Types Of Anodes Research Articles

Potassium storage behavior and low-temperature performance of typical carbon anodes in potassium-ion hybrid capacitors enabled by Co-intercalation graphite chemistry

Carbon materials are widely explored as anodes for potassium-ion storage, yet the slow K+ desolvation process in electrolyte at low temperatures presents a kinetic limitation that impedes reliable operation in specific conditions. In this work, we systematically investigate the potassium storage behavior of four typical carbon materials—graphite, hard carbon, activated carbon, and graphene—in a 1 M KFSI-Diglyme electrolyte, highlighting a co-intercalation approach that significantly reduces the desolvation energy barrier. The formation of ternary graphite intercalation compounds (t-GICs) through co-intercalation in graphite introduces weak interlayer interactions between the graphite layers and solvated K+, which accelerate K+ diffusion in the anode, thereby enhancing reaction kinetics. This unique mechanism enables the graphite anode to deliver remarkable rate performance (98 mAh g−1 at 0.05 A g−1 and 76 mAh g−1 at 1 A g−1) even at −20 °C. Furthermore, potassium-ion hybrid capacitors (PICs) using the graphite anode achieve impressive cycling stability, with 88 % capacity retention after 2000 cycles at 2 A g−1 and a high power density of 11.1 kW kg−1 (57 Wh kg−1) at −20 °C. These findings provide key insights into the design of robust potassium-ion storage devices capable of sustaining high performance in low-temperature environments.

High Performance Li-Ion Batteries Using Binder-Free Anodes

Li-ion batteries have polymeric binder in their electrodes resulting in high internal resistance and hence long charge times and compromised product lifetime. We previously developed Li-ion batteries utilizing binder-free NMC cathodes containing carbon nanotube (CNT). In this work, we extend the ‘binder-free’concept to two types of battery anodes - graphite and lithium titanate (LTO) anodes. Our proprietary processing of CNT into viscous organic or water-based slurry without surfactant or dispersant eliminates the need for organic binder and carbon black additives in both cathode and anode electrodes. To formulate the binder-free anodes, our processed CNT slurry was mixed with a target quantity of either battery-grade graphite or LTO in IPA solvent using a conventional planetary mixer. The IPA-based binder-free anode mixes were coated onto either Cu foil (graphite) or Al foil (LTO) using a commercial slot-die coater, resulting in uniform coatings after drying which did not exhibit any signs of flaking off or delamination from the respective current collector foils. LiB pouch cells rated at 1.5 Ah and 3 Ah were subsequently assembled containing NMC cathode paired with both types of binder-free anodes. LiB cells with binder-free graphitic anode exhibit very low impedance of 5.2 x 10-2 mΩ/cm2, or >35 % reduction in impedance compared to conventional LiB cell with binder containing graphitic anode, while LiB cells with binder-free LTO anode showed >75 % reduction in impedance compared to LiB cell with binder containing LTO anode. Moreover, the LiB cells with binder-free anodes exhibit superior high-rate capability compared to their counterpart cells containing electrodes with polymeric binder. The LiB pouch cells were tested for fast discharge rate performance at 10C. LiB cells with binder-free graphitic anode display >2x higher specific capacity compared to the cell with binder, while cells with binder-free LTO show 8x higher capacity at 10C rate than conventional LiB cell with polymeric binder after high discharge rate testing. Figure 1

Experimental Investigation of Fast-Charging Protocols Derived from Physicochemical and Thermal Simulations Using 5.4 Ah Multilayer Pouch Cells with Silicon-Dominant Anodes over Aging

