A method for preferentially extracting lithium from the cathode material of waste lithium-ion batteries

Abstract

A method for preferentially extracting lithium from the cathode material of waste lithium-ion batteries, comprising the following steps: (1) mixing the powder of the cathode material of waste lithium-ion batteries with a chlorine- and hydrogen-containing compound, placing the mixture in a tubular furnace, introducing an oxygen atmosphere, and performing chlorination roasting to obtain a roasted product; (2) grinding the roasted product obtained in step (1), adding water, stirring for leaching, filtering to obtain a lithium-rich leaching solution and a leaching residue. After evaporating and concentrating the lithium-rich leaching solution obtained in step (2), adding an alkali to the lithium-rich concentrated solution, aging, filtering, adding sodium carbonate to the filtrate, evaporating to crystallize, and washing the crystals to obtain a lithium carbonate product. The method of the present invention has a high recovery rate of lithium elements, a high purity of the lithium carbonate product, good separation effect, low price and wide source of the chlorinating agent, no metal element residue, simple process, low cost, and is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to a method for extracting lithium from the cathode material of a lithium-ion battery, and more particularly to a method for preferentially extracting lithium from the cathode material of waste lithium-ion batteries. Background Art

[0002] In recent years, with the maturity of high-energy-density lithium-ion batteries and policy guidance, the global new energy vehicle market has grown rapidly, further increasing the scale of retired lithium-ion batteries, and the problem of recycling waste lithium-ion batteries has become increasingly serious.

[0003] Currently, the lithium required for the production of lithium-ion batteries is mainly extracted from salt lake brines and high-grade lithium ores. Although the reserves of salt lake brines are abundant, the extraction of lithium requires a large amount of brine resources and a long production cycle. The mass contents of lithium in lithium ores such as lepidolite and spodumene are only 3.84% and 3.73% respectively, and the extraction of lithium from them has a greater impact on the environment and higher energy consumption in mining and processing. Compared with salt lake brines and lithium ores, the mass content of lithium in the cathode material of waste lithium-ion batteries is about 5-7%, and the energy consumption and pollution of extraction are far less than those of the above two sources. Therefore, extracting lithium from waste lithium-ion batteries is of great significance. From the perspective of environmental protection and resource conservation, the recycling of waste lithium-ion batteries is very necessary and urgent.

[0004] Currently, the main recycling methods for the cathode material of waste lithium-ion batteries are pyrometallurgical processes and hydrometallurgical processes. The pyrometallurgical process has a short process flow and is simple, but it has problems such as high energy consumption, large air pollution, and low lithium recovery rate. The hydrometallurgical process also has problems such as a long process flow, large water consumption, and low lithium recovery rate. Therefore, it is necessary to find an effective method for preferentially extracting lithium to further expand economic benefits.

[0005] CN112079369A discloses a method for preferentially extracting lithium and co-recovering manganese from waste lithium-ion batteries, which is to fully mix the pretreated cathode active material, carbonaceous reducing agent, and chlorinating agent, and then perform anaerobic roasting; the roasted ore is stirred with water and then filtered to obtain a filtrate and a filter residue, and the filtrate is subjected to subsequent treatment to obtain battery-grade lithium carbonate. However, using metal chlorides as chlorinating agents in this method may introduce metal impurities, making it difficult to recover and separate subsequent transition metals.

[0006] CN107964593A discloses a method for recovering lithium from waste lithium battery slag by chlorination roasting gas phase, which is to mix waste lithium battery slag with a certain amount of metal chlorides and perform roasting at a high temperature to collect volatile lithium chloride. However, the battery slag treated by this method does not contain transition metal elements, and the required roasting temperature of this method is relatively high, resulting in high energy consumption.

[0007] CN117127027A discloses a method for extracting valuable metal elements from waste ternary batteries using salt essence. The method involves mixing the powder obtained by discharging, crushing, and screening waste ternary lithium-ion batteries with ammonium chloride, roasting in a covered mullite crucible, and obtaining a filtrate after water leaching and filtration of the roasted product. Sodium hydroxide saturated solution is added to the filtrate and centrifuged to obtain nickel cobalt manganese hydroxide and a clear liquid. Sodium carbonate saturated solution is added to the clear liquid to obtain crude lithium carbonate crystals. However, this method separates transition metals by hydroxide precipitation and does not achieve preferential lithium extraction.

[0008] CN112062143A discloses a method for preparing lithium carbonate without acid using waste lithium-ion batteries as raw materials. The method involves mixing the positive electrode powder of waste lithium-ion batteries with calcium chloride for high-temperature roasting, filtering after washing the roasted product with water, adding lithium sulfate to the filtrate to remove calcium, filtering again, evaporating and concentrating the filtrate, and adding sodium carbonate to obtain high-purity sodium carbonate. However, this method introduces impurity calcium ions and requires impurity removal from the lithium-rich leaching solution. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the above-mentioned defects existing in the prior art and provide a method for preferentially extracting lithium from the positive electrode material of waste lithium-ion batteries, which has a high lithium element recovery rate, a high purity of lithium carbonate product, good separation effect, low price and wide source of chlorinating agent, no metal element residue, simple process, low cost, and is suitable for industrial production.

