A method for preparing high-performance magnesium-lithium alloy by alloying of waste lithium-ion battery cathode material

Abstract

This invention discloses a method for preparing high-performance magnesium-lithium alloys through alloying of cathode materials from spent lithium-ion batteries. The method involves mixing and smelting spent ternary lithium or spent lithium iron phosphate battery cathode materials with a magnesium-lithium alloy. During the cathode material refining process, the spent lithium-ion batteries are simply immersed in a 5-10% NaCl solution for 48-96 hours for discharge treatment, followed by battery crushing. Subsequently, the negative electrode and separator are removed using physical separation technology, yielding the cathode material mixed with the magnesium-lithium alloy. This invention eliminates the need for complex acid leaching processes, avoids the risk of powder explosion, has a simple operation process, and does not cause secondary environmental pollution.

Description

Technical Field

[0001] This invention relates to the simple alloying of waste ternary lithium and lithium iron phosphate battery cathode materials, utilizing rare earth elements to regulate composition and optimize processes to prepare high-performance magnesium-lithium alloy materials. It is a method for manufacturing high-performance magnesium-lithium alloys by recycling waste lithium-ion battery cathode materials. Background Technology

[0002] Ternary lithium batteries use ternary materials such as lithium nickel cobalt manganese oxide (NCM) and lithium nickel cobalt aluminum oxide (NCA) as their cathodes. They rely on the reversible migration of lithium ions between the positive and negative electrodes to function. They have high energy density, excellent charge and discharge performance, and excellent low-temperature adaptability, and are widely used in electric vehicles, energy storage systems, power tools, and other fields. They can significantly improve the range of electric vehicles, but their thermal stability is relatively weak, requiring a high-performance battery management system to ensure safety. Recycling can extract high-value elements such as lithium, cobalt, and nickel, achieving resource recycling and reducing environmental pollution. Lithium iron phosphate batteries use lithium iron phosphate as their cathode. They have excellent thermal stability, long cycle life, and do not contain harmful heavy metals. Although their energy density is slightly lower than that of ternary lithium batteries, they are widely used in electric vehicles, energy storage power stations, and backup power for communication base stations due to their safety and stability advantages. With the growth of the market, the demand for recycling them is becoming increasingly urgent.

[0003] Magnesium-lithium alloys are alloys formed by adding lithium to magnesium as a base. They are currently the lightest metallic structural materials, with a density as low as 1.35 g / cm³. 3 It is only 60% the weight of aluminum alloy and 25% the weight of steel. With its ultra-lightweight properties, excellent specific strength, specific stiffness, electromagnetic shielding performance and processing performance, it is widely used in aerospace, 3C electronics, rail transportation, national defense and military industries. Different scenarios have different requirements for its mechanical properties. The aerospace field focuses on high tensile strength, specific strength and low temperature toughness, and weld joint strength retention rate. Consumer electronics focus on elongation and impact resistance. Medical devices need to match human mechanical properties and have high fatigue resistance. Automotive non-load-bearing parts have clear standards for yield strength and cyclic fatigue strength. In practical applications, processingability and environmental tolerance also need to be comprehensively considered to achieve a high degree of adaptability to various scenarios.

[0004] Patent CN 120248865 A discloses a method and application for preparing fluorescent materials based on waste NCM ternary lithium batteries. It involves disassembling waste ternary lithium batteries to obtain nickel-cobalt-manganese lithium oxide waste, which is then powdered. This waste powder is further mixed, heated, and stirred, and then a perovskite fluorescent raw material solution is added for reaction. After cooling, manganese-doped perovskite fluorescent material is obtained. This material, loaded onto a carrier, can be used for chloride ion detection, realizing the recycling of waste batteries while reducing the cost of fluorescent material preparation. Patent CN120097309 B relates to a method for recycling waste lithium iron phosphate to prepare lithium iron phosphate. It involves oxidizing and acid-leaching waste lithium iron phosphate battery powder, adjusting pH, secondary acid leaching, filtering and adjusting pH, mixing and co-precipitating, and anaerobic drying and sintering to obtain carbon-coated lithium iron phosphate. The reaction byproduct, ammonium sulfate, can also be used as fertilizer. However, both of these waste battery recycling methods require complex acid leaching processes, which are cumbersome and pose a risk of powder explosion. The acid solution needs additional recycling and treatment, and improper handling may cause secondary environmental pollution. Summary of the Invention

