Low Electrochemical Potential Research Articles

Highly Effective Polyacrylonitrile-Rich Artificial Solid-Electrolyte-Interphase for Dendrite-Free Li-Metal/Solid-State Battery.

Lithium metal anode batteries have attracted significant attention as a promising energy storage technology, offering a high theoretical specific capacity and a low electrochemical potential. Utilizing lithium metal as the anode material can substantially increase energy density compared with conventional lithium-ion batteries. However, the practical application of lithium metal anodes has encountered notable challenges, primarily due to the formation of dendritic structures during cycling. These dendrites pose safety risks and degrade battery performance. Addressing these challenges necessitates the development of a reliable and effective protection layer for lithium metal. This study presents a cost-effective and convenient method to spontaneously produce lithium metal protective layers by creating polymeric layers by using acrylonitrile (AN). This method remarkably extends 6× of the lifetime of lithium metal anodes under high current density (1 mA/cm2) cycling conditions. While the cycle life of bare lithium metal is approximately 150 h under high current cycling conditions, AN-treated lithium metal anodes exhibit an impressive longevity of over 900 h. The AN-treated lithium metal anodes are further integrated and tested with sulfide-based Li10GeP2S12 (LGPS) solid-state electrolytes to evaluate its interfacial stability at a solid-solid interface. The formation of the polyacrylonitrile (PAN)-rich ASEI, due to AN-treatment, effectively reduces and stabilizes the cell overpotential to only one-tenth of that with the interface without treatment. This strategy paves a route to enable a highly efficient and highly stable Li/LGPS solid-state battery interface.

Dynamic Processes at the Electrode‐Electrolyte Interface: Implications for Lithium Deposition Stability

AbstractLithium (Li) metal is a promising negative electrode material for high‐energy‐density rechargeable batteries, owing to its exceptional specific capacity, low electrochemical potential, and low density. However, challenges such as dendritic Li deposits, leading to internal short‐circuits, and low Coulombic efficiency hinder the widespread adoption of lithium‐metal batteries (LMBs). These issues stem from the morphological instability of Li deposition, influenced by dynamic processes at the electrolyte|Li interface. Understanding the interplay between electrolyte properties, interfacial kinetics, and Li deposition stability is crucial yet challenging due to their simultaneous occurrence and the complexity of the solid electrolyte interphase (SEI) layer. This review discusses three key dynamic processes influencing Li deposition: desolvation of Li+ ions, transport through the SEI, and electrochemical reduction. The effects of electrolyte properties on these processes and their interplay with electroplating stability are discussed, highlighting contradictions in the literature and proposing explanations for the discrepancies. Despite numerous reviews on SEI structure and composition effects, this article emphasizes the kinetic aspects at interfaces, aiming to provide clarity and direction for future research in achieving stable Li deposition in LMBs.

Bi-Functional Interfacial Modification enables Highly-Exposed Zn(002) Crystal Facet towards Durable Zn Metal Batteries.

Zn-ion batteries (ZIBs) have garnered growing interest in large-scale energy storage devices for the high safety, high theoretical capacity and low electrochemical potential. Nevertheless, their widespread applications are significantly impeded by dendrite formation, hydrogen evolution and corrosion reactions of Zn anodes. Herein, a bi-functional polyacrylic acid (PAA) modified-Zn anode (Zn-PAA) is designed to concurrently inhibit Zn dendrite formation and alleviate side reactions. The bi-functional PAA coating not only selectively acid-etches the active Zn crystal facets to guide the planar deposition along the highly-exposed Zn(002) crystal facet, but also facilitate uniform Zn deposition through coordination between the polymer functional groups and Zn2+. Meanwhile, the electrically-insulated PAA protective layer effectively separates Zn anodes from the electrolyte and modulates the solvation structure of Zn2+.6H2O, significantly suppressing side reactions. Consequently, the assembled Zn-PAA//Zn-PAA symmetrical cell delivers an outstanding cycling stability of 1600 h at 1 mA cm-2 and 1 mAh cm-2. The assembled KVO//Zn-PAA full cell shows exceptional cycling stability over 1500 cycles at 2.0 A g-1 with a high Coulombic efficiency approaching 100%. The facile bi-functional surface modification strategy, which enables to finely tune the crystal facet texture and ion distribution manner, opens up a groundbreaking path towards safe and durable ZIBs.

