Synthesis and characterization of carbon coated sponge-like tin oxide (SnOx) films and their application as electrode materials in lithium-ion batteries

Abstract

Nanoporous metal oxides are widely used for the development of various functional nanostructures. We report on the synthesis of sponge-like tin oxide films on copper foil by anodization of electrochemically deposited tin films. The thin films are functionalized using a surface-anchoring carbon precursor-polymer (poly(acrylonitrile-b-dopamine acrylamide)) followed by annealing at elevated temperature to convert the polymer coating into a carbonaceous coating. The as prepared and the carbon coated films are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Raman spectroscopy. Subsequently, both SnO_x films are employed as anode materials in lithium ion batteries. Carbon coating has a beneficial effect on the battery performance with respect to the rate capability, increasing the capacity by 200 mA h g⁻¹ for all applied current densities. After 20 cycles, coated samples show a reversible specific charge capacity of 497 mA h g⁻¹. Ex situ scanning electron microscopy reveals the retention of the sponge-like morphology even after cycling.