Exchange of Li and AgNO3 Enabling Stable 3D Lithium Metal Anodes with Embedded Lithophilic Nanoparticles and a Solid Electrolyte Interphase Inducer

Three-dimensional (3D) current collectors can effectively mitigate the volumetric expansion of working lithium metal anodes (LMAs). However, the practical utilization of 3D current collectors for lithium metal batteries remains unsatisfactory because of inhomogeneous deposition of lithium ions and an unstable solid electrolyte interphase (SEI). Herein, a facile method based on the exchange reaction between Li and AgNO₃ is exploited to embed Ag nanoparticles (NPs) and LiNO₃ in a carbon paper (ALCP@Li). The Ag NPs act as a seed for even lithium deposition inside the carbon matrix by virtue of their excellent lithiophilicity. Simultaneously, LiNO₃ plays an effective role in stabilizing LMAs by evolving a robust N-rich SEI. As a result, such 3D LMAs show a high Coulombic efficiency in half-cells (200 cycles, 99% at 1 mA cm^-2, 1 mAh cm^-2) and a low overpotential (60 mV). When paired with commercial thick NCM622 and LiFePO₄ cathodes, the 3D LMA-based full cells exhibit stable cycling in carbonate electrolytes.

Coupling a 3D Lithophilic Skeleton with a Fluorine-Enriched Interface to Enable Stable Lithium Metal Anode

Lithium (Li) metal anode is known as a potential anode candidate for next-generation high-energy-density rechargeable batteries. Nevertheless, the challenge caused by the uncontrollable Li dendrites' growth and the fragile solid electrolyte interface (SEI) layer seriously hinders the commercial application of Li metal batteries. Herein, we report a fluorine-enriched nitrogen-doped hollow carbon spheres decorated carbon fibers (FNCS@CF) skeleton which effectively integrates the uniformly distributed lithophilic sites and mechanically robust LiF-enriched SEI, thus endowing the composite Li metal anode with durable and dendrite-free features. The Li nucleation barrier is greatly reduced owing to the strong lithiophilicity characteristics of pyridinic/pyrrolic nitrogen. The fluorinated hollow carbon spheres can not only provide a powerful setting for Li deposition but can also promote the in situ formation of LiF-enriched SEI. As a result, the prepared FNCS@CF skeleton demonstrates excellent electrochemical performances such as ultrahigh average Coulombic efficiency of 99.6% over 240 cycles at 3 mA h cm^-2 and remarkable cyclability (1300 h) with a low deposition overpotential of 10 mV. Furthermore, a FNCS@CF-Li|NCM full cell was also assembled which exhibits a prominent cycling stability and capacity retention even under simulated practical working conditions, i.e., low negative-to-positive capacity (N/P) ratio of 1.5 and lean electrolyte of 10 uL mAh^-1.

Stabilizing Zinc Electrodeposition in a Battery Anode by Controlling Crystal Growth

Reversible electrodeposition of metals at liquid-solid interfaces is a requirement for long cycle life in rechargeable batteries that utilize metals as anodes. The process has been studied extensively from the perspective of the electrochemical transformations that impact reversibility, however, the fundamental challenges associated with maintaining morphological control when a intrinsically crystalline solid metal phase emerges from an electrolyte solution have been less studied, but provide important opportunities for progress. A crystal growth stabilization method to reshape the initial growth and orientation of crystalline metal electrodeposits is proposed here. The method takes advantage of polymer-salt complexes (PEG-Zn²⁺ -aX^- ) (a = 1,2,3) formed spontaneously in aqueous electrolytes containing zinc (Zn²⁺ ) and halide (X^- ) ions to regulate electro-crystallization of Zn. It is shown that when X = Iodine (I), the complexes facilitate electrodeposition of Zn in a hexagonal closest packed morphology with preferential orientation of the (002) plane parallel to the electrode surface. This facilitates exceptional morphological control of Zn electrodeposition at planar substrates and leads to high anode reversibility and unprecedented cycle life. Preliminary studies of the practical benefits of the approach are demonstrated in Zn-I2 full battery cells, designed in both coin cell and single-flow battery cell configurations.

