Highly alkaline brines comprising mixtures of alkali metal cations are an important component of safe, aqueous chemistries for (long-duration) energy storage, electrowinning for the direct reduction of metal oxides to metal, industrial electrolysis, and many other technological applications. Physicochemical studies of the ion association, solvation dynamics, and transport in this highly concentrated regime are sparse, particularly with LiOH as a mixture component approaching its saturation limit, and could provide key inputs for physics-based modeling efforts and defining operational limits. To this end, this study maps the composition space for KOH/LiOH and KOH/NaOH ranging from total ionic strengths of 1 to 9 M, with a series of alkali cation mixtures at each ionic strength and an emphasis on contrasting the solvation dynamics and transport of brines with Li+ cocations versus Na+. Combining NMR chemical shift, diffusivity, ionic conductivity, density, viscosity, and NMR relaxation measurements yields a detailed understanding of the hydroxide affinity of Li+ compared to K+ and Na+ as well as the evolution of the solution structure as the Li+ saturation limit is approached, culminating in the elucidation of a distinct solvation regime in these mixed cation electrolytes at ionic strengths above 6 M for both KOH/LiOH and KOH/NaOH.

It is well known that the internal gradient (g i) that exists within pores haunts the diffusion coefficient (D) as measured by the pulsed-field gradient (PFG) nuclear magnetic resonance (NMR). Several PFG-NMR methods developed to determine accurate D were not successful. Then, the steady-state diffusion coefficient (D app,infinity) for the cation [C4mim]+ of [C4mim][Tf2N] [1-butyl-3-methylimidazolium][bis(trifluoromethylsulfonyl)imde] ionic liquid confined in ordered mesoporous carbon (OMC) was determined by comparing D app,infinity obtained from 1H PFG-NMR performed with three different stimulated echo sequences: STE, alternating pulsed-field gradient (APFG), and magic pulsed-field gradient (MPFG) under the two external magnetic field strengths, B 0 = 9.4 and 14.1 T. The measured D app,infinity, which is an order of magnitude smaller than D of bulk [C4mim][Tf2N], is in good agreement between APFG and MPFG in both B 0 = 9.4 and 14.1 T. However, the strong g i artifact, which caused apparent diffusion coefficient (D app), depending strongly and weakly on B 0 and temperature, respectively, in diffusion time-dependent D app, D app(Delta), obtained from a sequence with monopolar gradients (STE), was suppressed by using sequences employing bipolar gradients (APFG and MPFG) in the region of steady-state diffusion. However, the incompletely suppressed g i artifact resulting in the different behaviors of the early part of D app(Delta) between the sequences leads to alpha approximate to 0.6 and 0.9 in MPFG and APFG, respectively, in the relationship between mean-squared displacement and diffusion time: < z(t)2 > = 2Dt alpha, where alpha = 0.5 and 1 for one-dimensional single-file diffusion and 3D bulk diffusion, respectively. The above observations clearly show that the diffusion behavior of ions/molecules within the pores and pore structure, such as the surface-to-volume ratio ( D app ( Delta ) = D 0 [ 1 - 4 9 pi S V D 0 Delta ] ) and tortuosity (T equivalent to D 0/D app,infinity), is possible to be misunderstood, especially in systems with a non-negligible g i. This work demonstrates that it may be necessary to test several PFG sequences under multiple external magnetic fields for the correct determination of the diffusion behavior of ions or molecules in the pores with a larger internal gradient, g i.

The feasibility of using TEMPO catholyte in long-cycling aqueous redox flow batteries depends on the effective mitigation of the ring-opening side reactions.

Transient nanoclusters in aqueous ZnSO 4 electrolytes are revealed with X-ray scattering and molecular dynamics simulations. These nanoclusters exhibit diverse sizes and geometries, influencing ion correlations and transport properties.