[0005] The purpose of this invention is to address the problems of solid waste treatment from large quantities of spent lithium-ion batteries and the high-cost recycling of magnesium-lithium alloys. It provides a method for preparing high-performance magnesium-lithium alloys through alloying of cathode materials from spent lithium-ion batteries. This method involves mixing and melting spent ternary lithium and spent lithium iron phosphate battery cathode materials with magnesium-lithium alloys. In the cathode material refining process, the spent lithium-ion batteries only need to be immersed in a 5-10% NaCl solution for 48-96 hours for discharge treatment, followed by battery crushing. Then, the negative electrode and separator are removed using physical separation technology, resulting in the cathode material mixed with the magnesium-lithium alloy. This method eliminates the need for complex acid leaching processes, avoids the risk of powder explosion, has a simple operation process, and does not cause secondary environmental pollution. This invention introduces multi-element alloying elements such as Ni, Co, Mn, or Fe into the cathode material of spent batteries, enabling the formation of a fine second phase within the magnesium-lithium matrix to achieve precipitation and dispersion strengthening. Simultaneously, the addition of Li and Al optimizes the solid solution strengthening effect. Furthermore, the use of trace rare earth elements for modification optimizes the process for preparing high-performance magnesium-lithium alloys. This breakthrough overcomes the bottleneck of high processing costs in existing magnesium-lithium alloy preparation, contributing to the recycling of artificial mineral resources and sustainable environmental development. High-performance magnesium-lithium alloy materials can be prepared.

[0006] The technical solution of this invention is as follows: A method for preparing high-performance magnesium-lithium alloys by alloying waste lithium-ion battery cathode materials, the method comprising the following steps: 1) Soak used lithium-ion batteries in a 5-10% NaCl solution for 48-96 hours to complete the discharge treatment; Among them, the lithium-ion battery is one or more of ternary lithium-ion batteries and lithium iron phosphate batteries; The ternary lithium battery is NCM523; the lithium iron phosphate battery is 280Ah. 2) Remove the discharged battery, take out the positive terminal and dry it; The drying process involves maintaining a temperature of 360-500℃ for 3-6 hours. 3) Preheat the metal raw materials to remove moisture. The metal raw materials need to be cut into pieces and preheated and dried for smelting. Then, mix the dried battery positive electrode from step 2) with the metal raw materials to obtain a smelting mixture, and finally melt it to obtain M. m A a B b C c D d E e F f Or M m A a B b C c G g Magnesium-lithium alloy; subscripts indicate the mass percentage of the relevant element in the alloy. The metal raw material is a magnesium source, or a magnesium source and a rare earth alloy; the magnesium source is a magnesium alloy, and the magnesium alloy is LA91 or LA141. The rare earth alloy is a magnesium yttrium master alloy, and the magnesium yttrium master alloy is Mg-30Y; The preheating temperature is 200~300℃, and the holding time is 10~30min; When waste ternary lithium battery cathode material is used as raw material and smelted with metal raw materials in a certain proportion, M is obtained. m A a B b C c D d E e F f Magnesium-lithium alloy, M is the base element Mg, A is the element Y, B is the element Li, C is the element Al, D is the element Ni, E is the element Co, and F is the element Mn; m = 71.00 wt.%~78.50 wt.%, a = 0.00 wt.%~2.00 wt.%, b = 8.00 wt.%~10.00 wt.%, c = 4.00 wt.%~5.00 wt.%, d = 5.00 wt.%~6.00 wt.%, e = 2.00 wt.%~2.50 wt.%, f = 2.50 wt.%~3.50 wt.%; When the value is 0, it means that the element is not present. When waste lithium iron phosphate battery cathode material is used as raw material and smelted with metal raw materials in a certain proportion, M is obtained. m A a B b C c G gMagnesium-lithium alloy, M is the base element Mg, A is the element Y, B is the element Li, C is the element Al, and G is the element Fe; m = 77.00 wt.%~83.00 wt.%, a = 0.00 wt.%~2.00 wt.%, b = 12.50 wt.%~14.50 wt.%, c = 2.00 wt.%~3.00 wt.%, g = 2.50 wt.%~3.50 wt.%; When the value is 0, it means that the element is not present. When smelting the positive electrode of a waste ternary lithium-ion battery, the smelting temperature is 900~1050℃, and the mixture is mechanically stirred 2~3 times, with each stirring time lasting 3~5 minutes. The mixture is then left to stand at the temperature for 15~30 minutes before casting. When smelting the positive electrode of a waste lithium iron phosphate battery, the smelting temperature is 950~1100℃, and the mixture is mechanically stirred 2~3 times, with each stirring time lasting 3~5 minutes. The mixture is then left to stand at the temperature for 15~30 minutes before casting. The elements and their contents contained in the positive electrode of the NCM523 ternary lithium battery are Al: 18.00%, Li: 5.90%, Ni: 24.92%, Co: 10.01%, Mn: 14.00%, and O: 27.17%. The elements and their contents in the positive electrode of a used 280Ah lithium iron phosphate battery are Al: 18.00%, Li: 3.61%, Fe: 29.03%, P: 16.10%, and O: 33.27%. A smelting aid is also added during the smelting process; the ratio of the smelting aid is anhydrous magnesium chloride (MgCl2): potassium chloride (KCl): calcium fluoride (CaF2) = 4:3:2, with an additional 0.2% lanthanum-cerium mixed rare earth and 0.1% calcium-silicon alloy, and the whole is a powdered composite smelting aid; The amount of additive is 2% to 2.5% of the total mass of the alloy melt. After refining, let the melt stand for 5 to 10 minutes. After the slag has completely floated to the surface, thoroughly remove the slag to prevent the slag phase from falling back and causing secondary pollution.

