Method for recovering lithium precursor

Abstract

In a method for recovering a lithium precursor, a preliminary lithium precursor solution containing a lithium salt including carbonate-based ions is generated by reacting an electrode powder, an oxidizing agent, and carbon dioxide in a solvent. A lithium precursor solution is generated by adding a metal salt to the preliminary lithium precursor solution. The lithium precursor can be recovered in an environmentally friendly and efficient manner.

Description

Lithium precursor recovery method

[0001] The present disclosure relates to a method for recovering a lithium precursor. More specifically, it relates to a method for recovering a lithium precursor from a lithium secondary battery.

[0002]

[0003] Rechargeable batteries are batteries capable of repeated charging and discharging, and with the advancement of the information and communication and display industries, they are widely applied as power sources for portable electronic communication devices such as camcorders, mobile phones, and laptop PCs. Furthermore, recently, battery modules or battery packs containing rechargeable batteries are being developed and applied as power sources for eco-friendly vehicles.

[0004] For example, a secondary battery may include an electrode assembly comprising a positive electrode, a negative electrode, and a separator, and an electrolyte impregnating the electrode assembly. The secondary battery may further include an outer casing that accommodates the electrode assembly and the electrolyte. Depending on the shape of the outer casing, the secondary battery may be classified as a coin-type, prismatic, cylindrical, or pouch-type secondary battery.

[0005] Secondary batteries include, for example, lead-acid batteries, nickel-cadmium batteries (NiCd), nickel-metal hydride batteries (Ni-MH), lithium secondary batteries, etc. The lithium secondary batteries include lithium-ion batteries (Li-ion), lithium polymer batteries (Li-Po), lithium iron phosphate batteries (LiFePO4), lithium sulfur batteries (Li-S), etc.

[0006] With the increasing demand for secondary batteries, research on recycling methods is on the rise due to environmental protection issues and the cost of metal materials. For example, secondary batteries can be crushed to form electrode powder, and the metal can be recovered by oxidizing the electrode powder. However, this recovery process requires numerous steps, and costs associated with waste generation may increase. Therefore, there is a need for methods to efficiently recycle secondary batteries.

[0007]

[0008] One objective of the present disclosure is to provide a method for recovering a lithium precursor with high efficiency.

[0009]

[0010] In a method for recovering a lithium precursor according to exemplary embodiments, an electrode powder, an oxidizing agent, and carbon dioxide are reacted in a solvent to produce a preliminary lithium precursor solution containing a lithium salt containing carbonate ions. A metal salt is added to the preliminary lithium precursor solution to produce a lithium precursor solution.

[0011] According to exemplary embodiments, the reaction temperature of the step of generating the lithium precursor solution may be 10°C to 80°C.

[0012] According to exemplary embodiments, heating may be excluded in the step of generating the lithium precursor solution.

[0013] According to exemplary embodiments, the lithium precursor solution may include lithium hydroxide.

[0014] According to exemplary embodiments, the solvent may include an aqueous solvent from which strong acids are excluded.

[0015] According to exemplary embodiments, the electrode powder contains iron, and the molar ratio of the oxidizing agent to the iron in the electrode powder may be 0.9 to 3.0.

[0016] According to exemplary embodiments, a solid containing iron may be produced in the step of producing the preliminary lithium precursor solution.

[0017] According to exemplary embodiments, the step of separating the solid containing iron from the liquid may be further included.

[0018] According to exemplary embodiments, the carbon dioxide may be injected into the solvent at a pressure of 0.5 bar to 10.0 bar.

[0019] According to exemplary embodiments, the molar ratio of the metal salt to the lithium salt containing the carbonate ion may be 0.8 to 2.5.

[0020] According to exemplary embodiments, the molar ratio of the metal salt to the lithium salt containing the carbonate ion may be 1.0 to 2.0.

[0021] According to exemplary embodiments, the pH can be maintained at 12 or higher in the step of producing the lithium precursor solution.

[0022] According to exemplary embodiments, the metal salt may include a hydroxide of an alkali metal or an alkaline earth metal.

[0023] According to exemplary embodiments, a solid comprising an alkali metal or an alkaline earth metal may be produced in the step of producing the lithium precursor solution.

[0024] According to exemplary embodiments, the step of separating the solid containing the alkali metal or alkaline earth metal into solid and liquid may be further included.

[0025] According to exemplary embodiments, the method may further include the step of heat-treating a solid containing the alkali metal or alkaline earth metal; and the step of regenerating the alkali metal or alkaline earth metal into a hydroxide by a hydration reaction.

[0026] According to exemplary embodiments, the hydroxide of a recycled alkali metal or alkaline earth metal can be reused in the step of generating the lithium precursor solution.

[0027] According to exemplary embodiments, the oxidizing agent may include one or more of hydrogen peroxide, ozone water, perbromic acid, perchloric acid, and periodic acid.

[0028]

[0029] According to the lithium precursor recovery method of the present disclosure, lithium precursors can be efficiently recovered from a lithium secondary battery.

[0030] According to exemplary embodiments, lithium precursors can be recovered in an environmentally friendly manner using metal salts, and the recovery efficiency of lithium precursors can be improved.

[0031]

[0032] FIG. 1 is a schematic flowchart illustrating a method for recovering a lithium precursor according to exemplary embodiments.

