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The concept of embedding a spinel component in high capacity, composite xLi2MnO3•(1−x)LiMO2 (M = Mn, Ni) ‘layered-layered’ structures to improve their electrochemical properties and cycling stability has been exploited. In this paper, we report the preparation and electrochemical characterization of three-component ‘layered-layered-spinel’ electrodes, synthesized by lowering the lithium content of a parent ‘layered-layered’ 0.3Li2MnO3•0.7LiMn0.5Ni0.5O2 material while maintaining a Mn:Ni ratio of 0.65:0.35; such compounds can be designated generically by the system, LixMn0.65Ni0.35Oy, for which the end members are 0.3Li2MnO3•0.7LiMn0.5Ni0.5O2 (x = 1.3; y = 2.3), in which the average manganese and nickel oxidation states are 4+ and 2+, respectively, and LiMn1.3Ni0.7O4 (x = 0.5; y = 2) in which the corresponding average oxidation states are expected to lie between 4+ and 3.77+ for Mn, and 2.57+ and 3+ for Ni, respectively. For this study, compounds with a lithium content of x = 1.3, i.e., the parent ‘layered-layered’ composition, and 1.25 were selected for detailed and comparative investigation, the latter value corresponding to a targeted spinel content of 6%. The beneficial effects of 1) using Mg2+ as a dopant ion and 2) treating the electrode particle surface with an acidic solution of AlF3 to enhance cycling stability, reduce first-cycle capacity loss, and to slow voltage decay on cycling are discussed.

Molecular simulations for hydrogen physisorption with corannulene molecules arranged according to their crystal structure result in good agreement with the weight-percent hydrogen stored as determined experimentally employing a 3-g sample of highly crystalline corannulene at ambient temperatures and 72 bar of pressure. Calculated enthalpies of adsorption for corannulene/hydrogen molecular systems obtained from ab initio calculations which take into account electron correlation via second-order Möller-Plesset perturbation theory are in good agreement with literature experimental enthalpies of adsorption for activated carbons interacting with molecular hydrogen. Ab initio results also show that corannulene molecules arranged in a sandwich structure are important for approximately doubling the binding energy of corannulene interacting with molecular hydrogen through a cooperative interaction. To test the effects of finite temperatures and pressures, stack arrays were used as input for molecular dynamics simulations and indicate that physisorption mechanisms including van der Waals forces and dipole-induced dipole interactions may yield enhanced adsorption capacity in relation to other carbon-based materials. These results will be instrumental in identifying interlayer separations of an array of corannulene or related molecules that may provide a high weight percent of physisorbed hydrogen.