Abstract

Herein, the core-shell structured N-doped carbon coated Fe₇S₈ nano-aggregates (Fe₇S₈@NC) were controllably prepared via a simple three-step synthesis strategy. The appropriate thickness of N-doped carbon layer outside Fe₇S₈ nano-aggregates can not only inhibit the particle pulverization induced by the big volume changes of Fe₇S₈, but can increase the electron transfer efficiency. The hierarchical Fe₇S₈ nano-aggregates composed of some primary nanoparticles can accelerate the lithium or sodium diffusion kinetics. As anode materials for Li-ion batteries (LIBs), the well-designed Fe₇S₈@NC nanocomposites exhibit outstanding lithium storage performance, which is better than that of pure Fe₇S₈, Fe₃O₄@NC and Fe₇S₈@C. Among these nanocomposites, the N-doped carbon coated Fe₇S₈ with carbon content of 26.87 wt.% shows a high reversible specific capacity of 833 mAh·g⁻¹ after 1,000 cycles at a high current density of 2 A·g⁻¹. The above electrode also shows excellent high rate sodium storage performance. The experimental and theoretical analyses indicate that the outstanding electrochemical performance could be attributed to the synergistic effect of hierarchical Fe₇S₈ nanostructure and conductive N-doped carbon layer. The quantitative kinetic analysis indicates that the charge storage of Fe₇S₈@NC electrode is a combination of diffusion-controlled battery behavior and surface-induced capacitance behavior.

中文翻译：

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伪电容增强了N掺杂的碳包覆的Fe 7 S 8纳米骨料作为锂和钠存储的有希望的阳极材料

摘要

本文中，通过简单的三步合成策略可控地制备了核壳结构的N掺杂碳包覆的Fe ₇ S ₈纳米聚集体（Fe ₇ S ₈ @NC）。Fe ₇ S ₈纳米聚集体外部适当的N掺杂碳层厚度不仅可以抑制Fe ₇ S ₈的大量体积变化引起的颗粒粉碎，而且可以提高电子转移效率。由一些初级纳米颗粒组成的分层Fe ₇ S ₈纳米聚集体可以加速锂或钠的扩散动力学。设计精良的铁作为锂离子电池（LIB）的负极材料₇ S ₈ @NC纳米复合材料具有出色的锂存储性能，优于纯Fe ₇ S ₈，Fe ₃ O ₄ @NC和Fe ₇ S ₈ @C。在这些纳米复合材料中，碳含量为26.87 wt。％的N掺杂的碳包覆的Fe ₇ S ₈在2 A·g ^-1的高电流密度下经过1000次循环后显示出833 mAh·g ^-1的高可逆比容量。。上述电极还显示出优异的高速率钠存储性能。实验和理论分析表明，优异的电化学性能可归因于Fe ₇ S ₈纳米级结构与导电N掺杂碳层的协同作用。定量动力学分析表明，Fe ₇ S ₈ @NC电极的电荷存储是扩散控制的电池行为和表面感应电容行为的组合。