Method for extracting lithium from waste lithium battery positive electrode material through sulfuration roasting

Abstract

The invention relates to a method for extracting lithium from a waste lithium battery positive electrode material through sulfuration roasting, which comprises the following steps of: mixing the waste lithium battery positive electrode material and sulfuration salt, and sequentially roasting and leaching to obtain sulfuration slag and leachate; and evaporating and precipitating the leachate in sequence to obtain the lithium-containing compound. According to the method, a pyrogenic process-wet process combined process is adopted, sulfide salt is used as a roasting auxiliary agent to improve the roasting selectivity, nickel, cobalt, manganese and other impurities can form stable insoluble sulfide or oxide, and efficient separation of the lithium element is achieved; meanwhile, the sulphide salt is not easy to explode and volatilize and does not generate toxic and harmful gas, so that the requirements of process equipment can be reduced, the utilization rate of raw materials is improved, and the process cost is reduced. The method has the advantages of high selectivity, high lithium extraction efficiency, economy and energy saving, solves the problems of energy consumption, acid consumption, poor selectivity, complex route, low product purity and the like in the prior art, reduces the harm of waste lithium batteries to the environment, and accords with green sustainable development.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery recycling, and in particular to a method for extracting lithium from the cathode material of a lithium battery, and more particularly to a method for extracting lithium by sulfation roasting of the cathode material of a waste lithium battery. Background Art

[0002] The new energy vehicles in China have developed rapidly. Lithium batteries are the core components of new energy vehicles and are widely used for their high energy density, high cycle life, environmental friendliness and other characteristics. It is predicted that by 2050, the demand for lithium batteries will exceed 9000 GWh, with a large market share. At the same time, it also means that there is huge pressure on the supply of metal elements that make up lithium batteries. The International Energy Agency predicts that there will be shortages of lithium, nickel, cobalt and manganese in the future, and the supply-demand gap will further widen. After 3 to 8 years, a large number of lithium-ion batteries will face retirement, causing great pressure on the environment. The recycling of waste lithium batteries has become a research hotspot. Waste batteries contain a large amount of valuable metals, which can relieve the pressure on China's lithium, nickel, cobalt and manganese mineral resources, reduce dependence on imports, and also solve the safety hazards and environmental problems caused by retired lithium batteries.

[0003] At present, the main methods for recovering lithium from waste lithium battery cathode materials are pyrometallurgical lithium extraction and hydrometallurgical lithium extraction. Most hydrometallurgical lithium extraction methods use strong acid leaching. During the leaching process, various metal elements are leached synchronously, with poor selectivity and strong corrosion to equipment. The step-by-step recovery of nickel, cobalt, manganese and lithium has low purity, a cumbersome process, large consumption of acid and water, and large lithium loss. The use of organic reagents such as formic acid, oxalic acid, tartaric acid, etc. can achieve selective extraction of lithium, but they are expensive and not conducive to large-scale production. Pyrometallurgical lithium extraction metallurgy technology mostly uses a high-temperature furnace to treat waste lithium batteries. Among them, non-metallic elements are decomposed into gases, and metal elements are reduced to alloys. This process is simple, efficient and has a large processing capacity. However, pyrometallurgical lithium extraction can only recover valuable metals such as nickel, cobalt and manganese, and lithium remains to be processed in the slag, thus increasing the cost of lithium extraction. The newly developed pyrometallurgical-hydrometallurgical combined smelting technology combines the advantages of pyrometallurgy and hydrometallurgy. Generally, hydrogen, natural gas, carbon powder or salt, etc. are used as reducing agents, and after roasting reaction in a reduction furnace, hydrometallurgical lithium extraction is carried out to achieve the priority, high-efficiency and energy-saving extraction of lithium.

[0004] In the combined pyrometallurgical-hydrometallurgical recovery process, common roasting methods include carbonization reduction roasting, salt roasting, and sulfidation roasting. Regarding carbonization reduction roasting, a mixture of hydrogen and carbon monoxide can be used as a reducing agent, or the negative electrode of battery materials, carbon powder, lithium-containing fertilizers, or organic carbon sources (such as lemon sugar, sucrose, oxalic acid) can be used as reducing agents. However, the leaching rate is generally low, the water consumption is large, and the reagents are expensive, which brings certain difficulties to subsequent processing. CN114032384A discloses a method of reducing roasting with natural graphite powder as a reducing agent in an argon atmosphere. The roasting temperature is 650°C - 700°C, and the lithium extraction efficiency by water leaching can reach 90.07% - 91.86%. However, the solid-liquid ratio of water leaching is large, which is not conducive to large-scale production.

