Core-shell Si@TiO2 nanosphere anode by atomic layer deposition for Li-ion batteries

• Si nanospheres are precisely coated with TiO2 by ALD method.
• The Si@TiO2 composite with a 3 nm TiO2 layer exhibits the best cycling stability.
• TiO2 thickness is critical to balance structural stability and conductivity of Si.
• The difference in coating electrode and active material by ALD is also revealed.

Silicon (Si) has been regarded as next-generation anode for high-energy lithium-ion batteries (LIBs) due to its high Li storage capacity (4200 mA h g−1). However, the mechanical degradation and resultant capacity fade critically hinder its practical application. In this regard, we demonstrate that nanocoating of Si spheres with a 3 nm titanium dioxide (TiO2) layer via atomic layer deposition (ALD) can utmostly balance the high conductivity and the good structural stability to improve the cycling stability of Si core material. The resultant sample, Si@TiO2-3 nm core–shell nanospheres, exhibits the best electrochemical performance of all with a highest initial Coulombic efficiency and specific charge capacity retention after 50 cycles at 0.1C (82.39% and 1580.3 mA h g−1). In addition to making full advantage of the ALD technique, we believe that our strategy and comprehension in coating the electrode and the active material could provide a useful pathway towards enhancing Si anode material itself and community of LIBs.