Method for recovering valuable metals from waste lithium ion batteries

Abstract

The invention relates to the technical field of secondary resource recycling, in particular to a method for recycling valuable metals from waste lithium ion batteries. The method comprises the following steps: soaking and roasting a positive plate of the waste lithium ion battery in an organic solvent in sequence to obtain a roasted product; mixing the roasted product with a waste biomass material, and performing reduction roasting in a protective atmosphere to obtain a reduction product; carrying out carbonic acid water leaching reaction on the reduction product, and then filtering the obtained carbonic acid water leaching reaction liquid; concentrating and crystallizing the filtrate to obtain lithium carbonate; carrying out acid leaching on the filter residues, and then filtering the obtained acid leaching solution to obtain a solution of salt containing valuable metals; the temperature of reduction roasting is 550-600 DEG C, the time is 60-100 minutes, and the mass ratio of the roasted product to the waste biomass material is 1: (0.10-0.15). According to the method, under the specific reduction roasting condition, the valuable metal in the material exists in the form of oxide, leaching is better facilitated, the acid consumption is reduced, and the leaching rate of the valuable metal is effectively increased.

Description

Technical Field

[0001] The invention relates to the technical field of secondary resource recycling and reuse, and in particular to a method for recycling valuable metals from waste lithium-ion batteries. Background Art

[0002] Waste lithium-ion batteries are classified as hazardous solid waste because they contain heavy metals and toxic organic matter. If they are discarded without proper treatment, they will pose a huge threat to the ecological environment and public health. At the same time, waste ternary lithium-ion batteries are rich in precious metal resources such as Li, Ni, Co, and Mn, and their content is even higher than that of natural ores. Therefore, recycling these precious metals is not only conducive to resource protection, but also effectively alleviates the shortage of resources such as Li, Ni, Co, and Mn.

[0003] To recover valuable metals from waste ternary lithium-ion batteries, hydrometallurgical or pyrometallurgical processes can be used. Although the specific operations of these two recycling methods are different, their basic principles are to reduce the valence state of transition metals, destroy MAO bonds, and then destroy the material structure. Hydrometallurgical methods usually use inorganic acids such as H2SO4, HNO3, HCl, or organic acids such as oxalic acid, citric acid, tartaric acid, and formic acid for treatment, and often require the use of reducing agents such as H2O2, NaHSO3, glucose, and cellulose. However, excess H2O2 is easily decomposed during the leaching process, which not only increases costs and causes waste of resources, but also increases the difficulty of pollutant treatment. Pyrometallurgical processes usually use reducing agents such as graphite and lignite to leach waste LiNi x Co y Mn z O2 (ternary lithium-ion battery) is reduced to Co and Ni metal phases, but the preferential extraction of lithium cannot be achieved. In addition, in the subsequent acid leaching process, metal Co and Ni react with acid to produce flammable and explosive hydrogen, and the leaching rate of metal Co and Ni is low and the amount of acid used is large. At the same time, reducing agents such as graphite and lignite are expensive or contain impurities, which is not conducive to reducing production costs and the concept of green and low-carbon. Therefore, how to develop an environmentally friendly method that can preferentially recover lithium from waste lithium-ion batteries, and effectively improve the leaching rate of valuable metals nickel, cobalt and manganese during acid leaching and reduce the amount of acid used has become a difficult problem that needs to be solved urgently in this field. Summary of the invention

[0004] The purpose of the present invention is to provide a method for recovering valuable metals from waste lithium-ion batteries to solve the problems existing in the above-mentioned prior art.

[0005] In one aspect, the present invention provides a method for recovering valuable metals from waste lithium-ion batteries, comprising the following steps:

[0006] (1) soaking and calcining the positive electrode sheet of the waste lithium-ion battery in an organic solvent in sequence to obtain a calcined product;

[0007] (2) mixing the roasted product with waste biomass materials, and then performing reduction roasting under a protective atmosphere to obtain a reduced product;

[0008] (3) subjecting the reduction product to a carbonic acid water leaching reaction, and then filtering the obtained carbonic acid water leaching reaction liquid to obtain a filtrate and a filter residue;

[0009] (4) concentrating and crystallizing the filtrate to obtain lithium carbonate;

[0010] (5) acid leaching the filter residue, and then filtering the obtained acid leaching solution to obtain a salt solution containing the valuable metals nickel, cobalt and manganese;

[0011] There is no order of precedence between steps (4) and (5);

[0012] The reduction roasting temperature is 550-600° C., the time is 60-100 min, and the mass ratio of the roasting product to the waste biomass material is 1:(0.10-0.15).

[0013] Preferably, the solvent used for the organic solvent soaking is N-methylpyrrolidone, the temperature of the organic solvent soaking is 90-110° C., the time of the organic solvent soaking is 2.5-3.5 hours, and the organic solvent soaking process is ultrasonicated for 8-12 minutes.

[0014] Preferably, the calcination temperature is 500-800° C., and the calcination time is 2-6 hours.

[0015] Preferably, the waste biomass material includes at least one of straw powder and sawdust powder.

