Facile synthesis of Cu2SnSe3 decorated with reduced graphene oxide as pseudocapacitive sodium storage materials

Binary metal selenides—combining a transition metal and a main-group metal—offer synergistic conversion–alloying reactions, representing a promising yet underexplored anode strategy for sodium-ion batteries (SIBs). Among ternary selenides, Cu 2 SnSe 3 (CTS) is a prototypical candidate, yet its potential as an SIB anode remains largely unexplored. Herein, CTS nanoparticles uniformly anchored on reduced graphene oxide (rGO) are synthesized via a simple one-pot hydrothermal method. Crucially, the surfactant—polyvinylpyrrolidone (PVP) or hexadecyltrimethylammonium bromide (CTAB)—controls nanoparticle morphology and electrochemical performance. PVP yields well-dispersed spherical nanoparticles that shorten Na + diffusion paths, enhance electrolyte accessibility, and mitigates volume changes. In contrast, CTAB produces nanosheet-like aggregates with inferior performance. Ex situ and in situ characterizations reveal a multi-step reaction pathway—Na + insertion, followed by conversion and alloying—and confirm high structural reversibility. Kinetic analysis shows predominantly pseudocapacitive charge storage (84.8% at 1.0 mV s −1 ), enabling exceptional rate capability (183 mAh g −1 at 5 A g −1 ) and long-term cycling stability. A full cell paired with a Na 3 V 2 (PO 4 ) 3 cathode delivers a reversible capacity of 153.4 mAh g −1 at 1 A g −1 after 200 cycles. This work establishes surfactant-mediated morphological control combined with rGO hybridization as a rational and generalizable strategy to unlock the sodium-storage potential of CTS and other binary metal selenide anodes.