Composite organic radical-inorganic hybrid cathode for lithium-ion batteries

A new organic radical-inorganic hybrid cathode comprised of poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA)/LiFePO4 composite system was developed and reported for the first time. The hybrid electrodes' voltammetry contains three pairs of reversible redox peaks indicating the combination of electrochemical characteristics between LiFePO4 and PTMA electrodes and shows a decrease in voltage gap between oxidation and reduction that corresponds to an improvement in the rate and reversibility of the redox couples. Results from electrochemical impedance spectroscopy show lower charge-transfer resistance of cycled hybrid cathodes suggesting an enhanced electrode/electrolyte interface formed in hybrid systems which leads to faster migration of Li ions through the interface and longer cycle life capability when compared with pure LiFePO4 or PTMA cathode system. Optimizing the hybrid cathode's ratio of PTMA/LiFePO4 yields a significant improvement in high pulse power performance (30 mAh cm(-3)) over the pure PTMA (16 mAh cm(-3)) or LiFePO4 (3.0 mAh cm(-3)) cathode. Further characterization of the hybrid electrodes using SEM showed a more compact surface morphology after high rate pulse experiments. The demonstrated properties of hybrid cathodes are promising for transportation and other high pulse power applications that require long cycle life and low cost. (C) 2013 Published by Elsevier B.V.