Method for recovering metal lithium from waste lithium battery material

Abstract

The invention relates to the technical field of solid waste treatment, in particular to a method for recycling metal lithium from a waste lithium battery material. The method comprises three core steps of leaching, adsorption and desorption precipitation: firstly, leaching LFP positive electrode powder by adopting a mixed leaching agent of dilute sulphuric acid and hydrogen peroxide; li < + > in the leachate is directionally adsorbed in a fixed bed through a specific modified resin adsorbent; and finally, analyzing, depositing lithium and the like to obtain the battery-grade lithium carbonate. Wherein the modified resin adsorbent is prepared from acrylonitrile and dimethylaminoethyl methacrylate through crosslinking copolymerization, nitrile group conversion and methylphosphonic acid group grafting modification, and PO4 < 3-> interference can be efficiently resisted. The method solves the problems of high acid consumption, poor adsorption selectivity, low lithium recovery rate and the like in the prior art, and has remarkable economic and environment-friendly values.

Description

Technical Field

[0001] This application relates to the field of solid waste management technology, specifically to a method for recovering metallic lithium from waste lithium battery materials. Background Technology

[0002] With the large-scale application of lithium iron phosphate batteries in new energy vehicles and energy storage, their scrap volume is increasing year by year. Recycling the lithium resources can not only alleviate the pressure of lithium ore shortage, but also reduce environmental pollution, which has significant economic and environmental value.

[0003] Existing lithium extraction technologies from spent lithium iron phosphate batteries are mainly based on hydrometallurgy, but they suffer from the following key challenges:

[0004] High acid consumption and severe equipment corrosion: Traditional processes require the use of high-concentration sulfuric acid (1.5-2 mol / L) to leach lithium, resulting in an acid consumption of 1.5-2 tons per ton of electrode material. The highly acidic environment accelerates the corrosion of equipment such as reactors and pipelines, leading to high equipment maintenance costs.

[0005] Phosphate (PO4) 3- Significant interference: PO4 in LFP (lithium iron phosphate) leachate 3- With a concentration as high as 1-3 g / L, it easily competes with lithium for adsorption sites, leading to a decrease in lithium adsorption capacity and an increase in the difficulty of subsequent lithium salt purification; the adsorbent has poor stability: existing adsorbents (such as lithium ion sieves and unmodified ammonia oxime resins) have a swelling rate of ≥25% in low acid environments, and the adsorbent is lost or becomes ineffective quickly, increasing operating costs.

[0006] Low lithium recovery rate and low product purity: affected by PO4 3- Due to interference and limitations in separation processes, the total recovery rate of lithium by traditional wet process is only 85%-90%, and the purity of lithium carbonate products is mostly 99.0%-99.3%, requiring additional refining to meet battery-grade standards.

[0007] For example, Chinese patent application CN109439914A discloses a method for extracting lithium using crown ethers. Although it uses low-acid leaching (0.3-0.5 mol / L H2SO4), crown ethers are effective against PO4. 3- While lacking a repulsive effect, additional phosphorus removal agents are required, and the extractant is readily soluble in organic solvents, resulting in poor recycling efficiency. Chinese patent application CN116351401A discloses an EDTMP (ethylenediaminetetramethylenephosphonic acid) modified MOF (metal-organic framework) adsorbent. Although it achieves multivalent ion adsorption through phosphonic acid groups, MOF materials are costly, have poor mechanical strength, and are difficult to adapt to the high-pressure environment of industrial fixed beds. Furthermore, it does not target the PO4 in LFP leachate. 3- -Li + Separate scene design.

[0008] Therefore, there is an urgent need to develop a PO4-resistant agent. 3- A method for recovering metallic lithium from waste lithium battery materials that is stable in terms of interference and adsorbents and has a high lithium recovery rate is proposed to overcome the limitations of existing technologies. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this application provides a method for recovering metallic lithium from waste lithium battery materials, comprising the following steps:

[0010] S1: After mechanical separation and dealuminization, waste lithium iron phosphate batteries are screened and purified to obtain LFP cathode powder;

[0011] S2: Mix LFP cathode powder with leaching agent, stir evenly, and filter to obtain leaching solution;

[0012] S3: The modified resin adsorbent is filled into a fixed bed, the leachate is pumped into the fixed bed, and after adsorption for 2-3 hours, the leachate is discharged.

[0013] S4: The eluent is reverse-flowed into the fixed bed, saturated Na2CO3 solution is added, stirred, filtered, washed with deionized water, centrifuged, the solid is collected and dried to obtain battery-grade lithium carbonate;

[0014] The modified resin adsorbent is obtained by cross-linking and copolymerizing acrylonitrile and dimethylaminoethyl methacrylate and then grafting methylphosphonic acid groups onto it.

