Electrode

Abstract: Rechargeable solid-state batteries have long been considered an attractive power source for a wide variety of applications, and in particular, lithium-ion batteries are emerging as the technology of choice for portable electronics. One of the main challenges in the design of these batteries is to ensure that the electrodes maintain their integrity over many discharge-recharge cycles. Although promising electrode systems have recently been proposed, their lifespans are limited by Li-alloying agglomeration or the growth of passivation layers, which prevent the fully reversible insertion of Li ions into the negative electrodes. Here we report that electrodes made of nanoparticles of transition-metal oxides (MO, where M is Co, Ni, Cu or Fe) demonstrate electrochemical capacities of 700 mA h g(-1), with 100% capacity retention for up to 100 cycles and high recharging rates. The mechanism of Li reactivity differs from the classical Li insertion/deinsertion or Li-alloying processes, and involves the formation and decomposition of Li2O, accompanying the reduction and oxidation of metal nanoparticles (in the range 1-5 nanometres) respectively. We expect that the use of transition-metal nanoparticles to enhance surface electrochemical reactivity will lead to further improvements in the performance of lithium-ion batteries.

Abstract: Each cell of a battery stores electrical energy as chemical energy in two electrodes, a reductant (anode) and an oxidant (cathode), separated by an electrolyte that transfers the ionic component of the chemical reaction inside the cell and forces the electronic component outside the battery. The output on discharge is an external electronic current I at a voltage V for a time Δt. The chemical reaction of a rechargeable battery must be reversible on the application of a charging I and V. Critical parameters of a rechargeable battery are safety, density of energy that can be stored at a specific power input and retrieved at a specific power output, cycle and shelf life, storage efficiency, and cost of fabrication. Conventional ambient-temperature rechargeable batteries have solid electrodes and a liquid electrolyte. The positive electrode (cathode) consists of a host framework into which the mobile (working) cation is inserted reversibly over a finite solid–solution range. The solid–solution range, which is...

Abstract: Raman spectroscopy has been employed for the first time to study the role of adsorption at electrodes. It has been possible to distinguish two types of pyridine adsorption at a silver electrode. The variation in intensity and frequency of some of the bands with potential in the region of the point of zero charge has given further evidence as to the structure of the electrical double layer; it is shown that the interaction of adsorbed pyridine and water must be taken into account.

Abstract: 1 Introduction and Historical Perspective 2 Similarities and Differences between Supercapacitors and Batteries for Electrical Energy Storage 3 Energetics and Elements of Kinetics of Electrode Processes 4 Elements of Electrostatics Involved in Treatment of Double-Layers and Ions at Capacitors Electrode Interfaces 5 Behavior of Dielectrics in Capacitors and Theories of Dielectric Polarization 6 The Double-Layer at Capacitor Electrode Interfaces: Its Structure and Capacitance 7 Theoretical Treatment and Modeling of the Double-Layer at Electrode Interfaces 8 Behavior of the Double-Layer in Non-Aqueous Electrolytes and Non-Aqueous Electrolyte Capacitors 9 The Double-Layer and Surface Functionalities at Carbon 10 Electrochemical Capacitors Based on Pseudocapacitance 11 The Electrochemical Behavior of Ruthenium Oxide (RuO2) as a Material for Electrochemical Capacitors 12 Capacitance Behavior of Films Conducting, Electrochemically Reactive Polymers 13 The Electrolyte Factor in Supercapacitor Design and Performance: Conductivity, Ion-Pairing and Solvation 14 Electrochemical Behavior at Porous Electrodes Applications to Capacitors 15 Energy-Density and Power-Density of Electrical Energy Storage Devices 16 AC Impedance Behavior of Electrochemical Capacitors and Other Electrochemical Systems 17 Treatments of Impedance Behavior of Various Circuits and Modeling of Double-Layer Capacitor Frequency Response 18 Self-Discharge of Electrochemical Capacitors in Relation to that of at Batteries 19 Technology Development 20 Patent Survey

Abstract: Carbon materials have attracted intense interests as electrode materials for electrochemical capacitors, because of their high surface area, electrical conductivity, chemical stability and low cost. Activated carbons produced by different activation processes from various precursors are the most widely used electrodes. Recently, with the rapid growth of nanotechnology, nanostructured electrode materials, such as carbon nanotubes and template-synthesized porous carbons have been developed. Their unique electrical properties and well controlled pore sizes and structures facilitate fast ion and electron transportation. In order to further improve the power and energy densities of the capacitors, carbon-based composites combining electrical double layer capacitors (EDLC)-capacitance and pseudo-capacitance have been explored. They show not only enhanced capacitance, but as well good cyclability. In this review, recent progresses on carbon-based electrode materials are summarized, including activated carbons, carbon nanotubes, and template-synthesized porous carbons, in particular mesoporous carbons. Their advantages and disadvantages as electrochemical capacitors are discussed. At the end of this review, the future trends of electrochemical capacitors with high energy and power are proposed.