BN-codoped CNT based nanoporous brushes for all-solid-state flexible supercapacitors at elevated temperatures

Abstract

Abstract Porous graphitic carbon based nanostructured electrodes offer several advantages for energy storage applications, such as, high specific surface area, high active charge storage sites, suitable ion diffusion and excellent charge transport properties. Vertically aligned carbon nanotubes (CNTs) have widely been exploited for electrochemical energy storage in different architectures using various electrolytes. However, a 3D carbon based electrode with high mechanical flexibility, reliability along with high charge storage capacity with solid-state electrolyte have yet to be realized. Here we develop a simple spray pyrolysis process for synthesizing nanoporous brush-like CNTs grown radially on individual carbon fibers of a carbon cloth (CC) substrate and simultaneously codoping with boron (B) and nitrogen (N) heteroatoms. The obtained BNCNT-CC electrodes were utilized to fabricate highly flexible all solid state symmetrical supercapacitor cells. The cells demonstrated high aerial capacitance of 106.8 mF/cm2 (~21.4 F/cm3), excellent flexibility without any performance degradation, attractive capacitance retention (86.4%) even after 5000 charge/discharge cycles, stability above room temperature, 741.8 mWh/cm3 specific energy at 25 W/cm3 specific power and conservation of 56% of its initial energy at specific power of 1 kW/cm3. The results are distinctly better than previous reports as a whole in terms of different performance parameters and are attributed to the unique nanoporous structure, low combined series resistance, BN-codoping and diffusion controlled modulation in electrochemical energy storage characteristics.