Method for recycling valuable metal lithium from waste ternary lithium ion battery

Abstract

The invention relates to a method for recovering valuable metal lithium from a waste ternary lithium ion battery, which comprises the following steps of: (1) discharging the waste ternary lithium ion battery, crushing, and sorting into black powder mixed with positive and negative electrode materials; (2) mixing the mixed black powder with a catalyst, and carrying out high-speed ball milling to improve the reduction activity of graphite; (3) roasting the powder in an inert atmosphere to obtain reduction roasting slag; and (4) putting the reduction roasting slag into a high-pressure kettle, adding deionized water, carrying out pressure boiling and lithium leaching reaction under the conditions of pressurization and heating, filtering after the reaction is completed, adding sodium carbonate into filtrate to precipitate lithium, and then filtering and drying to obtain a lithium carbonate product. According to the method, the graphite contained in the negative electrode is activated into the reducing agent, the ternary positive electrode material is reduced, the reduced ternary positive electrode material is directly autoclaved with water to extract lithium, an extra exogenous reducing agent is not needed, a chemical reagent is not needed, the method is simple, environment-friendly and low in cost, and the lithium extraction yield is relatively high.

Description

Technical Field

[0001] The invention relates to a method for recovering valuable metals from waste lithium-ion batteries, and in particular to a method for recovering valuable metal lithium from waste ternary lithium-ion batteries. Background Art

[0002] Ternary lithium-ion batteries are widely used in the new energy vehicle industry for their high energy density and excellent cycle performance. It is estimated that by 2025, the market share of ternary lithium-ion batteries will exceed 40%. The grade of valuable metal lithium in retired ternary lithium-ion batteries is much higher than that of natural ores, and they are called "urban minerals". The effective recycling of valuable metal lithium can not only solve the problem of environmental pollution, but also alleviate the contradiction between the supply and demand of lithium resources to a certain extent, and has high environmental and economic benefits.

[0003] The recycling of waste lithium-ion batteries is currently a hot research topic. So far, the number of related patent documents published in the China Patent Literature Database alone has reached more than 1,800.

[0004] The existing recycling technology of waste lithium-ion batteries can be roughly divided into two categories: one is the pyrometallurgical recycling method, and the other is the wet recycling method.

[0005] The pyrometallurgical recovery method is favored in industrial applications because of its simple process, high efficiency, and good adaptability to different types of raw materials. However, this method requires an extremely high reduction temperature (usually 1300-1500°C, such as the reduction temperature used in a pyrometallurgical recovery method for waste lithium-ion batteries disclosed in CN113061725A; after some improvements, it still requires 600-1000°C, such as the pyrometallurgical recovery process for waste lithium-ion battery powder disclosed in CN112111651A), which leads to high energy consumption and a large loss of lithium elements, thus affecting its economic benefits.

[0006] Wet recovery technology has high recovery rate, good selectivity and relatively mild operating conditions. However, the existing wet recovery process is relatively lengthy, and requires the use of chemical leaching agents and / or extractants, with complicated operating steps, low efficiency, high cost, and a large amount of wastewater discharge, polluting the environment. For example, CN102569941A discloses a method for wet recovery of negative electrode materials of lithium-ion batteries, CN115449636A discloses a recycling and regeneration process for positive electrode materials of lithium-ion batteries, CN 104745823A discloses a method for recovering lithium from waste lithium-ion batteries, and CN108504868A discloses a method for recovering metallic lithium from waste lithium-ion batteries. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for recovering valuable metallic lithium from waste ternary lithium-ion batteries, which is simple to operate, does not require the use of acids, alkalis and / or organic chemical reagents, has mild reaction conditions, is environmentally friendly, has high efficiency, low cost and good economic benefits.

[0008] The technical solution adopted by the present invention to solve the technical problem is a method for recovering valuable metal lithium from waste ternary lithium-ion batteries, comprising the following steps:

[0009] (1) Discharging the waste ternary lithium-ion batteries, crushing and sorting them to obtain mixed black powder;

[0010] (2) mixing the mixed black powder obtained in step (1) with a catalyst and then subjecting the mixture to high-speed ball milling to improve the reduction activity of graphite;

[0011] (3) roasting the mixed black powder after high-speed ball milling in step (2) under a protective atmosphere to obtain reduced roasted slag;

[0012] (4) placing the reduced roasted slag obtained in step (3) in an autoclave, adding deionized water, and performing pressure cooking and lithium leaching reaction under pressurized and heated conditions. After the reaction is completed, filtering to obtain a filtrate; adding sodium carbonate to the obtained filtrate to precipitate lithium. After the lithium precipitation reaction is completed, filtering to obtain a filter cake, and drying to obtain a lithium carbonate product.

