Li Metal Anode Research Articles

Cycling performance of Li metal anode in localized high concentration electrolyte and dynamic mechanism analysis

In this work, we investigated the apparent cycling performance of lithium metal at different chemical compositions and series current densities; examined the microscopic morphology and thickness variation of the deposition layer on the surface of lithium metal anode and the concentration-depth distribution of trace elements in the solid electrolyte interphase (SEI) film; and characterized the kinetic behavior and features of the elementary steps (mass transfer, charge transfer, electro-crystallization) at Li-electrolyte interface using microelectrode technology and various electrochemical test methods. The results show that the lithium metal anode has better cycling performance in high concentration and localized high concentration electrolyte. At the same time, the experimental results confirm that the formation of spherical crystal nucleus is favored only under certain chemical conditions and certain reaction rate; under these conditions, the induction period and the self-smoothing process of critical crystal nucleus can be found. It suggests that there are determined causal among the apparent performance of lithium metal anode, the kinetic parameters of the interfacial charge transfer step and the electro-crystallization step, and these correlations can be used as a reference for screening and evaluating electrolyte systems and battery operating conditions, providing a reliable kinetic basis for future work.

Saccharin Sodium Coupling Fluorinated Solvent Enabled Stable Interface for High-Voltage Li-Metal Batteries.

Optimizing the electrode/electrolyte interface structure is the key to realizing high-voltage Li-metal batteries (LMBs). Herein, a functional electrolyte is introduced to synergetically regulate the interface layer structures on the high-voltage cathode and the Li-metal anode. Saccharin sodium (NaSH) as a multifunctional electrolyte additive is employed in fluorinated solvent-based electrolyte (FBE) for robust interphase layer construction. On the one hand, combining the results of ex-situ techniques and in-situ electrochemical dissipative quartz crystal microbalance (EQCM-D) technique, it can be seen that the solid electrolyte interface (SEI) layer constructed by NaSH-coupled fluoroethylene carbonate (FEC) on Li-metal anode significantly inhibits the growth of lithium dendrites and improves the cyclic stability of the anode. On the other hand, the experimental results also confirm that the cathode-electrolyte interface (CEI) layer induced by NaSH-coupled FEC effectively protects the active materials of LiCoO2 and improves their structural stability under high-voltage cycling, thus avoiding the material rupture. Moreover, theoretical calculation results show that the addition of NaSH alters the desolvation behavior of Li+ and enhances the transport kinetics of Li+ at the electrode/electrolyte interface. In this contribution, the LiCoO2ǁLi full cell containing FBE+NaSH results in a high capacity retention of 80% after 530 cycles with a coulombic efficiency of 99.8%.

Constructing an Ion‐Wall to Achieve Excellent Lithium Anodes in Li–O2 Batteries with High DN Electrolytes

AbstractFor the lithium (Li) metal anode, constructing a strong and durable protective layer with lithium‐ion permeability is crucial, especially in high donor number (DN) solvent system. High DN solvent‐based electrolytes can support both higher capacity and lower charge overpotential in the rechargeable lithium–oxygen batteries (LOBs). However, Li anodes in high DN solvent system suffer from severe corrosion and uncontrolled dendrite growth due to the unstable solid‐electrolyte interphase (SEI). Typically, this interface is formed in situ through electrochemical processes with complicated component and spatial distribution. Here, a functional molecule is introduced to construct an ion‐wall (IW) on Li surface by prechemical sequential reactions (p‐CSRs), through which the crystalline nanoparticles as bricks and amorphous hybrid compounds as the mortar can be produced to build such a “wall.” Different from the conventional SEI, this wall is not only compact and uniform, but also possess high strength, excellent passivation properties and high ionic conductivity. With these properties, the IW could suppress Li dendrites and inhabit the side reaction, supporting highly reversible Li plating/stripping behavior in high DN solvent system. As a result, the cycle stability of LOBs based on the IW protected Li anode is significantly improved.

In Situ Plasma Polymerization of Self-Stabilized Polythiophene Enables Dendrite-Free Lithium Metal Anodes with Ultra-Long Cycle Life.

