A method and system for purifying lithium salt products using waste battery by-products

Abstract

The application provides a method and system for purifying lithium salt products by using waste battery by-products. The method comprises the following steps: 1) after the waste battery is subjected to crushing and pyrolysis treatment, first separation treatment is performed to obtain mixed waste gas containing hydrogen fluoride, solid-phase waste material containing silicon, and positive electrode solid-phase waste material; 2) the mixed waste gas is introduced into a first mixed system containing a silicon-containing system, and after first reaction in a subcritical state, second separation treatment is performed to obtain a mixed solution containing fluorosilicic acid and a reduction system; and 3) a mixed system containing the mixed solution and a lithium-containing system is subjected to second reaction, and after third separation treatment, lithium salt is obtained; wherein the pH of the mixed system is 5-10. The method provided by the application can simultaneously realize efficient fixation of fluorine and purification of lithium salt products, and has the advantages of simple process flow, environmental friendliness and economic efficiency.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more particularly to a method and system for purifying lithium salt products using waste battery byproducts. Background Technology

[0002] With the rapid development of new energy vehicles, consumer electronics and energy storage industries, the production and consumption of lithium-ion batteries have increased dramatically.

[0003] On the one hand, the sources of lithium salts for batteries can be broadened by extracting lithium from waste batteries or salt lakes. However, both waste battery lithium extraction and salt lake lithium extraction have problems such as high processing costs and low lithium purity.

[0004] On the other hand, during the pretreatment pyrolysis process, a large number of waste lithium-ion batteries produce hydrogen fluoride (HF) through the decomposition of electrolyte salts and binders. HF poses a significant threat to human health and the ecological environment, making it a problem that the lithium battery recycling industry must address. Currently, alkaline spraying (such as NaOH solution) is generally used to neutralize and absorb HF, often combined with activated carbon adsorption and secondary combustion technologies to form a multi-stage purification system. However, multi-stage purification systems require the use of corrosion-resistant special materials, have high equipment requirements, high investment costs, and offer no additional benefits. Furthermore, the combustion of organic matter produces greenhouse gases such as carbon dioxide.

[0005] Therefore, if we can simultaneously achieve efficient fixation of hydrogen fluoride from waste batteries, improve lithium extraction purity, simplify the process, and make it environmentally friendly, it will be of great significance to promoting the development of the lithium-ion battery industry. Summary of the Invention

[0006] This invention provides a method for purifying lithium salt products using byproducts from waste batteries. The method involves recycling hydrogen fluoride generated from waste battery processing and silicon-based negative electrode waste or photovoltaic silicon panels. The resulting solution reacts with a lithium-containing system to selectively remove impurities such as potassium and sodium, thereby obtaining lithium salts with high purity.

[0007] This invention provides a system for purifying lithium salt products using waste battery byproducts. This system can achieve the value-added and harmless recycling of waste hydrogen fluoride, silicon-based anode waste, and photovoltaic silicon panels, while selectively removing difficult-to-separate impurities such as sodium and potassium from lithium salts in a short process.

[0008] This invention provides a method for purifying lithium salt products using waste battery byproducts, comprising the following steps:

[0009] 1) The waste batteries are crushed and pyrolyzed. After the first separation process, a mixed waste gas containing hydrogen fluoride, silicon-containing solid waste and positive electrode solid waste are obtained.

[0010] 2) The mixed waste gas is introduced into a silicon-containing system and undergoes a first reaction under the subcritical state of hydrogen fluoride. After a second separation process, a mixed liquid containing fluorosilicic acid and reducing materials are obtained.

[0011] 3) The mixture including the above-mentioned mixture and the lithium-containing system is subjected to a second reaction, followed by a third separation process to obtain lithium salt;

[0012] The pH of the mixture is 5-10.

[0013] As described above, the pH of the mixed system satisfies 5 ≤ ​​pH ≤ 6, and the mixed system further includes hydrofluoric acid;

[0014] And / or, the pH of the mixture satisfies 6 < pH < 8.

[0015] In step 2) of the method described above, the silicon-containing system includes the silicon-containing solid waste.

[0016] And / or, in step 2), the temperature of the first reaction is A, and the pressure is B, satisfying 20℃≤A<188℃ and 1.01325bar≤B<64.8bar;

[0017] And / or, in step 2), the molar ratio of hydrogen fluoride in the mixed waste gas to Si in the silicon-containing system is ≥6.5:1.

[0018] The method described above further includes mixing the positive electrode solid waste and the reducing material and then sequentially performing reduction roasting, leaching, and impurity removal treatments to obtain a lithium-containing mother liquor.

[0019] The reducing materials include reducing gases and carbon-containing solid waste.

[0020] In step 3), the lithium-containing system includes the lithium-containing mother liquor.

[0021] The leaching treatment, as described above, includes the following steps:

[0022] The roasted product after the reduction roasting treatment is immersed in an acidic leachate and stirred.

[0023] The acid used in the acidic leachate is 120% to 200% of the stoichiometric ratio.

[0024] And / or, the solid-liquid ratio of the roasted product to the acidic leachate is (50g~500g):1L;

[0025] And / or, the leaching temperature is 40~80℃, the leaching time is 10~240min, and the rotation speed is 100~1000rpm.

[0026] The method described above uses a purification solution for the impurity removal process.

[0027] The impurity removal solution includes at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, and potassium bicarbonate.

[0028] In the method described above, in the second reaction, the amount of fluorosilicic acid in the mixed system is 100% to 110% of the stoichiometric ratio.

[0029] And / or, the temperature of the second reaction is 10℃~60℃.

[0030] The method described above, wherein the crushing and pyrolysis treatment includes sequentially performing an electrified crushing treatment and a pyrolysis treatment;

[0031] Wherein, the oxygen content of the charged crushing process is <0.5%, and the temperature of the pyrolysis process is 480~600℃.

[0032] In another aspect, the present invention provides a system for purifying lithium salt products from waste battery by-products, for implementing the method described above;

[0033] The system includes a pretreatment unit, a subcritical reaction unit, and a recovery reaction unit;

[0034] The pretreatment unit includes a feed inlet, a mixed waste gas outlet, a silicon-containing solid waste outlet, and a positive electrode solid waste outlet; the subcritical reaction unit includes a mixed waste gas inlet, a silicon-containing system inlet, a mixed liquid outlet, and a reducing material outlet; and the recovery reaction unit includes a mixed liquid inlet, a lithium-containing system inlet, and a lithium salt outlet.

[0035] The mixed exhaust gas outlet is connected to the mixed exhaust gas inlet, and the mixed liquid outlet is connected to the mixed liquid inlet.

[0036] In the system described above, the silicon-containing solid waste outlet is connected to the silicon-containing system inlet;

[0037] And / or, it also includes a positive electrode reduction unit, which includes a positive electrode solid waste inlet, a reduction system inlet, and a lithium-containing mother liquor outlet;

[0038] The positive electrode solid waste outlet is connected to the positive electrode solid waste inlet, the reducing material outlet is connected to the reduction system inlet, and the lithium-containing mother liquor outlet is connected to the lithium-containing system inlet.

[0039] This invention achieves multiple benefits through "waste-to-waste" and reaction-separation coupling technology, realizing the value-added utilization of waste resources. It comprehensively utilizes HF generated during battery recycling, and uses fluorosilicic acid regenerated through subcritical reaction-separation coupling technology for low-cost selective separation of lithium and sodium / potassium, as well as the preparation of lithium salt products. On one hand, it achieves value-added treatment of hydrogen fluoride waste gas generated during the pretreatment pyrolysis of waste batteries and waste silicon-based anodes or photovoltaic silicon panels from waste batteries, providing a positive-return alternative to unprofitable environmental practices. On the other hand, by controlling the pH and using fluorosilicic acid to remove impurities such as sodium and potassium ions from lithium-containing systems, it significantly reduces the process difficulty and cost of lithium salt purification and lithium-sodium separation. It not only achieves efficient fixation and resource utilization of hydrogen fluoride but also highly selective removal of lithium, with a highly integrated, simple, and efficient process that is environmentally friendly and economically sound. Attached Figure Description

[0040] Figure 1 This is a system diagram of purifying lithium salt products using waste battery by-products in a specific embodiment of the present invention;

[0041] Figure 2 This is a system diagram for purifying lithium salt products using waste battery byproducts in another specific embodiment of the present invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0043] The reducing gas produced by the roasting of organic matter in the existing lithium battery recycling process contains HF, which has an adverse effect on the treatment of cathode materials. It can easily lead to the formation of insoluble metal fluorides, thereby reducing the leaching rate of valuable metals in the subsequent leaching process. Therefore, this reducing gas has no utilization value.

