Selective conversion and separation method for lithium of positive electrode material of waste lithium battery

Abstract

The invention belongs to the technical field of waste lithium ion battery recovery, and particularly relates to a waste lithium battery positive electrode material lithium selective conversion and separation method which comprises the following steps: 1) pretreating a waste lithium battery to obtain positive electrode powder; (2) heating the positive electrode powder to 550-700 DEG C under the protection of inert gas; 3) taking inert gas as carrier gas, introducing aerosol formed by ammonia water to react with the positive electrode powder to obtain a roasted product; and 4) mixing the roasted product with water, and filtering to obtain a lithium-containing filtrate and a filter residue containing transition metal, thereby realizing selective conversion and separation of lithium, the method has the advantages of high lithium leaching rate, high purity, high separation degree of lithium and other valuable metals, safety, no by-product, and great reduction of the recovery cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of waste lithium-ion battery recycling, and particularly relates to a method for selective conversion and separation of lithium in waste lithium battery positive electrode materials. BACKGROUND

[0002] With the wide application of lithium-ion batteries in electric vehicles, energy storage systems and consumer electronics, the number of retired lithium-ion batteries is growing rapidly. As one of the most valuable components of lithium-ion batteries, the positive electrode material is rich in lithium and transition metals such as nickel, cobalt and manganese, and has significant recycling value.

[0003] In the existing positive electrode material recycling process, the hydrometallurgical route usually uses an excess of inorganic acid (commonly sulfuric acid) to leach the positive electrode material to achieve the dissolution and separation of lithium and transition metals. However, this method generally requires the introduction of alkaline reagents such as sodium hydroxide in the subsequent neutralization and impurity removal process, inevitably producing a large amount of inert salt by-products such as sodium sulfate. At the same time, even if lithium sulfate solution is obtained, the further conversion of lithium sulfate solution into battery-grade lithium carbonate or lithium hydroxide will still produce sodium sulfate by-products, resulting in the continuous accumulation of inert salts in the system, increasing the burden of wastewater treatment and solid waste disposal.

[0004] In the calcination-water leaching process, sulfate (commonly ammonium sulfate) calcination is a commonly used route, which recovers lithium in the form of lithium sulfate by reacting the positive electrode material with the sulfate at high temperature. In addition to sulfate calcination, carbonthermal reduction routes have also attracted widespread attention, such as the introduction of organic carbon sources such as glucose for reduction treatment of the positive electrode material. However, this method usually converts lithium into lithium carbonate, which has a low solubility in water, limiting the efficiency of water leaching separation and making it difficult to meet the requirements of high-efficiency lithium leaching in actual recycling processes, thereby restricting its engineering application.

[0005] Therefore, how to avoid the introduction of sulfate system and inert by-products while achieving the directional conversion of lithium into water-soluble and high-value forms during calcination or high-temperature treatment is still a key problem to be solved in the field of recycling of positive electrode materials of lithium-ion batteries. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a method for selective conversion and separation of lithium in waste lithium battery positive electrode materials, which has high leaching rate, high purity, high separation degree of lithium and other valuable metals, is safe, has no by-products, and greatly reduces the recycling cost.

[0007] The present application provides a method for selective conversion and separation of lithium in waste lithium battery positive electrode materials, comprising the following steps: 1) pretreating the waste lithium battery to obtain a positive electrode powder; 2) heating the positive electrode powder to 550-700℃ under inert gas protection; 3) introducing the aerosol formed by ammonia water into the positive electrode powder to react with the positive electrode powder under the inert gas as carrier gas to obtain a calcined product; 4) mixing the calcined product with water, filtering to obtain a lithium-containing filtrate and a transition metal-containing residue, thereby realizing selective conversion and separation of lithium.

[0008] The pretreatment of the present application generally comprises disassembling the discharged waste lithium battery, separating to obtain waste positive electrode sheets, removing the binder and aluminum foil, and crushing to obtain the positive electrode powder.

[0009] The aerosol formed by ammonia water generates a reaction atmosphere containing ammonia and water vapor at high temperature, and reacts with the positive electrode powder to reduce the transition metal in the positive electrode powder from high valence to low valence oxide and / or metal state, and at the same time convert lithium into lithium hydroxide.

[0010] After mixing the calcined product with water, lithium hydroxide enters the aqueous phase, and other transition metals are in the solid phase, thereby realizing separation.

[0011] The positive electrode powder is a positive electrode material containing high-valence transition metal oxide, including but not limited to lithium cobaltate, nickel-cobalt-manganese ternary material, spinel lithium manganate, high-voltage nickel-manganese oxide or lithium-rich manganese-based layered oxide.

[0012] Preferably, the heating method in step 2) is conventional calcination or fluidized calcination.

[0013] Preferably, the inert gas is nitrogen or argon.

