Unveil the origin of voltage oscillation for sodium-ion batteries operating at -40 °C.

Voltage oscillation at subzero in sodium-ion batteries (SIBs) has been a common but overlooked scenario, almost yet to be understood. For example, the phenomenon seriously deteriorates the performance of Na3V2(PO4)3 (NVP) cathode in PC (propylene carbonate)/EC (ethylene carbonate)-based electrolyte at -20 °C. Here, the correlation between voltage oscillation, structural evolution, and electrolytes has been revealed based on theoretical calculations, in-/ex-situ techniques, and cross-experiments. It is found that the local phase transition of the Na3V2(PO4)3 (NVP) cathode in PC/EC-based electrolyte at -20 °C should be responsible for the oscillatory phenomenon. Furthermore, the low exchange current density originating from the high desolvation energy barrier in NVP-PC/EC system also aggravates the local phase transformation, resulting in severe voltage oscillation. By introducing the diglyme solvent with lower Na-solvent binding energy, the voltage oscillation of the NVP can be eliminated effectively at subzero. As a result, the high capacity retentions of 98.3% at -20 °C and 75.3% at -40 °C are achieved. The finding provides insight into the abnormal SIBs degradation and brings the voltage oscillation behavior of rechargeable batteries into the limelight.

Unipolar Ionic Diode Nanofluidic Membranes Enabled by Stepped Mesochannels for Enhanced Salinity Gradient Energy Harvesting.

Developing ionic diode membranes featuring asymmetric structures is in high demand for salinity gradient energy harvesting. These membranes offer benefits in mitigating ion concentration polarization, thereby promoting ion permeability. However, most reported works focus on the role of heterogeneous charge-based bipolar ionic diode membranes for ion concentration polarization suppression, with comparatively less attention given to maintaining ion selectivity. Herein, unipolar ionic diode nanofluidic mesoporous silica membranes featuring stepped mesochannels were developed via a micellar sequential oriented interfacial self-assembly strategy as a salinity gradient energy harvester. Due to the asymmetric mesochannels and unipolar structure (both sides carry negative charge), the ionic diode membranes exhibit a strong rectification ratio of ∼15.91 to facilitate unidirectional ion transport while maintaining excellent cation selectivity (cation transfer number of ∼0.85). Besides, the vertically aligned mesochannels significantly reduce ion transport resistance, generating a high ionic flux. Consequently, the unipolar ionic diode nanofluidic membranes demonstrate a power output of 5.88 W/m2 between artificial sea and river water. The unipolar feature gives notable enhancements of 296% and 144% in power output compared to the symmetric membrane and bipolar ionic diode membrane, respectively. This work opens up new routes for designing ionic diode membranes for salinity gradient energy harvesting.

Tandem Chemistry with Janus Mesopores Accelerator for Efficient Aqueous Batteries.

A reliable solid electrolyte interphase (SEI) on the metallic Zn anode is imperative for stable Zn-based aqueous batteries. However, the incompatible Zn-ion reduction processes, scilicet simultaneous adsorption (capture) and desolvation (repulsion) of Zn2+(H2O)6, raise kinetics and stability challenges for the design of SEI. Here, we demonstrate a tandem chemistry strategy to decouple and accelerate the concurrent adsorption and desolvation processes of the Zn2+ cluster at the inner Helmholtz layer. An electrochemically assembled perforative mesopore SiO2 interphase with tandem hydrophilic -OH and hydrophobic -F groups serves as a Janus mesopores accelerator to boost a fast and stable Zn2+ reduction reaction. Combining in situ electrochemical digital holography, molecular dynamics simulations, and spectroscopic characterizations reveals that -OH groups capture Zn2+ clusters from the bulk electrolyte and then -F groups repulse coordinated H2O molecules in the solvation shell to achieve the tandem ion reduction process. The resultant symmetric batteries exhibit reversible cycles over 8000 and 2000 h under high current densities of 4 and 10 mA cm-2, respectively. The feasibility of the tandem chemistry is further evidenced in both Zn//VO2 and Zn//I2 batteries, and it might be universal to other aqueous metal-ion batteries.

Unlocking Dynamic Solvation Chemistry and Hydrogen Evolution Mechanism in Aqueous Zinc Batteries.

