Zinc (Zn) metal batteries are promising candidates for large-scale energy storage due to their high energy density, safety, and material abundance. However, dendrite growth during Zn electrodeposition remains a major challenge. In this study, an asymmetric and nonlinear phase field model is employed to investigate the morphological evolution during Zn electrodeposition. The roles of Langevin noise, applied overpotential, and nucleation site distribution on the growth of Zn dendrites are systematically analyzed. The simulations reveal that higher overpotentials enhance the tip effect, accelerating dendritic growth, while increasing nucleation site density promotes competition that suppresses tip dominance. Notably, the spatial distribution of nucleation sites strongly influences the overall deposition time, which can be quantitatively predicted using a linear regression model based on inter-site spacing and spacing asymmetry parameters. The seed-IHJ-inspired pre-deposition strategy is further evaluated, showing an extended deposition time and improved morphological uniformity at-0.1 V, but offering negligible improvement at-0.3 V. This study provides mechanistic insights into the growth of Zn dendrites in Zn metal batteries.

In water electrolysis, achieving smaller bubble detachment diameters and shorter detachment times could enhances the efficiency of the electrolysis process. This study investigates the impact of H2SO4 and HNO3 electrolytes on the detachment of both oxygen and hydrogen bubbles from a platinum microelectrode with a diameter of 50 um, using high-speed photography and electrochemical measurements. The experiments show that oxygen bubbles exhibit shorter lifetimes and smaller detachment diameters than hydrogen bubbles in 1 mol/L H2SO4 electrolytes. Conversely, in 1 mol/L HNO3 electrolytes, hydrogen bubbles have shorter lifetimes and smaller detachment diameters than oxygen bubbles. The results indicate that Marangoni convection plays a critical role in the detachment of bubbles. These insights provide a new approach to accelerating bubble detachment from electrode surfaces during electrochemical bubble formation.

In proton exchange membrane fuel cells, the dynamic process of water vapor freezing to ice in the gas diffusion layer (GDL) is simulated using a multi-relaxation-time/Lattice Boltzmann method model that combines the multi-component multi-phase pseudopotential model and the enthalpy-based model. The evolution of the liquid water and ice distribution inside the GDL during the freezing process is explored, and the effects of contact angle, porosity, and fiber size of the GDL are analyzed. The results indicate that ice nucleation is commonly formed in narrow gaps ranging from 7 to 10 mu m, and the ice region typically remains small in size due to the restriction imposed by carbon fibers. However, in specific regions where carbon fibers are more sparsely distributed, the ice can grow to a larger size. Increased hydrophobicity and porosity reduce the effective density of ice nucleation sites in the GDLs. This leads to a slower transition from water vapor to liquid water and ice. This work demonstrates that the pore structure of the GDL significantly influences the freezing process and should be considered when studying the cold start processes of PEMFCs.

Understanding the dynamics of interacting gas bubbles is crucial for optimizing the efficiency of water electrolysis. This study systematically investigates the evolution behavior of dual hydrogen and oxygen bubbles and their impact on electrolysis performance using dual Pt microelectrodes with a fixed interelectrode distance of 1 mm in 1 mol/L H2SO4 and HNO3 solutions. Using high-speed imaging and electrochemical analysis, three distinct dual-bubble detachment modes are identified under different applied potentials: Mode I (buoyancy-driven detachment), Mode II (buoyancy- and wake effect-driven detachment), and Mode III (coalescence-driven detachment). The results show that the production rates of both H-2 and O-2 exhibit a nonlinear dependence on the applied potential, with an optimal potential observed for each system. Notably, simultaneous dual-electrode operation does not always enhance efficiency: compared to two independent single electrodes, the efficiency of dual hydrogen bubbles increases by 18% at -3 V in H2SO4 but decreases by 21.1% at -8 V in H2SO4, while that of dual oxygen bubbles decreases by up to 57.6% at 3 V in HNO3. With a fixed interelectrode distance, the performance of the dual-bubble system is governed by two factors: the operating potential, which primarily determines the plateau current magnitude, and the electrolyte type, which influences both the magnitude and direction of the solutal Marangoni force. These findings provide valuable insights into electrolyte selection and operational parameters aimed at enhancing the efficiency of water electrolysis.

