Dual‐Phase Single‐Ion Pathway Interfaces for Robust Lithium Metal in Working Batteries

The lithium (Li) metal anode is confronted by severe interfacial issues that strongly hinder its practical deployment. The unstable interfaces directly induce unfavorable low cycling efficiency, dendritic Li deposition, and even strong safety concerns. An advanced artificial protective layer with single‐ion pathways holds great promise for enabling a spatially homogeneous ionic and electric field distribution over Li metal surface, therefore well protecting the Li metal anode during long‐term working conditions. Herein, a robust dual‐phase artificial interface is constructed, where not only the single‐ion‐conducting nature, but also high mechanical rigidity and considerable deformability can be fulfilled simultaneously by the rational integration of a garnet Al‐doped Li_6.75La₃Zr_1.75Ta_0.25O₁₂‐based bottom layer and a lithiated Nafion top layer. The as‐constructed artificial solid electrolyte interphase is demonstrated to significantly stabilize the repeated cell charging/discharging process via regulating a facile Li‐ion transport and a compact Li plating behavior, hence contributing to a higher coulombic efficiency and a considerably enhanced cyclability of lithium metal batteries. This work highlights the significance of rational manipulation of the interfacial properties of a working Li metal anode and affords fresh insights into achieving dendrite‐free Li deposition behavior in a working battery.     

A 3D and Stable Lithium Anode for High‐Performance Lithium–Iodine Batteries

Lithium metal is considered as the most promising anode material due to its high theoretical specific capacity and the low electrochemical reduction potential. However, severe dendrite problems have to be addressed for fabricating stable and rechargeable batteries (e.g., lithium–iodine batteries). To fabricate a high‐performance lithium–iodine (Li–I₂) battery, a 3D stable lithium metal anode is prepared by loading of molten lithium on carbon cloth doped with nitrogen and phosphorous. Experimental observations and theoretical calculation reveal that the N,P codoping greatly improves the lithiophilicity of the carbon cloth, which not only enables the uniform loading of molten lithium but also facilitates reversible lithium stripping and plating. Dendrites formation can thus be significantly suppressed at a 3D lithium electrode, leading to stable voltage profiles over 600 h at a current density of 3 mA cm^?2. A fuel cell with such an electrode and a lithium–iodine cathode shows impressive long‐term stability with a capacity retention of around 100% over 4000 cycles and enhanced high‐rate capability. These results demonstrate the promising applications of 3D stable lithium metal anodes in next‐generation rechargeable batteries.     

The Interaction in Electrolyte Additives Accelerates Ion Transport to Achieve High-Energy Non-Aqueous Lithium Metal Batteries

Electrolyte engineering is a feasible strategy to realize high energy density lithium metal batteries. However, stabilizing both lithium metal anodes and nickel-rich layered cathodes is extremely challenging. To break through this bottleneck, a dual-additives electrolyte containing fluoroethylene carbonate (10 vol.%) and 1-methoxy-2-propylamine (1 vol.%) in conventional LiPF₆-containing carbonate-based electrolyte is reported. The two additives can polymerize and thus generate dense and uniform LiF and Li₃N-containing interphases on both electrodes’ surfaces. Such robust ionic conductive interphases not only prevent lithium dendrite formation in lithium metal anode but also suppress stress-corrosion cracking and phase transformation in nickel-rich layered cathode. The advanced electrolyte enables Li||LiNi_0.8Co_0.1Mn_0.1O₂ stably cycle for 80 cycles at 60 mA g⁻¹ with a specific discharge capacity retention of 91.2% under harsh conditions.     

