Preparation And Electrochemical Study Of Si/SWNT Composite As Anode Materials

In this paper,we have prepared three kinds of materials with different methods,in order to accommodate the volume change,promote electron transfer and the electrochemical performance.The composite materials were characterized by SEM,TEM,XRD,XPS and Raman spectrum.The galvanostatic charge-discharge test was conducted to characterize the electrochemical performance.The main research results are as follows:?1?A 3D-composite-nanonetwork material of Si/SWNT was synthesized through an electrostatic induced self-assembly process and the following film transfer technique.It revealed that the Si nanospheres were well encapsulated into the SWNT nanonetwork.The continuous 3D conductive network consisting of SWNTs could serve as a “buffering matrix” and provide a rapid electronic transport pathway,thus ensuring a superior cycling stability and rate capability.The Si/SWNT 3D-composite-nanonetwork maintained a capacity up to 941 mAh·g^-1 after 50 cycles at a current density of 400 mA·g^-1.It was able to maintain a high specific capacity of more than 740 mAh·g^-1 at a high current density of 1600 mA·g^-1.When the current density recovered to 200 mA·g^-1,it demonstrated a retention capacity of 950 mAh·g^-1,demonstrating a good rate capability.?2?A multilayered Si/SWNT nanocomposite was synthesized through a method of vacuum filtration.The results displayed that the weight percentage of silicon was 50%.The composite with more layers has better electrochemical performance.In the composite material,Si layer sandwiched between two layers of SWNT,which can effectively buffer the volume change of Si during the charging and discharging process.The more layered Si/SWNT-2 maintained a specific capacity of 330 mAh·g^-1 at a high current density of 200 mA·g^-1 after 50 cycles while the specific capacity of the less layered Si/SWNT^-1 was 217 mAh·g^-1.The prepared Si/SWNT-2 maintained a specific capacity of 160 mAh·g^-1 at a high current density of 1600 mA·g^-1.When the current density recovered to 200 mA·g^-1,it demonstrated a retention capacity of 295 mAh·g^-1.?3?A Si/SWNT composite was prepared through the electrodeposition of Si in ionic liquids?ILs?.It proved that the electrodeposited silicon was amorphous.Compared with crystalline silicon,amorphous silicon has better cycling performance owing to the smaller volume expansion.We also investigated the effect of electrodeposition time on the mass of Si.More Si could be obtained by increasing the electrodeposition time.