F. Bonino

Anatase as a cathode material in lithium—organic electrolyte rechargeable batteries

A preliminary investigation of anatase, TiO2, as a positive electrode material in secondary lithium—organic electrolyte batteries is reported. Up to 0.6 lithium equivalents can react with 1 mole of TiO2. However, optimum cycling behaviour is obtained for regimes involving compositions between 0.15 and 0.45 Li/TiO2 mole ratio. Under these conditions, prolonged cycling at 0.25 – 0.5 mA cm−2 gives satisfactory results.

Characteristics of the lithium electrode in organic and polymeric electrolytes

Abstract The characteristics of the lithium electrode were examined in an organic and a polymeric electrolyte of interest for the development of rechargeable batteries. Results obtained by frequency response analysis and by polarization curves, were used to identify charge-transfer resistance, double layer capacity and properties of passivation films.

Synthesis and characterization of Li2MxMn4−xO8 (M=Co, Fe) as positive active materials for lithium-ion cells

We describe the preparation and the electrochemical properties of Li2MxMn4−xO8, spinel-structured compounds. The results demonstrate that these materials may operate as high-voltage cathodes in new concept lithium-ion batteries. An example of these batteries has been fabricated and successfully tested.

Electrochemical Behavior of Solid Cathode Materials in Organic Electrolyte Lithium Batteries: Copper Sulfides

The characteristics of copper sulfide cathodes have been evaluated in typical organic electrolyte lithium batteries. The behaviour of ..cap alpha..-Cu/sub 2/S (chalcocite), Cu /SUB 1.76/ S (digenite) and CuS (covellite) is discussed in terms of mechanism of reaction, discharge properties and energy content. In view of possible use in primary, voltage-compatible lithium batteries, Cu/sub 2/S shows the most interesting performance, either in terms of constancy of the operational voltage and in terms of discharge rates.

Electrode processes at the lithium-polymer electrolyte interface

Abstract The electrochemical deposition and stripping of lithium have been examined using three-electrode cells with a polyethylene oxide-lithium trifluorometha

Synthesis and characterization of LiCoyNi(1-y)VO4 lithium insertion materials

Abstract A family of mixed LiCo y Ni (1− y ) VO 4 ( y =0.2, 0.5 and 0.8) compounds of potential use as high voltage cathode materials in lithium batteries, has been synthesized and characterized. The X-ray diffraction analysis showed that these compounds adopt an inverse spinel structure where in average 85% of the Ni 2+ and Co 2+ ions occupy octahedral sites and the other 15% occupy tetrahedral sites with the V 5+ ions, although this occupation share is somewhat influenced by the preparation temperature. The annealing temperature plays also a key role in determining the particle size, as demonstrated by scanning electron microscope analysis. Cycling voltammetry tests showed that the lithium insertion–deinsertion process in the LiCo y Ni (1− y ) VO 4 electrode materials occurs reversibly around 4.3–4.4 V vs. Li, as also confirmed by cycling tests. The cycling capacity is somewhat modest; however, the trend of the cycling curves leads to foresee that a consistent increase in capacity may be obtained by extending the charging process beyond 4.6 V vs. Li, once a stable electrolyte will be available.

Study of lithium diffusion in RF sputtered Nickel–Vanadium mixed oxides thin films

Abstract The kinetics of electrochemical lithium insertion inside RF sputtered Ni/V mixed oxides thin films have been investigated employing different electrochemical techniques. The AC electrochemical impedance spectra, recorded after 10 cycles, showed three steps clearly involved in the intercalation mechanism of lithium in the oxide films: (i) a charge transfer process to the electrolyte/electrode interface; (ii) a solid-state diffusion of Li; and (iii) a space limited diffusion due to the finite volume of the film. This latter portion of the impedance spectra was used to calculate the Li chemical diffusion coefficients ( D Li ). D Li values show an initial increase up to an injected charge of 30 mC cm −2 and then, upon further intercalation, a decay probably due to the limited Li motion through a decreased number of available sites. These results are in good agreement with the ones obtained by potentiostatic intermittent titration technique applied to the same electrodes. Both techniques agree in giving the same trend for D Li upon Li intercalation. The same sets of measurements were carried out after 100 and 1000 Li insertion/deinsertion cycles in order to analyze the effect of prolonged cycling on the mechanism of lithium diffusion.

Rechargeable lithium batteries based on Li1 + xV3O8 thin films

Abstract Low-temperature thin films of Li 1 + x V 3 O 8 have been fabricated and tested in LiClO 4 /propylene carbonate-1,2-dimethoxyethane/Li cells. These cells show very good intercalation kinetics, and at 0.4 C discharge rate produce a specific energy of ≈ 110 Wh/kg. The films could be used in microbatteries for electronic devices, and applications requiring more power could also be envisaged.

Fe-containing CeVO4 films as Li intercalation transparent counter-electrodes

Iron containing CeVO4 films were prepared using the sol‐gel method. The crystalline structure of powders and films with Fe:Ce:V ratios of 0.1:1:1, 0.3:1:1 and 0.5:1:1 were investigated by X-ray diffraction (XRD) and infrared (IR) spectroscopy. XRD revealed the predominance of a CeVO4-W (wakefieldite) crystalline phase with a small amount of monoclinic CeVO4 ,C eO 2 and Fe2O3. Ex situ IR absorbance spectra of charged and discharged films show the changes in intensity of the V‐O stretching mode at 770 cm 1 . Cyclic voltammetry showed that Li intercalation occurs in three steps with total capacities of 22 mC cm 2 (Fe:Ce0.1), 32 mC cm 2 (Fe:Ce0.3) and 37 mC cm 2 (Fe:Ce 0.5). The increase in the overall charge capacity with increasing Fe content is accompanied by a loss of capacity with cycling. The lithium diffusion coefficient, calculated by the galvanostatic intermittent titration method (GITT), the potentiostatic intermittent titration method (PITT) and electrochemical impedance spectroscopy (EIS), ranges from 10 12 to 10 14 cm 2 s 1 . UV‐vis in situ transmittance spectra showed that these films are highly transparent with a photopic transmittance TVis 0.85 for intercalated and deintercalated states. This suggests that Fe:Ce:V oxide films are good candidates for optically passive counter-electrodes in electrochromic (EC) devices.

Copper polymer electrolytes

Abstract Multivalent salt polymer complexes offer important prospects of the investigation and understanding of the fundamental properties of polymer electrolytes. In this work we present some recent results obtained by complex impedance, cyclic voltammetry and electron spin resonance on a series of polymer electrolyte systems based on the combination of poly(ethyleneoxide) PEO and copper salts of the Cu(CF 3 SO 3 ) 2 type. The data appear to confirm that copper ions contribute to the overall transport in these complexes. However, the mechanism of conductivity may also include a mixed ionic-electronic effect.