Lithiophilic Cu‐CuO‐Ni Hybrid Structure: Advanced Current Collectors Toward Stable Lithium Metal Anodes

Metallic lithium (Li) is a promising anode material for next‐generation rechargeable batteries. However, the dendrite growth of Li and repeated formation of solid electrolyte interface during Li plating and stripping result in low Coulombic efficiency, internal short circuits, and capacity decay, hampering its practical application. In the development of stable Li metal anode, the current collector is recognized as a critical component to regulate Li plating. In this work, a lithiophilic Cu‐CuO‐Ni hybrid structure is synthesized as a current collector for Li metal anodes. The low overpotential of CuO for Li nucleation and the uniform Li⁺ ion flux induced by the formation of Cu nanowire arrays enable effective suppression of the growth of Li dendrites. Moreover, the surface Cu layer can act as a protective layer to enhance structural durability of the hybrid structure in long‐term running. As a result, the Cu‐CuO‐Ni hybrid structure achieves a Coulombic efficiency above 95% for more than 250 cycles at a current density of 1 mA cm^?2 and 580 h (290 cycles) stable repeated Li plating and stripping in a symmetric cell.     

A Natural Biopolymer Film as a Robust Protective Layer to Effectively Stabilize Lithium‐Metal Anodes

Li metal is considered as an ideal anode for Li‐based batteries. Unfortunately, the growth of Li dendrites during cycling leads to an unstable interface, a low coulombic efficiency, and a limited cycling life. Here, a novel approach is proposed to protect the Li‐metal anode by using a uniform agarose film. This natural biopolymer film exhibits a high ionic conductivity, high elasticity, and chemical stability. These properties enable a fast Li‐ion transfer and feasiblity to accomodate the volume change of Li metal, resulting in a dendrite‐free anode and a stable interface. Morphology characterization shows that Li ions migrate through the agarose film and then deposit underneath it. A full cell with the cathode of LiFPO₄ and an anode contaning the agarose film exhibits a capacity retention of 87.1% after 500 cycles, much better than that with Li foil anode (70.9%) and Li‐deposited Cu anode (5%). This study provides a promising strategy to eliminate dendrites and enhance the cycling ability of lithium‐metal batteries through coating a robust artificial film of natural biopolymer on lithium‐metal anode.     

In Situ Construction of Stable Tissue‐Directed/Reinforced Bifunctional Separator/Protection Film on Lithium Anode for Lithium–Oxygen Batteries

To achieve a high reversibility and long cycle life for Li–O₂ battery system, the stable tissue‐directed/reinforced bifunctional separator/protection film (TBF) is in situ fabricated on the surface of metallic lithium anode. It is shown that a Li–O₂ cell composed of the TBF‐modified lithium anodes exhibits an excellent anodic reversibility (300 cycles) and effectively improved cathodic long lifetime (106 cycles). The improvement is attributed to the ability of the TBF, which has chemical, electrochemical, and mechanical stability, to effectively prevent direct contact between the surface of the lithium anode and the highly reactive reduced oxygen species (Li₂O₂ or its intermediate LiO₂) in cell. It is believed that the protection strategy describes here can be easily extended to other next‐generation high energy density batteries using metal as anode including Li–S and Na–O₂ batteries.     

All‐Solid‐State Batteries with a Limited Lithium Metal Anode at Room Temperature using a Garnet‐Based Electrolyte

Metallic lithium (Li), considered as the ultimate anode, is expected to promise high‐energy rechargeable batteries. However, owing to the continuous Li consumption during the repeated Li plating/stripping cycling, excess amount of the Li metal anode is commonly utilized in lithium‐metal batteries (LMBs), leading to reduced energy density and increased cost. Here, an all‐solid‐state lithium‐metal battery (ASSLMB) based on a garnet‐oxide solid electrolyte with an ultralow negative/positive electrode capacity ratio (N/P ratio) is reported. Compared with the counterpart using a liquid electrolyte at the same low N/P ratios, ASSLMBs show longer cycling life, which is attributed to the higher Coulombic efficiency maintained during cycling. The effect of the species of the interface layer on the cycling performance of ASSLMBs with low N/P ratio is also studied. Importantly, it is demonstrated that the ASSLMB using a limited Li metal anode paired with a LiFePO₄ cathode (5.9 N/P ratio) delivers a stable long‐term cycling performance at room temperature. Furthermore, it is revealed that enhanced specific energies for ASSLMBs with low N/P ratios can be further achieved by the use of a high‐voltage or high mass‐loading cathode. This study sheds light on the practical high‐energy all‐solid‐state batteries under the constrained condition of a limited Li metal anode.     

