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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Charge-Transfer Luminescence in a Molecular Donor–Acceptor Complex: Computational Insights

Donor–acceptor molecular complexes are a popular class of materials utilizing charge-transfer states for practical applications. A recent class of donor–acceptor dyads based on the fluorescent BODIPY functionalized with triphenylamine (TPA) shows the peculiar property of dual fluorescence. It is hypothesized that instead of the sensitized charge-transfer state being optically dark, it provides an additional bright radiative pathway. In this study, we use time-dependent density functional theory to characterize the energetic alignment of excitonic and charge-transfer states in a BODIPY-TPA molecular complex. We observe that using a long-range exchange corrected functional in combination with state-specific solvation scheme gives a qualitatively correct alignment of the exciton and charge-transfer states and an enhancement in oscillator strength for the equilibrium solvated charge-transfer state, in agreement with experiment. Furthermore, this work provides rationalization of charge-transfer state emission and provides a foundation to explore charge-transfer using ab initio excited-state nonadiabatic dynamics.

36 MATERIALS SCIENCE↗
DOE OSTI2023

The Back Door to the Surface Hydrated Electron

We use a Mg + metal to extend the size regime of water clusters to extrapolate to the bulk limit of the Vertical Detachment Energy (VDE) of the solvated electron to >3,200, a value between one to over two orders of magnitude for clusters previously measured experimentally or computed theoretically. We relate the VDE to the energy difference between the Mg + (H 2 O) $n$ and Mg 2+ (H 2 O) $n$ systems and the metal’s second ionization potential. The extrapolated bulk VDEs of the localized surface electron, which moves away from the metal as n increases, are 1.89 ± 0.01 eV for semiempirical ($n$ ~ 3,200; PM6-D 3 H 4 ) and 1.73 ± 0.03 eV ($n$ ~ 150; HF), 1.83 ± 0.02 eV ($n$ ~ 150; MP2) for ab-initio, in excellent agreement with the 1.6 – 1.8 eV range of experimental results. In conclusion, the VDEs converge from above (larger values) to the bulk limit, in a manner qualitatively different than previous studies and experiments, a fact justifying the “back door” approach to the solvated electron.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Fast Interconversion of Hydrogen Bonding at the Hematite (001)–Liquid Water Interface

The interface between transition-metal oxides and aqueous solutions plays an important role in biogeochemistry and photoelectrochemistry, but the atomistic structure is often elusive. Here we report on the surface geometry, solvation structure, and thermal fluctuations of the hydrogen bonding network at the hematite (001)–water interface as obtained from hybrid density functional theory-based molecular dynamics. We find that the protons terminating the surface form binary patterns by either pointing in-plane or out-of-plane. The patterns exist for about 1 ps and spontaneously interconvert in an ultrafast, solvent-driven process within 50 fs. This results in only about half of the terminating protons pointing toward the solvent and being acidic. The lifetimes of all hydrogen bonds formed at the interface are shorter than those in pure liquid water. The solvation structure reported herein forms the basis for a better fundamental understanding of electron transfer coupled to proton transfer reactions at this important interface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Probing Electric Double-Layer Composition via in Situ Vibrational Spectroscopy and Molecular Simulations.

At an electrode, ions and solvent accumulate to screen charge, leading to a nanometer-scale electric double layer (EDL). The EDL guides electrode passivation in batteries, while in (super)capacitors, it determines charge storage capacity. Despite its importance, quantification of the nanometer-scale and potential-dependent EDL remains a challenging problem. Here, we directly probe changes in the EDL composition with potential using in situ vibrational spectroscopy and molecular dynamics simulations for a Li-ion battery electrolyte (LiClO 4 in dimethyl carbonate). The accumulation rate of Li + ions at the negative surface and ClO 4 - ions at the positive surface from vibrational spectroscopy compares well to that predicted by simulations using a polarizable APPLE&P force field. The ion solvation shell structure and ion-pairing within the EDL differs significantly from the bulk, especially at the negative electrode, suggesting that the common rationalization of interfacial electrochemical processes in terms of bulk ion solvation should be applied with caution.

