Method for recovering rare and precious metals in lithium ion battery cathode material by pyrolysis

Abstract

The application discloses a method for pyrolysis recycling of rare and precious metals in lithium ion battery positive materials, which comprises the following steps: disassembling and crushing waste lithium ion batteries, using waste paper as a reducing agent, mechanically mixing ternary positive electrode powder and waste paper powder, and carrying out pyrolysis reduction under a nitrogen atmosphere; roasting products are leached with water, CO2 is continuously introduced during the leaching process, and filtrate and residue are obtained by filtration; the filtrate is heated and decomposed to obtain lithium carbonate precipitation; the residue is leached with an organic acid, oxalic acid is added to the leaching solution to obtain cobalt oxalate precipitation; sodium carbonate is added and the pH is adjusted, and manganese carbonate and nickel carbonate are sequentially precipitated. The application realizes the preferential separation of lithium in the lithium ion battery recycling process by using waste paper and lithium ion battery positive materials for co-pyrolysis, reduces the reduction roasting temperature, improves the lithium leaching rate, and then sequentially separates and precipitates other metals, thereby realizing the comprehensive and efficient recycling of rare and precious metals in ternary positive materials. Meanwhile, the process uses waste paper as a reducing agent, and has the advantages of being green and economical.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery recycling technology, and in particular to a method for pyrolysis recovery of rare and precious metals in lithium-ion battery cathode materials. Background Technology

[0002] Lithium-ion batteries play a vital role in people's lives due to their excellent performance, and high demand has led to a year-on-year increase in lithium-ion battery production. Consequently, the disposal of large quantities of waste lithium-ion batteries has received widespread attention. As the most expensive part of lithium-ion battery production, the cathode material has a metal grade far exceeding that of natural metal ores, giving it high recycling value.

[0003] Recycling spent lithium-ion batteries generally involves several steps: pre-discharge, disassembly, grinding, and extraction. Metals can be recovered from the ground cathode powder using wet or pyrometallurgical processes. Rare elements such as cobalt and lithium have significant strategic and economic value, and their prices have been rising continuously in recent years. It is anticipated that raw material supplies from ores alone will be insufficient to meet future demand, making their recycling from spent lithium-ion batteries crucial. Wet processes offer high recovery rates, but require large quantities of chemical reagents, are difficult to treat, and currently, lithium is typically extracted last, significantly reducing the recovery rate. Pyrometallurgical processes involve adding slag-forming agents to cathode powder and smelting it in a high-temperature furnace to separate valuable metals. While pyrometallurgical processes offer large throughput and simplicity, lithium metal remains in the slag due to its high reactivity, making recovery difficult.

[0004] Currently, several methods attempt to combine wet processing with high-temperature roasting to improve lithium separation efficiency. For example, patent CN201711355295.4 proposes impregnating roasted electrode materials with sulfuric acid solution to obtain an acid leachate. Lithium in the leachate is then extracted with 2-ethylhexyl phosphate mono-2-ethylhexyl ester. Carbonate is added to the aqueous phase after extraction, and the mixture is filtered to obtain Li2CO3. However, this method has a complex process and a long cycle. Patent CN202010848801.9 proposes mixing positive electrode material with negative electrode graphite and then roasting the mixture. Lithium is then separated from other metals by leaching the roasted product with water under microwave assistance. However, this method involves high roasting temperatures and high energy consumption. Patent CN202110803934.9 proposes first pyrolyzing materials such as coal or biomass to obtain pyrolytic coke, and then mixing and roasting the positive electrode material with the pyrolytic coke. However, this process is cumbersome, the reduction activity of the pyrolytic coke is affected by the pyrolysis process parameters, and the lithium recovery rate is low. Patent CN202010635859.5 proposes a microwave-assisted pyrolysis method to recover lithium from cathode powder and biomass powder, with other metals recovered as ternary precursors. However, this process uses microwave heating, resulting in high energy consumption and making industrial-scale operation impossible. Patent CN202210369312.4 proposes using a diaphragm to pyrolyze and reduce cathode material, followed by leaching the reduced cathode powder with hot sulfuric acid solution. However, this method requires a large amount of diaphragm, resulting in low cathode material throughput, and the leaching wastewater is difficult to treat, causing significant environmental impact.

[0005] Furthermore, current recycling processes only focus on the recovery and utilization of lithium and cobalt, but do not give much consideration to other rare and precious metals (such as manganese and nickel) in ternary cathode materials. Therefore, there is an urgent need to develop a simple and effective method for the complete recovery of rare and precious metals in lithium-ion battery cathode materials, ensuring the recovery rate of lithium and cobalt while reducing the energy consumption of reduction roasting and achieving comprehensive metal recovery. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a cheap, environmentally friendly, and efficient method for pyrolysis recovery of rare and precious metals in lithium-ion battery cathode materials.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0008] This invention provides a method for pyrolytic recovery of rare and precious metals from lithium-ion battery cathode materials, comprising the following steps:

[0009] (1) Provide waste lithium-ion battery cathode materials and waste paper;

[0010] (2) The waste lithium-ion battery cathode material and waste paper are crushed and sieved to obtain cathode material powder and waste paper powder respectively.

[0011] (3) The positive electrode material powder and waste paper powder are mechanically mixed to obtain a mixture;

[0012] (4) The mixture is subjected to a pyrolysis reduction reaction under a nitrogen atmosphere and cooled to room temperature under a nitrogen atmosphere to obtain the reduced roasted product;

[0013] (5) The lithium in the reduction roasting product is recovered by CO2 water leaching, and other metals are recovered by organic acid leaching.

