Assembly of MnO/CNC/rGO fibers from colloidal liquid crystal for flexible supercapacitors via a continuous one-process method.

Flexible supercapacitors based on fiber shaped electrodes exhibit great potential for practical applications in smart fabrics owing to their light weight, good flexibility, and excellent weaveability. Herein, manganosite/carbonized cellulose nanocrystal/reduced graphene oxide (MnO/CNC/rGO) ternary composite fibers were fabricated from liquid crystal spinning dopes through a continuous one-process method. The assembly of CNC and manganese oxide nanoparticles in GO aqueous dispersion not only prevents GO nanosheets from restacking, but also ensures a uniform intercalation of nanoparticles. After a chemical and thermal reduction, the carbonized CNC contributes for additional electrical double layer capacitance while the MnO for faradaic pseudocapacitance. A fiber supercapacitor was assembled by arranging two MnO/CNC/rGO ternary composite fibers coated with PVA/H3PO4 gel electrolyte in parallel and it exhibited an energy density of 0.14 mWh cm-3 at 4 mW cm-3 and the maximum power density of 40 mW cm-3. The fiber supercapacitor also demonstrated a good cycling stability (retains 82% of its initial capacitance after 6000 cycles) and bending robustness. This assembly approach is facile and scalable. More importantly the homogeneous dispersion of the nanoparticles in the ternary composite fibers shows promise for the future spreading of wearable electronic products.

Coupled Chiral Structure in Graphene-Based Film for Ultrahigh Thermal Conductivity in Both In-Plane and Through-Plane Directions.

The development of high-performance thermal management materials to dissipate excessive heat both in plane and through plane is of special interest to maintain efficient operation and prolong the life of electronic devices. Herein, we designed and constructed a graphene-based composite film, which contains chiral liquid crystals (cellulose nanocrystals, CNCs) inside graphene oxide (GO). The composite film was prepared by annealing and compacting of self-assembled GO-CNC, which contains chiral smectic liquid crystal structures. The helical arranged nanorods of carbonized CNC act as in-plane connections, which bridge neighboring graphene sheets. More interestingly, the chiral structures also act as through-plane connections, which bridge the upper and lower graphene layers. As a result, the graphene-based composite film shows extraordinary thermal conductivity, in both in-plane (1820.4 W m-1 K-1) and through-plane (4.596 W m-1 K-1) directions. As a thermal management material, the heat dissipation and transportation behaviors of the composite film were investigated using a self-heating system and the results showed that the real-time temperature of the heater covered with the film was 44.5 °C lower than a naked heater. The prepared film shows a much higher efficiency of heat transportation than the commonly used thermal conductive Cu foil. Additionally, this graphene-based composite film exhibits excellent mechanical strength of 31.6 MPa and an electrical conductivity of 667.4 S cm-1. The strategy reported here may open a new avenue to the development of high-performance thermal management films.

Construction of SnO2-Graphene Composite with Half-Supported Cluster Structure as Anode toward Superior Lithium Storage Properties.

Inspired by nature, herein we designed a novel construction of SnO2 anodes with an extremely high lithium storage performance. By utilizing small sheets of graphene oxide, the partitioned-pomegranate-like structure was constructed (SnO2@C@half-rGO), in which the porous clusters of SnO2 nanoparticles are partially supported by reduced graphene oxide sheets while the rest part is exposed (half-supported), like partitioned pomegranates. When served as anode for lithium-ion batteries, SnO2@C@half-rGO exhibited considerably high specific capacity (1034.5 mAh g-1 after 200 cycles at 100 mA g-1), superior rate performance and remarkable durability (370.3 mAh g-1 after 10000 cycles at 5 A g-1). When coupled with graphitized porous carbon cathode for lithium-ion hybrid capacitors, the fabricated devices delivered a high energy density of 257 Wh kg-1 at ∼200 W kg-1 and maintained 79 Wh kg-1 at a super-high power density of ∼20 kW kg-1 within a wide voltage window up to 4 V. This facile and scalable approach demonstrates a new architecture for graphene-based composite for practical use in energy storage with high performance.

Confined SnO2 quantum-dot clusters in graphene sheets as high-performance anodes for lithium-ion batteries.

Construction of metal oxide nanoparticles as anodes is of special interest for next-generation lithium-ion batteries. The main challenge lies in their rapid capacity fading caused by the structural degradation and instability of solid-electrolyte interphase (SEI) layer during charge/discharge process. Herein, we address these problems by constructing a novel-structured SnO2-based anode. The novel structure consists of mesoporous clusters of SnO2 quantum dots (SnO2 QDs), which are wrapped with reduced graphene oxide (RGO) sheets. The mesopores inside the clusters provide enough room for the expansion and contraction of SnO2 QDs during charge/discharge process while the integral structure of the clusters can be maintained. The wrapping RGO sheets act as electrolyte barrier and conductive reinforcement. When used as an anode, the resultant composite (MQDC-SnO2/RGO) shows an extremely high reversible capacity of 924 mAh g(-1) after 200 cycles at 100 mA g(-1), superior capacity retention (96%), and outstanding rate performance (505 mAh g(-1) after 1000 cycles at 1000 mA g(-1)). Importantly, the materials can be easily scaled up under mild conditions. Our findings pave a new way for the development of metal oxide towards enhanced lithium storage performance.

