Volumetric Energy Research Articles

Hydrogen storage methods by lithium borohydride

This paper addresses the urgent need for efficient hydrogen storage methods in the context of combating climate change and transitioning to sustainable energy sources. Among various storage options, LiBH4 is highlighted for its high volumetric and gravimetric energy densities, critical factors in determining its suitability for energy applications. However, challenges arise due to its high thermolysis temperature, which poses difficulties, especially in applications like automotive use where high temperatures are required. The commercial viability of LiBH4 remains a significant obstacle due to the nascent stage of chemical hydride technology and the absence of large-scale production facilities. Environmental concerns also loom large, as the production of LiBH4 relies on extensive mining of lithium and boron, known for their environmental impact. Furthermore, the economic feasibility of LiBH4 as a hydrogen storage medium is questioned, given the substantial portion of total expenses attributed to hydrogen costs, affecting all methods except those based on fossil fuels or electricity. Nevertheless, there is optimism that with technological advancements and improved infrastructure, the costs associated with LiBH4 and hydrogen storage overall may decrease over time.In conclusion, while LiBH4 presents promising energy density characteristics, its practical implementation faces challenges such as high production costs, environmental concerns, and technological limitations. Overcoming these obstacles is crucial for realizing a sustainable and carbon-free energy landscape driven by hydrogen.

2.5 μm‐Thick Ultrastrong Asymmetric Separator for Stable Lithium Metal Batteries

Lithium metal batteries (LMBs) are considered the ideal choice for high volumetric energy density lithium‐ion batteries, but uncontrolled lithium deposition poses a significant challenge to the stability of such devices. In this paper, we introduce a 2.5 μm‐thick asymmetric and ultrastrong separator, which can induce tissue‐like lithium deposits. The asymmetric separator, denoted by utPE@Cu2O, was prepared by selective synthesis of Cu2O nanoparticles on one of the outer surfaces of a nanofibrous (diameter ~10 nm) ultrastrong ultrahigh molecular weight polyethylene (UHMWPE) membrane. Microscopic analysis shows that the lithium deposits have tissue‐like morphology, resulting in the symmetric lithium cells assembled using utPE@Cu2O with symmetric Cu2O coating exhibiting stable performance for over 2000 h of cycling. This work demonstrates the feasibility of a facile approach ultrathin separators for the deployment of lithium metal batteries, providing a pathway towards enhanced battery performance and safety.

Cross-Sectional Melt Pool Geometry of Laser Scanned Tracks and Pads on Nickel Alloy 718 for the 2022 Additive Manufacturing Benchmark Challenges

AbstractThe Additive Manufacturing Benchmark Series (AM Bench) is a NIST-led organization that provides a continuing series of additive manufacturing benchmark measurements, challenge problems, and conferences with the primary goal of enabling modelers to test their simulations against rigorous, highly controlled additive manufacturing benchmark measurement data. To this end, single-track (1D) and pad (2D) scans on bare plate nickel alloy 718 were completed with thermography, cross-sectional grain orientation and local chemical composition maps, and cross-sectional melt pool size measurements. The laser power, scan speed, and laser spot size were varied for single tracks, and the scan direction was varied for pads. This article focuses on the cross-sectional melt pool size measurements and presents the predictions from challenge problems. Single-track depth correlated with volumetric energy density while width did not (within the studied parameters). The melt pool size for pad scans was greater than single tracks due to heat buildup. Pad scan melt pool depth was reduced when the laser scan direction and gas flow direction were parallel. The melt pool size in pad scans showed little to no trend against position within the pads. Uncertainty budgets for cross-sectional melt pool size from optical micrographs are provided for the purpose of model validation.

