High Discharge Power Density Research Articles

Tailoring ORR Activity in Fe-N-C Catalysts through Phosphorus Incorporation.

Atomically dispersed iron and nitrogen co-doped carbon materials (Fe-N-C) represent promising non-precious metal catalysts for the oxygen reduction reaction (ORR), offering potential alternatives to noble metal-based benchmarks. In our study, we investigated the influence of phosphorus doping on the catalytic activity of Fe-N-C. The experimental research demonstrate that the doping of phosphorus significantly enhances the ORR activity. Specifically, the resulting Fe-NPC exhibits high metal loading and excellent ORR activity in 0.1 M KOH with an onset potential of 1.00 V and a half-wave potential of 0.864 V. Density functional theory (DFT) simulations reveal that phosphorus improves the electrocatalytic activity by activating O2 molecules and reducing the energy barrier (the hydrogenation reaction *OH→H2O) of the rate-determining step. Furthermore, Fe-NPC exhibits promising application prospects as an air cathode in Zn-air batteries, delivering a high maximum discharge power density of 180.3 mW cm-2 and outstanding discharge specific capacity (758.8 mAh g-1Zn) at a discharge current density of 10 mA cm-2.

A High Discharge Power Density Single Cell of Hydrogen–Vanadium Flow Battery

A High Discharge Power Density Single Cell of Hydrogen–Vanadium Flow Battery

Ru doping induced interface engineering in flower-liked CoMoO4-RuO2 boosts oxygen electrocatalysis for rechargeable Zn-air battery

Constructing heterogeneous catalysts can significantly boost the electrocatalytic activity due to the improved intrinsic catalytic activity induced by tailored electronic structure and optimized chemisorption to the reaction intermediates. RuO2 based electrocatalysts are especially attractive due to the high catalytic activity of RuO2. To reduce the usage of noble metal and improve the catalytic activity of catalyst, CoMoO4-RuO2 micro-flower was synthesized using a facile hydrothermal-calcination method in this work. CoMoO4-RuO2 exhibits a low overpotential of 177 mV at 10 mA cm−2 for oxygen evolution reaction (OER) and a high half-wave potential of 0.858 V for oxygen reduction reaction (ORR). Moreover, the Zn-air battery assembled using CoMoO4-RuO2 exhibit shows a high maximum discharge power density of 149 mW cm−2 and a large open circuit voltage of 1.38 V. The good performance can be attributed to the incorporation of RuO2, which not only induces extra catalytic active sites, but also forms heterojunction with CoMoO4 to optimize the electronic structure of CoMoO4-RuO2, thereby achieving a better equilibrium of absorption and desorption of intermediates. The work provides insights into designing RuO2 based electrocatalysts for advanced electrocatalysis.

Significant improvement of comprehensive energy storage performance and transparency in Sr0.7La0.2TiO3-doped (K,Na)NbO3 lead-free ceramics

Although transparent ceramics are highly desirable for practical applications, it is challenging to achieve outstanding energy storage properties and high transparency simultaneously in (K, Na)NbO3 ceramics. Herein, through a combination of modifying crystal symmetry and refining domain size and grain size, a high recoverable energy storage density Wrec ≈ 4.04 J cm−3, a high efficiency η ≈ 73 %, and good optical transmittance (≈ 77 % at 2000 nm, ≈ 60 % at 780 nm) are realized. Of particular significance is that an excellent discharge energy density of ≈ 2.43 J cm−3, a superior discharge current density of ≈ 1551 A cm−2, and a high discharge power density of ≈ 233 MW cm−3 are simultaneously achieved in 0.93(K0.5Na0.5)NbO3-0.07 Sr0.7La0.2TiO3 ceramics, outperforming all reported KNN-based transparent ceramics. This work exhibits a paradigm for achieving high performance KNN-based ceramics, and the transparent dielectric ceramics reported here are expect to expand hybrid electronic device applications.

