Lithiophilic Zn-modified soft carbon host for stable lithium deposition in lithium metal batteries

Lithium metal batteries are widely considered to be a next-generation battery technology due to their high energy density, fast charging capability, and potential to power a wide range of applications, from portable electronics to electric vehicles.Compared to conventional lithium-ion batteries, which use graphite as the anode material, lithium metal batteries have the potential to offer significantly higher energy density. This is because lithium metal has a much higher theoretical capacity than graphite, meaning it can store more energy per unit weight or volume. As a result, lithium metal batteries could potentially offer longer run times and smaller form factors than lithium-ion batteries, which are already widely used in consumer electronics and electric vehicles.In addition to their high energy density, lithium metal batteries also offer fast charging capabilities. This is because the lithium metal anode can be charged more quickly than the graphite anode used in conventional lithium-ion batteries. This could enable faster charging times for electric vehicles and other applications, reducing the time required for recharging and improving their overall usability.However, one of the major challenges with lithium metal batteries is dendrite growth, which can occur when lithium metal ions deposit unevenly on the surface of the anode during charging. These dendrites are needle-like structures that can penetrate the separator and cause short-circuits, leading to reduced battery performance and safety issues. As a result, much of the research on lithium metal batteries has focused on developing strategies to prevent dendrite growth, such as using coatings or electrolytes with additives that can stabilize the lithium metal anode.Despite these challenges, lithium metal batteries continue to be a promising next-generation battery technology. Researchers are working on improving their energy density, charging speed, and safety, and they are exploring a range of applications, from portable electronics to electric vehicles and grid-scale energy storage. If these challenges can be overcome, lithium metal batteries could revolutionize the energy storage industry and enable a wide range of new and exciting applications.To address this issue, we have explored the use of various coatings on the lithium metal anode to prevent dendrite growth. In this study, ordered mesoporous silica with different pore sizes and pore structures, such as SBA-15 and KIT-6, were used as coatings between the lithium metal anode and separator.SBA-15 and KIT-6 are two types of mesoporous silica materials that are widely used in various applications due to their unique properties. The synthesis of these materials involves the use of templates to control the pore size and structure.They are synthesized using a combination of a surfactant(pluronic P123 or cetyltrimethylammonium bromide;CTAB) as the template and tetraethyl orthosilicate(TEOS) as the silica source. The synthesis involves mixing a solution of surfactant and TEOS in acidic conditions, followed by aging and calcination steps. The resulting materials have a highly ordered hexagonal pore structure(SBA-15) and body-centered cubic pore structure(KIT-6) with a pore size ranging from 5 to 20 nm.By coating the surface of the lithium metal with a uniform pore structure material such as ordered mesoporous silica, dendrite growth can be suppressed and lithium deposition can occur more uniformly.The uniform pore structure material acts as a physical barrier to lithium ion diffusion and helps to control the deposition of lithium ions onto the surface of the lithium metal. When lithium ions are deposited onto the surface of the lithium metal, they can form a layer of lithium that can grow and become thick over time. If the lithium layer is too thick, it can become unstable and form dendrites. However, the uniform pore structure material can help to limit the thickness of the lithium layer and promote the deposition of lithium ions in a more uniform manner, thus reducing the likelihood of dendrite formation.Additionally, the uniform pore structure material can help to reduce the concentration of lithium ions at the surface of the lithium metal, which is another factor that can contribute to dendrite growth. By limiting the concentration of lithium ions at the surface, the uniform pore structure material can help to prevent the formation of high-concentration regions that can promote dendrite growth.Overall, the mechanism by which a uniform pore structure material can suppress dendrite growth involves controlling the deposition of lithium ions onto the surface of the lithium metal, limiting the thickness of the lithium layer, and reducing the concentration of lithium ions at the surface. These factors help to promote more uniform lithium deposition and prevent the formation of dendrites, leading to improved battery performance and safety.

