The Synthesis Of Porous Graphitic Carbon And Its Applications In Hybrid Battery Capacitor

The development of HEVs has urged worldwide researchers to develop fastcharging and high energy density electrochemical energy storage cells. Up to date, oneof the most promising electrochemical cells to achieve fast charging and discharging isthe hybrid battery capacitor. Herein, we developed a one-step route bycombiningchemical activation with catalytic graphitization to synthesize porous graphitic carbon(PGC) from mesocarbon microbeads and petroleum coke. In order to balance theactivation and graphitization effects, the orthogonal experimental design was used tooptimize the experiment factors. Then we investigated two hybrid battery capacitorbased on the synthesized PGCs, which were internal serial device and internal paralleldevice.The PGC synthesized by petroleum coke was denoted as NF8215, whose BETsurface area was1119m2g-1.The NF8215based internal parallel devices wereassembled with a LiFePO4cathode, and an anode based on a mixture of NF8215andLi4Ti5O12. Then the hybrid devices were characterized by galvanostaticcharge/discharge, rate charge/discharge and cycle performance testing. The resultsshowed that PGC hybrid devices possess better performance than the commercialactivated carbon hybrid device.The PGC synthesized by MCMB was denoted as MCMB-PGC characterized by aunique structure of graphitic shell and an amorphous core. The abundant porosity andthe high surface area not only offered sufficient reaction sites to store electrical chargephysically, but accelerated the liquid electrolyte to penetrate the electrode and the ionsto reach the reacting sites. The graphitic shells at the surface of the porous carbonmicrobeads contributed to a conductive network which facilitates the electrontransportation. As a result, the internal serial device with a unique core-shell cathodeand Li4Ti5O12anode can construct a high-rate, high-capability hybrid battery capacitor,especially under high current densities.