Agar templated electrodeposition of binary zinc-cobalt alloy and formation of zinc-cobalt-carbon nanocomposite for application in secondary lithium batteries

Thin layer electrodeposition of binary Zn-Co alloy on Cu substrate is carried out using different concentrations of agar, namely, 0.0029 M, 0.0074 M, and 0.0148 M as a template for application in lithium-ion battery anodes. The concentration of agar highly influences the morphology of the deposited films and the formation of nanoflake structures over their surfaces. The optimal agar templated electrode shows good morphological characteristics with a well-defined nanoflake structure, as confirmed by texture coefficient (T-c) values calculated from X-ray diffraction (XRD) results and by field emission scanning electron microscopy (FE-SEM) images. Zn-Co-C nanocomposite electrodes are prepared by subjecting the electrodeposited materials to a calcination step to decompose the agar into C; the resulting electrode shows the initial specific capacity of 827 mAh g(-1) and 92% capacity retention after 100 cycles (vs. 20th discharge capacity) whereas Zn-Co alloy electrode shows 829 mAh g(-1), with 62% capacity retention after 100 cycles. The chemical compositions of the electrodeposited films are further confirmed by X-ray photoelectron spectroscopy (XPS). Electrochemical studies including charge edischarge cycles and electrochemical impedance spectroscopy (EIS) provide information regarding the lithiation and delithiation processes, and electrode/electrolyte interactions before and after cycling in the prepared electrodes. (C) 2016 Elsevier B.V. All rights reserved.