Stable Li Metal Anodes via Regulating Lithium Plating/Stripping in Vertically Aligned Microchannels

Li anodes have been rapidly developed in recent years owing to the rising demand for higher‐energy‐density batteries. However, the safety issues induced by dendrites hinder the practical applications of Li anodes. Here, Li metal anodes stabilized by regulating lithium plating/stripping in vertically aligned microchannels are reported. The current density distribution and morphology evolution of the Li deposits on porous Cu current collectors are systematically analyzed. Based on simulations in COMSOL Multiphysics, the tip effect leads to preferential deposition on the microchannel walls, thus taking full advantage of the lightening rod theory of classical electromagnetism for restraining growth of Li dendrites. The Li anode with a porous Cu current collector achieves an enhanced cycle stability and a higher average Coulombic efficiency of 98.5% within 200 cycles. In addition, the resultant LiFePO₄/Li full battery demonstrates excellent rate capability and stable cycling performance, thus demonstrating promise as a current collector for high‐energy‐density, safe rechargeable Li batteries.     

A 3D Lithiophilic Mo2N‐Modified Carbon Nanofiber Architecture for Dendrite‐Free Lithium‐Metal Anodes in a Full Cell

The pursuit for high‐energy‐density batteries has inspired the resurgence of metallic lithium (Li) as a promising anode, yet its practical viability is restricted by the uncontrollable Li dendrite growth and huge volume changes during repeated cycling. Herein, a new 3D framework configured with Mo₂N‐mofidied carbon nanofiber (CNF) architecture is established as a Li host via a facile fabrication method. The lithiophilic Mo₂N acts as a homogeneously pre‐planted seed with ultralow Li nucleation overpotential, thus spatially guiding a uniform Li nucleation and deposition in the matrix. The conductive CNF skeleton effectively homogenizes the current distribution and Li‐ion flux, further suppressing Li‐dendrite formation. As a result, the 3D hybrid Mo₂N@CNF structure facilitates a dendrite‐free morphology with greatly alleviated volume expansion, delivering a significantly improved Coulombic efficiency of ≈99.2% over 150 cycles at 4 mA cm^?2. Symmetric cells with Mo₂N@CNF substrates stably operate over 1500 h at 6 mA cm^?2 for 6 mA h cm^?2. Furthermore, full cells paired with LiNi_0.8Co_0.1Mn_0.1O₂ (NMC811) cathodes in conventional carbonate electrolytes achieve a remarkable capacity retention of 90% over 150 cycles. This work sheds new light on the facile design of 3D lithiophilic hosts for dendrite‐free lithium‐metal anodes.     

High Performance Low-Temperature Lithium Metal Batteries Enabled by Tailored Electrolyte Solvation Structure

The electrochemical performances of lithium metal batteries are determined by the kinetics of interfacial de-solvation and ion transport, especially at low-temperature environments. Here, a novel electrolyte that easily de-solvated and conducive to interfacial film formation is designed for low-temperature lithium metal batteries. A fluorinated carboxylic ester, diethyl fluoromalonate (DEFM), and a fluorinated carbonate, fluoroethylene carbonate (FEC) are used as solvents, while high concentrated lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is served as the solute. Through tailoring the electrolyte formulation, the lithium ions in the high concentrated fluorinated carboxylic ester electrolyte are mainly combined with anions, which weakens the bonding strength of lithium ions and solvent molecules in the solvation structure, beneficial to the de-solvation process at low temperature. The fluorinated carboxylic ester (FCE) electrolyte enables the LiFePO₄ (LFP) | Li half-cell achieves a high capacity of 91.9 mAh g⁻¹ at −30 °C, with high F content in the interface. With optimized de-solvation kinetics, the LFP | Li full cell remains over 100 mAh g⁻¹ at 0 °C after cycling 100 cycles. Building new solvents with outstanding low-temperature properties and weaker solvation to match with Li metal anode, this work brings new possibilities of realizing high energy density and low temperature energy storage batteries.     

