Direct patterning processes for high-performance microsupercapacitors

QC 20230908

Abstract

The surge in miniaturized electronic components driven by the Internet of Things (IoT) has prompted an interest in non-traditional energy storage solutions. For these applications, reduction of size while preserving power and energy densities are of great importance. Within this context, planar microsupercapacitors (MSCs) have emerged as strong candidates for energy storage. Their unique two-dimensional structure, rapid charge-discharge capabilities, high power density, and enduring stability make them highly appealing as power units for on-chip integration.

However, the intricate nature of MSC fabrication remains a substantial challenge. Conventionally used indirect patterning processes, such as photolithography, are limiting the implementation of novel functional nanomaterials with high charge storing capacities. As a result, other kinds of direct patterning processes can be used to fabricate state-of-the-art MSCs. Recent studies mainly focused on improving the patterning geometry, minimizing electrode dimensions and narrowing the electrode gap to maintain high resolution of MSCs. However, these efforts were made at the expense of process scalability potential and degree of complexity of the fabrication processes. This thesis aims to develop fabrication process flows with emphasis on simplicity and versatility without sacrificing the possibility for large-scale fabrication of MSCs with high-performance.

The first part of this thesis describes the implementation of highly scalable inkjet printing process for fabrication of high-performance MSCs. Typically, inkjet printing can be used to deposit thin films of materials. However, to fabricate MSCs with high-performance, the thickness is a crucial parameter that requires scaling up. The contribution of the first work is dealing with overcoming printing limitations by describing a step-like fabrication process that was developed to overcome the limitations of inkjet printing to increase the thickness of the electrode material, and, therefore its electrochemical performance. The outcome graphene-based solid-state MSCs free from metallic current collector exhibit high areal capacitance of 0.1mF cm−2 and hold promise for on-chip fabrication. In the second work, a facile integration of inkjet printing with an electrodeposition technique is used to fabricate hybrid flexible MSCs based on graphene, Fe2O3, and MnO2 nanomaterials with∼90% capacitance retention after 10 000 charge-discharge cycles.

In the second part of this thesis, direct laser writing process is implemented as a viable alternative to fabrication of planar MSCs, based on a variety of highly electrochemically active nanomaterials that are not compatible with inkjet printing. In the third, fourth, and fifth works binder-free ink formulation approaches were developed to fabricate composite nanomaterial films based on graphene, graphene oxide, carbon nanotubes (CNTs), and polyaniline (PANI). Efficient patterning of these films, thanks to the wide range of controls over the laser beam, was realized highlighting the simplicity of the developed fabrication processes for MSCs with high areal capacitance of 172 mF cm−2. Furthermore, it enabled the fabrication of MSCs that can operate in a wide temperature range from 25 to 250 °C.

In summary, this thesis reshapes the MSC fabrication process by considering performance, scalability, and process adaptability towards novel functional nanomaterials. These proposed methods are further strengthened by innovative ink formulation strategies using these materials, highlighting their potential applicability in emergent energy storage devices.

urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-335732