Uniform Dissolution Research Articles

A new insight on the mechanisms of corrosion deactivation of a typical Ti/IrO2 + RuO2 +TiO2 coating in the presence of Ta2O5 in chlor-alkali medium

Mixed metal oxide (MMO) anodes are commonly used in chlor-alkaline industry. They have a longer lifetime than conventional graphite anodes due to the presence of valuable and expensive metal oxides such as iridium and ruthenium. However, they can suffer from pitting corrosion. This makes them to lose their stability, which necessitates the application of stabilizers to delay this process as one of the most accepted preventive measures. Hence, this study to aims to increase the life of MMO anodes, by altering corrosion mechanisms from localized to uniform corrosion. To achieve this objective, electrodes of different nominal compositions were prepared by adding 2 and 5 wt% of tantalum oxide into the base coating composition (Ti/(38IrO2-36RuO2-(26-X)TiO2-XTa2O5)). Accelerated lifetime and electrochemical impedance tests were employed in order to evaluate the corrosion pathways at different time intervals. Furthermore, morphological properties and composition of the anode were addressed via scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis. In addition, cyclic voltammetry test was performed to investigate electrochemical properties. It was understood that the addition of tantalum oxide leads to increment in active surface area and current density of the anode reaction. More importantly, tantalum oxide was found to be an effective inhibitor of the pitting corrosion while altering the dominant corrosion pathway from pitting to uniform dissolution in ternary coatings. However, it resulted in the service life of the anode to be reduced in the accelerated life test.

The corrosion resistance and discharge performance of as-extruded AZ91 alloy synergistically improved by the addition of submicron SiCp

In order to reveal the influence of submicron SiCp on the corrosion and discharge behaviors of extruded AZ91 alloy, the extruded AZ91 alloy and 0.5 μm SiCp (0.5 vol.%)/AZ91 composite were subjected to immersion, electrochemical, and Mg-air battery tests. The results show that the introduction of submicron SiCp not only reduces the weightless corrosion rate of the extruded AZ91 alloy from 3.09 mm/y to 2.18 mm/y, but also increases its discharge voltage and stability at current densities ranging from 2.5 mA cm−2 to 40 mA cm−2. The improvement of corrosion resistance and discharge activity are attributed to the refined grains and precipitates, as well as the weakened basal texture owing to the addition of the minor submicron SiCp. Extruded AZ91 alloy has a coarse and unevenly distributed Mg17Al12 phase and strong basal texture. The coarse phase and more grains with basal texture as cathode lead to the local corrosion of magnesium in the corrosion process and the local dissolution of magnesium in the discharge process. After adding 0.5 vol.% submicron SiCp, the Mg17Al12 phase is fined and evenly distributed, and the basal texture is weakened, which not only weakens the galvanic corrosion but also promotes the uniform corrosion of magnesium. As a result, the corrosion resistance is improved. In addition, the discharge activity benefits from refined grains and the easily dissolving discharge product resulting from uniform dissolution of magnesium. This work provides new ideas for achieving the synergistic improvement of corrosion resistance and discharge performance of magnesium alloy.

Development of facile image processing techniques regarding crevice corrosion of U75V high-speed rail steel

In-situ crevice corrosion images of U75V high-speed rail steel samples before and after heat treatment for microstructure refinement were obtained by a self-developed monitoring device, and facile image processing techniques have been developed. Gray value and entropy have been demonstrated to be the significant parameters able to describe the process of crevice corrosion. Gray value has been found to have good correlation with corrosion depth, and distribution of column average gray value can be applied to obtain corrosion depth profiles along crevice depth. Gray histogram is a good indicator to distinguish local preferential dissolution and uniform dissolution via deviation from original peak position and valley height. Entropy means uncertainty of how corrosion patterns develop. Its increase indicates high activity for change of corrosion patterns, while low activity leads to cease of increase. When metal surface has been corroded extensively, entropy will decrease, indicating less potential routes for development of corrosion patterns. This work has provided new ideas on the application of image processing on corrosion study.