Advanced Electrolyte Design for High-Energy-Density Li-Metal Batteries under Practical Conditions

Given the limitations inherent in current intercalation-based Li-ion batteries, much research attention has focused on potential successors to Li-ion batteries such as lithium-sulfur (Li-S) batteries and lithium-oxygen (Li-O₂ ) batteries. In order to realize the potential of these batteries, the use of metallic lithium as the anode is essential. However, there are severe safety hazards associated with the growth of Li dendrites, and the formation of "dead Li" during cycles leads to the inevitable loss of active Li, which in the end is undoubtedly detrimental to the actual energy density of Li-metal batteries. For Li-metal batteries under practical conditions, a low negative/positive ratio (N/P ratio), a electrolyte/cathode ratio (E/C ratio) along with a high-voltage cathode is prerequisite. In this Review, we summarize the development of new electrolyte systems for Li-metal batteries under practical conditions, revisit the design criteria of advanced electrolytes for practical Li-metal batteries and provide perspectives on future development of electrolytes for practical Li-metal batteries.

Realizing Compact Lithium Deposition via Elaborative Nucleation and Growth Regulation for Stable Lithium-Metal Batteries

Metallic lithium (Li) has been regarded as an ideal candidate for anode materials in next-generation high-energy-density batteries. However, a ubiquitous spongy Li deposition results in low reversibility, huge interfacial impedance, and even safety issues, hindering its practical application. Herein, we proposed a bifunctional electrolyte (BiFE) to avoid the spongy Li deposition, in which lithium nitrate (LiNO₃) facilitates a uniform granular Li nucleation via forming a kinetically favorable solid electrolyte interphase and silicon dioxide (SiO₂) adsorbs anions to stabilize the electric field distribution near the electrode surface. Such a BiFE provides an even Li⁺ ion flux for the subsequent growth of electrochemical Li deposition, which was verified by ζ potential, Raman spectra, and specific capacitance characterizations, thus realizing a compact and uniform Li deposition via elaborative nucleation and growth regulation. An improved Li Coulombic efficiency of 99.1% can be achieved within BiFE. When used in Cu∥Li half-cells and Li∥Li symmetric cells, the high Li utilization prolonged the cycling life span to above 300 cycles and 1200 h, respectively. The compact Li deposition also resisted the corrosion of polysulfides to enhance the cycling performance of Li∥S full cells.

A high performance lithium metal anode enabled by CF4 plasma treated carbon paper

To substantially boost the energy density of secondary batteries, research studies on lithium metal anodes are booming to develop technologies on lithium metal batteries. However, suffering from lithium dendritic growth and volume expansion, the batteries are still far from practical applications. Herein, carbon paper (CP) is superficially fluorinated by CF4 plasma to endow the obtained composite lithium metal anode with both high areal capacity and long lifespan. The decreasing intensity of plasma from the upper surface to the bottom in the CP matrix achieves a higher F content and a lower conductivity on the top side, thus guiding more lithium to deposit inside the matrix. Besides, the fluorinated carbon paper (FCP) possesses flatter lithium plating in contrast to typical dendrites. As a result, the cells employing FCP as the anode achieve stable cycling over 350 cycles at a high areal capacity of 3 mA h cm-2 and a current density of 1 mA cm-2.

Characterising lithium-ion electrolytes via operando Raman microspectroscopy

Knowledge of electrolyte transport and thermodynamic properties in Li-ion and beyond Li-ion technologies is vital for their continued development and success. Here, we present a method for fully characterising electrolyte systems. By measuring the electrolyte concentration gradient over time via operando Raman microspectroscopy, in tandem with potentiostatic electrochemical impedance spectroscopy, the Fickian "apparent" diffusion coefficient, transference number, thermodynamic factor, ionic conductivity and resistance of charge-transfer were quantified within a single experimental setup. Using lithium bis(fluorosulfonyl)imide (LiFSI) in tetraglyme (G4) as a model system, our study provides a visualisation of the electrolyte concentration gradient; a method for determining key electrolyte properties, and a necessary technique for correlating bulk intermolecular electrolyte structure with the described transport and thermodynamic properties.

