Inorganic Cathode Research Articles

Alcohol dehydrogenase as bioanode for methanol and ethanol oxidation in a microfluidic fuel cell

In this work, an enzymatic bioanode was developed using functionalized carbon nanofibers for the immobilization of alcohol dehydrogenase enzyme, using Nafion, tetrabutylammonium bromide and glutaraldehyde onto Toray carbon paper. Two alcoholic fuels, methanol (MeOH) and ethanol (EtOH) were used to demonstrate the oxidation versatility of the electrode created as well as being able to convert energy from these fuels using an air-breathing microfluidic device. Commercial Pt/C (30% E-TEK) onto carbon nanofoam (Marketech Inc) was using as inorganic cathode. Carbon nanofibers were previously treated with nitric acid to produce oxygen-containing functional groups in order to facilitate the enzyme immobilization. A phosphates buffer solution pH 8.86 was used as electrolyte. The use of ethanol as fuel shows a better performance obtaining 8.643mAcm−2 and 0.847 V as current density and open circuit voltage respectively, compared to that use methanol as fuel (2.655 mAcm−2 and 0.567V).

Aromatic Polyimide Based Composites for Ultrafast and Sustainable Lithium Ion Batteries

Although lithium-ion batteries based on inorganic cathodes have been utilized in a wide range of applications, they still face challenges such as safety, power density and sustainability. Thus, efforts have been directed to look for alternative, greener and naturally abundant electrode materials for application in lithium ion batteries. As a result, different organic electrodes have been intensively investigated. Among them, aromatic polyimide is a very promising candidate with a theoretical capacity approaching 400 mA h g-1 and a working voltage around 2.5 V vs. Li/Li+. During the discharge process (lithium intake), aromatic polyimide can stepwise accept two electrons, resulting in the formation of a delocalized radical anion and dianion. Currently, there are two common issues preventing the practical application of aromatic polyimide. One is poor rate capability due to their low electronic conductivity and the other one is the rapid capacity fading during cycling due to the dissolution of the active organic cathodes. To overcome the intrinsic electrical insulation of aromatic polyimides and obtain high rate performance, highly conductive carbon additives such as graphene or carbon nanotubes and electron conductive polymers were used to make the polyimide composites. The effect of the type and the amount of conducting agents on the rate performance and long cycling stability of the aromatic polyimide composites based lithium ion batteries will be presented.

Immobilization of the Alcohol Dehydrogenase Enzyme on TiO2 Nanotubes for Application in Microfluidic Fuel Cell

Microfluidic fuel cells are a low-power demand fuel cells which work without the need of a physical membrane and have a wide range of potential applications. Biological catalysts such as immobilized enzymes can be used in electrodes to carry out the oxidation processes of different organic fuels using the immobilization technology of enzymes; they are carried out under moderate conditions of pH and temperature, and the specificity of the catalytic reactions. The alcohol dehydrogenase enzyme has been used for the development of bioanodes for the oxidation of different alcohols such as ethanol and methanol. In this work, the immobilization of this enzyme was carried out using nanotubes of titanium dioxide for the development of electrodes for an air-breathing microfluidic fuel cell. TiO2 nanotubes has excellent properties such as pH resistance, superior mechanical strength, good biocompatibility making it a great candidate for the process of immobilization of the enzyme alcohol dehydrogenase. TiO2 nanotubes were fabricated by electrochemical anodic oxidation on Ti foils. The foils were pre-treated with sand-paper, thereafter immersed in ethanol, placed in ultrasonic bath, dried under N2 flow. An ethylene glycol-based solution with a concentration of 0.1M NH4F (96% purity, Alfa-Aesar) and 2% w/w deionized water was used as electrolyte. The anodization times used was 1 h with a voltage step of 60 V via a power source. Using this nanostructure, the enzymatic electrode was constructed using a catalityc ink with enzyme, tetrabutylammonium bromide and Nafion to carry out the immobilization process. We carried out the characterization of the electrode developed by means of different electrochemical and kinetic techniques, where it was demonstrated that the enzyme is present and active in the electrode, as well as its capacity to oxidize ethanol. Then the bioanode was evaluated in the microfluidic device also using an inorganic cathode of Pt / C, obtaining a good performance over an open circuit potential greater than 0.93V.

