Methyllithium Research Articles

Decomposition Mechanism of Lithium Methyl Carbonate with Electrolyte in the Solid Electrolyte Interphase to Elucidate the Early Stages of Thermal Runaway in Lithium-Ion Batteries

With the growing demand for electric vehicles, the safety of lithium-ion batteries has been greatly emphasized. Thermal runaway caused by the continuous side reactions inside the battery makes it difficult to extinguish fires caused by abnormal activity. The temperature at which a typical thermal runaway begins is around 100°C, the temperature at which several elements in the solid electrolyte interphase (SEI) layer on the anode surface experience thermal decomposition reactions (causing gas generation and heat production). Therefore, to understand the first stage of thermal runaway and increase battery safety, it is necessary to describe the thermal decomposition process of the SEI layer.To investigate the thermal decomposition process of the SEI layer, it is necessary to understand the various organic components. During the initial charging phase, the reduction reaction between the lithium ions and the electrolyte produces a series of components that make up the SEI layer. On the surface of the anode active material, the SEI layer is a thin layer with an overall thickness of 10-50 nm. It is composed of various organic (inner layer) and inorganic (outer layer) elements. Under thermal stress, the unstable organic SEI layer decomposes into an inorganic SEI layer due to its low stability in the presence of heat and gas generation, which is mostly caused by the decomposition of lithium carbonate (ROCOOLi). It is important to note that the most used electrolytes in batteries today are ethylene carbonate and ethyl methyl carbonate (EMC) dissolved in salts based on lithium hexafluorophosphate. Due to the application of EMC, lithium methyl carbonate (LMC) accounts for more than 50% of the SEI layer in the ROCOOLi compounds.This study used both theoretical and experimental techniques to fully elucidate the pyrolysis process of high-purity synthesized LMC with the electrolyte. First, LMC was chemically synthesized using a nucleophilic substitution reaction. Then, in-situ thermogravimetry analysis (TGA)-mass spectrometer(MS), attenuated total reflectance (ATR)- fourier transform infrared (FTIR), and nuclear magnetic resonance (NMR) results along with bond dissociation energy (BDE)/spectral analysis/energy diagrams obtained by density functional theory (DFT) calculations were analyzed to propose the elementary reaction steps involved in the pyrolysis reaction. We propose six elementary reaction steps for the pyrolysis reaction of LMC. To verify the validity of the proposed basic reaction mechanisms, chain reactions involving radicals generated during pyrolysis were finally calculated using GRI-MECH 3.0, and the calculated results were compared with the composition of the actual gas. We hope to utilize the techniques used in this study to obtain the reaction steps of additional SEI components (LEMC, Li2CO3, etc.). The precise mechanisms obtained through modeling studies can be used to predict the self-heating phase of thermal runaway and to develop materials that can stop the SEI decomposition reaction.

Thermal decomposition mechanism of lithium methyl carbonate in solid electrolyte interphase layer of lithium-ion battery

To predict the early stages of thermal runaway and improve the safety of lithium-ion batteries, it is necessary to examine the elementary reaction steps for the thermal decomposition of individual solid electrolyte interphase (SEI) components. This study elucidates a detailed decomposition mechanism of lithium methyl carbonate (LMC) which is one of SEI components and accounts for the majority of SEI components formed in commercial electrolytes. The detailed reaction mechanism for the thermal decomposition of LMC is proposed based on the in-situ/ex-situ experiments and density functional theory calculations. LMC underwent six reactions before finally converting to Li2CO3 at 300 °C. To supplement the reliability of the proposed reaction mechanism, the actual gas composition measured using mass spectrometry (MS) are compared with the chain reactions of radicals generated through the thermal decomposition reactions, which is calculated using GRI-MECH 3.0, a gas-phase reaction mechanism. The methodology proposed in this study can be used both for analyzing the reaction mechanisms of different SEI components and their coupling effects with the electrolyte in the future. Understanding these reaction mechanism sets will help us to understand the degradation reactions of real complex SEI and the initial self-heating stage during thermal runaway.

