Good Retention Rate Research Articles

Long-Term Storage of Ti3C2Tx Aqueous Dispersion with Stable Electrochemical Properties

MXenes possess high metallic conductivity and excellent dispersion quality and pseudocapcitance. Their good hydrophilicity makes them particularly suitable as eco-friendly inks for printing applications. However, MXenes are prone to oxidization in aqueous dispersions, and it is very important to improve their stability. Here, the long-term storage of MXene aqueous dispersions was realized by the introduction of sodium L-ascorbate (NaAsc) as the antioxidant. The preserved MXenes exhibited very stable electrochemical properties. Even after 60-day storage, the supercapacitor with preserved MXenes as the electrode still demonstrated an excellent specific capacitance of 381.1 F/g at a scan rate of 5 mV/s and a good retention rate of 92.6% after 10,000 consecutive cyclic voltammetry measurements, which was nearly the same as that of fresh MXenes. The results indicate a facile and efficient method to realize the long-term storage of MXene aqueous dispersions for mass use in future energy storage.

Improved HER/OER Performance of NiS2/MoS2 Composite Modified by CeO2 and LDH.

In recent years, there has been significant interest in transition-metal sulfides (TMSs) due to their economic affordability and excellent catalytic activity. Nevertheless, it is difficult for TMSs to achieve satisfactory performance due to problems such as low conductivity, limited catalytic activity, and inadequate stability. Therefore, a catalyst with a heterostructure constituted of a nickel-iron-layered double hydroxide, nickel sulfide, molybdenum disulfide, and cerium dioxide was designed. At the current density of 10 mA cm-2 in an alkaline solution, the catalyst exhibits a HER overpotential of 116 mV. In addition, an overpotential of 235 mV@150 mA cm-2 was displayed for OER. The catalyst showed a good retention rate (94.7% for HER, 98.6% for OER) after 160 h stability tests. The excellent electrochemical performance is attributed to the following points: 1. The self-supporting three-dimensional hierarchical structure provides abundant sites, fast ion diffusion channels, and electron transfer paths, and ensures structural stability. 2. The strong interfacial electron interaction between Ni3S2/MoS2 heterojunction and NiFe-LDH improves the OER reaction kinetics. 3. The Ce3+ and oxygen vacancies in CeO2 promote the dissociation of H2O and promote the HER reaction kinetics. This approach paves the way for developing highly efficient electrocatalysts for various electrochemical applications.

Bimolecular Salt Strategy Enhances Heteroatom Doping and Porosity Optimization of Porous Carbon for Supercapacitors.

The incompatibility between electrolyte ions and electrode pore sizes, coupled with the extensive use of activators and dopants, significantly restricts the fabrication of porous carbon materials. Consequently, developing environmentally sustainable and efficient methodologies that exploit the intrinsic properties and pretreatment of materials to facilitate self-activation and self-doping becomes crucial. In this study, potassium histidine and magnesium histidine molecular salts were synthesized as precursors, enabling specific ion activation and bimetallic template-directed tunable porosity through a one-step carbonization process. Notably, the ratio of bimolecular salts significantly influenced the porous structure of carbon, the properties of heteroatoms, and the electrochemical performance. By optimizing the ratio, the porous carbon materials exhibited high accessibility to electrolyte ions and effective ion/electron transport channels. Consequently, the optimal sample (NOSPC-2) achieved a high specific capacitance of 318 F g-1 at 0.1 A g-1 and a good capacitance retention rate of 98.8% after 50,000 cycles at 5 A g-1. In addition, NOSPC-2 also boasted high energy density and power density, reaching 22 Wh kg-1 and 25 kW kg-1, respectively. This research represents a significant stride in advancing preparation technologies for small molecule derived porous carbon materials, providing valuable insights for the rational design of carbon electrode materials for capacitive energy storage.

The impact of processing voltage of wire electric discharge machining on the performance of Mo doped V-VO0.2 based Archimedean micro-supercapacitors.

