Insight into Tib2/Tio2 Mott-Schottky Heterostructure for Accelerating Electrocatalysis Sulfur Conversion

Heterostructure host materials usually combine the physical and chemical properties of multifarious materials to immobilize lithium polysulfides (LiPSs) and accelerate sulfur conversion reactions in lithium-sulfur (Li-S) batteries. Herein, a sea urchin-like TiB2/TiO2 Mott-Schottky heterostructure as a model catalyst was synthesized by hydrothermal reaction. The TiB2/TiO2 Mott-Schottky heterostructure integrates the advantages of adsorptive TiO2 with high conductive TiB2. Meanwhile, the aid of the spontaneous built-in electric field at the TiB2/TiO2 interfaces could provide abundant electrocatalysis sites, catalyzing the electrochemical conversion of lithium polysulfides. Density functional theory (DFT) calculations and systematic electrochemical tests have been conducted to further verify the built-in electric field induced by the Mott-Schottky heterostructure, which could facilitate the polysulfide migration and electron transfer at the interface, thereby enhancing the intrinsic catalytic activity for sulfur electrochemistry. The S@TiB2/TiO2 cathode delivers a stable cycle performance with a capacity degradation of 0.071% per cycle over 500 cycles at 0.5C and a rate capability up to 3C in the coin cell, and it presents a high system-level gravimetric energy density of 309 Wh.kg-1 with high sulfur loading and low electrolyte usage in a multilayer-pouch cell at 0.1C. This work offers a valid way to elevate sulfur redox in Li-S batteries through rationally-designed heterostructures.