Abstract All-solid-state batteries (ASSBs) have enhanced safety features and potential for high energy density. However, their path to commercialization has obstacles because of the inadequate solid–solid contact and mismatched ionic and electronic transport properties in composite cathodes. In this study, we investigate the effect of Li6PS5Cl (LPSC) solid-state electrolyte particle size and CAM/SSE ratio (using high-Ni NCM90) on interfacial transport kinetics and coupled electrochemical–mechanical stability. Three-dimensional simulations with LAMMPS and multiscale characterization methods reveal a trade-off between ionic and electronic pathways: refined LPSC refined enhances void filling, reduces Li-ion tortuosity, and improves ionic continuity, but also increases the tortuosity of electronic pathways. A volume ratio of 50:50 between CAM and SSE results in a balance between ionic continuity and electronic percolation, stabilizes the growth of CEI, and maintains 65.8% of the capacity after 2C cycling when returning to a low rate. Insufficient cathode electrolyte interphase (CEI) results in interfacial contact degradation, uneven CEI layer formation, and impedance hotspots over extended periods, as well as microcracking and accelerated capacity loss. These findings provide design guidelines for stable, high-performance sulfide composite cathodes.
Abstract The rapid growth of flexible and wearable electronics has created an increasing demand for lithium-ion batteries that can maintain high electrochemical performance while withstanding repeated mechanical deformation. In this research, we investigate the incorporation of single-walled carbon nanotubes (SWCNTs) as a conductive carbon dopant together with a polymer binder (VT475) in LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes. SWCNTs play a dual role in cathode performance. Mechanically, their one-dimensional nanostructure mitigates particle pulverization and improves tolerance to mechanical deformation (e.g., bending), which is essential for flexible and wearable applications. Electrochemically, SWCNTs form a percolated conductive network within the cathode, significantly improving electronic conductivity and facilitating efficient electron transport. This synergistic effect enhances capacity retention and cycling stability, even at high C-rates (132 mAh/g@5C). Pouch cells incorporating the SWCNT-doped cathodes were extensively characterized using galvanostatic testing at various C-rates, long-term cycling (1000 cycles), electrochemical impedance spectroscopy, and adhesion testing (ASTM D3359), among other methods. Relative to reference electrodes, the SWCNT-doped cathodes demonstrate synergistic improvement in electrochemical and mechanical performance. Based on the experimental results, a physics-informed semiempirical formulation model is developed to describe how the binder content influences the electrochemical and mechanical performance of the cathodes. The model supports slurry formulation selection by mapping the trade-off between rate capability, cycling stability, and adhesion according to application requirements.
Abstract With the continuous development of society and the improvement of living standards, the need for renewable resources has become increasingly urgent. In the field of electrochemical energy storage systems, supercapacitors garner significant attention due to their rapid charging and discharging capabilities, high power density, and environmentally friendly nature. However, the effectiveness of electrocatalytic reactions largely depends on the kinetics of the hydrogen evolution reaction and oxygen evolution reaction (OER). This study explores the impact of Li+ doping on the electrochemical properties of Co9S8/Ni9S8 materials. Li-Co9S8/Ni9S8 is successfully synthesized via a two-step hydrothermal method, and the Li-Co9S8/Ni9S8-0.3 material demonstrates a mass specific capacitance of 855 F g−1 at a current density of 0.5 A g−1. The assembled asymmetric supercapacitor achieves a power density of 4050 W kg−1 at an energy density of 86.7 Wh kg−1. In a 1.0 M KOH electrolyte, the Li-Co9S8/Ni9S8-0.3 material exhibits efficient OER performance, with an overpotential of 191.4 mV at a current density of 20 mA cm−2. Moreover, the material exhibits a low battery voltage of 1.50 V at 20 mA cm−2 and maintains excellent stability over 30 h of cycling.
