Attractive Energy Research Articles

(Invited) Delineating the Intricacies Involved in the Synthesis of Cobalt-Free High-Nickel Layered Oxide Cathodes for Lithium-Ion Batteries

Improving the energy density and cost of lithium-ion batteries (LIBs) requires a rational compositional design of layered oxide LiNi1-x-yMnxCoyO2 (NMC) cathodes. The prevailing trend is to increase the nickel content in the cathode to maximize energy density, but high-nickel NMC generally suffers from surface and bulk instabilities that shorten battery life. Dopants, such as cobalt, can help mitigate these issues, but its supply shortage issue prohibits its usage especially in the massive electric vehicle market. Our recent finding suggests that a combination of manganese and aluminum in LiNi0.9Mn0.05Al0.05O2 (NMA-90) promotes attractive energy density, cycle life, rate capability and thermal stability, proving that cobalt can be eliminated in high-nickel cathodes. Post-mortem analysis further reveals that the Mn-Al combination provides synergistic improvements in structural and surface stabilities compared to LiNi0.9Mn0.05Co0.05O2 (NMC-90) and LiNi0.9Co0.05Al0.05O2 (NCA-90). A thorough understanding of the relationship between the synthesis condition and optimal materials properties of NMA-90 is necessary to enable its large-scale deployment. We will present findings from the calcination and coprecipitation study of several cobalt-free cathodes to elucidate this relationship. It is revealed that the cycle stability of LiNi0.9Mn0.1O2 (NM-90) is not dependent on Li/Ni mixing or primary particle size, but is dependent on the calcination temperature. Incorporating Al into NM-90 during coprecipitation reactions cause high internal porosity in the hydroxide precursor, which impacts the final morphology of the calcined cathodes and thus their electrochemical stability. The ongoing work in our lab provides insight on the synthesis sensitivity of NMA and strategizes methods to control its electrochemical properties.

Core-shell Fe3O4@carbon aerogels assembled aqueous zinc ion hybrid capacitor with ultra-wide voltage window

The unsatisfactory energy density seriously hinders the practical application of supercapacitors. Herein, core-shell Fe3O4@carbon aerogels (Fe3O4@CAs) with high specific capacity are synthesized by the hydrothermal self-assembly method, which can contribute both electric double-layer capacitance (EDLC) and pseudo-capacitance under the synergistic mechanism of Fe3O4 and CAs. The zinc ion hybrid supercapacitor (ZHSC) is constructed using Fe3O4@CAs, zinc foil, and 2 M ZnSO4 as the cathode, anode, and electrolyte, respectively. The assembled ZHSC exhibits an ultra-wide voltage window (0–2.1 V in the aqueous electrolyte) and high specific capacitance (342.1 F g−1 at a current density of 0.5 A g−1) characteristics, successfully achieving an attractive energy density (284.7 Wh kg−1 at a power density of 210 W kg−1). This study provides a highly universal hydrothermal self-assembly method for the composite preparation of Fe3O4 and various carbon materials.

Perspectives on the development of highly active, stable, and cost‐effective OER electrocatalysts in acid

AbstractPolymer electrolyte membrane water electrolysis (PEMWE) is an attractive hydrogen energy production technology that offers various advantages such as compact design, high operating pressure, high current densities, and high hydrogen gas purity. However, PEMWE still faces several critical challenges, particularly with respect to the oxygen evolution reaction (OER) at the anode. Highly active, corrosion‐resistant electrocatalytic materials are required for the acidic OER owing to its sluggish kinetics involving four‐electron transfer under harsh anodic potentials. To date, IrO2‐ or RuO2‐based noble metal electrocatalysts have been employed as commercial acidic OER electrocatalysts for PEMWE. However, they remain inadequate in terms of satisfying the industrial activity/stability‐related requirements. Above all, the two noble metals are too rare and expensive, which significantly inhibits widespread commercialization of PEMWE. Therefore, low‐cost, highly active, and highly stable OER electrocatalysts that can operate in acidic media must be urgently developed. This review paper presents various state‐of‐the‐art strategies employed to address the aforementioned issues by classifying them according to objectives such as improving activity, enhancing stability, and reducing cost. Then, finally, we summarize major tasks and strategies to overcome them and put forward a few issues in this field.

