Method for recycling lithium batteries

Abstract

The invention relates to a method for recycling used lithium batteries containing the steps: (a) digestion of comminuted material (10), which contains comminuted components of electrodes of lithium batteries, using concentrated sulphuric acid (12) at a digestion temperature (T.sub.A) of at least 100? C., in particular at least 140? C., so that waste gas (14) and a digestion material (16) are produced, (b) discharge of the waste gas (14) and (c) wet chemical extraction of at least one metallic component of the digestion material (16).

Claims

1. A method for recycling lithium batteries containing: digesting comminuted material which contains comminuted components of electrodes of lithium batteries, using concentrated sulphuric acid at a digestion temperature of at least 100? C., so that waste gas and a digestion material are produced, wherein the comminuted material is not pyrometallurgically treated prior to digesting with concentrated sulphuric acid, discharging of the waste gas, and performing wet chemical extraction of at least one metallic component of the digestion material, wherein the communited material contains fluoride components and wherein the digestion is conducted in such a way that the fluoride components in the comminuted material pass into the waste gas as hydrogen fluoride.

2. The method according to claim 1 wherein the digesting is conducted until a concentration of water-soluble fluoride in the digestion material is lower than 100 mg/kg.

3. The method according to claim 1 wherein the concentrated sulphuric acid is utilised at least stoichiometrically during digestion.

4. The method according to claim 1 further comprising separating hydrogen fluoride from the waste gas.

5. The method according to claim 1, wherein the comminuted material contains graphite and wherein the method further comprises: leaching of the digestion material, and separating graphite from the digestion material thereby producing a raw fluid.

6. The method according to claim 5, wherein the comminuted material contains copper and wherein the method further comprises separating copper from the raw fluid so that a de-copperised raw fluid is obtained.

7. The method according to claim 6, wherein the de-copperised raw fluid contains Fe.sup.2+ ions, iron, aluminum, and titanium, and the method further comprises: oxidizing Fe.sup.2+ ions in the de-copperised raw fluid to Fe.sup.3+ ions, and precipitating iron and/or aluminium and/or titanium, so that a pure fluid is obtained.

8. The method of claim 7 wherein the oxidizing is performed with an oxygen compound.

9. The method according to claim 7, wherein when the pure fluid contains cobalt, nickel and/or manganese, the method further comprises: solvent extraction of cobalt, and/or solvent extraction of nickel, and/or removal of manganese, so that a target fluid is obtained.

10. The method according to claim 9, further comprising: precipitating lithium from the target fluid when the pure fluid contains cobalt, nickel and/or manganese, or precipitating lithium from the pure fluid when the pure fluid contains neither cobalt, nickel nor manganese.

11. The method of claim 9, further comprising using a complexing agent for one or more of cobalt, nickel or manganese.

12. The method according to claim 1, further comprising the following steps prior to digesting: comminuting batteries such that raw comminuted material is obtained, and deactivating the raw comminuted material by drying such that the comminuted material is obtained.

13. The method of claim 1 wherein the digesting is performed at at least 140? C.

14. The method of claim 1, wherein the concentration of water soluble fluoride in the digestion material is lower than 10 mg/kg.

Description

(1) In the following, the invention will be explained in more detail by way of the attached figures. They show:

(2) FIG. 1 a flow diagram of a method according to the invention and

(3) FIG. 2 a schematic view of a recycling installation according to the invention,

(4) FIG. 3 a flow diagram for a method according to the invention for processing comminuted material that is free of cobalt, nickel and manganese,

(5) FIG. 4 the flow diagram of a method for processing comminuted material that is free of cobalt and nickel but contains manganese, and

(6) FIG. 5 a flow diagram of a method according to the invention for comminuted material that is free of manganese and nickel but contains cobalt.

(7) FIG. 6 a flow diagram for the processing of comminuted material that is free of manganese but contains cobalt and nickel.

(8) FIG. 7 a schematic view of a comminution unit of a recycling installation according to the invention.

(9) FIG. 1 shows a flow diagram of a method according to the invention. First of all, the comminuted material, for example in the form of comminuted electrode active material, is provided. This may be achieved, for instance, using a method described in DE 10 2015 207 843 A1. In particular, it is possible that batteries are initially comminuted, thereby resulting in raw comminuted material. In a subsequent step, the raw comminuted material is deactivated via drying, so that deactivated raw comminuted material is obtained.

(10) The deactivation is preferably a drying. The drying occurs, for example, in an inert gas atmosphere or under a vacuum. It is favourable if a pressure is at most 300 hPa and a temperature during drying is at most 80? C. This results in comminuted material 10 that can no longer react electrochemically to a significant degree, as the proportion of low boilers in the electrolyte is too low.

