Efficient Charge Research Articles

Unripe Plantain Peel Biohydrogel for Methylene Blue Removal from Aqueous Solution

Dye contamination is a serious environmental issue, particularly affecting water bodies, driving efforts to synthesize adsorbent materials with high dye-removal capacities. In this context, eco-friendly and cost-effective materials derived from bioresidues are being explored to recycle and valorize waste. This study investigates the synthesis, characterization, and application of a biohydrogel made from unripe plantain peel (PP), modified with carboxymethyl groups and crosslinked using varying concentrations of citric acid (CA), an eco-friendly and economical organic acid. The materials were characterized by ATR-FTIR, TGA, and SEM, confirming the successful synthesis of hydrogels, which exhibited rough, irregular surfaces with micropores. Additionally, the materials were analyzed for their pH point of zero charge, swelling capacity, and methylene blue (MB) dye removal efficiency. The results indicate that the biohydrogel formed with 1% CA exhibited the most favorable characteristics for MB removal. Kinetic studies revealed that the adsorption mechanism is pH-dependent, with equilibrium being reached in 720 min. The Freundlich isotherm model provided the best fit for the adsorption data, suggesting a heterogeneous surface and a multilayer adsorption process, with a maximum retention capacity of 600.8 ± 2.1 mg/g at pH 4. These findings contribute to the development of cost-effective and efficient materials for dye removal, particularly from water bodies.

Unobstructive and safe-to-wear watt-level wireless charger

A wearable microgrid that centralizes and distributes harvested energy across different body regions can optimize power utilization and reduce overall battery weight. This setup underscores the importance of developing cable-free wireless power transfer (WPT) systems for mobile and portable devices to eliminate the risks posed by wired connections, especially in dynamic and hazardous environments. We introduce a thin, stretchable, and safe hand band capable of watt-level wireless charging through the widely adopted Qi protocol operating at 130 kHz. The implementation of non-adhesive fabric encapsulation serves to protect the 50-μm-thin spiral copper antenna from mechanical strain, ensuring an overall hand band stretchability of 50%. We also create a stretchable “Ferrofabric”, characterized by a magnetic permeability of 11.3 and a tensile modulus of 75.3 kPa, that provides magnetic shielding for the antenna without compromising wearability. The “Ferrofabric” improves the coil inductance but induces core loss in AC application. By fully understanding and managing loss mechanisms such as the skin effect, proximity effect, core loss, and joule heating, we achieve a wireless charging efficiency of 71% and power delivery of 3.81 W in the kHz frequency range. Our WPT hand band is unobstructive to hand motion and can charge a handheld smartphone as fast as a desktop charger or power a battery-free chest-laminated e-tattoo sensor, with well-managed thermal and electromagnetic safety. Through a holistic electromagnetic, structural, and thermal design, our device culminates in a safe, rugged, and versatile solution for wearable WPT systems.

Influence of Electrolyte Saturation on the Performance of Li-O2 Batteries.

Electrolyte saturation can strongly affect the Li-O2 battery performance. However, it is unclear to what extent saturation reduction will impact the battery capacity. In this study, we investigated the influence of electrolyte saturation and distribution within a porous positive electrode on the deep discharge-charge capacities and cycling stability. The study used both models and experiments to investigate the change of electrolyte distribution, double-layer capacitance, ohmic resistance, and O2 concentration in the positive electrode at different electrolyte saturations. Results revealed that electrodes with 60% electrolyte saturation achieved almost the same maximum discharge (6.38 vs 6.76 mAh/cm2) and charge (5.52 vs 5.65 mAh/cm2) capacities with fully saturated electrodes. The partially wet positive electrode (40% saturation) obtained more cycles than the electrode with 100% saturation before the discharge capacity dropped below the cutoff point. However, the electrode with 40% saturation had a low average charging efficiency of 88.76%, whereas the fully saturated electrode obtained 98.96% charging efficiency. Moreover, the fully wet positive electrode had the lowest overpotential during cycling (1.26-1.39 V). The measured electrochemically active surface areas showed that even 40% saturation could sufficiently wet the positive electrode surface and obtain a double-layer capacitance (18.12 mF) similar to that with 100% saturation (20.4 mF). Furthermore, a considerable increase in O2 concentration at wetted surface areas was observed for the electrolyte saturation of less than 60% due to the significantly higher O2 diffusivity in the gas phase.