A rigid free-standing supercapacitor electrode material made from fat coal-based activated carbon foam

A free-standing electrode material is a competitive candidate for supercapacitor due to its excellent capacity and volumetric energy density. Currently, most of the studies are focused on the preparations and performances of flexible free-standing electrode materials, whereas few on the development of rigid free-standing electrode materials. Herein, a vitrinite concentrate of fat coal is used as a raw material and carbon black as an addition agent to prepare a carbon foam by way of high-pressure pyrolysis. The prepared carbon foam is activated by KOH solution to further achieve an activated carbon foam by which we have fabricated a rigid free-standing electrode material. The assembled symmetric device with the rigid free-standing electrode material demonstrates an extremely high areal specific capacitance of 2304.41 mF cm−2 at 4 mA cm−2, an outstanding cycling stability of 100 % after 40 000 cycles, and an excellent volume energy density of 10.23 mWh cm−3 at 31.78 mW cm−3. These fascinating electrochemical performances of the electrode material are attributed to unique 3D interconnected porous structure of the activated carbon foam. The micron-sized 3D interconnected pores facilitate the transport of electrolyte ions within the electrodes. Meanwhile, micropores on the 3D interconnected pore wall provide abundant active sites for electrolyte ions.

Design Principles and Routes for Calcium Alkoxyaluminate Electrolytes.

Multivalent-ion battery technologies are increasingly attractive options for meeting diverse energy storage needs. Calcium ion batteries (CIB) are particularly appealing candidates for their earthly abundance, high theoretical volumetric energy density, and relative safety advantages. At present, only a few Ca-ion electrolyte systems are reported to reversibly plate at room temperature: for example, aluminates and borates, including Ca[TPFA]2, where [TPFA]- = [Al(OC(CF3)3)4]- and Ca[B(hfip)4]2, [B(hfip)4]2- = [B(OCH(CF3)2)4]-. Analyzing the structure of these salts reveals a common theme: the prevalent use of a weakly coordinating anion (WCA) consisting of a tetracoordinate aluminum/boron (Al/B) center with fluorinated alkoxides. Leveraging the concept of theory-aided design, we report an innovative, one-pot synthesis of two new calcium-ion electrolyte salts (Ca[Al(tftb)4]2, Ca[Al(hftb)4]2) and two reported salts (Ca[Al(hfip)4]2 and Ca[TPFA]2) where hfip = (-OCH(CF3)2), tftb = (-OC(CF3)(Me)2), hftb = (-OC(CF3)2(Me)), [TPFA]- = [Al(OC(CF3)3)4]-. We also reveal the dependence of Coulombic efficiency on their inherent propensity for cation-anion coordination.

Seasonal abundance, lipid storage, and energy density of Calanus finmarchicus and other copepod preyfields along the Northwest Atlantic continental shelf

Abstract Calanus finmarchicus is an abundant calanoid copepod in the New York Bight (NYB) that has energy-dense lipid stores. This study measured C. finmarchicus abundance, lipid storage and energy density and compared it to two other abundant calanoid species in the region. We compared the NYB C. finmarchicus preyfield characteristics with data from two other NW Atlantic coastal ecosystems, the Gulf of Maine (GoM) and Cape Cod Bay (CCB). Copepods from net tows were identified, enumerated, photographed and measured. These data were used to calculate animal biovolume and lipid content as well as the volumetric energy density of the copepod preyfield. C. finmarchicus were most abundant in spring and summer and the mean lipid storage of C. finmarchicus remained largely constant regardless of season and location within the NYB. Centropages typicus were abundant enough in the winter to be more energy-rich than C. finmarchicus. Temora longicornis, while also abundant, never surpassed the energy density of C. finmarchicus. C. finmarchicus in the NYB were comparably lipid-rich to those from the GoM and CCB. C. finmarchicus in the NYB can be a reliable energy source for local predators due to their high spring and summer abundances and year-round storage of high-energy wax esters.

Potential of Aluminum as a Metal Fuel for Supporting EU Long‐Term Energy Storage Needs

AbstractThe EU's energy transition necessitates availability of green energy carriers with high volumetric energy densities for long‐term energy storage (ES) needs. A fully decarbonized scenario considering renewable energy availability is analyzed underpinning the need for such carriers. Considering the shortcomings of Power‐to‐X technologies in terms of efficiency and low volumetric density, Aluminum (Al) is identified as a potential alternative showing significantly high volumetric energy densities (23.5 kWh L−1). In this paper, an Al‐based long‐term ES concept is investigated, taking advantage of the inherent recycling of the active species (i.e., Al2O3 to Al) coupling decarbonized Hall–Héroult process with an Al‐steam oxidation for simultaneous hydrogen (H2) and heat generation. This work demonstrates an innovative lab‐scale fine Al powder‐steam oxidation process at ≈900 °C without use of catalysts or additives, exploiting alumina as inert material. Conducted SEM‐EDX analysis on oxidized Al provides supporting evidence in favor of employed oxidation pathway, hindering tendency of aluminum oxide (Al2O3) clumping and enabling direct use of oxides in the smelting process for fully recyclability. Moreover, outcomes of XRD analyses are presented to validate the measured total H2 yields.

