Lattice Engineering on Li2CO3‐Based Sacrificial Cathode Prelithiation Agent for Improving the Energy Density of Li‐Ion Battery Full‐Cell

Abstract Developing sacrificial cathode prelithiation technology to compensate for active lithium loss is vital for improving the energy density of lithium‐ion battery full‐cells. Li 2 CO 3 owns high theoretical specific capacity, superior air stability, but poor conductivity as an insulator, acting as a promising but challenging prelithiation agent candidate. Herein, extracting a trace amount of Co from LiCoO 2 (LCO), a lattice engineering is developed through substituting Li sites with Co and inducing Li defects to obtain a composite structure consisting of (Li 0.906 Co 0.043 ▫ 0.051 ) 2 CO 2.934 and ball milled LiCoO 2 (Co‐Li 2 CO 3 @LCO). Notably, both the bandgap and Li ─ O bond strength have essentially declined in this structure. Benefiting from the synergistic effect of Li defects and bulk phase catalytic regulation of Co, the potential of Li 2 CO 3 deep decomposition significantly decreases from typical >4.7 to ≈4.25 V versus Li/Li + , presenting >600 mAh g −1 compensation capacity. Impressively, coupling 5 wt% Co‐Li 2 CO 3 @LCO within NCM‐811 cathode, 235 Wh kg −1 pouch‐type full‐cell is achieved, performing 88% capacity retention after 1000 cycles.