Investigation of the Prussian Blue Analog Co<sub>3</sub> [Co(CN)<sub>6</sub> ]<sub>2</sub> as an Anode Material for Nonaqueous Potassium-Ion Batteries.

Deng, Leqing; Yang, Zhao; Tan, Lulu; Zeng, Liang; Zhu, Yujie; Guo, Lin · Adv Mater · 2018

basic_science · Level V

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Abstract

Nonaqueous potassium-ion batteries (KIBs) are attracting increasing attention as a potential low-cost energy-storage system due to the abundance of potassium resources. Here, cobalt hexacyanocobaltate (Co<sub>3</sub> [Co(CN)<sub>6</sub> ]<sub>2</sub> ), a typical Prussian blue analog (PBA), is reported as an anode material for nonaqueous KIBs. The as-prepared Co<sub>3</sub> [Co(CN)<sub>6</sub> ]<sub>2</sub> exhibits a highly reversible capacity of 324.5 mAh g<sup>-1</sup> at a current density of 0.1 A g<sup>-1</sup> , a superior rate capability (221 mAh g<sup>-1</sup> at 1 A g<sup>-1</sup> ), and a favorable long-term cycling stability (200 cycles with 82% capacity retention). Based on a series of characterizations, it is found that potassiation/depotassiation in Co<sub>3</sub> [Co(CN)<sub>6</sub> ]<sub>2</sub> proceeds via solid-state diffusion-limited K-ion insertion/extraction process, in which both carbon- and nitrogen-coordinated cobalt are electrochemically active toward K-ion storage. Finally, the reaction pathway between potassium and Co<sub>3</sub> [Co(CN)<sub>6</sub> ]<sub>2</sub> is proposed. The present study provides new insights on further exploration of PBAs as high-performance electrode materials for KIBs.