Low Specific Capacity Research Articles

The heat transfer mechanism coupling pyrolysis and flow of hydrocarbon fuel in heated tube under supercritical pressure

The coupling mechanism between pyrolysis and fluid flow of endothermic hydrocarbon fuels plays a crucial role in the design of regenerative cooling systems for advanced aircraft. In this work, the convective heat transfer for HF-1 with pyrolysis including 18 species and 24 reactions is numerically investigated in a horizontal circle tube under supercritical pressure (5 MPa). The results show that the mechanism of small molecule products on different heat transfer phenomena varies. In the inlet heat transfer deterioration region, small molecule products exacerbate the non-uniform radial distribution of fluid density and dynamic viscosity. At the outlet position, it significantly enhances the physical heat sink of the mixture with its high thermal conductivity and specific heat capacity. Additionally, the aromatic hydrocarbons significantly contribute to non-uniformities in thermal conductivity and specific heat capacity due to the low specific heat capacity and thermal conductivity in inlet HTD region. When the radial non-uniformity coefficient of fuel conversion keeps between −0.1 and 0, the pyrolysis of the fuel enhances heat transfer, remarkably.

Deep eutectic solvents formed by novel metal-based amino acid salt and dihydric alcohol for highly efficient capture of CO2

Deep eutectic solvents (DESs) are considered to be potential absorbents for CO2 capture compared to traditional amine solutions, because they have many advantages such as lower volatility and better thermal stability. In this study, a series of novel γ− and ε− m−based amino acid salts (AASs) were prepared through one-step hydrolysis reaction of accessible and cheap lactams as hydrogen bond acceptor (HBA). The chemical structures of these AASs were characterized by ESI-MS and NMR. Dihydric alcohol was selected as hydrogen bond donor (HBD) to prepare AAS-based DESs because of its low specific heat capacity and high boiling point. The physical properties of AAS-based DESs, such as density at 313.2–353.2 K, viscosity at 313.2–353.2 K, the melting temperature from 173.2 to 273.2 K, and thermal decomposition temperature from 300 to 750 K, were also determined. The gas absorption experiments were carried out on a dual-chamber at temperatures from 313.2 to 333.2 K and pressures up to 1.1 bar. It is found that K[Gaba]-EG has the largest CO2 uptake capacity with 0.12 g·g−1 at 1.0 bar and 313.2 K, better than almost all absorbent with AASs reported in literatures (0.02 g·g−1 ∼ 0.07 g·g−1). The CO2 absorption mechanisms were proved to be a combination of 2:1 and 1:1 stoichiometric reaction through thermomechanical analysis and NMR. This paper will present distinctive insights into the preparation of CO2 absorbent for effective carbon capture.

Optimizing Mn in Prussian blue analogs with double redox active sites to induce boosted Zn2+ storage

Prussian Blue analogs (PBAs) are a suitable aqueous zinc-ion batteries (AZIBs) cathode material, but they face issues related to low specific capacity and cycling lifespan due to insufficient active sites and poor ion de-intercalation structural stability. In this study, Mn-Prussian Blue Analog (Mn-PBA) is fabricated using a simple co-precipitation method and the morphology of Mn-PBA is further optimized through artificially manipulating concentration gradients strategy, effectively enhancing the structural stability of Zn2+ de-intercalation. Furthermore, the introduction of Mn established dual Zn2+ active centers in Mn-PBA (Mn-O and Fe(CN)6]4−/[Fe(CN)6]3−), leading to an increased specific capacity. As a proof of concept for AZIBs, the optimized Mn-PBA-3 cathode exhibits a high reversible specific capacity of 143.5 mAh/g and maintains a capacity retention of 88.5 % after 250 cycles at 1 A/g, surpassing commercial MnO2 (30.5 mAh/g after 100 cycles). Mn-PBA-3 also delivers a high capacity of 79.0 mA h g−1 after 2000 cycles of 10 A/g. The mechanism of the Zn2+ double redox reaction of Mn-PBA-3 has been revealed in detail by in situ Raman and a series of ex situ techniques. Under a high operating voltage window of 0–1.9 V, Zn//Mn-PBA-3 demonstrates a capacity of 99.3 mAh/g after 800 cycles (5 A/g) by assembling zinc ion button battery. This work has reference significance for structurally modulated PBAs used in high performance AZIBs.