High Volumetric Energy Density Supercapacitor of Additive-Free Quantum Dot Hierarchical Nanopore Structure.

The high surface-area-to-volume ratio of colloidal quantum dots (QDs) positions them as promising materials for high-performance supercapacitor electrodes. However, the challenge lies in achieving a highly accessible surface area, while maintaining good electrical conductivity. An efficient supercapacitor demands a dense yet highly porous structure that facilitates efficient ion-surface interactions and supports fast charge mobility. Here we demonstrate the successful development of additive-free ultrahigh energy density electric double-layer capacitors based on quantum dot hierarchical nanopore (QDHN) structures. Lead sulfide QDs are assembled into QDHN structures that strike a balance between electrical conductivity and efficient ion diffusion by employing meticulous control over inter-QD distances without any additives. Using ionic liquid as the electrolyte, the high-voltage ultrathin-film microsupercapacitors achieve a remarkable combination of volumetric energy density (95.6 mWh cm-3) and power density (13.5 W cm-3). This achievement is attributed to the intrinsic capability of QDHN structures to accumulate charge carriers efficiently. These findings introduce innovative concepts for leveraging colloidal nanomaterials in the advancement of high-performance energy storage devices.

Creep-type all-solid-state cathode achieving long life

Electrochemical-mechanical coupling poses enormous challenges to the interfacial and structural stability but create new opportunities to design innovative all-solid-state batteries from scratch. Relying on the solid-solid constraint in the space-limited domain structure, we propose to exploit the lithiation-induced stress to drive the active materials creep, thereby improving the structural integrity. For demonstration, we fabricate the creep-type all-solid-state cathode using creepable Se material and an all-in-one rigid ionic/electronic conducting Mo6Se8 framework. As indicated by the in-situ experiment and numerical simulation, this cathode presents unique capabilities in improving interparticle contact and avoiding particle fracture, leading to its superior electrochemical performance, including a superior long-cycle life of more than 3000 cycles at 0.5 C and a high volumetric energy density of 2460 Wh/L at the cathode level. We believe this innovative strategy to utilize mechanics to boost the electrochemical performance could shed light on the future design of all-solid-state batteries for practical applications.

Synergy of Modulating In-Plane Pores and Zincophilic Sites On the Flexible Graphene Paper for Efficient and Dendrite-Free Hosted Zn Anode

The practical advancement of Zn-ion batteries (ZIBs) in the portable/wearable electronics field is still hindered by the notorious Zn dendrites formation and the lack of an appropriate host to construct a highly effective flexible Zn anode. Herein, we present a three-dimensional (3D) N-doped graphene paper framework with abundant in-plane pores (rHGP-N) as an efficient Zn plating/stripping scaffold. Remarkably, the rHGP-N paper electrode exhibits an unprecedentedly low Zn nucleation overpotential of 5.2 mV and maintains a high average Coulombic efficiency (∼99.3%) over a superior long Zn plating/stripping cycling of 1400 h. DFT calculation results demonstrate that pyrrolic-nitrogen on graphene possess the strongest adsorption energy for Zn2+, serving as zincophilic sites to guide Zn uniform nucleation. Moreover, the finite elements simulation results illustrate that flexible graphene paper with abundant in-plane pores can mitigate structural stress and inhibit the formation of Zn dendrites by spatially homogenizing Zn2+ ions flux throughout the entire electrode. The assembled ZIBs full cell (rHGP-N@Zn//rHGP-N@Mn3(PO4)2) demonstrates an impressive volumetric energy density of 77 mWh cm-3, as well as excellent flexibility and mechanical stability with negligible capacity decay under harsh deformation conditions. Our approach can be potentially utilized in designing dendrite-free metal-based flexible anodes for Mg, Ca, or Al-ion batteries.

