3D Wettable Framework for Dendrite‐Free Alkali Metal Anodes

The infinite volume change and dendritic behavior in alkali metal anodes lead to low Coulombic efficiency and short‐circuit issues that significantly hamper renewed efforts at commercialization. Here, a dendrite‐free alkali metal anode, made by thermally preloading molten Li or Na into a 3D framework with high alkali wettability, is reported. In the mechanically robust 3D framework, carbon fiber (CF) serves as an electrical highway that provides fast charge transfer for the redox reaction. Through a facile solution‐based process, a SnO₂ coating is introduced to modify the poor wetting behavior of the carbon framework and drastically improve both the electrochemical performance and reliability. The kinetic barrier to adhesion of molten alkali metals on the CF framework is eliminated by the mixed reaction with SnO₂. The growth of dendrites is effectively repressed under the decreased local current density of the 3D framework. In full‐cell configurations with LiFePO₄ cathodes, the Li–CF electrode shows reduced polarization and 90% capacity retention after 500 cycles in traditional carbonate electrolyte. Comparable improvements are also observed in 3D electrodes for Na metal batteries. These findings on a stable 3D carbon framework with improved wetting behavior provide significant practical implications for achieving safe and commercially viable alkali metal anodes.     

Air‐Stable and Dendrite‐Free Lithium Metal Anodes Enabled by a Hybrid Interphase of C60 and Mg

Li metal is an ideal anode material for rechargeable high energy density batteries, but its sensitivity to humid air and uncontrolled dendrite growth limit its practical applications. A novel hybrid interphase is fabricated to address these issues. This interphase consists of dense fullerene (C₆₀) and magnesium metal bilayers, which are deposited successively on lithium foil by vacuum evaporation deposition and contribute to moisture resistance and lithium dendrite suppression. Thanks to this dual‐functional feature, the assembled cells with the modified anodes and commercial LiFePO₄ cathodes exhibit long cycle life (>200 cycles) with high capacity retention (>98.5%). Moreover, even the modified anodes that are exposed to humid air (30% relative humidity) for over 12 h; the cells still deliver excellent performance, comparable to those without exposure. Such a unique hybrid interphase provides a new promising method for fabricating air‐stable and dendrite‐free lithium metal batteries.     

S‐Doped Graphene‐Regional Nucleation Mechanism for Dendrite‐Free Lithium Metal Anodes

Lithium metal is the most promising anode material for next‐generation batteries, owing to its high theoretical specific capacity and low electrochemical potential. However, the practical application of lithium metal batteries (LMBs) has been plagued by the issues of uncontrollable lithium deposition. The multifunctional nanostructured anode can modulate the initial nucleation process of lithium before the extension of dendrites. By combing the theoretical design and experimental validation, a novel nucleation strategy is developed by introducing sulfur (S) to graphene. Through first‐principles simulations, it is found that S atom doping can improve the Li adsorption ability on a large area around the S doping positions. Consequently, S‐doped graphene with five lithiophilic sites rather than a single atomic site can serve as the pristine nucleation area, reducing the uneven Li deposition and improving the electrochemical performance. Modifying Li metal anodes by S‐doped graphene enables an ultralow overpotential of 5.5 mV, a high average Coulombic efficiency of 99% over more than 180 cycles at a current density of 0.5 mA cm^?2 for 1.0 mAh cm^?2, and a high areal capacity of 3 mAh cm^?2. This work sheds new light on the rational design of nucleation area materials for dendrite‐free LMB.     

Graphitic Carbon Nitride Induced Micro‐Electric Field for Dendrite‐Free Lithium Metal Anodes

Uncontrolled dendrites resulting from nonuniform lithium (Li) nucleation/growth and Li volume expansion during charging cause serious safety problems for Li anode‐based batteries. Here the coating of nickel foam with graphitic carbon nitride (g‐C₃N₄) to have a 3D current collector (g‐C₃N₄@Ni foam) for dendrite‐free Li metal anodes is reported. The lithiophilic g‐C₃N₄ coupled with the 3D framework is demonstrated to be highly effective for promoting the uniform deposition of Li and suppressing the formation of dendrites. Both density functional theory calculations and experimental studies indicate the formation of a micro‐electric field resulting from the tri‐s‐triazine units of g‐C₃N₄, which induces numerous Li nuclei during the initial nucleation stage, effectively guiding the following Li growth on the 3D Ni foam to be well distributed. Furthermore, the 3D porous framework is favorable for absorbing any volume change and stabilizing the solid–electrolyte interphase layer during repeated Li plating/stripping. As such, a Li metal anode based on the g‐C₃N₄@Ni foam has a remarkable electrochemical performance with a high Coulombic efficiency (98% retention after 300 cycles), an ultralong lifespan up to 900 h, as well as a low overpotential (<15 mV at 1.0 mA cm^?2) at a Li deposition of 9.0 mA h cm^?2.     

