Nitrogen and sulfur dual-doped carbon films as flexible free-standing anodes for Li-ion and Na-ion batteries

Heteroatom doping is considered to be one of the most effective approaches to improve the electrochemical activity of carbon-based electrode materials for both Li-ion batteries (LIBs) and Na-ion batteries (SIBs) due to introduction of unbalanced electron atmosphere and enlarged interlayers of carbon materials. Here, we present nitrogen and sulfur dual-doped flexible carbon (NS-C) film as a promising freestanding anode for stable high-power and high-energy LIBs or SIBs. The NS-C film delivers high reversible capacities of 965.7 mAh g(-1) in LIBs and 520.1 mAh g(-1) in SIBs at a current density of 100 mA g(-1). Particularly, the film electrodes exhibit excellent high-rate capability and remarkable longterm cyclability. For instance, as a LIBs anode, the NS-C film remained a high capacity of 357.2 mAh g(-1) at 2.0 A g(-1)(similar to 10 min to full charge) after 2000 cycles; even in SIBs, a capacity of 155 mAh g(-1) can also be reached at 1.0 A g(-1). It is believed that the interconnected conducting structure of carbon backbones, heteroatomic defects and increased carbon interlayers distance by stable S-C and N-C bonds are beneficial to ultrafast ion diffusion and electron transport, making the NS-C film become a high performance free-standing anode for LIBs or SIBs application. (C) 2017 Elsevier Ltd. All rights reserved.