Green ammonia production: Process technologies and challenges

Ammonia, a vital player in the global economy, propels economic growth through its key role in fertilizer production, boosting agricultural output significantly. While traditional methods dominate its production, recent efforts focus on sustainable pathways like green ammonia, produced using renewable energy. This colourless gas, beyond agriculture, becomes a versatile input in chemical manufacturing, finding applications in solvents and fertilizers. Industries are increasingly adopting green pathways to reduce carbon footprints, exploring methods using green hydrogen and CO2 by-products. Green ammonia, a beacon for decarbonization, surpasses hydrogen in volumetric energy density, making it a preferred energy carrier. Power-to-Ammonia technology supports energy storage and transfer capabilities, aiding renewable energy integration. Despite challenges like low reactivity, NOx emissions, and toxicity, ammonia's global demand is projected to rise to 350 million tonnes/year by 2050. This review article emphasizing the need for sustainable ammonia production to achieve economic competitiveness, environmental sustainability, and a carbon–neutral future.

Data-driven Approach to Explore the Contribution of Process Parameters for Laser Powder Bed Fusion of a Ti-6Al-4V Alloy

In order to predict the process window of laser powder bed fusion (LPBF) for printing metallic components, the calculation of volumetric energy density (VED) has been widely calculated for controlling process parameters. However, because it is assumed that the process parameters contribute equally to heat input, the VED still has limitation for predicting the process window of LPBF-processed materials. In this study, an explainable machine learning (xML) approach was adopted to predict and understand the contribution of each process parameter to defect evolution in Ti alloys in the LPBF process. Various ML models were trained, and the Shapley additive explanation method was adopted to quantify the importance of each process parameter. This study can offer effective guidelines for fine-tuning process parameters to fabricate high-quality products using LPBF.

Numerical study of the effect of helical fuel rod geometry on single-phase flow and heat transfer characteristics

Helical fuel is a promising nuclear fuel proposed to improve the core power density and safety margin. In this study, the effect of helical fuel rod geometry on single-phase flow and heat transfer characteristics in helical fuel annuli has been investigated. The volumetric energy source is applied to the fuel pin, and coupled walls are used at the coolant-cladding and cladding-fuel interfaces. The numerical method with SST k-ω turbulence model has been validated with the results of bare annulus. The flow field, fuel central temperature, friction factor, and the circumferential distribution of swirl intensity, heat flux and wall temperature are obtained based on the numerical simulation. The increase in R2/R1 will result in broadening transverse flow region, reducing the gradient of surface heat flux and wall temperature, lowering the maximum wall temperature, but increasing the fuel central temperature and has no significant effect on the friction resistance. The decrease of helical pitch increases the swirl intensity and friction factor, but worsens the heat transfer at the blade roots.

Metal sulfide-decorated lamellar porous carbon framework hybrids for fast lithium storage with high volumetric capacity

Porous carbon nanosheets have shown great potential in electrochemical energy storage devices, yet their intrinsic limited volumetric capacity and energy density remain a great concern. Herein, lamellar porous carbon framework hybrids (LPCFHs) have been facilely developed by thermal-induced bulk self-assembly of block copolymers with precisely controllable molecular structure, followed by stepwise chemical crosslinking and morphology-persistent carbonization processes. The as-obtained LPCFHs consist of densely covalent connected alternate layers (porous carbon nanosheets and porous carbon spacers) and homogenously dispersed metal sulfide nanoparticles. The ordered compact stacking structure of carbon nanosheets endows LPCFHs with a high tap density and fast electron transfer both in lateral and vertical dimension, while the porous carbon spacers enable fast channels for ion transfer. Moreover, the metal sulfide nanoparticles strongly interacted with carbon nanosheets are homogenously distributed in LPCFHs, resulting in sufficient active sites. As a result, when used as anode materials in lithium-ion batteries (LIBs), tin sulfide-decorated LPCFHs (LPCFHs-SnS) deliver a volumetric capacity of up to 1285 mAh cm−3; meanwhile, high-rate capability (488 mAh g−1 at 5 A g−1) and excellent cycling stability (capacity retention of 88.3 % after 500 cycles at 1 A g−1) are also achieved, demonstrating great potential for practical application in LIBs.