Life extension of AC-DC converters for hydrogen electrolysers operating as part of offshore wind turbines

Energy resources based on green hydrogen are nowadays beginning to enjoy wide adoption and draw considerable interest. There are different types of hydrogen production, but it is green hydrogen that is becoming an attractive energy development capable of replacing blue and grey hydrogen as well as fossil fuels, Thereby the carbon footprint will be reduced for a number of industrial processes. Proton exchange membrane electrolyzers used for the production of environmentally friendly hydrogen have one key shortcoming, which is the short service life of the equipment. This paper presents a comparative study of the commonly applied PLL control of AC-DC converters. To improve the control of the proton exchange membrane of the electrolyzer, a vector control arrangement is adopted, which allows, by relying on cascade control loops, maintaining different DC link voltage levels and thereby extending the DC link input voltage variation range.

Heat release characteristics of ammonia flames in MILD conditions

Ammonia (NH3) combustion is an attractive energy source with zero carbon dioxide (CO2) emissions and a potential hydrogen-combustion enabler. In addition, the availability of ammonia and its amenability to transportation make it appealing to future energy supply. To provide fundamental insights into the heat release characteristics of ammonia in moderate or intense low oxygen dilution (MILD) combustion, one-dimensional laminar and two-dimensional turbulent premixed flames are studied numerically. In particular, the flame structure and heat release distribution of ammonia and ammonia-hydrogen premixed flames are examined under conventional and MILD, and preheated conditions, respectively. The results show that stoichiometric ammonia MILD flames differ from normal ammonia flames producing NH2 earlier, which results in the formation of a radical pool that shifts the chemical pathway towards hydrogen-related chemistry. The NH2 radical serves as a precursor for the ammonia flame and characterizes the reaction zone, and plays a crucial role in bringing the explosive nature into the system. For fixed ratios of the root-mean-square turbulent velocity fluctuation to the laminar flame speed and integral length scale to the laminar flame thickness, the flame surface wrinkling is comparable between the stoichiometric ammonia flame at MILD and non-MILD conditions. Furthermore, the hydrogen enrichment of the lean ammonia flame results in a significant increase in heat release rate due to the preferential diffusion effect. The study also examines chemical markers to identify heat-releasing regions of the flames and proposes the use of NH2 × O (on a mass fraction basis) as a suitable indicator of regions with high chemical activity and correlates well with the heat release for the MILD and non-MILD ammonia flames as well as ammonia-hydrogen flames at both laminar and turbulent conditions.

Spray fabrication of additive-free electrodes for advanced Lithium-Ion storage technologies

Polymer binders and carbon conductivity enhancers are inevitably required to make improvements in structural durability and electrochemical performance of lithium-ion battery (LIB) electrodes, although these additive constituents incur weight and volume penalties on the overall battery capacity. Here, additive-free electrode architectures were successfully fabricated over 20 × 20 cm2 electrode areas using a layer-by-layer spray coating approach, with the ultimate goal to boost gravimetric/volumetric electrode capacity and to reduce the total cost of LIB cells. Initially, the binder fraction of spray-coated Li4Ti5O12 (LTO) electrodes was reduced progressively, from 40 to 0 wt%. The electrochemical behavior of electrodes was then re-optimized as a proportion of conductivity enhancers within the binder-free electrode decreased to zero. Further, the otherwise identical spray coating process was applied to manufacture LiFePO4 (LFP) positive electrodes, leading to all-additive-free full-cell LIB configurations with attractive energy density of ∼310 Wh/kg and power performance of ∼1500 W/kg.

Integrating wind energy and compressed air energy storage for remote communities: A bi-level programming approach

The integration of compressed air energy storage and wind energy offers an attractive energy solution for remote areas with limited access to reliable and affordable energy sources. This study presents a design approach for an energy system comprising wind turbines, compressed air energy storage, and diesel generators. The proposed method is based on bi-level programming, enabling the simultaneous optimization of the size and operation of the system while considering the interaction between them. Detailed mechanical design and configuration of the compressed air energy storage system are considered, including the number and size of compressors and turbines, valves, recuperator operating conditions, etc. In contrast with conventional compressed air energy storage systems, operating once a day for peak shaving, the proposed compressed air energy storage system aims to mitigate wind fluctuations. Therefore, it would operate under partial load conditions most of the time, and as a result, the system's off-design modeling is also considered. The results indicate that the proposed system is a promising, cost-effective, reliable energy solution for remote areas, significantly decreasing the average daily total cost and CO2 emissions by 69 % and 76 %, respectively. Additionally, by studying the system's performance under both design and off-design conditions, it is concluded that considering the off-design conditions is critical to ensure a more realistic performance of the system as the system is less likely to utilize the compressed air energy storage in low charging and discharging opportunities.

