Search

Abstract: Flexible all-solid-state supercapacitors (SCs) are fabricated using graphene/carbon black nanoparticle (GCB) film electrodes and cross-linked poly(vinyl alcohol)–H2SO4 porous gel electrolytes (gPVAP–H2SO4). The GCB composite films, with carbon black (CB) nanoparticles uniformly distributed in the graphene nanosheets, greatly improve the active surface areas and ion transportation of pristine graphene film. The porous structure of as-prepared gPVAP–H2SO4 membrane improves the equilibrium swelling ratio in electrolyte and provides interconnected ion transport channels. The chemical crosslinking solves the fluidity problem of PVA–H2SO4 gel electrolyte at high temperature. As-fabricated GCB//gPVAP(20)–H2SO4//GCB flexible SC displays an increased specific capacitance (144.5 F g−1 at 0.5 A g−1) and a higher specific capacitance retention (67.9% from 0.2 to 4 A g−1). More importantly, the flexible SC possesses good electrochemical performance at high temperature (capacitance retention of 78.3% after 1000 cycles at 70 °C). [Copyright &y& Elsevier]

Maximizing the rate capability of carbon materials optimizes sodium ion battery (SIB) performance. This study develops nanoscale nitrogen-doped carbon material (NNCM), in which nano-sized primary particles aggregate. These aggregates form a meso–macro-hierarchical porous structure, which facilitates Na+ diffusion from outside the aggregates into the primary nanoparticles. The large specific surface area of carbon black improves Na+ accessibility by forming large interfaces, and Na+ is easily solvated through defect sites and pores on the primary particle surfaces. Furthermore, primary nanoparticles have short Na+ diffusion pathways, while turbostratic structures provide broad pathways aiding Na+ diffusion. Nitrogen improves the electrical conductivity of the carbon matrix and provides abundant active sites by creating extrinsic defects. Together, these factors afford NNCM good capacity retention (38% at 100 A/g vs. 1 A/g), reversible capacity (~101 mAh/g at 100 A/g), ultrahigh cycling stability (11,000 cycles at 100 A/g), high initial coulombic efficiency (80%), and remarkable rate capability. • A solution plasma process doped nitrogen into hierarchical porous carbon materials. • Carbon materials facilitated co-intercallation of Na+-DEGDME. • Nitrogen doping increased conductivity and active sites for Na+ adsorption. • Cells showed high rate capability , retaining 38% of capacity at 100 A/g vs. 1 A/g. [ABSTRACT FROM AUTHOR]