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A setaria viridis-like TiN nanofibers with hierarchical structure (noted HSTFs) is synthesized via electrospinning and hydrothermal method. The results reveal that the synthesized HSTFs nanofibers belong to the TiN crystalline phase. The surface of the fibers is uniformly distributed with pore-structured nanorods, which have an average diameter of 55 nm. The HSTFs exhibits a higher specific surface area. Comparing to the TFs||TFs symmetric supercapacitor device, the HSTFs||HSTFs device demonstrates a significantly higher specific capacitance of 177 F g−1 at a current density of 10 mA g−1. The enhanced electrochemical performance is attributed to the hierarchical and porous structure of TiN fibers, which provides a larger surface contact area and more active sites. This structure is conducive to the construction of a conductive network and improves the reversible proton insertion and chemisorption of electrolyte-electron. This research presents a promising approach for the design and synthesizes of high-performance supercapacitor materials. [Display omitted] • Construction of TiN nanofibers with a setaria viridis-like hierarchical structure. • The assembled supercapacitor of HSTFs.||HSTFs has a large specific capacitance. • The elevation of the specific capacitance was achieved by hierarchical structure. [ABSTRACT FROM AUTHOR]

A new approach for synthesizing heteroatom-doped carbon nanostructures has been developed, in which nitrogen and oxygen have been effectively infused into the graphitic core using the required precursors. The heteroatoms incorporated into the carbon matrix and their corresponding structural features are examined. The observed X-ray diffraction pattern reveals the presence of amorphous carbon forms that resemble carbon nitride in their structure. The presence of additional N–O and C–O bonds gives strong evidence of a graphitic structure with oxygen and nitrogen incorporation, as shown by the Fourier transform-infrared peaks. The X-ray photoelectron spectroscopy analysis reveals important information regarding the bond formation in the graphitic core of the sample. The study focused on examining the porous and intricately interconnected network structures, showcasing a variety of particle morphologies, and was carried out using scanning electron and transmission electron microscopy. The lattice defects are investigated using transmission electron microscopy-high angle annular dark field technique to explore the surface morphology. The influence of incorporated O and N in carbon structure drastically reduced the electron density of the graphitic core. As a result, the absorption bands observed were around 300–400 nm, showing the semiconductors' absorption characteristics. Three-electrode electrochemical systems are fabricated with working electrodes based on COx and CNx materials. The COx and CNx-modified electrodes were meticulously tested for their performance in supercapacitor applications. The COx samples exhibit a significant specific capacity value of 439.20 C g−1 under a low current density of 4 A g−1. The CNx samples demonstrate a specific capacity of 420.00 C g−1 under 4 A g−1 current density. [Display omitted] • New carbon materials with highly incorporated nitrogen and oxygen were reported. • The carbon structures were elucidated by PXRD, FT-IR, and XPS analysis. • The impact of N and O incorporation on optical and electrochemistry was studied. • CNx and COx show the highest specific capacities are 439 C g−1 and 420 C g−1. [ABSTRACT FROM AUTHOR]

A solid-state deep eutectic electrolyte supported by cross-linked polyvinyl alcohol (PVA) and sulphur succinic acid (SSA), functionalized with sodium (Na) groups, is a promising candidate for Ah-scale all-solid-state batteries due to its tunable ionic conductivity of over 2.910 ± 0.10 mS cm⁻1. Understanding the origin of this ionic conductivity is critical for industrial production. Herein, Distribution of Relaxation Times (DRT) analysis, using Tikhonov regularization and cross-validation, was applied for the first time to reveal that ionic conductivity in the electrolytes is governed by hydrogen bond dynamics (HBDy) and Na⁺ diffusion, with relaxation times of 0.199 × 10⁻³ seconds and 6.960 × 10⁻³ seconds, respectively. The DRT peak frequencies for Na⁺ diffusion and HBDy are 84.05 Hz, and 22.879 Hz, respectively, with corresponding polarization impedances of 12.900 kΩ, and 52.870 kΩ. Detailed coordination of –CO– O - crosslinking between PVA and SSA was confirmed by a harmonic at 1090 cm⁻1. Additionally, Na groups were identified through a Na₂SO₄ phase diffraction peak at 29.080° on the (040) plane with 0.832 ± 0.05 transference number. This work provides a novel DRT-assisted analysis protocol for investigating the origin of ionic conductivity in energy storage materials, providing valuable guidance for industrial production. [Display omitted] • Synthesis of Novel solid-state deep eutectic electrolyte (SSDEE). • DRT method was used to analyse the EIS spectra of SSDEE in a symmetric cell. • First successful application of Tikhonov Regularization with Cross Validation. • SSDEE ionic conductivity is primarily governed by Hydrogen bond dynamics (HBDy). • The deconvolution separated HBDy, and grain boundary relaxation time. [ABSTRACT FROM AUTHOR]

The hydrolysis of silicon and its compounds to produce hydrogen for fuel cell remains a major problem. In this work, the active metal calcium and lithium are introduced into the silicon system by preparing Li–Ca–Si ternary alloy. The preferential hydrolysis of active metal in the alloy led to the formation of weakly alkaline environment. It is proved that 25 % Li–CaSi 2 alloy (25 Li) with a large number of secondary nano-phase has the highest electrochemical activity through electrochemical tests, the presence of the secondary nano-phase optimizes the reaction kinetics. Then the 25 Li shows the rapidest kinetics and highest yield in 0.5 M NaF solution, delivering a hydrogen yield of 590 mL g−1 in 20 min and maintain a long-term stable dehydrogenation. In addition, the system still reaches a retention rate of 89 % after exposing to air for 24 h. Furthermore, the above system achieves hydrogen-electric conversion in fuel cell tests. This work provides a novel idea for the research of Si-water system for hydrogen production, and provides a reference for the practical applications on fuel cells in the future. • The Li–Ca–Si ternary alloy were prepared by two-step solid reaction. • Secondary nano-phase improve the electrochemical activity and hydrolysis kinetics. • The 25 % Li–CaSi 2 alloy reached a high yield of 590 mL g−1 in 0.5 M NaF solution. • The hydrogen-electricity conversion property of the hydrolytic system has explored. [ABSTRACT FROM AUTHOR]

P2-type Mn-based oxides are promising cathode materials for sodium-ion batteries due to their low cost and high capacity virtue. However, the irreversible phase transition and unstable anion redox at high operating voltages (∼4.2 V) will cause structural distortions, leading to slow sodium-ion diffusion kinetics and severe capacity degradation. Herein, a multi-elemental composition regulation strategy is proposed to enhance the structural stability of P2-type cathode by optimizing the structure and modulating the irreversible oxygen redox during high-voltage cycling. A series of multi-element cathodes Na 0.67 (Fe 1/4 Co 1/4 Ni 1/4 Ti 1/4) 1-x Mn x O 2 (x = 0.4,0.5,0.6,0.7,0.8,0.9) are designed and the effects of component modulation on their structure and electrochemical behavior are systematically investigated. Especially, the optimized Na 0.67 Fe 0.05 Co 0.05 Ni 0.05 Ti 0.05 Mn 0.8 O 2 cathode maintains P2 phase during the initial charging/discharging between 1.5 V and 4.5 V, inhibits irreversible oxygen redox, and exhibits small lattice expansion. Impressively, the above optimized cathode exhibits superior cycling stability with capacity retention of nearly 90 % and reversible capacity of 130.1 mAhg−1 after 100 cycles at 1C rate. Furthermore, the optimized cathode also displays an excellent rate capability (capacity of 108.2 mAh g−1 at 5 C rate) due to the enhanced Na+ diffusion kinetics. This work provides new insight into developing high-stable Mn-based oxide cathodes operating at high voltage for sodium-ion batteries. [Display omitted] • The effects of multi-element component modulation are investigated. • The Mn-rich multi-element samples maintain excellent structural stability. • The Mn-rich multi-element samples suppressed the irreversible oxygen redox. [ABSTRACT FROM AUTHOR]

