Method for recycling positive electrode material of lithium ion battery

Abstract

The invention relates to the technical field of waste battery recovery, and discloses a method for recovering a positive electrode material of a lithium ion battery. The method comprises the following steps: (1) roasting the positive electrode material of the waste lithium ion battery and a sulfur-carbon compound to obtain an intermediate I; (2) sequentially carrying out water leaching and first solid-liquid separation on the intermediate I to obtain a solid I and a lithium-containing solution; (3) sequentially carrying out first mixing and second solid-liquid separation on the solid I and a deep eutectic solvent to obtain leaching residues and leaching liquid; and drying the lithium-containing solution to obtain lithium sulfate, and (4) the leachate and oxalic acid are subjected to a precipitation reaction, and transition metal is recycled in a precipitation form. According to the method provided by the invention, the lithium is preferentially extracted in a manner of taking the sulfur-carbon compound as an auxiliary roasting agent, the positive electrode material of the waste battery is selectively separated in a manner of leaching metal inorganic matters through the eutectic solvent, and the problem that metal ions are difficult to separate is solved.

Description

Technical Field

[0001] This invention relates to the field of waste battery recycling technology, specifically to a method for recycling lithium-ion battery cathode materials. Background Technology

[0002] Sulfide roasting is a common method for recovering lithium from lithium-ion batteries. It involves adding excess sulfate to simultaneously convert lithium, nickel, cobalt, and manganese into lithium sulfate, cobalt sulfate, nickel sulfate, and manganese sulfate. Lithium, nickel, cobalt, and manganese are then leached into a solution using water leaching. Nickel, cobalt, and manganese are then separated through chemical precipitation, extraction, or adsorption. Finally, sodium carbonate is added to the solution to prepare lithium carbonate. However, this method consumes a large amount of roasting agent. Secondly, the process of separating transition metal ions such as nickel, cobalt, and manganese inevitably carries away lithium ions, resulting in a low lithium ion extraction rate. Furthermore, the obtained lithium carbonate is prone to containing impurity cations, leading to low purity.

[0003] Leaching spent lithium-ion batteries using eutectic solvents is a newly emerging leaching method. Eutectic solvents are favored due to their advantages such as simple preparation, low volatility, biodegradability, recyclability, and high efficiency in leaching metal ions. US20200399737A1 discloses the use of the eutectic solvent choline chloride:ethylene glycol for leaching cathode materials, but the reaction conditions are quite stringent, requiring a reaction time greater than 12 h at temperatures above 150 °C.

[0004] CN115537567A uses a eutectic solvent to separate the cathode material from the aluminum foil. However, eutectic solvent leaching will leach out lithium ions and transition metal ions together, which will make subsequent separation difficult. Moreover, the eutectic solvent cannot be reused.

[0005] CN118272658A uses a ternary eutectic solvent composed of choline chloride, malic acid, and glycerol to leach waste NCM cathodes. Lithium ions are also leached together with nickel, cobalt, and manganese ions, and the eutectic solvent cannot be recycled. Summary of the Invention

[0006] The purpose of this invention is to solve the problem of low lithium extraction rate and selectivity during the leaching of spent lithium-ion batteries using eutectic solvents.

[0007] To achieve the above objectives, a first aspect of the present invention provides a method for recycling lithium-ion battery cathode materials, the method comprising: (1) In the presence of a protective gas, waste lithium-ion battery cathode material is calcined with sulfur and carbon compounds to obtain intermediate I; (2) The intermediate I is subjected to water immersion and first solid-liquid separation in sequence to obtain solid I and lithium-containing solution; (3) The solid I is subjected to a first mixing and a second solid-liquid separation with a eutectic solvent to obtain leaching residue and leachate; and The lithium-containing solution was dried to obtain lithium sulfate; (4) The leachate is reacted with oxalic acid to precipitate the transition metals; The sulfur-carbon compound is selected from at least one of carbon disulfide, carbonyl sulfide, tricarbon disulfide, and carbon monosulfide; The eutectic solvent contains vitamins and amino acids in a molar ratio of 1:(3-12).