[0010] The technical solution adopted by the present invention to solve its technical problems is as follows: A method for preferentially extracting lithium from the positive electrode material of waste lithium-ion batteries, comprising the following steps:

[0011] (1) Mix the positive electrode material powder of waste lithium-ion batteries with a chlorine and hydrogen-containing compound, place it in a tubular furnace, introduce an oxygen atmosphere, and perform chlorination roasting to obtain a roasted product.

[0012] (2) Grind the roasted product obtained in step (1), add water, stir and leach, and filter to obtain a lithium-rich leaching solution and a leaching residue.

[0013] The objective of the method of the present invention is to achieve efficient conversion of lithium in the cathode material through chlorination roasting by adding chlorine- and hydrogen-containing compounds. Its main principle is as follows: The metal elements in the waste lithium-ion battery cathode material powder can react with hydrogen chloride gas generated by the decomposition of chlorine- and hydrogen-containing compounds to form metal chlorides. In an oxygen atmosphere and at a certain temperature, the metal chlorides are selectively transformed, that is, lithium has been transformed into soluble lithium chloride salt. During the oxidation process, due to the harsh oxidation conditions of lithium chloride and the requirements for the atmosphere, it is difficult to be oxidized, while the transition metals that have been transformed into chlorides are transformed into corresponding oxides. Then, through water leaching, the soluble lithium chloride salt enters the lithium-rich leaching solution, and the oxides of the transition metals enter the leaching residue and are filtered, thereby achieving the preferential extraction of lithium.

[0014] The reaction equations involved in the chlorination roasting process of the method of the present invention are as follows:

[0015] NH4Cl = NH3↑+ HCl↑;

[0016] (C2H3Cl) n = nHCl↑+ nC2H2↑;

[0017] 12LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2= 6Li2O + 4NiO + 4CoO + 4MnO2+ O2↑;

[0018] Li2O + 2HCl↑= 2LiCl + H2O↑;

[0019] NiO + 2HCl↑= NiCl2+ H2O↑;

[0020] CoO + 2HCl↑= CoCl2+ H2O↑;

[0021] Co3O4+ 8HCl↑= 3CoCl2+ 4H2O↑+ Cl2↑;

[0022] MnO + 2HCl↑= MnCl2+ H2O↑;

[0023] MnO2+ 4HCl↑= MnCl2+ 2H2O↑+ Cl2↑;

[0024] 2NiCl2+ O2↑= 2NiO + 2Cl2↑;

[0025] 5CoCl2+ 3O2↑= 2CoO + Co3O4+ 5Cl2↑;

[0026] 3MnCl2 + 2O2↑ = 2MnO + MnO2 + 3Cl2↑。

[0027] The above reaction equation mainly includes three reactions: the decomposition of the chlorinating agent and the cathode material, the chlorination of metal oxides, and the oxidation of metal chlorides that occur during the roasting process. The HCl gas generated by the decomposition of the chlorinating agent at high temperature chlorinates the waste lithium-ion battery cathode material powder to form metal chlorides. During the subsequent roasting process, the transition metal chlorides are oxidized to transform into metal oxides, achieving the selective chlorination of lithium.

[0028] Preferably, in step (1), the waste lithium-ion battery cathode material powder includes one or more of single-element, binary, or ternary cathode materials containing Ni, Co, and Mn, etc. The waste lithium-ion battery cathode material powder can be obtained by pretreating waste lithium-ion battery materials using existing technologies. The waste lithium-ion battery cathode material powder used in the method of the present invention is sourced from GEM Co., Ltd.

[0029] Preferably, in step (1), in the waste lithium-ion battery cathode material powder, the mass content of Li is 1 - 10%, the mass content of Ni is 0 - 70%, the mass content of Co is 0 - 70%, the mass content of Mn is 0 - 70%, and Ni, Co, and Mn are not simultaneously 0.

[0030] Preferably, in step (1), before use, the waste lithium-ion battery cathode material powder is first sieved, and the fraction passing through a 200-mesh sieve is taken, and then dried at 50 - 70°C for 20 - 30 h.

[0031] Preferably, in step (1), the molar ratio of chlorine in the chlorine- and hydrogen-containing compound to lithium in the waste lithium-ion battery cathode material powder is 1.0 - 3.0:1 (more preferably 1.5 - 3.0:1). This dosage can ensure the complete chlorination of lithium without allowing excessive chlorination of other transition metal elements.

[0032] Preferably, in step (1), the chlorine- and hydrogen-containing compound includes one or more of ammonium chloride, polyvinyl chloride, or concentrated hydrochloric acid, etc. The polyvinyl chloride is a powder with a particle size passing through a 200-mesh sieve. The mass fraction of the concentrated hydrochloric acid is 36 - 38%.

