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One of the primary challenges in the development of a breakthrough lithium ion battery technology is to identify a composition that can effectively provide high power densities as well as high energy densities. Conventional graphitic anodes are considerably limited in this regard, owing to a limited charge storage capacity and constrained ionic and electrical conductivity. In this work, we report the use of a facile, scalable and low-cost Far Infrared (FIR) reduction strategy for the synthesis of graphene anodes as an alternative to conventional graphitic anodes. FIR irradiation was found to effectively reduce graphene oxide to graphene in under 3 min and displayed exceptional charge/discharge rates and charge storage capacities when used as an anode in lithium ion batteries. The binder-free FIR graphene anodes provided a very high reversible capacity of ~1016 mA h/g at a C-rate of ~1 C. Further, the FIR-reduced graphene anodes displayed impressive rate capabilities, delivering remarkably steady capacities as high as ~181 mA h/g at a C-rate of ~40 C over 1000 charge/discharge cycles, corresponding to an average power density of ~14 kW/kg.

This paper involves preparation of four different crystal phases (δ, γ, α and λ) of MnO2 by redox, solid reaction, hydrothermal routes and delithiation of LiMn2O4, respectively. The obtained MnO2 samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and the Brunauer–Emmett–Teller (BET) method for micro-structural, morphological and porosity studies. Cyclic voltammetric and galvanostatic tests were carried out to evaluate their capacitive properties in an anti-freezing aqueous electrolyte at different operating temperatures ranging from 25 to −35 °C. The δ-MnO2 prepared by a redox method exhibits the best electrochemical performances when conducted either in the single electrode tests (from 174.7 to 148.6 F g−1) or in the capacitor measurements (from 47.4 to 42 F g−1) as the operating temperature decreased from 25 °C down to the low temperature of −35 °C. Moreover, electrochemical impedance spectroscopy has been investigated and the activation energy values of different impedance components have been analyzed. It has been discovered that the operation temperature has more effect on the charge transfer resistance than diffusion resistance. To some degrees, these results have guiding significance for the low-temperature applications of manganese oxides-based electrochemical capacitors.

A series of La-doped Li3V2(PO4)3/C cathode materials for Li-ion batteries are synthesized by a sol–gel-assisted, low-temperature sintering process. La(NO3)3 acts not only as the La source, but also, together with the intermediate product LiNO3, promotes combustion, the ultrahigh exothermic energy that is advantageous for the nucleation process. The subsequent sintering process at 600 °C for 4 h is sufficient to produce highly crystalline La-doped Li3V2(PO4)3/C composites. The as-prepared cathode materials display smaller particle size, lower electron-transfer resistance and faster Li ion migration, which is ascribed to enhanced Li-ion transfer because of the La doping. The resulting Li3V1.96La0.04(PO4)3/C cathode has a stable specific capacity of 160 mA h g−1 at low charge–discharge rates over 100 cycles, and retained a stable capacity of up to 116 mA h g−1 at a rate of 5 C, which is 40% higher than the undoped pristine cathode.

We report a novel far-infrared (FIR) thermal reduction process to effectively reduce graphene oxide films for supercapacitor electrode applications. The binder-free graphene oxide films used in this study were produced by electro-spray deposition of a graphene oxide colloidal solution onto stainless steel current collectors. The reduction of graphene oxide was performed using a commercial FIR convection oven that is ubiquitous in homes for cooking and heating food. The reduction process incorporated a simple, one-step FIR irradiation carried out in ambient air. Further, the FIR irradiation process was completed in ∼3 min, wherein neither special atmosphere nor high temperature was employed, resulting in an economic, efficient and simplified processing technique. The as-produced FIR graphene electrode gave a specific capacitance of ∼320 F/g at a current density of ∼0.2 A/g with less than 94% loss in specific capacitance over 10,000 charge/discharge cycles. This is one of the best specific capacitances reported for all-carbon electrodes without any additives. Even at ultrafast charge/discharge rates (current densities as high as ∼100 A/g), the FIR graphene electrode still delivered specific capacitances in excess of 90 F/g. The measured energy and power densities of the FIR supercapacitors were found to be ∼3–6 times higher than commercial (activated carbon) supercapacitor devices. This excellent electrochemical performance of the FIR graphene coupled with its ease of production (in air at low temperatures) using a commercial home-use FIR convection oven indicates the significant potential of this concept for large-scale commercial electrochemical supercapacitor applications.