Effect of explosives charges types on the jet characteristics, penetration performance and fragmentation patterns of shaped charges

Different explosive materials have been studied numerically and experimentally to assess the efficiency of a small diameter shaped charge in terms of produced jet characteristics and penetration depth into RHA steel targets. 26 different explosives have been simulated numerically using Autodyn hydrocode, whereas recommended explosives have been loaded into small diameter shaped charges by pressing technique and tested by static firing against RHA targets in order to validate the numerical calculations. The numerical analysis has presented an intensive global view about the variation of the shaped charge jets as a potential of the loaded explosive charge efficiencies. A successful trial has been performed to measure the shaped charge jet velocity using detonation velocity VOD 812 apparatus, where its measured value was only 3.6% different from the numerical one for HMX-V5 explosive. Besides, TITAN (L3) flash X-ray radiograph has also been implemented to explore the jet profile using the same explosive type and to measure its jet tip velocity, which has only 2.1% different from that estimated numerically. Extensive fragmentation analysis has been presented, which showed increase in both the fragment number and the fragment speed when the used explosive charge is of high detonation velocity. CL-20 explosive exhibited the largest jet tip velocity and its scaled collapse velocity was found to be 140% of TNT explosive. The calculated average fragment speed has been validated and the measured fragment speed has only 2.3% difference when compared to the SPH calculations.

Effects of 10 keV Electron Irradiation on the Performance Degradation of SiC Schottky Diode Radiation Detectors

The silicon carbide (SiC) Schottky diode (SBD) detector in a SiC hybrid photomultiplier tube (HPMT) generates signals by receiving photocathode electrons with an energy of 10 keV. So, the performance of the SiC SBD under electron irradiation with an energy of 10 keV has an important significance for the application of the SiC-HPMT. However, studies on 10 keV radiation effects on the SiC SBDs were rarely reported. In this paper, the performance degradation of the SiC SBDs irradiated by 10 keV electrons at different fluences was investigated. After the irradiation, the forward current of the SiC SBDs increased, and the turn-on voltage decreased with the irradiation fluences until 1.6 × 1016 cm−2. According to the capacitance–voltage (C-V) curves, the effective doping concentration increased slightly after the irradiation, and an obvious discrepancy of C-V curves occurred below 5 V. Moreover, as a radiation detector, the peak position of the α-particles’ amplitude spectrum changed slightly, and the energy resolution was also slightly reduced after the irradiation due to the high collection charge efficiency (CCE) still being larger than 99.5%. In addition, the time response of the SiC SBD to the 50 ns pulsed X-ray was almost not affected by the irradiation. The results indicated that the performance degradation of the SiC SBD irradiated at the fluence of 1.5 × 1017 cm−2 would not result in a deterioration of the properties of the SiC-HPMT and showed an important significance for the supplement of the radiation resistance of the SiC SBD radiation detector.

Bi-Directional Charging with V2L Integration for Optimal Energy Management in Electric Vehicles

Electric vehicles (EVs) are becoming increasingly popular as an efficient transportation solution but they also present unique challenges for energy management. Bi-directional charging (BDC) is a solution that allows EVs to not only consume energy from the grid but also supply energy back to the grid. This facilitates vehicle-to-load (V2L) integration, where EVs can act as mobile power sources for homes, buildings, and the grid. V2L enables better energy management by utilizing EVs as a flexible resource to balance grid demand and supply in the proposed system. This is achieved through intelligent coordination between the EVs, charging stations, and the grid, using smart meters and communication networks. Integration of BDC and V2L also enables EVs to provide backup power during grid outages, reduce the need for costly grid infrastructure, and support renewable energy integration. BDC with V2L integration is a promising approach for optimal energy management in EVs and can play a significant role in the future of sustainable transportation and energy systems. The proposed model reached 95.13% charging efficiency, 95.03% energy management, 95.69% power rating, 96.28% voltage support and 87.99% temperature management.

