A methodical approach for fabrication of binder-free Li2S-C composite cathode with high loading of active material for Li-S battery

Lithium sulfide (Li2S), which has a theoretical capacity of 1166 mA h/g, is considered as a promising cathode material for the Li-S battery. The electrochemical performance of microsized Li2S is impaired, however, by its low electrical conductivity as well as first cycle high activation potential problem. In this work, microsized Li2S powder had been ball-milled with different carbon sources to synthesize Li2S-C composites as well as to find the suitable carbon sources, which were then capillary-deposited in three-dimensional multi-layered Ni foam from a dioxolane-containing mixture to fabricate a binder-free Li2S-C composite cathode. A large amount of active material (∼5 mg/cm2) was loaded in each cathode with the help of conventional capillary deposition method. Scanning electron micrographs show that the Li2S-C composite successfully fills the pores in the Ni foam through capillary action and maintains the integrity of the structure before and after cycling performance. Electrochemical performance testing shows that the capillary-deposited binder-free Li2S-C composite showed excellent cycling performance along with superior rate capability. For further improvement of electrochemical performance, a single-walled carbon nanotube free-standing layer was inserted in between the cathode and the separator which minimized polysulfides shuttle phenomenon thus improved the discharge capacity and the capacity retention.