Search Results (333)

Vanadium redox flow batteries (VRFBs) experience performance losses driven by electrode ageing, yet the underlying mechanisms remain poorly resolved under operational conditions. This work presents a novel application of dynamic electrochemical impedance spectroscopy (DEIS) in both full-cell and three-electrode configurations to monitor kinetic and transport processes throughout complete charge–discharge cycles. Carbon felt electrodes subjected to thermal activation, chemical degradation, and electrochemical ageing were systematically examined to capture a broad range of ageing-induced modifications. Complementary electrochemical impedance spectroscopy (EIS) measurements at selected states of charge were performed to highlight the substantial differences between spectra recorded under load and at open-circuit conditions. The results reveal that the impedance response of the full cell is dominated by processes occurring at the negative electrode, and that ageing leads to increased charge-transfer resistance and enhanced state of charge-dependent variation. X-ray photoelectron spectroscopy (XPS) analysis confirms significant modifications in surface chemistry, including variations in the sp²/sp³ carbon distribution and the enrichment of oxygen-containing functional groups, which correlate with the observed electrochemical behavior. Overall, this study demonstrates—for the first time under realistic VRFB cycling conditions—that DEIS provides unique diagnostic capabilities, enabling mechanistic insights into electrode ageing that are inaccessible to conventional impedance approaches. Full article

The power allocation in Vanadium Redox Flow Battery (VRB) energy storage systems faces a conflict between long-term lifespan and real-time power coupling. Using a single-layer optimization method to directly address multiple objectives simultaneously may lead to conflicts among these objectives. Therefore, this paper presents a multi-objective two-layer optimization allocation strategy. Its core is hierarchical scheduling for long/short-term goals to optimize multi-attribute objectives precisely. A two-layer model comprising an initial allocation layer and an operational optimization layer is constructed to ensure the prioritization of long-term lifespan objectives based on a predefined hierarchical structure. The initial allocation layer focuses on the long-term objective of energy storage capacity lifespan, by prioritizing minimal capacity degradation. A differential evolution algorithm is then applied to perform preliminary allocation of the total power demand. The operational optimization layer aims to achieve optimal State of Charge (SOC) balance across all units and minimize power losses. An Adaptive Multi-Objective Harris Hawks Optimizer (ASAMOHHO) based on adaptive simulated annealing is established to find the Pareto optimal solution set, and ultimately determining the real-time power allocation plan for each unit. Comparative simulations with conventional methods were conducted, and the results demonstrate that the proposed strategy provides an efficient and practical solution for efficient VRB scheduling. Full article

Vanadium redox flow batteries, as a key technology for energy storage systems, have gained application in recent years. Investigating the thermal behavior and performance of these batteries is crucial. This study establishes a three-dimensional model of a vanadium redox flow battery featuring a serpentine flow channel design. By adjusting key battery parameters, changes in ion concentration and uniformity are examined. The model integrates electrochemical, fluid dynamics, and Physico-Chemical Kinetics phenomena. Electrolyte flow velocity and current density are critical parameters. Results indicate that increasing the electrolyte inlet flow velocity leads to convergence in the battery’s charge/discharge cell voltage, ${\mathrm{VO}}_2^{+}{/\mathrm{VO}}^{2+}$, ${\mathrm{V}}^{2+}{/\mathrm{V}}^{3+}$ and concentration distribution across the carbon felt and flow channels. Coincidently, the uniformity of vanadium ions across all oxidation states improves. Furthermore, the observed ion uniformity and battery cell voltage are shown to be significantly modulated by the system’s State of Charge, which sets the baseline electrochemical environment for flow rate effects. Full article

The EU’s green transition hinges on secure access to critical raw materials; vanadium is pivotal for microalloyed steels and emerging long-duration energy storage (VRFBs). Methods: We combine a market and technology review with PESTEL and Porter-5+2 analyses, complemented by a value-chain assessment and a SWOT-to-CAME strategy for the EU. Results: Vanadium supply is highly concentrated (VTM-derived, largely in CN/RU/ZA), prices are volatile, and >85% of demand remains tied to steel; yet VRFBs could shift demand shares by 2030 if costs—dominated by electrolyte—are mitigated. EU weaknesses include lack of primary mining and refining capacity; strengths include research leadership, regulatory frameworks and circularity potential (slag/catalyst recovery, electrolyte reuse). Conclusions: A resilient EU strategy should prioritize circular supply, selective upstream partnerships, battery-grade refining hubs, and targeted instruments (strategic stocks, offtake/price-stabilization, LDES-ready regulation) to de-risk vanadium for grid storage and low-carbon infrastructure. This study also discusses supply chain concentration and price volatility, and outline circular-economy pathways and decarbonization policy levers relevant to the EU’s green energy transition. Full article

