Stable and High-Capacity Li-Ion Battery Anodes Enabled by Uniformly Distributed Fe Nanoclusters

Conversion-type iron oxide (FeO x ) anodes for lithium-ion batteries (LIBs) face critical practical challenges, including large voltage hysteresis, severe electrode degradation, and active material pulverization. To overcome these limitations, we develop a carbon-encapsulated amorphous FeO x /graphene composite (CE-aFeO x /G) via a facile synthesis route, providing a viable strategy for advancing conversion-type transition metal oxide (TMO) anodes. Owing to its amorphous nature, absence of grain boundaries, loose packing, strong interfacial bonding, and isotropic properties imparted by carbon encapsulation, CE-aFeO x /G facilitates spatially uniform electrochemical phase transitions during lithiation. This promotes the in situ formation of ultrafine Fe clusters with high electrochemical activity, which is essential for achieving long-term cycling stability. As a result, the composite anode exhibits outstanding electrochemical performance: a reversible capacity of 1134.5 mAh g –1 at 100 mA g –1 with nearly 100% retention over 270 cycles and only 4.1% capacity decay after 1130 cycles at 300 mA g –1 . This work not only sheds light on the degradation mechanisms of FeO x -based anodes but also opens a promising avenue for enhancing the durability of conversion-type Fe-based TMO anodes in high-performance LIBs.