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

Tian Carey,Hanne R Hagland,Jong M Kim,Harneet Kaur,Ruiyuan Tian,Lidija Šiller,Eoin Caffrey,Adrees Arbab,Dominik Horvath,Abdelnour Alhourani,Adam Kelly,Jack Maughan,Shayan Seyedin,Jonathan N Coleman

doi:10.1038/s41699-021-00279-0

Abstract

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 Yw ~ 100% yield by weight and throughput of ϕ ~ 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 ~ 105. We demonstrate highly conductive graphene material with conductivities as high as σ ∼ 1.5 × 104 S m−1 leading to sheet-resistances as low as Rs ∼ 2.6 Ω □−1 (t ∼ 25 μm). The process is ideal for formulating non-toxic, biocompatible and highly concentrated (c ∼ 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 ∼ 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.

Highlights

Graphene and other 2D materials are expected to find major commercial applications in the coming years[1]
Without any post-processing or centrifugation, we find that the 6000 cycles graphene ink has an Rs of ∼ 37 Ω □−1 at t ∼ 24 μm, corresponding to σ ∼ 1.1 × 103 S m−1, one order of magnitude higher than σ of graphite, indicating graphite’s exfoliation to few-layer graphene
The resolution of ~ 50 μm is as expected and comparable to previous works on inkjet printing[47,53]. These results indicate that the high concentration (5.9 mg ml−1) printable graphene inks can be produced using in-line shear mixing and can be inkjet printed at high resolution (~ 50 μm) in desirable patterns for flexible electronics

Summary

INTRODUCTION

Graphene and other 2D materials are expected to find major commercial applications in the coming years[1]. To increase the σ, printed films are typically annealed at high temperatures >300 °C45,57 This process is incompatible with many second cycle, the cathodic peak at 1 V is not observed, indicating the oxygen-containing functional groups on the graphene flakes are completely reduced. To the best of our knowledge, this is one of the highest c that has demonstrated LPE graphene’s biocompatibility with human cells to date, which is essential for applications in printed electronics that use c of at least 1 mg ml−1 43 We attribute the biocompatibility on the ink to the lack of oxygen functional groups (~5.7%, determined by XPS) as graphene oxide dispersions have previously demonstrated toxicity to human cells as low as 1–10 μg ml−1 72,73 attributed to its high oxygen content (~47%) that induces the formation of reactive oxygen species that can be toxic to cells[74]. We observe no dose-dependent toxicity up to 48 h indicating the graphene flakes’ biocompatibility at high concentrations ∼1 mg ml−1, which is essential to utilise graphene in textile electronics, composites and printed interconnects that could involve human contact with high concentrations of graphene

DISCUSSION

Findings

METHODS