Ionene - ionic liquid (IL) composites are promising materials for CO2 separation, yet a molecular-level understanding of their structure and its impact on CO2 speciation, solubility, rotation, and diffusivity remains unclear. Herein, using multimodal nuclear magnetic resonance (NMR), time-of-flight secondary ion mass spectrometry (ToF-SIMS), atomic force microscopy (AFM), and molecular dynamics (MD) simulations, we reveal that the composites contain IL-rich domains extending across hundreds of nanometres within the ionene matrix, and these bicontinuous domains span the entire membrane depth. CO2 also absorbs into the ionene matrix, with the distribution between two CO2 species varying with temperature and time. The rotational correlation times of these two species are on the timescale of 0.1 and 1 ns, respectively. As IL content increases, the ionic domains expand, resulting in higher CO2 solubility due to enhanced molecular dynamics and increased free volume in both ionene backbones and IL-rich regions. Although CO2 diffusion in the membranes is an order of magnitude slower than in bulk IL, the activation energy for CO2 diffusion remains comparable. Ionene-IL composites represent a promising platform for designing CO2 separation membranes, offering enhanced CO(2)diffusion and selectivity through IL-rich domains, and increased CO2 solubility and mechanical integrity from the ionene matrix.

The thermal stability of electrolytes at an elevated temperature induced by battery charge-discharge cycling is critical for the long cycling performance of a rechargeable battery. For many multivalent systems, such as rechargeable magnesium batteries, which offer great potential for high energy density and utilize earth-abundant resources, electrolyte instability and electrode surface passivation, arising from electrolyte decomposition, remain as major roadblocks. Understanding the electrolyte decomposition pathways at the electrode-electrolyte interface is essential to provide guidance in overcoming this challenge. In this work, in situ 13C magic angle spinning nuclear magnetic resonance (MAS NMR) and first-principles calculations were used to investigate the thermal decomposition of the electrolyte in a system consisting of MgV2O4, a novel cathode for magnesium batteries, mixed with a bulk electrolyte consisting of magnesium bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2) in diglyme (G2). We show that significant electrolyte decomposition is observed in bulk 1.0 M Mg(TFSI)2 in G2 mixed with nanometer sized MgV2O4 powder at elevated temperatures. This observation is to mimic the possible thermal decomposition that might happen during battery cycling. We demonstrate that the MgV2O4 surface is covered by a layer of decomposed G2 products. We conclude that the dominant reaction pathway for electrolyte decomposition is the thermal decomposition of the pure electrolytes at elevated temperatures, followed by adsorption of G2 decomposition products to the MgV2O4 surface. The activation energy for the major decomposition pathway is obtained. This work highlights the importance of studying thermal decomposition of electrolytes for overall system stability and explores electrolyte stability at significantly elevated temperatures.

The effects of short-chain branching (SCB) on phase distribution, free volume formation, and structural stability in polyethylene under hydrogen pressurization were investigated using medium- and high-density polyethylene (MDPE and HDPE) samples (MDPE-M, MDPE-I, HDPE-G, and HDPE-D). Comprehensive nuclear magnetic resonance (NMR) techniques, including liquid-state 1H/13C NMR and solid-state 1H/129Xe NMR under 250 psi hydrogen and xenon atmospheres, respectively, were employed to characterize SCB content, semicrystalline phase distribution, chain mobility, and free volume. SCB levels ranged from 1.94 to 2.66 branches per 1000 carbon atoms, with a free volume range of 0.297-0.533 cm3/g and a consistent free volume element diameter of ∼0.63 nm. Hexene branches correlated positively with free volume formation, whereas longer branches, such as heptene and octene, suppressed it. Increased SCB content and SCB length reduced crystallinity and chain mobility. Results support a mechanistic model in which randomly distributed SCBs enhance chain stiffness and hydrogen permeability into crystalline regions. In contrast, a lower SCB content allows greater chain flexibility and contraction under hydrogen pressure, limiting gas penetration into the crystalline phase. Hydrogen accumulation in the amorphous phase contributes to crystalline stabilization through resistive stress, yielding a higher failure strain strength under hydrogen pressure. These effects are attributed to hydrogen's smaller kinetic diameter, enabling access to pore networks inaccessible to air, such as nitrogen and oxygen.

