Method for preferential extraction of lithium from waste lithium ion battery waste

Abstract

The application discloses a method for preferentially extracting lithium from waste lithium ion battery waste materials. First, the waste lithium ion battery waste materials are mixed with composite salt to obtain a mixture, and high-temperature roasting is performed to obtain a roasted clinker. The roasted clinker is leached to obtain a lithium-containing leaching solution and a leaching residue. The leaching residue is subjected to acid leaching, impurity removal and extraction treatment to obtain a nickel sulfate solution and a cobalt sulfate solution. Compared with the prior art, the application uses solid sulfate and calcium-containing substances to replace liquid strong acid, realizes preferential extraction of lithium during roasting, and only needs water leaching to obtain a high-purity lithium-rich solution, thereby realizing efficient separation of lithium and other metals from the source, simplifying the subsequent separation and purification process, and producing leaching residues rich in valuable metals such as nickel and cobalt, which can be used as high-quality metallurgical raw materials, realizing high-value utilization of all components, and having significant industrial application value and economy.

Description

Technical Field

[0001] This invention relates to the field of battery recycling technology, and in particular to a method for preferentially extracting lithium from waste lithium-ion batteries. Background Technology

[0002] As power batteries enter their retirement phase, China's retired power battery volume will reach 820,000 tons in 2025, and is projected to increase to 3.5 million tons by 2030. These retired batteries contain both high-value metals and hazardous substances, possessing both resource and environmental attributes. Among various battery materials, lithium has become a key target for recycling due to its high value, low boiling point, and unique chemical properties. Traditional processes mainly focus on high-value metals such as nickel and cobalt, often recovering lithium at the end of the process as low-value compounds, resulting in low recovery rates. Prioritized lithium extraction technology has emerged to address this need, with its core idea being to preferentially separate lithium at the beginning of the recycling process to improve overall recycling efficiency.

[0003] Currently, the main lithium extraction technologies include sulfation roasting, carbon reduction roasting, and hydrogen reduction roasting. Sulfation roasting converts lithium into soluble lithium sulfate through the reaction of sulfuric acid with battery black powder, offering advantages such as a simple process and high lithium selectivity. However, this process consumes large amounts of sulfuric acid and produces significant amounts of sodium sulfate as a byproduct. Carbon reduction roasting utilizes existing graphite in the battery or adds an external carbonaceous reducing agent, avoiding the introduction of sulfur and making it suitable for high-nickel ternary batteries. However, it involves high reaction temperatures, high energy consumption, and a high risk of lithium volatilization loss. Hydrogen reduction roasting uses hydrogen as a reducing agent, producing pure reduction products that can directly generate battery-grade lithium hydroxide. However, it suffers from high safety risks, high catalyst costs, and extremely high system sealing requirements.

[0004] Therefore, there is an urgent need to develop a high-efficiency, green, low-cost, and widely adaptable priority lithium extraction technology. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preferentially extracting lithium from waste lithium-ion batteries. This method employs a composite salt additive composed of solid sulfate and calcium-containing substances to replace liquid strong acid. During the roasting process, lithium undergoes sulfation conversion, valuable metals such as nickel, cobalt, and manganese are inertized, and impurities such as fluorine and phosphorus are solidified. A high-purity lithium-rich solution can then be obtained simply by water leaching, achieving efficient separation of lithium from other metals at the source and simplifying subsequent separation and purification processes.

[0006] To achieve this technical objective, the present invention adopts the following solution: A method for preferentially extracting lithium from waste lithium-ion batteries includes the following steps: S1. Mix waste lithium-ion battery materials with composite salt to obtain a mixture, and roast the mixture at 600~700℃ for 2~3 hours to obtain roasted clinker. S2. The roasted clinker obtained in step S1 is leached to obtain a lithium-containing leachate and leaching residue. The leaching residue is then subjected to acid leaching, impurity removal, and extraction treatment to obtain nickel sulfate and cobalt sulfate solutions.

