High‐Performance Integrated Self‐Package Flexible Li–O2 Battery Based on Stable Composite Anode and Flexible Gas Diffusion Layer

With the rising development of flexible and wearable electronics, corresponding flexible energy storage devices with high energy density are required to provide a sustainable energy supply. Theoretically, rechargeable flexible Li–O₂ batteries can provide high specific energy density; however, there are only a few reports on the construction of flexible Li–O₂ batteries. Conventional flexible Li–O₂ batteries possess a loose battery structure, which prevents flexibility and stability. The low mechanical strength of the gas diffusion layer and anode also lead to a flexible Li–O₂ battery with poor mechanical properties. All these attributes limit their practical applications. Herein, the authors develop an integrated flexible Li–O₂ battery based on a high‐fatigue‐resistance anode and a novel flexible stretchable gas diffusion layer. Owing to the synergistic effect of the stable electrocatalytic activity and hierarchical 3D interconnected network structure of the free‐standing cathode, the obtained flexible Li–O₂ batteries exhibit superior electrochemical performance, including a high specific capacity, an excellent rate capability, and exceptional cycle stability. Furthermore, benefitting from the above advantages, the as‐fabricated flexible batteries can realize excellent mechanical and electrochemical stability. Even after a thousand cycles of the bending process, the flexible Li–O₂ battery can still possess a stable open‐circuit voltage, a high specific capacity, and a durable cycle performance.     

Binding S0.6Se0.4 in 1D Carbon Nanofiber with CS Bonding for High‐Performance Flexible Li–S Batteries and Na–S Batteries

A one‐step synthesis procedure is developed to prepare flexible S_0.6Se_0.4@carbon nanofibers (CNFs) electrode by coheating S_0.6Se_0.4 powder with electrospun polyacrylonitrile nanofiber papers at 600 °C. The obtained S_0.6Se_0.4@CNFs film can be used as cathode material for high‐performance Li–S batteries and room temperature (RT) Na–S batteries directly. The superior lithium/sodium storage performance derives from its rational structure design, such as the chemical bonding between Se and S, the chemical bonding between S_0.6Se_0.4 and CNFs matrix, and the 3D CNFs network. This easy one‐step synthesis procedure provides a feasible route to prepare electrode materials for high‐performance Li–S and RT Na–S batteries.     

Fundamental Understanding of Water‐Induced Mechanisms in Li–O2 Batteries: Recent Developments and Perspectives

Modern sustainability challenges in recent years have warranted the development of new energy storage technologies. Practical realization of the lithium–O₂ battery holds great promise for revolutionizing energy storage as it holds the highest theoretical specific energy of any rechargeable battery yet discovered. However, the complete realization of Li–O₂ batteries necessitates ambient air operations, which presents quite a few challenges, as carbon dioxide (CO₂) and water (H₂O) contaminants introduce unwanted byproducts from side reactions that greatly affect battery performance. Although current research has thoroughly explored the beneficial incorporation of CO₂, much mystery remains over the inconsistent effects of H₂O. The presence of water in both the cathode and electrolyte has been observed to alter reaction mechanisms differently, resulting in a diverse range of effects on voltage, capacity, and cyclability. Moreover, recent preliminary research with catalysts and redox mediators has attempted to utilize the presence of water to the battery's benefit. Here, the key mechanism discrepancies of water‐afflicted Li–O₂ batteries are presented, concluding with a perspective on future research directions for nonaqueous Li–O₂ batteries.     

Component‐Interaction Reinforced Quasi‐Solid Electrolyte with Multifunctionality for Flexible Li–O2 Battery with Superior Safety under Extreme Conditions

