Stable Na Plating and Stripping Electrochemistry Promoted by In Situ Construction of an Alloy-Based Sodiophilic Interphase

In-Depth Understanding of Interfacial Na+ Behaviors in Sodium Metal Anode: Migration, Desolvation, and Deposition

Interfacial Na+ behaviors of sodium (Na) anode severely threaten the stability of sodium-metal batteries (SMBs). This review systematically and in-depth discusses the current fundamental understanding of interfacial Na+ behaviors in SMBs including Na+ migration, desolvation, diffusion, nucleation, and deposition. The key influencing factors and optimization strategies of these behaviors are further summarized and discussed. More importantly, the high-energy-density anode-free sodium metal batteries (AFSMBs) are highlighted by addressing key issues in the areas of limited Na sources and irreversible Na loss. Simultaneously, recent advanced characterization techniques for deeper insights into interfacial Na+ deposition behavior and composition information of SEI film are spotlighted to provide guidance for the advancement of SMBs and AFSMBs. Finally, the prominent perspectives are presented to guide and promote the development of SMBs and AFSMBs.

An autotransferable alloy overlayer toward stable sodium metal anodes

Sodium (Na) metal anodes receive significant attention due to their high theoretical specific energy and cost-effectiveness. However, the high reactivity of Na foil anodes and the irregular surfaces have posed challenges to the operability and reliability of Na metals in battery applications. In the absence of inert environmental protection conditions, constructing a uniform, dense, and sodiophilic Na metal anode surface is crucial for homogenizing Na deposition, but remains less-explored. Herein, we fabricated a Tin (Sn) nanoparticle-assembled film conforming to separator pores, which provided ample space for accommodating volumetric expansion during the Na alloying process. Subsequently, a seamless Na-Sn alloy overlayer was formed and transferred onto the Na foil during Na plating through a separator-assisted technique, thereby overcoming conventional operational limitations of metallic Na. As compared to traditional volumetrically expanded cracked ones, the present autotransferable, highly sodiophilic, ion-conductive, and seamless Na-Sn alloy overlayer serves as uniform nucleation sites, thereby reducing nucleation and diffusion barriers and facilitating the compact deposition of metallic Na. Consequently, the autotransferable alloy layer enables a high average Coulombic efficiency of 99.9 % at 3.0 mA cm-2 and 3.0 mAh cm-2 in the half cells as well as minimal polarization overpotentials in symmetric cells, both during prolonged cycling 1200 h. Furthermore, the assembled Na||Sn-1.0h-PP||Na3V2(PO4)3@C@CNTs full cell delivers high capacity retention of 97.5 % after 200 cycles at a high cathodic mass loading.

High Young's Modulus LixTiO2 Layer Suppressing the Pulverization and Deactivation of Lithiophilic Ag Nanoparticles

Anode-free Lithium metal batteries, with their high energy density (>500 Wh/kg), are emerging as a promising solution for high-energy-density rechargeable batteries. However, the Coulombic Efficiency and capacity often decline due to interface side reactions. To address this, a lithiophilic layer is introduced, promoting stable and uniform Li deposition. Despite its effectiveness, this layer often undergoes electrochemical deactivation over time. This work investigates lithiophilic silver (Ag), prepared via magnetron sputtering on a copper (Cu) current collector. Finite element simulations identify stress changes from alloying reactions as a key cause of Ag particle pulverization and deactivation. A high Young's modulus coating layer is proposed to mitigate this. The Ag2TiO3@Ag@TiO2@Cu composite electrode, designed with multi-layer structures, demonstrates a slower deactivation process through galvanostatic electrochemical cycling. Characterization methods such as SEM, AFM, and TEM confirm the suppression of Ag particle pulverization, while uncoated Ag fractures and deactivates. This work uncovers a potential failure mechanism of lithiophilic metallic nanoparticles and proposes a strategy for deactivation suppression using an artificial coating layer.

Sodiophilic Substrate Induces NaF-Rich Solid Electrolyte Interface for Dendrite-Free Sodium Metal Anode

3D substrate with abundant sodiophilic active sites holds promise for implementing dendrite-free sodium metal anodes and high-performance sodium batteries. However, the heightened electrode/electrolyte side reactions stemming from high specific surface area still hinder electrode structure stability and cycling reversibility, particularly under high current densities. Herein, the solid electrolyte interface (SEI) component is regulated and detrimental side reactions are restrained through the uniform loading of Na-Sn alloy onto a porous 3D nanofiber framework (NaSn-PCNF). The strong interaction between Na-Sn alloy and PF6 - anions facilitates the dissociation of sodium salts and releases more free sodium ions for effective charge transfer. Simultaneously, the modulations of the interfacial electrolyte solvation structure and the construction of a high NaF content SEI layer stabilize the electrode/electrolyte interface. NaSn-PCNF symmetrical battery demonstrates stable cycling for over 600 h with an ultralow overpotential of 24.5 mV under harsh condition of 10 mA cm-2 and 10 mAh cm-2. Moreover, the full cells and pouch cells exhibit accelerated reaction kinetics and splendid capacity retention, providing valuable insights into the development of advanced Na substrates for high-energy sodium metal batteries.

Electro-Chemo-Mechanically Stable and Sodiophilic Interface for Na Metal Anode in Liquid-based and Solid-State Batteries

Na metal batteries (NMBs) are attracting increasing attention because of their high energy density. However, the widespread application of NMBs is hindered by the growth of Na dendrites and interface instability. The design of artificial solid electrolyte interphase (SEI) with tuned chemical/electrochemical/mechanical properties is the key to achieving high-performance NMBs. This work develops a metal-doped nanoscale polymeric film with tunable composition, sodiophilic sites and improved stiffness. The incorporation of metal crosslinkers in the polymer chains results in exceptional electrochemical stability for Na metal anodes, leading to a significantly prolonged lifespan even at high current densities, which is at the top of the reported literature. The mechanical properties measurements and electro-chemo-mechanical phase-field model are performed to interpret the impact of the ionic transportation capability (decoupled mechanical) and mechanic property in the metal-doped polymer interface. In addition, this approach provides a promising strategy for the rational design of electrode interfaces, providing enhanced mechanical stability and improved sodiophilicity, which can open up opportunities for the fabrication of next-generation energy storage.