A lithium-oxygen (Li-O2) battery model incorporating both surface and solution reaction mechanisms is proposed for electrolyte partially wetting electrodes (PWE). This model integrates O2 transport, electrode surfacepassivation induced by film-like Li2O2deposition, and the dynamic evolution of electrolyte saturation within the electrode. It also accounts for the relative contributions of the solution mechanism and for variations in active-surface-area and pore-size distribution. The model is validated against experimental discharge profiles obtained at various initial electrolyte saturations (s0) using two representative electrolytes. For Super P-based electrodes, the discharge capacity in tetraethylene glycol dimethyl ether (TEGDME) electrolyte increases by 250 % as s0 decreases from 1.0 to 0.5, with discharge termination governed primarily by electrode surfacepassivation. In contrast, with dimethyl sulfoxide (DMSO) electrolyte, the same reduction in s0 yields only a 42.5 % capacity gain, and the discharge is limited predominantly by O2 transport. Replacing Super P with Ketjenblack (KB) significantly attenuates the capacity enhancement upon lowering s0. The optimal s0 that maximizes discharge capacity is 0.52 for TEGDME and 0.45 for DMSO in Super P-based electrodes, whereas KB-based electrodes exhibit higher optimal s0 values. Optimal s0 decreases with increasing electrode thickness but rises with greater electrode porosity or O2 diffusivity. Furthermore, the capacity advantage of PWE over flooding electrodes (FE) widens with increasing electrode thickness or current density, but narrows with higher electrode porosity or O2 diffusivity.

As traditional microwave and electronic integrated circuits encounter increasing power consumption and bandwidth limitations, photonic integrated circuits have emerged as a promising solution for 6G communication systems due to their low latency and low power consumption. This paper investigates and designs an on chip integrated power divider based on an all silicon topological valley photonic crystal (VPC). By exploiting the valley momentum locking property of the topological edge states, robust transmission through complex paths is achieved with strong suppression of backscattering. The proposed design utilizes the symmetry difference between AB and BA topological boundary states to realize output channels with intrinsic 0° and 180° phase differences, while the results show that the amplitude of the two output ports of the designed power distributor is about -6dB within the bandwidth. These exceptional amplitude and phase characteristics highlight the device's substantial promise for next-generation high-density photonic integrated circuits and multifunctional topological photonic networks.

This study investigates the influence of a battery's formation process on its long-term performance and proposes a management strategy that integrates formation optimization with controlled over-discharge recovery. The results indicate that the initial formation is a critical prerequisite determining the effectiveness of subsequent capacity recovery. The proposed controlled over-discharge strategy aims to "reset" the battery degradation process by controllably oxidizing and decomposing the aged SEI and in situ reconstructing a new SEI. The efficacy of this strategy highly depends on the SEI substrate characteristics determined by the initial formation: different formation processes result in initial SEI layers with significant differences in structure and composition, which directly affect their reconstructability during over-discharge and the upper limit of performance recovery. Experiments confirm that batteries subjected to an optimized formation process achieve a maximum SOH improvement of 3.11% and a maximum cycle life extension of 19.7%. In contrast, batteries with a non-optimized formation show only a 2.01% SOH improvement and a 12.8% life extension. Therefore, optimizing the formation process is not only fundamental for enhancing the initial battery state but also a necessary prerequisite for fully unleashing the potential of subsequent recovery strategies. This study provides theoretical and technical foundations for establishing an integrated battery management strategy spanning from manufacturing formation to regeneration.