Conductive few-layered 1T-MoSe2/MXene as a highly-efficient catalyst for accelerating bidirectional sulfur redox kinetics in Li-S batteries

Lithium-sulfur batteries (LSBs) have been regarded as a prospective candidate for next-generation late-model energy storage device due to their merits in gravimetric/ volumetric capacity. However, the practical use of LSBs is still severely limited by the shuttle behavior and extremely slow bidirectional sulfur redox kinetics. Herein, a dual-functional conductive 1T-MoSe2/MXene bidirectional catalyst as a high-efficiency sulfur host was constructed by few-layer 1T-MoSe2 in-situ growth on MXene nano-flakes through one-step solvothermal reaction. Experimental and DFT theoretical analysis reveal that 1T-MoSe2/MXene possess a high electronic conductivity, strong adsorption ability, and abundant active sites, which can provide the strong capture and catalytic conversion ability for LiPSs and uniform deposition and dissolution of Li2S, thus effectively inhibiting the LiPSs shuttle behavior in LSBs. Benefiting from the enhanced bidirectional sulfur redox kinetics and adsorption capacity, the S/1T-MoSe2/MXene cathode delivers a stable long cycling stability with a capacity retention of64.2% (capacity fading per cycle of 0.07%) after 500 cycles at 0.2 C. Furthermore, a high areal capacity of 6.9 mAh cm−2 and good capacity retention of ∼73.1% were obtained after 200 cycles at 0.1 C. This work provides a novel way for the development of dual-functional conductive catalyst to accelerate the catalytic conversion of LiPSs.

Revealing the role of Ca on the electrochemical properties of Al–Mg–Sn–Ga–Ca alloy as anodes for Al-air batteries

In this paper, we investigated the influence of calcium (Ca) on the electrochemical and corrosion properties of Al–Mg–Sn–Ga alloys in neutral and alkaline electrolytes, respectively. Results indicate that Ca element promotes the uniform dissolution of the anode and improve its discharge efficiency. The peak energy densities of the Al-0.5Mg-0.1Sn-0.05Ga-0.1Ca alloy in neutral and alkaline solutions are 3361 and 3581 Wh kg−1, respectively. Compared with calcium-free alloy, the increase is 5.3% and 26.5%, respectively. Additionally, the severe intergranular corrosion behavior of Al-0.5Mg-0.1Sn-0.05Ga alloy can be significantly inhibited by adding Ca element under alkaline conditions. Therefore, the addition of Ca element further optimizes the discharge performance of Al–Mg–Sn–Ga-based anodes and enhances its environmental adaptability.

Dilution-induced changes in room temperature ionic liquids. Persistent compositional heterogeneity and the importance of dipolar interactions

Room temperature ionic liquids (RTILs) exhibit several unusual properties, including the ability to support an induced free charge density gradient, ρf. Upon dilution with water, RTILs form micelle-like structures, and compositional non-uniformity has been reported in other solvents, such as methanol and acetonitrile. The dependence of ρf on dilution is not consistent with uniform dissolution of the RTIL in the diluent. We report here our examination of two imidazolium RTILs diluted with polar aprotic solvents dimethyl sulfoxide (DMSO) and propylene carbonate (PC). Using the cationic fluorophore cresyl violet (CV+), we evaluate the dependence of ρf magnitude and persistence length on dilution with these two solvents. These properties are found to depend on the identity of the RTIL anion (BF4- and TFSI-). In regions of the RTILs not affected by the induced charge density gradient, we find evidence for the formation of aggregated domains of RTIL in the binary systems. The characteristic domain size is seen to depend on the identity of the diluent and RTIL anion, and for all systems examined, domain size increases with increasing dilution. We discuss these findings in the context of the magnitude of the RTIL ion pair dipole moments.

Epitaxial growth of SiGe films by annealing Al–Ge alloyed pastes on Si substrate

A simple, low-cost, and non-vacuum epitaxial growth method to realize large-area semiconductors on crystalline silicon will become the game-changer for various applications. For example, we can expect the disruptive effect on the cost of large-scale III–V multi-junction solar cells if we could replace the high-cost germanium substrate with silicon–germanium (SiGe) on Si. For SiGe epitaxial growth, we attempted to develop a process using original Al–Ge pastes for screen printing and subsequent annealing. We compare two pastes including Al–Ge alloyed pastes with compositional uniformity in each particle and Al–Ge mixed pastes. We revealed that Al–Ge alloyed paste could form flatter SiGe film with much less residual pastes, supported by in-situ observations. The uniform and sufficient dissolution of the alloyed paste is responsible for these and led to higher average Ge-composition by annealing at 500 °C. The composition in SiGe was vertically graded up to ~ 90% at the topmost surface. These results show that printing and firing of Al–Ge alloyed paste on Si is the desirable, simple, and high-speed process for epitaxial growth of SiGe, which could be potentially used as the lattice-matched virtual substrate with III–V semiconductors.