Constructing a flexible and chemically stable multifunctional layer for the lithium (Li) metal anodes is a highly effective approach to improve the uneven deposition of Li+ and suppress the dendrite growth. Herein, an organic protecting layer of polythiophene is in situ polymerized on the Li metal via plasma polymerization. Compared with the chemically polymerized thiophene (C-PTh), the plasma polymerized thiophene layer (P-PTh), with a higher Young's modulus of 8.1GPa, shows strong structural stability due to the chemical binding of the polythiophene and Li. Moreover, the nucleophilic C─S bond of polythiophene facilitates the decomposition of Li salts in the electrolytes, promoting the formation of LiF-rich solid electrolyte interface (SEI) layers. The synergetic effect of the rigid LiF as well as the flexible PTh-Li can effectively regulate the uniform Li deposition and suppress the growth of Li dendrites during the repeated stripping-plating, enabling the Li anodes with long-cycling lifespan over 8000h (1mAcm-2, 1 mAhcm-2) and 2500h (10mAcm-2, 10 mAhcm-2). Since the plasma polymerization is facile (5-20min) and environmentally friendly (solvent-free), this work offers a novel and promising strategy for the construction of the forthcoming generation of high-energy-density batteries.

Regulating Electrolyte Solvation Structures via Diluent-Solvent Interactions for Safe High-Voltage Lithium Metal Batteries.

Local high concentration electrolytes (LHCEs) have been proved to be one of the most promising systems to stabilize both high voltage cathodes and Li metal anode for next-generation batteries. However, the solvation structures and interactions among different species in LHCEs are still convoluted, which bottlenecks the further breakthrough on electrolyte development. Here, it is demonstrated that the hydrogen bonding interaction between diluent and solvent is crucial for the construction of LHCEs and corresponding interphase chemistries. The 2,2,2-trifluoroethyl trifluoromethane sulfonate (TFSF) is selected as diluent with the solvent dimethoxy-ethane (DME) to prepare a non-flammable LHCE for high voltage LMBs. This is first find that the hydrogen bonding interaction between TFSF and DME solvent tailors the electrolyte solvation structures by weakening the coordination of DME molecules to Li+ cations and allows more participation of anions in the first solvation shell, leading to the formation of aggregates (AGGs) clusters which are conducive to generating inorganic solid/cathodic electrolyte interphases (SEI/CEIs). The proposed TFSF based LHCE enables the Li||NCM811 (LiNi0.8Mn0.1O2) batteries to realize >80% capacity retention with a high average Coulombic efficiency of 99.8% for 230 cycles under aggressive conditions (NCM811 cathode: 3.4mAhcm-2, cut-off voltage: 4.4V, and 20µm Li foil).

In-situ formation of quasi-solid polymer electrolyte for wide-temperature applicable Li-metal batteries

As next-generation rechargeable batteries, the development of solid-state lithium-metal batteries (LMBs) in a multitude of applications is confronted with a trade-off between high energy density, safety, and wide-temperature tolerance. Especially in cold climates, their applications are challenged by insufficient dynamics in bulk electrolyte and at electrode/electrolyte interface. Herein, a flexible, highly ionic conductive, and low-temperature applicable quasi-solid polymer electrolyte (QSPE) is designed and fabricated, which achieves a stable Li-metal anode over a wide-temperature range (−20 ∼ 60 °C). The QSPEs prepared via in-situ polymerization of polyethylene glycol (PEO)-based monomers in low-melting solvent (1,3-dioxolane (DOL) or ethyl difluoroacetate (EDFA)) endow low-temperature tolerance, prominent ionic conductivity (4.5 × 10−4 S cm−1 at −20 °C) and exceptional electrochemical performance over a wide-temperature range. Consequently, with the DOL-based QSPE (D-QSPE), the Li/D-QSPE/LiFePO4 cell presents stable, long-term cycling at −20 °C (minimal capacity degradation over 550 cycles) and excellent fast-charging capacity (capacity retention of 81 % over 1300 cycles at 5 C). Even utilizing a thin lithium foil (25 μm) and a high mass loading LiFePO4 cathode (2.5 mAh cm−2), the assembled Li/LFP cell with a N/P ratio of 1.96 still exhibits good cycling performance at −20 °C. Additionally, the EDFA-based QSPE (E-QSPE) allows LMBs with NCM811 cathodes cycling over 140 cycles (capacity retention > 95 %) at −20 °C. With the capability of circumventing sluggish ion transport kinetics of quasi-solid polymer LMBs in cold climates, the developed polymer electrolyte provides new pathways for safe, high-capability, and wide-temperature operable batteries.

