3 D Porous CoS2 Hexadecahedron Derived from MOC toward Ultrafast and Long-Lifespan Lithium Storage.

A new hexadecahedron assembled by core-shell CoS2 particles@N-doped carbon (CoS2 @NCH) is prepared successfully through the self-templating method. The CoS2 @NCH hybrid electrode delivers a high lithium-storage capacity of 778 mA h g-1 after 1000 cycles at a high current density of 1 A g-1 , which is the longest cycle lifespan among the reported CoS2 anode materials in lithium-ion batteries. Furthermore, the CoS2 @NCH hybrid electrode shows excellent rate capability with a discharge capacity of 220 mA h g-1 at an extremely high current density of 20 A g-1 , and a charge capacity of 649 mA h g-1 is restored upon returning the current density back to 2 A g-1 . The superior performance is attributed to the unique construction of CoS2 @NCH. The N-doped interconnected porous carbon shells form highly conductive skeletons for quick electron transfer and prevent the electrode from collapsing. Moreover, the porous characteristic of the materials plays a key role: as some effective channels, the mesopores on the porous carbon shells provide greater access for lithium, and the mesopores derived from the particle interspace enables the complete immersion of the electrodes in electrolyte, which alleviates the volume expansion and ensures the integrity of the electrode. In addition, the nanosized CoS2 particles, which shorten the ion-transport path and provide extra electroactive sites, also improve the reaction kinetics.

Electrochemical In Situ Formation of a Stable Ti-Based Skeleton for Improved Li-Storage Properties: A Case Study of Porous CoTiO3 Nanofibers.

Bimetallic transition-metal oxides, which exhibit superior electrochemical properties compared with pristine single-metal oxides, have recently become a topic of significant research interest for applications in lithium-ion batteries (LIBs). Herein, we report a simple and scalable electrospinning method to synthesize porous CoTiO3 nanofibers as the precursor for nanostructured bimetallic transition-metal oxides formed electrochemically in situ. This strategy ensures uniform mixing and perfect contact between two constituent transition-metal oxides during the lithiation/delithiation process. Furthermore, CoTiO3 nanofibers based on ultrafine CoTiO3 nanocrystals are interconnected to form a nano/microstructured 3D network, which ensures the high stability of the in situ formed structure composed of bimetallic transition-metal oxides, and also fast ion/electron transfer and electrolyte penetration into the electrode. Electrochemical measurements revealed the excellent lithium storage (647 mAh g-1 at 0.1 Ag-1 ) and retention properties (600 mAh g-1 at 1 Ag-1 after 1200 cycles) of the CoO/TiO2 electrode. Moreover, the electrochemical reaction mechanism was explored by using ex situ X-ray photoelectric spectroscopy and cyclic voltammetry tests, which confirmed the two-phase reaction processes in the electrodes. These results clearly validate the potential of CoTiO3 with a unique nano/microstructured morphology as the precursor for a bimetallic transition-metal oxide for use as the anode material for long-life LIBs.

Oxygen-Deficient Titanium Dioxide Nanosheets as More Effective Polysulfide Reservoirs for Lithium-Sulfur Batteries.

In this work, oxygen-deficient anatase TiO2 nanosheets (A-TiO2-x NSs) are proposed as a substrate to improve the electrochemical properties of sulfur electrodes for lithium-sulfur (Li-S) batteries. The A-TiO2-x NSs are prepared by partly reducing pristine TiO2 nanosheets (A-TiO2 NSs) in NaBH4 solution. With some oxygen vacancies on the surface of the TiO2 nanosheets, A-TiO2-x NSs not only promote electronic transfer, but also act as more effective polysulfide reservoirs to minimize the dissolution of lithium polysulfides (LiPSs) than the A-TiO2 NSs control. Hence, upon utilization as modifiers for cathodes of Li-S batteries, the A-TiO2-x NSs-modified sulfur (A-TiO2-x NSs-S) cathode exhibits a higher reversible specific capacity and greater cycling performance and rate capability than the A-TiO2 NSs-modified one (A-TiO2 NSs-S). For example, A-TiO2-x NSs-S delivers an initial specific capacity of 1277.1 mAh g-1 at 0.1 C and maintains a stable Coulombic efficiency of approximately 99.2 % after the first five cycles; these values are higher than those of 997.3 mAh g-1 and around 96.7 %, respectively, for A-TiO2 NSs-S. The enhanced electrochemical properties of the A-TiO2-x NSs-S cathode can be ascribed mainly to the more effective adsorption of dissolvable and diffused LiPSs by the oxygen vacancies. Therefore, utilization of the structure of oxygen vacancies in Li-S batteries demonstrates great prospects for practical application.

