Li-O2 Batteries Research Articles

Crown Ether Electrolyte Induced Li2O2 Amorphization for Low Polarization and Long Lifespan Li-O2 batteries.

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 cycle life, which lay a significant gap between laboratory research and commercial applications. In this work, we adapt 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.

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.

Addressing redox shuttling in Li-O2 batteries: Mechanistic insights by synchrotron X–ray tomography

In situ characterization on interface stability has been hardly tried in redox mediator (RM)-involved Li-O2 battery thus far. Here, benzyltriethylammonium iodide (BTEAI) can act as a self-defensive RM in the electrolyte LiTFSI/TEGDME to enhance the reaction kinetics and increase the cycling stability by suppressing the redox shuttling. I- effectively reduces the charging overpotential by changing decomposition route for Li2O2. BTEA+ can facilitate LiTFSI decomposition in the electrolyte, and participate in formation of an organic–inorganic composite SEI-contained layer on Li anode. Moreover, for the first time, non-destructive synchrotron X-Ray tomography is used to investigate the mechanism of suppressing shuttle effect by monitoring the morphological evolution of electrodes interface. This work provides an insight into the development of functional RM and in situ protection strategies for Li anodes in Li-O2 batteries.

A Rotating Cathode with Periodical Changes in Electrolyte Layer Thickness for High-Rate Li‒O2 Batteries.

Li‒O2 batteries possess the highest theoretical gravimetric energy density among all types of secondary batteries, but they are still far from practical applications. The poor rate performance resulting from the slow mass transfer is one of the primary obstacles in Li‒O2 batteries. To solve this issue, we have designed a rotating cathode with periodic changes of the electrolyte layer thickness, decoupling the maximum transfer rate of Li+ and O2. During rotating, the thinner electrolyte layer on cathode facilitates the O2 transfer and the thicker electrolyte layer enhances the Li+ transfer. As a result, the rotating cathode enables the Li-O2 batteries to undergo 58 cycles at 2.5mA cm-2 and discharge stably even at a high current density of 7.5 ‍mA ‍cm-2. Besides, it also makes the batteries exhibit a large discharge capacity of 6.8 ‍mAh ‍cm‒‍2, and the capacity decay is much slower with increasing current density. Notably, this rotating electrode holds great promise for utilization in other electrochemical cells involving gas-liquid-solid triple-phase interfaces, suggesting a viable approach to enhance the mass transfer in such systems. This article is protected by copyright. All rights reserved.

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.

First Principles Study of the Structure-Performance Relation of Pristine Wn+1Cn and Oxygen-Functionalized Wn+1CnO2 MXenes as Cathode Catalysts for Li-O2 Batteries.

Li-O2 batteries are considered a highly promising energy storage solution. However, their practical implementation is hindered by the sluggish kinetics of the oxygen reduction (ORR) and oxygen evolution (OER) reactions at cathodes during discharging and charging, respectively. In this work, we investigated the catalytic performance of Wn+1Cn and Wn+1CnO2 MXenes (n = 1, 2, and 3) as cathodes for Li-O2 batteries using first principles calculations. Both Wn+1Cn and Wn+1CnO2 MXenes show high conductivity, and their conductivity is further enhanced with increasing atomic layers, as reflected by the elevated density of states at the Fermi level. The oxygen functionalization can change the electronic properties of WC MXenes from the electrophilic W surface of Wn+1Cn to the nucleophilic O surface of Wn+1CnO2, which is beneficial for the activation of the Li-O bond, and thus promotes the Li+ deintercalation during the charge-discharge process. On both Wn+1Cn and Wn+1CnO2, the rate-determining step (RDS) of ORR is the formation of the (Li2O)2* product, while the RDS of OER is the LiO2* decomposition. The overpotentials of ORR and OER are positively linearly correlated with the adsorption energy of the RDS LixO2* intermediates. By lowering the energy band center, the oxygen functionalization and increasing atomic layers can effectively reduce the adsorption strength of the LixO2* intermediates, thereby reducing the ORR and OER overpotentials. The W4C3O2 MXene shows immense potential as a cathode catalyst for Li-O2 batteries due to its outstanding conductivity and super-low ORR, OER, and total overpotentials (0.25, 0.38, and 0.63 V).

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.

Boosting the ORR/OER Activity of Cobalt-Based Nano-Catalysts by Co 3d Orbital Regulation.