Optimization of the Form Factors of Advanced Li-S Pouch Cells.

Lithium-sulfur (Li-S) batteries hold immense promise as next-generation energy storage due to their high theoretical energy density (2600Whkg⁻¹), low cost, and non-toxic nature. However, practical implementation faces challenges, primarily from Li polysulfide (LiPS) shuttling within the cathode and Li dendrite growth at the anode. Optimized electrodes/electrolytes design effectively confines LiPS to the cathode, boosting cycling performance in coin cells to up to hundreds of cycles. Scaling up to larger pouch cells presents new obstacles, requiring further research for long-term stability. A 1.45Ah pouch cell, with optimized sulfur loading and electrolyte/sulfur ratio is developed, which delivers an energy density of 151Whkg-1 with 70% capacity retention up to 100 cycles. Targeting higher energy density (180Whkg-1), the developed 1Ah pouch cell exhibits 68% capacity retention after 50 cycles. Morphological analysis reveals that pouch cell failure is primarily from Li metal powdering and resulting polarization, rather than LiPS shuttling. This occurs for continuous Li ion stripping/plating during cycling, leading to dendrite growth and formation of non-reactive Li powder, especially under high currents. These issues increase ion diffusion resistance and reduce coulombic efficiency over time. Therefore, the study highlights the importance of a protected Li metal anode for achieving high-energy-dense batteries.

Electrolyte Additive for Interfacial Engineering of Lithium and Zinc Metal Anodes

AbstractElectrolytes play a crucial role in facilitating the ionic movement between cathode and anode, which is essential for the flow of electric current during the charging and discharging process of the rechargeable batteries. In particular, electrolyte additives are considered as effective and economical approaches into the advancements of the battery technologies in both the conventional non‐aqueous and burgeoning aqueous electrolyte systems. Herein, a systematic and comprehensive review of the electrolyte additives is reported for the interfacial engineering of Li and Zn metal anodes in the non‐aqueous and aqueous electrolytes, respectively. The types of electrolyte additives and their corresponding functionalities for the protection of these two metal anodes are discussed along with the electrochemical features of solid electrolyte interphase (SEI) derived from electrolyte additives. The recent progress on electrolyte additives for these two battery systems are also addressed from the perspectives of electrode, electrolyte, and the associated SEI. Finally, the outlook and perspective on the current issues and future directions in the field of electrolyte additive engineering are presented for next‐generation battery technologies beyond the conventional Li‐ion batteries.

Mechanically Interlocked Interphase with Energy Dissipation and Fast Li-Ion Transport for High-Capacity Lithium Metal Batteries.

Constructing an artificial solid electrolyte interphase (ASEI) on Li metal anodes (LMAs) is a potential strategy for addressing the dendrite issues. However, the mechanical fatigue of the ASEI caused by stress accumulation under the repeated deformation from the Li plating/stripping is not taken seriously. Herein, this work introduces a mechanically interlocked [an]daisy chain network (DC MIN) into the ASEI to stabilize the Li metal/ASEI interface by combining the functions of energy dissipation and fast Li-ion transport. The DC MIN featured by large-range molecular motions is cross-linked via efficient thiol-ene click chemistry; thus, the DC MIN has flexibility and excellent mechanical properties. As an ASEI, the crown ether units in DC MIN not only interact with the dialkylammonium of a flexible chain, forming the energy dissipation behavior but also coordinate with Li ion to support the fast Li-ion transport in DC MIN. Therefore, a stable 2800h-symmetrical cycling (1mA cm-2 ) and an excellent 5 C-rate (full cell with LiFePO4 ) performance are achieved by DC MIN-based ASEI. Furthermore, the 1-Ah pouch cell (LiNi0.88 Co0.09 Mn0.03 O2 cathode) with DC MIN-coated LMA exhibits improved capacity retention (88%) relative to the Control. The molecular design of DC MIN provides new insights into the optimization of an ASEI for high-energy LMAs.