Printable Single‐Ion Polymer Nanoparticle Electrolytes for Lithium Batteries

New material solutions are searched for the manufacturing and safety of current batteries. Herein, an extrusion printable polymer separator for lithium batteries based on single‐ion polymer electrolytes is presented. The polymer electrolytes are based on methacrylic polymeric nanoparticles (NPs) functionalized with a lithium sulfonamide group combined with different organic plasticizers such as sulfolane and carbonates. The synthesis of the polymer NPs is carried out by emulsion copolymerization of methyl methacrylate and lithium sulfonamide methacrylate in the presence of a crosslinker, resulting in particle sizes of less than 30 nm, as shown by electron microscopy. Then polymer electrolytes are prepared by mixing polymer NPs with varying lithium sulfonamide content and different plasticizers such as carbonates and sulfolane. The polymer electrolytes show ionic conductivities between 2.9 × 10−4 and 2.3 × 10−5 S cm−1 at 85 °C with the highest values for the small‐sized NPs with the highest lithium content. As a proof‐of‐concept application, layer‐by‐layer printing of a sulfolane‐based polymer electrolyte is evaluated via direct ink writing directly onto classic battery electrodes. The electrochemical characterization of the printed solid electrolyte indicates favorable properties, ionic conductivity, lithium transfer number, electrochemical stability window, and cyclability in lithium symmetrical cells, to be used in lithium batteries.

Synthesis and trapping of spiro [bicyclo[4.2.0]octa-2,3-diene-7,2'-[1,3]dioxolane

Spiro[bicyclo[3.2.0]hept-2-ene-6,2'-[1,3]dioxolane] was synthesized by the reaction of bicyclo[3.2.0]hept-2-en-6-one with ethylene glycol in yield of 92%. Addition of dichlorocarbene to Spiro[bicyclo[3.2.0]hept-2-ene-6,2'-[1,3]dioxolane] gave the 3',3'-Dichlorospiro[1,3-dioxolane-2,7'-tricyclo[4.2.0.02,4]octane] in 50 % yields. Finally, the 3',3'-Dichlorospiro[1,3-dioxolane-2,7'-tricyclo[4.2.0.02,4]octane] was submitted to Doering-Moore-Skatebol reaction for the synthesis of allene precursors. The reaction of the 3',3'-Dichlorospiro[1,3-dioxolane-2,7'-tricyclo[4.2.0.02,4] octane] with methyl lithium (MeLi) in the presence of 1,3-diphenylisobenzofuran (DBI) as a trapping reagent under a nitrogen atmosphere at ca. 0 ℃ was started and continued at room temperature for four hours, resulting in the formation of four cyclo adduct isomers of spiro[bicyclo[4.2.0]octa-2,3-diene-7,2'-[1,3]dioxolane].

Gradual Coordination and Reversible P-P Bond Activation of a P3 -Unit with Transition Metal Carbonyls.

Coordination of a stereochemically defined P3 -chain to a series of transition metal carbonyls [M(CO)x ]z- (M=Mn (x=5, z=1), Fe (x=4, z=2) or Co (x=4, z=1)) is explored using a [3]ferrocenophane scaffold. A gradual transition from η1 -, η2 - toη3 -coordination is observed where in the η2 -mode the terminal positions of the phosphorus chain are bridged. With an excess of cobalt carbonyl successive P-P bond activation and gradual separation of the central phosphorus atoms from the phosphorus chain has been observed. This process is reversible and with suitable reagents such as methyl lithium, the P3 -unit is regenerated in stereospecific manner. The bonding situation and steps of the gradual P-P bond activation are investigated by DFT calculations as well as experimental methods (e.g., NMR spectroscopy, X-ray crystallography).

Construction of quaternary stereocenters at carbon 2′ of nucleosides

The non-natural nucleosides with a quaternary stereogenic center at C2′ are crucial to drug discovery. They have become a cornerstone for the treatment of cancer and various viral infections as exemplified by gemcitabine and sofosbuvir. Major research effort has been expended to gain synthetic access to these nucleoside analogues with a significant steric bulk at C2′ in the furanoside ring. The 2′-ketonucleosides and 2′-deoxy-2′-methylenenucleosides emerged as key intermediates in these synthetic strategies. For example, α-face addition of methyl lithium to the 2′-ketonucleosides followed by fluorination of resulting tertiary arabino alcohol with DAST provided 2′-fluoro-2′-C-methyluridine - a core nucleoside component of sofosbuvir. The α-face addition of HCN or HN3 to the 2′-deoxy-2′-methylene nucleosides gave access to the synthetically versatile 2′-cyano-2′-C-methyl and 2′-azido-2′-C-methyl nucleosides. Likewise, the addition of diazomethane to the 2′-exomethylene group gave access to the 2′-spirocyclopropyl analogue. This review primarily discusses synthetic strategies which employs natural nucleosides as substrates but selected approaches involving coupling of the preelaborated sugar precursors with nucleobases are also examined.

