Imine compound with extended conjugated structure and multi-active centers as cathode for high performance aqueous zinc-ion batteries

Abstract

Aqueous zinc ion batteries (AZIBS) are receiving much attentions because of the high capacity and stable safety performance. Organics are considered as one of the potential candidates for cathodes materials in aqueous zinc ion batteries owing to their wide range of sources, designable structures and green safety advantages. However, the existing organic cathodes face problems such as high solubility and low density of active sites in the electrolyte. Increasing multiple active sites of the molecule and expanding the conjugated structure are expected to solve these problems. Based on this, the imine compound 11,11′-dipyrido [3,2-a:2′, 3′- c] phenazine (DBZQ) was synthesized through refluxing using 1,10-o-phenanthrene-5,6-dione (PDO) and 3,3′-diaminobenzidine (3,3-DBZ) as precursors, and the electrochemical performance and zinc storage mechanism of DBZQ were analyzed. The results showed that DBZQ exhibited a first discharge specific capacity is 188.7 mAh g⁻¹ at 50 mA g⁻¹, and after gradual stabilization, it reached a high specific capacity of 125.7 mAh g⁻¹. In addition, DBZQ exhibited excellent rate performance (68.1 mAh g⁻¹ at 5 A g⁻¹) and long cycling ability (77.7 % retention under 1 A g⁻¹ over 2000 cycles). Moreover, DBZQ with multiple active sites demonstrated a capacitive control process during the insertion of Zn²⁺. The electrochemical mechanism of DBZQ is revealed via experimental and theoretical calculations, which is a mixed insertion into the unsaturated CN bond involving zinc ions and hydrogen ions. In response to the disadvantages of conventional batteries, the introduction of organic electrodes materials has brought new opportunities to the battery industry.