Cycling Durability Research Articles

Analysis of the cyclic strength of technical systems in conditions of complex operation loading

The main cyclic thermomechanical loads, as well as changeable in time vibration and aerohydrodynamic loadings accompanying them affect modern energy facilities, space, air, water and ground transport. At the same time the total number of loading cycles taking into account the duration of service turns out to be within in very wide limits. It is shown that a general spectrum of loads changing in time which affect the aforementioned objects is very complicated in terms of load levels, frequency ratios and time of their action. Taking into account a large variation of service impacts in the loading levels, frequency ratio and total number of loading cycles we performed a generalized analysis of the resistance to deformation, damage and fracture of high-loaded objects of modern technics. The results obtained revealed that in conditions of combined mechanical, vibration and aero-, gidro-, acoustic loadings the limit state (by criteria of cyclic strength using the rule of linear summation of damages expressed in deformation parameters) will be attained earlier, than that obtained only with allowance of the main thermomechanical loading. To substantiate the strength and service life of the objects under consideration, traditional standard and unified mechanical isothermal tests for static and cyclic loading are carried out to determine the basic characteristics of the mechanical properties of the material, as well as special mechanical programmed tests with variable modes that simulate complex processes of operational thermomechanical, vibration and aerohydrodynamic impacts. The results of testing are taken into account in computation and experimental estimations of the strength and the fatigue life for the corresponding spectra of operational loads. A refined verification calculation of the cyclic strength and durability is becoming increasingly relevant for modern machines and units operating under conditions of increasing speeds of movement, operating pressures with increased levels of pulsations, as well as in the occurrence of accompanying mechanical oscillations, vibrations and aerohydroacoustic impacts.

Deciphering Electrolyte Dominated Na+ Storage Mechanisms in Hard Carbon Anodes for Sodium-Ion Batteries.

Although hard carbon (HC) demonstrates superior initial Coulombic efficiency, cycling durability, and rate capability in ether-based electrolytes compared to ester-based electrolytes for sodium-ion batteries (SIBs), the underlying mechanisms responsible for these disparities remain largely unexplored. Herein, ex situ electron paramagnetic resonance (EPR) spectra and in situ Raman spectroscopy are combined to investigate the Na storage mechanism of HC under different electrolytes. Through deconvolving the EPR signals of Na in HC, quasi-metallic-Na is successfully differentiated from adsorbed-Na. By monitoring the evolution of different Na species during the charging/discharging process, it is found that the initial adsorbed-Na in HC with ether-based electrolytes can be effectively transformed into intercalated-Na in the plateau region. However, this transformation is obstructed in ester-based electrolytes, leading to the predominant storage of Na in HC as adsorbed-Na and pore-filled-Na. Furthermore, the intercalated-Na in HC within the ether-based electrolytes contributes to the formation of a uniform, dense, and stable solid-electrolyte interphase (SEI) film and eventually enhances the electrochemical performance of HC. This work successfully deciphers the electrolyte-dominated Na+ storage mechanisms in HC and provides fundamental insights into the industrialization of HC in SIBs.

Cu doped crystalline carbon nitride with increased carrier migration efficiency for uranyl photoreduction

Graphitic carbon nitride (g-C3N4) has been widely used in photocatalytic removal of uranium pollutants due to its promising metal-free visible light-responsive semiconductor material. Herein, the heteroatom introduction decorated crystal g-C3N4 (Cu-CCN) photocatalysts were successfully synthesized through element doping and molten salt method. Photocatalytic activity experimental results showed that the Cu-CCN-50 exhibits high U(Ⅵ) removal efficient (nearly 100 % after 10 mins under irradiation) and durable cycle performance. The enhanced photocatalytic activity was primarily attributed to the higher specific surface area, red-shift in the absorption band and the high separation efficiency of light-induced electron-hole (e-/h+) pairs. Finally, the possible active species and mechanism based on the photocatalytic reduction results were proposed. Thus, the synergistic strategy of element doping and molten salt crystallization inspires new insights for visible light removal of U(Ⅵ) in toxic wastewater.

