Postpone Interfacial Impoverishment of Zn‐Ions via Neodymium‐Based Conversion Films for Stable Zn Metal Anodes

A neodymium-based film (NCF-Zn) is presented that attracts Zn²⁺ while repelling OH⁻ and SO₄ ²⁻ anions, postponing the impoverishment of Zn²⁺ to enhance cycling stability on Zn anode in aqueous zinc-ion batteries. This approach enables over 2500 h of stable cycling in symmetric cells and 97.2% capacity retention in MnO₂|NCF-Zn full cells after 1000 cycles, advancing the development of highly reversible AZIBs.

Abstract

The widespread adoption of aqueous zinc-ion batteries (AZIBs) is significantly limited by the diminished cycling stability and reduced lifetime caused by the formation of rampant dendrites and detrimental side reactions, resulting from over-fast depletion of Zn²⁺ at the interface. In this contribution, a negatively charged neodymium-based film via in situ conversion (NCF-Zn) is presented that attracts Zn²⁺ ions and repels OH⁻ and SO₄ ²⁻ anions. Thereby, a higher Zn²⁺ concentration is mentioned to postpone the impoverishment of Zn²⁺ due to the over-fast kinetics, lower the nucleation barrier, and thus uniform the electrodeposition. Meanwhile, the side reactions on the Zn anode can be suppressed due to the repelling of OH⁻ and SO₄ ²⁻ anions. Taking these synergetic advantages, the NCF-Zn anode enables ultra-stable cycles for more than 2500 h in Zn|Zn symmetric cells at a current density of 10 mA cm⁻² and impressive reversibility of 99.93% Coulombic efficiency in Zn|Cu asymmetric cells at a current density of 5 mA cm⁻². Notably, the assembled MnO₂|NCF-Zn full cell demonstrates remarkable long-term cycling stability, retaining 97.2% of its capacity at 1 A g⁻¹ after 1000 cycles. This work offers a straightforward yet effective strategy for constructing a stable protective layer, advancing the development of highly reversible AZIBs.