A novel nickel-based mixed rare-earth oxide/activated carbon supercapacitor using room temperature ionic liquid electrolyte

Mesopore nickel-based mixed rare-earth oxide (NMRO) and activated carbon (AC) with rich oxygen-contained groups were prepared as electrode materials in a supercapacitor using room temperature ionic liquid (RTIL) electrolyte. These electrode materials were characterized by XPS, XRD, N₂ adsorption, SEM as well as various electrochemical techniques, and showed good properties and operated well with RTIL electrolyte. A 3 V asymmetrical supercapacitor was fabricated, which delivered a real power density of 458 W kg⁻¹ as well as a real energy density of 50 Wh kg⁻¹, and during a 500-cycle galvanostatic charge/discharge measurement, no capacity decay was visible. Such promising energy-storage performance was to a large extent ascribed to nonvolatile RTIL electrolyte with wide electrochemical windows and high stable abilities worked with both electrode materials.     

Synthesis and characterization of Ru doped CuO thin films for supercapacitor based on Bronsted acidic ionic liquid

The synthesis of nanostructured ruthenium (Ru) doped copper oxide (CuO) thin films by colloidal solution method and ionic liquid are presented. The prepared colloidal solution was spin coated on the stainless steel substrates. The coated films were used to measure the specific capacitance in the task specific Bronsted acidic that is in 3-carboxymethyl-1-methylimidazolium bisulfate [CMIM] [HSO₄] ionic liquid (IL). Further, the films were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Fourier transform Raman spectroscopy (FT-Raman) and cyclic voltammetry (CV). The Ru doped CuO films exhibit higher specific capacitance, C_sp (C_sp = ratio of average current in CV and a product of scan rate and mass deposited on the film) with the larger potential window as compared to undoped CuO film. The highest C_sp of 406 F g⁻¹ was observed for 15 volume percent of Ru doping concentration. This is the first successful step towards development of ecofriendly CuO based supercapacitors in task specific IL synthesized by green technology.     

Improving the durability of Prussian blue based on nano-composite thin film in Li based liquid electrolyte

In this paper, we present a fabrication of a nano-composite Prussian blue (NPB) film to improve the durability of a regular PB film in an anhydrous Li⁺ based liquid electrolyte. The NPB film consists of random arrangement of indium tin oxide (ITO) nano-particles electrodeposited of PB. The improvement in durability of the NPB film is examined with quantitative comparison of the regular PB film from cyclic voltammetry (CV) and transmittance experiments. The improvement in durability in relationship with the crack formation and the porosity in PB and NPB films is discussed and examined. Our results demonstrate that NPB films can efficiently enhance the long-term cycling stability in anhydrous Li⁺ based liquid electrolytes.     

Electrochemical and interfacial behavior of a FeSi2.7 thin film electrode in an ionic liquid electrolyte

A FeSi_2.7 thin film is deposited on a copper substrate by RF magnetron sputtering of a Fe–Si alloy target. The electrochemical behavior of the FeSi_2.7 electrode in ionic liquid electrolyte based on 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide is investigated and compared with that of a FeSi_2.7 electrode in conventional liquid electrolyte. The FeSi_2.7 electrode in the ionic liquid electrolyte delivers an initial discharge capacity of 756 mAh g⁻¹ at room temperature, and its discharge capacity is maintained to be 92% of the initial discharge capacity after the 100th cycle. AC impedance and FTIR analysis reveal that the formation of a stable solid electrolyte interphase (SEI) layer on the FeSi_2.7 electrode in the ionic liquid electrolyte leads to a good capacity retention. This study demonstrates that the FeSi_2.7 electrode exhibits stable cycling behavior and good interfacial characteristics in the ionic liquid electrolyte without any solvents and additives.     

Hybrid supercapacitor based on poly(aniline-co-m-anilicacid) and activated carbon in non-aqueous electrolyte

A hybrid asymmetrical super capacitor has been fabricated based on p-doped poly(aniline-co-m-anilicacid) and activated carbon coated on SS electrodes. The characterization of material, electrode and performance of the super capacitor has been studied by FTIR, Cyclic Voltammetry, TGA/DTA, AC Impedance spectroscopy, and galvanostatic charge-discharge tests. The super capacitor showed a maximum specific capacitance of 102 F/g at a scan rate of 10 mV/s. The normalized active-reactive power behavior of the capacitor has been determined. The time constant calculated for the super capacitor is 6 milliseconds, indicating the suitability of the system for efficient use at low frequency range.     