The morphological variation of four semicrystalline polyamides─PA6, PA11, PA66, and PA612─under 250 psi hydrogen gas exposure was investigated using 13C cross-polarization (CP) and direct-polarization (DP) magic angle spinning (MAS) NMR. Additionally, two-dimensional 13C-1H wide-line separation (2D WISE) NMR provided insight into site-specific molecular dynamics. While all samples exhibited broadly similar segmental mobilities, PA6 showed slightly enhanced mobility at carbonyl sites, whereas PA612 displayed reduced mobility. The average chain mobility followed the trend: PA612 > PA6 > PA11 > PA66. Quantitative 13C NMR revealed the presence of a mobile amorphous or interfacial phase, most prevalent in PA11 (16%) and least in PA612 (9%). Initial crystallinity was highest in PA11 (36%) and lowest in PA612 (21%). Hydrogen exposure led to a marked reduction in crystallinity─up to 38% in PA612─followed by partial recovery upon depressurization. Site-specific analysis indicated the lowest crystallinity at carbonyl sites, with the unit end sites (CO and NH sites) showing distinct behavior between one-monomer (PA6 and PA11) and two-monomer (PA66 and PA612) polyamides. These findings suggest that hydrogen preferentially interacts with carbonyl and amide groups. A strong correlation was observed between chain mobility, the degree of crystallinity, and the reduction in the crystalline phase resulting from pressurization with 250 psi H2 gas. Among the polyamides studied, PA66 exhibited the greatest resistance to hydrogen-induced morphological changes, attributed to its higher crystallinity and reduced chain mobility. This underscores the importance of structural rigidity in enhancing polymer resilience under high-pressure hydrogen environments.

The effects of short-chain branching (SCB) on phase distribution, free volume formation, and structural stability in polyethylene under hydrogen pressurization were investigated using medium- and high-density polyethylene (MDPE and HDPE) samples (MDPE-M, MDPE-I, HDPE-G, and HDPE-D). Comprehensive nuclear magnetic resonance (NMR) techniques, including liquid-state 1H/13C NMR and solid-state 1H/129Xe NMR under 250 psi hydrogen and xenon atmospheres, respectively, were employed to characterize SCB content, semicrystalline phase distribution, chain mobility, and free volume. SCB levels ranged from 1.94 to 2.66 branches per 1000 carbon atoms, with a free volume range of 0.297-0.533 cm3/g and a consistent free volume element diameter of ∼0.63 nm. Hexene branches correlated positively with free volume formation, whereas longer branches, such as heptene and octene, suppressed it. Increased SCB content and SCB length reduced crystallinity and chain mobility. Results support a mechanistic model in which randomly distributed SCBs enhance chain stiffness and hydrogen permeability into crystalline regions. In contrast, a lower SCB content allows greater chain flexibility and contraction under hydrogen pressure, limiting gas penetration into the crystalline phase. Hydrogen accumulation in the amorphous phase contributes to crystalline stabilization through resistive stress, yielding a higher failure strain strength under hydrogen pressure. These effects are attributed to hydrogen's smaller kinetic diameter, enabling access to pore networks inaccessible to air, such as nitrogen and oxygen.

In nonaqueous redox-flow batteries (NRFBs), redox-active organic molecules (ROMs) and supporting salts compete for solvation sites, limiting achievable energy density. We combine automated high-throughput experimentation (HTE) with camera-based saturation monitoring and quantitative NMR to measure paired (ROM, salt) solubilities across single and mixed organic solvents. Using 2,1,3-benzothiadiazole (BTZ) with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as a model system, we find that a binary m-xylene/acetonitrile mixture dissolves approximate to 3 M of both BTZ and LiTFSI-surpassing the previously reported 2 M ceiling for neat acetonitrile-by leveraging complementary solvation (MX is BTZ-philic and salt-phobic; ACN stabilizes LiTFSI). A random-forest model (RMSE approximate to 0.24) trained on solvent descriptors highlights log P and salt concentration as dominant predictors and predicts MX/ACN approximate to 0.3/0.7 (v/v) to be near-optimal. These formulations retain practical viscosity and similar to 5 mS.cm-1 conductivity at high loading. The workflow provides a reproducible, data-centric route to NRFB electrolyte design and motivates an open, standardized dual-solute solubility resource for accelerated electrolyte discovery.

