Batteries: Recent Advances in Carbon Materials

Abstract

We welcome readers to this Special Issue of C. From the standpoint of economics of energy storage, carbon electrodes offer the practicality of large-scale applications with the promise of improved performance. Key to increases in energy storage and power delivery are the heterogeneous electron transfer (HET) rates with dissolved redox species. Perhaps the most common allotrope of carbon, graphite suffers from slow HET kinetics across its basal plane. Two papers in this issue specifically examine the HET rates for carbon electrodes with aqueous redox species. One study examines the HET rate with V 3+/2+ for application in the proposed application of the vanadium redox flow battery [1]. The carbon material of this investigation, GUITAR (Graphene from the University of Idaho Thermolyzed Asphalt Reaction) superficially resembles a crystalline graphite but with much improved HET kinetics across its basal plane. Paradoxically, it was found that parasitic hydrogen evolution reaction rates were slower on GUITAR's basal plane relative to graphite's. The second paper examines various carbon materials in the application of mediatorless sulfide sensing [2]. An edge plane material, glassy carbon (GC) and carbon screen printed electrodes (SPE) proved to be kinetically the fastest in the electro-oxidation of sulfide when compared with other carbon materials. The basal plane graphite electrode was voltammetrically non-responsive towards sulfide. Sensor fouling by irreversible sulfide adsorption afflicted both GC and SPE, however the latter offers the ability of one-shot disposable analyses with greater reproducibility over the former.The importance of carbon materials in batteries cannot be underemphasized, especially in the area of ion intercalation anodes. It is remarkable that the lithium ion battery has seen its energy density increase by a few hundred percent since its introduction in 1991 with the market growing to over $20 billion (2016) in the US alone. Applications range from personal electronic devices, automotive to grid-level storage. The Li ion graphite anode offers a theoretical storage capacity of 372 mA·h/g. There is ongoing research into the materials that offer an increase over that quantity while maintaining cycling capacity. Bhat et al. describe the formation of B-C-N ceramics as lithium ion intercalation anodes. The BC 4 N material demonstrates a stable capacity of 500 mA·h/g over 135 cycles [3]. While the Li ion storage mechanism is not fully characterized, the authors hypothesize that boron can act as an electron acceptor giving fast Li ion diffusion through the disordered network of doped carbon. Sodium ion offers a cost-effective alternative to Li + . The review in this issue offers insights into the considerations for sodium ion anodes [4]. As Na is a larger ion, it is less favorable to insertion than Li. The d 002 spacing (i.e., between graphene layers) of graphite is 3.34 Å. This review explores the literature aimed at increasing that spacing with empirical methods of deriving carbons from biomasses....

Design, fabrication, and metrology of 10 × 100 multi-planar integrated photonic routing manifolds for neural networks

“…Because photons are uncharged and massless, photons avoid charge-based wiring parasitics. Using light for communica-2 tion in neural systems is very promising [11][12][13][14][15][16] , but constructing a network of nodes each with thousands of connections presents a formidable routing challenge. Using WDM alone is untenable, as it would require an extremely fine and precise wavelength spacing to be constantly maintained.…”

Solution‐Based in–situ Synthesis of Transition Metal Sulfides as Efficient Counter Electrodes for Dye‐Sensitized Solar Cells

“…[6,7] However, Pt is rare and expensive, which restricts the extensive commercial application of DSSCs. [8][9][10][11][12] To replace Pt, cheaper materials such as carbon materials, [13][14][15] conductive polymers, [16][17][18] transition-metal compounds, [19][20][21] metal alloys, [22,23] and their composites [24][25][26][27] have been explored. Among these alternatives, transition-metal compounds including carbides, nitrides, chalcogenides and etc owning attractive electrocatalytic activity have demonstrated excellent performances.…”