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The influence of Jahn-Teller (JT) distortion on the electrochemical behavior of LiMn2O4 is not fully understood nowadays. This paper concerns the role that structural defects play in reducing the magnitude of JT distortion. Structural defects were induced in micrometric and nanometric LiMn2O4 using 60Co gamma radiation. Techniques such as X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and magic angle spinning spectroscopy (7Li MAS NMR) were used to detect and investigate the defects created by 60Co gamma irradiation in micrometric and nanometric LiMn2O4. Differential scanning calorimetry (DSC) was used to study the effect on the JT distortion enthalpy. Spectroscopic and microstructural modifications of LiMn2O4 produced by the action of radiation are shown for the first time. The results revealed that partial and total edge dislocations are generated after the oxides are irradiated. In the formed dislocations, manganese and lithium ions modified their surroundings and coordination, while the atomic positions of oxygen atoms changed in the fcc structure. These modifications gave rise to a decrease in the magnitude of JT distortion in the micrometric oxides, while no distortion was detected in the nanometric oxides. Because of the defects in LiMn2O4 caused by 60Co gamma irradiation, a minor distortion in the cell parameter (c/a) should be expected when this material is used as a cathode in lithium-ion batteries.

Reducing the particle size to improve the electrochemical properties of LiMn2O4 has been a common practice along the last years claiming that, by doing this, the Jahn-Teller (JT) distortion in its 3 V region is reduced. However, only a few papers have proved actual links between the mitigation of the JT effect and particle size; therefore, the JT effect is often entangled with mechanical and kinetic improvements, which are also associated to diminishing the particle size. Regardless that, there is a consensus that reducing particle size positively impacts Li+ insertion into LiMn2O4, particularly in its 3 V plateau. On the other hand, defects have emerged as factors determining the electrochemical behaviours of LiMn2O4. Several works pointed out that certain defects such as Mnitet, F and V colour centres, dislocations or voids, could improve the 3 V performance of the LiMn2O4 by decreasing the JT distortion. Nevertheless, the preponderant defect causing this enhancement has not yet been established. The present paper aims to determine, among Mnitet, F and V centres as well as dislocations, which defect impacts the most on the JT transition, specific capacity and stability of nanometric LiMn2O4. The aforementioned defects were detected by HRTEM, XRD, UV–Vis as well as magnetic measurements. Their implications on the potential drop caused by the JT effect, specific capacity and stability were recorded by potentiometric and galvanostatic charge/discharge measurements. The results indicate that only Mnitet-related defect reduces the JT distortion, increasing the stability and capacity within the 3 V region, especially when particle are small.

We have synthesized and electrochemically tested a carbon sample that was suitable as anode for lithium secondary battery. The synthesis was based on the use of the palygorskite clay as template and sugar cane molasses as carbon source. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Brunauer–Emmett–Teller (BET) measurements and High Resolution Transmission Electron Microscope (HRTEM) analysis showed that the nanometric carbon material has a highly disordered graphene-like wrinkled structure and large specific surface area (467 m 2 g −1 ). The compositional characterization revealed a 14% of heteroatoms-containing groups (O, H, N, S) doping the as-prepared carbon. Thermophysical measurements revealed the good thermal stability and an acceptable thermal diffusivity (9·10 −7 m 2 s −1 ) and conductivity (1.1 W m −1 K −1 ) of this carbon. The electrical properties showed an electronic conductivity of hole-like carriers of approximately one S/cm in a 173–293 K range. The testing of this material as anodes in a secondary lithium battery displayed a high specific capacity and excellent performance in terms of number of cycles. A high reversible capacity of 356 mA h g −1 was reached.

