Electrochemical characteristics of Sn1-xSixO2 as anode for lithium-ion batteries

Fine powders of tin oxide doped with traces of silicon in combination with highly dispersed amorphous silicon oxide have been synthesized by an advanc ed ultrasonic spray method. The mixtures have been analyzed by XRD and IR. The electrochemical results showed that addition of silicon decreases the t in oxidation state, and, hence, reduces the irreversible capacity during th e first discharge/charge cycle. SiO2 and Li2SiO3 appeared during the first discharging as confirmed by IR spectroscopy. Furthermore, a reversible capa city of 900 mA h/g to 950 mA h/'g for these composites has been found, whic h is even higher than the theoretical value (783 mA h/g according to the Li 4.4Sn). The chemical diffusion coefficients of lithium in the Li-Sn alloy p hases formed (Li0.4Sn, LiSn, Li3Sn7, Li3.5Sn and Li4.4Sn) have been measure d by galvanostatic intermittent titration technique (GITT). Below a Li cont ent corresponding to Li3Sn7, a reduced voltage polarization as well as an i ncreased lithium chemical diffusion coefficient were observed. This improve d performance is due to an enhanced interfacial diffusion, caused by highly dispersed inert second phases, i.e., SiO2 and LiSi2O3. (C) 1999 Elsevier S cience S.A. All rights reserved.