Method for preparing lead-based alloy and co-producing micron silicon through fused salt electrolysis method

Abstract

The invention discloses a method for preparing a lead-based alloy and co-producing micron silicon through a fused salt electrolysis method, and relates to the technical field of lead-acid storage battery production. According to the method, liquid metal lead serves as a cathode, calcium-silicon alloy or barium-silicon alloy serves as an anode, mixed eutectic fused salt serves as electrolyte, electrolysis is carried out in a protective gas environment, and liquid calcium-lead alloy / liquid barium-lead alloy and anode Si powder are collected; and the anode Si powder is taken to be subjected to ball milling, acid pickling, water washing and drying, and the micron Si powder is prepared. The mixed eutectic molten salt consists of sodium chloride and calcium chloride or consists of sodium chloride and barium chloride. The method provided by the invention is low in raw material cost, simple in process, safe, environment-friendly, pollution-free and suitable for large-scale production. The prepared calcium-lead alloy or liquid barium-lead alloy is high in calcium or barium content, only contains trace Na doping, and is high in current efficiency; the prepared micron Si powder shows excellent electrochemical performance when being used for preparing a lithium ion battery negative electrode material.

Description

Technical Field

[0001] The invention relates to the technical field of lead-acid battery production, and in particular to a method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis. Background Art

[0002] The grid is the main component of the lead-acid battery. It is the collector skeleton of the electrode, which conducts, collects and evenly distributes the current. It also supports the active material and is the carrier of the active material. Adding active metals, such as calcium (Ca) or barium (Ba), to the grid alloy of the lead-acid battery can significantly improve the battery performance. For example, the mechanical strength and corrosion resistance of the lead alloy can be enhanced, thereby extending the service life of the battery. Active metal alloying can reduce the tendency of deep cycle sulfation, improve the deep discharge capacity, and enable the lead-acid battery to have better high load and frequent charge and discharge performance.

[0003] At present, in the production process of grid alloy, calcium-lead or barium-lead master alloy (Ca content of about 2wt.%) is usually added to liquid lead to reduce the concentration of calcium and barium to meet the production standards. However, when preparing calcium-lead or barium-lead master alloy, there are still problems such as active metal burnout, high production cost, high risk and poor alloy uniformity.

[0004] From the perspective of production technology, the high potential difference and rapid mixing between active metals and lead will lead to violent heat release, making the active metal easy to burn. Chinese invention patent application CN116949517A discloses a device and application for preparing lead-barium alloy by molten salt primary battery method, which uses lead as the positive electrode and barium as the negative electrode, and controls the reaction rate through the self-discharge process, thereby reducing the burning of active metals. However, the difficulty in storing and transporting single barium and its high price may limit the practical application of this technology. Chinese authorized invention patent CN110195243B discloses a method for extracting rare earths and preparing lead-rare earth alloys by electrolysis of liquid cathode molten salt. However, when this method is used to produce lead-rare earth alloys, the anode will release chlorine. This shortcoming makes it difficult to apply this technology on a large scale in industry.

[0005] Therefore, it is crucial to develop a low-cost, chlorine-free and environmentally friendly lead-based alloy preparation technology. Summary of the invention

[0006] The present invention provides a method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis. The method has a cost advantage because the raw material source is abundant and cheap; the process is simple and no chlorine is generated, which can reduce the risk of environmental pollution. Therefore, the method is suitable for scaled-up production and has the potential for large-scale production. The method is specifically implemented by the following technologies.

[0007] In a first aspect of the present invention, a method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis is provided, wherein liquid metal lead is used as a cathode, M-silicon alloy is used as an anode, and mixed eutectic molten salt is used as an electrolyte, and electrolysis is performed in a protective gas environment to collect liquid M-lead alloy and anode Si powder; the anode Si powder is ball-milled, pickled, washed with water, and dried to prepare micron Si powder;

[0008] The mixed eutectic molten salt consists of sodium chloride and M chloride, where M is calcium or barium.