Vanadium oxide-based electrode materials have attracted increasing attention owing to their extraordinary capacitance and prolonged lifespan, excellent conductivity and outstanding electrochemical reversibility. However, the development of vanadium oxide-based integrated electrodes with outstanding capacitive performance is an enduring challenge. This research reports a facile method for structuring 3D Archimedean micro-supercapacitors (AMSCs) composed of Mo doped V-VO0.2 (Mo@V-VO0.2) based integrated electrodes with designable geometric shape, using computer-aided wire electric discharge machining (WEDM). The performance of Mo@V-VO0.2 based AMSCs manufactured by different processing voltages of 60 V, 80 V and 100 V were evaluated. It was found that 80 V is the optimal processing voltage for manufacturing Mo@V-VO0.2 based AMSCs with the best electrochemical performance. This device demonstrates superior capacitive behavior even at an ultra-high scan rate of 50, 000 mV s-1, and achieves a good capacitance retention rate of 94.4% after 2000 cycles. Additionally, the characteristics of electric field distribution were also simulated for optimizing the geometric structure of the microdevices. This WEDM fabrication technique, which is easy, secure, patternable, efficient, economical, eco-friendly, and does not require binders or conductive additives, enables the development of high-capacity 3D pseudocapacitive micro-supercapacitors and demonstrates the great potential for metal oxide synthesis and microdevice manufacturing.

N‐Doped Carbon Coated Bimetallic CoFe2O4 Nanomembranes as An Enhanced Negative Electrode for Asymmetric Supercapacitors

AbstractIn‐suit nitrogen‐doped carbon layer coated on CoFe2O4 nanomembrane (NC−CoFe2O4) directly grown on carbon cloth was successfully fabricated. The electrochemical performance was conveniently manipulated by regulating the molar ration of Co2+ : Fe3+ (molar ration=1 : 2, CoFe2O4 nanomembrane, 2.9 F cm−2). Nitrogen‐doped (N‐doped) carbon coating strategy on CoFe2O4 nanomembrane (NC−CoFe2O4) via annealing of polypyrrole (PPy) was presented and NC−CoFe2O4 nanomembranes displayed a prominent capacitance of 12.1 F cm−2 (2563.8 F g−1) at 5 mA cm−2. More important, the composite demonstrated more stable microstructure and showed long‐term cycling stability (16.0 % decrease after 7000 cycles), which was significantly better than the unmodified CoFe2O4 (55.8 % decrease after 1000 cycles). To verify the practicability of the materials, an aqueous asymmetric supercapacitor has been fabricated using NC−CoFe2O4 composite anode and MnO2/CNTs cathode, and the device has a remarkable wide operating voltage range of 1.9 V. In addition, the assembled device has an exceptional specific capacity of 1.3 F cm−2 at 10 mA cm−2, high energy density (43.3 Wh kg−1 at a power density of 642.9 W kg−1), and also with a good capacity retention rate of 84.9 % after 1000 cycles.

Polyethersulfone mixed matrix membrane with abundant sponge pores for high‐separation performance with high flux retention and cycling stability

AbstractIn recent years, a series of high‐performance ultrafiltration membranes have been developed, but maintaining high flux and high pollutant retention rate without sacrificing service life remains a long‐standing challenge. In this study, a porous polyethersulfone ultrafiltration membrane enriched with ZIF‐8 and TiO2 additives is prepared based on a non‐solvent induced phase separation method. During the phase transition process, the addition of organic nanocrystals ZIF‐8 and inorganic nanocrystals TiO2 delayed the phase transition rate, resulting in the transformation of the polyethersulfone modified membrane from a finger‐like pore structure to a sponge‐like pore structure. Compared to other structures, the sponge‐like modified membrane has a uniform and narrow pore size distribution, fewer surface defects, stable retention performance, and can simultaneously improve membrane permeability and mechanical strength. Therefore, the polyethersulfone modified membrane with a sponge‐like pore structure prepared in this research exhibits high flux for small molecules and good retention rate for large molecules. Long‐term cycling stability tests of the modified membrane shows high retention rate (over 98%), high flux, long service life, and good cycling stability for solute molecules. The study indicates that the prepared polyethersulfone modified membrane has high potential for application in relevant environmental separation processes.

