Nanocomposite polymer electrolytes (NCPE), with different proportions of poly(ethylene oxide)/LiClO4/chitin were prepared by a hot press method. Nanochitin, a biopolymer, poly(beta(1 -> 4)-N acetyl-D-glucosamine) was incorporated as a filler in poly(ethylene oxide) (PEO). The ionic conductivity of the composite polymer electrolytes was enhanced by one order upon addition of nanochitin. The lithium transference number, t(Li)(+), was increased front 0.24 to 0.51 upon chitin addition. The membranes were subjected to scanning electron microscopy, themogravimetric-differential thermal analysis, differential scanning calorimetry, ionic conductivity, and Fourier transform infrared (FTIR) spectroscopy analysis. The free volume V-f was probed by positron annihilation lifetime spectroscopy studies at 30 degrees C. Li/NCPE/Li symmetric cells were assembled, and the thickness of the solid electrolyte interface as a function of time was analyzed. This paper also describes FTIR spectroscopic studies of the interface between lithium metal and NCPE, which suggests that the surface chemistry of lithium electrodes in contact with NCPE is dominated by compounds with C-N-Li and C-O-Li bonding.