Interface control in TiO₂/BaTiO₃ ferroelectric heterostructures: A bidirectional catalytic pathway toward...

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 (TiO₂/BaTiO₃) heterostructure with an ultrathin carbon coating, designed to act as a bidirectional electrocatalyst, enhancing the sequential conversion of sulfur (S₈) to Li₂S₄ and then to lithium sulfide (Li₂S). The ferroelectric nature of BaTiO₃ enhances LiPS adsorption, reducing the shuttling effect and improving battery performance. The interface-induced electric field directs LiPS migration to TiO₂, facilitating the redox process. An applied electric field polarizes the heterostructure, optimizing the dipole moment of BaTiO₃ and further enhancing performance. Electrochemical measurements and theoretical calculations confirm the superior electrocatalytic activity of TiO₂/BaTiO₃@C for LiPS redox kinetics. The composite electrode achieves a high initial capacity of 836 mAh g^-1 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^-2; electrolyte/sulfur (E/S) ratio: 6.5 μL mg^-1), the as-fabricated LSBs still demonstrate good areal capacities of 5.18, 4.09, 3.84, 3.64, and 3.15 mAh cm^-2, 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.