Pre-electrolyzing the molten salt after pretreatment; using a graphite carbon rod as an anode, using molybdenum wire to wrap nickel foam around the molybdenum rod as a cathode, so that the cathode and the anode are immersed in the molten salt at the same time, and pre-electrolyzing with a DC regulated power supply in an argon environment, the control voltage is 2.4V, and the electrolysis time is 2h;
[0033] (3) preparing an electrolytic cathode using silicon-containing ore raw materials or biomass materials as raw materials, using a graphite carbon rod as an anode, and performing electrolysis in a pre-electrolyzed molten salt to obtain a cathode product;
[0034] An electrolytic cathode is prepared using silicon-containing ore raw materials or biomass materials as raw materials: 0.5 g of silicon oxide and ammonium bicarbonate are weighed according to a mass ratio of silicon oxide to ammonium bicarbonate of 4:6, a PVA binder is added and mixed evenly, and then loaded into a cylindrical compression molding mold with a diameter of 20 mm, and the above raw materials are pressed into a sheet with a diameter of 20 mm and a thickness of about 1 mm by compression molding (molding pressure 10 MPa, holding time 30 s), and the sheet is sintered in a tube furnace at 800° C. in an air atmosphere for 2 h to obtain a silicon oxide porous electrode material, and the silicon oxide porous electrode prepared above is wrapped with nickel foam, and the porous electrode wrapped with the nickel foam is wound and tied to a molybdenum rod with molybdenum wire as a cathode;
[0035] The electrolysis was carried out under an argon atmosphere at an electrolysis temperature of 650°C using stage constant voltage and stage constant current segmented electrolysis. The first 0.5 h of the electrolysis was electrolyzed using constant current with a current of 1.2 A. The last 0.5 h of the electrolysis was electrolyzed using constant voltage with a voltage of 3.2 V. The total electrolysis time was 1 h.
[0036] (4) The cathode product was transferred to liquid nitrogen for auxiliary cooling, and the temperature was rapidly reduced (placed in 400 mL of liquid nitrogen) for 1 min, and then immersed in ultrapure water for 5 h. The electrolytic product was taken out from the foam nickel wrapping wrapped with molybdenum wire and placed in a 2 wt % dilute hydrochloric acid solution for stirring and pickling for 5 h. It was then filtered and washed with deionized water and dried in a vacuum oven at 60 ° C for 12 h to obtain an amorphous silicon powder material.
[0037] The X-ray diffraction pattern (XRD) of the amorphous silicon powder material prepared in this embodiment is as follows: Figure 1 As shown, the figure shows a weaker silicon diffraction peak, indicating that the prepared material has a low degree of crystallinity and is amorphous as a whole.
[0038] Example 2: Figure 1 As shown, the method for preparing the amorphous silicon powder material comprises the following steps:
[0039] (1) Pretreatment of molten salt; wherein the molten salt is NaCl and CaCl in a molar ratio of 1:1 2 The pretreatment process of the mixed molten salt is as follows: the molten salt is heated at a heating rate of 5°C / min, and kept at 100°C for 2 hours to remove the free water in the molten salt; then kept at 400°C for 3 hours to remove the bound water in the molten salt;
[0040] (2) Pre-electrolyzing the molten salt after pretreatment; using a graphite carbon rod as an anode, using molybdenum wire to wrap nickel foam around the molybdenum rod as a cathode, so that the cathode and the anode are immersed in the molten salt at the same time, and pre-electrolyzing with a DC regulated power supply in an argon environment, the control voltage is 2.4V, and the electrolysis time is 2h;
[0041] (3) preparing an electrolytic cathode using silicon-containing ore raw materials or biomass materials as raw materials, using a graphite carbon rod as an anode, and performing electrolysis in a pre-electrolyzed molten salt to obtain a cathode product;
[0042] An electrolytic cathode is prepared using silicon-containing ore raw materials or biomass materials as raw materials: 0.5 g of silicon oxide and ammonium bicarbonate are weighed according to a mass ratio of silicon oxide to ammonium bicarbonate of 4:6, a PVA binder is added and mixed evenly, and then loaded into a cylindrical compression molding mold with a diameter of 20 mm, and the above raw materials are pressed into a sheet with a diameter of 20 mm and a thickness of about 1.5 mm by compression molding (molding pressure 10 MPa, holding time 30 s), and the sheet is sintered in a tube furnace at 800° C. in an air atmosphere for 5 h to obtain a silicon oxide porous electrode material, and the silicon oxide porous electrode prepared above is wrapped with nickel foam, and the porous electrode wrapped with nickel foam is wound and tied to a molybdenum rod with molybdenum wire as a cathode;
[0043] The electrolysis was carried out under an argon atmosphere at an electrolysis temperature of 700°C with stage constant voltage and stage constant current. The first 0.5 h of the electrolysis was electrolyzed with a constant current of 1.2 A; the last 2.5 h of the electrolysis was electrolyzed with a constant voltage of 3.2 V. The total electrolysis time was 3 h.
