Submerged comminution of lithium-ion batteries ( LIB) has been developed as a pretreatment in the recycling process. Wastewater treatment is necessary in this process because electrolyte used in LIBs is mixed into the water bath. Especially, carbonate esters which are used as the typical solvents in LIBs must be removed to decrease the chemical oxygen demand (COD). In this paper, the removal of organics derived from the solvents was discussed for the development of the submerged comminution process in lime water. It is generally known that in alkaline solutions such as lime water, carbonate esters are readily hydrolyzed to alcohols. Therefore, the hydrolysis behaviors of the carbonate esters used as the solvents were investigated in detail. As a result, the carbonate esters with high solubilities were almost completely hydrolyzed, though one that hardly dissolves in water, such as diethyl carbonate, was not hydrolyzed enough. In addition to the investigation of the hydrolysis, the removal of the alcohols generated in the hydrolysis is important to decrease the COD of the wastewater. Ozonation was employed as a removal method of the alcohols in this work. It was confirmed that the alcohols formed in the hydrolysis of the carbonate esters could be removed in the ozonation. [doi:10.2320/matertrans.M-M2026801]

Controlling the electrodeposition morphology of zinc from alkaline electrolytes is a critical challenge for advancing hydrometallurgical electrowinning and rechargeable zinc batteries. In this study, we systematically investigated the effects of electrolyte flow velocity and current density on zinc morphology, constructing a comprehensive morphology map. At high current densities, dendritic growth observed under stagnant conditions is suppressed by forced convection, consistent with mitigation of mass-transfer limitations. Conversely, at low current densities (-10 to -30 mA cm-2), an anomalous "mossy" morphology emerges after a distinct incubation period. Our in-situ observations and ex-situ SEM/EBSD analyses revealed that stable layer-by-layer growth is dependent and proceeds slowest on the (0001) basal plane, while mossy initiation occurs irrespective of substrate orientation. Crucially, we provide novel experimental evidence that increasing the flow velocity effectively suppresses mossy initiation. Based on these findings, we propose a new mechanism that mossy initiation is triggered by the breakdown of surface intermediates (zinc hydroxide/oxide film). We hypothesize that the accumulation of hydroxide ions (OH-) near the interface destabilizes the surface intermediates, initiating a self-accelerating cycle of disordered deposition. This mechanism elucidates the roles of the incubation period (time for OH- accumulation) and convection (mitigation of OH- accumulation), providing a unified and mechanistic understanding of morphological control in alkaline zinc electrodeposition.

Controlling the electrodeposition morphology of zinc in alkaline electrolytes is a critical challenge for advancing hydrometallurgical electrowinning and rechargeable zinc batteries. We systematically investigated the effects of electrolyte flow velocity and current density on zinc deposition morphology. At high current densities, forced convection suppressed dendritic growth observed under stagnant conditions, consistent with mitigation of mass-transport limitations. In contrast, at low current densities (−10 to −30 mA cm −2 ), an anomalous mossy morphology emerged after a distinct incubation period. In situ observations and ex situ SEM/EBSD analyses revealed that stable layer-by-layer growth depends on crystallographic orientation and proceeds most slowly on the (0001) basal plane, whereas mossy initiation was observed on both polycrystalline and near-single-crystalline Zn substrates, suggesting that the initial crystallographic orientation of the substrate alone does not uniquely determine the onset of mossy growth. We further show that increasing the flow velocity effectively suppresses mossy initiation. The observed incubation period and flow-dependent suppression suggest that time-dependent changes in the interfacial environment play an important role in the transition from compact to mossy deposition. A possible involvement of hydroxide- or oxide-related surface species is discussed as a working hypothesis, although direct verification remains necessary.

Lithium-ion batteries have a significant safety risk of extensive fire and explosion accidents due to thermal runaway. One of the key issues of the recycling of end-of-life lithium-ion batteries is safe deactivation prior to the separation and recovery of the elements. This study aimed to improve the safety in the deactivation process of wastes of lithium-ion batteries by crushing in lime water under an inert atmosphere by investigating the reaction at the positive electrode. Especially, the solution conditions to generate O2 gas at the positive electrode were investigated to avoid hydrogen explosion caused by H2 gas generated at the negative electrode. The positive electrode retrieved from lithium-ion batteries was solely immersed in Li salt-added solutions. The generated gas was analysed by gas chromatography, and the shift of immersion potential was measured. The generation of O2 gas was accelerated and suppressed by the existence of Li+ cation and halide anions, respectively. The gas species was consistent with the immersion potential of the positive electrode. The behavior of waste of lithium-ion batteries during the deactivation by immersion in salt water is discussed. In addition, several reductants were added to the solution to utilize the function of sacrificial anode.