Ammonia/syngas MILD combustion by a novel burner

Ammonia has received increasing attention as one of the most attractive energy carriers because of its carbon-free nature and the established reliable and economic infrastructure for its storage and distribution. However, the low burning velocity and nitrogen-containment of pure NH3 can cause some challenges for its combustion control such as flame instability and large NOx emissions. To overcome these issues, strategies of co-burning NH3 with highly reactive fuels such as CH4 or H2 have been developed and applied. Syngas, which can be produced from biomass pyrolysis, is a promising alternative fuel in the transition from carbon-based fuels to carbon-free fuels. Therefore, comparing to co-firing NH3 with CH4, co-firing NH3 with syngas is a better environmentally friendly option to improve the NH3 combustion property. However, co-firing NH3 with syngas faces severer combustion instability, NOx emissions and NH3 leakage due to the low heating value of syngas. To the best of the authors’ knowledge, the NH3/syngas combustion with low NOx emissions and zero NH3 leakage has not been achieved in a lab-scale combustor. In the present study, NH3/syngas MILD combustion was carried out in a novel burner developed in our previous work. In the novel burner, the high-temperature and diluted air produced by the lean premixed syngas combustion is the key to accomplish the MILD combustion of NH3. The impact of the temperature and O2 mole fraction of the HTDA on the emissions of NO, NO2, N2O, NH3, and CO was experimentally investigated with varying equivalence ratios and NH3 flow rates. The chemical reactor network was employed to analyze the experimental observation from the chemical kinetic aspect.

Bimetallic RuNi Electrocatalyst Coated MWCNTs Cathode for an Efficient and Stable Li-CO2 and Li-CO2 Mars Batteries Performance with Low Overpotential.

Rechargeable lithium-CO2 (Li-CO2 ) batteries are an attractive energy storage technology that can reduce fossil fuel usage and limit the adverse environmental impact of CO2 emissions. However, the high charge overpotential, unstable cycling, and incomplete understanding of the electrochemical process limit its advancement for practical applications. Herein, we develop a Li-CO2 battery by designing a bimetallic ruthenium-nickel catalyst onto multi-walled carbon nanotubes (RuNi/MWCNTs) catalyst as cathode by solvothermal method, which exhibits a lower overpotential of 1.15 V and a discharge capacity of 15,165 mAh g-1 with outstanding coulombic efficiency of 97.4 %. The battery can also operate at high rates and have a stable cycle of more than 80 cycles at a current density of 200 mA g-1 with a fixed 500 mAh g-1 capacity. Furthermore, Mars exploration is made feasible with the Li-CO2 Mars battery composed of the RuNi/MWCNTs as cathode catalyst, which performs very similarly to that of pure CO2 atmosphere. This approach may simplify the process of developing high-performance Li-CO2 batteries to achieve carbon negativity on Earth and for future interplanetary Mars missions.

HTL interface engineering in CsPbI3 perovskite photovoltaics

Perovskite photovoltaics are attractive energy conversion device due to > 20% power conversion efficiencies. However, these perovskite semiconductors are highly susceptible to environmental factors such as H2O and O2. To address the device stability, various experimental and simulation investigation on both materials and device level studies were carried out. With the continuous studies and understanding single junction perovskite photovoltaics efficiency crossed 23%. Retaining the fresh device efficiency is the challenging due to afore mentioned reasons. However, to address the stability various strategies were adopted. In this work, various stable and highly interacting HTLs with CsPbI3 were configured in the perovskite photovoltaics to study the output efficiencies. The photovoltaic efficiency of the well configured CsPbI3 device is around ∼ 20% however the hybrid perovskite photovoltaics efficiency is around ∼25%. To obtain the high possible efficiency various device parameters such as semiconductor thickness (t), conduction band position, valence band position, Eg, defect density, Rs, Rsh, device temperature was studied in addition to novel HTLs. Simulation result infer that CuSbS2 shows equivalent/slightly higher PV efficiency (20.56%) as compared with spiroOMeTAD HTL PV. The experimental efficiency and the corresponding device stability will be carried out in the continuation of this work.