25 ENERGY STORAGE↗
DOE OSTI2019

The Role of Excited State Proton Relays on the Photochemical Dynamics of Water Nanodroplets

In this work, we applied non-adiabatic excited state molecular dynamics in tandem with ab initio electronic structure theory to illustrate a complete mechanistic landscape underpinning the UV absorption initiated photochemical dynamics in water nanodroplets. The goal is to understand the nonequilibrium excited state molecular dynamics initiated by the relaxation of solvated photoelectron, and consequential photochemical processes. The lowest-lying excited state shows the proton dissociation for a single water molecule forming intermediate hydronium complexes through a proton relay. At approximately 100 femtoseconds, the proton relay process gives rise to the relaxation of the excited state accompanied with a rapid increase in the non-adiabatic coupling strength with the ground state, and the nanodroplet non-radiatively decays. The non-adiabatic transition to the ground state produces excited vibrational states that facilitate the recombination of the dissociated proton and hydroxyl group, eventually leading to the desorption of water molecules from the nanodroplet. Additionally, lifetimes of transient photochemical events are also resolved for the relaxation of solvated electron, excited state proton relay, and non-radiative transition.

Stetina, Torin F.↗
DOE OSTI2020

New Insights into the Charge-Transfer-to-Solvent Spectrum of Aqueous Iodide: Surface versus Bulk

Liquid phase charge-transfer-to-solvent (CTTS) transitions are important, as they serve as photochemical routes to solvated electrons. Here in this work, broadband deep-ultraviolet electronic sum frequency generation (DUV-ESFG) and two-photon absorption (2PA) spectroscopic techniques were used to assign and compare the nature of the aqueous iodide CTTS excitations at the air/water interface and in bulk solution. In the one-photon absorption (1PA) spectrum, excitation to the 6s Rydberg-like orbital (5p → 6s) gives rise to a pair of spin–orbit split iodine states, 2 P 3/2 and 2 P 1/2 . In the 2PA spectra, the lower-energy 2 P 3/2 peak is absent and the observed 2PA peak, which is ~0.14 eV blue-shifted relative to the upper 2 P 1/2 CTTS peak seen in 1PA, arises from 5p → 6p electronic promotion. The band observed in the ESFG spectrum is attributed to mixing of excited states involving 5p → 6p and 5p → 6s promotions caused by both vibronic coupling and the external electric field generated by asymmetric interfacial solvation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Protein–Mineral Interactions: Molecular Dynamics Simulations Capture Importance of Variations in Mineral Surface Composition and Structure

Molecular dynamics simulations, conventional and metadynamics, were performed to determine the interaction of model protein Gb1 over kaolinite (001), Na+-montmorillonite (001), Ca2+-montmorillonite (001), goethite (100), and Na+-birnessite (001) mineral surfaces. Gb1, a small (56 residue) protein with a well-characterized solution-state nuclear magnetic resonance (NMR) structure and having α-helix, four-fold β-sheet, and hydrophobic core features, is used as a model protein to study protein soil mineral interactions and gain insights on structural changes and potential degradation of protein. From our simulations, we observe little change to the hydrated Gb1 structure over the kaolinite, montmorillonite, and goethite surfaces relative to its solvated structure without these mineral surfaces present. Over the Na+-birnessite basal surface, however, the Gb1 structure is highly disturbed as a result of interaction with this birnessite surface. Unraveling of the Gb1 β-sheet at specific turns and a partial unraveling of the α-helix is observed over birnessite, which suggests specific vulnerable residue sites for oxidation or hydrolysis possibly leading to fragmentation.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2026

