Tailored Properties of Carbon for Supercapacitors by Blending Lignin and Cellulose to Mimic Biomass as Carbonaceous Precursor.

KOH-activated carbon materials prepared from biomass-derived carbon source, cellulose and lignin, were compared. Mixtures of different ratios of cellulose and lignin were used to partially mimic biomass as carbon source. This allows tailoring and optimizing of the KOH activated carbon materials by getting rid of the restriction of the intrinsic proportion of cellulose and lignin in specific biomass. The results indicate that cellulose use results in a more porous structure, whereas lignin use leads to more partially activated graphite structure. The activated carbon material (CL1) prepared from blend of cellulose with lignin in mass ratio of 1 : 1 exhibits a high specific surface area of 2000.39 m2 g-1 , and in TEABF4 /ACN (tetraethylammonium tetrafluoroborate dissolved in acetonitrile) electrolyte it showed a maximum specific capacitance of 136.10 F g-1 , a maximum energy density of 18.11 Wh kg-1 , and a capacitance retention of 85.04 % under current density as high as 15 A g-1 .

High-Efficacy and Polymeric Solid-Electrolyte Interphase for Closely Packed Li Electrodeposition.

The industrial application of lithium metal anode requires less side reaction between active lithium and electrolyte, which demands the sustainability of the electrolyte-induced solid-electrolyte interface. Here, through a new diluted lithium difluoro(oxalato)borate-based (LiDFOB) high concentration electrolyte system, it is found that the oxidation behavior of aggregated LiDFOB salt has a great impact on solid-electrolyte interphase (SEI) formation and Li reversibility. Under the operation window of Cu/LiNi0.8Co0.1Mn0.1O2 full cells (rather than Li/Cu configuration), a polyether/coordinated borate containing solid-electrolyte interphase with inner Li2O crystalline can be observed with the increasing concentration of salt, which can be ascribed to the reaction between aggregated electron-deficient borate species and electron-rich alkoxide SEI components. The high Li reversibility (99.34%) and near-theoretical lithium deposition enable the stable cycling of LiNi0.8Co0.1Mn0.1O2/Li cells (N/P < 2, 350 Wh kg-1) under high cutoff voltage condition of 4.6 V and lean electrolyte condition (E/C ≈ 3.2 g Ah-1).

Explicit Gain Equations for Hybrid Graphene-Quantum-Dot Photodetectors.

Graphene is an attractive material for broadband photodetection but suffers from weak light absorption. Coating graphene with quantum dots can significantly enhance light absorption and create extraordinarily high photogain. This high gain is often explained by the classical gain theory which is unfortunately an implicit function and may even be questionable. In this work, explicit gain equations for hybrid graphene-quantum-dot photodetectors are derived. Because of the work function mismatch, lead sulfide quantum dots coated on graphene will form a surface depletion region near the interface of quantum dots and graphene. Light illumination narrows down the surface depletion region, creating a photovoltage that gates the graphene. As a result, high photogain in graphene is observed. The explicit gain equations are derived from the theoretical gate transfer characteristics of graphene and the correlation of the photovoltage with the light illumination intensity. The derived explicit gain equations fit well with the experimental data, from which physical parameters are extracted.

Ni-Co Binary Hydroxide Nanotubes with Three-Dimensionally Structured Nanoflakes: Synthesis and Application as Cathode Materials for Hybrid Supercapacitors.

Nickel-cobalt binary hydroxide nanotubes were fabricated by a facile synthetic approach by using Cu2 O nanowires as sacrificial templates. The surface morphology of the binary hydroxide nanotubes can be easily controlled by adjusting the molar ratio of Ni to Co. With increasing Co content, the surfaces of the nanotubes tend to form hierarchical nanoflakes. The obtained nanotubes with high specific surface area exhibit typical battery-like electrochemical behavior. Among them, Ni-Co hydroxide nanotubes with Ni:Co=48:52 showed outstanding electrochemical characteristics, with a specific capacity of 209.9 mAh g-1 at 1 Ag-1 and remarkable cycling stability with 84.4 % capacity retention after 10 000 cycles at 20 A g-1 . With the advantages of their unique nanostructure and the synergistic effect of the two elements, the Ni-Co binary hydroxide nanotubes are expected to be effective potential cathode materials for hybrid supercapacitors.

Extraordinarily Stretchable All-Carbon Collaborative Nanoarchitectures for Epidermal Sensors.

Multifunctional microelectronic components featuring large stretchability, high sensitivity, high signal-to-noise ratio (SNR), and broad sensing range have attracted a huge surge of interest with the fast developing epidermal electronic systems. Here, the epidermal sensors based on all-carbon collaborative percolation network are demonstrated, which consist 3D graphene foam and carbon nanotubes (CNTs) obtained by two-step chemical vapor deposition processes. The nanoscaled CNT networks largely enhance the stretchability and SNR of the 3D microarchitectural graphene foams, endowing the strain sensor with a gauge factor as high as 35, a wide reliable sensing range up to 85%, and excellent cyclic stability (>5000 cycles). The flexible and reversible strain sensor can be easily mounted on human skin as a wearable electronic device for real-time and high accuracy detecting of electrophysiological stimuli and even for acoustic vibration recognition. The rationally designed all-carbon nanoarchitectures are scalable, low cost, and promising in practical applications requiring extraordinary stretchability and ultrahigh SNRs.

Template-Assisted Synthesis of Nickel Sulfide Nanowires: Tuning the Compositions for Supercapacitors with Improved Electrochemical Stability.

Ni nanowires were first synthesized via a chemical method without surfactants or a magnetic field. A series of nickel sulfide nanowires (Ni3S2-Ni, Ni3S2-NiS-Ni, and Ni3S2-NiS) have been successfully prepared by a controlled sacrificial template route based on the conductive Ni nanowire template. Electrochemical characterizations indicate that Ni3S2-NiS nanowires present superior redox reactivity with a high specific capacitance of 1077.3 F g(-1) at 5 A g(-1). Besides, its specific capacitance can remain about 76.3% after 10 000 cycles at 20 A g(-1). On the contrary, the nickel-preserving sulfide nanowires (Ni3S2-Ni and Ni3S2-NiS-Ni) deliver enhanced cycling stability as 100% of the initial specific capacitance of Ni3S2-Ni is retained after 10 000 cycles. The outstanding electrochemical stability can be attributed to the interaction between nickel sulfides and the conductive nickel nanowires.

Template Synthesis of Shape-Tailorable NiS2 Hollow Prisms as High-Performance Supercapacitor Materials.

Uniform NiS2 hollow nanoprisms have been controllably synthesized by a facial sacrificial template method including two-step refluxed reactions. The morphology of the hollow NiS2 prisms can be easily tailored by the low cost nickel complex template. With unique hollow structure, efficient electron, and ion transport pathway as well as single crystal structure, the NiS2 hollow prisms electrode exhibits excellent pseudocapacitive performance in LiOH electrolyte. It can deliver a specific capacitance of 1725 F g(-1) at a current density of 5 A g(-1) and 1193 F g(-1) even at a current density of 40 A g(-1). Furthermore, the materials also present an amazing cycling stability, that is, the specific capacitance can increase from 1367 F g(-1) to 1680 F g(-1) after 10,000 cycles of charge-discharge at the current density of 20 A g(-1).