A wideband two dimensional beam scanning liquid crystal based phased array antenna is presented. The proposed array employs a 4 × 4 element configuration, in which each element integrates a dual layer patch radiator and a liquid crystal phase shifter. The dual layer radiating structure enables wideband operation with a relative bandwidth of 20.5%, covering the frequency range from 17.5 to 21.5 GHz. By incorporating a spiral transmission line and a defected ground structure (DGS), the liquid crystal phase shifter achieves a wide phase tuning range of 456.8° within a compact footprint, enabling effective beam steering across a broad frequency band. Simulation results demonstrate that the proposed phased array maintains stable radiation characteristics over the entire operating band and realizes two dimensional electronic beam scanning of ± 45° in both the φ = 0° and φ = 90° planes. The combination of wide bandwidth and continuous beam scanning capability makes the proposed liquid crystal based phased array a promising candidate for broadband millimeter wave beamforming applications.

This work proposes a recovery strategy based on controlled over-discharge to address the issue of capacity fading in lithium-ion batteries due to solid electrolyte interphase (SEI) degradation after long-term cycling. Unlike conventional recycling approaches that rely on disassembly, the proposed method offers a non-destructive and practical alternative. The underlying mechanism involves applying a controlled over-discharge to decompose the aged SEI and then in situ reconstructing a new SEI during subsequent charging. This process effectively resets the battery degradation cycle, restoring the SEI to a healthier and more stable state. Experimental results demonstrate that notable capacity recovery and extended cycle life of the degraded lithium-ion batteries are achieved, with a maximum SOH improvement of 3.11% after one over-discharge operation, and a maximum cycle-life extension of 19.7% after controlled over-discharge cycles. This strategy presents a cost-effective and promising way for the performance recovery and sustainable management of lithium-ion batteries.

Bubble coverage on the electrode surface significantly reduces the efficiency of water electrolysis. This study investigates the effects of current density and microelectrode size on the growth and detachment dynamics of hydrogen and oxygen bubbles during water electrolysis. A high-speed camera is used to capture the dynamic behavior of bubble evolution and electrochemical measurements are conducted to record the instantaneous potential fluctuations. The results reveal that the bubble detachment size depends on the electrode size. At identical current densities, as the diameter of microelectrodes decreases, the generated hydrogen and oxygen bubbles exhibit smaller detachment diameters. Moreover, as the current density increases, the detachment diameter of bubbles increases. The results indicate that solutal Marangoni convection plays a critical role in the detachment of bubbles. These findings provide critical insights into bubble dynamics for optimizing electrolysis efficiency.

This study systematically elucidates the impact of rib-channel non-uniform compression on the structural evolution and transport properties of gas diffusion layers (GDLs) in proton exchange membrane fuel cells. The 3D microstructure of compressed GDLs was reconstructed by XCT, and thickness distribution, porosity, tortuosity, effective diffusivity, permeability, electrical/thermal conductivity, and liquid water transport were comprehensively investigated. Results show that non-uniform compression induces a characteristic three-region distribution. Based on this, an empirical logarithmic function was proposed to approximate the deformed profile, providing support for macro-scale modeling. For compression ratios below 35 %, GDL properties exhibit consistent trends: porosity decreases, tortuosity increases, and diffusivity declines. Effective diffusivity in the inplane direction agrees with the Bruggeman model, whereas the through-plane direction is significantly lower, requiring an exponent correction from 1.5 to 3.6. Accordingly, empirical formulas describing IP and TP diffusivities as functions of compression ratio were established. Electrical and thermal conductivity increase with compression, although the enhancement in the through-plane direction weakens between 25 % and 35 %. Localized damage occurs at 35 % compression, while pore collapse at 45 % leads to abnormal behavior. Compression above 25 % alters liquid water transport patterns and reduces drainage continuity. Overall, compression should be limited to below 25 % during fuel cell assembly. These findings provide new insights into the structure-property-transport coupling of GDLs under non-uniform compression and offer guidance for optimizing PEM fuel cell design and operation.