[0014] Waste paper is an important type of organic solid waste, its main component being cellulose. This invention utilizes waste paper as a reducing agent, co-pyrolyzing it with the positive electrode of lithium batteries. Taking advantage of the weak thermal stability of cellulose in waste paper, a large amount of small-molecule reducing gases (such as CO, H2, CH4, etc.) are generated, enhancing the gas-solid reduction reaction rate of the lithium battery positive electrode. Simultaneously, the pyrolytic carbon formed from waste paper is loose and porous, with a large number of active groups on its surface, which can also accelerate its solid-solid reduction reaction with the lithium battery positive electrode material. These two processes synergistically enhance the reduction and conversion of rare and precious metals in the positive electrode material to lower valence states. Lithium oxide readily reacts with CO2 to form water-soluble Li2CO3, thus enabling its recovery through water leaching. The water-insoluble metal residues can be further recovered through a stepwise leaching process using organic acids. In summary, coupling waste paper co-pyrolysis, CO2-enhanced leaching, and organic acid stepwise leaching can achieve the full recovery of rare and precious metals from waste lithium battery positive electrode materials, while simultaneously achieving the harmless disposal and resource utilization of waste paper.

[0015] The following is a detailed explanation of each step.

[0016] Step (1)

[0017] The spent lithium-ion batteries can be one or more of the following: spent lithium cobalt oxide batteries, spent lithium manganese oxide batteries, or spent nickel-cobalt-manganese ternary lithium-ion batteries, preferably spent nickel-cobalt-manganese ternary lithium-ion batteries. That is, the cathode material is preferably a ternary cathode material.

[0018] In some embodiments, the cathode material from spent lithium-ion batteries is obtained by the following methods:

[0019] (1-1) Pre-discharge the waste lithium-ion batteries. When the internal voltage of the waste lithium-ion batteries drops below the safe voltage, they are manually disassembled to separate the positive electrode.

[0020] (1-2) The obtained positive electrode is placed in a muffle furnace, and the binder is removed by pyrolysis. The aluminum foil is recycled, and the remaining black powder is the positive electrode material of waste lithium-ion batteries.

[0021] Preferably, the pre-discharge treatment in step (1-1) uses a 5-15 wt% sodium chloride solution, and the soaking time is 18-72 h, preferably 24 h.

[0022] Preferably, the pyrolysis temperature in steps (1-2) is 500-650°C and the pyrolysis time is 30-60 min.

[0023] The waste paper can be recyclable waste paper with high cellulose content, such as printing waste paper (e.g., books, newspapers), as well as non-recyclable waste paper such as napkins and paper cups.

[0024] Step (2)

[0025] The crushing and screening in this step can be carried out using methods known in the art.

[0026] Preferably, the particle size of the positive electrode material powder obtained after sieving is 0.07-0.15 mm; the particle size of the waste paper powder obtained after sieving is 0.08-0.12 mm.

[0027] Step (3)

[0028] The mechanical mixing in this step can be performed in a manner known in the art.

[0029] Preferably, the mixing speed is 100-300 r / min.

[0030] Preferably, the waste paper powder accounts for 18-30% of the mass of the mixture in step (3).

[0031] Step (4)

[0032] In some embodiments, the pyrolysis reduction reaction temperature in step (4) is 450–550°C and the reaction time is 30–60 min.

[0033] Step (5)

[0034] In this step, lithium and other metals are recovered separately. Lithium oxide is leached with CO2 to form Li2CO3. The metal residues that are insoluble in water can be further leached with organic acids to achieve graded recovery.

[0035] In some implementations, taking a nickel-cobalt-manganese ternary cathode material as an example, step (5) includes:

[0036] (5-1) The reduced roasting product is placed in an aqueous solution, and carbon dioxide gas is introduced into the aqueous solution. Carbonation leaching is carried out under stirring conditions, and solid-liquid separation is performed to obtain filtrate and filter residue.

[0037] (5-2) The filtrate was evaporated and crystallized to obtain lithium carbonate;

[0038] (5-3) The filter residue was leached with organic acid and filtered to obtain a leachate rich in cobalt ions, manganese ions and nickel ions;

[0039] (5-4) Add oxalic acid to the leachate to obtain cobalt oxalate precipitate, and then separate the solid and liquid to obtain a manganese-rich nickel solution with cobalt ions removed.

[0040] (5-5) The pH of the manganese-nickel rich solution was adjusted to 7-8 (e.g., 7.5) using sodium hydroxide solution, and saturated sodium carbonate solution was added to precipitate manganese. The solid and liquid were separated to obtain manganese carbonate and nickel-rich filtrate.

[0041] (5-6) Adjust the pH of the nickel-rich filtrate to 9-10 (e.g., 9), and continue to precipitate nickel ions with sodium carbonate to obtain nickel carbonate.

[0042] Preferably, the carbonation leaching temperature in step (5-1) is room temperature, and / or the volumetric flow rate of carbon dioxide is 40-60 mL / min, and / or the stirring rate is 500-800 r / min.

[0043] Preferably, the organic acid in step (5-3) is selected from tartaric acid, citric acid, malic acid, ascorbic acid and lactic acid.

[0044] Preferably, the concentration of the organic acid in step (5-3) is 1 to 4 mol / L.

[0045] Preferably, the oxalic acid concentration in step (5-4) is 1 to 1.5 mol / L.

