Microstructure and phase analyses of melt-spun Si-Ni base anode materials for Li-ion battery

Abstract

Si-based anode composite materials have been studied to improve the performance and the durability of Li-ion secondary batteries in this study. Si-Ni-Al, Si-Ni-Cu and Si-Ni-Cu-Al base alloys were designed and rapidly solidified at the cooling rate of about 10⁶ °C/sec by optimizing the melt spinning. The ribbons were characterized using FE-SEM equipped with EDS, X-ray diffractometer and HR-TEM. The thin ribbons of Si-Ni-Al alloy consisted of nano-sized Si particles and amorphous matrix, which was regarded as an ideal microstructure for the anode material. At the wheel side of the ribbon, 20–30 nm of Si particles were formed (Zone A); whereas at the air side relatively large Si particles were distributed (Zone B). The Si-Ni-Cu alloy showed coarser Si particles than the Si-Ni-Al alloy, and its matrix consisted of NiSi₂, Cu₃Si and amorphous structures. Finally, the microstructure of the Si-Ni-Cu-Al alloy strips was composed of coarse Si particles, CuNi, Al₄Cu₉, NiSi₂, and unknown phases, and the size of those Si particles were too large to be used for the anode materials.