Cyclic production of biocompatible few-layer graphene ink with in-line shear-mixing for inkjet-printed electrodes and Li-ion energy storage

The scalable production of two-dimensional (2D) materials is needed to accelerate their adoption to industry. In this work, we present a low-cost in-line and enclosed process of exfoliation based on high-shear mixing to create aqueous dispersions of few-layer graphene, on a large scale with a Y-w similar to 100% yield by weight and throughput of phi similar to 8.3 g h(-1). The in-line process minimises basal plane defects compared to traditional beaker-based shear mixing which we attribute to a reduced Reynolds number, Re similar to 10(5). We demonstrate highly conductive graphene material with conductivities as high as sigma similar to 1.5 x 10(4) S m(-1) leading to sheet-resistances as low as R-s similar to 2.6 Omega square(-1) (t similar to 25 mu m). The process is ideal for formulating non-toxic, biocompatible and highly concentrated (c similar to 100 mg ml(-)(1)) inks. We utilise the graphene inks for inkjet printable conductive interconnects and lithium-ion battery anode composites that demonstrate a low-rate lithium storage capability of 370 mAh g(-1), close to the theoretical capacity of graphite. Finally, we demonstrate the biocompatibility of the graphene inks with human colon cells and human umbilical vein endothelial cells at high c similar to 1 mg ml(-1) facilitating a route for the use of the graphene inks in applications that require biocompatibility at high c such as electronic textiles.