Weiqian Tian

Bio-inspired beehive-like hierarchical nanoporous carbon derived from bamboo-based industrial by-product as a high performance supercapacitor electrode material

Bio-inspired beehive-like hierarchical nanoporous carbon (BHNC) with a high specific surface area of 1472 m2 g−1 and a good electronic conductivity of 4.5 S cm−1 is synthesized by carbonizing the industrial waste of bamboo-based by-product. The BHNC sample exhibits remarkable electrochemical performances as a supercapacitor electrode material, such as a high specific capacitance of 301 F g−1 at 0.1 A g−1, still maintaining a value of 192 F g−1 at 100 A g−1, negligible capacitance loss after 20 000 cycles at 1 A g−1, and a high power density of 26 000 W kg−1 at an energy density of 6.1 W h kg−1 based on active electrode materials in an aqueous electrolyte system. Moreover, an enhanced power density of 42 000 W kg−1 at a high energy density of 43.3 W h kg−1 is obtained in an ionic liquid electrolyte system, which places the BHNC-based supercapacitors in the Ragone chart among the best energy–power synergetic outputting properties ever reported for carbon-based supercapacitors.

Preparing two-dimensional microporous carbon from Pistachio nutshell with high areal capacitance as supercapacitor materials

Two-dimensional (2D) porous carbon AC-SPN-3 possessing of amazing high micropore volume ratio of 83% and large surface area of about 1069 m2 g−1 is high-yield obtained by pyrolysis of natural waste Pistachio nutshells with KOH activation. The AC-SPN-3 has a curved 2D lamellar morphology with the thickness of each slice about 200 nm. The porous carbon is consists of highly interconnected uniform pores with the median pore diameter of about 0.76 nm, which could potentially improve the performance by maximizing the electrode surface area accessible to the typical electrolyte ions (such as TEA+, diameter = ~0.68 nm). Electrochemical analyses show that AC-SPN-3 has significantly large areal capacitance of 29.3/20.1 μF cm−2 and high energy density of 10/39 Wh kg−1 at power of 52/286 kW kg−1 in 6 M KOH aqueous electrolyte and 1 M TEABF4 in EC-DEC (1:1) organic electrolyte system, respectively.

Renewable graphene-like nitrogen-doped carbon nanosheets as supercapacitor electrodes with integrated high energy–power properties

The development of supercapacitors with integrated high energy–power properties coupled with long cyclic life is an urgent demand in the energy storage field. The key to the assembly of such devices is to design and fabricate novel high-performance electrode materials in conjunction with matched electrolytes. In this study, a renewable graphene-like nitrogen-doped carbon nanosheet (RGNC-NS) has been constructed by using simultaneous carbonization and auto-activation followed by ultrasonic-assisted liquid exfoliation from natural layered shrimp shells. The final RGNC-NS had an optimum integration of graphene-like nanostructures (∼5 nm thick), large specific surface area (1946 m2 g−1), and rich nitrogen doping (8.75 wt%), resulting in high conductivity (7.8 S cm−1) and good surface wettability with an electrolyte. The RGNC-NS as a supercapacitor electrode exhibited an excellent rate capability with an ultrahigh capacitance of 322 F g−1 at 0.5 A g−1 and 241 F g−1 at 100 A g−1 (75% retention), as well as a long cyclic stability of 98.3% capacitance retention after 20 000 cycles at 10 A g−1 in 6 M KOH. Moreover, the RGNC-NS in a mixed ionic liquid electrolyte displayed an integrated high energy–power density of 30 W h kg−1 energy density at 64 000 W kg−1 power density and 93.2% capacitance retention after 8000 cycles at 5 A g−1.

Biomass‐Derived Porous Carbon with Micropores and Small Mesopores for High‐Performance Lithium–Sulfur Batteries

Biomass-derived porous carbon BPC-700, incorporating micropores and small mesopores, was prepared through pyrolysis of banana peel followed by activation with KOH. A high specific BET surface area (2741 m2  g-1 ), large specific pore volume (1.23 cm3  g-1 ), and well-controlled pore size distribution (0.6-5.0 nm) were obtained and up to 65 wt % sulfur content could be loaded into the pores of the BPC-700 sample. When the resultant C/S composite, BPC-700-S65, was used as the cathode of a Li-S battery, a large initial discharge capacity (ca. 1200 mAh g-1 ) was obtained, indicating a good sulfur utilization rate. An excellent discharge capacity (590 mAh g-1 ) was also achieved for BPC-700-S65 at the high current rate of 4 C (12.72 mA cm-2 ), showing its extremely high rate capability. A reversible capacity of about 570 mAh g-1 was achieved for BPC-700-S65 after 500 cycles at 1 C (3.18 mA cm-2 ), indicating an outstanding cycling stability.

One-dimensional porous nanofibers of Co3O4 on the carbon matrix from human hair with superior lithium ion storage performance.

