Thermally-enhanced microstructures of Si/TiNi film electrodes for improved electrochemical properties

•Active diffusion of Ni occurred in Si/TiNi electrodes above 600 °C.•Ti2Ni intermediate layer and Ni2Si particles were formed in high-temperature annealed Si/TiNi film electrodes.•The modified microstructures in Si/TiNi film electrodes improved the initial coulombic efficiency and cycle performance. [Display omitted] The structural and electrochemical properties of annealed Si film electrodes with titanium–nickel (TiNi) current collectors have been investigated to identify compounds and microstructures that improve electrochemical performances. The as-deposited Si/TiNi electrode consisted of amorphous Si (α–Si) and crystalline B2–TiNi alloy at room temperature. Only a thin oxide layer was formed at the interface, and any significant microstructural change was not found at 500 °C compared to the as-deposited electrode. The Ni atoms started to migrate from the TiNi alloy to the Si film at 600 °C, which resulted in the formation of a Ti-rich (Ti2Ni) layer at the interface. A large amount of Ni diffused into the Si film at 700 °C led to the formation of nickel silicide (NiSi2) particles being dispersed in the film. The Si/TiNi electrodes that were annealed at a temperature exceeding 600 °C showed improved electrochemical properties such as initial efficiency (~90%) and cycle performance (50% capacity retention after 300 cycles). The excellent electrochemical performance was achieved by enhancing the structural stability in annealed Si/TiNi electrodes.