Lithium Iodide Research Articles

Suppressing dendrite growth by a functional electrolyte additive for robust Li metal anodes

Lithium (Li) metal is considered as an attractive anode for next-generation energy storage systems due to its higher energy density and the lowest redox potential. However, great challenges including safety issues associated with dendrite growth and low Coulombic efficiency (CE) related to poor cycle stability, especially at high charge current densities, are still impeding its practical uses in Li metal secondary batteries. Herein we propose that an optimal amount of lithium iodide (LiI) as a functional additive in ether-based electrolyte for dendrite-free Li deposition. The additive could induce the electrolyte polymerization to in-situ form a robust solid electrolyte interphase (SEI) layer enriched with elastic oligomer on Li surface. Furthermore, the LiI in the electrolyte heightens the ionic conductive of formed SEI and facilitates the migration of Li ion, remarkably promoting the uniform deposition of Li at Li/electrolyte interface and suppressing the growth of Li dendrite. With a controlled Li deposition in an optimal amount (2 wt%) of LiI as an additive in ether-based electrolytes, a prolonged cycling lifespan (>1200 h) with a hysteresis voltage of ∼250 mV at 2 mA cm−2, as well as a very high CE up to 98.1% for 200 cycles at 0.5 mA cm−2. Moreover, the fabricated Li||Se battery system delivers an improved cycling stability and decreased polarization.

Crystallization temperature, vapor pressure, density and viscosity of lithium bromide + lithium iodide + ethylene glycol + water system for absorption refrigerators for automotive use

Absorption refrigerators are expected for automotive use due to their advantage of utilizing waste heat from exhaust gas. The compactness and efficiency of the refrigeration system required for such use indicates a pair of water/lithium bromide (LiBr) as a promising working fluid. However, operation of absorption refrigerators for automotive use would be hampered by the crystallization of LiBr solution, because relatively high concentration of LiBr solution is necessary for automotive use in which the absorber should be air-cooled. Therefore, the crystallization temperature of LiBr solution needs to be reduced. In this study, we focused on LiBr + lithium iodide (LiI) + ethylene glycol (C2H4(OH)2) aqueous solution as an absorbent, due to its lower crystallization temperature compared with LiBr solution. We measured the crystallization temperature, saturated vapor pressure, density and viscosity of these solutions with different composition ratios. The measured saturated vapor pressure, density and viscosity were then correlated using proper regression equations.

All Organic Interface Layer Formed from Vinylene Carbonate and Stable Plating of Lithium Metal

Prevailing demand for lithium-ion batteries with higher energy density draws more researcher's attentions on the use of lithium metal as the anode material. An order of magnitude higher specific capacity and much lower reduction potential of lithium metal compared to graphite makes lithium metal suitable anode for the next-generation lithium-sulfur and lithium-air batteries. However, nonuniform plating or dendrite formation of lithium metal is a major issue for shorting batteries. Stable interface between lithium metal and electrolyte is the key to the uniform growth of lithium. Vinylene carbonate (VC) is a widely used additive in commercial electrolyte for lithium-ion batteries, and the effect of VC on stabilizing lithium metal has been reported. VC is proposed to polymerize on lithium surface to form flexible thin coating layer, which regulates the lithium-ion flux at the interface and put a mechanical pressure on the growing lithium dendrite. The interface layer is composed of multiple decomposition products from organic solvents and fluorinated salt and extremely complex to analyze. Here we propose a gel electrolyte composed of vinylene carbonate and lithium iodide (LiI) to form polymer coating layer on the lithium surface. FTIR, NMR, and GC-FID analysis confirm polymerization of vinylene carbonate is triggered by lithium iodide through decarboxylation and forms poly(vinylene catbonate). Because iodide is electrochemically irreducible anion, no decomposition occurs on the lithium surface and simplifies the interface composition. Without the formation of inorganic compounds in VC-LiI gel electrolyte, Li//Li symmetric cell cycles for 1000 hours at 1 mA cm-2 and 1 mAh cm-2, with a practical electrolyte thickness of 25 μm (separator free). Coulombic efficiency of lithium plating/stripping in VC-LiI gel electrolyte is 98.6%, which is significantly higher than conventional carbonate-based electrolyte. Cross-sectional SEM image of cycled lithium metal reveals dense polymer coating and dendrite free morphology. Therefore, the simple all-organic interface, differing from conventional heterogeneous inorganic/organic mixture, can stabilize the lithium surface. We present a new perspective on the design of electrolyte and lithium interface.

