ABSTRACT
Environmental protection and new energy development have recently become growing industries, in which energy-storage devices are highlighted as crucial components. The electrochemical or double-layer capacitors constitute an important transient-energy-storage technology for rapid-charge/discharge applications. Electrochemical capacitors (double-layer capacitors [EDLC] and pseudo-capacitors) are intrinsically high-power devices (between 5 and 15 kW/kg) of limited energy-storage capability and long cycle life. Compared with batteries, supercapacitors have higher power density with shorter charge/discharge time, longer shelf and cycle life, but relatively lower energy density. In some aspects, they bridge the gap between conventional capacitors and batteries in that they display energy density higher than that of conventional capacitors and higher power density than batteries (Ye et al. 2005; Huang et al. 2008; Largeot et al. 2008; Simon & Gogotsi 2008; Sharma & Bhatti 2010; Gileadi 2011; Bittner et al. 2012; Choi et al. 2012; Shukla et al. 2012; M. Li et al. 2013; Oakes et al. 2013; A. Yu et al. 2013; G. Yu et al. 2013; Cheng et al. 2014; Gu & Yushin 2014; Kang et al. 2014) (Figure 16.1).
