Investigation On Preparation And Performance Of Tin-based Anode For Lithium Ion Batteries

Tin-based anode material is popular for high theoretical specific capacity (990 mAh/g), strong adaptability for high current charge-discharge. However, tin’s volume changes so large in charging and discharging that causes active materials collapse and inactivation, lastly reduces the service life of battery. Prepare nano-powders and tin-based alloys can improve the cycle life of tin effectively. Large specific surface area of nano-powders and inert element as framework can buffer the volume expansion and improve the cyclic life.This work had prepared tin film with whiskers on the stainless steel substrate by adding sodium dodecyl sulfate(SDS) in bath by pulse electrodeposition, whose compositon, structure and morphology was analyzed by X-ray diffraction(XRD), Scanning electron microscope(SEM), Linear sweep voltammetry(LSV) and Infrared spectroscopy(IR). The sorption of SDS on electrode led to compressive stress in coating increasing, then whiskers formed on the surface. Tin anodes were got by changing temperature, time and current density in electrodeposition, of which charge-discharge performance and cycle performance had been studied by charge/discharge, cyclic voltammetry(CV)and AC impedance. Results:when the current density was 0.4 mA/dm2 and plating 900 s, tin film with uniform grain size got better electrochemical performance. The first-discharging specific capacity was 1037.1 mAh/g. Until the 15th cycle, the discharge capacity decreased to 149.5 mAh/g, and then decayed slowly in the subsequent cycles by SEI and porous electrode, showing the tin electrode had some electrochemical stability, keeping at 90 mAh/g after 50 cycles; in addition, whiskers on the surface could buffer the pulverization and exfoliation.This research had studied the electrochemical properties of oxide and Sn-Fe alloy after heat treatment of tin anode. It was showed that inert O and Fe doping in tin-based electrode could availably reduce the volume effect, improve the cycle stability and initial coulomb efficiency. Sn-Fe alloy anode was got at 200 ℃ in argon for 24 h, whose most-discharge specific capacity was 650.6 mAh/g, and remaining higher than 500 mAh/g in the subsequent 15 cycles. Due to the alloying reaction carried out fully at 240 ℃ in argon for 24 h, tin whisker has reduced sharply; the coulomb efficiency increased to 87.2%. The maximum discharge capacity of Sn-Fe alloy anode was 724.1 mAh/g, decreasing to 240 mAh/g in 30th cycle. Tin film treated at 200 ℃ in air make part of Sn oxidized to SnO, which had a certain impact on cyclic performance and electrode reaction of anode. The first discharge capacity was 496.4 mAh/g, rising to 594.9 mAh/g till the 2nd cycle; the specific capacity maintain about 300 mAh/g in 10～25 cycles, showing good cycling stability, decreasing to 164.6 mAh/g gradually.