A method for treating waste ternary lithium battery black powder based on pre-solid fluorine treatment

Abstract

This application belongs to the field of waste lithium-ion battery recycling technology, specifically relating to a method for treating waste ternary lithium battery black powder based on pre-fixed fluoride treatment, including the following steps: S1, obtaining waste ternary lithium battery black powder and a fluoride-fixing agent as raw materials, wherein the fluoride-fixing agent consists of quicklime, sodium carbonate, and fly ash; adding the raw materials to water for stirring, a first reaction, and filtration to obtain a first solid residue; S2, calcining and cooling the first solid residue to obtain a second solid residue; S3, adding the second solid residue to water and introducing carbon dioxide for a second reaction, and filtration to obtain a lithium-containing solution and a fluorine-containing solid. This application achieves dual fluorine locking and efficient lithium recovery through the synergistic fluoride fixation of quicklime-sodium carbonate-fly ash and low-temperature calcination.

Description

Technical Field

[0001] This application relates to the field of waste lithium-ion battery recycling technology, specifically, this application relates to a method for treating waste ternary lithium battery black powder based on pre-solid fluorine treatment. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the number of retired ternary lithium batteries has increased dramatically. The "black powder" obtained after crushing and sorting of waste ternary lithium batteries is rich in high-value metals such as nickel, cobalt, manganese, and lithium, and has extremely high recycling value. However, the black powder contains fluorine impurities in the form of polyvinylidene fluoride (PVDF) and lithium hexafluorophosphate (LiPF6).

[0003] The core hazard of fluorine impurities to subsequent recovery processes lies in their irreversible binding with lithium. In traditional acid leaching recovery processes, PVDF decomposes during acid leaching, releasing fluorine. - Simultaneously, the dissolution of the cathode material generates a high concentration of Li. + In an acidic environment, the two combine instantaneously to form insoluble LiF (with very low Ksp). Once LiF is formed, even if calcium salt is added for precipitation later, the fixed lithium cannot be recovered, resulting in permanent loss of lithium.

[0004] Existing defluorination pretreatment technologies have the following main drawbacks: 1. Water washing for defluorination: This method uses water washing to remove water-soluble fluoride (such as residual LiPF6) from PVDF. However, this method can only remove some water-soluble fluoride and cannot effectively remove organically bound fluoride from PVDF. During the washing process, some lithium will also dissolve, resulting in lithium loss, and a large amount of fluoride-containing wastewater will be generated, leading to high treatment costs.

[0005] 2. High-temperature roasting defluorination: PVDF is thermally decomposed at 500-600℃ to release HF gas. This method is energy-intensive, suffers from significant lithium volatilization losses at high temperatures, and requires equipment with extremely high corrosion resistance. The HF tail gas generated by PVDF pyrolysis requires a complex absorption and treatment system; otherwise, it will cause serious secondary pollution.

[0006] 3. Wet process for solid fluoride conversion: This method uses acidic media such as calcium sulfate and hydrochloric acid to leach and pretreat black powder, converting fluoride into a less soluble form. For example, bismuth chloride can be added and roasted to solidify fluoride, or calcium salts can be used to precipitate fluoride under acidic conditions. These methods either use precious metal salts, leading to high reagent costs, or the acidic system can severely corrode equipment. Furthermore, the reaction conditions require strict control, making industrialization difficult.

[0007] The common problem with existing technologies can be summarized by a fundamental contradiction: the chemical conditions for fluorine removal (high temperature or strong acid) inevitably lead to lithium loss. In the high-temperature roasting route, lithium is lost due to volatilization; in the acidic wet process route, the acidic environment creates conditions for LiF formation, resulting in lithium loss through precipitation. How to effectively remove fluorine while maximizing lithium recovery is a critical technical bottleneck that urgently needs to be overcome in this field.

[0008] Therefore, there is an urgent need to develop a pretreatment method that can efficiently fix fluorine under mild conditions, avoid LiF generation at the source, and ensure a high lithium recovery rate. This is of great significance for the high-value recycling of waste ternary lithium batteries. Summary of the Invention

[0009] To solve the above-mentioned technical problems, this application provides a method for pre-fixed fluoride treatment of waste ternary lithium battery black powder, comprising the following steps: S1, obtaining waste ternary lithium battery black powder and a fluoride-fixing agent as raw materials, wherein the fluoride-fixing agent consists of quicklime, sodium carbonate and fly ash; adding the raw materials to water for stirring, a first reaction, and filtration to obtain a first solid slag; S2, calcining and cooling the first solid slag to obtain a second solid slag; S3, adding the second solid slag to water and introducing carbon dioxide for a second reaction, and filtration to obtain a lithium-containing solution and a fluorine-containing solid.

