Synthesis and Characterization of Flexible and Free-Standing Carbon Nanotube, Graphene Films and Their Composites for Li-Ion Batteries

Abstract

The objective of this communication is to present our results on the synthesis and the characterization of flexible and free standing films made from Carbon Nanotube (CNT), reduced graphene oxide (rGO) [1] and their composites (CNT/rGO). The films were obtained by filtration method from aqueous suspension of CNT, rGO, or CNT/rGO. The obtained materials are used as negative electrode in Li-ion systems. CNT films with a thickness below 50 µm are integrated on an electrodeposited Cu current collector (15 µm thick) according to the method describe by Luais et al [2], whereas CNT or CNT/rGO flexible free standing films with a thickness of 50 µm can be directly used without the need of a metallic current collector as anode material for battery cycling. All results will be discussed on the basis of SEM observations (as synthetized films and after cycling for post-mortem characterizations), Raman spectroscopy analysis, galvanostatic cycling, and electrochemical impedance spectroscopy. CNT free standing electrodes exhibit specific discharge capacities up to 300 mA.h.g-1 at C/20 and 200 mA.h.g-1at 5C. The effect of rGO/CNT ratio in composite electrodes will be presented as an improvement of the electrochemical performances compared to CNT free standing electrodes. Figure : a-Evolution of the specific capacity of CNT free standing film in Li-ion half-cell. SEM images of b1: as synthetized free standing CNT film, and b2: after cycling in EC/PC/3DMC 1M LiPF6 electrolyte; Photographs of c1: a flexible free-standing film, and c2: the same film roll up around a plastic rod [1] Qian Cheng, Jie Tang, Jun Ma, Han Zhang, Norio Shinya, Lu-Chang Qin, CARBON 49 (2011) 2917–2925[2] E.Luais, J. Sakai, S. Desplobain, G. Gautier, F. Tran-Van, F.Ghamouss. Journal of Power Sources, 242, 2013,166-170