Interfacial challenges and recent advances of solid‐state lithium metal batteries

AbstractGrowing market demands on portable electronics, electric vehicles, and energy storage system calls for the development of high‐energy density lithium (Li) batteries. Li metal is considered as a promising anode material owing to their high capacity and low electrochemical potential. However, high reactivity of Li metal with conventional flammable liquid electrolytes easily forms Li dendrites, which may cause short‐circuit and even catching fire, obstructing the wide application of Li metal batteries. Although non−/less‐flammable solid electrolytes have replaced the conventional liquid electrolytes, solid‐state Li metal batteries (SSLMBs) suffer from lower Li+ conductivities, chemical/electrochemical incompatibilities toward Li metal, and inhomogeneous Li+ flux at the interfaces. Therefore, many researchers have devoted themselves to solve these problems. For a better understanding on the current issues and recent advances, this article provides (1) a review on various solid electrolytes with high Li+ conductivity and their interfacial issues in SSLMBs, and (2) recent progress in stabilization of the interface between the Li node and solid electrolytes, including an electrolyte modification (e.g., composition, additives) and introduction of an interlayer.

Polymerized Acrylonitrile Artificial SEI for Long-Life Li-Metal Battery and Enhanced Stability for Li/Li10GeP2S12 Interface

Lithium metal anode batteries have attracted significant attention as a promising energy storage technology, offering a high theoretical specific capacity and low electrochemical potential. Utilizing lithium metal as the anode material can substantially increase energy density compared to conventional lithium-ion batteries. However, the practical application of lithium metal anodes has encountered notable challenges, primarily due to the formation of dendritic structures during cycling. These dendrites pose safety risks and degrade battery performance. Addressing these challenges necessitates the development of a reliable and effective protection layer for lithium metal. This study presents a cost-effective and convenient method to produce lithium metal protective layers by creating ex-situ polymer layers using acrylonitrile (AN). This method extends the lifetime of lithium metal anodes by a remarkable factor of six under high current (1 mA/cm²) cycling conditions. While the cycle life of bare lithium metal is approximately 150 hours under high current conditions, AN-treated lithium metal anodes exhibit an impressive longevity of over 900 hours.Furthermore, with the increasing attentions on solid-state electrolytes – which address the safety concerns and energy density limitations associated with conventional liquid electrolytes in lithium-ion batteries, the interface between Li metal and solid-state electrolytes has been the major challenges. For example, Li10GeP2S12 (LGPS) stands out among these solid electrolyte materials, boasting high ionic conductivity (1 x 10⁻² S cm⁻¹). Nonetheless, the severe instability of the interface between lithium metal anodes and solid electrolytes, including dendrite formation and electrolyte degradation, hindering their practical implementation. This work also goes deeply to explore the stability and performance of Li | LGPS systems by utilizing a polymerized acrylonitrile interfacial. By elucidating the mechanisms governing the interfacial layers, this low-cost fabrication of AN-treated lithium metal holds significant potential for advancing the commercialization of future lithium-metal batteries, surpassing the capabilities of traditional lithium-ion batteries.

Unlocking the Capability of the Lithium Metal Battery Anode through Organofluorine Additives

Metallic lithium as the anode material in batteries offer extraordinarily high specific capacity and low electrochemical potential, allowing lithium metal batteries (LMBs) to achieve gravimetric energy densities unobtainable by traditional intercalation-based chemistry. However, one must control the morphology and composition of its solid electrolyte interphase (SEI) in order to suppress the growth of separator-piercing Li dendrites and combat electrolyte depletion. Here, we find the usage of small amounts of organofluorine additives to the commercial ethylene carbonate and diethyl carbonate (EC-DEC) electrolyte mixture improves the specific capacity and capacity retention (>99% over 100 cycles at C/3 rate) of LiNi8.15Co1.5Al0.35O2 (NCA) LMB cells. Esters, carboxylic acids, and ketoesters with various degrees of fluorination were explored as potential electrolyte additives. Figure 1

Li-Sn Alloyed Layer Containing Artificial SEI on Li-Metal Anode for Superior Lithium Metal Batteries: Development and Understanding of Anode/Electrolyte Interfacial Phenomena

