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 Li₂S_n 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 Li₂S_n and nucleation of Li₂S, which provides a profound guidance for efficient and rational catalyst design.