Quantification of Oxygen Loss from Li[sub 1+x](Ni[sub 1/3]Mn[sub 1/3]Co[sub 1/3])[sub 1−x]O[sub 2] at High Potentials by Differential Electrochemical Mass Spectrometry

(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 at potentials positive to 4.5 V vs . No oxygen evolution was detected for the stoichiometric NMC compound . 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.