High-Performance Si/SiO_x Nanosphere Anode Material by Multipurpose Interfacial Engineering with Black TiO_2-x

Silicon oxides (SiO_x) have attracted recent attention for their great potential as promising anode materials for lithium ion batteries as a result of their high energy density and excellent cycle performance. Despite these advantages, the commercial use of these materials is still impeded by low initial Coulombic efficiency and high production cost associated with a complicated synthesis process. Here, we demonstrate that Si/SiO_x nanosphere anode materials show much improved performance enabled by electroconductive black TiO_2-x coating in terms of reversible capacity, Coulombic efficiency, and thermal reliability. The resulting anode material exhibits a high reversible capacity of 1200 mAh g^-1 with an excellent cycle performance of up to 100 cycles. The introduction of a TiO_2-x layer induces further reduction of the Si species in the SiO_x matrix phase, thereby increasing the reversible capacity and initial Coulombic efficiency. Besides the improved electrochemical performance, the TiO_2-x coating layer plays a key role in improving the thermal reliability of the Si/SiO_x nanosphere anode material at the same time. We believe that this multipurpose interfacial engineering approach provides another route toward high-performance Si-based anode materials on a commercial scale.