Method for preparing carbon-coated silver powder material through molten salt electrolysis

Abstract

The invention provides a method for preparing a carbon-coated silver powder material through molten salt electrolysis. The method comprises the following steps that a silver-containing material and chloride molten salt are mixed to obtain mixed molten salt; and by taking a carbon material as a cathode and the mixed molten salt as an electrolyte, heating and electrifying in an inert atmosphere for electrolytic reduction, so as to obtain the carbon-coated silver powder material at the cathode. According to the preparation method, organic matter such as a reducing agent and a dispersing agent does not need to be added, green, efficient and large-scale preparation of the carbon-coated silver powder material can be achieved, the preparation process is simple, the equipment requirement is low, the electrochemical reduction reaction speed is high, the production efficiency is high, and the requirement for the silver content of the raw material is low.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and more specifically, to a method for preparing a carbon-coated silver powder material by molten salt electrolysis. Background Art

[0002] Conductive agents are used to ensure that the electrodes have good charge and discharge performance. A certain amount of conductive material is usually added during the production of electrodes. It collects microcurrents between active materials and between active materials and current collectors to reduce the contact resistance of the electrodes and accelerate the movement rate of electrons. It can also effectively increase the migration rate of lithium ions in the electrode materials, thereby improving the charge and discharge efficiency of the electrodes.

[0003] Carbon-coated silver is a composite material composed of silver nanoparticles and carbon layers. During the preparation process, the silver nanoparticles are evenly wrapped by the carbon layer to form a unique crystal structure. This structure makes carbon-coated silver have both the high conductivity of silver and the stability and corrosion resistance of carbon, and has broad application prospects in the development of high-performance energy storage devices. Summary of the invention

[0004] In view of the deficiencies in the prior art, one of the purposes of the present invention is to solve one or more problems in the prior art. For example, one of the purposes of the present invention is to provide a method for preparing a carbon-coated silver powder material with a simple preparation process and uniform particle size.

[0005] The present invention provides a method for preparing a carbon-coated silver powder material by molten salt electrolysis, which can include the following steps: mixing a silver-containing material with a chloride molten salt to obtain a mixed molten salt; using a carbon material as a cathode and the mixed molten salt as an electrolyte, heating and applying electricity in an inert atmosphere for electrolytic reduction, and obtaining a carbon-coated silver powder material at the cathode.

[0006] Furthermore, the method may also include removing the cathode for cold extraction after the molten salt electrolysis is completed.

[0007] Furthermore, the cold extraction process may include rapidly cooling the cathode at a temperature of -196°C to 0°C.

[0008] Furthermore, the molten salt electrolysis temperature may be 650° C. to 850° C., the electrolysis current may be 1.0A to 2.5A, and the electrolysis time may be 30s to 90s.

[0009] Furthermore, the carbon material may be carbon materials such as carbon fiber cloth, carbon mesh or carbon nanofiber.

[0010] Furthermore, the chloride may be sodium chloride, calcium chloride or a combination thereof.

[0011] Furthermore, the silver-containing material may be one or more combinations of argillite, silver chloride, silver bromide, silver nitrate and silver iodide.

[0012] Furthermore, the carbon-coated silver powder material may be in the form of microspheres, the surface carbon is a nano-carbon layer, and the particle size may be 100 nm to 600 nm.

[0013] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0014] (1) The preparation method of the present invention does not require the addition of organic substances such as reducing agents and dispersants, and can achieve green, efficient, and large-scale preparation of carbon-coated silver powder materials. The preparation process is simple, the equipment requirements are low, the electrochemical reduction reaction rate is fast, the production efficiency is high, and the requirements for the silver content of the raw materials are low.

[0015] (2) The method of the present invention can achieve rapid electrochemical reduction to obtain nano-silver and simultaneously realize carbon coating in one step. The prepared carbon-coated silver powder particles have high purity, good dispersibility, controllable morphology and complete structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects and features of the present invention will become more apparent through the following description in conjunction with the accompanying drawings, in which:

[0017] Figure 1 This is the XRD pattern of the carbon-coated silver powder material obtained in Example 1.

[0018] Figure 2 This is a scanning electron microscope image of the carbon-coated silver powder material obtained in Example 1. DETAILED DESCRIPTION

[0019] Hereinafter, a method for preparing a carbon-coated silver powder material by molten salt electrolysis according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.

[0020] The present invention provides a method for preparing a carbon-coated silver powder material by molten salt electrolysis. In some embodiments, the method may include the following steps:

[0021] S01, preparing a mixed molten salt; mixing a silver-containing material with a chloride molten salt to obtain a mixed molten salt.