Modified sodium alginate-based three-dimensional network hydrogel dust suppressant: Preparation, characterization, and performance

Chemical dust suppression is typically associated with high economic costs, unclear efficacy, and poor degradability. In this study, sodium alginate (SA) was extracted from kelp and cross-linked with polyvinyl alcohol (PVA) and polyacrylamide (PAM). Sulfonated castor oil (CAS) was subsequently added to generate a three-dimensional network hydrogel dust suppressant (PVA-SA-PAM/CAS). Using single-factor experiments, the optimal reaction temperature (60 °C) and dosages of PVA, PAM, and the cross-linking agent (2.5, 4.5, and 0.1 g, respectively) were determined. The viscosity and compressive strength of the prepared hydrogel were 86 mPa·s and 218 kPa, respectively, which meet the requirements for mine dust suppression. Various analyses revealed the hydrogel's reaction process and microstructure changes. Additionally, thermogravimetric experiments proved that the hydrogel had good thermal stability. The specific surface area and pore size of the hydrogel were 0.0278 m2/g and 11.8 nm, respectively, improving its adsorption capacity. Additionally, PVA-SA-PAM/CAS exhibited a good water retention rate. The dust suppression efficiency of PVA-SA-PAM/CAS was >98 % under strong winds (12 m/s). Moreover, the degradation rate of PVA-SA-PAM/CAS was 37 % after eight cycles (56 d) under environmental conditions. Therefore, PVA-SA-PAM/CAS exhibits good wetting, dust suppression, and degradation properties, which can effectively alleviate mine dust pollution.

Enhancing the electrochemical properties of TiNb2O7 anodes with SP-CNT binary conductive agents for both liquid and solid state lithium ion batteries.

A high performance oxide composite electrode is obtained with a two-step solid state calcined titanium niobium oxide TiNb2O7 (TNO) anode and super P-carbon nanotube (SP-CNT) binary conductive agents. The solid state synthesized TNO-0.2C (the proportion of CNTs in the binary conductive agent is 20% wt) anode exhibits a high reversible discharge capacity of 278.6 mA h g-1 at 0.5C, a competitive rate capability with reported works that employed wet chemical methods at moderate rates (178.1 mA h g-1 at 10C), and an excellent capacity retention of 92.2% after 200 cycles at 1.5C/1.5C. The enhancement in electrochemical properties of the TNO-0.2C anode is mainly attributed to the combination of the short range and long range conductive agents in the SP-CNT binary conductive system, which guarantees an efficient electronic conductive network. The Li|Li1.3Al0.3Ti1.7(PO4)3 composite polymer electrolyte (LATPCPEs)|TNO-0.2C solid state batteries are also assembled, which deliver a high initial reversible discharge capacity of 241.3 mA h g-1 at 1C and a good capacity retention rate of 93% after 50 cycles. This work provides an efficient way to improve the electrochemical properties of TNO anodes in lithium ion batteries, especially for solid state batteries.

O vacancy-rich doped WO3/GF as a novel electrode for an aqueous DHAQ/ K4Fe(CN)6 redox flow battery

In this study, a graphite felt (GF) electrode was modified with N and S heteroatoms before being loaded with Ti-doped or Nb-doped WO3 to produce Ti-WO3/GF-N-S and Nb-WO3/GF-N-S electrodes. X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy were used to analyze the crystal structure, morphology, and elemental state of the modified GF electrodes and investigate the impact of nonmetallic and metallic element doping. The influence of metal doping on the electronic distribution of the oxide was determined using first-principle calculations. The electrochemical properties of the modified GF were studied using cyclic voltammetry, electrochemical impedance spectroscopy, and single-cell tests. The results showed that Ti or Nb doping changed the energy band structure, bond length, and bond angle in the WO3 crystal and formed O vacancies. The chemical properties of Ti and Nb resulted in different numbers of O vacancies for the two doped-WO3.The doping of N and S heteroatoms on the carbon fibres altered the O vacancy concentration of WO3. The synergism between the two doping methods accelerated electron transfer in the anthraquinone redox reaction. In addition, the N-containing functional groups provide lone-pair electrons, which accelerate electron transfer and anthraquinone adsorption. Therefore, compared to the pristine GF, the discharge capacities of the Ti-WO3/GF-N-S and Nb-h-WO3/GF-N-S graphite GF electrodes increased by 58 % and 41 %, respectively, and the Nb-h-WO3/GF-N-S graphite GF electrodes exhibited a good capacity retention rate. This study broadens the practical applications of aqueous anthraquinone redox flow batteries.