[0015] In this scenario, impurities are removed through mechanical separation and dealuminization to provide pure LFP feedstock for subsequent lithium extraction; the leaching step selectively dissolves Li using a low-acid system. + At the same time, Fe is fixed 3+ and PO4 3- The modified resin utilizes the adsorption of Li⁺ by the amine oxime group and the repulsion of PO₄ by the methylphosphonic acid group. 3- The dual function of Li + Targeted capture; desorption and precipitation of lithium through ion competition and dissociation equilibrium, thereby capturing Li... + The process involves transferring the lithium from resin to solution and converting it into high-purity lithium carbonate. Through the synergy of each step, the overall process overcomes the challenges posed by PO4 in traditional methods. 3- The pain points include interference and low lithium selectivity.

[0016] Preferably, the mass-to-volume ratio of LFP cathode powder to leaching agent in S2 is 1g:(9-15)mL; the leaching agent is a mixture of H2SO4 with a concentration of 0.3-0.5mol / L and H2O2 with a concentration of 0.04-0.06mol / L in a volume ratio of (3-5):(4-6).

[0017] In this case, dilute sulfuric acid provides H₂. +Disrupting the olivine lattice of LFP can both ensure Li + It achieves efficient dissolution while avoiding equipment corrosion and excessive subsequent acid consumption caused by high acid levels; H2O2 acts as an oxidant to dissolve Fe²⁺. + Oxidized to Fe³ + Fe³ + With PO4 3- This combination forms a sparingly soluble FePO4 precipitate, reducing the PO4 content in the leachate. 3- Concentration, to reduce interference with subsequent adsorption.

[0018] Preferably, the uniform stirring in S2 is carried out at 35-45°C and at a speed of 180-220 rpm for 80-100 minutes.

[0019] In this case, this temperature range can accelerate the LFP lattice destruction rate while avoiding excessively high temperatures that could lead to H2O2 decomposition, thus ensuring oxidation efficiency.

[0020] Preferably, the amount of modified resin adsorbent in S3 is 70-75% of the volume of the fixed bed.

[0021] Preferably, the eluent in step S4 includes any one of sulfuric acid, hydrochloric acid, and citric acid, and the concentration of the eluent is 0.7-1.2 mol / L; the centrifugation rate is 1800-2000 rpm / min; the drying temperature is 60-70℃, and the drying time is 5-6 h.

[0022] In this case, the acidic reagent can provide H + Or competing ions, through protonation, competitively destroy Li + The "O-Li-N" coordination bond with the resin's amine oxime group enables Li + Desorption.

[0023] Preferably, the preparation of the modified resin adsorbent in S3 includes the following steps:

[0024] T1: Mix acrylonitrile, dimethylaminoethyl methacrylate and crosslinking agent, purge with nitrogen, heat to 60-70℃, add ammonium persulfate, react for 4-5 hours, and polymerize to obtain copolymer microspheres;

[0025] T2: The copolymer microspheres were completely dispersed in anhydrous ethanol, and a 40-50% (w / w) hydroxylamine solution was added, followed by a 6-10% (w / w) NaOH solution. The pH was adjusted to 8-9, and the mixture was stirred at 150-200 rpm for 6-8 hours at 70-80°C. 0.6-1 mol / L hydrochloric acid was added to adjust the pH of the system to 6-7. The solid was then filtered and washed with deionized water to obtain the amylopectin resin intermediate.

[0026] T3: Add the above-mentioned amylopyridine resin intermediate to toluene, stir at 300-400 rpm for 4-5 h, add diethyl phosphite and catalyst in sequence, reflux at 100-110℃ for 8-10 h, collect the resin by filtration, wash with toluene and deionized water alternately 6-10 times each, and vacuum dry at 70-80℃ for 8-10 h to obtain the modified resin adsorbent.

[0027] In this case, nitrile and amino groups are introduced through the free radical polymerization of acrylonitrile and dimethylaminoethyl methacrylate. Hydroxylamine converts the nitrile group into a hydroxylamine oxime group (-C(NOH)NH2), forming Li + Adsorption core sites; simultaneously, the amino groups of diethyl phosphite and dimethylaminoethyl methacrylate on the resin surface are grafted with methylphosphonic acid groups (-CH2PO(OH)2) via Michael addition reaction, thus preventing PO4 from adsorbing through a combination of electrostatic repulsion and steric hindrance. 3- Interference occurs when the methylphosphonic acid groups partially dissociate in the weakly acidic environment of the leachate. After dissociation, the negatively charged group reacts with the similarly negatively charged PO4 group. 3- It generates strong electrostatic repulsion of the same charge, hindering PO4 3- It diffuses into the resin interior; simultaneously, the relatively large molecular size of the methylphosphonic acid group forms a physical barrier on the resin surface, further reducing PO4. 3- The probability of contact with the inner-layered amine oxime groups, thereby enabling the modified resin adsorbent to adsorb Li + Highly selective capture.

