Cycling Durability Research Articles

A Mn-based ternary NASICON-type Na3.5MnTi0.5Cr0.5(PO4)3/C cathode for high-performance sodium-ion batteries

The Mn-based Natrium superionic conductor (NASICON)-type materials are promising cathode materials for sodium-ion batteries (SIBs) due to their environmental friendliness and cost-effectiveness. However, the practical application of Mn-based materials is hindered by their poor cycle performance, arising from intrinsic kinetic limitation and negative structural degradation caused byMn. Herein, a Mn-based ternary NASICON-type Na3.5MnTi0.5Cr0.5(PO4)3/C (NMTCP-50) is designed featuring multi-metal synergy with enhanced effect from each component, which contributes to breaking through the bottleneck of inferior cycle performance for Mn-based NASICON-type materials. The results of ex-situ X-ray diffraction corroborate that both solid-solution and bi-phase electrochemical reactions are involved in the sodiation/desodiation processes, and the volume variation is only 2.55 %. Galvanostatic intermittent titration technique tests and density functional theory calculations further demonstrate the fast reaction kinetics of the NMTCP-50 electrode. NMTCP-50 can deliver an excellent cycling durability of 75 % after 5000 cycles at 2 A g−1 and a high reversible capacity of 137.6 mAh g−1. The availability of NMTCP-50 has been evaluated by a full cell assembled with hard carbon. This work offers theoretical support for understanding the multi-metal synergistic effect in NASICON materials and provides a blueprint for designing low-cost NASICON cathodes.

Gradient Nitrogen Doping in the Garnet Electrolyte for Highly Efficient Solid-State-Electrolyte/Li Interface by N2 Plasma.

Solid-state lithium batteries (SSBs) have been widely researched as next-generation energy storage technologies due to their high energy density and high safety. However, lithium dendrite growth through the solid electrolyte usually results from the catastrophic interface contact between the solid electrolyte and lithium metal. Herein, a gradient nitrogen-doping strategy by nitrogen plasma is introduced to modify the surface and subsurface of the garnet electrolyte, which not only etches the surface impurities (e.g., Li2CO3) but also generates an in situ formed Li3N-rich interphase between the solid electrolyte and lithium anode. As a result, the Li/LLZTON-3/Li cells show a low interfacial resistance (3.50 Ω cm2) with a critical current density of about 0.65 mA cm-2 at room temperature and 1.60 mA cm-2 at 60 °C, as well as a stable cycling life for over 1300 h at 0.4 mA cm-2 at room temperature. A hybrid solid-state full cell paired with a LiFePO4 cathode exhibits excellent cycling durability and rate performance at room temperature. These results demonstrate a rational strategy to enable lithium utilization in SSBs.

Bimetal Oxide Reduction-Induced Perforation Strategy for Preparing a Multi-Microchannel Graphene-Based Anode Material with Rapid Sodium-Ion Diffusion.

A sodium-ion battery, with a wide operating range, is much cheaper and safer than a lithium battery. Graphene is regarded as a promising carbon material in the preparation of anode materials. However, the large two-dimensional (2D) graphene sheets restrain the cross-plane diffusion of electrolyte ions, limiting the further improvement of rate performance. Herein, a nanohybrid of FeCo2Se4 and holey graphene (FeCo2Se4/HG) has been successfully prepared by the synchronism of pore creation and active material growth. Specifically, FeCo-oxide nanoparticles serve as the etching agents, generating in-plane nanoholes and subsequently converted into FeCo2Se4. The nanoholes provide a high density of cross-plane diffusion channels for sodium ions, serving as ionic diffusion shortcuts between different graphene layers to accelerate ion transport across the entire electrode. The unique architecture endows FeCo2Se4/HG with superior rate capability (411.2 mA h g-1 at 20 A g-1) and a specific capacity of 432.4 mA h g-1 at 2.0 A g-1 after 2000 cycles with a capacity retention rate of 92.4%. Therefore, pore engineering makes it possible for holey graphene-based electrodes to achieve outstanding rate performance and superb cycling durability.