[0044] Extracting lithium salts from waste batteries typically involves repetitive, tedious, and complex processes, such as pH adjustment for impurity removal and filtration, evaporation and concentration, cooling and sodium precipitation, re-evaporation and crystallization, washing, re-evaporation, concentration and crystallization, dissolution, adsorption for impurity removal, evaporation, concentration and drying crystallization, resulting in high processing costs.

[0045] Furthermore, in the case of lithium extraction from salt lakes, lithium and sodium are separated using adsorption or reaction-separation coupling technology. The lithium concentration of the desorbed lithium solution is very low (around 0.1 g / L), requiring concentration of about 200-300 times to reach the suitable lithium concentration for preparing lithium carbonate. This results in a large consumption of fresh water, and the subsequent evaporation of a large amount of water from the desorbed lithium solution leads to high concentration costs.

[0046] If we can achieve waste-to-waste treatment, using hydrogen fluoride generated from recycled waste batteries for lithium salt purification, we can solve the hydrogen fluoride recycling problem and reduce the cost of lithium salt recycling.

[0047] Based on this, the present invention provides a method for purifying lithium salt products using waste battery by-products, comprising the following steps:

[0048] 1) The waste batteries are crushed and pyrolyzed. After the first separation process, a mixed waste gas containing hydrogen fluoride, silicon-containing solid waste and positive electrode solid waste are obtained.

[0049] 2) The mixed waste gas is introduced into a silicon-containing system, and the first reaction is carried out under the subcritical state of hydrogen fluoride. After the second separation treatment, a mixed liquid containing fluorosilicic acid and reducing materials are obtained.

[0050] 3) The mixture including the mixed liquid and the lithium-containing system is subjected to a second reaction, followed by a third separation process to obtain lithium salt;

[0051] The pH of the mixed system is 5-10.

[0052] This invention does not limit the specific type of waste battery, and can select common waste batteries, such as ternary batteries, lithium iron phosphate batteries, lithium cobalt oxide batteries, lithium manganese iron phosphate batteries, lithium-rich manganese batteries, lithium manganese oxide batteries, etc.

[0053] Step 1) The waste batteries are crushed and pyrolyzed. Organic matter in the battery components, such as binders, electrolytes, and separators, undergoes pyrolysis. Then, in the first separation process, the mixed waste gas in the first reaction system is collected by the ventilation equipment. The solid materials are separated by the screening process to obtain silicon-containing solid waste and positive electrode solid waste.

[0054] Specifically, the mixed exhaust gas includes HF, CO, CO2, CH4, H2O, etc.

[0055] This invention does not limit the specific method of the screening process. Appropriate screening methods can be selected according to the actual situation, such as magnetic separation, air separation, flotation, etc.

[0056] In step 2), the mixed waste gas is introduced into the silicon-containing system. The hydrogen fluoride in the mixed waste gas dissolves in water and is converted into hydrofluoric acid. Under the subcritical state of hydrogen fluoride, the hydrofluoric acid reacts with the silicon-containing substances in the silicon-containing system to generate a mixed liquid including fluorosilicic acid and reducing materials.

[0057] The subcritical state of this invention refers to the fluid state formed when a substance is at a temperature above its boiling point but below its critical temperature and at a pressure below its critical pressure. It possesses both gaseous diffusion and liquid solubility. For HF, the boiling point of HF at normal pressure is 19.5°C; therefore, the subcritical state is defined as the temperature between 19.5°C and 188°C, and the pressure between 1 atm and 64.8 bar.

[0058] The silicon-containing system in this invention refers to a system including elemental silicon, silicon oxide, silicon carbide, silicate or other active silicon, wherein the silicon-containing solid phase waste obtained in step 1) can be selected, or silicon-containing waste such as silicon-carbon anode waste, silicon-oxygen anode waste, photovoltaic silicon board, etc.

[0059] When the silicon-containing system includes elemental silicon, the reaction process includes the following steps:

[0060] Elemental silicon first reacts with hydrogen fluoride to produce gaseous silicon tetrafluoride (SiF4) and hydrogen (H2):

[0061] Si(s)+4HF(aq)→SiF4(g)↑+2H2(g)↑

[0062] The generated silicon tetrafluoride gas is unstable and readily hydrolyzes with water (usually from the hydrofluoric acid solution in the reaction system). During this process, if additional fluoride ions (F...) are present... - In the presence of , silicon tetrafluoride will further react with hydrogen fluoride to generate stable hexafluorosilicate ions (SiF6). 2- ), thus obtaining a fluorosilicic acid solution.

[0063] SiF4(g) + 2HF(aq) → H2SiF6(aq)

[0064] A more accurate understanding of the hydrolysis process can be:

[0065] 3SiF4(g)+2H2O(l)→SiO2(s)+2H2SiF6(aq)

[0066] Therefore, the overall reaction equation can be summarized as follows:

[0067] Si(s)+6HF(aq)→H2SiF6(aq)+2H2(g)↑

[0068] Secondly, when the silicon-containing system includes silicon oxides and / or silicates, the silicon oxides and silicates react with hydrofluoric acid, the core of which is the replacement of the Si-O bond by F⁻, ultimately transforming into H₂SiF₆; when the silicon-containing system includes silicon carbide, silicon carbide reacts with hydrofluoric acid to generate H₂SiF₆.

[0069] The second reaction system includes fluorosilicic acid, hydrogen, and carbonaceous solid waste. Through a second separation process, a mixed solution containing fluorosilicic acid and reducing materials are recovered.

[0070] In order to ensure the complete progress of the second reaction and make full use of the silicon material, an excess of mixed waste gas can be introduced into the silicon-containing system. It is understood that residual hydrofluoric acid may be present in the final second mixed system.

[0071] In step 3), the lithium-containing system refers to a mixed solution including lithium ions, sodium ions, potassium ions, etc. This invention does not limit the specific source of the lithium-containing system; it may include lithium-containing systems extracted from waste batteries, or lithium-rich sodium-potassium solutions extracted from salt lake brine.

[0072] Specifically, a mixture including fluorosilicic acid is mixed with a lithium-containing system to obtain a mixed system. The fluorosilicic acid reacts with impurities such as sodium ions and potassium ions in the lithium-containing system to form insoluble salts, thereby selectively removing sodium ions and potassium ions from the lithium-containing system.

[0073] The reaction process is as follows:

[0074] H2SiF6+2Na + +OH - →Na₂SiF₆↓+2H₂O

[0075] H2SiF6+2K + +OH - →K2SiF6↓+2H2O

[0076] After the third separation process, the solid phase is removed, leaving a lithium-ion-rich solution, which is then purified to obtain lithium salt.

[0077] This invention does not limit the specific method of purification; common methods can be used for purification. In one specific embodiment, a lithium-ion-rich solution is concentrated by evaporation, cooled and crystallized, washed with diethyl ether, and then dried to obtain a lithium salt.

[0078] It is understandable that multiple washes with ether can be used to improve the purity of lithium salts.

[0079] In some embodiments, in order to improve the purity of lithium salt, the obtained lithium salt can also be subjected to reduction treatment, such as roasting using a reduction system.

[0080] In the third reaction process, pH control is crucial. Too high a pH can lead to alkaline decomposition; too low a pH can cause hydrolysis of fluorosilicate ions. The pH of the mixture can be controlled by adding common acidic or alkaline solutions, such as dilute sulfuric acid or lithium hydroxide.

[0081] In detail, the pH of the mixed system includes, but is not limited to, a range of 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or any two of these.

