Li/ Li1+xV3O8 secondary batteries. Syntesis and characterization of an amorphous form of the cathode.

A new synthesis route has been applied to obtain Li1+xV3O8. Instead of the conventional high-temperature technique leading to the crystalline form, a solution technique producing the amorphous form has been used. This material, after dehydration, shows an electrochemical performance exceeding that of the crystalline one. The rationale for this behavior mainly lies in microscopic factors, i.e., in the possibility for the unit cell of amorphous Li1+xV3O8 to insert up to 9 Li +, instead of six for crystalline Li1+xV3O8. Furthermore, the absence of a long-range crystallographic order reduces the length of the pathways through which Li + ions diffuse. This and the favorable morphology endow amorphous Li1+xV3O8 with a high rate capability. The higher energy content afforded by this new form (theoretical value, 935 Wh/kg, based on the electrodes weight) can be exploited in long-cycling cells at high rates.