[0007] 4) Heat-treat the sample from step 3); Take the above-mentioned smelted sample and subject it to heat treatment. The heat treatment temperature is 200~400℃, and the holding time is 4~12h.

[0008] 5) After heat treatment, the sample is air-cooled to room temperature and then machined to make the sample surface smooth. 6) Take the sample obtained in step 5) and perform compression treatment.

[0009] After machining, the sample is preheated and then extruded. The preheating temperature is 200~360℃, and the holding time is 0.5~1h. The extrusion temperature is 200~360℃, the die holding temperature is 200~360℃, the extrusion speed is 0.1~0.5mm / s, and the extrusion ratio is 4~50.

[0010] The essential features of this invention are: This invention utilizes waste ternary lithium and lithium iron phosphate battery cathode materials as sources of multi-element alloying elements such as lithium, nickel, and cobalt, directly mixing and smelting them with a magnesium-lithium alloy matrix, thus achieving high-value utilization of solid waste. The introduced multi-element alloying elements such as Ni, Co, Mn, or Fe can form fine second phases in the magnesium-lithium matrix to achieve precipitation and dispersion strengthening, while the supplemented Li and Al optimize the solid solution strengthening effect. The heat treatment and hot extrusion process also achieves grain refinement and dislocation strengthening through dynamic recrystallization, taking into account both strength improvement and plasticity retention. Furthermore, Mg-30Y magnesium yttrium master alloy is introduced as a rare earth modifier, utilizing rare earth elements to form stable intermetallic compounds with the magnesium-lithium matrix, and can also produce a synergistic strengthening effect with the multi-element elements in the cathode material.

[0011] Furthermore, the invention designs a one-stop powdered composite additive that can simultaneously complete deoxidation, decarbonization, and dephosphorization operations, effectively ensuring alloy purity. It can also precisely control differentiated melting thermodynamic and kinetic process parameters for different types of cathode materials to achieve uniform dissolution and diffusion of multiple elements in the magnesium-lithium matrix.