Ni0.85Se anchored on N-doped MoSe2 hybrids for long-life asymmetric supercapacitors

The layered molybdenum diselenide (MoSe2) is an ideal electrode material for supercapacitors. However, its widespread application is severely hampered due to low capacity, poor rate performance, and inferior cycling durability. Herein, the Ni0.85Se anchored on N-doped MoSe2 (Ni0.85Se/N-MoSe2) hybrids have been successfully produced using a facile hydrothermal route, in which formamide and water served as the mixed solvent. Compared to the Ni0.85Se or N-MoSe2, the specific capacity of Ni0.85Se/N-MoSe2 hybrids was substantially enhanced due to the cooperative effect between Ni0.85Se and N-doped MoSe2 as well as unique mesoporous architecture. The Ni0.85Se/N-MoSe2 hybrids could deliver 276.5 C g−1 at 250 mA g−1. Moreover, a Ni0.85Se/N-MoSe2//activated carbon (AC) asymmetric supercapacitor (Ni0.85Se/N-MoSe2//AC ASC) could offer 58.4 F g−1 at 500 mA g−1, and a considerable energy density of 20.8 Wh kg−1 at 200 W kg−1. Impressively, the Ni0.85Se/N-MoSe2//AC ASC demonstrated outstanding cyclic durability (105.1 % of initial capacity could be retained after 15,000 cycles at 1000 mA g−1). A Ni0.85Se/N-MoSe2//AC ASC device could drive a timer for about 15 min. Therefore, the Ni0.85Se/N-MoSe2 hybrid is a promising positive electrode material for ASCs.

Highly dispersed conductive and electrocatalytic mediators enabling rapid polysulfides conversion for lithium sulfur batteries

The practical application of Li-S batteries encounters hurdles in maintaining cycling durability and rate capability under realistic conditions. Electrostatic self-assembly stands as a captivating avenue for exploring new frontiers in nanoscale catalysis. Leveraging renewable bio-oil both as a carbon source and self-polymerization precursor, ultrafine Mo2C nanocrystals anchored on bio-oil-derived 3D hierarchical carbon matrix (Mo2C@BOC) are fabricated by a facile NaCl template-assisted electrostatic self-assembly and followed annealing procedure. Densely anchored ultrafine Mo2C nanocrystals, intertwined with highly conductive carbon nanosheets, unveil an enhanced exposure of catalytically active sites for lithium polysulfide immobilization, conversion, and supply amply nucleation sites to mediate the fast precipitation of Li2S2/Li2S. Attributed to these favorable features, Li-S cells based on the as-designed catalytic host attain satisfactory cyclability with a minimum capacity fading rate of 0.0144 % over 1000 cycles and excellent rate capability. Decent performance can be achieved even at a high sulfur loading of 8.0 mg cm−2 and a low electrolyte-to-sulfur ratio of 3.5 µL mg−1. This strategy for solving the shuttle effect under high sulfur loading provides a promising solution for the further development of high-performance Li-S batteries. This work provides a rational strategy for solving the shuttle effect under high sulfur loading and sheds light on the great potential of Mo2C@BOC for developing more practical Li-S batteries.

Constructing heterostructured CoSe2-SnSe nanoparticles incorporated carbon nanofibers for robust sodium storage

Metal selenides receive significant attention as sodium-ion battery (SIB) materials by virtue of their high theoretical capacity and remarkable electrical conductivity. Nonetheless, the large volume change during cycling limits their large-scale employment on account of unsatisfied cyclic durability and rate performance. To tackle these problems, CoSe2-SnSe nanoparticles anchored on carbon nanofibers (CoSe2-SnSe@CNF) are initiated. The electrochemical property of CoSe2-SnSe@CNF in SIBs is found to be superior to those of CoSe2@CNF and SnSe@CNF, which is also illustrated by density functional theory (DFT) calculations. It is noteworthy that the CoSe2-SnSe heterostructures with built-in electric fields greatly stimulate charge transfer and Na+ transportation. Moreover, CNF, as the critical scaffold, immobilizes the CoSe2-SnSe nanoparticles, effectively suppressing the volume swelling and accelerating charge transportation. As expected, the CoSe2-SnSe@CNF exhibits a high capacity of 356.4 mAh g-1 after 100 cycles at 0.1 A g-1 and a reversible capacity of 248.7 mAhg-1 at 1 A g-1 underneath 1000 cycles..

