The Effects of Gas Saturation of Electrolytes on the Performance and Durability of Lithium‐Ion Batteries

Abstract

Traces of species in batteries are known to impact battery performance. The effects of gas species, although often reported in the electrolyte and evolving during operation, have not been systematically studied to date and are therefore barely understood. This study reveals and compares the effects of different gases on the charge-discharge characteristics, cycling stability and impedances of lithium-ion batteries. All investigated gases have been previously reported in lithium-ion batteries and are thus worth investigating: Ar, CO 2 , CO, C 2 H 4 , C 2 H 2 , H 2 , CH 4 and O 2 . Gas-electrolyte composition has a significant influence on formation, coulombic and energy efficiencies, C-rate capability, and aging. Particularly, CO 2 and O 2 showed a higher C-rate capability and a decrease in irreversible capacity loss during the first cycle compared to Ar. Similar discharge capacities and aging behaviors are observed for CO, C 2 H 4 and CH 4 . Acetylene showed a large decrease in performance and cycle stability. Furthermore, electrochemical impedance spectroscopy revealed that the gases mainly contribute to changes in charge transfer processes, whereas the effects on resistance and solid electrolyte interphase performance were minor. Compared to all other gas-electrolyte mixtures, the use of CO 2 saturated electrolyte showed a remarkable increase in all performance parameters including lifetime.

Analysis of Lithium‐Ion Battery State and Degradation via Physicochemical Cell and SEI Modeling

“…Although these cracks would heal by a rapid formation of new SEI, this would alter its surface structure. Alternatively, the observed improvement of kinetics could also relate to a change in interfacial species that may fascilitate, e. g., electrolyte stripping [76] . As such, the increased surface site density may refer to either a larger active surface area, faster kinetics at the same surface sites, or most likely a combination of both.…”

“…Alternatively, the observed improvement of kinetics could also relate to a change in interfacial species that may fascilitate, e. g., electrolyte stripping. [76] As such, the increased surface site density may refer to either a larger active surface area, faster kinetics at the same surface sites, or most likely a combination of both. Again, additional experiments like depth profiling, [77] spatial resistivity mapping, [78] or imaging of the SEI [11,79,80] could help to identify the underlying reason for this parameter change by providing a better understanding of SEI structure and composition.…”