PEDOT:Vitamin K1 Composites: An Electrochemical Study on Stable, Water‐Permeable, Proton‐Bonding Thin‐Film Electrodes

AbstractHerein we report detailed electrochemical studies of a conducting polymer composite that is engineered to selectively react with protons and that has reactive sites across the entirety of the volume due to the excellent water permeability throughout the film. This chemically modified electrode (CME) utilises a conducting polymer as the source of charge carrier and Vitamin‐K as the water‐insoluble redox species that bonds protons in reduction and releases protons in oxidation. The overall number of active proton bonding sites was found to be 1.36 × 1016 sites/cm2, with a redox capacity of ∼64 mAh/g, which makes this CME comparable to modern inorganic cathodes. The electrode exhibited insignificant degradation after 500 cycles. The composite is relatively simple to manufacture as it requires no purification steps as part of the processing.

Twisted Perylene Diimides with Tunable Redox Properties for Organic Sodium‐Ion Batteries

AbstractOrganic rechargeable batteries gain huge scientific interest owing to the design flexibility and resource renewability of the active materials. However, the low reduction potentials still remain a challenge to compete with the inorganic cathodes. This study demonstrates a simple and efficient approach to tune the redox properties of perylene diimides (PDIs) as high voltage cathodes for organic‐based sodium‐ion batteries (SIBs). With appropriate electron‐withdrawing groups as substituents on perylene diimides, this study shows a remarkable tunability in the discharge potential from 2.1 to 2.6 V versus Na+/Na with a sodium intake of ≈1.6 ions per molecule. Further, this study explores tuning the shape of the voltage profiles by systematically tuning the dihedral angle in the perylene ring and demonstrates a single plateau discharge profile for tetrabromo‐substituted perylene diimide (dihedral angles θ1 & θ2 = 38°). Detailed structural analysis and electrochemical studies on substituted PDIs unveil the correlation between molecular structure and voltage profile. The results are promising and offer new avenues to tailor the redox properties of organic electrodes, a step closer toward the realization of greener and sustainable electrochemical storage devices.

Progress in inorganic cathode catalysts for electrochemical conversion of carbon dioxide into formate or formic acid

As a greenhouse gas, carbon dioxide in the atmosphere is one of the key contributors to climate change. Many strategies have been proposed to address this issue, such as CO2 capture and sequestration (CCS) and CO2 utilization (CCU). Electroreduction of CO2 into useful fuels is proving to be a promising technology as it not only consumes CO2 but can also store the redundant electrical energy generated from renewable energy sources (e.g., solar, wind, geothermal, wave, etc.) as chemical energy in the produced chemicals. Among all of products from CO2 electroconversion, formic acid is one of the highest value-added chemicals, which is economically feasible for large-scale applications. This paper summarizes the work on inorganic cathode catalysts for the electrochemical reduction of CO2 to formic acid or formate. The reported metal and oxide cathode catalysts are discussed in detail according to their performance including current density, Faradaic efficiency, and working potentials. In addition, the effects of electrolyte, temperature, and pressure are also analyzed. The electroreduction of CO2 to formic acid or formate is still at an early stage with several key challenges that need to be addressed before commercialization. The major challenges and the future directions for developing new electrocatalysts for the reduction of CO2 to formic acid are discussed in this review.

Redox-Active Organic Electrodes for Pseudocapacitor Applications

Current lithium-ion battery technology depends on inorganic cathode materials, such as LiCoO2 and LiFePO4. However, large-scale energy storage applications, including renewable energy storage and load-leveling, require more sustainable and cost-effective electrode materials. Organic electrode materials have been studied owing to their potential advantages, including the use of earth-abundant sources, environmental friendliness, and high energy density.1 We also have been investigating various redox-active organic electrodes by utilizing dopamine,1 pyrene derivatives,2 and glucose.3 Here, we further investigate the charge storage properties of the biomass-derived carbonaceous materials with Li- and Na-ions. We reveal that the synthesized carbonaceous materials can exhibit high capacities over 180 mAh/g in both Li- and Na-ions by based on double layer capacitance and redox reactions. These carbonaceous materials can be fabricated as the composite electrodes by mixing with conductive nanocarbons, including carbon nanotubes or reduced graphene oxides. These carbon-based composite electrodes show a high rate-capability and remarkable cycling stability. These high-performance organic electrodes could be promising candidates for developing large-scale energy storage devices.