(11) According to a preferred embodiment, the deactivation is followed by a separation of the electrode active material from the raw comminuted material. This preferably comprises a combination of mechanical stress, magnetic separation, non-ferrous metal separation, sieving and density separation. It is practical to use air jet sieving, wherein the use of smaller mesh sizes for sieving results in a purer sieved material.

(12) The comminuted material 10 is mixed with sulphuric acid 12. The mixing may be, for instance, an agitation using an agitator. However, it is also possible for the mixing to be a simple addition. In particular, this is possible if the comminuted material 10 is in a reactor in the form of a rotary kiln. In addition, it is possible that the comminuted material and the sulphuric acid are mixed in a reaction container, preferably made of steel. The resulting mixed comminuted material is then added to a reactor, especially a rotary kiln.

(13) The sulphuric acid 12 is preferably at least 95%. The comminuted material 10 and the sulphuric acid 12 are brought up to a digestion temperature T.sub.A, for example at least T.sub.A=140? C., especially at least 150? C. Insofar as a pH value can be determined, it is below 1.5 for the mix of comminuted material and sulphuric acid. In general, however, the water content of the mixture is too low to determine the pH value.

(14) The digestion produces waste gas 14, which contains hydrogen fluoride HF in particular. The digestion occurs until a fluorine compound content, particularly a hydrogen fluoride content, in the waste gas 14 is below a predetermined threshold of, for instance, 0.83 mg per cubic metre, as determined in a discontinuous comparative test in a container without a continuous addition of material. This is checked using a fluoride detector 15, which continuously measures a fluoride concentration.

(15) If the digestion occurs in a charging process, the digestion is conducted until the fluorine compound content, especially a hydrogen fluoride content, is below a predetermined threshold of, for example, 0.83 mg per cubic metre.

(16) Alternatively or additionally, the digestion is conducted until a fluoride concentration c.sub.F of water-soluble fluoride in the digestion material is lower than 100 milligrams per kilogramme of digestion material, preferably lower than 10 mg/kg and especially preferably below the traceability threshold. In other words, the retention time of the comminuted material 10 and the sulphuric acid 12 is selected in such a way that the digestion material has a fluoride concentration c.sub.F of water-soluble fluoride that does not exceed the specified values.

(17) In addition, digestion material 16 is obtained that can be deemed, to a good approximation, to be fluoride-free. Water 18 is added to the digestion material 16, thereby leaching it. The leaching may occur in the same container in which the digestion of the comminuted material occurred; however, this is not essential. For instance, it is possible that the digestion material is put in a container that preferably already contains water. The leaching occurs at a pH value of ?0.7 to 4 and preferably without an active addition or discharge of heat.

(18) Following leaching, graphite 20 is separated using a graphite separation device 22. In the present case, the graphite separation device 22 is a filter with a pore size of at most 15 micrometres, preferably at most 10 micrometres. It is beneficial if the pore size is at least 0.5 micrometres.

(19) The graphite 20 can be cleaned in a subsequent step in the method, for example with water, an alcohol, an organic solvent or a mineral acid, so that electrode graphite is obtained. Electrode graphite is a graphite that is suitable for the production of electrodes, especially for lithium batteries. This results in a raw fluid 24.

(20) Metallic copper Cu is obtained from the raw fluid 24, for instance via cementation. To this end, metallic iron is brought into contact with the raw fluid 24, for example, so that iron ions dissolve and copper precipitates metallically.

(21) Alternatively, the copper is separated in the form of copper sulphide. This is achieved, for instance, via precipitation by adding sodium hydrogensulphide NaHS. The separation of the copper results in de-copperised raw fluid 26. This has a pH value between 0 and 4, for instance pH 1.

(22) The Fe.sup.2+ ions in the de-copperised raw fluid 26 are then oxidised to form Fe.sup.3+ ions. In the present case, this is achieved by adding hydrogen peroxide H.sub.2O.sub.2. However, a different oxidising agent can also be used. The pH value of the de-copperised raw fluid is below 4.3 prior to oxidation. This step is preferably conducted without an active heat supply or extraction.

(23) In a subsequent step, iron, aluminium and, where applicable, titanium are precipitated in the form of a hydroxide. To this end, the pH value is increased to a value between 4.3 and 8.7. This is achieved by adding sodium hydroxide and then separating, especially filtering out or centrifuging, the resulting precipitation. In addition to the separated hydroxides, a pure fluid 28 is also obtained. Solvent extraction is used to extract nickel and cobalt from the pure fluid. In the present case, this is achieved using Cyanex 301, which is dissolved in an organic solvent, generally kerosene.