The transition metal oxides/sulfides are considered promising catalysts due to their abundant resources, facile synthesis, and reasonable electrocatalytic activity. Herein, a significantly improved intrinsic catalytic activity is achieved for constructing a Co-based nanocrystal (Co-S@NC) with the coordination of Co─S, Co─S─C, and Co─Nx─C. The calculational and experimental results demonstrate that the diversified chemical environment of Co-cations induces the transition of 3d orbitals to a high spin-state that exhibits the coexistence of Co2+ with fully occupied dπ orbitals and Co3+ with unpaired electrons in dπ orbitals. The diverse dπ orbitals occupation contributes to an elevated d-band center of Co ions, which accelerates oxygen reduction reaction and oxygen evolution reaction electrocatalytic kinetics of the Co-S@NC nanocrystal. Therefore, the Li-O2 batteries with Co-S@NC as cathode catalyst exhibit 300 cycles at the current density of 500 mA g-1 with a cut-off capacity of 1000 mAh g-1. Moreover, the ultrahigh discharge specific capacity of 34 587 mAh g-1 is obtained at a current density of 1000 mA g-1, corresponding to the energy density 949 Wh kg-1 of a prototype Li-O2 battery. The study on 3d orbital regulation of nanocrystals provides an innovative strategy for bifunctional electrocatalysts toward the practical application of metal-air batteries.

Compositionally engineered NiCoLDH@rGO as bifunctional cathode catalyst for rechargeable Li-O2/Li-CO2 battery

Compositionally tuned nickel-cobalt layered double hydroxides (NCLDHs) and NCLDH@reduced graphene-oxide (NCLDH@rGO) were synthesized through a facile solvothermal synthesis route. The formation of the synthesized NCLDH and the NCLDH@rGO with the intercalated carbonate and nitrate anions, has been confirmed utilizing different characterization techniques. Microscopic results revealed the flaky morphology with thickness about 30 nm. Rotating ring disc electrode (RRDE) voltammetry was utilized to analyze the oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and carbon dioxide reduction reaction (CO2RR) kinetics on each of the pristine (1:1), (2:1), (3:1) and (4:1) NCLDH catalysts and the NCLDH@rGO composites. The RRDE data revealed that the electrochemical activity towards ORR/OER/CO2RR could be largely increased by tuning mole ratio of the (Ni2+/Co3+) or the amount of the rGO in the NCLDH. It turned out that among the pristine electrocatalysts, the (1:1) NCLDH catalyst exhibited enhanced ORR/OER kinetics. While the NCLDH acted as a catalyst center, the rGO provided conductive network that facilitated passable overpotential with increased current density for the ORR/OER/ CO2RR. Better adsorption of O2 and CO2 on the NCLDH@rGO catalyst also contributed for the electrocatalytic activity. Consequently, the NCLDH@rGO composites as cathode catalyst for Li-O2 battery in the CR2032 prototype coin-cell exhibited a stable open circuit voltage (OCV). Among the NCLDH@rGO composites, the NCLDH with 15 wt.% rGO (NCRGO15) exhibited a high discharge capacity of 3616 mAh g−1 at 50 Ag−1 for the Li-O2 battery and a discharge capacity of 45 mAh g−1 at a current density of 100 Ag−1 for the CR2032 coin-type Li-CO2 battery. As a practical use, a commercial 2.8 V green LED bulb was lit continuously for about 20 h using the fabricated Li-O2 battery that consisted of lithium anode and (1:1) NCLDH@rGO15 wt.% (NCRGO15) air-breathing cathode.

Probing the reactivity of protonated oxygen intermediate in aprotic media with in situ surface-enhanced infrared spectroscopy

A fundamental understanding of electrochemical reactions is essential to drive the practicality of batteries. The oxygen reduction reaction (ORR) that occurs on discharge in aprotic lithium-oxygen (Li-O2) batteries, invariably encounters interference from impurities (e.g., protons) in practical environments. It has been shown that moderate proton-mediated ORR can improve discharge capacity without altering the overall pathway; however, the reactivity of protonated oxygen intermediates formed towards aprotic electrolytes during ORR, remains controversial and unexplored. Herein, we interrogate the reactivity of protonated oxygen intermediates at the model Au | propylene carbonate and Au | trimethyl phosphate interfaces containing phenol as the moderate proton source, using in situ attenuated total reflection surface-enhanced infrared spectroscopy coupled with theoretical calculations. Direct spectroscopic evidence presents that the preferential reaction between superoxide and available protons to form protonated oxygen intermediates (e.g., HO2), can significantly mitigate superoxide anion (O2−)-induced solvent degradations while not triggering additional secondary parasitic reactions. Consequently, practical Li-O2 batteries containing phenol have also exhibited improved electrochemical performance and reversibility. We believe that the fundamental insights will provide important lessons for future practical design (e.g., protons control of electrolytes) of Li-O2 batteries and other related electrochemical devices.

