Recovery of phosphorus and iron compounds from LFP- and / or LFMP-containing materials

Abstract

The present invention relates to a method for obtaining phosphorus and iron compounds from LFP-containing and / or LFMP-containing materials, characterized in that: i) reacting an LFP-containing and / or LFMP-containing material with chlorine gas at a temperature of 300 to 900°C in the presence of a carbon source; and ii) conducting the chlorine-phosphorus compounds formed, in particular phosphorus oxychloride and any phosphorus trichloride, and iron chloride, into an off-gas stream; and iii) iron chloride and iv) Chlorine-phosphorus compounds are separated from the off-gas stream at various temperatures.

Description

[Technical Field]

[0001] The present invention relates to a method for recovering phosphorus and iron compounds from LFP-containing and / or LFMP-containing materials. [Background technology]

[0002] Lithium iron phosphate (LFP) and lithium iron manganese phosphate (LFMP), as well as modifications thereof which may be doped with further elements, in particular metals, are used as cathode materials (also called cathode active materials (CAM)) for batteries and are preferred for use in electric vehicles and stationary batteries.

[0003] The lithium-ion battery market is growing rapidly, and since every car battery contains between 100 and 200 kg of CAM, there are also large amounts of valuable elements such as lithium, phosphorus, and iron, as well as other components, which means that recycling such used batteries to recover their raw materials is extremely important.

[0004] This typically involves mechanically disassembling the battery (if possible) and crushing the remainder, which includes the cathode and anode materials, various binders, and additional components, into a mass that is black due to the dark LFP and graphite-containing anode material and is therefore referred to as "black mass." The black mass may also contain other battery components, such as metal residues, due to technical incompleteness of the separation.

[0005] Several recycling approaches have been pursued to recover valuable components from the black material.

[0006] Various approaches have been proposed in the literature for recycling LFP-containing black materials or pure used LFP. For example, in (Non-Patent Document 1), used LFP-containing materials are subjected to a heat treatment to obtain a low-Li material, which is then reconverted into LFP by appropriately adding lithium carbonate and a carbon source. However, the low-Li starting material thus obtained is highly unstable, and therefore the resulting LFP is also unstable. The same applies to the process described in (Non-Patent Document 2), but in this case, the recycled LFP results in a mixture of old and new LFP, along with specific Li, Fe, and P reactants and a carbon source, which is also difficult to implement precisely.

[0007] In another method, the iron(II) present in LFP is oxidized in another way, for example with hypochlorite or peroxodisulfate, to iron(III), and the lithium released from its crystalline form is extracted, as in (Non-Patent Document 3). However, the iron phosphates obtained in the same way, which are typically contaminated, can only be used to a very limited extent in the production of LFP due to the impurities present.

[0008] Similar drawbacks apply to processes involving dissolving LFP-containing materials in strong acids, as described, for example, in (Non-Patent Document 4), which also result in contaminated iron phosphate.

[0009] Other recycling approaches, such as that described in US Pat. No. 5,629,393, recover individual components through pyrometallurgical processes that involve large energy inputs at ultra-high temperatures.

[0010] Although most LFP recycling methods aim at recovering lithium, the weight ratios of iron and phosphorus are much higher than that of lithium, based on the total amount of black material. Therefore, black material is also an interesting source of raw materials for these components, which can be reused as feedstock for recycling purposes in the production of novel cathode materials.

[0011] For example, Patent Document 2 describes the aqueous treatment of black materials, but the method employed there generates large amounts of waste, often results in incomplete separation of elements, and the resulting reaction products are not always pure.

[0012] Patent Document 3 describes a process for treating LFP, in which LFP is mixed with a chloride, preferably MgCl, and first calcined at 400°C. The resulting reaction product is then reacted with chlorine gas at 400°C to obtain an off-gas stream, apparently containing exclusively Fe(III) chloride, from which it is separated by resublimation. The residue is absorbed in water, dissolving the LiCl (which enters the filtrate), and Mg phosphate or other alkaline earth metal phosphates remain in the solid filtration residue.

