Bacterial cellulose (BC) is used as both template and precursor for the synthesis of nitrogen-doped carbon networks through the carbonization of polyaniline (PANI) coated BC. The as-obtained carbon networks can act not only as support for obtaining high capacitance electrode materials such as activated carbon (AC) and carbon/MnO2 hybrid material, but also as conductive networks to integrate active electrode materials. As a result, the as-assembled AC//carbon-MnO2 asymmetric supercapacitor exhibits a considerably high energy density of 63 Wh kg−1 in 1.0 m Na2SO4 aqueous solution, higher than most reported AC//MnO2 asymmetric supercapacitors. More importantly, this asymmetric supercapacitor also exhibits an excellent cycling performance with 92% specific capacitance retention after 5000 cycles. Those results offer a low-cost, eco-friendly design of electrode materials for high-performance supercapacitors.