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 higher theoretical energy density than lithium-ion batteries by utilizing oxygen conversion reactions.
• Practical Li-O2 batteries face limitations due to sluggish kinetics, resulting in low discharge voltages (<2.85 V) and a compromise between capacity and power.
• This "high capacity, low power output" dilemma hinders their commercial viability and achievable energy/power densities.

Purpose of the Study:

• To redefine oxygen redox chemistry in Li-O2 batteries by optimizing gas composition and catalytic architecture.
• To overcome the kinetic limitations and enhance the discharge voltage for improved energy and power densities.
• To explore a new paradigm for metal-gas battery commercialization.

Main Methods:

• Construction of a CO2-mediated Li-O2 battery (CLOB) with optimized gas composition.
• Integration of iron phthalocyanine (FePc) as a soluble molecular carrier to mitigate kinetic constraints.
• Electrochemical characterization using a two-electrode cell to determine equilibrium voltage and performance metrics.

Main Results:

• The CLOB successfully elevates the discharge voltage to 3.30 V, comparable to LiFePO4-based lithium-ion batteries.
• Oxygen and CO2 are reduced through intermediates (Li2CO4, Li2C2O6) to Li2CO3, achieving an equilibrium voltage of 3.30 V.
• The FePc-based CLOB demonstrates an exceptional discharge voltage of 3.30 V, and a pouch cell achieved 1.38 Ah capacity with 870.1 Wh/kg energy density.

Conclusions:

• The CO2-mediated approach and FePc catalyst significantly enhance the discharge voltage and mitigate kinetic limitations in Li-O2 batteries.
• The achieved voltage enhancement substantially improves energy output, addressing the power density challenge.
• This work presents a promising new direction for the commercialization of high-energy metal-gas batteries.