High‐performance flexible lithium–oxygen (Li–O₂) batteries with excellent safety and stability are urgently required due to the rapid development of flexible and wearable devices. Herein, based on an integrated solid‐state design by taking advantage of component‐interaction between poly(vinylidene fluoride‐co‐hexafluoropropylene) and nanofumed silica in polymer matrix, a stable quasi‐solid‐state electrolyte (PS‐QSE) for the Li–O₂ battery is proposed. The as‐assembled Li–O₂ battery containing the PS‐QSE exhibits effectively improved anodic reversibility (over 200 cycles, 850 h) and cycling stability of the battery (89 cycles, nearly 900 h). The improvement is attributed to the stability of the PS‐QSE (including electrochemical, chemical, and mechanical stability), as well as the effective protection of lithium anode from aggressive soluble intermediates generated in cathode. Furthermore, it is demonstrated that the interaction among the components plays a pivotal role in modulating the Li‐ion conducting mechanism in the as‐prepared PS‐QSE. Moreover, the pouch‐type PS‐QSE based Li–O₂ battery also shows wonderful flexibility, tolerating various deformations thanks to its integrated solid‐state design. Furthermore, holes can be punched through the Li–O₂ battery, and it can even be cut into any desired shape, demonstrating exceptional safety. Thus, this type of battery has the potential to meet the demands of tailorability and comformability in flexible and wearable electronics.     

A Highly Reversible Long‐Life Li–CO2 Battery with a RuP2‐Based Catalytic Cathode

Rechargeable Li–CO₂ batteries have attracted worldwide attention due to the capability of CO₂ capture and superhigh energy density. However, they still suffer from poor cycling performance and huge overpotential. Thus, it is essential to explore highly efficient catalysts to improve the electrochemical performance of Li–CO₂ batteries. Here, phytic acid (PA)‐cross‐linked ruthenium complexes and melamine are used as precursors to design and synthesize RuP₂ nanoparticles highly dispersed on N, P dual‐doped carbon films (RuP₂‐NPCFs), and the obtained RuP₂‐NPCF is further applied as the catalytic cathode for Li–CO₂ batteries. RuP₂ nanoparticles that are uniformly deposited on the surface of NPCF show enhanced catalytic activity to decompose Li₂CO₃ at low charge overpotential. In addition, the NPCF its with porous structure in RuP₂‐NPCF provides superior electrical conductivity, high electrochemical stability, and enough ion/electron and space for the reversible reaction in Li–CO₂ batteries. Hence, the RuP₂‐NPCF cathode delivers a superior reversible discharge capacity of 11951 mAh g^?1, and achieves excellent cyclability for more than 200 cycles with low overpotentials (<1.3 V) at the fixed capacity of 1000 mAh g^?1. This work paves a new way to design more effective catalysts for Li–CO₂ batteries.     

Flexible,Flame‐Resistant,and Dendrite‐Impermeable Gel‐Polymer Electrolyte for Li–O2/Air Batteries Workable Under Hurdle Conditions

Gel‐polymer electrolytes are considered as a promising candidate for replacing the liquid electrolytes to address the safety concerns in Li–O₂/air batteries. In this work, by taking advantage of the hydrogen bond between thermoplastic polyurethane and aerogel SiO₂ in gel polymer, a highly crosslinked quasi‐solid electrolyte (FST‐GPE) with multifeatures of high ionic conductivity, high mechanical flexibility, favorable flame resistance, and excellent Li dendrite impermeability is developed. The resulting gel‐polymer Li–O₂/air batteries possess high reaction kinetics and stabilities due to the unique electrode–electrolyte interface and fast O₂ diffusion in cathode, which can achieve up to 250 discharge–charge cycles (over 1000 h) in oxygen gas. Under ambient air atmosphere, excellent performances are observed for coin‐type cells over 20 days and for prototype cells working under extreme bending conditions. Moreover, the FST‐GPE electrolyte also exhibits durability to protect against fire, dendritic Li, and H₂O attack, demonstrating great potential for the design of practical Li–O₂/air batteries.     

Conjugated Cobalt Polyphthalocyanine as the Elastic and Reprocessable Catalyst for Flexible Li–CO2 Batteries

Li–CO₂ batteries represent an attractive solution for electrochemical energy storage by utilizing atmospheric CO₂ as the energy carrier. However, their practical viability critically depends on the development of efficient and low‐cost cathode catalysts for the reversible formation and decomposition of Li₂CO₃. Here, the great potential of a structurally engineered polymer is demonstrated as the cathode catalyst for rechargeable Li–CO₂ batteries. Conjugated cobalt polyphthalocyanine is prepared via a facile microwave heating method. Due to the crosslinked network, it is intrinsically elastic and has improved chemical, physical, and mechanical stability. Electrochemical measurements show that cobalt polyphthalocyanine facilitates the reversible formation and decomposition of Li₂CO₃, and therefore enables high‐performance Li–CO₂ batteries with large areal capacity and impressive cycling performance. In addition, the elastic and reprocessable property of the polymeric catalyst renders it possible to fabricate flexible batteries.     