Modern civilization and cutting-edge technologies and tools are highly dependent on energy storage devices and demand efficient and long-lasting high-energy-density storage devices. Lithium metal batteries have surpassed their competitors concerning energy density due to their inherent high specific capacity (3860 mAh/g) and the lowest electrochemical potential (-3.04 V vs. standard hydrogen electrode), proving to be one of the most favorable energy storage devices for smart and mobile gadgets, electric automobiles, grid storage, etc. However, safety-threatening and performance-decay challenges associated with lithium metal anodes, such as lithium dendrite formation, uncontrolled parasitic reactions between Li-metal and electrolyte, low coulombic efficiency, dead Li-formation, etc., restrict its employment in practical batteries. The root cause of the dendrite formation is poor Li-ion conductivity of bulk lithium metal, which results in an uneven electric field distribution, leading to non-uniform Li deposition/stripping upon repeated charge/discharge. Herein, a facile chemical reduction process is being opted to fabricate a highly Li-ion diffusive Li-Sn-based artificial SEI layer on the lithium metal surface to prevail over the above-mentioned issues. Therefore, upon careful concentration investigation of reactants, 25 mM precursor concentration (SnCl4 in EC: DMC in 1:1 volume ration) demonstrated the best electrochemical performance, revealing a cumulative capacity of over 700 mAh/cm2 at a current density of 1 mA/cm2 for 1 h in a symmetric cell. Physical characterizations (XRD and SEM-EDS) showed a thin layer containing Li-Sn alloys along with LiCl formed at the lithium metal surface. Possessing high Li-ion diffusivity, Li-Sn alloyed hybrid anode illustrated a gradual decrease in the charge transfer resistance on increasing the concentration, thus, lower overpotential in symmetric cells, in contrast to pristine Li-metal. However, an increase in the electrical resistance has been observed on increasing the precursor concentration due to the presence of the insulating LiCl phase in the protective layer. Moreover, in-situ optical microscopy demonstrated more uniform and on-surface Li-deposition for the hybrid electrode, whereas mossy and dendritic growth on bare Li-metal. Full cells prepared with Li-Sn alloyed anode against NMC532 cathode illustrated stable cycling up to 150 cycles; contrastingly, the cell with pristine Li-metal showed a drastic capacity fade just after 100 cycles, demonstrating the inclination towards safer lithium metal batteries.

Unraveling the Dynamics of Solid-Electrolyte Interphase (SEI) Formation on Lithium Metal: Insights from Multiscale Modeling

We need batteries to get the best out of renewable energies and other low-carbon energy sources, and the most promising path forward is to invest in high-energy-density battery technologies. In this regard, lithium metal is the best candidate for the anode electrode as it is the lightest metal on earth and has the lowest electrochemical potential (-3.04 V vs. SHE). However, the challenge to overcome for mass commercializing lithium-metal batteries (LMB) is stabilizing the solid electrolyte interphase that naturally grows at the electrode-electrolyte interface to avoid uncontrolled reactions leading to lithium depletion. Since the successful introduction of lithium-ion batteries (LIB), it has been known that tuning of the SEI composition and morphology is fundamental to prolong the battery life span; a well-engineered SEI layer simultaneously serves as an electron barrier and favors Li+ ion conduction across it, ensuring proper battery performance. However, the engineering of the SEI layer in LMB is more complex than its counterpart LIB batteries, given that lithium metal is overwhelmingly more reactive than graphite and the overall Li+ ion current across it is orders of magnitude higher. The up-to-date knowledge on the SEI morphology indicates that inorganic phases produced upon the decomposition of lithium salts present in the electrolyte tends to grow dominantly buried within the SEI layer, acting as an intermediate between the surviving lithium metal and the outermost organic SEI phase grown after decomposition of solvent molecules. The effect of electrolyte additives and diluents is to tweak the SEI composition. The narrative built after years of experimentation tells that proper battery functioning depends heavily on the ability of the incoming Li+ ions to desolve near the SEI outermost layer without triggering further side reactions, penetrate the inner SEI, and deposit in the anode as reduced lithium. However, the intricacies of the elementary reactions and the stage where the reduction takes place still fall beyond detailed comprehension, even though the development of in situ and operando analytical techniques has brought us a level of understanding on the subject that was unimaginable a few decades ago.In this talk, we discuss the instrumental impact that multiscale modeling techniques have played in clarifying the elementary steps of the SEI formation on pristine lithium metal, providing a comprehensive understanding of the precursors formed in the early stages of Solid-Electrolyte Interphase (SEI) growth. For instance, density functional theory (DFT) calculations have revealed that electrolyte diluents, such as TTE, previously considered inert to lithium metal, actively modify the liquid electrolyte solvation structure by weakly interacting with Li+ ions. Additionally, these diluents decompose against lithium metal, releasing fluoride ions and inundating the SEI layer with LiF. Similarly, DFT-based molecular dynamics (MD) techniques, including ab initio (AIMD) and reactive classical molecular dynamics methods (ReaxFF MD, among others), have facilitated a picoseconds (ps) scale observation of the temporal evolution of these SEI precursors, propelling a mechanistic understanding of the dynamics of the SEI formation; it is now recognized that there is an initial and rapid electrolyte decomposition occurring within the first tens of picoseconds after contact with lithium metal, preceding a longer-scale mass transfer segregation process leading to the formation of a myriad of organic and inorganic microphases within the SEI structure. However, the accessible time and space windows to MD methods fall within few hundred ps, leaving out the study of the morphological aspects of the SEI over extended cycling. In this sense, we discuss through kinetic Monte Carlo (kMC) calculations the evolution of the SEI formation on lithium metal and confirm the critical role that dislocations and grain boundaries play in ensuring proper lithium plating and mobility within the SEI layer over cycling. We confirm that bulk lithium diffusion within the inorganic SEI microphases, such as LiF and Li2O, is significantly lower than lithium mobility across LiF/Li2O interfaces. We also discuss the impact of electrolyte tunning on SEI morphology and provide insights into developing an SEI formation strategy based on the electrolyte molecules electrochemical stability and their relative contents of heteroatom species, such as F and O, to seed in the SEI composition and morphology, which we believe could have a significant impact on the development of stable LMB batteries.

