Li Metal Research Articles

Tailoring superstructure units for improved oxygen redox activity in Li-rich layered oxide battery’s positive electrodes

AbstractThe high-voltage oxygen redox activity of Li-rich layered oxides enables additional capacity beyond conventional transition metal (TM) redox contributions and drives the development of positive electrode active materials in secondary Li-based batteries. However, Li-rich layered oxides often face voltage decay during battery operation. In particular, although Li-rich positive electrode active materials with a high nickel content demonstrate improved voltage stability, they suffer from poor discharge capacity. Here, via physicochemical and electrochemical measurements, we investigate the correlation between oxygen redox activity and superstructure units in Li-rich layered oxides, specifically the fractions of LiMn6 and Ni4+-stabilized LiNiMn5 within the TM layer. We prove that an excess of LiNiMn5 hinders the extraction/insertion of lithium ions during Li metal coin cell charging/discharging, resulting in incomplete oxygen redox activity at a cell potential of about 3.3 V. We also demonstrate that lithium content adjustment could be a beneficial approach to tailor the superstructure units. Indeed, we report an improved oxygen redox reversibility for an optimized Li-rich layered oxide with fewer LiNiMn5 units.

Constructing Angstrom‐Level Ion Pocket Array in 1D Channel Wall for Efficient Lithium Ion Sieving

AbstractThe rapid development of new energy industry is leading to the scarcity of lithium (Li) metal. Rational design of adsorbents for efficient separation of Li+ ion from aqueous media is pivotal to solve the recovery of this valuable resource. Current adsorbents generally suffer from the drawbacks in adsorption capacity, kinetics, and selectivity. Herein, a novel and ultra‐stable metal–organic framework is designed for Li+ separation. The dense oxygen atoms on the cambered wall of its 1D channel encircle to form angstrom‐level tetrahedral ion pockets array, acting as the dominant adsorption sites. This rational distribution of the array avoids the pore blockage caused by the pre‐adsorbed ions, thereby accelerating the diffusion of subsequent ions into the interior pore. Meanwhile, this tetrahedral pocket shows distinct electronegativity and strong chelation effect for Li+. Benefiting from these specifics, this adsorbent exhibits a record‐breaking adsorption capacity for Li+ (76.1 mg g−1) and short equilibrium time (30 min). Moreover, the selective adsorption of Li+ over Na+, K+, Ca2+, and Mg2+ is achieved due to the matched Li+ ion diameter with the pocket/channel sizes and lower energy barrier for dehydration. Thus, this work proposes a feasible strategy for the construction of novel MOFs for ions adsorption.

Interface engineering enabling thin lithium metal electrodes down to 0.78 μm for garnet-type solid-state batteries.

Controllable engineering of thin lithium (Li) metal is essential for increasing the energy density of solid-state batteries and clarifying the interfacial evolution mechanisms of a lithium metal negative electrode. However, fabricating a thin lithium electrode faces significant challenges due to the fragility and high viscosity of Li metal. Herein, through facile treatment of Ta-doped Li7La3Zr2O12 (LLZTO) with trifluoromethanesulfonic acid, its surface Li2CO3 species is converted into a lithiophilic layer with LiCF3SO3 and LiF components. It enables the thickness control of Li metal negative electrodes, ranging from 0.78 μm to 30 μm. Quasi-solid-state lithium-metal battery with an optimized 7.54 μm-thick lithium metal negative electrode, a commercial LiNi0.83Co0.11Mn0.06O2 positive electrode, and a negative/positive electrode capacity ratio of 1.1 shows a 500 cycles lifespan with a final discharge specific capacity of 99 mAh g-1 at 2.35 mA cm-2 and 25 °C. Through multi-scale characterizations of the thin lithium negative electrode, we clarify the multi-dimensional compositional evolution and failure mechanisms of lithium-deficient and -rich regions (0.78 μm and 7.54 μm), on its surface, inside it, or at the Li/LLZTO interface.

Crystalline Electrolyte Boosts High Performance of All-Solid-State Lithium-Ion Batteries.