[0013] Further, in step (1), the chemical formula of the positive electrode material in the waste ternary lithium-ion battery is LiNi x Co y Mn z O2, where 0≤x≤1, 0≤y≤1, 0≤z≤1, x+y+z=1.

[0014] Furthermore, in step (1), the mixed black powder is a mixed powder of positive electrode material powder and negative electrode material powder;

[0015] Furthermore, in step (2), the rotation speed of the high-speed ball mill is 500-1500 rpm; the catalyst is one or more of a chromium catalyst, a titanium catalyst, and a niobium catalyst; and the amount of the catalyst added is 0.1-1.5% of the mass of the mixed black powder.

[0016] Furthermore, in step (3), the protective atmosphere is one or more of nitrogen, argon, natural gas, argon-hydrogen mixture, and hydrogen; the calcination temperature is 470-530° C. (preferably 480-520° C.); and the calcination time is 4-13 h (preferably 6-12 h).

[0017] Furthermore, in step (4), the temperature of the autoclave lithium leaching reaction is 120-210° C. (preferably 160-200° C.), and the reaction time is 30-50 h (preferably 35-45 h).

[0018] Furthermore, in step (4), the solid-liquid mass volume ratio between the reduced roasted slag and the added deionized water is 1:15 to 25.

[0019] The method of recovering valuable metals from waste ternary lithium-ion batteries of the present invention utilizes the activated graphite powder contained in the negative electrode of the waste battery as a reducing agent to reduce the high-valent positive electrode powder to low-valent oxides of nickel, cobalt and manganese, lithium oxides and hydroxides, thereby reducing the difficulty of wet leaching and improving the efficiency of lithium leaching. The preferred solution is to roast the positive and negative electrode mixed powders within a temperature range of 470 to 530°C, so that the binder that acts as a bond between the positive and negative electrode powders and the copper and aluminum foils is decomposed and inactivated, thereby improving the powder removal rate of the battery powder loaded on the copper and aluminum foils. In addition, the F in the binder polyvinylidene fluoride (PVDF) on the positive electrode sheet will be removed in the form of gaseous HF, thereby reducing the fluorine content in the positive and negative electrode mixed powders of the battery, making the lithium contained therein easier to leach, and further improving the efficiency of lithium leaching.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1) the graphite contained in the lithium-ion battery itself has the characteristic of being reducible after activation, and the positive electrode material is reduced and roasted without the need for an exogenous reducing agent, thereby reducing the cost and improving the lithium yield; 2) the positive electrode powder obtained by reduction is directly pressure-boiled and leached with water as a solvent to extract lithium, without the need for using an acid or alkaline leaching agent or an organic extractant, which is environmentally friendly and reduces the leaching cost; 3) the operation is simple, the reaction conditions are relatively mild, the efficiency is high, and the economic benefits are good. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The XRD pattern of the lithium carbonate product obtained in Example 1;

[0022] Figure 2 The following are SEM morphologies of the lithium carbonate products obtained in Examples 2 and 3. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with specific embodiments and accompanying drawings, but the present invention is not limited to the following embodiments. Unless otherwise defined, all professional terms used hereinafter have the same meaning as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present application.

[0024] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0025] Example 1

[0026] The method for recovering valuable metallic lithium from waste ternary lithium-ion batteries in this embodiment comprises the following steps:

[0027] (1) Discarded ternary lithium-ion batteries are soaked in salt water and discharged, and then crushed and sorted after drying to obtain mixed black powder of positive and negative electrode materials;

[0028] (2) mixing the mixed black powder obtained in step (1) with catalyst Cr powder equivalent to 0.2% by mass of the mixed black powder, and then subjecting the mixed black powder to high-speed ball milling to improve the reducibility of graphite; the ball milling speed is 600 rpm;

[0029] (3) subjecting the mixed black powder after high-speed ball milling in step (2) to reduction roasting in a nitrogen atmosphere to obtain reduction roasted slag; the roasting temperature is 520° C., and the roasting time is 8 h;

[0030] (4) 3 g of the reduced roasted slag obtained in step (3) was placed in an autoclave, 60 ml of deionized water was added, so that the mass volume solid-liquid ratio between the reduced roasted slag and the deionized water was 1:20 g / ml, stirred for 20 min, pressurized to 0.15 MPa, heated to 180° C., reacted for 40 h, filtered, and a filtrate was obtained; the lithium ion content in the filtrate was detected by ICP, and the Li + :CO3 2- The molar ratio is 2:1, sodium carbonate is added to the obtained filtrate to precipitate lithium, and then filtered to obtain a filter cake, which is dried to obtain 0.560 g of lithium carbonate product.