[0033] Preferably, in step (1), when using grinding and mixing, the grinding and mixing time is 10 - 60 min. This grinding time can ensure the uniformity of the reaction.

[0034] Preferably, in step (1), the flow rate of the oxygen atmosphere introduced is 20 - 100 mL / min.

[0035] Preferably, in step (1), the volume fraction of oxygen in the oxygen atmosphere is ≥70%. The inventors of the present invention have found through research that the oxidation of transition metal chlorides during roasting needs to be carried out under oxygen-rich conditions.

[0036] Preferably, in step (1), the chlorination roasting means: heating to 500-550°C at a rate of 3-20°C / min, then holding for 1.0-3.0 h (more preferably 1.5-2.5 h), or heating to >550-650°C and then holding for 0.5-3.0 h (more preferably 0.5-1.5 h). The inventors of the present invention have found through research that, as Figure 2 shown, in an oxygen atmosphere, the superimposed diagram of the dominant regions of the Li / Ni / Co / Mn-Cl-O system is divided into three regions, where lithium chloride and transition metal oxides can stably exist under appropriate temperatures and Cl2 partial pressures, indicating that the selective chlorination of lithium and transition metals is feasible. During the roasting process, chlorine- and hydrogen-containing compounds first chlorinate the waste lithium-ion battery cathode material powder, and then the transition metal chlorides gradually transform into oxides in an oxygen atmosphere, while lithium chloride remains in the form of chloride unchanged.

[0037] Preferably, in step (2), it is ground to pass through a 200-mesh sieve. At such a particle size, it is more conducive to ensuring the water leaching efficiency.

[0038] Preferably, in step (2), the solid-liquid ratio of the roasted product to water is 50-250 g / L (more preferably 100-200 g / L). At such a solid-liquid ratio, it is more conducive to ensuring a high concentration of lithium in the leaching solution.

[0039] Preferably, in step (2), the temperature of the stirring leaching is from room temperature to 50°C, the stirring speed is 100-800 rpm, and the time is 0.5-3.0 h. Under such leaching conditions, it is more conducive to ensuring the full leaching of lithium.

[0040] Preferably, after evaporating and concentrating the lithium-rich leaching solution obtained in step (2), alkali is added to the lithium-rich concentrated solution, aged, filtered, sodium carbonate is added to the filtrate, evaporated to crystallize, and the crystals are washed to obtain lithium carbonate products.

[0041] Preferably, the temperature for evaporating and concentrating the lithium-rich leaching solution is 80-95°C, and it is evaporated and concentrated until the mass concentration of lithium ≥10 g / L (more preferably ≥20 g / L).

[0042] Preferably, the pH value of the alkali added to the lithium-rich concentrated solution is 10-12. The alkali is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. At such a pH value, the yield of lithium carbonate can be increased.

[0043] Preferably, the aging time is 2-4 h.

[0044] Preferably, the molar ratio of the sodium carbonate to the lithium in the lithium-rich leaching solution is 0.60 to 0.75:1. The dosage of the sodium carbonate can ensure that lithium forms lithium carbonate precipitate as much as possible.

[0045] Preferably, the temperature of the evaporation crystallization is 80 to 95 °C, and evaporation and concentration are carried out until crystals precipitate.

[0046] Preferably, the crystals are washed with hot water at 90 to 100 °C for ≥2 times.

[0047] The beneficial effects of the method of the present invention are as follows:

[0048] (1) The method of the present invention uses the chlorination roasting - water leaching process to preferentially extract lithium from the spent lithium-ion battery cathode material. The recovery rate of lithium element is as high as 97.81%, and the purity of the lithium carbonate product is as high as 99.56%. The separation effect is good, solving the problems of low lithium recovery rate and low purity of lithium products in the traditional recovery process;

[0049] (2) The method of the present invention uses the process conditions of chlorination first and then oxidation transformation, broadening the selection types of chlorinating agents in the chlorination roasting process. The introduced chlorinating agent is low in price and wide in source, and there is no metal element residue after roasting, solving the problem of removing impurities of metal elements introduced by chlorinating agents in the traditional chlorination roasting process;

[0050] (3) The method of the present invention has a simple process and low cost, and is suitable for industrial production. Description of the Drawings

[0051] Figure 1 is the XRD pattern of the roasted product obtained in step (1) of Example 1 and Comparative Examples 1-1 to 1-4 of the present invention;

[0052] Figure 2 is the predominance area diagram of the Li / Ni / Co / Mn-Cl-O system under the oxygen atmosphere of the method of the present invention. Detailed Embodiments

[0053] The present invention will be further described below in conjunction with examples and drawings.

