Assessment of ecologically prepared carbon-nano-spheres for fabrication of flexible and durable supercell devices

Abstract

We report the production parameters of single-stage, ecologically fabricated, flexible Carbon-Nano-Spheres (CNS) supercells. These supercells can deliver a total energy, E_D, of 100.0 W h kg⁻¹ and power density, P_D, of 50.0 W kg⁻¹@38.4 V and 20 mA for a payload of 15 g (5.0 × 2.5 cm²). According to the material analysis, CNS consists of a spherically (40.0 to 50.0 nm) coagulated, interconnected, 3D network of hetero-structured sp²/sp³ carbon with a low crystalline length, L_a, of ∼3.0 nm and containing a native O-moiety (12.0 at%). They have an appreciably high specific surface area, S_A, of ∼790.0 m² g⁻¹ and an average pore size of ∼3.42 nm combined with multi-channel pore size distribution. Upon integration in electrodes, CNS provided excellent electrochemical performance without any material modification. CNS showed a nearly rectangular cyclic voltammetry (CV) response in 1 M HCl for both two- and three-electrode systems, yielding superior specific capacitances, C_SP, of ∼1080.0 and 570.0 F g⁻¹, respectively (@10 mV s⁻¹). They maintained a high cyclic stability of ∼86.0% (@20 000 cycles), with no material degradation according to post-investigations at a molecular level. The electrode showed hybrid battery/electric double layer capacitor (EDLC) behavior, as revealed by Ragone studies. In Nyquist studies, a shift in the Knee frequency with cycling indicated mitigation of the charge transfer process. In Bode studies, the ionic phase shift decreased insignificantly from ∼80 ° to ∼77 ° after 1000 cycles. The performance characteristics of CNS from laboratory scale measurements to supercell-level device development are discussed.