Average Cell Potential Research Articles

Marine shrimp/tin waste as a negative electrode for rechargeable sodium-ion batteries

This work aims to valorize the shrimp wastes as a template for obtaining nanoparticulate tin battery electrodes. Using shrimp waste skins is possible to get a network material made of nanominerals (NMN) with elements such as Ca, Mg, Na, and Al and containing a rich source of nitrogen. Three different electrode materials prepared under different conditions validated this study. Shrimp wastes (SW), SW-tin prepared at room temperature (ST-RT) and SW-tin prepared by carbothermal reduction (ST-CT) are studied. 119 Sn Mössbauer spectroscopy determined the atomic fraction is 59.5 and 40.5% of SnO 2 and β-Sn co-existing in the ST-CT sample. SEM and TEM micrographs confirmed a particle size of 2–5 nm of tin-based materials homogeneously distributed on the NMN matrix. Electrochemical investigation in Na-half cells demonstrated superior electrochemical performance of ST-CT with 162 mA h g −1 reversible capacity which can be retained at 60% over 200 cycles under different rates (C/10 to 2 C). The SW and ST-RT displayed the worse reversible capacities. Eventually, a Na-ion full cell is assembled versus Na 3 V 2 (PO 4 ) 3 showing good properties in terms of energy density. • We use shrimp/tin waste (STW) material, which has never been tested for energy storage. • Advanced storage properties in Na-ion full cells are proposed for first time using natural sources. • Na-half cells shows a 162 mA h g −1 of reversible capacity retained 60% over 200 cycles. • Combined with NVP cathode, it exhibits average cell potential of 2.5 V reaching 310 W h kg −1 .

Cost and price projections of synthetic active materials for redox flow batteries

Synthetic organic and organometallic active materials for flow batteries offer a large design space in terms of solubility, redox potential, kinetic activity, and stability. Price is also a key metric. Here we focus on the estimated cost of manufacturing and sales price for synthetic organic negolytes based on anthraquinones and posolytes based on ferrocyanides. We find that derivatives of anthraquinones with simple production processes have an estimated sales price of ~25 $/kWh at an annual production volume of ~10 GWh/y. We also considered contract manufacturing of AQDS at ~200 MWh/y for early-stage commercialization; this results in an estimated sales price of ~40 $/kWh. We find that ferrocyanides, produced in a variety of ways and with several different cations, also result in an estimated sales prices of ~25 $/kWh at ~10 GWh/y. Because low-cost precursors and simple processing result in a couple price of ≥50 $/kWh for synthetic reactants, research should focus on active material equivalent weights of <100 g/eq, an average cell potential of >1.5 V, the avoidance of organic solvents, and precursors that cost no more than a few $/kg. It is also clear that integration with existing production of upstream precursors is the preferred route to cost-effective synthetic active materials.

Reversible Multi-Electron Storage Enabled by Na5V(PO4)2F2 for Rechargeable Magnesium Batteries

Rechargeable magnesium batteries (RMB) are one of the utmost promising post-lithium energy storage technologies due to their high theoretical energy density, affordable low cost, and inherent safety with moisture and air. Nonetheless, the research of RMB has been limited due to the low power and reversible energy densities of available cathode materials. Herein, we report a new Mg battery cathode of trigonal Na5V(PO4)2F2 (t­-NVPF) which performs 136 mA h g−1 reversible capacity realizing multi-electron storage through the V4+/V3+ and V5+/V4+ redox couples. After the first reversible cycle MgNa3V(PO4)2F2 is formed. The geometry optimization and energy calculations on the systems MgxNa3V(PO4)2F2 were carried within the density functional theory (DFT) demonstrating Mg insertion can fill the Na6, Na8, and Na9 sites, and evidenced a 1.5 V difference for the same redox couple comparing with the experimental results. Some facets of its crystal and local structure are determined by XRD, EPR, XPS, and 31P and 51V solid-state NMR spectroscopy. The cells cycled 2.5 – 0.2 V vs. Mg2+/Mg and at low current densities exhibited diminished polarization. The average cell potential is 1.4 V, entailing an energy density of 190 W h kg-1­ at the materials’ level. This piece of work provides an effective strategy for designing multi-electron storage for high-energy rechargeable Mg batteries, but more efforts are required to overcome high polarization during charge-discharge cycles which are commonly found in Mg batteries.