[0013] Patent document 4 describes a two-stage reaction in which, in the first step, conversion from red-hot molten slag with chlorine proceeds to produce iron and manganese in the form of their chlorides, which are removed by resublimation. In the second step, the residue thus obtained from the first chlorination step is reacted with charcoal and chlorine at 700-800 °C, producing only phosphorus oxychloride, which is collected. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] U.S. Patent Application Publication No. 20220263147A1 [Patent Document 2] International Publication No. 2021174348A1 Brochure [Patent Document 3] Chinese Patent No. 107180999 [Patent Document 4] German Patent No. 332118 [Non-patent literature]

[0015] [Non-Patent Document 1] Qifang Sun et al,Journal of Alloys and Compounds,818(2020)153292 [Non-patent document 2] Lingyu Guan et al., Renewable Energy, 175(2021)559-567 [Non-patent document 3] Liu,Fei et al,JOM,vol.74,5,1934-1944,2022 [Non-patent document 4] Kumar et al,Waste Management,113(2020),32-40 Summary of the Invention [Problem to be solved by the invention]

[0016] The problem addressed by the present invention is therefore to find a method for obtaining very high purity phosphorus and iron compounds from LFP-containing and / or LFMP-containing materials without generating large amounts of waste streams. [Means for solving the problem]

[0017] The present invention therefore relates to a method for obtaining phosphorus and iron compounds from LFP-containing and / or LFMP-containing materials, characterized in that: i) reacting an LFP-containing and / or LFMP-containing material with chlorine gas (Cl) at a temperature of 300 to 900°C in the presence of a carbon source; and ii) conducting the chlorine-phosphorus compounds formed, in particular phosphorus oxychloride and any phosphorus trichloride, and iron chloride, into an off-gas stream; and iii) iron chloride, preferably by resublimation, and iv) Chlorine-phosphorus compounds, particularly phosphorus oxychloride and optionally phosphorus trichloride, are separated from the off-gas stream, preferably by condensation at various temperatures. DETAILED DESCRIPTION OF THE INVENTION

[0018] LFP-containing and / or LFMP-containing substances The LFP- and / or LFMP-containing substances used for the method according to the invention are in particular substances which contain LFP and / or LFMP in a proportion of 5% to 100% by weight, preferably 40% to 99% by weight, in particular 50% to 99% by weight, more preferably 70% to 99% by weight.

[0019] The description of the composition of the substances used can preferably also be made by measuring the weight proportion of certain elements in the LFP- and / or LFMP-containing substances, in each case based on the amount of LFP- and / or LFMP-containing substance, with the substances used preferably containing the following amounts: 1 wt% to 36 wt% Fe, 1% to 20% by weight of P, 0% to 35% by weight of Mn, 1 wt% to 8 wt% Li, and 1% to 55% by weight, preferably 1% to 40% by weight, especially 1% to 30% by weight of carbon.

[0020] These amounts may primarily come from the LFP or LFMP, but may also result from other components of the substances used, such as residual metal components, the contents of which are preferably determined by conventional elemental analysis methods.

[0021] Preferably, the material used further comprises 1% to 55% by weight, preferably 1% to 40% by weight, in particular 1% to 30% by weight, of carbon, in particular graphite and / or carbon black.

[0022] It is preferred that the total amount of LFP and / or LFMP and carbon in the LFP-containing and / or LFMP-containing material is greater than 70 wt %, preferably greater than 80 wt %, more preferably greater than 90 wt %.

[0023] It is preferred that the LFP-containing and / or LFMP-containing material has a carbon / phosphorus molar ratio of 1 or greater, preferably 1-20, more preferably 1-10, especially 1-5, and most preferably 1-4.

[0024] If the material used contains less than 1 mole of carbon per mole of phosphorus, preferably based on the LFP and LFMP present in the material, it is preferred to add sufficient carbon to the material prior to reaction to achieve the desired ratio.

[0025] Examples of carbon sources include carbon monoxide, phosgene, CCl4, and / or preferably graphite or carbon black.

[0026] It is preferred that the material used contains at least 1 mol, preferably 1 to 4 mol, of carbon per mol of phosphorus.

[0027] Preferably, 0% to 15% by weight, preferably 0% to 5% by weight of metals, in particular Al, Cu, Co and Ni, may also be present.

