Electrochemical redox behavior of organic quinone compounds in aqueous metal ion electrolytes. (July 2020) - Yan, Lijing
Abstract: Organic quinone compounds are promising electrode materials for aqueous rocking-chair batteries due to chemical inert toward aqueous solutions and wide feasibility of various charge carriers. However, in aqueous electrolytes, the ion-pairing effect of different charge carriers on the electrochemical properties of organic quinone compounds remains unclear. Herein, we selecte a small molecule 9, 10-anthraquinone as a study model and propose that the proton assisted metathesis reaction between anthrahydroquinone and M n+ results in stabilizing electrode reaction. Meantime, the possibility of anthraquinone as anode for aqueous multivalent metal-ion (Al 3+, Mg 2+, Zn 2+ ) batteries is illustrated. Typically for aluminum-ion battery, a reversible capacity of 211.4 mA h g -1 at 800 mA g -1 after 500 full cycles with a capacity retention of 94.5% can be obtained. This work may provide guidance to design and explore more organic quinone compounds for aqueous batteries. Graphical abstract: Here, two redox mechanisms of AQ in different aqueous metal ion electrolytes were proposed. In 1 M LiCl, NaCl, KCl, CaCl2 and BaCl2, AQ molecule obtains an electron and becomes a radical anion [AQ] -, then a metal ion pairs with radical anion to form red [AQ-M n+ ] (n-1)+ ; In 1 M AlCl3, MgCl2 and ZnCl2, AQ molecules undergoes one step two-electron redox process assisted by protons in electrolyte. Then metathesis reactions between AQ-H2 and metal-ions occur and induce morphology evolution in electrode. Image 1 Highlights: Different electrochemical redox behaviors of AQ in different aqueous electrolytes were observed. The spin density distribution of red species result in poor redox stability of AQ in 1M LiCl, NaCl, KCl, CaCl2 and BaCl2 . Metathesis reactions assisted by protons induce the reversible redox reaction of AQ in 1 M AlCl3, MgCl2 and ZnCl2 . The possibility of AQ as anode for aqueous multivalent metal-ion (Al 3+, Mg 2+, Zn 2+ ) batteries was demonstrated.