Design and Synthesis of Sb-Doped CuS@C Hollow Nanocubes as Efficient Anode Materials for Sodium-Ion Battery

Copper sulfide has received widespread attention for application as anode materials in sodium-ion batteries due to their potent capabilitiess and eco-friendly properties. However, it is a challenge to achieve a high rate capability and long cycle stability owing to the heterogeneous transfer of sodium ions during charge-discharge, the interior poor electron conductivity and repeated volumetric expansion of copper sulfide. In this study, Sb-doped copper sulfide hollow nanocubes coated with carbon shells (Sb-CuS@C) was designed and constructed as anode nanomaterials in sodium-ion batteries. Thanks to the intrinsic good electron conductivity and chemical stability of carbon shells, Sb-CuS@C possesses a higher overall electron transfer as anode material, avoids agglomeration and structural destruction during the cycling. As a result, the synthesized Sb-CuS@C achieved an excellent reversible capacity of 595 mA h g-1 after 100 cycles at 0.5 A g-1 and a good rate capability of 340 mA h g-1 at a higher 10 A g-1. DFT calculations clarify that the uniformly doped Sb would act as active sodiophilic nucleation sites to help adsorbing sodium-ion during discharging and leading uniform sodium deposition. This work provides a new insight into the structural and componential modification for common transition-metal sulfides towards application as anode materials in sodium-ion battery.

Activating reversible carbonate reactions in Nasicon solid electrolyte-based Na-air battery via in-situ formed catholyte

Out of practicality, ambient air rather than oxygen is preferred as a fuel in electrochemical systems, but CO2 and H2O present in air cause severe irreversible reactions, such as the formation of carbonates and hydroxides, which typically degrades performance. Herein, we report on a Na-air battery enabled by a reversible carbonate reaction (Na2CO3·xH2O, x = 0 or 1) in Nasicon solid electrolyte (Na3Zr2Si2PO12) that delivers a much higher discharge potential of 3.4 V than other metal-air batteries resulting in high energy density and achieves > 86 % energy efficiency at 0.1 mA cm-2 over 100 cycles. This cell design takes advantage of moisture in ambient air to form an in-situ catholyte via the deliquescent property of NaOH. As a result, not only reversible electrochemical reaction of Na2CO3·xH2O is activated but also its kinetics is facilitated. Our results demonstrate the reversible use of free ambient air as a fuel, enabled by the reversible electrochemical reaction of carbonates with a solid electrolyte.

Building Stable Anodes for High-Rate Na-Metal Batteries

Due to low cost and high energy density, sodium metal batteries (SMBs) have attracted growing interest, with great potential to power future electric vehicles (EVs) and mobile electronics, which require rapid charge/discharge capability. However, the development of high-rate SMBs has been impeded by the sluggish Na+ ion kinetics, particularly at the sodium metal anode (SMA). The high-rate operation severely threatens the SMA stability, due to the unstable solid-electrolyte interface (SEI), the Na dendrite growth, and large volume changes during Na plating-stripping cycles, leading to rapid electrochemical performance degradations. This review surveys key challenges faced by high-rate SMAs, and highlights representative stabilization strategies, including the general modification of SMB components (including the host, Na metal surface, electrolyte, separator, and cathode), and emerging solutions with the development of solid-state SMBs and liquid metal anodes; the working principle, performance, and application of these strategies are elaborated, to reduce the Na nucleation energy barriers and promote Na+ ion transfer kinetics for stable high-rate Na metal anodes. This review will inspire further efforts to stabilize SMAs and other metal (e.g., Li, K, Mg, Zn) anodes, promoting high-rate applications of high-energy metal batteries towards a more sustainable society.

An Ultrastable Low-Temperature Na Metal Battery Enabled by Synergy between Weakly Solvating Solvents

The low ionic conductivity and high desolvation barrier are the main challenges for organic electrolytes in rechargeable metal batteries, especially at low temperatures. The general strategy is to couple strong-solvation and weak-solvation solvents to give balanced physicochemical properties. However, the two challenges described above cannot be overcome at the same time. Herein, we combine two different kinds of weakly solvating solvents with a very low desolvation energy. Interestingly, the synergy between the weak-solvation solvents can break the locally ordered structure at a low temperature to enable higher ionic conductivity compared to those with individual solvents. Thus, facile desolvation and high ionic conductivity are achieved simultaneously, significantly improving the reversibility of electrode reactions at low temperatures. The Na metal anode can be stably cycled at 2 mA cm-2 at -40 °C for 1000 h. The Na||Na3V2(PO4)3 cell shows the reversible capacity of 64 mAh g-1 at 0.3 C after 300 cycles at -40 °C, and the capacity retention is 86%. This strategy is applicable to other sets of weak-solvation solvents, providing guidance for the development of electrolytes for low-temperature rechargeable metal batteries.

Design principles of heterointerfacial redox chemistry for highly reversible lithium metal anode

High electrochemical reversibility is required for the application of high-energy-density lithium (Li) metal batteries; however, inactive Li formation and SEI (solid electrolyte interface)-instability-induced electrolyte consumption cause low Coulombic efficiency (CE). The prior interfacial chemical designs in terms of alloying kinetics have been used to enhance the CE of Li metal anode; however, the role of its redox chemistry at heterointerfaces remains a mystery. Herein, the relationship between heterointerfacial redox chemistry and electrochemical transformation reversibility is investigated. It is demonstrated that the lower redox potential at heterointerface contributes to higher CE, and this enhancement in CE is primarily due to the regulation of redox chemistry to Li deposition behavior rather than the formation of SEI films. Low oxidation potential facilitates the formation of the surface with the highly electrochemical binding feature after Li stripping, and low reduction potential can maintain binding ability well during subsequent Li plating, both of which homogenize Li deposition and thus optimize CE. In particular, Mg hetero-metal with ultra-low redox potential enables Li metal anode with significantly improved CE (99.6%) and stable cycle life for 700 cycles at 3.0 mA cm-2. This work provides insight into the heterointerfacial design principle of next-generation negative electrodes for highly reversible metal batteries.

Study of Na Deposition Formation in Mixed Ethylene: Propylene Carbonate Electrolytes by Inert/Cryoelectron Microscopy

The sodium anode-free combines low-cost and high energy density, demonstrating a promising alternative to the Li battery counterpart. Nevertheless, the uptake of a sodium anode-free battery is greatly impeded by the uncontrollable dendrite proliferation upon the chemically active metallic Na. An insightful mechanistic understanding of Na deposition nucleation and growth behavior in ethylene carbonate and propylene carbonate (EC/PC, 1:1) is revealed via various inert and/or cryo-electron microscopy characterization techniques. The deposit morphology, size, and distribution were studied with different current densities and areal capacity. The Na deposit distribution changes from nonparametric distribution to normal distribution which can be attributed to the effect of interparticle diffusion coupling (IDP). The atomic information on the Na deposit was revealed via cryogenic transmission electron microscopy.