[0012] The microscopic mechanism by which the performance of magnesium-lithium alloys is improved in this invention is the synergistic effect of four strengthening mechanisms: solid solution, precipitation / dispersion, grain refinement, and dislocation. Heat treatment achieves controllable precipitation of the strengthening phase and homogenization of the matrix composition through thermodynamic phase equilibrium regulation. Hot extrusion, through kinetic processes, achieves grain refinement, dislocation proliferation, and disperses the strengthening phase to form a dispersed distribution. The two mechanisms form a closed-loop regulation, resulting in a superior alloy microstructure. The key element combination is precisely designed according to the battery system, with Mg and Li as core matrix elements, Al as the basic alloying element, Ni-Co-Mn or Fe as core strengthening elements, and Y as an optional modification element. All elements perform their respective functions without redundancy. Waste battery components can serve as a natural source of multi-element alloying elements, replacing commercial alloy raw materials and realizing high-value utilization of solid waste. Their element content and proportion are perfectly suited to the strengthening requirements of magnesium-lithium alloys and can also form a synergistic strengthening effect with other elements. At the same time, it simplifies the dual processes of battery recycling and alloy preparation, achieving innovation from multiple dimensions of resources, performance, and cost.

[0013] The beneficial effects of this invention are as follows: This invention successfully prepared a high-performance magnesium-lithium alloy by low-cost recycling of waste ternary lithium and lithium iron phosphate batteries, combined with simple alloying and process optimization. As shown in Table 1, the mechanical property test results indicate that each embodiment exhibits superior comprehensive mechanical properties compared to the comparative example, with significant improvements in both yield strength and tensile strength. For example, in Example 2, the yield strength and tensile strength increased by 26 MPa and 39 MPa respectively compared to Comparative Example 1; in Example 4, the yield strength increased by 37 MPa and the tensile strength increased by 41 MPa compared to Comparative Example 2. Furthermore, Examples 1 and 2, while improving strength, also retained or even improved elongation, achieving synergistic optimization of strength and plasticity, effectively avoiding the problem of decreased plasticity accompanying strength improvement in traditional strengthening methods. This invention provides an efficient and feasible new solution for the development of high-performance non-ferrous metal alloys while realizing the high-value utilization of waste resources. Attached Figure Description

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further illustrated below with reference to the accompanying drawings.

[0015] Figure 1 The present invention provides a process flow diagram for preparing high-performance magnesium-lithium alloys based on alloying of cathode materials from waste lithium-ion batteries.

[0016] Figure 2 The room temperature tensile stress-strain curves of magnesium-lithium alloys from Examples 1, 2, 3, and 4, and Comparative Examples 1 and 2 are shown. Detailed Implementation

[0017] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. 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.

[0018] Unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as encompassing rather than being exclusive or exhaustive; that is, meaning "including but not limited to."

[0019] The waste lithium-ion batteries involved in the following examples were first soaked in a 5% NaCl solution for 72 hours before being removed to complete the discharge treatment; Example 1: Mg 76.15 Li 8.86 Al 4.65 Ni 5.27 Co 2.11 Mn 2.96 Preparation of magnesium-lithium alloys: 1) Material preparation: Prepare waste ternary lithium-ion batteries by discharging and crushing them, and then dry the positive electrode material after removing it. 2) Surface treatment: The surface of the LA91 magnesium-lithium alloy is sanded with sandpaper to remove the surface oxide scale and machining marks, and then dried at 200℃ for 30 minutes. The composition of the LA91 magnesium-lithium alloy is: Mg: 90.00wt.%, Li: 9.00wt.%, Al: 1.00wt.%. 3) Vacuum melting: Take the dried waste ternary lithium battery cathode material, LA91 magnesium-lithium alloy (the mass ratio of the two is 1:4 - that is, the mass percentage of the seven elements is: Mg: 72.01wt.%, Li: 8.38wt.%, Al: 4.40wt.%, Ni: 4.98wt.%, Co: 2.00wt.%, Mn: 2.80wt.%, O: 5.43wt.% (O element will be removed in the end due to the action of the additive, and this element will not be contained in the subsequent alloy)), and additive (the amount added is 2% of the total mass of the alloy melt) and vacuum melt them. The melting temperature is 1000℃, and mechanical stirring is performed twice during the process, with each stirring time being 5 minutes. The total melting time is 90 minutes. Before casting, the material is kept at the heat for 15 minutes and then cast. In this process, a flux is added to remove impurities such as C, O, and P. This flux enables one-stop impurity removal without the need for multiple treatments: it removes oxidized inclusions such as MgO and Al2O3 from the melt through the slag-forming and adsorption effects of chloride and fluoride salts, achieving efficient deoxidation; it gently oxidizes carbon impurities through alkaline flux, generating CO / CO2 gas that escapes, which, combined with flux encapsulation and adsorption, thoroughly removes carbon; and it utilizes the chemical reaction of calcium-silicon alloys and rare earth elements to generate stable compounds such as high-melting-point Ca3P2, which are incorporated into the slag, achieving deep dephosphorization while isolating air and preventing secondary oxidation pollution of the melt.

