What is it about?
This review provides fundamentals of the similarities and differences between electrochemical capacitors and batteries from kinetic and material point of view. Basic techniques and analysis methods to distinguish the capacitive and battery-like behavior are discussed. Furthermore, guide-lines for material selection, the state-of-the-art materials, and the electrode design rules to advanced electrode are proposed
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Why is it important?
Tremendous efforts have been dedicated into the development of high-perfor-mance energy storage devices with nanoscale design and hybrid approaches. The boundary between the electrochemical capacitors and batteries becomes less distinctive. The same material may display capacitive or battery-like behavior depending on the electrode design and the charge storage guest ions. Therefore, the underlying mechanisms and the electrochemical pro-cesses occurring upon charge storage may be confusing for researchers who are new to the field as well as some of the chemists and material scientists already in the field.
Perspectives
he full potential of nanostructured capacitive materials, espe-cially extrinsic pseudocapacitive materials, and hybrid elec-trodes has not yet been realized. The performance, in terms of the capacitance, rate capability, and cycle stability, needs to be further improved and a proper balance needs to be considered. However, some fundamental criteria for identifying poten-tial high-performance pseudocapacitive electrode materials have been proposed, along with strategies for hybrid electrode design. Intrinsic and extrinsic pseudocapacitive materials have been identified from both thermodynamic and kinetic point of view. Advanced approaches, aiming at introducing more elec-trochemically active sites and shortening the transport path for electrons and diffusion length for ions, have been discussed. This is achieved through the selection of an appropriate pseu-docapacitive material and the careful design of the hybrid elec-trode architecture. Furthermore, the ability to quantitatively differentiate between the capacitive and diffusion-controlled processes assists in tailoring the hybrid electrode for different applications.
LIU JILEI
Nanyang Technological University
Read the Original
This page is a summary of: Advanced Energy Storage Devices: Basic Principles, Analytical Methods, and Rational Materials Design, Advanced Science, November 2017, Wiley,
DOI: 10.1002/advs.201700322.
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