Anions Regulation Engineering Enables a Highly Reversible and Dendrite-Free Nickel-Metal Anode with Ultrahigh Capacities

The development of safe and high-energy metal anodes represents a crucial research direction. Here, the achievement of highly reversible, dendrite-free transition metal anodes with ultrahigh capacities by regulating aqueous electrolytes is reported. Using nickel (Ni) as a model, theoretical and experimental evidence demonstrating the beneficial role of chloride ions in inhibiting and disrupting the nickel hydroxide passivation layer on the Ni electrode is provided. As a result, Ni anodes with an ultrahigh areal capacity of 1000 mAh cm-2 (volumetric capacity of ≈6000 mAh cm-3 ), and a Coulombic efficiency of 99.4% on a carbon substrate, surpassing the state-of-the-art metal electrodes by approximately two orders of magnitude, are realized. Furthermore, as a proof-of-concept, a series of full cells based on the Ni anode is developed. The designed Ni-MnO2 full battery exhibits a long lifespan of 2000 cycles, while the Ni-PbO2 full battery achieves a high areal capacity of 200 mAh cm-2 . The findings of this study are important for enlightening a new arena toward the advancement of dendrite-free Ni-metal anodes with ultrahigh capacities and long cycle life for various energy-storage devices.

Fluorinated porous frameworks enable robust anode-less sodium metal batteries

Sodium metal batteries hold great promise for energy-dense and low-cost energy storage technology but are severely impeded by catastrophic dendrite issue. State-of-the-art strategies including sodiophilic seeding/hosting interphase design manifest great success on dendrite suppression, while neglecting unavoidable interphase-depleted Na+ before plating, which poses excessive Na use, sacrificed output voltage and ultimately reduced energy density. We here demonstrate that elaborate-designed fluorinated porous framework could simultaneously realize superior sodiophilicity yet negligible interphase-consumed Na+ for dendrite-free and durable Na batteries. As elucidated by physicochemical and theoretical characterizations, well-defined fluorinated edges on porous channels are responsible for both high affinities ensuring uniform deposition and low reactivity rendering superior Na+ utilization for plating. Accordingly, synergistic performance enhancement is achieved with stable 400 cycles and superior plateau to sloping capacity ratio in anode-free batteries. Proof-of-concept pouch cells deliver an energy density of 325 Watt-hours per kilogram and robust 300 cycles under anode-less condition, opening an avenue with great extendibility for the practical deployment of metal batteries.

Space-Confined Guest Synthesis to Fabricate Sn-Monodispersed N-Doped Mesoporous Host toward Anode-Free Na Batteries

Severe issues including volume change and dendrite growth on sodium metal anodes hinder the pursuit of applicable high-energy-density sodium metal batteries. Herein, an in situ reaction approach is developed that takes metal-organic frameworks as nano-reactor and pore-former to produce a mesoporous host comprised of nitrogen-doped carbon fibers embedded with monodispersed Sn clusters (SnNCNFs). The hybrid host shows outstanding sodiophilicity that enables rapid Na infusion and ultralow Na nucleation overpotential of 2 mV. Its porous structure holds a high Na content and guides uniform Na deposition. Such host provides favorable Na plating/stripping with an average Coulombic efficiency of 99.96% over 2000 cycles (at 3 mA cm-2 and 3 mA h cm-2 ). The Na-infused SnNCNF anode delivers extreme Na utilization of 86% in symmetric cells (at 10 mA cm-2 and 10 mA h cm-2 ), outstanding rate capability and cycle life in Na-SnNCNF||Na3 V2 (PO4 )3 full cells (at 1 A g-1 for over 1000 cycles with capacity retention of 92.1%). Furthermore, high-energy/power-density anode-less and anode-free Na cells are achieved. This work presents an effective heteroatom-doping approach for fabricating multifunctional porous carbon materials and developing high-performance metal batteries.

Na Storage in Sb2S3@C Composite: A Synergistic Capacity Contribution Mechanism with Wider Temperature Adaptability

The practical applications of metallic anodes are limited due to dendritic growth, propagation in an infinite volume during the plating process, and parasitic interfacial reactions between sodium (Na) and the electrolyte. Herein, we developed Sb₂S₃ microrods as a template to regulate the nucleation of metallic Na. Additionally, the propagation of the deposited metal could be spatially regulated via a "nanoconfinement effect", that is, within the conformal hard carbon (C) layer of nanothickness. Moreover, we carefully studied the seed effect of the in situ-formed Na-Sb and Na-S alloys within the hard C sheath during the Na plating process. The symmetrical cells of the Sb₂S₃@C composite anode achieved dendrite-free cycling at 1 mA cm^-2 for 1100 h at a high capacity loading of 1 mA h cm^-2 and considerably mitigated a nucleation overpotential of 20 mV. Pairing a NaVPO₄F (NVPF) cathode (4.6 mg cm^-2) with an in situ presodiation Sb₂S₃@C composite (2*Na excess) prototype delivered a high energy density and a high power density of 173.75 W h kg^-1 and 868.57 W kg^-1, respectively. Therefore, this study provides tremendous possibilities for employing the proposed hybrid storage mechanism in low-cost and practical applications of high-energy-density Na metal batteries.

Superfast Mass Transport of Na/K Via Mesochannels for Dendrite-Free Metal Batteries

Fast ion diffusion in anode hosts enabling uniform distribution of Li/Na/K is essential for achieving dendrite-free alkali-metal batteries. Common strategies, e.g. expanding the interlayer spacing of anode materials, can enhance bulk diffusion of Li but are less efficient for Na and K due to their larger ionic radius. Herein, a universal strategy to drastically improve the mass-transport efficiency of Na/K by introducing open mesochannels in carbon hosts is proposed. Such pore engineering can increase the accessible surface area by one order of magnitude, thus remarkably accelerating surface diffusion, as visualized by in situ transmission electron microscopy. In particular, once the mesochannels are filled by the Na/K metals, they become the superfast channels for mass transport via the mechanism of interfacial diffusion. Thus-modified carbon hosts enable Na/K filling in their inner cavities and uniform deposition across the whole electrodes with fast kinetics. The resulting Na-metal anodes can exhibit stable dendrite-free cycling with outstanding rate performance at a high current density of up to 30 mA cm^-2 . This work presents an inspiring attempt to address the sluggish transport issue of Na/K, as well as valuable insights into the mass-transport mechanism in porous anodes for high-performance alkali-metal storage.

