Ultrahigh Rate Research Articles

Degradation analysis of lithium-ion batteries under ultrahigh-rate discharge profile

Lithium-ion batteries (LIBs) demonstrate significant potential in military applications. While, in application scenarios such as electromagnetic emission, directional energy, LIBs need to be discharged under ultrahigh rates for a long time, which can lead to accelerated performance degradation. To conduct an in-depth study on the degradation behaviour of LIBs under these conditions, this study proposes a peak decomposition method for incremental capacity analysis. This method permits a nuanced quantification of distinct degradation modes within LIBs. The effects of ultrahigh-rate constant-current discharge, ultrahigh-rate pulse discharge, and standard-rate discharge on battery degradation mode are compared. Furthermore, we delve into the fundamental processes potentially underpinning the disparities observed among these degradation modes. The results show that the degradation mode of the batteries aged under ultrahigh-rate discharge profile is dominated by the loss of active material compared with that of the batteries aged under standard-rate discharge profile. Upon reaching 80% state of health, the batteries aged under ultrahigh-rate constant-current discharge and ultrahigh-rate pulse discharge retain 87.3% and 88.51% of their initial active material content, respectively. In addition, lithium plating may have occurred in the charging process of the battery aged under ultrahigh-rate pulse discharge.

Early Inflammation and Interferon Signaling Direct Enhanced Intestinal Crypt Regeneration after Proton FLASH Radiotherapy.

Ultra-high dose rate ("FLASH") radiotherapy (>40-60 Gy/s) is a promising new radiation modality currently in human clinical trials. Previous studies showed that FLASH proton radiotherapy (FR) improves toxicity of normal tissues compared to standard proton radiotherapy (SR) without compromising anti-tumor effects. Understanding this normal tissue sparing effect may offer insight into how toxicities from cancer therapy can be improved. Here, we show that compared to SR, FR resulted in improved acute weight recovery and survival in mice after whole-abdomen irradiation. Improved morbidity and mortality after FR were associated with greater proliferation of damage-induced epithelial progenitor cells followed by improved tissue regeneration. FR led to the accelerated differentiation of revival stem cells (revSCs), a rare damage-induced stem cell required for intestinal regeneration, and to qualitative and quantitative changes in activity of signaling pathways important for revSC differentiation and epithelial regeneration. Specifically, FR resulted in greater infiltration of macrophages producing TGF-β, a cytokine important for revSC induction, that was coupled to augmented TGF-β signaling in revSCs. In pericryptal fibroblasts, FR resulted in greater type I IFN (IFN-I) signaling, which directly stimulates production of FGF growth factors supporting revSC proliferation. Accordingly, the ability of FR to improve epithelial regeneration and morbidity was dependent on IFN-I signaling. In the context of SR, however, IFN-I had a detrimental effect and promoted toxicity. Thus, a tissue-level signaling network coordinated by differences in IFN-I signaling and involving stromal cells, immune cells, and revSCs underlies the ability of FLASH to improve normal tissue toxicity without compromising anti-tumor efficacy.

Characterizing devices for validation of dose, dose rate, and LET in ultra high dose rate proton irradiations.

Ultra high dose rate (UHDR) radiotherapy using ridge filter is a new treatment modality known as conformal FLASH that, when optimized for dose, dose rate (DR), and linear energy transfer (LET), has the potential to reduce damage to healthy tissue without sacrificing tumor killing efficacy via the FLASH effect. Clinical implementation of conformal FLASH proton therapy has been limited by quality assurance (QA) challenges, which include direct measurement of UHDR and LET. Voxel DR distributions and LET spectra at planning target margins are paramount to the DR/LET-related sparing of organs at risk. We hereby present a methodology to achieve experimental validation of these parameters. Dose, DR, and LET were measured for a conformal FLASH treatment plan involving a 250-MeV proton beam and a 3D-printed ridge filter designed to uniformly irradiate a spherical target. We measured dose and DR simultaneously using a 4D multi-layer strip ionization chamber (MLSIC) under UHDR conditions. Additionally, we developed an "under-sample and recover (USRe)" technique for a high-resolution pixelated semiconductor detector, Timepix3, to avoid event pile-up and to correct measured LET at high-proton-flux locations without undesirable beam modifications. Confirmation of these measurements was done using a MatriXX PT detector and by Monte Carlo (MC) simulations. MC conformal FLASH computed doses had gamma passing rates of>95% (3mm/3% criteria) when compared to MatriXX PT and MLSIC data. At the lateral margin, DR showed average agreement values within 0.3% of simulation at 100Gy/s and fluctuations ∼10% at 15Gy/s. LET spectra in the proximal, lateral, and distal margins had Bhattacharyya distances of<1.3%. Our measurements with the MLSIC and Timepix3 detectors shown that the DR distributions for UHDR scenarios and LET spectra using USRe are in agreement with simulations. These results demonstrate that the methodology presented here can be used effectively for the experimental validation and QA of FLASH treatment plans.

