All-Solid-State Lithium Ion Batteries Using Self-Organized TiO2 Nanotubes Grown from Ti-6Al-4V Alloy.

All-solid-state batteries were fabricated by assembling a layer of self-organized TiO2 nanotubes grown on as anode, a thin-film of polymer as an electrolyte and separator, and a layer of composite LiFePO4 as a cathode. The synthesis of self-organized TiO2 NTs from Ti-6Al-4V alloy was carried out via one-step electrochemical anodization in a fluoride ethylene glycol containing electrolytes. The electrodeposition of the polymer electrolyte onto anatase TiO2 NTs was performed by cyclic voltammetry. The anodized Ti-6Al-4V alloys were characterized by scanning electron microscopy and X-ray diffraction. The electrochemical properties of the anodized Ti-6Al-4V alloys were investigated by cyclic voltammetry and chronopotentiometry techniques. The full-cell shows a high first-cycle Coulombic efficiency of 96.8% with a capacity retention of 97.4% after 50 cycles and delivers a stable discharge capacity of 63 µAh cm-2 µm-1 (119 mAh g-1) at a kinetic rate of C/10.

Direct Pre-lithiation of Electropolymerized Carbon Nanotubes for Enhanced Cycling Performance of Flexible Li-Ion Micro-Batteries.

Carbon nanotubes (CNT) are used as anodes for flexible Li-ion micro-batteries. However, one of the major challenges in the growth of flexible micro-batteries with CNT as the anode is their immense capacity loss and a very low initial coulombic efficiency. In this study, we report the use of a facile direct pre-lithiation to suppress high irreversible capacity of the CNT electrodes in the first cycles. Pre-lithiated polymer-coated CNT anodes displayed good rate capabilities, studied up to 30 C and delivered high capacities of 850 mAh g-1 (313 µAh cm-2) at 1 C rate over 50 charge-discharge cycles.

Optical and Electrochemical Properties of Self-Organized TiO2 Nanotube Arrays From Anodized Ti-6Al-4V Alloy.

Due to their high specific surface area and advanced properties, TiO2 nanotubes (TiO2 NTs) have a great significance for production and storage of energy. In this paper, TiO2 NTs were synthesized from anodization of Ti-6Al-4V alloy at 60 V for 3 h in fluoride ethylene glycol electrolyte by varying the water content and further annealing treatment. The morphological, structural, optical and electrochemical performances of TiO2 NTs were investigated by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), UV-Visible spectroscopy and electrochemical characterization techniques. By varying the water content in the solution, a honeycomb and porous structure was obtained at low water content and the presence of (α + ß) phase in Ti-6Al-4V alloy caused not uniform etching. With an additional increase in water content, a nanotubular structure is formed in the (α + ß) phases with different morphological parameters. The anatase TiO2 NTs synthesized with 20 wt% H2O shows an improvement in absorption band that extends into the visible region due the presence of vanadium oxide in the structure and the effective band gap energy (Eg) value of 2.25 eV. The TiO2 NTs electrode also shows a good cycling performance, delivering a reversible capacity of 82 mAh.g-1 (34 µAh.cm-2.µm-1) at 1C rate over 50 cycles.

Porous NASICON-Type Li3Fe2(PO4)3 Thin Film Deposited by RF Sputtering as Cathode Material for Li-Ion Microbatteries.

We report the electrochemical performance of porous NASICON-type Li3Fe2(PO4)3 thin films to be used as a cathode for Li-ion microbatteries. Crystalline porous NASICON-type Li3Fe2(PO4)3 layers were obtained by radio frequency sputtering with an annealing treatment. The thin films were characterized by XRD, SEM, and electrochemical techniques. The chronoamperometry experiments showed that a discharge capacity of 88 mAhg(-1) (23 µAhcm(-2)) is attained for the first cycle at C/10 to reach 65 mAhg(-1) (17 µAhcm(-2)) after 10 cycles with a good stability over 40 cycles.