Life After Death: Re‐Purposing End‐of‐Life Supercapacitors for Electrochemical Water Desalination

AbstractThis study explores the potential of re‐purposing end‐of‐life commercial supercapacitors as electrochemical desalination cells, aligning with circular economy principles. A commercial 500‐Farad supercapacitor was disassembled, and its carbon electrodes underwent various degrees of modification. The most straightforward modification involved NaOH‐etching of the aluminum current collector to produce free‐standing carbon films. More advanced modifications included CO2 activation and binder‐added wet processing of the electrodes. When evaluated as electrodes for electrochemical desalination via capacitive deionization of low‐salinity (20 mM) NaCl solutions, the minimally modified NaOH‐etched carbon electrodes achieved an average desalination capacity of 5.8 mg g−1 and a charge efficiency of 80 %. In contrast, the CO2‐activated, wet‐processed electrodes demonstrated an improved desalination capacity of 7.9 mg g−1 and a charge efficiency above 90 % with stable performance over 20 cycles. These findings highlight the feasibility and effectiveness of recycling supercapacitors for sustainable water desalination applications, offering a promising avenue for resource recovery and re‐purposing in pursuing environmental sustainability.

Effect of thermal shock on energy density of biaxially oriented polypropylene films for pulsed power capacitors

In this paper, thermal shock experiments are performed on the biaxially oriented polypropylene (BOPP) films, and the changes in dielectric and energy storage properties before and after the experiments are explored. The experimental results show that the films have reduced comprehensive performance with the thermal shock time and frequency increasing. After the thermal shock, both the permittivity and the dielectric loss increase slightly. And, the direct current (DC) conductivity has risen by 73.6%–714.2%. The lowest DC breakdown strength of film is 604.4 kV mm−1, showing a 13.5% reduction compared to that of pristine film. In addition, energy storage performance has also deteriorated. The maximum discharge energy density decreased from 4.62 J cm−3 of pristine film to 3.26 J cm−3 of treated film. There is a decrease in charge and discharge efficiency under the same electric field. The metallization layer of the film receives less influence; the capacitance is reduced by only 0.37%. The causes and mechanisms of performance changes are analyzed and discussed. The disruption of molecular chains during thermal shock is the most important factor leading to the degradation of films. This paper provides a powerful perspective and reference for studying the performance degradation and failure of polymer dielectrics under extreme operating conditions.

Efficient charge abstraction and oriented accumulation driven by strong interfacial interaction facilitate photocatalytic selective oxidation of furfuralcohol coupled with H2 evolution

S-scheme heterostructures are promising strategies for photogenerated charge transport and spatial separation, yet the intrinsic mechanism of interfacial interaction on carrier dynamics remains under exploration. Herein, an S-scheme NiTiO3/Cd0.6Zn0.4S (NTO/CZS) heterostructure with strong interfacial interaction was fabricated to synchronously drive redox half-reactions. The KPFM, SPV, in-situ ESR, in-situ XPS, and fs-TA combined with and DFT simulation confirmed the reinforced IEF’s role in efficient charge abstraction and oriented accumulation on RP and OP surfaces, respectively, thereby synchronously triggering redox half-reactions. In addition, the furfuryl alcohol (FOL) to furfural (FAL) conversion was driven by αC-H bond cleavage, with H2O playing a crucial role in achieving efficient photocatalytic selective oxidation of FOL coupled with H2 evolution reaction (HER). The optimized 35 % NTO/CZS exhibited exceptional photocatalytic performance, achieving FOL selective oxidation coupled with HER, surpassing that of CZS and NTO for HER of 3.3 mmol g−1 h−1 by 6 times and 50 times, respectively. The present work provides new insights into constructing S-scheme heterostructures with strong interfacial electric field (IEF) for efficient charge abstraction and oriented accumulation to synchronously facilitate redox half-reactions.

