Interface control in TiO/BaTiO ferroelectric heterostructures: A bidirectional catalytic pathway toward high-performance Li-S batteries.

Li-S batteries (LSBs), noted for their high energy density and low cost, face challenges due to sluggish lithium polysulfide (LiPS) redox kinetics and complex phase transformations during charge/discharge cycles. Herein, we introduce a novel hollow nanocomposite, a titanium oxide/barium titanate (TiO/BaTiO) heterostructure with an ultrathin carbon coating, designed to act as a bidirectional electrocatalyst, enhancing the sequential conversion of sulfur (S) to LiS and then to lithium sulfide (LiS). The ferroelectric nature of BaTiO enhances LiPS adsorption, reducing the shuttling effect and improving battery performance. The interface-induced electric field directs LiPS migration to TiO, facilitating the redox process. An applied electric field polarizes the heterostructure, optimizing the dipole moment of BaTiO and further enhancing performance. Electrochemical measurements and theoretical calculations confirm the superior electrocatalytic activity of TiO/BaTiO@C for LiPS redox kinetics. The composite electrode achieves a high initial capacity of 836 mAh g at 1C, retaining 64 % of its capacity after 400 cycles with a low fading rate of 0.075 % per cycle. Under practical operation conditions (sulfur areal loading: 6.02 mg cm; electrolyte/sulfur (E/S) ratio: 6.5 μL mg), the as-fabricated LSBs still demonstrate good areal capacities of 5.18, 4.09, 3.84, 3.64, and 3.15 mAh cm, respectively, at current densities from 0.05 to 0.5C. This study elucidates the critical synergy between self-induced electric fields and heterostructure engineering in polysulfide conversion, providing fundamental guidance for designing advanced catalysts in high-energy LSBs and related electrochemical energy systems.