Advancing Towards Commercialization with Enhanced Stability and Efficiency in Lithium Metal Batteries Using TTE as a Co-Solvent in Carbonate Electrolytes

Lithium metal batteries are considered ideal anode materials for next-generation battery systems due to their high theoretical specific capacity (3,860 mAh g-1) and low negative electrochemical potential (−3.040 V vs. the standard hydrogen electrode), which are essential for high energy density. However, the fatal dendritic growth on the lithium metal surface, which occurs during repetitive cycling, acts as a significant barrier to commercially successful lithium metal battery application. Therefore, regulating the morphology of lithium plating in commercial carbonate-based electrolytes is a critical challenge for the stable operation of lithium metal batteries. Additionally, this leads to the formation of inhomogeneous lithium dendrites in carbonate-based electrolytes, manifesting as uneven current density and lithium-ion concentration gradients. The uneven current leads to inconsistent charging/discharging rates in the corresponding Ni-rich cathode, which in turn causes overpotentials and deteriorates cell safety, culminating in a reduction of capacity. this has been clarified through Kelvin probe force microscopy analysis to demonstrate an uneven state of charge distribution in the Ni-rich cathode.In this work, we propose a new strategy for high-performance lithium metal batteries, utilizing 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) as a co-solvent with carbonate electrolytes. By using TTE as a co-solvent, we observed a reduction in the viscosity of the electrolyte, leading to improved ionic conductivity and a decrease in the overpotential during the lithium plating/stripping process via in-situ electrochemical atomic force microscopy. This resulted in more uniform Li deposition compared to conventional carbonate-based electrolytes, forming a dense and stable Li metal layer. Furthermore, by leveraging our control over stable lithium plating morphologies via TTE co-solvent system, we observed long-term cycling stability (capacity retention of 78% at 300 cycles) with the use of an ultra-thin Li layer (40 µm). Through these results, we have effectively enhanced the stability and efficiency of high-energy-density (380 Wh kg-1) electrodes based on carbonate electrolytes, and we believe that this study can contribute to the commercialization of lithium metal batteries. Figure 1

Stability and performance of lithium metal batteries using silicon and silver alloyed separator surfaces

Lithium metal is renowned for its exceptional theoretical capacity and the lowest electrochemical potential, making it a cornerstone for batteries that can push the boundaries of energy and power density. However, its widespread adoption has been hindered by significant drawbacks, such as an unstable solid electrolyte interface (SEI) layer, substantial volume changes during charge-discharge cycles, and the formation of lithium dendrites. In our study, we have addressed these challenges by employing an innovative alloying technique to modify the surface of the separator with silicon (Si) and silver (Ag). This approach facilitates the formation of LiSi and LiAg alloys on the separator surface, leading to the creation of a novel lithium metal-lithium alloy composite anode. Our electrochemical tests have demonstrated that batteries equipped with this surface-modified lithium alloy composite anode exhibit superior coulombic efficiency and an impressively extended cycle life. Furthermore, when utilizing an ether-based electrolyte, the LiAg and LiSi alloy composite anodes have shown remarkable capacity retention rates of 89.1 % and 86.3 %, respectively, after 200 cycles in full cell tests. These results are notably superior to those of anodes made with bare lithium metal. In conclusion, the development of the face-to-face lithium alloy composite anode holds great promise for the practical application of lithium batteries with enhanced stability and performance. This advancement is a significant step towards realizing the full potential of lithium metal batteries in a variety of applications.

