Multifunctional ZnCo2O4 Quantum Dots Encapsulated In Carbon Carrier for Anchoring/Catalyzing Polysulfides and Self-Repairing Lithium Metal Anode in Lithium-Sulfur Batteries

Lithium-sulfur batteries have recently attracted academic/industrial attention due to the high theoretical energy density. However, the capacity decay mainly caused by the polysulfides shuttle effect and poor conductivity of sulfur. Herein, in situ growth of ZnCo2O4 quantum dots (ZCO-QDs) embedded into the hollow carbon-carrier sphere (HCS) to form the ZnCo2O4 quantum dots nanocapsule (ZCO-QDs@HCS) as the multifunctional sulfur host is rationally demonstrated. Based on density-functional theory calculations, in situ spectroscopic techniques, and electrochemical studies, the synergistic effects on anchoring/catalyzing polysulfide of the ZCO-QDs@HCS composite in Li-S batteries is investigated. Interestingly, the ZCO-QDs@HCS also allows for the controlled release of ZCO-QDs into the Li-S electrolyte. Subsequently, it is first discovered that these diffused ZCO-QDs can act as self-repairing initiators to stabilize Li metal anodes via rebuilding the damaged solid electrolyte interphase and suppressing Li dendrites growth. With this concept, quantum dots-based catalyst delivery systems is first constructed in a Li-S battery, which is similar to the use of nanocarrier-based drug delivery systems in cancer therapy. The Li-S cells with the S@ZCO-QDs@HCS cathode display significantly superior electrochemical performances with a high specific capacity (1350.5 mAh center dot g(-1) at 0.1 C) and excellent cycling stability (capacity decay rate of 0.057% per cycle after 1000 cycles at 3.0 C).

Automated summary

A novel sulfur host material for lithium-sulfur batteries, ZnCo2O4 quantum dots nanocapsule, effectively addresses the capacity decay issue in Li-S batteries. Through density-functional theory calculations and experimental studies, it is found that the ZCO-QDs@HCS composite exhibits good catalytic and stability performance in Li-S batteries. Additionally, the material allows for controlled release of ZCO-QDs, which act as stabilizing agents for Li metal anodes.