Electrolytic Extraction Research Articles

Protocol for Quantifying All Electrolyte Compositions in Aged Lithium‐ion Batteries

AbstractThe aging of lithium‐ion batteries (LIBs) typically accompanies the degradation of electrolyte, but the relationship between them remains unclear. Therefore, quantifying residual electrolyte in batteries at different states of health (SOH) is a crucial issue. Here, we have developed a comprehensive characterization method to quantitatively analyze the electrolyte salts, solvents, and additives in commercial pouch cell, achieving quantification of all electrolyte compositions with high accuracy. Compared to the reported external standard method used in gas chromatography‐mass spectrometry (GC‐MS), we developed an internal standard method, which offers higher accuracy and reliability, with the maximum error decreased from 9.54 % to 3.48 %. Moreover, the quantitative accuracy of the calibration curves remains unchanged after 2 months. Multi‐instruments analysis is also utilized for the extraction and quantitative analysis of electrolyte in practical battery systems, achieving less than 5 % quantification error for all compositions. With our proposed method, it becomes possible to determine the absolute amounts of all electrolyte compositions, rather than obtaining limited information such as concentration or relative content. It is believed that this protocol of quantifying electrolyte compositions in commercial cells could serve as a baseline for further studies to reveal the relationship between electrolyte degradation and battery aging.

Innovative approach for efficient extraction of Nd from electrorefining waste salt into nuclear waste forms

Electrorefining of the high-burnup spent nuclear fuels is critical to the closed fuel cycle in fast reactors for the sustainable development of nuclear energy. However, a remaining challenge in the electrorefining process is the separation of radioactive rare earth fission products to reduce the geological waste volume. In this work, the extraction of a major radionuclide Nd from the molten waste salt into durable waste forms was investigated through a two-step approach consisting of electrolytic reduction and oxidative extraction. Liquid Bi was found to be effective in the electrolytic extraction of Nd, leading to an extraction efficiency of up to 98.6% and a current efficiency of 93.5%. The Nd target in the resulting Nd–Bi cathode alloy was then selectively extracted using specific oxidizers in a glass melting step. High loadings of Nd2O3 in the converted zinc-in-titania glass ceramic and aluminoborosilicate glass waste forms were achieved, demonstrating the prospect of the proposed method in terms of minimizing radioactive waste generation and recycling of the electrorefining waste salt.

Effect of hafnium and molybdenum addition on inclusion characteristics in Co-based dual-phase high-entropy alloys

Specific grades of high-entropy alloys (HEAs) can provide opportunities for optimizing properties toward high-temperature applications. In this work, the Co-based HEA with a chemical composition of Co47.5Cr30Fe7.5Mn7.5Ni7.5 (at%) was chosen. The refractory metallic elements hafnium (Hf) and molybdenum (Mo) were added in small amounts (1.5at%) because of their well-known positive effects on high-temperature properties. Inclusion characteristics were comprehensively explored by using a two-dimensional cross-sectional method and extracted by using a three-dimensional electrolytic extraction method. The results revealed that the addition of Hf can reduce Al2O3 inclusions and lead to the formation of more stable Hf-rich inclusions as the main phase. Mo addition cannot influence the inclusion type but could influence the inclusion characteristics by affecting the physical parameters of the HEA melt. The calculated coagulation coefficient and collision rate of Al2O3 inclusions were higher than those of HfO2 inclusions, but the inclusion amount played a larger role in the agglomeration behavior of HfO2 and Al2O3 inclusions. The impurity level and active elements in HEAs were the crucial factors affecting inclusion formation.

Separation of molten electrolyte from the graphene nanocarbon product subsequent to electrolytic CO2 capture