Enhanced high-rate and long-cycle performance of Mg2+-Al3+ co-doped spinel LiMn2O4 cathode materials for Li-ion batteries

Spinel LiMn2O4 has the potential to be used as a cathode material in lithium-ion batteries because of its affordability, low toxicity, and excellent charge/discharge capability. However, severe capacity attenuation results from the degradation of its long-cycle and high-rate performance caused by the Jahn-Teller distortion and Mn dissolution. Herein, a simple solid-state combustion process is used to successfully prepare the Mg2+-Al3+ co-doped LiMn2O4 with truncated octahedral morphology. The Jahn-Teller distortion is inhibited by the stable Mn-O framework and the decreased lattice constant, which in turn lowers the dissolution of Mn. Moreover, Mg2+-Al3+ co-doped LiMn2O4 have lower activation energy and greater Li+ diffusion coefficient. As a result, the optimized LiMg0.03Al0.10Mn1.87O4 delivers satisfied initial capacity of 102.1 mAh‧g−1 with a capacity retention of 76.2 % after 1000 cycles at 10 C. Even at the ultra-high rate of 15 C and 20 C, Mg2+-Al3+ co-doped sample also remain desired structure stability and cycling performance, which remains 73.8 % of its original capacity after 1000 cycles at 20 C. This work provides a reference for developing high-performance and stability cathode materials for lithium-ion battery.

Regulating the anion solvation and cathode-electrolyte interphase to improve the reversibility and kinetics of high-voltage dual-ion batteries

The development of high-voltage dual-ion batteries (DIBs) is greatly hindered by the structure degradation of graphite cathodes during the (de-)intercalation of bulky anions, the electrolyte oxidative decomposition at high voltages, and inadequate cathode-electrolyte interphase (CEI) protection. Here, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) is introduced as an electrolyte additive, which preferentially enters into the first shell structure of PF6− solvation, contributing to high oxidation stability of the electrolyte and formation of an inorganic LiF-rich CEI layer. This layer stabilizes the graphite structure and enhances the anion (de-)intercalation reversibility and transport kinetics. Consequently, the Li||graphite half cell with TTE in the electrolyte exhibits an ultrahigh rate capability (95.6 % at 30 C) and a remarkable capacity retention (67.6 % after 5000 cycles). The impressive performance is further demonstrated in the graphite||graphite full cell, showcasing exceptional cycle stability (91.9 % after 1000 cycles). This study underscores the significance of anionic solvent chemistry and CEI components on cathode materials for DIBs.

Hydrogel-based 3D evaporator with cross-linked fixation by carbon dots for ultra-high and stable solar steam generation

Solar-driven water steam generation had been recognized as a promising strategy to address water scarcity in an environmentally friendly and cost-effective manner, and the development of an evaporator capable of efficient evaporation and stable long-term operation remains a huge challenge in the field. Herein, a three-dimensional (3D) hydrogel-based evaporator consisting of sodium alginate (SA), polyvinyl alcohol (PVA) and carbon dots (CDs) integrated into a melamine sponge (MS) structure was constructed, in which the CDs were firmly bonded to the SA/PVA double crosslinked network through hydrogen bonding, which improved the mechanical properties and load-bearing capacity of the evaporator. Crucially, as highly efficient light-absorbing carbon-based materials, the CDs were homogeneously dispersed in the hydrogel, significantly enhancing the photothermal conversion capability of the evaporator. The test results indicated that the evaporation rate of the 3D-CDs/SA/PVA-MS evaporator reached up to ultra-high solar steam generation rate of 4.79 kg m-2h−1 in 3.5 wt% NaCl solution at 1 sun irradiation, and exhibited the relatively excellent evaporation rate (4.13 kg m-2h−1) in high saline seawater (25 wt%). This study aimed to provide a simple and reliable modification method to enhance the evaporation performance and improve the hydrogel network of SA/PVA-based hydrogel evaporator and demonstrate their potential applications in seawater desalination and purification.

