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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]

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]

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]

The sluggish oxygen reaction kinetics concomitant with the high overpotentials and parasitic reactions from cathodes and solvents is the major challenge in aprotic lithium‐oxygen (Li–O2) batteries. Herein, PtIr multipods with a low Lewis acidity of the Pt atoms are reported as an advanced cathode for improving overpotentials and stabilities. DFT calculations disclose that electrons have a strong disposition to transfer from Ir to Pt, since Pt has a higher electronegativity than Ir, resulting in a lower Lewis acidity of the Pt atoms than that on the pure Pt surface. The low Lewis acidity of Pt atoms on the PtIr surface entails a high electron density and a down‐shifting of the d‐band center, thereby weakening the binding energy towards intermediates (LiO2), which is the key in achieving low oxygen‐reduction‐reaction (ORR) and oxygen‐evolution‐reaction (OER) overpotentials. The Li–O2 cell based on PtIr electrodes exhibits a very low overall discharge/charge overpotential (0.44 V) and an excellent cycle life (180 cycles), outperforming the bulk of reported noble‐metal‐based cathodes. [ABSTRACT FROM AUTHOR]

Redox molecules (RMs) as electron carriers have been widely used in electrochemical energy‐storage devices (ESDs), such as lithium redox flow batteries and lithium‐O2 batteries. Unfortunately, migration of RMs to the lithium (Li) anode leads to side reactions, resulting in reduced coulombic efficiency and early cell death. Our proof‐of‐concept study utilizes a biphasic organic electrolyte to resolve this issue, in which nonafluoro‐1,1,2,2‐tetrahydrohexyl‐trimethoxysilane (NFTOS) and ether (or sulfone) with lithium bis(trifluoromethane)sulfonimide (LiTFSI) can be separated to form the immiscible anolyte and catholyte. RMs are extracted to the catholyte due to the enormous solubility coefficients in the biphasic electrolytes with high and low polarity, resulting in inhibition of the shuttle effect. When coupled with a lithium anode, the Li‐Li symmetric, Li redox flow and Li‐O2 batteries can achieve considerably prolonged cycle life with biphasic electrolytes. This concept provides a promising strategy to suppress the shuttle effect of RMs in ESDs. [ABSTRACT FROM AUTHOR]

Lithium–oxygen (Li–O2) batteries have attracted extensive research interest due to their high energy density. Other than Li2O2 (a typical discharge product in Li–O2 batteries), LiOH has proved to be electrochemically active as an alternative product. Here we report a simple strategy to achieve a reversible LiOH‐based Li–O2 battery by using a cation additive, sodium ions, to the lithium electrolyte. Without redox mediators in the cell, LiOH is detected as the sole discharge product and it charges at a low charge potential of 3.4 V. A solution‐based reaction route is proposed, showing that the competing solvation environment of the catalyst and Li+ leads to LiOH precipitation at the cathode. It is critical to tune the cell chemistry of Li–O2 batteries by designing a simple system to promote LiOH formation/decomposition. [ABSTRACT FROM AUTHOR]

The limited triple‐phase boundaries (TPBs) in solid‐state cathodes (SSCs) and high resistance imposed by solid electrolytes (SEs) make the achievement of high‐performance all‐solid‐state lithium‐oxygen (ASS Li‐O2) batteries a challenge. Herein, an adjustable‐porosity plastic crystal electrolyte (PCE) has been fabricated by employing a thermally induced phase separation (TIPS) technique to overcome the above tricky issues. The SSC produced through the in‐situ introduction of the porous PCE on the surface of the active material, facilitates the simultaneous transfer of Li+/e−, as well as ensures fast flow of O2, forming continuous and abundant TPBs. The high Li+ conductivity, softness, and adhesion of the dense PCE significantly reduce the battery resistance to 115 Ω. As a result, the ASS Li‐O2 battery based on this adjustable‐porosity PCE exhibits superior performances with high specific capacity (5963 mAh g−1), good rate capability, and stable cycling life up to 130 cycles at 32 °C. This novel design and exciting results could open a new avenue for ASS Li‐O2 batteries. [ABSTRACT FROM AUTHOR]

Redox mediators (RMs) are considered an effective countermeasure to reduce the large polarization in lithium‐oxygen batteries. Nevertheless, achieving sufficient enhancement of the cyclability is limited by the trade‐offs of freely mobile RMs, which are beneficial for charge transport but also trigger the shuttling phenomenon. Here, we successfully decoupled the charge‐carrying redox property of RMs and shuttling phenomenon by anchoring the RMs in polymer form, where physical RM migration was replaced by charge transfer along polymer chains. Using PTMA (poly(2,2,6,6‐tetramethyl‐1‐piperidinyloxy‐4‐yl methacrylate)) as a polymer model system based on the well‐known RM tetramethylpiperidinyloxyl (TEMPO), it is demonstrated that PTMA can function as stationary RM, preserving the redox activity of TEMPO. The efficiency of RM‐mediated Li2O2 decomposition remains remarkably stable without the consumption of oxidized RMs or degradation of the lithium anode, resulting in an improved performance of the lithium‐oxygen cell. [ABSTRACT FROM AUTHOR]

