Electrodeposition is a vital technique for producing a metal matrix composite. In part one of this work, the authors showed that Ni matrix composite coatings with uniformly distributed different-sized particles were successfully fabricated by different electroplating techniques from Ethaline DES. Here, it is shown that the size of the particles had a significant influence on the tribology of the Ni composite coatings. The maximum contents of micro-sized Cr3C2 particles incorporated into the Ni matrix were between 11.11% and 22.2% in weight. Further, Ni-cBN-Cr3C composite coatings exhibited a higher wear resistance than Ni-cBN composite coatings. Additionally, the friction coefficient of the composite coatings to the third phase (Ni-cBN-Cr3C2) decreases when Cr3Cr2 has been incorporated between cBN particles. The wear tracks of the two coating layers have been examined using SEM, and the images of morphology show that the wear tracks of the first and second layers have no wear, and the wear tracks appear very shallow. EDX analysis was performed on these areas, and the concentration of Fe element in the wear track of the Ni-cBN layer is significantly higher than that of the Ni-cBN-Cr3C2 layer. This indicates that the residual Fe from the steel ball is greater on the first layer surface during the wear test. Consistently, the grinding balls were significantly worn; the diameters of wear scars from the first and second layers are 1645 and 1530 mu m, respectively. These also suggest that cBN from this layer has a stronger cutting action on the steel ball than cBN with Cr3C2 layers. This work demonstrates that Ni matrix composite coatings with uniformly distributed microparticles of different sizes were successfully developed by using electroplating from Ethaline-based DESs..

The properties of metallic matrix materials can be modified by the addition of different types of composite materials (ceramic, polymer and carbide). Electrodeposition is a vital technique for producing metal matrix composites. This work shows that Ni matrix composite coatings with uniformly distributed different-sized particles were successfully fabricated by different electroplating techniques from the deep eutectic solvent (DES) known as Ethaline. Particulate dispersions are generally more stable in DES media than in aqueous electrolytes because of the higher viscosity and more favourable wetting characteristics (surface tension). This work demonstrates, by characterisation from electrochemical methods and electron microscopy, that Ni matrix composite coatings with uniformly distributed microparticles of cBN and Cr3C2, of different sizes, were successfully developed by using simple electroplating facilitated by the Ethaline-based DESs either in suspension or as a paste. The work of this study is reported in two parts. In part one, here, the electrochemical characterisation and temperature dependence of the nickel-based DES solutions containing different fractions of the microparticles, both cubic boron nitride (cBN) and chromium carbide (Cr3C2), are presented. The electrochemical fabrication in DES of the composites and characterisation of the resultant coatings are discussed. Consequently, the viable route to generating such particulate composites in a DES electrolyte has been demonstrated. In part two,a detailed hardness and wear study of composite coatings of nickel containing cBN, Cr3C2 particles, together with mixed systems, is presented. This will appear in a subsequent issue of this journal.

Current-voltage curves in voltammetry are underpinned by the much intertwined applied potential and the rate of mass transport of the analyte to and from the semi-infinite bulk solution. In the absence of natural convection or migration, the diffusion of analyte to macro-electrode interfaces in most electrolyte media is often the rate-determining step at overpotentials. This poses significant limitations for ultra-low concentration sensor applications and material processing where current density is key. To overcome these limitations, the rate of mass transport to the electrode could either be increased through a reduction of electrode size, which is applicable for sensing purposes but not material processing, and/or by introducing forced convection into the matrix which is discussed more below.

