A lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons and its application

Abstract

This invention provides a lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons (PAHs) and its application, belonging to the field of battery recycling. The method includes the following steps: leaching the negative electrode material of spent lithium-ion batteries using a lithium extraction reagent to obtain a solid-liquid mixture. The solute in the lithium extraction reagent is a heteroatom-substituted PAH or a mixture of heteroatom-substituted PAHs and unsubstituted PAHs, and the solution is an organic solvent. The obtained solid-liquid mixture is separated to obtain a lithium-rich solution, thereby achieving efficient lithium recovery from spent lithium-ion batteries with the assistance of heteroatom-substituted PAHs. This invention, by adding heteroatom-substituted PAHs with stronger electronegativity to the lithium extraction reagent, can increase the solubility of PAHs in the reagent, thereby increasing the concentration of extracted lithium. It also enhances the binding ability of PAHs to active lithium, further accelerating the lithium extraction reaction kinetics and improving the lithium extraction efficiency.

Description

Technical Field

[0001] This invention belongs to the field of battery recycling, and more specifically, relates to a lithium recycling method based on heteroatom-substituted polycyclic aromatic hydrocarbons and its application. Background Technology

[0002] Lithium-ion power batteries are widely used, but their lifespan is relatively short, with an effective lifespan as short as 4 to 6 years. Therefore, a large number of lithium-ion power batteries face the issue of retirement. Based on factors such as environmental protection, resource scarcity, economic efficiency, and policy requirements, the recycling of lithium from lithium-ion power batteries is imperative. Currently, battery recycling technologies mainly rely on pyrometallurgy and hydrometallurgy. Pyrometallurgy suffers from high energy consumption, significant resource waste, and harmful gas emissions, while hydrometallurgy is characterized by complex processes and the extensive use of inorganic acids and organic reagents.

[0003] Existing technologies involve directly immersing spent battery anode materials in an organic reagent containing aromatic compounds to obtain a lithium-enriched solution. This lithium-containing enriched solution is then used as a chemical pre-lithiation reagent for reuse in lithium-ion battery anodes (CN113061726B). Alternatively, recycled spent cathode materials can be added to the lithium-enriched solution for lithium replenishment and regeneration (CN113846235A). However, the anode materials in spent lithium-ion batteries develop a passivation film on their surface due to long-term charge-discharge cycles. Furthermore, the presence of a solid-liquid interface between the organic reagent and the anode material slows down the lithium extraction rate and reduces the extraction efficiency. Therefore, using a single aromatic compound for lithium recovery has limited efficiency, is time-consuming and costly in large-scale applications, and results in significant resource waste. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons and its application, aiming to solve the problem of low efficiency of existing lithium recovery methods.

[0005] To achieve the above objectives, the present invention provides a lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons, the method comprising the following steps:

[0006] S1 uses a lithium extraction reagent to leach the negative electrode material of waste lithium-ion batteries to obtain a solid-liquid mixture. The solute of the lithium extraction reagent is a heteroatom-substituted polycyclic aromatic hydrocarbon or a mixture of heteroatom-substituted polycyclic aromatic hydrocarbon and unsubstituted polycyclic aromatic hydrocarbon. The solution is an organic solvent. During operation, the strong electronegativity of the heteroatom-substituted polycyclic aromatic hydrocarbon is used to increase the concentration of the lithium extraction reagent and promote the combination of lithium with polycyclic aromatic hydrocarbon, thereby improving the lithium extraction efficiency.

[0007] S2 separates the solid-liquid mixture obtained in step S1 to obtain a lithium-rich solution, and then achieves efficient recovery of lithium from waste lithium-ion batteries with the assistance of heteroatom-substituted polycyclic aromatic hydrocarbons.

[0008] As a further preferred embodiment, the organic solvent is a weakly polar organic solvent to retain the electron-withdrawing effect of the large π bond of the unsubstituted polycyclic aromatic hydrocarbon, thereby improving the lithium leaching rate and efficiency.

