In this study, composite anode structures (FOC) of Fe3O4 nanoparticles (NPs) anchored on C substrates of synthetic cellulose derived from Nypa fruticants shell was prepared successfully via chemical methods. The pre-synthesized samples were carbonized at 600 °C under N2 gas for different annealing times such as 2 h (noted as FOC_2h), 3 h (noted as FOC_3h), and 4 h (noted as FOC_4h) before used as anode materials for Li-ion batteries (LIBs). The advanced investigation revealed that the quantity of the C phase and Fe3O4 NPs in the FOC materials was closely dependent on the duration of annealing time. The FOC anodes have exceptional electrochemical characteristics in LIBs, including high capacity, outstanding rate performance, and long-lasting charge/discharge capability. The FOC_3h electrode exhibits superior electrochemical performance compared to the FOC_2h and FOC_4h electrodes. The FOC_3h electrode exhibited a reversible capacity of 802.1 mAh g⁻¹ at a current density of 0.1 A g⁻¹ after 35 cycles, with a retention capacity of 93.7%. The decrease in volume expansion phenomena and enhanced rate diffusion of Li⁺ ions during cycling in the FOC_3h composite can be attributed to the overall impacts of the nanostructures of Fe3O4 phase and C substrates. Those results demonstrated that the mentioned methods in this study could be considered as promising routes to produce advanced anodes for LIBs using recycled Nypa fruticants shell.