[0016] Preferably, the heating rate to the reduction roasting temperature is 5-10°C / min.

[0017] Preferably, the steps of the carbonic acid water leaching reaction are:

[0018] The reduction product is ground and mixed with water to obtain a mixed solution,

[0019] Carbon dioxide is introduced into the mixed solution to carry out a carbonic acid water leaching reaction.

[0020] Preferably, the temperature of the carbonated water immersion reaction is 20-80° C., the mass volume ratio of the reduction product to water is 1 g:(25-100) mL, the introduction rate of the carbon dioxide is 100-150 mL / min, and the time of the carbonated water immersion reaction is 1-5 h.

[0021] Preferably, the acid solution used in the acid leaching is a sulfuric acid solution with a concentration of 0.6-1.2 mol / L.

[0022] Preferably, the acid leaching temperature is 30-75°C, and the acid leaching time is 40-100 min.

[0023] Preferably, the mass volume ratio of the filter residue to the sulfuric acid solution is 1 g:(4-10) mL.

[0024] The present invention has the following beneficial effects:

[0025] The invention provides a method for recovering valuable metals of waste lithium ion batteries, comprising the following steps: (1) soaking and roasting a positive electrode sheet of the waste lithium ion battery in an organic solvent in sequence to obtain a roasting product; (2) mixing the roasting product with a waste biomass material, and then performing reduction roasting under a protective atmosphere to obtain a reduction product; (3) performing a carbonic acid water leaching reaction on the reduction product, and then filtering the obtained carbonic acid water leaching reaction liquid to obtain a filtrate and a filter residue; (4) concentrating and crystallizing the filtrate to obtain lithium carbonate; (5) performing an acid leaching on the filter residue, and then filtering the obtained acid leaching liquid to obtain a solution containing salts of valuable metals nickel, cobalt and manganese; wherein step (4) and step (5) are performed in no order; the temperature of the reduction roasting is 550-600°C, the time is 60-100min, and the mass ratio of the roasting product to the waste biomass material is 1:(0.10-0.15).

[0026] The present invention adjusts the temperature of reduction roasting to 550-600°C. The lower temperature reduces energy consumption, and the main components of the reduction product obtained by combining with other reduction roasting conditions are cobalt oxide, nickel oxide, manganese oxide and lithium carbonate. In the subsequent acid leaching process, the valuable metal oxides are more easily leached by acid. In addition, the inventors have also found that at the reduction roasting temperature within the above range, the amount of acid used is reduced, thereby achieving more environmentally friendly green production.

[0027] In addition, the present invention adopts the method of carbonated water leaching to preferentially extract lithium element, thereby improving the recovery rate and purity of lithium element, and further improving the efficiency and value of resource utilization.

[0028] The recycling method provided by the present invention has a reasonable design of the entire process and clear steps, and is suitable for recycling various types of waste lithium-ion batteries such as waste lithium cobalt oxide batteries, waste ternary batteries and waste high-nickel batteries. It has the potential to recycle waste lithium-ion batteries on an industrial scale and increase the added value of recycled positive electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and other objects, features and advantages of the present invention will be apparent from the following description of preferred embodiments and accompanying drawings which illustrate the subject matter of the present invention and its use, in which:

[0030] Figure 1 The figure is a schematic flow chart of the method for recovering valuable metals from waste lithium-ion batteries of the present invention;

[0031] Figure 2 The XRD test diagrams of the reduction products obtained in Examples 1-2 and Comparative Examples 1-2 and 7;

[0032] Figure 3 The XRD test diagrams of the reduction products obtained in Examples 1, 3, 4 and Comparative Examples 3-4;

[0033] Figure 4 The XRD test diagrams of the reduction products obtained in Examples 1, 5, 6 and Comparative Examples 5-6;

[0034] Figure 5 The XPS test results of the calcined product and the reduced product obtained in Example 1 are shown;

[0035] Among them, (a) is the Li 1s test result at a binding energy of 59-52 eV, (b) is the Ni 2p test result at a binding energy of 883-850 eV, (c) is the Co 2p test result at a binding energy of 810-775 eV, and (d) is the Mn 2p test result at a binding energy of 660-635 eV;

[0036] Figure 6 The X-ray diffraction pattern of lithium carbonate obtained in Example 1;

[0037] Figure 7 This is a SEM characterization image of lithium carbonate obtained in Example 1;

[0038] Figure 8 This is a SEM image of the filter residue obtained in step (7) of Example 1;

[0039] Fig. 9 This is the EDS test image of the filter residue obtained in step (7) of Example 1;

[0040] Fig.10 This is the distribution diagram of each atom in the filter residue insoluble in sulfuric acid obtained in step (7) of Example 1. DETAILED DESCRIPTION

[0041] The present invention will be described below by specific embodiments, and it will be appreciated by those skilled in the art that the following specific embodiments are only for illustrative purposes, and do not limit the scope of the present invention in any way. In addition, in the following embodiments, unless otherwise specified, the reagents and equipment used are all commercially available. If in the following embodiments, specific treatment conditions and treatment methods are not clearly described, then conditions and methods known in the art can be adopted to process.