Evolution of Protrusions on Lithium Metal Anodes Stabilized by a Solid Block Copolymer Electrolyte Studied Using Time-Resolved X-ray Tomography

Growing demand for rechargeable batteries with higher energy densities has motivated research focused on enabling the lithium metal anode. A prominent failure mechanism in such batteries is short circuiting due to the uncontrolled propagation of lithium protrusions that often have a dendritic morphology. In this paper, the electrodeposition of metallic lithium through a rigid polystyrene-b-poly(ethylene oxide) (PS-b-PEO or SEO) block copolymer electrolyte was studied using hard X-ray microtomography. In this system, protrusions were approximately ellipsoidal globules: we take advantage of this simple geometry to quantify their growth as a function of polarization time and electrolyte salt concentration. The growth of 47 different globules was tracked with time to obtain average velocities of globule growth into the electrolyte. The globule diameter was a linear function of globule height in the electrolyte with a slope of about 6, independent of time and electrolyte salt concentration.

3D Printed Lithium-Metal Full Batteries Based on a High-Performance Three-Dimensional Anode Current Collector

A three-dimensional (3D) printing method has been developed for preparing a lithium anode base on 3D-structured copper mesh current collectors. Through in situ observations and computer simulations, the deposition behavior and mechanism of lithium ions in the 3D copper mesh current collector are clarified. Benefiting from the characteristics that the large pores can transport electrolyte and provide space for dendrite growth, and the small holes guide the deposition of dendrites, the 3D Cu mesh anode exhibits excellent deposition and stripping capability (50 mAh cm^-2), high-rate capability (50 mA cm^-2), and a long-term stable cycle (1000 h). A full lithium battery with a LiFePO₄ cathode based on this anode exhibits a good cycle life. Moreover, a 3D fully printed lithium-sulfur battery with a 3D printed high-load sulfur cathode can easily charge mobile phones and light up 51 LED indicators, which indicates the great potential for the practicability of lithium-metal batteries with the characteristic of high energy densities. Most importantly, this unique and simple strategy is also able to solve the dendrite problem of other secondary metal batteries. Furthermore, this method has great potential in the continuous mass production of electrodes.

Self-Assembly Lightweight Honeycomb-Like Prussian Blue Analogue on Cu Foam for Lithium Metal Anode

As a next-generation anode material for lithium batteries, Li metal anode suffers from inherent drawbacks such as infinite volume expansion and uneven Li plating/stripping. Herein, we propose a lightweight lithiophilic Prussian blue analogue (PBA) with honeycomb-like structure on Cu foam by self-assembly method to address these issues. The unique honeycomb-like architecture could provide enlarged surface areas and abundant deposition sites for homogenizing Li⁺ flux during Li plating. Consequently, the elaborate PBA-decorated Cu foam current collector enables long-term (1800 h) reversible plating/stripping behavior and an observably improved Coulombic efficiency (98.3% after 350 cycles). The concept of the direct self-assembly synthesis method on metal foam provides new insights into the design of a lightweight 3-dimensional current collector for Li metal anode.

Comparative performance of ex situ artificial solid electrolyte interphases for Li metal batteries with liquid electrolytes

The design of artificial solid electrolyte interphases (ASEIs) that overcome the traditional instability of Li metal anodes can accelerate the deployment of high-energy Li metal batteries (LMBs). By building the ASEI ex situ, its structure and composition is finely tuned to obtain a coating layer that regulates Li electrodeposition, while containing morphology and volumetric changes at the electrode. This review analyzes the structure-performance relationship of several organic, inorganic, and hybrid materials used as ASEIs in academic and industrial research. The electrochemical performance of ASEI-coated electrodes in symmetric and full cells was compared to identify the ASEI and cell designs that enabled to approach practical targets for high-energy LMBs. The comparative performance and the examined relation between ASEI thickness and cell-level specific energy emphasize the necessity of employing testing conditions aligned with practical battery systems.

Single-atom catalysts for high-energy rechargeable batteries

Clean and sustainable electrochemical energy storage has attracted extensive attention. It remains a great challenge to achieve next-generation rechargeable battery systems with high energy density, good rate capability, excellent cycling stability, efficient active material utilization, and high coulombic efficiency. Many catalysts have been explored to promote electrochemical reactions during the charge and discharge process. Among reported catalysts, single-atom catalysts (SACs) have attracted extensive attention due to their maximum atom utilization efficiency, homogenous active centres, and unique reaction mechanisms. In this perspective, we summarize the recent advances of the synthesis methods for SACs and highlight the recent progress of SACs for a new generation of rechargeable batteries, including lithium/sodium metal batteries, lithium/sodium-sulfur batteries, lithium-oxygen batteries, and zinc-air batteries. The challenges and perspectives for the future development of SACs are discussed to shed light on the future research of SACs for boosting the performances of rechargeable batteries.