[0007] Furthermore, the mixing in step S1 is performed using dry ball milling with a ball-to-material ratio of 5-9:1, a rotation speed of 300-500 rpm, and a milling time of 2-4 hours. Dry ball milling ensures more uniform mixing of the reactants, increases the contact area of ​​the reactants, and further improves the lithium conversion rate.

[0008] Furthermore, in step S1, the composite salt includes sulfate and calcium-containing substances. The sulfate includes at least one of sodium sulfate, potassium sulfate, and ammonium sulfate, which can provide active sulfate ions during the roasting process and react selectively with lithium. The calcium-containing substances are calcium oxide or calcium hydroxide, which react with impurities such as fluorine (from the decomposition of electrolyte LiPF6), phosphorus, and aluminum (from the current collector) contained in the battery waste to generate stable insoluble compounds such as calcium fluoride (CaF2), calcium phosphate (Ca3(PO4)2), and calcium aluminum oxide, preventing them from entering the lithium-containing leachate during the water leaching process and ensuring the purity of the lithium product. On the other hand, the calcium-containing substances can act as mineralizers, forming local eutectic compounds at temperatures below the melting point of sulfate, improving the mass transfer conditions of the reaction system and promoting the contact and reaction between sulfate ions and lithium.

[0009] Furthermore, the molar ratio of battery waste, sulfate, and calcium-containing substances is 1:1.2~1.5:0.2~0.5, wherein the molar amount of battery waste is calculated based on lithium element, ensuring that the amount of sulfate is sufficient to achieve complete lithium conversion, while the amount of calcium-containing substances is also sufficient to fix all potential impurities.

[0010] Furthermore, the conditions for leaching the roasted clinker in step S2 are: temperature not exceeding 40°C, time of 2-4 hours, and liquid-solid ratio of water to roasted clinker of 2-5:1. In this invention, the liquid-solid ratio is the mass ratio of water to roasted clinker.

[0011] The principle of lithium extraction in this invention is to use roasting to cause a solid-phase reaction between sulfate and lithium compounds in battery waste, generating soluble lithium sulfate through ion exchange. This soluble lithium sulfate is then dissolved in the solution through leaching, while transition metals such as nickel, cobalt, and manganese form stable oxides or complex salts and remain in the slag phase, thus achieving effective separation from lithium. Since the solubility of lithium sulfate decreases with increasing temperature, the temperature must be controlled below 40°C to ensure sufficient solubility of lithium sulfate while minimizing the dissolution of trace amounts of impurities such as nickel and cobalt in the roasted clinker, thereby achieving highly selective lithium leaching. After processing by this invention, the lithium salt is transferred to the leaching solution, while nickel, cobalt, and impurity elements such as silicon, aluminum, phosphorus, and iron are separated from the lithium along with the slag and enter subsequent recycling processes.

[0012] Furthermore, the battery waste in step S1 is powder obtained by crushing one or more of lithium cobalt oxide, lithium manganese oxide, and lithium nickel cobalt manganese oxide batteries, which contains impurities such as iron, copper, zinc, aluminum, fluorine, phosphorus, calcium, and magnesium.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: Intrinsically safe and environmentally friendly: By using solid sulfates and calcium oxide to replace liquid strong acids, safety hazards such as equipment corrosion and acid mist volatilization are fundamentally solved. Calcium oxide can effectively solidify harmful impurities such as fluorine and phosphorus, avoiding secondary pollution and achieving clean production.

[0014] Highly efficient and selective lithium extraction: Lithium is selectively extracted during the roasting process. Sulfation causes it to precipitate as soluble lithium sulfate, while valuable metals such as nickel, cobalt, and manganese are retained in the slag phase. This achieves highly efficient separation of lithium from other metals at the source, greatly simplifying the subsequent separation and purification process.

[0015] Process flow and economic advantages: This process completes lithium conversion and impurity solidification through a one-step roasting process, followed by water leaching to obtain a high-purity lithium-rich solution. The process is concise, energy consumption is reduced, and the resulting leaching residue is rich in valuable metals such as nickel and cobalt, which can be used as high-quality metallurgical raw materials, achieving high-value utilization of all components and possessing significant industrial application value. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0017] Unless otherwise specified, all experimental methods used in this application are conventional methods. All materials and reagents used are commercially available unless otherwise specified.