Design and analysis of a high-efficiency bi-directional DAB converter for EV charging

The escalating demand for electric vehicles (EVs) arises from apprehensions regarding fossil fuel depletion and the ecological repercussions of conventional combustion engines, propelling the transition towards environmentally sustainable alternatives. EVs are conventionally comprised of a powertrain, battery management system, and communication infrastructure, with the battery playing a pivotal role. Achieving an efficient EV battery charger necessitates the implementation of a proficient charging algorithm and a high-power converter capable of adeptly regulating battery parameters. Among the array of available options, a bi-directional DC/DC converter is often employed for this purpose. This study predominantly focuses on the Bi-Directional Dual Active Bridge Converter with Single-Phase Shift Control. It is renowned for attaining a broad voltage range through transformer turn ratio adjustments. Its controllable parameters, such as phase shift ratio and duty cycle, bolster its versatility. Moreover, due to its input–output isolation and minimal passive elements, this converter exhibits superior efficiency due to its soft-switching capabilities. The analytical framework encompasses steady-state and dynamic assessments, small-signal modeling, and system transfer function analysis, all of which contribute to formulating an optimized controller design. Additionally, the study conducts simulations of various battery charging techniques, including constant current (CC), constant voltage (CV), and CCCV mode, employing a 1.5 kW Dual Active Bridge DAB-based charger through MATLAB/SIMULINK. Furthermore, voltage mode control simulations for a 5 kW DAB converter augment the study's insights into effective EV charging strategies.

Unlocking the charge efficiency of γ’-V2O5 for Na-ion battery through a solution synthesis technique

In this study, the γ’-V2O5 cathode material was prepared through a solution synthesis technique leading to homogeneous, fine and porous particles 100–200 nm in size. This successful preparation allows to overcome the huge drawback of the microsized material in terms of charge efficiency and to take benefit of the attractive Na insertion properties of γ’-V2O5, i. e. a significant available capacity of 145 mAh g- 1, a high working potential of about 3.25 V vs. Na+/Na, an excellent charge efficiency, a high-rate capability and good cycle life. A detailed structural study upon Na insertion/extraction shows that the proposed nanosizing approach promotes a homogeneous Na solubility and solid solution behavior in a wider composition range (0.4 < x ≤ 1 in γ-NaxV2O5) compared to the results previously reported for solid-state synthesized γ’-V2O5. Furthermore, highly reversible structural changes are evidenced. Key kinetic parameters governing the Na insertion-extraction reaction are discussed thanks to an impedance spectroscopy study revealing a faster Na diffusivity in the one-phase region. The obtained results allow a comprehensive understanding of the enhanced performance exhibited by the present sub-micronic γ’-V2O5 material.

Impact of Nickel Strip Configurations on Resistance and Voltage Drop in Lithium Ion Battery Packs

The impact of nickel strip designs on the resistance and voltage drop in lithium ion battery packs is examined in this study. In a series parallel battery pack configuration, the effectiveness of coated and pure nickel strips is assessed, with particular attention paid to how they influence voltage drop, internal resistance, and overall efficiency. Each of the 24 series and 3 parallel cells that make up the battery pack has an internal resistance of 6 mΩ. Two configurations are analyzed: one utilizing pure nickel strips and another with coated nickel strips. The resistivity, cross sectional area, and length of the material are used to compute the equivalent resistance of the nickel strips for each arrangement. Voltage dips at a load current of 50A are determined to compare the performance of both strip. The study also looks at the voltage drop at key locations in the battery pack, including particular bent strips. The findings show that the coated nickel design displays a larger resistance (0.237Ω) and voltage drop (11.735V) than the pure nickel configuration, which has a lower total resistance (0.048Ω) and voltage drop (2.82V). Evaluation of the voltage drop during charging is also done for charging currents of 6A and 10A, demonstrating that the pure nickel arrangement allows for more efficient charging. One of the main elements affecting battery pack performance is internal resistance, which has a direct impact on the system's voltage drop and overall energy efficiency. The thickness, width, resistivity, and number of parallel strips utilized in this nickel strip material all have a major effect on the battery pack's total resistance. Because of this, the nickel strip design can improve or worsen the pack's power delivery, particularly in high load scenarios.