A facile superlithiophilic 3D host with a transition metal oxide heterostructure for ultrastable zero-volume-expansion lithium metal anodes

Lithium metal batteries (LMBs) are widely recognized as the candidate for next-generation energy devices due to their unprecedented capacity and low electrochemical potential. Nonetheless, their practical implementation has been hindered by the dendrite formation and unstable solid electrolyte interface (SEI). In this study, we introduce a novel approach involving the in-situ growth of a ZnO–CuO heterostructure within a crack shield construction on a three-dimensional (3D) copper foam host. Computational COMSOL simulations reveal remarkable improvements in homogenizing lithium ion flux subsequent to decoration. Through galvanostatic measurements, the Li@ZnO-CuO-CF electrode exhibits an exceptionally low 0.2 V hysteresis, no volume expansion and uniform lithium deposition in symmetry cells under a 50 mA cm−2 current density. Furthermore, the electrode retains 95.4 % initial capacity after 600 cycles at 0.5C and 85.5 % initial capacity after 220 cycles at 1 C when coupled with a LiFePO₄ (LFP) cathode. This work sheds light on the facile fabrication of practical Li metal anodes for high-energy-density LMBs.

Energy Band Specific to Injected Li-Ion-Induced Formation of Lithium Dendrites in Garnet Solid Electrolytes.

As one of the most significant challenges in solid-state batteries, thorough investigation is necessary on the formation process of lithium dendrites in solid-state electrolytes. Here, we reveal that the growth of lithium dendrites in solid electrolytes is a physical-electrochemical reaction process caused by injected lithium ions and electron carriers, which requires a low electrochemical potential. A unique energy band specific to injected Li ions is identified at the bottom of the conduction band, which can be occupied by electron carriers from low-potential electrodes, leading to dendrite formation. In this case, it is quantitatively determined that the employed anodes with higher working voltages (>0.2 V versus Li/Li+) can effectively prevent dendrite formation. Moreover, lithium dendrite formation exclusively occurs during the charging process (i.e., lithium plating), where lithium ions meet electrons at mixed conductive grain boundaries under highly reductive potentials. The proposed model has significant scientific significance and application value.

Enhancing Lithium-Ion Diffusion Kinetics in a 3D Lithium Metal Host through Surface Modification with Hierarchical Multimetal Oxides.

Lithium metal is a promising anode candidate to achieve high-energy-density lithium metal batteries (LMBs) due to its ultrahigh theoretical capacity (3860 mA h g-1) and low electrochemical potential (-3.04 V vs S.H.E). Unfortunately, the commercialization of lithium metal anodes is hindered by the growth of Li dendrites and the infinite Li volume changes during the cycling process. Herein, we introduce a 3D hierarchical multimetal oxide nanowire framework as a current collector for Li metal anodes. The hierarchical metal oxide layers of CoO and CuxO provide abundant Li nucleation sites and thus offer uniform Li plating and regulate Li nucleation during the charge/discharge process. As a result, half cells present a prolonging Coulombic efficiency of 97% at 1 mA cm-2 with a capacity of 1 mA h cm-2 for over 300 cycles. A stable cyclability of symmetric cells is demonstrated under 1 mA cm-2 with a capacity of 1 mA h cm-2 for 1500 h. Full cells paired with an LFP cathode show a stable capacity of 131.5 mA h g-1 with a capacity retention of 92% for 200 cycles. These results will shed insights into the design of 3D Cu current collectors for high-performance composite Li metal anodes.