[0009] As a further preferred embodiment, the weakly polar organic solvent is an organic solvent with a dielectric constant less than 7, specifically including tetrahydrofuran containing 1 to 3 substituents, tetrahydropyran containing 1 to 3 substituents, ethers containing 2 ether bonds and at least 5 carbons and substituents, diethyl ether, dimethoxymethane, 1,4-dioxane, 2-ethoxy-4-(trifluoromethyl)-1,3-dioxane, 2-ethoxy-4-(trifluoromethyl)-1,3-dioxane, cyclopentyl methyl ether, hexafluoroisopropyl methyl ether, and bis(2,3-dioxane). One or more of 2,2-trifluoroethyl ether, 1,1,1,3,3,3-hexafluoroisopropylmethyl ether, 1,1,2,2-tetrafluoroethyl ether-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, and tris(2,2,2)-trifluoroethyl orthoformate, wherein the substituent is one or more of alkyl, hydroxyl, nitro, halogen, amino, carboxyl, aldehyde, and carbonyl groups.

[0010] As a further preferred embodiment, in step S1, ultrasonic-assisted leaching is used to destroy the passivation film on the surface of the negative electrode material.

[0011] As a further preferred embodiment, the ultrasonic power is 300W to 3000W.

[0012] As a further preferred embodiment, in step S1, leaching is carried out under an inert atmosphere, ensuring that the water content is ≤50ppm and the oxygen content is ≤50ppm; the leaching time is 0.5h to 10h, preferably 0.5h to 4h; and the leaching temperature is 20℃ to 100℃, preferably 20℃ to 80℃.

[0013] As a further preferred embodiment, in step S1, the mass ratio of the negative electrode material to the solute in the lithium extraction solvent is 1:1 to 1:3; the concentration of the lithium extraction reagent is 0.01 mol / L to 6 mol / L, preferably 0.5 mol / L to 2 mol / L.

[0014] As a further preferred embodiment, the mass percentage of heteroatom-substituted polycyclic aromatic hydrocarbons in the mixture is 0.01% to 50%, preferably 1% to 10%; the heteroatoms in the heteroatom-substituted polycyclic aromatic hydrocarbons are N, O, or S, and the heteroatom-substituted polycyclic aromatic hydrocarbons are one or more of pyridine, bipyridine, thiophene, quinoline, isoquinoline, carbazole, pyrimidine, pteridine, acridine, phenazine, pyrazine, and phenothiazine; the number of carbon atoms in the unsubstituted polycyclic aromatic hydrocarbons is 10 to 20, and the unsubstituted polycyclic aromatic hydrocarbons are one or more of biphenyl, naphthalene, phenanthrene, pyrene, anthracene, perylene, and their derivatives.

[0015] According to another aspect of the present invention, a lithium recycling method based on heteroatom-substituted polycyclic aromatic hydrocarbons is provided. The method uses the above-mentioned lithium recycling method based on heteroatom-substituted polycyclic aromatic hydrocarbons to obtain a lithium-rich solution, and then uses the lithium-rich solution to soak the material to be treated to achieve lithium recycling. The material to be treated includes one or more of waste positive electrode materials, new negative electrode materials, and high-specific-capacity lithium-free positive electrode materials, thereby realizing the regeneration of waste positive electrode materials, the pre-physicochemical treatment of new negative electrode materials, and the replenishment of lithium to high-specific-capacity lithium-free positive electrode materials.

[0016] As a further preferred embodiment, the lithium recycling method based on heteroatom-substituted polycyclic aromatic hydrocarbons further includes calcining the recycled waste cathode material at 500℃~1000℃ for 1h~24h to remove the binder and restore the internal structure.

[0017] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:

[0018] 1. This invention introduces heteroatoms with stronger electronegativity into polycyclic aromatic hydrocarbons (PAHs) to replace PAHs. On the one hand, it can improve the solubility of PAHs in the lithium extraction reagent, thereby increasing the concentration of the extraction reagent. On the other hand, it can also enhance the binding ability of PAHs with active lithium, attracting more active lithium to be adsorbed on the surface of the lithium extraction reagent, thereby accelerating the lithium extraction reaction kinetics and improving the lithium extraction efficiency.

[0019] 2. In particular, the present invention uses a weakly polar organic solvent. Due to the weak Lewis basicity of the solvent, the electron-withdrawing effect of the large π bond of the aromatic compound can be retained, thereby ensuring that it has a strong interaction with the elemental lithium in the negative electrode material. This not only significantly improves the lithium leaching rate, but also greatly increases the lithium content extracted by the aromatic compound per unit volume of solvent, thus increasing the lithium extraction efficiency.

[0020] 3. At the same time, the present invention proposes to use ultrasonic-assisted leaching, which can destroy the passivation film on the surface of the negative electrode material, promote the peeling of graphite from the current collector, and make it more conducive to the uniform mixing of lithium extraction reagent and lithium-containing graphite, thereby accelerating lithium leaching and further improving the lithium leaching rate and efficiency.