MXene, without a doubt, has emerged as the fastest-growing family of materials in the past decade. Its potential in emerging solid-state batteries (SSBs) is particularly promising, as it offers new opportunities to create novel redox-active and ionically permeable phases. The diverse chemical compositions, exceptional electrochemical properties, and surface tunability of MXenes provide fertile ground for composite design, potentially leading to significant advancements in the next generation of SSBs. This review, specifically focusing on SSBs, explores the potential and promises of MXene-based materials in advanced energy storage systems while highlighting the current progress. Additionally, the review discusses the challenges that need to be addressed to fully exploit the potential of MXenes for integration into safe and high-energy density electrochemical storage technologies. [Display omitted] • Recent advances in using MXene in Solid State Batteries (SSBs) are presented. • The potential benefits of using and the role of MXene in SSBs are highlighted. • The scalability issues associated with MXene production are discussed. [ABSTRACT FROM AUTHOR]

Performance degradation of ternary layered oxide cathodes largely originates from their loss of structural integrity in cyclic usage. Mechanical damage, such as intergranular fracture of the active particles, is not only a mechanical cleavage process but also interferes with electrochemical kinetics such as infiltration of liquid electrolyte, surface corrosion of the constituent primary particles, and may eventually isolate the primary grains from the electron conducting network. Here we develop a computational framework that integrates electrochemistry of a LiNi x Mn y Co 1−x−y O 2 (NMC) composite cathode with mechanical damage of the active particles. To fully examine the intricate chemomechanical behavior of the electrode, we evaluate the effects of the anisotropic material properties, the influence of mechanical potential on Li transport, and the concurrent intergranular fracture and electrolyte penetration along the grain boundaries upon multiple cycles. Electrolyte infiltration benefits capacity retention but aggravates further mechanical damage by corrosion. Structural failure mostly occurs in the first charging due to the anisotropic mechanical strain between the primary grains, while the resulting damage remains stable in the later few cycles. The results are consistent with experimental observations and the integration of electrochemistry and mechanical failure enables a step further understanding of the complex mechanism of battery degradation. [Display omitted] • A coupled electro-chemo-damage computational framework. • Mechanical damage due to intergranular fracture of NMC cathode particles. • Electrolyte infiltration along the damaged polycrystalline grain boundaries. • Corrosion and impeded interfacial charge transfer at the fractured surfaces. • Increased capacity but aggravated mechanical damage due to electrolyte infiltration. [ABSTRACT FROM AUTHOR]

The redox-amphoteric nature of graphite is tactically utilized to store cations and anions simultaneously in a dual graphite battery (DGB). The major differences between cation and anion storage electrochemistry of graphite are identified here and their impacts on the electrochemical performances of DGBs are analyzed. All the differences are found to originate primarily from ionic size mismatch (76 p.m. of Li+ vs. 254 p.m. of PF 6 −) that further induces kinetic and thermodynamic limitations upon intercalation. The electrochemical studies reveal that the anion intercalation lags behind the cation because of a higher energy barrier for the interconversion among (PF 6)C x stages, the occurrence of a valley-type region in the discharge profile that delays deintercalation by 500 mV, dynamic changes in organic-rich cathode electrolyte interphase, and sluggish diffusion inside graphite bulk. In contrast, cation intercalation affects DGBs' performance negatively due to higher desolvation barriers and lithium plating on the anode surface at higher current densities. Therefore, the cathode limits the capacity and cycling efficiency, whereas the anode restricts cycle life and power density. This work also explores the strategies to mitigate the degradation pathways by electrolyte modification. [Display omitted] • Cation and anion storage in graphite are mechanistically different. • These differences result rapid degradation in dual graphite battery. • Cathode is capacity and cycling efficiency limiting. • Anode restricts cycle life and power density. • Electrochemical performances can be improved by electrolyte modifications. [ABSTRACT FROM AUTHOR]

A nanoscale pseudo-graphite hard carbon offers marvelous electrochemistry properties for the sodium ion battery as anode, exhibiting a superb initial Coulombic efficiency of 86% with the sodium alginate binder, which is presumably ascribed to thin and smooth solid electrolyte interface layer. The aforesaid binder system delivers an optimal reversible capacity of 344.4 mA h g−1, maintaining 324.8 mA h g−1 (94.3% at 100th cycle) and 284.8 mA h g−1 (82.6% at 200th cycle) at 0.1C. However, this capacity collapses from 230th cycle with a representative " bluff" curve, which frequently occurs in hydrophilic binders noteworthily. Consequently, the characteristics of the sodium alginate binder are intensively explored: (a) carboxy groups build up the typical multi-dimensional infiltration network by constructing renewable hydrogen bonds (H-bonds) skeleton. (2) This network mitigates the intergranular spacing, infiltrates the micropores and decorates the solid-electrolyte-interface layer, (c) which restrains the network from decomposition caused by the electrolyte. (d) Repeated current impacting and the oxidative decomposition from the NaClO 4 electrolyte eventually break the network structure, leading to in-adhesion and " bluff" capacity fading. Image 1 • Pseudo-graphite possesses a capacity of 344.4 mA h g−1 with an ICE of 86%. • Multi-dimensional infiltration network is established to describe the binder. • The "bluff" phenomenon is investigated based on the interface interactions. [ABSTRACT FROM AUTHOR]

Abstract Vanadium redox flow battery (VRFB) is one of the most promising large-scale energy storage system; however, a widespread VRFB development is still limited by the poor electrochemical activity of graphite electrodes and a poor understanding of redox reactions occurring at electrode/electrolyte interface. In this work, DFT was performed to study the first solvation shell structure of all vanadium ions and to investigate the reactivity of modified graphite electrodes toward the V2+/V3+ redox species. The results suggest that the presence of oxygen and nitrogen functionalities at the electrode edges provides more active sites for adsorption of the V2+/V3+ redox couple, and therefore improve electron transfer kinetics. These results have been experimentally validated by means of Cyclic Voltammetry and Electrochemical Impedance Spectroscopy with carbon black electrode having different density of oxygen and nitrogen-containing surface groups. Highlights • DFT study of model systems of graphite electrode/V2+/V3+ redox couple system. • Electrochemical behavior of doped carbon-based electrodes for redox flow battery. • Aim is to provide more active sites for adsorption of V2+/V3+ redox couple. • Beneficial effect of electrode doping with N and O. [ABSTRACT FROM AUTHOR]

Abstract A carbon nanotube sheet having homogeneously distributed BaTiO 3 is applied to the Li-S cell system as a pseudo-current collector between the cathode and separator. This interlayer serves as a site distributor, where polysulfide eluted from the cathode continuously reacts, and it is expected to play a role as a more effective current collector by mixing the ferroelectric material. A cell utilizing a ferroelectricity embedded interlayer exhibits a higher capacity (908 mAh g−1) at 0.2C than that of carbon alone (740 mAh g−1) at 200th cycle. This result corresponds to a capacity retention ratio enhancement from 67.5% to 75.6%. Furthermore, it is confirmed that the retention of the coulombic efficiency is effectively maintained in long cycles at 0.5C (94.5%–99.6%). This is not only because the modified interlayer functions as an effective current collector owing to the high affinity of the ferroelectric material to polysulfide, but also because ferroelectricity in the interlayer acts as a polysulfide anchor. The evenly distributed polarization leads to a uniform deposition of sulfur, which results in the prevention of inactive sulfur agglomeration and dissolution of polysulfide. Thus, the utilization of active material can be improved with stabilized reaction. Graphical abstract Image 1 Highlights • Nano-BaTiO 3 embedded MWCNT interlayer is fabricated by vacuum filtration method. • BaTiO 3 interlayer cell performs higher specific capacity and coulombic efficiency. • BaTiO 3 interlayer cell enhances rate capability. • BaTiO 3 interlayer induces homogeneous S distribution with strong affinity. • BaTiO 3 interlayer acts as an efficient pseudo-current collector. [ABSTRACT FROM AUTHOR]

