CN110611136B - A method for recovering and preparing cobalt element from waste lithium batteries by using molten salt method - Google Patents

Abstract

The invention relates to the field of solid waste recovery, in particular to a method for recovering and preparing a cobalt simple substance from a waste lithium battery anode material by using a molten salt method, which comprises the following steps: s1, weighing quantitative NaCl and CaCl ₂ And LiCoO ₂ Uniformly mixing and grinding the mixture, and then placing the mixture in a vacuum drying oven to remove water; s2, placing the mixed reagent in a tubular resistance heating furnace for heating; s3, preparing an electrode; s4, placing the electrode in molten salt for electrodeposition; and S5, taking out the cathode iron sheet at room temperature and washing to finally obtain the cobalt simple substance. The method can directly recover simple substance cobalt from the anode material of the waste lithium battery; the equipment is simple and easy to control, the difficulty of the production process is reduced, and meanwhile, the temperature is controlled at 750 ℃, so that compared with the traditional method, the energy consumption is low, and the environmental pollution is small; in addition, the salt in the molten salt system is common salt, has no corrosivity, avoids the use of strong acid or strong base, and is safe.

Description

A method for recovering and preparing cobalt element from waste lithium batteries by using molten salt method

technical field

The invention relates to the field of solid waste recovery, in particular to a method for recovering and preparing cobalt element from a positive electrode material of a waste lithium battery by a molten salt method.

Background technique

Cobalt is an important raw material for the production of heat-resistant alloys, cemented carbides, anti-corrosion alloys, magnetic alloys and various cobalt salts. However, the lack of cobalt resources in my country is low, less than 4% of the world's total reserves. The mass fraction of cobalt in lithium-ion batteries can reach 15%, and the content of cobalt is about 850 times that of the associated cobalt ore, which is much higher than the grade of cobalt mines, and the cobalt resource raw materials are relatively concentrated. In addition, according to the calculation of 100 million lithium-ion batteries scrapped each year, about 600 tons of cobalt can be recovered, so the recovery of cobalt metal in waste lithium batteries is of great significance to the recycling of resources.

The recovery methods mainly include dry metallurgy technology and hydrometallurgy technology, as well as some emerging recovery technologies such as biological dissolution method and ion exchange method. The recycling of waste batteries by dry metallurgy technology is mainly by roasting a large number of batteries collected in a high temperature environment, and using the organic matter and carbon of the battery itself to reduce metal substances, and finally obtain metal alloys. The dry recovery technology has high requirements on equipment, and a large amount of waste gas will be generated during the recovery process, causing environmental pollution, and the final product is an alloy, which is not conducive to later separation. The wet recovery process is mainly to leaching the positive electrode material by acid and alkali, so that the valuable metal in the positive electrode material enters the solution in the form of ion, and the metal element or metal compound is obtained by different recovery methods. However, due to the use of acid and alkali in the wet recovery process, the equipment is corroded to a certain extent, and the recovery cost is high, and the intermediate products are harmful to the human body and the environment. Biometallurgy is the use of microorganisms to dissolve valuable metals, but the efficiency is low, and it is difficult to produce and recover in large quantities. The ion exchange method utilizes the selective adsorption of the valuable metals in the solution by the ion exchange resin, and then elutes the metal ions with the eluent, so that the valuable metal ions accumulate in the solution, and finally obtains by precipitation, organic solvent extraction and other methods. metal products. However, due to the large difference in the adsorption coefficients of different ions, the operation is complicated and the steps are cumbersome.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the shortcomings existing in the prior art, and proposes a method for recovering and preparing cobalt element from waste lithium batteries by using a molten salt method.

