Structural dynamics of receptor recognition and pH-induced dissociation of full-length Clostridioides difficile Toxin B.

Clostridioides difficile secretes Toxin B (TcdB) as one of its major virulence factors, which binds to intestinal epithelial and subepithelial receptors, including frizzled proteins and chondroitin sulfate proteoglycan 4 (CSPG4). Here, we present cryo-EM structures of full-length TcdB in complex with the CSPG4 domain 1 fragment (D1401-560) at cytosolic pH and the cysteine-rich domain of frizzled-2 (CRD2) at both cytosolic and acidic pHs. CSPG4 specifically binds to the autoprocessing and delivery domains of TcdB via networks of salt bridges, hydrophobic and aromatic/proline interactions, which are disrupted upon acidification eventually leading to CSPG4 drastically dissociating from TcdB. In contrast, FZD2 moderately dissociates from TcdB under acidic pH, most likely due to its partial unfolding. These results reveal structural dynamics of TcdB during its preentry step upon endosomal acidification, which provide a basis for developing therapeutics against C. difficile infections.

Interplay between lncRNA RP11-367G18.1 variant 2 and YY1 plays a vital role in hypoxia-mediated gene expression and tumorigenesis.

BACKGROUND: The hypoxia-responsive long non-coding RNA, RP11-367G18.1, has recently been reported to induce histone 4 lysine 16 acetylation (H4K16Ac) through its variant 2; however, the underlying molecular mechanism remains poorly understood. METHODS: RNA pull-down assay and liquid chromatography-tandem mass spectrometry were performed to identify RP11-367G18.1 variant 2-binding partner. The molecular events were examined utilizing western blot analysis, real-time PCR, luciferase reporter assay, chromatin immunoprecipitation, and chromatin isolation by RNA purification assays. The migration, invasion, soft agar colony formation, and in vivo xenograft experiments were conducted to evaluate the impact of RP11-367G18.1 variant 2-YY1 complex on tumor progression. RESULTS: In this study, RNA sequencing data revealed that hypoxia and RP11-367G18.1 variant 2 co-regulated genes were enriched in tumor-related pathways. YY1 was identified as an RP11-367G18.1 variant 2-binding partner that activates the H4K16Ac mark. YY1 was upregulated under hypoxic conditions and served as a target gene for hypoxia-inducible factor-1α. RP11-367G18.1 variant 2 colocalized with YY1 and H4K16Ac in the nucleus under hypoxic conditions. Head and neck cancer tissues had higher levels of RP11-367G18.1 and YY1 which were associated with poor patient outcomes. RP11-367G18.1 variant 2-YY1 complex contributes to hypoxia-induced epithelial-mesenchymal transition, cell migration, invasion, and tumorigenicity. YY1 regulated hypoxia-induced genes dependent on RP11-367G18.1 variant 2. CONCLUSIONS: RP11-367G18.1 variant 2-YY1 complex mediates the tumor-promoting effects of hypoxia, suggesting that this complex can be targeted as a novel therapeutic strategy for cancer treatment.

Recent Configurational Advances for Solid-State Lithium Batteries Featuring Conversion-Type Cathodes.

Solid-state lithium metal batteries offer superior energy density, longer lifespan, and enhanced safety compared to traditional liquid-electrolyte batteries. Their development has the potential to revolutionize battery technology, including the creation of electric vehicles with extended ranges and smaller more efficient portable devices. The employment of metallic lithium as the negative electrode allows the use of Li-free positive electrode materials, expanding the range of cathode choices and increasing the diversity of solid-state battery design options. In this review, we present recent developments in the configuration of solid-state lithium batteries with conversion-type cathodes, which cannot be paired with conventional graphite or advanced silicon anodes due to the lack of active lithium. Recent advancements in electrode and cell configuration have resulted in significant improvements in solid-state batteries with chalcogen, chalcogenide, and halide cathodes, including improved energy density, better rate capability, longer cycle life, and other notable benefits. To fully leverage the benefits of lithium metal anodes in solid-state batteries, high-capacity conversion-type cathodes are necessary. While challenges remain in optimizing the interface between solid-state electrolytes and conversion-type cathodes, this area of research presents significant opportunities for the development of improved battery systems and will require continued efforts to overcome these challenges.