Research on faradic capacitive deionization regeneration method for absorption air conditioning system

The development of renewable energy driven air conditioning system is of importance for curbing the CO2 emission. Absorption air conditioning systems could be a good choice but for its low regeneration efficiency. Capacitive deionization (CDI) regeneration method has been proposed to improve the efficiency of absorption system by eliminating the energy waste in the traditional thermal regeneration method. The core part of CDI is the electrode normally made from porous carbon materials, which often suffers from low charge storage capacity and co-ion repulsion. On the purpose of performance optimization, this paper proposes a hybrid deionization (HCDI) regeneration method by fabricating the electrode from Faraday materials. Experimental research has been made on the regeneration capacity of the prepared electrodes. Investigation has been conducted on the performance of the HCDI method based absorption system. The influence of different parameters has been revealed. Compared with the porous carbon electrode, the Faraday electrode has raised the charge efficiency by 20%, and raised both the regeneration capacity and overall performance by 40%. Under optimized working conditions, the COP of the HCDI based absorption system has reached 3.51 in the experiments, which shows great potential for future application.

Flow-electrode capacitive separation of organic acid products and recovery of alkali cations after acidic CO2 electrolysis

Acidic CO2 electrolysis, enhanced by the introduction of alkali cations, presents a strategic approach for improving carbon efficiency compared to processes conducted in neutral and alkaline environments. However, a significant challenge arises from the dissolution of both organic acids and alkali cations in a strongly acidic feed stream, resulting in a considerable energy penalty for downstream separation. In this study, we investigate the feasibility of using flow-electrode capacitive deionization (FCDI) technology to separate organic acids and recover alkali cations from a strongly acidic feed stream (pH ~ 1). We show that organic acids, such as formic acid and acetic acid, are retained in molecular form in the separation chamber, achieving a rejection rate of over 90% under all conditions. Alkali cations, such as K+ and Cs+, migrate to the cathode chamber in ionic form, with their removal and recovery significantly influenced by their concentration and the pH of the feed stream, but responding differently to the types and concentrations of organic acids. The energy consumption for the removal and recovery of K+ is 4 to 8 times higher than for Cs+, and the charge efficiency is significantly influenced by the types of organic acid products and alkali cations. We conduct a series of electrochemical measurements and analyze the impedance spectroscopy, identifying that hindered mass transfer governed the electrode process. Our findings underscore the potential of FCDI as an advanced downstream separation technology for acidic electrocatalysis processes.

A Data-Driven Online Prediction Model for Battery Charging Efficiency Accounting for Entropic Heat

This study proposes a charging efficiency calculation model based on an equivalent internal resistance framework. A data-driven neural network model is developed to predict the charging efficiency of lithium titanate (LTO) batteries for 5% state of charge (SOC) segments under various charging conditions. By considering the impact of entropy change on the open-circuit voltage (OCV) during the charging process, the accuracy of energy efficiency calculations is improved. Incorporating battery data under various charging conditions, and comparing the predictive accuracy and computational complexity of different hyperparameter configurations, we establish a backpropagation neural network model designed for implementation in embedded systems. The model predicts the energy efficiency of subsequent 5% SOC segments based on the current SOC and operating conditions. The results indicate that the model achieves a prediction error of only 0.29% under unknown charging conditions while also facilitating the deployment of the neural network model in embedded systems. In future applications, the relevant predictive data can be transmitted in real time to the cooling system for thermal generation forecasting and predictive control of battery systems, thereby enhancing temperature control precision and improving cooling system efficiency.