Enhanced H2O adsorption by Ca2+ doping substantially improves the catalytic performance for light-driven thermocatalytic steam cellulose reforming on Ni/Ca1/8-SiO2

Using renewable biomass to produce syngas can form a closed carbon cycle, curbing carbon emissions. However, thermocatalysis suffers from high energy consumption, while the reaction rates of photocatalysis are relatively low. Here, we report the light-driven thermocatalytic steam cellulose reforming to hydrogen-rich syngas on the Ni nanoparticles loaded on Ca2+ doping SiO2 (Ni/Ca1/8-SiO2). It exhibits a high production rate of hydrogen-rich syngas (H2 3059.4 and CO 1612.1 mmol gcatalyst−1 h−1) and good cycling durability. Tar from cellulose pyrolysis, which is inherently challenging to prevent, is substantially decreased by the involvement of H2O. Ca2+ doping dramatically enhances H2O adsorption, resulting in a significant improvement in catalytic performance. The efficient light-driven thermocatalysis derives from the strong absorption over the whole solar spectrum of Ni/Ca1/8-SiO2 on the one hand. On the other hand, noticeable photoactivation effect is observed to promote the oxidation of carbon species by oxygen due to the surface Ni-O bonds being activated upon light illumination.

Enthalpy-driven synthesis of magnetic high entropy oxide catalyst for efficient oxidative desulfurization and high-value product recovery

High entropy metal oxides (HEOs) have shown remarkable catalytic potential owing to their multifaceted and tunable chemical composition, coupled with their exceptional thermodynamic stability. Specifically, magnetic HEOs demonstrate enhanced effectiveness in terms of catalyst separation and recovery owing to their magnetic properties. Nevertheless, current synthesis methods for magnetic HEOs often involve high-temperature conditions (typically > 1100 °C) to maximize the contribution of mixing entropy (ΔSmix) in the Gibbs equation (ΔGmix = ΔHmix - TΔSmix). Herein, unlike previous approaches, a reduction in the mixing enthalpy (ΔHmix) is proposed to result in a negative Gibbs free energy for the crystallization of HEOs. Based on this principle, a magnetic high entropy oxide, CoCrFeMnMoOx (MHEO), is successfully synthesized, at a relatively low temperature (900 °C). Notably, the MHEO catalyst demonstrated outstanding catalytic activity in the oxidative desulfurization (ODS) system utilizing O2 as the oxidant, achieving a rapid and complete sulfur removal of 100% within 3 h. Moreover, it demonstrates remarkable cycling durability, allowing for continuous operation over 20 cycles without significant loss in ODS efficiency. Furthermore, the magnetic properties of the MHEO catalyst facilitated the efficient separation and recovery of both the catalyst and high-value products. These findings offer significant insights into the design of high entropy catalysts and contribute to the advancement of sustainable green development.

Double-pinning effect assisting Na4VMn(PO4)3 with superior structural and electrochemical stabilization for sodium-ion batteries

The Na superionic conductor of (NASICON)-type Na4VMn(PO4)3 (NVMP) with a three-dimensional framework and high operating voltage has been extensively investigated for sodium-ion batteries (SIBs). However, unexpected Jahn-Teller effect and sluggish Na+ diffusion kinetics inevitably lead to rapid capacity fade and unfavorable structural distortion. Herein, the double-pinning effect of Al/F co-doping was adopted for the NVMP system to enhance structural stability and facilitate Na+ diffusion. The as-synthesized NVMP-Al&F presents a highly reversible capacity of 110 mAh g−1 at 0.1 C, accompanied with a long-term lifespan of 1000 cycles at 5 C (capacity retention of 86.1 %). Moreover, in situ X-ray diffraction affirms the reversible structural evolution and small volume variation (∼4.43 %) during the highly reversible sodiation/desodiation processes. Benefiting from the double-pinning effect, the lowered Na+ migration barrier effectively facilitates Na+ diffusion and increases to higher reversible capacity by combining theoretical calculation and kinetic analysis. The assembled NVMP-Al&F//hard carbon (HC) full cell manifests a high energy density of 353.9 Wh kg−1 and excellent cycling durability of 91.3 % at 1 C after 100 cycles. This work sheds light on the double-pinning as a novel strategy to boost the cycling stability of high-performance NASICON-type cathodes.

