Azo compounds as a family of organic electrode materials for alkali-ion batteries

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 115; no. 9; pp. 2004 - 2009
• Main Authors: Luo, Chao, Borodin, Oleg, Ji, Xiao, Hou, Singyuk, Gaskell, Karen J., Fan, Xiulin, Chen, Ji, Deng, Tao, Wang, Ruixing, Jiang, Jianjun, Wang, Chunsheng
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 27.02.2018
• Subjects: Azo compounds; Batteries; Current density; Decay rate; Density functional theory; Electrochemical analysis; Electrochemistry; Electrode materials; Electrodes; Lithium; Lithium-ion batteries; Metal ions; Organic chemicals; Organic compounds; Physical Sciences; Reaction mechanisms; Rechargeable batteries; alkali-ion batteries; organic electrode materials; sustainable batteries; high power density; azo compounds
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1717892115

Organic compounds are desirable for sustainable Li-ion batteries (LIBs), but the poor cycle stability and low power density limit their large-scale application. Here we report a family of organic compounds containing azo group (N=N) for reversible lithiation/delithiation. Azobenzene-4,4′-dicarboxylic acid lithium salt (ADALS) with an azo group in the center of the conjugated structure is used as a model azo compound to investigate the electrochemical behaviors and reaction mechanism of azo compounds. In LIBs, ADALS can provide a capacity of 190 mAh g−1 at 0.5 C (corresponding to current density of 95 mA g−1) and still retain 90%, 71%, and 56% of the capacity when the current density is increased to 2 C, 10 C, and 20 C, respectively. Moreover, ADALS retains 89% of initial capacity after 5,000 cycles at 20 C with a slow capacity decay rate of 0.0023% per cycle, representing one of the best performances in all organic compounds. Superior electrochemical behavior of ADALS is also observed in Na-ion batteries, demonstrating that azo compounds are universal electrode materials for alkali-ion batteries. The highly reversible redox chemistry of azo compounds to alkali ions was confirmed by density-functional theory (DFT) calculations. It provides opportunities for developing sustainable batteries.