[0044] (4) Move the cathode product to ice cubes and cool it down rapidly by auxiliary cooling (introduce cold air at a temperature of 5°C and a cold air flow rate of 1m 3 / h) for 30s, soak it in ultrapure water for 5h, take out the electrolytic product from the foam nickel wrapping wrapped with molybdenum wire and place it in a 2wt% dilute hydrochloric acid solution for stirring and pickling for 5h, then filter and wash it with deionized water, and dry it in a vacuum oven at 60°C for 12h to obtain an amorphous silicon powder material.
[0045] Example 3: Figure 1 As shown, the method for preparing the amorphous silicon powder material comprises the following steps:
[0046] (1) Pretreatment of molten salt; wherein the molten salt is NaCl and CaCl in a molar ratio of 1:1 2 The pretreatment process of the mixed molten salt is as follows: the molten salt is heated at a heating rate of 5°C / min, and kept at 100°C for 2 hours to remove the free water in the molten salt; then kept at 400°C for 3 hours to remove the bound water in the molten salt;
[0047] (2) Pre-electrolyzing the molten salt after pretreatment; using a graphite carbon rod as an anode, using molybdenum wire to wrap nickel foam around the molybdenum rod as a cathode, so that the cathode and the anode are immersed in the molten salt at the same time, and pre-electrolyzing with a DC regulated power supply in an argon environment, the control voltage is 2.4V, and the electrolysis time is 2h;
[0048] (3) preparing an electrolytic cathode using silicon-containing ore raw materials or biomass materials as raw materials, using a graphite carbon rod as an anode, and performing electrolysis in a pre-electrolyzed molten salt to obtain a cathode product;
[0049] An electrolytic cathode is prepared using silicon-containing ore raw materials or biomass materials as raw materials: 0.5 g of silicon dioxide and ammonium bicarbonate are weighed according to a mass ratio of silicon dioxide to ammonium bicarbonate of 4:6, a PVA binder is added and mixed evenly, and then loaded into a cylindrical compression molding mold with a diameter of 20 mm, and the above raw materials are pressed into a sheet with a diameter of 20 mm and a thickness of about 1.5 mm by compression molding (molding pressure 10 MPa, holding time 30 s), and the sheet is sintered in a tube furnace at 800° C. in an air atmosphere for 5 h to obtain a silicon oxide porous electrode material, and the silicon oxide porous electrode prepared above is wrapped with nickel foam, and the porous electrode wrapped with nickel foam is wound and tied to a molybdenum rod with molybdenum wire as a cathode;
[0050] The electrolysis was carried out under argon atmosphere at an electrolysis temperature of 750°C using stage constant voltage and stage constant current segmented electrolysis. The first 0.5 h of the electrolysis was electrolyzed using constant current with a current of 1.2 A; the last 2.5 h of the electrolysis was electrolyzed using constant voltage with a voltage of 3.2 V. The total electrolysis time was 3 h.
[0051] (4) The cathode product was transferred to ice cubes for auxiliary cooling, and the temperature was rapidly reduced (1 kg of ice cubes were added) for 2 minutes, and then immersed in ultrapure water for 5 hours. The electrolytic product was taken out from the foam nickel wrapping wrapped with molybdenum wire and placed in a 2wt% dilute hydrochloric acid solution for stirring and pickling for 5 hours. After that, it was filtered and washed with deionized water and dried in a vacuum oven at 60°C for 12 hours to obtain an amorphous silicon powder material.
[0052] The specific implementation modes of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.
Claims
1. A method for preparing an amorphous silicon powder material, characterized in that The steps include, (1) preparing an electrolytic cathode using silicon-containing ore raw materials or biomass materials as raw materials, using a graphite carbon rod as an anode, and performing electrolysis in a pre-electrolyzed molten salt to obtain a cathode product; (2) The cathode product is subjected to auxiliary cooling to rapidly reduce the temperature to obtain an amorphous silicon powder material.
2. The method for preparing amorphous silicon powder material according to claim 1, characterized in that: The silicon-containing ore raw material or biomass material in (1) is one or a mixture of any proportion of silicon dioxide, silicon monoxide, calcium silicate, montmorillonite and quartz.
3. The method for preparing amorphous silicon powder material according to claim 2, characterized in that: A binder is added to the silicon-containing ore raw material or biomass material to prepare an electrode material, the electrode material is wrapped with nickel foam, and the electrode material wrapped with nickel foam is tied to a molybdenum rod with molybdenum wire as a cathode.
4. The method for preparing amorphous silicon powder material according to claim 3, characterized in that: The electrode material can be in any one or more of porous, tubular, linear, and spherical shapes, or can be directly used as a cathode.
5. The method for preparing amorphous silicon powder material according to claim 4, characterized in that: The electrolysis in (1) is performed under an argon atmosphere at an electrolysis temperature of 650-850° C. using stage constant voltage and stage constant current segmented electrolysis. The first 0.5 h of the electrolysis is performed using constant current electrolysis with a current of 1.2A-1.8A; the last 0.5-2.5 h of the electrolysis is performed using constant voltage electrolysis with a voltage of 2.8-3.2V. The total electrolysis time is 1-3 h.
6. The method for preparing amorphous silicon powder material according to claim 1, characterized in that: The auxiliary cooling in (2) is a rapid cooling process in which the cathode is quickly transferred to an atmosphere of cold air, ice, dry ice, liquid nitrogen, liquid ammonia, liquid argon, liquid helium, etc. for rapid cooling at the end of electrolysis.