Zhiqiang Niu Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), College of Chemistry Nankai University Tianjin, 300071, P. R. China
Guozhen Shen State Key Laboratory for Superlattices and Microstructures Institute of Semiconductors, Chinese Academy of Science Beijing, 100083, China
Peng Sun Siyuan Laboratory, Guangdong Provincial Engineering Technology Research Center of Vacuum Coating Technologies and New Energy Materials, Department of Physics Jinan University Guangzhou, 510632, PR China
Hua Wang State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology (Shenzhen) Shenzhen, 518055, Guangzhou, China; and Flexible Printed Electronics Technology Centre Harbin Institute of Technology (Shenzhen) Shenzhen, 518055, Guangzhou, China
Jiaqi Wang State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology (Shenzhen) Shenzhen, 518055, Guangzhou, China; and Flexible Printed Electronics Technology Centre Harbin Institute of Technology (Shenzhen) Shenzhen, 518055, Guangzhou, China
Panpan Wang State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology (Shenzhen) Shenzhen, 518055, Guangzhou, China; and Flexible Printed Electronics Technology Centre Harbin Institute of Technology (Shenzhen) Shenzhen, 518055, Guangzhou, China
Qiufan Wang Key laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education & Hubei Key Laboratory of Catalysis and Materials Science, Hubei R&D Center of Hyperbranched Polymers Synthesis and Applications South‐Central University for Nationalities 182 Minzu Road, Wuhan, 430074, China
Rui Wang Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education) College of Chemistry, Nankai University Tianjin, 300071, P. R. China
Xiang Wu School of Materials Science and Engineering Shenyang University of Technology China
Jing Xu School of Materials Science and Engineering Nanjing University of Science and Technology Xuanwu District, Nanjing 210094, China; and Herbert Gleiter Institute of Nanoscience Nanjing University of Science and Technology Xuanwu District, Nanjing 210094, China
Daohong Zhang Key laboratory of Catalysis and Energy Materials Chemistry of Ministry of Education & Hubei Key Laboratory of Catalysis and Materials Science, Hubei R&D Center of Hyperbranched Polymers Synthesis and Applications South‐Central University for Nationalities 182 Minzu Road, Wuhan 430074, China
Xiyue Zhang MOE of the Key Laboratory of Bioinorganic and Synthetic Chemistry, The Key Lab of Low‐Carbon Chem and Energy Conservation of Guangdong Province, School of Chemistry Sun Yat‐Sen University Guangzhou, Guangdong, 510275, People's Republic of China
Yizhou Zhang State Key Laboratory of Organic Electronics and Information Displays (SKLOEI), Institute of Advanced Materials (IAM) Nanjing University of Posts & Telecommunications 9 Wenyuan Road, Nanjing, 210023, Jiangsu, China; and Institute of Advanced Materials and Flexible Electronics (IAMFE), School of Chemistry and Materials Science Nanjing University of Information Science & Technology 219 Ningliu Road, 210044, Nanjing, Jiangsu, China
Preface
As an emerging and exciting research field, flexible electronics have attracted tremendous interests from both the academic and industrial communities. Till now, many kinds of flexible electronic devices and systems have been developed, such as flexible displays, electronic skins, health monitoring bioelectronics, chemical and biosensors, wearable smart textile, and intelligent soft robots, etc. This area develops very fast and some flexible products are already commercially available. For example, flexible organic light‐emitting diode displays have been widely used in smart phones, smart watches, and tablet personal computers.
The booming development of flexible electronics has driven the demand for compatible flexible energy storage devices, ideally to make the whole electronic system flexible. Although conventional energy storage devices, such as lithium‐ion batteries, lead acid batteries, supercapacitors, have been widely used in our modern society and affected our daily life, their rigid shape, heavy weight, and thickness make them not suitable for flexible electronics. Among different energy storage devices, supercapacitors have the advantages of simple device structure, high power density, short charge and discharge time, long cycle life and wide operating temperature range. When making supercapacitor flexible, it will also possesses the required features of excellent flexibility, portability, stretchability, miniaturized size, ultrathin thickness for flexible electronic devices. During the past several years, researches on flexible supercapacitors are very active and this field expanded very fast. Thus, it is considered timely to provide a survey of a number of important developments in this filed.
This book provides an up‐to‐date survey of the state of flexible supercapacitors. It contains a selection of 11 chapters contributed by a number of research teams. All the contributors are active researchers in the field of flexible supercapacitors. The most important topics related to flexible supercapacitors are included in this book, ranging from the selection and design of different active electrode materials, the design of different device structures, suitable fabrication techniques, and different functions. I hope this book will be a source of inspiration for graduate students, researchers, and industrial engineers, and will stimulate new developments in this challenging but exciting field.
1 Flexible Asymmetric Supercapacitors: Design, Progress, and Challenges
Dun Lin, Xiyue Zhang and Xihong Lu
MOE of the Key Laboratory of Bioinorganic and Synthetic Chemistry, The Key Lab of Low‐Carbon Chem and Energy Conservation of Guangdong Province, School of Chemistry, Sun Yat‐Sen University, Guangzhou, Guangdong, 510275, People’s Republic of China
1.1 Introduction
Recently, flexible electronic products, such as flexible microphones [1], elastic circuits [2–4], pressure and strain sensors [5–7], artificial skin sensors [8–10], intelligent garments [11], and wearable health monitoring devices have boomed as a new and important field of modern electronics (Figure 1.1). Therefore, the development of suitable energy storage devices, which can serve as an excellent power supply while sustaining high mechanical flexibility, are becoming increasingly necessary to power these electronics [13–21]. Supercapacitors (SCs), also known as electrochemical capacitors or ultracapacitors, have emerged as the bridge between batteries and traditional capacitors due to their promising merits of high power density (about 10 kW kg−1), good reversibility, excellent cyclic stability (over 106 cycles), and safety [22, 23]. Meanwhile, accompanied with the advanced development of lightweight, foldable, and stretchable materials, substantial effort has been invested in the fabrication of flexible supercapacitors (FSCs) [24–28].
In order to satisfy the further demand for practical usage, the configuration of the two electrodes as well as the geometry of the devices are of vital importance and worth careful considerations [29]. The major obstacle of early designed FSCs is their relatively low energy density (E) to mismatch basic requirements of future applications. Thus, tremendous efforts have been denoted to optimize the overall performance of FSCs according to the Eq. (1.1), without sacrificing their power density and service life.