Dissolution Of Ions Research Articles

Feasibility of carbon dioxide uptake cementitious materials preparation by combining γ-C2S with red mud

To evaluate the feasibility of preparing a carbon-capture cementitious material by combining γ-C2S with red mud (RM), the physicochemical features of bulk red mud specimens with γ-C2S content of 20%, 40%, and 60% were investigated after carbonation curing. The carbonation mechanism was analyzed using x-ray diffraction (XRD), thermogravimetric-differential scanning calorimetric analysis (TG-DSC), mercury-pressure porosimetry (MIP), and scanning electron microscopy (SEM) techniques. The results show that the compressive strength of RM specimens containing 60% γ-C2S carbonized for 28 d can be increased by 180% compared with hydrated samples. The introduction of γ-C2S promotes the transformation of the carbonation products aragonite and vaterite to calcite, which is able to fill the pores, resulting in a decrease in the porosity of the samples and an increase in the strength. In addition, the expected CO2 uptake ability of RM powder is higher than the experimental results due to the precipitation of calcite on the surface of γ-C2S to form a dense layer, which hinders the dissolution of calcium ions and further diffusion of CO2 inside. A conceptual model is proposed to explore the mechanism of the influence of γ-C2S on the performance of RM. Such a study provides an alternative solution for the RM recycling and zero carbon cementitious material preparation.

A real time study of the coupled electrochemical and mechanical behaviors of the spinel cathodes in LIBs.

Spinel cathode materials have great application prospects in lithium batteries (LIBs) due to their characteristics of abundant raw materials, simple preparation processes, and cobalt-free nature. During the electrochemical cycles, the specific capacity of the electrodes decreases significantly due to the dissolution of excess metal ions and mechanical degradation, which hinder their further application and development. Here, a bending curvature measurement system (BCMS) was designed to simultaneously measure the mechanical properties of the spinel cathodes during the electrochemical reaction. Three types of cathodes were chosen as the working cathode, and the coupled mechanical and electrochemical properties were analyzed to understand their degradation mechanism. During cycling, a hysteresis loop is observed for the curvature, modulus, plain strain, and stress, where LiMn2O4 (LMO) has the largest loop for the mechanical response while the LiNi0.5Mn1.5O4@Al2O3 (LNMO@Al) one has the smallest loop. Besides, the changing trend of LNMO@Al is the smallest in multiple cycles and it shows the more stable mechanical properties. This study shows from in situ mechanical measurements that the mechanical properties can greatly affect the electrochemical performance of the cathodes. These findings could offer new insights into the understanding of the electrochemical performance degradation in the spinel cathodes and can help develop strategies to enhance the performance of LIBs.

All-element recovery and regeneration of mixed LiNixCoyMn1-x-yO2/LiFePO4 cathode materials by synergistic redox processes.

Given the rising lithium-ion battery retirement trend, there is a pressing need for a sustainable, cost-effective, versatile, and industrially viable positive active powder reprocessing method. The current treatment methods require significant amounts of acids, reducing agents, and other additives, resulting in increased treatment expenses and detrimental environmental consequences. This paper proposes a synergistic redox strategy, based on thermodynamic calculations of potential self-promoting reactions in mixed LFP/NCM systems, for the recovery of spent LFP and NCM batteries without the need for additional agents in a milder acidic atmosphere. In this cooperative redox strategy, the spontaneous extraction and oxidation of Fe2+ to Fe3+ took place within the acidic solution atmosphere encapsulating LFP. Simultaneously, NCM underwent further reduction, yielding Ni2+ and Fe2+, thereby enabling the proficient dissolution and segregation of lithium and transition metal ions. The leaching rate of lithium, nickel, cobalt and manganese was close to 100% when the reaction was carried out at 20 °C for 40 min. The final raw material was reprepared into a battery with a capacity of 168.8 mA h g-1 at 1C, and the cycle retention rate was 76.78% after 300 cycles. Regenerating FPO into LFP cathode material achieves closed-loop recycling of all elements and generates 12% higher profits compared to separate processes. Our method proposes a zero-additive battery recycling process and successfully explains the intrinsic redox process.

Моделирование процессов переноса с учетом химических взаимодействий в программном комплексе GeRa

The paper considers a transport model with geochemical couplings implemented in the GeRa software. It evaluates the scope of application typical for such models focused on the safety assessment of nuclear facilities. The paper presents a few typical case studies to demonstrate the accountability of different chemical processes: ion exchange, surface complexation, dissolution and mineral phase precipitation. It overviews some typical radionuclide transport problems with an account taken of sorption, as well as the one of concrete decalcification.

