Excess Salts Research Articles

Research Review on the Improvement and Utilization Technologies of Saline-Alkali Soils

Saline-alkali soil refers to land where excessive soluble salts in the soil lead to increased soil osmotic pressure, affecting the normal growth of plants and crop yields. Saline-alkali soils are widely distributed in arid and semi-arid regions globally, posing severe challenges to agricultural production, ecological environment, and regional economic development. Therefore, the improvement and utilization of saline-alkali soils have become a hot issue of global concern. In recent years, scholars both domestically and internationally have made significant progress in saline-alkali soil improvement technologies, cultivation of salt-tolerant crops, and ecological restoration of saline-alkali soils. This paper reviews relevant literature, analyzing the current research status, existing problems, and future development directions of saline-alkali soil improvement and utilization technologies.

Manufactured soil: A new use for bauxite residue

Bauxite processing residue produced at an Alumina refinery was used to produce manufactured soil. The residue was first acidified and then leached to remove excess salts. Green waste compost was added at rates of 5 and 10 % w/w, with or without the addition of 20 % w/w dune sand. The products were dried, crushed and sieved and the chemical, physical and microbial properties of the materials characterized. Products had an electrical conductivity and pH of 1.0–1.1 dS m−1 and 8.0–8.1 respectively in 1:5 soil:water extracts and corresponding values in saturation paste extracts were 5.4–5.7 dS m−1 and 7.4–7.5. The effective cation exchange capacity was 202–351 mmolc kg−1, exchangeable Na percentage was 41–46 %, Colwell-extractable P was 108–119 mg kg−1 and the Toxicity Characteristic Leaching Procedure showed that extractable metal concentrations were an order of magnitude below regulatory limits so the material can be considered as non-hazardous. Diethylenetriaminepentaacetic acid-extractable Cu, Zn and Mn were below reported critical levels. Addition of compost lowered concentrations of extractable Cr, As and V and drying the material further reduced extractable levels. When the material was dried it shrunk and solidified and the aggregates produced had a low macroporosity and high microporosity and water holding capacity compared with dune sand. Aggregates were very stable as measured by wet sieving. Compost addition increased organic C content, and the size (microbial biomass C) and activity (basal respiration and the activity of enzymes involved in C, N, S and P mineralization) of the soil microbial community. It was concluded that the materials produced had soil-like chemical, physical and microbial properties and could potentially be used as a soil substitute.

Soil Properties Classification in Sustainable Agriculture Using Genetic Algorithm-Optimized and Deep Neural Networks

Optimization of land management and agricultural practices require precise classification of soil properties. This study presents a method to fine-tune deep neural network (DNN) hyperparameters for multiclass classification of soil properties using genetic algorithms (GAs) with knowledge-based generation of hyperparameters. The focus is on classifying soil attributes, including nutrient availability (0.78 ± 0.11), nutrient retention capacity (0.86 ± 0.05), rooting conditions (0.85 ± 0.07), oxygen availability to roots (0.84 ± 0.05), excess salts (0.96 ± 0.02), toxicity (0.96 ± 0.01), and soil workability (0.84 ± 0.09), with these accuracies representing the results from classification with variations from cross-validation. A dataset from the USA, which includes land-use distribution, aspect distribution, slope distribution, and climate data for each plot, is utilized. A GA is applied to explore a wide range of hyperparameters, such as the number of layers, neurons per layer, activation functions, optimizers, learning rates, and loss functions. Additionally, ensemble methods such as random forest and gradient boosting machines were employed, demonstrating comparable accuracy to the DNN approach. This research contributes to the advancement of precision agriculture by providing a robust machine learning (ML) framework for accurate soil property classification. By enabling more informed and efficient land management decisions, it promotes sustainable agricultural practices that optimize resource use and enhance soil health for long-term ecological balance.