[0082] The method provided by this invention can regenerate fluorosilicic acid from hydrogen fluoride, a byproduct of the pretreatment of waste batteries, and silicon-based waste, effectively utilizing it for the selective extraction and separation of sodium and potassium impurities in crude lithium. The process has a high degree of integration and meets the requirements of a green circular economy. By crushing and pyrolyzing waste batteries, organic components are decomposed, and fluorine-containing components (such as LiPF6 in the electrolyte) in the batteries decompose under heating conditions, releasing hydrogen fluoride gas, thus achieving preliminary separation of fluorine from other solid components (such as silicon-containing materials and cathode materials). Subsequently, under subcritical conditions, the waste gas including hydrogen fluoride is passed into a silicon-containing system (such as sodium silicate solution or silicon-containing solid suspension). Under these conditions, hydrogen fluoride reacts efficiently with silicates or active silicon to generate soluble fluorosilicic acid (H2SiF6), with a reaction rate and conversion rate much higher than under normal pressure conditions, thereby achieving efficient and deep fixation of hydrogen fluoride. The generated fluorosilicic acid solution is then mixed with a lithium-containing solution. By precisely controlling the pH of the mixing system between 5 and 10, fluorosilicate (SiF6) is utilized. 2- ) with sodium and potassium ions (Na⁺, K⁻) + Within a specific pH range, it can form sparingly soluble salts (such as Na2SiF6 and K2SiF6), thereby achieving efficient separation of lithium ions from sodium and potassium ions.

[0083] In some embodiments of the present invention, the pH of the mixed system satisfies 5 ≤ ​​pH ≤ 6, and the mixed system also includes hydrofluoric acid.

[0084] Specifically, the pH of the mixed system is a range of 5, 5.2, 5.4, 5.6, 5.8, 6, or any two of these.

[0085] Hydrogen fluoride in the gaseous phase can be introduced into the mixture, or hydrofluoric acid can be added directly to the mixture.

[0086] While controlling the pH to 5-6, an appropriate amount of hydrofluoric acid (HF) was added to the system. According to the principle of chemical equilibrium, the addition of HF effectively inhibits the hydrolysis side reaction of fluorosilicic acid (H₂SiF₆), fundamentally preventing the formation of silica gel. This solves the technical problems caused by silica gel, such as difficult filtration, product inclusions, and equipment scaling, making the reaction system stable and easy to separate. However, the addition of HF increases the concentration of free fluoride ions in the system, which will lead to the formation of insoluble lithium fluoride during the precipitation and removal of sodium fluorosilicate and potassium fluorosilicate, resulting in a decrease in the final lithium product yield.

[0087] In some embodiments of the present invention, the pH of the mixed system satisfies 6 < pH < 8.

[0088] In detail, the pH of the mixed system includes, but is not limited to, a range of 6, 6.2, 6.4, 6.6, 6.8, 7, 7.2, 7.4, 7.6, 7.8, 8, or any two of these.

[0089] When pH < 6, a hydrolytic decomposition side reaction of fluorosilicate ions will occur, as shown in the following equation: H2SiF6 + (n + 2)H2O → SiO2⋅nH2O↓ + 6HF.

[0090] The silica hydrate (silica gel) generated in the reaction is an amorphous, difficult-to-filter gel-like precipitate. It coats the surface of the target product, sodium fluorosilicate crystals, leading to product impurity, clumping, and extreme difficulty in filtration and washing. The hydrolysis of fluorosilicate ions reduces the effective component for sodium fluorosilicate formation, resulting in a decrease in both lithium salt yield and purity.

[0091] When pH > 8, fluorosilicate ions undergo alkaline decomposition, and the generated silicate ions rapidly combine with H⁺ (or in water) to form monosilicic acid. Monosilicic acid readily polymerizes under non-strongly acidic conditions, ultimately producing silica gel, which affects the impurity removal effect of lithium salts. The reaction formula is shown below:

[0092] SiF6 2− +4OH − →SiO4 4− +6F −

[0093] SiO4 4− +4H + →H4SiO=(monosilicon)SiO4 4− +4H + →H4SiO4

[0094] nH4SiO4→(SiO2)n⋅2nH2O.

[0095] In some embodiments of the present invention, in step 2), the silicon-containing system includes silicon-containing solid waste.

[0096] The silicon-containing solid waste obtained from the first separation process will be used in a silicon-containing system. The silicon-containing system can use all of the silicon-containing solid waste or use a portion of it.

[0097] When the silicon-containing system includes silicon-containing solid waste, it is possible to further recycle the solid waste in waste batteries and realize the value-added utilization of waste resources.

[0098] In some embodiments of the present invention, in step 2), the temperature of the first reaction is A and the pressure is B, satisfying 20℃≤A<188℃ and 1.01325bar≤B<64.8bar.

[0099] In detail, the temperature of the second reaction includes, but is not limited to, 20°C, 40°C, 60°C, 80°C, 100°C, 120°C, 140°C, 160°C, 180°C, 187°C, or any other range greater than or equal to 20°C and less than 188°C; the pressure includes, but is not limited to, 1.01325 bar, 10 bar, 20 bar, 30 bar, 40 bar, 50 bar, 60 bar, 64 bar, 64.5 bar, or any range greater than or equal to 1.01325 bar and less than 64.8 bar.

[0100] When the temperature and pressure are within the aforementioned range, this broad range provides great flexibility in process operation, allowing for optimal selection between low-energy, mild conditions and high-efficiency, intensified conditions based on raw material characteristics and product requirements. Secondly, this range works synergistically with the pH control window (6-8) to ensure that lithium ions can be efficiently and selectively precipitated into the target lithium salt, while effectively suppressing the co-precipitation of impurity metals, thereby obtaining a high-purity product. Thirdly, this range avoids extreme conditions such as supercriticality, reducing the requirements for equipment materials and energy consumption while ensuring excellent technical results, making the entire process route innovative, efficient, and industrially feasible.

[0101] In some embodiments of the present invention, in step 2), the molar ratio of hydrogen fluoride in the mixed waste gas to Si in the silicon-containing solid waste is ≥6.5:1.

[0102] When hydrogen fluoride in the mixed waste gas reacts with active silicon in the silicon-containing solid waste, the intermediate product SiF4 may react with water in the system to form silicon dioxide precipitate, increasing the cost of impurity removal.

[0103] To avoid the formation of unwanted silica (SiO2) precipitates, excess hydrogen fluoride (HF) can be added to the system. The excess HF reacts with the generated SiO2 to regenerate soluble SiF4, thus ensuring that all silicon is converted into H2SiF6.

[0104] The chemical formula is as follows: SiO2(s) + 4HF(aq) → SiF4(g) + 2H2O(l)

[0105] Therefore, in some embodiments, the molar ratio of hydrogen fluoride in the mixed exhaust gas to Si in the silicon-containing solid waste includes, but is not limited to, 6.5:1, 6.6:1, 6.8:1, 7.0:1, 7.2:1, 7.4:1 or any other range ≥6.5:1.

[0106] A higher HF / Si molar ratio ensures that the silicon component in silicon-containing solid waste is completely consumed by the reaction, thereby maximizing the conversion of hydrogen fluoride in the waste gas, avoiding its residue or escape, and achieving efficient and thorough fixation of fluorine. Moreover, this ratio is conducive to the reaction proceeding fully in the direction of generating fluorosilicic acid (H2SiF6), ensuring that fluorine enters the solution phase in the form of stable and soluble fluorosilicic acid, providing a sufficient and highly active fluorine source for the subsequent selective lithium extraction step.

[0107] In some embodiments of the present invention, the positive electrode solid phase waste and the reduction system are mixed and then subjected to reduction roasting, leaching and impurity removal treatment in sequence to obtain lithium-containing mother liquor;

[0108] The reduction system includes reducing gas and carbonaceous solid waste.

[0109] In step 3), the lithium-containing system includes lithium-containing mother liquor.

[0110] Specifically, the reduction system is mixed with the cathode solid waste and then subjected to reduction roasting treatment. After reduction roasting treatment, the metal ions in the cathode solid waste are converted into oxides or soluble salts. Subsequently, the metal ions are dissolved in the solution through leaching treatment, and the cathode material precursor is removed by impurity removal treatment to obtain lithium-containing mother liquor.

