Hard-soft carbon with tailored graphitization for high performance supercapacitors

There is always a mutual inhibition relationship between porosity and electrical conductivity. Rational design of hard-soft carbon to regulate the graphitization degree is an effective strategy to solve this problem. Herein, we reported an efficient method to synthesize hard-soft carbon by grafting polyaniline (PANI) onto carboxymethyl chitosan (CMC), followed by calcination with potassium oxalate. The CMC-PANI derived carbon (CPC) exhibits an interconnected framework with a high specific surface area. The graphitization degree can be controlled by the grafting ratio of PANI. The highly uniform distribution of hard-soft carbon increases the electrical conductivity which permits fast electrons/ions transfer. Benefiting from these features, CPC-3 delivers an enhanced specific capacitance of 337 F g−1 at 1 A g−1. The CV curves of the assembled symmetric supercapacitors (SCs) have no obvious distortion even at the scan rate of 500 mV s−1, indicating a favorable rate capability. The SCs manifest the maximum energy density of 28.72 Wh Kg−1 at a power density of 450 W kg−1, as well as excellent cycle stability with 97.5 % capacity retention after 5000 cycles at 10 A g−1. This work affords a new sight to prepare uniformly distributed hard-soft carbon materials for SCs with high cycle stability and rate performance.