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[Display omitted] • NiFe 2 O 4 /CeO 2 composites with the optimal Ce concentration were synthesized. • The unique structure allows the material to maximize the exposure of the active sites. • The oxygen vacancy introduced by CeO 2 can improve the conductivity of the catalyst. • The oxygen vacancy and the composite cooperate to achieve great catalytic performance. The development of efficient catalysts to accelerate the three-phase reaction at the cathode side represents a crucial step in enhancing the performance of lithium-oxygen batteries (LOBs) with high energy density. In this study, NiFe 2 O 4 /CeO 2 composites with an appropriate Ce concentration were prepared as cathode catalysts for LOBs, and the unique micro-flower structure maximally exposed the active sites of the materials. The catalyst cleverly integrates the excellent oxygen evolution reaction (OER) activity of NiFe 2 O 4 and the outstanding oxygen reduction reaction (ORR) activity of CeO 2. The high concentration of oxygen vacancies and the composite structure synergistically enhanced the charge transfer ability, altered the charge distribution of the active sites, and modulated the electronic structure of the material, thereby achieving an appropriate adsorption energy for oxygen-containing intermediates. Consequently, the composite material displays 343 stable cycles, a round-trip efficiency of 97.8 %, and a discharge specific capacity of 7478 mAh/g. Additionally, it exhibits fast charging and slow discharging capabilities for up to 726 h. This work offers insights into the design of efficient bifunctional cathode catalysts for LOBs. [ABSTRACT FROM AUTHOR]

The generation of oxygen vacancies and Bi-metal on BiVO 4 enhances conductivity, extending both catalytic activity and cyclability in Li–O 2 batteries. [Display omitted] Bismuth Vanadate (BiVO 4) is a promising oxide-based photoanode for electrochemical applications, yet its practical use is constrained by poor charge transport properties, particularly under dark conditions. This study introduces a novel BiVO 4 variant (Bi-BiVO 4 -10) that incorporates abundant oxygen vacancies and in-situ formed Bi metal, significantly enhancing its electrical conductivity and catalytic performance. Bi-BiVO 4 -10 demonstrates superior electrochemical performances compared to conventional BiVO 4 (C-BiVO 4), demonstrated by its most positive half-wave potential with the highest diffusion-limiting current in the oxygen reduction reaction (ORR) and earliest onset potential in the oxygen evolution reaction (OER). Notably, Bi-BiVO 4 -10 is explored for the first time as an electrocatalyst for lithium-oxygen (Li–O 2) cells, showing reduced overcharge (610 mV) in the first cycle and extended cycle life (1050 h), outperforming carbon (320 h) and C-BiVO 4 (450 h) references. The enhancement is attributed to the synergy of oxygen vacancies, Bi metal formation, increased surface area, and improved electrical conductivity, which collectively facilitate Li 2 O 2 growth, enhance charge transport kinetics, and ensure stable cycling. Theoretical calculations reveal enhanced chemical interactions between intermediate molecules and the defect-rich surfaces of Bi-BiVO 4 -10, promoting efficient discharge and charge processes in Li–O 2 batteries. This research highlights the potential of unconventional BiVO 4 -based materials as durable electrocatalysts and for broader electrochemical applications. [ABSTRACT FROM AUTHOR]

Aprotic lithium–oxygen batteries (LOBs) may deliver exceptionally high energy density but struggle to attain rapid reversibility and substantial capacity simultaneously, due to typical surface or solution‐formed insulating solid Li2O2. Tuning the structure of Li2O2 to create a large‐area amorphous layer on the cathode is predicted to overcome the multiperformance limitations. Here, an isolated nickel single atom to nitrogen‐doped graphene as a cathode catalyst (Ni─NG SAC) for LOBs is presented via a green click‐trapping strategy. Derived from the maximized exposure of atomic active sites of the cathode, the formation/decomposition mechanisms of Li2O2 are tailored, and a large area of thin Li2O2 amorphous film is achieved. The structure and functions of Ni─NG SAC are explored by theoretical computation and synchrotron radiational investigation. Consequently, the abundant Ni─N4 sites enhance redox kinetics and stand out to deliver an impressive specific discharge/charge capacity of 24 248/17 656 mAh g−1 at 200 mA g−1, together with a long cycle life of over 500 cycles. This study contributes helpful insights to achieve high‐capacity LOBs with long lifespans, by constructing unique single‐atom catalysts to optimize the formation of amorphous discharge Li2O2 products. [ABSTRACT FROM AUTHOR]

Highlights Strategic materials design of polyrotaxane-based electrolytes was suggested by aligning the ion conduction pathways and dispersing hydrophobic chains for solid-state Li–O2 batteries. Owing to intentional design, solid-state Li–O2 battery resulted in stable potential over 300 cycles at 25 °C.

