A method for recovering metal elements in lithium batteries using wet extraction

Abstract

The present invention provides a method for recovering metal elements in a lithium battery by using a wet extraction method, which comprises the following steps: step 1, pretreating the lithium battery to obtain a powder mixture containing a positive electrode active material; step 2, acid leaching to obtain a leachate; step 3, if the lithium battery to be recovered contains a lithium iron phosphate battery, heating the solid component obtained by solid-liquid filtration after acid leaching in an oxygen-containing environment, burning and removing carbon, and the remaining is iron phosphate; step 4, if the lithium battery to be recovered contains a ternary lithium battery, extracting the leachate obtained by solid-liquid filtration after acid leaching, wherein diisooctyl phosphate is used as an extractant to obtain a raffinate containing lithium elements and an organic phase containing Ni / Co / Mn elements.

Description

Technical Field

[0001] The invention relates to a method for recovering metal elements in a lithium battery by using a wet extraction method. Background Art

[0002] Waste lithium batteries contain many substances that are harmful to the environment, such as heavy metals, electrolyte (LiPF6), and benzene and ester compounds, which are difficult to degrade and are highly toxic.

[0003] Toxic substances in discarded lithium batteries can cause damage to the environment. If not treated, heavy metals from the cathode materials will pollute the soil and groundwater; graphite will produce dust and cause air pollution; if not treated properly, the electrolyte will cause fluorine pollution and organic pollution; the diaphragm cannot be degraded and will form white pollution. In addition, discarded lithium batteries contain many high-value metals (such as lithium, nickel, cobalt, manganese, copper, iron, aluminum, etc.). Therefore, efficient recovery of metals in discarded lithium-ion batteries is of great value.

[0004] However, the existing lithium battery recycling technology has the disadvantages of complex processing flow, low recycling efficiency, and high recycling cost, so we still need further improvement. Summary of the invention

[0005] The content of the present invention is set forth in the claims.

[0006] A method for recovering metal elements in lithium batteries by wet extraction, comprising the following steps:

[0007] Step 1, pre-treating the lithium battery to obtain a powder mixture containing a positive electrode material;

[0008] Step 2, acid leaching to obtain a leachate;

[0009] Step 3: If the lithium battery to be recycled contains a lithium iron phosphate battery, the solid component obtained after acid leaching and solid-liquid filtration is heated in an oxygen-containing environment and burned to remove carbon, and the remaining is iron phosphate;

[0010] Step 4: If the lithium battery to be recycled contains a ternary lithium battery, the leachate obtained after solid-liquid filtration after acid leaching is extracted using diisooctyl phosphate as an extractant to obtain a raffinate containing lithium elements and an organic phase containing Ni / Co / Mn elements.

[0011] Optionally, step 4 further comprises stripping the organic phase containing Ni / Co / Mn with an aqueous sulfuric acid solution to obtain a first stripping solution containing Ni / Co / Mn.

[0012] Optionally, step 4 further comprises adding sodium carbonate as a precipitant to the lithium-containing raffinate to obtain lithium carbonate precipitate.

[0013] Optionally, the iron phosphate in step 3 can be used as a raw material for preparing a positive electrode material for a lithium iron phosphate battery, and the first stripping solution containing Ni / Co / Mn obtained in step 4 can be used as a raw material for preparing a ternary positive electrode material.

[0014] Optionally, step 1 includes removing the binder to separate the positive electrode active material and the current collector.

[0015] Optionally, in step 1, the binder is removed by anaerobic pyrolysis to separate the positive electrode active material and the current collector.

[0016] Optionally, step 1 includes physical sorting, by which the current collector metal sheet is separated, and what remains is a powder mixture containing the positive electrode material.

[0017] Optionally, step 1 does not include the step of separating the positive electrode material and the negative electrode material, so the powder mixture obtained in step 1 contains the positive electrode material and carbon.

[0018] The present invention has at least one of the following advantages:

[0019] 1. Based on the two most popular lithium battery positive electrode materials (lithium iron phosphate and ternary materials), the present invention designs and optimizes a method for recovering the positive electrode material metal using a wet method.

[0020] 2. The process of the present invention involves the recycling of both ternary electrodes and lithium iron phosphate electrodes. Therefore, in the pretreatment stage, it is not necessary to manually pre-separate the ternary battery and the lithium iron phosphate battery, but to separate and recycle the two different types of positive electrode active materials in the wet process stage.

[0021] 3. The recycled materials have high utilization value and can be directly used in the reproduction of lithium battery positive electrode materials.

[0022] 4. The extraction method can select different metal ions and can efficiently separate different metals in the leaching solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 This is a schematic diagram of step type 1 of a method for recovering metal elements in lithium batteries using a wet extraction method according to the present invention;

[0025] Figure 2This is a schematic diagram of step type 2 of a method for recovering metal elements in lithium batteries using a wet extraction method according to the present invention;

[0026] Figure 3 This is a schematic diagram of step type 3 of a method for recovering metal elements in lithium batteries using a wet extraction method according to the present invention;

[0027] Figure 4 This is a schematic diagram of step type 4 of a method for recovering metal elements in lithium batteries using a wet extraction method according to the present invention;

[0028] Figure 5 This is a schematic diagram of step type 5 of a method of using wet extraction to recover metal elements in lithium batteries according to the present invention. DETAILED DESCRIPTION

[0029] In the present invention, "lithium battery" is a synonym for "lithium ion battery".