The solubility data of lithium bis(oxalate)borate (LiBOB) were measured in six different solvents using the synthetic method and laser monitoring technique at temperatures ranging from (293.15 to 363.15) K under atmospheric pressure. The experimental solubilities of LiBOB in different solvents were correlated by the modified Apelblat equations. It is found the calculated solubility data show good consistency with the experimental values. On this basis, some thermodynamic parameters of LiBOB in different solvents, such as dissolution enthalpy, dissolution entropy, and dissolution Gibbs free energy, are also calculated. These results concerning the solubility of LiBOB in different solvents will provide fundamental data in the commercial application of LiBOB.

In this paper, a series of Ce-doped Li3V2(PO4)3/C composite cathode materials for Li-ion batteries were synthesized by a facile and fast microwave assisted sol–gel route. The investigation of the influence of Ce doping on the structural and electrochemical characteristics of Li3V2(PO4)3/C shows that the resulting composite exhibits smaller particle size, lower electron-transfer resistance, and faster lithium ion migration, which are attributed to improved lithium ion transfer by the Ce doping. At low charge/discharge rates, the Ce-doped Li3V1.98Ce0.02(PO4)3/C composite delivers a stable specific capacity of ∼170 mAh g−1 for over 100 cycles. At high rates (e.g. 10C), the Ce-doped composite is still able to deliver stable capacities of up to ∼120 mAh g−1 which is ∼60% greater than its un-doped counterpart.

The modification techniques of applying carbon coating on particle surface and doping vanadium at Fe site were applied to make the LiFePO4 cathode materials achieve high rate performance in lithium ion batteries. To design and synthesize these LiFe(1−x)V x PO4/C (x = 0, 0.02, 0.05, or 0.08) composites, an aqueous solution–evaporation method was taken, in which every kind of raw material was distributed at a high degree of uniformity. The LiFe0.95V0.05PO4/2.57 wt% C composite displayed the best electrochemical performances. At rates of 0.1, 0.5, 2, 5, and 10 C (1 C = 170 mAg−1), it delivered a discharge capacity of 157.8, 156.9, 149, 139.6, and 130.1 mAh g−1, respectively. The composite exhibited perfect cycle stabilities as well, maintaining 100 % (0.5 C), 99.7 % (2 C), 98.9 % (5 C), and 96.6 % (10 C) of the first discharge capacity after 100 cycles at different rates, respectively.

Mesoporous manganese oxides (MnO2) were synthesized via a facile chemical deposition strategy. Three kinds of basic precipitants including sodium carbonate (Na2CO3), sodium bicarbonate (NaHCO3), and sodium hydroxide (NaOH) were employed to adjust the microstructures and surface morphologies of MnO2 materials. The obtained MnO2 materials display different microstructures. Great differences are observed in their specific surface area and porosity properties. The microstructures and surface morphologies characteristics of MnO2 materials largely determine their pseudocapacitive behavior for supercapacitors. The MnO2 prepared with Na2CO3 precipitant exhibits the optimal microstructures and surface morphologies compared with the other two samples, contributing to their best electrochemical performances for supercapacitors when conducted either in the single electrode tests or in the capacitor measurements. The optimal MnO2 electrode exhibits a high specific capacitance (173 F g–1 at 0.25 A g−1), high-rate capability (123 F g−1 at 4 A g−1), and excellent cyclic stability (no capacitance loss after 5,000 cycles at 1 A g−1). The optimal activated carbon//MnO2 hybrid capacitor exhibits a wide working voltage (1.8 V), high-power and high-energy densities (1,734 W kg−1 and 20.9 Wh kg−1), and excellent cycling behavior (93.8 % capacitance retention after 10,000 cycles at 1 A g−1), indicating the promising applications of the easily fabricated mesoporous MnO2 for supercapacitors.

