Showing papers on "Power density published in 2022"

Supercapattery: Merging of battery-supercapacitor electrodes for hybrid energy storage devices

Abstract: Supercapattery devices have grasped attention due to their remarkable specific energy (Es) without affecting their specific power (Ps), which is significantly higher compared to batteries and supercapacitors (SCs). In contrast to the traditional electric double layer capacitors (EDLCs) and pseudocapacitors (PCs), supercapattery devices have shown larger specific capacitance. Metal oxides, sulfides, phosphates, and metal-organic frameworks (MOFs) based materials have been extensively utilized for the advancement of hybrid energy storage devices (HESDs). Currently the challenges faced by this technology, is to improve the energy density without compromising the power density. The advantage of two merged technologies (battery and supercapacitor (SC)) into a single system, delivered tremendous power from capacitive components while high specific energy from battery grade material (BGM). This review covers the most recent improvements in vastly used electrode materials, with significant capacity as well as long cyclic life for high-performance supercapattery devices. Furthermore, this study aims to elaborate the electrochemical performance of the metal oxides, sulfides, phosphates, and MOFs for energy storage applications.

All pseudocapacitive MXene-MnO2 flexible asymmetric supercapacitor

Abstract: As a newly emerging 2D materials, MXene as electrode materials can be widely used in supercapacitors. However, symmetric supercapacitors based on MXene have a narrow voltage window due to oxidation occurs at a high anode potential. In this study, flexible asymmetric supercapacitor device is designed and fabricated by combining MXene/carbon fabric (CF) as the negative electrode and CF/MnO2 as the positive electrode in neutral electrolyte. The voltage window of the asymmetric device is successfully increased to 1.5 V, which is more than twice wider than that of the symmetric device. The maximum specific capacitance is 20.5 F g−1 at 1.5 A g−1. The specific capacitance remains at 84% after 3000 charge-discharge cycles at 1.5 A g−1. Furthermore, two asymmetric devices after bending 1000 times greater than 90° connected in series can easily power a 3 V LED for 90 min. The energy density of the asymmetric device is 6.4 W h kg−1 at 1107.7 W kg−1 power density. The work presented here shows that the asymmetric device based on MXene//MnO2 have excellent application prospects for the next generation of electrochemical energy storage devices.

Thermophotovoltaic efficiency of 40%

Abstract: Thermophotovoltaics (TPVs) convert predominantly infrared wavelength light to electricity via the photovoltaic effect, and can enable approaches to energy storage1,2 and conversion3-9 that use higher temperature heat sources than the turbines that are ubiquitous in electricity production today. Since the first demonstration of 29% efficient TPVs (Fig. 1a) using an integrated back surface reflector and a tungsten emitter at 2,000 °C (ref. 10), TPV fabrication and performance have improved11,12. However, despite predictions that TPV efficiencies can exceed 50% (refs. 11,13,14), the demonstrated efficiencies are still only as high as 32%, albeit at much lower temperatures below 1,300 °C (refs. 13-15). Here we report the fabrication and measurement of TPV cells with efficiencies of more than 40% and experimentally demonstrate the efficiency of high-bandgap tandem TPV cells. The TPV cells are two-junction devices comprising III-V materials with bandgaps between 1.0 and 1.4 eV that are optimized for emitter temperatures of 1,900-2,400 °C. The cells exploit the concept of band-edge spectral filtering to obtain high efficiency, using highly reflective back surface reflectors to reject unusable sub-bandgap radiation back to the emitter. A 1.4/1.2 eV device reached a maximum efficiency of (41.1 ± 1)% operating at a power density of 2.39 W cm-2 and an emitter temperature of 2,400 °C. A 1.2/1.0 eV device reached a maximum efficiency of (39.3 ± 1)% operating at a power density of 1.8 W cm-2 and an emitter temperature of 2,127 °C. These cells can be integrated into a TPV system for thermal energy grid storage to enable dispatchable renewable energy. This creates a pathway for thermal energy grid storage to reach sufficiently high efficiency and sufficiently low cost to enable decarbonization of the electricity grid.

