Positive Electrode Potentials Research Articles

Effect of Ni Incorporation in KCoPO4 on the Charge Storage Capacity of KCo1 − xNixPO4 (0 ≤ x ≤ 0.5) Electrodes for the Fabrication of High‐Performing Hybrid Supercapacitors

ABSTRACTFulfilling the increasing energy demands of the world through renewable energy sources requires the utilization of a highly efficient large‐scale electrochemical energy storage device. A hybrid supercapacitor (HSC) that consists of a battery‐type electrode coupled with a counter‐capacitive electrode, while in principle offering supercapacitor‐like power, cyclability, and higher energy density, can be a potential device for large‐scale energy storage to cater to the energy needs through renewable energy sources. The KCo0.5Ni0.5PO4 electrode demonstrated notably enhanced electrochemical performance, attributed to the synergistic interaction of Co2+ and Ni2+ ions in a phosphate framework. The incorporation of redox‐mediated diffusive charge storage through the incorporation of Ni2+ on the Co2+ site resulted in a large‐scale charge storage capacity, coupled with capacitive‐type surface charge storage on the KCo1−xNixPO4 electrodes. The KCo0.5Ni0.5PO4 delivers 173 mAh/g (capacitance: 1038 F/g) at a current density of 0.5 A/g in an aqueous 2 M KOH electrolyte, accompanied by cyclic stability up to 5000 cycles. HSC mode consists of activated carbon as the negative electrode along with KNi0.5Co0.5PO4 as the positive electrode, displaying high energy density and power density of 183.7 Wh/kg and 7952 W/kg, respectively, in 2 M aqueous KOH electrolyte. The superior performance in HSC mode makes KCo0.5Ni0.5PO4 a potential positive electrode for the development of high‐performing HSCs.

Improved Voltammetric Procedure for Chloride Determination in Highly Acidic Media.

Cyclic voltammetry (CV) can be applied as a reliable method for the determination of chloride ions in a range from several to a couple hundred (about 200) ppm. Since the standard potential of chloride ion/gaseous chlorine is 1.36 V vs. normal hydrogen electrode (NHE), the efficient oxidation of Cl- ion occurs at very positive electrode potentials, usually higher than +1.7 V vs. NHE. It is possible to observe this phenomenon only at noble-metal or inert carbon electrodes. Many other solutes, usually organic compounds, are often oxidized at this potential. This is the reason why the determination of Cl- content directly from an increase in the oxidation current is not reliable and could lead to overestimated values. However, gaseous chlorine, generated at a positive potential dissolve in the analyzed solution, could be reduced in the reverse scan of a cyclic voltammetric curve. Optimization of the experimental procedure using statistical tools enables the development of an improved method for the direct quantification of chloride ions in acid copper electroplating baths. Under the proposed experimental conditions, the calibration curve (Cl2 voltammetric reduction current vs. chloride ions concentration) is represented by the linear model for the concentration of chlorides ranging from 10 to 200 mg/dm3. The developed method for analyzing chloride ions in an acid sulfate electroplating copper bath has many unique properties. It is fast; the time of a single analysis is less than 20 min. In automatic mode, it can be repeated up to 50 times a day. The method does not require processing of the sample of the analyzed bath before measurement. As a result, no additional chemical reagents are used, and the test sample can be returned to the plating bath.

A Reduced Order Modeling Approach to Capture Transport within a Three-Electrode System Towards Fast Charge Applications

In support of GM's traction battery efforts, we derive and implement a reduced order modeling method to describe the electrochemical performance of a battery cell through the combination of a modified Newman Pseudo-2-Dimensional model and a three-electrode experimental apparatus. To assess the capability of the method, we compare the modeling results with experimental data for a lithiated graphite electrode and a lithiated nickel rich electrode system. The model is applied to simulate the electrochemical and transport processes within the battery cell to predict the negative electrode potential and positive electrode potential with respect to a lithium iron phosphate reference electrode, as well as the terminal voltage.The manufacture and set up of the three-electrode system, model development and reduction approaches, as well as a discussion of applicability to fast charge considerations to avoid lithium plating at the anode during a charging event will be presented.

