Abstract
The increasing demand for portable, wearable, and miniaturized electronics has substantially promoted the immense development of planar microsupercapacitors (MSCs) built on a single substrate. Atomically thin two-dimensional (2D) nanosheets, by virtue of their intrinsically unique structure and fascinating electrochemical properties, provide a new material platform for the creation of high performance planar MSCs in which the electrolyte ions can completely utilize flat architecture and ultrathin thickness of 2D nanosheets, parallel to the direction of ionic diffusion along the plane of 2D nanosheets. Herein, we present an overview and perspective on diverse 2D materials for planar MSCs. First, an introduction is presented to highlight the advances of MSCs, the uniqueness of 2D materials in the assembly of planar MSCs with three different configurations, i.e., stacked, interdigital, and 3D planar geometries, and the progress of microfabrication techniques for microelectrodes of MSCs. Second, the state-of-the-art 2D materials to manufacture planar MSCs, including graphene, transition metal oxides/hydroxides, transition metal dichalcogenides, metal carbides, metal nitrides, phosphorene, boron nitride, metal-organic frameworks, and covalent-organic frameworks, are systemically discussed in detail. Special emphasis is given to the multiple roles of 2D materials for functional components as active materials, current collectors, additives/binders, and separators for planar MSCs. Finally, the existing challenges and prospective solutions of 2D materials for planar MSCs with high performance and various innovative form factors are proposed.
Highlights
The ongoing proliferation of flexible, miniaturized electronics and their integrated microsystems has intensively stimulated the urgent requirement for microscale electrochemical energy storage devices (MEESDs).1–5 Among those MEESDs, microbatteries (MBs) and microsupercapacitors (MSCs) are two representative and complementary systems in which the total footprint area of the devices ranges from micrometer to centimeter scale.6–9 Compared with MBs, MSCs exhibit great advantages such as high power density, fast charge/discharge rate, and long operating lifetime, proving the enormous potential as ideal stand-alone and complementary microscale power sources for miniaturized electronics.10–12In particular, planar MSCs constructed on a planar substrate can fully adapt to the on-chip microfabrication processes and directly couple with implantable biomedical devices, maintenance-free wireless sensor networks, active radio frequency identification systems, and wearable and flexible electronics
An introduction is presented to highlight the advances of MSCs, the uniqueness of 2D materials in the assembly of planar MSCs with three different configurations, i.e., stacked, interdigital, and 3D planar geometries, and the progress of microfabrication techniques for microelectrodes of MSCs
It is clear that reduced graphene oxide (rGO) nanosheets from chemical, thermal, photo, laser, or plasma reduction of graphene oxide (GO) have been extensively used as active materials and current collectors in interdigital planar MSCs, owing to the simplicity of preparation and ease of processing
Summary
The ongoing proliferation of flexible, miniaturized electronics and their integrated microsystems has intensively stimulated the urgent requirement for microscale electrochemical energy storage devices (MEESDs). Among those MEESDs, microbatteries (MBs) and microsupercapacitors (MSCs) are two representative and complementary systems in which the total footprint area of the devices ranges from micrometer to centimeter scale. Compared with MBs, MSCs exhibit great advantages such as high power density, fast charge/discharge rate, and long operating lifetime, proving the enormous potential as ideal stand-alone and complementary microscale power sources for miniaturized electronics.. MICROFABRICATION TECHNIQUES OF PLANAR MSCs. For planar MSCs, various microfabrication techniques, including photolithography, plasma-etching, laser scribing, printing techniques (e.g., inkjet printing, screen printing, and 3D printing), electrochemical deposition, and mask-assisted filtration, have been extensively used to construct microelectrodes based on 2D materials (Fig. 2).. For planar MSCs, various microfabrication techniques, including photolithography, plasma-etching, laser scribing, printing techniques (e.g., inkjet printing, screen printing, and 3D printing), electrochemical deposition, and mask-assisted filtration, have been extensively used to construct microelectrodes based on 2D materials (Fig. 2).3,10 Various microfabrication technologies have been developed to construct the interdigital planar MSCs, such as photolithography, plasmaetching, laser scribing, electrochemical deposition, inkjet printing, screen printing, spray coating, and mask-assisted filtration.. Graphene and emerging analogue 2D materials have been gradually demonstrated as a new class of highly attractive microelectrode materials for planar MSCs
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