The molten electrolysis of CO2 and its simultaneous transformation to graphene nanocarbons is a growing path to decarbonization of both anthropogenic CO2, and CO2 directly from the air. By tuning the electrolysis conditions a variety of pure graphene nanocarbons are produced from CO2. The carbon in CO2 is transformed at the cathode, growing as a carbanogel containing a matrix of the Graphene NanoCarbons (GNCs) and the molten electrolyte. This study demonstrates that one GNC product, carbon nanotubes from CO2, can be effectively separated from the carbanogel by removing the majority of the electrolyte for reuse in the electrolysis chamber. A molten electrolyte extraction efficiency of 98.5% from the carbanogel is achieved using filtration at high temperature and pressure. Optimization of the (1) press time, (2) filtration pressure applied to the carbanogel, and (3) filter type leads to a sequential increase in optimization. An increase of press time from 5 to 17 ​min increases the electrolyte extraction from 53.8% to 92% at 540 psi, and to 97.8% at 3700 psi. An increase in electrolyte extraction of 98.5% from the carbanogel occurs with the inclusion of a Dutch-weave screen in the multilayer filter. The optimization is conducted on 10 ​kg carbanogel samples, but instrumentation for up to 0.25-tonne carbanogel electrolyte separation is shown.

Electrochemical behavior and effective extraction of Er in fused LiCl-KCl eutectic

For the efficient electrolytic extraction of Er from spent nuclear fuel, a series of electrochemical methods was used to research the electrochemical behavior of Er(III) in the LiCl-KCl system on inert (Mo) electrode and on reactive (Ni) electrodes. On the inert Mo electrode, the reduction of Er(III) to Er(0) is a one-step with three-electron and quasi-reversible reaction process. Meanwhile, the apparent generation Gibbs free energy and activity coefficients of Er(III) on the inert electrode were determined. Thereafter, the electrochemical reduction of Er(III) on the Ni electrode was emphatically investigated. Er(III) is reduced at a corrected potential owing to the formation of Ni-Er alloys. In addition, thermodynamic parameters such as partial excess Gibbs free energy change of Er in Ni, activity and apparent generation Gibbs free energy of the Ni-Er alloys were determined by the electromotive force method. Finally, different Ni-Er alloys were produced using potentiostatic electrolysis on the Ni cathode by controlling different potentials. Moreover, electrolytic extraction was carried out on the Ni cathode at the potential of –2.0 V, and the separation efficiency of Er reaches 99.72%, which proves the practicability of separating Er from LiCl-KCl eutectic on the reactive Ni cathode.

Study on the air atmosphere molten salt electrolytic extraction of tungsten and cobalt from cemented carbide scrap

In this study, tungsten and cobalt were extracted from cemented carbide scrap by three-stage electrodeposition in Na2WO4 molten salt at 900 °C in air atmosphere. The cemented carbide scrap was used as the consumable anode, while the cemented carbide calcined material was used as the electrolytically active substance additive. The composition of the cemented carbide calcined material was determined by thermodynamic calculations combined with XRD phase analysis. The study investigated the promoting effect of air atmosphere on anode oxidation and the effect of varying the molar ratio of tungsten to cobalt in the molten salt on product composition. Cyclic voltammetry was used to analysed the cathodic reduction behaviour of tungsten and cobalt. The nucleation mechanism of tungsten and cobalt was determined to be instantaneous by chronoamperometry. Finally, metallic tungsten and cobalt were successfully separated and extracted by three-stage constant current electrolysis.

Electrochemical and kinetic studies on the electrolytic extraction of Gd on Bi electrode in LiCl–KCl melt

Advancements in science and technology are heavily dependent on the development and utilization of rare earth materials.

Research on the influence mechanism of titanium on corrosion resistance of ferritic stainless steel in aluminum solution

The immersion corrosion test of ferritic stainless steel with different titanium content was carried out in molten aluminum at 750 °C. Scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were used to observe the microstructure and basic morphology of ferritic stainless steel with different titanium content, and the corrosion cross-section morphology after corrosion was observed. The types and contents of carbides in steel were analyzed by electrolytic extraction device and X-ray diffractometer (XRD), and the influence mechanism of Ti element on the corrosion resistance of experimental steel was studied. The test results show that the corrosion resistance of the test steel is significantly improved by adding 0.8%Ti. At this time, the microstructure of the test steel is ferrite matrix and carbides dispersed in the grain, including TiC, TiN and Cr23C6. Carbide dispersed in the grain and Fe–Ti intermetallic compound formed at the intersection of two intermetallic compound layers (IMC1 and IMC2) during the corrosion of molten aluminum simultaneously hindered the diffusion of Al atoms and improved the corrosion resistance of the tested steel.