Polymer electrolytes based PAN for dye-sensitized solar cells

Solar cells has been assembly with electrolytes including I−/I−3 redox duality employ polyacrylonitrile (PAN), ethylene carbonate (EC), propylene carbonate (PC), with double iodide salts of tetrabutylammonium iodide (TBAI) and Lithium iodide (LiI) and iodine (I2) were thoughtful for enhancing the efficiency of the solar cells. The rendering of the solar cells has been examining by alteration the weight ratio of the salts in the electrolyte. The solar cell with electrolyte comprises (60% wt. TBAI/40% wt. LiI (+I2)) display elevated efficiency of 5.189% under 1000 W/m2 light intensity. While the solar cell with electrolyte comprises (60% wt. LiI/40% wt. TBAI (+I2)) display a lower efficiency of 3.189%. The conductivity raises with the raising TBAI salt weight ratio and attains the maximum value of 1.7×10−3 S. cm−1 at room temperature with 60% wt. TBAI, and the lower value of ionic conductivity of 5.27×10−4 S. cm−1 for electrolyte with 40% wt. TBAI. The results display that the conductivity rises with rising temperature. This may be attributed to the extending of the polymer and thereby output the free volume. The alteration in ionic conductivity with temperature obeys the Arrhenius type thermally activated process. The differences in activation energy mightily backup the alteration in the electrical conductivity.

In situ formed polymer gel electrolytes for lithium batteries with inherent thermal shutdown safety features

An in situ formed poly(vinylene carbonate)–lithium iodide gel electrolyte enables stable cycling of lithium metal and a thermal shutdown function.

The quasi-low temperature behaviour of specific heat.

A new mathematical approach to condensed matter physics, based on the finite temperature field theory, was recently proposed. The field theory is a scale-free formalism; thus, it denies absolute values of thermodynamic temperature and uses dimensionless thermal variables, which are obtained with the group velocities of sound and the interatomic distance. This formalism was previously applied to the specific heat of condensed matter and predicted its fourth power of temperature behaviour at sufficiently low temperatures, which was tested by experimental data for diamond lattice materials. The range of temperatures with the quartic law varies for different materials; therefore, it is called the quasi-low temperature regime. The quasi-low temperature behaviour of specific heat is verified here with experimental data for the fcc lattice materials, silver chloride and lithium iodide. The conjecture that the fourth order behaviour is universal for all condensed matter systems has also supported the data for glassy matter: vitreous silica. This law is long known to hold for the bcc solid helium-4. The characteristic temperatures of the threshold of the quasi-low temperature regime are found for the studied materials. The scaling in the specific heat of condensed matter is expressed by the dimensionless parameter, which is explored with the data for several glasses. The explanation of the correlation of the ‘boson peak’ temperature with the shear velocity is proposed. The critique of the Debye theory of specific heat and the Born–von Karman model of the lattice dynamics is given.

Addition of 1-butyl-3-methylimidazolium iodide to the N-phthaloylchitosan based gel polymer electrolyte

Various percentages of 1-butyl-3-methylimidazolium iodide (BMII) from 1 to 5 wt.% were introduced into the most efficient N-phthaloylchitosan (PhCh) based GPEs with lithium iodide (LiI)-tetrapropylammonium iodide (TPAI) binary salts system. Addition of BMII to the PhCh-EC-DMF-TPAI-LiI-I2 electrolyte improved the DSSC efficiency. The value of the efficiency enhanced to 6.69 % with the JSC of 16.53 mA cm‾2, VOC of 0.62 V and fill factor of 0.65.

Improvement of Cycle Capability of Fe-Substituted Li2S-Based Positive Electrode Materials by Doping with Lithium Iodide

For an attempt to improve the cycle capability of the Li8FeS5 cells, we have prepared LiI-doped Li8FeS5 composite positive electrode materials. The obtained Li8FeS5·xLiI sample cells showed the improved cycle capability, though the initial capacity value decreased with proportional to the mass of LiI. The improved cycle performance was attributable to the suppressed resistance rise of the cells, due probably to the suppression of high-resistive surface precipitates formed by the reaction between the active material and the electrolyte. The dopant LiI would stabilize the local structure against Li extraction/insertion reactions, as well as suppress the reaction with the electrolyte, leading to the improved cycle performance.