High‐Capacity and High‐Rate Discharging of a Coenzyme Q10‐Catalyzed Li–O2 Battery

Discharging of the aprotic Li–O₂ battery relies on O₂ reduction to insulating solid Li₂O₂, which can either deposit as thin films on the cathode surface or precipitate as large particles in the electrolyte solution. Toward realizing Li–O₂ batteries with high capacity and high rate capability, it is crucially important to discharge Li₂O₂ in the electrolyte solution rather than on the cathode surface. Here, a soluble electrocatalyst of coenzyme Q₁₀ (CoQ₁₀) that can efficaciously drive solution phase formation of Li₂O₂ in current benchmark ether‐based Li–O₂ batteries is reported, which would otherwise lead to Li₂O₂ surface‐film growth and premature cell death. In the range of current densities of 0.1–0.5 mA cm^?2_areal, the CoQ₁₀‐catalyzed Li–O₂ battery can deliver a discharge capacity that is ≈40–100 times what the pristine Li–O₂ battery could achieve. The drastically enhanced electrochemical performance is attributed to the CoQ₁₀ that not only efficiently mediates the electron transfer from the cathode to dissolve O₂ but also strongly interacts with the newly formed Li₂O₂ in solution retarding its precipitation on the cathode surface. The mediated oxygen reduction reaction and the bonding mechanism between CoQ₁₀ and Li₂O₂ are understood with density functional theory calculations.     

The Salt Matters: Enhanced Reversibility of Li–O2 Batteries with a Li[(CF3SO2)(n‐C4F9SO2)N]‐Based Electrolyte

The safety hazards and cycle instability of lithium metal anodes (LMA) constitute significant barriers to progress in lithium metal batteries. This situation is worse in Li–O₂ batteries because the LMA is prone to be chemically attacked by O₂ shuttled from the cathode. Notwithstanding, efforts on LMA are much sparse than those on the cathode in the realm of Li–O₂ batteries. Here, a novel lithium salt of Li[(CF₃SO₂)(n‐C₄F₉SO₂)N] (LiTNFSI) is reported, which can effectively suppress the parasitic side reactions and dendrite growth of LMA during cycling and thereby significantly enhance the overall reversibility of Li–O₂ batteries. A variety of advanced research tools are employed to scrutinize the working principles of the LiTNFSI salt. It is revealed that a stable, uniform, and O₂‐resistive solid electrolyte interphase is formed on LMA, and hence the “cross‐talk” between the LMA and O₂ shuttled from the cathode is remarkably inhibited in LiTNFSI‐based Li–O₂ batteries.     

Binding S0.6Se0.4 in 1D Carbon Nanofiber with C?S Bonding for High‐Performance Flexible Li–S Batteries and Na–S Batteries

A one‐step synthesis procedure is developed to prepare flexible S_0.6Se_0.4@carbon nanofibers (CNFs) electrode by coheating S_0.6Se_0.4 powder with electrospun polyacrylonitrile nanofiber papers at 600 °C. The obtained S_0.6Se_0.4@CNFs film can be used as cathode material for high‐performance Li–S batteries and room temperature (RT) Na–S batteries directly. The superior lithium/sodium storage performance derives from its rational structure design, such as the chemical bonding between Se and S, the chemical bonding between S_0.6Se_0.4 and CNFs matrix, and the 3D CNFs network. This easy one‐step synthesis procedure provides a feasible route to prepare electrode materials for high‐performance Li–S and RT Na–S batteries.     