Surface engineering of TiSiO4 nano-coating for high-voltage nickel-rich ternary cathodes: An approach to improve cyclic performance

In recent years, layered ternary transition metal oxides with a high nickel content have gained substantial attention as a potential positive electrode material for lithium-ion batteries. However, its poor rate capability, cyclability, and capacity retention at high working voltages limit its use in commercial lithium-ion batteries. To overcome these challenges, we synthesize a cost-effective wet-chemical deposition of novel TiSiO4 nano-coatings over the surface of LiNi0.83Mn0.06Co0.11O2 (NMC-83). X-ray diffraction and electron microscopy confirm the presence of a coating and verify that the deposition process did not alter the crystallinity and morphology of the NMC-83 particles. In addition, during cycling, it completely protects NMC-83 with enhancements in hexagonal phase transitions between H2 and H3, resulting in excellent cycling stability at upper cut-off voltages. Likewise, when the amount of coated material is equal to 1 wt%, it provides faster ion kinetics and a stable electrode-electrolyte interface. The 1 wt% TiSiO4 coating provides 35 % retention after 250 cycles at a 0.5C rate, while the pristine NMC-83 shows only 13.7 %. From postmortem analysis, the 1 wt% TiSiO4-coated NMC-83 cathode maintains its stable polycrystalline nature compared with pristine NMC-83. Thus, this novel TiSiO4 nanocoating has significant implications for developing high-performance rechargeable batteries for energy applications.

Remembering the Old Propensity Rules of the Electromagnetic Enhancement Mechanism of SERS: Reorientation of Pyridine on a Silver Electrode Induced by the Applied Potential.

Electrochemical SERS of pyridine adsorbed on a silver electrode has been analyzed by comparing the spectra to the calculated normal Raman and resonance Raman intensities of model systems of pyridine bonded to linear silver clusters with different densities of charge through the nitrogen (Ag-NPy) or flipped through the hydrogen in the para-position (Ag-HPy). The changes observed in the ν(CH) region of the SERS have been investigated for the first time and related to a molecular reorientation at negative surface excess of charge of the metal in such a way that the ν(CH) bands with the highest (mode 2) and lowest (mode 13) wavenumber dominate this spectral region at positive or negative electrode potentials, respectively. The calculations support that the ν(CH) region is dominated by a specific vibration depending on pyridine orientation and suggest that both species coexist in the SERS recorded at negative potentials. This conclusion is supported by the SERS of centrosymmetric pyrazine which do not show this behavior and remembers the predictions from the old propensity rules of the so-called electromagnetic mechanism of SERS.

Polyaniline-Coated Na3V2(PO4)2F3 Cathode Enables Fast Sodium Ion Diffusion and Structural Stability in Rechargeable Batteries.

Na3V2(PO4)2F3 (NVPF), a typical sodium superionic conductor (NASICON) type structure, has attracted much interest as a potential positive electrode in sodium-ion battery. However, the inherently poor electronic conductivity of phosphates compromises the electrochemical properties of this material. Here, we develop a general strategy to improve the electrochemical performance by preparing a new composite material "polyaniline (PANI)@NVPF" using a Pickering emulsion method. The X-ray diffraction and Raman results indicated a successful PANI coating without affecting the NASICON-type structure of NVPF, and they enhanced the interfacial bonding between the two components. Also, thermogravimetric analysis and scanning electron microscopy analyses revealed that the PANI content influenced the thermal stability and morphology of the nanocomposites. As a result, the sodium test cells exhibited multielectron reactions and a better rate performance for PANI@NVPF nanocomposites as compared to NVPF. Specifically, 2%PANI@NVPF maintained 70% of its initial capacity at 5C. Ex-situ electron paramagnetic resonance revealed the existence of mixed valence states of vanadium (V4+/V3+) in both discharge and charge processes. Consequently, the successful PANI coating into the sodium superionic conductor framework improved the sodium diffusion channels with a measurable increase of diffusion coefficients with cycling (ca. 3.25 × 10-11 cm2 s-1). Therefore, PANI@NVPF nanocomposites are promising cathode candidates for high-rate sodium-ion battery applications.