Ag NPs-modified NiCoMn layered double hydroxides electrodes for high-performance asymmetric supercapacitors

The development of supercapacitor technology has been hindered by limitations in achieving both high power density and long cycle stability. Layered double hydroxides (LDHs) have emerged as promising candidates to address these challenges. In this study, we synthesized three distinct electrodes: NiCoMn LDH (LDH), Ag-citrate nanoparticles (Ag NPs), and a composite of Ag-citrate/NiCoMn LDH (AgNPs/LDH), to explore their electrochemical performance. The structural and morphological characteristics of the synthesized materials were confirmed using scanning electron microscopy (SEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), and raman spectroscopy. Among the materials, the Ag NPs/LDH composite exhibited superior electrochemical properties, with distinct anodic and cathodic peaks of higher current intensity and an expanded integrated area in the current-voltage curve. Additionally, impedance analysis revealed the lowest charge transfer resistance, indicating efficient charging and discharging processes. In addition, the Ag-NPs/NiCoMn composite exhibited a remarkable aerial-specific capacitance of 2764 mF.cm−2 at 5 mA cm−2 in a three-electrode configuration. Furthermore, in an asymmetric supercapacitor (ASC) device configuration of AgNPs/LDH as a working electrode and Activated carbon as a working electrode (shorthand form AgNPs/LDH ||AC ASC), a specific capacitance of 1850 mF.cm−2 at 5 mA.cm−2 was achieved. Encouragingly, the AgNPs/LDH||AC ASC device exhibited an energy density of 0.593 mWhcm−2 at a power density of 10 mW.cm−2, maintaining a 0.175 mWhcm−2 at a high-power density of 90 mWcm−2, while retaining 102 % of its capacitance after 4000 charging and discharging cycles. Overall, the AgNPs/LDH electrode material demonstrates significant potential for advancement in supercapacitor technology.

Hybrid Radial‐Axial Flow for Enhanced Thermal Performance in Packed Bed Energy Storage

ABSTRACTIn this work, a hybrid radial‐axial (HRA) system is used to store thermal energy in a packed bed. The heat transfer fluid (HTF) is delivered via a perforated radial pipe placed at the center of the packed bed along the axial length. Hot fluid flows from the center toward the wall through the holes (like other radial systems), but then leaves via the traditional axial flow exit, creating the HRA flow configuration. A computational fluid dynamics (CFD) model is used to analyze the thermal performance of the packed bed during the charging process utilizing the new HRA system. Alumina beads of 6 mm were filler materials and air was HTF with inlet temperature of 75°C for proof of concept. The present paper focuses on two aims: (1) utilizing CFD models to analyze flow and temperature profiles in the packed bed; (2) comparing the model results to experimental results published in a previous HRA flow study and to traditional axial flow. Two HRA configurations were considered based on previous experimental designs, one with uniform holes in the central pipe (R1) and one with gradients in the hole sizes to promote even flow from the central pipe into the bed (R2). The numerical results agree with the experimental results in both cases. The HRA system performance depends on the flow profile created by the hole designs, and it can perform better than the axial flow depending on the design of the radial pipe. Design R2, which promotes even flow from the central pipe into the bed, has higher charging efficiency than standard axial flow methods. For HRA design R2 at 0.0048 m3/s (7 SCFM, standard cubic feet per minute), numerical results for charging efficiency were 75.5% versus 73.8% for traditional axial flow. For HRA design R2 at 0.0061 m3/s (9 SCFM), numerical charging efficiency was 80.5% versus 78.1% for traditional axial flow. These results are consistent with experimental data.

Co-doped Ni-PBA anchored on optimized ZIF-67-derived Co/N-doped hollow carbon framework for high-performance hybrid capacitive deionization

Prussian blue analogues (PBAs) are considered to be a promising electrode material for hybrid capacitive deionization (HCDI) due to their open lattice structure, adjustable composition and high theoretical capacity. Nevertheless, the performance of PBAs in practical applications is limited by their low intrinsic conductivity and structural degradation. Herein, we demonstrate an advanced heterostructure CoNi-PBA@Co/N-HC by anchoring cobalt-doped nickel hexacyanoferrate (CoNi-PBA) on cobalt/nitrogen-doped hollow porous carbon (Co/N-HC) derived from cobalt-based metal–organic frameworks (ZIF-67). Co/N-HC as the conductive growth framework of CoNi-PBA can not only promote the rapid charge transfer and efficient ion diffusion, but also mitigate the structural degradation of CoNi-PBA crystals during ion intercalation/deintercalation. Moreover, the doped Co in CoNi-PBA is derived from Co/N-HC, allowing the heterostructures to form more stable and tighter interconnections. Therefore, the optimal PBA@Co/N-HC300 electrode exhibits reduced equivalent series resistance (Rs 1.10 Ω < Rs (PBA) 1.41 Ω), enhanced ion diffusion rate (DNa+ 2.86 × 10−16 > DNa+(PBA) 4.65 × 10−18) and exceptional electrochemical stability (99 % capacitance retention, 500 times CV tests). Correspondingly, the HCDI cell PBA@Co/N-HC300//Co/N-HC demonstrates good Na+ removal capacity (33.37 mg·g−1), excellent charge efficiency (83.65 %), diminished energy consumption (0.657 kWh kg−1-NaCl) and improved cycle stability (90.8 % capacity retention, 40 cycles).