[0014] Preferably, the aerosol in step 3) is produced by mechanical atomization, ultrasonic atomization or heating atomization.

[0015] Preferably, the reaction time in step 3) is not less than 15 minutes.

[0016] Preferably, in step 3), the mass concentration of the ammonia water is not less than 15%.

[0017] Preferably, in steps 2) and 3), the inert gas is used as the carrier gas at the same time, and the flow rate is not less than 100 mL / min.

[0018] Preferably, it further comprises: condensing and recycling the unreacted ammonia gas in step 3), and recycling it to prepare ammonia water to produce the aerosol.

[0019] Preferably, in step 4), the solid-liquid ratio of the calcined product to water is 100-400 g / L.

[0020] Preferably, lithium enters the filtrate in the form of lithium hydroxide, and the filtrate is obtained by evaporation crystallization, freeze crystallization, freeze drying or a combination thereof to obtain lithium hydroxide.

[0021] The beneficial effects of the present application are that the present application uses ammonia in the form of atomized spray to reduce the positive electrode material of lithium ion battery under high temperature conditions, so that the lithium in the positive electrode material is directly converted into lithium hydroxide form in the reaction process, thereby avoiding the inevitable generation of lithium sulfate and a large amount of sodium sulfate by-product in the subsequent conversion process in the roasting or acid leaching process of lithium sulfate, significantly reducing the accumulation of inert salts and the burden of wastewater treatment.

[0022] Compared with the problem that lithium is mainly converted into lithium carbonate in the carbon thermal reduction route, which limits the water leaching separation efficiency, the present application realizes the directional conversion of lithium to lithium hydroxide with higher water solubility through the reduction reaction with ammonia, which is beneficial to the subsequent efficient separation of lithium and transition metals through the water leaching step, and improves the lithium recovery efficiency.

[0023] The present application uses ammonia water atomization as a reducing medium, which significantly reduces the safety risk in the high-temperature reduction process compared with the use of flammable or toxic reducing gases such as hydrogen, carbon monoxide or natural gas, and reduces the dependence on high-pressure gas storage and complex safety systems, thereby improving the safety and operability of the process.

[0024] The process flow of the present application is simple, and the reaction steps and water leaching separation process are matched with each other, which can realize the separation and recovery of lithium and transition metals without introducing additional inorganic salt systems, and has good industrial application prospect. DETAILED DESCRIPTION

[0025] Example 1 A method for selective conversion and separation of lithium in waste lithium battery positive electrode material, comprising the following steps: 1. Raw material pretreatment: discharging the waste lithium ion battery (the positive electrode material is lithium cobaltate) to 0V, separating the positive electrode sheet after manual disassembly, removing the PVDF binder, mechanically peeling off the aluminum foil, and crushing to obtain lithium cobaltate powder; 2. Atomization reduction: ammonia water with a mass concentration of 20% is atomized by an ultrasonic atomizer, the carrier gas is nitrogen, and the atomized ammonia water is introduced into a tubular calcination furnace together with nitrogen, and nitrogen is also introduced into the furnace and circulated, the calcination temperature is controlled at 600℃, the reaction time is 30 min, and the carrier gas flow rate is 100 mL / min; 3. Water leaching separation: after the calcination product is cooled to room temperature, deionized water is added at a solid-liquid ratio of 250 g / L, stirring and leaching for 20 min, and then vacuum filtering to obtain LiOH leaching liquid and CoO filter residue; 4. Ammonia water recovery: unreacted ammonia water in the calcination tail gas is collected by a condensation recovery device, the recovery efficiency is ≥90%, and the recovered ammonia water is recycled for the atomization step. 5. Evaporative crystallization: The LiOH leaching solution is evaporated and crystallized under N2 atmosphere to obtain lithium hydroxide product, the purity of lithium hydroxide is ≥99.5 wt%.

[0026] It is detected that the lithium leaching rate in this embodiment is 97.8%, the cobalt leaching rate is 0.008%, and no by-products such as sodium sulfate are generated in the whole process.

[0027] Example 2 On the basis of Example 1, the roasting temperature is adjusted, and the roasting temperature is set to 500 ℃, 550 ℃, 650 ℃ and 700 ℃ respectively, and the remaining conditions remain unchanged.

[0028] It is detected that when the roasting temperature is 500 ℃, 550 ℃, 650 ℃ and 700 ℃, the lithium leaching rate is 32.2%, 71.1%, 97.6% and 97.7% respectively, and the cobalt leaching rate under the corresponding conditions is less than 0.01%.

[0029] The results show that the roasting temperature has a significant influence on the conversion and leaching effect of lithium. At a lower roasting temperature, the lithium leaching rate is significantly reduced; with the increase of the roasting temperature, the lithium leaching rate is significantly improved and tends to be stable above 650 ℃. Further composition analysis of the roasting product shows that under the condition of higher roasting temperature, the proportion of metal cobalt in the product increases.