A Single Center Observational Study of Spirometry Assessments in Children with Congenital Heart Disease after Surgery.

Background: Children with congenital heart disease (CHD) have impaired pulmonary function both before and after surgery; therefore, pulmonary function assessments are important and should be performed both before and after open-heart surgery. This study aimed to compare pulmonary function between variant pediatric CHD types after open-heart surgery via spirometry. Methods: In this retrospective study, the data for forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and the ratio between FEV1 and FVC (FEV1/FVC) were collected from patients with CHD who underwent conventional spirometry between 2015 and 2017. Results: A total of 86 patients (55 males and 31 females, with a mean age of 13.24 ± 3.32 years) were enrolled in our study. The diagnosis of CHD included 27.9% with atrial septal defects, 19.8% with ventricular septal defects, 26.7% with tetralogy of Fallot, 7.0% with transposition of the great arteries, and 46.5% with other diagnoses. Abnormal lung function was identified by spirometry assessments after surgery. Spirometry was abnormal in 54.70% of patients: obstructive type in 29.06% of patients, restrictive type in 19.76% of patients, and mixed type in 5.81% of patients. More abnormal findings were found in patients who received the Fontan procedure (80.00% vs. 35.80%, p = 0.048). Conclusions: Developing novel therapies to optimize pulmonary function will be critical for improving clinical outcomes.

Hierarchical natural move Monte Carlo refines flexible RNA structures into cryo-EM densities.

Ribonucleic acids (RNAs) play essential roles in living cells. Many of them fold into defined three-dimensional (3D) structures to perform functions. Recent advances in single-particle cryo-electron microscopy (cryo-EM) have enabled structure determinations of RNA to atomic resolutions. However, most RNA molecules are structurally flexible, limiting the resolution of their structures solved by cryo-EM. In modeling these molecules, several computational methods are limited by the requirement of massive computational resources and/or the low efficiency in exploring large-scale structural variations. Here we use hierarchical natural move Monte Carlo (HNMMC), which takes advantage of collective motions for groups of nucleic acid residues, to refine RNA structures into their cryo-EM maps, preserving atomic details in the models. After validating the method on a simulated density map of tRNA, we applied it to objectively obtain the model of the folding intermediate for the specificity domain of ribonuclease P from Bacillus subtilis and refine a flexible ribosomal RNA (rRNA) expansion segment from the Mycobacterium tuberculosis (Mtb) ribosome in different conformational states. Finally, we used HNMMC to model atomic details and flexibility for two distinct conformations of the complete genomic RNA (gRNA) inside MS2, a single-stranded RNA virus, revealing multiple pathways for its capsid assembly.

Immunoglobulin profiling identifies unique signatures in patients with Kawasaki disease during intravenous immunoglobulin treatment.

Identifying the causes of high fever syndromes such as Kawasaki disease (KD) remains challenging. To investigate pathogen exposure signatures in suspected pathogen-mediated diseases such as KD, we performed immunoglobulin (Ig) profiling using a next-generation sequencing method. After intravenous Ig (IVIG) treatment, we observed disappearance of clonally expanded IgM clonotypes, which were dominantly observed in acute-phase patients. The complementary-determining region 3 (CDR3) sequences of dominant IgM clonotypes in acute-phase patients were commonly observed in other Ig isotypes. In acute-phase KD patients, we identified 32 unique IgM CDR3 clonotypes shared in three or more cases. Furthermore, before the IVIG treatment, the sums of dominant IgM clonotypes in IVIG-resistant KD patients were significantly higher than those of IVIG-sensitive KD patients. Collectively, we demonstrate a novel approach for identifying certain Ig clonotypes for potentially interacting with pathogens involved in KD; this approach could be applied for a wide variety of fever-causing diseases of unknown origin.

Structures of Qß virions, virus-like particles, and the Qß-MurA complex reveal internal coat proteins and the mechanism of host lysis.