The rigid solid-solid contact at the interface between the solid electrolyte and electrodes in full-solid-state lithium-ion batteries (ASSBs) presents a considerable challenge to lithium ion transport. To address this, we propose using Li-concentrated succinonitrile (Li-SN45) as an efficient bilateral interface modifier in ASSBs. This material boasts exceptional ionic conductivity of 3.38 mS cm-1 and excellent corrosion resistance to the Li metal anode. The assembled ASSBs using layered cathodes and Li metal demonstrate outstanding discharge capacity (170 mAh g-1 @ 20 mA g-1) and superior long-term cycling performance (97% capacity retention after 100 cycles). MALDI-TOF results suggest the formation of a crystalline structure in Li-SN45, which facilitates smooth "anion-free" Li+ hopping paths assisted by the oxygen atoms, as revealed by the solved crystal structure. Our findings enriched the understanding of Li transport dynamics in electrolytes of ASSBs, paving the way to designing superior next-generation ASSBs with fast Li transport.

Enhancing High‐Voltage LNMO Cathode Performance in Li‐Metal Batteries Via Anionic Electrolyte Additive‐Integrated CEI Engineering

AbstractAn anionic‐additive electrolyte system is introduced by incorporating Lithium tetrafluoroborate (LiBF4) into a conventional base electrolyte for high‐voltage LiNi₀.₅Mn₁.₅O₄ (LNMO) cathodes in lithium‐metal batteries. At high voltages, the sacrificial oxidation of LiBF4 mitigates electrolyte degradation and forms a robust cathode electrolyte interface (CEI) enriched with boron and fluorine‐based components, which protects against active material corrosion. Density Functional Theory (DFT) studies reveal that BF₄⁻ is more readily oxidized, while MD simulations validate the CEI's inorganic composition. Initial cycling with a specialized charge‐discharge protocol ensures optimal use of the additive, resulting in a uniform, thin (4–6 nm) CEI on the LNMO cathode. The CEI formed in anionic‐additive electrolyte system effectively suppresses transition metal dissolution and surface degradation, enhancing long‐term cycling performance. The LiBF4‐enhanced electrolyte also lowers overpotential and promotes more uniform Li deposition compared to the base electrolyte. At a 1 C‐rate, the LNMO cathode with a Li metal anode and optimized electrolyte achieves a discharge capacity of 115 mA h g⁻¹ and an energy density of 540 Wh kg⁻¹ over 500 cycles. These findings underscore LiBF4’s dual role in protecting LNMO cathodes and Li metal anodes, highlighting the critical role of additives in CEI development for advanced lithium‐metal batteries.

High-voltage and intrinsically safe electrolytes for Li metal batteries.

Current electrolytes of mixing different functional solvents inherit both merits and weaknesses of each solvent, thus cannot simultaneously meet all the requirements of high energy, long cycle life, and high safety for Li metal batteries (LMBs). Here, we design a high voltage and safe electrolyte (VSE) by integrating different functional groups into one molecule. The VSE electrolyte has a wide electrochemical stability window of ~5.6 V enabling a Li anode to achieve high Coulombic efficiency of >99.3%, Li | |LiNi0.8Co0.1Mn0.1O2 coin cell to maintain capacity retention of 92% after 500 cycles, and the 3.5-Ah-grade Li | |LiNi0.8Co0.1Mn0.1O2 pouch cell to deliver a high energy density of 531 Wh kg-1 without any flame and expansion after cycled under extreme conditions. The VSE electrolyte even enables 5.0 V Li | |LiNi0.5Mn1.5O4 cells to charge/discharge for 200 cycles without capacity decay. This work provides a promising direction for the rational design of high-voltage and intrinsically safe electrolytes for LMBs.