[0028] It is preferred that the material used contains preferably less than 10% by weight, in particular less than 1% by weight, more preferably less than 0.1% by weight of polymer particles, in particular plastics such as polyethylene and / or polypropylene.

[0029] It is also preferred that the materials used contain less than 5% by weight of PVDF (polyvinylidene fluoride) and / or other binders, such as carboxymethylcellulose and / or alginate, with the total binder content preferably being less than 5% by weight.

[0030] The VOC content of the substances used is preferably less than 1% by weight, in particular less than 0.1% by weight, more preferably less than 0.01% by weight. VOCs (volatile organic compounds) are understood to mean organic compounds which preferably have a boiling point in the range of 50 to 260°C at a standard pressure of 101.3 kPa.

[0031] Preferably, the LFP-containing and / or LFMP-containing material used is black material from shredded batteries.

[0032] The substances used preferably have an average particle size of 0.1 μm to 10 mm. Depending on the size, the particle size can be easily determined by sieving or, for smaller particles, by laser diffraction or laser scattering. The most suitable method to use in each case is known to those skilled in the art.

[0033] The LFP-containing and / or LFMP-containing materials used may be coated materials, preferably including carbon, especially graphite, and metal oxides.

[0034] If the material used has a binder content of more than 1% by weight, based on the material, it is preferable to carry out a leaching process by treatment with organic solvents, in particular acetone, ethyl acetate, methyl ethyl ketone, tetrahydrofuran (THF), ethyl acetoacetate, acetylacetone, dioxane and / or acetic anhydride, and mixtures thereof, in order to reduce the binder content to less than 0.1% by weight.

[0035] If the material contains more than 1% by weight of polymer, especially plastic, it is advantageous to first subject the material to a heat treatment, preferably under inert gas, at a temperature of 300-600° C. to reduce the polymer content to less than 0.1% by weight. If the binder content may be greater than 1% by weight, it can be reduced to less than 0.1% by weight by heat treatment, preferably under inert gas, at a temperature of 300-700° C., in addition to, or alternatively or in addition to, leaching with organic solvents.

[0036] reactor The materials used in the process according to the invention are preferably introduced into a reactor equipped with a layer that is durable under the set reaction conditions. Preferred reactor materials are nickel- or graphite-coated reactors. The reactor used may be a tubular reactor, such as a rotating barrel reactor, or other reactor. Particularly preferred are reactors that allow the movement of materials during the reaction and ensure highly effective contact between the materials and chlorine gas. Reactions in fluidized bed and rotating barrel reactors, or extruder devices using screw extrusion, are preferred.

[0037] In the case of a tubular reactor, the length of the reactor is preferably 0.2 to 40 m. The residence time in the reactor during the reaction is generally determined by the temperature and the feasibility of contacting the substance with chlorine gas. The residence time in the reactor can be, for example, 1 minute to 5 hours. The process according to the present invention can be carried out in a batch or continuous manner.

[0038] method: The reaction is preferably carried out in an air-free atmosphere, and any air present in the reactor is preferably replaced by an inert gas, such as nitrogen.

[0039] The reaction with chlorine gas is carried out at temperatures of 300 to 900° C., in particular 350 to 750° C. When the process is carried out at temperatures of 300 to 320° C., it is advantageous to then drive off any iron chloride that has not been completely discharged from the reactor by increasing the temperature to 350 to 400° C. The temperature is preferably increased after the content of phosphorus compounds in the off-gas, measured using a gas-phase IR spectrometer and converted into the corresponding weight percentage, is less than 0.1% by weight, in particular less than 0.01% by weight.

[0040] Chlorine gas can be contacted with the material in various ways. Preferably, chlorine is passed over the material, with the material being kept in motion during the reaction to ensure effective conversion. This can be carried out in a rotary tube kiln or paddle dryer, in which the material is kept in motion. Alternatively, chlorine gas can be passed through the material, which can be achieved, for example, in a fluidized or fixed bed. For this purpose, the material may optionally be previously subjected to shaping, such as compaction or pelletization.