Influence of binary lithium salts on 49% poly(methyl methacrylate) grafted natural rubber based solid polymer electrolytes

Effect of binary lithium salts (lithium tetrafluoroborate, LiBF4 with lithium trifluoromethanesulfonate, LiCF3SO3) and (lithium tetrafluoroborate, LiBF4 with Lithium iodide, LiI) as charge carriers in solid polymer electrolyte based 49% poly(methyl methacrylate) grafted natural rubber (MG49) for Li-ion battery application has been investigated. The polymer electrolytes were prepared by solution casting technique. The effect of binary lithium salts on chemical interaction, structural, thermal studies, ionic conductivity and ion transference number of MG49 films are analyzed by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and electrochemical impedance spectroscopy (EIS). Infrared analysis indicated the interaction occurred between Li ions and oxygen atoms at the carbonyl group (CO) and the ether group (COC) on methyl methacrylate (MMA) segments. XRD studies exhibited a reduction of the MMA peak intensity at 29.5° after the addition of different ratios of binary Li salts due to the plasticizing effect of the salts. The larger anion size tends to create bigger free volume in the polymer electrolyte. In addition, this confirms that the degree of crystallinity of the electrolyte films is reduced leading to enhancement of ionic conductivity. DSC results revealed the highest conductivity sample has the lowest Tg implying the ions can flow with more ease throughout the polymer chain. The ratios of LiBF4:LiI presenting the higher overall performance in terms of ionic conductivity comparing to LiBF4:LiCF3SO3 ratios in MG49. The highest room temperature conductivity was obtained at 1.89 × 10−6 S cm−1 for (30:70) LiBF4:LiI percentages ratio. Moreover, tion is observed to increase with the ionic conductivities.

Nitrogen, phosphorus co-doped carbon cloth as self-standing electrode for lithium-iodine batteries

Rechargeable lithium-iodine (Li-I2) battery is a promising energy storage system because of the high energy and power density. However, the shuttle effects of iodine species and the unstable features of I2 block the practical applications of Li-I2 batteries. Herein, a dual heteroatom doped porous carbon cloth is fabricated as the host material for lithium iodide (LiI). Specifically, the self-standing nitrogen, phosphorus co-doped carbon cloth with high LiI loading exhibits a large specific capacity (221 mAh·g−1 at 1 C), excellent rate capability (95.8% capacity retention at 5 C) and superior long cycling stability (2,000 cycles with a capacity retention of 96%). Electrochemical kinetic analysis confirms the dominant contribution of capacitive effects at high scan rates, which is responsible for the good high-rate performance. The improved electrochemical performance mainly stems from two unique features of nitrogen, phosphorus co-doped porous carbon cloth. Heteroatom doping provides extra active sites for strong adsorption of iodine species while the highly porous structure with large surface area favors the capacitive effects at high rates. This work provides a facile yet efficient approach to regulating both redox reaction and capacitive effects via adjusting surface composition and pore structure of carbon materials for enhanced battery performance.

A Dual Ionic Liquid-Based Low-Temperature Electrolyte System.

Ionic liquids (ILs) show a promising future as electrolytes in electrochemical devices. In particular, IL-based electrolytes bring operations at extreme temperatures to realization that conventional electrolytes fail to accomplish. Although IL electrolytes demonstrate considerable progress in high-temperature applications, their breakthroughs in devices operating at low temperatures are still very limited due to undesirable phase transitions and unsatisfying transport properties. In this study, we present an approach where, by tuning molecular interactions in the system, the designed electrolyte of an IL-based mixture can reach a lower operating temperature with improved transport properties. We have discovered that the incorporation of the IL, ethylammonium nitrate ([EA][N]), can contribute to reforming the molecular interactions within the system, which effectively resolve the crystallization accompanied with the excess of water and retain a low glass transition temperature. The reported liquid electrolyte systems based on a mixture of 1-butyl-3-methylimidazolium iodide ([BMIM][I]), [EA][N], water, and lithium iodide exhibit a glass transition temperature below -105 °C. Furthermore, the optimized electrolyte system shows significant viscosity reduction and ionic conductivity enhancement from 25 to -75 °C. The influence is also noticeable on the increased ionicity, which made the developed electrolyte comparable with other good ILs under the Walden rule. The electrochemical stability of the electrolyte system is revealed by a steady and reproducible profile of iodide/triiodide redox reactions at room temperature over a proper potential window via cyclic voltammetry. The results from this work not only provide a potential solution to applications of the iodide/triiodide redox couple-based electrochemical devices at low temperatures but also show a practical approach to obtain tailored properties of a mixture system via modifying molecular interactions.

Photoiodocarboxylation of Activated C═C Double Bonds with CO2 and Lithium Iodide.