Covalently Anchoring an Ultrathin Conformal SiOx Coating on Polyolefin Separator for Enhanced Lithium Metal Battery Performance

AbstractSurface modification of separators with inorganic oxide ceramics such as SiOx, Al2O3, and TiO2 has emerged as a promising strategy to suppress lithium dendrite growth in lithium metal batteries, thereby enhancing safety and extending battery life. However, the binder‐dependent nature of these modifications often leads to increased separator thickness and a heightened risk of detachment during lithium plating, ultimately compromising both battery performance and energy density. In this study, a conformal, ultrathin (≈20 nm) SiOx coating with strong covalent bonding is grown on a porous separator through a liquid polymer‐derived method. Compared to the pristine polyethylene (PE) separators, this SiOx‐co‐PE separator exhibits significantly improved electrolyte wettability, mechanical strength, and thermal stability without any increase in thickness, leading to vastly enhanced cycling stability and dendrite resistance in cells with Li metal anodes. In a practical demonstration, a 402.9 Wh·kg−1 Li‐S pouch cell, with a high sulfur loading of 9 mg cm−2 and a low E/S ratio of 3.3 µL mg−1, is assembled with the SiOx‐co‐PE separator, achieving stable cycling over 70 cycles at 25 °C.

Magnesium Fluoride Interlayers Enabled by Wet‐Chemical Process for High‐Performance Solid‐State Batteries

AbstractGarnet‐type solid‐state electrolytes (SSEs) exemplified by Li6.5La3Zr1.5Ta0.5O12 (LLZT) are chemically unstable when exposed to air, leading to the formation of impurities and poor wettability with Li metal. Herein, a protocol to address this Li/LLZT interface challenge is demonstrated by constructing a lithiophilic MgF2 nanofilm on the LLZT pellet. Specifically, a solution‐based process is developed for the surface engineering of LLZT, utilizing magnesium trifluoroacetate (MTF) as the molecular precursor while poly(acrylic acid) (PAA) as the coordinating agent in a sol‐gel process. It is demonstrated that a facile spin‐coating treatment followed by high‐temperature annealing reliably forms crack‐free MgF2 nanofilms with precise thickness control. Introduction an MgF2 interlayer transforms the LLZT pellet into a highly lithophilic, facilitating close contact with the lithium anode, thereby leading to a significantly reduced interfacial resistance from 1190 Ω cm2 to 6 Ω cm2. Such an interfacial engineering enables stable cycling of full batteries with high reversibility and rate capability using commercial LiFePO4 and LiNi0.83Co0.07Mn0.1O2 as cathodes. This study unfolds the possibility of a solution‐based method as a facile and scalable process for the construction of fluoride nanofilms, which is promising to address the critical interfacial challenges of solid‐state batteries (SSBs) to facilitate its practical applications.

Study on the Thermal Control Performance of Mg-Li Alloy Micro-Arc Oxidation Coating in High-Temperature Environments

This paper reports on the successful preparation of a low absorption–emission thermal control coating on the surface of LAZ933 magnesium–lithium alloy using the micro-arc oxidation method. This study analyzed the microstructure, phase composition, and thermal control properties of the coating using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), UV–visible near-infrared spectroscopy (UV-VIS-NIR) and infrared emissivity measurements. The results indicate that the hemispherical emissivity of the coating remains unaffected with an increase in temperature and holding time, while the solar absorption ratio gradually increases. The thermal control performance of the coating after a high-temperature experiment was found to be related to the diffusion of the Li metal element in the magnesium lithium alloy matrix, as determined by X-ray photoelectron spectroscopy (XPS), flame graphite furnace atomic absorption spectrometry (GFAAS) and Glow Discharge Optical Emission Spectroscopy (GD-OES). As the holding time is extended, the coating structure gradually loosens under thermal stress. The Li metal element in the substrate diffuses outward and reacts with O2, H2O and CO2 in the air, forming LiO2, LiOH, Li2CO3 and other products. This reaction affects the coating’s solar absorption ratio in the end.

High-Performance Solid-State Lithium Metal Batteries of Garnet/Polymer Composite Thin-Film Electrolyte with Domain-Limited Ion Transport Pathways.

