Synthesis of the Ni2P–Co Mott–Schottky Junction as an Electrocatalyst to Boost Sulfur Conversion Kinetics and Application in Separator Modification in Li-S Batteries

To overcome the shuttling effect and sluggish conversion kinetics of polysulfides, a large number of catalysts have been designed for lithium–sulfur (Li–S) batteries. Herein, a Mott–Schottky junction catalyst composed of Co nanoparticles and Ni2P was designed to improve polysulfide kinetics. Our investigations reveal the rearrangement of charges at the Schottky junction interface and the construction of the built-in electric field are crucial for lowering the activation energy of the dissolved Li2Sn reduction and Li2S nucleation reaction. Furthermore, a series of experimental and electrochemical tests were performed to demonstrate that the Schottky catalytic effect enhanced the synergistic catalytic effect. With a Ni2P–Co@CNT catalyst, the battery exhibits an initial specific capacity of 874 mAh g–1 at a rate of 4.0 C, and the decay rate per cycle is 0.049% in 700 cycles. Meanwhile, the battery shows 0.118% decay rate per cycle at 0.5 C in 100 cycles at a high sulfur loading of 10 mg cm–2. The Schottky heterojunction structure proposed here has been shown to have a good catalytic effect on the reduction of Li2Sn and nucleation of Li2S, which provides a profound guidance for efficient and rational catalyst design.