In single-stranded RNA bacteriophages (ssRNA phages) a single copy of the maturation protein binds the genomic RNA (gRNA) and is required for attachment of the phage to the host pilus. For the canonical Allolevivirus Qß the maturation protein, A2, has an additional role as the lysis protein, by its ability to bind and inhibit MurA, which is involved in peptidoglycan biosynthesis. Here, we determined structures of Qß virions, virus-like particles, and the Qß-MurA complex using single-particle cryoelectron microscopy, at 4.7-Å, 3.3-Å, and 6.1-Å resolutions, respectively. We identified the outer surface of the ß-region in A2 as the MurA-binding interface. Moreover, the pattern of MurA mutations that block Qß lysis and the conformational changes of MurA that facilitate A2 binding were found to be due to the intimate fit between A2 and the region encompassing the closed catalytic cleft of substrate-liganded MurA. Additionally, by comparing the Qß virion with Qß virus-like particles that lack a maturation protein, we observed a structural rearrangement in the capsid coat proteins that is required to package the viral gRNA in its dominant conformation. Unexpectedly, we found a coat protein dimer sequestered in the interior of the virion. This coat protein dimer binds to the gRNA and interacts with the buried α-region of A2, suggesting that it is sequestered during the early stage of capsid formation to promote the gRNA condensation required for genome packaging. These internalized coat proteins are the most asymmetrically arranged major capsid proteins yet observed in virus structures.

Structural insights into species-specific features of the ribosome from the human pathogen Mycobacterium tuberculosis.

Ribosomes from Mycobacterium tuberculosis (Mtb) possess species-specific ribosomal RNA (rRNA) expansion segments and ribosomal proteins (rProtein). Here, we present the near-atomic structures of the Mtb 50S ribosomal subunit and the complete Mtb 70S ribosome, solved by cryo-electron microscopy. Upon joining of the large and small ribosomal subunits, a 100-nt long expansion segment of the Mtb 23S rRNA, named H54a or the 'handle', switches interactions from with rRNA helix H68 and rProtein uL2 to with rProtein bS6, forming a new intersubunit bridge 'B9'. In Mtb 70S, bridge B9 is mostly maintained, leading to correlated motions among the handle, the L1 stalk and the small subunit in the rotated and non-rotated states. Two new protein densities were discovered near the decoding center and the peptidyl transferase center, respectively. These results provide a structural basis for studying translation in Mtb as well as developing new tuberculosis drugs.

Evaluation of the Relationship Between the 18S rRNA/rDNA Ratio and Population Growth in the Marine Diatom Skeletonema tropicum via the Application of an Exogenous Nucleic Acid Standard.

Ribosomal RNA (rRNA) has been regarded as a proxy for metabolic activity and population growth in microbes, but the limitations and assumptions of this approach should be better defined, particularly in eukaryotic microalgae. In this study, the 18S rRNA/rDNA ratio of a marine diatom, Skeletonema tropicum, was examined in batch and semi-continuous cultures subjected to low nitrogen and phosphorus treatments at a temperature of 20 °C. In the semi-continuous cultures, the measured 18S rRNA/rDNA ratio ranged from 4.0 × 102 to 5.0 × 103 , and the logarithmic form of this ratio increased linearly with the population growth rate under both low nitrogen and low phosphorus conditions. In batch cultures grown under low nitrogen or low phosphorus conditions, log (rRNA/rDNA) also increased linearly with growth rate when the latter ranged between -0.4 and 1.5 day-1 . The 18S rRNA/rDNA ratios of Skeletonema sampled from in the southern East China Sea were substantially lower than measured from laboratory cultures. Among the field samples, ratios obtained at a coastal station were higher than those obtained farther offshore. These results imply higher growth rate at the coastal station, but the influences of other factors, such as cell size and temperature, cannot be ruled out.

CXCL10/IP-10 is a biomarker and mediator for Kawasaki disease.

