Large Power Density Research Articles

Single-atom palladium on nonstoichiometric tungsten oxide as bifunctional electrocatalyst for zinc-air battery

Searching for an excellent bifunctional electrocatalyst used in zinc-air batteries (ZABs) is a long-term and challenging task. Single-atom catalysts have been becoming potential bifunctional electrocatalysts because of their maximum metal atom utilization and low content of metal itself. Herein, noble metal palladium (Pd) is uniformly anchored in the supported WO2.72 to form single-atom Pd/WO2.72 owing to the special 4d orbit of Pd and nonstoichiometric 2D planar structure of WO2.72. Single-atom 5 % Pd/WO2.72 is prepared in this work, showing excellent bifunctional electrocatalytic behaviors with high E1/2 of 0.86 V for ORR and low Ej=10 of 1.59 V for OER in alkaline medium, and the ∆E is 0.73 V, which outperforms the Pt/C and RuO2. Furthermore, the 5 % Pd/WO2.72-ZAB has a high open-circuit voltage (OCV) value of 1.491 V, a large power density of 168 mW cm−2, and a large specific capacity of 633 mAh g−1. Besides, the 5 % Pd/WO2.72-ZAB also has good cycling stability.

Superior Energy Storage Capability and Fluorescence Negative Thermal Expansion of NaNbO3-Based Transparent Ceramics by Synergistic Optimization.

Transparent dielectric ceramics are splendid candidates for transparent pulse capacitors (TPCs) due to splendid cycle stability and large power density. However, the performance and service life of TPCs at present are threatened by overheating damage caused by dielectric loss. Here, a cooperative optimization strategy of microstructure control and superparaelectric regional regulation is proposed to simultaneously achieve excellent energy storage performance and real-time temperature monitoring function in NaNbO3-based ceramics. By introducing aliovalent ions and oxides with large bandgap energy, the size of polar nanoregions is continuously reduced. Due to the combined effect of increased relaxor behavior and fine grains, excellent comprehensive performances are obtained through doping appropriate amounts of Bi, Yb, Tm, and Zr, Ta, Hf in A- and B-sites of the NaNbO3 matrix, including recoverable energy storage density (5.39Jcm-3), extremely high energy storage efficiency (91.97%), ultra-fast discharge time (29ns), and superior optical transmittance (≈47.5% at 736nm). Additionally, the phenomenon of abnormal fluorescent negative thermal expansion is realized due to activation mechanism of surface phonon at high temperatures that can promote the formation of [Yb···O]-Tm3+ pairs, showing great potential in real-time temperature monitoring of TPCs. This research provides ideas for developing electronic devices with multiple functionalities.

Optimized physical properties of [001]-textured (Na, K)NbO3-based lead-free piezoceramics for high power piezoelectric energy harvesters

The [001]-textured 0.96NK(N0.99S0.01)–0.01CZ–0.03BAZ piezoceramic has large kp and d33 × g33 values; therefore, the piezoelectric energy harvester fabricated using this piezoceramic exhibits a large power density.

Graphene nanosheet-supported ultrafine RuO2 quantum dots as electrochemical energy materials

