10.1021/acs.chemmater.5b02364.s001 Palanichamy Sennu Palanichamy Sennu Maria Christy Maria Christy Vanchiappan Aravindan Vanchiappan Aravindan Young-Gi Lee Young-Gi Lee Kee Suk Nahm Kee Suk Nahm Yun-Sung Lee Yun-Sung Lee Two-Dimensional Mesoporous Cobalt Sulfide Nanosheets as a Superior Anode for a Li-Ion Battery and a Bifunctional Electrocatalyst for the Li–O<sub>2</sub> System American Chemical Society 2015 LIB nanothickness sheetlike morphology presence transmission electron microscopy core 3S impedance spectroscopy studies mAh discharge capacity Li electrochemical application performance 2015-08-25 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Two_Dimensional_Mesoporous_Cobalt_Sulfide_Nanosheets_as_a_Superior_Anode_for_a_Li_Ion_Battery_and_a_Bifunctional_Electrocatalyst_for_the_Li_O_sub_2_sub_System/2137912 We report the synthesis of two-dimensional (2D) Co<sub>3</sub>S<sub>4</sub> in a nanothickness sheetlike morphology via simple hydrothermal process and its application to electrochemical energy-storage devices. The presence of unique mesopores with a combination of core/shell nanoparticles in the nanosheets showed superior electrochemical performances as a negative electrode for a Li-ion battery (LIB) and an electrocatalyst in Li–O<sub>2</sub> battery applications. A high discharge capacity of ∼968 mAh g<sup>–1</sup> is noted after 60 cycles with excellent cycling stability when evaluated as an anode for a LIB. On the other hand, the first discharge capacity of ∼5917 mAh g<sup>–1</sup> is observed with a high reversibility of 95.72% for the Li–O<sub>2</sub> battery point of view. This exceptional electrochemical performance in both applications is mainly attributed to the presence of mesoporous with core/shell 2D nanostructure, which translates more catalytic bifunctional (oxygen reduction reaction/oxygen evolution reaction) active sites for Li–O<sub>2</sub> and sustains the volume variations that occur in a three-dimensional manner upon the charge–discharge process for LIB applications. <i>Ex situ</i> studies, such as transmission electron microscopy, X-ray photoelectron spectroscopy, and impedance spectroscopy studies, are also conducted to validate the reaction mechanisms.