RESUMEN
Sodium-ion batteries (NIBs) are promising candidates for specific stationary applications considering their low-cost and cost-effective energetic property compared to lithium-ion batteries (LIBs). Additional cost cutbacks are achievable by employing natural materials as active cathode materials for NIBs. In this work, we report the use of natural pyrolusite (ß-MnO2) as a precursor for the synthesis of a NaMnO blend (a mixture of layered P2-Na0.67Mn0.85Al0.15O2 without any doping technique combined with a post-spinel NaMn2O4 without any high-pressure synthesis). The synthesized powder was characterized by XRD, evidencing these two phases, along with two additional phases. Tests for Na-ion insertion registered a reversible discharge capacity of 104 mA h/g after 10 cycles with a well-defined plateau at 2.25 V. After 500 cycles at a C/4 current density, a high Coulombic efficiency between 96 and 99% was achieved, with an overall 25% capacity retention loss. These pilot tests are encouraging; they provide economic relief since the natural material is abundant (low-cost). Desirable, energetic assurances and ecological confirmations are obtainable if these materials are implemented in large-scale stationary applications. The synthesis technique does not use any toxic metals or toxic solvents and has limited side product formation.
RESUMEN
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.