Ruthenium oxide (RuO2) shows great promise as an electrode material for supercapacitors, which are energy storage devices that have large power densities. However, RuO2 materials suffer low surface area, poor electrical conductivity and a tendency to aggregate after reactions, limiting their rate capability and cycle stability and can lead to inadequate redox reactions with electrolytes. To address these problems, this work synthesized homogeneous ultrafine-RuO2 quantum dots (QDs) materials with a size of around 2 nm on the surface of graphene nanosheets (GNS) via a facile hydrothermal method. The small size and uniform distribution of RuO2 QDs in the composite electrode material allowed for a high concentration of active adsorption sites for ions in the electrolyte while also facilitating efficient electrochemical redox reactions. The resulting RuO2/GNS composite exhibited a large specific area of 177.34 m2g‐1 and demonstrated an excellent capacitance performance of 1138.5 Fg‐1 at a current density of 0.5 Ag‐1. Additionally, a retention rate of 91.4 % when applying current densities from 0.5 to 10 Ag‐1 and cycling stability with 94.5 % retention after 20000 cycles, demonstrates the occurrence of a rapid and reversible faradaic redox reaction on the electrode surface. The symmetrical supercapacitor configuration with two identical RuO2/GNS electrodes was fabricated and demonstrated a high capacity (309.16 Fg‐1 at a current density of 0.5 Ag‐1) and an outstanding retention rate of 91.2 % at a current density of 10 A g−1). A device operated within a 1.8 V potential window showed high energy density from 126 Whkg‐1 to 139.2 Whkg‐1 and a power density from 440.1 Wkg‐1 to 8494.4 Wkg‐1 at current densities ranging from 0.5 Ag‐1 to 10 Ag‐1, respectively. This ultrafine-RuO2 quantum dots composite is a potentially promising advanced functional electrode material for electrochemical applications beyond supercapacitors and may be suitable for a broader range of energy storage and conversion applications.

A bottom-up puzzle strategy for P/B co-doped carbon nanosheets as efficient oxygen reaction electrocatalysts

Preparing metal-free and non-N-doped carbon-based electrocatalysts via pyrolysis encounters a significant challenge of low controllability for microstructure modulation and limited electrocatalytic activity. Herein, a bottom-up puzzle strategy is proposed to fabricate a series of phosphorus and boron co-doped carbon (P-BC) nanosheets. These P-BC nanosheets manifest diverse morphologies and distinct heteroatom doping levels, achieved through the innovative utilization of four similar P onium salts featuring varying benzene ring arrangements, coupled with a fixed B onium salt. Among them, the flat 4P-BC nanosheets with abundant P/B heteroatoms exhibit the optimal oxygen reduction reaction (ORR) performance (E1/2 = 0.79 V, jL = 5.77 mA cm−2), and the assembled zinc-air battery displays a large power density (163 mW cm−2) and excellent long-term durability (450 cycles), which is attributed to the high specific surface area, enhanced defects or disorder, and ample P/B-doping induced active sites for electrochemical reaction. The assembly mechanism of functional units in solution and their intricate evolution at high temperature are elucidated for various P-BC nanosheets. This work elaborates the influence of precursors functional units on the resulting microstructure attributes and active sites properties, providing a novel avenue for the rational design and optimization of metal-free and heteroatom-doped carbon electrocatalysts.

High Thermoelectric Power Factors in Plastic/Ductile Bulk SnSe2 -Based Crystals.

The recently discovered plastic/ductile inorganic thermoelectric (TE) materials open a new avenue for the fabrication of high-efficiently flexible TE devices, which can utilize the small temperature difference between human body and environment to generate electricity. However, the maximum power factor (PF) of current plastic/ductile TE materials is usually around or less than 10 µW cm-1 K-2 , much lower than the classic brittle TE materials. In this work, a record-high PF of 18.0 µW cm-1 K-2 at 375 K in plastic/ductile bulk SnSe2 -based crystals is reported, superior to all the plastic inorganic TE materials and flexible organic TE materials reported before. The origin of such high PF is from the modulation of material's stacking forms and polymorph crystal structures via simultaneously doping Cl/Br at Se-site and intercalating Cu inside the van der Waals gap, leading to the significantly enhanced carrier concentrations and mobilities. An in-plane fully flexible TE device made of the plastic/ductile SnSe2 -based crystals is successfully developed to show a record-high normalized maximum power density to 0.18W m-1 under a temperature difference of 30 K. This work indicates that the plastic/ductile material can realize high TE power factor to achieve large output electric power density in flexible TE technology.