Uniform Lithium Deposition Assisted by Single‐Atom Doping toward High‐Performance Lithium Metal Anodes

For a long time lithium (Li) metal has been considered one of the most promising anodes for next‐generation rechargeable batteries. Despite decades of concentrated research, its practical application is still hindered by dendritic Li deposition and infinite volume change of Li metal anodes. Here, atomically dispersed metals doped graphene is synthesized to regulate Li metal nucleation and guide Li metal deposition. The single‐atom (SA) metals, supported on the nitrogen‐doped graphene can not only increase the Li adsorption energy of the localized area around the metal atomic sites with a moderate adsorption energy gradient but also improve the atomic structural stability of the overall materials by constructing a coordination mode of M‐N_x‐C (M, N, and C denoted as metal, nitrogen, and carbon atoms, respectively). As a result, the as‐obtained electrode exhibits an ultralow voltage hysteresis of 19 mV, a high average Coulombic efficiency of 98.45% over 250 cycles, and a stable Li plating/stripping performance even at a high current density of 4.0 mA cm^?2. This work demonstrates the application of SA metal doping in the rational design of Li metal anodes and provides a new concept for further development of Li metal batteries.     

Mixed Ion and Electron‐Conducting Scaffolds for High‐Rate Lithium Metal Anodes

Li metal batteries are considered a promising candidate for next‐generation rechargeable batteries. However, the practical application of Li metal batteries has been hindered by many challenges, especially the cycling stability of Li anodes due to their uncontrollable dendrite growth, volume fluctuation, and side reactions. These problems are more severe under high‐rate charge/discharge process. Therefore, the realization of stable cycling of Li anodes under high current density is crucial for the practical application of Li metal batteries. In this Progress Report, the authors focus on the stability of metallic Li through interphase design or microstructure construction. The advantages and drawbacks of the first‐generation 3D scaffolds are summarized, and a review of recent research progress in this area is generated. As high‐rate cycling of metallic Li is a complex dynamic problem, a scaffold with high mixed ionic and electronic conductivity may be a promising approach. The different design strategies of mixed ion and electron‐conductive scaffolds working with liquid and solid electrolytes are discussed, along with their technical challenges. Further directions of mixed ion and electron‐conductive scaffolds are also proposed.     

Marginal Magnesium Doping for High‐Performance Lithium Metal Batteries

Due to unparalleled theoretical capacity and operation voltage, metallic Li is considered as the most attractive candidate for lithium‐ion battery anodes. However, Li metal electrodes suffer from uncontrolled dendrite growth and consequent interfacial instability, which result in an unacceptable level of performance in cycling stability and safety. Herein, it is reported that a marginal amount (1.5 at%) of magnesium (Mg) doping alters the surface properties of Li metal foil drastically in such a way that upon Li plating, a highly dense Li whisker layer is induced, instead of sharp dendrites, with enhanced interfacial stability and cycling performance. The effect of Mg doping is explained in terms of increased surface energy, which facilitates plating of Li onto the main surface over the existing whiskers. The present study offers a useful guideline for Li metal batteries, as it largely resolves the longstanding shortcoming of Li metal electrodes without significantly sacrificing their main advantages.     

3D TiC/C Core/Shell Nanowire Skeleton for Dendrite‐Free and Long‐Life Lithium Metal Anode

Construction of stable dendrite‐free Li metal anode is crucial for the development of advanced Li–S and Li–air batteries. Herein, self‐supported TiC/C core/shell nanowire arrays as skeletons and confined hosts of molten Li forming integrated trilayer TiC/C/Li anode are described. The TiC/C core/shell nanowires with diameters of 400–500 nm exhibit merits of good lithiophilicity, high electrical conductivity, and abundant porosity. The as‐prepared TiC/C/Li anode exhibits prominent electrochemical performance with a small hysteresis of less than 85 mV beyond 200 cycles (3.0 mA cm^?2) as well as a very high Coulombic efficiency up to 98.5% for 100 cycles at 1.0 mA cm^?2. When the structured anode is coupled with lithium iron phosphate or sulfur cathode, the assembled full cells with trilayer TiC/C/Li anodes display enhanced capability retention and improved Coulombic efficiency. This is ascribed to the unique TiC/C matrix, which can not only provide interspace for accommodating “hostless” Li, but also afford interconnected rapid transfer paths for electrons and ions with low local current densities, leading to effective inhabitation growth of Li dendrites and lower interfacial resistance. A fresh way for construction of advanced stable Li metal anodes is provided in this work.     