Extreme temperatures (<‐20 °C or >50 °C) would seriously impair the performance of lithium batteries through deteriorating bulk ion transport and electrode interfaces. Here, a rational design of weak solvent and anti‐solvent combination is presented for wide‐temperature electrolytes. The weak solvent provides accelerated desolvation kinetics of Li+ around the anode region, while the anti‐solvent not only functions as an antifreeze agent for smooth ion migration at low temperatures but also interacts with the weak solvent to boost the formation of ionic aggregates. The weak and anti‐solvent electrolyte (WAE) exerts excellent compatibility with both lithium metal and graphite. Under −40 °C, Li anode delivers 98.5% Coulombic efficiency and graphite outputs capacity over 230 mAh g‐1. Lithium‐ion/metal batteries by pairing graphite anode with LiCoO2 cathode with a negative to positive capacity ratio of 0.75 can realize steady operation at −50 °C with an average coulombic efficiency of 99.9%. Lithium metal batteries with 4.2 mAh cm‐2 high LiCoO2 cathode loading and 50 µm thin lithium anode deliver 73.8% capacity output at −40 °C. Besides, the cells are stable up to 80 °C with an average coulombic efficiency of 99.7%. This research demonstrates a relatively loose Li+ solvation environment in WAE systems and provides wide‐temperature electrolyte for high‐performance lithium ion and metal batteries.

Rechargeable lithium metal batteries (LMBs) are hindered by uncontrolled dendrite growth and interfacial instability driven by erratic ion migration and unstable electrochemical dynamics at the anode interface. In this study, a multifunctional three-dimensional interpenetrating Co-DPBB metal-organic framework (MOF) coating as an artificial solid electrolyte interphase was introduced to homogenize ion migration and expedite transport behaviors across the electrode-electrolyte interface. Through synergistic density functional theory (DFT) calculations and comprehensive in situ/ex situ characterizations, the relationship of orchestrated lithium-ion desolvation kinetics, charge transfer efficiency, and deposition topography with Co-DPBB's nanoarchitectural channels and lithiophilic anchoring moieties were decoupled. Co-DPBB-modified electrodes exhibit exceptional electrochemical performance, with reduced polarization, extended cycle life (>8000 h), and stable lithium deposition. This work introduces a transformative interfacial engineering approach, laying the groundwork for high-energy-density LMBs.

Lithium ion batteries (LIB) are representing a milestone in electrochemical energy storage and are still the state-of-the-art battery system for various mobile and stationary energy storage applications. However, the practical energy density of LIBs starts to reach an asymptotic limit. Beside LIBs, an auspicious variety of battery systems comprising a better option for specific applications in terms of e.g. energy density, so establishing a diversity of specific battery systems for specific applications is a good strategy.[1 ] After initially paving the way for the LIB, the lithium metal battery (LMB) experiences a revival due to an outstanding theoretical specific capacity (3 860 mAh g−1) and low electrochemical potential (−3.04 V vs. SHE). However, continuous electrolyte consumption, the formation of an inhomogeneous SEI and high surface area lithium (HSAL), whose growth is induced by the heterogeneous and fragile structure of the SEI film, are still dominant challenges that need to be overcome. The liquid electrolytes also deal with safety issues like risk of leakage and flammability. The combination of Li metal with solid polymer electrolytes (SPE) could supress HSAL formation and avoid those safety hazards. However, SPEs deal with poor ionic conductivity at room temperature (10−8 S cm−1 ≤ σ ≤ 10−5 S cm−1) and, additionally, it is necessary to control the Li morphology during electrodeposition/dissolution to realize high-energy all-solid-state batteries (ASSB) based on Li metal anodes.[2 ,3 ] Several artificial protective coatings have been proposed to improve the LMA/SPE interface by facilitating the Li ion flux, promoting a homogeneous Li electrodeposition/dissolution and protecting the LMA against electrolyte degradation as well as enhancing the Li wetting interface. The SPE induces a more flexible interphase that withstands the volume change. Recently, metal oxides coated by atomic layer deposition (ALD) have gained attention due to a great thickness control, the possibility of monolayer deposition as well as a consequential homogeneity of the deposited protection layer. Furthermore, ALD is suitable for roll-to-roll coatings which is feasible for industrial application.[3,4 ] Herein, the setup of Li-metal-polymer batteries (LMP® technology) commercialized by Blue Solutions and applied in their “blue cars” (30 kWh, 100 Wh kg-1) was modified in several points. Li metal was coated with a metal oxide via atomic layer deposition (ALD) to form an intermetallic phase as protective layer and to improve the Li+ flux. The artificial protective coating at Li metal was combined with a PEO- and/or polyether-based SPE and the effect of the modifications on the electrochemical performance in different ASSB setups was investigated and characterized.[1] Placke, T.; Kloepsch, R.; Dühnen, S.; Winter, M. Lithium ion, lithium metal, and alternative rechargeable battery technologies: the odyssey for high energy density. Journal of Solid State Electrochemistry 2017, 21, 1939-1964.[2] Cheng, X.-B.; Zhang, R.; Zhao, C.-Z.; Zhang, Q. Toward Safe Lithium Metal Anode in Rechargeable Batteries: A Review. Chemical Reviews 2017, 117, 10403-10473.[3] Han, Z.; Zhang, C.; Lin, Q.; Zhang, Y.; Deng, Y.; Han, J.; Wu, D.; Kang, F.; Yang, Q. H.; Lv, W. A Protective Layer for Lithium Metal Anode: Why and How. Small Methods 2021, 5, 2001035.[4] Han, Y.; Liu, B.; Xiao, Z.; Zhang, W.; Wang, X.; Pan, G.; Xia, Y.; Xia, X.; Tu, J. Interface issues of lithium metal anode for high‐energy batteries: Challenges, strategies, and perspectives. InfoMat 2021, 3, 155-174.