Graphene quantum dots as sulfiphilic and lithiophilic mediator toward high stability and durable life lithium-sulfur batteries

The development of lithium-sulfur (Li-S) battery as one of the most attractive energy storage systems among lithium metal batteries is seriously hindered by low sulfur utilization, poor cycle stability and uneven redeposition of Li anode. It is necessary to propose strategies to address the problems as well as improve the electrochemical performance. One of the effective solutions is to improve the sulfiphilicity of sulfur cathode and the lithiophilicity of the Li anode. Herein, we reported that a synergistic functional separator (graphene quantum dots (GQDs)-polyacrylonitrile (PAN) @polypropylene (PP) separator) improved the electrochemical activity of sulfur cathode as well as the stability of Li anode. GQDs induced uniform Li+ nucleation and deposition, which slowed down the passivation of Li anode and avoided short-circuit. Further, three-dimensional network constructed by electrospinning nanofibers and the polar functional groups of GQDs could both effectively inhibit the shuttle of LiPSs and improve the sulfur utilization. The stability of Li-S battery was improved by the synergistic effect. In addition, GQDs and electrospinning nanofibers protector increased lifetime of separators. Benefiting from the unique design strategy, Li//Li symmetric battery with GQDs-PAN@PP separators exhibited stably cycling for over 600 h. More importantly, the Li-S full batteries based GQDs-PAN@PP separators enabled high stability and desirable sulfur electrochemistry, including high reversibility of 558.09 mA h g−1 for 200 cycles and durable life with a low fading rate of 0.075% per cycle after 500 cycles at 0.5 C. Moreover, an impressive areal capacity of 3.23 mA h cm−2 was maintained under high sulfur loading of 5.10 mg cm−2. This work provides a new insight for modification separator to improve the electrochemical performance of Li-S/Li metal batteries.

Microporous Polymer Coatings Enable Uniform Zn Stripping/Plating for Long-Life Aqueous Zinc-Ion Batteries

Because of their low cost, safety, and green nature, aqueous zinc-ion batteries (AZIBs) have become attractive energy storage devices. However, problems such as zinc dendrites have been hindering the development of AZIBs. In this paper, two materials polyacrylamide (PAM) and polypropylene (PAN) are used to modify the surface of the zinc. The experimental results show that the coating of the two organic membranes can effectively improve the electrochemical performance of the AZIBs. Symmetric Zn/PAM||Zn/PAM and Zn/PAN||Zn/PAN cells can steadily work over 12000 min at 0.5 mA cm−2, which are greater than that of bare Zn||Zn. At 0.2C multiplicity, the full cells with the zinc modified by both materials as negative electrode exhibited a stable cycle retention rate close to 40% of the initial value after 100 cycles.

Incorporation of Heteroatomic Fe Activates Rapid Catalytic Behaviors of Co3O4 Hollow Nanoplates Toward Advanced Lithium–Sulfur Batteries

AbstractLithium–sulfur (Li–S) battery is a highly attractive energy storage system due to its high capacity and great affordability. However, the parasitic shuttle effect and sluggish redox kinetics are perplexing the fulfillment of efficient battery electrochemistry. To tackle these challenges, herein, a hierarchical and hollow nanoplate assembled by Fe‐doped Co3O4 nanosheets (Fe–Co3O4 HHNPs) is meticulously designed as an advanced sulfur nanoreactor. The interlaced nanosheets establish a robust and porous network for fast charge transfer and efficient active site exposure. More importantly, the heteroatomic Fe incorporation tailors the electronic structure via local structure distortion and electron redistribution, contributing to massive active sites that lower the energy barrier for sulfur conversions. The resulting sulfur adsorption and catalyzation endow the Li–S cells with minimum capacity decay of 0.08% per cycle over 500 cycles and decent rate performance up to 5 C. Moreover, a high areal capacity of 9.0 mAh cm−2 after 55 cycles is also achievable under raised sulfur loading of 11 mg cm−2 and limited electrolyte (E/S = 3.9 µL mg−1). This work provides an elaborate and instructive paradigm for designing catalytic nanoreactors toward superior Li–S electrochemistry.