[0030] Example 3 On the basis of Example 1, the roasting time is adjusted, and the roasting time is set to 15 min, 45 min and 60 min respectively, and the remaining conditions remain unchanged.

[0031] It is detected that when the roasting time is 15 min, 45 min and 60 min, the lithium leaching rate is 95.3%, 97.5% and 97.5% respectively, and the cobalt leaching rate under the corresponding conditions is less than 0.01%.

[0032] The results show that the roasting time has a certain influence on the conversion and leaching effect of lithium. Under the condition of shorter roasting time, the lithium leaching rate is relatively low; with the extension of the roasting time, the lithium leaching rate is improved and tends to be stable. Further composition analysis of the roasting product shows that under the condition of longer roasting time, the proportion of metal cobalt in the product increases.

[0033] Example 4 On the basis of Example 1, the mass concentration of ammonia water is adjusted, and ammonia water with a mass concentration of 10%, 15% and 25% is selected respectively, and the remaining conditions remain unchanged.

[0034] The detection shows that when the mass concentration of ammonia water is 10%, 15% and 25%, the leaching rates of lithium are 55.3%, 74.8% and 97.5% respectively, and the leaching rates of cobalt under the corresponding conditions are all less than 0.01%.

[0035] The results show that the concentration of ammonia water has a significant influence on the conversion and leaching effect of lithium. With the increase of the concentration of ammonia water, the leaching rate of lithium is obviously improved; when the concentration of ammonia water is further increased, the leaching rate of lithium tends to be stable. Further composition analysis of the calcined product shows that under the condition of higher concentration of ammonia water, the proportion of metal cobalt in the product increases.

[0036] Example 5 On the basis of example 1, the leaching solid-liquid ratio of the calcined powder is adjusted, and the leaching solid-liquid ratio is set to 100 g / L, 150 g / L, 200 g / L, 250 g / L, 300 g / L and 400 g / L respectively, and the remaining conditions remain unchanged.

[0037] The detection shows that when the leaching solid-liquid ratio is 100 g / L, 150 g / L, 200 g / L, 250 g / L, 300 g / L and 400 g / L, the leaching rates of lithium are 97.4%, 97.1%, 97.9%, 97.8%, 88.6% and 80.1% respectively, and the leaching rates of cobalt under the corresponding conditions are all less than 0.01%.

[0038] The results show that in the method of the application, the leaching solid-liquid ratio can be set to 250 g / L without reducing the leaching rate of lithium, so that a lithium-containing leaching solution with a higher concentration (lithium concentration of about 17.1 g / L) is obtained.

[0039] Example 6 On the basis of example 1, the flow rate of the inert carrier gas in the calcination process is adjusted, and the carrier gas flow rate is set to 50 mL / min, 200 mL / min and 300 mL / min respectively, and the remaining conditions remain unchanged.

[0040] The detection shows that when the carrier gas flow rate is 50 mL / min, 200 mL / min and 300 mL / min, the leaching rates of lithium are 72.1%, 98.1% and 97.6% respectively, and the leaching rates of cobalt under the corresponding conditions are all less than 0.01%.

[0041] The results show that the carrier gas flow rate has a significant influence on the conversion and leaching effect of lithium. With the increase of the carrier gas flow rate, the leaching rate of lithium is obviously improved; when the carrier gas flow rate is further increased, the leaching rate of lithium remains at a high level and tends to be stable. Further composition analysis of the calcined product shows that under the condition of higher carrier gas flow rate, the proportion of metal cobalt in the product increases.

[0042] Example 7 On the basis of embodiment 1, the roasting carrier gas is changed from nitrogen to argon, and the remaining conditions remain unchanged.

[0043] It is detected that the leaching rate of lithium in the embodiment is 97.7%, and the leaching rate of cobalt is less than 0.01%.

[0044] The results show that changing the type of inert carrier gas does not significantly affect the conversion and leaching effect of lithium.

[0045] Embodiment 8 On the basis of embodiment 1, the positive electrode material is changed from lithium cobaltate to nickel-cobalt-manganese ternary positive electrode (NCM523), and the remaining conditions remain unchanged.

[0046] It is detected that the leaching rate of lithium in the embodiment is 97.3%, and the leaching rates of nickel, cobalt and manganese are all less than 0.01%, and no by-products such as sodium sulfate are produced during the whole process.

[0047] The results show that the method of the application is also applicable to ternary positive electrode materials, and can realize high-selective conversion and separation of lithium while maintaining low leaching rate of transition metals and process cleanliness.

