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Zn 2+ Induced Phase Transformation of K 2 MnFe(CN) 6 Boosts Highly Stable Zinc‐Ion Storage
Author(s) -
Deng Wenjun,
Li Zhengang,
Ye Yaokun,
Zhou Zhuqing,
Li Yibo,
Zhang Man,
Yuan Xinran,
Hu Jun,
Zhao Wenguang,
Huang Zhongyuan,
Li Chang,
Chen Haibiao,
Zheng Jiaxin,
Li Rui
Publication year - 2021
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.202003639
Subject(s) - materials science , valence (chemistry) , cathode , octahedron , ion , crystallography , manganese , structural stability , phase (matter) , crystal structure , inorganic chemistry , chemical physics , chemistry , metallurgy , organic chemistry , structural engineering , engineering
Prussian blue analogues (PBAs), featuring an open framework for accommodating large ions and tunable valence states, have garnered wide interest in the context of aqueous zinc‐ion batteries (ZIBs). However, PBAs in ZIBs currently still suffer from low capacity and poor cycling stability due to structural instability. Here a K 2 MnFe(CN) 6 cathode achieving a very stable capacity of 100 mAh g −1 is reported in a ZIB charged/discharged to 400 cycles. Interestingly, such a stable capacity is attributed to the fact that the K 2 MnFe(CN) 6 cathode is gradually transformed to rhombohedral K 2 Zn 3 [Fe(CN) 6 ] 2 , a process that is induced by Zn 2+ insertion. The mechanism of the phase transformation is further investigated through ab initio calculations and detailed characterizations. The inserted Zn 2+ is found to induce an intense Jahn‐Teller effect of the trivalent manganese, resulting in a strong lattice distortion. Coupled with the disproportionation reaction of manganese, the MnN 6 octahedra are replaced by ZnN 4 tetrahedra and produce the new K 2 Zn 3 [Fe(CN) 6 ] 2 phase eventually. The robust structure of the resulting K 2 Zn 3 [Fe(CN) 6 ] 2 phase contains wider channels for accommodating divalent ions and thus enables highly stable and reversible storage of Zn 2+ ions. The findings of this work lead to a new understanding on the evolution of PBAs in ZIBs, and provide a promising cathode material.