Lithium Tetrakis Research Articles

A fluorine rich borate ionic additive enabling high-voltage Li metal batteries

Lithium-metal batteries (LMBs) are promising alternatives to state-of-the-art Lithium-ion batteries (LIBs) to achieve higher energy densities. However, the poor cyclability of LMBs resulting from Li metal anode (Li0) irreversibility and concomitant electrolyte decompositions limits their practical applications. In this study, we reported a per-fluorinated salt, lithium tetrakis(perfluoro-tertbutyloxy)borate (abbreviated as Li-TFOB) as an electrolyte additive for Li-metal batteries, which contains 36 F atoms per molecule. This newly designed ionic additive tuned the chemical composition of the solid-electrolyte interphase (SEI) on Li0 by increasing the amount of LiF and Li-B-O inorganic species. DFT calculations and Molecular dynamics (MD) simulations indicated the preferential reduction of the TFOB anions at Li0, which occurs with a lower free energy change than PF6− anions. The designed ionic additive enables the 4.6 V Li||LiNi0.6Mn0.2Co0.2O2 (NMC622) cell to achieve an average CE of 99.1 % and a high-capacity retention of > 50 % after 500 cycles. This experiment-simulation joint study illustrated an attractive approach to accelerating the design of electrolytes and interphases for LMBs.

An Update on Phosphine‐Imidazolin‐2‐Imine Iridium(I) Catalysts for Hydrogen Isotope Exchange

AbstractThe reaction of the bidentate P,N ligand [2‐(1,3,4,5‐tetramethylimidazolin‐2‐imino)phenyl]di‐tert‐butylphosphine (1) with [Ir(COD)Cl]2 (COD=1,5‐cyclooctadiene) followed by addition of sodium tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate, NaBArF24, or lithium tetrakis(nonafluoro‐tert‐butoxy)aluminate, Li[Al{OC(CF3)3}4], afforded the complexes [(1)Ir(COD)][BArF24] (2 a) and [(1)Ir(COD)][Al{OC(CF3)3}4] (2 b). Exposure of 2 b to one atmosphere of dihydrogen gas afforded the diiridium tetrahydride [(1)2Ir2H4][Al{OC(CF3)3}4]2 (3 b). The molecular structures of 2 a, 2 b, and 3 b were determined by single‐crystal X‐ray diffraction analyses. In the latter complex, the positions of the hydrogen atoms in the Ir2H4 core could be refined freely, which had previously proved impossible for the corresponding complex 3 a containing the BArF24 anion. Since 2 a is an established catalyst for ortho‐directed hydrogen isotope exchange (HIE), the performance of 2 a and 2 b in deuterium labelling reactions was compared for various substrates, including phenylacetic acid derivates and nitrogen‐containing aromatic compounds.magnified image

A Single‐Ion Conducting Network as Rationally Coordinating Polymer Electrolyte for Solid‐State Li Metal Batteries

AbstractSolid state single‐ion conducting polymer electrolytes (SSPEs) are one of the most promising candidates for long‐life lithium‐metal batteries. However, the traditional polyanion‐type structure of SSPEs inevitably gives rise to insufficient conductivity and inferior mechanical stability, which limits their practical application. Herein, an interpenetrating single‐ion network polymer (PTF‐4EO) is fabricated by crosslinking lithium tetrakis(4‐(chloromethyl)‐2,3,5,6‐tetrafluorophenyl)borate salt with tetraethylene glycol. The unique structure enables a PTF‐4EO with weakly interacting anions and coordinating ether oxygen segments that functions as a high‐performing SSPE, that delivers a high room‐temperature conductivity of 3.53 × 10−4 S cm−1, exceptional superior lithium‐ion transference number of 0.92, wide electrochemical window > 4.8 V, and good mechanical properties. Moreover, the resultant SSPE can directly participate in constructing a favorable Janus solid electrolyte interphase, which further enhances the interfacial stability of the metallic lithium anode. The as‐assembled LiFePO4||Li solid batteries present prominent cycling stability, coulombic efficiency, and capacity retention over 200 cycles between 2.50 and 4.25 V. Furthermore, LiNi0.7Mn0.2Co0.1O2||Li pouch cells exhibit remarkable safety even under harsh conditions. This study thereby offers a promising strategy for SSPE design to simultaneously achieve high ionic conductivity and good interfacial compatibility toward practical high‐energy‐density solid‐state lithium metal batteries.

