Defect-Driven TiO2– x /SrTiO3– x Heterostructure with Ferroelectricity Enables Shuttle Suppression and Dendrite-Free Growth

The inherent Li dendrite growth, notorious shuttle effect, and severe redox reaction kinetics of lithium polysulfides (LiPSs) impede the feasibility of practical development of lithium–sulfur (Li–S) batteries. Herein, a bi-functional defect-rich TiO2–x/SrTiO3–x nanocube, embedded in a N-doped carbon (NC) freestanding fabric, was prepared and effectively used as a sulfur host and an interlayer between the separator and lithium anode for Li–S full batteries. The spontaneous formation of a built-in electric field (BIEF) between TiO2–x and SrTiO3–x guides self-driven charge rearrangement, resulting in strong directional LiPS migration to boost sulfur redox kinetics and fast, uniform Li+ transfer to avoid Li dendrite growth. Meanwhile, the introduction of oxygen vacancies can induce a ferroelectric phase and provide more active sites for lithium/sulfur storage. The whole 3D framework, enabled with fast electron/ion transport, reduces the Li nucleation overpotential and lowers the energy barrier for LiPS conversion. Consequently, Li||Li cells with the TiO2–x/SrTiO3–x@NC interlayer cycled stably over 600 h at 5 mA cm–2 and 5 mAh cm–2. Furthermore, Li–S full batteries delivered 1285 mAh g–1 at 0.1 C with merely 0.074% per-cycle capacity decay. Our findings emphasized the efficacy of a defect-rich TiO2–x/SrTiO3–x ferroelectric heterostructure implanted into a 3D conductive framework.