In Situ Phase Separation Strategy to Construct Zinc Oxide Dots-Modified Vanadium Nitride Flower-like Heterojunctions as an Efficient Sulfur Nanoreactor for Lithium-Sulfur Batteries.

Abstract

Exploring advanced sulfur cathode materials is important for the development of lithium-sulfur batteries (LSBs), but they still present challenges. Herein, zinc oxide dots-modified vanadium nitride flower-like heterojunctions (Zn-QDs-VN) as sulfur hosts are prepared by a phase separation strategy. Characterizations confirm that the flower structure with high specific surface area and pores improves active site exposure and electron/mass transfer. In situ phase separation enriches the Zn-QDs-VN interface, addressing the issues of uneven distribution and interface reduction of Zn-QDs-VN. Further theoretical computations reveal that ZnO-QDs-VN with optimized intermediate spin states can constitute a stable LiS* bond sequence, which can conspicuously facilitate the adsorption and conversion of LiPSs and reduce the battery reaction energy barrier. Therefore, the ZnO-QDs-VN@S cathode shows a high initial specific capacity of 1109.6 mAh g^-1 at 1.0 C and long cycle stability (maintaining 984.2 mAh g^-1 after 500 cycles). Under high S loading (8.5 mg cm^-2) and lean electrolyte conditions (E/S = 6.5 μL mg^-1), it also exhibits a high initial area capacity (10.26 mAh cm^-2) at 0.2 C. The interfacial synergistic effect accelerates the adsorption and conversion of LiPSs and reduces the energy barriers in cell reactions. The study provides a new method for designing heterojunctions to achieve high-performance LSBs.