Thermodynamic study of lithium insertion in V6O13 and Li1+xV3O8

Abstract The enthalpies of Li + insertion into two V oxides of interest as cathodes for secondary Li batteries, i.e. V 6 O 13 and Li 1+ x V 3 O 8 have been directly measured by solution calorimetry. By comparing the integral molar enthalpies Δ H 0 / x with the corresponding Δ G 0 / x values, Δ S 0 / x higher than expected have been found for Li 1+ x V 3 O 8 . This has been correlated to a reorganization of its distorted structure induced by the initial Li + insertion. Two other cathode materials, having the same variation of the potential with Li + content, i.e. MoO 3 and (Mo 0.3 V 0.7 ) 2 O 5 , show even higher Δ S 0 / x values. The entropic values stemming from structural reorganizations add to the configurational entropies of inserted ions in determining the initial profile of E as a function of Li + .