The catanionic surfactant-assisted syntheses of 26-faceted and hexapod-shaped Cu2O and their electrochemical performances

Abstract

Crystalline materials with a well-defined morphology and/or a narrow size distribution might exhibit a specific shape- and/or size-dependent performances. In the first instance, the catanionic surfactants of anionic sodium dodecyl sulfate (SDS) and cationic cetyltrimethylammonium hydroxide (CTAOH) were added as crystal modifiers into the 60 °C reaction systems of copper chloride and sodium hydroxide for the syntheses of cuprous oxide (Cu₂O). Then, the reversible reaction activity of crystalline Cu₂O with metal lithium was conducted to investigate its electrochemical performance as rechargeable lithium ion battery anodes. The presence of SDS-rich catanionic surfactants could induce the formation of polyhedral Cu₂O structures with 8 triangular {111}, 6 square {100}, and 12 rectangular {110} faces outside, while the presence of CTAOH-rich catanionic surfactants, especially the doping methanol in CTAOH, led to the generation of hexapod-shaped Cu₂O mesostructures with tiny nanoparticles on these symmetrical branches. At a discharge–charge cycling current of 80 mA g⁻¹, the 26-faceted Cu₂O crystals with rough {110} faces displayed an initial capacity of 756 mA h g⁻¹ and a reversible capacity of 280 mA h g⁻¹ at the first cycling. In comparison with the electrochemical performance of Cu₂O hexapod-shaped mesocrystals at the same cycling current, the 26-faceted crystals of Cu₂O could be capable of remaining a relatively high capacity (∼145 mA h g⁻¹) and keeping an excellent Coulombic efficiency (∼100%) over 50 discharge–charge cycles. As a whole, the catanionic surfactants at different anionic/cationic molar ratios were used as additives to highlight the secondary nucleation and growth mechanism for the formation of Cu₂O, then, the resulting 26-faceted crystallites and hexapod-shaped mesoparticles were separately used as active materials in the assembled Cu₂O/Li half-cells to study their shape-dependent electrochemical performances.