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• Effect of galvanically structured copper current collector on performance of Li 4 Ti 5 O 12 anodes. • Improved C-rate capability due to increased surface. • EIS applied for quantification of electro-active interface area. • Comparison of physical and electro-active surface increase. A copper current collector is treated by electrolytic deposition of copper dendrites at the surface of the foil. This treatment results in a more structured surface leading to an improved contact between the electrode materials and the current collector. The contact to the electrode material particles of different sizes is investigated. Active materials of submicron size exhibit a drastically reduced internal resistance and a clearly improved C-rate capability. BET surface area measurement and calculation of roughness factor resulted in the finding of dendritic copper foil to provide an 8-fold larger surface area compared to the untreated foil. A comprehensive electrochemical impedance spectroscopy study is conducted for elucidation of electrochemical utilisation of the surface area increase. As a result, both fitting parameters for capacitance and surface resistance correspond to a similar normalization shift, indicating a clear improvement in the electro-active interface area. [ABSTRACT FROM AUTHOR]

An in-depth understanding of the thermal behavior of lithium-ion battery materials is valuable for two reasons: one is to devise strategies for inhibiting the risk of catastrophic thermal runaway and the other is to respond to the increasing demand for sustainable batteries using a direct regeneration method. Li 1+ x [Li 1/3 Ti 5/3 ]O 4 (LTO) is regarded as a suitable negative electrode under the type of severe conditions that cause this thermal runaway, such as in ignition systems for automobiles. Thus, in this study, we used differential scanning calorimetry to systematically analyze lithiated LTO combined with ex situ and in situ high-temperature X-ray diffraction measurements. The observed thermal reactions with a LiPF 6 -based electrolyte were divided into three processes: (i) the decomposition of the initially formed solid electrolyte interphase below 200 °C, (ii) the formation of a LiF phase at 200 °C ≤ T ≤ 340 °C, and (iii) the formation of a TiO 2 phase at T > 340 °C. Because the enthalpy change in process (ii) mainly contributed to the total heat generation, fluorine-free Li salts and/or stabilization of the LTO lattice may be effective in coping with the thermal runaway. Even in various lithiated states, a direct regeneration method returned the discharge capacity of LTO to ∼90% of its initial value, if we ignore the contributions from the electrochemically inactive LiF and TiO 2 rutile phases. Hence, it can be concluded that the recycling performance of LTO is far superior to those of lithium transition metal oxides for a positive electrode, whose delithiated states easily convert into electrochemical-inactive phases at high temperatures.

Abstract: In this study, we investigated the potential of highly polar polyacrylonitrile (PAN) as a binder for negative electrodes in lithium-ion batteries (LIBs). The electrochemical performance of PAN on three representative active materials, commercial graphite, high-capacity silicon/graphite, and high-power Li4Ti5O12 (LTO), was characterized and compared to the performance of conventional polyvinylidene fluoride (PVdF) and sodium-carboxymethyl cellulose (CMC) binders. The high polarity of nitrile groups in PAN leads to larger binder coverage on the surface of active materials, resulting in strong adhesion and low irreversible capacity. Additionally, PAN-containing electrodes showed good electrolyte wettability and low charge transfer resistance. These contribute to excellent electrochemical performance of PAN binder. [Copyright &y& Elsevier]

• Li 4 Ti 5 O 12 doped Eu3+ ions powders were synthesized by solid state method. • Microstructure was determined using AFM and SEM analysis. • Binding energies of Eu 4d doublet peaks corresponded to Eu3+ oxidation state. • The highest emission intensity at 589.5 nm was observed for LTO24-PT-A sample. • Li 4 Ti 5 O 12 doped Eu3+ ions could be potential material in white light emitting diodes. In this work we report our recent efforts on the investigation of the compositional and structural features of series of nanocrystalline Li 4 Ti 5 O 12 (LTO) doped with Eu3+ ions powders, which were synthesized in a high-energy ball-milling (HEBM) process. Lithium carbonate, titanium and europium oxides were used as starting reagents. The ball-milled materials were turned into nanocrystalline powders due to the heating that was carried out in the air in the temperature range from 500 to 800 °C. The synthesized LTO doped with Eu3+ powders were examined by a number of physicochemical techniques: X-ray powder diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), absorption and emission spectroscopy (photoluminescence and excitation spectra were recorded), diffuse reflection spectroscopy (UV-vis DRS), scanning electron (SEM), transmission (TEM) and atomic force (AFM) microscopy. Structural, morphological and photoluminescent properties were correlated and examined for the first time in this work. The obtained results suggest that LTO material doped with rare earth ions like europium could serve as a material for applications in optoelectronic devices such as white light emitting diodes (WLEDs). [ABSTRACT FROM AUTHOR]