Abstract Layered transition-metal oxides are promising cathodes for sodium-ion batteries, but their performance is often complicated by oxygen vacancy (OV) formation and management. Intrinsic OVs, induced by external factors such as doping, play a pivotal role in regulating their physicochemical properties. However, precisely how these OVs can be strategically leveraged to concurrently optimize both the kinetics and structural stability remains a key challenge. In this work, a synergistic strategy combining the construction of a Na-rich P2 structure with Mg/Ti co-doping is proposed to synthesize Na0.8Mg0.05Ni0.25Mn0.65Ti0.05O2 (NMNMTO-1). Experimental and theoretical results suggest that Mg/Ti co-doping is associated with intrinsic OV-related local configurations through coupled charge compensation, which, together with the expanded Na-layer spacing, lowers the Na+ migration barrier. Meanwhile, Mg/Ti-assisted lattice stabilization increases the oxygen-vacancy formation energy, helping reinforce the oxygen framework and mitigate irreversible oxygen loss and unfavorable P2-O2 transition. This dual-regulation mechanism promotes reversible P2-OP4 structural evolution during cycling. The NMNMTO-1 cathode delivers enhanced electrochemical performance, retaining 110 mAh g–1 at 10 C and 87.3% capacity after 100 cycles at 2 C, while also showing improved sodium-storage performance at –25 °C.
Abstract Selenium-based cathodes represent an attractive alternative to sulfur for high-energy-density lithium batteries owing to their high intrinsic electrical conductivity, superior active material utilization, and enhanced volumetric capacity. Unlike sulfur, selenium cathodes in carbonate electrolytes undergo a direct solid–solid conversion with negligible polyselenide dissolution, offering an intrinsic pathway to suppress the shuttle effect. However, the sluggish kinetics and high energy barriers associated with this conversion necessitate the rational design of catalytic reaction interfaces. Here, we demonstrate a metal-organic framework-derived manganese single-atom catalyst anchored to nitrogen-doped carbon (Mn-NC) that fundamentally regulates the selenium conversion pathway in Li–Se batteries. The Mn-NC host, synthesized via Mn2+ incorporation into ZIF-8, features a hierarchical bimodal pore architecture and atomically dispersed Mn active sites stabilized within a defect-rich nitrogen–carbon matrix. These structural attributes synergistically enable uniform selenium confinement, improved Se-host adherence, and accelerated Se redox kinetics, offering discharge capacities of 508 and 333 mAh g–1 at 0.1 and 5 C, respectively. Density functional theory (DFT) analyses substantiate that Mn–N4 centers significantly lower the energy barriers for Se8 ↔ Li2Se conversion, induce strong chemisorptive interactions with Se, and promote fast, reversible solid-state redox processes. The present work establishes a general strategy for engineering solid–solid chalcogen conversion pathways using atomically precise active centers. Furthermore, the in situ incorporation of earth-abundant Mn single atoms into a template-free hierarchical carbon host provides a potentially scalable route toward advanced chalcogen-based energy storage systems.
Abstract Operating proton exchange membrane (PEM) water electrolyzers at elevated temperatures is a potential pathway to increase operational efficiency and reduce hydrogen production costs. In this study, an in-house developed elevated temperature PEM electrolysis test station operated with liquid water is coupled with online mass spectrometry to investigate the true H2 production efficiency of perfluorosulfonic acid-based 5 cm2 single cells in the temperature window of 60 to 120 °C via electrochemical characterization techniques and a product gas analysis. Thermodynamic and kinetic improvements responsible for reducing the required cell voltage for water splitting by 103 ± 4 mV at low current densities when increasing the operating temperature by 60 K are analyzed. A temperature-induced reduction in ohmic and anode catalyst layer resistances is observed and possible reasons considering intrinsic and interfacial property changes are postulated. The H2 production rate increases by approximately 80% when elevating the operating temperature from 60 to 120 °C at a given cell potential of 1.8 V. Furthermore, hydrogen crossover and true Faradaic efficiencies are determined by closing the hydrogen and oxygen mass balance, revealing that operation at 120 °C with the given cell configuration is neither efficient (the Faradaic efficiency decreases on average by about 4%) nor safe, presumably due to microstructural changes resulting from enhanced creep operating in the vicinity of the ionomer’s glass transition temperature.
