Lithiated NiCo2O4 Nanorods Anchored on 3D Nickel Foam Enable Homogeneous Li Plating/Stripping for High-Power Dendrite-Free Lithium Metal Anode

3D-hosted lithium metal anodes

Lithium metal anodes are an appealing choice for rechargeable batteries due to their exceptionally high theoretical capacity of about 3860 mA h g-1. However, the uneven plating/stripping of lithium metal anodes leads to serious dendrite growth and low coulombic efficiency, curtailing their practical applications. The 3D scaffold/host strategy emerges as a promising approach that concurrently mitigates volume changes and dendrite growth. This review provides an overview of the regulating mechanisms behind scaffold/host materials for dendrite-free applications, tracing their historical development and recent progress across five key stages: material texture selection, lithiophilic modification, structural design, multi-strategy integration, and practical implementation. Additionally, scaffold/host materials are categorized based on their material texture, with a thorough examination of their respective advantages and drawbacks. Furthermore, this tutorial outlines the obstacles and complexities associated with implementing scaffold/host strategies. Finally, the determining factors that affect the electrochemical performances of scaffold/host materials are discussed, along with possible design criteria and future development prospects. This tutorial aims to provide guidance for researchers on the design of advanced scaffold/host materials for advanced Li metal anodes for batteries.

A Three-Dimensional (3D) Framework of Freestanding Vanadium Nitride Nanowires for Dendrite-Free and Long Life-Span Lithium Metal Anodes

Lithium (Li) metal is a promising anode candidate for high-energy-density batteries owing to its high theoretical capacity and low electrochemical potential. However, uneven Li nucleation, uncontrollable dendritic growth, infinite voltage change and even safety issues hinder its commercial application. Herein, a three-dimensional (3D) framework of freestanding vanadium nitride nanowires (VN NWs) is established as Li host for dendrite-free Li metal anode. A lithiophilic Li3 N interlayer which in situ formed by the surface reaction between molten Li and VN NWs is utilized to guide a uniform Li nucleation and deposition within the skeleton, as well as avoid the dendrite formation. Meanwhile, VN NWs can decrease local current density, homogenize Li-ion flux and accommodate volume fluctuations of the anode due to its 3D structure with high electron conductivity. Thus, the corresponding composite Li metal anode delivers a long-life span of 500 cycles (1000 h) at a current density of 0.5 mA cm-2 , and exhibits lower nucleation over-potential and voltage hysteresis at different current densities from 0.5~5 mA cm-2 in carbonate electrolyte. In conclusion, this work provides a new type of scaffold with both high electronic conductivity and excellent lithiophilicity for stable Li anodes.

Spatially Confined Li Growth on Honeycomb-like Lithiophilic Layered Double Hydroxide Nanosheet Arrays toward a Stable Li Metal Anode

A lithium metal anode (LMA) is appealing due to its high theoretical capacity and low electrochemical potential. Unfortunately, the practical application of LMAs is restricted by the uncontrollable Li dendrite growth and tremendous volume change. Herein, lithiophilic honeycomb-like layered double hydroxide (LDH) nanosheet arrays supported on a flexible carbon cloth (NiMn-LDHs NAs@CC) are synthesized as the Li host to spatially confine the Li deposition, guiding Li growth via a conformal and uniform manner. First, the lithiophilic NiMn-LDHs NAs as nucleation seeds render the CC substance outstanding lithiophilicity and reduce the nucleation barrier. The hierarchical honeycomb-like structure then directs the oriented Li deposition and provides an open channel for fast ion transport. Finally, the CC skeleton offers a high specific surface for decreasing the inhomogeneous distribution of the current density and enough space for alleviating the volume variations, synergistically inhibiting the dendritic Li growth. As a consequence, the NiMn-LDHs NAs@CC symmetric cell exhibits a low overpotential of less than 17 mV at 2 mA cm^-2 and a long lifespan of 2100 h at 3 mA cm^-2. In addition, when paired with the LiNiCoMnO₂ (NCM111) cathode, the NiMn-LDHs NAs@CC@Li full cell presents enhanced cycling stability and rate capability in comparison to the CC@Li full cell, implying the great potential of the NiMn-LDHs NAs@CC in stabilizing the LMA.

