Ether-Water Hybrid Electrolyte Contributing to Excellent Mg Ion Storage in Layered Sodium Vanadate

Magnesium ion batteries have potential for largescale energy storage. However, the high charge density of Mg2+ ions establishes a strong intercalation energy barrier in host materials, causing sluggish diffusion kinetics and structural degradation. Here, we report that the kinetic and dissolution issues connected to cathode materials can be resolved simultaneously using a tetraethylene glycol dimethyl ether (TEGDME)-water hybrid electrolyte. The lubricating and shielding effect of water solvent could boost the swift transport of Mg2+, contributing to a high diffusion coefficient within the sodium vanadate (NaV8O20 center dot nH(2)O) cathode. Meanwhile, the organic TEGDME component can coordinate with water to diminish its activity, thus providing the hybrid electrolyte with a broad electrochemical window of 3.9 V. More importantly, the TEGDME preferentially amassed at the interface, leading to a robust cathode electrolyte interface layer that suppresses the dissolution of vanadium species. Consequently, the NaV8O20 center dot nH(2)O cathode achieved a specific capacity of 351 mAh g(-1) at 0.3 A g(-1) and a long cycle life of 1000 cycles in this hybrid electrolyte. A mechanism study revealed the reversible interaction of Mg2+ during cycles. This organic water hybrid electrolyte is effective for overcoming the difficulty of multivalent ion storage.

Automated summary

This article reports a new organic-water hybrid electrolyte that can address the diffusion and dissolution issues of cathode materials in magnesium ion batteries, improving battery performance. By forming a robust shielding layer at the interface, the dissolution of cathode species is suppressed, resulting in a higher specific capacity and longer cycle life for the battery.