A Stable Solid Electrolyte Interphase for Magnesium Metal Anode Evolved from a Bulky Anion Lithium Salt.

Rechargeable magnesium (Mg) metal batteries are a promising candidate for "post-Li-ion batteries" due to their high capacity, high abundance, and most importantly, highly reversible and dendrite-free Mg metal anode. However, the formation of passivating surface film rather than Mg2+ -conducting solid electrolyte interphase (SEI) on Mg anode surface has always restricted the development of rechargeable Mg batteries. A stable SEI is constructed on the surface of Mg metal anode by the partial decomposition of a pristine Li electrolyte in the electrochemical process. This Li electrolyte is easily prepared by dissolving lithium tetrakis(hexafluoroisopropyloxy)borate (Li[B(hfip)4 ]) in dimethoxyethane. It is noteworthy that Mg2+ can be directly introduced into this Li electrolyte during the initial electrochemical cycles for in situ forming a hybrid Mg2+ /Li+ electrolyte, and then the cycled electrolyte can conduct Mg-ion smoothly. The existence of this as-formed SEI blocks the further parasitic reaction of Mg metal anode with electrolyte and enables this electrolyte enduring long-term electrochemical cycles stably. This approach of constructing superior SEI on Mg anode surface and exploiting novel Mg electrolyte provides a new avenue for practical application of high-performance rechargeable Mg batteries.

Ionic Porous Organic Polymers Based on Functionalized Tetraarylborates.

Lithium tetrakis(4-boronatoaryl)borates were subjected to polycondensation reactions with selected polyhydroxyl monomers such as 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) and 2,3,6,7-tetrahydroxy-9,10-dimethylanthracene (THDMA). Obtained boronate-type ionic porous polymers TAB1–4 were characterized by PXRD, 6Li and 11B magic-angle spinning nuclear magnetic resonance (MAS NMR), FT-IR, SEM, and TGA. They exhibit relatively good sorption of H2 (up to 75 cm3/g STP), whereas N2 uptake at 77 K for lower pressure range is relatively poor (up to 50 cm3/g STP below P/P0 = 0.8). In addition, the effect of elongation of aryl arms in the tetraarylborate core on the materials’ properties was studied. Thus, it was found that replacement of the 4-boronatophenyl with 4-boronatobiphenylyl group has a negative impact on the sorption characteristics.

Anionic multiblock copolymer membrane based on vinyl addition polymerization of norbornenes: Applications in anion-exchange membrane fuel cells

Stable, non-hydrolysable, hydroxide-conducting polymers are of interest for electrochemical devices such as fuel cells, electrolyzers and flow-batteries. In this study, a series of tetrablock copolymers containing an all-hydrocarbon backbone were synthesized. The synthesis is based on vinyl addition polymerization of norbornene using (η3-allyl)Pd(iPr3P)Cl as the catalyst and lithium tetrakis(pentafluorophenyl)-borate·(2.5Et2O) (Li[FABA]) as the activator. The tetrablock polymers were cast into membranes with an ion-exchange capacity (IEC) between 1.55 and 2.60 milliequivalents per gram (meq/g). The number of bound and unbound water molecules per ion pair was measured and correlated with conductivity. The membrane with the highest IEC (2.60 meq/g) had 10.6 unbound (i.e. free) and 17.9 bound water molecules per ion pair within the polymer. The presence of excess unbound water has led to flooding of the ion conductive channels and low hydroxide ion conductivity. The optimal anion conductivity was found with about 6.7 unbound and 11.9 bound water molecules per ion pair. Excellent hydroxide conductivity (>120 mS/cm at 80 °C) was obtained at an ion-exchange capacity of 1.88 meq/g. The results show that hydroxide mobility is aided by phase segregation within the copolymer. The ion conducting polymer was stable in 1 M NaOH solution at 80 °C, showing essentially no loss in ion conductivity in 1200 h. Thermogravimetric analysis showed that the membrane backbone was stable up to 400 °C, consistent with previous polynorbornene-based materials. The peak power density of a H2/O2, hydroxide conducting fuel cell containing one of these membranes was 542.57 mW/cm2 at 0.43 V and current density of 1.26 A/cm2 at 60 °C.