[0020] 4) Cool the smelted sample to room temperature and shape it. Then heat the sample at 300℃ for 6 hours. Afterward, air cool the sample to room temperature and machine it to make the surface smooth. 5) Preheat the machined sample in a resistance furnace to 270℃ for 0.5 hours. Then hot extrude the sample at 270℃, with the die maintained at 270℃, an extrusion speed of 0.5 mm / s, and an extrusion ratio of 15 to obtain Mg. 76.15 Li 8.86 Al 4.65 Ni 5.27 Co 2.11 Mn 2.96 Magnesium-lithium alloy. Before extrusion, the die surface is sprayed with BN release agent to reduce friction and improve the surface quality of the finished product.

[0021] Example 2: Mg 75.08 Y 1.59 Li 8.39 Al 4.60 Ni 5.27 Co 2.11 Mn 2.96 Preparation of magnesium-lithium alloys: 1) Material preparation: Prepare waste ternary lithium-ion batteries by discharging and crushing them, and then dry the positive electrode material after removing it. 2) Surface treatment: The surfaces of LA91 magnesium-lithium alloy and Mg-30Y rare earth master alloy are sanded with sandpaper to remove surface oxide scale and machining marks, and then dried at 200℃ for 30 minutes. The composition of the LA91 magnesium-lithium alloy is: Mg: 90.00wt.%, Li: 9.00wt.%, Al: 1.00wt.%. 3) Vacuum melting: Take the dried waste ternary lithium-ion battery cathode material, LA91 magnesium-lithium alloy, Mg-30Y rare earth master alloy (the mass ratio of the three is 4:15:1 - that is, the mass percentage of the eight elements is: Mg:71.01wt.%, Y:1.50wt.%, Li:7.93wt.%, Al:4.35wt.%, Ni:4.98wt.%, Co:2.00wt.%, Mn:2.80wt.%, O:5.43wt.% (the O element will be removed in the end due to the action of the additive, and it will not be contained in the subsequent alloy)), and additive (the amount added is 2% of the total mass of the alloy melt) and vacuum melt them at a melting temperature of 1000℃. During the process, mechanically stir 3 times, each stirring time is 5min, the total melting time is 90min, and the holding time before casting is 15min, and then casting is performed. 4) Cool the smelted sample to room temperature and shape it. Then heat the sample at 350℃ for 10 hours. Afterward, air cool the sample to room temperature and machine it to make the surface smooth. 5) Preheat the machined sample in a resistance furnace at 320℃ for 1 hour. Then hot extrude the sample at 320℃, with the die maintained at 320℃, an extrusion speed of 0.2 mm / s, and an extrusion ratio of 25 to obtain Mg. 75.08 Y 1.59 Li 8.39 Al 4.60 Ni 5.27 Co 2.11 Mn 2.96 Magnesium-lithium alloy. Before extrusion, the die surface is sprayed with BN release agent to reduce friction and improve the surface quality of the finished product.