Carbon coated hetero sulfides nanoboxes with efficient pseudocapacitive behavior for sodium storage

Engineering heterojunction with the interfacial synergism is an effective anode design strategy to innovate the surface pseudocapacitive reaction and facilitate the charge transfer dynamics, thus resulting in improved properties for sodium-ion batteries. Herein, the heterogeneous structure of Sb2S3-CoS2 nanoboxes coated with nitrogen-doped carbon shell (Sb2S3-CoS2@NC) is fabricated through the replacement of Co2+ with Sb3+, and the subsequent sulfurization reaction. The advantages of exquisite hollow structure and carbon coating not only effectively buffer the vast volumetric variation to prevent the collapse of electrode but also accelerate the charge transfer to optimize rate property. Moreover, the interfacial synergism between Sb2S3-CoS2 heterojunction improves surface pseudocapacitive Na+ uptake and boosts the Na+ transport. Consequently, the developed Sb2S3-CoS2@NC nanoboxes exhibit advanced anode performances of high specific capacity, stable cyclic durability, and good rate capability. This approach can be utilized to develop other hollow structured heterogeneous materials for high performance energy storage and conversion application.

Engineering a Ni-Al Brucite-Based Interface Layer with Regulated Zn2+ Flux for Highly Reversible Zn Metal Anodes.

Practical aqueous Zn-ion batteries are appealing for grid-scale energy storage with intrinsic safety and cost-effectiveness, yet their cycling stability and reversibility are limited by unwanted dendrite growth and water-induced erosions on Zn. Herein, a hydrophilic and Zn2+-conductive Ni-Al layered double hydroxide (NiAl-LDH) interphase layer is constructed on the surface of Zn, in which NiAl-LDH enables a more uniformly distributed Zn2+ concentration and interfacial electric field owing to its large internal Zn2+ channels and favorable charge redistribution effect. Consequently, the NiAl-LDH-integrated Zn anode achieves low voltage hysteresis and high reversibility of Zn plating/stripping with uniform underneath deposition behaviors. Remarkably, the resultant NiAl-2 LDH@Zn delivers superior cycling durability over 2800 h (∼4 months, 0.5 mA cm-2), realizes high reversibility with 99.4% average Coulombic efficiency over 1400 cycles, and confers stable operation of full Zn cells with high V2O5 mass loadings. This work offers a facile and instructive interface design approach for achieving highly stable Zn metal anodes.

Design of a syringe extension device (Chloe SED®) for low-resource settings in sub-Saharan Africa: a circular economy approach.

Underfunded healthcare infrastructures in low-resource settings in sub-Saharan Africa have resulted in a lack of medical devices crucial to provide healthcare for all. A representative example of this scenario is medical devices to administer paracervical blocks during gynaecological procedures. Devices needed for this procedure are usually unavailable or expensive. Without these devices, providing paracervical blocks for women in need is impossible resulting in compromising the quality of care for women requiring gynaecological procedures such as loop electrosurgical excision, treatment of miscarriage, or incomplete abortion. In that perspective, interventions that can be integrated into the healthcare system in low-resource settings to provide women needing paracervical blocks remain urgent. Based on a context-specific approach while leveraging circular economy design principles, this research catalogues the development of a new medical device called Chloe SED® that can be used to support the provision of paracervical blocks. Chloe SED®, priced at US$ 1.5 per device when produced in polypropylene, US$ 10 in polyetheretherketone, and US$ 15 in aluminium, is attached to any 10-cc syringe in low-resource settings to provide paracervical blocks. The device is designed for durability, repairability, maintainability, upgradeability, and recyclability to address environmental sustainability issues in the healthcare domain. Achieving the design of Chloe SED® from a context-specific and circular economy approach revealed correlations between the material choice to manufacture the device, the device's initial cost, product durability and reuse cycle, reprocessing method and cost, and environmental impact. These correlations can be seen as interconnected conflicting or divergent trade-offs that need to be continually assessed to deliver a medical device that provides healthcare for all with limited environmental impact. The study findings are intended to be seen as efforts to make available medical devices to support women's access to reproductive health services.