[0046] Preferably, the concentration of the sodium hydroxide solution in step (5-5) is 1.5 to 2.5 mol / L.

[0047] In one specific embodiment, a method for pyrolytic recovery of rare and precious metals from the cathode material of a nickel-cobalt-manganese ternary lithium-ion battery is provided, such as... Figure 1 As shown, it includes the following steps:

[0048] (1) Pre-discharge the waste ternary lithium-ion batteries. When the internal voltage of the waste lithium battery drops below the safe voltage, it is manually disassembled and the positive electrode is separated.

[0049] (2) The obtained positive electrode is placed in a muffle furnace, the binder is removed by pyrolysis, the aluminum foil is recovered, and the remaining black powder is the ternary positive electrode material;

[0050] (3) The ternary cathode material and waste paper are crushed and screened to obtain ternary cathode material powder and waste paper powder, respectively.

[0051] (4) Mechanically mix the ternary cathode material powder and waste paper powder to obtain a mixture;

[0052] (5) The mixture is pyrolyzed and reduced in a muffle furnace under a nitrogen atmosphere and cooled to room temperature with the furnace under a nitrogen atmosphere to obtain the reduced roasted product.

[0053] (6) The reduced roasting product is placed in an aqueous solution, and carbon dioxide gas is introduced into the aqueous solution. Carbonation leaching is carried out under stirring conditions, and solid-liquid separation is performed to obtain filtrate and filter residue.

[0054] (7) The filtrate was evaporated and crystallized to obtain lithium carbonate;

[0055] (8) The filter residue was leached with organic acid, and the leachate was obtained by filtration and was rich in cobalt ions, manganese ions and nickel ions.

[0056] (9) Add oxalic acid to the leachate to obtain cobalt oxalate precipitate, and then separate the solid and liquid to obtain a manganese-rich nickel solution with cobalt ions removed.

[0057] (10) The pH of the manganese-nickel rich solution was adjusted to 7-8 using sodium hydroxide, and saturated sodium carbonate solution was added to precipitate manganese. The solid and liquid were separated to obtain manganese carbonate and nickel-rich filtrate.

[0058] (11) Adjust the pH of the nickel-rich filtrate to 9-10, and continue to precipitate nickel ions with sodium carbonate to obtain nickel carbonate.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] (1) This invention makes full use of the high cellulose content in waste paper. After co-pyrolysis with waste lithium battery cathode material, a large amount of reducing gas and highly reducing active pyrolytic carbon can be generated. At a lower reduction temperature, the reduction of metal materials can be enhanced, and the subsequent metal leaching rate (or recovery rate) can be improved. Compared with reducing agents such as graphite, the reduction roasting temperature can be significantly reduced and energy consumption can be reduced.

[0061] (2) The reduced lithium battery metal materials can be recycled by water immersion, which can achieve priority and efficient recovery of lithium. Compared with the traditional leaching method, no lithium extraction waste liquid is generated.

[0062] (3) For the leaching of metals such as cobalt, manganese and nickel, it is proposed to use organic acid leaching method to avoid the use of strong acids such as sulfuric acid and nitric acid in the leaching process and reduce the damage to the environment.

[0063] (4) This invention uses waste paper and waste lithium-ion battery cathode material for co-pyrolysis reduction roasting, realizing the joint recycling of waste paper and lithium-ion batteries, providing a new path for the comprehensive and separate recycling of metals. It realizes the resource utilization of waste paper. Attached Figure Description

[0064] Figure 1 This is a process flow diagram of one embodiment of the present invention. Detailed Implementation

[0065] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0066] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0067] The waste paper from printing comes from waste paper recycling stations.

[0068] Used ternary lithium-ion batteries originate from the electronics market.

[0069] The recovery rate R of a single metal is calculated using the following formula:

[0070]

[0071] Where M0 is the relative molecular mass of the single metal compound in the original electrode material, M a It is the relative molecular mass of the metal as a recycled product, m a m0 is the mass of the metal recovered as a product, and m0 is the mass of the metal compound in the original electrode material.

[0072] The positive electrode of the battery was pyrolyzed at 500℃ for 2 hours. The black powder on the aluminum foil was then manually scraped off. The mass of the black powder is the total mass m of the mixed metals in the original electrode material. t The metal composition and relative content μ in the black powder were determined by atomic emission spectrometry (ICP). The mass m0 of the metal compound in the original electrode material is calculated using the following formula:

[0073] m0=μ×m t

[0074] Example 1:

[0075] (1) Soak the waste ternary lithium-ion battery in a 5wt% sodium chloride solution for 72 hours for pre-discharge treatment. When the internal voltage of the waste lithium battery drops below the safe voltage, disassemble it manually and separate the positive electrode.

[0076] (2) The obtained positive electrode is placed in a muffle furnace and pyrolyzed at 500°C for 30 min to remove the binder and recover the aluminum foil. The remaining black powder is the ternary positive electrode material.

[0077] (3) The ternary cathode material and the waste paper are crushed and sieved to obtain ternary cathode material powder and waste paper powder respectively; wherein the particle size of the ternary cathode material powder is 0.07-0.08 mm; and the particle size of the waste paper powder is 0.08-0.09 mm.