[0028] Preferably, the crosslinking agent in T1 includes any one of N,N'-methylenebisacrylamide, ethylene glycol dimethacrylate, divinylbenzene, and trimethylolpropane triacrylate.

[0029] Preferably, the mass ratio of acrylonitrile, dimethylaminoethyl methacrylate, crosslinking agent and ammonium persulfate in T1 is (6-8):(4-2):(0.5-1):(0.5-1).

[0030] Preferably, the feeding ratio of the hydroxylamine solution to the copolymerized microspheres in T2 is (4-5) mL / g.

[0031] Preferably, the catalyst in T3 includes any one of acetic acid, formic acid, and propionic acid; the feed ratio of diethyl phosphite to the amylopectin resin intermediate is (1.5-2.5) mL / g; and the feed ratio of the catalyst to the amylopectin resin intermediate is (0.3-0.5) mL / g.

[0032] In this case, diethyl phosphite needs to be in excess to ensure sufficient reaction with the amino group; if the ratio is too low, grafting will be insufficient, and PO4 will be lost. 3-The rejection rate should be less than 98%; if it is too high, there will be too much residual reagent, increasing the washing cost.

[0033] Beneficial technical effects:

[0034] This application addresses lithium extraction from spent lithium iron phosphate battery electrode materials. The process begins with leaching using dilute acid combined with H₂O₂. + Disruption of the LFP olivine lattice causes Li + Dissolution, H2O2 will dissolve Fe 2+ Oxidized to Fe 3+ and PO4 3- FePO4 precipitate is formed, achieving lithium dissolution and impurity retention. The core adsorption process involves cross-linking and copolymerizing acrylonitrile with dimethylaminoethyl methacrylate, converting the nitrile groups into amylopectin groups, and then grafting methylphosphonic acid groups to obtain a modified resin adsorbent. The amylopectin groups (-C(NOH)NH2) in the resin framework are responsible for capturing Li from the leachate. + At the core site, the hydroxyl (-OH) and amino (-NH2) groups in the amine oxime group serve as electron donors, Li + It can form stable O-Li-N five-membered ring chelates with these two groups. This coordination interaction is highly selective. + The ionic radius of Fe has a much higher degree of spatial structure matching with that of the amylopyridine group than other metal ions (such as Fe). 3+ PO4 3- Furthermore, the stability of this coordinate bond is significantly stronger than that of PO4. 3- Due to weak hydrogen bonding with the amine oxime group, Li + It can preferentially occupy adsorption sites, thus increasing the adsorption rate; the methylphosphonic acid groups (-CH2PO(OH)2) grafted on the resin surface prevent PO4 from adsorbing through a combination of electrostatic repulsion and steric hindrance. 3- Interference occurs when the methylphosphonic acid groups partially dissociate in the weakly acidic environment of the leachate. After dissociation, the negatively charged group reacts with the similarly negatively charged PO4 group. 3- It generates strong electrostatic repulsion of the same charge, hindering PO4 3- It diffuses into the resin interior; simultaneously, the relatively large molecular size of the methylphosphonic acid group forms a physical barrier on the resin surface, further reducing PO4. 3- The probability of contact with the inner-layered amine oxime groups, thereby enabling the modified resin adsorbent to adsorb Li + Highly selective capture.

[0035] Finally, the desorbent is used via H + Competitive binding of the amine oxime group disrupts the coordination bond, achieving Li +Efficient elution and enrichment are achieved; finally, saturated Na2CO3 is added to the desorption solution, and precipitation purification is achieved by utilizing the low solubility of Li2CO3 to obtain battery-grade lithium carbonate. Through the synergistic effect of the reaction principles in each step, the goal of lithium recovery with low acid consumption, high selectivity and high yield is achieved. Attached Figure Description

[0036] Figure 1 This application provides a flowchart of a method for recovering metallic lithium from waste lithium battery materials. Specific implementation methods

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0038] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0039] Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application. The application will be further described below with reference to embodiments, but is not limited thereto.

[0040] Example 1

[0041] like Figure 1 As shown, this embodiment provides a method for recovering metallic lithium from waste lithium battery materials, including the following steps:

[0042] S1: Waste lithium iron phosphate batteries are mechanically separated and dealuminized, then screened and purified to obtain LFP cathode powder.

[0043] S2: 0.3 mol / L sulfuric acid and 0.06 mol / L H2O2 are mixed at a volume ratio of 3:5 to obtain a leaching agent. LFP cathode powder and leaching agent are mixed at a mass-volume ratio of 1 g: 9 mL. The mixture is stirred at 220 rpm for 100 min at 45 °C and then filtered to obtain a leaching solution.

