Shoichi Tsujioka

Conductivities and Electrochemical Stabilities of Lithium Salts of Polyfluoroalkoxyaluminate Superweak Anions

Six lithium salts of tris- and tetrakis(polyfluoroalkoxy)aluminate superweak anions have been studied for their potential use as battery electrolytes. Four of the six are based on the formula LiAl(OCR(CF 3 ) 2 ) 4 (R = H, Me, CF 3 , Ph); the other two are LiAl(OCH 2 CF 3 ) 4 and LiAIF(OCPh(CF 3 ) 2 ) 3 . The thermally stable electrolytes LiAk(OCH(CF 3 ) 2 ) 4 and LiAl(OCPh(CF 3 ) 2 ) 4 were not oxidized at potentials less than or equal to 5.0 V vs. Li +/0 in dimethoxyethane (DME) or in 50:50% ethylene carbonate:dimethylcarbonate (EC:DMC). The LiAl(OCH(CF 3 ) 2 ) 4 electrolyte was not reduced at 0 V vs. Li +/0 in DME. Neither LiAl(OCH(CF 3 ) 2 ) 4 nor LiAl(OCPh(CF 3 ) 2 ) 4 promoted the corrosion of aluminum at 5.0 V vs. Li +/0 . The electrolyte LiAl(OCH(CF 3 ) 2 ) 4 underwent efficient, reversible reductive intercalation of Li + with MCMB carbon or LiCoO 2 electrodes over the potential ranges 0-2 and 2.4-4.8 V, respectively, vs. Li +/0 , but did not react in any other way with these electrode materials. The conductivities of some of the LiAl(OR F ) 4 electrolytes in DME or in EC:DMC were high enough for them to be considered as potential replacements for LiPF 6 in primary and secondary lithium batteries.

New or improved syntheses of the polyfluoroalcohols HOC(cyclo-C6H11)2(CF3), HO(cyclo-C6H11)(CF3)2, and HOC(Ar)(CF3)2 (Ar = 4-C6H4(t-Bu), 2,4,6-C6H2(CF3)3, 4-Si(i-Pr)3-2,6-C6H2(CF3)2, 3,5-C6H3(CH3)2), and 2-C6H4(C(OH)(CF3)2)

Abstract Five new polyfluoroalcohols, HOC(cyclo-C6H11)2(CF3), HO(cyclo-C6H11)(CF3)2, HOC(2,4,6-C6H2(CF3)3)(CF3)2, HOC(4-Si(i-Pr)3-2,6-C6H2(CF3)2)(CF3)2, and HOC(3,5-C6H3(CH3)2)(CF3)2, have been synthesized, and new procedures with improved yields for two known polyfluoroalcohols (HOC(cyclo-C6H11)(CF3)2, HOC(4-C6H4(t-Bu))(CF3)2) have been developed. Variable temperature 19 F NMR spectra and the X-ray structure of one of the new polyfluoroalcohols, HOC(2,4,6-C6H2(CF3)3)(CF3)2, are also reported. In hydrocarbon solution, the OH hydrogen atom of this compound interacts with one of the fluorine atoms of one of the o-CF3 groups in a manner identical to that previously reported by us for HOC(4-Si(i-Pr)3-2,6-C6H2(CF3)2)(CF3)2. In the solid-state, however, the OH hydrogen atom in HOC(2,4,6-C6H2(CF3)3)(CF3)2 appears to interact with one fluorine atom from each of the two geminal CF3 groups.

Electrochemical properties of lithium electrolytes based on bis(polyfluorodiolato)borate and tetrakis(polyfluoroalkoxy) aluminate superweak anions

This chapter provides information on the electrochemical properties of lithium electrolytes based on bis (polyfluorodiolato) borate and tetrakis (polyfluoroalkoxy) aluminate superweak anions. Many lithium salts of molecular anions have been considered as potential ionic components of electrolytes for primary and secondary lithium-ion batteries. Simple salts such as LiClO 4 , LiBF 4 , LiPF 6 , LiAsF 6 , and LiCF 3 SO 3 fail to meet one or more of the accepted performance criteria. A growing class of new lithium salts contains a variety of new borate anions that contain two or more fluorine atoms. This improves the electrochemical stability and generally increases the conductivity at a given salt concentration. The chapter reviews work on the electrochemical properties of nine electrolyte salts based on the formula LiB(OC(2-OC 6 H 4 _ n F n )(CF 3 ) 2 ) 2 ( n _ 0–3) [5] and, for comparison, the six related electrolyte salts LiAl(OCR(CF 3 ) 2 ) 4 (R _ H, Me, CF 3 , Ph), LiAl(OCH 2 CF 3 ) 4 , and LiAlF(OCPh(CF 3 ) 2 ) 3 . It aims to arrive at a practical replacement for LiPF 6 in lithium batteries. It also emphasizes the understanding of the steric and electronic factors.

New synthesis of polyfluorodiols: nine new derivatives of HOC(2-OH-C6H4)(CF3)2

Abstract Nine new polyfluorodiols, HOC(2-OH-3-C6H3F)(CF3)2, HOC(2-OH-5-C6H3F)(CF3)2, HOC(2-OH-3,5-C6H2F2)(CF3)2, HOC(2-OH-4,5-C6H2F2)(CF3)2, HOC(2-OH-4,6-C6H2F2)(CF3)2, HOC(2-OH-3,4,5-C6HF3)(CF3)2, HOC(2-OH-4,5,6-C6HF3)(CF3)2, HOC(2-OH-3-t-Bu-5-Me-C6H2)(CF3)2, HOC(2-OH-3-I-C6H3)(CF3)2, have been synthesized and characterized by GC, NMR spectroscopy, and high-resolution mass spectrometry.