Functional carbon dots induced defect configuration entropy strengthening polyanion cathode for ultrafast-charging sodium ion batteries in a wide temperature

The development of fast-charging and wide-temperature sodium-ion batteries (SIBs) is of great significance to all-climate energy storage. However, the gigantic challenge lies in achieving super dynamic performance and stability of cathode materials. Herein, the defect configuration entropy (DCE) is conceptualized in Na3V2(PO4)3/carbon composite (NVP/C) cathode by manipulating heteroatoms and vacancies in the surface carbon layer. It is found that the bonding energy between the carbon layer and NVP interface increases with the DCE. Accompanying, the Na+ migration energy barrier is reduced and the electronic conductivity is enhanced, which are pivotal factors underpinning the low-temperature performance. Furthermore, the increase of DCE engenders the formation of a NaF-rich cathode-electrolyte interface, furnishing support for high-temperature stability. As a result, the DCE-strengthened NVP/carbon composite cathode exhibits a high capacity of ∼88 mAh g−1 at an ultrahigh rate of 200 C (13 s per charge process). Moreover, the superior electrochemical performance in the wide temperature range of −30–60 °C is achieved with 0.101 % capacity decay per cycle at −20 ℃, and 0.0047 % capacity decay per cycle at 60 ℃.

Ultrafast Conversion of Water and Oxygen Molecules With Dissociation of Hydrogen Bonding Effect to Achieve Extra-High Energy Efficiency of Secondary Metal-Air Batteries.

Metal-air secondary batteries with ultrahigh specific energies have received vast attention and are considered new promising energy storage. The slow redox reactions between oxygen-water molecules lead to low energy efficiency (55-71%) and limited applications. Herein, it is proposed that the MIL-68(In)-derived porous carbon nanotube supports the CoNiFeP heteroconjugated alloy catalyst with an overboiling point electrolyte to achieve the ultrahigh oxidation rate of water molecules. Structural characterization and density functional theorycalculations reveal that the new catalyst greatly reduces the free energy of the process, and the overboiling point further accelerates the dissociation of O─H and hydrogen bonds, and the release of O2 molecules, achieving an extra-low overpotential of 110mV@10mAcm-2 far lower than commercial Ir/C catalysts of 192mV at 125°C and state-of-the-art. Furthermore, the energy efficiency of assembled rechargeable zinc-air batteries begins to break through at 85°C, jumps at 100°C, and reaches ultrahigh energy efficiency of 88.1% at 125°C with an ultralow decay rate of 0.0068% after 150 cycles far superior to those of reported metal-air batteries. This work provides a new catalyst and electrolyte joint-design strategy and reexamines the battery operating temperature to construct higher energy efficiency for secondary fuel cells.

Salt-Assisted Recovery of Sodium Metal Anodes for High-Rate Capability Sodium Batteries.

Rechargeable sodium metal batteries are considered to be one of the most promising high energy density and cost-effective electrochemical energy storage systems. However, their practicality is constrained by the high reactivity of sodium metal anodes that readily brings about excessive accumulation of inactive Na species on the surface, either by chemical reactions with oxygen and moisture during electrode handling or through electrochemical processes with electrolytes during battery operation. Herein, this paper reports on an alkali, salt-assisted, assembly-polymerization strategy to recover Na activity and to reinforce the solid-electrolyte interphase (SEI) of sodium metal anodes. To achieve this, an alkali-reactive coupling agent 3-glycidoxypropyltrimethoxysilane (GPTMS) is applied to convert inactive Na species into Si-O-Na coordination with a self-assembly GPTMS layer that consists of inner O-Si-O networks and outer hydrophobic epoxides. As a result, the electrochemical activity of Na metal anodes can be fully recovered and the robust GPTMS-derived SEI layer ensures high capacity and long-term cycling under an ultrahigh rate of 30 C (93.1 mAh g-1, 94.8% after 3000 cycles). This novel process provides surface engineering clues on designing high power density and cost-effective alkaline metal batteries.

