High-Voltage Aqueous Magnesium Ion Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Nonaqueous magnesium (Mg) batteries face challenges with complex, moisture-sensitive electrolytes and slow Mg²⁺ diffusion in electrode materials.
• The development of practical Mg batteries is hindered by limitations in electrolyte chemistry and electrode performance.

Purpose of the Study:

• To demonstrate a rechargeable aqueous magnesium ion battery (AMIB) with high energy density, fast kinetics, and reversibility.
• To overcome the limitations of nonaqueous Mg batteries by utilizing an aqueous electrolyte system.

Main Methods:

• A superconcentration approach was used to expand the electrochemical stability window of the aqueous electrolyte to 2.0 V.
• Development and application of two new Mg ion host materials: Li₃V₂(PO₄)₃ as a cathode and poly pyromellitic dianhydride as an anode.
• Comparative analysis of aqueous and nonaqueous Mg systems to understand the role of water in Mg ion mobility.

Main Results:

• The developed AMIB exhibits an unprecedented high power density of 6400 W kg^-1.
• The battery retains 92% of its initial capacity after 6000 cycles, demonstrating excellent reversibility and stability.
• Water's role was identified as critical for Mg ion mobility in intercalation hosts without significantly hindering non-diffusion controlled processes.

Conclusions:

• The successful demonstration of a high-performance AMIB marks a significant advancement in magnesium battery technology.
• The novel electrode materials and electrolyte strategy pave the way for practical and efficient aqueous magnesium ion batteries.
• This work pushes the performance boundaries of Mg ion cells, offering a promising alternative for energy storage.