[0044] S3: The modified resin adsorbent fills the fixed bed with 70% of the bed volume, and after 3 hours of adsorption by pumping in the leachate, the leachate is discharged.

[0045] S4: 1.0 mol / L dilute hydrochloric acid was reverse-flowed into a fixed bed for desorption, saturated Na2CO3 was added, the mixture was stirred, filtered, washed with deionized water, centrifuged at 2000 rpm, the solid was collected, and dried at 70℃ for 4 h to obtain battery-grade lithium carbonate.

[0046] The preparation of the modified resin adsorbent includes the following steps:

[0047] T1: Weigh acrylonitrile, dimethylaminoethyl methacrylate, N,N'-methylenebisacrylamide and ammonium persulfate in a mass ratio of 6:4:0.5:0.5. Mix acrylonitrile, dimethylaminoethyl methacrylate and N,N'-methylenebisacrylamide and purge with nitrogen gas. Heat to 70°C, add ammonium persulfate, and react for 5 hours to obtain copolymer microspheres.

[0048] T2: The copolymer microspheres were completely dispersed in anhydrous ethanol, and a 42 wt.% hydroxylamine solution was added. The pH was adjusted to 8 using a 6% NaOH solution. The mixture was stirred at 70°C and 200 rpm for 7 hours. The pH was then adjusted to 7 using 1 mol / L hydrochloric acid. The solid was filtered and washed with deionized water to obtain the amylopyridine resin intermediate.

[0049] T3: Add the amylopyridine resin intermediate to toluene, stir at 300 rpm for 4 h, add diethyl phosphite and acetic acid, reflux at 100 °C for 9 h, collect the resin by filtration, wash with toluene and deionized water 6 times each, and dry under vacuum at 75 °C for 9 h to obtain the modified resin adsorbent.

[0050] The feeding ratio of the hydroxylamine solution to the copolymerized microspheres is 4.5 mL / g;

[0051] The feeding ratio of diethyl phosphite to the amygdoxime resin intermediate is 2 mL / g;

[0052] The feed ratio of acetic acid to the amylopectin resin intermediate is 0.5 mL / g.

[0053] Example 2

[0054] like Figure 1 As shown, this embodiment provides a method for recovering metallic lithium from waste lithium battery materials, including the following steps:

[0055] S1: Waste lithium iron phosphate batteries are mechanically separated and dealuminized, then screened and purified to obtain LFP cathode powder.

[0056] S2: A leaching agent is obtained by mixing 0.4 mol / L sulfuric acid and 0.05 mol / L H2O2 at a volume ratio of 3:4. The LFP cathode powder and the leaching agent are mixed at a mass-volume ratio of 1 g: 12 mL. The mixture is stirred at 200 rpm for 90 min at 40 °C and then filtered to obtain the leachate.

[0057] S3: The modified resin adsorbent fills the fixed bed with 72% of the bed volume, the leachate is pumped in and adsorbed for 2.5 hours, and then the leachate is discharged.

[0058] S4: 0.6 mol / L dilute sulfuric acid was reverse-flowed into a fixed bed for desorption, saturated Na2CO3 was added, stirred, filtered, washed with deionized water, centrifuged at 2000 rpm / min, the solid was collected, and dried at 60℃ for 5 h to obtain battery-grade lithium carbonate.

[0059] The preparation of the modified resin adsorbent includes the following steps:

[0060] T1: Weigh acrylonitrile, dimethylaminoethyl methacrylate, N,N'-methylenebisacrylamide, and ammonium persulfate in a mass ratio of 7:3:0.5:0.5. Mix acrylonitrile, dimethylaminoethyl methacrylate, and N,N'-methylenebisacrylamide and purge with nitrogen gas. Heat to 65°C, add ammonium persulfate, and react for 4.5 h to obtain copolymer microspheres.

[0061] T2: The copolymer microspheres were completely dispersed in anhydrous ethanol, and a 40 wt.% hydroxylamine solution was added. The pH was adjusted to 8 using an 8% NaOH solution. The mixture was stirred at 75°C and 180 rpm for 7 hours. The pH was then adjusted to 6.5 using 0.8 mol / L hydrochloric acid. The solid was filtered and washed with deionized water to obtain the amylopyridine resin intermediate.

[0062] T3: Add the amylopyroxime resin intermediate to toluene, stir at 350 rpm for 5 h, add diethyl phosphite and propionic acid, reflux at 105 °C for 8 h, collect the resin by filtration, wash with toluene and deionized water alternately 8 times each, and dry under vacuum at 75 °C for 10 h after washing to obtain the modified resin adsorbent.

