Understanding the Solution-Phase Catalysis Process inside the Li-O₂ Battery Using Redox Mediator─Butylated...

Area of Science:

• Electrochemistry
• Materials Science
• Computational Chemistry

Background:

• Redox mediators are crucial for preventing cathode passivation and facilitating lithium peroxide (Li2O2) dynamics in Li-O2 batteries.
• Understanding soluble catalysts at an atomic level is key to developing advanced Li-O2 battery technologies.
• Butylated hydroxytoluene (BHT) has shown promise as an experimentally reported soluble catalyst.

Purpose of the Study:

• To elucidate the atomic-level mechanistic properties of butylated hydroxytoluene (BHT) as a soluble catalyst in Li-O2 batteries.
• To investigate how BHT mediates the stabilization of reactive intermediates and the formation/decomposition of Li2O2.
• To explore the cooperative effect of BHT with tetraethylene glycol dimethyl ether solvent.

Main Methods:

• Density Functional Theory (DFT) calculations.
• Atom-centered density matrix propagation molecular dynamics simulations.
• Mulliken charge distribution analysis.

Main Results:

• BHT's hydroxy group stabilizes O2•− via hydrogen bonding and solvates key lithium-oxygen species (Li+, LiO2•, Li2O2).
• BHT promotes the solution-phase mechanism, suppresses parasitic reactions, and facilitates Li2O2 formation/decomposition through hydrogen bonding dynamics.
• BHT and BHT•+ reversibility, driven by electron delocalization, aids the charging process; BHT facilitates decomposition via protonation, while BHT•+ promotes it through LiO2• and BHT:Li+ complex formation.

Conclusions:

• BHT acts as a multifunctional soluble catalyst, enhancing Li-O2 battery performance by stabilizing intermediates and mediating Li2O2 redox reactions.
• The presence and absence of hydrogen bonding involving BHT are crucial for efficient Li2O2 formation and decomposition, respectively.
• BHT exhibits cooperative activity with tetraethylene glycol dimethyl ether solvent, further improving the stabilization of lithium-oxygen species.