ABSTRACT
Lithium-sulfur batteries are the most promising candidates for next-generation energy storage devices owing to their high theoretical specific capacity of 1675â mAh g-1 and high theoretical energy density of approximately 3500â Wh kg-1 . However, the lack of cathode active materials with appropriate electrical conductivities and stability coupled with an inexpensive and industrially compatible production process has so far hindered the development of practical devices. Here, a facile preparation pathway is reported for the production of a sulfur-carbon composite active material by drying a mixture of highly conductive few-layer graphene (FLG) flakes (produced by exploiting an innovative wet jet milling process with a yield of ≈100 % and production capability of ≈23.5â g h-1 ) with elemental sulfur, using ethanol as an environmentally friendly solvent. The designed sulfur-FLG composite shows excellent electrochemical results. The assembled lithium-sulfur battery exhibits a stable rate capability up to a current rate of 2C, a coulombic efficiency approaching 100 % for 300â cycles at the current rate of C/4 (420â mA g-1 ), and a long cycle life up to 500â cycles delivering around 600â mAh g-1 at 2C (3350â mA g-1 ).
ABSTRACT
The fabrication of electrochemical double-layer capacitors (EDLCs) with high areal capacitance relies on the use of elevated mass loadings of highly porous active materials. Herein, we demonstrate a high-throughput manufacturing of graphene/carbon nanotubes hybrid EDLCs. The wet-jet milling (WJM) method is exploited to exfoliate the graphite into single-few-layer graphene flakes (WJM-G) in industrial volumes (production rate ca.â 0.5â kg/day). Commercial single-/double-walled carbon nanotubes (SDWCNTs) are mixed with graphene flakes in order to act as spacers between the flakes during their film formation. The WJM-G/SDWCNTs films are obtained by one-step vacuum filtration of the material dispersions, resulting in self-standing, metal- and binder-free flexible EDLC electrodes with high active material mass loadings up to around 30â mg cm-2 . The corresponding symmetric WJM-G/SDWCNTs EDLCs exhibit electrode energy densities of 539â µWh cm-2 at 1.3â mW cm-2 and operating power densities up to 532â mW cm-2 (outperforming most of the reported EDLC technologies). The EDCLs show excellent cycling stability and outstanding flexibility even in highly folded states (up to 180°).