Density of lithium fluoride—lithium carbonate-based molten salts

The density of the LiF-Li₂CO₃ melts system was measured using the Archimedean method. Using the quadratic regression orthogonal design with two factors, a regression equation for the density of LiF-Li₂CO₃ melts was obtained in which the concentration of LiF and temperature were considered. The results indicated that the density of the LiF-Li₂CO₃ melts decreased with either increasing the concentration of LiF or increasing temperature; a linear relation was observed between density and temperature. In addition, the influences of NaF, KF, NaCl, and KCl additives on the densities of the given systems were studied. The addition of NaF and KF increased the density of the melts, whereas NaCl and KCl resulted in an initial increase and subsequent decrease with an increasing additive concentration. The density attained a maximum at NaCl and KCl mass fraction of approximately 15%.     

Enhancing electrochemical conversion of lithium polysulfide by 1T-rich MoSe2 nanosheets for high performance lithium–sulfur batteries

The sluggish conversion kinetics and shuttle effect of lithium polysulfides (LiPSs) severely hamper the commercialization of lithium–sulfur batteries. Numerous electrocatalysts have been used to address these issues, amongst which, transition metal dichalcogenides have shown excellent catalytic performance in the study of lithium–sulfur batteries. Note that dichalcogenides in different phases have different catalytic properties, and such catalytic materials in different phases have a prominent impact on the performance of lithium–sulfur batteries. Herein, 1T-phase rich MoSe₂ (T-MoSe₂) nanosheets are synthesized and used to catalyze the conversion of LiPSs. Compared with the 2H-phase rich MoSe₂ (H-MoSe₂) nanosheets, the T-MoSe₂ nanosheets significantly accelerate the liquid phase transformation of LiPSs and the nucleation process of Li₂S. In-situ Raman and X-ray photoelectron spectroscopy (XPS) find that T-MoSe₂ effectively captures LiPSs through the formation of Mo-S and Li-Se bonds, and simultaneously achieves fast catalytic conversion of LiPSs. The lithium–sulfur batteries with T-MoSe₂ functionalized separators display a fantastic rate performance of 770.1 mAh/g at 3 C and wonderful cycling stability, with a capacity decay rate as low as 0.065% during 400 cycles at 1 C. This work offers a novel perspective for the rational design of selenide electrocatalysts in lithium–sulfur chemistry.     

Constructing a uniform lithium iodide layer for stabilizing lithium metal anode

The metallic lithium(Li)is the ultimate option in the development of anodes for high-energy secondary batteries.Unfortunately,inferior cycling reversibility and Li dendrites growth of Li metal as anode enormously impede its commercialization.Here,a uniform Li I protective layer is constructed on Li metal anode via a facile and direct solid-gas reaction of Li metal with iodine vapor.The pre-constructed Li I layer possesses more steadily and faster Li ion transport than the conventional SEI layer and contributes to a steady interface for the Li metal anode,which affords a smooth Li deposition morphology without Li dendrites formation.The symmetrical cell with the Li metal anode protected by Li I layer exhibits a longer cycling lifetime of over 700 h at a current density of 1 m A cm^-2 with Li plating capacity of 1 m Ah cm^-2.Moreover,the Li I layer protected Li metal anode can still remain high capacity retention of 74.6%after 500 cycles in the full cell paired with NCM523 cathode.The work proposes an easy and effective method to fabricate a uniform and stable protective layer on the Li metal anode and offers a practicable thinking for the commercial implementation of Li metal batteries.     

α-Fe2O3 nanotubes with superior lithium storage capability

Polycrystalline α-Fe(2)O(3) nanotubes with thin walls have been synthesized by one-step template-engaged precipitation of Fe(OH)(x) followed by thermal annealing. In virtue of the unique structural features, these α-Fe(2)O(3) nanotubes exhibit superior lithium storage capabilities with exceptional high-rate capacity retention as a potential anode material for lithium-ion batteries.     

Quantum-chemical modeling of lithium removal from lithium–silicon–silicon carbide composite

The quantum-chemical modeling of the delithiation-induced reorganization of a Li _m Si _n layer applied to the surface of nitrogen-doped silicon carbide is performed by means of non-empirical molecular dynamics in the frame of the gradient-corrected density functional method with the goal for finding promising anode materials for lithium ion batteries. The ratios Li/Si are considered from 8/3 to 1/4. Partial removal of lithium atoms from the surface of the Li _m Si _n layer and annealing at a moderate temperature (400 K) is found to recover rapidly (as soon as within 10 ps) the uniform metal distribution over the layer when the ratio Li/Si is at least 3/4. At lower values of this ratio, the equalization slows down dramatically.     