The lifespan of lithium (Li) metal batteries (LMBs) can be greatly improved by the formation of inorganic-rich electrode-electrolyte interphases (EEIs) (including solid-electrolyte interphase on anode and cathode-electrolyte interphase on cathode). In this work, a localized high-concentration electrolyte containing lithium bis(fluorosulfonyl)imide (LiFSI) salt, 1,2-dimethoxyethane (DME) solvent and 1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane (BTFEE) diluent is optimized. BTFEE is a fluorinated ether with weakly-solvating ability for LiFSI so it also acts as a co-solvent in this electrolyte. It can facilitate anion decomposition at electrode surfaces and promote the formation of more inorganic-rich EEI layers. With an optimized molar ratio of LiFSI:DME:BTFEE = 1:1.15:3, LMBs with a high loading (4 mAh cm-2) lithium nickel manganese cobalt oxide (LiNi0.8 Mn0.1 Co0.1) cathode can retain 80% capacity in 470 cycles when cycled in a voltage range of 2.8-4.4 V. The fundamental understanding on the functionality of BTFEE revealed in this work provides new perspectives on the design of practical high-energy density battery systems. A localized high-concentration electrolyte contains a fluorinated ether (1,2-bis(1,1,2,2-tetrafluoroethoxy)ethane (BTFEE)) with weakly-solvating ability is optimized. BTFEE acts as a diluent for the salt-solvent clusters and enhances anion decomposition kinetics, promoting the formation of inorganic-rich electrode-electrolyte interphase (EEI) layers. It also partially decomposes and forms part of EEI layers, therefore improves the cycling stability of lithium metal batteries. image

The US natural gas infrastructure is a national asset that could be used to deliver hydrogen and hydrogen blends of natural gas as a pathway to reduce carbon emissions. The distribution system comprises nearly 50% plastic pipe composed of medium-and high-density polyethylene materials (MDPE and HDPE). While these materials perform adequately for natural gas, research on their hydrogen compatibility is essential to understand if any immediMDPEate and long-term risks are associated with hydrogen addition. The Blended Gas CRADA, a HyBlend project, has established a comprehensive test method for evaluating MDPE and HDPE of various plastic resin compositions of pipeline material in pure hydrogen and 20% hydrogen/80% methane blends. Both in-situ and ex-situ measurements were performed to capture hydrogen-induced changes in the polyethylene material's crystalline, amorphous, and interphase regions. We investigated MDPE and HDPE pipeline materials made from different polymer resin systems to evaluate the effects of hydrogen gas. The materials were characterized by their density, diffusion coefficient, free volume ratio, and degree of crystallinity. Various advanced characterization methods, including in-situ high-pressure NMR, ex-situ XRD, ex-situ DSC, and ex-situ TDA, were used to analyze the effects of changes in crystalline, amorphous, and interphase regions due to gas exposure. Time-dependent post-decompression quasi-static tensile tests were conducted to explore the effects of gas exposure time on the mechanical behavior of the pipe materials. This work will highlight the time sensitivities during and after gas exposure. The correlation between gas-induced polyethylene morphology changes and the associated material performance will be addressed for the intended applications. These studies will show that polyethylene resin composition and material exposure are important factors when considering whether hydrogen gas affects pipeline materials positively or negatively.

The solubility of redox-active organic molecules (ROMs) in non-aqueous redox flow batteries (NRFBs) is a critical factor determining the energy density of the system. However, the scarcity of comprehensive solubility data has hindered electrolyte development. In this study, we systematically investigate the solubility behavior of ROMs in the presence of supporting salts to propose practical electrolyte formulations for NRFBs. Using automated high-throughput experimentation, we screen the solubility of 2,1,3-benzothiadiazole (BTZ) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in various organic solvents. Leveraging a Random Forest inference model, we identify a binary solvent mixture of mxylene and acetonitrile, which dissolves 3 M of both BTZ and LiTFSI—exceeding the previously reported 2 M limit in pure acetonitrile. This enhanced solubility is achieved by the inclusion of a LiTFSI-phobic yet BTZ-philic solvent, which counterbalances the solubility competition between BTZ and LiTFSI, with the latter favoring highly polar solvents. This work introduces a promising electrolyte design strategy for NRFBs and highlights the effectiveness of high-throughput screening combined with advanced data analysis for optimizing complex multi-component systems. Furthermore, it emphasizes the urgent need for more comprehensive solubility data to facilitate the development of practical NRFB electrolytes.

