Gas Generation in Lithium Cells with High-Nickel Cathodes and Localized High-Concentration Electrolytes

Abstract

High-nickel layered-oxide cathodes (LiNi_xMn_yCo_1-x-yO₂, x ≥ 0.8) exhibit high capacities but also experience rapid capacity fade during cycling, and are susceptible to heat generation and gas release. Advanced electrolytes, such as localized high-concentration electrolytes (LHCEs), substantially stabilize the cathode during cycling and have lower flammability than conventional electrolytes, but gas generation with these electrolytes is yet to be assessed. We demonstrate here that gas generation from a high-nickel cathode in an LHCE is half as much as in a conventional electrolyte at 4.4 V. The gas generation in the LHCE is further reduced at 4.3 V, but the LHCE generates a similar amount of gas as the conventional electrolyte at 4.6 V. Neither electrolyte can prevent gas generation after cycling; cathodes after 200 cycles generate similar amounts of gas as pristine cathodes during high-voltage hold. It is shown that, in both electrolytes, oxygen from the cathode lattice plays a critical role in gas generation.