Method for preparing lithium dihydrogen phosphate by recycling lithium battery
By breaking the battery while it is charged and using oxidative acid leaching and an extractant to separate impurities, lithium phosphate is precipitated as phosphate, which solves the problem of relying on external raw materials in traditional methods and achieves efficient lithium recovery and cost reduction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-18
- Publication Date
- 2026-04-14
AI Technical Summary
Traditional methods for preparing lithium dihydrogen phosphate rely on external raw materials, resulting in high costs and low lithium recovery rates, making it difficult to efficiently recycle lithium resources from spent lithium-ion batteries.
By mechanically breaking the battery while it is charged, an internal short circuit is triggered to release energy. Impurities are then separated using an oxidative acid leaching method and an extractant to generate lithium phosphate precipitate. Lithium is then recovered by combining this with alkaline treatment, reducing dependence on external raw materials and improving lithium recovery rate.
It reduces production costs, improves the overall lithium recovery rate, achieves efficient lithium resource recovery and impurity removal, and simplifies the process flow.
Smart Images
Figure CN121849873A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium dihydrogen phosphate preparation technology, specifically a method for preparing lithium dihydrogen phosphate from lithium battery recycling. Background Technology
[0002] The preparation of lithium dihydrogen phosphate refers to the process of obtaining lithium dihydrogen phosphate crystals that meet specific purity, morphology and performance requirements through specific physical and chemical methods, using compounds containing elements such as lithium, phosphorus and hydrogen as raw materials, and going through a series of reaction and purification steps.
[0003] The current method for recycling waste lithium-ion battery materials to prepare battery-grade lithium dihydrogen phosphate involves discharging waste lithium-ion batteries, disassembling and separating the casing, separator, and foil, collecting the lithium-ion battery materials, and then obtaining battery-grade lithium carbonate or battery-grade lithium hydroxide through leaching, impurity removal, and lithium precipitation reactions. The battery-grade lithium carbonate or battery-grade lithium hydroxide is then reacted with purified phosphoric acid to prepare crude lithium phosphate. After removing alkali metal potassium and sodium ions, the crude lithium phosphate is acidified to obtain a battery-grade lithium dihydrogen phosphate solution. This solution is then evaporated at low temperature to become a supersaturated solution. The supersaturated solution is then cooled, crystallized, centrifuged, and dried to obtain battery-grade lithium dihydrogen phosphate.
[0004] Traditional methods for preparing lithium dihydrogen phosphate require first preparing battery-grade lithium carbonate or lithium hydroxide, then reacting it with purchased or additionally purified phosphate (trisodium phosphate) to obtain crude lithium phosphate, followed by acidification. Traditional methods rely heavily on external raw materials, so we need to propose a method for preparing lithium dihydrogen phosphate from lithium battery recycling. Summary of the Invention
[0005] The purpose of this invention is to provide a method for preparing lithium dihydrogen phosphate from lithium battery recycling. This method safely releases residual battery energy through a controllable internal short circuit, making the crushed material easier to process. A small portion of the lithium-containing leachate is treated with an alkaline solution, which not only removes metallic impurities but also utilizes the phosphorus and lithium to generate phosphate for lithium precipitation. Lithium in the diverted solution is also recovered. The prepared phosphate is mixed with the purified lithium-containing filtrate to directly precipitate lithium phosphate, reducing dependence on external raw materials and production costs. Furthermore, the diversion process simultaneously recovers lithium throughout the entire process, avoiding lithium loss due to diversion, thereby improving the overall lithium recovery rate and solving the problems mentioned in the background art.
[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing lithium dihydrogen phosphate from lithium battery recycling, comprising the following steps:
[0007] S1. Mechanically crush waste batteries while they are charged;
[0008] S2. The crushed material is sieved to separate components of different particle sizes to obtain battery powder;
[0009] S3. Use the oxidative acid leaching method to leach the battery powder, converting the valuable metal from a solid state into an ionic state dissolved in the solution, to obtain a lithium-containing leachate.
[0010] S4. Add an extractant to most of the lithium-containing leachate to separate the impurity metal ions from the lithium-containing leachate and obtain a high-purity lithium-containing filtrate.
[0011] S5. Add alkaline solution to a small portion of lithium-containing leachate and react. After filtration and resin adsorption, obtain phosphate for lithium precipitation.
[0012] S6. Add phosphate to the high-purity lithium-containing filtrate and mix to cause a precipitation reaction, thus obtaining lithium phosphate precipitate.
