Ion Conduction Pathway Research Articles

Gating pore currents occur in CaV1.1 domain III mutants associated with HypoPP.

Mutations in the voltage sensor domain (VSD) of CaV1.1, the α1S subunit of the L-type calcium channel in skeletal muscle, are an established cause of hypokalemic periodic paralysis (HypoPP). Of the 10 reported mutations, 9 are missense substitutions of outer arginine residues (R1 or R2) in the S4 transmembrane segments of the homologous domain II, III (DIII), or IV. The prevailing view is that R/X mutations create an anomalous ion conduction pathway in the VSD, and this so-called gating pore current is the basis for paradoxical depolarization of the resting potential and weakness in low potassium for HypoPP fibers. Gating pore currents have been observed for four of the five CaV1.1 HypoPP mutant channels studied to date, the one exception being the charge-conserving R897K in R1 of DIII. We tested whether gating pore currents are detectable for the other three HypoPP CaV1.1 mutations in DIII. For the less conserved R1 mutation, R897S, gating pore currents with exceptionally large amplitude were observed, correlating with the severe clinical phenotype of these patients. At the R2 residue, gating pore currents were detected for R900G but not R900S. These findings show that gating pore currents may occur with missense mutations at R1 or R2 in S4 of DIII and that the magnitude of this anomalous inward current is mutation specific.

Two P domain potassium channels in GtoPdb v.2021.2

The 4TM family of K channels mediate many of the background potassium currents observed in native cells. They are open across the physiological voltage-range and are regulated by a wide array of neurotransmitters and biochemical mediators. The pore-forming α-subunit contains two pore loop (P) domains and two subunits assemble to form one ion conduction pathway lined by four P domains. It is important to note that single channels do not have two pores but that each subunit has two P domains in its primary sequence; hence the name two P domain, or K2P channels (and not two-pore channels). Some of the K2P subunits can form heterodimers across subfamilies (e.g. K2P3.1 with K2P9.1). The nomenclature of 4TM K channels in the literature is still a mixture of IUPHAR and common names. The suggested division into subfamilies, described in the More detailed introduction, is based on similarities in both structural and functional properties within subfamilies and this explains the "common abbreviation" nomenclature in the tables below.

Vitrification of maricite NaFePO4 crystal by laser irradiation and enhanced sodium ion battery performance

Maricite NaFePO4 crystal is expected to be an active cathode material for sodium-ion batteries (SIBs) because of its high theoretical capacity of 155 mAhg−1. NaFePO4 crystal is, however, inactive as a cathode material due to the absence of Na+ ion conduction pathways. A continuous-wave Yb:YVO4 fiber laser (the wavelength of λ = 1080 nm) was irradiated onto NaFePO4 crystal in order to modify its structure and to enhance Na+ ion conductivity. The vitrification of NaFePO4 crystals by laser irradiations was clarified from differential scanning calorimetry (DSC), differential thermal analysis (DTA), X-ray diffraction (XRD), and Raman scattering spectrum analyses. The discharge capacity in the first cycle is 40 mAhg−1 for the rate of 0.01 C, suggesting the development of three-dimensional conduction pathways for Na+ ions by vitrification.

Enhanced Safety and Performance of High-Voltage Solid-State Sodium Battery through Trilayer, Multifunctional Electrolyte Design

Solid-state electrolytes are promising to resolve the safety hazards and low energy density of traditional liquid batteries. However, the practical application of these electrolytes has been impaired by the low ionic conductivity and an unstable interface present with a high-voltage cathode. Here, an improvement of ionic conductivity, interface, and safety was achieved by impregnating anti-oxidation polyacrylonitrile (PAN) and anti-reduction poly(ethylene oxide) (PEO) into a sandwich sodium superionic conductor (NASICON) framework with a dense core and porous outer layers. Using this sandwich composite electrolyte (SCE), a high ionic conductivity of 4.13×10−4 S cm−1 at 30°C was obtained owing to long-range and continuous ionic conduction pathways in the porous network. The interfacial resistance was greatly improved through the creation of a compact and stable interface. More importantly, the safety of this SCE is improved through the in-situ formation of a central, dense NASICON layer, which suppressed dendrite growth. Furthermore, a high-voltage solid-state battery combining Na3V2(PO4)2F3 (NVPF) with this SCE exhibited an impressive rate performance with long cycle life. This study offers a promising strategy to design ultra-safe, high energy density, solid-state batteries.