The design of the chemical structure of ion-conductive membranes is critical to enhance proton/vanadium ion selectivity and the performance of vanadium redox flow batteries (VRFBs). Herein, camphorsulfonic acid is proposed as a novel proton-conductive group and grafted on polybenzimidazole (PBICa). The pendant sulfonic acid group on the end of the grafted side chains is flexible to promote the aggregation of ionic clusters at even a relatively low ion-exchange capacity (IEC) of 2.14 mmol g⁻¹. The formation of these high-quality clusters underscores the remarkable efficacy of this structural strategy in driving nanoscale phase separation, which is a prerequisite for creating efficient proton-conducting pathways. The bulky and non-coplanar architecture of the camphorsulfonic acid group helps to increase the proportion of free volume compared with the conventional sulfonated polybenzimidazole, which not only promotes water uptake to facilitate proton transport but also exerts a sieving effect to effectively block vanadium ion permeation. The well-formed ionic clusters, together with the expanded free volume architecture, endow the membrane with both high proton conductivity (30.5 mS cm⁻¹) and low vanadium ion permeability (0.15 × 10⁻⁷ cm² s⁻¹), achieving excellent proton/vanadium ion selectivity of 9.85 × 10⁹ mS s cm⁻³, which is about 5.6-fold that of a Nafion 212 membrane. Operating at 200 mA cm⁻², the PBICa-based VRFB achieves an energy efficiency of 78.4% and a discharge capacity decay rate of 0.32% per cycle, outperforming the Nafion 212-based battery (EE of 76.9%, capacity decay of 0.79% per cycle). Full article

Accurate and real-time state of charge (SOC) monitoring is critical for the safe, efficient, and stable long-term operation of vanadium redox flow batteries (VRFBs). Traditional monitoring methods are susceptible to errors arising from side reactions, cumulative drift, and electrolyte imbalance. This study develops a non-invasive optical sensor module for the negative electrolyte (anolyte), utilizing the favorable spectral properties of V(II)/V(III) ions at 850 nm for real-time SOC tracking. A fifth-order polynomial model was employed for calibration, successfully managing the non-linear optical response of highly concentrated electrolytes and achieving exceptional accuracy (adjusted R² > 0.9999). The optical sensor reliably tracked capacity degradation over 50 galvanostatic cycles, yielding a degradation curve that showed a high correlation with the conventional coulomb counting method, thus confirming its feasibility for assessing battery’s state of health. Contrary to initial expectations, operating at higher current densities resulted in a lower capacity degradation rate (CDR). This phenomenon is primarily attributed to the time-dependent nature of parasitic side reactions. Higher current densities reduce the cycle duration, thereby minimizing the temporal exposure of active species to degradation mechanisms and mitigating cumulative ion imbalance. This mechanism was corroborated by physicochemical analysis via UV-Vis spectroscopy, which revealed a strong correlation between the severity of spectral deviation and the CDR ranking. This non-invasive optical technology offers a low-cost and effective solution for precise VRFB management and preventative maintenance. Full article

Energy storage systems (ESSs) have recently emerged as a common solution for mitigating the variability of intermittent renewable energy sources. A major challenge linked to ESSs is their expense. This study focuses on investigating techniques to decrease the size of an ESS while maintaining its performance levels. Data were gathered from a grid-connected 2MW PV system in Malaysia over multiple days, with numerous variables showing considerable hour-to-hour variations from hour to hour due to solar irradiation. A Python code was created to examine the impact of different ESS sizes on power grid stabilization utilizing the power conservation technique. The suggested ESS size derived from the program outcomes was evaluated utilizing a hybrid ESS, incorporating a vanadium redox battery (VRB) as the high-energy-density component and supercapacitors (SCs) as the high-power-density component. The effects of altering the output period lengths were examined. The result must stay consistent for at least five minutes as the minimum required duration. The findings show that an ESS capacity of approximately 10% of the overall produced power can meet the above duration requirement. A straightforward test was employed in the system to assess the power generation level in the upcoming time period. Simulink was employed to model the produced system, and the outcomes met the ESS requirements, enhancing efficiency and extending the battery lifespan. Full article