[0010] As a preferred embodiment of the method for treating waste ternary lithium battery black powder based on pre-fixed fluorine as described in this application, in step S1, the mass ratio of quicklime, sodium carbonate and fly ash is 1:(0.1-0.6):(0.05-0.4).

[0011] As a preferred embodiment of the method for treating waste ternary lithium battery black powder based on pre-fixed fluorine treatment described in this application, in step S1, the composition of the waste ternary lithium battery black powder, by mass percentage, is: Li: 2%-6%, F: 0.5%-1.5%, with the remainder being C and unavoidable impurities, and the mass ratio of the waste ternary lithium battery black powder to the fluorine-fixing agent is 100:(8-16).

[0012] As a preferred embodiment of the method for treating waste ternary lithium battery black powder based on pre-solid fluorine treatment described in this application, in step S1, the temperature of the first reaction is 80-105℃, the time of the first reaction is 1-4h, and the pH of the first reaction is 11-13.

[0013] As a preferred embodiment of the method for treating waste ternary lithium battery black powder based on pre-solid fluorine treatment described in this application, in step S1, the solid-liquid ratio of the raw material to water is 1:(3-6)g / mL.

[0014] As a preferred embodiment of the method for treating waste ternary lithium battery black powder based on pre-solidified fluorine as described in this application, in step S2, the calcination temperature is 350-550℃ and the calcination time is 0.5-2h.

[0015] As a preferred embodiment of the method for treating waste ternary lithium battery black powder based on pre-solidified fluorine as described in this application, in step S3, the solid-liquid ratio of the second solid residue to water is 1:(3-5)g / mL.

[0016] As a preferred embodiment of the method for treating waste ternary lithium battery black powder based on pre-solidified fluorine as described in this application, in step S3, the pH of the second reaction is 6.5-9.5, the temperature of the second reaction is 20-60℃, and the time of the second reaction is 20-60min.

[0017] As a preferred embodiment of the method for treating waste ternary lithium battery black powder based on pre-solidified fluorine as described in this application, in step S3, the fluorine in the fluorine-containing solid is locked in a material structure in which the core is calcium fluoride and the surface is a dense inert mineralized coating layer, and the component of the dense inert mineralized coating layer is fluoroaluminosilicate.

[0018] As a preferred embodiment of the method for treating waste ternary lithium battery black powder based on pre-solid fluorine treatment described in this application, in step S3, the content of F in the lithium-containing solution is ≤10mg / L, and the comprehensive recovery rate of lithium is ≥96%.

[0019] The beneficial effects of this application are as follows: This application proposes a method for treating waste ternary lithium battery black powder based on pre-fluorine solidification. This application achieves dual fluorine locking and efficient lithium recovery through the synergistic solidification of quicklime-sodium carbonate-fly ash and low-temperature calcination.

[0020] This application uses quicklime as a solid slow-release alkali source, which reacts with water to generate Ca(OH)2, while simultaneously providing the Ca required for fluorine fixation. 2 + and the OH required to drive PVDF hydrolysis - Quicklime is slightly soluble in water, reacting as it dissolves, producing OH-. - The release rate is naturally regulated by dissolution kinetics, avoiding runaway reactions caused by the instantaneous release of high concentrations of soluble alkali. Sodium carbonate is used as an auxiliary alkali source to provide CO3. 2- This provides a carbon source for subsequent lithium carbonation and regenerates NaOH through a mild reaction with Ca(OH)2, forming an alkaline buffer system. Fly ash acts as a physical dispersing framework, preventing the black powder from agglomerating during the reaction; its surface active Al2O3 / SiO2 components catalyze and promote the hydrolysis of PVDF in an alkaline environment and can synergistically adsorb trace amounts of F. -This forms a secondary solid fluorine protection system.

