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RESOURCES PROCESSING

Original Paper

A Novel Flow Sheet for Processing of Used Lithium-ion Batteries for Recycling

Yuta YAMAJI

1

, Gjergj DODBIBA

1

, Seiji MATSUO

1

, Katsunori OKAYA

1

, Atsushi SHIBAYAMA

2

and Toyohisa FUJITA

1

1Department of Systems Innovation, Graduate School of Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

2Faculty of Engineering and Resource Science, Akita University,1-1, Akita 010-8502, Japan

Abstract

In recent years, the demand for the lithium-ion battery is increasing due to the increasing demand for laptop computer, cellular phone and automobiles. The positive electrode of the lithium- ion secondary battery is made of lithium oxide with mainly cobalt, nickel and manganese etc.. An effective recycling method not only would collect cobalt and lithium, but also separate other mate- rials from the used batteries. In this research, the optimum processing flow sheet is investigated and their efficiency is evaluated. The battery is safely decomposed by underwater explosion and then cutter mill. After the over 1mm in size particles are separated by the magnetic separation, eddy cur- rent separation and gravity separation by air table, the plastic, Al, Fe, and Cu products are obtained.

On the other hand, the particles less than 1mm in size are effectively separated by flotation and car- bon and positive electrode powders are recovered. The lithium cobalt powders are leached, neutral- ized and heated as Co3O4 and lithium is recovered by the adsorption method.

Key words: Lithium-ion, Battery, Recycling, Crushing, Separation, Leaching

1. Introduction

Lithium-ion batteries production is increasing since the demand for batteries to be used in laptop computer, cellular phone and automobiles is ris- ing. Therefore, the reuse system of batteries has to be developed. The quality of battery has also been improved and therefore, it is important to recycle the used battery. The production amount of lithium-ion battery in Japan1 is shown in Fig. 1.

Between 2000 and 2008, the production of the lithium-ion battery was increased to about six times.

Many kinds of lithium-ion batteries are produced, therefore, not only the reuse but also material re- cycling becomes important. Many investigations of recycling of lithium-ion batteries have been re- ported recently for the crushing and physical separation2,3, solvent extraction4,5, incineration and chemical process6 and in the review7.

Nowadays for the recycling of lithium-ion bat- tery, the batteries are directly put into rotary kiln and roasted, followed by crushing and solvent ex- traction and so on to recover cobalt, copper and iron. However, the recycling is not enough and there are many problems that should be dealt, par- ticularly the resin recovery, crushing method and recovering process of various metals.

The composition of lithium-ion battery used in this experiment and photographs of two different types (cylindrical and rectangular) of lithium-ion battery are shown in Fig. 2. These are only battery parts. Also the plastic resin such as ABS, which covers the battery, is important to be recovered from lithium-ion battery package. Nowadays, the positive electrode of battery are made of different materials, LiCoO2, LiMn2O4, LiNiO2, LiFePO4 etc.. In this experiment the main cathode is LiCoO2.

2. Experimental

In this experiment, the flow sheet for recovering

Paper presented at the 8th Japan/Korea International Sympo- sium on Materials Science and Resources Recycling, 24–25 June 2010, Seoul, Korea

Accepted 13 February, 2011

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lithium ion battery is shown in Fig. 3. At first, the lithium-ion battery package is disintegrated by the explosion under water. Normal mechanical crush- ing of battery causes the explosion by electrical breakdown and the emission of HF gas. Electro- lyte containing lithium- hexa- fluoro- phosphate with ethylene carbonate reacts with water as the following equation.

LiPF6+ H2O→ LiF + POF3+ 2HF

If the water in the explosion contains calcium ion, fluorine ion can be precipitated as follows,

CaCl2+ 2HF → CaF2+ 2HCl

By under water explosion, the battery package can be safely separated into plastic parts and cylindri- cal and rectangular battery parts. Next, the battery parts are crushed by cutter mill for the separation of iron and aluminum frame, copper foil, plastic film, anode graphite powder and cathode LiCoO2 etc. powders. Those crushed parts are sieved into +1 mm and −1 mm fractions.

The +1 mm size particles are magnetically sep- arated by the rare earth roll magnetic separator.

The magnetic materials are mainly iron flame. The nonmagnetic particles are fed into eddy current separator. The nonconductive parts are mainly plastic film like PVC, etc.. The conductive parti- cles are separated by air table into lighter and heavier fractions. At first the aluminum plate and cupper films are separated as lighter parts and they are separated again by the gravity separation. On the other hand, as the heavier fraction mainly in- cludes non crushed batteries, they are returned to the cutter mill.

The −1 mm size particles are fed into floatation cell and separated as float product of graphite powders and sink product of cathode LiCoO2 etc.

powders. The separated LiCoO2 powders are dis- solved in sulfuric acid aqueous solution and neu- tralized by alkaline and precipitated as cobalt hydroxide. The cobalt hydroxide is heated and Co3O4 is recovered. On the other hand, the salts are removed from filtrate, Li ion is recovered by the adsorption.

