Vat Orange 7 as an organic electrode with ultrafast hydronium-ion storage and super-long life for rechargeable aqueous zinc batteries

Organic electrode materials (OEMs) with various advantages are attracting much attention. However, the serious dissolution problem of OEMs has puzzled people for many years without being fundamentally addressed. Here, an aqueous Zn-ion battery using organic bisbenzimidazo[2,1-b:2 ',1 '-i]benzo[lmn][3,8]phenanthroline-8,17dione (BBPD, also known as Vat Orange 7) as cathode material is developed. Due to the special H3O+ charge carrier insertion mechanism, both the BBPD and its discharged product H2BBPD as covalent compounds are not soluble in aqueous electrolytes, which make active materials integrity during long term cycles. Moreover, the special one-dimensional (1-D) square ion tunnels structure of the BBPD enables fast ion and electron transfer abilities in three dimensional directions, leading to an outstanding rate capability and power density. The assembled aqueous Zn-BBPD battery displays high rate performance (76.4 % capacity retention from 0.78 C to 153.85 C), excellent power density (13.4 kW kg-1) and capacity retention of 90.7 % after 10,000 cycles at 153.85 C. The kinetic and thermodynamic investigations on the exact dissolution mechanism of OEMs are first carried out in this work.

Automated summary

In this study, an aqueous Zn-ion battery using BBPD as cathode material was developed, which maintains the integrity of the active materials during long term cycles and exhibits outstanding rate performance and power density due to the special charge carrier insertion mechanism and one-dimensional square ion tunnel structure.