Mechanosensitive channel YnaI has lipid-bound extended sensor paddles

The general mechanism of bacterial mechanosensitive channels (MS) has been characterized by extensive studies on a small conductance channel MscS from Escherichia coli (E. coli). However, recent structural studies on the same channel have revealed controversial roles of various channel-bound lipids in channel gating. To better understand bacterial MscS-like channels, it is necessary to characterize homologs other than MscS. Here, we describe the structure of YnaI, one of the closest MscS homologs in E. coli, in its non-conducting state at 3.3 Å resolution determined by cryo electron microscopy. Our structure revealed the intact membrane sensor paddle domain in YnaI, which was stabilized by functionally important residues H43, Q46, Y50 and K93. In the pockets between sensor paddles, there were clear lipid densities that interact strongly with residues Q100 and R120. These lipids were a mixture of natural lipids but may be enriched in cardiolipin and phosphatidylserine. In addition, residues along the ion-conducting pathway and responsible for the heptameric assembly were discussed. Together with biochemical experiments and mutagenesis studies, our results provide strong support for the idea that the pocket lipids are functionally important for mechanosensitive channels.

Fast Ion-Conducting Thioboracite with a Perovskite Topology and Argyrodite-like Lithium Substructure.

We report a new fast ion-conducting lithium thioborate halide, Li6B7S13I, that crystallizes in either a cubic or tetragonal thioboracite structure, which is unprecedented in boron-sulfur chemistry. The cubic phase exhibits a perovskite topology and an argyrodite-like lithium substructure that leads to superionic conduction with a theoretical Li-ion conductivity of 5.2 mS cm-1 calculated from ab initio molecular dynamics (AIMD). Combined single-crystal X-ray diffraction, neutron powder diffraction, and AIMD simulations elucidate the Li+-ion conduction pathways through 3D intra- and intercage connections and Li-ion site disorder, which are all essential for high lithium mobility. Furthermore, we demonstrate that Li+ ordering in the tetragonal polymorph impedes lithium-ion conduction, thus highlighting the importance of the lithium substructure and lattice symmetry in dictating transport properties.

The Ion-Translocating NrfD-Like Subunit of Energy-Transducing Membrane Complexes.

Several energy-transducing microbial enzymes have their peripheral subunits connected to the membrane through an integral membrane protein, that interacts with quinones but does not have redox cofactors, the so-called NrfD-like subunit. The periplasmic nitrite reductase (NrfABCD) was the first complex recognized to have a membrane subunit with these characteristics and consequently provided the family's name: NrfD. Sequence analyses indicate that NrfD homologs are present in many diverse enzymes, such as polysulfide reductase (PsrABC), respiratory alternative complex III (ACIII), dimethyl sulfoxide (DMSO) reductase (DmsABC), tetrathionate reductase (TtrABC), sulfur reductase complex (SreABC), sulfite dehydrogenase (SoeABC), quinone reductase complex (QrcABCD), nine-heme cytochrome complex (NhcABCD), group-2 [NiFe] hydrogenase (Hyd-2), dissimilatory sulfite-reductase complex (DsrMKJOP), arsenate reductase (ArrC) and multiheme cytochrome c sulfite reductase (MccACD). The molecular structure of ACIII subunit C (ActC) and Psr subunit C (PsrC), NrfD-like subunits, revealed the existence of ion-conducting pathways. We performed thorough primary structural analyses and built structural models of the NrfD-like subunits. We observed that all these subunits are constituted by two structural repeats composed of four-helix bundles, possibly harboring ion-conducting pathways and containing a quinone/quinol binding site. NrfD-like subunits may be the ion-pumping module of several enzymes. Our data impact on the discussion of functional implications of the NrfD-like subunit-containing complexes, namely in their ability to transduce energy.

