Sodium-ion diffusion and charge transfer kinetics of sodium-ion hybrid capacitors using bio-derived hierarchical porous carbon

Even though Li-ion based energy storages can provide high specific energy and good cycling stability, the scarcity and high price of Li-based materials may limit their applications in the future. In this work, we have investigated Na-ion hybrid capacitors (NICs) with both high specific energy and power. Bio-derived or Jasmine rice-derived hierarchical porous carbon (j-HPC) with a specific BET surface area of 2377 m2 g−1 and a mean pore diameter of 2.53 nm containing 73.17 at.% C, 2.24 at.% N, and 24.59 at.% O is used as a new electrode of NICs. We have found that a fast Na ion diffusion of 10−8-10−11 cm2 s−1 and a fast-standard heterogeneous rate constant of electron transfer of ca. 10−5 cm s−1 are two reasons leading to high-performance NIC. The NIC exhibits a maximum operating cell voltage of 3.8 V, a maximum specific energy of 116 Wh kg−1 (142 μWh cm−2) and a maximum specific power of 11,121 W kg−1 (13,618 μW cm−2) with 90% capacity retention after 5000 cycles. Our NIC using j-HPC may be an ideal device for high power and energy storage technology.