Stable Li Metal Anodes via Regulating Lithium Plating/Stripping in Vertically Aligned Microchannels

Li anodes have been rapidly developed in recent years owing to the rising demand for higher‐energy‐density batteries. However, the safety issues induced by dendrites hinder the practical applications of Li anodes. Here, Li metal anodes stabilized by regulating lithium plating/stripping in vertically aligned microchannels are reported. The current density distribution and morphology evolution of the Li deposits on porous Cu current collectors are systematically analyzed. Based on simulations in COMSOL Multiphysics, the tip effect leads to preferential deposition on the microchannel walls, thus taking full advantage of the lightening rod theory of classical electromagnetism for restraining growth of Li dendrites. The Li anode with a porous Cu current collector achieves an enhanced cycle stability and a higher average Coulombic efficiency of 98.5% within 200 cycles. In addition, the resultant LiFePO₄/Li full battery demonstrates excellent rate capability and stable cycling performance, thus demonstrating promise as a current collector for high‐energy‐density, safe rechargeable Li batteries.     

Interlayered Dendrite‐Free Lithium Plating for High‐Performance Lithium‐Metal Batteries

For its high theoretical capacity and low redox potential, Li metal is considered to be one of the most promising anode materials for next‐generation batteries. However, practical application of a Li‐metal anode is impeded by Li dendrites, which are generated during the cycling of Li plating/stripping, leading to safety issues. Researchers attempt to solve this problem by spatially confining the Li plating. Yet, the effective directing of Li deposition into the confined space is challenging. Here, an interlayer is constructed between a graphitic carbon nitrite layer (g‐C₃N₄) and carbon cloth (CC), enabling site‐directed dendrite‐free Li plating. The g‐C₃N₄/CC as an anode scaffold enables extraordinary cycling stability for over 1500 h with a small overpotential of ≈80 mV at 2 mA cm^?2. Furthermore, prominent battery performance is also demonstrated in a full cell (Li/g‐C₃N₄/CC as anode and LiCoO₂ as cathode) with high Coulombic efficiency of 99.4% over 300 cycles.     

Self‐Suppression of Lithium Dendrite in All‐Solid‐State Lithium Metal Batteries with Poly(vinylidene difluoride)‐Based Solid Electrolytes

Polymer‐based electrolytes have attracted ever‐increasing attention for all‐solid‐state lithium (Li) metal batteries due to their ionic conductivity, flexibility, and easy assembling into batteries, and are expected to overcome safety issues by replacing flammable liquid electrolytes. However, it is still a critical challenge to effectively block Li dendrite growth and improve the long‐term cycling stability of all‐solid‐state batteries with polymer electrolytes. Here, the interface between novel poly(vinylidene difluoride) (PVDF)‐based solid electrolytes and the Li anode is explored via systematical experiments in combination with first‐principles calculations, and it is found that an in situ formed nanoscale interface layer with a stable and uniform mosaic structure can suppress Li dendrite growth. Unlike the typical short‐circuiting that often occurs in most studied poly(ethylene oxide) systems, this interface layer in the PVDF‐based system causes an open‐circuiting feature at high current density and thus avoids the risk of over‐current. The effective self‐suppression of the Li dendrite observed in the PVDF–LiN(SO₂F)₂ (LiFSI) system enables over 2000 h cycling of repeated Li plating–stripping at 0.1 mA cm^?2 and excellent cycling performance in an all‐solid‐state LiCoO₂||Li cell with almost no capacity fade after 200 cycles at 0.15 mA cm^?2 at 25 °C. These findings will promote the development of safe all‐solid‐state Li metal batteries.     

