- Improving the performance at elevated temperature of high voltage graphite/LiNi0.5Mn1.5O4 cells with added lithium catechol dimethyl borate
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Performance of LiNi0.5Mn1.5O4/graphite cells cycled to 4.8 V at 55?C with the 1.2 M LiPF6 in EC/EMC (3/7, STD electrolyte) with and without added lithium catechol dimethyl borate (LiCDMB) has been investigated. The incorporation of 0.5 wt% LiCDMB to the STD electrolyte results in an improved capacity retention and coulombic efficiency upon cycling at 55?C. Ex-situ analysis of the electrode surfaces via a combination of SEM, TEM, and XPS reveals that oxidation of LiCDMB at high potential results in the deposition of a passivation layer on the electrode surface, preventing transition metal ion dissolution from the cathode and subsequent deposition on the anode. NMR investigations of the bulk electrolyte stored at 85?C reveals that added LiCDMB prevents the thermal decomposition of LiPF6.
- Dong, Yingnan,Demeaux, Julien,Zhang, Yuzi,Xu, Mengqing,Zhou, Liu,MacIntosh, Alex D.,Lucht, Brett L.
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- Alkoxycyanoborates: Metal salts and low-viscosity ionic liquids
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Syntheses of alkoxytricyanoborates and dialkoxydicyanoborates are described using different readily available boron-based starting compounds such as tetrahydrido-, tetrafluoro-, and tetraalkoxyborates, as well as trimethoxyborane and trimethylsilylcyanide as cyano sources. The salts obtained have been characterized by NMR and vibrational spectroscopy, elemental analysis, and DSC and DTA measurements. In addition to alkali metal salts, room temperature ionic liquids [EMIm][ROB(CN)3] (R = CH3, C2H5, CH2CF3) have been prepared. These ionic liquids exhibit very low melting points or glass transition temperatures, low viscosities, and high chemical, thermal, and electrochemical stabilities. The influence of alkyl chain length and the effect of partial fluorination of the alkoxy group on these properties have been elucidated. The advantageous physicochemical properties, in general, and in conjunction with the easy accessibility make alkoxytricyanoborate-ILs interesting compounds for potential applications in materials sciences. Furthermore, the Li salt of the [CH3OB(CN)3]- ions was prepared and found to provide a significantly higher solubility in propylene carbonate compared to lithium tetracyanoborate. Alkali metal salts Li[CH3OB(CN)3]·H2O, Na[CH3OB(CN)3]·H2O, K[CH3OB(CN)3], Na[C2H5OB(CN)3], and Na[CF3CH2OB(CN)3]·0.5H2O have been characterized by single-crystal X-ray diffraction. This journal is
- Finze, Maik,Ignat'Ev, Nikolai V.,Reiss, Guido J.,Schopper, Nils,Sprenger, Jan A. P.,Zapf, Ludwig
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- Polyfluoroorganoboron-oxygen compounds. 5 Feasible routes to perfluoroalkyltrimethoxyborates M[CnF2n+1B(OMe) 3] (n ≥ 3)
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A well applicable preparative method for lithium perfluoroalkyltrimethoxyborates, Li[CnF2n+1B(OMe) 3] (n = 3, 4, 6), was elaborated which is based on the reaction of B(OMe)3 with CnF2n+1Li generated from C nF2n+1H and t-BuLi. Alternative perfluoroalkylation reactions of B(OMe)3 with perfluoropropyllithium generated from C3F7I and RLi, perfluoropropylmagnesium bromide, or perfluoropropyltrimethylsilane and potassium fluoride gave less satisfactory results for M[C3F7B(OMe)3]. The conversion of M[CnF2n+1B(OMe)3] salts (M = Li, BrMg) into K[CnF2n+1B(OMe)3] salts and basic properties of the new salts are reported.
- Adonin, Nicolay Yu.,Bardin, Vadim V.,Frohn, Hermann-Josef
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p. 647 - 652
(2008/10/09)
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- Electrolytic salts for lithium batteries
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Orthoborate salts suitable for use as electrolytes in lithium batteries and methods for making the electrolyte salts are provided. The electrolytic salts have one of the formulae (I). In this formula anionic orthoborate groups are capped with two bidentate chelating groups, Y1 and Y2. Certain preferred chelating groups are dibasic acid residues, most preferably oxalyl, malonyl and succinyl, disulfonic acid residues, sulfoacetic acid residues and halo-substituted alkylenes. The salts are soluble in non-aqueous solvents and polymeric gels and are useful components of lithium batteries in electrochemical devices.
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- Tris(trimethylsilyl)methyl and Tris(dimethylphenylsilyl)methyl Derivatives of Boron. Crystal Structures of Dihydroxyborane and of the Lithium-Boron Complex
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Tris(trimethylsilyl)methyl-lithium, LiC(SiMe3)3, reacts with trimethoxyborane to give the compound (Me3Si)3CB(OMe)2 (7) and the lithium-boron complex LiB(OMe)4 (8).The latter is converted on crystallisation from methanol into the solvate (11), which has been characterised by X-ray diffraction.The hydrolysis of (7) gives the dihydroxyborane (Me3Si)3CB(OH)2 (2), which may be converted into the dichloride (Me3Si)3CBCl2 (12), the difluoride (Me3Si)3CBF2 (14), the fluoride hydroxide (Me3Si)3CB(F)OH (15), the boranes(Me3Si)3CBR2 , and the hydride (3) (thf=tetrahydrofuran).An X-ray study shows that crystals of (2) consist of hydrogen-bonded dimers.Tris(dimethylphenylsilyl)methyl-lithium, LiC(SiMe2Ph)3, reacts with boron trifluoride-diethyl ether to give (PhMe2Si)3CBF2 (5), which may be hydrolysed to the dihydroxyborane (PhMe2Si)3CB(OH)2 (6).
- Al-Juaid, Salih S.,Eaborn, Colin,El-Kheli, Mohamed N. A.,Hitchcock, Peter R.,Lickiss, Paul D.,et al.
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p. 447 - 452
(2007/10/02)
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- Contributions to the Chemistry of Boron, 124. Tris(trimethylsilyl)silyl Boranes and Tris(trimethylsilyl)silyl Borates
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The reactions of several boron halides, methoxides, alkyls and hydrides with tris(trimethylsilyl)silyllithium, which was isolated as the solvate 3SiLi*3C4H8O, 1 (TMSSLi) have been studied. (CH3)2B-Si3 and 9-3Si-9-BBN, were isolated, while 3Si-B(tC4H9)2 could only be detected by 11B NMR.In addition TMSS-B2, (TMSS)2BNMe2 and (TMSS)2BOCH3 were prepared.The methoxyboranes (CH3)3-nB(OCH3)n add to 1 forming silylborates; however, no OCH3/Si3 substitution occurs.The hydrogen bridge in 9-BBN is cleaved symmetrically.The results can be explained by the basicity and the steric requirements of the TMSS group.The TMSS group exhibits a deshielding effect at the boron nucleus relative to the (CH3)3Si group for silylboranes as well as for silylborates. - Keywords: Silylboranes, Silylborates, Steric effects, 11B NMR Spectra
- Biffar, Werner,Noeth, Heinrich
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p. 1509 - 1515
(2007/10/02)
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- Process for preparing aldehydes from olefins
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Aldehydes are prepared by reacting an olefin with hydrogen peroxide in the presence of at least one boron compound and at least one compound of one of the metals of the fifth and/or sixth Secondary Group of the Periodic Table.
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- Process for preparing aldehydes from oxirane compounds
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Aldehydes are prepared by reacting an oxirane compound with hydrogen peroxide in the presence of a boron compound.
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