A study on the renewable power generation capacity of microalgae microbial fuel cells for powering GIoT sensor nodes

Microalgae-Microbial Fuel Cell (mMFC) is a novel and attractive green renewable energy source for bio-electricity generation. Its capacity to generate energy is of particular interest for the design of sustainable green internet of things (GIoT) sensor networks. However, this capacity needs to be assessed due to critical limitations in their low-level output voltage and possible bioelectrochemical disturbances. This study investigates the renewable energy generation capacity of an mMFC-harvester system for powering low-power wireless sensor nodes. A two-chamber mMFC prototype is designed as a proof of concept using the CMI7000 membrane and the BQ25570 circuit to harvest the energy. A sensor node based on Nordic nRF52840 ultra-low-power microcontroller implements a uniform power management strategy and the energy capacity is analyzed in terms of the number of Bluetooth low energy (BLE) transmissions. Experimental results show that after an initial cold-start period in the harvester circuit, the system stores the energy in a 0.1 F supercapacitor in 6.25 h, representing 3.26 J. The maximum power density generation is 80.10 mW/m2, and the energy harvested is suitable to perform up to 9 continuous transmissions using BLE.

The Use of Reductive Agents for Developing Capacity Balanced Aqueous Sodium‐Ion Batteries

AbstractAqueous sodium‐ion batteries (Na‐ion batteries) represent an attractive low cost stationary energy storage technology. However, limited electrochemical stability of water and issues related to complex aqueous chemistry, component corrosion, and materials dissolution limit their lifetime. Oxygen reduction reaction is considered to be the main parasitic process in aqueous Na‐ion batteries leading to self‐discharge, materials degradation and Na‐ion inventory loss. Herein, we present a comprehensive study on novel electrolyte design which allows to mitigate the main parasitic reactions and prepare capacity balanced (N/P=1) aqueous battery cells. For this purpose, aqueous symmetric Na2VTi(PO4)3|Na2VTi(PO4)3 system is used as a model to demonstrate that the introduction of a small concentration of strongly reducing agent such as hydrazine into purely aqueous or hybrid (water and dimethyl sulphoxide) electrolyte could chemically reduce the dissolved oxygen and significantly improve the capacity retention of N/P=1 cells during cycling. The low concentrations and self‐consuming nature of hydrazine in a closed cell do not pose any health or chemical risks and presents a viable strategy for practical design. We believe, these results to be applicable not only to aqueous Na‐ion batteries but also other aqueous or hybrid battery chemistries where such parasitic processes play a significant role.

Heterogeneously catalyzed transesterification reaction using waste snail shell for biodiesel production

Biodiesel as an attractive energy source; a low-cost and green synthesis technique was utilized for biodiesel preparation via waste cooking oil methanolysis using waste snail shell derived catalyst. The present work aimed to investigate the production of biodiesel fuel from waste materials. The catalyst was greenly synthesized from waste snail shells throughout a calcination process at different calcination time of 2–4 h and temperature of 750–950 °C. The catalyst samples were characterized using X-Ray Diffraction (XRD), Brunauer-Emmett-Teller (BET), Energy Dispersive X-ray (EDX), and Fourier Transform Infrared (FT-IR). The reaction variables varying in the range of 10:1–30:1 M ratio of MeOH: oil, 3–11 wt% catalyst loading, 50–70 °C reaction temperature, and 2–6 h reaction time. The designed model optimization was set its parameters at 21.5 methanol molar ratio, 9.8 wt% catalyst loading, 4.8 h reaction time, and 62.2 °C reaction temperature, resulting in a mixture comprised of 95% esters content.