(24) FIG. 1 shows that two solvent extraction steps are nested inside one another. First, cobalt and nickel are extracted using Cyanex 301, which is dissolved in kerosene.

(25) Stripping with acid, especially with hydrochloric acid or sulphuric acid, is used to obtain a solution 30 that contains nickel and cobalt. Following further separation using Cyanex 272, they are crystallised separately.

(26) If a metal, such as manganese, is specifically named, as it is here or generally in the description, this generally refers to the metals in their elementary form and compounds contained in the metal; it generally also includes the metal ions. The statement that manganese, cobalt and nickel are extracted thus also means that manganese, cobalt and nickel ions and any compounds, and especially ions, containing manganese, cobalt and nickel are removed.

(27) The extraction of cobalt and nickel results in a target fluid 32 that contains manganese. The pH value of the target fluid 32 may be between ?0.7 and 10.5.

(28) There are (at least) three options for the further processing of the target fluid 32. According to a first option, the manganese in the target fluid 32 that contains manganese is removed by solvent extraction. This may occur, for instance, using D2EHPA dissolved in kerosene.

(29) According to a second and third option, the manganese is removed by precipitation, which may occur, for instance, by adding sodium hydroxide. According to a third option the precipitation may occur by adding sodium carbonate.

(30) The removal of the manganese produces a target fluid 34. The most important component of this fluid is lithium ions. The lithium is precipitated out of the target fluid 34.

(31) This is done, for instance, using sodium carbonate. A favourable temperature is a maximum of 30 Kelvin below the boiling point of the target fluid 34 and preferably above 50? C.

(32) The lithium carbonate may be washed with water at 50-100? C., preferably 80-100? C., and/or ethanol.

(33) It is beneficial if the precipitation step is preceded by a concentration step, thereby increasing the concentration of lithium. Alternatively, the lithium may be precipitated as lithium phosphate; to this end, sodium phosphate can be added, for example.

(34) The concentration may occur, for instance, via reverse osmosis and/or evaporation.

(35) FIG. 2 depicts a schematic view of a recycling installation 36 according to the invention for processing lithium batteries, in the present case in the form of comminuted material 10 produced from lithium batteries. Alternatively, it is also possible that electrode material that does not need to be comminuted is processed in the recycling installation. In the present case, the recycling installation 36 features a reactor 40 in the form of a rotary kiln, in which the comminuted material 10 is digested with sulphuric acid 12. The comminuted material 10 and the sulphuric acid 12 have been previously mixed together in a mixer 42. The mixer 42 is an advantage but not essential. The sulphuric acid 12 is added by means of a sulphuric acid supply device 43, which may refer, for instance, to a dosing device, comprising a sulphuric acid container and a controllable valve. However, it is also possible that the sulphuric acid 12 is poured in from a container.

(36) The recycling installation 36 has a discharge device 44 in the form of a waste gas pipe, which can be connected to a vacuum generator so that the waste gas 14 is sucked out of the reactor 40. Alternatively, it is possible that the excess pressure in the reactor 40 pushes the waste gas 14 through the discharge device 44. The discharge device 44 may feature a washer for washing out hydrogen fluoride. For example, in this washer, the waste gas 14 is brought into contact with a calcium compound, for instance an aqueous solution that contains calcium ions, so that hydrogen fluoride in the waste gas 14 is washed out. Of course, other methods for removing hydrogen fluoride from the waste gas 14 are conceivable. It is also possible that the waste gas 14 is added to a reactor by means of the discharge device 44, in which the hydrogen fluoride reacts, for example, with an organic substance.

(37) The fluoride concentration c.sub.F is identified using a fluoride detector 15.

(38) A leaching device 46 is arranged behind the reactor 40 in the direction of material flow M, wherein the digestion material 16 is leached, for instance with water, in said leaching device.

(39) A graphite recovery device 48 is arranged behind the leaching device 46 in the direction of material flow M, wherein said graphite recovery device only features the graphite separation device 22 in the form of a filter in the present case. An optional wash-out device for washing out adherent leaching solution from the graphite is not depicted. It is also possible to initially fill a transport container with the graphite and to conduct the washing-out of adherent leaching solution following transportation to another location.