[0013] S7. Add concentrated phosphoric acid to the lithium phosphate precipitate for acidification treatment to obtain a lithium dihydrogen phosphate solution.
[0014] Preferably, in step S1, the charged state refers to the battery being crushed directly using crushing equipment while it has not been discharged and still has residual voltage and charge. During crushing, the battery casing and separator are damaged under the action of mechanical extrusion and shearing force, and the positive and negative electrode materials inside the battery come into direct contact, causing a controllable internal short circuit.
[0015] Preferably, in step S2, the mixture after being charged and crushed includes electrode materials and fragments of different particle sizes. The mixture is screened through a multi-layer vibrating screen with different sieve openings, and impurity metals are removed by magnetic separation.
[0016] Preferably, in step S3, the oxidative acid leaching method uses concentrated phosphoric acid and hydrogen peroxide to leach the battery powder. Concentrated phosphoric acid reacts with metal oxides and salts to convert them into soluble phosphates or free metal ions, and phosphate ions react with metal ions to form soluble complexes. Hydrogen peroxide acts as a reducing agent to reduce the high-valence metal ions in the metal oxides to low-valence metal ions that are easily soluble in acids.
[0017] Preferably, in step S4, the extractant is selected as dioctyl phosphate and sulfonated kerosene. During extraction, the lithium-containing leachate containing impurity metal ions comes into countercurrent contact with the extractant. The hydrogen ions in dioctyl phosphate undergo an ion exchange reaction with the low-valence metal ions in the aqueous phase. The metal ions form a metal-organic complex and enter the organic phase, while the hydrogen ions enter the aqueous phase.
[0018] Preferably, in step S5, sodium hydroxide solution is added to the lithium-containing leachate to carry out a neutralization reaction. The acid in the lithium-containing leachate is neutralized, and the metal ions form hydroxide or phosphate precipitates under alkaline conditions. The pH value of the solution is controlled so that phosphate ions preferentially combine with sodium ions to generate a phosphate solution mainly composed of trisodium phosphate.
[0019] Preferably, lithium ions in the solution are precipitated in the form of lithium phosphate or lithium hydroxide to recover lithium ions from the diverted lithium-containing leachate. The phosphate solution is then tightly filtered using plate and frame filtration or chamber filtration to achieve solid-liquid separation. Finally, resin is used to adsorb trace heavy metal ions in the solution.
[0020] Preferably, in step S6, the phosphate solution is mixed with the lithium-containing filtrate, and the lithium ions in the solution react with phosphate ions and sodium ions to generate a lithium phosphate precipitate with low solubility. The precipitate is then filtered to separate it. The filter cake containing the lithium phosphate precipitate is then washed with deionized water to remove soluble impurities. Finally, the lithium phosphate filter cake is dried at low temperature.
[0021] Preferably, in step S7, dilute phosphoric acid is first added to the reactor as a base liquid, and then dried lithium phosphate filter cake is added and stirred to form a slurry. Then concentrated phosphoric acid is slowly added and stirred, and the pH value of the solution is monitored in real time until the lithium phosphate dissolution and conversion are completed.
[0022] Preferably, after the reaction is completed, the saturation of the lithium dihydrogen phosphate solution is changed by evaporation and concentration to precipitate lithium dihydrogen phosphate. The slurry containing lithium dihydrogen phosphate crystals is then filtered to obtain lithium dihydrogen phosphate crystals, which are then washed and dried.
[0023] Compared with the prior art, the beneficial effects of the present invention are:
[0024] 1. This invention safely releases residual battery energy through a controllable internal short circuit, making the crushed material easier to process. A small portion of the lithium-containing leachate is treated with alkaline solution, which not only removes metallic impurities but also utilizes its own phosphorus and lithium to generate phosphate for lithium precipitation and recovers lithium from the diverted liquid. The prepared phosphate is mixed with the purified lithium-containing filtrate to directly precipitate lithium phosphate, reducing dependence on external raw materials and production costs. Furthermore, the diversion process simultaneously recovers lithium from the entire process, avoiding lithium loss caused by diversion, thereby improving the overall lithium recovery rate.
