Room-temperature sodium-based batteries have the potential for meeting large-scale grid energy storage needs. Inspired by the advancement of the design and building of electrode materials in lithium ion batteries, improved nano-architectured electrodes can be created for sodium-ion batteries, allowing increased electron transport kinetics and conductivities. Here, nanocomposites with 3D porous structures are reported as a high-capacity anode material for sodium-ion batteries by using an easy, low-cost and environmentally friendly synthesis of pyrolyzed bacterial celluloses (PBCs). Bacterial celluloses (BCs) produced by the Gluconacetobacter xylinus strain are pyrolyzed at 500, 750 and 1000 A degrees C, resulting 50, 130 and 110 mAh g(-1) capacities over 80 numbers of cycles, respectively, in the presence of the binary ethylene carbonate-propylene carbonate mixture. In order to increase the cell performances, in situ coated SnO2 nanoparticles with bacterial cellulose (SnO2@PBC) are produced by addition as synthesized 5-nm-sized SnO2 nanoparticles into the BC growth medium together with the G. xylinus strain. Following the pyrolysis at 500 A degrees C, the SnO2@PBC composite is better able to handle the accommodation of the dramatic volume change of the incorporated SnO2 nanoparticles because of the interaction of oxygen-containing moieties of bacterial cellulose nanofibrils with the SnO2 nanoparticles during cellulose production. The resulting SnO2@PBC composite presents highly stable capacity retention of around 400 mAh g(-1) capacities at C/10 current density over 50 numbers of cycles.