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 (∼200 mAh g -1 ) and good Na-ion diffusion (2.97 × 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-Na 5 V(PO 4 ) 2 F 2 and MgMnSiO 4 cathodes, respectively, reaching 250 and 110 W h kg -1 based on the anode mass. The simultaneous Mg (de)insertion from/into MgMnSiO 4 and the adsorption/desorption of bistriflimide ions on the NGHSPC surface is responsible for capacity enhancement.