The photolysis at 254 nm of lithium iodide and olefins 1 carrying an electron-withdrawing Z-substituent in CO2-saturated (1 bar) anhydrous acetonitrile at room temperature produces the atom efficient and transition metal-free photoiodocarboxylation of the C═C double bond. The reaction proceeds well for terminal olefins 1 to form the new C-I and C-C σ-bonds at the α and β-positions of the Z-substituent, respectively, and is strongly inhibited by polar protic solvents or additives. The experimental results suggest that the reaction channels through the radical anion [CO2•-] in acetonitrile, yet involves different intermediates in aqueous medium. The stabilizing ion-quadrupole and electron donor-acceptor interactions of CO2 with the iodide anion play a crucial role in the reaction course as they allow CO2 to penetrate the solvation shell of the anion in acetonitrile, but not in water. The reaction paths and the reactive intermediates involved under different conditions are discussed.

Halogen-Mediated Partial Combustion of Methane in Molten Salts To Produce CO2-Free Power and Solid Carbon

The partial oxidation of methane to carbon and steam was investigated in molten salts for a process to produce CO2-free electrical power and solid carbon. Lithium iodide and lithium bromide catalys...

Effect of lithium iodide on the performance of dye sensitized solar cells (DSSC) using poly(ethylene oxide) (PEO)/poly(vinyl alcohol) (PVA) based gel polymer electrolytes

In this work, different concentrations of lithium iodide (LiI) have been added to the gel polymer electrolyte (GPE) containing PEO and PVA in equal ratio, tetrabutylammonium iodide (TBAI), ethylene carbonate (EC), dimethyl sulfoxide (DMSO) and iodine crystals (I2). The effect of introducing lithium iodide (LiI) into PEO-PVA blended GPE system having TBAI has been investigated in terms of optical, electrical, thermal and electrochemical characteristics. Fourier transform infrared (FTIR) spectroscopy has been carried out to study the interaction of LiI with the GPEs. The GPE without LiI showed the highest conductivity of 5.50 mS cm−1 at room temperature. With the incorporation of LiI, decrement in conductivity was observed. Dye-sensitized solar cells (DSSCs) with configuration FTO/TiO2/N3-dye/GPE/Pt/FTO have been fabricated and tested under white light of intensity 100 mW cm−2. The DSSC made of GPE with 1.34 wt% LiI exhibited highest efficiency, η of 6.26%.

Ordered Mesoporous Titanium Nitride As a Promising Carbon-Free Cathode for Aprotic Li-O2 Batteries

Despite the extraordinary gravimetric energy densities, Li-O2 batteries are still facing a technological challenge;[1] limited round trip efficiency leading to insufficient cycle life. Recently, carbonaceous electrode materials were found to be one of the primary origins of the limited cycle life,[2] as they produce irreversible side products during discharge. A few investigations based on noncarbonaceous materials have demonstrated largely suppressed accumulation of irreversible side products,[3] but such studies have focused mainly on the materials themselves rather than delicate morphology control. As such, here, we report the synthesis of mesoporous titanium nitride (m-TiN) with a 2D hexagonal structure and large pores (>30 nm), which was templated by a block copolymer with tunable chain lengths, and introduce it as a stable air-cathode backbone. Due to the well-aligned pore structure and decent electric conductivity of TiN, the battery reaction was quite reversible, resulting in robust cycling performance for over 100 cycles under a voltage cutoff condition. Furthermore, by protecting the Li metal with a poreless polyurethane separator[4] and engaging a lithium iodide redox mediator[3], the original capacity was retained for 280 cycles under a consistent capacity condition (430 mAh/g). This study reveals that when the appropriate structure and material choice of the air-cathode are coupled with an advanced separator and an effective solution-phase redox mediator, the cycle lives of Li-O2 batteries can be enhanced dramatically. Reference s : [1] J. W. Choi, D. Aurbach, Nat. Rev. Mater. 1 (2016) 16013. [2] M.M. Ottakam Thotiyl, S.A. Freunberger, Z. Peng, P.G. Bruce, J. Am. Chem. Soc.135 (2013) 494−500. [3] N. Feng, P. He, H. Zhou, Adv. Energy Mater. 6 (2016) 1502303. [4] B.G. Kim, J. Kim, J. Min, Y. Lee, J.H. Choi, M.C. Jang, S.A. Freunberger, J.W. Choi, Adv. Funct. Mater. 26 (2016) 1747-1756. Figure 1

Improved ionic conductivity in guar gum succinate–based polymer electrolyte membrane