Interfacial oxygen bridge bonding with Mo-O-Ti units in MoOx@Ti3C2 MXene harness efficient Li-O2 Battery at high rate

The rational pursuit of competent bifunctional catalysts for facilitating oxygen redox kinetics is critical in boosting the Li-O2 battery commercial application. Here, we report the preparation of efficient MoOx@Ti3C2 MXene catalysts with optimized electronic structure by in-situ incorporation of interfacial oxygen bridge bonding with Mo-O-Ti units. MoOx@Ti3C2 MXene delivers tailored chemical bonding, amplified electrical conductivity, and outstanding high-rate stability. The as-constructed MoOx@Ti3C2 MXene-based Li-O2 battery achieves lower discharge/charge polarization of 0.75 V and long-term lifespan of 300 hours (over 300 cycles) under 2500 mA g−1, exceeding those of reported related catalysts. Density functional theory analysis and ex-situ experiments reveal the critical role of bimetallic-oxygen coupling in regulating the micro-chemical constitution and controlling the Li2O2 formation mode. This work could provide consideration insights in the rational design of competent and stable MXene-based cathode catalyst with bimetallic heterostructure for high-rate Li-O2 batteries.

Mixture electrolyte suppressing water-induced parasitic reactions on Zn anode by tuning multilayer solvating structure

Though aqueous zinc ion batteries have been identified as a feasible option for energy storage, there are still some challenges that block the development of aqueous zinc ion battery, especially the issues from zinc metal anode. Tuning solvating structure of Zn2+ and adjusting the electrolyte in recent years is considered to be a simple but potential strategy to improve stability of zinc anode. In this work, a mixture electrolyte was obtained by dessolving LiTFSI/TEGDME Li-O2 battery electrolyte into 2 M aqueous ZnSO4 solution to tune solvating structure and adjust the striping/plating process of anode. Molecular spectrum and X-ray based method clarified that the mixture electrolyte plays dual functions to protect anode during electrochemical process. From one aspect, TEGDME partially replaced water and reconstructed a new multilayer solvating shell with TFSI-, which is beneficial for fast dendrite-free deposition. From the other aspect, surface spectrum also revealed that due to the participation of Li+ and TFSI-, a surface layer with ZnOHS framework and ZnF2 fillings formed on anode which further inhibit the dendrite growth and stabilize anode. This work combines the method of tuning solvation structure and construct SEI together and opens a new view designing new electrolytes for aqueous Zn-ion battery.

Modulating the d-Band Center of RuO2 via Ni Incorporation for Efficient and Durable Li-O2 batteries.

Rechargeable Li-O2 batteries (LOBs) are considered as one of the most promising candidates for new-generation energy storage devices. One of major impediments is the poor cycle stability derived from the sluggish reaction kinetics of unreliable cathode catalysts, hindering the commercial application of LOBs. Therefore, the rational design of efficient and durable catalysts is critical for LOBs. Optimizing surface electron structure via the negative shift of the d-band center offers a reasonable descriptor for enhancing the electrocatalytic activity. In this study, the construction of Ni-incorporating RuO2 porous nanospheres is proposed as the cathode catalyst to demonstrate the hypothesis. Density functional theory calculations reveal that the introduction of Ni atoms can effectively modulate the surface electron structure of RuO2 and the adsorption capacities of oxygen-containing intermediates, accelerating charge transfer between them and optimizing the growth pathway of discharge products. Resultantly, the LOBs exhibit a large discharge specific capacity of 19658mA h g-1 at 200mA g-1 and extraordinary cycle life of 791 cycles. This study confers the concept of d-band center modulation for efficient and durable cathode catalysts of LOBs.

