A Li-O₂/air battery using an inorganic solid-state air cathode

Three Birds with One Stone: An Integrated Cathode-Electrolyte Structure for High-Performance Solid-State Lithium-Oxygen Batteries

Constructing solid-state lithium-oxygen batteries (SSLOBs) holds a great promise to solve the safety and stability bottlenecks faced by lithium-oxygen batteries (LOBs) with volatile and flammable organic liquid electrolytes. However, the realization of high-performance SSLOBs is full of challenges due to the poor ionic conductivity of solid electrolytes, large interfacial resistance, and limited reaction sites of cathodes. Here, a flexible integrated cathode-electrolyte structure (ICES) is designed to enable the tight connection between the cathode and electrolyte through supporting them on a 3D SiO₂ nanofibers (NFs) framework. The intimate cathode-electrolyte structure and the porous SiO₂ NFs scaffold combination are favorable for decreasing interfacial resistance and increasing reaction sites. Moreover, the 3D SiO₂ NFs framework can also behave as an efficient inorganic filler to enhance the ionic conductivity of the solid polymer electrolyte and its ability to inhibit lithium dendrite growth. As a result, the elaborately designed ICES can simultaneously tackle the issues that limit the performance liberation of SSLOBs, making the batteries deliver a high discharge capacity and a long lifetime of 145 cycles with a cycling capacity of 1000 mAh g^-1 at 60 °C, much superior to coventional SSLOBs (50 cycles).

Deciphering the Enigma of Li2CO3 Oxidation Using a Solid-State Li-Air Battery Configuration

Li₂CO₃ is a ubiquitous byproduct in Li-air (O₂) batteries, and its accumulation on the cathode could be detrimental to the devices. As a result, much efforts have been devoted to investigating its formation and decomposition, in particular, upon cycling of Li-O₂ batteries. At high voltages, Li₂CO₃ is expected to decompose into CO₂ and O₂. However, as recognized from the work of many authors, only CO₂, and no O₂, has been identified, and the underlying mechanism remains uncertain so far. Herein, a solid-state Li-O₂ battery (Li|Li_6.4La₃Zr_1.4Ta_0.6O₁₂|Au) has been designed to interrogate the Li₂CO₃ oxidation without interferences from the decomposition of other battery components (organic electrolyte, binder, and carbon cathode) widely applied in conventional Li-O₂ batteries. It is revealed that Li₂CO₃ can indeed be oxidized to CO₂ and O₂ in a more stable solid-state Li-O₂ battery configuration, highlighting the feasibility of reversible operation of Li-O₂ batteries with ambient air as the feeding gas.

Transition of the Reaction from Three-Phase to Two-Phase by Using a Hybrid Conductor for High-Energy-Density High-Rate Solid-State Li-O2 Batteries

Solid-state Li-O₂ batteries possess the ability to deliver high energy density with enhanced safety. However, designing a highly functional solid-state air electrode is the main bottleneck for its further development. Herein, we adopt a hybrid electronic and ionic conductor to build solid-state air electrode that makes the transition of Li-O₂ battery electrochemical mechanism from a three-phase process to a two-phase process. The solid-state Li-O₂ battery with this hybrid conductor solid-state air electrode shows decreased interfacial resistance and enhanced reaction kinetics. The Coulombic efficiency of Li-O₂ battery is also significantly improved, benefiting from the good contact between discharge products and electrode materials. In situ environmental transmission electron microscopy under oxygen was used to illustrate the reversible deposition and decomposition of discharge products on the surface of this hybrid conductor, visually verifying the two-phase reaction.

Critical Advances in Ambient Air Operation of Nonaqueous Rechargeable Li-Air Batteries

Over the past few years, great attention has been given to nonaqueous lithium-air batteries owing to their ultrahigh theoretical energy density when compared with other energy storage systems. Most of the research interest, however, is dedicated to batteries operating in pure or dry oxygen atmospheres, while Li-air batteries that operate in ambient air still face big challenges. The biggest challenges are H₂ O and CO₂ that exist in ambient air, which can not only form byproducts with discharge products (Li₂ O₂ ), but also react with the electrolyte and the Li anode. To this end, recent progress in understanding the chemical and electrochemical reactions of Li-air batteries in ambient air is critical for the development and application of true Li-air batteries. Oxygen-selective membranes, multifunctional catalysts, and electrolyte alternatives for ambient air operational Li-air batteries are presented and discussed comprehensively. In addition, separator modification and Li anode protection are covered. Furthermore, the challenges and directions for the future development of Li-air batteries are presented.

Interface Issues and Challenges in All-Solid-State Batteries: Lithium, Sodium, and Beyond

Owing to the promise of high safety and energy density, all-solid-state batteries are attracting incremental interest as one of the most promising next-generation energy storage systems. However, their widespread applications are inhibited by many technical challenges, including low-conductivity electrolytes, dendrite growth, and poor cycle/rate properties. Particularly, the interfacial dynamics between the solid electrolyte and the electrode is considered as a crucial factor in determining solid-state battery performance. In recent years, intensive research efforts have been devoted to understanding the interfacial behavior and strategies to overcome these challenges for all-solid-state batteries. Here, the interfacial principle and engineering in a variety of solid-state batteries, including solid-state lithium/sodium batteries and emerging batteries (lithium-sulfur, lithium-air, etc.), are discussed. Specific attention is paid to interface physics (contact and wettability) and interface chemistry (passivation layer, ionic transport, dendrite growth), as well as the strategies to address the above concerns. The purpose here is to outline the current interface issues and challenges, allowing for target-oriented research for solid-state electrochemical energy storage. Current trends and future perspectives in interfacial engineering are also presented.