[0021] In OH - Under sustained attack, the CF bond in the PVDF molecule breaks, the PVDF undergoes alkaline hydrolysis to defluorinate, and the organic fluorine is converted into free F. - Released into the solution, the PVDF binder coating on the surface of the cathode material particles is simultaneously peeled off, exposing the reaction interface; the Ca provided by quicklime... 2+ F released by PVDF hydrolysis - Instantaneous binding occurs, fluorine is fixed in situ, forming CaF2 precipitate. The fluorine is locked in the solid phase, preventing it from entering the gas phase or significantly entering the liquid phase; PVDF hydrolysis consumes OH... - While CaF2 precipitate is formed, OH- is simultaneously produced. - Return it to the solution, so that OH- - Continue driving the next round of PVDF hydrolysis, OH - A catalytic cycle is formed throughout the reaction process, with net consumption close to zero, requiring no additional alkali replenishment; after the PVDF coating is peeled off, the exposed lithium on the surface of the cathode material particles reacts with CO3 in an alkaline environment. 2- The reaction transforms the material into a water-soluble Li2CO3 shell, laying the physical phase foundation for subsequent water leaching lithium extraction.

[0022] Calcination is employed to promote the reduction of graphite and cathode materials inherent in waste ternary lithium battery black powder at 350-550℃, thereby disrupting the layered crystal structure of the ternary cathode material and releasing lithium from the crystal lattice. Under the conditions of 350-550℃ and in the presence of water vapor, trace amounts of hydrolysis occur on the surface of calcium fluoride to produce active fluorine substances, which then undergo in-situ mineralization reactions with the adjacent fly ash silica-alumina components, directly forming a dense, inert mineralized coating layer on the surface of the calcium fluoride particles. The composition of this dense, inert mineralized coating layer is fluoroaluminosilicate, which permanently isolates the fluorine. CaF2 generated under alkaline conditions undergoes lattice thermal vibration rearrangement within this temperature range, reducing defects, promoting grain growth, and further improving chemical stability.

[0023] The final carbonation conversion is completed by reacting CO2 with the trace amounts of Li2O / LiOH that may remain after calcination; the introduced CO2 bubbles nucleate and grow at the solid-liquid interface, exposing the Li2CO3 encased under CaF2 or carbon particles; CO2 converts the slightly soluble Li2CO3 into highly soluble LiHCO3, accelerating lithium dissolution.

[0024] The specific beneficial effects are as follows: (1) Thorough fluorine fixation, dual locking: Ca 2+ In-situ instant capture F -CaF2 precipitate is generated. In the calcination section, the silica-alumina components of fly ash are used to generate a dense, inert mineralized coating layer of fluoroaluminosilicate on the surface of CaF2 in situ. The dual isolation of chemical precipitation and physical coating makes it extremely difficult for fluorine to dissolve back in subsequent acid leaching.

[0025] (2) High lithium recovery rate: Alkali catalytic cycling enables OH... - Simultaneous in-situ regeneration during CaF2 formation continuously drives PVDF hydrolysis to expose the cathode interface; the black powder itself contains carbon source that breaks the lattice and releases lithium at a mild temperature; carbonation flotation leaching uses both physical stripping of bubbles and chemical enhancement by CO2 to drive efficient lithium dissolution, and lithium is extracted in a weakly alkaline environment throughout the process, thus avoiding LiF formation at the source.

[0026] (3) Low energy consumption at normal pressure and near-zero emissions: The boiling point reaction at normal pressure and the calcination temperature are much lower than the existing high-temperature routes. The carbonation flotation leaching can utilize the flue gas produced in the calcination section to achieve the cascade utilization of materials and energy. The filtrate is recycled, resulting in near-zero wastewater discharge. Fly ash is used as industrial solid waste and is utilized as a resource, realizing the treatment of waste with waste. Detailed Implementation

