Activating Organic Electrode for Zinc Batteries via Adjusting Solvation Structure of Zn Ions

Abstract

Zinc-organic batteries, combining the low cost and high capacity of Zn anodes with the tunable and sustainable properties of organic cathodes, have garnered significant attention. Herein, we present a zinc-organic battery featuring a poly(benzoquinonyl sulfide) (PBQS) cathode, a Zn anode, and an N,N-dimethylformamide (DMF)-based electrolyte, which delivers a high capacity (200 mAh g-1), excellent rate capability, and an ultra-long cycle life (10,000 cycles) when tested with a low PBQS loading (2 mg cm-2). The charge storage mechanism in the PBQS cathode involves solvated Zn2+ adsorption and consequent Zn2+ coordination with PBQS companied by de-solvation process, as confirmed by in-situ FT-IR analysis. However, sluggish Zn2+ de-solvation leads to a loss of Zn2+ coordination capacity when tested with higher PBQS loading (8 mg cm-2) even at a low current density of 0.2 A g-1. Remarkably, the addition of 2% H2O to the DMF electrolyte incorporates 0.24 H2O into the primary solvation sheath of Zn2+, significantly facilitating the de-solvation process. As a result, the PBQS cathode (8 mg cm-2) retains its Zn2+ storage capacity when using the modified electrolyte. This approach offers a new strategy for improving the rate performance of organic electrodes, complementing existing conductivity enhancements.