Recovery of LiCoO 2 from Wasted Lithium Ion Batteries by using Mineral Processing Technology

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1 3 Recovery of LiCoO 2 from Wasted Lithium Ion Batteries by using Mineral Processing Technology RESOURCES PROCESSING Younghun KIM a, Mitsuaki MATSUDA b Atsushi SHIBAYAMA c and Toyohisa FUJITA d a Korea Resources Corporation (KORES), , Shindaebang-Dong, Dongjak-Gu, Seoul, , Korea b Akita Prefectural Resources Technology Development Organization, 9-3, Kosaka-Kozan Aza Furudate, Kosaka-machi, Kazuno-Gun, Akita Pref., , Japan c Faculty of Engineering and Resource Science, Akita University, 1-1 Tegata-Gakuen cho, Akita, , Japan d RACE, Department of Geosystem Engineering, Graduate School of Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, , Japan Abstract Lithium cobalt oxide from a wasted lithium ion secondary battery (LIB) is recovered by means of flotation. At first, the wasted LIB was crushed by vertical cutting mill and classified by air table and vibration screen. Referring to the crushing and separating results, wasted LIB is represented by light materials (organic separator of anode and cathode of battery), metallic materials (aluminum & copper foil, aluminum case etc.) and electrode materials (mixture of lithium cobalt oxide (LiCoO 2) and graphite). Electrode materials were thermally treated in a muffle furnace at 773K, followed by flotation to separate LiCoO 2 and graphite. The fact that the surface of particles was changed from hydrophobic to hydrophilic due to the removal of binder from the surface at 773K. Considering the results, 92% LiCoO 2 was recovered from electrode materials, whereas the purity was higher than 93%. The optimum conditions of flotation process were as follows: 0.2 kg/t kerosene as a collector, 0.14 kg/t MIBC as a frother and 10% pulp density. The experimental results suggested that this process by using mineral processing technology, such as crushing, screening, flotation, etc., is feasible to recover LiCoO 2 from the wasted LIB representing a new recycling technique. 1. Introduction In recent years, the production of informationcommunication and small portable devices are increasing rapidly. To operate these devices, Lithium ion secondary battery (LIB) as the main stream of batteries is mentioned. LIB system has become increasingly popular in applications such as portable computer, camcorders and cellular phones. LIB is a useful battery due to good physical and electrical properties, high energy density, high voltage, low self-discharge rate and long cycle time [1 3]. The amount of LIB production had increased about over 10 times during past 5 years from 1995 to 2000, which is approximately from 40 million into 470 million unit [4]. LIB has a high value for recycling, because it consists of useful constituent units such as aluminum and copper foil and an oxide such as LiCoO 2. The recycling of LIB has been performed in the industry and research papers have been reported as well [5 7]. Consequently, the primary purpose of this study is the development of a process to recycle aluminum and copper foil as metal resources and to recover LiCoO 2 particles by means of flotation. By this study, it is manifest that the recovery and grade of LiCoO 2 recovered from wasted LIB is high, approximately over 90%. Accepted 15 December 2003