Fast-charging capability remains a main concern for consumers buying an electric vehicle as a sustainable transportation solution. For lithium-ion batteries with typical graphite anodes, lithium-plating and temperature limitations due to the electrolyte are the two main limitations for fast-charging. Silicon as next-generation anode active material promises faster charging times due to its higher averaged potential versus 0 V Li+/Li avoiding lithium plating,[1] especially if silicon is only partially lithiated.[2] Further advantages are the lower coating thickness and the lower ionic resistance for silicon-dominant anodes when compared to graphite anodes with the same areal capacity, also leading to better fast-charging capability.[1]In this study, a validated physicochemical Newman-type p2D model[3] for a 70 wt% microscale silicon||NCA cell is extended by a 3D thermal model to account for thermal limitations at high-currents for a 5.4 Ah multilayer pouch cell (MLP). The thermal model includes the MLP, compression pads, and the cell holder, while the tab temperature was measured for validation. Experimental and theoretical parameterization of the thermal model includes the heat capacity and the thermal conductivity.[4] The coupled thermal-physicochemical model is depicted in Figure 1 and was used to simulatively derive different fast-charging protocols for the following input parameters: different state-of-charge windows (SoC Start and SoC End), different electrochemical limitations as security buffers to prevent lithium plating (U Sec vs. 0 V Li+/Li), and different thermal limits as different maximal cell temperatures T Cell,max were simulated. The cell’s charging current I Cell was controlled according to four different charging phases: constant current (CC), constant anode potential (CAP), temperature-limited (TDER), and constant voltage (CV) are switched and the applied cell current is controlled based on the simulated anode potential U Anode or the simulated maximal cell temperature in the cell core T Cell,max. The resulting simulated cell voltage U Cell during fast-charging was then experimentally applied to 5.4 Ah multilayer pouch cells as a voltage trajectory, while the cell current I Cell followed according to the voltage trajectory and the cell impedance. In total, 12 MLPs were aged until 70% state of health (SoH) for 25% - 75% SoC for USec=140 mV and 170 mV as well as for 10%-70% for USec=140 mV. As fast-charging reference, charging at 2C was tested for 25%-75% SoC and all results are compared to our previous study[6] aging identical MLPs at C/2.In the electrochemical results, the capacity retention could be significantly improved by utilizing the SoC window from 25%-75% SoC compared to 100% SoC from our previous study[6]. At the beginning of life, fast-charging times of 10.2 (±0.3) min for 25%-75% SoC with USec=140 mV and 11.8 (±0.1) mins for 25%-75% SoC with USec=140 mV were achieved. Fast-charging simulations for 25%-75% SoC with USec=140 mV predicted a comparable fast-charging time of 11.2 mins. Comparing the different fast-charging profiles over aging, a similar capacity retention is experimentally measured hinting towards loss of lithium inventory being the main aging mechanism while no charging profile seems to be particularly harmful to the cells. Regarding fast-charging time over aging, an increase in charging time is measured since the cell resistance increases over aging leading to a decreased overpotential being released during fast-charging according to the voltage trajectory.The trade-off between protecting the MLPs over lifetime versus the increased charging time could be further investigated in future work by adjusting the voltage trajectory based on the SoH. Moreover, even more aggressive charging protocols could be tested to derive the physicochemical limitation U Sec, e.g., 0 V Li+/Li. Acknowledgments: S.F. gratefully acknowledges the financial support from the BMBF (Federal Ministry of Education and Research, Germany) under the auspices of the ExZellTUM III project (grant number 03XP0255). The authors want to thank the research battery production team of iwb at TUM for the multilayer pouch cell production. We also thank Wacker Chemie AG for providing the microscale silicon material (CLM 00001).

Investigating the Effect of Catalyst Configuration on the Performance of Silver-Based Membrane Electrode Assemblies for Electrochemical CO2 Reduction