[0030] The present invention takes several lithium batteries on the market as examples. Lithium batteries on the market can be divided into ternary lithium batteries, lithium iron phosphate batteries, etc. according to the positive electrode material. According to the shell material, they can be divided into soft-pack lithium batteries, aluminum shell lithium batteries and steel shell lithium batteries. For soft-pack lithium batteries, aluminum-plastic film is usually used as a soft shell to encapsulate the battery. For aluminum shell lithium batteries, aluminum or aluminum alloy is used as an aluminum hard shell to encapsulate the battery. For steel shell lithium batteries, stainless steel is used as a hard shell to encapsulate the battery.

[0031] In one embodiment, the lithium battery to be recycled mainly contains the following components: positive and negative electrode current collectors, binders, positive and negative electrode active materials, porous separators, electrolytes and shells.

[0032] For example, the positive electrode current collector can be aluminum foil, and the negative electrode current collector can be copper foil. The positive electrode active material of the ternary lithium battery can be NCM (nickel, cobalt, and manganese) or NCA (nickel, cobalt, and aluminum). Different battery performances can be obtained by configuring the three elements in different proportions. For example, LiNi is used in the embodiment of the present invention. x Co y Mn z O2 and LiCoO2 are used as positive electrode active materials. The positive electrode active material of lithium iron phosphate battery can be lithium iron phosphate (LiFePO4).

[0033] The positive electrode active material particles and the binder are mixed and then evenly coated on the positive electrode current collector (aluminum foil) to form the positive electrode of the battery. Sometimes a conductive agent can also be added, that is, the positive electrode active material, the conductive agent and the binder are mixed and then evenly coated on the positive electrode current collector (aluminum foil).

[0034] The negative electrode active material is generally graphite or graphene. For example, the negative electrode active material is mixed with a binder (a conductive agent may be optionally added), and then evenly coated on the negative electrode current collector (copper foil) to form the negative electrode of the battery.

[0035] Common binders include polyvinylidene fluoride (PVDF), cellulose binders such as sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), styrene-butadiene rubber (SBR), conductive binders, etc.

[0036] Lithium battery conductive agents can be divided into traditional conductive agents (such as carbon black, conductive graphite, carbon fiber, etc.) and new conductive agents (such as carbon nanotubes, graphene and mixed conductive slurry, etc.). Conductive agents on the market include acetylene black (AB), Ketjen black (KB), vapor grown carbon fiber (VGCF), carbon nanotubes (CNT), etc.

[0037] The electrolyte contains lithium salt and organic solvent. The lithium salt commonly used in lithium batteries is LiPF6. The organic solvent is generally a carbonate organic substance, such as ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, etc.

[0038] The porous membrane is generally a polyolefin membrane, such as polyethylene (PE) or polypropylene (PP). It can be a single-layer or three-layer structure, such as a single-layer PE, a single-layer PP, a PP / PE / PP composite membrane, etc.

[0039] The goal of lithium battery recycling is to separate and / or transform the above components in the mixture using physical and / or chemical methods. First, some elements (especially high-value metal elements) can be purified and reused, and second, the pollutants emitted can be reduced.

[0040] The present invention provides a method for recovering metal elements in lithium batteries by wet extraction, which comprises the following steps:

[0041] Step 1, pre-treating the lithium battery to obtain a powder mixture containing a positive electrode material;

[0042] Step 2, acid leaching to obtain a leachate;

[0043] Step 3: If the lithium battery to be recycled contains a lithium iron phosphate battery, the solid component obtained after acid leaching and solid-liquid filtration is heated in an oxygen-containing environment and burned to remove carbon, and the remaining is iron phosphate;

[0044] Step 4: If the lithium battery to be recycled contains a ternary lithium battery, the leachate obtained after solid-liquid filtration after acid leaching is extracted, wherein P204 (diisooctyl phosphate) is used as an extractant to obtain a raffinate containing lithium elements and an organic phase containing Ni / Co / Mn elements.

[0045] For example, step 1 may include discharging the battery. Battery discharging is generally the first step in battery recycling. Completely discharging the battery pack can prevent the waste battery from concentrated heat release or short circuit during subsequent processing, thereby avoiding fire and explosion. For example, discharge can be performed by chemical methods, that is, using the positive and negative metals of the battery as the cathode and anode, and consuming the residual power in the battery through an electrolysis process in a solution. For example, a lithium-ion battery can be discharged using a sodium chloride solution as an electrolyte.

[0046] For example, step 1 may also include a disassembly step. For a battery pack, battery module, or battery system, a single battery may be obtained by disassembly. In addition, the single battery may be separated from structural parts, wires, and / or connectors (such as battery terminals) by disassembly.

[0047] For example, step 1 may also include a crushing step. The crushing step is to disassemble the battery by a crusher to obtain a crushed material. Preferably, the longest side size of the crushed material is ≤ 6 cm, more preferably ≤ 4 cm. If it is a steel shell lithium battery, a hammer crusher can be used for crushing. If it is a soft pack lithium battery, the shell can be torn by a shredder first, and then crushed by a crusher.

[0048] For example, for steel-shell lithium batteries, after crushing, step 1 may also include a magnetic separation step. Through magnetic action, ferromagnetic materials such as stainless steel can be easily separated, thereby achieving the separation and recovery of ferromagnetic materials such as stainless steel.

[0049] For example, step 1 may also include a wind selection step. For example, the crushed materials are thrown into the rising airflow, and under the action of the upward suction suspension force generated by the exhaust fan, the lightest materials float on the upper part and are first sucked out from the side pipe. This achieves the separation and recovery of the (porous) diaphragm. In addition, removing the diaphragm can also reduce the waste gas generated by the pyrolysis of organic matter in the subsequent pyrolysis.