[0054] The spent lithium nickel cobalt manganese oxide cathode material powder, spent lithium nickel oxide cathode material powder, and spent lithium cobalt oxide cathode material powder used in the examples and comparative examples of the method of the present invention all come from GEM Co., Ltd.; before use, the above-mentioned spent lithium-ion battery cathode material powder is first sieved, and the material under 200 mesh is taken, and then placed in an oven and dried at 60 °C for 24 h; the mass fraction of the concentrated hydrochloric acid used in the examples of the method of the present invention is 36%, and the density is 1.178 g / cm 3 ; the purity of the oxygen used in the examples and comparative examples of the method of the present invention is ≥99.9%; the raw materials or chemical reagents used in the examples of the present invention are all obtained through conventional commercial channels unless otherwise specified.

[0055] Example 1

[0056] (1)10 g of waste lithium nickel cobalt manganese oxide cathode material powder (the mass contents of Li, Ni, Co, and Mn are 7.62% (0.762 g, 0.110 mol), 23.0%, 16.8%, and 15.5% respectively) and 8.826 g (0.165 mol) of ammonium chloride were placed in a mortar, ground and mixed for 30 min, then placed in a corundum boat, and the boat was transferred into a tubular furnace. Oxygen was introduced at a flow rate of 50 mL / min, and the temperature was raised to 600 °C at a rate of 5 °C / min, then held for 0.5 h for chlorination roasting to obtain 11.96 g of roasted product;

[0057] (2)After grinding the 11.96 g of roasted product obtained in step (1) to pass through a 200-mesh sieve, 100 mL of deionized water was added, and it was stirred and leached at room temperature with a stirring speed of 300 rpm for 0.5 h, then filtered to obtain 100 mL of lithium-rich leaching solution and transition metal oxide leaching residue.

[0058] As Figure 1 shown, in step (1), the phases of the product roasted at 600 °C for 0.5 h are LiCl, LiCl·H2O, MnCo2O4, and NiO, indicating that NCM (lithium nickel cobalt manganese oxide) has been completely decomposed, lithium has been completely chlorinated to form soluble lithium chloride, while the transition metals remain in the oxide state.

[0059] Detected by ICP-OES, the mass concentrations of Li, Ni, Co, and Mn in the lithium-rich leaching solution obtained in the example of the present invention are 7.453 g / L, 0.1518 g / L, 0.1764 g / L, and 0.00775 g / L in sequence; after calculation, the leaching rates of Li, Ni, Co, and Mn are 97.81%, 0.66%, 1.05%, and 0.05% in sequence.

[0060] The lithium-rich leaching solution obtained in step (2) was evaporated and concentrated to 25 mL (the mass concentration of lithium is 29.812 g / L) at 95 °C, then sodium hydroxide was added to the lithium-rich concentrated solution until the pH value reached 12, aged for 3 h, filtered, 7.419 g (0.07 mol) of sodium carbonate was added to the filtrate, evaporated and concentrated at 85 °C until crystals precipitated, and the crystals were washed 3 times with deionized hot water at 95 °C to obtain 3.61 g of lithium carbonate product.

[0061] Detected by ICP-OES, the purity of the lithium carbonate product obtained in the example of the present invention is 99.40%.

[0062] Example 2

[0063] (1) Place 10 g of the cathode material powder of waste lithium nickel cobalt manganese oxide batteries (the mass contents of Li, Ni, Co, and Mn are 7.62% (0.762 g, 0.110 mol), 23.0%, 16.8%, and 15.5% respectively) and 17.65 g (0.33 mol) of ammonium chloride in a mortar and grind and mix them for 40 min. Then place them in a corundum boat and transfer the boat into a tube furnace. Pass oxygen atmosphere at a flow rate of 80 mL / min, heat up to 650 °C at a rate of 20 °C / min, keep warm for 0.5 h, and carry out chlorination roasting to obtain 12.03 g of roasted product;

[0064] (2) Grind the 12.03 g of roasted product obtained in step (1) to pass through a 200-mesh sieve, then add 50 mL of deionized water, and stir and leach at 50 °C and a stirring speed of 600 rpm for 2 h to obtain 50 mL of lithium-rich leaching solution and transition metal oxide leaching residue.

[0065] After detection, in step (1), the phases of the roasted product are LiCl, LiCl·H2O, MnCo2O4, and NiO, indicating that lithium nickel cobalt manganate has been completely decomposed, lithium has been completely chlorinated to form soluble lithium chloride, while the transition metals remain in the state of oxides.

[0066] After ICP-OES detection, the mass concentrations of Li, Ni, Co, and Mn in the lithium-rich leaching solution obtained in the embodiment of the present invention are 14.05 g / L, 0.0552 g / L, 0.0303 g / L, and 0.0031 g / L in sequence; after calculation, the leaching rates of Li, Ni, Co, and Mn are 92.19%, 0.12%, 0.09%, and 0.01% in sequence.

[0067] Heat and concentrate the lithium-rich leaching solution obtained in step (2) to 25 mL (the mass concentration of lithium is 28.10 g / L) under the heating condition of 85 °C, then add potassium hydroxide to the lithium-rich leaching solution until the pH value is 10, age for 2 h, filter, add 7.949 g (0.075 mol) of sodium carbonate to the filtrate, evaporate and concentrate at 95 °C until crystals precipitate, wash the crystals twice with deionized hot water at 90 °C to obtain 3.25 g of lithium carbonate product.