As one of the most dominant greenhouse gases, CO2 plays a critical role in climate change. Electrochemical CO2 reduction (eCO2R) is a promising approach to mitigate this impact, as it is capable of converting the excess gas into valuable chemicals, especially concerning electrical energy storage from renewable sources at peak times. However, due to high overpotentials, the technology is still in a rather early stage of development and not yet feasible for economic implementation on industrial scale. One of these limitations results from the poor solubility of CO2 in water or commonly used aqueous electrolytes, leading to insufficient transport of the reactant gas to the cathode in classical H-cell setups. Therefore, gas diffusion electrodes (GDEs) are typically employed to reduce the according mass transport resistances [1]. Furthermore, ohmic resistances, among others caused by the electrolyte gaps in the system, contribute to overpotentials. To decrease these constraints, conducting CO2 reduction at membrane electrode assemblies (MEAs) is an interesting opportunity that has been gaining more and more attention in research throughout the past years. Exemplarily, fig. 1 shows that the elimination of only the catholyte compartment and thus implementation of an exchange MEA can already decrease the cell potential by more than 30 % at 2 kA m-2 in comparison to GDE [2] setup.Depending on the cathodic catalyst, there are various reaction routes of eCO2R, one of which aims to synthesize the target product carbon monoxide. This is possible e. g. at silver catalysts, providing high CO selectivity and hydrogen as the only byproduct [3]. The combination of these products, syngas, is an important feedstock for many chemical processes such as Fischer-Tropsch synthesis. Although the majority of studies regarding silver-based MEAs for eCO2R uses pure silver as a catalyst, the configuration of the material is varying: While we usually disperse a mix of powder and flakes to obtain our catalyst suspension, nanoparticles are more frequently used in literature [3-5]. Moreover, porous silver membranes [6, 7] or silver deposited from solutions such as AgNO3 [8] and various other structures have already been investigated. Anyways, when comparing the results yielded with the different configurations of silver (cf. fig. 1), it becomes clear that there is no obvious trend in which material generates the best performances. A closer look at the conditions of the corresponding experiments reveals that this is quite plausible, as there is, on the one hand, no uniform MEA manufacturing procedure: Not only are there deviations in the employed material form, but also the gas diffusion layer, ionomer and membrane as well as ink fabrication and processing. On the other hand, the electrochemical measurements are alternating between galvanostatic and potentiostatic methods with no constant active electrode area, let alone type of test cell or setup.Therefore, this study aims to investigate the influence of differing catalyst configuration used for MEAs while maintaining other parameters concerning manufacturing and characterization procedure. The base of all MEAs is a carbon-based gas diffusion layer of the same supplier and type. An anion exchange ionomer is chosen to enhance the mass transport of the reactants to the catalyst. Only the form of the catalyst, e. g. powder, nanoparticles or fixed structures, is varied. The catalyst and ionomer are attached to the gas diffusion layer which is then sandwiched with the membrane corresponding to the ionomer. Conducting galvanostatic step experiments in exchange MEA setup with a fixed type of anode, the performance of the resulting MEAs is evaluated. This way, important effects on parameters such as Faradaic efficiency for the target product and cell potential can be unraveled.Literature:[1] T. Burdyny, W. A. Smith, Energy Environ. Sci. 12 (5), 2019.[2] I. Moussallem et al., Chem. Eng. and Proc. 52 (2012).[3] Y. Hori et al., Chem. Lett. 14 (11), 1985.[4] Z. Liu et al., J. Electrochem. Soc. 165 (15), 2018.[5] R. B. Kutz et al., Energy Technol. 5 (6), 2017.[6] Y. C. Li et al., ACS Energy Lett. 1 (6), 2016.[7] G. O. Larrazábal et al., ACS Appl. Mater. Interfaces 11 (44), 2019.[8] W. H. Lee et al., J. Mater. Chem. 9 (29), 2021.[9] Y. Hori et al., Electrochim. Acta 48 (18), 2003. Figure 1

Enhanced Electrochemical Performances of Silicon Based Anodes By Carbon-Coated Copper Current Collectors: Towards Effective Strategy for High-Capacity Lithium Ion Batteries

Silicon, despite having a higher theoretical capacity and a lower operating voltage range compared to graphite, which is a typical anode material for lithium-ion batteries (LIBs), is gaining attention as the next-generation anode material for LIBs. However, due to its significant volume expansion from lithium-ion insertion/extraction, lower electrical conductivity compared to graphite, and poor bonding strength between active materials and adhesion to the current collector, it has not been widely adopted as the main anode material in LIBs. Numerous studies have been conducted to enhance the performance of silicon anodes. Research aimed at controlling the size of silicon has shown that electrode pulverization can be mitigated, reducing the incidence of electrode cracks or pulverization. To improve the electrical conductivity of silicon, methods such as coating the silicon surface with carbon or using highly conductive materials like graphene and carbon nanotubes (CNT) have been explored. The application of binders that can form crosslinking networks, such as Poly (acrylic acid) (PAA) or alginate, has been shown to enhance the bonding strength between active materials and improve lifespan characteristics. Delamination of electrodes from the current collector during repeated charging/discharging is also a factor that shortens the lifespan of silicon anodes. However, research on the adhesion between the current collector and the silicon electrode has been limited. Most studies have increased cohesiveness between the anode active material and the current collector by coating conductive carbon on copper foil. Using spherical conductive materials can cause point bonding between the anode active material and the current collector, potentially providing insufficient pathways for electron movement. Alternatively, using carbon rods of several millimeters can increase the thickness of the current collector, posing a problem. In this study, a carbon-coated Cu foil was fabricated to improve the mechanical adhesion, interfacial resistance and electrochemical properties of the silicon anode. A carbon paste was prepared by mixing carbon fibers and a resin-based binder in a solution, and a carbon layer was coated on the copper foil using the doctor blade method. The morphology of the carbon-coated Cu foil was observed using Scanning Electron Microscopy (SEM). The optimal carbon-binder formulation and thin film uniform-coating method are crucial factors for the effective under-layer coated current collector. The enhanced mechanical adhesion and surface roughness with proper corrugation reveal high electrochemical performances of silicon-based anodes. Specifically, the application of the carbon-coated Cu foil resulted in reduced interfacial resistance and improved adhesion between the current collector and the electrode. The carbon fibers coated on the current collector facilitated faster electron transport, which not only increased capacity but also improved lifespan characteristics. Fast charging performance were also enhanced, and it was evident that close contact and improved electron conductivity between the current collector and the anode electrode significantly enhanced the characteristics of the silicon electrode.