RATIONALE: Kawasaki disease (KD), an acute febrile vasculitis, is the most common cause of acquired heart disease in childhood; however, diagnosing KD can be difficult. OBJECTIVE: To identify unique proteomic biomarkers that can be used to facilitate earlier diagnosis of KD. METHODS AND RESULTS: We enrolled 214 children with fever and clinical features suggestive of KD. Of those, only 100 were diagnosed with KD. Their plasma samples were globally analyzed for cytokines, chemokines, and cell adhesion molecules using an unbiased, large-scale, quantitative protein array. This study was conducted in 3 stages: discovery, replication, and blinded validation. During the discovery phase (n [KD]=37; n [control]=20), the expression of interleukin-17F, sCD40L, E-selectin, CCL23 (myeloid progenitor inhibitory factor 1), and CXCL10 (IFN-γ-inducible protein 10 [IP-10]) were upregulated during the acute phase in patients with KD when compared with that in the controls. A notable increase was observed in the IP-10 levels (KD, 3037 ± 226.7 pg/mL; control, 672 ± 130.4 pg/mL; P=4.1 × 10(-11)). Receiver-operating characteristic analysis of the combined discovery and replication data (n [KD]=77; n [control]=77) showed that the IP-10 level had high area under the curve values (0.94 [95% confidence interval, 0.9055-0.9778]; sensitivity, 100%; and specificity, 77%). With 1318 pg/mL as the optimal cutoff, the blinded validation study confirmed that the IP-10 levels were a good predictor of KD. With intravenous immunoglobulin treatment, the IP-10 levels returned to normal. The downstream receptor of IP-10, CXCR3, was activated in the T cells of patients with acute KD. CONCLUSIONS: IP-10 may be used as a biomarker to facilitate KD diagnosis, and it may provide clues about the pathogenesis of KD.

Controlled multimodal hierarchically porous electrode self-assembly of electrochemically exfoliated graphene for fully solid-state flexible supercapacitor.

Supercapacitors constructed from three-dimensional (3D) graphene electrodes with high ion-accessible surface area and durable mechanical flexibility have great potential for wearable devices. For the development of a highly efficient graphene electrode for electrical double layer capacitors (EDLCs), proper control over not only the specific surface area but also the type of pore (macro-, meso- and micro-porous networks) adapted for an appropriate type of electrolyte is crucial to ensure an ideal performance in terms of both energy density and power delivery rate. However, there is still a lack of technology to create graphene structures that combine macro-, meso- and micro-pores by a one-step and facile method. In addition, the ion/electron transport of a solid state electrolyte among such multimodal pore structures is not fully investigated. Here, we report a novel cost-effective technique of concentration dependent self-assembly of electrochemically exfoliated graphene (EC-graphene) to obtain a 3D architecture with controllable macropores (0.39-4.99 µm) and multimodal hierarchical meso- and micro-pores. The better performance of the 3D architecture is obtained due to its optimum micron-sized macropore diameter (∼5 µm) that serves as an ion buffering reservoir, followed by facile ion diffusion kinetics through the well-modulated combination of macro-, meso- and micro-pores. The binder and conductive carbon additive free supercapacitor constructed from the 3D graphene electrode exhibited a specific capacitance of 45.40 F g-1 (6 M KOH) and 23.89 F g-1 (1 M H2SO4 gel electrolyte). A capacitance retention of above 90% (up to 180° folding angle) after 50 bending-relaxing cycles is obtained, implying the superior durability of the device and the worthiness of the synthesis procedure. The method reported here may pave the way for the development of an environment friendly, large scale producible and controlled porous graphene-based architecture for the high performance next generation flexible, all-solid-state and binder-free energy storage devices.

Regression of Neonatal Cardiac Rhabdomyoma in Two Months Through Low-Dose Everolimus Therapy: A Report of Three Cases.

