High lithium capacity M(x)V(2)O(5)A(y)center dot nH(2)O for rechargeable batteries

The aqueous synthesis and electrochemical properties of nanocrystalline M(x)V(2)O(5)A(y) . nH(2)O are described. It is easily and quickly prepared by precipitation from acidified vanadate solutions.M(x)V(2)O(5)A(y) . nH(2)O has been characterized by X-ray powder diffraction, electron microscopy, TGA, chemical analyses, and electrochemical studies. The atomic structure is related to that of xerogel-derived V2O5 . nH(2)O. In M(x)V(2)O(5)A(y) . n H2O, M is a cation from the starting vanadate salt and A is an anion from the mineral acid. This material exhibits high, reversible Li capacity and may be considered for use in a cathode in primary and secondary batteries. The lithium capacity of an electrode composed Of M(x)V(2)O(5)A(y).nH(2)O/EPDM/carbon (88/4/8) is similar to 380 (mA h)/g (C/80 rate) and the energy density is similar to 1000 (W h)/kg (120-mum-thick cathode, 4-1.5 V, versus Li metal anode). Critical parameters identified in the synthesis of M(x)V(2)O(5)A(y) . nH(2)O, with respect to achieving high Li-ion insertion capacity, are acid/vanadium ratio, starting vanadate salt, and temperature. Inclusion of carbon black in the synthesis yields a composite that maintains the high Li capacity, lowers the electrochemical-cell polarization, and preserves the lithium capacity at higher discharge rates. Li-ion coin cells, using prelithiated graphite anodes, exhibit electrochemical performance comparable to that of Li-metal coin cells. (C) 2002 Elsevier Science.