A Facile Way to Construct Stable and Ionic Conductive Lithium Sulfide Nanoparticles Composed Solid Electrolyte Interphase on Li Metal Anode

Due to the high theoretical capacity and low reduction potential, metallic lithium is a promising anode material for the next generation of high-energy-density batteries. However, the dynamic Li plating/stripping process can easily destroy the unstable solid electrolyte interphase (SEI) and cause dendrite growth. Here, an artificial lithium sulfide nanoparticle composed SEI layer with superior stability and high ionic conductivity is designed by a spray quenching method. The artificial SEI layer on Li surface can effectively minimize the side reactions and suppress Li dendrite growth, and the metal electrode delivers stable cycling for 500 cycles in the symmetrical cell with carbonate electrolyte. Moreover, when this SEI-modified Li anode is coupled with a LiFePO₄ cathode, the full cell shows promoted cycling stability and rate capability. This work provides a broadly applicable and facile strategy to address the intrinsic issues of lithium metal anodes.     

3D Porous Cu Current Collector/Li‐Metal Composite Anode for Stable Lithium‐Metal Batteries

Lithium‐metal batteries are of particular interest for next‐generation electrical energy storage because of their high energy density on both volumetric and gravimetric bases. Effective strategies to stabilize the Li‐metal anode are the prerequisite for the progress of these exceptional storage technologies, such as Li–S and Li–O₂ batteries. Various challenges, such as uneven Li electrodeposition, anode volume expansion, and dendrite‐induced short‐circuit have hindered the practical application of rechargeable Li‐metal batteries. Herein, a one‐step facile and cost‐effective strategy for stabilizing lithium‐metal batteries via 3D porous Cu current collector/Li‐metal composite anode is reported. The porous structure of the composite electrode provides a “cage” for the redeposition of “hostless” lithium and accommodates the anode volume expansion during cycling. Compared with planar Cu foil, its high specific surface area favors the electrochemical reaction kinetics and lowers the local current density along the anode. It leads to low interfacial resistance and stabilizes the Li electrodeposition. On this basis, galvanostatic measurements are performed on both symmetric cells and Li/Li₄Ti₅O₁₂ cells and it is found that the electrodes exhibit exceptional abilities of promoting cell lifetime and stabilizing the cycling behavior. Although this work focuses on lithium metal, this novel tactic is easy to generalize to other metal electrodes.     

Ultrafast Electrochemical Growth of Lithiophilic Nano-Flake Arrays for Stable Lithium Metal Anode

Lithium dendrites caused by nonuniform Li⁺ flux leads to the capacity fade and short-circuit hazard of lithium metal batteries. The solid electrolyte interface (SEI) is critical to the uniformity of Li⁺ flux. Here, an ultrafast preparation of uniform and vertical Cu₇S₄ nano-flake arrays (Cu₇S₄ NFAs) on the Cu substrate is reported. These arrays can largely improve the lithiophilicity of the anode and form Li₂S-enriched SEI due to the electrochemical reduction of Cu₇S₄ NFAs with lithium. A further statistical analysis suggests that the SEI, with a higher content of Li₂S, is more effective to inhibit the formation of lithium dendrites and yields less dead lithium. A quite stable coulombic efficiency of 98.6% can be maintained for 400 cycles at 1 mA cm^–2. Furthermore, at negative to positive electrode capacity ratio of 1.5 (N/P = 1.5), the full battery of Li@Cu₇S₄ NFAs||S shows 83% capacity retention after 100 cycles at 1 C, much higher than that of Li@Cu||S (33%). The findings demonstrate that high Li₂S content in the SEI is crucial for the dendrite inhibition to achieve better electrochemical performance.     