Locally Concentrated Deep Eutectic Liquids Electrolytes for Low-Polarization Aluminum Metal Batteries.

Low-cost and nontoxic deep eutectic liquid electrolytes (DELEs), such as [AlCl3]1.3[Urea] (AU), are promising for rechargeable non-aqueous aluminum metal batteries (AMBs). However, their high viscosity and sluggish ion transport at room temperature lead to high cell polarization and low specific capacity, limiting their practical application. Herein, non-solvating 1,2-difluorobenzene (dFBn) is proposed as a co-solvent of DELEs using AU as model to construct a locally concentrated deep eutectic liquid electrolyte (LC-DELE). dFBn effectively improves the fluidity and ion transport without affecting the ionic dynamics in the electrolyte. Moreover, dFBn also modifies the solid electrolyte interphase growing on the aluminum metal anodes and reduces the interfacial resistance. As a result, the lifespan of Al/Al cells is improved from 210 to 2000h, and the cell polarization is reduced from 0.36 to 0.14V at 1.0mAcm-2. The rate performance of Al-graphite cells is greatly improved with a polarization reduction of 0.15 and 0.74V at 0.1 and 1Ag-1, respectively. The initial discharge capacity of Al-sulfur cells is improved from 94 to 1640mAhg-1. This work provides a feasible solution to the high polarization of AMBs employing DELEs and a new path to high-performance low-cost AMBs.

Study of Zinc Diffusion Based on S, N-Codoped Honeycomb Carbon Cathodes for High-Performance Zinc-Ion Capacitors.

Capacitors with zinc ions, with excellent stabilities, low cost, and high energy density, are expected to be promising energy storage devices. However, the development of zinc-ion capacitors is quietly restricted by low specific capacity and cycling stability. Herein, to overcome these limitations, honeycomb-structured S, N-codoped carbon (SNPC) is constructed by one-pot calcination of waste corn bracts and thiourea. The honeycomb structure of SNPC is demonstrated to provide abundant active sites that can enhance the extron/ion transport, conductivity for high power export, and ion adsorption capacity in energy storage applications, leading to a higher electrochemical performance achieved. The electrolytes of zinc salt have also been studied. It reveals that the SNPC electrode presents the best electrochemical performance in a 2 M ZnSO4 and 0.5 M ZnCl2 electrolyte mixture because in the electrolyte mixture, Cl- can replace the existing bound water in the solvation structure to form an anion-type water-free solvation structure ZnCl42-. The SNPC-800 electrode with a highly improved surface area (∼909.0 m2 g-1) is proved to be more suitable as the electrode than other materials. Aqueous zinc-ion capacitors (ZICs) have been assembled by the honeycomb-structured SNPC-800 as the cathode, which can achieve a relatively wide working voltage range of 0.1-1.8 V. The SNPC-800 ZICs exhibit a superior specific capacity of 179.1 mA h g-1 at 0.1 A g-1. The energy density of SNPC-800 ZICs reaches an impressive value of 89.6 Wh kg-1 at 53.8 W kg-1, and it sustains 28.3 Wh kg-1 at 1997.6 W kg-1. In addition, there is 99.8% capacity retention in the SNPC-800 ZICs over 5000 cycles. The absorption energy in SPNC is much higher than that in undoped CPC, as confirmed by density functional theory, which reveals that introducing of heteroatoms (S, N) has a comparatively active advantage at increasing the Zn-ion storage capacity. This work proposes a practical strategy for the effective recycling of waste biomass materials into honeycomb carbon electrode materials. Moreover, the honeycomb carbon-based ZICs with excellent electrochemical performance and long-term cycling stability possess great potential to be a superior cathode in practical applications.