Horizontal Growth of Lithium on Parallelly Aligned MXene Layers towards Dendrite‐Free Metallic Lithium Anodes

Although metallic lithium is an extremely promising anode for lithium‐based batteries due to its high theoretical capacity, the uncontrollable growth of lithium dendrites, in particular under deep stripping and plating, have stagnated its application. It is demonstrated that parallelly aligned MXene (Ti₃C₂T_x ) layers enable the efficient guiding of lithium nucleation and growth on the surface of 2D MXene nanosheets, giving rise to horizontal‐growth lithium anodes. Moreover, the inherent fluorine terminations in MXene afford a uniform and durable solid electrolyte interface with lithium fluoride at the anode/electrolyte interface, efficiently regulating electromigration of lithium ions. Thus, a dendrite‐free lithium anode with a long cycle life up to 900 h and excellent deep stripping–plating capabilities up to 35 mAh cm^?2 is achieved, which can further serve as an anode for a lithium metal battery, exhibiting high cycle stability up to 1000 cycles.     

High‐Voltage Lithium‐Metal Batteries Enabled by Localized High‐Concentration Electrolytes

Rechargeable lithium‐metal batteries (LMBs) are regarded as the “holy grail” of energy‐storage systems, but the electrolytes that are highly stable with both a lithium‐metal anode and high‐voltage cathodes still remain a great challenge. Here a novel “localized high‐concentration electrolyte” (HCE; 1.2 m lithium bis(fluorosulfonyl)imide in a mixture of dimethyl carbonate/bis(2,2,2‐trifluoroethyl) ether (1:2 by mol)) is reported that enables dendrite‐free cycling of lithium‐metal anodes with high Coulombic efficiency (99.5%) and excellent capacity retention (>80% after 700 cycles) of Li||LiNi_1/3Mn_1/3Co_1/3O₂ batteries. Unlike the HCEs reported before, the electrolyte reported in this work exhibits low concentration, low cost, low viscosity, improved conductivity, and good wettability that make LMBs closer to practical applications. The fundamental concept of “localized HCEs” developed in this work can also be applied to other battery systems, sensors, supercapacitors, and other electrochemical systems.     

Additive‐Assisted Novel Dual‐Salt Electrolyte Addresses Wide Temperature Operation of Lithium–Metal Batteries

In this study, self‐synthesized lithium trifluoro(perfluoro‐tert‐butyloxyl)borate (LiTFPFB) is combined with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to formulate a novel 1 m dual‐salt electrolyte, which contains lithium difluorophosphate (LiPO₂F₂) additive and dominant carbonate solvents with low melting point and high boiling point. The addition of LiPO₂F₂ into this novel dual‐salt electrolyte dramatically improves cycleability and rate capability of a LiNi_0.5Mn_0.3Co_0.2O₂/Li (NMC/Li) battery, ranging from ?40 to 90 °C. The NMC/Li batteries adopt a Li–metal anode with low thickness of 100 µm (even 50 µm) and a moderately high cathode mass loading level of 10 mg cm^?2. For the first time, this paper provides valuable perspectives for developing practical lithium–metal batteries over a wide temperature range.     

A Scalable Approach to Dendrite‐Free Lithium Anodes via Spontaneous Reduction of Spray‐Coated Graphene Oxide Layers

Li‐metal batteries (LiMBs) are experiencing a renaissance; however, achieving scalable production of dendrite‐free Li anodes for practical application is still a formidable challenge. Herein, a facile and universal method is developed to directly reduce graphene oxide (GO) using alkali metals (e.g., Li, Na, and K) in moderate conditions. Based on this innovation, a spontaneously reduced graphene coating can be designed and modulated on a Li surface (SR‐G‐Li). The symmetrical SR‐G‐Li|SR‐G‐Li cell can run up to 1000 cycles at a high practical current density of 5 mA cm^?2 without a short circuit, demonstrating one of the longest lifespans reported with LiPF₆‐based carbonate electrolytes. More significantly, a practically scalable paradigm is established to fabricate dendrite‐free Li anodes by spraying a GO layer on the Li anode surface for large‐scale production of LiFePO₄/Li pouch cells, reflected by the continuous manufacturing of the SR‐G‐Li anodes based on the roll‐to‐roll technology. The strategy provides new commercial opportunities to both LiMBs and graphene.     