Fabrications of Graphene Oxide and Silver Nanowire Hybrid Nanocomposites for Li-Metal Anodes with Dendrite Suppression

Lithium (Li) metal is the most promising anode material for Li-metal batteries due to its high theoretical capacity (3,860 mAh g-1) and low electrochemical potential (-3.04 V vs. the standard hydrogen electrode). However, many of previously studies for Li-metal batteries utilized a relatively thick ~ 50 μm Li metal foils, which lowers overall energy densities of the cells. Therefore, there have been growing research to reduce the thickness of the Li-metal anode to improve the energy density of batteries. Typical anode current collector of a copper foil show low affinity of Li metals with great initial deposition overpotentials when Li-metals are eletrodeposited. Such lithiophobicity accelerate the problems of Li dendritic growth with reduction in cycle life, which has been critical problems in practical applications of pristine Cu current collectors for Li-metal batteries. Therefore, various types of surface modification methods have been reported so far, such as coatings of carbon materials such as GO or metal-based materials such as Ag, Au. However, only carbon or metal modifications have been suffering from the relatively low lithiophilicity of the carbons and pulverizations of metals during cyclings by alloying and dealloying with Li-metals, respectively. Carbon and metal hybrid composites were also studied to mitigate these problems, but there still large rooms for further improvements showing unstable cycle performances at high C-rates.Herein, we report the fabrication of lithiophilic graphene oxide (GO) and silver nanowire (AgNW) nanocomposite anodes by Layer-by-Layer (LbL) assembly methods for uniform Li depositions. GO provides a fast Li ion movement channel with high ionic conductivity, and AgNW shows low nucleation overpotential behavior due to the formation of an alloy with Li. Therefore, we alternately stack these two materials using the LbL assembly method to induce a synergistic effect of their advantages. The resulting GO and AgNW nanocomposite films show uniformly deposited morphology after Li depositions and low nucleation overpotential compared to copper foils when pre-deposited at capacity of 4 mAh cm-2. The symmetric cells with the GO-AgNW composite electrodes with 4 mAh cm-2 of Li pre-depositions show stable behavior for 400 cycles with an overpotential of 10 mV at 1 mA cm-2 and 1 mAh cm-2. In addition, the full cells using LFP cathode materials operate more than 400 cycles at 1 C-rate and 200 cycles even at high 3 C-rate, showing longer cycle life and capacity retention than copper foil. These LbL self-assembled anodes provides a facile route to prepare lithiophillic anode coatings that can be advantageous for the preparations of high energy density Li-metal batteries.

In-Situ Neutron Depth Profiling Studies (Measurements and Simulations) to Characterize the Surface of Silicon Anodes and Complementary Neutron Techniques for in-Situ and Operando Characterization

In-situ methods for characterizing electrochemical systems are becoming increasingly important to understand the mechanism of lithiation and delithiation processes. The characterization of surfaces that have been under electrochemical influence is of great interest because many electrochemical processes originate here and are therefore crucial for cell performance. Pure silicon anodes with their large volume expansion, which leads to a short service life, can be modified at WACKER company by partial lithiation of microscale silicon particles [1]. Such anode types promise higher specific capacity. Neutron depth profiling (NDP) is a very well suitable technique to study the Li quantity with depth dependence on the first micrometers. The NDP method uses the capture reaction of Li atoms and neutrons with subsequent decay into ions of well-defined energies. The depth at which ions are created in the material is defined from their energy loss through the material to the detector with an accuracy of tens of nanometers [2, 3]. After formation different lithiation stages of SiG anodes are presented and compared with simulations. The lithiation process involving SEI formation, electrode swelling and phase transformation from crystalline to amorphous is presented. In the second part, a brief overview of other neutron techniques for in-situ and operando characterization of individual battery components or entire cells is given [4].

Analytical and numerical models for impedance of a button SOFC anode

We report a physics-based model for the anode impedance of a button-type anode-supported SOFC. The model includes ion and electron charge conservation equations and a Fick’s diffusion transport equation for hydrogen in the anode support layer. In the limit of small overpotentials, an analytical solution for the anode impedance is derived. For typical SOFC anode parameters, this solution is valid from open–circuit voltage (OCV) up to the cell current density of about 5 mA cm−2. Fast least-squares fitting of the model impedance to an experimental spectrum measured at OCV is demonstrated and the resulting fitting parameters are compared with literature data. A high-current numerical version of the model is also suitable for fast fitting of experimental impedance spectra.

