Sustainable Lithium Replenishment: A Lifespan Strategy Enabled by Mixed Ionic-Electronic Conductive (MIEC) Li-Mg-Al Alloy Foil

Prelithiation is widely recognized as an effective strategy for prolonging battery cycle life. However, previous prelithiation typically involves adding limited lithium inventory (LiInv) to compensate initial LiInv loss solely, while neglecting the long-term battery cycling. We propose for the first time to increase prelithiation degree and pre-store LiInv as stable LiCx to enable sustainable lithium replenishment which significantly extends battery cycle life and enhances energy density. To achieve this strategy, we developed Li-Mg-Al ultrathin alloy with enhanced mechanical workability for contact prelithiation to replace commercial ultrathin lithium. Li-Mg-Al preserves a mixed ionic-electronic conductive network during delithiation, ensuring efficient transfer of lithium to graphite rather than being randomly distributed on the anode surface. By utilizing a 5-μm 96Li2Mg2Al foil for full lifespan prelithiation, we achieved a high lithium utilization rate of 95.6% and remarkable full-cell capacity retention rate of 99.17% over the first 500 cycles, effectively tripling the battery cycle life.