All‐Solid‐State Batteries with a Limited Lithium Metal Anode at Room Temperature using a Garnet‐Based Electrolyte

Metallic lithium (Li), considered as the ultimate anode, is expected to promise high‐energy rechargeable batteries. However, owing to the continuous Li consumption during the repeated Li plating/stripping cycling, excess amount of the Li metal anode is commonly utilized in lithium‐metal batteries (LMBs), leading to reduced energy density and increased cost. Here, an all‐solid‐state lithium‐metal battery (ASSLMB) based on a garnet‐oxide solid electrolyte with an ultralow negative/positive electrode capacity ratio (N/P ratio) is reported. Compared with the counterpart using a liquid electrolyte at the same low N/P ratios, ASSLMBs show longer cycling life, which is attributed to the higher Coulombic efficiency maintained during cycling. The effect of the species of the interface layer on the cycling performance of ASSLMBs with low N/P ratio is also studied. Importantly, it is demonstrated that the ASSLMB using a limited Li metal anode paired with a LiFePO₄ cathode (5.9 N/P ratio) delivers a stable long‐term cycling performance at room temperature. Furthermore, it is revealed that enhanced specific energies for ASSLMBs with low N/P ratios can be further achieved by the use of a high‐voltage or high mass‐loading cathode. This study sheds light on the practical high‐energy all‐solid‐state batteries under the constrained condition of a limited Li metal anode.     

金属铋纳米颗粒原位修饰碳纳米管促进锂均匀沉积

锂金属具有高理论比容量和低电化学电位, 是发展高能量密度电池最有吸引力的负极材料之一。然而, 锂金属负极在反复的沉积/剥离过程中, 不可避免地会出现不规则的锂枝晶生长, 这将严重影响锂金属电池的循环寿命和使用安全性。本研究发展了一种简单温和的策略, 在碳纳米管上原位修饰铋纳米颗粒, 并涂覆在商业铜箔表面用作锂金属负极的集流体。研究表明, 原位修饰的铋纳米颗粒可显著促进锂均匀沉积, 抑制锂枝晶生长, 从而提高锂金属电池的电化学性能。在电流密度为1 mA·cm^-2的条件下, 基于Bi@CNT/Cu集流体的锂铜电池循环300圈后库仑效率可稳定在98%。基于Li@Bi@CNT/Cu负极的对称电池可稳定循环1000 h。基于Bi@CNT/Cu集流体的磷酸铁锂(LFP)全电池也获得了优异的电化学性能, 在1C(170 mA·g^-1)倍率下可稳定循环700圈。本研究为抑制锂金属负极枝晶生长提供了新的思路。     

Redistributing Li-Ion Flux by Parallelly Aligned Holey Nanosheets for Dendrite-Free Li Metal Anodes

Li metal is the most ideal anode material to assemble rechargeable batteries with high energy density. However, nonuniform Li-ion flux during repeated Li plating and stripping leads to continuous Li dendrite growth and dead Li formation, which causes safety risks and short lifetime and thus impedes the commercialization of Li metal batteries. Here, parallelly aligned holey nanosheets on a Li metal anode are reported to simultaneously redistribute the Li-ion flux in the electrolyte and in the solid-electrolyte interphase, which allows uniform Li-ion distribution as well as fast Li-ion diffusion for reversible Li plating and stripping. With holey MgO nanosheets as an example, the protected Li anodes achieve Coulombic efficiency of ≈99% and ultralong-term reversible Li plating/stripping over 2500 h at a high current density of 10 mA cm⁻². A full-cell battery, using the protected anode, a 4 V Li-ion cathode, and a commercial carbonate electrolyte, shows capacity retention of 90.9% after 500 cycles.     

A Novel Organic “Polyurea” Thin Film for Ultralong‐Life Lithium‐Metal Anodes via Molecular‐Layer Deposition

Metallic Li is considered as one of the most promising anode materials for next‐generation batteries due to its high theoretical capacity and low electrochemical potential. However, its commercialization has been impeded by the severe safety issues associated with Li‐dendrite growth. Non‐uniform Li‐ion flux on the Li‐metal surface and the formation of unstable solid electrolyte interphase (SEI) during the Li plating/stripping process lead to the growth of dendritic and mossy Li structures that deteriorate the cycling performance and can cause short‐circuits. Herein, an ultrathin polymer film of “polyurea” as an artificial SEI layer for Li‐metal anodes via molecular‐layer deposition (MLD) is reported. Abundant polar groups in polyurea can redistribute the Li‐ion flux and lead to a uniform plating/stripping process. As a result, the dendritic Li growth during cycling is efficiently suppressed and the life span is significantly prolonged (three times longer than bare Li at a current density of 3 mA cm^?2). Moreover, the detailed surface and interfacial chemistry of Li metal are studied comprehensively. This work provides deep insights into the design of artificial SEI coatings for Li metal and progress toward realizing next‐generation Li‐metal batteries.     