Extracellular cap domain is an essential component of the TRPV1 gating mechanism

Transient receptor potential (TRP) channels are polymodal molecular sensors involved in numerous physiological processes and implicated in a variety of human diseases. Several structures of the founding member of the TRP channel family, TRPV1, are available, all of which were determined for the protein missing the N- and C-termini and the extracellular S5-P-loop. Here, we present structures of the full-length thirteen-lined ground squirrel TRPV1 solved by cryo-EM. Our structures resolve the extracellular cap domain formed by the S5-P-loops and the C-terminus that wraps around the three-stranded β-sheet connecting elements of the TRPV1 intracellular skirt. The cap domain forms a dome above the pore’s extracellular entrance, with four portals leading to the ion conductance pathway. Deletion of the cap increases the TRPV1 average conductance, reduces the open probability and affects ion selectivity. Our data show that both the termini and the cap domain are critical determinants of TRPV1 function.

Bio-inspired construction of ion conductive pathway in covalent organic framework membranes for efficient lithium extraction

Summary As the most sophisticated separation system, biological membranes have served as natural prototypes for the design of artificial membranes because they provide high permeability and solute selectivity, owing to the presence of specialized ion channels. However, developing stable and selective artificial ion channels remains a formidable challenge. Herein, we demonstrate the construction of lithium nanochannels in two-dimensional covalent organic frameworks (COFs) to create biomimetic membranes. Implanted lithiophilic oligoethers conferred specificity and facilitated Li+ diffusion along the pore pathway of the COF. The ion channel characteristics were indicated by reversal potential measurements, showing that the relative permeability decreased in the order Li+ > K+ > Na+ > Ca2+ > Mg2+. The Li+ transfer was enhanced, while other ions were obstructed, allowing for high selectivity and permeability. A Li+/Mg2+ separation factor of 64 was achieved, confirming high lithium affinity. This study may serve as a design principle to develop selective artificial membranes for effective ion separation.

Structural plasticity of the selectivity filter in a nonselective ion channel.

The sodium potassium ion channel (NaK) is a nonselective ion channel that conducts both sodium and potassium across the cellular membrane. A new crystallographic structure of NaK reveals conformational differences in the residues that make up the selectivity filter between the four subunits that form the ion channel and the inner helix of the ion channel. The crystallographic structure also identifies a side-entry, ion-conduction pathway for Na+ permeation that is unique to NaK. NMR studies and molecular dynamics simulations confirmed the dynamical nature of the top part of the selectivity filter and the inner helix in NaK as also observed in the crystal structure. Taken together, these results indicate that the structural plasticity of the selectivity filter combined with the dynamics of the inner helix of NaK are vital for the efficient conduction of different ions through the non-selective ion channel of NaK.

Nanostructured Polymer Composite Electrolytes with Self-Assembled Polyoxometalate Networks for Proton Conduction

Nanostructured Polymer Composite Electrolytes with Self-Assembled Polyoxometalate Networks for Proton Conduction

Low-cost wire-electrospun sulfonated poly(ether ether ketone)/poly(vinylidene fluoride) blend membranes for hydrogen-bromine flow batteries

Cost-effective dense membranes were developed by blending proton-conductive sulfonated poly(ether ether ketone) (SPEEK) with inert, mechanically stable poly(vinylidene fluoride) (PVDF) for hydrogen-bromine flow batteries (HBFBs). Wire-electrospinning followed by hot-pressing was employed to prepare dense membranes. Their properties and performance were compared to solution-cast membranes of similar composition and thickness. Electrospinning improved the ionic conductivity and bromine diffusion properties by providing interconnected ion-conductive SPEEK nanofiber pathways through a PVDF matrix. Relatively thin (~50–60 μm) electrospun membranes with a SPEEK/PVDF ratio (wt%/wt%) of 90/10 and 80/20 showed comparable Br3− diffusion rates as the relatively thick and commercially available perfluorosulfonic acid (PFSA) membrane (~100 μm) at a 35%–42% lower proton conductivity. The latter can be attributed to the poorer ion conductivity of SPEEK compared to PFSA and the presence of PVDF. The HBFB single cell featured the best polarization behavior and ohmic area resistance with the electrospun membrane containing 80/20 (wt%/wt%) SPEEK/PVDF. However, the low thickness and insufficient chemical/mechanical stability of the ES 80/20 causes a rapid decay in the HBFB cycling performance. This study promotes a life-time comparison study between the low-cost wire-electrospun SPEEK/PVDF blend membranes (~€100 m−2) and the typically used PFSA membranes (~€400 m−2) for a long-term HBFB performance.

Designing Highly Conductive Block Copolymer-Based Anion Exchange Membranes by Mesoscale Simulations.