The practical application of vanadium-based cathode materials in aqueous zinc-ion batteries (AZIBs) is severely hindered by vanadium dissolution, low electronic conductivity, and sluggish reaction kinetics in aqueous electrolytes. In this work, a three-dimensional confined V₂O₅@ nitrogen-doped carbon (V₂O₅@NC) composite was rationally designed and constructed through a dual-regulation strategy combining oxygen-vacancy engineering and conductive network enhancement. In this architecture, the nitrogen-doped carbon framework provides a highly conductive network and robust structural support, while in situ carbonization induces the generation of oxygen vacancies within V₂O₅. These oxygen vacancies cause lattice distortion and expand the interlayer spacing, thereby accelerating Zn²⁺ diffusion and improving reaction kinetics. Benefiting from this synergistic effect, the V₂O₅@NC electrode exhibits an excellent specific capacity of 437 mAh g⁻¹ at 0.1 A g⁻¹ and maintains a remarkable 89.3% capacity retention after 2000 cycles at 3 A g⁻¹, demonstrating outstanding rate performance and cycling stability. This study provides new insights and an effective design strategy for developing high-performance cathode materials for next-generation aqueous zinc-ion batteries. Full article

Magnesium metal boasts a high theoretical volumetric specific capacity and abundant reserves. Magnesium batteries offer high safety and environmental friendliness. In recent years, magnesium-ion batteries (MIBs) with Mg or Mg alloys as anodes have garnered extensive interest and emerged as promising candidates for next-generation competitive energy storage technologies. However, MIBs are plagued by issues such as sluggish desolvation kinetics and slow migration kinetics, which lead to limitations including a limited electrochemical window and poor magnesium storage reversibility. Herein, the sodium vanadium phosphate @ carbon (Na₃V₂(PO₄)₃@C, hereafter abbreviated as NVP@C) cathode material was synthesized via a sol–gel method. The electrochemical performance and magnesium storage mechanism of NVP@C in a 0.5 M magnesium bis(trifluoromethanesulfonyl)imide/ethylene glycol dimethyl ether (Mg(TFSI)₂/DME) electrolyte were investigated. The as-prepared NVP@C features a pure-phase orthorhombic structure with a porous microspherical morphology. The discharge voltage of NVP@C is 0.75 V vs. activated carbon (AC), corresponding to 3.5 V vs. Mg/Mg²⁺. The magnesium storage process of NVP@C is tentatively proposed to follow a ‘sodium extraction → magnesium intercalation → magnesium deintercalation’ three-step intercalation–deintercalation mechanism, based on the characterization results of ICP-OES, ex situ XRD, and FTIR. No abnormal phases are generated throughout the process, and the lattice parameter variation is below 0.5%. Additionally, the vibration peaks of PO₄ tetrahedrons and VO₆ octahedrons shift reversibly, and the valence state transitions between V³⁺ and V⁴⁺/V⁵⁺ are reversible. These results confirm the excellent reversibility of the material’s structure and chemical environment. At a current density of 50 mA/g, NVP@C delivers a maximum discharge specific capacity of 62 mAh/g, with a capacity retention rate of 66% after 200 cycles. The observed performance degradation is attributed to the gradual densification of the CEI film during cycling, leading to increased Mg²⁺ diffusion resistance. This work offers valuable insights for the development of high-voltage MIB systems. Full article

