High Power Research Articles

Low-cost single-source 17 level multilevel inverter with reduced switch count

Abstract This paper introduces an innovative multi-level inverter (MLI) topology operating with a single DC source. The proposed structure consists of a DC-DC rectifier (HFL), a switched capacitor (SC) unit and a Packaged U-Cell (PUC) module. The topology synthesizes 17 voltage levels at the output with only 10 power switches, offering low control complexity and high power efficiency. The high number of levels at the output voltage provides a high quality output voltage wave. A soft charging cell (SCC) is used to suppress impulsive charging currents in the switched capacitors. Experimental results show that SCC effectively suppresses impulsive currents in switched capacitors. The high frequency link (HFL) used to provide high voltage gain improves the cost efficiency of the system by reducing transformer sizes and costs. Simulation and experimental results show that the proposed topology achieves 96.92% efficiency, near sinusoidal current output and total harmonic distortion (THD) values between 4.99% and 1.23%. Moreover, with a low cost function (CF) value of 1.60, it is proven to offer a viable alternative for applications such as Renewable Energy Systems (RES) and Electric Vehicles (EVs). These findings demonstrate the applicability of the proposed MLI topology in these areas with low cost, high efficiency and quality power output.

Ultralow Power Cold-Fuse Memory Based on Metal-Oxide-CNT Structure.

One-time programmable (OTP) memory is an essential component in chips, which has extremely high security to protect the stored critical information from being altered. However, traditional OTP memory based on the thermal breakdown of the dielectric has a large programming current, which leads to high power consumption. Here, we report a gate tunneling-induced "cold" breakdown phenomenon in carbon nanotube (CNT) field-effect transistors, and based on this we construct a "cold" fuse (C-fuse) memory where applying a mild gate voltage can break down the CNT channel without damaging the gate dielectric. The C-fuse is intrinsically different from dielectric-breakdown OTP, and it exhibits extremely low programming current (10-12 A), a large high-low resistance ratio (>1011), and a long retention time (>10 years). As the first reported OTP memory based on low-dimensional nanomaterials, C-fuse memory exhibits excellent storage performance and good uniformity, demonstrating great potential in constructing next-generation secure storage circuits.

High-Modulus Homochiral Torsional Oxide Ceramic Artificial Muscles.

Fiber-based artificial muscles are soft actuators used to mimic the movement of human muscles. However, using high modulus oxide ceramics to fabricate artificial muscles with high energy and power is a challenge as they are prone to brittle fracture during torsion. Here, a ceramic metallization strategy is reported that solves the problem of low torsion and low ductility of alumina (Al2O3) ceramics by chemical plating a thin copper layer on alumina filaments. These filaments with a high modulus of ≈180GPa can be twisted into chiral coiled artificial muscles, exhibiting a unique electric thermal actuation mechanism. This tough and robust alumina artificial muscle can carry objects equivalent to 0.28 million times its weight and provide high actuation stress of up to 483.5MPa. In addition, it exhibits 18 times higher contraction power and 240 times higher energy density than human muscles, as well as a high energy conversion efficiency of up to 7.59%, which far exceeds most reported actuated carbon and polymer artificial muscles. This work has achieved large-scale manufacturing of high-modulus oxide ceramic muscles for the first time.

Gradient Design with Low-tortuosity Overcoming Kinetic Limitations in High-Loading Solid-State Cathodes.

The extensive commercialization of practical solid-state batteries (SSBs) necessitates the development of high-loading solid-state cathodes with fast charging capability. However, electrochemical kinetics are severely delayed in thick cathodes due to tortuous ion transport pathways and slow solid-solid ion diffusion, which limit the achievable capacity of SSBs at high current densities. In this work, we propose a conductivity gradient cathode with low-tortuosity to enable facile ion transport and counterbalance ion concentration gradient, thereby overcoming the kinetic limitations and achieving fast charging capabilities in thick cathodes. The LiNi0.8Co0.1Mn0.1O2 cathodes deliver a room-temperature (RT) capacities of 147 and 110 mAh g-1 at 5 C and 10 C, respectively, and meanwhile achieve a RT areal capacity of 3.3 mAh cm-² at 3 C, enabling SSBs simultaneously high energy and power densities. The universality of this strategy is demonstrated in LiFePO4 cathodes, providing a novel solution for fast charging and large-scale application of high-loading SSBs.

