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

Abstract Sodium (Na)-ion batteries offer an attractive option for low cost large scale energy storage due to the earth abundance of Na. SnO 2 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 SnO 2 nanocrystal layer grown on hierarchical microfibers of carbon cloth (CC) with extra surface coating to addresses the above challenges associated with SnO 2 anodes. The soft nature of CC and the nanocrystal structure of SnO 2 layers can effectively accommodate the volume change associated with the sodiation process. In addition, the effect from an extra coating layer of carbon (C/SnO 2 /CC) and Al 2 O 3 (Al 2 O 3 /SnO 2 /CC) have been explored and the results showed that the extra coating layer can further enhance the performance of SnO 2 anode. The C/SnO 2 /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 Al 2 O 3 /SnO 2 /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.