In recent years, aprotic lithium–oxygen (Li–O2) batteries have received extensive academic attention for their ultrahigh capacity. However, their practical development faces the problems of low capacity, low rate, and short lifetime. Soluble catalysis with efficient redox mediators (RMs) is considered a feasible strategy owing to its good interfacial contact and flexible action. However, the mutual constraints of RMs charging/discharging catalysis, the erosion of anode by RMs shuttle effect leading to deactivation, and the decomposition of RMs or the initiation of side reactions have greatly limited the effectiveness of RMs in Li–O2 batteries. Therefore, it is necessary to optimize RMs and find traceable principles and directions. Based on this, this work systematically reviews the mechanism, effectiveness, and characterization of RMs in Li–O2 batteries. The design principles of novel RMs constructed by two research tendencies of kinetics and thermodynamics are pioneered, and the key roles of ionization energy and site‐resistive groups are especially pointed out. In addition, the current optimization design strategies for RMs are summarized. Specifically, the introduction of functional groups such as adsorption, conductivity, active sites, and the use of intermolecular forces for efficient RMs are highlighted, designed to provide direction for optimization and development of RMs. [ABSTRACT FROM AUTHOR]

Rechargeable lithium‐oxygen batteries (LOBs) are gaining interest as next‐generation energy storage devices due to their superior theoretical energy density. While recent years have seen successful operation of LOBs with high cell‐level energy density, the technology for cell fabrication is still in its infancy. This is because the cell fabrication procedure for LOBs is quite different from that of conventional lithium‐ion batteries. The study presents a fully automated sequential robotic experimental setup for the fabrication of stacked‐type LOB cells. This approach allows for high accuracy and high throughput fabrication of the cells. The developed system enables the fabrication of over 80 cells per day, which is 10 times higher than conventional human‐based experiments. In addition, the high alignment accuracy during the electrode stacking and electrolyte injection process results in improved battery performance and reproducibility. The effectiveness of the developed system was also confirmed by investigating a multi‐component electrolyte to maximize battery performance. We believe the methodology demonstrated in the present study is beneficial for accelerating the research and development of LOBs. [ABSTRACT FROM AUTHOR]

Adjusting the morphology and structure of the catalyst to optimize the structure of the discharge product is an effective strategy for improving the electrocatalytic activity of lithium–oxygen batteries (LOBs). In this paper, a novel high‐orientation layered manganese‐based metal–organic frameworks (Mn‐MOFs) catalyst for the air cathode of a LOB is synthesized via a facile solvothermal method using 2,4‐pyridine dicarboxylic acid combined with the metal Mn2+ ion. The presence of layered structure increases the specific surface area of the catalytic material, and the interlayer spacing can be used as a channel for electron and oxygen transport, thus promoting ion diffusion and catalyzing reactions. Otherwise, the coordination of the N element and metal ion in the organic ligand significantly improves the electrical conductivity and oxygen reduction reaction/oxygen extraction reaction (ORR/OER) performance of LOB. The effective combination of Mn2+ and 2,4‐pyridine dicarboxylic acid improves the overall catalytic capacity of the material, leading to a high LiO2 adsorption capacity so as to induce the formation of film discharge products and extend the cycle life of LOBs. When using Mn‐MOFs at 140°C as the cathode catalyst, the specific discharge capacity of the LOB can achieve 5579 mAh/g with a 0.2 mA/cm2 current density and maintain 140 stable cycles, limiting the specific discharge capacity to 500 mAh/g. [ABSTRACT FROM AUTHOR]

2D materials exhibit remarkable electrochemical performance as the cathode catalyst in lithium–oxygen batteries (LOBs). Their catalytic capability mainly derives from their 2D surface with tunable surface chemistry and unique electronic states. Herein, Ti0.87O2 and Ti3C2 MXene monolayers are applied to construct a face/face 2D heterostructure to enhance the catalytic performance in LOBs. It is demonstrated that electronic compensation from the O‐terminated MXene to Ti0.87O2 side is achieved through the built‐in electric field and the overlap of Ti 3d and O 2p orbitals between Ti0.87O2 and MXene units. As a result, the ORR/OER catalytic activity is improved in Ti0.87O2/MXene heterojunction due to the modulated p‐band center that optimizes the s–p coupling with the key intermediate LiO2. The Ti0.87O2/MXene cathode presents a structural stability and long‐term cycling life of 425 cycles (2534 h) at 200 mA g−1 and 407 cycles at 1000 mA g−1 with a fixed capacity of 600 mAh g−1, being nearly five and three times higher than that of pure Ti0.87O2 and MXene cathodes, respectively. [ABSTRACT FROM AUTHOR]

Highlights: Strategic materials design of polyrotaxane-based electrolytes was suggested by aligning the ion conduction pathways and dispersing hydrophobic chains for solid-state Li–O2 batteries. Owing to intentional design, solid-state Li–O2 battery resulted in stable potential over 300 cycles at 25 °C. A critical challenge hindering the practical application of lithium–oxygen batteries (LOBs) is the inevitable problems associated with liquid electrolytes, such as evaporation and safety problems. Our study addresses these problems by proposing a modified polyrotaxane (mPR)-based solid polymer electrolyte (SPE) design that simultaneously mitigates solvent-related problems and improves conductivity. mPR-SPE exhibits high ion conductivity (2.8 × 10−3 S cm−1 at 25 °C) through aligned ion conduction pathways and provides electrode protection ability through hydrophobic chain dispersion. Integrating this mPR-SPE into solid-state LOBs resulted in stable potentials over 300 cycles. In situ Raman spectroscopy reveals the presence of an LiO2 intermediate alongside Li2O2 during oxygen reactions. Ex situ X-ray diffraction confirm the ability of the SPE to hinder the permeation of oxygen and moisture, as demonstrated by the air permeability tests. The present study suggests that maintaining a low residual solvent while achieving high ionic conductivity is crucial for restricting the sub-reactions of solid-state LOBs. [ABSTRACT FROM AUTHOR]

Highlights A carbon free self supported Mott-Schottky heterostructure was constructed as an efficient cathode catalyst for lithium oxygen batteries, achieving homogeneous contact between the two materials for strong interfacial interactions. The heterostructure triggered interfacial perturbations and band structure changes, which accelerated oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics, resulting in an extremely long cycle life of 800 cycles and an extremely low overpotential of 0.73 V. Combined with advanced characterization techniques and density functional theory calculations, the underlying mechanism behind the boosted ORR/OER activities and the electrocatalytic mechanism were revealed.

