Recent Development of the Synthetic Method for Si/Graphite Anode Materials

Rechargeable lithium-ion batteries (LIBs) are recognized as the most important power supply for portable electronic devices, electric vehicle and hybrid electric vehicle. There is a continuing demand for advanced LIBs with longer life spans and higher capacity. Graphite based anode materials are now widely employed in LIBs due to their excellent cycling stability and good conductivity. However, the theoretical capacity of graphite is as low as 372 mA center dot h center dot g(-1) that is hard to meet the ever-increasing demand of high energy density LIBs. Recent years, Si based anode materials have attracted enormous attention due to its high reversible capacity (3579 mA center dot h center dot g(-1)). However, the main challenge facing Si is the huge volume change during lithiation/delithiation process. It is well accepted that nanostructured Si could effectively release the strain stress caused by volume variation, thus maintaining the conductive and structural integrity of the electrode. But, the high surface area of nanostructured anode materials would result in serious side reactions between electrode materials and electrolyte, which would consume a lot of Li+, and leading to low coulombic efficiency. Very recently, preparation of nano-Si/graphite composite as anode for LIBs has been demonstrated as a promising high-capacity anode. The Si/graphite anode is able to take full advantages of the properties of these two materials such as the high specific capacity of nano-sized Si, mechanical flexibility and good conductivity of graphite. These beneficial features make Si/graphite hybrid composite as an ideal anode candidate for high-performance LIBs. To date, a lot of fabricating strategies have been reported to prepare Si/graphite composite. The keys and interests are focused on how to make the nanosized Si and graphite particles distributed uniformly, and how to construct a stable framework with three-dimensional conductive network. An overview of the methodologies proposed in the last decade for combining nanosized Si and graphite is summarized, which are composed of a series of technological means. Here, these methodologies are classified in three categories on basis of the composite step, including solid-state approach, liquid-phase mixture method, and chemical vapor deposition process.