[0111] In one specific embodiment, waste lithium-ion ternary batteries are selected as raw materials, and nickel-cobalt-manganese precursors are obtained after impurity removal treatment.

[0112] Step 3) The lithium-containing system includes lithium-containing mother liquor. Specifically, the lithium-containing system can be entirely composed of lithium-containing mother liquor or partially composed of lithium-containing mother liquor.

[0113] Using the reduction system for the reduction roasting treatment of cathode solid waste further improves the utilization rate of waste and realizes the value-added utilization of waste.

[0114] In some embodiments of the present invention, the leaching treatment includes the following steps:

[0115] The roasted product after reduction roasting is immersed in an acidic leachate and stirred.

[0116] The acid content in the acidic leachate is 120% to 200% of the stoichiometric ratio.

[0117] This invention does not limit the specific type of acidic leachate; common acidic leachates such as hydrochloric acid and sulfuric acid can be selected.

[0118] The amount of acid used in the acidic leachate refers to the theoretical molar amount of acid required to completely dissolve the target metal (such as lithium, cobalt, nickel, etc.) in the cathode waste according to the leaching reaction equation.

[0119] For example, the theoretical molar ratio H + :Li + =1, 2H + :Ni 2+ =1; therefore, the theoretically required n(H) + )=n(Li + )+2n(Ni 2+ )+2n(Co 2+ )+2n(Mn 2+ )+2n(Cu 2+ )+3n(Al 3+ ).

[0120] Specifically, the acid dosage includes, but is not limited to, a range of 120%, 130%, 140%, 150%, 160%, 170%, 180%, 190%, 200% of the stoichiometric ratio, or any combination thereof. Acid dosages within the aforementioned ranges can effectively balance leaching efficiency and leaching costs.

[0121] In some embodiments of the present invention, the solid-liquid ratio of the roasted product to the acidic leachate is (50g~500g):1L.

[0122] In detail, the solid-liquid ratio includes, but is not limited to, 50g:1L, 100g:1L, 150g:1L, 200g:1L, 250g:1L, 300g:1L, 350g:1L, 400g:1L, 450g:1L, 500g:1L, or any combination thereof.

[0123] When the solid-liquid ratio of the positive electrode solid waste to the acidic leachate is within the above range, it ensures sufficient reaction while reducing excessive acid consumption (avoiding acid waste and subsequent neutralization costs). This helps maintain a suitable acidity in the leaching system, promotes the selective leaching of target metals (such as lithium), and inhibits the excessive dissolution of impurities (such as iron and aluminum), thereby improving the purity of the leachate.

[0124] In some embodiments of the present invention, the leaching temperature is 40~80°C, the leaching time is 10~240 min, and the rotation speed is 100~1000 rpm.

[0125] In detail, the leaching temperature includes, but is not limited to, 40°C, 50°C, 60°C, 70°C, 80°C, or any combination thereof.

[0126] The leaching time includes, but is not limited to, 10 min, 40 min, 70 min, 100 min, 130 min, 160 min, 190 min, 220 min, 240 min, or any combination thereof.

[0127] The rotational speed includes, but is not limited to, 100 rpm, 200 rpm, 400 rpm, 600 rpm, 800 rpm, 1000 rpm, or any combination thereof.

[0128] When the leaching conditions are within the above range, it can improve the leaching efficiency of lithium ions and help suppress the excessive dissolution of impurity metals (such as iron and aluminum), thereby reducing the burden of subsequent impurity removal.

[0129] In some embodiments of the present invention, the impurity removal process uses an impurity removal solution, which includes at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, and potassium bicarbonate.

[0130] It is understandable that a mixture of various alkaline substances can be used to obtain a purification solution, such as a mixture of sodium hydroxide and sodium carbonate.

[0131] After adding a purification solution to the leachate obtained from the leaching process, manganese and ferric ions in the leachate precipitate, thus achieving the separation of manganese and ferric ions from lithium ions.

[0132] In some embodiments of the present invention, in the second reaction, the amount of fluorosilicic acid in the mixed system is 100% to 110% of the stoichiometric ratio.

[0133] The amount of fluorosilicic acid used is 100% to 110% of the stoichiometric ratio. This means that the theoretical molar amount of fluorosilicic acid required to completely precipitate lithium ions in the lithium-containing mother liquor is calculated based on the chemical equation for the reaction of fluorosilicic acid with lithium ions to generate the target lithium salt (such as lithium fluoride, lithium silicate, etc.). The actual molar amount is 100% to 110% of the theoretical molar amount.

[0134] Controlling the amount of fluorosilicic acid used within this narrow range (100%~110%) can precisely balance precipitation efficiency and reagent cost: too low a dosage (<100%) may lead to incomplete lithium precipitation and reduce lithium recovery rate, while too high a dosage (>110%) may slightly increase the precipitation rate, but it will lead to waste of fluorosilicic acid, increase the burden of subsequent wastewater treatment, and may introduce excessive fluoride ions, affecting product purity.

[0135] In some embodiments of the present invention, the temperature of the second reaction is 10°C to 60°C.

[0136] In detail, the temperature of the second reaction includes, but is not limited to, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, or any two of these ranges.

[0137] When the temperature of the second reaction is within the above range, the probability of side reactions can be effectively reduced, the purity of the product can be improved, and the burden of subsequent impurity removal can be reduced.

[0138] In some embodiments of the present invention, the crushing and pyrolysis treatment includes sequentially performing an electrically charged crushing treatment and a pyrolysis treatment;

[0139] Among them, the oxygen content of the electric crushing treatment is <0.5%, and the temperature of the pyrolysis treatment is 480℃~600℃.

[0140] Specifically, under a certain oxygen content, charged waste batteries are crushed by a crushing device to obtain a crushed mixture. Then, the crushed mixture is pyrolyzed by a pyrolysis device to decompose the organic matter in the crushed mixture and generate mixed waste gas.

[0141] Common crushing and pyrolysis devices in the field can be selected. For example, a shredder can be selected as the crushing device, and a pyrolysis furnace can be selected as the pyrolysis device.

[0142] By controlling the oxygen content in the electrically charged crushing process, the oxidation of the material is fundamentally eliminated, ensuring the "purity" of the chemical composition of the material entering the pyrolysis section. This makes the subsequent pyrolysis reaction more likely to generate the designed target products (such as pyrolysis oil and gas). Moreover, it completely eliminates the possibility of igniting combustible dust or volatiles due to frictional heat and sparks during the crushing process, resulting in a high level of inherent safety in the process.

[0143] The pyrolysis temperature includes, but is not limited to, 480℃, 500℃, 520℃, 540℃, 560℃, 580℃, 600℃, or any combination thereof. This temperature range is ideal for the pyrolysis of common organic compounds in waste batteries. Too low a temperature results in incomplete pyrolysis and a high residue rate; too high a temperature leads to severe secondary cracking of gaseous products, increasing the yield of small-molecule non-condensable gases, reducing liquid oil yield, and potentially accelerating coking.

[0144] In another aspect, the present invention provides a system for purifying lithium salt products from waste battery byproducts, for implementing the method described above;

[0145] like Figure 1 As shown, the system includes a pretreatment unit, a subcritical reaction unit, and a recovery reaction unit.

[0146] The pretreatment unit includes a feed inlet, a mixed waste gas outlet, a silicon-containing solid waste outlet, and a positive electrode solid waste outlet; the subcritical reaction unit includes a mixed waste gas inlet, a silicon-containing system inlet, a mixed liquid outlet, and a reducing material outlet; and the recovery reaction unit includes a mixed liquid inlet, a lithium-containing system inlet, and a lithium salt outlet.

[0147] The mixed exhaust gas outlet is connected to the mixed exhaust gas inlet, and the mixed liquid outlet is connected to the mixed liquid inlet.

[0148] Specifically, the pretreatment unit includes a crushing and pyrolysis subunit and a first separation subunit. Waste batteries enter the crushing and pyrolysis subunit through the feed inlet. After being crushed and pyrolyzed in the pretreatment unit, the waste batteries obtain a first reaction system, which then undergoes a first separation process in the first separation subunit to obtain a mixed waste gas containing hydrogen fluoride, silicon-containing solid phase waste, and positive electrode solid phase waste.

