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.