Lithium 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. [ABSTRACT FROM AUTHOR]

Rechargeable Li‒O2 batteries have attracted considerable attention owing to their high specific energy density compared to those of other lithium secondary batteries. However, the high charging overpotential remains one of the challenges for the application of Li-O2 batteries in specific energy storage systems. To solve this problem, various catalyst materials such as metal/metal oxides (Pt, Au, MnO2, CuO, etc.) have been developed. In this study, a new CaCO3 catalyst embedded in carbon is investigated for the first time for a nonaqueous Li‒O2 battery application. The overpotential of the Li‒O2 cell containing the CaCO3-embedded carbon cathode decreases by ~ 6.5% on an average over 40 cycles. [ABSTRACT FROM AUTHOR]

Highlights: A carbon free self supported Mott-Schottky heterostructure was constructed as an efficient cathode catalyst for lithium oxygen batteries, achieving homogeneous contact between the two materials for strong interfacial interactions. The heterostructure triggered interfacial perturbations and band structure changes, which accelerated oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics, resulting in an extremely long cycle life of 800 cycles and an extremely low overpotential of 0.73 V. Combined with advanced characterization techniques and density functional theory calculations, the underlying mechanism behind the boosted ORR/OER activities and the electrocatalytic mechanism were revealed. Lithium-oxygen batteries (LOBs) with high energy density are a promising advanced energy storage technology. However, the slow cathodic redox kinetics during cycling causes the discharge products to fail to decompose in time, resulting in large polarization and battery failure in a short time. Therefore, a self-supporting interconnected nanosheet array network NiCo2O4/MnO2 with a Mott–Schottky heterostructure on titanium paper (TP-NCO/MO) is ingeniously designed as an efficient cathode catalyst material for LOBs. This heterostructure can accelerate electron transfer and influence the charge transfer process during adsorption of intermediate by triggering the interface disturbance at the heterogeneous interface, thus accelerating oxygen reduction and oxygen evolution kinetics and regulating product decomposition, which is expected to solve the above problems. The meticulously designed unique structural advantages enable the TP-NCO/MO cathode catalyst to exhibit an astounding ultra-long cycle life of 800 cycles and an extraordinarily low overpotential of 0.73 V. This study utilizes a simple method to cleverly regulate the morphology of the discharge products by constructing a Mott–Schottky heterostructure, providing important reference for the design of efficient catalysts aimed at optimizing the adsorption of reaction intermediates. [ABSTRACT FROM AUTHOR]

Lithium‐oxygen batteries possess an extremely high theoretical energy density, rendering them a prime candidate for next‐generation secondary batteries. However, they still face multiple problems such as huge charge polarization and poor life, which lay a significant gap between laboratory research and commercial applications. In this work, we adopt 15‐crown‐5 ether (C15) as solvent to regulate the generation of discharge products in lithium‐oxygen batteries. The coronal structure endows C15 with strong affinity to Li+, firmly stabilizes the intermediate LiO2 and discharge product Li2O2. Thus, the crystalline Li2O2 is amorphized into easily decomposable amorphous products. The lithium‐oxygen batteries assembled with 0.5 M C15 electrolyte show an increased discharge capacity from 4.0 mAh cm−2 to 5.7 mAh cm−2 and a low charge overpotential of 0.88 V during the whole lifespan at 0.05 mA cm−2. The batteries with 1 M C15 electrolyte can cycle stably for 140 cycles. Furthermore, the amorphous characteristic of Li2O2 product is preserved when matched with redox mediators such as LiI, with the charge polarization further decreasing to 0.74 V over a cycle life of 190 cycles. This provides new possibilities for electrolyte design to promote Li2O2 amorphization and reduce charge overpotential in lithium‐oxygen batteries. [ABSTRACT FROM AUTHOR]

Sustainable energy is the key issue for the environment protection, human activity and economic development. Ionic liquids (ILs) and deep eutectic solvents (DESs) are dogmatically regarded as green and sustainable electrolytes in lithium-ion, lithium-metal (e.g., lithium-sulphur, lithium-oxygen) and post-lithium-ion (e.g., sodium-ion, magnesium-ion, and aluminum-ion) batteries. High electrochemical stability of ILs/DESs is one of the prerequisites for green, sustainable and safe energy; while easy electrochemical decomposition of ILs/DESs would be contradictory to the concept of green chemistry by adding the cost, releasing volatile/hazardous by-products and hindering the recyclability. However, (1) are ILs/DESs-based electrolytes really electrochemically stable when they are not used in batteries? (2) are ILs/DESs-based electrolytes really electrochemically stable in real batteries? (3) how to design ILs/DESs-based electrolytes with high electrochemical stability for batteries to achieve sustainability and green development? Up to now, there is no summary on this topic, to the best of our knowledge. Here, we review the effect of chemical structure and non-structural factors on the electrochemical stability of ILs/DESs in simulated conditions. More importantly, electrochemical stability of ILs/DESs in real lithium-ion, lithium-metal and post-lithium-ion batteries is concluded and compared. Finally, the strategies to improve the electrochemical stability of ILs/DESs in lithium-ion, lithium-metal and post-lithium-ion batteries are proposed. This review would provide a guide to design ILs/DESs with high electrochemical stability for lithium-ion, lithium-metal and post-lithium-ion batteries to achieve sustainable and green energy.

