Electrochemical characterization of polypyrrole–LiNi1/3Mn1/3Co1/3O2 composite cathode material for aqueous rechargeable lithium batteries
A series of polypyrrole (PPy)–LiNi1/3Mn1/3Co1/3O2 composite electrodes are formed by physical mixing of polypyrrole with LiNi1/3Mn1/3Co1/3O2 cathode material. LiNi1/3Mn1/3Co1/3O2 is synthesized by reaction under autogenic pressure at elevated temperature method. Highly resolved splitting of 006/102 and 108/110 peaks in the XRD pattern provide an evidence to well-ordered layered structure of the compound. The ratios of the intensities of 003 and 104 peaks are found to be >1, which indicate no pronounced mixing of the cation. Cyclic voltammetry and AC impedance studies revealed that the addition of polypyrrole significantly decreases the charge-transfer resistance of LiNi1/3Mn1/3Co1/3O2 electrodes. The electrochemical reactivity of PPy–LiNi1/3Mn1/3Co1/3O2 composite electrode is examined during lithium ion insertion and de-insertion by galvanostatic charge–discharge testing; 10 wt.% PPy–LiNi1/3Mn1/3Co1/3O2 composite electrode exhibits better electrochemical performance by increasing the reaction reversibility and capacity compared to that of the pristine LiNi1/3Mn1/3Co1/3O2 electrode. The cell with 10 wt.% PPy added cathode shows significant improvement in the electrochemical performance compared with that having pristine cathode. The capacity remains about 70% of the initial value after 50 cycles while for cell with pristine cathode only about 28% of initial capacity remains after 40 cycles.