Abstract Metal plating in industrial battery packs is a critical degradation pathway that can induce capacity loss, internal short circuits, and ultimately thermal runaway. Even a single compromised cell can propagate failure across an entire pack, making early detection of metal deposition essential yet challenging in practical systems. Plug-and-play nuclear magnetic resonance (PnP NMR) is inherently robust to the complexity, opacity, and scale of practical battery architectures, circumventing limitations associated with restricted RF penetration. Here, we demonstrate that PnP NMR enables direct, chemically specific detection of metal plating at the battery-pack level, addressing a key diagnostic gap arising from the indirect nature of conventional electrochemical techniques. Using multicell assemblies of industrial-format pouch cells based on both Li- and Na-ion chemistries, we show that pack-level spectra are well described by the superposition of individual-cell responses, allowing defective cells to be identified within otherwise healthy assemblies. Metallic Li and Na produce distinct, narrow resonances that remain clearly resolved at the pack level due to their large Knight-shift separation from non-metallic species. These results establish PnP NMR as a scalable, non-invasive, and time-efficient diagnostic platform for battery packs, capable of directly detecting metal plating under realistic operating conditions.
Abstract Photocatalytic H2O2 production from the oxygen reduction reaction (ORR) has emerged as a sustainable and green approach to address the global energy crisis and environmental challenges. However, its practical application is still limited by sluggish reaction kinetics and fast recombination of photogenerated excitons. Yet, these limitations can be effectively mitigated by rational photocatalyst design strategies that enhance charge separation and accelerate ORR kinetics. Herein, we designed a nanocomposite C/N-CeO2/Bi2Te3 (CBT) by a two-step solvothermal and calcination synthesis process of Ce-MOF-derived C/N-CeO2 combined with in situ growth of Bi2Te3 to obtain a composite of C/N-CeO2 nanorods with Bi2Te3 nanoflowers. The strong interfacial interaction between the two pure materials is substantiated by using various microscopic, electrochemical, and spectroscopic characterizations. The photocatalytic H2O2 production of 5 wt % Bi2Te3-loaded C/N-CeO2 (CBT-5) sample achieved 1889 μmol g–1 h–1 under light illumination, with an apparent quantum yield (AQY) of 4.23% at a wavelength of 340 nm. The superior photocatalytic performance of CBT-5, reflected by its high TOF value of 0.325 h–1, can be attributed to the unique characteristics of Bi2Te3 as a cocatalyst; its topological insulator nature provides highly conductive surface channels that promote rapid electron transport, effectively suppress the recombination of photogenerated charge carriers, and thereby enhance the photocatalytic two-electron ORR for H2O2 production. This work can inspire exploration of the construction of MOF-derived, oxide-based, defect-rich hybrid structures for photocatalytic sustainable energy applications.
Abstract Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) represent key processes underpinning fuel cell and water-splitting technologies, respectively. In this scenario, boron-doped carbon nanomaterials have emerged as promising and metal-free bifunctional systems to promote both electrochemical processes while offering a sustainable alternative to the use of critical raw materials in electrocatalysts of the state-of-the-art. Herein, we describe the surface engineering of pristine multiwalled carbon nanotubes (MWCNTs) through the covalent grafting of precise boronic acid [R-B(OH)2] or boronic ester [R-B(OR′)2] functionalities, using an aryl-diazonium salt method. Materials were then evaluated as ORR and OER electrocatalysts under alkaline conditions uncovering clear-cut structure–activity relationships commonly overlooked in the literature. DFT simulations on modeled boron-functionalized graphene systems unveiled the role of structural energetics linked to the dynamic evolution of B-active sites [R-B(OH)2 vs R-B(OR′)2] under both electrochemical processes.
Abstract Anion exchange membranes play a critical role in the performance and durability of the CO2 electrolyzers, yet membrane stability and salt precipitation remain major challenges at high current densities. Here, we investigate third-generation Aemion+ anion exchange membranes in a single-cell CO2 electrolyzer. Salt precipitation at the cathode outlet was effectively mitigated by periodic rinsing of the cathode with water or closed-loop circulation of 10 mM KHCO3 anolyte, resulting in stable operation for more than 300 h at 300 mA cm–2. The thickness of the membrane was found to strongly influence performance, with 25 µm membranes exhibiting longer durability compared to 15 µm membranes. Enhanced durability is attributed to the membrane’s enhanced permselectivity and reduced rate of K+ ion crossover, resulting in reduced salt accumulation and sustained CO selectivity. These findings highlight the importance of membrane thickness and permselectivity in achieving durable and selective CO2 electrolysis.
