1,721,046 research outputs found
Primary 1.5 V lithium cells with BiVO4 cathodes.
No full textFergusonite, a monocline variety of bismuth orthovanadate, has been tested as a cathode in lithium cells. The reduction process, leading to the formation of Bi and Li3VO4, corresponds to a potential of 1.6 V a 100 μA. Button cells, based on the Li/BiVO4 couple, have been built mainly in the IEC R 42 size (100 mA h) and have provided a volumetric energy density of 432 W h/l at 100 μA. This new material also features good capacity retention at low temperatures, under 500 μA pulses, and after storage
Pila primaria al litio del tipo a bottone con voltaggio nominale di 1.5 V
No full textPile al litio primarie aventi voltaggio nominale di 1.5 volts, comprendenti un anodo di litio, una soluzione elettrolitica non acquosa contenente un sale di litio in un solvente aprotonico o in una miscela di due o più di tali solventi, e un catodo a base di vanadato di bismuto, BiVO4; tali pile realizzate nella forma a bottone, si presentano per tutte le applicazioni specifiche delle batterie a bottone per basse correnti
Lithium passivation in electrolytes used in secondary cells: an impedance spectroscopy study.
No full textLITHIUM INTERCALATION IN NA1+XV3O8 SYNTHESIZED BY A SOLUTION TECHNIQUE
No full textNa1+xV3O8 has been synthesized with a simple precipitation technique. Its performance as a cathode for rechargeable Li cells is far superior to that of the analogous material perpared at high temperature in terms of specific capacity and rate capability. As a result of the possibility of intercalating about 4.5 Li+ mol-1, low temperature Na1+xV3O8 has a theoretical energy density of 900 Wh kg-1. The diffusion coefficients, measured by impedance spectroscopy, have values of 10(-8)-10(-9) cm2 s-1, this matching the fast kinetics observed. A comparison is made of the performance of this new material with that of Li1+xV3O8 prepared with the same technique
Storage characteristics of polyanilines. An investigation by cyclic voltammetry and impedence spectroscopy.
No full textThe stability of pure polyaniline films prepared by cyclic voltammetry in a sulfuric solution has been tested by long-term storage under different conditions. The samples were kept for up to several days, on open circuit, in different solutions or in air. At selected storage times, cyclic voltammetry and impedance spectroscopy tests were run. A particularly severe degradation was observed in pure H2O, in LiClO4-PC and upon exposure to air. Degradation was also observed in a 1 M H2SO4-0.5 M Na2SO4 solution. This contradicts previous inferences of a lack of hydrolysis reactions, leading to quinone formation, at open circuit iri acidic solutions. Certainly, the degradation proceeds much faster if a potential of 0.7 V versus SCE is applied for some time. Five ring-substituted anilines, o- and m-toluidine, o- and m-sulfonic aniline and o-anisidine, have been polymerized with the same technique. Their degradation has been evaluated in an aqueous acidic solution and in two organic solutions based on PC and THF, respectively. The degradation of these substituted polyanilines is favoured by electron donor substituents and by protophilic solvents
(Mo0.3V0.7)2O5 as a solid solution cathode for Li cells. Part. II°. Structure characteristies and secondary cells.
No full textIt has been shown in Part I of this work that (Mo0.3V0.7)2O5 has an electrochemical behaviour different from that of V2O5. The two oxides have similar structures, with the MO6 octahedra linked by corner and edge sharing to form interconnected zig-zag chains. These structures can incorporate Li+ ions in bicapped cuboctahedron cavities of perovskite-type. This results, for V2O5, in an elongation of the weak VO bond along (010) and eventual bone breaking for x > 1 in LixV2O5. By contrast, (Mo0.3V0.7)2O5 can incorporate more than 2 Li+/mole in its cavities without substantial structure reorganization and with only 10% expansion of the cell. Li/(Mo0.3V0.7)2O5 cells are rechargeable and more than 100 cycles were achieved at 0.5 - 1.0 mA/cm2. After the 2nd cycle some structural alterations are produced which remain almost unchanged during further cycling
Accumulatori al litio con catodi di Li1+xV3O8
No full textSintesi e caratterizzazione elettrochimica del LiV3O8 come catodo in batterie al litio
Nonstoichiometric molybdenum oxides as cathodes for lithium cells. Part V. Thermodynamic, kinetic and structural aspects of the behaviour of Mo8O23 and Mo18O52.
No full textA deeper insight in the electrochemical behaviour of Li cells based on two non-stoichiometric Mo oxides, Mo8O23 and Mo18O52, was obtained by determining the OCV's, the diffusion coefficients and the variations of lattice parameters as a function of depth of discharge. The first material is a monoclinic framework-structured compound endowed with large channels which provide easy paths for Li+. Occupation of sites in the cavities of this structure produces at first a shrinkage of the unit cell, followed by a moderate re-expansion. Mo18O52 is a triclinic step-layered material which markedly expands upon Li+ intercalation. Li+ diffuses in it relatively slowly for x0.4 due to coulombic repulsion between Li+ ions
- …