[0033] According to embodiments of the present disclosure, a preliminary lithium precursor solution can be produced by reacting electrode powder, an oxidizing agent, and carbon dioxide. A lithium precursor solution can be produced by reacting the preliminary lithium precursor solution with a metal salt. A lithium precursor can be recovered through the lithium precursor solution.

[0034] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the attached drawings. However, this is merely illustrative and the present disclosure is not limited to the specific embodiments described illustratively.

[0035] As used in this specification, the term "precursor" is used to collectively refer to a compound containing a specific metal to provide the specific metal included in the electrode active material. For example, a lithium precursor is a compound containing lithium, and may include lithium hydroxide (LiOH), lithium carbonate (Li2CO3), lithium fluoride (LiF), etc.

[0036] As used in this specification, the term "electrode powder" is used to comprehensively refer to a material in powder form generated from a battery. For example, the electrode powder may include a positive electrode active material, a conductive material, a binder, etc., generated by grinding a lithium secondary battery (e.g., a lithium nickel-manganese-cobalt battery, a lithium nickel-cobalt-manganese-aluminum battery, a lithium iron phosphate battery, etc.).

[0037] FIG. 1 is a schematic flowchart illustrating a method for recovering a lithium precursor according to exemplary embodiments.

[0038] Referring to FIG. 1, electrode powder can be prepared (e.g., process S10).

[0039] For example, electrode powder can be prepared from a lithium secondary battery. The lithium secondary battery may include a nickel-based lithium secondary battery containing nickel, cobalt, and manganese, and / or an iron phosphate-based lithium secondary battery containing iron and phosphorus, etc.

[0040] The above lithium secondary battery may include an electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The positive electrode and the negative electrode may each include a positive active material layer and a negative active material layer coated on a positive current collector and a negative current collector, respectively.

[0041] The above cathode includes a cathode current collector (e.g., copper (Cu)) and a cathode active material layer, and the cathode active material layer may include a cathode active material, a conductive material, and a binder together.

[0042] For example, the above-mentioned negative electrode active material capable of absorbing and extracting lithium ions may be used without special limitation if it is known in the art. For example, the above-mentioned negative electrode active material may include carbon-based materials such as crystalline carbon, amorphous carbon, carbon composites, carbon fibers; lithium alloys; silicon (Si)-based compounds or tin, etc.

[0043] The conductive material may include, for example, carbon-based materials such as graphite, carbon black, graphene, carbon nanotubes, etc. The binder may include, for example, resin materials such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidenefluoride (PVDF), polyacrylonitrile, and polymethylmethacrylate.

[0044] The above-mentioned anode comprises an anode current collector (e.g., aluminum (Al)) and an anode active material layer, and the anode active material layer may include the anode active material together with the aforementioned conductive material and binder.

[0045] The above-mentioned anode may be obtained from spent lithium secondary batteries. For example, the above-mentioned anode may include a used spent lithium secondary battery anode, an anode that was damaged or defective during the manufacturing process, etc.

[0046] In some embodiments, the anode may be obtained from a spent lithium iron phosphate battery.

[0047] According to exemplary embodiments, the anode can be crushed to recover electrode powder containing an anode active material.

[0048] In some embodiments, the powder may include black powder obtained by physically crushing spent lithium iron phosphate batteries. When introduced into a solvent in the form of black powder, a reaction with an oxidizing agent, metal salt, etc., may be promoted.

[0049] The above positive active material may include metals such as lithium, nickel, cobalt, manganese, and iron, for example. The above positive active material may include non-metals such as phosphoric acid, for example.

[0050] According to exemplary embodiments, the positive electrode active material may include lithium. For example, the positive electrode active material may include lithium and nickel. For example, the positive electrode active material may include lithium and iron.

[0051] In some embodiments, the positive electrode active material may comprise a lithium iron phosphate (LiFePO4, LFP)-based lithium oxide comprising lithium, iron, and phosphoric acid.

[0052] In some embodiments, the electrode powder containing the positive active material may be heat-treated. The heat treatment may be performed before being introduced into the solvent described below. For example, the heat treatment may be performed at 100°C to 900°C, or at 350°C to 800°C.

[0053] Impurities such as conductive materials and binders can be removed or reduced by the above heat treatment. Accordingly, a lithium precursor can be recovered from electrode powder containing a high-purity positive electrode active material.

[0054] According to exemplary embodiments, the electrode powder, oxidizing agent, and carbon dioxide can be reacted in a solvent to produce a preliminary lithium precursor solution (e.g., process S20). The preliminary lithium precursor may contain a lithium salt.

[0055] According to exemplary embodiments, the lithium salt may include carbonate ions. The carbonate ions are carbonate ions (CO3 2- ), bicarbonate ion (HCO3 - It may include one or more ions derived from carbonic acid (H2CO3). In one embodiment, the carbonate ion may include carbonic acid. A lithium salt containing a carbonate ion can react with a metal salt described below, and accordingly, a lithium precursor can be recovered in a single step without additional conditions such as changing the reaction solvent or changing the reaction conditions.

[0056] In some embodiments, the lithium salt containing the carbonate ion may include lithium bicarbonate (LiHCO3). In some embodiments, the lithium salt containing the carbonate ion may also include lithium carbonate (Li2CO3).

[0057] The above oxidizing agent can oxidize the positive active material contained in the electrode powder together with carbon dioxide and convert it into a lithium salt form.