[0149] The subcritical reaction unit includes a first reaction subunit and a second separation subunit. A mixed waste gas containing hydrogen fluoride enters the first reaction subunit through a mixed waste gas inlet, and a silicon-containing system, including a silicon-containing system, enters the first reaction subunit through a silicon-containing system inlet. In the first reaction subunit, the hydrogen fluoride in the mixed waste gas and the elemental silicon in the silicon-containing system undergo a first reaction under subcritical conditions to obtain a second reaction system. Subsequently, the second reaction system undergoes a second separation process in the second separation subunit to obtain a second mixed system and a reduction system containing fluorosilicic acid.

[0150] The recovery reaction unit includes a second reaction subunit and a third separation subunit. A second mixed system containing fluorosilicic acid enters the second reaction subunit through a mixed liquid inlet, and a lithium-containing system enters the second reaction subunit through a lithium-containing system inlet. In the second reaction subunit, the mixed system comprising the second mixed system and the lithium-containing system undergoes a second reaction at a specific pH to obtain a third reaction system. The third reaction system is then separated and purified in the third separation subunit to obtain lithium salt.

[0151] In some embodiments of the present invention, the silicon-containing solid waste outlet is connected to the silicon-containing system inlet.

[0152] The silicon-containing solid waste obtained after pretreatment enters the subcritical reaction unit through the silicon-containing solid waste outlet and the silicon-containing system inlet. It undergoes a subcritical reaction with the mixed waste gas that enters the subcritical reaction unit through the mixed waste gas inlet in a liquid environment to obtain the second reaction system.

[0153] In some embodiments of the present invention, a positive electrode reduction unit is also included, which includes a positive electrode solid waste inlet, a reduction system inlet, and a lithium-containing mother liquor outlet.

[0154] The cathode solid waste outlet is connected to the cathode solid waste inlet, the reducing material outlet is connected to the reduction system inlet, and the lithium-containing mother liquor outlet is connected to the lithium-containing system inlet.

[0155] Specifically, the cathode reduction unit includes a reduction roasting subunit, a leaching subunit, and a purification subunit connected in sequence. The cathode solid waste obtained from the pretreatment unit enters the cathode reduction unit through the cathode solid waste outlet and cathode solid waste inlet. The reduction system obtained from the subcritical reaction unit enters the cathode reduction unit through the reducing material outlet and reduction system inlet. In the cathode reduction unit, the cathode solid waste and the reduction system undergo reduction roasting, leaching, and purification treatments sequentially to obtain a lithium-containing mother liquor. The lithium-containing mother liquor enters the recovery reaction unit through the lithium-containing mother liquor outlet and lithium-containing system inlet, where it undergoes subsequent reactions with the second mixed system.

[0156] In one embodiment of the present invention, such as Figure 2 As shown, the system includes a pretreatment unit, a subcritical reaction unit, a recovery reaction unit, and a positive electrode reduction unit.

[0157] The pretreatment unit includes a crushing and pyrolysis subunit and a first separation subunit; the subcritical reaction unit includes a first reaction subunit and a second separation subunit; the recovery reaction unit includes a second reaction subunit and a third separation subunit; and the positive electrode reduction unit includes a reduction roasting subunit, a leaching treatment subunit, and a purification treatment subunit.

[0158] Waste batteries enter the crushing and pyrolysis subunit through the feed inlet. After pyrolysis, mixed waste gas including hydrogen fluoride is collected. The solid waste is separated and processed by the first separation subunit to obtain silicon-containing solid waste and positive electrode solid waste.

[0159] Silicon-containing solid waste enters the first reaction subunit through the silicon-containing system inlet. Mixed waste gas enters the first reaction subunit through the mixed waste gas inlet. Hydrogen fluoride dissolves in the solution and is converted into hydrofluoric acid. Hydrofluoric acid reacts with elemental silicon in a subcritical state to generate fluorosilicic acid. Subsequently, it is processed by the second separation subunit to obtain a second mixed system including fluorosilicic acid, which is a reduction system.

[0160] The cathode solid waste enters the reduction roasting sub-unit through the cathode solid waste inlet. The reduction system enters the reduction roasting sub-unit through the reduction system inlet. In the reduction roasting sub-unit, the cathode solid waste is reduced. The reduced cathode solid waste enters the leaching treatment sub-unit and is leached under the action of acidic leaching solution. Then it enters the impurity removal treatment sub-unit, where the precursor product and lithium-containing mother liquor are obtained under the action of impurity removal solution.

[0161] The lithium-containing mother liquor enters the second reaction subunit via the lithium-containing mother liquor outlet and the lithium-containing system inlet. The mixed liquid enters the second reaction subunit via the mixed liquid inlet. In the second reaction subunit, fluorosilicic acid reacts with sodium and potassium ions in the lithium-containing mother liquor to generate sodium fluorosilicate precipitate, potassium fluorosilicate precipitate, and lithium solution. Subsequently, it undergoes a third separation process in the third separation subunit to obtain lithium salt.

[0162] This invention does not limit the type of equipment used in each unit and subunit. Equipment commonly used in the field can be selected according to actual conditions. For example, the crushing and pyrolysis subunit can use (crushing: hammer crusher, rotor centrifugal crusher, jaw crusher, roller crusher, air jet mill, etc.) and (pyrolysis: pyrolysis rotary furnace, multi-stage pyrolysis furnace, vertical kiln, track kiln, spray pyrolysis, etc.). The first separation subunit can use (magnetic separator, flotation machine, air separator, screening machine, etc., in free combination). The reduction and roasting subunit can use rotary kiln, vertical kiln, track kiln, spray pyrolysis equipment, etc., and the leaching treatment subunit can use a stirred reactor. The impurity removal subunit can be selected from stirred reactors, eddy reactors, centrifugal reactors, continuous flow reactors, etc. The first reaction subunit can be a high-pressure reactor. The second separation subunit can be a filter press, centrifuge, vacuum filter, ceramic filter, precision filter, membrane filter, etc. The third separation subunit can be a filter press, centrifuge, vacuum filter, ceramic filter, precision filter, membrane filter, etc.

[0163] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0164] Example 1

[0165] This embodiment selects Figure 2 The system shown extracts lithium from hydrogen fluoride in waste batteries. The system includes a pretreatment unit, a subcritical reaction unit, a recycling reaction unit, and a positive electrode reduction unit.

[0166] The pretreatment unit includes a crushing and pyrolysis subunit and a first separation subunit; the subcritical reaction unit includes a first reaction subunit and a second separation subunit; the recovery reaction unit includes a second reaction subunit and a third separation subunit; and the positive electrode reduction unit includes a reduction roasting subunit, a leaching treatment subunit, and a purification treatment subunit.

[0167] A method for purifying lithium salt products using waste battery byproducts includes the following steps:

[0168] 1. Waste lithium-ion ternary batteries enter the crushing and pyrolysis subunit through the waste battery inlet. In the crushing and pyrolysis subunit, the batteries are crushed under N2 protection while charged. The oxygen content in the environment under N2 protection is <0.5%. The crushed material is transported by conveyor belt to a 500℃ closed kiln for pyrolysis for 30 minutes. A first separation subunit (gas exchange device and screening device) is set up. The mixed waste gas (HF, N2, CO, CO2, CH4, etc.) generated during the pyrolysis process is collected through the gas exchange device. The waste is screened by the screening device into positive electrode solid phase waste and silicon-containing solid phase waste.

[0169] 2. The mixed waste gas including hydrogen fluoride enters the first reaction subunit through the mixed waste gas inlet. The silicon-containing system (containing silicon solid waste and photovoltaic silicon mixed powder) enters the first reaction subunit through the silicon-containing system inlet. The molar ratio of hydrogen fluoride to Si in the silicon-containing system is 6.5:1. Under the conditions of 180℃ and 12 bar, hydrogen fluoride and silicon elemental undergo the first reaction to obtain the first reaction system. Subsequently, it is separated by the second separation subunit to obtain a mixed liquid including fluorosilicic acid and a reduction system.