The integrated approach of interfacial engineering and composite electrolytes is crucial for the market application of Li metal batteries (LMBs). A 22 μm thin-film type polymer/Li6.4La3Zr1.4Ta0.6O12 (LLZTO) composite solid-state electrolyte (LPCE) was designed that combines fast ion conduction and stable interfacial evolution, enhancing lithium metal interface stability and cycling performance. The ether-based molecular coordination groups/clusters formed by triethylene glycol dimethyl ether (TGDE) and anions facilitated the movement of Li+ between the polymer chain segments. These specific coordination clusters significantly "constrained" the interaction between anions and Li+, inducing the anions to follow the clusters to the Li metal and preferentially participate in solid electrolyte interface (SEI) derivatization. The inorganic salt-rich gradient SEI modulates Li+ deposition and inhibits uncontrolled dendrite growth, achieving stable cycling of Li symmetric cell at 0.2 mA cm-2 for over 2000 h. Furthermore, the Li||NCM811 cell at a rate of 0.1 C exhibits an initial discharge capacity of 194.5 mAh g-1, maintaining a capacity retention rate of over 90% after 500 cycles. This work demonstrates the importance of domain-limited ion clusters in ion transport and interfacial evolution, providing a perspective for solid-state LMBs.

Ferroelectric Dipoles Tailoring Solid‐Electrolyte‐Interphase Chemistry to Enable Reversible Lithium Metal Batteries

AbstractSolid‐electrolyte interphase (SEI) plays a decisive role in building reliable Li metal batteries. However, the scarcity of anions in Helmholtz layer (HL) caused by electrostatic repulsion usually leads to the inferior SEI derived from solvents, resulting in dendrites and ‘dead’ Li. Therefore, regulating the distribution of anions in electric double layer (EDL) and continuously introducing more anions into HL to tailor anions‐derived SEI is crucial for achieving stable Li plating/stripping. Herein, by jointly utilizing the controlled defects of reduced graphene oxide (rGO) and the oriented dipoles of ferroelectric BaTiO3 (BTO), the rGO‐BTO composite layer sustainedly brings more TFSI− and NO3− into anion‐defecient HL, promoting favorable decomposition of anions and guiding the generation of robust and fast‐Li+‐transport SEI containing more inorganics LiF and Li3N species. Thus, the resulting Li deposit shows smooth and dense morphologies without dendrites, leading to high average Coulombic efficiency. The Li//Cu@rGO‐BTO (10 mAh cm−2 plated Li) cell exhibits an enhanced Li plating/stripping stability (2700 h) and a higher rate capability. The LiFePO4 full cell (N/P≈6.3) using rGO‐BTO displays an enhanced capacity retention (82.0 % @ 430 cycles). This work provides a new insight on the construction of robust SEI by regulating the distribution of anions within EDL.

Dynamic Transition Metal Network via Orbital Population Design Stabilizes Lattice Oxygen Redox in Stoichiometric Layered Cathodes.

Li-ion batteries employing stoichiometric layered Li metal oxides as cathodes are now reaching the energy density limits due to single cationic redox chemistry. Lattice oxygen redox (LOR) has been discovered in these materials, as a high-energy-density paradigm observed in Li-rich materials. Nevertheless, the origin of this process is not understood, preventing the rational design of better cathode materials. Here, employing stoichiometric Ni-based cathodes, it is demonstrated that LOR originates from a dynamic transition metal (TM) network caused by ion migration during the electrochemical process. This network is confirmed to be ribbon through both ex- and in-situ STEM observations, facilitating reversible LOR. Finally, a t2g orbital population rule is proposed to guide the design of ordered TM networks, supported by calculated structures and the synthesized ordered TM oxides reported. This work explains the mechanism of LOR in stoichiometric layered cathode materials, and sets a promising direction for the design of high-energy-density cathodes through the regulation of TM ordering.

Three-dimensional Covalent Organic Framework with Dense Lithiophilic Sites as Protective Layer to Enable High-Performance Lithium Metal Battery.