[0042] A method for recovering valuable metals from waste lithium-ion batteries comprises the following steps:

[0043] (1) soaking and calcining the positive electrode sheet of the waste lithium-ion battery in an organic solvent in sequence to obtain a calcined product;

[0044] (2) mixing the roasted product with waste biomass materials, and then performing reduction roasting under a protective atmosphere to obtain a reduced product;

[0045] (3) subjecting the reduction product to a carbonic acid water leaching reaction, and then filtering the obtained carbonic acid water leaching reaction liquid to obtain a filtrate and a filter residue;

[0046] (4) concentrating and crystallizing the filtrate to obtain lithium carbonate;

[0047] (5) acid leaching the filter residue, and then filtering the obtained acid leaching solution to obtain a salt solution containing the valuable metals nickel, cobalt and manganese;

[0048] There is no order of precedence between steps (4) and (5);

[0049] The reduction roasting temperature is 550-600° C., the time is 60-100 min, and the mass ratio of the roasting product to the waste biomass material is 1:(0.10-0.15).

[0050] The present invention controls the reduction roasting conditions, controls the reduction roasting temperature at 550-600°C, and combines with other reduction roasting conditions to mainly convert the material into CoO, NiO, MnO and Li2CO3, rather than the Co and Ni metal single phases that are currently commonly converted. Metal oxides are more easily leached by acid than metal single phases, which is beneficial to the subsequent acid leaching process, increases the leaching rate of valuable metals, reduces the amount of acid used, and is green and environmentally friendly; in addition, a lower reduction roasting temperature can reduce energy consumption, thereby reducing process costs.

[0051] The invention sequentially soaks and roasts the positive electrode sheet of the waste lithium ion battery in an organic solvent to obtain a roasted product.

[0052] In some embodiments of the present invention, the positive electrode sheet of the waste lithium ion battery is obtained by a method comprising the following steps: discharging the waste lithium ion battery until its voltage is ≤2V, disassembling the waste lithium ion battery after the discharge treatment in a glove box, removing the aluminum shell, positive and negative terminals, sealing rings, cover plates, negative electrode sheets and diaphragms, and obtaining the positive electrode sheet of the waste lithium ion battery. In some embodiments of the present invention, there is an electrolyte on the surface of the positive electrode sheet of the waste lithium ion battery. At this time, dimethyl carbonate (DMC) is used for washing to remove the electrolyte and obtain a clean positive electrode sheet of the waste lithium ion battery for use in subsequent steps.

[0053] In some embodiments of the present invention, the waste lithium-ion batteries include at least one of waste lithium cobalt oxide batteries, waste ternary batteries and waste high-nickel batteries; the discharge treatment method includes salt solution immersion discharge, liquid nitrogen freezing discharge, graphite powder short-circuit discharge or charger discharge.

[0054] In some embodiments of the present invention, when the selected discharge treatment method is salt solution immersion discharge, the salt solution is a sodium chloride solution, and the mass concentration of the sodium chloride solution is 4%-6%, specifically 4%, 5%, and 6%.

[0055] In the present invention, the organic solvent immersion can dissolve the binder in the positive electrode sheet to facilitate the stripping of aluminum and the positive electrode material.

[0056] In some embodiments of the present invention, the solvent used for the organic solvent soaking is N-methylpyrrolidone (NMP); the temperature of the organic solvent soaking is 90-110°C, specifically 90°C, 100°C or 110°C; the time of the organic solvent soaking is 2.5-3.5h, specifically 2.5h, 3h or 3.5h; the ultrasonic wave is applied for 8-12min during the organic solvent soaking, specifically 8min, 10min or 12min, the power of the ultrasonic wave is 100-150W, and the ultrasonic wave is applied in the last stage of the organic solvent soaking, that is, the ultrasonic wave is assisted in the last 8-12min of the organic solvent soaking. The present invention has no special limitation on the solid-liquid ratio during the organic solvent soaking, and it is sufficient to soak the positive electrode sheet of the waste lithium-ion battery.

[0057] In some embodiments of the present invention, the positive electrode sheet of the waste lithium-ion battery is cut into fragments before being soaked in an organic solvent, and the size of the fragments is 1.5 cm×1.5 cm.

[0058] In some embodiments of the present invention, the positive electrode sheet of the waste lithium-ion battery is soaked in an organic solvent, the obtained organic soaking solution is centrifuged, and the obtained precipitate is washed, dried, and then roasted to obtain a roasted product. In some embodiments of the present invention, the centrifugal speed is 6000-8000 rpm and the time is 5-10 min.

[0059] In some embodiments of the present invention, the filter residue obtained after filtering the organic solvent soaking liquid is washed with ethanol. After ethanol washing, the organic solvent used for organic solvent soaking can be effectively removed; the drying temperature is 60-100°C, and the drying time is 10-16h.