Enhancing the durability of Prussian white based sodium batteries through the lithium salt-mediated electrode interface

LiDFOB mitigates dendritic growth in Na||PW batteries and forms a low impedance LiF and B–O rich interface at the cathode, combating electrolyte erosion, metal ion dissolution, and irreversible phase transitions.

Effect of mechanical activation on hydration properties of natural volcanic rock towards partially replacing cement in composite cementitious materials

With the rapid increase in the consumption of various mineral admixtures, using regional distinctive raw materials to prepare cement mineral admixtures is an effective approach to achieve green and sustainable development. In this paper, the natural volcanic rocks (NVR) in Western Sichuan are mechanically activated at different times, subsequently, the ion dissolution characteristics of NVR powder at different activation times and the hydration mechanism of NVR powder composite cementitious material are studied. In a simulated alkaline environment of cementitious liquid phase, based on the dissolution behavior of Si4+, Al3+, and Ca2+ ions in NVR powder and the morphological analysis of NVR powder before and after dissolution, it is indicated that SiO2 and Al2O3 are the primary sources of reactivity in NVR powder and the reduction in particle size promotes the breakage of Si–O and Al–O bonds in NVR powder. Analysis of the hydration process, mineral composition of hydration products, and their microscopic morphology reveals that an appropriate amount (15 %) of NVR powder, after 45 min of mechanical activation, can promote the generation of hydration products and denser mortar structure, enhancing the strength of the composite cementitious material. Mainly attributed to the increased volcanic ash activity of NVR powder through mechanical activation, as well as the nucleation induction and filling effects of NVR powder. This study provides theoretical and technical supports for the efficient use of raw materials with regional characteristics to prepare mineral admixtures.

Effect of oxidizing agents on the treatment of a Colombian lead ore by alternative hydrometallurgical processes

The metallurgy of lead presents significant environmental and public health challenges due to its toxicity. This is why it has been necessary to develop hydrometallurgical processes as alternatives for obtaining metal with a more sustainable and environmentally safe approach. However, these processes may involve complex chemical reactions and the use of specific chemical reagents, which may require rigorous control and monitoring to ensure the efficiency of the process and the safety of the personnel involved. In this research, the recovery of lead from a Colombian mineral with low metal content was studied by hydrometallurgical processes in carboxylic media under ambient conditions. A preliminary chemical treatment was necessary to improve the metal extraction. For this purpose, two hydrometallurgical treatments were used: i) pneumatic agitation with ozone injection and ii) mechanical agitation with hydrogen peroxide dosing. The lead extractions from the pretreated ore were similar to those from the leach without pretreatment. This situation attributed the dissolution of the lead to the complexing effect of the carboxylic agent rather than to the effect of the pretreatments. The direct addition of peroxide to the citrate leach resulted in an extraction of 50% of the metal, an improvement of more than 30% over the leach without the addition of the oxidizing agent. The leaching of the ore with 0.5M citrate and pH 4.5 yielded a redox potential of 926 mV, which ensured the high activity of the electrons in the chemical reaction and therefore the lead ions dissolution.

GEOELECTRIC SIGNATURES FROM A LEACHATE PLUME MAPPED FROM A BASEMENT COMPLEX TERRAIN IN AKURE, NIGERIA

In this study, we investigated the implications of a leachate plume within an aquifer system, unravelling the intricate dynamics that govern contaminant transport and dispersion. An integrated approach of geophysical investigations is used to establish the impact of an open-waste disposal site around Aromed, in a part of Akure, in the Precambrian Basement Complex of Southwestern Nigeria. Investigations using eight (8) Vertical Electrical Sounding (VES) and Double-Dipole Resistivity Tomography (ERT) along two (2) traverses were conducted. The geoelectric interpretation and the inverted two-dimensional electrical resistivity tomography (ERT) images provided insights into the underlying geological composition, identifying three distinct units: the topsoil, the weathered column, and the fractured Basement/fresh Basement bedrock. The geoelectric tomography structures in the 2-D interpretation reveal that the dumpsite area exhibits low apparent resistivity estimated to be between 12 to 71 ohm-m in both the topsoil and the weathered column aquiferous zone. These values closely agree with results from the geoelectric sections, which range between 11 - 68 ohm-m, respectively. The relatively low apparent resistivity results are suggestive to be due to the presence of leachate’s chemical composition from the open waste disposal sites, which are suspected to be generated from the dissolution of ions of iron and other conductive minerals producing the leachate plume. The probable leachate depth of migration as revealed by the 2-D tomography structures varies from about <1 – > 14 m beneath the dumpsites. The leachate migration, which is structurally controlled, has a southward flow, majorly in the orientation with the observed structures. The subsurface depression-relief is also attributed to influence the direction of leachate flow. In conclusion, it is suggested that groundwater in the aquiferous zones in the vicinity of the dumpsites have entered a significant pollution level; hence water in the aquifer is not safe for consumption.