Preparation and characterization of chitosan/polyvinyl alcohol antibacterial sponge materials

This study utilized the freeze-drying method to create a chitosan (CS) and polyvinyl alcohol (PVA) sponge. To enhance its antibacterial properties, curcumin and nano silver (Cur@Ag) were added for synergistic antibacterial. After adding curcumin and nano silver, the mechanical properties of the composite sponge dressing (CS-PVA-Cur@Ag) were improved. The porosity of the composite sponge dressing was closed to 80%, which was helpful for drug release, and it had good water absorption and water retention rate. The nano silver diameter was 50–80 nm, which was optimal for killing bacteria. Antibacterial tests used Escherichia coli and Staphylococcus aureus demonstrated that little nano silver was required to eliminate bacteria. Finally, in the rat full-thickness skin wound model, the composite sponge dressing can promote wound healing in a short time. In summary, CS-PVA-Cur@Ag wound dressing could protect from bacterial infection and accelerate wound healing. Thus, it had high potential application value for wound dressing.

Patients With Psoriatic Arthritis-Related Enthesitis and Persistence on Tofacitinib Under Real-World Conditions.

Information on the persistence of tofacitinib (TOF) in psoriatic arthritis (PsA) is scarce in real-world conditions. Our objective was to analyze the persistence and safety of TOF under these conditions. This was a single-center retrospective longitudinal observational study of all patients with PsA who received at least 1 dose of TOF. The main focus was on adverse events (AEs) and drug survival. Drug survival was analyzed by Kaplan-Meier curves and persistence explanatory factors by multivariate Cox regression models. The hazard ratio (HR) was used to measure association. Seventy-two patients were included, 54 women and 18 men, mean age 51.9 (SD 11.1) years, mean disease duration of 10.4 (SD 6.99) years. TOF was ≥ third line of therapy in > 70% of cases. The median survival was 13.0 (IQR 5.3-29.0) months. One-year retention rate was 52.7% (95% CI 42.4-65.6). TOF survival was not influenced by sex, disease duration, comorbidities, or line of treatment. Younger patients (HR 0.96, P = 0.01) and those with enthesitis (HR 0.37, P = 0.03) showed lower odds of drug discontinuation. The overall rate of AEs was 52.9 (95% CI 38.5-70.6)/100 person-years. Most AEs occurred during the first 6 months of exposure. In this real-world study, TOF showed a reasonably good retention rate in a PsA population that was mostly refractory to biologic and oral targeted synthetic disease-modifying antirheumatic drugs. There were no new causes for concern regarding safety. Patients with refractory PsA and enthesitis might be a specific target population for this drug.

A Lower Working Potential and Real-Time H2S Sensor Based on Nano-CuFe2O4 and Lotus Leaf Derived Carbon Material Composite

The CuFe2O4 nanoparticles and the biomass carbon material (Bcn) were respectively synthesized by solid phase reaction method and pyrolysis method. Based on the good electrocatalytic performance of the composite of CuFe2O4 and Bcn for the oxidation of H2S, a sensor for continuous determination of H2S in real-time at lower working potential was constructed. The sensor can response to H2S in the concentration range of 5.0 nM–10.0 μM with high sensitivity, and it has good retention rate to H2S in simulated wound fluid. The use of the composite materials can avoid the deposition of sulfur as a by-product on the electrode surface, as well as avoid the interference of electroactive substances in the biological environment because the working potential of −0.2 V is lower than that used in other H2S sensors.

