Incorporation Of Li Ions Research Articles

K0.5FeF3 as a New Zero-Strain Cathode Material for Lithium-Ion Batteries

The stability of the cathode is of crucial importance for the service life of lithium-ion batteries (LIB). In the cathode, the lattice parameter usually changes during (de-)insertion of lithium, which causes various signs of aging that have a negative effect on the capacity of the cell. This problem can be tackled using a specific type of materials called zero-strain (ZS) materials. These materials do not show any (de-)intercalation-induced structural changes and stresses. Such a zero-strain effect was already demonstrated with fluorine-containing materials [1] and even for the similar material K0.6FeF3 [2] for sodium-ion batteries (SIB). In this case, potassium ions are removed in the first cycle and the vacant lattice sites can be used for the incorporation of sodium ions, while keeping the structural integrity of the host material.Complementary to experiments, theoretical atomistic simulations are powerful to develop design criteria for further ZS-materials. Combining experiments and simulations in this work, the structural behavior of the material K0.5FeF3 was investigated when used as a cathode material in a LIB. The synthesis of K0.5FeF3 was achieved by a Rapid Microwave-Enhanced Solvothermal Process, which allowed to obtain the material in a TTB-type (Tetragonal Tungsten Bronze) phase with a high degree of purity. The material was then processed into electrodes, which were galvanostatically cycled against lithium metal. It was shown that the material is suitable for LIB as a cathode material. X-ray diffraction experiments showed that the lattice parameter changed by less than 1% after the incorporation of Li-Ions, in good agreement with the theoretical calculations conducted in parallel. Lattice Parameter Charged Discharged a[Å] 12.74±0.024 12.73±0.006 c[Å] 3.99±0.008 4.00±0.002 Volume [Å3] 647.57±2.67 647.75±0.76 This work was supported by the German Research Foundation (DFG) BI 1636/7-1 and EL 155/29-1.

Write-Once-Read-Many-Times Memory Characteristics with a Large Memory Window Operating at a Low Voltage by Li-Ion Incorporation from the LiCoOx Ion-Supplying Layer into the InGaZnO Channel of a Thin-Film Transistor

Write-once-read-many-times (WORM) memory characteristics with a large memory window are demonstrated in a thin-film transistor (TFT) composed of an indium-gallium-zinc oxide (IGZO) channel and a lithium-cobalt oxide (LiCoOx) ion-supplying layer in the gate oxide. While the device with a thicker (5 nm) tunneling oxide showing a threshold voltage shift (ΔVT) of about 5 V by electron charging upon positive gate voltage (VGS) sweep to +25 V, the device with a 2 nm-thick tunneling oxide exhibits a large memory window with ΔVT > 20 V by Li-ion migration from LiCoOx to IGZO channel, which can be controlled as multilevel states with respect to the VGS amplitude. Incorporation of Li ions into the IGZO channel acting as p-type dopants reduces carrier concentration in the channel and consequently increases VT. The increased VT and the consequently reduced drain current are not instantly restored back by applying negative VGS, featuring WORM memory characteristics. Although the device undergoes partial retention loss, the retention remains up to about 90% after 100 min of retention time. These results verify WORM memory operations in the IGZO TFTs through gate voltage-driven Li-ion incorporation into the IGZO channel to modify its conductive states instead of using a typical electrical charging route.

Improving Electrocatalytic Activity of MoO3 for the Oxygen Evolution Reaction by Incorporation of Li Ions

Several polymorphs of MoO3 with different crystal and electronic structures provide many opportunities to find suitable electrocatalysts for water splitting hydrogen generation. So far, promising electrocatalytic activity for hydrogen evolution reaction (HER) has been found for α-MoO3 (orthorhombic), while the polymorph has shown a poor oxygen evolution reaction (OER) activity. In this work, it is found that the intrinsic OER activity of α-MoO3 is remarkably improved by incorporating guest ions of lithium-ion (Li+). α-MoO3 nanoparticles were deposited on a carbon fiber paper (α-MoO3/CFP) by chemical vapor transport and a subsequent lithiation process was applied to prepare lithiated α-MoO3/CFP (Li-α-MoO3/CFP), showing the robust η10 of 458 mV. The improved OER activity in the lithiated electrode is attributed to the incorporation of Li+ into the MoO3, which increases the electron carrier density and the corresponding electrical conductivity, thereby improving the interfacial charge transfer kinetics as well as activating a large number of ECSA.

Li-Doped ZnO Electron Transport Layer for Improved Performance and Photostability of Organic Solar Cells.

