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

Abstract

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.