[0022] Example 3: Mg 80.48 Li 13.63 Al2.84 Fe 3.05 Preparation of magnesium-lithium alloys: 1) Material preparation: Prepare waste lithium iron phosphate batteries by discharging and crushing them, and then dry the positive electrode material after removing it. 2) Surface treatment: The prepared LA141 magnesium-lithium alloy surface is sanded with sandpaper to remove the surface oxide scale and machining marks, then dried at 200℃ for 30 minutes; the composition of the LA141 magnesium-lithium alloy is: Mg: 85.00wt.%, Li: 14.00wt.%, Al: 1.00wt.%. 3) Vacuum melting: Take the dried waste lithium iron phosphate battery cathode material, LA141 magnesium-lithium alloy (the mass ratio of the two is 1:9 - that is, the mass percentage of the six elements is: Mg:76.50wt.%, Li:12.96wt.%, Al:2.70wt.%, Fe:2.90wt.%, P:1.61wt.%, O:3.33wt.% (P and O elements will be removed in the end due to the action of the additive, and the subsequent alloy does not contain these two elements)), and additive (the amount added is 2.5% of the total mass of the alloy melt) and vacuum melt them at a melting temperature of 1050℃. During the process, mechanical stirring is performed twice, each stirring time is 5min, the total melting time is 100min, and the holding time before casting is 15min, and then casting is performed. 4) Cool the smelted sample to room temperature and shape it. Then heat the sample at room temperature to 200℃ for 8 hours. Afterward, air cool the sample to room temperature and machine it to make the surface smooth. 5) Preheat the machined sample in a resistance furnace at 220℃ for 0.5 hours. Then hot extrude the sample at 220℃, with the die maintained at 220℃, an extrusion speed of 0.5 mm / s, and an extrusion ratio of 20 to obtain Mg. 80.48 Li 13.63 Al 2.84 Fe 3.05 Magnesium-lithium alloy. Before extrusion, the die surface is sprayed with BN release agent to reduce friction and improve the surface quality of the finished product.

[0023] Example 4: Mg 79.68 Y 1.58 Li 12.90 Al 2.79 Fe 3.05 Preparation of magnesium-lithium alloys: 1) Material preparation: Prepare waste lithium iron phosphate batteries by discharging and crushing them, and then dry the positive electrode material after removing it. 2) Surface treatment: The prepared LA141 magnesium-lithium alloy and Mg-30Y rare earth master alloy surfaces are sanded with sandpaper to remove surface oxide scale and machining marks, then dried at 200℃ for 30 minutes; the composition of the LA141 magnesium-lithium alloy is: Mg: 85.00wt.%, Li: 14.00wt.%, Al: 1.00wt.%. 3) Vacuum melting: Take the dried waste lithium iron phosphate battery cathode material, LA141 magnesium lithium alloy, Mg-30Y rare earth master alloy (the mass ratio of the three is 2:17:1 - that is, the mass percentage of the seven elements is: Mg:75.75wt.%, Y:1.50wt.%, Li:12.26wt.%, Al:2.65wt.%, Fe:2.90wt.%, P:1.61wt.%, O:3.33wt.% (P and O elements will be removed in the end due to the action of the additive, and the subsequent alloy does not contain these two elements)), and additive (the amount added is 2.5% of the total mass of the alloy melt) and vacuum melt them at a melting temperature of 1050℃. During the process, mechanically stir 3 times, each stirring time is 5min, the total melting time is 100min, and the holding time before casting is 15min, and then casting is performed. 4) Cool the smelted sample to room temperature and shape it. Then heat the sample at 300℃ for 10 hours. Afterward, air cool the sample to room temperature and machine it to make the surface smooth. 5) Preheat the machined sample in a resistance furnace at 300℃ for 1 hour. Then hot extrude the sample at 300℃, with the die maintained at 300℃, an extrusion speed of 0.2 mm / s, and an extrusion ratio of 15 to obtain Mg. 79.68 Y 1.58 Li 12.90 Al 2.79 Fe 3.05 Magnesium-lithium alloy. Before extrusion, the die surface is sprayed with BN release agent to reduce friction and improve the surface quality of the finished product.

[0024] Comparative Example 1: 1) Material preparation: Prepare LA91 magnesium-lithium alloy material; 2) Surface treatment: Use sandpaper to polish the prepared LA91 magnesium-lithium alloy surface to remove the surface oxide scale and machining marks, and then dry it at 200℃ for 30 minutes. 3) Vacuum melting: Take LA91 magnesium-lithium alloy material for vacuum melting at a temperature of 750℃. During the process, mechanically stir twice for 5 minutes each time. Before casting, keep it at the temperature for 15 minutes and then cast. 4) Cool the smelted sample to room temperature and shape it. Then heat the sample at room temperature to 300℃ for 6 hours. After that, air cool the sample to room temperature and machine it to make the surface smooth.