MXene‐enhanced environmentally stable organohydrogel ionic diode toward harvesting ultralow‐frequency mechanical energy and moisture energy

AbstractWith the accelerating advancement of distributed sensors and portable electronic devices in the era of big data, harvesting energy from the surrounding environment to power electrical devices has become increasingly attractive. However, most mechanical energy harvesters often require high operating frequencies to function properly. Moreover, for practical applications, the survivability of devices in harsh operating environments is a vital issue which must be addressed. Besides, the single‐stimulus responsiveness limits their further applications in complex external environments. Here, a pressure and moisture dual‐responsive ionic diode consisting of two organohydrogels with opposite charges as an energy harvester is proposed. The organohydrogel ionic diode utilizes the migration of cations and anions to form the depletion zone and followed by an enhancement of the built‐in potential along the depletion zone as a result of mechanical stress or humidity, converting ultralow‐frequency mechanical energy or moisture energy into electrical energy. Meanwhile, this mechanism is further confirmed by the finite element analysis. With the increased rectification ratio due to the introduction of MXene, the ionic diode exhibits a relatively large output current (∼10.10 μA cm−2) and power density (∼0.10 μW cm−2) at a mechanical pressure of 0.01 Hz, outperforming most currently available mechanical energy harvesters. More impressively, the incorporation of ethylene glycol provides the hydrogel ionic diode with excellent temperature tolerance and long‐term environmental stability. The organohydrogel ionic diode can also be applied as a moisture‐driven power generator and self‐powered humidity sensor. This study presents promising prospects for the efficient collection of renewable and sustainable energy and the practical application of hydrogel‐based energy harvesters in extreme environments.

A facile and green strategy for mass production of dispersive FeCo-rich phosphides@N,P-doped carbon electrocatalysts toward efficient and stable rechargeable Zn-air battery and water splitting

One key step for advancing the widespread practical application of rechargeable metal-air batteries and water electrolysis fundamentally relies on the development of cost-effective multifunctional electrocatalysts toward oxygen and hydrogen-involving reactions. The present work initiates a tofu-derived one-pot strategy for green, facile, and mass production of highly active and stable catalyst toward oxygen reduction/evolution and hydrogen evolution reactions, through the preparation of Fe/Co cross-linked tofu gel and the subsequent pyrolysis. Despite the free use of additional N/P precursors or pore-forming agents, the as-prepared materials comprise highly dispersive FeCo-rich phosphides nanoparticles and porous N,P co-doped carbon network inherited from the tofu skeleton. The resultant catalysts exhibit remarkably enhanced trifunctional activities as compared to the Fe2P and Co2P counterparts, along with better long-term stabilities than the benchmark RuO2 and Pt/C catalysts. Accordingly, the as-assembled Zn-air battery delivers a large power density (174 mW cm−2) with excellent cycle stability (the gap of charge/discharge voltage@10 mA cm−2 increases by 0.01 V after 720 h of operation, vs. 0.16 V of Pt/C-RuO2 based battery after 378 h). Furthermore, the as-constructed alkaline electrolyzer just requires a small voltage of 1.55 V@10 mA cm−2, which outperforms nearly all of those of biomass-derived electrocatalysts ever reported, and that of noble metal catalysts-based electrolyzers (1.72 V@10 mA cm−2 for Pt/C-RuO2), underscoring their bright future toward commercial applications in green energy conversion devices.

Superior energy-storage performances achieved in NaNbO3-based antiferroelectric ceramics by phase-structure and relaxation regulation

Lead-free NaNbO3-based antiferroelectric (AFE) ceramics are highly considered as promising substitutes of lead-based ones in dielectric energy-storage field. However, their low breakdown strength and large electric hysteresis loss originating from the field-induced metastable ferroelectric (FE) Q phase and/or AFE P phase still remains challenging, which severely impedes the further improvement of energy-storage performances. Herein, an effective phase-structure and relaxation regulation via A-site cation substitution strategy has been proposed to solve this issue. The phase-structures of the designed NN-based AFE ceramics evolve from orthorhombic P phase to R phase accompanying with the enhancement of relaxation behavior. Accordingly, an effective transformation from a plump and pinched polarization–electric field (P–E) hysteresis loop to a slim and slanted one has undergone, contributing to superior energy-storage performances. Noticeably, an expected large recoverable energy density (Wrec) of 4.0 J/cm3 with a high energy conversion efficiency (η) of 80.0 % was realized in 0.94(Na0.88Sm0.04NbO3)-0.06(BiFeO3) relaxor AFE ceramics at 460 kV/cm. Meanwhile, a great discharge energy density (Wdis) of 1.2 J/cm3 and a large power density (PD) of 92.4 MW/cm3 were achieved at 200 kV/cm. Furthermore, the favorable functional reliabilities in frequency, temperature, and fatigue cycle were also confirmed. These results not only demonstrate the great potential of NaNbO3-based relaxor AFE ceramics for dielectric energy-storage applications, but also confirm the validity of the strategy proposed in this work to obtain superior energy-storage performances.

