Mixed Electrolyte Research Articles

Enhancing electrochemical performance and stabilizing zinc anode in mild acidic electrolyte using combined additive

Rechargeable zinc-based batteries having aqueous electrolytes are renowned as promising alternatives for large scale energy storage systems (ESSs). However, in mild acidic electrolytes, zinc anodes pose several issues that have yet to be overcome. For tackling the major difficulties of zinc anodes, electrolyte engineering is the most practical and cost-effective strategy. Notwithstanding the broad variety of mechanisms associated with different electrolyte additives, the function of a single additive is straightforward. Finding combined additives with broader functionalities and greater efficacy is crucial. In this work, the combination of ionic liquid (IL) 1-butyl-1-methylpyrrolidinium dicyanamide ([BMPY][DCN]) and ethylene glycol (EG) as additives in an aqueous electrolyte 3 M ZnSO4 proves to be an effective strategy for simultaneously enhancing both zinc dissolution and deposition. IL significantly enhances zinc (Zn) dissolution and deposition while EG plays an important role in suppressing hydrogen evolution reaction (HER)and corrosion. Thus, 13.50 % improvement in capacity is achieved by the mixed additive EG + IL/ZnSO4 compared with the 3 M ZnSO4 electrolyte. In the Zn//Zn symmetrical system at 2 mA cm−2, the mixed additive greatly augments the cyclability of zinc, reaching over 400 h while maintaining excellent coulombic efficiency (CE). In-situ XAS and FT-EXAFS analyses confirm the high activities of both zinc oxidation/reduction in the mixed additive electrolyte. Results demonstrate that EG + IL/ZnSO4 can be applied to increase the cyclability of aqueous zinc-based batteries while sustaining high performance.

Computational design of a mixed A-site cation halide solid electrolyte for all-solid-state lithium batteries

All-solid-state Li-ion batteries (ASSBs) are considered as ideal next-generation energy storage devices owing to their safe operation and high energy densities.

Redox mediator-enhanced charge storage in dimensionally tailored nanostructures towards flexible hybrid solid-state supercapacitors.

Although extensive research has been performed on metal oxide-based supercapacitors during recent years, they remain lacking in their intrinsic conductivity and stability. To resolve this, 1D/2D heterostructure materials are being utilized, which significantly improves the performance and stability of both materials while employing their synergistic advantage consisting of morphologically tuned surfaces and superior electroactive sites. However, the performance remains unsatisfactory due to the sluggish faradaic reaction at the electrode/electrolyte interface. To address this challenge, we combined the synergistic advantage of morphological nanoengineering and the fast reaction kinetics of redox mediators, thus anticipating superior energy storage performance. A novel 1D/2D heterostructure of ZnCo2O4 (ZCO) and GaN was designed and implemented for the first time, and it demonstrated an excellent specific capacitance of 1693 F g-1 in the mixed electrolyte of KOH and K4[Fe(CN)6]. The all-solid-state flexible hybrid supercapacitor delivered an energy density of 92.63 W h kg-1 at a power density of 1287.52 W kg-1, with superb stability and mechanical endurance that outperformed previously reported ZCO-based materials. Additionally, we delineated the underlying mechanism governing the utilization of redox mediators along with morphological nanoengineering, which will facilitate the current development of state-of-the-art energy storage systems.

Ultra-fast synthesis of three-dimensional porous Cu/Zn heterostructures for enhanced carbon dioxide electroreduction.

The construction of metal hetero-interfaces has great potential in the application of electro-catalytic carbon dioxide reduction (ECR). Herein, we report a fast, efficient, and simple electrodeposition strategy for synthesizing three-dimensional (3D) porous Cu/Zn heterostructures using the hydrogen bubble template method. When the deposition was carried out at -1.0 A for 30 s, the obtained 3D porous Cu/Zn heterostructures on carbon paper (CP) demonstrated a nearly 100% CO faradaic efficiency (FE) with a high partial current density of 91.8 mA cm-2 at -2.1 V vs. Ag/Ag+ in the mixed electrolyte of ionic liquids/acetonitrile in an H-type cell. In particular, the partial current density of CO could reach 165.5 mA cm-2 and the FE of CO could remain as high as 94.3% at -2.5 V vs. Ag/Ag+. The current density is much higher than most reported to date in an H-type cell (Table S1). Experimental and density functional theory (DFT) calculations reveal that the outstanding electrocatalytic performance of the electrode can be ascribed to the formation of 3D porous Cu/Zn heterostructures, in which the porous and self-supported architecture facilitates diffusion and the Cu/Zn heterostructures can reduce the energy barrier for ECR to CO.

