Highly Stable Cycling of Amorphous Li₂CO₃-Coated α-Fe₂O₃Nanocrystallines Prepared via a New Mechanochemical Strategy for Li-Ion Batteries

In this study, an amorphous Li2CO3-coated nanocrystalline α-Fe2O3 hierarchical structure is synthesized for the first time using a facile one-step mechanochemical process at room temperature, taking advantage of the concurrence of repeated fracture-cold welding of material's particles and a gas-solid redox reaction. The conformal coating and hierarchical structure significantly increase the cycling durability and rate capability. Typically, a 1–3 nm thick amorphous Li2CO3 layer is conformally coated on Fe2O3 nanocrystallines (≈10 nm in size) that form hierarchically aggregated particles 400–800 nm in size by ball milling α-Fe2O3 with LiH in CO2. The prepared Li2CO3-coated nanocrystalline α-Fe2O3 exhibits highly stable long-term cyclability as it delivers a reversible capacity of 975 mAh g−1 with 99% of retention after 400 cycles at 100 mA g−1. At a high rate of 3000 mA g−1, its reversible capacity still remains at 537 mAh g−1, superior to the uncoated counterpart (311 mAh g−1). Moreover, amorphous Li2O and Li2CO3 coatings are also similarly produced on Fe2O3 and NiO nanocrystallines, respectively, representing the general applicability of this mechanochemical approach.