Collaborative integration of Fe-Nx active center into defective sulfur/selenium-doped carbon for efficient oxygen electrocatalysts in liquid and flexible Zn-air batteries

Strategic active site organization is imperative for the advancement of effective and long-lasting catalysts of oxygen reduction reactions. However, the controllable multi-active site design is a highly intricate topic for catalyst synthesis. Employing pre-trapping and post-activation strategy, Fe-N bonding structure and S, Se functionalized heteroatom are integrated into a conductive porous carbon. In this process, the nitrogen-abundant polymer 1,3,5-triformylbenzene-tris(4-aminophenyl)benzene (Tf-TAPA) adsorbs Fe3+ under the intrinsically metal anchoring ability of N atoms and simultaneously in-situ assembles long-chain thiophene-S. Subsequently, the Fe3+ is transformed into Fe-Nx moieties with the conversion of the organic chain to incompletely graphitized carbon. Furthermore, the alteration of the electronic configuration achieved through the introduction of dual-atom S and Se leads to a pronounced enhancement in catalytic efficiency. Benefitting from the Fe-Nx bonding structure, dense structural defects, and conductive carbon networks, the resultant Fe-S,Se/NCNs possesses a positive half-wave potential of 0.86 V and a 90% current retention rate, outstripping the Pt/C benchmark. Moreover, the liquid and flexible ZAB driven by Fe-S,Se/NCNs achieves large power densities of 259.7 and 164.7 mW/cm2, respectively. This study provides a new comprehension in developing an efficient and stable M-N-C oxygen electrocatalyst.

2D ReS2 nanosheets embedded on porous carbon framework for efficient and stable all-solid-state flexible supercapacitor

All-solid-state flexible supercapacitors with high-efficiency and durable performance show a promising application prospect in wearable electronics, electrochemical energy storage. However, it still exists challenges to integrate flexible, efficient and stable performance for all-solid-state supercapacitor. In this work, we have synthesized the ultra-high density ReS2 nanosheets on the porous carbon framework (ReS2@PCF) by a hydrothermal method. Based on ReS2@PCF, we have further prepared a ReS2@PCF-based supercapacitor device. Electrochemical measurements demonstrate that the flexible ReS2@PCF electrode possesses a specific capability of 125.3 F/g and also a large power density of 10.278 kW/kg at a charge/discharge current density of 5 A/g, which is able to light up a red light-emitting diodes (LED). Moreover, it keeps a high 91.5% capacitance retention ratio after being tested for 6000 cycles. Our work offers a new insight into the solutions for the integration of flexible, highly efficient and stable supercapacitor. It shows a potential application in special cases, such as wearable electronic clothes, and it will also facilitate their development towards a practical application.

001]-texturing of (K, Na)NbO3-based piezoceramics with a pseudocubic structure and their application to piezoelectric devices