Understanding the interfacial hydrogen evolution reaction (HER) is crucial to regulate the electrochemical behavior in aqueous zinc batteries. However, the mechanism of HER related to solvation chemistry remains elusive, especially the time-dependent dynamic evolution of the hydrogen bond (H-bond) under an electric field. Herein, we combine in situ spectroscopy with molecular dynamics simulation to unravel the dynamic evolution of the interfacial solvation structure. We find two critical change processes involving Zn-electroplating/stripping, including the initial electric double layer establishment to form an H2O-rich interface (abrupt change) and the subsequent dynamic evolution of an H-bond (gradual change). Moreover, the number of H-bonds increases, and their strength weakens in comparison with the bulk electrolyte under bias potential during Zn2+ desolvation, forming a diluted interface, resulting in massive hydrogen production. On the contrary, a concentrated interface (H-bond number decreases and strength enhances) is formed and produces a small amount of hydrogen during Zn2+ solvation. The insights on the above results contribute to deciphering the H-bond evolution with competition/corrosion HER during Zn-electroplating/stripping and clarifying the essence of electrochemical window widened and HER suppression by high concentration. This work presents a new strategy for aqueous electrolyte regulation by benchmarking the abrupt change of the interfacial state under an electric field as a zinc performance-enhancement criterion.

Biomimetic Superstructured Interphase for Aqueous Zinc-Ion Batteries.

The practical application of aqueous zinc-ion batteries (AZIBs) is greatly challenged by rampant dendrites and pestilent side reactions resulting from an unstable Zn-electrolyte interphase. Herein, we report the construction of a reliable superstructured solid electrolyte interphase for stable Zn anodes by using mesoporous polydopamine (2D-mPDA) platelets as building blocks. The interphase shows a biomimetic nacre's "brick-and-mortar" structure and artificial transmembrane channels of hexagonally ordered mesopores in the plane, overcoming the mechanical robustness and ionic conductivity trade-off. Experimental results and simulations reveal that the -OH and -NH groups on the surface of artificial ion channels can promote rapid desolvation kinetics and serve as an ion sieve to homogenize the Zn2+ flux, thus inhibiting side reactions and ensuring uniform Zn deposition without dendrites. The 2D-mPDA@Zn electrode achieves an ultralow nucleation potential of 35 mV and maintains a Coulombic efficiency of 99.8% over 1500 cycles at 5 mA cm-2. Moreover, the symmetric battery exhibits a prolonged lifespan of over 580 h at a high current density of 20 mA cm-2. This biomimetic superstructured interphase also demonstrates the high feasibility in Zn//VO2 full cells and paves a new route for rechargeable aqueous metal-ion batteries.

Ultrafine Asymmetric Soft/Stiff Nanohybrids with Tunable Patchiness via a Dynamic Surface-Mediated Assembly.

Asymmetric soft-stiff patch nanohybrids with small size, spatially separated organics and inorganics, controllable configuration, and appealing functionality are important in applications, while the synthesis remains a great challenge. Herein, based on polymeric single micelles (the smallest assembly subunit of mesoporous materials), we report a dynamic surface-mediated anisotropic assembly approach to fabricate a new type of small asymmetric organic/inorganic patch nanohybrid for the first time. The size of this asymmetric organic/inorganic nanohybrid is ∼20 nm, which contains dual distinct subunits of a soft organic PS-PVP-PEO single micelle nanosphere (12 nm in size and 632 MPa in Young' modulus) and stiff inorganic SiO2 nanobulge (∼8 nm, 2275 MPa). Moreover, the number of SiO2 nanobulges anchored on each micelle can be quantitatively controlled (from 1 to 6) by dynamically tuning the density (fluffy or dense state) of the surface cap organic groups. This small asymmetric patch nanohybrid also exhibits a dramatically enhanced uptake level of which the total amount of intracellular endocytosis is about three times higher than that of the conventional nanohybrids.

Zinc ion Batteries: Bridging the Gap from Academia to Industry for Grid-Scale Energy Storage.

