# An Investigation of the Highly Stable Interface in Zn2+/Mn2+-EG-Based Deep Eutectic Electrolytes for Zinc-Ion Batteries

## TL;DR

This paper introduces a new electrolyte for zinc-ion batteries that significantly improves their lifespan and performance by preventing dendrite growth and anode corrosion.

## Contribution

The novel HDES electrolyte reconfigures Zn2+ solvation and forms a protective coating, enabling dendrite-free zinc deposition and long-term stability.

## Key findings

- The HDES electrolyte enables over 2000 cycles with 95% capacity retention and 85% Coulombic efficiency.
- The electrolyte suppresses hydrogen evolution and anode corrosion through a robust hydrogen bond network.
- Traditional aqueous electrolytes fail within 200 cycles, highlighting the tenfold improvement of the HDES-based system.

## Abstract

Zinc-ion batteries have garnered significant research interest owing to their inherent safety, low cost, and environmental compatibility. Nevertheless, their widespread adoption is impeded by critical challenges including uncontrollable dendrite growth, parasitic side reactions stemming from active water molecules, and the corrosion of the zinc anode in conventional aqueous electrolytes. Herein, a hydrated deep eutectic solvent (HDES) electrolyte based on ZnSO4, MnSO4, and ethylene is proposed for high-performance zinc-ion batteries. This electrolyte demonstrates excellent stability and simultaneously enables the formation of a protective coating on the Zn anode surface. Spectroscopic analyses and theoretical simulations reveal that this electrolyte reconfigures the primary Zn2+ solvation shell by replacing water molecules with HDES components. This tailored solvation structure facilitates interfacial desolvation, elevates nucleation overpotential, and promotes uniform, dendrite-free zinc deposition. Simultaneously, a robust hydrogen bond network effectively sequesters free water, significantly suppressing the hydrogen evolution reaction and anode corrosion. Benefiting from these features, the HDES-based full cell delivers exceptional long-term stability, achieving over 2000 cycles at 3 mA cm−2 with a capacity retention exceeding 95% and a Coulombic efficiency surpassing 85%. In sharp contrast, the traditional aqueous counterpart fails within only 200 cycles. This tenfold lifespan enhancement, coupled with cost-effectiveness and non-flammability, presents a promising strategy for advanced, grid-scale zinc-based energy storage.