Tailoring the discharge performance of extruded Mg-Sm-Al anode for Mg-air battery applications via control of Al content

We investigated the discharge performance and electrochemical properties of an as-extruded Mg-5Sm-xAl (x = 0,1,3) anode for Mg-air batteries. Adding Al modified the phase composition and grain size of the anode. The addition of 1 wt% Al (Mg-5Sm-1Al) induced a high discharge voltage and power density due to the stimulation of the evenly distributed, fine Al11Sm3 particles. However, these particles increased the parasitical anodic hydrogen reaction rate, resulting in a decrease in anodic efficiency. These properties make the anode suitable for high-power density applications. The addition of 3 wt % Al (Mg-5Sm-3Al) promoted the formation of an aluminium oxide film on the anode surface, which suppressed the anodic hydrogen reaction to improve the anodic efficiency. This film increased the battery's internal resistance resulting in low voltage. This anode is a good candidate for heavy-duty battery applications, where a steady voltage output and long service life are desired. By controlling the Al content, the tailoring of discharge performance of the Mg-Sm-Al anode is feasible to satisfy different battery load requirements.

Rational Design of Heterostructured Ru Cluster‐Based Catalyst for pH Universal Hydrogen Evolution Reaction and High‐Performance Zn‐H2O Battery

AbstractRuthenium (Ru) is an ideal substitute to commercial Pt/C for hydrogen evolution reaction (HER). Reducing the size of Ru to clusters can greatly increase the utilization of atoms, however, over‐strong RuH binding will be brought about. Additionally, the water dissociation ability of Ru clusters is unfavorable, leading to unsatisfactory activity in alkaline and neutral HER. Herein, a rational and versatile design strategy is proposed by exploring supports with both high work function and facilitated water dissociation ability to boost the pH‐universal HER activity of Ru clusters. As exemplified by Mo2C, density functional calculations verify that the introduction of Mo2C support can optimize the hydrogen adsorption energy and promote the kinetics of water dissociation. Guided by theoretical calculations, heterostructured Mo2C nanoparticles‐Ru clusters anchored carbon spheres (Mo2C‐Ru/C) are designed and prepared. A low overpotential of 22 mV at 10 mA cm−2 and a small Tafel slope of 25 mV dec−1 in alkaline solution is demonstrated by Mo2C‐Ru/C. The Mo2C‐Ru/C also exhibits excellent activity in alkaline seawater, acidic, and neutral solutions. When assembling Mo2C‐Ru/C with Zn foil to construct an alkaline‐acid Zn‐H2O battery, the as‐fabricated battery presents high discharge power density and excellent stability for simultaneous generation of electricity and hydrogen (H2).

Electrocatalytic performance of Ni-promoted Co nanoclusters supported by N-doped carbon foams for rechargeable Zn-air batteries

Ni/Co diatomic clusters supported on nitrogen-doped carbon foams are prepared via molten salt method to improve the density of surface active sites of zinc-air battery catalysts and further explore metal-modified carbon-based catalysts. The influence of Co and Ni atoms on the carbon foam structure is investigated by X-ray diffraction and high-resolution electron microscopy, and the presence of metal atoms in N-doped carbon foams is confirmed by X-ray spectroscopy. The left shift of the diffraction peak of Co doped graphitic carbon indicates an increase in the interlayer spacing and a reduced graphitization degree, while the introducton of Ni atoms promotes graphitization. For Ni–Co/NFC-2, Ni inhibits the insertion of Co in carbon layer by increasing graphitization, thus exposing more Co-active substances on the surface, which is important for improving the catalytic process of ORR and OER. According to electrochemical tests, Ni–Co co-doped carbons exhibited superior bi-functional electrocatalytic performance with oxygen reduction reaction (ORR) Eonset = 0.97 V and a Tafel slope of 49.5 mV dec−1, accompanied by oxygen evolution reaction (OER) Ej = 10 mA cm−2 = 1.46 V. Zinc-air battery (ZAB) cell, utilizing the developed material as a catalyst, exhibited a high discharge power density of 138 mW cm−2 with stable performance for up to 200 h.

