Enhancement of Li-O2 Battery Performance with Novel Bubble-like-Carbon-Based Oxygen Electrode

Abstract

In recent years, Li-O2 battery has emerged as one of promising next-generation energy storage systems with benefits of higher energy density and exceeding specific capacity than those of commercial Li-ion battery. Especially, it is expected to have an ability to power the electrical vehicle which is attracting great attention all over the world. Despite the potential application for high power consumption devices, however, the practical performance of Li-O2battery still need to be significantly improved in order to replace fossil fuels completely. Obviously, much effort has been devoted to develop commercially feasible Li-O2 battery up to date. Amongst various components, oxygen electrode has long been of great interest. Since formation, decomposition and storage of insoluble discharge product, Li2O2, strongly depend on the design of oxygen electrode; particularly the architecture of oxygen electrode material plays an important role in determining specific capacity and re-chargeability. According to previous studies, it has been revealed that nanostructured material with large surface area and high porosity is compatible for oxygen electrode of Li-O2 battery by alleviating pore clogging, which is a main effect that limits the battery performance1. In this respect, various carbon configurations, such as graphene, nanotubes, and nanofibers, have been investigated extensively as an electrode material2,3. Although recent efforts have made a considerable progress in developing novel materials for oxygen electrode, materials that can satisfy the requirements for Li-O2battery application are still scarce. Herein, we introduce a novel carbon structure, carbon bubble, as an electrode material and evaluate the battery performance with this electrode without any additional catalysts. Due to unique structure, such as high specific surface area and large pore volume which is derived from bubble-like pore structure with 100 ~ 200 nm diameters, and high availability from cheap source of vacuum residue, this novel carbon material can be widely used as outstanding electrode material for Li-O2 battery application. As for the result, battery performance was notably improved with carbon bubble introduction. Above all, specific discharge capacity increased over 3 times higher than that of commercial KB600J whose specific surface area is nearly same with carbon bubble, 1351 m2 g-1 and 1249 m2 g-1 respectively. Thus, specific surface area is not the crucial point of capacity improvement; it may be attributable to the favorable pore structure of carbon bubble. That is, large pore structure of carbon bubble acts as an efficient reservoir for the discharge product. It is also supported by several analyses, TEM, SEM and XRD. Based on these results from our study, it can be demonstrated that carbon bubble itself, without any additional catalyst, is a promising candidate for use as an ideal electrode in Li-O2 battery. S. B. Ma, D. J. Lee, V. Roev, D. Im and S. Doo, J. Power Sources, 244, 494 (2013). B. Sun, B. Wang, D. Su, L. Xiao, H. Ahn and G. Wang, Carbon, 50, 727 (2012). R. Mitchell, B. Gallant, C. Thompson and Y. Shao-Horn, Energy Environ. Sci. 4, 2952 (2011). Figure 1