Sol–gel preparation and characterization of nano-crystalline lithium–mica glass–ceramic

The nano-crystalline lithium–mica glass–ceramic with separated crystallite size of 13 nm was prepared using sol–gel technique. In such a process, the structural evolutions and microstructural characteristics of the synthesized samples were investigated through X-ray diffraction, transmission electron microscopy, thermal analysis and Fourier transform infrared spectroscopy. It was found that the crystallite size of the mica obtained from sol–gel method is smaller than the one synthesized via conventional melted method. The XRD results also showed that the crystallization of mica occurred above 675 °C and it could originate from MgF₂ so that the next stage will also be the transformation from mica to norbergite and norbergite to chondrodite. The activation energy of the crystallization and Avrami factor were measured as 376.7 kJ mol^?1 and 2.3, respectively. It is found that the bulk crystallization could be considered as the predominant crystallization mechanism for the glass–ceramic.     

Preparation,structural and thermo-mechanical properties of lithium aluminum silicate glass–ceramics

Lithium aluminum silicate glasses of composition (wt%) 12.6Li₂O–71.7SiO₂–5.1Al₂O₃–4.9K₂O–3.2B₂O₃–2.5P₂O₅ were prepared by the melt quench technique. These glasses were converted to glass–ceramics based on DTA data. X-ray diffraction (XRD) and Fourier transform infra-red spectroscopy (FTIR) were used to discern the phases evolved in the glass–ceramics. Phase morphology was studied using scanning electron microscopy (SEM). Thermal expansion coefficient (TEC) and glass transition temperature (T_g) of all samples were measured using thermo-mechanical analyzer (TMA). It was found that 3 h dwell time at crystallization temperature yielded samples with good crystallinity with a TEC of 9.461 × 10⁻⁶ °C⁻¹. Glass–ceramic-to-metal compressive seal with SS-304 was fabricated using LAS glass–ceramic. The presence of metal housing and compressive stresses at the glass–ceramic-to-metal interface reduced average grain size and changed the overall microstructure.     

Preparation and electrochemical performance of SiCN–CNTs composite anode material for lithium ion batteries

The composite of silicon carbonitride (SiCN) and carbon nanotubes (CNTs) was synthesized by sintering the mixture of polysilylethylenediamine-derived amorphous SiCN and multi-walled CNTs at a temperature of 1,000 °C for 1 h in argon. The as-prepared SiCN–CNTs material, which was used as anode active substance in a lithium ion battery, showed excellent electrochemical performance. Charge–discharge tests showed the SiCN–CNTs anode provided a high initial specific discharge capacity of 1176.6 mA h g⁻¹ and a steady specific discharge capacity of 450–400 mA h g⁻¹ after 30 charge–discharge cycles at 0.2 mA cm⁻². Both of the abovementioned values are higher than that of pure polymer-derived SiCN, CNTs, and commercial graphite at the same charge–discharge condition. It was deduced that the CNTs in the composite not only improved the electronic conductivity and offered channels and sites for the immigrating and intercalating of Li⁺ but also stabilized the structure of the composite.     

Shuttle inhibitor effect of lithium perchlorate as an electrolyte salt for lithium–sulfur batteries

Lithium perchlorate (LiClO₄), used as an electrolyte salt for lithium–sulfur batteries, has been shown to give rise to the effective inhibition of the chemical polysulfide shuttle and thereby to enhance the coulombic efficiency through the stabilized charge process. In 1,2-dimethoxy ethane (DME)/1,3-dioxolane (DOL) (50:50 by volume), LiClO₄ showed the lowest charge-transfer resistance among the various lithium salts studied and demonstrated the highest coulombic efficiency with an extreme reduction in the polysulfide shuttle. The origin of this behavior is considered to be the rapid formation of a passivation layer on the surface of the lithium metal anode. Hence, as well as being a good electrolyte salt in itself, LiClO₄ is shown to be an effective polysulfide shuttle inhibitor.     

