Vanadium oxides, rechargeable lithium cells

The use of SVO as a rechargeable cathode material is enticing due to the high-energy density (> 300 mAh/g) of this material. However, during the discharge reaction of a lithium/SVO cell, the reduced silver is replaced by lithium in the vanadium oxide matrix. Therefore, the reversibility of this lithium for silver substitution under charge conditions is still a matter of debate, as will be outlined below. 

Though the conductivity of the PEO-alkali metal complexes (10 ohm -cm at 140°C) is fairly low in comparison with inorganic solid electrolytes such as 8-alumina(Na), RbCui6l7Cli3 and RbAg4ls at the same temperature, this can be compensated for by the facile production of thin films typically 25-500 pm thick. A cell may thus consist of a lithium or lithium-based foil as anode, an alkali metal salt-PEO complex, such as (PEO)9 LiCFsSOs (25-50 pm), as the electrolyte, and a composite cathode (50-75 pm) containing a vanadium oxide (VeOis) as the active ingredient. The vanadium oxide is one of a number of insertion compounds that permits the physical insertion lithium ions reversibly into their structure and thus allows recharging of the cell. 

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