[0008] Compared with existing processes, the recycling method of the present invention has the following advantages: (1) This invention uses simple sulfur and carbon compounds as auxiliary roasting agents to achieve preferential lithium extraction; selective separation of waste battery cathode materials is achieved by leaching metal inorganic materials with eutectic solvent. After leaching with eutectic solvent, nickel, cobalt and manganese metal ions are co-precipitated and separated, which can be used to prepare precursors for cathode materials, thus solving the problem of difficult metal ion separation.

[0009] (2) The sulfur and carbon compounds in this invention are relatively inexpensive, the eutectic solvent components are widely available, the reaction conditions are mild, the recovery rate is high, and the solvent can be reused, making it suitable for future large-scale production.

[0010] (3) The present invention is applicable to a wide range of cathode materials and has low requirements for material quality. After screening, the cathode materials can be directly processed, reducing the pre-processing steps of cathode materials and improving production efficiency. Attached Figure Description

[0011] Figure 1 The image shows the XRD pattern of lithium sulfate extracted in Example 1. Figure 2 This is the XRD pattern of solid I in Example 1. Detailed Implementation

[0012] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0013] As mentioned above, the first aspect of the present invention provides a method for recycling lithium-ion battery cathode materials, the method comprising: (1) In the presence of a protective gas, waste lithium-ion battery cathode material is calcined with sulfur and carbon compounds to obtain intermediate I; (2) The intermediate I is subjected to water immersion and first solid-liquid separation in sequence to obtain solid I and lithium-containing solution; (3) The solid I is subjected to a first mixing and a second solid-liquid separation with a eutectic solvent to obtain leaching residue and leachate; and The lithium-containing solution was dried to obtain lithium sulfate; (4) The leachate is reacted with oxalic acid to precipitate the transition metals; The sulfur-carbon compound is selected from at least one of carbon disulfide, carbonyl sulfide, tricarbon disulfide, and carbon monosulfide; The eutectic solvent contains vitamins and amino acids in a molar ratio of 1:(3-12).

[0014] Preferably, the sulfur-carbon compound is carbon disulfide and / or carbonyl sulfide. The inventors have found that, in this preferred embodiment, the lithium recovery rate can be further improved.

[0015] In a preferred embodiment, the amino acid substance is an amino acid or its derivative; the vitamin substance is a vitamin and / or a vitamin-like substance.

[0016] More preferably, the vitamin-like substance is at least one of carnitine and inositol.

[0017] According to a particularly preferred embodiment, the vitamin-like substance is selected from carnitine, folic acid, inositol, dl-α-tocopherol, dimethylpyrimidinol menadione sulfite, sodium menadione bisulfite, and nicotinamide menadione bisulfite; the amino acid-like substance is selected from at least one of glycine, L-alanine, phenylalanine, and taurine. The inventors have discovered that, in this preferred embodiment, by forming a eutectic solvent with specific types of vitamin-like substances and specific types of amino acids, the leaching effect of transition metal ions such as nickel, cobalt, and manganese can be further improved, while reducing the amount of eutectic solvent used.

[0018] According to a particularly preferred embodiment, the eutectic solvent contains vitamin-like substances and amino acid-like substances in a molar ratio of 1:(5-10). The inventors have found that, under this preferred condition, the recovery rate and selectivity of transition metal ions in the cathode material can be further improved.

[0019] According to a preferred embodiment, in step (1), the mass ratio of the sulfur-carbon compound to the spent lithium-ion battery cathode material is (0.5-2):1. The inventors have found that under these conditions, the lithium-ion recovery rate can be improved more effectively.

[0020] According to one specific embodiment, the waste lithium-ion battery cathode material is selected from at least one lithium-ion battery cathode material among NCM, NCA, LCO, and LMO.

[0021] More preferably, the NCM (lithium nickel cobalt manganese oxide) lithium-ion battery is selected from at least one of NCM 333, NCM 523, NCM622, and NCM 811.

[0022] Preferably, the average particle diameter of the waste lithium-ion battery cathode material is ≤100 mesh.

[0023] The present invention does not impose any particular restrictions on the source of the waste lithium-ion battery cathode material. It can be obtained by direct purchase, or by mechanically crushing, chemically dissolving or heat-treating the waste lithium-ion battery according to known technical means in the art, and then passing it through a 100-mesh Chinese standard sieve, and taking the sieve-undersized material as the waste lithium-ion battery cathode material.