Anode-free Na metal batteries developed by nearly fully reversible Na plating on the Zn surface

The anode-free battery architecture has recently emerged as a promising platform for lithium and sodium metal batteries as it not only offers the highest possible energy density, but also eliminates the need for handling hazardous metal electrodes during cell manufacturing. However, such batteries usually suffer from much faster capacity decay and are much more sensitive to even trace levels of irreversible side reactions on the anode, especially for the more reactive Na metal. This work systematically investigates electrochemical interfaces for Na plating and stripping and describes the use of the Zn surface to develop nearly fully reversible Na anodes with 1.0 M NaPF₆ in a diglyme-based electrolyte. The high performance includes consistently higher than 99.9% faradaic efficiencies for a wide range of cycling currents between 0.5 and 10 mA cm^-2, much more stable interfacial resistance and nearly no formation of mossy Na after 500 cycles compared with conventional Al and Cu surfaces. This improved reversibility was further confirmed under lean electrolyte conditions with a wide range of electrolyte concentrations and cycling temperatures and can be attributed to the strong interfacial binding and intrinsic sodiophilic properties of the Zn surface with Na, which not only ensured uniform Na plating but also eliminated most side reactions that would otherwise cause electrolyte depletion. As a result, full cells assembled with Na-free Zn foil and a high capacity Na₃V₂(PO₄)₃ cathode delivered ∼90% capacity retention for 100 cycles, higher than the 73% retention of Cu foils and much higher than the 39% retention of Al foils. This work provides new approaches to enable stable cycling of anode-free batteries and contribute to their applications in practical devices.

Catalytic Effects of Electrodes and Electrolytes in Metal-Sulfur Batteries: Progress and Prospective

Metal-sulfur (M-S) batteries are promising energy-storage devices due to their advantages such as large energy density and the low cost of the raw materials. However, M-S batteries suffer from many drawbacks. Endowing the electrodes and electrolytes with the proper catalytic activity is crucial to improve the electrochemical properties of M-S batteries. With regard to the S cathodes, advanced electrode materials with enhanced electrocatalytic effects can capture polysulfides and accelerate electrochemical conversion and, as for the metal anodes, the proper electrode materials can provide active sites for metal deposition to reduce the deposition potential barrier and control the electroplating or stripping process. Moreover, an advanced electrolyte with desirable design can catalyze electrochemical reactions on the cathode and anode in high-performance M-S batteries. In this review, recent progress pertaining to the design of advanced electrode materials and electrolytes with the proper catalytic effects is summarized. The current progress of S cathodes and metal anodes in different types of M-S batteries are discussed and future development directions are described. The objective is to provide a comprehensive review on the current state-of-the-art S cathodes and metal anodes in M-S batteries and research guidance for future development of this important class of batteries.

Challenge and Strategies in Room Temperature Sodium-Sulfur Batteries: A Comparison with Lithium-Sulfur Batteries

Metal-sulfur batteries exhibit great potential as next-generation rechargeable batteries due to the low sulfur cost and high theoretical energy density. Sodium-sulfur (Na-S) batteries present higher feasibility of long-term development than lithium-sulfur (Li-S) batteries in technoeconomic and geopolitical terms. Both lithium and sodium are alkali metal elements with body-centered cubic structures, leading to similar physical and chemical properties and exposing similar issues when employed as the anode in metal-sulfur batteries. Indeed, some inspiration for mechanism researches and strategies in Na-S systems comes from the more mature Li-S systems. However, the dissimilarities in microscopic characteristics determine that Na-S is not a direct Li-S analogue. Herein, the daunting challenges derived by the differences of fundamental characteristics in Na-S and Li-S systems are discussed. And the corresponding strategies in Na-S batteries are reviewed. Finally, general conclusions and perspectives toward the research direction are presented based on the dissimilarities between both systems. This review attempts to provide important insights to facilitate the assimilation of the available knowledge on Li-S systems for accelerating the development of Na-S batteries on the basis of their dissimilarities.

Highly Reversible Sodium Metal Battery Anodes via Alloying Heterointerfaces

As a promising pathway toward low-cost, long-duration energy storage, rechargeable sodium batteries are of increasing interest. Batteries that incorporate metallic sodium as anode promise a high theoretical specific capacity of 1166 mAh g^-1 , and low reduction potential of -2.71 V. The high reactivity and poor electrochemical reversibility of sodium anodes render sodium metal anode (SMA) cells among the most challenging for practical implementation. Here, the failure mechanisms of Na anodes are investigated and the authors report that loss of morphological control is not the fundamental cause of failure. Rather, it is the inherently poor anchoring/root structure of electrodeposited Na to the electrode substrate that leads to poor reversibility and cell failure. Poorly anchored Na deposits are prone to break away from the current collector, producing orphaning and poor anode utilization. Thin metallic coatings in a range of chemistries are proposed and evaluated as SMA substrates. Based on thermodynamic and ion transport considerations, such substrates undergo reversible alloying reactions with Na and are hypothesized to promote good root growth-regardless of the morphology. Among the various options, Au stands out for its ability to support long Na anode lifetime and high reversibility (Coulombic Efficiency > 98%), for coating thicknesses in the range of 10-1000 nm. As a first step toward evaluating practical utility of the anodes, their performance in Na||SPAN cells with N:P ratio close to 1:1 is evaluated.

An Encapsulation-Based Sodium Storage via Zn-Single-Atom Implanted Carbon Nanotubes

The properties of high theoretical capacity, low cost, and large potential of metallic sodium (Na) has strongly promoted the development of rechargeable sodium-based batteries. However, the issues of infinite volume variation, unstable solid electrolyte interphase (SEI), and dendritic sodium causes a rapid decline in performance and notorious safety hazards. Herein, a highly reversible encapsulation-based sodium storage by designing a functional hollow carbon nanotube with Zn single atom sites embedded in the carbon shell (Zn_SA -HCNT) is achieved. The appropriate tube space can encapsulate bulk sodium inside; the inner enriched Zn_SA sites provide abundant sodiophilic sites, which can evidently reduce the nucleation barrier of Na deposition. Moreover, the carbon shell derived from ZIF-8 provides geometric constraints and excellent ion/electron transport channels for the rapid transfer of Na⁺ due to its pore-rich shell, which can be revealed by in situ transmission electron microscopy (TEM). As expected, Na@Zn_SA -HCNT anodes present steady long-term performance in symmetrical battery (>900 h at 10 mA cm^-2 ). Moreover, superior electrochemical performance of Na@Zn_SA -HCNT||PB full cells can be delivered. This work develops a new strategy based on carbon nanotube encapsulation of metallic sodium, which improves the safety and cycling performance of sodium metal anode.