This study investigates the efficacy of a polymer coating, PVdC-co-AN, in enhancing the stability and reversibility of the electrochemical Mg anode interface. Coated electrodes, immersed in a 0.25 M Mg(TFSI)2−0.50 M MgCl2/dimethoxyethane (DME) electrolyte, exhibit notable improvements. Cyclic voltammetry demonstrates consistent behavior with the coated electrode, while the uncoated electrode changes dramatically. During extended open circuit potential conditions, the coated electrode maintains much higher coulombic efficiency (93%) compared to the uncoated electrode (62%). Galvanostatic cycling test over 200 cycles further show the benefits of the PVdC-co-AN coating, decreasing the overpotential of Mg plating and improving long-term stability. The coated electrodes also demonstrate improved rate capability at higher current densities. Surface analysis reveals differences in the formation of byproducts between the coated and uncoated electrodes, indicating a more stable and uniform interface in the former. Nuclear magnetic resonance (NMR) spectroscopy suggests that the polymer influences ion mobility through tuning the solvation environments which results in better kinetics and fewer byproducts. In summary, the study affirms that the PVdC-co-AN coating significantly improves the stability and performance of Mg electrochemistry, offering a promising advancement for practical battery applications.

Rationally designing stable nonaqueous electrolytes for Mg metal anodes demands a thorough understanding of their interfacial behaviors. Here, the critical role of cation-anion pairing in improving the cathodic stabilities of amine-based electrolytes against solvent reduction and H-2 evolution is identified. It is demonstrated that strong coordination between solvating amine groups and the Mg2+ cation facilitates the dehydrogenation of the NH2 group, which is mainly responsible for low reversibility during Mg metal plating and stripping. Introducing ion-pairing into the primary solvation shell can effectively weaken the amine coordination such that its reduction is suppressed. A novel interfacial behavior regarding parasitic reaction product dissolution is also identified, which is responsible for the failure of interfacial passivation. An ion-pairing electrolyte is developed based on a weakly-solvated amine molecule and strongly coordinating Mg2+ salt. This electrolyte composition delivers long-term Mg metal anode cycling with 99.6% Coulombic efficiency for 800 cycles.

Passivation of both anode and cathode surfaces by the inorganic-rich solid electrolyte interphases (SEI) is a very efficient approach to extent the cycle life of rechargeable high-voltage lithium (Li) metal batteries (LMBs). In this work, a fluorinated ether with weakly-solvating ability, termed DB, was used as a diluent as well as a co-solvent in the localized high-concentration electrolyte (LHCE) system, which contains LiFSI salt, 1,2-dimethoxyethane solvent, and DB. Dissimilar to most reported inert diluents, DB is demonstrated to form an anion-rich solvation sheath and partially participate in the solvation structure as well, resulting in the relatively weakened FSI - -Li + coordination, which significantly enhanced anion decomposition kinetics at the Li metal surface, promoting the formation of inorganic-rich SEI. With an optimized electrolyte, the SEIs of both the anode and cathode consist of inorganic-rich components with F, N, S, and O-containing species. Consequently, the full-cell with Li metal and NMC811 cathode at 4.4 V achieved long cycle life of 478 cycles at 80% capacity retention, which provides new perspective toward practical high-voltage battery systems.

Lithium hexafluorophosphate (LiPF6)-based carbonate electrolytes are widely used in commercial lithium -ion batteries (LIBs), but their thermal instability limits the cycle life and safety of LIBs at elevated temperatures. Few studies have yielded insight into the initial PF6- decomposition reaction that promotes thermal instability of LiPF6- based electrolytes. Here, we find that lithium -ion hopping assisted by the overall reorientational motion of propylene carbonate molecules facilitates PF6- decomposition at elevated temperatures in 1 M LiPF6/propylene carbonate electrolyte. Further, we demonstrate that urea additives, by preventing lithium -ion hopping, suppress the initial LiPF6 decomposition reaction and enhance the thermal stability of the electrolyte. LIB cell tests with LiNi0.6Mn0.2Co0.2O2||Li4Ti5O12 show improved LIB performance at elevated temperatures with the thermally stabilized electrolyte. This study provides key insights into the design of thermally stable LiPF6-based carbonate electrolytes for improving the cycle life, calendar life, and safety of LIBs in elevated -temperature applications.