Limited Lithium Loading Promises Improved Lithium-Metal Anodes in Interface-Modified 3D Matrixes

Confining Li metal in a three-dimensional (3D) matrix has been proven effective in improving the Li-metal anodes; however, in most studies, the loading of Li in the 3D matrix is far excessive, resulting in a dense bulk Li-metal anode with a low Li-utilization rate, forfeiting the effect of the 3D matrix. Here, we show that limiting the loading of Li metal within an interface-modified 3D carbon matrix not only increases the Li-utilization rate but also improves the electrochemical performance of the Li-metal anode. We use lithiophilic Fe₂O₃ granules anchored on a 3D carbon fiber scaffold to guide molten Li dispersion onto the fibers with controlled Li loading. Limiting Li loading maximizes the interface lithiophilic effect of the Fe₂O₃ granules while preserving sufficient space for electrolyte infusion, collectively ensuring uniform Li deposition and fast Li⁺ transport kinetics. The Li anode with limited Li dosage achieves remarkably improved Li-anode performances, including long lifespan, low voltage polarization, and low electrochemical resistance in both the symmetric cells and full cells. The improved electrochemical performance of the limited Li anode substantiates the importance to reduce Li loading from a fresh perspective and provides an avenue for building practical Li-metal batteries.

Electrolyte Chemistry in 3D Metal Oxide Nanorod Arrays Deciphers Lithium Dendrite-Free Plating/Stripping Behaviors for High-Performance Lithium Batteries

Lithium dendrite-free deposition is crucial to stabilizing lithium batteries, where the three-dimensional (3D) metal oxide nanoarrays demonstrate an impressive capability to suppress dendrite due to the spatial effect. Herein, we introduce a new insight into the ameliorated lithium plating process on 3D nanoarrays. As a paradigm, novel 3D Cu₂O and Cu nanorod arrays were in situ designed on copper foil. We find that the dendrite and electrolyte decomposition can be mitigated effectively by Cu₂O nanoarrays, while the battery failed fast when the Cu nanoarrays were used. We show that Li₂O (i.e., formed in the lithiation of Cu₂O) is critical to stabilizing the electrolyte; otherwise, the electrolyte would be decomposed seriously. Our viewpoint is further proved when we revisit the metal (oxide) nanoarrays reported before. Thus, we discovered the importance of electrolyte stability as a precondition for nanoarrays to suppress dendrite and/or achieve a reversible lithium plating/stripping for high-performance lithium batteries.

Electroless Formation of a Fluorinated Li/Na Hybrid Interphase for Robust Lithium Anodes

Engineering a stable solid electrolyte interphase (SEI) is one of the critical maneuvers in improving the performance of a lithium anode for high-energy-density rechargeable lithium batteries. Herein, we build a fluorinated lithium/sodium hybrid interphase via a facile electroless electrolyte-soaking approach to stabilize the repeated plating/stripping of lithium metal. Jointed experimental and computational characterizations reveal that the fluorinated hybrid SEI mainly consisting of NaF, LiF, Li_xPO_yF_z, and organic components features a mosaic polycrystalline structure with enriched grain boundaries and superior interfacial properties toward Li. This LiF/NaF hybrid SEI exhibits improved ionic conductivity and mechanical strength in comparison to the SEI without NaF. Remarkably, the fluorinated hybrid SEI enables an extended dendrite-free cycling of metallic Li over 1300 h at a high areal capacity of 10 mAh cm^-2 in symmetrical cells. Furthermore, full cells based on the LiFePO₄ cathode and hybrid SEI-protected Li anode sustain long-term stability and good capacity retention (96.70% after 200 cycles) at 0.5 C. This work could provide a new avenue for designing robust multifunctional SEI to upgrade the metallic lithium anode.

Advances in the Design of 3D-Structured Electrode Materials for Lithium-Metal Anodes

Although the lithium-metal anode (LMA) can deliver a high theoretical capacity of ≈3860 mAh g^-1 at a low redox potential of -3.040 V (vs the standard hydrogen electrode), its application in rechargeable batteries is hindered by the poor Coulombic efficiency and safety issues caused by dendritic metal growth. Consequently, careful electrode design, electrolyte engineering, solid-electrolyte interface control, protective layer introduction, and other strategies are suggested as possible solutions. In particular, one should note the great potential of 3D-structured electrode materials, which feature high active specific surface areas and stereoscopic structures with multitudinous lithiophilic sites and can therefore facilitate rapid Li-ion flux and metal nucleation as well as mitigate Li dendrite formation through the kinetic control of metal deposition even at high local current densities. This progress report reviews the design of 3D-structured electrode materials for LMA according to their categories, namely 1) metal-based materials, 2) carbon-based materials, and 3) their hybrids, and allows the results obtained under different experimental conditions to be seen at a single glance, thus being helpful for researchers working in related fields.