[0021] 4. Furthermore, by optimizing the concentration of the lithium extraction reagent and the addition ratio of heteroatom-substituted polycyclic aromatic hydrocarbons (PAHs), this invention introduces the optimal amount of heteroatom-substituted PAH additives into the lithium extraction reagent at the optimal concentration. This not only enables the additives to effectively bind to the surface of unsubstituted PAHs, significantly improving the adsorption capacity for lithium, but also does not have a significant impact on the properties of the unsubstituted PAHs themselves, allowing them to exert their lithium extraction effect and thus improving the lithium extraction efficiency. In addition, the viscosity of the lithium-rich solution at this concentration is within an acceptable range, which is more conducive to subsequent utilization.

[0022] 5. This invention also proposes to directly use lithium-rich solutions for the regeneration of waste cathode materials, the pre-physicochemical treatment of new anode materials, and the lithium replenishment of high-specific-capacity lithium-free cathode materials, thereby enabling the rapid and convenient reuse of recycled lithium and greatly enriching existing battery manufacturing technologies. Attached Figure Description

[0023] Figure 1 This is a flowchart of lithium recovery based on heteroatom-substituted polycyclic aromatic hydrocarbons provided in an embodiment of the present invention;

[0024] Figure 2 These are the charge-discharge curves of the recycled lithium iron phosphate cathode material and the lithium metal anode half-cell of Example 1 of this invention.

[0025] Figure 3 The charge-discharge curves of the regenerated lithium iron phosphate cathode material and anode graphite material in Example 2 of this invention are shown below.

[0026] Figure 4 The cycling performance curves of the full battery of the regenerated lithium iron phosphate cathode material and graphite anode material in Example 3 of this invention are shown. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] like Figure 1 As shown, according to one aspect of the present invention, a lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons is provided, the method comprising the following steps:

[0029] S1 uses a lithium extraction reagent to leach the negative electrode material of waste lithium-ion batteries to obtain a solid-liquid mixture. The solute of the lithium extraction reagent is a heteroatom-substituted polycyclic aromatic hydrocarbon or a mixture of heteroatom-substituted polycyclic aromatic hydrocarbon and unsubstituted polycyclic aromatic hydrocarbon. The solution is an organic solvent. During operation, the strong electronegativity of the heteroatom-substituted polycyclic aromatic hydrocarbon is used to increase the concentration of the lithium extraction reagent and promote the combination of lithium with polycyclic aromatic hydrocarbon, thereby improving the lithium extraction efficiency.

[0030] S2 separates the solid-liquid mixture obtained in step S1 to obtain a lithium-rich solution, and then achieves efficient recovery of lithium from waste lithium-ion batteries with the assistance of heteroatom-substituted polycyclic aromatic hydrocarbons.

[0031] Considering the limited solubility of unsubstituted polycyclic aromatic hydrocarbons (PAHs) in lithium extraction reagents, which leads to limited lithium extraction efficiency, this invention introduces heteroatoms with stronger electronegativity to replace PAHs in the lithium extraction reagent. This effectively improves the solubility of PAHs, which is beneficial for increasing the concentration of the lithium extraction solution. Furthermore, the stronger electronegativity of the heteroatoms enhances the binding affinity between PAHs and lithium, attracting more active lithium to adsorb onto the PAH surface. Therefore, it is more conducive to binding with PAHs, accelerating the lithium extraction kinetics and improving the lithium extraction efficiency.

[0032] Furthermore, the method for obtaining the negative electrode material from waste lithium-ion batteries is as follows: The waste lithium-ion batteries are charged to 100% SOC (State of Charge), and then disassembled and sorted to obtain the negative electrode sheets in a safe environment with a relative humidity of less than 20%. The negative electrode includes, but is not limited to, carbon-based active materials and silicon-carbon-based active materials. Specifically, carbon-based active materials include, but are not limited to, one or more of natural graphite, artificial graphite, soft carbon, and hard carbon. Silicon-carbon-based active materials include, but are not limited to, one or more of carbon-coated nano-silicon, silicon suboxide carbon composite materials, silicon nanowires, variable-oxygen silicon suboxide carbon composite materials, and amorphous silicon alloys. The selected waste batteries can be batteries with different states of charge, SOC = 0–100%, preferably SOC = 20%–80%. The charging process includes one or more of constant current charging, constant voltage charging, and constant current / constant voltage charging. The constant current charging process includes simple constant current charging and multi-stage constant current charging, with the charging current range from 0.01C to 5C.

