Energy Materials

A multi-scale model is crucial for combining experiments and simulations to reveal the energy storage mechanism. As novel electrode materials, conductive metal–organic frameworks (c-MOFs) provide an ideal platform for understanding the energy storage process in supercapacitors. However, the prevailing circuit models lack consideration of the distinctive transmission path of c-MOFs, which hinders accurate descriptions of c-MOF supercapacitors. By proposing a concept for representing the c-MOF electrode as a crystal–matrix electrode according to the crystallinity, we developed a universal multi-scale circuit model considering crystal shape and porosity to describe the impedance and capacitance of c-MOF electrodes. For supercapacitors with c-MOF electrodes and ionic liquid electrolytes, results predicted from the new multi-scale circuit model, based on microscale parameters obtained from molecular dynamics simulations, demonstrate quantitative agreement with experimental data for electrodes with different crystallinities.

The significant demand for energy storage systems has spurred innovative designs and extensive research on lithium-ion batteries (LIBs). To that end, an in-depth examination of utilized materials and relevant methods in conjunction with comparing electrochemical mechanisms is required. Lithium titanate (LTO) anode materials have received substantial interest in high-performance LIBs for numerous applications. Nevertheless, LTO is limited due to capacity fading at high rates, especially in the extended potential range of 0.01–3.00 V versus Li+/Li, while delivering the theoretical capacity of 293 mAh g−1. This study demonstrates how the performance of the LTO anode can be improved by modifying the manufacturing process. Altering the dry and wet mixing duration and speeds throughout the manufacturing process leads to differences in particle sizes and homogeneity of dispersion and structure. The optimized anode at 5 A g−1 (≈17C) and 10 A g−1 (≈34C) yielded 188 and 153 mAh g−1 and retained 73% and 68% of their initial capacity after 1000 cycles, respectively. The following findings offer valuable information regarding the empirical modifications required during electrode fabrication. Additionally, it sheds light on the potential to produce efficient anodes using commercial LTO powder.

As we turn the page to a new year, it is a fitting moment to reflect on 2024, a year marked by remarkable strides in sustainable energy research and innovation. Energy Advances has been privileged to serve as a platform for groundbreaking studies that aim to address critical global challenges in energy generation, storage, and sustainability. This editorial revisits some of the year’s highlights, celebrates key accomplishments, and looks ahead to the exciting prospects of 2025. In 2024, we were delighted to hold the Energy Advances Editorial Board meeting in person at our London office, Burlington House. The day was filled with exciting discussions about the success and future of the journal. We were also fortunate to have Editorial Board members Matthew Suss, Raymond Wong and Michael Naguib attending in person.

Materials containing imidazole have been used as promising substances in the fields of life sciences, environmental science, and electrochemistry. In this study, tailored core–shell particles that respond to acidic solutions and fluorine-containing hydrophobic anions were synthesized through starved-feed emulsion polymerization. Imidazole, which responds to proton acids and hydrophobic anions, was incorporated as a functional moiety into the shell of the particles. The soft and viscoelastic matrix was composed of the copolymer, poly((n-butyl acrylate)-co-(1-vinylimidazole)), allowing for control of the hydrodynamic diameter of the core–shell particles due to the balance between hydrophilic and hydrophobic properties. The size comparison of monodisperse particles in the colloid state was investigated using dynamic light scattering (DLS) and transmission electron microscopy (TEM). Changes in the glass transition temperature, depending on the copolymer ratio, were calculated using the Fox equation. The particles were melt-sheared after extrusion to produce viscoelastic opal films, arranging the particles into colloidal crystal stacks showing vivid structural colors. The optical features changed in response to acidic solutions and hydrophobic anions and were examined using in situ ultraviolet–visible (UV–vis) spectroscopy. The degree of hydrophilicity of the film was compared through contact angle measurements. The manufactured smart opal film can be applied as an affordable sensor that exhibits optical color changes in response to acidic pH and hydrophobic anions.

Electrocoagulation (EC) technology features a promising prospect for coping with the formidable microplastics (MPs) pollution challenge, albeit the underlying abatement mechanism still needs to be further clarified. Accordingly, in this work, we evaluated the removal performance by EC for four typical MPs, including polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP), and polyethylene (PE). The Fourier transform infrared spectroscopies of MPs confirmed the presence of electrochemical oxidation during EC process, owing to its hydroxyl radical generation ability as demonstrated by the detected fluorescence spectroscopies and electron paramagnetic resonance results, which has been rarely reported in other works. Specifically, 21.2 ± 0.8 %, 10.8 ± 1.8 %, 15.6 ± 1.6 %, and 7.6 ± 1.4 % abatement efficiency for PVC, PS, PP, and PE, respectively, originated from the oxidation effect, and these values for flocculation effect were 77.2 ± 0.8 %, 74.0 ± 1.6 %, 70.8 ± 1.2 %, and 69.2 ± 1.2 %, successively. Many factors influence these differences, especially the MPs’ hydrophilicity, as it facilitates the mass transfer efficiency between MPs (like PVC and PP) and the generated flocs or radicals. To lay a foundation for practical application, we also optimized the operation parameters, demonstrating the wise choice of pH 7 to maintain a balance between the oxidation and flocculation effect. Therefore, we believe our work provides a good reference for promoting MPs abatement efficiency and elucidating the corresponding mechanism, especially the contribution of the oxidation part by EC.