This work proposes to unveil the underlying effect of Mn-interstitial defect as well as the particle size on the Jahn Teller distortion. Mn-interstitial defects and nanometric particles were characterized by HRTEM, Rietveld fitting and microstrain XRD analysis. The research was conducted by measuring the changes of the Fermi level, entropy, enthalpy and the redox potential due to the JT transition. Other dynamic electrochemical measurements were also carried out. The structural and microstructural measurements led to propose the presence of Mn ions in distorted tetrahedral 48f positions after using irradiation to induce Mn-interstitial defects. By using the proposed methodology it was possible to experimentally observe that this defect vanishes the JT effect and diminishes the shifting of the Fermi level during the phase transition. Subtle correlations between the capacity of the 3V region and the redox potential drop of these materials were revealed and explained. The surface pressure and bonding effects were set as important factors underlying stunning electrochemical and structural changes that characterise nanometric particles below 15 nm.

The zeta potential, isoelectric point, and agglomeration of Li0.5La0.5TiO3 (LLTO) nanoparticles dispersed in aqueous media at different ionic strengths have been studied. The zeta potential was determined from electrophoretic mobility measurements, according to Smoluchowski's equation, for Li0.5La0.5TiO3 suspensions in NaCl and KCl electrolytes with ionic strengths of 1, 10, and 100 mmol/dm3. The isoelectric point (IEP), zeta potential (ζ), and the agglomeration were shown to strongly depend on the ionic strength of the Li0.5La0.5TiO3 aqueous colloidal suspension in both NaCl and KCl electrolytes, which allows the determination of the effects of environmental conditions for Li0.5La0.5TiO3 manipulation in aqueous colloidal systems. The suspensions of Li0.5La0.5TiO3 nanoparticles reach the IEP in the pH range of 3–5. The ζ of Li0.5La0.5TiO3 nanoparticles varied from positive to negative values with a pH increase, which allows for the control of the surface charge depending on the purpose. The pH range of 7–8 and an ionic strength ≤1 mmol/dm3 are recommended as the most suitable conditions for both the LLTO colloidal shaping techniques application and the LLTO-based nanocomposite formation.

The influence of LLTO (Li0.33La0.56TiO3) nanoparticles on the conducting properties of PEO (polyethylene oxide)8-LiClO4 polymer-salt complex electrolyte still remains not fully understood. This paper aims to establish the role of LLTO filler concentration, its morphology, agglomeration and charge nanoparticles surface on the ionic transport of (PEO)8-LiClO4-based solid electrolytes. Four samples of (PEO)8-LiClO4- LLTO composites, with 0, 5, 10 and 15 wt% of LLTO filler, were prepared. Several techniques were used to verify the obtainment of the required samples and to find out how the LLTO filler can modify the conductivity of the (PEO)8-LiClO4 polymer-salt complex electrolyte. The obtained results suggest that the transport of Li ions in these nanocomposites occurs predominantly through the polymeric phase, not by the conducting LLTO ceramic employed as filler. The highest conductivity value (10−3 S/cm at 338 K) is reached for 10 wt % of LLTO filler in the composite, where the polymeric phase is completely amorphous.

Nanostructures of phosphorus doped and undoped LiMn2O4 have been obtained through the thermal decomposition of different citrate precursors. The oxides have been characterized by XRD, XPS, 7Li-NMR-MAS, STEM and electrochemical tests in aqueous electrolyte. XPS showed that no pyrophosphate species were formed during the doping process. The position of the phosphorus in the LiMn2O4 nanostructure were elucidated on both samples through analyses of STEM images and structural refinement using the Rietveld method. These analyses allowed to set the P in a 48f position with coordinates (1/8, 1/8, 0.338) at the crystalline structure of the LiMn2O4 spinel. Electrochemical tests corroborated the improvement of electrochemical properties of the oxide when phosphorus is used as dopant. XRD measurements on cycled electrodes showed the inhibition of segregated collateral phases during the cycling process. That allows to propose an explanation of the achieved advantages of doping the lithium manganese oxide spinel structure on the ground of the phosphorous position in the LiMn2O4 crystalline cell.

