MOF-Derived Nitrogen-Rich Hollow Nanocages as a Sulfur Carrier for High-Voltage Aluminum Sulfur Batteries
Tianming Liu, Guocheng Lv, Meng Liu, Xiaoya Cui, Hao Liu, Haodong Li, Changchun Zhao, Longfei Wang, Juchen Guo, Libing Liao
Abstract
Aluminum–sulfur batteries (ASBs) are emerging as promising energy storage systems due to their safety, low cost, and high theoretical capacity. However, it remains a challenge to overcome voltage hysteresis and short cycle life in the sulfur/Al 2 S 3 conversion reaction, which hinders the development of ASBs. Here, we studied a high-voltage ASB system based on sulfur oxidation in an AlCl 3 /urea electrolyte. Nitrogen-doped hollow nanocages (HNCs) synthesized from MOF precursors were rationally designed as sulfur/carbon composite electrodes (S@HNC), and the impact of the nitrogen species on the electrochemical performance of sulfur electrodes was systematically investigated. The S@HNC-900 achieved efficient conversion at 1.9 V, delivering a stable capacity of 197.3 mA h g –1 and a Coulombic efficiency of 93.28% after 100 cycles. Furthermore, the S@HNC-900 electrode exhibited exceptional rate capacity and 800th long-term cycling stability, retaining a capacity of 87.1 mA h g –1 at 500 mA g –1 . Ex situ XPS and XRD characterizations elucidated the redox mechanism, revealing a four-electron transfer process (S/AlSCl 7 ) at the S@HNC-900 electrode. Density functional theory calculations demonstrated that pyridinic nitrogen-enriched HNC-900 significantly enhanced the sulfur conversion reaction and facilitated the adsorption of sulfur intermediates (SCl 3 + ) on the carbon interface. This work provides critical insights into the high-voltage sulfur redox mechanism and establishes a foundation for the rational design of carbon-based electrocatalysts for the enhancement of ASB performance.