A Redox-Active Binder for Electrochemical Capacitor Electrodes

Radical chemistry in polymer science: an overview and recent advances

Radical chemistry is one of the most important methods used in modern polymer science and industry. Over the past century, new knowledge on radical chemistry has both promoted and been generated from the emergence of polymer synthesis and modification techniques. In this review, we discuss radical chemistry in polymer science from four interconnected aspects. We begin with radical polymerization, the most employed technique for industrial production of polymeric materials, and other polymer synthesis involving a radical process. Post-polymerization modification, including polymer crosslinking and polymer surface modification, is the key process that introduces functionality and practicality to polymeric materials. Radical depolymerization, an efficient approach to destroy polymers, finds applications in two distinct fields, semiconductor industry and environmental protection. Polymer chemistry has largely diverged from organic chemistry with the fine division of modern science but polymer chemists constantly acquire new inspirations from organic chemists. Dialogues on radical chemistry between the two communities will deepen the understanding of the two fields and benefit the humanity.

Redox-Mediator-Enhanced Electrochemical Capacitors: Recent Advances and Future Perspectives

Supercapacitors deliver exceptional power densities, high cycling stability, and inherent safety but suffer from low energy densities. Many methods to enhance the energy density are based on exploring electrode materials with well-developed structures and designing asymmetric systems with wide voltage windows. The energy density is substantially enhanced at the compromise of power density by utilizing the sluggish kinetics of pseudocapacitive materials. Redox-active electrolytes can contribute additional pseudocapacitance from the reactions of redox mediators at the interface, which have attracted increasing attention of researchers. Redox-mediator-enhanced supercapacitors deliver high energy densities while retaining high power densities. This Minireview highlights the recently prominent progresses of single-, dual-, and ambipolar-redox-mediator-enhanced supercapacitors, the challenges they face, and approaches to suppress self-discharge and develop high-concentration redox-active electrolytes for performance promotion.

Bioinspired Redox-Active Catechol-Bearing Polymers as Ultrarobust Organic Cathodes for Lithium Storage

Redox-active catechols are bioinspired precursors for ortho-quinones that are characterized by higher discharge potentials than para-quinones, the latter being extensively used as organic cathode materials for lithium ion batteries (LIBs). Here, this study demonstrates that the rational molecular design of copolymers bearing catechol- and Li⁺ ion-conducting anionic pendants endow redox-active polymers (RAPs) with ultrarobust electrochemical energy storage features when combined to carbon nanotubes as a flexible, binder-, and metal current collector-free buckypaper electrode. The importance of the structure and functionality of the RAPs on the battery performances in LIBs is discussed. The structure-optimized RAPs can store high-capacities of 360 mA h g^-1 at 5C and 320 mA h g^-1 at 30C in LIBs. The high ion and electron mobilities within the buckypaper also enable to register 96 mA h g^-1 (24% capacity retention) at an extreme C-rate of 600C (6 s for total discharge). Moreover, excellent cyclability is noted with a capacity retention of 98% over 3400 cycles at 30C. The high capacity, superior active-material utilization, ultralong cyclability, and excellent rate performances of RAPs-based electrode clearly rival most of the state-of-the-art Li⁺ ion organic cathodes, and opens up new horizons for large-scalable fabrication of electrode materials for ultrarobust Li storage.