Effect of Mo and Mo+Nb Additions on the Phase Transformation and Microstructure of a Developed Low-Carbon CrNiMnB Ultrahigh-Strength Steels with a Preceding Hot Deformation

The influence of molybdenum, and molybdenum with niobium addition on the phase transformation behaviour of a developed low-carbon CrNiMnB ultrahigh-strength steels, was investigated. Gleeble 3800 thermomechanical simulator was employed to simulate the hot-rolling process and to get the dilatation curves. After austenitization at 1250 °C for the complete dissolution of carbides, specimens received 0.6 total strain (i.e., 0.2 at 1100 °C and 2 x 0.2 at 900 °C) followed by cooling at various cooling rates (CRs) in the range of 2-60 °C/s. The final microstructures were investigated using laser scanning confocal microscopy, field emission scanning electron microscopy, and hardness measurements. Then the continuous cooling transformation diagrams were constructed based on the dilatation curves, microstructure, and hardness values. The electrolytic extraction method was used to assess the elements' distribution and the composition of the forming precipitates. The addition of Mo increased the hardenability, decreased the transformation temperatures, and promoted the formation of low-temperature transformation products i.e., martensite and bainite ferrite, at different CRs and inhibit the formation of polygonal ferrite. The formation of coarse precipitates neglected the effect of Mo+Nb addition, decreased the hardenability and expanded the region of BF formation to high CRs. The variation in the hardness with microstructural changes was discussed.

The effect of Nb2O5, CaO/SiO2, and TiO2 on the electrical conductivity of CaO-SiO2-Nb2O5-TiO2-CeO2-CaF2 melt

Electrical conductivity is a very important physical parameter in the process of electrolytic extraction of niobium from molten niobium-enriched slag or preparation of ferroniobium alloy by reduction melting separation in electric arc furnace. The effects of Nb2O5, CaO/SiO2 ratio and TiO2 on the electrical conductivity of CaO-SiO2-Nb2O5-TiO2-CeO2-CaF2 melt were studied by AC four-electrode method. The melt structure was studied by XPS to reveal the change rules of melt conductivity. The results show that the addition of Nb2O5 or increasing the CaO/SiO2 ratio in the melt can depolymerize the melt network structure and effectively improve the melt conductivity, and the activation energy of the conductivity is negatively correlated with the Nb2O5 content and the CaO/SiO2 ratio. With the increase of TiO2 content in the melt, the melt network structure polymerizes, the melt conductivity decreases, and the activation energy of conductivity also showed a decreasing trend.

Characterization and formation mechanism of non-metallic inclusions in single bcc-phase high entropy alloy

This work aims to provide a fundamental study of inclusion characteristics in the single bcc-phase high entropy alloy (HEA), Mn-rich and Al-contained multicomponent system (Al-Cr-Mn-Fe-Co-Ni) was selected as the prototype alloy in this study. According to the differential thermal analysis (DTA) measurements, the solidus (TS) and liquidus (TL) temperatures of this alloy were in the range of 1225–1228 °C (1226 ± 2 °C) and 1268–1271 °C (1270 ± 2 °C), respectively. Non-metallic inclusions were investigated in a two-dimensional (2D) cross-section method as well as extracted by a three-dimensional (3D) electrolytic extraction method. It was found that AlN was the dominant inclusion phase, also a small amount of Al2O3 inclusions were observed. They formed in the liquid alloy and mostly presented as Al2O3-AlN agglomerates, where the size range of the AlN inclusions was larger than that of Al2O3. The theoretical calculation showed that AlN inclusion has a higher coagulation coefficient and collision rate than those of Al2O3 inclusions, which agrees well with the experimental observations. The inclusion characteristics of Al2O3 and AlN were closely related to the relative contents of O and N in the presence of high Al content in the alloy. The impurity elements of N and O were the key issues in controling the stable inclusion phase in high entropic alloy.

