Effect of Pulse Parameters on Early Stage Nucleation Phenomena

Abstract

Pulse electrodeposition has garnered significant attention from decades to control important parameters of the growing electrodeposits such as grain size, crystal orientation, and microhardness. Recently, pulse charging has become a major research focus due to its ability to suppress dendritic growth during the charging process for metal-anode based rechargeable batteries. In this work, we have comprehensively studied the effect of pulse duty cycle, D (D = tON/(tON+tOFF)) and frequency on the nucleation phenomena using an in-situ visualization technique (Figure 1). The nuclei density of copper electrodeposits on Indium Tin Oxide (ITO) coated glass substrate is evaluated microscopically and quantified using image processing. The pulse parameters are made equivalent to the corresponding DC voltage (VDC) by two possible ways, i) increasing the peak voltage (VPeak) based on the duty cycle applied (VPeak = VDC/D) , and ii) expanding the total deposition time, or in other words equating the cumulative reaction time (tON) in pulses to the total DC time (tDC = ∑tON). Interestingly, exactly opposite trends are observed for the two aforementioned methods. A sharp increase (∼75%) and decrease (∼80%) in nuclei density as compared to DC are observed while reducing the duty cycle till D = 1/4 for the two methods respectively. However, a decline in nuclei density is noticed while increasing in frequency in both methods. The associated pulse time scales, and the coalescence of the evolving nuclei due to merging of the diffusion zones surrounding a growing nucleus are likely to play the leading role behind this observation. The results add insights to the governing process, and will be useful in designing efficient pulse parameters to control dendritic growth. Figure 1