Lithium hexafluorophosphate (LiPF6) has been synthesized using commercial hexafluorophosphoric acid (HPF6)as starting material. The neutralization of this acid monitored by conductimetry by lithium hydroxide in aqueous, alcoholic and acetonitrile media gives LiPF6 with yields of 42, 35 and 61% respectively. This salt may also be prepared by neutralizing similarly lithium hydroxide (LiOH) by pyridinium hexafluorophosphate (C5H5NHPF6) obtained by reaction from equimolar amounts of pyridine and HPF6 in alcoholic media (yield about 90%). From C5H5NHPF6 a new synthesis leads to LiPF6 in two steps. First the reaction of C5H5NHPF6 with ROLi (R = CH3, C2H5) in methyl or ethyl alcohol, acetonitrile and tetrahydrofuran media or with RLi (R = C4H9, tert-butyl) in pentane or hexane, gives lithium pyridinium hexafluorophosphate Li(C5H5N)PF6 in about 95% yield. Heating this at 30-50 degrees C under vacuum gives LiPF6 with a purity determined by lithium titration of about 99%. (C) 1998 Elsevier Science S.A. All rights reserved.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A new iron V2O5 bronze, Fe0.12V2O5, has been prepared via a sol-gel process. This compound exhibits an orthorhombic structure which closely resembles that of the parent oxide V2O5. A preliminary investigation of its electrochemical properties as rechargeable cathodic material for Li batteries is performed. The results are discussed in relation with the electrochemical behavior known for V2O5. Three reversible insertion steps appear in the potential range 3.8 to 2 V vs. Li/Li+. They correspond to a high faradaic yield of 2.5 F per mole of bronze mainly due to the unusually wide Li concentration range involved in the third process located near 2.3 V (DELTAx = 1.5). The presence of ferric ions in the orthorhombic host lattice is seen to induce interesting features especially in terms of cycle life (potential range: 3.8 to 2 V; C/4 discharge-charge rate) with a specific capacity of about 200 Ah/kg after 40 cycles.

The structural features of the potassium vanadium pentoxide bronze K0.25V2O5, as well as the main characteristics of its sol-gel synthesis are reported. The electrochemical properties of this bronze are discussed in terms of crystallographic data and compared to that obtained with the same bronze prepared through solid state reaction.

Electrochemical intercalation of lithium has been carried out using a cathode of pyrographite in a LiClO4-ethylene carbonate (EC) electrolyte. Charge and discharge curves present slopes and plateaus related to the existence of pure phases and biphasic systems respectively. Binary graphite-lithium intercalation compounds of stages I, II, III and IV were isolated and identified based on their (00l) X-ray diffraction diagrams. Our experimental conditions allow the obtention of compounds which do not contain coinserted solvent molecules, even for low stage materials.