Abstract The redox activity of tavorite LiFeSO 4 F coated with poly (3,4-ethylenedioxythiophene), i.e. PEDOT, is investigated by means of several spectroscopic techniques. The electronic changes and iron-ligand redox features of this LiFeSO 4 F-PEDOT composite are probed upon delithiation through X-ray absorption spectroscopy. The PEDOT coating, which is necessary here to obtain enough electrical conductivity for the electrochemical reactions of LiFeSO 4 F to occur, is electrochemically stable within the voltage window employed for cell cycling. Although the electronic configuration of PEDOT shows also some changes in correspondence of its reduced and oxidized forms after electrochemical conditioning in Li half-cells, its p-type doping is fully retained between 2.7 and 4.1 V with respect to Li+/Li during the first few cycles. An increased iron-ligand interaction is observed in Li x FeSO 4 F during electrochemical lithium extraction, which appears to be a general trend for polyanionic insertion compounds. This finding is crucial for a deeper understanding of a series of oxidation phenomena in Li-ion battery cathode materials and helps paving the way to the exploration of new energy storage materials with improved electrochemical performances. Graphical abstract Image 1 Highlights • Electronic changes in LiFeSO 4 F are not only due to Fe ions upon lithium extraction. • Enhanced iron-ligand interaction also plays a relevant role in lithium extraction. • The PEDOT coating shows an excellent stability in a wide voltage range upon cycling. • A deeper understanding of the redox processes in polyanionic compounds is gained. [ABSTRACT FROM AUTHOR]

Abstract Ni 0.5 TiOPO 4 oxyphosphate anode material was prepared via sol-gel method and coated with sucrose. This compound crystallizes in the monoclinic system (S.G. P2 1 /c) with a 3D framework providing convenient pathways for sodium ion diffusion and is able to accommodate 1.5 Na+/f.u. on the available sites (theoretical capacity of 256 mAh·g−1). The electrochemical performance of C-coated Ni 0.5 TiOPO 4 (NiTP-C) was investigated for the first time vs. Na+/Na in the potential window 0.2–3 V. The C-coated Ni 0.5 TiOPO 4 electrode material can exhibit an initial discharge capacity of 520 mAh·g−1 at C/10, with a long plateau at 0.75 V in the half cell against metallic Na. The subsequent charge profile clearly differs form that recorded during the discharge revealing an irreversibility in the electrochemical process in the first cycle. Rate capability tests have demonstrated satisfactory performances. The specific capacities delivered at 2C and 5C were 185 mAh·g−1 and 135 mAh·g−1, respectively. In situ diffraction using synchrotron radiation revealed that C-coated Ni 0.5 TiOPO 4 exhibits a conversion mechanism starting from 0.64 V in discharge, and at 0.49 V the compound shows a complete amorphization characterized by the disappearance of the Bragg reflections from crystalline phase. Highlights • Ni 0.5 TiOPO 4 was prepared and tested in sodium ion batteries. • Na//Ni 0.5 TiOPO 4 delivered an initial discharge capacity of 520 mAh g−1. • An irreversible behavior was evidenced upon sodiation. • In-situ SXRD revealed an amorphization Ni 0.5 TiOPO 4. [ABSTRACT FROM AUTHOR]

Abstract Cerium triflate (Ce(CF 3 SO 3) 3) is used as a superoxide radical scavenger in the ether-based liquid electrolyte for the Li O 2 batteries. The radical scavenging capability of Ce3+ is evaluated both in potassium superoxide + crown solution and the Li O 2 batteries. The chemical analyses further demonstrate cerium ions can effectively slow down the decomposition of electrolyte attacked by superoxide radicals. When the capacity is fixed to 1000 mAh g−1 at a current density of 500 mA g−1, the Li O 2 battery with 1M LiTFSI-TEGDME electrolyte begins to drop its discharge voltage rapidly to 2.0 V near 40th cycle while the electrolyte with Ce3+ additives is still above 2.0 V after 88 cycles, demonstrating the cycle life of the Li O 2 batteries show remarkably improved compared to the Li O 2 batteries without any additive into electrolyte. Highlights • Ce(CF 3 SO 3) 3 used as radical scavenger to improve chemical stability of electrolyte. • Li O 2 battery containing Ce(CF 3 SO 3) 3 shows good cycle stability and high capacity. • Battery with Ce3+ shows 820 mAh g−1 higher discharge capacity than without Ce3+. • No new NMR signals of electrolytes with Ce(CF 3 SO 3) 3 after cycling test observed. [ABSTRACT FROM AUTHOR]

Abstract We synthesize a series of cobalt species combined with carbon nanotubes loaded onto graphene-like titanium carbide (CoO x -N C/TiO 2 C), which are derived from bimetallic CoZn-based zeolitic imidazolite framework and Ti 3 C 2 T x MXene composite (CoZn-ZIF/Ti 3 C 2 T x). The as-result CoO x -N C/TiO 2 C composites are further explored as the trifunctional electrocatalysts for hydrogen evolution reaction, oxygen reduction reaction, and oxygen evolution reaction. Among composites containing different Ti 3 C 2 T x dosages, the CoO x -N C/TiO 2 C(22.7%) exhibits the most excellent electrochemical conductivity. When CoO x -N C/TiO 2 C(22.7%) is used as the electrocatalyst for water splitting, a current density of 10 mA cm−2 (E j = 10) is achieved at a low cell voltage of 1.45 V. Meanwhile, the overall oxygen activity of the CoO x -N C/TiO 2 C(22.7%) shows a small potential difference (0.72 V) between the E j = 10 for oxygen evolution reaction and the half-wave potential for oxygen reduction reaction. The outstanding catalytic performances are mainly attributed to the synergistic effect among the different components of the CoO x -N C/TiO 2 C composite, such as carbon nanotube content that is in favour of electronic mobility, hierarchical porosity that facilitates mass transport, and uniformly dispersed cobalt, cobalt oxide, and titanium dioxide active sites in the carbon framework. Consequently, the present work will shed light on the application of other metal-organic framework- and carbon-based electrocatalysts for energy conversion. Highlights • A novel catalyst fabricated by calcining a composite of CoZn-ZIF and MXene. • The synergistic effect in Co species, CNTs, TiO 2 nanoparticles and carbon framework. • Highly efficient trifunctional electrocatalysts for ORR, HER and OER. [ABSTRACT FROM AUTHOR]

Abstract The 2D transition metal carbide (MXene) is a new type of promising material for energy storage due to its metallic conductivity and highly active surface. This paper describes a new photo-responsive Azo-MXene hybrid that is fabricated through electrostatic interactions between the negatively charged MXene and the cationic Azo-surfactants. After performing systematical characterizations, we found a strong electrostatic interaction force between the MXene and Azo-surfactants in this hybrid and a uniform distribution of Azo groups in the MXene structure. Notably, this Azo-MXene hybrid can self-assemble to an aggregated structure due to the hydrophobization of Azo on the surface of MXene. Furthermore, the self-assembly of this hybrid can be modulated by ultraviolet light irradiation. This process of transition is also responsible for the hybrid's electrochemical performance upon ultraviolet light irradiation, which may be applied as a photo-responsive conductive material for photo-energy conversion and storage devices. Graphical abstract Image 1 Highlights • A photo-responsive Azobenzene-MXene hybrid is prepared for the first time. • The self-assembly of the hybrid can be modulated by UV irradiation. • This photoresponse is also responsible for its electrochemical performance. [ABSTRACT FROM AUTHOR]

Abstracts The effects of combinative Ca and rare earth (Samarium, Sm and Lanthanum, La) additions on the microstructures, electrochemical properties and discharge performance of the as-extruded Mg 9%Al 1%Zn (wt.%) anodes for magnesium-air batteries are systematically investigated. The combinative addition of Ca, Sm and La can bring additional Al 2 Ca and Al 2 (Sm,La,Ca) compound phase and reduce the grain size from 17.2 ± 1.9 μm to 11.7 ± 0.9 μm. The β-Mg 17 Al 12 phase gets refined and dispersed with the Al 2 Ca phase in the matrx. The modified Mg 9%Al 1%Zn anodes have more positive corrosion potential and better corrosion resistance than the original. The addition of Sm and La strongly increases the desorption resistance of surface product. Mg 9%Al 1%Zn with Ca, Sm and La anode exhibits stable discharge voltage and good discharge performance. It has high discharge capacity and anodic efficiency of 1381 mA h·g−1 and 61.9%, respectively, at 40 mA·cm−2. The prior corrosion of grain boundaries makes bulk of α-Mg grains peel away along the grain boundaries, significantly reducing the anodic efficiency. The disperse particle phase around grain boundaries can serve as strong barriers so as to achieve uniform dissolution. Highlights • The Ca and RE addition refine the grains and modify the Mg 17 Al 12 of AZ91 anode. • The modified AZ91 anode has better discharge performance than the original anode. • The disperse particles around grain boundaries help achieve uniform dissolution. • The RE additions strongly increase the desorption resistance of surface product. [ABSTRACT FROM AUTHOR]