Squaric Acid-Containing Hole-Collecting Monolayer Materials for p-i-n Perovskite Solar Cells.

The development of hole-collecting materials is indispensable to improving the performance of perovskite solar cells (PSCs). To date, several anchorable molecules have been reported as effective hole-collecting monolayer (HCM) materials for p-i-n PSCs. However, their structures are limited to well-known electron-donating skeletons, such as carbazole, triarylamine, etc. In this work, we developed a series of squaraine derivatives that have a π-conjugated core composed of a squaric acid moiety connected to an indoline moiety. Thanks to the polar carbonyl group of squaric acid, all of the molecules were found to form hydrophilic monolayers after being chemisorbed on transparent conducting oxide surfaces, which is beneficial for the subsequent deposition of the perovskite layer. The effect of the substituents on the squaric acid moiety and the anchoring groups connected to the indoline moiety on the molecular electronic structure as well as the solar cell device's performance was elucidated. The p-i-n PSC devices fabricated by using these squaraine derivatives as hole-collecting monolayer materials exhibited high power conversion efficiencies of up to 22.1%, together with good stability. This work highlights the potential of a simple squaric acid skeleton as the building block for hole-collecting monolayer materials to realize high-efficiency and cost-effective PSCs.

Effect of friction stir processing on wire arc additively manufactured ER70S-6/SS308L bimetallic FGM

In this research, wire arc additive manufacturing (WAAM) is employed to fabricate a bimetallic steels component using ER70S-6 and SS308L. However, this process involves high power densities and significant heat inputs, which elevate the risk of unfavorable grain structures and defects. To mitigate this issue, friction stir processing (FSP) is applied, utilizing a unique tool featuring a flat shoulder without a pin. The resulting samples undergo testing for mechanical and metallurgical properties. The microstructure of ER70S-6 reveals ferrite with small amounts of pearlite at the grain boundaries. The upper portion of the deposited sample exhibits more pronounced grain refinement compared to the lower section, largely due to the rapid cooling rate and thermal cycling effects during layer deposition. This grain refinement is attributed to dynamic recrystallization, which enhances the hardness of the FSP-treated sample relative to its initial as-deposited state. Tensile tests indicate a significant increase in tensile strength, accompanied by a reduction in percentage elongation after FSP. The fatigue crack growth rate is higher along the longitudinal direction of bi-metallic joint as compare to transverse to the joint.

Advances on Defect Engineering of Niobium Pentoxide for Electrochemical Energy Storage.

The reasonable design of advanced anode materials for electrochemical energy storage (EES) devices is crucial in expediting the progress of renewable energy technologies. Nb2O5 has attracted increasing research attention as an anode candidate. Defect engineering is regarded as a feasible approach to modulate the local atomic configurations within Nb2O5. Therefore, introducing defects into Nb2O5 is considered to be a promising way to enhance electrochemical performance. However, there is no systematic review on the defect engineering of Nb2O5 for the energy storage process. This review systematically analyzes first the crystal structures and energy storage mechanisms of Nb2O5. Subsequently, a systematical summary of the latest advances in defect engineering of Nb2O5 for EES devices is presented, mainly focusing on vacancy modulation, ion doping, planar defects, introducing porosity, and amorphization. Of particular note is the effects of defect engineering on Nb2O5: improving electronic conductivity, accelerating ion diffusion, maintaining structural stability, increasing active storage sites. The review further summarizes diverse methodologies for inducing defects and the commonly used techniques for the defect characterization within Nb2O5. In conclusion, the article proposes current challenges and outlines future development prospects for defect engineering in Nb2O5 to achieve high-performance EES devices with both high energy and power densities.

Strain-dependent structural, electronic, mechanical, optical and thermoelectric properties of Sr3NBr3 perovskites for solar cell applications.

