Bronze TiO2 as a cathode host for lithium-sulfur batteries

Abstract

Lithium-sulfur batteries (LSBs) are very promising for large-scale electrochemical energy storage. However, dissolution and shuttling of lithium polysulfides (LiPSs) intermediates have severely affected their overall electrochemical properties and limited their practical application. Designing polar cathode hosts that can effectively bind LiPSs and simultaneously promote their redox conversion is crucial for realizing high-performance LSBs. Herein, we report bronze TiO 2 (TiO 2 -B) nanosheets (~5 nm in thickness) chemically bonded with carbon as a novel multifunctional cathode host for advanced LSBs. Experimental observation and first-principles density functional theory (DFT) calculations reveal that the TiO 2 -B with exposed (100) plane and Ti 3+ ions exhibited high chemical affinity toward polysulfides and effectively confined them at surface. Meantime, Ti 3+ ions and interface coupling with carbon promoted electronic conductivity of the composite cathode, leading to enhanced redox conversion kinetics of LiPSs during charge/discharge. Consequently, the as-assembled TiO 2 -B/S cathode manifested high capacity (1165 mAh/g at 0.2 C), excellent rate capability (244 mAh/g at 5 C) and outstanding cyclability (572 mAh/g over 500 cycles at 0.2 C). This work sheds insights on rational design and fabrication of novel functional electrode materials for beyond Li-ion batteries. Bronze TiO 2 nanosheets were used as a novel multifunctional cathode host for LSBs that could tightly anchor lithium polysulfides and simultaneously catalyze their fast-redox conversion.