A Stable Solid Electrolyte Interphase for Magnesium Metal Anode Evolved from a Bulky Anion Lithium Salt

Rechargeable magnesium (Mg) metal batteries are a promising candidate for “post-Li-ion batteries” due to their high capacity, high abundance, and most importantly, highly reversible and dendrite-free Mg metal anode. However, the formation of passivating surface film rather than Mg²⁺-conducting solid electrolyte interphase (SEI) on Mg anode surface has always restricted the development of rechargeable Mg batteries. A stable SEI is constructed on the surface of Mg metal anode by the partial decomposition of a pristine Li electrolyte in the electrochemical process. This Li electrolyte is easily prepared by dissolving lithium tetrakis(hexafluoroisopropyloxy)borate (Li[B(hfip)₄]) in dimethoxyethane. It is noteworthy that Mg²⁺ can be directly introduced into this Li electrolyte during the initial electrochemical cycles for in situ forming a hybrid Mg²⁺/Li⁺ electrolyte, and then the cycled electrolyte can conduct Mg-ion smoothly. The existence of this as-formed SEI blocks the further parasitic reaction of Mg metal anode with electrolyte and enables this electrolyte enduring long-term electrochemical cycles stably. This approach of constructing superior SEI on Mg anode surface and exploiting novel Mg electrolyte provides a new avenue for practical application of high-performance rechargeable Mg batteries.     

High Areal Capacity and Lithium Utilization in Anodes Made of Covalently Connected Graphite Microtubes

Lithium metal is an attractive anode material for rechargeable batteries because of its high theoretical specific capacity of 3860 mA h g^?1 and the lowest negative electrochemical potential of ?3.040 V versus standard hydrogen electrode. Despite extensive research efforts on tackling the safety concern raised by Li dendrites, inhibited Li dendrite growth is accompanied with decreased areal capacity and Li utilization, which are still lower than expectation for practical use. A scaffold made of covalently connected graphite microtubes is reported, which provides a firm and conductive framework with moderate specific surface area to accommodate Li metal for anodes of Li batteries. The anode presents an areal capacity of 10 mA h cm^?2 (practical gravimetric capacity of 913 mA h g^?1) at a current density of 10 mA cm^?2, with Li utilization of 91%, Coulombic efficiencies of ≈97%, and long lifespan of up to 3000 h. The analysis of structure evolution during charge/discharge shows inhibited lithium dendrite growth and a reversible electrode volume change of ≈9%. It is suggested that an optimized microstructure with moderate electrode/electrolyte interface area is critical to accommodate volume change and inhibit the risks of irreversible Li consumption by side reactions and Li dendrite growth for high‐performance Li‐metal anodes.     

An Autotransferable g‐C3N4 Li+‐Modulating Layer toward Stable Lithium Anodes

Commercial deployment of lithium anodes has been severely impeded by the poor battery safety, unsatisfying cycling lifespan, and efficiency. Recently, building artificial interfacial layers over a lithium anode was regarded as an effective strategy to stabilize the electrode. However, the fabrications reported so far have mostly been conducted directly upon lithium foil, often requiring stringent reaction conditions with indispensable inert environment protection and highly specialized reagents due to the high reactivity of metallic lithium. Besides, the uneven lithium‐ion flux across the lithium surface should be more powerfully tailored via mighty interfacial layer materials. Herein, g‐C₃N₄ is employed as a Li⁺‐modulating material and a brand‐new autotransferable strategy to fabricate this interfacial layer for Li anodes without any inert atmosphere protection and limitation of chemical regents is developed. The g‐C₃N₄ film is filtrated on the separator in air using a common alcohol solution and then perfectly autotransferred to the lithium surface by electrolyte wetting during normal cell assembly. The abundant nitrogen species within g‐C₃N₄ nanosheets can form transient Li? N bonds to powerfully stabilize the lithium‐ion flux and thus enable a CE over 99% for 900 cycles and smooth deposition at high current densities and capacities, surpassing most previous works.     