Lithium (Li) metal batteries with remarkable energy densities are restrained by short lifetime and low Coulombic efficiency (CE), resulting from the accumulative Li dendrites and dead Li during cycling. Here, we prepared a new three-dimensional (3D) covalent organic framework (COF) with dense lithiophilic sites (heteoatom weight contents of 32.32wt%) as an anodic protective layer of Li metal batteries. The 3D COF was synthesized using a [6+4] synthesis strategy by inducing flexible 6-connected cyclotriphosphazene derivative aldehyde and 4-connected porphyrin-based tetraphenylamines. Both phosphazene and porphyrin rings in the COF served as electron-rich and lithiophilic sites, enhancing a homogeneous Li+ flux via 3D direction towards highly smooth and compact Li deposition. The Li/Por-PN-COF-Cu cells achieved a record average CE of 99.1% for 320 cycles with smooth Li deposition. Meanwhile, the abundant lithiophilic sites can promote fast Li+ transport with Li+ transference number of 0.87, enabling LiFePO4 full cell with stable stripping/plating processes even at a harsh rate of 5 C. Theoretical calculations revealed that the strong interaction force between Li+ and the COF facilitated the dissolution of Li+ from the electrolyte, and the low migration barrier of 1.08 eV indicated a favorable interaction between the Li+ ions and the π-electron system.

Three‐dimensional Covalent Organic Framework with Dense Lithiophilic Sites as Protective Layer to Enable High‐Performance Lithium Metal Battery

Lithium (Li) metal batteries with remarkable energy densities are restrained by short lifetime and low Coulombic efficiency (CE), resulting from the accumulative Li dendrites and dead Li during cycling. Here, we prepared a new three‐dimensional (3D) covalent organic framework (COF) with dense lithiophilic sites (heteoatom weight contents of 32.32wt%) as an anodic protective layer of Li metal batteries. The 3D COF was synthesized using a [6+4] synthesis strategy by inducing flexible 6‐connected cyclotriphosphazene derivative aldehyde and 4‐connected porphyrin‐based tetraphenylamines. Both phosphazene and porphyrin rings in the COF served as electron‐rich and lithiophilic sites, enhancing a homogeneous Li+ flux via 3D direction towards highly smooth and compact Li deposition. The Li/Por‐PN‐COF‐Cu cells achieved a record average CE of 99.1% for 320 cycles with smooth Li deposition. Meanwhile, the abundant lithiophilic sites can promote fast Li+ transport with Li+ transference number of 0.87, enabling LiFePO4 full cell with stable stripping/plating processes even at a harsh rate of 5 C. Theoretical calculations revealed that the strong interaction force between Li+ and the COF facilitated the dissolution of Li+ from the electrolyte, and the low migration barrier of 1.08 eV indicated a favorable interaction between the Li+ ions and the π‐electron system.

First‐Principles Molecular Dynamics Study on Reductive Stability of High Concentration Electrolyte on Zn Doped Cu Current Collector Surface

AbstractIn enhancing the lifespan of anode‐free Li metal batteries (AFLMBs), current collector (CC) engineering is crucial for achieving uniform and dendrite‐free lithium deposition. The commonly used copper (Cu) CC is unsatisfactory because of its poor lithiophilicity. Here, we consider Zn doping on the Cu CC surface (Zn−Cu) and explore the reductive stability of a high‐concentration electrolyte (HCE), consisting of 3.6 M Lithium Hexafluorophosphate (LiPF6) salt in a mixture of ethylene carbonate (EC) and diethylcarbonate (DEC), on the Zn−Cu (111) surface (HCE|Zn−Cu) using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. The interfacial reactions in the HCE|Zn−Cu system are compared to those on the pristine Cu (111) surface (HCE|Cu). We have also studied the effect of electron‐rich environments on the decomposition mechanism of the HCE mixture on both the CC surfaces. It is found that the HCE mixture is electrochemically stable on both Cu and Zn−Cu surfaces in a neutral environment. However, under electron‐rich conditions, only one DEC molecule has decomposed upon contact with the Cu CC surface, while the two PF6− anion groups from Li salts have decomposed much faster (within 100 fs) when the HCE mixture interacts with the Zn−Cu surface. Our results indicate that Zn doping suppresses undesirable solvent decomposition and improves the quality of the solid electrolyte interphase (SEI) layer.

