In this paper, CoFe₂O₄@pyrolyzed bacterial cellulose (CFO@PBC) nanocomposites were synthesized by a hydrothermal process and an in situ composite technique as the cathode for rechargeable Li-O₂ batteries (LOB). CoFe₂O₄@Ketjenblack (CFO@KB) were prepared in the same way as the comparison. The as-prepared materials were characterized by SEM, XRD, and BET. The LOB with CFO@PBC-3 showed a maximum initial discharge capacity of 2660 mAh g⁻¹ (electrode) at the current density of 100 mAg⁻¹, while the mass ratio of CoFe₂O₄ and pyrolyzed bacterial cellulose was 3. The cyclic voltammetry of the CFO@PBC nanocomposite electrodes was investigated at 0.1 mVs⁻¹ in the voltage window of 2.0–4.5 V. With the limited capacity of 640 mAh g⁻¹ (electrode), the CFO@PBC-3 electrode showed the best cycle stability and higher cutoff voltage of discharging. The pyrolyzed bacterial cellulose, as the fibrous 3D backbone in CFO@PBC nanocomposite electrodes, produced better results than the CFO@KB.

Herein, a three-step approach toward a multi-layered porous PBC/graphene sandwich has been developed, in which the chemical bonding interactions have been successfully enhanced via esterification between the layers of pyrolyzed bacterial cellulose (PBC) and graphene. Such a chemically induced compatible interface has been demonstrated to contribute significantly to the mass transfer efficiency when the PBC/graphene sandwich is deployed as electrode material for both supercapacitors and lithium–sulfur batteries. The high specific capacitance of the supercapacitors has been increased by three times, to 393 F g⁻¹ at 0.1 A g⁻¹. A high initial discharge specific capacity (~1100 mAhg⁻¹) and high coulombic efficiency (99% after 300 cycles) of the rPG/S-based lithium–sulfur batteries have been achieved.