Symmetric lithium-ion cell based on lithium vanadium fluorophosphate with ionic liquid electrolyte

Lithium vanadium fluorophosphate, LiVPO₄F, was utilized as both cathode and anode for fabrication of a symmetric lithium-ion LiVPO₄F//LiVPO₄F cell. The electrochemical evolution of the LiVPO₄F//LiVPO₄F cell with the commonly used organic electrolyte LiPF₆/EC-DMC has shown that this cell works as a secondary battery, but exhibits poor durability at room temperature and absolutely does not work at increased operating temperatures. To improve the performance and safety of this symmetric battery, we substituted a non-flammable ionic liquid (IL) LiBF₄/EMIBF₄ electrolyte for the organic electrolyte. The symmetric battery using the IL electrolyte was examined galvanostatically at different rates and operating temperatures within the voltage range of 0.01–2.8 V. It was demonstrated that the IL-based symmetric cell worked as a secondary battery with a Coulombic efficiency of 77% at 0.1 mA cm⁻² and 25 °C. It was also found that the use of the IL electrolyte instead of the organic one resulted in the general reduction of the first discharge capacity by about 20–25% but provided much more stable behavior and a longer cycle life. Moreover, an increase of the discharge capacity of the IL-based symmetric battery up to 120 mA h g⁻¹ was observed when the operating temperature was increased up to 80 °C at 0.1 mA cm⁻². The obtained electrochemical behavior of both symmetric batteries was confirmed by complex-impedance measurements at different temperatures and cycling states. The thermal stability of LiVPO₄F with both the IL and organic electrolytes was also examined.     

Solvent effect on the ion adsorption from ionic liquid electrolyte into sub-nanometer carbon pores

This paper presents the results from the investigation of the influence of ion size on the capacitance behaviour of TiC-derived carbon (CDC) powders in the ethyl-methylimmidazolium-bis(trifluoro-methane-sulfonyl)imide ionic liquid (EMI, TFSI) used as neat electrolyte at 60 °C or as salt dissolved in acetonitrile and tested at room temperature. These studies were carried out with the assembly of conventional 3-electrode electrochemical cells as well as using the Cavity-MicroElectrode (CME) technique. The issues regarding the extents of desolvation of the electrolyte ions when adsorbed in the pores of the CDCs under applied potential were studied, the CME technique was found to be particularly efficient in the deduction of the effective ion size under solvated conditions.     

Effect of methylsisesquioxane filler on the properties of ionic liquid based polymer electrolyte

Composite electrolyte comprising methylsisesquioxane (MSQ) filler and 1-butyl-3-methyl-imidazolium-tetrafluoroborate (BMImBF₄) ionic liquid (IL) in poly(2-hydroxyethyl methacrylate) (PHEMA) matrix had been prepared. The polymer matrix was formed by free radical polymerization of HEMA macromer, and MSQ was produced in situ from methyl-trimethoxysilane by the sol-gel method. Infrared spectroscopy and dynamic mechanical analysis were employed to give insight into the interactions among the methylsisesquioxane filler, BMImBF₄ and the PHEMA polymer matrix. The PHEMA-IL-MSQ hybrids and the PHEMA-IL electrolyte without MSQ were investigated regarding their ionic conductivity and thermal and electrochemical properties. BMImBF₄ increased the thermal stability of the polymer and provided the ion conductivity; MSQ filler as the additive increased the mechanical strength of the polymer and provided the ion conductive pathway. The electrolyte with MSQ at the 10 wt% showed the highest ionic conductivity of 5×10⁻⁴ S cm⁻¹ which was five times higher than that of the electrolyte without MSQ, and the electrochemical window was up to 3.6 V.     

Effects of specific surface area of electrode and different electrolyte on capacitance properties in nano porous-structure CrN thin film electrode for supercapacitor

Thickness and specific surface area of the film electrode are critical parameters for supercapacitors. The relationship between the thickness and the specific surface area of the film directly affects the capacitance and electrochemical stability performance of super supercapacitors, which virtually affects the contact chance of ion in the electrolyte on the surface of electrode and the ion transport path of electrode. In this paper, the CrN thin films with a thickness of 200–3500 nm are prepared using direct current magnetron sputtering. Atomic force microscopy (AFM) technique is introduced to investigate the relationship between thickness and the specific surface area of the CrN films. The electrochemical performances of CrN electrode with the nanoporousper structure is analyzed in different electrolytes H₂SO₄, Na₂SO₄ and NaCl aquous solutions. The specific surface area of the film increases linearly with the film thickness increases. The areal capacitance is also linearly related to the specific surface area. The spurtted CrN film with a thickness of 3370 nm has a specific surface of up to 43.59 cm² per cm² footprint area. Its areal and volume capacitances reache to 53.92 mF cm^?2 and 650 F cm^?3 at 5 mV s^?1, respectively. In addition, the areal capacitance of CrN film electrode with 655 nm possesses reaches to 40.53 mF cm^?2 for 0.5 M H₂SO₄ solution, 32.69 mF cm^?2 for 0.5 M Na₂SO₄ solution and 9.17 mF cm^?2 for NaCl solution at a scan rate of 5 mV s^?1. Furthermore, the CrN film electrode exhibits excellent capacitance retention of 95.3%, 93.8% and 89.9% in H₂SO₄, Na₂SO₄ and NaCl electrolytes, respectively, after 2000 cycles. Therefore, the sputtered CrN thin film is an potential electrode material for electrochemical supercapacitors.     