In order to achieve the above object, the present invention adopts the following technical solutions:

A method for recovering and preparing cobalt element from waste lithium batteries by using a molten salt method, comprising the following steps:

S1. Weigh quantitative amounts of NaCl, CaCl ₂ , and LiCoO ₂ , mix and grind the weighed reagents, and place them in a vacuum drying box to remove moisture;

S2. The dried mixed reagent is placed in a tubular resistance heating furnace, and the temperature is raised to 750° C. with the furnace and then kept at a constant temperature, so that LiCoO ₂ reaches a saturated and dissolved equilibrium state in the molten salt;

S3. Use high-purity nickel wire to connect the treated iron sheet and high-purity graphite sheet with stainless steel rods to prepare electrodes;

S4. Place the fabricated electrode in molten salt, so that the molten salt just immerses the iron sheet, and the high-purity graphite sheet is placed in parallel with the iron sheet for electrodeposition;

S5. After the deposition is completed, the electrode is cooled to room temperature with the furnace to remove the cathode iron sheet, washed with distilled water under microwave conditions, and vacuum dried to obtain cobalt elemental substance.

Preferably, the LiCoO ₂ in the step S1 is derived from the waste lithium battery of the mobile phone, and is recovered by manual disassembly and high temperature sintering.

Preferably, in the step S1, the consumption of NaCl and CaCl ₂ is 1:1 according to the molar ratio, and the consumption of the described LiCoO ₂ is 5% by mass.

Preferably, the vacuum drying conditions in the step S1 are: drying at a temperature of 200° C. for 12 hours.

Preferably, it is characterized in that, in the step S2, the heating rate is 10°C/min, and the temperature is kept at a constant temperature of 750°C for 2 hours.

Preferably, the processing process of the iron sheet in the step S3 is as follows: grinding the iron sheet with metallographic sandpaper in order from coarse to fine, cleaning it in a 10% sodium hydroxide solution under microwave conditions for about 5 minutes, and fully removing the surface Oil, soak it in dilute hydrochloric acid for 1~2min, remove the residual oxide layer on the surface, wash it with absolute ethanol and dry it for later use.

Preferably, the electrodeposition conditions in the step S4 are: at 750° C., the current density is 125-250 mA·cm ⁻² , and the deposition time is 8 h.

The beneficial effects of the present invention are:

The method can directly recover elemental cobalt from the positive electrode material of waste lithium batteries; the equipment is simple, easy to control, reduces the difficulty of the production process, and at the same time, the temperature is controlled at 750° C. Compared with the traditional method, the energy consumption is low and the environmental pollution is small; in addition, the molten salt The salts in the system are relatively common salts, which are not corrosive, and avoid the use of strong acids or alkalis, which is relatively safe.

Description of drawings

Fig. 1 is a kind of electron microscope image of the product obtained from the method for reclaiming and preparing cobalt elemental substance from waste and old lithium battery that utilizes molten salt method proposed by the present invention;

Fig. 2 is a kind of composition detection diagram of the product obtained from the method for recovering and preparing cobalt elemental substance from waste lithium battery by the molten salt method proposed by the present invention;

3 is a schematic XRD diagram of a product obtained by a method for recovering and preparing cobalt element from a waste lithium battery by a molten salt method proposed by the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments.

Cobalt is prepared by molten salt method, using lithium cobalt oxide recovered from the dismantling of used mobile phone batteries as the raw material. The molten salt system selects the binary system of sodium chloride and calcium chloride, namely NaCl-CaCl ₂ -LiCoO ₂ . The NaCl-CaCl ₂ system with an equal molar ratio can ensure a lower melting point, and the molar ratio of NaCl and CaCl ₂ is 1 : 1 has the lowest melting point, and the added amount of LiCoO ₂ is 5% of the total mass.

Mix NaCl, CaCl ₂ and LiCoO ₂ well in proportion, pour them into corundum crucible, and heat them in a resistance furnace. When the temperature in the furnace reaches 750°C, ensure that the lithium cobalt oxide is dissolved without decomposition reaction, and then the molten salt Incubate for 2h, so that LiCoO ₂ can reach the equilibrium state of dissolution.

The technology of the present invention will be further explained below in conjunction with the specific preparation process.