Stable Nano‐Encapsulation of Lithium Through Seed‐Free Selective Deposition for High‐Performance Li Battery Anodes

Metallic lithium has long been deemed as the ultimate anode material for future high‐energy‐density Li batteries. However, the commercialization of Li metal anodes remains hindered by some major hurdles including their huge volume fluctuation during cycling, unstable solid electrolyte interface (SEI), and dendritic deposition. Herein, the concept of nano‐encapsulating electrode materials is attempted to tackle these problems. Nitrogen‐doped hollow porous carbon spheres (N‐HPCSs), prepared via a facile and low‐cost method, serve as the nanocapsules. Each N‐HPCS has a lithophilic carbon shell with a thin N‐rich denser layer on its inner surface, which enables preferential nucleation of Li inside the hollow sphere. It is demonstrated by in situ electron microscopy that these N‐HPCS hosts allow Li to be encapsulated in a highly reversible and repeatable manner. Ultralong Li filling/stripping cycling inside single N‐HPCSs is achieved, up to 50 cycles for the first time. Li ion transport across multiple connected N‐HPCSs, leading to long‐range Li deposition inside their cavities, is visualized. In comparison, other types of carbon spheres with modified shell structures fail in encapsulating Li and dendrite suppression. The necessity of the specific shell design is therefore confirmed for stable Li encapsulation, which is essential for the N‐HPCS‐based anodes to achieve superior cycling performance.     

Viscoelastic and Nonflammable Interface Design–Enabled Dendrite‐Free and Safe Solid Lithium Metal Batteries

Herein, a composite polymer electrolyte with a viscoelastic and nonflammable interface is designed to handle the contact issue and preclude Li dendrite formation. The composite polymer electrolyte (cellulose acetate/polyethylene glycol/Li_1.4Al_0.4Ti_1.6P₃O₁₂) exhibits a wide electrochemical window of 5 V (vs Li⁺/Li), a high Li⁺ transference number of 0.61, and an excellent ionic conductivity of above 10^?4 S cm^?1 at 60 °C. In particular, the intimate contact, low interfacial impedance, and fast ion‐transport process between the electrodes and solid electrolytes can be simultaneously achieved by the viscoelastic and nonflammable layer. Benefiting from this novel design, solid lithium metal batteries with either LiFePO₄ or LiCoO₂ as cathode exhibit superior cyclability and rate capability, such as a discharge capacity of 157 mA h g^?1 after 100 cycles at C/2 and 97 mA h g^?1 at 5C for LiFePO₄ cathode. Moreover, the smooth and uniform Li surface after long‐term cycling confirms the successful suppression of dendrite formation. The viscoelastic and nonflammable interface modification of solid electrolytes provides a promising and general strategy to handle the interfacial issues and improves the operative safety of solid lithium metal batteries.     

An Interconnected Channel‐Like Framework as Host for Lithium Metal Composite Anodes

Lithium (Li) metal anodes have long been counted on to meet the increasing demand for high energy, high‐power rechargeable battery systems but they have been plagued by uncontrollable plating, unstable solid electrolyte interphase (SEI) formation, and the resulting low Coulombic efficiency. These problems are even aggravated under commercial levels of current density and areal capacity testing conditions. In this work, the channel‐like structure of a carbonized eggplant (EP) as a stable “host” for Li metal melt infusion, is utilized. With further interphase modification of lithium fluoride (LiF), the as‐formed EP–LiF composite anode maintains ≈90% Li metal theoretical capacity and can successfully suppress dendrite growth and volume fluctuation during cycling. EP–LiF offers much improved symmetric cell and full‐cell cycling performance with lower and more stable overpotential under various areal capacity and elevated rate capability. Furthermore, carbonized EP serves as a light‐weight high‐performance current collector, achieving an average Coulombic efficiency ≈99.1% in ether‐based electrolytes with 2.2 mAh cm^?2 cycling areal capacity. The natural structure of carbonized EP will inspire further artificial designs of electrode frameworks for both Li anode and sulfur cathodes, enabling promising candidates for next‐generation high‐energy density batteries.     