[0024] According to one specific embodiment, in step (1), the calcination conditions include: a heating rate of 2-8℃ / min, a temperature of 500-650℃, and a time of 60-300min.

[0025] Preferably, before the roasting, the waste lithium-ion battery cathode material is first stirred and mixed with sulfur and carbon compounds, and then the stirred and mixed material is roasted to obtain the intermediate I.

[0026] The present invention does not have any special requirements for the stirring and mixing conditions, as long as the two can be mixed evenly. For example, waste lithium-ion battery cathode material and sulfur and carbon compounds are stirred and mixed at 100-500 r / min for 20-40 min.

[0027] Preferably, the protective gas is selected from at least one of nitrogen, argon, and helium.

[0028] According to one specific embodiment, in step (2), the water immersion operation includes: subjecting the intermediate I to a first water immersion, filtering to obtain a first filter residue; and subjecting the first filter residue to a second water immersion.

[0029] In a preferred embodiment, the solid-liquid ratio of the first water immersion is 100-200 g / L.

[0030] Preferably, the volume ratio of the amount of water used in the first immersion to the amount of water used in the second immersion is 1:0.5-1.

[0031] Preferably, the conditions for the first and second water immersions each independently include: a rotation speed of 200-700 r / min and a time of 10-20 min.

[0032] According to one specific embodiment, the method further includes: in step (3), before performing the first mixing, the solid I is dried; and then the dried solid I is mixed with the eutectic solvent in the first mixing.

[0033] The present invention does not have special requirements for the drying conditions, as long as the solid I can be dried to a constant weight, and those skilled in the art can do so using known techniques in the field.

[0034] In a preferred embodiment, in step (3), before the first mixing is performed, the vitamin-like substance and the amino acid-like substance are first contacted to obtain the eutectic solvent.

[0035] According to another specific embodiment, the contact conditions include: a temperature of 50-80 ℃ and a time of 10-60 min.

[0036] In order to reduce the amount of eutectic solvent used in the first mixture, preferably, water is added to the first mixture in step (3).

[0037] According to one specific embodiment, the first mixing operation includes: dissolving the eutectic solvent in water, and then adding the solid I to perform the first mixing.

[0038] Preferably, in step (3), the mass ratio of the eutectic solvent to the solid I is 1.5-3:1.

[0039] Preferably, in step (3), the solid-liquid ratio of the solid I to the water is 20-100 g / L.

[0040] According to another specific embodiment, in step (3), the conditions for the first mixing include: a temperature of 90-140 ℃ and a time of 2-5 h.

[0041] In a preferred embodiment, in step (3), the lithium-containing solution is concentrated before it is dried.

[0042] The present invention does not impose any particular requirements on the concentration or drying methods, and those skilled in the art can use techniques known in the art. For example, the lithium-containing solution is concentrated and then dried at 120°C to constant weight.

[0043] The present invention does not have any special requirements on the methods of the first solid-liquid separation and the second solid-liquid separation, and those skilled in the art can use the technical means known in the art.

[0044] Preferably, in step (4), the specific operation of the precipitation reaction includes adjusting the pH of the leachate to 2-3 using oxalic acid.

[0045] In a preferred embodiment, in step (4), the precipitation conditions include a temperature of 40-70°C and a time of 20-90 min.

[0046] In a preferred embodiment, the method further includes: separating the product obtained from the precipitation reaction in step (4) to obtain the precipitate and the recovered eutectic solvent.

[0047] The present invention will be described in detail below through examples. Unless otherwise specified, the instruments, reagents, and materials involved in the following examples are all conventional instruments, reagents, and materials already existing in the prior art and can be obtained through legitimate commercial channels. Unless otherwise specified, the experimental methods and detection methods involved in the following examples are all conventional experimental methods and detection methods already existing in the prior art.

[0048] The percentage content of lithium and transition metal elements in each waste battery was tested using inductively coupled plasma optical emission spectrometry (ICP-OES), and the results are shown in Table 1. Table 1

[0049] Preparation Example 1 Vitamins (20g, L-carnitine) and amino acids (glycine) in a molar ratio of 1:3 were contacted at 70°C for 20 minutes to obtain eutectic solvent I.

[0050] Preparation Example 2 Vitamins (26g, folic acid) and amino acids (L-alanine) in a molar ratio of 1:5 were contacted at 50°C for 50 min to obtain eutectic solvent II.