In situ construction of a P-doped TiO2/Ti3C2Tx heterostructure with local site optimization to improve Li-O2 battery performance

The performance of Li-O2 batteries is seriously limited by the sluggish kinetics of the mass transition in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). To explore a useful strategy to overcome these limitations, herein, we constructed a P-doped TiO2/Ti3C2Tx heterostructure (PTT) with local active site optimization, in which the highly conductive substrate anchored the P-TiO2 nanoparticles with a selective adsorption and conversion of LiOx. In contrast to the TiO2/Ti3C2Tx heterostructure with a relatively uniform active site inducing typical toroidal Li2O2, the introduction of P-doping generates a unique nanosheet array Li2O2 on the PTT surface as a discharge product. This unique structure is endowed with a shorter Li+ diffusion path and benefits mass transfer in ORR and OER, facilitating the reaction kinetics. It presents obviously enhanced battery performance with a high specific capacity of 13,482 mAh g−1 and decreased discharge–charge overpotential, as well as superior cycling stability of 190 cycles. Furthermore, this novel and efficient electrocatalyst can stably operate for more than 650 cycles at 1000 mA g−1 with the addition of a LiI redox mediator. This study provides new insight into high-performance electrocatalyst design in Li2O2 related battery system.

D‐Band Center Regulation for Durable Catalysts and Constructing a Robust Hybrid Layer on Li Anode Enable Long‐Life Li‐O2 Batteries

AbstractRechargeable Li‐O2 batteries (LOBs) are regarded as promising candidates for the next generation of energy storage devices. One of the major impediments is the poor cycle stability resulting from unreliable cathode catalysts and serious corrosion of Li anode, hindering the commercial application of LOBs. Herein, a synergetic strategy is proposed, including the design of a stable Co3Ru cathode catalyst via d‐band center modulation and the construction of a robust LiF/Sn/Li5Sn2‐PFDTMS hybrid protective layer on Li anode. Theoretical calculations reveal that the negative shift of the d‐band center provides a dominant descriptor for improving the catalysis activity and stability of Ru‐based catalysts. In situ construction of the PFDTMS‐enhanced LiF/Sn/Li5Sn2 hybrid layer possesses excellent mechanical stability and toughness, which can effectively shield the Li anode from corrosive reaction and ensure good Li+ transport. Consequently, the LOBs exhibit a long cycle life of 990 cycles (≈1980 h). This work confers the concept for high‐performance LOBs via rationally constructing stable catalysts and Li anodes.

Thermal runaway propagation behavior and gas production characteristics of NCM622 battery modules at different state of charge

Due to the complex thermal runaway propagation behavior of lithium-ion battery modules and the generation of a substantial amount of combustible mixed gases during the process, their safety performance is compromised, hindering their large-scale application in the fields of energy storage and automotive industries. Therefore, in this paper, the thermal runaway propagation behavior and gas production characteristics of Li (Ni0.6Co0.2Mn0.2) O2 battery modules with different state of charge were investigated in closed space. The results show that no thermal runaway occurred in the battery module when the state of charge was below 25% in closed space. With the decrease of the state of charge, both the internal thermal propagation speed and the surface temperature of the lithium-ion battery were reduced. The total gas production volume from 17.48 mol to 6.17 mol when the state of charge was reduced from 100% to 50%. The main gases produced during thermal runaway were CO2, CO, H2, CH4, and C2H4. With the decrease of the state of charge, the content of CO2 increased, the content of C2H4 and CO decreased, and the content of H2 and CH4 remained unchanged with the state of charge. The results contribute to safety measures for preventing thermal runaway accidents in lithium-ion batteries, offering guidance for the secure design of lithium-ion battery packs, and thus enhancing the overall safety of lithium-ion batteries.

Dynamic Modulation of Li2O2 Growth in Li-O2 Batteries through Regulating Oxygen Reduction Kinetics with Photo-Assisted Cathodes.

Widely acknowledged that the capacity of Li-O2 batteries (LOBs) should be strongly determined by growth behaviors of the discharge product of lithium peroxide (Li2O2) that follows both coexisting surface and solution pathways. However until now, it remains still challenging to achieve dynamic modulation on Li2O2 morphologies. Herein, the photo-responsive Au nanoparticles (NPs) supported on reduced oxide graphene (Au/rGO) have been utilized as cathode to manipulate oxygen reduction reaction (ORR) kinetics by aid of surface plasmon resonance (SPR) effects. Thus, we can experimentally reveal the importance of matching ORR kinetics with Li+ migration towards battery performance. Moreover, it is found that Li+ concentration polarization caused "sudden death" of LOBs is supposed to be just a form of suspended animation that could timely recover under irradiation. This work provides us an in-depth explanation on the working mechanism of LOBs from a kinetic perspective, offering valuable insights for the future battery design.