Nanoporous Hybrid Electrolytes for High‐Energy Batteries Based on Reactive Metal Anodes

Successful strategies for stabilizing electrodeposition of reactive metals, including lithium, sodium, and aluminum are a requirement for safe, high‐energy electrochemical storage technologies that utilize these metals as anodes. Unstable deposition produces high‐surface area dendritic structures at the anode/electrolyte interface, which causes premature cell failure by complex physical and chemical processes that have presented formidable barriers to progress. Here, it is reported that hybrid electrolytes created by infusing conventional liquid electrolytes into nanoporous membranes provide exceptional ability to stabilize Li. Electrochemical cells based on γ‐Al₂O₃ ceramics with pore diameters below a cut‐off value above 200 nm exhibit long‐term stability even at a current density of 3 mA cm^?2. The effect is not limited to ceramics; similar large enhancements in stability are observed for polypropylene membranes with less monodisperse pores below 450 nm. These findings are critically assessed using theories for ion rectification and electrodeposition reactions in porous solids and show that the source of stable electrodeposition in nanoporous electrolytes is fundamental.     

Multifunctional Silanization Interface for High‐Energy and Low‐Gassing Lithium Metal Pouch Cells

Lithium (Li) metal has attracted unprecedented attention as the ultimate anode material for future rechargeable batteries, but the electrochemical behavior (such as Li dendrites and gassing problems) in real Li metal pouch cells has received little attention. To achieve realistic high‐energy Li metal batteries, the designed solid electrolyte interface to suppress both Li dendrites and catastrophic gassing problems is urgently needed at cell level. Here, an efficient multifunctional silanization interface (MSI) is proposed for high‐energy Li metal pouch cells. Such an MSI not only guides uniform nucleation and growth of Li metal but also suppresses interfacial parasitic reactions between Li metal and electrolyte. As a result, under harsh conditions (negative to positive electrode capacity ratio of 2.96 and electrolyte weight to cathode capacity ratio of 2.7 g Ah^?1), a long‐running lifespan (over 160 cycles with a capacity retention of 96% at 1 C), and low‐gassing behavior of realistic high‐energy Li metal pouch cell (1 Ah, 300 Wh kg^?1) is achieved. This work opens a promising avenue toward the commercial applications of high‐energy Li metal batteries.     

Synergistic Effect of 3D Current Collectors and ALD Surface Modification for High Coulombic Efficiency Lithium Metal Anodes

Improving the performance of Li metal anodes is a critical bottleneck to enable next‐generation battery systems beyond Li‐ion. However, stability issues originating from undesirable electrode/electrolyte interactions and Li dendrite formation have impaired long‐term cycling of Li metal anodes. Herein, a bottom‐up fabrication process is demonstrated for a current collector for Li metal electrodeposition and dissolution composed of highly uniform vertically aligned Cu pillars. By rationally controlling geometric parameters of the 3D current collector architecture, including pillar diameter, spacing, and length, the morphology of Li plating/stripping upon cycling can be controlled and optimal cycling performance can be achieved. In addition, it is demonstrated that deposition of an ultrathin layer of ZnO by atomic layer deposition on the current collector surface can facilitate the initial Li nucleation, which dictates the morphology and reversibility of subsequent cycling. This core–shell pillar architecture allows for the effects of geometry and surface chemistry to be decoupled and individually controlled to optimize the electrode performance in a synergistic manner. Using this platform, Li metal anodes are demonstrated with Coulombic efficiency up to 99.5%, providing a pathway toward high‐efficiency and long‐cycle life Li metal batteries with reduced excess Li loading.     

A Composite Gel Polymer Electrolyte with High Performance Based on Poly(Vinylidene Fluoride) and Polyborate for Lithium Ion Batteries

A composite membrane based on electrospun poly(vinylidene fluoride) (PVDF) and lithium polyvinyl alcohol oxalate borate (LiPVAOB) exhibiting high safety (self‐extinguishing) and good mechanical property is prepared. The ionic conductivity of the as‐prepared gel polymer electrolyte from this composite membrane saturated with 1 mol L^?1 LiPF₆ electrolyte at ambient temperature can be up to 0.26 mS cm^?1, higher than that of the corresponding well‐used commercial separator (Celgard 2730), 0.21 mS cm^?1. Moreover, the lithium ion transference in the gel polymer electrolyte at room temperature is 0.58, twice as that in the commercial separator (0.27). Furthermore, the absorbed electrolyte solvent is difficult to evaporate at elevated temperature. Its electrochemical performance is evaluated by using LiFePO₄ cathode. The obtained results suggest that this gel‐type composite membrane shows great possibilities for use in large‐capacity lithium ion batteries that require high safety.