Catalytic Chemistry Derived Artificial Solid Electrolyte Interphase for Stable Lithium Metal Anodes Working at 20 mA cm−2 and 20 mAh cm−2

A stable solid electrolyte interphase (SEI) layer is crucial for lithium metal anode (LMA) to survive in long-term cycling. However, chaotic structures and chemical inhomogeneity of natural SEI make LMA suffering from exasperating dendrite growth and severe electrode pulverization, which hinder the practical application of LMAs. Here, we design a catalyst-derived artificial SEI layer with an ordered polyamide-lithium hydroxide (PA-LiOH) bi-phase structure to modulate ion transport and enable dendrite-free Li deposition. The PA-LiOH layer can substantially suppress the volume changes of LMA during Li plating/stripping cycles, as well as alleviate the parasitic reactions between LMA and electrolyte. The optimized LMAs demonstrate excellent stability in Li plating/stripping cycles for over 1000 hours at an ultra-high current density of 20 mA cm⁻² in Li||Li symmetric cells. A high coulombic efficiency up to 99.2 % in Li half cells in additive-free electrolytes is achieved even after 500 cycles at a current density of 1 mA cm⁻² with a capacity of 1 mAh cm⁻².     

A Liquid/Liquid Electrolyte Interface that Inhibits Corrosion and Dendrite Growth of Lithium in Lithium‐Metal Batteries

A proof‐of‐concept study on a liquid/liquid (L/L) two‐phase electrolyte interface is reported by using the polarity difference of solvent for the protection of Li‐metal anode with long‐term operation over 2000 h. The L/L electrolyte interface constructed by non‐polar fluorosilicane (PFTOS) and conventionally polar dimethyl sulfoxide solvents can block direct contact between conventional electrolyte and Li anode, and consequently their side reactions can be significantly eliminated. Moreover, the homogeneous Li‐ion flow and Li‐mass deposition can be realized by the formation of a thin and uniform solid‐electrolyte interphase (SEI) composed of LiF, Li_xC, Li_xSiO_y between PFTOS and Li anode, as well as the super‐wettability state of PFTOS to Li anode, resulting in the suppression of Li dendrite formation. The cycling stability in a lithium–oxygen battery as a model is improved 4 times with the L/L electrolyte interface.     

Dendrite‐Free Epitaxial Growth of Lithium Metal during Charging in Li–O2 Batteries

Lithium (Li) dendrite formation is one of the major hurdles limiting the development of Li‐metal batteries, including Li‐O₂ batteries. Herein, we report the first observation of the dendrite‐free epitaxial growth of a Li metal up to 10‐μm thick during charging (plating) in the LiBr‐LiNO₃ dual anion electrolyte under O₂ atmosphere. This phenomenon is due to the formation of an ultrathin and homogeneous Li₂O‐rich solid‐electrolyte interphase (SEI) layer in the preceding discharge (stripping) process, where the corrosive nature of Br^? seems to give rise to remove the original incompact passivation layer and NO₃^? oxidizes (passivates) the freshly formed Li surface to prevent further reactions with the electrolyte. Such reactions keep the SEI thin (<100 nm) and facilitates the electropolishing effect and gets ready for the epitaxial electroplating of Li in the following charge process.     

Strategic Approaches to the Dendritic Growth and Interfacial Reaction of Lithium Metal Anode

Utilization of lithium (Li) metal anode is highly desirable for achieving high energy density batteries. Even so, the unavoidable features of Li dendritic growth and inactive Li are still the main factors that hinder its practical application. During plating and stripping, the solid electrolyte interphase (SEI) layer can provide passivation, playing an important role in preventing direct contact between the electrolyte and the electrode in Li metal batteries. Because of complexities of the electrolyte chemical and electrochemical reactions, the various formation mechanisms for the SEI are still not well understood. What we do know is that a strategic artificial SEI achieved through additives electrolyte can suppress the Li dendrites. Otherwise, the dendrites keep generating an abundance of irreversible Li, resulting in severe capacity loss, internal short-circuiting, and cell failure. In this minireview, we focus on the phenomenon of dendritic Li-growth and provide a brief overview of SEI formation. We finally provide some clear insights and perspectives toward practical application of Li metal batteries.     