Halide perovskites are a class of materials with excellent potential for solar cell applications due to their excellent optical and electronic properties. In this study, strain-dependent physical properties of Sr3NBr3 perovskites are investigated and theoretical results are reported here. The structural properties indicate that Sr3NBr3 has a cubic structure. Calculation of the formation energy confirms the thermodynamic stability of Sr3NBr3 in the pristine state and under compressive and tensile strain. Phonon dispersion curves confirm the dynamic stability of Sr3NBr3, while its mechanical stability is verified through elastic constant calculations. The material exhibits anisotropy, which diminishes under tensile strain. Additionally, the band structure and density of states are analyzed to investigate the strain-induced changes in its electronic properties. The results show that pristine and strained Sr3NBr3 systems have semiconducting nature. The Sr3NBr3 material shows excellent optical absorption in the visible range. In the energy range of 10 eV to 13 eV (ultraviolet region), an excellent reflection of up to 70% is observed for Sr3NBr3. Besides, we studied different thermoelectric features to explore the thermoelectric properties of Sr3NBr3. A high power factor of 4.46 × 1011 W m-1 K-2 s-1 is found for the hole-doped system.

One pot synthesis of poly m-toluidine incorporated silver and silver oxide nanocomposite as a promising electrode for supercapacitor devices

The design and fabrication of novel electrodes with strong electrochemical responses are crucial in advanced supercapacitor technology. In this study, a poly(m-toluidine)/silver-silver oxide (PMT/Ag-Ag2O) nanocomposite was prepared using the photopolymerization method. Various characterization techniques were employed to analyze the prepared nanomaterials. The resulting structure of Ag-Ag2O minimizes ion diffusion distances, increases active sites, and accelerates redox reactions. The electrochemical response of PMT and PMT/Ag-Ag2O electrodes was evaluated in three different electrolyte solutions (Na2SO4, H2SO4, and HCl). The specific capacitance of PMT/Ag-Ag2O nanocomposite was found to be higher than that of PMT alone. Among the tested electrolytes, HCl exhibited the highest specific capacitance of 443 F g−1 at a gravimetric current density of 0.4 A g−1, surpassing H2SO4 (104 F g−1) and Na2SO4 (32 F g−1). Also, the PMT/Ag-Ag2O nanocomposite has demonstrated good cycling stability. It exhibited a high specific power density of 156 W Kg−1 and a specific energy density of 1.8 Wh Kg−1. These results highlight the potential of the prepared PMT/Ag-Ag2O nanocomposite as a nanoelectrode material for high-performance supercapacitors.

Structural Regulation and Performance Enhancement of Carbon-Based Supercapacitors: Insights into Electrode Material Engineering.

The development of carbon-based supercapacitors is pivotal for advancing high energy and power density applications. This review provides a comprehensive analysis of structural regulation and performance enhancement strategies in carbon-based supercapacitors, focusing on electrode material engineering. Key areas explored include pore structure optimization, heteroatom doping, intrinsic defect engineering, and surface/interface modifications. These strategies significantly enhance electrochemical performance through increasing surface area, improving conductivity, facilitating charge transfer, introducing additional pseudocapacitive reactions, and optimizing the density of states at the Fermi level, among other mechanisms. After introducing these fundamental concepts, the review details various preparation methods and their effects on supercapacitor performance, highlighting the interplay between material structure and electrochemical properties. Challenges in scaling advanced fabrication techniques and ensuring the long-term stability of functionalized materials are discussed. Additionally, future research directions are proposed, emphasizing the development of cost-effective, scalable methods and interdisciplinary approaches to design next-generation supercapacitors, thereby meeting the growing demand for efficient and sustainable energy storage solutions.

Design Analysis of 26650 and 18650 LFP Cells for High Power and Low Temperature Use Cases

Design Analysis of 26650 and 18650 LFP Cells for High Power and Low Temperature Use Cases

High power output density organic thermoelectric devices for practical applications in waste heat harvesting.

