Thermal Lithiated-TiO2: A Robust and Electron-Conducting Protection Layer for Li-Si Alloy Anode.

Developing new electrode materials with high capacity and stability is an urgent demand in electric vehicle applications. Li xSi alloy, as a promising high-capacity and Li-containing anode candidate, has attracted much attention. However, the alloy anode suffers severely from intrinsic high chemical reactivity and poor cycling stability in battery fabrication and operation. Here, we have developed a facile coating-then-lithiation approach to prepare lithiated-TiO2 protected Li xSi nanoparticles (Li xSi-Li2O/Ti yO z NPs) as an attractive anode material. The robust lithiated-TiO2 protection matrix not only provides fast electron transport pathways to efficiently improve the electrical conductivity between Li xSi/Si NPs, but also spatially limits the direct solid electrolyte interphase formation on Li xSi/Si cores during cycling. More importantly, this dense coating layer protects most inner Li xSi alloys from ambient corrosion, leading to high dry-air stability. As a result, the resulting Li xSi-Li2O/Ti yO z anode achieves greatly enhanced cycling and chemical stability in half-cells. It maintains capacity of about 1300 mAh g-1 after prolonged 500 cycles at a high current rate of C/2, with 77% capacity retention. In addition, it exhibits excellent dry-air stability, with around 87% capacity retained after exposure to dry air (10% relative humidity) for 30 days.