[0005] Regarding salt roasting, calcium chloride, sodium bisulfate, sodium sulfate, or concentrated sulfuric acid mixture can be used as reducing agents, but it may also lead to a low leaching rate. CN113816402A discloses using calcium chloride as a reducing agent, mixing with waste lithium iron phosphate, and reducing roasting at 400°C - 600°C. The positive electrode powder of waste lithium iron phosphate batteries plays a role in reducing cobalt ions. Calcium chloride can destroy the crystal structure of the positive electrode material of waste lithium batteries, making the lithium ion leaching rate reach more than 85.2%.

[0006] Regarding sulfidation roasting, CN118006925A discloses a method for recovering waste lithium nickel cobalt manganese oxide batteries by sulfur-assisted roasting. By mixing lithium nickel cobalt manganese oxide with sulfur, the roasting temperature is 500°C. However, the liquid-solid ratio of water leaching is as high as 100 mL / g, and the water consumption is large. In addition, sulfur is volatile, resulting in low sulfidation efficiency, and most of the sulfur condenses at the end of the reduction furnace.

[0007] Therefore, developing a method for lithium extraction and recovery from waste ternary batteries with high selectivity, high lithium leaching efficiency, energy-saving, green, and low cost has become an urgent problem to be solved at present. Summary of the Invention

[0008] To solve the above technical problems, the present invention provides a method for lithium extraction by sulfidation roasting of the positive electrode material of waste lithium batteries. The present invention adopts a combined pyrometallurgical-hydrometallurgical process, and sulfide salts are used as roasting aids to improve the selectivity of roasting, which is conducive to the formation of stable insoluble sulfides or oxides of nickel, cobalt, manganese, and other impurities, realizing the efficient separation of lithium elements. At the same time, sulfide salts are not prone to explosion, volatilization, and do not produce toxic and harmful gases, which can reduce the requirements for process equipment, improve the utilization rate of raw materials, and reduce the process cost. This method has high selectivity, high lithium extraction efficiency, and is energy-saving and economical, solving the problems of high energy consumption, poor selectivity, complex process, and low product purity in the prior art, reducing the harm of waste lithium batteries to the environment, and meeting the requirements of green and sustainable development.

[0009] To achieve this purpose, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a method for extracting lithium from waste lithium battery cathode materials by sulfation roasting, the method comprising the following steps: after mixing the waste lithium battery cathode materials and a sulfide salt, roasting and leaching are carried out in sequence to obtain a sulfide residue and a leaching solution; the leaching solution is evaporated and precipitated in sequence to obtain a lithium-containing compound.

[0011] The present invention adopts a combined pyrometallurgical-hydrometallurgical process, and the sulfide salt is used as a roasting aid to improve the selectivity of roasting, which is beneficial to the formation of stable insoluble sulfides or oxides of nickel, cobalt, manganese and other impurities, realizing the efficient separation of lithium elements; at the same time, the sulfide salt is not easy to explode, volatilize, and does not generate toxic and harmful gases, which can reduce the requirements for process equipment, improve the utilization rate of raw materials, and reduce the process cost. This method has high selectivity, high lithium extraction efficiency, and is energy-saving and economical, solving the problems of high energy consumption, poor selectivity, complex route, and low product purity in the prior art, reducing the harm of waste lithium batteries to the environment, and meeting the requirements of green and sustainable development.

[0012] Preferably, the waste lithium battery cathode materials include any one or at least two combinations of lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium cobalt oxide or lithium iron phosphate. Typical but non-limiting combinations include the combination of lithium nickel cobalt manganese oxide and lithium manganese oxide, or the combination of lithium manganese oxide, lithium cobalt oxide and lithium iron phosphate.