Layer‑by‑layer assembled binder-free hydrated vanadium oxide-acetylene black electrode for flexible aqueous zinc ion battery

Vanadium oxides are potential positive electrode materials for aqueous zinc ion batteries (ZIBs) owing to their advantages of high theoretical capacity, low cost, and so on. Developments of methods for preparing binder-free vanadium oxide electrodes on a large scale and further investigation of their Zn2+ storage mechanisms are essential for expanding their uses in large-scale energy storage systems and wearable electronics. In this work, binder-free electrodes with hydrated vanadium oxide (V2O5·nH2O, denoted as VOH)-acetylene black (AB) on carbon cloth (VOH-AB/CC) are fabricated by a simple and scalable method which combined low-temperature hydrothermal treatment with layer-by-layer drop/spray-coating process. The AB can greatly improve the electrical conductivity of VOH, thereby enhancing the electrochemical performance. The as-prepared electrode with 20 wt% of AB (VOH-AB2/CC) delivers a high capacity of 280 mA h g−1 at 1 A/g and a good rate capability of 205 mA h g−1 at 4 A/g, which is better than many of the reported binder-free vanadium base electrodes. Besides, excellent cycling performance with 89 % retention rate after 3000 cycles at 4 A/g is achieved on the VOH-AB2/CC electrode. Furthermore, a storage mechanism of Zn2+/H+/H2O insertion accompanied by the formation of basic zinc salt precipitate during the discharging process is proposed by the aid of ex-situ XRD and XPS techniques. Additionally, the flexible Quasi-Solid-State ZIB constructed using VOH-AB/CC as positive electrode can work well at different bending states and two ZIBs connected in series can lighten a light-emitting diode even under bending state. This work provides a low-cost, time-saving, environmental-friendly and scalable method to fabricate binder-free hydrated vanadium oxide electrodes for flexible aqueous ZIBs.

Downsizing and coating effects on the electrochemical performance of Mn-doped iron fluorophosphate as cathode material for sodium-ion batteries

Sodium Mn-doped iron fluorophosphate Na2Fe0·5Mn0·5PO4F is a potential positive electrode material for lithium-ion and sodium-ion batteries. This study outlines the synthesis of Na2Fe0·5Mn0·5PO4F powder through a simplified and more accessible production method. The X-rays diffraction (XRD) technique showed a pure phase with monoclinic symmetry (S.G. P21/n). The resulting uncoated material (labeled as NFeMPF) was ball-milled with dopamine hydrochloride (mentioned as dopamine hereafter) as a carbon source to enhance the specific surface and improve its electronic conductivity. Raman spectra confirmed the presence of residual carbon after the pyrolysis process. Thermogravimetric analysis (TGA) demonstrated the stability of Mn-doped iron fluorophosphate up to 1000 °C. Additionally, Mössbauer spectroscopy disclosed structural improvements in the material, indicating the reduction of all Fe(III) when coated with dopamine. The uncoated material discharge capacity when cycled against sodium exhibits reversible capacities of only 80, 67, and 38 mAh/g during the first cycle at C/20, C/16, and C/5, respectively. The coated NFeMPF@D delivered improved capacities of 272 and 202 mAh/g at C/20 and C/16, respectively. This highlights the considerable promise of the investigated phosphate-based electrode material as a cathode composite for the next generation of sodium-ion batteries.

Investigation of work function and quantum capacitance of OH-terminated MXenes as supercapacitor electrodes: A theoretical perspective

MXene has shown promise in supercapacitor electrodes for energy storage devices. As key parameters to develop new electronic devices, the quantum capacitance and work function (WF) of OH-terminated MXenes with 3d, 4d, d transitional metals are investigated by density functional theory. The most stable configurations of 13 M2C(OH)2 MXenes are found, which are further confirmed by negative formation energies. The low WFs of M2C(OH)2 make them become potential candidates as thermionic electron emitters, especially for Sc2C(OH)2 and Lu2C(OH)2 with extra low WFs. Sc2C(OH)2, Cr2C(OH)2, Y2C(OH)2, and Lu2C(OH)2 are considered as negative electrodes, Other nine systems are potential positive electrodes for larger |Qp|/|Qn| than 1, especially for V2C(OH)2, Nb2C(OH)2, and Mo2C(OH)2. Th wide voltage maintains the electrode types of all systems unchanged, but drastically increases the |Qp|/|Qn| of V2C(OH)2. The quantum capacitance of M2CT2 with different terminations is further explored.