[0050] In step 1 of the present invention, organic matter is removed. For example, the binder is removed, thereby separating the positive electrode active material from the current collector. Preferably, the binder is removed by pyrolysis (such as anaerobic pyrolysis), thereby separating the positive electrode active material from the current collector.

[0051] Preferably, step 1 of the present invention includes removing F and organic matter in the lithium battery, for example, by anaerobic pyrolysis.

[0052] In one embodiment, the present invention does not intentionally separate the electrolyte in the lithium battery, but directly feeds the electrolyte into the anaerobic pyrolysis step.

[0053] "Anoxic" means under vacuum or under the protection of protective gas (nitrogen or argon). Therefore, the reactants will not react chemically with oxygen. Since the present invention preferably burns the gas products after pyrolysis, it is preferably pyrolyzed under vacuum conditions. This is to avoid the gas products containing too much inert protective gas affecting the subsequent combustion efficiency. In one embodiment, after feeding, vacuum is evacuated until the vacuum degree in the furnace is less than 1000 Pa, more preferably less than 500 Pa, and then heating is started. In another embodiment, a combination of nitrogen replacement and vacuuming is used to remove oxygen from the furnace until the vacuum degree in the furnace is less than 2000 Pa, more preferably less than 1000 Pa, and then heating is started.

[0054] The anaerobic pyrolysis temperature in the present invention is 400-600°C, preferably 400-500°C, more preferably 430-480°C, such as 450°C. In this pyrolysis process, organic matter such as the binder is thermally decomposed, making it easy to separate the positive / negative electrode active materials from the positive / negative electrode current collectors. In addition, the lithium hexafluorophosphate in the electrolyte will also be fully pyrolyzed under this condition, and the gas products after pyrolysis include phosphorus pentafluoride (PF5) and hydrogen fluoride (HF).

[0055] Preferably, the reaction time of anaerobic pyrolysis is not less than 30 min.

[0056] In the present invention, a gas-solid filter device can be used to separate the gas and solid of the pyrolysis product. When lithium hexafluorophosphate is used as the electrolyte of the present invention, phosphorus pentafluoride (PF5) and hydrogen fluoride (HF) are produced after pyrolysis. Among them, hydrogen fluoride (HF) is highly corrosive, and phosphorus pentafluoride (PF5) will enhance the corrosiveness of hydrogen fluoride (HF). Therefore, the gas-solid filter device of the present invention needs to use a filter material that is not easily corroded by HF and PF5.

[0057] The filter material that can be used in the present invention and is not easily corroded by HF and PF5 is preferably a metal material that is resistant to corrosion by HF and PF5.

[0058] The "metal" material mentioned in the present invention can be either a single metal (pure metal) or an alloy material.

[0059] The metal materials that can be used in the present invention and are resistant to HF and PF5 corrosion include nickel, nickel alloy, and molybdenum alloy. In addition, for chromium or titanium metal, since hydrogen fluoride without water will form a passivation film on the surface of chromium or titanium, chromium, titanium, or an alloy containing chromium / titanium is also feasible. In addition, precious metals such as platinum, gold, and silver will not be corroded by HF and are also feasible, but because of their high prices, they are not preferred.

[0060] In the present invention, the preferred material is nickel, or a nickel alloy containing 50% or more nickel. The nickel alloy containing 50% or more nickel is, for example, Hastelloy, Monel, or NS3301 alloy.

[0061] Hastelloy Alloy is a nickel-based corrosion-resistant alloy, mainly divided into two categories: nickel-chromium alloy and nickel-chromium-molybdenum alloy. Hastelloy Alloy is the general name of the commercial grades of nickel-based corrosion-resistant alloys produced by Hastelloy International, USA. For example, Hastelloy C276 and Hastelloy B-2 have excellent HF corrosion resistance.

[0062] Monel alloy is an alloy made of nickel as the matrix and other elements such as copper, iron, manganese, etc., such as Monel 400 alloy (Ni68Cu28Fe).

[0063] NS3301 alloy is a nickel-chromium-molybdenum alloy with low molybdenum content, which can withstand high temperature HF gas and is easy to process and form. The chemical composition of NS3301 alloy is as follows: C ≤ 0.03 wt%, Cr 14-17 wt%, Fe ≤ 8.0 wt%, Mo 2-3wt%, Ti 0.4-0.9 wt%, P ≤ 0.03 wt%, S ≤0.02wt%, Si≤0.7wt%, Mn≤1.0wt%, and the balance is Ni and unavoidable impurities.

[0064] Among the three alloys mentioned above, NS3301 alloy is the easiest to draw, followed by Monel alloy, and Hastelloy alloy is relatively difficult to draw.

[0065] In one embodiment, the filter material of the present invention is a metal wire mesh. For example, the corrosion-resistant metal material mentioned above is used for wire drawing and then woven into a mesh. For example, metal nickel or NS3301 alloy or monel alloy is used for wire drawing and then woven into a mesh. The diameter of the wire after wire drawing is preferably less than 0.5 mm, more preferably less than 0.3 mm, and more preferably less than 0.2 mm; the mesh size (the longest side length of the mesh) is preferably less than 0.5 mm, and more preferably less than 0.3 mm. The metal wire mesh can be plain woven or corrugated. In addition, the filtering effect can be increased by stacking multiple layers of metal mesh. When multiple layers are stacked, several layers of wire mesh can be arranged cross-over and overlapped at a certain angle, or the patterns of different layers can be arranged at a certain interval.