Cobalt loaded on concave hollow carbon octadecahedron for zinc–air batteries

For the development of high-performance zinc–air batteries, it is necessary to increase the kinetics of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) as much as possible. In this work, different coordination structures of Co loaded on concave hollow carbon octadecahedron (CNQD/CoNBs) were prepared by adding g-C3N4 into the synthesis process of Co-based zeolitic imidazolate framework and adjusting the stress balance of the framework structure in the pyrolysis process. This method can greatly increase the specific surface area and the number of micropores of the material for exposing more active sites to accelerate the reaction kinetics. The prepared catalyst shows excellent bi-functional performance for OER and ORR, and it is applied in efficient rechargeable zinc–air battery to achieve high discharge power density of 210 mW/cm2 and favorable stability over long charge/discharge cycles. This research provides an effective strategy to design high-efficiency bi-functional electrocatalysts.

Boosting Energy Storage Performance of Lead‐Free Ceramics via Layered Structure Optimization Strategy

Owing to the current global scenario of environmental pollution and the energy crisis, the development of new dielectrics using lead-free ceramics for application in advanced electronic and energy storage systems is essential because of the high power density and excellent stability of such ceramics. Unfortunately, most of them have low breakdown strength and/or low maximum polarization, resulting in low energy density and efficiency. To overcome this limitation here, lead-free ceramics comprising a layered structure are designed and fabricated. By optimizing the distribution of the layered structure, a large maximum polarization and high applied electric field (>500kV cm-1 ) can be achieved; these result in an ultrahigh recoverable energy storage density (≈7 J cm-3 ) and near ideal energy storage efficiency (≈95%). Furthermore, the energy storage performance without obvious deterioration over a broad range of operating frequencies (1-100Hz), working temperatures (30-160°C), and fatigue cycles (1-104 ). In addition, the prepared ceramics exhibit extremely high discharge energy density (4.52 J cm-3 ) and power density (405.50 MW cm-3 ). Here, the results demonstrate that the strategy of layered structure design and optimization is promising for enhancing the energy storage performance of lead-free ceramics.

Crystallization temperature dependence of structure, electrical and energy storage properties in BaO–Na2O–Nb2O5–Al2O3–B2O3 glass ceramics

For dielectric capacitors, high energy density and discharge power density are crucial for utilisation in pulsed power devices. In this paper, BaO–Na2O–Nb2O5–Al2O3–B2O3 (BNN-AB) glass ceramics were successfully fabricated by melt quenching and heat treatment techniques. With increasing crystallization temperature, both the dielectric permittivity and breakdown strength (BDS) first increased and then decreased. When the crystallization temperature was lower than 800 °C, the principal crystalline phase was Ba2NaNb5O15 and the secondary phase was NaNbO3. When crystallization temperature was increased from 800 °C to 830 °C, a small amount of a third phase (Al4B2O9) appeared. At the crystallization temperature of 770 °C, the compact glass ceramics with a fine grain structure had the highest permittivity (∼216 @ 25 °C) and high BDS (∼1170 kV/cm). A single-layer capacitor made of glass ceramics had a high power density (∼414 MW/cm3) and discharge energy density (∼1.93 J/cm3), measured by the charge-discharge test platform under the applied field strength of 500 kV/cm. The discharge energy density of glass ceramics sample was as much as 7.7 times that of the mother glass. The above evidences indicate that BNN-AB glass ceramic materials have broad application prospects in the field of dielectric energy storage.

Multi-cationic ionic liquid combination enabling 86-fold enhancement in frequency response and superior energy density in all-solid-state supercapacitors

Polymer ionic-conductor electrolytes with seamless electrode-electrolyte interface are indispensable for extracting the full potential of all-solid-state electrochemical double layer capacitors. While ionic liquids are among the best ionic conductors in liquid state and offer a wide potential window, translating their ionic mobility and activity to solid-state is important, yet challenging. In this direction, we report a mixed ionic liquid based solid electrolyte with an ionic conductivity of 1 mS/cm that delivers 86-fold higher scan-rate operability and 2.6 times lower relaxation time constant than their individual constituents. Specifically, a flexible polymeric matrix impregnated with a mixture of monocationic (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (BMIm TFSI)) and a dicationic ionic liquid (1,4-di(vinylimidazolium) butane bisbromide ([DVIM]Br)) facilitates rapid and extensive formation of electrical double layer when integrated with carbon-based electrodes. The resulting all-solid-sate flexible supercapacitor achieves superior scan rate operability (15,000 mV/s) and ultralow relaxation time constant (7.8 ms), translating to high discharge current density (>1 mA/cm2), energy density (26.4 Wh/kg) and power density (61,127 W/kg). The improved rate capability (~83 %) and energy storage performance is attributed to a synergistic interplay of ionic strength, conductivity and ion mobility of the mixed ionic-liquid that unfold newer avenues towards solid-electrolyte engineering for energy storage devices.

