Two Effective Method of Recycling Lithium-Ion Batteries

Environmentally friendly and low-cost recycling of lithium-ion batteries (LIBs) is becoming an urgent need to enable sustainable energy storage. This article describes two effective ways to recycle lithium-ion batteries;

Recycling of used lithium-ion batteries reclamation of cathode material from spent lithium-ion batteries.

Two methods are considered. The procedure is based on practices reported elsewhere in the world.

Two Effective Methods of Recycling Used Lithium-Ion Batteries are Given Below: 

Method 1: manual and labor-intensive and moderate turnover- very profitable.

Method 2: automatic; large-scale, high turnover; good recovery and profitable.

Method 1 Or method 3 can be chosen as per the requirement.

Read More: Battery Recycling Business for SSI

Method 1 for Recycling Used Lithium-Ion Batteries

This method primarily helps to convert the cathode (positive) material from the spent battery directly into a usable main cathode component. This bypasses the normal recovery method of breaking down cells and crushing them to remove valuable chemicals, signing the traditional chemical process.

Required Equipment for Recycling Lithium-Ion Batteries

Ultrasonic sonicator, Furnace to maintain temperature up to 800 degrees C, centrifuge or filtration system [ sonicator is a device which produces sound waves of high frequency ( 20 kilohertz -20 kHz) used to agitate and disperse particles at high amplitude and intensity] ethylene carbonate or dimethyl carbonate is used to wash down the solvents and lithium salts from the electrolyte.

Equipment to recover these valuable solvents is necessary. A fractional distillation set made of all-glass for low volume of scrap or SS- make fractional distillation unit for a larger quantity of scrap batteries will pay for itself within 2-3 years. 

Process 1:  Discharge the Cells from Spent Cells/Batteries

• Discharging the cells to a safe low voltage level is essential to ensure safe handling while opening the cells for subsequent processing steps. This can be done by discharging through a suitable resistance. Such a procedure is not practical when a large number of cells have to be discharged.
• Therefore, discharge through ferrous sulfate (2.5%) solution is proposed. All cells, cylindrical, pouched cells are soaked in 2.5 % ferrous sulfate solution. Use an open tray or tank made of stainless steel or HDP with a bottom drain facility. Complete draining should be possible. To 100 l of DM water in the tank, add 2.5kg of FeSO4, [ or 4.5kg of, FESO4, 7 H2O]. Stir with a plastic rod or a mechanical stirrer with SS blades. The Temperature of the water should be around 24-35 Degree C. 
• Drop the cells as such into the solution allow the discharge reaction to proceed for a minimum of 24 hrs. There will be an evolution of hydrogen and oxygen gases due to electrolysis. Therefore, carry out this operation in an open or under forced ventilation. 
• The next operation is to wash the cells free of Ferrous Sulphate. For this, drain the solution completely and again fill the water. Let the water stand for 30 min and drain again. Washin will remove the soluble ferrous sulfate. Repeat washing 2 times to remove all traces.
• Remove the cells and allow them to dry in an open shaded area, the cells should not be subjected to a temperature higher than 40 degrees C. use direct sun is not acceptable since the temperature can exceed 40 Degree C. use an industrial fan to evaporate the water. Compressed air directed at cells can also fast dry. Keep the cells for 24 hours or till they are completely dry. 
• Anywhere deposit on the cells shows that the ferrous sulfate is not completely removed. This will require repeated wash to remove all the salts 
• Thus, the cells are now discharged, washed free of sodium salt, and dry use of NANO3 – Sodium Nitrate ( 2.5%) in the place of Ferrous sulfate is another option. 

Principale Of Dishcharing:

The conductivity of water is increased by adding salts like FESO4, NACL, NA2SO4, etc. to keep the reaction under control, a low concentration of salt is used. The discharge should be slow and completed in 24 hours. 