[0066] In another embodiment, the filter material of the present invention is a porous metal material obtained by sintering powder. For example, a porous material obtained by sintering nickel powder or nickel alloy powder. In a certain embodiment, nickel powder with an average particle size of 100 microns or less is molded to form a sheet-like blank, and then vacuum sintered with a vacuum degree of less than 1 Pa, a sintering temperature of 1000-1300 ° C (such as 1200 ° C), and a sintering time of more than 1 hour to obtain a porous nickel material. The powder sintering method can easily adjust the pore size of the metal porous material. For example, the average particle size, particle size distribution, particle shape and sintering temperature of the powder may affect the pore size of the sintered metal. Therefore, compared with the metal wire mesh, the advantage of the powder sintering method is that it is convenient to prepare filter materials with smaller pore sizes (effective pore sizes).

[0067] In another embodiment, the filter material of the present invention is a porous metal material sintered on a porous substrate. The porous substrate may be a foam metal or a wire mesh. The foam metal / wire mesh has the advantages of good firmness and is not easy to break. However, the pore size of the foam metal / wire mesh is relatively large. By covering the sintered porous metal material on it, the effective pore size of the filter material can be reduced and the filtering effect can be improved. The foam metal used in the present invention is such as foam nickel. The wire mesh used in the present invention can be a wire drawn with metal nickel or NS3301 alloy or monel alloy, and then woven into a mesh, but the present invention is not limited thereto. In a certain embodiment, the wire mesh is a plain wire mesh obtained by drawing NS3301 alloy. For example, the wire after drawing preferably has a diameter of less than 0.5 mm, and the mesh size (the longest side length of the mesh) is preferably less than 0.5 mm. Then the slurry containing nickel powder is coated on the wire mesh and sintered. For example, nickel powder with a particle size of less than 10 microns, ethanol as a dispersant, and polyvinyl butyral (PVB) as a binder are mixed into a slurry. For example, the mass ratio of nickel powder: ethanol: PVB is 50-85:100:2-5. For example, the sintering temperature is 1000-1200 ℃ (such as 1100 ℃). The sintering time is not less than 1h. Thus, a sintered porous nickel material on the NS3301 alloy wire mesh is obtained. Since the slurry has a certain fluidity, it will move into the pores of the porous substrate, thereby forming an integrated filter material after sintering.

[0068] Preferably, the inner wall of the pyrolysis furnace of the present invention and the connected gas channel device are also made of metal materials that are not easily corroded by HF and PF5. For example, nickel, chromium, titanium or corresponding alloys mentioned above. For example, platinum, gold, and silver mentioned above are expensive but feasible. For example, Hastelloy, Monel alloy, or NS3301 alloy mentioned above.

[0069] In the present invention, the gas product obtained by gas-solid separation may contain one or more of the following components: H2, CH4, CO, HF, PF5, CO2.

[0070] As mentioned above, when lithium hexafluorophosphate is used as the electrolyte of the present invention, phosphorus pentafluoride (PF5) and hydrogen fluoride (HF) gas are generated after thermal decomposition.

[0071] During the pyrolysis process, the binder (such as polyvinylidene fluoride (PVDF)) pyrolyzes, so the positive and negative electrode materials fall off the current collector. The pyrolysis products of PVDF mainly include fluorides, such as hydrofluoric acid, carbon fluoride, etc., and there will also be a small amount of alkanes and hydrocarbons.

[0072] During the pyrolysis process, the organic solvent (such as ethylene carbonate, propylene carbonate, diethyl carbonate) in the electrolyte evaporates in the form of steam or decomposes into carbon monoxide, carbon dioxide, etc.

[0073] In addition, the mixture entering the pyrolysis may contain residual separators (polyethylene (PE) or polypropylene (PP). After pyrolysis, the carbon chain breaks and produces hydrogen, methane, hydrocarbons, aldehydes, carbon monoxide, etc.

[0074] In the present invention, the gas product obtained after gas-solid separation can be sent to the combustion furnace.

[0075] In the present invention, it is preferred that the high-temperature gas after pyrolysis is directly sent to the combustion furnace after gas-solid separation without an additional cooling step. That is, the high-temperature gas passes through the gas-solid filtration device at a high temperature (above 200°C, preferably above 300°C), and then is sent to the combustion furnace at a high temperature (above 200°C, preferably above 300°C). C. In this way, the heat of the flue gas can be fully utilized to promote combustion, thereby saving energy. In this way, the waste heat of the flue gas can be fully utilized to promote combustion, which is more energy-saving.

[0076] Preferably, oxygen-enriched combustion technology is adopted, preferably oxygen-enriched air with an oxygen content of 25% or more, or even 35% or more, or pure oxygen is used as the combustion-supporting gas. The oxygen excess coefficient is 100% or more, or even 120% or more. In one embodiment of the present invention, the high-temperature gas product with a temperature of more than 200°C is sprayed into the combustion furnace in batches, and spontaneous combustion will occur under oxygen-enriched conditions.

[0077] In a preferred embodiment, the flue gas after combustion uses a flue gas heat exchanger to recover waste heat.

[0078] In the present invention, the combustion products of the gas phase components are acidic substances (carbonic acid, phosphoric acid, hydrofluoric acid, etc.), and therefore, the acid radicals therein can be absorbed by an alkaline solution (such as lime milk). The salts thus produced, such as calcium salts, can be used for industrial applications, such as producing calcium fluoride, calcium phosphate, etc.

[0079] In one embodiment, the flue gas generated after combustion is deacidified by alkaline solution. For example, a flue gas purification device is used. For example, an injection device is used to spray alkaline solution into the flue gas of the purification furnace to perform a deacidification reaction. The alkaline solution can be lime water, such as a saturated aqueous solution of calcium hydroxide. Therefore, the phosphorus-containing acidic gas in the flue gas is converted into calcium phosphate, the fluorine-containing acidic gas in the flue gas is converted into calcium fluoride, and the like.