Zinc ion batteries (ZIBs) exhibit significant promise in the next generation of grid-scale energy storage systems owing to their safety, relatively high volumetric energy density, and low production cost. Despite substantial advancements in ZIBs, a comprehensive evaluation of critical parameters impacting their practical energy density (Epractical) and calendar life is lacking. Hence, we suggest using formulation-based study as a scientific tool to accurately calculate the cell-level energy density and predict the cycling life of ZIBs. By combining all key battery parameters, such as the capacity ratio of negative to positive electrode (N/P), into one formula, we assess their impact on Epractical. When all parameters are optimized, we urge to achieve the theoretical capacity for a high Epractical. Furthermore, we propose a formulation that correlates the N/P and Coulombic efficiency of ZIBs for predicting their calendar life. Finally, we offer a comprehensive overview of current advancements in ZIBs, covering cathode and anode, along with practical evaluations. This Minireview outlines specific goals, suggests future research directions, and sketches prospects for designing efficient and high-performing ZIBs. It aims at bridging the gap from academia to industry for grid-scale energy storage.

Electron-Donating Conjugation Effect Modulated Zn2+ Reduction Reaction for Separator-Free Aqueous Zinc Batteries.

Zinc-based aqueous batteries (ZABs) are attracting extensive attention due to the low cost, high capacity, and environmental benignity of the zinc anode. However, their application is still hindered by the undesired zinc dendrites. Despite Zn-surface modification being promising in relieving dendrites, a thick separator (i.e. glass fiber, 250-700 µm) is still required to resist the dendrite puncture, which limits volumetric energy density of battery. Here, we pivot from the traditional interphase plus extra separator categories, proposing an all-in-one ligand buffer layer (ca. 20 µm) to effectively modulate the Zn2+ transfer and deposition behaviors proved by in situ electrochemical digital holography. Experimental characterizations and density functional theory simulations further reveal that the catechol groups in the buffer layer can accelerate the Zn2+ reduction reaction (ZRR) through the electron-donating p-π conjugation effect, decreasing the negative charge in the coordination environment. Without extra separators, the elaborated system endows low polarization below 28.2 mV, long lifespan of 4950 h at 5 mA cm-2 in symmetric batteries, and an unprecedented volumetric energy density of 99.2 Wh L-1 based on the whole pouch cells. The concomitantly "separator-free" and "dendrite-free" conjugation effect with an accelerated ZRR process could foster the progression of metallic anodes and benefit energetic aqueous batteries.

High-Energy Sn-Ni and Sn-Air Aqueous Batteries via Stannite-Ion Electrochemistry.

Tin is promising for aqueous batteries (ABs) due to its multiple electrons' reactions, high corrosion resistance, large hydrogen overpotential, and excellent environmental compatibility. However, restricted to the high thermodynamic barrier and the poor electrochemical kinetics, efficient alkaline Sn plating/stripping at facile conditions has not yet been realized. Here, for the first time, we demonstrate a highly reversible stannite-ion electrochemistry and construct a novel paradigm of high-energy Sn-based ABs. Combined spectroscopic characterization, electrochemical evaluation, and theoretical computation reveal the thermodynamic merits with a low reaction energy barrier and feasible H2O participation in Sn-ion reduction as well as the kinetic merits with fastened surface charge transfer and SnO22- diffusion. The resultant alkaline Sn anode delivers a low potential of -1.07 V vs Hg/HgO, a specific capacity of 450 mA h g-1, a Coulombic efficiency of near 100%, superb rate capability at 45.5 A g-1, and excellent cycling durability without dendrite and dead Sn. As a proof of concept, we developed new high-energy Sn-based ABs, including 1.45 V Sn-Ni with 314 W h kg-1 (58 kW kg-1 and over 15,000 cycles) and 1.0 V Sn-air with 420 W h kg-1 (lifespan over 1900 h), on the basis of masses from cathode and anode active materials. The findings prove the feasibility of the alkaline Sn metal anode, and the new suite of high-energy Sn-based ABs may be of immediate benefit toward safe, reliable, and affordable energy storage.

Reviving Zn0 Dendrites to Electroactive Zn2+ by Mesoporous MXene with Active Edge Sites.