[0022] S02, molten salt electrolysis; using molten salt electrolysis, with carbon material as cathode, mixed molten salt as electrolyte, heating and power supply under inert atmosphere for molten salt electrolysis, and obtaining carbon-coated silver powder material at the cathode.

[0023] In some embodiments, the silver-containing material may be silver ore and / or silver salt, etc. For example, the silver-containing material may be one or more combinations of argillite, silver chloride, silver bromide, silver nitrate and silver iodide.

[0024] In some embodiments, the chloride molten salt may be one or more combinations of sodium chloride, calcium chloride, and potassium chloride.

[0025] In some embodiments, after the molten salt electrolysis is completed, the cathode can be taken out for cold extraction treatment to quickly cool the cathode. The cold extraction treatment can include placing the cathode at a temperature of -196°C to 0°C for rapid cooling. For example, it can be rapidly cooled in a range of -150°C to -50°C, -120°C to -70°C, -105°C to -95°C or a combination of the above. Compared with slow cooling, the cold extraction treatment can inhibit the growth of product grains. For example, the cathode can be quickly transferred to liquid nitrogen, liquid argon, liquid helium, liquid ammonia, liquid fluorine, ice, dry ice or cold air for rapid cooling. In certain embodiments, the cathode product can be ultrasonically treated after cold extraction, for example, the cathode product can be collected after ultrasonication for 1h to 2h.

[0026] In some embodiments, molten salt electrolysis can be constant current electrolysis. The temperature of molten salt electrolysis can be 650℃-850℃, the constant current can be 1.0A-2.5A, and the electrolysis time can be 30s-90s. Under the above-mentioned molten salt electrolysis temperature, electrolysis current and electrolysis time, the silver nucleation growth into linear, flaky and other shapes can be avoided to make the silver present granular, thereby realizing the carbon-coated silver material in the form of microspheres; and under the above-mentioned molten salt electrolysis temperature, electrolysis current and electrolysis time, the electrochemical one-step reduction can be achieved to obtain elemental silver while realizing carbon coating, and the obtained carbon-coated silver powder material has uniform particle size and complete structure. For example, the temperature of molten salt electrolysis can be 680℃~820℃, the current can be 1.2A~2.2A, and the electrolysis time can be 40s~80s. For another example, the temperature of molten salt electrolysis can be 720℃~800℃, the current can be 1.5A~1.8A, and the electrolysis time can be 50s~70s.

[0027] In some embodiments, the cathode carbon material can be a carbon material such as carbon fiber cloth or carbon mesh. For example, the cathode can be a carbon fiber mesh.

[0028] In some embodiments, the carbon-coated silver powder material is in the form of microspheres, a core-shell structure, a carbon layer on the surface, and a nano-element silver on the core. The thickness of the surface carbon can be nanometers. The particle size of the carbon-coated silver powder particles can be 100nm to 600nm. For example, the particle size of the carbon-coated silver powder particles can be 200nm to 500nm, 280nm to 470nm, 310nm to 430nm, or a combination of the above ranges.

[0029] In some embodiments, the molten chloride salt may be pretreated before the molten salt electrolysis. The pretreatment may include heating the molten chloride salt to remove free water and bound water in the molten salt, and then performing pre-electrolysis.

[0030] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with specific examples, but the content of the present invention is not limited to the following examples.

[0031] Example 1

[0032] The method for preparing carbon-coated silver powder material by molten salt electrolysis may include the following steps:

[0033] Step 1, preheating and pre-electrolyzing the chloride molten salt; preheating the chloride molten salt includes: using NaCl and CaCl2 with a molar ratio of 1:1 as a mixed chloride molten salt, heating the mixed chloride molten salt at a heating rate of 5°C / min, keeping it warm at 100°C for 2 hours to remove free water in the molten salt, and then keeping it warm at 400°C for 3 hours to remove bound water in the molten salt; pre-electrolyzing the molten salt after pretreatment includes using a graphite carbon rod as an anode, using molybdenum wire to wrap nickel foam around the molybdenum rod as a cathode, immersing the cathode and the anode in the molten salt at the same time, and performing pre-electrolysis in an argon environment using a DC regulated power supply, the pre-electrolysis voltage is 2.4V, and the electrolysis time is 2h.

[0034] Step 2, weigh 300 g of the mixed molten salt pretreated in step 1, add 2 g of AgCl to the molten salt and mix evenly to obtain a mixed molten salt.

[0035] Step 3, using the graphite rod as the anode and the carbon fiber cloth as the cathode, electrolyzing at 650° C. and 1.2A under argon atmosphere, with a constant current of 30 s.