Organic thermoelectric (TE) materials are of great interest for researchers in waste heat recovery, especially for waste heat harvesting at near room temperature. Significant progress has been achieved in terms of their figure of merit (zT) values recently, which has presented new insights into the development of organic TE materials. For numerous practical applications of thermoelectric generators, where waste heat is unlimited and cost negligible, the primary goal has been switched to achieve high power output density rather than improving their heat-to-electricity conversion efficiency. In this review, we first discussed the theoretical relationship between the thermoelectric properties of organic materials and the power output density of devices. Then, we analyzed the state-of-the-art strategies for improving the power factor of organic materials. Methods for modulating the structure of the TE legs were discussed with an aim to maintain the temperature difference between the hot side and the cold side of the devices. Finally, some representative devices were summarized for the potential applications of the TEGs along with an outlook on the future of organic thermoelectric materials and devices.

Study of the self-degradation performance of a passive direct methanol fuel cell with an Fe-N-C catalyst.

Fe-N-C catalysts are considered promising substitutes for Pt-based catalysts at the cathode in direct methanol fuel cells (DMFCs) owing to their great methanol tolerance. However, Fe-N-C-based DMFCs commonly suffer from a decreased performance under extremely high methanol concentrations and exhibit poor stability, while the underlying mechanism remains controversial. In this study, a self-degradation phenomenon in a passive Fe-N-C-based DMFC was investigated in detail. The DMFC with an optimized ionomer content and catalyst loading delivered an extremely high peak power density of 28.85 mW cm-2 when fed with 3 M methanol solution, while the peak power density of the cell rapidly declined to 16.61 mW cm-2 after standing for 10 days without any discharging operation. Several electrochemical measurements were designed and conducted to explore the mechanism for this phenomenon. The results of these measurements revealed that methanol molecules are chemically adsorbed on the surface of the Fe-N-C catalyst, and the bonding cannot be reversed using simple physical methods, leading to the isolation of active sites from oxygen. Herein, we provide a new perspective on passive Fe-N-C-based DMFCs that would be significant for the technological development of portable power devices.

Life Cycle Economic and Environmental Assessment for Emerging Heavy-Duty Truck Powertrain Technologies in China: A Comparative Study of Battery Electric, Fuel Cell Electric, and Hydrogen Combustion Engine Trucks.

Amid ambitious net-zero goals and growing demands for freight logistics, addressing the climate challenges posed by the heavy-duty truck (HDT) sector is an urgent and pivotal task. This study develops an integrated HDT model by incorporating vehicle dynamic simulation and life cycle analysis to quantify energy consumption, greenhouse gas (GHG) emissions, and total cost of ownership associated with three emerging powertrain technologies in various truck use scenarios in China, including battery electric, fuel cell electric, and hydrogen combustion engine trucks. The results reveal varying levels of economic suitability for these powertrain alternatives depending on required driving ranges and duty cycles: the battery electric for regional-haul applications, the hydrogen fuel cell for longer-haul and low-load driving conditions, and the hydrogen combustion engine to meet high power requirements. The GHG mitigation potential of these technologies, on the other hand, critically hinges on energy sources. All three powertrains could achieve over 55% GHG emission reductions if the power sector and hydrogen supply are substantially decarbonized by 2035. The analysis underscores the necessity for a broad policy approach on a life cycle basis to incorporate all powertrain technologies and all energy sources in a complementary manner for facilitating a low-carbon road freight future.