[0033] Furthermore, the organic solvent is mainly one or more of ethers, esters, and aromatics, preferably ethers or esters, including but not limited to tetrahydrofuran, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, ethyltetrahydrofuran, diethyltetrahydrofuran, 2,5-dimethoxytetrahydrofuran, phenyltetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, cyclopentyl methyl ether, etc.

[0034] Considering that strongly polar solvents are highly Lewis basic and readily interact with the large π bonds of polycyclic aromatic hydrocarbons, thereby weakening the electron-withdrawing effect of the large π bonds and resulting in a weakening of the interaction between the large π bonds and elemental lithium in the anode, weakly polar organic solvents are preferred to retain the electron-withdrawing effect of the large π bonds of unsubstituted polycyclic aromatic hydrocarbons, ensuring a strong interaction between them and active lithium, which is beneficial to the leaching rate and efficiency of lithium in the anode material. The weakly polar organic solvent is one or more of the following organic solvents with a dielectric constant of less than 7: ethers, esters, and aromatics. Preferably, it is one or more of the following organic solvents: ethers and esters with a dielectric constant of less than 7. This includes, but is not limited to, tetrahydrofuran containing 1-3 substituents, tetrahydropyran containing 1-3 substituents, ethers containing 2 ether bonds and at least 5 carbons and substituents, diethyl ether, dimethoxymethane, 1,4-dioxane, 2-ethoxy-4-(trifluoromethyl)-1,3-dioxane, 2-ethoxy-4-(trifluoromethyl)-1,3-dioxane, etc. One or more of cyclopentyl methyl ether, hexafluoroisopropyl methyl ether, bis(2,2,2-trifluoroethyl) ether, 1,1,1,3,3,3-hexafluoroisopropyl methyl ether, 1,1,2,2-tetrafluoroethyl ether-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, and tri(2,2,2-trifluoroethyl) orthoformate, wherein the substituents are one or more of alkyl, hydroxyl, nitro, halogen, amino, carboxyl, aldehyde, and carbonyl groups.

[0035] Furthermore, in step S1, ultrasound is used to assist leaching. Ultrasound breaks down the passivation film on the surface of the negative electrode material, promoting the peeling of graphite from the current collector. This facilitates more uniform mixing of the lithium extraction reagent and the lithium-containing graphite, thereby accelerating lithium leaching and further improving the leaching rate and efficiency. The ultrasonic power is preferably 300W to 3000W. The leaching time is 0.5h to 10h, preferably 0.5h to 4h; the leaching temperature is 20℃ to 100℃, preferably 20℃ to 80℃. Leaching is carried out under an inert atmosphere, ensuring that the water content is ≤50ppm and the oxygen content is ≤50ppm.

[0036] Further, in step S1, the mass ratio of the negative electrode material to the solute in the lithium extraction solvent is 1:1 to 1:3. Too low a concentration of the lithium extraction reagent will cause slow kinetics in the lithium extraction process, resulting in low lithium extraction efficiency and thus a low concentration of the lithium-rich solution, failing to improve lithium utilization. While too high a concentration of the lithium extraction reagent will accelerate the lithium extraction rate, it will also cause a sharp increase in the viscosity of the lithium-rich solution, which is detrimental to subsequent utilization. Therefore, the concentration of the lithium extraction reagent is 0.01 mol / L to 6 mol / L, preferably 0.5 mol / L to 2 mol / L. When the solute is a mixture of heteroatom-substituted polycyclic aromatic hydrocarbons (PAHs) and unsubstituted PAHs, the heteroatom-substituted PAHs account for 0.01% to 50% of the total solute mass in the lithium extraction reagent, preferably 1% to 10%.

[0037] Furthermore, the heteroatoms in the heteroatom-substituted polycyclic aromatic hydrocarbons are N, O, or S, and the heteroatom-substituted polycyclic aromatic hydrocarbons are one or more of pyridine, bipyridine, thiophene, quinoline, isoquinoline, carbazole, pyrimidine, pteridine, acridine, phenazine, pyrazine, phenothiazine, etc.