[0060] In some embodiments of the present invention, the calcination is carried out in an air atmosphere, the calcination temperature is 500-800°C, specifically 500°C, 600°C, 700°C or 800°C, and the calcination time is 2-6h, specifically 2h, 3h, 5h, 6h.

[0061] After calcination, the positive electrode sheets of waste lithium-ion batteries can effectively remove polyvinylidene fluoride (PVDF) and carbon black in the positive electrode sheets and retain the active substances therein.

[0062] After obtaining the roasted product, the present invention mixes the roasted product with waste biomass materials, and then performs reduction roasting under a protective atmosphere to obtain a reduced product.

[0063] The present invention uses waste biomass materials as reducing agents, which are low in price and abundant in source. Reducing gas and biochar are generated during the reduction roasting process, which promotes the decomposition of active substances in the positive electrode sheets of waste lithium-ion batteries. In addition, during the reduction process, there is no need to add H2O2 as a reducing agent, which saves costs.

[0064] In the present invention, the reduction roasting temperature is 550-600° C., specifically 550° C. and 600° C. In some embodiments of the present invention, the reduction roasting time is 60-100 min, specifically 60 min, 80 min or 100 min, and the heating rate to the reduction roasting temperature is 5-10° C. / min, preferably 8-10° C. / min, specifically 8° C. / min and 10° C. / min.

[0065] In some embodiments of the present invention, the method for preparing the waste biomass material comprises the following steps: crushing the waste biomass, washing and vacuum drying in sequence to obtain the waste biomass material; the washing can precipitate impurities such as soil adhering to the waste biomass. In some embodiments of the present invention, the washing method is soaking in deionized water, the number of times of soaking in deionized water is 2-6 times, after each soaking, preferably the solid-liquid separation is carried out by suction filtration, and the obtained solid is soaked for the next time, and the time of a single soaking is 5-20 minutes, preferably 15 minutes; the temperature of the vacuum drying is 110-120°C, preferably 110-115°C, and the time of the vacuum drying is not limited until the dry product has a constant weight.

[0066] In some embodiments of the present invention, the mass ratio of the roasting product to the waste biomass material is 1:(0.10-0.15), preferably 1:(0.10-0.14), specifically 1:0.10, 1:0.12, 1:0.14, the waste biomass material includes one or more of straw powder and sawdust powder, preferably straw powder, specifically corn straw powder; the particle size of the waste biomass material is 1mm-5mm.

[0067] In some embodiments of the present invention, the roasting product is mixed with the waste biomass material by ball milling, and the ball milling is performed at room temperature for 120-300 min, preferably 240 min.

[0068] In some embodiments of the present invention, the protective atmosphere is nitrogen or an inert gas atmosphere (such as argon).

[0069] After obtaining the reduction product, the present invention conducts a carbonic acid water leaching reaction on the reduction product, and then filters the obtained carbonic acid water leaching reaction liquid to obtain a filtrate and a filter residue.

[0070] In some embodiments of the present invention, the step of the carbonic acid water leaching reaction is: grinding the reduction product and mixing it with water to obtain a mixed solution, and introducing carbon dioxide into the mixed solution to carry out the carbonic acid water leaching reaction.

[0071] In some embodiments of the present invention, the grinding is performed at room temperature, and the grinding time is 2-10 min, specifically 2 min, 5 min, 10 min, preferably 5 min.

[0072] In some embodiments of the present invention, the temperature of the carbonated water immersion reaction is 20-80°C, specifically 20°C, 40°C, 45°C, 50°C, 70°C, 80°C, preferably 40-70°C, and more preferably 50-65°C; the time of the carbonated water immersion reaction is 1-5h, preferably 2-4h, and more preferably 3h; the mass volume ratio of the reduction product to water is 1g:(25-100)mL, preferably 1g:(50-75)mL, and more preferably 1g:70mL; the carbon dioxide introduction rate is 100-150mL / min, preferably 125-140mL / min, and more preferably 130mL / min.

[0073] The present invention concentrates and crystallizes the filtrate obtained by filtering the carbonic acid water immersion reaction liquid to obtain lithium carbonate.

[0074] In some embodiments of the present invention, the temperature of the concentrated crystallization is 100°C; the time of the concentrated crystallization treatment is not limited, until the volume of the filtrate is reduced to 15%-20% of the original volume of the carbonated water immersion reaction liquid; the washing solvent is boiling water, the number of times is ≥1; the drying temperature is 90-110°C; the present invention has no special limitation on the drying time, and it can be dried to constant weight.

[0075] The invention carries out acid leaching on the filter residue obtained by filtering the carbonated water leaching reaction liquid, and then filters the obtained acid leaching liquid to obtain a salt solution containing the valuable metals nickel, cobalt and manganese.

[0076] In some embodiments of the present invention, before the acid leaching, the filter residue is washed and dried in sequence; the washing can remove impurity ions; the washing method is water immersion washing, and the number of immersions is ≥3 times; the drying is vacuum drying, the vacuum drying temperature is 110-130°C, and the vacuum drying time is 10-14h.

