Insights into the Reaction Mechanisms of Nongraphitic High-Surface Porous Carbons for Application in Na- and Mg-Ion Batteries

The fabrication of low-cost carbon materials and high-performance sodium- and magnesium-ion batteries comprising hierarchical porous electrodes and superior electrolytes is necessary for complementing Li-ion energy storage. In this work, nongraphitic high-surface porous carbons (NGHSPCs) exhibited an unprecedented formation of n-stages (stage-1 and stage-2) due to the co-intercalation of sodium (Na(dgm)(2)C-20) with diglyme. X-ray diffraction patterns, Patterson diagram, Raman spectra, and IR spectra suggested the presence of n-stages. This phenomenon implies an increase of the initial capacity (similar to 200 mAh g(-1)) and good Na-ion diffusion (2.97 x 10(-13) cm(2) s(-1)), employing diglyme as compared to standard electrolytes containing propylene carbonate and fluoroethylene carbonate. Additionally, the current approach is scalable to full Na- and Mg-ion cells by using t-Na5V(PO4)(2)F-2 and MgMnSiO4 cathodes, respectively, reaching 250 and 110 W h kg(-1) based on the anode mass. The simultaneous Mg (de)insertion from/into MgMnSiO4 and the adsorption/desorption of bistriflimide ions on the NGHSPC surface is responsible for capacity enhancement.

Automated summary

In this study, low-cost carbon materials and high-performance sodium- and magnesium-ion batteries were fabricated using hierarchical porous electrodes and superior electrolytes. The use of non-graphitic high-surface porous carbons (NGHSPCs) led to the formation of unprecedented n-stages, resulting in increased initial capacity and improved sodium-ion diffusion. The current approach was also scalable to full sodium- and magnesium-ion cells, achieving high energy densities.