Changes in Ti K-edge X-ray absorption fine structure (XAFS) spectra of lithium titanium oxide (LTO) during the charge discharge cycle of lithium ion battery were investigated by using a specially designed cell for in situ X-ray measurement. Thought LTO is famous for zero-strain lattice during the charge/discharge cycle, the significant spectral changes might be attributed to Li migration in the lattice. The experimental results were compared with the theoretical simulation, and the spectral changes were caused both by the slight changes in oxygen position parameter that affected titanium neighbors and Li migration. • Investigation of lithium migration through the spectral changes of Ti XAFS. • Structure analysis inside the zero-strain lattice. • In situ XAFS cell for investigation of lithium titanium oxide anode material. [ABSTRACT FROM AUTHOR]

In this study, Li4Ti5O12 (LTO) electrodes with different types of water-soluble binders are successfully coated upon aluminum foil. Electrodes containing solely sodium alginate (SA) as a binder or a mixed PVDF/carboxymethyl cellulose (CMC) binder show the most stable performance in 1 M LiPF6 in EC/DMC 1:1 in half cell vs. Li, with respect to cycle stability over 100 cycles at 1 C. The electrodes processed with a mixture of PVDF/SA show considerable fading and slightly worse values for rate capability. Each one of the different binders used is eco-friendly, and the whole processing can be performed without the use of organic solvents. Further advantages covering the whole production and recycling process, as well as safety issues during operation, encourage deeper research in this area. [ABSTRACT FROM AUTHOR]

Layered H 2 TiO 3 has been studied as an ionic sieve material for the selective concentration of lithium from solutions. The accepted mechanism of lithium adsorption on H 2 TiO 3 ion sieves is that it occurs via Li + -H + ion exchange with no chemical bond breakage. However, in this work, we demonstrate that lithium adsorption on H 2 TiO 3 occurs via O-H bond breakage and the formation of O-Li bonds, contrary to previously proposed mechanisms. Thermogravimetric analysis results show that the weight loss due to dehydroxylation decreases from 2.96 wt % to 0.8 wt % after lithium adsorption, indicating that surface hydroxyl groups break during lithium adsorption. Raman and Fourier transform infrared spectroscopy studies indicate that H 2 TiO 3 contains isolated OH groups and hydrogen-bonded OH groups. Among these two hydroxyl groups, isolated OH groups present in the HTi 2 layers are more actively involved in lithium adsorption than hydrogen-bonded OH groups. As a result, the actual adsorption capacity is limited by the number of isolated OH groups, whereas hydrogen-bonded OH groups involved are for stabilizing the layered structure. We also show that H 2 TiO 3 contains a high concentration of stacking faults and structural disorders which play a crucial role in controlling lithium adsorption properties.

Lithium-ion batteries (LIBs) are nowadays widely used in many energy storage devices, which have certain requirements on size, weight, and performance. State-of-the-art LIBs operate very reliably and with good performance under restricted and controlled conditions but lack in efficiency and safety when these conditions are exceeded. In this work, the influence of outranging conditions in terms of charging rate and operating temperature on electrochemical characteristics was studied on the example of lithium titanate (Li 4 Ti 5 O 12 , LTO) electrodes. Structural processes in the electrode, cycled with ultrafast charge and discharge, were evaluated by operando synchrotron powder diffraction and ex situ X-ray absorption spectroscopy. On the basis of the Rietveld refinement, it was shown that the electrochemical storage mechanism is based on the Li-intercalation process at least up to current rates of 5 C , meaning full battery charge within 12 min. For applications at temperatures between -30 and 60 °C, four carbonate-based electrolyte systems with different additives were tested for cycling performance in half-cells with LTO and metallic lithium as electrodes. It was shown that the addition of 30 wt % [PYR 14 ][PF 6 ] to the conventional LP30 electrolyte, usually used in LIBs, significantly decreases its melting point, which enables the successful low-temperature application at least down to -30 °C, in contrast to LP30, which freezes below -10 °C, making battery operation impossible. Moreover, at elevated temperatures up to 60 °C, batteries with the LP30/[PYR 14 ][PF 6 ] electrolyte exhibit stable long-term cycling behavior very close to LP30. Our findings provide a guideline for the application of LTO in LIBs beyond conventional conditions and show how to overcome limitations by designing appropriate electrolytes.