[0051] Preparation Example 3 A vitamin (12g, inositol) and an amino acid (phenylalanine) in a molar ratio of 1:7 were contacted at 50°C for 50 minutes to obtain eutectic solvent III.

[0052] Preparation Example 4 A vitamin (11g, dl-α-tocopherol) and an amino acid (taurine) in a molar ratio of 1:9 were contacted at 50°C for 40 minutes to obtain eutectic solvent IV.

[0053] Preparation Example 5 A vitamin-like substance (17g, dimethylpyrimidinol menadione sulfite) and an amino acid-like substance (glycine) with a molar ratio of 1:10 were contacted at 50°C for 40 minutes to obtain a eutectic solvent V.

[0054] Comparative Preparation Example 1 Choline chloride (20g) in a molar ratio of 1:3 was contacted with ethylene glycol at 70°C for 20 min to obtain the eutectic solvent DI.

[0055] Comparative Preparation Example 2 Oxalic acid (20g) in a molar ratio of 1:8 was contacted with ethylene glycol at 70°C for 20 min to obtain eutectic solvent D-II.

[0056] Comparative preparation example 3 Choline chloride (20g) and aminosulfonic acid in a molar ratio of 1:1 were contacted at 70°C for 20 min to obtain eutectic solvent D-III.

[0057] Example 1 (1) After crushing the waste NCM523 battery, pass it through a 100-mesh Chinese standard sieve and take the sieve material to obtain waste battery positive electrode powder. Take 100g of waste battery positive electrode powder and sulfur carbon compound (carbonyl sulfide) and mix them at 300 r / min for 30 min. After mixing, put them into a corundum crucible and calcine them under nitrogen protection. Pass the tail gas into water to obtain intermediate I. The mass ratio of the sulfur-carbon compound to the waste battery cathode powder is 1.8:1; The calcination conditions were as follows: the temperature was increased to 580 ℃ at a heating rate of 5 ℃ / min, and held at that temperature for 180 min. (2) Take 75g of intermediate I and soak it in 500 ml of ultrapure water at 500 r / min for 15 min. Filter it to obtain the first filter residue. Add the filter residue to 250 ml of ultrapure water and soak it in 500 r / min for 15 min. Then perform the first solid-liquid separation to obtain solid I and lithium-containing solution. The solid-liquid ratio of the first water immersion was 150 g / L. (3) The obtained solid I was dried at 60°C to constant weight to obtain dried solid I; 37.5g of eutectic solvent I was dissolved in water, and 25g of dried solid I was added for the first mixing under reflux, followed by a second solid-liquid separation by centrifugation; leaching residue and leachate were obtained; and The lithium-containing solution was concentrated and then dried at 120 °C to constant weight to obtain lithium sulfate. The solid-liquid ratio of solid I to water is 20 g / L, and the mass ratio of solid I to eutectic solvent I is 1:1.5. The conditions for the first mixing were: temperature 110°C and time 150 min. (4) The pH of the leachate is adjusted to 2 using oxalic acid to carry out a precipitation reaction, and the transition metals are recovered in the form of precipitate; The precipitation reaction conditions were: temperature 50℃ and time 30 min.

[0058] Example 2 (1) After crushing the waste NCM622 battery, pass it through a 100-mesh Chinese standard sieve and take the sieve material to obtain waste battery positive electrode powder. Take 100g of waste battery positive electrode powder and sulfur carbon compound (carbon disulfide) and mix them at 300 r / min for 30 min. After mixing, put them into a corundum crucible and calcine them under nitrogen protection. Pass the tail gas into water to obtain intermediate I. The mass ratio of the sulfur-carbon compound to the waste battery cathode powder is 2:1; The calcination conditions were as follows: the temperature was increased to 500 °C at a heating rate of 5 °C / min, and held at that temperature for 180 min. (2) Take 90g of intermediate I and soak it in 500 ml of ultrapure water at 500 r / min for 15 min. Filter it to obtain the first filter residue. Add the filter residue to 250 ml of ultrapure water and soak it in 500 r / min for 15 min. Then perform the first solid-liquid separation to obtain solid I and lithium-containing solution. The solid-liquid ratio of the first water immersion was 180 g / L. (3) The obtained solid I was dried at 60°C to constant weight to obtain dried solid I; 50g of eutectic solvent II was dissolved in water, and 25g of dried solid I was added for the first mixing under reflux, followed by a second solid-liquid separation by centrifugation; leaching residue and leachate were obtained; and The lithium-containing solution was concentrated and then dried at 120 °C to constant weight to obtain lithium sulfate. The solid-liquid ratio of solid I to water is 30 g / L, and the mass ratio of solid I to eutectic solvent II is 1:2. The conditions for the first mixing were: temperature 120°C and time 210 min. (4) The pH of the leachate is adjusted to 3 using oxalic acid to carry out a precipitation reaction, and the transition metal is recovered in the form of a precipitate; The precipitation reaction conditions were: temperature 60℃ and time 60 min.