The photocatalyst with a strong internal electric field grown in situ on the surface of copper foam collaborates with peroxymonosulfate to enhance directional charge transfer and achieve ultra-fast Mn+/M(n+1)+ cycling

To address three pressing problems that limit the application of photocatalytic synergic peroxymonosulfate (PMS) technology, namely difficult reuse, low photogenerated carrier separation efficiency, and sluggish metallic ions redox cycle, we utilized an in-situ growth method to construct a vertical nanosheet heterojunction on the surface of copper foam (CF). This heterojunction is characterized by a strong internal electric field (IEF) that serves as both a “pump” for the rapid and efficient migration of electrons and a driving force for the activation of PMS by these electrons. In the CF@CCS@CO-3/7/Vis/PMS system, the photoelectrons generated by photocatalysis quickly replenish the high valence metals activated by PMS, allowing for highly efficient cycling of differently valenced metal ions and reducing the dissolution of high valence metal ions produced by PMS. As a result, close to 100 % of ciprofloxacin (CIP) was degraded within 60 min in the CF@CCS@CO-3/7/Vis/PMS system with a reaction rate constant k of 0.0621 min−1, which is about 3.22 times higher than that of the CF@CCS@CO-3/7/Vis system and 2.65 times higher than that of the CF@CCS@CO-3/7/PMS system. Moreover, the in-situ growth of active ingredients with vertical nanosheet structure on the CF surface can well maintain structure and reactivity in complex environments, allowing more than 10 cycles to be realized. The results of the free radical burst assay and EPR analysis indicated that SO4∙−, ∙O2− and h+ were the main reactive species involved in the catalytic process. Building upon CF@CCS@CO-3/7, we assembled a fixed-bed continuous treatment device that enables high mineralization flow treatment of pharmaceutical wastewater (after Secondary biological treatment).

Insight into Nb-sbustitution effects on Li1.17Mn0.57Ni0.24Nb0.02O2 cathode material for lithium-ion batteries application

Lithium-rich layered oxides (LLOs) have been intensively studied due to their high energy density, but still face the drawbacks such as capacity decay and voltage decay, and poor cycling stability. In this work, the Nb substituted Li1.17Mn0.57Ni0.24Nb0.02O2 (LMN-Nb) is successfully prepared, and the effects of Nb substitution on the microstructure, voltage attenuation, cycling stability and electrochemical kinetics are characterized and investigated compared with the host material Li1.17Mn0.58Ni0.25O2 (LMN). A proper amount of Nb substitution not only extends the interlayer spacing and increases conductivity of LMN-Nb, but also inhibits the release of lattice oxygen, the migration of transition metal ions into lithium layer and the dissolution of transition metal ions in the electrolyte. As a result, LMN-Nb exhibits significantly improved initial coulombic efficiency, specific capacity and excellent cycling stability (99.1 % remaining after 150 cycles at 2C rate). In addition, the LMN-Nb also shows good electrochemical performance in pouch-type cell (full cell). This results demonstrate that the strategy of using 4d/5d transition metals substitution to design high-performance LLOs is feasible in the following work.