Custom-form iron trifluoride Li-batteries using material extrusion and electrolyte exchanged ionogels

Custom-form factor batteries fabricated in non-conventional shapes can maximize the overall energy density of the systems they power, particularly when used in conjunction with energy dense materials (e.g., Li metal anodes and conversion cathodes). Additive manufacturing (AM), and specifically material extrusion (ME), have been shown as effective methods for producing custom-form cell components, particularly electrodes. However, the AM of several promising energy dense materials (conversion electrodes such as iron trifluoride) have yet to be demonstrated or optimized. Furthermore, the integration of multiple AM produced cell components, such as electrodes and separators, along with a custom package remains largely unexplored. In this work, iron trifluoride (FeF3) and ionogel (IG) separators are conformally printed using ME onto non-planar surfaces to enable the fabrication of custom-form Li-FeF3 batteries. To demonstrate printing on non-planar surfaces, cathodes and separators were deposited onto cylindrical rods using a 5-axis ME printer. ME printed FeF3 was shown to have performance commensurate with FeF3 cast using conventional means, both in coin cell and cylindrical rod formats, with capacities exceeding 700 mAh/g on the first cycle and ranging between 600 and 400 mAh/g over the next 50 cycles. Additionally, a ME process for printing polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) based IGs directly onto FeF3 is developed and enabled using an electrolyte exchange process. In coin cells, this process is shown to produce cells with similar capacity to cells built with Celgard separators out to 50 cycles, with the exception that cycling instabilities are observed during cycles 8–20. When using printed and exchanged IGs in a custom cylindrical cell package, 6 stable high-capacity cycles are achieved. Overall, this work demonstrates approaches for producing high-energy-density Li-FeF3 cells in coin and cylindrical rod formats, which are translatable to customized, arbitrary geometries compatible with ME printing and electrolyte exchange.

Synergistic Regulation of Intrinsic Lithiophilicity and Mass Transport Kinetics of Non‐Lithium‐Alloying Nucleation Sites for Stable Operation of Low N/P Ratio Lithium Metal Batteries

AbstractConstructing functional materials on a 3D host is an efficient strategy to tackle issues of lithium (Li) metal anodes. Although non‐Li‐alloying materials provide structural stability during cycling due to reduced lattice distortions, low lithiophilicity and sluggish mass transport kinetics limit their functionality. Herein, a synergistic strategy is proposed to improve intrinsic lithiophilicity and mass transport kinetics of non‐Li‐alloying nucleation sites and demonstrate its remarkable efficacy. Two carbon fiber (CF) hosts coated by non‐Li‐alloying nanosheets with and without oxygen‐enriched carbon filler (OCF) as lithiophilicity and mass transport booster (OCF‐DSC@CF and DSC@CF, respectively) are constructed and their physiochemical properties are systematically evaluated to reveal the efficacy of OCF. By advanced characterization techniques, including 3D tomography and location‐dependent electron energy loss spectroscopies, the complex heterostructure of OCF‐DSC@CF with distinctive roles of each constituent is clearly identified. As verified by theoretical and electrochemical analyses, the incorporation of OCF endows OCF‐DSC@CF with substantially improved lithiophilicity and mass transport kinetics. Moreover, OCF‐DSC@CF induces a multifunctional SEI enriched with LiF and LiCx, which exhibits well‐balanced electrical resistivity and ionic conductivity. Benefiting from these attributes, OCF‐DSC@CF exhibits an unprecedented cyclability under a low N/P ratio of 1.8, achieving 700 cycles at 0.5C with an exceptional capacity retention of 97.8%.