Effect of electrolyte systems on plasma electrolytic oxidation coatings characteristics on LPSO Mg-Gd-Y-Zn alloy

In order to solve the problem of poor corrosion resistance of Mg-Gd-Y-Zn alloy with high strength and high toughness. In this paper, two-step plasma electrolytic oxidation (PEO) was implemented on Mg-Gd-Y-Zn alloy with long period stacking ordered (LPSO) phase in seven different electrolyte systems. Optical microscope (OM), Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) were used to characterize the structure distribution and composition of the LPSO phase. X-ray diffraction (XRD), SEM, EDS, Mott-Schottky test (M-S), potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and immersion hydrogen evolution were used to study the morphology, composition, structure and corrosion resistance of the PEO coatings prepared using the various electrolytes. The PEO coating prepared by the mixed electrolyte of sodium aluminate, sodium phosphate and sodium silicate, referred to as PEO-APS coating, had the most excellent structure and corrosion resistance. The coating was dense and uniform, the coating thickness was 3.5 μm, the open porosity was 4.4 %, the average pore size was 0.12 μm, and the corrosion current density icorr was 2.09 × 10−8 A cm−2. In addition, the formation mechanism and corrosion resistance mechanism of the PEO-APS coating were discussed, and the effect of LPSO phase on the PEO-APS coating was proposed.

A Study of Electrolyte Imbalance in Coronavirus Disease-2019 at a Rural Tertiary Health Care Center

Background: With the ongoing onslaught of coronavirus disease-2019 (COVID-19) pandemic, identifying factors predicting the disease course and outcome become immensely important. Although globally reported, a potential association between electrolyte disturbance and COVID-19 disease has not been well researched. Dyselectrolytemia not only impacts patient care but also provides insight into the pathophysiology of COVID-19. Aims and Objectives: Our aim was to study electrolyte disturbances among COVID-19 patients and its impact on the disease outcome. Materials and Methods: This was a retrospective observational study conducted in a total of 397 patients detected to have electrolyte abnormalities among 2914 adult inpatients, diagnosed with COVID 19 infection in a tertiary care center over a period of 10 months (July 2020–December 2020 and April 2021–July 2021). Results: A total of 2914 patients were diagnosed with COVID-19 of whom 397 (13.62%) patients were found to have an electrolyte imbalance. Hyponatremia (n = 199) 51% was the most common electrolyte disturbance followed by hypokalemia (n = 94) 24.3% and mixed electrolyte abnormality (n = 81) 20.4%. Electrolyte imbalance was directly related to the clinical outcome of the disease which was statistically significant P = 0.0001. Conclusion: Hyponatremia has a significant direct correlation with mortality in patients with COVID-19. However, hypokalemia, hyperkalemia, and hypernatremia also influence the disease outcome. We recommend that the estimation of electrolytes should be done routinely for all hospitalized patients with COVID-19 as it adds to the prognostication of these patients.

Structurally and electrochemically tunable pyrylium platforms: A new class of redox anolyte for non-aqueous organic redox flow battery operating at a high-current density

Non-aqueous all-organic redox flow batteries (NORFB) are a proficient candidate for large-scale energy storage applications. The higher operating potential window of non-aqueous solvents, diversity of redox-active organic molecules (ROMs), and independent scaling of power and energy, etc., captivate NORFB to be a potential choice for grid energy storage applications. Besides, the invention of new redox-active motifs significantly expands the development of NORFBs; thus, it is highly demanded. But, the low operational current density and slower redox kinetics are the bottlenecks for the further development of NORFB. Herein, we introduced a new class of anolyte material based on pyrylium salt (2,4,6-triphenylpyrylium tetrafluoroborate (TPT)) and demonstrated for the first time its applicability as a potential anolyte in NORFB. The substitutions at the 2, 4, and 6th positions of pyrylium salt prominently tune the structural and electrochemical behavior, thus providing a versatile platform to explore them in flow battery chemistry. TPT exhibited a one-electron reduction process with a high electron transfer rate constant of 9.94 × 10−3 cm s−1 and diffusion coefficient of 5.83 × 10−6 cm2 s−1, which is higher for the non-aqueous medium. By coupling with N-decylphenothiazine (DPTZ) catholyte, a mixed electrolyte flow cell was demonstrated with a capacity of 1.08 Ah/L and coulombic efficiency of 97 % at a high current density of 40 mA cm−2.

