Method for recycling lithium from waste ternary lithium battery cathode material

Abstract

A method for recycling lithium from waste ternary lithium battery positive electrode material, characterized in that it comprises the following steps: disassembling the waste battery and separating the positive electrode; adding the positive electrode into calcium superphosphate acid leaching, and obtaining leaching residue and leaching solution after filtration; flowing the leaching solution into calcium and magnesium removing resin to obtain a lithium-rich solution; evaporating the lithium-rich solution to obtain lithium dihydrogen phosphate-containing crystals; mixing the lithium dihydrogen phosphate-containing crystals with iron oxide and a carbon source, and obtaining battery-grade lithium iron phosphate after calcination. The present application separates lithium from waste positive electrode material by combining wet process with pyrometallurgical process, and directly synthesizes lithium iron phosphate, realizing pollution-free and high recovery rate recycling of lithium resources.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery recycling, and more particularly to a method for recycling lithium from ternary lithium batteries. Background Technology

[0002] Lithium-ion batteries are a core component of new energy vehicles, and with the rapid development of new energy vehicles, the number of lithium-ion batteries in use has increased rapidly. At the same time, the recycling of used lithium-ion batteries has received widespread attention, especially the recycling of used ternary lithium-ion batteries, which has propelled the resource utilization of used ternary lithium-ion batteries into a fast track of development.

[0003] Currently, the main methods for recycling valuable metals from spent lithium-ion batteries are hydrometallurgical and pyrometallurgical processes. Hydrometallurgical processes typically involve acid or alkali leaching of the positive electrode from spent batteries, followed by multi-stage extraction, precipitation, and filtration to obtain a single metal product. However, hydrometallurgical recycling generates large volumes of wastewater and incurs high treatment costs, limiting its application. Pyrometallurgical processes have lower requirements for raw materials and can process large quantities of spent battery materials, yielding metal mixtures or alloys. However, pyrometallurgical processes are energy-intensive and generate large amounts of waste gas. A traditional combination of pyrometallurgical and hydrometallurgical methods typically involves first reducing the metal through pyrometallurgical calcination, followed by hydrometallurgical separation. However, this method mostly yields precursors that cannot be directly used in electrode materials.

[0004] Lithium iron phosphate has a theoretical specific capacity of 170 mAh / g, and the actual specific capacity of products can exceed 140 mAh / g. It is the safest cathode material for lithium-ion batteries, contains no heavy metal elements that are harmful to the human body, and is still widely used. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a method for recovering lithium from spent ternary lithium batteries. This method achieves efficient lithium recovery and utilization through wet selective lithium extraction and pyrometallurgical synthesis of battery-grade lithium iron phosphate.

[0006] A method for recycling lithium from waste ternary lithium battery cathode materials includes the following steps:

[0007] Disassemble used batteries and separate the positive electrode;

[0008] The positive electrode was leached with superphosphate, and after filtration, leaching residue and leaching solution were obtained.

[0009] The leachate was flowed into a calcium and magnesium removal resin to obtain a lithium-rich solution;

[0010] The lithium-rich solution was evaporated to dryness to obtain lithium dihydrogen phosphate crystals;

[0011] The lithium dihydrogen phosphate crystals were mixed with iron oxide and a carbon source, and then calcined to obtain battery-grade lithium iron phosphate.

[0012] This invention involves disassembling waste batteries to separate the positive electrode, which is then leached with a superphosphate solution. The superphosphate solution is slightly soluble in water and becomes weakly acidic after dissolution, allowing it to dissolve the lithium in the positive electrode material without dissolving other metals. The filtered leaching residue consists of insoluble positive electrode material and unreacted superphosphate, while the main component of the leachate is lithium dihydrogen phosphate. The leachate is then fed into a calcium and magnesium removal resin to remove a small amount of calcium ions and purify the lithium dihydrogen phosphate solution. Subsequently, the lithium dihydrogen phosphate solution is evaporated to dryness, and the resulting lithium dihydrogen phosphate crystals are mixed with iron oxide and a carbon source and calcined to obtain battery-grade lithium iron phosphate that meets national standards.