Process 2: Cut open the Cells and Harvest the Cathode Material

• Cut open cells manually or by using other non-metallic devices. Steel cutters can be used without short-circuiting the cells. Shorting will cause fire and explosion and hurt the operator. First, the safety devices like PTC and CID outside the cell are removed. the n the outer casing which is made of nickel-plated steel should be removed. In some designs, there will be plastic outer. Thai plastic covering has to be removed first. 
• On removing the outer casing, a ‘jelly-roll consisting ( positive) can be identified from the aluminum foil on which it is coated. The anode ( negative) is coated on the copper foil. 
• The paste or the coated cathode material should then be removed from both sides of the aluminum foil using a plastic knife edge or SS blade. Collect the same in an SS vessel. This is the main manual work involved. 
• Rinse the cathode paste with diethyl carbonate (DEC) to remove the soluble material this can be done by immersing the cathode role in this solvent and draining it 2 times. The solution containing the DEC is collected and kept separately for recovering DEC by distillation. 
• The carbon present in the cathode has a much lower density and can be removed by centrifuging. A large centrifuge is necessary to carry out the separation of active materials from carbon. 
• After 2 washes in DEC, the cathode Rolls are soaked in N-methyl-2- pyrrolidone (NMP). in the original/new cells, cathode particles would be of micron size and well -separated from each other. But washing made them aggregates of larger size. The benefits of the nanoparticle are lost. 
•  To disperse the agglomerates back again to nanoparticles and keep them dispersed and separated from each other, it is necessary to subject them to ultrasonic vibration- SONIFICATION. Equipment generating ultra-sonic waves called SONICAATORS are to be used for good dispersal of cathode particles. 

Process: 3 Heating at 300 Degree C for 4 hrs to get the Original Crystal Structure of Cathode Materials

• During the above processing Procedures, the cathode material loses its crystalline structure. The original structure has to be brought back. It is also necessary to replenish the lithium lost during the operation of the cells. 40% operation of the original lithium is expected to be lost during the working life of the battery. This needs replacement. 
• Therefore a mixture of lithium nitrate- LINo3-a and lithium Hydroxide-LIOH- is mixed in the molar ratio of 3:2. This translates to a ratio of LINO3: LIOH::4;1 by weight. A calculated quantity of the lithium sales mixture by weight of the reclaimed cathode material. Of the mixture of salts is added. For 1kg material, we need 1000/14=71 cells. The total weight of one cell is taken as 45 g including anodes, separators, electrolyte, and outer case. 
• The sonicated ( subjected to ultrasonic Cavitation) material mixed with the lithium salts is heated in an oven at a temperature of 300 degrees C for 4 hours. The heating will melt the lithium salts which then enter into the layered crystal structure of the nickel, cobalt, etc. this is a method of injecting back lithium ( called Interaclatin) and replenishing the lost lithium in the cathode. For example, LINCAO2 cathode which has nickel 80% cobalt 15% and aluminum 5% has lithium intercalated within the crystal structure of the element nickel, cobalt, and aluminum. 
• Thermal Annealing: Prof. Zheng Chen conducts annealing at 800 Degree C to get the original crystal structure as present in original cathodes. Therefore, after 4hrs of lithiation ( lithium introduction), the material is heated to 800 Degree C in a furnace and held for a short duration( about 1 hr) to facilitate crystallization. 
• The material after lithiation and short annealing is now new cathode material that can be used to make a new cathode paste. 

Method 2 for Recycling Used Lithium-Ion Batteries

Large – Scale, high turn-over; good recovery and profitable.

The main difference between method and method 2 is the cathode is taken for processing while in method 2, the cathode and anode are taken for treatment with sulphuric acid. The initial steps of processing are the same for method 1 and method 2.

Process: 1 Discharge the Cells from Spent Cells/batteries 

• Discharging the cells to a safe lower voltage level is essential to ensure safe handling during cutting open the cells for subsequent processing steps. This can be done by discharging through a suitable resistance. Such a procedure is not practical when a large number of cells are to be discharged. 
• Therefore, discharge through ferrous sulfate (2.5%) solution is proposed. All cells, cylindrical, pouched cells are soaked in 2.5 % ferrous sulfate solution. Use an open tray or tank made of stainless steel or HDP with a bottom drain facility. Complete draining should be possible. To 100 L of DM water in the tank, add 2.5 KG of FeSO4, [ or 5.7 kg of, FESO4 7 H2O]. the temperature of the water should be around 25-35 Degree C. 
• Drop the cells as such into the solution and allow the discharge reaction to proceed for a minimum of 24 hours. There will be an evolution of hydrogen and oxygen gases due to electrolysis. Therefore, carry out his operations in an open area or under forced ventilation. 
• The next operation is to wash the cells free of the ferrous sulfate. For this, drain the solution completely and again fill it with water. Let the water stand for 30 minutes and drain again. Washing will remove the soluble ferrous sulfate. Repeat washing 2 times to remove all traces. 
• Rehome the cells and allow them to dry in an open shaded area. The cells should not be subjected to a temperature higher than 40 degrees C . the direct sun is not acceptable since the temperature can exceed 40 degrees C. use an industrial fan to evaporate the water. Compressed air directed at cells can also help in faster drying. Keep the cells for 24 hrs or till they are completely dry. 
• Any white deposit on the cells shows that ferrous sulfate is not completely removed. This will require a repeated wash to remove all the salts. 
• Thus, the cells are now discharged, washed free of sodium salt, and dry. 

