Highly Stable Cycling of Amorphous Li 2 CO 3 ‐Coated α‐Fe 2 O 3 Nanocrystallines Prepared via a New Mechanochemical Strategy for Li‐Ion Batteries

In this study, an amorphous Li 2 CO 3 ‐coated nanocrystalline α‐Fe 2 O 3 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 Li 2 CO 3 layer is conformally coated on Fe 2 O 3 nanocrystallines (≈10 nm in size) that form hierarchically aggregated particles 400–800 nm in size by ball milling α‐Fe 2 O 3 with LiH in CO 2 . The prepared Li 2 CO 3 ‐coated nanocrystalline α‐Fe 2 O 3 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 Li 2 O and Li 2 CO 3 coatings are also similarly produced on Fe 2 O 3 and NiO nanocrystallines, respectively, representing the general applicability of this mechanochemical approach.