[0041] The reactor preferably has an outlet for an off-gas stream, which comprises gaseous reaction products, volatile components of the material, and excess chlorine gas, which can be simultaneously withdrawn from the reaction space.

[0042] The reaction is preferably terminated when the proportion of phosphorus compounds, measured using a gas phase IR spectrometer and converted into the corresponding weight percentage, is less than 0.1% by weight, in particular less than 0.01% by weight.

[0043] Step ii) The off-gas stream contains chlorine-phosphorus compounds, particularly phosphorus oxychloride and optionally phosphorus trichloride, as well as gaseous iron(III) chloride and possibly also AlCl3 if aluminum is present in the materials used.

[0044] Step iii) At reaction temperatures of 300-320°C, the proportion of iron chloride in the off-gas stream is generally quite low, but increases only at higher temperatures of 350-400°C. Iron(III) chloride and AlCl3 (if aluminum is present in the materials used) can be separated independently from each other from the off-gas stream, preferably by resublimation onto surfaces cooled to different temperatures. If iron chloride is present in the off-gas stream together with AlCl3, the boiling points of the chlorides are sufficiently different that they can be resublimated differentially onto different surfaces at different temperatures, thereby achieving a very clear separation.

[0045] The preferred deposition temperature for FeCl3 is 307°C or less, particularly 150 to 300°C, and for AlCl3 it is 150°C or less, particularly 110 to 149°C.

[0046] The iron recovered by the process according to the invention in the form of iron(III) chloride is already of very high purity and can then be converted into the desired source form of iron, such as iron sulfate, iron nitrate, iron phosphate, or a wide variety of different forms of iron oxide, for example, for the de novo production of LFP and / or LFMP.

[0047] Alternatively, iron chloride can be introduced directly as a gas stream into an aqueous medium containing sulfuric acid, nitric acid, or phosphoric acid to form the corresponding iron(III) sulfate, nitrate, or phosphate, without being separated by resublimation. If necessary, a suitable reducing agent is further used in the reaction to reach iron(II) sulfate, iron(II) nitrate, or iron(II) phosphate.

[0048] However, it is preferred to separate the iron chloride from the off-gas stream by resublimation.

[0049] Step iv) In the process according to the invention, chlorine-phosphorus compounds, preferably phosphorus oxychloride and any phosphorus trichloride formed in the same manner, may be removed from the off-gas stream, preferably by means of a condenser, and any excess chlorine gas may be recycled.

[0050] Phosphorus oxychloride, which is gaseous at room temperature, and the phosphorus trichloride produced in the same manner are preferably separated from the off-gas stream by means of a condenser. The product is generally a mixture of phosphorus oxychloride and phosphorus trichloride, which can be separated into their respective components by further distillation. As a result, the phosphorus components can be obtained in very high purity.

[0051] The process according to the invention is preferably characterized in that the off-gas stream derived from step ii) contains phosphorus trichloride, and that the phosphorus trichloride-containing chlorine-phosphorus compounds from step iv) or phosphorus trichloride after separation therefrom are reacted with chlorine gas at a temperature between 20 and 160°C.

[0052] The reaction forms phosphorus pentachloride, preferably with a chlorine / phosphorus trichloride molar ratio of (1:20).

[0053] The process according to the invention in which the phosphorus compounds are recovered in the form of chlorine-phosphorus compounds, in particular in the form of a mixture of phosphorus oxychloride and phosphorus trichloride, is preferred.

[0054] Depending on the method for producing the LFP or LFMP, the phosphorus oxychloride and / or phosphorus trichloride may be used as such or may first be converted via a hydrolysis step to the corresponding acids of phosphorus, and then, if necessary, by neutralization to produce their salts or their oxides.

[0055] Phosphorus oxychloride and phosphorus trichloride are typically obtained in the off-gas stream in a weight ratio of from (10:1) to (1:10).

[0056] The chlorine-phosphorus compounds from the process according to the invention can be operated in favor of phosphorus trichloride, a preferred reactant for the production of phosphorus pentachloride, in which case the process is preferably carried out at temperatures above 500° C. It is also preferred to carry out the process with a carbon / phosphorus molar ratio of greater than 3. In this way it is possible to achieve a phosphorus trichloride / phosphorus oxychloride weight ratio of greater than 1.

