Cooperative Effect of Multiple Active Sites and Hierarchical Chemical Bonds in Metal–Organic Compounds for Improving Cathode Performance

• Published in: ACS energy letters 2020-02, Vol.5 (2), p.477-485
• Main Authors: Zhao, Xiaolin, Cui, Mengnan, Ma, Chao, Qiu, Wujie, Wang, Youwei, Song, Erhong, Wang, Kaixue, Liu, Jianjun
• Format: Article
• Language: English
• ISSN: 2380-8195; 2380-8195
• DOI: 10.1021/acsenergylett.9b02630

Metal–organic cathode compounds with low solubility and more viable eco-efficient production still suffer from relatively low voltage and limited discharge capacity because their redox reactions solely rely on active organic functional groups or metal clusters. Here, a metal–organic compound Cu2(p-O2NC6H4CO2)4(EtO)2 was demonstrated to have high capacity of 243 mA h g–1 and high-voltage plateaus of 3.66, 3.15, 2.25, and 2.08 V vs Li+/Li through first-principles calculations. Electronic structure analysis reveals Cu2+ ↔ Cu x+ (1 < x < 2) and O y– (1 < y < 2) ↔ O2– in a metal–ligand moiety and N5+ ↔ N x+ (4 < x < 5) and O2– ↔ O z– (1 < z < 2) in −NO2 groups, achieving high voltage and capacity by operating cooperative cationic–anionic redox reactions based on multiple active sites and hierarchical chemical bonds. Furthermore, the Cu2(p-O2NC6H4CO2)4(EtO)2 is also predicted to have good electrochemical reversibility because the cationic conversion reaction is inhibited by a higher-voltage anionic reaction and hierarchical chemical bonds of [MO5] n−. The present study provides a strategy to design metal–organic cathode compounds with high performance.