Geologic mapping of Mawrth Vallis, Mars

Mawrth Vallis, generally counted among Mars’ giant outflow channels, has an atypical geomorphology that is less well-studied than its coinciding, thick (>150m) clay-bearing deposits. Here, we present ongoing work as part of the PLANMAP project to map the geomorphic features along the length of Mawrth Vallis in addition to a detailed map of the channel adjacent to the ExoMars 2018 landing ellipse to establish its history of erosion and deposition and relationship with the clay-bearing deposits

Potentiometric MRI of a Superconcentrated Lithium Electrolyte: Testing the Irreversible Thermodynamics Approach.

Superconcentrated electrolytes, being highly thermodynamically nonideal, provide a stringent proving ground for continuum transport theories. Herein, we test an ostensibly complete model of LiPF6 in ethyl-methyl carbonate (EMC) based on the Onsager-Stefan-Maxwell theory from irreversible thermodynamics. We perform synchronous magnetic resonance imaging (MRI) and chronopotentiometry to examine how superconcentrated LiPF6:EMC responds to galvanostatic polarization and open-circuit relaxation. We simulate this experiment using an independently parametrized model with six composition-dependent electrolyte properties, quantified up to saturation. Spectroscopy reveals increasing ion association and solvent coordination with salt concentration. The potentiometric MRI data agree closely with the predicted ion distributions and overpotentials, providing a completely independent validation of the theory. Superconcentrated electrolytes exhibit strong cation-anion interactions and extreme solute-volume effects that mimic elevated lithium transference. Our simulations allow surface overpotentials to be extracted from cell-voltage data to track lithium interfaces. Potentiometric MRI is a powerful tool to illuminate electrolytic transport phenomena

Geological mapping of Mawrth Vallis, Mars, by PLANMAP

Mawrth Vallis is generally considered to be the oldest of Mars’ outflow channels. It incises Noachian (> 3.7 Ga) terrain and is associated with thick (> 150 m), clay-bearing deposits. Clays are important astrobiologically because they are potential catalytic substrates for (pre)biotic chemistry and have a high potential to preserve biosignatures. The presence of clay-bearing deposits was an important factor in the decision to shortlist an area adjacent to Mawrth Vallis as a candidate landing site for the ExoMars “Rosalind Franklin” rover, whose mission is to search for signs of ancient life on Mars. Ultimately, Mawrth Vallis was not selected as the ExoMars landing site. The origin and geological context of the clay-bearing deposits is not well understood. Furthermore, the geomorphology of Mawrth Vallis, which records its history of deposition/burial and erosion/exhumation, is also less well-studied compared with its mineralogy. Here, we present our ongoing geological mapping of Mawrth Vallis, which we are conducting to investigate the relationship between the channel and the clay-bearing deposits. We are producing a detailed map of the main Mawrth Vallis channel adjacent to the proposed ExoMars landing ellipse. We will also produce an accompanying geomorphic feature map along the whole length of Mawrth Vallis at a smaller scale. We are creating this map as part of the Planmap project, which aims to provide standards for European researchers to adhere to in order to aid the dissemination of their maps. Planmap is producing exemplar maps of Mercury, the Moon, and Mars, where various datasets (visual images, elevation models, spectra, crater size-frequency distributions) will be fused to make more fully-intergrated geological maps. The abundance and diversity of data types at Mawrth Vallis, in addition to its scientific interest, make this region particularly suitable for Planmap

Revealing the role of fluoride‐rich battery electrode interphases by operando transmission electron microscopy

The solid electrolyte interphase (SEI), a complex layer that forms over the surface of electrodes exposed to battery electrolyte, has a central influence on the structural evolution of the electrode during battery operation. For lithium metallic anodes, tailoring this SEI is regarded as one of the most effective avenues for ensuring consistent cycling behavior, and thus practical efficiencies. While fluoride-rich interphases in particular seem beneficial, how they alter the structural dynamics of lithium plating and stripping to promote efficiency remains only partly understood. Here, operando liquid-cell transmission electron microscopy is used to investigate the nanoscale structural evolution of lithium electrodeposition and dissolution at the electrode surface across fluoride-poor and fluoride-rich interphases. The in situ imaging of lithium cycling reveals that a fluoride-rich SEI yields a denser Li structure that is particularly amenable to uniform stripping, thus suppressing lithium detachment and isolation. By combination with quantitative composition analysis via mass spectrometry, it is identified that the fluoride-rich SEI suppresses overall lithium loss through drastically reducing the quantity of dead Li formation and preventing electrolyte decomposition. These findings highlight the importance of appropriately tailoring the SEI for facilitating consistent and uniform lithium dissolution, and its potent role in governing the plated lithium's structure

The high-resolution map of Oxia Planum, Mars; the landing site of the ExoMars Rosalind Franklin rover mission

This 1:30,000 scale geological map describes Oxia Planum, Mars, the landing site for the ExoMars Rosalind Franklin rover mission. The map represents our current understanding of bedrock units and their relationships prior to Rosalind Franklin’s exploration of this location. The map details 15 bedrock units organised into 6 groups and 7 textural and surficial units. The bedrock units were identified using visible and near-infrared remote sensing datasets. The objectives of this map are (i) to identify where the most astrobiologically relevant rocks are likely to be found, (ii) to show where hypotheses about their geological context (within Oxia Planum and in the wider geological history of Mars) can be tested, (iii) to inform both the long-term (hundreds of metres to ∼1 km) and the short-term (tens of metres) activity planning for rover exploration, and (iv) to allow the samples analysed by the rover to be interpreted within their regional geological context