[0025] 2. The concentrated phosphoric acid of this invention can serve as an acid source, and its phosphate ions can form soluble complexes with metal ions. Together with the reducing effect of hydrogen peroxide, it can improve the leaching rate of valuable metals such as cobalt, nickel, and manganese. By selecting specific extractants and precisely controlling the pH, divalent impurity ions such as Co²⁺ and Ni²⁺ can be preferentially extracted and removed, while Li⁺ is retained in the aqueous phase. This achieves efficient separation of lithium from key impurities and yields a high-purity lithium-containing filtrate. Attached Figure Description
[0026] Figure 1 This is a flowchart of the present invention. Detailed Implementation
[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] Please see Figure 1 This invention provides a technical solution: a method for preparing lithium dihydrogen phosphate from lithium battery recycling, comprising the following steps:
[0029] S1. Mechanically crush waste batteries while they are charged;
[0030] A charged state refers to a battery that has not undergone discharge treatment and is subjected to crushing equipment while still retaining residual voltage and charge. During crushing, the battery's outer shell and separator are damaged under the action of mechanical extrusion and shearing forces, and the positive and negative electrode materials inside the battery come into direct contact, causing a controllable internal short circuit.
[0031] Through artificially induced internal short circuits, the residual chemical energy in the battery is released instantaneously in the form of heat within the controlled equipment cavity. It is worth noting that the crushing equipment is equipped with a cooling system and uses inert gas protection and explosion-proof design to safely conduct heat dissipation and prevent thermal runaway.
[0032] By breaking the battery while it is charged and releasing its energy, the internal materials of the battery are transformed into a mixture of physically stable, non-electrochemically active powder and current collector, ensuring the safe operation of subsequent processes.
[0033] S2. The crushed material is sieved to separate components of different particle sizes to obtain battery powder;
[0034] The mixture after being charged and crushed includes electrode materials (black powder) and fragments (broken copper foil, broken aluminum foil, broken diaphragm, steel shell fragments, plastic, etc.) of different particle sizes. The mixture is screened through a multi-layer vibrating screen with different sieve openings (such as coarse screen, medium screen, and fine screen), and impurity metals are removed by magnetic separation.
[0035] By utilizing the differences in the magnetic properties of materials, iron, nickel and their alloys are ferromagnetic, while copper, aluminum, graphite, diaphragms and other materials are non-magnetic. This method can effectively separate steel shell fragments and some nickel-containing materials, preventing impurities such as iron and nickel from entering the subsequent wet leaching system and interfering with the subsequent purification and impurity removal processes.
[0036] Electrode material powder is the main raw material for recovering valuable metals such as lithium, cobalt, nickel, and manganese. It enters the next acidification and transformation process for chemical leaching. Fragmented copper foil and aluminum foil, as high-value by-products, realize the initial separation and value-added of resources. Plastics, diaphragms, iron shells, etc., enter the corresponding resource recovery or harmless treatment channels according to their properties.
[0037] The electrode material powder has a uniform composition and a large surface area, allowing for full contact with the acid solution during acidification, thus improving the leaching rate of valuable metals such as lithium, cobalt, nickel, and manganese, and reducing acid consumption. By screening out impurity metals, the solubility of these metals in the acid solution is reduced, thereby lowering the difficulty and cost of subsequent extraction and separation.
[0038] S3. Use the oxidative acid leaching method to leach the battery powder, converting the valuable metal from a solid state into an ionic state dissolved in the solution, to obtain a lithium-containing leachate.
[0039] The oxidative acid leaching method uses concentrated phosphoric acid and hydrogen peroxide to leach battery powder. Concentrated phosphoric acid reacts with metal oxides and salts to convert them into soluble phosphates or free metal ions. For example, it reacts with lithium compounds to generate lithium phosphate or lithium ions, and phosphate ions react with metal ions to form soluble complexes. Hydrogen peroxide acts as a reducing agent to reduce high-valence metal ions in metal oxides to low-valence metal ions that are easily soluble in acid, thereby improving the leaching rate of metals such as cobalt, nickel, and manganese.
[0040] S4. Add an extractant to most of the lithium-containing leachate to separate the impurity metal ions from the lithium-containing leachate and obtain a high-purity lithium-containing filtrate.
[0041] The extractants used are dioctyl phosphate and sulfonated kerosene. During extraction, the lithium-containing leachate containing impurity metal ions comes into countercurrent contact with the extractant. The hydrogen ions in dioctyl phosphate undergo an ion exchange reaction with the low-valence metal ions in the aqueous phase. The metal ions form a metal-organic complex and enter the organic phase, while the hydrogen ions enter the aqueous phase.
[0042] Lithium-containing leachates mainly contain lithium ions and impurity ions that need to be removed, such as Co. 2+ Ni2+ Mn 2+ Cu 2+ Fe 2+ / 3+ Al 3+ ;
[0043] Dioctyl phosphate has a strong coordination ability for divalent metal ions. Under acidic conditions, it can selectively transfer these ions from the aqueous phase to the organic phase. Sulfonated kerosene is used to dissolve and dilute dioctyl phosphate, adjust its concentration and viscosity, and improve its physical properties.