Towards Sustainable Sulfide‐Based All‐Solid‐State‐Batteries: An Experimental Investigation of the Challenges and Opportunities Using Solid Electrolyte Free Silicon Anodes

AbstractSilicon is one of the most promising anode active materials for future high–energy lithium‐ion‐batteries (LIB). Due to limitations related to volume changes during de–/lithiation, implementation of this material in commonly used liquid electrolyte‐based LIB needs to be accompanied by material enhancement strategies such as particle structure engineering. In this work, we showcase the possibility to utilize pure silicon as anode active material in a sulfide electrolyte‐based all‐solid‐state battery (ASSB) using a thin separator layer and LiNi0.6Mn0.2Co0.2O2 cathode. We investigate the integration of both solid electrolyte blended anodes and solid electrolyte free anodes and explore the usage of non‐toxic and economically viable solvents suitable for standard atmospheric conditions for the latter. To give an insight into the microstructural changes as well as the lithiation path inside the anode soft X‐ray emission and X‐ray photoelectron spectroscopy were performed after the initial lithiation. Using standard electrochemical analysis methods like galvanostatic cycling and impedance spectroscopy, we demonstrate that both anode types exhibit commendable performance as structural distinctions between two‐dimensional and three‐dimensional interfaces became evident only at high charge rates (8 C).

An efficient state-of-health estimation method for lithium-ion batteries based on feature-importance ranking strategy and hybrid kernel extreme learning machine algorithm

The safe and reliable operation of battery systems depends critically on accurately and dependably estimating the state of health (SOH) of lithium-ion batteries (LIBs). However, accurate prediction of SOH still needs improvement due to the complex battery aging mechanism. This paper introduces a hybrid kernel extremum learning machine (HKELM) for estimating battery SOH. To improve estimation accuracy, we enhance the standard dung beetle optimization algorithm (DBO) with a new initialized population, adaptive weights method, and improved population diversification. We then use the enhanced IDBO algorithm to optimize the parameters of HKELM. This study examines two distinct anode types of LIBs from NASA and Oxford datasets. Fifty significant features are extracted from charging voltage, current, temperature, and incremental capacity (IC) curves. The importance indices of these features are then computed using statistical analyses, including Pearson's correlation coefficient and Spearman's rank correlation coefficient, followed by optimal ranking. The optimal number of final features is determined by comparing various combinations of high-level features, thus reducing model complexity and improving estimation accuracy. This paper proposes the IDBO-HKELM algorithm for SOH estimation. Compared to other methods, the algorithm shows superior estimation performance and anti-interference capability. Both B0007 and Cell8 estimate SOH with MAE < 0.15, RMSE <0.2, and R2 > 99.9 %. Experimental results demonstrate the robustness of the proposed method, achieving accurate and noise-immune SOH estimation.

Tuning the electrochemical performance of a biphenylene coated metal as the anode for K+-ion batteries

The researchers employed density functional theory (DFT) computations to assess suitability of BP-biphenylene (b-BP) monolayers for application in potassium-ion battery systems. In their evaluations, the researchers considered various factors, like adsorption energy (Ead) of the b-BP monolayer with adsorbed potassium adatoms, in addition to diffusion energy barrier (Ebar) and storage capacity and of potassium ions on this surface. The results indicated that the b-BP monolayer has significantly higher potassium-ion storage capacities, reaching 1026 mAh/g, compared to typical graphite anodes and other carbon materials. The Ebar for potassium ions on the b-BP monolayer was determined to be 0.22 eV. Furthermore, anticipated open-circuit voltage (OCV) values for this material were found to lie within acceptable range of 0.25–1.2 V, making it suitable for use as an anode. These research findings underscore the potential of the b-BP monolayer as an appropriate anode material for potassium-ion battery (KIBs) applications.

Electrospun Nanofiber Catalyst Support for Polymer Electrolyte Membrane Fuel Cells

Increased energy demand and environmental concerns are driving the search for cleaner, more efficient power generation. Fuel cells (FCs) offer a solution by converting chemical energy from fuel and oxidant directly into electricity with high efficiency (40-70%) and zero carbon emissions. Enhancing the performance and durability of polymer electrolyte membrane fuel cells (PEMFC) while reducing costs remains a significant challenge. The current planar FC design presents various issues, including high costs and weight due to metal or graphite bipolar plates, high-pressure drop-in reactant gas diffusion channels, reactant gas transport losses in the agglomerate-type catalyst layers, water flooding, to name just a few. Exploring novel biomimetic designs may offer solutions to these challenges.This research is inspired by vascular plant structures to improve mass transport and efficiency. The cathode uses carbon nanofibers (CNF) made via electrospinning, with Pt nanorod catalyst on the surface in an open electrode layout. This CNF-type cathode was used to create a membrane electrode assembly (MEA), using a commercial membrane and typical anode. A number of parameters were varied, including overall Pt loading, Pt concentration on the fibers, design with and without gas diffusion layer, using CNF mat. The MEAs were tested to establish links between structure, properties, and performance. Performance was evaluated through polarization curves and electrochemical impedance spectroscopy, while beginning of test and end of test structure was investigated using microscopy. CNF-based MEAs achieved a higher current density compared to the commercial MEA at lower Pt loading. This suggests that reduced loading still maintained acceptable Pt utilization, reducing the Pt amount in the MEA. In summary, the CNF catalyst support displayed improved durability, mass transport, Pt utilization, and efficiency thanks to its porous mesh structure.

