In today’s world, portable electronics are an integral part of our lives. For example, with a mobile phone, we wake up in the morning, read the news, communicate, send and receive emails, listen to music, diagnose health issues and capture important fleeting moments in photos and videos. We no longer carry heavy stacks of documents and books but hold on to our laptop and wear an electronic watch not merely to know the time, but to monitor and record our health in real-time even while we sleep. Portable electronics bring comfort and convenience to our lives and are consequently found in every walk of our lives.
The dramatic growth in portable electronics has naturally led to the search for energy storages with high energy and power density to keep our devices long lasting and reduce the time we spend for charging a device. Among many types of energy storages, supercapacitors of high power density, fast charging, discharge capability and long cycle life have drawn much attention as a promising class of energy storage which may bridge the gap between lithium-ion batteries and conventional electrostatic capacitors [1–4]. Great effort has been particularly devoted to the development of lightweight and flexible electrode materials with a high capacity for practical applications of supercapacitors [5–10]. Despite their achievements, most electrode materials to date are susceptible to fracture under anomalous mechanical deformations to which our daily garments are frequently subjected such as folding, cutting and pressing. Some electrode materials have shown improved mechanical robustness with high bendability by having active conducting materials coated on flexible templates or scaffolds such as papers, fabrics and polymeric substrates [10–14]. Nevertheless, this approach of using inactive mechanical supports generates dead mass and volume involves which may not be ideal for the development of lightweight and mechanically durable supercapacitors with high capacity and power . This report introduces a new electrode material, namely activated carbon fiber (ACF) veil, which may broaden the design options and improve mechanical durability and comfort of wearable energy storages.
The organization of the report is as follows. Chapter 2 describes the electrochemical double layer (EDL) effect which accounts for the working mechanism of supercapacitors that are categorized as EDL capacitors. Helmholtz model is introduced to highlight the parameters which determine the capacitor of a supercapacitor. Chapter 3 reports the strategies of achieving high energy density in reference to various electrode materials in literature, followed by examples of electrode materials for wearable applications. Chapter 4 proposes a method of fabricating ACF veil, a novel fabric-like electrode, which exhibits electrochemical stability under various mechanical deformations to highlight the importance of mechanical reliability for the development of daily-wearable energy storage
May 31, 2018
Shin, D. (2018). Textile Supercapacitor for Wearable Energy Storage. United States: University of California, Berkeley.