Formation of lipid corona on Ag nanoparticles and its impact on Ag+ ion dissolution and aggregation of Ag nanoparticles against external stimuli

The application of lipid coated nanoparticles has been expanding in nanoscience over the past few years. Lipid corona formation is one of the novel ways for the lipid conjugation around the nanoparticles. Although several properties of nanoparticles and lipids are well reported in literature in last few years, the dependency of lipid corona formation on metallic core and surface ligands is poorly understood. The aggregation, surface oxidation and metal ions dissolution of nanoparticles limit their usefulness in various applications. Besides all the reported methods to overcome all of these limitations, lipid corona could be an alternative, feasible, and more efficient method. In the current manuscript, we investigate the interaction of aromatic amino acids (tyrosine and tryptophan) functionalized silver nanoparticles (Ag-Tyr and Ag-Trp NPs) with different surface charged and phase states lipid vesicles and compare them with the reported amino acid functionalized gold nanoparticles (Au-AA NPs). The effectiveness of different zwitterionic and positively charged lipid coated Ag-Tyr and Ag-Trp NPs to prevent the aggregation and Ag+ ion dissolution of Ag NPs against different external stimuli (acidic pH, high NaCl concentration, and freeze-thaw cycles) are investigated. Our results reveal that surface ligands around the NPs play crucial role for lipid corona formation irrespective of the metallic core of NPs. Although all the lipid coated Ag NPs exhibit greater stability against external stimuli than native Ag NPs, zwitterionic lipid coated Ag NPs is better choice than positively charged lipid coated Ag NPs. This study on lipid corona and its stability will help the nanoresearcher to choose the suitable lipid for lipid corona formation.

Strain Imaging of Electrode Materials in Li-Ion Batteries

Li-ion batteries operate through the migration of Li ions between the electrodes. Therefore, non-destructive observation of the migration with high spatial resolution is important.When charging and discharging, Li-ions are extracted or inserted into electrode materials, which generally causes changes in volume. An atomic force microscope (AFM) can detect and image these volume changes through current collectors with high spatial resolution, which enables us to investigate Li-ion migration without destruction. AFM detects surface displacements synchronizing the charging/discharging cycle, and provides strain images along with topography of the current collector.1) Here, we present our results of lithium titanate oxide (LTO: Li x Ti5O12). LTO is an anode material with high safety having a theoretical capacity of 160 mA h g−1 (from LiTi2O4 to Li2Ti2O4). But the phase change from spinel to rock-salt lead to very small volume changes. Therefore, it might be difficult to observe the Li migration by this method.However, Li4Ti5O12 with a spinel structure has high resistivity, whereas charged Li7Ti5O12 with a rock-salt structure is a conductor. The former is a transparent semiconductor and the latter is a dark metal. The state of charge of LTO can be observed by an optical microscope. The spatial resolution is not enough though the method is easy-to-use.2) High-resolution method has been proposed.3) Photoinduced strain imaging discriminates semi-conductors having bandgap from metallic materials with no bandgap. The method images bandgap variations based on the detection of electric strains caused by electron-hole pair generation. When electron-hole pairs are generated by photon injection, strains are induced, because the lattice constants are determined as the energy of the electron band structure becomes minimum, and the generation changes the energy configuration. The generation of electron-hole pairs is determined from the magnitude relationship between photon and bandgap energies. Bandgap energies can be measured quantitatively by scanning the injected photon energy. When the photon energies are larger than bandgap energies, strains are generated by electron-hole pairs generation. Therefore, mapping of the strains reveals changes in bandgap energies, that is, state-of-charge of LTO.The lithium metal anode has fruitful advantages that are the lowest electrode potential of Li+/Li and low density of Li, which are −3.04 V and 0.534 g/cm3, respectively. However, the lithium dendrite issue is a serious barrier standing in way of the development of high-energy-density batteries with a lithium metal anode.We have been successful in imaging electrochemical reactions in the interface between lithium metal and electrolyte using strain imaging. Precipitation and dissolution of lithium ions in the surface of lithium metal, and electrolyte flow induced by the gradient of lithium-ion concentration should cause the surface displacements of the current collector. We will be able to get a lot of knowledge and information from this observation.

(Invited) First Principles Examination of Multiple Criteria of Organic Solvent Oxidative Stability in Batteries

Oxidative instability of the liquid electrolyte at or near battery cathode oxide surfaces has significant detrimental effects on batteries. Organic solvent molecules are often the fuel and precurors of such degradation processes, releasing electrons and protons that react with cathode oxides and electrolyte anions. These reactions contribute to cathode electrolyte interphase (CEI) film formation, transition metal ion dissolution, and phase transformation of the surface regions of the cathode. Here we apply Density Functional Theory calculations to examine four criteria of oxidative stability (oxidation potential, hydrogen removal energies, and initial reactivity on two types of oxide facets) using four different solvent/additive molecules (ethylene carbonate, fluoroethylene carbonate, 1,3-dioxolane, and dimethyl ether). The ranking of molecular stability differs with each criterion. Surprisingly, the all-oxygen terminated basal planes of layered oxides exhibit lower reaction barriers than spinel surface facets with exposed transition metal cations, especially for ether solvents; the calculations also suggest basal planes contribute to the dissolution of transition metal ions. The structure-degradation relation complexity underscores the challenge of understanding the function of the CEI, but also offers a guide to future degradation-mitigation strategies including facet-engineering. Our predictions and models help establish a framework for future studies relevant to high voltage conditions.Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the document do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Suppression of PEFC Membrane Degradation By Using SnO2 As Electrocatalyst Support

