Search

Cobalt and nickel are vital metals for the transition to a decarbonized society, currently in critical supply conditions to meet future demands. The recovery of those metals from secondary sources can mitigate this issue, as well as treating hazardous waste and increasing its economic value. In this work, ionic polymers inspired by deep eutectic solvents (DES) were studied for cobalt and nickel recovery from representative recycling solutions. These polymers were prepared by simple and fast photopolymerization process combining [2-(methacryloyloxy) ethyl] trimethylammonium chloride (METAC) with a series of hydroxylated compounds (e.g. alcohol and phenolic compounds). Different driving forces for metal absorption; ionic interactions, hydrogen bonding coordination, acidity of the media and polymer swelling have been investigated. The poly(METAC:1-butanol) polymer showed the highest absorption capacity (46 ± 5 mg g−1 and 46 ± 4 mg g−1 for cobalt and nickel, respectively), competing with conventional materials. Moreover, the metal stripping and recovery step was investigated. Favourably, deionized water presented the highest desorption efficiency, in comparison with HCl, rendering this process 'greener' and highly cost-effective. Finally, the ionic polymers were successfully reused as absorbents for five absorption/desorption cycles, maintaining structural integrity. This approach can pose an alternative way of using systems inspired by DES, with application at a larger scale upon further optimizations. [ABSTRACT FROM AUTHOR]

Cobalt has a vital role in the manufacturing of reliable and sustainable clean energy technologies. However, the forecasted supply deficit for cobalt is likely to reach values of 150 kT by 2030. Therefore, it is paramount to consider end-of-life devices as secondary resources for cobalt. Electrorecovery of cobalt from leached solutions has attracted attention due to the sustainability of the recovery process over solvent extraction followed by chemical precipitation. Recently, we reported Co electrorecovery from two different cobalt sources (CoCl2·6H2O and CoSO4·7H2O) using ethylene glycol : choline chloride (EG : ChCl) in a 4.5 : 1 molar ratio, leading to higher purity and easier electrodeposition when sulfate was present as an additive. Here, Co2+ speciation is reported for the two EG : ChCl systems depending on the cobalt source using several spectroscopic techniques (e.g. NMR, EPR, FTIR) in combination with molecular dynamics simulations. Monodentate coordination of SO42− to Co2+, forming the tetrahedral [CoCl3(SO4)]3− was observed as the dominant structure in the system containing CoSO4·7H2O, whereas the system comprising CoCl2·6H2O shows a homoleptic tetrahedral [CoCl4]2− as the dominant structure. This resulted in knowledge being gained regarding Co2+ speciation and the correlation with electrochemistry will contribute to the science required for designing safe electrolytes for efficient electrorecovery. [ABSTRACT FROM AUTHOR]

Block copolymers (BCPs) as solid electrolytes for batteries are usually designed to have an ion-solvating block for ion conduction and an ionophobic block for providing mechanical strength. Here, we show a novel solid polymer electrolyte (SPE) for sodium batteries based on a poly(vinyl benzoate)-b-poly(diallyldimethyl ammonium bis(trifluoromethanesulfonyl)imide) PVBx-b-PDADMATFSIy-b-PVBx ABA triblock copolymer. The SPE triblock copolymer comprises a polymerized ionic liquid (PIL) ion-solvating block combined with NaFSI salt as an internal block and an ionophilic PVB as an external block. Four distinct compositions with varying chain lengths of the blocks were synthesized by reversible addition−fragmentation chain-transfer (RAFT) polymerization. The neat copolymers were subsequently mixed with NaFSI in a 2:1 mol ratio of Na to ionic monomer units. Through comprehensive analysis using differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR), it was revealed that the ion coordination within the polymer–salt mixtures undergoes changes based on the composition of the starting neat polymer. Electrochemical evaluations identified the optimal composition for practical application as PVB11.5K-b-PDADMATFSI33K-b-PVB11.5K, showing an ionic conductivity at 70 °C of 4.2 × 10−5 S cm−1. This polymer electrolyte formulation was investigated for sodium in Na|Na symmetrical cells, showing an overpotential of 200 mV at 70 °C at 0.1 mA cm−2. When applied in a sodium–air battery, the polymer electrolyte membrane achieved a discharge capacity of 1.59 mAh cm−2 at 50 °C. [ABSTRACT FROM AUTHOR]

Recovery of critical metals from waste is becoming very important to bridge the gap between the limited natural resources available and their ever-increasing demand. One such vital metal is neodymium (Nd), which plays an essential role in advancing sustainable clean energy technologies. Therefore, in this work, the key parameters to selectively recover Nd over iron (Fe) from their oxides, as model systems were investigated. By investigating the effect of key parameters, we aim to understand the underpinning science principles necessary for the safe and efficient recovery of critical metals from secondary sources. A series of deep eutectic solvents, consisting of a hydrogen bond donor (HBD), lactic acid or acetic acid, and hydrogen bond acceptor (HBA), guanidine hydrochloride (GUC), have been investigated in HBA–HBD combinations, and individually in the presence of water to determine the role of the HBD and HBA towards Nd and Fe leaching efficiency and selectivity. The combination of GUC with HBDs was less beneficial for the leaching of Nd2O3, with a maximum value of 78% in comparison with the individual systems, in the absence of GUC, which demonstrated a maximum dissolution of 95%. Among the different combinations, the acetic acid aqueous solution led to the highest dissolution efficiency and selectivity, probably due to the high basicity and strong stability constants for Nd-acetate complexes. Other parameters, such as the impact of the molar ratio Nd2O3 : Fe2O3 were also explored, and a synergetic effect that promotes Nd2O3 solubility at 1 : 1 Nd : Fe weight ratio is observed across the samples. However, when increasing the amount of Fe2O3 in the mixture to simulate realistic ratios present in spent magnets, selectivity is strongly affected, and only the acetic acid solution is capable of selectively dissolving Nd2O3 with a separation factor of up to 5038, which is higher than the current state of the art (1608). Finally, the acetic acid concentration was also studied as a factor to assess its effect on selectivity while also reducing cost. [ABSTRACT FROM AUTHOR]

