Investigation of the carbon electrode changes during lithium oxygen cell operation in a tetraglyme-based electrolyte

Functional and stability orientation synthesis of materials and structures in aprotic Li–O2batteries

This review presents the recent advances made in the functional and stability orientation synthesis of materials/structures for Li–O₂batteries.

3D web freestanding RuO2–Co3O4 nanowires on Ni foam as highly efficient cathode catalysts for Li–O2 batteries

The mechanism of Li–O₂ batteries is based on the reactions of lithium ions and oxygen, which hold a theoretical higher energy density of approximately 3500 W h kg⁻¹. In order to improve the practical specific capacity and cycling performance of Li–O₂ batteries, a catalytically active mechanically robust air cathode is required. In this work, we synthesized a freestanding catalytic cathode with RuO₂ decorated 3D web Co₃O₄ nanowires on nickel foam. When the specific capacity was limited at 500 mA h g⁻¹, the RuO₂–Co₃O₄/NiF had a stable cycling life of up to 122 times. The outstanding performance can be primarily attributed to the robust freestanding Co₃O₄ nanowires with RuO₂ loading. The unique 3D web nanowire structure provides a large surface for Li₂O₂ growth and RuO₂ nanoparticle loading, and the RuO₂ nanoparticles help to promote the round trip deposition and decomposition of Li₂O₂, therefore enhancing the cycling behavior. This result indicates the superiority of RuO₂–Co₃O₄/NiF as a freestanding highly efficient catalytic cathode for Li–O₂ batteries.

Freestanding RuO₂–Co₃O₄ nanowires on Ni foam were synthesized and applied as a cathode in Li–O₂ battery. This cathode can deliver a high capacity of 9620 mA h g⁻¹ and stable long-term operation exceeding 122 cycles at 100 mA g⁻¹.

Catholyte Formulations for High-Energy Li-S Batteries

The sulfur electrode in LiS batteries suffers from rapid capacity loss and low efficiency due to the solubility of long chain polysulfides formed during discharge. Herein, we demonstrate the beneficial effect of original catholyte formulations containing redox active organyl disulfides (PhS₂Ph) on the capacity utilization and retention as well as the efficiency in LiS batteries. Resulting from the chemical equilibria in the electrolyte between the sulfur/polysulfides (S₈/S_x^2-) and disulfide/thiolates (PhS₂Ph/PhS_x^-), the polysulfide redox shuttle phenomenon is minimized due to the suppression of formation of soluble polysulfides (S_x^2-, x > 4). Using the catholyte containing 0.4 M Ph₂S₂ as an additive in a standard base electrolyte (DOL/DME + LiTFSI/LiNO₃), a stable capacity of 1050 mAh·g^-1 is obtained under galvanostatic cycling at C/5 with a Coulombic efficiency of >99.5%. At 45 °C, it is shown that the formulated catholyte enables galvanostatic cycling at a high c-rate of 1C over 500 cycles with a capacity above 900 mAh·g^-1 and a high energy efficiency of 82%.

Catalyst morphology matters for lithium-oxygen battery cathodes

The effectiveness of using catalyst nanoparticles to reduce the overpotential and energy efficiency of lithium-oxygen (or lithium-air) batteries (LOBs) is usually attributed to the inherent catalytic properties of individual nanoparticles. Here, we demonstrate that the morphology of the catalyst layer is equally important in maintaining integrity of the catalyst coating during product formation in LOBs. We demonstrate this by comparing the performance of smooth, conformal coated Mn₂O₃ catalyst nanoparticles prepared by electric field-assisted deposition, and more irregular coatings using conventional film assembly techniques both on three-dimensional mesh substrates. Smooth coatings lead to an improved overpotential of 50 mV during oxygen reduction and 130 mV during oxygen evolution in addition to a nearly 2X improvement in durability compared to the more irregular films. In situ electrochemical impedance spectroscopy combined with imaging studies elucidates a mechanism of morphology-directed deactivation of catalyst layers during charging and discharging that must be overcome at practical electrode scales to achieve cell-level performance targets in LOBs.

Artificial Protection Film on Lithium Metal Anode toward Long-Cycle-Life Lithium-Oxygen Batteries

An artificial while very stable solid electrolyte interphase film is formed on lithium metal using an electrochemical strategy. When this protected Li anode is first used in a Li-O2 battery, the film formed on the anode can effectively suppress the parasitic reactions on the Li anode/electrolyte interface and significantly enhance the cycling stability of the 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.

The lithium/air battery: still an emerging system or a practical reality?

Lithium/air is a fascinating energy storage system. The effective exploitation of air as a battery electrode has been the long-time dream of the battery community. Air is, in principle, a no-cost material characterized by a very high specific capacity value. In the particular case of the lithium/air system, energy levels approaching that of gasoline have been postulated. It is then not surprising that, in the course of the last decade, great attention has been devoted to this battery by various top academic and industrial laboratories worldwide. This intense investigation, however, has soon highlighted a series of issues that prevent a rapid development of the Li/air electrochemical system. Although several breakthroughs have been achieved recently, the question on whether this battery will have an effective economic and societal impact remains. In this review, a critical evaluation of the progress achieved so far is made, together with an attempt to propose future R&D trends. A forecast on whether Li/air may have a role in the next years' battery technology is also postulated.

Vertically aligned N-doped coral-like carbon fiber arrays as efficient air electrodes for high-performance nonaqueous Li-O2 batteries

High energy efficiency and long cycleability are two important performance measures for Li-air batteries. Using a rationally designed oxygen electrode based on a vertically aligned nitrogen-doped coral-like carbon nanofiber (VA-NCCF) array supported by stainless steel cloth, we have developed a nonaqueous Li-O2 battery with an energy efficiency as high as 90% and a narrow voltage gap of 0.3 V between discharge/charge plateaus. Excellent reversibility and cycleability were also demonstrated for the newly developed oxygen electrode. The observed outstanding performance can be attributed to its unique vertically aligned, coral-like N-doped carbon microstructure with a high catalytic activity and an optimized oxygen/electron transportation capability, coupled with the microporous stainless steel substrate. These results demonstrate that highly efficient and reversible Li-O2 batteries are feasible by using a rationally designed carbon-based oxygen electrode.