Sulfurized polyacrylonitrile (SPAN) recently emerges as a promising cathode for high-energy lithium (Li) metal batteries owing to its high capacity, extended cycle life, and liberty from costly transition metals. As the high capacities of both Li metal and SPAN lead to relatively small electrode weights, the weight and specific energy density of Li/SPAN batteries are particularly sensitive to electrolyte weight, highlighting the importance of minimizing electrolyte density. Besides, the large volume changes of Li metal anode and SPAN cathode require inorganic-rich interphases that can guarantee intactness and protectivity throughout long cycles. This work addresses these crucial aspects with an electrolyte design where lightweight dibutyl ether (DBE) is used as a diluent for concentrated lithium bis(fluorosulfonyl)imide (LiFSI)-triethyl phosphate (TEP) solution. The designed electrolyte (d = 1.04 g mL-1) is 40%-50% lighter than conventional localized high-concentration electrolytes (LHCEs), leading to 12%-20% extra energy density at the cell level. Besides, the use of DBE introduces substantial solvent-diluent affinity, resulting in a unique solvation structure with strengthened capability to form favorable anion-derived inorganic-rich interphases, minimize electrolyte consumption, and improve cell cyclability. The electrolyte also exhibits low volatility and offers good protection to both Li metal anode and SPAN cathode under thermal abuse.

Elevated temperature molten Na batteries are seeing a resurgence of interest for low-cost electrochemical energy storage for the grid. Of the many recent innovations in this battery concept, new methods focused on intermediate temperature operation (e.g. 110-190 °C) have gained prominence as a way to enable comparable performance with less thermal energy loss and lower-cost materials of construction. However, the poor wettability of molten Na on suitable solid-electrolyte separators such as sodium Beta Alumina Solid-Electrolyte (Na-β”-Al2O3, ‘BASE’) requires continued innovation in interface engineering to promote full utilization of the solid-electrolyte surface area and minimize cell resistance. There have been many successful approaches to improve Na-wettability to-date including heat treatment in an inert atmosphere to remove adsorbed surface species, deposition of alloying metals such as Pb, Sn, or Bi, and use of carbon-based interfacial layers. However, these approaches either lack the ability to provide good wetting at very low temperatures (near the melting point of Na) or rely on non-scalable processes and/or toxic/expensive metals. To solve these issues, a new carbon-based sodiophilic treatment is demonstrated, which utilizes inexpensive components to form a meso/macroporous sodiophilic layer, is easily applied via drop-casting or spray-coating, provides excellent wetting as low as 110 °C, and is completely metal-free. It is found that the good sodium wetting can be attributed to the wider range of pore sizes in the carbon layers demonstrated in this study. Na wetting may occur as surface tension is initially broken by larger pores, followed by the intrusion of molten Na into smaller pores due to the apparent intrinsic affinity of Na-metal for carbon surfaces, in conjunction with the capillarity effect. Low cell-level area specific resistances of 20-30 and 13-15 Ω·cm2 are demonstrated at 110 and 140 °C respectively. Finally, the utility of this metal-free wetting layer for solid-Na anodes is explored, showing that the metal-free wetting layer can reach a critical current density of 1.88mA·cm-2 at 30 °C.

Multivalent battery chemistries have been explored in response to the increasing demand for high-energy rechargeable batteries utilizing sustainable resources. Solvation structures of working cations have been recognized as a key component in the design of electrolytes; however, most structure-property correlations of metal ions in organic electrolytes usually build upon favorable static solvation structures, often overlooking solvent exchange dynamics. We here report the ion solvation structures and solvent exchange rates of magnesium electrolytes in various solvents by using multimodal nuclear magnetic resonance (NMR) analysis and molecular dynamics/density functional theory (MD/DFT) calculations. These magnesium solvation structures and solvent exchange dynamics are correlated to the combined effects of several physicochemical properties of the solvents. Moreover, Mg2+ transport and interfacial charge transfer efficiency are found to be closely correlated to the solvent exchange rate in the binary electrolytes where the solvent exchange is tunable by the fraction of diluent solvents. Our primary findings are (1) most battery-related solvents undergo ultraslow solvent exchange coordinating to Mg2+ (with time scales ranging from 0.5 mu s to 5 ms), (2) the cation transport mechanism is a mixture of vehicular and structural diffusion even at the ultraslow exchange limit (with faster solvent exchange leading to faster cation transport), and (3) an interfacial model wherein organic-rich regions facilitate desolvation and inorganic regions promote Mg2+ transport is consistent with our NMR, electrochemistry, and cryogenic X-ray photoelectron spectroscopy (cryo-XPS) results. This observed ultraslow solvent exchange and its importance for ion transport and interfacial properties necessitate the judicious selection of solvents and informed design of electrolyte blends for multivalent electrolytes.