Aqueous zinc–iodine (Zn−I2) batteries are gaining significant attention due to their low‐cost, high safety and high theoretical capacity. Nevertheless, their long cycle and durability have been hampered due to the use of aqueous media that, over time, lead to Zn dendrite formation, hydrogen evolution reaction, and polyiodide dissolution. Xiao et al. recently reported the addition of an imidazolium‐based ionic liquid (IL) to an aqueous electrolyte and found that the IL plays a key role in modifying the solvation of Zn2+ ions in the bulk electrolyte and the inner Helmholtz plane, repelling H2O molecules away from the Zn anode surface. UV/Vis and NMR spectroscopy also indicates a strong interaction between imidazolium cation [EMIM]+ and I3−, thereby reducing polyiodide shuttling and enhancing the cycle life of the battery. Overall, a capacity decay rate of only 0.01 % per cycle after over 18,000 cycles at 4 A g−1, is observed, making the use of IL additives in aqueous electrolytes highly promising candidates for Zn−I2 batteries. [ABSTRACT FROM AUTHOR]

Sodium–air batteries (SABs) are receiving considerable attention for the development of next generation battery alternatives due to their high theoretical energy density (up to 1105 W h kg−1). However, most of the studies on this technology are still based on organic solvents; in particular, diglyme, which is highly flammable and toxic for the unborn child. To overcome these safety issues, this research investigates the first use of a branched ether solvent 1,2,3-trimethoxypropane (TMP) as an alternative electrolyte to diglyme for SABs. Through this work, the reactivity of the central tertiary carbon in TMP towards bare sodium metal was identified, while the addition of N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C4mpyr][TFSI]) as a co-solvent proved to be an effective strategy to limit the reactivity. Moreover, a Na-β-alumina disk was employed for anode protection, to separate the TMP-based electrolyte from the sodium metal. The new cell design resulted in improved cell performance: discharge capacities of up to 1.92 and 2.31 mA h cm−2 were achieved for the 16.6 mol% NaTFSI in TMP and 16.6 mol% NaTFSI in TMP/[C4mpyr][TFSI] compositions, respectively. By means of SEM, Raman and 23Na NMR techniques, NaO2 cubes were identified to be the major discharge product for both electrolyte compositions. Moreover, the hybrid electrolyte was shown to hinder the formation of side-products during discharge – the ratio of NaO2 to side-products in the hybrid electrolyte was 2.4 compared with 0.8 for the TMP-based electrolyte – and a different charge mechanism for the dissolution of NaO2 cubes for each electrolyte was observed. The findings of this work demonstrate the high potential of TMP as a base solvent for SABs, and the importance of careful electrolyte composition design in order to step towards greener and less toxic batteries. [ABSTRACT FROM AUTHOR]

The recovery of critical metals from spent lithium‐ion batteries (LIBs) is rapidly growing. Current methods are energy‐intensive and hazardous, while alternative solvent‐based strategies require more studies on their 'green' character, metal dissolution mechanism and industrial applicability. Herein, we bridged this gap by studying the effect of dilute HCl solutions in hydroxylated solvents to dissolve Co, Ni and Mn oxides. Ethylene glycol emerged consistently as the most effective solvent, dissolving up to four times more Co and Ni oxides than using aqueous acidic media, attributed to improved chloro‐complex formation and solvent effects. These effects had a significant contribution compared to acid type and concentration. The highest Co dissolution (0.27 M) was achieved in 0.5 M HCl in 25 % (v/v) glycerol in water, using less acid and a significant amount of water compared to other solvent systems, as well as mild temperatures (40 °C). This solvent was applied to dissolve battery cathode material, achieving 100 % dissolution of Co and Mn and 94 % dissolution of Ni, following what was concluded to be a mixed mechanism. These results offer a simple alternative to current leaching processes, reducing acid consumption, enhancing atomic efficiency, and paving the way for optimized industrial hydrometallurgical processes leaning to 'greener' strategies. [ABSTRACT FROM AUTHOR]

Rechargeable zinc batteries (RZBs) are of immense interest as low‐cost and sustainable energy storage devices. However, formation of Zn dendrites, Zn corrosion, and undesired side reactions in aqueous electrolytes as well as the use of costly fluorinated salts in organic electrolytes, have hindered the commercialization of RZBs. In this work, a cost‐efficient and environmentally friendly, non‐aqueous electrolyte comprised of zinc dicyanamide (Zn(dca)2) in dimethyl sulfoxide (DMSO) is shown to support the electrochemical cycling of zinc. Fourier‐transform infrared (FT‐IR) spectroscopy complemented with theoretical studies suggest that the solvation of Zn2+ is stabilized with both [dca]− anions and DMSO molecules at high concentrations (≥1.0 M) of the zinc salt content. Stable charge/discharge cycles in zinc symmetrical cells with low overpotentials (0.05 V) were especially observed for 1.0 M Zn(dca)2/DMSO over 90 cycles at 1.0 mA cm−2 with scanning electron microscopy (SEM) images confirming the formation of a dense and smooth zinc morphology on metal anode surface post‐cycling. X‐ray photoelectron spectroscopy (XPS) also shows that the presence of zinc nitride (Zn3N2) helps form a stable SEI layer in the presence of 1.0 M and 2.5 M systems, making [dca]‐based electrolytes highly promising candidates in rechargeable zinc batteries. [ABSTRACT FROM AUTHOR]