[0057] When the process according to the invention is carried out without using a stoichiometric excess of chlorine, i.e., with only traces or no chlorine present in the off-gas stream, the off-gas stream containing chlorine-phosphorus compounds, in particular phosphorus oxychloride and optionally phosphorus trichloride, after removal of iron chloride, can be introduced into aqueous solutions to obtain the corresponding phosphorus acids, such as phosphoric and phosphonic acids, from which various other phosphorus derivatives, such as their esters, can then be prepared.

[0058] After the process according to the invention has been completed, all components of the substances used which are non-volatile under the reaction conditions or of their non-volatile reaction products are present in the residue, in particular in the form of chlorides, including LiCl. To further process the residue and recover valuable substances, in particular lithium, the residue can be dissolved in water, preferably at temperatures between 10 and 40° C., and separated from the insoluble components.

[0059] One particular insoluble residue from the process according to the invention is graphite (if present in the raw materials used). These water-soluble components can then be separated and isolated in the form of their sulfides, chlorides, phosphates, fluorides or other precipitable compounds, optionally after confirming their possible presence by conventional H2S separation sequences.

[0060] The Li salts remaining after such an HS separation sequence can then be precipitated and recovered as Li carbonate, phosphate, or fluoride. For example, such isolation methods are part of the process described in WO 2022 / 219223 A1.

[0061] The refractory manganese sulfide remaining after such an H2S separation sequence can then be reacted with air to form manganese sulfate, which can then be recovered or reused to produce LFMP. [Example]

[0062] Analysis: Analysis of phosphorus compounds, especially POCl3 and PCl3, is preferably carried out by online IR in the off-gas stream. For this purpose, the gas stream from the reactor is passed through a glass cell, which is made to allow the passage of IR light in its full spectral range, for example by using windows made of thallium compounds. Prior calibration (total evaporation of a known mass flow of PCl3 or POCl3 in a nitrogen gas stream with a known volumetric flow rate and determination of the characteristic absorption in the IR spectrum) makes it possible to ascertain the quantitative ratio of phosphorus compounds in the off-gas stream.

[0063] Example 1 10 g of lithium-ion battery cathode material (lithium iron phosphate) having the following analytical data is intimately dry blended with finely ground carbon (3.3 moles of carbon per mole of phosphorus): 34.6% Fe, 19.5% P, 1.8% C, average particle size distribution of d10 0.35 μm, d50 0.62 μm, d100 6.7 μm, and 4.6% Li.

[0064] The powder mixture is heated to 800°C in a nitrogen stream on a quartz glass dish in a heated tubular reactor (quartz glass, 120 mm diameter). The stream is then switched to a 30 mL / min chlorine gas stream. This temperature is maintained until the content of phosphorus compounds in the off-gas is less than 0.01 wt%, as measured using a gas-phase IR spectrometer and converted to an equivalent weight percentage.

[0065] What remains in the dish is lithium chloride and excess carbon residue. The residue is absorbed in distilled water and the carbon is filtered off. In some cases, high-purity lithium fluoride or lithium carbonate can be obtained by adding water-soluble fluorides or carbonates.

[0066] The iron chloride so obtained is deposited from the off-gas stream onto a surface cooled to 160°C, then collected and, if necessary, reacted with sulfuric acid to obtain iron sulfate.

[0067] Purity of iron chloride: The iron chloride has a content of 90-100%.

[0068] The distillate thus obtained, containing PCl3 and POCl3 in a weight ratio of (2:1), can be used in a chemical process, such as a process for producing phosphate or phosphonate esters, after distillation in a suitable column. POCl3 can also be used to produce polyphosphoric acid or phosphoric acid. Depending on the process, they are feedstocks from which LFP or LFMP can be produced.

[0069] Example 2 50 g of "black material" obtained from the recycling of used lithium iron phosphate batteries is used, with the following analytical data: LFP content 55%, C content 30%, 4% metallic Fe (resulting in a total iron content of 23.3%), 4% aluminum (trace metals from the shredder process), and 3% plastic particles (polyethylene and / or polypropylene), 2% binder, and 2% VOC. The mixture is washed with acetone until the VOC content (excluding acetone) is less than 1%. The polymer and binder are then dried and pyrolyzed in an oxygen-free gas atmosphere at 600 °C for 4 hours.

