Oxygen vacancies in open-hollow microcapsule enable accelerated kinetics for stable Li-S battery

The fast development of lithium-sulfur (Li-S) batteries is catching more attention to improve cycling stability and kinetics. Herein, a hierarchical porous Ni/NiO/C microsphere (NIONC) with openings assembled by ultrathin nanosheets is introduced to solve the poor conductivity, shuttle effect, and slow electrochemical kinetics of Li-S batteries. The structure of NIONC open-hollow microcapsules combines several advantageous properties for the improvement of electrochemical performances. Primarily, a well-developed hollow structure and openings can perform as containers and doors for sulfur immobilization. Therefore, the confinement effect to sulfur species is obtained by this hollow sphere. Secondly, the nanosheets with oxygen vacancies and Ni active sites provide abundant active sites for the chemical absorption of polysulfides. Based on the open structure and oxygen vacancies of Ni/NiO, both the physical absorption and chemical immobilization of sulfur are realized, with high stability and fast kinetics. The S-injected NIONC (NIONC/S) cathode exhibits outstanding rate performance at 5 A g^-1 with a high capability of 794 mAh g^-1 and excellent long-cycle performance of 653 mAh g^-1 after 300 cycles at 1 A g^-1. We proposed a simple and controllable route to fabricate sulfur hosts by structure and composition adjustment, which will inspire the commercial application of Li-S batteries.