Regulating Lithium Nucleation and Deposition via MOF‐Derived Co@C‐Modified Carbon Cloth for Stable Li Metal Anode

Lithium metal is an exciting anode candidate with extra high theoretical specific capacity for new high‐energy rechargeable batteries. However, uncontrolled Li deposition and an unsteady solid electrolyte interface seriously obstruct the commercial application of Li anodes in Li metal batteries. Herein, 3D carbon cloth (CC) supporting N‐doped carbon (CN) nanosheet arrays embedded with tiny Co nanoparticles (CC@CN‐Co) are employed as a lithiophilic framework to regulate homogenous Li nucleation/growth behavior in a working Li metal anode. The emergence of Li dendrites is supposed to be inhibited by the conductive 3D scaffold that reduces local current density. The uniform nucleation of Li can be guided by N‐containing functional groups as they have a strong interaction with Li atoms, and the tiny Co nanoparticles can provide active sites to guide Li deposition. As a result, the current CC@CN‐Co host exhibits Li dendrite–free features and stable cycling performance with a low overpotential (20 mV) throughout 800 h cycles. When paired with the typical LiFePO₄ (LFP) cathode, the assembled CC@CN‐Co@Li//LFP@C full cell exhibits outstanding rate capability and improved cycling performance.     

A Novel 3D Li/Li9Al4/Li-Mg Alloy Anode for Superior Lithium Metal Batteries

Lithium metal has been recognized as the most promising anode material due to its high capacity and low electrode potential. However, the high reactivity, infinite volume variation, and uncontrolled dendrites growth of Li during long-term cycling severely limit its practical applications. To address these issues, herein, a novel 3D Al/Mg/Li alloy (denoted as AM-Li) anode is designed and constructed by a facile smelting-rolling strategy, which improves the surface stability, electrochemical cycling stability, and rate capability in lithium metal batteries. Specifically, the optimized AM-Li|AM-Li symmetric cell exhibits low polarization voltage (< 20 mV) and perfect cycling stability at 1 mA cm⁻²-1 mAh cm⁻² for more than 1600 h. Moreover, the AM-Li|NCM811 full cell exhibits superior rate capability up to 5 C and excellent cyclability for 100 cycles at 0.5 C with a high capacity retention of 90.8%. The realization of lithium-poor or lithium-free anode materials will be a major development trend of anode materials in the future. Therefore, the research shows that the construction of 3D alloy framework is beneficial to improve the cycling stability of Li anodes by suppressing the volume expansion effect and Li dendrite growth, which will promote the further development of lithium-poor metal anodes.     

A Soft Lithiophilic Graphene Aerogel for Stable Lithium Metal Anode

The lithium metal anode is one of the most promising anodes for next‐generation high‐energy‐density batteries. However, the severe growth of Li dendrites and large volume expansion leads to rapid capacity decay and shortened lifetime, especially in high current density and high capacity. Herein, a soft 3D Au nanoparticles@graphene hybrid aerogel (Au? GA) as a lithiophilic host for lithium metal anode is proposed. The large surface area and interconnected conductive pathways of the Au? GA significantly decrease the local current density of the electrode, enabling uniform Li deposition. Furthermore, the 3D porous structure effectively accommodates the large volume expansion during Li plating/stripping, and the Li_xAu alloy serves as a solid solution buffer layer to completely eliminate the Li nucleation over‐potential. Symmetric cells can stably cycle at 8 mA cm^?2 for 8 mAh cm^?2 and exhibit ultra‐long cycling: 1800 h at 2 mA cm^?2 for 2 mAh cm^?2, and 1200 h at 4 mA cm^?2 for 4 mAh cm^?2, with low over‐potential. Full cells assemble with a Cu@Au? GA? Li anode and LiFePO₄ cathode, can sustain a high rate of 8 C, and retain a high capacity of 59.6 mAh g^?1 after 1100 cycles at 2 C.     

