Importance of Carbonaceous Material for Enhanced Cycling Stability of Cobalt Oxide Anode

Transition metal oxide anode (M_xO_y, M=Fe, Co, Ni or Cu) has been considered as one of the most promising options for high performance lithium ion batteries due primarily to its large specific capacity. However, its practical use is seriously hindered because the formation of electrical insulating lithia matrix and large volume change during lithiation/delithiation process cause poor energy efficiency and reduced cycling stability, respectively. In order to figure out such problems, there are a number of studies about the composite of nano-sized active materials and various carbon-based conducting materials (e.g.graphine). The recent researches about different conducting materials revealed that performance of transition metal oxide anode is very sensitive to the content of conducting materials. Nevertheless, the in-depth study about the conducting material effect on electrochemical property has not been carried out yet.

In this work, the effect of conducting material on reaction mechanism of cobalt oxide with lithium is investigated. For this purpose, electrochemical properties of samples containing different amounts of conducting materials were analyzed by using electrochemical techniques such as chronopotentiometry, chronoamperometry, and impedance spectroscopy. In addition, their crystal structures were characterized as a function of depth of discharge. From these results, it is suggested that there is another delithiation mechanism competing with typical one to reach delithiated cobalt oxide. It is proved that the larger amounts of conducting material makes it more activated.

In this presentation, the difference in reaction mechanism between the cobalt oxides with and without conductive material will be suggested. Moreover, capacity fading mechanism of cobalt oxide will be accordingly discussed.