Charge Dependence of Local Hydration Dynamics in Poly(Acrylic Acid) Solutions

Localized measurements of hydration dynamics surrounding poly(acrylic acid) (pAA) chains are executed using Overhauser dynamic nuclear polarization relaxometry to determine the role of polymer protonation state on the polymer solvation environment. Alterations in polymer concentration and solution pH uncovered three different regimes of local water dynamics ranging from bulk-water-like to subdued water diffusivity. These experiments, combined with molecular dynamics simulations, reveal that the presence of deprotonated carboxylic acid groups promotes a hydrophilic local environment and extended polymer chain configurations that together incentivize the incorporation of bulk-like water near the polymer. This results in a stretched polymer conformation that leads to faster observed hydration dynamics in the local hydration environment. Meanwhile, protonated carboxylic acid groups are expected to engage in intrapolymer hydrogen bonding between monomer groups, resulting in a more collapsed conformation and slower observed hydration dynamics. The importance of the carboxylic acid groups on mediating hydration behavior is further illustrated by their role in dictating the solvation environment around poly(acrylic acid-stat-(poly(ethylene glycol) methyl ether acrylate) (p(AA-stat-PEGMEA)) copolymers with varying monomer ratios. Furthermore, these local hydration measurements establish a connection between local water dynamics and polymer chain conformation and may provide additional molecular perspective into poly(acrylic acid)’s classification as a superabsorbent polymer.

Conformation↗
DOE OSTI2018

Optimizing Ion Transport in Polyether-Based Electrolytes for Lithium Batteries

In this paper, we report on the synthesis of poly(diethylene oxide-alt-oxymethylene), P(2EO-MO), via cationic ring-opening polymerization of the cyclic ether monomer, 1,3,6-trioxocane. We use a combined experimental and computational approach to study ion transport in electrolytes comprising mixtures of P(2EO-MO) and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt. Mixtures of poly(ethylene oxide) (PEO) and LiTFSI are used as a baseline. The maximum ionic conductivities, σ, of P(2EO-MO) and PEO electrolytes at 90 °C are 1.1 × 10 –3 and 1.5 × 10 –3 S/cm, respectively. This difference is attributed to the T g of P(2EO-MO)/LiTFSI (-12 °C), which is significantly higher than that of PEO/LiTFSI (-44 °C) at the same salt concentration. Self-diffusion coefficients measured using pulsed-field gradient NMR (PFG-NMR) show that both Li + and TFSI – ions diffuse more rapidly in PEO than in P(2EO-MO). However, the NMR-based cation transference number in P(2EO-MO) (0.36) is approximately twice that in PEO (0.19). The transference number measured by the steady-state current technique, t +,ss , in P(2EO-MO) (0.20) is higher than in PEO (0.08) by a similar factor. We find that the product σt +,ss is greater in P(2-EO-MO) electrolytes; thus, P(2EO-MO) is expected to sustain higher steady-state currents under dc polarization, making it a more efficacious electrolyte for battery applications. Molecular-level insight into the factors that govern ion transport in our electrolytes was obtained using MD simulations. These simulations show that the solvation structures around Li + are similar in both polymers. The same is true for TFSI – . However, the density of Li + solvation sites in P(2EO-MO) is double that in PEO. Finally, we posit that this is responsible for the observed differences in the experimentally determined transport properties of P(2EO-MO) and PEO electrolytes.

25 ENERGY STORAGE↗
DOE OSTI2023

Dynamic Molecular Investigation of the Solid-Electrolyte Interphase of an Anode-Free Lithium Metal Battery Using In Situ Liquid SIMS and Cryo-TEM

Solid electrolyte interphase (SEI) has been widely perceived to play a critical role in the stable cycling of rechargeable batteries. However, associated with the fragile and air-sensitive nature of the SEI layer, delineation of the formation process and the nature of SEI remains a big challenge. Here, we use in situ liquid time-of-flight secondary ion mass spectroscopy (TOF-SIMS), cryo- transmission electron microscope (TEM) and density functional theory (DFT) calculation to delineate molecular process on the formation of SEI layer under the dynamic operating condition. We discover that the onset potential for SEI layer formation and the thickness of the SEI show dependence on the solvation shell structure. Using LiCoO 2 as a cathode and Cu film as an anode, the SEI is noticed to start to form at around 2.0 V and reach its final thickness (irreversible part, ~ 40-50 nm) at about 3.0 V in the 1 M LiPF 6 –EC/DMC electrolyte, while for the case of 1 M LiFSI–DME, the SEI starts to form at around 1.5 V and reaches its final thickness (~ 20 nm) at about 2.0 V. The in situ TOF-SIMS clearly indicates the outer SEI layer formation and dissipation upon charging and discharging, implying a continued evolution of electrolyte structure with extended cycling. In conclusion, the present work establishes a direct correlation between the molecular signature of SEI layer with solvation feature of electrolytes in lithium batteries, providing insights for tailoring SEI layer toward improved electrochemical properties of lithium batteries.

