FeS₂ is considered as a high capacity electrode materials based on a conversion reaction mechanism, and mainly applied in primary batteries and rechargeable thermal Li-FeS₂ batteries for decades. However, the widely application of FeS₂ in rechargeable battery is still hindered by the low efficiency and poor cycle performance caused by the generation of elemental Fe and S during fully discharge and charge. Herein, we demonstrate a facile but effective strategy to improve the energy efficiency and cycling stability of Li-FeS₂ battery by rational design of a novel micro/nano-structured FeS₂ electrode, which exhibits as a microsphere constructed by numerous nanosheets. By optimizing the electrochemical experiments conditions, a high energy efficiency of 80.4% and a high reversible capacity of 216.8 mAh g^-1 retained after 730 cycles at the optimized voltage window of 1.0-2.4 V. The conversion process at higher (> 2.4 V) potentials to form FeS_y and S has been suppressed as demonstrated by multiple characterizations. And the Li⁺ insertion/extraction reaction between Li₂FeS₂ and Li_2-xFeS₂ and the conversion reaction at lower potential range coexist and are highly reversible. The high reversibility could be mainly ascribed to the micro/nano-structured feature of FeS₂ and the optimization of the voltage window. We believe that, our work could further enhance the fundamental understanding of battery reaction mechanism in the rechargeable Li-FeS₂ battery.

中文翻译：

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微米/纳米结构的FeS ₂用于高能效可充电Li-FeS ₂电池

FeS ₂被认为是基于转化反应机理的高容量电极材料，并且几十年来主要应用于原电池和可充电热式Li-FeS ₂电池。然而，FeS ₂在可再充电电池中的广泛应用仍然由于在完全放电和充电过程中由于元素Fe和S的产生而导致的低效率和较差的循环性能而受到阻碍。本文中，我们通过合理设计新型微/纳米结构的FeS ₂展示了一种可行但有效的策略来提高Li-FeS ₂电池的能量效率和循环稳定性。电极，其表现为由许多纳米片构成的微球。通过优化电化学实验条件，在1.0-2.4 V的最佳电压窗口下，经过730次循环后，保留了80.4％的高能量效率和216.8 mAh g ^-1的高可逆容量。更高的转换过程（> 2.4 V）如多重表征所示，形成FeS _y和S的电势已被抑制。并且Li ₂ FeS ₂和Li _2-x FeS ₂之间的Li ⁺插入/萃取反应较低电势范围的转化反应并存且高度可逆。高可逆性主要归因于FeS ₂的微/纳米结构特征和电压窗口的优化。我们相信，我们的工作可以进一步增强对可充电Li-FeS ₂电池中电池反应机理的基本了解。