bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nb-Based Oxides As High Power Negative Electrode Materials
Authors: Crosnier Olivier , Le Calvez Etienne , Dupre Nicolas , Dunn Bruce S. , Brousse Thierry 
Published: February 2024

Today, one of the main challenges of lithium-ion batteries is to have the ability to charge faster and to provide high power during longer periods, thus allowing a larger development of intermittent electric power sources [1]. The actual negative electrode materials (graphite and silicon mainly) cannot sustain such high rate capabilities. In this work, we are therefore investigated some materials of the plentiful family of niobium-based oxides. A presentation of old and interesting structures will be briefly reviewed. As an example, the case of KTiNbO5 will be discussed and proposed as efficient negative electrode materials for next generation of lithium ion batteries.
The layered KTiNbO5 with a two-dimensional framework represents a playground to produce a large range of closely related phases.[2] The protonated HTiNbO5 analogue is obtained by ion exchange in acidic solution and it preserves a layered structure with a smaller interlayer distance. After dehydration of HTiNbO5 at 400°C, the so-obtained Ti2Nb2O9 phase displays a 2D arrangement with empty channels unlike tunnels of H(K)TiNbO5.
In this work, all the synthesized phases were studied as negative electrode materials in lithium-ion batteries. Tested in 1M LiPF6 in EC/DMC between 1.0V and 3.0V vs Li/Li+, these phases have shown different electrochemical behaviors. When HTiNbO5 exhibits a typical plateau during the charge/discharge experiment corresponding to a biphasic phenomenon, lithiation of Ti2Nb2O9 is governed by a solid—solution mechanism. For a better understanding of the charge storage mechanism, we have combined electrochemical experiments with in situ XRD measurements. We have shown that multielectron redox and corner/edge sharing system of Ti/Nb octaedra are at the origin of an interesting capacity of more than 100 mAh.g-1 at a rate of 0.2 A.g-1. A good observed cyclability (< 500 cycles) is in accordance with in situ XRD results showing a reversible behavior of the structure during cycling. Another synthesis method, using Chimie Douce techniques, leads to nanoparticules for both HTiNbO5 and Ti2Nb2O9 and allows an increase of the electrochemical performance of these materials.

References :

[1] Choi, C. et al, Nature Rev. Mat. 5, 5-19 (2020).
[2] A. D. Wadsley, Acta Cryst. 623, 17-41 (1964).
Understanding the Thermal Stability of Li-Rich Disordered Rock-Salt Oxyfluorides
Authors: Sunariwal Neelam , Cabana Jordi 
Published: February 2024

Li-rich disordered rock-salt oxyfluorides (DRS) are a new class of cathode material with unprecedented electrochemical properties. [1,2] DRS materials have already gained popularity by showing high reversible discharge capacity by substituting oxygen (O) with fluorine (F). They are a possible candidate of cathode materials for future high-energy Li-ion batteries with high capacity. Although DRS materials are explored widely for their structure and electrochemical performance, very little is known about their thermal stability. DRS oxyfluorides can be synthesized via solid state and mechanochemical ball milling. [3-5] The solid-state synthesis method is limited because of less fluorine solubility than the mechanochemical ball milling method; however, mechanochemical ball milling produces metastable materials. Few reports utilized thermal treatment on DRS to obtain structural stability and better capacity retention than the pristine DRS. [5,6] The in-depth understanding of the inherent stability of the DRS materials on thermal treatment remains poorly understood. [7] To address this gap, we investigated the thermal stabilities of Li2MO2F stoichiometries with a variety of M (M= Mn, Ni, and Co) and defined the structural transformations at different temperatures, from changes in the local structure of the oxyfluoride to decomposition into other phases, using X-ray diffraction, NMR and X-ray absorption spectroscopy. In this presentation, we will show how thermal treatments affect chemical and structural features by utilizing unique spectral characteristics. Additionally, we will discuss a complete understanding of these thermally treated F-rich phases' better electrochemical performance and capacity retention as battery cathode materials.
References:

