Hyun SC  Na BK

Vol. 24,  No. 1, pp. 77-84, Mar.  2018
10.7464/ksct.2018.24.1.077

Lithium secondary batteries Anode materials Li4Ti5O12 Carbon coating

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In this study, Li4Ti5O12 anode materials for lithium ion battery were synthesized by dry ball-mill method. Polyvinyl chloride (PVC) as a carbon source was added to improve electrochemical properties. When the PVC was added after Li4Ti5O12 formation, the spinel structure was well synthesized and it was confirmed by X-ray diffraction (XRD) experiments. When the carbon material was added before the synthesis and the heat treatment was performed, it was confirmed that a material having a different crystal structure was synthesized even when a small amount of carbon material was added. In the case of Li4Ti5O12 without the carbon material, the electrical conductivity value was about 10 μS m-1, which was very small and similar to that of the nonconductor. As the carbon was added, the electrical conductivity was greatly improved and increased up to 10,000 times. Electrochemical impedance spectroscopy (EIS) analysis showed that the size of semicircle corresponding to the resistance decreased with the carbon addition. This indicates that the resistance inside the electrode is reduced. According to the Cyclic voltammetry (CV) analysis, the potential difference between the oxidation peak and the reduction peak was reduced with carbon addition. This means that the rate of lithium ion insertion and deinsertion was increased. Li4Ti5O12 with 9.5 wt% PVC added sample showed the best properties in rate capabilities of 180 mA h g-1 at 0.2 C-rate, 165 mA h g-1 at 0.5 C-rate, and 95.8 mA h g-1 at 5 C-rate.