A Lithium‐Organic Primary Battery

Lithium primary batteries are still widely used in military, aerospace, medical, and civilian applications despite the omnipresence of rechargeable Li‐ion batteries. However, these current primary chemistries are exclusively based on inorganic materials with high cost, low energy density or severe safety concerns. Here, a novel lithium‐organic primary battery chemistry that operates through a synergetic reduction of 9,10‐anthraquinone (AQ) and fluoroethylene carbonate (FEC) is reported. In FEC‐presence, the equilibrium between the carbonyl and enol structures is disabled, and replaced by an irreversible process that corresponds to a large capacity along with methylene and inorganic salts (such as LiF, Li₂CO₃) generated as products. This irreversible chemistry of AQ yields a high energy density of 1300 Wh/(kg of AQ) at a stable discharge voltage platform of 2.4 V as well as high rate capability (up to 313 mAh g^?1 at a current density of 1000 mA g^?1), wide temperature range of operation (?40 to 40 °C) and low self‐discharge rate. Combined with the advantages of low toxicity, facile and diverse synthesis methods, and easy accessibility of AQ, Li‐organic primary battery chemistry promises a new battery candidate for applications that requires low cost, high environmental friendliness, and high energy density.     

Anode Interface Engineering and Architecture Design for High‐Performance Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries are considered as one of the most promising options to realize rechargeable batteries with high energy capacity. Previously, research has mainly focused on solving the polysulfides' shuttle, cathode volume changes, and sulfur conductivity problems. However, the instability of anodes in Li–S batteries has become a bottleneck to achieving high performance. Herein, the main efforts to develop highly stable anodes for Li–S batteries, mainly including lithium metal anodes, carbon‐based anodes, and alloy‐based anodes, are considered. Based on these anodes, their interfacial engineering and structure design are identified as the two most important directions to achieve ideal anodes. Because of high reactivity and large volume change during cycling, Li anodes suffer from severe side reactions and structure collapse. The solid electrolyte interphase formed in situ by modified electrolytes and ex situ artificial coating layers can enhance the interfacial stability of anodes. Replacing common Li foil with rationally designed anodes not only suppresses the formation of dendritic Li but also delays the failure of Li anodes. Manipulating the anode interface engineering and rationally designing anode architecture represents an attractive path to develop high‐performance Li–S batteries.     

Mixed Ionic and Electronic Conductor for Li‐Metal Anode Protection

Li‐metal is the optimal choice as an anode due to its highest energy density. However, Li‐anodes suffer safety problems from dendritic Li‐growth and continuous corrosion by liquid electrolytes. Here, an effective strategy of using ultrathin and conformal mixed ionic and electronic ceramic conductor (MIEC) is proposed to stabilize Li‐anodes. An ultrathin Li_0.35La_0.52[V]_0.13TiO₃ (LLTO) ceramic film with superior ionic conductivity is first obtained by sintering single‐crystal LLTO nanoparticles, which have controlled surface facets and particle sizes. Then the MIEC property is developed in the LLTO film by introducing toluene as catalyst, which triggers the chemical reactions between LLTO and Li‐metal, leading to high electronic conductivity in the LLTO film. After evaporating toluene, a hybrid LLTO/Li anode with a conformal and stable interface is formed. When applying the hybrid anodes in Li‐metal batteries, the MIEC ceramic film blocks Li‐corrosion from electrolyte and the formation of Li‐dendrites by buffering the Li‐ion concentration gradient and leveling secondary current distribution on Li‐metal surface. At the same time, the Coulombic efficiency of batteries reaches to 98%. This finding will impact the general approach for tailoring the properties of Li‐metal anodes for achieving better Li‐metal battery performance.