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Surface Modification of Manganese-Rich Cathode Materials in Lithium Ion Batteries
High energy density of Li-ion batteries becomes more and more important for electric vehicle and hybrid electric vehicle. The many researches have been focused on cathode materials to substitute the commercial LiCoO2. Among various cathode materials, Over-lithiated Layered Oxide (OLO), recently investigated, is the layered transition metal oxide having more than unit Li concentration. Because OLO exhibits much higher capacity over 250mAh/g as well as lower cost, high safety and thermal stability [1,2]. So the OLO is considered as attractive candidate for cathode material because of the high capacity, reduced toxicity and low cost. However this material generates gas inevitably during charge/discharge process and exhibits not good cycle performance and poor electrical conductivity compared to other cathodes. As one of the approaches to solve these problems, we introduced surface modification with conducting polymer. Field Emission Scanning Electron Microscopy, X-ray diffraction, Fourier Transform Infrared Spectroscopy and Various Charge-discharge measurements were also performed to investigate the effect of surface-coating layer.
Experimental
To prepare Samples, modified OLO is made by wet-type coating method. Electrode slurry has been made of 94% of cathode materials, 3% of Denka black, 3% of PVdF. The slurry was casted on the Al foil for current collector and assembled with 2032 coin cell. Field Emission Scanning Electron Microscopy, X-ray diffraction, Fourier Transform Infrared Spectroscopy and Various Charge-discharge measurements were also performed to investigate the effect of surface-coating layer.
Results and discussion
Fig. 1 show the discharge profiles of the rate capability for the pristine, 1wt.% PEDOT:PSS coated OLO and 3 wt.%PEDOT:PSS coated OLO electrode between 2 and 4.6 V. Surface-modification of cathode electrodes with conducting polymer leads to the more good rate properties.
Reference
1. M. M. Thackeray, S.-H. Kang, C. S. Johnson, J. T. Vaughey, R. Benedek, S. A. Hackney, J. Mater. Chem. 17, 3053-3272(2007).
2. X. Lie, H. Li, D. Li, M. Ishida, H. Zhou, J. Power Sources 243, 374-380. (2013).