微米级SiO合成多孔氧化硅/硅/碳储锂复合材料

以微米级SiO为原料,通过简单的高温煅烧、碳包覆和酸刻蚀制备多孔氧化硅/硅/碳复合材料,复合材料比表面积和平均孔径分别为32.9 m~2/g和3 nm。纳米硅分散在缓冲介质氧化硅多孔体系中,表面包覆一层薄而均匀的碳层。所得的复合材料具有较好的循环稳定性,在0.3 m A/g下,50次循环后可逆容量保持在645.1 m A·h/g。多孔结构、氧化硅缓解了硅在脱嵌锂过程的体积膨胀,碳层提高了复合材料的导电性和结构稳定性。

Synthesis of Porous Silicon Oxide/Silicon/Carbon Composite Material from Micro-SiO for Lithium Storage

Porous silicon oxide/silicon/carbon composite was derived from micro-silicon monoxide with simple calcination, chemical vapor deposition and HF etching. The obtained c-SiO_x/Si/C(c-refers to calcination) composite after etching possesses a high specific surface area of 32.9 m²/g and an average/mean pore distribution of 3 nm. The atomic ratio of Si/O in c-SiO_x/Si/C is increased comparing to that of c-SiO/C without etching. The Si nano-crystallites were embedded in porous Si-suboxide, and the particles are covered by a uniform carbon layer with a thickness of 6 nm on the surface. The c-SiO_x/Si/C with this particular structure exhibits a stable reversible capacity of ca. 645.1 mA·h/g after 50 cycles with the current density at 0.3 mA/g. In contrast, c-SiO/C composite without pores presents a reversible capacity of only ca. 466 mA·h/g under the same carbon coating condition. The different cycling performances of c-SiO_x/Si/C and c-SiO/C may be consequences of their structural differences. It is believed that the rich nanopores of the c-SiO_x/Si/C can endure and buffer the severe volume change of silicon upon lithium insertion and extraction and improve the mechanical integrity of composite.