Accommodating succinonitrile rotators in micro-pores of 3D nano-structured cactus carbon for assisting micro-crystallite organization, ion transport and surplus pseudo-capacitance: An extreme temperature supercapacitor behavior

Abstract The 3D nano-structured cactus activated carbon, AC and its composites containing 0 to 10 wt % succinonitrile, SN rotators are prepared and investigated in PVdF-HFP/Na-TFSI/EC-PC gel polymer electrolyte. Against AC, the modified porosity, micro-structure and surface chemistry for 5 wt % SN rotators in optimized AC/SN-5 electrodes leads to ∼5 times faster diffusion of ions inside pores, D ∼1.25 × 10−4 vs. 2.50 × 10−5 cm2/s, enhanced electrical conductivity, σ ∼2.36 vs. 0.76 S cm−1, meso-pores, SMESO/SMICRO = 0.192 vs. 0.148 and surplus pseudo-capacitance. Compared with AC, the AC/SN-5 electrodes offer higher specific energy, E ∼34 vs. 20 Wh kg−1, specific power, P ∼200 vs. 40 kW kg−1, knee frequency, fk ∼25 vs. 2 Hz and specific capacitance, Cs ∼244–250 vs. 145–150 F g−1 with higher retention ∼ (90 vs. 64%) at 10 A g−1. Further, at 100 °C, contrary to AC, the AC/SN-5 electrodes can deliver a maximum power, P ∼333 vs. 66 kW kg−1 with fk ∼30 vs. 3 Hz. However, at −50 °C, reduced values of P ∼3 vs. 7 kW kg−1 and fk ∼0.5 vs. 1 Hz are observed due to death of SN rotators below – 40 °C.