A lithium and vanadium oxide is described having the formula Li.sub.1+xV.sub.3O.sub.8, wherein 0.1.ltoreq..times..ltoreq.0.25. The oxide has a monoclinic crystalline structure and comprises non-agglomerated grains in the form of monocrystalline pellets having a length L of between 1 and 100 .mu.m, a width W such that 4