Redox-active poly(imide-quinone) covalent organic framework anodes for high-efficient and durable aqueous proton batteries

Hydrogen ions (protons), as the lightest and smallest non-metallic charge carriers, have aroused great interest in the field of aqueous batteries. Unfortunately, most anode materials used for these proton batteries still suffer from low specific capacity and/or unsatisfactory cycle durability due to structural deterioration resulted from corrosion of strong acid electrolytes. Here, we report for the first time a robust poly(imide-quinone) (PIQ) covalent organic framework (COF) with dual redox-active naphthalene diimide-paraquinone motifs in its periodic skeletons for proton storage, which can afford a high reversible capacity of ∼ 255.6 mAh/g at a current density of 1 A/g with outstanding cycling stability. The aqueous proton battery (APB) fabricated with this PIQ-COF anode and a copper hexacyanoferrate (CuHCF) cathode demonstrates an unprecedentedly remarkable combination of reversible capacity (about 138 mAh/g at 0.5 A/g), rate capability (76.5 % capacity retention at 20 A/g), and long-term cyclability (99.999 % per cycle for 10,000 cycles at 3 A/g). The ex situ FTIR characterization reveals that the C = O groups in naphthalene imides and paraquinones contribute abundant and accessible redox-active sites for proton storage.

Optimal HDR exploitation siting of gravity heat pipe geothermal systems via reservoir simulation

Gravity heat pipe system has previously been proven as an environmental and efficient technology in exploiting hot dry rock. However, it is unclear what geothermal reservoir siting is more favorable for the system’s heat extraction performance. Herein, we analyzed the influences of geothermal field siting (rock property and reservoir environment) on heat extraction performance of gravity heat pipe systems through a 3D thermal–hydraulic coupled model. It is found that rock properties have huge influences on heat compensation, heat extraction ratio and heat compensation ratio. Low rock density, low rock specific heat capacity and high thermal conductivity could increase heat compensation, heat extraction ratio and heat compensation ratio. It is also found that geothermal reservoir environment affects the heat extraction rate seriously. High initial temperatures and low temperature gradients increase heat extraction rates. Geothermal reservoir pressure affects the heat extraction performance slightly, and low initial pressures increase heat extraction rate. The study results would provide suggestions on deep geothermal exploitation locations.

Enhanced electrocatalytic conversion of tellurium with MnO hollow nanospheres modified hierarchical n-doped carbon nanosheets in high-performance aqueous Zn-Te battery

Rechargeable aqueous zinc batteries (AZBs) are increasingly recognized as an alternative to conventional energy storage systems due to their environmentally safe nature, abundant zinc resources, and high theoretical capacity. However, the intercalation or surface redox mechanisms limit the development of AZBs cathode materials due to low specific capacity and energy density. The tellurium-based (Te) materials with conversion mechanisms are promising cathode materials for AZBs. Nevertheless, the slow kinetics are detrimental to the increase in specific capacity and energy density for Zn-Te battery. Therefore, a hierarchical structure of manganese oxide (MnO) hollow nanospheres loaded on nitrogen-doped carbon nanosheets (MnO@NC) was rationally designed and used as Te hosts (Te/MnO@NC) for Zn-Te battery. This hierarchical structure facilitates the loading of more Te species. Meanwhile, the MnO hollow nanospheres can expose more active sites, which can promote the kinetics of Te redox reactions thereby lowering the reaction energy barrier. The Te/MnO@NC cathode exhibits high specific capacity and high energy density (429 mAh g−1 and 407 Wh Kg−1 at 0.1 A g−1). Additionally, the conversion mechanism was investigated by systematic characterization and density functional theory (DFT) calculations. This study presents a new design platform for developing AZBs with high specific capacity and energy density.

Dendrite-suppressed Li deposition enabled by surface-tailored carbon-based current collectors for high-rate and stable Li-metal batteries

Lithium (Li)-metal batteries (LMBs) are considered as one of the most promising next-generation batteries due to the exceptionally low redox potential and high specific capacity of the Li metal anode. However, their practical application remains challenging due to problems such as Li dendrites growth and poor Coulombic efficiency (CE) during cycling. Among the various approaches proposed to solve these challenges, the introduction of 3D current collectors has been proven effective for suppressing the growth of dendritic Li. Nevertheless, the surface properties of 3D current collectors have been somewhat overlooked in existing studies. In this work, we assessed three distinct carbon nanotube (CNT)-based current collectors (namely, CNT, oxidized CNT (ONT), and reduced ONT (rONT)) to investigate the effects of their surface properties and compositions on the Li deposition process and, hence, the electrochemical stability of the resulting LMBs. The pristine CNT-based current collector exhibits a poor electrolyte wettability, thus resulting in a rapid decline in CE over successive cycles. In contrast, the ONT current collector shows enhanced electrolyte wettability with lithiophilic surface, which significantly improves the interfacial kinetics and cycling stability. Moreover, after the subsequent reduction process, the rONT current collector exhibits a higher electrical conductivity than the ONT current collector while maintaining the favorable electrolyte wettability. Consequently, the Li|rONT cell delivers a more stable cycling performance than the Li|ONT cell at high current densities. These results demonstrate that the electrochemical performances of the LMBs can be significantly improved by suitably modifying the surface characteristics of the current collectors.

