| Sn has received much attention as a new lithium ion anode material for its high theoretical capacity. However, pure Sn anodes have not been put into practical use because of its large volumetric change during Li+insertion and extraction, which causes the cracking and delamination of the active materials from current collector during cycling. In order to overcome the problems of capacity decay of pure Sn anodes, researchers have turned their attention to Sn based alloy, Sn based oxide and Sn based composite thin film anodes.In this work, the Sn-Cu alloy anode materials were prepared on copper foil by direct current and pulse electrodeposition techniques in a pyrophosphate based bath with the graphite as the positive electrode. The effects of the electrodeposition factors on the material composition, surface morphology and electrochemical properties were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance (EIS) and constant current charge-discharge testing, etc.Using different kinds of amino acid as the surface active agents, the cyclability and specific capacity of Sn-Cu alloy anode materials prepared by direct current electrodeposition were successfully improved. Among them, acid glycine was the best surface active agent. Electrochemical tests indicated that the material prepared with a deposition time of4min and a current density of5mA·cm-2delivered a discharge special capacity of678.8mAh·g-1at0.1C and485.2mAh·g-1at0.5C. After50cycles, the capacity retention was81.4%.The Sn-Cu anode material was prepared by pulse electrodeposition with a pulse frequency of10Hz, a pulse current density of10mA·cm-2, a pulse duty cycle of20%and a pulse deposition time of5min (the true deposition time). The electrochemical tests indicated that this anode material delivered a discharge special capacity of821.8mAh·g-1at0.1C and494.5mAh·g-1at0.5C. After50cycles, the capacity retention was66.0%. |
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