Ether‐based electrolytes are commonly used in Li–O2 batteries (LOBs) because of their relatively high stability. But they are still prone to be attacked by superoxides or singlet oxygen via hydrogen abstract reactions, which leads to performance decaying during long‐term operation. Herein we propose a methylated cyclic ether, 2,2,4,4,5,5‐hexamethyl‐1,3‐dioxolane (HMD), as a stable electrolyte solvent for LOBs. Such a compound does not contain any hydrogen atoms on the alpha‐carbon of the ether, and thus avoids hydrogen abstraction reactions. As the result, this solvent exhibits excellent stability with the presence of superoxide or singlet oxygen. In addition the CO2 evolution during charge process is prohibited. The LOB with HMD‐based electrolyte was able to run up to 157 cycles, 4 times more than with 1,3‐dioxolane (DOL) or 1,2‐dimethoxyethane (DME) based electrolytes. Full methyl jacket: A fully methylated cyclic ether 4,4,5,5‐hexamethyl‐1,3‐dioxolane is used as an electrolyte solvent for Li–O2 batteries. It exhibits excellent stability in the presence of superoxide or singlet oxygen because all the active α‐H atoms are substituted with methyl groups. The cycling performance is 4 times greater that of conventional ether electrolytes. [ABSTRACT FROM AUTHOR]

Abstract: Rechargeable Li‐O2 batteries have aroused much attention for their high energy density as a promising battery technology; however, the performance of the batteries is still unsatisfactory. Lithium anodes, as one of the most important part of Li‐O2 batteries, play a vital role in improving the cycle life of the batteries. Now, a very simple method is introduced to produce a protective film on lithium surface via chemical reactions between lithium metals and 1,4‐dioxacyclohexane. The film is mainly composed of ethylene oxide monomers and endows Li‐O2 batteries with enhanced cycling stability. The film could effectually reduce the morphology changes and suppress the parasitic reactions of lithium anodes. This simple approach provides a new strategy to protect lithium anodes in Li‐O2 batteries. [ABSTRACT FROM AUTHOR]

Large over-potentials owing to the sluggish kinetics of battery reactions have always been the drawbacks of Li−O2 batteries, which lead to short cycle life. Although redox mediators have been intensively investigated to overcome this issue, side-reactions are generally induced by the solvated nature of redox mediators. Herein, we report an alternative method to achieve more efficient utilization of tetrathiafulvalene (TTF) in Li−O2 batteries. By coordinating TTF+ with LiCl during charging, an organic conductor TTF+Cl x− precipitate covers Li2O2 to provide an additional electron-transfer pathway on the surface, which can significantly reduce the charge over-potential, improve the energy efficiency of Li−O2 batteries, and eliminate side-reactions between the lithium metal anode and TTF+. When a porous graphene electrode is used, the Li−O2 battery combined with TTF and LiCl shows an outstanding performance and prolonged cycle life. [ABSTRACT FROM AUTHOR]

As an electrochemical energy-storage technology with the highest theoretical capacity, lithium-oxygen batteries face critical challenges in terms of poor stabilities and low charge/discharge round-trip efficiencies. It is generally recognized that these issues are connected to the parasitic chemical reactions at the anode, electrolyte, and cathode. While the detailed mechanisms of these reactions have been studied separately, the possible synergistic effects between these reactions remain poorly understood. To fill in the knowledge gap, this Minireview examines literature reports on the parasitic chemical reactions and finds the reactive oxygen species a key chemical mediator that participates in or facilitates nearly all parasitic chemical reactions. Given the ubiquitous presence of oxygen in all test cells, this finding is important. It offers new insights into how to stabilize various components of lithium-oxygen batteries for high-performance operations and how to eventually materialize the full potentials of this promising technology. [ABSTRACT FROM AUTHOR]

Non-aqueous lithium-oxygen batteries are considered as most advanced power sources, albeit they are facing numerous challenges concerning almost each cell component. Herein, we diverge from the conventional and traditional liquid-based non-aqueous Li-O2 batteries to a Li-O2 system based on a solid polymer electrolyte (SPE-) and operated at a temperature higher than the melting point of the polymer electrolyte, where useful and most applicable conductivity values are easily achieved. The proposed SPE-based Li-O2 cell is compared to Li-O2 cells based on ethylene glycol dimethyl ether (glyme) through potentiodynamic and galvanostatic studies, showing a higher cell discharge voltage by 80 mV and most significantly, a charge voltage lower by 400 mV. The solid-state battery demonstrated a comparable discharge-specific capacity to glyme-based Li-O2 cells when discharged at the same current density. The results shown here demonstrate that the safer PEO-based Li-O2 battery is highly advantageous and can potentially replace the contingent of liquid-based cells upon further investigation. [ABSTRACT FROM AUTHOR]

A promotor for lithium batteries: Nanocrystalline cobalt(II,III) oxide supported on graphene enhances the transport kinetics for both oxygen reduction and oxygen evolution in the lithium–oxygen cell. On cycling the lithium–oxygen cell, the effect of the promoter is, however, eventually overwhelmed by side reactions in the cell, such as, the deposition of carbonates (see picture). [ABSTRACT FROM AUTHOR]