A high efficiency electrolyte enables robust inorganic-organic solid electrolyte interfaces for fast Li metal anode

Developing a high-rate Li metal anode with superior reversibility is a prerequisite for fast-charging Li metal batteries. However, the build-up of large concentration gradients under high current density leads to inhomogeneous Li deposition and unstable passivation layers of Li metal, resulting in lower Coulombic efficiency. Here we report a concentrated dual-salts LiFSI-LiNO₃/DOL electrolyte to improve the high-rate performance of Li metal anode. Sufficient Li salts help passivate the fresh Li deposition quickly. Further, DOL contributes to the formation of flexible organic layers that can accommodate the rapid volume change of Li metal upon cycling. Li metal in the electrolyte remains stable over 240 cycles with the average Coulombic efficiency of 99.14% under a high current density of 8.0 mA cm^-2.

Non-Solvating and Low-Dielectricity Cosolvent for Anion-Derived Solid Electrolyte Interphases in Lithium Metal Batteries

Lithium (Li) metal anodes hold great promise for next-generation high-energy-density batteries, while the insufficient fundamental understanding of the complex solid electrolyte interphase (SEI) is the major obstacle for the full demonstration of their potential in working batteries. The characteristics of SEI highly depend on the inner solvation structure of lithium ions (Li⁺ ). Herein, we clarify the critical significance of cosolvent properties on both Li⁺ solvation structure and the SEI formation on working Li metal anodes. Non-solvating and low-dielectricity (NL) cosolvents intrinsically enhance the interaction between anion and Li⁺ by affording a low dielectric environment. The abundant positively charged anion-cation aggregates generated as the introduction of NL cosolvents are preferentially brought to the negatively charged Li anode surface, inducing an anion-derived inorganic-rich SEI. A solvent diagram is further built to illustrate that a solvent with both proper relative binding energy toward Li⁺ and dielectric constant is suitable as NL cosolvent.

A highly stable lithium metal anode enabled by Ag nanoparticle-embedded nitrogen-doped carbon macroporous fibers

Lithium metal has been considered as an ideal anode candidate for future high energy density lithium batteries. Herein, we develop a three-dimensional (3D) hybrid host consisting of Ag nanoparticle-embedded nitrogen-doped carbon macroporous fibers (denoted as Ag@CMFs) with selective nucleation and targeted deposition of Li. The 3D macroporous framework can inhibit the formation of dendritic Li by capturing metallic Li in the matrix as well as reducing local current density, the lithiophilic nitrogen-doped carbons act as homogeneous nucleation sites owing to the small nucleation barrier, and the Ag nanoparticles improve the Li nucleation and growth behavior with the reversible solid solution-based alloying reaction. As a result, the Ag@CMF composite enables a dendrite-free Li plating/stripping behavior with high Coulombic efficiency for more than 500 cycles. When this anode is coupled with a commercial LiFePO₄ cathode, the assembled full cell manifests high rate capability and stable cycling life.

Endogenous Symbiotic Li3 N/Cellulose Skin to Extend the Cycle Life of Lithium Anode

Nitrocellulose (NC) is proposed to stabilize the electrolytes for Li metal batteries. The nitro group of NC preferentially reacts with Li metal, and along with the cellulose skeleton is tightly wrapped on the surface, so that the polymer-inorganic double layer is formed on the Li surface. XPS profile analysis and corroborative cryo-environmental TEM reveal that the flexible outer layer of the bilayer is a C-O organic layer, while the dense inner layer is mainly composed of crystalline lithium oxide, lithium oxynitride, and lithium nitride. The Li deposition process was observed via in situ optical microscopy, which indicated that the NC-derived bilayer facilitates the uniform deposition of Li ions and inhibits the growth of dendrites. After the introduction of NC into the electrolyte, the cycle life of the Li battery is twice than that of the Li battery without NC at 1.0 and 3.0 mA cm^-2 .

