Printing nanostructured carbon for energy storage and conversion applications

Abstract

Printing is rapidly emerging as a novel fabrication technique for energy storage and conversion technologies. As nanostructured carbons replace traditional materials in energy devices due to their unique structures and properties, intensive research efforts have focused on developing methods to print these new materials. Inkjet printing, screen printing, transfer printing, and 3D printing are increasingly used to print carbon nanomaterials. After a brief introduction of the basic operating principles of each of these techniques, methods for printing fullerenes, graphene, carbon nanotubes, carbon black, and activated carbon are reviewed. Subsequently, the applications of printing techniques for fabricating batteries, supercapacitors, fuel cells, and solar cells are discussed, followed by a perspective on the current challenges and future outlook of printing nanostructured carbon materials for these devices.

Introduction

Printing techniques have existed in a variety of forms for millennia. The invention of the printing press was one of the most significant advances in history and it transformed the way information was distributed, having widespread social implications. Since then, many printing techniques have been developed, enabling faster throughput and higher quality prints on a multitude of different substrates. Some of these techniques include screen printing, lithography, inkjet printing, transfer printing, and recently, 3D printing.

The most common use of printing is the reproduction of text with ink on paper, however recently there has been a noteworthy rise in the development of printable functional materials. Most printing inks have evolved considerably since the earliest printing, and the blossoming of nanotechnology in recent decades has brought with it an opportunity for further advancements. Similarly, computers and controlled machinery mean super-fast and precise printing is available at low costs. Now techniques exist for printing nanoparticle dispersions, conductive polymers, biological molecules, and nanostructured carbons. Using these techniques, printing has become much more than the transfer of words onto pages. Functional printing technology has been used to fabricate displays, biological tissue scaffolds, battery electrodes, supercapacitors, fuel cell catalysts, and solar cells.

Carbon exists in many forms including nanostructures such as graphene, carbon nanotubes (CNTs), and fullerenes, which are some of the most fervently and widely studied nanomaterials today. These three materials are similar in their atomic bonding structure, comprised of sp² bonded carbon, but are manifest as sheets, tubes, and spheres in 2, 1, and 0 dimensions, respectively. Both graphene and CNTs exhibit highly attractive properties such as good thermal and electrical conductivity, mechanical strength, and chemical stability. Fullerenes also possess unique optical and electronic properties, especially when functionalized. As a result, nanostructured carbons are being used in a growing number of established and emerging applications. Printing these materials has been recognized as an excellent approach for preparing functional structures and films with precise thickness control, patternability, and minimal wasted material.

Here we review printing of carbon nanomaterials and the application of printed carbons for energy storage and conversion (Fig. 1). This review begins with an introduction of basic printing methods and principles, highlighting and comparing several of the most important techniques. Subsequently, a detailed review of printed carbon nanomaterials is given. Essential parameters for printing these materials such as functionalization, surface treatment, and ink preparation will be discussed with specific examples from the literature given throughout. Finally, applications of printed carbon nanomaterials for energy storage and conversion are discussed, followed by an outlook on potential future trends in printing nanostructured carbon research and technology.