Preparation Of Tin-based Anode For Lithium-ion Battery And Its Electrochemical Property

Lithium-ion battery has been an ideal power for mobile electronic products due to its high output voltage, long cycle life and high energy density. Comparing with the existing carbon anode material for lithium-ion battery, tin-based material is noticed for its high theoretical specific capacity (990 mAh/g). However pure tin experiences a high-volume expansion while lithium inserting and extracting, which leads to the active materials cracking and shedding and deteriorates the cycling performance. Using nanomaterials or establishing a buffer system can solve this problem. Nano particles agglomerate and its efficiency of charging and discharging declines due to the large SEI membrane area. Doped with oxygen or other non-reactive metal elements can buff the volume change during lithium-ion deintercalation process which effectively suppress the swelling of the electrode and finally improve the cycling performance of the cell.In order to improve the stability of the lithium-ion deintercalation tin films were prepared on copper substrate by pulsed electrodeposition in this work and their thickness, structure and morphology were investigated by controlling deposition time, different sintering atmosphere, temperature and time. The composition, structure and morphology of the films were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM). The electrochemical properties of the films were studied by constant current charge/discharge, cyclic voltammetry (CV) and AC impedance (EIS) for comparatively analysis of the relationship between the structure, morphology and performance of the materials. It was showed that tin film in better uniformity, density and crystallinity was obtained by electrodepositing at 40℃ in the current density of 4 mA/cm2 for 60 min. The film showed very good electrochemical properties. The films were sintered at different conditions. Tin film anode sintered in argon at 200℃ for 12 h showed good cycle performance. Its first-discharging specific capacity is as high as 702.5 mAh/g with little decaying rate. The discharge capacity in 15th cycle is still as high as 348.4 mAh/g. The "inert" buffering effect of Cu atom in the film enhanced adhesion force between the film and the substrate. The film sintered at 200℃ in air for 48 h showed the best electrochemical performances with the initial discharging capacity of 572.2 mAh/g and the charging capacity of 436.8 mAh/g due to Cu and O doped simultaneously. In the subsequent cycles, the capacity increased steadily and showed the largest discharge capacity of 373.2 mAh/g in the 15th cycle and then declined. Its discharging capacity in the 30th cycle is still as high as 295.9 mAh/g.