The goal of limiting global warming to 1.5 °C requires a drastic reduction in CO2 emissions across many sectors of the world economy. Batteries are vital to this endeavor, whether used in electric vehicles, to store renewable electricity, or in aviation. Present lithium-ion technologies are preparing the public for this inevitable change, but their maximum theoretical specific capacity presents a limitation. Their high cost is another concern for commercial viability. Metal-air batteries have the highest theoretical energy density of all possible secondary battery technologies and could yield step changes in energy storage, if their practical difficulties could be overcome. The scope of this review is to provide an objective, comprehensive, and authoritative assessment of the intensive work invested in nonaqueous rechargeable metal-air batteries over the past few years, which identified the key problems and guides directions to solve them. We focus primarily on the challenges and outlook for Li-O2 cells but include Na-O2, K-O2, and Mg-O2 cells for comparison. Our review highlights the interdisciplinary nature of this field that involves a combination of materials chemistry, electrochemistry, computation, microscopy, spectroscopy, and surface science. The mechanisms of O2 reduction and evolution are considered in the light of recent findings, along with developments in positive and negative electrodes, electrolytes, electrocatalysis on surfaces and in solution, and the degradative effect of singlet oxygen, which is typically formed in Li-O2 cells.

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Lithium-Oxygen Batteries and Related Systems: Potential, Status, and Future

Transition metal based battery-type electrodes in hybrid supercapacitors: A review

Nonaqueous lithium–air batteries have garnered considerable research interest over the past decade due to their extremely high theoretical energy densities and potentially low cost. Significant adv...

Current challenges and routes forward for nonaqueous lithium–air batteries

Recent Advances in Vanadium-Based Aqueous Rechargeable Zinc-Ion Batteries

Developing single-site catalysts featuring maximum atom utilization efficiency is urgently desired to improve oxidation-reduction efficiency and cycling capability of lithium-oxygen batteries. Here, we report a green method to synthesize isolated cobalt atoms embedded ultrathin nitrogen-rich carbon as a dual-catalyst for lithium-oxygen batteries. The achieved electrode with maximized exposed atomic active sites is beneficial for tailoring formation/decomposition mechanisms of uniformly distributed nano-sized lithium peroxide during oxygen reduction/evolution reactions due to abundant cobalt-nitrogen coordinate catalytic sites, thus demonstrating greatly enhanced redox kinetics and efficiently ameliorated over-potentials. Critically, theoretical simulations disclose that rich cobalt-nitrogen moieties as the driving force centers can drastically enhance the intrinsic affinity of intermediate species and thus fundamentally tune the evolution mechanism of the size and distribution of final lithium peroxide. In the lithium-oxygen battery, the electrode affords remarkably decreased charge/discharge polarization (0.40 V) and long-term cyclability (260 cycles at 400 mA g−1). The performance of Li-O2 batteries is largely determined by the oxygen electrocatalytic reactions at the cathode. Here, the authors report cobalt single-atom catalysts anchored on carbon nanosheets. The design improves oxygen redox kinetics and enables good electrochemical performance.

Atomically dispersed cobalt catalyst anchored on nitrogen-doped carbon nanosheets for lithium-oxygen batteries

V2O5 nanopaper as a cathode material with high capacity and long cycle life for rechargeable aqueous zinc-ion battery

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.

A Stable Lithium-Oxygen Battery Electrolyte Based on Fully Methylated Cyclic Ether.

Oxygen selective membrane based on perfluoropolyether for Li-Air battery with long cycle life

High areal capacity, long cycle life Li-O2 cathode based on highly elastic gel granules

As a candidate for next generation energy storage devices, the Li–O2 battery (LOB) has been extensively studied in the last decade because of its ultrahigh theoretical energy density (≈3500 W h kg−1) and inexhaustible “cathode material”—oxygen. Unlike other batteries with a closed configuration, the discharge/charge process of the LOB involves complicated electrochemical reactions at multi-phase interfaces. The mass/charge transfer in the oxygen cathode may limit the discharge/charge rate and capacity. Herein, a novel oxygen cathode with a rolled CNT film configuration is proposed to address the above issue. In such a configuration, the CNT film is vertically aligned, which serves as an excellent electron transfer expressway. Meanwhile, the partially wetted fluffy cotton layer between the CNT film layers endows the cathode with high ionic conductivity and oxygen diffusivity in the vertical direction. Electrons, ions and oxygen molecules may smoothly settle at both sides of the CNT film. Thus, the cathode exhibits an enhanced discharge capacity up to 13 564 mA h g−1, which is 2.5 times larger than the capacity of the conventional parallel aligned CNT film. Moreover, the cycle life is also improved by 5.5 times.

Zhaoming Huang

Papers

V2O5 nanopaper as a cathode material with high capacity and long cycle life for rechargeable aqueous zinc-ion battery

A Stable Lithium-Oxygen Battery Electrolyte Based on Fully Methylated Cyclic Ether.

Oxygen selective membrane based on perfluoropolyether for Li-Air battery with long cycle life

High areal capacity, long cycle life Li-O2 cathode based on highly elastic gel granules

A Li–O2 battery cathode with vertical mass/charge transfer pathways