Organic solar cells (OSCs) based on an inverted architecture generally have better stability compared to those based on a standard architecture. However, the photoactive area of the inverted solar cells increases under ultraviolet (UV) or solar illuminatiom because of the too-high conductivity of the UV-illuminated zinc oxide (ZnO) interlayer. This limits the potential of the inverted solar cells for industrial applications. Herein, lithium-doped ZnO (Li-ZnO) films are employed as the cathode interlayer to construct inverted OSCs. The incorporation of Li ions is found to reduce the lateral conductivity of the UV-treated ZnO films because of the presence of Li ions, preventing the high-quality-growth of ZnO nanocrystals. This addresses the problem of having too-high conductivity in the UV-treated ZnO layer, causing the increased photoactive area of inverted solar cells. The overall performance of the solar cell is shown to be higher after the incorporation of Li ions in the ZnO layer, mainly due to the increased fill factor (FF), originating from the reduced trap-assisted recombination losses. Finally, the inverted solar cells based on the Li-ZnO interlayer are demonstrated to have a much better long-term stability, as compared to those based on ZnO. This allows the ZnO-based interlayers to be used for the mass production of organic solar cell modules.

Solid-state pseudocapacitors based on MnO2-nanorod-electrodes and plastic crystal incorporated gel polymer electrolyte: synergistic effect of Li-salt addition in electrolyte and morphology of electrodes

We present a novel configuration of high-performance solid-state pseudocapacitors, fabricated with symmetric MnO2-nanorod-electrodes, prepared via chemical and hydrothermal routes, and plastic crystals-based gel polymer electrolytes (GPEs). Comparative studies are reported on capacitors employing GPEs comprising a mixture of non-ionic plastic crystal succinonitrile (SN) and organic ionic plastic crystal (OIPC) 1-ethyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (EMPTFSI), without and with Li-salt (LiTFSI), entrapped in a co-polymer poly(vinylidine fluoride-co-hexafluoropropylene) (PVdF-HFP). The MnO2-nanorods have been characterized for their morphological/structural aspects, specific surface area, and porosity and correlated the characteristics with their capacitive performance. Clean and uniform morphology and high surface area with mesoporous character are found to be responsible factors for superior supercapacitive performance of hydrothermally derived MnO2-nanorod-electrodes as compared to chemically derived MnO2-nanorods. Lithium salt incorporation in GPE has been found to be another important factor to improve the pseudoapacitive performance of the cells due to facile intercalation/extraction of Li-ions through MnO2-electrodes. The optimum performance of the pseudocapacitor cell has been observed in terms of specific capacitance (98–101 F g−1), specific energy (~ 13.7 W h kg−1), and maximum specific power (~ 32.6 kW kg−1) as observed from charge-discharge studies, due to synergistic effect of morphology of hydrothermally derived MnO2-nanorod-electrodes and incorporation of Li-ions in GPE. The hydrothermally derived MnO2-nanorod-electrodes also exhibit high rate capability; however, it reduces significantly when Li-salt incorporated GPE is employed. The optimum cell exhibits almost stable cyclic performance up to ~ 3300 charge-discharge cycles after only ~ 17% fading in specific capacitance for initial few cycles.

Stable Performance of Aluminum‐Metal Battery by Incorporating Lithium‐Ion Chemistry

AbstractBased on the recent discovery of the ionic liquid involving the AlCl4−‐Al2Cl7− redox couple as an electrolyte, aluminum (Al) rechargeable batteries have received revamped interest. However, the corrosive nature of the chloride ion and Al2Cl7− makes it challenging to find suitable current collectors and cathode materials. Here, we screen various metals and carbon materials as current collectors, and indeed find that none of the metals commonly used for battery current collectors is stable against corrosion from the electrolyte. Only pyrolytic graphite is stable, but exhibits undesired AlCl4− intercalation at 1.7 V vs. Al/Al3+. The addition of lithium chloride (LiCl) salt to the electrolyte not only eliminates AlCl4− intercalation through Li−AlCl4− coordination, but also extends the stable voltage window to 2.3 V vs. Al/Al3+. Moreover, the incorporation of Li ions allows us to engage the established LiFePO4 olivine cathode in Li‐ion batteries. This Al−Li hybrid cell exhibits an operation voltage of 1.3 V with robust cyclability (83.4 % retention after 400 cycles) and minimal self‐discharge. This series of results suggest that proper employment of Li‐ion chemistry can improve the electrochemical performance and safety of Al rechargeable batteries.

Photovoltaic properties of LixCo3−xO4/TiO2 heterojunction solar cells with high open-circuit voltage

All-oxide solar cells are presently attracting extensive research interest due to their excellent stability, low-cost and non-toxicity. However, the band gap of metal oxides is lack of effective optimization and results in poor photovoltaic performance, thus hindering their practical applications. In this work, Co3O4 was investigated for application as a photo-absorber in all-oxide solar cells, and its band gap was optimized by introducing Li dopant into the spinel structure. LixCo3−xO4 nanoparticles, prepared via the hydrothermal method, were homogenously coated onto TiO2 mesoporous films, which were then used to fabricate planar heterojunction TiO2/LixCo3−xO4 solar cells (SCs). The effects of Li-doping on the heterojunction solar cell performance were further investigated. The findings revealed that the incorporation of Li ions into Co3O4 led to a significant enhancement in short-circuit current density (Jsc). Remarkably, a high open-circuit voltage (Voc) of 0.70V was also achieved. Besides, reasons for the enhanced cell performance are the narrower band gap, reduced photogenerated carrier recombination and the more favorable energy band structure as compared with SCs assembled from pure Co3O4.