Dip coated nanostructured ZnO thin film: Synthesis and application

The preparation and characterization of highly selective room temperature ammonia sensorusing nanostructured dip coated ZnO thin films were discused. A highly viscous precursor solution was prepared using Zinc Nitrate hexahydrate as a starting material and Sodium Carboxymethyl Cellulose as a thickening agent. Morphology and structure of the annealed films were analyzed by field emission scanning electron microscopy and X-ray Diffractometer characterization techniques. The presence of zinc and oxygen in the sample was confirmed with Fourier Transform Infrared spectroscopy The gas sensing behavior of ZnO thin films was studied at room temperature. It exhibited very high selectivity and excellent sensing towards ammonia gas. Further, sensing behavior towards other gases like ethanol and formaldehyde and the various concentrations of NH₃ were studied.     

Sulfur-mesoporous carbon composites in conjunction with a novel ionic liquid electrolyte for lithium rechargeable batteries

Sulfur coated mesoporous carbon (S-C) composites have been synthesized and physically characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. Firstly, the electrochemical properties of the S-C composite cathode materials were tested in a conventional electrolyte consisting of 1 mol/L lithium bistrifluoromethanesulfonimidate in poly(ethylene glycol) dimethyl ether to compare them with pure sulfur electrode. The capacity and cyclic stability of the S-C composite were improved. Then the S-C composites were tested in a novel ionic liquid electrolyte consisting of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and lithium bistrifluoromethanesulfonimidate. The capacity and cyclic stability of the S-C composite using the ionic liquid electrolyte were much better than for the sample tested in a conventional organic solvent electrolyte.     

Investigation of polymer electrolyte hybrid supercapacitor based on manganese oxide-carbon electrodes

A hybrid supercapacitor based on manganese oxide, activated carbon and polymer electrolyte was developed and electrochemically investigated. The capacitive performance obtained from the polymer electrolyte based supercapacitor was similar to that of an aqueous electrolyte based supercapacitor, tested for comparison in the same operative conditions. A durability test carried out for 2500 cycles showed stable and slowly increasing performance. The specific capacitance of hybrid supercapacitor was 48 F g⁻¹ (192 F g⁻¹ as a mean one electrode capacitance), in which that of the positive electrode was 384 F g⁻¹ of MnO₂ and that of negative electrode 117 F g⁻¹ of carbon. The impedance analysis evidenced that although the polymer electrolyte based hybrid supercapacitor showed higher resistance compared to that of the liquid electrolyte based supercapacitor, this drawback was counterbalanced by better ion transport features, which were evident at lower frequencies, where similar values of capacitances were obtained from the different supercapacitors.     

基于低共熔溶剂体系的氮掺杂超级电容炭

以杉木屑为原料,氯化锌和尿素为低共熔溶剂,炭活化后制备了氮掺杂活性炭,采用正交实验设计考察了浸渍比、活化温度和活化时间对活性炭电化学性能的影响。采用比表面积(BET)、X射线光电子能谱(XPS)、循环伏安、恒流充放电等表征手段研究了材料的孔隙结构和表面化学元素及电化学性能。研究结果表明：最佳工艺条件是浸渍比为4,活化温度为750℃,保温时间为3h。对活性炭的孔隙结构进行分析,可以发现低共熔溶剂活化后的活性炭有利于微孔的形成且比表面积可达到797.82m²/g,氮含量为11.55%,其中氮元素化合态主要表现为吡啶型N、吡咯型N和石墨型N。在6mol/L的KOH电解液中,当电流密度1A/g时,可达233.85F/g的比电容,当电流密度增加到20A/g时,比电容依然能够维持在159.6F/g。     

Platinum-alloy nanostructured thin film catalysts for the oxygen reduction reaction

In an effort to study advanced catalytic materials for the oxygen reduction reaction (ORR), a number of metallic alloy nanostructured thin film (NSTF) catalysts have been characterized by rotating disk electrode (RDE). Optimal loadings for the ORR and activity enhancement compared to conventional carbon supported nanoparticles (Pt/C) were established. The most efficient catalyst was found to be PtNi alloy with 55 wt% of Pt. The enhancement in specific activity is more than one order of magnitude, while the improvement factor in mass activity is 2.5 compared to Pt/C. Further lowering of the platinum to nickel ratio in NSTF catalysts did not lead to increased mass activity values.     