Identification of sodicity-tolerant banana varieties to harness the salt-affected ecosystem

"Salt Affected Soils" (SAS) refers to a category of soils that contain either an excess of soluble salts or exchangeable sodium. Soils are divided into four categories: normal, saline, sodic, and saline-sodic, based on the electrical conductivity (EC), pH and exchangeable sodium percentage (ESP) measurements. At the Horticultural College and Research Institute for Women in Trichy, fifteen genotypes of bananas were assessed for growth, yield, and physiological parameters in a saline-sodic environment. Four replications of the field experiment were set up in RBD and evaluated for three years. The growth physiological and biochemical characters were recorded in the seventh month after planting (MAP), and the bunch characters were recorded at harvest time. FHIA 1 (83.4%), Saba (81.0%) and Karpooravalli (78.0%) had the highest relative water content. The highest yield was recorded in FHIA-1 (23.5 kg), Saba (22.2 kg), Udhayam (22.5 kg) and Karpooravalli (22.0 kg). The sodicity injury symptoms in the leaves were evaluated using a scoring technique, and the genotypes FHIA-1(1.0) Saba recorded the lowest score for sodicity damage. A significant negative correlation was observed between salt injury degree and leaf K+/Na+. So, the varieties that maintain higher K+/Na+ ratio in leaf and root are salt tolerant. The general ranking of the banana varieties for salt tolerance was FHIA 1 > Saba > Karpooravalli > Bangrier > Ash Monthan > Veneetu Mannan > Udhayam. A comparative field trial for the 15 banana types showed that Saba, FHIA-1 and Karpooravalli could withstand sodic conditions in the field in terms of bunch characteristics, biochemical parameters, and plant growth. Grand Naine, Rasthali and CO 1 were vulnerable to sodicity stress. Regardless of cultivar, sodicity stress increased the days needed for shooting and harvest.

Water Management Interventions, Organic Fertilization, and Harvest Time in Dry Land in the Biosaline Production of Cactus Pear.

Brackish water can promote physicochemical changes in the soil. Aiming to mitigate the effect of excess salts in the soil, the use of organic matter promotes restructuring. The aim was to evaluate the productive and nutritional characteristics of cactus pear under different brackish water depths (ID) and levels of organic matter (OM). A factorial arrangement of 4 × 4 × 4 with four replications was utilized. Plots consisted of ID (0, 12, 20, and 28% reference evapotranspiration-ETo), and subplots were composed of OM levels (0, 15, 30, and 45 t/ha) and days after planting (DAP; 180, 270, 360, and 450 days). The growth, yield, and chemical composition of cactus pear were affected by ID and OM and/or by their interaction. The regular and increasing application of ID from 192 to 456 mm/year and a rainfall of 110 mm/year in cactus pear crops in biosaline systems improves the growth, freshness, dry matter yields, accumulation capacity per unit area, and chemical composition of cactus pear. The increase in OM up to the range from 30 to 45 Mg/ha linearly increases the agronomic performance of cactus pear. Biosaline systems with cactus pear should be adopted with the combined use of regular supplementary ID and OM, measuring at 304 mm/year and 45 Mg/ha, respectively.

Understanding the limits of binary diffusion for enhanced clay barrier design.

Waste containment and isolation strategies often utilize bentonite as a buffer material due to its swelling capacity, sealing efficiency, low permeability, and limited diffusive transport. However, previous experimental studies of ionic diffusion through bentonite have shown discrepancies with binary diffusion assumptions. Meticulous experiments and complementary analyses reveal that the migration of preexisting ions in the medium enables the differential flux of diffusing anions and cations, while maintaining local electroneutrality in all cases. The separation between the cationic and anionic fronts is electrically tied to the motion of the preexisting ions and reflects the interplay between valence, concentration, and self-diffusion coefficients of the ions involved. Imposing binary diffusion conditions forces the faster anions to diffuse at the same rate as cations. Therefore, effective barriers to mitigate both cation and anion transport should have low surface charge and low excess salts to minimize the preexisting ionic concentration.