Modeling and Simulation of Single Flow Zinc–Nickel Redox Battery Coupled with Multi-Physics Fields

Metallic zinc (Zn) presents a compelling alternative to conventional electrochemical energy storage systems due to its environmentally friendly nature, abundant availability, high water compatibility, low toxicity, low electrochemical potential (−0.762 V vs. SHE), and cost-effectiveness. While considerable efforts have been devoted to enhancing the physical and chemical properties of zinc-ion battery materials to improve battery efficiency and longevity, research on multi-physics coupled modeling for a deeper understanding of battery performance remains relatively scarce. In this study, we established a comprehensive two-dimensional model for single-flow zinc–nickel redox batteries to investigate electrode reactions, current-potential behaviors, and concentration distributions, leveraging theories such as Nernst–Planck and Butler–Volmer. Additionally, we explored the distribution of the velocity field using the Brinkman theory in porous media and the Navier–Stokes equations in free-flow channels. The validated model, informed by experimental data, not only provides insights into the performance of the battery, but also offers valuable recommendations for advancing single-flow zinc–nickel battery technology. Our findings offer promising avenues for enhancing the design and performance of not only zinc–nickel flow batteries, but also applicable for other flow battery designs.

Guiding lithium growth direction by Au coated separator for improving lithium metal anode

Lithium metal is the most promising anode for next-generation batteries due to its highest theoretical capacity and lowest electrochemical potential. However, its dendritic growth hinders its practical use due to the consequent poor reversibility, potential short-circuit, and safety concerns. Suppressing lithium dendrite is difficult since dendritic growth is thermodynamically and kinetically favorable. Herein, we guide lithium to uniformly deposit along the opposite direction to normal by a nanolayer Au coating on a commercial polypropylene separator. It prevents lithium dendrites from piercing the separator, instead of inhibiting dendrites growth only. Au is lithiophilic, and lithium is calculated to be more attracted to Au and is confirmed to uniformly deposit on Au at the separator side rather than on the current collector side. Furthermore, Au also regulates the morphology of deposited lithium from a mossy state to a bulky state. In this work, the symmetric cell with the designed structure achieves excellent electrochemical performances of a long-life cycle over 2,000 h at 1 C for 1 mA h cm-2. Pairing with LiFePO4 cathode as a full cell, lithium metal anode with Au-modified polypropylene separator exhibits extraordinary performance with a high Coulombic efficiency of 99.23% over 800 cycles at 1 C.

Versatile multi-lithiophilic metal oxide nano seeds embedded in hollow carbon nanospheres via electrostatically functional template for dendrite-free lithium metal anodes

Lithium metal anodes, which are promising candidates for anode materials in Li-ion batteries, are highly regarded for their combination of high energy density and low electrochemical potential, making them a compelling option for next-generation anodes. However, the growth of dendritic Li during the charging and discharging processes, along with the resulting decrease in stability and efficiency, poses a significant obstacle to the commercialization of Li metal anodes. To address the challenges associated with Li metal anodes, we propose the use of hollow carbon incorporating zinc oxide (ZnO) and magnesium oxide (MgO) as anode materials. ZnO has high lithiophilicity, enabling selective reactions with Li ions, and MgO exhibits a low nucleation overpotential. By placing these two substances inside the hollow carbon structure, stable Li growth can occur within the hollow carbon, enabling the formation of a reliable Li metal anode. Furthermore, to simplify and precisely synthesize the proposed structure, polystyrene-b-polyacrylic acid was introduced. Metals such as Zn and Mg can be uniformly attached to the hollow carbon through the carboxylic group of acrylic acid. The synthesized structure exhibited significantly improved Li storage performance compared to that of hollow carbon. It demonstrated superior metrics, achieving a Coulombic efficiency of 99.8% over 350 cycles. The introduction of Zn and Mg with distinct properties effectively enhanced the internal storage performance of Li in hollow carbon.

In situ high‐quality LiF/Li3N inorganic and phenyl‐based organic solid electrolyte interphases for advanced lithium–oxygen batteries

AbstractLithium metal shows a great advantage as the most promising anode for its unparalleled theoretical specific capacity and extremely low electrochemical potential. However, uncontrolled lithium dendrite growth and severe side reactions of the reactive intermediates and organic electrolytes still limit the broad application of lithium metal batteries. Herein, we propose 4‐nitrobenzenesulfonyl fluoride (NBSF) as an electrolyte additive for forming a stable organic–inorganic hybrid solid electrolyte interphase (SEI) layer on the lithium surface. The abundance of lithium fluoride and lithium nitride can guarantee the SEI layer's toughness and high ionic conductivity, achieving dendrite‐free lithium deposition. Meanwhile, the phenyl group of NBSF significantly contributes to both the chemical stability of the SEI layer and the good adaptation to volume changes of the lithium anode. The lithium–oxygen batteries with NBSF exhibit prolonged cycle lives and excellent cycling stability. This simple approach is hoped to improve the development of the organic–inorganic SEI layer to stabilize the lithium anodes for lithium–oxygen batteries.