人工界面层在金属锂负极中的应用

金属锂具有极高的比容量(3860 mAh·g^?1)和最低的电化学反应电位(相对标准氢电位为?3.040 V),被认为是高能量密度二次电池最具潜力的负极材料。然而金属锂负极界面稳定性差、不可控的枝晶生长、沉积/剥离过程中巨大的体积变化等严重阻碍了金属锂负极的商业化应用。在金属锂表面构建一层物理化学性质稳定的人工界面保护层被认为是解决金属锂负极界面不稳定和枝晶生长,缓解体积膨胀带来的界面波动等一系列问题的有效手段。本综述依据界面传导性质,从离子导通而电子绝缘的人工固态电解质界面(SEI)层、离子/电子混合传导界面、纳米界面钝化层三个部分对人工界面保护层进行了归纳总结。分析了人工界面保护层的物质结构与性能之间的构效关系,探讨了如何提高人工界面保护层的物理化学稳定性、界面离子输运、界面强度与柔韧性、界面兼容性等。最后,指出用于金属锂负极的人工界面保护层目前面临的主要挑战,并对其未来的发展进行了展望。     

Interfacial Evolution of Lithium Dendrites and Their Solid Electrolyte Interphase Shells of Quasi‐Solid‐State Lithium‐Metal Batteries

Unstable electrode/solid‐state electrolyte interfaces and internal lithium dendrite penetration hamper the applications of solid‐state lithium‐metal batteries (SSLMBs), and the underlying mechanisms are not well understood. Herein, in situ optical microscopy provides insights into the lithium plating/stripping processes in a gel polymer electrolyte and reveals its dynamic evolution. Spherical lithium deposits evolve into moss‐like and branch‐shaped lithium dendrites with increasing current densities. Remarkably, the on‐site‐formed solid electrolyte interphase (SEI) shell on the lithium dendrite is distinctly captured after lithium stripping. Inducing an on‐site‐formed SEI shell with an enhanced modulus to wrap the lithium precipitation densely and uniformly can regulate dendrite‐free behaviors. An in‐depth understanding of lithium dendrite evolution and its functional SEI shell will aid in the optimization of SSLMBs.     

Gel electrolyte via in situ polymerization to promote durable lithium-air batteries

Aprotic lithium-air batteries (LABs) have been known as the holy grail of energy storage systems due to their extremely high energy density. However, their real-world application is still hindered by the great challenges from the Li anode side, like dendrite growth and corrosion reactions, thus a pure oxygen atmosphere is usually adopted to prolong the lifetime of LABs, which is a major obstacle to fully liberate the energy density advantages of LABs. Here, a gel polymer electrolyte has been designed through in-situ polymerization of 1,3-dioxolane (DOL) by utilizing the unique semi-open nature of LABs to protect the Li anode to conquer its shortcomings, enabling the high-performance running of LABs in the ambient air. Unlike common liquid electrolytes, the in-situ formed gel polymer electrolyte could facilitate constructing a gradient SEI film with the gradual decrease of organic components from top to bottom, preventing the Li anode from dendrite growth and air-induced corrosion reactions and thus realizing durable Li repeated plating/stripping (2000 h). Benefiting from the anode protection effects of the gradient SEI film, the LABs display a long lifetime of 170 cycles, paving an avenue for practical, long-term, and high-efficiency operation of LABs.     

Electrolyte Regulation towards Stable Lithium‐Metal Anodes in Lithium–Sulfur Batteries with Sulfurized Polyacrylonitrile Cathodes

Lithium–sulfur (Li–S) batteries are highly regarded as the next‐generation energy‐storage devices because of their ultrahigh theoretical energy density of 2600 Wh kg^?1. Sulfurized polyacrylonitrile (SPAN) is considered a promising sulfur cathode to substitute carbon/sulfur (C/S) composites to afford higher Coulombic efficiency, improved cycling stability, and potential high‐energy‐density Li–SPAN batteries. However, the instability of the Li‐metal anode threatens the performances of Li–SPAN batteries bringing limited lifespan and safety hazards. Li‐metal can react with most kinds of electrolyte to generate a protective solid electrolyte interphase (SEI), electrolyte regulation is a widely accepted strategy to protect Li‐metal anodes in rechargeable batteries. Herein, the basic principles and current challenges of Li–SPAN batteries are addressed. Recent advances on electrolyte regulation towards stable Li‐metal anodes in Li–SPAN batteries are summarized to suggest design strategies of solvents, lithium salts, additives, and gel electrolyte. Finally, prospects for future electrolyte design and Li anode protection in Li–SPAN batteries are discussed.     