[0063] The feeding ratio of the hydroxylamine solution to the copolymerized microspheres is 5 mL / g;

[0064] The feeding ratio of diethyl phosphite to the amylopectin resin intermediate is 1.5 mL / g;

[0065] The feeding ratio of propionic acid to the amylopectin resin intermediate is 0.5 mL / g.

[0066] Example 3

[0067] like Figure 1 As shown, this embodiment provides a method for recovering metallic lithium from waste lithium battery materials, including the following steps:

[0068] S1: Waste lithium iron phosphate batteries are mechanically separated and dealuminized, then screened and purified to obtain LFP cathode powder.

[0069] S2: 0.5 mol / L sulfuric acid and 0.05 mol / L H2O2 are mixed at a volume ratio of 5:6 to obtain a leaching agent. LFP cathode powder and leaching agent are mixed at a mass-volume ratio of 1 g: 10 mL. The mixture is stirred at 220 rpm for 90 min at 40 °C and then filtered to obtain a leaching solution.

[0070] S3: The modified resin adsorbent fills the fixed bed with 75% of the bed volume, and after 2 hours of adsorption by the leachate, the leachate is discharged.

[0071] S4: 1.2 mol / L dilute citric acid was reverse-flowed into a fixed bed for desorption, saturated Na2CO3 was added, stirred, filtered, washed with deionized water, centrifuged at 2000 rpm / min, the solid was collected, and dried at 60℃ for 5 h to obtain battery-grade lithium carbonate.

[0072] The preparation of the modified resin adsorbent includes the following steps:

[0073] T1: Weigh acrylonitrile, dimethylaminoethyl methacrylate, trimethylolpropane triacrylate and ammonium persulfate in a mass ratio of 8:2:0.7:0.5. Mix acrylonitrile, dimethylaminoethyl methacrylate and trimethylolpropane triacrylate and purge with nitrogen gas. Heat to 70°C, add ammonium persulfate, and react for 4.5 h to obtain copolymer microspheres.

[0074] T2: The copolymer microspheres were completely dispersed in anhydrous ethanol, and a 45 wt.% hydroxylamine solution was added. The pH was adjusted to 8 using a 10% NaOH solution. The mixture was stirred at 75°C and 180 rpm for 7 hours. The pH was adjusted to 6.5 using 1 mol / L hydrochloric acid. The solid was filtered and washed with deionized water to obtain the amylopyridine resin intermediate.

[0075] T3: Add the amylopyroxime resin intermediate to toluene, stir at 350 rpm for 4 h, add diethyl phosphite and formic acid, reflux at 110 °C for 8 h, collect the resin by filtration, wash with toluene and deionized water 10 times each, and dry under vacuum at 80 °C for 8 h after washing to obtain the modified resin adsorbent.

[0076] The feeding ratio of the hydroxylamine solution to the copolymerized microspheres is 4 mL / g;

[0077] The feeding ratio of diethyl phosphite to the amylopectin resin intermediate is 2.5 mL / g;

[0078] The feeding ratio of formic acid to the amylopectin resin intermediate is 0.5 mL / g.

[0079] Example 4

[0080] like Figure 1As shown, this embodiment provides a method for recovering metallic lithium from waste lithium battery materials, including the following steps:

[0081] S1: Waste lithium iron phosphate batteries are mechanically separated and dealuminized, then screened and purified to obtain LFP cathode powder.

[0082] S2: A leaching agent is obtained by mixing 0.4 mol / L sulfuric acid and 0.06 mol / L H2O2 at a volume ratio of 3:5. LFP cathode powder and leaching agent are mixed at a mass-volume ratio of 1 g: 9 mL. The mixture is stirred at 200 rpm for 90 min at 40 °C and then filtered to obtain the leachate.

[0083] S3: The modified resin adsorbent fills the fixed bed with 70% of the bed volume, the leachate is pumped in and adsorbed for 3 hours, and then the leachate is discharged.

[0084] S4: 0.8 mol / L dilute hydrochloric acid was reverse-flowed into a fixed bed for desorption, saturated Na2CO3 was added, stirred, filtered, washed with deionized water, centrifuged at 2000 rpm / min, the solid was collected, and dried at 60℃ for 5 h to obtain battery-grade lithium carbonate.

[0085] The preparation of the modified resin adsorbent includes the following steps:

[0086] T1: Weigh acrylonitrile, dimethylaminoethyl methacrylate, divinylbenzene and ammonium persulfate in a mass ratio of 8:2:0.5:0.5. Mix acrylonitrile, dimethylaminoethyl methacrylate and divinylbenzene and purge with nitrogen gas. Heat to 65°C, add ammonium persulfate, and react for 4.5 h to obtain copolymer microspheres.

[0087] T2: The copolymer microspheres were completely dispersed in anhydrous ethanol, and a 47 wt.% hydroxylamine solution was added. The pH was adjusted to 8 with a 10% NaOH solution. The mixture was stirred at 80°C and 200 rpm for 7 hours. The pH was adjusted to 6.5 with 0.9 mol / L hydrochloric acid. The solid was filtered and washed with deionized water to obtain the amylopyridine resin intermediate.