Zinc metal-based aqueous batteries (ZABs) offer a sustainable, affordable, and safe energy storage alternative to lithium, yet inevitable dendrite formation impedes their wide use, especially under long-term and high-rate cycles. How the battery can survive after dendrite formation remains an open question. Here, we pivot from conventional Zn dendrite growth suppression strategies, introducing proactive dendrite-digesting chemistry via a mesoporous Ti3C2 MXene (MesoTi3C2)-wrapped polypropylene separator. Spectroscopic characterizations and electrochemical evaluation demonstrate that MesoTi3C2, acting as an oxidant, can revive the formed dead Zn0 dendrites into electroactive Zn2+ ions through a spontaneous redox process. Density functional theory reveals that the abundant edge-Ti-O sites in our MesoTi3C2 facilitate high oxidizability and electron transfer from Zn0 dendrites compared to their in-plane counterparts. The resultant asymmetrical cell demonstrates remarkable ultralong cycle life of 2200 h at a practical current of 5 mA cm-2 with a low overpotential (<50 mV). The study reveals the unexpected edge effect of mesoporous MXenes and uncovers a new proactive dendrite-digesting chemistry to survive ZABs, albeit with inevitable dendrite formation.

Surface Stretching Enables Highly Disordered Graphitic Domains for Ultrahigh Rate Sodium Storage.

Hard carbons (HCs) with high sloping capacity are considered as the leading candidate anode for sodium-ion batteries (SIBs); nevertheless, achieving basically complete slope-dominated behavior with high rate capability is still a big challenge. Herein, the synthesis of mesoporous carbon nanospheres with highly disordered graphitic domains and MoC nanodots modification via a surface stretching strategy is reported. The MoOx surface coordination layer inhibits the graphitization process at high temperature, thus creating short and wide graphite domains. Meanwhile, the in situ formed MoC nanodots can greatly promote the conductivity of highly disordered carbon. Consequently, MoC@MCNs exhibit an outstanding rate capacity (125 mAh g-1 at 50 A g-1 ). The "adsorption-filling" mechanism combined with excellent kinetics is also studied based on the short-range graphitic domains to reveal the enhanced slope-dominated capacity. The insight in this work encourages the design of HC anodes with dominated slope capacity toward high-performance SIBs.

Electrolyte Regulation of Bio-Inspired Zincophilic Additive toward High-Performance Dendrite-Free Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries hold attractive potential for large-scale energy storage devices owing to their prominent electrochemical performance and high security. Nevertheless, the applications of aqueous electrolytes have generated various challenges, including uncontrolled dendrite growth and parasitic reactions, thereby deteriorating the Zn anode's stability. Herein, inspired by the superior affinity between Zn2+ and amino acid chains in the zinc finger protein, a cost-effective and green glycine additive is incorporated into aqueous electrolytes to stabilize the Zn anode. As confirmed by experimental characterizations and theoretical calculations, the glycine additives can not only reorganize the solvation sheaths of hydrated Zn2+ via partial substitution of coordinated H2 O but also preferentially adsorb onto the Zn anode, thereby significantly restraining dendrite growth and interfacial side reactions. Accordingly, the Zn anode could realize a long lifespan of over 2000 h and enhanced reversibility (98.8%) in the glycine-containing electrolyte. Furthermore, the assembled Zn||α-MnO2 full cells with glycine-modified electrolyte also delivers substantial capacity retention (82.3% after 1000 cycles at 2 A g-1 ), showing promising application prospects. This innovative bio-inspired design concept would inject new vitality into the development of aqueous electrolytes.

Hierarchical Confinement Effect with Zincophilic and Spatial Traps Stabilized Zn-Based Aqueous Battery.

Zn-based aqueous batteries (ZABs) have been regarded as promising candidates for safe and large-scale energy storage in the "post-Li" era. However, kinetics and stability problems of Zn capture cannot be concomitantly regulated, especially at high rates and loadings. Herein, a hierarchical confinement strategy is proposed to design zincophilic and spatial traps through a host of porous Co-embedded carbon cages (denoted as CoCC). The zincophilic Co sites act as preferred nucleation sites with low nucleation barriers (within 0.5 mA h cm-2), and the carbon cage can further spatially confine Zn deposition (within 5.0 mA h cm-2). Theoretical simulations and in situ/ex situ structural observations reveal the hierarchical spatial confinement by the elaborated all-in-one network (within 12 mA h cm-2). Consequently, the elaborate strategy enables a dendrite-free behavior with excellent kinetics (low overpotential of ca. 65 mV at a high rate of 20 mA cm-2) and stable cycle life (over 800 cycles), pushing forward the next-generation high-performance ZABs.

Constructing Unique Mesoporous Carbon Superstructures via Monomicelle Interface Confined Assembly.

