A CO₂-Mediated Li-O₂ Battery With 3.3 V Discharge Voltage

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium-oxygen (Li-O2) batteries offer high capacity but suffer from sluggish kinetics, limiting discharge voltages below 2.85 V.
• This "high capacity, low power output" dilemma hinders practical energy and power densities in Li-O2 systems.

Purpose of the Study:

• To redefine oxygen redox chemistry in Li-O2 batteries by optimizing gas composition and catalytic architecture.
• To overcome kinetic limitations and enhance discharge voltage for improved energy and power density.

Main Methods:

• Construction of a CO2-mediated Li-O2 battery (CLOB) with optimized gas composition.
• Introduction of iron phthalocyanine (FePc) as a soluble molecular carrier to mitigate kinetic constraints.
• Electrochemical characterization of the CLOB system in a two-electrode cell.

Main Results:

• The CLOB achieved a significantly elevated equilibrium discharge voltage of 3.30 V.
• Oxygen and CO2 were reduced through intermediates (Li2CO4, Li2C2O6) to Li2CO3.
• The FePc-based CLOB demonstrated an exceptional discharge voltage of 3.30 V.
• An assembled pouch cell achieved 1.38 Ah capacity and 870.1 Wh/kg energy density.

Conclusions:

• The CO2-mediated approach successfully enhances discharge voltage and energy density in Li-O2 batteries.
• The use of FePc as a catalyst effectively mitigates kinetic limitations.
• This work presents a new paradigm for the commercialization of metal-gas batteries.