In Situ Monitored (N, O)-Doping of Flexible Vertical Graphene Films with High-Flux Plasma Enhanced Chemical Vapor Deposition for Remarkable Metal-Free Redox Catalysis Essential to Alkaline Zinc-Air Batteries.

Rechargeable zinc–air batteries (ZABs) have attracted great interests for emerging energy applications. Nevertheless, one of the major bottlenecks lies in the fabrication of bifunctional catalysts with high electrochemical activity, high stability, low cost, and free of precious and rare metals. Herein, a high‐performance metal‐free bifunctional catalyst is synthesized in a single step by regulating radicals within the recently invented high‐flux plasma enhanced chemical vapor deposition (HPECVD) system equipped with in situ plasma diagnostics. Thus‐derived (N, O)‐doped vertical few‐layer graphene film (VGNO) is of high areal population with perfect vertical orientation, tunable catalytic states, and configurations, thus enabling significantly enhanced electrochemical kinetic processes of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) with reference to milestone achievements to date. Application of such VGNO to aqueous ZABs (A‐ZABs) and flexible solid‐state ZABs (S‐ZABs) exhibited high discharge power density and excellent cycling stability, which remarkably outperformed ZABs using benchmarked precious‐metal based catalysts. The current work provides a solid basis toward developing low‐cost, resource‐sustainable, and eco‐friendly ZABs without using any metals for outstanding OER and ORR catalysis.

In-situ growth of CoNi bimetal anchored on carbon nanoparticle/nanotube hybrid for boosting rechargeable Zn-air battery

Exploring highly efficient non-precious metal based catalysts for bifunctional oxygen electrode is crucial for rechargeable metal-air batteries. In this study, with MOFs as precursors, a facile coprecipitation method is designed to realize in-situ growth of the CoNi anchored carbon nanoparticle/nanotube (CoNi/N-CNN) hybrid, which can achieve the simultaneous maximum exposure of both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) active centers. Benefiting from the unique structure, the CoNi/N-CNN catalyst exhibits excellent electrocatalytic performance for ORR (Eonset = 1.183 V, E1/2 = 0.819 V) and a low operating voltage of 1.718 V at 10 mA cm−2 (Ej=10) for OER. Delightfully, the home-made rechargeable Zn-air battery with CoNi/N-CNN delivers a high discharge power density up to 209 mW cm−2, and an outstanding charge–discharge cycling stability. The boosted bifunctional electrocatalytic activity can be ascribed to the strong coupling effect between Co/Ni center sites and defect-rich N-anchored carbon featured with porous and nanotube structure, which can introduce uniformly dispersed active sites, tailored electronic configuration, superb conductivity and convenient charge transfer process. The hybrid non-precious bimetal based electrocatalyst provides the possibility to develop the low-cost and high-efficient ORR/OER bifunctional electrocatalysts in rechargeable metal-air battery.