Suppressed Electrolyte Decomposition Behavior to Improve Cycling Performance of LiCoO2 under 4.6V through the Regulation of Interfacial Adsorption Forces.

Alleviating the decomposition of the electrolyte is of great significance to improving the cycle stability of cathodes, especially for LiCoO2 (LCO), its volumetric energy density can be effectively promoted by increasing the charge cutoff voltage to 4.6V, thereby supporting the large-scale application of clean energy. However, the rapid decomposition of the electrolyte under 4.6V conditions not only loses the transport carrier for lithium ion, but also produces HF and insulators that destroy the interface of LCO and increase impedance. In this work, the decomposition of electrolyte is effectively suppressed by changing the adsorption force between LCO interface and EC. Density functional theory illustrates the LCO coated with lower electronegativity elements has a weaker adsorption force with the electrolyte, the adsorption energy between LCO@Mg and EC (0.49eV) is weaker than that of LCO@Ti (0.73eV). Meanwhile, based on the results of time of flight secondary ion mass spectrometry, conductivity-atomic force microscopy, in situ differential electrochemical mass spectrometry, soft X-ray absorption spectroscopy, and nuclear magnetic resonance, as the adsorption force increases, the electrolyte decomposes more seriously. This work provides a new perspective on the interaction between electrolyte and the interface of cathode and further improves the understanding of electrolyte decomposition.

Fe3C and Fe3O4 decorated porous carbon as high volumetric capacitance/rate electrodes for supercapacitor

As the most attractive electrode for supercapacitors, renewable carbon-based material exhibits slow charge and discharge ability and low volumetric energy density, severely hindering its extended applications. Herein, a neotype and high-performance carbon-based nanocomposites were successfully prepared from Linum usitatissimum. L stems assisted with K4Fe(CN)6·3H2O through a green and straightforward high-temperature treatment method. Benefiting from the activation and decomposition of K4Fe(CN)6·3H2O, the carbon-based nanocomposite decorated by Fe3C and Fe3O4 possesses moderate porous volume, heteroatoms content, and graphitization degree. These characteristics endow the supercapacitor assembled from as-prepared carbon-based nanocomposite with fast charge/discharge ability, high volumetric capacitance (303.8 F cm−3, 1 A g−1), excellent rate performance (61.3%, 100 A g−1), and outstanding cycle life. Owing to abundant N/O-containing functional groups, high C=C content, and appropriate specific surface area, the resultant nanocomposite also exhibits excellent organic dye removal performance. Overall, this work offers a green and efficient avenue for designing multi-doped carbon-based nanocomposites in electrochemical energy storage and organic dye removal.

Cellulose-based high-loading flexible electrode for lithium-ion battery with high volumetric energy density

Thick electrodes with high loading are attractive for high-energy storage devices, but they face major challenges of slow ion transfer and poor mechanical stability. Carbon templates such as reduced graphene oxide and carbon nanotube can promote the electrons transfer of thick electrodes and enhance their strength, but they still exhibit a complex producing process, slow Li+ transfer and high cost. Herein, a nanofiber network with double fast Li+ and electrons transfer pathways by the self-assembly of carbon nanoparticles on the negatively charged natural cellulose fibers was designed. The abundant oxygen-containing functional groups from the cellulose fibers enabled the electrode with abundant negative charge which can adsorb the neutral particles with strong electrostatic interaction. And the Density Functional Theory calculation demonstrates that oxygen-containing functional groups also has stronger adsorption energy for PF6− anions in electrolyte which can promote the desolvation of the solvated Li salts, thus promote Li+ transfer. After integration with lithium iron phosphate, this network achieves a robust high-loaded electrode with good electrical conductivity and shortened ion transfer pathways without traditional current collector and binder. Based on the robust electrode structure and fast transfer kinetics of electrons and Li+, the batteries exhibit excellent cycle stability with capacity retention of 98 % after long 400 cycles and high volumetric energy density of 740 Wh/L, which greatly surpass the conventional batteries with coating LiFePO4 (LFP) cathode. Given the low-cost raw materials and convenient operation, the design of self-standing flexible electrodes with high loading will offer a promising and effective strategy for other storage devices with high energy.