Composition and Structure Optimized BiFeO3 -SrTiO3 Lead-Free Ceramics with Ultrahigh Energy Storage Performance.

Abstract: Dielectric ceramic capacitors have attracted increasing attention as advanced pulsed power devices and modern electronic systems owing to their fast charge/discharge speed and high power density. However, it is challenging to meet the urgent needs of lead-free ceramics with superior energy storage performance in practical applications. Herein, a strategy for the composition and structural modification is proposed to overcome the current challenge. The lead-free ceramics composed of BiFeO3 -SrTiO3 are fabricated. A low hysteresis and high polarization can be achieved via composition optimization. The experimental results and finite element simulations indicate that the two-step sintering method significantly influences the decrease in the grain size and improvement in the breakdown strength (EBDS ). A high EBDS of ≈750 kV cm-1 accompanied by a large maximum polarization (≈40 µC cm-2 ) and negligible remanent polarization (<2 µC cm-2 ) contribute to the ultrahigh energy density and efficiency values of the order of 8.4 J cm-3 and ≈90%, respectively. Both energy density and efficiency exhibit excellent stability over the frequency range of 1-100 Hz and temperatures up to 120 °C, along with the superior power density of 280 MW cm-3 , making the studied BiFeO3 -SrTiO3 ceramics potentially useful for high-power energy storage applications.

Covalent organic framework–based porous ionomers for high-performance fuel cells

Abstract: Lowering platinum (Pt) loadings without sacrificing power density and durability in fuel cells is highly desired yet challenging because of the high mass transport resistance near the catalyst surfaces. We tailored the three-phase microenvironment by optimizing the ionomer by incorporating ionic covalent organic framework (COF) nanosheets into Nafion. The mesoporous apertures of 2.8 to 4.1 nanometers and appendant sulfonate groups enabled the proton transfer and promoted oxygen permeation. The mass activity of Pt and the peak power density of the fuel cell with Pt/Vulcan (0.07 mg of Pt per square centimeter in the cathode) both reached 1.6 times those values without the COF. This strategy was applied to catalyst layers with various Pt loadings and different commercial catalysts. Description Helping fuel cells breathe In proton exchange membrane fuel cells, the Nafion ionomer usually overencapsulates and inhibits the platinum catalyst and can impede gas transport in the catalyst layer. Q. Zhang et al. showed that adding a sulfonated covalent organic framework (COF) to Nafion could improve the activity based on platinum by up to 60% (see the Perspective by Ma and Lutkenhaus). The hexagonal pores of the COF improve gas transport, and the sulfonic acid groups anchored on the pore walls decrease binding to platinum, which inhibits its activity. —PDS Adding a sulfonated ionic covalent organic framework into the Nafion ionomer improves gas transport to the catalyst layer.

Every bite of Supercap: A brief review on construction and enhancement of supercapacitor

Abstract: Supercapacitor is a potential energy storage device that has been used in various fields like automotive industries, energy harvesting and grid stabilization system due to its unique feature in terms of power density, life cycle, operating temperature range, charge/discharge period, and specific capacitance. Therefore, supercapacitors are used in grid systems to smooth the energy feeding and stabilize the grid system during peak demands. Supercapacitors can provide high power at a short period of time. Correspondingly, supercapacitors are postulated to be the potential replacement for batteries due to their excellent power density which reduces the charging period, longer cycle life than batteries, forgiving even it is overused and is environmentally friendly compared to batteries. However, supercapacitors lack in energy density compared to batteries; thus, it is often used as a short-term energy storage device. Supercapacitors are generally divided into three groups: a) electric double-layer capacitor (EDLC), b) pseudocapacitor, and c) hybrid supercapacitor. These three groups differ in charge storage mechanism, which is closely related to the type and nature of the materials used to design the supercapacitor's electrode. Over and above all, the electrode material is a contributing factor to the supercapacitor's electrochemical performance. Aside from electrode material, electrolyte also influences the electrochemical performance. Hence, it is essential to choose the appropriate electrode and electrolyte according to the desired outcome. To be able to choose, the nature and properties of the materials should be studied. So, in this paper, all three types of supercapacitors are discussed, along with the factors that influence the electrochemical performance. Besides, different electrode materials and electrolytes are included together with an overview of the future scope of supercapacitors. • Rise of supercapacitor and how it differs from battery and capacitor were explored. • Types of supercapacitor construction and mechanism were included. • Importance of supercapacitor components for enhancement process was discussed. • Selection of an appropriate electrode and electrolyte is critical. • Types of electrode materials and electrolytes were reviewed.