Introduction Long-term durability of polymer electrolyte fuel cells (PEFCs) is required for various applications such as automobiles. It has been suggested that certain ions dissolved from electrocatalyst materials accelerate radical formation and subsequent chemical degradation of polymer electrolyte membrane (PEM) by the Fenton reaction [1]. Membrane degradation increases hydrogen and oxygen permeability and decreases proton conductivity and mechanical strength [2]. These phenomena significantly affect the electrochemical performance and durability of PEFCs. Therefore, in case metal oxides are used as catalyst support, it is necessary to check the dissolution of metal ions and to evaluate their effects on membranes. Our research group has been studying Nb-doped SnO2 (Sn(Nb)O2), showing improved durability of the electrocatalysts [3]. Here in this study, we evaluate the effects of Sn(Nb)O2 on the chemical degradation of PEMs. Experimental A commercial Pt/C catalyst (TEC10E50E, Tanaka Kikinzoku Kogyo, Japan) was used as the anode catalyst, while three types of cathode catalysts were applied and compared: 1) the commercial Pt/C; 2) Pt/MC where Pt was directly deposited on mesoporous carbon (MC); and 3) Pt/Sn(Nb)O2/MC where Pt was deposited on the Sn(Nb)O2 decorated on the MC. The durability test at open circuit voltage (OCV) was performed for 100 h. Before and after the durability test, cell performance, hydrogen crossover current density, and electrochemical surface area (ECSA) were characterized. The degree of membrane degradation was evaluated by measuring fluorine emission rate (FER) by ion chromatography, and membrane thickness and elemental distribution by energy-dispersive x-ray spectroscopy (EDS) coupled with field-emission scanning electron microscopy (FESEM). Results and discussion It was found that the use of Pt/Sn(Nb)O2/MC led to better durability in the OCV durability test. The decrease in OCV using Pt/Sn(Nb)O2/MC was smaller than that using Pt/C and Pt/MC, less than half of that Pt/C, as shown in Figure 1. The membrane thickness with Pt/Sn(Nb)O2/MC after the durability test was the same as that before the durability test, indicating that SnO2 actually suppressed the membrane degradation as shown in Figure 2. EDS elemental analysis confirmed no Sn ion dissolution from the cathode side as shown in Figure 3, also suggesting that SnO2 at the cathode suppressed the membrane degradation. In this presentation, we will quantitatively analyze the membrane degradation in using SnO2 and discuss possible mechanisms. Acknowledgment This paper is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

New ALD ZnO Precursors and Processes for Protective Coatings on Lithium-Ion Battery Cathodes