[0058] According to exemplary embodiments, the oxidizing agent may include a peroxide. For example, the oxidizing agent may include hydrogen peroxide (H2O2), ozone water, perbromic acid, perchloric acid, periodic acid, sodium peroxide, sodium persulfate, ammonium persulfate, etc.

[0059] According to exemplary embodiments, the oxidizing agent may include one or more of hydrogen peroxide, ozone water, perbromic acid, perchloric acid, and periodic acid.

[0060] In some embodiments, the oxidizing agent may include hydrogen peroxide (H2O2). When hydrogen peroxide is used, the generation of impurities can be suppressed, thereby improving the efficiency of lithium precursor recovery. In addition, even if byproducts are generated, water (H2O) is produced, so the lithium precursor can be recovered in an environmentally friendly manner.

[0061] The content of the oxidizing agent can be determined based on the number of moles of elements included in the electrode powder.

[0062] For example, the electrode powder contains iron, and the number of moles of the oxidizing agent can be determined based on the total number of moles of iron.

[0063]

[0064] According to exemplary embodiments, the molar ratio of the oxidizing agent to the iron in the electrode powder may be 0.9 to 3.0.

[0065] According to exemplary embodiments, the molar ratio of the oxidizing agent to the iron in the electrode powder may be 0.9 or higher. In some embodiments, the molar ratio of the oxidizing agent to the iron in the electrode powder may be 0.95 or higher, 0.98 or higher, 1.10 or higher, 1.20 or higher, 1.25 or higher, 1.40 or higher, 1.55 or higher, 1.60 or higher, 1.65 or higher, 1.66 or higher, 1.80 or higher, 2.05 or higher, or 2.07 or higher.

[0066] According to exemplary embodiments, the molar ratio of the oxidizing agent to the iron in the electrode powder may be 3.0 or less. In some embodiments, the molar ratio of the oxidizing agent to the iron in the electrode powder may be 2.9 or less, 2.75 or less, 2.7 or less, 2.55 or less, 2.51 or less, 2.5 or less, 2.4 or less, 2.25 or less, 2.2 or less, or 2.15 or less.

[0067] Within the above content range, the formation and / or dissolution of lithium salts containing carbonate ions can be promoted, and accordingly, the reaction with metal salts can be promoted.

[0068] Carbon dioxide can produce a lithium salt containing carbonate ions together with the above-mentioned oxidizing agent.

[0069] For example, the generation of a lithium salt containing carbonate ions can be controlled by controlling the injection pressure of the carbon dioxide.

[0070] According to exemplary embodiments, the injection pressure of the carbon dioxide may be 0.5 bar or higher. In some embodiments, the injection pressure of the carbon dioxide may be 0.55 bar or higher, 0.60 bar or higher, 0.70 bar or higher, or 0.75 bar or higher.

[0071] According to exemplary embodiments, the injection pressure of the carbon dioxide may be 10.0 bar or less. In some embodiments, the injection pressure of the carbon dioxide may be 9.5 bar or less, 9.0 bar or less, 8.5 bar or less, 8.2 bar or less, 8.0 bar or less, or 7.5 bar or less.

[0072] In the above pressure range, the formation of lithium salts containing carbonate ions can be promoted, and accordingly, the lithium recovery rate can be improved.

[0073] The above solvent may include an aqueous solvent. For example, the above aqueous solvent may include water; water-soluble organic solvents such as ethanol, acetone, etc.

[0074] According to exemplary embodiments, the solvent may include an aqueous solvent from which strong acids are excluded.

[0075] For example, strong acids may include sulfuric acid, hydrochloric acid, nitric acid, etc. As strong acids are excluded, by-products such as sodium sulfate (Na2SO4) resulting from the reaction between the positive electrode active material in the electrode powder and the strong acid may not be generated. Therefore, since an additional process for removing by-products is not required, lithium precursors can be recovered efficiently and in an environmentally friendly manner.

[0076] According to exemplary embodiments, the content of the solvent may be 50 to 500 parts by weight, 60 to 350 parts by weight, or 70 to 200 parts by weight relative to 10 parts by weight of the electrode powder. Within the above content range, the electrode powder, oxidizing agent, and / or carbon dioxide are efficiently dissolved, and the reaction can be promoted.

[0077] In some embodiments, the reaction of the electrode powder, the oxidizing agent, and carbon dioxide may proceed according to the following reaction scheme 1.

[0078] [Reaction Equation 1]

[0079] 2LiFePO4(s) + H2O2(aq) + 2CO2(aq) → 2LiHCO3(aq) + 2FePO4(s)

[0080] According to exemplary embodiments, a solid containing iron can be produced by the reaction of the electrode powder, the oxidizing agent, and carbon dioxide.

[0081] According to exemplary embodiments, the solid containing iron can be separated through solid-liquid separation.

[0082] In some embodiments, the iron-containing solid may comprise iron phosphate (FePO4). The iron phosphate may be recycled by solid-liquid separation from the preliminary lithium precursor solution. For example, the separated iron phosphate may be recycled into a lithium iron phosphate battery.

[0083] According to exemplary embodiments, the preliminary lithium precursor solution may be in a state separated from the iron-containing solid. For example, a preliminary lithium precursor solution containing lithium bicarbonate may be produced by solid-liquid separation of lithium bicarbonate and iron phosphate formed as the reaction proceeds according to Reaction Scheme 1.