Synthesis of BI 894416 and BI 1342561, two potent and selective spleen tyrosine kinase inhibitors, labeled with carbon 14 and with deuterium.

(R)-4-((R)-1-((6-(1-[tert-butyl]-1H-pyrazol-4-yl)-2-methyl-2H-pyrazolo[3,4-d]pyridin-4-yl)oxy)ethyl)pyrrolidin-2-one (BI 894416, 1) and (R)-4-((R)-1-((6-(1-[tert-butyl]-1H-pyrazol-4-yl)-2,3-dimethyl-2H-indazol-4-yl)oxy)ethyl)pyrrolidin-2-one (BI 1342561, 2) are two new potent and selective spleen tyrosine kinase inhibitors developed to treat severe asthma. Both compounds have similar structures and they differ only in the bicyclic moiety 2-methyl-2H-pyrazolo[4,3-c]pyridine in 1 versus 2,3-dimethyl-2H-indazole in 2. In the carbon 14 synthesis, 1-(1-[tert-butyl]-1H-pyrazol-4-yl)ethan-1-one-1-14 C ([14 C]-8) was prepared from the cyanation of 4-bromopyrazole using zinc [14 C]cyanide followed by methyl lithium addition on the nitrile group. The enolate of [14 C]-8 was then used to access these two bicyclic moieties via pyrano-pyrazoles [14 C]-11 and [14 C]-12, which were further transformed in few more steps to [14 C]-(1) and [14 C]-2. Both inhibitors contain a tert-butyl group. Introducing tert-butyl-d9 will not only provide internal standards for bioanalytical studies, but it is also expected to slow down the metabolism of these two compounds. Most of the metabolites of compound 1, for example, are the result of tert-butyl oxidation, like alcohol 3, acid 4, and the further N-demethylation of 4 to 5. The detailed preparation of these deuterium-labeled metabolites is also described.

Synthesis and Characterization of Zr and Hf Triazenido Complexes with Rare κ1N-Coordination Built Directly in the Coordination Sphere of the Metal

The synthesis and characterization of triazenido complexes of the group IV metals zirconium and hafnium is reported. The reaction of the group IV pentafulvene complexes Cp*(π–η5:σ–η1-pentafulvene)-zirconium(IV) and -hafnium(IV)chlorides with the sterically demanding 2,6-dimesitylphenyl azide results in the insertion of the γ-nitrogen atom of the ligand precursor into the polarized M–Cexo (Cexo: exocyclic carbon atom) bond of the pentafulvene ligand, forming a formal Cp,N,N tridentate ligand system. The molecular structures of the furnished complexes reveal the rare κ1N coordination of the γ-nitrogen atom to the zirconium or hafnium center along with a localized Nα–Nβ double bond. Unusually, in one case, the ligand system shows additional coordination of the α-nitrogen atom to the central metal atom and well-balanced N–N distances, thus, forming the chelating κ2N,N coordination mode of the triazenido ligand. The potential use of the formed complexes as precursors for cationic group IV cationic complexes was investigated by reaction with methyl lithium.

Niobium Bis‐ and Mono(Pentafulvene) Complexes: E−H Bond Cleavage and Insertion Reactions (E=C, N, O)

AbstractBis(η5:η1‐(di‐para‐tolyl)pentafulvene)niobium chloride (1) reacts with methyl lithium via salt metathesis to the methylated bis(pentafulvene)niobium complex 2, and with lithium 2,6‐diisopropylanilide addition and subsequent N−H bond activation to the imido mono(pentafulvene)niobium complex 3. Avoiding the competing protonation of the chloride, bis(pentafulvene)niobium complex 2 reacts with primary aromatic and aliphatic amines to form terminal niobocene imido complexes, and with water to form the analog terminal oxo complex. Secondary methyl amines undergo a simultaneous N−H and C−H activation to form niobaaziridines under mild conditions. In contrast to other reported examples, 3 can be employed to investigate the uncontested reactivity of mono(pentafulvene)niobium complexes. Reaction with 4‐tert‐butylphenol selectively yields a niobocene phenolate complex. Unprecedented for mono(pentafulvene)niobium complexes, treating 3 with multiple‐bond‐containing substrates (nitriles, isocyanates) smoothly results the insertion into the Nb‐Cexo σ‐bond, forming the corresponding alkylidene amido and imidato complexes.

