Construction of a stable lithium sulfide membrane to greatly confine polysulfides for high performance lithium-sulfur batteries

A stable lithium sulfide membrane is constructed in situ to wrap the mixed sulfur/C material surface of a lithium-sulfur battery (LSB) by delicately tuning the galvanostatic discharge current. The membrane offers unique and selective channels which allow only ions/small sulfides to pass through and confine polysulfide transport, restricting the shuttle effect, and thus providing a large capacity of 685 mA h g^-1 at 1C and a long-lasting cycling stability (0.03% capacity decay per cycle). This LSB, which is much superior to the same sulfur-loaded battery without the membrane (0.26% capacity decay per cycle over 207 cycles and 213 mA h g^-1 at 1C), is the best among all reported plain carbonaceous host material-based LSBs. The mechanism responsible for such dramatically improved performance is discussed in detail. This work not only offers a facile approach to greatly improve the capacity and stability of LSBs for practical applications but also offers new scientific insights into LSB design.