Charge–discharge curves and discharge capacities of LiNi1−yCoyO2 synthesized from lithium carbonate and nickel and cobalt oxides

LiNi_1?yCo_yO₂ (y=0.1, 0.3, and 0.5) were synthesized by a solid-state reaction method at 800 °C and 850 °C using Li₂CO₃, NiO, and Co₃O₄ as the starting materials. The electrochemical properties of the synthesized LiNi_1?yCo_yO₂ were then investigated. For samples with the same composition, the particles synthesized at 850 °C were larger than those synthesized at 800 °C. The particles of all the samples synthesized at 850 °C were larger than those synthesized at 800 °C. LiNi_0.5Co_0.5O₂ synthesized at 850 °C had the largest first discharge capacity (159 mA h/g), followed in order by LiNi_0.7Co_0.3O₂ synthesized at 800 °C (158 mA h/g) and LiNi_0.9Co_0.1O₂ synthesized at 850 °C (151 mA h/g). LiNi_0.9Co_0.1O₂ synthesized at 850 °C had the best cycling performance with discharge capacities of 151 mA h/g at n=1 and 156 mA h/g at n=5.     

Controlled synthesis of lanthanide–lithium inverse crown ether complexes

An ytterbium–lithium inverse crown ether complex stabilized by amine-bridged bis(phenolate) ligands (LYbBr)₂(μ₄-O)(μ₃-Li) (1) [L = Me₂NCH₂CH₂N{CH₂-(2-O- C₆H₂-Bu^t₂-3,5)}₂] was isolated as a byproduct from the reaction of LYbCl(THF) with CH₃Li in THF in a very low isolated yield. Further study revealed that the inverse crown ether complexes can be synthesized in a controlled manner by the reaction of bis(phenolate) lanthanide chloride with an in situ mixture of n-BuLi with water in THF. A second inverse crown ether complex (L′YbCl)₂(μ₄-O)(μ₃-Li) (2) [L′ = Me₂NCH₂CH₂N{CH₂-(2-O-C₆H₂-Bu^t-3-Me-5)}₂] was prepared in high isolated yield and well characterized.     

Synthesis of lithium LiNi1−yCoyO2 from lithium carbonate,nickel oxide and cobalt carbonate and their electrochemical properties

LiNi_1?yCo_yO₂ (y = 0.1, 0.3 and 0.5) were synthesized by solid state reaction method at 800 °C and 850 °C from Li₂CO₃, NiO and CoCO₃ as starting materials. The electrochemical properties of the synthesized LiNi_1?yCo_yO₂ were investigated. As the content of Co decreases, particle size decreases rapidly and particle size gets more homogeneous. When the particle size is compared at the same composition, the particles synthesized at 850 °C are larger than those synthesized at 800 °C. Among LiNi_1?yCo_yO₂ (y = 0.1, 0.3 and 0.5) synthesized at 850 °C, LiNi_0.7Co_0.3O₂ has the largest intercalated and deintercalated Li quantity Δx at the first charge–discharge cycle, followed in order by LiNi_0.9Co_0.1O₂ and LiNi_0.5Co_0.5O₂. LiNi_0.7Co_0.3O₂ synthesized at 850 °C has the largest first discharge capacity (142 mAh/g), followed in order by LiNi_0.9Co_0.1O₂ synthesized at 850 °C (113 mAh/g), and LiNi_0.5Co_0.5O₂ synthesized at 800 °C (109 mAh/g).     

Large-scale synthesis of ordered mesoporous carbon fiber and its application as cathode material for lithium–sulfur batteries

A novel type of one-dimensional ordered mesoporous carbon fiber has been prepared via the electrospinning technique by using resol as the carbon source and triblock copolymer Pluronic F127 as the template. Sulfur is then encapsulated in this ordered mesoporous carbon fibers by a simple thermal treatment. The interwoven fibrous nanostructure has favorably mechanical stability and can provide an effective conductive network for sulfur and polysulfides during cycling. The ordered mesopores can also restrain the diffusion of long-chain polysulfides. The resulting ordered mesoporous carbon fiber sulfur (OMCF-S) composite with 63% S exhibits high reversible capacity, good capacity retention and enhanced rate capacity when used as cathode in rechargeable lithium–sulfur batteries. The resulting OMCF-S electrode maintains a stable discharge capacity of 690 mAh/g at 0.3 C, even after 300 cycles.     