[0084] When a solid containing iron is separated, the generation of impurities that can be dissolved in the preliminary lithium precursor solution is suppressed, thereby suppressing side reactions. Accordingly, the recovery efficiency of the lithium precursor can be improved.

[0085] According to exemplary embodiments, the preliminary lithium precursor solution may contain lithium, iron, and phosphorus.

[0086] According to exemplary embodiments, the content of lithium among the total content of lithium, iron, and phosphorus contained in the preliminary lithium precursor solution may be 70 wt% or more, 75 wt% or more, 80 wt% or more, 82 wt% or more, or 85 wt% or more.

[0087] The upper limit of the lithium content among the total content of lithium, iron, and phosphorus contained in the above preliminary precursor solution is not limited, but, for example, it may be 99% by weight or less, 97% by weight or less, 96% by weight or less, or 95% by weight or less.

[0088] A preliminary lithium precursor solution containing lithium within the above range can be rapidly converted into a lithium precursor solution by adding a metal salt.

[0089] In some embodiments, the phosphorus content among the total content of lithium, iron, and phosphorus contained in the preliminary lithium precursor solution may be 20% by weight or less, 18% by weight or less, 15% by weight or less, 12% by weight or less, or 10% by weight or less.

[0090] The lower limit of the phosphorus content among the total content of lithium, iron, and phosphorus contained in the above preliminary lithium precursor solution is not limited, but, for example, it may be 0.01 wt% or more, 0.05 wt% or more, 0.10 wt% or more, or 0.5 wt% or more.

[0091] The pH of a preliminary lithium precursor solution containing phosphorus within the above range can be easily adjusted by adding a metal salt. Accordingly, the conversion rate from a lithium salt containing carbonate ions to a lithium precursor can be improved.

[0092] A first lithium recovery rate can be calculated from the weight of lithium contained in the above preliminary lithium precursor solution according to the following Equation 1.

[0093] [Equation 1]

[0094] First Lithium Recovery Rate (%) = (Weight of Lithium in Preliminary Lithium Precursor Solution / Weight of Lithium in Electrode Powder) X 100

[0095] According to exemplary embodiments, the first lithium recovery rate may be 85% or more, 87% or more, 88% or more, 89% or more, 90% or more, 91% or more, 92% or more, 92.5% or more, or 93% or more. The upper limit of the first lithium recovery rate is not limited, but may be, for example, 99.9% or less, 99.5% or less, or 99% or less.

[0096] In the above recovery rate range, the lithium and metal salt contained in the preliminary lithium precursor solution can react sufficiently.

[0097] According to exemplary embodiments, a lithium precursor solution can be produced by adding a metal salt to a preliminary lithium precursor solution (e.g., process S30).

[0098] The above lithium precursor solution may include lithium hydroxide, lithium carbonate, lithium fluoride, etc.

[0099] According to exemplary embodiments, the lithium precursor solution may contain lithium hydroxide. For example, the lithium hydroxide may contain lithium hydroxide (LiOH). In some embodiments, the lithium precursor solution may substantially contain lithium hydroxide as the lithium precursor. A high-purity lithium precursor can be obtained in the form of lithium hydroxide.

[0100] By recovering the lithium precursor in the form of lithium hydroxide, lithium loss is reduced, and consequently, the lithium recovery rate can be improved. For example, when recovering the lithium precursor in the form of lithium carbonate, lithium loss may occur due to the solubility of lithium carbonate.

[0101] The above metal salt can react with a lithium salt containing carbonate ions to produce a lithium precursor. For example, the metal of the metal salt and the carbonate ions of the lithium salt can react to form a precipitate.

[0102] According to exemplary embodiments, the metal salt may include a hydroxide of an alkali metal or an alkaline earth metal.

[0103] Hydroxides of alkali metals or alkaline earth metals can react with lithium containing carbonate ions to produce lithium hydroxide. For example, hydroxides of alkali metals or alkaline earth metals can be represented as M1OH or M2(OH)2 (where M1 is an alkali metal and M2 is an alkaline earth metal), and can react with carbonate ions to produce alkali metal or alkaline earth metal carbonates represented as (M1)2CO3 or M2CO3.

[0104] The above alkali metals may include Na, K, Rb, Cs, Fr, etc., and the above alkaline earth metals may include Be, Mg, Ca, Sr, Ba, Ra, etc.

[0105] According to exemplary embodiments, the alkali metal hydroxide may include one or more of sodium hydroxide (NaOH) and potassium hydroxide (KOH).

[0106] According to exemplary embodiments, the alkaline earth metal hydroxide may comprise one or more of magnesium hydroxide (Mg(OH)2) and calcium hydroxide (Ca(OH)2). In some embodiments, the alkaline earth metal hydroxide may comprise calcium hydroxide.

[0107] When the above metal salt contains calcium hydroxide, calcium carbonate may be formed according to the reaction, and solid-liquid separation can be performed efficiently as calcium carbonate is formed. Accordingly, the recovery process of the lithium precursor can be performed efficiently. In addition, the regeneration and reuse efficiency of the metal salt described below can be improved.

[0108] According to exemplary embodiments, the molar ratio of the metal salt to the lithium salt containing the carbonate ion may be 0.8 or higher. In some embodiments, the molar ratio of the metal salt to the lithium salt containing the carbonate ion may be 0.85 or higher, 0.90 or higher, 0.92 or higher, 0.95 or higher, 0.97 or higher, 1.00 or higher, 1.02 or higher, 1.05 or higher, 1.07 or higher, or 1.10 or higher.