Nanoparticle-functionalized polymer surfaces must reconcile particle retention with interfacial accessibility, a balance central to catalytic and multifunctional surfaces. Existing architectures use binders, primers or grafting layers that bury active area or add chemical complexity. Here we show that mild annealing below the main bulk-softening regime partially embeds nanoparticles into cured polymer surfaces, forming a close-packed, one-particle-thick monolayer through two coupled self-limiting processes: particles above the polymer-contacting layer remain removable, while the retained layer approaches a finite embedding depth. On a commercial epoxy, CeO2 nanoparticles embed to approximately their radius, providing anchoring while remaining partially exposed. The monolayer withstands vortexing, ultrasonication and repeated tape peeling, retains reversible Ce3+/Ce4+ cycling, and suppresses degradation during peroxide cycling, short-term outdoor exposure and artificial-seawater immersion. Density-functional theory supports a vacancy-mediated peroxide-decomposition pathway consistent with redox regeneration. Spray deposition and Ag embedding on low-density and high-density polyethylene support transferability across deposition routes, nanoparticle chemistries and polymer substrates. Contact-layer-selective, depth-limited thermal embedding thus establishes a geometry-based, grafting-free design principle that provides mechanical retention while preserving interfacial accessibility, with broader relevance to catalytic and other functional polymer interfaces. Nanoparticle-functionalized polymer surfaces must balance particle retention with surface accessibility, but current methods often reduce active area or add complexity. Here, the authors show that mild thermal annealing creates a durable nanoparticle monolayer that preserves surface accessibility, catalytic activity, and stability without complex grafting methods.

Iodine is a strong oxidising agent for the dissolution of Ni powder to Ni ions. The subsequent electrodeposition of Ni ions to form a compact Ni deposit in choline chloride-ethylene glycol, ChCl-EG (Ethaline) as a deep eutectic solvent (DES) is considered since an Ethaline plating bath for deposition of Ni coatings from Ni powder has not been reported. Ni speciation in the plating bath in the presence of (I-2/I-) was established. This work aims to examine the deposition rate of Ni in the presence of iodine and NiCl2 from a deep eutectic solvent containing iodine and NiCl2, together with the morphology of the deposit. The deposition rate of both systems (NiCl2 and Ni powder) under identical conditions was measured at 90 degrees C. It was shown that the Ni deposits formed in the presence of iodine had a different structure from those formed from NiCl2 in pure DES. It is suggested that this is due to changes in the interaction of chloride and iodine ions together with their ability to adsorb at the cathode surface. The deposition of Ni in the presence of iodine resulted in a uniform, nanocrystalline deposit.

Polymer gel electrolytes based on EMIC-AlCl3 (1:1.5) and ultra-high molecular weight polyethylene oxide (UHMW PEO Mv = 8 x 106 g mol(-1)) were synthesised with PEO concentrations of 2, 3.5, 5, 10 wt% without the use of auxiliary solvents, by melting the polymer into the electrolyte. This method produced elastic gels with progressively increasing elastic modulus. The speciation of the chloroaluminate anions in the gel electrolytes was characterized by NMR and Raman spectroscopy, revealing a decrease in Al2Cl7- and corresponding increase in AlCl4- with rising PEO content. In particular, the gel with 10 wt% PEO showed no detectable Al2Cl7-. Electrochemical activity of these gels was evaluated using two configurations: a platinum disc electrode and parallel planar aluminium foil electrode, the latter mimicking a practical electrochemical cell operating geometry. Surprisingly, all gels exhibited electrochemical activity, even in the absence of the Al2Cl7- species. Increasing PEO concentration led to reduced current densities but enhanced coulombic efficiency. The study discusses the influence of the molecular weight of PEO on ionic speciation and electrochemical performance of the polymer gel electrolytes, providing insights into the interplay between polymer content, ionic speciation, and electrochemical behaviour. These findings contribute to the development of safer, more sustainable aluminium batteries.

The thermochromic and electrodeposition behavior of nickel chloride was investigated in two choline chloride-based deep eutectic solvents (DES), with either ethylene glycol or urea as the hydrogen bond donors. In the ethylene glycol DES, thermochromism was found to be reversible, with ligand exchange resulting in the main structural change from octahedral to tetrahedral coordination taking place between 90 and 100 °C. In the urea DES, a change in color only took place above 100 °C, at which point a suspected ammonia species was irreversibly formed from decomposition of the solvent. The speciation effects were studied by using UV-vis and EXAFS spectroscopies, together with the electrochemical methods of cyclic voltammetry and rotating disk voltammetry. The observed speciation changes evolving at higher temperatures were seen to correlate with more well-defined electrochemical behavior together with faster electron-transfer kinetics and higher Coulombic efficiency.

Long-loop recycling of spent lithium-ion batteries is neither sustainable nor economical at scale.