Methyl Carbamate‐Lithium Salt Deep Eutectic Electrolyte for Lithium‐Ion Batteries

AbstractDeep eutectic electrolytes (DEEs) represent a burgeoning field in electrolytes for energy storage applications. Compared to the more conventionally studied Li‐ion electrolyte systems, these electrolytes offer numerous advantages, such as high ion concentration, costs, lower temperature operation, and safety. In this work, the formation of a novel eutectic electrolyte based on lithium salts and methyl carbamate was reported. These DEEs were formed via mixing lithium salts and low‐cost methyl carbamate at ratios varying from 1 : 2 to 1 : 5 (mol:mol). The DEE formed from methyl carbamate and lithium hexafluorophosphate (LiPF6) at a 1 : 5 molar ratio generated a 4V stability window and a 25 °C conductivity of up to 3.16E−3 S cm−1. The DEE formed from methyl carbamate and lithium bis(trifluoromethane)sulfonimide (LiTFSI) at a 1 : 5 molar ratio generated a 3.2 V stability window and a 25 °C conductivity of up to 2.87E−3 S cm−1. The LiPF6 DEE also demonstrated a discharge capacity of 128 mAh g−1after 50 cycles with 93 % discharge capacity retention at moderate cycling rates of 0.5C in a lithium titanate (LTO)/lithium iron phosphate (LFP) full cell. These results demonstrate the potential for methyl carbamate to generate eutectics from lithium salts and offer alternative electrolytes for use in low‐temperature Li‐ion battery applications.

Single Component Protection Layers for Lithium Electrodes and Their Characterization in Lithium Metal Batteries

State-of-the art Lithium-ion batteries (LIBs) based on graphite intercalation compound (GIC) are reaching their theoretical energy density limits. Therefore, it has become prerequisite to implement active materials with higher specific energies.[1] In this direction, Lithium (Li) has reignited research interest mainly due to its high theoretical specific capacity (3860 mAh/g) and the lowest negative potential (-3.040 V vs. SHE). Many of the advantages are shadowed by its poor electrodeposition properties with the formation of high surface area lithium (HSAL) and continuous electrolyte consumption resulting in a solid electrolyte interphase (SEI) with inhomogeneous composition which still limits the practical application of Li metal electrodes in Lithium metal batteries (LMBs).[2] Overall, several published strategies can be summarized into improving the electrolyte with additives, development of 3D hosts or interface engineering by covering Li with a protective coating layer. An artificial protection layer on Lithium metal requires tuned characteristics to withstand the harsh conditions during cycling. Therefore, it is obligate for these coatings to fulfil several requirements, among many i) mechanical suppression of dendrites, ii) high Li-ion selectivity and conductivity and iii) chemical passivation against the liquid electrolytes, are mostly encountered with artificial SEI.[3],[4] In a recent study an in-situ generated lithium methyl carbonate (LMC) layer on the Li metal electrode was able to protect its surface by generating a homogeneous Li-ion flux and decreasing the electrolyte consumption process during cycling. This approach also enhanced the current distribution and effectively suppressed the lithium dendrite formation during the electrodeposition and -dissolution process. [5],[6] Herein, the LMC layer, synthesized and purified in order to exclude the presence of any halides, was coated on the surface of the Li metal electrode using an ex-situ procedure. Its characterization and the effect of LMC on the electrochemical performance of the coated Li metal electrode especially during the Li electrodeposition/dissolution process will be presented. Li metal electrodes coated with a dense LMC layer showed decreased overvoltages during the Li electrodeposition/dissolution process and reduced interfacial resistance as compared to uncoated Li metal electrodes. Beside its role as a protective layer, LMC was also employed as electrolyte additive due to its known solubility in carbonate-based electrolytes. Using ionic chromatography (IC) to investigate the electrolyte after cycling and cryo-SEM cross-section of the cycled Li metal electrodes, further characteristic properties of these LMC coating layers on Li metal electrodes will be revealed.[1] Placke, T.; Kloepsch, R.; Dühnen, S.; Winter, M., Journal of Solid State Electrochemistry 2017, 21, 1939-1964[2] Aurbach, D.; Zinigrad, E.; Cohen, Y.; Teller, H., Solid State Ionics 2002, 148, 405-416.[3] Kang, D.; Xiao, M.; Lemmon, J. P., Batteries & Supercaps 2021, 4, 445.[4] Yu, Z.; Cui, Y.; Bao Z., Cell Reports Physical Science, 2020 7, 100119.[5] Liu, H.; Zhou, H.; Lee, B., ACS Applied Materials and Interfaces 2017, 36, 30635-30642.[6] Liu, H.; Wang, X.; Zhou, H., ACS Applied Materials and Interfaces 2018, 5, 1864-1869.