[0059] Example 3 (1) After crushing the waste LCO batteries, pass them through a 100-mesh Chinese standard sieve and take the sieve material to obtain waste battery positive electrode powder. Take 100g of waste battery positive electrode powder and sulfur carbon compound (carbonyl sulfide) and mix them at 300 r / min for 30 min. After mixing, put them into a corundum crucible and calcine them under nitrogen protection. Pass the tail gas into water to obtain intermediate I. The mass ratio of the sulfur-carbon compound to the waste battery cathode powder is 1.5:1; The calcination conditions were as follows: the temperature was increased to 600 ℃ at a heating rate of 5 ℃ / min and held at that temperature for 120 min. (2) Take 100g of intermediate I and soak it in 500 ml of ultrapure water at 500 r / min for 15 min. Filter it to obtain the first filter residue. Add the filter residue to 250 ml of ultrapure water and soak it in 500 r / min for 15 min. Then perform the first solid-liquid separation to obtain solid I and lithium-containing solution. The solid-liquid ratio of the first water immersion was 200 g / L. (3) The obtained solid I was dried at 60°C to constant weight to obtain dried solid I; 75g of eutectic solvent III was dissolved in water, and 25g of dried solid I was added for the first mixing under reflux, followed by a second solid-liquid separation by centrifugation; leaching residue and leachate were obtained; and The lithium-containing solution was concentrated and then dried at 120 °C to constant weight to obtain lithium sulfate. The solid-liquid ratio of solid I to water is 25 g / L, and the mass ratio of solid I to eutectic solvent III is 1:3; The conditions for the first mixing were: temperature 90°C and time 150 min. (4) The pH of the leachate is adjusted to 2.5 using oxalic acid to carry out a precipitation reaction, and the transition metals are recovered in the form of precipitate; The precipitation reaction conditions were: temperature 55℃ and time 40 min.

[0060] Example 4 (1) After crushing the waste LMO batteries, pass them through a 100-mesh Chinese standard sieve and take the sieve material to obtain waste battery positive electrode powder. Take 100g of waste battery positive electrode powder and sulfur carbon compound (carbon disulfide) and mix them at 300 r / min for 30 min. After mixing, put them into a corundum crucible and calcine them under nitrogen protection. Pass the tail gas into water to obtain intermediate I. The mass ratio of the sulfur-carbon compound to the waste battery cathode powder is 0.5:1; The calcination conditions were as follows: the temperature was increased to 650 °C at a heating rate of 5 °C / min, and held at that temperature for 120 min. (2) 85 g of intermediate I was soaked in 500 ml of ultrapure water at 500 r / min for 15 min, filtered, and the first filter residue was obtained; the filter residue was added to 250 ml of ultrapure water and soaked in 500 r / min for 15 min, and then the first solid-liquid separation was performed to obtain solid I and lithium-containing solution. The solid-liquid ratio of the first water immersion was 170 g / L. (3) The obtained solid I was dried at 60°C to constant weight to obtain dried solid I; 37.5g of eutectic solvent IV was dissolved in water, and 25g of dried solid I was added for the first mixing under reflux, followed by a second solid-liquid separation by centrifugation; leaching residue and leachate were obtained; and The lithium-containing solution was concentrated and then dried at 120 °C to constant weight to obtain lithium sulfate. The solid-liquid ratio of solid I to water is 40 g / L, and the mass ratio of solid I to eutectic solvent IV is 1.5:1. The conditions for the first mixing were: temperature 100°C and time 240 min. (4) The pH of the leachate is adjusted to 3 using oxalic acid to carry out a precipitation reaction, and the transition metals are recovered in the form of precipitate; The precipitation reaction conditions were: temperature 60℃ and time 50 min.