[0068] After ICP-OES detection, the purity of the lithium carbonate product obtained in the embodiment of the present invention is 99.56%.

[0069] Example 3

[0070] (1) Mix 100 g of the cathode material powder of waste lithium cobalt oxide batteries (the mass contents of Li and Co are 6.54% (6.54 g, 0.942 mol) and 60.2% respectively) with 150 g of polyvinyl chloride powder (with a particle size passing through a 200-mesh sieve, and the number of moles of Cl is 2.40 mol) in a mixer. Then place them in a corundum boat and transfer the boat into a tubular furnace. Pass oxygen atmosphere at a flow rate of 30 mL / min, heat up to 550 °C at a rate of 10 °C / min, and keep it warm for 2 h for chlorination roasting to obtain 118.85 g of roasted product.

[0071] (2) Grind the 118.85 g of roasted product obtained in step (1) to pass through a 200-mesh sieve, then add 1000 mL of deionized water, and stir and leach for 3 h at room temperature with a stirring speed of 100 rpm to obtain 1000 mL of lithium-rich leaching solution and transition metal oxide leaching residue.

[0072] After detection, in step (1), the phases of the roasted product are LiCl, LiCl·H2O, and Co3O4, indicating that lithium cobalt oxide has been completely decomposed, lithium has been completely chlorinated to form soluble lithium chloride, while the transition metals remain in the oxide state.

[0073] After ICP-OES detection, the mass concentrations of Li and Co in the lithium-rich leaching solution obtained in the embodiment of the present invention are 6.18 g / L and 0.07224 g / L respectively; after calculation, the leaching rates of Li and Co are 94.50% and 0.12% respectively.

[0074] Evaporate and concentrate the lithium-rich leaching solution obtained in step (2) to 250 mL (the mass concentration of lithium is 24.72 g / L) at 85 °C, then add potassium hydroxide to the lithium-rich concentrated solution until the pH value is 12, filter, age for 3 h, add 61.37 g (0.579 mol) of sodium carbonate to the filtrate, evaporate and concentrate at 90 °C until crystals precipitate, and wash the crystals twice with deionized hot water at 95 °C to obtain 27.4 g of lithium carbonate product.

[0075] After ICP-OES detection, the purity of the lithium carbonate product obtained in the embodiment of the present invention is 99.56%.

[0076] Example 4

[0077] (1) Mix 50 g of the cathode material powder of waste lithium manganese oxide batteries (the mass contents of Li and Mn are 6.42% (3.21 g, 0.4625 mol) and 61.65% respectively) with 100 mL (1.163 mol) of concentrated hydrochloric acid in a beaker and stir well. Then place them in a corundum boat and transfer the boat into a tubular furnace. Pass oxygen atmosphere at a flow rate of 20 mL / min, heat up to 500 °C at a rate of 10 °C / min, and keep it warm for 1.5 h for chlorination roasting to obtain 61.22 g of roasted product.

[0078] (2) After grinding the 61.22 g of roasted product obtained in step (1) to pass through a 200-mesh sieve, 500 mL of deionized water was added, and it was stirred and leached at room temperature with a stirring speed of 800 rpm for 0.5 h to obtain 500 mL of lithium-rich leaching solution and transition metal oxide leaching residue.

[0079] After detection, in step (1), the phases of the roasted product were LiCl, LiCl·H2O, Mn2O3, and LiMn2O4, indicating that lithium manganate had been completely decomposed, lithium had been completely chlorinated to form soluble lithium chloride, while the transition metals remained in the state of oxides.

[0080] After ICP-OES detection, the mass concentrations of Li and Mn in the lithium-rich leaching solution obtained in the embodiment of the present invention were 6.189 g / L and 0.02466 g / L in sequence; after calculation, the leaching rates of Li and Mn were 96.40% and 0.04% in sequence.

[0081] The lithium-rich leaching solution obtained in step (2) was evaporated and concentrated to 100 mL (the mass concentration of lithium was 30.945 g / L) at 80 °C, then sodium hydroxide was added to the lithium-rich concentrated solution until the pH value reached 12, filtered, aged for 4 h, 35.4 g (0.334 mol) of sodium carbonate was added to the filtrate, evaporated and concentrated at 85 °C until crystals precipitated, and the crystals were washed 3 times with deionized hot water at 95 °C to obtain 15.5 g of lithium carbonate product.

[0082] After ICP-OES detection, the purity of the lithium carbonate product obtained in the embodiment of the present invention was 99.31%.

[0083] Comparative Example 1-1

[0084] The difference between this comparative example and Example 1 was only that: the chlorination roasting temperature in step (1) was 300 °C, and 13.17 g of roasted product was obtained. The rest was the same as in Example 1.