Ferrocene Appended Porphyrin-Based Bipolar Electrode Material for High-Performance Energy Storage.

The versatile properties of bipolar organic electrode materials have attracted considerable attention in the field of electrochemical energy storage (EES). However, their practical application is hindered by their inherent limitations including low intrinsic electrical conductivity, low specific capacity, and high solubility. Herein, a bipolar organic molecule combining both porphyrin and ferrocene moieties (CuDEFcP) [5,15-bis(ethynyl)-10,20-di ferrocenyl porphinato]copper(II)) has been developed. It is proposed as a new organic electrode material with multifunctional application for rechargeable organic lithium-based batteries (ROLBs) and dual-ion organic symmetric batteries (SDIBs). Superior performance was delivered as cathode material in lithium based dual-ion batteries (LDIBs), with a high initial discharge capacity of 300 mAh. g-1 at 0.2 A. g-1 and a reversible capacity of 58 mAh. g-1 after 5000 cycles at 1 A. g-1. However, employing it as an anode material in lithium-ion batteries (LIBs), a reversible capacity of 295 mAh. g-1 at 0.2 A. g-1 was delivered. In SDIBs, in which CuDEFcP is used as both anode and cathode, an average discharge voltage of 2.4 V and an energy density of 261 Wh.kg-1 were achieved.

Selective Capacitive Removal of Pb2+ from Wastewater over Biochar Electrodes by Zinc Regulation.

Biochar materials have shown great potential for broad catalytic application. However, using these materials in the capacitive deionization technology (CDI) system for heavy metal removal still faces a significant challenge due to their low specific capacity and removal capability. Here, a comprehensive regulation on the interfacial/bulk electrochemistry of biochar by Zn doping is reported, which suggests a high renewable capacity (20mgg-1) and outstanding selective capacitive removal ability (SCR) of Pb2+ from leachate. The SCR efficiency of Pb2+ is as high as 99% compared to K+ (8%), Na+ (13%), and Cd2+ (37%). This work proves that the doped Zn on the biochar can combine with OH- generated by water splitting to form M─OH bonds, which is beneficial for improving the specific capacity. Significantly, the relationship between double-layer capacitance and pseudo-capacitance can also be optimized by regulating the content of Zn, leading to different removal abilities of heavy metals. Therefore, this work offers insights into charge-storage kinetics, which provide valuable guidelines for designing and optimizing the biochar electrode for broader environmental applications.

Graphene‐Assisted Chemical Stabilization of Liquid Metal Nano Droplets for Liquid Metal Based Energy Storage

AbstractEnergy storage devices with liquid‐metal electrodes have attracted interest in recent years due to their potential for mechanical resilience, self‐healing, dendrite‐free operation, and fast reaction kinetics. Gallium alloys like Eutectic Gallium Indium (EGaIn) are appealing due to their low melting point and high theoretical specific capacity. However, EGaIn electrodes are unstable in highly alkaline electrolytes due to Gallium oxide dissolution. In this letter, this bottleneck is addressed by introducing chemically stable films in which nanoscale droplets of EGaIn are coated with trace amounts of graphene oxide (GO). It is demonstrated that a GO to EGaIn weight ratio as low as 0.01 provides enough protection for a thin film formed by GO@EGaIn nanocomposite against significantly acidic or alkaline environments (pH 1‐14). It is shown that GO coating significantly enhances the surface stability in such environments, thus improving the energy storage capacity by over 10x. Microstructural analysis confirms GO@EGaIn composite stability and enhanced electrochemical performance. Utilizing this, a thin‐film supercapacitor is fabricated. Results indicate that when coating the EGaIn with GO to EGaIn ratio of 0.001, the areal capacitance improves by 10 times, reaching 20.02 mF cm−2. This breakthrough paves the way for advanced liquid metal‐based thin‐film electrodes, promising significant improvements in energy storage applications.