Climate change induced salinization and quality deterioration of groundwater resources in Pakistan; Current scenario and future prospects

Climate change has triggered various catastrophic events including groundwater salinization resulted in quality deterioration worldwide leading to the environmental degradation and posed threat to natural ecosystems. Pakistan is among the countries severely affected by the climate change. Most of the Pakistani depends on groundwater resources for drinking and irrigation purposes but no clear policy exists regarding judicious extraction and usage of groundwater. Over extraction and exploitation of groundwater along with climate change events have deteriorated the quality of groundwater in Pakistan and most of the part is salinized and has excess of soluble salts and other chemical, physical and biological contaminants. This paper reviews the impacts of climate change on salinization and groundwater quality and possible remedies and solution for this problem especially with the perspective of Pakistan. It is the need of the hour of the time to introduce climate smart agricultural practices at farmer level to stop overexploitation of natural resources and to reduce the agriculture share to climate change. Policies should be developed and existing policies should be strictly implemented for the judicious use of surface water and ground water resources to avoid the risks of water scarcity in near future.

Efficient depolymerization of kraft lignin using zinc chloride based (molten) salts

Lignin is an attractive feed for biofuels and biobased chemicals. We here report the conversion of kraft lignin (Lignoboost) to liquids by hydropyrolysis using a zinc based (molten) salt in a semi-batch reactor. m-Cresol was used to dissolve and inject the lignin into the heated and pressurized reactor containing the molten salt. The liquid yield and fraction of organics in the liquid was optimized by varying the process parameters (hydropyrolysis temperature, pressure, hydrogen gas flow rate and salt to lignin ratio). The highest liquid yield of around 78 wt% was obtained using small amounts of salts (2.5 wt% of salts based on lignin input, 350 °C, 30 bar, 33 wt% lignin in m-cresol, hydrogen flow rate of 160 mL/min). A larger excess of salts gave a lower liquid yield, implying that catalytic amounts of salts are preferred. In addition, small amounts of salts are essential for depolymerization and the formation of lower molecular weight components, as was evident by comparing experiments with and without salts. The liquid product was shown to consist of low molecular weight phenolics like dimethyl- and ethyl-cresol, methyl guaiacol and oligomers (GC-MS, 2DGC-FID, NMR and GPC analysis). The product oil may have potential for biofuel production when coupled with a catalytic hydrotreatment step to obtain hydrocarbons or, after downstream processing and catalytic conversions, to important biobased chemicals like green phenol.

The influence of soil types and agricultural management practices on soil chemical properties and microbial dynamics

Soil provides essential nutrients for plant growth, but excess salts hinder development, making crops more vulnerable under climate change conditions. Soil microorganisms play a significant role in nutrient cycling. However, limited information is available on microbial behavior/community changes, and functional diversity in different soil types (normal, sodic, and highly sodic) and cropping systems [rice-wheat (RW); rice-wheat-mungbean (RWMb); maize-wheat-mungbean (MWMb)] and management practices in the north-western Indo-Gangetic Plains of India. We investigated the influence of different soil types on physical and chemical properties at the surface level (0–15 cm) in relation to soil microbial population, activities, and functional diversity, focusing on community-level physiological profiling (CLPP) under different agriculture systems. Seven treatment combinations of soil types, cropping systems, and management practices were evaluated. Soil pHs were found to be lower in zero-till (ZT)-based sodic soil than in conventional-till (CT) sodic soil. Soil organic carbon (SOC) (0.91 and 0.90%) content and available N (154.46 and 132.74 kg ha−1) were higher with the ZT-based system under normal (N) soils (ZT-RWMb-N and ZT-MWMb-N) than in CT-based normal soil (0.67 and 121.04 kg ha−1). Similarly, higher SOC and N (0.85 and 76.11 kg ha−1) were found under ZT management in sodic soils (S) than under CT management (0.73% and 121.05 kg ha−1). Substrate utilization (amino acids, amines, carbohydrates, carboxylic acids, phenolic compounds, and polymers) increased with the incubation period. During 0–120 h of incubation, the highest utilization of amino acids, amines, carboxylic acids, phenolic compounds, and polymers was observed for ZT-MWMb-S soils, while the lowest was recorded for ZT-MWMb-N soils. Under high salt conditions, soil enzymatic activities (dehydrogenase, acid phosphatase, alkaline phosphatase, etc.) declined significantly compared to normal soils, affecting soil chemical and physical conditions. Microbial population and enzyme activities decreased with increasing salt stress across all cropping systems. These findings suggest that adopting efficient crop management practices can help mitigate the adverse effects of soil salinity on microbial diversity and soil health, thereby enhancing sustainable agricultural productivity in salt-affected regions.