TC@MF phase change microcapsules with reversibly thermochromic property for temperature response and thermoregulation

A series of reversibly thermochromic phase-change microcapsules (TC@MF), demonstrating excellent energy storage and release properties, were synthesized using melamine formaldehyde resin (MF) encapsulated ternary complex consisting of crystal violet lactone (CVL), 2,2-Di-(4-hydroxyphenyl) propane (BPA), and n-hexadecanol. The microstructure, chemical composition, thermal storage capacity, thermal cycling durability, discoloration effect, and thermal regulation performance of TC@MF with different core contents were investigated in detail. With core contents gradually increasing, the chromatic aberration values (ΔE) value of TC@MF increased from 38.23 to 71.69, the melting enthalpy (ΔHm) gradually increased from 180.2 J/g to 218.6 J/g while the leak-proof performance decreased gradually. The TC@MF-2 with the best comprehensive performance has exhibited superior latent heat storage (ΔHm = 192.2 J/g), high chromatic aberration values (ΔE = 57.31), and well leak-proof properties (5.61 %). Furthermore, the thermal performance, morphology, and reversible color reliability of TC@MF-2 remained stable through 100 thermal heating and cooling cycles, demonstrating excellent thermal cycling stability. In summary, such multifunctional microcapsules can directly reflect the energy saturation and depletion states in phase change material applications through color changes. That might be conducive to expanding the value of its practical application in the field of latent heat energy storage, including smart fabrics or fibers, commodity packaging, thermal sensors, reversible thermochromic coatings and solar energy storage, and so on.

Mitigating water-related challenges in aqueous zinc-ion batteries through ether-water hybrid electrolytes

Aqueous zinc-ion batteries (AZIBs) are an attractive option for different energy storage applications due to their cost-effectiveness, safety benefits, and high capacity. Nevertheless, their development is constrained by challenges such as hydrogen evolution reaction (HER), significantly affecting the battery lifespan. This work presents a promising solution to this problem using a hybrid electrolyte, consisting of water and tetra ethylene glycol dimethyl ether (TEGDME) containing Zn(OTf)2. Results demonstrate that this hybrid electrolyte can suppress HER and can lessen zinc corrosion by reorienting hydrogen bonds with water and actively participating in the solvation structure of Zn2+ ions. Such reorientation reduces water activity and weakens the interactions between water molecules and between water and Zn2+ ions. By employing an optimal TEGDME/H2O ratio of 2:1 in the hybrid electrolyte, hydrogen evolution overpotential increased by 0.26 V. As a result, in the Zn//Zn symmetrical cells, the developed hybrid electrolyte is seen to enable the Zn electrode to exhibit excellent cycle durability, lasting over 4300 h with coulombic efficiency (CE) of 99.68% at 0.5 mA cm−2 and 0.5 mAh cm−2, surpassing the 92.79% achieved by the base electrolyte (1 M Zn(OTf)2 aqueous solution) cells. Moreover, when implemented in Zn/δ-MnO2 batteries, the hybrid electrolyte maintained its performance for over 1800 cycles at a discharge rate of 100 mA g−1. This cost-effective and adaptable strategy highlights its wide-ranging potential, offering vital insights for the enhancement of AZIB technology.

Aliovalent doping and structural design of MoSe2 with fast reaction kinetics for high-stable sodium-ion half/full batteries