[0027] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0028] This application provides a method for pre-solidification treatment of waste ternary lithium battery black powder, including the following steps: S1. Obtain waste ternary lithium battery black powder and solid fluoride agent as raw materials. The solid fluoride agent consists of quicklime, sodium carbonate and fly ash. Add the raw materials to water, stir, perform a first reaction, and filter to obtain a first solid residue. The mass ratio of quicklime, sodium carbonate, and fly ash is 1:(0.1-0.6):(0.05-0.4); the composition of the waste ternary lithium battery black powder by mass percentage is: Li: 2%-6%, F: 0.5%-1.5%, with the remainder being C and unavoidable impurities; the mass ratio of the waste ternary lithium battery black powder to the solid fluoride agent is 100:(8-16); the temperature of the first reaction is 80-105℃, the time of the first reaction is 1-4h, and the pH of the first reaction is 11-13; the solid-liquid ratio of the raw material to water is 1:(3-6)g / mL. Specifically, the temperature of the first reaction is any one of 80°C, 85°C, 90°C, 95°C, 100°C, and 105°C, or a range between any two of them. S2. The first solid slag is calcined and cooled to obtain the second solid slag; The calcination temperature is 350-550℃, and the calcination time is 0.5-2h; Specifically, the calcination temperature is any one of 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, and 550℃, and a range between any two of them. S3. Add the second solid residue to water and pass carbon dioxide through to carry out the second reaction, then filter to obtain a lithium-containing solution and a fluorine-containing solid. The solid-liquid ratio of the second solid residue to water is 1:(3-5)g / mL; the pH of the second reaction is 6.5-9.5; the temperature of the second reaction is 20-60℃; and the time of the second reaction is 20-60min. Specifically, the pH of the second reaction is any one of 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, and 9.5, or any two of them. In the fluorine-containing solid, fluorine is locked in a material structure with calcium fluoride as the core and a dense inert mineralized coating layer on the surface. The dense inert mineralized coating layer is composed of fluoroaluminosilicate. In the lithium-containing solution, the content of F is ≤10mg / L, and the overall recovery rate of lithium is ≥96%.

[0029] The technical solution of this application will be further described below with reference to specific embodiments.

[0030] Example 1 This application provides a method for pre-solidification treatment of waste ternary lithium battery black powder, including the following steps: S1. Obtain waste ternary lithium battery black powder and solid fluoride agent as raw materials. The solid fluoride agent consists of quicklime, sodium carbonate and fly ash. Add the raw materials to water, stir, perform the first reaction, and filter to obtain the first solid residue. The mass ratio of quicklime, sodium carbonate, and fly ash is 1:0.35:0.2; the composition of waste ternary lithium battery black powder by mass percentage is: Li: 3.1%, F: 1.2%, with the remainder being C and unavoidable impurities; the mass ratio of waste ternary lithium battery black powder to solidifying agent is 100:12; the temperature of the first reaction is 90℃, the time of the first reaction is 2.5h, and the pH of the first reaction is 12; the solid-liquid ratio of raw materials to water is 1:4 g / mL. S2. The first solid slag is calcined and cooled to obtain the second solid slag; The calcination temperature was 450℃, and the calcination time was 1.5 hours. S3. Add the second solid residue to water and pass carbon dioxide through to carry out the second reaction. Filter to obtain a lithium-containing solution and a fluorine-containing solid. The solid-liquid ratio of the second solid residue to water is 1:4 g / mL; the pH of the second reaction is 8.0, the temperature of the second reaction is 40℃, and the time of the second reaction is 40 min; Testing revealed that the fluorine in the fluorine-containing solid was locked within a material structure consisting of calcium fluoride as the core and a dense, inert mineralized coating layer on the surface. The dense, inert mineralized coating layer was composed of fluoroaluminosilicate. The lithium-containing solution contained 8.8 mg / L of F, and the overall lithium recovery rate was 96.8%.

[0031] Example 2 This application provides a method for pre-solidification treatment of waste ternary lithium battery black powder, including the following steps: S1. Obtain waste ternary lithium battery black powder and solid fluoride agent as raw materials. The solid fluoride agent consists of quicklime, sodium carbonate and fly ash. Add the raw materials to water, stir, perform the first reaction, and filter to obtain the first solid residue. The mass ratio of quicklime, sodium carbonate, and fly ash is 1:0.1:0.05; the composition of waste ternary lithium battery black powder by mass percentage is: Li: 3.1%, F: 1.2%, with the remainder being C and unavoidable impurities; the mass ratio of waste ternary lithium battery black powder to solidifying agent is 100:16; the temperature of the first reaction is 80℃, the time of the first reaction is 4h, and the pH of the first reaction is 11; the solid-liquid ratio of raw materials to water is 1:6 g / mL. S2. The first solid slag is calcined and cooled to obtain the second solid slag; The calcination temperature was 350℃, and the calcination time was 2 hours. S3. Add the second solid residue to water and pass carbon dioxide through to carry out the second reaction. Filter to obtain a lithium-containing solution and a fluorine-containing solid. The solid-liquid ratio of the second solid residue to water is 1:3 g / mL; the pH of the second reaction is 9.5, the temperature of the second reaction is 20℃, and the time of the second reaction is 60 min; Testing revealed that the fluorine in the fluorine-containing solid was locked within a material structure consisting of calcium fluoride as the core and a dense, inert mineralized coating layer on the surface. The dense, inert mineralized coating layer was composed of fluoroaluminosilicate. The lithium-containing solution contained 9.2 mg / L of F, and the overall lithium recovery rate was 96.3%.