Modulating pore nanostructure coupled with N/O doping towards competitive coal tar pitch-based carbon cathode for aqueous Zn-ion storage

Cathode materials with limited active sites to accommodate Zn2+ ions substantially hamper the development of high-performance aqueous Zn-ion hybrid capacitors (ZHCs). Thus, the dedicated design of cathode materials is pivotal for preparing high power/energy density ZHCs. Here, a hierarchically porous coal tar pitch-derived carbon (NPC) cathode with abundant N/O doping (8.7 and 2.4 at.%) was prepared via a template strategy combined with chemical activation. The engineered hierarchically porous framework with optimal pore size distribution facilitates rapid Zn2+ ion transport, provides numerous active sites, and guarantees high adsorption-site accessibility. Moreover, the N/O doping further improves the transmission kinetics and adsorption capability of Zn2+ ions. Therefore, the aqueous ZHCs assembled with the NPC cathode show a high capacity of 158.2 mAh g−1 at 0.25 A g−1 and remarkable rate performance with a capacity of 73.5 mAh g−1 at 15 A g−1. Impressively, the NPC-based flexible device exhibits significant cycling durability with a capacity retention rate of up to 96.8 % over 10000 cycles at 10 A g−1 and a preeminent energy density of up to 112.1 Wh kg−1 at 203.0 W kg−1. This work provides new insights to design advanced coal tar pitch-based carbon materials for superior ZHCs.

Unveiling a cutting-edge bi-ligand nickel metal-organic framework as an electrode material for symmetric supercapacitors

Perylene diimide (PDI)-based MOFs feature a substantial specific capacitance, terrific cycle durability, swift charge/discharge rates, exceptional chemical as well as thermal endurance, diversity in electrode design, and inexpensive production costs. In light of these benefits, PDI-based MOFs are intriguing options for utilization in energy storage. Inspired by the distinctive features of perylene diimide-based ligands, highly conjugated and nitrogen-rich organic ligands Perylene diimide-L-dopa (PDI-L-Dopa) were incorporated to create the Ni-MOF architecture. The resulting hierarchical flower-like microspheres of bi-ligand Ni-MOF had better electron transport, conductivity, and wettability. When applied as electrode material in a three-electrode system considering a specific capacitance of 198 F/g at a current density of 1 A/g, the Ni-MOF-24 h electrode showcased beneficial electrochemical efficiency. XRD, FT-IR, and XPS were used to validate the formation of Ni-MOF and disclose the exact chemical composition and valence state inside the material. The hierarchical flower-like microsphere structure of the Ni-MOF, formed of 2D petal-like nanosheets, was revealed by FE-SEM and TEM. Additionally, when Ni-MOF-24 h electrodes used to fabricate symmetric supercapacitor (SSC), it reveals a high energy density (Ed) of 23 Wh/kg at a corresponding power density (Pd) of 600 W/kg along with extraordinary cyclic stability over 10,000 charge/discharge cycles with retaining 99 % of the initial capacitance. This research sheds light on the design and manufacture of innovative materials for long-term and efficient energy storage devices based on MOFs.

Improving soil resilience to drought climate by an eco-friendly approach

With the intensification of global warming, the increasing extreme drought climate has seriously threatened the stability of critical geotechnical infrastructure. This study proposes a novel, eco-friendly approach to improve soil resilience to drought climate. In order to verify the feasibility and durability of the proposed approach, a series of simulated climatic wetting-drying (WD) cycles were carried out using four sets of soil specimens treated with different W-OH (an eco-friendly polymer) concentrations. During this period, the water evaporation history, desiccation cracking process, WD cycle durability and microstructure evolution of soil specimens treated with different W-OH concentrations were investigated. The results reveal that the W-OH modification has a significant suppression effect on the whole process of soil evaporation, which can effectively prolong the soil evaporation time of constant rate stage and falling rate stage. The addition of W-OH not only significantly reduces crack ratio, total crack length, and average crack width, but also slows down the crack growth rate. Compared with untreated soil specimen, the treatment with low concentration of W-OH (2% and 4%) can effectively mitigate the formation of desiccation cracks, while the treatment of higher concentration of W-OH (6%) can directly prevent the occurrence of such cracks. The microstructure analysis results indicate that the W-OH can transform the soil structure into a denser state through two ways of bridging and encapsulation, which significantly increases the migration resistance of pore water and improves soil strength properties. This investigation is expected to improve fundamental understanding of soil-atmosphere interactions under eco-friendly polymer modification and provides insights into the potential application of eco-friendly polymer modification in enhancing soil resilience to extreme drought climate.