[0085] As Figure 1 shown, in step (1), the phases of the product roasted at 300 °C for 0.5 h were NCM, NH4Cl, NH4NiCl3 / NH4CoCl3, and LiCl, indicating that NCM had not been completely decomposed, only part of the lithium had been chlorinated to form soluble lithium chloride, and the transition metals were still in the state of chlorides, which would affect the selectivity of lithium in the water leaching process.

[0086] By ICP-OES detection, the mass concentrations of Li, Ni, Co, and Mn in the lithium-rich leaching solution obtained in the comparative example of the present invention are 4.805 g / L, 11.7944 g / L, 7.113 g / L, and 7.280 g / L in sequence; after calculation, the leaching rates of Li, Ni, Co, and Mn are 63.06%, 51.28%, 42.34%, and 46.97% in sequence.

[0087] As can be seen from the above, compared with Example 1 of the present invention, due to the too low calcination temperature, the NCM has not been completely decomposed, only part of the lithium has been chlorinated to form soluble lithium chloride, and the transition metals are still in the state of chlorides, resulting in a large amount of them being leached into the lithium-rich leaching solution.

[0088] The lithium-rich leaching solution obtained in step (2) is evaporated and concentrated to 25 mL (the mass concentration of lithium is 19.22 g / L) at 95 °C, then sodium hydroxide is added to the lithium-rich concentrated solution until the pH value reaches 12, aged for 3 h, filtered, 5.2995 g (0.05 mol) of sodium carbonate is added to the filtrate, evaporated and concentrated at 85 °C until crystals precipitate, and the crystals are washed 3 times with deionized hot water at 95 °C to obtain 2.19 g of lithium carbonate product.

[0089] By ICP-OES detection, the purity of the lithium carbonate product obtained in the comparative example of the present invention is 97.33%.

[0090] Comparative Example 1-2

[0091] The difference between this comparative example and Example 1 is only that: the chlorination roasting temperature in step (1) is 400 °C, and 12.74 g of roasted product is obtained. The rest is the same as in Example 1.

[0092] As Figure 1 shown, in step (1), the phases of the product roasted at 400 °C for 0.5 h are NCM, LiCl, LiCl·H2O, NiCl2, and MnCl2, indicating that the NCM has not been completely decomposed, only part of the lithium has been chlorinated to form soluble lithium chloride, and the transition metals are still in the state of chlorides, which will affect the selectivity of lithium in the water leaching process.

[0093] By ICP-OES detection, the mass concentrations of Li, Ni, Co, and Mn in the lithium-rich leaching solution obtained in the comparative example of the present invention are 6.111 g / L, 14.341 g / L, 6.661 g / L, and 8.286 g / L in sequence; after calculation, the leaching rates of Li, Ni, Co, and Mn are 80.20%, 62.35%, 39.65%, and 53.46% in sequence.

[0094] As can be seen from the above, compared with Example 1 of the present invention, due to the too low calcination temperature, the NCM has not been completely decomposed, only part of the lithium has been chlorinated to form soluble lithium chloride, and the transition metals are still in the state of chlorides, resulting in being largely leached into the lithium-rich leaching solution.

[0095] The lithium-rich leaching solution obtained in step (2) was evaporated and concentrated to 25 mL (the mass concentration of lithium was 24.444 g / L) at 95 °C, then sodium hydroxide was added to the lithium-rich concentrated solution until the pH value reached 12, aged for 3 h, filtered, 6.359 g (0.06 mol) of sodium carbonate was added to the filtrate, evaporated and concentrated at 85 °C until crystals precipitated, and the crystals were washed 3 times with deionized hot water at 95 °C to obtain 2.72 g of lithium carbonate product.

[0096] Detected by ICP-OES, the purity of the lithium carbonate product obtained in the comparative example of the present invention was 97.91%.

[0097] Comparative Examples 1-3

[0098] The difference between this comparative example and Example 1 is only that: the chlorination roasting temperature in step (1) was 500 °C, and 12.15 g of roasted product was obtained. The rest was the same as in Example 1.

[0099] As Figure 1 shown, in step (1), the phases of the product roasted at 500 °C for 0.5 h were LiCl, LiCl·H2O, NiCl2, and MnCo2O4, indicating that the NCM had been completely decomposed, the lithium had been completely chlorinated to form soluble lithium chloride, but only part of the transition metals had been oxidized, and there were still some transition metals in the state of chlorides, which would affect the selectivity of lithium in the water leaching process.

[0100] Detected by ICP-OES, the mass concentrations of Li, Ni, Co, and Mn in the lithium-rich leaching solution obtained in the comparative example of the present invention were 7.12 g / L, 7.834 g / L, 1.092 g / L, and 3.884 g / L in sequence; calculated, the leaching rates of Li, Ni, Co, and Mn were 93.44%, 34.06%, 6.5%, and 25.06% in sequence.

