Organic hybrid supercapacitors that consist of a battery electrode and a capacitive electrode show greatly improved energy density, but their power density is generally limited by the poor rate capability of battery-type electrodes. In addition, flexible organic hybrid supercapacitors are rarely reported. To address the above issues, herein an in-plane assembled orthorhombic Nb 2 O 5 nanorod film anode with high-rate Li + intercalation to develop a flexible Li-ion hybrid capacitor (LIC) is reported. The binder-/additive-free film exhibits excellent rate capability (≈73% capacity retention with the rate increased from 0.5 to 20 C) and good cycling stability (>2500 times). Kinetic analyses reveal that the high rate performance is mainly attributed to the excellent in-plane assembly of interconnected single-crystalline two kinds based on the electrolytes used in the cells: one is aqueous and the other is organic system. In general, supercapacitors with organic electrolytes show much higher energy density than that of aqueous system, because the organic electrolytes permit much larger working voltage (≈3.0 V). In order to further improve the energy density of the supercapacitors, Li-ion hybrid capacitors (LICs) were introduced by combining the Li-ion battery electrode with the activated carbon (AC) capacitive electrode. [4] Thereafter, either low-potential anodes such as Li 4 Ti 5 O 12 (LTO) or high-potential cathodes including LiNi 0.5 Mn 1.5 O 4 and graphitic carbons were utilized in the hybrid LICs, [5][6][7] and the energy density of the hybrid systems can be significantly improved by approximately two to threefold.However, a point worth noting is that the power capability of the LIC devices is generally limited by the Li-ion battery electrode side. [3][4][5][6][7] In details, the capacitive electrode in LICs can exhibit very high rate capability as the electrical charges are stored/released by ion adsorption/desorption; by contrast, the Li-ion battery electrode stores the energy via Li-ion intercalation, and thus the rate performance may be significantly limited by the slow Li-ion diffusion in the solid phase. With the purpose to mitigate the rate-imbalance issue in LICs, much research effort has been devoted to the development of Li-ion intercalation materials with both ultrahigh rate capability and long cycle life. In particular, nanostructured materials with pseudocapacitive Li-ion intercalation behavior such as Nb 2 O 5 , V 2 O 5 , MoO 3−x , and MoS 2 , etc. have been investigated. [8][9][10][11][12][13] Among them, Nb 2 O 5 materials with specified crystal phases have attracted great interest due to their advantages of relatively low plateau voltage, high specific capacity (≈200 mA h g −1 ), and good cycling stability. However, Nb 2 O 5 may still suffer poor rate performance due to their limited electrical conductivity and low Li ion-diffusion rate. [14][15][16] Recent work demonstrated that Nb 2 O 5 nanomaterials of orthorhombic phase, which were carefully prepared with ordered porous architecture, showe...

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The synthesis of water-soluble and low-cytotoxicity quantum dots (QDs) in aqueous solution has received much attention recently. A one-step and convenient method has been developed for synthesis of water-soluble glutathione (GSH)-capped and Zn(2+)-doped CdTe QDs via a refluxing route. Because of the addition of Zn ions and the epitaxial growth of a CdS layer, the prepared QDs exhibit superior properties, including strong fluorescence, minimal cytotoxicity, and enhanced biocompatibility. The optical properties of QDs are characterized by UV-vis and fluorescence (FL) spectra. The structure of QDs was verified by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectrometry (XPS), energy dispersive spectroscopy (EDS), atomic absorption spectrometry (AAS), and Fourier transform infrared spectroscopy (FTIR). Furthermore, the low cytotoxicity of the prepared QDs was proved by the microcalorimetric technique and inductively coupled plasma-atomic emission spectrometry (ICP-AES).

