Composition-tuned SnxGe1−xS nanocrystals for enhanced-performance lithium ion batteries

Abstract

Germanium-or tin-based nanostructures have recently demonstrated outstanding lithium ion storage ability and are considered to be the most promising candidates to substitute current carbonaceous anodes in lithium ion batteries. Tin germanium sulfide (Sn_xGe_1−xS) ternary alloy nanocrystals (NCs) were synthesized by a gas-phase laser photolysis reaction with complete composition control (0 ≤ x ≤ 1). All of these composition-tuned nanocrystals showed excellent cycling performances in lithium ion batteries. Reversible capacities were in the range 800–1200 mA h g⁻¹ after 70 cycles, which is close to the theoretical capacities of each composition. As the tin composition (x) was increased, the rate capability greatly enhanced. This unique composition dependence of the electrochemical properties was explained by the lower charge transfer resistance due to the high conductivity of Sn_xGe_1−xS NCs as well as the Sn_xGe_1−x alloy NCs produced upon lithiation. Sn-rich Sn_xGe_1−xS NCs are, therefore, promising candidates for applications in high-performance energy conversion systems.