Carbon fibers, obtained by carbonizing poly(p-phenylene benzobisoxazole) (PBO) fibers at 900 °C, graphitize extensively upon heat treatment at higher temperatures (2700 °C). In this work, XRD, Raman spectroscopy, and HRTEM are used to monitor the structural and nanostructural transformations of the carbon material under heat-treatment at several temperatures in the interval 900–2800 °C. These different techniques provide complementary information, especially regarding the spatial resolution they achieve. They highlight a specific nonconventional mode of graphitization for this unexpectedly graphitizable precursor. The reliability in the determination of L a crystallite sizes from these three techniques is compared and discussed. The existence of four steps in the graphitization of PBO-derived carbon fibers is inferred.

The improvement of properties through strict morphology control often requires the use of difficult to scale up synthesis routes. Thus, a compromise between scalability and morphology control is required to partially exploit the advantages of this control in materials functionality. Here, we show that a scalable and continuous route (aerosol route) is able to produce Li3VO4 colloidal aggregates with different morphology (spherical and platelet-like) using easy to handle economic precursors (V2O5, LiOH, and LiNO3 in stoichiometric amounts). The key for these differences in morphology resides on controlling the nature of the intermediate stages that can occur during particle formation in aerosol synthesis. We also show that the electrochemical response of Li3VO4 is strongly dependent on morphology. Thus, optimization of morphology allows building anodes that to our knowledge outperform other reported Li3VO4 anodes and even compete with most of the reported Li3VO4/C composites at adequate high rates (2–8 A/g). Finally, we have developed a simple and scalable coating protocol (suspensions with solid concentrations of 100 g/L are used) that additionally improves the long-term stability of the optimized anodes. Combination of the two scalable methods leads to Li3VO4 anodes that operating at a safe cutoff voltage of 0.2 V can retain a high capacity (280 mAh/g) with excellent coulumbic efficiency (>99.9%), even after 500 cycles at a competitive rate (2 A/g discharge–charge).

Here we summarize some results on the use of TiO nanostructures as anode materials for more efficient Li-ion (LIBs) and Na-ion (NIBs) batteries. LIBs are the leader to power portable electronic devices, and represent in the short-term the most adequate technology to power electrical vehicles, while NIBs hold promise for large storage of energy generated from renewable sources. Specifically, TiO an abundant, low cost, chemically stable and environmentally safe oxide represents in LIBs an alternative to graphite for applications in which safety is mandatory. For NIBs, TiO anodes (or more precisely negative electrodes) work at low voltage, assuring acceptable energy density values. Finally, assembling different TiO polymorphs in the form of nanostructures decreases diffusion distances, increases the number of contacts and offering additional sites for Na storage, helping to improve power efficiency. More specifically, in this contribution we highlighted our work on TiO anatase mesocrystals of colloidal size. These sophisticate materials; showing excellent textural properties, have remarkable electrochemical performance as anodes for Li/Na-ion batteries, with conventional alkyl carbonates electrolytes and safe electrolytes based on ionic liquids.

The preparation of activated carbon fibers (ACFs) by phosphoric acid activation of poly(p-phenylene benzobisoxazole) (PBO) fibers was studied, with particular attention to the effects of impregnation ratio and carbonization temperature on porous texture. Phosphoric acid has a strong effect on PBO degradation, lowering the temperature range at which the decomposition takes place and changing the number of mass loss steps. Chemical analysis results indicated that activation with phosphoric acid increases the concentration of oxygenated surface groups; the resulting materials also exhibiting high nitrogen content. ACFs are obtained with extremely high yields; they have well-developed porosity restricted to the micropore and narrow mesopore range and with a significant concentration of phosphorus incorporated homogeneously in the form of functional groups. An increase in the impregnation ratio leads to increases in both pore volume and pore size, maximum values of surface area (1250 m(2)/g) and total pore volume (0.67 cm(3)/g) being attained at the highest impregnation ratio (210 wt % H(3)PO(4)) and lowest activation temperature (650 °C) used; the corresponding yield was as large as 83 wt %. The obtained surface areas and pore volumes were higher than those achieved in previous works by physical activation with CO(2) of PBO chars.

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