Li Intercalation In Nonwoven Carbon Nanotube/Carbon Fiber Felt Electrode: Influence Of Carbon Fiber Type

Binder-free electrodes resulting from nonwoven carbon fiber felt coated with carbon nanotubes (CNT/FELT) are a useful class of composites to explore the electrochemical properties of CNTs and derived nanostructures deposited on the CNT surface. Here, we show that, contrary to current literature knowledge, the nonwoven carbon fibers are not just a constituent of the CNT/FELT and do not have the exclusive function of holding the CNT network in the three-dimensional architecture. In fact, the nonwoven carbon fibers constituting the FELT and their electronic conductivity influence Li+ intercalation into the CNTs coating the FELT. By using FELT coated with cup-stacked-CNT (5% wt. CSCNT) and embedded with SWCNTs (CSCNT/FELTSWCNT) or MWCNTs (CSCNT/FELTMWCNT), we were able to tailor the Li specific capacity and Faradaic efficiency of the resulting electrode. From a technological standpoint, despite its huge specific surface area of around 1624 m2 g+1, CSCNT/ FELTMWCNT presented excellent reversible Li specific capacity (415 mAh g+1) with respect to the total electrode mass as well as excellent faradaic efficiency at initial discharge/charge (-93%, C-rate - 1.6). Some kind of hybridization effect took place between the CNTs and the nonwoven carbon fibers in the FELT. Therefore, the CSCNT/FELT(SW or MW)CNT is a hybrid composite whose electrochemical behavior is governed by its constituents and their eventual electronic interaction.