[0078] (4) 100g of ternary cathode material powder and waste paper powder are mechanically mixed; the mass of waste paper powder in the mixture accounts for 18%;

[0079] (5) Place the mixture in a muffle furnace, continuously introduce nitrogen, rapidly heat to 450°C and hold for 30 minutes to reduce metal ions in the waste paper pyrolysis products;

[0080] (6) The reduced roasting product was placed in an aqueous solution in a leaching vessel, and carbon dioxide gas was continuously introduced into the aqueous solution. Carbonation leaching was carried out for 1 hour under stirring conditions. After standing and layering, the product was filtered to achieve solid-liquid separation and obtain filtrate and filter residue. The volume flow rate of carbon dioxide was 40 mL / min, and the stirring rate was 500 r / min.

[0081] (7) The filtrate was evaporated and crystallized at 100°C to obtain lithium carbonate. The recovery rate of lithium recovered by lithium carbonate (Li2CO3) was 91%.

[0082] (8) The filter residue was leached with tartaric acid at a concentration of 2 mol / L. Oxalic acid at a concentration of 1 mol / L was added to the leachate to obtain cobalt oxalate precipitate. Solid-liquid separation was performed to obtain a manganese-nickel rich solution with cobalt ions removed. The recovery rate of cobalt by cobalt oxalate (CoC2O4) was 93%.

[0083] (9) The pH of the manganese-nickel rich solution was adjusted to 7.5 with sodium hydroxide at a concentration of 1.5 mol / L. Manganese was precipitated by adding saturated sodium carbonate solution. Manganese carbonate and nickel-rich filtrate were obtained by solid-liquid separation. The recovery rate of manganese recovered by manganese carbonate (MnCO3) was 94.1%.

[0084] (10) Adjust the pH of the filtrate to 9, and continue to precipitate nickel ions with sodium carbonate to obtain nickel carbonate; the recovery rate of nickel by nickel carbonate (NiCO3) is 95%.

[0085] Example 2:

[0086] (1) Soak the waste ternary lithium-ion battery in a 5wt% sodium chloride solution for 48 hours for pre-discharge treatment. When the internal voltage of the waste lithium battery drops below the safe voltage, disassemble it manually and separate the positive electrode.

[0087] (2) The obtained positive electrode is placed in a muffle furnace and pyrolyzed at 550°C for 30 min to remove the binder and recover the aluminum foil. The remaining black powder is the ternary positive electrode material.

[0088] (3) The ternary cathode material and the waste paper are crushed and sieved to obtain ternary cathode material powder and waste paper powder respectively; wherein the particle size of the ternary cathode material powder is 0.08-0.09 mm; and the particle size of the waste paper powder is 0.08-0.09 mm.

[0089] (4) 100g of ternary cathode material powder and waste paper powder are mechanically mixed; the mass of waste paper powder in the mixture accounts for 19%;

[0090] (5) Place the mixture in a muffle furnace, continuously introduce nitrogen, rapidly heat to 450°C and hold for 50 minutes to achieve the reduction of metal ions in the waste paper pyrolysis products;

[0091] (6) The reduced roasting product was placed in an aqueous solution in a leaching vessel, and carbon dioxide gas was continuously introduced into the aqueous solution. Carbonation leaching was carried out for 1 hour under stirring conditions. After standing and layering, the product was filtered to achieve solid-liquid separation and obtain filtrate and filter residue. The volume flow rate of carbon dioxide was 45 mL / min, and the stirring rate was 500 r / min.

[0092] (7) The filtrate was evaporated and crystallized at 100°C to obtain lithium carbonate. The recovery rate of lithium recovered by lithium carbonate (Li2CO3) was 91.2%.

[0093] (8) The filter residue was leached with ascorbic acid at a concentration of 2 mol / L. Oxalic acid at a concentration of 1 mol / L was added to the leachate to obtain cobalt oxalate precipitate. Solid-liquid separation was performed to obtain a manganese-nickel rich solution with cobalt ions removed. The recovery rate of cobalt by cobalt oxalate (CoC2O4) was 93.4%.

[0094] (9) The pH of the manganese-nickel rich solution was adjusted to 7.5 with sodium hydroxide at a concentration of 1.6 mol / L. Manganese was precipitated by adding saturated sodium carbonate solution. Manganese carbonate and nickel-rich filtrate were obtained by solid-liquid separation. The recovery rate of manganese recovered by manganese carbonate (MnCO3) was 94.2%.

[0095] (10) Adjust the pH of the filtrate to 9, and continue to precipitate nickel ions with sodium carbonate to obtain nickel carbonate; the recovery rate of nickel by nickel carbonate (NiCO3) is 95%.

[0096] Example 3:

[0097] (1) Soak the waste ternary lithium-ion battery in a 10wt% sodium chloride solution for 24 hours for pre-discharge treatment. When the internal voltage of the waste lithium battery drops below the safe voltage, disassemble it manually and separate the positive electrode.

[0098] (2) The obtained positive electrode is placed in a muffle furnace and pyrolyzed at 500°C for 40 min to remove the binder and recover the aluminum foil. The remaining black powder is the ternary positive electrode material.

[0099] (3) The ternary cathode material and the waste paper are crushed and sieved to obtain ternary cathode material powder and waste paper powder respectively; wherein the particle size of the ternary cathode material powder is 0.08-0.09 mm; and the particle size of the waste paper powder is 0.09-0.10 mm.