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Manganese carbonate (MnCO3) is an attractive anode material with high capacity based on conversion reaction for lithium-ion batteries (LIBs), but its application is mainly hindered by poor cycling performance. Building nanostructures/porous structures and nanocomposites has been demonstrated as an effective strategy to buffer the volume changes and maintain the electrode integrity for long-term cycling. It is widely believed that microsized MnCO3 is not suitable for use as anode material for LIBs because of its poor conductivity and the absence of nanostructure. Herein, different from previous reports, spherical MnCO3 with the mean diameters of 6.9 μm (MnCO3-B), 4.0 μm (MnCO3-M), and 2.6 μm (MnCO3-S) were prepared via controllable precipitation and utilized as anode materials for LIBs. It is interesting that the as-prepared MnCO3 microspheres demonstrate both high capacity and excellent cycling performance comparable to their reported nanosized counterparts. MnCO3-B, MnCO3-M, and MnCO3-S deliver reversible specific capacities of 487.3, 573.9, and 656.8 mA h g(-1) after 100 cycles, respectively. All the MnCO3 microspheres show capacity retention more than 90% after the initial stage. The advantages of MnCO3 microspheres were investigated via constant-current charge/discharge, cyclic voltammetry and electrochemical impedance spectroscopy. The results indicate that there should be substantial structure transformation from microsized particle to self-stabilized nanostructured matrix for MnCO3 at the initial charge/discharge stage. The evolution of EIS during charge/discharge clearly indicates the formation and stabilization of the nanostructured matrix. The self-stabilized porous matrix maintains the electrode structure to deliver excellent cycling performance, and contributes extra capacity beyond conversion reaction.

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Over the past few decades, electric doublelayer capacitors (EDLCs) have been one of the key components with high round trip efficiency and ultralong cycling lifetime in typical energy storage systems. [1][2][3][4][5][6] Unfortunately, EDLCs are subjected to limited energy density, which are inferior to that of secondary batteries and batterysupercapacitor hybrid devices. [7][8][9][10][11] As a well-known hybrid energy storage device, lithium-ion capacitors (LICs) consist of a capacitive electrode manifesting high rate capability and a battery-type electrode with high capacity, basically achieving both high power and energy densities. [12] In most cases, LICs employ Li + insertion anode and carbon-based capacitive cathode. [13][14][15][16] For instance, the state-ofthe-art LICs assembled with a prelithiated graphite anode and an activated carbon (AC) cathode were successfully commercialized. Nevertheless, the shortage of global lithium resources will bring great pressure on the development of sustainable electrochemical systems. Hybrid supercapacitors utilizing Na + instead of Li + are emerging as a possible substitute for addressing this issue due to the wide availability of sodium resources, low cost, and similar physiochemical properties between sodium and lithium. [17][18][19] As compared to LICs, sodium-ion capacitors (SICs) are still at their infant stage and need substantial advancement. Commercial graphite that is well employed as the Li-ion intercalation anode could not be directly used for SICs. Possible reasons are the insufficient interlayer spacing of graphite and the weakest chemical binding of Na to a given substrate, compared with the other alkali metals in the same column of the periodic table. [20] To search for potential carbon anodes, specific strategies have to be implemented, such as expanding the graphite interlayer, [21] forming house-of-cards structure, [22] and introducing defects. [23,24] While these functionalized carbon and structures demonstrate promoted sodium storage, the rate performance cannot always be guaranteed. Alternatively, layered titanates (A 2 Ti n O 2n+1 , A = Na, K, and H) represent a wide range of family with large interspacing of ≈0.7 nm for sodium storage. [8b] The Sodium-ion capacitors (SICs) have attracted increasing attention for sustainable energy utilization owing to their low cost and similar intercalation electrochemistry with lithium-ion capacitors. However, the practical application of SICs is seriously hindered by the low initial coulombic efficiency (ICE) and limited redox kinetics at the battery electrode side. Herein, taking a layered sodium titanate battery anode as an example, this study reports on the synergistic combination of ether electrolyte and binder-free array architecture to simultaneously achieve superior ICE and ultrafast Na + intercalation. The resulting Na 2 Ti 2 O 5 nanosheet array anode delivers extraordinary ICE (91%), high cycle CE (≈100%), and outstanding rate performance (66% capacity retention at 120 C). The key to the superior per...