Hierarchical CoP@NiMn-P Nanocomposites Grown on Carbon Cloth for High-Performance Supercapacitor Electrodes

Transition metal phosphides (TMPs) are potential candidates for supercapacitors. To improve their performance by adjusting their morphology and composition, hierarchical CoP@NiMn-P nanocomposites were successfully prepared by the hydrothermal method, electrodeposition, and low-temperature phosphorization. NiMn-P nanosheets were coated on CoP nanowires to form a hierarchical structure. Electrochemical analysis results indicated that the specific capacitance reached 2162.2 F g-1 at 1 A g-1 with a high capacitance retention ratio of 83.3% after 5000 cycles at a current density of 10 A g-1. This excellent electrochemical performance was attributed to the large specific surface area and enhanced conductivity. Furthermore, an asymmetric supercapacitor, CoP@NiMn-P//AC, was prepared using CoP@NiMn-P as the positive electrode and AC as the negative electrode. A large voltage window of 1.6 V and high energy density of 21.1 Wh kg-1 at 804.3 W kg-1 with a good capacity retention rate were achieved. The results confirm that CoP@NiMn-P has good potential for application in high-performance energy storage devices and provide a reference for the design of phosphide with morphology/composition optimization.

Flower-like FeCoNi ternary composite formed by interweaving nano needles for positive electrode material of supercapacitor

Ternary layered double hydroxide (LDH) are potential electrode material choices for supercapacitors (SCs) due to their various oxidation states and high theoretical specific capacitance. In this paper, FeCoNi-LDH composite with cross-braided flowers of nanoneedles has been prepared by a single-step hydrothermal method. By highlighting the structural and morphological advantages, the obtained ternary LDH shows lower resistivity in comparison with the binary LDH. As electrode material, the ternary LDH exhibits excellent electrochemical properties, such as superb specific capacitance of 2163.3 F·g−1 at 0.5 A·g−1 and good cycle retention rate of 93.8% after 5000 cycles at 20 A·g−1. Meanwhile, the assembled asymmetric flexible solid-state supercapacitor device can provide 44.8 Wh·kg−1 energy density at 807.5 W·kg−1. Moreover, two devices in series can also light up miniature light bulbs of different hues and maintain them for a long period when they are connected in series.

3D hierarchical fireproof gel polymer electrolyte towards high-performance and comprehensive safety lithium-ion batteries

Gel polymer electrolyte (GPE) stands as an extensively investigated solid-state electrolytes for next-generation lithium-ion batteries (LIBs). Nonetheless, their inherent flammability necessitates the addition of flame retardants, which adversely impact LIBs’ electrochemical performance. Herein, we propose a groundbreaking conceive of a fireproof cross-linking composite GPE that united phosphene and a P-N synergistic flame retardant (DPM), equipping a dual-enhanced conduction effect on Li+ ions and a cooperative P-N flame-retardant effect. By strategically manipulating the polymer segments hierarchy and incorporating efficient function groups from DPM, freely Li+ mobility has been propelled, thereby delivering satisfactory ionic conductivity (1.263 mS cm−1, 20 ℃), elevated oxidative stability (5.42 V vs. Li+/Li) and improved Li+ transference number (0.53). The composite GPE-based batteries (LFP||Li, NCM523||Li and LFP||Graphite) indicate acceptable specific capacities at 1 C, together with good reversible capacity retention rate and stable coulombic efficiency after 200 cycles. Noticeably, the pouch cells (LFP||Graphite) assembled with composite GPE demonstrate superior safety robustness and fire-resistance under mechanical mishandling and ignition situations. Finally, the elucidation of Li+ ions interaction mechanism with polymer matrix is unraveled through molecular orbital energy levels and density function theory (DFT) calculation. This study offers valuable insights for harnessing novel electrolyte materials in high-safety LIBs.