3. Results and Discussion

The experimental setup and photograph of un- derwater explosion to separate the lithium-ion bat- tery package is shown in Fig. 4. Only a small amount of explosive powder was used for disinte- grating the batteries. The plastic case and battery parts are separated. Therefore, it is easy to handle after explosion. Next, the separated parts are crushed by the cutter mill8 as shown in Fig. 5. The crushed size depends on the crushing time and the size distributions of 5 second and 10 seconds of crushing time are also shown in Fig. 5. After 5 seconds about 40% of crushed particles are under Fig. 1 Demand of Lithium and cobalt metals and lithium

ion battery production number in Japan1.

Fig. 2 Composition of lithium-ion battery used in this experiment and photographs of two types (cylin- drical and rectangular) of lithium-ion battery.

Fig. 3 Flow sheet for recovering the lithium-ion battery.

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1 mm size and it increases to 65% after 10 sec- onds. Next, the over 1 mm size fraction is fed into magnetic separator, while, less than 1 mm size fraction is separated by flotation.

The magnetic separation result for plus 1mm size fraction is shown in Table 1. The magnetic separator of rare earth roll9 is used and the magnet- ic flux density on the belt surface is 1.2 T. Almost 100% of iron particles over 1 mm size are separat- ed from nonmagnetic particles. Next, nonmagnet- ic particles are fed into eddy current separator3. The separation results are shown in Table 2. Parti- cles bigger than 4.8 mm in size, i.e. Al and Cu, can be well separated from other particles at about 70% and 80% recovery, respectively. In −4.8 + 1.0 mm size fraction, the conductive particles percentage increases in nonconductive fraction.

For finer size particles, it is necessary to process them in a lower belt speed in order to increase the efficiency.

After the eddy current separation, each conduc- tive parts and nonconductive parts are separated by gravity separation using air table10. In the con- ductive parts are separated by air table and the re- sult is shown in Fig. 6. At first the aluminum and copper metals are separated in the lighter fraction from the heavier fraction that is 90% of non- crushed battery. Next, aluminum plate is possible to separate from heavier copper foil or plate. Non-

conductive parts are PET, PVC and non-crushed battery. The heavier fraction is also non-crushed battery. Those non-crushed battery is returned to the cutter mill, again.

On the other hand, less than 1 mm size fraction of lithium ion battery, obtained by cutter mill is fed into a MS type flotation machine. The flota- tion of thermally treated electrode material has been reported2. The flotation results are shown in Table 3. The graphite is collected as a float prod- uct at 95% recovery. The LiCoO2 that is the main component of the positive electrode in battery has been recovered as a sink product at about 90% re- covery. In the sink product is contaminated by 0.5% aluminum and 1.4% copper.

The sink products of flotation powders are dis- solved with sulfuric acid aqueous solution. Next the sodium hydroxide aqueous solution is added, followed by the precipitation of cobalt hydroxide at pH 9. The solubility product constant11 of Co(OH)2 is 5.9× 10−15. After the filtrated cobalt hydroxide is washed and heated at 500°C for 2 hours. The recovered cobalt oxide is Co3O4 by the X-ray diffraction. The chemical reactions are Fig. 4 Experimental setup of explosion of lithium-ion

battery in water and photograph of decomposed batteries by explosion (Emulsion explosive 10 g, water 1.45 t, lithium-ion battery 5 kg)

Fig. 5 Cutter mill to crush the lithium-ion battery decomposed by explosion and the crushed size distribution depending on the crushing time.

Table 1 Magnetic separation result by rare earth roll for +1 mm size of crushed lithium ion bat- tery (Rectangular type battery, Magnetic flux density on the belt surface 1.2 T)

Magnetic separation

Grade, % Recovery, %

Fe Others Fe Others

Feed 28.4 71.6 100 100

+4.8 mm Magnetics 88.3 11.7 96.0 10.2

Non-magnetics 0 100 0 56.9

−4.8 mm

+ 1.0 mm Magnetics 18.1 81.9 3.8 4.8

Non-magnetics 0.6 99.4 0.2 28.1

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as follows,

2LiCoO2+ 3H2SO4

→ Li2SO4+ 2CoSO4+ 3H2O+ 1/2O2

CoSO4+ 2NaOH → Co(OH)2+ Na2SO4

3Co(OH)2+ 1/2O2→ Co3O4+ 3H2O

After recovering the cobalt, the lithium ion exists in the high concentration of sodium sulfate aqueous solution. To collect the lithium ion, the sodium sulfate should be removed. As the lithium ion concentration is low (about 1000 ppm), it is difficult to precipitate the lithium ion as Li2CO3. Here, the lithium ion is absorbed by the manga- nese oxide (MnO2), manganese nodule, and, blue green algae’s powder. The lithium ion has been adsorbed within 240 minutes as indicated in Fig. 7. The Li ion absorbing capacity of MnO2 is 11.7 mg/g. The adsorbed lithium is eluted with acid and concentrated about 2000 ppm.