An amine-Fe3O4 modified glassy carbon (GC) electrode was constructed for detecting Pb(II) ions in wastewater. The electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Square wave anodic stripping voltammetry (SWASV) was used to detect the Pb(II), and the detection limit of Pb(II) was 0.15 µM. The sensitivity of the electrode to detect Pb(II) was about 10.07 µA/µM, with a correlation coefficient of 0.991, which was approximately 10 times bigger than that of a pure Fe3O4 modified electrode. The electrode also showed good selectivity and stability. This results indicated that the amine-magnetite material could have some potential applications in heavy metal ions detection in wastewater.

We present a new method for specific detection of oxytetracycline (OTC) at nanomolar concentrations based on a microfabricated cantilever array. The sensing cantilevers in the array are functionalized with self-assembled monolayers (SAMs) of OTC-specific aptamer, which acts as a recognition molecule for OTC. While the reference cantilevers in the array are functionalized with 6-mercapto-1-hexanol SAMs to eliminate the influence of environmental disturbances. The cantilever sensor shows a good linear relationship between the deflection amplitude and the OTC concentration in the range of 1.0-100 nM. The detection limit of the cantilever array sensor is as low as 0.2 nM, which is comparable to some traditional methods. Other antibiotics such as doxycycline and tetracycline do not cause significant deflection of the cantilevers. It is demonstrated that the cantilever array sensors can be used as a powerful tool to detect drugs with high sensitivity and selectivity.

Carbon coated LiFePO 4 cathode materials were successfully synthesized by heating the precursors of FePO 4 @PAn (polyaniline) and equimolar LiOH·H 2 O under Ar flow. We demonstrated a method that could precisely control the carbon shell in a single reaction step. The precursors of FePO 4 @PAn were prepared by in situ polymerization of aniline and precipitation of FePO 4 in one pot in the presence of hydrogen peroxide as oxidizer. In the obtained core–shell cathode composite, the LiFePO 4 core phase was crystalline while the carbon shell had the thickness of several nanometers. The optimized cathode material exhibited satisfactory rate and cycle performance, which virtues are quite suitable for power lithium ion batteries.

In this paper, a novel room temperature molten salt electrolyte based on lithium bis(oxalato)borate (LiB(C2O4)2, LiBOB) and 2-Oxazolidinone (C3H5NO2, OZO) has been prepared as the electrolyte of electrochemical capacitors (EDLCs). The conductivity, thermal stability and electrochemical stability of the LiBOB-OZO electrolytes are investigated. It shows excellent thermal stability, high ionic conductivity (up to 10.4mS cm−1) and a wide electrochemical stability window (4.5 V). The temperature dependence of conductivity for the electrolytes follows the VFT equation, which demonstrates a solvent-assisted ionic conductivity mechanism. Based on it, a specific recipe of the LiBOB-OZO electrolytes (with a molar ratio of 1:6) is evaluated by cylic voltammetry, AC impedance spectroscopy, and galvanostatic charging-discharging in a test EDLC capacitor. It is found that the EDLC with the LiBOB-OZO complex electrolyte can be charged up to 2.5 V, the specific capacitance based on an activated carbon electrode can reach 92.5 F g−1 at 50°C, the equivalent series resistance (ESR) decreases sharply from 18.2 Ω at 30 °C to 7.2 Ω at 70 °C. Then, an EDLC of higher energy density and power density can be obtained，especially in the temperatures above 50 °C

Room temperature molten salts or ionic liquids are promising “solvent-free” electrolytes for high-voltage double layer supercapacitors. In this work, a novel binary room temperature molten salt electrolyte based on LiBOB and acetamide has been prepared. The electrolyte shows excellent thermal stability, high ionic conductivity and a wide electrochemical stability window, especially at higher temperatures. The temperature dependence of conductivity for the electrolytes follows the VFT equation, which demonstrates a solvent-assisted ionic conductivity mechanism. The EDLC with the LiBOB-acetamide complex electrolyte at molar ratio of 1:6 can be charged up to 2.5 V with better rate performance. The specific capacitance based on activated carbon electrodes can reach 103.1 F g−1. It is reasonable to assume that LiBOB-acetamide complex system has advantages as electrolyte for EDLCs with high energy density.