[0044] The extraction ability of dioctyl phosphate for divalent metal ions follows the order: Fe 3+ >Zn 2+ >Cu 2+ >Mn 2+ >Co 2+ >Ni 2+ >Mg 2+ >Ca 2+ >Li + By precisely controlling the pH value of the aqueous phase, Co can be preferentially extracted. 2+ Ni 2+ Mg 2+ And Li + To maximize the retention in the aqueous phase, Li + Efficient separation from impurities.
[0045] S5. Add alkaline solution to a small portion of lithium-containing leachate for reaction, and obtain phosphate for lithium precipitation after filtration and resin adsorption; the lithium-containing leachate contains lithium ions, phosphate ions, and a small amount of leached gas pressure metal ions.
[0046] Sodium hydroxide solution is added to the lithium-containing leachate to carry out a neutralization reaction. The acid in the lithium-containing leachate is neutralized, and the metal ions form hydroxide or phosphate precipitates under alkaline conditions. The pH value of the solution is controlled so that phosphate ions preferentially combine with sodium ions to generate a phosphate solution mainly composed of trisodium phosphate.
[0047] In an alkaline environment, lithium ions in the solution precipitate as lithium phosphate or lithium hydroxide, which is used to recover lithium ions from the lithium-containing leachate that has been diverted. This means that while generating the lithium precipitation reagent, lithium in the diverted solution is also recovered simultaneously, ensuring that the total lithium recovery rate is not lost due to diversion.
[0048] The phosphate solution is tightly filtered using plate and frame filtration or chamber filtration to achieve solid-liquid separation, and then resin is used to adsorb trace heavy metal ions in the solution.
[0049] S6. Add phosphate to high-purity lithium-containing filtrate and mix to produce a precipitation reaction, thereby obtaining lithium phosphate precipitate and realizing the separation and enrichment of lithium from the liquid phase to the solid phase.
[0050] The lithium-containing filtrate has removed major impurities such as cobalt, nickel, and manganese. Its core components are high-purity lithium ions and phosphates (lithium precipitation reagent solutions, such as trisodium phosphate). These lithium precipitation reagents are derived from phosphorus elements contained in waste battery materials and the process itself.
[0051] The phosphate solution is mixed with the lithium-containing filtrate. The lithium ions in the solution react with phosphate ions and sodium ions to form a lithium phosphate precipitate with low solubility. The precipitate is then filtered to separate it. The filter cake containing the lithium phosphate precipitate is washed with deionized water to remove soluble impurities. Finally, the lithium phosphate filter cake is dried at low temperature to obtain lithium phosphate precursor powder.
[0052] S7. Add concentrated phosphoric acid to the lithium phosphate precipitate for acidification treatment to obtain a lithium dihydrogen phosphate solution.
[0053] First, dilute phosphoric acid is added to the reactor as a base solution, followed by dried lithium phosphate filter cake. The mixture is stirred to form a slurry. Then, concentrated phosphoric acid is slowly added while stirring, and the pH value of the solution is monitored in real time until the lithium phosphate dissolves and is converted.
[0054] After the reaction is complete, the saturation of the lithium dihydrogen phosphate solution is changed by evaporation and concentration, causing lithium dihydrogen phosphate to precipitate. The slurry containing lithium dihydrogen phosphate crystals is then filtered to obtain lithium dihydrogen phosphate crystals and mother liquor. The lithium dihydrogen phosphate crystals are then washed and dried.
[0055] Lithium dihydrogen phosphate crystals are washed with organic solvents (such as ethanol or acetone) or low-temperature deionized water to remove the mother liquor (containing excessive phosphoric acid and other soluble impurities) adhering to the surface.
[0056] The washed lithium dihydrogen phosphate crystals were dried in a low-temperature vacuum drying oven to prevent the lithium dihydrogen phosphate from dehydrating or decomposing at high temperatures. After drying, white battery-grade lithium dihydrogen phosphate powder was obtained.