[0032] Example 3 This application provides a method for pre-solidification treatment of waste ternary lithium battery black powder, including the following steps: S1. Obtain waste ternary lithium battery black powder and solid fluoride agent as raw materials. The solid fluoride agent consists of quicklime, sodium carbonate and fly ash. Add the raw materials to water, stir, perform the first reaction, and filter to obtain the first solid residue. The mass ratio of quicklime, sodium carbonate, and fly ash is 1:0.6:0.4; the composition of waste ternary lithium battery black powder by mass percentage is: Li: 3.1%, F: 1.2%, with the remainder being C and unavoidable impurities; the mass ratio of waste ternary lithium battery black powder to solidifying agent is 100:8; the temperature of the first reaction is 105℃, the time of the first reaction is 1h, and the pH of the first reaction is 13; the solid-liquid ratio of raw materials to water is 1:3 g / mL. S2. The first solid slag is calcined and cooled to obtain the second solid slag; The calcination temperature was 550℃, and the calcination time was 0.5h. S3. Add the second solid residue to water and pass carbon dioxide through to carry out the second reaction. Filter to obtain a lithium-containing solution and a fluorine-containing solid. The solid-liquid ratio of the second solid residue to water is 1:5 g / mL; the pH of the second reaction is 6.5, the temperature of the second reaction is 60℃, and the time of the second reaction is 20 min. Testing revealed that the fluorine in the fluorine-containing solid was locked within a material structure consisting of calcium fluoride as the core and a dense, inert mineralized coating layer on the surface. The dense, inert mineralized coating layer was composed of fluoroaluminosilicate. The lithium-containing solution contained 9.4 mg / L of F, and the overall lithium recovery rate was 96.1%.

[0033] Comparative Example 1 The difference between this comparative example and Example 1 is that the fluorine-fixing agent does not contain sodium carbonate, while all other steps are the same as in Example 1.

[0034] Testing revealed that the fluorine in the fluorine-containing solid was locked within a material structure consisting of calcium fluoride as the core and a dense, inert mineralized coating layer on the surface. The dense, inert mineralized coating layer was composed of fluoroaluminosilicate. The lithium-containing solution contained 128 mg / L of fluorine, and the overall lithium recovery rate was 94.1%.

[0035] Comparative Example 2 The difference between this comparative example and Example 1 is that the fluorine-fixing agent does not contain fly ash, while all other steps are the same as in Example 1.

[0036] Testing revealed that fluorine in the fluorine-containing solid was locked in calcium fluoride; the F content in the lithium-containing solution was 156 mg / L, and the overall lithium recovery rate was 94.3%.

[0037] Comparative Example 3 The difference between this comparative example and Example 1 is that the temperature of the first reaction in step S1 is too low, at 70°C, while the other steps are the same as in Example 1.

[0038] Tests revealed that the fluorine in the fluorine-containing solid was locked within a material structure consisting of calcium fluoride as the core and a dense, inert mineralized coating layer on the surface. The dense, inert mineralized coating layer was composed of fluoroaluminosilicate. The lithium-containing solution contained 89 mg / L of fluorine, and the overall lithium recovery rate was 93.2%.

[0039] Comparative Example 4 The difference between this comparative example and Example 1 is that the temperature of the first reaction in step S1 is too high, at 110°C, while the other steps are the same as in Example 1.

[0040] Testing revealed that the fluorine in the fluorine-containing solid was locked within a material structure consisting of calcium fluoride as the core and a dense, inert mineralized coating layer on the surface. The dense, inert mineralized coating layer was composed of fluoroaluminosilicate. The lithium-containing solution contained 8.7 mg / L of F, and the overall lithium recovery rate was 93.4%.