Abstract We review the origins of capacitive phenomena at the nanoscale to demonstrate that electrochemistry cannot be understood without a critical re-reading of nanoscale electronics, and vice-versa. The fundamentals are stated at a mesoscopic physical level at which both classical and quantum mechanical terms are important to the explanation of different capacitive contributions. At this mesoscopic physical scale, a quantum mechanical Hamiltonian can be analytically solved for a metal-electrolyte interface modified with an ensemble of molecular-scale building blocks. This mesoscopic electrochemical state arises in most situations involving nanostructured electrochemical junctions, while the outcome of resolving the Hamiltonian associated with this mesoscopic problem is electrochemical capacitance. Therefore, in the present study, we departed from the conventional meaning of electrochemical capacitance to demonstrate that non-faradaic and faradaic charging events are identical phenomena. Using specific examples in which these approximations apply, we elucidate and generalize the common molecular origin of double-layer and pseudo-capacitive charging phenomena. This important fundamental knowledge obviously impacts the development of nanostructured super-capacitors, researchable batteries, etc. Additionally, we discuss the principle of operation of non-faradaic and faradaic capacitive sensing devices, which are notable for conforming to equivalent principles. In summary, super-capacitance phenomena are introduced and elucidated from first-principles quantum mechanics outcomes. [ABSTRACT FROM AUTHOR]

Abstract The safety design of systems using lithium-ion batteries (LIBs) as power sources, such as electric vehicles, cell phones, and laptops, is difficult due to the strong multiphysical coupling effects among mechanics, electrochemistry and thermal. An efficient and accurate computational model is needed to understand the safety mechanism of LIBs and thus facilitate fast safety design. In this work, a detailed mechanical model describing the mechanical deformation and predicting the short-circuit onset of commercially available 18650 cylindrical battery with a nickel cobalt aluminum oxide (NCA) system is established for the first time. The mechanical properties of anode, cathode, and separator are characterized. Based on the experiment results, the constitutive models of component materials are established and validated through numerical simulations. A detailed computational model including all components (i.e., separator, anode, cathode, winding, and battery casing) is then developed by evaluating four typical mechanical-loading conditions. Short-circuit criteria are subsequently established based on the separator failure, thereby enabling the mechanical model to predict the short circuit electrochemically. Results show that the model can describe LIB behaviors from mechanical deformation to internal short circuit. Results provide a powerful tool for the safety design of LIBs and related engineering systems. Graphical abstract Image 1 Highlights • A model describing the deformation and short-circuit onset is established. • Constitutive models of each component are developed based on the experiments. • Short-circuit criteria are established based on the separator failure. • Short-circuit triggering behavior under dynamic loading is discussed. [ABSTRACT FROM AUTHOR]

Abstract Electroactive materials with high electrochemical activity, good rate capability and excellent cycling stability are urgently needed for hybrid supercapacitors, but achieving those performances at the same time is still a big challenge. Here, α phase nickel−cobalt−manganese hydroxide (NiCoMn−OH) with a flower-like structure is synthesized and used as the battery materials for hybrid supercapacitor. The NiCoMn−OH exhibits strong synergetic electrochemistry between the transition metals, which contributes better charge storage performances. The NiCoMn−OH shows a specific capacity of 757 C g−1 at 1 A g−1 and retains 369 C g−1 at very high specific current of 50 A g−1, which are both much higher than the corresponding bimetal and nomometal hydroxides. Therefore, both high electrochemical activity and rate capability have been achieved. The α phase NiCoMn−OH also exhibits a long-term cycling stability because the specific role of Co, maintaining 100% of the specific capacity after 1200 cycles. The hybrid supercapacitor based on NiCoMn−OH also shows high specific capacity of 219 C g−1 at 1 A g−1, high rate performance of 53% capacity retention when the specific current increases 25 times and ultralong cycling stability of 83% capacity retention after 12,000 cycles. Graphical abstract Image 1 Highlights • α phase trimetal NiCoMn−OH with a flower-like structure are synthesized. • The NiCoMn−OH exhibits strong synergetic electrochemistry between transition metals. • The NiCoMn−OH shows both high electrochemical activity and rate capability. • The NiCoMn−OH based hybrid supercapacitor shows excellent performance. [ABSTRACT FROM AUTHOR]

Abstract Aluminum is an attractive anode material for electrochemical energy storage and conversion devices, but the passive film and parasitic corrosion of aluminum anode in aqueous solution limits its development. Herein, we investigated the electrochemical performance of Al-2Mg alloy in alkaline electrolyte containing stannate ion via hydrogen evolution tests, electrochemical measurements and surface analysis. It is found that the solid-solute magnesium in aluminum matrix activates the oxide film and decreases the cathodic sites, which negatively shift the aluminum anode potential. Furthermore, the doping magnesium ion in the oxide film facilitates the tin deposition reaction on the surface of aluminum anode, and the uniformly deposited tin inhibits the parasitic corrosion reaction. As a result, Al-2Mg alloy in 6 M NaOH solution with 0.05 M Na 2 SnO 3 exhibits low hydrogen evolution rate of 0.015 mL·cm−2·min−1 with the inhibition efficiency of 95% at open circuit and negative electrode potential of −1.81 V vs. saturated calomel electrode at 20 mA cm−2. Highlights • The passivating oxide film of aluminum anode is doped with magnesium ion. • Magnesium ion activates the Al-2Mg anode in alkaline solution. • Tin is uniformly deposited on the Al-2Mg anode surface. • Al-2Mg in 6 M NaOH +0.05 M Na 2 SnO 3 exhibits high inhibition efficiency of 95%. • The anode possesses negative electrode potential of −1.81 V vs. SCE at 20 mA cm−2. [ABSTRACT FROM AUTHOR]

Abstract This study compares the dispersion of submicron-silicon and nano-sized silicon powders and the electrochemistry of the prepared anodes using carboxymethyl cellulose or guar gum as the binder. Carboxymethyl cellulose is found to be a better binder than guar gum for the electrochemistry of the anodes when the electrode active powder is submicron-silicon because carboxymethyl cellulose helps the dispersion of submicron-silicon while guar gum gels submicron-silicon in the electrode slurry. In contrast, guar gum is a better binder than carboxymethyl cellulose for cell performance when the active anode material is nano-sized silicon, which is much more oxidized on its surface. Batteries prepared with nano-sized silicon present a capacity below 1500 mAh g−1 at a current of 420 mA g−1 and poor initial Coulombic efficiency below 85%. For anodes using submicron-silicon as the active material, the constructed cells exhibit a capacity above 2500 mAh g−1 and good initial Coulombic efficiency above 93%. Graphical abstract Image 1 Highlights • Carboxymethyl cellulose is a better binder than guar gum for submicron Si anodes. • Guar gum is a better binder than carboxymethyl cellulose for nano-Si anodes. • Using guar gum as a binder gels the slurry of submicron Si but not that of nano-Si. • Si nanopowder owns large content of silica on surface and presents poor capacity. • Anodes of nano-Si show poorer capacity than those of submicron Si. [ABSTRACT FROM AUTHOR]

Supercapacitors are fast-charging energy storage devices of great importance for developing robust and climate-friendly energy infrastructures for the future. Research in this field has seen rapid growth in recent years, therefore consistent reporting practices must be implemented to enable reliable comparison of device performance. Although several studies have highlighted the best practices for analysing and reporting data from such energy storage devices, there is yet to be an empirical study investigating whether researchers in the field are correctly implementing these recommendations, and which assesses the variation in reporting between different laboratories. Here we address this deficit by carrying out the first interlaboratory study of the analysis of supercapacitor electrochemistry data. We find that the use of incorrect formulae and researchers having different interpretations of key terminologies are major causes of variability in data reporting. Furthermore we highlight the more significant variation in reported results for electrochemical profiles showing non-ideal capacitive behaviour. From the insights gained through this study, we make additional recommendations to the community to help ensure consistent reporting of performance metrics moving forward. • Supercapacitor electrochemistry data analysed by 14 different laboratories. • Constant current tests gave lower variability in capacitance than CV tests. • Large variation in capacitance results obtained for 'non-ideal' devices. • Capacity should be reported for reliable comparison of device performance. • Researchers must be clear on their definition of 'specific capacitance'. [ABSTRACT FROM AUTHOR]