[0009] In the above method provided by the present invention, the M-silicon alloy is a calcium-silicon alloy or a barium-silicon alloy. The mixed eutectic molten salt is selected from sodium chloride and calcium chloride (CaCl2) / barium chloride (BaCl2) accordingly. The liquid M-lead alloy finally prepared is a liquid calcium-lead (Ca-Pb) alloy or a liquid barium-lead (Ba-Pb) alloy.

[0010] During the electrolysis process, Ca 2+ Or Ba 2+ Leaching, Ca 2+ Or Ba 2+ Under the action of the electric field, it is transferred to the cathode liquid Pb and transformed into the corresponding M-lead alloy (liquid calcium-lead alloy or liquid barium-lead alloy).

[0011] The obtained liquid M-Pb alloy flows out of the electrolytic cell and is cooled.

[0012] The entire electrolysis process of the above method needs to be carried out in a protective gas environment to prevent the anode from being oxidized.

[0013] When the liquid M-Pb alloy flows out of the electrolytic cell, there is no need to set up a protective gas environment, but it can be cooled in the air, with only a small amount of oxidation loss on the surface of the alloy. The oxide film generated by oxidation on the surface of the alloy can protect the internal alloy. The mixed eutectic molten salt is only volatilized and consumed during electrolysis, and no electrochemical loss occurs.

[0014] The method for preparing lead-based alloy and co-producing micron silicon provided by the present invention does not require special restrictions on the source of the liquid M-Si alloy, and is also applicable to the above method for use in the deoxidizer for the iron and steel metallurgical industry. The present invention uses the M-Si alloy, a deoxidizer for the iron and steel metallurgical industry with large output and low price, as the active metal source, and utilizes molten salt electrolysis technology and metal refining mechanism to prepare M-Pb alloy and micron Si material by electrochemical oxidation and reduction. Finally, the M-Pb alloy is used in the production of lead-acid battery grid alloys, and the micron Si powder is used for lithium-ion battery active materials, thereby achieving full recycling of the reaction products. The present invention solves the multiple shortcomings of active metal burnout, high production cost, high risk and poor alloy uniformity during the preparation of lead-based master alloys, realizes clean production, and promotes the sustainable development of resources.

[0015] Furthermore, in the mixed eutectic molten salt, the molar ratio of sodium chloride to chloride of M is (47.9-60.1):(39.9-52.1).

[0016] Furthermore, in the M-silicon alloy, the mass fraction of metal M is 28-32% (30±2 wt.%).

[0017] Furthermore, during the electrolysis process, the cathode liquid Pb is transformed into a liquid M-lead alloy, and the mass fraction of the metal M (metal calcium or barium) in the liquid M-lead alloy is controlled to be 4.8-5.2% (5±0.2 wt.%) to avoid excessive activity.

[0018] Furthermore, the operating temperature of the mixed eutectic molten salt is 600-700° C., and the electrolysis voltage is 0.6-1.0 V.

[0019] Furthermore, the liquid M-lead alloy is used as a master alloy to prepare grids of lead-acid batteries.

[0020] Furthermore, the anode Si powder is used as a material for preparing a negative electrode of a lithium-ion battery.

[0021] Optionally, in order to further improve the utilization rate of active metals and increase the reaction contact area, the M-silicon alloy can be crushed to less than 2 mm.

[0022] Optionally, in order to ensure the production of liquid M-Pb (calcium-lead or barium-lead) alloy as the cathode product, a relatively excessive amount of calcium-silicon alloy or barium-silicon alloy may be added to the anode.

[0023] Optionally, when the prepared anode Si powder is ball-milled, the ball-milling speed is 400-500 rpm for 2 h.

[0024] Optionally, the prepared anode Si powder is pickled using 2 M hydrochloric acid for 6 h.

[0025] The micron Si powder finally prepared has stable properties, can be stored in the air for a long time, and can be used as an active material for the negative electrode of lithium-ion batteries.

[0026] The second aspect of the present invention provides liquid M-lead alloy / micron Si powder prepared by any of the above methods.

[0027] The third aspect of the present invention provides an application of a liquid M-lead alloy in the preparation of a lead-acid battery, characterized in that the liquid M-lead alloy is prepared by any one of the above methods.