A monomeric (trimethylsilyl)methyl lithium complex: synthesis, structure, decomposition and preliminary reactivity studies.

Monomeric organolithium (LiR) complexes could provide enhanced Li-C bond reactivity and suggest mechanisms for a plethora of LiR-mediated reactions. They are highly sought-after but remain a synthetic challenge for organometallic chemists. In this work, we report the synthesis and characterisation of a monomeric (trimethylsilyl)methyl lithium complex, namely [Li(CH2SiMe3)(κ3-N,N',N''-Me6Tren)] (1), where Me6Tren is a tetradentate neutral amine ligand. The structure of 1 was comprehensively examined by single-crystal X-ray diffraction, variable temperature NMR spectroscopy and electron absorption spectroscopy. Complex 1 decomposes via ligand C-H and C-N activations to produce a Li amide complex 2. Preliminary reactivity studies of 1 reveal CO insertion and C-H activation reaction patterns.

Solvent-Free Procedure to Prepare Ion Liquid-Immobilized Gel Polymer Electrolytes Containing Li0.33La0.56TiO3 with High Performance for Lithium-Ion Batteries.

Based on the advantages of intrinsic safety, flexibility, and good interfacial contact with electrodes, a gel polymer electrolyte (GPE) is a promising electrolyte for lithium-ion batteries, compared with the conventional liquid electrolyte. However, the unstable electrochemical performance and the liquid state in a microscale limit the commercial application of GPE. Herein, we developed a novel gel polymer electrolyte for lithium-ion batteries by blending methyl methacrylate (MMA), N-butyl-N-methyl-piperidinium (Pyr14TFSI), and lithium salts in a solvent-free procedure, with SiO2 and Li0.33La0.56TiO3 (LLTO) additives. The prepared MMA-Pyr14TFSI-3 wt % LLTO electrolyte shows the best electrochemical performance and obtains a high ion conductivity of 4.51 × 10–3 S cm–1 at a temperature of 60 °C. Notably, the electrochemical window could be stable up to 5.0 V vs Li+/Li. Moreover, the batteries with the GPE also show excellent electrochemical performance. In the LiFePO4/MMA-Pyr14TFSI-3 wt % LLTO/Li cell, a high initial discharge capacity was achieved 150 mA h g–1 at 0.5C with a Coulombic efficiency over 99% and maintaining a good capacity retention of 90.7% after 100 cycles at 0.5C under 60 °C. In addition, the physical properties of the GPE have been investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) measurements, Fourier transform infrared (FTIR) spectroscopy, and thermogravimetry (TG).

10 μm-Thick High-Strength Solid Polymer Electrolytes with Excellent Interface Compatibility for Flexible All-Solid-State Lithium-Metal Batteries.

An ultrathin solid polymer electrolyte (SPE) consisting of modified polyethylene (PE) as the host and poly(ethylene glycol) methyl ether acrylate and lithium salts as fillers is presented. The porous poly(methyl methacrylate)-polystyrene interface layers closely attached on both sides of the PE effectively improve the interface compatibility among electrolytes and electrodes. The resultant 10 μm-thick SPEs possess an ultrahigh ionic conductance of 34.84mS at room temperature and excellent mechanical properties of 103.0MPa with elongation up to 142.3%. The Li//Li symmetric cell employing an optimized solid electrolyte can stably cycle more than 1500h at 60°C. Moreover, the LiFePO4 //Li pouch cell can stably cycle over 1000 cycles at 1C rate and with a capacity retention of 76.4% from 148.9 to 113.7mAhg-1 at 60°C. The LiCoO2 //Li pouch cell can stably operate at 0.1 and 0.2C rate for each 100 cycles. Furthermore, the LiFePO4 //Li pouch cell can work stably after curling and folding, which proves its excellent flexibility and safety simultaneously. This work offers a promising strategy to realize ultrathinness, excellent compatibility, high strength, as well as safe solid electrolytes for all-solid-state lithium-metal batteries.

