Promoting the activity of LiFePO4 (olivine) cathode of Li-ion battery by supramolecular complexes with single walled carbon nanotubes

The amphiphilic Ru-bipyridine complex, Z-907Na acts as a surfactant for solubilization of single walled carbon nanotubes (SWNTs) in acetonitrile+t-butanol. The supramolecular assembly Z-907Na/SWNT was characterized by optical and Raman spectro/electrochemistry. Its redox potential of 3.5 V vs. Li/Li + is matching almost exactly the formal potential of LiFePO4/FePO4 couple. The Z907Na/SWNT assembly is adsorbed on the surface of LiFePO4 (olivine) via the free carboxylic groups at the bipyridine ligand. This provides a composite material with roughly monolayer coverage by Z-907Na. Electrodes fabricated from Z-907Na/SWNT/LiFePO4 composite exhibited greatly enhanced activity for electrochemical Li + extraction/insertion compared to the performance of electrodes made from pure LiFePO4. Ke ywords: olivine cathode, Li-ion battery, carbon nanotubes, Ru-bipyridine complexes