[0041] Comparative Example 5 The difference between this comparative example and Example 1 is that the calcination temperature in step S2 is too low, at 300°C. All other steps are the same as in Example 1.

[0042] Testing revealed that the fluorine in the fluorine-containing solid was locked within a material structure consisting of calcium fluoride as the core and a dense, inert mineralized coating layer on the surface. The dense, inert mineralized coating layer was composed of fluoroaluminosilicate. The lithium-containing solution contained 143 mg / L of F, and the overall lithium recovery rate was 92.3%.

[0043] Comparative Example 6 The difference between this comparative example and Example 1 is that the calcination temperature in step S2 is too high, at 600°C. All other steps are the same as in Example 1.

[0044] Testing revealed that the fluorine in the fluorine-containing solid was locked within a material structure consisting of calcium fluoride as the core and a dense, inert mineralized coating layer on the surface. The dense, inert mineralized coating layer was composed of fluoroaluminosilicate. The lithium-containing solution contained 8.6 mg / L of F, and the overall lithium recovery rate was 90.8%.

[0045] Comparative Example 7 The difference between this comparative example and Example 1 is that the pH of the second reaction in step S3 is too low, at 5.5. All other steps are the same as in Example 1.

[0046] Testing revealed that the fluorine in the fluorine-containing solid was locked within a material structure consisting of calcium fluoride as the core and a dense, inert mineralized coating layer on the surface. The dense, inert mineralized coating layer was composed of fluoroaluminosilicate. The lithium-containing solution contained 229 mg / L of F, and the overall lithium recovery rate was 96.5%.

[0047] Comparative Example 8 The difference between this comparative example and Example 1 is that the pH of the second reaction in step S3 is too high, at 10.5. All other steps are the same as in Example 1.

[0048] Testing revealed that the fluorine in the fluorine-containing solid was locked within a material structure consisting of calcium fluoride as the core and a dense, inert mineralized coating layer on the surface. The dense, inert mineralized coating layer was composed of fluoroaluminosilicate. The lithium-containing solution contained 8.7 mg / L of F, and the overall lithium recovery rate was 90.3%.

[0049] As can be seen from the above embodiments and comparative examples: Example 1, combined with Comparative Example 1, shows that the reason for the slight decrease in the overall lithium recovery rate due to the increased F content in the lithium-containing solution is that the alkaline buffer regeneration mechanism fails after the absence of sodium carbonate. In Example 1, the reaction of sodium carbonate with Ca(OH)2 continuously replenishes OH. - Maintaining stable alkalinity drives the complete hydrolysis of PVDF. Comparative Example 1 relies solely on quicklime to provide OH-. - As the alkalinity gradually decreases due to the reaction, the hydrolysis of PVDF is incomplete. The incompletely hydrolyzed PVDF releases F2 during thermal decomposition in the S2 calcination section. - When lacking Ca 2+ Instant capture, S3 leaching F - As the PVDF dissolves into the solution, the F content increases. Simultaneously, incomplete PVDF stripping affects the exposure of the cathode interface, slightly impacting lithium carbonation and resulting in a slight decrease in recovery rate.

[0050] Example 1, combined with Comparative Example 2, shows that the significantly increased F content and slightly decreased overall lithium recovery rate in the lithium-containing solution are due to the loss of the triple function of fly ash, the loss of physical dispersion function leading to black powder agglomeration, and the decrease in Ca. 2+ and OH - Insufficient contact with PVDF hinders fluorine release and capture. The lack of alkaline catalysis limits the rate of CF bond breaking, resulting in incomplete PVDF hydrolysis. In the S2 calcination section, the absence of fly ash as a silicon-aluminum source prevents the formation of a dense, inert mineralized coating on the CaF2 surface. Fluorine in the fluorine-containing solid exists only as exposed CaF2, leading to more trace re-dissolution during S3 leaching and a significant increase in F content. Black powder agglomeration also causes partial encapsulation of the cathode material, resulting in incomplete lithium carbonation and a slight decrease in recovery rate.