Solvation plays a profound role in the behaviour of electroactive films and their exploitation in diverse applications. Examples include energy storage device performance via ion transport rate, electrocatalysis via reactant transport, electroanalysis via analyte partition and permeation, and actuator operation via viscoelastic properties. Optimization of electroactive film solvation is thus of wide interest. Most commonly, this is explored with a view to application in a specific solvent, so the strategy is to vary polymer lyophilicity by substitution chemistry; for example, the polymer can be made more hydrophobic or hydrophilic by appropriate functionalization [1]. An alternative strategy is dilution of the electroactive moiety by copolymerization with a monomer with divergent solvation characteristics [2]. Here we adopt a complementary strategy, in which we pre-select the polymer and determine aspects of solvent and ion populations and dynamics in divergent solvent types. Specifically, we consider poly(thiophene-co-pyrrole), poly(TP), based on a thiophene-pyrrole monomer (defining 1:1 thiophene: pyrrole stoichiometry), exposed to a molecular solvent (acetonitrile) or to the fully ionic environment of the eutectic solvent ChCl.2EG (choline chloride: ethylene glycol in 1:2 stoichiometric ratio). Poly(TP) is of interest for zinc anode/conducting polymer battery systems involving non-aqueous electrolytes [3]. Practical application requires exploitation of the high electronic conductivity of poly(TP) without undue limitation by the ion transport process(es) required to maintain electroneutrality. Use of a molecular solvent offers the prospect of enhancing ion transport by plasticizing the polymer, while use of a room temperature ionic liquid accomplishes this by increased ion availability. We seek to determine film ion and solvent populations and dynamics that dictate the merits of these alternative strategies for poly(TP). Imaging techniques predominantly yield external topography, yet most of the functionality lies within the film interior. Spectroscopic, optical and acoustic characterization methods, while providing many insights, yield information that is averaged “vertically” through the film; the value of such information is limited by the fact that polymer films in general have non-uniform segment density profiles perpendicular to the interface. In contrast, reflectivity methods (optical, X-ray and neutron) can provide internal film compositional profiles. In addition to in situ applicability, neutron reflectivity (NR) has the tremendous advantage of isotopic selectivity, allowing “vertical” spatial profiling of individual components of the system (polymer, ion or solvent). Here we selectively deuterate the solvent in acetonitrile media, and the ethylene glycol component in the eutectic solvent, and compare the resultant film neutron scattering length density profiles with those in the parent hydrogenous media. From these we deduce penetration profiles into poly(TP) of acetonitrile and the ionic components of the eutectic solvent as functions of coulometrically assayed polymer oxidation state. Supporting evidence for NR-determined film roughness at the polymer/solution interface is provided by AFM imaging. Unsurprisingly, in 0.1M LiClO 4 /CH 3 CN (or CD 3 CN), film electroneutrality following (un)doping is maintained by anion transfer. While this causes film swelling, the solvent volume fraction (φ S = 0.49) is independent of film charge state. In the eutectic solvent, the film is “solvated” by equivalent amounts of anion and cation, such that either transfer mechanism is potentially available to satisfy electroneutrality. Consequently, the facility selectively to deuterate one of these species (here, ethylene glycol that is complexed with chloride) is critical. Upon poly(TP) redox switching, we find that electroneutrality is satisfied by cation transfer (ejection upon polymer oxidation, injection upon polymer reduction); φ S decreases from 0.25 to 0.20 upon polymer oxidation. Historically, NR was limited by long data acquisition times (hours), so only static measurements were feasible. Recent instrumental developments now permit dynamic measurements on timescales typical of potentiodynamic experiments. We report data for dynamic electrochemical/NR experiments that provide insight into the dynamics of film transformation between the extremes of fully reduced and fully oxidized films described above. These address the possibility of transient phenomena due to kinetically facile ion transfers competing with slower thermodynamically preferred ion transfers, generating unexpected mobile species profiles en route to equilibrium solvent and ion populations. [1] R. Candeago, H. Wang, M.-T. Nguyen, M. Doucet, V.-A. Glezakou, J.F. Browning, X. Su, JACS Au, 2024, 4, 919-929. [2] R. Chen, H. Wang, M. Doucet, J.F. Browning, X. Su, JACS Au, 2023, 3, 3333-3344. [3] A. Guerfi, J. Trottier, I. Boyano, I. De Meatza, J.A. Blazquez, S. Brewer, K.S. Ryder, A. Vijh, K. Zaghib, J. Power Sources, 2014, 248, 1099-1104. [4] C. Beebee, E.B. Watkins, R.M. Sapstead, V.C. Ferreira, K.S. Ryder, E.L. Smith, A.R. Hillman, Electrochim. Acta, 2019, 295, 978-988.

