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

Developing sacrificial cathode prelithiation technology to compensate for active lithium loss is vital for improving the energy density of lithium‐ion battery full‐cells. Li2CO3 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 LiCoO2 (LCO), a lattice engineering is developed through substituting Li sites with Co and inducing Li defects to obtain a composite structure consisting of (Li0.906Co0.043▫0.051)2CO2.934 and ball milled LiCoO2 (Co‐Li2CO3@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 Li2CO3 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‐Li2CO3@LCO within NCM‐811 cathode, 235 Wh kg−1 pouch‐type full‐cell is achieved, performing 88% capacity retention after 1000 cycles. By precisely tuning the position of the Co dopant and inducing defects, Li2CO3 is transformed from an insulator into an exceptional sacrificial cathode prelithiation agent. It can be readily decomposed to CO2 through O2‐ intermediate releasing active Li+ to trade‐off solid electrolyte interface Li+‐consumption in anode, thereby improving the energy density of Li‐ion battery full‐cell.