The bZIP gene family in the halophyte Limonium bicolor: Identification, expression analysis, and regulation of salt stress tolerance

The basic region/leucine zipper transcription factors (bZIPs) are one of the largest transcription factor families in eukaryotes, and play a key role in growth, development, and response to abiotic stresses. Limonium bicolor is a typical recretohalophyte, which can excrete excess salts from body to outside through the salt glands located on the stems and leaves to maintain ionic balance in the body. In this study, 58 L. bicolor bZIP members (LbbZIP1–58) were identified, which were unevenly distributed on 8 chromosomes and divided into 11 groups. The bioinformatics analysis revealed strong colinearity between LbbZIPs and GmbZIPs of soybean (Glycine max). And promoter cis-acting elements of LbbZIPs were related to stress responses and phytohormone responses. Most LbbZIP members responded to abiotic stresses such as NaCl, PEG, and ABA. Silencing LbbZIP28 in L. bicolor increased salt glands density and salt secretion capacity of leaves, and salt tolerance by means of up-regulating the expression levels of genes involved in salt gland development and ion transport. These results provide new information for LbbZIPs and help to interpret salt gland development and salt secretion in L. bicolor. Our results will provide a reference for a deeper understanding of the molecular foundation of LbbZIPs in L.bicolor.

An Integrated Process of Struvite Precipitation/Membrane Filtration Using Flat Ceramic Membranes Is an Effective Method for the Treatment of Liquid Fraction Digestate from a Municipal Biogas Plant

One method of processing municipal waste biogas plant digestate is to separate it into solid and liquid fractions. Since the digestate can be a potential source of water, it must undergo the appropriate treatment. Pressurised membrane processes preceded by struvite precipitation can be particularly useful in this regard. Experiments were conducted to determine the effectiveness of treating the digestate liquid fraction from a municipal waste biogas plant using an integrated process that combines struvite precipitation with membrane filtration, employing flat ceramic membranes with different cut-off values. The results confirm that this integrated process is effective for digestate treatment. A significantly increased improvement in the final quality of the test solution and a reduction in membrane fouling intensity were observed compared to those of these processes conducted separately. It is noteworthy that the purest solution was obtained when struvite precipitation and filtration through a flat ceramic membrane with a cut-off of 1 kDa were combined. This approach enabled the precipitation of struvite, a valuable fertiliser; the protection of the membranes from fouling; and a high degree of organic compound removal. The recovered water from the digestate (after dilution or removal of excess salts) can be used in agriculture or horticulture.

Evaluation of Myostatin and Some Biochemical Variables in Both Type 2 Diabetic and Diabetic Nephropathy Patients

