Phytic acid mediated N, P co-doped hierarchical porous carbon with boosting capacitive storage for dual carbon lithium-ion capacitor

Abstract

Lithium-ion capacitors (LICs) merged the energy characteristic of lithium-ion batteries and power characteristic of supercapacitors have aroused intensive attention. Nevertheless, the low capacity of capacitor-type cathode confines the development of LICs. Herein, an economic and efficient approach is developed to fabricate nitrogen and phosphorus co-doped hierarchical porous carbon (NP-HPC) by carbonizing cross-linked phytic acid and poly pyrrole/aniline precursor (PACP), in which phytic acid acts not only as a chemical crosslinker to regulate the precursor structure, but also a phosphorus source for dopant, thus providing more active sites for Li storage and enhancing structural stability. As-prepared NP-HPC cathode with enlarged specific surface area (∼2750 m2 g−1) and more micropores (∼1.410 nm) delivered a high specific capacity of 89 mAh g−1, with an ultrahigh capacity retention of 88.6% after 10000 cycles at 1.0 A g−1. DFT calculations demonstrated the co-dopant of N and P atoms synergistically improve the Li+ adsorption energy and electrochemical stability. More importantly, the assembled dual carbon LICs employing homologous NP-HPC and N, P co-doped spherical carbon (NP-SC) electrodes from the same precursor exhibit a maximum energy density of 121 Wh kg−1 at a power density of 92 W kg−1, with long-term cycling stability over 3000 cycles at 1 A g−1 with 80.2% retention.