The development of high-quality anode materials is critical for the advancement of sodium-ion batteries (SIBs). MoSe2 is a candidate anode for SIBs, while its inherent limitations, such as the agglomeration of nanosheets, poor electron conductance and mechanical strain due to volume changes during cycling, which can lead to decreased performance and durability in SIBs. To overcome the challenges, a novel aliovalent doping and structural engineering was taken to prepare reduced graphene oxide (rGO) functionalized and phosphorus-doped MoSe2 flake (P-MoSe2@rGO) via in situ growth technique. The unique structural design of P-MoSe2@rGO addresses material limitations and optimizes performance by providing a high conductive grid for ion/electron transfer, a large surface area for full electrolyte penetration, and effective suppression of MoSe2 nanosheet agglomeration and mechanical strain due to volume change during charge/discharge in SIBs. The P-MoSe2@rGO inherits the enhanced electronic conductivity and enlarged layer spacing (from 0.652 to 0.668 nm), which boosts the reaction kinetics and facilitates the insertion/extraction of sodium ions. The P-MoSe2@rGO exhibits excellent long-cycle properties with a high reversible capacity of 384 mAh/g at 2 A/g and 338 mAh/g at 10 A/g after 1450 circulations. Detailed discussion of reaction kinetics is conducted. Theoretical calculations prove that doping of P atoms in MoSe2 reduces the forbidden band gap from 1.443 to 1.397 eV and accelerates ion and electron migration. Furthermore, the full cell P-MoSe2@rGO//Na3V2(PO4)3@C (NVP@C) demonstrates a remarkable cycling durability of 326 mAh/g after 200 cycles and a high energy density of 159.6 Wh kg−1. This process provides a reference for the adjustment and modification of MoSe2 to adapt to high performance SIBs anode.

Manipulating the morphology engineering of nickel phosphides to attain enhanced acidic electrocatalytic hydrogen evolution

Development of inexpensive non-composite nanomaterials contributes to achieve cost-effective scale-up synthesis on the premise of optimizing performance and configuration properly. Here, we focus on the inexpensive single nickel phosphides and achieve HER performance comparable to other reported counterparts with composite structure via well-designed morphology engineering strategy. More importantly, this batch of nickel phosphides also come with a variety of interesting morphologies. The introduction of quantitative ethylenediaminetetraacetic acid tetra-potassium salt (EDTA·4 K) induces a competitive coordination with urea, resulting in a significant transformation of sheet-like spherical Ni2P to high-density rod-like spherical Ni2P with abundant active sites, developed specific surface area, and three-dimensional extended space. Benefiting from above advantages, the rod-like spherical Ni2P only requires overpotential of 166 mV to provide 10 mA cm−2 in HER, and possesses satisfactory cycling durability. This work promotes the development of low-cost nickel-based materials and is expected to provide guidance for the morphology engineering of other materials.

A Study on the Electrochemical Performance of MOF Based HER Catalysts for Anion Exchange Membrane Water Electrolysis

Recently, research on anion exchange membrane water electrolysis (AEMWE) has been conducted, which has the advantage of using a non-noble transition metal catalyst to reduce cost and improve the activity and durability of the catalyst. In alkaline solutions, heterojunction catalysts are favored because the rational design of catalysts requires the ability to simultaneously dissociate water and bind hydrogen species.In this study, N-doped carbon hollow polyhedron (NCHP) supports were synthesized using two types of metal-organic frameworks (MOFs) to enhance catalyst durability by effective active site-support interactions. Moreover, well dispersed MoC on MOFs with regularly connected metal nodes and organic ligands increased the number of active sites and improved the reaction kinetics owing to the synergistic effects between MoC and Co@NC, which enhanced the hydrogen evolution reaction (HER).The formation mechanism of NCHP was confirmed by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. During the half-cell test, the incorporation of MoC (MoC-Co@NC/NCHP) reduced the HER overpotential by approximately 1.8 times at 10mA/cm2 compared with that of Co@NC/NCHP. Furthermore, durability cycling was conducted from 0.1 to -0.6 V versus a reversible hydrogen electrode (RHE). The durability tests revealed that after 3000 cycles, the reduction in the HER current of MoC-Co@NC/NCHP was 1.4 and 2.7 times lower than those of Co@NC/NCHP and commercial Pt/C, respectively. This study provides two strategies to obtain highly stable NC matrix supports and highly active heterojunction catalysts.