The poor electronic conductivity restricts the wide applications of Li4Ti5O12 as anode materials in Li‐ion batteries. We report a facile approach to fabricate nitrogen‐doped carbon‐coated Li4Ti5O12 through carbonizing pyrrole and pyridine at different temperatures. Comparative experiments demonstrated that the carbon content plays a key role in governing the cycling performance and rate capability of Li4Ti5O12. The composites with higher carbon content exhibited superior cycling performance, and the composite prepared at 600 °C using pyridine as the carbon source gave the best cycling and rate performance. [ABSTRACT FROM AUTHOR]

Lithium titanates are used in various applications, such as anode materials for lithium intercalation (Li4Ti5O12) or breeding materials in fusion reactors (Li2TiO3). Here, we report the formation of nano-crystalline lithium titanates by a mechanochemical approach and present a deeper insight into their structural characteristics by X-ray diffraction (XRD) and solid-state NMR spectroscopy. The compounds were synthesized in a high-energy planetary ball mill with varying milling parameters and different grinding tools. NaCl type Li2TiO3 (α-Li2TiO3) was formed by dry milling of lithium hydroxide with titania (rutile or anatase) and by a milling induced structure transformation of monoclinic β-Li2TiO3 or spinel type Li4Ti5O12. Heating of mechanochemical prepared α-Li2TiO3 induces a phase transformation to the monoclinic phase similar to hydrothermal reaction products, but a higher thermal stability was observed for the mechanochemical formed product. Microstructure and crystallographic structure were characterized by XRD via Rietveld analysis. Detailed phase analysis shows the formation of the cubic phase from the various educts. A set of two lattice parameters for α-Li2TiO3 was refined, depending on the presence of OH− during the milling process. An average crystallite size of less than 15 nm was observed for the mechanochemical generated products. The local Li environment detected by 6Li NMR revealed Li defects in the form of tetrahedral instead of octahedral site occupation. Subsequent adjustment of the structural model for Rietveld refinement leads to better fits, supporting this interpretation. [ABSTRACT FROM AUTHOR]

Flexible portable electronic devices have attracted increasing attention during the last decade. Energy consumption of such devices is ever increasing and performing power sources, that are moreover flexible, need to be developed to seamlessly integrate into such architectures. While lithium-ion batteries appear to be the best solution to meet the power and energy requirements, their structural and mechanical considerations still need to be addressed. Here, we realize and study the impact on the electrochemical performances of carbon nanotubes ( CNTs) based, current collector-free and binder-free, Li-ion battery electrodes. Multi-walled carbon nanotubes acting as a mechanical and electron conductive scaffold enable structural flexibility and good electrochemical performances. Flexible Li-ion cells made with such electrodes show promising performances while being realized through simple manufacturing approaches. [ABSTRACT FROM AUTHOR]

