# Revitalizing nanoscale solid–solid conversion enables ultrastable aqueous batteries

## TL;DR

A new coating strategy enables ultra-stable zinc-manganese batteries by controlling the growth of key components at the nanoscale, offering a practical path for large-scale renewable energy storage.

## Contribution

A size-revitalizing layer on MnO2 enables nanoscale solid–solid conversion, improving battery stability and reversibility.

## Key findings

- The size-revitalizing layer (SRL) reduces solid product size from >10 μm to the nanoscale.
- Bi2O3 is identified as the optimal modifier due to its strong orbital interaction and lattice compatibility.
- Coin cells with high-mass-loading cathodes achieve >1000 cycles at 2 C and stable operation for 110 days.

## Abstract

Aqueous zinc–manganese (Zn–Mn) batteries driven by deposition–dissolution reactions hold significant promise for large-scale grid energy storage. However, their lifetimes are limited by incomplete solid–solid conversion, driven by irreversible pathways forming large-sized solid products—a critical yet overlooked size-dependent challenge. Here, we construct a size-revitalizing layer (SRL) on MnO2 to regulate the interfacial microenvironment via sustained Mn release and strong interaction with solid products. The SRL governs growth kinetics, stabilizing nanoscale products formation. Such small solid products shorten ion-diffusion paths and reduce concentration polarization, enabling a reversible Mn (Ⅱ, l)–Mn (Ⅳ, s) pathway instead of an irreversible Mn (II, l)–Mn (III, s) route. Systematic screening identifies Bi2O3 as the optimal modifier based on its strong p–s (M–Zn) orbital interaction and lattice compatibility, which reduce solid product size from >10 μm to the nanoscale, achieving unparalleled stability and resolving irreversible capacity degradation. With a high-mass-loading cathode (9 mg cm−2), coin cells achieve >1000 cycles at 2 C and scaled iron-plate cells (16 mg cm−2, 26.3 mAh) operate stably for 110 days. This size-controlled solid–solid conversion strategy exhibits broad applicability to diverse electrode materials, highlighting its potential for widespread adoption in advanced energy-storage systems.

A new coating strategy enables ultra-stable zinc-manganese batteries by controlling the growth of key components at the nanoscale, offering a practical path for large-scale renewable energy storage.