Abstract The synthesis of Pt-based alloy nanoparticles (NPs) by Joule heating is an effective and scalable strategy for developing novel electrocatalysts for sustainable energy technologies. This study employs a custom-made Joule heating method to synthesize alloy NPs by drop casting precursor salt solutions of three immiscible elements on self-made carbon nanofibers (CNFs) supports. The resistive heating of carbon supports raises the temperature to approximately 1600 K and yields PtNiRu alloy NPs within seconds. To provide insight into the long-term durability of the Pt-based catalysts, the structure, morphology, and chemical composition of the synthesized NPs were characterized by various methods, including high-resolution transmission electron microscopy (HRTEM). This study addresses the limitation of widespread application of clean energy systems by systematically investigating the structural degradation and HER activity of PtNiRu electrocatalysts under both acidic and alkaline conditions. Compared with the overpotential drift of durability under acidic conditions, the synthesized PtNiRu/CNFs electrocatalysts demonstrate significantly improved long-term durability in alkaline media, maintaining stable HER performance for approximately fivefold higher than in acidic media at –10 mA/cm2. The corrosion of the carbon support, pronounced leaching of Ni, and the agglomeration and loss of PtNiRu NPs in the acidic electrolyte collectively contribute to significantly reduced stability for HER. Under alkaline condition, retained PtNiRu nanoparticles on the CNFs undergo some restructuring, facilitating the formation of stable Ru-rich particles and Ni(OH)2 surface phases. These findings highlight the critical role of both the catalyst surface and carbon support in achieving stability of electrocatalysts over prolonged testing of 50 h. This result demonstrates long-term operational stability, which is essential for electrolyzers and industrial hydrogen production.
Abstract Rapid evaporation of water at material surfaces offers a promising route for simultaneous water production and energy conversion. Here, we report an integrated evaporation-driven hydrovoltaic−thermoelectric device, in which a carbon black-modified nonwoven evaporation array serves as the core component to couple a hydrovoltaic unit with a thermoelectric module. During the daytime, photothermal evaporation establishes a temperature gradient between the evaporation interface and the bulk water, thereby enabling synergistic hydrovoltaic and thermoelectric outputs. At night, evaporative cooling lowers the interfacial temperature and continues to drive the thermoelectric module for sustained power generation. As a result, the device realizes continuous hydrovoltaic/thermoelectric power generation and simultaneous water harvesting over the day−night cycle. The device delivers a maximum output power density of 231.25 μW cm−2 during the day and 47.08 μW cm−2 at night, and achieves a saltwater evaporation rate of 1.25 kg m−2 h−1 under 1 kW m−2 solar irradiation. This work expands the application scope of interfacial evaporation from water production alone to the coupled co-generation of water and energy.
Abstract Modulating metal–support interactions is a relevant strategy for improving the efficiency of CO2 photoreduction. In this work, we investigated the effect of the cobalt precursor on the electronic structure and photocatalytic performance of CoO/Nb2O5 composites prepared from hydrated Nb2O5 modified with salts containing different anions (acetate, nitrate, and sulfate). The results indicate that the nature of the precursor influences the optical properties, oxidation states, and surface chemistry of the materials, reflecting differences in catalytic activity and selectivity. XPS analysis showed the predominant presence of Co2+ and, in the case of Nb/Co-S, the additional formation of Nb4+ species, indicating a modification of the material's electronic structure. The sulfate-derived material (Nb/Co-S) showed superior performance, achieving high yields of ethanol (55.2 μmol g−1) and methanol (49.7 μmol g−1), while pure Nb2O5-H exhibited high selectivity for CO (2163 μmol g−1). These results demonstrate a significant shift in selectivity from gaseous products to highly reduced liquids, an effect that is here linked directly to the anion-dependent formation of Nb4+ sites rather than to differences in cobalt loading, which remained comparable (∼10 wt %) across all composites. Furthermore, Nb/Co-S maintained its activity over three consecutive cycles, indicating good catalytic stability. In contrast, the material obtained from nitrate showed low activity for the formation of liquid products, underscoring that precursor anion choice, and not cobalt content alone, is the parameter governing product distribution in this system.