SMA polymer thin film electrodeposition on carbon particles

Electrodeposition of styrene-co-maleic anhydride (SMA) polymer, as thin films on carbon particle substrates, was carried out in a fluidized electrode bed reactor (FEBR). Feeder current, time of deposition, flow rate of anolyte (i.e., bed expansion or bed porosity), concentration of SMA in the anolyte, and pH of the anolyte were the key parameters investigated. The film characteristics were evaluated through SEM and FTIR analyses, the amounts determined by weighing. The effect of these parameters on the electrodeposition process is discussed and optimum conditions for deposition are proposed. Also, a possible mechanism for electrodeposition, particularly for the SMA–carbon system, is discussed. Furthermore, where relevant, the parameters and mechanism are compared with those for our parallel work on the ethylene-co-acrylic acid (EAA)–carbon system.     

Comparative investigation on electrochemical behavior of hydroquinone at carbon ionic liquid electrode, ionic liquid modified carbon paste electrode and carbon paste electrode

Ionic liquid, 1-heptyl-3-methylimidazolium hexafluorophosphate (HMIMPF₆), has been used to fabricate two new electrodes, carbon ionic liquid electrode (CILE) and ionic liquid modified carbon paste electrode (IL/CPE), using graphite powder mixed with HMIMPF₆ or the mixture of HMIMPF₆/paraffin liquid as the binder, respectively. The electrochemical behaviors of hydroquinone at the CILE, the IL/CPE and the CPE were investigated in phosphate buffer solution. At all these electrodes, hydroquinone showed a pair of redox peaks. The order of the current response and the standard rate constant of hydroquinone at these electrodes were as follows: CILE > IL/CPE > CPE, while the peak-to-peak potential separation was in an opposite sequence: CILE < IL/CPE < CPE. The results show the superiority of CILE to IL/CPE and CPE, and IL/CPE to CPE in terms of promoting electron transfer, improving reversibility and enhancing sensitivity. The CILE was chosen as working electrode to determine hydroquinone by differential pulse voltammetry, which can be used for sensitive, simple and rapid determination of hydroquinone in medicated skin cosmetic cream.     

Direct electron transfer of hemoglobin in a CdS nanorods and Nafion composite film on carbon ionic liquid electrode

In this paper the direct electron transfer of hemoglobin (Hb) was carefully investigated by using a room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF₆) modified carbon paste electrode (CILE) as the basal working electrode. Hb was immobilized on the surface of CILE with the nanocomposite film composed of Nafion and CdS nanorods by a step-by-step method. UV–vis and FT-IR spectra showed that Hb in the composite film remained its native structure. The direct electrochemical behaviors of Hb in the composite film were further studied in a pH 7.0 phosphate buffer solution (PBS). A pair of well-defined and quasi-reversible cyclic voltammetric peaks of Hb was obtained with the formal potential (E⁰′) at −0.295 V (vs. SCE), which was the characteristic of heme Fe(III)/Fe(II) redox couples. The direct electrochemistry of Hb was achieved on the modified electrode and the apparent heterogeneous electron transfer rate constant (k_s) was calculated to be 0.291 s⁻¹. The formal potentials of Hb Fe(III)/Fe(II) couple shifted negatively with the increase of buffer pH and a slope value of −45.1 mV/pH was got, which indicated that one electron transfer accompanied with one proton transportation. The fabricated Hb sensor showed good electrocatalytic manner to the reduction of trichloroacetic acid (TCA).     

Cycling stability of a hybrid activated carbon//poly(3-methylthiophene) supercapacitor with N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid as electrolyte

A long cycle-life, high-voltage supercapacitor featuring an activated carbon//poly(3-methylthiophene) hybrid configuration with N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid, a solvent-free green electrolyte, was developed. The cyclability of a laboratory scale cell with electrode mass loading sized for practical uses was tested at 60 °C over 16,000 galvanostatic charge-discharge cycles at 10 mA cm⁻² in the 1.5 and 3.6 V voltage range. The reported average and maximum specific energy and power, specific capacitance and capacity, equivalent series resistance and coulombic efficiency over cycling demonstrate the long-term viability of this ionic liquid as green electrolyte for high-voltage hybrid supercapacitors.