Sintering of Protonic Ceramics for Tubular Solid Oxide Fuel Cells

Protonic ceramics are considered to be the most promising candidates for intermediate-temperature solid oxide fuel cells (SOFCs) owing to their high proton conductivity and competitive electrochemical performance at intermediate temperatures (typically 500–700 °C). However, the fabrication of proton-conducting SOFCs has been challenging mainly due to the poor sinterability of common proton-conducting electrolyte materials. Significantly high sintering temperatures (1500–1600 °C) and long sintering times (up to 24 h) have been reported for obtaining dense, gas-tight proton-conducting electrolytes. These sintering conditions may lead to undesirable interfacial reactions and dense electrode microstructures, thereby limiting the cell performance. The present work focuses on optimizing the co-sintering temperature of tubular SOFCs with a traditional Ni–yttria-stabilized zirconia (YSZ) anode support and proton-conducting functional layers. BaZr0.3Ce0.5Y0.2O3 (BZCY), Ni–BZCY, and BZCY–BaCo0.4Fe0.4Ce0.1Y0.1O3 were used as the electrolyte, anode functional layer, and cathode, respectively. Various approaches to lowering the co-sintering temperature and resulting cell performances will be discussed. We will also examine the thermal cycling behavior and durability of the fabricated protonic SOFCs.

Reversible Solid Oxide Cells: Cycling and Long-Term Durability of Air Electrodes

Introduction Reversible solid oxide cell (r-SOC) enables both power generation and electrolysis, when the cell can be operated as a solid oxide fuel cell (SOFC) and as a solid oxide electrolysis cell (SOEC). Many studies are being conducted to improve their performance and durability (1,2).Lanthanum strontium cobalt ferrite (LSCF) is an air electrode material with a perovskite-type crystal structure which exhibits high electronic and ionic conductivity, oxygen diffusivity, and electrocatalytic activity (3). However, performance and durability of the cells with Sr-containing oxide air electrodes have to be carefully analyzed, as Sr ions tend to easily diffuse during sintering and in long-term operation, reacting with Zr ions from the solid electrolyte to form a highly resistance reaction layer such as SrZrO3 (4-6). While the performance and durability of LSCF-based air electrodes and the Sr diffusion in SOFC operation have been studied, there are still limited number of studies on the SOEC operation, and especially on the r-SOC operation. The diffusion of constituent ions such as Co and Fe may not be negligible in SOCs.Here in this study, we fabricate YSZ electrolyte-supported r-SOCs and conduct durability studies in both SOFC and SOEC modes. STEM-EDS observation of the air electrode materials is also made to investigate the durability and diffusion of various elements in the LSCF-based air electrode of r-SOCs. Experimental R-SOCs with yttria stabilized zirconia electrolytes (YSZ, 200 µm thick) were prepared. Ni-GDC co-impregnated fuel electrode was prepared, where a mixture of La0.1Sr0.9TiO3 (LST) and Gd0.1Ce0.9O2 (GDC) at a volume ratio of 50:50 was used as the porous electrode backbone, onto which Ni-containing solution of 1 µL was impregnated for Ni loading of 0.167 mg cm-2 (7). Gd0.1Ce0.9O2 (GDC) buffer layer was prepared between the electrolyte and the air electrode to prevent elemental diffusion (8). La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) was used for the air electrode. In addition, a Pt reference electrode was deposited onto the electrolyte on the fuel electrode side. The voltage measurement terminals of the electrochemical measurement setup were connected between the reference electrode and the air electrode to evaluate the air electrode potential. 50%-humidified hydrogen (100 ml min-1) was supplied to the fuel electrode, and air (150 ml min-1) was supplied to the air electrode. Negative current density means the value in the SOEC mode, while positive current density in the SOFC mode. Results and discussion As shown in Fig. 2 describing one cycle, current density was varied at 800°C for the 1000-cycle durability tests in the r-SOC operation. The range of current density was between -0.2 A cm-2 and 0.2 A cm-2. The air electrode potential at different current densities and the electrode impedance in every 100 cycles were measured. For the 1000-hour electrolysis durability test in the SOEC mode, current density of -0.2 A cm-2 was applied for 1000 hours at 800°C. The air electrode potential and the impedance in every 100 hours were measured (9). It has been found that a gradual degradation of the r-SOCs associated with an increase in air electrode potential in the SOEC mode and a decrease in the potential in the SOFC mode could be distinguished. However, such degradation tended to be stabilized with the number of cycles.STEM-EDS observations were performed to analyze the elemental distribution around the air electrode and the electrolyte in the cell. It was found that such elemental diffusion could occur during sintering and durability experiments.AcknowledgmentsA part of this study was supported by “Research and Development Program for Promoting Innovative Clean Energy Technologies Through International Collaboration” of the New Energy and Industrial Technology Development Organization (NEDO) (Project No. JPNP20005). Collaborative support by Prof. H. L. Tuller, and Prof. B. Yildiz at Massachusetts Institute of Technology (MIT) for their continuous support is gratefully acknowledged. Figure 1