Operando Stress Evolution in Hard Carbon Anodes – Insight into the Mechanical Degradation Induced Failure Mode in Rechargeable Sodium Ion Batteries

Microstructural instabilities in electrodes arising from cycling induced stress is a primary failure mode in rechargeable batteries. Therefore, a quantitative knowledge of the cycling induced stress evolution in rechargeable battery electrodes is important for understanding the electrode microstructural instabilities during cycling that can potentially inform the electrode design to prolong battery cycle life. The cycling induced stress in electrodes typically arises from the volume changes associated with insertion/extraction of the electroactive species in the electrode matrix. For example, operando measurement of lithiation-delithiation induced stress in graphite electrodes that typically show 10% volume change has previously resulted in useful information that correlates well with the lithiation-delithiation mechanism in graphite anodes1. The size of the shuttling-electroactive species can be taken as an indicator of the cycling induced stress magnitude that drives the electrode microstructural instabilities. In this regard, quantification of the cycling induced stress in rechargeable Na-ion battery electrodes is warranted for understanding mechanical degradation induced failure modes owing to the larger size of the electroactive species, i.e., Na ions (vs. Li-ion).Hard carbons as potential anodes in rechargeable sodium ion batteries has gained considerable attention in the recent past due to their superior Na-ion storage capability (vs. graphite that is a canonical anode in rechargeable lithium-ion batteries). However, hard carbon anodes typically show significant capacity fade that can potentially arise from cycling induced mechanical degradation of the anodes. Operando stress measurements coupled with comprehensive electrode microstructural characterization will provide valuable insights in this context. Here we report on the operando stress evolution in hard carbon anodes in rechargeable sodium ion batteries as probed by Multiple Optical-beam Sensing (MOS) technique that basically involves monitoring the spacings among a group of laser spot (Fig. 1). Preliminary measurements have shown that the stress correlates with the potential with a maximum around 12 MPa in compression during sodiation and tensile stress of ~ 2MPa during desodiation. Operando stress measurements are performed in hard carbon anodes in two different electrode configurations – typical composite anodes (with binder and conductive agents) and hard carbon thin film anodes (without binder and conductive agents). The thin film configuration is considered to evaluate intrinsic stress response in hard carbon anodes in absence of any secondary phase. A comparison of operando stress response in these two types of hard carbon anodes along with comprehensive electrode microstructural characterization will be presented. Additionally, attempts will be made to shed light on the current debate in the mechanism of sodium storage in hard carbon anodes by comparing operando stress response of hard carbons from multiple sources along with their structural characterization (Raman, XPS, surface area etc.). V. A. Sethuraman, N. Van Winkle, D. P. Abraham, A. F. Bower, and P. R. Guduru, Journal of Power Sources, 206, 334–342 (2012). Figure 1

Novel Cu(200)/Ti cathode for the enhancement of N2 selectivity in direct ammonia electrolysis: The controls of Cu cathode facet orientation

Direct electrochemical ammonia oxidation reaction (AOR) using NiCu-based anodes is effective in removing ammonia from wastewater. However, this type of anode frequently produces undesired byproducts NO3−. Here, we investigated three configurations of novel Cu/Ti cathodes (Cu(111)/Ti, Cu(200)/Ti, Cu(220)/Ti) coupled with Cu/Ni foam (Cu/NF) anode to enhance N2 selectivity (SN2) in a direct ammonia electrolysis cell. Cu(200)/Ti cathode improved SN2 from 35 % (bare Ti cathode) to 60 % and it achieved 10–15 % higher SN2 compared to Cu(111)/Ti and Cu(220)/Ti. The improvement of SN2 on Cu(200) facet was ascribed to the high nitrate electroreduction activity and its conversion to N2. In real wastewater, Cu/NF anode-Cu(200)/Ti cathode paired electrolysis system demonstrated its excellent capability of 88 % NH3 removal with 95 % SN2. Our electrolysis system was capable to maintain the residual NH3-N and the NO3-N below 8 mg L−1, meeting effluent discharge standards. Our findings highlighted the importance of the control of Cu cathode facet orientations for an efficient elimination of NO3– and improvement of N2 production during direct ammonia electrolysis.