The thermodynamic stability of palladium chloride (PdCl2) remains uncertain due to significant discrepancies in the standard enthalpy of formation (Delta fH degrees) values presented in various data compilations. This study aimed to obtain reliable thermodynamic quantities for PdCl2 by accurately measuring the equilibrium chlorine partial pressure (pCl2) over PdCl2/Pd. We employed the transpiration method, utilizing chlorine gas detector tubes for precise pCl2 determination in the temperature range of 661-741 K. Phase analysis and oxygen partial pressure dependence ofpCl2 confirmed that the equilibrium was governed by the dissociation of alpha-PdCl2 (s) into Pd(s) and Cl2 (g) in an Ar atmosphere. The temperature dependence of the equilibrium chlorine partial pressure was determined as follows: log(pCl2 /bar) = (6.176 +/- 0.985)-(7930.4 +/- 691.4) (T/K)-1. From this relationship, the Delta fH degrees value for alpha-PdCl2 (s) was calculated via second-law analysis as (-151.8 +/- 13.2) kJ mol-1 at 661-741 K. These results are consistent with early experimental reports and support earlier thermodynamic compilations (Barin(1977) and Knacke(1991)). The Delta fH degrees values in more recent compilations (Barin (1995), SGPS (2019), MALT (2024), FactPS (2025)) are inconsistent with the present experimental results. For a more definitive establishment of the thermodynamic properties, future research should focus on heat capacity measurements of PdCl2 (s) to facilitate the third-law analysis.

For the molten salt electrodeposition of Ti of smooth surfaces, control of the concentrations of Ti ions in a molten salt bath is important. However, the conventional measurement of Ti ions using chemical analysis requires laborious procedures and there is measurement lag-time. In this study, simple methods to measure the concentrations of Ti ions were investigated for the establishment of an industrial Ti electrodeposition process. We demonstrated that the concentration ratio of Ti2+ and Ti3+ is determined from electromotive force measurements between Ti and molybdenum electrodes in baths with different concentration ratio of Ti2+ and Ti3+. The electromotive force reflects the difference between the immersion potential of the Mo electrode, which depends on the the concentration ratio of Ti2+ and Ti3+ in the bulk, and that of the Ti electrode, which is governed by the local equilibrium between Ti2+ and Ti3+ near the electrode. Therefore, the electromotive force is directly related to the concentration ratio of Ti2+ and Ti3+ in the bulk. As the concentration of Ti2+ can be calculated by the polarization curve, the concentration of Ti2+ and Ti3+ can be obtained without inductively coupled plasma analysis and/or other instrumental analysis. An electrochemical method for in situ determination of Ti2+ and Ti3+ concentrations.EMF measurement based on local equilibrium formed by a comproportionation reaction.Applicable to industrial titanium electrodeposition processes in molten salts.

ABSTRACT For a sustainable society, the development of efficient and clean recycling processes for lithium‐ion batteries (LIBs) is highly demanded. Submerged crushing is one of the promising pretreatments for the recycling processes because it has a lower risk of combustion of LIBs during the crushing. A major bottleneck in the implementation of this process is the development of removal methods of organics originating from LIB electrolyte to control the chemical oxygen demand of the wastewater. It has been reported that alcohols such as ethylene glycol (EG), derived from the organic solvents, can be removed by ozonation under alkaline conditions. However, several issues remain, including the exploration of efficient removal methods applicable even under non‐alkaline conditions, and the investigation of removal processes for additives used in LIBs. In this paper, electro‐oxidation was utilized as an alternative method to ozonation, and the removal of EG by the electro‐oxidation was investigated. Additionally, the ozonation and the electro‐oxidation of adiponitrile (ADN) and 3‐hydroxypropanesulfonic acid (3‐HPSA), which come from the organic additives in LIBs, were conducted. It was experimentally observed that the electro‐oxidation of EG efficiently occurred. On the other hand, the oxidative removals of ADN and 3‐HPSA did not sufficiently occur in the electro‐oxidation, but they did in ozonation. Based on the results, the process for the organic removal in the LIB recycle was proposed.