Improving gas dispersion and decreasing bubble size in saline water with oscillatory air supply

The present paper describes gas dispersion in an air-sparged laboratory scale bubble column containing aqueous solutions of single electrolytes (NaCl, CaCl2, MgCl2, MgSO4, and AlCl3) and mixed electrolytes (NaCl-CaCl2 and NaCl-CaCl2-MgCl2-AlCl3) at different ionic strengths and air flow rates, with oscillatory air supply and conventional steady air supply, respectively. The gas dispersion was investigated by a light-scattering technique (turbidity measurement) and bubble size measurement. The oscillatory air supply was generated from steady air flow using a fast-switching solenoid valve and was characterized by measuring the pressure of the output air of the solenoid valve as a function of time. It was found that for each electrolyte solution tested, oscillatory air supply at a certain frequency and amplitude could give better gas dispersion than steady air supply, and the degree of improvement of gas dispersion varied with the electrolyte type and concentration and air flow rate. At each air supply mode tested, either the intensity of scattered light or the Sauter mean diameter of bubbles would scale with the ionic strength, following a decreasing trend. A cooperative effect of electrolyte addition and oscillatory air supply on gas dispersion was generally found. The combined effect of electrolyte addition and oscillatory air supply on bubble size was significant, being up to almost a 2/3 decrease in the Sauter mean diameter. The present work highlights the importance of flow condition for controlling bubble generation and coalescence in saline water and has significant implications for seawater flotation of minerals.

Thermodynamic modeling of aqueous lithium salt solutions with association electrolyte nonrandom two-liquid activity coefficient model

The high charge density of lithium ion and the resulting strong association phenomena make thermodynamic modeling of aqueous lithium electrolyte solutions extremely challenging. In this study, the association electrolyte nonrandom two-liquid activity coefficient model of Lin et al. (AIChE J. 2022, 68(2), e17422) is utilized to correlate and predict thermodynamic properties and solubility behavior of aqueous single electrolyte solutions of LiCl, LiBr, LiI, and LiNO3, and their mixed electrolyte solutions. Capturing self-association of water, cross-association of ion and water for hydration, and cross-association of cation and anion for ion-pairing, the association model accurately represents the literature experimental data up to saturation concentrations and at the temperature ranging from 263 K to 523 K. This study further investigated the effect of anions of the lithium salts, and re-confirmed that the order of solution non-ideality as LiI > LiBr > LiCl > LiNO3 because the anions with stronger association strengths are more likely to form ion pairs and thus lower the mean ionic activity coefficients.

Influence of Na2WO4 additive in electrolyte on properties of plasma electrolytic oxidation coatings on H62 brass

In order to improve the corrosion resistance of brass treated by plasma electrolytic oxidation (PEO), Na2WO4 additive was introduced into a mixed electrolyte of sodium silicate and sodium hydroxide, and a composite oxide coating was formed on the surface of H62 brass. The effect of Na2WO4 concentration from 0 to 3 g L−1 in silicate-based electrolyte on the properties of PEO coatings was investigated by SEM, EDS, XRD and electrochemical workstation. The results show that the element of W in the form of metal oxides can be successfully incorporated into PEO coatings. The addition of Na2WO4 can significantly improve the corrosion resistance of PEO coatings, and the best corrosion resistance is obtained when the addition amount is 1.0 g L−1.

Deep Eutectic Solvent for Facile Synthesis of Mn3O4@N-Doped Carbon for Aqueous Multivalent-Based Supercapacitors: New Concept for Increasing Capacitance and Operating Voltage.