[0080] In one embodiment, in the present invention, the gas after deacidification by alkali solution can meet the emission standards after simple post-treatment (such as dust removal by dust collector or activated carbon adsorption), so it can be directly discharged. For example, various dust collectors in the prior art can separate and remove particulate dust in the flue gas to meet the emission standards required by environmental protection. For example, an activated carbon adsorption tower can purify and remove particulate pollutants in the flue gas to meet the emission standards required by environmental protection.

[0081] In another embodiment, a dust removal device, such as a cyclone dust removal tower and / or a bag dust removal tower, may be provided before the alkaline solution is deacidified to pre-treat some dust particles.

[0082] In another alternative embodiment, the gas product obtained by gas-solid separation after pyrolysis is first passed through an alkali solution (to remove HF and PF5) and then sent to a combustion furnace for combustion (to remove H2, CH4, and CO). Therefore, the main products after combustion are water and carbon dioxide. Therefore, if the dust particles after combustion meet the standards, the waste gas can be discharged directly; if there are too many dust particles after combustion, the waste gas can be discharged after dust removal to meet the standards.

[0083] After pyrolysis and gas-solid separation, the solid product of the pyrolysis furnace is taken out to recover the metal elements; the metal elements include but are not limited to one or more of the following: lithium, aluminum, copper, iron, nickel, cobalt, and manganese.

[0084] In the present invention, the solid product after pyrolysis mainly has the following components: current collector (such as aluminum foil, copper foil), carbon (from negative electrode active material, and some organic matter pyrolysis product), positive electrode material (such as lithium iron phosphate or ternary material).

[0085] Preferably, step 1 of the present invention further comprises a physical sorting step. The current collector metal sheet (copper foil and / or aluminum foil) can be separated by physical sorting, and the remaining is a powdery mixture. The metal sheet and the powder can be separated by physical screening, such as vibration screening.

[0086] Preferably, two or more vibration screenings can be used. First, larger particles (larger metal flakes) are initially screened out, then medium particles (medium metal flakes) are screened out, and finally powder (powdered mixture) is left. In one embodiment, the first screening uses a 10-40 mesh screen, and the second screening uses a 100-200 mesh screen.

[0087] The metal flakes obtained by physical screening are generally copper foil and / or aluminum foil. Since aluminum foil is lighter and copper foil is heavier, copper foil and aluminum foil can be further separated by a shaking table.

[0088] In the present invention, the powdered mixture obtained by physical sieving contains carbon from the negative electrode active material in addition to the positive electrode material.

[0089] The present invention recovers metal elements from powder (powdered mixture) using a wet method.

[0090] The present invention proposes a method for recovering metal elements by a wet process, comprising the following steps:

[0091] Step 2, acid leaching to obtain a leachate;

[0092] Step 3: If the lithium battery to be recycled contains a lithium iron phosphate battery, the solid component obtained after acid leaching and solid-liquid filtration is heated in an oxygen-containing environment and burned to remove carbon, and the remaining is iron phosphate;

[0093] Step 4: If the lithium battery to be recycled contains a ternary lithium battery, the leachate obtained after solid-liquid filtration after acid leaching is extracted, wherein P204 (diisooctyl phosphate) is used as an extractant to obtain a raffinate containing lithium elements and an organic phase containing Ni / Co / Mn elements.

[0094] The acid leaching of the present invention preferably uses the following process: using an inorganic acid and an oxidant to leach the metal element. The inorganic acid is preferably sulfuric acid or hydrochloric acid. The oxidant is preferably hydrogen peroxide. For example, a mixed aqueous solution containing 0.5-5 mol / L (preferably 1-2 mol / L) sulfuric acid and 0.5-5 mol / L (preferably 1-2 mol / L) hydrogen peroxide is prepared and added to the powder, wherein the solid-liquid mass ratio (powder: mixed aqueous solution) is 1:2-20, preferably 1:5-10. Preferably, heating (for example, heating to 50°C-100°C, preferably 50°C-80°C, such as 60°C) and stirring (for example, stirring speed 50-250 r / min, such as 120 r / min) during the leaching process helps the lithium element to be leached quickly and fully. The duration of the leaching process is generally 30 minutes or more, preferably 1 hour or more.

[0095] The present invention does not need to separate the ternary lithium battery and the lithium iron phosphate battery in the pretreatment, but can mix the electrode active materials of the two batteries and send them to the acid leaching together, which saves more raw materials such as H2O2.

[0096] After acid leaching, lithium element is leached into the leaching solution.

[0097] If the lithium battery to be recycled contains lithium iron phosphate batteries, when the lithium element is leached out by acid leaching, the iron and phosphorus elements still exist in the solid phase. The solid component (filter residue) obtained after solid-liquid filtration after acid leaching mainly contains iron phosphate (FePO4) and carbon powder. Heating in an oxygen-containing environment and burning to remove carbon. What remains is iron phosphate. For example, it can be heated in an air or oxygen atmosphere at 600-700℃ for 2-4 hours.

[0098] The iron phosphate obtained by the invention can be used as a raw material for preparing positive electrode active materials of lithium iron phosphate batteries.

[0099] If the lithium battery to be recycled contains a Ni / Co / Mn ternary lithium battery, the Ni / Co / Mn elements will also be leached out under acid leaching.

[0100] For the filtrate (leaching solution) obtained after solid-liquid filtration after acid leaching, the present invention uses an extractant to separate the Li element and the ternary metal elements (Ni / Co / Mn). The present invention preferably uses P204 (diisooctyl phosphate) for extraction, which can obtain a raffinate containing lithium elements and an organic phase containing Ni / Co / Mn elements.