[0101] As can be seen from the above, compared with Example 1 of the present invention, due to the relatively low calcination temperature and short calcination time, although the lithium has been completely chlorinated to form soluble lithium chloride, only part of the transition metals have been oxidized, and there are still some transition metals in the state of chlorides, resulting in being partially leached into the lithium-rich leaching solution.

[0102] The lithium-rich leaching solution obtained in step (2) was evaporated and concentrated to 25 mL at 95 °C (the mass concentration of lithium was 28.48 g / L), then sodium hydroxide was added to the lithium-rich concentrated solution until the pH value reached 12, aged for 3 h, filtered, 7.419 g (0.07 mol) of sodium carbonate was added to the filtrate, evaporated and concentrated at 85 °C until crystals precipitated, and the crystals were washed 3 times with deionized hot water at 95 °C to obtain 3.42 g of lithium carbonate product.

[0103] Detected by ICP-OES, the purity of the lithium carbonate product obtained in the comparative example of the present invention was 98.43%.

[0104] Comparative Examples 1-4

[0105] The difference between this comparative example and Example 1 was only that: the chlorination roasting temperature in step (1) was 700 °C, and 11.59 g of roasting product was obtained. The rest was the same as in Example 1.

[0106] As Figure 1 shown, in step (1), the phases of the product roasted at 700 °C for 0.5 h were LiCl·H2O, MnCo2O4, and NiO, indicating that NCM had been completely decomposed, lithium had been completely chlorinated to form soluble lithium chloride, and the transition metals remained in the oxide state. However, at a higher temperature, the leaching rate of lithium chloride decreased due to volatilization.

[0107] Detected by ICP-OES, the mass concentrations of Li, Ni, Co, and Mn in the lithium-rich leaching solution obtained in the comparative example of the present invention were 5.139 g / L, 0.0552 g / L, 0.02016 g / L, and 0.0062 g / L in sequence; after calculation, the leaching rates of Li, Ni, Co, and Mn were 67.44%, 0.24%, 0.12%, and 0.04% in sequence.

[0108] As can be seen from the above, compared with Example 1 of the present invention, due to the too high calcination temperature, a large amount of lithium chloride volatilized, resulting in a significant decrease in the leaching rate of lithium.

[0109] The lithium-rich leaching solution obtained in step (2) was evaporated and concentrated to about 25 mL at 95 °C (the mass concentration of lithium was 20.556 g / L), then sodium hydroxide was added to the lithium-rich concentrated solution until the pH value reached 12, aged for 3 h, filtered, 5.2995 g (0.05 mol) of sodium carbonate was added to the filtrate, evaporated and concentrated at 85 °C until crystals precipitated, and the crystals were washed 3 times with deionized hot water at 95 °C to obtain 2.35 g of lithium carbonate product.

[0110] Detected by ICP-OES, the purity of the lithium carbonate product obtained in the comparative example of the present invention was 99.61%.

[0111] Comparative Example 2

[0112] (1) Place 10 g of waste lithium nickel cobalt manganese oxide cathode material powder (the mass contents of Li, Ni, Co, and Mn are 7.62% (0.762 g, 0.110 mol), 23.0%, 16.8%, and 15.5% respectively) and 20.594 g (0.385 mol) of ammonium chloride in a mortar, grind and mix for 30 min, then place it in a corundum boat, and transfer the boat into a tubular furnace. Pass oxygen at a flow rate of 30 mL / min, heat up to 600 °C at a rate of 5 °C / min, keep warm for 0.5 h, and carry out chlorination roasting to obtain 13.32 g of roasted product;

[0113] (2) After grinding the 13.32 g of roasted product obtained in step (1) to pass through a 200-mesh sieve, add 100 mL of deionized water, stir and leach at room temperature with a stirring speed of 300 rpm for 0.5 h, and filter to obtain 100 mL of lithium-rich leachate and transition metal oxide leaching residue.

[0114] Detected by ICP-OES, the mass concentrations of Li, Ni, Co, and Mn in the lithium-rich leachate obtained in the comparative example of the present invention are 7.564 g / L, 5.826 g / L, 2.947 g / L, and 1.465 g / L in sequence; after calculation, the leaching rates of Li, Ni, Co, and Mn are 99.27%, 25.33%, 17.54%, and 9.45% in sequence.

[0115] Evaporate and concentrate the lithium-rich leachate obtained in step (2) to 25 mL (the mass concentration of lithium is 30.256 g / L) at 95 °C, then add sodium hydroxide to the lithium-rich concentrated solution until the pH value is 12, age for 3 h, filter, add 7.419 g (0.07 mol) of sodium carbonate to the filtrate, evaporate and concentrate at 85 °C until crystals precipitate, wash the crystals 3 times with deionized hot water at 95 °C to obtain 3.37 g of lithium carbonate product.

[0116] Detected by ICP-OES, the purity of the lithium carbonate product obtained in the example of the present invention is 98.66%.