The capacitance and operating voltage of supercapacitors as well as their energy density have been increased by development of different materials and electrolytes. In this paper, two strategies, for the first time, were used to improve energy density: Mn3O4- and N-dual doped carbon electrode and aqueous mixture of multivalent ions as electrolyte. Mn3O4- and N-dual doped carbon was prepared by a novel and cost-effective procedure using deep eutectic solvent. XRD, XPS, and FTIR confirmed presence of Mn3O4 and nitrogen, while SEM and EDS elemental mapping showed micrometer-sized nanosheets with uniform distribution of C, O, N, and Mn atoms. Charge storage behavior of carbon was tested in aqueous multivalent-based electrolytes and their mixture (Ca2+-Al3+). Regarding both specific capacitance and workable voltage, the Ca2+-Al3+ mixed electrolyte was found as the best optimal solution. The calcium addition to the Al-electrolyte allows the higher operating voltage than in the case of individual Al(NO3)3 electrolyte while the addition of Al3+ ion in the Ca(NO3)2 electrolyte improves the multivalent-ion charge storage ability of carbon. As a result, the specific energy density of two-electrode Mn3O4@N-doped carbon//Al(NO3)2+Ca(NO3)2//Mn3O4@N-doped carbon supercapacitor (34 Wh kg-1 at 0.1 A g-1) overpasses the reported values obtained for Mn-based carbon supercapacitors using conventional aqueous electrolytes.

Clean preparation of mixed trivalent and quadrivalent vanadium electrolyte for vanadium redox flow batteries by catalytic reduction with hydrogen

The vanadium redox flow battery (VRFB) is a promising technology for large-scale stationary energy storage systems. However, the high preparation cost of mixed valent vanadium electrolyte hinders the large-scale commercial application of VRFB. In this work, a simple, green and low-cost method is proposed to prepare the mixed valent vanadium electrolyte for VRFB. The clean hydrogen is chosen as the reducing agent to obtain trivalent vanadium ions from quadrivalent vanadium ions. The Pt/C material is used as the catalyst to accelerate the reduction rate at atmospheric pressure. The impurity-free mixed valent vanadium electrolyte, with a mean valence number of 3.5, prepared by the catalytic reduction process exhibits excellent battery performance with CE of 93% and EE of 85%. Furthermore, a catalytic reactor using Pt/C decorated graphite felt is designed and used to continuously produce the mixed valent vanadium electrolyte. According to the result of simple cost analysis, the proposed catalytic hydrogen reduction process can reduce theoretically the manufacturing cost by approximately 22.6% compared with the present industrial electrolytic process. As a consequence, the simple, clean and low-cost manufacture method of the mixed valent vanadium electrolyte exhibits remarkable competitiveness and promising potential for the practical production application of VRFB.

Stabilizing Interface pH by Mixing Electrolytes for High-Performance Aqueous Zn Metal Batteries.

Aqueous zinc metal batteries with mild acidic electrolytes are considered promising candidates for large-scale energy storage. However, the Zn anode suffers from severe Zn dendrite growth and side reactions due to the unstable interfacial pH and the absence of a solid electrolyte interphase (SEI) protective layer. Herein, a novel and simple mixed electrolyte strategy is proposed to address these problems. The mixed electrolytes of 2M ZnSO4 and 2M Zn (CF3 SO3 )2 can efficiently buffer the interfacial pH and induce the in situ formation of the organic-inorganic SEI layer, which eliminates dendrite growth and prevents side reactions. As a result, Zn anodes in mixed electrolyte exhibit a lifespan enhancement over 400 times, endure stable cycling over 270h at a high DOD of 62% and achieve high Zn plating/stripping reversibility with an average CE of 99.5% for 1000 cycles at 1mA cm-2 . The findings pave the way for developing practical electrolyte systems for Zn batteries.