[0061] Example 5 (1) After crushing the waste NCA batteries, pass them through a 100-mesh Chinese standard sieve and take the sieve material to obtain waste battery positive electrode powder. Take 100g of waste battery positive electrode powder and sulfur carbon compound (carbon disulfide) and mix them at 300 r / min for 30 min. After mixing, put them into a corundum crucible and calcine them under nitrogen protection. Pass the tail gas into water to obtain intermediate I. The mass ratio of the sulfur-carbon compound to the waste battery cathode powder is 1:1; The calcination conditions were as follows: the temperature was increased to 550 °C at a heating rate of 5 °C / min and held at that temperature for 120 min. (2) 80g of intermediate I was soaked in 500 ml of ultrapure water at 500 r / min for 15 min, filtered, and the first filter residue was obtained; the filter residue was added to 250 ml of ultrapure water and soaked in 500 r / min for 15 min, and then the first solid-liquid separation was performed to obtain solid I and lithium-containing solution. The solid-liquid ratio of the first water immersion was 160 g / L. (3) The obtained solid I was dried at 60°C to constant weight to obtain a dried solid; 42.5 g of eutectic solvent V was dissolved in water, and 25 g of dried solid I was added for the first mixing under reflux, followed by a second solid-liquid separation by centrifugation; leaching residue and leachate were obtained; and The lithium-containing solution was concentrated and then dried at 120 °C to constant weight to obtain lithium sulfate. The solid-liquid ratio of solid I to water is 50 g / L, and the mass ratio of solid I to eutectic solvent V is 1:1.7. The conditions for the first mixing were: temperature 140°C and time 150 min. (4) The pH of the leachate is adjusted to 2.5 using oxalic acid to carry out a precipitation reaction, and the transition metals are recovered in the form of precipitate; The precipitation reaction conditions were: temperature 55℃ and time 45 min.

[0062] Comparative Example 1 The procedure was carried out using a method similar to that of Example 1, except that the sulfur carbon compound (carbonyl sulfide) in Example 1 was replaced by ammonium sulfide by mass. The remaining conditions are the same as in Example 1.

[0063] Comparative Example 2 The same method as in Example 1 was used, except that the mass of the eutectic solvent I in Example 1 was replaced with the eutectic solvent DI. The remaining conditions are the same as in Example 1.

[0064] Comparative Example 3 The procedure was carried out using a method similar to that in Example 1, except that the eutectic solvent I in Example 1 was replaced by an equal mass of eutectic solvent D-II. The remaining conditions are the same as in Example 1.

[0065] Comparative Example 4 The procedure was carried out using a method similar to that in Example 1, except that the eutectic solvent I in Example 1 was replaced by an equal mass of eutectic solvent D-III. The remaining conditions are the same as in Example 1.

[0066] Comparative Example 5 The method is similar to that in Example 1, except that steps (1) and (2) are omitted. Specifically: (1) After crushing the waste NCM523 battery, pass it through a 100-mesh Chinese standard sieve and take the sieve material to obtain waste battery positive electrode powder. The eutectic solvent I was dissolved in water, and 100g of waste battery positive electrode powder was added. The mixture was first mixed under reflux and then centrifuged to perform a second solid-liquid separation, resulting in leaching residue and leaching solution. The solid-liquid ratio of the waste battery positive electrode powder to the water is 20 g / L, and the mass ratio of the waste battery positive electrode powder to the eutectic solvent I is 1:1.5. The conditions for the first mixing were: temperature 110°C and time 150 min. (2) The pH of the leachate is adjusted to 2 using oxalic acid to carry out a precipitation reaction, and the metal is recovered in the form of a precipitate; The precipitation reaction conditions were: temperature 50℃ and time 30 min.

[0067] Test case The products obtained in the above examples were tested using inductively coupled plasma optical emission spectrometry (ICP-OES), and the specific results are shown in Table 2. Wherein, lithium salt recovery rate = actual recovered lithium salt mass / theoretically total recovered lithium salt mass × 100%; Nickel-cobalt-manganese recovery rate = (actually recovered mass of nickel-cobalt-manganese oxalate / theoretically recovered mass of nickel-cobalt-manganese) × 100%.