D. A. Kitchaev et al., Energy Environ. Sci., 11, 2159–2171 (2018).

D. Chen, J. Ahn, and G. Chen, ACS Energy Lett., 6, 1358–1376 (2021).

X. Xu et al., J. Electrochem. Soc., 168, 080521 (2021).

Y. S. Moghadam, A. E. Kharbachi, G. Melinte, T. Diemant, and M. Fichtner, J. Electrochem. Soc., 169, 120514 (2022).

I. Blumenhofer et al., ACS Mater. Au (2022) https://doi.org/10.1021/acsmaterialsau.2c00064.

J. Huang et al., Small Structures, 4, 2200343 (2023).

H. Ji et al., Chem. Mater., 31, 2431–2442 (2019).
Increasing Battery Performance with Ohmic Drop Compensation for an Electric Drone
Authors: Magne Tang Nicolas , Decaux Celine , Thivel Pierre Xavier , Lefrou Christine 
Published: February 2024

Lithium-ion batteries are now widely used in a wide variety of applications ranging from powering mobile equipment to electric vehicles (EV), through stationary electrical energy storage systems or the electrification of flying devices such as drones. The main reason for the rapid growth of this type of batteries in the market is their high specific energy (Wh/kg) and/or specific power density (W/kg) compared to older chemistries. In the case of drones, weight optimization requires that the battery not be oversized for the mission it must perform.. Moreover, batteries can be subjected to deep discharges and high currents during the mission. One of the phenomena that leads to a drop in energy at high power is the ohmic drop phenomenon. Thus a ohmic drop compensation method has been applied to the discharge of lithium batteries. In this study, four different types of NMC Li-ion batteries (18650 type) were compared; two cells typed "energy" and two cells typed "power". We have shown that the ohmic drop compensation method applied to the discharge is capable for one of the "energy" cells of greatly increasing its available capacity at high power: 21% at 4C.
A simplified electric Vertical Take-Off and Landing (e-VTOL) mission profile was applied to this energy cell. We have demonstrated, without a doubt, the interest of using this type of protocol in this case. This ohmic drop compensation method makes it possible either to extend the duration of the flight without increasing the embedded capacity of the battery (about 50% time as shown in figure 1), or to consider an emergency diversion scenario. Finally, a preliminary aging study was also carried out for this cell: the use of ohmic drop compensation has no effect on the decrease in low power performance during aging and a moderate impact on the performance at high power.

Figure 1
Improving Gas Diffusion Electrodes for Electrochemical CO2 Reduction: Influence of the Ionomer
Authors: Ubbenjans Vera , Bothe Jannik , Keller Robert , Wessling Matthias 
Published: February 2024

Electrochemical CO2 reduction is a promising way of harnessing greenhouse gas as an abundant resource for the production of value-added hydrocarbons. By employing copper as the catalyst, CO2 can be converted to multi-carbon compounds such as ethylene. Highly porous gas diffusion electrodes (GDEs) enable efficient contacting of gaseous CO2 and the electrolyte. Copper-coated GDEs are commonly manufactured by depositing a mixture of copper nanoparticles and ionomer on a gas diffusion layer. The ionomer not only acts as a binder, but also influences the GDE’s wetting behavior and can improve mass transport within the catalyst layer due to the combination of a hydrophobic PTFE-backbone and hydrophilic ion groups. Thus, optimizing the type and content of ionomer in the catalyst layer is of utmost importance.
In this study, we investigate how the composition of catalyst layers affects the faradaic efficiency (FE) toward ethylene during electrochemical CO2 reduction. For this purpose, we fabricate different GDEs with constant copper loading but varied ionomer content and type (Nafion, Sustainion). To assess the performance of the GDEs, we conduct electrolysis experiments in a flow cell (Flex-E-Cell) setup with KHCO3 as the catholyte. Preliminary screening experiments at up to 50 mA cm-2 reveal a strong effect of the Nafion/copper mass ratio (NCR) on the FE toward ethylene. Within the investigated range (NCRs of 0.1, 0.2, 0.3, 0.4 and 0.5), we identify a sweet spot at an NCR of approximately 0.4. We hypothesize that at higher NCRs negative effects, such as decreasing porosity and an increasingly acidic pH, outweigh the improved mass transport. To assess the performance of the different GDEs at industrially relevant conditions, we perform constant current experiments at ≥ 100 mA cm-2. Here, we corroborate the previously observed trend and find that increasing the NCR from 0.2 to 0.4 doubles the maximum observed FE toward ethylene. When replacing Nafion with an anion exchange ionomer such as Sustainion, the total FE toward carbon products remains nearly unchanged. However, the selectivity shifts from ethylene toward single-carbon species such as CO and formic acid. These results highlight that ionomers play a decisive role in hydrogen evolution mitigation and tuning of the product spectrum during electrochemical CO2 reduction.