Textile Inspired Lithium–Oxygen Battery Cathode with Decoupled Oxygen and Electrolyte Pathways

The lithium–air (Li–O₂) battery has been deemed one of the most promising next‐generation energy‐storage devices due to its ultrahigh energy density. However, in conventional porous carbon–air cathodes, the oxygen gas and electrolyte often compete for transport pathways, which limit battery performance. Here, a novel textile‐based air cathode is developed with a triple‐phase structure to improve overall battery performance. The hierarchical structure of the conductive textile network leads to decoupled pathways for oxygen gas and electrolyte: oxygen flows through the woven mesh while the electrolyte diffuses along the textile fibers. Due to noncompetitive transport, the textile‐based Li–O₂ cathode exhibits a high discharge capacity of 8.6 mAh cm^?2, a low overpotential of 1.15 V, and stable operation exceeding 50 cycles. The textile‐based structure can be applied to a range of applications (fuel cells, water splitting, and redox flow batteries) that involve multiple phase reactions. The reported decoupled transport pathway design also spurs potential toward flexible/wearable Li–O₂ batteries.     

A High‐Performance Li–O2 Battery with a Strongly Solvating Hexamethylphosphoramide Electrolyte and a LiPON‐Protected Lithium Anode

The aprotic Li–O₂ battery has attracted a great deal of interest because theoretically it can store more energy than today's Li‐ion batteries. However, current Li–O₂ batteries suffer from passivation/clogging of the cathode by discharged Li₂O₂, high charging voltage for its subsequent oxidation, and accumulation of side reaction products (particularly Li₂CO₃ and LiOH) upon cycling. Here, an advanced Li–O₂ battery with a hexamethylphosphoramide (HMPA) electrolyte is reported that can dissolve Li₂O₂, Li₂CO₃, and LiOH up to 0.35, 0.36, and 1.11 × 10^?3m , respectively, and a LiPON‐protected lithium anode that can be reversibly cycled in the HMPA electrolyte. Compared to the benchmark of ether‐based Li–O₂ batteries, improved capacity, rate capability, voltaic efficiency, and cycle life are achieved for the HMPA‐based Li–O₂ cells. More importantly, a combination of advanced research techniques provide compelling evidence that operation of the HMPA‐based Li–O₂ battery is backed by nearly reversible formation/decomposition of Li₂O₂ with negligible side reactions.     

Self‐Supported and Flexible Sulfur Cathode Enabled via Synergistic Confinement for High‐Energy‐Density Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries have attracted much attention in the field of electrochemical energy storage due to their high energy density and low cost. However, the “shuttle effect” of the sulfur cathode, resulting in poor cyclic performance, is a big barrier for the development of Li–S batteries. Herein, a novel sulfur cathode integrating sulfur, flexible carbon cloth, and metal–organic framework (MOF)‐derived N‐doped carbon nanoarrays with embedded CoP (CC@CoP/C) is designed. These unique flexible nanoarrays with embedded polar CoP nanoparticles not only offer enough voids for volume expansion to maintain the structural stability during the electrochemical process, but also promote the physical encapsulation and chemical entrapment of all sulfur species. Such designed CC@CoP/C cathodes with synergistic confinement (physical adsorption and chemical interactions) for soluble intermediate lithium polysulfides possess high sulfur loadings (as high as 4.17 mg cm^–2) and exhibit large specific capacities at different C‐rates. Specially, an outstanding long‐term cycling performance can be reached. For example, an ultralow decay of 0.016% per cycle during the whole 600 cycles at a high current density of 2C is displayed. The current work provides a promising design strategy for high‐energy‐density Li–S batteries.     

Design Principles for Heteroatom‐Doped Nanocarbon to Achieve Strong Anchoring of Polysulfides for Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries have been intensively concerned to fulfill the urgent demands of high capacity energy storage. One of the major unsolved issues is the complex diffusion of lithium polysulfide intermediates, which in combination with the subsequent paradox reactions is known as the shuttle effect. Nanocarbon with homogeneous nonpolar surface served as scaffolding materials in sulfur cathode basically cannot afford a sufficient binding and confining effect to maintain lithium polysulfides within the cathode. Herein, a systematical density functional theory calculation of various heteroatoms‐doped nanocarbon materials is conducted to elaborate the mechanism and guide the future screening and rational design of Li–S cathode for better performance. It is proved that the chemical modification using N or O dopant significantly enhances the interaction between the carbon hosts and the polysulfide guests via dipole–dipole electrostatic interaction and thereby effectively prevents shuttle of polysulfides, allowing high capacity and high coulombic efficiency. By contrast, the introduction of B, F, S, P, and Cl monodopants into carbon matrix is unsatisfactory. To achieve the strong‐couple effect toward Li₂S_x, the principles for rational design of doped carbon scaffolds in Li–S batteries to achieve a strong electrostatic dipole–dipole interaction are proposed. An implicit volcano plot is obtained to describe the dependence of binding energies on electronegativity of dopants. Moreover, the codoping strategy is predicted to achieve even stronger interfacial interaction to trap lithium polysulfides.     