Quasi-Solid-State Rechargeable Li-O2 Batteries with High Safety and Long Cycle Life at Room Temperature

As interest in electric vehicles and mass energy storage systems continues to grow, Li-O₂ batteries are attracting much attention as a candidate for next-generation energy storage systems owing to their high energy density. However, safety problems related to the use of lithium metal anodes have hampered the commercialization of Li-O₂ batteries. Herein, we introduced a quasi-solid polymer electrolyte with excellent electrochemical, chemical, and thermal stabilities into Li-O₂ batteries. The ion-conducting QSPE was prepared by gelling a polymer network matrix consisting of poly(ethylene glycol) methyl ether methacrylate, methacrylated tannic acid, lithium trifluoromethanesulfonate, and nanofumed silica with a small amount of liquid electrolyte. The quasi-solid-state Li-O₂ cell consisted of a lithium powder anode, a quasi-solid polymer electrolyte, and a Pd₃Co/multiwalled carbon nanotube cathode, which enhanced the electrochemical performance of the cell. This cell, which exhibited improved safety owing to the suppression of lithium dendrite growth, achieved a lifetime of 125 cycles at room temperature. These results show that the introduction of a quasi-solid electrolyte is a potentially new alternative for the commercialization of solid-state Li-O₂ batteries.

A Li-Air Battery with Ultralong Cycle Life in Ambient Air

The Li-air battery represents a promising power candidate for future electronics due to its extremely high energy density. However, the use of Li-air batteries is largely limited by their poor cyclability in ambient air. Herein, Li-air batteries with ultralong 610 cycles in ambient air are created by combination of low-density polyethylene film that prevents water erosion and gel electrolyte that contains a redox mediator of LiI. The low-density polyethylene film can restrain the side reactions of the discharge product of Li₂ O₂ to Li₂ CO₃ in ambient air, while the LiI can facilitate the electrochemical decomposition of Li₂ O₂ during charging, which improves the reversibility of the Li-air battery. All the components of the Li-air battery are flexible, which is particularly desirable for portable and wearable electronic devices.

Enhanced Electrochemical Stability of Quasi-Solid-State Electrolyte Containing SiO2 Nanoparticles for Li-O2 Battery Applications

A stable electrolyte is required for use in the open-packing environment of a Li-O2 battery system. Herein, a gelled quasi-solid-state electrolyte containing SiO2 nanoparticles was designed, in order to obtain a solidified electrolyte with a high discharge capacity and long cyclability. We successfully fabricated an organic-inorganic hybrid matrix with a gelled structure, which exhibited high ionic conductivity, thereby enhancing the discharge capacity of the Li-O2 battery. In particular, the improved electrochemical stability of the gelled cathode led to long-term cyclability. The organic-inorganic hybrid matrix with the gelled structure played a beneficial role in improving the ionic conductivity and long-term cyclability and diminished electrolyte evaporation. The experimental and theoretical findings both suggest that the preferential binding between amorphous SiO2 and polyethylene glycol dimethyl ether (PEGDME) solvent led to the formation of the solidified gelled electrolyte and improved electrochemical stability during cycling, while enhancing the stability of the quasi-solid state Li-O2 battery.

A Polymer Lithium-Oxygen Battery

Herein we report the characteristics of a lithium-oxygen battery using a solid polymer membrane as the electrolyte separator. The polymer electrolyte, fully characterized in terms of electrochemical properties, shows suitable conductivity at room temperature allowing the reversible cycling of the Li-O2 battery with a specific capacity as high as 25,000 mAh gC(-1) reflected in a surface capacity of 12.5 mAh cm(-2). The electrochemical formation and dissolution of the lithium peroxide during Li-O2 polymer cell operation is investigated by electrochemical techniques combined with X-ray diffraction study, demonstrating the process reversibility. The excellent cell performances in terms of delivered capacity, in addition to its solid configuration allowing the safe use of lithium metal as high capacity anode, demonstrate the suitability of the polymer lithium-oxygen as high-energy storage system.

Ternary Spinel MCo2O4 (M = Mn, Fe, Ni, and Zn) Porous Nanorods as Bifunctional Cathode Materials for Lithium-O2 Batteries

The development of Li-O2 battery electrocatalysts has been extensively explored recently. The Co3O4 oxide has attracted much attention because of its bifunctional activity and high abundance. In the present study, toxic Co(2+) has been replaced through the substitution on the tetrahedral spinel A site ions with environmental friendly metals (Mn(2+), Fe(2+), Ni(2+), and Zn(2+)), and porous nanorod structure are formed. Among these spinel MCo2O4 cathodes, the FeCo2O4 surface has the highest Co(3+) ratio. Thus, oxygen can be easily adsorbed onto the active sites. In addition, Fe(2+) in the tetrahedral site can easily release electrons to reduce oxygen and oxidize to half electron filled Fe(3+). The FeCo2O4 cathode exhibits the highest discharging plateau and lowest charging plateau as shown by the charge-discharge profile. Moreover, the porous FeCo2O4 nanorods can also facilitate achieving high capacity and good cycling performance, which are beneficial for O2 diffusion channels and Li2O2 formation/decomposition pathways.

Enhanced electrochemical performance of Li–O2 battery based on modifying the solid-state air cathode with Pd catalyst

A Pd catalyst has a positive effect on the performance of a Li–O₂ battery using a solid-state air cathode.