Electrochemistry of L-niobium pentoxide a lithium/non-aqueous cell

The electrochemical behaviour of L-Nb2O5 (orthorhombic; a = 6.162, b = 3.661, c = 3.919 A) was examined in a 1 M LiClO4-propylene carbonate/ tetrahydrofuran (1:1) solution at 30 °C. L-Nb2O5 exhibited an S-shaped discharge curve (mid-point about 1.58 V) under a low, continuous drain below 5 mA g−1 without addition of any conductive binder (such as graphite or acetylene black) and it could be reduced up to 2 F mol−1. The performance of Li/Nb2O5 cells was examined: these were found to belong to the 1.5 V class of lithium cell at both low and high discharge rates. The reaction mechanism of L-Nb2O5 in a lithium/non-aqueous cell was investigated by ex situ X-ray diffraction analysis together with a chronopotentiometric technique. Reversibility tests indicated that the reaction of L-Nb2O5 was basically reversible over 0 – 2 F mol−1 of reduction, which agreed with the analytical results of ex situ XRD studies. The electrochemistry of L-Nb2O5, especially the characteristic S-shaped electrode potential curve, is discussed in terms of a homogeneous phase reaction.