Recently emerging nanotechnological advancements has facilitated the embedment of metal-organic framework (MOFs) also referred as porous co-ordination polymers (PCPs), within conducting polymeric (CP) matrices (polyaniline, polypyrrole, poly(3,4-ethylenedioxythiophene) and so on), resulting in the fabrication of multifunctional MOF@CP nanoarchitectures for multifarious applications especially for electrochemical energy storage due to garnered enhanced features (low density, manipulatable porous architectures, elevated specific surface areas, aligned crystalline architectur)e, as well as controllable constitution at the molecular level. Therefore, this paper presents recently emerging trends in MOF@CP nanoarchitectures for applications in supercapacitors, lithium-sulfur batteries, metal-ion batteries, lithium-oxygen batteries, zinc-air batteries, batteries cover and other segments. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Carbon materials have shown significant potential as catalysts for lithium-oxygen batteries (LOBs). However, the intrinsic carbon sites are typically inert, necessitating extensive modifications and resulting in a limited density of active sites. Here we present C60 as a metal-free cathode catalyst for LOBs, using density functional theory calculations and experimental verifications. The lithiation reactions on the pristine carbon sites of C60 are energetically favorable due to its curved π-conjugation over the pentagon–hexagon networks. The kinetic analysis specifically reveals low energy barriers for Li2O2 decomposition and Li diffusion on C60. Consequently, C60 exhibits significantly higher catalytic activity than typical carbon materials such as graphene and carbon nanotubes. Our electrochemical measurements validate the predictions, notably demonstrating that the intrinsic activity of C60 is comparable to that of noble metals. [ABSTRACT FROM AUTHOR]

Facing high overpotential, severe Li corrosion and degradation of electrolytes caused by the reactive oxygen species, the development of lithium–oxygen batteries is seriously limited. Although the iodine species have been considered to be effective redox mediators (RMs) for lowering the charging overpotential, the shuttling of oxidized I3− may attack the Li metal anode, compromising the number of RMs, cycling stability and energy efficiency. Here the intend to introduce 3‐Iodooxetane (C3H5OI, IOD) into TEGDME‐based electrolyte to form a protective SEI layer on the Li surface for defending against the attack of I3−. However, the iodine in IOD is found difficult to dissociate. To solve this problem, hard Lewis acid, aluminum trichloride (AlCl3) is proposed as the catalytic agent for dissociating the I− and triggering the ring‐opening reaction of the detached C3H5O+ ions. The former can dissociate redox couple I3−/I− while the latter can form oligomers or polymers under the attack of a nucleophile. Meanwhile, AlCl3 can form Al2O3 and LiCl inorganic species. Taking together, the introduction of IOD and AlCl3 into electrolytes can effectively derive reduced overpotential and in situ SEI layers consisting of flexible organics and rigid inorganics, endowing lithium–oxygen batteries over 150 cycles with significantly enhanced stability and lifespan. [ABSTRACT FROM AUTHOR]

Abstract Lithium 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.

Lithium–oxygen batteries (LOBs) have extensive applications because of their ultra-high energy densities. However, the practical application of LOBs is limited by several factors, such as a high overpotential, poor cycle stability, and limited rate capacity. In this paper, we describe the successful uniform loading of Mn3O4 nanoparticles onto multi-walled carbon nanotubes (Mn3O4@CNT). CNTs form a conductive network and expose numerous catalytically active sites, and the one-dimensional porous structure provides a convenient channel for the transmission of Li+ and O2 in LOBs. The electronic conductivity and electrocatalytic activity of Mn3O4@CNT are significantly better than those of MnO@CNT because of the inherent driving force facilitating charge transfer between different valence metal ions. Therefore, the Mn3O4@CNT cathode obtains a low overpotential (0.76 V at a limited capacity of 1000 mAh g−1), high initial discharge capacity (16895 mAh g−1 at 200 mA g−1), and long cycle life (97 cycles at 200 mA g−1). This study provides evidence that transition metal oxides with mixed-valence states are suitable for application as efficient cathodes for LOBs.

Highlights The tailored KCoMnNiMgZnF3-HEC cathode delivers extremely high discharge capacity (22,104 mAh g−1), outstanding long-term cyclability (over 500 h), preceding majority of traditional catalysts reported. Entropy effect of multiple sites in KCoMnNiMgZnF3-HEC engenders appropriate regulation of 3d orbital structure, leading to a moderate hybridization with the p orbital of key intermediate. The homogeneous nucleation of Li2O2 is achieved on multiple cation site, contributing to effective mass transfer at the three-phase interface, and thus, the reversibility of O2/Li2O2 conversion.