A sodiophilic VN interlayer stabilizing a Na metal anode

Sodium (Na) metal is a very encouraging anode material for next-generation rechargeable batteries owing to its high specific capacity, earth-abundance and low-cost. However, the application of Na metal anodes (SMAs) is hampered by dendrite growth and "dead" Na formation caused by the uncontrollable Na deposition, leading to poor cycle life and even safety concerns. Herein, a high-performance Na anode is designed by introducing an artificial VN interlayer on the Na metal surface (Na/VN) by a simple mechanical rolling process to regulate Na nucleation/deposition behaviors. The density functional theory (DFT) and experiment results uncover that the VN possesses high "sodiophilicity", which can facilitate the initially homogeneous Na nucleation and cause Na to distribute evenly on the VN interlayer. Therefore, uniform Na deposition with dendrite-free morphology and prolonged cycling lifespan (over 1060 h at 0.5 mA cm^-2/1 mA h cm^-2) can be realized. Moreover, the full cell assembled by coupling a Na₃V₂(PO₄)₃ (NVP) cathode and Na/VN anode presents superior cycling performance (e.g., 96% capacity retention even after 800 cycles at 5C). This work provides a promising direction for regulating Na nucleation and deposition to achieve dendrite-free metal anodes.

Atomic Sn-enabled high-utilization, large-capacity, and long-life Na anode

Constructing robust nucleation sites with an ultrafine size in a confined environment is essential toward simultaneously achieving superior utilization, high capacity, and long-term durability in Na metal-based energy storage, yet remains largely unexplored. Here, we report a previously unexplored design of spatially confined atomic Sn in hollow carbon spheres for homogeneous nucleation and dendrite-free growth. The designed architecture maximizes Sn utilization, prevents agglomeration, mitigates volume variation, and allows complete alloying-dealloying with high-affinity Sn as persistent nucleation sites, contrary to conventional spatially exposed large-size ones without dealloying. Thus, conformal deposition is achieved, rendering an exceptional capacity of 16 mAh cm^-2 in half-cells and long cycling over 7000 hours in symmetric cells. Moreover, the well-known paradox is surmounted, delivering record-high Na utilization (e.g., 85%) and large capacity (e.g., 8 mAh cm^-2) while maintaining extraordinary durability over 5000 hours, representing an important breakthrough for stabilizing Na anode.

Synergistic Effect of 3D Flexible Framework with Sodiophilic Mesoporous SnO2 Nanosheet Arrays on Dendrite-Free Sodium Metal Batteries

Although tremendous efforts have been dedicated to promote the electrochemical stability of sodium metal batteries (SMBs), the uncontrollable dendrites growth and inevitable side reactions at the sodium (Na) anode/electrolyte interface have not been effectively resolved. In this work, a flexible and functionalized 3D framework with mesoporous SnO₂ nanosheet arrays (SnO₂@CC-12) is fabricated to serve as a sodiophilic matrix toward dendrite-free Na metal anode. The mesoporous SnO₂ nanosheet arrays provide abundant sodiophilic sites and sufficient internal voids, which can not only accelerate electron transport to reduce the local current density of Na anode surface but also manipulate the Na⁺ flux deposition to suppress the growth of Na dendrites. Therefore, the SnO₂@CC-12-Na symmetric cell exhibits an ultralow overpotential of 9 mV and superior Na plating/stripping stability over 2200 h at 1.0 mA cm^-2. Moreover, the full cells using Na₃V₂(PO₄)₃ cathode show favorable high-rate performance and impressive long cycling stability with 95.1% capacity retention over 1000 cycles at 500 mA g^-1. This work may provide a new insight into the design of functionalized interface layer with high sodiophilicity toward dendrite-free SMBs.

A 3D Hierarchical Host with Enhanced Sodiophilicity Enabling Anode-Free Sodium-Metal Batteries

Sodium-metal batteries (SMBs) are considered as a compliment to lithium-metal batteries for next-generation high-energy batteries because of their low cost and the abundance of sodium (Na). Herein, a 3D nanostructured porous carbon particle containing carbon-shell-coated Fe nanoparticles (PC-CFe) is employed as a highly reversible Na-metal host. PC-CFe has a unique 3D hierarchy based on sub-micrometer-sized carbon particles, ordered open channels, and evenly distributed carbon-coated Fe nanoparticles (CFe) on the surface. PC-CFe achieves high reversibility of Na plating/stripping processes over 500 cycles with a Coulombic efficiency of 99.6% at 10 mA cm^-2 with 10 mAh cm^-2 in Na//Cu asymmetric cells, as well as over 14 400 cycles at 60 mA cm^-2 in Na//Na symmetric cells. Density functional theory calculations reveal that the superior cycling performance of PC-CFe stems from the stronger adsorption of Na on the surface of the CFe, providing initial nucleation sites more favorable to Na deposition. Moreover, the full cell with a PC-CFe host without Na metal and a high-loading Na₃ V₂ (PO₄ )₃ cathode (10 mg cm^-2 ) maintains a high capacity of 103 mAh g^-1 at 1 mA cm^-2 even after 100 cycles, demonstrating the operation of anode-free SMBs.

A Sodium-Antimony-Telluride Intermetallic Allows Sodium-Metal Cycling at 100% Depth of Discharge and as an Anode-Free Metal Battery

Repeated cold rolling and folding is employed to fabricate a metallurgical composite of sodium-antimony-telluride Na₂ (Sb_2/6 Te_3/6 Vac_1/6 ) dispersed in electrochemically active sodium metal, termed "NST-Na." This new intermetallic has a vacancy-rich thermodynamically stable face-centered-cubic structure and enables state-of-the-art electrochemical performance in widely employed carbonate and ether electrolytes. NST-Na achieves 100% depth-of-discharge (DOD) in 1 m NaPF₆ in G2, with 15 mAh cm^-2 at 1 mA cm^-2 and Coulombic efficiency (CE) of 99.4%, for 1000 h of plating/stripping. Sodium-metal batteries (SMBs) with NST-Na and Na₃ V₂ (PO₄ )₃  (NVP) or sulfur cathodes give significantly improved energy, cycling, and CE (>99%). An anode-free battery with NST collector and NVP obtains 0.23% capacity decay per cycle. Imaging and tomography using conventional and cryogenic microscopy (Cryo-EM) indicate that the sodium metal fills the open space inside the self-supporting sodiophilic NST skeleton, resulting in dense (pore-free and solid electrolyte interphase (SEI)-free) metal deposits with flat surfaces. The baseline Na deposit consists of filament-like dendrites and "dead metal", intermixed with pores and SEI. Density functional theory calculations show that the uniqueness of NST lies in the thermodynamic stability of the Na atoms (rather than clusters) on its surface that leads to planar wetting, and in its own stability that prevents decomposition during cycling.