[0109] According to exemplary embodiments, the molar ratio of the metal salt to the lithium salt containing the carbonate ion may be 2.5 or less. In some embodiments, the molar ratio of the metal salt to the lithium salt containing the carbonate ion may be 2.4 or less, 2.3 or less, 2.2 or less, 2.1 or less, 2.0 or less, 1.9 or less, 1.8 or less, 1.7 or less, 1.6 or less, or 1.5 or less.

[0110] In the above molar ratio range, lithium precursors can be generated while the pH of the preliminary lithium precursor solution is controlled, and accordingly, the generation rate of lithium precursors can be improved.

[0111] According to exemplary embodiments, in the step of generating the lithium precursor solution from the preliminary lithium precursor solution, the pH may be maintained at 12.0 or higher, 12.05 or higher, or 12.1 or higher. Within this range, the formation of carbonates of alkali metals or alkaline earth metals may be promoted. Accordingly, the formation of the lithium precursor may also be promoted.

[0112] According to exemplary embodiments, the reaction temperature of the step of generating the lithium precursor solution may be 10°C or higher. In some embodiments, the reaction temperature of the step of generating the lithium precursor solution may be 12°C or higher, 14°C or higher, or 15°C or higher.

[0113] According to exemplary embodiments, the reaction temperature of the step of generating the lithium precursor solution may be 80°C or lower. In some embodiments, the reaction temperature of the step of generating the lithium precursor solution may be 75°C or lower, 70°C or lower, or 60°C or lower.

[0114] After being generated within the above temperature range, the lithium precursor may exist in a dissolved state, and the carbonates of alkali metals or alkaline earth metals may exist in a precipitated state. Accordingly, the efficiency of solid-liquid separation is improved, and the recovery rate of the lithium precursor can be substantially improved.

[0115] In some embodiments, the step of producing the lithium precursor solution may be performed at room temperature. The room temperature may be, for example, 15°C to 40°C.

[0116] In some embodiments, heating may be excluded in the step of generating the lithium precursor solution. In some embodiments, heating may be excluded in the step of generating the preliminary lithium precursor solution and in the step of generating the lithium precursor solution.

[0117] As heating is excluded, the generation of the preliminary lithium precursor solution and the generation of the lithium precursor solution can be carried out as a continuous reaction, and accordingly, the efficiency of lithium precursor recovery can be improved. For example, when recovering the lithium precursor through heating, the generation of carbonates of alkali metals or alkaline earth metals can be suppressed, and accordingly, the lithium recovery rate may be reduced.

[0118] In some embodiments, the reaction of the step of generating the lithium precursor solution may proceed according to the following reaction schemes 2-1 and 2-2.

[0119] [Reaction Equation 2-1]

[0120] 2LiHCO3(aq) + Ca(OH)2(s) → Li2CO3+ CaCO3(s) + 2H2O

[0121] [Reaction Equation 2-2]

[0122] Li2CO3+ Ca(OH)2(s) → 2LiOH (aq) + CaCO3(s)

[0123] For example, lithium bicarbonate contained in the preliminary lithium precursor solution can be converted into lithium carbonate according to the above reaction scheme 2-1. For example, lithium carbonate formed according to the above reaction scheme 2-1 can be converted into lithium hydroxide according to the above reaction scheme 2-2.

[0124] In some embodiments, the generation of the lithium precursor solution from the electrode powder can be carried out as a continuous reaction. For example, after generating the preliminary lithium precursor solution, the metal salt can be added without changing additional conditions.

[0125] In some embodiments, Reaction Scheme 2-1 and Reaction Scheme 2-2 may be carried out as a continuous reaction. For example, lithium hydroxide may be produced in a state where the formation of solid lithium carbonate in the preliminary lithium precursor solution is suppressed.

[0126] As the above reaction proceeds continuously, the recovery rate of lithium can be improved. For example, if the above reaction does not proceed continuously, a solid containing lithium may precipitate due to the low solubility of lithium carbonate during the conversion of lithium bicarbonate to lithium carbonate, and consequently, the production rate of lithium hydroxide may decrease.

[0127] In some embodiments, impurities contained in the preliminary lithium precursor solution may be removed by the metal salt.

[0128] For example, iron, aluminum, etc. contained in the above-mentioned preliminary lithium precursor solution may be precipitated in the form of hydroxides. For example, phosphorus contained in the above-mentioned preliminary lithium precursor solution may be precipitated in the form of alkaline earth metal phosphates. Accordingly, the purity and recovery efficiency of the lithium precursor can be improved.

[0129] According to exemplary embodiments, a solid comprising an alkali metal or an alkaline earth metal may be produced in the step of producing the lithium precursor solution.

[0130] In some embodiments, the solid containing the alkali metal or alkaline earth metal may contain a carbonate of the alkali metal or alkaline earth metal.

[0131] In some embodiments, the solid containing the alkali metal or alkaline earth metal may contain calcium carbonate.

[0132] According to exemplary embodiments, a solid containing the alkali metal or alkaline earth metal can be separated into solid and liquid phases.

[0133] Solids containing alkali metals or alkaline earth metals separated from solids can be recycled and reused.