[0038] Unsubstituted polycyclic aromatic hydrocarbons are aromatic hydrocarbons containing multiple carbon atoms (6 ≤ n(C) ≤ 30) and without substituents. Preferably, they are selected from single unsubstituted polycyclic aromatic hydrocarbons with 10 to 20 carbon atoms, including but not limited to one or more of biphenyl, naphthalene, phenanthrene, pyrene, anthracene, perylene and their derivatives.

[0039] According to another aspect of the present invention, a lithium recycling method based on heteroatom-substituted polycyclic aromatic hydrocarbons is provided. The method uses the above-mentioned lithium recycling method based on heteroatom-substituted polycyclic aromatic hydrocarbons to obtain a lithium-rich solution, and then uses the lithium-rich solution to soak the material to be treated to achieve lithium recycling. The material to be treated includes one or more of waste positive electrode materials, new negative electrode materials, and high-specific-capacity lithium-free positive electrode materials, thereby realizing the regeneration of waste positive electrode materials, the pre-physicochemical treatment of new negative electrode materials, and the replenishment of lithium to high-specific-capacity lithium-free positive electrode materials.

[0040] Furthermore, the material to be treated can be treated by room temperature immersion, heated immersion, or solvothermal reaction. Specifically: room temperature immersion is carried out at 20℃~25℃ with a stirring rate of 100rpm~1000rpm; heated immersion is carried out at 30℃~200℃ with a stirring rate of 100rpm~1000rpm; the solvothermal reaction is carried out in a reactor at a reaction temperature of 50℃~300℃. The solid-liquid ratio of the material to be treated to the lithium-rich solution is 5g / L~100g / L, preferably 10g / L~50g / L, and the reaction time is 0.5h~24h, preferably 0.5h~10h.

[0041] Waste cathode materials include, but are not limited to, layered cathode materials, spinel-type cathode materials, olivine-type cathode materials, and their corresponding doped and modified cathode materials, specifically including but not limited to Li.x CoO2, Li x FePO4, Li x Mn2O4, Li x Ni y CozMnIO2 (y + z + I = 1), LiNi y Co z Al I O2 (y + z + I = 1), Li x NiO2, Li x VO2, Li x CrO2, Li x CoMnO4, Li x NiMn3O8, Li x Ni 0.5 Mn 1.5 O4 (0 < x < 1), etc., one or more combinations thereof. The waste anode materials include, but are not limited to, carbon-based materials, silicon-based materials, tin-based materials, phosphorus-containing materials, sulfur-containing materials, and lithium titanate. Among them, the carbon-based materials include one or more of natural graphite, artificial graphite, soft carbon, hard carbon, and mesocarbon microbeads, and the silicon-based materials include one or more of elemental silicon, silicon alloys, and silicon monoxide. The high specific capacity lithium-free cathode materials include, but are not limited to, one or more of elemental sulfur, metal fluorides, metal oxides, and metal sulfides.

[0042] During soaking, a small amount of organic reducing agents including, but not limited to, one or more of citric acid, oxalic acid, and ascorbic acid can also be added. The addition amount of the reducing agent is 1 wt% - 10 wt% of the waste cathode material. By adding a small amount of reducing agent in the present invention, it is more conducive to the entry of active lithium into the cathode material precursor, achieving effective lithium supplementation, and at the same time, it can avoid the oxidation of the lithium supplementation solution by air.

[0043] At the same time, the washed recycled waste cathode material can also be calcined to remove the binder inside the material and restore the material structure. The calcination temperature is 500°C - 1000°C, preferably 800°C - 1000°C, the calcination time is 1 h - 24 h, and the calcination atmosphere includes argon, nitrogen, or oxygen.

[0044] The present invention can efficiently and conveniently separate lithium from other substances. The whole process avoids the use of high-energy-consuming and corrosive chemical reagents. The treatment process is simple to operate, has high safety, is compatible with the existing battery processes, has low requirements for equipment, is conducive to industrialization, and is suitable for large-scale promotion. At the same time, the lithium-rich solution obtained in the present invention is derived from waste lithium-ion batteries and can be directly used for the direct repair and regeneration of waste cathode materials and the prelithiation of waste anode materials, and can be reassembled into new batteries, greatly enriching the existing battery manufacturing technology and having extremely high economic benefits.

[0045] The technical solution provided by the present invention will be further described below with reference to specific embodiments.

[0046] Example 1

[0047] (a) Charge the waste lithium iron phosphate battery to 4.3V using constant current charging, and then charge it again with constant voltage until the charging current density drops to 10% of the initial constant current charging current density, the voltage remains stable, and then stop charging.