One-dimensional (1D) hierarchical porous nanofibers of Co3O4 possessing of (220) facets on the carbon matrix from human hair (H2@Co3O4) with 20–30 nm in width and 3–5 μm in length are prepared by a facile solvothermal and calcination approach. The well crystallized small Co3O4 particles with the diameter of about 8–12 nm were closely aggregated together in the nanofibers. Electrochemical analyses show that the first discharge capacity of H2@Co3O4 electrode is 1368 mAh g−1 at the current density of 0.1 A g−1 based on the total mass of composite. A high reversible capacity of 916 mAh g −1 was obtained over 100 cycles at 0.1 A g−1, presenting a good cycling stability. When cycled at a high current density of 1 and 2 A g−1, the specific capacity of 659 and 573 mAh g−1 could be still achieved, respectively, indicating a superior power capability.

Superlow load of nanosized MnO on a porous carbon matrix from wood fibre with superior lithium ion storage performance

A facile synthesis of an MnO/C nanocomposite material consisting of 5.3 wt% of MnO on the surface of porous carbon is introduced. Equally distributed nanosized MnO particles and the porous carbon matrix have fully developed a synergistic effect to achieve superior lithium ion storage performance. Using the MnO/C nanocomposite material as the anode of a Li-ion battery, a high discharge capacity of 952 mA h g−1 has been obtained at a current density of 0.1 A g−1 with a stable cycling performance over 100 charge–discharge cycles.

Solvothermally induced α-Fe2O3/graphene nanocomposites with ultrahigh capacitance and excellent rate capability for supercapacitors

Well crystallized Fe2O3 with the particle size mainly concentrated around 35–40 nm combined with graphene is fabricated under solvothermal conditions. The optimized Fe2O3/GH-2 composite sample possessing 49.7 wt% Fe2O3 has a high specific BET surface area of 215.3 m2 g−1. When used as a supercapacitor electrode, the capacitances are admirable 2310 F g−1 at 5 mV s−1 and 615 F g−1 at an amazingly high current density of 100 A g−1. When used as an anode material for asymmetric hybrid capacitors, the composite shows a promising future for energy storage with high energy density, high power density and excellent cycle life.

Constructing Free Standing Metal Organic Framework MIL-53 Membrane Based on Anodized Aluminum Oxide Precursor

Metal organic framework (MOF) materials have attracted great attention due to their well-ordered and controllable pores possessing of prominent potentials for gas molecule sorption and separation performances. Organizing the MOF crystals to a continuous membrane with a certain scale will better exhibit their prominent potentials. Reports in recent years concentrate on well grown MOF membranes on specific substrates. Free standing MOF membranes could have more important applications since they are independent from the substrates. However, the method to prepare such a membrane has been a great challenge because good mechanical properties and stabilities are highly required. Here, we demonstrate a novel and facile technique for preparing the free standing membrane with a size as large as centimeter scale. The substrate we use proved itself not only a good skeleton but also an excellent precursor to fulfill the reaction. This kind of membrane owns a strong mechanical strength, based on the fact that it is much thinner than the composite membranes grown on substrates and it could exhibit good property of gas separation.

Unique 1D Co3O4 crystallized nanofibers with (220) oriented facets as high-performance lithium ion battery anode material

A novel one-step hydrothermal and calcination strategy was developed to synthesize the unique 1D oriented Co3O4 crystal nanofibers with (220) facets on the carbon matrix derived from the natural, abundant and low cost wool fibers acting as both carbon precursor and template reagent. The resultant W2@Co3O4 nanocomposite exhibited very high specific capacity and favorable high-rate capability when used as anode material of lithium ion battery. The high reversible Li+ ion storage capacity of 986 mAh g−1 was obtained at 100 mA g−1 after 150 cycles, higher than the theoretical capacity of Co3O4 (890 mAh g−1). Even at the higher current density of 1 A g−1, the electrode could still deliver a remarkable discharge capacity of 720 mAh g−1 over 150 cycles.

Graphene-based carbon coated tin oxide as a lithium ion battery anode material with high performance

In this study, we synthesized an excellent ternary graphene-based carbon coated SnO2 (rGO/PC/SnO2) nanocomposite anode for lithium ion batteries (LIBs), in which carbon-coated SnO2 nanoparticles homogeneously grow on the surface of reduced graphene oxide (rGO) using glucose as the soft templating agent. Using glucose can limit the growth of the SnO2 particles; as a result, the size of the SnO2 particles would be relatively uniform. Moreover, the carbon coated on the surface of SnO2 particles can effectively prevent their agglomeration on the surface of rGO and limit their volume expansion during charge–discharge cycles. The porous structure of the rGO/PC/SnO2 nanocomposite can effectively accommodate the severe volume variation upon cycling and provide additional contact areas between the active material and the electrolyte. Significantly, the rGO/PC/SnO2 anode delivers an initial specific discharge capacity of 2238.2 mA h g−1 and retains 1467.8 mA h g−1 after 150 cycles at a current density of 0.1C (1C = 782 mA g−1). Even at the high specific current of 1C after 200 cycles, the reversible specific capacity is still as high as 618.3 mA h g−1. The rGO/PC/SnO2 anode exhibits excellent rate performances and possesses a reversible specific capacity of 445.9 mA h g−1 at 5C implying its good structural stability.