Permselective SPEEK/Nafion Composite-Coated Separator as a Potential Polysulfide Crossover Barrier Layer for Li-S Batteries.

Minimizing the shuttle effect by constraining polysulfides to the cathode compartment and activating the passive layer between cathode and separator are highly important for improving the Li-S cell performance, Coulombic efficiency, and cycle life. Here, we report a submicron thin coating of permselective sulfonated poly(ether ether ketone) (SPEEK) composite layer on the separator that would reduce polysulfide crossover, imparting a significant improvement in cycle life. It is observed that SPEEK increases the stability, and adding Nafion improves the capacity value. Among different ratios of Nafion and SPEEK (25:75, 50:50, and 75:25), the composite with a SPEEK/Nafion ratio of 50:50 showed a controlled shuttle effect with a stable cell capacity of 600 mA h g-1 up to 300 cycles. This modified separator with permselective coatings not only reduces the polysulfide shuttle but also improves the wettability and interfacial contact, which results in an improvement in average cell potential and lithium diffusivity. It is demonstrated here that the combination of functional (ionomer coating on separator) and nonfunctional (extra cathode layer) physical barriers effectively suppresses the polysulfide crossover and improves the electrochemical performance of Li-S batteries. The cell shows an initial capacity of 1300 mA h g-1 and a capacity retention of 650 mA h g-1 over 500 cycles with a 6 mg/cm2 sulfur loading.

Magnifying Opportunities in Mg Batteries through Metastability

In the March issue of Chem, Andrews, Banerjee, and colleagues devise a clever strategy to synthesize a metastable one-dimensional polymorph of V2O5 and demonstrate reversible chemical and electrochemical Mg intercalation, with 90 mAh/g capacity retained after 50 cycles at an average cell potential of 1.65 V versus Mg metal. Their approach proves fruitful not only in identifying a new functional multivalent cathode material, but also in validating a general concept that metastable compounds can offer sufficiently low migration energies to support reversible cycling with multivalent ions.

Energy efficient Na-aqueous-catholyte redox flow battery

ABSTRACT Redox flow battery (RFB) technologies have become play a significant role in the future for the storage of electrical energy produced from intermitted renewable energies such as solar, wind, and hydroelectric powers. Although the development of high-energy density RFB remains a challenging. Herein, we report the Na-aqueous-catholyte RFB (NaAqRFB) towards high-density electrical energy storage. Na-metal anode offers a high energy density and the use of an aqueous flowing catholyte decouples the energy and power. NASICON (Na3Zr2Si2PO12) is employed as a solid electrolyte in the NaAqRFB to separate the Na anode and a flowable aqueous catholyte. The constructed prototype NaAqRFB operates using a sodium-hexacyanoferrate solution as the aqueous catholyte with no added supporting salt/electrolyte, and yielded an average cell potential of ∼ 3.06 V (vs. Na/Na+), and an energy density of 54.16 Wh L−1 (based on the volume of catholyte) with high energy efficiency (∼ 92%, over 50 cycles), outperforming conventional RFB. The present work offers a new route for developing high-energy-density redox flow batteries.

