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Here, we report the preparation of carbon-coated cobalt-doped olivine nanoparticles (LiFePO4/C) by the citrate gel precursor combustion method. The major contribution of this work is to reveal insights and side effects of cobalt doping, not only in the structure, microstructure, and electrochemical performance of olivine nanoparticles, but also in the consequences on the carbon coating characteristics. Our structural and microstructural studies by means of several instrumentation techniques revealed that the presence of low amounts of cobalt during the synthesis leads to the apparent formation of more porous channels in the carbon coating. In consequence, the electrochemical characterization showed an enhancement in the capacity and diffusion constants for cobalt-doped LiFePO4/C samples in comparison with cobalt-undoped samples. [ABSTRACT FROM AUTHOR]

Three specimens were synthesized presenting the following stoichiometry: Zr1−xTixCr0.7Mo0.3Ni (x = 0.3; 0.5; 0.7). The substitution of zirconium atoms by a lower atomic radius metal, such as titanium, leads to the formation or inhibition of Laves and body-centered cubic phases. They are conformed as zirconium or titanium Laves phase multicomponent alloys. Titanium inclusion induces a volume contraction of the C14 Laves phases. Moreover, the abundance of the metallic titanium hexagonal phase is reduced, while the presence of crystalline phases with spatial group Im-3m is increased. Correlation between structural properties and electrochemical performances is studied before and after thermal treatments. It is concluded that segregation of metallic titanium, with a hexagonal crystalline system has a negative effect on thermodynamic and kinetic behaviors. However, body-centered cubic crystalline phases exhibit favorable outcomes for the storage capacity and time diffusion constant. TiNi phases have positive results on activation and reversibility. Laves phases are those that exhibit the larger capacity storage performance. [ABSTRACT FROM AUTHOR]

Recent reports are focusing on the structural evolution from the atomic-scale and also at the expenses of alkyl zinc alkoxide precursors towards (ZnO) n clusters and nanostructures with different interesting motifs, but still not much is known about their electronic properties. In this manuscript, we present a theoretical study using DFT and TD-DFT methodologies on the hydrolysis and condensation of zinc dimethoxide precursor in its monomeric, dimeric and trimeric forms towards thermodynamically stable hydroxyl-terminated (ZnO) n clusters with novel chain- and graphene-like fashions. For all cases, distinct vibrational and optical spectra features were assigned evidencing a global monotonic decrease in the opto-electronic gap with increasing oligomerization and cyclization stages. In addition, the electron-affinity of all clusters was also observed to be enhanced with increasing oligomerization and cyclization stages and the electronic charge localization in -e charged clusters was observed to be strongly related to the presence of zinc-oxo subunits and other particular structural features. Our calculations also indicate that the stabilization through hydroxyl termination of both chain- and graphene-like ZnO clusters not only could be a promising driving force to obtain larger atomic-scale 1D and 2D nanostructures but also envisage interesting properties, particularly as electronic acceptor materials for energy applications., (© 2021 Wiley-VCH GmbH.)