Cardiac rhabdomyoma (CR) is the most common cardiac tumor in newborns. Approximately 75% of cases are associated with tuberous sclerosis complex. Although these tumors usually spontaneously regress after 2 years of age, they can be life-threatening when they obstruct major cardiac inflow or outflow pathways. Everolimus is an inhibitor of the mammalian target of rapamycin, reducing its production of the proteins harmartin and tuberin. Everolimus has demonstrated a remarkable suppression effect in children with tuberous sclerosis complex at doses of 4.7-5.6 mg/M2/day and serum trough levels of 5-15 ng/mL. Since 2012, five case reports of neonates with CR have also reported the tumor-regressing effect of everolimus. However, the optimal dosage for neonates is still unknown. Over the past 2 years, we have deliberately used a low dose everolimus regimen (0.3-0.67 mg/M2/day) in three neonates with large CRs, in an effort to maintain serum trough levels at 3-7 ng/mL. In all three cases, the tumors regressed smoothly within 2 months. Regarding the drug's side effect of predisposing patients to infection, we observed that adenovirus pneumonia occurred in one case at 3 months of age, and chicken pox occurred in another case at 9 months of age; both recovered smoothly. Our three cases of neonatal CR demonstrate that a low-dose everolimus regimen is an effective treatment for tumor regression.

The expression of nitrate transporter genes reveals different nitrogen statuses of dominant diatom groups in the southern East China Sea.

In this study, the mRNA levels of the Nrt2 nitrate transporter gene were used as a molecular indicator of nitrogen status in two dominant diatom groups, Skeletonema and Chaetoceros, which inhabit the southern East China Sea (ECS). To accurately interpret the abundance of Nrt2 transcripts in situ, maximum and minimum expression levels were determined under conditions of nitrogen deprivation and ammonium addition, respectively. In August 2010, Nrt2 transcript levels in Skeletonema at the inner shelf region exhibited a mean of 111 mmole/(mole EFL); at the mid-shelf region, the mean Nrt2 mRNA levels were 298 mmole/(mole EFL), which was very close to the maximum levels observed under nitrogen starvation. By contrast, the Nrt2 transcript levels in Chaetoceros were low at all of the shelf locations, except at one station in the mid-shelf region. The cross-shelf mean was 2.86 mmole/(mole EFL), which was similar to the expression levels observed in cultured Chaetoceros under conditions of sufficient ammonium. Similar expression patterns were observed in diatoms in the southern ECS in June 2011, but the Nrt2 transcript levels in Skeletonema at the inner shelf region were reduced to a mean of 28.6 mmole/(mole EFL). Regression analysis indicated that cell abundance and Nrt2 expression were closely related to the nutricline depth in the coastward half of the southern ECS for Skeletonema but not for Chaetoceros. These results indicate that the evaluated species differ in nitrogen status, which may reflect their evolutionary strategies to survive in a fluctuating marine environment.

Strains of the Morphospecies Ploeotia costata (Euglenozoa) Isolated from the Western North Pacific (Taiwan) Reveal Substantial Genetic Differences.

Two phagotrophic euglenid strains (Strains Pac and Tam) were isolated from coastal locations in Taiwan. Ultrastructural characteristics of the strains included five pellicle strips joined at the posterior end. The strips were formed by major grooves with bifurcated edges. At the cell anterior, the feeding structure formed a lip. Underneath the lip was a comb composed of layers of microtubules. Farther back, two supporting rods tapered toward the posterior end, and a number of vanes with attached microtubules were present between the rods. The morphological characteristics agree with Ploeotia costata Strain CCAP 1265/1. However, the 18S rDNA sequences of Strains Pac/Tam lacked a group I intron and possessed three extra insertions of 116, 67, and 53 bp. Phylogenetic analysis indicated low sequence similarity between Strains Pac/Tam and CCAP 1265/1 (92%). The morphospecies P. costata apparently includes a substantial level of DNA sequence divergence, and likely represents multiple molecular species units.

Advancing Li-ion capacitors through dual wet chemical prelithiation.

Lithium-ion batteries (LIBs) and electrical double-layer capacitors (EDLCs) are widely used in commercial energy storage systems, but each has inherent limitations. To overcome these limitations, the lithium-ion capacitor (LIC) has emerged as a hybrid energy storage device, combining the benefits of LIBs and EDLCs. However, the introduction of active lithium into LICs poses challenges due to lithium's reactivity and instability. In this study, we propose a dual wet chemical prelithiation strategy to enhance LIC performance. By wet chemically prelithiating both the activated carbon cathodes and hard carbon anodes, significant improvements are achieved compared to traditional prelithiation methods. The dual prelithiation approach outperforms electrochemical prelithiation in terms of energy storage performance, cycle life, and process simplification. LICs with dual wet chemically prelithiated electrodes demonstrate the highest energy density and retain a substantial portion of reversible capacity even at high discharge rates. The strategy exhibits fast kinetics and wide operational stability. In contrast, LICs with metallic lithium anodes or electrochemically prelithiated hard carbon anodes exhibit inferior performance and limited cycle life. The dual wet chemical prelithiation strategy represents a breakthrough in LIC technology, offering superior performance, cycle stability, and scalability. It holds promise for alkali-ion energy storage systems and drives advancements in electrochemical energy storage technology.