Self‐Stabilized and Strongly Adhesive Supramolecular Polymer Protective Layer Enables Ultrahigh‐Rate and Large‐Capacity Lithium‐Metal Anode

Constructing a solid electrolyte interface (SEI) is a highly effective approach to overcome the poor reversibility of lithium (Li) metal anodes. Herein, an adhesive and self‐healable supramolecular copolymer, comprising of pendant poly(ethylene oxide) (PEO) segments and ureido‐pyrimidinone (UPy) quadruple‐hydrogen‐bonding moieties, is developed as a protection layer of Li anode by a simple drop‐coating. The protection performance of in‐situ‐formed LiPEO–UPy SEI layer is significantly enhanced owing to the strong binding and improved stability arising from a spontaneous reaction between UPy groups and Li metal. An ultrathin (approximately 70 nm) LiPEO–UPy layer can contribute to stable and dendrite‐free cycling at a high areal capacity of 10 mAh cm^?2 at 5 mA cm^?2 for 1000 h. This coating together with the promising electrochemical performance offers a new strategy for the development of dendrite‐free metal anodes.     

Vinylene carbonate–LiNO3: A hybrid additive in carbonic ester electrolytes for SEI modification on Li metal anode

A hybrid solid electrolyte interphase (SEI) formation additive, vinylene carbonate (VC)–LiNO₃, was investigated in carbonic ester electrolytes. An efficiency of lithium plating/stripping as high as nearly 100% and spherical Li deposits were obtained. The electrochemical impedance spectroscopy (EIS) results demonstrate that the modified SEI is very stable and of good conductivity. X-ray photoelectron spectroscopy (XPS) results indicate that VC–LiNO₃ dominates the surface chemistry of the Li anode. The formation of Li₃N in the SEI contributes to the enhancement of the anode performance.     

Flexible Amalgam Film Enables Stable Lithium Metal Anodes with High Capacities

Dendrite formation is a critical challenge for the applications of lithium (Li) metal anodes. In this work a new strategy is demonstrated to address this issue by fabricating an Li amalgam film on its surface. This protective film serves as a flexible buffer that affords repeated Li plating/stripping. In symmetric cells, the protected Li electrodes exhibit stable cycling over 750 hours at a high plating current and capacity of 8 mA cm^?2 and 8 mAh cm^?2, respectively. Coupled with high‐loading cathodes (ca. 12 mg cm^?2) such as LiFePO₄ and LiNi_0.6Co_0.2Mn_0.2O₂, the protected hybrid anodes demonstrate significantly improved cell stability, indicating its reliability for practical development of Li metal batteries. Interfacial analyses reveal a unique plating‐alloying synergistic function of the protective film, where Li beneath the film is actively involved in the electrode reactions upon cycling. Lithium amalgams enrich the alloy anode family and provide new perspectives for the rational design of dendrite‐free anodes.     

锂金属负极的挑战与改善策略研究进展

锂金属由于其高比容量和低电极电势等优点被认为是下一代高比能量电池体系中最有潜力的负极材料。然而由于锂金属的高活性,锂负极在循环过程中会产生大量的枝晶,导致SEI(solid-electrolyte interphase)破裂,并且枝晶增加了电极与电解液的接触面积,使得副反应进一步增加。此外,脱落的枝晶形成死锂,从而降低电池的充放电库仑效率。并且不可控的锂枝晶持续生长会刺穿隔膜引发电池短路,伴随着电池热失控等安全问题。本综述基于锂负极存在的主要挑战,结合理解锂枝晶的成核生长模型等机理总结并深度分析近些年来在液态和固态电解质体系中改善锂金属负极的主要策略及其作用机理,为促进高比能量锂金属电池的应用提供借鉴参考作用。     

Anchoring an Artificial Solid–Electrolyte Interphase Layer on a 3D Current Collector for High‐Performance Lithium Anodes

