Co3O4 nanoneedle arrays as a multifunctional “super-reservoir” electrode for long cycle life Li–S batteries†
Lithium–sulfur (Li–S) batteries are highly attractive as energy storage devices due to their low cost and high energy density. The undesired capacity degradation caused by the polysulfide shuttle, however, has hindered their commercialization. Herein, a Co3O4 nanoneedle array on carbon cloth (CC@Co3O4) nanocomposite has been prepared and demonstrated for the first time as a multifunctional “super-reservoir” electrode to prolong the cycle life of Li–S batteries. Owing to the polar surface of the Co3O4 nanoneedle array, soluble lithium polysulfides (Li2Sn, 4 < n < 8) can be effectively absorbed and then transformed to insoluble Li2S2/Li2S which evenly covers the surface of the Co3O4 nanoneedle during the discharge process. Further, during the charge process, the Co3O4 nanoneedle can catalyze the electrochemical transformation of Li2S2/Li2S into soluble polysulfides. A high initial capacity of 1231 mA h g−1 at 0.5C and a slow capacity decay of 0.049%/cycle at 2.0C over 500 cycles were achieved; excellent rate performance was also obtained.