The optimization of Citrate Precursor Method to obtain the LiNi0.8Co0.2O2 oxide from the thermal decomposition of the citrate precursor (NH4)3LiNi0.8Co0.2(C6H5O7) is presented. The optimization procedure consists of both the lithium atmosphere and the reaction time control during the decomposition of the citrate precursor. Were obtained and characterized two kind of the (Li1-xNix)(Ni0.8Co0.2)O2 oxides, with and without optimized synthesis conditions, identified as A and B oxides, respectively. The A and B oxides are characterized by compositional, structural and electrochemical studies. The results showed that is possible to reach the ordered oxide phase at smaller reaction time if the lithium atmosphere is controlled. From the combination of the chemical analysis by ICP and the DRX Rietveld structural refinement it is possible to establish the Li, Ni(II), Ni(III) and Co(III) composition with great accuracy. The resulted structural and compositional transformations have a close relation with technological parameters of the rechargeable lithium battery using Li Ni0.8Co0.2O2 oxide as cathode.

Preparation of nano-crystalline Li0.5La0.5TiO 3 perovskite material using citrate-nitrate redox reaction by the combustion technique is reported. The role of the ammonium nitrate concentration used to co-precipitate the Li0.5La0.5Ti-citrate precursor is revealed by ATD/TG, XRD, SEM-EDX and HRTEM techniques. Thermo-gravimetric analysis data show how the intensity of the exothermic peak associated with the citrate-nitrate redox reaction decreases until disappearance as the citrate/nitrate molar ratio increases. The XRD study indicates that a single-phase cubic Li0.5La0.5TiO3 phase is formed at 350 C when the citrate/nitrate ratio varies between 0.13 and 0.17. The formed Li0.5La0.5TiO3 powders show an average particle size of 15-20 nm. Electrochemical impedance spectroscopy technique reveals a relative high ionic conductivity inside the grain for the nanometric Li0.5La0.5TiO3 material, with values of around 10-4 S/cm at room temperature. © 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved., This work has been partially supported by the CONACYT (Projects: #129227, #17424 and #148997) and SIP-IPN (Project: 20111101), CICYT (Spain project MAT2012- 31759) and CNPq-MES Project # 490522/2010-6.

In this work, the synthesis of Li3xLa2/3-xTiO3 oxide is studied by thermal decomposition of citrate precursor at very low temperature which has not been yet reported in the literature for these compounds. The characterization of oxides and its precursor was realized by DRX, IR, ATD and TEM techniques. The results show the formation of a new chemical compound (precursor) as well as several advantages of the citrate method in relation to reported ones in the literature: the ostensible decreasing of temperature Li3xLa2/3-xTiO3 formation and the decreasing of particle size on the nanometric scale which is very desirable for the electrochemical application.

In this paper the optical, structural and electrical properties of CuCrO2 thin films deposited by ultrasonic spray pyrolysis at temperatures from 400 to 600 °C in steps of 50 °C are presented. Copper and chromium acetylacetonates were chosen as sources of Cu and Cr, respectively, and N,N-dimethylformamide was used as the solvent. X-ray results confirmed that the films as deposited showed the CuCrO2 phase without any post-deposition thermal annealing. The surface morphology was observed to be mirror like, and as the films were deposited at different temperatures, they gradually revealed the presence of small crystallites. The best film's optical percentage transmission (in the visible region), about 58%, was obtained in films deposited at 450 °C, and the highest band gap energy (3.17 eV) was measured in films deposited at 400 °C. The electrical properties of the films were obtained by the Hall effect. A hole concentration in the range 1019–1021 cm−3, conductivity as high as 35 S cm−1, and mobility lower than 1 cm2 V−1 s−1 were obtained in the films. p-type conductivity was confirmed using the hot point probe arrangement, and the Seebeck coefficient was estimated. The hole conductivity is thought to be due to excess oxygen in the films. Finally, the minimum energy required to transfer carriers from acceptor level to the valence band in the films was estimated by impedance spectroscopy.