Phase Engineering via Aluminum Doping Enhances the Electrochemical Stability of Lithium-Rich Cobalt-Free Layered Oxides for Lithium-Ion Batteries.

Lithium-rich, cobalt-free oxides are promising potential positive electrode materials for lithium-ion batteries because of their high energy density, lower cost, and reduced environmental and ethical concerns. However, their commercial breakthrough is hindered because of their subpar electrochemical stability. This work studies the effect of aluminum doping on Li1.26Ni0.15Mn0.61O2 as a lithium-rich, cobalt-free layered oxide. Al doping suppresses voltage fade and improves the capacity retention from 46% for Li1.26Ni0.15Mn0.61O2 to 67% for Li1.26Ni0.15Mn0.56Al0.05O2 after 250 cycles at 0.2C. The undoped material has a monoclinic Li2MnO3-type structure with spinel on the particle edges. In contrast, Al-doped materials (Li1.26Ni0.15Mn0.61-xAlxO2) consist of a more stable rhombohedral phase at the particle edges, with a monoclinic phase core. For this core-shell structure, the formation of Mn3+ is suppressed along with the material's decomposition to a disordered spinel, and the amount of the rhombohedral phase content increases during galvanostatic cycling. Whereas previous studies generally provided qualitative insight into the degradation mechanisms during electrochemical cycling, this work provides quantitative information on the stabilizing effect of the rhombohedral shell in the doped sample. As such, this study provides fundamental insight into the mechanisms through which Al doping increases the electrochemical stability of lithium-rich cobalt-free layered oxides.

Potassium ion doped manganese oxide nanoscrolls enhanced the performance of aqueous zinc-ion batteries

α-MnO2 is a potential positive electrode material for aqueous zinc-ion batteries, but its electrochemical performance of zinc storage requires further improvement. In this paper, potassium ion-doped manganese dioxide nanoscrolls (KMnO2) with oxygen vacancy were synthesized by a one-step hydrothermal method. It was observed that the electrochemical specific capacity was 250.9 mAh/g at a current density of 0.2 C, which was better than the existing commercial α-MnO2. At a high current of 1 C, these batteries demonstrate improved cycle stability. Synchrotron radiation and other experiments as well as DFT theoretical calculations provided additional evidence that K doping was efficient in regulating the metal bond type and the mean charge regulation of covalent bonds with oxygen atoms in MnO2. When MnO and MnK bonds are present, KMnO2 showed outstanding adsorption of Zn2+ and further enhanced the Zn2+ embedding process. Simultaneously, oxygen defects caused by doping boosted the development of the nanoscroll structure, leading to an increase in active sites available for electrochemical reactions and subsequently enhancing the electrical conductivity of α-MnO2. This study exhibits the potential of optimizing materials based on manganese with the introduction of a potassium doping strategy, resulting in improved performance for aquatic zinc-ion batteries, and presents novel perspectives for related research.

Feeling the strain: Enhancing the electrochemical performance of olivine LiMnPO[formula omitted] as cathode materials for Li-ion batteries through strain effects

Currently, the improvement of Li-ion batteries (LIBs) is more important than ever, especially due to the increasing spread and rapid progress of electric vehicles and high-tech applications. Materials used for positive electrodes are one of the main constituents of batteries, which typically determine their electrochemical efficiency. Phospho-olivine LiMnPO4 (LMP) material has been regarded as a potential positive electrode material for LIBs due to its outstanding properties. However, it suffers from low electronic and ionic conductivity. Therefore, this work aims to overcome these drawbacks by applying a biaxial strain to LMP. In this regard, we used density functional theory calculations to investigate the effect of biaxial strain on the dynamic and thermal stabilities, structural, electronic, ionic diffusion, electrochemical potential, and defect properties of LiMnPO4 (LMP) structure, as well as on the Average (Mn–O, Li–O and P–O) bond lengths, electrical conductivity, and charge transfer. Moreover, the influence of anti-site defects on the ionic conductivity of LMP compound was evaluated. Our findings suggest that the biaxial tensile strain has a remarkable effect on the rate performance of LMP cathode material. A biaxial tensile strain of +2% reduces the band gap of LMP from 3.51 to 3.41 eV, and ameliorates the diffusion coefficient by 100 times. Furthermore, the migration barrier was calculated to be 0.37 eV for strained (+2%) defective MP, lower than 1.12 eV for unstrained defective MP, indicating that biaxial tensile strain can mitigate the negative effect of anti-site defects on Li-ion migration. These results can prompt us to suggest biaxial tensile strain as a good strategy for improving the electrochemical performance of LMP as cathode material for LIBs. Furthermore, this study may supply insights to cathode material designers and engineers on the importance of an appropriate biaxial strain value to improve the rate performance of LiMnPO4 as cathode materials for LIB batteries.

