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Abstract: Li2Ti6O13 has been prepared from Na2Ti6O13 by Li ion exchange in molten LiNO3 at 325°C. Chemical analysis and powder X-ray diffraction study of the reaction product respectively indicate that total Na/Li exchange takes place and the Ti–O framework of the Na2Ti6O13 parent structure is kept under those experimental conditions. Therefore, Li2Ti6O13 has been obtained with the mentioned parent structure. An important change is that particle size is decreased significantly which is favoring lithium insertion. Electrochemical study shows that Li2Ti6O13 inserts ca. 5 Li per formula unit in the voltage range 1.5–1.0V vs. Li+/Li, yielding a specific discharge capacity of 250mAhg−1 under equilibrium conditions. Insertion occurs at an average equilibrium voltage of 1.5V which is observed for oxides and titanates where Ti(IV)/Ti(III) is the active redox couple. However, a capacity loss of ca. 30% is observed due to a phase transformation occurring during the first discharge. After the first redox cycle a high reversible capacity is obtained (ca. 160mAhg−1 at C/12) and retained upon cycling. Taking into consideration these results, we propose Li2Ti6O13 as an interesting material to be further investigated as the anode of lithium ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: The α-polymorph of Li3FeF6 has been obtained at room temperature by a precipitation reaction from aqueous solution. This easy procedure that does not require any further annealing at high temperature yields a white powder with particles sizes ranging from 250 to 400nm. After proper processing by mechanical milling, particle sizes clearly below 100nm are achieved and this fluoride reacts reversibly with lithium at an average voltage of 3.1V, which is expected for the Fe3+/Fe2+ redox couple. After 12h of ball milling observed average particle size is ca. 50nm and a reversible capacity of 100mAhg−1 is obtained. This corresponds to 70% of the theoretical capacity expected for the one electron reduction of Fe3+. The mentioned capacity is fairly kept upon cycling making the new material useful as the positive electrode in lithium batteries. This is the very first time that a material for cathode application in lithium batteries is prepared at room temperature and from aqueous solution, a procedure which is easily scalable and hence of high industrial interest. [Copyright &y& Elsevier]

Abstract: We present an electrochemical study of BiSbO4, an opened layered oxide having a structure related to Aurivillius phases. Li//BiSbO4 cells show a large specific capacity as high as 1250mAhg−1 during reduction down to 0.5V. This reaction involves 18Li atoms per formula unit, pointing it towards a very promising cathode material for primary lithium batteries, in particular for ICD devices. The characterization of the reduction products indicates that the reduction of BiSbO4 with lithium presumably goes along firstly with the formation of metallic Sb and Bi to follow the formation of the alloys Li3Bi and Li3Sb dispersed in a lithium oxide matrix. In situ X-ray diffraction experiments proved the amorphous nature of both metals and final alloys. On the other hand when Li//BiSbO4 cells are limited to discharge down to 1.2V, BiSbO4 reacts with 5Li atoms. After the first discharge, that develops a specific capacity of 350mAhg−1, high cyclability has been observed. [Copyright &y& Elsevier]

Abstract: Structural evolution during topotactical electrochemical lithium insertion and deinsertion reactions in ramsdellite-like Li x Ti2O4 has been followed by means of in situ X-ray diffraction techniques. The starting Li x Ti2O4 (x =1) exists as a single phase with variable composition which extends in the range 0.50≤ x ≤1.33. However, beyond the lower and upper compositional limits, two other single phases, with ramsdellite-like structure, are detected. The composition of these single phases are: TiO2 upon lithium deinsertion and Li2Ti2O4 upon lithium insertion. Both TiO2 and Li2Ti2O4 are characterized by narrow compositional ranges. The close structural relationship between pristine LiTi2O4 and the inserted and deinserted compounds together with the relative small volume change over the whole insertion–deinsertion range (not more than 1.1% upon reduction) is a guaranty for the high capacity retention after long cycling in lithium batteries. The small changes in cell parameters well reflect the remarkable flexibility of the ramsdellite framework against lithiation and delithiation reactions. [Copyright &y& Elsevier]

Abstract: Materials of the series La2−x Sr x NiTiO6−δ (0 ≤ x ≤ 0.5) have been characterized by both structural and electrochemical methods in order to assess their possible use as electrodes for SOFCs. Neutron and X-ray powder diffraction experiments have shown that they are stable under both oxidizing and reducing conditions while chemically compatible with YSZ at SOFC operating temperatures. Moreover, the thermal expansion has been determined to be isotropic with α L = 10.0(3) × 10−6 K−1. This value is similar to that found for other perovskite materials used in SOFCs. However, polarization resistances reveal modest values of electrochemical response under oxygen (1.5 Ω cm2 at 900 °C) and are quite poor in 5%H2/N2 mixtures (15 Ω cm2) at the same temperature. Nevertheless, microstructure has not been optimized fully enough to discard the material as a potential SOFC cathode. [Copyright &y& Elsevier]