[0101] Afterwards, the organic phase containing Ni / Co / Mn may be stripped using an aqueous sulfuric acid solution (eg, 15-20 wt % sulfuric acid, such as 18 wt % sulfuric acid) to obtain a first stripping solution containing nickel, cobalt and manganese.

[0102] In addition, lithium can be obtained from the lithium-containing raffinate. For example, by adding a precipitant, lithium salt precipitation can be obtained.

[0103] For example, if sodium carbonate is used as a precipitant, lithium carbonate will be precipitated. Because the solubility of sodium carbonate increases with increasing temperature, while the solubility of lithium carbonate decreases with increasing temperature, choosing a temperature close to boiling (such as above 90°C (for example, 95°C)) when precipitating lithium will achieve better results. For example, heat a 200-500g / L (such as 300g / L) sodium carbonate aqueous solution to above 90°C (for example, 95°C), and then add lithium solution. Keep the constant temperature for more than 30 minutes.

[0104] In one embodiment, the lithium concentration in the lithium solution is first determined, and then the amount of sodium carbonate used is in excess of 10% or more.

[0105] In another embodiment, after a period of constant temperature precipitation at above 90° C., the carbonate concentration in the mother liquor is sampled and analyzed to control the carbonate concentration at 13-18 g / L. If the carbonate concentration is too high, lithium solution is added, and if it is too low, sodium carbonate aqueous solution is added.

[0106] If the lithium battery to be recycled does not contain a ternary lithium battery, but only a lithium iron phosphate battery, during the acid leaching process of the present invention, the lithium element is leached into the leachate, while the iron and phosphorus remain in the solid phase. In this case, the leachate is rich in soluble lithium salts (such as lithium sulfate or lithium chloride), so it can be directly used to obtain lithium elements. For example, by adding a precipitant, a lithium salt precipitate can be obtained. For example, using sodium carbonate as a precipitant will obtain a lithium carbonate precipitate.

[0107] The lithium carbonate obtained by the present invention has wide industrial applications, for example, it can be used as a raw material for lithium batteries.

[0108] The Ni / Co / Mn elements in the first stripping solution do not need to be further separated, because the first stripping solution can be directly used as a raw material for preparing a ternary positive electrode active material.

[0109] In another embodiment, Ni / Co / Mn can also be further separated and purified by extraction. Preferably, the first stripping solution (containing nickel, cobalt and manganese) is sent to extraction, wherein the extractant is a mixture of P2O4 and sulfonated kerosene (preferably the content of sulfonated kerosene is 60-80% (v / v), such as 30% P2O4 + 70% sulfonated kerosene) and is subjected to alkali saponification (preferably the pH value after saponification is 7-8). Thus, an organic phase containing manganese and a second raffinate (containing nickel and cobalt) are obtained.

[0110] Since kerosene is obtained by primary distillation of petroleum, it contains a large amount of unsaturated hydrocarbons, sulfur and impurities. People add excess concentrated sulfuric acid (to react with the unsaturated alkanes in kerosene to undergo sulfonation), then use water to remove the excess sulfuric acid, use saturated sodium bicarbonate to neutralize the residual acid, and finally use anhydrous sodium sulfate to remove water. In this way, sulfonated kerosene can be obtained. Sulfonated kerosene has a high content of stable saturated alkanes and relatively few impurities, which can improve the extraction rate.

[0111] Optionally, the manganese-containing organic phase is stripped with an aqueous sulfuric acid solution (e.g., 15-20 wt % sulfuric acid, such as 18 wt % sulfuric acid) to obtain an aqueous solution containing manganese sulfate. Preferably, the pH value of the aqueous phase at the stripping outlet is 4-4.5.

[0112] Optionally, the second raffinate (containing nickel and cobalt) is subjected to acidic saponification extraction using P507 (2-ethylhexyl phosphoric acid) extractant. The saponification rate of the extractant is 60% to 70%; the pH of the extractant during extraction is 3 to 3.5. A cobalt-containing organic phase and a third raffinate (containing nickel) are obtained.

[0113] Optionally, the cobalt-containing organic phase (containing cobalt) is stripped with hydrochloric acid (preferably with a hydrochloric acid concentration of 4-5 mol / L) to obtain an aqueous solution containing cobalt chloride. Preferably, the pH value of the aqueous phase at the stripping outlet is 4-4.5.

[0114] In this way, lithium, nickel, cobalt and manganese can be separated from each other.

[0115] In order to better understand the present invention, specific examples are provided as follows. These examples are only used to illustrate the present invention and should not be construed as limiting the present invention. Example

[0116] Recycling lithium iron phosphate batteries using pyrolysis + wet method

[0117] The main components of the lithium iron phosphate battery in this embodiment; the positive electrode active material (lithium iron phosphate), the conductive agent (acetylene black) and the binder (polyvinylidene fluoride (PVDF)) are mixed and coated on the current collector Al foil to form the positive electrode. The negative electrode active material (graphite), the conductive agent (acetylene black) and the binder (styrene butadiene rubber (SBR)) are mixed and coated on the Cu foil to form the negative electrode. The electrolyte contains lithium salt (LiPF6) and organic solvent (dimethyl carbonate). The porous diaphragm is a polyethylene (PE) film. The battery casing is stainless steel.

[0118] The recycling method of this embodiment comprises the following steps:

[0119] 1. Battery discharge.

[0120] 2. Use a crusher to crush the material. The longest side of the crushed material should be ≤ 4 cm.