Abstract All-solid-state batteries require solid electrolytes with sufficient oxidative and reductive stability; however, the interfacial behavior of emerging silicon-based sulfide electrolytes remains poorly understood. In particular, the electrochemical stability of Li7Si2S7I under practical cell operation and the separate effects of cathode and anode interfaces on performance degradation have not been clarified. Here, we systematically evaluate Li7Si2S7I in LiNi0.82Mn0.07Co0.11O2 (NMC82) | solid electrolyte | Li-In all-solid-state cells using two- and three-electrode configurations combined with impedance analysis and ex situ Raman and X-ray photoelectron spectroscopy. Three-electrode measurements decouple the interfacial reactions and reveal concurrent interfacial decomposition at both the cathode and anode sides, with dominating effect from the cathode side. Symmetric cell tests using Li-In/Li7Si2S7I composite electrodes confirm slight reductive instability against Li-In for Li7Si2S7I as an anolyte. Spectroscopic analysis identifies polysulfides, oxidized iodide, and oxygenated SiOx and SOx species at the Li7Si2S7I/NMC82 interface, as well as In2S3 formation at the Li7Si2S7I/Li-In interface. Our findings provide mechanistic insight into the interfacial reactions of Si-based sulfide electrolytes and highlight the importance of electrode-decoupled diagnostics for evaluating the compatibility with electrode materials in all-solid-state batteries.
Abstract Synergistic architectures based on binary oxides and conducting polymers address the inherent limitations of individual components, thereby providing enhanced redox kinetics and structural stability for high-performance electrodes. Here, we explore the energy storage performance of Fe2(MoO4)3@polyindole (FMO@PIN) nanocomposites synthesized via in situ oxidative polymerization. The PFM2 (indole:FMO = 2:1 weight ratio) nanocomposite features a unique 3D criss-cross FMO framework with uniformly dispersed PIN globules. This optimized structure, along with multiple oxidation states of FMO, provides efficient conducting pathways and rich redox kinetics, enhancing the overall electrochemical performance. It achieves a high specific capacitance (Cs) of 567.6 F/g (at 5 mV/s) and outstanding stability, with 93.3% retention over 15,000 cycles at 5 A/g—performance metrics that significantly surpass those of its pristine constituents. Further, a symmetric device is assembled using PFM2 as both the counter and working electrodes with a PVA/H2SO4 gel electrolyte. The resulting symmetric device exhibits a Cs value of 288 F/g and a discharge time of 1296 s at 0.1 A/g. It delivers an impressive energy density of 32.23 Wh/kg at 90 W/kg. Three identical devices connected in series successfully powered a red light-emitting diode (LED) for up to 7 min, validating their potential as a compact, efficient energy storage solution.
Abstract Lithium metal batteries (LMBs) paired with Ni-rich cathodes offer high energy density but suffer from serious safety hazards due to the flammability of carbonate electrolytes and dendritic Li growth. Herein, a nonflammable electrolyte, denoted as D-TB37, is formulated by coupling a flame-retardant, strongly coordinating solvent (diethyl difluoromethanephosphonate, DDMP), with a weakly coordinating solvent (fluoroethylene carbonate, FEC), and a LiTFSI/LiDFOB dual-salt system. This hybrid-solvent strategy constructs an anion-rich solvation structure of Li+ with DDMP dominating the primary solvation shell. The steric hindrance of DDMP significantly lowers the activation energy of desolvation to 33.84 kJ mol−1, thereby enabling a high Li-ion transference number of 0.66. Meanwhile, the weakly coordinating FEC induces the participation of anions in the primary solvation shell. As a result, a stable inorganic SEI layer rich in F, B, and N species is formed, effectively suppressing dendrites. The as-designed electrolyte enables high-rate capability and stable cycling of the Li||NCM811 full cell, which exhibits a capacity retention of 80.7% after 1000 cycles at 10 C. This work provides an effective electrolyte design strategy for safe, high-power, and high-energy-density LMBs.