[0100] (4) Mechanically mix 100g of ternary cathode material powder and waste paper powder; the mass of waste paper powder in the mixture accounts for 20%;

[0101] (5) Place the mixture in a muffle furnace, continuously introduce nitrogen, rapidly heat to 500°C and hold for 30 minutes to reduce metal ions in the waste paper pyrolysis products;

[0102] (6) The reduced roasting product was placed in an aqueous solution in a leaching vessel, and carbon dioxide gas was continuously introduced into the aqueous solution. Carbonation leaching was carried out for 1 hour under stirring conditions. After standing and layering, the product was filtered to achieve solid-liquid separation and obtain filtrate and filter residue. The volume flow rate of carbon dioxide was 50 mL / min, and the stirring rate was 600 r / min.

[0103] (7) The filtrate was evaporated and crystallized at 100°C to obtain lithium carbonate. The recovery rate of lithium recovered by lithium carbonate (Li2CO3) was 94.2%.

[0104] (8) The filter residue was leached with malic acid at a concentration of 2.5 mol / L. Oxalic acid at a concentration of 1.1 mol / L was added to the leachate to obtain cobalt oxalate precipitate. Solid-liquid separation was performed to obtain a manganese-nickel rich solution with cobalt ions removed. The recovery rate of cobalt by cobalt oxalate (CoC2O4) was 95%.

[0105] (9) The pH of the solution was adjusted to 8 using sodium hydroxide with a concentration of 1.8 mol / L, and saturated sodium carbonate solution was added to precipitate manganese. Manganese carbonate and nickel-rich filtrate were obtained by solid-liquid separation. The recovery rate of manganese recovered by manganese carbonate (MnCO3) was 94.8%.

[0106] (10) Adjust the pH of the filtrate to 9, and continue to precipitate nickel ions with sodium carbonate to obtain nickel carbonate; the recovery rate of nickel by nickel carbonate (NiCO3) is 96%.

[0107] Example 4:

[0108] (1) Soak the waste ternary lithium-ion battery in a 10wt% sodium chloride solution for 24 hours for pre-discharge treatment. When the internal voltage of the waste lithium battery drops below the safe voltage, disassemble it manually and separate the positive electrode.

[0109] (2) The obtained positive electrode is placed in a muffle furnace and pyrolyzed at 600℃ for 30 min to remove the binder and recover the aluminum foil. The remaining black powder is the ternary positive electrode material.

[0110] (3) The ternary cathode material and the waste paper are crushed and sieved to obtain ternary cathode material powder and waste paper powder respectively; wherein the particle size of the ternary cathode material powder is 0.09-0.10 mm; and the particle size of the waste paper powder is 0.09-0.10 mm.

[0111] (4) 100g of ternary cathode material powder and waste paper powder are mechanically mixed; the mass of waste paper powder in the mixture accounts for 22%;

[0112] (5) Place the mixture in a muffle furnace, continuously introduce nitrogen, rapidly heat to 550°C and hold for 30 minutes to reduce metal ions in the waste paper pyrolysis products;

[0113] (6) The reduced roasting product was placed in an aqueous solution in a leaching vessel, and carbon dioxide gas was continuously introduced into the aqueous solution. Carbonation leaching was carried out for 1 hour under stirring conditions. After standing and layering, the product was filtered to achieve solid-liquid separation and obtain filtrate and filter residue. The volume flow rate of carbon dioxide was 50 mL / min, and the stirring rate was 600 r / min.

[0114] (7) The filtrate was evaporated and crystallized at 100°C to obtain lithium carbonate. The recovery rate of lithium recovered by lithium carbonate (Li2CO3) was 94.6%.

[0115] (8) The filter residue was leached with tartaric acid at a concentration of 2.5 mol / L. Oxalic acid at a concentration of 1.25 mol / L was added to the leachate to obtain cobalt oxalate precipitate. Solid-liquid separation was performed to obtain a manganese-nickel rich solution with cobalt ions removed. The recovery rate of cobalt by cobalt oxalate (CiC2O4) was 95.2%.

[0116] (9) The pH of the solution was adjusted to 8 using sodium hydroxide with a concentration of 2 mol / L. Saturated sodium carbonate solution was added to precipitate manganese. Manganese carbonate and nickel-rich filtrate were obtained by solid-liquid separation. The recovery rate of manganese recovered by manganese carbonate (MnCO3) was 94.3%.

[0117] (10) Adjust the pH of the filtrate to 9, and continue to precipitate nickel ions with sodium carbonate to obtain nickel carbonate; the recovery rate of nickel by nickel carbonate (NiCO3) is 96%.

[0118] Example 5:

[0119] (1) Soak the waste ternary lithium-ion battery in a 15wt% sodium chloride solution for 18 hours for pre-discharge treatment. When the internal voltage of the waste lithium battery drops below the safe voltage, disassemble it manually and separate the positive electrode.

[0120] (2) The obtained positive electrode is placed in a muffle furnace and pyrolyzed at 650°C for 30 min to remove the binder and recover the aluminum foil. The remaining black powder is the ternary positive electrode material.

[0121] (3) The ternary cathode material and the waste paper are crushed and sieved to obtain ternary cathode material powder and waste paper powder respectively; wherein the particle size of the ternary cathode material powder is 0.1-0.11 mm; and the particle size of the waste paper powder is 0.1-0.11 mm.

[0122] (4) 100g of ternary cathode material powder and waste paper powder are mechanically mixed; the mass of waste paper powder in the mixture accounts for 24%;

[0123] (5) Place the mixture in a muffle furnace, continuously introduce nitrogen, rapidly heat to 550°C and hold for 40 minutes to achieve the reduction of metal ions in the waste paper pyrolysis products;

[0124] (6) The reduced roasting product was placed in an aqueous solution in a leaching vessel, and carbon dioxide gas was continuously introduced into the aqueous solution. Carbonation leaching was carried out for 1 hour under stirring conditions. After standing and layering, the product was filtered to achieve solid-liquid separation and obtain filtrate and filter residue. The volume flow rate of carbon dioxide was 55 mL / min, and the stirring rate was 700 r / min.

