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Electric fields at the dye-sensitized interface of anatase TiO2nanocrystallites interconnected in a mesoporous thin film are reported using carboxylic acid-derivatized and phosphonic acid-derivatized ruthenium polypyridyl complexes. Systematic investigations with [Ru(dtb)2(dpb)](PF6)2, where dtb is 4,4′-di-tert-butyl-2,2′-bipyridine and dpb is 4,4′-bis-(PO3H2)-2,2′-bipyridine, were carried out in conjunction with its carboxylic acid structural analogue. Electric fields attributed to cation adsorption were measured from a bathochromic (red) shift of the sensitizer’s UV–visible absorption spectra upon replacement of neat acetonitrile solution with metal cation perchlorate acetonitrile electrolyte. Electric fields attributed to TiO2electrons were measured from the hypsochromic (blue) shift of the absorption spectra upon electrochemical reduction of the sensitized TiO2thin films. Electric fields, induced by either cation adsorption or electrochemically populated electrons, increase in magnitude following the same general cation-dependent trend (Na+< Li+< Ca2+≤ Mg2+< Al3+), regardless of the sensitizer’s anchoring group type. For the first time, surface electric fields in the presence of trivalent cations (i.e., Al3+) were measured using [Ru(dtb)2(dpb)](PF6)2. The magnitude of electric fields detected by the carboxylic acid sensitizer was 3 times greater than that detected by the phosphonic acid structural analogue under the same experimental conditions. The influence of protons and water in the acetonitrile electrolyte was also quantified. The added water was found to decrease the electric field, whereas protons had a very similar influence as did metal cations.

Li-rich layered-layered nickel manganese cobalt oxides (LLNMC) of the type Li2MnO3-LiMO2 (M = Mn, Co, Ni) are promising cathode materials due to their higher specific capacities and discharge voltages compared to state of art materials. However, these materials have yet to exhibit adequate cycle life and power characteristics in practical cells, partly due to the instability of electrolytes at these high voltages. Thin coatings of inorganic materials such as Al2O3, AlPO4, and AlF3 have been shown to minimize these degradation processes, especially on high voltage cathodes. Here, we report the use of a new aluminum borate-based coating material on the LLNMC cathode at high active mass loadings. AlBO3-coated cathodes demonstrate a sevenfold increase in lifetime compared to uncoated material, as well as higher specific discharge energies vs. analogous AlPO4-coated materials. SEM and TEM confirm the thin coatings of amorphous material. Detailed electrochemical studies including Tafel polarization, PITT, and Electrochemical Impedance Spectroscopy (EIS) show that the AlBO3 coating improves the kinetics of electron transfer.

Li-rich layered-layered nickel manganese cobalt oxides (LLNMC) of the type Li2MnO3-LiMO2(M = Mn, Co, Ni) are promising cathode materials due to their higher specific capacities and discharge voltages compared to state of art materials. However, these materials have yet to exhibit adequate cycle life and power characteristics in practical cells, partly due to the instability of electrolytes at these high voltages. Thin coatings of inorganic materials such as Al2O3, AlPO4, and AlF3have been shown to minimize these degradation processes, especially on high voltage cathodes. Here, we report the use of a new aluminum borate-based coating material on the LLNMC cathode at high active mass loadings. AlBO3-coated cathodes demonstrate a sevenfold increase in lifetime compared to uncoated material, as well as higher specific discharge energies vs. analogous AlPO4-coated materials. SEM and TEM confirm the thin coatings of amorphous material. Detailed electrochemical studies including Tafel polarization, PITT, and Electrochemical Impedance Spectroscopy (EIS) show that the AlBO3coating improves the kinetics of electron transfer.