(A04 Best Poster Award Winner) Formation Mechanism and Stability of Solid Electrolyte Interphases in Linear Carbonate-Based Electrolytes

Broad application of lithium batteries, necessitates improvements in their safety, cycle life, durability and energy density. Clear understanding of the electrode/electrolyte interfaces is one of the important factors in designing batteries with enhanced performance. Linear organic solvents are extensively used in electrolytes of lithium batteries to reduce viscosity and melting temperature of cyclic carbonates. However, these organic compounds are not stable in contact with anode, leading to decomposition of the electrolyte and formation of Solid Electrolyte Interphase (SEI). Although SEI is proven to be one of the most important parts of batteries, its structural complexity, mechanism of formation, and properties are not completely understood yet. In this work, we consider mechanism of formation and stability of SEIs composed of redox products of linear carbonate solvents. So far, the main focus of research was on decomposition products of cyclic carbonates. In case of linear carbonates, the SEI stability consideration is limited to the systems being in DMC solvent and to the best of our knowledge, there are no theoretical investigations on linear carbonate-based SEIs formation mechanism and properties.In this work, we study Lithium Methyl Carbonate (LMC), Lithium Ethyl Carbonate (LEC) and Lithium Propyl Carbonate (LPC), which are single-electron reduction products of carbonate solvents in contact with the electrode, in their corresponding solvents being Dilithium Methyl Carbonate (DMC), Dilithium Ethyl Carbonate (DEC) and Dilithium Propyl Carbonate (DPC), respectively (Figure 1). Our aim is to chemically, kinetically, and thermodynamically study the aggregation, formation and stability of SEI layer in these systems from experimental, Molecular Dynamics (MD) simulation and Density Functional Theory (DFT) calculation points of view. Our study indicates that in LMC/DMC mixture LMC molecules have strong tendency to self-assemble and have low barriers to undergo second-electron reduction to form stable Li2CO3. Stable SEI was also observed in LPC/DPC as well, which is believed to be a result of slow dynamics of larger molecules and therefore increased possibility of the second-electron reduction near electrode surface. In the LEC/DEC system, however, we did not observe a stable SEI formation due to low tendency of LEC molecules to self-assemble, low electronic affinity coupled with high energy barrier for possible second electron reduction reaction. Therefore, our work illustrates that the selection of the linear carbonate as a blending partner for cyclic carbonates, might have an important impact on the ability of electrolyte to form stable and compact SEI layer. Figure 1

(Invited) Structural Chemistry of Battery Materials: Metal Oxide Open Frameworks and Li Salts