[0031] Example 2

[0032] The method for recovering valuable metallic lithium from waste ternary lithium-ion batteries in this embodiment comprises the following steps:

[0033] (1) Discharging the waste ternary lithium-ion batteries by soaking them in salt water, drying them, crushing them, and sorting them to obtain mixed black powder of positive and negative electrode materials;

[0034] (2) mixing the mixed black powder obtained in step (1) with catalyst Nb powder equivalent to 0.1% by mass of the mixed black powder, and then subjecting the mixture to high-speed ball milling to improve the graphite reduction activity; the ball milling speed is 1500 rpm;

[0035] (3) reducing and roasting the mixed black powder after high-speed ball milling in step (2) in a 90% / 10% nitrogen / natural gas atmosphere to obtain reduced roasted slag; the roasting temperature is 500° C. and the roasting time is 6 hours;

[0036] (4) 3 g of reduced calcined slag was placed in an autoclave, 75 ml of deionized water was added, and the solid-liquid mass volume ratio between the reduced calcined slag and the added deionized water was 1:25. The mixture was stirred for 20 min, pressurized to 0.12 MPa, heated to 200 °C, reacted for 35 h, filtered, and a filtrate was obtained. The lithium ion content in the filtrate was detected by ICP. + : Sodium carbonate was added to the filtrate at a molar ratio of 2:1 to precipitate lithium, and then filtered to obtain a filter cake, which was dried to obtain 0.548 g of lithium carbonate product.

[0037] Example 3

[0038] The method for recovering valuable metallic lithium from waste ternary lithium-ion batteries in this embodiment comprises the following steps:

[0039] (1) Discharging the waste ternary lithium-ion batteries by soaking them in salt water, drying them, crushing them, and sorting them to obtain mixed black powder of positive and negative electrode materials;

[0040] (2) mixing the mixed black powder with catalyst Nb powder equivalent to 0.1% of the mass of the mixed black powder, and then performing high-speed ball milling to improve the graphite reduction activity; the ball milling speed is 1200 rpm;

[0041] (3) reducing and roasting the mixed black powder after high-speed ball milling in step (2) in a 90% / 10% nitrogen / natural gas atmosphere to obtain reduced roasted slag; the roasting temperature is 480° C. and the roasting time is 10 h;

[0042] (4) 3 g of the reduced calcined slag obtained in step (3) was placed in an autoclave, 45 ml of deionized water was added, and the solid-liquid mass volume ratio between the reduced calcined slag and the added deionized water was 1:15, stirred for 20 min, pressurized to 0.16 MPa, heated to 160° C., reacted for 45 h, filtered, and a filtrate was obtained; the lithium ion content in the filtrate was detected by ICP, and the Li + : Sodium carbonate was added to the filtrate at a molar ratio of 2:1 to precipitate lithium, and then filtered to obtain a filter cake, which was dried to obtain 0.553 g of lithium carbonate product.

[0043] Example 4

[0044] The method for recovering valuable metallic lithium from waste ternary lithium-ion batteries in this embodiment comprises the following steps:

[0045] (1) Discharging the waste ternary lithium-ion batteries by soaking them in salt water, drying them, crushing them, and sorting them to obtain mixed black powder of positive and negative electrode materials;

[0046] (2) mixing the mixed black powder with catalyst Ti powder equivalent to 0.8% of the mass of the mixed black powder and then performing high-speed ball milling to improve the graphite reduction activity; the ball milling speed is 1500 rpm;

[0047] (3) reducing and calcining the mixed black powder after high-speed ball milling in step (2) in a 95% / 5% argon / hydrogen atmosphere to obtain reduced calcined slag; the calcination temperature is 500° C. and the calcination time is 12 h;

[0048] (4) 3 g of the reduced calcined slag obtained in step (3) was placed in an autoclave, 60 ml of deionized water was added, and the solid-liquid mass volume ratio between the reduced calcined slag and the added deionized water was 1:20, stirred for 20 min, pressurized to 0.13 MPa, heated to 180° C., reacted for 40 h, filtered, and a filtrate was obtained; the lithium ion content in the filtrate was detected by ICP, and the Li + : Sodium carbonate was added to the filtrate at a molar ratio of 2:1 to precipitate lithium, and then filtered to obtain a filter cake, which was dried to obtain 0.551 g of lithium carbonate product.