For enhancement of lithium-ion transference number, lithium-ion-conductive polymer electrolytes have been prepared from polyethylene oxide (PEO), lithium salt of LiCF3SO3 or LiF, plasticizer of polyethylene glycol dimethylether (PEGDME), and anion receptor of tris(pentafluorophenyl)borane (TPFB). Transport properties of the resultant polymer electrolytes have been studied by AC impedance spectroscopy. As a result, lithium-ion transference number increased with increasing TPFB due to the restriction of anion conduction by the interaction between anion and anion receptor. Effects of anion receptor on transport properties are discussed.

The electrochemical properties Of PW12O403- (abbreviated as PW12) anion in poly(ethylene glycol) (PEG) have been studied by cyclic voltammetry, complex impedance and FT-IR spectroscopy. The PW12 anion in PEG-LiClO4 electrolyte shows reasonable facile electrochemistry, and the diffusion coefficients Of PW12 were measured with microelectrode. It is shown that ionic conductivity of polymer electrolytes based on low molecular weight PEG can be improved by the addition of PW12. The increase of conductivity is coupled with decrease of transient cross-links density of polymer chains which is evidenced by the downshift of C-O-C stretching mode. The phenomena are explained in view of ion-ion and ion-polymer interactions.

The effects of plasticizer ethylene carbonate (EC) on the AC impedance spectra and the ionic conductivity are reported. With increasing of EC concentration the semicircle in high frequency disappears, and the slope of the straight line in low frequency decreases. The data obtained from impedance experiments can be explained using an equivalent circuit proposed. On the other hand, the room temperature conductivity increases with EC concentration because of the increase of the segmental flexibility of PEO. For lower EC concentration samples, the temperature dependence of conductivity in low temperature range follows Arrhenius type, but when EC concentration is larger than 20%, the temperature dependence of conductivity obeys the Vogel-Tamman-Fulcher (VTF) equation in all temperature ranges.

Composite polymeric electrolytes of PEO-LiClO4-Al2O3 and PEO-LiClO4-EC were prepared and the ionic conductivity by a.c. impedance was calculated using four different methods, and three kinds of representations of a.c. impedance spectra were adopted. The first is based on the Nyquist impedance plot of the imaginary part (Z″) versus the real part (Z′) of the complex impedance. The second and the third correspond to the plots of imaginary impedance Z″ as a function of frequency (f), and the absolute value (|Z|) and phase angle (θ) as a function of f, respectively. It was found that the values of the ionic conductivity calculated using the three representations of a.c. impedance spectra are basically identical.

A composite solid polymer electrolyte (SPE) of (PEO)(10)LiClO4-Al2O3 was prepared and Pt and stainless steel(SS) blocking electrodes were used for an impedance study. It was found that the semicircle in the high frequency range and the straight line in the low frequency range depend upon different blocking electrodes and polarization potentials applied in the experiments. In the equivalent circuit. two constant phase elements (CPE) have been used instead of the pure geometrical and double layer capacitances. respectively. A theoretical line calculated from their estimated values has a good correlation with the experiment data. Moreover. the equivalent circuit also can be used to explain the impedance properties of Pt and stainless steel (SS) blocking electrodes both in the high and the low frequency ranges. (C) 2001 Elsevier Science Ltd. All rights reserved.

Heterogeneous electron transfer rate constants (k(s)) and diffusion coefficients (D) of the ferrocene and its derivatives. in a new synthetic comb polymer solvent, poly(dimethylsiloxane-g-monomethylether polyethylene glycol) (SCP), and several other polymer solvents were estimated by using microelectrodes. Also, the influence of various supporting electrolytes on k(s) and D of ferrocene was studied. It was shown that k(s) and D of ferrocene decreased with increasing anionic size of the supporting electrolyte, but k(s) tended to increase with increasing radius of the solvated cation. Also, the cationic size of the supporting electrolytes had little effects on D. The values of k(s) and D for the ferrocene derivatives in the polymer solvents were in sharp contrast to those in monomeric solvents. Thus. the k(s) values were proportional to D in the polymer solvents. which indicates that solvent dynamics control of the electrode reaction. The values of k(s) and D of ferrocene in SCP were larger than those in other polymer solvents indicating that SCP is a good polymer solvent. (C) 2000 Elsevier Science B.V. All rights reserved.

