Hydrogen-Bond-Assisted Solution Discharge in Aprotic Li-O₂ Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Aprotic lithium-oxygen (Li-O2) batteries offer high theoretical energy density but are limited by cathode passivation due to surface discharge mechanisms.
• Surface discharge leads to inefficient energy utilization and hinders the practical application of Li-O2 battery technology.

Purpose of the Study:

• To propose a novel hydrogen-bond-assisted solvation strategy to promote solution discharge in Li-O2 batteries.
• To overcome the limitations imposed by surface discharge mechanisms and cathode passivation.
• To enhance the energy density and cycling stability of Li-O2 batteries.

Main Methods:

• Introduction of 2,5-Di-tert-butylhydroquinone (DBHQ), an antioxidant with hydroxyl groups, as a soluble catalyst.
• Facilitation of solution discharge through hydrogen-bond-assisted solvation of superoxide (O2-) and lithium peroxide (Li2O2) species.
• Verification of the generalizability of the approach using other soluble catalysts with -OH or -NH groups.

Main Results:

• A Li-O2 battery with 50 × 10-3 m DBHQ achieved an exceptional discharge capacity of 18,945 mAh g-1 (9.47 mAh cm-2), surpassing state-of-the-art mediators.
• An ultrahigh Li2O2 yield of 97.1% was obtained due to the stabilized reduced oxygen species by DBHQ's solvating and antioxidative properties.
• DBHQ-modified Li-O2 batteries demonstrated excellent cycling lifetime and rate capability.

Conclusions:

• Hydrogen-bond-assisted solvation is an effective strategy to trigger solution discharge and mitigate cathode passivation in Li-O2 batteries.
• DBHQ serves as a highly effective soluble catalyst, significantly boosting battery performance.
• This approach offers a promising pathway toward realizing the potential of Li-O2 batteries as a viable energy storage technology.