Fluorinated Organic Magnesium Electrolytes for Enabling High-Performance and Chloride-Free Magnesium-Ion Batteries

Background

Magnesium-ion batteries represent a promising alternative to lithium-ion technology due to magnesium’s natural abundance, low cost, and the potential for higher volumetric energy density. In addition, magnesium metal anodes are less prone to dendrite formation, which enhances safety and cycle life. However, the development of practical magnesium-ion batteries has been hindered by the lack of suitable electrolytes that can efficiently conduct magnesium ions while supporting reversible magnesium deposition and stripping. The search for advanced electrolytes is crucial, as they directly impact the battery’s performance, stability, and commercial viability.

Current approaches to magnesium battery electrolytes often rely on systems containing chloride ions or require complex additives to achieve sufficient ionic conductivity and electrochemical stability. Chloride-based electrolytes, while enabling magnesium deposition, are highly corrosive and can degrade cell components, limiting battery lifespan and safety. Many existing organic magnesium salts either lack the necessary conductivity or are unstable during cycling, leading to poor efficiency and rapid capacity fade. Furthermore, the synthesis of these electrolytes can involve hazardous reagents or multi-step processes, increasing cost and environmental impact. As a result, there is a pressing need for new electrolyte chemistries that are both efficient and benign, overcoming the limitations of corrosion, low conductivity, and synthetic complexity that plague current solutions.

Technology

The technology centers on a new class of fluorinated organic magnesium-conducting electrolytes designed for magnesium-ion batteries. These electrolytes are composed of magnesium dialkoxides and diaryloxides, where the organic ligands are fluorinated to enhance performance. Synthesized via straightforward and scalable routes—either by direct reaction of dialkyl magnesium with fluorinated alcohols or aryl alcohols, or through a magnesium-anthracene intermediate—these electrolytes are notable for being chloride-free, thereby minimizing corrosion and safety risks. When dissolved in ethereal solvents like THF or glymes, the resulting solutions enable efficient, reversible magnesium electrodeposition and stripping, a critical requirement for rechargeable magnesium batteries. The electron-withdrawing nature of the fluorinated groups increases ionic conductivity and electrochemical stability, and the system’s performance can be further optimized by adding Lewis acids such as AlCl₃.

This technology is differentiated by its unique combination of chemical composition, synthetic accessibility, and electrochemical performance. Unlike conventional magnesium battery electrolytes that often rely on corrosive chloride ions or complex additives, these fluorinated magnesium salts are both safer and more environmentally friendly. The synthesis avoids hazardous reagents and produces no problematic byproducts, making it suitable for large-scale production. Experimental data demonstrate superior conductivity and cycling stability compared to non-fluorinated analogs, with the electron-withdrawing fluorine substituents playing a key role in enhancing both ionic mobility and the electrochemical window. The approach also eliminates the risk of co-deposition of non-magnesium metals, further improving battery reliability. Together, these features position this technology as a significant advancement in the development of practical, high-performance magnesium-ion batteries.

Benefits

• Chloride-free electrolyte composition reduces corrosion and enhances battery safety.
• High ionic conductivity and electrochemical stability due to fluorine’s electron-withdrawing effect.
• Supports reversible magnesium electrodeposition and stripping for efficient battery cycling.
• Simple, scalable, and environmentally friendly synthesis using abundant reagents.
• Improved coulombic efficiency and conductivity, especially with Lewis acid additives.
• Long-term cycling stability with increasing conductivity over extended use.
• Avoids co-deposition of non-magnesium metals, ensuring battery purity and performance.

Applications

• Magnesium-ion battery manufacturing
• Grid-scale energy storage systems
• Electric vehicle battery development
• Portable electronics power solutions

Additional info

These fluorinated magnesium dialkoxides and diaryloxides ($Mg-R_2$) function as chloride-free, organic electrolytes for magnesium-ion batteries. Synthesized via direct reaction or magnesium-anthracene intermediates, these compounds enable reversible electrodeposition in ethereal solvents. Electron-withdrawing fluorine substituents enhance ionic conductivity and electrochemical stability by lowering ligand pKa values. These materials offer a scalable, non-corrosive alternative to traditional systems, with performance further enhanced through Lewis acid additives like $AlCl_3$.