10000 ppm of Li ion solution is needed. The amount of the adsorbent is increased and the Li ion is adsorbed completely, elute it by acid, then concentrating the solution, recovering as the

Li2CO3 might become possible. Next it will be precipitated as Li2CO3 to recover.

4. Conclusions

Lithium-ion battery recycle has been studied and a flow sheet for recycling has been proposed.

The battery package is easily disintegrated by the explosion in the water containing Ca2+ ion. Next the disintegrated batteries are crushed by the cutter mill. The particles bigger than 1mm in size are fed into rare earth roll magnetic separator and the iron have been separated as a magnetic fraction. Non- magnetic parts are separated by the eddy current.

Aluminum and copper are recovered as conduc- tive, while, the non-conductive parts are mainly plastics. The each fraction separated by eddy current was then fed into gravity separator of air table. The metal and plastic parts are recovered and the heavier fraction is uncrushed battery. The uncrushed battery once again is returned to the cutter mill. On the other hand, the particles less than 1 mmin size are separated by flotation. The Table 2 Eddy current separation result of non-magnetics obtained by magnetic separation shown in Table 1 (Rectangu-

lar type battery, +1.0 mm, Drum rotation speed inside belt 2500 rpm, Belt speed 0.78 m/s)

Eddy current separation Grade, % Recovery, %

Al Cu Others Al Cu Others

Feed 7.3 10 82.7 100 100 100

+4.8 mm Conductive 26.3 47.4 26.3 68.7 78.2 13.3

Nonconductive 2.7 2.7 94.6 4.5 4.2 46.8

−4.8 mm

+ 1.0mm Conductive 27.3 18.1 54.6 10.8 4.8 6.3

Nonconductive 10.9 13.1 76 15.1 12.8 33.6

Fig. 6 Separation with air table of conductive particles obtained in Table 2 (Air blowing speed 1.2 m/s,

Vibration of deck in air table 10 Hz) Fig. 7 The lithium ion concentration depending on the agitation time after the addition of MnO2 powder (MnO2 mass, 2%)

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float product was mainly graphite whereas the sink one was lithium cobalt oxide. The lithium co- balt oxide is leached, neutralized and precipitated as cobalt hydroxide. The cobalt hydroxide is heated and recovered as Co3O4. The lithium ion in leached water is absorbed by manganese oxide, eluted and concentrated to prepare lithium carbonate.

Acknowledgement

The authors are appreciated the experiment of battery explosion in water by Dr. K. Murata, Nippon Koki Co., Ltd. and the support of JSPS Scientific Research (A), No. 22246118.

References

1. JOGMEC, Material flow of mineral resources, Mineral resources information center, http://

mric.jogmec.go.jp/mric_search/ (2008)

2. Y. Kim et al.: Recovery of LiCoO2 from waste lithium ion batteries by means of flotation, Shigen-to-Sozai, 118, pp. 687–693 (2002)

3. J. Li et al.: A combined recovery process of metals in spent lithium-ion batteries, Chemosphere, 77, pp. 1132–1136 (2009)

4. M. Niinae and T. Suzuki: Recovery of Co and Li from lithium-ion batteries with solvent extraction, Chemical Engineering, 55, pp. 735–742 (2010) 5. R.C. Wang et al.: A novel recovery process of

metal values from the cathode active materials of the lithium-ion secondary batteries, Hydrometal- lurgy, 99, pp. 194–201 (2009)

6. J. Shibata and N. Murayama: Recycling technolo- gy of lithium-ion secondary battery, Chemical plant, 52, 8, pp. 25–31 (2010)

7. J. Xu et al.: A review of processes and technolo- gies for the recycling of lithium-ion secondary batteries, J. of Power Sources, 177, pp. 512–527 (2008)

8. Orient Co., Ltd., http://www.orient-c.co.jp/ (2005) 9. Erize Magnteics Japan Co., Ltd., http://eriez.co.jp/

industry/nonferrous.html (2010)

10. T. Furuyama et al.: Recovering PVC by tribo- electric separation and air tabling, Resources Pro- cessing, 53, pp. 153–159 (2006)

11. D.R. Lide: Handbook of chemistry and physics, CRC press. 89th, 8-123, 4-91 (2008)

Table 3 Flotation result for −1 mm size of crushed lithium ion battery (Pulp density 10%, MIBC 0.14 kg/t, kerosene 3 kg/t)

Flotation Grade, % Recovery, %

Li Co Graphite Li Co Graphite

Feed (About 60% LiCoO2) about 30% 100 100 100

Float 0.7 3.3 90 15 12 95

Sink 3.8 24 5 85 88 5

References

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