Ordered macroporous V-doped ZnO framework impregnated with microporous carbon nanocages as multifunctional sulfur reservoir in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are considered as a promising energy storage device. However, their practical application is still hindered by the unsatisfactory cyclability and slow reaction kinetics. Here, we propose a conductive oxide-based macro-microporous framework, where ZIF-8-derived N-doped carbon (NC) nanocages are embedded within the three-dimensionally ordered macroporous (3DOM) V-doped ZnO matrix, as a high-performance sulfur host for Li-S batteries. The unique framework provides large surface area and high porosity for sulfur accommodation, while the V-doped ZnO skeleton enables a highly conducive substrate for electrochemical reactions. More importantly, such hybrid structure imposes strong fixation and effective catalysis of polysulfides, rendering reversible and rapid sulfur redox reactions. Due to these synergistic effects, the 3DOM NC@V-ZnO/S cathode exhibits an excellent cycling stability with a low capacity fading rate of 0.043 % per cycle during 500 cycles at 1C and a good rate capability of 767.6 mAh g(-1) at 3C. Moreover, a high initial areal capacity of 4.4 mAh cm(-2) was also achieved under a high sulfur loading of 5.8 mg cm(-2) with a low E/S ratio of 4.4 mu L m(-1) in coin cells, as well as decent flexibility and stable cycling in Li-S pouch cell configuration.

Automated summary

In this study, a new structure for the cathode of lithium-sulfur batteries was proposed. It consists of a conductive oxide-based matrix and N-doped carbon nanocages, which can effectively catalyze and fix sulfur for reversible and rapid redox reactions. The experimental results show that this cathode material exhibits excellent cycling stability and rate capability under various testing conditions.