[0028] A fourth aspect of the present invention provides an application of micron Si powder in preparing lithium ion batteries, wherein the micron Si powder is prepared by any one of the above methods.

[0029] A fifth aspect of the present invention provides a product, which is any one of the following:

[0030] (1) A lead-acid battery grid, the raw material of which includes a liquid M-lead alloy prepared by any one of the above methods;

[0031] (2) A lead-acid battery, the structure of which includes the lead-acid battery grid;

[0032] (3) A lithium-ion battery, wherein the raw material for preparing the negative electrode thereof comprises micronized Si powder prepared by any of the above methods.

[0033] Alternatively, micronized Si powder is assembled into lithium-ion batteries when used as negative electrode active materials of lithium-ion batteries; lithium sheets are used as counter electrodes, 1 M LiPF6 (dissolved in ethylene carbonate (EC)) is used as electrolyte, and commercial polyethylene membrane is used as separator to assemble lithium-ion button batteries of different models such as CR2025.

[0034] Compared with the prior art, the present invention is beneficial in that:

[0035] 1. M-silicon alloy (calcium-silicon and barium-silicon alloy) is usually used as a deoxidizer and desulfurizer in steel smelting. It has the advantages of low chemical activity, low price and abundant resources, and is a potential calcium and barium resource. The method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis provided by the present invention uses calcium-silicon alloy or barium-silicon alloy as raw materials, which are abundant in source and low in price, and has cost advantages; the process is simple and no chlorine is generated, which can reduce the risk of environmental pollution; it is suitable for scaled-up production and has the potential for large-scale production.

[0036] 2. The M-Pb alloy prepared by the method of the present invention has a high content of metal M (calcium or barium), contains only a trace amount of Na doping, and has high current efficiency.

[0037] 3. The method of the present invention can also be used to prepare micron Si powder, which exhibits excellent electrochemical performance when used to prepare negative electrode materials for lithium-ion batteries, which is much higher than the current graphite negative electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The present invention is a process flow chart for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis.

[0039] Figure 2 Schematic diagram of the principle of preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis.

[0040] Figure 3 Electrochemical performance of micron Si powder under 0.5C cycle. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] The method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis provided by the present invention comprises the following steps: using liquid metal lead as a cathode, using M-silicon alloy as an anode, and using a mixed eutectic molten salt as an electrolyte, and performing electrolysis in a protective gas environment to collect liquid M-lead alloy and anode Si powder; and taking the anode Si powder and performing ball milling, pickling, water washing and drying to prepare micron Si powder. The mixed eutectic molten salt is composed of sodium chloride and M chloride, and M is calcium or barium.

[0043] In some implementation cases of the present invention, the test methods without specific conditions are all selected according to conventional methods, conventional conditions, or according to the product instructions. The test materials not specifically specified are all commercially available conventional raw materials.

[0044] Example 1

[0045] The method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis provided in this embodiment comprises the following steps:

[0046] (1) Mix 118.8 g of NaCl and 281.2 g of BaCl2 evenly (at this time, it is the eutectic composition with a molar ratio of 60.1:39.9) and place it in a vacuum drying oven at 200°C for 24 h; then transfer it to a resistance furnace and heat it to 800°C and keep it warm for 30 min. After the NaCl-BaCl2 is fully melted, cool it to 700°C and keep it warm.

[0047] (2) Take 50 g of metal Pb as the cathode, put it into an alumina (Al2O3) crucible, place it at the bottom of the NaCl-BaCl2 molten salt, and use a φ=2 mm molybdenum (Mo) wire as the current collector to connect it to a DC power supply.

[0048] A stainless steel mesh (30 mesh) was used to wrap 10 g of Ba-Si alloy (particle size φ = 2 mm, Ba mass fraction 30%) as the anode, which was immersed in the molten salt and separated from the cathode by 3-5 cm.

