摘要
Introducing SiW 12 as a multifunctional redox mediator enables uniform Sn deposition. • SiW 12 chemically dissolves “dead Sn”, while its reduced state can be regenerated on the electrode. • The kinetic rate constant of SiW 12 is 2–3 orders of magnitude higher than that of commercial vanadium systems. • The battery delivers stable cycling for 350 cycles with a Coulombic efficiency of 99.5% and no capacity decay. Aqueous redox flow batteries (ARFBs) are promising technologies for grid-scale energy storage. However, metal-based ARFB systems suffer from severe capacity fading caused by the accumulation of inactive “dead metal”. Herein, we report a multifunctional polyoxometalate redox mediator, silicotungstic acid (H 4 SiW 12 O 40 , SiW 12 ), which simultaneously regulates uniform Sn deposition and oxidatively dissolves dead Sn in acidic Sn–iodine (Sn I) flow batteries. Mechanistically, reduced SiW 12 (SiW 12 (Re)) guides Sn 2+ to form a more uniform deposition layer via an optimized solvation structure and interfacial coordination. Meanwhile, SiW 12 oxidizes dead Sn into soluble Sn 2+ with fast electron transfer, and SiW 12 (Re) can be in situ regenerated on the electrode for continuous reuse. Electrochemical measurements reveal that the kinetic rate constant of SiW 12 is 2–3 orders of magnitude higher than that of the commercial vanadium redox couple. The as-assembled Sn I flow battery delivers stable cycling over 350 cycles at 50 mA cm −2 , with an average Coulombic efficiency of 99.5% and negligible capacity decay. Post-cycling characterizations confirm the complete elimination of dead Sn from both the electrode and electrolyte. This redox mediation strategy is generalizable to other polyoxometalate systems, providing a universal pathway to address the dead-metal challenge and realize long-life, high-efficiency metal-based flow batteries. Download: Download high-res image (80KB) Download: Download full-size image
危险品化学品经营许可证（带存储）