Voltage‐Induced Bromide Redox Enables Capacity Restoration of Fast‐Charging Batteries

Abstract Fast‐charging lithium‐ion batteries (LIBs) are essential for electric vehicles (EVs) to compete with conventional gasoline ones in terms of charging viability, yet the aggressive capacity drop in fast‐charging scenarios gives rise to concerns regarding durability and sustainability. Herein, it is clarified that for fast‐charging batteries, the excessive lithium (Li) plating on graphite anode inevitably brings capacity fading, and the concurrent accumulation of Li 2 O‐dominant passivation species that form dead Li is the main reason for their poor rechargeability. To refresh the passivated graphite, a voltage‐induced activation mechanism is developed to leverage bromide (Br − /Br 3 − ) redox couple for Li 2 O and isolated Li 0 activation in situ. Along with a tiny amount of lithium bromide (LiBr) added into the electrolyte, the cut‐off voltage of activation processes is controlled to initiate and maximize the effectiveness of Br − /Br 3 − redox couple. The capacity of degraded fast‐charging cells can increase from lower than 30 to ≈118 mAh g −1 before and after the activation, respectively. Notably, the process is not one‐off; a subsequent activation is feasible. For the same battery that suffered from another round of fast charging, this design still restores the reversible capacity to ≈100 mAh g −1 . Such a voltage‐mediated mechanism can effectively prolong the service life of practical fast‐charging batteries.