Abstract
Coal samples of different ranks were investigated through various compositional, morphological/structural, and textural experiments prior to their electrochemical implementation in Na-ion half-cells. The purity of coals proved insignificant while distinctions in the flake size, pore width, pore distribution, ID/IG ratio, crystallite parameters (La and Lc) along with adjacent parameters, such as the R-empirical parameter, i.e., limited parallel graphene stacking proved more relevant for Na+ storage into the negative host electrodes. Coal powders were identified via a two-step TGA analysis technique displaying the overall carbon content of the coals and the impurities. Coal-based anode materials were prepared from raw and pyrolyzed coals (at 800 °C under argon gas-flow) and cycled in Na-ion half-cells to further investigate the impact of the coal rank on the energetic properties. High volatile bituminous coal with lower graphene stacking and augmented nanoscopic pores delivered higher reversible capacity in comparison with semi-anthracite coal, whether in their raw (67 vs. 54 mAh/g) or pyrolyzed (214 vs. 64 mAh/g) states, respectively vs. Na/Na+. The dominance of HVBC over SAC due to enhanced properties as R-empirical parameter, ID/IG ratio, and internal porosity. This study provides an exhaustive methodology to assess other carbonaceous anode materials further to evaluate their energy storage capabilities.
Highlights
Coal samples of different ranks were investigated through various compositional, morphological/ structural, and textural experiments prior to their electrochemical implementation in Na-ion halfcells
The coal sample was identified as semi-anthracite coal (SAC)
As Dahn et al reported, the empirical value calculated from X-ray diffraction (XRD) can foresee the energy storage capability of coals in lithiumion batteries (LIBs) as it can provide the same information in NIBs
Summary
Coal samples of different ranks were investigated through various compositional, morphological/ structural, and textural experiments prior to their electrochemical implementation in Na-ion halfcells. NIBs deliver great cost cut-backs; challenges such as lower operating voltage, increased atomic weight leading to decreased gravimetric energy density, and higher equilibrium potential in aqueous solutions are reported[7] Implementing this technology in large-scale stationary energy storage is promising, in renewable energy collection providing economic and ecological a ssurances[8,9]. Calcination of eight different coal samples at 1000 °C and other carbon sources at 900–1100 °C led to the formation of limited parallel graphene stacking (i.e., R empirical parameter) By turn, this augments the number of nanoscopic pores leading to increased reversible lithium intercalation that expands the number of nanoscopic pores leading to increased reversible lithium intercalation[10,11]. The availability of different coals of various ranks suggests that each coal rank has a separate energetic property due to different intrinsic properties, a matter discussed in this work comparing two coals of distinct ranks
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