Polymorph Evolution Mechanisms and Regulation Strategies of Lithium Metal Anode under Multiphysical Fields

Lithium (Li) metal, a typical alkaline metal, has been hailed as the "holy grail" anode material for next generation batteries owing to its high theoretical capacity and low redox reaction potential. However, the uncontrolled Li plating/stripping issue of Li metal anodes, associated with polymorphous Li formation, "dead Li" accumulation, poor Coulombic efficiency, inferior cyclic stability, and hazardous safety risks (such as explosion), remains as one major roadblock for their practical applications. In principle, polymorphous Li deposits on Li metal anodes includes smooth Li (film-like Li) and a group of irregularly patterned Li (e.g., whisker-like Li (Li whiskers), moss-like Li (Li mosses), tree-like Li (Li dendrites), and their combinations). The nucleation and growth of these Li polymorphs are dominantly dependent on multiphysical fields, involving the ionic concentration field, electric field, stress field, and temperature field, etc. This review provides a clear picture and in-depth discussion on the classification and initiation/growth mechanisms of polymorphous Li from the new perspective of multiphysical fields, particularly for irregular Li patterns. Specifically, we discuss the impact of multiphysical fields' distribution and intensity on Li plating behavior as well as their connection with the electrochemical and metallurgical properties of Li metal and some other factors (e.g., electrolyte composition, solid electrolyte interphase (SEI) layer, and initial nuclei states). Accordingly, the studies on the progress for delaying/suppressing/redirecting irregular Li evolution to enhance the stability and safety performance of Li metal batteries are reviewed, which are also categorized based on the multiphysical fields. Finally, an overview of the existing challenges and the future development directions of metal anodes are summarized and prospected.

Interfacial Atomistic Mechanisms of Lithium Metal Stripping and Plating in Solid-State Batteries

All-solid-state batteries based on a Li metal anode represent a promising next-generation energy storage system, but are currently limited by low current density and short cycle life. Further research to improve the Li metal anode is impeded by the lack of understanding in its failure mechanisms at lithium-solid interfaces, in particular, the fundamental atomistic processes responsible for interface failure. Here, using large-scale molecular dynamics simulations, the first atomistic modeling study of lithium stripping and plating on a solid electrolyte is performed by explicitly considering key fundamental atomistic processes and interface atomistic structures. In the simulations, the interface failure initiated with the formation of nano-sized pores, and how interface structures, lithium diffusion, adhesion energy, and applied pressure affect interface failure during Li cycling are observed. By systematically varying the parameters of solid-state lithium cells in the simulations, the parameter space of applied pressures and interfacial adhesion energies that inhibit interface failure during cycling are mapped to guide selection of solid-state cells. This study establishes the atomistic modeling for Li stripping and plating, and predicts optimal solid interfaces and new strategies for the future research and development of solid-state Li-metal batteries.

Insight into the Critical Role of Exchange Current Density on Electrodeposition Behavior of Lithium Metal

Due to an ultrahigh theoretical specific capacity of 3860 mAh g-1, lithium (Li) is regarded as the ultimate anode for high-energy-density batteries. However, the practical application of Li metal anode is hindered by safety concerns and low Coulombic efficiency both of which are resulted fromunavoidable dendrite growth during electrodeposition. This study focuses on a critical parameter for electrodeposition, the exchange current density, which has attracted only little attention in research on Li metal batteries. A phase-field model is presented to show the effect of exchange current density on electrodeposition behavior of Li. The results show that a uniform distribution of cathodic current density, hence uniform electrodeposition, on electrode is obtained with lower exchange current density. Furthermore, it is demonstrated that lower exchange current density contributes to form a larger critical radius of nucleation in the initial electrocrystallization that results in a dense deposition of Li, which is a foundation for improved Coulombic efficiency and dendrite-free morphology. The findings not only pave the way to practical rechargeable Li metal batteries but can also be translated to the design of stable metal anodes, e.g., for sodium (Na), magnesium (Mg), and zinc (Zn) batteries.

An Anode-Free Zn-MnO2 Battery

Aqueous Zn-based batteries are attractive because of the low cost and high theoretical capacity of the Zn metal anode. However, the Zn-based batteries developed so far utilize an excess amount of Zn (i.e., thick Zn metal anode), which decreases the energy density of the whole battery. Herein, we demonstrate an anode-free design (i.e., zero-excess Zn), which is enabled by employing a nanocarbon nucleation layer. Electrochemical studies show that this design allows for uniform Zn electrodeposition with high efficiency and stability over a range of current densities and plating capacities. Using this anode-free configuration, we showcase a Zn-MnO₂ battery prototype, showing 68.2% capacity retention after 80 cycles. Our anode-free design opens a new direction for implementing aqueous Zn-based batteries in energy storage systems.