Immediate implant placement in combination with platelet rich-fibrin into extraction sites with periapical infection in the esthetic zone: A case report and review of literature.

BACKGROUND: In this case, platelet-rich fibrin (PRF) was added to guided tissue regeneration as a biomaterial in proper order for immediate planting in aesthetic area with periapical infection. CASE SUMMARY: With the history of endodontic failure in maxillary central incisor, a 34-year-old female patient required the extraction of maxillary anterior residual root and immediate implantation. Cone beam computed tomography and clinical observation were used to assess the regeneration of soft and bone tissue. Before operation, cone beam computed tomography showed the anterior residual root had serious periapical periodontitis with insufficient labial bone in the aesthetic zone. The patient underwent immediate implant placement and reconstruction of the bone substitution by modified guided bone regeneration. The barrier was a three-layer structure of PRF-collagen membrane-PRF that covered the mixture of PRF and Bio-Oss to promote both osteogenesis and soft tissue healing. At 6 mo postoperatively, the definitive crown was placed after accomplished finial impression. One-year follow-up showed a satisfactory aesthetic effect with no obvious absorption of the labial bone and soft tissue. CONCLUSION: The use of PRF in combination with guided bone regeneration can serve as a reliable and simple adjuvant for immediate implanting in infected socket and result in a stable osteogenic effect with good aesthetic outcome.

[Development of tilted implant for free end of maxillary posterior teeth].

Vertical bone insufficiency in the maxillary posterior teeth is a common clinical situation. At present, the bone insufficiency in the maxillary posterior teeth is mainly overcome by bone grafting through maxillary sinus floor elevation. Compared with traditional axial implantation, tilted implantation can better avoid bone grafting, reduce complications, shorten the treatment cycle, reduce the treatment cost for patients, and gradually be promoted in clinical settings. This article reviews the concept, biomechanics, clinical evaluation, and digital trend of tilted implants of maxillary posterior teeth.

Effective Cathode Design of Three-Layered Configuration for High-Energy Li-S Batteries.

A three-layered cathode structure was designed to minimize the shuttle effect of polysulfides and improve active material utilization. The three-layered configuration was fabricated by directly dropping pure sulfur composite slurry into multifunctional dual-barrier layers consisting of a self-standing TiO2/C interlayer and a very thin acetylene black layer (0.35 mg cm-2). In consequence, a decent discharge capacity of 963 mA h g-1 was acquired after 100 cycles at 0.1 C. With cycling at 0.1, 0.2, 0.5, 1, and 2 C, the cells displayed excellent reversible capacities of 1203, 1145, 1035, 934, and 820 mA h g-1, respectively. Furthermore, the cells still delivered a satisfactory discharge capacity of 799 mA h g-1 after 300 cycles at 0.5 C. The light mass of the three-layered configuration guarantees that the energy density is effectively improved, considering the overall mass of the cathode. The energy density (603 W h kg-1 after 100 cycles) was at a high level compared with those of the reported ones. Therefore, it is believed that the synergistic design for the three-layered cathode structure, which combines the mass-produced layer-by-layer structure, provides a novel protocol to the practical application of lithium-sulfur batteries.

Synergistic Design of Cathode Region for the High-Energy-Density Li-S Batteries.

The synergistic design of cathode region was conducted to minimize the shuttle effect of polysulfides and decrease the loading of inactive components in order to acquire high-energy-density lithium-sulfur (Li-S) batteries. The well-designed cathode region presented two special characteristics: one was the intertwined nanofibers interlayer based on ultrafine TiO2 nanocrystal uniformly embedded within N-doping porous carbon; the other was the lightweight and three-dimensional current collector of fibrous cellulose paper coated by reduced graphene oxide. In consequence, the decent reversible capacity of 874.8 mA h g-1 was acquired at 0.1 C with a capacity retention of 91.83% after 100 cycles. Besides, the satisfactory capacity of 670 mA h g-1 was delivered after 300 cycles at 1 C with the small decay rate of only 0.08%. Because of higher capacity and lower loading of inactive component in cathode region, the energy density of cell increased more than five times compared with unmodified cell. Moreover, to further enhance the energy density, the high-sulfur-loading electrode was fabricated. A good areal capacity of 4.27 mA h cm-2 was retained for the cell with the active material of 4 mg cm-2 and the cycle stability was also well-maintained. In addition, due to the flexibility of interlayer and current collector, Li-S full cell (in pouch cell format) was easily curved. Therefore, the synergistic design for cathode region, which combines the flexible and mass-produced interlayer and current collector together, provides an effective access to Li-S batteries with high energy density and flexibility for practical application.