[0013] Preferably, the waste lithium battery cathode materials further include any one or at least two combinations of carbon powder, copper foil or aluminum foil. Typical but non-limiting combinations include the combination of carbon powder and copper foil, or the combination of carbon powder, copper foil and aluminum foil.

[0014] Preferably, the particle size D50 of the waste lithium battery cathode materials is 50 μm - 100 μm. For example, it can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0015] Preferably, the sulfide salt includes any one or at least two combinations of sodium sulfide, calcium sulfide, potassium sulfide, iron disulfide or magnesium sulfide. Typical but non-limiting combinations include the combination of sodium sulfide and calcium sulfide, or the combination of calcium sulfide, potassium sulfide and magnesium sulfide.

[0016] The present invention uses a sulfide salt as a roasting aid. As a solid roasting aid, it can reduce the overall requirements for the process system; at the same time, the sulfide salt is non-toxic, not easy to explode, volatilize, and does not generate toxic and harmful gases, and is easy to separate and remove during the subsequent treatment process.

[0017] Preferably, the sulfide salt includes sodium sulfide.

[0018] The present invention uses sodium sulfide as a roasting aid, which can ensure the purity of the whole system and will not introduce impurity ions. Whether it is sulfide slag or lithium-containing compounds, sodium ions can be removed simply and efficiently. Moreover, during the precipitation process, using sodium carbonate as a precipitant, the sodium ions in sodium sulfide and the sodium ions in sodium carbonate can form metal double salts with impurity metals, thereby improving the leaching rate of lithium.

[0019] Preferably, the mass ratio of the waste lithium battery cathode material to the sulfide is 1:(0.2 - 3). For example, it can be 1:0.2, 1:0.5, 1:1, 1:2 or 1:3, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0020] By further regulating the dosage of the sulfide, the present invention can further improve the leaching rate and selectivity of lithium elements. Within the range of the preferred dosage of the sulfide, not only can the leaching rate of lithium elements be further improved, but also the selectivity of lithium elements can be further enhanced.

[0021] Preferably, the mixing includes mechanical mixing.

[0022] Preferably, the method of mixing includes ball milling.

[0023] Preferably, the rotation speed of the ball milling is 300 r / min - 425 r / min. For example, it can be 300 r / min, 350 r / min, 375 r / min, 400 r / min or 425 r / min, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0024] Preferably, the ball-to-material ratio of the ball milling is (2 - 10):1. For example, it can be 2:1, 4:1, 6:1, 8:1 or 10:1, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0025] Preferably, the mixing time is 0.5 h - 5 h. For example, it can be 0.5 h, 1 h, 2 h, 3 h, 4 h or 5 h, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0026] Preferably, the holding temperature for roasting is 500 °C - 750 °C. For example, it can be 500 °C, 550 °C, 600 °C, 650 °C, 700 °C or 750 °C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0027] By further controlling the holding temperature of roasting, the leaching rate of lithium element can be further increased. Within the preferred holding temperature of roasting, nickel, cobalt, manganese and other impurities can form stable insoluble sulfides or oxides, thereby increasing the leaching rate of lithium element and also avoiding the reduction of leaching rate caused by caking of lithium element during roasting.

[0028] Preferably, the holding time of the roasting is 0.5h - 3h, for example, it can be 0.5h, 1h, 1.5h, 2h, 2.5h or 3h, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0029] By further controlling the holding time of roasting, the leaching rate of lithium element is further increased. Within the preferred holding time of roasting, the leaching rate of lithium element is high.

[0030] Preferably, the heating rate of the roasting is 8℃ / min - 12℃ / min, for example, it can be 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min or 12℃ / min, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0031] Preferably, the leaching agent for leaching includes deionized water.

[0032] Preferably, the liquid - solid ratio of the leaching is 5mL / g - 30mL / g, for example, it can be 5mL / g, 10mL / g, 15mL / g, 20mL / g, 25mL / g or 30mL / g, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0033] Preferably, the temperature of the leaching is 40℃ - 90℃, for example, it can be 40℃, 50℃, 60℃, 70℃, 80℃ or 90℃, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0034] Preferably, the time of the leaching is 0.5h - 3h, for example, it can be 0.5h, 1h, 1.5h, 2h, 2.5h or 3h, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0035] Preferably, the method of evaporation includes vacuum evaporation.