Achieving high specific capacity of lithium-ion battery cathodes by modification with “N–O˙” radicals and oxygen-containing functional groups

Enhancing the cathode capacity of lithium ion batteries (LIBs) has been one strategy to improve the energy density of batteries for electric vehicle applications, because of the limitation of inorganic cathode capacity.

New Organic Electrode Materials As Cathode and Anode for All Organic Li-Ion Greener Batteries

Li-ion batteries (LIBs) meet nowadays some development bottlenecks because of the world high energy needs prompting the necessity of technology improvements particularly in terms of energy density of the inorganic cathode materials traditionally used. In addition to the environmental and safety concerns which become of primal importance.1,2 Because of their interesting electrochemical performance, their large structural diversity, their natural environmental friendliness, the flexibility they offer and their potential low cost, organic electrode materials become more-and-more promising candidates (for both positive and negative electrodes) for the next generation of sustainable LIBs.2,3,4 Conjugated carbonyl compounds have been early recognized as interesting electroactive materials characterized by high energy/power density and high cycling stability, but their implementation is still limited to Li cells with the serious safety issue caused by Li dendrite.3 To be successful the Li-ion organic battery technology needs first, the implementation of a lithiated positive electrode able of competing with LiCoO2 or LiFePO4and second, a negative electrode material operating at the target potentials just above 0.5 V (0.5-1.0 V) providing high output voltage as well as safety. Seeking for such efficient organic materials, our research group has reported recently, for positive electrode application, two organic salts able to reversibly deintercalate Li ions with promising electrochemical performance.5,6 However their operating redox potential were still too low which makes them unstable in ambient environment (difficult to store) and reduce the final output voltage. Concerning the negative electrode application, we proposed π-extended carboxylate core unit thus improving the cycling rate capability.7,8 Herein we would like to report on the design, the preparation and the electrochemical performance of an efficient lithiated organic structure able of being reversibly delithiated at high redox potential (>3.0 V vs. Li+/Li0) as a lithiated organic positive electrode stable to air. We will also present a new approach with the aim to decrease the redox potential of carboxylate-based systems leading to a low operating redox potential (<0.8 V vs. Li+/Li0) allowing in addition to substitute copper-based current collector by aluminum. Both materials will pave the way toward a novel n-type all-organic Li-ion cell with a working voltage greater than 2 Volts. (1) Scrosati, B.; Garche, J. J. Power Sources 2010, 195, 2419−2430. (2) Poizot, P.; Dolhem, F. Energy Environ. Sci. 2011, 4, 2003−2019. (3) Song, Z.; Zhou, H. Energy Environ. Sci. 2013, 6, 2280−2301 (4) Liang, Y.; Tao, Z.; Chen, J. Adv. Energy Mater. 2012, 2, 742−769 (5) Renault, S.; Gottis, S.; Courty, M.; Chauvet, O.; Dolhem, F.;Poizot, P. Energy Environ. Sci. 2013, 6, 2124−2133. (6) Gottis, S.; Barrès A-L.; Dolhem, F.;Poizot, P. ACS Appl. Mater. Interfaces. 2014, 6, 10870−10876. (7) Fédèle, L.; Sauvage, F.; Bois, J.; Tarascon, J.-M.; Bécuwe, M. Electrochem. Soc. 2014, 161, A46−A52 (8) Fédèle, L.; Sauvage, F.; Bécuwe, M. J. Mater. Chem. 2014, 6, 18225−18228. Figure 1