Background: The kidneys are essential organs that keep blood pH stable and eliminate excess water, salts, and aid in the body's waste removal. Aim of the study: The study aims to investigate the importance of myostatin in the development of diabetic nephropathy patients. In addition, the level of urea, creatinine, sodium, potassium, and phosphorus. Materials and methods: A Case-Control study lasted from- November 2023 to January 2024, at Al-Amal Kidney Dialysis Center and Azadi Teaching Hospital in Kirkuk Governorate. The 135 blood samples, their ages (25-70), were divided into three groups. The first group G1 (n:50) patients with T2DM. The second group G2 (n:55) with diabetic nephropathy. The third group G3 for control. Serum samples were utilized to measure MSTN by ELISA, blood urea, serum creatinine, S.PO4, S. Na+, S. K+, and S. Ca++ by spectrophotometer. Results: Significant variations (P<0.05) in MSTN were seen between study groups (8.43±4.69, 10.99±7.05, 5.63±3.38) ng/ml. Additionally, significant differences exist between (G1 vs G2), (G1 vs G3), and (G2 vs G3) with p-value <0.05 Diabetic nephropathy G2 had the highest mean urea and creatinine levels (136.69±38.21, 5.99±1.87), followed by G1 (34.92±9.06, 0.89±0.26) and control group G3 (31.00±4.72), with significant differences (p ≤ 0.001) among three groups. Additionally, G1 with G2, G2 with G3, and G1 with G3 had significant differences (p-value>0.01). Conclusion: This study found higher myostatin, urea, and creatinine in diabetic nephropathy and diabetic patients. The data also showed hyponatremia, hypocalcemia, hyperkalemia, and hyperphosphatemia in diabetic nephropathy and diabetic patients.

Phytoremediation: A Sustainable Approach to Combat Soil Salinity

Soil salinization is a significantconstraint affecting the productivity of agricultural land worldwide. This led to the abandoning of the production of farmcrops on colossalland. Soil salinity inversely affects seed germination and plant growth and influences the plant’s biological activities like photosynthesis, respiration, plant metabolism, enzymatic activities, hormone regulation, etc. Therefore, efforts are being made to bring the saline soil under cultivation by improving itthrough a proper drainage system to drain out the salts orapplying chemical amendments. However, these options are costly and energy-intensive for employment in large areas on a vast scale. In this direction, biologically cost-effective approaches are also being practiced to improve these degraded lands. Phytoremediation, a plant-based approach to improving degraded soil, may be an appropriate option. This is done by the plantation of salt-tolerant plant species, which can remove and leach down excess salts like sodium (Na<sup>+</sup>) from the soil and enhance calcium (Ca<sup>2+</sup>) salts through the cation exchange process from the root zone. During this process, remarkable properties like soil-aggregates stability, root proliferation, soil hydraulic properties, and nutrient availability to plants are also improved. Such improvement in soil properties facilitates the cultivation of less tolerant plants and improves the environment in general and the climatic conditions by enhancing carbon sequestration.

Characterization and Mapping of Soil Salinity Status at Small-Scale Irrigation Farm: The Case of Fantale Irrigation Project Sites

Agricultural production and productivity can be adversely affected by the presence of excessive salts in soils particularly in semi-arid and arid areas. Knowledge of the salinity/sodicity of the soil and the quality of the irrigation water is essential for managing agricultural fields effectively and increasing the output and productivity of the lands. This research was initiated with the objectives of characterizing and Mapping of soil salinity status at small scale irrigated areas of Fantale district and identifying the most affected irrigation scheme so as to design appropriate soil salinity management. The study was conducted at Fentale district of Galcha, Gola and Dire Sade irrigation schemes. Soil samples were collected from the surface using augur, and from pits at different depth interval and analyzed for pH, EC, Na+, ESP, SAR, Ca<sup>2+</sup>, Mg<sup>2+</sup>, K<sup>+</sup>, and CEC. The result was compared with the standards set by FAO system to classify soil and water salinity. Accordingly, it was identified that Galcha irrigation scheme was characterized as sodic due to very strong sodium concentration with average ESP of 53.2% and EC 3.95 mmhoms/cm and pH about 9.25. On the other hand, Gola and Dire Sade Irrigation schemes were characterized as moderately and slightly sodic respectively. Sodium was the dominant soluble cation, followed by calcium, magnesium, and potassium in all soil depths and schemes. Beside primary Salinization of natural processes such as physical or chemical weathering parent material, and discharge Basaka Lake to the downstream, was the main source of salt build-up in the upper layers of the soil at Galcha irrigation scheme. On the other hand, irrigation water analysis indicated that water used for irrigation at all irrigation schemes were slightly sodic. Therefore, the study underscores the need for a scientific reclamation of sodic soils primarily at Galcha Irrigation scheme where sodium concentration in the soil was very strong.

