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Lithium titanium oxide thin films are increasingly popular anode materials in microbatteries and hybrid supercapacitors, due to their improved safety, cost, and cycle lifetime. So far, research efforts have mainly focused on the pure spinel phase Li4Ti5O12 (LTO) and only a small fraction is dedicated to a broader spectrum of titanium-based metal oxide thin films. In this work, pulsed laser deposition is used in a multilayer approach by alternating LTO and Li2O ablations to create a heterogeneous landscape in the titania-based micro-anodes. This rich microstructure enables the safe extension of the accessible electrochemical window down to 0.2 V. This leads to extraordinary high specific capacities of 250–300 mAh/g at 1 C, maintaining a stable discharge capacity of 180 mAh/g at 16 C. Operando spectroscopic ellipsometry and Raman spectroscopy are used to track optical and structural changes as a function of the discharge voltage down to 0.01 V. A kinetically limited degradation mechanism based on the effective trapping of Li-ions at the octahedral 16c positions is proposed when cycling in the range of 0.2–0.01 V. In essence, our work contributes to titania-based nanoshapes as anodes of increased specific capacity due to a higher Li-site occupation, while maintaining their good stability and safety.

The lifetime performance of lithium-ion batteries is a critical issue for automobile and stationary applications. The difference in the side-reaction current (I_SR) of electrodes causes deviations of the state of charge (SOC) of the electrodes leading to the capacity fading of lithium-ion batteries. Establishment of a method to measure the I_SR is important...

The lifetime performance of lithium-ion batteries is a critical issue for automobile and stationary applications. The difference in the side-reaction current (I_SR) of electrodes causes deviations of the state of charge (SOC) of the electrodes leading to the capacity fading of lithium-ion batteries. Establishment of a method to measure the I_SR is important...

Lithium-ion batteries using Li[Li_1/3Ti_5/3]O_4 and Li[Li_0.1Al_0.1Mn_1.8]O_4 (LTO/LAMO) are very attractive for long-life and high-power applications. Capacity fading of the batteries mainly results from the deviation in the state of charges (SOCs) of LTO and LAMO electrodes caused by the difference in the side reaction currents of the electrodes....

Lithium titanium oxide prepared by the hydrogen reduction synthesis of Li[Li_1/3Ti_5/3]O_4 (LTO) exhibits electronic conductivity. The product demonstrated a superior rate capability than pristine LTO upon the examination of a pellet electrode in the absence of conductive additives....

Lithium-ion batteries using Li[Li_1/3Ti_5/3]O_4 and Li[Li_0.1Al_0.1Mn_1.8]O_4 (LTO/LAMO) are very attractive for long-life and high-power applications. Capacity fading of the batteries mainly results from the deviation in the state of charges (SOCs) of LTO and LAMO electrodes caused by the difference in the side reaction currents of the electrodes....

Lithium titanium oxide prepared by the hydrogen reduction synthesis of Li[Li_1/3Ti_5/3]O_4 (LTO) exhibits electronic conductivity. The product demonstrated a superior rate capability than pristine LTO upon the examination of a pellet electrode in the absence of conductive additives....

Building a lithium-ion cell with a third reference electrode which is stable and does not disturb the cell characteristics promises deep insights into the cell performance and aging behavior. In this study, a lithium titanium oxide coated aluminum mesh is introduced into lab size 28 mAh pouch cells, which allows the cells to be braced as usual. The influence of inserting the coated mesh together with an additional separator is analyzed using electrochemical impedance spectroscopy and cyclic aging tests. Cells with this reference electrode show small deviations in the Nyquist plot and an increased capacity fade compared to the standard cells. Nonetheless, these 3-electrode cells already allowed C-rate performance tests in a fresh and aged cell state. According to this, the charge current profiles for fresh and aged cells are optimized as step wise protocols to improve the utilization of the anode overpotential reserve while avoiding lithium plating. In order to realize this, the aged cells require a 60% slower protocol. This work shows that the overpotentials on the anode side increase during aging, which makes the cells more susceptible to lithium plating. However, compared to a constant current charge, a reduction in charging time of 30% is possible. © 2019 The Electrochemical Society.