An All-Organic Proton Battery

Rechargeable batteries that use organic matter as the capacity-carrying material have previously been considered a technology for the future. Earlier batteries in which both the anode and cathode consisted of organic material required significant amounts of conductive additives and were often based on metal-ion electrolytes containing Li+ or Na+. However, we have used conducting poly(3,4-ethylenedioxythiophene) (PEDOT), functionalized with anthraquinone (PEDOT-AQ) or benzonquinone (PEDOT-BQ) pendant groups as the negative and positive electrode materials, respectively, to make an all-organic proton battery devoid of metals. The electrolyte consists of a proton donor and acceptor slurry containing substituted pyridinium triflates and the corresponding pyridine base. This slurry allows the 2e-/2H+ quinone/hydroquinone redox reactions while suppressing proton reduction in the battery cell. By using strong (acidic) proton donors, the formal potential of the quinone redox reactions is tuned into the potential region in which the PEDOT backbone is conductive, thus eliminating the need for conducting additives. In this all-organic proton battery cell, PEDOT-AQ and PEDOT-BQ deliver 103 and 120 mAh g-1, which correspond to 78% and 75%, respectively, of the theoretical specific capacity of the materials at an average cell potential of 0.5 V. We show that PEDOT-BQ determines the cycling stability of the device while PEDOT-AQ provides excellent reversibility for at least 1000 cycles. This proof-of-concept shows the feasibility of assembling all-organic proton batteries which require no conductive additives and also reveals where the challenges and opportunities lie on the path to producing plastic batteries.

Mg intercalation into Ti2C building block

Generally, intercalation occurs when foreign atoms intercalate into multi-layer structures, while adsorption occurs when foreign atoms interact with monolayer structures or surfaces. We performed an investigation on the Mg intercalation into Ti2C building block (MXene) from first-principles simulation. We found that Mg can favorably intercalate into MXene, forming the stable compound Ti2MgC, which corresponds to the stage I in the Li intercalation into graphite. Based on the evaluation of the average cell potential and the energy barrier of Mg diffusion for the most energetically stable structure, our results suggest that Ti2MgC is a potential anode for Mg ion batteries.

Sodium‐Ion Batteries

AbstractThe status of ambient temperature sodium ion batteries is reviewed in light of recent developments in anode, electrolyte and cathode materials. These devices, although early in their stage of development, are promising for large‐scale grid storage applications due to the abundance and very low cost of sodium‐containing precursors used to make the components. The engineering knowledge developed recently for highly successful Li ion batteries can be leveraged to ensure rapid progress in this area, although different electrode materials and electrolytes will be required for dual intercalation systems based on sodium. In particular, new anode materials need to be identified, since the graphite anode, commonly used in lithium systems, does not intercalate sodium to any appreciable extent. A wider array of choices is available for cathodes, including high performance layered transition metal oxides and polyanionic compounds. Recent developments in electrodes are encouraging, but a great deal of research is necessary, particularly in new electrolytes, and the understanding of the SEI films. The engineering modeling calculations of Na‐ion battery energy density indicate that 210 Wh kg−1 in gravimetric energy is possible for Na‐ion batteries compared to existing Li‐ion technology if a cathode capacity of 200 mAh g−1 and a 500 mAh g−1 anode can be discovered with an average cell potential of 3.3 V.

Numerical studies of a separator for stack temperature control in a molten carbonate fuel cell

The use of a separator to control stack temperature in a molten carbonate fuel cell was studied by numerical simulation using a computational fluid dynamics code. The stack model assumed steady-state and constant-load operation of a co-flow stack with an external reformer at atmospheric pressure. Representing a conventional cell type, separators with two flow paths, one each for the anode and cathode gas, were simulated under conditions in which the cathode gas was composed of either air and carbon dioxide (case I) or oxygen and carbon dioxide (case II). The results showed that the average cell potential in case II was higher than that in case I due to the higher partial pressures of oxygen and carbon dioxide in the cathode gas. This result indicates that the amount of heat released during the electrochemical reactions was less for case II than for case I under the same load. However, simulated results showed that the maximum stack temperature in case I was lower than that in case II due to a reduction in the total flow rate of the cathode gas. To control the stack temperature and retain a high cell potential, we proposed the use of a separator with three flow paths (case III); two flow paths for the electrodes and a path in the center of the separator for the flow of nitrogen for cooling. The simulated results for case III showed that the average cell potential was similar to that in case II, indicating that the amount of heat released in the stack was similar to that in case II, and that the maximum stack temperature was the lowest of the three cases due to the nitrogen gas flow in the center of the separator. In summary, the simulated results showed that the use of a separator with three flow paths enabled temperature control in a co-flow stack with an external reformer at atmospheric pressure.