Correction for ‘Kinetics and mechanism of hydrolysis of PF 6 − accelerated by H + or Al 3+ in aqueous solution’ by Takuto Miyashita et al. , Environ. Sci.: Water Res. Technol. , 2025, 11 , 281–292, https://doi.org/10.1039/D4EW00758A.

Submerged crushing of the cells of lithium-ion batteries (LIBs) for hybrid electric vehicles and small home appliances in approximately 250 L of lime water, saturated calcium hydroxide (Ca(OH)2) solution, in inert N2 atmosphere has been investigated with an aim to establish a safe deactivation process of the spent LIBs even at the charged state. Analysis of hydrogen concentration just above the water surface and at the outlet of the equipment, observation of the crushing, and pH measurement of the lime water were conducted. In the crushing of LIBs for small home appliances, many viscous foams were generated on the water surface, and a large amount of white smoke was emitted as the foam broke up. A processing capacity about 20 kg/h for the LIB cells for hybrid electric vehicles and 200 kg/h for the mobile battery were achieved. Various issues for the industrialization were found through the tests.

In the deactivation of spent lithium‐ion batteries (LIBs) by crushing in water for small‐scale recycling, one of the most difficult challenges is the treatment of wastewater containing LiPF 6 due to the slow decomposition rate of PF 6 − . Additionally, the recovery of dissolved Li + in wastewater is required. This study aims to separate PF 6 − and Li + from wastewater containing LiPF 6 by electrodialysis. LiPF 6 solution is prepared as the feed, and PF 6 − and Li + are transferred into the anolyte and catholyte through an anion exchange membrane (AEM) and a cation exchange membrane (CEM), respectively. The transport numbers of PF 6 − and Li + in the AEM and CEM are measured as 0.22–0.32 and 0.22–0.50, respectively. Then, the effects of the compounds derived from LIBs electrolyte, ethylene glycol, and formic acid on the electrodialysis are investigated. In addition, the transport chemistry of LiPF 6 is discussed by comparing the electrodialysis of LiPF 6 with that of NaCl. The higher permselectivity of PF 6 − in the AEM is explained by the hydrophobicity of anions. Finally, the operation costs of wastewater treatment are estimated. This estimation suggests that electrodialysis has the potential to significantly reduce the cost of wastewater treatment.

Y-doped BaZrO3 (BZY) is a promising candidate for the electrolyte material of proton conducting fuel cell (PCFC). The impurity concentrations of Ni, Co, and Fe are often of interest in studies of cell processing because the electrochemical performances and the sinterability remarkably depend on the concentrations. This work proposes a simple technique to quantify the dissolved Fe, Co, and Ni in BZY sintered bodies by evaluating the color in the L*a*b* color space. Colorimetric measurements revealed a roughly linear relationship between L* and the logarithm of Fe, Co, and Ni concentrations in the dilute range from 0.001 to 0.1 at.%, providing an empirical calibration curve. L* values also depend on the raw BZY powders used as the starting material and the sintering procedure, resulting in variations in relative density, Ba deficiency and excess of the sintered body. Therefore, when applied to a series of sintered bodies with consistent starting material and same processes, this calibration curve is reliable.

Treatment of wastewater containing PF6- is required during hydrometallurgical recycling of lithium-ion batteries. Because of the kinetic stability of PF6- in aqueous solution, the decomposition study into PO43- or F- is required for wastewater treatment. In our previous report, the hydrolysis of PF6- was shown to be accelerated by adding Al3+ and elevating the solution temperature. In this work, the kinetics and mechanism of the hydrolysis of PF6- at several pH and Al3+ concentrations were investigated for more efficient wastewater treatment. The solutions containing LiPF6 at various pH and AlCl3 concentrations were kept at 90 degrees C, and the concentration changes of PF6-, PO2F2-, PO3F2-, PO43-, and F- were measured by ion chromatography. The measurement results were analyzed assuming pseudo-first-order kinetics. The results showed that Al3+ and H+ accelerated the hydrolysis of PO2F2- and PO3F2-, but the levels of accelerating effects were different. More specifically, the accelerating effects of Al3+ are higher in the order PF6- > PO2F2- > PO3F2-, while the accelerating effects of H+ are in the opposite order. Based on the discussion, a more efficient treatment process for wastewater containing PF6- was proposed. The proposed process is expected to reduce heating costs and processing time compared to previously reported ones.

