Unveiling organic–inorganic hybrids as a cathode material for high performance lithium-ion capacitors

Novel Li-ion hybrid supercapacitors were developed containing composite cathodes of a conducting polymer – either polyaniline (PANI) or polypyrrole (PPy) – with Li(Mn1/3Ni1/3Fe1/3)O2 nanoparticles. Activated carbon (AC) anodes were used in the presence of an organic electrolyte. Using a PANI composite electrode resulted in a cell with outstanding supercapacitive behavior, even at high currents. It showed better cycleability than the cells using a PPy composite electrode or pristine material. The cell with a PANI composite electrode delivered high specific capacitances of 140, 93, and 56 F g−1 at current densities of 0.72, 1.45 and 2.15 A g−1, respectively. The observed capacitances are the best yet reported for hybrid supercapacitors based on Li-intercalating materials in organic electrolytes. The hybrid supercapacitor containing PANI delivered maximum energy and power densities of 49 W h kg−1 and 3 kW kg−1, respectively. These results demonstrate the potential of developing polymer-encapsulated, Li-intercalating materials for high-performance, Li-ion, hybrid supercapacitors.