2 4 Younghun KIM, Mitsuaki MATSUDA, Atsushi SHIBAYAMA and Toyohisa FUJITA 2. Sample and experimental method 2.1 Sample A LIB consists of an IC chip, a plastic casing and several unit cell. The unit cell is composed of a cathode, an anode, an organic separator, an organic electrolyte and aluminum casing. The cathode is fabricated by pasting LiCoO 2 active materials, carbon-conducting additives and a binder pasted on aluminum foil. The anode is made by the same process with graphite active materials, carbon-conducting additives and a binder pasted on copper foil. Prismatic type LIB which is widely used as the parts of cellular phone and portable devices were tested as a sample in this study. In this experiment, exposed aluminum case after removing a plastic casing was treated. A shape and components of the LIB is shown Fig Experimental method Prismatic type LIB was crushed by means of a vertical cutting mill (VM-20 type, Orient Co., Japan), which had 3.7 kw of motor power and 1,000 rpm of rotation speed. Crushed products from vertical cutting mill were classified by using a sieve, air table and vibrating screen. A black mixed powder mainly including LiCoO 2 and graphite was recovered as a final Fig. 1 Structure of Lithium Ion battery (LIB). product of classification. This powder was separated by flotation recovering two products, LiCoO 2 and graphite. Flotation machine was a MS type which had 250 ml of cell capacity and 2,500 rpm of rotation speed of impeller. To float graphite powders against LiCoO 2, kerosene was used as a collector and MIBC (Methyl Iso Butyl Carbinol) as a frother during in the flotation process. The concentration of kerosene and MIBC were 0~3.2 kg/t and 0.14 kg/t respectively. Flotation time was 10 minutes and pulp density was 10%. 3. Results and discussion 3.1 Crushing and classifying of wasted LIB To recycle metal resources of LIB, it is necessary to perform crushing and separating process. Prismatic type LIB was crushed by means of vertical cutting mill and then separated by means of a sieve, air table and vibration screen. To investigate crushing conditions, samples were crushed by controlling a crushing time; 30, 60, 180, 300 seconds. The result was shown in table 1. As shown in table 1, approximately 42.9 through 48.0 wt% of crushed products remained on the 10 mesh sieve. An organic separator, aluminum foil, copper foil and aluminum case were found in this class of particle size. These components were found in 10 through 65 mesh as well. On the other side, only black mixed powders was recovered in under 65 mesh size class. These powders include LiCoO 2 powders as an active material of cathode electrode and graphite powders as it of anode of electrode. 3.2 Change of LiCoO 2 powder surface by thermal treatment Black mixed powders including LiCoO 2 particles were recovered by means of separating processes such as sieving. These powders were analyzed by means of X-Ray Diffraction (XRD). The result was proved that black mixed powders are composed of LiCoO 2 as active material of cathode electrode and graphite as anode electrode. Table 1 Results of crushing test: relationship between crushing time and recovery of crushed product Crushing time 30 s 60 s 180 s 300 s Initial weight (g) Weight after crushing (g) Yield (%) Wt.(%) (+10 mesh) Wt.(%) ( 10~+65 mesh) Wt.(%) ( 65 mesh) RESOURCES PROCESSING

3 Recovery of LiCoO 2 from Wasted Lithium Ion Batteries by using Mineral Processing Technology 5 Fig. 2 SEM image of LiCoO 2 for different heating temperature (a) LiCoO 2 (no treatment), (b) LiCoO 2 (773K, 2 hr) LiCoO 2 and graphite particles could be separated by flotation process because two powders have different surface properties. The property of LiCoO 2 and graphite particles was hydrophilic and hydrophobic respectively. However, the surface of LiCoO 2 and graphite powders in the black mixed powders were covered by PVDF (Polyvinyliden Difluoride) [8,9] which was a kind of Teflon-binder and had hydrophobic property. Thus, these powders could not be separated by flotation in nature. To change hydrophobic into hydrophilic property of LiCoO 2 powders, a thermal treatment to remove PVDF from the surface of these particles was needed and performed. To check the removal of the binder, the surface of LiCoO 2 powders after thermal treatment was observed by using SEM. SEM images of the surface of LiCoO 2 before and after thermal treatment at 773K were shown in Fig. 2. In Fig. 2(a), some materials estimated as binders are shown between particles and on the surface. In Fig. 2(b), the sample has been heated for 2 hours, it was obvious that most of them were volatilized and removed. As a result, the surface of LiCoO 2 powders was clear. It was necessary to remove binders from the surface of LiCoO 2 particles so that the property of the surface could be change from hydrophobic into hydrophilic. This change should contribute to separation of LiCoO 2 and graphite by flotation. It was expected that the separation of LiCoO 2 and graphite by flotation was possible. 3.3 Flotation of crushed LIB powder Flotation of mixed powders including LiCoO 2 and graphite of wasted LIB was performed. To investigate the effect of kerosene as a collector on Fig. 3 Effect of kerosene concentration on the flotation for the powder of crushed wasted LIB. (MIBC: 0.14 kg/t, pulp density: 10%) the recovery and grade of LiCoO 2, flotation was performed by controlling input amounts of kerosene from 0 kg/t to 3.2 kg/t MIBC, pulp density and flotation time was 0.14 kg/t, 10%, 10 minutes respectively. The result was shown in Fig. 3. As shown in Fig. 3, the grade (93%) and recovery (92%) of LiCoO 2 had a slight change even the amounts of kerosene changed from 0.2 kg/t up to 3.2 kg/t. Thus, it was interpreted that there is no effect of the addition of kerosene to the grade and recovery of LiCoO 2. However, no addition of kerosene could affect much lower grade and recovery than with the addition of kerosene. Consequently, it was verified that 0.2 kg/t of kerosene as a collector was the most economical amounts. In addition, the grade of LiCoO 2 is recovered by 93% be-