Phenyl Tellurosulfides as Cathode Materials for Rechargeable Lithium Batteries.

Phenyl ditelluride (PDTe) as a cathode material for rechargeable batteries has a low specific capacity (130.9 mAh g-1) due to limited active sites (two). To increase its capacity, additional active species need to be added to the structure of PDTe, like sulfur. Here, phenyl tellurosulfide (PDTeS) and phenyl tellurodisulfide (PDTeS2) can be formed via addition reactions and have specific capacities of 242.8 and 339.6 mAh g-1, respectively. The products are characterized by mass spectrometry and Raman spectroscopy. The Li/PDTeSn (n = 1-2) cells exhibit high material utilization (>85%) and unique redox mechanism. They can be cycled stably for more than 1000 cycles at an areal mass loading of 1.1 mg cm-2 and maintain capacity retentions of >72% after 100 cycles with PDTeSn loading of ∼6 mg cm-2. Moreover, the Li/PDTeS2 cell achieves a specific energy of up to 695 Wh kg-1 even when the electrolyte/PDTeS2 ratio is as low as 2.5 μL mg-1. The successful synthesis and application of PDTeSn prove that they are promising cathode materials for rechargeable lithium batteries.

Chemo-mechanical failure mechanisms of the silicon anode in solid-state batteries.

Silicon is a promising anode material due to its high theoretical specific capacity, low lithiation potential and low lithium dendrite risk. Yet, the electrochemical performance of silicon anodes in solid-state batteries is still poor (for example, low actual specific capacity and fast capacity decay), hindering practical applications. Here the chemo-mechanical failure mechanisms of composite Si/Li6PS5Cl and solid-electrolyte-free silicon anodes are revealed by combining structural and chemical characterizations with theoretical simulations. The growth of the solid electrolyte interphase at the Si|Li6PS5Cl interface causes severe resistance increase in composite anodes, explaining their fast capacity decay. Solid-electrolyte-free silicon anodes show sufficient ionic and electronic conductivities, enabling a high specific capacity. However, microscale void formation during delithiation causes larger mechanical stress at the two-dimensional interfaces of these anodes than in composite anodes. Understanding these chemo-mechanical failure mechanisms of different anode architectures and the role of interphase formation helps to provide guidelines for the design of improved electrode materials.

A Review of Degradation Mechanisms and Recent Achievements for Na‐Ion Layered Transition Metal Oxides

AbstractDue to the low price and high specific capacity, sodium ion batteries (SIBs) have become a crucial candidate for the future large‐scale energy storage power station, providing strong support for energy transition. Layered transition metal oxides (LTMOs), as one of the most promising cathode materials for SIBs, are usually accompanied by the sodiation/de‐sodiation during charging/discharging, which leads to the slippage and deformation of the layered structure, and consequently causes to the degradation of electrochemical performance. The degradation mechanisms of LTMOs attributed to the structural change are important references for improving the electrochemical performance of cathode materials. Here, this paper presents the main degradation mechanisms such as irreversible anion redox reaction, Na+/vacancy ordering transition and poor air stability as well as the corresponding modification means. It also summarizes the challenges faced by sodium‐ion LTMOs cathode materials, and gives an outlook on the key issues that need to be solved for future development.

Indolocarbazole‐Based Small Molecule Cathode‐Active Material Exhibiting Double Redox for High‐Voltage Li‐Organic Batteries

Most organic electrode materials (OEMs) for rechargeable batteries employ n‐type redox centers, whose redox potentials are intrinsically limited <3.0 V versus Li+/Li. However, p‐type materials possessing high redox potentials experience low specific capacities because they are capable of only a single redox reaction within the stable electrochemical window of typical electrolytes. Herein, we report 5,11‐diethyl‐5,11‐dihydroindolo[3,2‐b]carbazole (DEICZ) as a novel p‐type OEM, exhibiting stable plateaus at high discharge potentials of 3.44 and 4.09 V versus Li+/Li. Notably, the second redox potential of DEICZ is within the stable electrochemical window. The mechanism of the double redox reaction is investigated using both theoretical calculations and experimental measurements, including density functional theory calculations, ex situ electron spin resonance, and X‐ray photoelectron spectroscopy. Finally, hybridization with single‐walled carbon nanotubes (SWCNT) improves the cycle stability and rate performance of DEICZ owing to the π–π interactions between the SWCNT and co‐planar molecular structure of DEICZ, preventing the dissolution of active materials into the electrolyte. The DEICZ/SWCNT composite electrode maintains 70.4% of its initial specific capacity at 1‐C rate and also exhibits high‐rate capability, even performing well at 100‐C rate. Furthermore, we demonstrate its potential for flexible batteries after applying 1000 bending stresses to the composite electrode.