Synthesis of ternary Li–Mn–O phase at a temperature of 260 ∘C and electrochemical lithium insertion into the oxide

A lithium–manganese oxide, Li _x MnO₂ (x=0.30.6), has been synthesized by heating a mixture (Li/Mn ratio=0.30.8) of electrolytic manganese dioxide (EMD) and LiNO₃ in air at moderate temperature, 260 C. The formation of the Li–Mn–O phase was confirmed by X-ray diffraction, atomic absorption and electrochemical measurements. Electrochemical properties of the Li–Mn–O were examined in LiClO₄-propylene carbonate electrolyte solution. About 0.3 Li in Li _x MnO₂ (x=0.30.6) was removed on initial charging, resulting in characteristic two discharge plateaus around 3.5V and 2.8V vs Li/Li⁺. The Li _x MnO₂ synthesized by heating at Li/Mn ratio=0.5 demonstrated higher discharge capacity, about 250mAh (g of oxide)^–1 initially, and better cyclability as a positive electrode for lithium secondary battery use as compared to EMD.     

A review of high energy density lithium–air battery technology

Today’s lithium (Li)-ion batteries have been widely adopted as the power of choice for small electronic devices through to large power systems such as hybrid electric vehicles (HEVs) or electric vehicles (EVs). However, it falls short of meeting the demands of new markets in these areas of EVs or HEVs due to insufficient energy density. Therefore, new battery systems such as Li–air batteries with high theoretical specific energy are being intensively investigated, as this technology could potentially make long-range EVs widely affordable. So far, Li–air battery technology is still in its infancy and will require significant research efforts. This review provides a comprehensive overview of the fundamentals of Li–air batteries, with an emphasis on the recent progress of various elements, such as lithium metal anode, cathode, electrolytes, and catalysts. Firstly, it covers the various types of air cathode used, such as the air cathode based on carbon, the carbon nanotube-based cathode, and the graphene-based cathode. Secondly, different types of catalysts such as metal oxide- and composite-based catalysts, carbon- and graphene-based catalysts, and precious metal alloy-based catalysts are elaborated. The challenges and recent developments on electrolytes and lithium metal anode are then summarized. Finally, a summary of future research directions in the field of lithium air batteries is provided.     

VSe2−ySy electrodes in lithium and lithium-ion cells

Step potential electrochemical spectroscopy data of lithium anode cells using VSe2–ySy(0y0.5) compounds as cathode material and LiClO4 solutions in PC as electrolyte were studied. On increasing y, a lower extension of the intercalation process was observed, due to the loss of a second insertion step corresponding to lithium ion occupancy of tetrahedral sites. In contrast, the reaction rate increased with sulfur content. VSe2–ySy/LiCoO2 lithium-ion cells were cycled to test the electrochemical behaviour of the vanadium chalcogenides as anodic material. A better capacity retention was observed for y = 0.3. The effect of current density on the performance of the cells was also evaluated.     

Optimized sintering and mechanical properties of Y–TZP ceramics for dental restorations by adding lithium disilicate glass ceramics

The novel dental ceramics can be fabricated at lower temperatures when sol–gel derived lithium disilicate glass ceramics (LDGC) was used as an additive for yttr...     

Microemulsion-mediated hydrothermal growth of pagoda-like Fe3O4 microstructures and their application in a lithium–air battery

This paper reported the growth of novel pagoda-like Fe₃O₄ particles via a facile microemulsion-mediated hydrothermal procedure. The chemical compositions and morphologies of the as-grown Fe₃O₄ particles were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and field emission scanning electron microscopy (FE-SEM). The morphologies of the as-prepared sample evolved from pagoda-like to pinwheel-like to flower-like shapes with increasing reaction time. In addition, the NaOH concentration and polyethylene glycol (PEG)-2000 had key effects on the formation of the final product. The electrocatalytic properties of the prepared pagoda-like micro-Fe₃O₄, as catalytic materials for a lithium–air battery, were further evaluated by galvanostatic charge/discharge cycling and electrochemical impedance spectrometry (EIS). Results showed that the cell displayed an initial discharge capacity of 1429 mA h g⁻¹ at a voltage of 1.5–4.5 V at 100 mA g⁻¹.     

