Influence of Enhanced O2 Provision on the Discharge Performance of Li-air Batteries by Incorporating Fluoroether

Tetramethylpyrazine: an electrolyte additive for high capacity and energy efficiency lithium–oxygen batteries

Lithium–oxygen batteries have attracted great attention in recent years owing to their extremely high theoretical energy density, however, factors such as low actual capacity and poor rate performance hinder the practical application of lithium–oxygen batteries. In this work, a novel electrolyte additive, tetramethylpyrazine (TMP), is introduced into an electrolyte system to enhance the electrochemical performance of the lithium–oxygen batteries. TMP does not undergo its own redox reaction within the charge–discharge voltage range, which will not affect the electrochemical stability of the electrolyte. The results show that the addition of TMP can increase the reduction current of oxygen, which will promote the ORR process, and with an optimal TMP content (50 mM), the cell shows a high discharge capacity of 5712.3 mA h g⁻¹ at 0.1 mA cm⁻². And its rate capability is almost doubled compared with the system without TMP additive at a large current density of 1 mA cm⁻². Further analysis by SEM and XRD reveals that the addition of TMP can reduce the formation of by-products and promote the solution growth of large-size Li₂O₂ particles to achieve a large discharge capacity. This approach could provide a new idea for improving the electrochemical performance of lithium–oxygen batteries.

TMP has a strong interaction with Li⁺, which promotes the solution mechanism of Li₂O₂, thereby increasing the discharge capacity.

Current Challenges and Routes Forward for Nonaqueous Lithium-Air Batteries

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 advances have been achieved both in the mechanistic understanding of the cell reactions and in the development of effective strategies to help realize a practical energy storage device. By drawing attention to reports published mainly within the past 8 years, this review provides an updated mechanistic picture of the lithium peroxide based cell reactions and highlights key remaining challenges, including those due to the parasitic processes occurring at the reaction product-electrolyte, product-cathode, electrolyte-cathode, and electrolyte-anode interfaces. We introduce the fundamental principles and critically evaluate the effectiveness of the different strategies that have been proposed to mitigate the various issues of this chemistry, which include the use of solid catalysts, redox mediators, solvating additives for oxygen reaction intermediates, gas separation membranes, etc. Recently established cell chemistries based on the superoxide, hydroxide, and oxide phases are also summarized and discussed.

Electrolytes for Rechargeable Lithium-Air Batteries

Lithium-air batteries are promising devices for electrochemical energy storage because of their ultrahigh energy density. However, it is still challenging to achieve practical Li-air batteries because of their severe capacity fading and poor rate capability. Electrolytes are the prime suspects for cell failure. In this Review, we focus on the opportunities and challenges of electrolytes for rechargeable Li-air batteries. A detailed summary of the reaction mechanisms, internal compositions, instability factors, selection criteria, and design ideas of the considered electrolytes is provided to obtain appropriate strategies to meet the battery requirements. In particular, ionic liquid (IL) electrolytes and solid-state electrolytes show exciting opportunities to control both the high energy density and safety.

Binary Mixtures of Highly Concentrated Tetraglyme and Hydrofluoroether as a Stable and Nonflammable Electrolyte for Li-O2 Batteries

Developing a long-term stable electrolyte is one of the most enormous challenges for Li-O₂ batteries. Equally, the high flammability of frequently used solvents seriously weakens the electrolyte safety in Li-O₂ batteries, which inevitably restricts their commercial applications. Here, a binary mixture of highly concentrated tetraglyme electrolyte (HCG4) and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) was used for a novel electrolyte (HCG4/TTE) in Li-O₂ batteries, which exhibit good wettability, enhanced ionic conductivity, considerable nonflammability, and high electrochemical stability. Being a co-solvent, TTE can contribute to increasing ionic conductivity and to improving flame retardance of the as-prepared electrolyte. The cell with this novel electrolyte displays an enhanced cycling stability, resulting from the high electrochemical stability during cycling and the formation of electrochemically stable interfaces prevents parasitic reactions occurring on the Li anode. These results presented here demonstrate a novel electrolyte with a high electrochemical stability and considerable safety for Li-O₂ batteries.

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.