Boosting the Performance of Zn Electrode in Aqueous Electrolytes via Trace Amount of Organic Molecules

Trace amount of 2-Pyrrolidinone (Pr) additive manipulates solvation structure and alters the Zn anode-electrolyte interface via absorbing Pr molecules on the Zn surface, reducing water activity, suppressing corrosion and dendrite formation, and resulting in a boosted Zn electrode running over 1200 h with average CE 99. 9 % under 1 mA cm⁻² and 1 mAh cm⁻².

Abstract

The poor performance of Zn electrode in aqueous electrolytes prevents the practical application of aqueous zinc-ion batteries (AZIBs). Here, 2-Pyrrolidinone (Pr) is introduced into conventional ZnSO₄ electrolytes as additive and only 3 vol.% addition (Pr−to−H₂O volume ratio) enables boosted performance. The Pr molecules are preferentially adsorbed on the surface of Zn electrodes to promote the uniform deposition of Zn ions and modulate the solvation structure of Zn²⁺ to inhibit the side reactions. As a result, the Zn electrode is boosted to run over 1200 h during charge/discharge cycling processes and delivers high average coulombic efficiency (CE) of 99.9 % under 1 mA cm⁻², 1 mAh cm⁻². Even under harsh testing conditions of 20 mA cm⁻² and 20 mAh cm⁻², Zn electrode still run over 100 h, which is much longer than that at pristine electrolyte (25 h). Moreover, the Zn||MnO₂ full cells with the Pr additive exhibit a high capacity of 201 mAh g⁻¹ and good capacity retention of 89 % after 550 cycles at 0.5 A g⁻¹.

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