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Epitaxial Nickel Ferrocyanide Stabilizes Jahn–Teller Distortions of Manganese Ferrocyanide for Sodium‐Ion Batteries
Author(s) -
Gebert Florian,
Cortie David L.,
Bouwer James C.,
Wang Wanlin,
Yan Zichao,
Dou ShiXue,
Chou ShuLei
Publication year - 2021
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202106240
Subject(s) - prussian blue , ferrocyanide , nickel , manganese , jahn–teller effect , electrochemistry , materials science , ion , inorganic chemistry , battery (electricity) , layer (electronics) , chemical engineering , chemistry , nanotechnology , electrode , metallurgy , organic chemistry , engineering , power (physics) , physics , quantum mechanics
Manganese‐based Prussian Blue, Na 2−δ Mn[Fe(CN) 6 ] (MnPB), is a good candidate for sodium‐ion battery cathode materials due to its high capacity. However, it suffers from severe capacity decay during battery cycling due to the destabilizing Jahn–Teller distortions it undergoes as Mn 2+ is oxidized to Mn 3+ . Herein, the structure is stabilized by a thin epitaxial surface layer of nickel‐based Prussian Blue (Na 2−δ Ni[Fe(CN) 6 ]). The one‐pot synthesis relies on a chelating agent with an unequal affinity for Mn 2+ and Ni 2+ ions, which prevents Ni 2+ from reacting until the Mn 2+ is consumed. This is a new and simpler synthesis of core–shell materials, which usually needs several steps. The material has an electrochemical capacity of 93 mA h g −1 , of which it retains 96 % after 500 charge–discharge cycles (vs. 37 % for MnPB). Its rate capability is also remarkable: at 4 A g −1 (ca. 55 C) it can reversibly store 70 mA h g −1 , which is also reflected in its diffusion coefficient of ca. 10 −8 cm 2 s −1 . The epitaxial outer layer appears to exert an anisotropic strain on the inner layer, preventing the Jahn–Teller distortions it normally undergoes during de‐sodiation.