Artificial Soft–Rigid Protective Layer for Dendrite‐Free Lithium Metal Anode

Lithium (Li) metal has been pursued as “Holy Grail” among various anode materials due to its high specific capacity and the lowest reduction potential. However, uncontrolled growth of Li dendrites and extremely unstable interfaces during repeated Li plating/stripping ineluctably plague the practical applications of Li metal batteries. Herein, an artificial protective layer with synergistic soft–rigid feature is constructed on the Li metal anode to offer superior interfacial stability during long‐term cycles. By suppressing random Li deposition and the formation of isolated Li, such a protective layer enables a dendrite‐free morphology of Li metal anode and suppresses the depletion of Li metal and electrolyte. Additionally, sufficient ionic conductivity is guaranteed through the synergy between soft and rigid structural units that are uniformly dispersed in the layer. Dendrite‐free and dense Li deposition, as well as a greatly reduced interfacial resistance after cycling, is achieved owing to the stabilized interface, accounting for significantly prolonged cycle life of Li metal batteries. This work highlights the ability of synergistic organic/inorganic protective layer in stabilizing Li metal anode and provides fresh insights into the energy chemistry and mechanics of anode in a working battery.     

Building Artificial Solid‐Electrolyte Interphase with Uniform Intermolecular Ionic Bonds toward Dendrite‐Free Lithium Metal Anodes

Li metal has been widely regarded as a promising anode for next‐generation batteries due to its high theoretical capacity and low electrochemical potential. The unstable solid‐electrolyte interphase (SEI) and uncontrollable dendrite growth, however, incur severe safety hazards and hamper the practical application of Li metal anodes. Herein, an advanced artificial SEI layer constructed by [LiNBH]_n chains, which are crosslinked and self‐reinforced by their intermolecular Li? N ionic bonds, is designed to comprehensively stabilize Li metal anodes on a molecular level. Benefiting from its polymer‐like structure, the [LiNBH]_n layer is flexible and effectively tolerates the volume change of Li metal anodes. In addition, this layer with high polarity in its structure, helps to regulate the homogeneous distribution of the Li⁺ flux on Li electrodes via the further formation of Li? N bonds. The designed [LiNBH]_n layer is electrically nonconductive but highly ionically conductive, thus facilitating Li⁺ diffusion and confining Li deposition beneath the layer. Therefore, under the protection of the [LiNBH]_n layer, the Li metal anodes exhibit stable cycling at a 3 mA cm^?2 for more than 700 h, and the full cells with high lithium iron phosphate and sulfur cathodes mass loading also present excellent cycling stability.     

Controlling Li Ion Flux through Materials Innovation for Dendrite‐Free Lithium Metal Anodes

Lithium (Li) metal with high theoretical capacity and the lowest electrochemical potential has been proposed as the ideal anode for high‐energy‐density rechargeable battery systems. However, the practical commercialization of Li metal anodes is precluded by a short lifespan and safety problems caused by their intrinsically high reductivity, infinite volume change, and uncontrollable dendrite growth during deposition and dissolution processes. Plenty of strategies have been introduced to solve the above‐mentioned problems. Among these, controlling Li⁺ flux plays a vital role to directly influence the plating and stripping process. In this work, the fundamental effect of Li⁺ flux distribution on Li nucleation and early dendrite growth is discussed. Then, recent strategies of controlling Li⁺ flux to suppress dendrite formation and growth through materials design are summarized, including homogenizing Li⁺ flux, localizing Li⁺ flux, and guiding gradient Li⁺ distribution. Finally, underexplored materials are proposed and explored to control Li⁺ flux and further directions for dendrite‐free Li anodes. It is expected that this progress report will help to deepen the understanding of Li⁺ flow tuning and morphology control of Li anodes and eventually facilitate the practical application of Li metal batteries.     

Stable SiOC/Sn Nanocomposite Anodes for Lithium‐Ion Batteries with Outstanding Cycling Stability