Toward Practical High‐Energy and High‐Power Lithium Battery Anodes: Present and Future

Abstract: Abstract Lithium batteries are key components of portable devices and electric vehicles due to their high energy density and long cycle life. To meet the increasing requirements of electric devices, however, energy density of Li batteries needs to be further improved. Anode materials, as a key component of the Li batteries, have a remarkable effect on the increase of the overall energy density. At present, various anode materials including Li anodes, high‐capacity alloy‐type anode materials, phosphorus‐based anodes, and silicon anodes have shown great potential for Li batteries. Composite‐structure anode materials will be further developed to cater to the growing demands for electrochemical storage devices with high‐energy‐density and high‐power‐density. In this review, the latest progress in the development of high‐energy Li batteries focusing on high‐energy‐capacity anode materials has been summarized in detail. In addition, the challenges for the rational design of current Li battery anodes and the future trends are also presented.

Facile growth of nickel foam-supported MnCo2O4.5 porous nanowires as binder-free electrodes for high-performance hybrid supercapacitors

Abstract: In this work, porous MnCo2O4.5 nanowires (NWs) were directly grown on nickel foam (NF) via an initial hydrothermal route with an extra annealing treatment of precursor. Another comparative experiment was conducted with a lower amount of urea to obtain particle-based MnCo2O4.5 films. These binder-free MnCo2O4.5@NF electrodes exhibited battery-type electro-chemical response with superior electro-chemical performance. Especially, the MnCo2O4.5[email protected] delivered a huge capacity of 288.47 C g−1 at 1 A g−1 and 78.07% of capacity retention at 10 A g−1. Moreover, a hybrid supercapacitor (HSC) that was assembled using activated carbon (AC) as an anode could operate over a voltage of 1.7 V. The MnCo2O4.5[email protected]//AC HSC delivered an energy density of up to 29.57 W h kg−1 at the power density of 914.28 W kg−1, and it could still hold 20.82 W h kg−1 since the power density was improved to 8.24 kW kg−1. In addition, both these MnCo2O4.5 NWs- and films-based HSCs showed an impressive cyclic stability over continuous 6000 cycles at a high current density of 6 A g−1, but only a little capacity decay was observed. Such extraordinary electro-chemical performance makes the binder-free MnCo2O4.5[email protected] electrode material promising and very feasible to be applied for electro-chemical energy storage devices such as batteries, supercapacitors, and so on.

Co(OH)F@CoP/CC core-shell nanoarrays for high-performance supercapacitors

Abstract: The transition metal phosphides have drawn wide attention as positive material used in supercapacitors owing to the excellent conductivity and electrochemical activity. In this work, the novel composite Co(OH)F@CoP core-shell nanoarrays, used as electrode material for supercapacitors, was synthesized on conductive carbon cloth (CC) through the hydrothermal method and phosphating process. The specific capacitance of Co(OH)F@CoP/CC is 654mC cm−2 at 1 mA·cm−2, and maintains long-life cycling stability of 71.34 % retention after 10,000 cycles at 10 mA·cm−2 in a three electrode system. Furthermore, a two-electrode system assembled by Co(OH)F@CoP and reduced graphene oxide (RGO) exhibits performance with energy density of 17.933 Wh kg−1 at power density of 800 W kg−1. These results proved that the Co(OH)F@CoP composite is an advanced electrode material for the supercapacitors.