Synthesis and performance of ZnSnO₃/C composites as anode for lithium-ion battery

Being one of the ternary metal oxides, different zinc stannate (ZnSnO₃) nanostructures, including nanoparticles, nanowires, nanocubes, and nanosheets, have been synthesized and investigated for various applications, such as catalysts, phonics, sensors, piezoelectric, pyroelectric, and lithium-ion batteries (LIBs). The ZnSnO₃ has received immense attention as potential anode materials for LIBs due to their high theoretical specific capacity, moderate intercalation and delithiation potential, abundant reserves, low cost, high safety, and environmental protection. In this study, a carbon-coated ZnSnO₃ composite (ZnSnO₃/C) was prepared using a one-step in situ hydrothermal method with glucose as a carbon source. The microscopic morphology of the as-prepared materials was observed using scanning electron microscopy and transmission electron microscopy. X-ray diffraction, Raman spectra, and X-ray photoelectron spectroscopy were used to analyze the phase composition and structure of the composite. The electrochemical properties were investigated through constant charge–discharge tests, cyclic voltammetry, and electrochemical impedance spectroscopy. When used as anode materials of LIBs, the prepared ZnSnO₃/C composite electrode exhibited excellent lithium storage performance with an improved cycling performance and high capacities. A specific capacity value of 1274.9 mA·h·g⁻¹ for ZnSnO₃/C composite is much higher than that of pure ZnSnO₃ electrode (491 mA·h·g⁻¹) after 200 cycles at a current density of 200 mA·g⁻¹. The ZnSnO₃/C electrode retained a discharge capacity of 663.2 mA·h·g⁻¹ even after 500 cycles at a high current density of 5000 mA·g⁻¹, exhibiting excellent rate capability. Such remarkable electrochemical properties of the ZnSnO₃/C composite are preferable to those of complex and costly ZnSnO₃-based composites reported previously. The superior lithium storage performance of the ZnSnO₃/C composite is attributed to the synergistic effect between the carbon coating on the surface and ZnSnO₃ nanoparticles. Moreover, the composite exhibits the following attributes: (1) High conductivity of the carbon in the ZnSnO₃/C composite can considerably enhance the conductivity of the electrode for facilitating electron transmissions. (2) The structure of nanoparticles can reduce the diffusion distance of Li⁺ and provide a large electrode-electrolyte contact area for high Li⁺ flux across the interface, leading to a high reversible specific capacity. (3) The ZnSnO₃ nanoparticles and flexible carbon layer can generate a double buffering structure to retard the huge volume expansion of active materials during repeated charge–discharge cycles. (4) More importantly, the carbon coating layer can avoid side reactions by preventing direct contact between the ZnSnO₃ hollow cubes and electrolytes and inhibiting the agglomeration of ZnSnO₃ during the cycling process. Thus, this research may provide a new avenue for synthesizing bimetal oxide with a core–shell structure for high-performance energy storage materials, considering the simple principles involved in its preparation.