Abstract Slot-die coating has emerged as a promising deposition method for the industrial-scale production of perovskite solar cells (PSCs); it is compatible with roll-to-roll processing, has high material utilization, and gives precise control over coating parameters. One key challenge is that lead halide perovskites are highly sensitive to moisture. At the laboratory scale, strict environmental controls (i.e., N2-filled gloveboxes) can be used to mitigate these effects; however, this becomes increasingly challenging and costly as production is scaled up. This study therefore seeks to establish how relative humidity (RH) affects the performance of PSCs fabricated via slot-die coating, i.e., how dry is dry enough for the coating step? Our results show that PSCs fabricated in RHs above 30% show a pronounced decrease in power conversion efficiency (PCE), mainly due to a degradation in film quality; however, at or below 30% RH, the PCE is much less affected. Identifying this processing window is a critically important step in the scale-up of PSC technology that will help inform the level of environmental controls required during manufacture.
Abstract Photocatalytic saline (NaCl aqueous solution) splitting was carried out using Al-doped SrTiO3 particles under acidic conditions. Hydrogen and chlorine were simultaneously evolved in a flow-type reactor. Despite the acidic medium, the apparent quantum yield reached as high as 50%, which is comparable to that achieved in pure water splitting systems. The solar-to-hydrogen conversion efficiency was calculated to be 0.4%, while the total solar energy conversion efficiency reached 0.46% due to the concurrent production of chlorine. These results demonstrate the potential of this system as a feasible and cost-effective approach for photocatalytic energy conversion.
Abstract Molecular design of an active electrocatalyst can determine the primary product. Precise selection of the active metal center influences the adsorption of reactants, intermediates, and product selectivity and ultimately affects the efficiency of the process. Here, we predict a potent catalyst, namely, Fe@C6N6, with enhanced activity and low overpotential for CO2 reduction reactions (CO2RRs) utilizing the density functional theory (DFT) approach, coupled with machine-learning-based model building. A series of 24 transition-metal single-atom catalysts (SACs) anchored on the C6N6 monolayer were screened, among which 19 exhibit effective CO2 activation. Employing density functional theory (DFT), a systematic study on reaction pathways demonstrates that 13 catalysts favor CH4 formation, while the remaining 6 exhibit selectivity toward CH3OH production. Additionally, 9 among the 19 catalysts are further screened out as they preferentially promote the competing hydrogen evolution reaction (HER). The active SACs demonstrate strong CO2RR activity, with Fe@C6N6 emerging as the most promising catalyst with the lowest limiting potential (0.39 V). To further establish atomic–property relationships, a machine-learning (ML) regression model was developed to predict adsorption energies using statistically significant descriptors and identify key factors governing CO2 adsorption. Furthermore, a classification model developed using the elemental characteristics of the metal atoms shows excellent correlation with the DFT results across the dataset. This combined DFT and machine-learning approach provides mechanistic insights for the rational development of efficient SACs for CO2 electroreduction.
Abstract A high-performance photoanode comprising a TiO2 nanotube array (TNTA) co-modified with Au nanoparticles (Au NPs) and Bi2Se3 quantum dots (Bi2Se3 QDs) is reported for photoelectrochemical (PEC) hydrogen production. The Au NPs were deposited via photodeposition, followed by the deposition of Bi2Se3 QDs using the successive ionic layer adsorption and reaction (SILAR) method. This strategic integration achieves an optimal spectral overlap between the localized surface plasmon resonance of the Au NPs and the absorption edge of the Bi2Se3 QDs, significantly improving the PEC performance through Au-induced near-field enhancement. Systematic optimization of the SILAR cycles revealed that the PEC performance is governed by the interfacial charge-transfer kinetics at the TiO2/Bi2Se3 heterointerface, with the optimized configuration exhibiting a superior photocurrent density. These findings suggest that the synergistic integration of plasmonic metals and narrow-bandgap semiconductor QDs on TNTA supports is a promising route for efficient solar-to-fuel conversion.
