Examination of graphene nanoplatelets as cathode materials for lithium–oxygen batteries by differential electrochemical mass spectrometry

• Differential electrochemical mass spectrometry is employed to measure rechargeability of Li–O2 batteries.
• The quantitative evaluation of gas consumption and evolution is provided in graphene nanoplatelet cathodes.
• The cell with lithium nitrate–N,N-dimethylacetamide electrolyte exhibits a long cycle life.

In this study, in situ differential electrochemical mass spectrometry was employed to investigate the electrochemical rechargeability of two types of graphene nanoplatelets (GNPs) as electrode materials for lithium–oxygen batteries by evaluating oxygen efficiency as well as coulombic efficiency. GNPs having hydrophobic surfaces exhibit much higher specific capacity than those having hydrophilic surfaces. When lithium nitrate–N,N-dimethylacetamide (LiNO3–DMAc) is used as the electrolyte, the lithium–oxygen battery exhibits a long cycle life, and unwanted side reactions are effectively suppressed. The LiNO3–DMAc electrolyte is more stable than the lithium bis(trifluoromethane)sulfonamide–tetraethylene glycol dimethyl ether electrolyte, as evidenced by high O2 evolution and low CO2 evolution.

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