Highly Efficient Enrichment of Volatile Iodine by Charged Porous Aromatic Frameworks with Three Sorption Sites

AbstractThe targeted synthesis of a series of novel charged porous aromatic frameworks (PAFs) is reported. The compounds PAF‐23, PAF‐24, and PAF‐25 are built up by a tetrahedral building unit, lithium tetrakis(4‐iodophenyl)borate (LTIPB), and different alkyne monomers as linkers by a Sonogashira–Hagihara coupling reaction. They possess excellent adsorption properties to organic molecules owing to their “breathing” dynamic frameworks. As these PAF materials assemble three effective sorption sites, namely the ion bond, phenyl ring, and triple bond together, they exhibit high affinity and capacity for iodine molecules. To the best of our knowledge, these PAF materials give the highest adsorption values among all porous materials (zeolites, metal–organic frameworks, and porous organic frameworks) reported to date.

Highly Efficient Enrichment of Volatile Iodine by Charged Porous Aromatic Frameworks with Three Sorption Sites.

The targeted synthesis of a series of novel charged porous aromatic frameworks (PAFs) is reported. The compounds PAF-23, PAF-24, and PAF-25 are built up by a tetrahedral building unit, lithium tetrakis(4-iodophenyl)borate (LTIPB), and different alkyne monomers as linkers by a Sonogashira-Hagihara coupling reaction. They possess excellent adsorption properties to organic molecules owing to their "breathing" dynamic frameworks. As these PAF materials assemble three effective sorption sites, namely the ion bond, phenyl ring, and triple bond together, they exhibit high affinity and capacity for iodine molecules. To the best of our knowledge, these PAF materials give the highest adsorption values among all porous materials (zeolites, metal-organic frameworks, and porous organic frameworks) reported to date.

ChemInform Abstract: Synthesis of Ethyl Arylpropiolates Through Palladium‐Catalyzed Cross‐Coupling Reactions of Aryl Iodides with in situ Generated Lithium Tetrakis(ethoxycarbonylethynyl)indates.

An efficient synthetic method to access ethyl arylpropiolates has been developed; it involves a palladium-catalyzed cross-coupling reaction between a wide range of aryl iodides and lithium tetrakis(ethoxycarbonylethynyl)indates (0.35 equiv) generated in situ from indium trichloride and alkynides obtained from ethyl propiolate and n-butyllithium.

Synthesis of Ethyl Arylpropiolates through Palladium-Catalyzed Cross-Coupling­ Reactions of Aryl Iodides with In Situ Generated Lithium Tetrakis(ethoxycarbonylethynyl)indates

An efficient synthetic method to access ethyl arylpropiolates has been developed; it involves a palladium-catalyzed cross-coupling reaction between a wide range of aryl iodides and lithium tetrakis(ethoxycarbonylethynyl)indates (0.35 equiv) generated in situ from indium trichloride and alkynides obtained from ethyl propiolate and <i>n</i>-butyllithium.

An approach to creating novel anions: silylated triel compounds with –CH2– and –O– linkers, [InCl2{O(HO)Si(t-Bu)2}]2and Li[B(CH2SiMe3)4

Bis[μ-di-tert-butyl(hydroxy)silanolato]bis[chloridoindium(III)], [In2(C8H19O2Si)2Cl4], (I), is a centrosymmetric two-centre indium complex featuring a system of three annulated four-membered rings; the structure is the first example of an In2O2 ring which is annulated with two Si-O units to form a ring system composed of three rings. The coordination environment of the In centres is a distorted trigonal bipyramid. The crystal packing of (I) is characterized by chains of molecules connected by O-H···Cl hydrogen bonds. The crystal of (I) was a nonmerohedral twin. There is no known example of an In2O2 ring in which the In atoms carry any two halogen ligands. The structure of tetrakis(tetrahydrofuran)lithium tetrakis[(trimethylsilyl)methyl]borate, [Li(C4H8O)4](C16H44BSi4), (II), is composed of discrete cations and anions. The coordination geometries of the Li and B centres is tetrahedral. The cations and anions lie in planes parallel to the ab plane. There are no short contacts between the cations and anions. Compound (II) is the first example of a B centre bonded to four -CH2Si units.