Bifunctional Oxygen-Defect Bismuth Catalyst toward Concerted Production of H2O2 with over 150% Cell Faradaic Efficiency in Continuously Flowing Paired-Electrosynthesis System.

The electrosynthesis of hydrogen peroxide (H2O2) from O2 or H2O via the two-electron (2e-) oxygen reduction (2e- ORR) or water oxidation (2e- WOR) reaction provides a green and sustainable alternative to the traditional anthraquinone process. Herein, a paired-electrosynthesis tactic is reported for concerted H2O2 production at a high rate by coupling the 2e- ORR and 2e- WOR, in which the bifunctional oxygen-vacancy-enriched Bi2O3 nanorods (Ov-Bi2O3-EO), obtained through electrochemically oxidative reconstruction of Bi-based metal-organic framework (Bi-MOF) nanorod precursor, are used as both efficient anodic and cathodic electrocatalysts, achieving concurrent H2O2 production at both electrodes with high Faradaic efficiencies. Specifically, the coupled 2e- ORR//2e- WOR electrolysis system based on such distinctive oxygen-defect Bi catalyst displays excellent performance for the paired-electrosynthesis of H2O2, delivering a remarkable cell Faradaic efficiency of 154.8% and an ultrahigh H2O2 production rate of 4.3 mmol h-1 cm-2. Experiments combined with theoretical analysis reveal the crucial role of oxygen vacancies in optimizing the adsorption of intermediates associated with the selective two-electron reaction pathways, thereby improving the activity and selectivity of the 2e- reaction processes at both electrodes. This work establishes a new paradigm for developing advanced electrocatalysts and designing novel paired-electrolysis systems for scalable and sustainable H2O2 electrosynthesis.

Revealing the effect of annealing at Tg on the crystal growth in Au49Ag5.5Pd2.3Cu26.9Si16.3 metallic glass via nanocalorimetry

In this study, Au49Ag5.5Pd2.3Cu26.9Si16.3 metallic glass is annealed at Tg and its impact on crystal growth is demonstrated with nanocalorimetry. With annealing following the rapid quenching, an amorphous phase free of nuclei, a relaxed amorphous phase, an amorphous phase with nuclei, and an amorphous phase with crystals are sequentially produced. With the reheating at rates ranging from 100 to 50,000 K/s, these four stages are quantitatively distinguished. Additionally, crystal growth behaviors of these four stages are demonstrated by the Kissinger and Mauro-Yue-Ellison-Gupta-Allan model. For the quenched and relaxed amorphous phases, the apparent crystallization activation energy (Ea) decreases with increasing heating rate, with a noticeable upward deviation at ultrahigh heating rates. When nuclei and crystals form in the amorphous phase, Ea keeps decreasing with the heating rate. As the annealing time increases, the maximum growth rate (umax) exhibits a monotonic increase while the temperature corresponding to umax displays a maximum.

Modulation of Interlayer Nanochannels via the Moderate Heat Treatment of Graphene Oxide Membranes.

In response to the phenomenon of interlayer transport channel swelling caused by the hydration of oxygen-containing functional groups on the GO membrane surface, a moderate heat treatment method was employed to controllably reduce the graphene oxide (GO) membrane and prepare a reduced GO composite nanofiltration membrane (mixed cellulose membrane (MCE)/ethylenediamine (EDA)/reduced GO-X (RGO-X)). The associations of different heat treatment temperatures with the hydrophilicity, interlayer structure, permeability and dye/salt rejection properties of GO membranes were systematically explored. The results indicated that the oxygen-containing groups of the GO membrane were partially eliminated after heat treatment, and the hydrophilicity was weakened. This effectively weakened the hydration between the GO membrane and the water molecules and inhibited the swelling of the oxidized graphene membrane. In the dye desalination test, the MCE/EDA/RGO membrane exhibited an ultra-high rejection rate of over 97% for methylene blue (MB) dye molecules. In addition, heat treatment increased the structural defects of the GO membrane and promoted the fast passage of water molecules via the membrane. In pure water flux testing, the water flux of the membrane remained above 46.58 Lm-2h-1bar-1, while the salt rejection rate was relatively low.