[0088] T3: Add the amylopyridine resin intermediate to toluene, stir at 350 rpm for 4 h, add diethyl phosphite and acetic acid, reflux at 110 °C for 9 h, collect the resin by filtration, wash with toluene and deionized water 7 times each, and dry under vacuum at 75 °C for 9 h to obtain the modified resin adsorbent.

[0089] The feeding ratio of the hydroxylamine solution to the copolymerized microspheres is 5 mL / g;

[0090] The feeding ratio of diethyl phosphite to the amygdoxime resin intermediate is 2 mL / g;

[0091] The feed ratio of acetic acid to the amylopectin resin intermediate is 0.4 mL / g.

[0092] Example 5

[0093] like Figure 1 As shown, this embodiment provides a method for recovering metallic lithium from waste lithium battery materials, including the following steps:

[0094] S1: Waste lithium iron phosphate batteries are mechanically separated and dealuminized, then screened and purified to obtain LFP cathode powder.

[0095] S2: A leaching agent is obtained by mixing 0.4 mol / L sulfuric acid and 0.05 mol / L H2O2 at a volume ratio of 3:4. The LFP cathode powder and the leaching agent are mixed at a mass-volume ratio of 1 g: 15 mL. The mixture is stirred at 40℃ and 200 rpm for 90 min and then filtered to obtain the leachate.

[0096] S3: The modified resin adsorbent fills the fixed bed with 72% of the bed volume, the leachate is pumped in and adsorbed for 2.5 hours, and then the leachate is discharged.

[0097] S4: 1.0 mol / L dilute sulfuric acid was reverse-flowed into a fixed bed for desorption, saturated Na2CO3 was added, stirred, filtered, washed with deionized water, centrifuged at 2000 rpm / min, the solid was collected, and dried at 60℃ for 5 h to obtain battery-grade lithium carbonate.

[0098] The preparation of the modified resin adsorbent includes the following steps:

[0099] T1: Weigh acrylonitrile, dimethylaminoethyl methacrylate, ethylene glycol dimethacrylate and ammonium persulfate in a mass ratio of 7:3:0.7:0.5. Mix acrylonitrile, dimethylaminoethyl methacrylate and ethylene glycol dimethacrylate and purge with nitrogen gas. Heat to 65°C, add ammonium persulfate and react for 4.5 h to obtain copolymer microspheres.

[0100] T2: The copolymer microspheres were completely dispersed in anhydrous ethanol, and a 46 wt.% hydroxylamine solution was added. The pH was adjusted to 8 using a 9% NaOH solution. The mixture was stirred at 75°C and 180 rpm for 7 hours. The pH was then adjusted to 6.5 using 0.9 mol / L hydrochloric acid. The solid was filtered and washed with deionized water to obtain the amylopyridine resin intermediate.

[0101] T3: Add the amylopyroxime resin intermediate to toluene, stir at 350 rpm for 5 h, add diethyl phosphite and propionic acid, reflux at 105 °C for 9 h, collect the resin by filtration, wash with toluene and deionized water 7 times each, and dry under vacuum at 75 °C for 9 h to obtain the modified resin adsorbent.

[0102] The feeding ratio of the hydroxylamine solution to the copolymerized microspheres is 5 mL / g;

[0103] The feeding ratio of diethyl phosphite to the amylopectin resin intermediate is 1.5 mL / g;

[0104] The feeding ratio of propionic acid to the amylopectin resin intermediate is 0.5 mL / g.

[0105] Example 6

[0106] like Figure 1 As shown, this embodiment provides a method for recovering metallic lithium from waste lithium battery materials, including the following steps:

[0107] S1: Waste lithium iron phosphate batteries are mechanically separated and dealuminized, then screened and purified to obtain LFP cathode powder.

[0108] S2: A leaching agent is obtained by mixing 0.5 mol / L sulfuric acid and 0.06 mol / L H2O2 at a volume ratio of 5:4. The LFP cathode powder and the leaching agent are mixed at a mass-volume ratio of 1 g: 9 mL. The mixture is stirred at 200 rpm for 90 min at 40 °C and then filtered to obtain the leachate.

[0109] S3: The modified resin adsorbent fills the fixed bed with 75% of the bed volume, the leachate is pumped in and adsorbed for 2.5 hours, and then the leachate is discharged.

[0110] S4: 1.0 mol / L dilute sulfuric acid was reverse-flowed into a fixed bed for desorption, saturated Na2CO3 was added, stirred, filtered, washed with deionized water, centrifuged at 2000 rpm / min, the solid was collected, and dried at 60℃ for 5 h to obtain battery-grade lithium carbonate.