Preparation, characterization, and combustion properties of NGO/GF/B composite system

Boron is a potential fuel for energetic materials due to its high volumetric and gravimetric energy density. However, its application has long been constrained by ignition difficulties and insufficient combustion. In this study, a mixture of NGO and GF was introduced as an additive to boron particles. We prepared NGO/GF-coated B complexes and performed several characterizations, showing that NGO combined with GF had a good coating effect on B. The combustion heat was measured by an oxygen bomb calorimeter, while the combustion mechanism was proposed. Its effect on the thermal decomposition behavior of AP was also analyzed. The results showed that the combustion efficiency of NGO/GF-modified B was significantly improved, which was 14.34% higher than that of pure B. This enhancement was attributed to the synergistic effect of NGO and GF, which promoted ignition and combustion by releasing heat, gases, and fluorocarbon radicals. In addition, both boron and NGO/GF-modified boron accelerated the decomposition of AP, especially, in the presence of NGO/GF, the decomposition temperature of AP was advanced by 73.2 °C compared to that in the presence of boron alone. These findings may provide valuable theoretical guidance for the design and potential application of NGO/GF modified boron in energetic materials.

Advances and Future Prospects of Micro‐Silicon Anodes for High‐Energy‐Density Lithium‐Ion Batteries: A Comprehensive Review

AbstractSilicon (Si), stands out for its abundant resources, eco‐friendliness, affordability, high capacity, and low operating potential, making it a prime candidate for high‐energy‐density lithium‐ion batteries (LIBs). Notably, the breakthrough use of nanostructured Si (nSi) has paved the way for the commercialization of Si anodes. Despite this, challenges like high processing costs, severe side reactions, and low volumetric energy density have impeded widespread industrial adoption. Micron‐scale Si (µSi) has always faced setbacks compared to nSi due to its greater volume expansion. However, recent years have witnessed a resurgence of interest in µSi‐based anodes. Capitalizing on its inherent advantages, including low cost and high tap density, µSi has once again captured the attention of both academic and industrial communities. This review begins by contrasting the strengths and weaknesses of µSi and nSi, then outline potential solutions to enhance µSi performance, covering aspects like structural regulation, composite anodes, binder design, and electrolyte exploration. Additionally, this work explores the application of machine learning‐assisted high‐throughput screening. Concluding the review, this work provides insights into the future prospects of µSi in LIBs, outlining challenges and proposing integrated coping strategies. This review anticipates that it will provide valuable perspectives for the commercial application of high‐energy‐density Si‐based anodes.

Flexible films with three-dimensional ion transport channels: Carbon nanotubes@MnO2 as interlayer spacers in porous graphene electrodes for high-performance supercapacitors

Flexible supercapacitors have a high potential for application in wearable electronics and microdevices, but their commercial appeal is limited because of low energy density. To overcoming this challenge, this paper proposes a strategy to fabricate dense films with high specific capacitance. A composite film with rapid ion diffusion channels and a high density of 0.86 g cm–3 was synthesized by combining porous graphene nanosheets (PGNs), carbon nanotubes (CNTs), and MnO2 nanosheets. The incorporation of CNTs@MnO2 between graphene layers effectively mitigated aggregation and enhanced electrolyte ion diffusion within the dense graphene structure. PGNs and CNTs synergistically established a three-dimensional pathway for efficient ion transport while optimizing electron dynamics. In 1 mol L–1 Na2SO4 electrolyte, the material exhibited a gravimetric capacitance of up to 320 F g–1 at 1 A g–1 and a volumetric capacitance reached 275 F cm–3. Furthermore, the assembled asymmetric supercapacitors, PGNs-CNTs@MnO2//PGNs-CNTs, exhibited a gravimetric energy density of up to 26.4 Wh kg–1 and a volumetric energy density of up to 22.7 Wh L–1. These findings offer insights into advancing flexible supercapacitor technology for diverse applications.