Enhanced electrochemical performance of Si–Cu–Ti thin films by surface covered with Cu3Si nanowires

Abstract

Si–Cu–Ti thin films with Cu3Si nanowires on the surface and voids in the Cu layer are fabricated for the first time by magnetron sputtering combined with atomic layer deposition (ALD) of alumina. The formation of the surface Cu3Si nanowires is strongly dependent on the thickness of the coated alumina and cooling rate of the thin films during annealing. The maximum coverage of the surface Cu3Si nanowires is obtained with an alumina thickness of 2 nm and a cooling rate of 1 °Cmin−1. The electrode based on this thin film shows an excellent capacity retention of more than 900 mAh g−1 and a high columbic efficiency of more than 99% after 100 cycles. The improvement of the electrochemical performance of Si–Cu–Ti thin film electrode is attributed to the surface Cu3Si nanowires which reduce the polarization and inhomogeneous lithiation by formation of a surface conductive network, in addition to the alleviation of volume expansion of Si by voids in the Cu layer during cycling.