Stretchable hydrogels of chitosan/hyaluronic acid induced by polyelectrolyte complexation around neutral pH

In this work, we propose the formation of stretchable hydrogels at neutral pH from the physical crosslinking of chitosan (CS) and hyaluronic acid (HA) by polyelectrolyte complexation. A mixture of CS (Mw ≈ 600 kg/mol, degree of acetylation ≈ 50 %) solution and HA (Mw ≈ 77 kg/mol) solution was prepared with an excess of salts screening the electrostatic interactions CS/HA. In a controlled manner, the polyelectrolyte complexation was induced through the progressive dialysis of the salted polymer mixture against a sodium acetate solution (AcONa, 0.01 M) for 7 days. Depending on [HA], various materials were obtained: viscous solutions at [HA] = 0.75 % (w/v); hydrogels at [HA] = 1.50–2.24 % (w/v) with Young modulus of 14 kPa and stretchable to 200 %. The small angle X-ray scattering characterization of the hydrogels revealed a multiscale organization related to the conformation of the polymers induced by the physical interactions. The dialysis process with AcONa was optimized by adding a dialysis step against a zinc acetate solution containing Zn2+. The combination of polyelectrolyte complexation between CS/HA and metal complexation between Zn2+ and the polymers led to an enhancement of the hydrogel stretchability up to 400 %.

Designing alkali-exchanged ZSM-5 catalysts for the dehydration of lactic acid to acrylic acid

This report shows that complete control of the degree of alkali exchange is possible by controlling the pH strength, and that is possible to distinguish the selectivity of the cations themselves in the lactic acid (LA) dehydration reaction by excluding undesired active sites arising from excess salts. We discovered that strong base conditions induced by alkali hydroxides (e.g., KOH) increase the degree of alkali ion exchange, and that in the absence of additional salts−such as halogen anions, oxides−the KOH-ZSM-5 catalyst exhibited high acrylic acid (AA) selectivity (∼70%) and durability (100 h). Characterization via temperature-programmed desorption (TPD) and pyridine-infrared (Py-IR) analysis revealed a full exchange of the protons bound to the Si–O–Al sites with potassium in commercial ZSM-5. In addition, structural pore expansion due to the desilication by KOH leads to significant enhancement in the selectivity for AA. The mechanistic impact of KOH treatment on lactic acid dehydration is also systematically verified by in situ IR spectroscopy.

Salt extrusion, a new function of lenticels in red mangrove leaves

Halophytes are characterized by their ability to survive in environments with high salinity, and many of these species eliminate excess salts through secretory structures, such as salt glands or bladders. Rhizophora mangle, however, is a halophyte that does not have specialized structures for eliminating salts, but it does have lenticels located on the lower surface of the leaves. These lenticels are not only involved in oxygenating plant tissues, but they can also eliminate toxic substances. Thus, we hypothesized that the lenticels could act as structures involved in the elimination of excess salts. In this study, we used light microscopy to observe the occurrence of lenticels on the stipules and both young and adult leaves of R. mangle. Using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX), we also analyzed the composition of chemical elements found in the extrusion content of lenticels. The origin of lenticels, both stipular and foliar, is stomatal, and, at the end of development, the stomatal complex is degraded, generating the opening pore. Sea salt was observed on the surface of leaf lenticels, as evidenced by EDX-SEM. The most representative elements on the surface of the lenticels were Cl, Ca, and Na, respectively. In this way, we suggest that the lenticels in R. mangle act as pores through which minerals, such as Na, Cl, Ca, K, Mg, P, S, and Si, can be eliminated by the leaves, an important strategy to maintain the osmotic balance of a typical mangrove species growing in a tropical region.

Eliminating the Adverse Impact of Composition Modulation in Perovskite Light-Emitting Diodes toward Ultra-High Brightness and Stability.