[0170] 3. The positive electrode solid waste enters the reduction roasting sub-unit through the positive electrode solid waste outlet and the positive electrode solid waste inlet. The reduction system enters the reduction roasting sub-unit through the reduction system inlet and is reduced roasted at 700℃. Subsequently, the roasted residue enters the leaching treatment sub-unit, where it is leached with 1M dilute sulfuric acid to obtain a leachate. The sulfuric acid dosage is 120% of the stoichiometric ratio, the leaching temperature is 40℃, the solid-liquid ratio is 200g / L, the leaching time is 60min, and the rotation speed is 600rpm. It then enters the impurity removal treatment sub-unit, where the pH is adjusted to 4.9 using a mixed solution of sodium hydroxide and sodium carbonate, followed by filtration to remove impurities, yielding a purified solution. The purified solution is then used to precipitate nickel, cobalt, and manganese using a mixed solution of sodium hydroxide and ammonia. After filtration, lithium-ion battery ternary cathode nickel-cobalt-manganese precursor material and lithium-containing mother liquor are obtained. The lithium-containing mother liquor is a mixed solution of lithium sulfate and sodium hydroxide / potassium hydroxide.

[0171] 4. The lithium-containing mother liquor enters the second reaction subunit through the lithium-containing system inlet. A mixed solution including fluorosilicic acid enters the second reaction subunit through the mixed solution inlet, with the amount of fluorosilicic acid being 103% of the stoichiometric ratio. The pH of the mixed system is maintained between 6.9 and 7.1 by adding dilute sulfuric acid or lithium hydroxide solution, and the reaction temperature is 25°C. After the reaction, insoluble impurities are separated by filtration in the third separation subunit to obtain a lithium sulfate solution. This solution is then concentrated by evaporation, cooled for crystallization, and washed twice with ether at a 1:1 mass ratio, followed by drying to obtain lithium sulfate crystals.

[0172] Example 2

[0173] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0174] In step 3), sulfuric acid is replaced with hydrochloric acid to finally obtain lithium chloride crystals.

[0175] Example 3

[0176] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0177] The lithium sulfate crystals obtained in step 4) are subjected to a high-temperature reduction reaction at 700°C for 3 hours in the reducing atmosphere generated in step 2) to obtain the final lithium sulfide crystals.

[0178] Example 4

[0179] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0180] The reaction conditions for the first reaction in step 2) are 20°C and 1.01325 bar, and lithium sulfate crystals are finally obtained.

[0181] Example 5

[0182] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0183] In step 2), the reaction conditions for the first reaction are 20°C and 64 bar, and lithium sulfate crystals are finally obtained.

[0184] Example 6

[0185] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0186] In step 2), the reaction conditions for the first reaction are 180°C and 64 bar, and lithium sulfate crystals are finally obtained.

[0187] Example 7

[0188] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0189] In step 4), the pH of the mixed system is 10, and lithium sulfate crystals are finally obtained.

[0190] Example 8:

[0191] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0192] In step 4), the pH of the mixed system is 5, and lithium sulfate crystals are finally obtained.

[0193] Example 9:

[0194] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0195] In step 4), an additional 5% metric HF is introduced into the mixing system to finally obtain lithium sulfate crystals.

[0196] Example 10:

[0197] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0198] In step 4), the reaction temperature of the second reaction is 60°C, and lithium sulfate crystals are finally obtained.

[0199] Example 11

[0200] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0201] Step 4) reduces one ether wash, ultimately yielding lithium sulfate crystals.

[0202] Example 12

[0203] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0204] In step 4), sodium hydroxide and sodium carbonate reagents are replaced with potassium hydroxide and potassium carbonate to finally obtain lithium sulfate crystals.

[0205] Example 13

[0206] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0207] In step 2), only silicon-containing solid waste is used, and other conditions remain unchanged, ultimately obtaining lithium sulfate crystals.

[0208] Example 14

[0209] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0210] In step 2), only photovoltaic silicon powder is used, and other conditions remain unchanged, to finally obtain lithium sulfate crystals.

[0211] Example 15

[0212] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0213] In step 5), the lithium-containing mother liquor is replaced with a lithium sulfate sodium solution obtained by removing magnesium from salt lake brine with sodium hydroxide, while other conditions remain unchanged, and lithium sulfate crystals are finally obtained.

[0214] Example 16

[0215] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0216] In step 2), the reaction conditions for the first reaction are 188°C and 64 bar, and lithium sulfate crystals are finally obtained.

[0217] Example 17

[0218] The system used in this embodiment is the same as that in embodiment 1, and the steps in this embodiment are basically the same as those in embodiment 1, except that:

[0219] In step 2), the molar ratio of hydrogen fluoride in the mixed waste gas to silicon-containing substances in the silicon-containing system is 6:1, and lithium sulfate crystals are finally obtained.

[0220] Example 18

[0221] The system used in this embodiment is the same as that in Embodiment 1. The method for purifying lithium salt products using waste battery by-products includes the following steps:

[0222] 1. Waste lithium-ion ternary batteries enter the crushing and pyrolysis subunit through the waste battery inlet. In the crushing and pyrolysis subunit, the batteries are crushed under N2 protection while charged. The oxygen content in the environment under N2 protection is <0.5%. The crushed material is transported by conveyor belt to a 600℃ closed kiln for pyrolysis for 30 minutes. A first separation subunit (gas exchange device and screening device) is set up. The mixed waste gas (HF, N2, CO, CO2, CH4, etc.) generated during the pyrolysis process is collected through the gas exchange device. The waste is screened by the screening device into positive electrode solid phase waste and silicon-containing solid phase waste.

[0223] 2. The mixed waste gas including hydrogen fluoride enters the first reaction subunit through the mixed waste gas inlet. The silicon-containing system (containing silicon solid waste and photovoltaic silicon mixed powder) enters the first reaction subunit through the silicon-containing system inlet. The molar ratio of hydrogen fluoride to Si in the silicon-containing system is 7:1. Under the conditions of 160℃ and 40 bar, hydrogen fluoride and silicon elemental undergo the first reaction to obtain the first reaction system. Subsequently, it is separated by the second separation subunit to obtain a mixed liquid including fluorosilicic acid and a reduction system.

[0224] 3. The positive electrode solid waste enters the reduction roasting sub-unit through the positive electrode solid waste outlet and the positive electrode solid waste inlet. The reduction system enters the reduction roasting sub-unit through the reduction system inlet and is reduced roasted at 700℃. Subsequently, the roasted residue enters the leaching treatment sub-unit, where it is leached with 1M dilute sulfuric acid to obtain a leachate. The sulfuric acid dosage is 120% of the stoichiometric ratio, the leaching temperature is 80℃, the solid-liquid ratio is 50 g / L, the leaching time is 240 min, and the rotation speed is 1000 rpm. It then enters the impurity removal treatment sub-unit, where the pH is adjusted to 4.9 using a mixed solution of sodium hydroxide and sodium carbonate, followed by filtration to remove impurities, yielding a purified solution. The purified solution is then used to precipitate nickel, cobalt, and manganese using a mixed solution of sodium hydroxide and ammonia. After filtration, the lithium-ion battery ternary cathode nickel-cobalt-manganese precursor material and lithium-containing mother liquor are obtained. The lithium-containing mother liquor is a mixed solution of lithium sulfate and sodium hydroxide / potassium hydroxide.

[0225] 4. The lithium-containing mother liquor enters the second reaction subunit through the lithium-containing system inlet. A mixed solution including fluorosilicic acid enters the second reaction subunit through the mixed solution inlet, with the amount of fluorosilicic acid being 110% of the stoichiometric ratio. The pH of the mixed system is maintained at 6 by adding dilute sulfuric acid or lithium hydroxide solution, and the reaction temperature is 10°C. After the reaction, insoluble impurities are separated by filtration in the third separation subunit to obtain a lithium sulfate solution. This solution is then concentrated by evaporation, cooled for crystallization, and washed twice with ether at a 1:1 mass ratio, followed by drying to obtain lithium sulfate crystals.

