SnO2 coated carbon cloth with surface modification as Na-ion battery anode

Sodium (Na)-ion batteries offer an attractive option for low cost large scale energy storage due to the earth abundance of Na. SnO2 is considered as a high capacity anode for Na-ion batteries with a theoretical capacity of 1378 mA h/g. However, several limitations, such as large volume expansion with cycling, slow kinetics and low electrical conductance, have severely limited its performance. In this article, we demonstrate an anode consisting of a SnO2 nanocrystal layer grown on hierarchical microfibers of carbon cloth (CC) with extra surface coating to addresses the above challenges associated with SnO2 anodes. The soft nature of CC and the nanocrystal structure of SnO2 layers can effectively accommodate the volume change associated with the sodiation process. In addition, the effect from an extra coating layer of carbon (C/SnO2/CC) and Al2O3 (Al2O3/SnO2/CC) have been explored and the results showed that the extra coating layer can further enhance the performance of SnO2 anode. The C/SnO2/CC core-shell structure anode achieved a 501 mA h/g and a 144 mA h/g capacity at 0.1 C and 30 C charge/discharge rate, respectively. Meanwhile, a 375 mA h/g specific capacity after 100 deep cycles with an 80% retention is achieved by Al2O3/SnO2/CC anode. The designed surface-coating/nanocrystal-active-material-layer/conductive-soft-platform core-shell system paves the way to high performance Na-ion batteries. (C) 2015 Elsevier Ltd. All rights reserved.