Stabilizing the lithium metal interphase by calendar aging for enhanced battery lifespan

The lifespan of lithium metal batteries mainly depends on the stability of the solid electrolyte interphase (SEI). Battery aging is a non-chemical strategy that leverages the intrinsic reactivity of lithium metal and structural changes in the electrolyte to control SEI morphology, a crucial factor in interfacial stability. In the current study, we stabilize the SEI and extend the lifespan of lithium metal batteries by aging them for over 16 days before testing. This preconditioning process promotes the formation of a stable and porous SEI composed of solvent-anion complexes. The optimal performance of different cell configurations depends on a balance of ionic conductivity, SEI stability, electrochemical stability window, and the availability of the electrolyte during cycling. Consequently, 16 days of aging is optimal for a Li//Li cell, as it reduces the overpotential from 100 mV to 30 mV, and 30 days of aging is ideal for Li//Cu configuration, as it provides high CE and extends the cell's lifespan from 20 cycles to over 100 cycles. For high-voltage operations in LiCoO₂//Li cells, 16-day-aged cells demonstrate a higher capacity of 172 mA h g⁻¹ with a CE of 98 %, surpassing that of fresh cells (146 mA h g⁻¹ with a CE of 95 %). Additionally, capacity retention improves significantly from 20 mA h g⁻¹ to 100 mA h g⁻¹ after 90 cycles. This work presents a straightforward approach that challenges the prevailing notion that electrolyte additives or complex formulations are essential to achieving a longer battery lifespan.