Next-generation proton-exchange membrane fuel cells (PEMFCs) encounter significant challenges at elevated temperatures (OTs) and pressures (OPs) due to local thermal and mass fluctuations. In this study, a threedimensional transient model was developed to analyze these dynamics by incorporating the effects of the microporous layer and variations in the coolant temperature along the channel. The results indicate that increasing the OT from 80 degrees C to 90 degrees C decreases the output voltage by 34-78 mV, increases voltage undershoot/ overshoot by 0.2-16.6 mV, and raises the temperature difference between the cathode catalyst layer (cCL) and coolant from 1.2 to 2.1 degrees C, leading to more irregular temperature fluctuations in the cCL. These effects stem from the increased gas-liquid water outflow within the cCL that induces membrane dehydration, particularly in the electrolyte near the channel. Consequently, the lag in proton conduction relative to the oxygen reduction reaction (ORR), as quantified by the newly introduced Damkohler number, has emerged as a critical factor that influences both heat transfer and reaction kinetics. Conversely, increasing OPs from 130 kPa [anode]/120 kPa [cathode] to 400 kPa [anode]/390 kPa [cathode] improves output voltage by 50-150 mV and reduces proton conduction hysteresis by 12-54 % under dynamic loads. This improvement is linked to higher O2 concentration and membrane water facilitated by a 0.6-2 degrees C decrease in cCL temperature. However, the rise in OPs also results in an increased voltage undershoot/overshoot due to greater fluctuations in the membrane water content, ultimately leading to additional power loss. These findings are crucial for optimizing PEMFC performance under extreme conditions and advancing fuel cell technology.

Understanding the catalyst layer (CL) structure-process-performance relationship is essential for optimizing proton-exchange membrane fuel cells. This study stochastically reconstructs a high-resolution porous CL with a full thickness of 8 mu m. The liquid water distribution within CL is simulated by a capillary condensation model, and a pore-scale model coupling oxygen and proton transport with electrochemical reaction is developed to investigate the CL structure-performance relationship under different operating conditions. Results indicate that CL exhibits better performance at higher humidities, up to the flooding threshold at the water saturation of 0.41, as the benefits of increased electrochemical surface area, enhanced proton conductivity, and improved oxygen permeability through the ionomer film significantly outweigh the increased transport resistances through both the pores and the water film. Under the flooding condition at water saturation of 0.41, CL performance starts to decline due to the sharply increased pore resistance. Proper perforation of CL is suggested to alleviate the pore resistance in flooded electrodes. Additionally, reducing the Pt-to-C mass ratio is found to achieve better Pt dispersion in low Pt-loaded electrodes, thereby lowering the local oxygen resistance, and the bilayer CL design with higher Pt content on the membrane side is shown to further mitigate the performance degradation.

This article proposes a miniaturized, low-loss, and continuously tunable slow-wave (SW) liquid crystal (LC) phase shifter, designed specifically for the 60 GHz millimeter-wave band. The 60 GHz frequency range, with its wide bandwidth and short wavelength, enables compact and high-performance designs, making it ideal for next-generation communication systems. A three-parallel-stub slow-wave unit, incorporating fine rectangular branches and gaps, is proposed to enhance the slow-wave effect. A rectangular defected ground structure (DGS) is introduced to increase the bandwidth, while gradient stubs in the coplanar waveguide (CPW) are employed to improve impedance matching between the CPW port and the inverted microstrip line (IMSL) port. The equivalent circuit model of the proposed slow-wave unit is analyzed, and the evolutionary process of the structural design, along with its impact on phase velocity, is examined through comparison. Measurement results indicate that the structure achieves a phase shift of up to 250(degrees)/lambda and a figure of merit (FoM) of 41.7(degrees)/dB, with an insertion loss of more than -6 dB. The simulation and measured results are in good agreement, demonstrating the feasibility of the proposed design in the 60 GHz band.