[0025] 5) The machined sample was preheated in an electric resistance furnace at 270℃ for 0.5 hours. After preheating, it was hot-extruded at 300℃, with the die held at 270℃, an extrusion speed of 0.5 mm / s, and an extrusion ratio of 15 to obtain LA91 magnesium-lithium alloy. Before extrusion, BN release agent was sprayed onto the die surface to reduce friction and improve the surface quality of the finished product.

[0026] 6) The composition of the obtained LA91 magnesium-lithium alloy is: Mg: 90.00 wt.%, Li: 9.00 wt.%, Al: 1.00 wt.%.

[0027] Comparative Example 2: 1) Material preparation: Prepare LA141 magnesium-lithium alloy material; 2) Surface treatment: Use sandpaper to polish the prepared LA141 magnesium-lithium alloy surface to remove the surface oxide scale and machining marks, and then dry it at 200℃ for 30 minutes. 3) Vacuum melting: Take LA141 magnesium-lithium alloy material for vacuum melting at a temperature of 750℃. During the process, mechanically stir twice for 5 minutes each time. Before casting, keep it at the temperature for 15 minutes and then cast. 4) Cool the smelted sample to room temperature and shape it. Then heat the sample at 200℃ for 8 hours. Afterward, air cool the sample to room temperature and machine it to make the surface smooth. 5) The machined sample was preheated in an electric resistance furnace at 220℃ for 0.5 hours. After preheating, it was hot-extruded at 220℃, with the die held at 220℃, an extrusion speed of 0.5 mm / s, and an extrusion ratio of 20 to obtain LA141 magnesium-lithium alloy. Before extrusion, BN release agent was sprayed onto the die surface to reduce friction and improve the surface quality of the finished product.

[0028] 6) The composition of the obtained LA141 magnesium-lithium alloy is: Mg: 85.00 wt.%, Li: 14.00 wt.%, Al: 1.00 wt.%.

[0029] It will be readily understood by those skilled in the art that, without conflict, the above-mentioned preferred solutions can be freely combined and superimposed.

[0030] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, or improvements made within the spirit and principle of the present invention should be included within the scope of protection of the present invention.

[0031] To systematically characterize the mechanical properties of the alloy, the size design of the tensile specimens and the room temperature tensile testing procedure were strictly performed in accordance with the GB / T 228.1-2010 standard. A SUNS UTM5105G electronic universal testing machine was used for room temperature tensile testing, with a tensile rate set at 1.5 mm / min. Specimens were cut along the extrusion direction (ED). To eliminate the influence of experimental randomness, three parallel specimens were prepared for testing under each set of process parameters.

[0032] Table 1 shows the room temperature tensile properties of magnesium-lithium alloys in Examples 1, 2, 3, 4 and Comparative Examples 1 and 2.

[0033]

[0034] Matters not covered in this invention are common knowledge.