Expedient synthesis of 3-substituted-1,2,3,6-tetrahydropyridines

The treatment of alkyl or aryl halides with an excess of tetrakis(pyridine)lithium tetrakis( N-dihydropyridyl)aluminate affords the corresponding 3-substituted-1,2,3,6-tetrahydropyridines in moderate to good yields via a tandem alkylation–reduction reaction.

The composition and structure of lithium tetrakis(pentafluorophenyl)borate diethyletherate

Treatment of LiC6F5 with B(C6F5)3 in equal volumes of light petroleum and diethyl ether at low temperature followed by slow warming to room temperature precipitates a microcrystalline solid which dries under vacuum to a material with the composition [Li(OEt2)3][B(C6F5)4]. Crystallization from diethyl ether yields solvent dependent [Li(OEt2)4][B(C6F5)4], which has been crystallographically characterised.

Synthesis and Structural Characterization of the Tetrakis(methimazolyl)borates Li[Bmt4] and [Ru(p‐cymene)(Bmt4)][PF6

AbstractThe lithium tetrakis(methimazolyl)borate, Li[Bmt4], is accessible from the reaction of Li[BH4] with four equivalents of methimazole. The crystal structure of Li[Bmt4] supported by four water molecules is described. Reaction of Li[Bmt4] with [Ru(p‐cymene)Cl2]2 and subsequent treatment with NH4PF6 in CH3CN results in the formation of the complex [Ru(p‐cymene)(Bmt4)][PF6]. In addition, we report the result of the X‐ray structure analysis of the chiral Ru complex [Ru(p‐cymene)(Bmt4)][PF6].

Synthesis and characterization of solid single ion conductors based on poly[lithium tetrakis(ethyleneboryl)borate

Main chain anionic polymers with lithium cations, which have tetrakis(ethyleneboryl)borate as repeating units, were prepared and their ionic conductivities were determined. The polyelectrolyte is characterized both as-synthesized and after annealing at 275 °C by means of impedance spectroscopy, direct current measurements, 11B, 13C, 1H, static 7Li solid state NMR and IR spectroscopies, and DT/TG/MS techniques. The important feature of this novel solid polyelectrolyte is that the anion is immobilized on the polymer chain. The single ionic conduction was confirmed by the observation of constant current under dc electric field with non-blocking electrodes. The material exhibits a high Li+ transference number. The annealed polymer has an ionic conductivity of 1.6 × 10−6 S cm−1 at 275 °C with an activation energy of 70 kJ mol−1.

Lithium Ion Conductivity of Polymer Electrolytes Based on Insoluble Lithium Tetrakis(pentafluorobenzenethiolato)borate and Poly(ethylene oxide)

Lithium ion conductivity and the ion transport mechanism for heterogeneous polymer electrolytes composed of insoluble lithium tetrakis(pentafluorobenzenethiolato)borate (LiTPSB), which has weak interaction between the lithium ion and the counteranion, and high molecular weight poly(ethylene oxide) (PEO) have been investigated. In addition, the ionic conductivity of polymer electrolytes based on low molecular weight poly(ethylene glycol) dimethyl ether (PEGDME) or amorphous poly[tetra(ethylene glycol) methyl ether methacrylate] (PEGM) was also researched. LiTPSB is not soluble in any solvents and polymers, however its composites with poly(ether)s exhibited ionic conductivity. The lithium ion transport mechanism in the interfacial phase between LiTPSB and PEO was proposed. The apparent activation energy of ionic conductivity was smaller for LiTPSB/PEO (salt ) than lithium trifluoromethanesulfonate (Litrif)/PEO. A high lithium ion transference number of 0.65–0.75 was also obtained for the insoluble LiTPSB/PEO system. A new peak of the melting point of PEO was observed in differential scanning calorimetry measurements of LiTPSB/PEO polymer electrolytes, and it suggested the formation of a new ion conducting phase in the interfacial region between LiTPSB and PEO.

