No abstract

We report the use of vinyl ethylene carbonate as a new solid electrolyte interface (SEI)-forming additive for Li-metal anodes in carbonate-based electrolyte, which has the advantages of both good storage performance and low price. Compared to the SEI formed in vinyl ethylene carbonate-free electrolyte, the SEI film formed in 10% vinyl ethylene carbonate electrolyte contains a higher relative content of polycarbonate species and a greater amount of decomposition products of LiPF6 salt. Both components are expected to have positive effects on the passivation of Li-metal surface and the accommodation of volume changes of anode during cycling. Scanning electron microscopy images and COMSOL numerical simulation results further confirm that uniform Li deposition morphology can be achieved in the presence of vinyl ethylene carbonate additive. When cycling at the current density of 0.25 mA cm–2 with a cycling capacity of 1.0 mAh cm–2, the vinyl ethylene carbonate-contained Li–Cu cell exhibits a long life span of 816 h (100 cycles) and a relatively high Coulombic efficiency of 93.2%.

The lack of suitable high-voltage cathode materials has hindered the development of rechargeable magnesium batteries (RMBs). Here, mesoporous Na V (PO ) /C (NVP/C) spheres have been synthesized through a facile spray-drying-annealing method, and their electrochemically desodiated phase NaV (PO ) /C (ED-NVP/C) has been investigated as an intercalation host for Mg ions. The obtained ED-NVP/C exhibits an average discharge voltage of around 2.5 V (vs. Mg /Mg), higher than those of most previously reported cathode materials. In addition, it can deliver an initial discharge capacity of 88.8 mA h g at 20 mA g , with good cycling stability. Ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results demonstrate that the electrochemical reaction is based on an intercalation mechanism and shows good reversibility. Galvanostatic intermittent titration technique (GITT) data have revealed that the intercalation process involves a two-phase transition. The reported ED-NVP/C cathode material with high working voltage offers promising potential for application in RMBs.