Boosting Lithium-Ion Transport Kinetics by Increasing the Local Lithium-Ion Concentration Gradient in Composite...

Constructing composite electrodes is considered to be a feasible way to realize high-specific-capacity Li-ion batteries. The core-double-shell-structured Si@C@TiO₂ would be an ideal design for such batteries, considering that carbon (C) can buffer the volume change and TiO₂ can constrain the structural deformation of Si. Although the electrochemical performance of the shells themselves is relatively clear, the complexity of the multishell heterointerface always results in an ambiguous understanding about the influence of the heterointerface on the electrochemical properties of the core material. In this work, a multilayer film model that can simplify and simultaneously expand the area of the heterointerface is used to study the heterointerfacial behavior. First, a multilayer film TiO₂/C with different numbers of TiO₂/C heterointerfaces is studied. It shows that the electrochemical performance is enhanced apparently by increasing the number of TiO₂/C heterointerfaces. On the one hand, the TiO₂/C heterointerface exhibits a strong lithium-ion storage capacity. On the other hand, the TiO₂/C heterointerface appears to effectively promote the local Li-ion concentration gradient and thus boost the Li-ion transport kinetics. Then, TiO₂/C is combined with Si to construct a composite anode Si/C/TiO₂. An obvious advantage of TiO₂/C over single TiO₂ and C is observed. The utilization rate of Si is greatly improved in the first cycle and reaches up to 98% in Si/C/TiO₂. The results suggest that the electrochemical performance of Si can be greatly manipulated by the heterointerface between the multishells.