Highly Stable Cycling of Amorphous Li sub(2)CO sub(3)-Coated alpha -Fe sub(2)O sub(3) Nanocrystallines Prepared via a New Mechanochemical Strategy for Li-Ion Batteries

In this study, an amorphous Li sub(2)CO sub(3)-coated nanocrystalline alpha -Fe sub(2)O sub(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 sub(2)CO sub(3) layer is conformally coated on Fe sub(2)O sub(3) nanocrystallines ( approximately 10 nm in size) that form hierarchically aggregated particles 400-800 nm in size by ball milling alpha -Fe sub(2)O sub(3) with LiH in CO sub(2). The prepared Li sub(2)CO sub(3)-coated nanocrystalline alpha -Fe sub(2)O sub(3) exhibits highly stable long-term cyclability as it delivers a reversible capacity of 975 mAh g super(-1) with 99% of retention after 400 cycles at 100 mA g super(-1). At a high rate of 3000 mA g super(-1), its reversible capacity still remains at 537 mAh g super(-1), superior to the uncoated counterpart (311 mAh g super(-1)). Moreover, amorphous Li sub(2)O and Li sub(2)CO sub(3) coatings are also similarly produced on Fe sub(2)O sub(3) and NiO nanocrystallines, respectively, representing the general applicability of this mechanochemical approach. Nanocrystalline alpha -Fe sub(2)O sub(3) hierarchical structure conformally coated with 1-3 nm thick amorphous Li sub(2)CO sub(3) layer is successfully synthesized by one-step room-temperature mechanical milling of Fe sub(2)O sub(3) with LiH in CO sub(2) atmosphere. The conformal coating and hierarchical structure significantly increase the reversible capacity of the Fe sub(2)O sub(3) anode and double its capacity retention after 200 cycles.