α-MnO2 nanotubes: high surface area and enhanced lithium battery properties

A simple one-step route for preparing α-MnO(2) nanotubes is reported. The α-MnO(2) nanotubes exhibit a high surface area of 226 m(2) g(-1) and reversible capacity of 512 mA h g(-1) at a high current density of 800 mA g(-1) after 300 cycles, as well as cycling stability when measured as an anode in lithium batteries.     

Synthesis and study of lithium triuranate Li2U3O10 · 6H2O

Li₂U₃O₁₀ · 6H₂O crystal hydrate was synthesized by the reaction between synthetic schoepite UO₃ · 2.25H₂O and aqueous lithium nitrate solution under hydrothermal conditions at 200°C. The composition and structure of the obtained compound were established, and its dehydration and thermal decomposition were studied, by chemical analysis, X-ray diffraction, IR spectroscopy, and scanning calorimetry.     

P_4S_(10) modified lithium anode for enhanced performance of lithium–sulfur batteries

To address the corrosion and dendrite issues of lithium metal anodes, a protective layer was ex-situ constructed by P_4S_(10) modification. It was determined by X-ray photoelectron spectroscopy and Raman spectra that the main constituents of the protective layer were P_4S_(10), Li_3PS_4 and other LixPySztype derivatives. The protective layer was proved to be effective to stabilize the interphase of lithium metal. With the modified Li anodes, symmetric cells could deliver stable Li plating/stripping for 16000 h; Li–S batteries exhibited a specific capacity of 520 m A h g~(-1) after 200 cycles at 1000 m A g~(-1) with average Coulombic efficiency of 97.9%. Therefore, introducing LixPySzbased layer to protect Li anode provides a new strategy for the improvement of Li metal batteries.     

Surface tension of lead–lithium melts

The temperature and concentration dependences of the surface tension of lithium alloys based on lead are experimentally determined for the first time in a field of compositions with up to 20 at % lithium in lead in the temperature range from the liquidus up to 700 K. The isotherm of surface tension of the studied alloys in the range of compositions with ~10 at % Li in lead contains a minimum, as does the adsorption isotherm of lithium in the sub-eutectic area of PbLi compounds.     

Electrochemical lithium extraction from β-lithium nitride

In this paper we report the electrochemical characterization of mixtures of ball-milled lithium nitride and iron metal. Several samples were prepared with different lithium nitride to iron molar ratios. X-ray diffraction (XRD) spectra showed the presence of iron metal in all the samples and β-lithium nitride in the samples with higher Li₃N/Fe ratio. No evidence of other phases was detected. The milled powders were used to prepare composite cathodes for the electrochemical characterization. It was found that lithium can be extracted from the materials at a flat potential of 1.2 V vs. Li. The sample with Li₃N/Fe molar ratio 8:1 showed the highest specific capacity (1125 mAh g⁻¹) corresponding to the extraction of 1.8 Li equivalents per mole of lithium nitride. Only a fraction of the lithium extracted was re-inserted in the following discharge cycle. A drastic reduction of the capacity was observed for all the samples on further cycling. An enhancement of the cyclability was obtained by lowering the end-charge voltage that resulted in a reduction of the lithium extracted. The lithium extraction/insertion process was characterized by a large voltage difference indicating that the reaction is largely irreversible.     

Assignment of the vibrational spectra of lithium hydroxide monohydrate, LiOH·H2O

The assignment of the vibrational spectra of lithium hydroxide monohydrate, LiOH·H(2)O, has been controversial for more than half-a-century. Here we show that only the combination of all three forms of vibrational spectroscopy: infrared, Raman and inelastic neutron scattering spectroscopies coupled with periodic-density functional theory calculations is able to satisfactorily assign the spectra. All previous work based on empirical criteria is, at least partially, incorrect. The librational modes of water do not follow the expected rock > wag > twist order and the calculations indicate that complete or partial deuterium substitution would not be useful in assigning the modes.     

Morphology of lithium droplets electrolytically deposited in LiCl–KCl–Li2O melt

We report the growth of electrochemically deposited liquid lithium droplet in LiCl–KCl–Li₂O melt at 673–723 K. To understand the transient behavior of liquid lithium in the electrolyte, the interface between the electrodeposited molten metal phase and the molten salt system was observed in situ using a high-speed digital microscope. We found that the droplets on the electrode are slightly flattened, when the colloidal Li content decreases due to an increasing Li₂O content. This mechanism indicates that the heterogeneous distribution of the colloid Li may be due to the local Li solubility in the electrolyte.     

