Lithia formation mechanism in tin oxide anodes for lithium–ion rechargeable batteries

The lithia formation mechanism in tin oxide anode is investigated using electrochemical measurements and Auger spectroscopy. Based on the charge/discharge capacities for SnO electrode, the atomic ratio of Li to O in lithia is less than 2 at the discharge capacity of 400 mAh/g (∼0.9 V). The derivative capacity plots show that the irreversible reaction occurs throughout the entire discharge to 0 V, and the atomic ratio of Li to O is about 1 at ∼0.8 V and 2 at 0 V. Auger spectroscopy analysis also confirms that the atomic ratio of Li to O approaches to 2 only when discharged to 0 V. Thus, Li2O appears to have formed at 0 V in the first discharge, not ∼0.8 V as reported previously, such that the initial lithia composition is more like Li2O2.