Dynamic Modulation of Li2O2 Growth in Li‐O2 Batteries through Regulating Oxygen Reduction Kinetics with Photo‐Assisted Cathodes

AbstractWidely acknowledged that the capacity of Li‐O2 batteries (LOBs) should be strongly determined by growth behaviors of the discharge product of lithium peroxide (Li2O2) that follows both coexisting surface and solution pathways. However until now, it remains still challenging to achieve dynamic modulation on Li2O2 morphologies. Herein, the photo‐responsive Au nanoparticles (NPs) supported on reduced oxide graphene (Au/rGO) have been utilized as cathode to manipulate oxygen reduction reaction (ORR) kinetics by aid of surface plasmon resonance (SPR) effects. Thus, we can experimentally reveal the importance of matching ORR kinetics with Li+ migration towards battery performance. Moreover, it is found that Li+ concentration polarization caused “sudden death” of LOBs is supposed to be just a form of suspended animation that could timely recover under irradiation. This work provides us an in‐depth explanation on the working mechanism of LOBs from a kinetic perspective, offering valuable insights for the future battery design.

Engineering single-atom Mn on nitrogen-doped carbon to regulate lithium-peroxide reaction kinetics for rechargeable lithium-oxygen batteries

Precision engineering of catalytic sites to guide more favorable pathways for Li2O2 nucleation and decomposition represents an enticing kinetic strategy for mitigating overpotential, enhancing discharge capacity, and improving recycling stability of Li-O2 batteries. In this work, we employ metal–organic frameworks (MOFs) derivation and ion substitution strategies to construct atomically dispersed Mn-N4 moieties on hierarchical porous nitrogen-doped carbon (Mn SAs-NC) with the aim of reducing the overpotential and improving the cycling stability of Li-O2 batteries. The porous structure provides more channels for mass transfer and exposes more highly active sites for electrocatalytic reactions, thus promoting the formation and decomposition of Li2O2. The Li-O2 batteries with Mn SAs-NC cathode achieve lower overpotential, higher specific capacity (14290 mA h g−1 at 100 mA g−1), and superior cycle stability (>100 cycles at 200 mA g−1) compared with the Mn NPs-NC and NC. Density functional theory (DFT) calculations reveal that the construction of Mn-N4 moiety tunes the charge distribution of the pyridinic N-rich vacancy and balances the affinity of the intermediates (LiO2 and Li2O2). The initial nucleation of Li2O2 on Mn SAs-NC favors the O2 → LiO2 → Li2O2 surface-adsorption pathway, which mitigates the overpotentials of the oxygen reduction (ORR) and oxygen evolution reaction (OER). As a result, Mn SAs-NC with Mn-N4 moiety effectively facilitates the Li2O2 nucleation and enables its reversible decomposition. This work establishes a methodology for constructing carbon-based electrocatalysts with high activity and selectivity for Li-O2 batteries.

Cation Vacancy Modulated Interfacial Electronic Interactions for Enhanced Electrocatalysis in Lithium–Oxygen Batteries

AbstractLi–O2 batteries deliver ultrahigh theoretical specific energy while suffering from low energy efficiency and poor cyclability due to sluggish kinetics of oxygen electrode reactions. Herein, a strategy of engineering interfacial electron structure of MXene‐based composites is presented to boost oxygen electrode reactions for advancing Li–O2 batteries with the cation vacancy‐rich CoSe@MXene (VCo‐CoSe2@MXene) as the case study. The formation of interfacial Co─C bond between VCo‐CoSe2 and Ti3C2 MXene and its enhanced covalency after introducing Co vacancy leads to promoted electron transfer from Ti3C2 MXene to CoSe2 and optimized electronic structure of interfacial Co sites, especially the second Co sites neighboring Co vacancy, which serve as the active centers for oxygen redox reactions. On this basis, VCo‐CoSe2@MXene‐based Li─O2 batteries exhibit low overpotential (0.35 V) and excellent cycling stability (250 cycles at 500 mA g−1). This work proposes an effective strategy to develop MXene‐based electrocatalysts for Li–O2 batteries by tailoring interfacial electron structure.