Alternating Current Electrolytic Extraction of Transition Metals from NMC532 using Rotating Disc Cyclic Voltammetry in Dilute Chloride Solution

The rising application of portable electric devices has led to the rapid accumulation of electronic wastes such as lithium-ion batteries. These wastes pose significant environmental threats when improperly disposed of and contain valuable metals that could supplement the supply chain and reduce the need for certain conflict minerals. Recycling methods that limit the potential for environmental damage and improve separation of transition metals are vital to the sustainability of battery based electrical storage. Conventional aqueous recycling of lithium battery electrode materials utilizes oxidizing acids and a chemical reducing agent. This study investigates if chemical oxidizing and reducing agents may be aided or replaced by the application of an alternating electric field to reduce surface metal oxides and subsequently accelerate reoxidation with a solubilizing anion. The electrolytic leaching mechanics of commercial battery cathode material (NMC532) in dilute hydrochloric acid were investigated using rotating disc cyclic voltammetry (RDE-CV), solution analysis with inductively coupled plasma mass spectrometry (ICP-MS), and residue analysis with scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). We found evidence that applying an alternating electric field allows for adjustment of leaching rates for different transition metals based on electrochemical cell parameters. By applying up to one volt oscillating between reducing and oxidizing polarity, the relative molar leaching rate of nickel and manganese drastically increased while that of cobalt slightly decreased. Future research will be required to determine how this effect translates to different leaching systems and its applicability to an industrial scale process.The authors acknowledge financial support from the NSF IUCRC program for the “Center for solid-state electric power storage” (#2052631) and support from the South Dakota Board of Regents for the “Governor’s Research Center (GRC) for electrochemical energy storage”.

The Foreseeable Future of Spent Lithium-Ion Batteries: Advanced Upcycling for Toxic Electrolyte, Cathode, and Anode from Environmental and Technological Perspectives.

With the rise of the new energy vehicle industry represented by Tesla and BYD, the need for lithium-ion batteries (LIBs) grows rapidly. However, owing to the limited service life of LIBs, the large-scale retirement tide of LIBs has come. The recycling of spent LIBs has become an inevitable trend of resource recovery, environmental protection, and social demand. The low added value recovery of previous LIBs mostly used traditional metal extraction, which caused environmental damage and had high cost. Beyond metal extraction, the upcycling of spent LIBs came into being. In this work, we have outlined and particularly focus on sustainable upcycling technologies of toxic electrolyte, cathode, and anode from spent LIBs. For electrolyte, whether electrolyte extraction or decomposition, restoring the original electrolyte components or decomposing them into low-carbon energy conversion is the goal of electrolyte upcycling. Direct regeneration and preparation of advanced materials are the best strategies for cathodic upcycling with the advantages of cost and energy consumption, but challenges remain in industrial practice. The regeneration of advanced graphite-based materials and battery-grade graphite shows us the prospect of regeneration of anode. Furthermore, the challenges and future development of spent LIBs upcycling are summarized and discussed from technological and environmental perspectives.

Electrochemical and kinetic analysis of Ce recovery using Ga electrode in LiCl-KCl melt

Electrode material is an obstacle to the application of molten salt electrolysis in Ce recovery. Liquid Ga is a potential candidate for the cathode, but the corresponding reaction process on the electrode in the melt has yet to be fully understood and systematically studied. Herein, the electrochemical reaction and the kinetics of recovering Ce using Ga electrodes were investigated by various electrochemical methods. A concentration-dependent test of the co-deposition reaction revealed the continuous alloying process of reduced Ce. The electrolytic reduction of Ce ions on liquid Ga was studied by electrochemical impedance spectroscopy (EIS). The result shows that the reaction is controlled by diffusion. In addition, some important parameters such as exchange current density, activity coefficient and solubility were determined by pulsed electrolysis and coulomb titration, allowing a preliminary assessment of the electrolytic extraction of Ce on the Ga electrode.

Effect of Manufacturing Conditions and Al Addition on Inclusion Characteristics in Co-Based Dual-Phase High Entropy Alloy