4 6 Younghun KIM, Mitsuaki MATSUDA, Atsushi SHIBAYAMA and Toyohisa FUJITA Fig. 4 Influence of pulp density on the flotation for the powder of crushed wasted LIB. (kerosene: 0.2 kg/t, MIBC: 0.14 kg/t) cause impurities such as fine particles of aluminum foil and case were found with LiCoO 2 in this amount. To investigate about a recovery and grade of LiCoO 2, flotation in that 0.2 kg/t fixed amounts of kerosene was added and performed by controlling pulp density from 2,5% up to 20%. Other conditions were the same. The result was shown in Fig. 4. As shown in Fig. 4, if pulp density increases, the grade and recovery decreases. For example, in 10% pulp density, LiCoO 2 with over 93% grade was recovered by over 92%. Over 10% pulp density, however, it could be confirmed that the grade and recovery were decreasing. For instance, in 20% pulp density, it could be shown that the grade and recovery of LiCoO 2 was approximately 89% and 84% respectively. Throughout the result of preceding test, it could be determined that the best conditions of flotation separating black mixed powders into LiCoO 2 and graphite were as following; kerosene as collector, MIBC as frother and pulp density is 0.2 kg/t, 0.14 kg/t and 10% respectively. As a result, flow sheet of the recycling process of wasted LIB was shown in Fig. 5. First, wasted LIB was crushed by means of vertical cutting mill for 30 seconds. A crushed sample was sieved by a 10 mesh sieve. A product, which passed through a 10 mesh sieve was separated into black mixed powders (LiCoO 2 and graphite particles) and metal materials (aluminum foil, copper foil and aluminum case) by means of a 65 mesh vibrating screen, while a product which remains on it was separated into organic separator and metal materials (aluminum foil, copper foil and aluminum Fig. 5 Flow sheet of the recycling process of wasted LIB. RESOURCES PROCESSING

5 Recovery of LiCoO 2 from Wasted Lithium Ion Batteries by using Mineral Processing Technology 7 case) by means of air table. Next, in order to change the property of the surface of LiCoO 2 and graphite powders for flotation process, black mixed powders were heated at 773K for 2 hours. Then flotation was performed to recover LiCoO Conclusion In this study, recycling valuable metals and LiCoO 2 particles from wasted LIB by means of several separating method focused on flotation was performed. The results are as follows. 1) It is possible to separate the wasted LIB into metals, organic separator, aluminum foil, copper foil and aluminum case and black mixed powders, including LiCoO 2 particles and graphite, throughout separating processes by means of a vertical cutting mill, sieve, air table and vibrating screen. 2) It is possible to change the property of the surface of LiCoO 2 powders from hydrophobic to hydrophilic by thermal treatment for 2 hours at 773K to volatile the binder from the surface. After a thermal treatment the recovery of LiCoO 2 powders and graphite were over 98% by flotation. Thus, it is also possible to separate and recover LiCoO 2 powders effectively. 3) It is possible that the recovery of LiCoO 2 powders with over 93% grade was over 92% by flotation. The flotation was performed under optimum conditions; kerosene as collector, MIBC as frother, pulp density and flotation time was 0.2 kg/t, 0.14 kg/t, 10% and 10 minutes, respectively. References 1. Johnson B.A. et al., Characterization of commercially available lithium-ion batteries, J. of power sources, 70 (1998), Moshtev R. et al., State of the art of commercial Li ion batteries, J. of power sources, 91 (2000), Nishi Y., Lithium ion secondary batteries; past 10 years and the future, J. of power sources, 100 (2001), Battery association of Japan, homepage: 5. Contestabile M. et al., A laboratory-scale lithium-ion batteries recycling process, J. of power sources, 92 (2001), Michael J.L., Recycling of lithium ion cells and batteries, J. of power sources, (2001), Lee C.K. et al., Preparation of LiCoO 2 from spent lithium-ion batteries, J. of power sources, 109 (2002), Jarvis C.R et al., Use of grafted PVdFbased polymers in lithium batteries, J. of power sources, (2001), Shi O. et al., Structure and performance of porous polymer electrolytes based on P(VDF-HFP) for lithium ion batteries, J. of power sources, 103 (2002),