The aprotic lithium‐oxygen (Li‐O2) battery has an extremely high theoretical specific energy and potentially provides a tantalizing solution to the renewable energy storage challenge encountered by contemporary and future societies. Nevertheless, the realization of practical Li‐O2 batteries currently meets with substantial challenges that include, but are not limited to, low energy capability and short longevity. To address these obstacles, unveiling the reaction processes and degradation mechanisms of Li‐O2 batteries is crucially important. Over recent years, the research paradigm of in situ spectroscopy coupled with theoretical calculations performed on well‐designed model interfaces, has proved to be indispensable for the fundamental study and performance optimization of various energy storage devices. In this contribution, first representative illustrations of this research paradigm are offered in the study of both primary and parasitic reactions of Li‐O2 batteries, which significantly simplifies, but not degrade, the complex reaction conditions and decouples multiple processes occurring simultaneously in Li‐O2 cells. Then, the perspective is provided on the remaining issues as well as uncertainties and discuss future research directions. Finally, wider research community is encouraged to tailor‐design versatile model interfaces to better bridge in situ spectroscopy and theoretical calculations for the research and development of better Li‐O2 batteries and beyond. [ABSTRACT FROM AUTHOR]

Aprotic lithium‐oxygen (Li–O2) batteries hardly cycle at the condition of high area capacity for realizing their high energy density, because the unconducive lithium peroxide (Li2O2) discharge product limits the electron transfer between electrode and O2/Li2O2. Here, it is demonstrated that one of redox mediator (RM), triethylene glycol bis‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl radical (D‐TEMPO), can be effectively used to promote the electron transfer between electrode and Li2O2, which the shuttle effect of RM can be cooperatively inhibited by regulating the size of RM and the thickness of ion‐selective membrane. As a result, the Li–O2 battery coupled with double cathodes, D‐TEMPO, and ion‐selective membrane can be stably operated for 46 days at a capacity of 5 mAh cm−2. The concept in this work provides the cooperative design of a stable solution‐mediated pathway for high‐capacity Li–O2 battery with long cycle stability. [ABSTRACT FROM AUTHOR]

Although lithium–oxygen batteries have attracted attention due to their extremely high energy densities, rational design, and critical evaluation of high‐energy‐density cathode for practical Li–O2 batteries is still urgently needed. Herein, the multiscale, angstrom‐to‐millimeter, precisely controllable synthesis of binder‐free cathodes with minimally stacked graphene free from edge sites is demonstrated. The proposed Li–O2 battery, based on a hierarchically porous cathode with a practical mass loading of >4.0 mg cm−2, simultaneously exhibits an unprecedented specific areal (>30.0 mAh cm−2), mass (>6300 mAh g−1), and volumetric (>480 mAh cm−3) capacities. The battery displays the optimal energy density of 793 Wh kg−1 critically normalized to the total mass of all active materials including electrolytes and even discharge products Li2O2. Comprehensive in situ characterizations demonstrate a unique discharge mechanism in hierarchical pores which contributes to competitive battery performance. Superior rate performance in a current density range of 0.1 to 0.8 mA cm−2 and long‐cycle stability (>260 cycles) at a current density of 0.4 mA cm−2, outperforming state‐of‐the‐art carbon cathodes. This study yields insight into next‐generation carbon cathodes, not only for use in practical Li–O2 batteries, but also in other metal–gas batteries with high energy densities. [ABSTRACT FROM AUTHOR]

Aprotic Li‐O2 battery has attracted considerable interest for high theoretical energy density, however the disproportionation of the intermediate of superoxide (O2−) during discharge and charge leads to slow reaction kinetics and large voltage hysteresis. Herein, the chemically stable ruthenium tris(bipyridine) (RB) cations are employed as a soluble catalyst to alternate the pathway of O2− disproportionation and its kinetics in both the discharge and charge processes. RB captures O2− dimer and promotes their intramolecular charge transfer, and it decreases the energy barrier of the disproportionation reaction from 7.70 to 0.70 kcal mol−1. This facilitates the discharge and charge processes and simultaneously mitigates O2− and singlet oxygen related side reactions. These endow the Li‐O2 battery with reduced discharge/charge voltage gap of 0.72 V and prolonged lifespan for over 230 cycles when coupled with RuO2 catalyst. This work highlights the vital role of superoxide disproportionation for Li‐O2 battery. [ABSTRACT FROM AUTHOR]

Lithium-oxygen batteries (LOBs) have extensive applications because of their ultra-high energy densities. However, the practical application of LOBs is limited by several factors, such as a high overpotential, poor cycle stability, and limited rate capacity. In this paper, we describe the successful uniform loading of Mn3O4 nanoparticles onto multi-walled carbon nanotubes (Mn3O4@CNT). CNTs form a conductive network and expose numerous catalytically active sites, and the one-dimensional porous structure provides a convenient channel for the transmission of Li+ and O2 in LOBs. The electronic conductivity and electrocatalytic activity of Mn3O4@CNT are significantly better than those of MnO@CNT because of the inherent driving force facilitating charge transfer between different valence metal ions. Therefore, the Mn3O4@CNT cathode obtains a low overpotential (0.76 V at a limited capacity of 1000 mAh g-1), high initial discharge capacity (16895 mAh g-1 at 200 mA g-1), and long cycle life (97 cycles at 200 mA g-1). This study provides evidence that transition metal oxides with mixed-valence states are suitable for application as efficient cathodes for LOBs. [ABSTRACT FROM AUTHOR]