0.96(K0·5Na0.5-zLiz) (Nb0·92Sb0.08)O3-0.04(Ca0·5Sr0.5)ZrO3 [(KN0.5-zLz)NS-CSZ] piezoceramics (0 ≤ z ≤ 0.04) were aligned in the [001] orientation using 3% (in mole) NaNbO3 templates with a large Lotgering factor (>97%). Their crystal structures transformed from the orthorhombic-pseudocubic (OP) structure to the orthorhombic-tetragonal-pseudocubic (O-T-P) structure with an increasing z. The P structure was interpreted as a rhombohedral R3m structure. The piezoelectricity of the compositions increased after [001]-texturing, and the enhancement was proportional to the O phase quantity. The composition (z = 0.03) exhibited the highest piezoelectric constant (d33; 670 pC/N) and electromechanical coupling factor (kp; 0.56). Piezoelectric energy harvesters were produced using the untextured and textured samples (z = 0.03). The textured harvester delivered a large power density of 26.6 mW/mm3, which was larger than that of the untextured harvester owing to the enhanced kp and d33 × g33 of the textured piezoceramic. A multilayer actuator was produced using the textured sample (z = 0.03), and it exhibited a large acceleration (44.2 G) and displacement (±3,730 μm) at ±25 V. Therefore, the [001]-textured (KN0.47L0.03)NS-CSZ piezoceramic is suitable for piezoelectric energy harvesters and actuators.

Low-temperature sintering of PLSZT-based antiferroelectric ceramics in reducing atmosphere for energy storage

Due to their elevated sintering temperature, pure PLZST-based antiferroelectric ceramics are unsuitable for co-firing with copper internal electrodes as MLCC dielectric materials. In this work, PLZST ceramic materials sintered at low temperature in reducing atmosphere were obtained through a unique BASK glass additive and Y3+ co-doping. While the sintering temperature of ceramics is reduced to 1040 °C, stable defect association (YPb∙,YZr′) is formed by Y3+ solution entering A/B site, which effectively inhibits the increase of defect concentration and promotes ceramic sintering. The high breakdown strength of PLSZT ceramics is attributed to their compact grain and excellent insulation resistivity, which enhance their tolerance to electric fields. An ultrahigh recoverable energy density (Wrec) of 4.9 J/cm3 with a high energy storage efficiency (η) of 92.8% are achieved at an electric field of 400 kV/cm. Moreover, the AFE ceramics possess excellent discharge energy storage properties with a high discharge energy density (Wd) of 4.4 J/cm3 and a large power density (Pd) of 125 MW/cm3.

Batch fabrication of micro-tubular protonic ceramic fuel cells via a phase inversion-based co-spinning/co-sintering technique

Micro-tubular protonic ceramic fuel cells (MT-PCFCs) are prominently advantageous in energy conversion and storage, such as intermediate operating temperature, large volumetric power density, and low sealing requirements. Formation of thin and dense electrolyte film and efficient current collection, particularly from the micro lumen, are the primary challenges for preparing high-performance MT-PCFCs. The present work carries out a one-step fabrication of triple-layer hollow fibers (TLHFs) with anodic current collector/graded anode/electrolyte using BaCe0·7Zr0·1Y0·2O3-δ via the phase-inversion based co-spinning/co-sintering technique. A BaCo0·4Fe0·4Zr0·1Y0·1O3-δ based porous cathode is then applied on the TLHF's outer surface to create a complete fuel cell. The resultant single MT-PCFC yields a peak power density of 601.2 mW cm−2 at 700 °C. Furthermore, an MT-PCFC stack is made by bundling seven TLHFs using the porous cathode. With an effective area exceeding 12 cm2, the MT-PCFC stack generates a power output of 2.5 W at 700 °C. The stability test lasts for 100 h at 600 °C under 100 mA cm−2 and for next 60 h at varied temperatures from 700 to 600 °C under 200 mA cm−2. The inventive design of TLHFs facilitates the scale-up of fuel cells, promoting the development of a large-scale MT-PCFC stack or systems.

