Entrapment of polysulfides by a BiFeO3/TiO2 heterogeneous structure on separator for high-performance Li–S batteries

Owing to the environmental friendliness, high specific energy, high theoretical capacity, and low cost, lithium-sulfur (Li–S) battery has drawn great attention as the next-generation device. However, the poor conductivity of the sulfur and lithium sulfides, large volumetric expansion of S to Li2S after lithiation, and the dissolution of lithium polysulfides in electrolyte, lead to low specific capacity, high cyclic capacity loss, and bad cycle performance. Here, we propose a heterojunction structure of multiferroic BiFeO3 anchored on hollow spheric TiO2 coated on Celgard separator to overcome the “shuttle effect” of dissolved intermediate polysulfides, improving poor conductivity of S and its discharge products Li2S2/Li2S, and inhibiting lithium dendrites. The multiferroic BiFeO3 provides a spontaneous polarization to trap polysulfides, and hollow spheric TiO2 divides a large surface area for sulfur expansion and improves the poor conductivity of S and BiFeO3 simultaneously. As a result, the discharge capacity remained at 754 mAh g−1 with coulombic efficiency over 99.2% and 83.7% retention of the initial specific capacity after 800 cycles at 1.0C.