Study of n-type Amorphous Silicon Alloy as the Anode in Li-ion Batteries

Abstract

In recent years, the world has witnessed a dramatic advancement in sustainable energy development. Due to the inconsistent supply of such energy, a more efficient energy storage method is in need. Among many options, lithium-ion battery stands out due to its lightweight, high energy density, and high discharge potential. Currently, the most commonly adapted anode materials in lithium-ion batteries are carbon-based, most often graphite. It shows a layered structure that can be used to store Li+ ions based on the intercalation and de-intercalation mechanism. Although this material is stable and successfully commercialized, due to its low specific capacity efforts have been put into searching other potential anode materials. Potential materials are aluminum, tin, and silicon. Among them, silicon shows an ultra-high (theoretical) specific capacity that is 12 times higher than that of carbon. However, the volume taken up by the material increases by about 300% upon lithiation and de-lithiation. Hence, silicon anodes show a poor capacity retention ability comparing to its graphite counterpart. In this work, by using a silicon alloy, we aim to alleviate the effects of volume expansion of Si by introducing alloying species and by providing a porous structure. In this work it is demonstrated that this material structure is able to absorb the expansion, while still rendering a high specific capacity. Silicon alloy samples over a wide range of alloy concentration and porosity were synthesized using PECVD. Samples were assembled into pouch-cells and coin-cells and tests were performed to compare the battery performance of each sample. A FEM model was built, enabling more investigation opportunities. Together with the experiments, they revealed how alloy concentration and porosity influence the specific capacity and cycling ability of the anode.