The early-stage growth and reversibility of Li electrodeposition in Br-rich electrolytes

The physiochemical nature of reactive metal electrodeposits during the early stages of electrodeposition is rarely studied but known to play an important role in determining the electrochemical stability and reversibility of electrochemical cells that utilize reactive metals as anodes. We investigated the early-stage growth dynamics and reversibility of electrodeposited lithium in liquid electrolytes infused with brominated additives. On the basis of equilibrium theories, we hypothesize that by regulating the surface energetics and surface ion/adatom transport characteristics of the interphases formed on Li, Br-rich electrolytes alter the morphology of early-stage Li electrodeposits; enabling late-stage control of growth and high electrode reversibility. A combination of scanning electron microscopy (SEM), image analysis, X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and contact angle goniometry are employed to evaluate this hypothesis by examining the physical-chemical features of the material phases formed on Li. We report that it is possible to achieve fine control of the early-stage Li electrodeposit morphology through tuning of surface energetic and ion diffusion properties of interphases formed on Li. This control is shown further to translate to better control of Li electrodeposit morphology and high electrochemical reversibility during deep cycling of the Li metal anode. Our results show that understanding and eliminating morphological and chemical instabilities in the initial stages of Li electroplating via deliberately modifying energetics of the solid electrolyte interphase (SEI) is a feasible approach in realization of deeply cyclable reactive metal batteries.

Insights into the deposition chemistry of Li ions in nonaqueous electrolyte for stable Li anodes

Comprehensive understanding of the Li deposition chemistry from Li⁺ to Li atom is crucial for suppressing dendrite formation and growth.

Self-healing, Improved Efficiency Solid State Rechargeable Li/I2 Based Battery

Solid state electrolytes are receiving significant interest due to the prospect of improved safety, however, addressing the incidence and consequence of internal short circuits remains an important issue. Herein, a battery based on a LiI-LiI(HPN)₂ solid state electrolyte demonstrated self-healing after internal shorting where the cells recovered and continued to cycle effectively. The functional rechargeable electrochemistry of the self-forming Li/I₂-based battery was investigated through interfacial modification by inclusion of Li metal (at the negative interface), and/or fabricated carbon nanotube substrates at the positive interface. A cell design with lithium metal at the negative and a carbon substrate at the positive interface produced Coulombic efficiencies > 90% over 60 cycles. Finally, the beneficial effects of moderately elevated temperature were established where a 10°C temperature increase led to ~5X lower resistance.

Controlling electrochemical growth of metallic zinc electrodes: Toward affordable rechargeable energy storage systems

Scalable approaches for precisely manipulating the growth of crystals are of broad-based science and technological interest. New research interests have reemerged in a subgroup of these phenomena-electrochemical growth of metals in battery anodes. In this Review, the geometry of the building blocks and their mode of assembly are defined as key descriptors to categorize deposition morphologies. To control Zn electrodeposit morphology, we consider fundamental electrokinetic principles and the associated critical issues. It is found that the solid-electrolyte interphase (SEI) formed on Zn has a similarly strong influence as for alkali metals at low current regimes, characterized by a moss-like morphology. Another key conclusion is that the unique crystal structure of Zn, featuring high anisotropy facets resulting from the hexagonal close-packed lattice with a c/a ratio of 1.85, imposes predominant influences on its growth. In our view, precisely regulating the SEI and the crystallographic features of the Zn offers exciting opportunities that will drive transformative progress.

Noninvasive In Situ NMR Study of "Dead Lithium" Formation and Lithium Corrosion in Full-Cell Lithium Metal Batteries

