Multi-electron bipolar-type organic molecules for high-capacity dual-ion zinc batteries

Abstract

Organic materials featuring element sustainability and functional tunability have currently sprung up as viable cathode alternatives for zinc ion batteries. Nevertheless, organic materials generally suffer from performance deficiencies such as limited capacity and low stability. Here, a bipolar-type organic molecule indanthrone (IDT) is demonstrated as the cathode, with n-type (CO) and p-type (N–H) redox sites involved in multi-electron transfer processes that store both cations and anions, resulting in a significantly enhanced capacity. Meanwhile, the decoration of p-type N–H bridges into the n-type anthraquinone network expands the conjugate system and upgrades the high-voltage durability, maintaining 88.7% of its initial capacity after 3000 cycles at 10 A g⁻¹. The as-designed Zn//IDT battery provides a competitive specific capacity of 238 mA h g⁻¹ at 0.2 A g⁻¹ and an energy density of 159.1 W h kg⁻¹. In addition, bipolar-type N–H and CO moieties are confirmed to involve a mixed energy-storage mechanism with multi-electron participation through various ex situ characterization studies and electrochemical tests. The Zn²⁺ ion is the redox-related cation of CO, while the CF₃SO₃⁻ anion is involved in the conversion between NH⁺ and N–H during the storage process. This work provides a new approach for designing high-performance organic cathodes for advanced zinc batteries.