[0070] The solid thus obtained contains 58% LFP, 32% C content, as well as 5% Fe and 5% Al.

[0071] The black material is heated to 800°C in a nitrogen stream on a quartz glass dish in a heated tubular reactor (quartz glass, 120 mm diameter) without further treatment. The stream is then switched to a 30 mL / min chlorine gas stream. The temperature is maintained until the content of phosphorus compounds in the off-gas, as measured using a gas-phase IR spectrometer and converted to an equivalent weight percent, is less than 0.01 wt. %, and iron chloride from the off-gas stream is resublimated onto a surface cooled to 160°C, and aluminum chloride is deposited onto a surface cooled to 100°C.

[0072] The iron chloride thus obtained can then be collected and, if desired, reacted with sulfuric acid to obtain iron sulfate.

[0073] The aluminum chloride so obtained can then be collected and optionally used for chemical processes or as a precipitant in water treatment plants.

[0074] The distillate thus obtained, which contains PCl3 and POCl3 in a weight ratio of (2:1), can be used, after distillation in a suitable column, in chemical processes, for example, for the preparation of phosphate or phosphonate esters. The POCl3 can likewise be used to prepare polyphosphoric acid or phosphoric acid by reacting it with water.

[0075] The residue in the quartz glass dish contains lithium chloride, graphite, and trace amounts of polyvalent heavy metals, such as copper chloride. The residue is absorbed in distilled water. The solution is filtered, and the graphite remaining on the filter is washed with water and dried. Traces of heavy metals are removed from the solution by means of a suitable ion exchanger (Lewatit® TP208 or TP260). In some cases, pure lithium fluoride or lithium carbonate can be obtained from the thus purified lithium chloride solution by adding water-soluble fluorides or carbonates.

[0076] Example 3 50 g of "black material" obtained from the recycling of used lithium iron phosphate batteries is used, with the following analytical data: LFMP content 55%, C content 30%, and 4% Fe, 4% aluminum, copper (less than 1%) (trace metals from the shredder process), 3% plastic particles (PE and PP), 2% binder, and 2% VOC. The mixture is washed with acetone until the VOC content (excluding acetone) is less than 1%. The polymer and binder are then dried and pyrolyzed in an oxygen-free gas atmosphere at 600 °C for 4 hours.

[0077] The solid thus obtained contains 58% LFMP, 32% C content, as well as 5% Fe and 5% Al.

[0078] The black material is heated to 800°C in a nitrogen stream on a quartz glass dish in a heated tubular reactor (quartz glass, 120 mm diameter) without further treatment. The stream is then switched to a 30 mL / min chlorine gas stream. The temperature is maintained until the content of phosphorus compounds in the off-gas, as measured using a gas-phase IR spectrometer and converted to an equivalent weight percentage, is less than 0.01 wt.%, and iron chloride is deposited by resublimation onto a surface cooled to 160°C, and aluminum chloride is deposited onto a surface cooled to 100°C.

[0079] The iron chloride thus obtained can then be collected and, if desired, reacted with sulfuric acid to obtain iron sulfate.

[0080] The aluminum chloride so obtained can then be collected and used for chemical processes or as a precipitant in water treatment plants.

[0081] The distillate thus obtained, which contains PCl3 and POCl3 in a weight ratio of (2:1), can be used, after distillation in a suitable column, in chemical processes, for example, for the preparation of phosphate or phosphonate esters. The POCl3 can likewise be used to prepare polyphosphoric acid or phosphoric acid by reacting it with water.

[0082] The residue on the dish is absorbed in distilled water and filtered.

[0083] The pH of the filtrate so obtained is adjusted to 2 with H2SO4 and H2S is slowly bubbled in. The (small amount) precipitate is filtered, dried and heated under air to 600 °C to produce CuSO4.

[0084] H2S gas is again slowly bubbled through the resulting filtrate and the pH is adjusted to 8 with NaOH. The precipitate is filtered, dried, and heated under air to 600 °C to produce MnSO4.

