Fabio Rosciano

Quantification of Oxygen Loss from Li1 + x ( Ni1 / 3Mn1 / 3Co1 / 3 ) 1 − x O2 at High Potentials by Differential Electrochemical Mass Spectrometry

Li 1+x (Ni 1/3 Mn 1/3 Co 1/3 ) 1―x O 2 (NMC) oxides are believed to be among the most promising positive electrode materials for future lithium-ion batteries. Differential electrochemical mass spectrometry (DEMS) experiments on the NMC oxides revealed oxygen evolution for overlithiated NMC compounds (x = 0.1) at potentials positive to 4.5 V vs Li/Li + . No oxygen evolution was detected for the stoichiometric NMC compound (x = 0). An analytical procedure for the quantitative analysis of the DEMS data was developed and applied to the oxygen evolution from overlithiated NMC compounds in acetonitrile (AcN) and ethylene carbonate/ dimethylcarbonate-based electrolytes. The analysis of DEMS data acquired in the AcN-based solution was used to quantify the oxygen loss from the structure of the overlithiated compounds. A hypothesis on the origin of the considerably irreversible specific charge observed in the first cycle of the galvanostatic cycling experiments on the overlithiated compounds was formulated.