Mechanism of Gases Generation during Lithium-Ion Batteries Cycling

Abstract

© The Author(s) 2019. Published by ECS. This paper studied the gases release of a graphite//NMC111(LiNi1/3Mn1/3Co1/3O2) cell during cycle in the voltage ranges of 2.6-4.2V and 2.6-4.8V and the temperatures of at 25°C and 60°C. It was proved that the CO2, CO, and H2 gases are released as a result of electrolyte decomposition. And it shows that the CO and H2 gases evolution is a direct consequence of the electrochemical reaction of electrolyte decomposition, while the CO2 generation is a consequence of the additional chemical reaction of interaction between the O2 released from the cathode atomic lattice oxygen and CO released from the same place on the cathode (appearing because of the electrolyte decomposition). That is why at the same electrochemical reaction of electrolyte decomposition, the ratio CO2/CO varies in the wide range from 0.82 to 2.42 depending on cycling conditions (temperature and cutoff voltage). It was proved that a potential-independent H2 evolution is a consequence of its adsorption in pores of powdered graphite on anode. There was proposed the mechanism of the electrolyte decomposition and the gases evolution in lithium-ion cells at their cycling, which corresponds quantitatively to all obtained experimental results.