Self-Polymerized Dopamine As an Organic Cathode for Lithium-Ion Batteries

The redox-active organic materials have been intensively investigated as promising candidates for replacing the inorganic cathodes in lithium-ion batteries (LIBs). In particular, quinone-based organic molecules, such as benzoquinone, naphthoquinone, and anthraquinone, have received considerable attention owing to their high redox potential, high theoretical capacity (up to 500 mAh g−1), and possibility of being synthesized from earth-abundant resources. However, these quinone derivatives cannot be directly used in common LIBs because of their high solubility in non-aqueous electrolytes. Dopamine, which has a similar molecular structure with adhesive proteins in mussel, can be self-polymerized on various types of substrates. It is interesting to note that one of the oxidation intermediates of dopamine, 5, 6-indolequinone, resembles the structures of benzoquinone and naphthoquinone, having a high theoretical capacity of 364 mAh/g. Despite its intrinsic redox characteristic of the quinone groups,1 the redox-active properties of the polydopamine (PDA) with lithium ions have not been reported yet. Here, we first demonstrated PDA as a promising organic cathode in LIBs. PDA showed a specific capacity of ~235 mAh/g at 0.14 C and ~140 mAh/g at ~27.4 C. We also investigated the energy storage mechanism in PDA and confirmed the existence of both electrical double-layer capacitance and pseudocapaitance. By using carbon nanotubes (CNTs) as 1D templates for the polymerization of dopamine, we prepared flexible PDA and CNT composite films. The composite films exhibited enhanced rate capability and excellent cycling stability owing to the unique combination of redox-active PDA and superior electrical conductivity of CNT.

Design of Composite Electrodes with Anion-Absorbing Active Materials

Organic radical polymers [1] and conjugated polymers provide exceptionally high rate capability when used as cathode materials for lithium-ion batteries. Upon charge (oxidation), these materials absorb anions from the electrolyte. In contrast, traditional inorganic cathode materials release lithium cations into the electrolyte during charge. All known negative electrode materials for lithium-ion batteries absorb lithium cations during charge. If a lithium-absorbing negative electrode is paired with a lithium-releasing positive electrode, then there is no net change in the salt content of the electrolyte (although there will be gradients in salt composition as lithium ions are transported from the anode to the cathode). However, salt content will decrease during charge of a cell with lithium-absorbing negative electrode and anion-absorbing positive electrode. Most experimental results published to date [1] have used thin, highly porous cathodes in small flooded laboratory cells. Such cells have a large excess of electrolyte, so the effects of salt consumption have not been strongly evident. However, many important applications, such as electric vehicles and portable power, highly value both volumetric energy density and fast charge capability. These applications also want to minimize cell resistance, so the electrolyte composition is selected to maximize conductivity. Typical carbonate electrolytes show a maximum in conductivity between 1.0 and 1.1 M concentration of LiPF6 salt. In a conventional high-energy-density cell design, the salt needed for charging the organic-radical-polymer positive electrode would exceed the total salt content of such a typical electrolyte in the cell. Some [2,3] have explored composites of anion-absorbing active materials (eg polypyrrole or PTMA) with lithium-iron phosphate. However, even if the anion-absorbing material is limited to 10 volume% of the positive electrode, it will cause the overall cell salt content to decrease by > 0.6 M in practical high-energy cell designs. Full-cell-sandwich simulations [4] can evaluate the impact of electrode design on the salt concentration distribution in the battery. Here we use a model that includes a composite positive electrode containing both inorganic lithium-releasing active material and organic anion-absorbing active material. The model is used to evaluate design tradeoffs for maximizing volumetric energy density.

New Polyimides As Electrode Materials for Li-Ion Batteries

Currently, Li-ion batteries are based on inorganic oxides as cathodes, although they fail in terms of safety and sustainability. Recently redox-active polymers have attracted considerable attention as an alternative to inorganic cathode materials due to their low solubility in common electrolytes, film forming ability, excellent thermal stability and tunable redox properties. Among redox polymers, polyimides (PIs) are known for their ability to undergo reversible electrochemical reduction/oxidation as well as for offering high capacities. To extensively explore the influence of chemical structure on the electrochemical properties of polymers a series of PIs based on three aromatic dianhydrides and various diamines incorporating ether segments, ionic fragments and additional lactone cycle were synthesized (Fig. 1). The expected improvement in the performance of the cells based on ionic PIs through the additional solvation of Li+ by ionic fragments was not reached feasibly because of the electrostatic repulsion effect. In contrast, the insertion of short ether moieties in PI’s backbone allows for the desired Li+ solvation, increase of their mobility and rise in the batteries capacity. Among synthesized series, PIs derived from 1,4,5,8-naphthalene tetracarboxylic acid dianhydride and 4,7,10-trioxa-1,13-tridecanediamine showed best battery performance: excellent charge/discharge efficiency, high specific capacity (up to 140 mAh g-1) and the capability to reversibly operate at relatively high rates (up to C/5). This work was supported by the Russian Foundation for Basic Research (projects no. 14-29-04039_ofi_m and 16-03-00768_a) and by European Commission (project no. 318873 «IONRUN»). Electrochemical experiments were run at CIC Energigune through a collaboration with Polymat. Figure 1