Lithium-ion batteries play a crucial role in powering electric vehicles and portable electronics, making them indispensable in modern technology and driving a significant increase in global lithium demand. With more and more batteries reaching their end of life and the challenges of lithium extraction, including rising prices, geopolitical constraints, and environmental concerns, the efficient recovery of lithium from spent battery cells is crucial for sustainable battery recycling. While state-of-the-art battery recycling focuses mainly on pyro- and hydrometallurgical methods, electrochemical recycling methods can be an environmentally friendly, energy-efficient, and cost-effective alternative. This study optimizes an energy-efficient electrochemical method for selective LiCl extraction from leaching solutions derived from cathode materials of a typical battery cell format (lithium cobalt oxide (LCO)). This places our electrochemical separation within the hydrometallurgical processing of spent battery materials (black mass) and prior to subsequent lithium refining steps. Applying carbon-coated lithium iron phosphate (LFP) electrodes for selective lithium recovery yielded an average uptake capacity of 11.4 mgLi gLFP/C-1 over 300 cycles, maintaining a significant discharge capacity (30 mAh g-1) after 500 cycles.

In technologies for PFAS removal, one of the biggest challenges is combining high adsorption capacity with excellent regeneration capabilities. In recent years, metallopolymer-based materials have shown promising potential in both aspects. In this work, we present two convenient ways to functionalize organic microparticles with charged, functional moieties (cobaltocenium), either through a one-pot reaction via siloxane-condensation or by straightforward ring-opening reaction of epoxides. After characterization of the novel adsorbent materials by state-of-the-art analytics to verify the successful functionalization, their performance for PFAS adsorption and regeneration was investigated. To gain insight into the adsorption mechanism, experiments were first conducted at low concentrations (20 μg L−1) and in equilibrium, showing adsorption for both materials of up to 97 % for PFOA and PFOS. Furthermore, an increase in adsorption within an ionic matrix of commercial drinking water and an adsorbent preference at different pH values was demonstrated. Analysis of the influence of the concentration indicates multilayer adsorption beyond simple ion-paring, best described by a Brunauer-Emmett-Teller mechanism. Moreover, utilizing a straightforward column setup, the total PFOA capacity is analyzed, revealing a 4–5-fold increase upon functionalization, leading to 215 mg g−1 and 296 mg g−1 PFOA adsorption. Overall, column-based adsorption experiments showed promising results at low (20 μg L−1) and medium (2.25 mg L−1) PFAS concentrations. Finally, reusability and regeneration studies further revealed an excellent desorption performance upon multiple cycles and PFAS elution of up to 88 ± 4 %. © 2025 The Author(s)

The energy transition and the intermittent characteristic of renewable energy sources highlight the importance of materials research for energy storage systems. Hexacyanometalates (HCM) are promising candidates in energy storage systems due to their structure, capability of intercalating/extracting ions during the redox process, and the variety of synthesis techniques available. Among HCMs, nickel hexacyanoferrate (NiHCF) gains attention due to its long-life cycle and promising application in aqueous systems. Combining the properties of NiHCF along with freestanding films based on reduced graphene oxide (rGO) and polyaniline (PAni) offers a promising application in aqueous batteries as it includes both the electroactive material and the current collector in a single electrode. Herein, freestanding electrodes based on rGO/PAni/NiHCF are synthesized through the electrodeposition of NiHCF over rGO/PAni films, enabling control of the amount of NiHCF nanoparticles and the freestanding film thickness. Thinner electrodes achieve specific capacity values of 83 mAh g−1 at the current density of 50 mA g−1 in a three-electrode system, a specific capacity close to 61 mAh g−1 at the current density of 10 mA g−1 in a coin-cell system, approaching the theoretical capacity of NiHCF.

With rising demand for lithium-ion batteries, efficient recycling is crucial. While conventional methods face cost and environmental challenges, electrochemical recovery offers a sustainable and energy-efficient alternative. In this study, we investigate the electrochemical recovery of lithium-ions from spent lithium iron phosphate batteries using carbon-coated lithium iron phosphate electrodes, with a focus on the influence of pH adjustment and competing ion effects. Our results demonstrate that NaOH-adjusted electrolytes provide the highest lithium-ion recovery efficiency, with an average removal capacity of 18 mgLi gLFP−1 over 50 cycles. However, prolonged cycling leads to capacity fading, particularly in the presence of competing cations such as Na+ and K+, which impact lithium selectivity and electrode stability. These findings underscore the importance of optimizing electrolyte conditions and electrode materials to enhance long-term performance. Future research should explore alternative pH control strategies and scalable process designs to facilitate industrial implementation. Advancing electrochemical lithium-ion recovery aligns with broader sustainability goals, offering a viable route toward circular battery recycling and reduced environmental impact.

Lithium–sulfur batteries (Li–S), controlled by the sulfur cathode’s conversion reaction, are a promising technology due to their high theoretical capacities and the sustainability of sulfur. In contrast to commercially available lithium-ion cathodes, the Li–S system still suffers from unstable cycling performance due to the diffusion of soluble polysulfides out of the cathode. This study explored sulfur cathodes with varying pore sizes, mainly in the micropore regime (<2 nm). We conducted the work using carbonate-based and ether-based electrolytes to investigate the impact of the cathode/solid electrolyte interphase on the cycling performance of the battery. By infiltrating the carbon with different C/S ratios, we found that the maximum sulfur infiltration attained was 61 mass % with a C/S ratio of 1:1.5. The best sulfur utilization and cycling performance were achieved with carbonate electrolyte and 50 mass % S in carbon with a specific surface area of 2210 m2/g and a total pore volume of 1.20 cm3/g. Our findings emphasize the importance of designing cathodes with optimized pore structures to balance sulfur accommodation, minimize sulfur dissolution, and mitigate capacity degradation.