Chitosan derived porous carbon prepared by amino acid proton salt for high-performance quasi-state-solid supercapacitor

Abstract

The electrode material and electrolyte are the major factors influencing the performance of supercapacitor, and they are the current research hotspots in this field. Herein, three chitosan (CS) based gel electrolytes were prepared by mixing CS with different acidity of amino acids (acidic, neutral and basic) proton salts. The CS/[Asp]NO3 gel film is prepared from aspartate nitrate proton salt ([Asp]NO3) formed by acid amino acid (aspartic acid, Asp) and CS exhibits superior mechanical property. This gel film can immerse in KOH or Na2SO4 solution directly and get alkaline and neutral gel electrolyte films. It possesses high ionic conductivity and excellent mechanical properties when used as gel electrolyte and separator in supercapacitor. Furthermore, the gel film can use as carbon precursor to prepare N-doped porous carbon (HN-HPCs). The as-prepared porous carbon exhibits large specific surface area (1599 m2 g−1), high micropore ratio (88%), hierarchical porous honeycomb structure and high N doping content (7.04 at%). The specific capacitance can reach up to 459 F g−1 in 6 M KOH. The assembled flexible quasi-solid-state supercapacitor using HN-HPCs and prepared gel electrolyte exhibits high energy densities of 28.3 Wh kg−1. It demonstrates an efficient strategy to prepare CS based gel electrolyte and simultaneously use the gel to prepare high N doping and hierarchical porous carbon. This work will provide guidelines for designing high-performance electrode material and electrolyte for flexible supercapacitor.