A bifunctional auxiliary electrode for safe lithium metal batteries

Increasing demands for performance beyond the limit of current lithium ion batteries for higher energy densities have rejuvenated research using lithium metal as an anode. However, commercial implementation has still been hampered due to safety issues. Herein, we introduce a lithium rechargeable battery system with an auxiliary electrode that can detect the potential signs of an internal short-circuit and simultaneously prevent cell failure by inhibiting further dendritic growth of lithium metal. Based on this working principle, we provide guidelines for an auxiliary electrode design and demonstrate that it can act as both a safety sensor and a lithium scavenger. Finally, we show that our in-house designed cell, using a flexible and self-standing auxiliary electrode, can effectively alert the danger of a short circuit in real-time without additional dendrite growth. We expect that this finding will open up unexplored opportunities utilizing various auxiliary electrode chemistries for safe rechargeable lithium metal batteries.