Determining the effect of dissolved CO2 on solution phase Li+ diffusion in common Li-ion battery electrolytes

Abstract

Electrolyte decomposition in Li-ion batteries (LIB) and its entailing gas evolution significantly impacts cell performance. CO2 is one of the most abundantly evolved gases from common LIB electrolytes and could potentially affect Li+ solution transport during LIB operation. To this end, a comparative analysis of the Li+ diffusion coefficient (DLi+) which governs mass transport is required. Herein a methodology is established to saturate common battery electrolytes with a soluble gas without introducing other contaminants, so as to determine DLi+ in saturated and unsaturated samples. As a proof of concept, the values of DLi+ are determined in 1 M LiPF6 and 1 M LiClO4 in ethylene carbonate (EC):dimethyl carbonate (DMC) with and without dissolved CO2, confirmed by gas chromatography–mass spectrometry (GC–MS). The results obtained by pulse field gradient nuclear magnetic resonance (PFG-NMR) diffusion measurements agree for both electrolytes; saturating the electrolyte with CO2 has no measurable effect on DLi+ and therefore does not hinder Li+ mass transport.

Keywords

• CO2
• Lithium
• Diffusion
• Battery
• Electrolyte
• PFG-NMR