A feasibility study for the recovery of lithium from salt water with the protonated lithium titanium oxide ion-sieves was carried out in this work. Lithium ions (Li + ) in LiTi 2 O 4 having a similar ion density with H + allow repeated exchanges and regeneration with high selectivity. By Li 7 magic angle spinning solid-state magnetic resonance, it is apparent that chemical structure of lithium in the ion-sieves is not perturbed during the repeated Li + /H + exchange processes. As the dissolution of titanium is negligible (<0.1%), the secondary contamination during the capture process can be minimized. The ion-sieves exhibit lithium capture capacities of up to 9.5mg/g during the repeated Li + /H + exchanges with H 0.23 Li 0.77 Ti 2 O 4 /LiTi 2 O 4 for 24h, and the captured Li + may be recovered in the form of Li 2 CO 3 . Accordingly, the lithium capture method developed in this work could be integrated with current desalination processes for valuable lithium recovery., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Lithium titanium oxide (Li 4 Ti 5 O 12 )-based electrodes are very promising for long-life cycle batteries. However, the surface reactivity of Li 4 Ti 5 O 12 in organic electrolytes leading to gas evolution is still a problem that may cause expansion of pouch cells. In this study, we report the use of Schiff base (1,8-diazabicyclo[5.4.0]undec-7-ene) as an additive that prevents gas evolution during cell aging by a new mechanism involving the solid electrolyte interface on the anode surface. The in situ ring opening polymerization of cyclic carbonates occurs during the first cycles to decrease gas evolution by 9.7 vol % without increasing the internal resistance of the battery.

Conventional intercalated rechargeable batteries have shown their capacity limit, and the development of an alternative battery system with higher capacity is strongly needed for sustainable electrical vehicles and hand-held devices. Herein, we introduce a feasible and scalable multilayer approach to fabricate a promising hybrid lithium battery with superior capacity and multivoltage plateaus. A sulfur-rich electrode (90 wt % S) is covered by a dual layer of graphite/Li4Ti5O12, where the active materials S and Li4Ti5O12 can both take part in redox reactions and thus deliver a high capacity of 572 mAh gcathode(-1) (vs the total mass of electrode) or 1866 mAh gs(-1) (vs the mass of sulfur) at 0.1C (with the definition of 1C = 1675 mA gs(-1)). The battery shows unique voltage platforms at 2.35 and 2.1 V, contributed from S, and 1.55 V from Li4Ti5O12. A high rate capability of 566 mAh gcathode(-1) at 0.25C and 376 mAh gcathode(-1) at 1C with durable cycle ability over 100 cycles can be achieved. Operando Raman and electron microscope analysis confirm that the graphite/Li4Ti5O12 layer slows the dissolution/migration of polysulfides, thereby giving rise to a higher sulfur utilization and a slower capacity decay. This advanced hybrid battery with a multilayer concept for marrying different voltage plateaus from various electrode materials opens a way of providing tunable capacity and multiple voltage platforms for energy device applications.

The Li+-ion conductivity (σLi) in an electrolyte is an important parameter with respect to the performance of all-solid-state lithium-ion batteries (LIBs). However, little is known about how σLi in a porous electrolyte differs from that in a highly dense electrolyte. In this study, the relationship between the bulk density (dbulk) and apparent σLi (σLiapp) in a porous electrolyte of Li[Li1/3Ti5/3]O4 (LTO) was examined by theoretical and experimental approaches. The theoretical calculations demonstrated that dbulk and σLi have a simple relationship irrespective of the radius of the spherical pores in the electrolyte; i.e., σLi increases almost linearly with increasing ζ,where ζ is the ratio of d bulk to the theoretical density. In fact, the observed σLiapp of LTO, which was determined by four-probe alternating-current impedance measurements, increased with increasing ζ. Hence, with this relationship, σLiapp can be estimated by ζ and intrinsic σLi (σLiint) and vice versa; such estimations provide critical information for determining the optimum compositions of composite electrodes for all-solid-state LIBs. The temperature dependence of σLiapp in LTO and differences between the calculated and experimental results are also discussed.

Here we designed the kinetically favored Li4Ti5O12 by modifying its crystal structure to improve intrinsic Li diffusivity for high power density. Our first-principles calculations revealed that the substituted Na expanded the oxygen framework of Li4Ti5O12 and facilitated Li ion diffusion in Li4Ti5O12 through 3-D high-rate diffusion pathway secured by Na ions. Accordingly, we synthesized sodium-substituted Li4Ti5O12 nanorods having not only a morphological merit from 1-D nanostructure engineering but also sodium substitution-induced open framework to attain ultrafast Li diffusion. The new material exhibited an outstanding cycling stability and capacity retention even at 200 times higher current density (20 C) compared with the initial condition (0.1 C).