Rechargeable aluminum-ion batteries remain an important technological target as an alternative to lithium. Here, acidic room-temperature ionic liquid analogue electrolytes (ILAs) were synthesized from guanidine hydrochloride salt (GuanHCl) and aluminum chloride, with varying metal-to-salt (AlCl3/GuanHCl) ratios, and were characterized for their potential application in aluminum-ion batteries. The rheological properties of these electrolytes, including viscosity and electrical conductivity, were determined. The viscosity followed an increasing trend with AlCl3 content, while the conductivities followed the inverse trend consistent with Walden's rule. Both parameters showed an Arrhenius-type behavior with respect to temperature, although, interestingly, the activation energies were all very similar, around 23 kJ mol-1. This is comparable to other chloroaluminate liquids and suggests that the mobile charge-carrying species in all the compositions are similar. The speciation of the liquids was investigated by FT-IR and NMR spectroscopies, showing significant trends that indicate interaction between the guanidinium cation and the chloroaluminate center. Electrochemical activities were correlated with rheology, and the 2.0:1.0 formulation exhibited a gravimetric response closest to the Faradaic model. Coin cell testing of the 2.0:1.0 formulation showed interesting trends in cell specific capacity and efficiency as a function of charge/discharge rate that suggests this electrolyte could be a strong candidate for a rechargeable Al battery. The electrolytes are relatively low-cost, making them suitable for potential industrial-scale applications. Clearly, further detailed studies and life-cycle testing of the cells are required in order to realize this technological potential.

The photovoltaic (PV) sector is undergoing a transformative phase as it confronts the simultaneous challenges of unprecedented deployment and end-of-life system retirement. Early-generation PV modules are now entering the waste stream, creating a significant and growing volume of decommissioned material at the same time as global PV expansion accelerates. This convergence underscores an urgent need for scalable recycling technologies that support a circular economy for solar energy infrastructure. Legacy PV panels, characterized by complex material compositions and design variability, pose significant obstacles for conventional recycling techniques. These designs often consist of layered glass, polymers, silicon, and metal traces that resist mechanical or thermal separation. Addressing this, the Apollo Project introduces a robust, process-engineered framework for the maximum recovery of valuable materials from diverse PV waste streams. The project focuses on achieving a high-efficiency pathway for material separation through chemically selective, environmentally friendly techniques that leverage modern electrochemical processes and Deep Eutectic Solvents (DES) . A unique highlight of this approach is the combination of DES with ultrasound-assisted electrochemical extraction , yielding a cost-effective and accelerated recovery method. This hybrid system has demonstrated high selectivity in extracting critical raw materials such as silver, copper, and aluminum from aged modules, while significantly enhancing dissolution kinetics and overall process efficiency. The electrochemical separation of metals is achieved which are central to this recovery framework. This presentation will detail the Apollo Project’s technological innovations, focusing on both the engineering and electrochemical principles underpinning PV recycling. Emphasis will be placed on the electrochemistry-driven recovery strategies used to overcome mass transport limitations and enhance the space-time yield for the extraction and selective separation of valuable resources.

Lithium-ion battery anodes were produced and tested using gelatin and sodium alginate (NaAlg) biopolymers, modified with a deep eutectic solvent (DES). Anodes created with these alternative binder systems showed comparable capacities and Coulombic efficiencies to cells assembled using commercial PVDF and CMC/SBR binders. Rate tests of these cells found that DES-NaAlg possessed a higher rate capability than PVDF, showing a greater capacity (∼70 mAh.g−1 higher) when cycled at 1C. Anodes using gelatin materials exhibited lower rate stability, showing significant capacity fade at cycling rates <0.5C. EIS measurements showed that NaAlg anodes were similar to the cells using conventional binders, but gelatin possessed an extra impedance contribution relating to a polymeric coating of the graphite active materials. NaAlg binders were incorporated into graphite anodes reclaimed from a commercial pouch cell using an ultrasound delamination technique. These cells showed reduced rate performance, brought about by ultrasonic fracturing and particle agglomeration. The capacities at low cycling rates were, however, comparable to pristine materials and evidence of key processes such as SEI formation were observed.