Highlights: The tailored KCoMnNiMgZnF3-HEC cathode delivers extremely high discharge capacity (22,104 mAh g−1), outstanding long-term cyclability (over 500 h), preceding majority of traditional catalysts reported. Entropy effect of multiple sites in KCoMnNiMgZnF3-HEC engenders appropriate regulation of 3d orbital structure, leading to a moderate hybridization with the p orbital of key intermediate. The homogeneous nucleation of Li2O2 is achieved on multiple cation site, contributing to effective mass transfer at the three-phase interface, and thus, the reversibility of O2/Li2O2 conversion. High-entropy catalysts featuring exceptional properties are, in no doubt, playing an increasingly significant role in aprotic lithium-oxygen batteries. Despite extensive effort devoted to tracing the origin of their unparalleled performance, the relationships between multiple active sites and reaction intermediates are still obscure. Here, enlightened by theoretical screening, we tailor a high-entropy perovskite fluoride (KCoMnNiMgZnF3-HEC) with various active sites to overcome the limitations of conventional catalysts in redox process. The entropy effect modulates the d-band center and d orbital occupancy of active centers, which optimizes the d–p hybridization between catalytic sites and key intermediates, enabling a moderate adsorption of LiO2 and thus reinforcing the reaction kinetics. As a result, the Li–O2 battery with KCoMnNiMgZnF3-HEC catalyst delivers a minimal discharge/charge polarization and long-term cycle stability, preceding majority of traditional catalysts reported. These encouraging results provide inspiring insights into the electron manipulation and d orbital structure optimization for advanced electrocatalyst. [ABSTRACT FROM AUTHOR]

The lithium–oxygen battery has the highest theoretical specific energy among all battery systems, while the actual value falls significantly short. The hindered oxygen and/or electron transport result(s) in limited utilization of the porous air electrode, while achieving a quantitative understanding of the electrochemistry and mass transport coupling is challenging. Herein, a porous electrode with highly consistent and controllable channel units is pioneered that excludes the randomness of disordered pores and consequently enables the investigation of control mechanisms. A three‐dimensional dynamic heterogeneous model is developed, providing the first spatio‐temporal distribution of LiO2 and revealing its reversed diffusion trajectories at limited electron transport. The synergistic combination of experiments and models identifies the crucial role of channel sizes on mechanisms that are divided into mass, hybridization, and electron transport control. For macropores, improving Li2O2 conductivity and mitigating solid‐liquid interface damage are urgent compared to enhancing oxygen diffusion. The unit model offers a promising approach to quantitatively understand the reaction and transport mechanisms in other battery systems with porous electrodes. This work represents a break through in knowledge of control mechanisms and guides the design of disordered electrodes for high‐performance lithium–oxygen batteries. [ABSTRACT FROM AUTHOR]

Redox mediators (RMs) are reported to effectually encourage the inactive decomposition of discharge products in lithium–oxygen batteries (LOBs); however, oxidized RMs and other injurious species still attack the Li anodes. An ionic liquid (IL)‐modified PVDF single‐lithium‐ion conducting composite membrane that can permit Li+ only but blocks anions and other molecules is prepared. The PVDF is combined with the strong‐acid cation styrene exchange resin with cation exchange characteristics to make a heterogeneous composite single‐ionic conductor membrane and the IL modification causes the formation of a more‐dense groove inside the PVDF membrane apparently strengthening the conductivity of the membrane without losing its impermeability to cations and discharge intermediates. The utility of the modified composite PVDF (MCP) separator greatly extends the cycle life of the LOB from 66 to 347 cycles at 1000 mAg−1 and 1000 mAhg−1 compared to cells using glass fiber separators. Rate performance is significantly enhanced at 3000 and 5000 mAg−1, increasing from 33 and 21 cycles to 171 and 137 cycles. The full discharge capacity also expands from 3702 to 51 205 mAhg−1. The MCP separator enables iodide‐assisted cathode processes and improves lithium anode stripping/plating, which is essential to improve the performance of nonelectrolytic LOBs. [ABSTRACT FROM AUTHOR]

Despite theoretical predictions of exceptional gravimetric energy densities in Li‐O2 batteries (LOBs), the current research forefront faces challenges, including high charge overpotential, cathode clogging, parasitic reactions, and Li anode corrosion. Herein, benzo‐crown ethers (BCEs) with varying cavity sizes are used as electrolyte additives to exploit their strong binding toward Li+ and promote the solution growth of Li2O2 with reduced particle size. Notably, the cell with benzo‐18‐crown‐6 ether (B18C6) enables the largest discharge capacity of 14948 mAh g−1. Upon charging, these additives accelerate Li2O2 oxidation through the strong binding with Li+ and the extended electrolyte/Li2O2 interface, resulting in improved reversibility, reduced charge overpotential, and prolonged cycle life. Besides, these additives also stabilize the Li anode by regulating Li+ migration and electron exchange, reducing dendritic growth and anode corrosion. This work presents insights into the rational design of BCEs as additives for high‐performance LOBs. [ABSTRACT FROM AUTHOR]