Hydroxide ion conductivity is a key aspect of anion exchange membranes and is mainly determined by the nanoscale membrane morphologies. Fundamental understanding of the structural and transport properties of membranes in terms of polymer architectures is crucial for future development of membrane-based applications. Using mesoscale simulations, this work predicts the mesostructure of the hydrated triblock copolymers; the designed polymers are composed of aromatic (polyphenylene oxide, PPO) or aliphatic (polystyrene-ethylene-butylene-styrene, SEBS) backbones, with cationic side chains being modified by hydrophobic or hydrophilic spacers. For PPO-based polymers, using octyl spacers creates a meshlike water network, yielding ion conductivity equal to 30.6 mS/cm at room temperature. For SEBS-based polymers, the nonmodified form is sufficient to produce ion-conducting pathways. Adding hydrophobic spacers further enhances the nanosegregation, and the membranes provide similar conductivity at a lower ion exchange capacity and water content. Adding hydrophilic spacers, however, has negative impacts on the ion transport. The side chains are in the stretched configurations, which sterically hinder the mobility of water and hydroxide ions. Such a resistance can be overcome by adapting multication side-chain designs, where large water channels are formed, yielding ion conductivity as high as 32.8 mS/cm.

Self-assembled lamellar nanochannels in polyoxometalate-polymer nanocomposites for proton conduction

The construction of nanostructured ion-transport channels is highly desirable in the design of advanced electrolyte materials, as it can enhance ion conductivity by offering short ion-transport pathways. In this work, we present a supramolecular strategy to fabricate a nanocomposite electrolyte containing highly ordered lamellar proton-conducting nanochannels, by the electrostatic self-assembly of a polyoxometalate H3PW12O40 (PW) and a comb copolymer poly(4-methlstyrene)-graft-poly(N-vinyl pyrrolidone). PW can effectively regulate the self-assembling order of polymer moieties to form a large-range lamellar structure, meanwhile, introducing protons into the nanoscale lamellar domains to build proton transport channels. Moreover, the rigid PW clusters contribute a remarkable mechanical reinforcement to the nanocomposites. The lamellar nanocomposite exhibits a conductivity of 4.3 × 10−4 S/cm and a storage modulus of 1.1 × 107 Pa at room temperature. This study provides a new strategy to construct nanostructured ion-conductive pathways in electrolyte materials.

Zr- and Ce-doped Li6Y(BO3)3 electrolyte for all-solid-state lithium-ion battery.

The ionic conductivity of Li6Y(BO3)3 (LYBO) was enhanced by the substitution of tetravalent ions (Zr4+ and Ce4+) for Y3+ sites through the formation of vacancies at the Li sites, an increase in compact densification, and an increase in the Li+-ion conduction pathways in the LYBO phase. As a result, the ionic conductivity of Li5.875Y0.875Zr0.1Ce0.025(BO3)3 (ZC-LYBO) reached 1.7 × 10−5 S cm−1 at 27 °C, which was about 5 orders of magnitude higher than that of undoped Li6Y(BO3)3. ZC-LYBO possessed a large electrochemical window and was thermally stable after cosintering with a LiNi1/3Mn1/3Co1/3O2 (NMC) positive electrode. These characteristics facilitated good reversible capacities in all-solid-state batteries for both NMC positive electrodes and graphite negative electrodes via a simple cosintering process.

Bubbles: The Good, the Bad, and the Ugly

Bubbles are bad news for electrolysis due to undesired overpotentials, though their impact may be even further reaching than previously understood. In a recent report in Energy & Environmental Science, Kempler and researchers control the microstructure of electrodes to minimize overpotentials caused by bubbles in a photoelectrochemical cell.

