Graphite Composite Electrodes for Effective Charge Storage via Synergistically Improved Compositions Enriched with Kaolinite and Cement as Matrix Inducers

Abstract

The present work demonstrates the correlations between substrate composition and active material morphology, which is responsible for effective energy storage. The binary and ternary composite electrodes, including graphite-kaolinite (GKCE) and graphite-kaolinite-cement (GKCeCE) were carefully fabricated using a simple economical process that employed only mechanical compression and thermal activation. The microstructure related to composite electrodes, as examined via X-ray powder diffraction, reveals that graphite layer are tightly arranged in both electrodes compared to raw graphite, exhibiting the largest crystallite size in GKCeCE, indicating a better matrix owned to synergy between raw materials. Aniline electropolymerization on both GKCeCE and GKCE accounted for an interwoven polyaniline (PANI) nanofiber network that is embellished with distinctive features. PANI on GKCeCE is quite distinctive as it exhibits net-like PANI structural elements together with overlapped PANI nanofibers, which are the only structural elements available in PANI network that deposited on GKCE. The emeraldine salt formation in excess is greatly enhanced by GKCeCE synergetic matrix, resulting in a PANI network that is highly effective in charge storage. The supercapacitor cell constructed using PANI-GKCeCE accounts for the highest specific capacitance in comparison with PANI-GKCE device, supported by both Galvanostatic charge-discharge (GCD) and solid-state cyclic voltammetry. The more accurate and reliable GCD method accounts for a specific capacitance, which is 1,143 F·g^-1 for PANI-GKCeCE device, exhibiting nearly 100% coulombic efficiency, better cycle stability, high energy and power density over PANI-GKCE device. The PANI high electroactive surface area that is mainly due to overlapped nanofibers and net-like arrangement account for better energy storage performance over PANI-GKCE, which composed by overlapped PANI nanofibers only. The electrode composition greatly dominates the aniline electropolymerization, producing significantly different PANI structures, which determine the energy storage efficiency.