Figure 1
Process Intensification of Electrodialysis through the Investigation and Elimination of Maldistribution
Authors: Ledingham Jack , Howse Jonathan , Campbell Alasdair , Tyndale-Biscoe Elliot , Sedransk Campbell Kyra 
Published: February 2024

Often, advancements in electrochemical engineering processes stem from improvements at the microscale and in fundamental understanding. However, there is often much insight to be gained from identifying engineering challenges associated with process operation. Electrodialysis (ED) is an emerging electro separation technology which utilises a stack of ion selective membranes and an electric field to drive salt transfer between streams. Industrial implementation and intensification of ED is currently hindered by operational efficiencies being far from ideal. In this work, we explore a system-wide approach to investigate operational inefficiencies resulting from maldistribution in the flow between ED channels.
Through computational fluid dynamics (CFD) simulations, it was shown that maldistribution is prevalent in ED. Further, a simplified analytical model demonstrated that the degree of maldistribution will be far more severe upon scale-up. In order to examine the effects of maldistribution on ED performance, transport models were built. These demonstrated that the limiting current density, and thus the maximum salt flux, was reduced by as much as 23% for a standard lab-scale stack. This will be much more significant upon scaleup, and therefore, overcoming maldistribution in ED can have significant benefits for process intensification. Validation of this was conducted through particle image velocimetry (PIV) and desalination experiments.
A glass cell was constructed for PIV experiments with an identical geometry to that used for CFD simulations. A camera and telecentric lens was focussed on the channel centreline, and red and blue LEDs were sequentially pulsed. This light was scattered off particles in water flowing through the cell and collected by a single exposure image. The particle velocities were calculated from the superimposed red and blue images and a flow field was constructed. The experimentally determined flow field had excellent agreement with that found from CFD simulations, validating the existence of maldistribution in ED.
Desalination experiments were conducted on a PC64004 ED stack operating in a steady state mode. The degree of maldistribution was independently altered by changing the flow rate while ensuring that the overall salt convective flux was constant. The LCD was subsequently measured by collecting current-voltage curves. results showed excellent consistency with the transport model, thereby validating the relationship between increased maldistribution and a lower LCD.
In summary, in this work we have demonstrated and validated the presence of maldistribution in ED, as well as the significant detrimental effect it has on the upper limits of process intensification. Further, we have demonstrated the benefits of investigating system-wide inefficiencies in addition to fundamental phenomena. Future research will focus on developing methods to overcome maldistribution in ED.

Figure 1
Methods for Electrolyte Treatment and Hexavalent Chromium Reduction in Industrial Electrochemical Machining (ECM)
Authors: Jayasinghe Prabodha , Sneddon Scott , Gomez Gallegos Ares Argelia , Spicer Mark , De Silva Anjali K M 
Published: February 2024

Electrochemical Machining (ECM) is a metal removal process that operates on the principle of anodic dissolution. ECM has the ability to produce complex shapes in difficult-to-machine alloys with precision and excellent surface finish. However, since most of these alloys contain chromium, one of the major challenges to ECM’s wider utilisation in industry is how to eliminate the resulting hexavalent chromium (Cr+6) from the spent electrolyte. This paper presents methods for controlling the Cr+6 level to within the permitted guidelines for an industry application of ECM, and reducing it to trivalent chromium (Cr+3), to then precipitating it from the electrolyte solution,
The workpiece material – Triboloy (Co; Mo; Cr alloy) has hitherto not been machined by ECM and hence no literature exists on how to treat the by-products generated. This research involves experimental analysis of various Cr+6 to Cr+3 chemical reduction methods for ECM of Tribaloy in sodium nitrate electrolyte, using spent electrolyte samples. The reduction in Cr+6 is assessed over time. It was observed that the concentration of Cr+6 decreased within a span of two minutes. Subsequently, the solution pH level was increased by the addition of an alkali to precipitate the Cr+3 ions, which then can be filtered out from the solution. The optimum solution for hexavalent chromium is thus implemented in the industrial electrolyte system for successfully machining the Tribaloy component.
Electrochemical Degradation of Toluene Using TiO2 Nanotubes
Authors: Bolaños-Romero Karla Verónica , Sandoval-González Antonia , Oza Goldie , Manriquez Juan , Bustos Erika 
Published: February 2024