In this work, the potential of Li1.8Na0.2TiO3:Mn4+ for the lifetime-based luminescence thermometry is assessed. The material is prepared by the solid-state reaction of Li2CO3, Na2CO3, and nanostructured TiO2 at 800 °C, and its monoclinic structure (space group C2/c) is confirmed by X-ray diffraction analysis. In this host, Mn4+ provides strong absorption around 330 nm and 500 nm due to 4A2g → 4T1g and 4A2g→ 4T2g electric dipole forbidden and spin-allowed electron transitions, respectively, and emits around 679 nm on account of 2Eg→ 4A2g spin forbidden electron transition. Temperature dependences of emission intensity and emission decay are measured over the 10–350 K range. Due to the low value of energy of 4T2g level (20000 cm−1), the strong emission quenching starts at low-temperatures which favors the use of this material for the luminescence thermometry. It is demonstrated that the quite large value of relative sensitivity (2.27% K−1@330 K) facilitates temperature measurements with temperature resolution better than 0.15 K, and with the excellent repeatability. © 2019 Elsevier B.V.

In this work, the potential of Li1.8Na0.2TiO3:Mn4+ for the lifetime-based luminescence thermometry is assessed. The material is prepared by the solid-state reaction of Li2CO3, Na2CO3, and nanostructured TiO2 at 800 °C, and its monoclinic structure (space group C2/c) is confirmed by X-ray diffraction analysis. In this host, Mn4+ provides strong absorption around 330 nm and 500 nm due to 4A2g → 4T1g and 4A2g→ 4T2g electric dipole forbidden and spin-allowed electron transitions, respectively, and emits around 679 nm on account of 2Eg→ 4A2g spin forbidden electron transition. Temperature dependences of emission intensity and emission decay are measured over the 10–350 K range. Due to the low value of energy of 4T2g level (20000 cm−1), the strong emission quenching starts at low-temperatures which favors the use of this material for the luminescence thermometry. It is demonstrated that the quite large value of relative sensitivity (2.27% K−1@330 K) facilitates temperature measurements with temperature resolution better than 0.15 K, and with the excellent repeatability. © 2019 Elsevier B.V.

In this study, the application of neutron powder diffraction on studying the time-resolved structural evolution of a cell comprised with LiNi 0.5Mn1.5O4 cathode and Li4Ti 5O12 anode during charge-discharge cycling is demonstrated. As expected, the lattices of the LiNi0.5Mn 1.5O4 cathode and the Li4Ti5O 12 anode in the cell are found to simultaneously contract during charging and expand during discharging. It is found that for the LiNi 0.5Mn1.5O4 cathode a solid-solution reaction is associated with the lattice change and the Ni2+/Ni3+ redox couple between 3.06 and 3.16 V (vs. Li4Ti5O 12), and a two-phase reaction between LixNi 0.5Mn1.5O4 and Ni0.25Mn 0.75O2 is corresponding to the Ni3+/Ni 4+ redox couple at voltage higher than 3.22 V (vs. Li 4Ti5O12) without a corresponding change in lattice. The oxidation states of the metals in the electrodes are determined by tracking the associated change in the oxygen position. In addition, the Ti oxidation state is correlated to the intensity of the Li4Ti 5O12 222 reflection at the anode, and the determined oxidation state of the Ni is correlated to the lithium occupancy within the cathode. Furthermore, the small volume changes of the cathode and the anode upon cycling suggest that the cell chemistry is favorable for practical applications.

To study the influence of the synthesis method on the electrochemical performances of the Li4Ti5O12 spinel (LTO) several samples have been prepared by three different synthesis procedures (sol¿gel, self-combustion and solid-state). The use of the same Ti-source (TiCl4) and strictly the same experimental conditions has allowed performing a meaningful comparison analysis. The structural characterization by X-ray diffraction shown that cubic spinels, with similar cell parameter (ac ~ 8.35A¿ ), were obtained for the three methods. The purity of the samples prepared by sol¿gel (LTO-SG) and combustion (LTO-CB) was very high, >96%. FE-SEM studies revealed that the particle size (ps) and the particle aggregation notably changed with the synthesis method. The ps-values grow up from 301 nm for LTO-SG to 1580 nm for the sample synthesized by solid-state (LTO-SS). The comparison of the galvanostatic results permitted to demonstrate that LTO-electrochemical performances (capacity, cycleability and rate capability) strongly depend on the synthesis method. The LTO-SG sample exhibited the best electrochemical performances, with a discharge capacity of 146 mAh/g at 0.2 C, elevated cycleability and the highest rate capability. New formulation Li-ion full-cells with the synthesized LTO-samples as anode and LiCo2/3Ni1/6Mn1/6O2 as cathode have been assembled and studied. They have remarkable cycling performances with capacity retentions >90% after 50 cycles.

