Novel copper sulfide (CuS) nanowire bundles with a diameter of about 6 nm and a length up to several micrometers are successfully synthesized by a template- and surfactant-free method in a dimethyl sulfoxide (DMSO)-ethyl glycol (EG) mixed solvent The resulting CuS nanowire bundles are used as a cathode material in lithium-ion batteries and exhibit a large capacity and excellent cycling stability and rate capability. The unique structure of the CuS nanowire bundles is responsible for their excellent electrochemical performance. (C) 2014 Elsevier B.V. All rights reserved.