The anion storage electrochemistry of carbon cathode is bottlenecked by the severe electrolyte decomposition and significant volume expansion. A surface coating that can impart simultaneous protection against all the drawbacks is challenging to achieve. Herein, the multifaceted benefits of pitch-derived soft carbon are leveraged as a coating layer. An upscalable annealing treatment results in an ultrathin, polycrystalline, uniformly distributed, and porous layer of carbonized pitch on the redox-active core. The coated material demonstrates 25 and 5.5% improvement in capacity retention, and coulombic efficiency, respectively, and a 150 mV reduction in voltage hysteresis. The smooth surface topography of the coated sample alleviates the electrolyte decomposition during high-voltage cycling. The mechanical flexibility of the coated material to withstand the volume change and to preserve the structural integrity are uncovered by the nanoindentation experiments and further supported by the post-cycling characterizations. The coating offers mechanochemical robustness to the interface and minimizes the growth of resistance. The strategy of soft carbon coating on anion-storing cathode can be extended to dual graphite full cells and other anion-storing chemistries irrespective of the anode and electrolyte. [Display omitted] • Pitch derived soft carbon coating is easy to synthesize and upscalable. • The coating layer is 35 nm thin, polycrystalline, and uniformly distributed. • It improves electrochemical performances superiorly. • It enhances interfacial stability and withstands volume change. • The concept can be extrapolated to all anion storing battery chemistries. [ABSTRACT FROM AUTHOR]

Heterostructure materials hold promise as future-generation anodes for sodium-based energy storage. However, the complexity and time-intensity of heterojunction fabrication processes limit their large-scale application. This study utilizes an ultrafast, one-step microwave process to successfully design and fabricate bimetallic selenides heterojunction nanoparticles, anchored on a three-dimensional porous carbon substrate (NiSe 2 –SnSe 2 /C). The in-situ formation of NiSe 2 –SnSe 2 heterostructure optimizes sodium ion adsorption and transfer, which facilitates reaction kinetics and subsequently improves both the rate capability and cycle life. The NiSe 2 –SnSe 2 /C electrodes demonstrate a high-rate capability (719.8 mAh g−1 at 0.1 A g−1, and 667.9 mAh g−1 after a 50-fold increase in current density to 5 A g−1), maintaining high stability even after 10,000 cycles at 5 A g−1. The impact of the NiSe 2 –SnSe 2 heterostructure on reaction kinetics was examined using density functional theory. The NiSe 2 –SnSe 2 /C anode, when coupled with the Na 3 V 2 (PO 4) 3 cathode in a full battery, demonstrated an impressive energy density of 155 Wh kg−1. This work exemplifies an ultrafast synthetic method for constructing heterostructure materials having great rate, high capacity and strong stability for sodium storage, making them promising candidates for large-scale energy storage applications. [Display omitted] • A microwave strategy is developed to synthesize a heterostructure in just 20 min. • NiSe 2 –SnSe 2 /C Na-ion half batteries show excellent rate capability and long life. • Na 3 V 2 (PO 4) 3 //NiSe 2 –SnSe 2 /C full battery indicates potential practical application. • Na+ storage kinetics of NiSe 2 –SnSe 2 heterojunction are calculated by DFT. [ABSTRACT FROM AUTHOR]

Abstract Non-aqueous flow cells offer expanded electrochemical potential windows, which is desirable for energy storage. The performance of such electrochemical systems is however constrained by high cell resistance due to the low ionic conductivity of electrolytes and membranes in non-aqueous media. In this work, we apply membrane-less cell configurations with flow-through porous electrodes to address the ohmic losses and boost the performance of non-aqueous flow cells. Vanadium acetylacetonate redox chemistry is used as a model system and various performance aspects such as reaction kinetics, electrode wettability, cell resistance and crossover are investigated. The kinetics, measured in flow-through mode, is found competitive due to the enhanced mass transport and surface area utilization in the flow-through porous electrode. The electrode porosity is measured to be 79% and only 6.0% in acetonitrile and water, respectively, indicating superior wettability behaviour for non-aqueous electrolytes. A fully integrated co-laminar flow cell demonstrates negligible crossover and a combined ohmic cell resistance that meets techno-economic targets. Its discharge power density of 550 mW cm−2 is two orders of magnitude higher than for other non-aqueous flow cells, demonstrating that membrane-less cell designs with flow-through porous electrodes are favourable in order to overcome performance limitations in non-aqueous electrochemical systems. Graphical abstract Image 1 Highlights • Kinetics, wetting, resistance and crossover of non-aqueous cells are investigated. • Porous electrode wetting in acetonitrile (79%) is much higher than in water (6%). • The benefits of membrane-less cells and flow-through electrodes are leveraged. • A peak power density of 550 mW cm−2 is demonstrated with non-aqueous electrolyte. • Power density is two orders of magnitude higher than conventional non-aqueous cells. [ABSTRACT FROM AUTHOR]

Abstract Fracture in silicon anodes has fascinated the electrochemistry community for two decades, as it can result in a 80% capacity loss over the first few electrochemical cycles and is the limiting factor in commercializing such high capacity anodes. Although numerous experimental data exist illustrating severe fracture patterns and their dependence on the scale of the microstructure, no theoretical model has been able to re-produce and capture such behaviour. In this article, a multi-physics phase-field damage model is presented that can accurately capture the long standing problem of dry bed-lake crack patterns observed for Si thin film anodes. A promising aspect of the model is that, in addition to accounting for Li-ion diffusion, it can explicitly capture the microstructure, and therefore when applied to a Si film with a thickness below 100 nm no fracture was observed, which is consistent with experiments. As fracture in continuous thin films is random, micron-hole patterned Si films were also fabricated and cycled, resulting in ordered crack patterns. The proposed model was able to capture these elaborate, yet ordered, crack patterns, further validating its efficiency in predicting damage during lithiation of Si. This paves the way to using multiscale modeling for predicting the dimensions that limit and control fracture during lithiation, prolonging hence the electrode lifetime. Highlights • Fracture has not been simulated for Si thin films. • Multiphysics model can capture dry-bed lake fracture. • Fracture is inhibited for films less than 100 nm. [ABSTRACT FROM AUTHOR]

Abstract Symmetric solid oxide fuel cells (SSOFCs) based on the Co-free La 0·5 Sr 0·5 Fe 0·9 Nb 0·1 O 3-δ (LSFNb) perovskite oxide are prepared by the sol-gel method. The structural stability and catalytic activity of LSFNb as an electrode for both the hydrogen oxidation reaction and oxygen reduction reaction are studied. We show that Nb substitution in La 0·5 Sr 0·5 FeO 3-δ greatly improves its chemical and phase stability under reducing atmosphere. At 800 °C, the area specific polarization resistances (ASR p) of La 0·5 Sr 0·5 Fe 0·9 Nb 0·1 O 3-δ symmetric cells are as low as 0.06 and 0.24 Ω cm2 in air and wet H 2 (3% H 2 O), respectively. LSFNb based electrolyte-supported SSOFCs deliver peak power densities of 1000 mW cm-2 at 850 °C in wet H 2 /air. In addition to high performance, the symmetric cell shows stable power output under load (measured for 140 h at a current density of 520 mA cm−2, 800 °C) under air/humidified H 2 operation, indicating that LSFNb may be a particularly promising new symmetric electrode material for solid oxide fuel cells. Highlights • Nb improve the stability of La 0·5 Sr 0·5 FeO 3-δ in reducing atmosphere. • The ORR and HOR are investigated using distribution of relaxation times (DRT). • At 800 °C, The ASR of SSOFCs are as low as 0.06 and 0.24 Ω cm2 in air and wet H 2. [ABSTRACT FROM AUTHOR]