Stretchable textile with ultra-high electromagnetic interference shielding performance based on porous wrinkled conductive network

The soaring growth of flexible electronic devices has boosted the demand for electromagnetic interference (EMI) shielding materials with excellent stretchability, stability and even breathability. However, it is still a challenge to develop conductive materials with outstanding stretchable EMI shielding performance. In this work, we developed a textile with porous wrinkled conductive network through in situ polydopamine-assisted deposition of silver nanoparticles (AgNPs) on wrinkled fiber mat and polydimethylsiloxane post modification. This unique wrinkled conductive networks endows the textile with excellent electrical conductivity (103700 S/m), good breathability, superhydrophobicity, and ultra-high stretchable EMI shielding properties. The EMI shielding effectiveness (EMI SE) of the textile reaches 101.1 dB in unstretched state and still maintains at 94.1 dB at 100 % tensile strain. The superhigh EMI SE under such a high strain is much higher than the previously reported results so far. Moreover, the textile shows exceptionally good cyclic tensile durability under 100 % stain. After 1000 tensile cycles with 100 % strain, the EMI SE of sample only drops by 3.8 %. This work provides a new path for developing stretchable high EMI shielding performance materials, which is of great significance to solve the EMI problems of emerging flexible and wearable electronic devices.

Ultrafine Ni0.85Se nanoparticles encapsulated inside hollow porous carbon spheres and their excellent Na storage performance

As a novel anode material for sodium-ion batteries, ultrafine Ni0.85Se nanoparticles encapsulated inside hollow porous carbon spheres (HPCS@Ni0.85Se) are prepared by impregnating Ni(NO3)2 into HPCSs, calcination and selenization, which is based on the strong capillary effect of HPCSs. Material characterization reveals that Ni0.85Se nanoparticles with a diameter of 5–15 nm are evenly dispersed and intimately coupled to the internal wall of HPCSs, and the content of Ni0.85Se reaches 52.81%. HPCSs as unique reactors and Ni0.85Se carriers improve electronic conductivity of Ni0.85Se, facilitate electrolyte penetration and storage, buffer volume variation of Ni0.85Se, effectively confine Ni0.85Se during long-term cycles. Consequently, HPCS@Ni0.85Se exhibits excellent cycling durability and extraordinary rate capability. High reversible capacities of 341 mA h g−1 at 1 A g−1 after 1000 cycles, 280 mA h g−1 at 5 A g−1 after 2000 cycles and 305 mA h g−1 at 10 A g−1 after 540 cycles are achieved. The reaction kinetics and Na + storage mechanism are further analyzed by galvanostatic intermittent titration technique, cyclic voltammetry and electrochemical impedance spectra measurements. Ex-situ characterizations confirm outstanding structural stability of HPCS@Ni0.85Se. It is demonstrated that HPCS@Ni0.85Se is an excellent anode material, and this unique HPCS-based nanoencapsulation structure is an effective composite strategy for transition metal selenides.

Cerium oxide boosted CoFe-N codoped carbon nanotubes with abundant oxygen-vacancies toward efficient oxygen reduction and methanol oxidation reaction

In this study, we designed a novel strategy that utilizes N-doped carbon nanotubes as the chemical bond supporter to stabilize ultrafine CoFe alloy and introduces secondary CeO2 active sites into the hybrid, resulting in the formation of CeO2/CoFe-NCNTs heterostructures with exceptional bifunctional electrocatalytic capabilities. To be specific, solution dispersion and high-temperature calcination methods were employed to create the CoFe-NCNTs active sites through the introduction of ethylenediamine into the network interstitials of Co-EDTA and Fe-EDTA. The CeO2/CoFe-NCNTs hybrid not only promotes oxygen absorption and conversion of intermediates, but also accelerates charge transfer capability, thus enhancing oxygen reduction reaction (ORR) performance, while simultaneously inducing boosted the methanol oxidation reaction (MOR) activity. Moreover, the well-dispersed CoFe nanoparticles within the hybrid hold significant potential for establishing metal-nitrogen bonds with the N-doped carbon nanotube network, resulting in efficient catalytic behavior driven by synergistic effects with CeO2 nanoparticles, which contributes to reactant activation. As expected, the resultant CeO2/CoFe-NCNTs-2 exhibits remarkable electrocatalytic performance, with a current density of 281.40 mA cm−2 at a scan rate of 200 mV s−1 and a low Tafel slope (71.3 mV dec−1) for MOR, as well as achieving excellent half-wave potential and onset potential values of 0.834 and 0.90 V (vs. RHE) for ORR. Additionally, it exhibits durable cycle stability for both MOR and ORR, retaining 92.8% and 96.4% of its initial current density during the I-t test, respectively. This work establishes a highly efficient bifunctional earth-abundant electrocatalysts for both anode and cathode reactions in methanol fuel cells.