Synergistic modulation of ferroelectric polarization and relaxor behavior of Sr2NaNb5O15‐based tungsten bronze ceramic

AbstractDeveloping dielectric ceramics with high energy storage performance (ESP) is essential for miniaturizing and integrating high‐power pulse capacitors. Sr2NaNb5O15‐based tungsten bronze ferroelectric ceramics have been highly investigated for dielectric energy storage applications recently. However, the difficulty in concurrently obtaining large polarization and strong relaxor characteristics greatly hinders the ESP improvement. In this work, Bi3+ and Ti4+ ions were introduced into the Sr2NaNb5O15 ceramic, aiming to modulate the ferroelectric polarization and relaxor behavior synergistically. An excellent recoverable energy density (Wrec ∼ 4.08 J/cm3) and a high efficiency (η ∼ 84.59%) were concurrently attained in the Sr1.85Bi0.15NaNb4.85Ti0.15O15 composition due to the boosted polarization and enhanced relaxor nature. Moreover, this ceramic also exhibited a high current density (863.06 A/cm2) and a large power density (94.94 MW/cm3). All these characteristics demonstrate that the Bi3+ and Ti4+ ions co‐doped Sr2NaNb5O15 ceramics possess great potential for dielectric capacitor applications.

Harvesting and mapping ultrasonic vibration power using semiconducting wire-based tribovoltaic generators

Ultrasonic vibration is an excellent mechanical power source owing to its large power density. Harvesting ultrasonic vibrations has been demonstrated so far through piezoelectric effect, triboelectric effect, and electromagnetic induction. However, the majority of these devices only produce AC output which limits their potential applications. This work demonstrates, for the first time, the conversion of ultrasonic vibration power to DC output using semiconducting wire-based electric generators, in which one or several semiconductor wire/metal junction(s) are employed. A current density of up to 19 µA/cm2 and a peak power density of 5 µW/cm2 can be obtained under ultrasonic vibrations up to 37 kHz. The mapping of the ultrasonic vibrational strength has been achieved, demonstrating the capability of a self-driven powered ultrasonic sensor. The characteristics of individual semiconductor junctions and the series connection of several such junctions are studied using equivalent circuits.

Micro Tubular Solid Oxide Reversible Cell Using LaGaO3 Electrolyte Film Prepared on Channel Size Controlled NiO-YSZ Substrate

Reversible operation of SOFC is now important subjects from energy storage of renewable electric power from solar or wind power. At present, planer type cell design is widely used for this purpose, however, because of tight gas sealing, tubular type cell design is more suitable. In this study, micro tubular solid oxide cell using La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) thin electrolyte film was prepared by dip-coating and co-sintering process.NiO-YSZ porous substrate with 10 mm diameter and 30 mm length was used for preparation of the cell. LaGaO3 based oxide film was deposited with dip coating method. Two kinds of NiO and YSZ particles with different particle size (0.91 and 0.65 mm for NiO and 0.62 and 0.25 mm for YSZ) were mixed and extruded for tubular substrate. 4 types of NiO-YSZ anode porous substrate were Average porosity of each 4 tubular substrate was ca. 70% after reduction. However, from SEM observation, channel size in NiO-YSZ substrate was changed and NiO-YSZ using larger NiO and YSZ particles shows larger channel diameter.Power generation property of 4 tubular cell using different NiO and YSZ particle size for substrate. It was found that the cell deposited on NiO-YSZ using larger particles shows lager power density, in particular, the cell using both NiO and YSZ larger particles shows the largest power density (0.37 W/cm2 at 873 K), which is reasonably large power density. On the other hand, in case of electrolysis, channel size is also strongly influenced on the electrolysis current. As similar manner with fuel cell operation, the LSGM cell prepared on larger particles size of NiO and YSZ shows larger steam electrolysis current. Impedance analysis suggests that the effects of particle size of NiO and YSZ was explained by small concentration overpotential, and so larger channel size is effective for improving the initial performance of the SORC performance. Long term stability of the steam electrolysis was performed and it was found that the LSGM tubular cell prepared on NiO-YSZ with larger particles shows the reasonable stable electrolysis performance in long term stability (-4%/1000h average degradation rate). The main reason for degradation was assigned to the increased IR loss however overpotential was hardly changed over 600 h and so it seems most likely that the reoxidation of NiO or aggregation of NiO is the main reason for degradation of the cell.This study reveals that the control of channel size in NiO-YSZ porous substrate is highly important for initial performance and long-term stability of SORC.