Reversible Solid Oxide Cells: Selection of Fuel Electrode Materials for Improved Performance and Durability

Introduction Reversible solid oxide cells (r-SOCs) are attractive electrochemical energy devices that can operate as both solid oxide fuel cells (SOFCs) for power generation, and solid oxide electrolysis cells (SOECs) for steam electrolysis (1). Renewable power generation, such as wind and solar, depends on daily weather conditions and so that it is desirable to adjust the supply of fluctuating electricity to match demand using reversible energy devices such as r-SOCs. The operational concept of r-SOCs is schematically described in Figure 1. The aim of this study is to examine the electrochemical properties and durability of r-SOCs using alternative fuel electrode materials. Experimental Various r-SOCs were prepared using conventional and alternative fuel electrode materials. As the conventional materials, Ni-cermet with Sc2O3-doped ZrO2 (ScSZ) was used for the fuel electrode; dense 200 mm thick ScSZ membrane for the electrolyte; and La0.6Sr0.4Co0.2Fe0.8O0.3 oxide (LSCF) air electrode with Gd-doped CeO2 (Gd0.1Ce0.9O2) acting as a buffer layer between the ScSZ electrolyte and the LSCF air electrode. As alternative fuel electrode materials, GDC and/or La0.1Sr0.9TiO3 (LST) were used as the fuel electrode backbone. By applying the co-impregnation procedure of Ni and GDC, fuel electrodes with highly dispersed nanoparticles of Ni catalysts and GDC, denoted as Ni-GDC/LST-GDC, were prepared (2,3). A Pt-based reference electrode was deposited beside the air electrode, such that the fuel electrode potential was measured as the voltage between the fuel and reference electrodes.Current-voltage characteristics were characterized, including voltage cycle tests performed by switching the direction of current simulating r-SOC operation. Long-term durability tests in SOEC and SOFC modes were conducted at 800°C. Air was supplied to the air electrode, while 50%-humidified hydrogen gas was supplied to the fuel electrode. The current density in the SOFC and SOEC modes is denoted as positive and negative values, respectively. Results and discussion Figure 2 shows fuel electrode potential as a function of current density in both SOFC and SOEC modes. The cells with the Ni-zirconia cermet, GDC, LST, LST-GDC, and Ni-GDC/LST-GDC could be operated in both modes. In the SOFC mode, the conventional Ni-zirconia cermet exhibited the highest fuel electrode voltage among these materials studied. In contrast, in the SOEC mode, the GDC-containing materials exhibited lower (i.e. better) fuel electrode voltage compared to Ni-zirconia cermet even without Ni catalysts, indicating enhanced electrocatalytic activity of mixed-conducting GDC for the electrode reactions with water vapor at the fuel electrodes. Voltage cycle durability up to 1,000 cycles and long-term durability up to 1,000 hours could be measured. Latest results on the durability with various electrode materials will be presented. Acknowledgements A part of this study was supported by “Research and Development Program for Promoting Innovative Clean Energy Technologies Through International Collaboration” of the New Energy and Industrial Technology Development Organization (NEDO) (Project No. JPNP20005). References Q. Minh and M. B. Mogensen, Electrochem. Soc. Interface, 22, 55 (2013).Futamura, Y. Tachikawa, J. Matsuda, S. M. Lyth, Y, Shiratori, S. Taniguchi, and K. Sasaki, J. Electrochem. Soc., 164 (10), F3055 (2017).Futamura, A. Muramoto, Y. Tachikawa, J. Matsuda, S. M. Lyth, Y, Shiratori, S. Taniguchi, and K. Sasaki, International J. Hydrogen Energy, 44 (16), 8502 (2019). Figure 1

Macro-encapsulation of metallic phase change materials with sacrificial density less than 3.5 % for medium-temperature heat storage

