Lithion Recycling has developed a patented process for recycling lithium-ion batteries. Their solution recovers 95% of lithium-ion battery components that can be used to manufacture batteries. In 2023, they plan to launch their first commercial recycling operations.
Challenges: lithium battery recycling
Lithium and cobalt are used in the production of lithium-ion batteries; these materials must be recycled because they have a significant environmental impact. Today, only a small number of spent lithium-ion batteries are recycled, and the method for recycling these batteries has a significant environmental impact and fails to recover a significant amount of valuable materials.
The elements of a spent lithium-ion battery can be separated using pyrometallurgical techniques. Components of organics and polymers are burned by heating at a high temperature. Cobalt, copper, and nickel are melted to create an alloy, while the remaining elements become slag. Metal smelters purchase metal alloys for separation. Significantly, lithium is lost in these processes and cannot be recovered or resold. The sold alloy has a fraction of the value of the pure and separated metals.
Hydrometallurgical processes are often used to separate and purify the different metals contained in the cathode. In order to obtain relatively pure metals, these processes typically involve a leaching step to dissolve the metals oxide into the aqueous solution and various precipitations and separations steps. These processes are still in development and are expensive to operate. Also, the treatment of liquid waste is usually barely taken under consideration.
There is a need to be provided with a process which can economically process all types of used lithium-ion batteries at large scale industrial processes.
Lithion Recycling Technology
Lithion Recycling provides a method for recycling lithium-ion batteries comprising the processes:
- shredding lithium-ion batteries and immersing the residues in an organic solvent to safely discharge the batteries, thereby producing shredded batteries residues and a liquid containing organic compounds and lithium hexafluorophosphate;
- feeding the shredded batteries residues into a dryer to generate a gaseous organic phase and dried battery residues;
- feeding the dried batteries residues containing magnetic and non-magnetic batteries residues to a magnetic separator that removes magnetic particles from the dried batteries residues;
- grinding the residues of non-magnetic batteries to a particle size of between 0.1 and 10 millimeters, which produces a particle size distribution containing plastics in an upper range and aluminum, copper, metal and graphite in the middle and lower range of fine particles;
- mixing fine particles with an acid to create a slurry, then leaching the slurry to produce a leachate containing metal sulfate and non-leachable materials;
- removing non-leachable materials from the leachate by filtering the leachate;
- leachate is fed into a sulfide precipitation tank, which removes ionic copper impurities from the leachate;
- adjusting the pH of the leachate to between 3.5 and 5 and removing any remaining iron and aluminum;
- mixing the leachate with an organic extraction solvent producing an aqueous phase containing lithium, sodium and nickel and an organic phase containing cobalt, manganese and the remaining nickel;
- crystallizing sodium sulfate from the aqueous phase containing lithium producing a liquor containing lithium and sodium sulfate crystals;
- adding sodium carbonate to the liquor and heating up the sodium carbonate and the liquor producing a precipitate of lithium carbonate; and
- drying and recuperating the lithium carbonate.
The used batteries are shredded. The shredded battery residues are immersed in an organic solvent to safely discharge the batteries, producing shredded battery residues and a liquid containing organic compounds and lithium hexafluorophosphate.
Why are shredded battery residues immersed in an organic solvent?
- The used batteries may contain residual charge. When the inside components of a charged battery are exposed to the ambient air’s moisture, an exothermic reaction occurs which produces hydrogen gas. This poses a severe risk of hydrogen gas combustion. To minimize the risk of combustion, used batteries are shredded and then immersed in an organic solvent.
- The organic solvent can also dissolve and extract electrolyte salts, such as lithium hexafluorophosphate (LiPF6), from battery materials. It is miscible with the electrolyte solvent (an aliphatic carbonate).
- In addition, the organic solvent will serve as a heat sink in the event of an exothermic reaction, thereby reducing operating hazards. The temperature of the organic solvent is maintained below 40°C.
After shredding, the shredded battery residues and the solvent are extracted to ensure that the electrolyte salt is thoroughly washed. The extractant is the same solvent used in the step of shredding. The extraction is performed at temperatures between 40 to 60°C, with a residence time between 30 minutes to an hour and a half, and a tested operating point of 50°C for 1 hour.
The shredded batteries residues or particles are then separated from the liquid through sieving or filtration.
Recycle electrolyte solvents
In the obtained liquid phase, electrolyte solvents and organic solvents used in the shredding step are separated by distillation and condensation.
The liquid phase is fed to an evaporator operating at the mixture’s boiling point. At atmospheric pressure, the typical boiling point for a mixture of electrolyte salt and solvent is approximately 90°C.
At the outlet of the evaporator, the gaseous phase contains lighter molecules, primarily the solvent used in the shredding process. Light organics evaporated from the wetted battery residues dried by a dryer operating between 200 and 300°C are also introduced into the gaseous phase at the evaporator’s outlet.