Experimental investigation and characterization of NiTinol shape memory alloy during wire electrochemical machining

NiTinol-based microstructures have piqued interest in a variety of industrial applications. Nonetheless, due to material features and characteristics, micromachining of NiTinol shape memory alloy (SMA) offers a significant problem due to a detrimental combination of shape memory effect and super-elasticity. In this paper, an investigation into the wire electrochemical machining (WECM) of NiTinol SMA at a low concentration of 0.1 M H2SO4 aqueous acidic electrolyte with effect of small amplitude at low-frequency PZT vibration-assisted axial nozzle jet flushing is presented. During the machining process, initially, the effect of most influencing WECM process parameters i.e. electrolyte flow rate, tool PZT amplitude and frequency, electrolyte temperature during micromachining of NiTinol SMA was studied on machining characteristics for microslit fabrication. Additionally, the effect of pulse voltage, pulse frequency, pulse width and, the wire feed rate was also investigated during machining on micro slit width to understand the benefit of WECM on NiTinol SMA machining in sequential order. Furthermore, after several experiments for controlled machining conditions, finally, NiTinol SMA - based homogeneous minimum slit width of 110 μm with 0.57 μm standard deviation were obtained with 120 μm thick NiTinol sheet at a 100 μm initial inter-electrode gap. The characteristics of NiTinol SMA were analyzed before and after machining using scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX), X-ray diffraction (XRD) tests. Also, dissolution behavior of NiTinol SMA in 0.1 M H2SO4 aqueous acidic electrolyte was studied. The surface roughness Ra was observed as 0.108 μm on the machined surface confirming a uniform dissolution during WECM.

Flow field characteristics and experimental research on inner-jet electrochemical face grinding of SUS420J2 stainless steel

Electrochemical grinding (ECG) is processed by the combination of dissolution and grinding. It is very suitable for the processing of difficult-to-cut stainless steel, but its processing performance is restricted by the matching effect of dissolution and grinding. In this work, the processing of the torus surfaces of the stainless steel shaver cap was taken as the research object. A flow field model including the through-hole structure and the rotation of the grinding head was proposed to optimize the flow field distribution and promote the uniform dissolution of materials. The flow field simulation results showed that the rotational flow formed by the high-speed rotation prolonged the electrolyte flow path and was not conducive to the discharge of electrolytic products, and the reasonable selection of the diameter and distribution of the through-hole could reduce the velocity difference. The effects of rotational speed, feed rate, and inlet pressure on the flatness and surface roughness of the torus surfaces were experimentally investigated, and a better matching effect of dissolution and grinding was obtained. Moreover, the experimental results showed that the inner-jet ECG had a good prospect in the batch processing of high-hardness stainless steel parts.

Brushed Metals for Rechargeable Metal Batteries.

Battery designs are swiftly changing from metal-ion to rechargeable metal batteries. Theoretically, metals can deliver maximum anode capacity and enable cells with improved energy density. In practice, these advantages are only possible if the parasitic surface reactions associated with metal anodes are controlled. These undesirable surface reactions are responsible for many troublesome issues, like dendrite formation and accelerated consumption of active materials, which leads to anodes with low cycle life or even battery runaway. Here, a facile and solvent-free brushing method is reported to convert powders into films atop Li and Na metal foils. Benefiting from the reactivity of Li metal with these powder films, surface energy can be effectively tuned, thereby preventing parasitic reaction. In-operando study of P2 S5 -modified Li anodes in liquid electrolyte cells reveals a smoother electrode contour and more uniform metal electrodeposition and dissolution behavior. The P2 S5 -modified Li anodes sustain ultralow polarization in symmetric cell for >4000 h, ≈8× longer than bare Li anodes. The capacity retention is ≈70% higher when P2 S5 -modified Li anodes are paired with a practical LiFePO4 cathode (≈3.2mAhcm-2 ) after 340 cycles. Brush coating opens a promising avenue to fabricate large-scale artificial solid-electrolyte-interphase directly on metals without the need for organic solvent.

Corrosion Behavior of Al Modified with Zn in Chloride Solution.

