Heavy Water Enables High-Voltage Aqueous Electrochemistry via the Deuterium Isotope Effect

Aqueous electrolytes, which possess advantages of non-flammability and high ionic conductivity for safe and sustainable energy storage systems, are restricted by their narrow potential windows due to water electrolysis. Recent researches in high-voltage aqueous electrolytes are mainly focused on the molecular-level hydration structure of electrolyte salts, while the influence from subatomic-scale neutrons of water solvent has never been considered. Here for the first time, we report an electrochemical effect of isotope that, the numerically increased neutrons in water solvent extend the potential window of aqueous electrolytes. This effect is caused by following factors: the lower zero-point energy of deuterium compound, smaller ion product, and larger dehydration energy of heavy water. It is affected by ion species, electrolyte concentrations, and the ratio of deuterium-to-protium. Our finding brings a new insight into aqueous electrochemistry, that isotope in water molecular improves the performance of ...