The application of Li anodes is hindered by dendrite growth and side reactions between Li and electrolyte, despite its high capacity and low potential. A simple approach for this challenge is now demonstrated. In our strategy, the garnet‐type Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO)‐based artificial solid–electrolyte interphase (SEI) is anchored on Cu foam by sintering the Cu foam coated with LLZTO particles. The heat treatment leads to the interdiffusion of Cu and Ta₂O₅ at the Cu/LLZTO interface, through which LLZTO layer is fixed on Cu foam. 3D structure lowers the current density, and meanwhile the SEI reduces the contact of Li and electrolyte. Furthermore, the anchoring construction can endure Li‐deposition‐induced volume change. Therefore, LLZTO‐modified Cu foam shows much improved Li plating/stripping performance, including long lifespan (2400 h), high rate (maximum current density of 20 mA cm^?2), high areal capacity (8 mA h cm^?2 for 100 cycles), and high efficiency (over 98 %).     

In-situ nanoscale insights into the evolution of solid electrolyte interphase shells: revealing interfacial degradation in lithium metal batteries

The solid electrolyte interphase(SEI) has caught considerable attention as a pivotal factor affecting lithium(Li) metal battery performances. However, the understanding of the interfacial evolution and properties of the on-site formed SEI shells on Li deposits during cycling is still at a preliminary stage. Here, we provide a straightforward visualized evidence of SEI shells' evolution during Li deposition/stripping to reveal anode degradation via in-situ atomic force microscopy(AFM). Nucleation and growth of quasi-spherical Li particles are observed on a Cu substrate, followed by Li stripping and collapse of SEI shells. In the subsequent cycling, new Li deposits tend to nucleate at pristine sites with fresh SEI shells forming on Li. The previously collapsed SEI shells accumulate to increase interface impedance, eventually leading to capacity degradation. Revealing the electrochemical processes and interfacial degradation at the nanoscale will enrich fundamental comprehension and further guide improvement strategies of Li metal anodes.     

Regulating Lithium Plating and Stripping by Using Vertically Aligned Graphene/CNT Channels Decorated with ZnO Particles

Lithium (Li) metal is regarded as the ultimate anode material for use in Li batteries due to its high theoretical capacity (3860 mA h g⁻¹). However, the Li dendrites that are generated during iterative Li plating/stripping cycles cause poor cycling stability and even present safety risks, and thus severely handicap the commercial utility of Li metal anodes. Herein, we describe a graphene and carbon nanotube (CNT)-based Li host material that features vertically aligned channels with attached ZnO particles (designated ZnO@G-CNT-C) and show that the material effectively regulates Li plating and stripping. ZnO@G-CNT-C is prepared from an aqueous suspension of Zn(OAc)₂, CNTs, and graphene oxide by using ice to template channel growth. ZnO@G-CNT-C was found to be mechanically robust and capable of guiding Li deposition on the inner walls of the channels without the formation of Li dendrites. When used as an electrode, the material exhibits relatively low polarization for Li plating, fast Li-ion diffusion, and high Coulombic efficiency, even over hundreds of Li plating/stripping cycles. Moreover, full cells prepared with ZnO@G-CNT-C as Li host and LiFePO₄ as cathode exhibit outstanding performance in terms of specific capacity (155.9 mA h g⁻¹ at 0.5 C), rate performance (91.8 mA h g⁻¹ at 4 C), cycling stability (109.4 mA h g⁻¹ at 0.5 C after 800 cycles). The methodology described can be readily adapted to enable the use of carbon-based electrodes with well-defined channels in a wide range of contemporary applications that pertain to energy storage and delivery.     

三维大孔/介孔碳-碳化钛复合材料用于无枝晶锂金属负极

金属锂具有超高的理论容量(3860 mAh·g^-1)和低氧化还原电位(-3.04 V vs.标准氢电极),是极具吸引力的下一代高能量密度电池的负极材料。然而,循环过程中的体积膨胀、锂枝晶生长和“死锂”等问题严重的限制了其实际应用。合理设计三维骨架调控金属锂的成核行为是抑制锂枝晶生长的有效策略。本文中,我们发展了一种“软硬双模板”的方法合成了兼具大孔和介孔的三维碳-碳化钛(Three-dimensional macro-/mesoporous C-TiC,表示为3DMM-C-TiC)复合材料。多级孔道为金属锂的沉积提供了足够的空间,缓冲充放电中巨大的体积变化。此外,TiC的引入显著增强多孔骨架的导电性,改善锂金属的成核行为,促进金属锂的均匀成核和沉积,抑制锂枝晶生长。3DMM-C-TiC||Li电池测试表明,在循环300圈以后,库伦效率仍保持在98%以上。此外,所得材料与LiFePO₄ (LFP)组成的全电池也表现出优异的倍率和循环性能。本工作为无枝晶锂金属负极的设计提供了新的思路。     

