Analysis of anodic nanotubular oxide on homogeneous Ti-Si alloys for Li-ion battery anodes

Abstract

The porous anodization of pure Ti and arc melted Ti2Si, and Ti4Si alloys were studied, aiming to produce novel anodes for lithium-ion batteries. The annealed and quenched Ti2Si alloys were homogeneous β-martensite, while Ti4Si close to the maximal Si solubility presented Ti3Si and Ti5Si3 precipitates. The alloys anodized in standard HF + NH4F electrolyte showed an increasing tendency to detach the oxide layer with the Si content increase. The slope of the cell voltage transient ∂E/∂t was used to evaluate each material's current efficiency. Si addition decreases the oxide's electronic conductivity and the oxygen evolution reaction but increases the oxide dissolution rate due to a higher Si dissolution rate. Consequently, higher current efficiency of oxide formation is observed during the barrier layer and a lower one during the porous layer formation. Nevertheless, the specific Li mass capacity increased by around 15% with 2 at% Si addition to Ti.