25 ENERGY STORAGE↗
DOE OSTI2025

Automation-Accelerated Electrolyte Design Mitigates Solubility Competition between Redox-Active Molecules and Supporting Salts

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 ≈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 ≈ 0.24) trained on solvent descriptors highlights log P and salt concentration as dominant predictors and predicts MX/ACN ≈0.3/0.7 (v/v) to be near-optimal. These formulations retain practical viscosity and ∼5 mS·cm –1 conductivity at high loading. In conclusion, 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.

Electrolytes↗
DOE OSTI2020

Stabilized Electrode/Electrolyte Interphase by a Saturated Ionic Liquid Electrolyte for High-Voltage NMC532/Si-Graphite Cells

Nonaqueous electrolyte has become one of the technical barriers in enabling Li-ion battery comprising of a high voltage cathode and high capacity anode. Here, we demonstrate a saturated piperidinum bis(fluorosulfonyl)imide ionic liquid (IL) with a LiFSI salt not only supports the redox reaction on the cathode at high voltages, but also shows exceptional kinetic stability on the lithiated anode as evidenced by its improved cycling performance in a NMC532/Si-graphite full cells cycled between 4.6 and 3.0 V. On the basis of the spectroscopic/microscopic analysis and molecular dynamics (MD) simulations, the superior performance of the cells is attributed to the formation of solid-electrolyte-interphase on both electrode as well as unique solvation structure where a deadlocked coordination network is established at the saturated state, which prevents transition metal dissolution into the electrolyte via a solvation process.

25 ENERGY STORAGE↗
DOE OSTI2020

Engineering Surface Oxygenated Functionalities on Commercial Carbon toward Ultrafast Sodium Storage in Ether-Based Electrolytes

The pursuit of a high-capacity anode material has been urgently required for commercializing sodium-ion batteries with a high energy density and an improved working safety. In the absence of thermodynamically stable sodium intercalated compounds with graphite, constructing nanostructures with expanded interlayer distances is still the mainstream option for developing high-performance carbonaceous anodes. In this regard, a surface-functionalized and pore-forming strategy through a facile CO 2 thermal etching route was rationally adopted to engineer negligible oxygenated functionalities on commercial carbon for boosting the sodium storage process. Benefitted from the abundant ionic/electronic pathways and more active reaction sites in the microporous structure with noticeable pseudocapacitive behaviors, the functionalized porous carbon could achieve a highly reversible capacity of 505 mA h g -1 at 50 mA g -1 , an excellent rate performance of 181 mA h g -1 at 16,000 mA g -1 , and an exceptional rate cycle stability of 176 mA h g -1 at 3200 mA g -1 over 1000 cycles. These outstanding electrochemical properties should be ascribed to a synergistic mechanism, fully utilizing the graphitic and amorphous structures for synchronous intercalations of sodium ions and solvated sodium ion compounds, respectively. Finally, the controllable generation and evolution of a robust but thin solid electrolyte interphase film with the emergence of obvious capacitive reactions on the defective surface, favoring the rapid migration of sodium ions and solvated species, also contribute to a remarkable electrochemical performance of this porous carbon black.

