In situ and ex situ carbon coated Zn2SnO4 nanoparticles as promising negative electrodes for Li-ion batteries
Abstract
Zinc stannate, Zn2SnO4 nanoparticles are successfully synthesized by a facile hydrothermal method. Subsequently, a layer of carbon is coated on Zn2SnO4 nanoparticles by both in situ and ex situ methods using glucose as a carbon source. The phase purity, carbon content, oxidation state and morphological features are characterized by various techniques. The percentage of carbon present in the Zn2SnO4 is calculated using thermogravimetric analysis. The core–shell structure of Zn2SnO4@C is revealed through high resolution transmission electron microscope images. The electrochemical performance of the Zn2SnO4@C is examined by dQ/dV, charge–discharge, rate capability and electrochemical impedance spectroscopy analysis. Among these, the ex situ carbon coated Zn2SnO4 shows superior cycling stability and it delivered a stable specific discharge capacity of 533 mA h g−1 at 700 mA g−1 over 50 cycle. The EIS analysis indicates that the obtained low charge transfer resistance (Rct) and solid electrolyte interphase (SEI) film resistance (RSEI) of the ex situ carbon coated Zn2SnO4 controls the SEI film thickness on the outer surface of the active material. Overall, the electrochemical analysis elucidates that the ex situ carbon coated Zn2SnO4 shows an excellent cycling stability and good electronic conductivity compared with carbon free and in situ carbon coated Zn2SnO4.