Operando UV/Vis spectra deconvolution for comprehensive electrolytes analysis of vanadium redox flow battery

• 0.5 and 1 M vanadium electrolytes were successfully analyzed using the method. • The analysis provides reliable data regardless of supporting electrolyte composition. • V 2 O 3 3+ complex of posolyte was obtained using the proposed method. • Unknown residual absorbance of negolyte was registered using the deconvolution. • The method provides comprehensive data during VRFB cycling. Monitoring the state of charge (SoC) is one of the most important challenges of vanadium redox flow battery (VRFB) technology to solve. Among other methods, optical spectroscopy seems promising, however, existing approaches have their problems, primarily because of limited applicability for high vanadium concentrations, uncertainty in accounting for electrolyte imbalance during VRFB operation, and applicability limitations for mixed acid electrolytes. In this work, a method for determining SoC of VRFB based on the deconvolution of electrolyte absorption spectra is proposed. This method was successfully implemented for 0.5 M and 1 M vanadium electrolytes with 0.05 M phosphoric acid additive and demonstrated good accuracy for determining vanadium concentration and SoC in both half-cells, including analysis during VRFB galvanostatic cycling. Besides, this method allows us to obtain complex spectra: V 2 O 3 3+ in posolyte and a previously never demonstrated complex in negolyte that presumably corresponds to the V 3+ complex.

Simulation of potential and species distribution in a Li[formula omitted]Bi liquid metal battery using coupled meshes

In this work a 1D finite volume based model using coupled meshes is introduced to capture potential and species distribution throughout the discharge process in a lithium–bismuth liquid metal battery while neglecting hydrodynamic effects, focusing on the electrochemical properties of the cell and the mass transport in electrolyte and cathode. Interface reactions in the electrical double layer are considered through the introduction of a discrete jump of the potential modelled as periodic boundary condition to resolve interfacial discontinuities in the cell potential. A balanced-force like approach is implemented to ensure consistent calculation at the interface level. It is found that mass transport and concentration gradients have a significant effect on the cell overpotentials and thus on cell performance and cell voltage. By quantifying overvoltages in the Li||Bi cell with a mixed cation electrolyte, it is possible to show that diffusion and migration current density could have counteractive effects on the cell voltage. Furthermore, the simulated limiting current density is observed to be much lower than experimentally measured, which can be attributed to convective effects in the electrolyte that need to be addressed in future simulations. The solver is based on the open source library OpenFOAM and thoroughly verified against the equivalent system COMSOL multiphysics and further validated with experimental results.

Modeling on the phase equilibrium of gas hydrate in electrolytes containing system

The phase equilibrium of gas hydrate is fundamental for flow assurance, energy exploitation, and hydrate concerning technique. In this study, the electrolyte NRTL equation coupled with the two-step hydrate model of Chen and Guo was successfully applied to predict the phase equilibrium of gas hydrate in the presence of single and binary mixed electrolytes. The predicted results were in good agreement with the available experimental data over a wide range of electrolyte concentrations when taking into account the contributions of long-range and short-range interactions in saline solution. Validated with 943 hydrate experimental data of pure gas and gas mixture formed in single and mixed electrolytes, the average absolute deviations in pressure are 5.42 % and 4.71 %, respectively. More importantly, it is further investigated that the proposed model shows a better performance for the high-concentration saline solution with concentration up to the near-saturation, with an average deviation of 0.59 K for methane hydrate. Therefore, the proposed model in this work is significant for comprehending gas hydrate phase behavior in saline solution, and provides better guidance for hydrate exploitation and industrial applications.

Bimetallic Rechargeable Al/Zn Hybrid Aqueous Batteries Based on Al-Zn Alloys with Composite Electrolytes.

Aluminum is abundant and exhibits a high theoretical capacity and volumetric energy density. Additionally, the high safety of aqueous aluminum-ion batteries makes them strong candidates for large-scale energystorage systems. However, the frequent collapse of the cathode material and passive oxide film results in the difficult development of aqueous aluminum-ion batteries. This work provides a novel battery system, namely, Al-Zn/Al(OTF)3 +HOTF+Zn(OTF)2 /Alx Zny MnO2 ·nH2 O, with a mixed electrolyte. The cathode applies MnO topology transformation to ensure that the cathode forms Alx MnO2 ·nH2 O. Topology transformation alters the structure of the cathode material so that Zn2+ can be intercalated into the Alx MnO2 ·nH2 O spinel structure to provide support for the material structure. Regarding the anode, Zn2+ in the electrolyte is deposited onto Al of the anode to produce a regional Al-Zn alloy. Zn2+ is reduced to Zn metal during discharging, which adds a platform for secondary discharge beneficial for battery capacity enhancement. This system can provide a 1.6V discharge platform, while the first cycle discharge can reach 554 mAhg-1 , thereby maintaining a high capacity of 313 mAhg-1 after 100 cycles. This study provides a new idea for the further development of aqueous aluminum-ion batteries (AAIBs).

