Li-air Research Articles

Coordination environment modulation to optimize d-orbit arrangement of Mn-based MOF electrocatalyst for lithium-oxygen battery

Nowadays lithium-oxygen (Li-O2) batteries with metal-organic frameworks (MOFs) based oxygen electrodes have suffered from the sluggish kinetics and irreversible behavior of Li2O2 formation/decomposition, which originates from weak orbit coupling with oxygen species caused by narrow orbit arrangement of metal sites in MOFs. Modulation of coordination environment of metal sites has been regarded as the vital strategy to tune 3d orbit arrangement and electron distribution of metal sites, which is favorable for altering electron transfer pathway and oxygen electrode reaction kinetics. Herein, electron-rich ferrocene acid (FcA), as grafted ligand, is introduced on Mn sites of Mn-MOF-74 (named as Mn-MOF-74-FcA) for facilitating the oxygen electrode reactions in Li-O2 batteries. In details, due to the strong electron delocalization on electron-rich FcA ligand, the resulted metal-ligand interaction between FcA and Mn sites distorts [MnOx] coordination sphere, which induces 3d orbits rearrangement of Mn sites from (dx2-y2/dxy, dz2, dxz/dyz) to (dx2-y2, dz2, dxz, dyz, dxy) and electron transfer from electron-rich FcA to Mn sites. And the strong orbit overlapping between LiO2 intermediate and widened Mn d-band ensures the electron exchange with each other and thus reduces the energy barrier of oxygen electrode reactions. Moreover, electron transfer from FcA ligand to Mn sites also leads to the decreased energy gap between valence band (VB) and conduction band (CB). As expected, Li-O2 battery with Mn-MOF-74-FcA exhibits low overpotential of 0.82 V and long lifespan of 276 cycles at the current density of 200 mA g−1.

Recent Progress of Electrolyte Materials for Solid‐State Lithium–Oxygen (Air) Batteries

AbstractSolid‐state lithium–air batteries (SSLABs) have become the focus of next‐generation advanced batteries due to their safety and high energy densities. Current research on SSLABs is mainly centered on solid‐state electrolytes (SSEs). Although SSEs exhibit excellent properties, such as good stability, high safety, and great mechanical strength, they also display several distinct weaknesses of low ionic conductivities, poor stabilities in air, and high interfacial impedances, which will require sustained attentions for further investigations. This review first overviews the development history of SSEs achieved in terms of Li–air batteries. Subsequently, the fundamental properties, preparation methods, merits and drawbacks of different SSEs, along with their use in SSLABs, and the optimization strategy, especially for the inorganic solid electrolytes, polymer electrolytes, and hybrid electrolytes are comprehensively summarized. Finally, the research progresses made with SSEs are outlined, and critical insights and approaches for the remaining challenges of electrolytes and commercial application of SSLABs are proposed, which include advanced characterization, combining experiments and artificial intelligence such as theoretical calculations, and constructing selective permeability membranes. It is expected that this timely review will provide researchers with an integrated, systematic, and in‐depth understanding of SSEs and guidelines for future research, thus further promoting the commercial application of SSLABs.

Reducing Overpotential of Lithium-Oxygen Batteries by Diatomic Metal Catalyst Orbital Matching Strategy.

Aprotic Li-O2 batteries have sparked attention in recent years due to their ultrahigh theoretical energy density. Nevertheless, their practical implementation is impeded by the sluggish reaction kinetics at the cathode. Comprehending the catalytic mechanisms is pivotal to developing efficient cathode catalysts for high-performance Li-O2 batteries. Herein, the intrinsic activity map of Li-O2 batteries is established based on the specific adsorption mode of O2 induced by diatomic catalyst orbital matching and the transfer-acceptance-backdonation mechanism, and the four-step screening strategy based on the intrinsic activity map is proposed. Guided by the strategy, FeNi@NC and FeCu@NC promising durable stability with a low overpotential are screened out from 27 Fe-Metal diatomic catalysts. Our research not only provides insights into the fundamental understanding of the reaction mechanism of Li-O2 batteries but also accelerates the rational design of efficient Li-O2 batteries based on the structure-activity relationship.

