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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]

Different ceramic synthesis conditions of ramsdellite LiTiO have been investigated in order to determine the influence on the electrochemical performances as the negative electrode of lithium-ion batteries. Lithium source, thermal pretreatment, synthesis temperature, and time of reactions were the analyzed conditions. A convenient and cheap reagent like LiCO treated with TiO at high temperature (1250 °C) for very short time (2 h) provides a reliable active material. When tested versus lithium, the initial specific capacity (150 mAh g) is lower than that of ceramic samples prepared at lower temperature or for longer treatment times (ca. 170 mAh g). The lower initial capacity is attributed to the large particle size obtained at high temperature. However, advantageously the capacity retention of the former is superior. Thus, 115 mAh g at C/20 rate is fairly kept (77 % retention) after 100 cycles. The better cyclability of samples prepared at high temperature (with large particle size) is likely due to lower surface reactivity that compensates the lower initial discharge capacity when cycling. A compromise between high initial capacity and capacity retention must be reached when using LiTiO as a battery electrode. The good behavior of the optimized material is shown by testing it against commercial LiCoO as the positive electrode. The high capacity (ca. 135 mAh g) and outstanding cyclability observed prove that optimized ramsdellite may be effectively used as a long-life negative electrode material. [ABSTRACT FROM AUTHOR]

Structural features responsible for lithium conductivity in Li1+xTi2-xAlx(PO4)3 (x = 0, 0.2, and 0.4) samples have been investigated by Rietveld analysis of high-resolution neutron diffraction (ND) patterns. From structural analysis, variation of the Li site occupancies and atomic thermal factors have been deduced as a function of aluminum doping in the temperature range 100-500 K. Fourier map differences deduced from ND patterns revealed that Li ions occupy M1 sites and, to a lower extent, M3 sites, disposed around ternary axes. The occupation of M1 sites by Li ions is responsible for the preferential expansion of the rhombohedral R3...c unit cell along the c axis with temperature. The occupation of less symmetric M3 sites decreases electrostatic repulsions among Li cations, favoring ion conductivity in Li1+xTi2-xAlx(PO4)3 compounds. The variations detected on long-range lithium motions have been related to variations of the oxygen thermal factors with temperature. The information deduced by ND explains two lithium motion regimes deduced previously by 7Li NMR and impedance spectroscopy. [ABSTRACT FROM AUTHOR]