Room-temperature sodium–sulfur (RT Na–S) batteries offer the potential for inexpensive stationary energy storage at the grid and local level. However, their practical performance remains far from theoretical due to sluggish reaction kinetics, which limits both their energy and their rate characteristics. To overcome this, a conceptually new mechanism is demonstrated on the basis of the catalysis by stabilized free-radical species, as indicated by electron spin resonance measurements, generated on the surface of a Na₂S₆ catholyte-infiltrated activated carbon cloth cathode. X-ray photoelectron spectroscopy characterizations reveal that free-radical catalysis promotes reduction to end-discharged products, via a surface-bound intermediate state, ACC–S₃^–. Due to this free-radical catalytic activity, our RT Na–S cell achieves a high nominal cell potential of 1.85 V. At a rate of 0.5 C, the Na–S cell delivers a high specific capacity of 866 mA h g_(S)^–1 and retains 678 mA h g_(S)^–1 after 700 cycles. The concept of a free-radical mechanism, as described herein, could be adapted to enhance the electrochemical kinetics of other energy storage devices that involve radical intermediate species.

中文翻译：

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室温钠硫电池的自由基催化和氧化还原动力学的增强

室温钠硫（RT Na–S）电池为电网和地方一级廉价的固定式能量存储提供了潜力。然而，由于反应动力学缓慢，它们的实际性能与理论相差甚远，这限制了它们的能量和速率特性。为了克服这个问题，在Na ₂ S ₆浸渗的活性炭布阴极表面上产生的电子自旋共振测量表明，基于稳定的自由基物质的催化作用，从概念上证明了一种新的机理。X射线光电子能谱表征表明，自由基催化通过表面结合的中间态ACC–S ₃ ^–促进了最终放电产物的还原^。。由于这种自由基催化活性，我们的RT Na–S电池可实现1.85 V的高标称电池电势。在0.5 C的速率下，Na–S电池可提供866 mA hg _（S）的高比容量^{– 1，}并在700个循环后保持678 mA hg _（S）^–1。如本文所述，自由基机理的概念可适于增强涉及自由基中间物质的其他能量存储装置的电化学动力学。