[0068] Table 2

[0069] The results above show that the combined use of sulfur-carbon compound roasting and eutectic solvent leaching can significantly improve the recovery rates of lithium salts and nickel-cobalt-manganese. Using only one method can only improve the recovery rate of either lithium salt or nickel-cobalt-manganese, fully demonstrating the necessity of using both methods in combination.

[0070] This invention is in Figure 1 The XRD pattern of lithium sulfate extracted in Example 1 is provided as an example. Figure 1 It can be seen that the product obtained by water leaching after carbon and sulfur roasting of waste battery cathode black powder is lithium sulfate. This indicates that the roasting process removes lithium ions from the black powder and combines them with sulfur in sulfur carbon compounds to form lithium sulfate, which is more soluble in water, thus effectively reducing the amount of water used for leaching.

[0071] This invention is in Figure 2 The XRD pattern of solid I in Example 1 is provided as an example. Figure 1 It can be seen that the structure of the cathode powder from the waste battery was completely destroyed after water immersion lithium extraction, and it changed from LMO to nickel cobalt manganese oxide. No lithium ion peaks were observed, indicating that lithium ions were completely removed from the intermediate.

[0072] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for recycling positive electrode materials of lithium-ion batteries, characterized in that, The method includes: (1) In the presence of a protective gas, waste lithium-ion battery cathode material is calcined with sulfur and carbon compounds to obtain intermediate I; (2) The intermediate I is subjected to water immersion and first solid-liquid separation in sequence to obtain solid I and lithium-containing solution; (3) The solid I is subjected to a first mixing and a second solid-liquid separation with a eutectic solvent to obtain leaching residue and leachate; and The lithium-containing solution was dried to obtain lithium sulfate; (4) The leachate is reacted with oxalic acid to precipitate the transition metals; The sulfur-carbon compound is selected from at least one of carbon disulfide, carbonyl sulfide, tricarbon disulfide, and carbon monosulfide; The eutectic solvent contains vitamins and amino acids in a molar ratio of 1:(3-12).

2. The method according to claim 1, characterized in that, The sulfur-carbon compound is carbon disulfide and / or carbonyl sulfide; The vitamin-like substances are selected from carnitine, folic acid, inositol, dl-α-tocopherol, dimethylpyrimidinol menadione sulfite, sodium menadione bisulfite, and nicotinamide menadione bisulfite. The amino acid is selected from at least one of glycine, L-alanine, phenylalanine, and taurine.

3. The method according to claim 1 or 2, characterized in that, In step (1), the mass ratio of the sulfur-carbon compound to the waste lithium-ion battery cathode material is (0.5-2):

1.

4. The method according to claim 1 or 2, characterized in that, The cathode material of the waste lithium-ion battery is selected from at least one lithium-ion battery cathode material among NCM, NCA, LCO, and LMO.

5. The method according to claim 1 or 2, characterized in that, In step (2), the water immersion operation includes: subjecting the intermediate I to a first water immersion, filtering to obtain a first filter residue; and subjecting the first filter residue to a second water immersion.

6. The method according to claim 1 or 2, characterized in that, The solid-liquid ratio of the first water immersion is 100-200 g / L; and / or The volume ratio of the water used in the first immersion to the water used in the second immersion is 1:0.5-1.

7. The method according to claim 1 or 2, characterized in that, In step (3), before the first mixing, the vitamin-like substance and the amino acid-like substance are first contacted to obtain the eutectic solvent; The contact conditions include a temperature of 50-80 ℃ and a time of 10-60 min.

8. The method according to claim 1 or 2, characterized in that, In step (3), the mass ratio of the eutectic solvent to the solid I is 1.5-3:

1.

9. The method according to claim 1 or 2, characterized in that, In step (1), the calcination conditions include: a heating rate of 2-8°C / min, a temperature of 500-650°C, and a time of 60-300 min; and / or In step (3), the conditions for the first mixing include: a temperature of 90-140 °C and a time of 2-5 h; and / or In step (4), the precipitation conditions include a temperature of 40-70℃ and a time of 20-90min.

10. The method according to claim 1 or 2, characterized in that, The method further includes: separating the product obtained from the precipitation reaction in step (4) to obtain the precipitate and the recovered eutectic solvent.

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