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, CO2, CO, C2H4, C2H2, H2, CH4 and O2. Gas‐electrolyte composition has a significant influence on formation, coulombic and energy efficiencies, C‐rate capability, and aging. Particularly, CO2 and O2 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, C2H4 and CH4. 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 CO2 saturated electrolyte showed a remarkable increase in all performance parameters including lifetime.
Highlights
Electrolytes are essential components for all electrochemical energy storage technologies
In a first conclusion it seems that CO, C2H4 and CH4 lead to minor declines in 1C performance and lifetime
We have shown that presaturation of electrolytes with different gases leads to strong and characteristic changes in the performance and cycling stability of lithium-ion batteries
Summary
Electrolytes are essential components for all electrochemical energy storage technologies. A lower interfacial resistance was observed, and lithium dendrite formation was further suppressed This resulted in an enhanced cycling efficiency, C-rate capability and long-term stability of the negative electrode materials.[27,32,33,34,35,36,37] Strehle et al discovered that gases, such as CO2, are probably responsible for suppressing the transesterification of EMC.[38] Similar results were achieved by adding Li2CO3 to the electrolyte solution.[39,40] Shiraishi et al reported that treating lithium foil with mineral acids gave a thin bilayer surface structure with Li2O at the inner surface and further lithium salts at the outer surface/electrolyte interface.[41] In conclusion, gases play a crucial role in lithium metal electrodes, and might do so in lithium-ion batteries. The study paves the road for future tailoring of electrolyte pretreatment of lithiumion batteries to increase performance and lifetime
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