A Metal–Organic Compound as Cathode Material with Superhigh Capacity Achieved by Reversible Cationic and Anionic Redox Chemistry for High-Energy Sodium-Ion Batteries

Angewandte Chemie - International Edition

5 years ago

A Metal–Organic Compound as Cathode Material with Superhigh Capacity Achieved by Reversible Cationic and Anionic Redox Chemistry for High-Energy Sodium-Ion Batteries

Kongyao Chen, Yunhui Huang, Yaojun Liu, Qingju Liu, Ying Huang, Lixia Yuan, Yangyang Huang, Chun Fang, Weilun Chen, Jiantao Han

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 (CuIICuI) and anionic (TCNQ0TCNQ− TCNQ2−) 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 TCNQ0 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. CuTCNQ, a metal–organic compound that is composed of cuprous ions and a redox-active ligand, is able to achieve superhigh specific capacity of 255 mAh g−1 through a multiple electron transfer process as a cathode material for sodium-ion batteries. The redox reactions are monitored by UV/Vis, FTIR, and X-ray photoelectron spectroscopy. Both Cu cations and TCNQ anions participate in the electrochemical process.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/anie.201701213