Highly Stable Lithium/Sodium Metal Batteries with High Utilization Enabled by a Holey Two-Dimensional N-Doped TiNb2O7 Host

Lithium/sodium metal batteries have attracted enormous attention as promising candidates for high-energy storage devices. However, their practical applications are impeded by the growth of dendrites upon Li/Na plating. Here, we report that holey 2D N-doped TiNb₂O₇ (N-TNO) nanosheets with high electroactive surface area and large amounts of lithiophilic/sodiophilic sites can effectively regulate Li/Na deposition as an interfacial layer, leading to an excellent cycling stability. The N-TNO interfacial layer enables the Li||Li symmetric cell to sustain stable electrodeposition over 1000 h as well as the Na||Na cell to stably cycle for 2400 h at 1 mA cm^-2 and 3 mA h cm^-2 with a depth of discharge as high as 50%. The full cells of the Li/Na anodes based on the N-TNO layer paired with the LiFePO₄ and NaTi₂(PO₄)₃ cathodes, respectively, show a very stable cycling over 1000 cycles at a negative-to-positive electrode capacity (N/P) ratio up to 3.

Regulating Na deposition by constructing a Au sodiophilic interphase on CNT modified carbon cloth for flexible sodium metal anode

Na metal anode has attracted increasing attentions as the anode of sodium ion batteries (SIBs) due to its high theoretical capacity, low redox potential and high abundance. However, the formation of uncontrollable Na dendrite during repeated plating/stripping cycles hinders its further development and application. Herein, a sodiophilic Na metal anode host is developed by sputtering gold nanoparticles (Au NPs) into interconnected carbon nanotube modified carbon cloth (CNT/CC) to form a Au-CNT/CC architecture. Sodiophilic Au NPs effectively guide the Na metal uniform deposition and three-dimensional (3D) microporous structure offers a large surface area for nucleation and reducing the current densities. The regulated uniform Na metal deposition mechanism is investigated by the in-situ optical microscopy and simulation analysis. As a result, Au-CNT/CC electrode exhibits a low nucleation overpotential (2.2 mV) and stable cycle performance for 1600 h at 1 mA cm^-2 with 2 mAh cm^-2. Moreover, it even exhibits a long cycle stability for more than 800 h at 5 mA cm^-2 with 2 mAh cm^-2. To explore its application, a full cell coupled with a sodium vanadium phosphate coated with carbon layer (NVP@C) cathode is assembled and delivers an average discharge capacity of 80.6 mAh g^-1 and coulombic efficiency of 99.6% for 400 cycles at 100 mAh g^-1. Furthermore, a flexible pouch cell with Na@Au-CNT/CC as the anode is fabricated and demonstrated good flexibility and future application of wearable electronics.

Single Cobalt Atoms Decorated N-doped Carbon Polyhedron Enabled Dendrite-Free Sodium Metal Anode

Uncontrollable growth of sodium dendrites during the sodium deposition and stripping processes remains a huge challenge for achieving high-performance sodium metal batteries (SMBs), which results in ineffective utilization of metallic Na, low Coulombic efficiency, and inferior cycling life. Here, a single Co atom uniformly decorated porous nitrogen-doped carbon polyhedron (Co_SA @NC) matrix has been fabricated and introduced to control the Na growth and achieve uniform Na nucleation/deposition. Cryo-electron microscopy and in situ optical microscopy techniques have been utilized to analyze the morphology change of metallic Na during plating/stripping processes. The single Co atoms evenly embedded in NC electrodes can provide stable Na-philic sites for Na ions adsorption, which is helpful to guide the uniform sodium deposition and prevent Na dendrites growth. This work thus provides an effective solution to inhibit Na dendrite growth and control Na nucleation behavior from the perspective of atomic level, towards the fabrication of high-safety and long-cycling SMBs.

In Situ Constructed Ionic-Electronic Dual-Conducting Scaffold with Reinforced Interface for High-Performance Sodium Metal Anodes

The formation of severe dendritic sodium (Na) microstructure reduces the reversibility of anode and further hinders its practical implementation. In this work, an ionic-electronic dual-conducting (IEDC) scaffold composed of Na₃ P and carbon nanotubes is in situ developed by a scalable strategy with subsequent alloying reaction, for realizing dendrite-free Na deposition under high current density and large areal capacity. The in situ formed Na₃ P with high sodiophilicity not only sets up a hierarchically efficient ionic conducting network, but also participates in the construction of reinforced solid electrolyte interphase, while carbon nanotubes can assemble an electronic conducting framework. As a result, the multifunctional IEDC scaffold contributes to smooth Na plating and exceptionally reversible Na stripping. High average Coulombic efficiency of 99.8% after prolonged 1200 cycles at 3 mA cm^-2 and small overpotential of 20 mV over 250 h (equals to 530 cycles) at high rate of 5 mA cm^-2 are obtained. The high availability of Na in IEDC scaffold enables the impressive performance of full cell with limited Na, using Na₃ V₂ (PO₄ )₃ (NVP) cathode at practical level. More importantly, the as-developed anode-free full cell with IEDC||NVP configuration delivers a high capacity retention with long lifetime, indicating its great potential for practical Na metal batteries.

Smoothing the Sodium-Metal Anode with a Self-Regulating Alloy Interface for High-Energy and Sustainable Sodium-Metal Batteries

Because of the large abundance of sodium (Na) as a source material and the easy fabrication of Na-containing compounds, the sodium (Na) battery is a more environmentally friendly and sustainable technology than the lithium-ion battery (LIB). Na-metal batteries (SMBs) are considered promising to realize a high energy density to overtake the cost effectiveness of LIBs, which is critically important in large-scale applications such as grid energy storage. However, the cycling stability of the Na-metal anode faces significant challenges particularly under high cycling capacities, due to the complex failure models caused by the formation of Na dendrites. Here, a universal surface strategy, based on a self-regulating alloy interface of the current collector, to inhibit the formation of Na dendrites is reported. High-capacity (10 mAh cm^-2 ) Na-metal anodes can achieve stable cycling for over 1000 h with a low overpotential of 35 mV. When paired with a high-capacity Na₃ V₂ (PO₄ )₂ F₃ cathode (7 mAh cm^-2 ), the SMB delivers an unprecedented energy density (calculated based on all the cell components) over 200 Wh kg^-1 with flooded electrolyte, or over 230 Wh kg^-1 with lean electrolyte. The dendrite-free SMB also shows high cycling stability with a capacity retention per cycle over 99.9% and an ultrahigh energy efficiency of 95.8%.