[0117] As can be seen from the above, although the leaching rate of lithium in the comparative example is similar to that in Example 1, at the same time, because too much ammonium chloride is used in the comparative example of the present invention, part of Ni, Co, and Mn are chlorinated to form soluble chlorides, and the leaching rate of transition metals increases significantly, resulting in the destruction of the selectivity of preferential lithium extraction when leaching into the lithium-rich leachate in the leaching step; in addition, more alkali is needed to neutralize the lithium-rich concentrated solution, increasing the impurity content of the lithium carbonate product and reducing the purity of lithium carbonate.

Claims

1. A method for preferentially extracting lithium from the cathode material of waste lithium-ion batteries, characterized in that, It includes the following steps: (1) After mixing the waste lithium-ion battery cathode material powder with a chlorine- and hydrogen-containing compound, place it in a tube furnace, introduce an oxygen atmosphere, and carry out chlorination roasting to obtain a roasted product; the molar ratio of chlorine in the chlorine- and hydrogen-containing compound to lithium in the waste lithium-ion battery cathode material powder is 1.0 - 3.0:1; the flow rate of the introduced oxygen atmosphere is 20 - 100 mL / min; the volume fraction of oxygen in the oxygen atmosphere ≥ 70%; the chlorination roasting means: heating at a rate of 3 - 20 °C / min to 500 - 550 °C, then holding for 1.0 - 3.0 h, or heating to > 550 - 650 °C, then holding for 0.5 - 3.0 h; (2) After grinding the roasted product obtained in step (1), add water, stir and leach, and filter to obtain a lithium-rich leachate and leaching residue.

2. The method for preferentially extracting lithium from the cathode material of waste lithium-ion batteries according to claim 1, characterized in that: In step (1), the waste lithium-ion battery cathode material powder includes one or several of the primary, secondary, or ternary cathode materials containing Ni, Co, and Mn; in the waste lithium-ion battery cathode material powder, the mass content of Li is 1 - 10%, the mass content of Ni is 0 - 70%, the mass content of Co is 0 - 70%, the mass content of Mn is 0 - 70%, and Ni, Co, and Mn are not simultaneously 0; before use, first screen the waste lithium-ion battery cathode material powder, take the material passing through a 200-mesh sieve, and then dry it at 50 - 70 °C for 20 - 30 h; the chlorine- and hydrogen-containing compound includes one or several of ammonium chloride, polyvinyl chloride, or concentrated hydrochloric acid; when using grinding and mixing, the grinding and mixing time is 10 - 60 min.

3. The method for preferentially extracting lithium from the cathode material of waste lithium-ion batteries according to claim 1 or 2, characterized in that: In step (2), grind it to pass through a 200-mesh sieve; the solid-liquid ratio of the roasted product to water is 50 - 250 g / L; the temperature of the stirring leaching is from room temperature to 50 °C, the stirring speed is 100 - 800 rpm, and the time is 0.5 - 3.0 h.

4. The method for preferentially extracting lithium from the cathode material of waste lithium-ion batteries according to claim 1 or 2, characterized in that: After evaporating and concentrating the lithium-rich leachate obtained in step (2), add alkali to the lithium-rich concentrated solution, age, filter, add sodium carbonate to the filtrate, evaporate and crystallize, wash the crystals to obtain a lithium carbonate product.

5. The method for preferentially extracting lithium from the cathode material of waste lithium-ion batteries according to claim 3, characterized in that: After evaporating and concentrating the lithium-rich leachate obtained in step (2), add alkali to the lithium-rich concentrated solution, age, filter, add sodium carbonate to the filtrate, evaporate and crystallize, wash the crystals to obtain a lithium carbonate product.

6. The method for preferentially extracting lithium from the cathode material of waste lithium-ion batteries according to claim 4, characterized in that: The temperature for evaporating and concentrating the lithium-rich leachate is 80 - 95 °C, and evaporate and concentrate until the mass concentration of lithium ≥ 10 g / L; add alkali until the pH value of the lithium-rich concentrated solution is 10 - 12; the aging time is 2 - 4 h; the molar ratio of sodium carbonate to lithium in the lithium-rich leachate is 0.60 - 0.75:1; the temperature for evaporating and crystallizing is 80 - 95 °C, and evaporate and concentrate until crystals precipitate; wash the crystals with hot water at 90 - 100 °C ≥ 2 times.

7. The method for preferentially extracting lithium from the cathode material of waste lithium-ion batteries according to claim 5, characterized in that: The temperature for evaporation and concentration of the lithium-rich leaching solution is 80-95 °C, and it is evaporated and concentrated until the mass concentration of lithium ≥ 10 g / L; the pH value of adding alkali to the lithium-rich concentrated solution is 10-12; the aging time is 2-4 h; the molar ratio of sodium carbonate to lithium in the lithium-rich leaching solution is 0.60-0.75:1; the temperature for evaporation and crystallization is 80-95 °C, and it is evaporated and concentrated until crystals precipitate; the crystals are washed with hot water at 90-100 °C ≥ 2 times.

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