Search of high-capacity cathode materials based on lithium–iron silicate compounds

The crystal structures of 197 lithium–silicate compounds have been analyzed using the method of crystal chemistry analysis (TOPOS software package). The compounds whose structures are characterized with a combination of high values of such parameters as the channel radius, stability, gravimetric capacity, and capacity per volume unit have been revealed: LiFeSiO₄ (R3?), Li₄Fe₂Si₃O₁₀ (C2/c), Li₂FeSiO₄ (Pc2₁ n), and Li₂FeSiO₄ (C222₁). It has been demonstrated that lithium–iron silicates of the monoclinic syngony have high values of the capacity per volume unit, as compared to those of the rhombic syngony. The structural stability of the Li₂FeSiO₄ (Pc2₁ n) framework has been corroborated using the method of computer simulation within the scopes of the electron density functional theory. The obtained information could facilitate creation of novel cathode materials of high capacity and specific accumulated energy.     

Cathode materials based on carbon nanotubes for high-energy-density lithium–sulfur batteries

The rational integration of conductive nanocarbon scaffolds and insulative sulfur is an efficient method to build composite cathodes for high-energy-density lithium–sulfur batteries. The full demonstration of the high-energy-density electrodes is a key issue towards full utilization of sulfur in a lithium–sulfur cell. Herein, carbon nanotubes (CNTs) that possess robust mechanical properties, excellent electrical conductivities, and hierarchical porous structures were employed to fabricate carbon/sulfur composite cathode. A family of electrodes with areal sulfur loading densities ranging from 0.32 to 4.77 mg cm⁻² were fabricated to reveal the relationship between sulfur loading density and their electrochemical behavior. At a low sulfur loading amount of 0.32 mg cm⁻², a high sulfur utilization of 77% can be achieved for the initial discharge capacity of 1288 mAh g_S⁻¹, while the specific capacity based on the whole electrode was quite low as 84 mAh g_{C/S+binder+Al}⁻¹ at 0.2 C. Moderate increase in the areal sulfur loading to 2.02 mg cm⁻² greatly improved the initial discharge capacity based on the whole electrode (280 mAh g_{C/S+binder+Al}⁻¹) without the sacrifice of sulfur utilization. When sulfur loading amount further increased to 3.77 mg cm⁻², a high initial areal discharge capacity of 3.21 mAh cm⁻² (864 mAh g_S⁻¹) was achieved on the composite cathode.     

Negatively charged organic–inorganic hybrid silica nanofiltration membranes for lithium extraction

Effective extraction of lithium from high Mg~(2+)/Li+ratio brine lakes is of great challenge. In this work, organic–inorganic hybrid silica nanofiltration(NF) membranes were prepared by dip-coating a 1,2-bis(triethoxysilyl)ethane(BTESE)-derived separation layer on tubular TiO_2 support, for efficient separation of LiC l and MgCl_2 salt solutions. We found that the membrane calcinated at 400 °C(M1–400) could exhibit a narrow pore size distribution(0.63–1.66 nm) owing to the dehydroxylation and the thermal degradation of the organic bridge groups. All as-prepared membranes exhibited higher rejections to LiCl than to MgCl_2, which was attributed to the negative charge of the membrane surfaces. The rejection for LiCl and MgCl_2 followed the order: LiCl N MgCl_2, revealing that Donnan exclusion effect dominated the salt rejection mechanism. In addition, the triplecoated membrane calcined at 400 °C(M3–400) exhibited a permeability of about 9.5 L·m~(-2)·h~(-1)·bar~(-1) for LiCl or MgCl_2 solutions, with rejections of 74.7% and 20.3% to LiCl and MgCl_2,respectively, under the transmembrane pressure at 6 bar. Compared with the previously reported performance of NF membranes for Mg~(2+)/Li+separation, the overall performance of M3–400 is highly competitive. Therefore, this work may provide new insight into designing robust silica-based ceramic NF membranes with negative charge for efficient lithium extraction from salt lakes.     