Constructing hierarchical three-dimensional (3D) mesostructures with unique pore structure, controllable morphology, highly accessible surface area, and appealing functionality remains a great challenge in materials science. Here, we report a monomicelle interface confined assembly approach to fabricate an unprecedented type of 3D mesoporous N-doped carbon superstructure for the first time. In this hierarchical structure, a large hollow locates in the center (∼300 nm in diameter), and an ultrathin monolayer of spherical mesopores (∼22 nm) uniformly distributes on the hollow shells. Meanwhile, a small hole (4.0-4.5 nm) is also created on the interior surface of each small spherical mesopore, enabling the superstructure to be totally interconnected. Vitally, such interconnected porous supraparticles exhibit ultrahigh accessible surface area (685 m2 g-1) and good underwater aerophilicity due to the abundant spherical mesopores. Additionally, the number (70-150) of spherical mesopores, particle size (22 and 42 nm), and shell thickness (4.0-26 nm) of the supraparticles can all be accurately manipulated. Besides this spherical morphology, other configurations involving 3D hollow nanovesicles and 2D nanosheets were also obtained. Finally, we manifest the mesoporous carbon superstructure as an advanced electrocatalytic material with a half-wave potential of 0.82 V (vs RHE), equivalent to the value of the commercial Pt/C electrode, and notable durability for oxygen reduction reaction (ORR).

Surface-Electronic-Structure Reconstruction of Perovskite via Double-Cation Gradient Etching for Superior Water Oxidation.

Reconstructing the surface-electronic-structure of catalysts for efficient electrocatalytic activity is crucial but still under intense exploration. Herein, we introduce a double-cation gradient etching technique to manipulate the electronic structure of perovskite LaCoO3. With the gradient dissolution of cations, the surface was reconstructed, and the perovskite/spinel heterostructure V-LCO/Co3O4 (V-LCO refers to LaCoO3 with La and Co vacancies) can be realized. Its surface-electronic-structure is effectively regulated due to the heterogeneous interface effect and abundant vacancies, resulting in a significantly enhanced activity for oxygen evolution reaction (OER). The V-LCO/Co3O4 exhibits low electrochemical activation energy and 2 orders of magnitude higher carrier concentrations (1.36 × 1021 cm-3) compared with LCO (6.03 × 1019 cm-3). Density functional theory (DFT) calculation unveils that the directional reconstruction of surface-electronic-structure enables the d-band center of V-LCO/Co3O4 to a moderate position, endowing perfect adsorption strength for oxo groups and thus promoting the electrocatalytic activity.

Sulfur-Based Aqueous Batteries: Electrochemistry and Strategies.

While research interest in aqueous batteries has surged due to their intrinsic low cost and high safety, the practical application is plagued by the restrictive capacity (less than 600 mAh g-1) of electrode materials. Sulfur-based aqueous batteries (SABs) feature high theoretical capacity (1672 mAh g-1), compatible potential, and affordable cost, arousing ever-increasing attention and intense efforts. Nonetheless, the underlying electrochemistry of SABs remains unclear, including complicated thermodynamic evolution and insufficient kinetics metrics. Consequently, multifarious irreversible reactions in various application systems imply the systematic complexity of SABs. Herein, rather than simply compiling recent progress, this Perspective aims to construct a theory-to-application methodology. Theoretically, attention has been paid to a critical appraisal of the aqueous-S-related electrochemistry, including fundamental properties evaluation, kinetics metrics with transient and steady-state analyses, and thermodynamic equilibrium and evolution. To put it into practice, current challenges and promising strategies are synergistically proposed. Practically, the above efforts are employed to evaluate and develop the device-scale applications, scilicet flow-SABs, oxide-SABs, and metal-SABs. Last, chemical and engineering insights are rendered collectively for the future development of high-energy SABs.

Catalytic Oxidation of K2S via Atomic Co and Pyridinic N Synergy in Potassium-Sulfur Batteries.

Potassium-sulfur batteries hold practical promise for next-generation batteries because of their high theoretical gravimetric energy density and low cost. However, significant impediments are the sluggish K2S oxidation kinetics and a lack of atomic-level understanding of K2S oxidation. Here, for the first time, we report the catalytic oxidation of K2S on a sulfur host with Co single atoms immobilized on nitrogen-doped carbon. On the basis of combined spectroscopic characterizations, electrochemical evaluation, and theoretical computations, we show a synergistic effect of dynamic Co-S and N-K interactions to catalyze K2S oxidation. The resultant potassium-sulfur battery exhibited high capacities of 773 and 535 mAh g-1 under high current densities of 1 and 2 C, respectively. These findings provide atomic-scale insights for the rational design of highly efficient sulfur hosts.