(Invited) Ester and Carbonate-Based Low Temperature Electrolytes for Operation of Lithium-Ion Batteries in Extreme Environments for NASA Missions

NASA continues to have an interest in developing high specific energy and high power rechargeable batteries that can operate well over a wide temperature range. Potential applications that could be enabled or enhanced by such technology include: (i) future Mars and Lunar landers, (ii) future Mars and Lunar rovers, (iii) small robotic missions, and (iv) future planetary aerial vehicles, where high specific energy, high power and wide operating temperature range is desired. Future missions to some of the distant icy moons of Jupiter and Saturn are also anticipated to benefit from improved ultra-low temperature rechargeable batteries with high specific energy.1 A number of terrestrial applications, including automotive and aviation Li-ion batteries, also benefit from having wide temperature range capability. To meet these needs, the Electrochemical Research, Technology, and Engineering Group at the Jet Propulsion Laboratory (JPL) has developed a number of low temperature Li-ion electrolytes utilizing various approaches. Broadly speaking, the performance targets of this work are to provide operation over the temperature range of +60oC to -60oC (delivering over 100 Wh/kg at -40oC at reasonable rates).This paper will provide an overview of the low temperature electrolyte development activities that have taken place at JPL, with a focus on enabling ultra-low temperature operation for extreme environments. The electrolytes evaluated included blends which contain elements of various approaches, including (i) the use of ester co-solvents, (ii) low ethylene carbonate content-based blends, (iii) the use of electrolyte additives, and (iv) the use of mixed lithium electrolyte salts. Experimental studies were performed utilizing three-electrode cells to determine the influence that the electrolyte type has upon the electrode kinetics as a function of temperature. A number of electrochemical techniques were employed to study these cells, including Electrochemical Impedance Spectroscopy (EIS), Tafel polarization, and linear micro-polarization.Improved low temperature capability has been demonstrated in small and large capacity prototype cells with a number of chemistries (i.e., NCO, NCA, NMC, LCO and LFP-based chemistries), including the ability to deliver high specific energy down to -60oC, good charge acceptance at low temperature, and high-power capability at -40oC. Prototype cells incorporating JPL developed electrolytes were obtained from a number of vendors, including (i) Eagle Pitcher Technologies-Yardney Division, (ii) Enersys/Quallion, LLC, (iii) E-One Moli Energy Ltd., (iv) Saft America, and (iv) Navitas/A123. Emphasis was devoted to establishing the charge acceptance characteristics of the cells at very low temperatures, especially below -20oC. Given that lithium plating when charging at low temperatures is a known degradation mode of Li-ion cells in general, attention was focused upon characterizing the conditions in which its likelihood may be more pronounced, determining the influence of electrolyte type, and attempting to detect its occurrence indirectly.Early generations of electrolytes have been utilized in a number of NASA missions, including the 2003 Mars Exploration Rover, 2007 Phoenix Lander, 2011 Mars Science Laboratory (MSL) Curiosity Rover, 2018 Mars InSight Lander, and a JPL/CSUN CubeSat.1-5 Previous work has also targeted improved low temperature performance of Li-ion cells for automotive applications. Current work is focused primarily upon providing higher specific energy coupled with good power characteristics at very low temperatures. Studies have also been performed demonstrating operational capability down to -90oC in some systems, and survival capability to temperatures as low as -135oC.ACKNOWLEDGEMENT The work described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA). The information in this document is pre-decisional and is provided for planning and discussion only. REFERENCES M. C. Smart, B. V. Ratnakumar, R. C. Ewell, S. Surampudi, F. Puglia, and R. Gitzendanner, Electrochimica Acta, 268, 27-40 (2018). M. C. Smart, D. Muthulingam, M. E. Lisano, S. F. Dawson, R. B. Shaw, B. T. White, A. Buonanno, C. Deroy, and R. Gitzendanner, 236th Meeting of the Electrochemical Society (ECS), Atlanta, Georgia, October 15, 2019. M. C. Smart, F. C. Krause, and J. -P. Jones, CREB Bi-Annual Meeting, University of Maryland, December 10, 2021. K. B. Chin, G. B. Bolotin, M. C. Smart, S. Katz, J. A. Flynn, N. K. Palmer, E. J. Brandon, and W. C. West, IEEE A&E Systems Magazine, 36 (5), 24-36 (2021). M. C. Smart, B. V. Ratnakumar, F. Charlie Krause, William C. West and Erik J. Brandon, 2021 Space Power Workshop (Virtual), Pasadena, CA, April 19, 2021. M. C. Smart, F. C. Krause, J. -P. Jones, C. L. Fuller, J. A. Schwartz, and B. V. Ratnakumar, 2018 Conference on Advanced Power Systems for Deep Space Exploration, Pasadena, CA, October 22-24, 2018.