Graphite–lithium–europium system: Modulation of the structural and physical properties of the lamellar phases as a consequence of their chemical composition

This paper summarizes the whole chemical, structural and magnetic properties collected in the graphite–lithium–europium system. The intercalation mechanisms which occur during reactions between graphite and lithium–europium liquid alloys have been identified. The investigation of the experimental parameters leads to the optimized conditions to isolate europium-based graphite intercalation compounds (GICs) denoted α-phase and γ-phase. The ion beam analysis has been carried out to simultaneously quantify the amount of carbon, lithium and europium in a same sample. The α-phase shows a homogeneous distribution of the elements laterally and in depth, with a Li_0.2Eu₂C₆ chemical formula. The unexpected presence of lithium has been revealed in the γ-phase but the EuC₆ GIC is clearly detected, in agreement with X-ray diffraction experiments. The structural properties of Li_0.2Eu₂C₆ have been studied and a Li–Eu–Eu–Eu–Li poly-layered sheet intercalated between graphene planes has been showed along the c-axis, with c = 3.I_C = 2400 pm. The presence of lithium allows the building of a poly-layered metallic structure leading to specific magnetic properties different from those of EuC₆. In the latter case, lithium does not affect either the structural or the magnetic properties of the intercalation compound.     

Characterisation and modelling of CNT–epoxy and CNT–fibre–epoxy composites

Abstract

This research presents an experimental and theoretical investigation on the effects of carbon nanotube (CNT) integration within neat epoxy resin (nanocomposites) and a carbon fabric–epoxy composite (multiscale composites). An approach is presented for the prediction of mechanical properties of multiscale composites. This approach combines woven fibre micromechanics (MESOTEX) with the Mori-Tanaka model which was used for the prediction of mechanical properties of nanocomposites in this research. Nanocomposite and multiscale composite samples were manufactured using cast moulding, resin infusion, and hand lay-up process. The CNT concentrations in the composite samples were from 0 to 5 wt-%. The samples were characterised using tensile, shear and flexural tests. The discrepancy between the theoretical predictions and the experimental observations was hypothesised to be due to dispersion and bonding issues and SEM images are presented in support of the hypothesis.     

Synthesis and characterizations of BNT–BT and BNT–BT–KNN ceramics for actuator and energy storage applications

Dielectric and ferroelectric properties of 0.93Bi_0.5Na_0.5TiO₃–0.07BaTiO₃ (BNT–BT) and 0.93Bi_0.5Na_0.5TiO₃–0.06BaTiO₃–0.01K_0.5Na_0.5NbO₃ (BNT–BT–KNN) ceramics were studied in detail. An XRD analysis confirmed the single perovskite phase formation in both the samples. Room temperature (RT) dielectric constant (ε_r) ~1020 and 1370, respectively at 1 kHz frequency were obtained in the BNT–BT and BNT–BT–KNN ceramics. Temperature dependent dielectric and the polarization vs. electric field (P–E) studies confirmed the coexistence of ferroelectric (FE) and anti-ferroelectric (AFE) phases in the BNT–BT and BNT–BT–KNN ceramics. Substitution of KNN into the BNT–BT system decreased the remnant polarization, coercive field and the maximum strain percentage. The energy storage density values ~0.485 J/cm³ and 0.598 J/cm³ were obtained in the BNT–BT and BNT–BT–KNN ceramics, respectively. High induced strain% in the BNT–BT ceramics and the high energy storage density in the BNT–BT–KNN ceramics suggested about the usefulness of these systems for the actuator and the energy storage applications, respectively.