Lithiophilic Sites in Doped Graphene Guide Uniform Lithium Nucleation for Dendrite-Free Lithium Metal Anodes

Lithium (Li) metal is the most promising electrode for next-generation rechargeable batteries. However, the challenges induced by Li dendrites on a working Li metal anode hinder the practical applications of Li metal batteries. Herein, nitrogen (N) doped graphene was adopted as the Li plating matrix to regulate Li metal nucleation and suppress dendrite growth. The N-containing functional groups, such as pyridinic and pyrrolic nitrogen in the N-doped graphene, are lithiophilic, which guide the metallic Li nucleation causing the metal to distribute uniformly on the anode surface. As a result, the N-doped graphene modified Li metal anode exhibits a dendrite-free morphology during repeated Li plating and demonstrates a high Coulombic efficiency of 98 % for near 200 cycles.     

Graphene-Enabled Electric-Field Regulation and Ionic Redistribution Around Lithiophilic Aurum Nanoparticles Toward a Dendrite-Free and 2000-Cycle-Life Lithium Metal Battery

Lithium metal batteries (LMBs) have attracted extensive attention owing to their high energy density. However, the uncontrolled volume changes and serious dendrite growth of the Li metal anode have hindered their commercialization. Herein, a three-dimensional Cu foam decorated with Au nanoparticles and conformal graphene layer was designed to tune the Li plating/stripping behaviors. The 3D−Cu conductive host anchored by lithiophilic Au nanoparticles can effectively alleviate the volume expansion caused by the continuous plating/stripping of Li and reduce the nucleation energy barrier. Notably, the conductive graphene not only facilitates the transfer of electrons, but also acts as an ionic rectifier, thereby avoiding the aggregation of local current density and Li⁺ ions around Au nanoparticles and enabling the uniform Li⁺ flux. As a result, the G−Au@3D−Cu/Li anode ensures the non-dendritic and homogeneous Li⁺ plating/stripping. Electrochemical results show that the symmetric G−Au@3D−Cu/Li cell delivers a low voltage hysteresis of 110 mV after 1000 h at 1 mA cm⁻². Matched with a layered LiNi_0.6Co_0.2Mn_0.2O₂ cathode, the NCM622||G−Au@3D−Cu/Li full cell exhibits a long cycle life of 2000 cycles and an ultra-low capacity decay rate (0.01 % per cycle).     

一种有助于稳定锂金属循环的富氟化位点框架结构

锂金属是下一代高能量密度二次电池的理想负极材料,然而它的应用仍然受制于较差的循环稳定性。近期,二维氟化界面被广泛用于改善锂金属负极的成核机制、沉积形貌和循环稳定性。本工作通过将体积缩小化的氟化石墨颗粒与锂离子传导网络结合,获得了一种富氟化位点的三维框架结构。实验结果证明此类三维氟化结构可显著提升锂金属负极在不同电流密度和容量下的循环稳定性,且优于二维氟化界面结构。通过本工作的研究,证明了相较于单纯的二维氟化界面,三维锂离子传导网络和富氟化位点的合理结合可以成为一种改进的界面结构用于锂金属负极保护,为高能量密度锂金属电池的负极保护提供了新的设计思路。     

Self‐Healable Solid Polymeric Electrolytes for Stable and Flexible Lithium Metal Batteries

The key issue holding back the application of solid polymeric electrolytes in high‐energy density lithium metal batteries is the contradictory requirements of high ion conductivity and mechanical stability. In this work, self‐healable solid polymeric electrolytes (SHSPEs) with rigid‐flexible backbones and high ion conductivity are synthesized by a facile condensation polymerization approach. The all‐solid Li metal full batteries based on the SHSPEs possess freely bending flexibility and stable cycling performance as a result of the more disciplined metal Li plating/stripping, which have great implications as long‐lifespan energy sources compatible with other wearable devices.