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Carefully selecting the transition metal dopant in consideration of its redox potential allows for further increased energy and power densities.

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Boosted by costs benefits, the development of room temperature Na-ion batteries is strongly desired for stationary applications. In this study we explore the possible use of V 2 O 5 aerogel as anode material for sodium ion batteries. The aerogel is able to reversibly insert more than 3 Eq. of sodium in the voltage range 0.1 V-4 V vs. Na/Na + demonstrating to possess additional capacity when cycled to lower voltage. The anode delivers about 200 mAh g −1 in the voltage range 0.01 V-1.5 V vs. Na/Na + . The preliminary characterization of a full Na-ion cell made coupling the V 2 O 5 aerogel anode with carbon-coated Na 3 V 2 (PO 4 In the past years lithium ion batteries (LIBs) have strongly evolved, conquering the market of portable electronic devices and penetrating that of electro-mobility. However, issues related to lithium availability and costs of other materials used in LIBs are rising up. Therefore, special efforts are presently dedicated to the development of alternative battery chemistries based on different shuttling cations like Mg 2+ , 1,2 Al 3+3,4 and Na + . 5,6 In this context, sodium ion batteries (SIBs) are considered as a suitable alternative to the more expensive LIB technology in stationary energy storage applications because their production does not require any technological development aside from the development of appropriate electrodes' materials. In comparison with Li + , the Na + cation is heavier (23 g mol −1 vs 6.94 g mol −1 ) and larger (0.98 Å vs 0.69 Å) leading to lower gravimetric energy and, possibly, slower kinetics. On the other hand, sodium is widely available, therefore, its cost is noticeably low, and worldwide distributed. Moreover, the absence of known Na-Al electrochemically formed alloys permits the use of aluminum current collectors at the anode side, further reducing the cost of the final battery.Presently, the research stream in SIBs' development concerns with the identification of suitable electrode materials taking advantage of the mature background available in lithium ion systems. Several cathode materials are currently investigated, especially those based on layered oxides and polyanionic compounds.6-10 The latter exhibit the advantage of being thermally more stable, 11 thus, enabling safer energy storage.Vanadium-based compounds are of particular interest due to the different oxidation states accessible realizing multi-electrons redox reactions. Indeed, Na 3 V 2 (PO 4 ) 3 is able to reversibly release two equivalents of Na + ions (corresponding to a theoretical capacity of 118 mAh g −1 ), making use of the V 3+ /V 4+ redox couple at around 3.3 V. Additionally, the same material is also investigated as negative electrode as, at 1.5 V, one additional equivalent of Na + is reversibly hosted into the structure while V 3+ is partly reduced to V 2+ . 12 The main drawback of this material is represented by the rather low electronic conductivity, which, however, can be by-passed with the use of nano-sized particles, as well as their carbon-coating. 13Among the layered oxid...

The electronic structure and ligand environment of sulfur was investigated in various sulfur-containing compounds with different structures and chemical states by using X-ray emission spectroscopy (XES). Calculations were performed using density functional theory (DFT) as implemented in the StoBe code. The sulfur chemical state and atomic environment is discussed in terms of the molecular orbitals and partial charges that are obtained from the calculations. The main spectral features can be modeled using our calculational approach. The sensitivity of the Kbeta emission to the cation and the local symmetry is discussed.