Regulating of Lithium‐Ion Dynamic Trajectory by Ferromagnetic CoF2 to Achieve Ultra‐Stable Deep Lithium Deposition Over 10000 h

AbstractCurrently, the realization of controllable Li electrodeposits to further extend the cycling life of Li metal anode remains challenging. Herein, it is reported that carbon nanosheet array‐loaded ferromagnetic CoF2 nanoparticles on carbon cloth (CC@CoF2/C) as an internal micro‐magnetic field source to manipulate the dynamic trajectory of Li+ deposition via the magnetohydrodynamic effect. This approach ensures uniform lithium‐ion distribution and improves deep plating capacity, achieving a prolonged cycle life of the dendrite‐free Li anode. Finite element simulations, in situ characterizations, and electrochemical tests confirm that magnetic CoF2 not only guides Li+ migration through Lorentz force to prevent dendritic growth but also improves uniform Li deposition due to the in situ conversion of LiF‐rich solid electrolyte interphase during electroplating. Meanwhile, a CC@CoF2/C‐based half‐cell operates stably over 10 000 h at 1 mA cm−2 with a low 7.8 mV overpotential. When matched with a commercial LiFePO4 cathode, the full cell reveals a high capacity of 122.96 mAh g−1 at a 2 C rate after 1000 cycles, retaining 91.95% capacity. The proposed strategy can be effectively expanded and adapted to investigate the deposition behavior of a wide range of metal anodes, offering a versatile and robust analytical framework for addressing diverse metal‐based electrochemical systems.

Anion Modulation: Enabling Highly Conductive Stable Polymer Electrolytes for Solid‐State Li‐Metal Batteries

Solid polymer electrolytes (SPEs) are promising ionic conductors for developing high‐specific‐energy solid‐state lithium metal batteries. However, developing SPEs with both high ionic conductivity and interfacial compatibility remains a challenge. Here, we propose a design concept of an anion‐modulated polymer electrolyte (termed AMPE) for high‐voltage Li metal batteries. Specifically, we design the AMPE by incorporating high‐voltage‐resistant and high charge density units with an anion receptor unit. The high‐voltage‐resistant and high charge density segments contribute to achieving a decent voltage tolerance of the polymer chains and ensure sufficient carrier ions. The anion receptor, represented by a boron‐containing molecule, promotes the generation of free Li+ by dissociating anion‐cation pairs. More importantly, the strong interaction between the electron‐deficient B and the TFSI− in the matrix promotes the anion reduction to form a stable anion‐derived mosaic‐like solid electrolyte interphase on the Li‐metal anode. As a result, the AMPE exhibits a high Li+ conductivity of 3.80×10−4 S cm−1 and effectively suppresses lithium dendrites, enabling an all‐solid‐state Li|AMPE|LiCoO2 cell to achieve a cycle life of 700 cycles at an operating voltage of 4.40 V. This design concept would inspire efforts to develop high‐performance SPEs for high‐specific‐energy solid‐state lithium metal batteries.

Anion Modulation: Enabling Highly Conductive Stable Polymer Electrolytes for Solid-State Li-Metal Batteries.

