Systematic Effect for an Ultralong Cycle Lithium–Sulfur Battery

Rechargeable lithium-sulfur (Li-S) batteries are attractive candidates for energy storage devices because they have five times the theoretical energy storage of state-of-the-art Li-ion batteries. The main problems plaguing Li-S batteries are poor cycle life and limited rate capability, caused by the insulating nature of S and the shuttle effect associated with the dissolution of intermediate lithium polysulfides. Here, we report the use of biocell-inspired polydopamine (PD) as a coating agent on both the cathode and separator to address these problems (the "systematic effects"). The PD-modified cathode and separator play key roles in facilitating ion diffusion and keeping the cathode structure stable, leading to uniform lithium deposition and a solid electrolyte interphase. As a result, an ultralong cycle performance of more than 3000 cycles, with a capacity fade of only 0.018% per cycle, was achieved at 2 C. It is believed that the systematic modification of the cathode and separator for Li-S batteries is a new strategy for practical applications.