Electrodeposition and characterization of C/Sn thin films as a high-performance anode for li-ion batteries: effect of pulsed electrodeposition parameters

Abstract

A two-step electrodeposition approach was applied to deposit Sn/C layers on a Ni foam substrate. The first step was the deposition of the Sn layer using two electrodeposition modes (direct and pulsed electrodeposition) with different parameters (duty cycle, time on/off, and effective time). The second step was to deposit carbon on the Sn layer by direct electrodeposition. The surface morphology, chemical composition, and phases of deposited layers were investigated and the electrochemical behavior of Sn/Ni and C/Sn/Ni anodes was characterized. The pulsed electrodeposition technique with a lower duty cycle (15% duty cycle with time ratio t_on/_off = 3/17 for 2 min) produced more uniform and compacted deposits, compared to the non-uniform and dendritic morphology obtained after high duty cycles (50%) as well as direct electrodeposition. After the direct electrodeposition of carbon on the pulsed electrodeposited Sn, a uniform layer containing ~ 10% C, 38% Sn, 45% Ni, and 7% O, was detected. Analysis of this layer confirmed the presence of Ni, Sn, and amorphous C. Electrochemical characterization showed that the C/Sn/Ni anodes with a 94 Ω polarization resistance, a 0.105 V/decade anodic Tafel slope and 0.202 V/decade cathodic Tafel slope manifested the highest apparent and intrinsic catalytic activities. The peak current for the C/Sn/Ni samples was higher than the peak current for the Sn/Ni samples at all scan rates, indicating higher electrochemical reactivity. The linear relationship between the peak current and the scan rate's square root suggests that diffusion controls the charge transfer process.