Capacity-Limited Na-M foil Anode: toward Practical Applications of Na Metal Anode

The practical applications of Na metal anodes are severely plagued by unstable Na plating/stripping. Here the fabrication of Na-rich Na-M (M = Au, Sn, and In) alloy anodes is reported as promising alternatives to address this issue. As compared to metallic Na foil anodes, the alloy foils exhibit improved electrolyte/electrode interface and provide abundant sodiophilic sites for efficient Na plating, while the self-evolved porous Na-M structures accommodate volume variation on cycling. Among three alloy foils, the Na-Au system shows the most promising performance. Under practical conditions such as capacity-limited anodes (5 mAh cm^-2 ) and large stripping/plating capacity (1.0 mAh cm^-2 ), the Na_0.9 Au_0.1 anodes demonstrate stable plating/stripping over 350 h. The proof-of-concept full cells assembled with hard carbon or Prussian blue materials and this thin Na_0.9 Au_0.1 anode also have much elongated cycling life than for pristine Na metal anodes. These findings confirm that the rational design of Na-M alloy anodes can be a promising strategy to promote the development of Na metal batteries.

Liquid Alloying Na-K for Sodium Metal Anodes

The prospects of sodium (Na) metal batteries have been fatally plagued by interfacial Na dendrites, mainly affected by preferred nucleation on the metal anode and the steep gradient of Na ions in the electrolyte, leading to limited Coulombic efficiency and short lifespans. Herein, an electrochemically inert potassium-based Na-K alloy demonstrates a liquid alloying diffusion mechanism that enables dendrite-free Na anodes. The extremely small Na fluctuation and flexible Na-K bonds in the liquid alloy phase bring isotropic nucleation of Na upon electroplating/stripping, which is directly observed by in situ optical imaging. Spontaneously, serving as (de)sodiation buffer with faster electron/mass transportation, the liquid inertia also provides attenuated concentration distribution of Na. Significantly, a record capacity retention of approximately 100% is rendered when coupled with Na₃V₂(PO₄)₃ cathodes (ca. 2 mg cm^-2) over 500 cycles at 10C, advancing the possibility of using liquid alloy for stable metal anodes beyond Na storage systems.

Interfacial Protection Engineering of Sodium Nanoparticles toward Dendrite-Free and Long-Life Sodium Metal Battery

The instability of interfacial solid-electrolyte interphase (SEI) layer of metallic sodium (Na) anode during cycles results in the rapid capacity decay of sodium metal batteries (SMBs). Herein, the concept of interfacial protection engineering of Na nanoparticles (Na-NPs) is proposed first to achieve stable, dendrite-free, and long-life SMB. Employing an ion-exchange strategy, conformal Sn-Na alloy-SEI on the interface of Na-NPs is constructed, forming Sn@Na-NPs. The stable alloy-based SEI layer possesses the following three advantages: 1) significantly enhancing the transport dynamics of Na⁺ ions and electrons; 2) enabling the well-distributed deposition of Na⁺ ions to avoid the growth of dendrites; and 3) protecting the Sn@Na-NPs anode from the attack of electrolyte, thereby reducing the parasitic reaction and boosting the Coulombic efficiency of SMBs. Because of these virtues, the symmetric Sn@Na-NPs cell shows an ultralow voltage hysteresis of 0.54 V at 10 mA cm^-2 after 600 h. Paired with the Na₃ V₂ (PO₄ )₂ O₂ F (NaVPF) cathode, the NaVPF-Sn@Na-NPs full cell exhibits an initial discharge capacity of 89.2 mAh g^-1 at 1 C and a high capacity retention of 81.6% after 600 cycles.

Addressing the Low Solubility of a Solid Electrolyte Interphase Stabilizer in an Electrolyte by Composite Battery Anode Design

Metallic sodium (Na) has been regarded as one of the most attractive anodes for Na-based rechargeable batteries due to its high specific capacity, low working potential, and high natural abundance. However, several important issues hinder the practical application of the metallic Na anode, including its high reactivity with electrolytes, uncontrolled dendrite growth, and poor processability. Metal nitrates are common electrolyte additives used to stabilize the solid electrolyte interphase (SEI) on Na anodes, though they typically suffer from poor solubility in electrolyte solvents. To address these issues, a Na/NaNO₃ composite foil electrode was fabricated through a mechanical kneading approach, which featured uniform embedment of NaNO₃ in a metallic Na matrix. During the battery cycling, NaNO₃ was reduced by metallic Na sustainably, which addressed the issue of low solubility of an SEI stabilizer. Due to the supplemental effect of NaNO₃, a stable SEI with NaN_xO_y and Na₃N species was produced, which allowed fast ion transport. As a result, stable electrochemical performance for 600 h was achieved for Na/NaNO₃||Na/NaNO₃ symmetric cells at a current density of 0.5 mA cm^-2 and an areal capacity of 0.5 mAh cm^-2. A Na/NaNO₃||Na₃V₂(PO₄)₂O₂F cell with active metallic Na of ∼5 mAh cm^-2 at the anode showed stable cycling for 180 cycles. In contrast, a Na||Na₃V₂(PO₄)₂O₂F cell only displayed less than 80 cycles under the same conditions. Moreover, the processability of the Na/NaNO₃ composite foil was also significantly improved due to the introduction of NaNO₃, in contrast to the soft and sticky pure metallic Na. Mechanical kneading of soft alkali metals and their corresponding nitrates provides a new strategy for the utilization of anode stabilizers (besides direct addition into electrolytes) to improve their electrochemical performance.

Bi Nanoparticles Embedded in 2D Carbon Nanosheets as an Interfacial Layer for Advanced Sodium Metal Anodes

Sodium metal is regarded as one of the most prospective next-generation anodes material owing to its high theoretical capacity, low redox potential, low cost, and natural abundance. Its most notable problem is the dendrite growth during Na plating/striping, which causes not only the safety concern but also the generation of inactive Na. Here, it is demonstrated that 2D carbon nanosheets embedded by bismuth nanoparticles (NPs) (denoted as Bi⊂CNs) serve as a robust nucleation buffer layer to endow the sodium metal anodes (SMAs) with high Coulombic efficiencies (CEs) and dendrite-free deposition during long-term cycling. The embedded Bi nanoparticles significantly reduce the nucleation barrier through the "sodiophilic" Na-Bi alloy. Meanwhile, the carbon frameworks effectively circumvent the gradual failure of those Na-Bi nucleation sites. As a result, the metallic Na on the Bi⊂CNs nucleation layer is repeatedly plated/stripped for nearly 7700 h (1287 cycles) at 3 mA h cm^-2 with an average CE of 99.92%. Moreover, the Na||Na symmetric cells with the Bi⊂CNs buffer layer are stably plated/stripped for 4000 h at 1 mA cm^-2 and 1 mA h cm^-2 . It is found that the cycling stability is closely related to the Na utilization of SMAs and current rate.