[0051] Example 1, combined with Comparative Example 3, shows that the reason for the decrease in overall lithium recovery rate due to the increase in F content in the lithium-containing solution is that the alkaline hydrolysis of PVDF requires sufficient thermal energy to drive the CF bond breakage, and the molecular thermal kinetic energy is insufficient at 70°C. - The effective collision frequency of the CF bond decreases, resulting in insufficient hydrolysis of PVDF within the same reaction time, and some fluorine remains in an organically bound form. The residual PVDF releases fluorine during thermal decomposition in the S2 calcination section. - Ca in the time system 2+It has been largely consumed in stage S1 and cannot be captured immediately. During S3 leaching, F... - Leaching. Insufficient PVDF stripping also affects the exposure of the cathode interface, hindering lithium carbonation and reducing recovery rate.

[0052] Example 1, combined with Comparative Example 4, shows that the decrease in F content and overall lithium recovery rate in the lithium-containing solution is due to: high temperature accelerating the hydrolysis rate of PVDF, the release of fluorine, and Ca... 2+ The capture was more complete, and the fluorine fixation rate remained high or even slightly improved. However, the high-temperature and strong alkaline environment accelerated the trace dissolution of lithium on the surface of the cathode particles in the form of LiOH. This lithium was lost with the filtrate during S1 filtration and did not enter the subsequent recovery process, resulting in irreversible loss of lithium and a decrease in recovery rate.

[0053] Example 1, combined with Comparative Example 5, shows that the significant increase in F content and the significant decrease in overall lithium recovery rate in the lithium-containing solution are due to the following reasons: The calcination temperature was too low, resulting in incomplete triple reactions, insufficient self-reduction phase transformation, and insufficient reducing power of the carbon source in the black powder at 300℃, failing to effectively disrupt the cathode lattice, thus preventing the full release of lattice lithium and reducing the recovery rate. Insufficient CaF2 crystal repair, failure to eliminate lattice defects, and insufficient inherent stability led to increased trace re-dissolution during S3 leaching. The extremely slow self-mineralization coating reaction rate prevented the formation of a complete and dense coating layer on the CaF2 surface, resulting in a lack of effective physical isolation and protection for F, increased dissolution, and simultaneous deterioration of both fluorine and lithium indicators.

[0054] Example 1, combined with Comparative Example 6, shows that the decrease in F content and the significant drop in overall lithium recovery rate in the lithium-containing solution are due to the fact that the self-reduction phase transformation and self-mineralization coating reaction proceed fully at 600℃, maintaining a high or even better fluorine locking effect. However, lithium volatilizes as Li₂O vapor above 500℃, and the volatilization loss increases sharply at 600℃, constituting an irreversible and permanent loss. Although the fluorine fixation effect did not deteriorate, the lithium recovery rate decreased significantly.

[0055] Example 1, combined with Comparative Example 7, shows that the reason why the F content in the lithium-containing solution increased significantly while the overall lithium recovery rate remained basically unchanged is that the pH of 5.5 deviated from the stable range of CaF2 and the surface inert mineralization coating. + With F - The formation of the weak electrolyte HF shifts the CaF2 dissolution equilibrium to the right, resulting in a trace amount of CaF2 dissolution. Simultaneously, the mineralized coating layer is affected by H+ in a slightly acidic environment. + Erosion weakens the protective effect. The combined effect of these two factors... - The amount of remelted material increases significantly. Lithium dissolves more completely in a slightly acidic environment, and the recovery rate remains basically unchanged, but the excessive F content will seriously increase the subsequent purification cost.

[0056] Example 1, combined with Comparative Example 8, shows that the reason for the decrease in F content and the significant decrease in overall lithium recovery rate in the lithium-containing solution is that the CO2 introduction is severely insufficient at pH 10.5, resulting in insufficient HCO3 in the solution. - The concentration is extremely low. Li₂CO₃ cannot be fully converted into highly soluble LiHCO₃, and a large amount of lithium remains in the fluorine-containing solid as slightly soluble Li₂CO₃, failing to dissolve into the solution. Although a high pH environment is beneficial to the stability of CaF₂ and the mineralized coating, the fluorine fixation effect at the expense of lithium recovery rate has no technological value.