Weigh the analytical reagents NaCl and CaCl ₂ with a molar ratio of 1:1 with an electronic scale. The mass of LiCoO ₂ is 5% of the total mass, and the total mass of all salts is 150 g. Mix the three salts evenly and pour them into the dry corundum. In the pot, and placed in a vacuum drying box to dry at 200 ° C for 12 hours to remove residual moisture in the reagent, and then sealed and stored for later use;

Put the dried corundum kiln filled with medicine into the resistance to heat, heat the resistance furnace to 750 ℃, so that the raw material is in a completely molten state, and then keep the molten salt for 2 hours to make LiCoO ₂ reach saturation. The whole process is Under airtight conditions, flowing argon gas is introduced for atmosphere protection. Before the argon gas is introduced into the furnace, it first passes through a gas distillation column equipped with discolored silica gel to dry the argon gas. Argon gas is introduced from the argon gas inlet at the bottom of the furnace and discharged from the gas outlet at the top of the furnace. The upper and lower furnace covers are equipped with stainless steel to ensure the air tightness of the furnace. In order to prevent the furnace cover from being oxidized in a high temperature environment, the furnace cover is cooled with circulating water to prolong the service life of the furnace cover.

After the reaction is completed, it is cooled to room temperature. According to the characteristics that sodium chloride and calcium chloride are easily soluble in water, the product can be washed with hot distilled water to remove the residual salt to obtain iron flakes with products.

As shown in Figure 1, the prepared plated sheet was sent to a JEM-2800 field emission transmission electron microscope for inspection, and an electron microscope photograph of the surface coating of the sample was obtained. It can be seen from Figure 1 that the obtained pure cobalt has a good surface and a uniform texture.

As shown in Figure 2, the prepared plated sheet was sent to a field emission transmission electron microscope for component detection, and Fe and Co elements were mainly detected on the plated sheet, which proved that the method was feasible.

As shown in Figure 3, the composition of the plated sheet was tested by XRD, and it can be seen from the figure that pure cobalt was generated.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (5)

1. a method utilizing molten salt method to reclaim and prepare cobalt simple substance from waste and old lithium battery, is characterized in that, comprises the following steps: S1. Weigh quantitative NaCl, CaCl ₂ , and LiCoO ₂ , mix and grind the weighed reagents, and place them in a vacuum drying oven to remove moisture. The consumption of NaCl and CaCl ₂ is 1:1 according to the molar ratio. The amount of LiCoO ₂ is 5% by mass; S2. The dried mixed reagent is placed in a tubular resistance heating furnace, and the temperature is raised to 750° C. with the furnace and then kept at a constant temperature, so that LiCoO ₂ reaches a saturated and dissolved equilibrium state in the molten salt; S3. Use high-purity nickel wire to connect the treated iron sheet and high-purity graphite sheet with stainless steel rods to prepare electrodes. The iron sheet processing process is: grinding the iron sheet with metallographic sandpaper in order from coarse to fine, at a concentration of 10 Wash in % sodium hydroxide solution under microwave conditions for about 5 minutes, fully remove the surface grease, soak in dilute hydrochloric acid for 1-2 minutes, remove the residual oxide layer on the surface, rinse with anhydrous ethanol and dry it for later use; S4. Place the fabricated electrode in molten salt, so that the molten salt just immerses the iron sheet, and the high-purity graphite sheet is placed in parallel with the iron sheet for electrodeposition; S5. After the deposition is completed, the electrode is cooled to room temperature with the furnace to remove the cathode nickel sheet, washed with distilled water under microwave conditions, and cobalt element is obtained after vacuum drying. 2. a kind of method that utilizes molten salt method to recover and prepare cobalt simple substance from waste and old lithium battery according to claim ₁ , it is characterized in that, LiCoO in described step S1 Originates from mobile phone waste and old lithium battery, disassembles by hand , High temperature sintering method to recover. 3. A method for recovering and preparing cobalt element from waste lithium batteries by using molten salt method according to claim 1, characterized in that, in the step S1, the vacuum drying conditions are: drying at a temperature of 473K for 12h. 4. a kind of method that utilizes molten salt method to recover and prepare cobalt simple substance from waste lithium battery according to claim 1, is characterized in that, in described step S2, the heating rate is 10 ℃/min, at 750 ℃ of constant temperature insulation 4h . 5. a kind of method that utilizes molten salt method to recover and prepare cobalt simple substance from waste lithium battery according to claim 1, it is characterized in that, in described step S4, electrodeposition condition is: under 750 ℃, current density is 125 ~250mA·cm ^-2 , and the deposition time was 8h.

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