Geological mapping of Mawrth Vallis, Mars: First look

[Introduction] Mawrth Vallis (Figure 1) is generally understood to be one of Mars’ catastrophic out-flow channels. It is incised into Noachian (> 3.7 Ga) terrain and is associated with thick (> 150 m) clay deposits [1]. These clays are well-documented [e.g. 1–3], and have made Mawrth Vallis a candidate landing site for multiple rover missions. However, the atypical geomorphology of the channel is less well-studied. In the PLANMAP project, we will produce a geological map of Mawrth Vallis to establish its his-tory of erosion and deposition and relationship with the clays

Insights into Ionic Liquid Electrolyte Transport and Structure via Operando Raman Microspectroscopy

Ionic liquid electrolytes (ILEs) have become popular in various advanced Li-ion battery chemistries because of their high electrochemical and thermal stability, and low volatility. However, due to their relatively high viscosity and poor Li+ diffusion, it is thought large concentration gradients form, reducing their rate capability. Here, we utilised operando Raman microspectroscopy to visualise ILE concentration gradients for the first time. Specifically, using lithium bis(fluorosulfonyl)imide (LiFSI) in N-propyl- N-methylpyrrolidinium FSI, its "apparent" diffusion coefficient, lithium transference number, thermodynamic factor, ionic conductivity and resistance of charge-transfer against lithium metal, were isolated. Furthermore, the analysis of these concentration gradients led to insights into the bulk structure of ILEs, which we propose is composed of large, ordered aggregates

Characterising Lithium-Ion Electrolytes via Operando Raman Microspectroscopy

Knowledge of electrolyte transport and thermodynamic properties in Li-ion and ”beyond Li-ion” technologies is vital for their continued development and success. Here, we present a method for fully characterising electrolyte systems. By measuring the electrolyte concentration gradient over time via operando Raman microspectroscopy, in tandem with potentiostatic electrochemical impedance spectroscopy, the Fickian ”apparent” diffusion coefficient, transference number, thermodynamic factor, ionic conductivity and resistance of charge-transfer were quantified within a single experimental setup. Using lithium bis(fluorosulfonyl)imide (LiFSI) in tetraglyme (G4) as a model system, our study provides a visualisation of the electrolyte concentration gradient; a method for determining key electrolyte properties, and a necessary technique for correlating intermolecular electrolyte structure with the described transport and thermodynamic properties.</div

Paving the Way toward Highly Efficient, High-Energy Potassium-Ion Batteries with Ionic Liquid Electrolytes

Potassium-ion batteries (KIB) are a promising complementary technology to lithium-ion batteries because of the comparative abundance and affordability of potassium. Currently, the most promising KIB chemistry consists of a potassium manganese hexacyanoferrate (KMF) cathode, a Prussian blue analog, and a graphite anode (723 W h l–1 and 359 W h kg–1 at 3.6 V). No electrolyte has yet been formulated that is concurrently stable at the high operating potential of KMF (4.02 V vs K+/K) and compatible with K+ intercalation into graphite, currently the most critical hurdle to adoption. Here, we combine a KMF cathode and a graphite anode with a KFSI in Pyr1,3FSI ionic liquid electrolyte for the first time and show unprecedented performance. We use high-throughput techniques to optimize the KMF morphology for operation in this electrolyte system, achieving 119 mA h g–1 at 4 V vs K+/K and a Coulombic efficiency of >99.3%. In the same ionic liquid electrolyte, graphite shows excellent electrochemical performance and we demonstrate reversible cycling by operando X-ray diffraction. These results are a significant and essential step forward toward viable potassium-ion batteries

Ordered LiNi0.5Mn1.5O4 Cathode in Bis(fluorosulfonyl)imide-Based Ionic Liquid Electrolyte: Importance of the Cathode-Electrolyte Interphase

The high voltage (4.7 V vs. Li+ /Li) spinel lithium nickel manganese oxide (LiNi0.5 Mn1.5 O4 , LNMO) is a promising candidate for the next-generation of lithium ion batteries due to its high energy density, low cost and environmental impact. However, poor cycling performance at high cutoff potentials limits its commercialization. Herein, hollow structured LNMO is synergistically paired with an ionic liquid electrolyte, 1M lithium bis(fluorosulfonyl)imide (LiFSI) in N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (Pyr1,3 FSI) to achieve stable cycling performance and improved rate capability. The optimized cathode-electrolyte system exhibits extended cycling performance (>85% capacity retention after 300 cycles) and high rate performance (106.2mAhg–1 at 5C) even at an elevated temperature of 65 ◦C. X-ray photoelectron spectroscopy and spatially resolved x-ray fluorescence analyses confirm the formation of a robust, LiF-rich cathode electrolyte interphase. This study presents a comprehensive design strategy to improve the electrochemical performance of high-voltage cathode materials.</div