Structural characteristics of Mg-doped (1-x)(K0.5Na0.5)NbO3–xLiSbO3 lead-free ceramics as revealed by Raman spectroscopy

This paper presents a Raman spectroscopic study of compositional-change-induced structure variation and of the related mechanism of Mg doping in LiSbO3 (LS)-modified (K0.5Na0.5)NbO3 (KNN) ceramics. With increasing LS content from 0 to 0.06, a discontinuous shift towards higher wavenumbers was found for the band position of the A1g(v1) stretching mode of KNN, accompanied by a clearly nonlinear broadening of this band and a decrease in its intensity. Such morphological changes in the Raman spectrum result from two factors: (i) changes in polarizability/binding strength of the O–Nb–O vibration upon incorporation of Li ions in the KNN perovskitic structure and (ii) a polymorphic phase transition (PPT) from orthorhombic to tetragonal (O → T) phase at x > 0.04. Upon increasing the amount, w, of Mg dopant incorporated into the (1-x)KNN–xLS ceramic structure, the intensity of the Raman bands are enhanced, while the peak position and the full width at half maximum of the A1g(v1) mode was found to experience a clear dependence on both w and x. Raman characterization revealed that the mechanism of Mg doping is strongly correlated with the concentration of Li in the perovskite structure: Mg2+ ions will preferentially replace Li+ ions for low Mg doping while replace K/Na ions for higher doping of Mg. The PPT O → T was also found to be altered by the introduction of Mg and the critical value of LS concentration, xO−T, for incipient O → T transition in the KNN–xLS–wMT system was strongly dependent on Mg content, with xO → T being roughly equal to 0.04 + 2w, for the case of dilute Mg alloying.

Enhancement of cathodoluminescence intensities of Y 2O 3:Eu and Gd 2O 3:Eu phosphors by incorporation of Li ions

Li-doped Y 2O 3:Eu and Gd 2O 3:Eu phosphors have been studied as potential red phosphors for application to field emission displays. These phosphors showed cathodoluminescence increases when Li ions are doped. It is found that the lattice of Gd 2O 3:Eu phosphors transforms from monoclinic to cubic as the Li ions are doped. However, Y 2O 3:Eu phosphors keep their cubic phases upon Li doping. Also, this investigation has determined that the differences in intensity ratios originate from two different luminescent sites in each phosphor. From this study, it is understood that Li ions affect the luminescence of the Gd 2O 3:Eu phosphor by influencing its lattice symmetry. On the other hand, the luminescence of Y 2O 3:Eu phosphors is increased by a kind of charge compensation caused by Li doping.

Chemistry and kinetics of ZnO growth from alkaline hydrothermal solutions

Special features (polar growth and nonstoichiometry) of ZnO single crystals grown on seed plates of various crystallographic orientations in the ZnO–KOH–H2O and ZnO–KOH–LiOH–H2O hydrothermal systems are analyzed. The growth proceeds via the interaction of ZnO2- 2 anions with crystal surfaces, and its rate depends on the atomic structure and electric charge of the surface. The mechanism underlying the influence of Li+ ions on polar ZnO growth is considered. Partial replacement of Zn2+ by Li+ decreases the positive charge on the (0001) face and hinders the attachment of ZnO2- 2 anions. The incorporation of Li ions into the (0001¯) face decreases its negative charge and accelerates growth in the [0001¯] direction.

The influence of the reaction medium of oxidative methane coupling on the nature of bulk defects of the Li/CaO system

The relationship of the catalytic activity of Li/CaO (0 ⩽ Li ⩽ 1.7 at%) in CH4 oxidative coupling with the defectness of the matrix has been studied. It was shown that the activity of undoped CaO increases with the rise of concentration of anion and cation vacancies. The concentration and nature of defects in the pure CaO are independent of the composition of the gas (O2, N2O, CH4 or reaction mixture). The incorporation of Li ions into the CaO lattice and also the treatment of Li/CaO with the reaction mixture lead to a change of the character of bulk defects and catalytic properties of the oxide. The signals from O3−, CO2− and LiCO3− centers are detected in the EPR spectra of γ-irradiated Li/CaO catalysts after the contact with the CH4-O2 mixture. Such defects are not observed when a CH4-N2O mixture is used. Simultaneously, the replacement of O2 by N2O in the reaction mixture is accompanied by the decrease of the CO formation rate and the increase of activity in the C2-product formation.