Lithium ion conductivity of gel polymer electrolytes containing insoluble lithium tetrakis(pentafluorobenzenethiolato) borate

Lithium ion conducting gel polymer electrolytes composed of insoluble lithium tetrakis(pentafluorobenzenethiolato) borate (LiTPSB), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and ethylene carbonate–propylene carbonate mixed solvent (EC–PC) were prepared and their ionic conductivities and electrochemical stabilities were investigated. Ionic conductivity was largely dependent on the contents of EC–PC and LiTPSB. Gel polymer electrolyte containing optimized content of 50 (LiTPSB)–50 (PVDF-HFP/EC–PC (13:87 wt.%)) exhibited ionic conductivity of 4 × 10 −4 S cm −1 at 30 °C, lithium ion transference number of 0.33 and anodic oxidation potential of 4.2 V.

Polymer electrolytes composed of lithium tetrakis(pentafluorobenzenethiolato) borate and poly(fluoroalkylcarbon)s

Lithium ion conducting polymer electrolytes were prepared by mixing insoluble lithium tetrakis(pentafluorobenzenethiolato) borate (LiTPSB) with poly(vinylidene fluoride) (PVDF) or poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP). Their films were prepared by hot pressing and are investigated for ionic conductivity and thermal properties. LiTPSB is insoluble in PVDF. Ionic conductivity was largely dependent on the salt content for LiTPSB–PVDF composite polymer electrolytes, and exhibited higher ionic conductivity than homogeneous LiTFSI–PVDF based polymer electrolytes. Melting point and crystallinity of PVDF were independent on LiTPSB content, resulting in no difference for melting point and crystallinity between pure PVDF and LiTPSB–PVDF. Ionic conductivity was effectively improved by incorporation of 18-crown-6 or kryptofix222 for LiTPSB–PVDF based polymer electrolytes.

Syntheses and structures of [(Me3N)3SiNHLi]4, (C4H8O)Al[NHSi(NMe2)3]3, ((Me2N)3SiNH)3Al and Li(THF)2+[((Me2N)3SiNH)4Al

The preparation of lithium tris(dimethylamino)silylamide, [(Me3N)3SiNHLi]4, 2, and its reaction with aluminium trichloride to give tris(dimethylamino)silylamino)(tetrahydrofuran)alane, (C4H8O)Al[NHSi(NMe2)3]3, 3, and bis(tetrahydrofuran)lithium tetrakis(tris(dimethylamino)silylamino)alanate, Li(THF)2+[((Me2N)3SiNH)4Al]−, 6, is reported, together with the crystal structures of 2, 3 and 6. Tris(dimethylamino)alane, ((Me2N)3SiNH)3Al, was obtained by reaction of tris(dimethylamino)silylamine with aluminium triethyl. The ammonolytic gelation of 3 to an imidoaluminosilicate gel is also described.

Lithium Tetrakis(haloacyloxy)borate: An Easily Soluble and Electrochemically Stable Electrolyte for Lithium Batteries

Synthesis and properties of lithium tetrakis(haloacyloxy)borate, in which X represents a halogen atom, are described for use as an electrolyte in lithium batteries. In this series of compounds, the anions are of non-chelate type, and X (Cl or F) is introduced as an electron-withdrawing substituent. These salts were easily synthesized from boric acid, lithium halocarboxylate, and halocarboxylic anhydride. The salts were easily dissolved in a linear carbonate such as dimethyl carbonate (DMC) and diethyl carbonate (DEC) to give concentrations greater than 1 mol dm−3. These solutions were highly conductive and stable against oxidation up to 4.5 V vs. the reference. Lithium tetrakis(trifluoroacetoxy)borate (LiTFAB), which was found to exhibit the highest conductivity among these salts, did not cause aluminum to corrode. A Li/graphite cell containing 1.0 mol dm−3 LiTFAB in an ethylene carbonate/ethylmethyl carbonate (3/7 vol/vol) mixed solvent was found to give the highest cycling efficiency. © 2003 The Electrochemical Society. All rights reserved.