Study of the Mechanism of Electrolyte Decomposition and Gas Formation during Operation of Lithium-Ion Batteries

This paper is the first to prove the mechanism of decomposition of the standard electrolyte LP57 (1 M LiPF6 in EC:EMC, 3:7 by weight) and the release of gases in lithium-ion batteries during their operation, which quantitatively explains all known experimental results. It has been proven that the electrolyte decomposes with the release of CO and H2 gases. While the release of gas CO2 is associated with the occurrence of an additional chemical reaction between the released CO at the cathode (as a result of the decomposition of the electrolyte) with atomic lattice oxygen released from the cathode. Therefore, depending on the operating conditions of the battery (temperature and cutoff voltage), the ratio CO2/CO varies from 0.82 to 2.42. It has been proven that the accumulation of H2 in the anode graphite is the cause of its potential-independent release during battery cycling.