We find significant differences between degradation and healing at the surface or in the bulk for each of the different APbBr3 single crystals (A=CH3NH3+, methylammonium (MA); HC(NH2)2+, formamidinium (FA); and...

Lithium–sulfur (Li–S) batteries (LSBs) have high energy densities and employ inexpensive materials. However, the poor sulfur conductivity and rapid capacity fading hamper their applications. We developed a free-standing composite cathode based on multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs), whose fabrication follows a solution-based, scalable method. The two CNT types create a synergic effect: SWCNTs result in high conductivity, high surface area, and mechanical strength/flexibility; MWCNTs’ larger pores ensure facile ionic diffusion and trapping of lithium polysulfides. The composite cathode exhibits a peak discharge capacity of 1221 mAh/g, maintaining 876 mAh/g after 100 cycles at a 0.1C rate.