For several decades, since the discovery of the lithium batteries, the search for novel and improving existing cathode materials and other components of the rechargeable batteries became one of the top priorities of modern technology. In order to develop novel materials, establish structure-property relationship, and find more effective synthetic routes, the knowledge of the crystal structure and comprehensive understanding of the structural changes during battery performance are of the utmost importance.This presentation is based on our more than decade long research on crystallography and structural chemistry of battery materials [1], as well as Li salts and their solvates, conducted in the Institute for Materials Research at Binghamton University. The crystal structure of several dozens of novel compounds has been determined from the powder and single crystal diffraction data. The obtained structural information was used: to analyze the relationship between different structure types for vanadium oxide open frameworks [2]; to establish structural changes or the phase transition during the intercalation and deintercalation processes for an electrochemical cell in Li-VOPO4 systems [3]; to study the role of pH in the synthesis of the vanadium oxide frameworks and their structure types [4,5]; and to link the red-ox properties with the coordination of the transition metal [2]. Theoretical crystal-chemical analysis of open framework structures allowed us not only to understand known structures and establish a relationship between them but also to deduct and predict new structures. For example, it was possible to deduct 4 possible types of V3O7 layers, only 2 of which were known (tmaV3O7 [4] and [en 2Ni]V6O14 [6], tma – tetramethylammonium, en – ethylenediamine), and to predict ordered version (V5O11) of disordered “VO2” layer discovered in LixV1-yO2-y.nH2O (y = ~1/6) compound [7]. When new lithium bis-oxalatoborate (BOB) salt Li[(C2O4)B(C2O4)] was considered for use in the batteries, we have determined its crystal structure from powder diffraction data along with structure of sodium and potassium BOB salts that was quite challenging due to pseudo-hexagonal LiBOB lattice [8]. Recrystallization of LiBOB from the solvent used in the electrochemical cell resulted in solvates with water, acetonitrile, acetone, dimethoxyethylene, 1,3-dioxolane, ethylenecarbonate which crystal structures were determined and are discussed in [9].Recently the crystal structure determination was successfully performed for several important Li salts: lithium ethylene mono-carbonate (EMC), lithium methyl carbonate (MC) [10], and lithium acetylacetone oxalate borate Li[(acac)B(C2O4)] [11]. Interestingly LiEMC structure resulted from the compound that was for quite a while claimed to be Li salt with ethylene dicarbonate (EDC). M.S. Whittingham, Solid State Ionics, 134(1-2), 169-178 (2000); M.S. Whittingham, Chemical reviews, 104(10), 4271-4302 (2004).P.Y. Zavalij and M.S. Whittingham, Acta Cryst., B55, 627-663 (1999).Y. Song, P.Y. Zavalij, and M.S. Whittingham, J. Electrochem. Soc., 152, A721-A728 (2005).T.G. Chirayil, E.A. Boylan, M. Mamak, P.Y. Zavalij, and M.S. Whittingham, Chem. Comm., 33-34 (1997).T. Chirayil, P.Y. Zavalij, and M.S. Whittingham, Chem. Mater., 10, 2629-2640 (1998).P.Y. Zavalij, F. Zhang, and M.S. Whittingham, Acta Cryst., B55, 953-962 (1999).T. Chirayil, P. Zavalij, and M.S. Whittingham, Solid State Ionics, 84, 163-168 (1996).P.Y. Zavalij, S. Yang, and M.S. Whittingham, Acta Cryst., B59, 753–759 (2003).P.Y. Zavalij, S. Yang, and M.S. Whittingham, Acta Cryst., B60, 716-724 (2004).L. Wang, A. Menakath, F. Han, Y. Wang, P.Y. Zavalij, D. Iuga, S.P. Brown, C. Wang, K. Xu, and B.W. Eichhorn, Nature Chem., 11(9), 789-796 (2019).P.Y. Zavalij, L. Wang, and B.W. Eichhorn, CCDC (2019), doi: 10.5517/ccdc.csd.cc22h53w.

Effect of Additives on the Performance of PPBES Composite Forward Osmosis Hollow Fiber Membranes.

A polyamide composite forward osmosis (FO) hollow fiber membrane was successfully prepared with a novel copoly(phthalazinone biphenyl ether sulfone) (PPBES) polymer. Effects of different additives including ethylene glycol methyl ether (EGME) and lithium chloride anhydrous (LiCl) in the dope solution on the morphologies and properties of PPBES support membranes and composite FO hollow fiber membranes were investigated. With the increase of EGME content in the dope solution, the water flux of PPBES support membranes and FO hollow fiber membranes decreased. When LiCl was added into the dope solution, the water flux of FO hollow fiber membranes improved significantly with the increase of LiCl content. Additionally, the FO performance of the PPBES membrane was further optimized by adding triethylamine (TEA) in the interfacial polymerization (IP) process. In comparison with other FO membranes, the novel PPBES composite FO hollow fiber membrane displayed a remarkably high water flux of 45.3 L/m2 h and a low specific reverse salt flux of 0.15 g/L.

C-Methylation of Organic Substrates: A Comprehensive Overview. Part II—Methyl Metals as Methylating Agents

C-Methylation of organic substrates was achieved with a number of methyl metals, including trimethylaluminum (Me3Al), trimethylgallium (Me3Ga), trimethylindium (Me3In), dimethylzinc (Me2Zn), methyl zinc halide (MeZnX), methylboranes (MeBRR’), methylboronic acid (MeB(OH)2), methylboronates (MeB(OR)2), methylcopper (MeCu), methyllithium cuprate (Me2CuLi), methylmagnesium halides (MeMgX), tetramethyltin (Me4Sn), methyl lithium, and lead tetraacetate. Most of the related reactions required the presence of transition metal complexes as catalysts and phosphine ligands. Overall, the yields of the methylated products actually depended on the types of used catalyst and ligand. In some instances, additives were needed as specific promoters, such as p-benzoquinone in the methylation through coupling with methyl boron agents. Best of all, methylation of substrates with some of these methylating agents occurred with some features. For example, asymmetric reactions of carbonyl compounds could be accomplished using dimethyzinc along with a specific ligand, leading to moderate to excellent yields of the major enantiomer with high enantiomeric excess. Ortho-methylation regioselectively occurred on aromatic substrates when they bear moieties such as heteroarenes (pyridine), amide, azomethine, oxazoline, N-nitrosoamine, oxime, coined ‘ortho-directing groups’.