[0121] 3. Magnetic separation to separate ferromagnetic materials (stainless steel shell).

[0122] 4. Remove (recycle) the diaphragm material by air separation.

[0123] 5. Pyrolysis under vacuum. The vacuum degree in the furnace before heating is less than 500 Pa. The temperature in the pyrolysis furnace is controlled at 450±20℃ during pyrolysis. The pyrolysis time is 1 hour.

[0124] 6. Open the pyrolysis furnace outlet valve and draw the pyrolysis gas products into the outlet duct. After passing through the gas-solid filtration device, the gas products are sent to the combustion furnace and burned in an oxygen-rich atmosphere (the oxygen content of the combustion-supporting gas is 25% or above), with an oxygen excess coefficient of 100%.

[0125] 7. The flue gas after combustion is used to recover waste heat through the flue gas heat exchanger.

[0126] 8. The flue gas is deacidified by saturated lime water and passed through an activated carbon adsorption tower to meet emission standards.

[0127] 9. Take out the solid product after pyrolysis, separate the current collector metal sheet (copper foil and / or aluminum foil) through two-stage vibration screening, and the remaining is a powdery mixture (powder).

[0128] 10. The powder is subjected to acid leaching to obtain a leachate; in the acid leaching, a mixed aqueous solution containing 1.2 mol / L H2SO4 and 1.3 mol / LH2O2 is used, the mass ratio (powder: mixed aqueous solution) is 1:8, the leaching temperature is 60°C, the leaching time is 1 h, and the stirring speed is 120 r / min.

[0129] 11. The solid component obtained after acid leaching and solid-liquid filtration is heated to 600° C. in an oxygen-containing environment, and burned to remove carbon to obtain iron phosphate.

[0130] 12. The leaching solution obtained after solid-liquid filtration after acid leaching is used as lithium solution to recover lithium element. In which, an excess of 10% of a 300 g / L sodium carbonate aqueous solution is heated to 95°C, and then the lithium solution is added and kept at a constant temperature for more than 30 minutes. Lithium carbonate precipitate is obtained. Example

[0131] Recycling ternary lithium batteries using pyrolysis + wet method

[0132] The positive electrode active material of the ternary lithium battery in this embodiment is LiNi x Co y Mn z O2 and LiCoO2, and the rest are similar to the lithium iron phosphate battery in Example 1.

[0133] The recycling method of this embodiment comprises the following steps:

[0134] 1. Battery discharge.

[0135] 2. Use a crusher to crush the material. The longest side of the crushed material should be ≤ 4 cm.

[0136] 3. Magnetic separation to separate ferromagnetic materials (stainless steel shell).

[0137] 4. Remove (recycle) the diaphragm material by air separation.

[0138] 5. Pyrolysis under vacuum. The vacuum degree in the furnace before heating is less than 500 Pa. The temperature in the pyrolysis furnace is controlled at 450±20℃ during pyrolysis. The pyrolysis time is 1 hour.

[0139] 6. Open the pyrolysis furnace outlet valve and draw the pyrolysis gas products into the outlet duct. After passing through the gas-solid filtration device, the gas products are sent to the combustion furnace and burned in an oxygen-rich atmosphere (the oxygen content of the combustion-supporting gas is 25% or above), with an oxygen excess coefficient of 100%.

[0140] 7. The flue gas after combustion is used to recover waste heat through the flue gas heat exchanger.

[0141] 8. The flue gas is deacidified by saturated lime water and passed through an activated carbon adsorption tower to meet emission standards.

[0142] 9. Take out the solid product after pyrolysis, separate the current collector metal sheet (copper foil and / or aluminum foil) through two-stage vibration screening, and the remaining is a powdery mixture (powder).

[0143] 10. The powder is subjected to acid leaching to obtain a leachate; in the acid leaching, a mixed aqueous solution containing 1.2 mol / L H2SO4 and 1.3 mol / LH2O2 is used, the mass ratio (powder: mixed aqueous solution) is 1:8, the leaching temperature is 60°C, the leaching time is 1 h, and the stirring speed is 120 r / min.

[0144] 11. The leaching solution obtained after acid leaching is extracted, wherein P204 (diisooctyl phosphate) is used as an extractant to obtain a raffinate containing lithium elements and an organic phase containing Ni / Co / Mn elements.

[0145] 12. The organic phase containing Ni / Co / Mn elements is stripped using an aqueous sulfuric acid solution (18 wt % sulfuric acid) as a stripping agent to obtain a first stripping solution containing nickel, cobalt and manganese.

[0146] 13. Using sodium carbonate as a precipitant, lithium carbonate precipitate is obtained from the raffinate containing lithium. Herein, a 10% excess of 300 g / L sodium carbonate aqueous solution is heated to 95°C, and then lithium solution is added and kept at a constant temperature for more than 30 minutes. Example

[0147] Recycling hybrid lithium batteries using pyrolysis + wet method

[0148] The two lithium batteries are combined into a hybrid lithium battery, which includes the ternary lithium battery (positive electrode LiNi x Co y Mn z O2 and LiCoO2), including the lithium iron phosphate battery in Example 1. The battery shells are all stainless steel shells.

[0149] The recycling method of this embodiment comprises the following steps:

[0150] 1. Battery discharge.

[0151] 2. Use a crusher to crush the material. The longest side of the crushed material should be ≤ 4 cm.

[0152] 3. Magnetic separation to separate ferromagnetic materials (stainless steel shell).

[0153] 4. Remove (recycle) the diaphragm material by air separation.