Aluminum-based alloys have been considered candidate materials for cathodic protection anodes. However, the Al-based alloys can form a layer of alumina, which is a drawback in a sacrificial anode. The anodes must exhibit uniform corrosion to achieve better performance. Aluminum can be alloyed with Zn to improve their performance. In this sense, in the present research, the electrochemical corrosion performance of Al-xZn alloys (x = 1.5, 3.5, and 5 at.% Zn) exposed to 3.5 wt.% NaCl for 24 h was evaluated. Polarization curves, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) were used to identify the electrochemical behavior. The microstructure of the samples before the corrosion assessment was characterized by means of X-ray diffraction analyses (XRD) and scanning electron microscopy (SEM). In addition, microstructures of the corroded surfaces were characterized using X-ray mappings via SEM. Polarization curves indicated that Zn additions changed the pseudo-passivation behavior from what pure Al exhibited in a uniform dissolution regime. Furthermore, the addition of Zn shifted the corrosion potential to the active side and increased the corrosion rate. This behavior was consistent with the proportional decrease in polarization resistance (Rp) and charge transfer resistance (Rct) in the EIS. The analysis of EIS was done using a mathematical model related to an adsorption electrochemical mechanism. The adsorption of chloride at the Al-Zn alloy surface formed aluminum chloride intermediates, which controlled the rate of the process. The rate constants of the reactions of a proposed chemical mechanism were evaluated.

Radiolysis and Radiation-Driven Dynamics of Boehmite Dissolution Observed by In Situ Liquid-Phase TEM.

Over the last several decades, there have been several studies examining the radiation stability of boehmite and other aluminum oxyhydroxides, yet less is known about the impact of radiation on boehmite dissolution. Here, we investigate radiation effects on the dissolution behavior of boehmite by employing liquid-phase transmission electron microscopy (LPTEM) and varying the electron flux on the samples consisting of either single nanoplatelets or aggregated stacks. We show that boehmite nanoplatelets projected along the [010] direction exhibit uniform dissolution with a strong dependence on the electron dose rate. For nanoplatelets that have undergone oriented aggregation, we show that the dissolution occurs preferentially at the particles at the ends of the stacks that are more accessible to bulk solution than at the others inside the aggregate. In addition, at higher dose rates, electrostatic repulsion and knock-on damage from the electron beam causes delamination of the stacks and dissolution at the interfaces between particles in the aggregate, indicating that there is a threshold dose rate for electron-beam enhancement of dissolution of boehmite aggregates.

Engineering Sodium Metal Anode with Sodiophilic Bismuthide Penetration for Dendrite-Free and High-Rate Sodium-Ion Battery

Sodium (Na) metal batteries with a high volumetric energy density that can be operated at high rates are highly desirable. However, an uneven Na-ion migration in bulk Na anodes leads to localized deposition/dissolution of sodium during high-rate plating/stripping behaviors, followed by severe dendrite growth and loose stacking. Herein, we engineer the Na hybrid anode with sodiophilic Na3Bi-penetration to develop the abundant phase-boundary ionic transport channels. Compared to intrinsic Na, the reduced adsorption energy and ion-diffusion barrier on Na3Bi ensure even Na+ nucleation and rapid Na+ migration within the hybrid electrode, leading to uniform deposition and dissolution at high current densities. Furthermore, the bismuthide enables compact Na deposition within the sodiophilic framework during cycling, thus favoring a high volumetric capacity. Consequently, the obtained anode was endowed with a high current density (up to 5 mA∙cm−2), high areal capacity (up to 5 mA∙h∙cm−2), and long-term cycling stability (up to 2800 h at 2 mA∙cm−2).

The leakoff in acid fracturing kinetics control mechanism

To study the compacted carbonate leakoff mechanism during acid fracturing process, we introduced a new characterization method. Realized acid reaction violently with carbonate reservoirs, concentration within the natural crack, larger pores or natural fractures are excessive corrosion firstly and grow rapidly, to a certain extent, form a wormhole, acid leakoff area increases sharply, cause wormhole control mechanism; But in the process of compacted carbonate acid fracture, the wormhole will not generate in scale, main controlling factors of the leakoff by acid rock reaction kinetics parameter. Acid rock reaction kinetics parameters determined by experiments, and the acid leakoff experiments under different rock attracts many kinetic parameters obtained difference, put forward in the dense carbonate acid, acid rock reaction kinetics parameter controlling the leakoff. While fracturing in tight carbonate rocks, acid rock reaction rate can form larger acid intrusion area, so the wormhole connection rate will be higher. However, excessive CO2 will preventing uniform dissolution. Therefore, these two parameters should not be less than a certain value. When the Qibt is higher than 1, the purpose of enhance permeability will be reach.