Finite element modeling simulation of oxygen evolution during charging in lithium-oxygen batteries

The quest for advanced energy storage solutions has intensified the focus on developing next-generation secondary batteries, with lithium-oxygen batteries (LOB) standing out for their superior theoretical gravimetric energy density. This study introduces a novel model-based approach to battery development, enabling the detailed analysis of charge–discharge cycles and oxygen evolution efficiency within a virtual environment. Our model distinctively simulates the oxidative decomposition of lithium peroxide (Li2O2) and differentiates between its formation through solution and surface pathways, addressing the complexities of the charging process and its multiple elementary steps. The developed model further categorizes the oxidative decomposition species into four distinct types, facilitating a comprehensive understanding of their interactions, voltage profile changes, and O2 evolution within the battery's porous cathode. This approach not only enhances the understanding of battery behavior but also aids in refining the design of component materials, thereby propelling forward the development of LOBs with improved energy density and cycle performance.

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.

Effects of Central Metal Ion on Binuclear Metal Phthalocyanine-Based Redox Mediator for Lithium Carbonate Decomposition.

Li2CO3 is the most tenacious parasitic solid-state product in lithium-air batteries (LABs). Developing suitable redox mediators (RMs) is an efficient way to address the Li2CO3 issue, but only a few RMs have been investigated to date, and their mechanism of action also remains elusive. Herein, we investigate the effects of the central metal ion in binuclear metal phthalocyanines on the catalysis of Li2CO3 decomposition, namely binuclear cobalt phthalocyanine (bi-CoPc) and binuclear cobalt manganese phthalocyanine (bi-CoMnPc). Density functional theory (DFT) calculations indicate that the key intermediate peroxydicarbonate (*C2O62-) is stabilized by bi-CoPc2+ and bi-CoMnPc3+, which is accountable for their excellent catalytic effects. With one central metal ion substituted by manganese for cobalt, the bi-CoMnPc's second active redox couple shifts from the second Co(II)/Co(III) couple in the central metal ion to the Pc(-2)/Pc(-1) couple in the phthalocyanine ring. In artificial dry air (N2-O2, 78:22, v/v), the LAB cell with bi-CoMnPc in electrolyte exhibited 261 cycles under a fixed capacity of 500 mAh g-1carbon and current density of 100 mA g-1carbon, significantly better than the RM-free cell (62 cycles) and the cell with bi-CoPc (193 cycles).

Controllable Regulation of the Oxygen Redox Process in Lithium-Oxygen Batteries by High-Configuration-Entropy Spinel with an Asymmetric Octahedral Structure.

Designing bifunctional electrocatalysts to boost oxygen redox reactions is critical for high-performance lithium-oxygen batteries (LOBs). In this work, high-entropy spinel (Co0.2Mn0.2Ni0.2Fe0.2Cr0.2)3O4 (HEOS) is fabricated by modulating the internal configuration entropy of spinel and studied as the oxygen electrode catalyst in LOBs. Under the high-entropy atomic environment, the Co-O octahedron in spinel undergoes asymmetric deformation, and the reconfiguration of the electron structure around the Co sites leads to the upward shift of the d-orbital centers of the Co sites toward the Fermi level, which is conducive to the strong adsorption of redox intermediate LiO2 on the surface of the HEOS, ultimately forming a layer of a highly dispersed Li2O2 thin film. Thin-film Li2O2 is beneficial for ion diffusion and electron transfer at the electrode-electrolyte interface, which makes the product easy to decompose during the charge process, ultimately accelerating the kinetics of oxygen redox reactions in LOBs. Based on the above advantages, HEOS-based LOBs deliver high discharge/charge capacity (12.61/11.72 mAh cm-2) and excellent cyclability (424 cycles). This work broadens the way for the design of cathode catalysts to improve oxygen redox kinetics in LOBs.

Binder-Free Three-Dimensional Porous Graphene Cathodes via Self-Assembly for High-Capacity Lithium-Oxygen Batteries.

The porous architectures of oxygen cathodes are highly desired for high-capacity lithium-oxygen batteries (LOBs) to support cathodic catalysts and provide accommodation for discharge products. However, controllable porosity is still a challenge for laminated cathodes with cathode materials and binders, since polymer binders usually shield the active sites of catalysts and block the pores of cathodes. In addition, polymer binders such as poly(vinylidene fluoride) (PVDF) are not stable under the nucleophilic attack of intermediate product superoxide radicals in the oxygen electrochemical environment. The parasitic reactions and blocking effect of binders deteriorate and then quickly shut down the operation of LOBs. Herein, the present work proposes a binder-free three-dimensional (3D) porous graphene (PG) cathode for LOBs, which is prepared by the self-assembly and the chemical reduction of GO with triblock copolymer soft templates (Pluronic F127). The interconnected mesoporous architecture of resultant 3D PG cathodes achieved an ultrahigh capacity of 10,300 mAh g-1 for LOBs. Further, the cathodic catalysts ruthenium (Ru) and manganese dioxide (MnO2) were, respectively, loaded onto the inner surface of PG cathodes to lower the polarization and enhance the cycling performance of LOBs. This work provides an effective way to fabricate free-standing 3D porous oxygen cathodes for high-performance LOBs.

