High temperature solid state sodium (23Na) magic angle spinning (MAS) NMR spin lattice relaxation times (T1) were evaluated for a series of NASICON (Na3Zr2PSi2O12) materials to directly determine Na jump rates. Simulations of the T1 temperature variations that incorporated distributions in Na jump activation energies, or distribution of jump rates, improved the agreement with experiment. The 23Na NMR T1 relaxation results revealed that distributions in the Na dynamics were present for all of the NASICON materials investigated here. The 23Na relaxation experiments also showed that small differences in material composition and/or changes in the processing conditions impacted the distributions in the Na dynamics. The extent of the distribution was related to the presence of a disordered or glassy phosphate phase present in these different sol-gel processed materials. The 23Na NMR T1 relaxation experiments are a powerful tool to directly probing Na jump dynamics and provide additional molecular level details that could impact transport phenomena.

2D nanomaterials, when assembled into an ordered macrostructure, will present many great opportunities, including for Li-ion batteries (LIBs). We report densely-packed vertically-aligned VO2(B) nanobelts (NBs)-based forest structure synthesized on edge-oriented graphene (EOG) network. Using a EOG/Ni foam as a 3D scaffold, aligned VO2(B) NBs can be further synthesized into a folded 3D forest structure to construct a freestanding electrode for LIBs. Electrochemical studies found that such a freestanding VO2(B)/EOG electrode, which combines the unique merits of 2D VO2(B) NBs and 2D graphene sheets, has excellent charge-discharge rate performance. A discharge capacity of 178 mAh g-1 at a rate of 59 C and 100 mAh g-1 at 300 C was measured. A good charge-discharge cycling stability under a high current density was also demonstrated. The results indicate VO2(B)/EOG forest based freestanding electrode is very promising for developing high-rate LIBs.

We present a methodology to enhance the electrical capacitance of activated carbon (AC) electrodes based on the introduction of electrically charged defects through argon plasma processing. Extensive characterization using electrochemical techniques incorporating cyclic voltammetry, constant current charge/discharge, and electrical impedance spectroscopy indicated a close to seven-fold increase in capacitance with respect to untreated AC electrodes, not subject to plasma processing.

Bromophenyl moieties were attached to the carbon-coated LiFePO4 (LiFePO4/C) surface by spontaneous reduction of in-situ generated 4-bromobenzene diazonium ions in organic media. The presence of the surface organic species on the grafted LiFePO4/C powders was confirmed by X-ray photoelectron spectroscopy. Thermogravimetric analyses revealed a low loading (lower than 1 wt. %) of grafted molecules. The electrochemical characterization of the LiFePO4/C cathodes showed that a low loading of bromophenyl groups at the LiFePO4/C surface can enhance the rate of Li+ extraction, presumably due to the decrease of the LiFePO4/C agglomerate size and an increase of the wettability of the electrode. On the other hand, poor performances were obtained using the grafted cathode material with the highest loading of bromophenyl moieties.

The need for higher energy density batteries has spawned recent renewed interest in alternatives to lithium ion batteries, including multivalent chemistries that theoretically can provide twice the volumetric capacity if two electrons can be transferred per intercalating ion. Initial investigations of these chemistries have been limited to date by the lack of understanding of the compatibility between intercalation electrode materials, electrolytes, and current collectors. This work describes the utilization of hybrid cells to evaluate multivalent cathodes, consisting of high surface area carbon anodes and multivalent nonaqueous electrolytes that are compatible with oxide intercalation electrodes. In particular, electrolyte and current collector compatibility was investigated, and it was found that the carbon and active material play an important role in determining the compatibility of PF6-based multivalent electrolytes with carbon-based current collectors. Through the exploration of electrolytes that are compatible with the cathode, new cell chemistries and configurations can be developed, including a magnesium-ion battery with two intercalation host electrodes, which may expand the known Mg-based systems beyond the present state of the art sulfide-based cathodes with organohalide-magnesium based electrolytes.

The potential of Raman and UV-Vis diagnostics for spatially-resolved and in situ diagnostics of lithium-ion batteries is demonstrated. Regarding the use of in situ Raman diagnostics focus is put on LiCoO2 electrode materials, which were investigated in detail as composites of LiCoO2 with binder and conductive additives. The potential of in situ UV-Vis analysis is illustrated for carbon-based materials showing significant absorption changes during electrochemical cycling due to lithium de-/intercalation.

Currently the improvement of stand-alone PV power systems characteristics, including increase of their service life is the actual direction of ground solar power development. The analysis of stand-alone PV power systems efficiency with the use of ultra capacitors is carried out by the means of mathematical modeling. The obtained data shows that the use of ultra capacitors as additional short-term energy storage devices in stand-alone PV power systems contributes to considerable increase of storage batteries lifetime and the total system operating time.