The poor electrochemical stability window and low ionic conductivity in solid‐state electrolytes hinder the development of safe, high‐voltage, and energy‐dense lithium metal batteries. Herein, taking advantage of the unique electronic effect of nitrile groups, we designed a novel azanide‐based single‐ion covalent organic framework (CN−iCOF) structure that possesses effective Li+ transport and high‐voltage stability in lithium metal batteries. Density functional theory (DFT) calculations and molecular dynamics (MD) revealed that electron‐withdrawing nitrile groups not only resulted in an ultralow HOMO energy orbital but also enhanced Li+ dissociation through charge delocalization, leading to a high tLi+ of 0.93 and remarkable oxidative stability up to 5.6 V (vs. Li+/Li) simultaneously. Moreover, cyanation leveraging Strecker reaction transformed reversible imine‐linkage to a stable sp3‐carbon‐containing azanide anion, which facilitated contorted alignment of transport “ladders” along the one‐dimensional anionic channels and the ionic conductivity could reach 1.33×10−5 S cm−1 at ambient temperature without any additives. As a result, CN−iCOF allowed operation of solid‐state lithium metal batteries with high‐voltage cathodes such as LiNi0.8Mn0.1Co0.1O2 (NCM811), demonstrating stable lithium deposition up to 1,100 h and reversible battery cycling at ambient temperature up to 4.5 V, shedding light on the importance of discovering new functionality for forthcoming high‐performance batteries.

The poor electrochemical stability window and low ionic conductivity in solid-state electrolytes hinder the development of safe, high-voltage, and energy-dense lithium metal batteries. Herein, taking advantage of the unique electronic effect of nitrile groups, we designed a novel azanide-based single-ion covalent organic framework (CN-iCOF) structure that possesses effective Li+ transport and high-voltage stability in lithium metal batteries. Density functional theory (DFT) calculations and molecular dynamics (MD) revealed that electron-withdrawing nitrile groups not only resulted in an ultralow HOMO energy orbital but also enhanced Li+ dissociation through charge delocalization, leading to a high tLi+ of 0.93 and remarkable oxidative stability up to 5.6 V (vs. Li+/Li) simultaneously. Moreover, cyanation leveraging Strecker reaction transformed reversible imine-linkage to a stable sp3-carbon-containing azanide anion, which facilitated contorted alignment of transport "ladders" along the one-dimensional anionic channels and the ionic conductivity could reach 1.33×10-5 S cm-1 at ambient temperature without any additives. As a result, CN-iCOF allowed operation of solid-state lithium metal batteries with high-voltage cathodes such as LiNi0.8Mn0.1Co0.1O2 (NCM811), demonstrating stable lithium deposition up to 1,100 h and reversible battery cycling at ambient temperature up to 4.5 V, shedding light on the importance of discovering new functionality for forthcoming high-performance batteries.

