Self-tandem catalysis of fast Mg2+ desolvation and sulfur conversions for ultrahigh-performance Mg–S batteries via serially-assembled atomic reactors

Abstract

Rechargeable magnesium–sulfur (Mg–S) batteries are famous for their high volumetric energy density and much improved safety without possible dendrite formation. However, the performances of Mg–S batteries are severely hindered by the sluggish and dissatisfactory electrochemical kinetics of interfacial Mg²⁺ desolvation and successive sulfur species conversions. Herein, a self-tandem catalysis for achieving fast Mg²⁺ desolvation and sulfur conversions is pioneered and the serially-assembled train-like atomic reactors of zinc atomic catalysts employed in long-conductive nitrogen-doped nanocarbons are designed (STAR@LCNC), serving as electrochemical kinetic promotors. Benefitting from these, the STAR@LCNC provides the capability in propelling dissociation kinetics of bridged MgCl(THF)_x⁺ to form more Mg²⁺, and then guarantees high-speed electron exchange and highly active catalytic capability in catalyzing sulfur species at the interface, as thoroughly demonstrated from experimental and in situ spectroscopical characterizations i.e. sum frequency generation spectroscopy to theoretical calculations. The so-fabricated sulfur cathode with STAR@LCNC delivers a long lifespan (400 cycles at 0.5C) and the highest rate performance (612 mA h g⁻¹ at 2C) in the Mg–S battery systems reported so far. Also, the high sulfur loading cathode (4 mg cm⁻²) is capable of stabilizing at 2.92 mA h cm⁻² for 50 cycles, indicating a bright future for tandem catalysis in practical batteries.