[0048] (b) Disassemble the waste lithium-ion battery in an inert atmosphere, remove the negative electrode sheet, and cut it to the appropriate size;

[0049] (c) Prepare a lithium extraction reagent, the solute being pyrene and 5 wt% bipyridine, the solvent being 2-methyltetrahydrofuran solvent, add it to a reaction vessel and stir until a lithium extraction reagent with a concentration of 0.5 mol / L is formed;

[0050] (d) The cut negative electrode sheet is placed in the lithium extraction reagent. The lithium extraction temperature is room temperature, the solid-liquid ratio is 1:3, and the leaching time is 2 hours. After leaching, the solution is filtered to separate the liquid lithium-rich solution and the remaining negative electrode solid powder.

[0051] Example 2

[0052] Same as Example 1, except that the solutes in the lithium extraction reagent are pyrene and 5 wt% carbazole.

[0053] Example 3

[0054] Same as Example 1, except that the solutes in the lithium extraction reagent are pyrene and 5 wt% phenazine.

[0055] Example 4

[0056] Same as in Example 1, but the solutes were pyrene and 1 wt% bipyridine.

[0057] Example 5

[0058] Same as in Example 1, but the solutes were pyrene and 3 wt% bipyridine.

[0059] Example 6

[0060] Same as in Example 1, the solutes were biphenyl and 0.01% bipyridine, and the concentration of the lithium extraction reagent was 1 mol / L.

[0061] Example 7

[0062] Same as in Example 1, the solutes were biphenyl and 10% bipyridine, and the concentration of the lithium extraction reagent was 3 mol / L.

[0063] Example 8

[0064] Same as in Example 1, the solutes were biphenyl and 50% bipyridine, and the concentration of the lithium extraction reagent was 6 mol / L.

[0065] Example 9

[0066] Same as in Example 1, but the solutes were naphthalene and 1% bipyridine, and the concentration of the lithium extraction reagent was 1 mol / L.

[0067] Example 10

[0068] Same as in Example 1, the solutes were naphthalene and 10% bipyridine, and the concentration of the lithium extraction reagent was 2 mol / L.

[0069] Example 11

[0070] Same as in Example 1, the solutes were naphthalene and 50% bipyridine, and the concentration of the lithium extraction reagent was 4 mol / L.

[0071] Example 12

[0072] Same as in Example 1, the solutes were anthracene and 1% carbazole, and the concentration of the lithium extraction reagent was 0.1 mol / L.

[0073] Example 13

[0074] Same as in Example 1, the solutes were anthracene and 5% carbazole, and the concentration of the lithium extraction reagent was 0.1 mol / L.

[0075] Example 14

[0076] Same as in Example 1, the solutes were perylene and 1% phenazine, and the concentration of the lithium extraction reagent was 0.01 mol / L.

[0077] Example 15

[0078] Same as in Example 1, the solutes were perylene and 5% phenazine, and the concentration of the lithium extraction reagent was 0.02 mol / L.

[0079] Comparative Example 1

[0080] Same as in Example 1, except that the solute is only pyrene.

[0081] Comparative Example 2

[0082] Same as Example 6, except the solute is only biphenyl.

[0083] Comparative Example 3

[0084] Same as Example 9, except that the solute is only naphthalene.

[0085] Comparative Example 4

[0086] Same as in Example 12, except that the solute is only anthracene.

[0087] Comparative Example 5

[0088] Same as in Example 14, except that the solute is only perylene.

[0089] The reaction conditions and lithium extraction efficiencies of Examples 1-15 and Comparative Examples 1-4 are shown in Table 1. It can be seen that the lithium extraction reagent with added heteroatom-substituted polycyclic aromatic hydrocarbons has a higher lithium extraction efficiency compared to the reagent without heteroatom-substituted polycyclic aromatic hydrocarbons.