Silicon oxycarbide/tin nanocomposites (SiOC/Sn) are prepared by chemical modification of polysilsesquioxane Wacker‐Belsil PMS MK (SiOC_MK) and polysiloxane Polyramic RD‐684a (SiOC_RD) with tin(II)acetate and subsequent pyrolysis at 1000 °C. The obtained samples consist of an amorphous SiOC matrix and in‐situ formed metallic Sn precipitates. Galvanostatic cycling of both composites demonstrate a first cycle reversible capacity of 566 mAhg^?1 for SiOC_MK/Sn and 651 mAhg^?1 for SiOC_RD/Sn. The superior cycling stability and rate capability of SiOC_RD/Sn as compared to SiOC_MK/Sn is attributed to the soft, carbon‐rich SiOC matrix derived from the RD‐684a polymer, which accommodates the Sn‐related volume changes during Li‐uptake and release. The poor cycling stability found for SiOC_MK/Sn relates to mechanical failure of the rather stiff and fragile, carbon‐poor matrix produced from PMS MK. Incremental capacity measurements outline different final Li–Sn alloy stages, depending on the matrix. For SiOC_RD/Sn, alloying up to Li₇Sn₂ is registered, whereas for SiOC_MK/Sn Li₂₂Sn₅ stoichiometry is reached. The suppression of Li₂₂Sn₅ phase in SiOC_RD/Sn is rationalized by an expansion restriction of the matrix and thus prevention of a higher Li content in the alloy. For SiOC_MK/Sn on the contrary, the matrix severely ruptures, providing an unlimited free volume for expansion and thus formation of Li₂₂Sn₅ phase.     

High Dielectric,Robust Composite Protective Layer for Dendrite‐Free and LiPF6 Degradation‐Free Lithium Metal Anode

The development of lithium metal anodes for next generation batteries remains a challenge. Uncontrolled Li dendrite growth not only induces severe safety issues but also leads to capacity fading by continuously consuming the electrolyte. This study demonstrates the design and fabrication of a composite protective layer composed of a high dielectric polymer, inorganic particles, and an electrolyte to overcome these obstacles. This layer not only suppresses dendrite growth, but also prevents LiPF₆ degradation. The electrolyte introduced in the protective layer remains within the coating layer after solvent removal and acts as an ion transport channel at the interface. This enables the protective layer to exhibit high ionic conductivity and mechanical strength. The composite protective layer, which exhibits synergistic soft‐rigid characteristics, is placed on the Li metal anode and facilitates superior interfacial stability during long‐term cycles. LiMn₂O₄/coated lithium full cells using the composite protective layer show a superior rate capability and enhanced capacity retention compared to the cells using a bare lithium anode. The proposed strategy opens new avenues to fabricate a sustainable composite protective layer that affords superior performance in lithium metal batteries.     

Functionality of Dual‐Phase Lithium Storage in a Porous Carbon Host for Lithium‐Metal Anode

Lithium (Li) metal is regarded as the most attractive anode material for high‐energy Li batteries, but it faces unavoidable challenges—uncontrollable dendritic growth of Li and severe volume changes during Li plating and stripping. Herein, a porous carbon framework (PCF) derived from a metal–organic framework (MOF) is proposed as a dual‐phase Li storage material that enables efficient and reversible Li storage via lithiation and metallization processes. Li is electrochemically stored in the PCF upon charging to 0 V versus Li/Li⁺ (lithiation), making the PCF surface more lithiophilic, and then the formation of metallic Li phase can be induced spontaneously in the internal nanopores during further charging below 0 V versus Li/Li⁺ (metallization). Based on thermodynamic calculations and experimental studies, it is shown that atomically dispersed zinc plays an important role in facilitating Li plating and that the reversibility of Li storage is significantly improved by controlled nanostructural engineering of 3D porous nanoarchitectures to promote the uniform formation of Li. Moreover, the MOF‐derived PCF does not suffer from macroscopic volume changes during cycling. This work demonstrates that the nanostructural engineering of porous carbon structures combined with lithiophilic element coordination would be an effective approach for realizing high‐capacity, reversible Li‐metal anodes.     