Abstract The interaction between active materials and conductive additives is complicated but crucial within electrochemical energy storage devices. Here, we first identify that CH 2 groups drive the compositing process, leading to an effective formation of Co-O-C chemical bonding serving as the bridge between reduced graphene oxide(rGO) and hydroxide. Due to the enhanced electron transport, a dramatically improved specific capacity is achieved as high as 1368 F/g for rGO/Co(OH) 2 electrode at a current density of 0.5 A/g. Thus, we provide new insights into graphene/hydroxide compositing mechanism, which has a significant impact on enhancing electron transport for a variety of graphene/hydroxide in energy storage systems. Highlights • CH 2 groups transform into Co-O-C bonds as the bridge between graphene and Co(OH) 2. • rGO/Co(OH) 2 exhibits a highly crystalline feature. • BG/Co(OH) 2 holds more Co3+ ions and Co-O tetrahedral structures. • C-(O-Co) n affords abundant electron transport channels. • A dramatically high specific capacity of 1368 F/g is achieved for rGO/Co(OH) 2. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Due to their strong electronic interactions and excellent electrochemical properties, noble metal-based rare earth nanoalloys are considered to be promising electrocatalytic materials for fuel cell applications. However, due to the limitation of the very negative reduction potential for rare earth metals, the wet chemical or electrochemical preparation of noble metal/rare earth nanoalloys is still challenging. Herein, we report a novel and effective strategy for the electrochemical synthesis in deep eutectic solvents of concave cubic PtLa alloy nanocrystals with high-index facets and superior electrocatalytic properties for the ethanol oxidation reaction. Scanning electron microscopy and transmission electron microscopy characterizations confirm that the concave cubic PtLa alloy nanocrystals of approximately 47.5 nm in size are uniformly electro-deposited on the glassy carbon substrate in deep eutectic solvents and are bounded with the {410} and adjacent high-index facets. X-ray photoelectron spectroscopy analysis indicates the presence of strong charge transfer interactions from La to Pt atoms in the concave cubic PtLa alloy nanocrystals. Due to the synergetic effect of the high-index facets and the charge transfer interactions between Pt and La, the synthesized concave cubic PtLa alloy nanocrystals exhibit enhanced specific current activity and long-term durability for the ethanol oxidation reaction. Highlights • A concave cubic PtLa alloy NC catalyst with {410} high-index facets is reported. • The PtLa alloy NCs of ca. 47.5 nm are evenly electro-deposited on the GC substrate. • Strong charge transfer interaction from La to Pt atoms is present on the NC surface. • The PtLa alloy NCs exhibit much higher electrocatalytic properties for the EOR. [ABSTRACT FROM AUTHOR]

Abstract Continuously growing and miniaturizing autonomous electronic devices and sensors for large temperature window is mostly depends on stability and performance of power-up systems. The net achievable power and energy densities of such miniatured rechargeable energy storage systems are largely dominated by internal hardware and external packaging materials. Similarly, temperature stability of electrochemically active materials and packaging components is also crucial to realize desired activity at few millimeter scale devices. Herein, we explore energy storage devices at tunable miniatured scale by selecting optimal electroactive materials, thermally stable packaging components, and their fabrication process. Further, an assembled device is subjected to evaluate its energy and power density per foot-print-area along with other key electrochemical parameters such as internal resistance, self-discharge, and thermal stability. Detailed studies reveal that the presently packaged millimeter size rechargeable batteries (2 mm–5 mm) have the ability to work up to 120 °C with minimal load loss and compatible with energy harvesting renewable source of the solar cell. Highlights • Fabrication process for miniatured Li-ion batteries with high temperature stability. • Validated the assembled power sources for high temperature sensing applications. • Thermally stable electrochemical active materials and packaging components. • Compatible for energy harvesting, solar cell charging at room temperature. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Scalable manufacturing of yarn-based supercapacitors with high energy density is highly desired for powering wearable electronics and smart textiles. In this paper, we report a novel type of sheath-core polyaniline nanowire array grown on aligned carbon nanofibers/carbon fiber yarn electrode (CFY@CNFs@PANI NWA) based supercapacitors. The carbon fiber yarn can maintain the yarn electrode with high electrical conductivity and mechanical properties. The introduced PANI NWA can further enlarge the specific surface area of the electrode and introduce pseudo-capacitance. The assembled solid-state supercapacitors show high areal specific capacitance of 234 mF/cm2 at a current density of 0.1 mA/cm2, and corresponded energy density of 21.4 μW h/cm2 at power density of 0.52 mW/cm2 in EMIMBF 4 /PVDF/DMF gel electrolyte. The supercapacitors also exhibit ultrahigh rate capability (68%) and excellent cycle stability (90% after 8000 cycles). We also demonstrated that a 20-cm long supercapacitor can be readily to power up 36 pieces of red LEDs with a logo of “DHU”. The scalable strategy paves a way towards mass production of wearable energy storage devices for smart textiles. Highlights • We report the scalable fabrication of sheath-core carbon fiber yarn-based electrode. • The aligned carbon nanofibers were continuously coated on carbon fiber yarn. • We enhance its electrochemical performance via PANI nanowire array modification. [ABSTRACT FROM AUTHOR]

Abstract A configuration of multiple inlets is proposed for a micro laminar flow fuel cell with a bridge-shaped channel cross section. The operation of the micro laminar flow fuel cell involves the complex interplay of electrochemical and mass transport processes. A fully coupled three-dimensional numerical model is developed to evaluate the micro laminar flow fuel cell performance. The numerical model solves the three-dimensional Navier-Stokes, mass transport, and Butler-Volmer equations for the electrode kinetics. A novel concept of multiple inlets is introduced to deal with the greater mass transport losses associated with the larger channel length. The numerical model is validated using experimental data from a micro laminar flow fuel cell with a bridge-shaped microchannel. Up to 8 inlets are tested with various bridge aspect ratios to observe the peak power and current density. The multi-inlet configurations enhance the current density by multiple times in comparison to a simple bi-inlet micro laminar flow fuel cell. Highlights • Numerical model of a bridge-shaped μLFFC was validated using experimental data. • Multiple inlets were proposed for μLFFC and evaluated for various aspect ratios. • 8-inlets increased current density by a factor of about 15 compared to 2-inlets. • Multiple inlets also reduced the Ohmic losses and mass transport losses. [ABSTRACT FROM AUTHOR]

Abstract This article presents a combined experimental/theoretical approach to accurately predict electrochemical redox potentials based on potential energy calculations. The approach works for experimental setups using different solvents and different reference electrodes and compensates for shortcomings in the prediction of redox potentials originating from the choice of DFT functional, basis set, and solvation model. The methodology is applied to two different sets of iron containing complexes which are used as redox catalysts in Chemically Regenerative Redox Fuel Cells (CRRFCs). For both sets of iron complexes with different 5 N donor ligands, an average deviation to the experimental values of <0.02V is obtained. Expectedly, the deviation is slightly larger with changes being made in the first coordination shell, but is still within the predictive limit. The scheme is then applied to obtain ligands with both improved properties and lowest production cost. Highlights • Combined experimental/theoretical method to predict redox potentials of fuel cell catalysts. • Highly accurate results for broad set of experimental conditions and reference electrodes. • Simple side chain modifications allow improvement of open circuit voltage of up to 10%. • Newly identified catalyst with even higher potential providing improvement of ≈25%. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

A facile and simple solid-state reaction route is developed to synthesize F-doping and V-defect Na 3 V 1.98 (PO 4 ) 3-x F 3x /C composites. F-doping is facilitated to decrease the particle size to diminish the pathway of Na + diffusion. Beneficial by-products are generated due to F-doping and V-defect, Na 3 PO 4 is a typical Na ion conductor and NaVO 2 has the layer structure for rapid migration of Na + . The synergetic effect of F-doping and V-defect on the Na + diffusion is significant. The kinetic behavior is dramatically enhanced and it is beneficial to reinforcing the electrochemical performance. Meanwhile, the extraction of the third Na + at Na1 site is observed at 4.0 V corresponding to the V 4+ /V 5+ redox couple. The optimized Na 3 V 1.98 (PO 4 ) 2.9 F 0.3 /C composite delivers an initial charge capacity as high as 143.5 mAh g −1 and an 116.9 mAh g −1 discharge capacity at 0.1C. A reversible capacity of 100.6 mAh g −1 is obtained and it retains 89.3% capacity after 100 cycles at 1C. It presents the highest D Na + (3.66 × 10 −13 cm 2 s −1 ), close to three orders of magnitude higher than the Na 3 V 2 (PO 4 ) 3 /C (7.41 × 10 −16 cm 2 s −1 ). Moreover, Ex situ XRD results demonstrate that broadened channels along x and y directions are favorable to improving D Na + and it exhibits the highest D Na + when charging to 3.4 V. [ABSTRACT FROM AUTHOR]