Boosting Zinc Electrode Reversibility in Aqueous Electrolytes by Using Low-Cost Antisolvents.

Antisolvent addition has been widely studied in crystallization in the pharmaceutical industries by breaking the solvation balance of the original solution. Here we report a similar antisolvent strategy to boost Zn reversibility via regulation of the electrolyte on a molecular level. By adding for example methanol into ZnSO4 electrolyte, the free water and coordinated water in Zn2+ solvation sheath gradually interact with the antisolvent, which minimizes water activity and weakens Zn2+ solvation. Concomitantly, dendrite-free Zn deposition occurs via change in the deposition orientation, as evidenced by in situ optical microscopy. Zn reversibility is significantly boosted in antisolvent electrolyte of 50 % methanol by volume (Anti-M-50 %) even under harsh environments of -20 °C and 60 °C. Additionally, the suppressed side reactions and dendrite-free Zn plating/stripping in Anti-M-50 % electrolyte significantly enhance performance of Zn/polyaniline coin and pouch cells. We demonstrate this low-cost strategy can be readily generalized to other solvents, indicating its practical universality. Results will be of immediate interest and benefit to a range of researchers in electrochemistry and energy storage.

Simultaneous Regulation on Solvation Shell and Electrode Interface for Dendrite-Free Zn Ion Batteries Achieved by a Low-Cost Glucose Additive.

Dendrite growth and by-products in Zn metal aqueous batteries have impeded their development as promising energy storage devices. We utilize a low-cost additive, glucose, to modulate the typical ZnSO4 electrolyte system for improving reversible plating/stripping on Zn anode for high-performance Zn ion batteries (ZIBs). Combing experimental characterizations and theoretical calculations, we show that the glucose in ZnSO4 aqueous environment can simultaneously modulate solvation structure of Zn2+ and Zn anode-electrolyte interface. The electrolyte engineering can alternate one H2 O molecule from the primary Zn2+ -6H2 O solvation shell and restraining side reactions due to the decomposition of active water. Concomitantly, glucose molecules are inclined to absorb on the surface of Zn anode, suppressing the random growth of Zn dendrite. As a proof of concept, a symmetric cell and Zn-MnO2 full cell with glucose electrolyte achieve boosted stability than that with pure ZnSO4 electrolyte.

Revealing Principles for Design of Lean-Electrolyte Lithium Metal Anode via In Situ Spectroscopy.

Lean-electrolyte conditions are highly pursued for practical lithium (Li) metal batteries. The previous studies on the Li metal anodes, in general, exhibited good stability with a large excess of electrolyte. However, the targeted design of Li hosts under relatively low electrolyte conditions has been rarely studied so far. Herein, we have shown that electrolyte consumption severely affects the cycling stability of Li metal anode. Considering carbon hosts as typical examples, we innovatively employed in situ synchrotron X-ray diffraction, in situ Raman spectroscopy, and theoretical computations to obtain a better understanding of the Li nucleation/deposition processes. We also showed the usefulness of in situ electrochemical impedance spectra to analyze interfacial fluctuation at the Li/electrolyte interface, together with nuclear magnetic resonance data to quantify electrolyte consumption. We have found that uneven Li nucleation/deposition and the crack of surface-area-derived solid-electrolyte interface (SEI) layer both lead to a great consumption of electrolyte. Then, we suggested a design principle for Li host to overcome the electrolyte loss, that is, uneven growth of the Li structure and the crack of the SEI layer must be simultaneously controlled. As a proof of concept, we demonstrated the usefulness of a 3D low-surface-area defective graphene host (L-DG) to control Li nucleation/deposition and stabilize the SEI layer, contributing to a highly reversible Li plating/stripping. As a result, such a Li host can achieve stable cycles (e.g., 1.0 mAh cm-2) with a low electrolyte loading (10 µL). This work demonstrates the necessity to design Li metal anodes under lean-electrolyte conditions and brings Li metal batteries a step closer to their practical applications.