[0226] Example 19

[0227] The system used in this embodiment is the same as that in Embodiment 1. The method for purifying lithium salt products using waste battery by-products includes the following steps:

[0228] 1. Waste lithium-ion ternary batteries enter the crushing and pyrolysis subunit through the waste battery inlet. In the crushing and pyrolysis subunit, the batteries are crushed under N2 protection while charged. The oxygen content in the environment under N2 protection is <0.5%. The crushed material is transported by conveyor belt to a 480℃ closed kiln for pyrolysis for 30 minutes. A first separation subunit (gas exchange device and screening device) is set up. The mixed waste gas (HF, N2, CO, CO2, CH4, etc.) generated during the pyrolysis process is collected through the gas exchange device. The waste is screened by the screening device into positive electrode solid phase waste and silicon-containing solid phase waste.

[0229] 2. The mixed waste gas including hydrogen fluoride enters the first reaction subunit through the mixed waste gas inlet. The silicon-containing system (containing silicon solid waste and photovoltaic silicon mixed powder) enters the first reaction subunit through the silicon-containing system inlet. The molar ratio of hydrogen fluoride to Si in the silicon-containing system is 7.5:1. Under the conditions of 60℃ and 10 bar, hydrogen fluoride and silicon elemental undergo the first reaction to obtain the first reaction system. Subsequently, it is separated by the second separation subunit to obtain a mixed liquid including fluorosilicic acid and a reduction system.

[0230] 3. The positive electrode solid waste enters the reduction roasting sub-unit through the positive electrode solid waste outlet and the positive electrode solid waste inlet. The reduction system enters the reduction roasting sub-unit through the reduction system inlet and is reduced roasted at 700℃. Subsequently, the roasted residue enters the leaching treatment sub-unit, where it is leached with 1M dilute sulfuric acid to obtain a leachate. The sulfuric acid dosage is 200% of the stoichiometric ratio, the leaching temperature is 60℃, the solid-liquid ratio is 500g / L, the leaching time is 10min, and the rotation speed is 100rpm. It then enters the impurity removal treatment sub-unit, where the pH is adjusted to 4.9 using a mixed solution of sodium hydroxide and sodium carbonate, followed by filtration to remove impurities, yielding a purified solution. The purified solution is then used to precipitate nickel, cobalt, and manganese using a mixed solution of sodium hydroxide and ammonia. After filtration, the lithium-ion battery ternary cathode nickel-cobalt-manganese precursor material and lithium-containing mother liquor are obtained. The lithium-containing mother liquor is a mixed solution of lithium sulfate and sodium hydroxide / potassium hydroxide.

[0231] 4. The lithium-containing mother liquor enters the second reaction subunit through the lithium-containing system inlet. A mixture including fluorosilicic acid enters the second reaction subunit through the mixture inlet, with the amount of fluorosilicic acid being 100% of the stoichiometric ratio. The pH of the mixture is maintained at 8 by adding dilute sulfuric acid or lithium hydroxide solution, and the reaction temperature is 60℃. After the reaction, insoluble impurities are separated by filtration in the third separation subunit to obtain a lithium sulfate solution. This solution is then concentrated by evaporation, cooled for crystallization, and washed twice with ether at a 1:1 mass ratio, followed by drying to obtain lithium sulfate crystals.

[0232] Comparative Example 1

[0233] This comparative method for purifying lithium salt products using waste batteries includes the following steps:

[0234] 1. Waste lithium-ion ternary batteries enter the crushing and pyrolysis subunit through the waste battery inlet. In the crushing and pyrolysis subunit, the batteries are crushed under N2 protection while charged. The oxygen content in the environment under N2 protection is <0.5%. The crushed material is transported by conveyor belt to a 500℃ closed kiln for pyrolysis for 30 minutes. A first separation subunit (gas exchange device and screening device) is set up. The mixed waste gas (HF, N2, CO, CO2, CH4, etc.) generated during the pyrolysis process is collected through the gas exchange device. The waste is screened by the screening device into positive electrode solid phase waste and silicon-containing solid phase waste.

[0235] 2. The positive electrode solid waste enters the reduction roasting sub-unit through the positive electrode solid waste outlet and the positive electrode solid waste inlet. The mixed waste gas enters the reduction roasting sub-unit through the reduction system inlet and is reduced roasted at 700℃. Subsequently, the roasted residue enters the leaching treatment sub-unit, where it is leached with 1M dilute sulfuric acid to obtain a leachate. The sulfuric acid dosage is 120% of the stoichiometric ratio, the leaching temperature is 40℃, the solid-liquid ratio is 200g / L, the leaching time is 60min, and the rotation speed is 600rpm. Then, it enters the impurity removal treatment sub-unit, where the pH is adjusted to 4.9 using a mixed solution of sodium hydroxide and sodium carbonate, followed by filtration to remove impurities, yielding a purified solution. The purified solution is then used to precipitate nickel, cobalt, and manganese using a mixed solution of sodium hydroxide and ammonia. After filtration, lithium-ion battery ternary cathode nickel-cobalt-manganese precursor material and lithium-containing mother liquor are obtained. The lithium-containing mother liquor is a mixed solution of lithium sulfate and sodium hydroxide / potassium hydroxide.

[0236] 3. The lithium-containing mother liquor enters the second reaction subunit through the lithium-containing system inlet. A mixed solution, including fluorosilicic acid (purchased externally), enters the second reaction subunit through the mixed solution inlet. The amount of fluorosilicic acid used is 103% of the stoichiometric ratio. The pH of the mixed system is maintained between 6.9 and 7.1 by adding dilute sulfuric acid or lithium hydroxide solution, and the reaction temperature is 25°C. After the reaction, insoluble impurities are separated by filtration in the third separation subunit to obtain a lithium sulfate solution. This solution is then concentrated by evaporation, cooled for crystallization, and washed twice with ether at a 1:1 mass ratio, followed by drying to obtain lithium sulfate crystals.

[0237] Comparative Example 2

[0238] This comparative method for purifying lithium salt products using waste batteries includes the following steps:

[0239] 1. Waste lithium-ion ternary batteries enter the crushing and pyrolysis subunit through the waste battery inlet. In the crushing and pyrolysis subunit, the batteries are crushed under N2 protection while charged. The oxygen content in the environment under N2 protection is <0.5%. The crushed material is transported by conveyor belt to a 500℃ closed kiln for pyrolysis for 30 minutes. A first separation subunit (gas exchange device and screening device) is set up. The mixed waste gas (HF, N2, CO, CO2, CH4, etc.) generated during the pyrolysis process is collected through the gas exchange device. The waste is screened by the screening device into positive electrode solid phase waste and silicon-containing solid phase waste.

[0240] 2. The positive electrode solid waste enters the reduction roasting sub-unit through the positive electrode solid waste outlet and the positive electrode solid waste inlet. The mixed waste gas enters the reduction roasting sub-unit through the reduction system inlet and is reduced roasted at 700℃. Subsequently, the roasted residue enters the leaching treatment sub-unit, where it is leached with 1M dilute sulfuric acid to obtain a leachate. The sulfuric acid dosage is 120% of the stoichiometric ratio, the leaching temperature is 40℃, the solid-liquid ratio is 200g / L, the leaching time is 60min, and the rotation speed is 600rpm. Then, it enters the impurity removal treatment sub-unit, where the pH is adjusted to 4.9 using a mixed solution of sodium hydroxide and sodium carbonate, followed by filtration to remove impurities, yielding a purified solution. The purified solution is then used to precipitate nickel, cobalt, and manganese using a mixed solution of sodium hydroxide and ammonia. After filtration, lithium-ion battery ternary cathode nickel-cobalt-manganese precursor material and lithium-containing mother liquor are obtained. The lithium-containing mother liquor is a mixed solution of lithium sulfate and sodium hydroxide / potassium hydroxide.

[0241] 3. The lithium-containing mother liquor is concentrated by evaporation, cooled and crystallized, and washed twice with ether at a mass ratio of 1, and then dried to obtain lithium sulfate crystals.

[0242] Comparative Example 3

[0243] The system used in this comparative example is the same as that in Example 1, and the steps in this comparative example are basically the same as those in Example 1, except that:

[0244] In step 4), the pH of the mixed system is 4, and lithium sulfate crystals are obtained.