Functional metal-organic framework membranes with uniform unsaturated pyridine-nitrogen sites as separators for high-performance lithium metal batteries

Lithium metal batteries are a promising successor to lithium-ion batteries due to high specific capacity, low density, and low electrochemical reduction potential. However, inhomogeneous lithium deposition on the Li surface will result in the formation of lithium dendrites and eventually puncture the separator and cause a short circuit. Herein, a functional metal-organic framework membrane with uniform unsaturated pyridine-nitrogen sites is synthesized via coating UiO-67-BPY (2,2 -bipyridine- 5,5 -dicarboxylic acid, named as BPY) on a commercial polypropylene (PP) separator. By replacing the benzene ring with a pyridine ring, the functionalization and porosity of MOF is fully utilized while maintaining the excellent porosity and pore size of MOF. The Li-ion transference number (tLi+) with the functional separator is 0.69 and the ionic conductivity is improved by order of magnitude compared to a plain PP separator. The N atom of the pyridine ring on the UiO-67-BPY has a strong electrostatic interaction force, and a weak coordination bond (N–Li bonding lattice) is formed between N and Li, which leads to an increase in the concentration of free lithium ions and makes their distribution more uniform. This allows lithium ions to migrate more smoothly, which is conducive to ionic conductivity and hinders dendrite formation.

Lithiophilic ZnCu alloy sites on copper current collector for high performance Li metal anode

Lithium (Li) metal has been widely regarded as the optimal anode material for the high-energy density rechargeable batteries, due to its ultrahigh theoretical specific capacity and lowest electrochemical potential. However, the formation of Li dendrites presents a significant safety concern, which limits its practical application. In this paper, to address this issue, an efficient and cost-effective strategy was proposed to prepare a zinc-copper composite collector (ZCC) with outstanding electrochemical performance, which can effectively suppress the formation of lithium dendrites. The lithophilic surface with ZnCu alloy nanoparticles was achieved through physical vapor deposition followed by annealing treatment. The ZCC collector enables dendrite-free deposition of Li due to its negligible nucleation overpotential. Even at high area capacity of 3 mAh cm−2 at 1 mA cm−2 in half-cells, the ZCC exhibits exceptional cycling performance and high coulomb efficiency. Preloaded with Li, the composite electrode (Li/ZCC) delivers an enhanced lifespan with low overpotential evidently. Matched with LiFePO4 (LFP) cathode, LFP||Li/ZCC full cells reveal a superior cycling stability with enhanced capacity retention of 85 % (after 1000 cycles at 1 C) and 87 % (after 800 cycles at 3 C) respectively.

Recent advances in separator design for lithium metal batteries without dendrite formation: Implications for electric vehicles

Electric vehicle (EV) technology addresses the challenge of reducing carbon and greenhouse gas emissions. The power battery, which serves as the energy source for EVs, directly impacts their driving range, maximum speed, and service life. Considering the high energy density requirements for future EVs, lithium metal anodes possess several advantages such as high theoretical capacity, high energy and power density, and low electrochemical reduction potential which enable them to be a promising material for next-generation batteries. However, lithium metal anodes suffer from short cycle life and safety concerns due to the formation of dendritic and moss-like metal deposits that impede battery performance and reliability. This review will feature the recent advancement of functional separators to tackle these challenges. Firstly, this review presents a comprehensive review of the growth mechanism of lithium dendrites and delineates the underlying processes leading to battery failure. This aims to deepen understanding, which serves as a fundamental basis for classifying separators. Then, according to the growth of lithium dendrites and the failure process of lithium metal batteries, namely lithium-ion nucleation, growth of lithium dendrites, penetration of lithium dendrites into the separator, thermal runaway and even failure of the battery, four types of functional separators for different stages are proposed. The functions of these types of separators are to prevent the nucleation of lithium ions and regulate the uniform deposition of lithium ions, detect and eliminate dendrites, increase the mechanical strength of the separator and enhance the thermal stability and flame-retardancy of the separators, respectively. Finally, the recent advances of the above strategies are reviewed and discussed, existing critical problems are identified, and the future perspective of functional separators for the safety of lithium metal batteries is also discussed.