Covalent‐Organic‐Framework‐Based Li–CO2 Batteries

Covalent organic frameworks (COFs) are an emerging class of porous crystalline materials constructed from designer molecular building blocks that are linked and extended periodically via covalent bonds. Their high stability, open channels, and ease of functionalization suggest that they can function as a useful cathode material in reversible lithium batteries. Here, a COF constructed from hydrazone/hydrazide‐containing molecular units, which shows good CO₂ sequestration properties, is reported. The COF is hybridized to Ru‐nanoparticle‐coated carbon nanotubes, and the composite is found to function as highly efficient cathode in a Li–CO₂ battery. The robust 1D channels in the COF serve as CO₂^– and lithium‐ion‐diffusion channels and improve the kinetics of electrochemical reactions. The COF‐based Li–CO₂ battery exhibits an ultrahigh capacity of 27 348 mAh g^?1 at a current density of 200 mA g^?1, and a low cut‐off overpotential of 1.24 V within a limiting capacity of 1000 mAh g^?1. The rate performance of the battery is improved considerably with the use of the COF at the cathode, where the battery shows a slow decay of discharge voltage from a current density of 0.1 to 4 A g^?1. The COF‐based battery runs for 200 cycles when discharged/charged at a high current density of 1 A g^?1.     

Recent Progress in the Design of Advanced Cathode Materials and Battery Models for High‐Performance Lithium‐X (X = O2, S,Se, Te,I2, Br2) Batteries

Recent advances and achievements in emerging Li‐X (X = O₂, S, Se, Te, I₂, Br₂) batteries with promising cathode materials open up new opportunities for the development of high‐performance lithium‐ion battery alternatives. In this review, we focus on an overview of recent important progress in the design of advanced cathode materials and battery models for developing high‐performance Li‐X (X = O₂, S, Se, Te, I₂, Br₂) batteries. We start with a brief introduction to explain why Li‐X batteries are important for future renewable energy devices. Then, we summarize the existing drawbacks, major progress and emerging challenges in the development of cathode materials for Li‐O₂ (S) batteries. In terms of the emerging Li‐X (Se, Te, I₂, Br₂) batteries, we systematically summarize their advantages/disadvantages and recent progress. Specifically, we review the electrochemical performance of Li‐Se (Te) batteries using carbonate‐/ether‐based electrolytes, made with different electrode fabrication techniques, and of Li‐I₂ (Br₂) batteries with various cell designs (e.g., dual electrolyte, all‐organic electrolyte, with/without cathode‐flow mode, and fuel cell/solar cell integration). Finally, the perspective on and challenges for the development of cathode materials for the promising Li‐X (X = O₂, S, Se, Te, I₂, Br₂) batteries is presented.     

Yolk–Shelled C@Fe3O4 Nanoboxes as Efficient Sulfur Hosts for High‐Performance Lithium–Sulfur Batteries

Owing to the high theoretical specific capacity (1675 mA h g^?1) and low cost, lithium–sulfur (Li–S) batteries offer advantages for next‐generation energy storage. However, the polysulfide dissolution and low electronic conductivity of sulfur cathodes limit the practical application of Li–S batteries. To address such issues, well‐designed yolk–shelled carbon@Fe₃O₄ (YSC@Fe₃O₄) nanoboxes as highly efficient sulfur hosts for Li–S batteries are reported here. With both physical entrapment by carbon shells and strong chemical interaction with Fe₃O₄ cores, this unique architecture immobilizes the active material and inhibits diffusion of the polysulfide intermediates. Moreover, due to their high conductivity, the carbon shells and the polar Fe₃O₄ cores facilitate fast electron/ion transport and promote continuous reactivation of the active material during the charge/discharge process, resulting in improved electrochemical utilization and reversibility. With these merits, the S/YSC@Fe₃O₄ cathodes support high sulfur content (80 wt%) and loading (5.5 mg cm^?2) and deliver high specific capacity, excellent rate capacity, and long cycling stability. This work provides a new perspective to design a carbon/metal‐oxide‐based yolk–shelled framework as a high sulfur‐loading host for advanced Li–S batteries with superior electrochemical properties.     