25 ENERGY STORAGE↗
DOE OSTI2020

Structure and Dynamics of Aqueous Electrolytes Confined in 2D-TiO 2 /Ti 3 C 2 T 2 MXene Heterostructures

The synthesis of heterostructures of different two-dimensional (2D) materials offers an approach to combine advantages of different materials constituting the heterostructure and ultimately enhance their performance for applications such as electrochemical energy storage, achieving high energy, and high-power densities. Understanding the behavior of ions and solvents in confinement between these dissimilar layers is critical to understand their performance and control. Considering aqueous electrolytes, we explore the heterostructure of 2D lepidocrocite-type TiO 2 (2D-TiO 2 ) and hydroxylated or O-terminated Ti 3 C 2 MXene using ReaxFF molecular dynamics simulations and elastic/quasielastic neutron scattering techniques. Simulating a bilayer water intercalation, we find that the extent of interlayer hydration is impacted most by the surface terminations on the MXene and is marginally affected by 2D-TiO 2 . However, the introduction of 2D-TiO 2 decreases the water self-diffusion due to the notch sites (i.e., surface oxygen ridges) entrapping water molecules. Intercalating alkali cations into the heterostructures, we find that Li + is predominantly adsorbed at the 2D-TiO 2 surface instead of the MXenes with the preferential occupation of the notch sites. In contrast, Na+ forms a planar solvation with water, while K + is adsorbed both at the O-terminated MXene and 2D-TiO 2 . This behavior is altered when OH-terminated MXene is involved—the repulsion from the protons on the MXene surface forces the K + ions to be adsorbed exclusively to 2D-TiO 2 , while Na + retains some of its solvation in the water layer due to its smaller size. In OH-terminated MXenes, we see a consistent transfer of protons from the MXene surface toward 2D-TiO 2 , implying a greater capacity to store protons in the heterostructures. Of the three cations simulated, Na + hinders the proton migration the least and Li + the most because of its position near the 2D-TiO 2 surface. Furthermore, 2D-TiO 2 /MXene heterostructures are likely to exhibit a higher energy density but lower power density, especially with Na + intercalation.

25 ENERGY STORAGE↗
DOE OSTI2023

Electric-Field-Induced Assembly of an Ionic Liquid–Water Interphase Enables Efficient Heavy Metal Electrosorption

Controlling ion desolvation, transport, and charge transfer at the electrode-electrolyte interface (EEI) is critical to enabling the rational design of efficient and selective separation of targeted heavy metals and decontamination of industrial waste water. One challenge is to sufficiently resolve and interrogate the intermediate transformation steps between solvated metal cations and bare cations for electroreduction at the EEI and establish pathways to modulate these steps to achieve efficient energy transfer for targeted reactive separations. Herein, we obtained a predictive understanding of the effect of adding a hydrophobic ionic liquid, 1-ethyl-3-methylimidazolium chloride (EMIMCl), to an aqueous electrolyte on modulating the desolvation and electrosorption of Pb 2+ cations using a combination of experimental and theoretical techniques. Here, we reveal formation of a compact interphase layer consisting of EMIMCl-Pb complex clusters under an applied electric field using operando electrochemical Raman spectroscopy, atomic force microscopy, and electrochemical impedance spectroscopy measurements combined with classical molecular dynamics simulations. The application of a larger negative potential is shown to result in formation of a well oriented layer with the positive imidazolium ring of the EMIMCl lying on the electrode and the long hydrophobic alkyl chain extending into the bulk electrolyte. This oriented layer is demonstrated to facilitate desolvation of incoming solvated Pb 2+ cations and decrease the charge transfer resistance for Pb electrodeposition, which has important implications for selective removal of Pb from contaminated mixtures. Overall, our studies open up new opportunities to modulate ion desolvation using hydrophobic ionic liquids in aqueous electrolytes for efficient heavy metal separation.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Coupled Experimental–Theoretical Characterization of a Carbon Electrode in Vanadium Redox Flow Batteries using X-ray Absorption Spectroscopy