[0090] Table 1. Reaction conditions and lithium extraction efficiency of Examples 1-15 and Comparative Examples 1-4

[0091] solute solvent Concentration (mol / L) Lithium extraction efficiency (%) Example 1 Pyrene + 5% Bipyridine 2-Methyltetrahydrofuran 0.5 95 Example 2 Pyrene + 5% Carbazole 2-Methyltetrahydrofuran 0.5 93 Example 3 Pyrene + 5% phenazine 2-Methyltetrahydrofuran 0.5 90 Example 4 Pyrene + 1% Bipyridine 2-Methyltetrahydrofuran 0.5 90 Example 5 Pyrene + 3% Bipyridine 2-Methyltetrahydrofuran 0.5 92 Example 6 Biphenyl + 0.01% Bipyridine 2-Methyltetrahydrofuran 1 70 Example 7 Biphenyl + 10% Bipyridine 2-Methyltetrahydrofuran 3 73 Example 8 Biphenyl + 50% Bipyridine 2-Methyltetrahydrofuran 6 76 Example 9 Naphthalene + 1% Bipyridine 2-Methyltetrahydrofuran 1 75 Example 10 Naphthalene + 10% Bipyridine 2-Methyltetrahydrofuran 2 78 Example 11 Naphthalene + 50% Bipyridine 2-Methyltetrahydrofuran 4 82 Example 12 Anthracene+1% carbazole 2-Methyltetrahydrofuran 0.1 95 Example 13 Anthracene+5% carbazole 2-Methyltetrahydrofuran 0.1 97 Example 14 Perylene + 1% phenazine 2-Methyltetrahydrofuran 0.01 92 Example 15 Perylene + 5% phenazine 2-Methyltetrahydrofuran 0.02 94 Comparative Example 1 pyrene 2-Methyltetrahydrofuran 0.5 85 Comparative Example 2 Biphenyl 2-Methyltetrahydrofuran 1 65 Comparative Example 3 Naphthalene 2-Methyltetrahydrofuran 1 70 Comparative Example 4 Anthracene 2-Methyltetrahydrofuran 0.1 90 Comparative Example 5 Peripheral 2-Methyltetrahydrofuran 0.01 88

[0092] Waste iron phosphate precursor material or waste graphite anode material was added to the lithium-rich solution obtained in Examples 1-3 to achieve lithium replenishment of the cathode precursor material. The solid-liquid ratio was 20 g / L, and the mixture was stirred at room temperature for 2 h. The above mixed composite liquid was centrifuged and washed, and then the lithiated cathode material was sintered at 700 °C for 10 h to obtain regenerated lithium iron phosphate cathode material. Regenerated lithium iron phosphate cathode material was mixed with Super P and polyvinylidene fluoride binder at a mass ratio of 80:10:10 to form a slurry, which was then uniformly coated onto an aluminum foil current collector to serve as the cathode sheet. The pre-lithiated anode electrode sheet was prepared by mixing pre-lithiated commercial graphite anode material, Super P, and sodium carboxymethyl cellulose binder at a mass ratio of 80:10:10 to form a slurry, which was then uniformly coated onto a copper foil current collector to obtain the working electrode. The 2032 coin cell assembly was carried out in a glove box. The separator used was polypropylene (purchased from Celgard, USA), and the electrolyte was a commercially available lithium hexafluorophosphate electrolyte with a specific formulation of 1M LiPF6-EC / EMC (volume ratio 3:7). The assembled batteries were then subjected to charge-discharge performance tests using a Newway charge-discharge tester. The results are as follows: Figure 2-4 As shown, the coin cell half-cell, with the regenerated lithium iron phosphate cathode material and lithium metal matched, can achieve a capacity of approximately 160 mAh / g at 0.1C. The coin cell full-cell, with the regenerated lithium iron phosphate cathode material and pre-lithiated graphite anode sheet matched, can achieve a capacity of approximately 150 mAh / g at 0.1C. Furthermore, the pre-lithiated anode effectively compensates for lithium loss in the lithium iron phosphate cathode material during battery cycling tests, thus exhibiting high first-cycle coulombic efficiency and excellent cycle stability.

[0093] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons, characterized in that, The method includes the following steps: S1 utilizes a lithium extraction reagent to leach the negative electrode material of spent lithium-ion batteries to obtain a solid-liquid mixture. The solute of the lithium extraction reagent is a heteroatom-substituted polycyclic aromatic hydrocarbon (PAH) or a mixture of heteroatom-substituted PAHs and unsubstituted PAHs. The solution is an organic solvent. During operation, the strong electronegativity of the heteroatom-substituted PAHs is used to increase the concentration of the lithium extraction reagent and promote the binding of lithium with PAHs, thereby improving the lithium extraction efficiency. The heteroatoms in the heteroatom-substituted PAHs are N, O, and S, and the heteroatom-substituted PAHs are one or more of pyridine, bipyridine, thiophene, quinoline, isoquinoline, carbazole, pyrimidine, pteridine, acridine, phenazine, pyrazine, and phenothiazine. S2 separates the solid-liquid mixture obtained in step S1 to obtain a lithium-rich solution, and then achieves efficient recovery of lithium from waste lithium-ion batteries with the assistance of heteroatom-substituted polycyclic aromatic hydrocarbons.