[0077] In some embodiments of the present invention, the acid solution used for acid leaching is a sulfuric acid solution, and the concentration of the sulfuric acid solution is 0.6-1.2 mol / L, specifically 0.6 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L; the temperature of the acid leaching is 30-75°C, specifically 30°C, 45°C, 60°C, 75°C, and the time of the acid leaching is 40-100 min, specifically 40 min, 60 min, 80 min, 100 min.

[0078] In some embodiments of the present invention, the mass volume ratio of the filter residue to the sulfuric acid solution is 1g:(4-10)mL (solid-liquid ratio), specifically 1g:4mL, 1g:6mL, 1g:8mL, 1g:10mL.

[0079] The schematic diagram of the process for recovering valuable metals from waste lithium-ion batteries provided by the present invention is as follows: Figure 1 shown.

[0080] The technical scheme of the present invention will be described clearly and completely below in conjunction with the accompanying drawings and embodiments. The embodiments of the present application are only used as examples, and all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0081] Example 1

[0082] (1) The discarded biomass corn stalks were crushed and soaked in deionized water for five times. After each soaking, solid-liquid separation was performed by filtration. The obtained solid was soaked for the next time. The single soaking time was 10 minutes. Then, the corn stalks were vacuum dried at 120°C to constant weight to obtain corn stalk powder with a particle size of 1 mm to 5 mm.

[0083] (2) The used ternary 523 lithium-ion battery was placed in a sodium chloride solution with a mass concentration of 5% and discharged until its voltage dropped below 2V. It was then manually disassembled in a glove box with an argon atmosphere to remove the aluminum shell, positive and negative terminals, sealing rings, cover plates, negative electrode plates and diaphragms to obtain the positive electrode plates of the used lithium-ion battery. The residual electrolyte was washed with dimethyl carbonate (DMC) to obtain the clean positive electrode plates of the used lithium-ion battery. The clean positive electrode plates of the used lithium-ion battery were cut into 1.5 cm × 1.5 cm positive electrode plate fragments.

[0084] (3) 10 g of the above-mentioned positive electrode fragments were soaked in 500 mL of NMP at 100° C. for 3 h, and the last 10 min of soaking in NMP was assisted by ultrasonic treatment (power of 120 W), and then the obtained organic soaking solution was centrifuged at a speed of 6000 rpm for 8 min to obtain a precipitate. The obtained precipitate was washed with ethanol and dried at 80° C. for 12 h. The dried precipitate was calcined in air at 600° C. for 3 h to obtain a calcined product.

[0085] (4) The calcined product and the corn stalk powder were mixed at a mass ratio of 1:0.1, and ball-milled at room temperature for 240 min to obtain a ball-milled mixture. The ball-milled mixture was heated to 550° C. at a heating rate of 10° C. / min in an argon atmosphere, and reduction-roasted for 60 min to obtain a reduction product.

[0086] (5) The reduced product was ground at room temperature for 10 min, mixed with deionized water (solid-to-liquid ratio of 1 g:70 mL), and carbon dioxide was introduced into the deionized water at a flow rate of 130 mL / min for 3 h of carbonic acid water leaching reaction. The obtained carbonic acid water leaching reaction liquid was filtered to obtain a filtrate and a filter residue.

[0087] (6) The filtrate obtained in step (5) is concentrated at 100° C. until its volume is reduced to 20% of the original volume of the carbonate water leaching reaction solution. The concentrated solution is then filtered, and the filter residue is washed with boiling water. The washed filter residue is dried at 100° C. to constant weight to obtain lithium carbonate.

[0088] (7) The filter residue obtained in step (5) is washed by soaking in deionized water for three times, and then dried at 120° C. for 12 h to obtain a washed filter residue. The washed filter residue is mixed with 1 mol / L H2SO4 solution at a solid-liquid ratio of 1 g:6 mL, and acid-leached at 60° C. for 60 min. The obtained acid leaching solution is filtered to obtain a salt solution containing the valuable metals nickel, cobalt, and manganese and a filter residue insoluble in sulfuric acid.

[0089] Examples 2-6 and Comparative Examples 1-14 are substantially the same as Example 1, except that the reduction roasting conditions and sulfuric acid concentrations are different. The specific conditions are shown in Table 1.

[0090] Table 1 Reduction roasting conditions and sulfuric acid concentrations of Examples 1-6 and Comparative Examples 1-14

[0091]

[0092]

[0093] Examples 7-18 and Comparative Examples 15-16 are substantially the same as Example 1, except that the acid leaching conditions are different, as shown in Table 2.