[0036] Preferably, the end - point pressure of the vacuum evaporation is 90mbar - 480mbar, for example, it can be 90mbar, 100mbar, 200mbar, 300mbar, 400mbar or 480mbar, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0037] Preferably, the end temperature of the temperature rise during evaporation is 50°C - 90°C. For example, it can be 50°C, 60°C, 70°C, 80°C or 90°C, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0038] Preferably, the precipitating agent for the precipitation includes sodium carbonate.

[0039] Preferably, the heat preservation temperature for the precipitation is 80°C - 90°C. For example, it can be 80°C, 82°C, 84°C, 86°C, 88°C or 90°C, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0040] Preferably, after the precipitation, filtration and washing are successively carried out.

[0041] Preferably, the washing agent for the washing includes deionized water.

[0042] Preferably, the number of washing times is 2 - 5 times. For example, it can be 2 times, 3 times, 4 times or 5 times.

[0043] As a preferred technical solution of the present invention, the method includes the following steps:

[0044] (1) After mechanically mixing the waste lithium battery cathode material and the sulfide salt in proportion, a mixed material is obtained, and the time for the mechanical mixing is 0.5 h - 5 h.

[0045] (2) The mixed material is selectively sulfidized and roasted at 500°C - 750°C for 0.5 h - 3 h to obtain a roasted material.

[0046] (3) The roasted material is leached with deionized water, and the leachate and sulfide slag are separated. The temperature for the leaching is 40°C - 90°C, the time for the leaching is 0.5 h - 3 h, and the liquid-solid ratio for the leaching is 5 mL / g - 30 mL / g.

[0047] (4) After the leachate is subjected to vacuum evaporation, saturated sodium carbonate solution is first added, and then precipitation, filtration and washing are successively carried out to obtain lithium carbonate. The end temperature of the temperature rise during the vacuum evaporation is 50°C - 90°C, the heat preservation temperature for the precipitation is 80°C - 90°C, the washing agent for the washing includes deionized water, and the number of washing times is 2 - 5 times.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects:

[0049] (1) The present invention adopts a combined process of pyrometallurgy and hydrometallurgy, and the sulfide salt is used as a roasting aid to improve the selectivity of roasting, which is beneficial to the formation of soluble salts of lithium, making nickel, cobalt, manganese and other impurities in the raw materials form stable insoluble sulfides or oxides, and realizing the efficient selective separation of lithium elements.

[0050] (2) The sulfide salt of the present invention is non-toxic, not explosive, not volatile, and does not generate toxic and harmful gases, which can reduce the requirements for process equipment, improve the utilization rate of raw materials, and reduce process costs.

[0051] (3) The method of the present invention has high selectivity, high lithium extraction efficiency, and is energy-saving and economical. It solves the problems of high energy consumption, poor selectivity, complex route, and low product purity in the prior art, reduces the harm of waste lithium batteries to the environment, and conforms to green and sustainable development.

[0052] (4) The lithium ion leaching rate of the present invention is high and the selectivity is good, providing an efficient and economical new process for lithium extraction from waste lithium battery cathode materials, with broad application prospects. Description of the Drawings

[0053] Figure 1 is the process flow chart of the method for lithium extraction by sulfation roasting of waste lithium battery cathode materials of the present invention. Detailed Embodiments

[0054] The technical solutions of the present invention will be further described below in conjunction with the drawings and through specific embodiments. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0055] In all the following examples and comparative examples, the composition of the waste lithium battery cathode materials used is the same.

[0056] Example 1

[0057] This example provides a method for lithium extraction by sulfation roasting of waste lithium battery cathode materials, and the method includes the following steps:

[0058] (1) After ball-milling and mixing the waste lithium battery cathode materials and sodium sulfide at a mass ratio of 1:1, a mixed material is obtained. The rotation speed of the ball-milling and mixing is 400 r / min, the ball-to-material ratio of the ball-milling and mixing is 4:1, and the time of the ball-milling and mixing is 3 h;

[0059] (2) Selectively sulfating and roasting the mixed material at 550 °C for 2 h to obtain a roasted material, and the heating rate of the roasting is 10 °C / min;

[0060] (3) Leaching the roasted material with deionized water, and separating to obtain a leaching solution and a sulfide residue. The temperature of the leaching is 80 °C, the time of the leaching is 1 h, and the liquid-to-solid ratio of the leaching is 15 mL / g;

[0061] (4) After subjecting the leachate to vacuum evaporation, first add saturated sodium carbonate solution, and then successively carry out precipitation, filtration, washing and drying to obtain lithium carbonate. The end pressure of the vacuum evaporation is 300 mbar, the end temperature of the temperature rise during the vacuum evaporation is 80 °C, the heat preservation temperature of the precipitation is 85 °C, the detergent for the washing includes deionized water, and the number of washing times is 3 times.

