Query: capacitors

title: Materials for electrochemical capacitors.
abstract: Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo capacitors) They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high energy density devices using a variety of electrolytes. Combination of pseudo capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high energy and high power devices.

title: Review of Hybrid Ion Capacitors: From Aqueous to Lithium to Sodium.
abstract: In this critical Review we focus on the evolution of the hybrid ion capacitor (HIC) from its early embodiments to its modern form, focusing on the key outstanding scientific and technological questions that necessitate further in depth study. It may be argued that HICs began as aqueous systems, based on a Faradaic oxide positive electrode (e.g. Co3O4, RuO x) and an activated carbon ion adsorption negative electrode. In these early embodiments HICs were meant to compete directly with electrical double layer capacitors (EDLCs) rather than with the much higher energy secondary batteries. The HIC design then evolved to be based on a wide voltage ~4.2 V) carbonate based battery electrolyte, using an insertion titanium oxide compound anode (Li4Ti5O12, Li xTi5O12) versus a Li ion adsorption porous carbon cathode. The modern Na and Li architectures contain a diverse range of nanostructured materials in both electrodes, including TiO2, Li7Ti5O12, Li4Ti5O12, Na6LiTi5O12, Na2Ti3O7, graphene, hard carbon, soft carbon, graphite, carbon nanosheets, pseudocapacitor T Nb2O5, V2O5, MXene, conversion compounds MoS2, VN, MnO, and Fe2O3/Fe3O4, cathodes based on Na3V2(PO4)3, NaTi2(PO4)3, sodium super ionic conductor (NASICON) etc. The Ragone chart characteristics of HIC devices critically depend on their anode cathode architectures. Combining electrodes with the flattest capacity versus voltage characteristics, and the largest total voltage window, yields superior energy. Unfortunately "flat voltage" materials undergo significant volume expansion/contraction during cycling and are frequently lifetime limited. Overall more research on HIC cathodes is needed; apart from high surface area carbon, very few positive electrodes demonstrate the necessary 10 000 or 100 000 plus cycle life. It remains to be determined whether its lithium ion capacitors (LICs) or sodium ion capacitors (NICs) are superior in terms of energy power and cyclability. We discuss unresolved issues, including poorly understood fast charge storage mechanisms, prelithiation and presodiation, solid electrolyte interface (SEI) formation, and high rate metal plating.

title: Multilayer Lead Free Ceramic Capacitors with Ultrahigh Energy Density and Efficiency.
abstract: The utilization of antiferroelectric (AFE) materials is thought to be an effective approach to enhance the energy density of dielectric capacitors. However, the high energy dissipation and inferior reliability that are associated with the antiferroelectric ferroelectric phase transition are the main issues that restrict the applications of antiferroelectric ceramics. Here, simultaneously achieving high energy density and efficiency in a dielectric ceramic is proposed by combining antiferroelectric and relaxor features. Based on this concept, a lead free dielectric (Na0.5 Bi0.5 )TiO3 x(Sr0.7 Bi0.2 )TiO3 (NBT xSBT) system is investigated and the corresponding multilayer ceramic capacitors (MLCCs) are fabricated. A record high energy density of 9.5 J cm 3 together with a high energy efficiency of 92% is achieved in NBT 0.45SBT multilayer ceramic capacitors, which consist of ten dielectric layers with the single layer thickness of 20 um and the internal electrode area of 6.25 mm2 Furthermore, the newly developed capacitor exhibits a wide temperature usage range of 60 to 120 degC, with an energy density variation of less than 10% and satisfactory cycling reliability, with degradation of less than 8% over 106 cycles. These characteristics demonstrate that the NBT 0.45SBT multilayer ceramic is a promising candidate for high power energy storage applications.

title: Laser Scribing of High Performance and Flexible Graphene Based Electrochemical Capacitors
abstract: Infrared Route to Graphene Electrodes Electrochemical capacitors can deliver large amounts of power quickly, but have limited energy storage because only the surface regions of electrodes can store charge. Graphene represents an alternative to activated carbon electrodes because of their high conductivity and surface area, but graphene sheets tend to reassociate and lose surface area. El Kady et al. (p. 1326; see the Perspective by Miller) show that graphite oxide sheets can be converted by infrared laser irradiation into porous graphene sheets that are flexible, robust, and highly conductive. Infrared laser reduction of graphene oxide creates a strong porous electrode with both high surface area and high conductivity. Although electrochemical capacitors (ECs) also known as supercapacitors or ultracapacitors, charge and discharge faster than batteries, they are still limited by low energy densities and slow rate capabilities. We used a standard LightScribe DVD optical drive to do the direct laser reduction of graphite oxide films to graphene. The produced films are mechanically robust, show high electrical conductivity (1738 siemens per meter) and specific surface area (1520 square meters per gram) and can thus be used directly as EC electrodes without the need for binders or current collectors, as is the case for conventional ECs. Devices made with these electrodes exhibit ultrahigh energy density values in different electrolytes while maintaining the high power density and excellent cycle stability of ECs. Moreover, these ECs maintain excellent electrochemical attributes under high mechanical stress and thus hold promise for high power, flexible electronics.

