Adsorption-Catalysis-Conversion of Polysulfides in Sandwiched Ultrathin Ni(OH)2 -PANI for Stable Lithium-Sulfur Batteries.

ABSTRACT

Strong adsorption and catalysis for lithium polysulfides (LiPSs) are critical toward the electrochemical stability of Li-S batteries. Herein, a hollow sandwiched nanoparticle is put forward to enhance the adsorption-catalysis-conversion dynamic of sulfur species. The outer ultrathin Ni(OH)2 nanosheets not only confine LiPSs via both physical encapsulation and chemical adsorption, but also promote redox kinetics and accelerate the conversion of sulfur species, which is revealed by experiments and theoretical calculations. Meanwhile, the inner hollow polyaniline soft core provides a strong chemical bonding to LiPSs after vulcanization, which can chemically adsorpt LiPSs, and synergistically confine the shuttle effect. Moreover, the Ni(OH)2 nanosheets with a large specific area can enhance the wettability of electrolyte, and the flexible hollow sandwiched structure can accommodate the volume expansion, promoting sulfur utilization and structural stability. The obtained cathode exhibits excellent electrochemical performance with an initial discharge capacity of 1173 mAh g-1 and a small capacity decay of 0.08% per cycle even after 500 cycles at 0.2 C, among the best results of Ni(OH)2 -based materials for Li-S batteries. It is believed that the combination of adsorption-catalysis-conversion will shed a light on the development of cathode materials for stable Li-S batteries.