Homologous heterostructure of MoS2 and MoO2 coupled with carbon layers as cathode catalyst for rechargeable lithium–oxygen batteries

Homologous heterostructure of MoS2 and MoO2 coupled with carbon layers as cathode catalyst for rechargeable lithium–oxygen batteries

A magnetic/force coupling assisted lithium-oxygen battery based on magnetostriction and piezoelectric catalysis of CoFe2O4/BiFeO3 cathode

The high energy density of Li−O2 batteries surpasses all existing batteries, and it holds the potential to emerge as the most outstanding solution for energy storage in the future. However, the insulated, insoluble discharge product (Li2O2) has impeded the practical applications. Conventional catalyst design based on electronic structure and interfacial charge transfer descriptors are incapable of overcoming these limitations of Li2O2. Herein, a magnetic/force coupling assisted Li−O2 battery based on magnetostrictive and piezoelectric catalysis with CoFe2O4/BiFeO3 core-shell structure cathode was established for the first time. An external magnetic field is introduced to produce a magnetostrictive stress on CoFe2O4, contributing to the piezoelectric electron hole transport by the generated piezoelectric potential energy with a built-in electric field based on the piezoelectric catalytic mechanism, and thus promoting the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics, and reducing the overpotential during charge/discharge. The magnetic/force coupling assisted Li−O2 battery equipped with the unique CoFe2O4/BiFeO3 cathode deliver an ultra-low charging platform of 3.49 V and an ultra-high discharge platform of 2.83 V. This unique magnetic/force assisted strategy provides an important insight into solving the high overpotential in metal-air battery systems.

Selectively anchoring Pd single atoms on specific sites in defective cobalt oxides for efficient lithium-oxygen batteries

Selectively anchoring Pd single atoms on specific sites in defective cobalt oxides for efficient lithium-oxygen batteries

Hidden Negative Issues and Possible Solutions for Advancing the Development of High-Energy-Density in Lithium Batteries: A Review.

This review article discusses the hidden or often overlooked negative issues of large-capacity cathodes, high-voltage systems, concentrated electrolytes, and reversible lithium metal electrodes in high-energy-density lithium batteries and provides some feasible solutions that can realize the construction of realistic rechargeable batteries with higher energy densities. Similar objective discussion of the negative aspects of lithium-air batteries, multi-valent shuttles, anion shuttles, sulfur cathode systems, and all-solid ceramic batteries can help fabricate more realistic batteries.

Development of single-atom Ru and N, S-Co-doped carbon catalyst for enhanced cycling stability of lithium-oxygen batteries

Li-oxygen (Li-O2) battery is a novel energy storage equipment. However, its poor reaction reversibility relating to the insoluble lithium peroxide (Li2O2) generated during the discharge process, limits its application and development for large scale use. Therefore, the design and synthesis of effective catalysts which can efficiently catalyze the production and decomposition of Li2O2 and exclude the generation of side-products has become the primary task to develop Li-O2 batteries. Herein, a new type of electrocatalyst based on single-atom Ru and N, S-co-doped carbon materials (Ru/CNS/CNT) is introduced to reduce the overpotential of the battery reaction and accelerate the formation and decomposition of Li2O2. Galvanostatic charge-discharge tests were performed on the Li-oxygen (Li-O2) battery with Ru/CNS/CNT as the cathode catalyst material. With a limited specific capacity of 1000 mA h g−1, the battery can stably cycle for 79 cycles at a current density of 200 mA g−1. Furthermore, the existence of the single atom of Ru was demonstrated according to the characterization of HAADF-STEM. The experimental results showed that composite material Ru/CNS/CNT can accelerate the formation and decomposition of lithium peroxide (Li2O2), thereby greatly improving the cycling stability of the battery.