Solid polymer electrolytes (SPEs) are promising ionic conductors for developing high-specific-energy solid-state lithium metal batteries. However, developing SPEs with both high ionic conductivity and interfacial compatibility remains a challenge. Here, we propose a design concept of an anion-modulated polymer electrolyte (termed AMPE) for high-voltage Li metal batteries. Specifically, we design the AMPE by incorporating high-voltage-resistant and high charge density units with an anion receptor unit. The high-voltage-resistant and high charge density segments contribute to achieving a decent voltage tolerance of the polymer chains and ensure sufficient carrier ions. The anion receptor, represented by a boron-containing molecule, promotes the generation of free Li+ by dissociating anion-cation pairs. More importantly, the strong interaction between the electron-deficient B and the TFSI- in the matrix promotes the anion reduction to form a stable anion-derived mosaic-like solid electrolyte interphase on the Li-metal anode. As a result, the AMPE exhibits a high Li+ conductivity of 3.80×10-4 S cm-1 and effectively suppresses lithium dendrites, enabling an all-solid-state Li|AMPE|LiCoO2 cell to achieve a cycle life of 700 cycles at an operating voltage of 4.40 V. This design concept would inspire efforts to develop high-performance SPEs for high-specific-energy solid-state lithium metal batteries.

Achieving stable lithium metal anode via constructing lithiophilicity gradient and regulating Li3N-rich SEI

Three-dimensional (3D) current collectors are studied for the application of Li metal anodes in high-energy battery systems. However, they still suffer from the preferential accumulation of Li on the outermost surface, resulting from an inadequate regulation of the Li+ transport. Herein, we propose a deposition regulation strategy involving the creation of a 3D lithiophilicity gradient structure of MoN on Cu3N nanowire-grown Cu foam (MCNCF) to induce a “bottom-up” Li deposition. During the initial Li deposition, the reaction between Li and Cu3N leads to the formation of Li3N while the lithiophilic MoN located at the bottom promotes the downward Li+ migration, resulting in the generation of a Li3N gradient. Such a “bottom-up” Li3N distribution results in the formation of a stable and Li3N-rich solid electrolyte interphase layer, facilitating the Li⁺ transport and promoting a uniform Li nucleation. Computational simulations and experimental results corroborate the preferential deposition of Li on the bottom of the substrate, leading to a uniform Li nucleation and growth throughout the electrode. The MCNCF electrode offers a significantly improved reversibility of the Li deposition, achieving a lifespan of more than 1200 h at a current density of 1 mA cm−2 in symmetric Li||Li cells. Furthermore, full-cells incorporating MCNCF@Li as the negative electrode and LiFePO4 cathodes exhibit outstanding electrochemical performance with a capacity retention of over 99.5 % after 250 cycles at 1 C, which significantly surpasses the performance achieved with CF@Li or CCF@Li electrodes. This innovative design strategy for 3D metallic current collectors, featuring a lithiophilicity gradient, provides new perspectives for the development of stable Li metal anodes and, as a result, for the advancement of Li-metal batteries.

Functional Separator with Poly(Acrylic Acid)-Enabled Li2CO3-Free Garnet Coating for Long-Cycling Lithium Metal Batteries.

Lithium metal batteries (LMBs) possess a theoretical energy density far surpassing that of commercial lithium-ion batteries (LIBs), positioning them as one of the most promising next-generation energy storage systems. Modifying separators with composite coatings comprising oxide solid-state electrolyte (SSE) particles and polymers can improve the cycling stability and safety of LMBs. However, exposure to air forms Li2CO3 on oxide SSE particles, diminishing their ion flux regulation at the electrode/electrolyte interface. Utilizing the reaction of Li2CO3 with polyacrylic acid (PAA) to form lithium polyacrylate (LiPAA), an ultra-thin composite coating on polyethylene (PE) separator with Li2CO3-free Li6.4La3Zr1.4Ta0.6O12 (LLZTO) particles and LiPAA binder is fabricated in one step. The exposed Li2CO3-free LLZTO surface increases the ionic conductivity and lithium ion (Li+) transference number of the functional separator, resulting in small resistance and uniform Li deposition of the Li metal anode. Consequently, the Li//LiCoO2 cell with the functional separator exhibits a significantly improved life of 980 cycles with 80.9% capacity retention under lean-electrolyte conditions. Both the Li//LiCoO2 coin cell and pouch cell using thin Li foil anode demonstrate good cycling stability and high mechanical robustness. This study provides a green and scalable approach for fabricating advanced separators for LMBs.