[0094] Table 2 Acid leaching conditions of Examples 7-18 and Comparative Examples 15-16

[0095]

[0096]

[0097] Test Case

[0098] The reduced products obtained in Examples 1-2 and Comparative Examples 1-2 and 7 were subjected to XRD testing. The results are as follows: Figure 2 As shown. Figure 2 It can be seen that when the carbothermal reduction temperature is increased to 550°C (Example 1), LiNi 0.5 Co 0.2 Mn 0.3 The O2 phase disappears completely, indicating that when the temperature exceeds 550°C, LiNi 0.5 Co 0.2 Mn 0.3O2 is completely decomposed, and diffraction peaks of Li2CO3 and NiO appear. At 550°C, the main phases after straw reduction of waste positive electrode materials are Li2CO3 and NiO. For Co, except for very weak metallic Co, no phase of Co-based compounds was observed in the XRD spectrum (XPS analysis shows that cobalt exists in the form of CoO after reduction roasting). When the carbon thermal reduction temperature reaches 600°C (Example 2), from the XRD results, the most significant change is the disappearance of NiO, Ni and Co mainly exist in the form of simple substances, and hydrogen will be produced during the acid leaching process. It can be seen that when the carbon thermal reduction temperature is 550°C, nickel and cobalt mainly exist in the form of oxides, which are easier to leach, and no hydrogen will be produced, and the leaching process is safer.

[0099] The reduced products obtained in Examples 1, 3, 4 and Comparative Examples 3, 4 were subjected to XRD testing. The results are as follows: Figure 3 The reduction products obtained in Examples 1, 5, 6 and Comparative Examples 5 and 6 were subjected to XRD testing, and the results are as follows: Figure 4 shown.

[0100] from Figure 3 , Figure 4 It can be seen that when the reduction roasting time is less than 40 min or the mass ratio of roasted product to straw powder is less than 1:0.1, most of the diffraction peaks appearing in the reduction product point to LiNi 0.5 Co 0.2 Mn 0.3 O2, which indicates that when the roasting time is short or the amount of straw powder is small, the reducing gas produced is small and insufficient to completely reduce the ternary material, LiNi 0.5 Co 0.2 Mn 0.3 The O2 phase cannot be completely destroyed.

[0101] The leaching efficiency of Ni, Co and Mn in Examples 1-6 and Comparative Examples 1-14 was tested by ICP, and the recovery rate of lithium was calculated. The results are shown in Table 3.

[0102] Table 3 Test results of Examples 1-6 and Comparative Examples 1-14

[0103] Example nickel(%) cobalt(%) manganese(%) lithium(%) Example 1 96.54 97.01 95.31 88.86 Example 2 90.25 91.21 95.25 89.99 Example 3 87.56 87.69 95.58 90.28 Example 4 87.57 87.71 95.52 91.01 Example 5 88.89 89.02 95.59 90.25 Example 6 88.91 89.03 95.64 91.08 Comparative Example 1 54.25 55.62 28.24 76.12 Comparative Example 2 77.34 78.56 58.98 79.98 Comparative Example 3 43.23 44.43 28.53 88.23 Comparative Example 4 78.25 80.87 64.23 89.15 Comparative Example 5 71.86 72.10 33.23 72.52 Comparative Example 6 80.24 81.98 62.01 78.89 Comparative Example 7 85.35 87.56 95.23 90.12 Comparative Example 8 91.56 91.52 90.35 76.12 Comparative Example 9 93.02 93.24 91.11 79.98 Comparative Example 10 90.65 90.70 90.00 88.23 Comparative Example 11 93.12 93.65 90.92 89.15 Comparative Example 12 91.10 91.32 90.52 93.10 Comparative Example 13 94.08 94.65 91.89 94.08 Comparative Example 14 98.33 97.99 96.35 90.12

[0104] From the final data of Examples 1-2 and Comparative Examples 1-2 and 7, it can be seen that when the reduction roasting temperature is 450°C (Comparative Example 1), the recovery rate of lithium is at a relatively low level (76.12%). This is because the roasting process has just entered the gas reduction stage, most of the transition metal oxides have not yet reacted completely, and Li2O will be covered by them, making it difficult to recover. When the reduction roasting temperature is 500°C (Comparative Example 2), the recovery rate of lithium is significantly higher than that at 450°C, but it still does not reach 80%; when the reduction roasting temperature is 550°C (Example 1), the recovery rate of lithium ions reaches 88.86%, which is higher than Comparative Examples 1 and 2. This is because, at this temperature, the roasting process has just entered the carbon thermal reduction stage after the gas reduction stage, and a large amount of CO2 generated converts Li2O into Li2CO3. Subsequently, as the temperature increases, the leaching rate does not change much, reaching a maximum value (90.12%) at 650°C (Comparative Example 7). In addition, at 450°C, the leaching efficiency of the three metals Ni, Co, and Mn is relatively low, and the leaching rate gradually increases with the increase of temperature. In the process of increasing the temperature from 450°C to 550°C, the leaching rate increases significantly. When the carbon thermal reduction temperature is 550°C, Ni, Co, and Mn mainly exist in the form of NiO, CoO, and MnO. The metal oxide state is easier to be leached by acid than the metal element state, and no hydrogen will be produced, and the leaching process is safer. When the temperature is greater than 600°C, the manganese leaching rate does not change much, and the leaching rates of nickel and cobalt decrease. Manganese still exists in the form of oxides, but nickel and cobalt are mainly in the form of elements at this time, which are not easy to be leached by acid. Hydrogen will be produced during the acid leaching process, and the high temperature will increase the reaction energy consumption.