The majority of the condensate of light organics can be returned to the shredding step, while the remainder, which corresponds to the accumulation of organic solvent, is bled towards a separation step with various columns to purify the various molecules in the light organic phase.
The first column is operated at approximately 90°C to produce dimethyl carbonate (DMC) of battery grade in the column overhead.
The bottom of the first column, which contains ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and ethylene carbonate (EC), is fed to the second column. The second column is operated at around 107°C to produce battery-grade ethyl methyl carbonate (EMC) in the column overhead.
The third column is fed with the bottom of the second column and operated at around 126°C to produce battery-grade diethyl carbonate (DEC) in the column overhead and technical-grade ethylene carbonate (EC) from the column bottom.
The heavier organic molecules that still contain the electrolyte salt from the used batteries will remain as a slurry in the bottom of the evaporator, which is burned off at a temperature around 500°C to eliminate the toxic organic fluorophosphate molecules and remove all reactive fluoride compounds from the process.
The combustion gas will contain hydrofluoric acid (HF) and phosphorous pentoxide (P2O5); these molecules are highly reactive and must be treated before being released into the environment. HF is removed by a dry lime scrubber. P2O5 is neutralized in a wet scrubber using a caustic solution, forming waste products sodium phosphate (Na3PO4) which is environmentally harmless.
Recycle iron, copper, aluminum
Battery residues from the dryer outlet are fed to a magnetic separator to separate the iron (Fe) pieces and particles that are lifted to the magnets from the other solids.
The non-magnetic battery residues undergo a reduction of the average particle size between 0.1 to 2 millimeters using a hammer mill or an impact crusher. Plastics constitute the upper range of the particle size distribution. The aluminum (Al) and the copper (Cu) foils will be crushed to a ribbon-like form. Metal in the cathode and graphite in the anode will be pulverized to form the lower range of the particle size distribution.
The outlet from the crusher is then sieved at around 1 millimeter. The oversize fraction is fed to a second milling and sieving step that utilizes a high shear mixer or a cutting mill to remove the remaining anode and cathode materials adhered to the aluminum and copper foil. After a second sieving at the same size (1 mm), the fine particles of the cutting mill step are mixed with the fine particles from the previous sieving step.
The coarse particles, which consist mostly of plastics, copper, and aluminum, are then fed to an eddy current separator, which extracts the aluminum and copper foil. The remaining plastic can be sent to a recycling facility. The aluminum and copper foils are then separated by density classification using equipment such as an air classifier.
The fine particles from the sieving units are mixed with sulfuric acid and water in a leaching tank to produce a metal oxides slurry with an acidic mass concentration around 17% and solid concentration of 100 kg of solids per cubic meters of acid solution. The mixing needs to be maintained around ambient temperature for 3 hours.
A reduction agent such as hydrogen peroxide (H2O2), aluminum power (Al), and manganese oxide (MnO2) may also be added to the reaction tank in order to facilitate the leaching of transition metals (Co, Ni, Mn) that have been reduced or oxidized to a divalent oxidation state, at which they are more readily leachable. Solid non-leachable materials are filtered out.
The graphite and the other non-leachable elements are filtered out and sent to the graphite purification process. The filtrate, which contains lithium, cobalt, nickel, manganese, iron, aluminum, and copper as sulfate salt, is sent to the sulfide precipitation tank.
The obtained graphite cake is suspended back in a liquid similar to the leaching step’s aqueous solution. This solution dissolved the remaining metals in the graphite. The graphite is then filtered and thoroughly washed with water. The graphite cake is then fed into a 600°C furnace for the remaining plastics to be evaporated and the graphite dried.
Remove impurities of copper, aluminum, and iron
The sulfide precipitation removes the ionic copper in solution, coming from the leached metallic copper.
Copper impurities can be precipitated by binding with sulfide ions (S2-) provided by sodium sulfide (Na2S). At a pH below 2 and temperatures between 40 and 80°C, sulfide binds to copper selectively to form water-insoluble copper sulfide (CuS), which is filtered out of the main process line by filtration and sold.
The leachate is then neutralized to a pH between 3.5 and 5.0 with the addition of sodium hydroxide (NaOH) in order to precipitate the remaining iron and aluminum, which will form insoluble hydroxides (Al(OH)3, Fe(OH)3). The precipitate is filtered out of the process.
Al2(SO4)3 + 6NaOH ↔ 2Al(OH)3 + 3Na2SO4
NiSO4 + 2NaOH ↔ Ni(OH)2 + Na2SO4
Final Metal Separation
The leachate is mixed with an organic extraction solvent (extractant) dissolved in a petroleum-based reagent (diluent). The concentration of the extractant in the diluent may vary between 4 and 6 mass percentage. With the aqueous solution having a pH between 4.5 and 7, the divalent transition metals (Co, Mn, Ni) will be extracted by the organic phase, while the lithium and sodium will remain in the aqueous phase. If the pH is kept at values between 5.4 and 6.2, nickel will only be partially extracted. Within this pH range, nickel is separated from cobalt and manganese.