Metal-Doped NASICON/Polymer Composite Solid Electrolyte for Lithium Titania Anode in Lithium-Ion Batteries.

This study reports five types of metal-doped (Co, Cu, Sn, V, and Zr) NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP)/polymer composite solid electrolytes (CSEs) enabling Li4Ti5O12 (LTO) anodes to have high rate capability and excellent cycling performance. The high Li+-conductivity LATP samples are successfully synthesized through a modified sol-gel method followed by thermal calcination. We find that the cation dopants clearly influence the substitution of Al for Ti, with the type of dopant serving as a crucial factor in determining the ionic conductivity and interfacial resistance of the solid electrolyte. The CSE containing poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and Sn-LATP shows an ionic conductivity of 1.88 × 10-4 S cm-1 at ambient temperature. The optimum conductivity can be attributed to alterations in the lattice parameters and Li+ transport pathways owing to Sn doping. The solid-state cell equipped with the LTO-supported CSE containing Sn-LATP fillers demonstrates both excellent high rate capability at 5 C (with a capacity retention of 86% compared to the value measured at 0.2 C) and superior cycling stability, maintaining high Coulombic efficiency (>99.0%) over 510 cycles. These findings indicate that the proposed CSE is highly promising for use in solid-state lithium batteries with desirable charge-discharge properties and high durability.

Systematic study of Co-free LiNi0.9Mn0.07Al0.03O2 Ni-rich cathode materials to realize high-energy density Li-ion batteries.

The growing use of EVs and society's energy needs require safe, affordable, durable, and eco-friendly high-energy lithium-ion batteries (LIBs). To this end, we synthesized and investigated the removal of Co from Al-doped Ni-rich cathode materials, specifically LiNi0.9Co0.1Al0.0O2 (NCA-0), LiNi0.9Mn0.1Al0.0O2 (NMA-0), LiNi0.9Mn0.07Al0.03O2 (NMA-3), intending to enhance LIB performance and reduce the reliance on cobalt, a costly and scarce resource. Our study primarily focuses on how the removal of Co affects the material characteristics of Ni-rich cathode material and further introduces aluminum into the cathode composition to study its impacts on electrochemical properties and overall performance. Among the synthesized samples, we discovered that the NMA-3 sample, modified with 3 mol% of Al, exhibited superior battery performance, demonstrating the effectiveness of aluminum in promoting cathode stability. Furthermore, the Al-modified cathode showed promising cycle life under normal and high-temperature conditions. Our NMA-3 demonstrated remarkable capacity retention of âˆ¼ 88 % at 25 °C and âˆ¼ 81 % at 45 °C after 200 cycles at 1C, within a voltage range of 2.8-4.3 V, closely matching the performances of conventional NCM and NCA cathodes. Without cobalt, the cathodes exhibited increased cation disorder leading to inferior rate capabilities at high C-rates. In-situ transmission XRD analysis revealed that the introduction of Al has reduced the phase change and provided much-needed stability to the overall structure of the Co-free NMA-3. Altogether, the findings suggest that our aluminum-modified NMA-3 sample offers a promising approach to developing Co-free, Ni-rich cathodes, effectively paving the way toward sustainable, high-energy-density LIBs.

Core-Shell Si@SiOC Particles Synthesized Using Supercritical Carbon Dioxide Fluid for Superior Li-Ion Storage Performance.