To solve the problems of volume thermal expansion and high chemical activity of metallic phase change materials (PCMs), this paper successfully prepared millimeter/centimeter-size durable Bi@Void@Kaolin macrocapsules. Fortunately, carbon powder clusters from the thermal decomposition of adhesive CMC gathered on the core PCMs, cleverly adding a reducing atmosphere into the capsules. In particular, the buffer voids of macrocapsules were created from the pores and gaps between the accumulated Bi powders, and the method of improving the bulk density of powder cores as core precursors by the cold isostatic pressing (CIP) technology solves the problem of excessive cavity volume. Thermal analysis indicates that after CIP treatment, the heat storage density of the Bi@Kaolin macrocapsule with the unpressurized powder core volume accounting for 50% can be increased by 18.4%–275.0 J/cm3, which is about 2.5 times the heat storage density of the common medium-temperature heat storage materials - concrete and NaCl, under the working temperature range of 240–300 °C. Solid-liquid PCMs need to sacrifice their density in exchange for the necessary cavity volume, therefore the “actual volumetric heat storage density” of PCMs should be specified. The results show that the proportion of sacrificial density of Bi PCM (i.e. the cavity rate of Bi-based macrocapsule) can reach the optimal value of 3.5%, its actual volumetric heat storage density can reach 558.9 J/cm3 at 240–300 °C. Surprisingly, all the Bi@Kaolin macrocapsules showed excellent cycling durability and thermal stability during 500 cycles under air atmosphere and subsequent 24 h overload-temperature oxidation tests.

Spatial and electronic effects synergistically enhanced electrocatalytic oxygen evolution using atomic iridium-anchored cobalt oxyhydroxide nanosheets

Single-atom catalysts (SACs) based on noble metals play irreplaceable roles in the field of catalysis but unfortunately suffer from spatial constraints ranging from either lattice substitution, atomic dilution, or in-layer immobilization. Herein, this work was designed to overcome the limitation by locating discrete dangling coordinatively unsaturated [IrO5] motif atop γ-phase cobalt oxyhydroxide (γ-CoOOH) nanosheets to create a spatially novel catalyst (Ir1/CoOOHsur). For comparison, the lattice-doped catalyst (Ir1/CoOOHlat) was also synthesized via substituting Co in γ-CoOOH by Ir single atoms. The distinct location arrangements of Ir single atoms generated two different active sites that both weakened the adsorption of oxygenated intermediates relative to γ-CoOOH due to the upshifted O 2p-band center. Moreover, Ir1/CoOOHsur displayed a much weaker adsorption capability (closer to an ideal catalyst) than Ir1/CoOOHlat. Therefore, the spatial and electronic effects of discrete dangling [IrO5] motifs atop Ir1/CoOOHsur synergistically optimized the adsorption of oxygenated intermediates and thus gained the lowest energy barrier of the rate-determining step for oxygen evolution reaction. When used as the cathode catalyst in rechargeable zinc-air batteries, Ir1/CoOOHsur exhibited higher power density (101 mW cm−2) and cycling durability (800 h) than IrO2 (94 mW cm−2, 50 h). This study broadens noble metal-based SACs analogues and offers appealing opportunity to design target catalysts with the synergism of spatial and electronic effects for diverse catalytic applications.

Hierarchical nickel hydroxide hydrate assembled by ultrathin nanosheets for high-performance hybrid supercapacitors

Due to its unique nature, nickel hydroxide is an attractive cathode material for hybrid supercapacitors (HSCs). A facile solvothermal strategy was proposed to synthesize hierarchical nickel hydroxide hydrate (HNHH) assembled by ultrathin nanosheets. The reaction temperature (T) has a dramatic effect on the morphology and specific surface area (SSA). The prepared HNHH-T could offer large SSAs from 175.3 to 287.2 m2g−1 with rich mesopores at 3.3–4.3 nm, which are favorable for boosting the electrochemical activity. Among diverse HNHH-T electrodes, HNHH-120 delivered a maximum specific capacity of 718.0 C g−1 at 0.5 A g−1. Furthermore, the assembled HNHH-120//activated carbon (AC) HSC could acquire 95.0 F g−1 at 0.5 A g−1. Strikingly, this HSC could deliver 35.9 Wh kg−1 at 412.5 W kg−1 with robust cycle durability (82.6% after 15,000 cycles at 3 A g−1). Moreover, an HNHH-120//AC device can operate a micro-fan for 54 s, demonstrating its real application prospect. The dazzling energy storage capability of HNHH-120 is mainly thanks to its large SSA and rich mesopores.