[0111] The preparation of the modified resin adsorbent includes the following steps:

[0112] T1: Weigh acrylonitrile, dimethylaminoethyl methacrylate, N,N'-methylenebisacrylamide, and ammonium persulfate in a mass ratio of 7:3:0.8:0.8. Mix acrylonitrile, dimethylaminoethyl methacrylate, and N,N'-methylenebisacrylamide and purge with nitrogen gas. Heat to 65°C, add ammonium persulfate, and react for 4.5 h to obtain copolymer microspheres.

[0113] T2: The copolymer microspheres were completely dispersed in anhydrous ethanol, and a 46 wt.% hydroxylamine solution was added. The pH was adjusted to 8 using a 7% NaOH solution. The mixture was stirred at 75°C and 200 rpm for 7 hours. The pH was then adjusted to 6.5 using 0.7 mol / L hydrochloric acid. The solid was filtered and washed with deionized water to obtain the amylopyridine resin intermediate.

[0114] T3: Add the amylopyroxime resin intermediate to toluene, stir at 350 rpm for 4 h, add diethyl phosphite and formic acid, reflux at 105 °C for 9 h, collect the resin by filtration, wash with toluene and deionized water 9 times each, and dry under vacuum at 75 °C for 9 h to obtain the modified resin adsorbent.

[0115] The feeding ratio of the hydroxylamine solution to the copolymerized microspheres is 4.5 mL / g;

[0116] The feeding ratio of diethyl phosphite to the amygdoxime resin intermediate is 2 mL / g;

[0117] The feeding ratio of formic acid to the amylopectin resin intermediate is 0.3 mL / g.

[0118] Comparative Example 1

[0119] This comparative example provides a method for recovering metallic lithium from waste lithium battery materials. The difference from Example 1 is that the leaching agent in S2 is replaced with 2 mol / L H2SO4, and H2O2 is not used. The other parameters and operating steps are the same as in Example 1.

[0120] Comparative Example 2

[0121] This comparative example provides a method for recovering metallic lithium from waste lithium battery materials. The difference from Example 1 is that step T3 is omitted, and a non-grafted methylphosphonic acid group-containing ammonia oxime resin is used in step S3. The remaining parameters and operating steps are the same as in Example 1.

[0122] Comparative Example 3

[0123] This comparative example provides a method for recovering metallic lithium from waste lithium battery materials. The difference from Example 1 is that montmorillonite adsorbent is used instead of modified resin adsorbent in S3, while the other parameters and operating steps are the same as in Example 1.

[0124] The lithium recovery rate, lithium carbonate purity, and adsorbent swelling rate of metallic lithium recovered from waste lithium battery materials in Examples 1-6 and Comparative Examples 1-3 of this application were tested and compared. The test methods are as follows:

[0125] Lithium recovery rate: The lithium content was determined by ICP-OES after digesting raw material and product samples. The recovery rate was calculated by combining the initial lithium content of the raw material with the total lithium content in the product.

[0126] Lithium carbonate purity: The sample was titrated with a standard hydrochloric acid solution using an acid-base titration method (or potentiometric titration method), and the lithium carbonate content was calculated based on the volume consumed.

[0127] Adsorbent swelling rate: The dry adsorbent is immersed in the target medium until equilibrium is reached, and the swelling percentage is calculated by measuring the change in mass (or volume) before and after swelling.

[0128] The test results are shown in Table 1.

[0129]

[0130] The method for recovering metallic lithium from waste lithium battery materials provided in Examples 1-6 of this application all exhibit excellent performance. The core directional adsorption step involves crosslinking and copolymerizing acrylonitrile and dimethylaminoethyl methacrylate to convert the nitrile groups into ammonia oxime groups, followed by grafting methylphosphonic acid groups to obtain a modified resin adsorbent. The ammonia oxime groups (-C(NOH)NH2) in the resin skeleton are used to capture Li from the leachate. + core site, Li + The ionic radius of Fe has a much higher degree of spatial structure matching with that of the amylopyridine group than other metal ions (such as Fe). 3+ PO4 3- Furthermore, the stability of this coordinate bond is significantly stronger than that of PO4. 3- Due to weak hydrogen bonding with the amine oxime group, Li + It can preferentially occupy adsorption sites, thus increasing the adsorption rate; at the same time, the methylphosphonic acid groups (-CH2PO(OH)2) grafted on the resin surface prevent PO4 from adsorbing through a combination of electrostatic repulsion and steric hindrance. 3- Interference, thereby enabling the modified resin adsorbent to target Li + The high selectivity of the capture achieved high lithium recovery rate and low swelling rate; while the performance of Comparative Examples 1-3 was significantly reduced due to insufficient oxidizing power of the leaching system, lack of functional groups in the adsorbent, or poor selectivity of the material itself.

