# Multiredox Polyoxovanadate‐Based Ionic Liquids for Nonaqueous Redox Flow Batteries

## TL;DR

Researchers developed new ionic liquids based on polyoxovanadates that can store multiple electrons and work well in nonaqueous redox flow batteries.

## Contribution

A new family of multielectron redox-active ionic liquids based on polyoxovanadates is introduced for nonaqueous flow batteries.

## Key findings

- POV-ILs show reversible multielectron redox activity in a wide potential window.
- Symmetric nonaqueous redox flow batteries using POV-ILs operated stably for several days.
- Cation exchange improved solubility in organic solvents like acetonitrile and glymes.

## Abstract

Redox‐active ionic liquids (ILs) represent a promising class of energy carriers due to their intrinsic ionic conductivity, negligible volatility, and electron‐transfer capability. However, the design of ILs capable of reversible multielectron storage is still in its infancy. In this work, we report a family of mixed‐valence polyoxovanadate‐based ionic liquids (POV‐ILs) obtained by combining the highly redox‐active, mixed‐valence cluster (nBu4N)4)8[V14O34Cl][(MgOH)V13O33Cl] with a series of bulky quaternary ammonium cations. Cation exchange transforms the solid precursor into liquid‐like POV‐ILs, dramatically enhancing solubility in organic solvents, such as acetonitrile, THF, and glymes, making them ideal compounds for nonaqueous redox flow batteries (NRFBs). Electrochemical studies demonstrate that these POV‐ILs retain the reversible multielectron redox activity of the parent cluster across a wide potential window, enabling their use as symmetric electrolytes in NRFBs. Flow‐cell demonstration confirms stable multielectron cycling, with electrolyte remixing mitigating capacity fading. By integrating the redox versatility of POVs with the solubility and processability of ILs, this work establishes a new design strategy for redox‐active electrolytes and highlights the promise of POV‐ILs for next‐generation, high‐energy‐density NRFBs.

Here, we present a family of highly redox‐active polyoxovanadate‐based ionic liquids, that exhibit markedly enhanced solubility and multie‐lectron transfers in various nonaqueous media. We apply these mixed‐valence ionic liquids as redox‐active species in both catholyte and anolyte, and demonstrate symmetric nonaqueous redox flow batteries with stable operation over several days.© 2026 WILEY‐VCH GmbH