Bioinspired Carbon/SnO2 Composite Anodes Prepared from a Photonic Hierarchical Structure for Lithium Batteries.

A carbon/SnO2 composite (C-SnO2) with hierarchical photonic structure was fabricated from the templates of butterfly wings. We have investigated for the first time its application as the anode material for lithium-ion batteries. It was demonstrated to have high reversible capacities, good cycling stability, and excellent high-rate discharge performance, as shown by a capacitance of ∼572 mAh g(-1) after 100 cycles, 4.18 times that of commercial SnO2 powder (137 mAh g(-1)); a far better recovery capability of 94.3% was observed after a step-increase and sudden-recovery current. An obvious synergistic effect was found between the porous, hierarchically photonic microstructure and the presence of carbon; the synergy guarantees an effective flow of electrolyte and a short diffusion length of lithium ions, provides considerable buffering room, and prevents aggregation of SnO2 particles in the discharge/charge processes. This nature-inspired strategy points out a new direction for the fabrication of alternative anode materials.

A Fe/Fe3O4/N-carbon composite with hierarchical porous structure and in situ formed N-doped graphene-like layers for high-performance lithium ion batteries.

A Fe/Fe3O4/N-carbon composite consisting of a porous carbon matrix containing a highly conductive N-doped graphene-like network and Fe/Fe3O4 nanoparticles was prepared. The porous carbon has a hierarchical structure which is inherited from rice husk and the N-doped graphene-like network formed in situ. When used as an anode material for lithium batteries, the composite delivered a reversible capacity of approximately 610 mA h g(-1) at a current density of 200 mA g(-1) even after 100 cycles, due to the synergism between the unique hierarchical porous structures, highly electrically conductive N-doped graphene-like networks and nanosized particles of Fe/Fe3O4. This work provides a simple approach to prepare N-doped porous carbon activated nanoparticle composites which could be used to improve the electrochemical performance of lithium ion batteries.

N-doped porous carbon with magnetic particles formed in situ for enhanced Cr(VI) removal.

A newly designed N-doped porous carbon with magnetic nanoparticles formed in situ (RHC-mag-CN) was fabricated through simple impregnation then polymerization and calcination. The doped nitrogen in RHC-mag-CN was in the form of graphite-type layers with the composition of CN. The resultant nanocomposite maintained a high surface area of 1136 m(2) g(-1) with 18.5 wt% magnetic nanoparticles (Fe3O4 and Fe) inside, which showed a saturation magnetization (Ms) of 22 emu/g. When used as an adsorbent, the RHC-mag-CN demonstrated a very quick adsorption property for the removal of Cr(VI), during which 92% of Cr(VI) could be removed within 10 min for dilute solutions at 2 g L(-1) adsorbent dose. The high adsorption capacity (16 mg g(-1)) is related to the synergetic effects of physical adsorption from the surface area and chemical adsorption from complexation reactions between Cr(VI) and Fe3O4. Importantly, the basic CNs in RHC-mag-CN increase its negative charge density and simultaneously increase the adsorption of metallic cations, such as Cr(3+) formed in the acid solution from the reduction of Cr(VI). The formation of magnetic nanoparticles inside not only supplies complexing sites for the adsorption of Cr(VI), but also shows perfect magnetic separation performance from aqueous solution.

Controlled dynamization to enhance reconstruction capacity of tissue-engineered bone in healing critically sized bone defects: an in vivo study in goats.

Tissue-engineered bone (TEB) has shown to be an effective alternative to conventional gold-standard autogenous bone for the repair of critically sized bone defects (CSBD). Moderate axial interfragmentary movement (IFM) has been shown to promote bone healing in conventional models. This study explored the use of IFM to enhance the capacity of TEB in the repair of CSBD using a goat model. CSBD were created in a goat model. Dynamic intramedullary rods designed to supply axial IFMs within 10% of the interfragmentary strain were used to stabilize CSBD goat femur models, whose bone defects were filled with TEB. Bone regeneration was evaluated using radionuclide bone imaging, roentgenographic analysis, periosteal callus area, computed tomography value score, biomechanical analysis, and histological observation. Compared with the static intramedullary rods, the dynamic intramedullary rod group showed an increase in early-stage callus formation and blood supply to the callus tissue, better differentiation of fibrous and cartilaginous tissue into bone tissue, improved strength and stiffness of callus tissue in late-stage healing, and overall better functional recovery of the goat femur. This showed that moderate axial IFM could promote the osteogenesis and reconstruction of TEB in vivo.