Vanadium redox flow batteries (VRFBs) have emerged as promising solutions for stationary grid energy storage due to their high efficiency, scalability, safety, near room-temperature operation conditions, and the ability to independently size power and energy capacities. The performance of VRFBs heavily relies on the redox couple reactions of V 2+ /V 3+ and VO 2+ /VO 2 + on carbon electrodes. Therefore, a thorough understanding of the surface functionality of carbon electrodes and their propensity for degradation during electrochemical cycles is crucial for designing VRFBs with extended lifespans. In this study, we present a coupled experimental–theoretical approach based on carbon K edge X-ray absorption spectroscopy (XAS) to characterize carbon electrodes prepared under different conditions and identify relevant functional groups that contribute to unique spectroscopic features. Atomic models were created to represent functional groups, such as hydroxyl, carboxyl, methyl, and aldehyde, bonded to carbon atoms in either sp 2 or sp 3 environments. The interactions between functionalized carbon and various solvated vanadium complexes were modeled using density functional theory. A library of carbon K-edge XAS spectra was generated for distinct carbon atoms in different functional groups, both before and after interacting with solvated vanadium complexes. Here we demonstrate how these simulated spectra can be used to deconvolve ex situ experimental spectra measured from carbon electrodes and to track changes in the electrode composition following immersion in different electrolytes or extended cycling within a functional VRFB. By doing so, we identify the active species present on the carbon electrodes, which play a crucial role in determining their electrochemical performance.

25 ENERGY STORAGE↗
DOE OSTI2024

Binary Cation Matrix Electrolyte and Its Effect on Solid Electrolyte Interphase Suppression and Evolution of Si Anode

An unstable solid electrolyte interphase (SEI) has been recognized as one of the biggest challenges to commercializing silicon (Si) anodes for high-energy-density batteries. This work thoroughly investigates a binary cation matrix of Mg 2+ +Li + electrolyte and its role in SEI development, suppression, and evolution of a Si anode. Findings demonstrate that introducing Mg ions dramatically reduces the SEI growth before lithiation occurs, primarily due to the suppression of solvent reduction, particularly ethylene carbonate (EC) reduction. The Mg 2+ alters the Li + cation solvation environment as EC preferably participates in the oxophyllic Mg 2+ solvation sheath, thereby altering the solvent reduction process, resulting in a distinct SEI formation mechanism. The initial SEI formation before lithiation is reduced by 70% in the electrolyte with the presence of Mg 2+ cations. While the SEI continues to develop in the postlithiation, the inclusion of Mg ions results in an approximately 80% reduction in the postlithiation SEI growth. Continuous electrochemical cycling reveals that Mg 2+ plays a crucial role in stabilizing the deep-lithiated Si phases, which effectively mitigates side reactions, resulting in controlled SEI growth and stable interphase while eliminating complex Li x Si y formation. Mg ions promote the development of a notably more rigid and homogeneous SEI, characterized by a reduced dissipation (ΔD) in the Mg 2+ +Li + ion matrix compared to the solely Li + system. In conclusion, this report reveals how the Mg 2+ +Li + ion matrix affects the SEI evolution, viscoelastic properties, and electrochemical behavior at the Si interface in real time, laying the groundwork for devising strategies to enhance the performance and longevity of Si-based next-generation battery systems.

25 ENERGY STORAGE↗
DOE OSTI2015

The Role of Cesium Cation in Controlling Interphasial Chemistry on Graphite Anode in Propylene Carbonate-Rich Electrolytes

Propylene carbonate (PC) is seldom used in lithium-ion batteries (LIBs) due to its sustained co-intercalation into graphene structure and the eventual graphite exfoliation, despite potential advantages it brings, such as wider liquid range and lower cost. Here we discover that cesium cation (Cs+), originally used to suppress dendrite growth of Li metal anode, directs the formation of solid electrolyte interphase (SEI) on graphitic anode in PC-rich electrolytes through preferential solvation. Effective suppression of PC-decomposition and graphite-exfoliation was achieved when the ratio of ethylene carbonate (EC)/PC in electrolytes was so adjusted that the reductive decomposition of Cs+-(EC)m (1≤m≤2) complex precedes that of Li+-(PC)n (3≤n≤5). The interphase directed by Cs+ is stable, ultrathin and compact, leading to significant improvements in LIB performances. In a broader context, the accurate tailoring of SEI chemical composition by introducing a new solvation center represents a fundamental breakthrough in manipulating interfacial reactions processes that once were elusive.

cesium cation↗