Conversion Reaction of Copper Sulfide Based Nanohybrids for Sodium-Ion Batteries

Intercalation-based anode materials for Na-ion batteries show relatively unfavorable electrochemical performances compared with those of Li-ion batteries because of the larger and heavier Na ion, as well as its higher electrode potential. In contrast, conversion-reaction-based anode materials have great potential for use in Na-ion batteries. In this study, copper sulfide nanodisks (CuS-NDs) were fabricated by a simple low-temperature reaction and applied as the anode materials for Na-ion batteries with acid-treated single-walled carbon nanotubes (a-SWCNTs), which act as a paperlike nanohybrid. The nanohybrids had a high reversible capacity of ca. 610 mA h g(-1) and high rate capabilities at current rates from 0.1 to 3 A g(-1) during the conversion reaction that reversibly forms Na2S and Cu metal. In addition, their electrochemical performances were stable and were maintained over 500 repetitive cycles; this stability arises from the unique nanohybrid structure, in which CuS-NDs are bound together by the a-SWCNT network.