A Carbon Foam with Sodiophilic Surface for Highly Reversible, Ultra-Long Cycle Sodium Metal Anode

Sodium metal anodes combine low redox potential (-2.71 V versus SHE) and high theoretical capacity (1165 mAh g-1), becoming a promising anode material for sodium-ion batteries. Due to the infinite volume change, unstable SEI films, and Na dendrite growth, it is arduous to achieve a long lifespan. Herein, an oxygen-doped carbon foam (OCF) derived from starch is reported. Heteroatom doping can significantly reduce the nucleation resistance of sodium metal; combined with its rich pore structure and large specific surface area, OCF provides abundant nucleation sites to effectively guide the nucleation and subsequent growth of sodium metal, and the nature of this foam can accommodate the deposited sodium. Furthermore, a more uniform, robust, and stable SEI layer is observed on the surface of OCF electrode, so it can maintain ultra-high reversibility and excellent integrity for a long time without dendritic growth. As a result, when the current density is 10 mA cm-2, the electrode can maintain stable 2000 cycles and the coulombic efficiency can reach to 99.83%. Na@OCF||Na3V2(PO4)3 full cell also has extremely high capacity retention of about 97.53% over 150 cycles. These results provide a simple but effective method for achieving the safety and commercialization of sodium metal anode.

Sodiophilically Graded Gold Coating on Carbon Skeletons for Highly Stable Sodium Metal Anodes

Metallic sodium (Na) is an appealing anode material for high-energy Na batteries. However, Na metal suffers from low coulombic efficiencies and severe dendrite growth during plating/stripping cycles, causing short circuits. As an effective strategy to improve the deposition behavior of Na metal, a 3D carbon foam is developed that is sputter-coated with gold nanoparticles (Au/CF), forming a functional gradient through its thickness. The highly porous Au/CF host is proven to have gradually varying sodiophilicity, which in turn facilitates initially preferential Na deposition on the gold-rich, sodiophilic region in a "bottom-up growth" mode, leading to uniform plating over the entire Au/CF host. This finding contrasts with dendrite formation in the pristine CF host, as proven by in situ microscopy. The Na-predeposited Au/CF (Na@Au/CF) composite anode operates steadily for 1000 h at a low overpotential of ≈20 mV at 2 mA cm^-2 in a symmetric cell. When the composite anode is coupled with a Na₃ V₂ (PO₄ )₂ F₃ cathode, the full cell has a high capacity of 102.1 mAh g^-1 after 500 cycles at 2 C. The sodiophilicity gradient design that is explored in this study offers new insight into developing porous Na metal hosts with highly stable plating/stripping performance for next-generation Na batteries.

Core-Shell C@Sb Nanoparticles as a Nucleation Layer for High-Performance Sodium Metal Anodes

Sodium metal anode (SMA) is one of the most favored choices for the next-generation rechargeable battery technologies owing to its low cost and natural abundance. However, the poor reversibility resulted from dendrite growth and formation of unstable solid electrolyte interphase has significantly hindered the practical application of SMAs. Herein, we report that a nucleation buffer layer comprising elaborately designed core-shell C@Sb nanoparticles (NPs) enables the homogeneous electrochemical deposition of sodium metal for long-term cycling. These C@Sb NPs can increase active sites for initial sodium nucleation through Sb-Na alloy cores and keep these cores stable through carbon shells. The assembled cells with this nucleation layer can deliver continuously repeated sodium plating/stripping cycles for nearly 6000 h at a high areal capacity of 4 mA h cm^-2 with an average Coulombic efficiency 99.7%. This ingenious structure design of alloy-based nucleation agent opens up a promising avenue to stabilize sodium metal with targeted properties.

Engineering Sodium-Ion Solvation Structure to Stabilize Sodium Anodes: Universal Strategy for Fast-Charging and Safer Sodium-Ion Batteries

Sodium-ion batteries are promising alternatives for lithium-ion batteries due to their lower cost caused by global sodium availability. However, the low Coulombic efficiency (CE) of the sodium metal plating/stripping process represents a serious issue for the Na anode, which hinders achieving a higher energy density. Herein, we report that the Na⁺ solvation structure, particularly the type and location of the anions, plays a critical role in determining the Na anode performance. We show that the low CE results from anion-mediated corrosion, which can be tackled readily through tuning the anion interaction at the electrolyte/anode interface. Our strategy thus enables fast-charging Na-ion and Na-S batteries with a remarkable cycle life. The presented insights differ from the prevailing interpretation that the failure mechanism mostly results from sodium dendrite growth and/or solid electrolyte interphase formation. Our anionic model introduces a new guideline for improving the electrolytes for metal-ion batteries with a greater energy density.

Tutorial review on structure – dendrite growth relations in metal battery anode supports

This tutorial review explains surface and bulk chemistry – electrochemical performance relations of lithium, sodium and potassium metal anodes.

Combining theories and experiments to understand the sodium nucleation behavior towards safe sodium metal batteries

This review assesses both theoretical and experimental knowledge on sodium nucleation for the first time towards a safe sodium battery.

Investigation of Sodium Plating and Stripping on a Bare Current Collector with Different Electrolytes and Cycling Protocols

In the present study, stable sodium plating/stripping has been achieved on a bare aluminum current collector, without any surface modifications or artificial SEI deposition. The crucial role of predeposited sodium using cyclic voltammetry on bare aluminum as a matrix for plating/stripping has been highlighted using different protocols for cycling. The predeposition strategy ensures stable and efficient cycling of sodium in anode-free sodium batteries without dendritic formations. The study highlights the difference of sodium plating/stripping in carbonate and glyme solvent electrolytes on the bare aluminum current collector. Contrary to the carbonate solvent electrolyte, the cell with the tetraglyme solvent electrolyte and sodium loading of 1 mA h/cm² has an overpotential under 20 mV during the sodium plating/stripping cycles at 0.5 mA/cm² for a testing period of 650 h. Overpotentials under 40 and 100 mV have been achieved at current densities up to 1 and 2 mA/cm² for loadings up to 5 and 10 mA h/cm², respectively, for a testing time up to 1500 h. Density functional theory simulations have been performed to obtain the solvation energies, and the highest occupied molecular orbital-lowest unoccupied molecular orbital band gap of the solvent-sodium ion complexes for the glyme solvent electrolytes and their trends have been correlated with the experimental observations.