Uniform Lithium Nucleation/Growth Induced by Lightweight Nitrogen‐Doped Graphitic Carbon Foams for High‐Performance Lithium Metal Anodes

The lithium metal anode has attracted soaring attention as an ideal battery anode. Unfortunately, nonuniform Li nucleation results in uncontrollable growth of dendritic Li, which incurs serious safety issues and poor electrochemical performance, hindering its practical applications. Herein, this study shows that uniform Li nucleation/growth can be induced by an ultralight 3D current collector consisting of in situ nitrogen‐doped graphitic carbon foams (NGCFs) to realize suppressing dendritic Li growth at the nucleating stage. The N‐containing functional groups guide homogenous growth of Li nucleus nanoparticles and the initial Li nucleus seed layer regulates the following well‐distributed Li growth. Benefiting from such favorable Li growth behavior, superior electrochemical performance can be achieved as evidenced by the high Coulombic efficiency (≈99.6% for 300 cycles), large capacity (10 mA h cm^?2, 3140 mA h g^?1_NGCF‐Li), and ultralong lifespan (>1200 h) together with low overpotential (<25 mV at 3 mA cm^?2); even under a high current density up to 10 mA cm^?2, it still displays low overpotential of 62 mV.     

Large‐Scale Modification of Commercial Copper Foil with Lithiophilic Metal Layer for Li Metal Battery

The application and development of lithium metal battery are severely restricted by the uncontrolled growth of lithium dendrite and poor cycle stability. Uniform lithium deposition is the core to solve these problems, but it is difficult to be achieved on commercial Cu collectors. In this work, a simple and commercially viable strategy is utilized for large‐scale preparation of a modified planar Cu collector with lithiophilic Ag nanoparticles by a simple substitution reaction. As a result, the Li metal shows a cobblestone‐like morphology with similar size and uniform distribution rather than Li dendrites. Interestingly, a high‐quality solid electrolyte interphase layer in egg shell‐like morphology with fast ion diffusion channels is formed on the interface of the collector, exhibiting good stability with long‐term cycles. Moreover, at the current density of 1 mA cm^?2 for 1 mAh cm^?2, the Ag modified planar Cu collector shows an ultralow nucleation overpotential (close to 0 mV) and a stable coulombic efficiency of 98.54% for more than 600 cycles as well as long lifespan beyond 900 h in a Li|Cu‐Ag@Li cell, indicating the ability of this method to realize stable Li metal batteries. Finally, full cells paired with LiNi_0.8Co_0.1Mn_0.1O₂ show superior rate performance and stability compared with those paired with Li foil.     

In‐Plane Lithium Growth Enabled by Artificial Nitrate‐Rich Layer: Fast Deposition Kinetics and Desolvation/Adsorption Mechanism

An artificial lithium‐nitrate (LiNO₃)‐rich layer (LN‐RL) is developed to address dendritic lithium (Li) growth by a fusing–infusing strategy, in which LiNO₃ is loaded into stainless steel mesh and a Li‐metal anode (LN‐RL@Li) is obtained by casting this LN‐RL onto Li foil. The LN‐RL enables fast Li deposition kinetics in carbonates and endows LN‐RL@Li with excellent cycleability. The underneath mechanism on the contribution of LN‐RL is uncovered by detailed characterizations combining with theoretical simulations. The LN‐RL promotes the desolvation and capacitive adsorption of Li ions and induces in‐plane Li growth along the edges of preplated Li with planar morphology. The improved cycleability of LN‐RL(@Li) is demonstrated by Li∥Cu cell that presents a coulombic efficiency of 97.2% after 280 cycles and Li∥Li cell that proceeds over 1000 h at 0.5 mA cm^?2 in carbonates. Additionally, the Li∥LiFePO₄ cell shows a capacity retention of 58% after 400 cycles at 1 C (1 C = 170 mA g^?1), compared to the 35% after 180 cycles for the control. This work presents not only a promising strategy for practical applications of Li‐metal batteries, but also a new understanding on the role of nitrate in Li plating/stripping kinetics.     

