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

• Cu3Si nanowires covered Si–Cu–Ti thin film was fabricated for the first time.
• Fabrication of hollow-structured Si–Cu–Ti thin film by Kirkendall effect.
• Al2O3 coating and annealing process enhanced the formation of Cu3Si nanowires.
• Si–Cu–Ti electrode shows good cycling performance and high columbic efficiency.

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 °C min−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.

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