Dual LiF/LiCl‐Rich Solid Electrolyte Interphases with Robust and Li+‐conductive Characteristics for 4.8 V Lithium Metal Batteries

AbstractLithium metal batteries, which are constructed by lithium‐rich manganese‐based oxide (LRMO) cathode and Li metal anode, have attracted intensive attention due to its high energy density. However, the instability of both cathode and anode limits the practical application due to undesirable electrolyte decomposition at high voltage. To address these issues, an electrolyte engineering strategy is proposed for constructing robust, highly Li+‐conductive solid electrolyte interphases on both cathode and anode with chlorobenzene as the additive. Due to the high mechanical stability and interface dynamics of the LiCl‐endorsed, LiF‐rich cathode electrolyte interphase, both the electrolyte decomposition and transition metal ion dissolution are effectively inhibited. Meanwhile, robust LiF/LiCl‐rich solid electrolyte interphase can effectively repress the overgrowth of Li dendrites. The Li||LRMO battery with optimized 2.0 wt.% chlorobenzene demonstrates a high‐capacity retention of 86.1% after 200 cycles at 0.5 C.

A layered multifunctional framework based on polyacrylonitrile and MOF derivatives for stable lithium metal anode

Composite Li metal anodes based on three-dimensional (3D) porous frameworks have been considered as an effective material for achieving stable Li metal batteries with high energy density. However, uneven Li deposition behavior still occurs at the top of 3D frameworks owing to the local accumulation of Li ions. To promote uniform Li deposition without top dendrite growth, herein, a layered multifunctional framework based on oxidation-treated polyacrylonitrile (OPAN) and metal-organic framework (MOF) derivatives was proposed for rationally regulating the distribution of Li ions flux, nucleation sites, and electrical conductivity. Profiting from these merits, the OPAN/carbon nano fiber-MOF (CMOF) composite framework demonstrated a reversible Li plating/stripping behavior for 500 cycles with a stable Coulombic efficiency of around 99.0% at the current density of 2 mA/cm2. Besides, such a Li composite anode exhibited a superior cycle lifespan of over 1300 h under a low polarized voltage of 18 mV in symmetrical cells. When the Li composite anode was paired with LiFePO4 (LFP) cathode, the obtained full cell exhibited a stable cycling over 500 cycles. Moreover, the COMSOL Multiphysics simulation was conducted to reveal the effects on homogeneous Li ions distribution derived from the above-mentioned OPAN/CMOF framework and electrical insulation/conduction design. These electrochemical and simulated results shed light on the difficulties of designing stable and safe Li metal anode via optimizing the 3D frameworks.

Structural Design of 3D Current Collectors for Lithium Metal Anodes: A Review.

Due to the ultrahigh theoretical specific capacity (3860 mAh g-1) and low redox potential (-3.04 V vs. standard hydrogen electrode), Lithium (Li) metal anode (LMA) received increasing attentions. However, notorious dendrite and volume expansion during the cycling process seriously hinder the development of high energy density Li metal batteries. Constructing three-dimensional (3D) current collectors for Li can fundamentally solve the intrinsic drawback of hostless for Li. Therefore, this review systematically introduces the design and synthesis engineering and the current development status of different 3D collectors in recent years (the current collectors are divided into two major parts: metal-based current collectors and carbon-based current collectors). In the end, some perspectives of the future promotion for LMA application are also presented.

Compositionally Sequenced Interfacial Layers for High-Energy Li-Metal Batteries.