Toluene is a solvent widely used to produce paints, thinners, varnishes, and adhesives, as well as an octane rating improvement additive in gasoline. This compound can, unfortunately, be released into the environment in car exhaust fumes or when products containing toluene are used. Continuous exposure at high levels can cause permanent brain damage in animals. TiO2 nanotubes (TiO2,nt) increase the surface/volume ratio, as well as efficient electron transport, in the metallic substrate of Ti, enhancing the electrochemical degradation of organic compounds such as toluene.
An anodizing procedure has been performed to synthesize TiO2 in the present work. The team varied two anodizing operating conditions: potential (10, 20, 30, 40, and 50 V) and cathode material (titanium, Ti, and stainless-steel, SS) to achieve desirable results. The synthesized electrodes were characterized by Raman spectroscopy to identify the different crystallographic phases. We identified the presence of the three typical phases of TiO2 (anatase, rutile, and brookite), mainly in the synthesized electrodes at 30 V (using Ti and SS as the cathode). More significant intensity signals were observed than those corresponding to the anatase and rutile phases. Additionally, the different electrodes were analyzed by scanning electron microscopy with microanalysis (SEM-EDX) to identify the external morphology and validate their chemical composition. The toluene was hydrolyzed in ethanol with the different synthesized electrodes (Ci = 1.0 ppm, E = 2.0 V, t = 180 min, n = 150 rpm, cathode = Ti or SS). Toluene removal was monitored by gas chromatography with detector BID (CG-BID). Results indicate that the electrodes synthesized at 30 V show the highest removal efficiencies in a minimal time. The TiO2,nt|Ti synthesized using the TiO2,nt|Ti ||Ti configuration showed a toluene removal of 94.53 % in 12 min. In contrast, for the TiO2,nt|Ti synthesized using the TiO2,nt|Ti||SS configuration showed a 100 % toluene removal achieved in 6 min.
In conclusion, the best result for synthesizing the TiO2,nt|Ti reactive nanotube-rich surface was the configuration using stainless steel as the cathode (TiO2,nt|Ti||SS), applying a potential of 30 V during the 15 min anodizing treatment. This modified surface showed the highest toluene removal efficiency, 100 %, at 6 min when this VOC was dissolved in ethanol with 0.1 M KCl as the supporting electrolyte. This result is due to the anatase and rutile phases of TiO2, as verified with Raman spectroscopy. The corresponding stoichiometric relationship of two atoms of oxygen and one atom of titanium in the TiO2 nano-tubes when analyzed using SEM-EDX. After the electrolysis of toluene, the anatase phase was lost.
Fast and Durable Lithium Storage Enabled By Tuning Entropy in Wadsley-Roth Phase Titanium Niobium Oxides
Authors: Zheng Jie , Xia Rui , Yaqoob Najma , Kaghazchi Payam , ten Elshof Johan E. , Huijben Mark 
Published: February 2024

