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.