This investigation shows the effect of blending sodium alginate (NaAlg) and a conducting polymer, polyaniline (PANI), in lithium-ion battery (LIB) anodes. We demonstrate here that inclusion of the PANI into the binder improves the connectivity of the composite, resulting in better performance. Additionally, the blends are easily formulated without sophisticated methods or additional equipment. When these binders were combined into electrodes, the conductivity rose by between 3- and 5-fold compared with the unmodified NaAlg, depending on the PANI loading. The conducting polymer did not significantly change the thermal stability or cycling of the cells, but it did improve the Coulombic efficiency. During electrochemical testing, it was found that cells containing PANI within the binders exhibited evidence of essential processes, such as SEI formation and lithium intercalation. Evidence of side reactions was observed, predicted to be the lithiation of PANI to create lithium emeraldinate within the polymeric regions, which could increase the Coulombic efficiency of the cells and allow for the decrease in impedance contributions after extensive cycling. Capacities and rate capabilities comparable to anodes prepared using graphite and commercial binders PVDF and CMC/SBR were also observed. Crucially, after cycling, the NaAlg/PANI binder could be fully removed from the active material with mild ultrasonic agitation in water.

Ultrasonic delamination is a low energy approach for direct recycling of spent lithium-ion batteries. The efficiency of the ultrasonic delamination relies both on the thermophysical properties (such as viscosity, surface tension, and vapour pressure) of the solvent in which the delamination process is carried out, and the properties of the ultrasound source as well as the geometry of the containment vessel. However, the effect of tailoring solutions to optimise cavitation and delamination of battery cathode coatings has not yet been sufficiently investigated. Acoustic detection, high-speed imaging, and sonochemiluminescence (SCL) are employed to study the cavitation processes in water-glycol systems and identify the effect of tailoring solvent composition on cavitation strength. The addition of small volume fractions of organic solvent (ca. 10-30 vol%), including ethylene glycol or glycerol, to the aqueous delamination solution were found to significantly improve the delamination efficiency of lithium-ion battery cathode coatings due to the alteration of these thermophysical properties. However, greater volume fractions of glycol decrease delamination efficiency due to the signal-dampening effect of viscosity on the ultrasonic waves. The findings of this study offer valuable insights for optimising ultrasonic bath solution composition to enhance film delamination processes.

Developing new functionalities of two-dimensional materials (2Dms) can be achieved by their chemical modification with a broad spectrum of molecules. This functionalization is commonly studied by using spectroscopies such as Raman, IR, or XPS, but the detection limit is a common problem. In addition, these methods lack detailed spatial resolution and cannot provide information about the homogeneity of the coating. Atomic force microscopy (AFM), on the other hand, allows the study of 2Dms on the nanoscale with excellent lateral resolution. AFM has been extensively used for topographic analysis; however, it is also a powerful tool for evaluating other properties far beyond topography such as mechanical ones. Therefore, herein, we show how AFM adhesion mapping of transition metal chalcogenide 2Dms (i.e., MnPS3 and MoS2) permits a close inspection of the surface chemical properties. Moreover, the analysis of adhesion as relative values allows a simple and robust strategy to distinguish between bare and functionalized layers and significantly improves the reproducibility between measurements. Remarkably, it is also confirmed by statistical analysis that adhesion values do not depend on the thickness of the layers, proving that they are related only to the most superficial part of the materials. In addition, we have implemented an unsupervised classification method using k-means clustering, an artificial intelligence-based algorithm, to automatically classify samples based on adhesion values. These results demonstrate the potential of simple adhesion AFM measurements to inspect the chemical nature of 2Dms and may have implications for the broad scientific community working in the field.