[0105] From the results of Examples 1, 3, 4 and Comparative Examples 3-4, it can be seen that the lithium recovery rate does not change much with the roasting time, and the maximum leaching rate reaches 91% at 100 min. The reason why the leaching efficiency of Ni, Co and Mn is very low in a short time is that in such a short roasting time, LiNi 0.5 Co 0.2 Mn 0.3 O2 cannot be effectively destroyed. When the roasting time is 20 min (Comparative Example 3), the leaching rates of Ni, Co and Mn are only 43.23%, 44.43% and 28.53% respectively. When the roasting time is extended to 40 min (Comparative Example 4), LiNi 0.5 Co 0.2 Mn 0.3 The O2 phase disappears, and the extremely weak peak corresponding to Li2CO3 appears. The leaching efficiency of Ni, Co and Mn metals has improved, but it is still not ideal. When the roasting time is extended to 60min, the leaching rate of Ni and Co metals can reach more than 96%, and the leaching rate of Mn can reach more than 95%. With the extension of roasting time, the leaching rate of Mn does not change much, and the leaching rates of nickel and cobalt decrease.

[0106] It can be seen from the results of Examples 1, 5, 6 and Comparative Examples 5-6 that as the mass ratio of the roasted product to the corn stalk powder increases, the recovery rate of lithium also increases, reaching 88.86% when the mass ratio of the roasted product to the stalk powder is 1:0.10. It reaches a maximum value of 91.08% at a mass ratio of 1:0.14. The amount of corn stalk powder has little effect on the leaching efficiency of Ni and Co metals, while the leaching efficiency of Mn is greatly affected by the amount of stalk powder, especially when the feed ratio is lower than 0.10. It also shows that the carbon thermal reduction of Mn ions is more difficult than that of Ni ions and Co ions, so the straw may preferentially reduce Ni ions and Co ions during the reduction process. As the mass ratio increases from 0.06 to 0.10, the leaching rate of Mn increases from 33.23% to 95.31%, which may be due to the fact that at this mass ratio, it is sufficient to convert Ni and Co elements into a more soluble state, while more stalk powder is required to convert Mn elements into a lower oxidized or more soluble state.

[0107] As shown in Table 3 above, when the reduction roasting temperature is too high or too low, the leaching rates of valuable metals nickel, cobalt and manganese are all low, and a higher concentration of acid is required to obtain a good leaching rate of valuable metals; and when the reduction roasting time is too short or the amount of straw powder is too low, the leaching rate of valuable metals will also be reduced, and a higher concentration of acid is required to obtain a good leaching rate of valuable metals. It can be seen that the appropriate reduction roasting temperature, time and amount of waste biomass materials can reduce the amount of acid and reduce waste liquid pollution while ensuring a good leaching rate of valuable metals.

[0108] The leaching efficiency of the three metals Ni, Co and Mn in Examples 7-18 and Comparative Examples 15-16 was tested by ICP, as shown in Table 4.

[0109] Table 4 Test results of Examples 7-18 and Comparative Examples 15-16

[0110] Example nickel(%) cobalt(%) manganese(%) Example 7 87.18 88.59 84.24 Example 8 93.21 93.94 91.58 Example 9 97.69 97.82 95.68 Example 10 88.54 92.24 87.87 Embodiment 11 97.91 98.10 95.72 Example 12 97.95 98.12 95.89 Example 13 86.38 80.23 88.62 Embodiment 14 90.25 93.51 87.24 Embodiment 15 97.88 97.98 95.66 Example 16 91.25 92.21 89.05 Embodiment 17 97.92 98.10 96.02 Embodiment 18 98.00 98.12 96.01 Comparative Example 15 79.25 82.24 72.31 Comparative Example 16 79.33 75.51 81.82

[0111] It can be seen from the results of Examples 1 and 7-9 that the leaching rates of the three metals are good within the above concentration range, and gradually increase with the increase of the concentration of the H2SO4 solution. When the acid concentration increases from 0.6 mol / L to 1 mol / L, the leaching rate increases; when the concentration of the H2SO4 solution is greater than 1 mol / L, the leaching rate does not increase much.

[0112] From the results of Examples 1, 10-12 and Comparative Example 15, it can be seen that when the mass volume ratio of the filter residue to the sulfuric acid solution is 1g:(4-10)mL, the leaching rates of the valuable metals are all high. At the same time, as the amount of sulfuric acid solution increases, the convection and diffusion in the solution increase, and the solid-liquid contact area also increases, which is beneficial to improving the leaching rates of the three metals. However, when the ratio is 1g:2mL, the leaching rate of manganese is too low; when the mass volume ratio is 1g:(6-10)mL, the leaching rates of the three metals are all greater than 95%.