[0049] (3) After the electrolysis system is stable, constant voltage electrolysis is started with an electrolysis voltage of 1.0 V. Charging is stopped when the calculated amount of charge reaches 5 wt.% Ba content. At this time, the anode obtains Si powder with partial Ba removal, and the cathode obtains Ba-Pb alloy. In industrial production, the anode can be continuously dealloyed to ensure the utilization rate of the anode until it is free of Ba. The Ba-Pb alloy of the cathode will contain a small amount of impurity Na, but the content is low and does not affect its practical application in lead-acid batteries. Therefore, the Ba-Pb alloy can be used directly as a master alloy for preparing grids without subsequent treatment.

[0050] The product of this example is shown in Table 1.

[0051] Table 1

[0052] Example 2

[0053] The method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis provided in this embodiment comprises the following steps:

[0054] Steps (1) and (2) are the same as steps (1) and (2) of Example 1.

[0055] (3) After the system is stable, constant voltage electrolysis is started with an electrolysis voltage of 0.8 V. Charging is stopped when the calculated charge amount reaches 5 wt.% Ba content. Partially Ba-free Si powder is obtained at the anode, and Ba-Pb alloy is obtained at the cathode. In industrial production, it can be continuously dealloyed to ensure anode utilization.

[0056] The product of this example is shown in Table 2.

[0057] Table 2

[0058] Example 3

[0059] The method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis provided in this embodiment comprises the following steps:

[0060] Steps (1) and (2) are the same as steps (1) and (2) of Example 1.

[0061] (3) After the system is stable, constant voltage electrolysis is started with an electrolysis voltage of 0.6 V. Charging is stopped when the calculated charge amount reaches 5 wt.% Ba content. Si powder with partial Ba removal is obtained at the anode, and Ba-Pb alloy is obtained at the cathode. In industrial production, it can be continuously dealloyed to ensure the utilization rate of the anode.

[0062] The product of this example is shown in Table 3.

[0063] Table 3

[0064] Example 4

[0065] The method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis provided in this embodiment comprises the following steps:

[0066] (1) Mix 130.5 g of NaCl and 269.5 g of CaCl2 evenly (at this time, it is the eutectic composition with a molar ratio of 47.9:52.1) and place it in a vacuum drying oven at 200°C for 24 h; then transfer it to a resistance furnace and heat it to 800°C and keep it warm for 30 min. After the NaCl-CaCl2 is fully melted, cool it to 600°C and keep it warm.

[0067] (2) Take 50 g of metal Pb as the cathode, put it into an alumina (Al2O3) crucible, place it at the bottom of the NaCl-BaCl2 molten salt, and use a φ=2 mm molybdenum (Mo) wire as the current collector to connect it to a DC power supply.

[0068] A stainless steel mesh (30 mesh) was used to wrap 10 g of Ca-Si alloy (particle size φ = 2 mm, Ca mass fraction 30%) as the anode, which was inserted into the molten salt and separated from the cathode by 3-5 cm.

[0069] (3) After the electrolysis system is stabilized, constant voltage electrolysis is started with an electrolysis voltage of 0.8 V. Charging is stopped when the calculated amount of charge reaches 5 wt.% Ba content. At this time, the anode obtains Si powder with partial Ca removal, and the cathode obtains Ca-Pb alloy. Similar to Example 1, in industrial production, the anode can be continuously dealloyed to ensure the anode utilization rate until Ca is free. The Ca-Pb alloy of the cathode will contain a small amount of impurity Na, but the content is low and does not affect its practical application in lead-acid batteries. Therefore, the Ca-Pb alloy can be used directly as a master alloy for preparing grids without subsequent treatment.

[0070] The product of this example is shown in Table 4.

[0071] Table 4

[0072] Example 5

[0073] The method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis provided in this embodiment comprises the following steps:

[0074] Steps (1) and (2) are the same as steps (1) and (2) of Example 1.

[0075] (3) After the system is stable, constant voltage electrolysis is started with an electrolysis voltage of 0.6 V. Charging is stopped when the calculated amount of charge reaches 5 wt.% Ca content. Partially de-Ca Si powder is obtained at the anode, and Ca-Pb alloy is obtained at the cathode. In industrial production, it can be continuously dealloyed to ensure anode utilization.

[0076] The product of this example is shown in Table 5.