Evaluation of P3-Type Layered Oxides as K-Ion Battery Cathodes.

Given the increasing energy storage demands and limited natural resources of Li, K-ion batteries (KIBs) could be promising next-generation systems having natural abundance, similar chemistry, and energy density. Here, we have investigated the P3-type K0.5TMO2 (where TM = Ti, V, Cr, Mn, Co, or Ni) systems using density functional theory calculations as potential positive intercalation electrodes (or cathodes) for KIBs. Specifically, we have identified ground-state configurations and calculated the average topotactic voltages, electronic structures, on-site magnetic moments, and thermodynamic stabilities of all P3-K0.5TMO2 compositions and their corresponding depotassiated P3-TMO2 frameworks. Additionally, we evaluated the dynamic stability and K-mobility in select P3 structures. We find that K adopts the honeycomb or zig-zag configuration within each K-layer of all P3 structures considered, irrespective of the transition-metal (TM). In terms of voltages, we find the Co- and Ti-based compositions to exhibit the highest (4.59 V vs. K) and lowest (2.24 V) voltages, respectively, with the TM contributing to the redox behavior upon K (de-)intercalation. We observe all P3-K0.5TMO2 to be (meta)stable and hence experimentally synthesizable according to our 0 K convex hull calculations, while all depotassiated P3-TMO2 configurations are unstable and may appear during electrochemical cycling. Also, we verified the stability of the prismatic coordination environment of K compared to octahedral coordination at the K0.5TMO2 compositions using Rouxel and cationic potential models. Finally, combining our voltage and stability calculations, we find P3-KxCoO2 to be the most promising cathode composition, while P3-KxNiO2 is worth exploring. We also find P3-KxMnO2 to be worth pursuing given its dynamic stability and facile migration of K+ at both potassiated and depotassiated compositions. Our work should contribute to the exploration of strategies and materials required to make practical KIBs.

Corrosion processes at the GGG40 steel–bentonite interface

Abstract. Spheroidal graphite cast iron (GGG40/0.7040) is used as an overpack material for the reference Pollux 10 container, a prototype for the storage of fuel elements in different types of host rocks (Hassel et al., 2019). Corrosion processes are expected to be triggered after some decades, as the contacting bentonite, which is used as fill material, becomes soggy because of the decay of the fission heat generation and the intrusion of pore water as the temperature decreases under the condensation point (King and Padovani, 2011). The distinct electrochemical reactivities of the graphite, ferrite, pearlite, and cementite phases exposed by this material introduce local galvanic elements which influence the topographic evolution of degradation (Spence, 2005). The aim of this work is to elucidate the corrosion dynamics of active and passive areas by following the chemical evolution at the interface of cast iron–bentonite during the first stages after its saturation with geological pore water. Polarization experiments and electrochemical impedance spectroscopy were applied to monitor the corrosion process in a bentonite cell, where GGG40 steel is put into contact with a light compacted Wyoming bentonite slurry 1 : 10 w/w of bentonite to Opalinus Clay pore water (Fig. 1a). Experiments were performed at 30 and 50 ∘C for longer than 3 months. The surface chemistry and morphological changes were investigated by local XPS, SEM-EDX, and TEM (X-ray photoelectron spectroscopy, scanning electron microscopy with energy dispersive X-ray, and transmission electron microscopy, respectively). These experiments were complemented with corrosion studies performed in pore water under different temperatures, hydrostatic pressures, and pH and with and without dissolved oxygen. The polarization curves indicate a constant corrosion rate of GGG40 steel in saturated bentonite after 30 d. SEM micrographs reveal a preferential dissolution of the ferrite phase around the graphite spheres and the ferrite lamellae contained in the pearlitic eutectic. A strong localized dissolution of ferrite along the graphite boundary can be also observed; this is a typical case of crevice corrosion caused by the unhindered access of oxygen to the graphitic cathodic areas (Wang et al., 2022). The surface chemical studies indicate the accumulation of iron oxides, which can be attributed to a hydrated magnetite and the formation of iron silicates (Zhang et al., 2021). TEM pictures of a cross-sectional lamella, including part of graphite sphere, show the formation of a silicate film covering the corroding surface with an irregular adherence (Fig. 1b). The initial relatively high corrosion rate of GGG40 steel can be attributed to the dissolution of the more active ferrite with the formation of poorly passivating iron oxides and silicates. The system is driven towards the dissolution of pearlite at more positive electrode potentials. The bentonite slurry limits the access of oxygen to the graphitic cathodic areas, reducing the corrosion rate by 1 order of magnitude in comparison with that in aerated pore water. A surface enrichment of cementite with superior passive properties and the neutralization of the local elements by approaching the corrosion potential of graphite (Kadowaki et al., 2019) is also expected. Thus, the consumption of oxygen and the transport limitation of the cathodic reaction by bentonite forecast a considerable reduction in the degradation of the container after a sacrificial corrosion phase.