Optimizing the adsorption of intermediates through modulating Mn d-band centers by the Mn-Ce heterojunction for high-performance lithium-oxygen batteries

Admitting that rare-earth (RE)-based transition metal oxides (TMO) are emerging as a promising catalyst for lithium-oxygen (Li-O2) batteries, the understanding of their electrocatalytic mechanism and active sites remains ambiguous. In this study, CeO2 nanoparticles modified MnOOH nanowires (CeO2@MnOOH NWs) is prepared by a simple solvothermal method as highly effective cathode catalysts for Li-O2 batteries. The incorporation of CeO2 nanoparticles into MnOOH facilitates a robust interaction between the 3d electronic state of MnOOH and the 4f electronic state of CeO2 at the Fermi level (Ef). The strong electron interaction at the heterogeneous interface between MnOOH and CeO2 promotes internal electron transfer. Compared to pristine MnOOH, the prepared CeO2@MnOOH NWs exhibits enhanced electrocatalytic activity and improved electrocatalytic stability. According to experimental analysis and density functional theory (DFT) results, it is demonstrated that there is a slight negative shift in the d-band center of the Mn site, resulting in faster electron transfer rates and higher conductivity. This acceleration of charge transfer optimizes the adsorption strength of the oxygen-containing intermediate (LiO2), thereby promoting the kinetics of the oxygen reduction/evolution reactions (ORR/OER) and reducting the reaction over-potential. As a result, the electrochemical performances of Li-O2 batteries are greatly enhanced.

Self-Catalyzed Growth of Co4N and N-Doped Carbon Nanotubes toward Bifunctional Cathode for Highly Safe and Flexible Li-Air Batteries.

The practical application of high-energy density lithium-oxygen (Li-O2) batteries is severely impeded by the notorious cycling stability and safety, which mainly comes from slow kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at cathodes, causing inferior redox overpotentials and reactive lithium metal in flammable liquid electrolyte. Herein, a bifunctional electrode, a safe gel polymer electrolyte (GPE), and a robust lithium anode are proposed to alleviate above problems. The bifunctional electrode is composed of N-doped carbon nanotubes (N-CNTs) and Co4N by in situ chemical vapor deposition self-catalyzed growth on carbon cloth (N-CNTs@Co4N@CC). The self-supporting, binder-free N-CNTs@Co4N@CC electrode has a strong and stable three-dimensional (3D) interconnected conductive structure, which provides interconnectivity between the active sites and the electrode to promote the transfer of electrons. Furthermore, the N-CNT-intertwined Co4N ensures efficient catalytic activity. Hence, the electrode demonstrates improved electrochemical properties even under a large current density (2000 mA g-1) and long cycling operation (250 cycles). Moreover, a highly safe and flexible rechargeable cell using the 3D N-CNTs@Co4N@CC electrode, GPE, and robust lithium anode design has been explored. The open circuit voltage is stable at ∼3.0 V even after 9800 cycles, which proves the mechanical durability of the integrated GPE cell. The stable cable-type Li-air battery was demonstrated to stably drive the light-emitting diodes (LEDs), highlighting the reliability for practical use.

Direct Evidence of Reversible Changes in Electrolyte and its Interplay with LiO2 Intermediate in Li-O2 Batteries.

Lithium-oxygen batteries show promising energy storage potential with high theoretical energy density; however, further investigation of chemical reactions is required. In this study, experimental Raman and theoretical analyzes are performed for a Li-O2 battery with LiClO4/dimethyl sulfoxide (DMSO) electrolyte and carbon cathode to understand the role of intermediate species in the reactional mechanism of the cell using a high donor number solvent. Operando Raman results reveal reversible changes in the DMSO bands, in addition to the formation and decomposition of Li2O2. On discharge, a decrease in DMSO polarizability is observed and bands of DMSO-Li+-anion interactions are evidenced and supported by abinitio density functional theory (DFT) calculations. Molecular dynamics (MD) force field simulations and operando Raman show that DMSO interacts with LiO2(sol), highlighting the stability of the electrolyte compared to the interaction with reactive . On charging, the presence of Li+ indicates the formation of a lithium-deficient phase, followed by the release of Li+ and oxygen. Therefore, this study contributes to understanding the discharge/charge chemistry of a Li-O2 cell, employing a common carbon cathode and DMSO electrolyte. The combination of a simple characterization technique in operando mode and theoretical studies provides essential information on the mechanism of Li-O2system.