[0085] The lithium present in the filtrate is precipitated as lithium carbonate by adding sodium carbonate, filtered off and dried.

[0086] Example 4: 50 g of lithium-ion battery cathode material (lithium iron phosphate) having the following analytical data is intimately dry blended with 15 g of finely ground carbon: 34.6% Fe, 19.5% P, 1.8% C, average particle size distribution of d10 0.35 μm, d50 0.62 μm, d100 6.7 μm, and 4.6% Li.

[0087] The powder mixture is heated to 600°C in a nitrogen stream on a quartz glass dish in a heated tubular reactor (made of quartz glass, 120 mm diameter). The gas stream is then switched to a chlorine gas stream at 100 mL / min, and the reaction is carried out under these conditions for 6 hours. First, a mixture of iron chloride and phosphoryl chloride is isolated from the gas phase at 100°C, and the mixture is separated into POCl3 and FeCl3 at a pressure of 20 mbar and 200°C. POCl3 condenses in the condenser at about 10°C as a slightly cloudy, yellow liquid. The identity of the POCl3 thus obtained is confirmed by gas chromatography and by comparison with the retention time of commercially available POCl3.

[0088] Remaining in the dish are lithium chloride and unconverted carbon residues, along with a small amount of unconverted lithium iron phosphate, which is isolated by washing with water, precipitating as lithium carbonate with sodium carbonate, and drying.

Claims

1. 1. A method for obtaining phosphorus and iron compounds from an LFP-containing and / or LFMP-containing material, comprising: i) reacting an LFP-containing and / or LFMP-containing material with chlorine gas in the presence of a carbon source at a temperature of 300 to 900°C; and ii) conducting the chlorine-phosphorus compounds formed, in particular phosphorus oxychloride and any phosphorus trichloride, and iron chloride, into an off-gas stream; and iii) the iron chloride; and iv) separating the chlorine-phosphorus compounds from the off-gas stream at various temperatures; A method characterized by:

2. 2. The method of claim 1, wherein in step iii) the iron chloride is separated from the off-gas stream by resublimation.

3. 3. The method according to claim 1, wherein in step iv) the chlorine-phosphorus compounds, in particular phosphorus oxychloride and optionally phosphorus trichloride, are separated from the off-gas stream by condensation.

4. 4. The method according to claim 1, wherein the LFP-containing and / or LFMP-containing material used is a material containing LFP and / or LFMP in a proportion of 5% to 100% by weight, preferably 40% to 99% by weight, in particular 50% to 99% by weight, more preferably 70% to 99% by weight.

5. The LFP-containing and / or LFMP-containing material used is 1% to 36% by weight of Fe, 1% to 20% by weight of P, 0 wt.% to 35 wt.% Mn, 1 wt. % to 8 wt. % Li, and 1% to 55% by weight, preferably 1% to 40% by weight, in particular 1% to 30% by weight of carbon The method according to any one of claims 1 to 4, characterized in that the substance comprises:

6. 6. The method according to claim 1, wherein the LFP-containing and / or LFMP-containing material comprises 1% to 55% by weight, preferably 1% to 40% by weight, of carbon, in particular graphite and / or carbon black.

7. 7. The method according to any one of claims 1 to 6, characterized in that the LFP-containing and / or LFMP-containing material has a carbon / phosphorus molar ratio of 1 or more, preferably 1 to 20, more preferably 1 to 10, in particular 1 to 5, and most preferably 1 to 4.

8. 8. The method according to any one of claims 1 to 7, characterized in that the off-gas stream withdrawn in step ii) comprises phosphorus oxychloride and phosphorus trichloride, preferably in a weight ratio of from 10:1 to 1:

10.

9. 9. The method according to claim 1, wherein the off-gas stream derived from step ii) comprises phosphorus trichloride, and the phosphorus trichloride-containing chlorine-phosphorus compounds from step iv), or the phosphorus trichloride after separation therefrom, are reacted with chlorine gas at a temperature between 20 and 160° C.

10. 10. The method according to any one of claims 1 to 9, characterized in that in step iii) the iron chloride is separated at a temperature of not more than 300°C.

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