[0013] As a preferred embodiment, the acid leaching also involves the addition of oxalic acid, which has a moderate acidity and can accelerate the dissolution of lithium from the cathode material.

[0014] As a preferred embodiment, the mass fraction of oxalic acid in the acid leaching is 2-5%. If the concentration of oxalic acid is too low, the effect of accelerating dissolution will not be obvious; if the concentration is too high, other metals may be dissolved.

[0015] As a preferred embodiment, the liquid-to-solid ratio (ml:g) of the acid leaching is 5-20:1. If the liquid-to-solid ratio is too high, the lithium leaching rate will not be significantly improved, and the subsequent evaporation time will increase. If the liquid-to-solid ratio is too low, the lithium leaching rate will be low, resulting in a low recovery rate.

[0016] As a preferred embodiment, the acid leaching time is 4-10 hours and the acid leaching temperature is 60-100℃. If the acid leaching time is too short or the temperature is too low, the leaching may be incomplete and the lithium recovery rate may be too low. If the acid leaching time is too long or the temperature is too high, the lithium recovery rate will not be significantly improved and the oxalic acid will decompose rapidly.

[0017] As a preferred embodiment, the carbon source is at least one of glucose, sucrose, and graphite. The carbon source is inexpensive and readily available, and it easily forms a carbon film during calcination, resulting in a good coating effect.

[0018] As a preferred option, the evaporation temperature is 60-90℃. A moderate evaporation temperature can ensure efficiency while avoiding the decomposition of lithium dihydrogen phosphate crystals.

[0019] As a preferred embodiment, the calcination temperature is 400-800℃ and the calcination time is 3-8h. Lithium iron phosphate is prepared under high-temperature sintering to achieve in-situ carbon coating and uniform coating.

[0020] This invention combines wet and pyrometallurgical processes. First, lithium is leached and separated from the cathode material using superphosphate and oxalic acid, yielding a leachate primarily composed of lithium dihydrogen phosphate. This leachate is filtered and then further purified using a calcium- and magnesium-removing resin. Subsequently, it is evaporated to dryness and crystallized. Finally, the lithium dihydrogen phosphate crystals are sintered to obtain battery-grade lithium iron phosphate. This lithium recovery method ultimately yields battery-grade lithium iron phosphate. During the synthesis process, trivalent iron is reduced and carbon is coated in situ. The carbon source has strong reducing power, lowering the reaction temperature and shortening the reaction time. The carbon source is molecularly dispersed during reduction, enabling uniform coating of lithium iron phosphate, reducing the growth rate of lithium iron phosphate particles, and improving electrochemical performance. This achieves efficient recovery and utilization of lithium resources. Detailed Implementation

[0021] The present invention discloses a method for recycling lithium from waste ternary lithium battery cathode materials, comprising the following steps:

[0022] Disassemble the used batteries and separate the positive electrode.

[0023] The cathode material is acid-leached with an oxalic acid solution of 2-5% by mass, while an excess of superphosphate is added. The liquid-to-solid ratio (ml:g) of the oxalic acid solution to the cathode material is 5-20:1. The acid leaching temperature is 60-100℃ and the acid leaching time is 4-10h. After filtration, leaching residue and leaching solution are obtained.

[0024] The leachate is then fed into a calcium- and magnesium-free resin to obtain a lithium-rich solution.

[0025] The lithium-rich solution is evaporated to dryness at a temperature of 60-90°C to obtain lithium dihydrogen phosphate crystals.

[0026] The lithium dihydrogen phosphate crystals are mixed with iron oxide and a carbon source. The mixture is then calcined under an inert atmosphere at a temperature of 400-800°C for 3-8 hours to obtain battery-grade lithium iron phosphate.

[0027] Example 1

[0028] A method for recycling lithium from waste ternary lithium battery cathode materials includes the following steps:

[0029] Disassemble the used batteries and separate the positive electrode.