2. The lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons as described in claim 1, characterized in that, The organic solvent is a weakly polar organic solvent to retain the electron-withdrawing effect of the large π bond of the unsubstituted polycyclic aromatic hydrocarbon, thereby improving the lithium leaching rate and efficiency.

3. The lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons as described in claim 2, characterized in that, The weakly polar organic solvent is an organic solvent with a dielectric constant less than 7, specifically including tetrahydrofuran containing 1 to 3 substituents, tetrahydropyran containing 1 to 3 substituents, ethers containing 2 ether bonds and at least 5 carbons and substituents, diethyl ether, dimethoxymethane, 1,4-dioxane, 2-ethoxy-4-(trifluoromethyl)-1,3-dioxolane, 2-ethoxy-4-(trifluoromethyl)-1,3-dioxolane, cyclopentyl methyl ether, hexafluoroisopropyl methyl ether, and bis(2,2,2-tri)-dioxane. One or more of the following: fluoroethyl ether, 1,1,1,3,3,3-hexafluoroisopropylmethyl ether, 1,1,2,2-tetrafluoroethyl ether-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, and tris(2,2,2)-trifluoroethyl orthoformate, wherein the substituent is one or more of the following: alkyl, hydroxyl, nitro, halogen, amino, carboxyl, aldehyde, and carbonyl.

4. The lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons as described in any one of claims 1 to 3, characterized in that, In step S1, ultrasonic-assisted leaching is used to destroy the passivation film on the surface of the negative electrode material.

5. The lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons as described in claim 4, characterized in that, The power of ultrasound ranges from 300W to 3000W.

6. The lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons as described in claim 1, characterized in that, In step S1, leaching is carried out under an inert atmosphere, ensuring that the water content is ≤50 ppm and the oxygen content is ≤50 ppm; the leaching time is 0.5 h to 10 h; and the leaching temperature is 20℃ to 100℃.

7. The lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons as described in claim 6, characterized in that, In step S1, the leaching time is 0.5 h to 4 h, and the leaching temperature is 20℃ to 80℃.

8. The lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons as described in claim 1, characterized in that, In step S1, the mass ratio of the negative electrode material to the solute in the lithium extraction solvent is 1:1 to 1:3; the concentration of the lithium extraction reagent is 0.01 mol / L to 6 mol / L.

9. The lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons as described in claim 8, characterized in that, In step S1, the concentration of the lithium extraction reagent is 0.5 mol / L to 2 mol / L.

10. The lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons as described in claim 1, characterized in that, The mass percentage of heteroatom-substituted polycyclic aromatic hydrocarbons in the mixture is 0.01% to 50%; the number of carbon atoms in the unsubstituted polycyclic aromatic hydrocarbons is 10 to 20, and the unsubstituted polycyclic aromatic hydrocarbons are one or more of biphenyl, naphthalene, phenanthrene, pyrene, anthracene, perylene and their derivatives.

11. The lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons as described in claim 10, characterized in that, The mass percentage of heteroatom-substituted polycyclic aromatic hydrocarbons in the mixture is 1% to 10%.

12. A method for lithium recovery and utilization based on heteroatom-substituted polycyclic aromatic hydrocarbons, characterized in that, The method uses the lithium recovery method based on heteroatom-substituted polycyclic aromatic hydrocarbons as described in any one of claims 1 to 11 to obtain a lithium-rich solution, and then uses the lithium-rich solution to soak the material to be treated to achieve lithium recovery and utilization. The material to be treated includes one or more of waste cathode materials, new anode materials, and high-specific-capacity lithium-free cathode materials, thereby realizing one or more of the following: regeneration of waste cathode materials, pre-lithiation of new anode materials, and lithium replenishment of high-specific-capacity lithium-free cathode materials.

13. The lithium recovery and utilization method based on heteroatom-substituted polycyclic aromatic hydrocarbons as described in claim 12, characterized in that, The lithium recycling method also includes calcining the recycled waste cathode material at 500℃~1000℃ for 1h~24h to remove the binder and restore the internal structure.

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