Apparent conductivities of electrolytes in protonic ceramic fuel cells (PCFCs) are roughly one-third lower than the expected values for the pristine proton-conducting ceramics. This degradation is mainly derived from the Ni diffusion into the electrolytes from negative electrodes during the co-sintering process in the conventional fabrication method. Regrettably, it seems that only a little effort has been devoted to the solution at the primal level today. In this work, we fabricate negative-electrode-supported PCFCs using an alternative process that uses a concentrated paste of Ni fine particles and vacuum-infiltration techniques. This method enables uniform additions of Ni catalyst into negative electrodes without high-temperature treatment. The PCFCs have an excellent apparent conductivity of similar to 10 mS cm(-1) and exhibit performance comparable to or better than those fabricated by the co-sintering process. We believe our proposed process helps to break away from the conventional fabrication method and realize a hydrogen economy with highly efficient PCFCs.

This article investigated the recoverability of the Ga in bauxite by carbothermal reduction. Currently, Ga is mostly manufactured from bauxite through the Bayer process as a by-product of alumina, but it is worthwhile to consider alternative processes under stricter environmental regulations and a shortage of high-quality bauxite. This study focused on the Pedersen process, which is the alumina production process consisting of carbothermal reduction and alkaline leaching. The metal and slag phases were prepared by carbothermal reduction of bauxite at 1873 K, and then aluminium in the slag was leached with (Na2CO3 + NaOH) solution at 348 K. Evaluation by inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometry revealed that almost all Ga in bauxite was transferred to the metal phase, and the distribution to the slag phase was negligible in carbothermal reduction, which agrees with the thermodynamic consideration. These results suggest that the gallium recovery from pig iron is necessary to produce Ga in the Pedersen process.

We report a 139 La-NMR study of polycrystalline samples of multi( n )-layered nickelates, La 3 Ni 2 O 7 -delta ( n = 2) and La 4 Ni 3 O 10 -delta ( n = 3), at ambient pressure. Measurements of the nuclear magnetic resonance (NMR) spectra and nuclear spin relaxation rate (1 / T 1 ) indicate the emergence of a density wave order with a gap below T * - 150 K for La 3 Ni 2 O 7 -delta and - 130 K for La 4 Ni 3 O 10 -delta . The fi nite value of 1 / T 1 below T * indicates metallic ground states with the remaining density of states at the Fermi level ( E F ) under the density wave order. These features are attributed to multiple d electron bands with di ff erent characteristics. Above T * , the gradual decrease in 1 / T 1 T upon cooling implies the presence of a band with fi at dispersion near E F . From our microscopic probes, we point out that these nickelates ( n = 2 and 3) possess similar electronic states despite the di ff erence in the formal valence of the Ni d electron states, which provides a basis for understanding the novel high- T c superconductivity under high pressures.

We previously reported that Zr substitution improves the chemical stability of Ba3Y4O9 and nominally 20 mol% Zr-substituted Ba3Y4O9 is an oxide-ion conductor at intermediate temperatures (500-700 degrees C). However, the influence of Zr substitution on the structural properties of Ba3Y4O9 was poorly understood. This paper aims to comprehensively understand the crystal structure of Ba3Y4O9 with Zr substitution by powder X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS) measurements, and first-principles calculations. From the results, firstly we found that the hexagonal unit cell of Ba3Y4O9 reported in the database should be revised as doubled along the c-axis in terms of the periodicity of oxide-ion positions. The revised unit cell of Ba3Y4O9 consists of 18 layers of BaO3 and 24 layers of Y which periodically stack along the c-axis. In this work, we focused on the cationic lattice and noticed that the periodical stacking of Ba and Y layers comprises a similar sequence to that in the body-centered cubic (BCC) structure. There are two regions in the Ba3Y4O9 structure: one is a hetero-stacking region of Ba and Y layers (Ba-Y-Ba-Y-Ba) and the other is a homo-stacking region (Ba-Y-Y-Ba). It is noteworthy that the former region is similar to a cubic perovskite. In Zr-substituted Ba3Y4O9, Zr ions preferentially substitute for Y ions in the hetero-stacking region, and therefore the local environment of Zr ions in Ba3Y4O9 is quite similar to that in BaZrO3. Besides, the Zr substitution for Y in Ba3Y4O9 increases the fraction of the cubic-perovskite-like region in the stacking sequences. The structural change in the long-range order strongly affects the other material properties such as chemical stability and the ionic-conduction mechanism. Our adopted description of perovskite-related compounds based on the stacking sequence of the BCC structure should help in understanding the complex structure and developing new perovskite-related materials.