[0049] The filtrates obtained in Examples 1-4 were tested for nickel, cobalt, manganese and lithium ion concentrations, and the leaching rates were calculated and tested: where c L is the mass fraction of the relevant metal element in the leaching solution (mg / g), m L is the mass of the leaching solution (g); c S is the mass fraction of the relevant metal elements in the black powder raw material (mg / g), m S is the mass of the black powder raw material (g). The purity of the obtained lithium carbonate product was tested, and the test results are shown in Table 1.

[0050] Table 1 Nickel, cobalt, manganese, lithium leaching rates and lithium carbonate product purity test results of Examples 1-4

[0051]

[0052] As can be seen from Table 1, the recovery method of the present invention directly extracts lithium by hydrothermal method after pre-reduction treatment, and can separate and recover valuable metallic lithium in waste ternary lithium-ion batteries without using external reducing agent or external leaching agent, and has a high lithium element yield (see Table 2), which has the advantages of environmental protection, high efficiency, good economic benefits, etc.

[0053] Table 2 Lithium yield test results of Examples 1-4

[0054] Example 1 Example 2 Example 3 Example 4 Lithium yield (%) 92.0％ 89.5％ 90.6％ 90.2％

[0055] In each embodiment, the lithium content in the reduction roasting slag obtained in step (3) is 3.8%, and the total lithium content in 3g of reduction roasting slag is 0.114g. If all of it is converted into Li2CO3, 0.6069g of lithium carbonate can be obtained in theory. The lithium yield listed in Table 2 is calculated based on this and the quality and purity of the lithium carbonate products actually obtained in each embodiment.

[0056] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the patent of the present invention.

Claims

1. A method for recovering valuable metal lithium from waste ternary lithium-ion batteries, characterized in that: The steps include: (1) Discharging the used ternary lithium-ion batteries, crushing and sorting them to obtain mixed black powder; (2) mixing the mixed black powder obtained in step (1) with a catalyst and subjecting the mixture to high-speed ball milling to improve the reduction activity of graphite; (3) roasting the mixed black powder after high-speed ball milling in step (2) under a protective atmosphere to obtain reduced roasted slag; (4) placing the reduced roasted slag obtained in step (3) in an autoclave, adding deionized water, and performing pressure cooking and lithium leaching reaction under pressurized and heated conditions. After the reaction is completed, filtering is performed to obtain a filtrate; adding sodium carbonate to the obtained filtrate to precipitate lithium. After the lithium precipitation reaction is completed, filtering is performed to obtain a filter cake, and drying is performed to obtain a lithium carbonate product.

2. A method for recovering valuable metallic lithium from waste ternary lithium-ion batteries according to claim 1, characterized in that: In step (1), the mixed black powder is a mixed powder of positive electrode material powder and negative electrode material powder.

3. A method for recovering valuable metallic lithium from waste ternary lithium-ion batteries according to claim 1 or 2, characterized in that: In step (2), the rotation speed of the high-speed ball mill is 500-1500 rpm; the catalyst is one or more of chromium, titanium, and niobium, and the amount of the catalyst added is 0.1-1.5% of the mass of the mixed black powder.

4. A method for recovering valuable metallic lithium from waste ternary lithium-ion batteries according to claim 1 or 2, characterized in that: In step (3), the protective atmosphere is one or more of nitrogen, argon, natural gas, argon-hydrogen mixture, and hydrogen; the calcination temperature is 470-530° C., and the calcination time is 4-13 h.

5. A method for recovering valuable metallic lithium from waste ternary lithium-ion batteries according to claim 4, characterized in that: In step (3), the calcination temperature is 480-520°C, and the calcination time is 6-12 hours.

6. A method for recovering valuable metallic lithium from waste ternary lithium-ion batteries according to claim 1 or 2, characterized in that: In step (4), the temperature of the autoclave lithium leaching reaction is 120-210° C., and the reaction time is 30-50 h.

7. A method for recovering valuable metallic lithium from waste ternary lithium-ion batteries according to claim 6, characterized in that: The temperature of the autoclave lithium leaching reaction is 160-200°C, and the reaction time is 35-45h.

8. A method for recovering valuable metallic lithium from waste ternary lithium-ion batteries according to claim 1 or 2, characterized in that: In step (4), the solid-liquid mass volume ratio between the reduced roasted slag and the added deionized water is 1:15-25.

9. A method for recovering valuable metallic lithium from waste ternary lithium-ion batteries according to claim 1, characterized in that: The purity of the lithium carbonate product is >99%.

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