Of the attributes that determine the performance of electroactive film-based devices, the least well quantified and understood is the spatial distribution of the component species. This is critical since it dictates the transport rates of all the mobile species (electrons, counterions, solvent, analyte, and reactant) and the film mechanical properties (as exploited in actuator devices). One of the few techniques able to provide individual species population profiles in situ is specular neutron reflectivity (NR). Historically, this information is obtained at the cost of poor time resolution (hours). Here we show how NR measurements with event mode data acquisition enable both spatial and temporal resolution; the latter can be selected postexperiment and varied during the transient. We profile individual species at "buried" interfaces under dynamic electrochemical conditions during polypyrrole electrodeposition and Cu deposition/dissolution. In the case of polypyrrole, the film is homogeneous throughout growth; there is no evidence of dendrite formation followed by solvent (water) displacement. Correlation of NR-derived film thickness and coulometric assay allows calculation of the solvent volume fraction, ϕS = 0.48. In the case of Cu in a deep eutectic solvent, the complexing nature of the medium results in time-dependent metal speciation: mechanistically, dissolution does not simply follow the deposition pathway in reverse.

Sustainability is at the forefront of all research carried out at University of Leicester. There are three main groups contributing to the surface finishing effort: the Centre for Sustainable Materials Processing, the Mechanics of Materials research group and Space Park Leicester; however many collaborations occur across the institution and with industrial partners, including the Materials Innovation Centre with TWI Ltd. The ongoing projects vary across a range of themes, from forensic science to batteries and energy storage. This work aims to give a brief overview of the research groups, centres and institutes, and highlights some relevant projects that fall within the scope of Transactions of the IMF.

This paper uses targeted ultrasound on a surface undergoing anodic dissolution. The aim of these experiments was to etch metals that would normally passivate. The study was carried out in deep eutectic solvents (DESs) as these are technologically useful for metal processing but suffer the disadvantages that they are viscous and hence have slow mass transport which results in metal passivation. Linear sweep voltammetry showed a linear current-voltage response at potentials anodic of the oxidation potential under sonication. Passivation was observed in silent conditions. It was also shown that the dissolution current was roughly 14 times larger under sonication. High speed imaging showed asymmetric bubble collapse leading to enhanced removal of material from the surface with etch rates as high as 3.8 μm.min-1 under ultrasonic conditions.

Aluminum-based batteries are a promising alternative to lithium-ion as they are considered to be low-cost and more friendly to the environment. In addition, aluminum is abundant and evenly distributed across the globe. Many studies and Al battery prototypes use imidazolium chloroaluminate electrolytes because of their good rheological and electrochemical performance. However, these electrolytes are very expensive, and so cost is a barrier to industrial scale-up. A urea-based electrolyte, AlCl3:Urea, has been proposed as an alternative, but its performance is relatively poor because of its high viscosity and low conductivity. This type of electrolyte has become known as an ionic liquid analogue (ILA). In this contribution, we proposed two Lewis base salt precursors, namely, guanidine hydrochloride and acetamidine hydrochloride, as alternatives to the urea-based ILA. We present the study of three ILAs, AlCl3:Guanidine, AlCl3:Acetamidine, and AlCl3:Urea, examining their rheology, electrochemistry, NMR spectra, and coin-cell performance. The room temperature viscosities of both AlCl3:Guanidine (52.9 cP) and AlCl3:Acetamidine (76.0 cP) were significantly lower than those of the urea-based liquid (240.9 cP), and their conductivities were correspondingly higher. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) showed that all three electrolytes exhibit reversible deposition/dissolution of Al, but LSV indicated that AlCl3:Guanidine and AlCl3:Acetamidine ILAs have superior anodic stability compared to the AlCl3:Urea electrolyte, as evidenced by anodic potential limits of +2.23 V for both AlCl3:Guanidine and AlCl3:Acetamidine and +2.12 V for AlCl3:Urea. Coin-cell tests showed that both AlCl3:Guanidine and AlCl3:Acetamidine ILA exhibit a higher Coulombic efficiency (98 and 97%, respectively) than the AlCl3:Urea electrolyte system, which has an efficiency of 88% after 100 cycles at 60 mA g(-1). Overall, we show that AlCl3:Guanidine and AlCl3:Acetamidine have superior performance when compared to AlCl3:Urea, while maintaining low economic cost. We consider these to be valuable alternative materials for Al-based battery systems, especially for commercial production.