The semi‐open system of lithium‐oxygen batteries (LOBs) results in electrolyte depletion, lithium anode corrosion, and by‐product deposition, and therefore represents a major challenge that hinders their application. Here, the aligned and open microchannel structures of wood are fabricated as separators to provide low‐tortuosity pathways for rapid ionic transport and serve as reservoirs for retaining the electrolyte by capillary forces to improve the electrochemical kinetics. In an open environment, the wood separator can hold 39% of the initial adsorption electrolyte capacity after 40 days, much higher than that of glass fiber (GF, 15%). The cellulose in the wood can confine the crossover effect of water thereby inhibiting the corrosion of lithium anode and reducing the deposition of by‐products. Density functional theory calculations certify that the abundant functional groups and uniform electron distribution in cellulose increase lithium‐ion concentration on the wood surface and promote lithium‐ion migration with a low diffusion barrier. LOBs composed of the wood‐derived separator displayed excellent anodic reversibility (over 1200 h) and effectively improved cathodic lifetime over 300 cycles (1.6 times longer than that of GF separator). These findings illustrate the significant potential of this candidate separator for high‐performance LOBs and are expected to be extended to metal‐air batteries. [ABSTRACT FROM AUTHOR]

Redox mediators (RMs) are reported to effectually encourage the inactive decomposition of discharge products in lithium–oxygen batteries (LOBs); however, oxidized RMs and other injurious species still attack the Li anodes. An ionic liquid (IL)‐modified PVDF single‐lithium‐ion conducting composite membrane that can permit Li+ only but blocks anions and other molecules is prepared. The PVDF is combined with the strong‐acid cation styrene exchange resin with cation exchange characteristics to make a heterogeneous composite single‐ionic conductor membrane and the IL modification causes the formation of a more‐dense groove inside the PVDF membrane apparently strengthening the conductivity of the membrane without losing its impermeability to cations and discharge intermediates. The utility of the modified composite PVDF (MCP) separator greatly extends the cycle life of the LOB from 66 to 347 cycles at 1000 mAg−1 and 1000 mAhg−1 compared to cells using glass fiber separators. Rate performance is significantly enhanced at 3000 and 5000 mAg−1, increasing from 33 and 21 cycles to 171 and 137 cycles. The full discharge capacity also expands from 3702 to 51 205 mAhg−1. The MCP separator enables iodide‐assisted cathode processes and improves lithium anode stripping/plating, which is essential to improve the performance of nonelectrolytic LOBs.

Lewis‐base sites have been widely applied to regulate the properties of Lewis‐acid sites in electrocatalysts for achieving a drastic technological leap of lithium‐oxygen batteries (LOBs). Whereas, the direct role and underlying mechanism of Lewis‐base in the chemistry for LOBs are still rarely elucidated. Herein, we comprehensively shed light on the pivotal mechanism of Lewis‐base sites in promoting the electrocatalytic reaction processes of LOBs by constructing the metal–organic framework containing Lewis‐base sites (named as UIO‐66‐NH2). The density functional theory (DFT) calculations demonstrate the Lewis‐base sites can act as electron donors that boost the activation of O2/Li2O2 during the discharged‐charged process, resulting in the accelerated reaction kinetics of LOBs. More importantly, the in situ Fourier transform infrared spectra and DFT calculations firstly demonstrate the Lewis‐base sites can convert Li2O2 growth mechanism from surface‐adsorption growth to solvation‐mediated growth due to the capture of Li+ by Lewis‐base sites upon discharged process, which weakens the adsorption energy of UIO‐66‐NH2 towards LiO2. As a proof of concept, LOB based on UIO‐66‐NH2 can achieve a high discharge specific capacity (12 661 mAh g−1), low discharged‐charged overpotential (0.87 V) and long cycling life (169 cycles). This work reveals the direct role of Lewis‐base sites, which can guide the design of electrocatalysts featuring Lewis‐acid/base dual centers for LOBs. [ABSTRACT FROM AUTHOR]

Li‐O2 batteries have garnered much attention due to their high theoretical energy density. However, the irreversible lithium plating/stripping on the anode limits their performance, which has been paid little attention. Herein, a solvation‐regulated strategy for stable lithium anodes in tetraethylene glycol dimethyl ether (G4) based electrolyte is attempted in Li‐O2 batteries. Trifluoroacetate anions (TFA−) with strong Li+ affinity are incorporated into the lithium bis(fluorosulfonyl)imide (LiTFSI)/G4 electrolyte to attenuate the Li+‐G4 interaction and form anion‐dominant solvates. The bisalt electrolyte with 0.5 M LiTFA and 0.5 M LiTFSI mitigates G4 decomposition and induces an inorganic‐rich solid electrolyte interphase (SEI). This contributes to decreased desolvation energy barrier from 58.20 to 46.31 kJ mol−1, compared with 1.0 M LiTFSI/G4, for facile interfacial Li+ diffusion and high efficiency. It yields extended lifespan of 120 cycles in Li‐O2 battery with a limited Li anode (7 mAh cm−2). This work gains comprehensive insights into rational electrolyte design for Li‐O2 batteries. [ABSTRACT FROM AUTHOR]

Lithium-oxygen (Li-O2) batteries have a great potential in energy storage and conversion due to their ultra-high theoretical specific energy, but their applications are hindered by sluggish redox reaction kinetics in the charge/discharge processes. Redox mediators (RMs), as soluble catalysts, are widely used to facilitate the electrochemical processes in the Li-O2 batteries. A drawback of RMs is the shuttle effect due to their solubility and mobility, which leads to the corrosion of a Li metal anode and the degradation of the electrochemical performance of the batteries. Herein, we synthesize a polymer-based composite protective separator containing molecular sieves. The nanopores with a diameter of 4 Å in the zeolite powder (4A zeolite) are able to physically block the migration of 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) molecules with a larger size; therefore, the shuttle effect of TEMPO is restrained. With the assistance of the zeolite molecular sieves, the cycle life of the Li-O2 batteries is significantly extended from ∼ 20 to 170 cycles at a current density of 250 mA·g−1 and a limited capacity of 500 mAh·g−1. Our work provides a highly effective approach to suppress the shuttle effects of RMs and boost the electrochemical performance of Li-O2 batteries. [ABSTRACT FROM AUTHOR]