[0062] Figure 1 Figure is the process flow chart of the method for extracting lithium by sulfation roasting of waste lithium battery cathode materials according to the present invention. It can be seen from the figure that the present invention adopts a combined process of pyrometallurgy and hydrometallurgy, and uses sulfide as a roasting aid to improve the selectivity of roasting, which is beneficial to the formation of stable insoluble sulfides or oxides of nickel, cobalt, manganese and other impurities, and realizes the efficient separation of lithium elements.

[0063] Example 2

[0064] This example provides a method for extracting lithium by sulfation roasting of waste lithium battery cathode materials, and the method includes the following steps:

[0065] (1) After ball-milling and mixing waste lithium battery cathode materials and calcium sulfide according to a mass ratio of 1:0.2, a mixed material is obtained. The rotation speed of the ball-milling and mixing is 300 r / min, the ball-to-material ratio of the ball-milling and mixing is 2:1, and the time of the ball-milling and mixing is 5 h;

[0066] (2) Subject the mixed material to selective sulfation roasting at 600 °C for 3 h to obtain a roasted material. The heating rate of the roasting is 8 °C / min;

[0067] (3) Leach the roasted material with deionized water, and separate to obtain a leachate and sulfide slag. The temperature of the leaching is 40 °C, the time of the leaching is 3 h, and the liquid-solid ratio of the leaching is 5 mL / g;

[0068] (4) After subjecting the leachate to vacuum evaporation, first add saturated sodium carbonate solution, and then successively carry out precipitation, filtration, washing and drying to obtain lithium carbonate. The end pressure of the vacuum evaporation is 90 mbar, the end temperature of the temperature rise during the vacuum evaporation is 50 °C, the heat preservation temperature of the precipitation is 80 °C, the detergent for the washing includes deionized water, and the number of washing times is 5 times.

[0069] Example 3

[0070] This example provides a method for extracting lithium by sulfation roasting of waste lithium battery cathode materials, and the method includes the following steps:

[0071] (1) After ball-milling and mixing waste lithium battery cathode materials and potassium sulfide at a mass ratio of 1:3, a mixed material is obtained. The rotation speed of the ball-milling and mixing is 425 r / min, the ball-to-material ratio of the ball-milling and mixing is 10:1, and the time of the ball-milling and mixing is 0.5 h;

[0072] (2) The mixed material is selectively sulfidized and roasted at 750 °C for 0.5 h to obtain a roasted material. The heating rate of the roasting is 12 °C / min;

[0073] (3) The roasted material is leached with deionized water, and the leachate and sulfide slag are separated. The temperature of the leaching is 90 °C, the time of the leaching is 0.5 h, and the liquid-to-solid ratio of the leaching is 30 mL / g;

[0074] (4) After the leachate is subjected to vacuum evaporation, saturated sodium carbonate solution is first added, and then precipitation, filtration, washing and drying are carried out in sequence to obtain lithium carbonate. The end pressure of the vacuum evaporation is 480 mbar, the end temperature of the heating during the vacuum evaporation is 90 °C, the heat preservation temperature of the precipitation is 90 °C, the washing agent for the washing includes deionized water, and the number of washing times is 2 times.

[0075] Example 4

[0076] The difference between this example and Example 1 is only that, except that the mass ratio of the waste lithium battery cathode material to sodium sulfide in step (1) is 1:0.1, the rest are the same as in Example 1.

[0077] Example 5

[0078] The difference between this example and Example 1 is only that, except that the mass ratio of the waste lithium battery cathode material to sodium sulfide in step (1) is 1:3.2, the rest are the same as in Example 1.

