Electrochemical properties of a Si thin-film anode deposited on a TiNi shape-memory-alloy thin film

Abstract

Advances in electronics have generated an increasing demand for smaller, higher-capacity lithium-ion batteries, which will require alternatives to graphite as the battery anode material. To this end, a TiNi shape-memory-alloy (SMA) thin film was fabricated on Cu foil by DC magnetron sputtering. Si thin films were then deposited at a low temperature (LT) of 298 K (Si(LT)/TiNi/Cu) and a high temperature (HT) of 853 K (Si(HT)/TiNI/Cu). The Si thin films formed were amorphous regardless of the deposition temperature. The grain sizes of Si deposited at 298 K and 853 K were measured as 261 nm and 187 nm, respectively. The Si(HT)/TiNi/Cu electrode exhibited excellent capacity retention until approximately the 45th cycle, whereas rapid capacity fading occurred in the Si(LT)/TiNi/Cu electrode at the same current density of 200 μA/cm2. The better cycle performance is attributed to increased adhesion force between the Si film and the TiNi SMA thin film because the stress generated in the Si thin film during the charge and discharge process was transferred to the TiNi SMA thin film, resulting in a stress absorption effect.