Review of Electrolytes in Nonaqueous Lithium–Oxygen Batteries

Abstract

Based on an inexhaustible and ubiquitous source of oxygen, the lithium-oxygen batteries are currently the subject of much scientific investigation because of their potential for extremely high energy density. The electrocatalytic materials for them have been extensively researched during the past decade. Even though they are a key component in the lithium-oxygen batteries, however, the study of electrolytes is still in its primary stage. Electrolytes have an important influence on the electrochemical performance of lithium-oxygen batteries, especially on their cycling stability and rate capacity. Therefore, it is important to select an ideal electrolyte with excellent stability against attack by reaction intermediates, along with excellent oxygen solubility and diffusivity. In this review, the physicochemical and electrochemical properties of organic electrolytes for lithium-oxygen batteries are discussed and compared. Furthermore, possible research directions are proposed for the development of an ideal electrolyte for enhanced electrochemical performance. Disciplines Engineering | Physical Sciences and Mathematics Publication DetailsGuo, H., Luo, W., Chen, J., Chou, S., Liu, H. & Wang, J. (2018 Figure 1. Unlike the intercalation mechanism of lithium-ion batteries or sodium-ion batteries, the Li-O 2 battery systems employ a dissolution/ deposition reaction with an air electrode that uses oxygen as the cathode electrode during the electrochemical processes. Research on the Li-O 2 battery is complicated by the need for exposure the air cathode to O 2 atmosphere.Many advances have been achieved, which include advances on cathode materials, electrolytes, anode materials, and redox mediators. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Several excellent reviews have been published to summarize recent developments and our current understanding of Li-O 2 batteries, especially with respect to the cathode electrocatalytic materials. [25][26][27][28][29][30][31][32][33][34][35] These reviews have comprehensively discussed the relationship between the structure of electrocatalytic materials and the electrochemical performance of Li-O 2 batteries. There are, however, few reviews focused on the effects of different electrolytes on the electrochemical performance of the Li-O 2 batteries. [36][37][38] For the aqueous Li-O 2 batteries, LiOH is generated or oxidized at the cathode during discharge and charge processes because H 2 O and O 2 are involved in the reactions. In the case of the nonaqueous Li-O 2 batteries, there are two essential processes that determine their electrochemical performance: the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). During the ORR process, the Li 2 O 2 is precipitated as the final discharge product on the air cathode, while during the OER process, Li 2 O 2 is then decomposed and the O 2 is regenerated. Therefore, there are huge differences between aqueous and nonaqueous Li-O 2 batteries. Since the nonaqueous Li-O 2 batteries have dominated ...

Electrolytes for Rechargeable Lithium–Air Batteries

“… RTILs have low salt solubility and poor Li + mobility, which hinder the formation of an SEI on the surface of the Li anode and limit the rate performance of the battery. The O 2 diffusivity coefficients of RTILs are almost one order of magnitude lower than those of DME and DMSO, further limiting the capacity of Li–air batteries It is difficult for RTILs to effectively infiltrate the surface of the electrode because of their high viscosity, which leads to high mass‐transfer resistance and a high interface polarization voltage. The high cost of RTILs also limits their commercial application. …”

“…The O 2 diffusivity coefficients of RTILs are almost one order of magnitude lower than those of DME and DMSO, further limiting the capacity of Li–air batteries …”

Facile Synthesis of Sheet Stacking Structure NiCo2S4@PPy with Enhanced Rate Capability and Cycling Performance for Aqueous Supercapacitors

“…Greenhouse effect, environmental pollution, energy security, and sustainable development are in urgent need for serious energy reform about conventional fossil fuels and a shift to renewable sources, such as solar, wind, and hydro energy, which are the most likely solutions for settling the issues . However, the development of the renewable energy has no equilibrium in the time and territories, which significantly limits the popularity of renewable energy generation.…”

Phosphorous and Nitrogen Dual-Doped Carbon as a Highly Efficient Electrocatalyst for Sodium-Oxygen Batteries

“…1,2,3 Unfortunately, there are still many problems impede its practical application, such as high overpotential and poor cycling stability. 4,5,6,7,8,9 The main reason for these problems could be attributed to the formation of an extremely unstable superoxide intermediate (O 2 − ), which could not be stabilized by small Li + ions due to the mismatch according to the hard and soft acid base (HSAB) theory and can react with non-aqueous electrolytes or carbon-based air cathodes. 10,11,12 By contrast, as a soft Lewis acid compared with Li + , Na + could effectively stabilize the soft Lewis base O 2 − ions.…”