Equilibrium Properties of Lithium/Niobium Selenide, Nonaqueous Secondary Cells

Equilibrium-open-circuit potentials of Li/LiClO/sub 4/, PC/NbSe/sub x/ (x = 2, 3, 4, 4.5) cells were measured as a function of the state of charge of these cells. For NbSe/sub 2/ the emf decreased monotonically from approx. 2.3 to 1.65 V at full discharge (1 Li/Nb) and was independent of prior history. With NbSe/sub 3/ two distinct types of emf curves were found: a constant emf of approx. 1.7 V from 0-2 Li/Nb followed by a monotonic decrease in emf to approx. 1.5 V at 3 Li/Nb, and a ''stepped'' form with breaks at 1 and 2 Li/Nb. Neither type of curve was reproduced on cycling. The emf of NbSe/sub 4/ and NbSe/sub 4/ /sub 5/ was nearly constant at 1.83 V to approx. 4 Li/Nb. The NbSe/sub 4/ exhibits a monotonic decrease in emf to approx. 1.6 V at 5 Li/Nb. The emf curves obtained on the first charge and subsequent cycles were higher in value. The implications of this data on the chemistry of cell discharge is discussed. 6 figures.