Dietary behaviour change intervention for managing sarcopenic obesity among community-dwelling older people: a pilot randomised controlled trial

BackgroundThe effects of dietary intervention in managing sarcopenic obesity are controversial, and behavior change techniques are lacking in previous studies which are important for the success of dietary intervention. This study aimed to evaluate the feasibility and preliminary effects of a dietary behaviour change (DBC) intervention on managing sarcopenic obesity among community-dwelling older people in the community.MethodsA two-armed, RCT was conducted. Sixty community-dwelling older adults (≥ 60 years old) with sarcopenic obesity were randomised into either the experimental group (n = 30), receiving a 15-week dietary intervention combined with behaviour change techniques guided by the Health Action Process Approach model, or the control group (n = 30), receiving regular health talks. Individual semi-structured interviews were conducted with 21 experimental group participants to determine the barriers and facilitators of dietary behaviour changes after the intervention.ResultsThe feasibility of the DBC intervention was confirmed by an acceptable recruitment rate (57.14%) and a good retention rate (83.33%). Compared with the control group, the experimental group significantly reduced their body weight (p = 0.027, d = 1.22) and improved their dietary quality (p < 0.001, d = 1.31). A positive improvement in handgrip strength (from 15.37 ± 1.08 kg to 18.21 ± 1.68 kg), waist circumference (from 99.28 ± 1.32 cm to 98.42 ± 1.39 cm), and gait speed (from 0.91 ± 0.02 m/s to 0.99 ± 0.03 m/s) was observed only in the experimental group. However, the skeletal muscle mass index in the experimental group decreased. The interview indicated that behaviour change techniques enhanced the partcipants’ compliance with their dietary regimen, while cultural contextual factors (e.g., family dining style) led to some barriers.ConclusionThe DBC intervention could reduce body weight, and has positive trends in managing handgrip strength, gait speed, and waist circumference. Interestingly, the subtle difference between the two groups in the change of muscle mass index warrants futures investigation. This study demonstrated the potential for employing dietary behaviour change interventions in community healthcare.Trial registrationRegistered retrospectively on ClinicalTrailas.gov (31/12/2020, NCT04690985).

K-doped P2-Na0.67−xKxNi0.33−yMn0.67CuyO2 cathode material with enhanced cycle performance for sodium-ion batteries

As one of the typical compositions for Ni/Mn-based layered oxides, P2-Na0.67Ni0.33Mn0.67O2 is widely studied due to its high capacity and wide voltage. However, its electrochemical performance requires further improvement for practical application as a cathode material of sodium-ion batteries. In this study, we successfully synthesized a series of K-doped P2-Na0.67−xKxNi0.33−yMn0.67CuyO2 (x = 0, 0.01, 0.06, 0.10, 0 < y < 0.16) cathode materials using a convenient sol-gel method. During the initial discharge, the NKNMC0.06 electrode delivers a high capacity of 120.3 mAh g−1 at 100 mA g−1 when charged and discharged from 1.5 to 4.2 V. And the electrode retains a specific capacity of 101.6 mAh g−1, with a good capacity retention rate of 84.5 % after 100 cycles. The enhanced cycle performance can be attributed to the appropriate amount of K+ ions occupying the Na+ sites and providing support between the transition metal layers, which stabilizes the crystal structure and improves cycle stability of the electrode. Moreover, larger-sized K+ ions expand the Na+ diffusion channel, facilitating Na+ diffusion. Furthermore, the pouch cell of NKNMC0.06 delivers a capacity of 0.28 Ah during the first discharge and maintains a capacity retention rate of 78.2 % after 100 cycles.

Baricitinib retention rate: 'real-life' data from a mono-centric cohort of patients affected by rheumatoid arthritis.

