Exploring structural stability mechanism of TiO2 encapsulated in 3D flower-like SnS2 anode for lithium ion batteries

Abstract

SnS2 is considered as a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical specific capacity, low toxicity, and low cost. However, its development has been hindered by the volume expansion/contraction during lithiation/delithiation process and also the poor electronic conductivity. Even TiO2 has been widely employed to improve the stability of the bulk SnS2, the underlying mechanism and its interaction with SnS2 remains unclear. Here, we synthesize two different kinds of SnS2/TiO2 heterojunctions with 3D ball-like structures (denoted as BST-1 and BST-2) assembled from nanosprindle and nanosphere TiO2 encapsulated in 3D SnS2 flowers, aiming to investigate their electrochemical performance and structural stability. Compared with pristine SnS2, the 3D BST-1 and BST-2 demonstrate high specific capacity, remarkable rate capability and cycling stability. Ex-situ X-ray diffraction shows that four phase transitions occur to pure SnS2 during charge and discharge process whereas only two to BST-1 and BST-2. We attribute the difference to rapid ion transports introduced by in-situ lithiating TiO2, which helps stabilize the structure of SnS2.