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 per-formance. 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.

Automated summary

To overcome the issues of low specific capacity, high cyclic capacity loss, and poor cycle performance in lithium-sulfur (Li-S) batteries, a heterojunction structure of multiferroic BiFeO3 anchored on hollow spheric TiO2 coated on Celgard separator is proposed. The multiferroic BiFeO3 provides a spontaneous polarization to trap polysulfides, and the hollow spheric TiO2 divides a large surface area for sulfur expansion and improves the conductivity of sulfur 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.