Rechargeable batteries are regarded as the most promising candidates for practical applications in portable electronic devices and electric vehicles. In recent decades, lithium metal batteries (LMBs) have been extensively studied due to their ultrahigh energy densities. However, short lifespan and poor safety caused by uncontrollable dendrite growth hinder their commercial applications. Besides, a clear understanding of Li nucleation and growth has not yet been obtained. In this Review, the failure mechanisms of Li metal anodes are ascribed to high reactivity of lithium, virtually infinite volume changes, and notorious dendrite growth. The principles of Li deposition nucleation and early dendrite growth are discussed and summarized. Correspondingly, four rational strategies of controlling nucleation are proposed to guide Li nucleation and growth. Finally, perspectives for understanding the Li metal deposition process and realizing safe and high-energy rechargeable LMBs are given.

Solid state lithium metal batteries are the most promising next-generation power sources owing to their high energy density and safety. Solid polymer electrolytes (SPE) have gained wide attention due to the excellent flexibility, manufacturability, lightweight, and low-cost processing. However, fatal drawbacks of the SPE such as the insufficient ionic conductivity and Li + transference number at room temperature restrict their practical application. Here vertically aligned 2D sheets are demonstrated as an advanced filler for SPE with enhanced ionic conductivity, Li + transference number, mechanical modulus, and electrochemical stability, using vermiculite nanosheets as an example. The vertically aligned vermiculite sheets (VAVS), prepared by the temperature gradient freezing, provide aligned, continuous, run-through polymer-filler interfaces after infiltrating with polyethylene oxide (PEO)-based SPE. As a result, ionic conductivity as high as 1.89 × 10 −4 S cm −1 at 25 °C is achieved with Li + transference number close to 0.5. Along with their enhanced mechanical strength, Li|Li symmetric cells using VAVS-CSPE are stable over 1300 h with a low overpotential. LiFePO 4 in all-solid-state lithium metal batteries with VAVS-CSPE could deliver a specific capacity of 167 mAh g −1 at 0.1 C at 35 °C and 82% capacity retention after 200 cycles at 0.5 C.

Electroplating has been studied for centuries, not only in the laboratory but also in industry for machinery, electronics, automobile, aviation, and other fields. The lithium‐metal anode is the Holy Grail electrode because of its high energy density. But the recyclability of lithium‐metal batteries remains quite challenging. The essence of both conventional electroplating and lithium plating is the same, reduction of metal cations. Thus, industrial electroplating knowledge can be applied to revisit the electroplating process for lithium‐metal anodes. In conventional electroplating, some strategies like using additives, modifying substrates, applying pulse current, and agitating electrolyte have been explored to suppress dendrite growth. These methods are also effective in lithium‐metal anodes. Inspired by that, we revisit the fundamental electroplating theory for lithium‐metal anodes in this Minireview, mainly drawing attention to the theory of electroplating thermodynamics and kinetics. Analysis of essential differences between traditional electroplating and plating/stripping of lithium‐metal anodes is also presented. Thus, industrial electroplating knowledge can be applied to the electroplating process of lithium‐metal anodes to improve commercial lithium‐metal batteries and the study of lithium plating/stripping can further enrich the classical electroplating technique.

Lithium metal anodes are deemed as the “Holy Grail” for next generation high energy density batteries, due to the reported highest specific capacity (3860 mAh g−1) and the lowest negative electrochemical potential (−3.04 V vs the standard hydrogen electrode). However, the notorious tip‐induced dendrite growth leads to low Coulombic efficiency, restricted lifespan, and even catastrophic short‐circuits, blocking the roadmap of their commercialization. Here, a magnetic field is introduced into the lithium plating process. The Li+ concentrated around the tips by the uneven electric field distribution can be taken off the hotpots by the Lorentz force and the tip dendrite growth can be eliminated. The relationship between current density and magnetic flux intensity is established by monitoring the deposited lithium morphology as well as the electrochemical performance, which is confirmed by mathematic modeling and COMSOL Multiphysics simulation. It is also demonstrated that the Lorentz force–induced tip dendrite elimination can be utilized practically by assembling permanent magnet‐containing prototype coin cell. It is anticipated that this physical approach can be applied to other high energy density systems as well.

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.

