Preparation And Electrochemical Properties Of Si-based Anode Nanomaterials For Lithium Ion Battery

The ever-increasing requirements in rechargeable batteries are being driven by a rapid development in the field of electronic device and electric vehicle. The rechargeable batteries with high capacity, high charge-discharge rate, stable cyclic performance are the focus of research. At present, the carbon anode materials of commercial lithium ion batteries, which theoretical capacity is 372 mAh g"1, can not meet the demand for rechargeable batteries. In recent years, a number of researchers have turned their attention to silicon as it has the highest theoretical capacity. However, the volume of silicon extends seriously during the process of embedding and taking off lithium ion, it's easy to collapse the structure and make the materials deactivated. This paper aims to solve the issue that silicon has weak cyclic performance by means of making the Si-based anode materials of lithium ion batteries nano-compounding and structuring to improve the electrochemistry properties.Si/Al nano-composites were prepared by a DC arc discharge method with different ratios of the raw materials. The phase, composition and morphology of Si/Al nano-composites that prepared were confirmed by means of XRD, TEM and other techniques. As increasing the content of Al in raw materials, it was also increased in the powder products, showing a similar consistency between raw materials and products. It is indicated that the Si/Al nano-composites exhibited an orientation-induced growth,and their morphologies gradually changed from the nano-particles to the nano-wires shapes. The Si/Al nano-composites were used to fabricate the anode for lithium-ion batteries and their electrochemical properties were investigated. At the current density of 100 mA g-1, the reversible capacities of nanocomposite materials prepared in the ratios of Si:Al=9:1, Si:Al=7:3 and Si:Al=1:1(wt.%) maintained at 461.0 mAh g-1,321.1 mAh g-1 and 237.3 mAh g-1 after 50 cycles, respectively. The stable cycle performance and regular change in capacity have been confirmed.In order to further improve the electrochemical properties of Si-based anode materials, an etch procedure was carried out by 8% diluted hydrochloric acid onto the nano-composites (the ratios of Si:Al=1:1) for elimination of Al element and fabrication of a nano-structure with a number of defects. The results showed that Al in the composites can be completely removed, the morphology of products became rough and irregular, and its specific surface area increased to 103.09 m2/g. At the current density of 100 mA g-1, the reversible capacity of this etched nanocomposite maintained at 503.1 mAh g-1 after 61 cycles, which is significantly improved in comparison to that of the un-etched nanocomposite.