Iron phosphate glass-ceramic anodes for lithium-ion batteries

The oxide glass-based anodes for lithium-ion Batteries (LiBs) still suffer from two critical drawbacks, that is, low reversible capacity and low electrical conductivity. Here, we report a new way to overcome the two drawbacks. Specifically, we chose 50Fe₂O₃–50P₂O₅ (50Fe50P) glass as the anode material for LiBs, and then thermally treat it at 1118 K (T_g+345 K) for 0.5 h under reducing atmosphere (5 mol% H₂+95 mol% Ar). The thermal reduction treatment led to formation of Fe₂(P₄O₁₂) and Fe₂Fe₅(P₂O₇)₄ crystals. The reduced glass-based anode for LiBs exhibits the capacity of 373 mA h g⁻¹ after 1 000 charge/discharge cycles at 1 A g⁻¹, which is higher than that of the oxidized one. The reduction treatment greatly lowers the charge transfer resistance in the glass anode, indicating the enhancement of the electrical conductivity. This performance improvement could arise from the increase of accessible active sites for Li⁺ ion storage and transfer due to the existence of crystal–crystal/crystal–glass boundaries, as well as from the improvement of the electron transfer between Fe²⁺ and Fe³⁺ during cycling. This reduction–crystallization approach could help develop high-performance oxide glass-ceramics based anodes for advanced LiBs.