Finely-Dispersed Ni2Co Nanoalloys on Flower-Like Graphene Microassembly Empowering a Bi-Service Matrix for Superior Lithium-Sulfur Electrochemistry

Lithium-sulfur (Li-S) batteries present a promising solution to high-energy and low-cost energy storage. However, the conversion-type redox mechanism determines the poor fulfillment of battery chemistry in terms of reversibility and kinetics. Herein, a flower-like graphene microassembly decorated with finely-dispersed Ni2Co nanoalloy (Ni2Co@rGO) is developed as advanced host matrix for Li-S batteries. Combining computational, physicochemical, and electrochemical studies, Ni2Co nanoalloys are unveiled synergizing strong adsorbability against polysulfide shuttling and excellent catalytic activity for sulfur conversions. Meanwhile, the sophisticated architecture renders facile electron/ion transport and highly-exposed active interfaces. These virtues collaboratively contribute to fast and durable sulfur electrochemistry with a minimum capacity degradation of 0.034% per cycle over 500 cycles and a rate capability up to 5 C. Besides, the implementation of Ni2Co@rGO as the anode matrix tames the Li redox behavior benefiting from the enhanced lithiophilicity and reduced local current density. As such, the full cell configuration pairing S-Ni2Co@rGO cathode and Li-Ni2Co@rGO anode realizes a favorable areal capacity of 4.53 mAh cm(-2) under high sulfur loading (4.0 mg cm(-2)) and limited electrolyte (E/S = 6.0 mL g(-1)). This work offers an elaborate bi-service matrix engineering to simultaneously improve the conversion reversibility and kinetics for superior Li-S batteries.

Automated summary

In this work, a flower-like graphene microassembly decorated with finely-dispersed Ni2Co nanoalloy (Ni2Co@rGO) is developed as an advanced host matrix for Li-S batteries. The Ni2Co nanoalloys exhibit strong adsorbability against polysulfide shuttling and excellent catalytic activity for sulfur conversions. The sophisticated architecture of the microassembly facilitates electron/ion transport and highly-exposed active interfaces, enabling fast and durable sulfur electrochemistry. The use of Ni2Co@rGO as an anode matrix also improves the Li redox behavior.