Improved Reversibility of Fe<sup>3+</sup> /Fe<sup>4+</sup> Redox Couple in Sodium Super Ion Conductor Type Na<sub>3</sub> Fe<sub>2</sub> (PO<sub>4</sub> )<sub>3</sub> for Sodium-Ion Batteries.

Rajagopalan, Ranjusha; Chen, Bo; Zhang, Zhicheng; Wu, Xing-Long; Du, Yonghua; Huang, Ying; Li, Bing; Zong, Yun et al. · Adv Mater · 2017

basic_science · Level V

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Abstract

The methodology employed here utilizes the sodium super ion conductor type sodium iron phosphate wrapped with conducting carbon network to generate a stable Fe<sup>3+</sup> /Fe<sup>4+</sup> redox   couple, thereby exhibiting higher operating voltage and energy density of sodium-ion batteries. This new class of sodium iron phosphate wrapped by carbon also displays a cycling stability with >96% capacity retention after 200 cycles.