An Effective Mixed-Salt As Electrolyte Additive to Improve Calendar Life for Si Anode in Lithium Ion Batteries

For the next generation of Lithium-ion batteries, Silicon is drawing attention as the upcoming anode materials with higher capacity than commercial graphite ( Silicon : 3590 mA h g-1vs Graphite : 375 mA h g-1). Especially, Si is suitable for long range electric vehicle from being higher theoretical capacity. However, the chronic problem of Si anode such as large expansion with fracture or pulverization has effect on the calendar life performance. In order to achieve the enhanced calendar life, we suggest that Ca and Mg mixed additive with electrolyte for Si anode in this work, based on our previous reports. In this work, analytical techniques such as NMR and Rietveld refinement was conducted to clarify effect of mixed salt. Ca and Mg inserted to bulk Si to cause formation of quaternary Li-Ca-Mg-Si phase with thermodynamic stability, and Ca salt make dense and strong CaF2 SEI layer on the Si particle, which protect the side reaction between Si particle and electrolyte in coin cell system,. The full cell with mixed additive electrolyte (called Gen FMC) shows enhanced calendar life performance with lower measured current and current leakage than that of baseline electrolyte (called Gen F), being brought by less side reaction. In adding to that, full cell with Gen FMC could delivered high specific capacity after 100 cycles with 47.4 % of retention (Gen F : 36.3%) and high columbic efficiency. We were also able to find that Gen FMC tends to have less cracking electrode surface than that of Si electrode with Gen F.

Design Principles for Flow Batteries: Cation Dependent Membrane Resistance and Active Species Solubility

Aqueous redox flow batteries are generally adapted from polymer electrolyte membrane fuel cells that use proton exchange membranes to balance the charge of the cell. Such membranes are well understood and exhibit excellent performance in acidic electrolytes via transport of protons. For neutral pH flow batteries however, the primary cation in solution is not H+, but the cation of the active material or supporting electrolyte salt.The nature of the cation in solution, e.g., hydrated ionic radius and charge density, significantly affects the transport resistance through the membrane and thus the area specific resistance of the cell, a critical parameter that needs to be minimized for high power applications such as flow batteries. Additionally, different cations result in vastly different solubilities of active materials based on redox active anions such as ferrocyanides; the ammonium salt for example is ca. three times more soluble than the sodium salt (1.6 M vs. 0.5 M).[1] It is therefore critical to not only maximize the concentration of an electrolyte and thus its capacity, but to also choose cations that enable efficient transport across the membrane for efficient flow battery development.Here, we study the cation dependent resistance of NafionTM 212 cation exchange membranes for 12 different alkali and alkylammonium cations and determine the solubilities of 13 ferrocyanides as well as 35 metal-organic chelates based on aminopolycarboxylate ligands. The latter are a particularly promising family of compounds for application in negative electrolytes in near neutral pH aqueous flow batteries with demonstrated discharge voltages as high as 2.1 V and excellent power performance.[2] We further discuss cation-compatibility for mixed cation electrolytes as well as membrane pretreatments that affect the cells area specific resistance and active species crossover.[3]