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)2C20) 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 (∼200 mAh g-1) and good Na-ion diffusion (2.97 × 10-13 cm2 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)2F2 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.