Perylenediimide dyes as a cheap and sustainable cathode for lithium ion batteries

Perylenediimide dyes are a large family of conjugated small molecules with redox-active carbonyl/hydroxyl groups, which can uptake and release Li ions reversibly as low cost organic materials for next generation lithium ion batteries. In this paper, we report a series of industrially available, low price and non-toxic perylenediimide dyes, which can reversibly bind 2 Li+ ions per molecular unit, delivering a redox capacity of 100–130mAhg−1 with excellent rate capability and cycling stability, offering an attractive alternative to conventional transition-metal-based inorganic cathodes for sustainable Li ion batteries.

Effect of a cathode buffer layer on the stability of organic solar cells

We present the effect of a cathode buffer layer on the performance and stability of organic photovoltaics (OPVs) based on a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM). Six kinds of cathode buffer layers, i.e. lithium fluoride, sodium chloride, NaCl/Mg, tris-(8-hydroxy-quinoline) aluminum, bathocuproine and 1,3,5-tris(2-N-phenylbenzimidazolyl)benzene, were inserted between the photoactive layer and an Al cathode, which played a dominant role in the device’s performance. Devices with the cathode buffer layers above exhibited improved performance. The degradation of these devices with encapsulation was further investigated in an inert atmosphere. The results indicated that devices with inorganic cathode buffer layers exhibited better stability than those with organic cathode buffer layers.

Redox-active organics/polypyrrole composite as a cycle-stable cathode for Li ion batteries

A high capacity and cycle-stable organic molecule/polymer composite is synthesized by physical doping of redox-active perylene-3,4,9,10-tetracarboxydiimide (PTCDI) in polypyrrole (PPy). The as-prepared PTCDI/PPy composite demonstrates a synergistic electrochemical activation, in which the insoluble large PTCDI anions act as a redox-active dopant to activate the PPy backbones, while the activated PPy backbones form a conductive network to promote the redox activity of PTCDI molecules for Li insertion/extraction reactions. As a result, the PTCDI/PPy composite demonstrated a considerably high reversible capacity of >100 mAh g−1 and a stable cyclability with 92% capacity retention over 200 cycles, possibly serving as a low cost and renewable alternative to the inorganic cathode materials for Li-ion batteries. Since such a physical doping method is simple and easily adoptable for different organic molecules and polymers, it may offer a new route for developing low cost and electrochemically active organic electrode materials.

Iron Cyanides As a Cathode Material for Lithium-Ion Batteries

Lithium ion battery is one of the most popular power sources for clean and efficient electrochemical energy storage and conversion. There are increasing interests for both the cathode and anode, in accordance with the development of portable electronic equipments, and automotive industry. As one of the potential alternatives, organic cathode1has advantages of low cost, environmentally friendly, easy fabrication compared to the inorganic cathodes. However, the low voltage plateau and poor cycle performance restrict its applications. Iron cyanide and its analogs2 have been pursued as attractive materials for fundamental research and large scale industrial applications since its electrochemical activity was first reported in 1978. These zeolite-like compounds have perfectly 3D polymeric frameworks due to the asymmetric CºN anion. Its large open spaces can not only accommodate transition metal ions but also some small molecules. Redox reaction can also take place there thanks to the iron valence state for charge balance. These characteristics exactly offer the tunnels and spaces for the transport and storage of lithium ions.Fe4[Fe(CN)6]33 is the foretype of prussian blue, its theoretical specific capacity is about 100 mAh/g with one charge transport of Fe2+/Fe3+. Here we synthesize this compound by a simple one-step precipitation method. The cell shows an initial specific capacity of 95.1 mAh/g and about 75% of its original capacity is retained after 50 cycles. In order to increase the specific capacity, Fe2+ was replaced with Fe3+ to provide more redox active sites. The as-prepared FeFe(CN)6 has a regular cubic structure with the particle size of 50 nm. Two redox peaks at 2.88V/3.19V and 3.81V/3.91V are observed by cyclic voltammetry, corresponding to the oxidation/reduction of the low spin Fe2+/Fe3+ adjacent to the carbon and the high-spin of Fe2+/Fe3+bonding to the nitrogen, respectively. Galvanostatic charge/discharge cycling shows that its initial discharge capacity is 137.3 mAh/g, and the capacity retention is 60% after 100 cycles. In addition, its rate performance is very excellent.1. Y. Liang, Z. Tao and J. Chen, Advanced Energy Materials, 2012, 742-769.2. A. A. Karyakin, Electroanalysis, 2001, 13, 813-819.3. N. Imanishi, T. Morikawa, J. Kondo, R. Yamane, Y. Takeda, O. Yamamoto, H. Sakaebe and M. Tabuchi, J Power Sources, 1999, 81, 530-534.