The Tests of 1 kWe Diesel Reformer and Solid Oxide Fuel Cell System

The high temperatures required to operate solid oxide fuel cells (SOFCs) allow for internal reforming of hydrocarbon fuels over a Ni-based anode. With their capability of being fuel flexible, SOFCs have operated under a wide range of fuels including diesel as examined in this study. But in order to reduce high possibilities of deposit formation in diesel internal reforming, additional external reforming technology was used for our system. The final goal of this research is to develop 1 kWe diesel-powered SOFC systems for residential power generation. Before constructing a complete 1 kWe SOFC system, a series of durability experiments were conducted on individual components of the system including the fuel reformer and stack. After testing the full-scale 1 kWe diesel reformer, deposit formation was visible within the catalyst and on the surface of the reactor head, which seriously degraded the performance. With several individual components tested, the construction of one-box type 1 kWe SOFC system is in progress. In a preliminary six-cell stack test using sulfur-free synthetic diesel, the system initially showed an output power of ∼110 kWe at a 0.8 V average cell potential. However, there was a significant drop off in output power after a few hours of operation, which was likely caused by severe deposit formation on the SOFC stack. Light hydrocarbons such as ethylene and/or “less reformed” heavier hydrocarbons caused by gas reactions under the incomplete fuel mixing upstream of the catalyst were likely responsible for the deposit formation.

Lithium insertion into TiO 2 from aqueous solution – Facilitated by nanostructure

This work investigates the effect of mesoporosity of titanium dioxide on its electrochemical reactivity in water. Nanostructured titanium dioxide films formed by the surfactant template method, unlike films prepared without surfactant, have been found to be reduced when cathodically polarised in aqueous lithium hydroxide. The result is attributed to accelerated lithium ion diffusion within the porous nanostructure, allowing a rapidly reversible insertion of lithium ions forming Li x TiO 2 with x as high as 0.27, corresponding to a charge capacity of 127 mC cm −2 in a 1.3 μm thick film. Self-discharge is slower than expected, with half-life of a few minutes under oxygen-free conditions. An all-nanostructured supercapacitor constructed from Li x TiO 2 and NiOOH 2− x electrodes showed an average cell potential of 1.6 V, which is close to the maximum possible potential range in an aqueous solution. A specific energy of 90 W h kg −1 is calculated, based on the combined mass of the charged electrodes.

Enhancement of the performance and reliability of CO poisoned PEM fuel cells

CO poisoning is a major issue when reformate is used as a fuel in PEM fuel cells. Normally, it is necessary to reduce the CO to very low levels (∼5 ppm) and to use CO tolerant catalysts, such as Pt–Ru alloys. As an alternative approach, we have studied the use of pulsed oxidation for the regeneration of CO poisoned cells. Results are presented for the regeneration of Pt and Pt–Ru anodes in a PEM fuel cell fed with CO concentrations as high as 10,000 ppm. The results show that periodic removal of CO from the catalyst surface by pulsed oxidation can increase the average cell potential and overall efficiency. Although use of pulsed techniques has been studied before, the careful control of each cell's voltage that this approach requires has limited its use in large fuel cell stacks. When uniform pulsing is done on a stack of fuel cells in series, the variations in voltage across the cells can limit the usefulness of this approach. A novel method that allows each cell in a stack to be separately pulsed under controlled conditions has been developed to overcome this problem. Weak or defective cells in a fuel cell stack can also be supplemented to enhance the power output and reliability of fuel cells. We present the results of experiments and calculations that quantify these benefits, specifically as they relate to PEM fuel cells operating on impure hydrogen produced by reforming fuels.

