Surface layer formed on silicon thin-film electrode in lithium bis(oxalato) borate-based electrolyte

A Si thin-film electrode of 200 nm is prepared using E-beam evaporation and deposition on copper foil. The use of a lithium bis(oxalato) borate (LiBOB)-based electrolyte markedly improves the discharge capacity retention of a Si thin-film electrode/Li half-cell during cycling. The surface layer formed on Si thin-film electrode in ethylene carbonate/diethyl carbonate (3/7) with 1.3 M LiPF6 or 0.7 M LiBOB is characterized by means of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopic analysis. The surface morphology of the electrode after cycling is investigated using scanning electron microscopy. The relationship between the physical morphology and the electrochemical performance of Si thin-film electrode is discussed.