Li metal batteries are considered a promising candidate for next‐generation rechargeable batteries. However, the practical application of Li metal batteries has been hindered by many challenges, especially the cycling stability of Li anodes due to their uncontrollable dendrite growth, volume fluctuation, and side reactions. These problems are more severe under high‐rate charge/discharge process. Therefore, the realization of stable cycling of Li anodes under high current density is crucial for the practical application of Li metal batteries. In this Progress Report, the authors focus on the stability of metallic Li through interphase design or microstructure construction. The advantages and drawbacks of the first‐generation 3D scaffolds are summarized, and a review of recent research progress in this area is generated. As high‐rate cycling of metallic Li is a complex dynamic problem, a scaffold with high mixed ionic and electronic conductivity may be a promising approach. The different design strategies of mixed ion and electron‐conductive scaffolds working with liquid and solid electrolytes are discussed, along with their technical challenges. Further directions of mixed ion and electron‐conductive scaffolds are also proposed.

deteriorated performance. What is more, once the dendrite tip impales the separator, the short circuit between the two poles may release tremendous heat in a second, even causing combustion or explosion of the batteries. [3] Several strategies have been explored to improve the cycle stability of MAs. To suppress the dendrite morphology, additives are added into the liquid electrolytes to optimize the plating environment. These additives are mostly related to SEI stabilization and self-healing electrostatic shield formation. [4] Fabricating anions-fixed nanostructured electrolyte or using high salt concentration electrolyte can increase the cationic transference number to slow down the dendrite growth rate. [5] Another methodology is to build a physical barrier with high mechanical strength to prevent dendrite puncture, including fabricating artificial SEI, using solid-state electrolytes (SSEs), as well as modifying separators. [6] The shear modulus needs to be much higher than that of Li dendrites (3.4 GPa) to resist the tensile stress. [7] In addition, nanostructured anodes, including confining Li/Na metal into hosts and 3D current collectors design, can dissipate the current density and mitigate the volume change during cycles so that the plating/stripping morphology is well regulated. [8] Thanks to the unique chemical, physical, and mechanical properties, many scientists attempt to integrate two-dimensional (2D) materials into modifying metal battery systems. Some key developments are summarized in Figure 1 and Table 1. 2D materials are a class of sheet-like structured nanomaterials with atomic thickness. [9] The characteristic geometric construction endows 2D materials with ultrahigh specific surface area (SSA) and abundant surface chemistry. The interlaced covalent bonds in 2D plane ensure sufficient mechanical strength. [10] Furthermore, 2D materials are facile to be assembled into bulk form so that they can achieve high performance when applying to various energy storage systems. [11] Except for these generalities, each kind of 2D materials, briefly covering graphene, hexagonal boron nitride (h-BN), graphitic carbon nitride, transition metal dichalcogenides, black phosphorus, MXenes, clays, metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), metal oxides and so forth, possesses its own characteristic. [10] For instance, reduced graphene oxide (rGO), Ti 3 C 2 , and 1T-MoS 2 have compelling electronic conductivity whereas h-BN, vermiculite, and COFs are insulating. 2D materials have already successfully used in catalysis, sensors, optoelectronic devices, batteries, and supercapacitors. [12] In view of their high theoretical specific capacity and low electrochemical potential, lithium/sodium metal anodes (MAs) have been revisited in recent years in the context of high-energy-density storage systems. However, the infinite volume change and the uncontrollable dendrite growth of MAs during cycles are obstructing the development of commercialization. Numerous strategies have been explored t...

Rechargeable magnesium batteries have received extensive attention as the Mg anodes possess twice the volumetric capacity of their lithium counterparts and are dendrite-free. However, Mg anodes suffer from surface passivation film in most glyme-based conventional electrolytes, leading to irreversible plating/stripping behavior of Mg. Here we report a facile and safe method to obtain a modified Mg metal anode with a Sn-based artificial layer via ion-exchange and alloying reactions. In the artificial coating layer, Mg2Sn alloy composites offer a channel for fast ion transport and insulating MgCl2/SnCl2 bestows the necessary potential gradient to prevent deposition on the surface. Significant improved ion conductivity of the solid electrolyte interfaces and decreased overpotential of Mg symmetric cells in Mg(TFSI)2/DME electrolyte are obtained. The coated Mg anodes can sustain a stable plating/stripping process over 4000 cycles at a high current density of 6 mA cm−2. This finding provides an avenue to facilitate fast ion diffusion kinetics of Mg metal anodes in conventional electrolytes.