Chemical Etching of Cu98Be Alloy in Electrolyte Solutions

The process of chemical etching of Cu98Be alloy in solutions of various compositions was investigated. The rate of etching of beryllium bronze in the investigated solutions was deter-mined, and its change in time was studied. The selectivity of dissolution of the components of Cu98Be during prolonged etching in solutions of different electrolytes was established. A possibility of achieving uniform etching of Cu98Be alloy by varying the composition of the etching solution was shown. The concentrations of metal ions in the used etching solutions were determined, and the capacity of those solutions was calculated. The compositions of solutions with a high capacity for both alloy components during prolonged etching was estab-lished. The optimal compositions of etching solutions providing high-quality etching of beryl-lium bronze according to several criteria such as: a high process rate, uniform dissolution of alloy components, high capacity for both alloy components were proposed. The morphology of the Cu98Be electrode surface after etching in solutions, providing uniform dissolution for both alloy components, was studied. The absence of surface passivation after chemical etch-ing in these solutions was shown. The chemical nature of the compounds formed in the form of small inclusions on the etched surface of the electrode was established. The obtained results are of great importance in practical use because they allow selecting the appropriate composition of the etching solution, which, in turn, helps to optimize the technological etching process.

Revealing the influence of crystallographic orientation on the electrochemical and discharge behaviors of extruded diluted Mg–Sn–Zn–Ca alloy as anode for Mg-air battery

In this work, in order to reveal the role of crystallographic orientation in the electrochemical and discharge behaviors of the extruded diluted Mg-0.5Sn-0.5Zn-0.5Ca (wt.%) alloy through investigating the longitude surface (LS) and transversal surface (TS). The results show that the LS sample is mainly consisted of (0001) orientated grains, while the TS one is composed of (10-10)/(11–20) orientated grains. Although the self-corrosion rate for TS sample is higher than that of the counterpart as a result of the non-basal planes possess lower surface energy and higher activation energy, the real-time self-discharge rates for both samples are similar at constant applied current density. Nevertheless, the TS sample exhibits a remarkably higher anodic efficiency than that of the LS one, which can be attributed to the uniform dissolution of the substrate along with the weakened chunk effect (CE). Additionally, the Mg-air battery with the TS sample as anode exhibits a more stable discharge course and higher cell voltage due to the loose discharge products as well as enhanced discharge activity.

Microstructure Refinement on Crevice Corrosion of High-Speed Rail Steel U75V Visualized by an In Situ Monitoring System

Rail foot covered by a fastener will suffer from crevice corrosion, leading to thinning and localized attack of crevice interior posing a risk of failure. This work investigated crevice corrosion behavior of a typical pearlitic high-speed rail steel U75V, focusing for the first time on the effect of pearlitic microstructure refinement achieved by heat treatment with different cooling rates 2, 5, and 10°C/s. Under anodic polarization, localized dissolved spots presented on the as-received sample, where crevice corrosion mostly initiated from. For cooling rates 2 and 5°C/s, localized dissolved spots were also observed but crevice corrosion was mostly presented as general corrosion instead of from local spots, ascribed to enhanced tendency of uniform dissolution due to microstructure refinement and homogenization. For cooling rate 10°C/s, crevice corrosion expanded flocculently, ascribed to preferential dissolution of pearlitic nodules with entangled cementite due to over refinement. Crevice corrosion was obviously accelerated by microstructure refinement. Cooling rates 5 and 10°C/s led to the fastest and slowest expansion of the corroded area, respectively, while the corrosion depth was just the opposite based on the same amount of metal loss. This work provides important information regarding the effect of pearlitic microstructure refinement on crevice corrosion and introduces a facile method forin situmonitoring of crevice corrosion.

A ‘virtual sensing’ framework for µECM/hybrid laser- µECM for monitoring interelectrode gap conditions

