Coupling Zn²⁺ Ferrying Effect With Anion–π Interaction to Mitigate Space Charge Layer Enables Ultra‐High Utilization Rate Zn Anode

Abstract

A major dilemma faced by Zn anodes at a high zinc utilization rate (ZUR) is the insufficient supply of ionic carriers that initiate the space charge layer (SCL) subject to the rampant growth of Zn dendrites. Herein, an "anion-cation co-regulation" strategy, associated with a fundamental principle for screening potential electrolyte additives coupling the Zn²⁺ ferrying effect with anion-retention capability, is put forward to construct dendrite-free, high-ZUR Zn anode. Taking ninhydrin-modified ZnSO₄ system as a proof-of-concept, the multiple zincophilic polar groups of ninhydrin facilitate the transport of Zn²⁺ ions, while its electron-deficient aromatic ring retains SO₄ ^2- counterions via anion-π interaction, constructing an ion-rich interface that minimizes the SCL-driven Zn deterioration. Consequently, the Zn anode can endure ∼240 h continuous cycling at an ultrahigh ZUR of 87.3%. The superiority brought by ninhydrin is further reflected by the ultralong cycling durability of Zn-I₂ batteries (over 100 000 cycles). Even at an ultralow N/P ratio of 1.1 (∼90.6% ZUR), the battery with a capacity of ∼5.27 mAh cm^-2 can still sustain for 350 cycles, which has been hardly achieved in aqueous Zn batteries. Furthermore, the effectiveness of this strategy is fully validated by a series of additives sharing similar fundamentals.