Low-Temperature Molten Sodium Batteries

Gross, Martha; Percival, Stephen; Small, Leo J; Lamb, Joshua; Peretti, Amanda; Spoerke, Erik David

doi:10.1021/acsaem.0c02385

Cited by 20 publications

(24 citation statements)

References 45 publications

(70 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Sodium (Na) batteries have recently generated excitement for grid-scale energy storage. − Particularly, batteries that employ solid or liquid Na metal electrodes benefit from their extremely high theoretical specific capacity (1166 mAh g –1 ), low reduction potential (−2.71 V vs standard hydrogen electrode), and earth abundance. − However, solid Na metal does not form a highly stable solid electrolyte interphase (SEI) in the presence of liquid electrolytes, leading to continuous capacity degradation. − This drawback has motivated the use of solid electrolytes, such as NaSICON (Na 1+ x Zr 2 Si x P 3– x O 12 , 0 < x < 3) and β″-alumina, that are stable in the presence of Na metal and can serve as a conduction pathway for Na + . − Additionally, it was originally believed that solid electrolytes would eliminate the issue of dendrite formation that plagues solid Na metal electrodes due to their high mechanical strength . This expectation, however, has been disproven as dendrites still form easily within solid electrolytes above a critical current density (CCD) (typically ∼ 1 mA cm –2 at room temperature). − Dendrite formation can be alleviated by employing molten Na metal as an electrode, such as in Na-S and ZEBRA batteries.…”

Section: Introductionmentioning

confidence: 99%

“…This expectation, however, has been disproven as dendrites still form easily within solid electrolytes above a critical current density (CCD) (typically ∼ 1 mA cm –2 at room temperature). − Dendrite formation can be alleviated by employing molten Na metal as an electrode, such as in Na-S and ZEBRA batteries. This improvement is due to the increased conductivity of the solid electrolyte and better wetting of molten Na metal on the electrolyte surface at elevated temperatures (which reduces the interfacial resistance). − Despite these improvements, dendrites still form at sufficiently high current densities, limiting the high-current performance of these batteries. − Here, we seek to understand the mechanisms for Na dendrite formation in the highly conductive Na-ion conductor, NaSICON, which is recognized as a promising solid-state conductor, particularly for lower-temperature molten Na battery applications. − ,,,,− …”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Molten Sodium Penetration in NaSICON Electrolytes at 0.1 A cm^–2

Hill

Peretti

Small

et al. 2023

ACS Appl. Energy Mater.

Self Cite

View full text Add to dashboard Cite

High-conductivity solid electrolytes, such as the Na superionic conductor, NaSICON, are poised to play an increasingly important role in safe, reliable battery-based energy storage, enabling advanced sodium-based batteries. Coupled demands of increased current density (≥0.1 A cm–2) and low-temperature (<200 °C) operation, combined with increased discharge times for long-duration storage (>12 h), challenge the limitations of solid electrolytes. Here, we explore the penetration of molten sodium into NaSICON at high current densities. Previous studies of β″-alumina proposed that Poiseuille pressure-driven cracking (mode I) and recombination of ions and electrons within the solid electrolyte (mode II) are the two main mechanisms for Na penetration, but a comprehensive study of Na penetration in NaSICON is necessary, particularly at high current density. To further understand these modes, this work employs unidirectional galvanostatic testing of Na|NaSICON|Na symmetric cells at 0.1 A cm–2 over 23 h at 110 °C. While galvanostatic testing shows a relatively constant yet increasingly noisy voltage profile, electrochemical impedance spectroscopy (EIS) reveals a significant decrease in cell impedance correlated with significant sodium penetration, as observed in scanning electron microscopy (SEM). Further SEM analysis of sodium accumulation within NaSICON suggests that mode II failure may be far more prevalent than previously considered. Further, these findings suggest that total (dis)charge density (mAh cm–2), as opposed to current density (mA cm–2), may be a more critical parameter when examining solid electrolyte failure, highlighting the challenge of achieving long discharge times in batteries using solid electrolytes. Together, these results provide a better understanding of the limitations of NaSICON solid electrolytes under high current and emphasize the need for improved electrode–electrolyte interfaces.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Molten Sodium Penetration in NaSICON Electrolytes at 0.1 A cm^–2

Hill

Peretti

Small

et al. 2023

ACS Appl. Energy Mater.