Face consciousness: the impact of gift packaging shape on consumer perception

PurposeThis study aims to shed new light on the effect of gift packaging shape, specifically the distinction between horizontal and vertical orientations, on the face consciousness of both gift givers and recipients. The underlying mechanism of the main effect is examined, focusing on the perception of social status symbols. In addition, downstream outcome variables were included in the study to explore the effects of gift package shape on willingness to buy (WTB) and word-of-mouth (WOM) in the giver and receiver contexts, respectively. Furthermore, these effects were repeatedly verified in both China and the USA, revealing the significance of cultural differences. The study also investigated the moderating effects of an individual’s power state (low or high power) on the giver’s face consciousness.Design/methodology/approachSix studies were conducted to address the research objectives. Study 1 compared the gift givers’ face consciousness of a gift when presented with vertical package shapes versus horizontal. Subsequently, Study 2 investigated whether consumers’ perception of social status symbols mediates the effect of gift package shape on gift givers’ face consciousness. Study 3a expanded the conceptual model to include the downstream outcome variable of WTB in the context of gift-giving. Study 3b was validated with American participants, revealing the influence of cultural background differences on face consciousness. Study 4 introduced a gift-receiving context to investigate the chain-mediated effects of gift package shapes on consumer WOM. Lastly, Study 5 critically examined the boundary effect of personal power states on the interaction between the gift givers’ face consciousness and WTB.FindingsThe results indicate that gift givers and recipients attribute higher face consciousness to gifts with vertical package shapes compared to horizontal ones. In addition, consumers’ perception of gifts as status symbols was the underlying mechanism driving the impact of gift packaging shape on face consciousness. Furthermore, the face consciousness for gift packages of vertical shape was enhanced when people were in lower-power states as opposed to higher-power states, subsequently leading to an increase in the WTB.Research limitations/implicationsThe research is limited to an online virtual brand study; future field studies could be conducted to enhance the authenticity of the participants’ gift-giving experience and the overall external validity of the studies. In addition, gender-based stereotypes and the relationship between the giver and the receiver (transactional or intimate) may also influence the relationship between gift package shapes and face consciousness.Practical implicationsThe practical implications of this research focus on three points. First, gift brand managers should strategically employ vertical package shapes to signal high-end attributes and evoke face consciousness among consumers, aligning with the psychology of both givers and recipients. Second, managers must consider consumers’ power states in gift-giving scenarios, tailoring packaging recommendations to the dynamics between givers and recipients to maximize market share. Last, cultural differences in face consciousness, particularly between Asian and Western cultures, necessitate that managers adapt packaging designs to respect and enhance the social status of both givers and recipients in culturally sensitive ways. These findings underscore the importance of understanding and integrating consumer psychology, power dynamics, and cultural nuances into gift packaging strategies to boost market share.Originality/valueThe research contributes to understanding the impact of gift packaging shape on the perception of face consciousness among both gift givers and recipients. It highlights the mediating role of social status symbols and extends its scope by examining downstream effects such as WTB and WOM. It explores individual power states as a moderating factor, revealing how personal dynamics influence perceptions of face-saving consciousness. Also, the cross-cultural validation of these effects in China and the USA underscores the importance of considering cultural differences.

Defects Calculation and Accelerated Interfacial Charge Transfer in a Photoactive MOF-Based Heterojunction.

Photocatalytic hydrogen production is currently considered a clean and sustainable route to meet the energy and environmental issues. Among, heterojunction photocatalysts have been developed to improve their photocatalytic efficiency. Defect engineering of heterojunction photocatalysts is attractive due to it can perform as electron trap and change the band structure to optimize the interfacial separation rate of photogenerated electron-hole pairs. Here, the MOF-based heterojunction photocatalysts with theoretically high reduction and oxidation abilities are successfully synthesized, denoted ZrO2/Pt/Zr-MOF-X, with tuned linker defectivity through an in situ electrochemical route. The defectivity are rationally calculated from the TG and 1H NMR results. A positive correlation is found between the defectivity and photocatalytic activity, and ZrO2/Pt/Zr-MOF-6 with the optimized defectivity of ca. 35% exhibits the highest hydrogen production rate of up to 2923 µmol g-1 h-1, illustrating the importance of structural defects in heterojunction photocatalysts. Ultrafast transient absorption spectroscopy and electron spin resonance results unveil the highest carrier concentration and charge separation efficiency in the defected heterostructure of ZrO2/Pt/Zr-MOF-6 through a direct Z-scheme contact, leading to its efficient photocatalysis through the high redox power.

Revealing Crucial Influences of Boron Support on Regulating Geometric and Electronic Structures of 3D Catalyst for Hydrogen Evolution and Oxygen Reduction Reactions.