[0018] The battery waste used in this application comes from retired nickel-cobalt-manganese lithium batteries. After discharge, dismantling, crushing, and sorting, the battery waste yields black powder, the positive electrode active material. Its chemical composition is shown in Table 1.

[0019] Table 1. Composition of Battery Waste (unit: wt%) Example 1

[0020] A method for preferentially extracting lithium from waste lithium-ion batteries, the specific steps of which are as follows: Weigh the battery waste materials listed in Table 1 (based on the molar amount of lithium element). Weigh the corresponding mass of sodium sulfate and calcium oxide in a molar ratio of waste lithium-ion battery waste (Li), sodium sulfate, and calcium oxide of 1:1.5:0.3. After stirring and initially mixing the three materials, place them in a ball mill for dry ball milling and mixing. Zirconia balls are used as the grinding medium. The ball-to-material ratio is 5:1, the rotation speed is 400 rpm, and the ball milling time is 3 hours to obtain the mixture.

[0021] The mixture was roasted at 650℃ for 2 hours to obtain roasted clinker.

[0022] The roasted clinker was transferred to a leaching tank, and water was added at a liquid-to-solid ratio (mass ratio of water to roasted clinker) of 4:1 for leaching. The leaching temperature was 40℃, and the leaching time was 3 hours. After the reaction, solid-liquid separation was performed to obtain lithium-containing leachate and leaching residue. The leachate was analyzed and tested, and the leaching residue was treated with acid leaching, impurity removal, and extraction to obtain nickel sulfate and cobalt sulfate solutions. Example 2

[0023] The difference from Example 1 is that the waste lithium-ion battery material, sodium sulfate, and calcium oxide were initially mixed and then directly roasted at high temperature without dry ball milling. Example 3

[0024] The difference from Example 1 is that the mixture is roasted at 700°C for 2 hours to obtain roasted cooked material. Example 4

[0025] The difference from Example 1 is that waste lithium-ion battery materials, potassium sulfate, and calcium oxide are mixed in a molar ratio of 1:1.3:0.4. Example 5

[0026] The difference from Example 1 is that waste lithium-ion battery materials, sodium sulfate, and calcium hydroxide are mixed in a molar ratio of 1:1.2:0.5. Comparative Example 1

[0027] The difference from Example 1 is that the waste lithium-ion battery waste and sodium sulfate are mixed at a molar ratio of 1:1.5. Comparative Example 2

[0028] The difference from Example 1 is that waste lithium-ion battery materials and calcium oxide are mixed at a molar ratio of 1:0.3. Comparative Example 3

[0029] The difference from Example 1 is that the mixture is roasted at 500°C for 2 hours to obtain roasted cooked material.

[0030] Test method: The lithium ion content in the lithium-containing leachate obtained in the above examples and comparative examples was detected using ICP-OES, and the lithium leaching rate and nickel (cobalt) loss rate were calculated according to the following formulas: Lithium leaching rate (%) = Lithium content in leachate / Lithium content in waste × 100%, Nickel (cobalt) loss rate (%) = Nickel (cobalt) content in leachate / Nickel (cobalt) content in waste × 100%. The results are shown in Table 2.

[0031] Table 2 Test results for each embodiment and comparative example

[0032] As can be seen from Examples 1, 4, and 5, within the range of process parameters provided by the present invention, using different types of sulfates (sodium sulfate, potassium sulfate) or calcium-containing substances (calcium oxide, calcium hydroxide), the lithium leaching rate is stable at over 94%, and the nickel-cobalt loss rate is extremely low (≤1.1%), proving the reliability and universality of the process of the present invention.

[0033] As can be seen from Example 2, the lack of dry ball milling resulted in decreased mixing uniformity and incomplete local reactions, with the lithium leaching rate decreasing to 91.79%. This indicates that high-intensity mechanical activation energy optimizes material contact and makes a positive contribution to improving reaction efficiency.

