A cocklebur-like sulfur host with the TiO2-VOx heterostructure efficiently implementing one-step adsorption-diffusion-conversion towards long-life Li–S batteries

Abstract

Lithium-sulfur (Li–S) batteries are considered to be promising next-generation rechargeable system. However, the shuttle effect for lithium polysulfides (LiPSs) and slow sulfur reaction kinetics due to multistep phase transitions severely limit the practical application of Li–S batteries. Herein, via dual-strategy of heterogeneous interface and defect engineering, a cocklebur-like sulfur host with the TiO2-VOx heterostructure (CTVHs) for long-life Li–S batteries is fabricated, and atomic-level clarification of the chemical interaction between the substrate and LiPSs from a theoretical viewpoint is achieved. Benefiting from the heterostructure, the high adsorption energy heterojunction interface works as capturing centers to trap LiPSs which ensures rapid diffusion to VOx. In addition, the defect-rich spiny VOx is endowed with high catalytic activity towards LiPSs and fast lithium-ion migration so as to effectively implement one-step adsorption diffusion transformation. DFT calculations show that the introduction of a heterostructure can change the electronic structure, thereby improving the adsorption capacity of CTVHs. Electrochemical measurements reveal favorable kinetics for Li2S deposition, better cyclability, and an outstanding discharge capacity. The CTVHs/S cathode delivers a slow capacity decay rate of 0.029% per cycle and achieves nearly 100% coulombic efficiency (CE) at 0.5 C over 1400 cycles. This proposed strategy provides broad prospects to promote the adsorption-conversion of LiPSs for long-life Li–S batteries.