TiO2 quantum dots decorated multi-walled carbon nanotubes as the multifunctional separator for highly stable lithium sulfur batteries

Lithium sulfur battery is considered one of the most promising rechargeable energy storage devices due to its ultrahigh theoretical energy density and specific capacity. It still cannot be applied because of some key problems. In particular, the shuttle effect of soluble polysulfide compounds leads to the rapid attenuation of battery capacity, short cycle life and serious self-discharge effect. TiO2 quantum dots and polysulfide compounds have strong interactions and can capture soluble polysulfide compounds, thus inhibiting the shuttle effect. Herein, we introduce a battery separator based on TiO2 quantum dots modified multi walled carbon nanotubes to solve the shuttle effect and adapt to the expansion of electrodes during charging and discharging. The interlayer has abundant spacing and excellent conductivity. This strategy can significantly improve the stability of lithium sulfur batteries. As a result, Li-S cells with MWCNTs@TiO2 quantum dots modified separator deliver an initial capacity of 1083 mAh g−1 and keep a cycle capacity of 610 mAh g−1 after 600 cycles at the rate of 838 mA g−1, which maintains an average capacity decay of only 0.072% per cycle. This simple and effective method can greatly improve the application capacity of lithium sulfur batteries.