Improving the cycling performance of lithium-air batteries using a nitrite salt electrolyte

Lithium nitrate (LiNO3) has been used as the electrolyte salt for Lithium-air battery (LAB), both to protect the lithium metal anode and to generate NO2− anions that function as the redox mediator (RM) reducing the charging voltage. However, this RM effect minimally improves cycling performance because only a low NO2− concentration is produced. Instead, the use of lithium nitrite (LiNO2) as the supporting electrolyte salt can overcome this limitation. In this study, 1 M solutions of LiNO3 or LiNO2 in tetraethylene glycol dimethyl ether (TEGDME) or N-methyl-2-pyrrolidone (NMP) were prepared as LAB electrolytes. Walden plots of these electrolytes established a higher degree of dissociation in the NMP having a greater dielectric constant, thus enhancing ionic conductivity. Electrochemical impedance spectroscopy determined that an LAB cell incorporating the LiNO2/NMP electrolyte exhibited reduced diffusion resistance during discharge-charge cycling as a consequence of the enhanced RM effect of NO2− anions. Microscopic observation and pore distribution analysis of cathodes confirmed that the clogging of pores was minimized with the LiNO2/NMP electrolyte. As a result, the LAB cell using this electrolyte extended the cycle performance, more than doubling the cycle life. LiNO2 is considered to be an effective alternative for electrolyte salt for LAB.

Water-Capture Filter Paper Separator Realizing Ambient Li-Air Battery.

Lithium-air battery (LAB) is regarded as one of the most promising energy storage systems. However, the challenges arising from the lithium metal anode have significantly impeded the progress of LAB development. In this study, cellulose-based filter paper (FP) is utilized as a separator for ambient Li-air batteries to suppress dendrite growth and prevent H2O crossover. Thermogravimetric analysis and molecular spectrum reveal that FP enables ambient Li-air battery operation due to its surface functional groups derived from cellulose. The oxygen-enriched surface of cellulose not only enhances ion conductivity but also captures water and confines solvent molecules, thereby mitigating anode corrosion and side reactions. Compared with commercial glassfiber (GF) separator, this cellulose-based FP separator is cheaper, renewable, and environmentally friendly. Moreover, it requires less electrolyte while achieving prolonged and stable cycle life under real air environment conditions. This work presents a novel approach to realizing practical Li-air batteries by capturing water on the separator's surface. It also provides insights into the exploration and design of separators for enabling practical Li-air batteries toward their commercialization.

Integrately design hybrid lithium-air battery based on the nasicon solid electrolyte and zinc single atoms electrochemical catalysts

The instability of lithium metal and insoluble discharging products, [Formula: see text], has been a formidable challenge that hinders the widespread implementation of lithium-air batteries (LABs). Hybrid electrolyte-based LABs have been proposed as one of the most promising strategies to solve these issues. However, the complex device designs together with a suitable solid electrolyte membrane is one of the key parameters that determine the battery run. Herein, we present a novel approach featuring a three-phase “organic-solid-aqueous” hybrid electrolyte for LABs, incorporating a NASICON-based solid electrolyte and zinc single atoms catalysts. It is clarified that [Formula: see text] (LATP) shows much-enhanced stability compared with the pulverization of [Formula: see text] (LAGP) by the reduction of Ge upon the [Formula: see text] transport across. Combined with the bifunction of Zn SAs/CNF catalysts in ORR/OER, the 4[Formula: see text] pathway has been proven to be established as a primary contributor to the battery’s high efficiency, which can well run over 100 h in the ambient air at room temperature. These innovative methodologies and insights hold promise for advancing the practical application of safe LABs and may extend to various air battery technologies.

Elucidate the formation and consumption mechanism of lithium oxides in lithium-oxygen batteries by combining the transfer-reaction model and the DFT calculation

Lithium-oxygen (Li-O2) batteries are considered one of the most promising energy storage devices for the next generation due to their high theoretical energy density. However, its poor cycle efficiency and discharge performance hinder the large-scale application. Understanding the complicative positive electrode reaction of Li-O2 batteries can help overcome these difficulties. This work establishes a transfer-reaction model to simulate the multi-step reactions during the discharge of Li-O2 batteries. It is found that the internal diffusion of oxygen causes local deposition of Li2O2 at the interface, leading to deterioration of diffusion and the end of discharge. The intermediate product LiO2 accumulates uniformly through the electrode, while the generated singlet oxygen exhibits a characteristic of less at the interface and more inside. By using DFT to calculate the reaction rate constant, the model is proved to achieve the connection between macro and micro levels well. This work hopes to inspire future multi-scale research into Li-O2 batteries and contribute to the realization of high-performance metal-air battery design as soon as possible.