Excess ammonium halides as composition additives are widely employed in perovskite light-emitting diodes (PeLEDs), aiming to achieve high performance by controlling crystallinity and passivating defects. However, an in-depth understanding of whether excess organoammonium components affect the film physical/electrical properties and the resultant device instability is still lacking. Here, the trade-off between the performance and stability in high-efficiency formamidinium lead iodide (FAPbI3)-based PeLEDs with excess ammonium halides is pointed, and the underlying mechanism is explored. Systematic experimental and theoretical studies reveal that excess halide salt-induced ion-doping largely alters the PeLEDs properties (e.g., carrier injection, field-dependent ion-drifting, defect physics, and phase stability). A surface clean assisted cross-linking strategy is demonstrated to eliminate the adverse impact of composition modulation and boost the operational stability without sacrificing the efficiency, achieving a high efficiency of 23.6%, a high radiance of 964 W sr-1 m-2 (The highest value for FAPbI3 based PeLEDs), and a prolong lifetime of 106.1 h at large direct current density (100mA cm-2), concurrently. The findings uncovered an important link between excess halide salts and the device performance, providing a guideline for rational design of stable, bright, and high efficiency PeLEDs.

Sulfur-containing soft Lewis base polymers for improved lithium-ion conductivity under polymer-in-salt conditions

Abstract Solid polymer electrolytes have been intensively studied to improve the safety and energy density of lithium-ion batteries (LiBs). Although high-rate performance of LiBs has been reported in electrolytes under polymer-in-salt conditions with an excess of lithium salts and polymers, effective conditions for achieving high ionic conductivity remain unresolved. In this study, we elucidate the mechanism and high Li-ion transportability of poly(sulfone-thioether) under polymer-in-salt conditions. In particular, the composition of the polymer with an asymmetric Li salt, lithium(fluorosulfonyl)(trifluoromethane sulfonyl)imide (LiFTFSI), induced a high ionic conductivity above 10−5 S/cm, which is higher than that of the poly(ethylene oxide) (PEO)-Li salt system. Under polymer-in-salt conditions, the enhanced conductivity of poly(sulfone-thioether) contrasts with the conductivity drop observed in the conventional PEO system. These results show the superiority of polymers with soft Lewis bases, such as sulfur donor atoms, for Li-ion transport under polymer-in-salt conditions.

Effective upcycling of NMC 111 to NMC 622 cathodes by hydrothermal relithiation and Ni-enriching annealing

It is imperative that a sustainable approach to the recycling of lithium-ion batteries (LIBs)—in particular the spent NMC cathodes—which reach their end-of-life (EOL) is realized as 11 million metric tonnes are expected to reach EOL by 2030. The current recycling processes based on pyrometallurgy and hydrometallurgy are not fully sustainable options as they recover only the value metals. By contrast direct recycling that aims in regenerating EOL LIB cathodes without breaking down the active compound’s crystal structure offers the most sustainable option. In this paper the direct recycling of NMC cathodes is investigated in combination with their upcycling. Upcycling is going to be in growing demand since the first generation NMC 111 cathode chemistries evolve to higher energy/nickel-rich formulations. In this work, the baseline is established for direct recycling of low and high nickel NMC cathodes by analyzing the three key steps of chemical delithiation of pristine NMC cathode material, hydrothermal relithiation (4M LiOH for 4 h at 220 °C), and annealing (4 h at 850 °C) in order to set the ground for investigating the upcycling of NMC 111 to NMC 622. Upcycling is affected via the co-addition of pre-calculated excess NiSO4 and Li2CO3 salts during annealing, following the hydrothermal relithiation step. Use of NiSO4 that is commonly used as p-CAM provides a lower cost alternative to Ni(OH)2 as Ni source. Characterization revealed the upcycled material to have been endowed with the typical α-NaFeO2 layered structure and have surface morphology and composition similar to pristine NMC material. The upcycled NMC 622 cathode yielded good cycling stability (91.5% retention after 100 cycles) and >99% Coulombic efficiency albeit with certain polarization loss justifying further optimization studies.