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.
The two different kinds of SnS2/TiO2 heterojunctions with 3D ball-like structures (denoted as BST-1 and BST-2) assembled by nanosprindle and nanosphere TiO2 encapsulated in 3D flower-like structure SnS2 are successfully synthesized through a two-step solution process. After the introduction of TiO2, lithiation of TiO2 generate the abundant ion-permeable tunnels and facilitate quick ion transport, and share the two “tasks” that the formed Sn or LixSn need afford electron transfer and ion transport simultaneously. Therefore, the number of phase transitions are reduced in BST-1 and BST-2, which buffer the volume change of the SnS2 during charge and discharge process, resulting in greatly improved electrochemical performance in comparison with pure SnS2. [Display omitted]
•SnS2/TiO2 heterojunctions with 3D ball-like structures are assembled.•The introduction of TiO2 decreases phase transitions of SnS2.•The formation of LixTiO2 facilitates rapid ion transports of SnS2.•SnS2/TiO2 exhibits remarkable charge/discharge performance compared with pure SnS2.