Enhanced Energy‐Storage Properties and Good Temperature Stability in 0.92(Sr0.7Bi0.2)TiO3–0.08Bi(Mg0.5Hf0.5)O3 Relaxor Ferroelectric Ceramic

Herein, the (1 − x)(Sr0.7Bi0.2)TiO3–xBi(Mg0.5Hf0.5)O3 (SBT–100xBMH, x = 0.04–0.10) relaxor ferroelectric ceramics are fabricated via the high‐temperature solid‐state reaction method. Dielectric and ferroelectric measurements reveal a typical relaxor characteristic with diffused and frequency‐dependent dielectric peaks. The characteristic Weibull breakdown strength (BDS) of 470 kV cm−1 with satisfied reliability is obtained by DC breakdown measurement. A maximum recoverable energy density of 3.5 J cm−3 with the corresponding energy efficiency of 92% is simultaneously achieved at 380 kV cm−1. The recoverable energy density exhibits minor degradations from ambient temperature to 200 °C with variation below 20%, whereas the energy efficiency is maintained above 90%. In addition, the SBT–8BMH ceramic possesses a fast charge–discharge speed with high discharge power density of 2.9 MW cm−3. All the results make this lead‐free relaxor ferroelectric ceramic a promising potential candidate for high‐temperature energy‐storage capacitor applications.

High efficiency and power density relaxor ferroelectric Sr0.875Pb0.125TiO3- Bi(Mg0.5Zr0.5)O3 ceramics for pulsed power capacitors

Ferroelectric (1-x)Sr0.875Pb0.125TiO3-xBi(Mg0.5Zr0.5)O3 ((1-x)SPT-xBMZ, x = 0-0.2) ceramics with high discharge efficiency and power density were synthesized via a conventional solid-state sintering method. The prepared (1-x)SPT-xBMZ ceramics were detected as a pure perovskite structure and a dense microstructure, and a typical relaxor behavior and an excellent temperature stability were also observed. Although there is no direct correlation between the degree of diffuseness and the maximum polarization, the high degree of diffuseness can reduce the remanent polarization and significantly improve energy storage and release characteristics of ferroelectric ceramics. Based on a polarization electric-field loop measurement, a recoverable energy storage density of 0.762 J/cm3 and a very high efficiency of 96.34% are achieved when x = 0.2 under 150 kV/cm. The energy storage properties of 0.8SPT-0.2BMZ ceramic exhibit good temperature stability (25−130 °C) and frequency stability (2−80 Hz). In a practical charge-discharge circuit testing, a short discharge pulse-period about 94 ns, a high discharge energy density of 1.7 J/cm3 and an ultra-high-power density of 62.8 MW/cm3 are obtained for the 0.8SPT-0.2BMZ ceramic at 240 kV/cm. The results indicate that the 0.8SPT-0.2BMZ ceramic is a promising dielectric material for high-power pulse capacitors.

Hollow carbon nanoparticles derived from Co3O4/carbon black hybrid: solid-phase synthesis and applications in a Zn–air battery

Metal-free carbon materials are regarded as a promising catalyst for the oxygen reduction reaction (ORR), owing to their high activity in an alkaline environment. In this paper, using industrial carbon black-supported Co3O4 hybrid as a raw material, typical hollow carbon nanoparticles were synthesized by solid-phase annealing the hybrid at an elevated temperature, followed by HCl etching to remove the cobalt oxide. The specific surface area of the hollow carbon is significantly increased and the total nitrogen content of the carbon is 4.13 at%, providing massive active sites for ORR. In alkaline solution, compared with the commercial Pt/C, the nitrogen-doped hollow carbon nanoparticles display a superior ORR electrocatalytic activity with a half-wave potential of 0.88 V versus the reversible hydrogen electrode. Furthermore, the catalyst exhibits an excellent stability and high discharge power density in the Zn–air battery. This study provides a simple and feasible strategy of solid-phase synthesis for the production of high performance metal-free hollow carbon materials.

Hydrated hybrid vanadium oxide nanowires as the superior cathode for aqueous Zn battery

Zinc batteries are at the forefront of aqueous energy storage due to their intrinsic safety and low cost. Various vanadium oxides stand out among the few cathode candidates. Herein, we demonstrate a new heterogeneous vanadium oxide nanowire with V2O5·nH2O shell and V3O7·H2O core, named h-VOW, as a promising cathode candidate for Zn batteries. Thanks to the synergies of multivalent states of vanadium elements associated with inherent high conductivity, in an aqueous electrolyte, h-VOW/Zn battery delivers high discharge capacity (455 mAh g−1 at 0.1 A g−1), energy density (340 Wh kg−1) and power density (9105 W kg−1). Moreover, the gel electrolyte imparts satisfied deformability and weather resistance to the flexible quasi-solid-state battery, allowing it to withstand extremely harsh conditions without catastrophic failure.