Inhibiting dissolution strategy achieving high-performance sodium titanium phosphate hybrid anode in seawater-based dual-ion battery

Aqueous sodium-ion batteries (ASIBs) show great promise as candidates for large-scale energy storage. However, the potential of ASIB is impeded by the limited availability of suitable anode types and the occurrence of dissolution side reactions linked to hydrogen evolution. In this study, we addressed these challenges by developing a Bi-coating modified anode based on a sodium titanium phosphate (NTP)-carbon fibers (CFs) hybrid electrode (NTP-CFs/Bi). The Bi-coating effectively mitigates the localized enrichment of hydroxyl anion (OH–) near the NTP surface, thus addressing the dissolution issue. Notably, the Bi-coating not only restricts the local abundance of OH– to inhibit dissolution but also ensures a higher capacity compared with other NTP-based anodes. Consequently, the NTP-CFs/Bi anode demonstrates an impressive specific capacity of 216.8 mAh/g at 0.2 mV/s and maintains a 90.7 % capacity retention after 1000 cycles at 6.3 A/g. This achievement sets a new capacity record among NTP-based anodes for sodium storage. Furthermore, when paired with a cathode composed of hydroxy nickel oxide directly grown on Ni foam, we assembled a seawater-based cell exhibiting high energy and power densities, surpassing the most recently reported ASIBs. This groundbreaking work lays the foundation for a potential method to develop long-life NTP-based anodes.

State of the art on plasma-liquid route synthesis monometallic Au, bimetallic Au/Ag core–shell and alloy nanoparticles: Toxicological, сanalytical, antimicrobial activity for environmental control

Nanoparticles (Au monometallic, bimetallic structures Au-Ag alloy and Aucore – Agshell) were synthesized in aqueous solutions with traditional capping agent - sodium citrate, using a one-step (for monometalic and alloy structure) and two–step (for Aucore – Agshell NPs) liquid-phase anode type plasma process. The effects of parameters of synthesis: precursors concentration, the solution plasma process discharge time, molar contents Ag+/Au3+ for alloy NPs, and molar content of Ag+ for Au core NP to the characteristics of the synthesized NPs, including average size (the size distribution, polydispersity index), optical absorption properties ect.) were investigated. The synthesized nanoparticles have the following characteristics: Au NPs with λ=530–540 nm and d = 5–60 nm, the monometalic structure; Ag/Au with the λ=410–530 nm and d = 28–80 nm, bimatalic strucrure of alloy; NPs with significant blue-shift the λ=530→410 nm, depending the shell thickness (the thickness of the deposited Ag shells varied from ∼1–15 nm) and d = 21–35 nm for NPs core(Au)–shell(Ag). TEM images clearly confirm the effectiveness of a one- and two-step plasma-liquid treatment for the synthesis of monometallic Au NPs and the two different structures of the NPs (bimetallic structures Au-Ag alloy and Aucore@– Agshell). The effect of nanoparticle structure on antimicrobial and catalytic properties relative to their respective monometallic counterparts was demonstrated. Among the different investigated structure NPs only for bimetallic core−shell structured AucoreAgshell NPs was found strong synergistic effect for antimicrobial and catalytical activity.

Comparative study of the reduction techniques of Graphene Oxide for Zinc Ion hybrid Storage Application

The increasing demand for low cost and high energy storage devices has given rise to the hybrid supercapacitor device. To overcome the safety issues of the Lithium and Sodium-based devices Zinc ion hybrid supercapacitors (ZIHSCs) are a promising alternative. These devices amalgamate the energy density and power density requirements which makes them suitable for varied applications. The device construction comprises of a zinc anode, zinc-based electrolyte and capacitive type cathode material. Carbon based nanomaterials such as reduced graphene oxide (RGO) are predominantly used as potential cathodes. The strategies involved in obtaining RGO changes the structural characteristic of the samples. This study compares three different strategies such as Chemical reduction (c-RGO), Microwave reduction (m-RGO) and Solar reduction (s-RGO). It was observed that the employment of each these techniques render the change in the physical properties of the materials like number of defect, change in the surface are, porosity and in-situed developed functional group, especially oxygen species. These changes were analyzed thoroughly by various techniques like Raman, Fourier, X-ray diffraction and X-Ray photoelectron spectroscopy. The overall study reveals that solar reduction route shows enhanced surface area and porosity and decrease in defect concentration. Further due to this enhanced property in s-RGO the zinc ion storage capacitance of the fabricated ZIHSC was 200 F/g with a high cyclic stability of 5100 cycles at a current density of 10 A/g. The enhanced energy density thus obtained was 111 Wh/kg corresponding to a power density of 10 KW/kg.