[0134] According to exemplary embodiments, a solid containing the alkali metal or alkaline earth metal can be heat-treated to be converted into an alkali metal or alkaline earth metal oxide.

[0135] According to exemplary embodiments, the alkali metal or alkaline earth metal oxide can be hydrated to be regenerated into a hydroxide containing the alkali metal or alkaline earth metal.

[0136] For example, carbonates of alkali metals or alkaline earth metals can be heat-treated at 500°C to 1,000°C to be converted into alkali metal or alkaline earth metal oxides. Afterwards, the alkali metal or alkaline earth metal oxides can be dissolved in water to be regenerated in the form of alkali metal or alkaline earth metal hydroxides.

[0137] According to exemplary embodiments, a hydroxide containing a regenerated alkali metal or alkaline earth metal can be reused in the step of generating the lithium precursor solution.

[0138] For example, it can be reused in the same form as the hydroxide containing an alkali metal or alkaline earth metal used in the step of generating the lithium precursor solution. Accordingly, the production rate of the lithium precursor and the removal rate of impurities described above can be increased, thereby increasing the recovery amount and purity of the lithium precursor.

[0139] According to exemplary embodiments, the lithium precursor can be recovered by crystallizing the lithium precursor solution. For example, the lithium precursor can be recovered in the form of lithium hydroxide.

[0140] The above crystallization method is not limited and can be crystallized through vacuum filtration, pressure filtration, centrifugation, etc. Additional washing may be performed before performing the crystallization, and the purity of the lithium precursor may be further improved by additional washing.

[0141] A second lithium recovery rate can be calculated from the weight of lithium contained in the above-mentioned recovered lithium precursor according to the following Equation 2.

[0142] [Equation 2]

[0143] Second Lithium Recovery Rate (%) = (Weight of lithium contained in recovered lithium precursor / Weight of lithium contained in electrode powder) X 100

[0144] According to exemplary embodiments, the second lithium recovery rate may be 85% or more, 87% or more, 88% or more, 89% or more, 90% or more, 91% or more, 92% or more, 92.5% or more, or 93% or more. The upper limit of the second lithium recovery rate is not limited, but may be, for example, 99.9% or less, 99.5% or less, or 99% or less.

[0145] In some embodiments, the ratio of the second lithium recovery rate to the first lithium recovery rate may be 0.95 or higher, 0.96 or higher, 0.97 or higher, 0.98 or higher, 0.99 or higher, 0.995 or higher, 0.996 or higher, 0.997 or higher, 0.998 or higher, or 0.999 or higher. Since the lithium precursor is recovered from the lithium contained in the preliminary lithium precursor solution, the ratio of the second lithium recovery rate to the first lithium recovery rate cannot exceed 1.00.

[0146] In the above range, more than 98% of the lithium contained in the preliminary lithium precursor solution can be recovered. For example, substantially more than 99% of the lithium contained in the preliminary lithium precursor solution can be recovered.

[0147]

[0148] The embodiments of the present disclosure described above include the following aspects and can be implemented through at least one of the following aspects.

[0149] A method for recovering a lithium precursor according to the first aspect of the present disclosure comprises the steps of: reacting an electrode powder, an oxidizing agent, and carbon dioxide in a solvent to produce a preliminary lithium precursor solution containing a lithium salt containing carbonate ions; and adding a metal salt to the preliminary lithium precursor solution to produce a lithium precursor solution.

[0150] In the first aspect above, according to the second aspect, the reaction temperature of the step of generating the lithium precursor solution may be 10°C to 80°C.

[0151] In the first aspect or the second aspect, according to the third aspect, heating may be excluded in the step of generating the lithium precursor solution.

[0152] In any one of the first to third aspects above, according to the fourth aspect, the lithium precursor solution may include lithium hydroxide.

[0153] In any one of the first to fourth aspects above, according to the fifth aspect, the solvent may include an aqueous solvent from which strong acids are excluded.

[0154] In any one of the first to fifth aspects above, according to the sixth aspect, the electrode powder contains iron, and the molar ratio of the oxidizing agent to the iron in the electrode powder may be 0.9 to 3.0.

[0155] In the sixth aspect above, according to the seventh aspect, a solid containing iron may be produced in the step of producing the preliminary lithium precursor solution.

[0156] In the seventh aspect above, according to the eighth aspect, a step of solid-liquid separation of the solid containing iron may be further included.

[0157] In any one of the first to eighth aspects, according to the ninth aspect, the carbon dioxide can be injected into the solvent at a pressure of 0.5 bar to 10.0 bar.

[0158] In any one of the first to ninth aspects above, according to the tenth aspect, the molar ratio of the metal salt to the lithium salt containing the carbonate ion may be 0.8 to 2.5.

[0159] In the above 10th aspect, according to the 11th aspect, the molar ratio of the metal salt to the lithium salt containing the carbonate ion may be 1.0 to 2.0.

[0160] In any one of the first to eleventh aspects above, according to the 12th aspect, the pH can be maintained at 12 or higher in the step of producing the lithium precursor solution.

[0161] In any one of the first to twelfth aspects above, according to the twelfth aspect, the metal salt may include a hydroxide of an alkali metal or an alkaline earth metal.

[0162] In any one of the first to thirteenth aspects above, according to the fourth aspect, a solid comprising an alkali metal or an alkaline earth metal may be produced in the step of producing the lithium precursor solution.

