Borate, lithium

Lithium Borates. Lithium metaborate [13453-69-5], LLBO2 2H20, is prepared from reaction of lithium hydroxide and boric acid. It is used as the fluxing agent for the matrix for x-ray fluorescence analytical techniques and in specialty glasses and enamels. The anhydrous salt melts at 847°C. 

Lithium Borates. Two lithium borates are of minor commercial importance, the tetraborate trihydrate and metaborate hydrates. 

Table 16. Prices for Potassium, Ammonium, and Lithium Borates ...

Figure 8. Linear correlation of HOMOcO energies and anodic oxidation limits of lithium borates Li[B(C6 H4 jF102)2], x=0 (1), x=l (2), and x=4 (3) Li[B( O2C 0H6)2l (4) lithium bis[salicylato (2-)]borate (6) and lithium bis [ 2,2 - biphenyldio-lato (2 -) -0,0 lborate (5).

VI. Lithium Borate-Type Polymers via Polymer Reactions 186... 

VI. LITHIUM BORATE-TYPE POLYMERS VIA POLYMER REACTIONS... 

To immobilize such anions as borate, organoboron polymers were reacted with aryllithium reagents.31,32 The reaction of alkylborane polymers with n-BuLi was examined first however, the ionic conductivity of the resulting material was very low. Moreover, complicated peaks were observed in the H-NMR spectrum. Conversely, selective lithium borate formation was observed in the nB-NMR spectrum when PhLi was employed (scheme 6). An ionic conductivity of 9.45 X 10 7Scm 1 was observed at 50°C. The observed ionic conductivity was relatively low because of the decreased number of carrier ions compared with dissolved salt systems. However, the lithium transference number of this polymer was markedly high (0.82 at 30°C). 

Figure 7 Temperature dependence of ionic conductivity for lithium borate polymer electrolytes prepared via polymer reactions.

Table 4 Ionic Conductivity of Lithium Borate Polymers Prepared via Polymer Reactions...

To avoid problems associated with these polymer reactions, the direct synthesis of lithium borate polymer electrolytes37 was undertaken by dehydrocoupling polymerization using lithium mesitylhydroborate40 (scheme 7). 

Lithium mesitylhydroborate was prepared by reaction of mesitylmagnesium bromide with trimethoxyborane and subsequent reduction with LiAlH4. The polymerization was performed by adding a THF solution containing a slight excess of lithium mesitylhydroborate to oligo(ethylene oxide) in THF. After treatment with alcohol, the lithium borate polymers were obtained as transparent soft solids soluble in methanol, THF, and chloroform. 

Before treatment with alcohol, the ionic conductivity of lithium borate polymers was 6.23 X 10-5 to 2.07 X 10-7 Scm-1 at 50°C. The maximum ionic conductivity was observed for the polymer with a PE040o spacer unit. After the polymer reaction with alcohols, glass-transition temperatures of these polymers were found to be -52 to 39°C, which was higher than that of poly(lithium mesitylhydroborate) ( 69°C). 

The ionic conductivity of this lithium borate polymer bearing the methoxybo-rate unit (9a) was 8.77 X 10 6Scm 1 at 50°C (Fig. 8). This value was lower than that observed before the polymer reacted with methanol. However, it was still greater... 

As described in previous sections (Sections VI and VII), macromolecular design of polymer/salt hybrids with a highly dissociable lithium borate unit proved to be a valuable approach for single-ion conductive polymers. To further improve the degree of lithium salt dissociation, we have designed a polymer/salt hybrid bearing the boron-stabilized imidoanion (BSI)38 (Fig. 10). 

A variety of organoboron polymer electrolytes were successfully prepared by hydroboration polymerization or dehydrocoupling polymerization. Investigations of the ion conductive properties of these polymers are summarized in Table 7. From this systematic study using defined organoboron polymers, it was clearly demonstrated that incorporation of organoboron anion receptors or lithium borate structures are fruitful approaches to improve the lithium transference number of an ion conductive matrix. 

In the inductively coupled plasma atomic emission spectroscopy (ICPAES) method (ASTM DD 5600), a sample of petroleum coke is ashed at 700°C (1292°F) and the ash is fused with lithium borate. The melt is dissolved in dilute hydrochloric acid, and the resulting solution is analyzed by inductively coupled plasma atomic emission spectroscopy using aqueous calibration standards. Because of the need to fuse the ash with lithium borate or other suitable salt, the fusibility of ash may need attention (ASTM D1857). 

S.3.2.2. Lithium Borates with Aromatic Ligands. A new class of lithium salts was developed... 

S.3.2.3. Lithium Borates with Nonaromatic Ligands. The presence of aromatic ligands in Barthel s salts was believed to be responsible for the high melting points and basicity of the borate anions, which in turn translate into moderate or poor solubilities and ion conductivities as well as low anodic stabilities. To avoid use of these bulky aromatic substituents, Xu and Angell synthesized a series of borate anions that are chelated by various alkyl-based bidentate ligands, which serve as electron-withdrawing moieties by the presence of fluorine or carbonyl functionalities. Table 13 lists the... 

Another series of lithium borates with nonchelating alkyl ligands were briefly reported by Yamaguchi et al. recently, where perhalogenated carbonyls were used to make the ligands electron-withdrawing. ... 

On the basis of their previous experiences with lithium borates coordinated by substituted ligands. Barthel and co-workers modified the chelatophos-phate anion by placing various numbers of fluorines on the aromatic ligands. Table 13 lists these modified salts and their major physical properties. As expected, the introduction of the electron-with-drawing fluorines did promote the salt dissociation and reduce the basicity of phosphate anion, resulting in increased ion conductivity and anodic stability. The phosphate with the perfluorinated aromatic ligands showed an anodic decomposition limit of 4.3 V on Pt in EC/DEC solution. So far. these modified lithium phosphates have attracted only academic interest, and their future in lithium ion cell applications remains to be determined by more detailed studies. 

When the monosilylated precursor 26 was reacted in a similar manner with LiBH4 according to Scheme 11, the resulting product was the solvent-free lithium borate salt 27 (74% yield). This compound could be recrystallized from -hexane. 

Analytical and quality control details are summarised in Arne et al (2008). Gold was determined by fire assay, and major elements by ICP-OES following a four-acid digestion, with the exception of fresh drill core samples from Wildwood, which were analysed by lithium borate fusion and XRF. Trace elements were determined by ICP-MS. Refractory elements (W, Zr, Ba and Ti) were analysed by pressed powder XRF. 

LA-ICP-MS was used for in situ determination of ultratrace elements in quartz. The analytical protocol included the following elements Al, Ba, Be, Cr, Ee, Ge, K, Li, Mg, Mn, Pb, Rb, Sr, Th, Ti and U . Apphcation of the LA technique to heterogeneous samples usually requires preparing a homogeneous glass by fusing with lithium borate . A difficulty encountered with multi-element LA-ICP-MS analysis is the absence of standards... 

The sensitivities of elements measured by ICP-MS on standard solutions nebulized with an ultrasonic nebuhzer (USN) are roughly 5000 times higher than in LA-ICP-MS when analyzing a fused lithium borate target of geological standard (NIM-G) by quadrupole ICP-MS Elan... 

Figure 6.14 Comparison of sensitivities for several elements measured on a lithium borate fused target of geostandard NIM-C by LA-ICP-MS and standard solutions ICP-MS nebulized with a USN.

Figure 6.16 Calibration curves of U and Th measured on fused lithium borate targets of geological reference materials NIM-N, NIM-C and NIM-L by LA-ICP-MS.

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