Grid-like Fe3O4 nanocrystals enhance the performances of glass-ceramic anodes for lithium-ion batteries

Glasses hold great promise as high-energy anode materials in next generation lithium-ion batteries (LIBs). However, the electrochemical performances of the glass anodes still need to be greatly enhanced to meet the requirement for developing high energy density LIBs. Here we show that grid-like Fe₃O₄ nanocrystals enable a substantial enhancement of the electrochemical performances of iron borate glass ceramic anode for LIBs. We find that both Fe₂O₃ and Fe₃O₄ crystals precipitate in the glass matrix during melt-quenching if Fe₂O₃ content exceeds about 20 mol%. The ferrous/ferric ion ratio increases with Fe₂O₃ content, and thereby significantly raises the electronic conductivity of the Fe₂O₃-B₂O₃ glass-ceramics. The 90Fe₂O₃–10B₂O₃ anode exhibits the reversible capacity of ∼ 505 mA h g⁻¹ at 1 A g⁻¹ after 1000 cycles. The unique architecture of this anode, which involves grid-like arrangement of Fe₃O₄ nanocrystals in glass phase, provides more active sites for storing Li⁺ ions, and enhances Li⁺ ions transfer kinetics. This architecture prevents the propagation of microcracks in anode during lithiation/delithiation and thereby enhances the cycling stability.