Electrochemical Properties of Silicon with PVA as Carbon Source for Anode Material of Lithium-Ion Battery

摘要

Graphite is the anode active material of lithium secondary battery with a theoretical capacity of 372 mAh/g. It is required to develop a new anode active material for a high capacity battery. As a next-generation anode active material, Si has a much higher theoretical capacity (4200 mAh/g) than graphite, and many studies have been underway. Unlike graphite, Si forms an alloy at the time of charging and reacts reversibly with lithium through a non-alloying process during discharge. However, during the continuous charge/discharge reaction, the volume expansion of Si causes the cracking of Si particle, resulting in a drastic decrease of the capacity. In this study, nano-sized Si (<300 nm) was used to mitigate the volume expansion of Si. Si/C was prepared by carbon coating of Si with pyrolysis of PVA as a carbon precursor. Si and PVA were mixed and dried in a distilled water and heat treated at 800 ?C for 3 hours for pyrolysis of PVA. The compositions of Si and carbon were used as parameters. As a result, Si/C composites exhibit outstanding cycling stability of roughly 1500 mAh/g after 50 cycles at current density of 0.2 C. The prepared samples were analyzed by TGA, XRD, SEM. The electrical properties were measured with battery cycler, electrochemical impedance spectroscopy.