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

Abstract

<jats:title>Abstract</jats:title><jats:p>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 <jats:italic>Y</jats:italic><jats:sub>w</jats:sub> ~ 100% yield by weight and throughput of <jats:italic>ϕ</jats:italic> ~ 8.3 g h<jats:sup>−1</jats:sup>. The in-line process minimises basal plane defects compared to traditional beaker-based shear mixing which we attribute to a reduced Reynolds number, Re ~ 10<jats:sup>5</jats:sup>. We demonstrate highly conductive graphene material with conductivities as high as <jats:italic>σ</jats:italic> ∼ 1.5 × 10<jats:sup>4 </jats:sup>S m<jats:sup>−1</jats:sup> leading to sheet-resistances as low as <jats:italic>R</jats:italic><jats:sub><jats:italic>s</jats:italic></jats:sub> ∼ 2.6 Ω □<jats:sup>−1</jats:sup> (<jats:italic>t</jats:italic> ∼ 25 μm). The process is ideal for formulating non-toxic, biocompatible and highly concentrated (<jats:italic>c</jats:italic> ∼ 100 mg ml<jats:sup>−1</jats:sup>) 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<jats:sup>−1</jats:sup>, 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 <jats:italic>c</jats:italic> ∼ 1 mg ml<jats:sup>−1</jats:sup> facilitating a route for the use of the graphene inks in applications that require biocompatibility at high <jats:italic>c</jats:italic> such as electronic textiles.</jats:p>