[0245] Comparative Example 4

[0246] The system used in this comparative example is the same as that in Example 1, and the steps in this comparative example are basically the same as those in Example 1, except that:

[0247] In step 4), the pH of the mixed system is 11, and lithium sulfate crystals are obtained.

[0248] Test case

[0249] The lithium salt products provided in all embodiments and comparative examples were tested, including the following steps:

[0250] 1. The purity of lithium salts was determined using inductively coupled plasma atomic emission spectrometry (ICP-OES), including the following steps:

[0251] (1) Sample pretreatment: Accurately weigh approximately 0.1 g (accurate to 0.0001 g) of dried lithium sulfate crystal sample and place it in a polytetrafluoroethylene digestion vessel. Add 5 mL of concentrated nitric acid (analytical grade) and 1 mL of concentrated hydrochloric acid (analytical grade), and gently shake to moisten the sample. Place the digestion vessel in a microwave digester and digest according to the program (e.g., heat to 180℃ and hold for 20 minutes). After digestion, cool to room temperature and transfer the digestion solution to a 100 mL volumetric flask. Wash the digestion vessel several times with ultrapure water (resistivity ≥18.2 MΩcm) and dilute to the mark. Shake well. This is the mother solution to be tested.

[0252] According to the instrument's detection range, the mother liquor to be tested is further diluted with 2% dilute nitric acid by an appropriate factor (such as 100 times) to obtain the solution to be tested.

[0253] (2) Standard curve preparation: Using a lithium (Li) element standard solution (e.g., 1000 mg / L), prepare a series of standard working solutions with concentrations (e.g., 0.1, 0.5, 1.0, 5.0, 10.0 mg / L) using 2% dilute nitric acid.

[0254] Using an ICP-OES instrument, the emission intensity of the standard working solution was measured at the characteristic spectral line of lithium (e.g., 670.784 nm), and a concentration-intensity standard curve was plotted, requiring a correlation coefficient R² > 0.999.

[0255] (3) Sample determination and calculation: Under the same instrument conditions, the emission intensity of lithium in the test solution was determined.

[0256] Calculate the lithium concentration (C_Li, unit: mg / L) in the test solution based on the standard curve.

[0257] Purity calculation: Lithium sulfate purity (wt%) = [(C_Li × Dilution factor × Volume at final volume) / (Sample mass × 10] 6 )]×(M_Li2SO4 / (2×M_Li))×100%, where M_Li2SO4 is the molar mass of lithium sulfate (109.94 g / mol) and M_Li is the molar mass of lithium (6.94 g / mol).

[0258] 2. Yield testing includes the following steps:

[0259] (1) Determine the total amount of lithium in the raw materials: Take a known mass of “positive electrode solid phase waste” (obtained in step 1) and determine its lithium content (wt%) using the ICP-OES method (pretreatment as before).

[0260] (2) Calculate the total mass of lithium in the raw materials: m_Li raw materials = mass of positive electrode solid phase waste × its lithium content.

[0261] (3) Determine the total amount of lithium in the product: Weigh the total mass (m_product) of all the lithium sulfate crystal products obtained in the end. Based on the lithium sulfate purity (P) obtained from the purity test above, calculate the actual mass of lithium sulfate in the product: m_Li2SO4 actual = m_product × P.

[0262] Calculate the total lithium mass in the product: m_Li product = m_Li2SO4 actual × (2 × M_Li / M_Li2SO4). Calculate the yield: Lithium yield (%) = (m_Li product / m_Li raw material) × 100%. The test results are shown in Table 1.

[0263] Table 1

[0264]

[0265] As shown in Table 1, the method for purifying lithium salt products using waste battery byproducts provided by this invention involves recycling hydrogen fluoride and silicon-based negative electrode waste or photovoltaic silicon panels generated during waste battery processing. The resulting solution reacts with a lithium-containing system to selectively remove impurities such as potassium and sodium, yielding lithium salts with high purity. Simultaneously, it effectively ensures the lithium salt yield.

[0266] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for purifying lithium salt products using fluorosilicic acid, a byproduct of waste batteries, characterized in that, Includes the following steps: 1) The waste batteries are crushed and pyrolyzed. After the first separation process, a mixed waste gas containing hydrogen fluoride, silicon-containing solid waste and positive electrode solid waste are obtained. 2) The mixed waste gas is introduced into a silicon-containing system and undergoes a first reaction under the subcritical state of hydrogen fluoride. After a second separation process, a mixed liquid containing fluorosilicic acid and reducing materials are obtained. 3) The mixture including the above-mentioned mixture and the lithium-containing system is subjected to a second reaction, followed by a third separation process to obtain lithium salt; The pH of the mixture is 5-10.

2. The method according to claim 1, characterized in that, The pH of the mixture satisfies 5 ≤ ​​pH ≤ 6, and the mixture also includes hydrofluoric acid; And / or, the pH of the mixture satisfies 6 < pH < 8.

3. The method according to claim 1 or 2, characterized in that, In step 2), the silicon-containing system includes the silicon-containing solid waste; And / or, in step 2), the temperature of the first reaction is A, and the pressure is B, satisfying 20℃≤A<188℃ and 1.01325bar≤B<64.8bar; And / or, in step 2), the molar ratio of hydrogen fluoride in the mixed waste gas to Si in the silicon-containing system is ≥6.5:

1.

4. The method according to any one of claims 1-3, characterized in that, It also includes mixing the positive electrode solid waste and the reducing material and then sequentially performing reduction roasting, leaching, and impurity removal treatments to obtain a lithium-containing mother liquor; The reducing materials include reducing gases and carbon-containing solid waste. In step 3), the lithium-containing system includes the lithium-containing mother liquor.

5. The method according to claim 4, characterized in that, The leaching treatment includes the following steps: The roasted product after the reduction roasting treatment is immersed in an acidic leachate and stirred. The acid used in the acidic leachate is 120% to 200% of the stoichiometric ratio. And / or, the solid-liquid ratio of the roasted product to the acidic leachate is (50g~500g):1L; And / or, the leaching temperature is 40~80℃, the leaching time is 10~240min, and the rotation speed is 100~1000rpm.

6. The method according to claim 4 or 5, characterized in that, The impurity removal process uses an impurity removal solution. The impurity removal solution includes at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, and potassium bicarbonate.

7. The method according to any one of claims 1-6, characterized in that, In the second reaction, the amount of fluorosilicic acid in the mixed system is 100%~110% of the stoichiometric ratio; And / or, the temperature of the second reaction is 10℃~60℃.

8. The method according to any one of claims 1-7, characterized in that, The crushing and pyrolysis treatment includes sequentially performed charged crushing and pyrolysis treatments; Wherein, the oxygen content of the charged crushing process is <0.5%, and the temperature of the pyrolysis process is 480~600℃.

9. A system for purifying lithium salt products from waste battery byproducts, characterized in that, Used to implement the method according to any one of claims 1-8; The system includes a pretreatment unit, a subcritical reaction unit, and a recovery reaction unit; The pretreatment unit includes a feed inlet, a mixed waste gas outlet, a silicon-containing solid waste outlet, and a positive electrode solid waste outlet; the subcritical reaction unit includes a mixed waste gas inlet, a silicon-containing system inlet, a mixed liquid outlet, and a reducing material outlet; and the recovery reaction unit includes a mixed liquid inlet, a lithium-containing system inlet, and a lithium salt outlet. The mixed exhaust gas outlet is connected to the mixed exhaust gas inlet, and the mixed liquid outlet is connected to the mixed liquid inlet.

10. The system according to claim 9, characterized in that, The outlet of the silicon-containing solid waste is connected to the inlet of the silicon-containing system; And / or, it also includes a positive electrode reduction unit, which includes a positive electrode solid waste inlet, a reduction system inlet, and a lithium-containing mother liquor outlet; The positive electrode solid waste outlet is connected to the positive electrode solid waste inlet, the reducing material outlet is connected to the reduction system inlet, and the lithium-containing mother liquor outlet is connected to the lithium-containing system inlet.

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