Carboxyl-conjugated phthalocyanines used as novel electrode materials with high specific capacity for lithium-ion batteries

A novel molecular model of carbonyl-substituted phthalocyanine compounds used as the cathode material in a lithium-ion battery is demonstrated. Tetra-carboxyl and octa-carboxyl groups are substituted onto a phthalocyanine-conjugated system. The conductivities of phthalocyanine compounds are effectively improved by I-2 doping, without affecting the capacity and energy density. Taking lithium as the counter-electrode, the electrochemical properties of the microparticles are investigated, and the electrochemical mechanism of carboxyl groups substituted with phthalocyanines is analyzed. The results indicate that carboxyl-substituted phthalocyanines have high specific capacities. After 20 or 50 cycles, they still retain capacities of about 300 and 500 mA center dot h/g for tetra-carboxyl- and octa-carboxyl-substituted phthalocyanines, respectively. The multiple carbonyl groups and the large numbers of electrons on the phthalocyanine-conjugated system are the two factors contributing to the high specific capacity.