[0125] (7) The filtrate was evaporated and crystallized at 100°C to obtain lithium carbonate. The recovery rate of lithium recovered by lithium carbonate (Li2CO3) was 95%.

[0126] (8) The filter residue was leached with tartaric acid at a concentration of 3 mol / L. Oxalic acid at a concentration of 1.3 mol / L was added to the leachate to obtain cobalt oxalate precipitate. Solid-liquid separation was performed to obtain a manganese-nickel rich solution with cobalt ions removed. The recovery rate of cobalt by cobalt oxalate (CoC2O4) was 95.2%.

[0127] (9) The pH of the solution was adjusted to 7.5 using sodium hydroxide with a concentration of 2.2 mol / L. Saturated sodium carbonate solution was added to precipitate manganese. Manganese carbonate and nickel-rich filtrate were obtained by solid-liquid separation. The recovery rate of manganese recovered by manganese carbonate (MnCO3) was 96%.

[0128] (10) Adjust the pH of the filtrate to 9, and continue to precipitate nickel ions with sodium carbonate to obtain nickel carbonate; the recovery rate of nickel by nickel carbonate (NiCO3) is 96.3%.

[0129] Example 6:

[0130] (1) Soak the waste ternary lithium-ion battery in a 15wt% sodium chloride solution for 24 hours for pre-discharge treatment. When the internal voltage of the waste lithium battery drops below the safe voltage, disassemble it manually and separate the positive electrode.

[0131] (2) The obtained positive electrode is placed in a muffle furnace and pyrolyzed at 650°C for 30 min to remove the binder and recover the aluminum foil. The remaining black powder is the ternary positive electrode material.

[0132] (3) The ternary cathode material and the waste paper are crushed and sieved to obtain ternary cathode material powder and waste paper powder respectively; wherein the particle size of the ternary cathode material powder is 0.14-0.15 mm; and the particle size of the waste paper powder is 0.11-0.12 mm.

[0133] (4) Mechanically mix 100g of ternary cathode material powder and waste paper powder; the mass of waste paper powder in the mixture accounts for 30%;

[0134] (5) Place the mixture in a muffle furnace, continuously introduce nitrogen, rapidly heat to 550°C and hold for 60 minutes to reduce metal ions in the waste paper pyrolysis products;

[0135] (6) The reduced roasting product was placed in an aqueous solution in a leaching vessel, and carbon dioxide gas was continuously introduced into the aqueous solution. Carbonation leaching was carried out for 1 hour under stirring conditions. After standing and layering, the product was filtered to achieve solid-liquid separation and obtain filtrate and filter residue. The volume flow rate of carbon dioxide was 60 mL / min, and the stirring rate was 800 r / min.

[0136] (7) The filtrate was evaporated and crystallized at 100°C to obtain lithium carbonate. The recovery rate of lithium recovered by lithium carbonate (Li2CO3) was 93.2%.

[0137] (8) The filter residue was leached with citric acid at a concentration of 1.25 mol / L. Oxalic acid at a concentration of 1.5 mol / L was added to the leachate to obtain cobalt oxalate precipitate. Solid-liquid separation was performed to obtain a manganese-nickel rich solution with cobalt ions removed. The recovery rate of cobalt by cobalt oxalate (CoC2O4) was 94.8%.

[0138] (9) The pH of the solution was adjusted to 7 using sodium hydroxide with a concentration of 2.5 mol / L. Saturated sodium carbonate solution was added to precipitate manganese. Manganese carbonate and nickel-rich filtrate were obtained by solid-liquid separation. The recovery rate of manganese recovered by manganese carbonate (MnCO3) was 95%.

[0139] (10) Adjust the pH of the filtrate to 9, and continue to precipitate nickel ions with sodium carbonate to obtain nickel carbonate; the recovery rate of nickel by nickel carbonate (NiCO3) is 95.8%;

[0140] Referring to Example 4, the following comparative experiments were designed.

[0141] Comparative Example 1

[0142] In this comparative example, graphite powder was used as a reducing agent, and the specific preparation steps are as follows:

[0143] (1) Soak the waste ternary lithium-ion batteries in a 15wt% sodium chloride solution for 24 hours for pre-discharge treatment. When the internal voltage of the waste lithium battery drops below the safe voltage, disassemble it manually and separate the positive and negative electrodes.

[0144] (2) The positive electrode material and the negative electrode material are mixed, ball-milled, dried and sieved to obtain a mixture; wherein the negative electrode material accounts for 22% of the mixture during mixing, and the particle size of the mixture obtained during sieving is 0.09 to 0.10 mm;

[0145] (3) Place the mixture in a muffle furnace, continuously introduce nitrogen gas, rapidly heat to 550℃ and hold for 30 minutes to achieve graphite reduction of metal ions;

[0146] (4) The reduction product was placed in the aqueous solution in the leaching vessel, and carbon dioxide gas was continuously introduced into the aqueous solution. Carbonation leaching was carried out for 1 hour under stirring conditions. After standing and layering, the product was filtered to achieve solid-liquid separation and obtain filtrate and filter residue. The volume flow rate of carbon dioxide was 50 mL / min, and the stirring rate was 600 r / min.