Micro-ECM (µECM) has capability to process wide class of conductive materials ranging from metals, cermets to bulk metallic glasses and shape memory alloys. The process efficiency and speed is further enhanced by hybridization of micro-ECM process with laser which can act as a localized heat source or a cutting energy source depending on the fluence on the workpiece surface. The hybridization of micro-ECM with laser facilitates machining of materials/alloys with conductivity variations and promotes their uniform dissolution. The process mechanism involves several multiphysics phenomena occurring in the interelectrode gap (IEG) which is of the order of 20-50 µm. The technological limitations of putting sensors in this small IEG limits the monitoring of physical quantities (such as temperature, hydrogen and oxygen gas volume fraction, electrolyte conductivity, current density on workpiece surface) during the process. However, these physical quantities can be effectively estimated by multiphysics simulations.At first, the experimental experience with different sensors (temperature sensor, current sensor, high speed imaging and particle image velocimetry (PIV)) is presented for µECM/hybrid laser-µECM process and their limitations are discussed. Subsequently, this work proposes a ‘virtual sensing’ approach enabled by multiphysics simulations. A detailed multiphysics model is developed in Comsol® software which models several phenomena occurring in µECM/hybrid laser-µECM process such as temperature-dependent electrolyte properties, hydrogen and oxygen gas generation, heat generation due to joule heating and laser heating, laminar fluid flow and electric currents. The properties are evaluated at 5 different (virtual sensor) locations inside the IEG, more specifically on the workpiece surface, tool surface, in the center of IEG, just at the exit of IEG and at a specified location. These virtual sensors are implemented in the Comsol® software by employing a dynamic point probe which probes the model-solution at a defined point in a moving geometry. The evolution of the aforementioned parameters in the IEG is monitored and supported by fundamental explanations as well as observational experiments. This research is a first step towards facilitating predictive sensing of ECM and allied multiphysics processes thereby supporting process design and minimizing experimental efforts by virtual process monitoring.

Experimental Investigations into Machining Characteristics of Niobium Carbide Cermet with µECM / hybrid laser-µECM.

Niobium carbide (NbC) is a high hardness 1960 (HV30) cermet material which finds applications in the moulds for ceramic injection moulding as well as inserts for cutting tools. This material possesses excellent combination of hardness, toughness and thermal shock resistance. The use of nickel (Ni) binder makes it a promising material for such applications, especially in view of rising cobalt (Co) metal prices used as binder in conventional tungsten carbide (WC-Co) cermet. The tool-wear and tool-failure issues make it difficult for mechanical machining technologies to process this material, especially in the micromachining regime (< 2 mm). To address machinability challenges, electrically conductive Nb cermet has been developed inhouse with Ni as the binder material. This makes it a suitable workpiece candidate for electrochemical machining (ECM) and electrical discharge machining (EDM) processes.Therefore, experimental investigations are presented in this work to evaluate the machining characteristics of NbC cermet with micro-ECM process. Channels have been used as test-features for evaluating machinability. Furthermore, two different grades of NbC cermets have been machined to identify the effect of WC addition on the dissolution characteristics and possible passivation during ECM. A micro-second pulsed voltage source has been utilized for controlled and localized material removal. To further enhance removal mechanisms in terms of processing speed and weakening of passivating layer, the micro-ECM process has been assisted with a nano-second pulsed laser on an in-house developed hybrid machine-tool. The aim is to uniformly dissolve the NbC matrix and Ni binder with ECM process for a high integrity machined surface. The dissolution and passivation characteristics have been further analysed through a combination of current pulse acquisition and channel profile characterisation. Linear sweep voltammetry and channel machining revealed that the addition of WC has a significant impact on the stability of passive layer. Laser assistance could enhance the material removal for both the NbC grades and promote uniform dissolution, with the effect being more pronounced in the NbC grade without WC (41 % increase in average pulse peak current) due to the weaker passive film. The material dissolution was more localized in LECM of NbC grade with WC due to the strong passivation along the channel walls.

Electrochemical behaviors and discharge performance of Mg-Sn binary alloys as anodes for Mg-air batteries

In this work, the self-corrosion and discharge performance of the as-cast Mg-xSn (x = 1, 5, 9 wt%) anodes for primary Mg-air batteries were studied through microstructure characterization, electrochemical testing and discharge experiments. With the increase of Sn content, the volume fraction of the Mg2Sn phase increases, promoting dendrite refining. According to the electrochemical test, the Mg-1Sn anode shows a higher open circuit potential, resulting in a stronger electrochemical activity. The polarization curve and electrochemical impedance spectra show the corrosion resistance order as Mg-1Sn > Mg-5Sn > Mg-9Sn. In the discharge measurement, the Mg-1Sn anode achieves the best average discharge voltage, anode efficiency, specific capacity, and energy density under all current densities tested. At 10 mA cm−2, the energy density of Mg-1Sn is 1239.621 mWh g−1, which is higher than the Mg-5Sn anode and Mg-9Sn anode, 37% and 25%, respectively. The optimal discharge performance of the Mg-1Sn anode is mainly attributed to the high electrochemical activity and the micron-sized Mg2Sn phase dispersed in the matrix, which facilitates more uniform dissolution.