Electrolyte Development for Safe Li-Ion Battery Fast Charging: Decreasing Inactive Li on Graphite

Fast charging of lithium-ion batteries is limited primarily by the risks from lithium plating on the graphite anode. Plated lithium can become electrically isolated from the graphite (‘inactive Li’), causing rapid capacity fade and raising safety concerns. Thus, many studies have focused on detecting Li plating and designing operating conditions or materials to avoid it. Here we explore the reversibility of the lithium plating reaction as a tunable electrolyte property to mitigate inactive Li. We report a novel cycling technique to rigorously estimate the Li plating reversibility on graphite in Li/Graphite cells and then apply it to understand how additives, amount plated, and current density affect reversibility. Electrolyte compositions with reported high reversibility are tested under fast charging conditions in graphite/NMC cells, showing superior cycling performance and less inactive Li quantified by hydrogen gas evolution of extracted anodes. Finally, we consider limitations of reversibility measurements for Li plating/stripping on graphite and offer ways to address them.