# Methanesulfonate in Phosphate Electrolyte Superstructure Enables Ampere-Hour Practical Aqueous Batteries

## TL;DR

A new dilute aqueous electrolyte enables high-voltage, long-lasting batteries suitable for practical applications like electric bikes.

## Contribution

A novel methanesulfonate in phosphate electrolyte design achieves high voltage and long cycle life in dilute aqueous batteries.

## Key findings

- The electrolyte enables an electrochemical stability window up to 4.5 V and 10,000 cycles in a 1.1-m solution.
- A 60-V, 15-A·h aqueous battery can power an electric bike for 70 km.
- The electrolyte works with various high-voltage electrode pairs.

## Abstract

Present high-voltage Li-ion aqueous batteries largely rely on highly concentrated (up to 63 m) “water-in-salt” electrolyte with limited cycle life (<1,000 cycles) and little hope in practical application. To date, no dilute aqueous electrolyte (salt molality < 2 m) can reliably operate beyond 2 V with cycling life over 1,000 cycles. Here, we introduce a “methanesulfonate in phosphate” superstructure that simultaneously tailors Li+ migration in molecular crowding solvent and electrode surfaces, which enables an unprecedented electrochemical stability window (up to 4.5 V) and cyclability (up to 10,000 cycles) in a dilute 1.1-m aqueous electrolyte. In addition, Such methanesulfonate in phosphate electrolyte can be also applied in various high-voltage electrode couples, and the assembled 60-V, 15-A·h LiMn2O4/LiTi2(PO4)3 aqueous battery can drive an electric bike for 70 km, highlighting the power of such electrolyte design in the commercialization of high-voltage aqueous batteries.