MXene-PVA-TiO2-based photothermal-catalytic membrane with high structural stability for efficient desalination and photodegradation

Solar energy is regarded as the most attractive energy source for producing clean water and green energy, as well as for photocatalytic pollutants removal. MXene, a 2D photothermal material, has opened up new opportunities in solar energy harvesting due to its unique properties. However, it has limitations, such as strong oxidation and degradation tendencies, that affect its stability. To address these challenges, herein we fabricated a highly stable MXene-PVA-TiO2@PVDF Janus membrane and tested it in an advanced photothermal-catalytic membrane distillation (PMD) system. The modified MXene-PVA-TiO2@PVDF membrane demonstrated superior photothermal desalination flux (1.23 kg/m2h with 99.9% salt rejection) and efficient photodegradation capacity (methylene blue removal rate > 95%) under 1 sun irradiation. The superior photothermal desalination efficiency of the prepared membrane is attributed to the wide-spectrum optical absorption and exceptional light-to-heat conversion characteristics of MXene, while a substantial enhancement in the photodegradation performance is ascribed to the formation of the MXene-TiO2 2D/3D hierarchical structure acting as a direct Z-scheme photocatalyst. The chemical and mechanical strength was significantly enhanced due to the robust 2D network structure of MXene-PVA. Overall, this study demonstrates the feasibility of synergetic photothermal-catalytic membrane distillation and the promising prospects of MXene materials in this field.

Homogeneous regulation of arranged polymorphic manganese dioxide nanocrystals as cathode materials for high-performance zinc-ion batteries

Rechargeable aqueous zinc-ion batteries have emerged as attractive energy storage devices by virtue of their low cost, high safety and eco-friendliness. However, zinc-ion cathodes are bottlenecked by their vulnerable crystal structures in the process of zinc embedding and significant capacity fading during long-term cycling. Herein, we report the rational and homogeneous regulation of polycrystalline manganese dioxide (MnO2) nanocrystals as zinc cathodes via a surfactant template-assisted strategy. Benefiting from the homogeneous regulation, MnO2 nanocrystals with an ordered crystal arrangement, including nanorod-like polyvinylpyrrolidone-manganese dioxide (PVP-MnO2), nanowire-like sodium dodecyl benzene sulfonate-manganese dioxide and nanodot-like cetyltrimethylammonium bromide-manganese dioxide, are obtained. Among these, the nanorod-like PVP-MnO2 nanocrystals exhibit stable long-life cycling of 210 mAh g−1 over 180 cycles at a high rate of 0.3 A g−1 and with a high capacity retention of 84% over 850 cycles at a high rate of 1 A g−1. The good performance of this cathode significantly results from the facile charge and mass transfer at the interface between the electrode and electrolyte, featuring the crystal stability and uniform morphology of the arranged MnO2 nanocrystals. This work provides crucial insights into the development of advanced MnO2 cathodes for low-cost and high-performance rechargeable aqueous zinc-ion batteries.

Brueckner G -matrix approach to two-dimensional Fermi gases with finite-range attractive interactions

Two-dimensional spin-1/2 fermions with finite-range interactions are theoretically studied. Characterizing the attractive interaction in terms of the scattering length and the effective range, we discuss the finite-range effects on the ground-state properties in this system. The Brueckner $G$-matrix approach is employed to analyze the finite-range effects on an attractive Fermi-polaron energy and the equation of state throughout the BEC-BCS crossover in two dimensions, which can be realized in the population-imbalanced and -balanced cases between two components, respectively. The analytical formulas for these ground states obtained in this study would be useful for understanding many-body phenomena with finite-range interactions in low-dimensional systems.

Asphaltene aggregation under the influence of structural features and interaction energies: Combination of quantum mechanical and molecular dynamics approaches

The importance of the model to predict the aggregation behavior of asphaltene molecules at the molecular level was well established in different studies. Elucidation of the relationship between the interaction energy and the structural characteristics of asphaltene molecules to their aggregation behavior still needs further investigation. For this purpose, we combined the quantum mechanics and molecular dynamics approaches and analyzed the interaction energy of asphaltene to find out the effect of structural features on the aggregation behavior. The interaction energy of asphaltene is used in this study to evaluate the potential of aggregation. We found that asphaltene molecules with smaller aromatic cores and shorter side chains form longer but more unstable stacks in the aggregation phase. If these structures do not have polar groups in the side chains, they will not show significant aggregation behavior in the clustering phase. Also, the length of stacks formed in the accumulation phase can be interpreted and predicted based on the terms such as attractive dispersion energy and steric repulsion in the interaction energy of asphaltene dimers. The aggregation process is explained by analyzing the nature of the interaction energy. As a result, by examining the effect of structural features on interaction energy, a relatively acceptable picture of the aggregation behavior of the asphaltene molecules can be obtained.