Three Co-based dual-phase high-entropy alloys (HEAs) were produced by different manufacturing conditions: arc-melting with Ar protection (Ar-HEA), vacuum induction melting in Al2O3 crucible (Cr-HEA) and vacuum induction melting with 0.5 at. pct Al (Al-HEA), which resulted in different levels of impurity elements and inclusion characteristics. The inclusions that precipitated in different HEA samples were investigated through an electrolytic extraction process and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) characterization. The results showed that Mn(S,Se) inclusions were presented in all three alloys. MnCr2O4 inclusions were presented only in Ar-HEA, pure Al2O3 inclusions were presented in Cr-HEA and Al-HEA, and Mn–Cr–Al–O inclusions were also found in Al-HEA. Thermodynamic calculation software FactSage and Thermo-calc were used to predict the inclusion formations of the HEAs, which showed a good agreement with the experimental findings. The stable inclusions can transform from MnCr2O4 to Mn(Cr,Al)2O4 and then to pure Al2O3 with the increase of Al content. The inclusions in Al-containing HEA are spinel or Al2O3 depending on the content levels of Al and O. It is proposed that the formation of spinel and Al2O3 inclusions can be avoided in liquid HEA when the O content is controlled to be very low, which can result in smaller-sized inclusions. Moreover, the calculated coagulation coefficient of spinel inclusions is close but lower than that of Al2O3 inclusions. The collision growth of inclusions was affected by a combination of physical parameters of HEA and inclusions as well as the inclusion size and amount.Graphical

In Situ Continuous Measurement of Salinity in Estuarine and Coastal Sediments by All-Solid Potentiometric Sensors

Salinity is crucial for understanding the environmental and ecological processes in estuarine and coastal sediments. In situ measurements in sediments are scarce due to the low water content and particulate adsorption. Here, a new potentiometric sensor principle is proposed for the real-time in situ measurement of salinity in sediments. The sensor system is based on paper sampling and two all-solid electrodes, a cation-selective electrode (copper hexacyanoferrate, CuHCF) and an anion-selective electrode (Ag/AgCl). The spontaneous aqueous electrolyte extraction and redox reaction can produce a Nernstian response on both electrodes that is directly related to salinity. This potentiometric sensor allows for salinity acquisition in a wide salinity range (1-50 ppt), with high resolution (<1 ppt), and at a low water content (<30%), and it has been applied for the in situ measurement of salinity and the interpretation of cycling processes of metals in estuarine and coastal sediments. Moreover, the sensor coupled to a wireless monitoring system exhibited remote-sensing capability and successfully captured the salinity dynamic processes of the overlying water and pore water during the tidal period. This sensor with its low cost, versatility, and applicability represents a valuable tool to advance the comprehension of salinity and the salinity-driven dissolved-matter variations in estuarine and coastal sediments.

Monitoring Changes in Electrolyte Composition of Commercial Li-Ion Cells after Cycling using NMR Spectroscopy and Differential Thermal Analysis

We illustrate a simple and effective electrolyte extraction methodology from commercial 18650 lithium-ion cells. This methodology is based on a liquid-liquid extraction step, which is highlighted for robustness, reproducibility, and reliability. We assess the consumption of electrolyte by tracking compositional changes using liquid-state nuclear magnetic resonance (NMR) spectroscopy, supported by differential thermal analysis (DTA) before and after cell cycling. An analysis method that monitors compositional dynamics is presented and shows the impact of these changes throughout a cell’s lifetime. Such methodology can be employed in the understanding of electrolyte degradation mechanisms to enhance the understanding of performance fade in commercial cells. Moreover, it will help build robust mathematical models that are able to predict the drive of cell degradation and ultimate failure.

A model for converting thermal analysis to volume fraction of high carbon bearing steels during low-temperature tempering

• A model for predicting the phase content of tempered high carbon steels is proposed. • The microstructure during tempering are studied by thermal analysis, TEM, and XRD. • The predicted results are in good agreement with the experimental results. Quantitative prediction of phase content is of great importance to control and optimize the heat treatment process of steels. In this work, a model for predicting the phase content of tempered high carbon steels was proposed by taking a martensitic 100Cr6 bearing steel as a model case. The microstructural transformations during tempering were studied using thermal analysis, transmission electron microscopy (TEM), and X-ray diffraction (XRD). Kinetics analysis of thermal evolution by employing the isoconversional method, and assisted by TEM and XRD characterization, were performed to quantitatively estimate the volume fractions of different phases after tempering. A series of isothermal tempering experiments were designed to verify the model. The predicted results were in good agreement with the experimental results of XRD and electrolytic extraction measurements.