Effectively managing Li+ migration behaviors and addressing the issues of side reactions at the electrolyte-electrode interface is crucial for advancing high-performance lithium metal batteries (LMBs). Herein, this work introduces a two-dimensional hydrogen-bonded organic framework (HOF) enriched with multi-site H-bonding and lithiophilic sites for the first time to tailor the electronic structure and solvation chemistry in lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) based electrolyte and stabilize the lithium metal anodes (LMAs) interface. Initially, the abundant lithiophilic sites (C═O, C═N) in the HOF coordinate with Li+, acting as key electron donors to optimize the electronic structure while also reducing the desolvation energy barrier when Li+ dissociates from the solvent sheath. Moreover, the multifunctional hydrogen bonding not only acts as the "appended manipulator" to anchor -NH2 to LiTFSI and reduces the adverse reactions at the LMAs interface but also mitigates the mechanical stress during lithium deposition. As evidenced by various in/ex situ characterizations, the HOF-modified lithium-metal symmetric batteries exhibit ultra-long cycling performance (11000h) and low voltage fluctuations at 3mA cm-2. This unique strategy of hydrogen-bonded synergistic lithiophilic sites provides a new perspective on the design of artificial interfacial layers for stabilizing lithium metal batteries.

Lithium metal batteries (LMBs) are considered as one type of the most promising next‐generation energy storage devices with high‐energy‐density, and stabilizing the lithium metal anodes (LMAs) to overcome LMBs’ safety concerns and performance degradation has attracted extensive attention. Introducing advanced polymer materials into the critical components of LMBs has proven to be an effective and promising approach for stabilizing LMAs toward practical application of LMBs. In addressing the lack of a timely review on the emerging progress of advanced polymer materials in LMBs for stabilizing LMAs, a comprehensive article summarizing the most recent developments of multiscale cellulose materials, including micron cellulose (MC) and nanocellulose (NC), in LMBs is reviewed. First, the basic structures of cellulose, characteristics comparison, and the development history of introducing cellulose into LMBs are presented. Furthermore, the roles of multiscale cellulose materials and functional mechanisms in various components of LMBs for stabilizing LMAs are summarized. A general conclusion and a perspective on the current limitations and future research directions of cellulose‐based stable LMBs are proposed. The aim of this review is not only to summarize the recent progress of multiscale cellulose materials in stabilizing LMAs but also to lighten the pathways for realizing LMBs’ practical application.

A fast ionic transport copolymeric network for stable quasi-solid lithium metal battery

Anode-free sulfide-based all-solid-state lithium metal batteries (ASSLMBs), which eliminate the need for a lithium metal anode during fabrication, offer superior energy density, enhanced safety, and simplified manufacturing. Their performance is largely influenced by the interfacial properties of the current collectors. Although previous studies have investigated the degradation of sulfide electrolytes on commonly used copper (Cu) and stainless steel (SS) current collectors, the impact of spontaneously formed surface oxides, such as copper oxide (Cu2O/CuO) and chromium oxide (Cr2O3), on interfacial stability remains underexplored. This study systematically evaluates the neglected role of passivation layers of both Cu and SS. Results demonstrate that Cu facilitates more stable lithium deposition. Electrochemical impedance spectroscopy (EIS) reveals that interfacial resistance on SS is consistently higher than on Cu during cycling. In-situ X-ray absorption spectroscopy (XAS) and computational modelling confirm the formation of phosphate (PO4 3-) and sulfate (SO4 2-) species at both interfaces, attributed to reactions between the sulfide electrolyte and surface oxides. On SS, partial reversible formation of transition metal chlorides is also detected. Based on these findings, an artificial interface is engineered on Cu, significantly improving lithium plating/stripping efficiency. These insights contribute to solid-solid interface engineering strategies and advance the fundamental understanding of anode-free ASSLMBs.

Polymer electrolytes‐based lithium metal batteries have attracted much more attention for next‐generation energy storage devices owing to their high energy density and superior safety characteristics. However, there are still some obstacles to ameliorate interfacial compatibility between conventional polymer electrolytes with lithium metal anode and high‐voltage cathodes. It is noted that poly (maleic anhydride) copolymers (PMAC)‐based polymer electrolytes (PEs) exhibit superior interfacial compatibility with both lithium metal anode and high‐voltage cathodes in virtue of their distinctive structure. These superb characteristics will endow PMAC‐based PEs very promising candidate to develop highly safe and high‐energy‐density lithium metal batteries. So far, PMAC‐based PEs have been widely used in lithium metal batteries and high‐voltage lithium metal batteries because of their prominent advantages. Herein, recent key advances of PMAC‐based PEs are summarized. The key factors affecting ionic conductivity are elaborated in terms of structural control of PMAC, lithium salts, fillers, and plasticizers. Moreover, the interfacial compatibility of PMAC‐based PEs with lithium metal anode and high‐voltage cathodes is also discussed in details. Furthermore, potential challenges and prospects of PMAC‐based PEs are also envisioned at the end of this review. It is believed that this review will shed light on highly safe and high‐energy‐density lithium metal batteries.