Sequential Water Sorption/Desorption of a Nonporous Adaptive Organic Ligand Bridged Coordination Polymer for Atmospheric Moisture Harvesting.

Moisture harvesters with favourable attributes such as easy synthetic availability and good processability as alternatives for atmospheric moisture harvesting (AWH) are desirable. This study reports a novel nonporous anionic coordination polymer (CP) of uranyl squarate with methyl viologen (MV2+ ) as charge balancing ions (named U-Squ-CP) which displays intriguing sequential water sorption/desorption behavior as the relative humidity (RH) changes gradually. The evaluation of AWH performance of U-Squ-CP shows that it can absorb water vapor under air atmosphere at a low RH of 20 % typical of the levels found in most dry regions of the world, and have good cycling durability, thus demonstrating the capability as a potential moisture harvester for AWH. To the authors' knowledge, this is the first report on non-porous organic ligand bridged CP materials for AWH. Moreover, a stepwise water-filling mechanism for the water sorption/desorption process is deciphered by comprehensive characterizations combining single-crystal diffraction, which provides a reasonable explanation for the special moisture harvesting behaviour of this non-porous crystalline material.

3D porous MnCo2S4 network decorated nitrogen-doped monolayer Ti3C2 based supercapacitors with superior energy density

The development of supercapacitors generally suffers from the used anodes with insufficient energy density. In this paper, nitrogen-doped monolayered Ti3C2 (N-Ti3C2) is synthesized via a facile urea assisted solvothermal route and then abundant MnCo2S4 curved nanosheets are directly in-situ grown on their surface to form a novel 3D porous anode material (N-Ti3C2/MnCo2S4). The expanded interlayer spacing of nitrogen-doped Ti3C2 can effectively facilitate ion diffusion as well as regulate the growth of MnCo2S4 nanosheets. Subsequently, the highly conductive 3D MnCo2S4 porous network further gives a rapid pathway for ions and electrolyte transfer. Hence, N-Ti3C2/MnCo2S4 electrode delivers an ultra-high mass capacitance of 1243.1 Fg−1 at 5 mVs−1. Furthermore, the asymmetric supercapacitors (ASCs) based on N-Ti3C2/MnCo2S4 not only acquires a higher energy density of 162.8 Whkg−1 at the power density of 2700.0 Wkg−1 under a wide potential window of 0–1.5 V, but also exhibits an outstanding cycling durability with a minor loss of 6.20 % after 10,000 charge and discharge cycles.

Rapid synthesis of high-entropy antimonides under air atmosphere using microwave method to ultra-high energy density supercapacitors

Electrode materials based on battery-type energy storage principles have high capacity and energy density. However, the drastic structural volume changes caused by electrochemical reaction processes reduce the cyclic durability of the materials. The construction of high-entropy structures can enhance the material structure to accommodate the volume changes during ion embedding/detachment. In this study, a new high-entropy antimonide battery-type electrode material was synthesized for the first time using a domestic microwave oven under air atmosphere. Its lattice and structure were stabilized using high-entropy multi-element system to improve the electrode cycling stability while ensuring its high capacity. The high-entropy antimonides have a capacity of 1850.0 C g−1 at 1 A g−1 and maintain 82.0 % of the initial capacity after 10,000 cycles. Furthermore, the battery-supercapacitor hybrid device (BSH) assembled with Bi2O3 @single-walled carbon nanotube (SWCNT) has a reversible capacity of 600.0 C g−1, and the BSH showed an energy density of 125.0 Wh kg−1 at a power density of 750.0 W kg−1. The BSH meets the standard of secondary batteries, which provides a new feasible method for building energy storage devices with good performance.