[0113] From the results of Examples 1, 13-15 and Comparative Example 16, it can be seen that when the leaching temperature is in the range of 30-75°C, the leaching rates of the valuable metals are all high, and at the same time, they show a pattern of increasing with the increase of the acid leaching temperature. When the reaction temperature is 15°C, the leaching rates of the three valuable metals are all low. When the reaction temperature is 60°C, the leaching rates of nickel, cobalt and manganese are 97.61%, 97.72% and 95.71%, respectively.

[0114] From the results of Examples 1 and 16-18, it can be seen that when the leaching time is within the range of 40-100 min, the leaching rate of valuable metals is relatively high. It can also be seen that the acid leaching time affects the leaching rate of valuable metals, and as time goes by, the rate of increase of the metal leaching rate slows down. The reason is that as time goes by, the consumption of the reaction substances limits the rate of increase of the metal leaching rate, and further extension of the time has little effect on the leaching rate.

[0115] The reduction product obtained in Example 1 was subjected to XPS test. Figure 5 As shown. Figure 5 It can be seen that after low-temperature reduction calcination, the reduction product is mainly composed of NiO, CoO, MnO and Li2CO3.

[0116] The lithium carbonate prepared in Example 1 was subjected to X-ray diffraction and SEM scanning electron microscopy observations. Figure 6 and 7 As shown. Figure 6 and 7 It can be seen that there is only the diffraction peak of lithium carbonate, and the lithium carbonate is rod-shaped, which is the typical morphology of lithium carbonate, and there are no other impurities, which proves that the product is high-purity lithium carbonate (purity is 99.79%).

[0117] The filter residue insoluble in sulfuric acid obtained in step (7) of Example 1 was subjected to SEM and EDS tests. Figure 8-10 As shown. Figure 8 It can be seen that there are only lamellar substances in the filter residue that is insoluble in sulfuric acid, indicating that the valuable metals in the reduction roasting product are completely dissolved, and the composition of the filter residue is basically all undissolved carbon. EDS element distribution surface scan results ( Figure 9-10) is consistent with the SEM microscopic morphology results, which shows that the main element in the leached residue is C, while the content of valuable metal elements Ni, Co, and Mn is very small. Therefore, the characterization analysis of the leached residue confirmed that the valuable metals in the roasted product were effectively leached by sulfuric acid, and no metal elements remained.

[0118] While preferred embodiments of the present invention have been shown and described, it is contemplated that those skilled in the art may devise various modifications of the present invention within the spirit and scope of the appended claims.

Claims

1. A method for recovering valuable metals from waste lithium-ion batteries, characterized in that: The steps include: (1) soaking and calcining the positive electrode sheet of the waste lithium-ion battery in an organic solvent in sequence to obtain a calcined product; (2) mixing the roasted product with waste biomass materials, and then performing reduction roasting under a protective atmosphere to obtain a reduced product; (3) subjecting the reduction product to a carbonic acid water leaching reaction, and then filtering the obtained carbonic acid water leaching reaction liquid to obtain a filtrate and a filter residue; (4) concentrating and crystallizing the filtrate to obtain lithium carbonate; (5) acid leaching the filter residue, and then filtering the obtained acid leaching solution to obtain a salt solution containing the valuable metals nickel, cobalt and manganese; There is no order of precedence between steps (4) and (5); The reduction roasting temperature is 550-600° C., the time is 60-100 min, and the mass ratio of the roasting product to the waste biomass material is 1:(0.10-0.15).

2. The recycling method according to claim 1, characterized in that: The solvent used for the organic solvent soaking is N-methylpyrrolidone, the temperature of the organic solvent soaking is 90-110° C., the time of the organic solvent soaking is 2.5-3.5 hours, and the organic solvent soaking process is ultrasonicated for 8-12 minutes.

3. The recycling method according to claim 1, characterized in that: The calcination temperature is 500-800° C., and the calcination time is 2-6 hours.

4. The recycling method according to claim 1, characterized in that: The waste biomass material includes at least one of straw powder and sawdust powder.

5. The recycling method according to claim 1, characterized in that: The heating rate to the reduction roasting temperature is 5-10°C / min.

6. The recycling method according to claim 1, characterized in that: The steps of the carbonic acid water leaching reaction are: The reduction product is ground and mixed with water to obtain a mixed solution, Carbon dioxide is introduced into the mixed solution to carry out a carbonic acid water leaching reaction.

7. The recycling method according to claim 6, characterized in that: The temperature of the carbonic acid water immersion reaction is 20-80° C., the mass volume ratio of the reduction product to water is 1 g:(25-100) mL, the introduction rate of the carbon dioxide is 100-150 mL / min, and the time of the carbonic acid water immersion reaction is 1-5 h.

8. The recycling method according to claim 1, characterized in that: The acid solution used in the acid leaching is a sulfuric acid solution, and the concentration of the sulfuric acid solution is 0.6-1.2 mol / L.

9. The recycling method according to claim 8, characterized in that: The acid leaching temperature is 30-75°C, and the acid leaching time is 40-100 minutes.

10. The recycling method according to claim 8 or 9, characterized in that: The mass volume ratio of the filter residue to the sulfuric acid solution is 1 g:(4-10) mL.

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