The aim of this retrospective study was to evaluate baricitinib retention rate in patients affected by rheumatoid arthritis. Secondary aims were to compare the impact on treatment persistence of monotherapy and other variables such as systemic corticosteroid use, line of treatment, disease duration, sex, biomarkers positivity, and Herpes Zoster virus infection. Patients with Rheumatoid Arthritis undergoing baricitinib were consecutively enrolled. Rheumatoid Arthritis diagnosis was performed with 2010 ACR/EULAR classification criteria. The cohort's demographic, clinical and therapeutical data were retrospectively collected. The whole follow-up duration was 104 weeks. Ninety-five patients affected by rheumatoid arthritis and treated with baricitinib were consecutively enrolled. At the end of follow-up, the overall retention rate was 69.3%. No statistically significant difference in retention rate was observed between patients treated with baricitinib in monotherapy or in combination with methotrexate (p = 0.638) while patients undergoing a steroidal treatment showed a significantly reduced treatment retention (p = 0.028). Contrarily, patients treated with baricitinib as a first-line b/tsDMARD showed higher drug retention (p = 0.002) compared to further treatment lines. Steroid employment, steroid dosage and previous treatment with bDMARDs correlated with risk of treatment discontinuation and at univariate analysis (p = 0.028, p < 0.001, and p = 0.002 respectively). Multivariate analysis confirmed significance for higher steroid dosage and previous treatment with bDMARDs (p = 0.002 and p = 0.046). No adverse events such as deep venous thrombosis, pulmonary embolism or tubercular infection/reactivation were reported during the study observation. Our data show a good baricitinib retention rate after 12 and 24 months of observation (75.1 and 69.3%, respectively). In our cohort, concomitant treatment with methotrexate did not influence treatment persistence while retention was reduced in patients undergoing a steroidal treatment and/or in multi-failure subjects.

Graphene-Wrapped Composites of Si Nanoparticles, Carbon Nanofibers, and Pyrolytic Carbon as Anode Materials for Lithium-Ion Batteries

Silicon (Si) anode materials have received much attention on account of their unparalleled theoretical specific capacity, but they suffer from huge volumetric expansion and particle pulverization, which leads to rapid capacity fading and poor electrical conductivity as well. In this work, a quaternary silicon/carbon (Si/C) composite anode material is proposed which combines the advantages of both graphene and the three-dimensional carbon framework through rational structural design and simple synthesis methods. Nanosilicon/carbon nanofibers/pyrolytic carbon (SCC) composite particles are first synthesized by spray drying and pyrolysis, which are then wrapped by graphene nanosheets through a second spray drying and pyrolysis process to obtain the final product (SGCC). In this composite, a 3D carbon skeleton composed of carbon nanofibers and pyrolytic carbon serves as an electric conductive matrix that supports and stabilizes Si nanoparticles, while graphene nanosheets wrapped on the surface further improve the conductivity and structure stability of the composite particles, and isolate the particles from direct contact with electrolytes. Meanwhile, the rich pores of the composite particles can effectively provide space for the volume expansion of Si during lithiation. As a consequence, the as-prepared SGCC composite shows a high initial Coulomb efficiency of 84.7%, a high reversible capacity of 2150.8 mA h g–1, and a good capacity retention rate of 83.75% after 100 cycles.

Co-doping: An effective strategy for developing stable and high-speed Sb2Te-based phase-change memory

Balancing operation speed and thermal stability is a big challenge in phase change memory (PCM). In this work, a carbon (C) and chromium (Cr) co-doped Sb2Te strategy has been proposed for achieving high operation speed and high stability in PCM applications. In general, doping with the appropriate Cr element is beneficial to improve thermal stability, but it will sacrifice its operation speed. C-doping can enhance thermal stability and retain its fast phase transition properties due to the carbon elements tend to form agglomerates in the host that ameliorate disorder of the amorphous phase without loss of the phase transition rate. Intriguingly, the as-prepared C1.19Cr0.23Sb2Te material exhibits good data retention (T10-year @ 155.0 °C) and low-volume change rate (1.8%), as well as fast switching speed (4 ns) and good endurance (&amp;gt;1 × 105 cycles). This research indicates that C and Cr co-doping is an effective method to achieve excellent stability of phase-change materials without sacrificing the phase-transition rate of Sb2Te materials.