Porous polyaniline nanofiber/vanadium pentoxide layer-by-layer electrodes for energy storage

There has been long-standing interest in hybrid electrodes containing an electronically conductive polymer and an inorganic cathode material for electrochemical energy storage. Conductive polymers such as polyaniline serve to enhance the conductivity of the electrode, and are electrochemically active themselves. Here, we report the layer-by-layer (LbL) assembly of polyaniline (PANI) nanofibers and V2O5 to form hybrid electrodes for electrochemical energy storage. The resulting electrode is highly porous and significantly exceeds in performance relative to an analogous electrode assembled with conventional PANI in place of PANI nanofibers. By utilizing PANI nanofibers in place of conventional PANI, significant gains in capacity (3×), specific energy (40×), and specific power (4×) are realized. The growth of the film is investigated using profilometry and quartz crystal microbalance; the thickness of the film increases linearly with respect to the number of layer pairs deposited. It is found that the electrochemical response possesses contributions from both PANI nanofibers and V2O5, and that the electrochemical performance of this LbL system is dependent on film thickness. The electrode contains 59 wt% V2O5 and stores 0.8 mol Li+ per mol of V2O5. A film thickness of 1.2 μm yields optimum results, with a discharge capacity of 320 mA h g−1, a power density of 4000 mW g−1, and an energy density of 886 mW h g−1 (per mass of active cathode), depending on discharge current. After 100 cycles, the electrode retains 75% of its initial capacity, and no appreciable volumetric expansion after cycling is observed. These results highlight the promise of porous electrodes made via LbL assembly, where two dissimilar materials can be intimately blended to achieve synergistic properties.

62.4: Hybrid Polymer‐OLEDs with Doped Small‐molecule Electron Transport Layers for Display Applications

AbstractWe report on the development of hybrid P‐OLEDs for display applications. Hybrid P‐OLEDs combine polymeric hole side and emitter layers with small molecule layers as organic electron side. Experimental data for blue hybrid P‐OLEDs is presented and compared to standard P‐OLEDs with inorganic cathode side.

Lithium incorporation in crystalline and amorphous chalcogenides: Thermodynamics mechanism and structure

The reaction of inorganic cathodes in lithium batteries can occur by two major mechanisms, displacement or insertion. At ambient temperatures the latter tend to show varying degrees of reversibility whereas the former tend to be irreversible. This paper discusses the critical roles that thermodynamics and crystal structure play in the reaction path and hence the reversibility of lithium reactions. Emphasis is placed on the titanium sulfides, vanadium diselenide and the molybdenum sulfides.

Lithium incorporation in crystalline and amorphous chalcogenides: Thermodynamics, mechanism and structure

The reaction of inorganic cathodes in lithium batteries can occur by two major mechanisms, displacement or insertion. At ambient temperatures the latter tend to show varying degrees of reversibility whereas the former tend to be irreversible. This paper discusses the critical roles that thermodynamics and crystal structure play in the reaction path and hence the reversibility of lithium reactions. Emphasis is placed on the titanium sulfides, vanadium diselenide and the molybdenum sulfides.