[0079] Example 6

[0080] The difference between this example and Example 1 is only that, except that the roasting temperature in step (2) is 450 °C, the rest are the same as in Example 1.

[0081] Example 7

[0082] The difference between this example and Example 1 is only that, except that the roasting temperature in step (2) is 800 °C, the rest are the same as in Example 1.

[0083] Example 8

[0084] The difference between this example and Example 1 is only that, except that the liquid-to-solid ratio of the leaching in step (3) is 4 mL / g, the rest are the same as in Example 1.

[0085] Example 9

[0086] The difference between this embodiment and Embodiment 1 is only that, except that the liquid-solid ratio in step (3) for leaching is 32 mL / g, the rest are the same as those in Embodiment 1.

[0087] Comparative Example 1

[0088] The difference between this comparative example and Embodiment 1 is only that, except that sodium sulfide in step (1) is replaced by sodium metabisulfite, the rest are the same as those in Embodiment 1.

[0089] Comparative Example 2

[0090] The difference between this comparative example and Embodiment 1 is only that, except that sodium sulfide in step (1) is replaced by sulfur, the rest are the same as those in Embodiment 1.

[0091] Comparative Example 3

[0092] The difference between this comparative example and Embodiment 1 is only that, except that sodium sulfide in step (1) is replaced by carbon powder, the rest are the same as those in Embodiment 1.

[0093] Comparative Example 4

[0094] The difference between this comparative example and Embodiment 1 is only that, except that sodium sulfide in step (1) is replaced by sodium hydroxide, the rest are the same as those in Embodiment 1.

[0095] Comparative Example 5

[0096] The difference between this comparative example and Embodiment 1 is only that, except that sodium sulfide in step (1) is replaced by calcium oxide, the rest are the same as those in Embodiment 1.

[0097] Testing Method

[0098] The concentration of lithium ions in the lithium carbonate prepared in Embodiments 1 - 9 and Comparative Examples 1 - 5 was measured using an Avio 220Max (Perkin Elmer) atomic absorption spectrometer, and the leaching rate of lithium ions was calculated and the results were recorded in Table 1.

[0099] Table 1

[0100]

[0101]

[0102] It can be seen from the test results that:

[0103] (1) It can be seen from Examples 1 - 9 to Comparative Examples 1 - 5 that the present invention adopts a combined pyrometallurgical - hydrometallurgical process, using sulfide salts as roasting aids to improve the selectivity of roasting, which is conducive to the formation of stable insoluble sulfides or oxides of nickel, cobalt, manganese and other impurities, realizing the efficient separation of lithium elements. At the same time, sulfide salts are not prone to explosion, volatilization, and do not produce toxic and harmful gases, which can reduce the requirements for process equipment, improve the utilization rate of raw materials, and reduce process costs. This method has high selectivity, high lithium extraction efficiency, and is energy - saving and economical, solving the problems of high energy and acid consumption, poor selectivity, complex routes, and low product purity in the prior art, reducing the harm of waste lithium batteries to the environment, and conforming to green and sustainable development.

[0104] (2) It can be seen from Examples 1 and 4 - 5 that by further regulating the mass ratio of the waste lithium battery cathode material to sodium sulfide in the present invention, the leaching rate of lithium ions can be further improved.

[0105] (3) It can be seen from Examples 1 and 6 - 7 that by further regulating the holding temperature of roasting in the present invention, the leaching rate of lithium ions can be further improved.

[0106] (4) It can be seen from Examples 1 and 8 - 9 that by further regulating the liquid - solid ratio of leaching in the present invention, the leaching rate of lithium ions can be further improved.

[0107] (5) It can be seen from Examples 1 and Comparative Examples 1 - 5 that by using sulfide salts as roasting aids in the present invention, the selectivity of roasting can be improved, and nickel, cobalt, and manganese are retained in the slag during the leaching process (in Comparative Example 2, other elements will also be leached. Sulfur as a roasting aid has poor selectivity and is toxic, with relatively high requirements for production equipment), thus realizing the highly selective leaching of lithium ions. At the same time, sulfide salts are non - toxic, not prone to explosion, volatilization, and do not produce toxic and harmful gases, which can reduce the requirements for process equipment, improve the utilization rate of raw materials, and reduce process costs.

