Rest‐Pulse Interphase Reconstruction Enables Capacity Recovery in Aged Lithium‐Ion Batteries

ABSTRACT To address capacity loss associated with inactive Li‐related species and solid electrolyte interphase (SEI) growth, we developed a Rest‐Pulse (RP) protocol for aged LiFePO 4 /graphite diagnostic pouch cells. The protocol combines a 12 h discharged‐state rest with a short voltage pulse. The rest step partially dissolves and restructures the graphite‐side SEI, reducing interfacial blocking. Quantitative ex situ 7 Li solid‐state nuclear magnetic resonance (ssNMR) shows a pronounced decrease in NMR‐detectable residual metallic Li after RP treatment. Atomistic molecular‐dynamics simulations further indicate that the pulse produces a short‐range, field‐dependent directional bias of isolated Li‐rich domains within the porous interphase rather than long‐range migration. The RP protocol achieves a 99.3% average Coulombic efficiency and ∼10% absolute capacity recovery, exceeding the recovery obtained from rest alone (∼6%). A coupled recovery process occurs involving SEI reconstruction, improved interfacial kinetics, and changes in inactive Li‐related inventory. The RP protocol provides a proof‐of‐concept route for non‐destructive capacity recovery, although larger‐format validation and chemistry‐specific optimization are still required.