To elucidate the regulation mechanism of deposited product composition on the coupling process of mass transport and electron transfer in lithium-oxygen (Li-O2) batteries, a novel multi-step discharge/charge model with solid lithium superoxide (LiO2(s)) and lithium peroxide (Li2O2) as hybrid precipitation is proposed. This model couples the dynamic competitive growth mechanisms between LiO2(s) and Li2O2, while incorporating the asymmetric deposition and decomposition behaviors of Li2O2. The electrode surface passivation caused by the sluggish kinetic rate of electron across the Li2O2 film is solely responsible for the deep discharge termination based on the reduced graphene oxide cathode. LiO2(s) dominates the precipitation products with a limited capacity and a continuous decline in the LiO2(s) percentage with discharge depth. Although promoting the LiO2(s) formation is conducive to alleviating the electrode surface passivation, it aggravates the O2 transport resistance due to occupying more electrode pores with the same charge contribution. Hence the discharge capacity demonstrates a three-stage variation with increasing lithium superoxide (LiO2) formation rate, which rapidly grows by more than two times in stage 2 benefiting from the increased LiO2(s) percentage and enhanced solution mechanism. Whereas a slow rise of 32 % in the discharge capacity in stage 3 is attributed to the conversion of LiO2(s) to Li2O2 toroid for the discharge process controlled by O2 transport. An increase in the thickness or specific surface area of the cathode improves the discharge capacity mainly by facilitating the production of Li2O2 toroid despite the decrease in the LiO2(s) percentage, which is different from the regulatory mechanism of electrode porosity for accelerating the LiO2(s) formation. Increasing LiO2 solubility predominantly mitigates the electrode surface passivation through enhancement of the solution pathway, whereas the elevated O2 solubility synergistically facilitates the co-formation of LiO2(s) and Li2O2 toroid. In addition, the LiO2(s) percentage declines for the amorphous Li2O2 film with low resistance and the electrode surface passivation mainly originates from the coverage of reactive sites by Li2O2.

Rechargeable lithium metal batteries are regarded as one of the most promising candidates for future energy storage solutions owing to their superior energy density. However, the uncontrolled growth of lithium dendrites during charging remains a major obstacle to their practical application. A comprehensive understanding of dendrite growth mechanisms is therefore crucial for developing effective strategies to suppress lithium dendrite formation. In this study, a nonlinear phase-field model was employed to simulate the dynamic evolution of lithium dendrites on lithium metal electrodes during the charging process. The influences of interfacial anisotropy, temperature, electrode surface roughness, and anisotropy of Li + diffusivity on dendrite morphology were examined. The results reveal that increasing interfacial anisotropy strength facilitates the formation of secondary dendrites and promotes dendrite growth. Higher temperatures inhibit secondary dendrite growth, resulting in smoother lithium deposition. A rougher electrode surface retards dendrite propagation. Furthermore, adjusting the anisotropy of lithium-ion diffusion coefficients and introducing the perturbation in the Gibbs free energy function can regulate the deposition process, enabling control over the resulting lithium dendrite morphologies. These findings provide theoretical insights for controlling dendrite formation and improving the safety and reliability of lithium metal batteries.