Aqueous zinc-ion batteries (AZIBs) have attracted considerable attention due to their intrinsic safety, low cost, and environmental friendliness. However, drastic volume expansion, sluggish reaction kinetics, and the insufficient structural stability of electrode materials still remain key challenges. In this work, a cascade structure-guided electron transport strategy was used to construct a vanadium nitride@carbon nanosheet/carbon nanofiber (VN@CNS/CNF) composite as a high-performance cathode for AZIBs. In this rationally engineered architecture, carbon-coated VN nanoparticles are uniformly anchored on a conductive carbon nanofiber network, forming a multidimensional interconnected structure that enables fast electron/ion transport and robust mechanical stability. The carbon shell effectively alleviates volume expansion and prevents VN nanoparticle agglomeration, while the continuous carbon fiber backbone reduces charge transfer resistance and enhances reaction kinetics. Benefiting from this synergistic structural design, the VN@CNS/CNF electrode delivers a high specific capacity of 564 mAh g⁻¹ at 0.1 A g⁻¹, maintains 99% capacity retention after 50 cycles, and retains 280 mAh g⁻¹ even at 8 A g⁻¹ after prolonged cycling. This study provides a new structural engineering strategy for vanadium nitride-based electrodes and provides strategic guidance for the development of fast-charging, durable aqueous zinc-ion batteries. Full article

Redox flow batteries (RFBs) are an emerging class of large-scale energy storage devices, yet the commercial benchmark—vanadium redox flow batteries (VRFBs)—is highly constrained by a modest open-circuit potential (1.26 V) while posing an expensive and volatile material procurement costs. This review focuses on recent progress in diversifying redox-active species to overcome these limits, highlighting chemistries that increase overall cell voltage, energy density, and efficiency while maintaining long cycle life and safety. The study dwells deeper into manganese-based systems (e.g., Mn/Ti, Mn/V, Mn/S, M/Zn) that leverage Mn’s high positive potential while addressing Mn(III) disproportionation reactions; iron-based hybrids (Fe/Cr, Fe/Zn, Fe/Pb, Fe/V, Fe/S, Fe/Cd) that exploit the low cost, and its abundance, along with membrane and electrolyte strategies to prevent the potential issue involving crossover; cerium-anchored catholytes (Ce/Pb, V/Ce, Eu/Ce, Ce/S, Ce/Zn) that deliver high operational voltage by implementing an acid-base media, along with selective zeolite membranes; and halide systems (Zn–I, Zn–Br, Sn–Br, polysulfide–bromine/iodide) that combine fast redox kinetics and high solubility with advances such as carbon-coated membranes, bromine complexation, and ambipolar electrolytes. Across these various families of RFBs, the review highlights the modifications made to the flow-fields, membranes, and electrodes by utilizing a zero-gap serpentine flow field, sulfonated poly(ether ether ketone) (SPEEK) membranes, carbon-modified and zeolite separators, electrolyte additives to enhance the voltage (VE%), and thereby energy (EE%) efficiency, while reducing the overall system cost. These modifications to the existing RFB technology offer a promising alternative to traditional approaches, paving the way for improved performance and widespread adoption of RFB technology in large-scale grid-based energy storage solutions. Full article

This study focuses on the pre-treatment cleaning technology for the polyimide (PI) substrate of flexible nine-in-one microsensors. The environmentally friendly cleaning agent B, developed by Sea Energe, was innovatively used to replace traditional organic solutions (acetone, methanol, and isopropyl alcohol) to verify its feasibility and application potential in Micro-Electro-Mechanical Systems (MEMS) processes. Cleaning agent B, developed by Sea Energe, was used for the first time to clean the PI substrate of flexible nine-in-one microsensors, and the flexible nine-in-one microsensor was used as a verification platform to compare the cleaning performance with traditional organic solutions (acetone, methanol, and isopropyl alcohol). The experimental results proved that cleaning agent B developed by Sea Energe effectively removed contamination from the PI substrate surface while avoiding the environmental impact and process compatibility issues associated with traditional organic solvents. To verify its reliability, the developed flexible nine-in-one microsensor was embedded in the hydrogen end flow channel of a hydrogen/vanadium redox flow battery (HVRFB) to perform real-time monitoring of multiple parameters, including hydrogen concentration, voltage, current, conductivity, temperature, humidity, flow, pressure, and pH. The experimental results proved that using cleaning agent B, developed by Sea Energe, to clean the PI substrate and the subsequent flexible nine-in-one microsensor resulted in comparable operational stability and measurement accuracy to traditional organic solution (acetone, methanol, and isopropyl alcohol) cleaning processes. This experimental result verifies that cleaning agent B, developed by Sea Energe, not only has an excellent cleaning effect, but also meets the requirements for highly reliable microsensor development, potentially offering an alternative solution for the future introduction of green processes into semiconductors, MEMSs, and various application fields. Full article