Application of metal-organic frameworks to the anode interface in metal batteries

Metal batteries have attracted considerable attention from researchers because of their low reduction voltage and high specific capacity. However, the reduction in the capacity and lifespan of batteries caused by the dendrite growth of metal anode limits the development of metal batteries. Metal-organic frameworks (MOFs) can be used to protect metal anodes owing to their advantages of ideal specific surface area, tunable porosity, and physiochemical stability in electrolytes. Therefore, MOFs have been extensively investigated in metal batteries. The introduction of MOFs to the metal anode interface can greatly improve the performance of batteries. In this review, the synthesis methods of typical MOFs and their derivatives, their protective mechanism on the metal anode, including Li, Na, K, Zn, and Mg, and their effects on the performance of metal batteries were elucidated. This review would help to design and apply MOFs to the anode interface in metal batteries.

Application of carbon nanotubes in lithium-ion batteries

Battery demand as a power source has skyrocketed due to the electric car market’s explosive growth. Because of its high energy density, lack of memory effect, low self-discharge rate, environmental friendliness, and extended cycle life, lithium-ion batteries, or LIBs, are widely employed in electric cars, aircraft, and other sectors. However, the use of traditional carbon materials in LIBs has led to relatively low specific capacity, limited charging and discharging rates, and low first-time charging and discharging efficiencies Carbon nanotubes (CNTs), with their high electrical conductivity, excellent mechanical properties, and thermal conductivity, can bring higher capacity, better cycling stability, excellent thermal conductivity, as well as lightweight and flexibilization to LIBs. Therefore, this paper first introduces the basic properties of CNTs and their preparation methods. Then, their roles in the positive and negative electrodes of LIBs are discussed respectively. Finally, an outlook on the future development of LIBs is made. This has a reference value for the future development of LIBs.

Efficient sulfur atom-doped three-dimensional porous MXene-assisted sodium ion batteries.

Recently, it has been reported that MXene is a promising pseudocapacitive material for energy storage, primarily due to its intercalation mechanism. However, Ti3C2Tx MXenes face challenges, such as inadequate layer spacing and low specific capacity, which greatly hinder their potential as anode materials for sodium storage. In this study, MXene was doped with sulfur to create a three-dimensional porous structure that resulted in an increased layer spacing. The sulfur-doped porous MXene (SPM) demonstrated exceptional performance as sodium ion battery anodes, with a capacity of 335.2 mA h g-1 after 490 cycles at 2 A g-1 and a long-term cycling performance of 256.1 mA h g-1 even after 2480 cycles at 5 A g-1. It is worth noting that the porous structure formed after sulfur-doping exhibits superior sodium storage performance compared to previously reported MXene-based electrodes. This highlights the feasibility of the structural construction strategy, offering an effective solution for energy storage and conversion applications.

The application of graphene material in the negative electrode of lithium battery

With the development of science and technology, the massive consumption of traditional fossil fuels not only brings serious environmental pollution but also causes an energy crisis. As an indispensable new energy in today’s world, Lithium batteries have many advantages that other types of batteries do not have, such as high energy density, long life, low self-discharge rate advantages, green and environmental protection, etc., and widely used in various fields, such as automotive, medical, aerospace and so on. However, the drawbacks such as low specific capacity and high side reaction of graphite material in traditional lithium batteries limit the application of lithium batteries. Graphene, as a two-dimensional material composed of carbon atoms in a single layer thickness, possesses the advantages of huge surface area, high strength and hardness, good electrical and thermal conductivity, flexibility, and transparency, and has great potential for application in lithium batteries. In this paper, for graphene as the anode material of lithium batteries, its effects on the performance of lithium batteries, including cycling performance, charge/discharge rate, and energy density, are discussed respectively. In addition, this paper also summarizes the latest progress on the application of graphene anode materials in lithium batteries.