Stabilizing Li 5 FeO 4 Against Air Corrosion by In‐Situ Polymerization Engineering for High‐Performance Prelithiation

ABSTRACT Li 5 FeO 4 is widely regarded by the industry as one of the most promising pre‐lithiation additives, owing to its high capacity (867 mAh/g), low material cost, and excellent compatibility. However, the practical application of Li 5 FeO 4 is severely hampered by its poor air stability, with pronounced capacity fade due to CO 2 corrosion even in dry air. In this work, a uniform 10 nm organic layer was in‐situ polymerized on the Li 5 FeO 4 surface, which effectively blocks parasitic reactions between Li 5 FeO 4 and H 2 O/CO 2 and enhances the interparticle Li + kinetics. The coated Li 5 FeO 4 maintains its structural stability and a capacity of 580 mAh/g after 100 h (171 mAh/g for uncoated Li 5 FeO 4 after 6 h). With only 5% additive, it boosts cathode utilization by 15% and energy density by 18% in full‐cell applications. This surface modification strategy greatly improves the environmental adaptability of Li 5 FeO 4 , providing a viable solution for air‐sensitive materials.