Electrolyte decomposition and electrode corrosion stand as two primary side reactions in lithium-oxygen (Li-O2) batteries during their discharge/charge cycles. In this work, a comprehensive Li-O2 battery model combining multi-step lithium peroxide (Li2O2) formation, electrolyte decomposition, and electrode corrosion is proposed. Based on this model, the deposition behaviors and cycling performance of the Li-O2 battery under deep discharge/charge cycles are investigated. The stop of discharge is mainly ascribed to the loss of active surface area for the battery using tetraethylene glycol dimethyl ether (TEGDME) electrolyte, while both O2 transport limitation and active surface area loss lead to the discharge termination for battery using dimethyl sulfoxide (DMSO) electrolyte. The incomplete decomposition of Li2O2 and lithium carbonate (Li2CO3) clogs electrode pores, leading to a continuous decline in the discharge capacity of the Li-O2 battery. For the TEGDMEbased battery, the undecomposed Li2CO3 gradually dominates the deposition with cycles, wherein electrode corrosion becomes the primary source of the undecomposed Li2CO3 after 3 cycles. For the DMSO-based battery, undecomposed Li2O2 is always a dominant trigger for battery discharge capacity degradation, although electrode corrosion remains a key contributor to Li2CO3 generation. Despite the DMSO-based battery exhibiting lower rates of electrolyte decomposition and electrode corrosion, it demonstrates poorer cyclic performance than the TEGDME-based battery due to the generation of more toroidal Li2O2. Moreover, when the charging cut-off voltage is reduced to 4.2 V, discharge capacity diminishes more rapidly due to the increased accumulation of undecomposed Li2O2, despite suppressed Li2CO3 deposition. Finally, the results confirm that thick electrodes lead to deteriorating cycling performance, stemming from increased discharge/charge overpotential and extended discharge/charge times, thus intensifying the side reactions.

Silicon (Si) as the anode material for lithium-ion batteries (LIBs) has attracted much attention due to its high theoretical specific capacity (4200 mAh/g). However, the specific capacity and cycle stability of the LIBs are reduced due to the pulverization caused by the expansion of Si coated on Cu (copper) foil during cycles. In order to solve this problem, researchers have used an ultra-thin Si deposition layer as the electrode, which improves cyclic stability and obtains high initial coulomb efficiency of LIBs. However, suitable substrate selection is crucial to fabricate an ultrathin Si deposition layer electrode with excellent performance, and a substrate with a three-dimensional porous structure is desirable to ensure the deposition of an ultrathin Si layer on the whole surface of the substrate. In this paper, the Si thin layer has been deposited on a binder-free hybrid film of carbon nanotubes (CNTs) and carbon nanocoils (CNCs) by magnetron sputtering. Compared with densely packed CNT film and flat Cu foil, the loose and porous film provides a large surface area and space for Si deposition, and Si can be deposited not only on the surface but also in the interior part of the film. The film provides a large number of channels for the diffusion and transmission of Li+, resulting in the rapid diffusion rate of Li+, which improves the effective lithium storage utilization of Si. Furthermore, the CNC itself is super elastic, and film provides an elastic skeleton for the Si deposition layer, which eases its volume expansion during charge and discharge processes. Electrochemical tests have showed that the Si/CNT–CNC film electrode has excellent performance as anode for LIBs. After 200 cycles, the Si/CNT–CNC film electrode still had possessed a specific capacity of 2500 mAh/g, a capacity retention of 92.8% and a coulomb efficiency of 99%. This paper provides an effective way to fabricate high performance Si-nanocarbon composite electrodes for LIBs.

Numerical investigation on a proton exchange membrane fuel cell stack comprising 400 single cells under subzero temperatures is essential for automotive applications. In this work, a one-dimensional multi-phase PEMFC stack cold start model is built to investigate the effect of manifold configuration and endplates on the cold start process. It is noticed that the U-shape manifold configuration is more conducive to the distribution of reaction gas than the Z-shape, while the Z-shape manifold configuration is more likely to cause damage to the stack due to the dilute oxygen concentration in certain cells. The endplate effect has an important effect on the temperature, ice fraction, and cell voltage of the 20 cells near the endplates. The number of cells affected by the endplate effect is independent of the convective heat transfer coefficient. Finally, the strategy of leveraging the PEMFC stack's output energy to heat the stack can effectively boost the likelihood of a successful cold start, which can aid the stack achieve a successful cold start at -24 degrees C. The arrangement of two single cells separated by a heating pad provides the best cold start capacity and consistency in the stack.