title: Electrochemical capacitors: mechanism, materials, systems, characterization and applications.
abstract: Electrochemical capacitors (i.e. supercapacitors) include electrochemical double layer capacitors that depend on the charge storage of ion adsorption and pseudo capacitors that are based on charge storage involving fast surface redox reactions. The energy storage capacities of supercapacitors are several orders of magnitude higher than those of conventional dielectric capacitors, but are much lower than those of secondary batteries. They typically have high power density, long cyclic stability and high safety, and thus can be considered as an alternative or complement to rechargeable batteries in applications that require high power delivery or fast energy harvesting. This article reviews the latest progress in supercapacitors in charge storage mechanisms, electrode materials, electrolyte materials, systems, characterization methods, and applications. In particular, the newly developed charge storage mechanism for intercalative pseudocapacitive behaviour, which bridges the gap between battery behaviour and conventional pseudocapacitive behaviour, is also clarified for comparison. Finally, the prospects and challenges associated with supercapacitors in practical applications are also discussed.

title: Electrode Materials, Electrolytes, and Challenges in Nonaqueous Lithium Ion Capacitors.
abstract: Among the various energy storage systems, lithium ion capacitors (LICs) are receiving intensive attention due to their high energy density, high power density, long lifetime, and good stability. As a hybrid of lithium ion batteries and supercapacitors, LICs are composed of a battery type electrode and a capacitor type electrode and can potentially combine the advantages of the high energy density of batteries and the large power density of capacitors. Here, the working principle of LICs is discussed, and the recent advances in LIC electrode materials, particularly activated carbon and lithium titanate, as well as in electrolyte development are reviewed. The charge storage mechanisms for intercalative pseudocapacitive behavior, battery behavior, and conventional pseudocapacitive behavior are classified and compared. Finally, the prospects and challenges associated with LICs are discussed. The overall aim is to provide deep insights into the LIC field for continuing research and development of second generation energy storage technologies.

title: Electrochemical Capacitors for Energy Management
abstract: Rapid storage and efficient delivery of electrical energy in heavy duty applications are being enabled by electrochemical capacitors.

title: Pseudocapacitive Sodium Storage in Mesoporous Single Crystal like TiO2 Graphene Nanocomposite Enables High Performance Sodium Ion Capacitors.
abstract: Sodium ion capacitors can potentially combine the virtues of high power capability of conventional electrochemical capacitors and high energy density of batteries. However, the lack of high performance electrode materials has been the major challenge of sodium based energy storage devices. In this work, we report a microwave assisted synthesis of single crystal like anatase TiO2 mesocages anchored on graphene as a sodium storage material. The architecture of the nanocomposite results in pseudocapacitive charge storage behavior with fast kinetics, high reversibility, and negligible degradation to the micro/nanostructure. The nanocomposite delivers a high capacity of 268 mAh g 1 at 0.2 C, which remains 126 mAh g 1 at 10 C for over 18 000 cycles. Coupling with a carbon based cathode, a full cell of sodium ion capacitor successfully demonstrates a high energy density of 64.2 Wh kg 1 at 56.3 W kg 1 and 25.8 Wh kg 1 at 1357 W kg 1, as well as an ultralong lifespan of 10 000 cycles with over 90% of capacity retention.

title: Nonaqueous Hybrid Lithium Ion and Sodium Ion Capacitors.
abstract: Hybrid metal ion capacitors (MICs) (M stands for Li or Na) are designed to deliver high energy density, rapid energy delivery, and long lifespan. The devices are composed of a battery anode and a supercapacitor cathode, and thus become a tradeoff between batteries and supercapacitors. In the past two decades, tremendous efforts have been put into the search for suitable electrode materials to overcome the kinetic imbalance between the battery type anode and the capacitor type cathode. Recently, some transition metal compounds have been found to show pseudocapacitive characteristics in a nonaqueous electrolyte, which makes them interesting high rate candidates for hybrid MIC anodes. Here, the material design strategies in Li ion and Na ion capacitors are summarized, with a focus on pseudocapacitive oxide anodes (Nb2 O5 MoO3 etc. which provide a new opportunity to obtain a higher power density of the hybrid devices. The application of Mxene as an anode material of MICs is also discussed. A perspective to the future research of MICs toward practical applications is proposed to close.

title: Sustainable materials for electrochemical capacitors
abstract: Highly tunable properties of materials used for the construction of electrochemical capacitors make them a perfect choice for a broad scope of applications with high power demand. The ability to design the system according to the expected power/energy profile allows them being considered as powerful alternatives to conventional capacitors and batteries. Carbon materials with the developed specific surface area are the most common electrode components of electrochemical capacitors because of their cost, versatile form, availability, easiness of processing, and eco friendly character. Biomass is frequently used for carbon production, however, among many natural organic materials, only some of them should be regarded as a useful precursor. Ongoing research brings many novel concepts of using bio derived materials in high performance electrochemical capacitors. This review article summarizes the progress on the applications of abundant biomaterials and materials derived from biomass in the field. Various 'green' resources have been used as precursors for activated carbons, as binders, or as gel (gelating) agents for solid state electrolytes. The authors attempt to critically evaluate a commercial potential of these materials upon ongoing trends in research development of electrochemical capacitors. Pros and cons of utilizing the selected biomass materials are provided and perspectives for their advanced processing are discussed.