In this work, the scalable ceramic-polymer composite electrolytes composed of Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 , poly (ethylene oxide), lithium bis(trifluoromethane)sulfonimide, and solid plasticizer succinonitrile are prepared in the form of flexible membranes. The ionic transport properties, electrochemical stability, and interfacial behaviors against lithium electrode of this electrolyte are systematically investigated. Among these electrolytes, the sample containing 60 wt.% Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 and 10 wt.% succinonitrile presents a maximum conductivity of 1.22 × 10 −4  S cm -1  at 30 °C, and exhibits a broadened electrochemical stability window of 5.5 V vs. Li/Li + . Moreover, the ionic transference number of this electrolyte is improved to 0.41, and the interfacial compatibility against lithium electrode is excellent under both static and dynamic conditions. Excellent cycling and rate performance of the Li/LiFePO 4 cells are resulted from the enhanced ionic transport properties and improved interfacial contact between electrolyte and electrodes. The cell run at 0.5C delivers a discharge specific capacity of 151.1 mAh·g −1 after 200 cycles under 60 °C, and retains 98% of the maximum specific capacity. Notably, this cell also can be successfully charged and discharged at 45 °C and still delivers a discharge capacity of 124.1 mAh·g −1 after 70 cycles at 0.5 C. [ABSTRACT FROM AUTHOR]

Herein we investigate a lithium sulfur battery suitably combining alternative cathode design and relatively safe, highly conductive electrolyte. The composite cathode is formed by infiltrating sulfur in a N-doped 3D graphene framework prepared by a microwave assisted solvothermal approach, while the electrolyte is obtained by dissolving lithium bis(trifluoromethane)sulfonimide (LiTFSI) in diethylene glycol dimethyl ether (DEGDME), and upgraded by addition of lithium nitrate (LiNO 3 ) as a film forming agent. The particular structure of the composite cathode, studied in this work by employing various techniques, well enhances the lithium-sulfur electrochemical process leading to very stable cycling trend and specific capacity ranging from 1000 mAh g −1  at the highest rate to 1400 mAh g −1  at the lowest one. The low resistance of the electrode/electrolyte interphase, driven by an enhanced electrode design and a suitable electrolyte, is considered one of the main reasons for the high performance which may be of interest for achieving a promising lithium-sulfur battery. Furthermore, the study reveals a key bonus of the cell represented by the low flammability of the diglyme electrolyte, while comparable conductivity and interface resistance, with respect to the most conventional solution used for the lithium sulfur cell. [ABSTRACT FROM AUTHOR]

One demanding challenge in the development of high-power batteries is to achieve superior rate and cycling performances. Here, we report a two-step method to fabricate a hybrid material of surface-amorphized TiO 2 /reduced graphene oxide (SA- TiO 2 /RGO), which exhibits superior electrochemical properties as an anode material in lithium-ion batteries, high rate property of 135.6 mAh g −1 at a current density of 10 A g −1 and cycling stability of 98 mAh g −1 after 2000 cycles at 5 A g −1 . These excellent performances originate from the unique three-dimensional integrated structure of SA-TiO 2 /RGO, which provides: (i) a conductive substrate of RGO; (ii) higher conductivity of SA-TiO 2 relative to crystallized-TiO 2 ; (iii) ultra-small SA-TiO 2 nanoparticles; and (iv) excellent contact between SA-TiO 2 and RGO through C-O-Ti bonds. [ABSTRACT FROM AUTHOR]

Although the choice of binder is crucial in determining the electrochemical performance and durability of silicon-based electrodes, the underlying mechanisms (e.g., mechanical vs . chemical) are unclear. Here, we report a study of the effects of adhesion vs . cohesion on the electrochemical behavior of silicon nanoparticle/polymeric binder/carbon black (CB) electrodes on copper conductor by multiple techniques. Two types of polymeric binders, polyvinylidene fluoride (PVDF) and sodium alginate (SA), were chosen for this study. The results show that because of a sufficiently strong interface between polymer and the copper current collector, both Si/PVDF/CB and Si/SA/CB composite electrode laminates have sufficient adhesive strength with the Cu conductor to cause cohesive failure within the electrode laminate during peel test. However, the interfacial strength between SA and silicon is significantly higher than that between PVDF and silicon, resulting in stronger cohesion within the Si/SA/CB electrode (e.g., peel strength of 78.3 N/m for Si/SA/CB electrode and 8.7 N/m for Si/PVDF/CB electrode, respectively). With a higher cohesive strength provided by a stronger binder-silicon interface, superior cell performance was ensured for Si/SA/CB electrodes. Hydrogen bonding is likely responsible for the stronger SA-Si interface since neither PVDF nor SA bonds covalently with Si according to chemical analysis. [ABSTRACT FROM AUTHOR]

A free-standing unidirectional graphene aerogel/polyaniline (UGA/PANI) composite possessing the oriented PANI nanowire arrays on highly aligned and interconnected graphene network is obtained, through a facile in-situ polymerization of PANI on a unidirectional graphene aerogel scaffold. The resulted novel hierarchical structure can reduce the internal resistance and facilitate ion diffusion, which allows this electrode material to exhibit better electrochemistry performances. The UGA/PANI composite subsequently displays an enhanced specific capacitance of 538 F g -1  at 1.0 A g −1 with appreciable rate capability (keeps 73% even at 10 A g −1 ) as well as fine cycle stability (remains 74% of its initial specific capacitance after 1000 cycles at 3 A g −1 ). Besides, the electrochemical performances of UAG/PANI composite reported far excel that of conventional graphene aerogel/polyaniline (GA/PANI) composite with random graphene network and tortuous pores (345 F g -1  at 1.0 A g −1 , 39% retention at 10 A g −1 ), demonstrating that proper construction of oriented structure is beneficial for achieving potential of PANI. [ABSTRACT FROM AUTHOR]

Compared to research progress on cathode materials, progress on anode materials for sodium rechargeable batteries has been relatively slow. To bring sodium rechargeable batteries to a next level, it is necessary to explore feasible anode materials as well as understand clearly the reaction mechanism during electrochemical cycling. We herein introduce mesoporous and bulk molybdenum dioxide materials, which show excellent sodium storage performances under ether based electrolyte conditions, as anodes for sodium rechargeable batteries. Moreover, the pseudocapacitive sodium storage behavior in molybdenum dioxide anodes is proposed based on a quantitative analysis of the cyclic voltammetry responses. This result is systematically corroborated by using synchrotron radiation based analyses, X-ray photoelectron spectroscopy, scanning transmission electron microscope and ab initio molecular dynamics simulation. Comprehensive information on the electrochemical characterization as well as sodium storage mechanism of this transition metal oxide will provide a practical strategy to further advance anode materials for sodium rechargeable batteries. [ABSTRACT FROM AUTHOR]

Polymer electrolyte membrane water electrolysis (PEMEC) is a high-yield technique for hydrogen generation from renewable energy. One challenge for commercialisation of the technology is a low-cost and highly efficient flow plate. Flow plates are one of the most expensive parts of an electrolysis system, therefore a thorough study on alternative flow plate manufacturing methods pays off. Expanded metals have low manufacturing cost. Even though they are being used in different industries from electrochemistry to ventilation and air conditioning systems, there is little information available on their fluid flow behaviour. In this paper, the distribution of gas and liquid flow in expanded metal is analysed. Expanded metal flow resistance properties such as porosity, permeability and inertial resistance for two different sizes in both horizontal and vertical directions are determined. Alongside the experiments, two different computational fluid dynamic (CFD) simulations of flow in the experimental setup and the structure of the expanded metal was done. [ABSTRACT FROM AUTHOR]