Carbon coated Li3V2(PO4)3 derived from phytic acid with ultra-high rate performance for rechargeable Li ion batteries

The carbon coating strategy has great potential in improving the conductivity of Li3V2(PO4)3 (LVP). However, the preparation of carbon-coated LVP requires an additional carbon source and a complex synthesis process, such as the prereduction of V5+, which poses obstacles to large-scale production. In this article, the phytic acid, a kind of natural biological material with environmental benign and natural abundance, is directly chelated with V3+ and employed as both the phosphorus source and carbon source in the manufacturing procedure of LVP/C material for electrodes. The physical and electrochemical properties of LVP/C material may be tailored by carefully controlling the heat treatment temperature. This process leads to a remarkable boost in key performance metrics, including initial discharge capacity at 1 C (128.35 mAh·g-1), long cycle life at 10 C (115.75 mAh·g-1 after 1000 cycles), and rate capability at 50 C (101.83 mAh·g-1), all attributed to improved electronic conductivity and enhanced ion diffusion kinetics. The simple, novel, and energy-saving method demonstrates great potential for large-scale preparation for the high-performance cathode materials.

Engineering d-p Orbital Hybridization with P, S Co-Coordination Asymmetric Configuration of Single Atoms Toward High-Rate and Long-Cycling Lithium-Sulfur Battery.

Single-atom catalysts (SACs) have been increasingly explored in lithium-sulfur (Li-S) batteries to address the issues of severe polysulfide shuttle effects and sluggish redox kinetics. However, the structure-activity relationship between single-atom coordination structures and the performance of Li-Sbatteries remain unclear. In this study, a P, S co-coordination asymmetric configuration of single atoms is designed to enhance the catalytic activity of Co central atoms and promote d-p orbital hybridization between Co and S atoms, thereby limiting polysulfides and accelerating the bidirectional redox process of sulfur. The well-designed SACs enable Li-S batteries to demonstrate an ultralow capacity fading rate of 0.027% per cycle after 2000 cycles at a high rate of 5 C. Furthermore, they display excellent rate performance with a capacity of 619 mAh g-1 at an ultrahigh rate of 10 C due to the efficient catalysis of CoSA-N3PS. Importantly, the assembled pouch cell still retains a high discharge capacity of 660 mAh g-1 after 100 cycles at 0.2 C and provides a high areal capacity of 4.4 mAh cm-2 even with a high sulfur loading of 6mg cm-2. This work demonstrates that regulating the coordination environment of SACs is of great significance for achieving state-of-the-art Li-S batteries.

Toward real-time, volumetric dosimetry for FLASH-capable clinical synchrocyclotrons using protoacoustic imaging.

Fast low angle shot hyperfractionation (FLASH) radiotherapy (RT) holds promise for improving treatment outcomes and reducing side effects but poses challenges in radiation delivery accuracy due to its ultra-high dose rates. This necessitates the development of novel imaging and verification technologies tailored to these conditions. Our study explores the effectiveness of proton-induced acoustic imaging (PAI) in tracking the Bragg peak in three dimensions and in real time during FLASH proton irradiations, offering a method for volumetric beam imaging at both conventional and FLASH dose rates. We developed a three-dimensional (3D) PAI technique using a 256-element ultrasound detector array for FLASH dose rate proton beams. In the study, we tested protoacoustic signal with a beamline of a FLASH-capable synchrocyclotron, setting the distal 90% of the Bragg peak around 35mm away from the ultrasound array. This configuration allowed us to assess various total proton radiation doses, maintaining a consistent beam output of 21 pC/pulse. We also explored a spectrum of dose rates, from 15 Gy/s up to a FLASH rate of 48 Gy/s, by administering a set number of pulses. Furthermore, we implemented a three-dot scanning beam approach to observe the distinct movements of individual Bragg peaks using PAI. All these procedures utilized a proton beam energy of 180 MeV to achieve the maximum possible dose rate. Our findings indicate a strong linear relationship between protoacoustic signal amplitudes and delivered doses (R2=0.9997), with a consistent fit across different dose rates. The technique successfully provided 3D renderings of Bragg peaks at FLASH rates, validated through absolute Gamma index values. The protoacoustic system demonstrates effectiveness in 3D visualization and tracking of the Bragg peak during FLASH proton therapy, representing a notable advancement in proton therapy quality assurance. This method promises enhancements in protoacoustic image guidance and real-time dosimetry, paving the way for more accurate and effective treatments in ultra-high dose rate therapy environments.