A Reduced Order Modeling Approach to Capture Transport within a Three-Electrode System Towards Fast Charge Applications

In support of GM's traction battery efforts, we derive and implement a reduced order modeling method to describe the electrochemical performance of a battery cell through the combination of a modified Newman Pseudo-2-Dimensional model and a three-electrode experimental apparatus. To assess the capability of the method, we compare the modeling results with experimental data for a lithiated graphite electrode and a lithiated nickel rich electrode system. The model is applied to simulate the electrochemical and transport processes within the battery cell to predict the negative electrode potential and positive electrode potential with respect to a lithium iron phosphate reference electrode, as well as the terminal voltage.The manufacture and set up of the three electrode system, model development and reduction approaches, as well as a discussion of applicability to fast charge considerations to avoid lithium plating at the anode during a charging event will be presented.

Using Reference Electrodes to Validate Parameterization of Individual Electrode Soh in the Single Particle Model with Electrolyte

Most model parametrization techniques for reduced order physics-based Lithium-ion battery models like the single particle model rely on minimizing the error in the measured and predicted cell terminal voltage. The battery terminal voltage is the difference between the voltages of the positive and negative electrode solid phase potentials. If the individual contribution of each electrode overpotential to the terminal voltage, is not measured, there could be multiple combinations of parameters that provide similar RMSE for voltage prediction, yielding non-unique solutions and local minima. Misattributing the parameters for kinetics and diffusion in each electrode could result in increased plating or over-conservative designs at higher operating currents.Adding a reference electrode to the battery allows us to measure the individual electrode potentials experimentally. Using this extra measurement, we can parametrize the kinetic and diffusion reactions in positive and negative electrodes with better confidence [1], and validate the electrode-specific state of health parameterization, specifically the increased resistances due to SEI growth and shift in the stoichiometric window as the cell ages [2,3]. In our experiments, we used a pouch cell manufactured in the U of M Battery Lab with Targray NMC 622 Single Crystal cathode powder, Superior SLC 1520-T anode powder, and a custom fabricated Lithium Iron Phosphate (LFP) reference electrode deposited on a porous electrode layer. Further details of the reference electrode are given in [4]. The model was parametrized using discharge data at different C-rates and a modified Hybrid Pulse Power Characterization test. Finally, the RMSE for both the modeled negative and positive electrode potentials are calculated for the validation data set which uses the US06 Drive cycle.