RuO2 Particles Anchored on Brush‐Like 3D Carbon Cloth Guide Homogenous Li/Na Nucleation Framework for Stable Li/Na Anode

Lithium (sodium)‐metal batteries are the most promising batteries for next‐generation electrical energy storage due to their high volumetric energy density and gravimetric energy density. However, their applications have been prevented by uncontrollable dendrite growth and large volume expansion during the stripping/plating process. To address this issue, the key strategy is to realize uniform lithium (sodium) deposition during the stripping/plating process. Herein, a thin lithiophilic layer consisting of RuO₂ particles anchored on brush‐like 3D carbon cloth (RuO₂@CC) is prepared by a simple solution‐based method. After infusion of Li, the RuO₂@CC transfers to Li‐Ru@CC. Ru nanoparticles not only play a role in leading Li⁺ (Na⁺) to plate on the 3D carbon framework, but also lower local current density because of the good electrical conductivity. Furthermore, density functional theory calculations demonstrate that Ru metal, the reaction product of alkali metal and Ru, can lead Li⁺ to plate evenly around carbon fiber owing to the strong binding energy with Li⁺. The Li‐Ru@CC anode shows ultralong cycle life (1500 h at 5 mA cm^?2). The full cell of Li‐Ru@CC|LiFePO₄ exhibits lower polarization (90% capacity retention after 650 cycles). In addition, sodium metal batteries based on Na‐Ru@CC anodes can achieve similar improvement.     

Double‐Layer Polymer Electrolyte for High‐Voltage All‐Solid‐State Rechargeable Batteries

No single polymer or liquid electrolyte has a large enough energy gap between the empty and occupied electronic states for both dendrite‐free plating of a lithium‐metal anode and a Li⁺ extraction from an oxide host cathode without electrolyte oxidation in a high‐voltage cell during the charge process. Therefore, a double‐layer polymer electrolyte is investigated, in which one polymer provides dendrite‐free plating of a Li‐metal anode and the other allows a Li⁺ extraction from an oxide host cathode without oxidation of the electrolyte in a 4 V cell over a stable charge/discharge cycling at 65 °C; a poly(ethylene oxide) polymer contacts the lithium‐metal anode and a poly(N‐methyl‐malonic amide) contacts the cathode. All interfaces of the flexible, plastic electrolyte remain stable with no visible reduction of the Li⁺ conductivity on crossing the polymer/polymer interface.     

A 3D Lithiophilic Mo2N‐Modified Carbon Nanofiber Architecture for Dendrite‐Free Lithium‐Metal Anodes in a Full Cell

The pursuit for high‐energy‐density batteries has inspired the resurgence of metallic lithium (Li) as a promising anode, yet its practical viability is restricted by the uncontrollable Li dendrite growth and huge volume changes during repeated cycling. Herein, a new 3D framework configured with Mo₂N‐mofidied carbon nanofiber (CNF) architecture is established as a Li host via a facile fabrication method. The lithiophilic Mo₂N acts as a homogeneously pre‐planted seed with ultralow Li nucleation overpotential, thus spatially guiding a uniform Li nucleation and deposition in the matrix. The conductive CNF skeleton effectively homogenizes the current distribution and Li‐ion flux, further suppressing Li‐dendrite formation. As a result, the 3D hybrid Mo₂N@CNF structure facilitates a dendrite‐free morphology with greatly alleviated volume expansion, delivering a significantly improved Coulombic efficiency of ≈99.2% over 150 cycles at 4 mA cm^?2. Symmetric cells with Mo₂N@CNF substrates stably operate over 1500 h at 6 mA cm^?2 for 6 mA h cm^?2. Furthermore, full cells paired with LiNi_0.8Co_0.1Mn_0.1O₂ (NMC811) cathodes in conventional carbonate electrolytes achieve a remarkable capacity retention of 90% over 150 cycles. This work sheds new light on the facile design of 3D lithiophilic hosts for dendrite‐free lithium‐metal anodes.     