[0057] Examples 1-3, combined with Comparative Examples 1-8, demonstrate that: 1. The three components of the transforming agent are synergistic and inseparable: the absence of sodium carbonate leads to the failure of alkali buffer regeneration, an increase in F content, and a slight decrease in lithium recovery; the absence of fly ash results in the absence of a mineralized coating on fluorine-containing solids, and a significant increase in F content. All three components are indispensable. 2. The temperature of the first reaction (S1) has a limited window: if the temperature is too low, PVDF hydrolysis is insufficient, leading to an increase in F content and a decrease in lithium recovery; if the temperature is too high, lithium dissolves and is lost in strong alkali, resulting in a decrease in recovery. 3. The temperature of the calcination (S2) has a limited window: if the temperature is too low, self-reduction phase transformation, crystal repair, and mineralization are all insufficient, and both fluorine and lithium indicators deteriorate simultaneously; if the temperature is too high, lithium evaporates in large quantities in vapor form, resulting in irreversible and permanent loss. 4. The pH of the second reaction (S3) needs to be strictly controlled within a limited range: if the pH is too low, CaF2 and the mineralized coating are affected by H... + Erosion, F - Excessive re-dissolution occurs; if the pH is too high, the CO2 supply is insufficient, and Li2CO3 cannot be converted into LiHCO3, resulting in a sharp drop in lithium recovery rate.

[0058] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. All equivalent structural transformations made using the content of this application's specification under the inventive concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A method for treating waste ternary lithium battery black powder based on pre-fixing fluorine treatment, characterized in that, Includes the following steps: S1. Obtain waste ternary lithium battery black powder and solid fluoride agent as raw materials. The solid fluoride agent consists of quicklime, sodium carbonate and fly ash. Add the raw materials to water, stir, perform a first reaction, and filter to obtain a first solid residue. S2. The first solid slag is calcined and cooled to obtain the second solid slag; S3. Add the second solid residue to water and pass carbon dioxide through to carry out the second reaction, then filter to obtain a lithium-containing solution and a fluorine-containing solid. In step S1, the temperature of the first reaction is 80-105℃; In step S2, the calcination temperature is 350-550℃; In step S3, the pH of the second reaction is 6.5-9.

5.

2. The method for treating waste ternary lithium battery black powder based on pre-solidified fluorine treatment according to claim 1, characterized in that, In step S1, the mass ratio of quicklime, sodium carbonate, and fly ash is 1:(0.1-0.6):(0.05-0.4).

3. The method for treating waste ternary lithium battery black powder based on pre-solid fluorine treatment according to claim 1, characterized in that, In step S1, the composition of the waste ternary lithium battery black powder, by mass percentage, is: Li: 2%-6%, F: 0.5%-1.5%, with the remainder being C and unavoidable impurities. The mass ratio of the waste ternary lithium battery black powder to the solid fluoride agent is 100:(8-16).

4. The method for treating waste ternary lithium battery black powder based on pre-solid fluorine treatment according to claim 1, characterized in that, In step S1, the first reaction takes 1-4 hours and the pH of the first reaction is 11-13.

5. The method for treating waste ternary lithium battery black powder based on pre-solid fluorine treatment according to claim 1, characterized in that, In step S1, the solid-liquid ratio of the raw material to water is 1:(3-6)g / mL.

6. The method for treating waste ternary lithium battery black powder based on pre-solid fluorine treatment according to claim 1, characterized in that, In step S2, the calcination time is 0.5-2 hours.

7. The method for treating waste ternary lithium battery black powder based on pre-solid fluorine treatment according to claim 1, characterized in that, In step S3, the solid-liquid ratio of the second solid residue to water is 1:(3-5)g / mL.

8. The method for treating waste ternary lithium battery black powder based on pre-solid fluorine treatment according to claim 1, characterized in that, In step S3, the temperature of the second reaction is 20-60℃, and the reaction time is 20-60 min.

9. The method for treating waste ternary lithium battery black powder based on pre-solid fluorine treatment according to claim 1, characterized in that, In step S3, the fluorine in the fluorine-containing solid is locked in a material structure with calcium fluoride as the core and a dense inert mineralized coating layer on the surface. The dense inert mineralized coating layer is composed of fluoroaluminosilicate.

10. The method for treating waste ternary lithium battery black powder based on pre-solid fluorine treatment according to claim 1, characterized in that, In step S3, the content of F in the lithium-containing solution is ≤10mg / L, and the overall lithium recovery rate is ≥96%.