Ceramic-Doped in Cross-Linked Solid Polymer Electrolyte for Solid-State Batteries

Replacing liquid electrolytes with solid-state Li-ion conductors is one way to achieve safe rechargeable batteries with high energy density. Semi-interpenetrating polymer network (s-IPN) was synthesized from the mixture of poly(propylene carbonate), poly(ethylene glycol) methyl ether acrylate, poly(ethylene glycol) diacrylate (PEGDA), and lithium bis(trifluoromethane)sulfonamide salt via one-pot thermal curing method. The crosslinker PEGDA content and salt concentration were optimized and the best result was abtained at a molar ratio of EO:Li ∼ 14:1. The electrolyte with higher salt concentration had lower ionic conductivity, consistent with higher glass transition temperature of poly(ethylene glycol) chain. Differential scanning calorimetry has shown a low degree of crystallinity when lithium lanthanum zirconate doped tantalum (LLZTO) was added to the s- IPN electrolyte which corresponds to an increase in ionic conductivity, 4.5 x 10-4 S/cm at 40°C. The resulting composite polymer electrolyte (CPE) showed high electrochemical stability up to 5.5 V. Lithium plating and stripping at 0.1 mA/cm2 at room temperature revealed a stable Li/electrolyte interface and no dendrite formation. Cycling performance of a full solid-state cell made with the CPE using LiFePO4 as the cathode will be discussed. Figure 1

Formation Mechanism and Stability of Solid Electrolyte Interphases in Linear Carbonate-Based Electrolytes

Broad application of lithium batteries, necessitates improvements in their safety, cycle life, durability and energy density. Clear understanding of the electrode/electrolyte interfaces is one of the important factors in designing batteries with enhanced performance. Linear organic solvents are extensively used in electrolytes of lithium batteries to reduce viscosity and melting temperature of cyclic carbonates. However, these organic compounds are not stable in contact with anode, leading to decomposition of the electrolyte and formation of Solid Electrolyte Interphase (SEI). Although SEI is proven to be one of the most important parts of batteries, its structural complexity, mechanism of formation, and properties are not completely understood yet. In this work, we consider mechanism of formation and stability of SEIs composed of redox products of linear carbonate solvents. So far, the main focus of research was on decomposition products of cyclic carbonates. In case of linear carbonates, the SEI stability consideration is limited to the systems being in DMC solvent and to the best of our knowledge, there are no theoretical investigations on linear carbonate-based SEIs formation mechanism and properties.In this work, we study Lithium Methyl Carbonate (LMC), Lithium Ethyl Carbonate (LEC) and Lithium Propyl Carbonate (LPC), which are single-electron reduction products of carbonate solvents in contact with the electrode, in their corresponding solvents being Dilithium Methyl Carbonate (DMC), Dilithium Ethyl Carbonate (DEC) and Dilithium Propyl Carbonate (DPC), respectively (Figure 1). Our aim is to chemically, kinetically, and thermodynamically study the aggregation, formation and stability of SEI layer in these systems from experimental, Molecular Dynamics (MD) simulation and Density Functional Theory (DFT) calculation points of view. Our study indicates that in LMC/DMC mixture LMC molecules have strong tendency to self-assemble and have low barriers to undergo second-electron reduction to form stable Li2CO3. Stable SEI was also observed in LPC/DPC as well, which is believed to be a result of slow dynamics of larger molecules and therefore increased possibility of the second-electron reduction near electrode surface. In the LEC/DEC system, however, we did not observe a stable SEI formation due to low tendency of LEC molecules to self-assemble, low electronic affinity coupled with high energy barrier for possible second electron reduction reaction. Therefore, our work illustrates that the selection of the linear carbonate as a blending partner for cyclic carbonates, might have an important impact on the ability of electrolyte to form stable and compact SEI layer. Figure 1. Carbonate solvents and components studied in this work. Figure 1