[0034] As shown in Example 3, increasing the calcination temperature to 700°C increased the lithium leaching rate to 97.96%, but the nickel-cobalt loss rate increased slightly. This indicates that appropriately increasing the temperature is beneficial for complete reaction, but a trade-off between energy consumption and the slight increase in nickel-cobalt loss rate needs to be considered.

[0035] As can be seen from Comparative Examples 1-3, when only sulfate or calcium-containing substances are used, or when the calcination temperature is not reached for lithium extraction, the lithium leaching rate is less than 80%.

[0036] In Comparative Example 1, no calcium-containing substances were added, and the fluorine, phosphorus, aluminum, and other substances in the battery waste were not solidified. They entered the solution with the lithium leaching, resulting in a high concentration of impurities in the lithium-containing leachate and a significant reduction in the lithium leaching rate.

[0037] In Comparative Example 2, no sulfate was added, and lithium mainly existed in the form of oxides. During water leaching, some of the lithium hydroxide was converted into lithium hydroxide and adsorbed by the slag phase, resulting in a lithium leaching rate of only 39.46%. This confirms that sulfate is a necessary condition for the conversion of lithium into soluble lithium sulfate, and lithium cannot be effectively extracted without sulfate.

[0038] In Comparative Example 3, the mixture was calcined at 500°C, which slowed down the activation of sulfate and the solid-phase reaction kinetics, resulting in insufficient lithium conversion.

[0039] In summary, the present invention, through the synergistic effect of sulfates and calcium-containing substances under optimized process parameters, can efficiently and selectively extract lithium from waste lithium-ion batteries, achieving excellent lithium leaching rates while maintaining low nickel and cobalt loss rates. This provides a highly promising solution for the green and high-value recycling of battery materials.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; if these modifications and variations fall within the scope of the claims of the present invention and their equivalents, they should all be considered to be within the protection scope of the present invention.

Claims

1. A method for preferentially extracting lithium from waste lithium-ion batteries, characterized in that, Includes the following steps: S1. Mix waste lithium-ion battery materials with composite salt to obtain a mixture, and roast the mixture at 600~700℃ for 2~3 hours to obtain roasted clinker. S2. The roasted clinker obtained in step S1 is leached to obtain a lithium-containing leachate and leaching residue. The leaching residue is then subjected to acid leaching, impurity removal, and extraction treatment to obtain nickel sulfate and cobalt sulfate solutions.

2. The method for preferentially extracting lithium from waste lithium-ion batteries according to claim 1, characterized in that, The mixing in step S1 is carried out by dry ball milling, with a ball-to-material ratio of 5~9:1, a rotation speed of 300~500 rpm, and a milling time of 2~4 hours.

3. The method for preferentially extracting lithium from waste lithium-ion batteries according to claim 1, characterized in that, In step S1, the complex salt includes a sulfate and a calcium-containing substance. The sulfate includes at least one of sodium sulfate, potassium sulfate, and ammonium sulfate, and the calcium-containing substance is calcium oxide or calcium hydroxide.

4. The method for preferentially extracting lithium from waste lithium-ion batteries according to claim 3, characterized in that, The molar ratio of battery waste, sulfates and calcium-containing substances is 1:1.2~1.5:0.2~0.

5.

5. The method for preferentially extracting lithium from waste lithium-ion batteries according to claim 1, characterized in that, The conditions for leaching the roasted clinker in step S2 are: temperature not exceeding 40℃, time of 2~4h, and liquid-solid ratio of water to roasted clinker of 2~5:

1.

6. The method for preferentially extracting lithium from waste lithium-ion batteries according to claim 1, characterized in that, The battery waste in step S1 is powder obtained by crushing one or more of lithium cobalt oxide, lithium manganese oxide, and lithium nickel cobalt manganese oxide batteries, which contains impurities such as iron, copper, zinc, aluminum, fluorine, phosphorus, calcium, and magnesium.

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