Rechargeable lithium (Li) metal batteries (LMBs) have been revived in recent years because of the ever-increasing demand for high-energy-density batteries. 1,2 However, significant challenges, such as low Columbic efficiency (CE), pulverization and large volume expansion related to the Li metal anode still limit the large-scale application of these batteries. 3 Here, we report an approach to improve the Li CE and minimize the Li pulverization and volume expansion by using fluorinated orthoformate in electrolytes. 4 Tris(2,2,2-trifluoroethyl) orthoformate (TFEO) functions as an efficient diluent in electrolytes based on lithium bis(fluorosulfonyl)imide (LiFSI) and 1,2-dimethoxyethane (DME) and formulates highly concentrated LiFSI-DME clusters that are dispersed among the TFEO diluent. Such localized high-concentration electrolytes demonstrate superior electrochemical properties when used in LMBs with a high voltage LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode. The mechanisms behind the long cycle life of Li||NMC811 cells under practical conditions are mainly the formation of highly effective solid electrolyte interphase and cathode electrolyte interphase, which are monolithic and prevent continuous electrode/electrolyte side reactions. This work provides guidance for further development of electrolytes for high-energy-density LMBs. The details will be discussed during the presentation.References1 J.-G. Zhang, W. Xu, W. A. Henderson, Lithium Metal Anodes and Rechargeable Lithium Metal Batteries. XV, 194 (Springer International Publishing, 2017).2 J. Liu, et al. Pathways for practical high-energy long-cycling lithium metal batteries. Nature Energy 4, 180-186 (2019).3 C. Niu, et al. High-energy lithium metal pouch cells with limited anode swelling and long stable cycles. Nature Energy 4, 551-559 (2019).4 X. Cao, et al. Monolithic solid–electrolyte interphases formed in fluorinated orthoformate-based electrolytes minimize Li depletion and pulverization. Nature Energy 4, 796-805 (2019).

Lithium metal batteries, which use lithium metal as the anode, have the advantage of much higher energy density over the commercially used lithium-ion batteries with graphite as the anode. However, during repeated charge-discharge cycles, lithium dendrites may form due to uneven deposition of lithium on the lithium metal anode, and lithium dendrite growth induced short-circuits are always a problem preventing lithium-metal batteries from being used in a lot of applications. Using solid polymer electrolyte (SPE) for lithium metal batteries has the benefit of using the electrolyte as the electrode separator while inhibiting the growth of lithium dendrites. The current most significant issue for SPEs is low ionic conductivity at room temperature. Poly(ethylene glycol) (PEG) has been extensively used for SPE systems due to its strong lithium ion solvating ability and high dielectric constant. In this study, crosslinked PEG polymer electrolyte membranes were synthesized with different amount of plasticizers to produce samples with different ionic conductivities and mechanical properties. It was shown that, with the increase amount of small PEG molecules added, the ionic conductivities of the SPEs showed significant increase and mechanical properties decreases. Performance of the electrolytes was correlated with both properties, and the results were analyzed to propose the ideal design for PEG polymer electrolytes for lithium metal polymer batteries.

The commercialization of lithium metal batteries is hindered by critical challenges such as uncontrollable lithium dendrite growth and interfacial instability. Constructing functional nanocoatings on separator surfaces represents an effective strategy to address these issues. In this study, a uniform aluminum-doped zinc oxide (AZO) modification layer was deposited on the separator via magnetron sputtering to enhance the electrochemical performance and safety of lithium metal batteries. The AZO layer combines the functions of a physical barrier and an interfacial regulator. On one hand, it effectively suppresses lithium dendrite penetration through the separator. On the other hand, its surface properties facilitate uniform lithium-ion transport and reduce the deposition overpotential. Experimental results demonstrate that the symmetric cells employing AZO-modified separators exhibit significantly reduced and stable lithium deposition overpotentials. In full cells assembled with a nickel cobalt aluminum (NCA) cathode, the system demonstrates higher specific capacity and notably extended cycle life compared to cells using unmodified polyethylene (PE) separators. This work proposes a practical strategy based on AZO-modified separators, offering a promising pathway toward the development of next-generation lithium metal batteries with high energy density and improved safety.

Congener-derived template to construct lithiophilic organic-inorganic layer/interphase for high volumetric capacity dendrite-free Li metal batteries