Electrolyte additives with multiple functions enable the interfacial engineering of Li-metal batteries (LMBs). Owing to their unique reduction behavior, additives exhibit a high potential for electrode surface modification that increases the reversibility of Li-metal anodes by enabling the development of a hierarchical solid electrolyte interphase (SEI). This study confirms that an adequately designed SEI facilitates the homogeneous supply of Li+, nonlocalized Li deposition, and low electrolyte degradation in LMBs while enduring the volume fluctuation of Li-metal anodes on cycling. An in-depth analysis of interfacial engineering mechanisms reveals that multilayered SEI structures comprising mechanically robust LiF-rich species, electron-rich P-O species, and elastic polymeric species enabled the stable charge and discharge of LMBs. The polymeric outer SEI layer in the as-fabricated multilayered SEI could accommodate the volume fluctuation of Li-metal anodes, significantly enhancing the cycling stability Li||LiNi0.8Co0.1Mn0.1O2 full cells with an electrolyte amount of 3.6gAh-1 and an areal capacity of 3.2mAhcm-2. Therefore, this study confirms the ability of interfacial layers formed by electrolyte additives and fluorinated solvents to advance the performance of LMBs and can open new frontiers in the fabrication of high-performance LMBs through electrolyte-formulation engineering.

A Highly Stable Practical Li Metal Anode via Interphase Regulation and Nucleation Induction

AbstractThe practical utilization of Li metal anodes has been significantly plagued by the challenges of uncontrollable dendritic Li growth and poor interphase instability. Here, the study reports a novel strategy to strengthen interphase and give highly efficient active seeds concurrently to stabilize Li metal via a highly lithiophilic In2O3 decorated porous scaffold. In situ configurated fast‐ion‐transport Li2O‐strengthened interphase layer cooperatively with highly efficient Li13In3 nucleation induction can endow the uniform Li nucleation/growth and high Li utilization efficiency. As a result, the achieved modified Li metal manifests high Coulombic efficiency, ultrahigh rate performance (5 mA cm−2), and ultra‐long lifespan cycling durability (7975 cycles). Importantly, the established Li|LiFePO4 cells exhibit long‐term cycling durability over 600 cycles at 1 C with an ultralow decay rate of ca. 0.017% per cycle. Moreover, the Li|LiCoO2 pouch cells with ultrahigh areal capacity of ca. 3.89 mAh cm−2 also exhibit extraordinarily prolonged cycling performance with excellent capacity retention despite extremely harsh cycling conditions of low negative‐to‐positive‐capacity (N/P) ratio of ca. 1.7 and lean electrolyte of ca. 4.9 g Ah−1. This work enlightens a facile and effective avenue toward highly stable Li metal anode toward reliable practicability.

A crown-ether-enabled eutectic electrolyte for ultra-high temperature lithium metal batteries

Lithium metal batteries (LMBs) are generally restricted to operating below 60 °C and not suitable for high-temperature applications due to their thermally susceptible carbonate electrolytes. Deep eutectic electrolytes (DEE) with strong supramolecular interactions are a new emerging type of liquid-state ionic conductors, and here we present a novel DEE—which is composed of 18-crown-6 ether (18C6) and lithium difluoro(oxalate)borate (LiDFOB)—to extend the working temperature up to 150 °C. Via combined physiochemical and theoretical characterizations, it is identified that such high thermotolerance is a result of specific solvation structure of Li(18C6)4DFOB with multiple Li–O interactions. Moreover, our newly developed DEE triggers the formation of a B/F-rich solid electrolyte interphase, contributing to superior thermal stability and enhanced compatibility with Li-metal anodes. Consequently, Li|DEE|LiFePO4 cell exhibits great tolerance to extremely high temperatures with a capacity reversibility of 83 % after 250 cycles at 120 °C. Even at 150 °C, the cell can retain 77 % of the initial capacity (105 mAh g−1) after 100 cycles. To our knowledge, the DEE is the first liquid electrolyte for LMBs working at unprecedented high-temperature. This work opens intriguing perspectives to design novel electrolytes for demanded performance of LMBs across a wide temperature range.

High-Safety Electrolytes with an Anion-Rich Solvation Structure Tuned by Difluorinated Cations for High-Voltage Lithium Metal Batteries.