Ultra-high solar steam generation based on regulated water management strategy in 3D biomass hydrogels inspired by the “binding effect” of cell walls

Facing the global challenge of water scarcity, solar-driven seawater desalination has been emerged as a green, non-polluting and sustainable technology, but the practical application of existing solar evaporators was hindered by their low evaporation efficiency and poor mechanical property. Inspired by the binding effect of cell walls, a novel and high-efficiency three-dimensional (3D) evaporator (CDs/CF/CS-LF) was constructed, in which loofah (LF) served as a natural 3D skeleton to support the hydrogel evaporator, resisted deformation, and created an efficient dual water supply mode with the chitosan (CS) hydrogel ensuring that the evaporator maintains high evaporation rate even under high salt environment. Additionally, the cellulose nanofibers (CF) filler enhanced the mechanical property of the hydrogel, ensuring shape stability under pressure impact, and carbon dots (CDs) facilitated the aggregation and cross-linking of chitosan chains through hydrogen bonds, further improving the mechanical property of the evaporator, while also enhancing the photothermal conversion capability of the 3D-CDs/CF/CS-LF evaporator as a photothermal material. The experimental results indicated that the 3D-CDs/CF/CS-LF evaporator could achieve an ultra-high solar vapor production rate of 8.08 kg m−2 h−1 under 1 sunlight intensity in 3.5 wt% NaCl solution. Outdoor seawater desalination experiments demonstrated the utility of 3D-CDs/CF/CS-LF evaporator for practical applications. This work provided a new approach for the improvement of CS-based evaporators and demonstrated their potential application in seawater desalination and purification.

Tailoring d–p Orbital Hybridization to Decipher the Essential Effects of Heteroatom Substitution on Redox Kinetics

AbstractThe heteroatom substitution is considered as a promising strategy for boosting the redox kinetics of transition metal compounds in hybrid supercapacitors (HSCs) although the dissimilar metal identification and essential mechanism that dominate the kinetics remain unclear. It is presented that d‐p orbital hybridization between the metal and electrolyte ions can be utilized as a descriptor for understanding the redox kinetics. Herein, a series of Co, Fe and Cu heteroatoms are respectively introduced into Ni3Se4 cathodes, among them, only the moderate Co‐substituted Ni3Se4 can hold the optimal d‐p orbital hybridization resulted from the formed more unoccupied antibonding states π*. It inevitably enhances the interfacial charge transfer and ensures the balanced OH− adsorption‐desorption to accelerate the redox kinetics validated by the lowest reaction barrier (0.59 eV, matching well with the theoretical calculations). Coupling with the lower OH− diffusion energy barrier, the prepared cathode delivers ultrahigh rate capability (~68.7 % capacity retention even the current density increases by 200 times), and an assembled HSC also presents high energy/power density. This work establishes the principles for determining heteroatoms and deciphers the underlying effects of the heteroatom substitution on improving redox kinetics and the rate performance of battery‐type electrodes from a novel perspective of orbital‐scale manipulation.

Tailoring d-p Orbital Hybridization to Decipher the Essential Effects of Heteroatom Substitution on Redox Kinetics.