2D Nitrogen‐Doped Carbon Nanotubes/Graphene Hybrid as Bifunctional Oxygen Electrocatalyst for Long‐Life Rechargeable Zn–Air Batteries

AbstractThe rational construction of efficient bifunctional oxygen electrocatalysts is of immense significance yet challenging for rechargeable metal–air batteries. Herein, this work reports a metal–organic framework derived 2D nitrogen‐doped carbon nanotubes/graphene hybrid as the efficient bifunctional oxygen electrocatalyst for rechargeable zinc–air batteries. The as‐obtained hybrid exhibits excellent catalytic activity and durability for the oxygen electrochemical reactions due to the synergistic effect by the hierarchical structure and heteroatom doping. The assembled rechargeable zinc–air battery achieves a high power density of 253 mW cm−2 and specific capacity of 801 mAh gZn−1 with excellent cycle stability of over 3000 h at 5 mA cm−2. Moreover, the flexible solid‐state rechargeable zinc–air batteries assembled by this hybrid oxygen electrocatalyst exhibits a high discharge power density of 223 mW cm−2, which can power 45 light‐emitting diodes and charge a cellphone. This work provides valuable insights in designing efficient bifunctional oxygen electrocatalysts for long‐life metal–air batteries and related energy conversion technologies.

2-D rGO impregnated circular-tetragonal-bipyramidal structure of PPY-TiO2-rGO nanocomposite as ETL for OLED and supercapacitor electrode materials

Two dimensional rGO was decorated over circular-bipyramidal structure of PPY-TiO2 by chemical oxidative polymerization of pyrrole monomer. The structural analysis of PPY, GO, TiO2, PPY-TiO2 and PPY-TiO2-rGO nanocomposite was observed by XRD, FESEM and TEM analysis. Inflated non-radiative electron-hole recombination rate and lower value of decay time with better thermal stability were observed for PPY-TiO2-rGO nanocomposite. Enhanced current density (~ 300%), optimized low band gap (~ 1.32 eV), high dielectric constant and high specific surface area were also observed for ternary nanocomposite. The PPY-TiO2-rGO electrode also manifested the high specific capacitance value (~ 1171 F/g) and high discharge time (~ 3450 s) with high electrochemical reduction potential (~ +0.610 V). These increased rates of non-radiative recombination, reduced band gap, enhanced conductivity and thermal stability, high values of dielectric constant, improved electrochemical reduction potential, augmented specific capacitance, high discharge time and power density (~ 799.74 W/kg) with scant loss in energy density at high current density proposed that, PPY-TiO2-rGO nanocomposite can be employed as electron transport layer (ETL) material in OLED devices and supercapacitor electrode material.

Stabilizing temperature‐capacitance dependence of (Sr, Pb, Bi)TiO3‐Bi4Ti3O12 solutions for energy storage

Abstract(1‐x)Sr0.7Pb0.15Bi0.1TiO3‐xBi4Ti3O12 ((1‐x)SPBT‐xBIT, x = 0‐0.125) bulk ceramics were developed and calcined via the solid‐state method, aimed at the application of pulsed power capacitors. The phase structures, temperature stability, hysteresis loop, and discharge properties were systematically investigated. Considering both the temperature stability and dielectric properties, 0.925SPBT‐0.075BIT bulk ceramics with a capacitance variation satisfying the X7R specification were developed for pulsed power capacitors. The energy storage density was 0.252 J/cm3, and the ceramics showed high temperature stability at 80 kV/cm. The discharge current waveforms of the 0.925SPBT‐0.075BIT ceramics were recorded. A high discharge power density of approximately 1.01 × 108 W/kg with an 8 Ω load resistor and short discharge period of 84 ns were achieved at 50 kV/cm. The good temperature stability properties and high power density show that the 0.925SPBT‐0.075BIT ceramics are well suited for pulsed power capacitors with a wide temperature range.