[0163] In the above 14th aspect, according to the 15th aspect, a step of solid-liquid separation of a solid containing the alkali metal or alkaline earth metal may be further included.

[0164] In the above 15th aspect, according to the 16th aspect, the method may further include the step of heat-treating a solid containing the alkali metal or alkaline earth metal; and the step of regenerating the alkali metal or alkaline earth metal into a hydroxide by a hydration reaction.

[0165] In the above 16th aspect, according to the 17th aspect, the hydroxide of the regenerated alkali metal or alkaline earth metal can be reused in the step of generating the lithium precursor solution.

[0166] In any one of the first to seventh aspects above, according to the eighth aspect, the oxidizing agent may include one or more of hydrogen peroxide, ozone water, perbromic acid, perchloric acid, and periodic acid.

[0167]

[0168] Hereinafter, experimental examples including specific embodiments and comparative examples are presented to aid in understanding the present disclosure; however, these are merely illustrative of the present disclosure and are not intended to limit the appended claims. It is obvious to those skilled in the art that various changes and modifications to the embodiments are possible within the scope and spirit of the present disclosure, and that such variations and modifications fall within the scope of the appended claims.

[0169]

[0170] Examples and Comparative Examples

[0171] Example 1

[0172] After discharging the cells separated from the spent lithium iron phosphate battery, they were cut and ground into units of several centimeters to obtain black powder containing lithium iron phosphate (LiFePO4) as electrode powder. A solution was prepared by mixing 20 g of the black powder (iron content in the black powder: 0.12 mol), 17 g of 30% hydrogen peroxide (H2O2) (0.15 mol), and 185 g of distilled water (H2O).

[0173] The above solution was reacted for 2 hours at room temperature and atmospheric pressure while injecting CO2 gas, thereby obtaining a lithium salt solution containing lithium bicarbonate (LiHCO3) and a solid containing iron phosphate (FePO4). The injection pressure of the CO2 gas is shown in Table 1 below. The precipitate containing iron phosphate was separated to obtain a filtrate as a preliminary lithium precursor solution.

[0174] 22.2 g (0.30 mol) of calcium hydroxide (Ca(OH)2) was added to the above filtrate to obtain a lithium precursor solution containing calcium carbonate (CaCO3) and lithium hydroxide (LiOH). The precipitate containing calcium carbonate was solid-liquid separated and crystallized to recover the lithium precursor.

[0175] Examples 2 to 4

[0176] The same process as Example 1 was performed, except that the content of the hydrogen peroxide was changed according to Table 1 below.

[0177] Examples 5 to 7

[0178] The same process as Example 1 was performed, except that the injection pressure of the CO2 gas was changed according to Table 1 below.

[0179] Examples 8 to 14

[0180] The same process as Example 1 was performed, except that the conditions for adding the calcium hydroxide were changed according to Table 1 below.

[0181] Classification Hydrogen peroxide content (mol) Molar ratio of hydrogen peroxide to iron in black powder CO2 injection pressure (bar) Calcium hydroxide injection conditions Injection amount (mol) pH Temperature (°C) Example 1 0.15 1.25 10.30 13.525 Example 20.20 1.67 10.30 13.525 Example 30.25 2.08 10.30 13.525 Example 40.10 0.83 10.30 13.525 Example 50.15 1.25 3.5 0.30 13.525 Example 60.15 1.25 50.30 13.525 Example 70.15 1.25 0.20.30 13.525 Example 80.15 1.25 10.45 13.525 Example 90.151.2510.5513.525 Example 100.151.2510.1013.525 Example 110.151.2510.3013.040 Example 120.151.2510.3012.655 Example 130.151.2510.3011.7100 Example 140.151.2510.3014.00

[0182] Example 15

[0183] The same process as in Example 1 was performed, and the separated calcium carbonate was heat-treated at 800°C to convert it into calcium oxide (CaO). Afterwards, the calcium oxide was added to water to regenerate it into calcium hydroxide.

[0184] The regenerated calcium hydroxide was reintroduced into the above filtrate to obtain a lithium precursor solution containing calcium carbonate and lithium hydroxide from the remaining elements. Subsequently, the lithium precursor was recovered by solid-liquid separation and crystallization.

[0185] Comparative example

[0186] The same process as in Example 1 was performed, except that calcium hydroxide was not added to the above liquid and the lithium precursor was recovered by heating to 90°C.

[0187]

[0188] Experimental Example

[0189] (1) Evaluation of elemental content in the filtrate (preliminary lithium precursor solution)

[0190] The content of each element in the filtrate according to the examples and comparative examples was measured using ICP-OES (Inductively coupled plasma-optical emission spectrometry, Avio 500). The analysis results are shown in Table 2 below.

[0191] (2) Evaluation of lithium recovery rate

[0192] The lithium recovery rate during the process according to the examples and comparative examples was calculated. Specifically, the lithium recovery rate was calculated according to the following Equation 1 or Equation 2 from the weight of lithium contained in the black powder, the weight of lithium contained in the filtrate, and the weight of lithium contained in the recovered lithium precursor.

[0193] The weight of lithium contained in the above black powder, the weight of lithium contained in the filtrate, and the weight of lithium contained in the recovered lithium precursor were each measured by ICP-OES.

