Silicon suboxide is one of the promising anode materials for lithium-ion batteries (LIBs) due to its high specific capacity, low operating voltage (less than 0.4 V) and rich abundance. The SiOx electrode produces inert components (lithium oxide and lithium silicate) and nano-Si particles during initial lithiation/delithiation process. The former can act as buffer matrix to significantly reduce the volume change of nano-sized Si. Therefore, compared to pure Si, the SiOx electrode shows relatively good cycling stability and thus appears promising for high energy density Li-ion batteries. Nevertheless, the poor intrinsic electronic and ionic conductivity of SiOx often leads to a low specific capacity and inferior rate capability. In addition, the SiOx electrode cannot withstand long-period cycling due to the inevitable volume variation of SiOx.
In this work, we prepared SiOx-TiO2/C nanoparticles with unique watermelon-like structured by a simple sol-gel combined with a following carbon coating process. Ultrafine TiO2 nanocrystals are homogeneously distributed inside SiOx particles, forming SiOx-TiO2 dual-phase cores, which are coated with outer carbon shells. The incorporation of TiO2 component can effectively enhance the electronic and lithium ionic conductivities, release the structure stress caused by alloying/dealloying of Si component and maximize the capacity utilization by decreasing the O/Si ratio (x value). The synergetic combination of these advantages enables the synthesized SiOx-TiO2@C nanocomposite to have outstanding electrochemical performances, including high specific capacity, excellent rate capability and stable long term cycleability. A stable specific capacity of ~910 mAh g-1 is achieved after 200 cycles at the current density of 0.1 A g-1 . These results suggest the synthesized SiOx-TiO2/C composite is a promising high performance anode material for lithium ion batteries.