[0108] In summary, the present invention adopts a combined pyrometallurgical - hydrometallurgical process, using sulfide salts as roasting aids to improve the selectivity of roasting, which is conducive to the formation of stable insoluble sulfides or oxides of nickel, cobalt, manganese and other impurities, realizing the efficient separation of lithium elements. At the same time, sulfide salts are not prone to explosion, volatilization, and do not produce toxic and harmful gases, which can reduce the requirements for process equipment, improve the utilization rate of raw materials, and reduce process costs. This method has high selectivity, high lithium extraction efficiency, and is energy - saving and economical, solving the problems of high energy and acid consumption, poor selectivity, complex routes, and low product purity in the prior art, reducing the harm of waste lithium batteries to the environment, and conforming to green and sustainable development.

[0109] The applicant declares that the above description is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for extracting lithium from waste lithium battery positive electrode materials by sulfidation roasting, characterized in that: The method comprises the following steps: After mixing the waste lithium battery positive electrode material and the sulfide salt, roasting and leaching are carried out in sequence to obtain sulfide slag and leaching solution; the leaching solution is evaporated and precipitated in sequence to obtain a lithium-containing compound.

2. The method according to claim 1, characterized in that The positive electrode material of the waste lithium battery includes any one of lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium cobalt oxide or lithium iron phosphate, or a combination of at least two thereof; Preferably, the particle size D50 of the waste lithium battery positive electrode material is 50 μm-100 μm.

3. The method according to claim 1 or 2, characterized in that: The sulfide salt includes any one of sodium sulfide, calcium sulfide, potassium sulfide, iron disulfide or magnesium sulfide, or a combination of at least two thereof; Preferably, the sulfide salt comprises sodium sulfide; Preferably, the mass ratio of the waste lithium battery positive electrode material to the sulfide salt is 1:(0.2-3).

4. The method according to any one of claims 1 to 3, characterized in that: The mixing includes mechanical mixing; Preferably, the mixing method comprises ball milling; Preferably, the mixing time is 0.5h-5h.

5. The method according to any one of claims 1 to 4, characterized in that: The calcination temperature is 500°C-750°C; Preferably, the calcination holding time is 0.5h-3h.

6. The method according to any one of claims 1 to 5, characterized in that: The leaching agent for leaching includes deionized water; Preferably, the liquid-to-solid ratio of the leaching is 5 mL / g-30 mL / g; Preferably, the leaching temperature is 40°C-90°C; Preferably, the leaching time is 0.5h-3h.

7. The method according to any one of claims 1 to 6, characterized in that: The evaporation method includes evaporation under reduced pressure; Preferably, the terminal pressure of the reduced pressure evaporation is 90 mbar-480 mbar; Preferably, the heating end point temperature of the evaporation is 50°C-90°C.

8. The method according to any one of claims 1 to 7, characterized in that: The precipitating agent of the precipitation comprises sodium carbonate; Preferably, the precipitation is kept at a temperature of 80°C-90°C.

9. The method according to any one of claims 1 to 8, characterized in that: After the precipitation, filtering and washing are performed in sequence; Preferably, the washing detergent comprises deionized water; Preferably, the washing is performed 2 to 5 times.

10. The method according to claim 1, characterized in that The method comprises the following steps: (1) mechanically mixing the waste lithium battery positive electrode material and the sulfide salt in proportion to obtain a mixture, wherein the mechanical mixing time is 0.5h-5h; (2) selectively sulfurizing and roasting the mixture at 500° C.-750° C. for 0.5 h-3 h to obtain a roasted material; (3) leaching the roasted material with deionized water to separate the leaching solution and sulfide slag, wherein the leaching temperature is 40° C.-90° C., the leaching time is 0.5 h-3 h, and the liquid-to-solid ratio of the leaching is 5 mL / g-30 mL / g; (4) After the leachate is evaporated under reduced pressure, a saturated sodium carbonate solution is first added, and then precipitation, filtration and washing are performed in sequence to obtain lithium carbonate, the heating end temperature of the reduced pressure evaporation is 50°C-90°C, the insulation temperature of the precipitation is 80°C-90°C, the washing detergent includes deionized water, and the number of washing times is 2 times-5 times.

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