(Invited) Graphene-Based Scaffolds for Electrochemical Energy Storage

The efficient transport of charge species within energy storage devices is critical to realizing both large power and energy densities, especially when operating under extreme conditions (e.g. ultralow temperatures, high charge/discharge rates, etc.). A number of resistances can contribute to sluggish ion/electron transport in a cell such as charge transfer at interfaces, electrolyte resistance, electrode resistance, and diffusive transport within porous electrodes. Several strategies have been pursued to address these transport limitations. Electrolyte engineering is an effective approach as it can influence both electrolyte resistance and charge transfer resistances. Electrode materials discovery and development is another popular strategy as the charge storage mechanism and electrode resistance play a key role in kinetics of the device. Within electrode materials development, engineering of the electrode pore architecture is an extremely effective strategy to decrease the diffusive transport lengths and electrode resistances. This pore engineering can be achieved through synthetic chemistry for small pores (e.g. <10 um) and via additive manufacturing for larger pores (> 10 um). Here we show how electrolyte engineering and electrode materials development can be used to overcome sluggish transport in graphene-based electrodes. Particular focus will be given to the use of synthetic means to tune to the properties of a graphene aerogel scaffold (e.g. surface area, pore size, mechanical properties) and additive manufacturing to define the larger pore structure to facilitate uniform deposition of active materials (e.g. MnO2) and improve energy density and rate capability of the energy storage device. We explore a number of additive manufacturing techniques (e.g. direct ink write, projection microstereolithography, etc.) to print a variety of lattice structures and computer-guided designs to determine the optimal electrode architecture.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Tailoring Phase Fraction Induced Saturation Polarization Delay for High-Performance BaTiO3-Based Relaxed Ferroelectric Capacitors.

Electrostatic capacitors based on dielectric materials are essential for enabling technological advances, including miniaturization and integration of electronic devices. However, maintaining a high polarization and breakdown field strength simultaneously in electrostatic capacitors remains a major challenge for industrial applications. Herein, a universal approach to delaying saturation polarization in BaTiO3-based ceramic is reported via tailoring phase fraction to improve capacitive performance. The ceramic of 0.85(0.7BaTiO3-0.3Bi0.5Na0.5TiO3)-0.15Bi0.5Li0.5(Ti0.75Ta0.2)O3 delivers an ultrahigh recoverable energy density (Wrec) of 7.16 J cm-3 along with an efficiency (η) of approximately 90% at a breakdown electric field of 700 kV cm-1, outperforming the current BaTiO3-based ceramics and other lead-free ceramics. Meanwhile, the Wrec and η exhibit wide frequency, temperature, and cycling fatigue stability. Additionally, both an extremely fast discharge time of 115 ns and a large power density of 106.16 MW cm-3 are concurrently attained. This work offers a promising pathway for delaying saturation polarization design in order to create scalable high-energy-density ceramics capacitors and highlight the research prospects of pulse power applications.

Redox-active anthraquinone-based π-conjugated polymer anode for high-capacity aqueous organic hybrid flow battery

Organic molecules/polymers are currently investigated as redox species for aqueous low-cost hybrid flow batteries. In this work, a redox-active anthraquinone-based conjugated polymer synthesized via a facile electrochemical polymerization approach is reported, which can be employed as a high-capacity anode material for aqueous hybrid flow batteries. The redox-active anthraquinone polymer displays a two-electron-transfer redox reaction at −0.616 V (versus the standard hydrogen electrode, SHE) with fast redox kinetics in aqueous alkaline electrolytes (pH = 12). Paired with a potassium ferrocyanide catholyte, the aqueous hybrid flow battery employed this redox-active anthraquinone polymer as the anode material in aqueous supporting electrolyte of pH = 12 exhibits an open circuit voltage of about 1.09 V, high specific capacity (103.6 mA h g−1 at 2 A g−1) and large mass power density (9.41 W g−1 at 100 % SOC), along with excellent capacity retention (99.948 % per cycle) and energy efficiency (74.1 %) after 100 cycles.