A Full Li-S Battery with Ultralow Excessive Li Enabled via Lithiophilic and Sulfilic W2 C Modulation

The practical application of Li-S batteries demands low cell balance (Li_capacity /S_capacity ), which involves uniform Li growth, restrained shuttle effect, and fast redox reaction kinetics of S species simultaneously. Herein, with the aid of W₂ C nanocrystals, a freestanding 3D current collector is applied as both Li and S hosts owing to its lithiophilic and sulfilic property. On the one hand, the highly conductive W₂ C can reduce Li nucleation overpotentials, thus guiding uniform Li nucleation and deposition to suppress Li dendrite growth. On the other hand, the polar W₂ C with catalytic effect can enhance the chemisorption affinity to lithium polysulfides (LiPSs) and guarantee fast redox kinetics to restrain S species in cathode region and promote the utilization of S. Surprisingly, a full Li-S battery with ultralow cell balance of 1.5:1 and high sulfur loading of 6.06 mg cm^-2 shows obvious redox plateaus of S and maintains high reversible specific capacity of 1020 mAh g^-1 (6.2 mAh cm^-2 ) after 200 cycles. This work may shed new sights on the facile design of full Li-S battery with low excessive Li supply.

Advances of Carbon-Based Materials for Lithium Metal Anodes

Lithium metal with high theoretical specific capacity (3,860 mAh g^-1), low mass density, and low electrochemical potential (-3. 040 V vs. SHE) is an ideal candidate of the battery anode. However, the challenges including dendrite propagation, volume fluctuation, and unstable solid electrolyte interphase of lithium metal during the lithium plating impede the practical development of Lithium metal batteries (LMBs). Carbon-based materials with diverse structures and functions are ideal candidates to address the challenges in LMBs. Herein, we briefly summarize the main challenges as well as the recent achievements of lithium metal anode in terms of utilizing carbon-based materials as electrolyte additives, current collectors and composite anodes. Meanwhile, we propose the critical challenges that need to be addressed and perspectives for ways forward to boost the advancement of LMBs.

Recent advances in research on anodes for safe and efficient lithium-metal batteries

The revival of lithium metal anodes (LMAs) makes it a potent influence on the battery research community in the recent years after the popularity of Li-ion batteries with graphite anodes. The main reason is due to the over ten-fold increase in the capacity of LMAs when compared with that obtained when using graphite, as well as the low redox potential of Li/Li⁺. However, the full potential of LMAs is heavily inhibited by several factors, such as dendrite growth, pulverization, side reactions, and volume changes. These adversities lower the cell's Coulombic efficiency dramatically if operated without massively excessive Li usage. In this review, we first introduce some of the most significant progresses made in the understandings of the charging/discharging processes at the anode. The importance of combining advanced characterization techniques with classical methods is highlighted. In particular, we aim to explore the hidden links between those studies for obtaining deeper insights. Two main categories of solutions to address common problems, namely, lithium-electrolyte interfacial engineering and three-dimensional hosting of Li, are subsequently illustrated, where each subsection takes a different methodological perspective to demonstrate the relevant state-of-the-art studies. Some interesting approaches to stop dendrites and a brief note on the practical aspects of lithium-metal batteries are provided, too. This review concludes with our essential discoveries from the current literature and valuable suggestions for future LMA research.

Nitrogen-doped polymer nanofibers decorated with Co nanoparticles for uniform lithium nucleation/growth in lithium metal batteries

Lithium (Li) metal is deemed to be the most promising anode for new-generation lithium batteries due to its high specific capacity (3860 mA h g-1) and low redox potential (-3.04 V vs. SHE). However, Li dendritic formation during battery cycling results not only in poor performance, such as low coulombic efficiency and short cycling, but also serious safety risks such as fire and explosion. In this paper, we propose a novel interlayer with a 3D network which is rich in N-containing functional groups and Co nanoparticles to guide uniform Li nucleation/growth and thus relieve the Li dendritic formation. As a result, the as-designed composite delivers an ultra-long lifespan of 1500 h with a small and stable voltage profile of 38.1 mV for symmetric cells. The composite electrode also exhibits a prominent electrochemical performance in full cells with LiFePO4 as the cathode for lithium ion batteries (LIBs). Our findings provide strong support for inducing the uniform nucleation of Li by introducing lithiophilic sites, which is important for inhibiting Li dendritic formation.