3D Hollow α‐MnO2 Framework as an Efficient Electrocatalyst for Lithium–Oxygen Batteries

Lithium–oxygen (Li–O₂) batteries are attracting more attention owing to their superior theoretical energy density compared to conventional Li‐ion battery systems. With regards to the catalytically electrochemical reaction on a cathode, the electrocatalyst plays a key role in determining the performance of Li–O₂ batteries. Herein, a new 3D hollow α‐MnO₂ framework (3D α‐MnO₂) with porous wall assembled by hierarchical α‐MnO₂ nanowires is prepared by a template‐induced hydrothermal reaction and subsequent annealing treatment. Such a distinctive structure provides some essential properties for Li–O₂ batteries including the intrinsic high catalytic activity of α‐MnO₂, more catalytic active sites of hierarchical α‐MnO₂ nanowires on 3D framework, continuous hollow network and rich porosity for the storage of discharge product aggregations, and oxygen diffusion. As a consequence, 3D α‐MnO₂ achieves a high specific capacity of 8583 mA h g^?1 at a current density of 100 mA g^?1, a superior rate capacity of 6311 mA h g^?1 at 300 mA g^?1, and a very good cycling stability of 170 cycles at a current density of 200 mA g^?1 with a fixed capacity of 1000 mA h g^?1. Importantly, the presented design strategy of 3D hollow framework in this work could be extended to other catalytic cathode design for Li–O₂ batteries.     

Porous Materials Applied in Nonaqueous Li–O2 Batteries: Status and Perspectives

Porous materials possessing high surface area, large pore volume, tunable pore structure, superior tailorability, and dimensional effect have been widely applied as components of lithium–oxygen (Li–O₂) batteries. Herein, the theoretical foundation of the porous materials applied in Li–O₂ batteries is provided, based on the present understanding of the battery mechanism and the challenges and advantageous qualities of porous materials. Furthermore, recent progress in porous materials applied as the cathode, anode, separator, and electrolyte in Li–O₂ batteries is summarized, together with corresponding approaches to address the critical issues that remain at present. Particular emphasis is placed on the importance of the correlation between the function-orientated design of porous materials and key challenges of Li–O₂ batteries in accelerating oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) kinetics, improving the electrode stability, controlling lithium deposition, suppressing the shuttle effect of the dissolved redox mediators, and alleviating electrolyte decomposition. Finally, the rational design and innovative directions of porous materials are provided for their development and application in Li–O₂ battery systems.     

Strongly Coupled Carbon Nanosheets/Molybdenum Carbide Nanocluster Hollow Nanospheres for High‐Performance Aprotic Li–O2 Battery

A highly efficient oxygen electrode is indispensable for achieving high‐performance aprotic lithium–O₂ batteries. Herein, it is demonstrated that strongly coupled carbon nanosheets/molybdenum carbide (α‐MoC_1?x) nanocluster hierarchical hybrid hollow spheres (denoted as MoC_1?x/HSC) can work well as cathode for boosting the performance of lithium–O₂ batteries. The important feature of MoC_1?x/HSC is that the α‐MoC_1?x nanoclusters, uniformly incorporated into carbon nanosheets, can not only effectively prevent the nanoclusters from agglomeration, but also help enhance the interaction between the nanoclusters and the conductive substrate during the charge and discharge process. As a consequence, the MoC_1?x/HSC shows significantly improved electrocatalytic performance in an aprotic Li–O₂ battery with greatly reduced charge and discharge overpotentials and long cycle stability. The ex situ scanning electron microscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy studies reveal that the mechanism for the high‐performance Li–O₂ battery using MoC_1?x/HSC as cathode is that the incorporated molybdenum carbide nanoclusters can make oxygen reduction on their surfaces easy, and finally form amorphous film‐like Li‐deficient Li₂O₂ with the ability to decompose at a low potential. To the best of knowledge, the MoC_1?x/HSC of this paper is among the best cathode materials for lithium–O₂ batteries reported to date.