Hierarchical porous biomass activated carbon for hybrid battery capacitors derived from persimmon branches

Activated carbon materials are used in hybrid battery capacitors. They reduce energy density of devices, and can greatly improve the cycle life and power density. Herein, we used fast-growing persimmon branches in Shaanxi as a biomass carbon source. The persimmon branch activated carbon (PB-AC850) material was found to exhibit abundant graded pore structure similar to graphite structure after KOH activation. The macro/mesoporous structure in PB-AC850 facilitated the ions (solvated PF6-) transport, resulting in much better rate capability as compared to commercial activated carbon. It was moreover found from preparation of the hybrid battery capacitor that the addition of activated carbon reduced resistance and polarization of the device. LFP + PB-AC850 exhibited excellent cycle stability with high to 93.4% capacity reservation after 500 cycles at 5C.