Building insights into the structure-performance relationship of catalysts has been emphasized recently. However, it remains a challenge due to catalysts' various and complex structures, especially the easily overlooked influence of the support material. Here, we reveal the crucial influences of boron introduction on synthesizing 3D carbon nanotube monoliths with embedded multistate Co metals, i.e., single atoms, clusters, and nanoparticles (Co-BNCNTs), by an interesting chemical blowing-assisted calcination method. The boron introduction can contribute to forming captivating boron-nitrogen pairs, shaping a 3D frame, and regulating electronic structure. The 3D Co-BNCNT monoliths present good catalytic performance for both the hydrogen evolution reaction (HER) at all pH values and the oxygen reduction reaction (ORR). The theoretical calculations indicate that the B incorporation in Co-NCNTs can optimize the free energy of adsorbed hydrogen and facilitate the O2 adsorption and the protonation of the O2* species. Furthermore, the Co-BNCNTs-based zinc-air battery provides great battery performance with a high power density and discharge-charge durability.

Local Structure Regulation for Oxygen Redox and Structure Stability of P2-Type Cathodes.

The local structure plays a crucial role in oxygen redox reactions, which boosts the capacity of layered oxide cathodes for sodium-ion batteries. While studies on local structural ordering have primarily focused on the intra-layer ordering, there has been limited research on the inter-layer stacking for the layered cathode materials for sodium-ion batteries. In this work, the impact of the intra-layer and inter-layer local structural regulation on anionic kinetics and the structure stability are explored through experimental analysis and theoretical calculations. Cu2+ substitution is introduced to adjust the transition metal inter-layer structure of P2-Na0.67Mg0.28Mn0.72O2, obtaining a zig-zag stacked honeycomb superlattice structure in P2- Na0.67Cu0.14Mg0.14Mn0.72O2. The local structure regulation mitigates the cation migration, improves the structure reversibility even at a deeply desodiation state of Na0.05, and the reductive coupling between cationic and anionic redox processes facilitates electron transfer from oxygen to copper ions and governs the properties of electrochemical kinetics and hysteresis. A full cell with hard carbon anode shows commendable energy density at high power density. This study paves an optional path for enhancing the structure stability and dynamics of oxygen redox chemistry in P2-type cathode materials for sodium-ion battery systems.

A power dependence model of the impact of leader impostorism on supervisor support and undermining: The moderating role of power distance.

Leaders, often perceived as possessing exceptional confidence and competence, are not immune to feelings of self-doubt. Leader impostorism describes the experience that one's attributes, experiences, skills, and abilities fall short of the standards expected in the leadership role, resulting in a sense of deception in fulfilling leadership responsibilities. While existing research has examined the antecedents and individual outcomes of leader impostorism, its implications for leaders' treatment of subordinates remain largely unexplored. In this research, we investigate the downstream consequences of leader impostorism on behaviors directed toward subordinates. Integrating research on leader impostorism with power dependence theory, we propose that for leaders with a low power distance orientation, leader impostorism increases supervisor support through the mechanism of perceived power dependence on subordinates, whereas for leaders with a high power distance orientation, leader impostorism increases supervisor undermining through the mechanism of power threat. The findings from two field studies support our theoretical model. This research contributes to the literature by broadening the understanding of the impact of leader impostorism on subordinates, extending power dependence theory within leader-subordinate dynamics, and offering insights into the dual nature of impostorism and its contingent effects. (PsycInfo Database Record (c) 2025 APA, all rights reserved).

Multimode dynamics of a monolithically integrated, tunable, bidirectional, gain switched optical comb source

A three-sectioned, bidirectionally coupled, tunable, optical comb source is presented. The photonic integrated circuit (PIC) consists of a gain section, a slotted mirror section and a Fabry-Perot (FP) section. Optical frequency combs (OFCs) are produced by gain switching the FP section via a high power radio frequency (RF) signal. An investigation into the effect of the RF frequency on the quality of the OFC is performed. Multimode behavior is observed with OFCs produced in multiple modes as well as the overall degradation in the quality of the combs in each mode. A minimal extension multimode rate equation model is presented that reproduces the experimental results extremely well using experimentally determined values for numerical parameters. The appearance of multimode behavior is interpreted as relating to the modified relaxation oscillation frequency of the bidirectionally coupled system.