[0057] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A method for preparing lithium dihydrogen phosphate from lithium battery recycling, characterized in that, Includes the following steps: S1. Mechanically crush waste batteries while they are charged; S2. The crushed material is sieved to separate components of different particle sizes to obtain battery powder; S3. Use the oxidative acid leaching method to leach the battery powder, converting the valuable metal from a solid state into an ionic state dissolved in the solution, to obtain a lithium-containing leachate. S4. Add an extractant to most of the lithium-containing leachate to separate the impurity metal ions from the lithium-containing leachate and obtain a high-purity lithium-containing filtrate. S5. Add alkaline solution to a small portion of lithium-containing leachate and react. After filtration and resin adsorption, obtain phosphate for lithium precipitation. S6. Add phosphate to the high-purity lithium-containing filtrate and mix to cause a precipitation reaction, thus obtaining lithium phosphate precipitate. S7. Add concentrated phosphoric acid to the lithium phosphate precipitate for acidification treatment to obtain a lithium dihydrogen phosphate solution.
2. The method for preparing lithium dihydrogen phosphate from lithium battery recycling according to claim 1, characterized in that: In step S1, the charged state refers to the battery being crushed directly by crushing equipment while it has not been discharged and still has residual voltage and charge. During crushing, the battery casing and separator are damaged under the action of mechanical extrusion and shearing force, and the positive and negative electrode materials inside the battery come into direct contact, causing a controllable internal short circuit.
3. The method for preparing lithium dihydrogen phosphate from lithium battery recycling according to claim 1, characterized in that: In step S2, the mixture after being charged and crushed includes electrode materials and fragments of different particle sizes. The mixture is screened through a multi-layer vibrating screen with different sieve openings, and impurity metals are removed by magnetic separation.
4. The method for preparing lithium dihydrogen phosphate from lithium battery recycling according to claim 1, characterized in that: In step S3, the oxidative acid leaching method uses concentrated phosphoric acid and hydrogen peroxide to leach the battery powder. Concentrated phosphoric acid reacts with metal oxides and salts to convert them into soluble phosphates or free metal ions, and phosphate ions react with metal ions to form soluble complexes. Hydrogen peroxide acts as a reducing agent to reduce the high-valence metal ions in the metal oxides to low-valence metal ions that are easily soluble in acids.
5. The method for preparing lithium dihydrogen phosphate from lithium battery recycling according to claim 1, characterized in that: In step S4, the extractant is selected as dioctyl phosphate and sulfonated kerosene. During extraction, the lithium-containing leachate containing impurity metal ions comes into countercurrent contact with the extractant. The hydrogen ions in dioctyl phosphate undergo an ion exchange reaction with the low-valence metal ions in the aqueous phase. The metal ions form a metal-organic complex and enter the organic phase, while the hydrogen ions enter the aqueous phase.
6. The method for preparing lithium dihydrogen phosphate from lithium battery recycling according to claim 1, characterized in that: In step S5, sodium hydroxide solution is added to the lithium-containing leachate to carry out a neutralization reaction. The acid in the lithium-containing leachate is neutralized, and the metal ions form hydroxide or phosphate precipitates under alkaline conditions. The pH value of the solution is controlled so that phosphate ions preferentially combine with sodium ions to generate a phosphate solution mainly composed of trisodium phosphate.
7. The method for preparing lithium dihydrogen phosphate from lithium battery recycling according to claim 1, characterized in that: Lithium ions in the solution precipitate as lithium phosphate or lithium hydroxide, which is used to recover lithium ions from the diverted lithium-containing leachate. The phosphate solution is then tightly filtered using plate and frame filtration or chamber filtration to achieve solid-liquid separation. Finally, resin is used to adsorb trace heavy metal ions in the solution.
8. The method for preparing lithium dihydrogen phosphate from lithium battery recycling according to claim 1, characterized in that: In step S6, the phosphate solution is mixed with the lithium-containing filtrate. The lithium ions in the solution react with phosphate ions and sodium ions to form a lithium phosphate precipitate with low solubility. The precipitate is then filtered to separate it. The filter cake containing the lithium phosphate precipitate is washed with deionized water to remove soluble impurities. Finally, the lithium phosphate filter cake is dried at low temperature.
9. The method for preparing lithium dihydrogen phosphate from lithium battery recycling according to claim 1, characterized in that: In step S7, dilute phosphoric acid is first added to the reactor as a base liquid, followed by the addition of dried lithium phosphate filter cake. The mixture is stirred to form a slurry, and then concentrated phosphoric acid is slowly added while stirring. The pH value of the solution is monitored in real time until the lithium phosphate dissolves and is converted.
10. The method for preparing lithium dihydrogen phosphate from lithium battery recycling according to claim 9, characterized in that: After the reaction is complete, the saturation of the lithium dihydrogen phosphate solution is changed by evaporation and concentration, causing lithium dihydrogen phosphate to precipitate. The slurry containing lithium dihydrogen phosphate crystals is then filtered to obtain lithium dihydrogen phosphate crystals, which are then washed and dried.