Metal–Organic Framework-Derived Nanoconfinements of CoF2 and Mixed-Conducting Wiring for High-Performance Metal Fluoride-Lithium Battery

Metal fluoride (MF) conversion cathodes theoretically show higher gravimetric and volumetric capacities than Ni- or Co-based intercalation oxide cathodes, which makes metal fluoride-lithium batteries promising candidates for next-generation high-energy-density batteries. However, their high-energy characteristics are clouded by low-capacity utilization, large voltage hysteresis, and poor cycling stability of transition MF cathodes. A variety of reasons is responsible for this: poor reaction kinetics, low conductivities, unstable MF/electrolyte interfaces and dissolution of active species upon cycling. Herein, we combine the synthesis of the metal-organic-framework (MOF) with the low-temperature fluorination to prepare MOF-shaped CoF2@C nanocomposites that exhibit confinement of the CoF2 nanoparticles and efficient mixed-conducting wiring in the produced architecture. The ultrasmall CoF2 nanoparticles (5-20 nm on average) are uniformly covered by graphitic carbon walls and embedded in the porous carbon framework. Within the CoF2@C nanocomposite, the cross-linked carbon wall and interconnected nanopores serve as electron- and ion-conducting pathways, respectively, enabling a highly reversible conversion reaction of CoF2. As a result, the produced CoF2@C composite cathodes successfully restrain the above-mentioned challenges and demonstrate high-capacity utilization of ∼500 mAh g-1 at 0.2C, good rate capability (up to 2C), and long-term cycle stability over 400 cycles. Overall, the presented study not only reports on a simple composite design to achieve high-energy characteristics in CoF2-Li batteries but also may provide a general solution for many other metal fluoride-lithium batteries.

Suppressing Electrochemical Instabilities of Li Metal Using Ionomer-Based Interfaces

A fundamental challenge shared across many energy storage devices, is the complexity of electrochemistry at the electrode-electrolyte interfaces that impacts the faradaic efficiency, operational rate capability and lifetime. Specifically, in energy-dense lithium metal batteries, the charging process results in morphological heterogeneity of the metal anode, leading to battery failure by short-circuit or capacity fade. Perhaps, a facile way of addressing these challenges is designing a polymer thin-film at the electrode-electrolyte interface. We envision that an ideal interface should be based on several design principles including: presence of Li+ ion conduction pathway; chemically inert, mechanically robust, adaptive to volume changes and solution-processable for large scale thin-film casting.Here, we use free-radical polymerization technique to synthesize novel stimuli-responsive polymers which exhibit the aforementioned characteristics. Unlike, previous works where the electrode coating acts as a pure physical barrier, the designer polymers in this work possess multifunctional characteristics to suppress different electrochemical instabilities. Because of the viscoelastic and electroactive nature of the polymers, they respond to any morphological changes of the electrodes during electrodeposition, giving rise to an electrochemical shielding mechanism that modulates lithium ion migration pathway and prevents surface roughening.This work takes advantage of contemporary characterizations techniques like NMR, voltammetry and rheology to mechanistically understand the role of polymer dynamics and ion content on the electrodeposition morphology. We show that systematic optimization of these parameters can significantly boost the coulombic efficiency of the battery. Remarkably, we found that these polymer coatings can enhance the lifetime of conventional high-voltage lithium metal battery by at least two-times.

Understanding the Structural Disorder Related to Ionic Conductivity Enhancement in Anti-Perovskite Ion Conductors

Amongst known families of solid electrolytes of potential interest for solid-state batteries, the anti-perovskites (APs) have recently attracted great attention for the high ionic conductivities observed in certain compositions, and, like perovskites, the compositional flexibility provided by the possibility for ion substitution onto multiple lattice sites. [1] For example, variations in the extent of disorder, that are accompanied by changes in the distribution of lithium migration energies.[2] In surveying transport in this family of ion conductors, we observed a trend wherein numerous compositions show upwards curvature on an Arrhenius plot, indicating a non-constant activation energy. This is unusual as most solids exhibiting non-Arrhenius behavior exhibit a negative deviation. The structure origins of such deviations are not well understood.Among the AP-structure SSEs, Li2OHCl and its variants are particularly interesting because of their relatively high conductivities at room temperature. Unlike Li3OCl, where six Li atoms occupy the vertices of the Li6O octahedral, in Li2OHX the vertices are occupied by four lithium atoms with two other sites vacant. H in Li2OHX sits at the oxygen atom in the center of the octahedron. The Li defects and the movement of H around the oxygen atom give rise to a change in the ionic conduction pathway as temperature varies (Figure 1). Figure 1. The ionic conduction pathway of Li and H in Li2OHCl at different temperatureHerein, we explain the non-Arrhenius conduction behavior in relation to defect and H movement, and our attempts to understand the structural origin(s) of this behavior through temperature-dependent X-ray and neutron scattering, calorimetry, and other methods. Implications for the design of solid electrolytes for solid state batteries will be discussed.This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. Reference s : [1] Zhao, Y.; Daemen, L. L. Superionic conductivity in Lithium-rich anti-perovskites. J. Am. Chem. Soc. 2012, 134, 15042−15047.[2] Kwangnam Kim and Donald J. Siegel. "Correlating lattice distortions, ion migration barriers, and stability in solid electrolytes." Journal of Materials Chemistry A 7, no. 7 (2019): 3216-3227. Figure 1