Stable Potassium Metal Anodes with an All-Aluminum Current Collector through Improved Electrolyte Wetting

This is the first report of successful potassium metal battery anode cycling with an aluminum-based rather than copper-based current collector. Dendrite-free plating/stripping is achieved through improved electrolyte wetting, employing an aluminum-powder-coated aluminum foil “Al@Al,” without any modification of the support surface chemistry or electrolyte additives. The reservoir-free Al@Al half-cell is stable at 1000 cycles (1950 h) at 0.5 mA cm⁻², with 98.9% cycling Coulombic efficiency and 0.085 V overpotential. The pre-potassiated cell is stable through a wide current range, including 130 cycles (2600 min) at 3.0 mA cm⁻², with 0.178 V overpotential. Al@Al is fully wetted by a 4 m potassium bis(fluorosulfonyl)imide-dimethoxyethane electrolyte (θ_CA  = 0 ° ), producing a uniform solid electrolyte interphase (SEI) during the initial galvanostatic formation cycles. On planar aluminum foil with a nearly identical surface oxide, the electrolyte wets poorly (θ_CA  = 52 ° ). This correlates with coarse irregular SEI clumps at formation, 3D potassium islands with further SEI coarsening during plating/stripping, possibly dead potassium metal on stripped surfaces, and rapid failure. The electrochemical stability of Al@Al versus planar Al is not related to differences in potassiophilicity (nearly identical) as obtained from thermal wetting experiments. Planar Cu foils are also poorly electrolyte-wetted and become dendritic. The key fundamental takeaway is that the incomplete electrolyte wetting of collectors results in early onset of SEI instability and dendrites.     

Constructing Ionic Gradient and Lithiophilic Interphase for High‐Rate Li‐Metal Anode

Li metal is the optimal choice as an anode due to its high theoretical capacity, but it suffers from severe dendrite growth, especially at high current rates. Here, an ionic gradient and lithiophilic inter‐phase film is developed, which promises to produce a durable and high‐rate Li‐metal anode. The film, containing an ionic‐conductive Li_0.33La_0.56TiO₃ nanofiber (NF) layer on the top and a thin lithiophilic Al₂O₃ NF layer on the bottom, is fabricated with a sol–gel electrospinning method followed by sintering. During cycling, the top layer forms a spatially homogenous ionic field distribution over the anode, while the bottom layer reduces the driving force of Li‐dendrite formation by decreasing the nucleation barrier, enabling dendrite‐free plating‐stripping behavior over 1000 h at a high current density of 5 mA cm^?2. Remarkably, full cells of Li//LiNi_0.8Co_0.15Al_0.05O₂ exhibit a high capacity of 133.3 mA h g^?1 at 5 C over 150 cycles, contributing a step forward for high‐rate Li‐metal anodes.     

Gradient‐Distributed Nucleation Seeds on Conductive Host for a Dendrite‐Free and High‐Rate Lithium Metal Anode

Much attention is paid to metal lithium as a hopeful negative material for reversible batteries with a high specific capacity. Although applying 3D hosts can relieve the dendrite growth to some extent, gradient‐distributed lithium ion in 3D uniform hosts still induces uncontrolled lithium dendrites growth, especially at high lithium capacity and high current density. Herein, a 3D conductive carbon nanofiber framework with gradient‐distributed ZnO particles as nucleation seeds (G‐CNF) to regulate lithium deposition is proposed. Based on such a unique structure, the G‐CNF electrode exhibits a high average Coulombic efficiency (CE) of 98.1% for 700 cycles at 0.5 mA cm^?2. Even at 5 mA cm^?2, the G‐CNF electrode performs a stable cycling process and high CE of 96.0% for over 200 cycles. When the lithium‐deposited G‐CNF (G‐CNF‐Li) anode is applied in a full cell with a commercial LiFePO₄ cathode, it exhibits a stable capacity of 115 mAh g^?1 and high retention of 95.7% after 300 cycles. Through inducing the gradient‐distributed nucleation seeds to counter the existing Li‐ion concentration polarization, a uniform and stable lithium deposition process in the 3D host is achieved even under the condition of high current density.     