The heteroatom substitution is considered as a promising strategy for boosting the redox kinetics of transition metal compounds in hybrid supercapacitors (HSCs) although the dissimilar metal identification and essential mechanism that dominate the kinetics remain unclear. It is presented that d-p orbital hybridization between the metal and electrolyte ions can be utilized as a descriptor for understanding the redox kinetics. Herein, a series of Co, Fe and Cu heteroatoms are respectively introduced into Ni3Se4 cathodes, among them, only the moderate Co-substituted Ni3Se4 can hold the optimal d-p orbital hybridization resulted from the formed more unoccupied antibonding states π*. It inevitably enhances the interfacial charge transfer and ensures the balanced OH- adsorption-desorption to accelerate the redox kinetics validated by the lowest reaction barrier (0.59 eV, matching well with the theoretical calculations). Coupling with the lower OH- diffusion energy barrier, the prepared cathode delivers ultrahigh rate capability (~68.7 % capacity retention even the current density increases by 200 times), and an assembled HSC also presents high energy/power density. This work establishes the principles for determining heteroatoms and deciphers the underlying effects of the heteroatom substitution on improving redox kinetics and the rate performance of battery-type electrodes from a novel perspective of orbital-scale manipulation.

Priority-based subcarrier allocation algorithm for maximal network connectivity in 5G networks

With the widespread adoption of wireless technology, there has been a significant surge in the number of devices seeking wireless connectivity over the past decade. To meet the extensive demand for high-data-rate wireless connectivity, the fifth-generation (5G) cellular network plays a pivotal role. 5G cellular network aims to support a large number of applications with ultra-high data rates by maximizing device connectivity while satisfying quality of service (QoS) requirements. In this paper, we present an innovative priority-based subcarrier allocation (PSA) algorithm to address the challenge of maximizing connectivity in 5G new radio (5G NR) networks. Initially, we formulate the connectivity maximization problem as a subcarrier allocation problem by considering three key parameters: bandwidth requirement, waiting time, and energy level of user devices. The objective of the formulated problem is to optimally allocate subcarriers to multiple users in order to maximize connectivity while maintaining QoS requirements. To address the problem, we propose the PSA algorithm that prioritizes bandwidth, waiting time, and energy parameters using the R-method. To accommodate the network scenarios, we develop three variants of the PSA algorithm—PSA-1, PSA-2, and PSA-3. These variants allocate subcarriers based on the priority-based score of user. We carried out a simulation-based study to illustrate the effectiveness of our proposed algorithm in comparison to traditional methods. The simulation results reveal that our proposed algorithms outperform first come first serve (FCFS) and longest remaining time first (LRTF), and achieves comparable or superior results compared to priority and fairness-based resource allocation with 5G new radio numerology (PFRA-0N) in terms of the number of user allocations, average user allocation ratio, user drop ratios and average connectivity rate. Compared to the shortest job first (SJF) technique, our proposed PSA algorithm performance is slightly inferior in terms of the number of user allocations, average allocation ratio and average connectivity rate; however, it shows superior performance in drop ratios. Further, the proposed algorithms show significant improvements in execution time compared to the optimal exhaustive search solution.

Ultrahigh rate and cycling properties of Li2CuTi3O8 anode derived from HKUST-1 copper source for high-performance lithium-ion batteries

Rational design and preparation of titanium-based anode materials with superior fast charge and discharge are a key focuses of the lithium-ion batteries research. Herein, a novel and facile synthesis of uniformly carbon-coated Li2CuTi3O8 (LCuTO) nanoparticles with excellent high-rate lithium storage properties is presented using HKUST-1 with pore structure and active metal sites as a copper source. The well-designed LCuTO@HKUST with carbon bridges between the particles and the carbon layer on the outer surface offers high electronic conductivity for fast charge and discharge. The LCuTO@HKUST exhibits extraordinary lithium storage performance: high capacity (251.8 mAh/g after 1000 cycles at a current density of 1.0 A/g), a superior high-rate capability (160.3 mAh/g after 500 cycles at 3.0 A/g and 138.1 mAh/g after 500 cycles at 5.0 A/g), and excellent cycle reversibility and cycle stability under various current densities. In addition, the lower Li+ migration barrier in LCuTO@HKUST demonstrated by density functional theory (DFT) calculations is beneficial to the long-cycle stability and high-rate performance. The proposed preparation method and the strategy of using the MOF as a metal source for lithium-ion battery anode materials provide a new approach for advanced fast charge–discharge energy storage applications.