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A Metal–Organic Compound as Cathode Material with Superhigh Capacity Achieved by Reversible Cationic and Anionic Redox Chemistry for High‐Energy Sodium‐Ion Batteries
Author(s) -
Fang Chun,
Huang Ying,
Yuan Lixia,
Liu Yaojun,
Chen Weilun,
Huang Yangyang,
Chen Kongyao,
Han Jiantao,
Liu Qingju,
Huang Yunhui
Publication year - 2017
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201701213
Subject(s) - redox , electrochemistry , tetracyanoquinodimethane , chemistry , cationic polymerization , inorganic chemistry , cathode , lithium (medication) , ion , metal , polymer chemistry , electrode , organic chemistry , molecule , medicine , endocrinology
Although sodium‐ion batteries (SIBs) are considered as alternatives to lithium‐ion batteries (LIBs), the electrochemical performances, in particular the energy density, are much lower than LIBs. A metal–organic compound, cuprous 7,7,8,8‐tetracyanoquinodimethane (CuTCNQ), is presented as a new kind of cathode material for SIBs. It consists of both cationic (Cu II ↔Cu I ) and anionic (TCNQ 0 ↔TCNQ − ↔ TCNQ 2− ) reversible redox reactions, delivering a discharge capacity as high as 255 mAh g −1 at a current density of 20 mA g −1 . The synergistic effect of both redox‐active metal cations and organic anions brings an electrochemical transfer of multiple electrons. The transformation of cupric ions to cuprous ions occurs at near 3.80 V vs. Na + /Na, while the full reduction of TCNQ 0 to TCNQ − happens at 3.00–3.30 V. The remarkably high voltage is attributed to the strong inductive effect of the four cyano groups.