Abstract: The layered nitrides LiWN2 and Li0.84W1.16N2 are investigated related to their electrochemical performances as possible electrodes for rechargeable lithium batteries. In the case of LiWN2, for which Li and W atoms are ideally ordered in alternating Li and W layers, de-intercalation of lithium proceeds up to 50%. The de-intercalated lithium can be intercalated again subsequently. The reversible reaction is the origin of the high cyclability observed in the corresponding lithium cells. On the other hand, in Li0.84W1.16N2 the Li layers are statistically occupied by tungsten (16%) and lithium (84%). A clear effect of the disordered cationic occupation on the electrochemical behaviour has been found, since for Li0.84W1.16N2 a very low extraction rate is obtained during the first oxidation (0.03 Li per formula unit). In addition, cyclability is rather poor. The very different electrochemical behaviour is explained by the structural differences between both layered nitrides. [Copyright &y& Elsevier]

Abstract: New olivines LiMAsO4 (M=Mn, Fe, Co, and Ni) have been tested as positive electrode in lithium cells. Under the used experimental conditions we did not succeed to remove lithium ions from LiFeAsO4, LiMnAsO4 or LiNiAsO4. More work is needed in order to verify whether the lack of electrochemical activity is intrinsic to these materials, or it is due to kinetical limitations such as particle size and poor conductivity. On the contrary lithium ions could be reversibly deinserted/inserted from/into LiCoAsO4 at average voltages of 4.8 and 4.6V respectively; the delithiated compound maintaining the olivine structural framework. The high pressure polymorph of LiMAsO4 (M=Fe, Co, Ni) crystallizing with the spinel structure did not show any electrochemical activity potentially useful in rechargeable lithium batteries. [Copyright &y& Elsevier]

Abstract: Electron energy loss spectroscopy has been used to investigate the average oxidation state of Cr in both electrochemically and chemically delithiathed Li5/3−x Ti7/3CrO7. The O K edge, Ti L2,3 and Cr L2,3 edge were monitored. Upon removal of Li ions, the oxygen K edge shows a continuous change while the Cr L edges remain almost unchanged. The Cr 2p multiplet was compared with reference samples (Cr2O3, CrO2 and K2Cr2O7) in order to assess on the sensitivity of the Cr L-edge to the oxidation state of chromium ion. The similarity between the Cr L spectra of Cr2O3 and CrO2 makes the valence analysis difficult in Li5/3−x Ti7/3CrO7 but the presence of CrVI is excluded in oxidized samples. However, evolution of the low energy loss spectra observed in the 10–15eV region confirms the modification of the electronic structure and partial oxidation of CrIII to CrIV. [Copyright &y& Elsevier]

Abstract: In the search for new electrodes for lithium batteries processing under high pressure opens new paths to innovative materials. The High Pressure (HP) polymorph of α-FePO4 crystallizes in the CrVO4 structural-type; first principles calculations predict that Li insertion would occur at 3.36V. Accordingly, crystalline samples of HP-FePO4 display electrochemical activity with a lithium insertion process occurring at 3V, which has not been observed in the α-FePO4 polymorph. This reduction process is characterized by a large cell polarization that suggests a very slow kinetics. The poor electrochemical performance of highly crystalline HP-FePO4 is favored in iron phosphate samples obtained under mild conditions of pressure and temperature, that produce a partially amorphous material and prevent an excessive particle growth. [Copyright &y& Elsevier]

The effect of mechanical grinding (MG) on the electrochemical properties of Si3N4 is studied as the processing produces different particle size. The evolution of the amorphisation stage has been monitored by X-ray diffraction (XRD), although particle size has also been studied through transmission electron microscopy experiments. Processed Si3N4 has been used as the positive electrode in electrochemical cells, where the negative electrode is lithium. We do not expect an intercalation process during the discharge step of such a type of cell, but a behaviour similar to that named as “convertible compounds”. As the main result, the specific capacity of these lithium cells is increased up to 34% in relation to the starting, non-milled material. However, even though the size of the Si3N4 particles has been reduced, from micrometer to nanometer scale, no appreciable changes in the cycling behaviour is observed when compared with the pristine material. [Copyright &y& Elsevier]