Self Cite

View full text Add to dashboard Cite

show abstract

“…Batteries were assembled in an Ar-filled glovebox with <0.1 ppm of O 2 and H 2 O. Anode and cathode materials were housed in custom glass chambers with W rod current collectors glass sealed at one end, as described previously . The anode chamber contained 1.5 g of Sn-saturated metallic Na (6.7 × 10 –3 wt % Sn).…”

Section: Methodsmentioning

confidence: 99%

“…Batteries were assembled in an Ar-filled glovebox with <0. materials were housed in custom glass chambers with W rod current collectors glass sealed at one end, as described previously. 38 The anode chamber contained 1.5 g of Snsaturated metallic Na (6.7 × 10 −3 wt % Sn). Na was saturated in Sn to prevent dissolution of the Sn thin film deposited on the NaSICON.…”

Section: ■ Introductionmentioning

confidence: 99%

Impact of Catholyte Lewis Acidity at the Molten Salt–NaSICON Interface in Low-Temperature Molten Sodium Batteries

et al. 2023

Self Cite

View full text Add to dashboard Cite

Low-temperature molten sodium batteries comprising molten sodium anodes, a NaSICON solid-state separator, and molten halide salt catholytes offer promise as low-cost, earth-abundant energy storage technologies. The emergence of a specific, high-voltage, sodium iodide (NaI)-based catholyte chemistry has prompted the evaluation of chemical and electrochemical properties of the molten salts, particularly at critical interfaces with high-performance NaSICON separators. Herein, batteries operated at 110 °C with NaI-AlCl3-based catholytes of differing Lewis acidities were evaluated. Batteries with >50 mol % AlCl3 (acidic catholytes) experienced a linear decline in energy efficiency during cycling, whereas batteries with >50 mol % NaI (basic catholytes) maintained >95% energy efficiency for 50 cycles (>80 days) at 2.5 mA cm–2. A three-electrode cell was developed, enabling identification of the NaSICON–catholyte interface as the source of increased battery impedance. Complementary physical and chemical characterization of the NaSICON exposed to acidic and basic catholytes showed no changes in crystallinity, bulk morphology, or bulk chemical composition, but surface sensitive X-ray photoelectron spectroscopy (XPS), however, revealed subtle changes in local NaSICON surface chemistry. In addition, Raman spectroscopy indicated that stably performing basic catholytes lack the dimer species Al2Cl6I– present in acidic catholytes. Select thermodynamic and formal charge assessments suggest that preferential interactions between these acidic dimeric species and the NaSICON surface may be responsible for the observed increases in electrochemical impedance and degraded battery performance. These results indicate that maintaining a Lewis basic catholyte avoids such potentially deleterious interactions, enabling efficient and stable battery cycling.

show abstract

“…While these experimentally observed polarisation effects were attributed to the cathode, the existence of concentration gradients within the electrolyte have at least been subject of theoretical considerations. Especially the risk of electrolyte solidification due to compositional changes [38][39][40][41][42] has been discussed in this context.…”

Section: Liquid Metal Battery and Its Applicationmentioning

confidence: 99%

Modeling Potential and Species Distribution in a Li||Bi Liquid Metal Battery Using the Finite Volume Method