Claims

1. A method for preparing high-performance magnesium-lithium alloys by alloying waste lithium-ion battery cathode materials, characterized in that, The method includes the following steps: 1) Soak used lithium-ion batteries in a 5-10% NaCl solution for 48-96 hours to complete the discharge treatment; Among them, the lithium-ion battery is one or more of ternary lithium-ion batteries and lithium iron phosphate batteries; 2) Remove the discharged battery, take out the positive terminal and dry it; 3) Preheat the metal raw materials to remove moisture. The metal raw materials need to be cut into pieces and preheated and dried for smelting. Then, mix the dried battery positive electrode from step 2) with the metal raw materials to obtain a smelting mixture, and finally melt it to obtain M. m A a B b C c D d E e F f Or M m A a B b C c G g Magnesium-lithium alloy; subscripts indicate the mass percentage of the relevant element in the alloy. Among them, the metal raw material is a magnesium source, or a magnesium source and a rare earth alloy; the magnesium source is a magnesium alloy, and the rare earth alloy is a magnesium-yttrium master alloy. When waste ternary lithium battery cathode material is used as raw material and smelted with metal raw materials in a certain proportion, M is obtained. m A a B b C c D d E e F f Magnesium-lithium alloy, M is the base element Mg, A is the element Y, B is the element Li, C is the element Al, D is the element Ni, E is the element Co, and F is the element Mn; m = 71.00 wt.%~78.50 wt.%, a = 0.00 wt.%~2.00 wt.%, b = 8.00 wt.%~10.00 wt.%, c = 4.00 wt.%~5.00 wt.%, d = 5.00 wt.%~6.00 wt.%, e = 2.00 wt.%~2.50 wt.%, f = 2.50 wt.%~3.50 wt.%; When the value is 0, it means that the element is not present. When waste lithium iron phosphate battery cathode material is used as raw material and smelted with metal raw materials in a certain proportion, M is obtained. m A a B b C c G g Magnesium-lithium alloy, M is the base element Mg, A is the element Y, B is the element Li, C is the element Al, and G is the element Fe; m = 77.00 wt.%~83.00 wt.%, a = 0.00 wt.%~2.00 wt.%, b = 12.50 wt.%~14.50 wt.%, c = 2.00 wt.%~3.00 wt.%, g = 2.50 wt.%~3.50 wt.%; When the value is 0, it means that the element is not present. When smelting the positive electrode of a waste ternary lithium-ion battery, the smelting temperature is 900~1050℃, and the mixture is mechanically stirred 2~3 times, with each stirring time lasting 3~5 minutes. The mixture is then left to stand at the temperature for 15~30 minutes before casting. When smelting the positive electrode of a waste lithium iron phosphate battery, the smelting temperature is 950~1100℃, and the mixture is mechanically stirred 2~3 times, with each stirring time lasting 3~5 minutes. The mixture is then left to stand at the temperature for 15~30 minutes before casting. 4) Heat-treat the sample from step 3); 5) After heat treatment, the sample is air-cooled to room temperature and then machined to make the sample surface smooth. 6) Take the sample obtained in step 5) and perform compression treatment.

2. The method for preparing high-performance magnesium-lithium alloy by alloying waste lithium-ion battery cathode materials as described in claim 1, characterized in that, Take the machined sample, preheat the sample, and extrude it; the preheating temperature is 200~360℃, the holding time is 0.5~1h; the extrusion temperature is 200~360℃, the mold holding temperature is 200~360℃, the extrusion speed is 0.1~0.5mm / s, and the extrusion ratio is 4~50.

3. The method for preparing high-performance magnesium-lithium alloy by alloying waste lithium-ion battery cathode materials as described in claim 1, characterized in that, In step 2), the drying is carried out at 360~500℃ for 3~6 hours; in step 3), the preheating is carried out at 200~300℃ for 10~30 minutes; in step 4), the heat treatment temperature is 200~400℃ for 4~12 hours.

4. The method for preparing high-performance magnesium-lithium alloy by alloying waste lithium-ion battery cathode materials as described in claim 1, characterized in that, The magnesium alloy is LA91 or LA141; the magnesium-yttrium master alloy is Mg-30Y.

5. The method for preparing high-performance magnesium-lithium alloy by alloying waste lithium-ion battery cathode materials as described in claim 1, characterized in that, The ternary lithium battery is NCM523; the lithium iron phosphate battery is 280Ah.

6. The method for preparing high-performance magnesium-lithium alloy by alloying waste lithium-ion battery cathode materials as described in claim 1, characterized in that, A smelting aid is also added during the smelting process; the ratio of the smelting aid is anhydrous magnesium chloride (MgCl2): potassium chloride (KCl): calcium fluoride (CaF2) = 4:3:2, with an additional 0.2% lanthanum-cerium mixed rare earth and 0.1% calcium-silicon alloy, and the whole is a powdered composite smelting aid; The amount of additive is 2% to 2.5% of the total mass of the alloy melt. After refining, the melt is allowed to stand for 5 to 10 minutes.

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