The impedances of several electric double layer capacitors are analysed at high frequencies by using the Randles equivalent electric circuit with the semi-infinite Warburg impedance. The Warburg coefficient, the charge transfer resistance, the interfacial capacitance, as well as the geometric resistance of the devices are determined by means of a non-linear least squares fitting. Unlike other previous studies using this circuit, we identify the characteristic frequencies from the zero-pole representation at the limits of the Randles impedance at high and low frequencies. Our study includes the overlapping between the interfacial and porous transport processes in the equivalent series resistance at high frequencies and it additionally considers the frequency at the intersect point between the interfacial and porous regions in the impedance Nyquist plots. Evolution with time of the short-circuit current and the voltage drop in response to a current pulse in supercapacitors are theoretically analysed at the shortest times from numerical inversion of the Laplace transform by using PSpice ® . The numerical results obtained from the Randles impedance and those from the low-frequency Warburg approximation are compared, and the significance of the different time constants is analysed and discussed. [ABSTRACT FROM AUTHOR]

Herein, we present a detailed study by N 2 sorption and Small Angle X-ray Scattering (SAXS) of the carbonization and KOH activation of lignin for its application as active material for electrochemical energy storage. It has been observed that i) the carbonization of lignin above 700 °C leads to a hard carbon with a large amount of bulk (buried) fine structure microporosity and a good performance as Na-ion negative electrode, ii) when KOH activation is done after complete carbonization it is mainly increasing the accessibility of the initial bulk microporosity, leading to a carbon with good performance as symmetric supercapacitor in aqueous electrolyte and iii) when carbonization and KOH activation are done simultaneously, a distinct pore structure is generated with a large amount of mesopores, suitable for symmetric supercapacitor in organic electrolyte. By combining SAXS, which is sensitive to bulk as well as surface porosity, and N 2 sorption which probes surface porosity, it has been possible to follow the intricate mechanism of microporosity development. Finally, it is believed that these results can be extrapolated to various biomass based precursors. [ABSTRACT FROM AUTHOR]

A 5 B 19 compounds ( A  = rare earth, B  = transition metal) are promising materials as negative electrodes in Ni- M H batteries. They are built from stacking along the c axis of one [ A 2 B 4 ] and three [ AB 5 ] subunits. The former one exhibits a good ability to absorb hydrogen, and the later one a good cycling stability, thus A 5 B 19 compounds are expected to benefit the large capacity and the cycling stability of both units. In this paper, Gd 5 Ni 19 and Sm 5 Ni 19 were synthesized and their hydrogen sorption properties were investigated using the Sieverts' method. Calendar corrosion was also studied and X-ray diffraction, magnetic measurements and thermal gravimetric analysis were made to determine the amount of corroded alloy. Electrochemical cycling was performed for both compounds. After 100 cycles, the electrochemical capacity of Gd 5 Ni 19 remains constant whereas the Sm 5 Ni 19 one decreases sharply after five cycles. This good capacity retention is linked to the low corrosion rate of Gd 5 Ni 19 which corrodes 3 times less than Sm 5 Ni 19 after 18 weeks in KOH. For Sm 5 Ni 19 , we conclude that the capacity decrease was due for 19% to crystallinity loss and 53% to corrosion. Finally, a comparison is made between A 5 Ni 19 and A 2 Ni 7 -type compounds and the structure influence on the hydrogenation and corrosion properties is discussed. [ABSTRACT FROM AUTHOR]

Layered Ni-rich Li[Ni 0.6 Mn 0.2 Co 0.2- x Sn x ]O 2 cathode active materials with x  = 0–0.05 are synthesized via a co-precipitation synthesis route and the effect of doping content on the structural behavior and electrochemical performance are investigated. All synthesized materials show a well-defined layered structure of the hexagonal α -NaFeO 2 phase (space group R 3 ¯ m ) analyzed by X-ray diffraction (XRD). Electrochemical Li-metal/cathode cell studies exhibit that a Sn-content of 1%–2% is beneficial regarding specific discharge capacity and cycle life (≥20%). Detailed electrochemical investigations of Li-metal and lithium ion cells with cathodes consisting of LiNi 0.6 Mn 0.2 Co 0.2 O 2 and LiNi 0.6 Mn 0.2 Co 0.18 Sn 0.02 O 2 are conducted. Post mortem analyses by means of ICP-OES and TXRF show beneficial effects of the Sn-doping with regard to a lower transition metal dissolution and a higher available Li content in the cathode active material. The thermal analyses (TGA, DSC, ARC) show a stabilizing effect of Sn-doping, which results from a lower mass loss and less heat evolution of the charged cathode active materials at elevated temperatures. [ABSTRACT FROM AUTHOR]

Methods for characterizing and optimizing the internal resistance of electrodes are crucial for achieving the simultaneous goals of high energy density and high power density in lithium-ion batteries. In this study we propose—and confirm the efficacy of—a method for electrode design optimization based on the construction of an internal resistance map , a visualization tool for minimizing electrode resistance. The construction of the map proceeds by identifying the three primary components of the electrode resistance—charge-transfer resistance, ionic resistance, and contact resistance—and elucidating the dependence of each component on electrode density and thickness. We fabricate electrode sheets of various densities and thicknesses and conduct electrode impedance spectroscopy (EIS) measurements to measure the dependence of internal resistance on density and thickness, which we characterize via empirical formulas incorporated into our internal resistance map. Using our map, we predict that the resistance per unit area of a nickel-cobalt- manganese (NCM) electrode attains its minimum value at thickness 70 μm and density 2.9 g cm −3 . We then further use the map to predict variations in IR drop for NCM electrodes of different densities, obtaining results in excellent agreement with experimental measurements. [ABSTRACT FROM AUTHOR]

A magnesium (Mg) battery in the combination with the redox active polymers possesses attractive electrochemical properties as a future battery technology. This concept has been demonstrated by using quinone based polymers and the non-nucleophilic electrolytes, while polyimides were rarely investigated. In this work, a naphthalene-hydrazine diimide polymer (NP) has been tested as a cathode material for Mg organic battery in two different electrolytes. Average discharge voltage of the Mg-NP battery is 1.70 V with Coulombic efficiency above 99% in the TEGDME/DOL based electrolyte. The electrochemical mechanism was studied by in operando ATR IR spectroscopy and confirmed by DFT calculation of the IR spectra. We confirmed redox activity of carbonyl moieties, which undergo reversible reduction to enolate anion. Moreover, in operando IR spectroscopy shows charge delocalization in the reduced form since none of the bonds has pure single/double bond character. [ABSTRACT FROM AUTHOR]

The high capacity of silicon motivates its use as anode material for Li-ion batteries. While such Si-based electrodes are typically processed from aqueous slurries, elemental silicon is highly susceptible to hydrolysis, yielding flammable hydrogen gas as a byproduct. This gassing can present numerous safety and quality concerns for scaling up of the production. In this study we describe a method to quantify the volume of gases generated using the Archimedes principle. We show that the gas volumes are affected by various factors, which include the characteristics of the electrode slurry and attributes (particle size, surface coatings) of the silicon powders. A catalytic effect on gas evolution is observed when a lithiated polycarboxylate binder is present in the solution. On the other hand, negligible gas generation is observed in electrode slurries containing the N- methyl-2-pyrrolidone (NMP) solvent, which could be considered as an alternative to the water-based processes presently under consideration. Our study can be used as a guide for the development of slurry mixtures that can mitigate the safety concerns associated with the silicon-electrode fabrication process. [ABSTRACT FROM AUTHOR]

Solid Oxide Fuel Cell (SOFC) lifetime prognosis is a substantial challenge for market introduction. This paper illustrates an accelerated testing approach based on an extensive quantity of experimental degradation data and suggests derivable degradation quantities for SOFC with focus on a large number of tests. The semi-empirical degradation models are based on the underlying physical degradation phenomena in the cell and are used for projection of temperature and steam impact on SOFC aging. Degradation tests performed at seven different temperatures and four different p(H 2 O) in the fuel gas are used for evaluation. The key contribution of this study is parameterization of the aging model by experimental data while physical simulations in literature usually lack such robust empirical foundation. [ABSTRACT FROM AUTHOR]