(40) A copper extractor 50 is arranged behind the graphite recovery device 48 in the direction M of material flow. According to a first alternative, the copper extractor comprises a container 52 for cementing the copper following the addition of iron, especially in the form of sheet iron or iron filings, as well as a precipitation material separator 54 for separating selected copper compounds. The precipitation material separator 54 may be a filter, for example. The pore size of the filter is preferably smaller than 50 micrometres and at least 1 micrometre.

(41) According to an alternative embodiment, the precipitation material separator is designed to separate copper sulphide and the container 52 is for the reaction of the raw fluid 24 with NaHS, so that copper sulphide precipitates.

(42) An Fe/Al/Ti separator 56 is arranged behind the copper extractor 50 in the direction of the material flow, wherein an oxidising agent 58 is added to the de-copperised raw fluid 26 in said separator. This may occur in a first container 60.1. The resulting solution is then transferred, for example pumped, into a second container 60.2. In this second container 60.2, a hydroxide is added, in particular an alkaline hydroxide. For instance, sodium hydroxide is added. This results in the precipitation of aluminium, iron and, where applicable, titanium in the form of a hydroxide or a hydrated oxide. The precipitation is removed by means of a particle separator 62 arranged downstream in the direction of material flow. The particle separator 62 is formed of a filter, for example, which may have a maximum pore size of 15 micrometres.

(43) The resulting pure fluid 28 is added to a solvent extraction device 64, which features a Co/Ni solvent extraction device 66. This comprises a multitude of reaction containers 38.1, 38.2, . . . , which are connected to one another as shown in FIG. 2. The structure of a solvent extraction device is known from the prior art and will therefore not be explained in further detail. This produces the target fluid 32 containing manganese.

(44) The target fluid 32 is added to a manganese solvent extraction device 70, which generates target fluid 34.

(45) According to an alternative, the target fluid 32 containing manganese is added to a second precipitation reactor 72, in which the manganese is precipitated as manganese hydroxide following the addition of a hydroxide, especially an alkaline hydroxide such as sodium hydroxide.

(46) According to a third alternative, the target fluid 32 containing manganese is added to a precipitation reactor 74. Following the addition of a carbonate, in particular following the addition of sodium carbonate, manganese is precipitated in the form of manganese carbonate or separated.

(47) The lithium is precipitated in respective containers as carbonate by adding sodium carbonate or as phosphate by adding sodium phosphate. It is possible that the recycling installation 36 comprises a concentrator 74 for removing water from the target fluid 34 to facilitate precipitation.

(48) FIG. 3 shows a flow diagram for a method according to the invention for processing comminuted material and/or electrode material that is free of cobalt, nickel and manganese. It should be noted that the method corresponds to the method according to FIG. 1, wherein the steps related to the extraction of cobalt, nickel and manganese have been omitted.

(49) FIG. 4 shows a flow diagram for the processing of comminuted material and/or electrode material that is free of cobalt and nickel but contains manganese. For the extraction of manganese, only the variation with solvent extraction is depicted. The alternatives shown in FIGS. 1 and 2 for the removal of the manganese are also possible for the method according to FIG. 4 and represent preferred embodiments.

(50) FIG. 5 depicts the flow diagram of a method for processing electrode and/or comminuted material that is free of manganese and nickel but contains cobalt.

(51) FIG. 6 shows a flow diagram of a method according to the invention for electrode and/or comminuted material that is free of manganese but contains cobalt and nickel.

(52) FIG. 7 depicts a second embodiment of a recycling installation 36 according to the invention, wherein the components arranged behind the leaching device 46 in the direction of material flow have been omitted for the sake of clarity.

(53) It should be recognised that the recycling device 36 comprises a comminution unit 118 and a deactivation device 126. The deactivation device 126 is designed as a drying device.

(54) Lithium batteries 110.1, 110.2, . . . , in particular battery systems made up of several battery modules or battery stacks, which are in turn made up of several battery cells, are initially discharged in a discharge unit 112. This is followed by the dismantling of the lithium batteries 110 at a dismantling station 114, if this is necessary because the battery systems cannot otherwise be delivered into the comminution unit 118 for geometric or gravimetric reasons. To this end, where appropriate, the battery systems are opened and dismantled to the point at which the modules and/or stacks can be individually removed. If required, the individual lithium battery cells can also be separated from the drive electronics.

(55) The resulting sub-units (modules/stacks) and/or cells 116.1, 116.2, . . . are added to the comminution unit 118. For example, the comminution unit 118 may be a rotary shear with at least one rotor and at least one stator. The comminution unit 118 may also comprise a cutting mill with a rotor or several rotors.