[0147] (5) The filtrate was evaporated and crystallized at 100°C to obtain lithium carbonate. The recovery rate of lithium recovered by lithium carbonate (Li2CO3) was 81.6%.

[0148] (6) The filter residue was leached with tartaric acid at a concentration of 2.5 mol / L. Oxalic acid at a concentration of 1.25 mol / L was added to the leachate to obtain cobalt oxalate precipitate. Solid-liquid separation was performed to obtain a manganese-nickel rich solution with cobalt ions removed. The recovery rate of cobalt by cobalt oxalate (CoC2O4) was 85.2%.

[0149] (7) The pH of the solution was adjusted to 8 using sodium hydroxide with a concentration of 2 mol / L, and saturated sodium carbonate solution was added to precipitate manganese. Manganese carbonate and nickel-rich filtrate were obtained by solid-liquid separation. The recovery rate of manganese recovered by manganese carbonate (MnCO3) was 90.3%.

[0150] (8) Adjust the pH of the filtrate to 9, and continue to precipitate nickel ions with sodium carbonate to obtain nickel carbonate; the recovery rate of nickel by nickel carbonate (NiCO3) is 89%.

[0151] Comparative Example 2

[0152] In this comparative example, H2 is used as the reducing agent, and the specific preparation steps are as follows:

[0153] (1) Soak the waste ternary lithium-ion battery in a 15wt% sodium chloride solution for 24 hours for pre-discharge treatment. When the internal voltage of the waste lithium battery drops below the safe voltage, disassemble it manually and separate the positive electrode.

[0154] (2) Grind and sieve the positive electrode material to obtain positive electrode powder with a particle size of 0.09 to 0.10 mm;

[0155] (3) Place the positive electrode powder in a muffle furnace, continuously introduce hydrogen gas, rapidly heat up to 550℃ and keep it at that temperature for 30 minutes. The hydrogen gas flows at a speed of 4 m / s in the furnace.

[0156] (4) The reduction product was placed in the aqueous solution in the leaching vessel, and carbon dioxide gas was continuously introduced into the aqueous solution. Carbonation leaching was carried out for 1 hour under stirring conditions. After standing and layering, the product was filtered to achieve solid-liquid separation and obtain filtrate and filter residue. The volume flow rate of carbon dioxide was 50 mL / min, and the stirring rate was 600 r / min.

[0157] (5) The filtrate was evaporated and crystallized at 100°C to obtain lithium carbonate. The recovery rate of lithium recovered by lithium carbonate (Li2CO3) was 99.2%.

[0158] (6) The filter residue was leached with tartaric acid at a concentration of 2.5 mol / L. Oxalic acid at a concentration of 1.25 mol / L was added to the leachate to obtain cobalt oxalate precipitate. Solid-liquid separation was performed to obtain a manganese-nickel rich solution with cobalt ions removed. The recovery rate of cobalt by cobalt oxalate (CoC2O4) was 99.5%.

[0159] (7) The pH of the solution was adjusted to 8 using sodium hydroxide with a concentration of 2 mol / L, and saturated sodium carbonate solution was added to precipitate manganese. Manganese carbonate and nickel-rich filtrate were obtained by solid-liquid separation. The recovery rate of manganese recovered by manganese carbonate (MnCO3) was 99.3%.

[0160] (8) Adjust the pH of the filtrate to 9, and continue to precipitate nickel ions with sodium carbonate to obtain nickel carbonate; the recovery rate of nickel by nickel carbonate (NiCO3) is 99%.

[0161] Comparative Example 3

[0162] In this comparative example, a diaphragm is used as a reducing agent, and the specific preparation steps are as follows:

[0163] (1) Soak the waste ternary lithium-ion battery in a 10wt% sodium chloride solution for 24 hours for pre-discharge treatment. When the internal voltage of the waste lithium battery drops below the safe voltage, disassemble it manually to separate the positive electrode and the separator.

[0164] (2) The obtained positive electrode is placed in a muffle furnace and pyrolyzed at 600℃ for 30 min to remove the binder and recover the aluminum foil. The remaining black powder is the ternary positive electrode material.

[0165] (3) Cut the diaphragm into 2-3 mm pieces and mix it with the ternary cathode material powder obtained by crushing and sieving; wherein the particle size of the ternary cathode material powder is 0.09-0.10 mm; the mass of the diaphragm accounts for 22% of the mixture.

[0166] (4) Place the mixture in a muffle furnace, continuously introduce nitrogen gas, rapidly heat to 550°C and hold for 30 minutes to achieve the reduction of metal ions by the diaphragm pyrolysis products;

[0167] (6) The reduced roasting product was placed in an aqueous solution in a leaching vessel, and carbon dioxide gas was continuously introduced into the aqueous solution. Carbonation leaching was carried out for 1 hour under stirring conditions. After standing and layering, the product was filtered to achieve solid-liquid separation and obtain filtrate and filter residue. The volume flow rate of carbon dioxide was 50 mL / min, and the stirring rate was 600 r / min.

[0168] (7) The filtrate was evaporated and crystallized at 100°C to obtain lithium carbonate. The recovery rate of lithium recovered by lithium carbonate (Li2CO3) was 34.6%.