The electron self-exchange rates (kex) of viologen and its derivatives are estimated by using microelectrode voltammetry in poly(ethylene glycol) films. The dependences of supporting electrolyte concentration and sizes of viologen and its derivatives on kex and diffusion coefficients (D) are discussed. Results show that kex increases with the decrease of supporting electrolyte concentration and sizes of reactants. Keywords: Viologen, Electron self-exchange rate, Poly(ethylene glycol)

The heterogeneous electron transfer rate constant (ks) of dimethylferrocene (DMFc) was estimated using cyclic voltammetric peak potential separations taken typically in a mixed diffusion geometry regime in a polyelectrolyte, and the diffusion coefficient (D) of DMFc was obtained using a steady-state voltammogram. The heterogeneous electron transfer rate constant and diffusion coefficient are both smaller by about 100-fold in the polymeric solvent than in the monomeric solvent. The results are in agreement with the difference of longitudinal dielectric relaxation time (τL) in the two kinds of solvents, poly(ethylene glycol) (PEG) and CH3CN, indicating that ks varies inversely with τL; ks is proportional to D of DMFc. Both D and ks of DMFc in PEG containing different supporting electrolytes and at different temperatures have been estimated. These results show that D and ks of DMFc increase with increasing temperature in the polyelectrolyte, whereas they vary only slightly with changing the supporting electrolyte.

This paper presents a microelectrode voltammetric determination of heterogeneous electron transfer rate constants ( k s ) and diffusion coefficients ( D ) of 7,7,8′,8′-tetracyanoquinodimethane (TCNQ) in polyelectrolytes. The diffusion coefficients are estimated using cyclic voltammetry under linear diffusion conditions, and the heterogeneous electron transfer rate constants are obtained under mixed linear and radial diffusion in the polyelectrolyte. k s and D increase with increasing temperature, and the activation barriers of the electrode reaction for reduction of TCNQ are obtained. On the other hand, the dependencies of D and k s of TCNQ on the size and charge of the counterion are compared in the polyelectrolyte.

The heterogeneous electron transfer rate constants (k(s)) of seven ferrocene derivatives were estimated using cyclic voltammograms under mixed spherical/semi-infinite linear diffusion and steady-state voltammetry at a microdisk electrode in polymer electrolyte. The k(s) and diffusion coefficient (D) are both 100 to 1000-fold smaller in polymer solvent than in monomeric solvents, and the D and k(s) decrease with increasing polymer chain length. The results conform to the difference of viscosity (eta) or relaxation time (tau(L)) for these different solvents. The k(s) and D increase with increasing temperature, and the activation barriers of the electrode reaction are obtained. The influences of the substituting group in the ferrocene ring on k(s) and D are discussed. The k(s) are proportional to the D of the ferrocene derivatives, which indicates that solvent dynamics control the electrode reaction. (C) 1998 Elsevier Science S.A.

The diffusion coefficients (D) of quinhydrone were estimated in polymer electrolytes by using non-steady-state chronoamperometry and steady-state current voltammetry. The D values have been estimated in polyethylene glycol (PEG) containing different concentrations, and cations of supporting electrolytes, and in different solvents over a range of temperatures. The dependencies of electroactive probe diffusion coefficients on temperature, supporting electrolyte concentration and polymer chain length are discussed. The results show that D increases with increasing temperature and decreasing concentration of supporting electrolyte. The diffusion coefficient depends strongly on the length of polymer chain and decreases sharply with increasing polymer chain length. The contribution of electron self-exchange has been explored and it seems to be negligible here.

We report a simple and sensitive method for label-free detection of single-stranded DNA-binding protein (SSBP) based on an array of microfabricated cantilevers. The single-stranded DNA (ssDNA) was immobilized on the surface of the sensing cantilevers to detect SSBP, while the reference cantilevers were modified with 6-mercapto-1-hexanol to detect any unwanted cantilever deflection. The differential deflection signals that reveal specific SSBP-ssDNA binding have been found to depend on the SSBP concentration. Using the cantilever array sensor we can detect SSBP in the concentration range from 0.01 to 7 mu g mL(-1). Other proteins, such as thrombin or bovine serum albumin induced no significant deflection of the cantilevers. Our results show the potential for the application of cantilever array sensor system as a powerful tool to detect proteins with high sensitivity and specificity. (C) 2013 Elsevier B.V. All rights reserved.