[0077] Table 5

[0078] Example 6

[0079] The method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis provided in this embodiment is the same as that in Example 1. The method for processing and applying the prepared Si powder in this embodiment is as follows:

[0080] (1) Ball milling: The anode product Si powder was placed in a planetary ball mill and ball milled at 500 rpm for 2 h. The ball milled product was washed in 2 M hydrochloric acid for 6 h, and finally washed three times with deionized water and dried.

[0081] (2) Application: The treated micron Si powder was mixed with a conductive agent (acetylene black) and a binder (polyvinylidene fluoride) in a ratio of 8:1:1, and then loaded on a copper foil to make a circular electrode (φ=20 mm).

[0082] The prepared circular electrode and lithium sheet were then assembled into a CR2025 button battery, and the electrolyte was 1 M LiPF6 (inEC).

[0083] (3) Electrochemical performance test: The assembled CR2025 button battery was placed in a 25°C constant temperature box and cycled at 0.5°C. The cycle performance was as follows: Figure 3 As shown in Figure 2, it can be seen that the capacity of 927 mA·h / g is still maintained at the 300th cycle.

[0084] In summary, it is feasible to prepare lead-based alloy and co-produce micron silicon by using the preparation method of the present invention, using M-Si alloy anode and lead cathode for molten salt electrolysis. The produced M-Pb alloy has a high content of metal M (calcium or barium) and only contains a trace amount of Na doping (the Na content is relatively low, the lowest in Example 3 is only 0.02%), which can be directly used as a master alloy for preparing grids; the current efficiency is as high as 93.00%, which is much higher than the traditional active metal molten salt electrolysis (less than 80%). The prepared micron Si powder also exhibits excellent electrochemical properties, which is much higher than the current graphite negative electrode material, and can be used as an expandable lithium battery negative electrode material or additive.

[0085] The above specific embodiments describe the implementation of the present invention in detail, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, the technical solution of the present invention can be modified and changed in many simple ways, and these simple modifications all belong to the protection scope of the present invention.

Claims

1. A method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis, characterized in that: Using liquid metal lead as cathode, M-silicon alloy as anode, and mixed eutectic molten salt as electrolyte, electrolysis is performed in a protective gas environment to collect liquid M-lead alloy and anode Si powder; ball milling, pickling, water washing and drying the anode Si powder to prepare micron Si powder; The mixed eutectic molten salt consists of sodium chloride and M chloride, where M is calcium or barium.

2. The method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis according to claim 1, characterized in that: In the mixed eutectic molten salt, the molar ratio of sodium chloride to chloride of M is (47.9-60.1):(39.9-52.1).

3. The method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis according to claim 1, characterized in that: In the M-silicon alloy, the mass fraction of metal M is 28-32%.

4. The method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis according to claim 1, characterized in that: In the liquid M-lead alloy, the mass fraction of metal M is 4.8-5.2%.

5. The method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis according to claim 1, characterized in that: The working temperature of the mixed eutectic molten salt is 600-700° C., and the electrolysis voltage is 0.6-1.0 V.

6. The method for preparing lead-based alloy and co-producing micron silicon by molten salt electrolysis according to claim 1, characterized in that: The liquid M-lead alloy is used as a master alloy to prepare the grid of a lead-acid battery; and / or the anode Si powder is used as a material for preparing the negative electrode of a lithium-ion battery.

7. Liquid M-lead alloy / micron Si powder prepared by the method described in any one of claims 1 to 6.

8. Application of a liquid M-lead alloy in the preparation of a lead-acid battery, characterized in that: The liquid M-lead alloy is prepared by the method described in any one of claims 1-6.

9. Application of micron Si powder in preparing lithium ion batteries, characterized in that: The micron Si powder is prepared by the method according to any one of claims 1 to 6.

10. A product, characterized in that The product is any of the following: (1) A lead-acid battery grid, the raw material of which comprises a liquid M-lead alloy prepared by the method according to any one of claims 1 to 6; (2) A lead-acid battery, the structure of which includes the lead-acid battery grid; (3) A lithium-ion battery, wherein the raw material for preparing the negative electrode thereof comprises micronized Si powder prepared by the method described in any one of claims 1 to 6.

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