Multifunctional ZnCo_2O_4 Quantum Dots Encapsulated In Carbon Carrier for Anchoring/Catalyzing Polysulfides and Self-Repairing Lithium Metal Anode in Lithium-Sulfur Batteries

摘要

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).