[0030] The cathode material was acid-leached with a 3% oxalic acid solution, while an excess of superphosphate was added. The liquid-to-solid ratio (ml:g) of the oxalic acid solution to the cathode material was 15:1. The acid-leaching temperature was 90℃ and the acid-leaching time was 6 hours. After filtration, leaching residue and leaching solution were obtained.

[0031] The leachate is then fed into a calcium- and magnesium-free resin to obtain a lithium-rich solution.

[0032] The lithium-rich solution was evaporated to dryness at a temperature of 60°C to obtain lithium dihydrogen phosphate crystals.

[0033] The lithium dihydrogen phosphate crystals were mixed with iron oxide and graphite and calcined under an inert atmosphere at a temperature of 500°C for 6 hours to obtain battery-grade lithium iron phosphate.

[0034] The lithium recovery rate in the battery-grade lithium iron phosphate is greater than 97%, and it complies with the national standard GB / T 30835-2014.

[0035] Example 2

[0036] A method for recycling lithium from waste ternary lithium battery cathode materials includes the following steps:

[0037] Disassemble the used batteries and separate the positive electrode.

[0038] The cathode material was acid-leached with a 2% oxalic acid solution, while an excess of superphosphate was added. The liquid-to-solid ratio (ml:g) of the oxalic acid solution to the cathode material was 10:1. The acid-leaching temperature was 80℃ and the acid-leaching time was 8h. After filtration, leaching residue and leaching solution were obtained.

[0039] The leachate is then fed into a calcium- and magnesium-free resin to obtain a lithium-rich solution.

[0040] The lithium-rich solution was evaporated to dryness at a temperature of 80°C to obtain lithium dihydrogen phosphate crystals.

[0041] The lithium dihydrogen phosphate crystals were mixed with iron oxide and graphite, and then calcined under an inert atmosphere at a temperature of 400°C for 8 hours to obtain battery-grade lithium iron phosphate.

[0042] The lithium recovery rate in the battery-grade lithium iron phosphate is greater than 95%, and it complies with the national standard GB / T 30835-2014.

[0043] Example 3

[0044] A method for recycling lithium from waste ternary lithium battery cathode materials includes the following steps:

[0045] Disassemble the used batteries and separate the positive electrode.

[0046] The cathode material was acid-leached with a 5% oxalic acid solution, while an excess of superphosphate was added. The liquid-to-solid ratio (ml:g) of the oxalic acid solution to the cathode material was 20:1. The acid-leaching temperature was 60℃ and the acid-leaching time was 4 hours. After filtration, leaching residue and leaching solution were obtained.

[0047] The leachate is then fed into a calcium- and magnesium-free resin to obtain a lithium-rich solution.

[0048] The lithium-rich solution was evaporated to dryness at a temperature of 90°C to obtain lithium dihydrogen phosphate crystals.

[0049] The lithium dihydrogen phosphate crystals were mixed with iron oxide and graphite, and then calcined under an inert atmosphere at a temperature of 800°C for 3 hours to obtain battery-grade lithium iron phosphate.

[0050] The lithium recovery rate in the battery-grade lithium iron phosphate is greater than 97%, and it complies with the national standard GB / T 30835-2014.

[0051] Example 4

[0052] A method for recycling lithium from waste ternary lithium battery cathode materials includes the following steps:

[0053] Disassemble the used batteries and separate the positive electrode.

[0054] The cathode material was acid-leached with a 3% oxalic acid solution, while an excess of superphosphate was added. The liquid-to-solid ratio (ml:g) of the oxalic acid solution to the cathode material was 5:1. The acid leaching temperature was 100℃ and the acid leaching time was 10h. After filtration, leaching residue and leaching solution were obtained.

[0055] The leachate is then fed into a calcium- and magnesium-free resin to obtain a lithium-rich solution.

[0056] The lithium-rich solution was evaporated to dryness at a temperature of 75°C to obtain lithium dihydrogen phosphate crystals.