[0194] [Equation 1]

[0195] First Lithium Recovery Rate (%) = (Weight of lithium contained in filtrate (preliminary lithium precursor solution) / Weight of lithium contained in black powder (electrode powder)) X 100

[0196] [Equation 2]

[0197] Second Lithium Recovery Rate (%) = (Weight of lithium contained in recovered lithium precursor / Weight of lithium contained in black powder (electrode powder)) X 100

[0198] The calculation results of the first lithium recovery rate and the second lithium recovery rate above are shown in Table 2 below.

[0199] Elemental content in separated liquid (weight%) First lithium recovery rate (%) Second lithium recovery rate (%) LiFeP Example 1 0.439 0.026 0.0479 3.69 3.6 Example 2 0.439 0.027 0.0519 3.69 3.5 Example 3 0.440 0.027 0.0529 3.59 3.5 Example 4 0.305 0.056 0.09965.06 0.3 Example 5 0.430 0.025 0.0459 3.29 3.0 Example 6 0.450 0.032 0.0609 3.49 3.3 Example 7 0.320 0.052 0.10168 067.2 Example 80.4390.0280.04693.793.6 Example 90.4390.0260.04793.793.7 Example 100.4400.0300.04893.582.5 Example 110.4390.0270.04793.593.4 Example 120.4390.0290.04793.693.6 Example 130.4380.0270.04893.482.2 Example 140.4390.0270.04893.488.9 Example 150.4380.0280.04793.693.6Comparative Example 0.4390.0270.04893.568.8

[0200] Referring to Table 2 above, it was confirmed that in the lithium precursor recovery process according to the examples, iron and phosphorus in the filtrate are leached out, resulting in low content and high content of lithium, thus allowing for selective recovery of lithium. In addition, the first lithium recovery rate and the second lithium recovery rate were improved in the lithium precursor recovery process according to the examples.

[0201] In Example 4, which had a low hydrogen peroxide content, the first lithium recovery rate was relatively reduced.

[0202] In Example 7, where the CO2 gas injection pressure was low, the first lithium recovery rate was relatively reduced.

[0203] In Example 10, where the amount of calcium hydroxide input was relatively low, the recovery rate of the second lithium was relatively reduced.

[0204] In Examples 13 and 14, where the temperature was relatively high and the pH was relatively low when calcium hydroxide was added, the recovery rate of the second lithium was relatively reduced.

[0205] In the lithium precursor recovery process according to the comparative example, the second lithium recovery rate was significantly reduced.

Claims

1. A step of reacting electrode powder, an oxidizing agent, and carbon dioxide in a solvent to produce a preliminary lithium precursor solution containing a lithium salt containing carbonate ions; and A method for recovering a lithium precursor, comprising the step of adding a metal salt to the above-mentioned preliminary lithium precursor solution to produce a lithium precursor solution.

2. A method for recovering a lithium precursor according to claim 1, wherein the reaction temperature of the step of generating the lithium precursor solution is 10℃ to 80℃.

3. A method for recovering a lithium precursor according to claim 1, wherein heating is excluded in the step of generating the lithium precursor solution.

4. A method for recovering a lithium precursor according to claim 1, wherein the lithium precursor solution comprises lithium hydroxide.

5. A method for recovering a lithium precursor according to claim 1, wherein the solvent comprises an aqueous solvent from which strong acids are excluded.

6. A method for recovering a lithium precursor according to claim 1, wherein the electrode powder comprises iron, and the molar ratio of the oxidizing agent to the iron in the electrode powder is 0.9 to 3.

0.

7. A method for recovering a lithium precursor according to claim 6, wherein a solid containing iron is produced in the step of producing the preliminary lithium precursor solution.

8. A method for recovering a lithium precursor according to claim 7, further comprising the step of solid-liquid separation of the solid containing iron.

9. A method for recovering a lithium precursor according to claim 1, wherein the carbon dioxide is injected into the solvent at a pressure of 0.5 bar to 10.0 bar.

10. A method for recovering a lithium precursor according to claim 1, wherein the molar ratio of the metal salt to the lithium salt containing the carbonate ion is 0.8 to 2.

5.

11. A method for recovering a lithium precursor according to claim 10, wherein the molar ratio of the metal salt to the lithium salt containing the carbonate ion is 1.0 to 2.

0.

12. A method for recovering a lithium precursor according to claim 1, wherein the pH is maintained at 12 or higher in the step of generating the lithium precursor solution.

13. A method for recovering a lithium precursor according to claim 1, wherein the metal salt comprises a hydroxide of an alkali metal or an alkaline earth metal.

14. A method for recovering a lithium precursor according to claim 1, wherein a solid comprising an alkali metal or an alkaline earth metal is produced in the step of producing the lithium precursor solution.

15. A method for recovering a lithium precursor according to claim 14, further comprising the step of solid-liquid separation of a solid containing the alkali metal or alkaline earth metal.

16. The step of heat-treating a solid comprising the alkali metal or alkaline earth metal according to claim 15; and A method for recovering a lithium precursor, further comprising the step of regenerating it into an alkali metal or alkaline earth metal hydroxide by a hydration reaction.

17. A method for recovering a lithium precursor according to claim 16, wherein the recycled alkali metal or alkaline earth metal hydroxide is reused in the step of generating the lithium precursor solution.

18. A method for recovering a lithium precursor according to claim 1, wherein the oxidizing agent comprises one or more of hydrogen peroxide, ozone water, perbromic acid, perchloric acid, and periodic acid.

Images