Mechano-adaptable materials and structures for customizable electrochemical energy storage devices

• Main Author: Lv, Zhisheng
• Other Authors: Chen Xiaodong
• Format: Theses and Dissertations
• Language: English
• Published: 2019
• Subjects: DRNTU::Engineering::Materials
• Online Access: https://hdl.handle.net/10356/87337; http://hdl.handle.net/10220/48145
• Institution: Nanyang Technological University

The ever-advancing electronic industry is reshaping our daily life with various flexible and customizable electronics, requiring electrochemical energy storage (EES) device with concreted flexibility and customizability to finish the entire packaging system. In this thesis, based on the mechano-adaptive electrode materials and device structures, three new kind of mechano-adaptive composite materials for strain enhancement, device editability and effective stress relief of material expansion during charging/discharging process are coupled with two kind of mechano-adaptable structures to achieved flexible EES devices with customizable structures, shapes and enhanced energy density. An “editable strategy” was firstly proposed to make supercapacitors with customizable shapes and structures for versatile plug-and-play applications while maintain the electrochemical performance to power various flexible and wearable electronics. Supercapacitor units were made up of flexible materials assembled from freestanding interwoven ultralong MnO2 nanowire/CNT composites, the flexible units were then edited into a desirable structure. The stretchability of this editable structure (up to 500%) is much superior to conventional stretchable structure (usually less than 200%). Along with the customizable two-dimensional (2D) supercapacitor, stretchable supercapacitors with customizable three-dimensional (3D) shapes and enhanced areal capacitance is also developed, which is inspired by the traditional artifact-honeycomb lantern. With a honeycomb pop-up structure, the customizable 3D supercapacitors can overcome the limited device thickness of traditional 2D supercapacitors. Notably, a honeycomb-lantern-inspired 3D supercapacitor with a 1.0-cm-thick rectangular shape exhibited improved specific areal capacitance of 7.34 F cm-2, which is 61 times that of the conventional 2D planar supercapacitors (120 mF cm-2). The supercapacitor comprises flexible polypyrrole (PPy)/black phosphorous oxide (BPO)-carbon nanotube electrode configured in expandable honeycomb structures for maintaining the stable electrochemical performance (capacitance retention of 95%) under the reversible 2000% tensile strain after 10,000 stretch-and-release cycles. Furthermore, to achieve flexible and customizable EES device with higher energy storage performance, a biomass-based and elastic NC binder is employed to fabricate flexible high-voltage lithium ion battery cathode. The elastic nanocellulose (NC) binder was used to function as the porous freestanding framework to protect the intergranular of the LiNi0.5Co0.2Mn0.3O2 (NCM523) secondary particles from cracking. The NC-binder based electrode owns improved rate performance and more stable long-term capacity (145.8 mAh g−1 after 300 cycles at 1 C) at 4.6 V compared to that of conventional PVDF binder-based electrode (113.2 mAh g−1). The above results show that mechano-adaptive electrodes and device structures provide a new design platform for customizable EES devices. Following it and cooperating with functional materials, many other new methods and flexible and customizable harvesting and integrated electronics could be further developed.