The ever-increasing demand for Li-ion batteries commands their performance to increase while at the same time size and mass to decrease. One promising cathode material to achieve this is the Ni-rich LiNi0.8Mn0.1Co0.1, (NMC811), a high-capacity layered oxide cathode material. However, NMC811 suffers from capacity fading during electrochemical cycling of the cells. This phenomenon is connected to the dissolution of the active transition metal ions in the cathodes, phase changes and to side reactions happening at the interface of the cathode and the electrolyte or with formed HF but remains poorly understood.[1] To mitigate these problems, many different coating processes have been employed. In the realm of atomic layer deposition (ALD), the predominant coating material is the very stable insulating Al2O3 prepared from trimethyl aluminum and H2O. However, ZnO is an alternative transition metal oxide coating that shows promise since it is an amphoteric conductor. Recently, amorphous ZnO coatings prepared by sol-gel methods were shown to significantly boost the capacity retention of NMC cathodes.[2] Taking inspiration from a recent study that compared different ALD Al2O3 precursors and their ability to precisely tune the protective coating, we set out to investigate the suitability of ZnO ALD films as protective coatings and the influence of different precursors used for that purpose.[3] We selected four Zn precursors for cathode surface treatments in this study with different coordination motifs, metal-to-ligand bonds and reactivities, (Fig. 1). The ZnO ALD processes for these precursors were established by in-situ spectroscopic ellipsometry, and the resulting films were subjected to compositional analysis by XPS and RBS/NRA proving high purity ZnO. Further, UV-VIS measurements were conducted to investigate the band gaps of the materials which showed interesting precursor dependent differences. To analyze the growth behavior of the different precursors, in-situ FTIR studies were conducted hinting at distinct decomposition/deposition behavior of each precursor, as shown by the FTIR difference spectra for ZnEt(HMDS) in Fig. 2. The in-situFTIR studies also revealed different nucleation behaviors for the ALD ZnO precursors on the NMC811 cathode surface. Next, we coated NMC811 powder with 1 and 5 ZnO ALD cycles and performed XPS to verify successful ZnO ALD, analyze the surface species, and probe for potential oxidation state changes caused by the applied precursors. Whereas the observed changes in the oxidation states were small, a reproducible reduction was seen for the Ni, Co, and Mn transition metals in the cathode material, see exemplarily the ratio of Co 2+ and 3+ species in Fig. 3. Coin cell cycling tests of cathodes fabricated from the ALD ZnO-coated NMC811 powders prepared using the different Zn precursors are ongoing. These results will be especially noteworthy and showcase how the choice of ALD precursor influences the properties of a battery protective coating and allows fine tuning of the cathode surface properties.[1] Z. Ruff, C. Xu, C. P. Grey, J. Electrochem. Soc. 2021, 168, 060518.[2] Y. Li, X. Li, J. Hu, W. Liu, H. Maleki Kheimeh Sari, D. Li, Q. Sun, L. Kou, Z. Tian, L. Shao, C. Zhang, J. Zhang, X. Sun, Energy Environ. Mater. 2020, 3, 522–528.[3] D. Kang, R. E. Warburton, A. U. Mane, J. Greeley, J. W. Elam, Applied Surface Science 2022, 599, 153329. Figure 1

Effects of naphthalene superplasticizer on geopolymers activated by calcium carbide residue and Glauber's salt

Poor fluidity limits the large-scale applicability of geopolymers. This study aims to improve the fluidity of one-part geopolymer by naphthalene superplasticizer. Three types of systems were utilized as geopolymer precursors: fly ash (90 wt%), fly ash: silica fume (86 wt%: 4 wt%), and fly ash: flue gas desulfurization gypsum (85 wt%: 5 wt%). Then, activators comprising 5 wt% calcium carbide residue and 5 wt% Glauber's salt were used to prepare geopolymer composites. The resulting fluidity and mechanical strength of the developed geopolymer systems were evaluated. The 0.4 wt% naphthalene superplasticizer was found to have the optimal effect in the activated fly ash system, and the corresponding fluidity and strength increased by 17.2% and 22.8%, respectively. The results indicate that the increase in fluidity is attributed to the electrostatic repulsion between the naphthalene superplasticizer and the precursor particles. Further, the enhancement in compressive strength can be attributed to the increased gel formation resulting from intensified ion dissolution in the precursor due to the presence of the naphthalene superplasticizer, resulting in a denser microstructure with fewer pores.

Potassium Selenocyanate (KSeCN) Additive Enabled Stable Cathode Electrolyte Interphase and Iron Dissolution Inhibition toward Long‐Cycling Potassium‐Ion Batteries

AbstractPotassium‐ion batteries (KIBs) are promising energy storage devices owing to the close redox potential of potassium (K) to lithium and rich abundance of K resource, thus promoting the exploration of efficient cathode materials for K‐ions storage. Fe‐based Prussian blue analogues (KFeHCF) are promising cathode materials for KIBs due to their combined advantages in low cost and high energy density. However, the rapid capacity decay induced by unstable cathode electrolyte interphase (CEI) and dissolution of transition metal ions leads to limited lifespans (e.g., hundreds of cycles) of K∥KFeHCF batteries. Incorporating additives into electrolytes is an economical and effective way to construct robust CEI for high‐performance KIBs. Herein, a multifunctional electrolyte additive, potassium selenocyanate (KSeCN), is introduced to effectively construct stable, homogeneous and conductive CEI films, which leads to the inhibition of Fe dissolution and stabilization of KFeHCF structure during cycling. With 0.5 wt% of KSeCN in conventional carbonated electrolyte, the K∥KFeHCF battery exhibits promoted cycling performance with a capacity retention rate of 87% after 500 cycles at 4.5 V cutoff voltage. This finding provides a new paradigm for developing and designing potassium‐ion battery electrolytes.