Guar gum succinate (GGS) was chemically modified by reacting guar gum with succinic anhydride in the presence of 4-dimethylaminopyridine. Succination was confirmed by Fourier transform infrared (FTIR) spectroscopy with carbonyl bands at 1724 cm−1 and ester linkage at 1567 cm−1 of the succinate group. The resulting amorphous, GGS was used as a polymer host to prepare cost-effective solid polymer electrolyte (SPE) films via incorporating a blend of ethylene carbonate (EC), carboxymethyl cellulose (CMC), lithium triflate (LiTf) and lithium iodide (LiI). SPE system for GGS:EC (1.0:0.6) with 30 wt% LiTf showed highest conductivity of 6.29 × 10−5 S cm−1 and GGS:CMC:EC (0.5:0.5:0.6) with 25 wt% LiI showed highest conductivity of 2.10 × 10−4 S cm−1. FTIR revealed multiple complexation sites for ion mobility indicating that GGS possesses high prospects as a conductive SPE.

Super P Carbon Modified Lithium Anode for High‐Performance Li−O2 Batteries

AbstractRechargeable Li−O2 batteries represent a highly attractive battery technology, owing to a high theoretical energy density of 3500 Wh kg−1, but they suffer from large charging polarization and lithium anode degradation on cycling. Herein, we report a Li−O2 battery system with reduced polarization and a long lifespan, which is realized by using a novel Li@Super P composite anode integrated with lithium iodide in ether‐based electrolyte. Coating a Super P carbon layer, with an optimal thickness of approximately 30 μm, onto the lithium anode results in a lowered interface impedance and a decreased Li depositing/stripping overpotential (<15 mV) over 300 cycles at 0.3 mA cm−2. The Li−O2 batteries assembled with the Li@Super P anode and LiI additive could mitigate the detrimental shuttling effect of I3− and deliver a high reversible capacity of 1000 mAh g−1 with a median charge voltage lower than 3.3 V after 50 cycles. This study provides a simple yet effective way to protect the lithium anode and design high‐performance Li−O2 batteries.

A novel application for oil palm empty fruit bunch: extraction and modification of cellulose for solid polymer electrolyte

Biopolymer-based materials from renewable sources are the core target of the researchers in modern time. Following this motivation, we have developed solid polymer electrolytes (SPEs) from empty fruit branch (EFB) of oil palm. The cellulose was extracted from EFB and modified to carboxymethyl cellulose (CMC) by its reaction with monochloroacetic acid in a strongly alkaline medium. The samples were characterized by FTIR, 13C NMR, and XRD to confirm the presence of different functional groups, new connectivity, and crystalline/amorphous nature of the materials, respectively. The CMC-based SPEs were fabricated by blending it with different quantities of lithium iodide (LiI) as dopant. The existence of polymer-salt interactions was revealed by FTIR analysis. The maximum ionic conductivity of 5.58 × 10−3 S cm−1 was observed on sample containing 65 wt% LiI with the lowest activation energy of 0.249 eV.

Understanding the Role of Solvent and Added Water on the Effectiveness of Lithium Iodide As a Redox Mediator in Lithium Oxygen Batteries

Lithium iodide has been widely studied as a soluble redox mediator for lithium oxygen batteries in order to help promote more effective charging. Despite this research effort, ambiguities exist regarding the effectiveness of lithium iodide as a redox mediator. In a recent work, we have helped explain how lithium iodide influences the product formed during discharge; shifting from Li2O2, to LiOH, to LiOH-H2O and LiOOH-H2O depending on the amount and chemical environment of water present in the electrolyte. In this work, we provided a detailed framework for understanding how these various discharge products can be oxidized during charge based on solvent properties as well as the amount of water present. The importance of differing interactions between iodide, triioidide and iodine with glyme-based electrolytes with added water is discussed and a number of important behavior transitions at differing water concentrations are uncovered. Figure 1

Cooperative Iodide Pd(0)-Catalysed Coupling of Alkoxyallenes and N-Tosylhydrazones: A Selective Synthesis of Conjugated and Skipped Dienes.

Palladium(0)-catalysed hydro-alkylation or -alkenylation of alkoxyallenes with N-tosylhydrazones gives direct access to conjugated and skipped 1-alkoxydienes with high efficiency and excellent functional-group compatibility. The reaction is proposed to involve the in situ-formed t-butanol as proton source in the key step of the allylpalladium(II) species generation. Moreover, lithium iodide or iodobenzene are employed as an unprecedented iodide (I- ) reservoir to sustain the catalytic cycle.