Synthesis and electrochemical properties of sulfur doped-LixMnO2−ySy materials for lithium secondary batteries

Sulfur doped lithium manganese oxides (Li_xMnO_2−yS_y) were prepared by ion exchange of sodium for lithium in Na_xMnO_2−yS_y precursors obtained by a sol–gel method. These materials had the nano-crystallite size, which was composed of grain size of about 100–200 nm. Especially, Li_0.56MnO_1.98S_0.02 delivered the initial discharge capacity of 170 mAh g⁻¹ and gradually increased the discharge capacity of 220 mAh g⁻¹ until 50 cycles. Moreover, it showed an excellent cycling behavior, although its original structure transformed into the spinel phase during cycling.     

Quasiemulsion-templated formation of α-Fe2O3 hollow spheres with enhanced lithium storage properties

α-Fe(2)O(3) hollow spheres with sheet-like subunits are synthesized by a facile quasiemulsion-templated method. Glycerol is dispersed in water to form oil-in-water quasiemulsion microdroplets, which serve as soft templates for the deposition of the α-Fe(2)O(3) shell. When tested as anode materials for lithium-ion batteries, these α-Fe(2)O(3) hollow spheres manifest greatly enhanced Li storage properties.     

Synthesis and crystal structure of the lithium perrhenate monohydrate LiReO4·H2O

A new monohydrate of lithium perrhenate LiReO₄·H₂O was prepared by dehydration of LiReO₄·1.5H₂O at room temperature. The single crystals of LiReO₄·H₂O were obtained by crystallisation from the isoamyl acetate solution of LiReO₄·1.5H₂O. The structure of monohydrate (a=5.6674(4), b=10.771(1), c=7.4738(7) Å, β=102.422(7)°, R₁=0.0414, space group P2₁/a, Z=4) is built up from LiO₃(H₂O)₂ trigonal bipyramids and ReO₄ tetrahedra sharing common edges and corners inside the layers. The layers are connected together by hydrogen bonds. The relationships between the structures of sesquihydrate, monohydrate and anhydrous LiReO₄ are discussed.     

Enhanced performance of lithium polymer batteries using a V2O5–PEG composite cathode

A new concept is proposed to realize solid-state high-performance lithium polymer batteries in which two different polymers are used as ionically conductive matrices in the cathode and in the separator. A solid, low molecular weight poly(ethylene glycol) was used in the cathode while a blend with a higher molecular weight poly(ethylene oxide) (PEO) was used in the separator. The enhanced transport properties in the cathodic compartment allow us to discharge the battery (190 mAh g⁻¹) at a moderate temperature (65°C) in a reasonable time (about 3.3 h). Batteries cycled at 100°C showed enhanced performance with respect to PEO-based batteries. At a power density of about 416 W kg⁻¹, energy density as high as 460 Wh kg⁻¹, based on the weight of the active material, was achieved in about 1 h of discharge. The work was developed within the ALPE (Advanced Lithium Polymer Electric Vehicle Battery) project, an Italian integrated project devoted to the realization of lithium polymer batteries for electric vehicle applications, in collaboration with the Osaka National Research Institute.     

Alloying of electrodeposited silicon with lithium—a principal study of applicability as anode material for lithium ion batteries

The possibility to electrodeposit silicon directly on a copper current collector out of organic electrolyte and ionic liquid was investigated with the aim to alloy the deposited silicon with lithium to prove the possible use as negative electrode in lithium ion batteries. Cyclovoltammetric analyses have shown in comparison to electrodes containing high crystalline silicon similar behaviour during the electrochemical alloying and dealloying process. SEM analyses have shown a particle size of the deposited silicon in submicron range.     

What's going on with these lithium reagents?

This Perspective describes a series of research projects that led the author from an interest in lithium reagents as synthetically valuable building blocks to studies aimed at understanding the science behind the empirical art developed by synthetic chemists trying to impose their will on these reactive species. Understanding lithium reagent behavior is not an easy task; since many are mixtures of aggregates, various solvates are present, and frequently new mixed aggregates are formed during their reactions with electrophiles. All of these species are typically in fast exchange at temperatures above -78 °C. Described are multinuclear NMR experiments at very low temperatures aimed at defining solution structures and dynamics and some kinetic studies, both using classic techniques as well as the rapid inject NMR (RINMR) technique, which can in favorable cases operate on multispecies solutions without the masking effect of the Curtin-Hammett principle.