[0131] It should be understood that the above are only some embodiments of this application. It should be pointed out that for those skilled in the art, other modifications and improvements can be made without departing from the inventive concept of this application, and these all fall within the protection scope of this application.

Claims

1. A method for recovering metallic lithium from waste lithium battery materials, characterized in that, Includes the following steps: S1: After mechanical separation and dealuminization, waste lithium iron phosphate batteries are screened and purified to obtain LFP cathode powder; S2: Mix LFP cathode powder with leaching agent, stir evenly, and filter to obtain leaching solution; S3: The modified resin adsorbent is filled into a fixed bed, the leachate is pumped into the fixed bed, and after adsorption for 2-3 hours, the leachate is discharged. S4: The eluent is reverse-flowed into the fixed bed, saturated Na2CO3 solution is added, stirred, filtered, washed with deionized water, centrifuged, the solid is collected and dried to obtain battery-grade lithium carbonate; The modified resin adsorbent is obtained by cross-linking and copolymerizing acrylonitrile and dimethylaminoethyl methacrylate and then grafting methylphosphonic acid groups onto it.

2. The method for recovering metallic lithium from waste lithium battery materials according to claim 1, characterized in that, The mass-to-volume ratio of LFP cathode powder to leaching agent in S2 is 1g:(9-15)mL; the leaching agent is a mixture of H2SO4 with a concentration of 0.3-0.5mol / L and H2O2 with a concentration of 0.04-0.06mol / L in a volume ratio of (3-5):(4-6).

3. The method for recovering metallic lithium from waste lithium battery materials according to claim 1, characterized in that, The uniform stirring in S2 is carried out at 35-45℃ and at a speed of 180-220 rpm for 80-100 minutes.

4. The method for recovering metallic lithium from waste lithium battery materials according to claim 1, characterized in that, The amount of modified resin adsorbent in S3 is 70-75% of the volume of the fixed bed.

5. A method for recovering metallic lithium from waste lithium battery materials according to claim 1, characterized in that, The eluent in S4 includes any one of sulfuric acid, hydrochloric acid, and citric acid, and the concentration of the eluent is 0.7-1.2 mol / L; the centrifugation rate is 1800-2000 rpm / min; the drying temperature is 60-70℃, and the drying time is 5-6 h.

6. A method for recovering metallic lithium from waste lithium battery materials according to claim 1, characterized in that, The preparation of the modified resin adsorbent described in S3 includes the following steps: T1: Mix acrylonitrile, dimethylaminoethyl methacrylate and crosslinking agent, purge with nitrogen, heat to 60-70℃, add ammonium persulfate, react for 4-5 hours, and polymerize to obtain copolymer microspheres; T2: The copolymerized microspheres were dispersed in anhydrous ethanol, and a 40-50% (w / w) hydroxylamine solution was added, followed by a 6-10% (w / w) NaOH solution. The pH was adjusted to 8-9, and the mixture was stirred at 150-200 rpm for 6-8 hours at 70-80°C. 0.6-1 mol / L hydrochloric acid was added to adjust the pH of the system to 6-7. The solid was then filtered and washed with deionized water to obtain the amylopyridine resin intermediate. T3: Add the above-mentioned amylopyridine resin intermediate to toluene, stir at 300-400 rpm for 4-5 h, add diethyl phosphite and catalyst in sequence, reflux at 100-110℃ for 8-10 h, collect the resin by filtration, wash with toluene and deionized water alternately 6-10 times each, and vacuum dry at 70-80℃ for 8-10 h to obtain the modified resin adsorbent.

7. A method for recovering metallic lithium from waste lithium battery materials according to claim 6, characterized in that, The crosslinking agent in T1 includes any one of N,N'-methylenebisacrylamide, ethylene glycol dimethacrylate, divinylbenzene, and trimethylolpropane triacrylate.

8. A method for recovering metallic lithium from waste lithium battery materials according to claim 6, characterized in that, The mass ratio of acrylonitrile, dimethylaminoethyl methacrylate, crosslinking agent and ammonium persulfate in T1 is (6-8):(4-2):(0.5-1):(0.5-1).

9. A method for recovering metallic lithium from waste lithium battery materials according to claim 6, characterized in that, The feeding ratio of hydroxylamine solution to copolymerized microspheres in T2 is (4-5) mL / g.

10. A method for recovering metallic lithium from waste lithium battery materials according to claim 6, characterized in that, The catalyst in T3 includes any one of acetic acid, formic acid, and propionic acid; the feed ratio of diethyl phosphite to the amygdoxime resin intermediate is (1.5-2.5) mL / g; the feed ratio of the catalyst to the amygdoxime resin intermediate is (0.3-0.5) mL / g.

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