et al. 2022

View full text Add to dashboard Cite

To match the growing demand for grid scale energy storage in order to balance out renewable energies, the liquid metal battery (LMB) technology is highly promising. Key elements of these batteries are the liquid electrodes, which require LMBs operating at elevated temperatures. Hereby, the electrolyte can be liquid or solid state. Based on density differences, the battery is self-assembling since the components self-segregate when the system is heated. Additionally, many of the possible materials are earth-abundant and not expensive. This results in a very cost effective technology. Moreover, the molten electrodes feature superior kinetics and transport properties as well as high voltage efficiencies at high current densities. Otherwise, the liquidity has the disadvantage that high operating temperatures are necessary. Further, there is a risk of corrosion, self-discharge and short-circuiting. The latter makes the battery not applicable for portable applications [Kim, H. et al. Chem. Rev. 113 (3) (2013)]. Among all LMBs, the Li||Bi cell has been investigated to a large extend and therefore, most material properties are readily available. This is the reason why the present study focuses on this material pairing. A schematic of this cell during discharge is shown in figure 1a. Here, the anode metal Lithium is oxidized and the ion crosses the electrolyte layer. Then it alloys with the molten Bismuth. At charge, this process is reversed. A picture of a real cell can be found in figure 1b. Nevertheless, there are other very promising cell chemistries such as NaZn batteries [Xu, J. et al. J. Power Sources 332 (2016)]. For theoretical investigations and numerical simulations, electromagnetic fields, electrochemistry and fluid dynamics need to be considered. Coupling of the corresponding fundamental equations and the different regions in the battery is challenging. Further, there are multiple fluid flow phenomena – like surface instabilities, Tayler instability, electro-vortex flow, thermal convection,solutal convection or Marangoni convection [Kelley, D. H. and Weier, T. Appl. Mech. Rev. 70 (2) (2018)] – that might occur when the battery is operated. To determine the operating voltage of a cell, overpotentials need to be investigated. Generally, there are three types of overpotentials: the ohmic loss, the mass transfer and the charge transfer overpotential. However, the latter can be neglected [Newhouse, J. M. Ph.D. thesis, MIT (2014)]. Determining the ohmic overpotential is quite straightforward using Ohm’s law, while the concentration overpotential requires the calculation of the species distribution in the electrolyte and the positive electrode. The present study will focus on the electrochemical behavior of an all liquid Li||Bi battery and neglects fluid flow. Hereby, the whole cell is modeled using the parent-child-mesh technique from Weber et al. [Weber, N. et al. Computers & Fluids 168 (2018)]. This implies that the species distribution in the electrolyte and the distribution of the dissolved species in the cathode are calculated locally and the potential and current density distribution are calculated globally. The equations to solve are coupled between the used meshes. To account for the potential distribution, it is necessary to consider the electrochemical double layer at the electrode-electrolyte interfaces. Macroscopically, the latter can be described as a potential jump at both interfaces in accordance to the Nernst equation. Weber et al. [Weber, N. et al. Electrochim. Acta 318 (2019)] introduced to model this jump using a source term. In the present study, the approach to use internal jump boundary conditions for modeling the potential jump is proposed. To the best knowledge of the authors, species distributions in the electrolyte have not been investigated previously. When there is no mixing of the electrolyte of LMBs, concentration gradients of each species might be significant [Vallet, C. E. et al. J. Electrochem. Soc. 130 (12) (1983)]. Based on the solution for the species distribution, the potential jump at each interface can be calculated. Further, the charge transfer overpotentials can be obtained. The equations are solved quasi-one-dimensional using the finite volume method and are implemented in the open source library OpenFOAM. To validate this new approach, a comparative study with Comsol is performed. Lastly, an application case is simulated, which confirms that concentration layers in the electrolyte are indeed present. This is, for the case of an Li+ ion in a LiCl-KCl eutectic molten salt, exemplarily shown in figure 1d. Further, as it can be seen in figure 1c, the simulation is able to solve the potential distribution in the cell with respect to the potential jump at the interface. Acknowledgment: This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 963599. Figure 1

show abstract

Low-Temperature Molten Sodium Batteries

Cited by 20 publications

References 45 publications

Molten Sodium Penetration in NaSICON Electrolytes at 0.1 A cm^–2

Molten Sodium Penetration in NaSICON Electrolytes at 0.1 A cm^–2

Impact of Catholyte Lewis Acidity at the Molten Salt–NaSICON Interface in Low-Temperature Molten Sodium Batteries

Modeling Potential and Species Distribution in a Li||Bi Liquid Metal Battery Using the Finite Volume Method

Contact Info

Product

Resources

About

Low-Temperature Molten Sodium Batteries

Cited by 20 publications

References 45 publications

Molten Sodium Penetration in NaSICON Electrolytes at 0.1 A cm–2

Molten Sodium Penetration in NaSICON Electrolytes at 0.1 A cm–2

Impact of Catholyte Lewis Acidity at the Molten Salt–NaSICON Interface in Low-Temperature Molten Sodium Batteries

Modeling Potential and Species Distribution in a Li||Bi Liquid Metal Battery Using the Finite Volume Method

Contact Info

Product

Resources

About

Molten Sodium Penetration in NaSICON Electrolytes at 0.1 A cm^–2

Molten Sodium Penetration in NaSICON Electrolytes at 0.1 A cm^–2