Oxidized Ti3Al(1-x)SnxC2 MAX phases as negative electrode materials for sodium ion batteries

Materials proposed for the negative electrodes in sodium-ion batteries often include oxides capable of reacting with Na+ through intercalation, conversion, or alloying. While these oxides offer high specific capacities, they suffer from poor mechanical stability. A novel approach to address this issue involves designing tailored nanocomposites based on the (Ti/Sn)Ox system, achieved through partial oxidation of tin-containing MAX phase (Ti3Al(1-x)SnxC2, x = 0.4 and 0.7). By employing this strategy, we have developed composite electrodes based on Ti(1-y)SnyO2 and MAX phase, which exhibit remarkable durability, withstanding over 600 cycles in half-cells. These electrodes also demonstrate charge efficiencies higher than 99.8 % and specific capacities comparable to MXenes electrodes. These outstanding electrochemical performances are further validated at the full-cell level when combined with Na0.44MnO2 positive electrodes. The reaction mechanism between the composite and the sodium ion was also studied using in-situ techniques (Raman and XAS) and the contribution of the different components during sodiation and de-sodiation was highlighted.

Comprehensive analysis of thermal performance and low-grade energy charging efficiency of pipe-embedded building envelopes enhanced with single-level tree-shaped fin structures

Pipe-embedded walls (CnPWs) are structural and energy composite building components that can resist external disturbances by forming stealth thermal shielding layers. To tackle the mismatch between the heat charging rate and heat diffusion rate during energy charging processes, as well as the unsatisfactory robustness of stealth thermal shielding layers, the single-level tree-shaped metal finnd pipe-embedded walls (TfPWs) are proposed. To verify the effectiveness of TfPWs and obtain dynamic performances, a simulation study is conducted on 8 risk variables in 4 pairs through the validated numerical model. Results showed that the improved design was effective in obtaining more robust thermal shielding layers in auxiliary energy supply mode, the effect gained prominence as both the injection temperature and pipe spacing were augmented. In room heat load reduction mode, favorable benefits arise when pipe spacing exceeds 400 mm. The maximum increase rate of total injected energy under different reduction ratios of external insulation layer was 11.83%–31.91 %, while the maximum extra total heat loss was 5.33 %. Secondly, the trunk fins and branch fins played different roles in minimizing the excessive heat accumulation surrounding pipes, and the vertical and horizontal sizes of heat accumulation region mainly increased with the increase in trunk fin size and branch fin size respectively. Meanwhile, the utilization efficiency of fin material was higher when trunk fin size was smaller, and parameter combinations with trunk fin size of 0.2b and branch fin size of 0.4a/0.6a could achieve a better balance between material input and performance increase. Thirdly, the improvement effect of single left branch fin schemes was close to that of double branch fin schemes and significantly better than that of single right branch fin schemes. It was recommended to use single left branch fin schemes with an inclination angle of 60°. Finally, even if the reduction ratio of external insulation layer in different cities increased to 80 %, the inside surface temperature of TfPWs was still greater than room air. Taking CnPWs with standard external insulation layer as references, the TfPWs applied in Harbin, Beijing, and Shanghai could achieve similar or better results even when the reduction ratio of external insulation layer increased to 60 %, while TfPWs applied in Guangzhou could exhibit better performance even when the reduction ratio of external insulation layer increases to 80 %.