A Series of Hybrid Multifunctional Interfaces as Artificial SEI Layer for Realizing Dendrite Free,and Long-Life Sodium Metal Anodes (Adv. Funct. Mater. 42/2023)

Sodium metal (Na) anodes are considered the most promising anode for high-energy-density sodium batteries because of their high capacity and low electrochemical potential. However, Na metal anode undergoes uncontrolled Na dendrite growth, and unstable solid electrolyte interphase layer (SEI) formation during cycling, leading to poor coulombic efficiency, and shorter lifespan. Herein, a series of Na-ion conductive alloy-type protective interface (Na-In, Na-Bi, Na-Zn, Na-Sn) is studied as an artificial SEI layer to address the issues. The hybrid Na-ion conducting SEI components over the Na-alloy can facilitate uniform Na deposition by regulating Na-ion flux with low overpotential. Furthermore, density functional study reveals that the lower surface energy of protective alloys relative to bare Na is the key factor for facilitating facile ion diffusion across the interface. Na metal with interface layer facilitates a highly reversible Na plating/stripping for ≈790 h, higher than pristine Na metal (100 h). The hybrid self-regulating protective layers exhibit a high mechanical flexibility to promote dendrite free Na plating even at high current density (5 mA cm⁻²), high capacity (10 mAh cm⁻²), and good performance with Na₃V₂(PO₄)₃ cathode. The current study opens a new insight for designing dendrite Na metal anode for next generation energy storage devices.     

A Li–Al–O Solid‐State Electrolyte with High Ionic Conductivity and Good Capability to Protect Li Anode

Using a solid‐state electrolyte (SSE) to stabilize the Li metal anode is widely considered a promising route to develop next‐generation high energy density lithium batteries. Here, a new polycrystalline aluminate‐based SSE (named Li–Al–O SSE) with good capability is introduced to protect Li metal. The SSE is formed on the Li metal surface via a chemical reaction between LiOH and triethylaluminum (TEAL) with the existence of LiTFSI‐based electrolyte. It is a continuous film that consists of polycrystalline LiAlO₂, Li₃AlO₃, Al₂O₃, Li₂CO₃, LiF, and some organic compounds. Such Li–Al–O SSE possesses a room‐temperature ionic conductivity as high as 1.42 × 10^?4 S cm^?1. Meanwhile, it effectively protects the Li anode from the corrosion of H₂O, O₂, and organic solvent, and suppresses the growth of Li dendrite. With the protection of the Li–Al–O SSE, the cycle life of Li|Li symmetric cell and Li|O₂ cell is substantially elongated, indicating that the SSE exhibits an excellent protective effect under both inert and oxidizing circumstances.     

Synergistically Assembled Li2S/FWNTs@Reduced Graphene Oxide Nanobundle Forest for Free‐Standing High‐Performance Li2S Cathodes

Lithium sulfide (Li₂S) has attracted increasing attention as a promising cathode because of its compatibility with more practical lithium‐free anode materials and its high specific capacity. However, it is still a challenge to develop Li₂S cathodes with low electrochemical overpotential, high capacity and reversibility, and good rate performance. This work designs and fabricates a practical Li₂S cathode composed of Li₂S/few‐walled carbon nanotubes@reduced graphene oxide nanobundle forest (Li₂S/FWNTs@rGO NBF). Hierarchical nanostructures are obtained by annealing the Li₂SO₄/FWNTs@GO NBF, which is prepared by a facile and scalable solution‐based self‐assembly method. Systematic characterizations reveal that in this unique NBF nanostructure, FWNTs act as axial shafts to direct the structure, Li₂S serves as the internal active material, and GO sheets provide an external coating to minimize the direct contact of Li₂S with the electrolyte. When used as a cathode, the Li₂S/FWNTs@rGO NBF achieve a high capacity of 868 mAh g^?1_Li2S at 0.2C after 300 cycles and an outstanding rate performance of 433 mAh g^?1_Li2S even at 10C, suggesting that this Li₂S cathode is a promising candidate for ultrafast charge/discharge applications. The design and synthetic strategies outlined here can be readily applied to the processing of other novel functional materials to obtain a much wider range of applications.     

Multi‐Functional Dual‐Layer Polymer Electrolytes for Lithium Metal Polymer Batteries

We prepared a novel multi‐functional dual‐layer polymer electrolyte by impregnating the interconnected pores with an ethylene carbonate (EC)/dimethyl carbonate (DMC)/lithium hexafluorophosphate (LiPF₆) solution. The first layer, based on a microporous polyethylene, is incompatible with a liquid electrolyte, and the second layer, based on poly (vinylidenefluoride‐co‐hexafluoropropylene), is submicroporous and compatible with an electrolyte solution. The maximum ionic conductivity is 7 × 10^?3 S/cm at ambient temperature. A unit cell using the optimum polymer electrolyte showed a reversible capacity of 198 mAh/g at the 500th cycle, which was about 87% of the initial value.     

