Simple additive strategy to boost initial coulombic efficiency by mitigating PTFE decomposition in dry battery electrodes

Abstract

Dry-processed electrodes eliminate energy/capital-intensive solvent drying processes, but indispensable polytetrafluoroethylene (PTFE) binders suffer from electrochemical reduction by lithium due to the inherently low energy level of their lowest unoccupied molecular orbital (LUMO). We present a strategy to overcome this problem by elevating the LUMO with amine-containing additives, which remove the reduction signature – shoulder in voltage profiles – observed during anode lithiation. The modification, achieved via interaction between PTFE's fluorine atoms and the additive's amine group, has been validated by multiple experimental techniques and density functional theory calculations. The additive boosted both initial coulombic efficiency and mechanical durability. Our readily implementable approach involving simple mixing of PTFE with additives opens the door for broader adoption of dry-processed electrodes, addressing one of the most significant impediments in industrialization.