To date, Wadsley−Roth phase materials are one of the most promising intercalation-type hosts for fast lithium transport because of the unique crystalline diffusion channels. However, the volume expansion as well as sluggish ion/electron transport kinetics retards its application in grid scale. In recent years, various strategies have been suggested to further improve the overall performance of micro-sized Wadsley-Roth phase materials, such as oxygen vacancy creation or cation substitution.
Lately, entropy tuning has received considerable interest due to the favorable entropy-dominated phase-stabilization and ionic conductivity boosting effects.[1,2] However, it has only been applied in a few materials and the understanding of its function is still limited. It has been suggested that entropy-stabilized Wadsley−Roth shear phases with a more ordered structure would be stable upon electrochemical lithium (de-)insertion without a phase transition, while a more disordered structure would compromise the stability of the active material.[3] Therefore, suitable entropy tuning in entropy-stabilized Wadsley−Roth phase materials remains challenging and detailed knowledge about its effect on crystal structure and lithium storage is still lacking.
Here, we have successfully realized entropy-stabilized Wadsley-Roth phase Fe0.4Ti1.6Nb10O28.8 (FTNO) in which the increased entropy, due to iron substitution, leads to a reduced grain size, and therefore, a shortened Li+ diffusion channel length.[4] Secondly, the diffusion coefficient and the reaction rate constant are enhanced leading to a reduced overpotential and an improved rate performance. Benefiting from this, the micro-sized FTNO electrode exhibits an enhanced rate ability of 73.7 mAh·g-1 at 50 C as compared to 37.9 mAh·g-1 for its TNO counterpart. Thirdly, the increased entropy results in an extended cycling durability of FTNO electrode which can deliver a specific capacity of 130.0 mAh g-1 after 6000 cycles at high rate of 10 C. Operando XRD analysis demonstrates a suppression of the a-axis deformation during the first stage of the lithiation process. The mechanism is revealed by DFT calculations and found that Fe-O bond lengths undergo less changes than Ti-O during lithiation. Finally, the potential practical application of FTNO anodes has been demonstrated by successfully constructing fast charging and stable LiFePO4‖FTNO full cells.
Our results demonstrate the effectiveness of tuning entropy by iron substitution to stabilize the Wadsley-Roth phase with fast charging ability, which can be extended to other intercalation electrodes for enhanced battery applications.
[1] Y. Zeng et al., Science
2022, 378, 1320-1324.
[2] R. Zhang et al., Nature
2022, 610, 67-73.
[3] A. A. Voskanyan et al., Chem.
Mater.
2020, 32, 5301-5308
[4] J. Zheng et al., Small, smll.202301967R1, accepted.
Characterization of Nanostructured Tin Oxide Anodes Obtained By Electrolytic Oxidation for High-Energy Lithium-Ion Batteries
Authors: Lohrberg Oliver , Weiser Mathias , Heubner Christian , Michaelis Alexander 
Published: February 2024

In recent years, the growing electric vehicle market has increased the need for cost efficient and high energy materials for batteries drastically. Tin and tin oxide materials bear great potential as anode materials for Li-Ion batteries due to low cost and high theoretical capacity. Nevertheless, the development of commercial tin anodes has so far been hindered due to several drawbacks related to high volume expansion during operation leading to fast cell degradation. To circumvent these issues, nanostructured electrodes can be applied to mitigate volume changes. Typically, the production process of such electrodes is challenging, leading to high cost and issues in terms of scalability. Electrochemical processes, such as the electrolytic oxidation of tin, has been found a promising alternative to fabricate nanostructured electrodes. The additive-free tin oxide anodes obtained from this process exhibit high gravimetric and volumetric capacity, excellent rate capability as well as promising cycle life. The morphology and microstructure have high impact on the rate capability and cycling stability of tin oxide anodes. Since structural properties can be precisely adjusted by controlling the electrochemical oxidation process, a deeper understanding of the structure-property relationship is needed to optimize the production process and pave the way for commercialization.
Herein an in-depth characterization of nanostructured tin oxide anodes formed by electrochemical oxidation is presented. The rate capability and the cycling stability are investigated by means of electrochemical measurements in battery cells. Operando electrochemical dilatometry is used to investigate the thickness change of the anodes during cycling (cell breathing). In-situ XRD measurements are applied to elucidate the reaction mechanism. The anodes are carefully analyzed by SEM/EDS at different state of lithiation to understand the impact of volume changes on the inner porosity and morphology. Finally, the cycling stability of tin oxide anodes is improved by applying an electrochemical prelithiation step. Therefore, the impact of different prelithiation regimes on the cycling stability is evaluated in full cells. The results contribute to the understanding of electrochemical behavior of nanostructured tin oxide anodes and the derivation of optimal design criteria adjusted by electrochemical surface engineering.