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0972-AA07-03-BB08-03

Nanosized Amorphous Materials as Anodes for Lithium Batteries Quan Fan and M. Stanley Whittingham Dept. of Chemistry, State Univ. of New York at Binghamton, Binghamton, NY, 13902 ABSTRACT The carbon anode presently used in commercial lithium ion batteries has a relatively low capacity and may pose safety problems particularly under fast charging. Nanosized amorphous materials have excellent electrochemical behavior when applied as anodes for lithium ion batteries; especially they have advantages over bulk materials on capacity retention and rate capability. The initial studies on some amorphous compounds are promising. A commercialized tin-cobalt-carbon amorphous material, which is composed of ~5nm nanoparticles, shows a capacity retention of >350 mAh/g for 50+ cycles. Manganese oxide nanofibers were synthesized by polymer templated electrospinning followed by calcinations. The fibers have 200-500 nm diameter and the main composition is Mn3O4. The capacity remains 400 mAh/g for at least 50 cycles.

INTRODUCTION Lithium ion batteries are ideal power sources for portable electronic devices. While the next generation of lithium batteries will require safer and less costly electrodes, particularly for large applications such as hybrid electric vehicles and all-electric vehicles [1, 2] where high current rate is applied. Materials such as lithium iron phosphate, LiFePO4, and related compounds [3, 4] offer the opportunity for a low-cost and high rate cathode. As for the anodes, the current commercialized graphitic carbon has questionable rate capability on lithium intercalation, and its potential that is very close to that of lithium metal raises the safety concern and the possiblity lithium plating and subsequent dendrite formation. In addition, its relatively low theoretical gravimetric capacity of ~370 mAh/g and very poor volumetric capacity demands that an alternative be found. Simple metals and alloys have been extensively investigated at first. Among all of them, pure tin [5, 6] and tin based alloys are possible candidates due to their high theoretical capacity. But the capacity retention is a big issue when large volume expansion and contraction on lithium insertion and removal breaks down the particles and the resistive SEI layers are formed. Then a number of transition metal oxides have been proposed as anodes. Initiated by P. Poizot and J. M. Tarascon et al. [7], nanoparticles of some non-intercalating simple oxides such as MO (where M is Co, Ni, Cu or Fe) show excellent behaviors as anode materials, with capacities of around 700 mAh/g and nearly 100% capacity retention for up to 100 cycles. And later a large family of nanosized transition metal oxides with different synthetic method and particle size/morphology are examined [8-10], among which non-toxic and low cost manganese oxides series are attractive [11-13]. It turnd out that the synthetic method and particle size/morphology of oxides plays a critical role in their electrochemical activity, and the nano-structure improves the rate cap