We investigated a three-layer electrolysis process utilizing porous holding materials with poor wettability to molten metal, which enables to establish a three-layer configuration of metal(l)/electrolyte(l)/metal(l) by holding metals above the electrolyte regardless of their densities. In this study, porous carbon or silica sheets were used as the holding materials for electrorefining experiments of Zn metal in molten LiCl–KCl–ZnCl2 at 723 K. Three types of experiments were carried out focusing on anodic polarization, electrorefining with cathodic carbon, and three-layer electrolysis using liquid Zn as cathode. The concentration of impurity elements in the Zn was reduced by a factor of 8 to 200 in this experimental condition, highlighting the purification effectiveness of the method. From the results obtained, we have identified certain challenges associated with the three-layer electrolysis process. Furthermore, we discuss potential prospects for industrialization.

During hydrometallurgical recycling of lithium-ion batteries (LIBs), one important challenge is the efficient treatment of wastewater containing LiPF 6 used as a lithium salt in the LIBs.

We report a ^139La-NMR study of polycrystalline samples of multi(n)-layered nickelates, La_3Ni_2O_7-δ (n=2) and La_4Ni_3O_10-δ (n=3), at ambient pressure. Measurements of the nuclear magnetic resonance (NMR) spectra and nuclear spin relaxation rate (1/T_1) indicate the emergence of a density wave order with a gap below T^*∼150 K for La_3Ni_2O_7-δ and ∼130 K for La_4Ni_3O_10-δ. The finite value of 1/T_1 below T^* indicates metallic ground states with the remaining density of states at the Fermi level (E_ F) under the density wave order. These features are attributed to multiple d electron bands with different characteristics. Above T^*, the gradual decrease in 1/T_1T upon cooling implies the presence of a band with flat dispersion near E_ F. From our microscopic probes, we point out that these nickelates (n=2 and 3) possess similar electronic states despite the difference in the formal valence of the Ni-d electron states, which provides a basis for understanding the novel high-T_ c superconductivity under high pressures.

We have reported that Zr substitution for Y in Ba3Y4O9 enhances the chemical stability in humidified atmospheres at intermediate temperatures and the Zr-substituted Ba3Y4O9 exhibits oxide-ion conduction probably mediated by oxide-ion vacancies. However, in addition to the problem of Si contamination in the samples, the long-time chemical stability and the transport number of ionic conductions were uncleared. In this work, we revisited the chemical stability and conductivity behavior of Ba3Y4O9 with Zr substitution prepared by a modified procedure to suppress the contamination. Besides, we prepared Ba3Y4O9 substituted by the other tetravalent cations (Ce, Sn, and Ti) and investigated the difference in the material properties from the Zr substitution samples. We carried out powder X-ray diffraction analyses for the evaluation of chemical stability in humidified atmospheres and electrochemical impedance spectroscopy to measure total conductivities of the substituted Ba3Y4O9. As a result, we confirmed that Ce and Sn as well as Zr can substitute 20 mol% Y in Ba3Y4O9 whereas the solubility of Ti in Ba3Y4O9 is about 3 mol% at 1600 degrees C. Besides, the chemical stability of the substituted Ba3Y4O9 strongly depended on not only the substitution level but also the substitution elements. Moreover, the substituted Ba3Y4O9 was considered to be an almost pure oxide-ion conductor because of the little sensitivity of electrical conductivity to both humidity and partial oxygen pressure.