Wastewater treatment, hydrogen and energy recovery using electrochemical advanced oxidation

Electrochemical advanced oxidation processes (EAOPs) offer several advantages over conventional Advanced Oxidation Processes (AOPs) such as UV/H2O2 and H2O2/O3. This includes the absence of chemical additives and ease of control. However, high energy consumption hampers the industrial application of EAOPs. Currently, the hydrogen generated at the cathode is vented and wasted, because of its low gas purity and difficulty in collecting it. But it also underscores an opportunity where the reactor design can be improved to facilitate the collection of high-purity hydrogen for energy savings. In our study, The EAOPs reactor was designed with a proton exchange membrane (PEM) for hydrogen generation. The hydrogen at the cathode chamber is then supplied to a fuel cell to generate electricity. The energy efficiency of the EAOPs-fuel cell system is evaluated through the wastewater treatment performance and energy saving that fuel cells achieve. To optimize the EAOPs-fuel cell system, various operational conditions, including different anode types, salt concentrations, and target organic compounds, were examined to optimize the system. Our experimental results indicate that the EAOPs-fuel cell system exhibits energy-efficient performance across various operational conditions. Notably, the highest energy efficiency and recovery ratio were achieved when operating at 3 V with boron-doped diamond (BDD) as the anode. Furthermore, we investigated the impact of mass transfer on the system's energy efficiency, considering both the initial organic concentration and flow velocity. This study provided valuable insights into combining the effect of EAOPs and hydrogen fuel cells, contributing to the understanding and optimizing the oxidation performance. It also contributes to developing sustainable and cost-effective advanced oxidation technologies with wide-ranging water treatment applications.

Dual-Carbon Phase-Encapsulated Prelithiated SiOx Microrod Anode for Lithium-Ion Batteries.

Among silicon-based anode family for Li-ion battery technology, SiOx, a nonstoichiometric silicon suboxide holds the potential for significant near-term commercial impact. In this context, this study mainly focuses on demonstrating an innovative SiOx@C anode design that adopts a pre-lithiation strategy based on in situ pyrolysis of Li-salt of silsesquioxane trisilanolate without the need for lithium metal or active lithium compounds and creates dual carbon encapsulation of SiOC nanodomains by simply one-step thermal treatment. This ingenious design ensures the pre-lithiation process and pre-lithiation material with high-environmental stability. Moreover, phenyl-rich organosiloxane clusters and polyacrylonitrile polymers are expected to serve as internal and external carbon source, respectively. The formation of an interpenetrating and continuous carbon matrix network would not only synergistically offer an improved electrochemical accessibility of active sites but also alleviate the volume expansion effect during cycling. As a result, this new type of anode delivered a high reversible capacity, remarkable cycle stability as well as excellent high-rate capability. In particular, the L2-SiOx@C material has a high initial coulomb efficiencof 80.4% and, after 500 cycles, a capacity retention as high as 97.5% at 0.5 A g-1 with a reversible specific capacity of 654.5mA h g-1.

The nano-sheet structure adjustment and long-term stability of Zn-doped NiO electrochromic films

NiO is a typical anode electrochromic material based on its excellent electrochemical performance. However excellent cycle stability has always been the most important goal pursued by researchers. This study successfully prepared the complex multi-channel self-assembled nanosheet structure of low concentration and different Zn content doped NiO films with outstanding cycle stability on FTO by the low-temperature hydrothermal method. This excellent cycle stability provides a basis for applying NiO as a complementary layer in electrochromic devices. Zn doping influences the surface microstructure and electrochromic properties of NiO films. It is worth noting that all samples show large modulation amplitude, high coloring efficiency, and fast response time at the wavelength of 550 nm. The samples doped with 1% Zn exhibited more outstanding electrochromic properties than the samples without Zn doping, including fast switching speed (6.4 s and 3.8 s), significantly high coloration efficiency (52.49 cm2·C−1), transmittance modulation (68.57 % at 550 nm), and especially outstanding cycle stability (99.47 % after 5000 cycles). Zn doping affects the microstructure of the film surface, which greatly improves the cycle stability of the film by combining doping and structure control. We consider that the 1 % Zn-doped sample has the best cyclic stability because of the lower interface barrier between the 1 % Zn-doped sample and the FTO, the Zn-doped film forms a complex multi-channel structure, and the coupling effect makes the sample more conducive to the charge entry and exit.