Electrochemical characteristics of bundle-type silicon nanorods as an anode material for lithium ion batteries

Abstract

In order to prepare bundle-type silicon nanorods, a silver-assisted chemical etching technique was used to modify a 1.6 mu m silicon thin film, which was deposited on Cu foil by Electron Cyclotron Resonance Plasma Enhanced Chemical Vapor Deposition. The bundle-type silicon nanorods on Cu foil were employed as anodes for a lithium secondary battery, without further treatment. The electrochemical characteristics of the pristine silicon thin film anodes and the bundle-type silicon nanorod anodes are different from one another. The electrochemical performance of the bundle-type silicon nanorod anodes exceeded that of the pristine Si thin film anodes. The specific capacity of the bundle-type silicon nanorod anodes is much higher than 3000 mAh g(-1) at the first charge (Li insertion) cycle. The coulombic efficiency of bundle-type silicon anodes was stable at more than 97%, and the charge capacity remained at 1420 mAh g(-1), even after 100 cycles of charging and discharging. The results from the differential voltage analysis showed a side reaction at around 0.44-0.5 V. and the specific potential of this side reaction decreased after each cycle. The apparent diffusion coefficients of the two anode types were in the range of 10(-13)-10(-16) cm(2) s(-1) in the first cycle. In subsequent charge cycles, these values for the silicon thin film anodes and the silicon nanorod bundle anode were approximately 10(-12)-10(-14) and 10(-13)-10(-15) cm(2) s(-1), respectively. (C) 2012 Elsevier Ltd. All rights reserved.