A hollow Co0.12Ni1.88S2/NiO heterostructure that synergistically facilitates lithium polysulfide adsorption and conversion for lithium-sulfur batteries

Abstract

• An ingenious Co 0.12 Ni 1.88 S 2 /NiO heterostructure with a hollow and semi-open architecture was engineered in situ , which synergistically enhanced lithium polysulfide adsorption and conversion for lithium-sulfur batteries. • The considerable electrochemical impedance variation was observed via in situ EIS measurements, which was proved to be related to the content of soluble LiPSs in the electrolyte. • The mechanisms of the strong affinities between Co 0.12 Ni 1.88 S 2 /NiO and lithium polysulfides, and the catalytic effect were further investigated by theoretical calculations. The significant capacity deterioration and inadequate cycling lifespan that are mainly caused by the undesirable “shuttle effect” and torpid redox kinetics have encumbered the development of practically applicable lithium-sulfur (Li-S) battery technology. Modifying sulfur cathodes with lithium polysulfide (LiPS) adsorptive and electrocatalytic host materials is a promising approach to resolving these issues. Herein, a Co 0.12 Ni 1.88 S 2 /NiO heterostructure, which has multiple merits, is designed and serves as a sulfur host to improve the electrochemical performance of Li-S batteries. Possessing strong LiPS adsorbability and excellent electrocatalytic activity, the heterostructural Co 0.12 Ni 1.88 S 2 /NiO exhibits favorable synergistic effects, which effectively facilitate the anchoring and converting of diffused LiPSs. As a result, the corresponding cell delivers rapid redox kinetics and higher sulfur utilization. An impressive initial discharge capacity of 1424.8 mAh g −1 and a reversible capacity near 1056.7 mAh g −1 at 1 C over 1000 cycles are achieved with an average Coulombic efficiency of 98.8%. Benefiting from the unique nanoarchitecture and superior catalytic efficiency, only a very small amount of Co 0.12 Ni 1.88 S 2 /NiO (∼7 wt% in the cathode) is used as the sulfur host. The rational design of Co 0.12 Ni 1.88 S 2 /NiO in this work will hopefully offer inspiration for exploring advanced heterostructure materials for Li-S batteries and other electrochemical devices. Heterostructural Co 0.12 Ni 1.88 S 2 /NiO was engineered as a sulfur host for lithium-sulfur batteries. The catalytic effect and strong LiPS adsorbability synergistically promoted redox kinetics and LiPS conversion, which significantly improved the sulfur utilization during the charging and discharging processes.