Tantalum (Ta) doping in lithium titanium oxide, Li4Ti5O12 (Li4Ti4.95Ta0.05O12), as function of different heat-treatment atmospheres (oxidizing/reducing) was investigated and compared to Li4Ti5O12 to determine its effect on electrical conductivity and rate capability. The ionic conductivity value of the white colored Li4Ti4.95Ta0.05O12 heated under an oxidizing atmosphere was ~3 x 10-8 S/cm with a DC electronic conductivity value of ~1 x 10-9 S/cm. These values are similar to values observed for Li4Ti5O12 heated under the same oxidizing atmosphere. These results suggest that both materials are predominately ionic conductors, with the extra charge of Ta compensated by a lattice defect, most likely titanium (Ti) vacancies. For the case of Li4Ti4.95Ta0.05O12 heated under a reducing atmosphere, it was purple colored with an electronic conductivity value of ~1 x 10-3 S/cm. Li4Ti5O12 heated under a reducing atmosphere was also purple colored with an electronic conductivity value of ~3 x 10-5 S/cm. These results suggest both of these materials are predominately electronic conductors where the electronic conductivity is a result of the reduction of some Ti+4 ions into Ti+3 ions. For Li4Ti4.95Ta0.05O12 this reduction is a result of the extra charge of the Ta whereas for Li4Ti5O12 it is a result of nonstoichiometry.

In this thesis an investigation of two spinel materials, Li4Ti5O12 and LiMn2O4 used for Li-ion battery applications is performed interms of formation and reactivity towards acidic solutions. Subsequent characterizations such as structural, magnetic, chemical, and electrochemical characterizations are performed and discussed., Applied Sciences

One major problem that limits the rate capability at low temperatures of the current Li-ion batteries is the anode material, graphite. In order to overcome the limitations associated with graphite. new anode materials must be developed. One such potential new anode material that could lead to higher rates at the low temperatures required by the Future Army Combat and Force Warrior Systems is Li4Ti5O12 with a nanophase particle size. At present, no information on the rate capability at low temperature of nanophase Li4Ti5O12 is available. Hence, such information is needed. Two different nanophase Li4Ti5O12 particle sizes were investigated, 350 and 700 nm, over the temperature range 20, 0, -10, -20, and -30 C at low rates (0.1 C, C=theoretical capacity) to high rates (5C). Electrochemical testing revealed that the 350 nm Li4Ti5O12 material exhibited higher capacity compared to the 700 nm Li4Ti5O12 at all rates tested at room temperature and at low rates at low temperatures (< 0 C). This expected behavior is a result of the shorter diffusion lengths and higher number of lithium insertion sites in the smaller particle size material. This result also reveals the importance of reducing the Li4Ti5O12 particle size as small (i.e., from micron to nano) as possible for enhancing low temperature performance. However, at high rates at low temperatures (< 0 C) a change in behavior was observed, in that the larger particle size Li4Ti5O12 exhibited the higher capacity. It was observed that as the temperature was decreased the rate at which this transition occurred was also lowered. It is believed that the origin of this transition behavior is that as temperature is lowered the resistance of the Li4Ti5O12 interparticle contacts increases and controls the discharge rate. This result was unexpected and suggests that at low temperatures and high rates just reducing the Li4Ti5O12 particle size to the nanoscale is not enough to enhance low temperature performance., See also ADM002075. Presented at the Army Science Conference (25th) held in Orlando, FL on 27-30 Nov 2006. Document includes briefing charts (22 slides, title same as report). The original document contains color images.