Impact of air impurities (H2O and CO2) on Li-air/O2 batteries performance: A multiscale modeling approach

For Li O 2 based electric vehicles (EVs), operation in air is often considered detrimental because trace H 2 O/CO 2 are assumed to degrade performance. Using an integrated multiscale framework, a coupled reactive forcefield molecular dynamics (reaxFF-MD) and 2-D continuum cell model, we show that realistic ambient levels of these species can enhance discharge performance, making them actionable design variables for air-breathing Li O 2 batteries. We evaluate three atmospheres: pure O 2 (21%), O 2 /H 2 O (65% RH), and O 2 /CO 2 (420 ppm). Relative to pure O 2 , 65% RH increases capacity by ∼34% (∼3320.6 mAh g c −1 ), with energy and power densities of ∼9950.4 Wh kg c −1 (+38%) and ∼ 1402.8 W kg c −1 (+6%). Likewise, 420 ppm CO 2 yields ∼21% higher capacity (∼2772.8 mAh g c −1 ) and + 22% energy (∼7844.8 Wh kg c −1 ), with a modest power gain (∼1325.1 W kg c −1 ). The improvement stems from a mechanistic shift: impurities bias Li 2 O 2 formation toward solution-mediated growth, sustaining a higher discharge plateau and delaying passivation; concomitant LiOH/Li 2 CO 3 remain modest at these levels. Moreover, the present work reports a practical operating window, RH ≈ 4–65% and CO 2 ≤ ambient (∼420 ppm), that captures benefits while limiting side-product accumulation. These findings dispel the prevailing view that air contaminants are inherently harmful and show how they can be strategically managed to accelerate the practical deployment of air-breathing Li–O₂ batteries for high-range EV applications.