[0169] (8) The filter residue was leached with tartaric acid at a concentration of 2.5 mol / L. Oxalic acid at a concentration of 1.25 mol / L was added to the leachate to obtain cobalt oxalate precipitate. Solid-liquid separation was performed to obtain a manganese-nickel rich solution with cobalt ions removed. The recovery rate of cobalt by cobalt oxalate (CoC2O4) was 35.2%.

[0170] (9) The pH of the solution was adjusted to 8 using sodium hydroxide with a concentration of 2 mol / L. Saturated sodium carbonate solution was added to precipitate manganese. Manganese carbonate and nickel-rich filtrate were obtained by solid-liquid separation. The recovery rate of manganese recovered by manganese carbonate (MnCO3) was 34.3%.

[0171] (10) Adjust the pH of the filtrate to 9, and continue to precipitate nickel ions with sodium carbonate to obtain nickel carbonate; the recovery rate of nickel by nickel carbonate (NiCO3) is 36%.

[0172] In Comparative Example 1, only a solid-solid reduction reaction occurred between graphite and the cathode metal. Due to the limited contact area of ​​the reactants and the high activation energy required for the reaction, the reduction effect was not significant at 550°C, resulting in a low metal recovery rate. In Comparative Example 2, H2 was used as the reducing agent, and the metal was almost completely recovered. However, hydrogen is expensive and poses a high risk during operation, making large-scale industrial application difficult. In Comparative Example 3, the cathode metal was reduced using pyrolysis gas generated by heating the diaphragm, which is economical and environmentally friendly. However, when the amount of diaphragm used is low, the generated pyrolysis gas is insufficient to reduce the metal, thus limiting the metal recovery rate. In summary, compared with the above reducing agents, this invention uses waste paper as the reducing agent to enhance the gas-solid reduction reaction, and still exhibits excellent recovery performance when the ratio of reducing agent content to cathode material content is fixed.

[0173] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for pyrolytic recovery of rare and precious metals from lithium-ion battery cathode materials, characterized in that, Includes the following steps: (1) Provide waste lithium-ion battery cathode materials and waste paper; (2) The waste lithium-ion battery cathode material and waste paper are crushed and screened to obtain cathode material powder and waste paper powder respectively; (3) The positive electrode material powder and waste paper powder are mechanically mixed to obtain a mixture; (4) The mixture is subjected to pyrolysis reduction reaction under nitrogen atmosphere and cooled to room temperature under nitrogen atmosphere to obtain reduction calcination product; (5) The lithium in the reduction roasting product is recovered by CO2 water leaching, and other metals are recovered by organic acid leaching. Step (1) The cathode material from waste lithium-ion batteries is obtained through the following method: (1-1) Pre-discharge the waste lithium-ion batteries. When the internal voltage of the waste lithium-ion batteries drops below the safe voltage, they are manually disassembled to separate the positive electrode. (1-2) The obtained positive electrode is placed in a muffle furnace, and the binder is removed by pyrolysis. The aluminum foil is recycled, and the remaining black powder is the positive electrode material of waste lithium-ion batteries. The pre-discharge treatment in step (1-1) uses a 5-15 wt% sodium chloride solution and the soaking time is 18-72 h; The pyrolysis temperature in steps (1-2) is 500~650ºC, and the pyrolysis time is 30~60 min; In step (3), the mass of waste paper powder in the mixture accounts for 18-30%; In step (4), the pyrolysis-reduction reaction temperature is 450~550ºC and the reaction time is 30~60 min; Step (5) includes: (5-1) The reduction roasting product is placed in an aqueous solution, and carbon dioxide gas is introduced into the aqueous solution. Carbonation leaching is carried out under stirring conditions, and solid-liquid separation is performed to obtain filtrate and filter residue. (5-2) The filtrate was evaporated and crystallized to obtain lithium carbonate; (5-3) The filter residue was leached with organic acid and filtered to obtain a leachate rich in cobalt ions, manganese ions and nickel ions; (5-4) Add oxalic acid to the leachate to obtain cobalt oxalate precipitate, and then separate the solid and liquid to obtain a manganese-nickel rich solution with cobalt ions removed. (5-5) The pH of the manganese-nickel-rich solution was adjusted to 7-8 using sodium hydroxide solution, and saturated sodium carbonate solution was added to precipitate manganese. The solid and liquid were separated to obtain manganese carbonate and nickel-rich filtrate. (5-6) Adjust the pH of the nickel-rich filtrate to 9-10, and continue to precipitate nickel ions with sodium carbonate to obtain nickel carbonate; In step (5-1), the carbonation leaching temperature is room temperature, and / or the carbon dioxide volume flow rate is 40~60 mL / min, and / or the stirring rate is 500~800 r / min; In step (5-3), the organic acid is selected from tartaric acid, citric acid, malic acid, ascorbic acid and lactic acid; and / or, the concentration of the organic acid is 1~4 mol / L; In step (5-4), the concentration of oxalic acid is 1~1.5 mol / L; In step (5-5), the concentration of the sodium hydroxide solution is 1.5~2.5 mol / L.

2. The method according to claim 1, characterized in that, In step (1), The spent lithium-ion batteries are selected from one or more of the following types: spent lithium cobalt oxide batteries, spent lithium manganese oxide batteries, or spent nickel-cobalt-manganese ternary lithium-ion batteries; and / or Waste paper is selected from one or more of the following: printing waste paper, napkins, or paper cups.

3. The method according to claim 1, characterized in that, In step (2), The particle size of the cathode material powder obtained after sieving is 0.07~0.15 mm; the particle size of the waste paper powder obtained after sieving is 0.08~0.12 mm.

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