[0036] Step 4, after the electrolysis is completed, the cathode product is moved to liquid nitrogen for auxiliary cooling, the temperature is rapidly reduced for 1 minute, and it is immersed in ultrapure water for 4 hours to wash away the adhering molten salt, and then placed in ultrapure water for ultrasonic treatment. After ultrasonic collection, a 2wt% dilute hydrochloric acid solution is added and stirred for acid washing for 5 hours, and then filtered and washed with deionized water, and dried in a vacuum oven at 60°C for 12 hours to obtain a carbon-coated silver powder material, and its XRD is as follows Figure 1 As shown, SEM Figure 2 As shown. Figure 1 and 2 It can be seen that the carbon-coated silver powder material is composed of carbon and silver, and the particle size is uniform, and the particle size is between 100nm and 600nm.

[0037] Example 2

[0038] The method for preparing carbon-coated silver powder material by molten salt electrolysis may include the following steps:

[0039] Step 1, preheating and pre-electrolyzing the chloride molten salt; preheating the chloride molten salt includes: using NaCl and CaCl2 with a molar ratio of 1:1 as a mixed chloride molten salt, heating the mixed chloride molten salt at a heating rate of 5°C / min, keeping it warm at 100°C for 2 hours to remove free water in the molten salt, and then keeping it warm at 400°C for 3 hours to remove bound water in the molten salt; pre-electrolyzing the molten salt after pretreatment includes using a graphite carbon rod as an anode, using molybdenum wire to wrap nickel foam around the molybdenum rod as a cathode, immersing the cathode and the anode in the molten salt at the same time, and performing pre-electrolysis in an argon environment using a DC regulated power supply, the pre-electrolysis voltage is 2.4V, and the electrolysis time is 2h.

[0040] Step 2, weigh 300 g of the mixed molten salt pretreated in step 1, take 1 g of silver ore and add it to the molten salt and mix evenly to obtain a mixed molten salt.

[0041] Step 3, using the graphite rod as the anode and the carbon fiber cloth as the cathode, electrolyzing at a constant current of 1.0 A at an electrolysis temperature of 650° C. under an argon atmosphere for 60 seconds.

[0042] Step 4, after the electrolysis is completed, the cathode product is moved to liquid nitrogen for auxiliary cooling, the temperature is rapidly reduced for 1 minute, and it is immersed in ultrapure water for 4 hours to wash away the adhering molten salt, and then placed in ultrapure water for ultrasonic treatment. After ultrasonic collection, a 2wt% dilute hydrochloric acid solution is added and stirred for pickling for 5 hours, and then filtered and washed with deionized water, and dried in a vacuum oven at 60°C for 12 hours to obtain a carbon-coated silver powder material.

[0043] Although the present invention has been described above by combining with exemplary embodiments, it will be apparent to those skilled in the art that various modifications and changes may be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined in the claims.

Claims

1. A method for preparing carbon-coated silver powder material by molten salt electrolysis, characterized in that: The following steps are involved: The silver-containing material is mixed with chloride molten salt to obtain a mixed molten salt; The carbon material is used as the cathode and the mixed molten salt is used as the electrolyte. The material is heated and powered under an inert atmosphere for electrolytic reduction, and a carbon-coated silver powder material is obtained at the cathode.

2. The method for preparing carbon-coated silver powder material by molten salt electrolysis according to claim 1, characterized in that: It also includes removing the cathode for cold extraction after the molten salt electrolysis is completed.

3. The method for preparing carbon-coated silver powder material by molten salt electrolysis according to claim 2, characterized in that: The cold extraction process involves rapidly cooling the cathode at -196°C to 0°C.

4. The method for preparing carbon-coated silver powder material by molten salt electrolysis according to any one of claims 1 to 3, characterized in that: The molten salt electrolysis temperature is 650°C to 850°C, the electrolysis current is 1.0A to 2.5A, and the electrolysis time is 30s to 90s.

5. The method for preparing carbon-coated silver powder material by molten salt electrolysis according to any one of claims 1 to 3, characterized in that: The carbon material is carbon fiber cloth or carbon mesh.

6. The method for preparing carbon-coated silver powder material by molten salt electrolysis according to any one of claims 1 to 3, characterized in that: The chloride is one or a combination of sodium chloride, calcium chloride and potassium chloride.

7. The method for preparing carbon-coated silver powder material by molten salt electrolysis according to any one of claims 1 to 3, characterized in that: The silver-containing material is one or more combinations of argillite, silver chloride, silver bromide, silver nitrate and silver iodide.

8. The method for preparing carbon-coated silver powder material by molten salt electrolysis according to any one of claims 1 to 3, characterized in that: The carbon-coated silver powder material is in the shape of microspheres, the surface carbon is a nano-carbon layer, and the particle size is 100nm to 600nm.

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