CsI as Multifunctional Redox Mediator for Enhanced Li–Air Batteries

Abstract

We introduce CsI as a multifunctional redox mediator to enhance the performance of Li-air batteries. CsI dissolved in the electrolyte is ionized into Cs(+) and I(-), which perform their roles in the Li anode and air electrode, respectively. The I(-) ions in the electrolyte facilitate the dissolution of Li2O2 in the air electrode as a redox mediator, which reduces the overpotential of the cell. The low overpotential also leads to the suppression of parasitic reactions occurring in the high-voltage range, such as the decomposition of the electrolyte and the reaction between Li2O2 and carbon. At the same time, the Cs(+) ions act as an electrostatic shield at the sharp points of the Li anode, hindering the growth of Li dendrite. The combined effects of reduced parasitic reactions and hindered Li-dendrite growth successfully improve the cyclic performance of Li-air cells.

Electrolytes for Rechargeable Lithium–Air Batteries

“…Interestingly, halides such as CsI and RbI show promise as multifunctional OERMs because a low concentration of Cs + or Rb + can remain in the electrolyte even when Li + is reduced to Li. Cs + or Rb + can act as an electrostatic shield to protect the Li anode and hinder Li dendritic growth caused by Li + reduction . Moreover, InI 3 has been proposed to be a self‐defense RM to increase the efficiency of Li–air batteries.…”

“…Cs + or Rb + can act as an electrostatic shield to protect the Li anode and hinder Li dendritic growth caused by Li + reduction. [94] Moreover,I nI 3 has been proposed to be as elf-defense RM to increase the efficiency of Li-air batteries.I n 3+ can form as table indium layer on the Li anode,w hich protects the Li anode from attack by the soluble I 3 À .T he predeposited indium layer also suppresses the growth of dendrites. [95] Another kind of inorganic OERM is LiNO 3 ,w hich can serve as not only aL i salt but also auseful OERM in Li-O 2 batteries.…”

Promoting Li–O2 Batteries With Redox Mediators

“…Attempts have been made to combine RM disch and RM char to solve both discharge and charge problems through a bifunctional RM . However, this is somewhat difficult.…”

“…Attempts have been made to combineR M disch and RM char to solve both discharge and charge problems through ab ifunctional RM. [12][13][14][15][16]38] However,t his is somewhat difficult. RMs such as Fe(heme) are struggling to meet the requirements for dischargea nd charge at the same time.…”

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

“…As shown in Figure S8, the cell with 50 % FE1 shows only marginally better cycle life (17 cycles)t han that withoutF E1 (14 cycles), indicating that the improved mass transfer does not exert as ignificant facilitating effect on charging. Suitable catalysts, such as redox mediators,a re required to efficiently decompose the deposited products, [39,[46][47][48][49][50] including the parasitic Li 2 CO 3 and carboxylates, which will be discussed in future work from our group.…”