[0154] 5. Pyrolysis under vacuum. The vacuum degree in the furnace before heating is less than 500 Pa. The temperature in the pyrolysis furnace is controlled at 450±20℃ during pyrolysis. The pyrolysis time is 1 hour.

[0155] 6. Open the pyrolysis furnace outlet valve and draw the pyrolysis gas products into the outlet duct. After passing through the gas-solid filtration device, the gas products are sent to the combustion furnace and burned in an oxygen-rich atmosphere (the oxygen content of the combustion-supporting gas is 25% or above), with an oxygen excess coefficient of 100%.

[0156] 7. The flue gas after combustion is used to recover waste heat through the flue gas heat exchanger.

[0157] 8. The flue gas is deacidified by saturated lime water and passed through an activated carbon adsorption tower to meet emission standards.

[0158] 9. Take out the solid product after pyrolysis, separate the current collector metal sheet (copper foil and / or aluminum foil) through two-stage vibration screening, and the remaining is a powdery mixture (powder).

[0159] 10. The powder is subjected to acid leaching to obtain a leachate; in the acid leaching, a mixed aqueous solution containing 1.2 mol / L H2SO4 and 1.3 mol / LH2O2 is used, the mass ratio (powder: mixed aqueous solution) is 1:8, the leaching temperature is 60°C, the leaching time is 1 h, and the stirring speed is 120 r / min.

[0160] 11. The solid component obtained after acid leaching and solid-liquid filtration is heated to 600° C. in an oxygen-containing environment, and burned to remove carbon to obtain iron phosphate.

[0161] 12. The leaching solution obtained after acid leaching is extracted, wherein P204 (diisooctyl phosphate) is used as an extractant to obtain a raffinate containing lithium elements and an organic phase containing Ni / Co / Mn elements)

[0162] 13. The organic phase containing Ni / Co / Mn elements is stripped using an aqueous sulfuric acid solution (18 wt % sulfuric acid) as a stripping agent to obtain a first stripping solution containing nickel, cobalt and manganese.

[0163] 14. Using sodium carbonate as a precipitant, lithium carbonate precipitate is obtained from the raffinate containing lithium. Here, a 10% excess of 300 g / L sodium carbonate aqueous solution is heated to 95°C, and then lithium solution is added and kept at a constant temperature for more than 30 minutes. Example

[0164] The Ni / Co / Mn elements in the first stripping solution obtained in Example 2 or 3 are further separated by extraction.

[0165] It includes the following steps:

[0166] 1. The first stripping solution (containing nickel, cobalt and manganese) is sent to extraction, wherein the extractant is a mixture of P2O4 and sulfonated kerosene (30% P2O4 + 70% sulfonated kerosene (v / v)) and is subjected to alkali saponification (pH value after saponification is 7-8). Thus, an organic phase containing manganese and a second raffinate (containing nickel and cobalt) are obtained.

[0167] 2. The manganese-containing organic phase is stripped with an 18 wt% sulfuric acid aqueous solution to obtain an aqueous solution containing manganese sulfate. The pH value of the stripping outlet aqueous phase is 4-4.5.

[0168] 3. The second raffinate (containing nickel and cobalt) is extracted with P507 (2-ethylhexyl phosphoric acid) extractant, acidic saponification extraction. The extractant saponification rate is 65%; the extractant pH is 3-3.5 during extraction. The cobalt-containing organic phase and the third raffinate (containing nickel) are obtained.

[0169] 4. The cobalt-containing organic phase (containing cobalt) is stripped with 4 mol / L hydrochloric acid to obtain an aqueous solution containing cobalt chloride. The pH value of the stripping outlet aqueous phase is 4-4.5.

Claims

1. A method for recovering metal elements in lithium batteries by wet extraction, comprising the following steps: Step 1, pre-treating the lithium battery to obtain a powder mixture containing a positive electrode material; including removing the binder and separating the positive electrode active material and the current collector; Step 2, acid leaching to obtain a leachate; Step 3, if the lithium battery to be recycled contains a lithium iron phosphate battery, the solid component obtained after acid leaching and solid-liquid filtration is heated in an oxygen-containing environment and burned to remove carbon, and the remaining is iron phosphate; the iron phosphate can be used as a raw material for preparing the positive electrode material of the lithium iron phosphate battery; Step 4, if the lithium battery to be recycled contains a ternary lithium battery, the leachate obtained after solid-liquid filtration after acid leaching is extracted at a pH of 1.5-2.5 using 0.5-1.5 mol / L diisooctyl phosphate as an extractant at a temperature of 50-70°C, wherein diisooctyl phosphate is used as an extractant to obtain a raffinate containing lithium elements and an organic phase containing Ni / Co / Mn elements; the organic phase containing Ni / Co / Mn is stripped with an aqueous sulfuric acid solution to obtain a first stripping solution containing Ni / Co / Mn; sodium carbonate is added as a precipitant to the lithium-containing raffinate to obtain a lithium carbonate precipitate; the obtained first stripping solution containing Ni / Co / Mn can be used as a raw material for preparing a ternary positive electrode material.

2. A method for recovering metal elements in lithium batteries by wet extraction according to claim 1, wherein: In step 1, the binder is removed by anaerobic pyrolysis to separate the positive electrode active material and the current collector.

3. A method for recovering metal elements in lithium batteries using wet extraction according to claim 1, wherein step 1 includes physical sorting, and the current collector metal sheet is separated by physical sorting, and the remaining is a powder mixture containing positive electrode materials.

4. According to claim 1, a method for recovering metal elements in lithium batteries using wet extraction, wherein step 1 does not include the step of separating the positive electrode material and the negative electrode material, so the powder mixture obtained in step 1 contains positive electrode material and carbon.

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