Amorphous Lithium-Phosphate-Encapsulated Fe₂O₃ as a High-Rate and Long-Life Anode for Lithium-Ion Batteries

Fe2O3 has been considered as a promising anode candidate for lithium-ion batteries (LIBs) due to high specific capacity, low cost, and environmental friendliness but still suffers from fast capacity fading and insufficient rate performance. The essential problem can be attributed to the phase aggregation and slow ion diffusion. Herein, a nanoreactor–container, an amorphous lithium-phosphate-encapsulated Fe2O3 anode, is successfully developed. Such a fine nanoreactor–container is constructed by lithium phosphate oligomer electrostatic adsorption and cross-linking on a hydroxylated precursor, which can effectively inhibit Fe2O3 coarsening and promote fast lithium-ion transfer, thus facilitating the reversible and fast conversion reactions of the Fe2O3 anode during lithiation/delithiation. As a result, the optimized hybrid Fe2O3 anode with 5 wt % amorphous lithium phosphate (5% LixPO4@Fe2O3) delivers a maximum capacity of 1100 mA h g–1 at 0.2 A g–1 as well as 615 mA h g–1 even at 20 A g–1 and retains almost 100% after 900 cycles at 0.5 A g–1, very competitive compared to other iron oxide anode materials. This ingenious structure design and facile synthesis method, coupled with the excellent comprehensive performances, indicate that this hybrid composite could contribute a unique type of iron oxide anode material for battery applications.