Unraveling Metal Oxide Role in Exfoliating Graphite: New Strategy to Construct High‐Performance Graphene‐Modified SiOx‐Based Anode for Lithium‐Ion Batteries

Exfoliating graphite to graphene has attracted great attention due to the fantastic properties of graphene available for designing graphene‐based materials or devices. Besides the classic solution method, herein a unique role of TiO₂ in exfoliating graphite to be graphene layers effectively is reported. As a paradigm, this discovered effect of TiO₂ is significant for preparing high‐performance graphene‐modified SiO_x‐based anode in lithium‐ion batteries (LIBs), in which the graphite is in situ exfoliated mechanically by TiO₂ to be multilayered graphene (i.e., MLG) and then the SiO_x is wrapped by the MLG to construct a SiO_x/TiO₂@MLG. In this case, an extremely high capacity of 1484 mAh g^?1, long lifespan over 1200 cycles at 2 A g^?1, as well as good performance in full LIBs (vs nickel‐rich cathode) are demonstrated. It is confirmed that the MLG can enhance electric conductivity, mitigate electrolyte decomposition, and alleviate volume effect of the SiO_x effectively. This result is hard to be achieved using other kinds of metal oxide besides TiO₂. It is hoped that the SiO_x/TiO₂@MLG is practical for pursuing LIBs with an energy density beyond 300 Wh kg^?1. In addition, it is believed the ingenious strategy is applicable for designing more functional materials with greater capabilities.     

A Sieve‐Functional and Uniform‐Porous Kaolin Layer toward Stable Zinc Metal Anode

Zinc metal is considered as one of the best anode choices for rechargeable aqueous Zn‐based batteries due to its high specific capacity, abundance, and safety. However, dendrite and corrosion issues remain a challenge for this system. Herein, sieve‐element function (selective channel of Zn²⁺) and uniform‐pore distribution (≈3.0 nm) of a kaolin‐coated Zn anode (KL‐Zn) is proposed to alleviate these problems. Based on the artificial Zn metal/electrolyte interface, the KL‐Zn anode not only ensures dendrite‐free deposition and long‐time stability (800 h at 1.1 mA h cm^?2), but also retards side reactions. As a consequence, KL‐Zn/MnO₂ batteries can deliver high specific capacity and good capacity retention as well as a reasonably well‐preserved morphology (KL‐Zn) after 600 cycles at 0.5 A g^?1. This work provides a deep step toward high‐performance rechargeable Zn‐based battery system.     

Nanostructured Li2MnSiO4/C Cathodes with Hierarchical Macro‐/Mesoporosity for Lithium‐Ion Batteries

Li₂MnSiO₄/C nanocomposite with hierarchical macroporosity is prepared with poly(methyl methacrylate) (PMMA) colloidal crystals as a sacrificial hard‐template and water‐soluble phenol‐formaldehyde (PF) resin as the carbon source. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses confirm that the periodic macropores are ≈400 nm in diameter with 20–40 nm walls comprising Li₂MnSiO₄/C nanocrystals that produce additional large mesopores (< 30 nm) between the nanocrystals. The nanostructured Li₂MnSiO₄/C cathode exhibits a high reversible discharge capacity of 200 mAh g^?1 at C/10 (16 mA g^?1) rate at 1.5–4.8 V at 45 °C. Although the discharge capacity can be further increased on operating at 55 °C, the sample exhibits a relatively fast capacity fade at 55 °C, which can be partially solved by simply narrowing the voltage window to avoid side reactions of the electrolyte. The good performance of the Li₂MnSiO₄/C cathodes is attributed to the unique macro‐/mesostructure of the silicate coupled with uniform carbon coating.