3D Printed High‐Performance Lithium Metal Microbatteries Enabled by Nanocellulose

Batteries constructed via 3D printing techniques have inherent advantages including opportunities for miniaturization, autonomous shaping, and controllable structural prototyping. However, 3D‐printed lithium metal batteries (LMBs) have not yet been reported due to the difficulties of printing lithium (Li) metal. Here, for the first time, high‐performance LMBs are fabricated through a 3D printing technique using cellulose nanofiber (CNF), which is one of the most earth‐abundant biopolymers. The unique shear thinning properties of CNF gel enables the printing of a LiFePO₄ electrode and stable scaffold for Li. The printability of the CNF gel is also investigated theoretically. Moreover, the porous structure of the CNF scaffold also helps to improve ion accessibility and decreases the local current density of Li anode. Thus, dendrite formation due to uneven Li plating/stripping is suppressed. A multiscale computational approach integrating first‐principle density function theory and a phase‐field model is performed and reveals that the porous structures have more uniform Li deposition. Consequently, a full cell built with a 3D‐printed Li anode and a LiFePO₄ cathode exhibits a high capacity of 80 mA h g^?1 at a charge/discharge rate of 10 C with capacity retention of 85% even after 3000 cycles.     

Novel Co2VO4 Anodes Using Ultralight 3D Metallic Current Collector and Carbon Sandwiched Structures for High‐Performance Li‐Ion Batteries

A novel spinel Co₂VO₄ is studied as the Li‐ion battery anode material and it is sandwiched with a 3D ultralight porous current collector (PCC) and amorphous carbon. Co₂VO₄ demonstrates the high capacity and excellent cyclability because of the mixed lithium storage mechanisms. The 3D composite structure requires no binders and replaces the conventional current collector (Cu foil) with a 3D ultralight porous metal scaffold, yielding the high electrode‐based capacity. Such a novel composite anode also enables the close adhesion of Co₂VO₄ to the PCC scaffold. The resulting monolithic electrode has the rapid electron pathway and stable mechanical properties, which lead to the excellent rate capabilities and cycling properties. At a current density of 1 A g^?1, the PCC and carbon sandwiched Co₂VO₄ anode is able to deliver a stable reversible capacity of about 706.8 mAh g^?1 after 1000 cycles. Generally, this study not only develops a new Co₂VO₄ anode with high capacity and good cyclability, but also demonstrates an alternative approach to improve the electrochemical properties of high capacity anode materials by using ultralight porous metallic current collector instead of heavy copper foil.     

A 3D and Stable Lithium Anode for High‐Performance Lithium–Iodine Batteries

Lithium metal is considered as the most promising anode material due to its high theoretical specific capacity and the low electrochemical reduction potential. However, severe dendrite problems have to be addressed for fabricating stable and rechargeable batteries (e.g., lithium–iodine batteries). To fabricate a high‐performance lithium–iodine (Li–I₂) battery, a 3D stable lithium metal anode is prepared by loading of molten lithium on carbon cloth doped with nitrogen and phosphorous. Experimental observations and theoretical calculation reveal that the N,P codoping greatly improves the lithiophilicity of the carbon cloth, which not only enables the uniform loading of molten lithium but also facilitates reversible lithium stripping and plating. Dendrites formation can thus be significantly suppressed at a 3D lithium electrode, leading to stable voltage profiles over 600 h at a current density of 3 mA cm^?2. A fuel cell with such an electrode and a lithium–iodine cathode shows impressive long‐term stability with a capacity retention of around 100% over 4000 cycles and enhanced high‐rate capability. These results demonstrate the promising applications of 3D stable lithium metal anodes in next‐generation rechargeable batteries.