Renewable energy sources, such as photovoltaic panels and wind turbines, are increasingly integrated into domestic systems to address energy scarcity, rising demand, and climate change. However, their intermittent nature requires efficient energy storage systems (ESS) for stability and reliability. This systematic review, conducted in accordance with PRISMA guidelines, aimed to evaluate the size and chemical composition of battery energy storage systems (BESS) in household renewable energy applications. A literature search was conducted in Scopus in August 2025 using predefined keywords, and studies published in English from 2015 onward were included. Exclusion criteria included book chapters, duplicate conference proceedings, geographically restricted case studies, systems without chemistry or size details, and those focusing solely on electric vehicle batteries. Of 308 initially retrieved records, 83 met the eligibility criteria and were included in the analysis. The majority (92%) employed simulation-based approaches, while 8% reported experimental setups. No formal risk-of-bias tool was applied, but a methodological quality check was conducted. Data were synthesized narratively and tabulated by chemistry, nominal voltage, capacity, and power. Lithium-ion batteries were the most prevalent (49%), followed by lead–acid (13%), vanadium redox flow (3.6%), and nickel–metal hydride (1.2%), with the remainder unspecified. Lithium-ion dominated due to high energy density, long cycle life, and efficiency. Limitations of the evidence include reliance on simulation studies, heterogeneity in reporting, and limited experimental validation. Overall, this review provides a framework for selecting and integrating appropriately sized and composed BESS into domestic renewable systems, offering implications for stability, efficiency, and household-level sustainability. The study was funded by the PNRR NEST project and Sapienza University of Rome Grant. Full article

Owing to the inherent safety, environmental friendliness, and high theoretical capacity (820 mAh g⁻¹) of zinc metal, aqueous zinc-ion batteries (AZIBs) have emerged as up-and-coming alternatives to organic lithium-ion batteries. However, the insufficient electrochemically active sites, poor structural stability, and severe interfacial side reactions of cathode materials have always been key challenges, restricting battery gravimetric energy density and cycling stability. This article systematically reviews current mainstream AZIB cathode material systems, encompassing layered manganese- and vanadium-based metal oxides, Prussian blue analogs, and emerging organic polymers. It focuses on analyzing the energy storage mechanisms of different material systems and their structural evolution during Zn²⁺ (de)intercalation. Furthermore, mechanisms of innovative strategies for improving cathodes are thoroughly examined here, such as nanostructure engineering, lattice doping control, and surface coating modification, to address common issues like structural degradation, manganese/vanadium dissolution, and interface passivation. Finally, this article proposes future research directions: utilizing multi-scale in situ characterization to elucidate actual reaction pathways, constructing artificial interface layers to suppress side reactions, and optimizing full-cell design. This review provides a new perspective for developing practical AZIBs with high specific energy and long lifespans. Full article

This study proposes a novel sensorless maximum power capture control strategy for variable-speed wind energy conversion systems employing a permanent magnet synchronous generator (PMSG). The proposed method integrates a fuzzy probabilistic neural network (FPNN) with an improved particle swarm optimization (IPSO) algorithm to enable adaptive learning capabilities. Additionally, support vector regression (SVR) is employed to estimate wind speed without the use of mechanical sensors, thereby enhancing system reliability and reducing maintenance requirements. A vanadium redox battery (VRB) is integrated to enhance power stability under fluctuating wind conditions. Simulation results demonstrate that the proposed FPNN-IPSO-based controller achieves superior performance compared to conventional Takagi–Sugeno–Kang (TSK) fuzzy and proportional–integral (PI) controllers. Specifically, the FPNN-IPSO controller exhibits notable improvements in average power output, tracking accuracy, and overall system efficiency. The proposed method increases power output by 9.71% over the PI controller and supports Plug-and-Play operation, making it suitable for intelligent microgrid integration. This work demonstrates an effective approach for intelligent, sensorless MPC control in hybrid wind–battery microgrids. Full article