Enhancement of the stability window of PEO for high voltage all-solid-state lithium batteries

Polyethylene oxide (PEO), one of the leading polymer electrolytes recommended against the safety concerns of liquid electrolytes, is unsuitable for high potential positive electrodes (e.g. LiNixMnyCozO2) needed to meet the increasing energy demand. Herein PEO main chain has been stabilized by modifying its (-OH) reactive terminal group. Modification of the reactive (-OH) group with (-OCH3) and (−CN) terminal groups exhibit a remarkable increase in the ionic conductivity at ambient temperature (4.52 × 10−4 S cm−1). In addition, electrochemical stability window (ESW) has been expanded (>4.18 V). The modified gel polymer electrolyte (GPE) has exhibited 150 mAh g−1 discharge capacity and has retained 92% of its capacity for 50 cycles in charge-discharge tests. Instead of increasing the ESW with inorganic additives, modification of PEO's (-OH) reactive terminal groups and making the PEO main chain a stable matrix can be a more permanent solution/strategy in the first instance. Moreover, developed solid electrolyte promise stability, safety and flexibility, making their utilization possible even with complex geometry batteries with high energy density.

Carbon felt-polypyrrole-silver chloride composite as a rechargeable positive electrode for the seawater magnesium cell

In the paper, for the first time, the new concept of rechargeable cathode for Mg-based seawater cells is demonstrated. The pristine carbon felt (CF) is functionalized with electrodeposited polypyrrole (PPy), and the composite with silver chloride (AgCl) is prepared by the modified successive ion layer adsorption and reaction (SILAR) method. Pristine carbon felt – polypyrrole (CF/PPy) and carbon felt - polypyrrole - silver chloride (CF/PPy-AgCl) are investigated as potential rechargeable positive electrodes for the magnesium seawater cell. During charge, which can be accomplished with small photovoltaic cells, polypyrrole, and silver are oxidized while on Mg hydrogen is evolved. During discharge dissolution of Mg alloy, and reduction of doped polypyrrole and silver chloride occurred. The specific capacity, energy, and power of the cell, as well as cyclic stability, are estimated. The possible application of the cell is also proposed.

Electrochemical capacitance properties of pre-sodiated manganese oxide for aqueous Na-ion supercapacitors.

Mn-based oxides are widely investigated as electrode materials for electrochemical supercapacitors, because of their high specific capacitance in addition to the high abundance, low cost, and environmental friendliness of Mn. The pre-insertion of alkali metal ions is found to improve the capacitance properties of MnO2. While the capacitance properties of MnO2, Mn2O3, P2-Na0.5MnO2, and O3-NaMnO2etc. are reported, there is no report yet on the capacitive performance of P2-Na2/3MnO2, which has already been studied as a potential positive electrode material for Na-ion batteries. In this work, we have synthesized sodiated manganese oxide, P2-Na2/3MnO2 by a hydrothermal method followed by annealing at a high temperature of about 900 °C for 12 h. For comparison, manganese oxide Mn2O3 (without pre-sodiation) is synthesized by following the same method, but annealing at 400 °C. While P2-Na2/3MnO2 exhibits a high specific capacitance of 234 F g-1, Mn2O3 can deliver only 115 F g-1 when cycled at 0.4 A g-1 in an aqueous electrolyte of 1.0 M Na2SO4 in a three-electrode cell. An asymmetric supercapacitor Na2/3MnO2‖AC is assembled, which can exhibit a SC of 37.7 F g-1 at 0.1 A g-1 with an energy density of 20.9 W h kg-1, based on the total weight of Na2/3MnO2 and AC with an operational voltage of 2.0 V and possesses excellent cycling stability. This asymmetric Na2/3MnO2‖AC supercapacitor can be cost-effective considering the high abundance, low-cost and environmental friendliness of Mn-based oxides and aqueous Na2SO4 electrolyte.

Modeling Electrochemical Transport within a Three-Electrode System Towards Fast Charge Applications

In support of GM's traction battery efforts, we derive and implement a method to describe the electrochemical performance of a battery cell through the combination of a modified Newman Pseudo 2-Dimensional model and a three-electrode experimental apparatus. To assess the capability of the method, we compare model results with experimental data for a lithiated graphite and lithium nickel manganese cobalt oxide system. The model is applied to simulate the electrochemical and transport processes within the battery cell to predict the negative electrode potential and positive electrode potential with respect to a lithium iron phosphate reference electrode, as well as the terminal voltage. We extend this discussion to cover applicability to fast charge considerations to avoid lithium plating at the anode during a fast charge event.