Multilayer composites of electrode/electrolyte septum materials can be used as ideal electrode materials for supercapacitors. In this work, bacterial cellulose (BC) was used as a septum to separate the toluene/aniline solution with an aqueous oxidant acidic solution, and the aniline was polymerized in situ on the surface of the BC. Because toluene disperses aniline and controls the migration rate of aniline toward the aqueous oxidant acidic solution through BC, it can limit the oxidative polymerization to a single side of interface between the aqueous oxidant acidic solution and BC. A bacterial cellulose/polyaniline (PANI) composite with a single conductive surface and a surface resistivity of 40.1 Omega cm was successfully produced. The BC component in the new BC/PANI composite can absorb the electrolyte solution and change to a multilayer composite of electrode/electrolyte septum material that could be used in supercapacitors.