Recycle cobalt and manganese
For carrying out the solvent extraction processes, mixer-settlers, extraction columns, columns with internal stirring using rotating impellers, reciprocating-plate extraction columns, hollow fiber membrane, and the like may be used. The lighter organic phase is typically pumped out from the top of a buffer zone (where there is no longer any mixing) and the heavier aqueous phase is pumped out from the bottom of the equipment, passing through another buffer zone where it is given sufficient time to separate by decantation. The organic phase is then sent to a scrubbing and stripping stage, while the aqueous phase (raffinate) is sent to further precipitation steps.
In the scrubbing stage, the organic phase is contacted with an aqueous solution containing a high concentration of cobalt and manganese in order to selectively strip nickel from the organic phase. This scrubbing solution is a portion of the (Co, Mn)-rich stripping solution, with its pH adjusted between 3 and 4 with sodium hydroxide. The two phases are mixed and separated in similar equipment as previously described above. The aqueous solution is returned and mixed with the solvent extraction inlet.
In the stripping stage, the organic phase is contacted with an aqueous solution containing sulfuric acid with a pH between 1 and 2 to strip the cobalt and manganese together. Once again, similar equipment as previously described are used here to mix and separate the two phases. The cleaned organic solvent is then fed back to the extraction stage and the now-(Co, Mn)-rich aqueous phase is split between the scrubbing stage and the cobalt electrowinning step.
Cobalt and manganese must be separated. Due to their different standard reduction potentials (−0.28 V for cobalt and −1.18 V for manganese), they can be separated by an electrowinning process.
The cobalt will be plated on the cathode in its metallic form and then scrapped off. On the anode, manganese will be oxidized to MnO2 and deposited. Using an undivided electrolysis cell with a cobalt blank cathode and a DSA anode with a current density between 150 and 350 A/m2 and a voltage between 2.7 and 5 V, cobalt is electrowon by means of electrolysis. The electrolyte is fed at a pH between 2.5 and 5 at a temperature between 45 and 70°C.
The electrode reactions are as follows:
Co2+ + 2e− ↔ Co(s)
2H+ + 2e− ↔ H2
H2O ↔ ½O2+2H+ + 2e−
MnO2(s) + 2e− + 4H+ ↔ Mn2+ + 2H2O
The spent electrolyte is returned as the stripping solution during the stripping step.
After the solvent extraction step, the aqueous raffinate contains a large proportion of dissolved nickel sulfate (NiSO4). The pH of the solution is increased to 10.8 with the addition of sodium hydroxide to precipitate nickel hydroxide (Ni(OH)2). The precipitation takes 1 hour to stabilize. The nickel hydroxide is filtrated, washed, and dried to be sold.
NiSO4 + 2NaOH ↔ Ni(OH)2 + Na2SO4
Recycle Na2SO4, NaOH, and H2SO4
At this point in the process, the remaining aqueous solution contains an important proportion of sodium sulfate (Na2SO4). The high concentration of sodium sulfate makes it appealing for surface cooled crystallization. By cooling the neutralized leachate between 0°C and 10°C, a large proportion of the sodium sulfate is crystallized into a decahydrate crystal, Na2SO4∙10H2O. Removing sodium sulfate also has the benefit of concentrating the remaining lithium in the aqueous solution (mother liquor).
The absence of contamination enables electrolysis. The electrolysis of sodium sulfate will produce sulfuric acid at the anode and sodium hydroxide at the cathode. This step eliminates the need for fresh sulfuric acid and sodium hydroxide to be introduced into the process. For this type of process, the current density may be 1 kA/m2 with a voltage of 10 V and a feed Na2SO4 mass percentage of around 18%. The electrode reactions are as follows:
2H2O + 2e– ↔ H2 + 2OH–
2Na+ + 2OH– ↔ 2NaOH
H2O ↔ ½O2 + 2H+ + 2e–
SO42- + 2H+ ↔ H2SO4
The mother liquor out of the crystallizer is heated up to a temperature between 80 to 100°C, and sodium carbonate (Na2CO3) is added to the aqueous solution. The reaction between carbonate ions and lithium ions produces lithium carbonate (Li2CO3), which is slightly soluble in water. The precipitation takes 1 hour. The precipitate is filtered and dried and sold as dried lithium carbonate.
Li2SO4 + Na2CO3 ↔ Li2CO3 + Na2SO4
The remaining aqueous solution is recycled back to the primary leaching sector.
Lithion Recycling Patent
- US20210376399A1 Lithium-ion batteries recycling process
Lithion Recycling Products
Lithion Recycling aims to develop its technology for global commercialization. In December of 2020, Lithion Recycling completed construction of a lithium-ion battery recycling pilot plant in Anjou with an annual capacity of 200 metric tones, the equivalent of 300 to 650 electric car batteries.
Lithion Recycling Funding
Lithion Recycling Investors
Lithion Recycling Founder
Benoit Couture is Founder.
Lithion Recycling CEO
Benoit Couture is CEO.