Capacity retention in lithium metal batteries needs to be improved if they are to be commercially viable, the low cycling stability and Li corrosion during storage of lithium metal batteries being even more problematic when there is no excess lithium in the cell. Herein, we develop in situ NMR metrology to study "anode-free" lithium metal batteries where lithium is plated directly onto a bare copper current collector from a LiFePO4 cathode. The methodology allows inactive or "dead lithium" formation during plating and stripping of lithium in a full-cell lithium metal battery to be tracked: dead lithium and SEI formation can be quantified by NMR and their relative rates of formation are here compared in carbonate and ether-electrolytes. Little-to-no dead Li was observed when FEC is used as an additive. The bulk magnetic susceptibility effects arising from the paramagnetic lithium metal were used to distinguish between different surface coverages of lithium deposits. The amount of lithium metal was monitored during rest periods, and lithium metal dissolution (corrosion) was observed in all electrolytes, even during the periods when the battery is not in use, i.e., when no current is flowing, demonstrating that dissolution of lithium remains a critical issue for lithium metal batteries. The high rate of corrosion is attributed to SEI formation on both lithium metal and copper (and Cu+, Cu2+ reduction). Strategies to mitigate the corrosion are explored, the work demonstrating that both polymer coatings and the modification of the copper surface chemistry help to stabilize the lithium metal surface.

Tuning the Interfacial Electronic Conductivity by Artificial Electron Tunneling Barriers for Practical Lithium Metal Batteries

The native solid electrolyte interphase (SEI) in lithium metal batteries (LMBs) cannot effectively protect Li metal due to its poor ability to suppress electron tunneling, which may account for the increase of the SEI and even dead Li. It is desirable to introduce artificial electron tunneling barriers (AETBs) with ultrahigh insulativity and chemical stability to maintain a sufficiently low electronic conductivity of the SEI. Herein, a nanodiamond particle (ND)-embedded SEI is constructed by a self-transfer process. The ND serving as the AETB reduces the risk of electron penetration through the SEI, readjusts the electric field at the interface, and eliminates the tip effect. As a result, a dendrite-free morphology and dense massive microstructure of Li deposition are realized even with high areal capacity. Notably, full cells using ultrathin Li anodes (45 μm) and LiNi_0.8Co_0.1Mn_0.1O₂ cathodes (4.3 mA h cm^-2) can cycle stably over 110 cycles, demonstrating that the AETB-embedded SEI significantly alleviates the anode pulverization and safety concerns in practical LMBs.

Sustained-Release Nanocapsules Enable Long-Lasting Stabilization of Li Anode for Practical Li-Metal Batteries

A robust solid-electrolyte interphase (SEI) enabled by electrolyte additive is a promising approach to stabilize Li anode and improve Li cycling efficiency. However, the self-sacrificial nature of SEI forming additives limits their capability to stabilize Li anode for long-term cycling. Herein, we demonstrate nanocapsules made from metal-organic frameworks for sustained release of LiNO3 as surface passivation additive in commercial carbonate-based electrolyte. The nanocapsules can offer over 10 times more LiNO3 than the solubility of LiNO3. Continuous supply of LiNO3 by nanocapsules forms a nitride-rich SEI layer on Li anode and persistently remedies SEI during prolonged cycling. As a result, lifespan of thin Li anode in 50 μm, which experiences drastic volume change and repeated SEI formation during cycling, has been notably improved. By pairing with an industry-level thick LiCoO2 cathode, practical Li-metal full cell demonstrates a remarkable capacity retention of 90% after 240 cycles, in contrast to fast capacity drop after 60 cycles in LiNO3 saturated electrolyte.

Free-standing lithiophilic Ag-nanoparticle-decorated 3D porous carbon nanotube films for enhanced lithium storage

Lithium metal batteries are promising candidates for next generation high energy batteries. However, an undesirable dendrite growth hinders their practical applications. Herein, a three-dimensional (3D) porous carbon nanotube film decorated with Ag nanoparticles (CNT/Ag) has been synthesized via the thermal decomposition reaction of AgNO₃ into Ag nanoparticles, and then is transformed into a 3D porous CNT/Ag/Li film via thermal infusion to obtain a high-performance free-standing lithium host. This as-formed 3D CNT/Ag/Li host can effectively restrain the dendrite growth by guiding Li deposition via the highly lithiophilic Ag nanoparticle seeds and lowering local current density of the highly conductive matrix. The as-prepared CNT/Ag/Li electrode exhibits long-term cycling stability over 200 cycles at a current density of 1 mA cm⁻² with an areal capacity of 1.0 mA h cm⁻². Moreover, the full cell paired with a sulfur/C cathode shows good cycling stability. Therefore, the 3D porous CNT/Ag/Li film formed via a facile three-step fabrication process can enlarge the cycle lifetime of a lithium metal anode.

A 3D porous CNT/Ag/Li film as a high-performance free-standing lithium host has been synthesized via combining a thermal decomposition process and thermal infusion process.