[0057] The lithium dihydrogen phosphate crystals were mixed with iron oxide and glucose, and then calcined under an inert atmosphere at a temperature of 500°C for 4 hours to obtain battery-grade lithium iron phosphate.

[0058] The lithium recovery rate in the battery-grade lithium iron phosphate is greater than 96%, and it complies with the national standard GB / T 30835-2014.

[0059] Example 5

[0060] A method for recycling lithium from waste ternary lithium battery cathode materials includes the following steps:

[0061] Disassemble the used batteries and separate the positive electrode.

[0062] The cathode material was acid-leached with a 5% oxalic acid solution, while an excess of superphosphate was added. The liquid-to-solid ratio (ml:g) of the oxalic acid solution to the cathode material was 15:1. The acid leaching temperature was 70℃ and the acid leaching time was 5 hours. After filtration, leaching residue and leaching solution were obtained.

[0063] The leachate is then fed into a calcium- and magnesium-free resin to obtain a lithium-rich solution.

[0064] The lithium-rich solution was evaporated to dryness at a temperature of 60°C to obtain lithium dihydrogen phosphate crystals.

[0065] The lithium dihydrogen phosphate crystals were mixed with iron oxide and sucrose, and then calcined under an inert atmosphere at a temperature of 700°C for 5 hours to obtain battery-grade lithium iron phosphate.

[0066] The lithium recovery rate in the battery-grade lithium iron phosphate is greater than 97%, and it complies with the national standard GB / T 30835-2014.

[0067] Example 6

[0068] A method for recycling lithium from waste ternary lithium battery cathode materials includes the following steps:

[0069] Disassemble the used batteries and separate the positive electrode.

[0070] The cathode material was acid-leached with a 3% oxalic acid solution, while an excess of superphosphate was added. The liquid-to-solid ratio (ml:g) of the oxalic acid solution to the cathode material was 10:1. The acid-leaching temperature was 70℃ and the acid-leaching time was 8 hours. After filtration, leaching residue and leaching solution were obtained.

[0071] The leachate is then fed into a calcium- and magnesium-free resin to obtain a lithium-rich solution.

[0072] The lithium-rich solution was evaporated to dryness at a temperature of 60°C to obtain lithium dihydrogen phosphate crystals.

[0073] The lithium dihydrogen phosphate crystals were mixed with iron oxide and graphite, and then calcined under an inert atmosphere at a temperature of 400°C for 8 hours to obtain battery-grade lithium iron phosphate.

[0074] The lithium recovery rate in the battery-grade lithium iron phosphate is greater than 96%, and it complies with the national standard GB / T 30835-2014.

[0075] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for recovering lithium from waste ternary lithium battery cathode materials, characterized in that, Includes the following steps: Disassemble used batteries and separate the positive electrode; The positive electrode is added to an oxalic acid solution with a mass fraction of 2-5%, wherein the liquid-solid ratio of the oxalic acid solution to the positive electrode material is 5-20 ml: 1 g. At the same time, superphosphate is added for acid leaching, and after filtration, leaching residue and leaching solution are obtained. The leachate was flowed into a calcium and magnesium removal resin to obtain a lithium-rich solution; The lithium-rich solution was evaporated to dryness to obtain lithium dihydrogen phosphate crystals; The lithium dihydrogen phosphate crystals were mixed with iron oxide and a carbon source, and then calcined to obtain battery-grade lithium iron phosphate.

2. The method for recovering lithium from waste ternary lithium battery cathode materials according to claim 1, characterized in that, The acid leaching temperature is 60-100℃, and the acid leaching time is 4-10h.

3. The method for recovering lithium from waste ternary lithium battery cathode materials according to claim 1, characterized in that, The carbon source is at least one of glucose, sucrose, and graphite.

4. The method for recovering lithium from waste ternary lithium battery cathode materials according to claim 1, characterized in that, The evaporation temperature is 60-90℃.

5. The method for recovering lithium from waste ternary lithium battery cathode materials according to claim 1, characterized in that, The calcination temperature is 400-800℃, and the calcination time is 3-8h.