Study of lithium/polypyrrole secondary batteries with Lithium as cathode and polypyrrole anode

Abstract

Lithium/polypyrrole (Li/PPy) batteries were fabricated using lithium sheet as cathode, PPy as anode, microporous membrane polypropylene/polyethylene/polypropylene (PP/PE/PP) composite as separator and LiPF6/ethylene carbonate-dimethyl carbonate-methyl ethyl carbonate (EC-DMC-EMC) as electrolyte. Polypyrrole was prepared by chemical polymerization. Certain fundamental electrochemical performances were investigated. Properties of the batteries were characterized and tested by SEM, galvanostatic charge/discharge tests, cyclic voltammetry (CV), and a.c. impedance spectroscopy. The influences of separator, morphology, and conductivity of PPy anode, cold-molded pressure, and electric current on the performances of the batteries were studied. Using PP/PE/PP membranes as separator, the battery showed good storage stability and cycling property. The conductivity of materials rather than morphology affected the behavior of the battery. The higher the conductivity, the better performances the cells had. Proper cold-molded pressure 20 MPa of the anode pellet would make the properties of the cells good and the fitted charge/discharge current was 0.1 mA. The cells showed excellent performance with 97%-100% coulombic efficiency. The highest discharge capacity of 95.2 mAh/g was obtained.