[0048] Embodiment 9 On the basis of embodiment 1, the conventional static roasting method is changed to fluidized roasting method: the lithium cobaltate powder is placed in a vertical fluidized roasting furnace, 20% concentration of ammonia water is ultrasonically atomized and then introduced into the furnace together with nitrogen carrier gas (flow rate 3 L / min) to keep the powder in a fluidized state, and the remaining conditions remain unchanged.

[0049] It is detected that the leaching rate of lithium in the embodiment is 97.4%, and the leaching rate of cobalt is 0.005%, and no additional by-products are produced.

[0050] The results show that the method of the application can also realize high-selective conversion and separation of lithium under fluidized roasting conditions while maintaining low leaching rate of transition metals.

[0051] Comparative example 1 A positive electrode material lithium-selective conversion and separation method, comprising the following steps: 1. Raw material pretreatment: the waste lithium ion battery (the positive electrode material is lithium cobaltate) is discharged to a voltage of 0V, and after manual disassembly, the positive electrode sheet is separated and the PVDF binder is removed, the aluminum foil is mechanically peeled off, and the lithium cobaltate powder is obtained after crushing; 2. Reduction roasting: the lithium cobaltate powder is mixed with glucose (carbon source) at a mass ratio of 10:1, and is placed in a tube furnace and heated to 550 ℃ under nitrogen atmosphere (550 ℃ is the optimal temperature for glucose roasting), and is roasted for 60 min, so that the lithium cobaltate is reduced and decomposed, and the lithium is converted into a mixture of lithium oxide, lithium hydroxide and lithium carbonate; 3. Water leaching separation: low solid-liquid ratio (50 g / L, lower than 300 g / L of Example 1) was used, deionized water was added to the calcined product, and the mixture was stirred at room temperature for 60 min, and then vacuum filtration was performed to obtain a lithium-containing leaching solution and a cobalt-containing residue; 4. Lithium precipitation treatment: due to the extremely low lithium concentration in the leaching solution, the leaching solution was concentrated 5 times, and then CO2 was introduced, the aeration rate was controlled at 50 mL / min, and the reaction was performed for 30 min, and then filtration, washing and drying were performed to obtain a lithium carbonate product.

[0052] It was detected that the lithium leaching rate in the Comparative Example 1 was 90.3%, and the cobalt leaching rate was 0.3%. Since lithium mainly exists in the form of low water-soluble lithium carbonate, the leaching time needs to be prolonged, and high-efficiency leaching of lithium can be achieved under low solid-liquid ratio conditions, and an additional leaching solution concentration step is required, which is complicated and has high energy consumption.

[0053] It should be understood by those skilled in the art that the above discussion of any of the embodiments is merely exemplary and is not intended to suggest that the scope of protection of the present application is limited to these examples; under the idea of the present application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of one or more embodiments of the present application as described above. In order to be brief, they are not provided in detail.

[0054] One or more embodiments of the present application are intended to cover all such alternatives, modifications and variations falling within the broad scope of the present application. Therefore, any omissions, modifications, equivalent replacements, improvements, etc. made in the spirit and principles of one or more embodiments of the present application should be included in the scope of protection of the present application.

Claims

1. A method for selective conversion and separation of lithium in waste lithium battery cathode materials, characterized in that, Includes the following steps: 1) Pre-treat used lithium batteries to obtain positive electrode powder; 2) The positive electrode powder is heated to 550-700℃ under inert gas protection; 3) Using an inert gas as a carrier gas, an aerosol formed by ammonia water is introduced to react with the positive electrode powder to obtain the calcined product; 4) The roasting product is mixed with water and filtered to obtain a lithium-containing filtrate and a filter residue containing transition metals, thereby achieving selective conversion and separation of lithium.

2. The method according to claim 1, characterized in that, The heating method in step 2) is conventional roasting or fluidized bed roasting.

3. The method according to claim 1, characterized in that, The inert gas is nitrogen or argon.

4. The method according to claim 1, characterized in that, The aerosol mentioned in step 3) is generated by mechanical atomization, ultrasonic atomization or thermal atomization.

5. The method according to claim 1, characterized in that, The reaction time in step 3) shall be no less than 15 minutes.

6. The method according to claim 1, characterized in that, In step 3), the mass concentration of the ammonia water is not less than 15%.

7. The method according to claim 1, characterized in that, In steps 2) and 3), the inert gas also serves as a carrier gas, with a flow rate of not less than 100 mL / min.

8. The method according to claim 1, characterized in that, Also includes: The unreacted ammonia gas from step 3) is condensed and recovered, and then recycled for the preparation of ammonia water to generate aerosol.

9. The method according to claim 1, characterized in that, In step 4), the solid-liquid ratio of the calcined product to water is 100-400 g / L.

10. The method according to claim 1, characterized in that, Lithium enters the filtrate in the form of lithium hydroxide, and the filtrate is subjected to evaporation crystallization, freeze crystallization, freeze drying, or a combination thereof to obtain lithium hydroxide.