The redox reaction mechanism of a poly(phenanthrene quinone)/graphene composite (PFQ/rGO) was investigated using operando attenuated total reflection infrared (ATR-IR) spectroscopy during cycling of Li and Mg batteries. The reference phenanthrene quinone and the Li and Mg salts of the hydroquinone monomers were synthesized and their IR spectra were measured. Additionally, IR spectra were calculated using DFT. A comparison of all three spectra allowed us to accurately assign the C=O and C-O- vibration bands and confirm the redox mechanism of the quinone/Li salt of hydroquinone, with radical anion formation as the intermediate product. PFQ/rGO also showed exceptional performance in an Mg battery: A potential of 1.8 V versus Mg/Mg2+, maximum capacity of 186 mAh?g-1 (335 Wh?kg-1 of cathode material), and high capacity retention with only 8?% drop/100 cycles. Operando ATR-IR spectroscopy was performed in a Mg/organic system, revealing an analogous redox mechanism to a Li/organic cell.
COBISS.SI-ID: 6811674
Lithium (Li) metal has been considered as an important anode candidate to reach more powerful energy storage devices with higher gravimetric and volumetric capacities. Nevertheless, the growth of high surface area lithium (HSAL) and dendrites during the stripping/deposition of Li causes safety concerns and a low cycle life of Li metal batteries. Here, we report the obtained results for protection of metallic lithium surface by using a gel polymer ionic liquid cross-linked by activation with UV radiation (UV-PIL). The UV-PIL protects Li against the constant degradation caused by the formation of unstable lithium metal–electrolyte interphase and cell dry out due to continuous electrolyte consumption. We observed retarded growth of dendrites when lithium metal was protected with UV-PIL, and due to the lower ionic conductivity of UV-PIL, some differences of mass transport are present compared to carbonate-based liquid electrolyte. Nevertheless, the UV-PIL@Li negative electrode was successfully applied in a Li-ion battery with a lithium iron phosphate (LFP) positive electrode, showing similar behavior compared to the bare Li surface.
COBISS.SI-ID: 6795034