ZIF-derived Fe,Co coordinated N/O-codoped three-dimensional tungsten–carbon matrix for the performance-enhanced zinc-air flow battery and water splitting

Constructing efficient and cost-effective electrocatalysts with oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) for the development of zinc-air flow batteries (ZAFBs) and overall water splitting (OWS) is significant, but still challenging. Herein, we have fabricated a heterojunction catalyst (Fe,CoZn9+9-NO/WC) featuring uniformly dispersed Fe and Co coordinated with riched-nitrogen/oxygen codoped into a three-dimensional highly porous tungsten–carbon matrix modified carbon nanotube by a simple stepwise construction route using water as the solvent. The resultant Fe,CoZn9+9-NO/WC exhibits a positive half-wave potential (E1/2) of 0.889 V for ORR, a low overpotential at 10 mA·cm−2 for OER (290 mV) and HER (84 mV), and excellent electrochemical durability in alkaline electrolyte, outperforming even benchmark catalysts. Moreover, Fe,CoZn9+9-NO/WC as a bifunctional air cathode for ZAFBs delivers higher open circuit voltage, peak power density (190 mW·cm−2), and specific capacity (814 mAh·g−1), lower charge/discharge voltage gap and prolonged operational cycles durability, largely exceeding those of the hybrid Pt/C+RuO2 bifunctional catalyst. The alkaline OWS electrolyzer is constructed by Fe,CoZn9+9-NO/WC with good stability and requires only 1.556 V cell voltage at 10 mA·cm−2. Impressively, the self-constructed Fe,CoZn9+9-NO/WC electrodes were applied to practical ZAFBs and OWS devices, demonstrating superior performance to the recently reported ZIF/MOF-derived catalysts in organic solvents. This work offers an economical synthetic strategy to prepare highly efficient multifunctional catalysts with practical potential for commercial production, promising to facilitate the development of clean energy storage and conversion devices.

In Situ Insertion of Silicon Nanowires into Hollow Porous Co/NC Polyhedra Enabling Large-Current-Density Hydrogen Evolution Electrocatalysis.

N-doped carbon (NC)-encapsulated transition metal (TM) nanocomposites are considered as alternatives to Pt-based hydrogen evolution reaction (HER) electrocatalysts; however, their poor electron transfer and mass diffusion capability at high current densities hinder their practical application. Herein, an oriented coupling strategy for the in situ grafting of ultrafine Co nanoparticle-embedded hollow porous C polyhedra onto Si nanowires (Co/NC-HP@Si-NWs) is proposed to address this concern. Experimental investigations reveal that the intimate coupling between the Si-NW and Co/NC nanocage forms a multithreaded conductive network, lowering the energy barrier for internal electron transfer. When functionalized as an HER electrocatalyst in 0.5m H2 SO4 , Co/NC-HP@Si-NWs deliver overpotentials as low as 57 and 440mV at 10 and 500mA cm-2 , respectively, which are much better than those of the pristine Co/NC-HP. Moreover, Co/NC-HP@Si-NWs show an outstanding cycle durability of 24h at 10 and 500mA cm-2 . The findings of this study are expected to inspire revolutionary work on the development of Si-mediated TM-based electrocatalysts for the HER.

Polyethylene Glycol Confined in SiO2-Modified Expanded Graphite as Novel Form-Stable Phase Change Materials for Thermal Energy Storage.

