Synergistic engineering of fluorine doping Fe_xMn_1-xMoO₄/graphene heterojunction as ultrahigh-rate anode for LIBs

The development of advanced anode materials is critical for high-energy and high-power lithium-ion batteries (LIBs). Conventional conversion-type anodes, such as transition metal molybdates, suffer from poor conductivity, severe volume expansion, and structural degradation, leading to rapid capacity fading. To overcome these limitations, we propose a synergistic design strategy that integrates heterojunction engineering with fluorine doping. A fluorine-doped, heterojunction-structured F-Fe_xMn_1-xMoO₄/graphene (F-FMMO/G) was successfully synthesized via a facile solvothermal route. Structural characterizations confirm the formation of a well-defined FeMoO₄/Mn₂Mo₃O₈ heterojunction with effective fluorine incorporation. When evaluated as an anode for LIBs, the F-FMMO/G composite exhibits an ultrahigh initial specific capacity of 1158 mAh g^- 1 at 0.1 C and maintains 780 mAh g^- 1 after 150 cycles, substantially outperforming the undoped counterpart. Notably, it delivers excellent rate performance, sustaining ~ 100 mAh g^- 1 at 10 C and rapidly recovering to > 900 mAh g^- 1 when cycled back to 0.1 C. The enhanced electrochemical performance is attributed to the synergistic effects of the built-in electric field at the heterojunction interface, which promotes rapid charge transfer, and fluorine doping, which optimizes the electronic structure and stabilizes the electrode-electrolyte interface. This study offers a rational design framework combining interfacial and bulk modifications for next-generation high-rate LIB anodes. The facile solvothermal synthesis, utilizing low-cost precursors and scalable reaction conditions, suggests good potential for commercial translation.