As next-generation energy storage devices, lithium metal batteries (LMBs) must offer high safety, high-voltage resistance, and a long life span. Electrolyte engineering is a facile strategy to tailor the interfacial chemistry of LMBs. In particular, the solvation structure and derived solid electrolyte interphase (SEI) are crucial for a satisfactory battery performance. Herein, a novel middle-concentrated ionic liquid electrolyte (MCILE) with an anion-rich solvation structure tuned by difluorinated cations is demonstrated to achieve ultrahigh safety, high-voltage stability, and excellent ternary-cathode compatibility. Novel gem-difluorinated cations first synthesized for prestoring fluorine on positively charged species, not only preferentially adsorb in the inner-Helmholtz layers, but also participate in regulating the Li+ solvation structure, resulting in a robust interphase. Moreover, these weak interactions in the Li+ solvation structure including anion-solvent and ionic liquid (IL) cation-solvent pairs are first revealed, which are beneficial for promoting an anion-dominated solvation structure and the desolvation process. Benefiting from the unique anion-rich solvation structure, a stable hetero-SEI structure is obtained. The designed MCILE exhibits compatibility with Li metal anode and the high-voltage ternary cathode at high temperatures (60°C). This work provides a new approach for regulating the solvation structure and electrode interphase chemistry of LMBs via difluorinated IL cations.

Lateral growth of Lithium dendrite enforced by 3D porous Core@Shell-Cu@Li3N protective layer toward Long-Life Lithium metal anode

Li metal is promising as the anode for next-generation Li-ion batteries; however, uncontrollable dendrite growth and severe side reactions between the Li metal and electrolyte greatly restrict its commercialization. Here, a 3D porous protective layer constructed by core@shell-Cu@Li3N particles is developed to solve the above issues. This protective layer is easily prepared just by one-step dip coating in Cu(NO3)2/N-methyl-2-pyrrolidone (NMP) solution. Due to rapid Li+ transport and good wettability of the protective layer, it effectively modulates Li+ flux and thus homogenizes Li deposition. More importantly, as confirmed by both the experimental results and phase-field simulations, the 3D porous protective layer enforces the Li dendrite to laterally grow to form an interconnected network, which causes that the subsequent Li deposition is constrained and filled in the inner space rather than savage growth. Therefore, both the symmetric battery and full cell constructed by the protected Li electrode displays much longer lifespan than the one with bare Li even in unstable liquid carbonate electrolyte. Also, this protective layer is demonstrated to be compatible with Li1+xAlxTi2−x (PO4)3 (LATP) solid-state electrolyte by suppressing the side reactions. This work paves a new and facile strategy for developing high-performance Li metal anode.

Dendrite-suppressed Li deposition enabled by surface-tailored carbon-based current collectors for high-rate and stable Li-metal batteries

Lithium (Li)-metal batteries (LMBs) are considered as one of the most promising next-generation batteries due to the exceptionally low redox potential and high specific capacity of the Li metal anode. However, their practical application remains challenging due to problems such as Li dendrites growth and poor Coulombic efficiency (CE) during cycling. Among the various approaches proposed to solve these challenges, the introduction of 3D current collectors has been proven effective for suppressing the growth of dendritic Li. Nevertheless, the surface properties of 3D current collectors have been somewhat overlooked in existing studies. In this work, we assessed three distinct carbon nanotube (CNT)-based current collectors (namely, CNT, oxidized CNT (ONT), and reduced ONT (rONT)) to investigate the effects of their surface properties and compositions on the Li deposition process and, hence, the electrochemical stability of the resulting LMBs. The pristine CNT-based current collector exhibits a poor electrolyte wettability, thus resulting in a rapid decline in CE over successive cycles. In contrast, the ONT current collector shows enhanced electrolyte wettability with lithiophilic surface, which significantly improves the interfacial kinetics and cycling stability. Moreover, after the subsequent reduction process, the rONT current collector exhibits a higher electrical conductivity than the ONT current collector while maintaining the favorable electrolyte wettability. Consequently, the Li|rONT cell delivers a more stable cycling performance than the Li|ONT cell at high current densities. These results demonstrate that the electrochemical performances of the LMBs can be significantly improved by suitably modifying the surface characteristics of the current collectors.