미량의 은이 첨가된 바나듐산화물 전극

졸-겔법을 이용하여 미량의 은이 도핑된 <TEX>$Ag_xV_2O_5$</TEX> xerogel(x=0.06, 0.11, 0.22)을 합성하여 리튬이차전지용 양극 소재로서 전기화학적 특성을 연구하였다. <TEX>$Ag_xV_2O_5$</TEX> xerogel은 무정형의 층상구조로 열처리하면 orthorhombic 구조로 전환되었으며, 표면구조는 <TEX>$V_2O_5$</TEX>와 유사한 단위체가 서로 얽혀 일정한 방향으로 성장하여 비등방성 fibril을 형성하고 있다. <TEX>$Li/Ag_xV_2O_5$</TEX> xerogel셀의 전지 용량(specific capacity)은 10mA/g의 방전율에서 평균 359mAh/g, 싸이클 효율 <TEX>$94\%$</TEX>이상이었으며, 바나듐산화물에 첨가된 미량의 은에 의해 전기화학적 특성이 향상되었다. NMR실험으로 서로 다른 환경의 <TEX>$Li^{+}$</TEX>이온이 전극에 존재함을 확인하였다. Silver doped vanadium pentoxides with a doping ratio Ag/V ranging from 0.03 to 0.11 were synthesized by sol-gel process, and <TEX>$Li/Ag_xV_2O_5$</TEX> cell was investigated by the electrochemical methods. It appears to be amorphous layered material and entangled fibrous textures has been grown to form anisotropic corrugated fibrils. NMR measurements revealed that several different kinds of <TEX>$Li^+$</TEX> ions exist in the lithium intercalated xerogel electrodes and the average cell potential was about 3.0V vs. <TEX>$Li/Li^+$</TEX>. The cell capacity of the silver doped <TEX>$Ag_xV_2O_5$</TEX> xerogel cathodes was more than 359 mAh/g at discharge current 10mA/g and cycle efficiency <TEX>$94\%$</TEX> was achieved.

Analysis of temperature and pressure fields in molten carbonate fuel cell stacks

AbstractA mathematical model based on fluid dynamics and heat‐transfer theories was applied to predict gas dynamic pressure and temperature distribution in a coflow molten carbonate fuel cell (MCFC) stack. The mass balance was simplified to obtain exact solutions with an assumption of uniform current density in the cell. The simulations were compared with data from a pilot‐scale MCFC stack. The effect of internal geometry of gas channels was simulated to accurately predict the gas‐pressure drop. A close prediction of pressure drop was possible from a partially blocked gas channel model that approximates the significant flow resistance. The effect of external boundary conditions on stack temperature profile was also analyzed. Temperatures were accurately predicted from a boundary heat conduction model with a reasonable assumption of wet seal temperatures. The 2‐D boundary conditions could be extended to 3‐D simulations to predict temperature distribution with the same accuracy. The model was applied to see the effect of scale‐up on the maximum temperature rise and average cell potential. The result verified a significant effect of cell size on the maximum stack temperature.

Structure, morphology and electrochemistry of doped lithium cobalt oxides

The structure, morphology and electrochemical performance of LiCoO2 powders doped with various trivalent cations such as M3+=Ni3+, Al3+, and B3+ have been investigated. X-ray diffraction patterns and FTIR data show that LiCo1−yNiyO2 oxides display a solid solution in the whole range 0≤y≤1, while the solubility limit of LiCo1−yAlyO2 and LiCo1−yByO2 materials is about y=0.35. Electrochemical features of LiCo1−yNiyO2 cathode materials show remarkable stability in their charge-discharge profiles. Aluminum substitution also stabilizes the two-dimensional framework and induces an increasing average cell potential than for LiCoO2. The overall capacity of the LiCo1−yByO2 oxides has been reduced due to the sp metal substitution, however, a more stable charge-discharge cycling characteristic has been observed when electrodes are charged up to 4.4 V as compared to the performances of the native oxides.