Form-stable phase change materials (FSPCMs) composed of poly(ethylene glycol) (PEG) encapsulated in SiO2-modified expanded graphite (EG@SiO2) were prepared and investigated for thermal energy storage behaviors. The modification of SiO2 on EG was done using a simple sol-gel method, and then the resulting EG@SiO2 was introduced to confine PEG at varying content (60-90 wt %). Surface properties (including microstructure, morphology, and functional groups), PEG adsorptivity, leakage-proof ability, and thermal energy storage of the prepared materials were thoroughly characterized and discussed. The EG@SiO2 with 15 wt % SiO2 outstandingly adsorbed PEG as compared to the pristine EG, showing up >80 wt % of PEG. As a result, PEG was well stabilized in EG@SiO2 porous network without leakage, owing to capillary force, surface tension, and hydrogen bonding interactions. The optimal 80 wt % PEG/EG@SiO2 composite possessed high crystallinity (93.5%), high thermal energy storage capacity (132.5 J/g), and excellent thermal conductivity (4.086 W/m·K). In addition, it exhibited good cycling durability after 500 repeated melting/crystallization cycles. The high thermal efficacy and inexpensiveness would make the PEG/EG@SiO2 FSPCMs suitable for scale-up applications in thermal energy storage.

In situ tellurization strategy for crafting nickel ditelluride/cobalt ditelluride hierarchical nanostructures: A leap forward in hybrid supercapacitor electrode materials

Advancements in renewable energy conversion can be significantly propelled by optimizing the performance of transition-metal-based electrodes. In this study, we introduce an innovative, in situ tellurization strategy to synthesize novel, flower-like hierarchical structures of nickel ditelluride/cobalt ditelluride (NiTe2/CoTe2) on a nickel foam substrate (labeled as NF/FNCT), making them promising candidates for electrodes in hybrid supercapacitors. Initially, we utilized a hydrothermal method to create flower-like NiCo-layered double hydroxide (NiCo-LDH) nanoarrays on nickel foam (NF/FNCLDH). This process was followed by the tellurization of these nanoarrays, which yields the NiTe₂/CoTe₂ nanostructures. The strategic assembly of active materials on a conductive substrate effectively obviates the need for inert, slow-conductive binders, thereby facilitating redox chemistry. Capitalizing on the synergistic effects of the conductive tellurium and hierarchical flower-like nanomorphology, the NF/FNCT showcases expedited electron/ion transport, enhanced efficiency, and exceptional electrochemical performance. The NF/FNCT electrode discloses an impressive capacity of 1388.9 (±3) C/g, superior rate capability (83.45 % capacity retention at 30 A/g), and remarkable cycling durability of 96.67 %. Furthermore, when integrated with activated carbon (AC), the resultant hybrid supercapacitor delivers a desirable energy density of 58.85 Wh kg−1 at a power density of 806.85 W kg−1, demonstrating commendable rate capability and cycling durability. This investigation opens new avenues for the synthesis of materials for hybrid supercapacitors.

Gallium regulated MnO2 toward high performance Zn ion batteries

α-MnO2 with open tunnel structure has received ever-increasing attention because of its superior specific capacity, yet generally undergoes unstable phase transition from the tunnel architecture to layered structure upon Zn2+ insertion as well as the disadvantages of low electrical conductivity and slow Zn2+ diffusion kinetics, thereafter triggering inactive reaction dynamics. In this regard, a gallium (Ga) doped α-MnO2 nanowires (denoted as MnO2-Ga) is firstly built in this work to address the abovementioned issue and the MnO2-Ga2 displays enhanced performance with reversible capacity of 205.1 ± 5 mAh g−1 undergoing 200 cycles at 0.2 A g−1. After repeated 2000 cycles at 1 A g−1, a capacity of 123.7 ± 5 mAh g−1 can be still obtained. Validated by the theoretical calculation, it is noted that the Ga could effectively regulate the electronic distribution of α-MnO2 and narrows the bandgap, prompting the electronic cloud polarization of O and therafter accelerating ion diffusion efficiency. Fundamentally, the Ga intercalation results in the formation of Ga–O bonds. This special building not only guarantees the reversible phase transition and alleviates the Mn dissolution of Ga-MnO2, but also weakens the Zn2+-O2- interactions, leading to elevated cyclic durability and capacity.