Use of NANO3 – Sodium Nitrate (2.5%) in the place of ferrous sulfate is another option. 

Principle OF Discharging:

The conductivity of water is increased by adding salets like FESO4, NACL, NA2SO4, NA2 CO3, etc. to keep the reaction under control, a low concentration of salt is used. The discharge should be slow and completed in 24 hours. 

Process 2: Cut-open the Cells and take out the Cathode and Anode 

• Cut open cells manually or by using other non-metallic devices. Steel cutters can be used but without short-circuiting the cells. Shorting will cause fire and explosion and hurt the operator. First, the safety devices like PTC and CID outside the cell are removed. Then the outer casing which is made of nickel-plastic steel should be removed. In some designs, there will be a plastic other. This plastic covering has to be removed first. 
• On removing the outer casing, a ‘jelly-roll consisting of cathode, anode separator soaked in the electrolyte will be seen. 
• Rinse the jelly roll with ethyl alcohol to remove the soluble material. This can be done by immersing the jelly roll in Ethyl alcohol for 30 min. Heat the alcohol to 40 degrees C before immersing the jelly rolls. two washes with soaking for 30 minutes each and draining should be sufficient.
• [ Keep the drained solution containing the solvent and the lithium salts aside for recovery y distillation of alcohol]. 
• Now the jelly roll is free of the electrolyte and the dissolved lithium salts and is ready for further processing by conventional methods. 

Process 3. Leaching Jelly Roll with dilute Sulphuric Acid

Open jelly roll and remove the separator. The rolls of cathode and anode are then immersed and leached in sulphuric acid of specific gravity 1.3 ( 4molar) and kept at 70 degrees C for 4 hours. 

{ one jelly roll is opened and the separator is removed. Cathode and anode rolls are subjected to acid treatment, an SS vessel. For larger quantities, a jacketed SS digester of up to requires capacity can be sued. It would e advisable to have 3 sets of digesters and filtration units for smooth continuous working. Circulating hot water or steam through the jacket will increase the temperature to 70 Degree C. continuous recording of PH is also necessary.

Principle of Methods: Recycling Used Lithium-Ion Batteries

From the jelly roll, remove the separator. Digest or treat the balance with sulphuric acid 1.3 sp. Gr. all materials except the carbons, graphite, and silica will dissolve. Leaching is done at 70 Degree C. with continuous stirring. The undissolved materials are removed by filtration. 

• To the solution obtained after acid treatment, sodium hydroxide – NaOH is added. In order not to increase the total volume, add solid Na OH in small quantities at a time, stirring and measuring PH continuously. At PH value 5-5.5 copper, aluminum and iron will precipitate as hydroxides. This operation is done at room temperature with good sitting. Again, the precipitated hydroxides are removed by the filtration and the solution took to the next stage.
• Increase the pH by further addition of sodium hydroxide NaOH with continuous measurement of pH. At pH 8-10, all transition metals the main constituents of cathode cobalt, nickel, agency will be precipitated as hydroxides, the hydroxides are removed by filtration. The residue can be kept aside for sale as such or after further separation is required. 
• The Solution obtained from above is treated with Na2CO3 to precipitate Li2CO3. This is also washed and dried
• Yield is good as reported by many recyclers. 

A Better method is to segregate the cells by the chemistry of the cathode at the start. This presupposes a huge stock of scrap. The cathode material obtained after the treatment will be the same as an original cathode. If possible, segregate to get cleaner products. This involves manual sorting.