Depletion of Lithium Inventory and Devolution of Lithium-Electrolyte Interface in Lithium-Sulfur Batteries

The lithium-sulfur (Li-S) chemistry holds tremendous potential for realizing the next generation of rechargeable batteries with high energy density and low cost. Despite its promise, the practical development of Li-S batteries is hindered by its limited cyclability, which is mainly caused by the poor plating and stripping efficiency of the lithium-metal anode. In liquid electrolytes, lithium deposits adopt a mossy dendritic filamentous morphology with high surface area. Due to the reactive nature of lithium, the electrolyte irreversibly decomposes on the lithium surface, which consumes both the lithium and electrolyte supply in the cell. However, significant questions remain about the mechanisms that underlie lithium inventory loss and the role of the lithium-electrolyte interface. Further commercial adoption of Li-S batteries is conditional on developing an effective strategy for improving the reversibility of lithium deposition, which is in turn dependent on developing a clear mechanistic understanding of lithium degradation with cycling.In this study, we use the anode-free full cell configuration, which pairs a Li2S cathode with a bare nickel foil as the anode current collector. Since there is no excess lithium in the system (N/P ratio = 1), the cyclability of anode-free full cells depends on the electrochemically accessible lithium inventory in the system. By identifying the sulfur-limited and lithium-limited regimes in the cycling of anode-free full cells, the lithium inventory loss rate per cycle (LILR) can be quantitatively estimated. This parameter provides an effective, robust, and quantifiable description of lithium degradation with cycling in cells with a limited lithium inventory. Lithium degradation displays a strong dependence on the applied current density, with the LILR increasing from 0.6% per cycle to 1.8% per cycle when the current rate is increased from C/10 to C/5.Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was applied to analyze the chemical composition of the deposited lithium in the anode-free full cells with different cycle numbers. The integrated intensity for Li2 -, which is indicative of metallic lithium, was found to show negligible variation with cycle number. In contrast, the electrochemically accessible lithium inventory is known to show a clear decrease with cycling. Thus, there is poor correlation between the lithium inventory available with cycle number and the amount of metallic lithium detected with ToF-SIMS. This indicates that lithium inventory depletion in Li-S batteries is not just due to the loss of lithium in parasitic side reactions with the electrolyte to form lithium SEI compounds (Li+), but largely due to the formation of electrochemically inaccessible “dead” metallic lithium. Further analysis with ToF-SIMS revealed the growth of a thick layer of electrolyte decomposition products on the surface of the deposited lithium. Since the decomposition products are expected to be ionically insulating, lithium-ion access to and from the metallic lithium underneath is blocked, which renders it electrochemically inaccessible or “dead”.The bulk of the deposited lithium is found to be composed of fully reduced decomposition products, such as Li2O, Li2S, LiH, and LiOH. In particular, the hydrogen-containing decomposition products such as LiH and LiOH are found to show a sharp decrease in concentration with cycling. This is attributed to the substantial gas evolution that occurs at the lithium anode during cell operation. These gases include H2, CH4, and C2H4, and their generation is correlated with the loss of lithium inventory with cycling. This could play an additional role in limiting electrochemical accessibility to the trapped metallic lithium by blocking off ionic and electronic conduction pathways, especially if the gases themselves are trapped in void spaces of the porous lithium deposit.This work illuminates the mechanisms that underlie the loss of lithium inventory in Li-S batteries by a careful application of the anode-free full cell configuration and analytical tools, such as ToF-SIMS. The role of the devolving lithium-electrolyte interface in engendering lithium degradation with cycling is clarified. The framework demonstrated in this work and the conclusions drawn are applicable not just to Li-S batteries, but to lithium-metal-based batteries in general. It is hoped that the insights generated in this work can motivate efforts towards enabling stable operation of lithium-metal anodes and long cycle life for energy-dense Li-S batteries. Figure 1