A supercritical carbon dioxide (SCCO2) fluid, characterized by gas-like diffusivity, near-zero surface tension, and excellent mass transfer properties, is used as a precursor to produce silicon oxycarbide (SiOC) coating. SCCO2 disperses and reacts with Si particles to form an interfacial layer consisting of Si, O, and C. After an 850 °C annealing process, a conformal SiOC coating layer forms, resulting in core-shell Si@SiOC particles. High-resolution transmission electron microscopy and its X-ray line-scan spectroscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy, are used to examine the SiOC formation mechanism. Effects of SCCO2 interaction time on the SiOC properties are investigated. The SiOC layer connects the Si@SiOC particles, improving electron and Li+ transport. Cyclic voltammetry, galvanostatic intermittent titration technique, and electrochemical impedance spectroscopy are employed to examine the role of SiOC during charging/discharging. Operando X-ray diffraction data reveal that the SiOC coating reduces crystal size of the formed Li15Si4 and increases its formation/elimination reversibility during cycling. The Si@SiOC electrode shows a capacitiy of 2250 mAh g-1 at 0.2 A g-1. After 500 cycles, the capacity retention is 72% with Coulombic efficiency above 99.8%. A full cell consisting of Si@SiOC anode and LiNi0.8Co0.1Mn0.1O2 cathode is constructed, and its performance is evaluated.

Enhanced Electrochemical Performance of Ca-Doped Na3V2(PO4)2F3/C Cathode Materials for Sodium-Ion Batteries.

Na3V2(PO4)2F3 (NVPF) with a NASICON structure has garnered attention as a cathode material owing to its stable 3D structure, rapid ion diffusion channels, high operating voltage, and impressive cycling stability. Nevertheless, the low intrinsic electronic conductivity of the material leading to a poor rate capability presents a significant challenge for practical application. Herein, we develop a series of Ca-doped NVPF/C cathode materials with various Ca2+ doping levels using a simple sol-gel and carbon thermal reduction approach. X-ray diffraction analysis confirmed that the inclusion of Ca2+ does not alter the crystal structure of the parent material but instead expands the lattice spacing. Density functional theory calculations depict that substituting Ca2+ ions at the V3+ site reduces the band gap, leading to increased electronic conductivity. This substitution also enhanced the structural stability, preventing lattice distortion during the charge/discharge cycles. Furthermore, the presence of the Ca2+ ion introduces two localized states within the band gap, resulting in enhanced electrochemical performance compared to that of Mg-doped NVPF/C. The optimal NVPF-Ca-0.05/C cathode exhibits superior specific capacities of 124 and 86 mAh g-1 at 0.1 and 10 C, respectively. Additionally, the NVPF-Ca-0.05/C demonstrates satisfactory capacity retention of 70% after 1000 charge/discharge cycles at 10 C. These remarkable results can be attributed to the optimized particle size, excellent structural stability, and enhanced ionic and electronic conductivity induced by the Ca doping. Our findings provide valuable insight into the development of cathode material with desirable electrochemical properties.

Double Nitrogenation Layer Formed Using Nitric Oxide for Enhancing Li+ Storage Performance, Cycling Stability, and Safety of Si Electrodes.

To enhance Li storage properties, nitrogenation methods are developed for Si anodes. First, melamine, urea, and nitric oxide (NO) precursors are used to nitrogenize carbon-coated Si particles. The properties of the obtained particles are compared. It is found that the NO process can maximize the graphitic nitrogen (N) content and electronic conductivity of a sample. In addition, optimized N functional groups and O─C species on the electrode surface increase electrolyte wettability. However, with a carbon barrier layer, NO hardly nitrogenizes the Si cores. Therefore, bare Si particles are reacted with NO. Core-shell Si@amorphous SiNx particles are produced using a facile and scalable NO treatment route. The effects of the NO reaction time on the physicochemical properties and charge-discharge performance of the obtained materials are systematically examined. Finally, the Si@SiNx particles are coated with N-doped carbon. Superior capacities of 2435 and 1280 mAh g-1 are achieved at 0.2 and 5 A g-1, respectively. After 300 cycles, 90% of the initial capacity is retained. In addition, differential scanning calorimetry data indicate that the multiple nitrogenation layers formed by NO significantly suppress electrode exothermic reactions during thermal runaway.