| Electrochemical and in-situ x-ray diffraction experiments are reported on a variety of tin oxide based compounds; SnO, SnO{dollar}rmsb2, Lisb2SnOsb3,{dollar} and SnSiO{dollar}sb3{dollar} glass, as cathodes opposite lithium metal in a rechargeable Li-ion coin cell. These materials demonstrate discharge capacities on the order of 1000mAh/(g Sn), which is consistent with the alloying capacity limit of 4.4 Li atoms per Sn atom, or 991mAh/(g Sn). These materials also demonstrate significant irreversible capacities ranging from 200mAh/(g active) to 700mAh/(g active). In-situ x-ray diffraction experiments on these materials show that by introducing lithium, lithium oxide and tin form first, which is then followed by the formation of the various Li-Sn alloy phases. When lithium is removed the original material does not reform. The ending composition is metallic tin, presumably mixed with amorphous lithium oxide. The oxygen from the tin oxide in the starting material bonds irreversibly with lithium to form an amorphous Li{dollar}sb2{dollar}O matrix. The Li-Sn alloying process is quite reversible; perhaps due to the formation of this lithia 'matrix' which helps to keep the electrode particles mechanically connected together. |