(56) The comminution unit 118 comminutes the lithium batteries 110.i under shielding gas 120, which is extracted, for example, from a shielding gas cylinder 122. Alternatively or additionally, liquid nitrogen from a liquid nitrogen source 119 may be may be injected. The shielding gas may refer, for example, to nitrogen, a noble gas, carbon dioxide, nitrous oxide or another gas which is preferably not toxic.

(57) Shredded material 124 is produced during comminution, which is fed into a deactivation device in the form of a drying device 126. An airlock 128 is arranged between the comminution unit 118 and the drying device 126, the airlock being so gas-tight that the drying device 126 isto a good approximationseparated from the comminution unit 118 so as to be gas-tight.

(58) The drying device 126 is connected to a vacuum installation 129 that comprises a vacuum pump 130 and creates a vacuum. A pressure p.sub.126 from p.sub.126?100?60 hPa, preferably 50 hPa, is present in the drying device 126. It should be noted that, within the scope of the present description, the vacuum pump should be understood particularly generally to mean a device that creates a vacuum. It is possible and preferred, but not necessary, for the vacuum pump to simultaneously work as a compressor, such that gas is emitted from it under a pressure that is greater than the ambient pressure.

(59) In the case depicted in FIG. 7, the vacuum pump is a compressor which sucks in and compresses gas 131 that is present in the drying device 126. Alternatively or additionally, the vacuum installation 129 may have a jet pump, wherein a jet medium in the form of a liquid is directed at a high speed through at least one Venturi nozzle. The jet medium is preferably alkaline and has a pH value of at least pH 13 and is, for example, a 10% potassium hydroxide solution.

(60) The vacuum installation 129 comprises a gas purification device 132 that is arranged between the drying device 126 and the vacuum pump 130, and which has a condenser 134 and/or an activated carbon filter 136 in the present case. The condenser is operated at a temperature of, for instance, ?10? C. so that dimethyl carbonate and ethyl methyl carbonate condense and can be dispensed into a condensate container 138. In addition, any water present is separated by freezing. A control valve 140 is designed to open if the pressure p.sub.26 becomes too great and to close if the pressure p.sub.126 becomes too small, i.e. when a pre-determined threshold value is not reached.

(61) The drying material is preferably moved in the drying device 126. This may be achieved by agitating with an agitator 141, such as an anchor agitator or a rod agitator with, for example, rods arranged perpendicular to the agitator shaft. Alternatively, it can be achieved by way of a drying container that is moved.

(62) The drying of the shredded material 124 results in deactivated comminuted material 10, which is added to the mixer 42.

(63) Alternatively, a transport container 146 is then filled with the deactivated comminuted material 10 under a vacuum and/or shielding gas. The transport container 146 is preferably gas-tight. It is possible, but not necessary, for the transport container 146 to be filled with inert gas prior to transportation such that it is under normal pressure. Alternatively, it is also possible for the transport container to be sealed under vacuum and transported. It is possible that, instead of the transport container, a vacuum-sealed foil is selected, such as an aluminium compound foil.

(64) The comminution unit 118 is fed with shielding gas 120 from the vacuum pump 130 via a flushing line 148. If the vacuum pump 130 also functions as a compressoras in the present casewhich represents a preferred embodiment, the shielding gas 120 can be drawn from a pressurised gas cylinder 150. Alternatively or additionally, the shielding gas 120 can be given off into the surroundings, following additional cleaning if necessary.

(65) TABLE-US-00001 Reference list 10 comminuted material 12 sulphuric acid 14 waste gas 15 fluoride detector 16 digestion material 18 water 20 graphite 22 graphite separation device 24 raw fluid 26 de-copperised raw fluid 28 pure fluid 30 solution 32 target fluid containing manganese 34 target fluid 36 recycling installation 38 electrode material 40 reactor 42 mixer 43 sulphuric acid supply device 44 discharge device 46 leaching device 48 graphite recovery device 50 copper extractor 52 container 54 precipitation material separator 56 Fe/Al/Ti precipitation material separator 58 oxidising agent 60 container 62 particle separator 64 solvent extraction device 66 Co/Ni solvent extraction device 68 reaction container 70 Mn solvent extraction device 72 precipitation reactor 74 concentrator 110 lithium battery 114 dismantling station 116 cells 118 comminution unit 119 liquid nitrogen source 120 shielding gas 124 shredded material 126 drying device 128 airlock 129 vacuum installation 130 vacuum pump 131 gas 132 gas purification device 134 condenser 136 activated charcoal filter 138 condensate container 140 control valve 141 agitator 146 transport container 148 flushing line 150 pressurised gas cylinder c.sub.F fluoride concentration T.sub.A digestion temperature M direction of material flow