SURFACE QUALITY AND CORROSION RESISTANCE OF 316L STAINLESS STEEL ELECTROPOLISHED USING PHOSPHORIC – SULFURIC ACIDS

Electropolishing is an electrochemical surface finishing technique. It is commonly applied to equipment that requires a gleaming finish. This surface property is frequently required in 316L stainless steel (SS) medical implants. Electropolishing removes a thin layer from the metal's surface through electrochemical processes. This results in a very clean, smooth, and bright metal surface. The process parameters, such as electrolyte solution, electrical current, and electropolishing time, influence surface roughness and glossiness. The dissolution of metallic ions during the process may also affect the corrosion resistance of the treated material in addition to producing a shiny surface. This study investigated the surface glossiness, surface roughness, and corrosion of electropolished 316L SS. Electropolishing experiments on 316 SS were carried out using various H3PO4 (50%) and H2SO4 (32%) electrolyte solution compositions. The influences of electrolyte solution composition, electric current, and electropolishing time were studied. The results showed that increasing the H2SO4 content of the mixture and electropolishing the 316L SS for a longer period of time improved the surface roughness and glossiness. Under 10 Amp electric currents, the best surface glossiness was discovered. A corrosion test revealed that the electropolishing produced a Cr and Ni-rich layer that improved the corrosion resistance of the samples.

Co/Mn ratio-regulated hexacyanoferrates as a long-life and high-rate cathode for aqueous Zn-ion batteries

Among all kinds of cathodes for aqueous Zn-ion batteries, Mn-based hexacyanoferrates exhibit advantages of high-voltage and abundant resources. However, they suffer from inferior cycle-life and rate capability, which may be attributed to the structural instability and metal ion dissolution. In this work, a continuous element substitution (Mn replaced by Co) is employed to modify the electrochemical performance of Mn-based hexacyanoferrates. With the increasing ration of Co/Mn, the Mn, Co-based hexacyanoferrate (MnCoHCF) samples show unchanged crystalline phase with similar morphology and increasing Co dopant. Additionally, the initial specific capacity gradually decreases, but the electrochemical polarization is alleviated. Among the samples, MnCoHCF-4 (ratio of Co/Mn of 3:1) exhibits excellent cycling life (71.4% after 3000 cycles at 5 C) and rate performance (81.4 mA h g−1 at 10 C). In-situ techniques reveal the obvious metal ion dissolution with a low ratio of Co/Mn during the electrochemical process, resulting in poor structure stability and reaction kinetics of MnHCF electrode. However, When the ratio of Co/Mn is increased, the metal ion dissolution is effectively suppressed, and the MnCoHCF electrode shows improved structure stability and reaction kinetics. This work proposes an effective modification for hexacyanoferrates and other high-voltage Prussian blue analogues, which may promote the application of aqueous Zn-ion batteries.

Molybdenum/selenium based heterostructure catalyst for efficient hydrogen evolution: Effects of ionic dissolution and repolymerization on catalytic performance

Transition metal chalcogenides (TMCs) are recognized as highly efficient electrocatalysts and have wide applications in the field of hydrogen production by electrolysis of water, but the real catalytic substances and catalytic processes of these catalysts are not clear. The species evolution of Mo and Se during alkaline hydrogen evolution was investigated by constructing MoSe2@CoSe2 heterostructure. The real-time evolution of Mo and Se in MoSe2@CoSe2 was monitored using in situ Raman spectroscopy to determine the origin of the activity. Mo and Se in MoSe2@CoSe2 were dissolved in the form of MoO42- and SeO32-, respectively, and subsequently re-adsorbed and polymerized on the electrode surface to form new species Mo2O72- and SeO42-. Theoretical calculations show that adsorption of Mo2O72- and SeO42- can significantly enhance the HER catalytic activity of Co(OH)2. The addition of additional MoO42- and SeO32- to the electrolyte with Co(OH)2 electrodes both enhances its HER activity and promotes its durability. This study helps to deepen our insight into mechanisms involved in the structural changes of catalyst surfaces and offers a logical basis for revealing the mechanism of the influence of species evolution on catalytic performance.