Novel applications of ferroalloys for manufacturing of ultra-clean CoCrFeMnNi high-entropy alloy by slagging method

The present study provides a benchmark of a sustainable solution utilizing ferroalloys to prepare ultra-clean CoCrFeMnNi high-entropy alloy (HEA). The designed CaO-MgO-Al2O3 slags saturated with CaAl2O4-MgAl2O4 (CA-MA, Slag A) and CaO-MgO (C-M, Slag M) were used to refine the HEA in Al2O3 and MgO refractory in an induction furnace under high-purity Ar atmosphere at 1773 K. The characteristics of non-metallic inclusions in the sampled HEA at different time intervals were quantitatively investigated. The results showed that three types of inclusions, i.e., sulfide (MnS), oxide, and complex type (oxide+sulfide), were found in the HEA regardless of refractory and slag types. The oxide inclusions such as MnAl2O4 and MgAl2O4 spinel particles can exist stably in the HEA melted in Al2O3 and MgO refractories with slag A and slag M, respectively. This fact is also confirmed not only by the electrolytic extraction method with elimination of the alloy matrix affection but also by the thermodynamic stability diagram for the HEA. For the structure of the complex inclusions, the core of oxide inclusions usually can act as the subsequent nucleation site for MnS since the precipitation temperature of the oxide inclusions (above the liquidus temperature of the HEA, TL ≅ 1623 K) is higher than that of MnS (below the solidus temperature of the HEA, TS ≅ 1573 K). The HEA melted in the MgO refractory with slag M had a higher cleanliness compared with that melted in the Al2O3 refractory with slag A, indicating that the MgO refractory with C-M saturated CaO-MgO-Al2O3 slag is suitable for producing an ultra-clean CoCrFeMnNi HEA prepared by the ferroalloys feedstock as the raw materials.

Towards a Better Understanding of Redox Shuttle Generation in Lfp/Graphite and NMC811/Graphite Cells By Systematic Investigation of Different Electrolyte Additives

Recent observations by our group show the creation of a reversible shuttle species in LFP/graphite and NMC811/graphite cells with 3:7 ethylene carbonate:dimethyl carbonate (EC:DMC) based electrolytes. This is indicated by a high reversible self-discharge of these cells in the absence of electrolyte additives. Electrolyte extraction from pouch cells after formation allowed to directly investigate the electrolytes for redox shuttle currents. For this purpose, the extracted electrolytes were inserted into coin cells with an Al foil as the working electrode (WE) and a Li foil as the counter electrode (CE). The measured cyclic voltammetry (CV) of the coin cells show a clear relationship between high formation temperature and high shuttle currents. Interestingly, the addition of vinylene carbonate (VC) to the electrolyte completely prevents the shuttle current, even at elevated formation temperatures. [1]In this study, we systematically investigate the effect of various electrolyte additives on the generation of shuttle molecules. LFP/graphite and NMC811/graphite pouch cells were filled with electrolyte consisting of 3:7 EC:DMC with 1.5 M lithium hexafluorophosphate (LiPF6) and different additives. The pouch cells were formed at different temperatures, TF. The electrolytes were then extracted and inserted into the aforementioned coin cell setup for CV measurements.We have found that additives such as VC, fluoroethylene carbonate (FEC), ethylene sulfate (DTD), prop-1-ene-1,3-sultone (PES), and triallyl phosphate (TAP), which are known to create a stable solid electrolyte interphase (SEI), [2-4] prevent shuttle current in the CV. On the other hand, additives such as succinonitrile (SN) and trimethylsilyl isothiocyanate (TMSNCS), which do not contribute to the formation of a better SEI, [5,6] cannot prevent the shuttle current. This suggests that the formation of the shuttles is due to a poor SEI and therefore occurs at the interface between electrolyte and graphite anode.Analogue experiments with DMC as only solvent instead of 3:7 EC:DMC show similar shuttle currents in CVs, which suggests that linear carbonates such as DMC are required to form the shuttle.Figure 1 shows CVs for 1.5 M LiPF6 DMC electrolyte. The shuttle current appears to be the same for electrolyte extracted from LFP/graphite and NMC811/graphite cells ranging up to 6 μA in both cases. This indicates that the shuttle is formed independently of the cathode material, and therefore gives rise to the hypothesis that it is formed at the anode-electrolyte interface. Figure 1 also shows that the shuttle current increases with higher formation temperatures TF.