Manipulating the Electronic Structure of Nickel via Alloying with Iron: Toward High-Kinetics Sulfur Cathode for Na-S Batteries.

The sluggish conversion kinetics and severe shuttle effect in room-temperature Na-S (RT Na-S) batteries cause knotty issues, such as poor rate performance, fast capacity decay as well as low Coulombic efficiency, which seriously impede their practical application. Therefore, exploiting cost-effective and efficient electrocatalysts for absorbing soluble long-chain sodium polysulfides (NaPSs) and expediting NaPSs conversion is of paramount importance. Herein, catalyst mining is first conducted by density functional theory calculations, which reveal that the alloying of Fe into Ni can tailor the electronic structure, leading to lower reaction energy barrier for polysulfide conversion. Based on this, FeNi3@hollow porous carbon spheres (FeNi3@HC) as a promising sulfur host for RT Na-S batteries are rationally designed and fabricated. As expected, the S@FeNi3@HC cathode exhibits an excellent cycling stability (591 mAh g-1 after 500 cycles at 2 A g-1) and outstanding rate performance (383 mAh g-1 at 5 A g-1). Our work demonstrates an effective strategy (i.e., alloying strategy with a rich electron state) to design superior electrocatalysts for RT Na-S batteries.