Digital platforms, electric vehicles, and renewable energy grids all rely on energy storage systems, with lithium-ion batteries (LIBs) as the predominant technology. However, the current energy density of LIBs is insufficient to meet the long-term objectives of these applications, and traditional LIBs with flammable liquid electrolytes pose safety concerns. All-solid-state lithium–oxygen batteries (ASSLOBs) are emerging as a promising next-generation energy storage technology with potential energy densities up to ten times higher than those of current LIBs. ASSLOBs utilize non-flammable solid-state electrolytes (SSEs) and offer superior safety and mechanical stability. However, ASSLOBs face challenges, including high solid-state interface resistances and unstable lithium-metal anodes. In recent years, significant progress has been proceeded in developing new materials and interfaces that improve the performance and stability of ASSLOBs. This review provides a comprehensive overview of the recent advances and challenges in the ASSLOB technology, including the design principles and strategies for developing high-performance ASSLOBs and advances in SSEs, cathodes, anodes, and interface engineering. Overall, this review highlights valuable insights into the current state of the art and future directions for ASSLOB technology. [ABSTRACT FROM AUTHOR]

Practical working environment (O2-saturated base electrolyte), architecture and operation mechanism/processes of Li-O2 batteries (LOBs) endows severe O2 and superoxide (O2-)-derived attack on Li-metal and solid electrolyte interface (SEI) at Li/electrolyte interface, limiting stability of Li anodes and LOBs. Herein, how O2/O2--derived attack on Li-metal and structure/composition of SEI are revealed by cryogenic transmission electron microscopy (cryo-TEM) and comprehensive spectroscopic characterizations. Specifically, generated from O2-reduction on Li-anode, the Li2O-induced nucleophilic attack on base electrolyte decomposition and Li corrosion especially during long-term aging, and more aggressive O2- created in cycling aggravates Li anodes and SEI. Moreover, to address O2/O2--derived attack on Li-metal, 1, 2-difluorobenzene (F-ben) was introduced as cosolvent in base electrolyte to make an F-ben electrolyte, in which F-ben preferentially reacted with Li-metal to form dual-functional SEI. Tuned SEI not only separate Li2O from bulk electrolyte thus suppresses O2-derived chemical attack, also acts as protective film protecting Li-metal against O2- attack. Eventually, electro-stability/reversibility of Li-metal in practical working environment of LOBs and battery performance of LOBs are significantly enhanced with help of F-ben cosolvent. This work sheds light on behavior of O2/O2--derived attack on Li-metal and SEI, sets an effective and practicable path towards practical applications of LOBs.

Lithium–oxygen (Li–O2) batteries have great potential for applications in electric devices and vehicles due to their high theoretical energy density of 3500 ​Wh kg−1. Unfortunately, their practical use is seriously limited by the sluggish decomposition of insulating Li2O2, leading to high OER overpotentials and the decomposition of cathodes and electrolytes. Cathode electrocatalysts with high oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities are critical to alleviate high charge overpotentials and promote cycling stability in Li–O2 batteries. However, constructing catalysts for high OER performance and energy efficiency is always challenging. In this mini-review, we first outline the employment of advanced electrocatalysts such as carbon materials, noble and non-noble metals, and metal–organic frameworks to improve battery performance. We then detail the ORR and OER mechanisms of photo-assisted electrocatalysts and single-atom catalysts for superior Li–O2 battery performance. Finally, we offer perspectives on future development directions for cathode electrocatalysts that will boost the OER kinetics.

Catalysts with a refined electronic structure are highly desirable for promoting the oxygen evolution reaction (OER) kinetics and reduce the charge overpotentials for lithium--oxygen (Li-O2) batteries. However, bridging the orbital interactions inside the catalyst with external orbital coupling between catalysts and intermediates for reinforcing OER catalytic activities remains a grand challenge. Herein, we report a cascaded orbital--oriented hybridization, namely alloying hybridization in intermetallic Pd3Pb followed by intermolecular orbital hybridization between low-energy Pd atom and reaction intermediates, for greatly enhancing the OER electrocatalytic activity in Li-O2 battery. The oriented orbital hybridization in two axes between Pb and Pd first lowers the d band energy level of Pd atoms in the intermetallic Pd3Pb; during the charging process, the low-lying 4dxz/yz and 4dz² orbital of the Pd further hybridizes with 2π* and 5σ orbitals of lithium superoxide (LiO2) (key reaction intermediate), eventually leading to lower energy levels of antibonding and, thus, weakened orbital interaction toward LiO2. As a consequence, the cascaded orbital--oriented hybridization in intermetallic Pd3Pb considerably decreases the activation energy and accelerates the OER kinetics. The Pd3Pb-based Li-O2 batteries exhibit a low OER overpotential of 0.45 V and superior cycle stability of 175 cycles at a fixed capacity of 1,000 mAh g-1, which is among the best in the reported catalysts. The present work opens up a way for designing sophisticated Li-O2 batteries at the orbital level. [ABSTRACT FROM AUTHOR]